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Surface tension is an important concept when considering any aspect of droplet behavior. Surface tension causes the spherical geometry that droplets form and determines the liquid pressure within the droplet as a function of droplet size. As the critical point for the liquid is approached, the surface tension goes to zero and droplets no longer form, a defining aspect for supercritical conditions. The surface tension of liquid oxygen droplets in gaseous oxygen and helium environments at a variety of pressures was calculated in the course of a molecular dynamics simulation. The surface tension was calculated by averaging the net interatomic attractive force experienced by atoms in the simulation. The calculated values of surface tension as a function of pressure compared well with experimentally measured values. The effect of the helium environment in raising the critical point of the oxygen was reproduced by the simulations. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the atomization of a cryogenic nitrogen jet under thermodynamic conditions typical for high-pressure LOX/GH2 rocket combustors. Atomization of fluids near the critical point; Free gas jet limit and the liquid spray limit; Results and discussion.

We present a case of a 52-year-old male who was evaluated due to anorexia, persistent diarrhea, weight loss, and liver enzyme elevations, with no hematologic laboratory abnormalities. Imaging modalities revealed several tissue lesions involving the pancreas, the right kidney, and an axillary lymph node. Diagnosis of Castleman disease was reached only due to the tissue obtained from the lymph node. Chemotherapy and immunosuppression led to a short remission. The patient underwent autologous stem cell transplantation, and has since been in remission. This case demonstrates the cryptogenic and chameleon-like nature of Castleman disease. Challenges in treating Castleman disease patients reflect current limitations and the need for a greater understanding of disease pathogenesis.

Background & Aims: Transplantation of neural stem cells (NSC) has been shown to be successful in a variety of experimental models of nongastrointestinal diseases. The aim of this study was to assess the potential of NSC transplantation as a therapeutic strategy for neuronal replacement in disorders of the enteric nervous system., Methods: Central nervous system-derived NSC (CNS-NSC) were obtained from the subventricular zone of rat brain (E17). Expression of RET, GFRalpha1, and neuronal nitric oxide synthase (nNOS) was assessed by Western blot and immunocytochemistry. Nitric oxide (NO) production was assessed using the NO-sensitive fluorescent indicator DAF-2. CNS-NSC (labeled with CM-DiI) were transplanted into the pylorus of mice and fluorescent double-labeling immunostaining for betaIII-tubulin or PGP 9.5 and nNOS was performed at 2, 4, and 8 weeks after transplantation., Results: Our results show that CNS-NSC express both the receptors (RET and GFRalpha1) for the enteric neurotrophin, GDNF; GDNF, in turn, induces expansion of the RET-expressing CNS-NSC population. Furthermore, CNS-NSC express nNOS and produce NO in vitro. When transplanted into the gut, CNS-NSC differentiate into neurons, continue to express nNOS and survive at least 8 weeks., Conclusions: We conclude that transplantation of CNS-NSC bears promise as a potential cellular replacement strategy for enteric neurons.

Background & Aims: In somatic pain models, increases in nerve growth factor (NGF) are linked to the development of pain and hyperalgesia. The aim of this study was to examine a rat model of acute necrotizing pancreatitis for changes in NGF expression., Methods: NGF protein and messenger RNA (mRNA) levels in the pancreas were correlated with histopathologic changes during the course of acute necrotizing pancreatitis in rats induced by the intraperitoneal injection of L-arginine. Immunohistochemistry for NGF localization was performed on the pancreatic tissue., Results: Two phases of NGF production were observed in the inflamed pancreas: an early release from pancreatic islets at 2 and 6 hours and a later increase in mRNA (18-fold at maximum) at 3 days and in protein levels (7-fold at maximum) at 5 days coinciding with maximum parenchymal necrosis. The intense NGF-like immunoreactivity was observed predominantly in the ductal cells in pancreas from rats with pancreatitis at 5 days., Conclusions: The development of acute necrotizing pancreatitis in this model leads to a significant increase in NGF production and appears to shift the major cellular sites of NGF production from the islets to the ductal cells. It is conceivable that NGF production in the inflamed pancreas is responsible for plastic changes in the sensory neurons that mediate peripheral sensitization and contribute to the generation of pain.

Characteristics of Alzheimer's disease include loss of brain neurons associated with the deposit of beta-amyloid protein (A beta) which is thought to be toxic to neurons possibly via induction of intracellular calcium and generation of free radicals. On this basis, we have determined the effect of ascorbic acid on the cell death and calcium increase induced by A beta in PC12 cells. We found that ascorbic acid completely abolished A beta-induced calcium increase and cell death in PC12 cells, indicating that calcium elevation and cell death are associated phenomena induced by A beta that can be rescued by antioxidants. These results are important to understand the mechanisms by which A beta is toxic to neurons and suggest that antioxidants may be part of future treatments for Alzheimer's disease.

The role of the Na+/Ca2+ exchanger in intracellular Ca2+ regulation was investigated in freshly dissociated catfish retinal horizontal cells (HC). Ca2+-permeable glutamate receptors and L-type Ca2+ channels as well as inositol 1,4,5-trisphosphate-sensitive and caffeine-sensitive intracellular Ca2+ stores regulate intracellular Ca2+ in these cells. We used the Ca2+-sensitive dye fluo 3 to measure changes in intracellular Ca2+ concentration ([Ca2+]i) under conditions in which Na+/Ca2+ exchange was altered. In addition, the role of the Na+/Ca2+ exchanger in the refilling of the caffeine-sensitive Ca2+ store following caffeine-stimulated Ca2+ release was assessed. Brief applications of caffeine (1-10 s) produced rapid and transient changes in [Ca2+]i. Repeated applications of caffeine produced smaller Ca2+ transients until no further Ca2+ was released. Store refilling occurred within 1-2 min and required extracellular Ca2+. Ouabain-induced increases in intracellular Na+ concentration ([Na+]i) increased both basal free [Ca2+]i and caffeine-stimulated Ca2+ release. Reduction of external Na+ concentration ([Na+]o) further and reversibly increased [Ca2+]i in ouabain-treated HC. This effect was not abolished by the Ca2+ channel blocker nifedipine, suggesting that increases in [Na+]i promote net extracellular Ca2+ influx through a Na+/Ca2+ exchanger. Moreover, when [Na+]o was replaced by Li+, caffeine did not stimulate release of Ca2+ from the caffeine-sensitive store after Ca2+ depletion. The Na+/Ca2+ exchanger inhibitor 2',4'-dimethylbenzamil significantly reduced the caffeine-evoked Ca2+ response 1 and 2 min after store depletion.

The authors evaluated, at scanning electron microscope (S.E.M.), the morphological aspects of composite resin surfaces applied on dentin subjected, "in vitro", to chemical or chemo-mechanical treatments. S.E.M. photographs of dentinal surfaces of composite, applied on dentin treated with acid agents or Caridex, showed extensive penetration of resin tags into dentinal tubules and their deep adaptation to rough and winding dentinal surfaces. The obtained results have been evaluated in the light of recent advances in biocompatibility and long-term stability of composite fillings, in particular, to setting up new materials and methods in cavities preparation and treatment.

A wear test was conducted to evaluate carbide and diamond dental burs, in air turbines at 400,000 r.p.m., by using a dentine-enamel substrate. There is less variability within each bur type. All of the burs showed a decreased ability to make a standard cut with succeeding trials. Generally, a linear dulling rate was observed with a progressive reduction of cutting effectiveness, except for middle grain burs, that showed better characteristics among tested burs.

In this report the Authors examined the protective action obtained on the dentin by using a varnish before acid etching. Sectional surfaces of twelve extracted teeth were observed by SEM, analysing the cover, the polymerization and the efficiency of dentine protection. The result show the effectiveness of the applied technique.