Observations on the electrical resistivity of steel fibre reinforced concrete

Steel fibre reinforced concrete (SFRC) is in many ways a well-known construction material, and its use has gradually increased over the last decades. The mechanical properties of SFRC are well described based on the theories of fracture mechanics. However, knowledge on other material properties, including the electrical resistivity, is sparse. Among others, the electrical resistivity of concrete has an effect on the corrosion process of possible embedded bar reinforcement and transfer of stray current. The present paper provides experimental results concerning the influence of the fibre volume fraction and the moisture content of the SFRC on its electrical resistivity. The electrical resistivity was measured by alternating current (AC) at 126 Hz. Moreover, an analytical model for the prediction of the electrical resistivity of SFRC is presented. The analytical model is capable of predicting the observed correlation between the fibre volume fraction and the electrical resistivity of the composite (the SFRC) for conductive fibres and moisture saturated concrete. This indicates that the steel fibres were conducting when measuring the electrical resistivity by AC at 126 Hz. For partly saturated concrete the model underestimated the influence of the addition of fibres. The results indicate that the addition of steel fibres reduce the electrical resistivity of concrete if the fibres are conductive. This represents a hypothetical case where all fibres are depassivated (corroding) which was created to obtain a conservative estimate on the influence of fibres on the electrical resistivity of concrete. It was observed that within typical ranges of variation the influence of the moisture content on the electrical resistivity was larger than the effect of addition of conductive steel fibres, but also that the relative impact on the electrical resistivity due to conductive steel fibres increased when the moisture content of the concrete was reduced.     

Construction of a Fuzzy and Boolean Logic Gates Based on DNA

Logic gates are devices that can perform logical operations by transforming a set of inputs into a predictable single detectable output. The hybridization properties, structure, and function of nucleic acids can be used to make DNA‐based logic gates. These devices are important modules in molecular computing and biosensing. The ideal logic gate system should provide a wide selection of logical operations, and be integrable in multiple copies into more complex structures. Here we show the successful construction of a small DNA‐based logic gate complex that produces fluorescent outputs corresponding to the operation of the six Boolean logic gates AND, NAND, OR, NOR, XOR, and XNOR. The logic gate complex is shown to work also when implemented in a three‐dimensional DNA origami box structure, where it controlled the position of the lid in a closed or open position. Implementation of multiple microRNA sensitive DNA locks on one DNA origami box structure enabled fuzzy logical operation that allows biosensing of complex molecular signals. Integrating logic gates with DNA origami systems opens a vast avenue to applications in the fields of nanomedicine for diagnostics and therapeutics.     

作为设计工具的公共空间研究

1成功的公共空间哥本哈根是一个综合了成功的城市发展和城市空间环境各主要成功要素的独特范例。首先,对于改善城市总体环境,特别是城市的公共空间,哥本哈根政府具有强烈的意愿和关注度。这个政府意愿源自     

The social recruitment of medical students at Copenhagen University 1992/1993

As part of a prospective survey of medical students' conditions and of the different kinds of influence they are subjected to during their study periods, we looked into the question of from which social strata the students were recruited. Two hundred and fifty-four (79%) of 323 medical students matriculated during the summer of 1992 answered a structured questionnaire forwarded to them. One hundred and thirty-one (52%) medical students were recruited from the highest social class (I), whereas only 19 (7%) were recruited from the lowest social class (V). In comparison, the underlying population in the age groups relevant for the survey is made up as follows: 7% in social class I and 20% in social class V. A comparison with earlier surveys shows that only insignificant changes in the medical students' social class profiles have taken place in spite of the introduction of better possibilities of financing medical studies irrespective of social class affiliations.     

In vitro maintenance of Schistosoma japonicum and surgical transfer from donor to na?ve recipient pigs

The insulin receptor (IR) is a membrane-bound glycoprotein composed of alpha and beta subunits derived from a common precursor. This processing is observed for both subtypes A and B of the IR and its physiological importance is poorly understood. In order to investigate the functional consequences of the absence of IR precursor cleavage, using site-directed mutagenesis of the hIRB cDNA, we have produced two mutants replacing the sequence Arg-Lys-Arg-Arg by either His-Lys-His-Arg or Arg-Lys-Arg-Ser. These two mutants, stably expressed in CHO, were structurally and functionally characterized in comparison to the wild-type human IR. These mutations result in the production of uncleaved receptors which are expressed normally at the cell surface. These receptors bind insulin with a normal affinity and activate the tyrosine-kinase resulting in normal phosphorylation of the receptors. These uncleaved receptors can mediate both the metabolic and mitogenic effects of insulin. These results provide evidence for a fully functional uncleaved insulin receptor of the B subtype (exon 11 + ) in contrast to the uncleaved A subtype (exon 11 -) described in the literature, which shows a reduced affinity for insulin and cannot therefore correctly transduce the insulin signal.     

Intestinal parasites in swine in the Nordic countries: prevalence and geographical distribution

In Denmark (DK), Finland (FIN), Iceland (I), Norway (N), and Sweden (S), 516 swine herds were randomly selected in 1986-1988. Individual faecal analyses (mean: 27.9 per herd) from eight age categories of swine showed that Ascaris suum, Oesophagostomum spp., Isospora suis, and Eimeria spp. were common, while Trichuris suis and Strongyloides ransomi-like eggs occurred sporadically. Large fatteners and gilts were most frequently infected with A. suum with maximum prevalences of 25-35% in DK, N and S, 13% in I and 5% in FIN. With the exception of the remarkably low A. suum prevalence rates in FIN, no clear national differences were observed. Oesophagostomum spp. were most prevalent in adult pigs in the southern regions (21-43% in DK and southern S), less common in the northern regions (4-17% adult pigs infected), and not recorded in I. I. suis was common in piglets in DK, I, and S (20-32%), while < 1% and 5% were infected in N and FIN, respectively. Eimeria spp. had the highest prevalences in adult pigs (max. 9%) without clear geographical differences. I. suis and Eimeria spp. were recorded for the first time in I, and I. suis for the first time in N.     

Iron staining of the acquired enamel pellicle after exposure to tannic acid or chlorhexidine: preliminary report

Extrinsic discoloration of teeth following a large consumption of tannin-containing beverages or a prolonged use of chlorhexidine mouthrinses is a well known observation. Tannins as well as chlorhexidine are denaturing agents. Based on preliminary studies revealing the presence of iron in chlorhexidine discolored pellicle material, the ability of iron to stain the integument after pretreatment with the two denaturants was studied in a human model. The denaturing effect of an acidic environment was also included. Enamel slabs fixed to acrylic appliances were carried in the oral cavity and alternately exposed to the test solutions in different sequences in vitro. Pretreatment with chlorhexidine or tannic acid led to marked discoloration upon iron application during 5-d tests, whereas the compounds individually had no such effect. A large content of the metal was found in the stained material. Stannous fluoride appeared to reduce the formation of the pigments, and strong oxidation completely bleached the established color. Possible mechanisms underlying the phenomena observed are discussed.     

The unconscious perception of the meaning of verbal stimuli.

"The hypothesis was investigated that the meaning of a verbal stimulus may be responded to without prior recognition of the stimulus. Four treatment groups were employed of 16 Ss each. The experimental procedure used… consisted essentially of obtaining the S's guesses to a series of verbal stimuli, dichotomized in affective connotation, which were presented at or slightly below the S's previously determined absolute threshold… . there was no evidence that the Ss could make better than chance matches… . It was concluded that no evidence was obtained that Ss respond to the meaning of verbal stimuli prior to recognition of the stimuli." From Psyc Abstracts 36:02:2HL32F. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is the general practitioner hospital a potential "patient trap"? A panel study of emergency cases transferred to higher level hospitals

PURPOSE: Assessment of the technical success and mid-term success of PTA of brachiocephalic occlusive disease. MATERIAL AND METHODS: 24 patients, who were treated interventionally because of stenoses of the brachiocephalic arteries were enrolled into this prospective study. In total there were 27 lesions (26 arteriosclerotic lesions and one dissection with pseudoaneurysma). 18 lesions were located in the subclavian artery (extending into the axillar artery in one case), 4 in the brachiocephalic trunk, three in the common carotid artery and two in the vertebral artery. As adjunctive to balloon dilatation 8 stents were implanted. RESULTS: Technical success was achieved in 24/27 lesions. There was an embolic complication in one of 27 interventions. 15/24 patients with 17 treated lesions underwent control angiography with a mean follow-up of 14 months. Follow-up angiography revealed one occlusion and three significant restenoses. 5/24 patients agreed only to clinical follow-up and Doppler examinations, three were lost and one patient died. CONCLUSION: PTA of brachiocephalic occlusive disease showed good technical success. Additional implantation of stents may be useful. Midterm success is satisfactory.     

Psychological defenses and "ego strength" in the recall of completed and incompleted tasks.

"The results of this study indicate: (a) ego strength is directly related to the tendency to recall relatively more incompleted than completed tasks when the situation is not objectively self-esteem threatening, and inversely related to this tendency when the situation does objectively threaten self-esteem." Scores on the hysteria and psychasthenia scales of the MMPI are discussed in relation to the recall of completed and incompleted tasks and the self-esteem threatening or non-threatening character of the situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)