To elucidate the response of different solvents such as isopropyl-alcohol (IPA) and acetone for polyaniline-emeraldine-base (PANI), the charge transport mechanism is investigated as a function of ...temperature in the presence of different solvents. From SEM and XRD characterization, it is noted that each solvent improves the surface smoothness and negligible solvent traces were observed in the final thin-film devices. It is further observed that all devices follow space-charge-limited-current (SCLC) model to define their electrical responses. Conductivity was measured directly through four-probe method, while mobility was estimated from SCLC model and then both conductivity and mobility of PANI are compared with the given solvent at different temperatures. Similarly, it is also realized that the IPA solvent improves conductivity, mobility and degradation of PANI thin-film due to complex behaviour of solvent induced self-organization of molecular chains and reduction of residual traps as a function of temperature.
Cubic and hexagonal AlN films have been prepared by vacuum arc discharge technique at different deposition temperatures 100, 200 and 300°C. The depositions were carried out from pure aluminum targets ...under nitrogen gas on p-type Si substrates, with Al forming the gate in a metal–insulator–semiconductor configuration. Preferential orientations (111) and (002) of the cubic and hexagonal phases have been affirmed by X-ray diffraction analysis. The Fourier transform infrared spectra revealed the manifestation of the two phases as well. The effect of deposition temperature on the crystalline quality and texture of the films has been also investigated and the grain size of which, has been evaluated as a function of temperature. The best crystalline quality i.e., largest grain size was found to be at 200°C. The composition and stoichiometry of the films have been determined by the time-of-flight elastic recoil detection analysis (TOF-ERDA) and Rutherford backscattering techniques. The Al/N ratio was found to be around 1, while the O content was less than 1.8%. Scanning electron microscopy and TOF-ERDA measurements demonstrated films thickness of 260nm. Current density versus electric field and capacitance–voltage (C–V) measurements were also investigated to reveal the field emission and conduction mechanism of the Al/AlN/p-Si devices. Schottky, Pool–Frenkel and Fowler–Nordheim conduction have been found to contribute to the electron transport, and the best emission properties were manifested at 200°C with a highest current density 525μA/cm2 at a field 71V/μm. From C–V curves, the density of traps has been estimated to be 18×109cm−2eV−1 indicating a good quality of the deposited films.
•AlN films containing its cubic phase were deposited by vacuum arc discharge.•MIS capacitors of these films of (111) preferential orientation were fabricated.•The best crystalline quality was found to be at 200°C deposition temperature.•The conduction mechanisms in the films were identified.•Trapped charges at interface were estimated to be of the order of 109cm−2·eV−1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
BackgroundEndothelial progenitor cells (EPCs) have been well-studied for their differentiation potential and paracrine activity in vitro and in experimental animal studies. EPCs are the precursors of ...endothelial cells (ECs) and a rich source of pro-angiogenic factors, and hence, possess enormous potential to treat ischemic heart through myocardial angiogenesis. Their proven safety and efficacy observed during the pre-clinical and clinical studies have portrayed them as a near ideal cell type for cell-based therapy of ischemic heart disease.In response to the chemical cues from the ischemic heart, EPCs from the bone marrow and peripheral circulation home-in to the ischemic myocardium and participate in the intrinsic repair process at the molecular and cellular levels through paracrine activity and EC differentiation. EPCs also release small extracellular vesicles (sEVs) loaded with bioactive molecules as part of their paracrine activity for intercellular communication to participate in the reparative process in the heart. AimThis literature review is based on the published data regarding the characteristic features of EPC-derived sEVs and their proteomic and genomic payload, besides facilitating safe and effective repair of the ischemic myocardium. In light of the encouraging published data, translational and clinical assessment of EPC-derived sEVs is warranted. We report the recent experimental animal studies and their findings using EPC-derived sEVs on cardiac angiogenesis and preservation of cardiac function. Relevance for PatientsWith the promising results from pre-clinical studies, clinical trials should be conducted to assess the clinical utility of EPC-derived sEVs in the treatment of the ischemic myocardium.
This paper examines literacy-related practices existing in elementary history classrooms and asks to what extent these practices are compatible with the ideals of historical literacy, i.e. ...disciplinary literacy specific to history. A total of 50 hours were spent observing nine Finnish classrooms. Data sources included numeric data, field notes and classroom artifacts. The results show that the most common text type used was the body text of a textbook while primary sources were few. The textbook was typically addressed as a neutral source of information. Teachers used visual texts only briefly and to support an existing narrative. None of the teachers modeled reading strategies specific to history. The teacher profiles suggest diverse approaches to literacy but the practices used by teachers point more to content-area and cultural literacy than disciplinary literacy. Implications for elementary literacy and history instruction are discussed.
We have performed extensive numerical simulations to study the effect of the size of pinning centers on the critical current density of driven vortex lattices interacting with square periodic arrays ...of pinning sites. The pinning centers considered here have radii larger than the superconducting coherence length of the vortices. These simulations have been carried out at different temperatures and for several values of pinning strengths. We have solved the overdamped equation of vortex motion taking into account the vortex–vortex repulsion interaction, the attractive vortex–pinning interaction, the thermal force, and the driving Lorentz force. We have found that, while the critical current density increases with pinning size at high-temperatures, it is almost independent of pinning size at low-temperatures. We have also found that increasing the size of the pinning centers suppresses the rate at which the critical current density decreases with temperature for all values of pinning strength.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Molecular dynamic simulations were carried out to investigate the properties of the critical depinning force in high temperature superconductors at several vortex densities at the first matching ...field. The study was conducted on samples with periodic square arrays of vortices and pinning sites. The variables in the simulations were the vortex density, the pinning sites density, the temperature, the pinning strength, the size of pinning sites. The critical depinning force is found to decrease with temperature for all first matching field densities. The rate of this decrease was found to be slower as the pinning strength and size of pinning site gets larger. At low temperatures and for large pinning strengths, the critical depinning force was found to decrease with increasing the first matching field density. But very interesting results were obtained at moderate temperatures where the critical depinning force was found to increase as the first matching field density increases. The same behavior of the critical depinning force was found at low temperatures, for small pinning strengths. These unexpected results were attributed to a vortex structural phase transition from a disordered state to an ordered state.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We have investigated the role of pinning strength and density on the equilibrium vortex-lattice to vortex-liquid phase transition under several applied magnetic fields. This study was conducted using ...a series of molecular dynamic simulations on several samples with different strengths and densities of pinning sites which are arranged in periodic square arrays. We have found a single solid-liquid vortex transition when the vortex filling factor n > 1. We have found that, for fixed pinning densities and strengths, the melting temperature, Tm, decreases almost linearly with increasing magnetic field. Our results provide direct numerical evidence for the significant role of both the strength and density of pinning centers on the position of the melting line. We have found that the vortex-lattice to vortex-liquid melting line shifts up as the pinning strength or the pinning density was increased. The effect on the melting line was found to be more pronounced at small values of strength and density of pinning sites.
We have conducted extensive series of molecular dynamic simulations on driven vortex lattices interacting with periodic square arrays of pinning sites. In solving the over damped equation of vortex ...motion we took into account the vortex–vortex repulsion interaction, the attractive vortex–pinning interaction, and the driving Lorentz force at several values of temperature. We have studied the effect of varying the driving Lorentz force and varying the pinning strength on the critical current for several pinning densities, and temperature values. We have found that the pinning strength play an important role in enhancing the critical current over the whole temperature range. At low temperatures, the critical current was found to increase linearly with increasing the pinning strengths for all pinning densities. As the temperature increases, the effect of small pinning strengths diminishes and becomes insignificant at high temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We have studied the effect of temperature and pinning density on the critical depinning force for several values of pinning strength through an extensive series of molecular dynamic simulations on ...driven vortex lattices interacting with square periodic arrays of pinning sites. We have solved the overdamped equation of vortex motion taking into account the vortex-vortex repulsion interaction, the attractive vortex pinning interaction, the thermal force, and the driving Lorentz force. We have found that the critical depinning force, as a function of the pinning density, may decrease, increase, or even remain constant, depending on the temperature and pinning strength values.
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