Structural silicone sealants after exposure to laboratory test for durability assessment

During the service life of structural sealant glazing (SSG) facades, the load-bearing capacity of the silicone bonds needs to be guaranteed. Laboratory tests can assess the durability of SSG-systems based on mechanical characteristics of the bond after simultaneous exposure to both climatic and mechanical loads. This article studies how the material characteristics of two common structural sealants are affected by laboratory and field exposure. Dynamic mechanical analysis (DMA) confirms a reduction in the dynamic modulus of exposed silicone samples. Results from thermogravimetric analysis, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and small-angle X-ray scattering/wide-angle X-ray scattering show differences between the two sealants and indicate no/minor changes in the composition and morphology of the laboratory and field exposed sealants. Mechanical characterization methods, such as DMA, and tensile and shear testing of the structural bond, are shown to be sensitive toward the combined climatic and mechanical loadings, and are hence suitable for studying degradation mechanisms of structural sealants.     

On the dynamics of the electric field induced breakdown in lipidmembranes

Electric field methods are powerful tools for cell characterization and manipulation. Important biotechnological applications, e.g., electrofusion of cells or electroinjection of macromolecules into living cells, rely on membrane breakdown. Despite the widespread use of these techniques, the process of membrane breakdown is poorly understood: a better understanding can be expected to lead to higher efficiencies. The present study used planar lipid bilayers in order to limit the number of experimental parameters. Membrane rupture was induced by careful application of short electric field pulses: measurement of the subsequent increase in membrane conductivity with time permitted the underlying mechanism to be characterized. The initial process of pore formation starts a few μs after the onset of the pulse, and the ensuing breakdown of the entire lipid membrane occurs within about a millisecond (pore widening velocity of a few cm/s). The kinetics of the pore-opening process could be influenced qualitatively by adding surfactants and lipid-attached macromolecules, respectively. Changing the effective mass per unit area of membrane, which could be brought about by using known percentages of lipids with covalently bound, hydrophilic polymers, allowed a model for the pore widening process to be quantitatively tested     

A Composite Index of Compliance for Chronic In‐Center Hemodialysis Patients

We developed a composite compliance index as the sum of the compliance scores for interdialytic weight gain (IDWG), pre‐dialysis serum potassium and phosphorus concentrations (each scored from zero to 3, with 3 indicating the poorest compliance), and skipping hemodialysis sessions (scored from zero to 9, with 9 indicating the poorest compliance). We used this composite score to prospectively evaluate compliance in 25 prevalent hemodialysis patients over a period of 1 year. We then followed these patients for another 3.5 years. The patients studied were divided into two groups: group A (poor compliance) consisted of 9 subjects with composite score ≥ 9 (13.2 ± 3.2); group B (better compliance) consisted of 16 subjects with composite score < 9 (4.7 ± 1.8). Age, duration of hemodialysis, and frequency of diabetes mellitus did not differ between the groups. Group A contained higher fractions of subjects with history of alcoholism (66.7% vs 12.5%, p = 0.010), other substance addiction (44.4% vs 0%, p = 0.010), and severe psychosocial problems (88.9% vs 18.8%, p = 0.002). Mean survival from the beginning of observation, estimated by actuarial life‐table survival analysis, was 1.19 years in group A and 2.60 years in group B (p = 0.0265). A composite compliance index incorporating domains indicating adherence to diet, medications, and dialysis schedule identified other behavioral problems in poorly compliant patients. Hemodialysis patients characterized by this composite index as poorly compliant had shortened survival.     

Endoscopic study of the small intestine with push enteroscopy. A prospective study

OBJECTIVE: To evaluate whether push enteroscopy of the small bowel (PES), undertaken after extensive previous investigations in suspected intestinal bleeding from an uncertain site, chronic diarrhoea or lymphoma of the small intestine, contributes to the diagnosis, and to ascertain the results of PES and its clinical significance. PATIENTS AND METHODS: 56 consecutive patients (29 men, 27 women; mean age 63 years) were investigated prospectively. The main indications for PES were the search for the source of intestinal bleeding in 79% of patients (group A), chronic diarrhoea or tropical sprue in 16% (group B) and search for tumour of lymphoma in 5% (group C). PES was always performed in fasting patients under sedation/analgesia using a video PES, which contrary to catheter enteroscopy provides a channel for intervention. RESULTS: In group A 27% of patients were found to have lesions, in particular angiodysplasias, or (in once case) leiomyoma. Half of these patients were successfully treated endoscopically without later surgical intervention being required (mean follow-up of six months). In the other half operation became necessary, either because the disease itself indicated it or the bleeding persisted, the source being in the more distant small intestine and thus not accessible to endoscopic intervention: only 50% of the length of the small intestine proved to be within reach of the instrument. No abnormalities were discovered in patients of groups B and C. CONCLUSION: In cases of gastrointestinal bleeding from an uncertain source PES should be performed first, because in many cases it may obviate surgical intervention. But PES seems to contribute little of diagnostic value in other indications.     

The multicultural perspective in therapy: A social constructionist approach.

Discusses the theoretical and clinical applications of the postmodern paradigm of social constructionism as a basis for counseling culturally different clients. Such applications avoid the trap of perpetuating the status-quo when working with minority and marginalized clientele. The main points of multiculturalism and social constructionism are summarized, and issues of mutual concern to both perspectives are examined. Applications to psychotherapy are explored, and the challenges of applying the social constructionist approach to culturally competent counseling are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do We Stand on Common Ground? A Threat Appraisal Model for Terror Alerts Issued by the Department of Homeland Security

The fabric and faces of threat, and the expediency and efficiency in the communication of threat, are examined with a threat appraisal model. This model is empirically tested on an ongoing communication challenge, the issuance of terror alerts by the United States' Department of Homeland Security (DHS), focusing on how threat is appraised by both the conservative and liberal audiences. Findings showed a shared view by the DHS and conservative audiences on the levels and nature of threats; liberal audiences thought otherwise. Though there appeared to be a consensus between the conservative and liberal audiences on the efficacy of threat communication, more internal consistency within DHS is needed to optimise its effectiveness.     

Neurotoxic effects of sodium nitroprusside in rat hippocampal slices

The effect of a permanent transection on myelin gene expression in a regenerating sciatic nerve and in an adult sciatic nerve was compared to establish the degree of axonal control exerted upon Schwann cells in each population. First, the adult sciatic nerve was crushed, and the distal segment allowed to regenerate. At 12 days post-crush, the sciatic nerve was transected distal to the site of crush to disrupt the Schwann cell-axonal contacts that had reformed. Messenger RNA (mRNA) levels coding for five myelin proteins were assayed in the distal segment of the crush-transected nerve after 9 days and were compared to corresponding levels in the distal segments of sciatic nerves at 21 days post-crush and 21 days post-transection using Northern blot and slot-blot analysis. Levels of mRNAs found in the distal segment of the transected and crush-transected nerve suggested that Schwann cells in the regenerating nerve and in the mature adult nerve are equally responsive to axonal influences. The crush-transected model allowed the genes that were studied to be classified according to their response to Schwann cell-axonal contact. The levels of mRNAs were 1) down-regulated to basal levels (P0 and MBP mRNAs), 2) down-regulated to undetectable levels (myelin-associated glycoprotein mRNAs), 3) upregulated (mRNAs encoding 2'3'-cyclic nucleotide phosphodiesterase and beta-actin), or 4) not stringently controlled by the removal of Schwann cell-axonal contact (proteolipid protein mRNAs). This novel experimental model has thus provided evidence that the expression of some of the important myelin genes during peripheral nerve regeneration is dependent on continuous signals from the ingrowing axons.     

Determination of Magnetic and Nuclear Quadrupole Interactions in La@C82 from EPR Linewidth Data

From the analysis of the temperature dependence of the EPR line width, an estimate of the anisotropic parts of the dipolar and quadrupolar hyperfine couplings of lanthanum was derived. Furthermore, the rotational correlation time of the nearly spherical molecule was found to deviate considerably from that of the solvent molecules.     

Fire evacuation skills: Cognitive-behavioral versus computer-mediated instruction

Fifty-six fourth-grade children participated in this study to assess three training procedures for relative effectiveness in acquiring fire emergency skills and attaining knowledge. The first training approach was behavioral, the second used animated graphics, and the third used still graphics. Each of the training groups was compared to a control group that received no treatment. Performance on dependent measures was assessed before and immediately after training. It was hypothesized that the behavioral and animated-graphics conditions would produce the greatest level of skill and knowledge acquisition. Results demonstrated a significantly higher level of fire emergency skill acquisition and knowledge attainment for both the behavioral and animated-graphics groups relative to the still-graphics group and the control group, which had no training. The value of using computer-mediated strategies for fire-safety skills training was demonstrated.