Thermodynamical Metrics and Black Hole Phase Transitions

An important phase transition in black hole thermodynamics is associated with the divergence of the specific heat with fixed charge and angular momenta, yet one can demonstrate that neither Ruppeiner's entropy metric nor Weinhold's energy metric reveals this phase transition. In this paper, we introduce a new thermodynamical metric based on the Hessian matrix of several free energy. We demonstrate, by studying various charged and rotating black holes, that the divergence of the specific heat corresponds to the curvature singularity of this new metric. We further investigate metrics on all thermodynamical potentials generated by Legendre transformations and study correspondences between curvature singularities and phase transition signals. We show in general that for a system with n-pairs of intensive/extensive variables, all thermodynamical potential metrics can be embedded into a flat (n,n)-dimensional space. We also generalize the Ruppeiner metrics and they are all conformal to the metrics constructed from the relevant thermodynamical potentials.Comment: Latex, 25 pages, reference added, typos corrected, English polished and the Hawking-Page phase transition clarified; to appear in JHE

3D thermal analysis of a permanent magnet motor with cooling fans

Overheating of permanent magnet (PM) machines has become a major technical challenge as it gives rise to magnet demagnetization, degradation of insulation materials, and loss of motor efficiency. This paper proposes a state-of-the-art cooling system for an axial flux permanent magnet (AFPM) machine with the focus on its structural optimization. A computational fluid dynamics (CFD) simulation with thermal consideration has been shown to be an efficient approach in the literature and is thus employed in this work. Meanwhile, a simplified numerical approach to the AFPM machine with complex configuration in 3D consisting of conduction, forced convection, and conjugate heat transfer is taken as a case study. Different simplification methods (including configuration and working conditions) and two optimized fans for forced convection cooling are designed and installed on the AFPM machine and compared to a natural convection cooling system. The results show that the proposed approach is effective for analyzing the thermal performance of a complex AFPM machine and strikes a balance between reasonable simplification, accuracy, and computational resource

Blood-based high sensitivity measurements of beta-amyloid and phosphorylated tau as biomarkers of Alzheimer's disease: a focused review on recent advances

Discovery and development of clinically useful biomarkers for Alzheimer’s disease (AD) and related dementias have been the focus of recent research efforts. While cerebrospinal fluid and positron emission tomography or MRI-based neuroimaging markers have made the in vivo detection of AD pathology and its consequences possible, the high cost and invasiveness have limited their widespread use in the clinical setting. On the other hand, advances in potentially more accessible blood-based biomarkers had been impeded by lack of sensitivity in detecting changes in markers of the hallmarks of AD, including amyloid-β (Aβ) peptides and phosphorylated tau (P-tau). More recently, however, emerging technologies with superior sensitivity and specificity for measuring Aβ and P-tau have reported high concordances with AD severity. In this focused review, we describe several emerging technologies, including immunoprecipitation-mass spectrometry (IP-MS), single molecule array and Meso Scale Discovery immunoassay platforms, and appraise the current literature arising from their use to identify plaques, tangles and other AD-associated pathology. While there is potential clinical utility in adopting these technologies, we also highlight the further studies needed to establish Aβ and P-tau as blood-based biomarkers for AD, including validation with existing large sample sets, new independent cohorts from diverse backgrounds as well as population-based longitudinal studies. In conclusion, the availability of sensitive and reliable measurements of Aβ peptides and P-tau species in blood holds promise for the diagnosis, prognosis and outcome assessments in clinical trials for AD

Investigating microbial diversity and UV radiation impact at the high-altitude lake Aguas Calientes, Chile

The High-Lakes Project is funded by the NAI and explores the highest perennial volcanic lakes on Earth in the Bolivian and Chilean Andes, including several lakes ∼6,000 m elevation. These lakes represent an opportunity to study the evolution of microbial organisms in relatively shallow waters not providing substantial protection against UV radiation. Aguas Calientes (5,870 m) was investigated (November 2006) and samples of water and sediment collected at 1, 3, 5, and 10 cm depth. An Eldonet UV dosimeter positioned on the shore records UV radiation and temperature, and is logging data year round. A UV SolarLight sensor allowed acquisition of point measurements in all channels at the time of the sampling. UVA, UVB, and PAR peaks between 11:00 am and 1:00 pm reached 7.7 mW/cm2, 48.5 μW/cm2, and 511 W/m 2, respectively. The chemical composition of the water sample was analyzed. DNA was extracted and DGGE analyses with bacterial and archaeal 16S fragments were performed to describe microbial diversity. Antibiotic resistances were established previously in similar environments in Argentine Andean wetlands. In order to determine these resistances in our samples, they were inoculated onto LB and R2A media and onto R2A medium containing either chloramphenicol, ampicillin or tetracycline. Bacterial was higher than archeal cell number determined by RT-PCR in all the samples, reaching maximum total values of 5×105 cell mL-1. DGGE results from these samples and Licancabur summit lake (5,916 m) samples were also compared. Eight antibiotic-resistant Gram negative strains have been isolated with distinct resistance patterns.Fil: Escudero, Lorena. Centro de Investigación Científica y Tecnológica para la Minería; ArgentinaFil: Chong, Guillermo. Centro de Investigación Científica y Tecnológica para la Minería; ArgentinaFil: Demergasso, Cecilia. Universidad Católica de Chile; ChileFil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Cabrol, Nathalie A.. Nasa Ames Research Center; Estados UnidosFil: Grin, Edmond. Nasa Ames Research Center; Estados UnidosFil: Minkley Jr., Edwin. University of Carnegie Mellon; Estados UnidosFil: Yu, Youngeob. University of Carnegie Mellon; Estados Unido

Effects of bowel preparation on intestinal bacterial associated urine and faecal metabolites and the associated faecal microbiome

Background Urinary and faecal metabolic profiling have been extensively studied in gastrointestinal diseases as potential diagnostic markers, and to enhance our understanding of the intestinal microbiome in the pathogenesis these conditions. The impact of bowel cleansing on the microbiome has been investigated in several studies, but limited to just one study on the faecal metabolome. Aim To compare the effects of bowel cleansing on the composition of the faecal microbiome, and the urine and faecal metabolome. Methods Urine and faecal samples were obtained from eleven patients undergoing colonoscopy at baseline, and then at day 3 and week 6 after colonoscopy. 16S rRNA gene sequencing was used to analyse changes in the microbiome, and metabonomic analysis was performed using proton nuclear magnetic resonance (1H NMR) spectroscopy. Results Microbiomic analysis demonstrated a reduction in alpha diversity (Shannon index) between samples taken at baseline and three days following bowel cleansing (p = 0.002), and there was no significant difference between samples at baseline and six weeks post colonoscopy. Targeted and non-targeted analysis of urinary and faecal bacterial associated metabolites showed no significant impact following bowel cleansing. Conclusions Bowel cleansing causes a temporary disturbance in bacterial alpha diversity measured in faeces, but no significant changes in the faecal and urine metabolic profiles, suggesting that overall the faecal microbiome and its associated metabolome is resistant to the effects of an induced osmotic diarrhoea

Brain atrophy and white matter hyperintensities are independently associated with plasma neurofilament light chain in an Asian cohort of cognitively impaired patients with concomitant cerebral small vessel disease

Introduction: Plasma neurofilament light chain (NfL) is a potential biomarker for neurodegeneration in Alzheimer's disease (AD), ischemic stroke, and non-dementia cohorts with cerebral small vessel disease (CSVD). However, studies of AD in populations with high prevalence of concomitant CSVD to evaluate associations of brain atrophy, CSVD, and amyloid beta (Aβ) burden on plasma NfL are lacking. Methods: Associations were tested between plasma NfL and brain Aβ, medial temporal lobe atrophy (MTA) as well as neuroimaging features of CSVD, including white matter hyperintensities (WMH), lacunes, and cerebral microbleeds. Results: We found that participants with either MTA (defined as MTA score ≥2; neurodegeneration [N]+WMH−) or WMH (cut-off for log-transformed WMH volume at 50th percentile; N−WMH+) manifested increased plasma NfL levels. Participants with both pathologies (N+WMH+) showed the highest NfL compared to N+WMH−, N−WMH+, and N−WMH− individuals. Discussion: Plasma NfL has potential utility in stratifying individual and combined contributions of AD pathology and CSVD to cognitive impairment

Health-state utilities in a prisoner population : a cross-sectional survey

Background: Health-state utilities for prisoners have not been described. Methods: We used data from a 1996 cross-sectional survey of Australian prisoners (n = 734). Respondent-level SF-36 data was transformed into utility scores by both the SF-6D and Nichol's method. Socio-demographic and clinical predictors of SF-6D utility were assessed in univariate analyses and a multivariate general linear model. Results: The overall mean SF-6D utility was 0.725 (SD 0.119). When subdivided by various medical conditions, prisoner SF-6D utilities ranged from 0.620 for angina to 0.764 for those with none/mild depressive symptoms. Utilities derived by the Nichol's method were higher than SF-6D scores, often by more than 0.1. In multivariate analysis, significant independent predictors of worse utility included female gender, increasing age, increasing number of comorbidities and more severe depressive symptoms. Conclusion: The utilities presented may prove useful for future economic and decision models evaluating prison-based health programs

Evaluation of the Osteogenic Potential of Growth Factorâ Rich Demineralized Bone Matrix In Vivo

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141502/1/jper0036.pd