Modelling the bleed port of a thermostatic expansion valve

This article presents a model to predict refrigerant flow rate through the bleed port of a thermostatic expansion valve using a separated flow model. Four types of inlet/outlet conditions: liquid/liquid; liquid/two-phase; two-phase/two-phase; and vapour/vapour are studied. Refrigerant flow rate predictions of the model are compared to measured data. The results of this comparison show that the model is within ±20% for 95% of the experimental data corresponding to either an inlet fluid in a sub-cooled or a two-phase state. When the inlet fluid is in a vapour state, the model is able to predict 96% of the experimental data within ±16%.     

沿冰层表面流注传播场稳定性的实验研究与分析(英文)

The electric field required for stable propagation of a positive streamer along an ice surface was investigated by measuring the currents associated with the streamer discharge.The influence of the surface properties,namely the existence of a water film on the ice surface and surface contamination,was analyzed.Results showed that in the presence of an ice surface,except in case of low conductive surface,streamers propagate stably with an external field lower than that generally measured for propagation in air alone(approximately 5 kV/cm).For higher contamination levels,the stability field was found to be slightly influenced by the temperature,while for lower contamination levels,it decreased significantly with an increase in temperature.     

Expanding an Efficient,Electrically Driven and CNT‐Tagged P450 System into the Third Dimension: A Nanowired CNT‐Containing and Enzyme‐Stabilising 3 D Sol–Gel Electrode

Although electrochemically catalysed P450 reactions have been described, their efficiency and applicability remained limited. This is mostly due to low enzyme activity, laborious protein immobilisation and the small electrode surface. We established a novel protein immobilisation method for a determined orientation and electrical wiring of the enzyme without post‐expression modification. By genetic introduction of an anchor‐peptide our method is applicable for screening medium to large mutant libraries and detection by an electrode system. The system was expanded by using wired carbon nanotubes within a sol‐gel matrix to create a three dimensional electrode.     

Gum acacia as a facile reducing,stabilizing, and templating agent for palladium nanoparticles

This article presents the findings of a facile and effective nanoparticle synthesis approach based on aqueous solutions of gum acacia (GA), also known as gum arabic without the addition of any toxic reagents either for the reduction or capping for the effective stabilization of palladium (Pd) nanoparticles with a narrow size distribution (with a H₂PdCl₄/GA ratio of 1:29.411, the solution the average diameter was 9.1 nm, and the standard deviation was ±0.3 nm). In this approach, the particle size was controlled by the manipulation of the temperature, time, and concentration of GA. The synthesized Pd nanoparticles were well characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, dynamic light scattering, and thermogravimetric analysis. This route was very simple and reproducible, and further study on the application of these nanoparticles for various organic transformations is underway. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Production of hydrogen by lignins fast pyrolysis

This paper reports the results of experiments performed on the flash pyrolysis of lignin samples submitted to controlled heat flux densities (short flashes of a concentrated radiation). Two types of lignins are used: Kraft and Organocell lignins. Microscopic observations of the reacted samples reveal the formation of an intermediate liquid compound that precedes the further formation of char, vapours and gases. The rates of mass loss and the production rates of the products are determined for both lignins. The results are compared to each other and to those obtained in former similar studies made with cellulose.

The analyses of the produced gases reveal high syngas and H₂ contents (respectively 87 and 50 mol%). This composition is compared to results obtained in other different thermal conditions with lignins and other types of biomasses. The possible mechanism of hydrogen formation is further discussed.     

A complete green protocol: wrapping of multiwall carbon nanotubes with silver nanoparticles

Silver nanoparticles have been wrapped on multiwall carbon nanotubes though a green synthesis approach that has advantages over other conventional methods that involve chemical agents associated with environmental toxicity and damage of carbon nanotubes. Acacia was used as a green stabilizer for multiwall carbon nanotubes as well as a stabilizer and reducing agent for silver nanoparticles. Generation of silver-decorated multiwall carbon nanotubes was confirmed by UV-Vis spectrophotometry and X-ray diffraction. Generation of silver nanoparticles (5-10 nm) wrapped on MWCNTs was confirmed by field emission scanning electron microscopy and transmission electron microscopy.     

Cardiac manifestations of polymyositis. Apropos of 2 Senegalese cases]

The relaxations mediated by the activation of 5-HT receptors in the guinea pig proximal colon were investigated. Longitudinal strips were cut from the colon segment and placed into the bath. In the presence of atropine (0.2 microM), the relaxations were evoked by adding increasing concentrations of 5-HT (1-100 microM). Noncumulative concentration-response curves were established in the absence and presence of either 5-HT or nitric oxide synthase (NOS) antagonists. Selective 5-HT3 antagonists tropisetron (10 and 100 nM) and ondansetron (1 microM) inhibited the relaxations and shifted the concentration-response curves to the right. Similar effects were observed in the presence of the NOS inhibitor N(G)-nitro-L-arginine (3.2, 10, 32 microM) and partly reversed with L-arginine (100, 320 microM). N(G)-nitro-D-arginine, serving as a negative control, was ineffective. The relaxations were further inhibited in the presence of the soluble guanylate cyclase blocker methylene blue (10 microM) or NO scavenger hemoglobin (32 microM). These results suggest that the 5-HT3 receptor plays a role in neurogenic relaxations of guinea pig proximal colon, which are at least partly mediated via release of NO from nerve endings.     

Enhanced electrical conductivity and structural,mechanical characterization of standalone poly(vinyl alcohol)-graphite nanoplatelets composite films

Polymer based nanocomposites are gaining attention in various fields of science and technology due to its tunable properties. In this work, we report for the first time, the preparation and study on electrical and mechanical properties of standalone poly(vinyl alcohol) (PVA) based graphite nanoplatelet (GnP) composite films using modified film casting technique. Our modified tape casting method can produce films with uniform thickness, and uniform dispersion of filler deprived of pinholes. This technique is scalable for the mass production of polymer composite films for device application. We have obtained a significant enhancement in the electrical conductivity of 9 orders of magnitude and a maximum value of 0.143 S/m using PVA–GnP composites. To the best of our knowledge, this increase is the highest among the reported values for PVA–GnP composite films. However, a reduction in crystallinity and tensile strength can be seen with the addition of GnP fillers. The maximum tensile strength obtained for PVA–GnP composite films was 15 MPa and is adequate for use in electronic applications and devices. The effect of filler addition in PVA is discussed in detail.     

Algal blooming patterns and anomalies in the Mediterranean Sea as derived from the SeaWiFS data set (1998–2003)

Optical remote sensing allows to monitor the space and time heterogeneity of phytoplankton growth in marginal and enclosed seas, a factor critical to understanding their ecosystem dynamics. SeaWiFS-derived (1998–2003) data were used to monitor algal blooming patterns and anomalies in the Mediterranean basin. Yearly and monthly means of chlorophyll-like pigment concentration (chl) were computed for the 6 years available, and climatological means derived. The data set statistical variability was assessed by computing yearly and monthly chl anomalies, as the difference between each individual year/month and the corresponding climatological year/month. The space and time patterns of the chl field appear to concur with the Mediterranean general oceanographic climate, while the chl anomalies describe trends and “hotspots” of algal blooming. The analysis shows a general decrease of chl values in the yearly and monthly means, an increasing negative trend of chl anomalies over the basin interior, and the anticipation of the north-western spring bloom, in comparison to what seen in historical CZCS (1979–1985) data. These have been interpreted as symptoms of an increased nutrient-limitation, resulting from reduced vertical mixing due to a more stable stratification of the basin, in line with the general warming trend of the Mediterranean Sea in the last 25 years. The patterns of high chl, coupled to a positive trend of chl anomalies, recurring at near-coastal hotspots, appear to be linked to continental runoff and to a growing “biological dynamism” at these sites, i.e. to the intensification of noxious or harmful algal blooms, in the north-west, and of coastal fisheries, in the south-east.