Significance of matrix diagonalization in modelling inelastic electron scattering.

Electron scattering is always applied as one of the routines to investigate nanostructures. Nowadays the development of hardware offers more and more prospect for this technique. For example imaging nanostructures with inelastic scattered electrons may allow to produce component-sensitive images with atomic resolution. Modelling inelastic electron scattering is therefore essential for interpreting these images. The main obstacle to study inelastic scattering problem is its complexity. During inelastic scattering, incident electrons entangle with objects, and the description of this process involves a multidimensional array. Since the simulation usually involves fourdimensional Fourier transforms, the computation is highly inefficient. In this work we have offered one solution to handle the multidimensional problem. By transforming a high dimensional array into twodimensional array, we are able to perform matrix diagonalization and approximate the original multidimensional array with its twodimensional eigenvectors. Our procedure reduces the complicated multidimensional problem to a twodimensional problem. In addition, it minimizes the number of twodimensional problems. This method is very useful for studying multiple inelastic scattering.

Wave-optical modeling beyond the thin-element-approximation.

The optical design and analysis of modern micro-optical elements with high index contrasts and large numerical apertures is still challenging, as fast and accurate wave-optical simulations beyond the thin-element-approximation are required. We introduce a modified formulation of the wave-propagation-method and assess its performance in comparison to different beam-propagation-methods with respect to accuracy, required sampling densities, and computational performance. For typical micro-optical components, the wave-propagation-method is found to be considerably faster and more accurate at even lower sampling densities compared to the different beam-propagation-methods. This enables realistic wave-optical simulations beyond the thin-element-approximation for micro-optical components. As an example, the modified wave-propagation-method is applied for in-line holographic measurements of strongly diffracting objects. From a direct comparison of experimental results and corresponding simulations, the geometric parameters of a test object could be retrieved with high accuracy.

Hepatitis E virus infection: an emerging occupational risk?

BACKGROUND: Hepatitis E virus (HEV) infection is endemic in many developing countries, causing substantial morbidity. Transmission is primarily faeco-oral and is associated with both sporadic infections and epidemics in areas where poor sanitation and weak public health infrastructures exist. Recently, it has become clear that HEV is also an endemic disease in industrialized countries. Moreover, a porcine reservoir and growing evidence of zoonotic transmission have been reported in these countries, suggesting the possibility of occupational transmission to man. AIMS: To summarize the current knowledge on the epidemiology and prevention of transmission of HEV infection in occupational settings. METHODS: The following key words were used to explore PubMed: hepatitis E, disease, epidemiology, profession(al), occupation(al). RESULTS: After screening of the results, 107 publications were retained. In non-endemic regions, seroprevalence varied from a few per cent (2-7.8%) in Europe, Japan and South America to 18.2-20.6% in the USA, Russia, UK, southern France and Asia. A meta-analysis of 12 cross-sectional studies evaluating HEV immunoglobulin G (IgG) seroprevalence in individuals occupationally exposed to swine showed greater odds of seropositivity in the exposed group but also a high degree of heterogeneity. A funnel plot suggested publication bias. CONCLUSIONS: There was a significant association between occupational exposure to swine and HEV IgG seroprevalence, but the level of prevalence detected depended also on the type of HEV IgG kits used. Further research, including on mechanisms and risk factors for infection, as well as the development of better serological tests for identification of infection, is required.

Hepatitis B vaccination policies for student healthcare workers in Europe.

Student healthcare workers represent a particular risk group for hepatitis B virus (HBV) transmission and should be vaccinated as early as possible after the start of their career. An overview of specific HBV policies in European Union countries was conducted through a cross-sectional survey. Answers were received from 17 countries. HBV vaccination was mandatory for medical students and student nurses in five countries and recommended in nine. Pre-vaccination testing was done in five countries and serotesting after vaccination in 12 countries. Policies to ensure student healthcare workers' immunity against HBV should be diverse due to different policies regarding universal HBV vaccination.

The influence of inelastic scattering on EFTEM images--exemplified at 20 kV for graphene and silicon.

We present model-based image simulations for zero-loss and plasmon-loss filtered images at 20 kV for graphene and silicon based on the mutual coherence approach. In addition, a new approximation for the mixed dynamic form factor is introduced. In our calculation multiple elastic scattering and one inelastic scattering are taken into account. The simulation shows that even the intensity of zero-loss filtered image is attenuated by the interference between inelastically scattered waves. Moreover, the intensity of plasmon-loss filtered images cannot be neglected, either.

Co-exposure to lead increases the renal response to low levels of cadmium in metallurgy workers.

PURPOSE: Research on the effect of co-exposure to Cd and Pb on the kidney is scarce. The objective of the present study was to assess the effect of co-exposure to these metals on biomarkers of early renal effect. METHODS: Cd in blood (Cd-B), Cd in urine (Cd-U), Pb in blood (Pb-B) and urinary renal biomarkers, i.e., microalbumin (µ-Alb), beta-2-microglobulin (ß2-MG), retinol binding protein (RBP), N-acetyl-ß-d-glucosaminidase (NAG), intestinal alkaline phosphatase (IAP) were measured in 122 metallurgic refinery workers examined in a cross-sectional survey. RESULTS AND CONCLUSIONS: The median Cd-B, Cd-U, Pb-B were: 0.8 µg/l (IQR = 0.5, 1.2), 0.5 µg/g creatinine (IQR = 0.3, 0.8) and 158.5 µg/l (IQR = 111.0, 219.3), respectively. The impact of Cd-B on the urinary excretion of NAG and IAP was only evident among workers with Pb-B concentrations ≥ 75th percentile. The association between Cd-U and the renal markers NAG and RBP was also evidenced when Pb-B ≥ 75th percentile. No statistically significant interaction terms were observed for the associations between Cd-B or Cd-U and the other renal markers under study (i.e., µ-Alb and ß2-MG). Our findings indicate that Pb increases the impact of Cd exposure on early renal biomarkers.

[Work related health risks among dentist's assistants in Flanders, Belgium]. / Arbeidsgebonden gezondheidsrisico's voor tandartsassistenten in Vlaanderen.

The aim of this research project was to learn more about work-related health risks among dental assistants in Flanders, Belgium. Forty-seven dental assistants completed an extensive questionnaire concerning ionized radiation, protection against infection and exposure to chemicals such as mercury, disinfectants and acrylates. Collective and personal means of protection, musculoskeletal disorders and work-related stress were also evaluated. Pain in the lower back, neck pain and shoulder pain were reported by, respectively, 15%, 17% and 22% of the respondents. Eczema resulting from skin irritation or contact-allergy was reported by 13%. Twenty-three percent of the assistants did not consistently make use ofa radiation badge; 80% wore a mouth mask and 33% wore protective glasses; and 82% was vaccinated against hepatitis B. Almost 10% reported verbal or physical aggression by patients. The mean stress score was 3.95 on a scale from 0 to 10. The results may contribute to the formulation of a number of recommendations for the improvement of the health of dental assistants.

Linear plasmon dispersion in single-wall carbon nanotubes and the collective excitation spectrum of graphene.

We have measured a strictly linear pi plasmon dispersion along the axis of individualized single-wall carbon nanotubes, which is completely different from plasmon dispersions of graphite or bundled single-wall carbon nanotubes. Comparative ab initio studies on graphene-based systems allow us to reproduce the different dispersions. This suggests that individualized nanotubes provide viable experimental access to collective electronic excitations of graphene, and it validates the use of graphene to understand electronic excitations of carbon nanotubes. In particular, the calculations reveal that local field effects cause a mixing of electronic transitions, including the "Dirac cone," resulting in the observed linear dispersion.

Anomalous angular dependence of the dynamic structure factor near Bragg reflections: graphite.

The electron energy-loss function of graphite is studied for momentum transfers q beyond the first Brillouin zone. We find that near Bragg reflections the spectra can change drastically for very small variations in q. The effect is investigated by means of first principle calculations in the random phase approximation and confirmed by inelastic x-ray scattering measurements of the dynamic structure factor S(q, omega). We demonstrate that this effect is governed by crystal local field effects and the stacking of graphite. It is traced back to a strong coupling between excitations at small and large momentum transfers.