Effect of temperature on the water retention properties of two high performance concretes

This contribution aims at (1) determining experimentally the first desorption isotherms of two high performance concretes (based on CEM I and CEM V cements), at three different temperature levels T = 20, 50 and 80 °C, and (2) showing whether these may be simply described by adsorption and capillarity.Results at 20 °C compare well with recently published results; in particular, an important desorption is observed at high RH (≥ 98%). A simple pore network model, based on Kelvin–Laplace's capillary theory, is implemented, and shows the existence of two main de-saturation modes, one at high pore radii (capillary pores), the other for pore radii on the order of a few nanometers (C-S-H porosity), where desorption is shown to occur. A complementary drying mechanism is evidenced at 80 °C, which is attributed to ettringite and/or C-S-H degradation. Finally, proper numerical fitting of all isotherm data is achieved using the well-known three-parameter BSB model.     

Cardiac output response to dynamic exercise after atrial switch repair for transposition of the great arteries

Results from this study showed that patients who underwent successful operation for transposition of the great arteries had no appropriate increase in stroke volume in response to exercise of a nature similar to common recreational activities. The impairment, most likely due to disturbances in both venous return and ventricular systolic function, is compensated for by an increase in peripheral oxygen extraction; however, this increase may not be adequate with maturation or during prolonged exercise when cardiovascular constraints are more important.     

Morphology and physico-chemical properties of Bacillus spores surrounded or not with an exosporium: Consequences on their ability to adhere to stainless steel

This study was designed to elucidate the influence of spore properties such as the presence of an exosporium, on their ability to adhere to materials. This analysis was performed on 17 strains belonging to the B. cereus group and to less related Bacillus species. We first demonstrated that spores of the B. cereus group, surrounded by an exosporium, differed in their morphological features such as exosporium size, number of appendages or hair-like nap length. We also found that the saccharidic composition of exosporium differed among strains, e.g. concerning a newly identified rhamnose derivative: the 2,4-O-dimethyl-rhamnose. Conversely, spores of distant Bacillus species shared morphological and physico-chemical properties with B. cereus spores. Some external features were also observed on these spores, such as a thin loose-fitting layer, whose nature is still to be determined, or a thick saccharidic layer (mainly composed of rhamnose and quinovose). The ability of spores to adhere to stainless steel varied among strains, those belonging to the B. cereus group generally being the most adherent. However, the presence of an exosporium is not sufficient to explain the ability of spores to adhere to inanimate surfaces. Indeed, when the 17 strains were compared, hydrophobicity and the number of appendages were the only significant adhesion parameters. Furthermore, the differences in spore adhesion observed within the B. cereus group were related to differences in the number of appendages, the exosporium length and to a lesser extent, the zeta potential.     

防止潜在危险的安全工程一个设计安全产品的理想工具

随着IEC62368—1第一版（影音、信息与通讯技术设备安全标准）在2009年10月初拍扳成为最终国际标准草案（108／325／FDIS）,其正式发布的时间指日可待。由于IEC62368—1所牵动的产业及影响范围甚广,因此我们建议产品研发或制造商能够及早为新标准的颁布做好准备,不妨从现在开始了解该标准涉及的全新安全思维一防止潜在危险的安全工程（Hazard—based Safety Engineering,简称HBSE）一这套追求更理想产品安全目标的工具。     

阻燃剂的两难：细说外部引燃（上）

今年恰逢信息科技(IT)与消费类电子(CE)产品标准面临修订,同时我们也注意到,有一本涵盖这两项产品范畴的全新标准(IEC TS 62441)已进入最后审批阶段.其中,外部引燃(Extemal Ignition)成为最具争议的议题.     

Distribution of acid extractable P and exchangeable K in a grassland soil as affected by long-term surface application of N, P and K fertilizers

Information on the fate and distribution of surface-applied fertilizer P and K in soil is needed in order to assess their availability to plants and potential for water contamination. Distribution of extractable P (in 0.03 M NH₄F + 0.03 M H₂SO₄ solution) and exchangeable K (in neutral 1.0 M ammonium acetate solution) in the soil as a result of selected combinations of 30 years (1968–1997) of N fertilization (84–336 kg N ha^–1), 10 years of P fertilization (0–132 kg P ha^–1), and 14 years of K fertilization (0 and 46 kg K ha^–1) was studied in a field experiment on a thin Black Chernozem loam under smooth bromegrass (Bromus inermis Leyss.) at Crossfield, Alberta, Canada. Soil samples were taken at regular intervals in October 1997 from 0–5, 5–10, 10–15, 15–30, 30–60, 60–90 and 90–120 cm layers. Soil pH decreased with N rate and this declined with soil depth. Increase in extractable P concentration in the soil reflected 10 years of P fertilization relative to no P fertilization, even though it had been terminated 20 years prior to soil sampling. The magnitude and depth of increase in extractable P paralleled N and P rates. The extractable P concentration in the 0–5 cm soil layer increased by 2.2, 20.7, 30.4 and 34.5 mg P kg^–1 soil at 84, 168, 280 and 336 kg N ha^–1, respectively. The increase in extractable P concentration in the 0–15 cm soil depth was 1.5 and 12.8 mg P kg^–1 soil with application of 16 and 33 kg P ha^–1 (N rate of 84 N ha^–1 for both treatments), respectively; and it was 81.6 and 155.2 mg P kg^–1 soil with application of 66 and 132 kg P ha^–1 (N rate of 336 N ha^–1 for both treatments), respectively. The increase in extractable P at high N rates was attributed to N-induced soil acidification. Most of the increase in extractable P occurred in the top 10-cm soil layer and almost none was noticed below 30 cm depth. Surface-applied K was able to prevent depletion of exchangeable K from the 0–90 cm soil, which occurred with increased bromegrass production from N fertilization in the absence of K application. As only a small increase of exchangeable K was observed in the 10–30 cm soil, 46 kg K ha^–1 year^–1 was considered necessary to achieve a balance between fertilization and bromegrass uptake for K. The potential for P contamination of surface water may be increased with the high N and P rates, as most of the increase in extractable P occurred near the soil surface.     

Sexual Isolation and Cuticular Hydrocarbon Differences between <Emphasis Type="Italic">Drosophila santomea</Emphasis> and <Emphasis Type="Italic">Drosophila yakuba</Emphasis>

Drosophila santomea and Drosophila yakuba are two sister species inhabiting Saõ Tomé island. Previous studies showed that both species display strong reproductive isolation, although they can produce a few viable hybrids. Our study tried to understand the mechanism of this ethological isolation between two allopatric strains. A strong sexual isolation was confirmed, with a marked asymmetry. Comparisons of latency times to either courtship or copulation suggest that males do not discriminate females, whereas D. yakuba females, but not D. santomea females, accept their homospecifics more quickly. Cuticular hydrocarbon compositions of both species and sexes were also established with gas chromatography (GC) and GC/mass spectrometry analysis. All have (Z)-7-tricosene as their major compound. There are several quantitative differences between species for few minor compounds. The largest difference concerns n-heneicosane, which is more abundant in D. santomea than in D. yakuba flies (up to seven times more between males). A similar quantitative difference was also found in a pair of sympatric strains. Furthermore, D. yakuba males artificially perfumed with n-heneicosane were discriminated negatively by D. yakuba females, suggesting a role for this compound in the sexual isolation between these two species.     

Secretagogue and bacteriostatic active fractions derived from a peptic hydro‐ lysate of alfalfa RuBisCO small purified subunit

For the first time a purification process for small RuBisCO (ribulose‐1,5‐bisphosphate carboxylase/oxygenase) subunit (SRS) was developed from an industrial by‐product of alfalfa, taking advantage of its solubility at low pH. Only one protein strip (14 kDa) was clearly detected in the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) profile of the supernatant at pH 2. The recovery of SRS was 48% by this method, with a purity estimated as 98% by densitometry and reverse phase high‐performance liquid chromatography (RP‐HPLC). Moreover, most polyphenolic compounds were discarded, as confirmed by spectrophotometry and RP‐HPLC. SRS hydrolysis was performed for 20 h at 37 °C using pepsin in ammonia/formic acid buffer at pH 3. The hydrolysate was fractionated on a Sephadex G25 column equilibrated with ethanolamine/HCl buffer. Biological activities were found in two fractions. The first fraction showed slight bacteriostatic properties against two pathogenic bacteria, Salmonella arizonae and Shigella sonnei. The second fraction, tested by radioimmunoassay (RIA), presented a secretagogue activity comparable to that of gastrin. Copyright © 2006 Society of Chemical Industry