Isotropic-to-nematic transition in confined liquid crystals: an essentially nonuniversal phenomenon.

Computer simulations are presented of the isotropic-to-nematic transition in a liquid crystal confined between two parallel plates a distance H apart. The plates are neutral and do not impose any anchoring on the particles. Depending on the shape of the pair potential acting between the particles, we find that the transition either changes from first order to continuous at a critical film thickness H=H(x) , or that the transition remains first order irrespective of H . This demonstrates that the isotropic-to-nematic transition in confined geometry is not characterized by any universality class, but rather that its fate is determined by microscopic details. The resulting capillary phase diagrams can thus assume two topologies: one where the isotropic and nematic branches of the binodal meet at H=H(x), and one where they remain separated. For values of H where the transition is strongly first order the shift Deltaepsilon of the transition temperature is in excellent agreement with the Kelvin equation. Not only is the relation Deltaepsilon proportional, variant 1/H recovered but also the prefactor of the shift is in quantitative agreement with the independently measured bulk latent heat and interfacial tension.

Nematics with quenched disorder: violation of self-averaging.

We consider the isotropic-to-nematic transition in liquid crystals confined to aerogel hosts, and assume that the aerogel acts as a random field. We generally find that self-averaging is violated. For a bulk transition that is weakly first order, the violation of self-averaging is so severe that even the correlation length becomes non-self-averaging: no phase transition remains in this case. For a bulk transition that is more strongly first order, the violation of self-averaging is milder, and a phase transition is observed.

Therapy for the Brugada syndrome.

The Brugada syndrome is a congenital syndrome of sudden cardiac death first described as a new clinical entity in 1992. Electrocardiographically characterized by a distinct coved-type ST segment elevation in the right precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young and otherwise healthy adults, and less frequently in infants and children. The ECG manifestations of the Brugada syndrome are often dynamic or concealed and may be revealed or modulated by sodium channel blockers. The syndrome may also be unmasked or precipitated by a febrile state, vagotonic agents, alpha-adrenergic agonists, beta-adrenergic blockers, tricyclic or tetracyclic antidepressants, a combination of glucose and insulin, and hypokalemia, as well as by alcohol and cocaine toxicity. An implantable cardioverter-defibrillator (ICD) is the most widely accepted approach to therapy. Pharmacological therapy aimed at rebalancing the currents active during phase 1 of the right ventricular action potential is used to abort electrical storms, as an adjunct to device therapy, and as an alternative to device therapy when use of an ICD is not possible. Isoproterenol and cilostazol boost calcium channel current, and drugs like quinidine inhibit the transient outward current, acting to diminish the action potential notch and thus suppress the substrate and trigger for ventricular tachycardia/fibrillation (VT/VF).

Mandibular bone growth induced by a hydroxylapatite-coated subperiosteal implant: a case report.

History of the tripodal mandibular subperiosteal implant and the evolution of its design are discussed. Basic principles of bone physiology are reviewed especially as they relate to bone response to loading. Modeling and remodeling are controlled by a strain-related environment. Modeling can alter the shape and volume of bone. This aspect of bone growth has been reported with transosteal implants. A case report is presented in which apparent bone growth occurred following placement of a hydroxylapatite-coated subperiosteal implant. The implant was successfully revised following an acute infection around one of the permucosal sites.

Effects of graded thermal injury on microvascular permeability at the site of injury.

To define whether capillary permeability traits at the site of a burn differ according to injury severity, a canine hind leg lymphatic was cannulated to measure macromolecular permeability in response to three different scalding solutions. Leg venous pressure was raised to approximately 40 mm Hg and maintained until a minimal lymph-to-plasma total protein ratio (CL/CP)min and steady-state lymph flow (QL; microliter/min/100 g) was attained. The protein reflection coefficient (1-CL/CP), fluid filtration coefficient (Kf; microliter/min/mm Hg/100 g), and QL were determined before and for 6 hr after a 5-sec hind paw immersion in either 100 degrees C (n = 7), 80 degrees C (n = 7), or 70 degrees C (n = 7) water. A group of five animals served as controls. In the absence of any systemic hemodynamic alterations, the 100 and 80 degrees C scald groups experienced significant (P < 0.05, ANOVA) increases in QL, CL/CP, and Kf as compared to respective preburn values and time-matched unburned control values. Most monitored parameters were significantly higher following 100 degrees C injury vs 80 degrees C injury. Parameters in the 70 degrees C group did change after scald, but were not significantly different from preburn values or from the control group. Alterations in capillary permeability to protein and fluid flux measured at the burn site are graded, not all or none phenomena, being dependent upon the severity of injury.

Effects of pentafraction administration on microvascular permeability alterations induced by graded thermal injury.

BACKGROUND: Pentafraction is a pentastarch derivative hypothesized to limit burn edema by "sealing" damaged capillaries, restoring a barrier to fluid translocation and macromolecular (protein) flux. METHODS: Canine hind paw lymph flow (QL) and lymph (CL) and plasma (CP) protein concentrations were measured before and for 6 hours after (1) 5-second 100 degrees C (n = 6) or 80 degrees C (n = 6) foot paw scald, (2) 100 degrees C (n = 5) or 80 degrees C (n = 5) foot paw scald followed 30 minutes later by a 4 cc/kg bolus of 6% pentafraction, or (3) pentafraction infusion without scald (n = 5). Before scald or pentafraction infusion, hind paw venous pressure was elevated and maintained by outflow restriction until a steady state, minimal CL/CP was reached. The reflection coefficient, sigma d, was determined as 1-CL/CP, and the (fluid) filtration coefficient (Kf) was calculated. RESULTS: Scalding uniformly produced statistical (p < 0.05, ANOVA) increases in QL, CL/CP, sigma d, Kf, and paw weight gain. Postburn pentafraction infusion produced no enduring alterations in any measured parameter as compared with those of animals who received a matched severity scald without pentafraction. CONCLUSIONS: Pentafraction does not appreciably ameliorate the adverse microcirculatory consequences observed at the site of burn injury.

Dexamethasone downregulates vitamin D receptors in rat kidney, unmasking a high affinity binding site.

Dexamethasone exerted tissue-specific effects on rat vitamin D receptor levels: upregulation of receptors in intestine, downregulation in kidney, and no effect on receptors in testis, heart, and lung. Scatchard analysis showed selective downregulation of the low affinity receptor site (Kd = 0.9 nM) in kidney, thus unmasking a high affinity binding site (Kd = 0.05 nM). The single low affinity site in intestine (Kd = 0.3-0.7 nM) was upregulated, while the single high affinity site in testis (Kd = 0.07-0.09 nM) was not changed. These results demonstrate the existence of two types of nuclear binding sites in rat kidney and establish that there are similarities between the high affinity binding site in the rat kidney and the single high affinity receptor site in the testis.

Irrigation of the abdominal cavity in the treatment of experimentally induced microbial peritonitis: efficacy of ozonated saline.

Ozone is an oxidizing agent possessing potent in vitro microbicidal capacity. This study was designed to address the extent to which irrigation of the contaminated abdominal cavity using a saline solution primed with ozone is effective in reducing morbidity and mortality. Gelatin capsules containing different quantities of a premixed slurry of filtered human fecal material were implanted in the peritoneal cavities of a preliminary series of rats. Three inocula concentrations were selected for later experiments, based upon their ability to produce morbid consequences: (1) high (100% 1-day mortality), (2) medium (70% 3-day mortality, 100% abscess rate in survivors), and (3) low (100% 10-day survival, 100% abscess rate). Fecal and abscess bacteriology were similar in all rats. The peritoneal cavities of 240 rats then underwent fecal-capsule implantation (three groups of 80 rats/inoculum concentration). At celiotomy 4 hours later, equal numbers of rats from each group were randomly assigned to one of four protocols: (1) no irrigation, (2) normal saline irrigation, (3) saline-cephalothin irrigation, and (4) ozonated saline irrigation. Each treatment lasted 5 minutes, using 100 ml of irrigation fluid. Mortality was significantly reduced when, in lieu of no irrigation, any of the irrigation solutions were used. Additionally, ozonated saline statistically proved the most effective irrigating solution for reducing abscess formation in survivors.

False negatives, Canter's Background Interference Procedure, the trail making test, and epileptics.

This study correlated the Canter's Background Interference Procedure (BIP) scores of 141 adult epileptics with the five variables of age at onset of symptoms, etiology, type of symptoms, severity of generalized background dysrhythmia, and locus of lesion. These variables did not correlate significantly with the BIP scores, contrary to expectations. The BIP's nearly 50% false negative rate was much higher than that of the Trail Making Test, using either Reitan's or Russell's cutting scores for Trails A (33% and 21%, respectively) or Trails B (35% and 28.5%, respectively). The BIP often does not agree with abnormal neurological diagnoses, but often does agree with psychiatric diagnoses of Organic Brain Syndrome (OBS). The authors argue that this is due to the BIP's normative history and to its sensitivity to organic concreteness. The authors suggest that future BIP validity studies include a behavioral measure of OBS as criterion.