Anionic surfactant solutions under shear using dissipative particle dynamics

We present a dissipative particle dynamics study of surfactant solutions under shear, which allows us to investigate their rheological properties. We consider a variety of concentrations and phase structures, including micellar solutions and liquid crystal phases. It is shown that the viscosity of micellar solutions increases as a function of concentration, in agreement with what is expected from experimental data. We also show that micelles can exhibit shear-thinning behaviour when a shear force is applied, which is a result of micelles breaking down into smaller aggregates. Lamellar and hexagonal phases are found to orientate under the application of shear, in agreement with experimental observations. It is normally suggested that lamellar phases under shear can exhibit a transition between orientations, as the shear rate is increased, usually suggested to be a result of lower viscosity. We calculate the viscosity for different lamellar phase orientations, showing that, although the viscosity of perpendicular orientations is lower than that of parallel orientations, we do not observe a transition to the perpendicular phase at high shear rates. Finally, we show that the choice of Schmidt number has a significant impact on the results, which is of importance for determining the correct behaviour via simulations

Renormalisation-theoretic analysis of non-equilibrium phase transitions I: The Becker-Doring equations with power law rate coefficients

We study in detail the application of renormalisation theory to models of cluster aggregation and fragmentation of relevance to nucleation and growth processes. We investigate the Becker-Dorging equations, originally formulated to describe and analyse non-equilibrium phase transitions, and more recently generalised to describe a wide range of physicochemical problems. In the present paper we analyse how the systematic coarse-graining renormalisation of the \BD system of equations affects the aggregation and fragmentation rate coefficients. We consider the case of power-law size-dependent cluster rate coefficients which we show lead to only three classes of system that require analysis: coagulation-dominated systems, fragmentation-dominated systems and those where coagulation and fragmentation are exactly balanced. We analyse the late-time asymptotics associated with each class.Comment: 18 pages, to appear in J Phys A Math Ge

Расчет электромагнитного поля в электронных модулях с использованием интеграла Зоммерфельда

Излагается подход с использованием интеграла Зоммерфельда. Метод позволяет избежать интегрирования в комплексной области и снизить объем вычислений по сравнению с известными методами

Selection of workers and firm heterogeneity

A model based on differences between workers regarding their preferences for wage and leisure drives the heterogeneity of firms result. The more industrious workers are driven to small firms due to free riding in large firms. An industry consisting of small and large firms turns out to produce more output than an industry consisting of only large firms. Some comparative statics results are derived with respect to the size of large firms, the productivity difference between firms, and monitoring capabilities

Recommended implementation of arterial spin‐labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study group and the European consortium for ASL in dementia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109790/1/mrm25197.pd

Distribution of cerebral blood flow in the caudate nucleus, lentiform nucleus and thalamus in patients with carotid artery stenosis

To investigate the influence of internal carotid artery (ICA) stenosis on the distribution of blood flow to the caudate nucleus, lentiform nucleus, and thalamus. We studied 18 healthy control subjects, 20 patients with a unilateral asymptomatic ICA stenosis, and 15 patients with a recently symptomatic unilateral ICA stenosis. The contribution of the ICAs and the basilar artery to the perfusion of the deep brain structures was assessed by perfusion territory selective arterial spin labeling (ASL) MRI. Differences were tested with a two-tailed Fishers' exact test. The caudate nucleus was predominantly supplied with blood by the ipsilateral ICA in all groups. In 4 of the 15 (27%) the symptomatic patients, the caudate nucleus partially received blood from the contralateral ICA, compared to none of the 18 healthy control subjects (p = 0.03). The lentiform nucleus and the thalamus were predominantly supplied with blood by the ipsilateral ICA and basilar artery respectively in all groups. In patients with a symptomatic ICA stenosis, the caudate nucleus may be supplied with blood by the contralateral ICA more often than in healthy controls.Neuro Imaging Researc

Risk of Stroke before Revascularisation in Patients with Symptomatic Carotid Stenosis: A Pooled Analysis of Randomised Controlled Trials.

OBJECTIVE: Current guidelines recommending rapid revascularisation of symptomatic carotid stenosis are largely based on data from clinical trials performed at a time when best medical therapy was potentially less effective than today. The risk of stroke and its predictors among patients with symptomatic carotid stenosis awaiting revascularisation in recent randomised controlled trials (RCTs) and in medical arms of earlier RCTs was assessed. METHODS: The pooled data of individual patients with symptomatic carotid stenosis randomised to stenting (CAS) or endarterectomy (CEA) in four recent RCTs, and of patients randomised to medical therapy in three earlier RCTs comparing CEA vs. medical therapy, were compared. The primary outcome event was any stroke occurring between randomisation and treatment by CAS or CEA, or within 120 days after randomisation. RESULTS: A total of 4 754 patients from recent trials and 1 227 from earlier trials were included. In recent trials, patients were randomised a median of 18 (IQR 7, 50) days after the qualifying event (QE). Twenty-three suffered a stroke while waiting for revascularisation (cumulative 120 day risk 1.97%, 95% confidence interval [CI] 0.75 - 3.17). Shorter time from QE until randomisation increased stroke risk after randomisation (χ2 = 6.58, p = .011). Sixty-one patients had a stroke within 120 days of randomisation in the medical arms of earlier trials (cumulative risk 5%, 95% CI 3.8 - 6.2). Stroke risk was lower in recent than earlier trials when adjusted for time between QE and randomisation, age, severity of QE, and degree of carotid stenosis (HR 0.47, 95% CI 0.25 - 0.88, p = .019). CONCLUSION: Patients with symptomatic carotid stenosis enrolled in recent large RCTs had a lower risk of stroke after randomisation than historical controls. The added benefit of carotid revascularisation to modern medical care needs to be revisited in future studies. Until then, adhering to current recommendations for early revascularisation of patients with symptomatic carotid stenosis considered to require invasive treatment is advisable

Early Endarterectomy Carries a Lower Procedural Risk Than Early Stenting in Patients With Symptomatic Stenosis of the Internal Carotid Artery: Results From 4 Randomized Controlled Trials.

Patients undergoing carotid endarterectomy (CEA) for symptomatic stenosis of the internal carotid artery benefit from early intervention. Heterogeneous data are available on the influence of timing of carotid artery stenting (CAS) on procedural risk. We investigated the association between timing of treatment (0-7 days and >7 days after the qualifying neurological event) and the 30-day risk of stroke or death after CAS or CEA in a pooled analysis of individual patient data from 4 randomized trials by the Carotid Stenosis Trialists' Collaboration. Analyses were done per protocol. To obtain combined estimates, logistic mixed models were applied. Among a total of 4138 patients, a minority received their allocated treatment within 7 days after symptom onset (14% CAS versus 11% CEA). Among patients treated within 1 week of symptoms, those treated by CAS had a higher risk of stroke or death compared with those treated with CEA: 8.3% versus 1.3%, risk ratio, 6.7; 95% confidence interval, 2.1 to 21.9 (adjusted for age at treatment, sex, and type of qualifying event). For interventions after 1 week, CAS was also more hazardous than CEA: 7.1% versus 3.6%, adjusted risk ratio, 2.0; 95% confidence interval, 1.5 to 2.7 (P value for interaction with time interval 0.06). In randomized trials comparing stenting with CEA for symptomatic carotid artery stenosis, CAS was associated with a substantially higher periprocedural risk during the first 7 days after the onset of symptoms. Early surgery is safer than stenting for preventing future stroke. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00190398; URL: http://www.controlled-trials.com. Unique identifier: ISRCTN57874028; URL: http://www.controlled-trials.com. Unique identifier: ISRCTN25337470; URL: http://www.clinicaltrials.gov. Unique identifier: NCT00004732

Characterization of Antibodies against Receptor Activity-Modifying Protein 1 (RAMP1): A Cautionary Tale

Calcitonin gene-related peptide (CGRP) is a key component of migraine pathophysiology, yielding effective migraine therapeutics. CGRP receptors contain a core accessory protein subunit: receptor activity-modifying protein 1 (RAMP1). Understanding of RAMP1 expression is incomplete, partly due to the challenges in identifying specific and validated antibody tools. We profiled antibodies for immunodetection of RAMP1 using Western blotting, immunocytochemistry and immunohistochemistry, including using RAMP1 knockout mouse tissue. Most antibodies could detect RAMP1 in Western blotting and immunocytochemistry using transfected cells. Two antibodies (844, ab256575) could detect a RAMP1-like band in Western blots of rodent brain but not RAMP1 knockout mice. However, cross-reactivity with other proteins was evident for all antibodies. This cross-reactivity prevented clear conclusions about RAMP1 anatomical localization, as each antibody detected a distinct pattern of immunoreactivity in rodent brain. We cannot confidently attribute immunoreactivity produced by RAMP1 antibodies (including 844) to the presence of RAMP1 protein in immunohistochemical applications in brain tissue. RAMP1 expression in brain and other tissues therefore needs to be revisited using RAMP1 antibodies that have been comprehensively validated using multiple strategies to establish multiple lines of convincing evidence. As RAMP1 is important for other GPCR/ligand pairings, our results have broader significance beyond the CGRP field