Stress singularities and the formation of birefringent strands in stagnation flows of dilute polymer solutions

We consider stagnation point flow away from a wall for creeping flow of dilute polymer solutions. For a simplified flow geometry, we explicitly show that a narrow region of strong polymer extension (a birefringent strand) forms downstream of the stagnation point in the UCM model and extensions, like the FENE-P model. These strands are associated with the existence of an essential singularity in the stresses, which is induced by the fact that the stagnation point makes the convective term in the constitutive equation into a singular point. We argue that the mechanism is quite general, so that all flows that have a separatrix going away from the stagnation point exhibit some singular behaviour. These findings are the counterpart for wall stagnation points of the recently discovered singular behaviour in purely elongational flows: the underlying mechanism is the same while the different nature of the singular stress behaviour reflects the different form of the velocity expansion close to the stagnation point.Comment: 15 pages, 6 figure

High gamma oscillations in medial temporal lobe during overt production of speech and gestures

The study of the production of co-speech gestures (CSGs), i.e., meaningful hand movements that often accompany speech during everyday discourse, provides an important opportunity to investigate the integration of language, action, and memory because of the semantic overlap between gesture movements and speech content. Behavioral studies of CSGs and speech suggest that they have a common base in memory and predict that overt production of both speech and CSGs would be preceded by neural activity related to memory processes. However, to date the neural correlates and timing of CSG production are still largely unknown. In the current study, we addressed these questions with magnetoencephalography and a semantic association paradigm in which participants overtly produced speech or gesture responses that were either meaningfully related to a stimulus or not. Using spectral and beamforming analyses to investigate the neural activity preceding the responses, we found a desynchronization in the beta band (15-25 Hz), which originated 900 ms prior to the onset of speech and was localized to motor and somatosensory regions in the cortex and cerebellum, as well as right inferior frontal gyrus. Beta desynchronization is often seen as an indicator of motor processing and thus reflects motor activity related to the hand movements that gestures add to speech. Furthermore, our results show oscillations in the high gamma band (50-90 Hz), which originated 400 ms prior to speech onset and were localized to the left medial temporal lobe. High gamma oscillations have previously been found to be involved in memory processes and we thus interpret them to be related to contextual association of semantic information in memory. The results of our study show that high gamma oscillations in medial temporal cortex play an important role in the binding of information in human memory during speech and CSG production

From short-term store to multicomponent working memory: The role of the modal model

The term “modal model” reflects the importance of Atkinson and Shiffrin’s paper in capturing the major developments in the cognitive psychology of memory that were achieved over the previous decade, providing an integrated framework that has formed the basis for many future developments. The fact that it is still the most cited model from that period some 50 years later has, we suggest, implications for the model itself and for theorising in psychology more generally. We review the essential foundations of the model before going on to discuss briefly the way in which one of its components, the short-term store, had influenced our own concept of a multicomponent working memory. This is followed by a discussion of recent claims that the concept of a short-term store be replaced by an interpretation in terms of activated long-term memory. We present several reasons to question these proposals. We conclude with a brief discussion of the implications of the longevity of the modal model for styles of theorising in cognitive psychology

Central automorphisms of free nilpotent Lie algebras

Let Lm,n be the free nilpotent Lie algebra of finite rank m, m ? 2 and nilpotency class n - 1 over a field of characteristic zero. We give a characterization of central automorphisms of Lm,n and we find sufficient conditions for an automorphism of Lm,n to be a central automorphism. © 2017 World Scientific Publishing Company

Relationship of brain natriuretic peptide with metabolic syndrome parameters: An observational study [Beyin natriüretik peptidin metabolik sendrom parametreleri ile ilişkisi: Gözlemsel bir çalışma]

PubMedID: 22037102Objective: Metabolic syndrome (MS) was independently associated with increased risk of incident heart failure and coronary artery disease. In this study, we sought to identify whether there is an association between metabolic syndrome components and left ventricular diastolic functions and brain natriuretic peptide (BNP) levels. Methods: This study is a cross-sectional, observational study. Two hundred consecutive patients with MS were selected to form the study population. Echocardiographic parameters and BNP were determined. Mann-Whitney U test and Kruskal-Wallis test were used to compare BNP levels in categorical variables. Spearman rank correlation analysis was used to investigate the correlation between BNP level and other numerical variables. Linear regression analysis was used to find the variables affecting the BNP level. Results: BNP level was higher in females than males [11.14 (0.12-87) vs 7.49 (0.01-99) pg/dl, p=0.04]. None of the MS parameters affects the BNP level in MS patients. MS criteria number that the patient had was not related to BNP level. Sixty seven percent of patients had left ventricular (LV) diastolic dysfunction. BNP was independent from LV diastolic function. Multiple linear regression analysis demonstrated that having diabetes mellitus increases BNP level by 7.73 unit (ß=7.73, 95% CI - 2.321 - 13.149, p=0.006). Conclusion: None of the MS parameters affects the BNP level in MS patients. Diastolic dysfunction existence did not affect the BNP level of MS patients. There is an association between diabetes mellitus and BNP, independent of left ventricle diastolic functions. © 2011 by AVES Yayincilik Ltd

Pseudoaneurysm of the right ventricular outflow tract complicating balloon dilatation for tetralogy of Fallot

Balloon dilatation is one of the treatment options in symptomatic infants with tetralogy of Fallot and hypoplastic pulmonary annulus and pulmonary artery. A balloon dilatation was performed on a 28-day-old infant with tetralogy of Fallot with an appropriate balloon. The patient developed two pseudoaneurysms on the right ventricular outflow tract after the procedure which were diagnosed when the patient was admitted for total correction at 20 months of age. This case demonstrates an unusual but potentially life-threatening long-term complication of this procedure