Добірка наукової літератури з теми "TR-EPR"

EPR-insulated cables for distribution power network are not commonly used in Australia. This is due to the higher DDF of common EPR cables when compared with XLPE that contributes to the power loss and economics in transmitting electricity. This led to the development of EPR called TR-EPR with significantly lower DDF and uses silane curing process to address concerns about cost-effectiveness. The thermal behavior of low DDF silane cure TR-EPR is investigated for 30 months of exposure to the maximum operating temperature of material. The physical changes in the samples throughout the long-term aging are examined to create an opportunity to model the expected life cycle of TR-EPR cable under thermal stress. The cross-linking characteristics of TR-EPR cable are also examined by ambient curing that simulates the storage condition for unused cable and by cable heating process that simulates the condition when the cable is energized. The results are tabulated for a better understanding of the time for the material to cross-link at various conditions. The improved partial discharge values after cross-linking are also presented.

Our level one trauma center with a service area covering a population of approximately four-million people treats approximately 80,000 patients per year. In 2010, we anticipate more than 23,000 patients admitted, and to experience more than 850,000 patient encounters within the network. Trauma research is an important component to any level one trauma center, as well as a requirement of the American College of Surgeons/Committee on Trauma (ACS/COT). Our trauma center has recently gained level one designation and began an emergency preparedness research and trauma research (EPR/TR) program in earnest. We are fortunate to have support from executive administrators. Stewardship is a necessary element of our planning, in part because we are a county hospital serving a large uninsured patient population. The following are a few of the necessary steps we took to build an (EPR/TR) department from the beginning, to the point of submitting abstracts, manuscripts, funding grants, and presentations to regional, national, and international conferences, journals, and agencies. Structure the Emergency Preparedness Office to be a component of Trauma Services, allowing a unique opportunity for real-time disaster and mass casualty research. Secure a commitment from senior executives. Secure an experienced researcher, capable of research administration. Ensure the (EPR/TR) director, trauma medical director, trauma services director, and emergency preparedness coordinator can be a cohesive team with complimentary skills. Encourage trauma surgeons to perform research with assistance from the (EPR/TR) Office. Seek federal and foundation funding. Seek alliances with appropriate consortiums and associations. Develop a research relationship with pre-hospital emergency services. The above steps represent only some of the components used to build our (EPR/TR) department. We anticipate the planned expansion of the above steps will take our EPR/TR to the next level and increase extramural funding.

Abstract Electron spin resonance (ESR, aka electron paramagnetic resonance, EPR) investigations have been conducted on radicals formed during radical polymerizations and provide a detailed characterization of the active radical species. Active propagating radicals can be observed during actual radical polymerizations by ESR/EPR. The chain lengths of the observed radicals were estimated by a combination of atom transfer radical polymerization (ATRP) and ESR/EPR. The structures of the chain end radicals were determined by analysis of the ESR/EPR spectra. An increase in the dihedral angles between terminal p-orbital of radical and Cβ–H bonds was observed with increasing chain lengths of methacrylate polymers. Radical transfer reactions were observed during radical polymerization of acrylates. A combination of ATRP and ESR/EPR clarified a 1,5-hydrogen shift mechanism of the radical transfer reactions using model adamantyl acrylate radicals. Penultimate unit effects were also observed. Time-resolved ESR/EPR (TR ESR) spectroscopy clarified the initiation processes of an alternating copolymerization of styrene with maleic anhydride and the copolymerization of styrene with 1,3-butadiene. Several unsolved problems in conventional radical polymerization processes have been clarified using combinations of ATRP with ESR/EPR and TR ESR. Characterization of the radicals in radical polymerizations using various ESR techniques would definitely provide interesting and useful information on conventional radical polymerizations.

Synthetic eumelanin produced using 5,6-dihydroxyindole-2-carboxylic acid as precursor and H2O2/horseradish peroxidase as oxidative reagent, in form of dry powder, has been investigated under photoexcitation by TR-EPR spectroscopy. The formation of spin polarized radical pairs from triplet excited states of melanin has been observed both in absence and in presence of oxygen and has been followed as a function of the temperature in the range 140–290 K. The triplet mechanism explains the observed polarization pattern in net emission. In the presence of oxygen new radical pairs are formed by interaction of melanin with molecular oxygen.

The aim of this article is to develop a method for determining the dose of radiation in the processing of chilled fish and its effect on the antioxidant activity and thermophysical characteristics of muscle tissue. Radiation processing of chilled fish was performed using a linear electron accelerator model LEA-10-10S2. The dose of radiation was determined by the method of electron-paramagnetic resonance. After being treated with ionizing radiation, the cooled fish meets the requirements of the technical regulations of TR TU 021/2011 “On food safety” and TR EAEU 040/2016 “On the safety of fish and fish products”. As a result of our research, a correlation was established between the area of the Electron Paramagnetic Resonance (EPR) signal and the absorbed dose of the radiation dose. We proved a decrease in the antioxidant activity of muscle tissue of fish with an increase in radiation dose. It is established that radiation treatment of chilled fish affects the thermophysical properties of muscle tissue.

AbstractUnusual physical properties of ionic liquids (ILs) can be implemented in many different applications and are very sensitive to the structure of IL. In this work we investigate the spin dynamics of probe molecule Zn tetraphenylporphyrin (ZnTPP) dissolved in a series of ILs using time-resolved electron paramagnetic resonance (TR EPR). We compare the TR EPR characteristics in C2-methylated imidazolium-based ILs [bmmim]BF

The photo-driven process of singlet fission generates coupled triplet pairs (TT) with fundamentally intriguing and potentially useful properties. The quintet 5 TT 0 sublevel is particularly interesting for quantum information because it is highly entangled, is addressable with microwave pulses, and could be detected using optical techniques. Previous theoretical work on a model Hamiltonian and nonadiabatic transition theory, called the JDE model, has determined that this sublevel can be selectively populated if certain conditions are met. Among the most challenging, the molecules within the dimer undergoing singlet fission must have their principal magnetic axes parallel to one another and to an applied Zeeman field. Here, we present time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy of a single crystal sample of a tetracenethiophene compound featuring arrays of dimers aligned in this manner, which were mounted so that the orientation of the field relative to the molecular axes could be controlled. The observed spin sublevel populations in the paired TT and unpaired (T+T) triplets are consistent with predictions from the JDE model, including preferential 5 TT 0 formation at z ‖ B 0 , with one caveat—two 5 TT spin sublevels have little to no population. This may be due to crossings between the 5 TT and 3 TT manifolds in the field range investigated by TR-EPR, consistent with the intertriplet exchange energy determined by monitoring photoluminescence at varying magnetic fields.

The world energy consumption is increasing at an average rate of 2.1 % per year, spurred by the economic growth in most of Asian countries, Europe and Canada. The consequent depletion of fossil fuels reservoirs and the reinforced need of environmental sustainability are making the challenge of clean and renewable energy sources one of the most urgent challenges for humankind. Solar power is among the best candidates for the leading role in the energy revolution, being clean, infinite and well distributed over the planet. For this reason, photovoltaic technologies for electricity production are gaining increasing popularity. Although inorganic silicon solar cells dominate the market of photovoltaics, organic and hybrid materials attract considerable interest since their properties like flexibility, light-weight, transparency and low-cost could make the difference in the raising of solar electricity. So far, these materials could not yet outperform conventional silicon, stimulating intensive scientific research on both the development of new materials and the understanding of the photophysical mechanisms governing the photovoltaic behavior of organic/hybrid semiconductors. In this thesis, a series of new organic and hybrid photoactive materials is studied using Electron Paramagnetic Resonance spectroscopy (EPR). This technique, combined with photoexcitation, allows to unambiguously characterize the photoinduced processes involving the formation of paramagnetic states like radicals and triplet states. As shown in the thesis, EPR can also give useful information about molecular ordering in the materials, which is known to be intimately connected with charge transport properties. Conjugated polymers are known for their semiconducting properties and their blends with strong electron accepting fullerene derivatives are among the best performing organic photovoltaic systems. Donor-acceptor alternating copolymers have been introduced to enhance the light-harvesting properties of the blends. Compared to homopolymers, they usually display a lower crystallinity of the deposited films. Thus, XRD techniques are often not suitable to investigate their molecular ordering features. We apply EPR to the analysis of molecular orientational order in the films of two polymers representative of this class, showing that a consistent degree of preferential orientation occurs with two common deposition methods. Fullerene-free materials for polymer solar cells have been recently introduced and overcome some of the drawbacks of fullerene acceptors like the limited absorption and the poor bandgap tunability. In this framework, we study two blends of electron-donor and acceptor polymers to probe their properties with respect to the common fullerene/donor combination, showing that they avoid charge recombination to triplet states which is an active loss mechanism in fullerene-containing blends. Furthermore, the all-polymer films provide a high degree of orientational order and efficient interaction between the donor and acceptor phases that make them promising alternatives to polymer-fullerene blends. A reduced graphene oxide-triphenylamine covalently-linked nanohybrid is studied as potential photosensitizer for TiO2 in dye-sensitized solar cells, able to improve the conductivity and the stability of the system. EPR shows that efficient photoinduced electron transfer from the sensitizer to the semiconductor occurs, paving the way to this new class of photosensitizers. Finally, we investigate the photoactivity of a supramolecular soft-material, forming a gel, composed of small self-assembling donor and acceptor molecules. In this case, EPR allows to verify the efficiency of charge transport across the supramolecular structures, suggesting appealing semiconducting properties of the material. The results of this thesis show the relevance of EPR for unraveling functional and morphological properties of photovoltaic materials and provide a useful characterization of the photophysics of new systems that may be further explored to bring substantial progresses to the field of organic photovoltaics.
Il consumo mondiale di energia ha un tasso medio di crescita del 2.1 % all’anno, trainato dalla crescita economica di molti Paesi asiatici, dell’Europa e del Canada. Il conseguente depauperamento delle risorse di combustibili fossili e il più stringente bisogno di proteggere l’ambiente stanno facendo della sfida delle energie rinnovabili una delle più urgenti sfide che l’umanità deve affrontare. L’energia solare è tra i migliori candidati a svolgere il ruolo di punta nella rivoluzione energetica, essendo una fonte di energia pulita, infinita e ben distribuita nel pianeta. Per questo motivo le tecnologie fotovoltaiche per la produzione di energia elettrica stanno acquistando crescente popolarità. Sebbene le celle solari a base di Silicio dominino il mercato del fotovoltaico, materiali organici e ibridi sono fonte di crescente interesse grazie alle loro peculiari proprietà, come la flessibilità, la leggerezza e la trasparenza, il basso costo, che ci si aspetta possano fare la differenza nell’affermazione del fotovoltaico. Fino ad ora questi materiali non hanno superato il rendimento dei materiali convenzionali a base di Silicio, stimolando la ricerca scientifica verso lo sviluppo di nuovi materiali e lo studio dei meccanismi fotofisici che governano il comportamento fotovoltaico dei semiconduttori organici e ibridi. In questa tesi, una serie di nuovi materiali fotoattivi, organici e ibridi, è stata studiata utilizzando la spettroscopia di Risonanza Paramagnetica Elettronica (EPR). Tale tecnica, combinata con la fotoeccitazione, permette di caratterizzare i processi fotoindotti che portano alla formazione di stati paramagnetici come radicali e stati di tripletto. Come mostrato nella tesi, la tecnica EPR può essere anche utilizzata per ottenere informazioni circa l’ordine molecolare nei materiali, che è noto essere strettamente collegato alle loro proprietà di trasporto di carica. I polimeri coniugati sono noti per le loro proprietà di semiconduttori e le loro miscele con derivati fullereneci - forti electron-accettori - sono tra i sistemi fotovoltaici organici più efficienti. Copolimeri alternanti composti da unità elettron-accettrici e donatrici sono stati introdotti per aumentare l’efficienza di assorbimento dello spettro solare. Rispetto ai classici omopolimeri, questi mostrano solitamente una minore cristallinità dei film depositati. Pertanto, tecniche diffrattometriche si rivelano spesso inadeguate per caratterizzarne l’ordine molecolare. In questa tesi l’EPR viene utilizzato per analizzare l’ordine orientazionale in due polimeri rappresentativi di questa classe, mostrando che un grado consistente di orientazione preferenziale è presente nei film ottenuti con due diverse tecniche di deposizione. Materiali fullerene-free per le celle solari polimeriche sono stati recentemente introdotti per superare alcuni degli svantaggi degli accettori fullerenici, come il limitato assorbimento della luce solare e la difficoltà nel regolare il bandgap e le proprietà elettroniche. In questo conteso, abbiamo studiato due blend costituiti da polimeri elettron-accettori e donatori al fine di investigarne le proprietà e di compararle a quelle dei convenzionali blend di polimeri donatori con derivati fullerenici, dimostrando che essi eliminano la ricombinazione di cariche a formare stati di tripletto, meccanismo noto come fonte di perdita di efficienza nei materiali contenti fullereni. Inoltre, i film polimerici mostrano un elevato grado di ordine orientazionale e un’efficiente interazione tra le fasi di donatore e di accettore che li rendono promettenti alternative ai blend di polimero e fullerene. Un nanoibrido composto da grafene ossido ridotto e molecole di trifenilammina legati covalentemente, è stato studiato come potenziale colorante per la titania in celle solari sensibilizzate a colorante, capace di migliorare la conducibilità e la stabilità del sistema. L’EPR ha mostrato che un efficiente trasferimento elettronico fotoindotto avviene tra l’ibrido e il semiconduttore, aprendo la strada all’applicazione di una nuova classe di coloranti. Infine, la fotoattività di un materiale supramolecolare, un gel composto da piccole molecole di donatore e accettore che autoassemblano, è stata studiata. In questo caso l’EPR ha permesso di verificare un efficiente trasporto di carica attraverso le strutture supramolecolari, suggerendo interessanti proprietà semiconduttive del materiale. I risultati di questa tesi dimostrano la rilevanza dell’EPR per l’indagine su aspetti funzionali e morfologici di materiali fotovoltaici e forniscono una caratterizzazione della fotofisica di nuovi sistemi che potrebbero essere ulteriormente esplorati per apportare progressi sostanziali nel campo del fotovoltaico organico e ibrido.

Cross-linked Polyethylene (XLPE) underground cables are widely used in Victorian power distribution networks due to its lower Dielectric Dissipation Factor (DDF) over Ethylene Propylene Rubber (EPR) cable. Advancement in compounding technology led to the reduction of DDF in some EPR proprietary material. This research investigated the viability of silane-cured low-DDF Tree-Retardant EPR (TR-EPR) cable as an alternative over standard XLPE cable in Victoria. The thermal ageing behaviour of TR-EPR was studied by means of laboratory-based experimentation using accelerated ageing test to observe the time variation of its mechanical properties: tensile strength and elongation at break. Measurements of Partial Discharge (PD) were also conducted prior and after cable heating at service temperature. The results of the thermal ageing test and PD measurements were visually presented through graphs and plots. For the thermal ageing, a theoretical life model was used with the parameters determined using Least Square Regression Method (LSRM). Data from the TR- EPR thermal ageing test were mathematically extrapolated to service temperature through the Arrhenius law to determine the extent of validity of the results. The economic viability of the TR- EPR was also analysed. The results obtained can be utilised by network operators and large industrial companies when designing their underground cable system and taking into consideration the reliability and economy of the power system.