Early markers of major adverse events in children after cardiac operations

OBJECTIVES: The purpose of this study was to determine the physiologic variables that predict major adverse events in children in the intensive care unit after cardiac operations. METHODS: A cohort observational study was conducted. At the time of admission to the intensive care unit and 4, 8, 12, and 24 hours later the following variables were recorded: mean arterial pressure, heart rate, cardiac index, oxygen delivery, mixed venous oxygen saturation, base deficit, blood lactate, gastric intramucosal pH, carbon dioxide difference (the difference between arterial carbon dioxide tension and gastric intraluminal carbon dioxide tension), and toe-core temperature gradient. Major adverse events were prospectively identified as cardiac arrest, need for emergency chest opening, development of multiple organ failure, and death. RESULTS: Ninety children were included in the study; 12 had major adverse events and there were 4 deaths. Blood lactate level, mean arterial pressure, and duration of cardiopulmonary bypass were the only significant, independent predictors of major adverse events when measured at the time of admission to the intensive care unit. The odds ratio (95% confidence intervals) for major adverse events if a lactate level was greater than 4.5 mmol/L was 5.1 (1.2 to 21.1), for admission hypotension 2.3 (0.5 to 9.8), and for a cardiopulmonary bypass time greater than 150 minutes 13.7 (3.3 to 57.2). Four hours after admission lactate and carbon dioxide difference, and 8 hours after admission lactate and base deficit, were independently significant predictors. The odds ratios for major adverse events if the blood lactate level was greater than 4 mmol/L at 4 and 8 hours were 8.3 (1.8 to 38.4) and 9.3 (1.9 to 44.3), respectively. At no time in the first 24 hours were cardiac output, oxygen delivery, mixed venous oxygen saturation, toe-core temperature gradient, or heart rate significant predictors of major adverse events. CONCLUSIONS: In the context of our current treatment strategies, the duration of cardiopulmonary bypass and blood lactate level, measured in the early postoperative period, were the best predictors of impending major adverse events.     

Histoplasma capsulatum sinusitis

Sinusitis is commonly reported in patients with AIDS. In addition to the usual bacterial pathogens isolated from immunocompetent patients, sinusitis in patients with AIDS may be caused by a variety of unusual bacteria, viruses, fungi, parasites, and mycobacteria. Histoplasma capsulatum has not typically been associated with sinusitis in either group of patients. We report a case of sinusitis caused by H. capsulatum in a patient with AIDS.     

A probabilistic fouling and cost model for plate‐and‐frame heat exchangers

Fouling in plate‐and‐frame heat exchangers (PHEs) may be defined as the deposition of unwanted material on the heat transfer surface that reduces heat‐transfer and increases the resistance to fluid flow. Once the thermal–hydraulic performance decreases to a minimum acceptable level, cleaning of the equipment has to be done to restore the performance. The decision regarding periodic off‐line maintenance of the heat exchangers is generally based on a thermal–economic performance of the process. In this paper, we discuss a probabilistic maintenance model for PHE by incorporating the risk level and scatter parameter of the four random fouling growth models, namely linear, power law, falling rate and asymptotic models, which are integrated in the dimensionless cost model for a heat exchanger used in a steel plant. All the results are presented in terms of non‐dimensional plots. The results show that there is a strong relationship between t_down and the uptime, particularly in the region where the costs of operation and maintenance are minimum. Copyright © 2005 John Wiley & Sons, Ltd.     

Investigation of active slip-systems in some body-centered cubic metals

Tensile tests were performed on high-purity W and Mo polycrystals at room temperature for a range of axial strain-rates 2.1 × 10⁻⁴–2.1 × 10⁻² s⁻¹. The critical resolved shear stress (CRSS) data was analyzed by using the analytical formulation for the strain-rate dependence of the CRSS derived in the kink-pair nucleation (KPN) model of flow stress in crystals with high intrinsic lattice friction. On evaluation of various microscopic slip-parameters of the model, the active slip-system in both W and Mo polycrystals was identified as {110}〈111〉. This is in good agreement with that deduced from the published data on the temperature dependence of the CRSS of these crystals as well as from the observed slip-lines on the deformed crystals reported in the literature. Moreover, the available data on the temperature dependence of the CRSS of Mo, Nb, Fe, V, and K crystals were also analyzed within the framework of the KPN model of flow stress. Peierls mechanism was found to be responsible for the CRSS of these metals; the active slip-systems in refractory metals Mo, Nb, Fe, and V were {110}〈111〉 and {211}〈111〉 whereas that in alkali metal K was {321}〈111〉.     

Review of liquid metal corrosion issues for potential containment materials for liquid lead and lead–bismuth eutectic spallation targets as a neutron source

Lead (Pb) and lead–bismuth eutectic (44Pb–56Bi) have been the two primary candidate liquid metal target materials for the production of spallation neutrons. Selection of a container material for the liquid metal target will greatly affect the lifetime and safety of the target subsystem. For the liquid lead target, niobium–1 wt% zirconium (Nb–1Zr) is a candidate containment material for liquid lead, but its poor oxidation resistance has been a major concern. In this paper, the oxidation rate of Nb–1Zr was studied based on the calculations of thickness loss resulting from oxidation. According to these calculations, it appeared that uncoated Nb–1Zr may be used for a 1-year operation at 900°C at P_O2=1×10^–6 Torr, but the same material may not be used in argon with 5-ppm oxygen. Coating technologies to reduce the oxidation of Nb–1Zr are reviewed, as are other candidate refractory metals such as molybdenum, tantalum, and tungsten. For the liquid lead–bismuth eutectic target, three candidate containment materials are suggested, based on a literature survey of the materials’ compatibility and proton irradiation tests: Croloy 2-1/4, modified 9Cr–1Mo, and 12Cr–1Mo (HT-9) steel. These materials seem to be used only if the lead–bismuth is thoroughly deoxidized and treated with zirconium and magnesium.     

Water diffusion in polymer nano-films measured with microcantilevers

We present a method to measure the absorption of water molecules from the liquid and the vapour phase into polymer nano-films and the diffusion inside these films. Film thickness can be down to 45 nm. To demonstrate the possibilities of this method we use polymer films that are deposited on the upper side of a silicon cantilever by plasma polymerization of norbornene. When a microdrop of water is deposited onto the initially straight cantilever, the drop causes the cantilever to bend while it evaporates. Evaporation of such small water drops usually takes less than a second. An upwards bending is due to capillary forces and a downwards bending is due to the diffusion of water into the polymer film – and the consequent volume expansion (swelling) of the film. The magnitude of the capillary forces and the extent of swelling continuously change during drop evaporation. When drop evaporation is over the cantilever returns to its initial straight position. We simulate the time dependent bending with a numerical model that qualitatively agrees with the experiment. From the time dependence of cantilever bending we are able to determine the diffusion coefficient of water in the thin polymer film.     

The U─Zr─C Ternary Phase Diagram above 2473 K

The U─Zr─C tertnary phase diagram is optimized by graphical and numerical curve fitting of self-consistent thermodynamic and phase diagram data reported in the literature. The system is described from 2473 to 3693 K using isothermal ternary phase diagrams. The solidus and liquidus curves of the U_xZr_1−xC_y solid solution were estimated from combined thermodynamic and phase diagram data. The solidus and liquidus curves in the ternary system were calculated using a modified form of a free-energy minimization method developed by Rudy and Chang. The calculated curves agree with experimental data.     

Ion channels in isolated mouse jejunal crypts

The patch-clamp technique was used to characterise the ion channels in cells located in the mid region of mouse jejunal crypts. Six different channels were seen. A large outwardly rectified K+ channel (BK) (conductance, g at 0 mV = 92 +/- 6 pS), which was highly selective for K+ [PK+ (1) > PRb+ (0.6) > PCs+ (0.09) approximately PNa+ (0.07) > PLi+ (0.04)], had a low, voltage-independent open probability (Po) in the on-cell (O/C) configuration and appeared in 66% of the patches. In inside-out (I/O) patches, this channel had a linear current/voltage (I/V) relationship (g = 132 +/- 3 pS), Po was voltage dependent and it was blocked by cytoplasmic Ba2+ (5 mmol/l). An intermediate K+ channel (IK) which was present in 49% of O/C patches, had a linear I/V (g = 38 +/- 3 pS), ran-down in O/C patches, and was not seen in I/O patches. A number of smaller channels (SC) with conductances ranging from 5 to 20 pS were seen in 16% of O/C patches. Also present in the basolateral membrane were a Cl- channel (ICOR) and a nonselective cation channel (NSCC). These channels were only seen in I/O patches. ICOR had an outwardly rectified conductance (g at 0 mV = 36 +/- 2 pS), its Po was independent of voltage and unaffected by variations in cytoplasmic Ca2+ (100 nmol/l to 1 mmol/l) or ATP (0-1 mmol/l). The NSCC had a linear conductance (20 +/- 1 pS), its Po increased with depolarisation and elevation of cytoplasmic [Ca2+] (> or = 10 micromol/l), but was reduced by cytoplasmic ATP. None of the basolateral channels described here were activated by cAMP-dependent secretagogues, although a Cl- conductance was activated. This cAMP-dependent Cl- conductance was distinct from the basolateral Cl- channel and thus is most likely located in the apical membrane.