On geometry of hypersurfaces of a pseudoconformal space of Lorentzian signature

There are three types of hypersurfaces in a pseudoconformal space C^n_1 of Lorentzian signature: spacelike, timelike, and lightlike. These three types of hypersurfaces are considered in parallel. Spacelike hypersurfaces are endowed with a proper conformal structure, and timelike hypersurfaces are endowed with a conformal structure of Lorentzian type. Geometry of these two types of hypersurfaces can be studied in a manner that is similar to that for hypersurfaces of a proper conformal space. Lightlike hypersurfaces are endowed with a degenerate conformal structure. This is the reason that their investigation has special features. It is proved that under the Darboux mapping such hypersurfaces are transferred into tangentially degenerate (n-1)-dimensional submanifolds of rank n-2 located on the Darboux hyperquadric. The isotropic congruences of the space C^n_1 that are closely connected with lightlike hypersurfaces and their Darboux mapping are also considered.Comment: LaTeX, 21 page

Increased risk of HIV and other drug-related harms associated with injecting in public places: national bio-behavioural survey of people who inject drugs

Background: Whilst injecting drugs in public places is considered a proxy for high risk behaviour among people who inject drugs (PWID), studies quantifying its relationship with multiple drug-related harms are lacking and none have examined this in the context of an ongoing HIV outbreak (located in Glasgow, Scotland). We aimed to: 1) estimate the prevalence of public injecting in Scotland and associated risk factors; and 2) estimate the association between public injecting and HIV, current HCV, overdose, and skin and soft tissue infections (SSTI). Methods: Cross-sectional, bio-behavioural survey (including dried blood spot testing to determine HIV and HCV infection) of 1469 current PWID (injected in last 6 months) recruited by independent interviewers from 139 harm reduction services across Scotland during 2017–18. Primary outcomes were: injecting in a public place (yes/no); HIV infection; current HCV infection; self-reported overdose in the last year (yes/no) and SSTI the last year (yes/no). Multi-variable logistic regression was used to determine factors associated with public injecting and to estimate the association between public injecting and drug-related harms (HIV, current HCV, overdose and SSTI). Results: Prevalence of public injecting was 16% overall in Scotland and 47% in Glasgow city centre. Factors associated with increased odds of public injecting were: recruitment in Glasgow city centre (aOR=5.45, 95% CI 3.48–8.54, p<0.001), homelessness (aOR=3.68, 95% CI 2.61–5.19, p<0.001), high alcohol consumption (aOR=2.42, 95% CI 1.69–3.44, p<0.001), high injection frequency (≥4 per day) (aOR=3.16, 95% CI 1.93–5.18, p<0.001) and cocaine injecting (aOR=1.46, 95% CI 1.00 to 2.13, p = 0.046). Odds were lower for those receiving opiate substitution therapy (OST) (aOR=0.37, 95% CI 0.24 to 0.56, p<0.001) and older age (per year increase) (aOR=0.97, 95% CI 0.95 to 0.99, p = 0.013). Public injecting was associated with an increased risk of HIV infection (aOR=2.11, 95% CI 1.13–3.92, p = 0.019), current HCV infection (aOR=1.49, 95% CI 1.01–2.19, p = 0.043), overdose (aOR=1.59, 95% CI 1.27–2.01, p<0.001) and SSTI (aOR=1.42, 95% CI 1.17–1.73, p<0.001). Conclusions: These findings highlight the need to address the additional harms observed among people who inject in public places and provide evidence to inform proposals in the UK and elsewhere to introduce facilities that offer safer drug consumption environments

Quantum Langevin theory of excess noise

In an earlier work [P. J. Bardroff and S. Stenholm], we have derived a fully quantum mechanical description of excess noise in strongly damped lasers. This theory is used here to derive the corresponding quantum Langevin equations. Taking the semi-classical limit of these we are able to regain the starting point of Siegman's treatment of excess noise [Phys. Rev. A 39, 1253 (1989)]. Our results essentially constitute a quantum derivation of his theory and allow some generalizations.Comment: 9 pages, 0 figures, revte

A higher order control volume based finite element method to prodict the deformation of heterogeneous materials

Materials with obvious internal structure can exhibit behaviour, under loading, that cannot be described by classical elasticity. It is therefore important to develop computational tools incorporating appropriate constitutive theories that can capture their unconventional behaviour. One such theory is micropolar elasticity. This paper presents a linear strain control volume finite element formulation incorporating micropolar elasticity. Verification results from a micropolar element patch test as well as convergence results for a stress concentration problem are included. The element will be shown to pass the patch test and also exhibit accuracy that is at least equivalent to its finite element counterpart

Neural mechanisms underlying probalistic category learning in normal aging.

Probabilistic category learning engages neural circuitry that includes the prefrontal cortex and caudate nucleus, two regions that show prominent changes with normal aging. However, the specific contributions of these brain regions are uncertain, and the effects of normal aging have not been examined previously in probabilistic category learning. In the present study, using a blood oxygenation level-dependent functional magnetic resonance imaging block design, 18 healthy young adults (mean age, 25.5 ± 2.6 years) and 15 older adults (mean age, 67.1 ± 5.3 years) were assessed on the probabilistic category learning "weather prediction" test. Whole-brain functional images acquired using a 1.5T scanner (General Electric, Milwaukee, WI) with gradient echo, echo planar imaging (3/1 mm; repetition time, 3000 ms; echo time, 50 ms) were analyzed using second-level random-effects procedures [SPM99 (Statistical Parametric Mapping)]. Young and older adults displayed equivalent probabilistic category learning curves, used similar strategies, and activated analogous neural networks, including the prefrontal and parietal cortices and the caudate nucleus. However, the extent of caudate and prefrontal activation was less and parietal activation was greater in older participants. The percentage correct and reaction time were mainly positively correlated with caudate and prefrontal activation in young individuals but positively correlated with prefrontal and parietal cortices in older individuals. Differential activation within a circumscribed neural network in the context of equivalent learning suggests that some brain regions, such as the parietal cortices, may provide a compensatory mechanism for healthy older adults in the context of deficient prefrontal cortex and caudate nuclei responses. Copyright © 2005 Society for Neuroscience

Neural correlates of probabilistic category learning in patients with schizophrenia

Functional neuroimaging studies of probabilistic category learning in healthy adults report activation of cortical-striatal circuitry. Based on previous findings of normal learning rate concurrent with an overall performance deficit in patients with schizophrenia, we hypothesized that relative to healthy adults, patients with schizophrenia would display preserved caudate nucleus and abnormal prefrontal cortex activation during probabilistic category learning. Forty patients with schizophrenia receiving antipsychotic medication and 25 healthy participants were assessed on interleaved blocks of probabilistic category learning and control tasks while undergoing blood oxygenation level-dependent functional magnetic resonance imaging. In addition to the whole sample of patients with schizophrenia and healthy adults, a subset of patients and healthy adults matched for good learning was also compared. In the whole sample analysis, patients with schizophrenia displayed impaired performance in conjunction with normal learning rate relative to healthy adults. The matched comparison of patients and healthy adults classified as good learners revealed greater caudate and dorsolateral prefrontal cortex activity in the healthy adults and greater activation in a more rostral region of the dorsolateral prefrontal, cingulate, parahippocampal and parietal cortex in patients. These results demonstrate that successful probabilistic category learning can occur in the absence of normal frontal-striatal function. Based on analyses of the patients and healthy adults matched on learning and performance, a minority of patients with schizophrenia achieve successful probabilistic category learning and performance levels through differential activation of a circumscribed neural network which suggests a compensatory mechanism in patients showing successful learning. Copyright © 2009 Society for Neuroscience

Quantum statistics of overlapping modes in open resonators

We study the quantum dynamics of optical fields in weakly confining resonators with overlapping modes. Employing a recently developed quantization scheme involving a discrete set of resonator modes and continua of external modes we derive Langevin equations and a master equation for the resonator modes. Langevin dynamics and the master equation are proved to be equivalent in the Markovian limit. Our open-resonator dynamics may be used as a starting point for a quantum theory of random lasers.Comment: 6 pages, corrected typo

Mechanism of polarization of Listeria monocytogenes surface protein ActA

The polar distribution of the ActA protein on the surface of the Gram-positive intracellular bacterial pathogen, Listeria monocytogenes, is required for bacterial actin-based motility and successful infection. ActA spans both the bacterial membrane and the peptidoglycan cell wall. We have directly examined the de novo ActA polarization process in vitro by using an ActA–RFP (red fluorescent protein) fusion. After induction of expression, ActA initially appeared at distinct sites along the sides of bacteria and was then redistributed over the entire cylindrical cell body through helical cell wall growth. The accumulation of ActA at the bacterial poles displayed slower kinetics, occurring over several bacterial generations. ActA accumulated more efficiently at younger, less inert poles, and proper polarization required an optimal balance between protein secretion and bacterial growth rates. Within infected host cells, younger generations of L. monocytogenes initiated motility more quickly than older ones, consistent with our in vitro observations of de novo ActA polarization. We propose a model in which the polarization of ActA, and possibly other Gram-positive cell wall-associated proteins, may be a direct consequence of the differential cell wall growth rates along the bacterium and dependent on the relative rates of protein secretion, protein degradation and bacterial growth

Nuclear Shadowing in DIS: Numerical Solution of the Evolution Equation for the Green Function

Within a light-cone QCD formalism based on the Green function technique incorporating color transparency and coherence length effects we study nuclear shadowing in deep-inelastic scattering at moderately small Bjorken x_{Bj}. Calculations performed so far were based only on approximations leading to an analytical harmonic oscillatory form of the Green function. We present for the first time an exact numerical solution of the evolution equation for the Green function using realistic form of the dipole cross section and nuclear density function. We compare numerical results for nuclear shadowing with previous predictions and discuss differences.Comment: 21 pages including 3 figures; a small revision of the tex

Описание клинических случаев меланомы кожи

Skin melanoma is a malignant tumor originating in the cells of the melanocytic system, which is characterized by an aggressive clinical course, significant metastatic potential and unfavorable prognosis. These features of the tumor stipulate the need to improve measures to optimize early diagnosis of tumors. The article presents cases of pigmented skin melanoma to demonstrate the variability of clinical manifestations of this tumor requiring dermatologist skills in the differential diagnostics of neoplasms.Меланома кожи - злокачественное новообразование, происходящее из клеток меланоцитарной системы, характеризуется агрессивным клиническим течением, значительным метастатическим потенциалом, неблагоприятным прогнозом. Данные особенности опухоли указывают на необходимость совершенствования мер по оптимизации ранней диагностики новообразования. Описаны случаи пигментной меланомы кожи с целью демонстрации вариабельности клинических проявлений данного новообразования, требующих от врача-дерматолога навыков его дифференциальной диагностики