Preparation and physical characteristics of graphene ceramics.

Graphene, a two-dimensional structure of carbon, due to its structure has unique physico-chemical properties that can be used in numerous research and industry areas. Although this structure is already well known, there are still technological (and cost) barriers which do not allow to produce this material in large quantities and hence prevent its use in various applications. For this reason, many technologies are currently being developed to obtain graphene in forms that would enable its widespread use. The graphene-like ceramics were fabricated by the high isostatic pressure method at different temperatures. This technique allows to obtain dense ceramics with various shapes. The structure and morphology of sintered graphene were investigated by XRD, SEM and the Raman spectroscopy. The hardness, thermal conductivity and electric transport measurements recorded in a wide range of temperatures were used to analyze the physical properties of the obtained ceramics.

Glassy Anomalies in the Low-Temperature Thermal Properties of a Minimally Disordered Crystalline Solid.

The low-temperature thermal and transport properties of an unusual kind of crystal exhibiting minimal molecular positional and tilting disorder have been measured. The material, namely, low-dimensional, highly anisotropic pentachloronitrobenzene has a layered structure of rhombohedral parallel planes in which the molecules execute large-amplitude in-plane as well as concurrent out-of-plane librational motions. Our study reveals that low-temperature glassy anomalies can be found in a system with minimal disorder due to the freezing of (mostly in-plane) reorientational jumps of molecules between equivalent crystallographic positions with partial site occupation. Our findings will pave the way to a deeper understanding of the origin of the above-mentioned universal glassy properties at low temperature.

Glassy Dynamics versus Thermodynamics: The Case of 2-Adamantanone.

The heat capacity and thermal conductivity of the monoclinic and the fully ordered orthorhombic phases of 2-adamantanone (C10H14O) have been measured for temperatures between 2 and 150 K. The heat capacities for both phases are shown to be strikingly close regardless of the site disorder present in the monoclinic crystal which arises from the occupancy of three nonequivalent sites for the oxygen atom. The heat capacity curves are also well accounted for by an evaluation carried out within the harmonic approximation in terms of the g(ω) vibrational frequency distributions measured by means of inelastic neutron scattering. Such spectral functions show however a significant excess of low frequency modes for the crystal showing statistical disorder. In contrast, large differences are found for the thermal conductivity which contrary to what could be expected, shows the substitutionally disordered crystal to exhibit better heat transport properties than the fully ordered orthorhombic phase. Such an anomalous behavior is understood from examination of the crystalline structure of the orthorhombic phase which leads to very strong scattering of heat-carrying phonons due to grain boundary effects able to yield a largely reduced value of the conductivity as well as to a plateau-like feature at intermediate temperatures which contrasts with a bell-shaped maximum shown by data pertaining the disordered crystal. The relevance of the present findings within the context of glassy dynamics of the orientational glass state is finally discussed.

An improved clinically relevant sepsis model in the conscious rat.

OBJECTIVE: To develop an improved small animal experimental paradigm that more closely mimics human sepsis. DESIGN: Prospective, randomized, controlled animal study. SETTING: Medical school research laboratory. SUBJECTS: Male Sprague-Dawley rats (280-320 g). INTERVENTIONS: We monitored the hemodynamic, hematologic, and biochemical consequences of abdominal sepsis produced by intraperitoneal implantation of a fibrin clot containing Escherichia coli in conscious, antibiotic-treated, rats. MEASUREMENTS AND MAIN RESULTS: Similar to human sepsis, the implanted, infected clot (LD50 = 5-7 x 10(8) colony forming units/mL, n = 6) elevated cardiac index (>7% vs. sterile clot, p < .05, at 4 hrs), whereas mean arterial pressure and heart rate remained unaffected. The total peripheral resistance index and stroke volume index tended to decrease and increase, respectively. In contrast, an intravenous bolus injection of endotoxin (LD50 of E. coli lipopolysaccharide = 5.6 mg/kg, n = 7), the most commonly used sepsis model, induced profound hypodynamic responses manifested by a 27% decrease (vs. endotoxin vehicle, p < .01) in cardiac index, a 28% increase in the total peripheral resistance index (p < .01), and a 33% decrease in the stroke volume index (P < .01). The infectious peritonitis model also displayed dose-dependent thrombocytopenia (<61%, p < .05), leukopenia (<60%, p < .05), and mortality rate (50% at 5-7 x 10(8) colony forming units/mL, p < .05) with a minimally elevated serum tumor necrosis factor-alpha level (145 vs. 12 +/- 6 pg/mL in controls, p < .05). CONCLUSION: This rodent model of antibiotic-treated, intra-abdominal infection features key characteristics of clinical sepsis. Although the hyperdynamic response observed in septic patients undergoing resuscitation was not clearly elicited, this paradigm better mimics clinical sepsis compared with the commonly used endotoxin model. Thus, utilization of this paradigm may provide additional opportunities to explore mechanisms of sepsis and to examine novel therapeutics.

Admission patterns of an urban level I trauma center.

Because trauma admission and hospitalization patterns have profound effects on the organization and utilization of urban trauma-care systems, the objective of this study was to identify and analyze these patterns. As an example, admissions to an urban Level I trauma center were reviewed. Retrospective review of all 2029 trauma admissions to a Level I trauma center was conducted from 1993 to 1996. The result was that most trauma patients were young (40% < 30 years of age) and male (74%). Mechanisms of injury were motor vehicle accident (36%), fall (27%), gunshot (17%), stab (7%), assault (6%), and swimming or diving accident (3%). Half of the patients were directly admitted from the scene. Injury Severity Score, length of stay, and mortality were 14.1 +/- 0.3, 10.5 +/- 0.3 days, and 5.1%, respectively. Admissions tended to occur more frequently between 4:00 PM and midnight (46%), between Friday and Sunday (52%), and between July and October (41%). The following patterns were identified: admissions per year decreased (-21%) because of reduced penetrating trauma (-43%, P < .01); pediatric patients (< 15 years) had similar incidence of penetrating trauma as adults (ages 15-45). Length of stay for all mechanisms of injury was not statistically different; most mortalities occurred within the first day (33%, P < .01) or after 6 days (36%, P < .01); early mortality was mainly due to penetrating injury (74%, P < .01), whereas late mortality was related to blunt trauma (92%, P < .01). The conclusion was that admission and demographic patterns were identified, which may be useful in the utilization, modification, and future design of trauma systems.

Platelet-activating factor (PAF) in experimental and clinical sepsis.

Despite considerable progress in understanding the pathogenic mechanisms of Gram-negative sepsis, the outcome of septic patients has not significantly improved. There are ample data that support a role for inflammatory mediators in sepsis that act in synergy with infectious agents to initiate and propagate the disease process. One such mediator is the glycerophospholipid platelet-activating factor (PAF). The objective of the present review is to summarize experimental and clinical evidence implicating PAF as a mediator in the pathomechanism of sepsis. This review is timely because many potent and selective PAF antagonists have matured for clinical development and a careful analysis of the data that support or refute the merit of clinical trials with such compounds may be important for both academic and pharmaceutical applications.

Candida pericarditis: clinical profile and treatment.

BACKGROUND: Candida pericarditis is a rare medical and surgical emergency which, unless treated, leads to impaired cardiac function and death. To facilitate early diagnosis, the clinical features of this condition should be identified. METHODS: Twenty-five cases of Candida pericarditis reported in the last 30 years along with 1 new case were reviewed with regard to demographics, precipitating factors, diagnosis, treatment, and outcome. RESULTS: The syndrome occurred in immunocompromised (73%), antibiotic-treated (62%), or postpericardiotomy (54%) patients. The clinical presentation was frequently subtle and nonspecific. Nevertheless, unexplained fever, an increasing cardiac shadow on chest roentgenogram, or the development of cardiac tamponade may be suggestive. Positive culture for Candida in pericardial fluid or histologic evidence of yeast forms in pericardial tissue establishes the diagnosis. A combination of pericardiocentesis followed by operative drainage and antifungal agents is the usual treatment. Untreated, Candida pericarditis is 100% lethal, whereas prompt diagnosis and treatment lead to cure (mean follow-up, 19 months). CONCLUSIONS: Fever and evolving cardiac tamponade in immunocompromised or postpericardiotomy patients may be suggestive of Candida pericarditis; the presence of organisms in pericardial fluid is diagnostic. Pericardiocentesis followed by operative drainage and antifungal agents appears to be the treatment that is most likely to be curative.