Cyclic bond behaviour of plain bars. Part I: Experimental investigation

In recent years there has been wide use of non-linear dynamic analysis for the evaluation of existing structures in areas of high seismic risk. In the simulation of the cyclic behaviour of elements in reinforced concrete (RC) its bonding performance cannot be ignored. There are numerous numerical models developed in recent decades which can explicitly account for the slip between reinforcing bars and the surrounding concrete through the definition of the local hysteretic bond–slip relationship. As for plain bars, commonly used in reinforced concrete buildings before the 1970s, there are almost no references to hysteretic bond mechanisms.This paper describes the results of a series of monotonic and cyclic pull-out tests aimed at the assessment of the bond performances of plain round bars. Monotonic behaviour is characterized by a first ascending branch, up to the maximum bond strength; in this phase, as the slip increases, chemical–physical adhesion and micro-interlocking between the cement paste and the indentations of the bar surface progressively activate. During post-peak phase the only frictional contribute is present, gradually degrading towards a minimum value as the slip increases. The two parameters, maximum bond strength and minimum frictional bond, in spite of the high variability shown, seem to reflect well the literature indications about bond performances of plain bars. In cyclic field, where the only frictional mechanism is present, experimental results show a significant degradation of bond capacities. Hysteretic cycles show a singular shape, characterized by a reloading phase showing a slight reduction for slip values approaching zero and a subsequent increase in bond stress towards the maximum imposed slip. Bond stresses in cyclic field show a high variability, but it is generally possible to recognize a decreasing trend both with the number of cycles and with the maximum imposed slip.     

Structural models of critical regions in old-type r.c. frames with smooth rebars

Structural assessment of existing reinforced concrete constructions under gravity loads and seismic actions has a high social and economical impact; actually in many European countries, most of the buildings dates back to 1960s and 1970s and cannot ensure satisfactory seismic response, since many areas have been later classified as seismic or since design has been carried out according to obsolete codes. These structures are generally reinforced with smooth bars that exhibit poor bond and need specific anchoring end details. In the present paper, some key aspects of structural models of smooth reinforcement for old-type r.c. frame analysis are reported. Results of experimental tests on smooth reinforcement and circular hook anchoring devices are also used to discuss some aspects of behavioural models of beam to column critical regions.     

光面钢筋混凝土柱的地震响应 第一部分：单调试验

最新国内和国际的抗震规范对既有建筑和新设计结构抗震评估之间的差异进行了论述。发布了材料结构特征的详细指南,以及完成可靠性分析的特有程序。光面钢筋混凝土结构的抗震性能模型具有重要作用,需要进一步完善。对钢筋混凝土柱的试验结果进行了报道,这些钢筋混凝土柱按照老规范设计,可追溯到20世纪40-70年代。研究聚焦在单调荷载下构件的转动能力以及对两个文献中拓展研究报告的第一部分进行描述,两个文献均对单调和循环问题进行研究。     

The membrane-binding domain of the Rous sarcoma virus Gag protein

The Gag protein of Rous sarcoma virus (RSV) can direct particle assembly and budding at the plasma membrane independently of the other virus-encoded products. A previous deletion analysis has suggested that the first 86 amino acids of RSV Gag constitute a large membrane-binding domain that is absolutely required for these processes. To test this hypothesis, we inserted these residues in place of the N-terminal membrane-binding domain of the pp60v-src, a transforming protein whose biological activity requires plasma membrane localization. The ability of the Src chimera to induce cellular transformation suggests that the RSV sequence indeed contains an independent, functional domain.     

Ornithine decarboxylase over-expression stimulates mitogen-activated protein kinase and anchorage-independent growth of human breast epithelial cells

Inactivation of one X chromosome (X inactivation) in female mammals results in dosage compensation of X-chromosomally encoded genes between sexes. In the embryo proper of most mammals X inactivation is thought to occur at random with respect to the parental origin of the X chromosome. We determined on the cellular level the expression of the X-chromosomally encoded protein dystrophin in skeletal and cardiac muscle of female mice heterozygous for a null mutation of the dystrophin gene (mdx/+). In all muscles investigated (cardiac, anterior venter of digastric muscle, biceps brachii and tibialis anterior muscle) we found a mosaic expression of dystrophin-expressing versus non-expressing cells and determined their proportion with respect to the parental origin of the X chromosome. In all groups of mdx/+ mice the level and pattern of dystrophin expression were found to be dependent on the parental origin of the mdx mutation. Additionally, the extent of dystrophin expression was clearly dependent on the mouse strains (C57BL/10 and BALB/c) used to produce heterozygous mdx/+ mice. Variable differences and patterns of dystrophin expression in skeletal versus cardiac muscle were found that were strictly dependent on the parental source of the mdx mutation and the strain used to breed mdx/+ mice. Moreover, dystrophin expression was found to be different between the right side and the left side of the body in individual muscles, and this difference was clearly dependent on the parental origin of the X chromosome. Our data provide evidence that in the mouse embryo proper there is a non-random distribution of cells showing inactivation of the paternal versus the maternal X chromosome in skeletal and cardiac muscle, indicating a non-random X-inactivation. Besides gametic imprinting, strain-, tissue and position-dependent factors also appear to bias X inactivation.     

光面钢筋混凝土柱的地震响应 第二部分：循环试验

既有建筑的抗震性能评估中,钢筋混凝土构件的转动能力评估是一个关键问题。在现代安全评估体系中,必须进行抗震需求和抗震能力的比较。然而,可采用的性能模型只能反映允许钢筋变形的新结构的试验结果,其变形和强度机制并非必须反映旧构件的响应。众所周知,按照旧规范设计的钢筋混凝土构件,通过不同的结构细节、不完善的约束、光面钢筋和混凝土之间弱的粘结来描绘其特性。与新结构相比,出现了不同的屈服后机制。根据意大利1940-1970年的指南设计了光面钢筋混凝土柱,并报道其第二阶段试验结果。在循环荷载下,对构件的研究结果清楚地显示了在转动能力发展过程中弱粘结的作用。相关的研究涉及柱的单调响应和由欧洲规范8规定的经验公式所确定的弦的转动。     

Cyclodextrin-Promoted Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Commercial Milk Products

The detection of polycyclic aromatic hydrocarbons (PAHs) and their metabolites in food and in agricultural sources is an important research objective due to the PAHs’ known persistence, carcinogenicity, and toxicity. PAHs have been found in the milk of lactating cows and in the leaves and stems of plants grown in PAH-contaminated areas, thereby making their way into both cow milk and plant milk alternatives. Reported herein is the rapid, sensitive, and selective detection of 10 PAHs and PAH metabolites in a variety of cow milks and plant milk alternatives using fluorescence energy transfer from the PAH to a high quantum yield fluorophore, combined with subsequent array-based statistical analyses of the fluorescence emission signals. This system operates with high sensitivity (low micromolar detection limits), selectivity (100% differentiation even between structurally similar analytes), and general applicability (for both unmodified lipophilic PAHs and highly polar oxidized PAH metabolites, as well as for different cow and plant milk samples). These promising results show significant potential to be translated into solid-state devices for the rapid, sensitive, and selective detection of PAHs and their metabolites in complex, commercial food products.     

Molecular and Histological Effects of Glyphosate on Testicular Tissue of the Lizard Podarcis siculus

The expansion of agriculture produces a steady increase in habitat fragmentation and degradation due to the increased use of pesticides and herbicides. Habitat loss and alteration associated with crop production play an important role in reptile decline, among which lizards are particularly endangered. In this study, we evaluated testicular structure, steroidogenesis, and estrogen receptor expression/localization after three weeks of oral exposure to glyphosate at 0.05 and 0.5 μg/kg body weight every other day in the field lizard Podarcis siculus. Our results show that glyphosate affected testicular morphology, reduced spermatogenesis, altered gap junctions and changed the localization of estrogen receptors in germ cells, increasing their expression; the effects were mostly dose-dependent. The result also demonstrates that glyphosate, at least at these concentrations, did not influence steroidogenesis. Overall, the data indicate that this herbicide can disturb the morphophysiology of the male lizard’s reproductive system, with obviously detrimental effects on their reproductive fitness. The effects of glyphosate must be considered biologically relevant and could endanger the reproductive capacity not only of lizards but also of other vertebrates, including humans; a more controlled and less intensive use of glyphosate in areas devoted to crop production would therefore be advisable.