Stellar Spectroscopy: New Methods and Insights

The study of the chemical evolution of stars is of crucial importance since they play a major role in the enrichment of the chemistry of the universe. Throughout their lifetime, stars undergo several processes that can alter their chemistry. Gradually, the nucleosynthesis products from the interior of the star are radiatively and convectively levitated and mixed with the upper layers of the atmosphere. In the later stages of their evolution, low to intermediate mass stars (0.8-8.0~M☉) eject a significant fraction of these nucleosynthesis products, resulting in a circumstellar envelope of gas and dust around the central star with a very different and intriguing chemical composition. Through radiation pressure, this material will sail into the interstellar medium. We offer the first extensive study concerning the atmospheric abundance determination using ultraviolet spectra, for two slow rotating non-magnetic early A-type (HD72660) and B-type (iota Herculis) stars. We carry out spectrum synthesis of the available UV spectra using the program ZEEMAN followed by a detailed abundance analysis. We find lines of several previously unstudied elements in the atmospheres of the two stars under study, implying the activity ofphenomena such as radiative levitation against gravity. In addition to finding new elements, we demonstrate that spectrum synthesis using ZEEMAN in the ultraviolet is indeed a reliable source for abundance determination.This study is followed by a very careful and detailed infrared spectroscopy of a sample of evolved AGB stars in the final stages of their evolution. The sample is unique in a sense that properties such as distance, metallicity, initial mass of the parent star are comparable while the only variable is the age on the AGB phase. Throughout this study we shed light on the significance of interstellar extinction and its previously under-acknowledged influence on the infrared spectra. We introduce tools and methods that will allow us to separately model the spectrum of the photosphere and the molecular layers alone. We extract the dust spectra and present a qualitative analysis of the intriguing peculiarities

Comparison and aggregation of event sequences across ten cohorts to describe the consensus biomarker evolution in Alzheimer's disease

BACKGROUND: Previous models of Alzheimer's disease (AD) progression were primarily hypothetical or based on data originating from single cohort studies. However, cohort datasets are subject to specific inclusion and exclusion criteria that influence the signals observed in their collected data. Furthermore, each study measures only a subset of AD-relevant variables. To gain a comprehensive understanding of AD progression, the heterogeneity and robustness of estimated progression patterns must be understood, and complementary information contained in cohort datasets be leveraged. METHODS: We compared ten event-based models that we fit to ten independent AD cohort datasets. Additionally, we designed and applied a novel rank aggregation algorithm that combines partially overlapping, individual event sequences into a meta-sequence containing the complementary information from each cohort. RESULTS: We observed overall consistency across the ten event-based model sequences (average pairwise Kendall's tau correlation coefficient of 0.69 ± 0.28), despite variance in the positioning of mainly imaging variables. The changes described in the aggregated meta-sequence are broadly consistent with the current understanding of AD progression, starting with cerebrospinal fluid amyloid beta, followed by tauopathy, memory impairment, FDG-PET, and ultimately brain deterioration and impairment of visual memory. CONCLUSION: Overall, the event-based models demonstrated similar and robust disease cascades across independent AD cohorts. Aggregation of data-driven results can combine complementary strengths and information of patient-level datasets. Accordingly, the derived meta-sequence draws a more complete picture of AD pathology compared to models relying on single cohorts

Comparison of the efficacy of a neutral wrist splint and wrist splint with lumbrical unit for the treatment of patients with carpal tunnel syndrome

Purpose: The purpose of this study was to compare the effect of a neutral wrist splint or a wrist splint with an additional metacarpophalangeal (MCP) unit on pain, function, grip and pinch strength in patients with mild-to-moderate carpal tunnel syndrome (CTS). Methods: Twenty four patients received conservative treatment using either the neutral wrist splint or wrist splint with the MCP unit for a period of 6 weeks. Primary outcome measures were pain, function, grip and pinch strength. Data was collected immediately before and after using the two types of splints at baseline (0 weeks) and 6 weeks. Statistical analysis was performed using the paired t-test and independent T-test. Results: Compared to baseline, both the neutral wrist splint and the wrist splint with an MCP unit significantly decreased pain, increased function and pinch and grip strength. Comparisons of the two types of splints for grip (P =0.675) and pinch strength (P =0.650) revealed that there were no significant differences between the two after 6 weeks of wear. However, there were significant differences in pain levels (P =0.022) and the DASH score (P =0.027) between the two types of splints from baseline to 6 weeks. Conclusion: The wrist splint with an MCP unit was more effective than the neutral wrist splint in pain reduction and improvement of function

Infrared spectroscopy of asymptotic giant branch stars in the Galactic bulge

We have selected a homogeneous sample of asymptotic giant branch (AGB) stars in the Galactic bulge population from the ISOGAL survey. Our target stars cover a wide range of mass-loss rates (∼10−8-10−4 M⊙ yr−1) and differ primarily by their age on the AGB. This homogeneous sample is thus ideally suited to study the dust formation process as a function of age on the AGB. We observed our sample with Spitzer-Infrared Spectrograph, and studied the overall properties of the infrared spectra of these targets. The analysis is complicated by the presence of strong and variable background emission, and the extracted infrared AGB star spectra are affected by interstellar extinction. Several stars in our sample have no detectable dust emission, and we used these ‘naked stars’ to characterize the stellar and molecular contributions to the infrared spectra of our target stars. The resulting dust spectra of our targets do indeed show significant variety in their spectral appearance, pointing to differing dust compositions for the targets. We classify the spectra based on the shape of their 10-μm emission following the scheme by Sloan & Price. We find that the early silicate emission classes associated with oxide dust are generally under-represented in our sample due to extinction effects. We also find a weak 13-μm dust feature in two of our otherwise naked star spectra, suggesting that the carrier of this feature could potentially be the first condensate in the sequence of dust condensation

One life ends, another begins: Management of a brain-dead pregnant mother - A systematic review -

Background: An accident or a catastrophic disease may occasionally lead to brain death (BD) during pregnancy. Management of brain-dead pregnant patients needs to follow special strategies to support the mother in a way that she can deliver a viable and healthy child and, whenever possible, also be an organ donor. This review discusses the management of brain-dead mothers and gives an overview of recommendations concerning the organ supporting therapy. Methods: To obtain information on brain-dead pregnant women, we performed a systematic review of Medline, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL). The collected data included the age of the mother, the cause of brain death, maternal medical complications, gestational age at BD, duration of extended life support, gestational age at delivery, indication of delivery, neonatal outcome, organ donation of the mothers and patient and graft outcome. Results: In our search of the literature, we found 30 cases reported between1982 and 2010. A nontraumatic brain injury was the cause of BD in 26 of 30 mothers. The maternal mean age at the time of BD was 26.5 years. The mean gestational age at the time of BD and the mean gestational age at delivery were 22 and 29.5 weeks, respectively. Twelve viable infants were born and survived the neonatal period. Conclusion: The management of a brain-dead pregnant woman requires a multidisciplinary team which should follow available standards, guidelines and recommendations both for a nontraumatic therapy of the fetus and for an organ-preserving treatment of the potential donor

Can load carriage system weight, design and placement affect pain and discomfort? A systematic review

Purpose: A systematic review of the literature was conducted to answer the following questions: 1. Does usage or weight of load carriage system cause pain, perceived exertion or discomfort? 2. Can load carriage system placement on the spine influence pain, perceived exertion or discomfort? 3. Can load carriage system design influence the amount of pain, perceived exertion or discomfort caused by their use? Method: Eight databases were searched. Each included study was analysed and quality appraised by two independent reviewers. Results: Forty-seven articles that addressed the research questions were included in the study. Significant variability in the study design and populations of the studies prevented data pooling and the evidence is conflicting. However, qualitative synthesis of the studies shows that carrying loads may provoke low back pain; and it may also trigger neck, thoracic and shoulder pain. Backpack weight can influence perceived pain, however other factors are involved. Discussion: There is conflicting but positive evidence on the correlation between backpack load carrying and experiencing pain during different stages of life. The research to date is lacking with the most commonly identified methodological deficiencies being poor overall design, the lack of justification of sample size, providing training sessions for examiners, and not utilising calibrated, valid and reliable instruments for measurement

Backpacks. Several factors likely to influence design and usage: A systematic literature review

Objective: The purpose of this study was to systematically review the literature to answer three questions: 1) what is the best backpack positioning on the spine; 2) what are the human effects of front packs and double packs compared to backpacks; and 3) what is best shoulder strap design. Methods: A systematic review of the literature using eight databases was carried out. Studies relevant to backpack design were retrieved. Two independent reviewers assessed the papers; a third party was used for consensus decisions. Descriptive characteristics, type of research design and level of evidence of papers were evaluated with a view to pooling data. The trials were also quality appraised using a modified Crombie tool. Results: Thirty papers met the inclusion criteria. There were similarities in methods of measurement between some papers but subject's age group, tasks performed and backpack usages were so different between studies that it prevented data pooling and made it difficult to draw firm generic conclusions. Subsequent qualitative analysis shows that there are conflicting results on best backpack placement and shoulder strap design but front packs and double packs provide better posture than backpacks. Conclusions: Some recommendations for best practice design are made for children and adults based on elements of design and correct spinal placement

Backpack design and factors likely to influence design: A systematic literature review

Poster presentatio

The reliability of a portable clinical force plate used for the assessment of static postural control: repeated measures reliability study

Background Force plates are frequently used for postural control assessments but they are expensive and not widely available in most clinical settings. Increasingly, clinicians are using this technology to assess patients, however, the psychometric properties of these less sophisticated force plates is frequently unknown. The purposes of the study were to examine the test-retest reliability of a force plate commonly used by clinicians and to explore the effect of using the mean value from multiple repetitions on reliability. Methods Thirty healthy volunteer adults were recruited. Postural control measures were obtained using the Midot Posture Scale Analyzer (MPSA). Data were collected in 2 sessions. Five successive repetitions each of 60 seconds duration were obtained from each participant in each session. Results The reliability coefficients obtained using single measures were low (ICC3,1 = 0.06 to 0.53). The average of two measures allowed for reliable measurements of COP mean velocity and average location of COP. The average of three and five measures was required to obtain acceptable reliability (ICC [greater than or equal to] 0.70) of relative weight bearing on legs and sway area, respectively. Higher measurement precision values were seen by averaging four or five repetitions for all variables. Conclusion Single measures did not provide reliable estimates of postural sway, and the averaging of multiple repetitions was necessary to achieve acceptable levels of measurement error. The number of repetitions required to achieve reliable data ranged from 2 to 5. Clinicians should be wary of using single measures derived from similar equipment when making decisions about patients