Design of a high-pressure ebulliometer,with vapor-liquid equilibrium results for the systems CHF2 Cl + CF3 CH3 and CF3 CH2 F + CH2F2

We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF₂Cl + CF₃-CH, at 275 K and for the system CF₃-CH₂F + CH₂F₂, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given.     

Effects of sleeping in a chemical protective mask on sleep quality and cognitive performance

PURPOSE: We wanted to determine whether sleep is disrupted when soldiers sleep in a new chemical protective mask, the M40. Sleep quantity and quality, extent of protection provided by the mask during sleep, and next day performance were assessed. METHOD: After several days of training, 9 male soldiers slept with and without the M40 mask on four occasions. RESULTS: Soldiers were able to tolerate the mask for most or all of the night. However, sleep, as assessed by wrist-worn activity monitors, was significantly disturbed. Minutes (mean +/- SEM) of waking significantly increased, from 25 +/- 2.1 to 86 +/- 8.5 per night (p < 0.001), and number of awakenings rose from 8 +/- 0.6 to 20 +/- 0.9 (p < 0.0001). Soldiers reported that it took longer and was more difficult to fall asleep when wearing the mask. Errors on a choice reaction time task increased significantly and subjects reported greater fatigue and sleepiness the day after sleeping in the mask. Protection provided by the masks varied substantially among subjects and declined over the course of the study. Some soldiers were protected throughout the night but others were only protected intermittently. CONCLUSION: We conclude that sleeping in the chemical protective mask should only be done when necessary, given the adverse effects on sleep and daytime function, as well as the variability of protection, of the mask.     

Determination of glycyrrhizin and glycyrrhetinic acid in traditional Chinese medicinal preparations by capillary electrophoresis

A simple, rapid, accurate and reproducible capillary electrophoretic method was developed for the assay of glycyrrhizin and glycyrrhetinic acid in traditional Chinese medicinal preparations. The buffer solution used in this method was acetonitrile and 0.02 M sodium dihydrogen-phosphate solution adjusted to pH 7.5 with 0.05 M sodium hydroxide. The linear calibration range was 0.04-2.00 mg/ml (r = 0.9988) for glycyrrhizin and 0.007-0.35 mg/ml (r = 0.9985) for glycyrrhetinic acid and recoveries were 98.1-101.3% for glycyrrhizin and 98.5-101.4% for glycyrrhetinic acid. The relative standard deviations were 1.02% (n = 6) for glycyrrhizin and 0.91% (n = 6) for glycyrrhetinic acid. The content of these two acids in Glycyrrhizae Radix and Glycyrrhizae Radix-containing Chinese medicinal preparations was successfully determined within 10 min.     

N-acetyl-cysteine causes a late re-specification of the anteroposterior axis in the Xenopus embryo

N-acetyl cysteine is an agent which has been shown to interrupt signal transduction processes linking a wide range of stimuli to the activation of NF-kappa B in mammalian cells. We have investigated its effect on the early development of Xenopus embryos by injecting it into blastulae, using concentrations comparable to those effective on cultured cells. High concentrations at the late blastula or early gastrula stage suppress posterior and enhance anterior development, yielding embryos with enlarged cement glands and otherwise consisting of little except head in extreme cases. Reducing the amount of N-acetyl cysteine injected leads to progressively more posterior structures developing. Injection into one- or two-cell embryos gives similar phenotypes, but of reduced severity and the cement gland is not so enlarged. Explants of animal cap cells taken several hours after injection develop to give large amounts of cement gland material. We have examined the expression of a number of genes in the anteriorised embryos. Posterior markers and Xsna are reduced. Noggin and Goosecoid mRNA are up-regulated through the gastrula and persist at these levels until at least the late neurula stage, whereas in controls Noggin is much lower and Goosecoid is absent at these stages. The most anteriorised phenotype may be a consequence of this changed expression.     

Carbon based electronic materials: applications in electron field emission

The influence of the different types of bonding present in a range of carbon based materials is discussed as a precursor to describing the field emission characteristics of carbon cold cathode materials. Some of the controlling factors which govern electron emission from carbon based cathodes are discussed. It is shown that from disordered carbon films the interplay between the clustered sp² phase and the insulating sp³ matrix is important. The transition from a ‘back contact’ to ‘front surface’ controlled emission mechanism is described in terms of the sp² content and field penetration. A possible reason for high field enhancement factors found in disordered films also is provided. It is further shown that changes to the sp² phase by current stressing can improve the field emission characteristics. Emission from carbon nanotubes is also discussed and the prospects for new types of nanotube – polymer composite based cathodes are also considered.     

Rheological behaviour of processed avocado pulp emulsions

Shear rate vs. shear stress data were obtained on avocado pulp in water emulsions using a concentric cylinder rheometer and fitted to a power law model. Dilution, as volume fraction of water, had a pronounced effect on the apparent viscosity of the pulp emulsions and the Richardson equation, (η_R= exp.( a φ) for the emulsion viscosity fitted the data well. A mean slope coefficient, a , of 4.57 can be used as a first approximation. Enzymatic treatment (40°C, 1 h), is slightly more effective than thermal treatment (65°C, 1 h), in reducing the initial apparent viscosity of the pulp-water emulsions     

The microbiology of mixed salad containing raw and cooked ingredients without dressing

Growth of aerobic mesophilic bacteria in mixed salad without dressing, containing cooked sweet corn and raw endive, was similar to that of raw endive alone. At 9°C, sweet corn permitted the growth of the lactic acid bacterium Leuconostoc mesenteroides , whenever the bacterium was present on raw endive, whereas no growth of lactic acid bacteria was recorded on raw endive alone. Listeria monocytogenes , artificially inoculated in the samples, grew more in the mixed salad than in the raw endive alone, for products stored at 6°C and 9°C. Acidification of sweet corn to pH 5.0 was proposed to reduce the development of L. monocytogenes in the mixed salad to a level similar to that recorded in the raw endive alone. Acidification with citric acid reduced spoilage of sweet corn, whereas acetic acid caused necrosis on the leaves of raw endive.     

Localization by immunoelectron microscopy of Schistosoma mansoni antigens in the glomerulus of the hamster (Mesocricetus auratus) kidney

Gene therapy has the potential to provide cancer treatments based on novel mechanisms of action with potentially low toxicities. This therapy may provide more effective control of loco-regional recurrence in diseases such as non-small cell lung cancer (NSCLC), as well as systemic control of micrometastases. Despite current limitations, retroviral and adenoviral vectors can in certain circumstances provide an effective means of delivering therapeutic genes to tumour cells. Although multiple genes are involved in the process of carcinogenesis, mutations of the p53 gene are the most frequent abnormality identified in human tumours. Pre-clinical studies both in vitro and in vivo have shown that restoration of p53 function can induce apoptosis in cancer cells. Phase I clinical trials now show that p53 gene replacement therapy is feasible and safe using both retroviral and adenoviral vectors, and that it induces tumour regression in patients with advanced NSCLC and recurrent head and neck cancer. Other pre-clinical studies indicate that gene therapy may have useful synergy with cytotoxic and radiation therapy. This paper describes the different gene therapy strategies under investigation and the pre-clinical data that provides a rationale for the gene replacement approach, reviews clinical trial data and presents novel ideas for improving current vectors and gene delivery to tumours.     

Morphologic comparison of atherosclerotic lesions in native coronary arteries and saphenous vein graphs with intracoronary angioscopy in patients with unstable angina

The purpose of this study was to investigate platelet effects on postischemic heart function in conjunction with adenosine effects on intracoronary platelet adhesion. Homologous platelets were infused into the coronaries of isolated guinea pig hearts, either during low-flow ischemia or during reperfusion, and external heart work (EHW) and intracoronary platelet adhesion were determined. In most experiments, thrombin was added to the perfusate. The influence of endogenous adenosine was studied by use of the uptake blocker dipyridamole and the unspecific adenosine-receptor blocker theophylline, the A1-receptor blocker 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), and the A2-receptor blocker 3,7-dimethyl-1-propargylxanthine (DMPX). The importance of nitric oxide and prostaglandin I2 (PGI2) was tested by using nitro-L-arginine (NOLAG) and indomethacin, respectively. When platelets were applied with thrombin during low-flow ischemia, EHW recovered to only 63 +/- 4% of the preischemic value, as compared with 89 +/- 3% without platelets (p < 0.05). Despite thrombin, platelets incurred no significant functional loss when applied in the first minute of reperfusion (but again in the fifth minute); however, when theophylline was also present, recovery of EHW amounted to only 42 +/- 12%. Intracoronary adhesion of platelets was negligible without thrombin, and highest during low-flow ischemia with thrombin (35 +/- 3% of the applied number). No adhesion occurred during the first minute of reperfusion, whereas in the fifth minute, adhesion was again 20.8 +/- 4%. Dipyridamole increased adenosine release and attenuated adhesion at this time. Theophylline increased adhesion in the first minute of reperfusion (33 +/- 6.4%), whereas NOLAG and indomethacin proved to be ineffective. DPCPX and DMPX each increased platelet retention during the first minute of reperfusion, their effects being additive. Intracoronary adhesion of platelets induced by thrombin in isolated hearts can reduce postischemic recovery of heart function. During reperfusion, but not during low-flow, endogenous adenosine can prevent platelet adhesion and loss of myocardial function, an action mediated both by A1- and A2-receptor-dependent mechanisms.