Modified Gutenberg–Richter Coefficient for Damage Evaluation in Reinforced Concrete Structures Subjected to Seismic Simulations on a Shaking Table

This paper presents analysis and discussion of the \(b\) - and ib-values calculated from the acoustic emission (AE) signals recorded during dynamic shake-table tests conducted on a reinforced concrete (RC) frame subjected to several uniaxial seismic simulations of increasing intensity until collapse. The intensity of shaking was controlled by the peak acceleration applied to the shake-table in each seismic simulation, and it ranged from 0.08 to 0.47 times the acceleration of gravity. The numerous spurious signals not related to concrete damage that inevitably contaminate AE measurements obtained from complex dynamic shake-table tests were properly filtered with an RMS filter and the use of guard sensors. Comparing the \(b\) - and ib-values calculated through the tests with the actual level of macro-cracking and damage observed during testing, it was concluded that the limit value of 0.05 proposed in previous research to determine the onset of macro-cracks should be revised in the case of earthquake-type dynamic loading. Finally, the \(b\) - and ib-values were compared with the damage endured by the RC frame evaluated both visually and quantitatively in terms of the inter-story drift index.     

Gas chromatographic-mass spectrometric confirmation of selected benzophenones from benzodiazepines in human urine following automatic screening

This paper reports a simple, expeditious procedure for confirming the presence of benzodiazepines in previously screened positive urine samples. Samples are manually hydrolysed to the corresponding benzophenones in an acid medium. The hydrolysis products are continuously aspirated into a photometric flow system for screening; positive samples are then confirmed and benzodiazepines identified by using a different flow system that conditions the analytes for gas chromatographic separation and unequivocal mass spectrometric confirmation. Detection limits for benzodiazepines in the nanogram-per-millilitre region are thus achieved by using 0.5 ml of hydrolysed urine; also, repeatability, as R.S.D., is less than 6.5%. The high specificity and sensitivity of the proposed method enables the confirmation of different benzodiazepines in urine samples obtained from drug addicts and patients from a local hospital.     

ATM network testing and measurement

This contribution addresses some very general problems of testing and measuring in ATM networks. The paper outlines important aspects of the basic types of test such as conformance, functionality and performance. Furthermore, it highlights the several aspects and problems of tests at the level of an interface, a switch and a whole network. As ATM traffic has almost no structure, it is impossible to make rules for testing and measurement from traffic modeling. We demonstrate the limitations of the standardized performance parameters, which are generally used as estimators. This e.g. shows that it is possible to obtain with the same estimator completely different cell loss ratios for the same traffic flow.     

A pilot experience launching a national dose protocol for vascular and interventional radiology

The design of a national dose protocol for interventional radiology has been one of the tasks during the European SENTINEL Coordination Action. The present paper describes the pilot experience carried out in cooperation with the Spanish Society on Vascular and Interventional Radiology (SERVEI). A prospective sample of procedures was initially agreed. A common quality control of the X-ray systems was carried out, including calibration of the air kerma area product (KAP) meters. Occupational doses of the radiologists involved in the survey were also included in the survey. A total of 10 Spanish hospitals with interventional X-ray units were involved. Six hundred and sixty-four patient dose data were collected from 397 diagnostic and 267 therapeutic procedures. Occupational doses were evaluated in a sample of 635 values. The obtained KAP median/mean values (Gy.cm(2)) for the gathered procedures were: biliary drainage (30.6/68.9), fistulography (4.5/9.8), lower limb arteriography (52.2/60.7), hepatic chemoembolisation (175.8/218.3), iliac stent (45.9/73.2) and renal arteriography (39.1/59.8). Occupational doses (mean monthly values, in mSv) were 1.9 (over apron); 0.3 (under apron) and 4.5 (on hands). With this National experience, a protocol was agreed among the SENTINEL partners to conduct future similar surveys in other European countries.     

A density-functional study of the structures, binding energies and magnetic moments of the clusters Mo(N) (N = 2-13), Mo(12)Fe, Mo(12)Co and Mo(12)Ni

We report the results of density-functional calculations of the structures, binding energies and magnetic moments of the clusters Mo(N) (N = 2-13), Mo(12)Fe, Mo(12)Co and Mo(12)Ni that were performed using the SIESTA method within the generalized gradient approximation for exchange and correlation. For pure Mo(N) clusters, we obtain collinear magnetic structures in all cases, even when the self-consistent calculations were started from non-collinear inputs. Our results for these clusters show that both linear, planar and three-dimensional clusters have a strong tendency to form dimers. In general, even-numbered clusters are more stable than their neighbouring odd-numbered clusters because they can accommodate an integer number of tightly bound dimers. As a consequence, the binding energies of pure Mo(N) clusters, in their lowest-energy states, exhibit an odd-even effect in all dimensionalities. Odd-even effects are less noticeable in the magnetic moments than in the binding energies. When comparing our results for pure Mo clusters with those obtained recently by other authors, we observe similarities in some cases, but striking differences in others. In particular, the odd-even effect in three-dimensional Mo clusters was not observed before, and our results for some clusters (e.g.?for planar Mo(3) and Mo(7) and for three-dimensional Mo(7) and Mo(13)) differ from those reported by other authors. For Mo(12)Fe and Mo(12)Ni, we obtain that the icosahedral configuration with the impurity atom at the cluster surface is more stable than the configuration with the impurity at the central site, while the opposite occurs in the case of Mo(12)Co. In Mo(12)Co and Mo(12)Ni, the impurities exhibit a weak magnetic moment parallely coupled to the total magnetic moment of the Mo atoms, whereas in Mo(12)Fe the impurity shows a high moment with antiparallel coupling.     

Engineering the magnetic structure of Fe clusters by Mn alloying

We propose to tailor the magnetic structure of atomic clusters by suitable doping, which produces the nanometric equivalent to alloying. As a proof of principle, we perform a theoretical analysis of Fe(6-x)Mn(x) clusters (x = 0-5), which shows a modulation of the magnetic moment of the clusters as a function of Mn doping and, more importantly, a collinear to noncollinear transition at x = 4.     

Influence of blending sequence on micro‐ and macrostructure of PA6/mEPDM/EPDMgMA blends reinforced with organoclay

The structure of the PA6/mEPDM/EPDMgMA/organoclay ternary hybrids was characterized and related to its properties. The nanoblends were prepared through four different blending sequences based on one‐ or two‐step processes: (1) The PA6/organoclay nanocomposite was prepared and then mixed with the mEPDM+ EPDMgMA compound; (2) the mEPDM+EPDMgMA+ organoclay compound was first prepared and then mixed with PA6; (3) the PA6, mEPDM, EPDMgMA, and organoclays were blended in one step; and (4) the PA6/mEPDM/EPDMgMA blend was prepared and then mixed with the organoclay. The microscopic study of the nanoblends showed a relationship between the blending sequence and the dispersion of the organoclay and the rubber. Nevertheless, the mechanical characterization showed slight differences bet ween the blending sequence because of the presence of the organoclay in the matrix, rubber, or interface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Real-time interferometric characterization of a polyvinyl alcohol based photopolymer at the zero spatial frequency limit

We characterize the optical modulation properties of a polyvinyl alcohol/acrylamide (PVA/AA) photopolymer at the lowest end of recorded spatial frequencies. To achieve this goal we have constructed a double beam interferometer in combination with the setup to expose the recording material. This is a novel approach since usually holographic recording materials are only characterized at high spatial frequencies. Some benefits are provided by the approach we propose: a direct calculation of the properties of the material is possible, and on the other hand additional information can be obtained since the results are not influenced by diffusion processes. Furthermore, this characterization is needed to optimize the PVA/AA photopolymers for another range of applications, such as recording of diffractive optical elements, where very low spatial frequencies are recorded. Different PVA/AA compositions and layer thicknesses have been analyzed. We have found that, depending on the layer characteristics, we can achieve high values of the phase-shift modulation depth and enhance the sensitivity of the material.     

Heparin Modulates the Mitogenic Activity of Fibroblast Growth Factor by Inducing Dimerization of its Receptor. A 3D View by Using NMR

In vitro mitogenesis assays have shown that sulfated glycosaminoglycans (GAGs; heparin and heparan sulfate) cause an enhancement of the mitogenic activity of fibroblast growth factors (FGFs). Herein, we report that the simultaneous presence of FGF and the GAG is not an essential requisite for this event to take place. Indeed, preincubation with heparin (just before FGF addition) of cells lacking heparan sulfate produced an enhancing effect equivalent to that observed when the GAG and the protein are simultaneously added. A first structural characterization of this effect by analytical ultracentrifugation of a soluble preparation of the heparin‐binding domain of fibroblast growth factor receptor 2 (FGFR2) and a low molecular weight (3 kDa) heparin showed that the GAG induces dimerization of FGFR2. To derive a high resolution structural picture of this molecular recognition process, the interactions of a soluble heparin‐binding domain of FGFR2 with two different homogeneous, synthetic, and mitogenically active sulfated GAGs were analyzed by NMR spectroscopy. These studies, assisted by docking protocols and molecular dynamics simulations, have demonstrated that the interactions of these GAGs with the soluble heparin‐binding domain of FGFR induces formation of an FGFR dimer; its architecture is equivalent to that in one of the two distinct crystallographic structures of FGFR in complex with both heparin and FGF1. This preformation of the FGFR dimer (with similar topology to that of the signaling complex) should favor incorporation of the FGF component to form the final assemblage of the signaling complex, without major entropy penalty. This cascade of events is probably at the heart of the observed activating effect of heparin in FGF‐driven mitogenesis.