341 research outputs found
Unwinding of a cholesteric liquid crystal and bidirectional surface anchoring
We examine the influence of bidirectional anchoring on the unwinding of a planar cholesteric liquid crystal induced by the application of a magnetic field. We consider a liquid crystal layer confined between two plates with the helical axis perpendicular to the substrates. We fixed the director twist on one boundary and allow for bidirectional anchoring on the other by introducing a high-order surface potential. By minimizing the total free energy for the system, we investigate the untwisting of the cholesteric helix as the liquid crystal attempts to align with the magnetic field. The transitions between metastable states occur as a series of pitchjumps as the helix expels quarter or half-turn twists, depending on the relative sizes of the strength of the surface potential and the bidirectional anchoring. We show that secondary easy axis directions can play a significant role in the unwinding of the cholesteric in its transition towards a nematic, especially when the surface anchoring strength is large
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On the price of morals in markets: an empirical study of the Swedish AP-Funds and the Norwegian Government Pension Fund
This study empirically analyses the exclusion of companies from investors’ investment universe due to a
company’s business model (sector-based exclusion) or due
to a company’s violations of international norms (normbased exclusion). We conduct a time-series analysis of the performance implications of the exclusion decisions of two leading Nordic investors, Norway’s Government Pension Fund-Global (GPFG) and Sweden’s AP-funds. We find that their portfolios of excluded companies do not generate an abnormal return relative to the funds’ benchmark index. While the exclusion portfolios show higher risk than the respective benchmark, this difference is only statistically
significant for the case of GPFG. These findings suggest
that the exclusion of the companies generally does not
harm funds’ performance. We interpret these findings as
indicative that with exclusionary screening, as practiced by the sample funds, asset owners can meet the ethical
objectives of their beneficiaries without compromising
financial returns
Global and local fMRI signals driven by neurons defined optogenetically by type and wiring
Despite a rapidly-growing scientific and clinical brain imaging literature based on functional magnetic resonance imaging (fMRI) using blood oxygenation level-dependent (BOLD) signals, it remains controversial whether BOLD signals in a particular region can be caused by activation of local excitatory neurons. This difficult question is central to the interpretation and utility of BOLD, with major significance for fMRI studies in basic research and clinical applications. Using a novel integrated technology unifying optogenetic control of inputs with high-field fMRI signal readouts, we show here that specific stimulation of local CaMKIIα-expressing excitatory neurons, either in the neocortex or thalamus, elicits positive BOLD signals at the stimulus location with classical kinetics. We also show that optogenetic fMRI (ofMRI) allows visualization of the causal effects of specific cell types defined not only by genetic identity and cell body location, but also by axonal projection target. Finally, we show that ofMRI within the living and intact mammalian brain reveals BOLD signals in downstream targets distant from the stimulus, indicating that this approach can be used to map the global effects of controlling a local cell population. In this respect, unlike both conventional fMRI studies based on correlations and fMRI with electrical stimulation that will also directly drive afferent and nearby axons, this ofMRI approach provides causal information about the global circuits recruited by defined local neuronal activity patterns. Together these findings provide an empirical foundation for the widely-used fMRI BOLD signal, and the features of ofMRI define a potent tool that may be suitable for functional circuit analysis as well as global phenotyping of dysfunctional circuitry
Communication Impairments in Mice Lacking Shank1: Reduced Levels of Ultrasonic Vocalizations and Scent Marking Behavior
Autism is a neurodevelopmental disorder with a strong genetic component. Core symptoms are abnormal reciprocal social interactions, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior with restricted interests. Candidate genes for autism include the SHANK gene family, as mutations in SHANK2 and SHANK3 have been detected in several autistic individuals. SHANK genes code for a family of scaffolding proteins located in the postsynaptic density of excitatory synapses. To test the hypothesis that a mutation in SHANK1 contributes to the symptoms of autism, we evaluated Shank1−/− null mutant mice for behavioral phenotypes with relevance to autism, focusing on social communication. Ultrasonic vocalizations and the deposition of scent marks appear to be two major modes of mouse communication. Our findings revealed evidence for low levels of ultrasonic vocalizations and scent marks in Shank1−/− mice as compared to wildtype Shank1+/+ littermate controls. Shank1−/− pups emitted fewer vocalizations than Shank1+/+ pups when isolated from mother and littermates. In adulthood, genotype affected scent marking behavior in the presence of female urinary pheromones. Adult Shank1−/− males deposited fewer scent marks in proximity to female urine than Shank1+/+ males. Call emission in response to female urinary pheromones also differed between genotypes. Shank1+/+ mice changed their calling pattern dependent on previous female interactions, while Shank1−/− mice were unaffected, indicating a failure of Shank1−/− males to learn from a social experience. The reduced levels of ultrasonic vocalizations and scent marking behavior in Shank1−/− mice are consistent with a phenotype relevant to social communication deficits in autism.National Institute of Mental Health (U.S.) (Intramural Research Program)Simons Foundatio
Historical Research Approaches to the Analysis of Internationalisation
Historical research methods and approaches can improve understanding of the most appropriate techniques to confront data and test theories in internationalisation research. A critical analysis of all “texts” (sources), time series analyses, comparative methods across time periods and space, counterfactual analysis and the examination of outliers are shown to have the potential to improve research practices. Examples and applications are shown in these key areas of research with special reference to internationalisation processes. Examination of these methods allows us to see internationalisation processes as a sequenced set of decisions in time and space, path dependent to some extent but subject to managerial discretion. Internationalisation process research can benefit from the use of historical research methods in analysis of sources, production of time-lines, using comparative evidence across time and space and in the examination of feasible alternative choices
Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector
We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope
150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a
complete background model for this isotope, including a measurement of the two-neutrino double-β decay
half-life of T2ν
1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents
the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays
in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay
mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the standard model. The observed lower limit, assuming light
Majorana neutrino exchange mediates the decay, is T0ν
1=2 > 2.0 × 1022 y at the 90% C.L., corresponding to
an upper limit on the effective neutrino mass of hmνi < 1.6–5.3 eV
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
Meeting abstrac
Fibrous dysplasia – differential diagnosis of cystic lesions in the proximal femur:a case report
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability
Excessive HDAC activation is critical for neurodegeneration in the rd1 mouse
Inherited retinal degenerations, collectively termed retinitis pigmentosa (RP), constitute one of the leading causes of blindness in the developed world. RP is at present untreatable and the underlying neurodegenerative mechanisms are unknown, even though the genetic causes are often established. Acetylation and deacetylation of histones, carried out by histone acetyltransferases (HATs) and histone deacetylases (HDACs), respectively, affects cellular division, differentiation, death and survival. We found acetylation of histones and probably other proteins to be dramatically reduced in degenerating photoreceptors in the rd1 human homologous mouse model for RP. Using a custom developed in situ HDAC activity assay, we show that overactivation of HDAC classes I/II temporally precedes photoreceptor degeneration. Moreover, pharmacological inhibition of HDACs I/II activity in rd1 organotypic retinal explants decreased activity of poly-ADP-ribose-polymerase and strongly reduced photoreceptor cell death. These findings highlight the importance of protein acetylation for photoreceptor cell death and survival and propose certain HDAC classes as novel targets for the pharmacological intervention in RP
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