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Selected AbstractsDesign of a Multistage Optical Packet SwitchEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2000Carla Raffaelli Optical packet switching is considered as a means to achieve high speed networking in future optical multi-service networks, Optical switches of limited size are feasible with present-day photonic technology, so solutions for the design and implementation of large switches are proposed here. They are based on a multistage architecture built using small switching modules with output queuing, organised according to a Clos topology. Many degrees of freedom are available for switch design and they are exploited to achieve performance optimisation in relation to packet loss. Simulation and analytical tools are developed to evaluate switch architecture performance. Results and application examples are given to show the feasibility of the multistage architecture for optical networking. [source] Long-term ozone effects on vegetation, microbial community and methane dynamics of boreal peatland microcosms in open-field conditionsGLOBAL CHANGE BIOLOGY, Issue 8 2008SAMI K. MÖRSKY Abstract To study the effects of elevated ozone concentration on methane dynamics and a sedge species, Eriophorum vaginatum, we exposed peatland microcosms, isolated by coring from an oligotrophic pine fen, to double ambient ozone concentration in an open-air ozone exposure field for four growing seasons. The field consists of eight circular plots of which four were fumigated with elevated ozone concentration and four were ambient controls. At the latter part of the first growing season (week 33, 2003), the methane emission was 159±14 mg CH4 m,2 day,1 (mean±SE) in the ozone treatment and 214±8 mg CH4 m,2 day,1 under the ambient control. However, towards the end of the experiment the ozone treatment slightly, but consistently, enhanced the methane emission. At the end of the third growing season (2005), microbial biomass (estimated by phospholipid fatty acid biomarkers) was higher in peat exposed to ozone (1975±108 nmol g,1 dw) than in peat of the control microcosms (1589±115 nmol g,1 dw). The concentrations of organic acids in peat pore water showed a similar trend. Elevated ozone did not affect the shoot length or the structure of the sedge E. vaginatum leaves but it slightly increased the total number of sedge leaves towards the end of the experiment. Our results indicate that elevated ozone concentration enhances the general growth conditions of microbes in peat by increasing their substrate availability. However, the methane production did not reflect the increase in the concentration of organic acids, probably because hydrogenotrophic methane production dominated in the peat studied. Although, we used isolated peatland microcosms with limited size as study material, we did not find experimental factors that could have hampered the basic conclusions on the effects of ozone. [source] Selecting Predictor Subsets: Considering validity and adverse impactINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 3 2010Wilfried De Corte The paper proposes a procedure for designing Pareto-optimal selection systems considering validity, adverse impact and constraints on the number of predictors from a larger subset that can be included in an operational selection system. The procedure determines Pareto-optimal composites of a given maximum size thereby solving the dual task of identifying the predictors that will be included in the reduced set and determining the weights with which the retained predictors will be combined to the composite predictor. Compared with earlier proposals, the simultaneous consideration of both tasks makes it possible to combine several strategies for reducing adverse impact in a single procedure. In particular, the present approach allows integrating (a) investigating a large number of possible predictors (such as multitest battery of ability tests, or a collection of ability and nonability measures); (b) explicit predictor weighting within feasible test procedures of a given limited size. [source] Calculation of the instrumental function in X-ray powder diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2006A. D. Zuev A new method for calculating the total instrumental function of a conventional Bragg,Brentano diffractometer has been developed. The method is based on an exact analytical solution, derived from diffraction optics, for the contribution of each incident ray to the intensity registered by a detector of limited size. Because an incident ray is determined by two points (one is related to the source of the X-rays and the other to the sample) the effects of the coupling of specific instrumental functions, for example, equatorial and axial divergence instrumental functions, are treated together automatically. The intensity at any arbitrary point of the total instrumental profile is calculated by integrating the intensities over two simple rectangular regions: possible point positions on the source and possible point positions on the sample. The effects of Soller slits, a monochromator and sample absorption can also be taken into account. The main difference between the proposed method and the convolutive approach (in which the line profile is synthesized by convolving the specific instrumental functions) lies in the fact that the former provides an exact solution for the total instrumental function (exact solutions for specific instrumental functions can be obtained as special cases), whereas the latter is based on the approximations for the specific instrumental functions, and their coupling effects after the convolution are unknown. Unlike the ray-tracing method, in the proposed method the diffracted rays contributing to the registered intensity are considered as combined (part of the diffracted cone) and, correspondingly, the contribution to the instrumental line profile is obtained analytically for this part of the diffracted cone and not for a diffracted unit ray as in ray-tracing simulations. [source] Two-electron integral evaluation on the graphics processor unitJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2008Koji Yasuda Abstract We propose the algorithm to evaluate the Coulomb potential in the ab initio density functional calculation on the graphics processor unit (GPU). The numerical accuracy required for the algorithm is investigated in detail. It is shown that GPU, which supports only the single-precision floating number natively, can take part in the major computational tasks. Because of the limited size of the working memory, the Gauss-Rys quadrature to evaluate the electron repulsion integrals (ERIs) is investigated in detail. The error analysis of the quadrature is performed. New interpolation formula of the roots and weights is presented, which is suitable for the processor of the single-instruction multiple-data type. It is proposed to calculate only small ERIs on GPU. ERIs can be classified efficiently with the upper-bound formula. The algorithm is implemented on NVIDIA GeForce 8800 GTX and the Gaussian 03 program suite. It is applied to the test molecules Taxol and Valinomycin. The total energies calculated are essentially the same as the reference ones. The preliminary results show the considerable speedup over the commodity microprocessor. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Probing the limits of molecular imprinting: strategies with a template of limited size and functionalityJOURNAL OF MOLECULAR RECOGNITION, Issue 1 2009Miruna Petcu Abstract A series of polymers molecularly imprinted with the general anaesthetic propofol were synthesized using both semi- and non-covalent approaches. The polymers were evaluated with respect to template rebinding in both aqueous and organic media. In aqueous media, the observed propofol binding in these polymer systems was largely hydrophobic and non-specific in nature. In non-polar solvents such as hexane, electrostatic (hydrogen bonding) interactions dominate resulting in some selectivity. The implication of these results, in conjunction with those obtained using structures of similar size in other studies, is that propofol, a template possessing limited functionality and size, appears to define the lower limit for template size and degree of functionalization that can be used for the creation of ligand-selective recognition sites in molecularly imprinted polymers. Furthermore, studies with alternative ligands indicate that the steric crowding of a ligand's functionality to the polymer contributes to the extent of polymer,ligand recognition. Copyright © 2008 John Wiley & Sons, Ltd. [source] FIB-Nanotomography of Particulate Systems,Part II: Particle Recognition and Effect of Boundary TruncationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Beat Münch The focused ion beam-nanotomography (FIB-nt) technique presented in Part I of this article is a novel high-resolution three-dimensional (3D) microscopy method that opens new possibilities for the microstructural investigation of fine-grained granular materials. Specifically, FIB-nt data volumes allow particle size distributions (PSD) to be determined, and the current paper discusses all the processing steps required to obtain the PSD from 3D data. This includes particle recognition and the subsequent PSD estimation. A refined watershed approach for 3D particle recognition that tolerates concavities on the particle surfaces is presented. Particles at the edge of the 3D data volume are invariably clipped, and because the data volume is of a very limited size, this effect of boundary truncation seriously affects the PSD and needs to be corrected. Therefore, two basic approaches for the stereological correction of the truncation effects are proposed and validated on artificially modeled particle data. Finally, the suggested techniques are applied to real 3D-particle data from ordinary portland cement and the resulting PSDs compared with data from laser granulometry. [source] A new sample of broad absorption-line quasars exhibiting the ghost of Lyman ,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Matthew North ABSTRACT We have searched the broad absorption-line quasar (BAL QSO) sample presented recently by Reichard et al. for objects exhibiting the so-called ,ghost of Lyman ,'. This ghost manifests as a hump near ,5900 km s,1 in the troughs of the broad absorption lines and provides strong evidence for the importance of line driving in powering the outflows from BAL QSOs. Of the 224 sample BAL QSOs selected from the Sloan Digital Sky Survey Early Data Release, 198 satisfy our redshift constraints and 58 show clear evidence of multiple-trough (MT) structure in the C iv 1550 Å line. A composite spectrum constructed from this MT sample already shows evidence for a ghost feature. Narrowing our classification scheme further, we define a set of 36 objects that individually show evidence of a ghost feature, and then apply further cuts to arrive at a final ,best sample' that contains our seven strongest ghost candidates. A further five objects show evidence for a ghost feature that is almost strong enough to merit inclusion in our best sample. Despite its limited size, our best sample more than doubles the number of known BAL QSOs with clear ghost signatures and should make an excellent basis for detailed follow-up studies. [source] Multimethodological approach to investigate chamber tombs in the Sabine Necropolis at Colle del Forno (CNR, Rome, Italy)ARCHAEOLOGICAL PROSPECTION, Issue 2 2009Salvatore Piro Abstract Non-destructive geophysical prospecting methods are increasingly used for the investigation of archaeological sites, especially where a detailed physical and geometrical reconstruction of structures is required prior to any excavation work. Often, due to the limited size and depth of an archaeological structure, it may be rather difficult to single out its position and extent because of the generally low signal-to noise (S/N) ratio. This can be overcome by improving data acquisition and processing techniques and integrating different geophysical methods. In this work the results of a multimethodological surveys, used with the aim of detecting sharp discontinuities (boundary of cavities and fractures in the host medium) at the Archaeological Test Site of Sabine Necropolis at Research Area of National Research Council of Rome (Montelibretti, Italy) are shown. For the survey a combination of passive and active methods (magnetic, ground-penetrating radar (GPR), and dipole,dipole geoelectric (DDG)), topographical and three-dimensional laser scanner surveys and archaeological excavations were used to study the state of conservation of underground tombs. With all geophysical methods a high-resolution data acquisition was adopted with the aim of reconstructing a global vision of the study area. Signal processing and amplitude time-slice representation techniques were used for the analysis of GPR data. The bi-dimensional cross-correlation technique was applied to enhance the S/N ratio of the magnetic data. An example of the integration (both qualitative and quantitative) of these results is presented for a portion of the investigated area in the Sabine Necropolis at Colle del Forno (Rome, Italy). Archaeological excavations were then conducted systematically after completing the geophysical surveys and interpretations (from 2000 to 2006), which confirmed the location and shape of the individual chamber tombs with associated corridors. Copyright © 2009 John Wiley & Sons, Ltd. [source] Developmental consequences of abnormal folate transport during murine heart morphogenesis ,BIRTH DEFECTS RESEARCH, Issue 7 2004Louisa S. Tang Abstract BACKGROUND Folic acid is essential for the synthesis of nucleotides and methyl transfer reactions. Folic acid,binding protein one (Folbp1) is the primary mediator of folic acid transport into murine cells. Folbp1 knockout mouse embryos die in utero with multiple malformations, including severe congenital heart defects (CHDs). Although maternal folate supplementation is believed to prevent human conotruncal heart defects, its precise role during cardiac morphogenesis remains unclear. In this study, we examined the role of folic acid on the phenotypic expression of heart defects in Folbp1 mice, mindful of the importance of neural crest cells to the formation of the conotruncus. METHODS To determine if the Folbp1 gene participates in the commitment and differentiation of the cardiomyocytes, relative levels of dead and proliferating precursor cells in the heart were examined by flow cytometry, Western blot, and immunohistostaining. RESULTS Our studies revealed that impaired folic acid transport results in extensive apoptosis-mediated cell death, which concentrated in the interventricular septum and truncus arteriosus, thus being anatomically restricted to the two regions of congenital heart defects. Together with a reduced proliferative capacity of the cardiomyocytes, the limited size of the available precursor cell pool may contribute to the observed cardiac defects. Notably, there is a substantial reduction in Pax-3 expression in the region of the presumptive migrating cardiac neural crest, suggesting that this cell population may be the most severely affected by the massive cell death. CONCLUSIONS Our findings demonstrate for the first time a prominent role of the Folbp1 gene in mediating susceptibility to heart defects. Birth Defects Research (Part A), 2004. © 2004 Wiley-Liss, Inc. [source] Comparison between differentcell kinetic variables in human breast cancerCELL PROLIFERATION, Issue 2 2000F. Barzanti Cell kinetics holds a prominent role among biological factors in predicting clinical outcome and response to treatment in neoplastic patients. Different cell kinetic variables are often considered as valid alternatives to each other, but the limited size of case series analysed in several studies and the lack of simultaneous determinations of all the variables on the same tumours do not justify this conclusion. In the present study, the correlation between [3H]thymidine labelling index ([3H]dT LI), flow cytometric S phase cell fraction (FCM-S) and Ki-67 immunoreactivity (Ki-67/MIB-1) was verified and the type of correlation with the most important clinical, pathological and biological patient and tumour characteristics was investigated in a very large series of breast cancer patients. Ki-67/MIB-1, FCM-S and [3H]dT LI were determined in 609, 526 and 485 patients, respectively, and all three cell proliferation indices were evaluated in parallel on the same tumour in a series of 330 breast cancer patients. All the cell kinetic determinations were performed within the context of National Quality Control Programmes. Very poor correlation coefficients (ranging from 0.37 to 0.18) were observed between the different cell kinetic variables determined in parallel on the same series of breast cancers. Moreover, Ki-67/MIB-1 and FCM-S showed a significant relationship with histological type, grade and tumour size, whereas statistically significant correlations were not observed for [3H]dT LI. In conclusion, the results show that the different cell kinetic variables provide different biological information and cannot be considered as alternatives to each other. [source] | |||||||||||||