Aggregation behaviour of stereoregular poly(methyl methacrylates) in dilute solution: light scattering and proton n.m.r. study

The aggregation behaviour of syndiotactic and isotactic poly(methyl methacrylate) in methyl ethyl ketone, n-butyl acetate, and 2-ethoxyethanol was investigated by light scattering and ¹H n.m.r. spectroscopy. Syndiotactic poly(methyl methacrylate) remains in its molecular form in solution at temperatures above 60°–70°C; on cooling it undergoes aggregation followed by macroscopic separation (precipitation) of the polymer from solution. The rate of these processes depends on temperature, concentration of the polymer, and solvent. Molecular solutions of isotactic poly(methyl methacrylate) can be prepared only by long-term heating at temperatures above 100°–130°C. During cooling, isotactic macromolecules prior to separation form stable associates in the region limited by discrete temperatures, and below this region polymer precipitates. The individual stereo forms of poly(methyl methacrylate) are separated from solution at different temperatures which are above the θ-temperatures of the atactic polymer.     

LED‐backlit computer screens influence our biological clock and keep us more awake

Abstract— In commodity LC flat‐panel displays, the traditional CCFL backlight is being replaced more and more by LEDs. The typical spectrum of LED‐lit displays shows a significantly higher amount of blue light in the range around 464 nm. Blue light in this wavelength area suppresses the melatonin level in humans and thus effects the biological clock. Our hypothesis was that the amount of blue light reaching the human eye from a LED‐backlit display is sufficient to have a significant effect on the biological clock. The results of clinical user studies comparing the effects of LED‐ vs. CCFL‐backlit displays on humans, resulting from the emitted amount of 464‐nm light, will be presented. It was found that the LED‐backlit display causes significant suppression of melatonin, which effects the biological clock of the test persons, indicating the necessity for displays with a controllable 464‐nm emission. A technical concept for a display with such functionality will be presented.     

Fracture toughness and shear behavior of composite bonded joints based on a novel aerospace adhesive

In this paper, the mechanical performance of the newly developed LMB aerospace structural adhesive has been characterized experimentally. To this end, a comparison has been performed with the Epibond 1590 A/B adhesive on the basis of the effects of thermal aging, wet aging and adhesive thickness on the fracture toughness and shear behavior (static and fatigue) of bonded joints between CFRP laminates. Mode-I and -II fracture toughness was measured through tensile and 3-point bending tests on double-cantilever beam specimen, respectively, while the shear behavior of the joints was assessed through static and fatigue double-lap shear tests. A fractographic analysis of the fracture surfaces was performed in order to detect the failure mode of the bonded joint. The experimental results show a higher fracture toughness and improved fatigue behavior for the LMB adhesive.     

Effect of thermal treatment on the tensile and in‐plane shear behavior of carbon fiber‐reinforced poly(phenylene sulfide) composite specimens

The effect of PPS matrix evolution occurring during thermal treatment of carbon fiber‐reinforced PPS plies prior to their consolidation to laminates on the mechanical behavior of the composite material has been investigated. The thermal treatments were performed at temperatures and times, which are relevant for processing PPS composites. All thermal treatments were carried out in an oven in air to facilitate the presence of oxygen, while the subsequent consolidation was performed in an autoclave. The tensile and in‐plane shear behavior of both, thermal‐treated and untreated materials, was investigated. Differential scanning calorimetry and microscopy analyses were made to evaluate the effect of the performed thermal treatments on degree of crystallinity and porosity of the laminates. The mechanical tests carried out have shown an appreciable degradation of the mechanical properties investigated. The observed degradation increases with increasing thermal treatment temperature and time when thermal treatments were carried out on each single composite ply prior to the consolidation. On the other hand, when, prior to the consolidation, the whole set of plies was subjected to thermal treatment, improved mechanical properties were observed. The results were discussed under the viewpoint of PPS matrix evolution during processing of the composite plies in the presence of oxygen. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Performances of a hybrid adsorption/submerged membrane biological process for toxic waste removal.

This study focuses on a hybrid process, which combines adsorption on powdered activated carbon (PAC), membrane separation using immersed hollow fibers and biological activity. The first part shows that PAC addition in a complex system (containing dissolved molecules and biological particles) can reduce membrane fouling. In that system, DMP removal is function of the activated carbon concentration. Then, respirometric experiments allowed comparison of toxic sensitivity and biological degradation of different bioreactors (membrane bioreactor (MBR), adsorptive membrane bioreactor (PAC-MBR) and classical activated sludge bioreactor (AS)). Results point out that MBR sludge is less sensitive to the toxic than the AS. For high toxic concentration, PAC addition in the MBR decreases rapidly the toxic concentration under the EC50 in the bioreactor, which allows a better biodegradation of the toxic compound. DMP assimilation is completed more rapidly with the PAC-MBR than the MBR.     

Diagnostic angiography in life-threatening colonic hemorrhage in Crohn disease

Life-threatening colonic hemorrhage is a very rare condition in Crohn's disease. Lower gastrointestinal hemorrhage in Crohn's disease occurs in 0.6-2.5% of cases. In a patient presenting with severe gastrointestinal bleeding after ileocolectomy, mesenteric angiography provided precise localisation of the bleeding site in the area of the splenic flexure.     

Paradox segmentation along inter- and intrasomitic borderlines is followed by dysmorphology of the axial skeleton in the open brain (opb) mouse mutant

In open brain (opb) mutant embryos, developmental defects of the trunk spinal cord were spatially correlated with severe defects of the epaxial somite derivatives including sclerotomes, whereas hypaxial somite derivatives are much less affected. Later in development, the neural arches (epaxial sclerotome derivatives) formed but were severely disorganized, and also the distal ribs (hypaxial sclerotome derivatives) were malformed. Adjacent neural arches and vertebral bodies were often fused where joints should have formed suggesting defects of the intrasomitic borderlines. Moreover, neural arches frequently and ribs sometimes were split into halves at distinct levels along the dorso-ventral body axis. This suggests that 'resegmentation' of sclerotomes across the somite borders did not completely occur. These prominent skeletal defects were preceded by reduced expression of Pax1 along the intrasomitic borderlines, and incomplete maintenance of somite borders between central sclerotome moieties. The defects of the axial skeleton were accompanied by segmentation defects of the myotomes which were split distally, and also partly fused from adjacent segments across somite borders. The segmentation defects observed suggest that in opb mutants both segmental borderlines, the somite borders and the intrasomitic borderlines (fissures), were affected and behaved paradoxically.     

Hereditary angioedema. A rare cause of acute abdominal pain with ascites

HISTORY AND CLINICAL FINDINGS: Since the age of 16 years a now 25-year-old woman had been known to have C1-inhibitor (C1-INH) deficiency. She presented herself at the emergency department because of acute severe lower abdominal cramps. A urinary infection had been treated with antibiotics for the previous 4 days. There was marked pain on pressure over the lower abdomen, but there were no signs of peritonitis and bowel sound were normal. There had been no nausea or vomiting and the stools had been normal. INVESTIGATIONS: There was a leukocytosis of 10,200/microliter, moderately elevated C-reactive protein (44.8 mg/l), haemoglobin concentration of 17 g/dl and haematocrit of 51%. Radiology revealed oedema of the duodenum and sonography showed free fluid in the abdomen. TREATMENT AND COURSE: After excluding an acute abdomen and in view of the C1-INH deficiency treatment was symptomatic. All symptoms completely disappeared after 2 days. CONCLUSIONS: Exclusively gastrointestinal symptoms and ascites are rare in patients with hereditary angioedema. But knowledge of this manifestation of the disease is important because patients are sometimes operated under the false diagnosis of acute abdomen. In severe cases symptomatic treatment may have to be supplemented by C1-INH administration. Prevention with attenuated androgens should be started or modified, respectively.     

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