Revealing the pure confinement effect in glass-forming liquids by dynamic mechanical analysis

Many molecular glass forming liquids show a shift of the glass transition Tg to lower temperatures when the liquid is confined into mesoporous host matrices. Two contrary explanations for this effect are given in literature: First, confinement induced acceleration of the dynamics of the molecules leads to an effective downshift of Tg increasing with decreasing pore size. Secondly, due to thermal mismatch between the liquid and the surrounding host matrix, negative pressure develops inside the pores with decreasing temperature, which also shifts Tg to lower temperatures. Here we present novel dynamic mechanical analysis measurements of the glass forming liquid salol in Vycor and Gelsil with pore sizes of d = 2.6, 5.0 and 7.5 nm. The dynamic complex elastic susceptibility data can be consistently described with the assumption of two relaxation processes inside the pores: A surface induced slowed down relaxation due to interaction with rough pore interfaces and a second relaxation within the core of the pores. This core relaxation time is reduced with decreasing pore size d, leading to a downshift of Tg in perfect agreement with recent DSC measurements

On-treatment function testing of platelets and long-term outcome of patients with peripheral arterial disease undergoing transluminal angioplasty

OBJECTIVE: To assess the clinical importance of on-treatment function testing of platelets in patients on aspirin after catheter-based vascular interventions. MATERIALS AND METHODS: In 109 patients with symptomatic peripheral arterial disease (PAD) of the lower limbs, platelet function testing (adenosine diphosphate-, collagen- and epinephrine-induced aggregation using light transmission aggregometry) was performed before and at multiple time points up to 1 year after a percutaneous angioplasty. Using univariate mixture models and Box-Cox transformation to ensure normally distributed individual variances, we investigated if an intraindividual variability exists and if it has a consequence for clinical outcome. RESULTS: Response to aspirin as measured by platelet aggregometry varies considerably over time in most patients. However, the intraindividual variance over time was not significantly correlated either with restenosis/reocclusion after 1 year or with adverse long-term outcome (occurrence of death for cardiovascular cause, stroke or myocardial infarction in up to 8 years follow-up). CONCLUSIONS: Response to aspirin does not seem to have a role in determining long-term outcome in patients with symptomatic PAD. The fact that testing of platelet function at only one time point has reduced significance may have implications for all clinical settings in which aspirin is used for the prevention of thrombo-embolic events

Secondary School Enrolment and Teenage Childbearing: Evidence from Brazilian Municipalities

This article investigates whether increasing secondary education opportunities influences childbearing among young women in Brazil. We examine a novel dataset reflecting the vast expansion of secondary education in Brazil between 1997 and 2009 and exploit variation in the introduction of schools across 4,884 municipalities to instrument for school enrolment. Our most conservative estimate suggests that for every 9.7 students enrolled there is one fewer teenage births. These findings are robust to a number of specifications and sensitivity tests. Our estimates imply that Brazil’s secondary school expansion accounts for 34% of the substantial decline in teenage childbearing observed over the same period. We further look at heterogeneous effects across a number of municipal characteristics and discuss what these results suggest about the mechanisms underlying the school-childbearing relationship

Understanding access barriers to public services : lessons from a randomized domestic violence intervention

We study the effect of decreasing barriers to accessing non-police services on the demand for police services in cases of police-reported domestic violence. Variation comes from a large case-level randomised control trial designed to assist victims in accessing non-police services. Our data link information from local and national police administrative records, and a survey of victims. The intervention led to a robust 21% decrease in the demand for police services, as measured by the provision of a statement by victims. Despite a strong correlation between statements and criminal sanctions against perpetrators, we do not find a corresponding effect of the intervention on perpetrator arrest, charges or sentencing. This suggests that the victims who do not provide a statement because of treatment had a relatively low statement effectiveness. Consistent with this result, we find treatment group statements are significantly less likely to be withdrawn than are control group statements

Are there Local Minima in the Magnetic Monopole Potential in Compact QED?

We investigate the influence of the granularity of the lattice on the potential between monopoles. Using the flux definition of monopoles we introduce their centers of mass and are able to realize continuous shifts of the monopole positions. We find periodic deviations from the $1/r$-behavior of the monopole-antimonopole potential leading to local extrema. We suppose that these meta-stabilities may influence the order of the phase transition in compact QED.Comment: 11 pages, 5 figure

The impact of improving access to support services for victims of domestic violence on demand for services and victim outcomes

We conducted a randomised controlled trial of an intervention designed to assist victims of domestic violence in accessing non-police support services. The intervention led to a 22% decrease in the fraction of victims providing a witness statement to police. Witness statements are an important piece of evidence and a key input in the prosecution of perpetrators. Despite this, we do not find a significant change in perpetrator arrest and convictions to in reported future violence. Survey reponses provide evidence of an increase in non-police service use, a reduction in future victimisation risk, but also a potential decrease in short-run well-being

Confinement effects on glass forming liquids probed by DMA

Many molecular glass forming liquids show a shift of the glass transition T-g to lower temperatures when the liquid is confined into mesoporous host matrices. Two contrary explanations for this effect are given in literature: First, confinement induced acceleration of the dynamics of the molecules leads to an effective downshift of T-g increasing with decreasing pore size. Second, due to thermal mismatch between the liquid and the surrounding host matrix, negative pressure develops inside the pores with decreasing temperature, which also shifts T-g to lower temperatures. Here we present dynamic mechanical analysis measurements of the glass forming liquid salol in Vycor and Gelsil with pore sizes of d=2.6, 5.0 and 7.5 nm. The dynamic complex elastic susceptibility data can be consistently described with the assumption of two relaxation processes inside the pores: A surface induced slowed down relaxation due to interaction with rough pore interfaces and a second relaxation within the core of the pores. This core relaxation time is reduced with decreasing pore size d, leading to a downshift of T-g proportional to 1/d in perfect agreement with recent differential scanning calorimetry (DSC) measurements. Thermal expansion measurements of empty and salol filled mesoporous samples revealed that the contribution of negative pressure to the downshift of T-g is small (<30%) and the main effect is due to the suppression of dynamically correlated regions of size xi when the pore size xi approaches

Finite strain Landau theory of high pressure phase transformations

The properties of materials near structural phase transitions are often successfully described in the framework of Landau theory. While the focus is usually on phase transitions, which are induced by temperature changes approaching a critical temperature T-c, here we will discuss structural phase transformations driven by high hydrostatic pressure, as they are of major importance for understanding processes in the interior of the earth. Since at very high pressures the deformations of a material are generally very large, one needs to apply a fully nonlinear description taking physical as well as geometrical nonlinearities (finite strains) into account. In particular it is necessary to retune conventional Landau theory to describe such phase transitions. In Troster et al (2002 Phys. Rev. Lett. 88 55503) we constructed a Landau-type free energy based on an order parameter part, an order parameter-(finite) strain coupling and a nonlinear elastic term. This model provides an excellent and efficient framework for the systematic study of phase transformations for a wide range of materials up to ultrahigh pressures

Understanding public speakers’ performance: first contributions to support a computational approach

Communication is part of our everyday life and our ability to communicate can have a significant role in a variety of contexts in our personal, academic, and professional lives. For long, the characterization of what is a good communicator has been subject to research and debate by several areas, particularly in Education, with a focus on improving the performance of teachers. In this context, the literature suggests that the ability to communicate is not only defined by the verbal component, but also by a plethora of non-verbal contributions providing redundant or complementary information, and, sometimes, being the message itself. However, even though we can recognize a good or bad communicator, objectively, little is known about what aspects – and to what extent—define the quality of a presentation. The goal of this work is to create the grounds to support the study of the defining characteristics of a good communicator in a more systematic and objective form. To this end, we conceptualize and provide a first prototype for a computational approach to characterize the different elements that are involved in communication, from audiovisual data, illustrating the outcomes and applicability of the proposed methods on a video database of public speakers.publishe