310 research outputs found
Si/SiGe bound-to-continuum quantum cascade emitters
Si/SiGe bound-to-continuum quantum cascade emitters designed
by self-consistent 6-band k.p modeling and grown by low energy
plasma enhanced chemical vapour deposition are presented
demonstrating electroluminescence between 1.5 and 3 THz. The
electroluminescence is Stark shifted by an electric field and
demonstrates polarized emission consistent with the design.
Transmission electron microscopy and x-ray diffraction are also
presented to characterize the thick heterolayer structure
Occurrence and profiles of PCBs and PBDEs in harbour seals and harbour porpoises from the southern North Sea
Harbour porpoises (Phocoena phocoen) and harbour seals (Phoca vitulina), two representative top coastal pollution. Concentrations of sum PCBs were 1-2 orders of magnitude higher than concentrations of sum PBDEs (with median values of 23.1 μg.g- lw (lipid weight) and 12.4 μ.g-1 lw for sum PCBs and 0.33 μ.g- lw and 0.76 μ.g-1 lw for sum PBDEs in harbour seals and harbour porpoises respectively) and were highly dependent of age group and gender. For both species, the highest PCB concentrations were observed in adult males as the result of accumulation for years and years, while the highest PBDE concentrations were measured in juveniles probably due to better developed metabolic capacities for these congeners with age in adults. Results for PCBs were higher than observations in harbour seals and porpoises from other areas, while results for PBDEs were comparable indicating that the North Sea is a highly contaminated area. Relative PCB and PBDE profiles were constructed to compare metabolic capacities between harbour seals and porpoises. A higher contribution of lower chlorinated and nonpersistent congeners, such as CB 52, CB 95, CB 101, CB 118 and CB 149 indicated that harbour porpoises are unable to metabolize these compounds. Similar to PCBs, higher contributions of other PBDEs than BDE 47 were observed in harbour porpoises, suggesting that this species has difficulties to metabolize these congeners. In contrast, harbour seals showed a higher ability to metabolize PCBs and PBDEs
Si/SiGe quantum cascade superlattice designs for terahertz emission
Quantum cascade lasers are compact sources that have demonstrated high output powers at THz frequencies.
To date all THz quantum cascade lasers have been realized in III-V materials. Results are presented from
Si1−xGex quantum cascade superlattice designs emitting at around 3 THz which have been grown in two
different chemical vapor deposition systems. The key to achieving successful electroluminescence at THz
frequencies in a p-type system has been to strain the light-hole states to energies well above the radiative
subband states. To accurately model the emission wavelengths, a 6-band k.p tool which includes the effects
of non-abrupt heterointerfaces has been used to predict the characteristics of the emitters. X-ray diffraction
and transmission electron microscopy have been used along with Fourier transform infrared spectroscopy to
fully characterise the samples. A number of methods to improve the gain from the designs are suggested
Electromagnetic levitation containerless processing of metallic materials in microgravity: thermophysical properties
Transitions from the liquid to the solid state of matter are omnipresent. They form a crucial step in the industrial solidification of
metallic alloy melts and are greatly influenced by the thermophysical properties of the melt. Knowledge of the thermophysical
properties of liquid metallic alloys is necessary in order to gain a tight control over the solidification pathway, and over the obtained
material structure of the solid. Measurements of thermophysical properties on ground are often difficult, or even impossible, since
liquids are strongly influenced by earth’s gravity. Another problem is the reactivity of melts with container materials, especially at
high temperature. Finally, deep undercooling, necessary to understand nucleus formation and equilibrium as well as nonequilibrium solidification, can only be achieved in a containerless environment. Containerless experiments in microgravity allow
precise benchmark measurements of thermophysical properties. The electromagnetic levitator ISS-EML on the International Space
Station (ISS) offers perfect conditions for such experiments. This way, data for process simulations is obtained, and a deeper
understanding of nucleation, crystal growth, microstructural evolution, and other details of the transformation from liquid to solid
can be gained. Here, we address the scientific questions in detail, show highlights of recent achievements, and give an outlook on
future work
Efeito da sistematização sobre atributos fÃsicos, quÃmicos e biológicos de um solo de várzea no Rio Grande do Sul.
bitstream/item/110873/1/Boletim-189-web.pd
Pregnant women’s awareness, knowledge and beliefs about pelvic floor muscles: a cross-sectional survey
Introduction and hypothesis: Pregnant women benefit from completing pelvic floor muscle exercises (PFMEs). The aims of the study were to evaluate pregnant women’s levels of awareness, knowledge, and beliefs about the pelvic floor muscles (PFMs) and PFMEs. Methods: A cross-sectional survey was conducted. Respondents were pregnant women over the age of 18 years who attended antenatal clinics in Western Australia (WA). Questionnaire items measured awareness and knowledge about PFMs, confidence and beliefs about engaging in PFMEs, and attendance at antenatal education (ANE) classes. Chi-squared tests examined potential associations between questionnaire items and respondent characteristics. Results: Mean gestation of respondents (n = 633 out of 850; 74% response rate) was 28.7 (+7.8) weeks and 50% were giving birth for the first time. Although 76% of respondents knew that PFMs can prevent urinary incontinence, only 27% knew that they prevented faecal incontinence and 41% thought it was normal to leak urine when pregnant. Only n = 72 (11%) were practicing PFMEs. Respondents who had attended ANE (28%) were significantly more knowledgeable about pelvic floor function (p < .001) and significantly less likely to believe that leaking urine during pregnancy was normal (p = 0.02), compared with those who had not attended ANE. Respondents who did not speak English at home (18%) were significantly less knowledgeable about PFMs and PFMEs, and significantly less likely to have attended, or planned to attend, ANE classes. Conclusion: Pregnant women require more health education regarding PFMs. Education should be provided using diverse modes, especially for women from migrant backgrounds and women who do not plan to attend formal ANE classes
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