53,345 research outputs found
Fast Polynomial Factorization and Modular Composition
No full textWe obtain randomized algorithms for factoring degree n univariate polynomials over requiring bit operations. When , this is asymptotically faster than the best previous algorithms [J. von zur Gathen and V. Shoup, Comput. Complexity, 2 (1992), pp. 187–224; E. Kaltofen and V. Shoup, Math. Comp., 67 (1998), pp. 1179–1197]; for , it matches the asymptotic running time of the best known algorithms. The improvements come from new algorithms for modular composition of degree n univariate polynomials, which is the asymptotic bottleneck in fast algorithms for factoring polynomials over finite fields. The best previous algorithms for modular composition use field operations, where is the exponent of matrix multiplication [R. P. Brent and H. T. Kung, J. Assoc. Comput. Mach., 25 (1978), pp. 581–595], with a slight improvement in the exponent achieved by employing fast rectangular matrix multiplication [X. Huang and V. Y. Pan, J. Complexity, 14 (1998), pp. 257–299]. We show that modular composition and multipoint evaluation of multivariate polynomials are essentially equivalent, in the sense that an algorithm for one achieving exponent implies an algorithm for the other with exponent , and vice versa. We then give two new algorithms that solve the problem near-optimally: an algebraic algorithm for fields of characteristic at most , and a nonalgebraic algorithm that works in arbitrary characteristic. The latter algorithm works by lifting to characteristic 0, applying a small number of rounds of multimodular reduction, and finishing with a small number of multidimensional FFTs. The final evaluations are reconstructed using the Chinese remainder theorem. As a bonus, this algorithm produces a very efficient data structure supporting polynomial evaluation queries, which is of independent interest. Our algorithms use techniques that are commonly employed in practice, in contrast to all previous subquadratic algorithms for these problems, which relied on fast matrix multiplication
Effects of intranasal estradiol treatment on serum lipoprotein(a) and lipids in hysterectomized women
No full textThe aim of the present study was to evaluate the effects of intranasal estradiol on lipid metabolism and lipoprotein(a)[Lp(a)] levels. A prospective comparative study was designed: 49 hysterectomized, healthy postmenopausal women received intranasal 17beta-estradiol (E-2; 300 mug/day). Blood samples were collected at baseline and at the end of the 3 and 6 months of therapy. After 6 months, the serum levels of total cholesterol, LDL-cholesterol and triglycerides did not show any significant change with intranasal 17beta-E-2 therapy. HDL-cholesterol levels at 3 and 6 months of treatment were significantly increased compared with baseline levels (p=0.031, p=0.000, respectively). There was a significant change in serum Lp(a) levels at the 6th month (p=0.003) but not at the 3rd month (p=0.183) compared with the baseline levels. Further studies are needed to detect whether these changes are significant and permanent or not. Copyright (C) 2004 S. Karger AG, Basel
Why don’t we share? Social networks and privacy concerns, a comparative analysis of academics of communication field in Turkiye and Malaysia
No full textExperimental investigation of plasma impedance in Linac4 source
No full textCERN ’s new particle accelerator Linac4 is part of the upgrade of the LHC accelerator chain. Linac4 is required to deliver 160 MeV H− beam to improve the beam brightness and luminosity in the Large Hadron Collider (LHC). The Linac4 H− source must deliver 40-50 mA, 45 keV H− beam in the RFQ acceptance. Since the RF power coupled to the H− source plasma is one of the important parameters that determines the quality of the H− beam, the experimental investigation of the dependence of the load impedance on the operational parameters is mandatory. In this study, we have measured the impedance of the H− source plasma varying the RF power coupled to the plasma and the condition of the hydrogen gas. Also, optical emission spectroscopy (OES) measurements have been carried out simultaneously with the impedance measurement in order to determine the plasma parameters. The determination of the plasma parameters allows us to compare the experimental results with the analytic model of the plasma parameters, which is useful to discuss the results from a physical point of view
Influence of essential and non-essential amino acids on calcium oxalate crystallization
No full textThe investigation on the mechanism of nucleation and growth of crystals at organic-inorganic interfaces is crucial for understanding biological and physiological calcification processes such as the formation of urinary stones. The effects of five different amino acids on the crystallization of calcium oxalate have been investigated at pH 4.5 and 37 degrees C in aqueous solutions in the batch type crystallizer. The products were characterized by Scanning Electron Microscopy (SEM), Fourier Transfer Infrared Spectroscopy (FT/IR) and X-Ray diffraction (XRD) analysis. Crystal size distribution (CSD) and filtration rate measurements were done. In order to determine the adsorption characteristics of amino acids on the calcium oxalate crystal surfaces, zeta potential measurements were also done and discussed. The results indicate that in the presence of all investigated amino acids, calcium oxalate monohydrate (COM) crystals were preferentially produced, but the crystal morphology varied with amino acid types and concentrations. Various crystal morphologies such as elongated hexagonal, coffin or platy habits were observed. In the presence of all investigated amino acids, the calcium oxalate crystallized in a monohydrate form. Electrostatic/ionic interaction, different adsorption properties and special functional effects of amino acids led to find different crystal morphology. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Influence of the cusp field on the plasma parameters of the Linac4 H− ion source
No full textWhen the H ion source of CERN’s Linac4 is operated in volume mode, a maximum of the extracted current is obtained at varying RF power. The power required for this maximum and its absolute value is strongly influenced by the cusp magnets installed at the source for electron confinement: without magnets, 15−20 mA are typically obtained at 20 kW whereas with magnets a factor of two more power is needed and 25−30 mA are achieved. In order to access the reasons behind the peaked performance with varying RF power and for determining the influence of the cusp field on the discharge, optical emission spectroscopy (OES) measurements of the atomic Balmer series and of the molecular Fulcher transition have been carried out. In all investigated cases, the gas temperature of the discharge has been virtually equal to the ambient temperature as the short discharge pulse length of 500 s is not long enough for considerable heavy particle heating. When no cusp magnets are installed, the plasma parameters evaluated with the collisional radiative models Yacora H and Yacora H show a minimum in the electron temperature of 3.25 eV and a maximum in the electron density of and also in the vibrational excitation of the hydrogen molecule at 20 kW. Assessing the relevant production and destruction processes demonstrates that the H yield is maximal at this point thereby explaining the optimum ion source performance. When the cusp magnets are applied, the same general trends are observed but the required RF power is a factor of two higher. The OES results indicate an optimum performance around 30 kW whereas the highest H current is actually achieved around 40 kW. Furthermore, a higher H yield is indicated without cusp magnets but a better ion source performance is observed with magnets. These differences can most likely be attributed to changing gradients in the plasma parameters which are not accessible by OES. Nevertheless, the obtained plasma parameters can be used as benchmark for RF coupling codes simulating the Linac4 ion source
Calcium oxalate crystallization in the presence of amino acids, proteins and carboxylic acids
No full textReactive crystallization of calcium oxalate was investigated in the presence of amino acids, proteins and carboxylic acids at different pH and temperatures. Average particle size, filtration rates of calcium oxalate crystals obtained in the absence and presence of additives were determined. The influence of pH, temperatures and additives on crystal morphology of calcium oxalate were also investigated and discussed by SEM analysis. TG-DTA, FT/IR and XRD analysis were carried out for all investigated conditions. Average particle size of calcium oxalate was affected significantly by the additive type and concentration. Variation of crystal morphology depending on type and concentration of the additives affected the filtration characteristics. Majority of calcium oxalate crystals occurred in the form of calcium oxalate monohydrate except those in the presence of tartaric acid. TG-DTA, FT/IR and XRD analysis proved that calcium oxalate monohydrate and calcium oxalate dihydrate mixtures are formed in the presence of tartaric acid. The effect of all additives on scale formation was also investigated. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
A molecular dynamics study of N-A-S-H gel with various Si/Al ratios
No full textThe understanding of sodium aluminosilicate hydrate (N-A-S-H) gel is still limited due to its complex and amorphous structure. Recently, molecular dynamics simulation has provided a unique opportunity to better understand the structure of N-A-S-H gel from nanoscale. In this work, the N-A-S-H gel structure was obtained by simulating the polymerization of Si and Al monomers by molecular dynamics. The simulated polymerization process is in good agreement with the experimental results especially in terms of the reaction rate of Si and Al species. The atomic structural features of the N-A-S-H gel were analyzed in terms of bond length and bond angle information, simulated X-ray diffraction (XRD) and Qn distribution. A significant finding is the existence of pentacoordinate Al in all simulated N-A-S-H structures, indicating that pentacoordinate Al in geopolymer does not only come from raw material. Besides, the results show that a smaller Si/Al ratio led to a more crosslinked and compacted structure of N-A-S-H gel
Birth size and physical activity in a cohort of Indian children aged 6-10 years
No full textThere is evidence of a reduction in children’s physical activity in India in the last decade. Our objective was to assess whether size and body composition at birth are associated with physical activity in school-aged children. Children from a prospective observational cohort study born in Mysore, South India between 1997 and 1998 (n5663) had neonatal anthropometric measurements made within 72 h of delivery [weight, mid-upper arm circumference (MUAC), chest, abdomen and head circumference, crown–heel, crown–buttock and leg length, triceps and subscapular skinfolds]. At 6–10 years, children (n5449) were asked to wear AM7164 or GT1M Actigraph accelerometers for 7 days. Body composition was measured within 6 months of activity monitoring. Arm muscle area at birth and time of activity monitoring was calculated from MUAC and skinfold measurements. Activity outcome measures were: mean accelerometer counts per minute (cpm); counts per day and proportion of time spent in moderate and vigorous activity. The mean (S.D.) number of days with >500 min of recorded accelerometer data was 7.0 (1.1). Linear regression models showed no significant associations between any of the neonatal anthropometric measures and the activity variables. Body fat percentage at 7.5 years was negatively associated with all activity variables (B524.69, CI: 27.31, 22.07 for mean cpm). In conclusion, this study showed no associations between body size and skinfold thickness at birth and objectively measured physical activityin childhood
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
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