Experimental evidence of selective heating of molecules adsorbed in nanopores under microwave radiation.

We have performed in situ quasielastic neutron scattering (QENS) measurements on zeolite-guest systems under microwave irradiation, for comparison with corresponding simulations. Both experiment and simulation reveal selective heating of methanol in silicalite, but little to no heating of benzene in silicalite. Effective translational and rotational temperatures extracted from QENS data under microwave heating were found to depend on microwave power. In agreement with simulation, QENS rotational temperatures significantly exceed translational ones at high microwave power, thus providing the first microscopic proof for athermal effects in microwave-driven nanopores.

Temperature distributions within zeolite precursor solutions in the presence of microwaves.

While microwave enhancement of chemical syntheses has been demonstrated for a broad variety of chemical reactions, there is no accepted universal mechanism. Is the enhancement due to more efficient heating, to overheating, to nonuniform heating, or to nonthermal effects? Analyses are complicated due to the often significant spatial and temporal temperature variations in microwave reactor systems, particularly within microwave ovens. To address this, we employ multiple fiber-optic temperature probes throughout a cylindrical reactor with a focus on zeolite synthesis solutions being the dielectric medium. First, we vary the modes of power delivery (pulsed versus continuous) to quantify differences in local temperatures within a reaction vessel with water being the dielectric medium. The temperature distribution at steady state in the center of the water increased by 10 degrees C in pulsed delivery mode compared to the temperature distribution obtained in continuous delivery mode at the same average power. Then, we measured the temperature distributions for several zeolite synthesis solutions (NaY, silicalite, and SAPO-11) and water under microwave heating to investigate the temperature variations within these dielectric media. These measured temperature variations were found to be significant, depending on the dielectric permittivities of the reaction medium and their changes with temperature. Temperature profiles also depend on the microwave delivery mode and reactor configuration, i.e., the microwave reactor engineering. NaY synthesis solution exhibited the smallest penetration depth (2.6 mm at room temperature and 2.45 GHz); as a result, the solution temperature near the wall increased by 65 degrees C over the target temperature when the temperature at the center of the solution was targeted to 60 degrees C. To demonstrate the effect of overheating on zeolite synthesis, we synthesized NaY zeolite at 95 degrees C by controlling the temperature of the reaction near the wall, close to the penetration depth, and in the center away from the penetration depth. Controlling the center temperature results in greater overheating and consequently reduced nucleation time by 80 min, from 130 to 50 min.

Hysteresis and scanning behavior of mesoporous molecular sieves.

Sorption hysteresis is a widely studied phenomenon whose predicted behavior is well documented and researched. On the other hand, there is much less known about the region that lies between sorption isotherms, believed to be a metastable region. Scanning curves are a way of understanding the mechanism of hysteresis and a tool for hysteresis model validation. Scanning curves were produced for mesoporous materials: SBA-15 and MCM-41 for N(2) sorption at 77 K and Ar sorption at 87 K. A limited set of different scanning behaviors is identified. Like most hysteresis theories, it was found that a single model for scanning behavior cannot be extended to all materials under the same or different experimental conditions. Two behaviors are consistent with recent theories and simulations; however, several are not. The implications as to the characterization of pore dimensions and structure are discussed.

A prospective analysis of patients undergoing silicone breast implant explantation.

Despite the lack of a scientifically proven link between silicone implants and disease, many women have chosen to have their implants removed out of concern for their health. Unfortunately, there are few studies in the literature that have investigated the outcome of explanations, and there are no prospective analyses of the effect explantation has on a patient's general health. The goal of this study was to use a prospective database to determine whether there were any preoperative parameters that could be used to predict which patients would be improved following removal of silicone breast implants and to provide a quantifiable measure of that improvement. A total of 38 patients with silicone breast implants underwent operative removal of their breast implants by faculty at the University of Texas Southwestern Medical Center. They were given questionnaires regarding several personal and medical parameters to be completed preoperatively, at 6 weeks postoperatively, and at 6 months postoperatively. In addition, their physicians completed preoperative and postoperative evaluations of the patient's general health status. A control group of 38 patients was established; they were matched with the experimental group with regard to age and other initial parameters. Their responses to questionnaires were then grouped according to standard subscales to evaluate physical functioning, physical role, bodily pain, general health, vitality, social functioning, emotional role, mental health, appearance evaluation, appearance orientation, illness orientation, and body area satisfaction. When compared with the control group, we found that patients who had undergone explantation showed a temporary decrease in musculoskeletal symptoms and bodily pain, as well as an increase in vitality, mental health, and body area satisfaction. Of the experimental group, those who initially indicated a higher number of musculoskeletal symptoms and a higher appearance evaluation were more likely to indicate a significant improvement in general health since explantation.

Sustained nitric oxide production via l-arginine administration ameliorates effects of intestinal ischemia-reperfusion.

BACKGROUND: The role of nitric oxide in intestinal ischemia-reperfusion is unclear-some studies link it to the harmful effects of ischemia-reperfusion, while others report it to be protective. We propose that nitric oxide levels diminish in the reperfusion period in conjunction with the onset of increased capillary permeability. The aim of this study is to determine the effect of supplementing nitric oxide synthase with its substrate, l-arginine, on development of local mucosal injury and systemic capillary leak. MATERIALS AND METHODS: Rats underwent 30 min of superior mesenteric artery occlusion followed by 4 h of reperfusion. The vehicle groups received l-arginine either intravenously (4 mg/kg/min) or into the intestinal lumen. The intravenous groups received l-arginine either before the ischemic event or after 30 min of reperfusion. Capillary leak in the gut and lung were measured, as were degree of mucosal injury and number of infiltrating neutrophils. Appropriate controls were performed. RESULTS: Thirty minutes of mesenteric ischemia followed by 4 h of reperfusion significantly increased gut and lung leak, neutrophil infiltration, and the severity of mucosal injury. l-Arginine given iv prior to ischemia inhibited lung leak, mucosal injury, and neutrophil infiltration. When arginine was given during the reperfusion period, lung leak and neutrophil infiltration but not mucosal injury were reduced. Intraluminal l-arginine reduced mucosa injury, but had no effect on capillary leak. CONCLUSIONS: Supplementation with l-arginine enhances NO production, resulting in reduced systemic endothelial dysfunction. This may act as a useful clinical adjunct in the management of trauma patients in preventing the development of ARDS and multiple organ failure.

Optimizing breast pocket irrigation: an in vitro study and clinical implications.

Subclinical infections have been implicated in the etiology of capsular contracture. Intraoperatively, breast pocket irrigation with povidone-iodine or other antibiotic solutions has been popularized; however, detrimental effects on wound healing for these agents have been reported and their efficacy against common organisms found around breast implants has not been studied. The purpose of this study was to compare the in vitro efficacy of serial dilutions of povidone-iodine and two double antibiotic solutions DAB-1 (gentamicin/polymyxin B) and DAB-2 (gentamicin/cefazolin), against organisms most commonly found around breast implants. In phase I trials, serial dilutions of povidone-iodine and DAB were combined 1:1 with cultures of five common organisms found around implants. In phase II, povidone-iodine was serially diluted in DAB-1 rather than saline. In phase III, povidone-iodine was serially diluted with DAB-2. Efficacy for all phases was determined by plating the mixture onto agar plates and incubating at 37 degrees C for 48 hours. Povidone-iodine was 100 percent effective at a dilution of 12.5% against Staphylococcus epidermidis and 25% against Staphylococcus aureus but relatively ineffective against Escherichia coli and Pseudomonas, DAB-1 was found to be ineffective against S. epidermidis but effective against S. aureus, Propionibacterium acnes, E. coli, and Pseudomonas. In phase II trials, a concentration of 12.5% povidone-iodine in DAB was effective at killing all experimental bacteria. In phase III trials, 10% povidone-iodine in DAB-2 was effective at killing all bacteria tested. In conclusion, to maximize bacterial control of common breast implant organisms and to minimize the detrimental effects on wound healing, 10% povidone-iodine in gentamycin/cefazolin may be used with excellent results and its use clinically may reduce the incidence of capsular contracture.

Overlapping and divergent actions of estrogen and the neurotrophins on cell fate and p53-dependent signal transduction in conditionally immortalized cerebral cortical neuroblasts.

The developing cerebral cortex undergoes overlapping periods of neurogenesis, suicide, and differentiation to generate the mature cortical plate. The following experiments examined the role of the gonadal hormone estrogen in comparison to the neurotrophins, in the regulation of p53-dependent cortical cell fate. To synchronize choices between neurogenesis, apoptosis, and neural differentiation, embryonic rat cerebral cortical neuroblasts were conditionally immortalized with the SV40 large T antigen containing the tsA58/U19 temperature-sensitive mutations. At the nonpermissive temperature, cessation of large T antigen expression was accompanied by induction of p53, as well as the p53-dependent proteins, wild-type p53-activated fragment-1/Cdk (cyclin-dependent kinase)-interacting protein-1 (p21/Waf1), Bcl (B-cell lymphoma)-associated protein (Bax), and murine double minute 2 (MDM2), that lead to cell cycle-arrest, suicide, and p53 inhibition, respectively. Simultaneously, neuroblasts exit cell cycle and die apoptotically or differentiate primarily into astrocytes and immature postmitotic neuroblasts. At the nonpermissive temperature, estrogen specifically induced an antagonist-independent increase in phosphorylated p53 expression, while increasing p21/Waf1 and decreasing Bax. Coincidentally, estrogen rapidly increased and then decreased MDM2 relative to controls, suggesting temporal modulation of p53 function. Both estrogen and neurotrophins prevented DNA fragmentation, a marker for apoptosis. However, estrogen also induced a transient increase in released lactate dehydrogenase, suggesting that estrogen simultaneously induced rapid cell death in a subpopulation of cells. In contrast to the neurotrophins, estrogen also increased cell proliferation. Both estrogen and the neurotrophins supported neuronal differentiation. However, in contrast to the neurotrophins, estrogen only supported the expression of a subset of oligodendrocytic markers. These results suggest that estrogen and the neurotrophins support overlapping and distinct aspects of differentiation in the developing cerebral cortex.

Neutrophil priming state predicts capillary leak after gut ischemia in rats.

BACKGROUND: Multiple organ failure after serious injury or illness is a major determinant of mortality. An initial insult is believed to "prime" circulating neutrophils and induce systemic inflammation. Thereafter, a second insult will precipitate distant organ injury. The aim of these studies was to evaluate circulating neutrophil function after mesenteric ischemia-reperfusion to determine the neutrophil "priming state," a quantitative and clinically useful predictor of multiple organ failure. MATERIALS AND METHODS: Anesthetized Sprague-Dawley rats underwent superior mesenteric artery occlusion for 30 min or sham operation and were euthanized after 2, 6, or 24 h of reperfusion. Control animals had blood taken without any intervention. To determine changes in lung capillary permeability, another group of rats received Evan's blue, a dye that binds albumin, 1 h before sacrifice. Flow cytometric analysis was performed on 5 million white blood cells after removal of red cells by lysis and centrifugation. Neutrophil number, oxidative burst, and CD18 expression were measured. RESULTS: The number of circulating neutrophils was elevated similarly in rats subjected to sham operation or ischemia-reperfusion. Oxidative burst potential was increased at 2 h, maximum at 6 h, and normal at 24 h after reperfusion, but not in sham rats. CD18 expression was similar in all groups. There was a significant temporal correlation between the "priming state" of the circulating neutrophil, defined as the product of the neutrophil number times oxidative burst, and lung leak. CONCLUSIONS: The neutrophil "priming state" may allow the clinician to better predict those patients at greatest risk for multiple organ failure.

Management and prevention of lumbar herniation following a latissimus dorsi flap.

Lumbar herniation is a rare complication of flank surgery. We present a case of lumbar herniation that followed the mobilization of a latissimus dorsi flap for breast reconstruction. This is an unusual complication, which, to our knowledge, has only been presented twice in the literature. The roles of computed tomography for diagnosis and synthetic mesh for repair are discussed. The anatomy of the lumbar region is reviewed, and preventative measures are discussed.

Traumatic aneurysms of the face and temple: a patient report and literature review, 1644 to 1998.

The branches of the external carotid artery are protected from injury in most locations by an adequate buffer of soft tissue. On occasion, the vessels approach the surface to cross bone structures, and in these key areas they become vulnerable to blunt trauma. The facial, superficial temporal, and terminal branches of the internal maxillary arteries are the branches most often affected via this mechanism of injury. In addition, damage to deeper branches of the internal maxillary artery and to the subparotid portion of the superficial temporal artery has been reported secondary to maxillary fractures and craniofacial surgery. A brief patient report illustrates the highlights of clinical examination, diagnostic study, and surgical management of an aneurysm of the facial artery. A review of the world literature since 1644 has revealed 386 patients with traumatic aneurysms of the face and temple.