Extremely low secondary electron emission from metal/dielectric particulate coatings

Research on low secondary electron emission coatings is essential for the design and manufacture of space high-power RF devices without multipactor discharge. This paper discusses some of the factors that reduce secondary electron emission for metal-dielectric surfaces. We have studied the total electron yield (TEY) behavior of a particulate coating composed of a mixture of a metal (aluminum) nanoparticulates in solid state contact with a particulate dielectric material (polyimide thermosetting resin). Surface charging, roughness, and volume fraction are utilized as the main parameters to characterize the electron emission behavior, which can effectively be determined by continuous (total dose 42.5 nC/mm2) and pulsed (1,1 fC/mm2/pulse) electron irradiation methods. Apart from the important role played by surface composition in the TEY, the influence of the dielectric volume fraction has demonstrated to be critical to achieve a significant reduction of TEY. Analytical surface techniques such as field emission scanning microscopy and X-ray photoelectron spectroscopy were used, because they are very effective in providing insight into the effect of charging on the surface. Typical TEY parameters of the aluminum foil exposed to the air are: the first crossover energy, E1=20 eV, TEY maximum, σmax = 2.9, and Emax = XXX eV; these contrast with the dielectric values: E1= 30 eV, σmax = 2.5, and Emax = XXX eV. However, it was found that E1 of the particulate sample increased with increasing dielectric volume fraction. An extremely high first crossover energy, E1\u3e1000eV, was obtained after the gold metallization of the metal/dielectric coatings of 0.75 volume fraction. It is also remarkable that TEY was 0.2 for E\u3c1000\u3eeV, the low energy emitted electrons appear to be reabsorbed. Another remarkable fact is that TEY curves measured by using either the continuous or the pulsed methods overlap in the whole primary energy range, dissipate the much larger electron dose of the continuous method as compared to the very low dose of the pulsed method; this result is usually understood as an indication of minimal influence of charging on TEY

Propedéutica a una definición del "maestro colombiano" Una mirada desde las Prácticas Pedagógicas

The colombian teacher In order to approach, understand and then write about the identity of the teacher (hereinafter IM), it is necessary to examine its history from the pedagogical practices in order to identify the theories that have supported the curricular and administrative organization of the educational institution and thus project in the world of today that type of teacher is needed to face the current challenges as it is a globalized world with all its economic, technological, social, personal and cultural implications.El maestro colombiano Para acercarse, comprender y luego escribir sobre la identidad del maestro (en adelante IM), es necesario examinar su historia desde las prácticas pedagógicas con el fin de identificar las teorías que han sustentado la organización curricular y administrativa de la institución educativa y así proyectar en el mundo de hoy que tipo de docente se precisa para enfrentar los retos actuales como es un mundo globalizado con todas sus implicaciones económicas, tecnológicas, sociales, personales y culturales

Siderophore production by Bacillus megaterium : effect of growth-phase and cultural conditions

Siderophore production by Bacillus megaterium was detected, in an iron-deficient culture medium, during the exponential growth phase, prior to the sporulation, in the presence of glucose; these results suggested that the onset of siderophore production did not require glucose depletion and was not related with the sporulation. The siderophore production by B. megaterium was affected by the carbon source used. The growth on glycerol promoted the very high siderophore production (1,182 μmol g−1 dry weight biomass); the opposite effect was observed in the presence of mannose (251 μmol g−1 dry weight biomass). The growth in the presence of fructose, galactose, glucose, lactose, maltose or sucrose, originated similar concentrations of siderophore (546–842 μmol g−1 dry weight biomass). Aeration had a positive effect on the production of siderophore. Incubation of B. megaterium under static conditions delayed and reduced the growth and the production of siderophore, compared with the incubation in stirred conditions.The authors thank Porto University/Totta Bank for their financial support through the project "Microbiological production of chelating agents" (Ref: 180). The authors also thank the Fundacao para a Ciencia e a Tecnologia (FCT) through the Portuguese Government for their financial support of this work through the grants Strategic project-LA23/2013-2014 (IBB) and PEST-C/EQB/LA0006/2011 (REQUIMTE). Manuela D. Machado gratefully acknowledges the postdoctoral (SFRH/BPD/72816/2010) grant from FCT

DAX-1 expression in human breast cancer: comparison with estrogen receptors ER-α, ER-β and androgen receptor status

BACKGROUND: So far there have been no reports on the expression pattern of DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1) in human breast cells and its relationship to the estrogen receptors, ER-α and ER-β, and the androgen receptor (AR). METHODS: In this study we evaluated, by immunohistochemistry and Western blot analysis, the presence and distribution of DAX-1 in benign breast disease (BBD), in situ carcinoma (CIS), and ductal and lobular breast carcinomas. RESULTS: In BBD and breast carcinomas, DAX-1 was present in both the nuclei and the cytoplasm of epithelial cells, although in infiltrative carcinomas the percentage of nuclear immunoreaction was higher than in CIS. An important relation was observed between DAX-1 and AR expression and between this orphan receptor and nodal status. CONCLUSION: DAX-1 might modify the AR and ER-β intracellular location, and because a direct positive relation between the expression of these three receptors was found it could be assumed that the presence of DAX-1 in neoplastic cells might indicate a possible failure of endocrine therapies

Antimalarial Exposure Delays Plasmodium falciparum Intra-Erythrocytic Cycle and Drives Drug Transporter Genes Expression

BACKGROUND: Multi-drug resistant Plasmodium falciparum is a major obstacle to malaria control and is emerging as a complex phenomenon. Mechanisms of drug evasion based on the intracellular extrusion of the drug and/or modification of target proteins have been described. However, cellular mechanisms related with metabolic activity have also been seen in eukaryotic systems, e.g. cancer cells. Recent observations suggest that such mechanism may occur in P. falciparum. METHODOLOGY/PRINCIPAL FINDINGS: We therefore investigated the effect of mefloquine exposure on the cell cycle of three P. falciparum clones (3D7, FCB, W2) with different drug susceptibilities, while investigating in parallel the expression of four genes coding for confirmed and putative drug transporters (pfcrt, pfmdr1, pfmrp1 and pfmrp2). Mefloquine induced a previously not described dose and clone dependent delay in the intra-erythrocytic cycle of the parasite. Drug impact on cell cycle progression and gene expression was then merged using a non-linear regression model to determine specific drug driven expression. This revealed a mild, but significant, mefloquine driven gene induction up to 1.5 fold. CONCLUSIONS/SIGNIFICANCE: Both cell cycle delay and induced gene expression represent potentially important mechanisms for parasites to escape the effect of the antimalarial drug

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Characteristics of slow progression to diabetes in multiple islet autoantibody-positive individuals from five longitudinal cohorts:the SNAIL study

Aims/hypothesis Multiple islet autoimmunity increases risk of diabetes, but not all individuals positive for two or more islet autoantibodies progress to disease within a decade. Major islet autoantibodies recognise insulin (IAA), GAD (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A). Here we describe the baseline characteristics of a unique cohort of ‘slow progressors’ (n = 132) who were positive for multiple islet autoantibodies (IAA, GADA, IA-2A or ZnT8A) but did not progress to diabetes within 10 years. Methods Individuals were identified from five studies (BABYDIAB, Germany; Diabetes Autoimmunity Study in the Young [DAISY], USA; All Babies in Southeast Sweden [ABIS], Sweden; Bart’s Oxford Family Study [BOX], UK and the Pittsburgh Family Study, USA). Multiple islet autoantibody characteristics were determined using harmonised assays where possible. HLA class II risk was compared between slow progressors and rapid progressors (n = 348 diagnosed <5 years old from BOX) using the χ2 test. Results In the first available samples with detectable multiple antibodies, the most frequent autoantibodies were GADA (92%), followed by ZnT8A (62%), IAA (59%) and IA-2A (41%). High risk HLA class II genotypes were less frequent in slow (28%) than rapid progressors (42%, p = 0.011), but only two slow progressors carried the protective HLA DQ6 allele. Conclusion No distinguishing characteristics of slow progressors at first detection of multiple antibodies have yet been identified. Continued investigation of these individuals may provide insights into slow progression that will inform future efforts to slow or prevent progression to clinical diabetes

Development and evaluation of real time RT-PCR assays for detection and typing of Bluetongue virus

Bluetongue virus is the type species of the genus Orbivirus, family Reoviridae. Bluetongue viruses (BTV) are transmitted between their vertebrate hosts primarily by biting midges (Culicoides spp.) in which they also replicate. Consequently BTV distribution is dependent on the activity, geographic distribution, and seasonal abundance of Culicoides spp. The virus can also be transmitted vertically in vertebrate hosts, and some strains/serotypes can be transmitted horizontally in the absence of insect vectors. The BTV genome is composed of ten linear segments of double-stranded (ds) RNA, numbered in order of decreasing size (Seg-1 to Seg-10). Genome segment 2 (Seg-2) encodes outer-capsid protein VP2, the most variable BTV protein and the primary target for neutralising antibodies. Consequently VP2 (and Seg-2) determine the identity of the twenty seven serotypes and two additional putative BTV serotypes that have been recognised so far. Current BTV vaccines are serotype specific and typing of outbreak strains is required in order to deploy appropriate vaccines. We report development and evaluation of multiple ‘TaqMan’ fluorescence-probe based quantitative real-time type-specific RT-PCR assays targeting Seg-2 of the 27+1 BTV types. The assays were evaluated using orbivirus isolates from the ‘Orbivirus Reference Collection’ (ORC) held at The Pirbright Institute. The assays are BTV-type specific and can be used for rapid, sensitive and reliable detection / identification (typing) of BTV RNA from samples of infected blood, tissues, homogenised Culicoides, or tissue culture supernatants. None of the assays amplified cDNAs from closely related but heterologous orbiviruses, or from uninfected host animals or cell cultures