Multiscale constitutive modeling of polymer materials

Materials are inherently multi-scale in nature consisting of distinct characteristics at various length scales from atoms to bulk material. There are no widely accepted predictive multi-scale modeling techniques that span from atomic level to bulk relating the effects of the structure at the nanometer (10-9 meter) on macro-scale properties. Traditional engineering deals with treating matter as continuous with no internal structure. In contrast to engineers, physicists have dealt with matter in its discrete structure at small length scales to understand fundamental behavior of materials. Multiscale modeling is of great scientific and technical importance as it can aid in designing novel materials that will enable us to tailor properties specific to an application like multi-functional materials. Polymer nanocomposite materials have the potential to provide significant increases in mechanical properties relative to current polymers used for structural applications. The nanoscale reinforcements have the potential to increase the effective interface between the reinforcement and the matrix by orders of magnitude for a given reinforcement volume fraction as relative to traditional micro- or macro-scale reinforcements. To facilitate the development of polymer nanocomposite materials, constitutive relationships must be established that predict the bulk mechanical properties of the materials as a function of the molecular structure. A computational hierarchical multiscale modeling technique is developed to study the bulk-level constitutive behavior of polymeric materials as a function of its molecular chemistry. Various parameters and modeling techniques from computational chemistry to continuum mechanics are utilized for the current modeling method. The cause and effect relationship of the parameters are studied to establish an efficient modeling framework. The proposed methodology is applied to three different polymers and validated using experimental data available in literature.

The copper-responsive repressor CopR of Lactococcus lactis is a 'winged helix' protein

CopR of Lactococcus lactis is a copper-responsive repressor involved in copper homoeostasis. It controls the expression of a total of 11 genes, the CopR regulon, in a copper-dependent manner. In the absence of copper, CopR binds to the promoters of the CopR regulon. Copper releases CopR from the promoters, allowing transcription of the downstream genes to proceed. CopR binds through its N-terminal domain to a 'cop box' of consensus TACANNTGTA, which is conserved in Firmicutes. We have solved the NMR solution structure of the N-terminal DNA-binding domain of CopR. The protein fold has a winged helix structure resembling that of the BlaI repressor which regulates antibiotic resistance in Bacillus licheniformis. CopR differs from other copper-responsive repressors, and the present structure represents a novel family of copper regulators, which we propose to call the CopY family.

Diastolic dysfunction of the cardiac allograft and maximal exercise capacity

BACKGROUND: Peak oxygen uptake (peak Vo(2)) is an established integrative measurement of maximal exercise capacity in cardiovascular disease. After heart transplantation (HTx) peak Vo(2) remains reduced despite normal systolic left ventricular function, which highlights the relevance of diastolic function. In this study we aim to characterize the predictive significance of cardiac allograft diastolic function for peak Vo(2). METHODS: Peak Vo(2) was measured using a ramp protocol on a bicycle ergometer. Left ventricular (LV) diastolic function was assessed with tissue Doppler imaging sizing the velocity of the early (Ea) and late (Aa) apical movement of the mitral annulus, and conventional Doppler measuring early (E) and late (A) diastolic transmitral flow propagation. Correlation coefficients were calculated and linear regression models fitted. RESULTS: The post-transplant time interval of the 39 HTxs ranged from 0.4 to 20.1 years. The mean age of the recipients was 55 +/- 14 years and body mass index (BMI) was 25.4 +/- 3.9 kg/m(2). Mean LV ejection fraction was 62 +/- 4%, mean LV mass index 108 +/- 22 g/m(2) and mean peak Vo(2) 20.1 +/- 6.3 ml/kg/min. Peak Vo(2) was reduced in patients with more severe diastolic dysfunction (pseudonormal or restrictive transmitral inflow pattern), or when E/Ea was > or =10. Peak Vo(2) correlated with recipient age (r = -0.643, p < 0.001), peak heart rate (r = 0.616, p < 0.001) and BMI (r = -0.417, p = 0.008). Of all echocardiographic measurements, Ea (r = 0.561, p < 0.001) and Ea/Aa (r = 0.495, p = 0.002) correlated best. Multivariate analysis identified age, heart rate, BMI and Ea/Aa as independent predictors of peak Vo(2). CONCLUSIONS: Diastolic dysfunction is relevant for the limitation of maximal exercise capacity after HTx.

Gender - an Issue for German Welfare Organisation

During the last months and years the English expression 'gender' has become a well-known word all over Germany, often with the annex 'mainstreaming'. Gender mainstreaming was initiated as a political strategy by the Women's World Conference in Beijing in 1995 and adopted by the European Union in 1997 (COM(96)76 final). It basically means that all actions and initiatives planned have to be tested as to their effects on women and men and should not be taken if they disadvantage either one. But gender is also a category in the discussion about democratic features. Gender democracy means that males and females should be represented equally in the public, political, cultural, social and economic sphere of a society. On this background, this paper traces the gender issue in the field of organizations in the social sector of Germany, in particular the 'welfare organizations'. In this article, 'welfare organizations' is used as a translation of the German word 'Wohlfahrtsverbände'. The reason for this choice is the endeavor to indicate their difference from for instance English 'charitable associations' or French 'associations sociale et sanitaire', because social organizations in the EU-member states differ considerably in regard to their history, function, self-image , financing, political power etc.. The terms 'social non-governmental organizations' (NGOs) or 'social nonprofit organizations' (NPOs ) are used synonymously.

Implantattherapie nach Frontzahntrauma - Eine neue Methode zum Erhalt des Alveolarkammes nach posttrauma­tischer Ankylose und externer Wurzelresorption

The therapy of traumatized front teeth with ankylosis and additional root resorption is a real challenge for the clinician. Due to the infraposition ankylosed teeth are useless and esthetically unsatisfactory. The progressive replacement resorption and the vertical growth inhibition render an intervention inevitable. In the following case report, the prophylaxis of the alveolar ridge is brought into focus. The treatment of two ankylosed teeth by decoronation, preservation of the alveolar ridge and an implant-supported supraconstruction will be presented. The additional histological assessment confirms the diagnosis and the choice of treatment.

Early troponin T and prediction of potentially correctable in-hospital complications after coronary artery bypass grafting surgery

BACKGROUND Peak levels of troponin T (TnT) reliably predict morbidity and mortality after cardiac surgery. However, the therapeutic window to manage CABG-related in-hospital complications may close before the peak is reached. We investigated whether early TnT levels correlate as well with complications after coronary artery bypass grafting (CABG) surgery. METHODS A 12 month consecutive series of patients undergoing elective isolated CABG procedures (mini-extra-corporeal circuit, Cardioplegic arrest) was analyzed. Logistic regression modeling was used to investigate whether TnT levels 6 to 8 hours after surgery were independently associated with in-hospital complications (either post-operative myocardial infarction, stroke, new-onset renal insufficiency, intensive care unit (ICU) readmission, prolonged ICU stay (>48 hours), prolonged need for vasopressors (>24 hours), resuscitation or death). RESULTS A total of 290 patients, including 36 patients with complications, was analyzed. Early TnT levels (odds ratio (OR): 6.8, 95% confidence interval (CI): 2.2-21.4, P=.001), logistic EuroSCORE (OR: 1.2, 95%CI: 1.0-1.3, P=.007) and the need for vasopressors during the first 6 postoperative hours (OR: 2.7, 95%CI: 1.0-7.1, P=.05) were independently associated with the risk of complications. With consideration of vasopressor use during the first 6 postoperative hours, the sum of specificity (0.958) and sensitivity (0.417) of TnT for subsequent complications was highest at a TnT cut-off value of 0.8 ng/mL. CONCLUSION Early TnT levels may be useful to guide ICU management of CABG patients. They predict clinically relevant complications within a potential therapeutic window, particularly in patients requiring vasopressors during the first postoperative hours, although with only moderate sensitivity.