Understanding crack versus cavitation in pressure-sensitive adhesives: the role of kinetics

We perform traction experiments on viscous liquids highly confined between parallel plates, a geometry known as the probe-tack test in the adhesion community. Direct observation during the experiment coupled to force measurement shows the existence of several mechanisms for releasing the stress. Bubble nucleation and instantaneous growth had been observed in a previous work. Upon increasing further the traction velocity or the viscosity, the bubble growth is progressively delayed. At high velocities, cracks at the interface between the plate and the liquid appear before the bubbles have grown to their full size. Bubbles and cracks are thus observed concomitantly. At even higher velocities, cracks develop fully so early that the bubbles are not even visible. We present a theoretical model that describes these regimes, using a Maxwell fluid as a model for the actual fluid, a highly viscous silicon oil. We present the resulting phase diagramme for the different force peak regimes. The predictions are compatible with the data. Our results show that in addition to cavitation, interfacial cracks are encountered in a probe-tack traction test with viscoelastic, \emph{liquid} materials and not solely with viscoelastic solids like adhesives.Comment: 44 page

The dual hit hypothesis of schizophrenia:evidence from animal models

Schizophrenia is a heterogeneous psychiatric disorder, which can severely impact social and professional functioning. Epidemiological and clinical studies show that schizophrenia has a multifactorial aetiology comprising genetic and environmental risk factors. Although several risk factors have been identified, it is still not clear how they result in schizophrenia. This knowledge gap, however, can be investigated in animal studies. In this review, we summarise animal studies regarding molecular and cellular mechanisms through which genetic and environmental factors may affect brain development, ultimately causing schizophrenia. Preclinical studies suggest that early environmental risk factors can affect the immune, GABAergic, glutamatergic, or dopaminergic system and thus increase the susceptibility to another risk factor later in life. A second insult, like social isolation, stress, or drug abuse, can further disrupt these systems and the interactions between them, leading to behavioural abnormalities. Surprisingly, first insults like maternal infection and early maternal separation can also have protective effects. Single gene mutations associated with schizophrenia did not have a major impact on the susceptibility to subsequent environmental hits

Prefrontal cortex markers of suicidal vulnerability in mood disorders: a model-based structural neuroimaging study with a translational perspective

Open access article. Available from the publisher via doi: 10.1038/tp.2015.1The vulnerability to suicidal behavior has been modeled in deficits in both valuation and cognitive control processes, mediated by ventral and dorsal prefrontal cortices. To uncover potential markers of suicidality based on this model, we measured several brain morphometric parameters using 1.5T magnetic resonance imaging in a large sample and in a specifically designed study. We then tested their classificatory properties. Three groups were compared: euthymic suicide attempters with a past history of mood disorders and suicidal behavior (N=67); patient controls with a past history of mood disorders but not suicidal behavior (N=82); healthy controls without any history of mental disorder (N=82). A hypothesis-driven region-of-interest approach was applied targeting the orbitofrontal cortex (OFC), ventrolateral (VLPFC), dorsal (DPFC) and medial (including anterior cingulate cortex; MPFC) prefrontal cortices. Both voxel-based (SPM8) and surface-based morphometry (Freesurfer) analyses were used to comprehensively evaluate cortical gray matter measure, volume, surface area and thickness. Reduced left VLPFC volume in attempters vs both patient groups was found (P=0.001, surviving multiple comparison correction, Cohen's d=0.65 95% (0.33-0.99) between attempters and healthy controls). In addition, reduced measures in OFC and DPFC, but not MPFC, were found with moderate effect sizes in suicide attempters vs healthy controls (Cohen's d between 0.34 and 0.52). Several of these measures were correlated with suicidal variables. When added to mood disorder history, left VLPFC volume increased within-sample specificity in identifying attempters in a significant but limited way. Our study, therefore, confirms structural prefrontal alterations in individuals with histories of suicide attempts. A future clinical application of these markers will, however, necessitate further research.American Foundation for Suicide PreventionFondation pour la Recherche MédicaleRoyal SocietyProjet Hospitalier de Recherche CliniqueAcadémie Nationale de MédecineInstitut Servie

Cancer Du Sein Inflammatoire Chez La Femme Camerounaise

Introduction : Le cancer du sein inflammatoire (CSI), est relativement fréquent chez la jeune femme camerounaise. L’objectif était de présenter les caractéristiques du CSI en milieu camerounais. Patients et méthodes : Il s’est agi d’une étude transversale descriptive, multicentrique à collecte rétrospective allant du 1er Janvier 2010 au 31 Décembre 2014. Ont été inclues toutes les femmes de nationalité camerounaise diagnostiquées pour un CSI histologiquement confirmé. Résultats : Vingt-et-un cas de CSI ont été colligés et représentaient 3% de l’ensemble des mastopathies dans quatre hôpitaux. L’âge moyen des patientes était de 37,7 ans. Quatorze (66,7%) femmes avaient consulté après un intervalle supérieur à six mois. La localisation de la tumeur était unilatérale dans tous les cas. Dix-huit (85,7%) des patientes avaient un statut ganglionnaire cliniquement positif. La taille tumorale médiane était de 5cm. Les patientes étaient classées respectivement PEV3 dans 52,4%, PEV2 dans 28, 6% et PEV1 dans 19%. Huit patientes (38%) étaient métastatiques. Seize (76,2%) femmes avaient une négativité aux récepteurs œstrogènes et progestérones. Le carcinome canalaire infiltrant était le plus fréquent (66,6%). Treize (62%) patientes ont recouru au traitement traditionnel rituel. Une chimiothérapie néoadjuvante et adjuvante était systématiquement instituée. Dix-huit (85,7%) patientes étaient opérables et avaient bénéficié d’une mastectomie. Six cas de récidive ont été notés au cours du suivi. La survie à cinq ans était de 42, 9%. Conclusion : L’utilisation systématique de la chimiothérapie neoadjuvante et adjuvante a amélioré le pronostic du CSI. Introduction: Inflammatory breast cancer (IBC) is relatively common in young Cameroonian women. This paper aims to present the characteristics of the IBC in the Cameroonian environment. Patients and Methods: The paper uses a descriptive, multicentre cross-sectional study with retrospective collection from 1st of January 2010 to 31st of December 2014. All Cameroonian women affected by an IBC diagnosed and histologically confirmed were included in the study. Results: Twenty-one cases of IBC, which represented 3% of all treated mastopathies, was collected in four Church Hospitals. The mean age of the patients was 37.7 years. Fourteen (66.7%) consulted after an interval more than six months. The location of the tumour was unilateral in all of the cases. Eighteen (85.7%) of the patients had clinically positive lymph node status. The median tumour size was 5cm. The patients were classified into PEV3 52.4%, PEV2 28.6% and PEV1 19%, respectively. Eight patients (38%) were metastatic. Sixteen (76.2%) women had negative oestrogen and progesterone receptors. The most common histologic type was invasive ductal carcinoma with 66.6% of cases. Thirteen (62%) patients used traditional ritual treatment. Neo-adjuvant and adjuvant chemotherapy were systematically instituted. Eighteen (85.7%) patients were operable and had undergone mastectomy. Six (33.3%) cases of recurrence were observed during the follow-up. The 5-years survival was 42.9%. Conclusion: Systematic use of neo-adjuvant and adjuvant chemotherapy improved the prognosis of IBC

Maternal infection during pregnancy aggravates the behavioral response to an immune challenge during adolescence in female rats

Prenatal and early postnatal infection have been associated with changes in microglial activity and the development of psychiatric disorders. Here, we investigated the effect of prenatal immune activation and postnatal immune challenge, alone and combined, on behavior and microglial cell density in female Wistar rats. Pregnant rats were injected with poly I:C to induce a maternal immune activation (MIA). Their female offspring were subsequently exposed to a lipopolysaccharide (LPS) immune challenge during adolescence. Anhedonia, social behavior, anxiety, locomotion, and working memory were measured with the sucrose preference, social interaction, open field, elevated-plus maze, and Y-maze test, respectively. Microglia cell density was quantified by counting the number of Iba-1 positive cells in the brain cortex. Female MIA offspring were more susceptible to the LPS immune challenge during adolescence than control offspring as demonstrated by a more pronounced reduction in sucrose preference and body weight on the days following the LPS immune challenge. Furthermore, only the rats exposed to both MIA and LPS showed long-lasting changes in social behavior and locomotion. Conversely, the combination MIA and LPS prevented the anxiety induced by MIA alone during adulthood. MIA, LPS, or their combination did not change microglial cell density in the parietal and frontal cortex of adult rats. The results of our study suggest that the maternal immune activation during pregnancy aggravates the response to an immune challenge during adolescence in female rats.</p

Detectable Viral Load in Late Pregnancy among Women in the Rwanda Option B+ PMTCT Program: Enrollment Results from the Kabeho Study.

There are limited viral load (VL) data available from programs implementing Option B+, lifelong antiretroviral treatment (ART) to all HIV-positive pregnant and postpartum women, in resource-limited settings. Extent of viral suppression from a prevention of mother-to-child transmission of HIV program in Rwanda was assessed among women enrolled in the Kigali Antiretroviral and Breastfeeding Assessment for the Elimination of HIV (Kabeho) Study. ARV drug resistance testing was conducted on women with VL\u3e2000 copies/ml. In April 2013-January 2014, 608 pregnant or early postpartum HIV-positive women were enrolled in 14 facilities. Factors associated with detectable enrollment VL (\u3e20 copies/ml) were examined using generalized estimating equations. The most common antiretroviral regimen (56.7%, 344/607) was tenofovir/lamivudine/efavirenz. Median ART duration was 13.5 months (IQR 3.0-48.8); 76.1% of women were on ART at first antenatal visit. Half of women (315/603) had undetectable RNA-PCR VL and 84.6% (510) had36 months compared to those on ART 4-36 months (72/191, 37.7% versus 56/187, 29.9%), though the difference was not significant. The odds of having detectable enrollment VL decreased significantly as duration on ART at enrollment increased (AOR = 0.99, 95% CI: 0.9857, 0.9998, p = 0.043). There was a higher likelihood of detectable VL for women with lower gravidity (AOR = 0.90, 95% CI: 0.84, 0.97, p = 0.0039), no education (AOR = 2.25, (95% CI: 1.37, 3.70, p = 0.0004), nondisclosure to partner (AOR = 1.97, 95% CI: 1.21, 3.21, p = 0.0063) and side effects (AOR = 2.63, 95% CI: 1.72, 4.03, p36 months with genotyping available. Most women were receiving ART at first antenatal visit, with relatively high viral suppression rates. Shorter ART duration was associated with higher VL, with a concerning increasing trend for higher viremia and drug resistance among women on ART for \u3e3 years

A single dose of ketamine cannot prevent protracted stress-induced anhedonia and neuroinflammation in rats

Worldwide, millions of people suffer from treatment-resistant depression. Ketamine, a glutamatergic receptor antagonist, can have a rapid antidepressant effect even in treatment-resistant patients. A proposed mechanism for the antidepressant effect of ketamine is the reduction of neuroinflammation. To further explore this hypothesis, we investigated whether a single dose of ketamine can modulate protracted neuroinflammation in a repeated social defeat (RSD) stress rat model, which resembles features of depression. To this end, male animals exposed to RSD were injected with ketamine (20 mg/kg) or vehicle. A combination of behavioral analyses and PET scans of the inflammatory marker TSPO in the brain were performed. Rats submitted to RSD showed anhedonia-like behavior in the sucrose preference test, decreased weight gain, and increased TSPO levels in the insular and entorhinal cortices, as observed by [11C]-PK11195 PET. Whole brain TSPO levels correlated with corticosterone levels in several brain regions of RSD exposed animals, but not in controls. Ketamine injection 1 day after RSD disrupted the correlation between TSPO levels and serum corticosterone levels, but had no effect on depressive-like symptoms, weight gain or the protracted RSD-induced increase in TSPO expression in male rats. These results suggest that ketamine does not exert its effect on the hypothalamic-pituitary-adrenal axis by modulation of neuroinflammation

Colloquium: Mechanical formalisms for tissue dynamics

The understanding of morphogenesis in living organisms has been renewed by tremendous progressin experimental techniques that provide access to cell-scale, quantitative information both on theshapes of cells within tissues and on the genes being expressed. This information suggests that ourunderstanding of the respective contributions of gene expression and mechanics, and of their crucialentanglement, will soon leap forward. Biomechanics increasingly benefits from models, which assistthe design and interpretation of experiments, point out the main ingredients and assumptions, andultimately lead to predictions. The newly accessible local information thus calls for a reflectionon how to select suitable classes of mechanical models. We review both mechanical ingredientssuggested by the current knowledge of tissue behaviour, and modelling methods that can helpgenerate a rheological diagram or a constitutive equation. We distinguish cell scale ("intra-cell")and tissue scale ("inter-cell") contributions. We recall the mathematical framework developpedfor continuum materials and explain how to transform a constitutive equation into a set of partialdifferential equations amenable to numerical resolution. We show that when plastic behaviour isrelevant, the dissipation function formalism appears appropriate to generate constitutive equations;its variational nature facilitates numerical implementation, and we discuss adaptations needed in thecase of large deformations. The present article gathers theoretical methods that can readily enhancethe significance of the data to be extracted from recent or future high throughput biomechanicalexperiments.Comment: 33 pages, 20 figures. This version (26 Sept. 2015) contains a few corrections to the published version, all in Appendix D.2 devoted to large deformation

The orbit and stellar masses of the archetype colliding-wind binary WR 140

We present updated orbital elements for the Wolf-Rayet (WR) binary WR 140 (HD 193793; WC7pd + O5.5fc). The new orbital elements were derived using previously published measurements along with 160 new radial velocity measurements across the 2016 periastron passage of WR 140. Additionally, four new measurements of the orbital astrometry were collected with the CHARA Array. With these measurements, we derive stellar masses of $M_{\rm WR} = 10.31\pm0.45 M_\odot$ and $M_{\rm O} = 29.27\pm1.14 M_{\odot}$. We also include a discussion of the evolutionary history of this system from the Binary Population and Spectral Synthesis (BPASS) model grid to show that this WR star likely formed primarily through mass loss in the stellar winds, with only a moderate amount of mass lost or transferred through binary interactions.Comment: 10 pages, 5 figure