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Huang, Jianzhong, Glenn S. Van Aller, Amy N. Taylor, et al. "Phylogenomic and Biochemical Characterization of Three Legionella pneumophila Polypeptide Deformylases." Journal of Bacteriology 188, no. 14 (2006): 5249–57. http://dx.doi.org/10.1128/jb.00866-05.
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ABSTRACT Legionella pneumophila is a gram-negative facultative intracellular human pathogen that can cause fatal Legionnaires' disease. Polypeptide deformylase (PDF) is a novel broad-spectrum antibacterial target, and reports of inhibitors of PDF with potent activities against L. pneumophila have been published previously. Here, we report the identification of not one but three putative pdf genes, pdfA, pdfB, and pdfC, in the complete genome sequences of three strains of L. pneumophila. Phylogenetic analysis showed that L. pneumophila PdfA is most closely related to the commonly known γ-proteobacterial PDFs encoded by the gene def. PdfB and PdfC are more divergent and do not cluster with any specific bacterial or eukaryotic PDF. All three putative pdf genes from L. pneumophila strain Philadelphia 1 have been cloned, and their encoded products have been overexpressed in Escherichia coli and purified. Enzymatic characterization shows that the purified PDFs with Ni2+ substituted are catalytically active and able to remove the N-formyl group from several synthetic polypeptides, although they appear to have different substrate specificities. Surprisingly, while PdfA and PdfB with Zn2+ substituted are much less active than the Ni2+ forms of each enzyme, PdfC with Zn2+ substituted was as active as the Ni2+ form for the fMA substrate and exhibited substrate specificity different from that of Ni2+ PdfC. Furthermore, the catalytic activities of these enzymes are potently inhibited by a known small-molecule PDF inhibitor, BB-3497, which also inhibits the extracellular growth of L. pneumophila. These results indicate that even though L. pneumophila has three PDFs, they can be effectively inhibited by PDF inhibitors which can, therefore, have potent anti-L. pneumophila activity.
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Chamadol, Nittaya, Narong Khuntikeo, Bandit Thinkhamrop, et al. "Association between periductal fibrosis and bile duct dilatation among a population at high risk of cholangiocarcinoma: a cross-sectional study of cholangiocarcinoma screening in Northeast Thailand." BMJ Open 9, no. 3 (2019): e023217. http://dx.doi.org/10.1136/bmjopen-2018-023217.
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ObjectivesTo assess associations between periductal fibrosis (PDF) and bile duct dilatation (BDD) in ultrasonography (US) screening of population at risk of cholangiocarcinoma (CCA) due to residence in an endemic area for Opisthorchis viverrini. CCA survival rates are low, and early identification of risk factors is essential. BDD is one symptom that can identify patients at risk of CCA. Detection of PDF by US can also identify at-risk patients, at an earlier stage of CCA development. Identification of association between PDF and BDD will inform screening practices for CCA risk, by increasing the viability of PDF screening for CCA risk.SettingNine tertiary care hospitals in Northeast Thailand.DesignCross-sectional study.ParticipantsStudy subjects in the Cholangiocarcinoma Screening and Care Program (CASCAP) in Northeast Thailand. CASCAP inclusion criteria are all residents of Northeast Thailand aged ≥40 years. Participants are recruited through CCA screening centres and through primary healthcare units. So far, 394 026 have been enrolled.MethodsPDF and BDD were identified through US. PDF was categorised into three groups, PDF1, 2 and 3, depending on their high echo locality in the peripheral, segmental and main bile duct, respectively. Associations between PDF and BDD were determined by adjusted OR and 95% CI using multiple logistic regression.ResultsBDD was found in 6.6% of PDF3, 1.7% of PDF2 and 1.4% of PDF1 cases. Among PDF cases, especially in PDF3, BDD was found in men more than in women (8.9% and 4.6%, respectively). Compared with non-PDF, the association between PDF3 and BDD was highly significant (adjusted OR=5.74, 95% CI 4.57 to 7.21, p<0.001).ConclusionsOur findings reveal that there is a relationship between PDF and BDD, which is associated with CCA. Therefore, PDF can also be an indicator for suspected CCA diagnosis through US.
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Zyka, Vit. "TeX a PDF." Zpravodaj Československého sdružení uživatelů TeXu 12, no. 3-4 (2002): 140–51. http://dx.doi.org/10.5300/2002-3-4/140.
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Hovmöller, Sven, Linus Hovmöller Zou, Xiaodong Zou, and Benjamin Grushko. "Structures of pseudo-decagonal approximants in Al−Co−Ni." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1969 (2012): 2949–59. http://dx.doi.org/10.1098/rsta.2011.0310.
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Quasi-crystals shocked the crystallographic world when they were reported in 1984. We now know that they are not a rare exception, and can be found in many alloy systems. One of the richer systems for quasi-crystals and their approximants is Al−Co−Ni. A large series of pseudo-decagonal (PD) approximants have been found. Only two of them, PD4 and PD8, have been solved by X-ray crystallography. We report here the structures of PD1, PD2, PD3 and PD5, solved from the limited information that is provided by electron diffraction patterns, unit cell dimensions and high-resolution electron microscopy images.
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Roman, David. "A preference for PDF." Communications of the ACM 53, no. 11 (2010): 12. http://dx.doi.org/10.1145/1839676.1839681.
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Bethel, R. E., and G. J. Paras. "A PDF multitarget tracker." IEEE Transactions on Aerospace and Electronic Systems 30, no. 2 (1994): 386–403. http://dx.doi.org/10.1109/7.272262.
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Ghorbani, Asghar, Gerd Steinhilber, Detlev Markus, and Ulrich Maas. "A PDF projection method: A pressure algorithm for stand-alone transported PDFs." Combustion Theory and Modelling 19, no. 2 (2015): 188–222. http://dx.doi.org/10.1080/13647830.2014.999129.
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Gifuni, Angelo, Antonio Sorrentino, Giuseppe Ferrara, and Maurizio Migliaccio. "An Estimate of the Probability Density Function of the Sum of a Random Number N of Independent Random Variables." Journal of Computational Engineering 2015 (April 6, 2015): 1–12. http://dx.doi.org/10.1155/2015/801652.
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A new estimate of the probability density function (PDF) of the sum of a random number of independent and identically distributed (IID) random variables Xi (i=1, 2, …, N) is shown. The sum PDF is represented as a sum of normal PDFs weighted according to the N PDF. The analytical model is verified by numerical simulations. The comparison is made by the Chi-Square Goodness-of-Fit test.
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Griffin, Brian M., and Vincent E. Larson. "A new subgrid-scale representation of hydrometeor fields using a multivariate PDF." Geoscientific Model Development 9, no. 6 (2016): 2031–53. http://dx.doi.org/10.5194/gmd-9-2031-2016.
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Abstract. The subgrid-scale representation of hydrometeor fields is important for calculating microphysical process rates. In order to represent subgrid-scale variability, the Cloud Layers Unified By Binormals (CLUBB) parameterization uses a multivariate probability density function (PDF). In addition to vertical velocity, temperature, and moisture fields, the PDF includes hydrometeor fields. Previously, hydrometeor fields were assumed to follow a multivariate single lognormal distribution. Now, in order to better represent the distribution of hydrometeors, two new multivariate PDFs are formulated and introduced.The new PDFs represent hydrometeors using either a delta-lognormal or a delta-double-lognormal shape. The two new PDF distributions, plus the previous single lognormal shape, are compared to histograms of data taken from large-eddy simulations (LESs) of a precipitating cumulus case, a drizzling stratocumulus case, and a deep convective case. Finally, the warm microphysical process rates produced by the different hydrometeor PDFs are compared to the same process rates produced by the LES.
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Morris, Paul J., Nachiketa Chakraborty, and Garret Cotter. "Deviations from normal distributions in artificial and real time series: a false positive prescription." Monthly Notices of the Royal Astronomical Society 489, no. 2 (2019): 2117–29. http://dx.doi.org/10.1093/mnras/stz2259.
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ABSTRACT Time-series analysis allows for the determination of the Power Spectral Density (PSD) and Probability Density Function (PDF) for astrophysical sources. The former of these illustrates the distribution of power at various time-scales, typically taking a power-law form, while the latter characterizes the distribution of the underlying stochastic physical processes, with Gaussian and lognormal functional forms both physically motivated. In this paper, we use artificial time series generated using the prescription of Timmer & Koenig to investigate connections between the PDF and PSD. PDFs calculated for these artificial light curves are less likely to be well described by a Gaussian functional form for steep (Γ⪆1) PSD indices due to weak non-stationarity. Using the Fermi LAT monthly light curve of the blazar PKS2155-304 as an example, we prescribe and calculate a false positive rate that indicates how likely the PDF is to be attributed an incorrect functional form. Here, we generate large numbers of artificial light curves with intrinsically normally distributed PDFs and with statistical properties consistent with observations. These are used to evaluate the probabilities that either Gaussian or lognormal functional forms better describe the PDF. We use this prescription to show that PKS2155-304 requires a high prior probability of having a normally distributed PDF, $P(\rm {G})~$ ≥ 0.82, for the calculated PDF to prefer a Gaussian functional form over a lognormal. We present possible choices of prior and evaluate the probability that PKS2155-304 has a lognormally distributed PDF for each.
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Bethel, R. E., and G. J. Paras. "A PDF multisensor multitarget tracker." IEEE Transactions on Aerospace and Electronic Systems 34, no. 1 (1998): 153–68. http://dx.doi.org/10.1109/7.640271.
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Drümmer, Olaf, and Thomas Zellmann. "Langzeitarchivierung mit PDF/A-2." Informatik-Spektrum 34, no. 5 (2011): 496–500. http://dx.doi.org/10.1007/s00287-011-0560-9.
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Choi, Hoon Young, Dong Ki Kim, Tae Hee Lee, et al. "The Clinical Usefulness of Peritoneal Dialysis Fluids with Neutral pH and Low Glucose Degradation Product Concentration: An Open Randomized Prospective Trial." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 28, no. 2 (2008): 174–82. http://dx.doi.org/10.1177/089686080802800214.
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Background Long-term peritoneal dialysis (PD) is associated with the development of various structural and functional changes to the peritoneal membrane when bioincompatible conventional peritoneal dialysis fluids (PDFs) are used. In this study, we looked at patients that were treated with conventional PDFs and then changed to novel biocompatible PDFs with a neutral pH and a low concentration of glucose degradation products (GDPs) to investigate whether this change could result in the arrest or reversal of peritoneal membrane deterioration. Methods In an open label, randomized prospective trial, the clinical effects of conventional PDFs and biocompatible PDFs with neutral pH and very low concentration of GDPs were compared in 104 patients equally divided between both study PDFs. Blood and effluent dialysate samples, peritoneal equilibration tests, and adequacy evaluation were undertaken at baseline, 4, 8, and 12 months. The target variables were the ratio of dialysate-to-plasma (D/P) creatinine, peritoneal ultrafiltration, residual renal function, dialysis adequacy indices, and effluent cancer antigen 125 (CA125). Results D/P creatinine values were not different in the two groups. Peritoneal ultrafiltration was significantly higher in the low-GDP PDF group than in the conventional PDF group at all follow-up times (4 months: 9.1 ± 4.3 vs 6.0 ± 3.0; 8 months: 8.3 ± 3.4 vs 6.0 ± 3.0; 12 months: 8.9 ± 3.3 vs 6.1 ± 3.3 mL/g dextrose/day; p < 0.05). Peritoneal Kt/V urea values and total weekly Kt/V urea values at 4 months were significantly higher in the low-GDP PDF group than in the conventional PDF group. Residual renal function was not statistically significant. Effluent CA125 levels were significantly higher in the low-GDP PDF group at all follow-up visits (4 months: 37.8 ± 20.8 vs 22.0 ± 9.5; 8 months: 41.2 ± 20.3 vs 25.9 ± 11.3; 12 months: 40.4 ± 21.4 vs 28.6 ± 13.0 U/mL; p < 0.05). Among anuric patients, peritoneal ultrafiltration at 4, 8, and 12 months, total weekly Kt/V at 4 and 8 months, and CA125 levels at all follow-up visits were significantly higher in patients treated with low-GDP PDF than those treated with conventional PDF. However, among anuric patients, D/P creatinine showed no significant differences between the low-GDP PDF group and the conventional PDF group. Conclusion The use of biocompatible PDFs with neutral pH and low GDP concentration can contribute to improvement of peritoneal ultrafiltration and peritoneal effluent CA125 level, an indicator of peritoneal membrane integrity in PD patients.
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Fan, Zhouyou, Rui Zhang, and Huey-Wen Lin. "Nucleon gluon distribution function from 2 + 1 + 1-flavor lattice QCD." International Journal of Modern Physics A 36, no. 13 (2021): 2150080. http://dx.doi.org/10.1142/s0217751x21500809.
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The parton distribution functions (PDFs) provide process-independent information about the quarks and gluons inside hadrons. Although the gluon PDF can be obtained from a global fit to experimental data, it is not constrained well in the large-[Formula: see text] region. Theoretical gluon-PDF studies are much fewer than those of the quark PDFs. In this work, we present the first lattice-QCD results that access the [Formula: see text]-dependence of the gluon unpolarized PDF of the nucleon. The lattice calculation is carried out with nucleon momenta up to 2.16 GeV, lattice spacing [Formula: see text] fm, and with valence pion masses of 310 and 690 MeV. We use reduced Ioffe-time distributions to cancel the renormalization and implement a one-loop perturbative pseudo-PDF gluon matching. We neglect mixing of the gluon operator with the quark singlet sector. Our matrix-element results in coordinate space are consistent with those obtained from the global PDF fits of CT18 NNLO and NNPDF3.1 NNLO. Our fitted gluon PDFs at both pion masses are consistent with global fits in the [Formula: see text] region.
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Kühl, Norbert, Christoph Gebhardt, Thomas Litt, and Andreas Hense. "Probability Density Functions as Botanical-Climatological Transfer Functions for Climate Reconstruction." Quaternary Research 58, no. 3 (2002): 381–92. http://dx.doi.org/10.1006/qres.2002.2380.
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AbstractWe present a new procedure, the pdf method (pdf=probability density function), for reconstructing Quaternary climate utilizing botanical data. The procedure includes the advantages of the indicator species method by considering the fossil and modern presence and absence of taxa rather than their frequencies, thus avoiding the need for modern analog plant communities. Overcoming the problematic use of absolute limits to describe climate response ranges is the main progress of the pdf method in comparison to the indicator species method. This advantage results from estimating probability density functions (pdfs) for monthly mean January and July temperature conditional on the present day occurrence of single taxa. Gaussian distributions sufficiently approximate pdfs of many, although not all, studied taxa. On the assumption of statistical independence, the procedure calculates a joint pdf as the product of the pdfs of the individual taxa. This algorithm weights each taxon according to the extent of its climate response range expressed by its covariance structure. We interpret the maximum of the resulting pdf as the most likely climate and its confidence interval as the uncertainty range. To avoid an artificial reduction of uncertainty arising from the use of numerous similar pdfs, a preselection method is proposed based on the Mahalanobis distance between pdfs. The pdf method was applied to the Carpinus phase of a profile from Gröbern, Germany, that spans the last interglaciation (Eemian). The reconstructed most probable January and July temperatures of about 0.0°C and 18.4°C barely differ from the modern values of −0.5°C and 18.3°C.
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Bintari, Yoni Rina, and Rio Risandiansyah. "In Silico Study to Assess Antibacterial Activity from Cladophora Sp. on Peptide Deformylase: Molecular Docking Approach." Borneo Journal of Pharmacy 2, no. 1 (2019): 20–23. http://dx.doi.org/10.33084/bjop.v2i1.717.
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Increasing antibiotic-resistant pathogenic bacteria is a severe problem in the world. Therefore, there is a need to identify new drugs from natural products and also new drug targets. Cladophora sp. is a marine organism which is known to have bioactive compounds and a potential antibacterial. On the other hand, Peptide Deformylase (PDf) may prove to be a novel drug target since it is crucial for native peptide functioning in most pathogenic bacteria. This study screens for PDf inhibition activity of compounds from Cladophora sp. using molecular docking approach and screening the binding affinity of bioactive compounds against the peptide receptor PDf using Pyrex Autodock Vina software. Docking results were stored and visualized using Biovia Discovery Studio and PyMOL ligand. Ligands were obtained from previous literature in PubChem, and receptor peptide PDf from pathogenic bacteria: Pseudomonas aeruginosa (PDB ID:1N5N), Escherichia coli (PDB ID:1BSK), Enterococcus faecium (PDB ID:3G6N) and Staphylococcus aureus (PDB ID:1LQW), was obtained from the peptide data bank. The results of this screening show with ligand the highest binding affinity against PDf of P. aeruginosa, E. coli, E. faecium, and S. aureus is stearic acid (-5.9 kcal/mol), eicosapentaenoic acid (-6.6 kcal/mol), stearic acid (-5.8 kcal/mol), and stearic acid (-6.2 kcal/mol) respectively. The binding of natural compounds from Cladophora sp. with PDf models may provide a new drug with a different drug target for antibacterial potential.
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Huang, Louis L., Ellen Ramas, Priti Prasad, et al. "Non-touch Aseptic technique Maintains Sterility of Antibiotic-Admixed peritoneal Dialysis Fluid." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 38, no. 1 (2018): 65–67. http://dx.doi.org/10.3747/pdi.2017.00106.
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There is a paucity of data on the sterility of peritoneal dialysis fluid (PDF) after drug admixture. International Society for Peritoneal Dialysis (ISPD) guidelines suggest using sterile technique when admixing antibiotics; however, the degree of sterility remains unclear. This issue is most pertinent when preparing take-home PDF for outpatient treatment of peritonitis. This study compares the sterility of PDF admixed with antibiotics using a non-touch aseptic technique (NTAT) versus sterile technique. Groups of 8 PDF mixtures (1.5% Dianeal or Icodextrin [Baxter International Inc., Spring Grove, IL, USA]) were admixed with 1 g/L ceftazidime and vancomycin, or 20 mL saline, either by a pharmacist using sterile technique in a sterile suite, or a nurse in a clinical room using NTAT. Dianeal inoculated with 1 x 106 colony-forming units (CFU)/L of coagulase-negative Staphylococcus (CNS), with and without antibiotics, served as positive controls. Admixed PDFs were left at room temperature for 72 hours, then cultured using the BacT/ALERT system. A positive culture by day 5 constituted a contamination. Differences in proportion of contamination between groups were assessed using the Chi-squared test. Eighty PDF bags underwent microbiological testing. Sterility was maintained in all bags, independent of technique (NTAT versus sterile technique), type of PDF (Dianeal versus Icodextrin), or whether antibiotics were admixed. Of the positive controls, CNS-inoculated PDFs without antibiotics were all culture positive; however, when inoculated into antibiotic-admixed PDFs, only S. haemolyticus remained culture-positive ( p < 0.0001). In conclusion, PDF sterility can be maintained using NTAT for up to 3 days at room temperature. Currently, there is insufficient evidence to adopt sterile technique in sterile suites when admixing take-home PDF.
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Lee, Ho Yung, Hyeong Cheon Park, Bo Jeung Seo, et al. "Superior Patient Survival for Continuous Ambulatory Peritoneal Dialysis Patients Treated with a Peritoneal Dialysis Fluid with Neutral pH and Low Glucose Degradation Product Concentration (Balance)." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 25, no. 3 (2005): 248–55. http://dx.doi.org/10.1177/089686080502500308.
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Background In recent years, laboratory and clinical research has suggested the need for peritoneal dialysis fluids (PDFs) that are more biocompatible than the conventional PDFs commonly used today. Bioincompatibility of PDF has been attributed to low pH, lactate, glucose, glucose degradation products (GDPs), and osmolality. PDFs with neutral pH and low GDPs are now available commercially. In vitro and early clinical studies suggest that these solutions are indeed more biocompatible but, as of now, there is no evidence that their use improves patient outcome. Methods Using a dedicated database of over 2000 patients treated with PD in Korea, we were able to conduct a retrospective observational study comparing outcomes for incident continuous ambulatory PD patients treated with a standard, conventional, heat-sterilized PDF to the outcomes for patients treated with a novel, low GDP, neutral-pH PDF prepared in a dual-compartment, double-bag PD system (Balance; Fresenius Medical Care, St. Wendel, Germany). In an intention-to-treat analysis, patient and technique survival, peritonitis-free survival, and peritonitis rates were compared in 611 patients treated with Balance for up to 30 months and 551 patients with a standard PDF (stay·safe; Fresenius Medical Care) treated in the same era and with equivalent follow-up. Results The patients were well matched for most relevant characteristics except older age distribution for the patients treated with the standard PDF. Patients treated with Balance had significantly superior survival compared to those treated with the standard PDF (74% vs 62% at 28 months, p = 0.0032). In a multivariate Cox regression model including age, diabetes, and gender, the survival advantage persisted (relative risk of death for Balance 0.75, 95% confidence interval 0.56 – 0.99, p = 0.0465). Modality technique survival was similar in Kaplan–Meier analysis for both PDFs. No differences were detected in peritonitis-free survival or in peritonitis rates between the two solutions. Conclusion This study, for the first time, suggests that treatment with a novel biocompatible PDF with low GDP concentration and neutral pH confers a significant survival advantage. The exact mechanisms for such a survival advantage cannot be determined from this study. The usual criticisms of observational studies apply and the results reported here strongly warrant the undertaking of appropriately designed, randomized, controlled clinical trials.
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Kogan, Yefim L., and David B. Mechem. "A PDF-Based Formulation of Microphysical Variability in Cumulus Congestus Clouds*." Journal of the Atmospheric Sciences 73, no. 1 (2015): 167–84. http://dx.doi.org/10.1175/jas-d-15-0129.1.
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Abstract Calculating unbiased microphysical process rates over mesoscale model grid volumes necessitates knowledge of the subgrid-scale (SGS) distribution of variables, typically represented as probability distribution functions (PDFs) of the prognostic variables. In the 2014 Journal of the Atmospheric Sciences paper by Kogan and Mechem, they employed large-eddy simulation of Rain in Cumulus over the Ocean (RICO) trade cumulus to develop PDFs and joint PDFs of cloud water, rainwater, and droplet concentration. In this paper, the approach of Kogan and Mechem is extended to deeper, precipitating cumulus congestus clouds as represented by a simulation based on conditions from the TOGA COARE field campaign. The fidelity of various PDF approximations was assessed by evaluating errors in estimating autoconversion and accretion rates. The dependence of the PDF shape on grid-mean variables is much stronger in congestus clouds than in shallow cumulus. The PDFs obtained from the TOGA COARE simulations for the calculation of accretion rates may be applied to both shallow and congestus cumulus clouds. However, applying the TOGA COARE PDFs to calculate autoconversion rates introduces unacceptably large errors in shallow cumulus clouds, thus precluding the use of a “universal” PDF formulation for both cloud types.
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Firl, Grant J., and David A. Randall. "Fitting and Analyzing LES Using Multiple Trivariate Gaussians." Journal of the Atmospheric Sciences 72, no. 3 (2015): 1094–116. http://dx.doi.org/10.1175/jas-d-14-0192.1.
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Abstract Assumed-PDF methods for the parameterization of subgrid-scale processes in atmospheric models provide many benefits. Many currently used assumed-PDF schemes reconcile the high number of required PDF parameters with the relative paucity of input moments by employing simplifying assumptions that are difficult to test. This paper explores the possibility of constructing a trivariate double-Gaussian PDF from the first three orders of moments without simplifying assumptions and proves that no unique solution exists. In an effort to provide a path for future improvement of current assumed-PDF schemes, the expectation maximization (EM) algorithm for Gaussian mixture models is used with LES output of shallow cumulus, stratocumulus, and deep convection cases to determine “best fit” PDFs using from one through four Gaussian clusters. The EM PDFs are evaluated using PDF-diagnosed higher-order moments, PDF-diagnosed cloud statistics, and the Akaike information criterion. It was found that two Gaussian clusters were almost always adequate to represent both higher-order moments and cloud statistics like cloud fraction, water content, and vertical fluxes of cloud water and buoyancy in layered clouds such as stratocumulus and deep convective anvils. However, higher-order moments and higher-order cloud statistics were only properly represented when three or four Gaussians were used in the upper regions of shallow cumulus layers and throughout the active portion of deep convection. Evidence is also provided that several common assumptions employed to diagnose trivariate double-Gaussian PDFs from a minimum number of input moments are weak.
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Lin, Huey-Wen. "Parton Distribution Functions and Lattice QCD." EPJ Web of Conferences 206 (2019): 01003. http://dx.doi.org/10.1051/epjconf/201920601003.
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Recently, there have been rapid developments in lattice-QCD calculations of proton structure, especially in the parton distribution functions (PDFs). We overcame a longstanding obstacle and for the first time in lattice-QCD are able to directly calculate the Bjorken-x dependence of the quark, helicity and transversity distributions. The PDFs are obtained using the large-momentum effective field theory (LaMET) framework where the full Bjorken-x dependence of finite-momentum PDFs, called “quasi-PDFs”, can be calculated on the lattice. The quasi-PDF nucleon matrix elements are renormalized non-perturbatively in RI/MOM-scheme. Following a nonperturbative renormalization of the parton quasi-distribution in a regularization-independent momentum-subtraction scheme, we establish its matching to the $ \overline {{\rm{MS}}} $ PDF and calculate the non-singlet matching coefficient at next-to-leading order in perturbation theory. In this proceeding, I will show the progress that has been made in recent years, highlighting the latest state-of-the art PDF calculations at the physical pion mass. Future impacts on the large-x global PDF fits are also discussed.
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Huang, Chen, and Andrei N. Lipatnikov. "Comparison of Presumed PDF Models of Turbulent Flames." Journal of Combustion 2012 (2012): 1–15. http://dx.doi.org/10.1155/2012/564621.
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Over the past years, the use of a presumed probability density function (PDF) for combustion progress variable or/and mixture fraction has been becoming more and more popular approach to average reaction rates in premixed and partially premixed turbulent flames. Commonly invoked for this purpose is a beta-function PDF or a combination of Dirac delta functions, with the parameters of the two PDFs being determined based on the values of their first and second moments computed by integrating proper balance equations. Because the choice of any of the above PDFs appears to be totally arbitrary as far as underlying physics of turbulent combustion is concerned, the use of such PDFs implies weak sensitivity of the key averaged quantities to the PDF shape. The present work is aimed at testing this implicit assumption by comparing mean heat release rates, burning velocities, and so forth, averaged by invoking the aforementioned PDFs, with all other things being equal. Results calculated in the premixed case show substantial sensitivity of the mean heat release rate to the shape of presumed combustion-progress-variable PDF, thus, putting the approach into question. To the contrary, the use of a presumed mixture-fraction PDF appears to be a sufficiently reasonable simplification for modeling the influence of fluctuations in the mixture fraction on the mean burning velocity provided that the mixture composition varies within flammability limits.
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Suciu, N., L. Schüler, S. Attinger, C. Vamoș, and P. Knabner. "Consistency issues in PDF methods." Analele Universitatii "Ovidius" Constanta - Seria Matematica 23, no. 3 (2015): 187–208. http://dx.doi.org/10.1515/auom-2015-0055.
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Abstract Concentrations of chemical species transported in random environments need to be statistically characterized by probability density functions (PDF). Solutions to evolution equations for the one-point one-time PDF are usually based on systems of computational particles described by Itô equations. We establish consistency conditions relating the concentration statistics to that of the Itô process and the solution of its associated Fokker-Planck equation to that of the PDF equation. In this frame, we use a recently proposed numerical method which approximates PDFs by particle densities obtained with a global random walk (GRW) algorithm. The GRW-PDF approach is illustrated for a problem of contaminant transport in groundwater.
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Bartlett, M. S., E. Daly, J. J. McDonnell, A. J. Parolari, and A. Porporato. "Stochastic rainfall-runoff model with explicit soil moisture dynamics." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2183 (2015): 20150389. http://dx.doi.org/10.1098/rspa.2015.0389.
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Stream runoff is perhaps the most poorly represented process in ecohydrological stochastic soil moisture models. Here we present a rainfall-runoff model with a new stochastic description of runoff linked to soil moisture dynamics. We describe the rainfall-runoff system as the joint probability density function (PDF) of rainfall, soil moisture and runoff forced by random, instantaneous jumps of rainfall. We develop a master equation for the soil moisture PDF that accounts explicitly for a general state-dependent rainfall-runoff transformation. This framework is then used to derive the joint rainfall-runoff and soil moisture-runoff PDFs. Runoff is initiated by a soil moisture threshold and a linear progressive partitioning of rainfall based on the soil moisture status. We explore the dependence of the PDFs on the rainfall occurrence PDF (homogeneous or state-dependent Poisson process) and the rainfall magnitude PDF (exponential or mixed-exponential distribution). We calibrate the model to 63 years of rainfall and runoff data from the Upper Little Tennessee watershed (USA) and show how the new model can reproduce the measured runoff PDF.
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Li, Dong Dong, Ming Ming Xu, Li Ming Xu, and De Jin Hu. "Modeling and Simulation of NC Precision Sphere Grinding Machine Feed Drive System." Applied Mechanics and Materials 130-134 (October 2011): 585–89. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.585.
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The feed drive system model of NC precision sphere grinding machine (MD6040) is constructed. Although a large number of researchers pay more attention on advanced controllers, most high performance machine tools still adopt PID (Proportion Integration Differentiation) controller today. In this paper, PDF (Pseudo-Derivative Feedback) controller and PDFF (Pseudo-Derivative Control with feedforward Gain) controller which evolved from PID controller are studied. The performance of PID controller, PDF controller and PDFF controller is investigated by simulation and experiment. Both simulation results and experiment results showed that PID controller has severe overshoot and less rise time, PDF controller has strong robustness and long rise time and PDFF controller possesses the advantages of the other two controllers. PDFF controller is more suitable for NC precision sphere grinding machine feed drive system.
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Fieulaine, Sonia, Michel Desmadril, Thierry Meinnel, and Carmela Giglione. "Understanding the highly efficient catalysis of prokaryotic peptide deformylases by shedding light on the determinants specifying the low activity of the human counterpart." Acta Crystallographica Section D Biological Crystallography 70, no. 2 (2014): 242–52. http://dx.doi.org/10.1107/s1399004713026461.
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Peptide deformylases (PDFs), which are essential and ubiquitous enzymes involved in the removal of theN-formyl group from nascent chains, are classified into four subtypes based on the structural and sequence similarity of specific conserved domains. All PDFs share a similar three-dimensional structure, are functionally interchangeablein vivoand display similar propertiesin vitro, indicating that their molecular mechanism has been conserved during evolution. The human mitochondrial PDF is the only exception as despite its conserved fold it reveals a unique substrate-binding pocket together with an unusual kinetic behaviour. Unlike human PDF, the closely related mitochondrial PDF1As from plants have catalytic efficiencies and enzymatic parameters that are similar to those of other classes of PDFs. Here, the aim was to identify the structural basis underlying the properties of human PDF compared with all other PDFs by focusing on plant mitochondrial PDF1A. The construction of a chimaera composed of plant PDF1A with the nonrandom substitutions found in a conserved motif of its human homologue converted it into an enzyme with properties similar to the human enzyme, indicating the crucial role of these positions. The crystal structure of this human-like plant PDF revealed that substitution of two residues leads to a reduction in the volume of the ligand-binding site together with the introduction of negative charges, unravelling the origin of the weak affinity of human PDF for its substrate. In addition, the substitution of the two residues of human PDF modifies the transition state of the reaction through alteration of the network of interactions between the catalytic residues and the substrate, leading to an overall reduced reaction rate.
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Larson, Vincent E., and Jean-Christophe Golaz. "Using Probability Density Functions to Derive Consistent Closure Relationships among Higher-Order Moments." Monthly Weather Review 133, no. 4 (2005): 1023–42. http://dx.doi.org/10.1175/mwr2902.1.
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Parameterizations of turbulence often predict several lower-order moments and make closure assumptions for higher-order moments. In principle, the low- and high-order moments share the same probability density function (PDF). One closure assumption, then, is the shape of this family of PDFs. When the higher-order moments involve both velocity and thermodynamic scalars, often the PDF shape has been assumed to be a double or triple delta function. This is equivalent to assuming a mass-flux model with no subplume variability. However, PDF families other than delta functions can be assumed. This is because the assumed PDF methodology is fairly general. This paper proposes closures for several third- and fourth-order moments. To derive the closures, the moments are assumed to be consistent with a particular PDF family, namely, a mixture of two trivariate Gaussians. (This PDF is also called a double Gaussian or binormal PDF by some authors.) Separately from the PDF assumption, the paper also proposes a simplified relationship between scalar and velocity skewnesses. This PDF family and skewness relationship are simple enough to yield simple, analytic closure formulas relating the moments. If certain conditions hold, this set of moments is specifically realizable. By this it is meant that the set of moments corresponds to a real Gaussian-mixture PDF, one that is normalized and nonnegative everywhere. This paper compares the new closure formulas with both large eddy simulations (LESs) and closures based on double and triple delta PDFs. This paper does not implement the closures in a single-column model and test them interactively. Rather, the comparisons are diagnostic; that is, low-order moments are extracted from the LES and treated as givens that are input into the closures. This isolates errors in the closures from errors in a single-column model. The test cases are three atmospheric boundary layers: a trade wind cumulus layer, a stratocumulus layer, and a clear convective case. The new closures have shortcomings, but nevertheless are superior to the double or triple delta closures in most of the cases tested.
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Falk, L., and E. Schaer. "A PDF modelling of precipitation reactors." Chemical Engineering Science 56, no. 7 (2001): 2445–57. http://dx.doi.org/10.1016/s0009-2509(00)00447-4.
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Eyre, Timothy. "PDFdiff: A PDF File Comparison Script." Zpravodaj Československého sdružení uživatelů TeXu 20, no. 3 (2010): 208–14. http://dx.doi.org/10.5300/2010-3/208.
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Koo, Jamin, and Carol C. H. Chou. "PDF to PDF/A: Evaluation of Converter Software for Implementation in Digital Repository Workflow." New Review of Information Networking 18, no. 1 (2013): 1–15. http://dx.doi.org/10.1080/13614576.2013.771989.
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Han, Yan, and Xueheng Wan. "Digitization of Text Documents Using PDF/A." Information Technology and Libraries 37, no. 1 (2018): 52–64. http://dx.doi.org/10.6017/ital.v37i1.9878.
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The purpose of this article is to demonstrate a practical use case of PDF/A file format for digitization of textual documents, following recommendation of using PDF/A as a preferred digitization file format. The authors showed how to convert and combine all the TIFFs with associated metadata into a single PDF/A-2b file for a document. Using open source software with real-life examples, the authors show readers how to convert TIFF images, extract associated metadata and ICC profiles, and validate against the newly released PDF/A validator. The generated PDF/A file is a self-contained and self-described container which accommodates all the data from digitization of textual materials, including page-level metadata and/or ICC profiles. With theoretical analysis and empirical examples, PDF/A file format has many advantages over traditional preferred file format TIFF / JPEG2000 for digitization of textual documents.
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Azizi, M., A. Khorramian, H. Abdolmaleki, and S. Paktinat Mehdiabadi. "Impact of the top quark cross-section data on parton distribution functions." International Journal of Modern Physics A 33, no. 24 (2018): 1850142. http://dx.doi.org/10.1142/s0217751x18501427.
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Recent measurements of top quark pair production cross-section, which is performed at the LHC and the Tevatron collider, are studied using Hessian profiling technique to obtain their impact on the parton distribution functions (PDFs). The top quark production data covers different center-of-mass energies [Formula: see text], 5.02, 7, 8 and 13 TeV in either [Formula: see text] or [Formula: see text] collisions. It is explained how the Hessian profiling method may be used to assess the impact of these new data on PDFs and consequently on their predictions. In this research, the impact of recent measurements of top quark pair cross-sections on different CT14, MMHT2014 and NNPDF3.0 PDF sets is investigated. The analysis results show that the recent top quark production at the LHC and Tevatron data provide significant constraints in particular on the central value, relative uncertainties or both for the [Formula: see text]-quark distribution and the gluon PDFs in both CT14 and MMHT2014 PDF sets and are insensitive to valence-quark PDFs. A small constraint on the [Formula: see text]-sea quark distribution for CT14 PDF is also observed. There is no impact on the NNPDF3.0 PDF set in presence of these data.
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Consolini, G., B. Bavassano, and P. De Michelis. "A probabilistic approach to heterogeneity in space plasmas: the case of magnetic field intensity in solar wind." Nonlinear Processes in Geophysics 16, no. 2 (2009): 265–73. http://dx.doi.org/10.5194/npg-16-265-2009.
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Abstract. Since the early 90s it was shown that Probability Distribution Functions (PDFs) of small scale differences (fluctuations) of several quantities in space plasmas display significant departures from Gaussianity. The non-Gaussian shape of PDFs was ascribed to intermittency and discussed in the framework of intermittent MHD turbulence. Here, we put the attention to the PDF of magnetic field intensity instead of its differences showing how the PDF of such quantity in a quiet solar wind can be related with the occurrence of heterogeneity. In detail, we derive the shape of the PDFs by simple statistical considerations based on the concept of subordination in probability theory. An interpretation and a discussion in terms of existing coherent magnetic structures in a mechanical near-equilibrium state are also presented.
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Pírez, Nicolás, Bethany L. Christmann, and Leslie C. Griffith. "Daily rhythms in locomotor circuits in Drosophila involve PDF." Journal of Neurophysiology 110, no. 3 (2013): 700–708. http://dx.doi.org/10.1152/jn.00126.2013.
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The neuropeptide pigment-dispersing factor (PDF) has been studied extensively in Drosophila, and its role in circadian time-keeping has been firmly established. The role of PDF outside of the clock circuit, however, is poorly understood. A recent study suggested that PDF may act on the ellipsoid body (EB) to link the clock and sleep/activity circuits. We performed whole brain optical imaging with the fluorescence resonance energy transfer (FRET)-based cAMP sensor Epac1-camps expressed under control of the pdfR promoter to address how the clock and sleep deprivation affect the physiology of these cells. Basal cAMP levels in EB were regulated both by PDF and synaptic inputs that are controlled by the circadian clock. Acute application of PDF to the brain caused a significant, and PDF-receptor-dependent, increase in cAMP in EB cells. Application of TTX to block circuit-mediated effects of PDF increased the morning response but not the response at night, implying the existence of a temporally regulated, PDF-stimulated input that blocks cAMP generation. ACh produced both direct (TTX-insensitive) and indirect (TTX-sensitive) increases in cAMP during the day but was totally TTX-insensitive at night, indicating that ACh-stimulated inputs to the EB are suppressed at night. Sleep deprivation did not affect the cAMP responses of these cells to either PDF or ACh. These results suggest a novel role for PDF as a modulator of activity outside of the clock circuit. By elucidating the mechanisms by which the neuropeptide PDF act on its target cells, our work contributes to our understating of how the central clock coordinates activity and sleep.
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Vidybida, Alexander. "Relation Between Firing Statistics of Spiking Neuron with Instantaneous Feedback and Without Feedback." Fluctuation and Noise Letters 14, no. 04 (2015): 1550034. http://dx.doi.org/10.1142/s0219477515500340.
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We consider a class of spiking neuron models, defined by a set of conditions which are typical for basic threshold-type models like leaky integrate-and-fire, or binding neuron model and also for some artificial neurons. A neuron is fed with a point renewal process. A relation between the three probability density functions (PDF): (i) PDF of input interspike intervals ISIs, (ii) PDF of output interspike intervals of a neuron with a feedback and (iii) PDF for that same neuron without feedback is derived. This allows to calculate any one of the three PDFs provided the remaining two are given. Similar relation between corresponding means and variances is derived. The relations are checked exactly for the binding neuron model stimulated with Poisson stream.
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Kogan, Yefim L., and David B. Mechem. "A PDF-Based Microphysics Parameterization for Shallow Cumulus Clouds." Journal of the Atmospheric Sciences 71, no. 3 (2014): 1070–89. http://dx.doi.org/10.1175/jas-d-13-0193.1.
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Abstract Unbiased calculations of microphysical process rates such as autoconversion and accretion in mesoscale numerical weather prediction models require that subgrid-scale (SGS) variability over the model grid volume be taken into account. This variability can be expressed as probability distribution functions (PDFs) of microphysical variables. Using dynamically balanced large-eddy simulation (LES) model results from a case of marine trade cumulus, the authors develop PDFs of the cloud water, droplet concentration, and rainwater variables (qc, Nc, and qr). Both 1D and 2D joint PDFs (JPDFs) are presented. The authors demonstrate that accounting for the JPDFs results in more accurate process rates for a regional-model grid size. Bias in autoconversion and accretion rates are presented, assuming different formulations of the JPDFs. Approximating the 2D PDF using a product of individual 1D PDFs overestimates the autoconversion rates by an order of magnitude, whereas neglecting the SGS variability altogether results in a drastic underestimate of the grid-mean autoconversion rate. PDF assumptions have a much smaller impact on accretion, largely because of the near-linear dependence of the variables in the accretion rate formula and the relatively weak correlation between qc and qr over the small LES grid volumes. The latter is attributed to the spatial decorrelation in the vertical between the two fields. Although the full PDFs are both height and time dependent, results suggest that fixed-in-time and fixed-in-height PDFs give an acceptable level of accuracy, especially for the crucial autoconversion calculation.
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Lira, Ignacio, and Dieter Grientschnig. "Bayesian Analysis of a Simple Measurement Model Distinguishing between Types of Information." Measurement Science Review 15, no. 6 (2015): 274–83. http://dx.doi.org/10.1515/msr-2015-0038.
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Abstract Let a quantity of interest, Y, be modeled in terms of a quantity X and a set of other quantities Z. Suppose that for Z there is type B information, by which we mean that it leads directly to a joint state-of-knowledge probability density function (PDF) for that set, without reference to likelihoods. Suppose also that for X there is type A information, which signifies that a likelihood is available. The posterior for X is then obtained by updating its prior with said likelihood by means of Bayes’ rule, where the prior encodes whatever type B information there may be available for X. If there is no such information, an appropriate non-informative prior should be used. Once the PDFs for X and Z have been constructed, they can be propagated through the measurement model to obtain the PDF for Y, either analytically or numerically. But suppose that, at the same time, there is also information of type A, type B or both types together for the quantity Y. By processing such information in the manner described above we obtain another PDF for Y. Which one is right? Should both PDFs be merged somehow? Is there another way of applying Bayes’ rule such that a single PDF for Y is obtained that encodes all existing information? In this paper we examine what we believe should be the proper ways of dealing with such a (not uncommon) situation.
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Mu, He-Qing, Han-Teng Liu, and Ji-Hui Shen. "Copula-Based Uncertainty Quantification (Copula-UQ) for Multi-Sensor Data in Structural Health Monitoring." Sensors 20, no. 19 (2020): 5692. http://dx.doi.org/10.3390/s20195692.
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The problem of uncertainty quantification (UQ) for multi-sensor data is one of the main concerns in structural health monitoring (SHM). One important task is multivariate joint probability density function (PDF) modelling. Copula-based statistical inference has attracted significant attention due to the fact that it decouples inferences on the univariate marginal PDF of each random variable and the statistical dependence structure (called copula) among the random variables. This paper proposes the Copula-UQ, composing multivariate joint PDF modelling, inference on model class selection and parameter identification, and probabilistic prediction using incomplete information, for multi-sensor data measured from a SHM system. Multivariate joint PDF is modeled based on the univariate marginal PDFs and the copula. Inference is made by combing the idea of the inference functions for margins and the maximum likelihood estimate. Prediction on the PDF of the target variable, using the complete (from normal sensors) or incomplete information (due to missing data caused by sensor fault issue) of the predictor variable, are made based on the multivariate joint PDF. One example using simulated data and one example using temperature data of a multi-sensor of a monitored bridge are presented to illustrate the capability of the Copula-UQ in joint PDF modelling and target variable prediction.
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He, Shun, Yu Hui Li, Bo Li, and Yu Lian. "A Method about Embedding Watermark in PDF Document." Applied Mechanics and Materials 530-531 (February 2014): 841–45. http://dx.doi.org/10.4028/www.scientific.net/amm.530-531.841.
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A method about embedding watermark in PDF document is proposed in this paper. First, PDF document is converted into a image format. Watermark image is converted into a scrambling image by Arnold transformation.And then the watermark is embedded into the PDF document image by discrete wavelet transform for PDF document image and matrix singular value decomposition for watermark image. Not only can watermark be extracted without the original image, but also increase the safety by this means. Experiment express, on the condition that the same size of the watermark image,the method made more copyright information as watermark be embedded into PDF document and the amount of the watermarked PDF document data be affected less with the increase of copyright information.
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Yang, Long, Elizabeth A. Culbertson, Nancy K. Thomas, et al. "A cloud platform for atomic pair distribution function analysis: PDFitc." Acta Crystallographica Section A Foundations and Advances 77, no. 1 (2021): 2–6. http://dx.doi.org/10.1107/s2053273320013066.
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A cloud web platform for analysis and interpretation of atomic pair distribution function (PDF) data (PDFitc) is described. The platform is able to host applications for PDF analysis to help researchers study the local and nanoscale structure of nanostructured materials. The applications are designed to be powerful and easy to use and can, and will, be extended over time through community adoption and development. The currently available PDF analysis applications, structureMining, spacegroupMining and similarityMapping, are described. In the first and second the user uploads a single PDF and the application returns a list of best-fit candidate structures, and the most likely space group of the underlying structure, respectively. In the third, the user can upload a set of measured or calculated PDFs and the application returns a matrix of Pearson correlations, allowing assessment of the similarity between different data sets. structureMining is presented here as an example to show the easy-to-use workflow on PDFitc. In the future, as well as using the PDFitc applications for data analysis, it is hoped that the community will contribute their own codes and software to the platform.
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Lai, Kar Neng, Man Fai Lam, Joseph C. K. Leung, et al. "A Study of the Clinical and Biochemical Profile of Peritoneal Dialysis Fluid Low in Glucose Degradation Products." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 32, no. 3 (2012): 280–91. http://dx.doi.org/10.3747/pdi.2010.00176.
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ObjectiveAlthough peritoneal dialysis (PD) is a widely accepted form of renal replacement therapy, concerns remain regarding the bioincompatible nature of standard PD fluid (PDF). Short-term studies of new biocompatible PDFs low in glucose degradation products (GDPs) reveal divergent results with respect to peritoneal integrity.MethodsWe studied 125 patients on maintenance PD who were assigned, by simple randomization, to receive either conventional or low-GDP PDF at PD initiation. Parameters of dialysis adequacy and peritoneal transport of small solutes were determined at initiation and after a period of maintenance PD at the time when serum and overnight effluent dialysate were simultaneously collected and assayed for various cytokines, chemokines, adipokines, and cardiac biomarkers. All patients were further followed prospectively for an average of 15 months from the day of serum and effluent collection to determine patient survival and cardiovascular events.ResultsPatients treated with conventional or low-GDP PDF were matched for sex, age, duration of dialysis, dialysis adequacy, and incidence of cardiovascular disease or diabetes. After an average of 2.3 years of PD treatment, the weekly total and peritoneal creatinine clearance, and the total and peritoneal Kt/V were comparable in the groups. However, urine output was higher in patients using low-GDP PDF despite there having been no difference between the groups at PD initiation. Patients using low-GDP PDF also experienced a slower rate of decline of residual glomerular filtration and urine output than did patients on conventional PDF. Compared with serum concentrations, effluent concentrations of tumor necrosis factor α, hepatocyte growth factor, macrophage migration inhibitory factor, interleukins 8 and 6, C-reactive protein, and leptin were found to be higher in both groups of patients after long-term PD, suggesting that the peritoneal cavity was the major source of those mediators. Compared with patients on low-GDP PDF, patients on conventional fluid showed elevated leptin and reduced adiponectin levels in serum and effluent. The effluent concentration of interleukin 8 was significantly lower in patients using low-GDP PDF. The survival rate and incidence of cardiovascular complications did not differ between these groups after maintenance PD for an average of 3.6 years.ConclusionsIt appears that low-GDP PDF results in an improvement of local peritoneal homeostasis through a reduction of chronic inflammatory status in the peritoneum.
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Chen, Qing, Qi Wen Hu, Shao Kun Feng, and Ze Fu. "A Blind Digital Watermarking for PDF Document." Applied Mechanics and Materials 392 (September 2013): 1006–9. http://dx.doi.org/10.4028/www.scientific.net/amm.392.1006.
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In this paper, a text blind watermarking is proposed and implemented for copyright protection. Based on the characteristics of PDF format, this algorithm uses character spacing coding throughout whole PDF document to embed watermark into it. Robustness and security is further increased by using synchronous coding, cycle encryption and majority decision. Watermark embedding and extracting are implemented under the software environment of VC++ 6.0, and performances are tested and analyzed. Experiments show that the algorithm has good transparency, large capacity and good robustness. It can apply to both of Chinese and English PDF documents.
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Arbanas, Goran, Jinghua Feng, Zia J. Clifton, et al. "Bayesian optimization of generalized data." EPJ Nuclear Sciences & Technologies 4 (2018): 30. http://dx.doi.org/10.1051/epjn/2018038.
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Direct application of Bayes' theorem to generalized data yields a posterior probability distribution function (PDF) that is a product of a prior PDF of generalized data and a likelihood function, where generalized data consists of model parameters, measured data, and model defect data. The prior PDF of generalized data is defined by prior expectation values and a prior covariance matrix of generalized data that naturally includes covariance between any two components of generalized data. A set of constraints imposed on the posterior expectation values and covariances of generalized data via a given model is formally solved by the method of Lagrange multipliers. Posterior expectation values of the constraints and their covariance matrix are conventionally set to zero, leading to a likelihood function that is a Dirac delta function of the constraining equation. It is shown that setting constraints to values other than zero is analogous to introducing a model defect. Since posterior expectation values of any function of generalized data are integrals of that function over all generalized data weighted by the posterior PDF, all elements of generalized data may be viewed as nuisance parameters marginalized by this integration. One simple form of posterior PDF is obtained when the prior PDF and the likelihood function are normal PDFs. For linear models without a defect this PDF becomes equivalent to constrained least squares (CLS) method, that is, the χ2 minimization method.
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Uhlemann, Cora, Oliver Friedrich, Francisco Villaescusa-Navarro, Arka Banerjee, and Sandrine Codis. "Fisher for complements: extracting cosmology and neutrino mass from the counts-in-cells PDF." Monthly Notices of the Royal Astronomical Society 495, no. 4 (2020): 4006–27. http://dx.doi.org/10.1093/mnras/staa1155.
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ABSTRACT We comprehensively analyse the cosmology dependence of counts-in-cells statistics. We focus on the shape of the one-point probability distribution function (PDF) of the matter density field at mildly non-linear scales. Based on large-deviation statistics, we parametrize the cosmology dependence of the matter PDF in terms of the linear power spectrum, the growth factor, the spherical collapse dynamics, and the non-linear variance. We extend our formalism to include massive neutrinos, finding that the total matter PDF is highly sensitive to the total neutrino mass Mν and can disentangle it from the clustering amplitude σ8. Using more than a million PDFs extracted from the Quijote simulations, we determine the response of the matter PDF to changing parameters in the νΛCDM model and successfully cross-validate the theoretical model and the simulation measurements. We present the first νΛCDM Fisher forecast for the matter PDF at multiple scales and redshifts, and its combination with the matter power spectrum. We establish that the matter PDF and the matter power spectrum are highly complementary at mildly non-linear scales. The matter PDF is particularly powerful for constraining the matter density Ωm, clustering amplitude σ8 and the total neutrino mass Mν. Adding the mildly non-linear matter PDF to the mildly non-linear matter power spectrum improves constraints on Ωm by a factor of 5 and σ8 by a factor of 2 when considering the three lowest redshifts. In our joint analysis of the matter PDF and matter power spectrum at three redshifts, the total neutrino mass is constrained to better than 0.01 eV with a total volume of 6 (Gpc h−1)3. We discuss how density-split statistics can be used to translate those encouraging results for the matter PDF into realistic observables in galaxy surveys.
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Rademacher, Nadine, Luke L. Daemen, Eric L. Chronister, and Thomas Proffen. "Pair distribution function analysis of molecular compounds: significance and modeling approach discussed using the example ofp-terphenyl." Journal of Applied Crystallography 45, no. 3 (2012): 482–88. http://dx.doi.org/10.1107/s0021889812016159.
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Modeling the pair distribution function (PDF) of molecular compounds is a challenging task because intra- and intermolecular interactions lead to very different features in the PDF. This article discusses the different peak shapes in PDFs of molecular compounds in detail. Moreover, the common methods to calculate PDFs from structural models are summarized and evaluated with respect to molecular systems and an approach to calculate PDFs from molecular crystals more accurately is introduced.p-Terphenyl was chosen as a test compound. It adopts a crystal structure with disordered features and short-range order. The short-range order was previously investigated by analyzing single-crystal diffuse scattering and it was also extracted from experimental PDFs during this study.
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Schubert, Carolyn. "PDF Applications on the iPad: A Review." Collaborative Librarianship 2, no. 3 (2010): 177–79. http://dx.doi.org/10.29087/2010.2.3.11.
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Cline, D., A. Razdan, and P. Wonka. "A Comparison of Tabular PDF Inversion Methods." Computer Graphics Forum 28, no. 1 (2009): 154–60. http://dx.doi.org/10.1111/j.1467-8659.2008.01197.x.
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Jo, Sungho. "A robust approach to empirical PDF estimate." Neurocomputing 67 (August 2005): 288–96. http://dx.doi.org/10.1016/j.neucom.2005.01.005.
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Lee, Suiang-Shyan, Shuo-Fang Hsu, and Ja-Chen Lin. "Protection of PDF Files: a Sharing Approach." International Journal of u- and e-Service, Science and Technology 7, no. 2 (2014): 27–40. http://dx.doi.org/10.14257/ijunesst.2014.7.2.03.
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OKONG'O, NORA A., and JOSETTE BELLAN. "Direct numerical simulation of a transitional supercritical binary mixing layer: heptane and nitrogen." Journal of Fluid Mechanics 464 (August 10, 2002): 1–34. http://dx.doi.org/10.1017/s0022112002008480.
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Direct numerical simulations (DNS) of a supercritical temporal mixing layer are conducted for the purpose of exploring the characteristics of high-pressure transitional mixing behaviour. The conservation equations are formulated according to fluctuation-dissipation (FD) theory, which is consistent with non-equilibrium thermodynamics and converges to kinetic theory in the low-pressure limit. According to FD theory, complementing the low-pressure typical transport properties (viscosity, diffusivity and thermal conductivity), the thermal diffusion factor is an additional transport property which may play an increasingly important role with increasing pressure. The Peng–Robinson equation of state with appropriate mixing rules is coupled to the dynamic conservation equations to obtain a closed system. The boundary conditions are periodic in the streamwise and spanwise directions, and of non-reflecting outflow type in the cross-stream direction. Due to the strong density stratification, the layer is considerably more difficult to entrain than equivalent gaseous or droplet-laden layers, and exhibits regions of high density gradient magnitude that become very convoluted at the transitional state. Conditional averages demonstrate that these regions contain predominantly the higher-density, entrained fluid, with small amounts of the lighter, entraining fluid, and that in these regions the mixing is hindered by the thermodynamic properties of the fluids. During the entire evolution of the layer, the dissipation is overwhelmingly due to species mass flux followed by heat flux effects with minimal viscous contribution, and there is a considerable amount of backscatter in the flow. Most of the species mass flux dissipation is due to the molecular diffusion term with significant contributions from the cross-term proportional to molecular and thermal diffusion. These results indicate that turbulence models for supercritical fluids should primarily focus on duplicating the species mass flux rather than the typical momentum flux, which constitutes the governing dissipation in atmospheric mixing layers. Examination of the passive-scalar probability density functions (PDFs) indicates that neither the Gaussian, nor the beta PDFs are able to approximate the evolution of the DNS-extracted PDF from its inception through transition. Furthermore, the temperature–species PDFs are well correlated, meaning that their joint PDF is not properly approximated by the product of their marginal PDFs; this indicates that the traditional reactive flow modelling based on replacing the joint PDF representing the reaction rate by the product of the marginal PDFs is not appropriate. Finally, the subgrid-scale temperature–species PDFs are also well correlated, and the species PDF exhibits important departures from the Gaussian. These results suggest that classic PDFs used in atmospheric pressure flows would not capture the physics of this supercritical mixing layer, either in an assumed PDF model at the larger scale, or at the subgrid scale.