Ion-implantation-caused special damage profiles determined by spectroscopic ellipsometry in crystalline and in relaxed (annealed) amorphous silicon

We previously developed a fitting method of several parameters to evaluate ion-implantation-caused damage profiles from spectroscopic ellipsometry (SE) (M. Fried et al., J. Appl. Phys., 71 (1992) 2835). Our optical model consists of a stack of layers with fixed and equal thicknesses and damage levels described by a depth profile function (coupled half Gaussians). The complex refractive index of each layer is calculated from the actual damage level by Bruggeman effective medium approximation (EMA) using crystalline (c-Si) and amorphous (a-Si) silicon as end-points. Two examples are presented of the use of this method with modified optical models. First, we investigated the surface damage formed by room temperature B+ and N+ implantation into silicon. For the analysis of the SE data we added a near surface amorphous layer to the model with variable thickness. Second, we determined 20 keV B+ implantation-caused damage profiles in relaxed (annealed) amorphous silicon. In this special case, the complex refractive index of each layer was calculated from the actual damage level by the EMA using relaxed a-Si and implanted a-Si as end-points. The calculated profiles are compared with Monte Carlo simulations (TRIM code); good agreement is obtained

Ion-implantation induced anomalous surface amorphization in silicon

Spectroscopic ellipsometry (SE), high-depth-resolution Rutherford backscattering (RBS) and channeling have been used to examine the surface damage formed by room temperature N and B implantation into silicon. For the analysis of the SE data we used the conventional method of assuming appropriate optical models and fitting the model parameters (layer thicknesses and volume fraction of the amorphous silicon component in the layers) by linear regression. The dependence of the thickness of the surface-damaged silicon layer (beneath the native oxide layer) on the implantation parameters was determined: the higher the dose, the thicker the disordered layer at the surface. The mechanism of the surface amorphization process is explained in relation to the ion beam induced layer-by-layer amorphization. The results demonstrate the applicability of Spectroscopic ellipsometry with a proper optical model. RBS, as an independent cross-checking method supported the constructed optical model

Surface and bulk magnetic behaviour of sputtered CoCr films

The magnetic hysteresis curve at the surface of RF- and magnetron-sputtered CoCr (81/19 at.%), in the thickness range of 20-2500 nm, was measured with a rotating-analyser apparatus using the magneto-optic Kerr effect. The Kerr rotation of CoCr films (13-19 at.% Cr) decreases with increasing Cr content, and depends slightly on wavelength, showing a faint minimum between 550 and 600 nm. The surface hysteresis is compared with the bulk hysteresis as measured with a VSM. For RF films the maximum surface coercivity is higher than the bulk coercivity, being 120 and 95 kA m-1 respectively for 80 nm thick films but an abrupt decrease in only the surface coercivity was found at t=125 nm. The coercivity of magnetron-sputtered CoCr deviates from that of RF-sputtered films. Until a maximum coercivity is reached at approximately=1 mu m, the surface coercivity is about 20% higher, but at approximately=2 mu m both coercivities decrease strongly. The existence of reversed domains within the main domains of CoCr is proposed, and the reversal mechanism is thought to be one in which the reversed domains grow at the expense of the main domain

Ziekterisico kan flink omlaag

Aankoop van vee is een grote risicofactor voor de insleep van dierziekten. Mensen die in contact komen met dieren op verschillende bedrijven dienen bedrijfskleding aan te trekken. Jongvee is erg gevoelig voor bepaalde ziektekiemen. De overdracht van ziektekiemen van oudere dieren via bijvoorbeeld mest en melk moeten dan ook voorkomen worden

The effects of foreign language programmes in early childhood education and care: a systematic review

This systematic review investigates the effects of foreign language programmes in early childhood education and care (ECEC), which are increasingly popular. Foreign language ECEC centres familiarise very young children with a foreign language, and in general also expose them to the majority language. This review synthesises research on the effects of foreign language ECEC on children’s development of the foreign language, majority language, first language, and wellbeing, as well as programme-related and child-related factors that influence language development and wellbeing. The reviewed studies indicate that foreign language ECEC fosters foreign language development, without negatively impacting the majority and first language. Children can experience positive wellbeing in these programmes, but only if programmes are play-based and if the language policy is not too strict. Some studies report that programme characteristics, such as input quantity, language policy, and teacher strategies, modulate the effects of foreign language ECEC on language development and wellbeing. Few of the reviewed studies examined child characteristics, but the available findings indicate that children’s age, as well as their temperament and in-class behaviour, are related to foreign language learning. However, these findings need to be interpreted with caution, because research into foreign language ECEC is still in its infancy

Immunomodulation Through Low-Dose Radiation for Severe COVID-19:Lessons From the Past and New Developments

Low-dose radiation therapy (LD-RT) has historically been a successful treatment for pneumonia and is clinically established as an immunomodulating therapy for inflammatory diseases. The ongoing COVID-19 pandemic has elicited renewed scientific interest in LD-RT and multiple small clinical trials have recently corroborated the historical LD-RT findings and demonstrated preliminary efficacy and immunomodulation for the treatment of severe COVID-19 pneumonia. The present review explicates archival medical research data of LD-RT and attempts to translate this into modernized evidence, relevant for the COVID-19 crisis. Additionally, we explore the putative mechanisms of LD-RT immunomodulation, revealing specific downregulation of proinflammatory cytokines that are integral to the development of the COVID-19 cytokine storm induced hyperinflammatory state. Radiation exposure in LD-RT is minimal compared to radiotherapy dosing standards in oncology care and direct toxicity and long-term risk for secondary disease are expected to be low. The recent clinical trials investigating LD-RT for COVID-19 confirm initial treatment safety. Based on our findings we conclude that LD-RT could be an important treatment option for COVID-19 patients that are likely to progress to severity. We advocate the further use of LD-RT in carefully monitored experimental environments to validate its effectiveness, risks and mechanisms of LD-RT

Cytotoxicity models of Huntington's disease and relevance of hormetic mechanisms: A critical assessment of experimental approaches and strategies.

Abstract This paper assesses in vivo cytotoxicity models of Huntington's disease (HD). Nearly 150 agents were found to be moderately to highly effective in mitigating the pathological sequelae of cytotoxic induction of HD features in multiple rodent models. Typically, rodents are treated with a prospective HD-protective agent before, during, or after the application of a chemical or transgenic process for inducing histopathological and behavioral symptoms of HD. Although transgenic and knockout rodent models (1) display relatively high construct and face validity, and (2) are ever more routinely employed to mimic genetic-to-phenotypic expression of HD features, toxicant models are also often employed, and have served as valuable test beds for the elucidation of biochemical processes and discovery of therapeutic targets in HD. Literature searches of the toxicant HD rodent models yielded nearly 150 agents that were moderately to highly effective in mitigating pathological sequelae in multiple mouse and rat HD models. Experimental models, study designs, and exposure protocols (e.g., pre- and post-conditioning) used in testing these agents were assessed, including dosing strategies, endpoints, and dose-response features. Hormetic-like biphasic dose responses, chemoprotective mechanisms, and the translational relevance of the preclinical studies and their therapeutic implications are critically analyzed in the present report. Notably, not one of the 150 agents that successfully delayed onset and progression of HD in the experimental models has been successfully translated to the treatment of humans in a clinical setting. Potential reasons for these translational failures are (1) the inadequacy of dose-response analyses and subsequent lack of useful dosing data; (2) effective rodent doses that are too high for safe human application; (3) key differences between the experimental models and humans in pharmacokinetic/pharmacodynamic features, ages and routes of agent administration; (4) lack of robust pharmacokinetic, mechanistic or systematic approaches to probe novel treatment strategies; and (5) inadequacies of the chemically induced HD model in rats to mimic accurately the complex genetic and developmental origin and progression of HD in humans. These deficiencies need to be urgently addressed if pharmaceutical agents for the treatment of HD are going to be successfully developed in experimental models and translated with fidelity to the clinic

A software pipeline for processing and identification of fungal ITS sequences

<p>Abstract</p> <p>Background</p> <p>Fungi from environmental samples are typically identified to species level through DNA sequencing of the nuclear ribosomal internal transcribed spacer (<it>ITS</it>) region for use in BLAST-based similarity searches in the International Nucleotide Sequence Databases. These searches are time-consuming and regularly require a significant amount of manual intervention and complementary analyses. We here present software – in the form of an identification pipeline for large sets of fungal <it>ITS </it>sequences – developed to automate the BLAST process and several additional analysis steps. The performance of the pipeline was evaluated on a dataset of 350 <it>ITS </it>sequences from fungi growing as epiphytes on building material.</p> <p>Results</p> <p>The pipeline was written in Perl and uses a local installation of NCBI-BLAST for the similarity searches of the query sequences. The variable subregion <it>ITS2 </it>of the <it>ITS </it>region is extracted from the sequences and used for additional searches of higher sensitivity. Multiple alignments of each query sequence and its closest matches are computed, and query sequences sharing at least 50% of their best matches are clustered to facilitate the evaluation of hypothetically conspecific groups. The pipeline proved to speed up the processing, as well as enhance the resolution, of the evaluation dataset considerably, and the fungi were found to belong chiefly to the <it>Ascomycota</it>, with <it>Penicillium </it>and <it>Aspergillus </it>as the two most common genera. The <it>ITS2 </it>was found to indicate a different taxonomic affiliation than did the complete <it>ITS </it>region for 10% of the query sequences, though this figure is likely to vary with the taxonomic scope of the query sequences.</p> <p>Conclusion</p> <p>The present software readily assigns large sets of fungal query sequences to their respective best matches in the international sequence databases and places them in a larger biological context. The output is highly structured to be easy to process, although it still needs to be inspected and possibly corrected for the impact of the incomplete and sometimes erroneously annotated fungal entries in these databases. The open source pipeline is available for UNIX-type platforms, and updated releases of the target database are made available biweekly. The pipeline is easily modified to operate on other molecular regions and organism groups.</p