Born unwanted: Observations from the Prague Study.

The authors followed 220 children born in 1961-1963 to women twice denied abortion for the same pregnancy in Prague (Czech Republic) and 220 pair-matched controls, whose mothers were pair-matched for age and socioeconomic status and the partner's presence in the home. They were medically, psychologically, and socially assessed in ages 9, 14-16, 21-23, 30, and 35. Although differences between the unwanted study participants and pair-matched controls were not dramatic and changed over time, the differences were consistently in disfavor of the unwanted pregnancy participants. When siblings were used as controls, the findings supported the hypothesis that being born from an unwanted pregnancy is a risk factor for poor mental health in adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A tabu search heuristic for the single vehicle pickup and delivery problem with time windows

The single vehicle pickup and delivery problem with time windows is a generalization of the traveling salesman problem. In such a problem, a number of transportation requests have to be satisfied by one vehicle, each request having constraints to respect: a pickup at its origin and a delivery at its destination, and a time window at each location. The capacity of the vehicle has to be respected. The aim is to minimize the total distance traveled by the vehicle. A number of exact and approximate solution methods exists in the literature, but to the authors knowledge none of them make use of metaheuristics, still promising with other vehicle routing problems. In this paper we present tabu search and probabilistic tabu search. Results obtained on classical traveling salesman problems and a class of randomly generated instances indicate that our approach often produces optimal solutions in a relatively short execution time.     

Improved prediction model for time-dependent deformations of concrete: Part 3-Creep at drying

Part 3 of the present series gives the prediction formulae for the average compliance function in the cross-section of a specimen exposed to drying at constant temperature. The formulae describe the additional creep due to drying by means of the shrinkage function, which automatically introduces the consequences of diffusion theory, such as the dependence of creep on cross-section thickness and shape. The prediction formulae are compared with 19 different data sets from the literature, which reveal relatively good agreement, better than that with previous models. The main source of error is insufficient knowledge of the effect of mix composition and concrete strength. It is advisable to avoid this error by carrying out short-time measurements whenever possible.

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Resume Dans le troisième volet de cette série, on présente les formules de prédiction pour la fonction de compliance moyenne dans la section transversale d’une éprouvette soumise au séchage à température constante. Les formules décrivent le fluage additionnel causé par le séchage au moyen de la fonction de retrait qui introduit automatiquement les aboutissements de la théorie de diffusion, tels ceux qui font dépendre le fluage de l’épaisseur et de la forme de la section transversale. On compare les formules de prédiction à 19 séries de données prises dans la littérature, qui présentent une assez bonne concordance, supérieure à celle obtenue avec les modèles précédents. La source principale d’erreur réside dans une connaissance insuffisante du dosage et de la résistance du béton. On conseille d’éviter cette erreur en effectuant des mesures à court terme chaque fois que c’est possible.

     

Effect of Orifice Geometry on Particle Discharge Rate for a Flat-Bottomed,Cylindrical Hopper

In this work, the influence of the geometry of a cylindrical flat-bottomed hopper orifice on the mass discharge rate of six free-flowable powder excipients with the size fraction 0.050–0.063 cm was investigated. Sixteen combinations of the orifice diameter and the height were used. The influence of the orifice diameter was described by the flow equation. However, the discharge rate was also affected by the orifice height. The influence of the orifice geometry on the powder discharge rate was indirectly studied by the parameters of the Beverloo equation. The value of the coefficient of determination and the precision of the discharge rate prediction were the basic criteria. The mean relative differences between the actual discharge rate at the combination of the orifice diameter and its height and the average discharge rate allowed a direct study of the effect of the orifice geometry. The complex nature of the orifice height impact on the powder discharge rate through the hopper opening has been determined. Based on the results, the orifice diameter of 0.8 cm with the height less than 0.8 cm is recommended. The method of powder flow evaluation proposed here can be used in testing of other powder fractions in future.     

Application of two-dimensional CSI for absolute quantification of phosphorus metabolites in the human liver

There have recently been a number of studies dealing with the absolute quantification of concentrations of MR-visible phosphorus compounds in different tissues. The use of absolute values rather than intensity ratios may furnish additional information about metabolic changes associated with different diseases. The purpose of this study was to develop a general procedure for measuring molar metabolite concentrations and to apply it with respect to the evaluation of human liver 31P-MRS data measured using a standard slice-selective two-dimensional CSI sequence and commercial¹H/³¹P surface coil. The experimental determination of all surface coil-related factors influencing signal intensity was undertaken using a gradient echo imaging technique that can be adapted to commercial systems. The resulting values for healthy volunteers (N = 9) showed concentrations of PME = 2.8 ± 1.3 mM, PDE = 9.9 ± 2.7 mM,P _i = 1.7 ± 0.7 mM, and ATP = 3.6 + 0.9 mM in the human liver. The data are quite consistent with published findings.     

Influence of the surface etching on the corrosion behaviour of a three-dimensional printed Ti–6Al–4V alloy

Recently, there has been an extension of three-dimensional (3D) printing technology of metal materials in the medical field. Additive technology has made it possible to manufacture customized implants. However, 3D printing products often require surface treatment. The possible treatments include acid etching. This study investigated the effect of surface etching on the corrosion resistance of Ti–6Al–4V alloy concerning biological applications. The samples were etched in a mixture of hydrofluoric acid and nitric acid. The corrosion behaviour was described by measuring the time dependence of polarization resistance in a saline solution and surface analysis. The results showed that etching creates a fluoride-rich layer on the surface, which negatively affects the corrosion behaviour of the material for up to 24 hr. Cytocompatibility tests showed that the resulting layer does not affect the biocompatibility of the material.     

Plasma Spraying of Silica-Rich Calcined Clay Shale

Silica-rich clay shale is a viable candidate for replacement of mullite in many applications, especially when outstanding refractoriness and chemical resistance to various agents are desirable. In this contribution, instead of the commonly used synthetic mullite feedstock, the thermal stability of inexpensive calcined natural raw clay shale sprayed using water stabilized plasma system is reviewed. Phase stability and phase changes at elevated temperatures up to 1500 °C were studied by an array of experimental techniques ranging from measurements of thermal conductivity and the heat flow as functions of temperature, scanning electron microscopy, x-ray diffraction (XRD) of the annealed samples, and in situ high temperature XRD. The mostly amorphous as-sprayed coatings with less than 10 wt.% of mullite are temperature stable up to 800 °C and rapid crystallization occurs between 920 and 940 °C. Performed analyses gave evidence about the increase of mullite grain sizes for temperatures higher than 1200 °C and, moreover, certain saturation of crystallinity, not surpassing the threshold of 60 wt.% even for 1500 °C, is observed. The microstructure after annealing at 1500 °C is notable by clusters of fine needle-like mullite crystallites with sizes within the range of tens of nanometers in Si-rich amorphous matrix.     

Failure analysis of thermally cycled columnar thermal barrier coatings produced by high-velocity-air fuel and axial-suspension-plasma spraying: A design perspective

Axial-suspension-plasma spraying (ASPS) is a fairly recent thermal spray technology which enables production of ceramic top coats in TBCs, incorporating simultaneously the properties of both the conventional-plasma sprayed (highly insulating porous structures) and electron-beam-physical-vapor-deposited (strain-tolerant columnar structures) top coats. TBCs are required to insulate the hot components in a gas turbine engine against high temperature and harsh operating conditions. Periodic heating and cooling of turbine engines during operation can create severe thermal cyclic fatigue conditions which can degrade the performance of these coatings eventually leading to the failure. An in-depth experimental investigation was performed to understand the failure behavior of columnar TBCs subjected to thermal cyclic fatigue (TCF) test at 1100?C. The study revealed that the TCF performance was influenced to an extent, by the top coat microstructure, but was primarily affected by the severity of thermally grown oxide (TGO) growth at the bond coat-top coat interface. Mixed failure modes comprising crack propagation through the bond coat-TGO interface, through TGO and within the top coat were identified. Based on the analysis of the experimental results and thorough discussion a novel design of microstructure for the high TCF performance columnar TBC is proposed.