Parametric FEM simulation of composite barrier FTJs under external bias at room temperature

A study on a parametrized model of a composite barrier FTJ (three-interface system, with a non-polar dielectric layer) under an external bias voltage and at room temperature, using FEM-based simulations, was performed. The approach involves the Thomas-Fermi model assuming incomplete screening of polarization charges for building the energy barrier profile, and numerically simulates the electron transport through the barrier by bias-voltage-dependent tunneling, using Tsu-Esaki formulation. That naturally include the temperature dependent contributions to the total current density. The TER coefficient and current densities are computed considering variation of a large set of parameters that describe the composite barrier FTJ system in realistic physical range of values with respect to a reference (prototypical) system. In this study, the parametric simulations were performed starting from selected data reported on the SRO/STO/BTO/SRO heterostructure. The most important results of our work can be stated as follows: i) The FEM simulations prove to be reliable approach when we are interested in the prediction of FTJ characteristics at temperatures close to 300 K, and ii) We show that several configurations with large TER values may be predicted, but at the expense of very low current densities in the ON state. We suggest that the results may be useful for assessing the FTJ performances at ambient temperature, as well as to design preoptimized FTJs by using different combinations of materials to comply with a set of properties of a specific model

Surface reconstruction of polycrystalline TiO_2 in oxygen atmosphere

Polyerystalline TiO2 surface reconstruction in oxygen atmosphere has been investigated by atomic force microscopy (AFM) and cathodoluminescence in the scanning electron microscopy (SEM-CL). The reactivity to oxygen is related to the presence of defects as interstitial Ti ions, that induce growth of protrusions, large terraces and polygonal shaped structures

Priming with Vitamin U Enhances Cold Tolerance of Lettuce (Lactuca sativa L.)

Priming may be an efficient pre-treatment of plants in order to enhance their ability to cope with unfavourable growth conditions, and to improve defensive metabolism through elevated levels of protective substances which may also act as health-promoting agents upon human consumption. The aim of this work was to evaluate the beneficial influence of priming with the naturally occurring, but scarcely known vitamin U (S-methylmethionine) on cold stress tolerance of lettuce (the frequently grown ‘May King’ cultivar). Effects on germination, photosynthetic efficiency, as well as on health-promoting carotenoid and vitamin C contents were investigated. Photosynthetic capacity, strongly related to productivity, was evaluated with parameters of induced chlorophyll fluorescence and of leaf gas exchange through stomata, using plants grown in hydroponic cultures. Priming with vitamin U significantly compensated for the delaying effect of low temperature (5 °C) on seed germination, as well as for inhibition of light-converting photochemical reactions and of carbon dioxide assimilation by cold stress. Use of vitamin U to prime lettuce plantlets for low temperature stress resulted in an elevated content of carotenoid pigments and of vitamin C in leaves, which improve the quality of consumed lettuce with respect to the health-promoting capacity. This beneficial influence of vitamin U was not proportional with its concentration (2 mM had no stronger effects than 0.25 mM), so small amounts of this substance were sufficient for a sustained efficiency in promoting hardening against chilling temperatures. This is the first report on priming of lettuce for cold tolerance by using S-methylmethionine (vitamin U), with a possible application in improvement of crop quality and productivity

Cathodoluminescence from mechanically cracked porous silicon

Cathodoluminescence of porous silicon after mechanical damage with a tip has been studied in the scanning electron microscope. Mechanical damage results in the exposure of new surfaces related to fracture and to small particles appearing over the porous silicon layer. The freshly generated surfaces caused an increase of several orders of magnitude in the luminescence efficiency

Ideal models of good inpatient care for adults with intellectual disability: Lessons from England

Background: In recent years, a significant proportion of inpatient facilities for people with intellectual disabilities and/or autism has been de-commissioned in England, This has resulted in individuals with intellectual disabilities being sent to distant hospitals far away from their families and carers leading to challenges in follow-up, community care and interventions. The impact of de-institutionalisation, has often caused patient trauma, family distress and subsequent discharge difficulties. Not every individual with intellectual disabilities and/or autism requires inpatient care but inpatient care when needed has to be local, adequate and appropriate. Aims: To evaluate current evidence of utility of inpatient models for people with intellectual disabilities and outline best clinical practice. Method: PubMed, CINAHL, EMBASE, Cochrane Library, Scopus, Web of Science were searched with key search terms. The search was conducted by the information specialist and identified abstracts screened further for inclusion criteria, methodological issues, and other appropriate characteristics. Twenty-three papers were included in the rapid review. Papers shortlisted had the inclusion criteria applied against the full text version independently by two reviewers. Disagreements regarding eligibility of studies was resolved by discussion and consensus within the project team. Key data related to in-patient models of care was extracted from the included papers, which included year of study, design, study objectives, target population, method/s tested, outcomes reported, country of study/studies, and results. Data extraction was performed by two reviewers and reviewed by the project team. Results: From the review of services for people with intellectual disabilities, we came across four broad models/frameworks/approaches. Evidence on what worked for inpatient service provision tended to be based on models developed and implemented locally. Conclusions: We make recommendations for the best clinical practice and standards. Both clinical service providers and policymakers need to be aware of specific needs of individuals with intellectual disability and/or autism. </jats:sec

Synthesis and Cathodoluminescence of Undoped and Cr^3^+-Doped Sodium Titanate Nanotubes and Nanoribbons

We report on the synthesis of Cr^3^+-doped sodium titanate nanotubes and nanoribbons by a hydrothermal method. The presence of dopant ions in these nanostructures was confirmed by high angle annular dark field scanning transmission electron microscopy in combination with electron energy loss spectroscopy measurements. Luminescence properties of undoped and Cr^3^+-doped sodium titanate nanotubes and nanoribbons were investigated by cathodoluminescence in the scanning electron microscope. A broad visible band in the range 1.7−2.7 eV is observed in these nanostructures. Such emission is similar to that observed in bulk anatase TiO_2 and titanate powders, and is related to TiO_6 octahedra, which is a common feature to all the samples investigated. Near-infrared emission, sometimes attributed to Ti^3^+ interstitials, is observed in bulk powders but is absent in the titanate nanotubes and nanoribbons. Incorporation of Cr^3^+ between the titanate layers of the nanostructures is revealed by the characteristic intraionic emission line at 1.791 eV. Sodium titanate nanoribbons appear to be an effective host for optically active Cr^3^+ ions, as compared with nanotubes or bulk powder

Serum concentrations of cytokines and adhesion molecules as markers of endothelial dysfunction

Citokīnu un adhēzijas molekulu koncentrācijas serumā kā endotēlija disfunkcijas pakāpes rādītāji Anotācija Pētījuma mērķis ir novērtēt, kuru ar endotēlija šūnu funkcijām saistīto molekulu koncentrācijas serumā ir pārliecinošākie endotēlija šūnu funkcionālā stāvokļa rādītāji, kā arī noteikt atšķirīgām endoteliālās disfunkcijas attīstības stadijām raksturīgās izmaiņas. Materiāls ietver 234 personas ar plašu endoteliālās funkcijas variabilitāti. Tika noteikta endotēlija vazodilatējošā atbilde uz acetilholīna, siltuma un postokluzīvās cērpjošās asinsplūsmas stimuliem, kā arī ar endotēlija funkcijām saistītu molekulu seruma koncentrācijas. Rezultāti liecina, ka endotēlija šūnu vazodilatējošo aktivitāte pozitīvi korelē ar adiponektīna, IL-10 un IL-4, bet negatīvi – ar sEselektīna, sICAM-1, TNFα un VEGF koncentrācijām, kā arī vairākas būtiskas rādītāju atšķirības četrās atšķirīgas endotēlija disfunkcijas pakāpes pārstāvošajās pētījuma grupās. Atslēgas vārdi: endotēlija disfunkcija, insulīna rezistence, vazodilatācijas testi, adhēzijas molekulas, adiponektīnsSerum concentrations of cytokines and adhesion molecules as markers of endothelial dysfunction Abstract The aim of this study is to select the serum markers that are most convincing for detection of endothelial function as well as to select the markers characteristic for varied degrees of endothelial dysfunction. The study material includes 234 persons with wide variablilty of endothelial dysfunction. The vasodilatory response of endothelium was detected by acetylcholine-, heat- and post-occlusive shear stress-induced vasodilatation tests and serum concentrations of molecular markers associated with endothelial function was detected. The study results show positive correlations of vasodilatory function with adiponectin, IL-10 and IL-4, and negative correlations with sE-selectin, sICAM-1, TNFα and VEGF concentrations as well as several significant differences between the four study groups representing varied degrees of endothelial dysfunction. Key words: endothelial dysfunction, insulin resistance, vasodilatation tests, adhesion molecules, adiponecti

Resonant excitation of Er ion luminescence in a nanocrystalline silicon matrix

The luminescence of amorphous silicon layers either implanted with Er or co-implanted with Er and O has been studied by photoluminescence (PL) and cathodoluminescence (CL) in the scanning electron microscope. Annealing in nitrogen causes the formation of oxide species and Er-Si complexes or precipitates as well a spectral changes in the visible and infrared ranges. The main CL emission takes place in the visible range while PL spectra reveal intense visible and infrared emission. CL spectra show blue-violet, or green, emission bands whose relative intensities depend on the post-implantation annealing temperature. The PL spectra show a blue-violet band with a series of lines in the violet region related to phonon assisted transitions as well as different emission bands in the range 1200-1500 nm. The influence of the annealing-induced structural changes on the observed spectra is discussed

Cathodoluminescence enhancement in porous silicon cracked in vacuum

An increase of the cathodoluminescence (CL) signal of porous silicon (PS) cracked in vacuum of up to three orders of magnitude has been achieved. Under high electron-beam currents, the samples cracked in interconnected pieces of tens of microns, exposing new surfaces to the electron beam. This treatment enhances the radiative intensity in PS associated with a broadband peaked at 720 nm, which is highly stable while the sample is kept in vacuum. Cross-sectional CL observations show that most of the light is generated in the top surface of the porous layer. The spectral depth dependence of the emitted light reveals a relatively weak blue emission in the region closer to the substrate

Charge carriers photogeneration in pentacene field effect transistors

Organic FET transistors (OFETs) were fabricated on silicon substrates using pentacene as active organic layer and gold source and drain contacts. OFETs were used as test structures in order to study carriers photogeneration effect in organic layers. Photogeneration process was induced by exposing organic layers to a laser beam with 625 nm wavelength and an applied power varying in the range 10-40 mu W. As an effect of light exposure, OFET drain current is increased by three-to-six orders of magnitude, depending on devices operation conditions and their geometry. It is suggested that both electrons and holes generated in pentacene layer contribute to current increase. We put in evidence that electrons trapped at the pentacene-dielectric interface can act as a negative biased gate, demonstrating new operating capabilities of OFETs as well as light sensing functionality