Designing and optimizing gratings for soft X-ray diffraction efficiency

The diffraction efficiency is critical to the speed and sensitivity of grating-based spectroscopy instruments. This becomes particularly important for soft x-ray instruments, used on material science beamlines at synchrotrons around the world, where the low reflectivity of materials makes it challenging to create efficient optics. The efficiency of soft x-ray gratings is examined from a rigorous electromagnetic approach using the differential method, adapted for deep gratings using the S-matrix propagation algorithm. New software is written to provide an open-source implementation with fast performance on cluster computing resources. Trends in diffraction efficiency are examined as a function of grating materials, coatings, groove geometry, and incidence conditions; these trends are used to provide recommendations for instrument design, including the identification of a new principle of optimal incidence angle. Efficiency calculations and optimizations are applied to the design of a high-performance soft x-ray emission spectrometer for the REIXS beamline at the Canadian Light Source. The process produces an innovative design that exploits an efficiency peak in the third diffraction order to offer higher resolution than would otherwise be possible given the space constraints of the machine. Finally, the spectrometer's actual gratings are measured for diffraction efficiency as a function of wavelength. Although the real-world efficiencies differ substantially from the nominal calculations, the differences are explained by incorporating real-world effects: geometry errors, groove variation, oxidation, and surface roughness. A fitting process is proposed to match the calculated to the measured efficiency spectra. The geometry parameters predicted by the fitting process are found to agree exactly with atomic force microscopy (AFM) measurements for all the gratings studied. Because each grating parameter affects the shape of the efficiency spectrum in a different way, the spectrum can be considered as a unique "fingerprint" or "hash"; we conclude that this might be extended to use efficiency measurements and fitting calculations to characterize grating parameters that are difficult or impossible to measure directly

A Mobile-based Healthcare Utilization Assessment in Rural Ghana

AbstractBackgroundIdentifying the needs of disadvantaged populations is essential to addressing those needs. Investigations of healthcare access in rural sub-Saharan Africa rely on in-person interviews and SMS, which have distinct limitations.ObjectivesTo use interactive-voice-response (IVR) technology to survey healthcare utilization patterns in rural Ghana.MethodsThis project used IVR to survey healthcare behavior by mobile phone users in rural Ghana. Automated voice messages offered an 18-question survey in 5 local languages.ResultsOut of >64,000 placed calls, 8,601 proceeded to the survey. Survey completion rate was 1.3%, for 827 full respondents, at a total cost of 5 USD for each full survey response.ConclusionsIVR has limitations, but the ability to engage rural populations with low time and resource investment is valuable

Spatial Pattern Switching Enables Cyclic Evolution in Spatial Epidemics

Infectious diseases often spread as spatial epidemic outbreak waves. A number of model studies have shown that such spatial pattern formation can have important consequences for the evolution of pathogens. Here, we show that such spatial patterns can cause cyclic evolutionary dynamics in selection for the length of the infectious period. The necessary reversal in the direction of selection is enabled by a qualitative change in the spatial pattern from epidemic waves to irregular local outbreaks. The spatial patterns are an emergent property of the epidemic system, and they are robust against changes in specific model assumptions. Our results indicate that emergent spatial patterns can act as a rich source for complexity in pathogen evolution

Relationships between cardiorespiratory fitness, hippocampal volume, and episodic memory in a population at risk for Alzheimer’s disease

Introduction: Cardiorespiratory fitness (CRF) has been shown to be related to brain health in older adults. In individuals at risk for developing Alzheimer\u27s disease (AD), CRF may be a modifiable risk factor that could attenuate anticipated declines in brain volume and episodic memory. The objective of this study was to determine the association between CRF and both hippocampal volume and episodic memory in a cohort of cognitively healthy older adults with familial and/or genetic risk for Alzheimer\u27s disease (AD). Methods: Eighty‐six enrollees from the Wisconsin Registry for Alzheimer\u27s Prevention participated in this study. Participants performed a graded maximal exercise test, underwent a T‐1 anatomical magnetic resonance imaging scan, and completed the Rey Auditory Verbal Learning Test (RAVLT). Results: There were no significant relationships between CRF and HV or RAVLT memory scores for the entire sample. When the sample was explored on the basis of gender, CRF was significantly associated with hippocampal volume for women. For men, significant positive associations were observed between CRF and RAVLT memory scores. Summary: These results suggest that CRF may be protective against both hippocampal volume and episodic memory decline in older adults at risk for AD, but that the relationships may be gender specific

Resource use, governance and case load of rapid response teams in Australia and New Zealand in 2014

Background: Rapid response teams (RRTs) are a mandatory element of Australian national health care policy. However, the uptake, resourcing, case load and funding of RRTs in Australian and New Zealand hospitals remain unknown.Aim: To assess the clinical activity, funding, staffing and governance of RRTs in Australian and New Zealand hospitals.Methods: Survey of Australian and New Zealand hospitals as part of a biannual audit of intensive care resources and capacity.Results: Of 207 hospitals surveyed, 165 (79.7%) participated, including 22 (13.3%) from New Zealand. RRTs were present in 138/143 (95.5%) Australian and 11/22 (50%) New Zealand hospitals equipped with intensive care units (P < 0.001). Additional funding was provided in 43/146 hospitals (29.4%) but was more likely in tertiary ICUs (P < 0.001) and in New Zealand (P = 0.012). ICU staff participated in 147/148 RRTs (99.3%), which involved medical staff only (10.2%), nursing staff only (6.8%), and both medical and nursing staff (76.2%). Isolated ICU nursing involvement was more common in smaller ICUs (P = 0.005), in rural/regional and metropolitan hospitals (P = 0.04), and in New Zealand (P = 0.006). Dedicated ICU outreach registrars and consultants were present in 19/146 hospitals (13.0%) and 14/145 hospitals (9.7%), respectively. The ICU provided oversight for 122/147 RRTs (83%). In the 2013–14 financial year, there were more than 104 000 RRT calls.Conclusion: In cases where data were known, ICU staff provided staff for most RRTs, and oversight for more than 80% of RRTs. However, additional funding for ICU RRT staff and dedicated doctors was relatively uncommon

Two Component Systems: Physiological Effect of a Third Component

Signal transduction systems mediate the response and adaptation of organisms to environmental changes. In prokaryotes, this signal transduction is often done through Two Component Systems (TCS). These TCS are phosphotransfer protein cascades, and in their prototypical form they are composed by a kinase that senses the environmental signals (SK) and by a response regulator (RR) that regulates the cellular response. This basic motif can be modified by the addition of a third protein that interacts either with the SK or the RR in a way that could change the dynamic response of the TCS module. In this work we aim at understanding the effect of such an additional protein (which we call “third component”) on the functional properties of a prototypical TCS. To do so we build mathematical models of TCS with alternative designs for their interaction with that third component. These mathematical models are analyzed in order to identify the differences in dynamic behavior inherent to each design, with respect to functionally relevant properties such as sensitivity to changes in either the parameter values or the molecular concentrations, temporal responsiveness, possibility of multiple steady states, or stochastic fluctuations in the system. The differences are then correlated to the physiological requirements that impinge on the functioning of the TCS. This analysis sheds light on both, the dynamic behavior of synthetically designed TCS, and the conditions under which natural selection might favor each of the designs. We find that a third component that modulates SK activity increases the parameter space where a bistable response of the TCS module to signals is possible, if SK is monofunctional, but decreases it when the SK is bifunctional. The presence of a third component that modulates RR activity decreases the parameter space where a bistable response of the TCS module to signals is possible

Management of labor in Eisenmenger syndrome with inhaled nitric oxide

Administration of nitric oxide by means of inhalation during the labor of a woman with Eisenmenger's syndrome caused by an atrial septal defect resulted in improved oxygenation and initial pulmonary arterial pressure. She gave birth to a live infant at 34 weeks' gestation but died of worsening pulmonary hypertension and heart failure 21 days post partum