Evaluation of Slow Crack Growth Resistance in Ceramics for High-Temperature Applications

The slow (subcritical) crack growth (SCG) resistance of Si₃N₄ and SiC ceramics has been evaluated by a stepwise loading test on bending bars precracked by Vickers indentation. Three highly refractory materials were selected for the evaluation: i.e., (1) high-purity Si₃N₄ sintered by hot isostatic pressing (HIP) without additives and (2,3) α - and β - SiC pressureless sintered with B and C addition. Under the hypothesis of linear elastic behavior at high temperature, which was found satisfied in the present materials, the SCG resistance was expressed in terms of initial stress intensity factor critical for SCG failure within a predetermined lifetime. The present method was found useful in shortening the testing time and consistent with other traditional fatigue tests (e.g., static-fatigue test): It is recommended as a screening test for materials under research and development. Among the materials tested in the present study, the highest SCG resistance up to 1440°C was found in the high-purity Si₃N₄ without additives.     

3-D gust effect factor for slender vertical structures

Original studies on gust factor buffeting dealt with the alongwind displacement of structures. Research on this topic carried out since the nineties followed two distinct lines: the first determines the maximum effects due to the alongwind response; the second extends the original method from the alongwind response to crosswind and torsional responses. This paper represents the junction point of these research lines with reference to cantilever slender vertical structures. It derives the most relevant effects associated with the three-dimensional (3-D) wind-excited response of this structural type and shows that a suitable definition of one non-dimensional quantity, referred to as the 3-D gust effect factor, provides such effects at any level through a wide set of experimental, numerical and analytical procedures. A new definition of a 3-D equivalent static force consistent with this method is also introduced and critically compared with previous analogous statements.     

Hematological malignancies with a deletion of 11q23: cytogenetic and clinical aspects. European 11q23 Workshop participants

OBJECTIVE: Using receiver-operating characteristic (ROC) curves, we tried to determine the diagnostic threshold of amniotic fluid index (AFI) that will identify abnormal fetal size (birth weights under 2500 g or at least 4000 g) at 37 weeks or beyond. METHODS: We analyzed prospectively over 2 years all parturients with intact membranes and known AFI in early labor. Patients with the following conditions were excluded: pregestational or gestational diabetes, known anomalies, and preterm labor. Two ROC curves were constructed, and the areas (+/- standard error of the mean [SE]) under the curves were calculated. P < .05 was considered significant. RESULTS: Of the 1038 subjects meeting study criteria, 3.6% and 11.5% gave birth to infants who were small for gestational age (SGA) or macrosomic, respectively. Overall, 28.7% had oligohydramnios (AFI at most 5.0 cm) and 3.6% had hydramnios (AFI at least 24.0 cm). Small for gestational age was more common in patients with AFI at most 5.0 cm (6.4%) than in those with adequate fluid (AFI 5.1-23.9; 2.5%), or hydramnios (2.7%; P = .012). Macrosomic newborns were less likely to be born to women with oligohydramnios (7.7%) than to those with adequate amniotic fluid (13.1%) or hydramnios (13.5%). Areas under ROC curves are not significantly different from the area under the nondiagnostic line, indicating that AFI (0-34 cm) cannot differentiate between newborns under 2500 g and at or over 2500 g or under 4000 and at or more 4000 g. CONCLUSION: Intraparterium AFI appears to be a poor screening test to identify risk for delivery of SGA or macrosomic fetus.     

Molecular dynamics simulations of polyphosphazenes: poly[bis(chloro)phosphazene][NPCl2] n

Suitable parameter sets for the CHARMm force field were derived for the structural units in polychlorophosphazene [P=N, P N, P Cl] using the Dinur Hagler energy second derivative procedure based on quantum mechanical SCI calculations using the 6–31G^* basis set. To validate the reliability of the parameter set, structural results obtained with CHARMm for the adopted model compounds (OP₂NCl₅ and OP₃N₂Cl₅) were compared with those derived fromab initio quantum mechanics using the 6–31G^* basis set. Application of molecular dynamics (MD) simulations in combinatioin with the available X-ray diffraction data provided structural and conformational information on the polymer. The calculation made using the periodic boundary conditions (PBC) agree well with the polychlorophosphazene ordered in a monoclinic unit cell (a=5.98,b=12.99,c=4.92 A; β=111.7). This model was stabilized mainly by the image atoms contribution to the electrostatic energy term and had aquasi-planar conformation of the backbone chain (glide symmetry). The MD calculations also provided evidence that the difference between single and double PN bonds is less marked than that measured experimentally. This result is, however, in agreement with more recent and accurate X-ray studies on poly(methylphosphazene). Validation of the polymer model provided a complete picture, otherwise experimentally inaccessible, of the internal fluctuations of the polymeric chains.     

Analysis of the validity of vaginal-cervical cytologic examination in 162 pre- and post-menopausal patients

The authors examine 162 cervico-vaginal smears of women in peri-menopause presenting cellular alterations (ASCUS). These patients were treated with a local topic therapy as the persistence of these alterations in 23 cases (14.2%) second level analyses were performed: gynecological visit, colposcopy and biopsy. In addition to inflammatory aspects 2 in situ carcinomas and 2 moderate dysplasias were recorded. We believe therefore that cytology could be a valid aid also in pre-menopausal women in the cervico-vaginal pathology.     

Low-Power Adaptive Biased Integrated Amplifiers

In this paper the author will present the working principle and the applications of a novel adaptive biasing topology, designed to decrease the stand-by power dissipation without affecting the transient performance of low-power amplifiers. The proposed circuit, whose principle and circuit topology can be implemented both in CMOS and in bipolar standard technologies, gives a biasing current whose value depends on the applied input differential voltage and can be set according to the requested transient performance constraints. The adaptive architecture can be utilized in the design of high-efficient low-power operational amplifiers, for the biasing of both the input stage (where the input source current is dynamically increased) and the output stage (where the output current can be controlled and limited). These amplifiers show a very good behaviour, evaluated in terms of two efficiency factors, if compared with those of other adaptive solutions and class-AB topologies, proposed in the literature. Simulation results and also measurements on a chip prototype, fabricated in a standard CMOS technology, are finally presented.     

The beneficial effects of storage on the quality of wastewater for irrigation: a case study in Sicily.

Although the main function of reservoirs in agriculture is to allow the storage and temporal shifting of large volumes of waters, further benefits emerge from their application in wastewater reuse systems. In fact, as observed in several other studies carried out on such complex natural systems, the storage period, under proper conditions, can lead to a significant improvement of the water quality for irrigation thanks to concurrent physical, chemical and biological processes. In order to investigate the reservoir dynamics, an experimental research was carried out in a farm reservoir (volume of 11,000 m3, maximum depth of 6.3 m and mean depth of about 5 m), receiving treated wastewater and subject to scheduled highly variable input to volume ratios, in order to observe the broadest range of behaviour responses. Specifically, over a monitoring period lasted 4 months, the reservoir was operated as a standard batch reactor in the first and third phases and as a continuous flow reactor in the second one. Based on correlation analysis between the chemical, physical and biological water parameters and operational ones, a new operative index is proposed which integrates the morphological characteristics of the tank and the management ones, and shows a significant correlation with the qualitative characteristics of the stored water.     

交流信号电平移位电路

交流信号可由多种信号源产生,其中不少信号源与诸如TTL等最常用的接口电压不兼容。人们通常使用电容来耦合AC信号,因为电容耦合能滤除直流分置电平。但是电容耦合有时不适用,这是因为被耦合的信号电压在地电平上下摆动,所以必须增加直流偏置,以使被耦合的信号与接口电压兼容。此外,被耦合的信号所含的直流电压分量V_(DC)随脉冲宽度变化而变化。当被耦合的信号振幅较大时,这种直流变化会对接口电压产生干扰。本电路能测量     

In-vitro iron dialysability from legumes: Influence of phytate and extrusion cooking

In-vitro iron dialysability from five Italian legumes (mottled bean, white bean, faba bean, chickpea, lentil) and the influence of phytate and extrusion cooking on it were evaluated. Iron dialysability was 2·3 and 2·4% in mottled and white bean respectively, 1·2% infaba bean, 2·7% in chickpea and 1·1% in lentil. After extrusion cooking the flours showed a marked iron contamination and a decrease in iron dialysability, but these changes were significant only for mottled bean. Enzymic phytate removal induced an increase in iron dialysability > 100% in all the raw legumes except mottled bean which showed an increase of only 57%. This finding indicates that, although phytate consistently modifies iron dialysability, it is difficult to identify a quantitative relationship between phytate content and iron dialysability.