Academic literature on the topic 'Disordered t-J-model'

The antiferromagnetic phase transition associated with the breaking of the magnetic SU(2) symmetry of the t-J model is investigated by means of the cluster variation method in the pair approximation. The disordered and antiferromagnetic phases are characterized by means of their symmetry properties, and an analytical implicit expression is given for the Néel temperature.

We apply the spin-wave theory with the additional constraint of zero staggered magnetization to investigate the two-dimensional t–J model in the paramagnetic state in the ranges of hole concentrations 0.02 ≲ x ≲ 0.17 and temperatures T ≲ 100 K. In this region the hole spectrum is nonmetallic and contains a pseudogap with properties similar to those observed in Bi2212 photoemission. The calculated spin correlation length, susceptibility, spin-lattice relaxation times at the Cu and O sites and Cu spin-echo decay time are in qualitative and in some cases in quantitative agreement with experiment in underdoped YBa2Cu3O 6+y. The temperature dependences of these quantities are typical for the quantum disordered regime with a pseudogap in the spectrum of magnetic excitations. In the Eliashberg formalism the hole–magnon interaction was found to be unable alone to give rise to superconductivity. With inclusion of a moderate interaction with apex oxygen vibrations, high-T c 's are obtained for even frequency dx2-y2 pairing.

A large N expansion technique, based on symplectic (Sp(N)) symmetry, for frustrated magnetic systems is studied. The phase diagram of a square lattice, spin S, quantum antiferromagnet with first, second and third neighbor antiferromagnetic coupling (the J1-J2-J3 model) is determined in the large-N limit and consequences of fluctuations at finite N for the quantum disordered phases are discussed. In addition to phases with long range magnetic order, two classes of disordered phases are found: (i) states similar to those in unfrustrated systems with commensurate, collinear spin correlations, confinement of spinons, and spin-Peierls or valence-bond-solid order controlled by the value of 2S (mod 4) or 2S (mod 2) ; (ii) states with incommensurate, coplanar spin correlations, and unconfined bosonic spin-1/2 spinon excitations. The occurrence of “order from disorder” at large S is discussed. Neither chirally ordered nor spin nematic states are found. Initial results on superconductivity in the t—J model at N=∞ and zero temperature are also presented.

AbstractWe study the properties of an ODE description of schools of fish (B. Birnir, An ODE model of the motion of pelagic fish, J. Stat. Phys. 128(1/2) (2007), 535–568.) and how they change in the presence of a random acceleration. The model can be reduced to one ODE for the direction of the velocity of a generic fish and another ODE for its speed. These equations contain the mean speed $\bar{v}$ and a Kuramoto order parameter $r$ for the phases of the fish velocities. In this paper, we give a complete qualitative analysis of the system for large number of particles. We show that the stationary solutions of the ODEs consist of an incoherent unstable solution with $r\!\!=\!\!\bar{v}\!\!=\!\!0$ and a globally stable solution with $r\!=\!1$ and a constant $\bar{v}\!>\!0$. In the latter solution, all the fish move uniformly in the same direction with $\bar{v}$ and the direction of motion determined by the initial configuration of the school. This is called the “migratory solution”. In the second part of the paper, the directional headings of the particles are perturbed, in two distinct ways, and the speeds accelerated in order to obtain two distinct classes of non-stationary, complex solutions. We show that the perturbed systems have similar behavior as the unperturbed one, and derive the resulting constant value of the average speed, verifying the numerical observations. Finally, we show that the system exhibits a similar bifurcation to that in Vicsek and Czirok (T. Vicsek, A. Czirók, E. Ben-Jacob, I. Cohen and O. Shochet, Novel type of phase transition in a system of self-driven particles, Phys. Rev. Lett. 75(6) (Aug 1995), 1226–1229.) between phases of synchronization and disorder. Either increasing the variance of the Brownian angular noise, or decreasing the turning rate, or coupling between the particles, cause a similar phase transition. These perturbed models represent a more realistic view of schools of fish found in nature. We apply the theory to compute the order parameter for a simulation of the Chile-Peru anchovy fishery.

The two-layer Heisenberg antiferromagnet exhibits a zero temperature quantum phase transition from a disordered dimer phase to a collinear Neel phase, with long range order in the ground state. The spin-wave gap vanishes as Δ ∝ (J ⊥ – J ⊥ c) ν approaching the transition point. To account for strong correlations, the S = 1 elementary excitations triplets are described as a dilute Bose gas with infinite on-site repulsion. We apply the Brueckner diagram approach which gives the critical index ν ≈ 0 . 5. We demonstrate also that the linearised in density Brueckner equations give the mean field result ν = 1. Finally, an expansion of the Brueckner equations in powers of the density, combined with the scaling hypothesis, gives ν ≈ 0 . 67. This value agrees reasonably with that of the nonlinear O(3) σ model. Our approach demonstrates that for other quantum spin models the critical index can be different from that in the nonlinear σ model. We discuss the conditions for this to occur.

Cancer progression, relapse and resistance are the result of an evolutionary optimization process. Vast intra-tumoral diversity provides the critical substrate for cancer to evolve and adapt to the selective pressures provided by effective therapy. Our previous work has shown that genetically distinct subpopulations compete and mold the genetic makeup of the malignancy (1, 2). Additionally, we have shown that epigenetic changes in cancer may be similar to the process of genetic diversification, in which stochastic trial and error leads to rare fitness enhancing events (3). These studies demonstrate the need to integrate genetic, epigenetic and transcriptional information in the study of cancer evolution, specifically at the single-cell resolution - the atomic unit of somatic evolution. To enable this work, we have developed a single-cell multi-omics toolkit, and apply it to chart the evolutionary history and developmental topographies of normal and malignant blood cells. First, we have applied single-cell multi-omics to chronic lymphocytic leukaemia (CLL), a highly informative model for cancer evolution (4). We applied multiplexed single-cell reduced-representation bisulfite sequencing to healthy B and CLL cells, and demonstrated that epimutations serve as a molecular clock. Heritable epimutation information therefore allows to infer high-resolution lineages with single-cell data, directly in patient samples. CLL tree topography showed earlier branching and longer branch lengths than normal B cell trees. These features reflect rapid drift after malignant transformation and CLL's greater proliferative history. Multi-omic single-cell Integration of methylome sequencing with whole transcriptome and genotyping capture validated tree topology inferred solely on the basis of epimutation information. To examine potential lineage biases during therapy, we profiled serial samples during ibrutinib-associated lymphocytosis, and identified clades of cells that were preferentially expelled from the lymph node after treatment, marked by distinct transcriptional profiles involving TLR pathway activation. The single-cell integration of genetic, epigenetic and transcriptional information thus charts the lineage history of CLL and its evolution with therapy. Second, charting the transcriptomes of clonally mutated cells is challenging in the absence of surface markers that distinguish cancer clones from one another, or from admixed non-neoplastic cells. To tackle this challenge, we developed Genotyping of Transcriptomes (GoT), a technology to integrate genotyping with high-throughput droplet-based single-cell RNA sequencing(5). With GoT we profiled thousands of CD34+ cells from patients myeloproliferative neoplasms to study how somatic mutations corrupt the process of human hematopoiesis. These data allow to superimpose the two differentiation trees; the native wildtype tree and the one corrupted by mutation. High-resolution mapping of malignant versus normal progenitors showed increased fitness with myeloid differentiation with CALR mutation. We identified the unfolded protein response as a predominant outcome of CALR mutations, with dependency on cell identity. Notably, stem cells and more differentiated progenitors show distinct transcriptional programs as a result of somatic mutation, suggesting differential sensitivity to therapeutic targeting. We further extended the GoT toolkit to genotype multiple targets and loci that are distant from transcript ends. Together, these findings reveal that the transcriptional output of somatic mutations in blood neoplasms is dependent on the native cell identity. Landau, D. A., Carter, S. L., Stojanov, P. et al., Evolution and impact of subclonal mutations in chronic lymphocytic leukemia. Cell152, 714-726 (2013).Landau, D. A., Tausch, E., Taylor-Weiner, A. N. et al., Mutations driving CLL and their evolution in progression and relapse. Nature526, 525-530 (2015).Landau, D. A., Clement, K., Ziller, M. J. et al., Locally disordered methylation forms the basis of intratumor methylome variation in chronic lymphocytic leukemia. Cancer Cell26, 813-825 (2014).Gaiti, F., Chaligne, R., Gu, H. et al., Epigenetic evolution and lineage histories of chronic lymphocytic leukaemia. Nature569, 576-580 (2019).Nam, A. S., Kim, K. T., Chaligne, R. et al., Somatic mutations and cell identity linked by Genotyping of Transcriptomes. Nature571, 355-360 (2019). Disclosures Landau: Pharmacyclics: Research Funding; Celgene: Research Funding; Illumina Inc: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.

List of abstracts and authors:1. Comparative benefits of Atypical antipsychoticsDiana P Morrison2. Evidence-based management of depression in SchizophreniaAndre F Joubert3. Second generation Antipsychotics: An African updateDave Swingler4. The drug management of patients with HIV/Aids in the Mental Health Care setting: A therapeutic challengeDenise White5. New developments in the treatment of Bipolar depressionJospeh R Calabrese6. Dual action antidepressants: Faster onset, more remission, better value?Roger M Pinder7. Antisocial personality disorder: A reviewDonald W Black8. The South African study of stress and health: An overviewDavid R Williams9. Ugliness is in the eye of the beholder: Psychiatric apsects of body image disturbanceDavid Castle10. Over diagnosed or under recognized? Treating ADHDDora Wynchank11. The contagious effects of trauma and their impact on human service organisationsKerry Gibson12. Temporal lobe epilepsy in adolescence - 'Understanding the narrative'Helen Clark13. The effectiveness of treatment programs for Methaqualone (Mandrax) dependenceGreg McCarthy, Nandi Siegfried, Bronwyn Myers14. Community influence on alcohol and marijuanaAlan J Flisher, Robyn Mallett, Gary King, Neo Morojele, Martie Muller, Carl Lombard15. Psychiatric presentations of medical illnessSebastian Akalula16. Imaging of brain function using SpectJames Warwick17. Selected neuropsychological test performances and SSRI usageTheophilus Lazarus18. Comparative effectiveness and safety of antipsychotic treatments for outpatient SchizophreniaFrans Korb, Adel Sadak, Aly Akram, Sunar Birsoz, Abderrahmane Belaid19. Evidence-based mental healthcare - What do you know, think, feel?Nandi Siegfried, George Swingler, Soraya Seedat, Martie Muller, Rachel Churchill, Dan Stein20. Competitions Act - Anti-competitive health care practicesZ Nthakwana21. Unique approach to mental wellness by medical SchemesPetro Kempen22. What happens to my medical aid contribution?Eugene Allers23. Financial issues in a modern private practiceMike Edwards24. Transcranial magnetic stimulation: Uses in brain function research and medical interventionAlan St Clair Gibson25. The Neurochemistry of dreams: Implications for PsychiatryMark Solms26. Tenascin-R expression in the Central Nervvous system of lower vertebratesRuth Jarvis, N-. Hsu, P. Pesheva and D.M. Lang25. Localisation of the Nogo-A receptor in Neronal Lipid raftsEdward Nyatia, D.M. Lang26. Characterising an animal model for early life trauma using time dependent sensitisationJoachim D.K. Uys, Willie M.U. Daniels, Dan J. Stein27. Tolmetin affords protection against Quinoclinic acid induced Neurotoxixity in Rat brainAmichand Dairam, S Daya28. Acetaminophen and aspirin inhibit superoxide anion generation and Lipid Peroxidation, and protect against 1-Methyl-4Phenyl Pyridinim-induced Dopaminergic Neurotoxicity in ratsH. Maharaj, D.S. Maharaj, K. S. Saravanan, K.P. Mohanakumar, S. Daya29. Can exercise provide Neuroprotection in a rat model for Parkinson's disease?M Mabandla, L Kellaway, A St Clair Gibson, M Lambert, V Russell30. Treatment of rapid cycling Bipolar disorderJoseph R. Calabrese31. Depression as a Neurodegenerative Disorder: The need for achieving remissionRoger M Pinder32. Side-effects induced by modern antidepressants- Overview and managementFranco Colin33. The Placebo response in antidepressant clinical trialsRobin Emsley34. Impulse control disorders: An overviewDonald W. Black35. Post traumatic stress disorder: The Wits trauma clinic experienceUgash Subramaney36. Post traumatic stress disorder among recently diagnosed patients with HIV in South AfricaSoraya Seedat, Bo Olley, D J Stein37. Improving outcome in SchizophreniaDiana P Morrison38. Reviewing post Graduate trainingCliff W Allwood39. Ethics in HIV ResearchKeimanthro Moodley40. Improving and maintaining ethical standrads in Psychiatric researchTuviah Zabow=============================================================Posters: Neurosciences section (Presenting author only)1. Blunted Acth response correlates with altered Neurotransmitter function in maternally separatedratsW M U Daniels2. A mechanism for zinc toxicity in Neuroblastoma cellsW M U Daniels3. The effects of Hypericum Perforatum, Quercetin, and Fluoxetine on receptor densities in the Rat BrainL Heiderman4. Trichotillomania and obsessive-compulsive disorder: Clinical and genetic comparisons within a South African populationS M J Hemmings5. Expression of Nogo-A in the amphibian central nervous systemN. J. Hsu6. Biochemical model for inflammation of the brain: The role of iron, transferring and toxiferring in Lipid PeroxidationS J Van Rensburg7. Improvement in Alzheimer's disease patients with antioxidant supplementation over 15 monthsS J Van Rensburg8. The Placebo effect - Is it all in the mind?S J Van Rensburg9. Very low serum iron concentrations in elderly patients with active CarcinomaS J van Rensburg10. Melatonin affords protection against Rotenone-induced NeurotoxicityR John11. Effect of enriched environment on Ca uptake via NMDA receptors into barrel cortex slices of spontaneously HypertensiveratsM Lehohla12. Effects of Methylpenidate in a rat model for Attention Deficit Hyperactivity DisorderG. L. S. Lelaka13. 6-Hydroxymelatonin converts Fe (III) to Fe(II) and reduces iron-induced Lipid PeroxidationD S Maharaj14. Metrofinate Potentiates Quinolinic Acid and Potassium Cyanide induced NeurotoxicityA Ramsunder15. The effect of chronic Intra-Amylgdala CRF injections on rat behaviour and HPA-Axis functionL Richter16. Effect of Glutamate in the Prefrontal Cortex of a rat model for Attention-Deficit Hyperactivity DisorderV Russell17. An investigation into the relationship between Corticosterone and Neuron Cell deathP J Van Vuuren=============================================================41. Blunted Acth response correlates with altered Neurotransmitter function in maternally separated RatsW M U Daniels, C Y Pietersen, M E Carstens, D J Stein42. A mechanism for Zinc Toxicity in NeuroBlastoma CellsW M U Daniels, J Hendricks, R Salie, S J Van Rensburg43. The effects of Hypericum Perforatum, Quercetin and Fluoxetine on receptor densities in the rat brainL Heideman and S Daya44. Trichotillomania and obsessive-compulsive disorder: Clinical and genetic comparisons withn a South African populationS M J Hemmings, C J Kinnear, C Lochner, H Moolman-Smook, D J H Niehaus, V Corfield, D J Stein45. Expression of Nogo-A in the amphibian central nervous systemN. J. Hsu, R Jarvis, D. M. Lang46. Biochemical model for inflammation of the brain: The role of iron, transferring and Toxiferring in Lipid PeroxidationS J Van Rensburg, R T Erasmus, J M van Zyl, D Hon, W M U Daniels, F C V Potocnik, M J Kotze, N J De Villiers, P R Hurly47. Improvement in Alzheimer's Disease patients with antioxidant supplementation over 15 monthsS J van Rensburg, F C V Potocnik, J M Van Zyl, B J Van der Walt, D Hon, A Roos, E Rienhardt, R T Erasmus48. The Placebo effect - Is it all in the mind?S J van Rensburg, R A Emsley, C M Smuts, M Kidd, S Van der Merwe, C C Myburgh, P Oosthuizen, H Bleeker49. Very low serum Iron concentrations in elderly patients with active CarcinomaS J van Rensburg, R Erasmus, D Hon, C Bouwens50. Melatonin affords protection against Rotenone-induced NeurotoxicityR John, S Daya51. Effect of enriched environment on Ca uptake via NMDA Receptors into barrel Cortex slices of spontaneously Hypertensive ratsM Lehohla, V Russell, L Kellaway52. Effects of Methylpenidate in a rat model for Attention-Deficit Hyperactivity DisorderG. L. S. Lelaka, V. A. Russel, L. A. Kellaway53. 6-Hydroxymelatonin converts Fe (III) to Fe (II) and reduces iron-induced Lipid PeroxidationD S Maharaj, S Daya54. Metrofinate Potentiates Quinolinic Acid and Potassium Cyanide induced NeurotoxicityA Ramsunder, S Daya55. The effect of chronic Intra-Amygdala CRF injections on rat behaviour and HPA-Axis functionL Richter, W Daniels, D J Stein56. Effect of Glutamate in the Prefrontal Cortex of a rat model for Attention-Deficit Hyperactivity DisorderV Russell, M Lehohla, L Kellaway57. An investigation into the relationship between Corticosterone and Neuron cell deathP J Van Vuuren, J Hendricks, W M U Daniels=============================================================Posters: Psychiatry Section1. Descriptive study of Tardive Dyskinesia in a South African Xhosa populationS Brink2. Alcohol drinking problems at three urban High Schools in UmtataO Alonso Betancourt3. Childhood and adolescent sexual abuse - Demographic, traumatic and clinical signpostsP D Carey4. Inositol in the treatment of Obsessive Compulsive DisorderP D Carey5. A review of factors associated with Suicidal behaviour in children and adolescents admitted to Tygerberg HospitalT Du Plessis6. Psychological and physical outcomes fo elective abortion; Local Anaesthesia vs Intravenous SedationT Ericksen7. Mental health literacy of Human Resource Practitioners in South AfricaC J Hugo8. The importance of a specialized clinic for the care of patients with first episodes of psychosisN Keyter9. Self-report vs Urinary drug screening in Schizophrenia: A pilot studyL Koen10. The effect of aggression on the use of Psychotropics in Schizophrenia: A naturalistic studyH Lategan11. Factor analysis of obsessive-compulsive spectrum disorders in patients with obssessive-compulsive disorder: Clinical and Genetic correlatesC Lochner12. Experiences in obsessive-compulsive Disorder and Trichotillomania: Role of childhood traumaC Lochner13. Delusional systems in Xhosa Schizophrenia SibpairsJ E Muller14. OCD Heteogeneity reflected by lack of Genealogically determined founder effectD J H Niehaus15. The efficacy and tolerbaility of low-dose vs standard dose Haloperidol in first episode Psychosis. A randomised, double-blind studyP P Oosthuizen16. Treatment with low-dose Haloperidol does not protect against Tardive DyskinesiaP P Oosthuizen17. Do healthcare funders discriminate against members on the grounds of mental illness?O Scholtz18. Treatment strategies in patients with Clozaopine-resistant Schizophrenia at Stikland Hospital: A critical evaluation of one optionA Schulte19. Early coadministration of Clonazepam with Paroxetine for generalized social anxiety disorderS Seedat20. Trauma exposure and post-traumatic stress symptoms in adolescents: A schools' survey in Cape Town (South Africa) and Nairobi (Kenya)S Seedat21. The QTC effects of Thioridazine when used as a second line Anti-psychotic ( at Stikland Hospital)C Seller22. Brain imaging and substance related disordersD J Stein23. Gender differences in trauma exposure & post traumatic stress disorder in a clinic sampleS Suliman24. Assessing the prevalence of anxiety and depressive symptoms among clinica at Tygerbeg Academic Hospital and controlsH Van der Bijl25. Pharmacological challenge with a serotonin ID Agonist in alcohol dependenceB Vythilingum26. The treatment of ADHD in adultsW Verbeeck=============================================================58. Descriptive study of Tardive Dyskinesia in a South African Xhosa populationS Brink, D J H Niehaus, L Koen, J E Muller59. Alcohol drinking problems at three Urban High Schools in UmtataO Alonso Betancourt, M Morales Herrera60. Childhood and adolescent sexual abuse - Demographic, traumatic and clinical signpostsP D Carey, J Walker, S Seedat, D J Stein61. Inositol in the treatment of obsessive compulsive DisorderP D Carey, S Seedat, D J Stein62. A review of factors associated with suicidal behaviour in children and adolescents admitted to Tygerberg HospitalT Du Plessis, S M Hawkridge, F H Theron, S A Du Plessis63. Psychological and physical outcomes of elective abortion: Local anaestheisa vs Intravenous sedationT Ericksen, S Seedat, P Labuschagne, D J Stein64. Mental health literacy of Human resource practitioners in South AfricaC J Hugo, H D Vos, D J Stein65. The importance of a specialized clinic for the care of patients with first episodes of psychosisN Keyter, P P Oosthuizen, R A Emsley, H J Turner66. Self-reort vs urinary drug screening in Schizophrenia: A pilot studyL Koen, D J H Niehaus, J E Muller, C Seller, N Keyter67. The effect of aggression on the use of Psychotropics in Schizophrenia: A naturalistic studyH Lategan, L Koen, D J H Niehaus68. Factor analysis of obsessive-compulsive spectrum disorders in patients with obsessive-compulsive Disorder: Clinical and genetic correlatesC Lochner, D J H Niehaus, S M J Hemmings, C J Kinnear, V A Corfield, J C Moolman-Smook, D J Stein69. Experiences in obsessive-compulsive disorder and Trichotillomania: Role of childhood traumaC Lochner, S Seedat, P D Carey, D J Stein70. Delusional systems in Xhosa Schizophrenia SibpairsJ E Muller, D J H Niehaus, L Koen, C Seller, N Keyter, C Laurent, R A Emsley71. OCD Heteogeneity reflected by lack of Genealogically determined founder effectD J H Niehaus, L Endeman, I Bosman, S Hemmings, C Lochner, L Koen, H Moolman-Smook, V A Corfield, D J Stein72. The efficacy and tolerability of low-dose vs standard dose Haloperidol in first episode Psychosis. A randomised, double-blind studyP P Oosthuizen, R A Emsley, H J Turner, N Keyter73. Treatment with low-dose Haloperidol does not protect against Tardive DyskinesiaP P Oosthuizen, R A Emsley, H J Turner, N Keyter74. Do healthcare funders discriminate against members on the grounds of mental illness?O Scholtz, P P Oosthuizen, C Hugo, B Richards75. Treatment strategies in patients with Clozapine resistant Schizophrenia at Stikland Hospital: A critical evaluation of one optionA Schulte, D J H Niehaus, L Koen, J E Muller, P P Oosthuizen, R A Emsley76. Early coadministration of Clonazepam with Paroxetine for generalised Social Anxiety DisorderS Seedat, M B Stein77. Trauma exposure and post-traumatic stress symptoms in adolescents: A schools' survey in Cape Town (South Africa) and Nairobi (Kenya)S Seedat, C Nyamap, F Njenga, B Vythilingum, D J Stein78. The QTC effects of Thioridazine when used as a second line Antipsychotic (at Stikland Hospital)C Seller, P P Oosthuizen79. Brain imaging and substance related disordersD J Stein80. Gender differences in trauma exposure & post traumatic stress disorder in a clinic sampleS Suliman, S Seedat, F Gxama, J Walker, W Rossouw81. Assessing the prevalence of anxiety and depressive symptoms among clinicians at Tygerberg Academic Hospital and controlsH Van der Bijl, P P Oosthuizen82. Pharmacological challenge with a Serotonin ID agonist in alcohol dependenceB Vythilingum, C Wessels, S Maritz, W P Pienaar, D J Stein83. The treatment of ADHD in adultsW Verbeeck

The debate about diagnoses and treatment of attention deficit hyperactive disorder (ADHD) in children continue to range on between the developmental and biological perspectives. While there is increasing evidence that support the biological susceptibility of the disorder, a number of researches also emphasized the significant effect of environment on the syndrome. This study used developmental perspectives to evaluate and bring together various bio-psychosocial factors that impact on children diagnosed with ADHD. The study explored and integrated the existing and advancing study on ADHD to a more refined pattern that embraced developmental perspectives. The study also discussed how the linkage in childhood ADHD fits within the developmental psychopathology perspective. The study revealed that ADHD as a developmental disorder is influenced by prenatal, biological and psychosocial environmental risk factors, and suggested that better understanding of genomic susceptibilities, family environment and parental characteristics would transform the pathway for development of ADHD in children. References American Psychiatric Association.(2000). Diagnostic and StatisticalManual of MentalDisorders. 4th ed. Washington, DC: American Psychiatric Association. American Psychiatric Association.(2013). Diagnostic and StatisticalManual of MentalDisorders.5th ed. Washington, DC: American Psychiatric Association. Arnsten, A.F, (2007). Catecholamine and second messenger influenceson prefrontalcortical networks of “representational knowledge”:a rational bridge between genetics andthe symptoms of mental illness. Cerebral Cortex, 17, i6–i15. Arnsten, A.F, & Pliszka, S.R. (2011). 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Für die theoretische Beschreibung verschiedener Substanzen, so z.B. für diverse Kuprate die Anwendungen als Hochtemperatur-Supraleiter finden, spielt das t-J-Modell eine wichtige Rolle. In vielen Fällen kann man Abweichungen der Verbindungen vom idealen translationsinvarianten Festkörper vernachlässigen, für bestimmte Eigenschaften ist jedoch der Einfluß von Störstellen,z.B. Dotieratomen, bedeutsam. Um solche Verunreinigungen einzubeziehen, behandelt die vorliegende Arbeit das t-J-Modell mit einer zusätzlichen on-site-Energie mit über die Gitterpläte zufallsverteilten Werten. Um für dieses Modell die Einteilchen-Greensfunktion zu bestimmen, wird ein Verfahren entwickelt, welches auf der Projektionstechnik basiert und die Einbeziehung des Unordnungsterms ermöglicht. Die notwendige Mittelung über die möglichen Unordnungskonfigurationen erfolgt näherungsweise durch Faktorisierung und ist verwandt mit der sogenannten average T-matrix approximation, wird hier jedoch auf ein stark korreliertes System erweitert. Zur Illustration wird der Grundzustand von La2−xSrxCuO4 und Nd2−xCexCuO4 bei einem zusätzlichen Ladungsträger über Halbfüllung untersucht. Wie Bandstrukturrechnungen zeigen, ruft die Dotierung der elektronendotierten Substanz gerade einen solchen Zufallsterm hervor. Dies wurde in der bisherigen Literatur meist vernachlässigt. Bei der Übertragung der Bandstrukturergebnisse in die Modellparameter des t-t′-t′′-J-Modells zeigt sich, daß der Einfluß der Dotieratome bei La2−xSrxCuO4 um etwa eine Größenordnung geringer ist als in Nd2−xCexCuO4 . Als wichtige Ursache hierfür wird der Einfluß der Apex-Sauerstoffatome angesehen, die im Fall von La2−xSrxCuO4 die Seltenerd- Dotieratome gegenüber der Kupferoxidebene abschirmen. Für das mit diesen Parametern belegte Modell wird anschließend die Einteilchen- Greensfunktion berechnet, die Ausgangspunkt der Berechnung verschiedener Observablen ist. Die für die elektronendotierte Substanz auftretende lokale Mode gibt zu dem Vorschlag Anlaß, daß die unterschiedliche Stabilität der antiferromagnetischen Phase für die beiden betrachteten Substanzen nicht nur auf die Art der Ladungsträger zurückzuführen ist, sondern auch auf die Struktur der Elementarzelle
The t-J-Modell can be applied to several classes of materials, e.g. high-Tc cuprate superconductors. Often translational invariance can be assumed, but sometimes it is necessary to take into account the effects of the doping atoms at randomly distributed sites. Therefore a t-J-Modell with an additional randomly distributed on-site energy is investigated. To calculate the one-particle Green’s function considering this term of disorder, a method is developed which bases on projection technique. The average over the possible configurations of the dopand atoms is approximated by factorization and is similar to the so-called average T-matrix approximation. Here it is extended to a model with strong correlations. In order to illustrate the methode the single-particle ground state of La2−xSrxCuO4 and Nd2−xCexCuO4 is analyzed. Band-structure calculations exhibit that for the electron-doped case the doping atoms (in first approximation) induce indeed a term of disordered on-site energies. The transformation of the values of this energies at the copper sites into the parameters in the t − t′ − t′′ − J-model shows that the influence of doping in La2−xSrxCuO4 is by about an order of magnitude smaller than in Nd2−xCexCuO4 . The existence of apex oxygen atoms between the rare-earth plane and the copper-oxygen plane in La2−xSrxCuO4 is one important reason for that effect. The single-particle Greens function for the t-t′-t′′-J-model with these parameters is calculated. A local mode appears in the electron-doped case, which suggests that the differences of the stability of the antiferromagnetic phases in both compounds are not only due to the type of charge carriers but also due to the structure of the unit cell

Für die theoretische Beschreibung verschiedener Substanzen, so z.B. für diverse Kuprate die Anwendungen als Hochtemperatur-Supraleiter finden, spielt das t-J-Modell eine wichtige Rolle. In vielen Fällen kann man Abweichungen der Verbindungen vom idealen translationsinvarianten Festkörper vernachlässigen, für bestimmte Eigenschaften ist jedoch der Einfluß von Störstellen,z.B. Dotieratomen, bedeutsam. Um solche Verunreinigungen einzubeziehen, behandelt die vorliegende Arbeit das t-J-Modell mit einer zusätzlichen on-site-Energie mit über die Gitterpläte zufallsverteilten Werten. Um für dieses Modell die Einteilchen-Greensfunktion zu bestimmen, wird ein Verfahren entwickelt, welches auf der Projektionstechnik basiert und die Einbeziehung des Unordnungsterms ermöglicht. Die notwendige Mittelung über die möglichen Unordnungskonfigurationen erfolgt näherungsweise durch Faktorisierung und ist verwandt mit der sogenannten average T-matrix approximation, wird hier jedoch auf ein stark korreliertes System erweitert. Zur Illustration wird der Grundzustand von La2−xSrxCuO4 und Nd2−xCexCuO4 bei einem zusätzlichen Ladungsträger über Halbfüllung untersucht. Wie Bandstrukturrechnungen zeigen, ruft die Dotierung der elektronendotierten Substanz gerade einen solchen Zufallsterm hervor. Dies wurde in der bisherigen Literatur meist vernachlässigt. Bei der Übertragung der Bandstrukturergebnisse in die Modellparameter des t-t′-t′′-J-Modells zeigt sich, daß der Einfluß der Dotieratome bei La2−xSrxCuO4 um etwa eine Größenordnung geringer ist als in Nd2−xCexCuO4 . Als wichtige Ursache hierfür wird der Einfluß der Apex-Sauerstoffatome angesehen, die im Fall von La2−xSrxCuO4 die Seltenerd- Dotieratome gegenüber der Kupferoxidebene abschirmen. Für das mit diesen Parametern belegte Modell wird anschließend die Einteilchen- Greensfunktion berechnet, die Ausgangspunkt der Berechnung verschiedener Observablen ist. Die für die elektronendotierte Substanz auftretende lokale Mode gibt zu dem Vorschlag Anlaß, daß die unterschiedliche Stabilität der antiferromagnetischen Phase für die beiden betrachteten Substanzen nicht nur auf die Art der Ladungsträger zurückzuführen ist, sondern auch auf die Struktur der Elementarzelle.
The t-J-Modell can be applied to several classes of materials, e.g. high-Tc cuprate superconductors. Often translational invariance can be assumed, but sometimes it is necessary to take into account the effects of the doping atoms at randomly distributed sites. Therefore a t-J-Modell with an additional randomly distributed on-site energy is investigated. To calculate the one-particle Green’s function considering this term of disorder, a method is developed which bases on projection technique. The average over the possible configurations of the dopand atoms is approximated by factorization and is similar to the so-called average T-matrix approximation. Here it is extended to a model with strong correlations. In order to illustrate the methode the single-particle ground state of La2−xSrxCuO4 and Nd2−xCexCuO4 is analyzed. Band-structure calculations exhibit that for the electron-doped case the doping atoms (in first approximation) induce indeed a term of disordered on-site energies. The transformation of the values of this energies at the copper sites into the parameters in the t − t′ − t′′ − J-model shows that the influence of doping in La2−xSrxCuO4 is by about an order of magnitude smaller than in Nd2−xCexCuO4 . The existence of apex oxygen atoms between the rare-earth plane and the copper-oxygen plane in La2−xSrxCuO4 is one important reason for that effect. The single-particle Greens function for the t-t′-t′′-J-model with these parameters is calculated. A local mode appears in the electron-doped case, which suggests that the differences of the stability of the antiferromagnetic phases in both compounds are not only due to the type of charge carriers but also due to the structure of the unit cell.

Affecting 1 in 68 children, Autism Spectrum Disorder (ASD) is one of the most prevalent cognitive disorders in the global population. Symptoms of ASD, although typically not life-threatening, have a large impact on the social wellbeing of diagnosed individuals. Inflammation in the brain, or neuroinflammation, has previously been shown to increase the severity of the behavioral deficits associated with ASD. The exact etiology of the neuroinflammation observed in ASD remains unclear, especially in regards to protein expression that initiates the inflammatory pathway. This experiment examines two specific markers of neuroinflammation, glial fibrillary acidic protein (GFAP) and myelin-associated glycoprotein (MAG) in a previously characterized mouse model of ASD. GFAP is astrocyte-specific, cytoplasmic, and has been shown to be upregulated in trauma or disease pathologies in the brain. MAG is found in the membrane of oligodendrocytes and is a major regulator of development and regeneration of nervous tissue. Control C57bl/6j mice and ASD-representative BTBR T+tf/J (BTBR) mice were sacrificed twenty-one days after birth. Immunoblotting was performed on cingulate cortical tissue using anti-GFAP and anti-MAG primary antibodies to quantify levels of GFAP and MAG protein expression between the control and ASD models. These findings provide further evidence that changes in GFAP and MAG expression may alter the neuroinflammatory pathways observed in ASD-representative mice.