Use of LEU in the aqueous homogeneous medical isotope production reactor
Energy Technology Data Exchange (ETDEWEB)
Ball, R.M. [Babock & Wilcox, Lynchburg, VA (United States)
1997-08-01
The Medical Isotope Production Reactor (MIPR) is an aqueous solution of uranyl nitrate in water, contained in an aluminum cylinder immersed in a large pool of water which can provide both shielding and a medium for heat exchange. The control rods are inserted at the top through re-entrant thimbles. Provision is made to remove radiolytic gases and recombine emitted hydrogen and oxygen. Small quantities of the solution can be continuously extracted and replaced after passing through selective ion exchange columns, which are used to extract the desired products (fission products), e.g. molybdenum-99. This reactor type is known for its large negative temperature coefficient, the small amount of fuel required for criticality, and the ease of control. Calculation using TWODANT show that a 20% U-235 enriched system, water reflected can be critical with 73 liters of solution.
AQUEOUS HOMOGENEOUS REACTORTECHNICAL PANEL REPORT
Energy Technology Data Exchange (ETDEWEB)
Diamond, D.J.; Bajorek, S.; Bakel, A.; Flanagan, G.; Mubayi, V.; Skarda, R.; Staudenmeier, J.; Taiwo, T.; Tonoike, K.; Tripp, C.; Wei, T.; Yarsky, P.
2010-12-03
Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; the fission product barriers being the vessel and attached systems; the production and release of radiolytic and fission product gases and their impact on operations and their control by a gas management system; and the movement of fuel into and out of the reactor vessel.
Energy Technology Data Exchange (ETDEWEB)
Perez, Daniel Milian; Lorenzo, Daniel E. Milian; Garcia, Lorena P. Rodriguez; Llanes, Jesus Salomon; Hernandez, Carlos R. Garcia, E-mail: dperez@instec.cu, E-mail: dmilian@instec.cu, E-mail: lorenapilar@instec.cu, E-mail: cgh@instec.cu [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba); Lira, Carlos A. Brayner de Oliveira, E-mail: cabol@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife (Brazil); Rodriguez, Manuel Cadavid, E-mail: mcadavid2001@yahoo.com [Tecnologia Nuclear Medica Spa, TNM (Chile)
2015-07-01
{sup 99m}Tc is the most common radioisotope used in nuclear medicine. It is a very useful radioisotope, which is used in about 30-40 million procedures worldwide every year. Medical diagnostic imaging techniques using {sup 99m}Tc represent approximately 80% of all nuclear medicine procedures. Although {sup 99m}Tc can be produced directly on a cyclotron or other type of particle accelerator, currently is almost exclusively produced from the beta-decay of its 66-h parent {sup 99}Mo. {sup 99}Mo production system in an Aqueous Homogeneous Reactor (AHR) is potentially advantageous because of its low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing and purification characteristics. In this paper, an AHR conceptual design using Low Enriched Uranium (LEU) is studied and optimized for the production of {sup 99}Mo. Aspects related with the neutronic behavior such as optimal reflector thickness, critical height, medical isotopes production and the reactivity feedback introduced in the solution by the volumetric expansion of the fuel solution due to thermal expansion of the fuel solution and the void volume generated by radiolytic gas bubbles were evaluated. Thermal-hydraulics studies were carried out in order to show that sufficient cooling capacity exists to prevent fuel overheating. The neutronic and thermal-hydraulics calculations have been performed with the MCNPX computational code and the version 14 of ANSYS CFX respectively. The neutronic calculations demonstrated that the reactor is able to produce 370 six-day curies of {sup 99}Mo in 5 days operation cycles and the CFD simulation demonstrated that the heat removal systems provide sufficient cooling capacity to prevent fuel overheating, the maximum temperature reached by the fuel (89.29 deg C) was smaller to the allowable temperature limit (90 deg C). (author)
Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts
Binder, Joseph B.; Blank, Jacqueline J.; Raines, Ronald T.
2008-01-01
Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water–organic mixtures, finding that the second-generation Hoveyda–Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71–95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems. PMID:17949009
Choudhary, Vinit; Pinar, Ana B; Lobo, Raul F; Vlachos, Dionisios G; Sandler, Stanley I
2013-12-01
Herein, the first comparison of the mechanisms of glucose-to-fructose isomerization in aqueous media enabled by homogeneous (CrCl3 and AlCl3 ) and heterogeneous catalysts (Sn-beta) by using isotopic-labeling studies is reported. A pronounced kinetic isotope effect (KIE) was observed if the deuterium label was at the C2 position, thus suggesting that a hydrogen shift from the C2 to C1 positions was the rate-limiting step with the three catalysts. (13) C and (1) H NMR spectroscopic investigations confirmed that an intra-hydride-transfer reaction pathway was the predominant reaction channel for all three catalysts in aqueous media. Furthermore, the deuterium atom in the labeled glucose could be mapped onto hydroxymethylfurfural and formic acid through reactions that followed the isomerization step in the presence of Brønsted acids. In all three catalysts, the active site appeared to be a bifunctional Lewis-acidic/Brønsted-basic site, based on a speciation model and first-principles calculations. For the first time, a mechanistic similarities between the homogeneous and heterogeneous catalysis of aldose-to-ketose isomerization is established and it is suggested that learning from homogeneous catalysis could assist in the development of improved heterogeneous catalysts.
Wang, Qiang; Zhao, Lishan; Li, Chenxi; Cao, Zexian
2016-05-26
It is a challenging issue to quantitatively characterize how the solute and pressure affect the homogeneous ice nucleation in a supercooled solution. By measuring the glass transition behavior of solutions, a universal feature of water-content dependence of glass transition temperature is recognized, which can be used to quantify hydration water in solutions. The amount of free water can then be determined for water-rich solutions, whose mass fraction, Xf, is found to serve as a universal relevant parameter for characterizing the homogeneous ice nucleation temperature, the meting temperature of primary ice, and even the water activity of solutions of electrolytes and smaller organic molecules. Moreover, the effects of hydrated solute and pressure on ice nucleation is comparable, and the pressure, when properly scaled, can be incorporated into the universal parameter Xf. These results help establish the decisive role of free water in determining ice nucleation and other relevant properties of aqueous solutions.
Directory of Open Access Journals (Sweden)
Jun Kobayashi
2015-01-01
Full Text Available We propose a robust method to distinguish isolated single gold nanoparticles (AuNP monomers and their dimers under Brownian motion, a key for ultrasensitive homogeneous bioassays, including AuNP sandwich assays. To detect dimers and distinguish them from a larger number of monomers in aqueous solution, single-particle polarization microscopy was performed. For the accurate detection of individual particles, the optical anisotropy and rotational diffusion time are measured because a dimer is much more anisotropic than the nearly spherical monomer and the rotational diffusion time of a dimer is four times that of a monomer. By employing an autocorrelation analysis, we defined a measure of distinguishing that simultaneously enables high detection probability and low error probability. The detection platform offers homogeneous DNA hybridization assays and immunoassays at the subpicomolar level.
Zhang, Hairong; Guo, Haijun; Wang, Bo; Shi, Silan; Xiong, Lian; Chen, Xinde
2016-01-20
In this work, bacterial cellulose (BC) was activated by ethylenediamine (EDA) and then dissolved in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) aqueous solutions. The resulting transparent solution was cast on a glass plate to prepare regenerated BC. Then cationic BC was prepared homogeneously by the reaction between regenerated BC and 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride (CHPTAC) in a NaOH/urea aqueous solution. Structure and properties of the BC and its products were characterized by different techniques such as X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The results showed that there was no significant difference between the structures of BC, activated BC and regenerated BC. The effects of different temperature and molar ratio of CHPTAC to anhydroglucose unit (AGU) on the degree of substitution (DS) value were examined. The DS values of cationic BC ranged between 0.21 and 0.51.
Liang, Hai-chao; Li, Xiang-zhong; Yang, Yin-hua; Sze, Kong-hung
2010-06-01
In this work, the homogeneous and heterogeneous degradations of diphenamid (DPA) in aqueous solution were conducted by direct photolysis with UVC (254nm) and by photocatalysis with TiO(2)/UVA (350nm), and the experimental results were compared. It was found that the homogeneous photolysis by UVC irradiation alone was quite efficient to degrade DPA up to 100% after 360min, but was very inefficient to mineralize its intermediates in terms of dissolved organic carbon reduction of only 8%. In contrast, the heterogeneous photocatalysis with TiO(2)/UVA showed relatively a lower degree of DPA degradation (51%), but a higher degree of its mineralization (11%) after 360min. These results reveal that the photocatalysis process has relatively poor selectivity to degrade different compounds including various intermediates from the DPA degradation, which is beneficial to its mineralization. In addition, over 20 intermediates were identified by LC-MS and (1)H NMR analyses. Based on the identified intermediates, the reaction mechanisms and the detailed pathways of the DPA degradation by photolysis and photocatalysis were proposed, and are presented in this paper.
Institute of Scientific and Technical Information of China (English)
Soheil Sayyahi; Jafar Saghanezhad
2011-01-01
In this letter, a mild and efficient procedure for synthesis of phenacyl derivatives under homogenous catalysis in the presence of tetrabutylammonium bromide in aqueous media is described. The nucleophilic substitution reactions were performed under ecofriendly conditions and gave the corresponding products in high yields and short reaction times.
Energy Technology Data Exchange (ETDEWEB)
Nygaard, E. T. [Babcock and Wilcox Technical Services Group, 800 Main Street, Lynchburg, VA 24504 (United States); Pain, C. C.; Eaton, M. D.; Gomes, J. L. M. A.; Goddard, A. J. H.; Gorman, G.; Tollit, B.; Buchan, A. G.; Cooling, C. M. [Applied Modelling and Computation Group, Dept. of Earth Science and Engineering, Imperial College London, SW7 2AZ (United Kingdom); Angelo, P. L. [Y-12 National Security Complex, Oak Ridge, TN 37831 (United States)
2012-07-01
Babcock and Wilcox Technical Services Group (B and W) has identified aqueous homogeneous reactors (AHRs) as a technology well suited to produce the medical isotope molybdenum 99 (Mo-99). AHRs have never been specifically designed or built for this specialized purpose. However, AHRs have a proven history of being safe research reactors. In fact, in 1958, AHRs had 'a longer history of operation than any other type of research reactor using enriched fuel' and had 'experimentally demonstrated to be among the safest of all various type of research reactor now in use [1].' While AHRs have been modeled effectively using simplified 'Level 1' tools, the complex interactions between fluids, neutronics, and solid structures are important (but not necessarily safety significant). These interactions require a 'Level 2' modeling tool. Imperial College London (ICL) has developed such a tool: Finite Element Transient Criticality (FETCH). FETCH couples the radiation transport code EVENT with the computational fluid dynamics code (Fluidity), the result is a code capable of modeling sub-critical, critical, and super-critical solutions in both two-and three-dimensions. Using FETCH, ICL researchers and B and W engineers have studied many fissioning solution systems include the Tokaimura criticality accident, the Y12 accident, SILENE, TRACY, and SUPO. These modeling efforts will ultimately be incorporated into FETCH'S extensive automated verification and validation (V and V) test suite expanding FETCH'S area of applicability to include all relevant physics associated with AHRs. These efforts parallel B and W's engineering effort to design and optimize an AHR to produce Mo99. (authors)
Institute of Scientific and Technical Information of China (English)
张先付; 许慧君; 沈涛
1995-01-01
Rate constants for electron transfer between excited states of several tetrasulfonated phthalocyanines (MTSPC, M = H2, Zn, ClAl, ClGa) and tyrosine or trptophan have been measured in homogeneous aqueous and aqueous micellar media. Cationic micelles formed by surfactant cetyl trimethyl ammonium chloride (CTAC) promote the electron transfer reaction, whereas neutral micelles formed by Triton X-100 depress this process. The calculated free energy change shows that phthalocyanines act as electron donors in the electron transfer reaction of its excited singlet states with tyrosine or trptophan (Type Is), whereas they act as electron acceptors in the reaction of its excited triplet states with tyrosine or trptophan (type IT). The two different electron transfer processes involving singlet and triplet of sensitizer respectively compete with each other and form different intermediates which may induce the formation of different products. Factors that govern the importance of Type Is in the whole reaction includ
Energy Technology Data Exchange (ETDEWEB)
Samuel, Jorice, E-mail: jorice.samuel@gmail.com [AREVA T and D UK Ltd, AREVA T and D Research and Technology Centre (United Kingdom); Raccurt, Olivier [NanoChemistry and Nanosafety Laboratory (DRT/LITEN/DTNM/LCSN), CEA Grenoble, Department of NanoMaterials (France); Mancini, Cedric; Dujardin, Christophe; Amans, David; Ledoux, Gilles [Universite de Lyon, Laboratoire de Physico Chimie des Materiaux Luminescents (LPCML) (France); Poncelet, Olivier [NanoChemistry and Nanosafety Laboratory (DRT/LITEN/DTNM/LCSN), CEA Grenoble, Department of NanoMaterials (France); Tillement, Olivier [Universite de Lyon, Laboratoire de Physico Chimie des Materiaux Luminescents (LPCML) (France)
2011-06-15
Gadolinium oxide nanoparticles are more and more used. They can notably provide interesting fluorescence properties. Herein they are incorporated into a non-aqueous-based polymer, the poly(methyl methacrylate). Their dispersion within the polymer matrix is the key to improve the composite properties. As-received gadolinium oxide nanopowders cannot be homogeneously dispersed in such a polymer matrix. Two surface treatments are, therefore, detailed and compared to achieve a good stability of the nanoparticles in a non-aqueous solvent such as the 2-butanone. Then, once the liquid suspensions have been stabilized, they are used to prepare nanocomposites with homogeneous particles dispersion. The two approaches proposed are an hybrid approach based on the growth of a silica shell around the gadolinium oxide nanoparticles, and followed by a suitable silane functionalization; and a non-hybrid approach based on the use of surfactants. The surface treatments and formulations involved in both methods are detailed, adjusted and compared. Thanks to optical methods and in particular to the use of a 'home made' confocal microscope, the dispersion homogeneity within the polymer can be assessed. Both methods provide promising and conclusive results.
Conceptual design of a new homogeneous reactor for medical radioisotope Mo-99/Tc-99m production
Energy Technology Data Exchange (ETDEWEB)
Liem, Peng Hong [Nippon Advanced Information Service (NAIS Co., Inc.) Scientific Computational Division, 416 Muramatsu, Tokaimura, Ibaraki (Japan); Tran, Hoai Nam [Chalmers University of Technology, Dept. of Applied Physics, Div. of Nuclear Engineering, SE-412 96 Gothenburg (Sweden); Sembiring, Tagor Malem [National Nuclear Energy Agency (BATAN), Center for Reactor Technology and Nuclear Safety, Kawasan Puspiptek, Serpong, Tangerang Selatan, Banten (Indonesia); Arbie, Bakri [PT MOTAB Technology, Kedoya Elok Plaza Blok DA 12, Jl. Panjang, Kebun Jeruk, Jakarta Barat (Indonesia)
2014-09-30
To partly solve the global and regional shortages of Mo-99 supply, a conceptual design of a nitrate-fuel-solution based homogeneous reactor dedicated for Mo-99/Tc-99m medical radioisotope production is proposed. The modified LEU Cintichem process for Mo-99 extraction which has been licensed and demonstrated commercially for decades by BATAN is taken into account as a key design consideration. The design characteristics and main parameters are identified and the advantageous aspects are shown by comparing with the BATAN's existing Mo-99 supply chain which uses a heterogeneous reactor (RSG GAS multipurpose reactor)
Farajzadeh, Mir Ali; Feriduni, Behruz; Afshar Mogaddam, Mohammad Reza
2015-07-23
In this paper, a new version of salting-out homogenous liquid-liquid extraction based on counter current mode combined with dispersive liquid-liquid microextraction has been developed for the extraction and preconcentration of some pesticides from aqueous samples and their determination by gas chromatography-flame ionization detection. In order to perform the method, aqueous solution of the analytes containing acetonitrile and 1,2-dibromoethane is transferred into a narrow bore tube which is filled partially with NaCl. During passing the solution through the tube, fine droplets of the organic phase are produced at the interface of solution and salt which go up through the tube and form a separated layer on the aqueous phase. The collected organic phase is removed and injected into de-ionized water for more enrichment of the analytes. Under the optimum extraction conditions, the method shows broad linear ranges for the target analytes. Enrichment factors and limits of detection for the selected pesticides are obtained in the ranges of 3480-3800 and 0.1-5μgL(-1), respectively. Relative standard deviations are in the range of 2-7% (n=6, C=50 or 100μgL(-1), each analyte). Finally, some aqueous samples were successfully analyzed using the developed method.
Cardoso, Daniel R; Olsen, Karsten; Skibsted, Leif H
2007-07-25
Tocopherols (alpha, beta, gamma, and delta) and Trolox were found to deactivate triplet-excited riboflavin in homogeneous aqueous solution (7:3 v/v tert-butanol/water) with second-order reaction rates close to diffusion control [k2 between 4.8 x 10(8) (delta-tocopherol) and 6.2 x 10(8) L mol(-1) s(-1) (Trolox) at 24.0 +/- 0.2 degrees C] as determined by laser flash photolysis transient absorption spectroscopy. In aqueous buffer (pH 6.4) the rate constant for Trolox was 2.6 x 10(9) L mol(-1) s1 and comparable to the rate constant found for ascorbate (2.0 x 10(9) L mol(-1) s(-1)). The deactivation rate constant was found to be inferior in heterogeneous systems as shown for alpha-tocopherol and Trolox in aqueous Tween-20 emulsion (approximately by a factor of 4 compared to 7:3 v/v tert-butanol/water). Neither beta-carotene (7:3 v/v tert-butanol/water and Tween-20 emulsion), lycopene (7:3 v/v tert-butanol/water), nor crocin (aqueous buffer at pH 6.4, 7:3 v/v tert-butanol/water, and Tween-20 emulsion) showed any quenching on the triplet excited state of riboflavin. Therefore, all carotenoids seem to reduce the formation of triplet-excited riboflavin through an inner-filter effect. Activation parameters were based on the temperature dependence of the triplet-excited deactivation between 15 and 35 degrees C, and the isokinetic behavior, which was found to include purine derivatives previously studied, confirms a common deactivation mechanism with a bimolecular diffusion-controlled encounter with electron (or hydrogen atom) transfer as rate-determining step. DeltaH for deactivation by ascorbic acid, Trolox, and homologue tocopherols (ranging from 18 kJ mol(-1) for Trolox in Tween-20 emulsion to 184 kJ mol(-1) for ascorbic acid in aqueous buffer at pH 6.4) showed a linear dependence on DeltaS (ranging from -19 J mol(-1) K(-1) for Trolox in aqueous buffer at pH 6.4 to +550 J mol(-1) K(-1) for ascorbic acid in aqueous buffer pH 6.4). Among photooxidation products from the
Chen, Fengli; Zhang, Qiang; Gu, Huiyan; Yang, Lei
2016-11-04
In this study, a novel approach involving homogenate-circulating ultrasound in combination with aqueous enzymatic extraction (H-CUAEE) was developed for extraction of kernel oil from Pinus pumila. Following comparison of enzyme types and concentrations, an enzyme mixture consisting of cellulase, pectinase and hemicellulase (1:1:1, w/w/w) at a concentration of 2.5% was selected and applied for effective oil extraction and release. Several variables potentially influencing extraction yields, namely, homogenization time, incubation temperature, incubation time, mark-space ratio of ultrasound irradiation, ultrasound irradiation power, liquid-solid ratio, pH and stirring rate, were optimized by Plackett-Burman design. Among the eight variables, incubation temperature, incubation time and liquid-solid ratio were statistically significant and were further optimized by Box-Behnken design to predict optimum extraction conditions and ascertain operability ranges for maximum extraction yield. Under optimum operating conditions, extraction yields of P. pumila kernel oil were 31.89±1.12% with a Δ5-unsaturated polymethylene interrupted fatty acid content of 20.07% and an unsaturated fatty acid content of 93.47%. Our study results indicate that the proposed H-CUAEE process has enormous potential for efficient and environmentally friendly extraction of edible oils.
Szajna-Fuller, Ewa; Huang, Yulin; Rapp, Jennifer L; Chaka, Gezahegn; Lin, Victor S Y; Pruski, Marek; Bakac, Andreja
2009-05-07
A comparative study of catalytic activity under homogeneous and heterogeneous conditions was carried out using the (salen)Cr(III)-catalyzed oxidation of tetramethylbenzidine (TMB) with iodosobenzene as a model reaction. Amine-functionalized mesoporous silica nanoparticles (MSN) were synthesized in a co-condensation reaction and functionalized with salen via a covalent Si-C bond. A Cr(III) complex of this supported ligand, MSN-(salen)Cr(III), was prepared and characterized. Data from powder XRD, BET isotherms and BJH pore size distribution all showed that MSN-(salen)Cr(III) still had the typical MSN high surface area, narrow pore size distribution, and ordered hexagonal pore structure, which were further confirmed by transmission electron microscopy (TEM) images. (13)C and (29)Si solid-state NMR data provided structural information about the catalyst and verified successful functionalization of the salen ligand and coordination to Cr(III). No unreacted salen or Cr(III) were observed. The loadings of salen and salen-Cr(III) complex were determined via TGA and EDX, respectively. Both measurements indicated that approximately 0.5 mmol/g of catalyst was loaded on the surface of MSN. The oxidation of TMB with iodosobenzene using MSN-(salen)Cr(III) as a heterogeneous catalyst exhibited both similarities and differences with the analogous homogeneous reaction using (salen)Cr(III)(H(2)O)(+) as a catalyst in aqueous acetonitrile. In the presence of 0.10 M HClO(4), the two catalytic reactions proceeded at similar rates and generated the doubly oxidized product TMB(2+). In the absence of acid, the radical cation TMB (+) was produced. The kinetics of the heterogeneous reaction in the absence of added acid responded to concentrations of all three reagents, i.e. (salen)Cr(III), TMB, and PhIO.
溶液堆物理计算程序FMCAHR开发%Development of Fuel Management Code for Aqueous Homogeneous Reactors
Institute of Scientific and Technical Information of China (English)
汪量子; 姚栋; 王侃
2011-01-01
Fuel Management Code for Aqueous Homogeneous Reactors (FMCAHR) is developed based on the Monte Carlo transport method. FMCAHR has the ability of doing resonance treatment, searching for critical control rods height, and calculating the thermal hydraulic parameters, bubble volume fraction and bum-up. The main structure and development process of FMCAHR is introduced in this paper, and the verification shows that the computing results of FMCAHR are precise.%针对溶液型燃料反应堆,基于蒙特卡罗输运计算方法,开发了溶液堆物理计算程序FMCAHR,该程序具有共振处理、搜索临界棒位、热工水力参数计算、气泡体积含量计算和燃耗计算的功能.对程序进行校算的结果证明该程序计算精度较高.
Meddahi-Pellé, Anne; Legrand, Aurélie; Marcellan, Alba; Louedec, Liliane; Letourneur, Didier; Leibler, Ludwik
2014-06-16
Sutures are traumatic to soft connective tissues, such as liver or lungs. Polymer tissue adhesives require complex in vivo control of polymerization or cross-linking reactions and currently suffer from being toxic, weak, or inefficient within the wet conditions of the body. Herein, we demonstrate using Stöber silica or iron oxide nanoparticles that nanobridging, that is, adhesion by aqueous nanoparticle solutions, can be used in vivo in rats to achieve rapid and strong closure and healing of deep wounds in skin and liver. Nanoparticles were also used to fix polymer membranes to tissues even in the presence of blood flow, such as occurring after liver resection, yielding permanent hemostasis within a minute. Furthermore, medical devices and tissue engineering constructs were fixed to organs such as a beating heart. The simplicity, rapidity, and robustness of nanobridging bode well for clinical applications, surgery, and regenerative medicine.
Robertson, Wesley D; Bovell, Adonis M; Warncke, Kurt
2013-08-01
Components of a protein-integrated, earth-abundant metal macrocycle catalyst, with the purpose of H2 production from aqueous protons under green conditions, are characterized. The cobalt-corrin complex, cobinamide, is demonstrated to produce H2 (4.4 ± 1.8 × 10(-3) turnover number per hour) in a homogeneous, photosensitizer/sacrificial electron donor system in pure water at neutral pH. Turnover is proposed to be limited by the relatively low population of the gateway cobalt(III) hydride species. A heterolytic mechanism for H2 production from the cobalt(II) hydride is proposed. Two essential requirements for assembly of a functional protein-catalyst complex are demonstrated for interaction of cobinamide with the (βα)8 TIM barrel protein, EutB, from the adenosylcobalamin-dependent ethanolamine ammonia lyase from Salmonella typhimurium: (1) high-affinity equilibrium binding of the cobinamide (dissociation constant 2.1 × 10(-7) M) and (2) in situ photoreduction of the cobinamide-protein complex to the Co(I) state. Molecular modeling of the cobinamide-EutB interaction shows that these features arise from specific hydrogen-bond and apolar interactions of the protein with the alkylamide substituents and the ring of the corrin, and accessibility of the binding site to the solution. The results establish cobinamide-EutB as a platform for design and engineering of a robust H2 production metallocatalyst that operates under green conditions and uses the advantages of the protein as a tunable medium and material support.
Simental-Martínez, Jesús; Rito-Palomares, Marco; Benavides, Jorge
2014-01-01
Superoxide dismutase (SOD; EC 1.15.1.1) is an antioxidant enzyme that represents the primary cellular defense against superoxide radicals and has interesting applications in the medical and cosmetic industries. In the present work, the partition behavior of SOD in aqueous two-phase systems (ATPS) (using a standard solution and a complex extract from Kluyveromyces marxianus as sample) was characterized on different types of ATPS (polymer-polymer, polymer-salt, alcohol-salt, and ionic liquid (IL)-salt). The systems composed of PEG 3350-potassium phosphate, 45% TLL, 0.5 M NaCl (315 U/mg, 87% recovery, and 15.1-fold purification) and t-butanol-20% ammonium sulfate (205.8 U/mg, 80% recovery and 9.8-fold purification), coupled with a subsequent 100 kDa ultrafiltration stage, allowed the design of a prototype process for the recovery and partial purification of the product of interest. The findings reported herein demonstrate the potential of PEG-salt ATPS for the potential recovery of SOD.
Pigolkin, Iu I; Skovorodnikov, S V; Dubrovin, I A
2014-01-01
The objective of the present study was to develop the criteria for forensic-medical diagnostics of an electrical injury inflicted in the aqueous environment based on the characteristics of the electrical mark. The specific morphological features of the electrical injuries inflicted in the aqueous environment that were discovered in the materials available for the forensic medical expertise were analysed taking into consideration the results of the relevant research reported in the forensic medical literature. It was shown that an electrical injury inflicted in the aqueous environment results in the formation of an unusual mark in the form of blisters containing no watery liquid associated with electrogenic oedema in the surrounding tissues. Macroscopic and microscopic studies of the electrical mark failed to reveal the signs of grade III and IV grade thermal burning or thermally affected hair. It is concluded that the consistent characteristics of the electrical mark resulting from the injury inflicted by technical electricity in the aqueous environment include cell lengthening, blister formation inside the corneal layer, and the separation of epidermis from the skin proper.
Institute of Scientific and Technical Information of China (English)
汪量子; 姚栋; 王侃
2011-01-01
介绍了FMCAHR程序的燃耗计算模型及流程,并使用燃耗基准题和DRAGON程序对燃耗计算结果进行验证.验证结果表明,FMCAHR燃耗计算功能的准确性较高,适用于溶液堆的燃耗计算分析.%Fuel Management Code for Aqueous Homogeneous Reactors(FMCAHR)is developed based on the Monte Carlo transport method,to analyze the physics characteristics of aqueous homogeneous reactors. FMCAHR has the ability of doing resonance treatment,searching for critical rod heights,thermal hydraulic parameters calculation,radiolytic-gas bubbles' calculation and burn-up calculation. This paper introduces the theory model and scheme of its bum-up function,and then compares its calculation results with benchmarks and with DRAGON'S burn-up results,which confirms its burn-up computing precision and its applicability in the burn-up calculation and analysis for aqueous solution reactors.
Plante, Ianik
2011-08-01
The importance of the radiolysis of water in irradiation of biological systems has motivated considerable theoretical and experimental work in the radiation chemistry of water and aqueous solutions. In particular, Monte-Carlo simulations of radiation track structure and non-homogeneous chemistry have greatly contributed to the understanding of experimental results in radiation chemistry of heavy ions. Actually, most simulations of the non-homogeneous chemistry are done using the Independent Reaction Time (IRT) method, a very fast technique. The main limitation of the IRT method is that the positions of the radiolytic species are not calculated as a function of time, which is needed to simulate the irradiation of more complex systems. Step-by-step (SBS) methods, which are able to provide such information, have been used only sparsely because these are time consuming in terms of calculation. Recent improvements in computer performance now allow the regular use of the SBS method in radiation chemistry. In the present paper, the first of a series of two, the SBS method is reviewed in detail. To these ends, simulation of diffusion of particles and chemical reactions in aqueous solutions is reviewed, and implementation of the program is discussed. Simulation of model systems is then performed to validate the adequacy of stepwise diffusion and reaction schemes. In the second paper, radiochemical yields of simulated radiation tracks calculated by the SBS program in different conditions of LET, pH, and temperature are compared with results from the IRT program and experimental data.
Zeh, A.; Gerdes, A.
2014-08-01
Results from laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS) and isotope dilution (ID) analyses of minerals and rocks from a single outcrop of the Venetia Klippe of the Limpopo Belt indicate that the U-Pb and Hf isotope system homogenized on the decimetre scale under amphibolite-facies conditions of ⩽645 ± 25 °C and ⩽7.0 ± 1.1 kbar, i.e. in the presence of an aqueous fluid phase. For a metabasite sample, homogenization is supported by isotope analyses of metamorphic zircon, garnet, and whole rock, which yield a six-point Lu-Hf isochron age of 2039.7 ± 3.4 Ma, with initial 176Hf/177Hf of 0.28126 ± 0.00001, and a U-Pb zircon age of 2042 ± 10 Ma. The occurrence of a few inherited magmatic zircon cores with ages up to 2705 Ma, and with significantly lower initial 176Hf/177Hf of 0.28112, however, indicate that homogenization was incomplete. For a chlorite-biotite-garnet schist isotope homogenization is reflected by within error identical zircon and monazite U-Pb ages of 2045 ± 10 Ma and 2041 ± 8 Ma, respectively, and by a zircon-garnet-whole rock Lu-Hf isochron age of 2083 ± 63 Ma, with an initial 176Hf/177Hf of 0.28140 ± 0.00003. Contemporaneous formation of metamorphic zircon, monazite and garnet in the chlorite schist is not only supported by the isotope data, but also by chlorite inclusions in all three minerals, and by inclusions of metamorphic zircon in garnet. The inclusion textures and the identical initial 176Hf/177Hf support the conclusion that metamorphic zircon grains precipitated from an aqueous fluid phase, after dissolution of zirconium-bearing phases elsewhere, followed by a major HFSE transport, and Hf isotope homogenization. This fluid perhaps was Ca-bearing, as is suggested by the fact that garnet in the schist sample is the only Ca-bearing phase, and that metamorphic monazite, dating the metamorphic peak, is partially replacement by apatite. The fact that the metamorphic zircon rims in the metabasite sample have
Li, Taihua; Choi, Yo Han; Shin, Yong-Beom; Kim, Hwa-Jung; Kim, Min-Gon
2016-05-01
A fluorescence enhancement-based immunoassay has been developed for the detection of the polycyclic aromatic hydrocarbons (PAH), benzo[a]pyrene (BaP), in aqueous solutions. The results of this study show that BaP, which inefficiently fluoresces in aqueous solution, displays enhanced fluorescence when bound to the anti-BaP antibody (anti-BaP), as part of a label-free immunoassay system. Binding to anti-BaP results in a 3.12-fold increase in the fluorescence intensity of BaP, which emits at 435 nm when excited at 280 nm, due to the hydrophobic interaction and fluorescence resonance energy transfer (FRET) between antibody and antigen. As result of this phenomenon, the antibody-based fluorescence immunoassay system can be used to detect BaP specifically with a limit of detection (LOD) of 0.06 ng mL(-1). Finally, extraction recoveries of BaP from spiked wheat and barley samples were found to be in the range of 80.5-87.0% and 92.9-92.1%, respectively.
Chadwick, John C; Freixa, Zoraida; van Leeuwen, Piet W N M
2011-01-01
This first book to illuminate this important aspect of chemical synthesis improves the lifetime of catalysts, thus reducing material and saving energy, costs and waste.The international panel of expert authors describes the studies that have been conducted concerning the way homogeneous catalysts decompose, and the differences between homogeneous and heterogeneous catalysts. The result is a ready reference for organic, catalytic, polymer and complex chemists, as well as those working in industry and with/on organometallics.
Mine, Y; Fukunaga, K; Maruoka, N; Nakao, K; Sugimura, Y
2000-01-01
A novel method of preparing detergent-enzyme complexes that can be employed in organic media was developed utilizing newly synthesized water-soluble nonionic gemini-type detergents, N,N-bis(3-D-gluconamidopropyl)-3-(dialkyl-L-glutamatecarbonyl)propanamides (BIG2CnCA: n = 10,12,14,16,18) and N,N-bis(3-D-lactonamidopropyl)-3-(dialkyl-L-glutamatecarbonyl)propanamides (BIL2CnCA: n = 16,18), and nonionic twin-headed detergents, N,N-bis(3-D-gluconamidopropyl)alkanamides (BIG1Cn: n = 12,14,16,18,delta9). This method simply entails mixing a selected enzyme with an appropriate detergent in an aqueous solution followed by lyophilization, and it offers the advantages of enhanced enzymatic activity in organic solvents and eliminates both enzyme loss and the necessity for an organic solvent in the preparation stage. Using various modified lipases originating from Aspergillus niger (Lipase A), Candida rugosa (Lipase C), Pseudomonas cepacia (Lipase P), and porcine pancreas (PPL), prepared using the novel method and detergents, including conventional synthesized nonionic detergents such as dialkyl N-D-glucona-L-glutamates (2CnGE: n = 12,18delta9) and octanoyl-N-methylglucamide (MEGA-8), enantioselective transesterifications of 6-methyl-5-hepten-2-ol (sulcatol) and 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) with a vinyl or isopropenyl carboxylate were carried out in an organic solvent. The modified lipase activity was influenced by both the lipases and the structure of the detergents. The value for the hydrophile-lipophile balance (HLB) of the detergent provided a means of correlating the structure and the obtained modified lipase activity. For detergents of the same class with a HLB value of approximately 9 and 12, the highest activity was obtained for Lipase A and Lipase P, and Lipase C and PPL, respectively. Among detergents of the same HLB value tested, the gemini-type detergents possessing the most bulky head and tail were most effective as a modifier for lipases of all
Farajzadeh, Mir Ali; Khiavi, Elahe Behboudi; Khorram, Parisa; Mogaddam, Mohammad Reza Afshar
2017-01-01
In the present study, a simple and rapid method for the extraction and preconcentration of some polycyclic aromatic hydrocarbons in water samples has been developed. In this method, two sample preparation methods were combined to obtain high extraction recoveries and enrichment factors for sensitive analysis of the selected analytes. In the first stage of the method, a homogeneous solution containing an aqueous solution and cyclohexyl amine is broken by the addition of a salt. After centrifugation, the upper collected phase containing the extracted analytes is subjected to the following dispersive liquid-liquid microextraction method. Rapid injection of the mixture of cyclohexyl amine resulted from the first stage and 1,1,2-trichloroethane (as an extraction solvent) into an acetic acid solution is led to form a cloudy solution. After centrifuging, the fine droplets of the extraction solvent are settled down in the bottom of the test tube, and an aliquot of it is analyzed by gas chromatography. Under the optimum extraction conditions, enrichment factors and limits of detection for the studied analytes were obtained in the ranges of 616-752 and 0.08-0.20 μg/L, respectively. The simplicity, high extraction efficiency, short sample preparation time, low cost, and safety demonstrated the efficiency of this method relative to other approaches.
Phungamngoen Chanthima; Asawajinda Tippunsa; Santad Rujira; Sawedboworn Wanticha
2016-01-01
Coconut milk is one of the most important protein-rich food sources available today. Separation of an emulsion into an aqueous phase and cream phase is commonly occurred and this leads an unacceptably physical defect of either fresh or processed coconut milk. Since homogenization steps are known to affect the stability of coconut milk. This work was aimed to study the effect of homogenization steps on quality of coconut milk. The samples were subject to high speed homogenization in the range ...
Zervou, Maria I; Myrthianou, Efsevia; Flouri, Irene; Plant, Darren; Chlouverakis, Gregory; Castro-Giner, Francesc; Rapsomaniki, Panayiota; Barton, Anne; Boumpas, Dimitrios T; Sidiropoulos, Prodromos; Goulielmos, George N
2013-01-01
Treatment strategies blocking tumor necrosis factor (anti-TNF) have proven very successful in patients with rheumatoid arthritis (RA), showing beneficial effects in approximately 50-60% of the patients. However, a significant subset of patients does not respond to anti-TNF agents, for reasons that are still unknown. The aim of this study was to validate five single nucleotide polymorphisms (SNPs) of PTPRC, CD226, AFF3, MyD88 and CHUK gene loci that have previously been reported to predict anti-TNF outcome. In addition, two markers of RA susceptibility, namely TRAF1/C5 and STAT4 were assessed, in a cohort of anti-TNF-treated RA patients, from the homogeneous Greek island of Crete, Greece. The RA patient cohort consisted of 183 patients treated with either of 3 anti-TNF biologic agents (infliximab, adalimumab and etanercept) from the Clinic of Rheumatology of the University Hospital of Crete. The SNPs were genotyped by TaqMan assays or following the Restriction Fragments Length Polymorphisms (RFLPs) approach. Disease activity score in 28 joints (DAS28) at baseline and after 6 months were available for all patients and analysis of good versus poor response at 6 months was performed for each SNP. None of the 7 genetic markers correlated with treatment response. We conclude that the gene polymorphisms under investigation are not strongly predictive of anti-TNF response in RA patients from Greece.
Directory of Open Access Journals (Sweden)
Maria I Zervou
Full Text Available Treatment strategies blocking tumor necrosis factor (anti-TNF have proven very successful in patients with rheumatoid arthritis (RA, showing beneficial effects in approximately 50-60% of the patients. However, a significant subset of patients does not respond to anti-TNF agents, for reasons that are still unknown. The aim of this study was to validate five single nucleotide polymorphisms (SNPs of PTPRC, CD226, AFF3, MyD88 and CHUK gene loci that have previously been reported to predict anti-TNF outcome. In addition, two markers of RA susceptibility, namely TRAF1/C5 and STAT4 were assessed, in a cohort of anti-TNF-treated RA patients, from the homogeneous Greek island of Crete, Greece. The RA patient cohort consisted of 183 patients treated with either of 3 anti-TNF biologic agents (infliximab, adalimumab and etanercept from the Clinic of Rheumatology of the University Hospital of Crete. The SNPs were genotyped by TaqMan assays or following the Restriction Fragments Length Polymorphisms (RFLPs approach. Disease activity score in 28 joints (DAS28 at baseline and after 6 months were available for all patients and analysis of good versus poor response at 6 months was performed for each SNP. None of the 7 genetic markers correlated with treatment response. We conclude that the gene polymorphisms under investigation are not strongly predictive of anti-TNF response in RA patients from Greece.
Directory of Open Access Journals (Sweden)
Wang B
2011-07-01
Full Text Available Bin Wang1,2, Weimin Jiang1,2, Hao Yan1,2, Xiaoxi Zhang1,2, Li Yang1,2, Lihong Deng1,2, Gurinder K Singh1,2, Jun Pan1,2 1Bioengineering College, Chongqing University, Chongqing, People’s Republic of China; 2Key Laboratory of Biorheological Science and Technology (Chongqing University, Ministry of Education, Chongqing, People’s Republic of China The first two authors contributed equally to this workAbstract: This study concerns the encapsulation and controlled release of both hydrophobic and hydrophilic medications with one polymer, which are delivered together as a combined therapy to treat diseased tissue. To test our hypothesis that the novel PEG-graft-PLA (PEG, polyethylene glycol; PLA, polylactic acid can deliver both the hydrophobic and hydrophilic medications on account of its amphiphility, charge, and graft structure, PEG-graft-PLA (molecular weight of PEG = 1900 with very low critical micelle concentration was synthesized. One hydrophilic (insulin and one hydrophobic (naproxen model medication were loaded in separately during its self-assembly in aqueous solution. The resulting nanoparticles (NPs were narrowly distributed and spherical, with average particle size around 200 nm, zeta potential >—10 mV, and encapsulation efficiency >50%. The NPs realized controlled release of insulin and naproxen for over 24 and 160 hours, respectively. Specifically, the bioactivity of the insulin released from the NPs was maintained. Owing to encapsulation, both for hydrophobic and hydrophilic medicines, and NPs obtained with similar size and zeta potential, as well as maintenance of bioactivity of loaded protein, we expect the applications of PEG-graft-PLA NPs in combination therapy.Keywords: NPs, insulin, naproxen, controlled release, combination therapy
Institute of Scientific and Technical Information of China (English)
许新胜; 史蕾; 刘毅; 崔执凤
2011-01-01
The photochemical reaction mechanism of phenanthrenequione in ethylene glycol homogenous and its TX-100 aqueous micellar solution has been studied through time resolved ESR and transient absorptive spectra technique. In EG homogenous solution, CIDEP spectra and transient absorptive spectra indicate that neutral radical (PAQH) was formed through hydrogen transfer reaction between excited triplet phenanthrenequinone (3PAQ*) and EG. Triplet mechanism is the mainly mechanism to generate CIDEP. In TX-100 aqueous micellar solution, the signals of CIDEP of phenanthrenequinone anion radical were observed, which were generated from the dissociation of PAQH accompanying spin polarization transfer.%用时间分辨电子自旋共振(TR-ESR)和瞬态吸收光谱技术,研究了菲醌在乙二醇均相及其TX-100含水胶束溶液中的光化学反应机理.化学诱导动态电子极化(CIDEP)谱和瞬态吸收光谱都表明,在乙二醇均相溶液中,菲醌光激发三重态3PAQ*夺取氢原子形成中性自由基PAQH·,三重态机理是CIDEP形成的主要机理.在TX-100含水胶束溶液中,光解主要得到菲醌负离子基PAQ·-,PAQ·-由PAQH·解离形成,解离过程中伴随着极化转移.
Lifting locally homogeneous geometric structures
McKay, Benjamin
2011-01-01
We prove that under some purely algebraic conditions every locally homogeneous structure modelled on some homogeneous space is induced by a locally homogeneous structure modelled on a different homogeneous space.
Functionality and homogeneity.
2011-01-01
Functionality and homogeneity are two of the five Sustainable Safety principles. The functionality principle aims for roads to have but one exclusive function and distinguishes between traffic function (flow) and access function (residence). The homogeneity principle aims at differences in mass, spe
Homogeneity of Inorganic Glasses
DEFF Research Database (Denmark)
Jensen, Martin; Zhang, L.; Keding, Ralf;
2011-01-01
Homogeneity of glasses is a key factor determining their physical and chemical properties and overall quality. However, quantification of the homogeneity of a variety of glasses is still a challenge for glass scientists and technologists. Here, we show a simple approach by which the homogeneity...... of different glass products can be quantified and ranked. This approach is based on determination of both the optical intensity and dimension of the striations in glasses. These two characteristic values areobtained using the image processing method established recently. The logarithmic ratio between...... the dimension and the intensity is used to quantify and rank the homogeneity of glass products. Compared with the refractive index method, the image processing method has a wider detection range and a lower statistical uncertainty....
Benchmarking monthly homogenization algorithms
Directory of Open Access Journals (Sweden)
V. K. C. Venema
2011-08-01
Full Text Available The COST (European Cooperation in Science and Technology Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative. The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random break-type inhomogeneities were added to the simulated datasets modeled as a Poisson process with normally distributed breakpoint sizes. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide trend was added.
Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including (i the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii the error in linear trend estimates and (iii traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve
Directory of Open Access Journals (Sweden)
Phungamngoen Chanthima
2016-01-01
Full Text Available Coconut milk is one of the most important protein-rich food sources available today. Separation of an emulsion into an aqueous phase and cream phase is commonly occurred and this leads an unacceptably physical defect of either fresh or processed coconut milk. Since homogenization steps are known to affect the stability of coconut milk. This work was aimed to study the effect of homogenization steps on quality of coconut milk. The samples were subject to high speed homogenization in the range of 5000-15000 rpm under sterilize temperatures at 120-140 °C for 15 min. The result showed that emulsion stability increase with increasing speed of homogenization. The lower fat particles were generated and easy to disperse in continuous phase lead to high stability. On the other hand, the stability of coconut milk decreased, fat globule increased, L value decreased and b value increased when the high sterilization temperature was applied. Homogenization after heating led to higher stability than homogenization before heating due to the reduced particle size of coconut milk after aggregation during sterilization process. The results implied that homogenization after sterilization process might play an important role on the quality of the sterilized coconut milk.
Plante, Ianik
2011-08-01
The importance of the radiolysis of water in the initial events following irradiation of biological systems has motivated considerable theoretical and experimental work in the field of radiation chemistry of water and aqueous systems. These studies include Monte-Carlo simulations of the radiation track structure and of the non-homogeneous chemical stage, which have been successfully used to calculate the yields of radiolytic species (H(·), (·)OH, H(2), H(2)O(2), e (aq) (-) , …). Most techniques used for the simulation of the non-homogeneous chemical stage such as the independent reaction time (IRT) technique and diffusion kinetics methods do not calculate the time evolution of the positions of the radiolytic species. This is a major limitation to their extension to the simulation of the irradiation of radiobiological systems. Step-by-step (SBS) simulation programs provide such information, but they are very demanding in term of computer power and storage capacity. Recent improvements in computer performance now allow the regular use of the SBS method in radiation chemistry simulations. In the first of a series of two papers, the SBS method has been reviewed in details and the implementation of a SBS code has been discussed. In this second paper, the results of several studies are presented: (1) the time evolution of the radiolytic yields from the formation of the radiation track to 10(-6) s; (2) the effect of pH on yields (pH ~ 0.4-7.0); (3) the effect of proton energy (and LET) on yields (300 MeV-0.1 MeV), and iv) the effect of the ion type ((1)H(+), (4)He(2+), (12)C(6+)) on yields. Nonbiological applications, i.e., the study of the temperature on the yields (about 25-300°C) and the simulation of the time evolution of G(Fe(3+)) in the Fricke dosimeter are also discussed.
Tignanelli, H. L.; Vazquez, R. A.; Mostaccio, C.; Gordillo, S.; Plastino, A.
1990-11-01
RESUMEN. Presentamos una metodologia de analisis de la homogeneidad a partir de la Teoria de la Informaci6n, aplicable a muestras de datos observacionales. ABSTRACT:Standard concepts that underlie Information Theory are employed in order design a methodology that enables one to analyze the homogeneity of a given data sample. Key : DATA ANALYSIS
Dynamics of homogeneous nucleation
DEFF Research Database (Denmark)
Toxværd, Søren
2015-01-01
The classical nucleation theory for homogeneous nucleation is formulated as a theory for a density fluctuation in a supersaturated gas at a given temperature. But molecular dynamics simulations reveal that it is small cold clusters which initiates the nucleation. The temperature in the nucleating...
Synthesis of silica nanosphere from homogeneous and heterogeneous systems
Indian Academy of Sciences (India)
N Venkatathri
2007-12-01
Silica nanosphere was synthesized using homogeneous and heterogeneous systems, respectively. In homogeneous system, silica spheres were synthesized without cetyltrimethylammonium bromide (CTABr), which gave bimodal particle size and lower yield (77%). To improve the yield, CTABr was added and found that the yield was very high (100%). The particle was in nm range, but the particle sizes are bimodal. To avoid it, reaction in heterogeneous system using CTABr was carried out. Nanosized silica sphere with uniform size (yield, 94%) was observed. Homogeneous system contains a mixture of ethanol, water, aqueous ammonia and tetraethylorthosilicate (TEOS). In the case of heterogeneous system, only ethanol was absent.
Homogenous finitary symmetric groups
Directory of Open Access Journals (Sweden)
Otto. H. Kegel
2015-03-01
Full Text Available We characterize strictly diagonal type of embeddings of finitary symmetric groups in terms of cardinality and the characteristic. Namely, we prove the following. Let kappa be an infinite cardinal. If G=underseti=1stackrelinftybigcupG i , where G i =FSym(kappan i , (H=underseti=1stackrelinftybigcupH i , where H i =Alt(kappan i , is a group of strictly diagonal type and xi=(p 1 ,p 2 ,ldots is an infinite sequence of primes, then G is isomorphic to the homogenous finitary symmetric group FSym(kappa(xi (H is isomorphic to the homogenous alternating group Alt(kappa(xi , where n 0 =1,n i =p 1 p 2 ldotsp i .
Homogeneous group, research, institution
Directory of Open Access Journals (Sweden)
Francesca Natascia Vasta
2014-09-01
Full Text Available The work outlines the complex connection among empiric research, therapeutic programs and host institution. It is considered the current research state in Italy. Italian research field is analyzed and critic data are outlined: lack of results regarding both the therapeutic processes and the effectiveness of eating disorders group analytic treatment. The work investigates on an eating disorders homogeneous group, led into an eating disorder outpatient service. First we present the methodological steps the research is based on including the strong connection among theory and clinical tools. Secondly clinical tools are described and the results commented. Finally, our results suggest the necessity of validating some more specifical hypothesis: verifying the relationship between clinical improvement (sense of exclusion and painful emotions reduction and specific group therapeutic processes; verifying the relationship between depressive feelings, relapses and transition trough a more differentiated groupal field.Keywords: Homogeneous group; Eating disorders; Institutional field; Therapeutic outcome
Homogenization of resonant chiral metamaterials
DEFF Research Database (Denmark)
Andryieuski, Andrei; Menzel, C.; Rockstuhl, Carsten
2010-01-01
Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as, e.g., propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size...... an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all....
Figueroa-O'Farrill, José
2015-01-01
Motivated by the search for new gravity duals to M2 branes with $N>4$ supersymmetry --- equivalently, M-theory backgrounds with Killing superalgebra $\\mathfrak{osp}(N|4)$ for $N>4$ --- we classify (except for a small gap) homogeneous M-theory backgrounds with symmetry Lie algebra $\\mathfrak{so}(n) \\oplus \\mathfrak{so}(3,2)$ for $n=5,6,7$. We find that there are no new backgrounds with $n=6,7$ but we do find a number of new (to us) backgrounds with $n=5$. All backgrounds are metrically products of the form $\\operatorname{AdS}_4 \\times P^7$, with $P$ riemannian and homogeneous under the action of $\\operatorname{SO}(5)$, or $S^4 \\times Q^7$ with $Q$ lorentzian and homogeneous under the action of $\\operatorname{SO}(3,2)$. At least one of the new backgrounds is supersymmetric (albeit with only $N=2$) and we show that it can be constructed from a supersymmetric Freund--Rubin background via a Wick rotation. Two of the new backgrounds have only been approximated numerically.
Deng, Shaoqiang
2012-01-01
"Homogeneous Finsler Spaces" is the first book to emphasize the relationship between Lie groups and Finsler geometry, and the first to show the validity in using Lie theory for the study of Finsler geometry problems. This book contains a series of new results obtained by the author and collaborators during the last decade. The topic of Finsler geometry has developed rapidly in recent years. One of the main reasons for its surge in development is its use in many scientific fields, such as general relativity, mathematical biology, and phycology (study of algae). This monograph introduc
Energy Technology Data Exchange (ETDEWEB)
Bershadskii, A.G.
1985-06-01
An exact solution for the nonlinear problem of the spectral energy function of a homogeneous turbulence is derived under the assumption that energy transfer under the effect of inertial forces is determined mainly by the interactions among vortices whose wavenumbers are only slightly different from each other. The results are experimentally verified for turbulence behind grids. Similar problems are solved for MHD turbulence and for a nonstationary spectral energy function. It is shown that at the initial stage of degeneration, the spectral energy function is little influenced by the Stewart number; this agrees with experimental data for the damping of longitudinal velocity pulsations behind a grid in a longitudinal magnetic field. 15 references.
Symmetries of homogeneous cosmologies
Cotsakis, S; Pantazi, H; Cotsakis, Spiros; Leach, Peter; Pantazi, Hara
1998-01-01
We reformulate the dynamics of homogeneous cosmologies with a scalar field matter source with an arbitrary self-interaction potential in the language of jet bundles and extensions of vector fields. In this framework, the Bianchi-scalar field equations become subsets of the second Bianchi jet bundle, $J^2$, and every Bianchi cosmology is naturally extended to live on a variety of $J^2$. We are interested in the existence and behaviour of extensions of arbitrary Bianchi-Lie and variational vector fields acting on the Bianchi variety and accordingly we classify all such vector fields corresponding to both Bianchi classes $A$ and $B$. We give examples of functions defined on Bianchi jet bundles which are constant along some Bianchi models (first integrals) and use these to find particular solutions in the Bianchi total space. We discuss how our approach could be used to shed new light to questions like isotropization and the nature of singularities of homogeneous cosmologies by examining the behaviour of the vari...
Fuel preparation for use in the production of medical isotopes
Policke, Timothy A.; Aase, Scott B.; Stagg, William R.
2016-10-25
The present invention relates generally to the field of medical isotope production by fission of uranium-235 and the fuel utilized therein (e.g., the production of suitable Low Enriched Uranium (LEU is uranium having 20 weight percent or less uranium-235) fuel for medical isotope production) and, in particular to a method for producing LEU fuel and a LEU fuel product that is suitable for use in the production of medical isotopes. In one embodiment, the LEU fuel of the present invention is designed to be utilized in an Aqueous Homogeneous Reactor (AHR) for the production of various medical isotopes including, but not limited to, molybdenum-99, cesium-137, iodine-131, strontium-89, xenon-133 and yttrium-90.
Universum Inference and Corpus Homogeneity
Vogel, Carl; Lynch, Gerard; Janssen, Jerom
Universum Inference is re-interpreted for assessment of corpus homogeneity in computational stylometry. Recent stylometric research quantifies strength of characterization within dramatic works by assessing the homogeneity of corpora associated with dramatic personas. A methodological advance is suggested to mitigate the potential for the assessment of homogeneity to be achieved by chance. Baseline comparison analysis is constructed for contributions to debates by nonfictional participants: the corpus analyzed consists of transcripts of US Presidential and Vice-Presidential debates from the 2000 election cycle. The corpus is also analyzed in translation to Italian, Spanish and Portuguese. Adding randomized categories makes assessments of homogeneity more conservative.
Chemical reactions at aqueous interfaces
Vecitis, Chad David
2009-12-01
Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1
Homogeneous Spaces and Equivariant Embeddings
Timashev, DA
2011-01-01
Homogeneous spaces of linear algebraic groups lie at the crossroads of algebraic geometry, theory of algebraic groups, classical projective and enumerative geometry, harmonic analysis, and representation theory. By standard reasons of algebraic geometry, in order to solve various problems on a homogeneous space it is natural and helpful to compactify it keeping track of the group action, i.e. to consider equivariant completions or, more generally, open embeddings of a given homogeneous space. Such equivariant embeddings are the subject of this book. We focus on classification of equivariant em
Homogenization of Partial Differential Equations
Kaiser, Gerald
2005-01-01
A comprehensive study of homogenized problems, focusing on the construction of nonstandard models: non-local models, multicomponent models, and models with memory. This work is intended for graduate students, applied mathematicians, physicists, and engineers.
Operator estimates in homogenization theory
Zhikov, V. V.; Pastukhova, S. E.
2016-06-01
This paper gives a systematic treatment of two methods for obtaining operator estimates: the shift method and the spectral method. Though substantially different in mathematical technique and physical motivation, these methods produce basically the same results. Besides the classical formulation of the homogenization problem, other formulations of the problem are also considered: homogenization in perforated domains, the case of an unbounded diffusion matrix, non-self-adjoint evolution equations, and higher-order elliptic operators. Bibliography: 62 titles.
Chae, Bora; Cakiner-Egilmez, Tulay; Desai, Manishi
2013-01-01
Glaucoma is a common eye condition that affects millions of individuals worldwide, making it the second-leading cause of blindness. Because glaucoma is associated with increased IOP level, the primary goal in treatment of glaucoma includes lowering IOP to prevent further progression of the disease. While various surgical interventions exist, medical therapy is currently the first line of treatment. Medical treatment of glaucoma includes topical beta-blockers, alpha-2 agonists, prostaglandins, parasympathomimetics and CAIs. Anti-glaucoma agents help reduce IOP by affecting the production of aqueous humor or increasing the outflow of aqueous through the trabecular or uveoscleral pathway. Choosing an appropriate medical regimen can be challenging and various factors such as efficacy, safety, cost and patient compliance must be considered. First-line treatment is often topical beta-blockers or prostaglandin analogs. However, beta-blocking agents can be associated with systemic side effects and need to be used cautiously in patients with serious concomitant cardiopulmonary disease. Alpha-2 agonists and parasympathomimetics are often considered second- or third-line treatment options but good adjunctive agents. Oral CAIs are often indicated for patients with elevated IOP in an acute setting or for patients resistant to other glaucoma medications and patients who are not good surgical candidates.
Toxicological studies of aqueous extract of Acacia nilotica root
Directory of Open Access Journals (Sweden)
Alli Lukman Adewale
2015-03-01
Full Text Available Acacia nilotica is a widely used plant in traditional medical practice in Northern Nigeria and many African countries. The aim of this study was to determine the toxicological effects of a single dose (acute and of repeated doses (sub-acute administration of aqueous extract of A. nilotica root in rodents, following our earlier study on antiplasmodial activity. In the acute toxicity test, three groups of Swiss albino mice were orally administered aqueous extract of A. nilotica (50, 300 and 2000 mg/kg body weight and signs of toxicity were observed daily for 14 days. In the sub-acute toxicity study, four groups of 12 rats (6 male and 6 female were used. Group 1 received 10 ml/kg b.w distilled water (control, while groups 2, 3 and 4 received 125, 250 and 500 mg/kg b.w of the extract, respectively, for 28 consecutive days by oral gavage. Signs of toxicity/mortality, food and water intake and body weight changes were observed. Biochemical parameters were analysed in both plasma and liver homogenate. In the acute and sub-acute toxicity studies, the extract did not cause mortality. A significant reduction in the activity of lactate dehydrogenase was observed at 250 and 500 mg/kg b.w, while alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase activities were significantly higher than control values at 500 mg/kg b.w. The aqueous extract of A. nilotica was found to be safe in single dose administration in mice but repeated administration of doses higher than 250 mg/kg b.w of the extract for 28 days in rats may cause hepatotoxicity.
Preparation of Hydroxyapatite Fibers by the Homogeneous Precipitation Method
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
This paper discussed the preparing process of hydroxyapatite fibers which were widely used as reinforcement for biomedical materials by homogeneous precipitation method.The needle-like hydroxyapatite crystals were synthesized in an aqueous system.They were transferred from precursors-dicalcium phosphate anhydrate and octacalcium phosphate crystals.The reaction conditions were well controlled in order to obtain crystals in given morphology.The products were characterized by X-ray powder diffractometry(XRD),scanning electron microscopy (SEM) and infrared spectroscopy(IR).They were verified to be hydroxyapatite crystals with needle-like in shape.
Homogenization method for elastic materials
Directory of Open Access Journals (Sweden)
Seifrt F.
2007-11-01
Full Text Available In the paper we study the homogenization method and its potential for research of some phenomenons connected with periodic elastic materials. This method will be applied on partial differential equations that describe the deformation of a periodic composite material. The next part of the paper will deal with applications of the homogenization method. The importance of the method will be discussed more detailed for the exploration of the so called bandgaps. Bandgap is a phenomenon which may appear during vibrations of some periodically heterogeneous materials. This phenomenon is not only observable during vibrations for the aforementioned materials, but we may also observe similar effects by propagation of electromagnetic waves of heterogeneous dielectric medias.
Homogeneous vs. heterogeneous nucleation in water-dicarboxylic acid systems
Directory of Open Access Journals (Sweden)
A. I. Hienola
2008-10-01
Full Text Available Binary heterogeneous nucleation of water-succinic/glutaric/malonic/adipic acid on nanometer-sized particles is investigated within the frame of classical heterogeneous nucleation theory. Homogeneous nucleation is also included for comparison. It is found that the nucleation probabilities depend on the contact angle and on the size of the seed particles. New thermodynamical properties, such as saturation vapor pressure, density and surface tension for all the dicarboxylic acid aqueous solutions are included in the calculations. While the new surface tension and density formulations do not bring any significant difference in the computed nucleation rate for homogeneous nucleation for succinic and glutaric acids, the use of the newly derived equations for the vapor pressure decrease the acid concentrations in gas phase with 3 orders of magnitude. According to our calculations, the binary heterogeneous nucleation of succinic acid-water and glutaric acid-water – although it requires a 3–4 orders of magnitude lower vapor concentrations than the homogeneous nucleation – cannot take place in atmospheric conditions. On the other hand binary homogeneous nucleation of adipic acid-water systems might be possible in conditions occuring in upper boundary layer. However, a more detailed characterization of the interaction between the surface and the molecules of the nucleating vapor should be considered in the future.
DEFF Research Database (Denmark)
Horn, Anna Frisenfeldt; Barouh, Nathalie; Nielsen, Nina Skall;
2013-01-01
The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used...... it decreased the oxidative stability of emulsions with α-lactalbumin and β-lactoglobulin. For both types of emulsions the partitioning of proteins between the interface and the aqueous phase appeared to be important for the oxidative stability. The effect of pre-heating the aqueous phase with the milk proteins...... prior to homogenization did not have any clear effect on lipid oxidation in either of the two types of emulsions....
Heterotic strings on homogeneous spaces
Israel, D; Orlando, D; Petropoulos, P M; Israel, Dan; Kounnas, Costas; Orlando, Domenico
2004-01-01
We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU(2)/U(1) ~ S^2 (already described in a previous paper) and the SU(3)/U(1)^2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton.
Homogenization scheme for acoustic metamaterials
Yang, Min
2014-02-26
We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials’ eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial\\'s structural unit cell with a piece of homogenized material. From the Green\\'s theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme\\'s validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.
ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.
Energy Technology Data Exchange (ETDEWEB)
BULLOCK,R.M.; BENDER,B.R.
2000-12-01
The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.
Homogenization of a nonlinear degenerate parabolic equation
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The homogenization of one kind of nonlinear parabolic equation is studied. The weak convergence and corrector results are obtained by combining carefully the compactness method and two-scale convergence method in the homogenization theory.
The Calkin algebra is not countably homogeneous
Farah, Ilijas; Hirshberg, Ilan
2015-01-01
We show that the Calkin algebra is not countably homogeneous, in the sense of continuous model theory. We furthermore show that the connected component of the unitary group of the Calkin algebra is not countably homogeneous.
Coherence delay augmented laser beam homogenizer
Rasmussen, P.; Bernhardt, A.
1993-06-29
The geometrical restrictions on a laser beam homogenizer are relaxed by ug a coherence delay line to separate a coherent input beam into several components each having a path length difference equal to a multiple of the coherence length with respect to the other components. The components recombine incoherently at the output of the homogenizer, and the resultant beam has a more uniform spatial intensity suitable for microlithography and laser pantogography. Also disclosed is a variable aperture homogenizer, and a liquid filled homogenizer.
Improving homogeneity by dynamic speed limit systems.
Nes, N. van Brandenberg, S. & Twisk, D.A.M.
2010-01-01
Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12
Orthogonality Measurement for Homogenous Projects-Bases
Ivan, Ion; Sandu, Andrei; Popa, Marius
2009-01-01
The homogenous projects-base concept is defined. Next, the necessary steps to create a homogenous projects-base are presented. A metric system is built, which then will be used for analyzing projects. The indicators which are meaningful for analyzing a homogenous projects-base are selected. The given hypothesis is experimentally verified. The…
Homogeneous models for bianisotropic crystals
Ponti, S; Oldano, C
2002-01-01
We extend to bianisotropic structures a formalism already developed, based on the Bloch method for defining the effective dielectric tensor of anisotropic crystals in the long-wavelength approximation. More precisely, we provide a homogenization scheme which yields a wavevector-dependent effective medium for any 3D, 2D, or 1D bianisotropic crystal. We illustrate our procedure by applying this to a 1D magneto-electric smectic C*-type structure. The resulting equations confirm that the presence of dielectric and magnetic susceptibilities in the periodic structures generates magneto-electric pseudo-tensors for the effective medium. Their contribution to the optical activity of structurally chiral media can be of the same order of magnitude as the one present in dielectric helix-shaped crystals. Simple analytical expressions are found for the most important optical properties of smectic C*-type structures which are simultaneously dielectric and magnetic.
Projective duality and homogeneous spaces
Tevelev, E A
2006-01-01
Projective duality is a very classical notion naturally arising in various areas of mathematics, such as algebraic and differential geometry, combinatorics, topology, analytical mechanics, and invariant theory, and the results in this field were until now scattered across the literature. Thus the appearance of a book specifically devoted to projective duality is a long-awaited and welcome event. Projective Duality and Homogeneous Spaces covers a vast and diverse range of topics in the field of dual varieties, ranging from differential geometry to Mori theory and from topology to the theory of algebras. It gives a very readable and thorough account and the presentation of the material is clear and convincing. For the most part of the book the only prerequisites are basic algebra and algebraic geometry. This book will be of great interest to graduate and postgraduate students as well as professional mathematicians working in algebra, geometry and analysis.
Effective Gravity and Homogenous Solutions
Müller, Daniel
2013-01-01
Near the singularity, gravity should be modified to an effective theory, in the same sense as with the Euler-Heisenberg electrodynamics. This effective gravity surmounts to higher derivative theory, and as is well known, a much more reacher theory concerning the solution space. On the other hand, as a highly non linear theory, the understanding of this solution space must go beyond the linearized approach. In this talk we will present some results previously published by collaborators and myself, concerning solutions for vacuum spatially homogenous cases of Bianchi types $I$ and $VII_A$. These are the anisotropic generalizations of the cosmological spatially "flat", and "open" models respectively. The solutions present isotropisation in a weak sense depending on the initial condition. Also, depending on the initial condition, singular solutions are obtained.
Effective Gravity and Homogenous Solutions
Müller, Daniel
2015-01-01
Near the singularity, gravity should be modified to an effective theory, in the same sense as with the Euler-Heisenberg electrodynamics. This effective gravity surmounts to higher derivative theory, and as is well known, a much more reacher theory concerning the solution space. On the other hand, as a highly non linear theory, the understanding of this solution space must go beyond the linearized approach. In this talk we will present some results previously published by collaborators and myself, concerning solutions for vacuum spatially homogenous cases of Bianchi types I and VIIA. These are the anisotropic generalizations of the cosmological spatially "flat", and "open" models respectively. The solutions present isotropisation in a weak sense depending on the initial condition. Also, depending on the initial condition, singular solutions are obtained.
The homogeneous geometries of real hyperbolic space
DEFF Research Database (Denmark)
Castrillón López, Marco; Gadea, Pedro Martínez; Swann, Andrew Francis
We describe the holonomy algebras of all canonical connections of homogeneous structures on real hyperbolic spaces in all dimensions. The structural results obtained then lead to a determination of the types, in the sense of Tricerri and Vanhecke, of the corresponding homogeneous tensors. We use ...... our analysis to show that the moduli space of homogeneous structures on real hyperbolic space has two connected components.......We describe the holonomy algebras of all canonical connections of homogeneous structures on real hyperbolic spaces in all dimensions. The structural results obtained then lead to a determination of the types, in the sense of Tricerri and Vanhecke, of the corresponding homogeneous tensors. We use...
Ototoxic Medications (Medication Effects)
... Information for the Public / Hearing and Balance Ototoxic Medications (Medication Effects) By Barbara Cone, Patricia Dorn, Dawn Konrad- ... Audiology Information Series [PDF]. What Is Ototoxicity? Certain medications can damage the ear, resulting in hearing loss, ...
Pharmaceutical Industry Oriented Homogeneous Catalysis
Institute of Scientific and Technical Information of China (English)
Zhang Xumu
2004-01-01
Chiral therapeutics already makes up over one-third of pharmaceutical drugs currently sold worldwide. This is a growing industry with global chiral drug sales for 2002 increasing by 12%to $160 billion (Technology Catalysts International) of a total drug market of $410bn. The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.We aim to become a high value technology provider and partner in the chiral therapeutics industry by offering proprietary catalysts, novel building blocks, and collaborative synthetic solutions. In decade, we have developed a set of novel chiral homogeneous phosphorus ligands such as Binaphane, Me-KetalPhos, TangPhos, f-Binaphane, Me-f-KetalPhos, C4TunePhos and Binapine,which we called Chiral Ligand ToolKit. Complementing the ToolKit, (R, S, S, R)-DIOP*, T-Phos,o-BIPHEP, o-BINAPO and FAP were added recently[1].These ligands can be applied to a broad variety of drug structural features by asymmetric hydrogenation of dehydroamino acid derivatives, enamides, unsatisfied acids and esters, ketones,beta ketoesters, imines and cyclic imines. And ligand FAP had been apllied succefully in allylic alkylation and [3+2] cycloaddition.
Reciprocity theory of homogeneous reactions
Agbormbai, Adolf A.
1990-03-01
The reciprocity formalism is applied to the homogeneous gaseous reactions in which the structure of the participating molecules changes upon collision with one another, resulting in a change in the composition of the gas. The approach is applied to various classes of dissociation, recombination, rearrangement, ionizing, and photochemical reactions. It is shown that for the principle of reciprocity to be satisfied it is necessary that all chemical reactions exist in complementary pairs which consist of the forward and backward reactions. The backward reaction may be described by either the reverse or inverse process. The forward and backward processes must satisfy the same reciprocity equation. Because the number of dynamical variables is usually unbalanced on both sides of a chemical equation, it is necessary that this balance be established by including as many of the dynamical variables as needed before the reciprocity equation can be formulated. Statistical transformation models of the reactions are formulated. The models are classified under the titles free exchange, restricted exchange and simplified restricted exchange. The special equations for the forward and backward processes are obtained. The models are consistent with the H theorem and Le Chatelier's principle. The models are also formulated in the context of the direct simulation Monte Carlo method.
A Class of Homogeneous Einstein Manifolds
Institute of Scientific and Technical Information of China (English)
Yifang KANG; Ke LIANG
2006-01-01
A Riemannian manifold (M,g) is called Einstein manifold if its Ricci tensor satisfies r=c·g for some constant c. General existence results are hard to obtain,e.g., it is as yet unknown whether every compact manifold admits an Einstein metric. A natural approach is to impose additional homogeneous assumptions. M. Y. Wang and W. Ziller have got some results on compact homogeneous space G/H. They investigate standard homogeneous metrics, the metric induced by Killing form on G/H, and get some classification results. In this paper some more general homogeneous metrics on some homogeneous space G/H are studies, and a necessary and sufficient condition for this metric to be Einstein is given. The authors also give some examples of Einstein manifolds with non-standard homogeneous metrics.
The Homogeneity Scale of the universe
Ntelis, Pierros
2016-01-01
In this study, we probe the cosmic homogeneity with the BOSS CMASS galaxy sample in the redshift region of $0.43 < z < 0.7$. We use the normalised counts-in-spheres estimator $\\mathcal{N}(
Wan, Ying-chun; Ma, Hui-ting; Lu, Bin
2015-01-01
When organic solvent-compatible molecularly imprinted polymers (MIPs) are used in aqueous environment, how to reduce nonspecific binding is a major challenge. By modifying the binding solvents and introducing appropriate washing and elution steps, even relatively hydrophobic MIPs can gain optimal rebinding selectivity in aqueous conditions. Furthermore, water-compatible MIPs that can be used to treat aqueous samples directly have been prepared. The use of hydrophilic co-monomers, the controlled surface modification through controlled radical polymerization, and the new interfacial molecular imprinting methods are different strategies to prepare water-compatible MIPs. By combining MIPs with other techniques, both organic solvent-compatible and water-compatible MIPs can display better functional performances in aqueous conditions. Intensive studies on MIPs in aqueous conditions can provide new MIPs with much-improved compatibilities that will lead to more interesting applications in biomedicine and biotechnology.
Self-consolidating concrete homogeneity
Directory of Open Access Journals (Sweden)
Jarque, J. C.
2007-08-01
Full Text Available Concrete instability may lead to the non-uniform distribution of its properties. The homogeneity of self-consolidating concrete in vertically cast members was therefore explored in this study, analyzing both resistance to segregation and pore structure uniformity. To this end, two series of concretes were prepared, self-consolidating and traditional vibrated materials, with different w/c ratios and types of cement. The results showed that selfconsolidating concretes exhibit high resistance to segregation, albeit slightly lower than found in the traditional mixtures. The pore structure in the former, however, tended to be slightly more uniform, probably as a result of less intense bleeding. Such concretes are also characterized by greater bulk density, lower porosity and smaller mean pore size, which translates into a higher resistance to pressurized water. For pore diameters of over about 0.5 Î¼m, however, the pore size distribution was found to be similar to the distribution in traditional concretes, with similar absorption rates.En este trabajo se estudia la homogeneidad de los hormigones autocompactantes en piezas hormigonadas verticalmente, determinando su resistencia a la segregación y la uniformidad de su estructura porosa, dado que la pérdida de estabilidad de una mezcla puede conducir a una distribución no uniforme de sus propiedades. Para ello se han fabricado dos tipos de hormigones, uno autocompactante y otro tradicional vibrado, con diferentes relaciones a/c y distintos tipos de cemento. Los resultados ponen de manifiesto que los hormigones autocompactantes presentan una buena resistencia a la segregación, aunque algo menor que la registrada en los hormigones tradicionales. A pesar de ello, su estructura porosa tiende a ser ligeramente más uniforme, debido probablemente a un menor sangrado. Asimismo, presentan una mayor densidad aparente, una menor porosidad y un menor tamaño medio de poro, lo que les confiere mejores
The Case Against Homogeneous Sets in Mathematics
Jackman, M. K.
1973-01-01
A point-by-point criticism is made of F. H. Flynn's article, The Case for Homogeneous Sets in Mathematics'' (Mathematics in School, Volume 1 Number 2, 1972) in an attempt to show that the arguments used in trying to justify homogeneous grouping in mathematics are invalid. (Editor/DT)
DETERMINISTIC HOMOGENIZATION OF QUASILINEAR DAMPED HYPERBOLIC EQUATIONS
Institute of Scientific and Technical Information of China (English)
Gabriel Nguetseng; Hubert Nnang; Nils Svanstedt
2011-01-01
Deterministic homogenization is studied for quasilinear monotone hyperbolic problems with a linear damping term.It is shown by the sigma-convergence method that the sequence of solutions to a class of multi-scale highly oscillatory hyperbolic problems converges to the solution to a homogenized quasilinear hyperbolic problem.
Finalization report: homogeneous PVM/PARIX
B.J. Overeinder; P.M.A. Sloot; J. Petersen
1994-01-01
This document reports on the design and implementation considerations of PVM/PARIX, homogeneous version 1.0. This version is for use with PARIX 1.2 only. Further, it contains information how to use Homogeneous PVM/PARIX and the appendix contains the installation notes.
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
Karnal H.Yasir; TANG Yun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented. This classification is an extension of the result given by Takens to the cubic homogeneous parameterized vector fields with six parameters.
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
KamalH.Yasir; TNAGYun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented.This classification is an extension of the result given by takens to the cubic homogeneous parameterized vector fields with six parameters.
Investigations into homogenization of electromagnetic metamaterials
DEFF Research Database (Denmark)
Clausen, Niels Christian Jerichau
This dissertation encompasses homogenization methods, with a special interest into their applications to metamaterial homogenization. The first method studied is the Floquet-Bloch method, that is based on the assumption of a material being infinite periodic. Its field can then be expanded in term...
Multilevel Monte Carlo Approaches for Numerical Homogenization
Efendiev, Yalchin R.
2015-10-01
In this article, we study the application of multilevel Monte Carlo (MLMC) approaches to numerical random homogenization. Our objective is to compute the expectation of some functionals of the homogenized coefficients, or of the homogenized solutions. This is accomplished within MLMC by considering different sizes of representative volumes (RVEs). Many inexpensive computations with the smallest RVE size are combined with fewer expensive computations performed on larger RVEs. Likewise, when it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison to a standard Monte Carlo method. Numerical results are presented for both one-dimensional and two-dimensional test-cases that illustrate the efficiency of the approach.
Statistical methods for assessment of blend homogeneity
DEFF Research Database (Denmark)
Madsen, Camilla
2002-01-01
In this thesis the use of various statistical methods to address some of the problems related to assessment of the homogeneity of powder blends in tablet production is discussed. It is not straight forward to assess the homogeneity of a powder blend. The reason is partly that in bulk materials...... as powder blends there is no natural unit or amount to define a sample from the blend, and partly that current technology does not provide a method of universally collecting small representative samples from large static powder beds. In the thesis a number of methods to assess (in)homogeneity are presented....... Some methods have a focus on exploratory analysis where the aim is to investigate the spatial distribution of drug content in the batch. Other methods presented focus on describing the overall (total) (in)homogeneity of the blend. The overall (in)homogeneity of the blend is relevant as it is closely...
Homogeneity of Prototypical Attributes in Soccer Teams
Directory of Open Access Journals (Sweden)
Christian Zepp
2015-09-01
Full Text Available Research indicates that the homogeneous perception of prototypical attributes influences several intragroup processes. The aim of the present study was to describe the homogeneous perception of the prototype and to identify specific prototypical subcategories, which are perceived as homogeneous within sport teams. The sample consists of N = 20 soccer teams with a total of N = 278 athletes (age M = 23.5 years, SD = 5.0 years. The results reveal that subcategories describing the cohesiveness of the team and motivational attributes are mentioned homogeneously within sport teams. In addition, gender, identification, team size, and the championship ranking significantly correlate with the homogeneous perception of prototypical attributes. The results are discussed on the basis of theoretical and practical implications.
Photodegradation of chlorbromuron, atrazine, and alachlor in aqueous systems under solar irradiation
Directory of Open Access Journals (Sweden)
Cristina Lizama Bahena
2006-01-01
Full Text Available Homogeneous and heterogeneous aqueous systems of the herbicides of chlorbromuron, atrazine, and alachlor were irradiated with a nonexpensive solar irradiation using a photoreactor with recirculation. Photodegradation of these herbicides occurred in both aqueous systems; however the presence of TiO2 clearly accelerated the degradation of the three herbicides in comparison with direct photolysis. Degradation was followed by measuring the chemical oxygen demand (COD as a function of reaction time for each aqueous system. Over 90% of COD abatement in the heterogeneous aqueous system was obtained in a short time period showing that mineralization of chlorbromuron, atrazine, and alachlor was achieved.
The role of organic aerosols in homogeneous ice formation
Directory of Open Access Journals (Sweden)
B. Kärcher
2004-10-01
Full Text Available Recent field observations suggest that the fraction of organics containing aerosol particles in ice cloud particles is diminished when compared to the background aerosol prior to freezing. In this work, we use model calculations to investigate possible causes for the observed behavior. In particular, homogeneous freezing processes in cooling air parcels containing aqueous inorganic particles (represented by sulfuric acid and organic particles (represented by pure malonic acid and mixed malonic/sulfuric acid are studied with a detailed microphysical model. A disparate water uptake and resulting size differences that occur between organic and inorganic particles prior to freezing are identified as the most likely reason for the poor partitioning of organic aerosols into the ice phase. The differences in water uptake can be caused by changes in the relationship between solute mass fraction and water activity of the supercooled liquid phase, by modifications of the accommodation coefficient for water molecules, or by a combination thereof. The behavior of peak ice saturation ratios and total ice crystal number concentrations is examined, and the dependence of the results on cooling rate is investigated. Finally, processes are discussed that could possibly modify the homogeneous freezing behavior of organic particles.
Towards a methanol economy based on homogeneous catalysis: methanol to H2 and CO2 to methanol
DEFF Research Database (Denmark)
Alberico, E.; Nielsen, Martin
2015-01-01
The possibility to implement both the exhaustive dehydrogenation of aqueous methanol to hydrogen and CO2 and the reverse reaction, the hydrogenation of CO2 to methanol and water, may pave the way to a methanol based economy as part of a promising renewable energy system. Recently, homogeneous...
Cavegn, Martin; Douglas, Ryan; Akkermans, Guy; Kuentz, Martin
2011-08-01
There are currently no adequate process analyzers for nanoparticulate viscosity enhancers. This article aims to evaluate ultrasonic resonator technology as a monitoring tool for homogenization of nanoparticulate gels. Aqueous dispersions of colloidal microcrystalline cellulose (MCC) and a mixture of clay particles with xanthan gum were compared with colloidal silicon dioxide in oil. The processing was conducted using a laboratory-scale homogenizing vessel. The study investigated first the homogenization kinetics of the different systems to focus then on process factors in the case of colloidal MCC. Moreover, rheological properties were analyzed offline to assess the structure of the resulting gels. Results showed the suitability of ultrasound velocimetry to monitor the homogenization process. The obtained data were fitted using a novel heuristic model. It was possible to identify characteristic homogenization times for each formulation. The subsequent study of the process factors demonstrated that ultrasonic process analysis was equally sensitive as offline rheological measurements in detecting subtle manufacturing changes. It can be concluded that the ultrasonic method was able to successfully assess homogenization of nanoparticulate viscosity enhancers. This novel technique can become a vital tool for development and production of pharmaceutical suspensions in the future.
Deforestation homogenizes tropical parasitoid-host networks.
Laliberté, Etienne; Tylianakis, Jason M
2010-06-01
Human activities drive biotic homogenization (loss of regional diversity) of many taxa. However, whether species interaction networks (e.g., food webs) can also become homogenized remains largely unexplored. Using 48 quantitative parasitoid-host networks replicated through space and time across five tropical habitats, we show that deforestation greatly homogenized network structure at a regional level, such that interaction composition became more similar across rice and pasture sites compared with forested habitats. This was not simply caused by altered consumer and resource community composition, but was associated with altered consumer foraging success, such that parasitoids were more likely to locate their hosts in deforested habitats. Furthermore, deforestation indirectly homogenized networks in time through altered mean consumer and prey body size, which decreased in deforested habitats. Similar patterns were obtained with binary networks, suggesting that interaction (link) presence-absence data may be sufficient to detect network homogenization effects. Our results show that tropical agroforestry systems can support regionally diverse parasitoid-host networks, but that removal of canopy cover greatly homogenizes the structure of these networks in space, and to a lesser degree in time. Spatiotemporal homogenization of interaction networks may alter coevolutionary outcomes and reduce ecological resilience at regional scales, but may not necessarily be predictable from community changes observed within individual trophic levels.
Directory of Open Access Journals (Sweden)
Z. Gholamzadeh
2015-12-01
Full Text Available The use of subcritical aqueous homogenous reactors driven by accelerators presents an attractive alternative for producing 99Mo. In this method, the medical isotope production system itself is used to extract 99Mo or other radioisotopes so that there is no need to irradiate common targets. In addition, it can operate at much lower power compared to a traditional reactor to produce the same amount of 99Mo by irradiating targets. In this study, the neutronic performance and 99Mo, 89Sr, and 131I production capacity of a subcritical aqueous homogenous reactor fueled with low-enriched uranyl nitrate was evaluated using the MCNPX code. A proton accelerator with a maximum 30-MeV accelerating power was used to run the subcritical core. The computational results indicate a good potential for the modeled system to produce the radioisotopes under completely safe conditions because of the high negative reactivity coefficients of the modeled core. The results show that application of an optimized beam window material can increase the fission power of the aqueous nitrate fuel up to 80%. This accelerator-based procedure using low enriched uranium nitrate fuel to produce radioisotopes presents a potentially competitive alternative in comparison with the reactor-based or other accelerator-based methods. This system produces ∼1,500 Ci/wk (∼325 6-day Ci of 99Mo at the end of a cycle.
Benchmarking homogenization algorithms for monthly data
Directory of Open Access Journals (Sweden)
V. K. C. Venema
2012-01-01
Full Text Available The COST (European Cooperation in Science and Technology Action ES0601: advances in homogenization methods of climate series: an integrated approach (HOME has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative. The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random independent break-type inhomogeneities with normally distributed breakpoint sizes were added to the simulated datasets. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide trend was added.
Participants provided 25 separate homogenized contributions as part of the blind study. After the deadline at which details of the imposed inhomogeneities were revealed, 22 additional solutions were submitted. These homogenized datasets were assessed by a number of performance metrics including (i the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii the error in linear trend estimates and (iii traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve
Higher Order Macro Coefficients in Periodic Homogenization
Energy Technology Data Exchange (ETDEWEB)
Conca, Carlos; San Martin, Jorge [Departamento de IngenierIa Matematica, Facultad de Ciencias Fisicas y Matematicas, Universidad de Chile and Centro de Modelamiento Matematico, UMR 2071 CNRS-UChile, Casilla 170/3 - Correo 3, Santiago (Chile); Smaranda, Loredana [Department of Mathematics, Faculty of Mathematics and Computer Science, University of Pitesti, 110040 Pitesti, Str. Targu din Vale Nr.1, Arges (Romania); Vanninathan, Muthusamy, E-mail: cconca@dim.uchile.cl, E-mail: jorge@dim.uchile.cl, E-mail: smaranda@dim.uchile.cl, E-mail: vanni@math.tifrbng.res.in [TIFR-CAM, Post Bag 6503, GKVK Post, Bangalore - 560065 (India)
2011-09-15
A first set of macro coefficients known as the homogenized coefficients appear in the homogenization of PDE on periodic structures. If energy is increased or scale is decreased, these coefficients do not provide adequate approximation. Using Bloch decomposition, it is first realized that the above coefficients correspond to the lowest energy and the largest scale. This naturally paves the way to introduce other sets of macro coefficients corresponding to higher energies and lower scales which yield better approximation. The next task is to compare their properties with those of the homogenized coefficients. This article reviews these developments along with some new results yet to be published.
Prevedello, Andrea; Bazzan, Irene; Dalle Carbonare, Nicola; Giuliani, Angela; Bhardwaj, Sunil; Africh, Cristina; Cepek, Cinzia; Argazzi, Roberto; Bonchio, Marcella; Caramori, Stefano; Robert, Marc; Sartorel, Andrea
2016-04-20
Since the first report in 2012, molecular copper complexes have been proposed as efficient electrocatalysts for water oxidation reactions, carried out in alkaline/neutral aqueous media. However, in some cases the copper species have been recognized as precursors of an active copper oxide layer, electrodeposited onto the working electrode. Therefore, the question whether copper catalysis is molecular or not is particularly relevant in the field of water oxidation. In this study, we investigate the electrochemical activity of copper(II) complexes with two tetraaza macrocyclic ligands, distinguishing heterogeneous or homogeneous processes depending on the reaction media. In an alkaline aqueous solution, and upon application of an anodic bias to working electrodes, an active copper oxide layer is observed to electrodeposit at the electrode surface. Conversely, water oxidation in neutral aqueous buffers is not associated to formation of the copper oxide layer, and could be exploited to evaluate and optimize a molecular, homogeneous catalysis.
On the Cancellation Rule in the Homogenization
2008-01-01
We consider the possible ways of the homogenization of non-graded non-commutative algebra and show that it should be combined with the cancellation rule to get the mathematically adequate correspondence between graded and non-graded algebras.
Non-homogeneous fractal hierarchical weighted networks.
Dong, Yujuan; Dai, Meifeng; Ye, Dandan
2015-01-01
A model of fractal hierarchical structures that share the property of non-homogeneous weighted networks is introduced. These networks can be completely and analytically characterized in terms of the involved parameters, i.e., the size of the original graph Nk and the non-homogeneous weight scaling factors r1, r2, · · · rM. We also study the average weighted shortest path (AWSP), the average degree and the average node strength, taking place on the non-homogeneous hierarchical weighted networks. Moreover the AWSP is scrupulously calculated. We show that the AWSP depends on the number of copies and the sum of all non-homogeneous weight scaling factors in the infinite network order limit.
Magnifying absolute instruments for optically homogeneous regions
Tyc, Tomas
2011-01-01
We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.
Homogeneous cosmological models and new inflation
Turner, Michael S.; Widrow, Lawrence M.
1986-01-01
The promise of the inflationary-universe scenario is to free the present state of the universe from extreme dependence upon initial data. Paradoxically, inflation is usually analyzed in the context of the homogeneous and isotropic Robertson-Walker cosmological models. It is shown that all but a small subset of the homogeneous models undergo inflation. Any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness and horizon problems, the universe today would still be very isotropic.
Commensurability effects in holographic homogeneous lattices
Andrade, Tomas; Krikun, Alexander
2016-01-01
An interesting application of the gauge/gravity duality to condensed matter physics is the description of a lattice via breaking translational invariance on the gravity side. By making use of global symmetries, it is possible to do so without scarifying homogeneity of the pertinent bulk solutions, which we thus term as "homogeneous holographic lattices." Due to their technical simplicity, these configurations have received a great deal of attention in the last few years and have been shown to...
Homogeneous Dielectric Equivalents of Composite Material Shields
Directory of Open Access Journals (Sweden)
P. Tobola
2009-04-01
Full Text Available The paper deals with the methodology of replacing complicated parts of an airplane skin by simple homogeneous equivalents, which can exhibit similar shielding efficiency. On one hand, the airplane built from the virtual homogeneous equivalents can be analyzed with significantly reduced CPU-time demands and memory requirements. On the other hand, the equivalent model can estimate the internal fields satisfactory enough to evaluate the electromagnetic immunity of the airplane.
Significance tests and sample homogeneity loophole
Kupczynski, Marian
2015-01-01
In their recent comment, published in Nature, Jeffrey T.Leek and Roger D.Peng discuss how P-values are widely abused in null hypothesis significance testing . We agree completely with them and in this short comment we discuss the importance of sample homogeneity tests. No matter with how much scrutiny data are gathered if homogeneity tests are not performed the significance tests suffer from sample homogeneity loophole and the results may not be trusted. For example sample homogeneity loophole was not closed in the experiment testing local realism in which a significant violation of Eberhard inequality was found. We are not surprised that Bell type inequalities are violated since if the contextual character of quantum observables is properly taken into account these inequalities cannot be proven. However in order to trust the significance of the violation sample homogeneity loophole must be closed. Therefore we repeat after Jeffrey T.Leek and Roger D.Peng that sample homogeneity loophole is probably just the ...
On the homogeneous and heterogeneous nucleation of some organic compounds
Energy Technology Data Exchange (ETDEWEB)
Hienola, A.
2008-07-01
The conversion of a metastable phase into a thermodynamically stable phase takes place via the formation of clusters. Clusters of different sizes are formed spontaneously within the metastable mother phase, but only those larger than a certain size, called the critical size, will end up growing into a new phase. There are two types of nucleation: homogeneous, where the clusters appear in a uniform phase, and heterogeneous, when pre-existing surfaces are available and clusters form on them. The nucleation of aerosol particles from gas-phase molecules is connected not only with inorganic compounds, but also with nonvolatile organic substances found in atmosphere. The question is which ones of the myriad of organic species have the right properties and are able to participate in nucleation phenomena. This thesis discusses both homogeneous and heterogeneous nucleation, having as theoretical tool the classical nucleation theory (CNT) based on thermodynamics. Different classes of organics are investigated. The members of the first class are four dicarboxylic acids (succinic, glutaric, malonic and adipic). They can be found in both the gas and particulate phases, and represent good candidates for the aerosol formation due to their low vapor pressure and solubility. Their influence on the nucleation process has not been largely investigated in the literature and it is not fully established. The accuracy of the CNT predictions for binary water-dicarboxylic acid systems depends significantly on the good knowledge of the thermophysical properties of the organics and their aqueous solutions. A large part of the thesis is dedicated to this issue. We have shown that homogeneous and heterogeneous nucleation of succinic, glutaric and malonic acids in combination with water is unlikely to happen in atmospheric conditions. However, it seems that adipic acid could participate in the nucleation process in conditions occurring in the upper troposphere. The second class of organics is
Ahmad, R.
2016-07-01
This article reports an unbiased analysis for the water based rod shaped alumina nanoparticles by considering both the homogeneous and non-homogeneous nanofluid models over the coupled nanofluid-surface interface. The mechanics of the surface are found for both the homogeneous and non-homogeneous models, which were ignored in previous studies. The viscosity and thermal conductivity data are implemented from the international nanofluid property benchmark exercise. All the simulations are being done by using the experimentally verified results. By considering the homogeneous and non-homogeneous models, the precise movement of the alumina nanoparticles over the surface has been observed by solving the corresponding system of differential equations. For the non-homogeneous model, a uniform temperature and nanofluid volume fraction are assumed at the surface, and the flux of the alumina nanoparticle is taken as zero. The assumption of zero nanoparticle flux at the surface makes the non-homogeneous model physically more realistic. The differences of all profiles for both the homogeneous and nonhomogeneous models are insignificant, and this is due to small deviations in the values of the Brownian motion and thermophoresis parameters.
Commensurability effects in holographic homogeneous lattices
Andrade, Tomas
2015-01-01
An interesting application of the gauge/gravity duality to condensed matter physics is the description of a lattice via breaking translational invariance on the gravity side. By making use of global symmetries, it is possible to do so without scarifying homogeneity of the pertinent bulk solutions, which we thus term as "homogeneous holographic lattices." Due to their technical simplicity, these configurations have received a great deal of attention in the last few years and have been shown to correctly describe momentum relaxation and hence (finite) DC conductivities. However, it is not clear whether they are able to capture other lattice effects which are of interest in condensed matter. In this paper we investigate this question focusing our attention on the phenomenon of commensurability, which arises when the lattice scale is tuned to be equal to (an integer multiple of) another momentum scale in the system. We do so by studying the formation of spatially modulated phases in various models of homogeneous ...
Homogenity of Die Casting and Returning Material
Directory of Open Access Journals (Sweden)
J. Malik
2012-04-01
Full Text Available Homogeneity of die castings is influenced by wide range of technological parameters as piston velocity in filling chamber of die casting machine, filling time of mould cavity, temperature of cast alloy, temperature of the mould, temperature of filling chamber, surface pressure on alloy during mould filling, final pressure and others. Based on stated parameters it is clear, that main parameters of die casting are filling time of die mould cavity and velocity of the melt in the ingates. Filling time must ensure the complete filling of the mould cavity before solidification process can negatively influence it. Among technological parameters also belong the returning material, which ratio in charge must be constrained according to requirement on final homogeneity of die castings. With the ratio of returning material influenced are the mechanical properties of castings, inner homogeneity and chemical composition.
Homogenized thermal conduction model for particulate foods
Energy Technology Data Exchange (ETDEWEB)
Chinesta, Francisco [Laboratoire de mecanique des systemes et des procedes, Ecole nationale superieure d' arts et metiers, 151 boulevard de l' Hopital, 75013, Paris (France); Torres, Rafael [Departamento de Ingenieria Mecanica, Universidad Politecnica de Valencia, Camino de Vera s/n. 46071, Valencia (Spain); Ramon, Antonio [AIMPLAS, Gustave Eiffel 4, 46980 Paterna, Valencia (Spain); Rodrigo, Mari Carmen; Rodrigo, Miguel [Instituto de Agroquimica y Tecnologia de Alimentos, Consejo Superior de Investigaciones Cientificas, Apartado de correos 73, 46100, Burjasot (Spain)
2002-12-01
This paper deals with the definition of an equivalent thermal conductivity for particulate foods. An homogenized thermal model is used to asses the effect of particulate spatial distribution and differences in thermal conductivities. We prove that the spatial average of the conductivity can be used in an homogenized heat transfer model if the conductivity differences among the food components are not very large, usually the highest conductivity ratio between the foods components is lower than 5. In the general case we propose to use a standard spatial homogenization procedure. Although the heterogeneity give rise to an anisotropic heat transfer behaviour, this effect is negligible when the food particles are randomly distributed. When we use pre-mixed particulate foods a statistical average can be defined from a small number of possible particle arrangements. (authors)
Flows and chemical reactions in homogeneous mixtures
Prud'homme, Roger
2013-01-01
Flows with chemical reactions can occur in various fields such as combustion, process engineering, aeronautics, the atmospheric environment and aquatics. The examples of application chosen in this book mainly concern homogeneous reactive mixtures that can occur in propellers within the fields of process engineering and combustion: - propagation of sound and monodimensional flows in nozzles, which may include disequilibria of the internal modes of the energy of molecules; - ideal chemical reactors, stabilization of their steady operation points in the homogeneous case of a perfect mixture and c
Study on Homogeneous Particleboard of Wheat Straw
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
In the paper homogeneous particleboard of wheat straw is researched. The result shows the technology of homogeneous particleboard from cost and quality. The moisture content of straw particle is 2.0%~2.5 %. The temperature of hot-pressing is 150℃. The time of hot-pressing is 48 sec/mm ( panel thickness). The ratio between MDI and UF is 0.40. The glue content for surface layer of wheat straw particle is 10% (MDI 2.86%, UF 7.14%). The glue content for core layer of wheat straw particle is 8% (MDI 2.29%, U...
Homogenization of High-Contrast Brinkman Flows
Brown, Donald L.
2015-04-16
Modeling porous flow in complex media is a challenging problem. Not only is the problem inherently multiscale but, due to high contrast in permeability values, flow velocities may differ greatly throughout the medium. To avoid complicated interface conditions, the Brinkman model is often used for such flows [O. Iliev, R. Lazarov, and J. Willems, Multiscale Model. Simul., 9 (2011), pp. 1350--1372]. Instead of permeability variations and contrast being contained in the geometric media structure, this information is contained in a highly varying and high-contrast coefficient. In this work, we present two main contributions. First, we develop a novel homogenization procedure for the high-contrast Brinkman equations by constructing correctors and carefully estimating the residuals. Understanding the relationship between scales and contrast values is critical to obtaining useful estimates. Therefore, standard convergence-based homogenization techniques [G. A. Chechkin, A. L. Piatniski, and A. S. Shamev, Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point is that the Brinkman equations, in certain scaling regimes, are invariant under homogenization. Unlike in the case of Stokes-to-Darcy homogenization [D. Brown, P. Popov, and Y. Efendiev, GEM Int. J. Geomath., 2 (2011), pp. 281--305, E. Marusic-Paloka and A. Mikelic, Boll. Un. Mat. Ital. A (7), 10 (1996), pp. 661--671], the results presented here under certain velocity regimes yield a Brinkman-to-Brinkman upscaling that allows using a single software platform to compute on both microscales and macroscales. In this paper, we discuss the homogenized Brinkman equations. We derive auxiliary cell problems to build correctors and calculate effective coefficients for certain velocity regimes. Due to the boundary effects, we construct
Small codimension subvarieties in homogeneous spaces
Perrin, Nicolas
2010-01-01
We prove Bertini type theorems for the inverse image, under a proper morphism, of any Schubert variety in an homogeneous space. Using generalisations of Deligne's trick, we deduce connectedness results for the inverse image of the diagonal in $X^2$ where $X$ is any isotropic grassmannian. We also deduce simple connectedness properties for subvarieties of $X$. Finally we prove transplanting theorems {\\`a} la Barth-Larsen for the Picard group of any isotropic grassmannian of lines and for the Neron-Severi group of some adjoint and coadjoint homogeneous spaces.
An eigenelement method and two homogenization conditions
Institute of Scientific and Technical Information of China (English)
Yufeng Xing; Xingming Wang
2009-01-01
Under inspiration from the structure-preserving property of symplectic difference schemes for Hamiltonian systems, two homogenization conditions for a representa-tive unit cell of the periodical composites are proposed, one condition is the equivalence of strain energy, and the other is the deformation similarity. Based on these two homoge-nization conditions, an eigenelement method is presented, which is characteristic of structure-preserving property. It follows from the frequency comparisons that the eigenel-ement method is more accurate than the stiffness average method and the compliance average method.
New applications of the homogeneous balance principle
Institute of Scientific and Technical Information of China (English)
张金良; 王跃明; 王明亮; 方宗德
2003-01-01
The homogeneous balance principle has been widely applied to the exploration of nonlinear transformation, exact solutions (especially solitary wave solution), dromion and similarity reduction to the nonlinear partial differential equations in mathematical physics. In this paper, we use the homogeneous balance principle to derive Backlund transformations for nonlinear partial differential equations that have more nonlinear terms and more highest-order partial derivative terms. With the aid of the Backlund transformations derived here, we could obtain exact solutions to the nonlinear partial differential equations. The Davey-Stewartson equation and the Nizhnik-Novikov-Veselov equation are considered as the examples.
Treatment of Aqueous Solutions
Van Spronsen, J.; Witkamp, G.J.
2013-01-01
The invention is directed to a process for the recovery or removal of one or more crystallizable compounds from an aqueous solution containing, apart from the said crystallizable compounds, one or more organic or inorganic scale- forming or scale-inducing materials having a lower solubility in water
Frenod, Emmanuel
2013-01-01
In this note, a classification of Homogenization-Based Numerical Methods and (in particular) of Numerical Methods that are based on the Two-Scale Convergence is done. In this classification stand: Direct Homogenization-Based Numerical Methods; H-Measure-Based Numerical Methods; Two-Scale Numerical Methods and TSAPS: Two-Scale Asymptotic Preserving Schemes.
Hyperelastic bodies under homogeneous Cauchy stress induced by non-homogeneous finite deformations
Mihai, L Angela
2016-01-01
We discuss whether homogeneous Cauchy stress implies homogeneous strain in isotropic nonlinear elasticity. While for linear elasticity the positive answer is clear, we exhibit, through detailed calculations, an example with inhomogeneous continuous deformation but constant Cauchy stress. The example is derived from a non rank-one convex elastic energy. Connections to conforming and non-conforming finite element implementations are drawn.
On the Cancellation Rule in the Homogenization
Directory of Open Access Journals (Sweden)
Victor Ufnarovski
2008-04-01
Full Text Available We consider the possible ways of the homogenization of non-graded non-commutative algebra and show that it should be combined with the cancellation rule to get the mathematically adequate correspondence between graded and non-graded algebras.
Remarks on homogeneous manifolds satisfying Levi conditions
Huckleberry, Alan
2010-01-01
Homogeneous complex manifolds satisfying various types of Levi conditions are considered. Classical results which were of particular interest to Andreotti are recalled. Convexity and concavity properties of flag domains are discussed in some detail. A precise classification of pseudoconvex flag domains is given. It is shown that flag domains which are in a certain sense generic are pseudoconcave.
Local real analysis in locally homogeneous spaces
Bramanti, Marco
2011-01-01
We introduce the concept of locally homogeneous space, and prove in this context L^p and Holder estimates for singular and fractional integrals, as well as L^p estimates on the commutator of a singular or fractional integral with a BMO or VMO function. These results are motivated by local a-priori estimates for subelliptic equations.
Homogeneity in Social Groups of Iraqis
Gresham, J.; Saleh, F.; Majid, S.
2006-01-01
With appreciation to the Royal Institute for Inter-Faith Studies for initiating the Second World Congress for Middle Eastern Studies, this paper summarizes findings on homogeneity in community-level social groups derived from inter-ethnic research conducted during 2005 among Iraqi Arabs and Kurds li
Locally homogeneous structures on Hopf surfaces
McKay, Benjamin
2009-01-01
We study holomorphic locally homogeneous geometric structures modelled on line bundles over the projective line. We classify these structures on primary Hopf surfaces. We write out the developing map and holonomy morphism of each of these structures explicitly on each primary Hopf surface.
The homogeneous marginal utility of income assumption
Demuynck, T.
2015-01-01
We develop a test to verify if every agent from a population of heterogeneous consumers has the same marginal utility of income function. This homogeneous marginal utility of income assumption is often (implicitly) used in applied demand studies because it has nice aggregation properties and facilit
On chiral differential operators over homogeneous spaces
Directory of Open Access Journals (Sweden)
Vassily Gorbounov
2001-01-01
Full Text Available We give a classification and construction of chiral algebras of differential operators over semisimple algebraic groups G and over homogeneous spaces G/N and G/P where N is a nilpotent and P a parabolic subgroup.
String pair production in non homogeneous backgrounds
Bolognesi, Stefano; Tallarita, Gianni
2016-01-01
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is les...
Inverse acoustic problem of N homogeneous scatterers
DEFF Research Database (Denmark)
Berntsen, Svend
2002-01-01
The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...
Homogeneous Catalysis by Transition Metal Compounds.
Mawby, Roger
1988-01-01
Examines four processes involving homogeneous catalysis which highlight the contrast between the simplicity of the overall reaction and the complexity of the catalytic cycle. Describes how catalysts provide circuitous routes in which all energy barriers are relatively low rather than lowering the activation energy for a single step reaction.…
Delay differential equations with homogeneous integral conditions
Directory of Open Access Journals (Sweden)
Abdur Raheem
2013-03-01
Full Text Available In this article we prove the existence and uniqueness of a strong solution of a delay differential equation with homogenous integral conditions using the method of semidiscretization in time. As an application, we include an example that illustrates the main result.
Homogeneous protein analysis by magnetic core-shell nanorod probes
Schrittwieser, Stefan
2016-03-29
Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.
Anthracene and pyrene photolysis kinetics in aqueous, organic, and mixed aqueous-organic phases
Grossman, Jarod N.; Stern, Adam P.; Kirich, Makena L.; Kahan, Tara F.
2016-03-01
Condensed phases in the atmosphere, such as cloud droplets and aerosols, often contain both water and organic matter (OM). Reactivity can differ significantly between aqueous and organic phases. We have measured photolysis kinetics of the polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene in several organic solvents and in water, as well as in miscible and phase-separated aqueous-organic mixtures at atmospherically-relevant wavelengths. Photolysis rate constants generally increased with increasing solvent polarity; photolysis of both PAHs was more than ten times faster in water than in octanol. Local polarity had a much greater effect on PAH photolysis kinetics than changes in PAH absorptivity or singlet oxygen concentrations. Photolysis kinetics in homogeneous aqueous-organic mixtures varied monotonically with2 OM volume fraction. Kinetics in immiscible (phase-separated) solutions were more complex, with different dependences on OM content observed in stagnant and turbulent solutions. Our results suggest that OM could greatly affect the photochemical lifetimes of PAHs in atmospheric condensed phases such as aerosols, even if the OM does not itself absorb photons.
Kinematical uniqueness of homogeneous isotropic LQC
Engle, Jonathan; Hanusch, Maximilian
2017-01-01
In a paper by Ashtekar and Campiglia, invariance under volume preserving residual diffeomorphisms has been used to single out the standard representation of the reduced holonomy-flux algebra in homogeneous loop quantum cosmology (LQC). In this paper, we use invariance under all residual diffeomorphisms to single out the standard kinematical Hilbert space of homogeneous isotropic LQC for both the standard configuration space {{{R}}\\text{Bohr}} , as well as for the Fleischhack one {R}\\sqcup {{{R}}\\text{Bohr}} . We first determine the scale invariant Radon measures on these spaces, and then show that the Haar measure on {{{R}}\\text{Bohr}} is the only such measure for which the momentum operator is hermitian w.r.t. the corresponding inner product. In particular, the measure is forced to be identically zero on {R} in the Fleischhack case, so that for both approaches, the standard kinematical LQC-Hilbert space is singled out.
CUDA Simulation of Homogeneous, Incompressible Turbulence
Morin, Lee; Shebalin, John V.; Shum, Victor; Fu, Terry
2011-01-01
We discuss very fast Compute Unified Device Architecture (CUDA) simulations of ideal homogeneous incompressible turbulence based on Fourier models. These models have associated statistical theories that predict that Fourier coefficients of fluid velocity and magnetic fields (if present) are zero-mean random variables. Prior numerical simulations have shown that certain coefficients have a non-zero mean value that can be very large compared to the associated standard deviation. We review the theoretical basis of this "broken ergodicity" as applied to 2-D and 3-D fluid and magnetohydrodynamic simulations of homogeneous turbulence. Our new simulations examine the phenomenon of broken ergodicity through very long time and large grid size runs performed on a state-of-the-art CUDA platform. Results comparing various CUDA hardware configurations and grid sizes are discussed. NS and MHD results are compared.
Coupled quasi-homogeneous orthotropic laminates
York, C. B.
2011-09-01
Laminate stacking sequence configurations with quasi-homogeneous properties are derived, whereby the inplane and out-of-plane stiffness properties are concomitant. The stacking sequence configurations contain equal-thickness layers and identical orthotropic properties, differing only by their orientations, which are represented by standard angle- and cross-ply combinations. These simplifying assumptions are in fact representative of the common design practice, but help one to identify and isolate a range of highly complex physical coupling responses, which continue to be referred to collectively in the literature as bending-extension coupling. Dimensionless parameters are developed from which the elements of the extensional, coupling, and bending stiffness matrices are readily calculated for any fibre/resin properties. Feasible domains of lamination parameters are also illustrated for each coupling response to complement abridged listings of stacking sequences. Finally, hygrothermally curvature-stable configurations with quasi-homogeneous properties are identified, thus simplifying the manufacture of laminate configurations possessing tailored mechanical coupling responses.
Some dimensional results for homogeneous Moran sets
Institute of Scientific and Technical Information of China (English)
丰德军; 文志英; 吴军
1997-01-01
Let M({nk}k≥1,{ck}k≥1) be the collection of homogeneous Moran sets determined by {nk}k≥1and {ck}k≥1, where {nk}k≥1 is a sequence of positive integers and {ck}k≥1 a sequence of positive numbers. Then the maximal and minimal values of Hausdorff dimensions for elements in M are determined. The result is proved that for any value s between the maximal and minimal values, there exists an element in M{nk}k≥1, {ck}k≥1) such that its Hausdorff dimension is equal to s. The same results hold for packing dimension. In the meantime, some other properties of homogeneous Moran sets are discussed.
Broken Ergodicity in Ideal, Homogeneous, Incompressible Turbulence
Morin, Lee; Shebalin, John; Fu, Terry; Nguyen, Phu; Shum, Victor
2010-01-01
We discuss the statistical mechanics of numerical models of ideal homogeneous, incompressible turbulence and their relevance for dissipative fluids and magnetofluids. These numerical models are based on Fourier series and the relevant statistical theory predicts that Fourier coefficients of fluid velocity and magnetic fields (if present) are zero-mean random variables. However, numerical simulations clearly show that certain coefficients have a non-zero mean value that can be very large compared to the associated standard deviation. We explain this phenomena in terms of broken ergodicity', which is defined to occur when dynamical behavior does not match ensemble predictions on very long time-scales. We review the theoretical basis of broken ergodicity, apply it to 2-D and 3-D fluid and magnetohydrodynamic simulations of homogeneous turbulence, and show new results from simulations using GPU (graphical processing unit) computers.
Searching for the scale of homogeneity
Martínez, V J; Moyeed, R A; Graham, M J; Martinez, Vicent J.; Pons-Borderia, Maria-Jesus; Moyeed, Rana A.; Graham, Matthew J.
1998-01-01
We introduce a statistical quantity, known as the $K$ function, related to the integral of the two--point correlation function. It gives us straightforward information about the scale where clustering dominates and the scale at which homogeneity is reached. We evaluate the correlation dimension, $D_2$, as the local slope of the log--log plot of the $K$ function. We apply this statistic to several stochastic point fields, to three numerical simulations describing the distribution of clusters and finally to real galaxy redshift surveys. Four different galaxy catalogues have been analysed using this technique: the Center for Astrophysics I, the Perseus--Pisces redshift surveys (these two lying in our local neighbourhood), the Stromlo--APM and the 1.2 Jy {\\it IRAS} redshift surveys (these two encompassing a larger volume). In all cases, this cumulant quantity shows the fingerprint of the transition to homogeneity. The reliability of the estimates is clearly demonstrated by the results from controllable point sets...
Kinematical uniqueness of homogeneous isotropic LQC
Engle, Jonathan
2016-01-01
In a paper by Ashtekar and Campiglia, invariance under volume preserving residual diffeomorphisms has been used to single out the standard representation of the reduced holonomy-flux algebra in homogeneous loop quantum cosmology (LQC). In this paper, we use invariance under all residual diffeomorphisms to single out the standard kinematical Hilbert space of homogeneous isotropic LQC for both the standard configuration space $\\mathbb{R}_{\\mathrm{Bohr}}$, as well as for the Fleischhack one $\\mathbb{R} \\sqcup \\mathbb{R}_{\\mathrm{Bohr}}$. We first determine the scale invariant Radon measures on these spaces, and then show that the Haar measure on $\\mathbb{R}_{\\mathrm{Bohr}}$ is the only such measure for which the momentum operator is hermitian w.r.t. the corresponding inner product. In particular, the measure is forced to be identically zero on $\\mathbb{R}$ in the Fleischhack case, so that for both approaches, the standard kinematical LQC-Hilbert space is singled out.
Higher dimensional homogeneous cosmology in Lyra geometry
Indian Academy of Sciences (India)
F Rahaman; S Das; N Begum; M Hossain
2003-07-01
Assuming a homogeneous perfect ﬂuid with ρ = ρ() and = (), we have obtained exact solutions for cosmological models in higher-dimension based on Lyra geometry. Depending on the form of metric chosen, the model is similar to FRW type. The explicit solutions of the scale factor are found via the assumption of an equation of state = ρ, where is a constant. Some astrophysical parameters are also calculated.
Metric Diophantine approximation on homogeneous varieties
Ghosh, Anish; Nevo, Amos
2012-01-01
We develop the metric theory of Diophantine approximation on homogeneous varieties of semisimple algebraic groups and prove results analogous to the classical Khinchin and Jarnik theorems. In full generality our results establish simultaneous Diophantine approximation with respect to several completions, and Diophantine approximation over general number fields using S-algebraic integers. In several important examples, the metric results we obtain are optimal. The proof uses quantitative equidistribution properties of suitable averaging operators, which are derived from spectral bounds in automorphic representations.
Recent advances in homogeneous nickel catalysis.
Tasker, Sarah Z; Standley, Eric A; Jamison, Timothy F
2014-05-15
Tremendous advances have been made in nickel catalysis over the past decade. Several key properties of nickel, such as facile oxidative addition and ready access to multiple oxidation states, have allowed the development of a broad range of innovative reactions. In recent years, these properties have been increasingly understood and used to perform transformations long considered exceptionally challenging. Here we discuss some of the most recent and significant developments in homogeneous nickel catalysis, with an emphasis on both synthetic outcome and mechanism.
HSTEP -- Homogeneous Studies of Transiting Extrasolar Planets
Southworth, John
2014-01-01
I give a summary of the HSTEP project: an effort to calculate the physical properties of the known transiting extrasolar planets using a homogeneous approach. I discuss the motivation for the project, list the 83 planets which have already been studied, run through some important aspects of the methodology, and finish with a synopsis of the results. The results have been compiled into an online catalogue: TEPCat.
Homogeneous Biosensing Based on Magnetic Particle Labels
Schrittwieser, Stefan
2016-06-06
The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.
Equilibrium states of homogeneous sheared compressible turbulence
Riahi, M.; Lili, T.
2011-06-01
Equilibrium states of homogeneous compressible turbulence subjected to rapid shear is studied using rapid distortion theory (RDT). The purpose of this study is to determine the numerical solutions of unsteady linearized equations governing double correlations spectra evolution. In this work, RDT code developed by authors solves these equations for compressible homogeneous shear flows. Numerical integration of these equations is carried out using a second-order simple and accurate scheme. The two Mach numbers relevant to homogeneous shear flow are the turbulent Mach number Mt, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number Mg which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Validation of this code is performed by comparing RDT results with direct numerical simulation (DNS) of [A. Simone, G.N. Coleman, and C. Cambon, Fluid Mech. 330, 307 (1997)] and [S. Sarkar, J. Fluid Mech. 282, 163 (1995)] for various values of initial gradient Mach number Mg0. It was found that RDT is valid for small values of the non-dimensional times St (St 10) in particular for large values of Mg0. This essential feature justifies the resort to RDT in order to determine equilibrium states in the compressible regime.
Equilibrium states of homogeneous sheared compressible turbulence
Directory of Open Access Journals (Sweden)
M. Riahi
2011-06-01
Full Text Available Equilibrium states of homogeneous compressible turbulence subjected to rapid shear is studied using rapid distortion theory (RDT. The purpose of this study is to determine the numerical solutions of unsteady linearized equations governing double correlations spectra evolution. In this work, RDT code developed by authors solves these equations for compressible homogeneous shear flows. Numerical integration of these equations is carried out using a second-order simple and accurate scheme. The two Mach numbers relevant to homogeneous shear flow are the turbulent Mach number Mt, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number Mg which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Validation of this code is performed by comparing RDT results with direct numerical simulation (DNS of [A. Simone, G.N. Coleman, and C. Cambon, Fluid Mech. 330, 307 (1997] and [S. Sarkar, J. Fluid Mech. 282, 163 (1995] for various values of initial gradient Mach number Mg0. It was found that RDT is valid for small values of the non-dimensional times St (St 10 in particular for large values of Mg0. This essential feature justifies the resort to RDT in order to determine equilibrium states in the compressible regime.
Tits Satake projections of homogeneous special geometries
Fré, Pietro; Gargiulo, Floriana; Rosseel, Jan; Rulik, Ksenya; Trigiante, Mario; Van Proeyen, Antoine
2007-01-01
We organize the homogeneous special geometries, describing as well the couplings of D = 6, 5, 4 and 3 supergravities with eight supercharges, in a small number of universality classes. This relates manifolds on which similar types of dynamical solutions can exist. The mathematical ingredient is the Tits Satake projection of real simple Lie algebras, which we extend to all solvable Lie algebras occurring in these homogeneous special geometries. Apart from some exotic cases all the other, 'very special', homogeneous manifolds can be grouped into seven universality classes. The organization of these classes, which capture the essential features of their basic dynamics, commutes with the r- and c-map. Different members are distinguished by different choices of the paint group, a notion discovered in the context of cosmic billiard dynamics of non-maximally supersymmetric supergravities. We comment on the usefulness of this organization in universality class both in relation with cosmic billiard dynamics and with configurations of branes and orbifolds defining special geometry backgrounds.
Towards a methanol economy based on homogeneous catalysis: methanol to H2 and CO2 to methanol.
Alberico, E; Nielsen, M
2015-04-21
The possibility to implement both the exhaustive dehydrogenation of aqueous methanol to hydrogen and CO2 and the reverse reaction, the hydrogenation of CO2 to methanol and water, may pave the way to a methanol based economy as part of a promising renewable energy system. Recently, homogeneous catalytic systems have been reported which are able to promote either one or the other of the two reactions under mild conditions. Here, we review and discuss these developments.
Bacterial Acclimation Inside an Aqueous Battery.
Directory of Open Access Journals (Sweden)
Dexian Dong
Full Text Available Specific environmental stresses may lead to induced genomic instability in bacteria, generating beneficial mutants and potentially accelerating the breeding of industrial microorganisms. The environmental stresses inside the aqueous battery may be derived from such conditions as ion shuttle, pH gradient, free radical reaction and electric field. In most industrial and medical applications, electric fields and direct currents are used to kill bacteria and yeast. However, the present study focused on increasing bacterial survival inside an operating battery. Using a bacterial acclimation strategy, both Escherichia coli and Bacillus subtilis were acclimated for 10 battery operation cycles and survived in the battery for over 3 days. The acclimated bacteria changed in cell shape, growth rate and colony color. Further analysis indicated that electrolyte concentration could be one of the major factors determining bacterial survival inside an aqueous battery. The acclimation process significantly improved the viability of both bacteria E. coli and B. subtilis. The viability of acclimated strains was not affected under battery cycle conditions of 0.18-0.80 mA cm(-2 and 1.4-2.1 V. Bacterial addition within 1.0×10(10 cells mL(-1 did not significantly affect battery performance. Because the environmental stress inside the aqueous battery is specific, the use of this battery acclimation strategy may be of great potential for the breeding of industrial microorganisms.
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Homogenization and asymptotics for small transaction costs
Soner, H Mete
2012-01-01
We consider the classical Merton problem of lifetime consumption-portfolio optimization problem with small proportional transaction costs. The first order term in the asymptotic expansion is explicitly calculated through a singular ergodic control problem which can be solved in closed form in the one-dimensional case. Unlike the existing literature, we consider a general utility function and general dynamics for the underlying assets. Our arguments are based on ideas from the homogenization theory and use the convergence tools from the theory of viscosity solutions. The multidimensional case is studied in our accompanying paper using the same approach.
Homogeneity Analysis in Xlisp-Stat
Directory of Open Access Journals (Sweden)
Jason Bond
1996-08-01
Full Text Available In this paper a highly interactive, user-friendly Lisp program is introduced to perform homogeneity analysis. A brief introduction to the technique is presented as well as its modification in the presence of missing data. The algorithm and its Lisp implemenation is discussed, and an overview of the object oriented code that produces the interactive dialogs and plots is provided. In order to demonstrate the main features of the program, a small and a large dataset are analyzed. Finally, some comparisons are made with other currently available programs.
Relativistic effects in homogeneous gold catalysis.
Gorin, David J; Toste, F Dean
2007-03-22
Transition-metal catalysts containing gold present new opportunities for chemical synthesis, and it is therefore not surprising that these complexes are beginning to capture the attention of the chemical community. Cationic phosphine-gold(i) complexes are especially versatile and selective catalysts for a growing number of synthetic transformations. The reactivity of these species can be understood in the context of theoretical studies on gold; relativistic effects are especially helpful in rationalizing the reaction manifolds available to gold catalysts. This Review draws on experimental and computational data to present our current understanding of homogeneous gold catalysis, focusing on previously unexplored reactivity and its application to the development of new methodology.
Homogeneous asymmetric catalysis in fragrance chemistry.
Ciappa, Alessandra; Bovo, Sara; Bertoldini, Matteo; Scrivanti, Alberto; Matteoli, Ugo
2008-06-01
Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide, Phenoxanol, Citralis, and Citralis Nitrile, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol, Citralis, and Citralis Nitrile were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.
REITERATED HOMOGENIZATION OF DEGENERATE NONLINEAR ELLIPTIC EQUATIONS
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The authors study homogenization of some nonlinear partial differential equations of the form -div (a (hx,h2x,Duh)) = f,where a is periodic in the first two arguments and monotone in the third.In particular the case where a satisfies degenerated structure conditions is studied.It is proved that uh converges weakly in Wo1.1 (Ω) to the unique solution of a limit problem as h →∞.Moreover,explicit expressions for the limit problem are obtained.
Mechanisms in homogeneous and heterogeneous epoxidation catalysis
Oyama, S Ted
2011-01-01
The catalytic epoxidation of olefins plays an important role in the industrial production of several commodity compounds, as well as in the synthesis of many intermediates, fine chemicals, and pharmaceuticals. The scale of production ranges from millions of tons per year to a few grams per year. The diversity of catalysts is large and encompasses all the known categories of catalyst type: homogeneous, heterogeneous, and biological. This book summarizes the current status in these fields concentrating on rates, kinetics, and reaction mechanisms, but also covers broad topics including modeli
The Statistical Mechanics of Ideal Homogeneous Turbulence
Shebalin, John V.
2002-01-01
Plasmas, such as those found in the space environment or in plasma confinement devices, are often modeled as electrically conducting fluids. When fluids and plasmas are energetically stirred, regions of highly nonlinear, chaotic behavior known as turbulence arise. Understanding the fundamental nature of turbulence is a long-standing theoretical challenge. The present work describes a statistical theory concerning a certain class of nonlinear, finite dimensional, dynamical models of turbulence. These models arise when the partial differential equations describing incompressible, ideal (i.e., nondissipative) homogeneous fluid and magnetofluid (i.e., plasma) turbulence are Fourier transformed into a very large set of ordinary differential equations. These equations define a divergenceless flow in a high-dimensional phase space, which allows for the existence of a Liouville theorem, guaranteeing a distribution function based on constants of the motion (integral invariants). The novelty of these particular dynamical systems is that there are integral invariants other than the energy, and that some of these invariants behave like pseudoscalars under two of the discrete symmetry transformations of physics, parity, and charge conjugation. In this work the 'rugged invariants' of ideal homogeneous turbulence are shown to be the only significant scalar and pseudoscalar invariants. The discovery that pseudoscalar invariants cause symmetries of the original equations to be dynamically broken and induce a nonergodic structure on the associated phase space is the primary result presented here. Applicability of this result to dissipative turbulence is also discussed.
Modified Homogeneous Data Set of Coronal Intensities
Dorotovič, I.; Minarovjech, M.; Lorenc, M.; Rybanský, M.
2014-07-01
The Astronomical Institute of the Slovak Academy of Sciences has published the intensities, recalibrated with respect to a common intensity scale, of the 530.3 nm (Fe xiv) green coronal line observed at ground-based stations up to the year 2008. The name of this publication is Homogeneous Data Set (HDS). We have developed a method that allows one to successfully substitute the ground-based observations by satellite observations and, thus, continue with the publication of the HDS. For this purpose, the observations of the Extreme-ultraviolet Imaging Telescope (EIT), onboard the Solar and Heliospheric Observatory (SOHO) satellite, were exploited. Among other data the EIT instrument provides almost daily 28.4 nm (Fe xv) emission-line snapshots of the corona. The Fe xiv and Fe xv data (4051 observation days) taken in the period 1996 - 2008 have been compared and good agreement was found. The method to obtain the individual data for the HDS follows from the correlation analysis described in this article. The resulting data, now under the name of Modified Homogeneous Data Set (MHDS), are identical up to 1996 to those in the HDS. The MHDS can be used further for studies of the coronal solar activity and its cycle. These data are available at http://www.suh.sk.
Homogeneous cooling of mixtures of particle shapes
Hidalgo, R. C.; Serero, D.; Pöschel, T.
2016-07-01
In this work, we examine theoretically the cooling dynamics of binary mixtures of spheres and rods. To this end, we introduce a generalized mean field analytical theory, which describes the free cooling behavior of the mixture. The relevant characteristic time scale for the cooling process is derived, depending on the mixture composition and the aspect ratio of the rods. We simulate mixtures of spherocylinders and spheres using a molecular dynamics algorithm implemented on graphics processing unit (GPU) architecture. We systematically study mixtures composed of spheres and rods with several aspect ratios and varying the mixture composition. A homogeneous cooling state, where the time dependence of the system's intensive variables occurs only through a global granular temperature, is identified. We find cooling dynamics in excellent agreement with Haff's law, when using an adequate time scale. Using the scaling properties of the homogeneous cooling dynamics, we estimated numerically the efficiency of the energy interchange between rotational and translational degrees of freedom for collisions between spheres and rods.
Irregular Homogeneity Domains in Ternary Intermetallic Systems
Directory of Open Access Journals (Sweden)
Jean-Marc Joubert
2015-12-01
Full Text Available Ternary intermetallic A–B–C systems sometimes have unexpected behaviors. The present paper examines situations in which there is a tendency to simultaneously form the compounds ABx, ACx and BCx with the same crystal structure. This causes irregular shapes of the phase homogeneity domains and, from a structural point of view, a complete reversal of site occupancies for the B atom when crossing the homogeneity domain. This work reviews previous studies done in the systems Fe–Nb–Zr, Hf–Mo–Re, Hf–Re–W, Mo–Re–Zr, Re–W–Zr, Cr–Mn–Si, Cr–Mo–Re, and Mo–Ni–Re, and involving the topologically close-packed Laves, χ and σ phases. These systems have been studied using ternary isothermal section determination, DFT calculations, site occupancy measurement using joint X-ray, and neutron diffraction Rietveld refinement. Conclusions are drawn concerning this phenomenon. The paper also reports new experimental or calculated data on Co–Cr–Re and Fe–Nb–Zr systems.
Computational approaches to homogeneous gold catalysis.
Faza, Olalla Nieto; López, Carlos Silva
2015-01-01
Homogenous gold catalysis has been exploding for the last decade at an outstanding pace. The best described reactivity of Au(I) and Au(III) species is based on gold's properties as a soft Lewis acid, but new reactivity patterns have recently emerged which further expand the range of transformations achievable using gold catalysis, with examples of dual gold activation, hydrogenation reactions, or Au(I)/Au(III) catalytic cycles.In this scenario, to develop fully all these new possibilities, the use of computational tools to understand at an atomistic level of detail the complete role of gold as a catalyst is unavoidable. In this work we aim to provide a comprehensive review of the available benchmark works on methodological options to study homogenous gold catalysis in the hope that this effort can help guide the choice of method in future mechanistic studies involving gold complexes. This is relevant because a representative number of current mechanistic studies still use methods which have been reported as inappropriate and dangerously inaccurate for this chemistry.Together with this, we describe a number of recent mechanistic studies where computational chemistry has provided relevant insights into non-conventional reaction paths, unexpected selectivities or novel reactivity, which illustrate the complexity behind gold-mediated organic chemistry.
Si isotope homogeneity of the solar nebula
Energy Technology Data Exchange (ETDEWEB)
Pringle, Emily A.; Savage, Paul S.; Moynier, Frédéric [Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 (United States); Jackson, Matthew G. [Department of Earth Science, University of California, Santa Barbara, CA 93109 (United States); Barrat, Jean-Alix, E-mail: eapringle@wustl.edu, E-mail: savage@levee.wustl.edu, E-mail: pringle@ipgp.fr, E-mail: moynier@ipgp.fr, E-mail: jackson@geol.ucsb.edu, E-mail: Jean-Alix.Barrat@univ-brest.fr [Université Européenne de Bretagne, Université de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, F-29280 Plouzané Cedex (France)
2013-12-20
The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in {sup 29}Si/{sup 28}Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of {sup 29}Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.
On Shearing Fluids with Homogeneous Densities
Srivastava, D C; Kumar, Rajesh
2016-01-01
In this paper, we study shearing spherically symmetric homogeneous density fluids in comoving coordinates. It is found that the expansion of the four-velocity of a perfect fluid is homogeneous, whereas its shear is generated by an arbitrary function of time M(t), related to the mass function of the distribution. This function is found to bear a functional relationship with density. The field equations are reduced to two coupled first order ordinary differential equations for the metric coefficients, g 11 and g 22. We have explored a class of solutions assuming that M is a linear function of the density. This class embodies, as a subcase, the complete class of shear-free solutions. We have discussed the off quoted work of Kustaanheimo (1947) and have noted that it deals with shear-free fluids having anisotropic pressure. It is shown that the anisotropy of the fluid is characterized by an arbitrary function of time. We have discussed some issues of historical priorities and credentials related to shear-free sol...
Homogenization in micro-magneto-mechanics
Sridhar, A.; Keip, M.-A.; Miehe, C.
2016-07-01
Ferromagnetic materials are characterized by a heterogeneous micro-structure that can be altered by external magnetic and mechanical stimuli. The understanding and the description of the micro-structure evolution is of particular importance for the design and the analysis of smart materials with magneto-mechanical coupling. The macroscopic response of the material results from complex magneto-mechanical interactions occurring on smaller length scales, which are driven by magnetization reorientation and associated magnetic domain wall motions. The aim of this work is to directly base the description of the macroscopic magneto-mechanical material behavior on the micro-magnetic domain evolution. This will be realized by the incorporation of a ferromagnetic phase-field formulation into a macroscopic Boltzmann continuum by the use of computational homogenization. The transition conditions between the two scales are obtained via rigorous exploitation of rate-type and incremental variational principles, which incorporate an extended version of the classical Hill-Mandel macro-homogeneity condition covering the phase field on the micro-scale. An efficient two-scale computational scenario is developed based on an operator splitting scheme that includes a predictor for the magnetization on the micro-scale. Two- and three-dimensional numerical simulations demonstrate the performance of the method. They investigate micro-magnetic domain evolution driven by macroscopic fields as well as the associated overall hysteretic response of ferromagnetic solids.
Hydrogen Production by Homogeneous Catalysis: Alcohol Acceptorless Dehydrogenation
DEFF Research Database (Denmark)
Nielsen, Martin
2015-01-01
in hydrogen production from biomass using homogeneous catalysis. Homogeneous catalysis has the advance of generally performing transformations at much milder conditions than traditional heterogeneous catalysis, and hence it constitutes a promising tool for future applications for a sustainable energy sector...
The homogenization of a class of degenerate quasilinear parabolic equations
Institute of Scientific and Technical Information of China (English)
ZHANG Xingyou; HUANG Yong
2003-01-01
The homogenization of a class of degenerate quasilinear parabolic equations is studied. The Ap weight theory and the classical compensated compactness method are incorporated to obtain the homogenized equation.
MULTISCALE HOMOGENIZATION OF NONLINEAR HYPERBOLIC EQUATIONS WITH SEVERAL TIME SCALES
Institute of Scientific and Technical Information of China (English)
Jean Louis Woukeng; David Dongo
2011-01-01
We study the multiscale homogenization of a nonlinear hyperbolic equation in a periodic setting. We obtain an accurate homogenization result. We also show that as the nonlinear term depends on the microscopic time variable, the global homogenized problem thus obtained is a system consisting of two hyperbolic equations. It is also shown that in spite of the presence of several time scales, the global homogenized problem is not a reiterated one.
Non-homogeneous dynamic Bayesian networks for continuous data
Grzegorczyk, Marco; Husmeier, Dirk
2011-01-01
Classical dynamic Bayesian networks (DBNs) are based on the homogeneous Markov assumption and cannot deal with non-homogeneous temporal processes. Various approaches to relax the homogeneity assumption have recently been proposed. The present paper presents a combination of a Bayesian network with c
THE ANALYTICAL PROPERTIES FOR HOMOGENEOUS RANDOM TRANSITION FUNCTIONS
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The concepts of Markov process in random environment and homogeneous random transition functions are introduced. The necessary and sufficient conditions for homogeneous random transition function are given. The main results in this article are the analytical properties, such as continuity, differentiability, random Kolmogorov backward equation and random Kolmogorov forward equation of homogeneous random transition functions.
Radiolysis of berberine or palmatine in aqueous solution
Marszalek, Milena; Wolszczak, Marian
2011-01-01
The reactions of hydrated electron (eaq-), hydrogen atom (H rad ) (reducing species) and Cl2•-, Br2•-, N,O•H radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of eaq- and rad OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with eaq- and radicals generated during radiolysis are unstable and undergo further reactions.
On the Persistence of Homogeneous Matter
Butterfield, J
2004-01-01
Some recent philosophical debate about persistence has focussed on an argument against perdurantism that discusses rotating perfectly homogeneous discs (the `rotating discs argument'; RDA). The argument has been mostly discussed by metaphysicians, though it appeals to ideas from classical mechanics, especially about rotation. In contrast, I assess the RDA from the perspective of the philosophy of physics. After introducing the argument and emphasizing the relevance of physics (Sections 1 to 3), I review some metaphysicians' replies to the argument (Section 4). Thereafter, I argue for three main conclusions. They all arise from the fact, emphasized in Section 2, that classical mechanics (non-relativistic as well as relativistic) is both more subtle, and more problematic, than philosophers generally realize. The main conclusion is that the RDA can be defeated (Section 6 onwards). Namely, by the perdurantist taking objects in classical mechanics (whether point-particles or continuous bodies) to have only tempora...
Autophoretic self-propulsion of homogeneous particles
Michelin, Sebastien; Lauga, Eric; de Canio, Gabriele
2014-11-01
Phoretic mechanisms such as diffusiophoresis exploit short-ranged interactions between solute molecules in the fluid and a rigid wall to generate local slip velocities in the presence of solute gradients along the solid boundary. This boundary flow can result in macroscopic fluid motion or phoretic migration of inert particles. These mechanisms have recently received a renewed interest to design self-propelled ``autophoretic'' systems able to generate the required solute gradients through chemical reaction at their surface. Most existing designs rely on the asymmetric chemical treatment of the particle's surface to guarantee symmetry-breaking and the generation of a net flow. We show here, however, that chemical asymmetry is not necessary for flow generation and that homogeneous particles with asymmetric geometry may lead to self-propulsion in Stokes flow. Similarly, this principle can be used to manufacture micro-pumps using channel walls with uniform chemical properties.
Homogeneous cosmology with aggressively expanding civilizations
Olson, S Jay
2014-01-01
In the context of a homogeneous universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions covering several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available...
Leith diffusion model for homogeneous anisotropic turbulence
Rubinstein, Robert; Clark, Timothy; Kurien, Susan
2016-11-01
A new spectral closure model for homogeneous anisotropic turbulence is proposed. The systematic development begins by closing the third-order correlation describing nonlinear interactions by an anisotropic generalization of the Leith diffusion model for isotropic turbulence. The correlation tensor is then decomposed into a tensorially isotropic part, or directional anisotropy, and a trace-free remainder, or polarization anisotropy. The directional and polarization components are then decomposed using irreducible representations of the SO(3) symmetry group. Under the ansatz that the decomposition is truncated at quadratic order, evolution equations are derived for the directional and polarization pieces of the correlation tensor. Numerical simulation of the model equations for a freely decaying anisotropic flow illustrate the non-trivial effects of spectral dependencies on the different return-to-isotropy rates of the directional and polarization contributions.
Modeling of nanoplastic by asymptotic homogenization method
Institute of Scientific and Technical Information of China (English)
张为民; 何伟; 李亚; 张平; 张淳源
2008-01-01
The so-called nanoplastic is a new simple name for the polymer/layered silicate nanocomposite,which possesses excellent properties.The asymptotic homogenization method(AHM) was applied to determine numerically the effective elastic modulus of a two-phase nanoplastic with different particle aspect ratios,different ratios of elastic modulus of the effective particle to that of the matrix and different volume fractions.A simple representative volume element was proposed,which is assumed that the effective particles are uniform well-aligned and perfectly bonded in an isotropic matrix and have periodic structure.Some different theoretical models and the experimental results were compared.The numerical results are good in agreement with the experimental results.
Homogeneous spacelike singularities inside spherical black holes
Burko, L M
1997-01-01
Recent numerical simulations have found that the Cauchy horizon inside spherical charged black holes, when perturbed nonlinearly by a self-gravitating, minimally-coupled, massless, spherically-symmetric scalar field, turns into a null weak singularity which focuses monotonically to $r=0$ at late times, where the singularity becomes spacelike. Our main objective is to study this spacelike singularity. We study analytically the spherically-symmetric Einstein-Maxwell-scalar equations asymptotically near the singularity. We obtain a series-expansion solution for the metric functions and for the scalar field near $r=0$ under the simplifying assumption of homogeneity. Namely, we neglect spatial derivatives and keep only temporal derivatives. We find that there indeed exists a generic spacelike singularity solution for these equations (in the sense that the solution depends on enough free parameters), with similar properties to those found in the numerical simulations. This singularity is strong in the Tipler sense,...
Correlators of Matrix Models on Homogeneous Spaces
Kitazawa, Y; Tomino, D; Kitazawa, Yoshihisa; Takayama, Yastoshi; Tomino, Dan
2004-01-01
We investigate the correlators of TrA_{mu}A_{nu} in matrix models on homogeneous spaces: S^2 and S^2 x S^2. Their expectation value is a good order parameter to measure the geometry of the space on which non-commutative gauge theory is realized. They also serve as the Wilson lines which carry the minimum momentum. We develop an efficient procedure to calculate them through 1PI diagrams. We determine the large N scaling behavior of the correlators. The order parameter shows that fuzzy S^2 x S^2 acquires a 4 dimensional fractal structure in contrast to fuzzy S^2. We also find that the two point functions exhibit logarithmic scaling violations.
Inertial particles in homogeneous shear turbulence
Energy Technology Data Exchange (ETDEWEB)
Nicolai, Claudia; Jacob, Boris [CNR-INSEAN, via di Vallerano 139, 00128 Rome (Italy); Gualtieri, Paolo; Piva, Renzo, E-mail: claudia.nicolai@uniroma1.it [DMA, Sapienza Universita di Roma, Via Eudossiana 18, 00184 Rome (Italy)
2011-12-22
The characteristics of inertial particles distribution in a uniformly sheared turbulent flow are investigated, with the aim of quantifying the effects associated with the large-scale anisotropy induced by the mean velocity gradient. The focus of the analysis is on clustering aspects, and in particular on the dependence of the radial distribution function on both the directionality and the magnitude of the observation scale. We discuss experimental data measured in a homogeneous shear flow seeded with particles of size comparable with the Kolmogorov length scale and Stokes number St Almost-Equal-To 0.3, and discuss their distribution properties in comparison with results provided by related one-way coupled direct numerical simulations which make use of the point-force approximation.
Energy interactions in homogeneously sheared magnetohydrodynamic flows
Collard, Diane; Praturi, Divya Sri; Girimaji, Sharath
2016-11-01
We investigate the behavior of homogeneously sheared magnetohydrodynamic (MHD) flows subject to perturbations in various directions. We perform rapid distortion theory (RDT) analysis and direct numerical simulations (DNS) to examine the interplay between magnetic, kinetic, and internal energies. For perturbation wavevectors oriented along the spanwise direction, RDT analysis shows that the magnetic and velocity fields are decoupled. In the case of streamwise wavevectors, the magnetic and velocity fields are tightly coupled. The coupling is "harmonic" in nature. DNS is then used to confirm the RDT findings. Computations of spanwise perturbations indeed exhibit behavior that is impervious to the magnetic field. Computed streamwise perturbations exhibit oscillatory evolution of kinetic and magnetic energies for low magnetic field strength. As the strength of magnetic field increases, the oscillatory behavior intensifies even as the energy magnitude decays, indicating strong stabilization.
The homogeneity conjecture for supergravity backgrounds
Figueroa-O'Farrill, José Miguel
2009-06-01
These notes record three lectures given at the workshop "Higher symmetries in Physics", held at the Universidad Complutense de Madrid in November 2008. In them we explain how to construct a Lie (super)algebra associated to a spin manifold, perhaps with extra geometric data, and a notion of privileged spinors. The typical examples are supersymmetric supergravity backgrounds; although there are more classical instances of this construction. We focus on two results: the geometric constructions of compact real forms of the simple Lie algebras of type B4, F4 and E8 from S7, S8 and S15, respectively; and the construction of the Killing superalgebra of eleven-dimensional supergravity backgrounds. As an application of this latter construction we show that supersymmetric supergravity backgrounds with enough supersymmetry are necessarily locally homogeneous.
Homogenization analysis of complementary waveguide metamaterials
Landy, Nathan; Hunt, John; Smith, David R.
2013-11-01
We analyze the properties of complementary metamaterials as effective inclusions patterned into the conducting walls of metal waveguide structures. We show that guided wave metamaterials can be homogenized using the same retrieval techniques used for volumetric metamaterials, leading to a description in which a given complementary element is conceptually replaced by a block of material within the waveguide whose effective permittivity and permeability result in equivalent scattering characteristics. The use of effective constitutive parameters for waveguide materials provides an alternative point-of-view for the design of waveguide and microstrip based components, including planar lenses and filters, as well as devices with derived from a bulk material response. In addition to imparting effective constitutive properties to the waveguide, complementary metamaterials also couple energy from waveguide modes into radiation. Thus, complementary waveguide metamaterials can be used to modify and optimize a variety of antenna structures.
Temperature field simulation of laser homogenizing equipment
Institute of Scientific and Technical Information of China (English)
Juanjuan WANG; Yunshan WANG; Fudong ZHU
2009-01-01
The laser homogenizing equipment was devised using the ring scanning principle. Its working principle is explained. A laser scanning ring facula is obtained when the laser beam goes through the equipment's optical system rotating with high-frequency. The scanning ring facula's mathematic model is established based on the temperature field's superposing principle. The ring facula's light intensity distribution and temperature distribution characteristics are achieved by simulating its temperature field. By studying the effect of parameters on the temperature field, the best parameters can be found. Results show that favorable temperature distribution characteristics can be attained by choosing appropriate parameters, and even the thermal effect can be realized by utilizing the circumference power compensating for the heat exchange lost in the horizontal direction. The uniform hardness layer and better process quality can be attained using the ring facula optimized for metal laser heat treatment.
Homogenization of global radiosonde humidity data
Blaschek, Michael; Haimberger, Leopold
2016-04-01
The global radiosonde network is an important source of upper-air measurements and is strongly connected to reanalysis efforts of the 20th century. However, measurements are strongly affected by changes in the observing system and require a homogenization before they can be considered useful in climate studies. In particular humidity measurements are known to show spurious trends and biases induced by many sources, e.g. reporting practices or freezing of the sensor. We propose to detect and correct these biases in an automated way, as has been done with temperature and winds. We detect breakpoints in dew point depression (DPD) time series by employing a standard normal homogeneity test (SNHT) on DPD-departures from ERA-Interim. In a next step, we calculate quantile departures between the latter and the earlier part near the breakpoints of the time series, going back in time. These departures adjust the earlier distribution of DPD to the latter distribution, called quantile matching, thus removing for example a non climatic shift. We employ this approach to the existing radiosonde network. In a first step to verify our approach we compare our results with ERA-Interim data and brightness temperatures of humidity-sensitive channels of microwave measuring radiometers (SSMIS) onboard DMSP F16. The results show that some of the biases can be detected and corrected in an automated way, however large biases that impact the distribution of DPD values originating from known reporting practices (e.g. 30 DPD on US stations) remain. These biases can be removed but not corrected. The comparison of brightness temperatures from satellite and radiosondes proofs to be difficult as large differences result from for example representative errors.
Li, Feifei
2013-05-21
Lanthanide-doped core-shell upconversion nanocrystals (UCNCs) have tremendous potential for applications in many fields, especially in bio-imaging and medical therapy. As core-shell UCNCs are mostly synthesized in organic solvents, tedious organic-aqueous phase transfer processes are usually needed for their use in bio-applications. Herein, we demonstrate the first example of one-step synthesis of highly luminescent core-shell UCNCs in the "aqueous" phase under mild conditions using innocuous reagents. A microwave-assisted approach allowed for layer-by-layer epitaxial growth of a hydrophilic NaGdF4 shell on NaYF4:Yb, Er cores. During this process, surface defects of the nanocrystals could be gradually passivated by the homogeneous shell deposition, resulting in obvious enhancement in the overall upconversion emission efficiency. In addition, the up-down conversion dual-mode luminescent NaYF4:Yb, Er@NaGdF4:Ce, Ln (Eu, Tb, Sm, Dy) nanocrystals were also synthesized to further validate the successful formation of the core-shell structure. More significantly, based on their superior solubility and stability in water solution, high upconversion efficiency and Gd-doped predominant X-ray absorption, the as-prepared NaYF4:Yb, Er@NaGdF4 core-shell UCNCs exhibited high contrast in in vitro cell imaging and in vivo X-ray computed tomography (CT) imaging, demonstrating great potential as multiplexed luminescent biolabels and CT contrast agents.
Half-sandwich iridium complexes for homogeneous water-oxidation catalysis.
Blakemore, James D; Schley, Nathan D; Balcells, David; Hull, Jonathan F; Olack, Gerard W; Incarvito, Christopher D; Eisenstein, Odile; Brudvig, Gary W; Crabtree, Robert H
2010-11-17
Iridium half-sandwich complexes of the types Cp*Ir(N-C)X, [Cp*Ir(N-N)X]X, and [CpIr(N-N)X]X are catalyst precursors for the homogeneous oxidation of water to dioxygen. Kinetic studies with cerium(IV) ammonium nitrate as primary oxidant show that oxygen evolution is rapid and continues over many hours. In addition, [Cp*Ir(H(2)O)(3)]SO(4) and [(Cp*Ir)(2)(μ-OH)(3)]OH can show even higher turnover frequencies (up to 20 min(-1) at pH 0.89). Aqueous electrochemical studies on the cationic complexes having chelate ligands show catalytic oxidation at pH > 7; conversely, at low pH, there are no oxidation waves up to 1.5 V vs NHE for the complexes. H(2)(18)O isotope incorporation studies demonstrate that water is the source of oxygen atoms during cerium(IV)-driven catalysis. DFT calculations and kinetic experiments, including kinetic-isotope-effect studies, suggest a mechanism for homogeneous iridium-catalyzed water oxidation and contribute to the determination of the rate-determining step. The kinetic experiments also help distinguish the active homogeneous catalyst from heterogeneous nanoparticulate iridium dioxide.
Aqueous humor changes after experimental filtering surgery.
Radius, R L; Herschler, J; Claflin, A; Fiorentino, G
1980-02-01
We studied aqueous humor of rhesus and owl monkeys for its effect on the growth of subconjunctival fibroblasts in tissue culture. Aqueous humor samples obtained before glaucoma surgery inhibited the initiation of growth of fibroblasts. However, postoperative aqueous humor samples supported growth of fibroblasts. The change in aqueous humor physiology lasted for up to two months after glaucoma surgery. Our study indicated that possibly material added to the postoperative aqueous humor inactivates an inhibitor normally present in primary aqueous humor. An alternative explanation would be that primary aqueous humor, in contrast to secondary aqueous humor, lacks sufficient nutrient material to support fibroblast growth in tissue culture.
DEFF Research Database (Denmark)
Musaeus, Peter
2015-01-01
Purpose: To examine philosophical stances underpinning medical identity and assess the conceptual relationship between physician, medical practice and culture. Argument: Medical identity is about the ideals and moral positions that physicians take when justifying themselves. Medical identity...... hedonistic versus sentimentalist approaches to medical identity. The sociocultural philosophical analysis of medical identity can shed light on what it means conceptually for a physician to harbor beliefs associated with him/her being taken to be an autonomous professional. It is important because it touches...... on the meaning of being a compassionate, good and skilled physician, making its relevance to person-centered medicine self-evident. Conclusion: Medical identity should be analyzed with reference to literature, philosophy and medical practice in order for the physician to exercise a reflective position...
... email share facebook twitter google plus linkedin Medical Management Although there’s no cure for CMT, there are ... individualized physical therapy program. For more on medical management of CMT, see Surgery Sometimes, Bracing Often, Caution ...
On the decay of homogeneous isotropic turbulence
Skrbek, L.; Stalp, Steven R.
2000-08-01
Decaying homogeneous, isotropic turbulence is investigated using a phenomenological model based on the three-dimensional turbulent energy spectra. We generalize the approach first used by Comte-Bellot and Corrsin [J. Fluid Mech. 25, 657 (1966)] and revised by Saffman [J. Fluid Mech. 27, 581 (1967); Phys. Fluids 10, 1349 (1967)]. At small wave numbers we assume the spectral energy is proportional to the wave number to an arbitrary power. The specific case of power 2, which follows from the Saffman invariant, is discussed in detail and is later shown to best describe experimental data. For the spectral energy density in the inertial range we apply both the Kolmogorov -5/3 law, E(k)=Cɛ2/3k-5/3, and the refined Kolmogorov law by taking into account intermittency. We show that intermittency affects the energy decay mainly by shifting the position of the virtual origin rather than altering the power law of the energy decay. Additionally, the spectrum is naturally truncated due to the size of the wind tunnel test section, as eddies larger than the physical size of the system cannot exist. We discuss effects associated with the energy-containing length scale saturating at the size of the test section and predict a change in the power law decay of both energy and vorticity. To incorporate viscous corrections to the model, we truncate the spectrum at an effective Kolmogorov wave number kη=γ(ɛ/v3)1/4, where γ is a dimensionless parameter of order unity. We show that as the turbulence decays, viscous corrections gradually become more important and a simple power law can no longer describe the decay. We discuss the final period of decay within the framework of our model, and show that care must be taken to distinguish between the final period of decay and the change of the character of decay due to the saturation of the energy containing length scale. The model is applied to a number of experiments on decaying turbulence. These include the downstream decay of turbulence in
Institute of Scientific and Technical Information of China (English)
何宗岭; 李名立; 邓伟; 王强; 李寅飞; 陈壮飞; 韩媛媛; 蒋莉君; 李涛
2014-01-01
目的 探讨精神分裂症患者在静息状态下脑活动局部一致性(ReHo)特点.方法 对104例首次发病未服药精神分裂症患者(病例组)和104名健康对照者(对照组)进行静息态脑fMRI扫描,利用ReHo的方法分析数据并进行组间比较.采用偏相关分析功能活动异常脑区ReHo值与PANSS各因子间的相关性.结果 与对照组相比,病例组ReHo降低的区域位于右侧前额叶眶额皮质(ReHo值:0.7±0.1,t=-3.502,P＜0.05)及背外侧皮质(ReHo值:1.0±0.1,t=-4.613,P＜0.05)、左侧前额叶眶额皮质(ReHo值:0.8±0.1,t=-4.778,P＜0.05)、后扣带回/楔前叶(ReHo值:1.2±0.1,t=-3.838,P＜0.05)、右侧顶下小叶(ReHo值:1.1±0.1,t=-4.275,P＜0.05)和右侧中央后回(ReHo值:0.9±0.1,t=-3.520,P＜0.05).ReHo增高的区域位于左侧小脑前叶(ReHo值:1.1±0.1,=4.081,P＜0.05)和后叶(ReHo值:1.0±0.1,t=3.660,P＜0.05)、右侧小脑后叶(ReHo值:0.8±0.1,t=3.359,P＜0.05)、以舌回为中心的左侧枕叶(ReHo值:0.7±0.1,t =3.986,P＜0.05)和右侧枕叶(ReHo值:1.1±0.1,t=3.362,P＜0.05),左侧颞上回/颞中回(ReHo值:1.1±0.1,=3.708,P ＜0.05)、左侧壳核/豆状核(ReHo值:1.0±0.1,t=4.457,P＜0.05).病例组右侧中央后回ReHo与阴性症状因子(r=-0.262,P＜0.01)、瓦解性症状因子(r=-0.219,P＜0.01)相关,右侧前额叶眶额皮质的ReHo与退缩性因子相关(r=-0.242,P ＜0.01).结论 精神分裂症患者静息状态下的脑功能活动ReHo异常广泛分布,功能活动异常的脑区大多位于功能网络的节点脑区,可能与精神分裂症的病理机制有关.%Objective To explore the regional homogeneity (ReHo) of resting state brain activity in schizophrenia by using functional magnetic resonance imaging (fMRI).Methods One hundred and four first-episode treatment-naive schizophrenia (FES) patients,and 104 age/gender/education-matched healthy controls were examined by fMRI scans.ReHo of the resting-state brain activity was compared between the two
Mars Aqueous Processing System Project
National Aeronautics and Space Administration — Mars Aqueous Processing System (MAPS) is an innovative method to produce useful building materials from Martian regolith. Acids and bases produced from the regolith...
Mars Aqueous Processing System Project
National Aeronautics and Space Administration — The Mars Aqueous Processing System (MAPS) is a novel technology for recovering oxygen, iron, and other constituents from lunar and Mars soils. The closed-loop...
Keohane, Carol A; Bates, David W
2008-03-01
Patient safety is a state of mind, not a technology. The technologies used in the medical setting represent tools that must be properly designed, used well, and assessed on an on-going basis. Moreover, in all settings, building a culture of safety is pivotal for improving safety, and many nontechnologic approaches, such as medication reconciliation and teaching patients about their medications, are also essential. This article addresses the topic of medication safety and examines specific strategies being used to decrease the incidence of medication errors across various clinical settings.
Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase
Directory of Open Access Journals (Sweden)
Alessandra Magistrato
2011-01-01
Full Text Available The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen ‘fixation’ via an iron molybdenum cofactor (FeMo-co under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N2 to various degrees. However, to date Mo(N2(HIPTN3N with (HIPTN3N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N2. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.
Linear perturbations of spatially locally homogeneous spacetimes
Tanimoto, M
2003-01-01
Methods and properties regarding the linear perturbations are discussed for some spatially closed (vacuum) solutions of Einstein's equation. The main focus is on two kinds of spatially locally homogeneous solution; one is the Bianchi III (Thurston's H^2 x R) type, while the other is the Bianchi II (Thurston's Nil) type. With a brief summary of previous results on the Bianchi III perturbations, asymptotic solutions for the gauge-invariant variables for the Bianchi III are shown, with which (in)stability of the background solution is also examined. The issue of linear stability for a Bianchi II solution is still an open problem. To approach it, appropriate eigenfunctions are presented for an explicitly compactified Bianchi II manifold and based on that, some field equations on the Bianchi II background spacetime are studied. Differences between perturbation analyses for Bianchi class B (to which Bianchi III belongs) and class A (to which Bianchi II belongs) are stressed for an intention to be helpful for applic...
On the Homogeneous Model Of Euclidean Geometry
Gunn, Charles
2011-01-01
We attach the degenerate signature (n,0,1) to the projectivized dual Grassmann algebra over R(n+1). We explore the use of the resulting Clifford algebra as a model for euclidean geometry. We avoid problems with the degenerate metric by constructing an algebra isomorphism between this Grassmann algebra and its dual, that yields non-metric meet and join operators. We review the Cayley-Klein construction of the projective (homogeneous) model for euclidean geometry leading to the choice of the signature (n,0,1). We focus on the cases of n=2 and n=3 in detail, enumerating the geometric products between simple k- and m-vectors. We establish that versor (sandwich) operators provide all euclidean isometries, both direct and indirect. We locate the spin group, a double cover of the direct euclidean group, inside the even subalgebra of the Clifford algebra, and provide a simple algorithm for calculating the logarithm of such elements. We conclude with an elementary account of euclidean rigid body motion within this fra...
Dynamic contact angle cycling homogenizes heterogeneous surfaces.
Belibel, R; Barbaud, C; Mora, L
2016-12-01
In order to reduce restenosis, the necessity to develop the appropriate coating material of metallic stent is a challenge for biomedicine and scientific research over the past decade. Therefore, biodegradable copolymers of poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) were prepared in order to develop a new coating exhibiting different custom groups in its side chain and being able to carry a drug. This material will be in direct contact with cells and blood. It consists of carboxylic acid and hexylic groups used for hydrophilic and hydrophobic character, respectively. The study of this material wettability and dynamic surface properties is of importance due to the influence of the chemistry and the potential motility of these chemical groups on cell adhesion and polymer kinetic hydrolysis. Cassie theory was used for the theoretical correction of contact angles of these chemical heterogeneous surfaces coatings. Dynamic Surface Analysis was used as practical homogenizer of chemical heterogeneous surfaces by cycling during many cycles in water. In this work, we confirmed that, unlike receding contact angle, advancing contact angle is influenced by the difference of only 10% of acidic groups (%A) in side-chain of polymers. It linearly decreases with increasing acidity percentage. Hysteresis (H) is also a sensitive parameter which is discussed in this paper. Finally, we conclude that cycling provides real information, thus avoiding theoretical Cassie correction. H(10)is the most sensible parameter to %A.
Numerical Computation of Homogeneous Slope Stability
Directory of Open Access Journals (Sweden)
Shuangshuang Xiao
2015-01-01
Full Text Available To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM and particle swarm optimization algorithm (PSO to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759 were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS.
Development of a mechanical homogenizer coffee
Directory of Open Access Journals (Sweden)
Raphael Magalhães Gomes Moreira
2013-12-01
Full Text Available The crop Coffee demands investments to the machines development, which it enables the processes ofpost-harvesting, becoming them faster, meanwhile improving the working. The use of stationary layer dryers are responsible for good results at drying and product quality, but it requires a constant revolving, in order to homogenize the grain mass and improve the air distribution inside the drying chamber. The shortage of workmanship, associated to the need of constant revolving and the heavy working conditions, it becomes it indispensable to mechanize, in some way, this step. The agricultural machine design is considered of great complexity, regarding it must be concerned with the interactions among the operator, machine and environment. When designing a machine, the experience and the dominion of several standpoints have to be interpreted clearly. With the increasing competitiveness on the consumer market and agricultural machines, several companies have joined the research centers, because in general, do not make use of systematic procedures during the project, which can result in failures during operation. This article aimed to design and build a semi-mechanized revolving prototype used to mix the coffee beans. The revolving prototype with the helical screw principles proved to be able to performing the grains transport efficiently.
Convective mixing in homogeneous porous media flow
Ching, Jia-Hau; Chen, Peilong; Tsai, Peichun Amy
2017-01-01
Inspired by the flow processes in the technology of carbon dioxide (CO2) storage in saline formations, we modeled a homogeneous porous media flow in a Hele-Shaw cell to investigate density-driven convection due to dissolution. We used an analogy of the fluid system to mimic the diffusion and subsequent convection when CO2 dissolves in brine, which generates a heavier solution. By varying the permeability, we examined the onset of convection, the falling dynamics, the wavelengths of fingers, and the rate of dissolution, for the Rayleigh number Ra (a dimensionless forcing term which is the ratio of buoyancy to diffusivity) in the range of 2.0 ×104≤Ra≤8.26 ×105 . Our results reveal that the effect of permeability influences significantly the initial convective speed, as well as the later coarsening dynamics of the heavier fingering plumes. However, the total dissolved mass, characterized by a nondimensional Nusselt number Nu, has an insignificant dependence on Ra. This implies that the total dissolution rate of CO2 is nearly constant in high Ra geological porous structures.
Chemically homogeneous evolution in massive binaries
de Mink, S E; Langer, N; Pols, O R
2010-01-01
Rotation can have severe consequences for the evolution of massive stars. It is now considered as one of the main parameters, alongside mass and metallicity that determine the final fate of single stars. In massive, fast rotating stars mixing processes induced by rotation may be so efficient that helium produced in the center is mixed throughout the envelope. Such stars evolve almost chemically homogeneously. At low metallicity they remain blue and compact, while they gradually evolve into Wolf-Rayet stars and possibly into progenitors of long gamma-ray bursts. In binaries this type of evolution may occur because of (I) tides in very close binaries, as a result of (II) spin up by mass transfer, as result of (III) a merger of the two stars and (IV) when one of the components in the binary was born with a very high initial rotation rate. As these stars stay compact, the evolutionary channels are very different from what classical binary evolutionary models predict. In this contribution we discuss examples of ne...
Magnetic field homogeneity for neutron EDM experiment
Anderson, Melissa
2016-09-01
The neutron electric dipole moment (nEDM) is an observable which, if non-zero, would violate time-reversal symmetry, and thereby charge-parity symmetry of nature. New sources of CP violation beyond those found in the standard model of particle physics are already tightly constrained by nEDM measurements. Our future nEDM experiment seeks to improve the precision on the nEDM by a factor of 30, using a new ultracold neutron (UCN) source that is being constructed at TRIUMF. Systematic errors in the nEDM experiment are driven by magnetic field inhomogeneity and instability. The goal field inhomogeneity averaged over the experimental measurement cell (order of 1 m) is 1 nT/m, at a total magnetic field of 1 microTesla. This equates to roughly 10-3 homogeneity. A particularly challenging aspect of the design problem is that nearby magnetic materials will also affect the magnetic inhomogeneity, and this must be taken into account in completing the design. This poster will present the design methodology and status of the main coil for the experiment where we use FEA software (COMSOL) to simulate and analyze the magnetic field. Natural Sciences and Engineering Research Council.
Variation principle of piezothermoelastic bodies, canonical equation and homogeneous equation
Institute of Scientific and Technical Information of China (English)
LIU Yan-hong; ZHANG Hui-ming
2007-01-01
Combining the symplectic variations theory, the homogeneous control equation and isoparametric element homogeneous formulations for piezothermoelastic hybrid laminates problems were deduced. Firstly, based on the generalized Hamilton variation principle, the non-homogeneous Hamilton canonical equation for piezothermoelastic bodies was derived. Then the symplectic relationship of variations in the thermal equilibrium formulations and gradient equations was considered, and the non-homogeneous canonical equation was transformed to homogeneous control equation for solving independently the coupling problem of piezothermoelastic bodies by the incensement of dimensions of the canonical equation. For the convenience of deriving Hamilton isoparametric element formulations with four nodes, one can consider the temperature gradient equation as constitutive relation and reconstruct new variation principle. The homogeneous equation simplifies greatly the solution programs which are often performed to solve nonhomogeneous equation and second order differential equation on the thermal equilibrium and gradient relationship.
Homogenization in strength and durability analysis of reinforced tooth filling
Mikhailov, SE; Orlik, J
2002-01-01
An asymptotic homogenization procedure is employed to obtain effective elastic properties of the composite tooth filling, a homogenized macro– stress field and a first approximation to the micro-stress field, from properties of the components and applied macro–loads. Using the approximate micro–stress field, a non–local initial strength and fatigue durability macro–conditions for the composite filling material is expressed in terms of the homogenized macro–stresses. An illustrative example wi...
Quantitative determination of homogeneous strain value in superplastic tension
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
After load instability, a passage of homogeneous strain ε can be still continued in superplastic tensile deformation. But untill now, no one has given the precise value of ε corresponding to actual materials, neither in experimental measurements nor in theoretical calculations. Using the elaborate experimental measuring methods of m value and its function expressions, the note first gives the method to determine homogeneous ε, and the homogeneous ε value of typical superplastic alloy Zn-5% Al under 18℃ and 340℃ respectively.
Homogeneity of passively ventilated waste tanks
Energy Technology Data Exchange (ETDEWEB)
Huckaby, J.L.; Jensen, L.; Cromar, R.D.; Hayes, J.C. [and others
1997-07-01
Gases and vapors in the high-level radioactive waste underground storage tanks at the Hanford Site are being characterized to help resolve waste storage safety issues and estimate air emissions. Characterization is accomplished by collecting and analyzing air samples from the headspaces of the tanks. Samples are generally collected from a single central location within the headspace, and it is assumed that they are representative of the entire headspace. The validity of this assumption appears to be very good for most tanks, because thermally induced convection currents within the headspaces mix constituents continuously. In the coolest waste tanks, however, thermally induced convection may be suppressed for several months of each year because of the seasonal soil temperature cycle. To determine whether composition does vary significantly with location in a cool tank, the headspaces of three waste tanks have been sampled at different horizontal and vertical locations during that part of the year when thermally induced convection is minimized. This report describes the bases for tank selection and the sampling and analytical methods used, then analyzes and discusses the results. Headspace composition data from two risers at three elevations in Tanks 241-B-103, TY-103, and U-112 have been analyzed by standard analysis of variance (ANOVA) methods, which indicate that these tank headspaces are essentially homogeneous. No stratification of denser vapors (e.g., carbon tetrachloride, dodecane) or lighter gases (e.g., ammonia, hydrogen) was detected in any of the three tanks. A qualitative examination of all tentatively identified organic vapors in SUMMA{trademark} and TST samples supported this conclusion.
A non-asymptotic homogenization theory for periodic electromagnetic structures.
Tsukerman, Igor; Markel, Vadim A
2014-08-08
Homogenization of electromagnetic periodic composites is treated as a two-scale problem and solved by approximating the fields on both scales with eigenmodes that satisfy Maxwell's equations and boundary conditions as accurately as possible. Built into this homogenization methodology is an error indicator whose value characterizes the accuracy of homogenization. The proposed theory allows one to define not only bulk, but also position-dependent material parameters (e.g. in proximity to a physical boundary) and to quantify the trade-off between the accuracy of homogenization and its range of applicability to various illumination conditions.
Homogenization Theory for a Replenishing Passive Scalar Field
Institute of Scientific and Technical Information of China (English)
Peter R.KRAMER; Shane R.KEATING
2009-01-01
Homogenization theory provides a rigorous framework for calculating the effective diffusivity of a decaying passive scalar field in a turbulent or complex flow.The authors extend this framework to the case where the passive scalar fluctuations ore continuously replenished by a source(and/or sink).The basic structure.of the homogenized equations carries over,but in some eases the homogenized source can involve a non-trivial coupling of the velocity field and the source.The authors derive expressions for the homogenized source term for various multiscale source structures and interpret them physically.
Deterministic homogenization of parabolic monotone operators with time dependent coefficients
Directory of Open Access Journals (Sweden)
Gabriel Nguetseng
2004-06-01
Full Text Available We study, beyond the classical periodic setting, the homogenization of linear and nonlinear parabolic differential equations associated with monotone operators. The usual periodicity hypothesis is here substituted by an abstract deterministic assumption characterized by a great relaxation of the time behaviour. Our main tool is the recent theory of homogenization structures by the first author, and our homogenization approach falls under the two-scale convergence method. Various concrete examples are worked out with a view to pointing out the wide scope of our approach and bringing the role of homogenization structures to light.
... Projected Employment, 2024 Change, 2014-24 Employment by Industry Percent Numeric SOURCE: U.S. Bureau of Labor Statistics, Employment Projections program Medical scientists, except epidemiologists 19- ...
Markov Chain Computation for Homogeneous and Non-homogeneous Data: MARCH 1.1 Users Guide
Directory of Open Access Journals (Sweden)
Andre Berchtold
2001-03-01
Full Text Available MARCH is a free software for the computation of different types of Markovian models including homogeneous Markov Chains, Hidden Markov Models (HMMs and Double Chain Markov Models (DCMMs. The main characteristic of this software is the implementation of a powerful optimization method for HMMs and DCMMs combining a genetic algorithm with the standard Baum-Welch procedure. MARCH is distributed as a set of Matlab functions running under Matlab 5 or higher on any computing platform. A PC Windows version running independently from Matlab is also available.
Hein, John; Jeannot, Michael
2001-02-01
A simple and inexpensive experiment for the study of simultaneous homogeneous and heterogeneous equilibria is described using a common antihistamine drug, diphenhydramine. This experiment gives students an opportunity to study the distribution of a drug in a two-phase system by measuring the concentrations of two chemical species and predicting the others by considering charge balance, mass balance, and equilibrium constant expressions. Furthermore, the acid-dissociation constant and aqueous-organic distribution coefficient can be calculated. The experiment is attractive to students because it represents a simplified model for something experienced in everyday life, namely, drug distribution in the human body. Students also gain experience with two very important analytical techniques, gas chromatography and pH measurement with a glass electrode.
Valdés, Héctor; Zaror, Claudio A
2006-11-01
Ozone oxidation combined with activated carbon adsorption (O(3)/AC) has recently started to be developed as a single process for water and wastewater treatment. While a number of aspects of aqueous ozone decomposition are well understood, the importance and relationship between aqueous ozone decomposition and organic contaminant degradation in the presence of activated carbon is still not clear. This study focuses on determining the contribution of homogeneous and heterogeneous reactions to organic contaminants removal in O(3)/AC system. Benzothiazole (BT) was selected as a target organic pollutant due to its environmental concern. A reactor system based on a differential circular flow reactor composed by a 19 cm(3) activated carbon fixed bed column and 1 dm(3) storage tank was used. Ozone was produced from pure and dry oxygen using an Ozocav ozone generator rated at 5 g O(3)h(-1). Experimental results show that BT removal rate was proportional to activated carbon dosage. Activated carbon surface contribution to BT oxidation reactions with ozone, increased with pH in absence of radical scavengers. The radical reaction contribution within the pH range 2-11 accounted for 67-83% for BT removal in O(3)/AC simultaneous treatment. Results suggest that at pH higher than the pH of the point of zero charge of the activated carbon dissociated acid groups such as carboxylic acid anhydrides and carboxylic acids present on activated carbon surface could be responsible for the observed increase in the ozone decomposition reaction rate. A simplified mechanism and a kinetic scheme representing the contribution of homogeneous and heterogeneous reactions on BT ozonation in the presence of activated carbon is proposed.
Energy Technology Data Exchange (ETDEWEB)
Ullo, J.J.; Hardy, J. Jr.
1977-10-01
Thirty-two U233 and U235 homogeneous aqueous critical experiments were analyzed with ENDF/B-IV data. Calculated eigenvalues for both fuel types increased by nearly 2 percent over the range of hydrogen/uranium atomic ratio covered (from 2106 to 27.1). This is attributed mostly to an underprediction of fast leakage, with some contribution from the fission and capture resonance integrals of ENDF/B-IV U235. Eigenvalue sensitivities to several nuclear data changes were examined. Values of the thermal criticality parameter constraint K2 for U233 and U235 were derived from the Gwin-Magnuson critical experiments at the zero leakage limit.
Feeding premature infants banked human milk homogenized by ultrasonic treatment.
Rayol, M R; Martinez, F E; Jorge, S M; Gonçalves, A L; Desai, I D
1993-12-01
Premature neonates fed ultrasonically homogenized human milk had better weight gain and triceps skin-fold thickness than did a control group given untreated human milk (p homogenization of human milk appears to minimize loss of fat and thus allows better growth of premature infants.
Homogeneous Buchberger algorithms and Sullivant's computational commutative algebra challenge
DEFF Research Database (Denmark)
Lauritzen, Niels
2005-01-01
We give a variant of the homogeneous Buchberger algorithm for positively graded lattice ideals. Using this algorithm we solve the Sullivant computational commutative algebra challenge.......We give a variant of the homogeneous Buchberger algorithm for positively graded lattice ideals. Using this algorithm we solve the Sullivant computational commutative algebra challenge....
Is it possible to homogenize resonant chiral metamaterials ?
DEFF Research Database (Denmark)
Andryieuski, Andrei; Menzel, Christoph; Rockstuhl, Carsten
2010-01-01
Homogenization of metamaterials is very important as it makes possible description in terms of effective parameters. In this contribution we consider the homogenization of chiral metamaterials. We show that for some metamaterials there is an optimal meta-atom size which depends on the coupling...
Non-linear waves in heterogeneous elastic rods via homogenization
Quezada de Luna, Manuel
2012-03-01
We consider the propagation of a planar loop on a heterogeneous elastic rod with a periodic microstructure consisting of two alternating homogeneous regions with different material properties. The analysis is carried out using a second-order homogenization theory based on a multiple scale asymptotic expansion. © 2011 Elsevier Ltd. All rights reserved.
Large-scale Homogenization of Bulk Materials in Mammoth Silos
Schott, D.L.
2004-01-01
This doctoral thesis concerns the large-scale homogenization of bulk materials in mammoth silos. The objective of this research was to determine the best stacking and reclaiming method for homogenization in mammoth silos. For this purpose a simulation program was developed to estimate the homogeniza
A FORTRAN program for testing trend and homogeneity in proportions.
Thakur, A K; Berry, K J; Mielke, P W
1985-01-01
A FORTRAN program is provided for testing linear trend and homogeneity in proportions. Trend is evaluated by the Cochran-Armitage method and homogeneity is tested by an overall X2 test as well by multiple pairwise comparisons by the Fisher-Irwin exact method. The program should be easy to implement on any size of computer with a FORTRAN compiler.
Homogeneous Broadening of Optical Transitions in Organic Mixed Crystals
Vries, Harmen de; Wiersma, Douwe A.
1976-01-01
We have used the phenomenon of laser-induced molecular photodissociation to determine the homogeneous linewidth at 2 K of the origin (zero-phonon line) and a vibronic transition in the mixed-crystal absorption spectrum of dimethyl s-tetrazine in durene. From the measured 55-MHz (upper limit) homogen
Calderon type reproducing formula on spaces of homogeneous type
Institute of Scientific and Technical Information of China (English)
邓东皋; 韩永生
1995-01-01
By using the Calderon-Zygmund operator theory, a continuous version of the Calderon type reproducing formula associated to a para-accretive function on spaces of homogeneous type is proved. A new characterization of the Besov and Triebel-Lizorkin spaces on spaces of homogeneous type is also obtained.
Haroon Jamshaid Qazi; Hamid Majeed; Waseem Safdar; John Antoniou; Zhong Fang
2015-01-01
Microencapsulation is a promising technique to retain the physical attributes of nanoemulsions and to overcome the oxidation of bioactives that become more available to aqueous phase during emulsification. Purity Gum Ultra (PGU) and Hi-CAP 100 (HiCap) emulsified nanoemulsions of Clove Oil (CO) co-encapsulated with Canola oil (CA) and Medium Chain Triglyceride (MCT) (5:5% v/v CO:CA and CO:MCT) were prepared through high pressure homogenization. Microencapsulation of nanoemulsions was performed...
Preparation of nanosized barium zirconate powder by precipitation in aqueous solution
Boschini, Frédéric; Guillaume, Bernard; Rulmont, André; Cloots, Rudi
2004-01-01
Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through an homogeneous precipitation of barium and zirconium salts followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio have been determined by means of X-ray diffraction and Inductive Coupled Plasma analyses. It has been demonstrated that a...
Non-Aqueous Capillary Electrophoresis
Szumski, Michał; Buszewski, Bogusław
Non-aqueous capillary electrophoresis and capillary electrochromatography are special variants of these techniques. Here, organic solvents or their mixtures with or without dissolved electrolytes are used as separation buffer or mobile phase, respectively. The most important features of non-aqueous systems are: better solubility of more hydrophobic ionic substances (many natural products) than in water, much less current and Joule heating allows for using highly concentrated buffers and/or larger capillary internal diameters, polar interactions are enhanced in organic solvents which is often highly advantageous in chiral separation systems. This chapter presents most frequently used solvents, their properties, as well as shows pH* scale which is often used in non-aqueous systems.
Characterization of isolated homogeneous hypersurface singularities in C4
Institute of Scientific and Technical Information of China (English)
LIN; Kepao; TU; Zhenhan; YAU; Stephen; S; T
2006-01-01
Let V be a hypersurface with an isolated singularity at the origin in Cn+1. It is a natural question to ask when V is defined by weighted homogeneous polynomial or homogeneous polynomial up to biholomorphic change of coordinates. In 1971, a beautiful theorem of Saito gives a necessary and sufficient condition for V to be defined by a weighted homogeneous polynomial.For a two-dimensional isolated hypersurface singularity V, Xu and Yau found a coordinate free characterization for V to be defined by a homogeneous polynomial. Recently Lin and Yau gave necessary and sufficient conditions for a 3-dimensional isolated hypersurface singularity with geometric genus bi.er than zero to be defined by a homogeneous polynomial. The purpose of this paper is to prove that Lin-Yau's theorem remains true for singularities with geometric genus equal to zero.
Fibrations and globalizations of compact homogeneous CR-manifolds
Gilligan, B.; Huckleberry, Alan T.
2009-06-01
Fibration methods which were previously used for complex homogeneous spaces and CR-homogeneous spaces of special types [1]-[4] are developed in a general framework. These include the \\mathfrak{g}-anticanonical fibration in the CR-setting, which reduces certain considerations to the compact projective algebraic case, where a Borel-Remmert type splitting theorem is proved. This leads to a reduction to spaces homogeneous under actions of compact Lie groups. General globalization theorems are proved which enable one to regard a homogeneous CR-manifold as an orbit of a real Lie group in a complex homogeneous space of a complex Lie group. In the special case of CR-codimension at most two, precise classification results are proved and are applied to show that in most cases there exists such a globalization.
Fibrations and globalizations of compact homogeneous CR-manifolds
Energy Technology Data Exchange (ETDEWEB)
Gilligan, B [University of Regina, Regina (Canada); Huckleberry, Alan T [Ruhr-Universitaet Bochum, Mathematischer Institut, Bochum (Germany)
2009-06-30
Fibration methods which were previously used for complex homogeneous spaces and CR-homogeneous spaces of special types [1]-[4] are developed in a general framework. These include the g-anticanonical fibration in the CR-setting, which reduces certain considerations to the compact projective algebraic case, where a Borel-Remmert type splitting theorem is proved. This leads to a reduction to spaces homogeneous under actions of compact Lie groups. General globalization theorems are proved which enable one to regard a homogeneous CR-manifold as an orbit of a real Lie group in a complex homogeneous space of a complex Lie group. In the special case of CR-codimension at most two, precise classification results are proved and are applied to show that in most cases there exists such a globalization.
Scale-dependent homogeneity measures for causal dynamical triangulations
Cooperman, Joshua H
2014-01-01
I propose two scale-dependent measures of the homogeneity of the quantum geometry determined by an ensemble of causal triangulations. The first measure is volumetric, probing the growth of volume with graph geodesic distance. The second measure is spectral, probing the return probability of a random walk with diffusion time. Both of these measures, particularly the first, are closely related to those used to assess the homogeneity of our own universe on the basis of galaxy redshift surveys. I employ these measures to quantify the quantum spacetime homogeneity as well as the temporal evolution of quantum spatial homogeneity of ensembles of causal triangulations in the well-known physical phase. According to these measures, the quantum spacetime geometry exhibits some degree of inhomogeneity on sufficiently small scales and a high degree of homogeneity on sufficiently large scales. This inhomogeneity appears unrelated to the phenomenon of dynamical dimensional reduction. I also uncover evidence for power-law sc...
Is Alzheimer's disease a homogeneous disease entity?
Korczyn, Amos D
2013-10-01
The epidemic proportions of dementia in old age are a cause of great concern for the medical profession and the society at large. It is customary to consider Alzheimer's disease (AD) as the most common cause of dementia, and vascular dementia (VaD) as being the second. This dichotomous view of a primary neurodegenerative disease as opposed to a disorder where extrinsic factors cause brain damage led to separate lines of research in these two entities. New biomarkers, particularly the introduction of modern neuroimaging and cerebrospinal fluid changes, have, in recent years, helped to identify anatomical and chemical changes of VaD and of AD. Nevertheless, there is a substantial difference between the two entities. While it is clear that VaD is a heterogeneous entity, AD is supposed to be a single disorder. Nobody attempts to use CADASIL as a template to develops treatment for sporadic VaD. On the other hand, early-onset AD is used to develop therapy for sporadic AD. This paper will discuss the problems relating to this false concept and its consequences.
Turbulent Diffusion in Non-Homogeneous Environments
Diez, M.; Redondo, J. M.; Mahjoub, O. B.; Sekula, E.
2012-04-01
Many experimental studies have been devoted to the understanding of non-homogeneous turbulent dynamics. Activity in this area intensified when the basic Kolmogorov self-similar theory was extended to two-dimensional or quasi 2D turbulent flows such as those appearing in the environment, that seem to control mixing [1,2]. The statistical description and the dynamics of these geophysical flows depend strongly on the distribution of long lived organized (coherent) structures. These flows show a complex topology, but may be subdivided in terms of strongly elliptical domains (high vorticity regions), strong hyperbolic domains (deformation cells with high energy condensations) and the background turbulent field of moderate elliptic and hyperbolic characteristics. It is of fundamental importance to investigate the different influence of these topological diverse regions. Relevant geometrical information of different areas is also given by the maximum fractal dimension, which is related to the energy spectrum of the flow. Using all the available information it is possible to investigate the spatial variability of the horizontal eddy diffusivity K(x,y). This information would be very important when trying to model numerically the behaviour in time of the oil spills [3,4] There is a strong dependence of horizontal eddy diffusivities with the Wave Reynolds number as well as with the wind stress measured as the friction velocity from wind profiles measured at the coastline. Natural sea surface oily slicks of diverse origin (plankton, algae or natural emissions and seeps of oil) form complicated structures in the sea surface due to the effects of both multiscale turbulence and Langmuir circulation. It is then possible to use the topological and scaling analysis to discriminate the different physical sea surface processes. We can relate higher orden moments of the Lagrangian velocity to effective diffusivity in spite of the need to calibrate the different regions determining the
Yilmaz, Cihan; Cetin, Arif E; Goutzamanidis, Georgia; Huang, Jun; Somu, Sivasubramanian; Altug, Hatice; Wei, Dongguang; Busnaina, Ahmed
2014-05-27
Directed assembly of nano building blocks offers a versatile route to the creation of complex nanostructures with unique properties. Bottom-up directed assembly of nanoparticles have been considered as one of the best approaches to fabricate such functional and novel nanostructures. However, there is a dearth of studies on making crystalline, solid, and homogeneous nanostructures. This requires a fundamental understanding of the forces driving the assembly of nanoparticles and precise control of these forces to enable the formation of desired nanostructures. Here, we demonstrate that colloidal nanoparticles can be assembled and simultaneously fused into 3-D solid nanostructures in a single step using externally applied electric field. By understanding the influence of various assembly parameters, we showed the fabrication of 3-D metallic materials with complex geometries such as nanopillars, nanoboxes, and nanorings with feature sizes as small as 25 nm in less than a minute. The fabricated gold nanopillars have a polycrystalline nature, have an electrical resistivity that is lower than or equivalent to electroplated gold, and support strong plasmonic resonances. We also demonstrate that the fabrication process is versatile, as fast as electroplating, and scalable to the millimeter scale. These results indicate that the presented approach will facilitate fabrication of novel 3-D nanomaterials (homogeneous or hybrid) in an aqueous solution at room temperature and pressure, while addressing many of the manufacturing challenges in semiconductor nanoelectronics and nanophotonics.
Aqueous Geochemistry at High Pressures and High Temperatures
Energy Technology Data Exchange (ETDEWEB)
Bass, Jay D. [Univ. of Illinois, Urbana-Champaign, IL (United States)
2015-05-21
This project is aimed at experimental characterization of the sound velocities, equations of state (EOS), and derived physical and chemical properties of aqueous solutions and carbon dioxide at extreme pressure and temperature conditions relevant to processes occurring in the interior of the Earth. Chemical transport, phase changes (including melting), fluid-solid reactions, and formation of magmatic liquids at convergent plat boundaries are a key motivation for this project. Research in this area has long been limited by the extreme experimental challenges and lack of data under the appropriate pressure-temperature (P-T) conditions. The vast majority of studies of aqueous geochemistry relevant to terrestrial problems of fluid-rock interactions have been conducted at 0.3 GPa or less, and the widely used Helgeson-Kirkham-Flowers equation of state for aqueous species is applicable only at ~ < 0.5 GPa. These limits are unfortunate because fluid flow and reactions plays a central role in many deeper environments. Recent efforts including our own, have resulted in new experimental techniques that now make it possible to investigate properties of homogeneous and heterogeneous equilibria involving aqueous species and minerals over a much broader range of pressure and temperature appropriate for deep crustal and upper mantle processes involving water-rich fluids. We carried out 1) Brillouin scattering measurements of the equations of state and molar volume of water and carbon dioxide to over 10 GPa and 870K using precise resistance heating of samples under pressure in the diamond anvil cell, and 2) the phase diagrams of the water and CO2, and 3) Exploring new experimental approaches, including CO2 laser heating of samples in a diamond cell, to measurements of sound velocities, EOS, and phase relations by Brillouin scattering to far greater pressures and temperatures.
Kinetics of homogeneous and surface-catalyzed mercury(II) reduction by iron(II)
Amirbahman, Aria; Kent, Douglas B.; Curtis, Gary P.; Marvin-DiPasquale, Mark C.
2013-01-01
Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5–8.1) and aqueous Fe(II) concentration (0.1–1 mM). The homogeneous rate was best described by the expression, rhom = khom [FeOH+] [Hg(OH)2]; khom = 7.19 × 10+3 L (mol min)−1. Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression rhet = khet [>SOFe(II)] [Hg(OH)2], where >SOFe(II) is the total adsorbed Fe(II) concentration; khet values were 5.36 × 10+3, 4.69 × 10+3, and 1.08 × 10+2 L (mol min)−1 for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.
DEFF Research Database (Denmark)
Grembi, Veronica
2014-01-01
MM first came to the attention of policy makers primarily in the USA where, from the 1970s, healthcare providers denounced problems in getting insurance for medical liability, pointing out to a crisis in the MM insurance market (Sage WM (2003) Understanding the first malpractice crisis of the 21th...... in the last decades also among European countries (Hospitals of the European Union (HOPE) (2004) Insurance and malpractice, final report. Brussels, www.hope.be; OECD (2006) Medical malpractice, insurance and coverage options, policy issues in insurance n.11; EC (European Commission, D.G. Sanco) (2006) Special...... eurobarometer medical errors)...
Energy Technology Data Exchange (ETDEWEB)
Escher, A.; Boulouchos, K.
2007-07-01
This annual report for the Swiss Federal Office of Energy (SFOE), reports on work done in 2007 at the Swiss Federal Institute of Technology ETH in Zurich, Switzerland, on fuels for homogenous, self-igniting combustion processes. A single-stroke engine was used to test the combustion of n-heptane, n-butane and their combinations. The flexibility of the test-bed is discussed and the combustion characteristics observed are described. Also, the results obtained are presented and discussed. Multi-zone simulation and factors influencing the combustion are examined. Ignition and combustion of synthetic, diesel-like fuels are discussed. Co-operation with the project started in 2007 by the Society for Research on Combustion Engines which involves other universities and several industrial companies is noted.
Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity
Directory of Open Access Journals (Sweden)
Papazov Sava P
2003-12-01
Full Text Available Abstract Background Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities. Methods A detailed three-dimensional finite element model (FEM of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils. Results The results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed. Conclusion The model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium.
... for Medication For the treatment of heart failure Beta Blockers (Also known as Beta-Adrenergic Blocking Agents) Commonly ... have had a heart attack. Combined alpha and beta-blockers Combined alpha and beta-blockers are used as ...
... Accredited programs prepare students for a career in academic or research health science centers, industry, or consulting. As members of the health career profession with strong communication skills, medical illustrators work closely with clients to interpret ...
Analyses of beyond design basis accident homogeneous boron dilution scenarios
Energy Technology Data Exchange (ETDEWEB)
Kereszturi, Andras; Hegyi, Gyoergy; Maraczy, Csaba; Trosztel, Istvan; Tota, Adam [Hungarian Academy of Sciences, Centre for Energy Research, Budapest (Hungary); Karsa, Zoltan [NUBIKI Nuclear Safety Research Institute, Ltd., Budapest (Hungary)
2015-09-15
Homogeneous boron dilution scenarios in a VVER-440 reactor were analyzed using the coupled KIKO3D-ATHLET code. The scenarios are named ''homogeneous'' because of the very slow dilution caused by a rupture in the heat exchanger of the makeup system. Without the presented analyses, a significant contribution of the homogeneous boron dilution to the Core Damage Frequency (CDF) had to be assumed in the Probabilistic Safety Analyses (PSA). According to the combined results of the presented deterministic and probabilistic analyses, the final conclusion is that boron dilution transients don't give significant contribution to the CDF for the investigated VVER-440 NPP.
Killing vector fields and a homogeneous isotropic universe
Katanaev, M O
2016-01-01
Some basic theorems on Killing vector fields are reviewed. In particular, the topic of a constant-curvature space is examined. A detailed proof is given for a theorem describing the most general form of the metric of a homogeneous isotropic space-time. Although this theorem can be considered to be commonly known, its complete proof is difficult to find in the literature. An example metric is presented such that all its spatial cross sections correspond to constant-curvature spaces, but it is not homogeneous and isotropic as a whole. An equivalent definition of a homogeneous and isotropic space-time in terms of embedded manifolds is also given.
Homogenization and structural topology optimization theory, practice and software
Hassani, Behrooz
1999-01-01
Structural topology optimization is a fast growing field that is finding numerous applications in automotive, aerospace and mechanical design processes. Homogenization is a mathematical theory with applications in several engineering problems that are governed by partial differential equations with rapidly oscillating coefficients Homogenization and Structural Topology Optimization brings the two concepts together and successfully bridges the previously overlooked gap between the mathematical theory and the practical implementation of the homogenization method. The book is presented in a unique self-teaching style that includes numerous illustrative examples, figures and detailed explanations of concepts. The text is divided into three parts which maintains the book's reader-friendly appeal.
Krishnan, P
1992-01-01
In theory, the Medical Council of India (MCI) determines the standards and qualifications of medical schools. It also sanctions curricula and ensures standards. Yet no standards exist on the mode of selection in medical schools, duration of study, course content, student stipends or period of internship. It takes 4.5 years to finish medical school. Students undergo preclinical, paraclinical, and clinical training. Most courses are in English which tends to favor the urban elite. Students cannot always communicate with patients in local languages. Textbooks often provide medical examples unrelated to India. Pedagogy consists mainly of lectures and rote learning predominates. Curricula tend not to provide courses in community health. Students pick up on the elitist attitudes of the faculty. For example, faculty do not put much emphasis on community health, individual health, equity in health care delivery, and teamwork. Further the education system is not patient oriented, but hospital or disease oriented. Faculty should train students in creating sanitation programs, knowing local nutritious foods, and in making community diagnoses. Yet they tend to be practitioners 1st then educators. Further faculty are not paid well and are not always invited to take part in improving curriculum, so morale is often low. Moreover experience in health planning and management issues is not required for administrators. In addition, medical schools are not well equipped with learning aids, libraries, or teaching staff. Tax revenues finance medical education. 75% of graduating physicians set up a private practice. Further many physicians go to urban areas. 34-57% emigrate to other countries. The problems of medical education will not be solved until the political and economic system becomes more responsive to the health needs of the people.
Antinociceptive activity of Mentha piperita leaf aqueous extract in mice
Directory of Open Access Journals (Sweden)
Yousef A. Taher
2012-03-01
Full Text Available Mentha piperita L. (Labiatae is an herbaceous plant, used in folk medicine for the treatment of several medical disorders.In the present study, the aqueous extract of Mentha piperita leaf, at the i.p doses 200 and 400 mg/kg, showed significant analgesic effects against both acetic acid-induced writhing and hot plate-induced thermal stimulation in mice, with protection values of 51.79% and 20.21% respectively. On the contrary, the Mentha piperita leaf aqueous extract did not exhibit anti-inflammatory activity against carrageenan induced paw oedema.These findings indicate that Mentha piperita has a potential analgesic effect that may possibly have mediated centrally and peripherally, as well as providing a pharmacological evidence for its traditional use as a pain reliever.
Directory of Open Access Journals (Sweden)
G. Ganbavale
2014-05-01
Full Text Available This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K. Water activity (aw at low temperatures (T is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB, differential scanning calorimetry (DSC, and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids and aqueous 2-(2-ethoxyethoxyethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for TTaw can be reversed at low temperatures and that linear extrapolations of high temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.
Kanno, H; Kajiwara, K; Miyata, K
2010-05-21
Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for T(H) (homogeneous ice nucleation temperature) and T(m) (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the T(H) curve for a DMSO solution of R=20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at P(c2)= approximately 200 MPa and at T(c2)temperature of SCP). The presence of two T(H) peaks for DMSO solutions (R=15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (Rtemperatures (different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.
Fractal Dimension as a measure of the scale of Homogeneity
Yadav, Jaswant K; Khandai, Nishikanta
2010-01-01
In the multi-fractal analysis of large scale matter distribution, the scale of transition to homogeneity is defined as the scale above which the fractal dimension of underlying point distribution is equal to the ambient dimension of the space in which points are distributed. With finite sized weakly clustered distribution of tracers obtained from galaxy redshift surveys it is difficult to achieve this equality. Recently we have defined the scale of homogeneity to be the scale above which the deviation of fractal dimension from the ambient dimension becomes smaller than the statistical dispersion. In this paper we use the relation between the fractal dimensions and the correlation function to compute the dispersion for any given model in the limit of weak clustering amplitude. We compare the deviation and dispersion for the LCDM model and discuss the implication of this comparison for the expected scale of homogeneity in the concordant model of cosmology. We estimate the upper limit to the scale of homogeneity...
Spatial variability of chloride in concrete within homogeneously exposed areas
Angst, U.M.; Polder, R.B.
2014-01-01
The concept of variability is increasingly considered in service life predictions. This paper reports experimental data on the spatial distribution of chloride in uncracked concrete subjected to homogeneous exposure. Chloride concentrations were measured with potentiometric sensors embedded in concr
Homogenization of attractors for a class of nonlinear parabolic equations
Institute of Scientific and Technical Information of China (English)
WANG Guo-lian; ZHANG Xing-you
2004-01-01
The relation between the global attractors Aε for a calss of quasilinear parabolic equations and the global attractor A0for the homogenized equation is discussed, and an explicit error estimate between Aε and A0 is given.
Bridging heterogeneous and homogeneous catalysis concepts, strategies, and applications
Li, Can
2014-01-01
This unique handbook fills the gap in the market for an up-to-date work that links both homogeneous catalysis applied to organic reactions and catalytic reactions on surfaces of heterogeneous catalysts.
Reconsideration on Homogeneous Quadratic Riemann Boundary Value Problem
Institute of Scientific and Technical Information of China (English)
Lu Jian-ke
2004-01-01
The homogeneous quadratic Riemann boundary value problem (1) with Hǒlder continuous coefficients for the normal case was considered by the author in 1997. But the solutions obtained there are incomplete. Here its general method of solution is obtained.
Extended Homogeneous Balance Method and Lax Pairs, Backlund Transformation
Institute of Scientific and Technical Information of China (English)
BAI ChengLin
2002-01-01
Using the extended homogeneous balance method, which is very concise and primary, Lax pairs and Backlund transformation for most nonlinear evolution equations, such as the compound KdV-Burgers equation and nonlinear diffusion equation are obtained.
On acoustic band gaps in homogenized piezoelectric phononic materials
Directory of Open Access Journals (Sweden)
Rohan E.
2010-07-01
Full Text Available We consider a composite medium made of weakly piezoelectric inclusions periodically distributed in the matrix which ismade of a different piezoelectricmaterial. Themediumis subject to a periodic excitation with an incidence wave frequency independent of scale ε of the microscopic heterogeneities. Two-scale method of homogenization is applied to obtain the limit homogenized model which describes acoustic wave propagation in the piezoelectric medium when ε → 0. In analogy with the purely elastic composite, the resulting model allows existence of the acoustic band gaps. These are identified for certain frequency ranges whenever the so-called homogenized mass becomes negative. The homogenized model can be used for band gap prediction and for dispersion analysis for low wave numbers. Modeling such composite materials seems to be perspective in the context of Smart Materials design.
Homogenization of temperature field and temperature gradient field
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The homogenization of temperature field and temperature gradient field are very important for many devices, systems and equipments, such as satellites and electronic devices. This paper discusses the distribution optimization of the limited high conductivity material with the simulated annealing algorithm to homogenize the temperature field in a two-dimensional heat conduction problem. At the same time, the temperature gradient field is homogenized with the bionic optimization method. The results show that the two optimization targets are consistent to some extent, while the bionic optimization method could save much computing time. In addition, there are threshold values for the amount of high conductivity material and the ratio of the high conductivity to the low conductivity beyond which further increasing these values brings very little improvement on the homogenization of temperature field and temperature gradient field.
Ice nucleation from aqueous NaCl droplets with and without marine diatoms
Directory of Open Access Journals (Sweden)
P. A. Alpert
2011-06-01
Full Text Available Ice formation in the atmosphere by homogeneous and heterogeneous nucleation is one of the least understood processes in cloud microphysics and climate. Here we describe our investigation of the marine environment as a potential source of atmospheric IN by experimentally observing homogeneous ice nucleation from aqueous NaCl droplets and comparing against heterogeneous ice nucleation from aqueous NaCl droplets containing intact and fragmented diatoms. Homogeneous and heterogeneous ice nucleation are studied as a function of temperature and water activity, a_{w}. Additional analyses are presented on the dependence of diatom surface area and aqueous volume on heterogeneous freezing temperatures, ice nucleation rates, ω_{het}, ice nucleation rate coefficients, J_{het}, and differential and cumulative ice nuclei spectra, k(T and K(T, respectively. Homogeneous freezing temperatures and corresponding nucleation rate coefficients are in agreement with the water activity based homogeneous ice nucleation theory within experimental and predictive uncertainties. Our results confirm, as predicted by classical nucleation theory, that a stochastic interpretation can be used to describe the homogeneous ice nucleation process. Heterogeneous ice nucleation initiated by intact and fragmented diatoms can be adequately represented by a modified water activity based ice nucleation theory. A horizontal shift in water activity, Δa_{w, het} = 0.2303, of the ice melting curve can describe median heterogeneous freezing temperatures. Individual freezing temperatures showed no dependence on available diatom surface area and aqueous volume. Determined at median diatom freezing temperatures for a_{w} from 0.8 to 0.99, ω_{het}~0.11^{+0.06}_{−0.05} s^{−1}, J_{het}~1.0^{+1.16}_{−0.61}×10^{4} cm^{−2}
Zeng, Qinghui; Li, Qin; Ji, Wenyu; Bin, Xue; Song, Jie
2016-05-01
With growing concerns about health issues worldwide, elegant sensors with high sensitivity and specificity for virus/antigens (Ag) detection are urgent to be developed. Homogeneous immunoassays (HIA) are an important technique with the advantages of small sample volumes requirement and pretreatment-free process. HIA are becoming more favorable for the medical diagnosis and disease surveillance than heterogeneous immunoassays. An important subset of HIA relies on the effect of fluorescence resonance energy transfer (FRET) via a donor-acceptor (D-A) platform, e.g., quantum dots (QDs) donor based FRET system. Being an excellent plasmonic material, silver triangular nanoplates (STNPs) have unique advantages in displaying surface plasmon resonance in the visible to near infrared spectral region, which make them a better acceptor for pairing with QDs in a FRET-based sensing system. However, the reported STNPs generally exhibited broad size distributions, which would greatly restrict their application as HIA acceptor for high detection sensitivity and specificity purpose. In this work, uniform STNPs and red-emitting QDs are firstly applied to construct FRET nanoplatform in the advanced HIA and further be exploited for analyzing virus Ag. The uniform STNPs/QDs nanoplatform based medical sensor provides a straightforward and highly sensitive method for Ag analysis in homogeneous form.
Homogenization of aligned “fuzzy fiber” composites
Chatzigeorgiou, George
2011-09-01
The aim of this work is to study composites in which carbon fibers coated with radially aligned carbon nanotubes are embedded in a matrix. The effective properties of these composites are identified using the asymptotic expansion homogenization method in two steps. Homogenization is performed in different coordinate systems, the cylindrical and the Cartesian, and a numerical example are presented. © 2011 Elsevier Ltd. All rights reserved.
The Approach to Steady State Using Homogeneous and Cartesian Coordinates
Directory of Open Access Journals (Sweden)
D. F. Gochberg
2013-01-01
Full Text Available Repeating an arbitrary sequence of RF pulses and magnetic field gradients will eventually lead to a steady-state condition in any magnetic resonance system. While numerical methods can quantify this trajectory, analytic analysis provides significantly more insight and a means for faster calculation. Recently, an analytic analysis using homogeneous coordinates was published. The current work further develops this line of thought and compares the relative merits of using a homogeneous or a Cartesian coordinate system.
Catalysis at the Homogeneous-Heterogeneous Chemistry Interface
Institute of Scientific and Technical Information of China (English)
Howard; Alper
2007-01-01
1 Results Significant progress has been made in recent years in developing efficient, atom economical catalytic reactions of potential applicability to the pharmaceutical, petrochemical, and commodity chemical business sectors. In some cases, homogeneous catalytic processes offer advantages, but in others the use of heterogenized homogeneous catalysis provides a competitive advantage concerning recyclability and catalyst recovery. This presentation will consider new approaches to cyclization reactions a...
Matrix-dependent multigrid-homogenization for diffusion problems
Energy Technology Data Exchange (ETDEWEB)
Knapek, S. [Institut fuer Informatik tu Muenchen (Germany)
1996-12-31
We present a method to approximately determine the effective diffusion coefficient on the coarse scale level of problems with strongly varying or discontinuous diffusion coefficients. It is based on techniques used also in multigrid, like Dendy`s matrix-dependent prolongations and the construction of coarse grid operators by means of the Galerkin approximation. In numerical experiments, we compare our multigrid-homogenization method with homogenization, renormalization and averaging approaches.
On homogeneity and its application in sliding mode control
Bernuau, Emmanuel; Efimov, Denis; Perruquetti, Wilfrid; Polyakov, Andrey
2014-01-01
International audience; The paper is reviewing the tools to handle high-order sliding mode design and robustness. The main ingredient is homogeneity which can be checked using an algebraic test and which helps us in obtaining one of the most desired properties in sliding mode control that is finite-time stability. This paper stresses some recently obtained results about homogeneity for differential inclusions and robustness with respect to perturbations in the context of input-to-state stabil...
Orbits in Homogeneous Oblate Spheroidal Gravitational Space-Time
Directory of Open Access Journals (Sweden)
Chifu E. N.
2009-07-01
Full Text Available The generalized Lagrangian in general relativistic homogeneous oblate spheroidal gravitational fields is constructed and used to study orbits exterior to homogenous oblate spheroids. Expressions for the conservation of energy and angular momentum for this gravitational field are obtained. The planetary equation of motion and the equation of motion of a photon in the vicinity of an oblate spheroid are derived. These equations have additional terms not found in Schwarzschild's space time.
Toledo-Pereyra, Luis H
2015-06-01
The Medical Renaissance started as the regular Renaissance did in the early 1400s and ended in the late 1600s. During this time great medical personalities and scholar humanists made unique advances to medicine and surgery. Linacre, Erasmus, Leonicello and Sylvius will be considered first, because they fit the early classic Renaissance period. Andreas Vesalius and Ambroise Paré followed thereafter, making outstanding anatomical contributions with the publication of the "Human Factory" (1543) by Vesalius, and describing unique surgical developments with the publication of the "The Apologie and Treatise of Ambroise Paré." At the end of the Renaissance and beginning of the New Science, William Harvey, noted British medical doctor and cardiovascular researcher, discovered the general circulation. He published his findings in "The Motu Cordis" in 1628 (Figure 1). The Medical Renaissance, in summary, included a great number of accomplished physicians and surgeons who made especial contributions to human anatomy; Vesalius assembled detailed anatomical information; Paré advanced surgical techniques; and Harvey, a medical genius, detailed the circulatory anatomy and physiology.
Thermoreversible (Ionic-Liquid-Based) Aqueous Biphasic Systems.
Passos, Helena; Luís, Andreia; Coutinho, João A P; Freire, Mara G
2016-02-04
The ability to induce reversible phase transitions between homogeneous solutions and biphasic liquid-liquid systems, at pre-defined and suitable operating temperatures, is of crucial relevance in the design of separation processes. Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have demonstrated superior performance as alternative extraction platforms, and their thermoreversible behaviour is here disclosed by the use of protic ILs. The applicability of the temperature-induced phase switching is further demonstrated with the complete extraction of two value-added proteins, achieved in a single-step. It is shown that these temperature-induced mono(bi)phasic systems are significantly more versatile than classical liquid-liquid systems which are constrained by their critical temperatures. IL-based ABS allow to work in a wide range of temperatures and compositions which can be tailored to fit the requirements of a given separation process.
Radiolysis of berberine or palmatine in aqueous solution
Energy Technology Data Exchange (ETDEWEB)
Marszalek, Milena [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland); Wolszczak, Marian, E-mail: marianwo@mitr.p.lodz.p [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland)
2011-01-15
The reactions of hydrated electron (e{sub aq}{sup -}), hydrogen atom (H{sup {center_dot}}) (reducing species) and Cl{sub 2}{sup {center_dot}}{sup -},Br{sub 2}{sup {center_dot}}{sup -},{sup {center_dot}}N{sub 3},{sup {center_dot}}OH radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of e{sub aq}{sup -} and {sup {center_dot}}OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with e{sub aq}{sup -} and radicals generated during radiolysis are unstable and undergo further reactions.
Li, Zhen-Xing; Xue, Wei; Guan, Bing-Tao; Shi, Fu-Bo; Shi, Zhang-Jie; Jiang, Hong; Yan, Chun-Hua
2013-02-07
Translation of homogeneous catalysis into heterogeneous catalysis is a promising solution to green and sustainable development in chemical industry. For this purpose, noble metal nanoparticles represent a new frontier in catalytic transformations. Many challenges remain for researchers to transform noble metal nanoparticles of heterogeneous catalytic active sites into ionic species of homogeneous catalytic active sites. We report here a successful design on translating homogeneous gold catalysis into a heterogeneous system with a clear understanding of the catalytic pathway. This study initiates a novel concept to immobilize a homogeneous catalyst based on electron transfer between supporting base and supported nanoparticles. Meanwhile, on the basis of theoretical calculation, it has deepened the understanding of the interactions between noble metal nanoparticles and the catalyst support.
DEFF Research Database (Denmark)
Mønsted, Troels Sune
’. Theoretically the project departs from Computer Supported Cooperative Work and Participatory Design and is informed by Medical Informatics, Design Research and Science and Technology Studies. Methodically the project is founded on collaborative prototyping, ethnographic studies, and design interventions...... philosophy and building on theory on narrative reasoning, the dissertation offers the notions of emplotment and re-emplotment to describe how physicians marshal information from various sources, including the medical record, the patient and coSummary to form a narrative, when making sense of patients...
Holden, Elizabeth A
2012-01-01
Leases for medical space can have far-reaching (and sometimes unintentional) consequences for the future of the practice and the costs of the business. In order to prevent hardship and expense down the line, it is especially important to review the lease to make sure that it reflects the practice's goals, needs, and structure. This article provides a number of provisions that are especially crucial to review and negotiate when leasing medical space, including use restrictions, assignment and subleasing clauses, build-out terms, and legal compliance requirements.
Biscari, C
2014-01-01
The use of accelerators for medical applications has evolved from initial experimentation to turn-key devices commonly operating in hospitals. New applications are continuously being developed around the world, and the hadrontherapy facilities of the newest generation are placed at the frontier between industrial production and advanced R&D. An introduction to the different medical application accelerators is followed by a description of the hadrontherapy facilities, with special emphasis on CNAO, and the report closes with a brief outlook on the future of this field.
DEFF Research Database (Denmark)
Musaeus, Peter
2015-01-01
is the study of the sociocultural paragons that conceptually underlie the phenomenology of physician’s coming to take themselves as autonomous social agents. The paper relies on Hegel’s Phenomenology of Spirit and investigates dilemmas pertaining to first objectivist versus subjectivist views and second...... hedonistic versus sentimentalist approaches to medical identity. The sociocultural philosophical analysis of medical identity can shed light on what it means conceptually for a physician to harbor beliefs associated with him/her being taken to be an autonomous professional. It is important because it touches...
Land-use intensification causes multitrophic homogenization of grassland communities
Gossner, Martin M.; Lewinsohn, Thomas M.; Kahl, Tiemo; Grassein, Fabrice; Boch, Steffen; Prati, Daniel; Birkhofer, Klaus; Renner, Swen C.; Sikorski, Johannes; Wubet, Tesfaye; Arndt, Hartmut; Baumgartner, Vanessa; Blaser, Stefan; Blüthgen, Nico; Börschig, Carmen; Buscot, Francois; Diekötter, Tim; Jorge, Leonardo Ré; Jung, Kirsten; Keyel, Alexander C.; Klein, Alexandra-Maria; Klemmer, Sandra; Krauss, Jochen; Lange, Markus; Müller, Jörg; Overmann, Jörg; Pašalić, Esther; Penone, Caterina; Perović, David J.; Purschke, Oliver; Schall, Peter; Socher, Stephanie A.; Sonnemann, Ilja; Tschapka, Marco; Tscharntke, Teja; Türke, Manfred; Venter, Paul Christiaan; Weiner, Christiane N.; Werner, Michael; Wolters, Volkmar; Wurst, Susanne; Westphal, Catrin; Fischer, Markus; Weisser, Wolfgang W.; Allan, Eric
2016-12-01
Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity
2017-03-15
Medic Bleep is a secure instant messaging app that enables clinicians to discuss patient care quickly, securely and legally. It looks and feels like WhatsApp, but has been designed for the healthcare market to enable staff to communicate with each other, and to help speed up conversations between clinicians to increase efficiency.
Low-Cost Fabrication for ZrO2-Based Electrolyte Thin-Substrate by Aqueous Gel-Casting
Institute of Scientific and Technical Information of China (English)
刘晓光; 李国军; 仝建峰; 陈大明
2004-01-01
The possibility to fabricate yttria-stabilized zirconia (YSZ) thin-substrates by aqueous gel casting of high concentrated aqueous slurries was investigated. The effects of dispersant, pH value, and solid content of slurries for gel process on stability and viscosity of slurries were optimized. YSZ thin-substrates green bodies with 100 μm thickness and 100 mm×100 mm flat plate were fabricated. Microstructure observations, density and bending measurements show that these green bodies are homogeneous and highly densified. After sintering at 1873 K×2 h, the ionic conductivity reaches 0.155 S·cm-1 at 1273 K.
Vinay BC; Nikhitha MK; Patel Sunil B
2015-01-01
In this present review article, regarding medication errors its definition, medication error problem, types of medication errors, common causes of medication errors, monitoring medication errors, consequences of medication errors, prevention of medication error and managing medication errors have been explained neatly and legibly with proper tables which is easy to understand.
Zinc chloride aqueous solution as a solvent for starch.
Lin, Meiying; Shang, Xiaoqin; Liu, Peng; Xie, Fengwei; Chen, Xiaodong; Sun, Yongyi; Wan, Junyan
2016-01-20
It is important to obtain starch-based homogeneous systems for starch modification. Regarding this, an important key point is to find cheap, low-cost and low-toxicity solvents to allow complete dissolution of starch and its easy regeneration. This study reveals that a ZnCl2 aqueous solution is a good non-derivatizing solvent for starch at 50 °C, and can completely dissolve starch granules. The possible formation of a "zinc-starch complex" might account for the dissolution; and the degradation of starch, which was caused by the H(+) inZnCl2 aqueous solution, could not contribute to full dissolution. From polarized light microscopic observation combined with the solution turbidity results, it was found that the lowest ZnCl2 concentration for full dissolution was 29.6 wt.% at 50 °C, with the dissolving time being 4h. Using Fourier-transform infrared (FTIR), solid state (13)C nuclear magnetic resonance (NMR), and X-ray diffraction (XRD), it was revealed that ZnCl2 solution had no chemical reaction with starch glucosides, but only weakened starch hydrogen bonding and converted the crystalline regions to amorphous regions. In addition, as shown by intrinsic viscosity and thermogravimetric analysis (TGA), ZnCl2 solution caused degradation of starch macromolecules, which was more serious with a higher concentration of ZnCl2 solution.
Asymmetric Transfer Hydrogenation of ω -Bromo Acetophenones in Aqueous Media
Institute of Scientific and Technical Information of China (English)
Wang Fei; Liu Hui; Cui Xin; Cun Linfeng; Zhu Jin; Deng Jingen; Jiang Yaozhong
2004-01-01
Optical active ω-bromophenylethanols are useful building blocks for synthesis of various pharmaceuticals such as α 1-, β 2-, and β 3- adrenergic receptor agonists, which are always obtained though a biotransformative pathway and using boron reagent with rigorous conditions [1]. To our knowledge, the metal-catalysed transfer hydrogenation is seldom applied in this reaction. Recently we have developed a water-soluble chiral Ru-complex and applied successfully in transfer hydrogenation of ω-bromo acetophenones in aqueous media [2], which can not be performed in homogeneous system with HCOOH/NEt3 as hydrogen donor[3] .In this paper, we will report that asymmetric transfer hydrogenation of ω-bromo acetophenones was successfully performed in aqueous media by employing hydrophobic Rh-amido complex (TsDPEN-Rh) as catalyst and HCOONa as hydrogen donor. Moreover, marked increasing of activity and high enantioselectivity (up to 98%) of ω-bromo acetophenone 1a was found in the presence of different micelles or vesicles. This method was also applied successfully in preparation of the important chiral medicinal intermediates, such as the precursor of salbutamol, 2b and fermoterol, 2c with high enantioselectivity.
HEVC optimizations for medical environments
Fernández, D. G.; Del Barrio, A. A.; Botella, Guillermo; García, Carlos; Meyer-Baese, Uwe; Meyer-Baese, Anke
2016-05-01
HEVC/H.265 is the most interesting and cutting-edge topic in the world of digital video compression, allowing to reduce by half the required bandwidth in comparison with the previous H.264 standard. Telemedicine services and in general any medical video application can benefit from the video encoding advances. However, the HEVC is computationally expensive to implement. In this paper a method for reducing the HEVC complexity in the medical environment is proposed. The sequences that are typically processed in this context contain several homogeneous regions. Leveraging these regions, it is possible to simplify the HEVC flow while maintaining a high-level quality. In comparison with the HM16.2 standard, the encoding time is reduced up to 75%, with a negligible quality loss. Moreover, the algorithm is straightforward to implement in any hardware platform.
Context homogeneity facilitates both distractor inhibition and target enhancement.
Feldmann-Wüstefeld, Tobias; Schubö, Anna
2013-05-06
Homogeneous contexts were shown to result in prioritized processing of embedded targets compared to heterogeneous contexts (Duncan & Humphreys, 1989). The present experiment used behavioral and ERP measures to examine whether context homogeneity affects both enhancing relevant information and inhibiting irrelevant in contexts of varying homogeneity. Targets and distractors were presented laterally or on the vertical midline which allowed disentangling target- and distractor-related activity in the lateralized ERP (Hickey, diLollo, & McDonald, 2009). In homogeneous contexts, targets elicited an NT component from 150 ms on and a PD component from 200 ms on, showing early attention deployment at target locations and active suppression of distractors. In heterogeneous contexts, an NT component was also found from 150 ms on and PD was found from 250 ms on, suggesting delayed suppression of the distractor. Before 250 ms, distractors in heterogeneous contexts elicited a contralateral negativity, indicating attentional capture of the distractor prior to active suppression. In sum the present results suggest that top-down control of attention is more pronounced in homogeneous than in heterogeneous contexts.
Sife-Eldeen, Kh A
2013-04-01
The interest in studying γ-radiation effects on hexamethylenetetramine (HMTA) is due to its importance in nuclear fuel technology. The current study indicates that γ-radiation induces electrical conductivity (RIC) and pH changes in HMTA aqueous solutions. The effects of HMTA concentration, absorbed radiation dose, absorbed dose rate and storage time on RIC and pH changes were studied. HMTA aqueous solutions could be considered as a promising γ-radiation dosimeter, in both technical and medical fields.
Ilmi, Miftahul; Hommes, Arne; Winkelman, Jozef; Hidayat, C.; Heeres, Hero
2016-01-01
The kinetics of sunflower oil transesterification with 1-butanol using a homogeneous lipase (Rhizomucor miehei) in an aqueous-organic biphasic system were studied in a stirred batch reactor set-up. An initial screening study was performed to optimize relevant process conditions (enzyme concentration
Dynamic spreading behavior of homogeneous and heterogeneous networks
Institute of Scientific and Technical Information of China (English)
XIA Chengyi; LIU Zhongxin; CHEN Zengqiang; YUAN Zhuzhi
2007-01-01
The detailed investigation of the dynamic epidemic spreading on homogeneous and heterogeneous networks was carried out. After the analysis of the basic epidemic models, the susceptible-infected-susceptible (SIS) model on homogenous and heterogeneous networks is established, and the dynamical evolution of the density of the infected individuals in these two different kinds of networks is analyzed theoretically. It indicates that heterogeneous networks are easier to propagate for the epidemics and the leading spreading behavior is dictated by the exponential increasing in the initial outbreaks. Large-scale simulations display that the infection is much faster on heterogeneous networks than that on homogeneous ones. It means that the network topology can have a significant effect on the epidemics taking place on complex networks. Some containment strategies of epidemic outbreaks are presented according to the theoretical analyses and numerical simulations.
Permutation-based Homogeneous Block Content Authentication for Watermarking
Directory of Open Access Journals (Sweden)
S.Maruthuperumal
2013-02-01
Full Text Available In modern days, digital watermarking has become an admired technique for hitting data in digital images to help guard against copyright infringement. The proposed Permutation-based Homogeneous Block Content authentication (PHBC methods develop a secure and excellence strong watermarking algorithm that combines the reward of permutation-based Homogeneous block (PHB with that of significant and insignificant bit values with X0R encryption function using Max coefficient of least coordinate value for embedding the watermark. In the projected system uses the relationship between the permutation blocks to embed many data into Homogeneous blocks without causing solemn distortion to the watermarked image. The experimental results show that the projected system is very efficient in achieving perceptual invisibility with an increase in the Peak Signal to Noise Ratio (PSNR. Moreover, the projected system is robust to a variety of signal processing operations, such as image Cropping, Rotation, Resizing, Adding noise, Filtering , Blurring and Motion blurring.
HOMOGENIZATION, SYMMETRY, AND PERIODIZATION IN DIFFUSIVE RANDOM MEDIA
Institute of Scientific and Technical Information of China (English)
Alen Alexanderian; Muruhan Rathinam; Rouben Rostamian
2012-01-01
We present a systematic study of homogenization of diffusion in random media with emphasis on tile-based random microstructures.We give detailed examples of several such media starting from their physical descriptions,then construct the associated probability spaces and verify their ergodicity.After a discussion of material symmetries of random media,we derive criteria for the isotropy of the homogenized limits in tile-based structures.Furthermore,we study the periodization algorithm for the numerical approximation of the homogenized diffusion tensor and study the algorithm's rate of convergence.For one dimensional tile-based media,we prove a central limit result,giving a concrete rate of convergence for periodization.We also provide numerical evidence for a similar central limit behavior in the case of two dimensional tile-based structures.
Classical and quantum dissipation in non homogeneous environments
Illuminati, F; Sodano, P
1994-01-01
We generalize the oscillator model of a particle interacting with a thermal reservoir by introducing arbitrary nonlinear couplings in the particle coordinates.The equilibrium positions of the heat bath oscillators are promoted to space-time functions, which are shown to represent a modulation of the internal noise by the external forces. The model thus provides a description of classical and quantum dissipation in non homogeneous environments. In the classical case we derive a generalized Langevin equation with nonlinear multiplicative noise and a position-dependent fluctuation- dissipation theorem associated to non homogeneous dissipative forces. When time-modulation of the noise is present, a new force term is predicted besides the dissipative and random ones. The model is quantized to obtain the non homogenous influence functional and master equation for the reduced density matrix of the Brownian particle. The quantum evolution equations reproduce the correct Langevin dynamics in the semiclassical limit. T...
A Computationally Based Approach to Homogenizing Advanced Alloys
Energy Technology Data Exchange (ETDEWEB)
Jablonski, P D; Cowen, C J
2011-02-27
We have developed a computationally based approach to optimizing the homogenization heat treatment of complex alloys. The Scheil module within the Thermo-Calc software is used to predict the as-cast segregation present within alloys, and DICTRA (Diffusion Controlled TRAnsformations) is used to model the homogenization kinetics as a function of time, temperature and microstructural scale. We will discuss this approach as it is applied to both Ni based superalloys as well as the more complex (computationally) case of alloys that solidify with more than one matrix phase as a result of segregation. Such is the case typically observed in martensitic steels. With these alloys it is doubly important to homogenize them correctly, especially at the laboratory scale, since they are austenitic at high temperature and thus constituent elements will diffuse slowly. The computationally designed heat treatment and the subsequent verification real castings are presented.
A tree-based model for homogeneous groupings of multinomials.
Yang, Tae Young
2005-11-30
The motivation of this paper is to provide a tree-based method for grouping multinomial data according to their classification probability vectors. We produce an initial tree by binary recursive partitioning whereby multinomials are successively split into two subsets and the splits are determined by maximizing the likelihood function. If the number of multinomials k is too large, we propose to order the multinomials, and then build the initial tree based on a dramatically smaller number k-1 of possible splits. The tree is then pruned from the bottom up. The pruning process involves a sequence of hypothesis tests of a single homogeneous group against the alternative that there are two distinct, internally homogeneous groups. As pruning criteria, the Bayesian information criterion and the Wilcoxon rank-sum test are proposed. The tree-based model is illustrated on genetic sequence data. Homogeneous groupings of genetic sequences present new opportunities to understand and align these sequences.
Scaling of Lyapunov Exponents in Homogeneous, Isotropic DNS
Fitzsimmons, Nicholas; Malaya, Nicholas; Moser, Robert
2013-11-01
Lyapunov exponents measure the rate of separation of initially infinitesimally close trajectories in a chaotic system. Using the exponents, we are able to probe the chaotic nature of homogeneous isotropic turbulence and study the instabilities of the chaotic field. The exponents are measured by calculating the instantaneous growth rate of a linear disturbance, evolved with the linearized Navier-Stokes equation, at each time step. In this talk, we examine these exponents in the context of homogeneous isotropic turbulence with two goals: 1) to investigate the scaling of the exponents with respect to the parameters of forced homogeneous isotropic turbulence, and 2) to characterize the instabilities that lead to chaos in turbulence. Specifically, we explore the scaling of the Lyapunov exponents with respect to the Reynolds number and with respect to the ratio of the integral length scale and the computational domain size.
Defining least community as a homogeneous group in complex networks
Jiang, Bin; Ma, Ding
2015-06-01
This paper introduces a new concept of least community that is as homogeneous as a random graph, and develops a new community detection algorithm from the perspective of homogeneity or heterogeneity. Based on this concept, we adopt head/tail breaks-a newly developed classification scheme for data with a heavy-tailed distribution-and rely on edge betweenness given its heavy-tailed distribution to iteratively partition a network into many heterogeneous and homogeneous communities. Surprisingly, the derived communities for any self-organized and/or self-evolved large networks demonstrate very striking power laws, implying that there are far more small communities than large ones. This notion of far more small things than large ones constitutes a new fundamental way of thinking for community detection.
Defining Least Community as a Homogeneous Group in Complex Networks
Jiang, Bin
2015-01-01
This paper introduces a new concept of least community that is as homogeneous as a random graph, and develops a new community detection algorithm from the perspective of homogeneity or heterogeneity. Based on this concept, we adopt head/tail breaks - a newly developed classification scheme for data with a heavy-tailed distribution - and rely on edge betweenness given its heavy-tailed distribution to iteratively partition a network into many heterogeneous and homogeneous communities. Surprisingly, the derived communities for any self-organized and/or self-evolved large networks demonstrate very striking power laws, implying that there are far more small communities than large ones. This notion of far more small things than large ones constitutes a new fundamental way of thinking for community detection. Keywords: head/tail breaks, ht-index, scaling, k-means, natural breaks, and classification
Homogeneous sample preparation of raw shrimp using dry ice.
Bunch, E A; Altwein, D M; Johnson, L E; Farley, J R; Hammersmith, A A
1995-01-01
Sample homogeneity is critical to accurate and reproducible analysis of trace residues in foods. A method of uniform sample preparation using dry ice is described for shrimp. Other sample preparation techniques for raw shrimp produce nonhomogeneous samples. Sample homogeneity was determined through analysis of chloramphenicol added to intact tiger or white shrimp prior to sample preparation. Simulated chloramphenicol residue levels were 50, 15, 10, and 5 ppb. No significant differences were noted when analyses of shrimp inoculated with chlor-amphenicol prior to sample preparation with dry ice were compared with analyses of shrimp spiked after grinding with dry ice. Grinding shrimp with dry ice produced samples with homogeneous chloramphenicol residues. This technique should be applicable to other tissues and vegetable products.
Improved FFT-based Homogenization for Periodic Media
Vondřejc, Jaroslav
2014-01-01
Moulinec and Suquet introduced FFT-based homogenization in 1994, and twenty years later, their approach is still effective for evaluating the homogenized properties arising from the periodic cell problem. This paper builds on the author's (2013) variational reformulation approximated by trigonometric polynomials establishing two numerical schemes: Galerkin approximation (Ga) and a version with numerical integration (GaNi). The latter approach, fully equivalent to the original Moulinec-Suquet algorithm, was used to evaluate guaranteed upper-lower bounds on homogenized coefficients incorporating a closed-form double grid quadrature. Here, these concepts are employed for the Ga scheme. Despite Ga's higher computational requirements, it outperforms GaNi with improved guaranteed bounds together with more predictable and monotone behaviors for an increase in the number of grid points. Numerical integration heading to block-sparse linear systems is extended here to materials defined via high-resolution images in a w...
Encapsulation of volatiles by homogenized partially-cross linked alginates.
Inguva, Pavan K; Ooi, Shing Ming; Desai, Parind M; Heng, Paul W S
2015-12-30
Cross-linked calcium alginate gels are too viscous to be efficaciously incorporated into spray dried formulations. Thus, viscosity reduction is essential to ensure the processability of calcium alginate gels to be sprayed. Viscosity reduction by high pressure homogenization can open new formulation possibilities. Presently, testing of microcapsule integrity is also limited because either single particle tests neglect collective particle behaviours in bulk or bulk testing methods are often associated with single compressions which may not fully characterize individual particle strengths. The aim of this study was sub-divided into three objectives. First objective was to evaluate the impact of high pressure homogenization on gel viscosity. Second objective was to explore the use of the homogenized gels with modified starch for microencapsulation by spray drying. The final objective was to develop a stamping system as microcapsule strength tester that can assess microcapsules in bulk and evaluate the impact of multiple compressions. Collectively, this study would lead towards developing a pressure-activated patch of microcapsules with encapsulated volatiles and the method to assess the patch efficacy. The alginate gels largely experienced an exponential decay in viscosity when homogenized. Furthermore, the homogenized gels were successfully incorporated in spray drying formulations for microencapsulation. The custom-designed microcapsule strength tester was successfully used and shown to possess the required sensitivity to discern batches of microcapsules containing volatiles to have different release profiles. Addition of homogenized gels strengthened the microcapsules only at high wall to core ratios with low mass-load alginate gels. High mass-load gels weaken the microcapsules, exhibiting a higher release at low stamping pressures and wrinkling on the microcapsules surface.
Stochastic model of milk homogenization process using Markov's chain
Directory of Open Access Journals (Sweden)
A. A. Khvostov
2016-01-01
Full Text Available The process of development of a mathematical model of the process of homogenization of dairy products is considered in the work. The theory of Markov's chains was used in the development of the mathematical model, Markov's chain with discrete states and continuous parameter for which the homogenisation pressure is taken, being the basis for the model structure. Machine realization of the model is implemented in the medium of structural modeling MathWorks Simulink™. Identification of the model parameters was carried out by minimizing the standard deviation calculated from the experimental data for each fraction of dairy products fat phase. As the set of experimental data processing results of the micrographic images of fat globules of whole milk samples distribution which were subjected to homogenization at different pressures were used. Pattern Search method was used as optimization method with the Latin Hypercube search algorithm from Global Optimization Тoolbox library. The accuracy of calculations averaged over all fractions of 0.88% (the relative share of units, the maximum relative error was 3.7% with the homogenization pressure of 30 MPa, which may be due to the very abrupt change in properties from the original milk in the particle size distribution at the beginning of the homogenization process and the lack of experimental data at homogenization pressures of below the specified value. The mathematical model proposed allows to calculate the profile of volume and mass distribution of the fat phase (fat globules in the product, depending on the homogenization pressure and can be used in the laboratory and research of dairy products composition, as well as in the calculation, design and modeling of the process equipment of the dairy industry enterprises.
Delineating relative homogeneous G+C domains in DNA sequences.
Li, W
2001-10-03
The concept of homogeneity of G+C content is always relative and subjective. This point is emphasized and quantified in this paper using a simple example of one sequence segmented into two subsequences. Whether the sequence is homogeneous or not can be answered by whether the two-subsequence model describes the DNA sequence better than the one-sequence model. There are at least three equivalent ways of looking at the 1-to-2 segmentation: Jensen-Shannon divergence measure, log likelihood ratio test, and model selection using Bayesian information criterion. Once a criterion is chosen, a DNA sequence can be recursively segmented into multiple domains. We use one subjective criterion called segmentation strength based on the Bayesian information criterion. Whether or not a sequence is homogeneous and how many domains it has depend on this criterion. We compare six different genome sequences (yeast S. cerevisiae chromosome III and IV, bacterium M. pneumoniae, human major histocompatibility complex sequence, longest contigs in human chromosome 21 and 22) by recursive segmentations at different strength criteria. Results by recursive segmentation confirm that yeast chromosome IV is more homogeneous than yeast chromosome III, human chromosome 21 is more homogeneous than human chromosome 22, and bacterial genomes may not be homogeneous due to short segments with distinct base compositions. The recursive segmentation also provides a quantitative criterion for identifying isochores in human sequences. Some features of our recursive segmentation, such as the possibility of delineating domain borders accurately, are superior to those of the moving-window approach commonly used in such analyses.
Absolute homogeneity test of Kelantan catchment precipitation series
Ros, Faizah Che; Tosaka, Hiroyuki; Sasaki, Kenji; Sidek, Lariyah Mohd; Basri, Hidayah
2015-05-01
Along the Kelantan River in north east of Malaysia Peninsular, there are several areas often damaged by flood during north-east monsoon season every year. It is vital to predict the expected behavior of precipitation and river runoff for reducing flood damages of the area under rapid urbanization and future planning. Nevertheless, the accuracy and reliability of any hydrological and climate studies vary based on the quality of the data used. The factors causing variations on these data are the method of gauging and data collection, stations environment, station relocation and the reliability of the measurement tool affect the homogenous precipitation records. Hence in this study, homogeneity of long precipitation data series is checked via the absolute homogeneity test consisting of four methods namely Pettitt test, standard normal homogeneity test (SNHT), Buishand range test and Von Neumann ratio test. For homogeneity test, the annual rainfall amount from the daily precipitation records at stations located in Kelantan operated by Department of Irrigation and Drainage Malaysia were considered in this study. The missing values were completed using the correlation and regression and inverse distance method. The data network consists of 103 precipitation gauging stations where 31 points are inactive, 6 gauging stations had missing precipitation values more than five years in a row and 16 stations have records less than twenty years. So total of 50 stations gauging stations were evaluated in this analysis. With the application of the mentioned methods and further graphical analysis, inhomogeneity was detected at 4 stations and 46 stations are found to be homogeneous.
Townsend, David W
1996-01-01
Since the introduction of the X-ray scanner into radiology almost 25 years ago, non-invasive imaging has become firmly established as an essential tool in the diagnosis of disease. Fully three-dimensional imaging of internal organs is now possible, b and for studies which explore the functional status of the body. Powerful techniques to correlate anatomy and function are available, and scanners which combine anatomical and functional imaging in a single device are under development. Such techniques have been made possible through r ecent technological and mathematical advances. This series of lectures will review both the physical basis of medical imaging techniques using X-rays, gamma and positron emitting radiosiotopes, and nuclear magnetic resonance, and the mathematical methods used to reconstruct three-dimentional distributions from projection data. The lectures will trace the development of medical imaging from simple radiographs to the present-day non-invasive measurement of in vivo biochemistry. They ...
Successive pH- and heat-induced homogenous liquid-liquid extraction.
Farajzadeh, Mir Ali; Feriduni, Behruz
2016-08-12
A simple and efficient analytical method known as pH- and heat-induced homogenous liquid-liquid extraction combined with high-performance liquid chromatography has been successfully developed for the extraction and determination of neonicotinoid pesticides in aqueous samples. In this method, a few mL of a water-miscible basic extraction solvent is mixed with a high volume of an aqueous phase containing the analytes and passed through a tube which a portion of the tube is filled with sodium carbonate as a separating agent. By passing the solution, salt is dissolved and the fine droplets of the extraction solvent are formed. The produced droplets go up through the remained solution and collect as a separated layer. In the following, the collected organic phase is removed and placed into a micro tube. Then it is heated in a water bath to form two phases. Several experimental parameters that influence extraction efficiency such as type and volume of extraction solvent, type of phase separation agent, temperature, and extraction time were investigated. Under the optimum conditions, the extraction recoveries and enrichment factors ranged between 51 and 81% and 680 and 1080, respectively. Calibration curves showed a high-level of linearity for all target analytes with coefficients of determination ranging between 0.997 and 0.999. The repeatability of the proposed method expressed as relative standard deviation varied between 3 and 5% (n=6, C=50μgL(-1)), and the detection limits were in the range of 0.52-1.0μgL(-1). Finally, the performance of the method was evaluated by analyzing the selected pesticides in different fruit juice and vegetable samples.
Modeling the elution of organic chemicals from a melting homogeneous snow pack.
Meyer, Torsten; Wania, Frank
2011-06-01
Organic chemicals are often released in peak concentrations from melting snow packs. A simple, mechanistic snowmelt model was developed to simulate and predict the elution of organic substances from melting, homogeneous snow, as influenced by chemical properties and snow pack characteristics. The model calculates stepwise the chemical transport along with the melt water flow in a multi-layered snow pack, based on chemical equilibrium partitioning between the individual bulk snow phases. The model succeeds in reproducing the elution behavior of several organic contaminants observed in previously conducted cold room experiments. The model aided in identifying four different types of enrichment of organic substances during snowmelt. Water soluble substances experience peak releases early during a melt period (type 1), whereas chemicals that strongly sorb to particulate matter (PM) or snow grain surfaces elute at the end of melting (type 2). Substances that are somewhat water soluble and at the same time have a high affinity for snow grain surfaces may exhibit increasing concentrations in the melt water (type 3). Finally, elution sequences involving peak loads both at the beginning and the end of melting are simulated for chemicals that are partially dissolved in the aqueous melt water phase and partially sorbed to PM (type 4). The extent of type 1 enrichment mainly depends on the snow depth, whereby deeper snow generates more pronounced concentration peaks. PM influences the elution behavior of organic chemicals strongly because of the very large natural variability in the type and amount of particles present in snow. Urban and road-side snow rich in PM can generate type 2 concentration peaks at the end of the melt period for even relatively water soluble substances. From a clean, melting snow pack typical for remote regions, even fairly hydrophobic chemicals can be released in type 1 mode while being almost completely dissolved in the aqueous melt water phase. The
Photochemical Studies on Aqueous Carboplatin
Institute of Scientific and Technical Information of China (English)
刘伟平; 杨懿昆; 阙振寰; 熊惠周
1994-01-01
The photochemical products,quantum yields and mechanisms of aqueous Carboplatin havebeen studied at 313 and 254 nm irradiation.Excitation in the ligand field bands 1A1→1A2 and 1A1→1E leads tosubstitution reactions,giving diaquodiammineplatinum and tetraaquoplatinum.And then these complexesundergo thermally hydrolysis and polymerization producing polymeric hydroxo-bridged complexes.Oxygen isnot involved in the reactions.Excitation in the charge-transfer band 1A1→1A2u results in redox reaction.Metallic platinum and diaquodiammineplatinum are formed,respectively,in the absence and the presence ofoxygen.
Interfacial forces in aqueous media
van Oss, Carel J
2006-01-01
Thoroughly revised and reorganized, the second edition of Interfacial Forces in Aqueous Media examines the role of polar interfacial and noncovalent interactions among biological and nonbiological macromolecules as well as biopolymers, particles, surfaces, cells, and both polar and apolar polymers. The book encompasses Lifshitz-van der Waals and electrical double layer interactions, as well as Lewis acid-base interactions between colloidal entities in polar liquids such as water. New in this Edition: Four previously unpublished chapters comprising a new section on interfacial propertie
Load Balancing in a Networked Environment through Homogenization
Hossain, M Shahriar; Deb, Debzani; Khan, Kazi Muhammad Najmul Hasan; Joarder, Md Mahbubul Alam
2011-01-01
Distributed processing across a networked environment suffers from unpredictable behavior of speedup due to heterogeneous nature of the hardware and software in the remote machines. It is challenging to get a better performance from a distributed system by distributing task in an intelligent manner such that the heterogeneous nature of the system do not have any effect on the speedup ratio. This paper introduces homogenization, a technique that distributes and balances the workload in such a manner that the user gets the highest speedup possible from a distributed environment. Along with providing better performance, homogenization is totally transparent to the user and requires no interaction with the system.
Massive gravity: nonlinear instability of the homogeneous and isotropic universe
De Felice, Antonio; Mukohyama, Shinji
2012-01-01
We study the propagating modes for nonlinear massive gravity on a Bianchi type--I manifold. We analyze their kinetic terms and dispersion relations as the background manifold approaches the homogeneous and isotropic limit. We show that in this limit, at least one ghost always exists and that its frequency tends to vanish for large scales, meaning that it cannot be integrated out from the low energy effective theory. Since this ghost mode can be considered as a leading nonlinear perturbation around a homogeneous and isotropic background, we conclude that the universe in this theory must be either inhomogeneous or anisotropic.
Note on integrability of certain homogeneous Hamiltonian systems
Energy Technology Data Exchange (ETDEWEB)
Szumiński, Wojciech [Institute of Physics, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland); Maciejewski, Andrzej J. [Institute of Astronomy, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland); Przybylska, Maria, E-mail: M.Przybylska@if.uz.zgora.pl [Institute of Physics, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland)
2015-12-04
In this paper we investigate a class of natural Hamiltonian systems with two degrees of freedom. The kinetic energy depends on coordinates but the system is homogeneous. Thanks to this property it admits, in a general case, a particular solution. Using this solution we derive necessary conditions for the integrability of such systems investigating differential Galois group of variational equations. - Highlights: • Necessary integrability conditions for some 2D homogeneous Hamilton systems are given. • Conditions are obtained analysing differential Galois group of variational equations. • New integrable and superintegrable systems are identified.
Ergodic theory and the duality principle on homogeneous spaces
Gorodnik, Alexander
2012-01-01
We prove mean and pointwise ergodic theorems for the action of a discrete lattice subgroup in a connected algebraic Lie group, on infinite volume homogeneous algebraic varieties. Under suitable necessary conditions, our results are quantitative, namely we establish rates of convergence in the mean and pointwise ergodic theorems, which can be estimated explicitly. Our results give a precise and in most cases optimal quantitative form to the duality principle governing dynamics on homogeneous spaces. We illustrate their scope in a variety of equidistribution problems.
Computational Homogenization of Fresh Concrete Flow Around Reinforcing Bars
Kolařík, Filip; Zeman, Jan
2016-01-01
Motivated by casting of fresh concrete in reinforced concrete structures, we introduce a numerical model of a steady-state non-Newtonian fluid flow through a porous domain. Our approach combines homogenization techniques to represent the reinforced domain by the Darcy law with an interface coupling of the Stokes and Darcy flows through the Beavers-Joseph-Saffman conditions. The ensuing two-scale problem is solved by the Finite Element Method with consistent linearization and the results obtained from the homogenization approach are verified against fully resolved direct numerical simulations.
LETTER TO THE EDITOR: Homogeneous nucleation for superheated crystal
Iwamatsu, Masao
1999-01-01
Homogeneous nucleation of liquid droplets in superheated crystals is considered in order to estimate the maximum superheating of crystals. Using the previously derived universal order parameter model of the crystal-melt transition (Iwamatsu M and Horii K 1996 J. Phys. Soc. Japan 65 2311), it is determined that the catastrophic homogeneous nucleation occurs at 0953-8984/11/1/001/img1, where 0953-8984/11/1/001/img2 is the equilibrium melting point. This numerical estimation is consistent with the results of maximum-superheating experiments.
Homogeneous illusion device exhibiting transformed and shifted scattering effect
Mei, Jin-Shuo; Wu, Qun; Zhang, Kuang; He, Xun-Jun; Wang, Yue
2016-06-01
Based on the theory of transformation optics, a type of homogeneous illusion device exhibiting transformed and shifted scattering effect is proposed in this paper. The constitutive parameters of the proposed device are derived, and full-wave simulations are performed to validate the electromagnetic properties of transformed and shifted scattering effect. The simulation results show that the proposed device not only can visually shift the image of target in two dimensions, but also can visually transform the shape of target. It is expected that such homogeneous illusion device could possess potential applications in military camouflage and other field of electromagnetic engineering.
Homogeneity studies in reference materials with Zeeman solid sampling GFAAS
Energy Technology Data Exchange (ETDEWEB)
Mohl, C.; Stoeppler, M.; Grobecker, K.H.
1987-09-01
The homogeneity of lead and cadmium in reference materials was investigated by solid sampling GFAAS. The following materials were comparatively analyzed: Standard reference materials from NBS, Washington 1567 wheat flour, 1568 rice flour and 1577a bovine liver, certified reference materials from BCR, Brussels, No 63 milk powder, No 184 bovine muscle, No 185 bovine liver, No 186 pig kidney, No 189 wholemeal flour, No 191 brown bread and a whole fish (dab) homogenate from the environmental specimen bank in the FRG. The results are remarkably different for the investigated materials.
Quasi-single-mode homogeneous 31-core fibre
DEFF Research Database (Denmark)
Sasaki, Y.; Saitoh, S.; Amma, Y.
2015-01-01
A homogeneous 31-core fibre with a cladding diameter of 230 μm for quasi-single-mode transmission is designed and fabricated. LP01-crosstalk of -38.4 dB/11 km at 1550 nm is achieved by using few-mode trench-assisted cores.......A homogeneous 31-core fibre with a cladding diameter of 230 μm for quasi-single-mode transmission is designed and fabricated. LP01-crosstalk of -38.4 dB/11 km at 1550 nm is achieved by using few-mode trench-assisted cores....
Analysis of stability of a homogeneous state of anisotropic plasma
Energy Technology Data Exchange (ETDEWEB)
Zakharov, V. Yu., E-mail: vladiyuz@mail.ru; Chernova, T. G., E-mail: chernova-tg@yandex.ru; Stepanov, S. E., E-mail: stepanov@bmstu-kaluga.ru [Bauman Moscow State Technical University, Kaluga Branch (Russian Federation)
2015-04-15
Small-amplitude waves in collisionless magnetized plasma are considered in the framework of one-fluid anisotropic magnetohydrodynamics with allowance for the anisotropy of the pressure and thermal flux. Stability of a homogeneous plasma state is analyzed using an eighth-order dispersion relation. Restrictions on the parameters of the homogeneous state at which the dispersion relation has no complex roots at any value of the angle between the wave vector and the unperturbed magnetic field are obtained. The applied method also makes it possible to determine the types of unstable waves.
On the Mechanical Interaction of Light With Homogeneous Liquids
de Reus, Michiel
2013-01-01
We investigate one of the consequences of the three competing models describing the mechanical interaction of light with a dielectric medium. According to both the Abraham and Minkowski models the time-averaged force density is zero inside a homogeneous dielectric, whereas the induced-current Lorentz force model predicts a non-zero force density. We argue that the latter force, if exists, could drive a hydrodynamic flow inside a homogeneous fluid. Our numerical experiments show that such flows have distinct spatial patterns and may influence the dynamics of particles in a water-based single-beam optical trap.
Malek, Kourosh; van Santen, Rutger A.
Immobilized metal complexes on nanoporous materials have recently been proposed as a novel class of heterogeneous enantioselective catalyst for epoxidation of unfunctionalized olefins as well as hydrogenation, alkylation, and nitroaldol reactions. The porous hosted materials affect catalytic performance due to a cooperative interaction among the nanoporous solid, immobilizing linker, and metal complex asymmetry. The effects of mesoporous materials and immobilizing agents on chiral catalysis are not well understood, however, the catalysts confined in nanopores show comparable or even higher conversions and enantioselectivity compared to their homogeneous counterparts. This chapter highlights major scientific problems for fundamental understanding and design of heterogenized homogeneous catalysts. It describes in detail the pivotal role of a sound framework in physical theory and molecular modeling in systematic efforts towards better materials and catalytic performance optimization. The common threads of the various topics addressed is the wide range of scales that has to be considered in establishing relations between structure, physicochemical properties, and catalytic performance. Physical theory and modeling employ a variety of methods, encompassing ab-initio calculations, molecular simulations, and the continuum model of transport and reaction in nanoporous materials. We particularly describe how molecular simulations can be used to investigate the origin of enantioselectivity of an anchored metal complex in nanoporous materials. These studies provide new insights into the steric effects that relate to choices of substrate and linker and to the interplay with mesopore confinement. We also bring detailed example of employing molecular simulations to unravel the catalytic properties of metallomacrocyclics for the electrochemical reduction of molecular oxygen in aqueous media. We rationalize the importance of immobilization and show how it relates to the steric
Ma, Liang; Tu, Chunlai; Le, Phuong; Chitoor, Shweta; Lim, Sung Jun; Zahid, Mohammad U; Teng, Kai Wen; Ge, Pinghua; Selvin, Paul R; Smith, Andrew M
2016-03-16
Quantum dots are fluorescent nanoparticles used to detect and image proteins and nucleic acids. Compared with organic dyes and fluorescent proteins, these nanocrystals have enhanced brightness, photostability, and wavelength tunability, but their larger size limits their use. Recently, multidentate polymer coatings have yielded stable quantum dots with small hydrodynamic dimensions (≤10 nm) due to high-affinity, compact wrapping around the nanocrystal. However, this coating technology has not been widely adopted because the resulting particles are frequently heterogeneous and clustered, and conjugation to biological molecules is difficult to control. In this article we develop new polymeric ligands and optimize coating and bioconjugation methodologies for core/shell CdSe/Cd(x)Zn(1-x)S quantum dots to generate homogeneous and compact products. We demonstrate that "ligand stripping" to rapidly displace nonpolar ligands with hydroxide ions allows homogeneous assembly with multidentate polymers at high temperature. The resulting aqueous nanocrystals are 7-12 nm in hydrodynamic diameter, have quantum yields similar to those in organic solvents, and strongly resist nonspecific interactions due to short oligoethylene glycol surfaces. Compared with a host of other methods, this technique is superior for eliminating small aggregates identified through chromatographic and single-molecule analysis. We also demonstrate high-efficiency bioconjugation through azide-alkyne click chemistry and self-assembly with hexa-histidine-tagged proteins that eliminate the need for product purification. The conjugates retain specificity of the attached biomolecules and are exceptional probes for immunofluorescence and single-molecule dynamic imaging. These results are expected to enable broad utilization of compact, biofunctional quantum dots for studying crowded macromolecular environments such as the neuronal synapse and cellular cytoplasm.
Furusawa, Naoto
2004-05-01
A simple and hazardous chemical-free method for the high-performance liquid chromatographic determination of oxytetracycline (OTC) residues in milk and eggs has been developed. Sample preparation consists in homogenization with an aqueous solution by means of a handheld ultrasonic homogenizer followed by centrifugal ultrafiltration. HPLC is performed with an isocratic aqueous mobile phase and a photodiode array detector. Average recoveries of OTC (0.05, 0.1, and 0.2 microg mL(-1) for milk; 0.1, 0.2, and 0.4 microg mL(-1) for eggs) were > or =84% with relative standard deviations of < or =2.3%. The total time required for the analysis of one sample and LOQs were <30 min and <0.1 microg mL(-1), respectively. In all the processes, no organic solvents or hazardous reagents were used.
Medical revolution in Argentina.
Ballarin, V L; Isoardi, R A
2010-01-01
The paper discusses the major Argentineans contributors, medical physicists and scientists, in medical imaging and the development of medical imaging in Argentina. The following are presented: history of medical imaging in Argentina: the pioneers; medical imaging and medical revolution; nuclear medicine imaging; ultrasound imaging; and mathematics, physics, and electronics in medical image research: a multidisciplinary endeavor.
Thermal coupling at aqueous and biomolecular interfaces
Shenogina, Natalia B.
Heat flow in the materials with nanoscopic features is dominated by thermal properties of the interfaces. While thermal properties of the solid-solid and solid-liquid interfaces are well studied, research of the thermal transport properties across soft (liquid-liquid) interfaces is very limited. Such interfaces are, however, plentiful in biological systems. In such systems the temperature control is of a great importance, because biochemical reactions, conformation of biomolecules as well as processes in biological cells and membranes have strong temperature sensitivity. The critical ingredient to temperature control in biological systems is the understanding of heat flow and thermal coupling across soft interfaces. To investigate heat transfer across biological and aqueous interfaces we chose to study a number of soft interfacial systems by means of molecular dynamic simulations. One of the interfaces under our investigation is the interface between protein (specifically green fluorescent protein) and water. Using this model we concentrated on the importance of vibrational frequency on coupling between water and proteins, and on significant differences between the roles of low and high frequency vibrations. Our thermal interfacial analysis allowed us to shed new light on to the issue of protein to water slaving, i.e., the concept of water controlling protein dynamics. Considering that the surface of the protein is composed of a complicated mixture of the hydrophobic and hydrophilic domains, to systematically explore the role of interfacial interactions we studied less complicated models with homogenous interfaces whith interfacial chemistry that could be changed in a controlled manner. We demonstrated that thermal transport measurements can be used to probe interfacial environments and to quantify interfacial bonding strength. Such ability provides a unique opportunity to characterize a variety of interfaces, which can be difficult to achieve with more direct
Homogeneous Hyperbolic Systems for Terahertz and Far-Infrared Frequencies
Directory of Open Access Journals (Sweden)
Leonid V. Alekseyev
2012-01-01
Full Text Available We demonstrate that homogeneous naturally-occurring materials can form hyperbolic media, and can be used for nonmagnetic negative refractive index systems. We present specific realizations of the proposed approach for the THz and far-IR frequencies. The proposed structures operate away from resonance, thereby promising the capacity for low-loss devices.
Heterogeneous and homogeneous reactions of pyrolysis vapors from pine wood
Hoekstra, E.; Westerhof, R.J.M.; Brilman, D.W.F.; Swaaij, van W.P.M.; Kersten, S.R.A.; Hogendoorn, J.A.; Windt, M.
2012-01-01
To maximize oil yields in the fast pyrolysis of biomass it is generally accepted that vapors need to be rapidly quenched. The influence of the heterogeneous and homogeneous vapor-phase reactions on yields and oil composition were studied using a fluidized-bed reactor. Even high concentrations of min
Change in Homogeneous and Heterogeneous Sensitivity Training Groups
Pollack, Herbert B.
1971-01-01
Among the findings was that the heterogeneous groups showed more change on the FIRO scale. Also, on rating scales measuring positive feeling towards group, the initial superiority of homogeneous groups was reduced by the end of the T group and that heterogeneous groups manifested more significant increases. (Author/CG)
Kinetic theory of plasma waves: Part II homogeneous plasma
Westerhof, E.
2000-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold
KINETIC THEORY OF PLASMA WAVES: Part II: Homogeneous Plasma
Westerhof, E.
2010-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves are discussed in the limit of the cold
Kinetic theory of plasma waves - Part II: Homogeneous plasma
Westerhof, E.
2008-01-01
The theory of electromagnetic waves in a homogeneous plasma is reviewed. The linear response of the plasma to the waves is obtained in the form of the dielectric tensor. Waves ranging from the low frequency Alfven to the high frequency electron cyclotron waves axe discussed in the limit of the cold
EPR spectroscopy as a tool in homogeneous catalysis research
Goswami, M.; Chirila, A.; Rebreyend, C.; de Bruin, B.
2015-01-01
In the context of homogeneous catalysis, open-shell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often fut
A variational approach to homogeneous scalar fields in General Relativity
Giambo', R; Magli, G
2006-01-01
A result of existence of homogeneous scalar field solutions between prescribed configurations is given, using a modified version of Euler--Maupertuis least action variational principle. Solutions are obtained as limit of approximating variational problems, solved using techniques introduced by Rabinowitz.
Matrix algorithms for solving (in)homogeneous bound state equations.
Blank, M; Krassnigg, A
2011-07-01
In the functional approach to quantum chromodynamics, the properties of hadronic bound states are accessible via covariant integral equations, e.g. the Bethe-Salpeter equation for mesons. In particular, one has to deal with linear, homogeneous integral equations which, in sophisticated model setups, use numerical representations of the solutions of other integral equations as part of their input. Analogously, inhomogeneous equations can be constructed to obtain off-shell information in addition to bound-state masses and other properties obtained from the covariant analogue to a wave function of the bound state. These can be solved very efficiently using well-known matrix algorithms for eigenvalues (in the homogeneous case) and the solution of linear systems (in the inhomogeneous case). We demonstrate this by solving the homogeneous and inhomogeneous Bethe-Salpeter equations and find, e.g. that for the calculation of the mass spectrum it is as efficient or even advantageous to use the inhomogeneous equation as compared to the homogeneous. This is valuable insight, in particular for the study of baryons in a three-quark setup and more involved systems.
High deposition rate nanocrystalline silicon with enhanced homogeneity
Verkerk, A.; Rath, J.K.; Schropp, R.E.I.
2010-01-01
High rate growth of hydrogenated nanocrystalline silicon (nc-Si:H) brings additional challenges for the homogeneity in the growth direction, since the start-up effects affect a larger portion of the film, and the very high degree of depletion increases the influence of back diffusion from the inacti
Modes of Homogeneous Barrier Discharge at Atmospheric Pressure in Helium
Institute of Scientific and Technical Information of China (English)
WANG Yan-Hui; WANG De-Zhen
2004-01-01
@@ The discharge modes of a homogeneous barrier discharge at atmospheric pressure in helium are investigated with a one-dimensional fluid model It is found that, either in single peak discharge or in multipeak discharge, there are two discharge modes: glow and Townsend modes. The structure and features of the two modes are compared.The conditions forming the two modes are discussed.
RELAXATION OF FUNCTIONALS INVOLVING HOMOGENEOUS FUNCTIONS AND INVARIANCE OF ENVELOPES
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The authors compute the quasiconvex envelope of certain functions defined on the space Mmn of real m× n matrices via a homogeneous function on Mmn. They also deduce invariance properties for various convex envelopes from corresponding invariance properties satisfied by a function. Some applications related in particular to nonlinear elasticity are given.
Simple compactifications and polar decomposition of homogeneous real spherical spaces
DEFF Research Database (Denmark)
Knop, Friedrich; Krötz, Bernhard; Sayag, Eitan;
2015-01-01
Let Z be an algebraic homogeneous space Z = G/H attached to real reductive Lie group G. We assume that Z is real spherical, i.e., minimal parabolic subgroups have open orbits on Z. For such spaces, we investigate their large scale geometry and provide a polar decomposition. This is obtained from...
Applying homogeneous catalysis for the synthesis of pharmaceuticals.
Beller, M
2006-01-01
This article describes recent achievements of my research group in the Leibniz-Institut für Katalyse e.V. in the area of applied homogeneous catalysis for the synthesis of biologically active compounds. Special focus is given on the development of novel and practical palladium and copper catalysts for the functionalization of haloarenes and haloheteroarenes.
Synergy between experimental and computational approaches to homogeneous photoredox catalysis.
Demissie, Taye B; Hansen, Jørn H
2016-07-01
In this Frontiers article, we highlight how state-of-the-art density functional theory calculations can contribute to the field of homogeneous photoredox catalysis. We discuss challenges in the fields and potential solutions to be found at the interface between theory and experiment. The exciting opportunities and insights that can arise through such an interdisciplinary approach are highlighted.
Thick Plate Homogenization of Sandwich Panels Including Folded Cellular Cores
LEBEE, Arthur; Sab, Karam
2011-01-01
In the present work, we provide the Bending-Gradient homogenization scheme and apply it to a sandwich panel including the chevron pattern. It turns out that the shear forces stiffness of the sandwich panel is strongly influenced by a skin distortion phenomenon which cannot be neglected in conventional design.
IMPACT OF COOKING HOMOGENEITY ON PULP STRENGTH PROPERTIES
Institute of Scientific and Technical Information of China (English)
Bofeng Mao
2004-01-01
Cooking homogeneity of kraft pulping can have significant impact on pulp strength properties. We have studied cooking homogeneity of two kraft digesters within Stora Enso. One of the digesters is a one-vessel hydraulic continuous digester (digester A)and the other one is a two-vessel vapor/liquor phase continuous digester (digester B). They are located in the same mill and use the same softwood chip quality. Due to the differences in chip pre-steaming and cooking facilities and conditions, significant differences in pulp strength properties, reject contents and kappa variations have been found between the pulps produced in the two digesters. Digester A has a modem chip bin with efficient pre-heating and air removal, whereas digester B has poor chip pre-steaming conditions. Our strength delivery studies show that although the two digesters produce pulps with the same kappa number and viscosity, the pulp produced in digester A has about 20% higher strength delivery, l%-unit (based on wood) lower reject content and lower kappa variations based on FTIR spectra analysis on pulp sheet than the pulp produced in digester B.Results of the studies indicate that more homogeneous cooking, i.e., lower lignin/kappa variation in the fibers, leads to improved pulp strength properties. Efficient chip pre-steaming is important/essential for achieving homogeneous cooking. Rebuilding the equipment for improving chip pre-steaming conditions of digester B is to be carried out.
Nickel N-heterocyclic carbene complexes in homogeneous catalysis
Berding, Joris
2009-01-01
Described in this thesis are the investigations into the chemistry of N-heterocyclic carbene (NHC) ligands and transition-metal complexes thereof. Specifically, a variety of N-heterocyclic carbene complexes of nickel were prepared, characterized and used as catalysts in three types of homogeneous ca
Short wave stability of homogeneous shear flows with variable topography
Institute of Scientific and Technical Information of China (English)
窦华书; V. GANESH
2014-01-01
For the stability problem of homogeneous shear flows in sea straits of arbitrary cross section, a sufficient condition for stability is derived under the condition of inviscid flow. It is shown that there is a critical wave number, and if the wave number of a normal mode is greater than this critical wave number, the mode is stable.
On Euler's Theorem for Homogeneous Functions and Proofs Thereof.
Tykodi, R. J.
1982-01-01
Euler's theorem for homogenous functions is useful when developing thermodynamic distinction between extensive and intensive variables of state and when deriving the Gibbs-Duhem relation. Discusses Euler's theorem and thermodynamic applications. Includes six-step instructional strategy for introducing the material to students. (Author/JN)
Homogeneity of Moral Judgment? Apprentices Solving Business Conflicts.
Beck, Klaus; Heinrichs, Karin; Minnameier, Gerhard; Parche-Kawik, Kirsten
In an ongoing longitudinal study that started in 1994, the moral development of business apprentices is being studied. The focal point of this project is a critical analysis of L. Kohlberg's thesis of homogeneity, according to which people should judge every moral issue from the point of view of their "modal" stage (the most frequently…
Non-Homogeneous Riemann Boundary Value Problem with Radicals
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The solution of the non-homogeneous Riemann boundary value problem with radicals (1.2)together with its condition of solvability is obtained for arbitrary positive integers p and q, which generalizes the results for the case p=q=2.
Are Heterogeneous or Homogeneous Groups More Beneficial to Students?
Schullery, Nancy M.; Schullery, Stephen E.
2006-01-01
This study investigated the relative benefits to the student of working in homogeneous versus heterogeneous classroom groups. Correlation analysis of 18 desirable outcomes versus 8 personality-based heterogeneity variables reveals that heterogeneity associates with advantages as well as disadvantages. Ways in which group composition might be…
On the $psi$-dichotomy for homogeneous linear differential equations
Directory of Open Access Journals (Sweden)
Pham Ngoc Boi
2006-03-01
Full Text Available In this article we present some conditions for the $psi$-dichotomy of the homogeneous linear differential equation $x'=A(tx$. Under our condition every $psi$-integrally bounded function $f$ the nonhomogeneous linear differential equation $x'=A(tx +f(t$ has at least one $psi$-bounded solution on $(0,+infty$.
ON A SET OF h-HARMONIC HOMOGENEOUS POLYNOMIALS
Institute of Scientific and Technical Information of China (English)
Wang Renhong; Zhou Heng
2003-01-01
In this paper, we study the homogeneous polynomials orthogonal with the weight function h (x(d))= x2k11gree n. It is simpler than the formula in [2], and can be regarded as an extension of [1] under the weighted case.
On the transition between heterogeneous and homogeneous freezing
Directory of Open Access Journals (Sweden)
K. Gierens
2002-12-01
Full Text Available Box model simulations of an uplifting and adiabatically cooling cloud of aerosol have been performed in order to study the transition between cirrus formation dominated by homogeneous nucleation of ice to that dominated by heterogeneous nucleation. The aerosol was assumed to consist of an internal mixture of sulfuric acid solution droplets with inclusions of soot. The simulations show that the transition from heterogeneous to homogeneous nucleation occurs over a narrow range of soot concentration. Thus it seems to be possible to fix critical concentrations of heterogeneous ice nuclei which must be exceeded if heterogeneous freezing dominates cirrus formation. A formula has been derived that allows to compute the critical concentrations of heterogeneous ice nuclei as a function of temperature, updraft speed, ambient pressure, and supersaturation at which heterogeneous freezing occurs. Generally, homogeneous nucleation dominates in regions with updrafts stronger than 20 cmps, with the exception of heavily polluted areas which could be common in the northern hemisphere due to air traffic, where updrafts of the order 1 mps may be necessary to render heterogeneous nucleation unimportant. According to the present results it cannot be excluded that heterogeneous nucleation plays a more important role for cirrus formation in the northern midlatitudes than anywhere else. A possible consequence of these results is that air pollution may lead to a higher coverage of cirrus clouds, but then these clouds will be optically thinner than clouds formed by homogeneous freezing, with the exception of regions where condensation trails are frequent.
Homogenization of intergranular fracture towards a transient gradient damage model
Sun, G.; Poh, L. H.
2016-10-01
This paper focuses on the intergranular fracture of polycrystalline materials, where a detailed model at the meso-scale is translated onto the macro-level through a proposed homogenization theory. The bottom-up strategy involves the introduction of an additional macro-kinematic field to characterize the average displacement jump within the unit cell. Together with the standard macro-strain field, the underlying processes are propagated onto the macro-scale by imposing the equivalence of power and energy at the two scales. The set of macro-governing equations and constitutive relations are next extracted naturally as per standard thermodynamics procedure. The resulting homogenized microforce balance recovers the so-called 'implicit' gradient expression with a transient nonlocal interaction. The homogenized gradient damage model is shown to fully regularize the softening behavior, i.e. the structural response is made mesh-independent, with the damage strain correctly localizing into a macroscopic crack, hence resolving the spurious damage growth observed in many conventional gradient damage models. Furthermore, the predictive capability of the homogenized model is demonstrated by benchmarking its solutions against reference meso-solutions, where a good match is obtained with minimal calibrations, for two different grain sizes.
Simulation of homogeneous crystal nucleation close to coexistence
Wolde, P.R. ten; Ruiz-Montero, M.J.; Frenkel, D.
1997-01-01
We discuss a numerical scheme to study homogeneous crystal nucleation. Using this approach, it is possible to compute the height of the free energy barrier that separates the solid from the liquid phase and the rate at which this barrier is crossed. We point out that there is a fundamental differenc
On Homogeneous Production Functions with Proportional Marginal Rate of Substitution
Directory of Open Access Journals (Sweden)
Alina Daniela Vîlcu
2013-01-01
Full Text Available We completely classify homogeneous production functions with proportional marginal rate of substitution and with constant elasticity of labor and capital, respectively. These classifications generalize some recent results of C. A. Ioan and G. Ioan (2011 concerning the sum production function.
Lp-boundedness of flag kernels on homogeneous groups
Glowacki, Pawel
2010-01-01
We prove that the flag kernel singular integral operators of Nagel-Ricci-Stein on a homogeneous group are bounded on the Lp spaces. The gradation associated with the kernels is the natural gradation of the underlying Lie algebra. Our main tools are the Littlewood-Paley theory and a symbolic calculus combined in the spirit of Duoandikoetxea and Rubio de Francia.
Missing data analysis and homogeneity test for Turkish precipitation series
Indian Academy of Sciences (India)
Mahmut Firat; Fatih Dikbas; A Cem Koç; Mahmud Gungor
2010-12-01
In this study, missing value analysis and homogeneity tests were conducted for 267 precipitation stations throughout Turkey. For this purpose, the monthly and annual total precipitation records at stations operated by Turkish State Meteorological Service (DMI) from 1968 to 1998 were considered. In these stations, precipitation records for each month was investigated separately and the stations with missing values for too many years were eliminated. The missing values of the stations were completed by Expectation Maximization (EM) method by using the precipitation records of the nearest gauging station. In this analysis, 38 stations were eliminated because they had missing values for more than 5 years, 161 stations had no missing values and missing precipitation values were completed in the remaining 68 stations. By this analysis, annual total precipitation data were obtained by using the monthly values. These data should be hydrologically and statistically reliable for later hydrological, meteorological, climate change modelling and forecasting studies. For this reason, Standard Normal Homogeneity Test (SNHT), (Swed–Eisenhart) Runs Test and Pettitt homogeneity tests were applied for the annual total precipitation data at 229 gauging stations from 1968 to 1998. The results of each of the testing methods were evaluated separately at a signiﬁcance level of 95% and the inhomogeneous years were determined. With the application of the aforementioned methods, inhomogeneity was detected at 50 stations of which the natural structure was deteriorated and 179 stations were found to be homogeneous.
Medical History: Compiling Your Medical Family Tree
... family medical history, sometimes called a medical family tree, is a record of illnesses and medical conditions ... to consult family documents, such as existing family trees, baby books, old letters, obituaries or records from ...
Smoking cessation - medications; Smokeless tobacco - medications; Medications for stopping tobacco ... Creating a plan to help you deal with smoking urges. Getting support from a doctor, counselor, or ...
Voto Bernales, Juan; Facultad de Medicina, Universidad Nacional Mayor de San Marcos, Lima, Perú
2014-01-01
Medical Physics is to study the physical phenomena that occur in the body and exert action on the agents. It also addresses the manner taught natural agents in the study and exploration of the human body and in the way in the same agents for use in the treatment of disease can be used. La Física Médica tiene por objeto estudiar los fenómenos físicos que se realizan en el organismo y la acción que sobre el ejercen los agentes. Se ocupa, además, de enseñar la manera cómo pueden utilizarse lo...
Troccaz, Jocelyne
2013-01-01
In this book, we present medical robotics, its evolution over the last 30 years in terms of architecture, design and control, and the main scientific and clinical contributions to the field. For more than two decades, robots have been part of hospitals and have progressively become a common tool for the clinician. Because this domain has now reached a certain level of maturity it seems important and useful to provide a state of the scientific, technological and clinical achievements and still open issues. This book describes the short history of the domain, its specificity and constraints, and
Biotic homogenization of three insect groups due to urbanization.
Knop, Eva
2016-01-01
Cities are growing rapidly, thereby expected to cause a large-scale global biotic homogenization. Evidence for the homogenization hypothesis is mostly derived from plants and birds, whereas arthropods have so far been neglected. Here, I tested the homogenization hypothesis with three insect indicator groups, namely true bugs, leafhoppers, and beetles. In particular, I was interested whether insect species community composition differs between urban and rural areas, whether they are more similar between cities than between rural areas, and whether the found pattern is explained by true species turnover, species diversity gradients and geographic distance, by non-native or specialist species, respectively. I analyzed insect species communities sampled on birch trees in a total of six Swiss cities and six rural areas nearby. In all indicator groups, urban and rural community composition was significantly dissimilar due to native species turnover. Further, for bug and leafhopper communities, I found evidence for large-scale homogenization due to urbanization, which was driven by reduced species turnover of specialist species in cities. Species turnover of beetle communities was similar between cities and rural areas. Interestingly, when specialist species of beetles were excluded from the analyses, cities were more dissimilar than rural areas, suggesting biotic differentiation of beetle communities in cities. Non-native species did not affect species turnover of the insect groups. However, given non-native arthropod species are increasing rapidly, their homogenizing effect might be detected more often in future. Overall, the results show that urbanization has a negative large-scale impact on the diversity specialist species of the investigated insect groups. Specific measures in cities targeted at increasing the persistence of specialist species typical for the respective biogeographic region could help to stop the loss of biodiversity.
Detergency of stainless steel surface soiled with human brain homogenate: an XPS study
Energy Technology Data Exchange (ETDEWEB)
Richard, M. [Ecole Centrale de Lyon, UMR 5513 LTDS, 69 134 Ecully (France) and Laboratoires ANIOS, 59 260 Lille-Hellemmes (France)]. E-mail: marlene.richard@ec-lyon.fr; Le Mogne, Th. [Ecole Centrale de Lyon, UMR 5513 LTDS, 69 134 Ecully (France); Perret-Liaudet, A. [Hopital Neurologique de Lyon et INSERM U512, 69 394 Lyon (France); Rauwel, G. [Laboratoires ANIOS, 59 260 Lille-Hellemmes (France); Criquelion, J. [Laboratoires ANIOS, 59 260 Lille-Hellemmes (France); De Barros, M.I. [Ecole Centrale de Lyon, UMR 5513 LTDS, 69 134 Ecully (France); Cetre, J.C. [Unite d' Hygiene et d' Epidemiologie, Hopital de la Croix Rousse, 69 317 Lyon (France); Martin, J.M. [Ecole Centrale de Lyon, UMR 5513 LTDS, 69 134 Ecully (France)
2005-02-15
In the detergency field of re-usable medical devices, a special attention is focused on the non conventional transmissible agent called prions which is a proteinaceous infectious agent. Few cleaning procedures are effective against prions and few techniques are available to study cleaning effectiveness with respect to proteins in general. In our study, X-ray photoelectron spectroscopy (XPS) has been used to evaluate the effectiveness of detergent formulations to remove proteins from stainless steel surface soiled with a brain homogenate (BH) from human origin. Our results showed that XPS is a reliable surface analysis technique to study chemical species remaining on surface and substrate properties after cleaning procedures. A semi-quantitative evaluation of the detergency effectiveness could also be performed.
Ferrigno, Giancarlo; Baroni, Guido; Casolo, Federico; De Momi, Elena; Gini, Giuseppina; Matteucci, Matteo; Pedrocchi, Alessandra
2011-01-01
Information and communication technology (ICT) and mechatronics play a basic role in medical robotics and computer-aided therapy. In the last three decades, in fact, ICT technology has strongly entered the health-care field, bringing in new techniques to support therapy and rehabilitation. In this frame, medical robotics is an expansion of the service and professional robotics as well as other technologies, as surgical navigation has been introduced especially in minimally invasive surgery. Localization systems also provide treatments in radiotherapy and radiosurgery with high precision. Virtual or augmented reality plays a role for both surgical training and planning and for safe rehabilitation in the first stage of the recovery from neurological diseases. Also, in the chronic phase of motor diseases, robotics helps with special assistive devices and prostheses. Although, in the past, the actual need and advantage of navigation, localization, and robotics in surgery and therapy has been in doubt, today, the availability of better hardware (e.g., microrobots) and more sophisticated algorithms(e.g., machine learning and other cognitive approaches)has largely increased the field of applications of these technologies,making it more likely that, in the near future, their presence will be dramatically increased, taking advantage of the generational change of the end users and the increasing request of quality in health-care delivery and management.
Enhanced bioavailability of danazol nanosuspensions by wet milling and high-pressure homogenization
Kanthamneni, Naveen; Valiveti, Satyanarayana; Patel, Mita; Xia, Heather; Tseng, Yin-Chao
2016-01-01
Introduction: The majority of drugs obtained through synthesis and development show poor aqueous solubility and dissolution velocity, resulting in reduced bioavailability of drugs. Most of these problems arise from formulation-related performance issues, and an efficient way to overcome these obstacles and to increase dissolution velocity is to reduce the particle size of drug substances to form drug nanosuspensions. Materials and Methods: Danazol nanosuspensions were prepared by wet milling (WM) and high-pressure homogenization (HPH) methods. The nanosuspensions obtained using these fabrication methods were analyzed for their particle size, surface charge, and the crystallinity of the product was assessed by X-ray diffraction (XRD) and differential scanning calorimetry techniques. To determine in vitro and in vivo performances of the prepared nanosuspensions, dissolution velocity, and bioavailability studies were performed. Results: Particle size and zeta potential analysis showed the formation of nanosized particles with a negative charge on the surface. XRD depicted the nanocrystalline nature of danazol with low diffraction intensities. With increased surface area and saturation solubility, the nanosuspensions showed enhanced dissolution velocity and oral bioavailability in rats when compared to the bulk danazol suspension. Conclusions: The results suggest that the preparation of nanosuspensions by WM or HPH is a promising approach to formulate new drugs or to reformulate existing drugs with poorly water-soluble properties. PMID:28123991
Ghiasvand, A R; Shadabi, S; Mohagheghzadeh, E; Hashemi, P
2005-05-15
A new simple and efficient homogeneous liquid-liquid extraction method for the selective separation and preconcentration of molybdenyl ions was developed. alpha-Benzoin oxime (ABO) was investigated as a complexing ligand, and perfluorooctanoate ion (PFOA(-)) was applied as a phase-separator agent under strongly acidic conditions. Under the optimal conditions ([ABO]=2.1x10(-3)M, [PFOA(-)]=1.8x10(-2)M, [HNO(3)]=1.7M, [acetone]=11.8% (v/v)), 10mug of molybdenum in 5ml aqueous phase could be extracted quantitatively into 40mul of the sedimented phase. The maximum concentration factor was 125-fold. Thiocyanate was applied as a chromogenic reagent for the direct spectrophotometric determination of molybdenum in the sedimented phase. The reproducibility of the proposed method is at the most 2.4%. The influence of the type and concentration of acid solution, the concentration of ABO, the type and volume of the water-miscible organic solvent, the concentration of PFOA(-), and the effect of different diverse ions on the extraction and determination of molybdenum(VI) were investigated. The proposed method was applied to the extraction and determination of molybdenum(VI) in natural water, Spinach, and Lucerne samples. A satisfactory agreement exists between the results obtained by the proposed method and those reported by GF-AAS.
Li, Yong; Zhao, Xiuhua; Zu, Yuangang; Zhang, Yin
2015-07-25
The aim of this study was to develop an alternative, more bio-available, better tolerated paclitaxel nanosuspension (PTXNS) for intravenous injection in comparison with commercially available Taxol(®) formulation. In this study, PTXNS was prepared by emulsification method through combination of high speed homogenizer and high pressure homogenization, followed by lyophilization process for intravenous administration. The main production parameters including volume ratio of organic phase in water and organic phase (Vo:Vw+o), concentration of PTX, content of PTX and emulsification time (Et), homogenization pressure (HP) and passes (Ps) for high pressure homogenization were optimized and their effects on mean particle size (MPS) and particle size distribution (PSD) of PTXNS were investigated. The characteristics of PTXNS, such as, surface morphology, physical status of paclitaxel (PTX) in PTXNS, redispersibility of PTXNS in purified water, in vitro dissolution study and bioavailability in vivo were all investigated. The PTXNS obtained under optimum conditions had an MPS of 186.8 nm and a zeta potential (ZP) of -6.87 mV. The PTX content in PTXNS was approximately 3.42%. Moreover, the residual amount of chloroform was lower than the International Conference on Harmonization limit (60 ppm) for solvents. The dissolution study indicated PTXNS had merits including effect to fast at the side of raw PTX and sustained-dissolution character compared with Taxol(®) formulation. Moreover, the bioavailability of PTXNS increased 14.38 and 3.51 times respectively compared with raw PTX and Taxol(®) formulation.
Rosas, Juan G; Blanco, Marcelo
2012-11-01
This article is the second of a series of two articles detailing the application of mixing index to assess homogeneity distribution in oral pharmaceutical solid dosage forms by image analysis. Chemical imaging (CI) is an emerging technique integrating conventional imaging and spectroscopic techniques with a view to obtaining spatial and spectral information from a sample. Near infrared chemical imaging (NIR-CI) has proved an excellent analytical tool for extracting high-quality information from sample surfaces. The primary objective of this second part was to demonstrate that the approach developed in the first part could be successfully applied to near infrared hyperspectral images of oral pharmaceutical solid dosage forms such as coated, uncoated and effervescent tablets, as well as to powder blends. To this end, we assessed a new criterion for establishing mixing homogeneity by using four different methods based on a three-dimensional (M×N×λ) data array of hyperspectral images (spectral standard deviations and correlation coefficients) or a two-dimensional (M×N) data array (concentration maps and binary images). The four methods were used applying macropixel analysis to the Poole (M(P)) and homogeneity (H%(Poole)) indices. Both indices proved useful for assessing the degree of homogeneity of pharmaceutical samples. The results testify that the proposed approach can be effectively used in the pharmaceutical industry, in the finished products (e.g., tablets) and in mixing unit operations for example, as a process analytical technology tool for the blending monitoring (see part 1).
Aqueous supercapacitors on conductive cotton
Pasta, Mauro
2010-06-01
Wearable electronics offer the combined advantages of both electronics and fabrics. In this article, we report the fabrication of wearable supercapacitors using cotton fabric as an essential component. Carbon nanotubes are conformally coated onto the cotton fibers, leading to a highly electrically conductive interconnecting network. The porous carbon nanotube coating functions as both active material and current collector in the supercapacitor. Aqueous lithium sulfate is used as the electrolyte in the devices, because it presents no safety concerns for human use. The supercapacitor shows high specific capacitance (~70-80 F·g-1 at 0.1 A·g-1) and cycling stability (negligible decay after 35,000 cycles). The extremely simple design and fabrication process make it applicable for providing power in practical electronic devices. © 2010 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.
Soft matter at aqueous interfaces
Liu, Yi
2016-01-01
This book covers the science of interfaces between an aqueous phase and a solid, another liquid or a gaseous phase, starting from the basic physical chemistry all the way to state-of-the-art research developments. Both experimental and theoretical methods are treated thanks to the contributions of a distinguished list of authors who are all active researchers in their respective fields. The properties of these interfaces are crucial for a wide variety of processes, products and biological systems and functions, such as the formulation of personal care and food products, paints and coatings, microfluidic and lab-on-a-chip applications, cell membranes, and lung surfactants. Accordingly, research and expertise on the subject are spread over a broad range of academic disciplines and industrial laboratories. This book brings together knowledge from these different places with the aim of fostering education, collaborations and research progress.
27 CFR 21.96 - Ammonia, aqueous.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Ammonia, aqueous. 21.96 Section 21.96 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT... Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30 percent...
Directory of Open Access Journals (Sweden)
Diana Guzman-Villanueva
2013-01-01
Full Text Available Curcumin, a yellow polyphenol derived from the turmeric Curcuma longa, has been associated with a diverse therapeutic potential including anti-inflammatory, antioxidant, antiviral, and anticancer properties. However, the poor aqueous solubility and low bioavailability of curcumin have limited its potential when administrated orally. In this study, curcumin was encapsulated in a series of novel nano-microparticulate systems developed to improve its aqueous solubility and stability. The nano-microparticulate systems are based entirely on biocompatible, biodegradable, and edible polymers including chitosan, alginate, and carrageenan. The particles were synthesized via ionotropic gelation. Encapsulating the curcumin into the hydrogel nanoparticles yielded a homogenous curcumin dispersion in aqueous solution compared to the free form of curcumin. Also, the in vitro release profile showed up to 95% release of curcumin from the developed nano-microparticulate systems after 9 hours in PBS at pH 7.4 when freeze-dried particles were used.
Burruss, R.C.
1987-01-01
Calculations based on the observed behaviour of inclusions in fluorite under external confining P allows prediction of the T and depths of burial necessary to initiate re-equilibration of aqueous inclusions in the common size range 40-4 mu m. Heating of 20-60oC over the initial trapping T may cause errors of 10-20oC in the homogenization T. This suggests that re-equilibration may cause aqueous inclusions in carbonates to yield a poor record of their low-T history, but a useful record of the maximum T experienced by the host rock. Previous work suggests that inclusions containing petroleum fluids will be less susceptible to re-equilibration.This and the following six abstracts represent papers presented at a joint meeting of the Applied Mineralogy Group of the Mineralogical Society and the Petroleum Group of the Geological Society held in Newcastle upon Tyne in April 1986.-R.A.H.
Electrochemical characterisation of an Os (II) conjugated polymer in aqueous electrolytes
Energy Technology Data Exchange (ETDEWEB)
McCormac, Timothy [CREATE ' Centre for Research in Electroanalytical Technology' , Department of Applied Science, Institute of Technology Tallaght, Tallaght, Dublin 24 (Ireland)]. E-mail: tim.mccormac@it_tallaght.ie; Cassidy, John F. [School of Chemistry, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Crowley, Karl [School of Chemistry, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Trouillet, Lise [Laboratoire d' Electrochimie Moleculaire et Structures des Interfaces, UMR 5819 CEA-CNRS-University Grenoble 1, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Lafolet, Frederic [Laboratoire d' Electrochimie Moleculaire et Structures des Interfaces, UMR 5819 CEA-CNRS-University Grenoble 1, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Guillerez, Stephane [Laboratoire d' Electrochimie Moleculaire et Structures des Interfaces, UMR 5819 CEA-CNRS-University Grenoble 1, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France)
2006-04-25
The electrochemical behaviour of an Os (II) complex of the structurally well-defined conjugated polymer alternating regioregularly alkylated thiophene and 2,2'-bipyridine units (P4Os) has been elucidated in aqueous solution. In typical aqueous electrolyte systems, the cyclic voltammogram of the resulting P4Os film exhibits a one-electron reversible process corresponding to the Os{sup 3+/2+} redox system. However, the observance of this reversible couple did depend upon the concentration of the supporting electrolyte. It was found that the Os{sup 3+} form did form ion-pairs with an anion from the electrolyte solution. Preliminary investigations into the homogeneous charge transport dynamics associated with this redox couple have been undertaken. The technique of cyclic voltammetry, and hence the Randles-Sevick expression, in conjunction with platinum microelectrodes have been employed to determine the D{sub CT}C value.
... Science Education & Training Home Conditions Medication/Drug Allergy Medication/Drug Allergy Make an Appointment Find a Doctor ... immediate or delayed. What Is an Allergy to Medication/Drugs? Allergies to drugs/medications are complicated, because ...
Metal separations using aqueous biphasic partitioning systems
Energy Technology Data Exchange (ETDEWEB)
Chaiko, D.J.; Zaslavsky, B.; Rollins, A.N.; Vojta, Y.; Gartelmann, J.; Mego, W. [Argonne National Lab., IL (United States). Chemical Technology Div.
1996-05-01
Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that the authors have studied are generated by combining an aqueous salt solution with an aqueous polymer solution. They have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. They have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this report they review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.
Energy Technology Data Exchange (ETDEWEB)
Ciliberto, E.; Condorelli, G.G.; La Delfa, S.; Viscuso, E. [Universita di Catania, Dipartimento di Scienze Chimiche, Catania (Italy)
2008-07-15
This paper concerns the synthesis and the characterization of nanometer particles of Sr(OH){sub 2}, a moderately high water soluble hydroxide (Ksp=3.2 x 10{sup -4} at 25 C). The reported process yields strontium hydroxide nanoparticles starting from low cost raw materials in aqueous medium (homogeneous phase) at low temperature (below 100 C) by chemical precipitation from salt solutions, involving very simple operational steps and avoiding the use of organic solvents. Observations by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and Fourier transform infrared spectroscopy (FTIR) indicate that the particles are well-crystallized and have nanometer dimensions ({proportional_to}30 nm in diameter). Moreover, experimental evidence shows the potential use of this material for the protection and the consolidation of wall paintings (frescoes), paper, stone, wood and other artistic artefacts. (orig.)
Institute of Scientific and Technical Information of China (English)
朱文庆; 瞿芳; 陈浩军; 李卓; 刘斌
2014-01-01
SmOHCO3micro/nano particles were prepared in water/oil (W/O) reverse microemulsion composed of cetyltrimethyl ammonium bromide (CTAB), n-octane, n-butanol, Sm(NO3)3·6H2O and urea aqueous solution by the coupling route of homogeneous precipitation with microemulsion. The nanoparticles were characterized and analyzed by X-ray powder diffraction (XRD), thermal gravimetric and differential thermal gravimetric analysis (TG-DTG), Fourier transform infrared absorption spectra (FT-IR) and scan-ning electron microscope (SEM). The results showed that the phase SmOHCO3 micro/nano particles was in agreement with pure or-thorhombic phase. The different morphologies of SmOHCO3 micro/nano particles with good monodispersity and size were obtained by regulating the reaction temperature and reaction time. Possible formation mechanisms of the morphological structure of SmO-HCO3 were proposed and discussed.
Isolation of whiskers from natural sources and their dispersed in a non-aqueous medium
Directory of Open Access Journals (Sweden)
Mauro Vestena
Full Text Available Abstract Whiskers have been used as a nanomaterial dispersed in polymer matrices to modify the microscopic and macroscopic properties of the polymer. These nanomaterials can be isolated from cellulose, one of the most abundant natural renewable sources of biodegradable polymer. In this study, whiskers were isolated from sugarcane bagasse and corn cob straw fibers. Initially, the cellulose fiber was treated through an alkaline/oxidative process followed by acid hydrolysis. Dimethylformamide and dimethyl sulfoxide were used to replace the aqueous medium for the dispersion of the whiskers. For the solvent exchange, dimethylformamide or dimethyl sulfoxide was added to the aqueous dispersion and the water was then removed by fractional distillation. FTIR, TGA, XRD, TEM, Zeta and DLS techniques were used to evaluate the efficiency of the isolation process as well as the morphology and dimensions of the whiskers. The dimensions of the whiskers are comparable with values reported in the literature, maintaining the uniformity and homogeneity in both aqueous and non-aqueous solvents.
Naftali, Timna
2016-02-01
The cannabis plant has been known to humanity for centuries as a remedy for pain, diarrhea and inflammation. Current research is inspecting the use of cannabis for many diseases, including multiple sclerosis, epilepsy, dystonia, and chronic pain. In inflammatory conditions cannabinoids improve pain in rheumatoid arthritis and:pain and diarrhea in Crohn's disease. Despite their therapeutic potential, cannabinoids are not free of side effects including psychosis, anxiety, paranoia, dependence and abuse. Controlled clinical studies investigating the therapeutic potential of cannabis are few and small, whereas pressure for expanding cannabis use is increasing. Currently, as long as cannabis is classified as an illicit drug and until further controlled studies are performed, the use of medical cannabis should be limited to patients who failed conventional better established treatment.
Ferrell, Trinidad L.; Crilly, P. B.; Smith, S. F.; Wintenberg, Alan L.; Britton, Charles L., Jr.; Morrison, Gilbert W.; Ericson, M. N.; Hedden, D.; Bouldin, Donald W.; Passian, A.; Downey, Todd R.; Wig, A. G.; Meriaudeau, Fabrice
1998-05-01
Medical telesensors are self-contained integrated circuits for measuring and transmitting vital signs over a distance of approximately 1-2 meters. The circuits are unhoused and contain a sensor, signal processing and modulation electronics, a spread-spectrum transmitter, an antenna and a thin-film battery. We report on a body-temperature telesensor, which is sufficiently small to be placed on a tympanic membrane in a child's ear. We also report on a pulse-oximeter telesensor and a micropack receiver/long- range transmitter unit, which receives form a telesensor array and analyzes and re-transmits the vital signs over a longer range. Signal analytics are presented for the pulse oximeter, which is currently in the form of a finger ring. A multichip module is presented as the basic signal-analysis component. The module contains a microprocessor, a field=programmable gate array, memory elements and other components necessary for determining trauma and reporting signals.
Representations of Homogeneous Quantum Lévy Fields
Indian Academy of Sciences (India)
V P Belavkin; L Gregory
2006-11-01
We study homogeneous quantum Lévy processes and fields with independent additive increments over a noncommutative ∗-monoid. These are described by infinitely divisible generating state functionals, invariant with respect to an endomorphic injective action of a symmetry semigroup. A strongly covariant GNS representation for the conditionally positive logarithmic functionals of these states is constructed in the complex Minkowski space in terms of canonical quadruples and isometric representations on the underlying pre-Hilbert field space. This is of much use in constructing quantum stochastic representations of homogeneous quantum Lévy fields on Itô monoids, which is a natural algebraic way of defining dimension free, covariant quantum stochastic integration over a space-time indexing set.
A simple construction for a cylindrical cloak via inverse homogenization
Anderson, Tom H; Lakhtakia, Akhlesh
2011-01-01
An effective cylindrical cloak may be conceptualized as an assembly of adjacent local neighbourhoods, each of which is made from a homogenized composite material (HCM). The HCM is required to be a certain uniaxial dielectric-magnetic material, characterized by positive-definite constitutive dyadics. It can arise from the homogenization of remarkably simple component materials, such as two isotropic dielectric-magnetic materials, randomly distributed as oriented spheroidal particles. By carefully controlling the spheroidal shape of the component particles, a high degree of HCM anisotropy may be achieved, which is necessary for the cloaking effect to be realized. The inverse Bruggeman formalism can provide estimates of the shape and constitutive parameters for the component materials, as well as their volume fractions.
Microfluidic converging/diverging channels optimised for homogeneous extensional deformation
Zografos, K.; Oliveira, M. S. N.
2016-01-01
In this work, we optimise microfluidic converging/diverging geometries in order to produce constant strain-rates along the centreline of the flow, for performing studies under homogeneous extension. The design is examined for both two-dimensional and three-dimensional flows where the effects of aspect ratio and dimensionless contraction length are investigated. Initially, pressure driven flows of Newtonian fluids under creeping flow conditions are considered, which is a reasonable approximation in microfluidics, and the limits of the applicability of the design in terms of Reynolds numbers are investigated. The optimised geometry is then used for studying the flow of viscoelastic fluids and the practical limitations in terms of Weissenberg number are reported. Furthermore, the optimisation strategy is also applied for electro-osmotic driven flows, where the development of a plug-like velocity profile allows for a wider region of homogeneous extensional deformation in the flow field. PMID:27478523
Homogenization of long fiber reinforced composites including fiber bending effects
DEFF Research Database (Denmark)
Poulios, Konstantinos; Niordson, Christian Frithiof
2016-01-01
This paper presents a homogenization method, which accounts for intrinsic size effects related to the fiber diameter in long fiber reinforced composite materials with two independent constitutive models for the matrix and fiber materials. A new choice of internal kinematic variables allows...... to maintain the kinematics of the two material phases independent from the assumed constitutive models, so that stress-deformation relationships, can be expressed in the framework of hyper-elasticity and hyper-elastoplasticity for the fiber and the matrix materials respectively. The bending stiffness...... of the reinforcing fibers is captured by higher order strain terms, resulting in an accurate representation of the micro-mechanical behavior of the composite. Numerical examples show that the accuracy of the proposed model is very close to a non-homogenized finite-element model with an explicit discretization...
Homogenization of diffusion processes on scale-free metric networks
Directory of Open Access Journals (Sweden)
Fernando A. Morales
2016-10-01
Full Text Available This work studies the homogenization of diffusion processes on scale-free metric graphs, using weak variational formulations. The oscillations of the diffusion coefficient along the edges of a metric graph induce internal singularities in the global system which, together with the high complexity of large networks constitute significant difficulties in the direct analysis of the problem. At the same time, these facts also suggest homogenization as a viable approach for modeling the global behavior of the problem. To that end, we study the asymptotic behavior of a sequence of boundary problems defined on a nested collection of metric graphs. This paper presents the weak variational formulation of the problems, the convergence analysis of the solutions and some numerical experiments.
Effect of lead attenuators on dose in homogeneous phantoms
Energy Technology Data Exchange (ETDEWEB)
El-Khatib, E.E.; Podgorsak, E.B.; Pla, C.
1986-11-01
In radiotherapy, the radiation beam is sometimes shaped so as to deliver different doses to different organs or give a homogeneous dose to structures of different densities. This objective is achieved by the use of attenuating materials introduced into the beam. These attenuators alter the primary as well as the scattered radiation components of the beam. There is at present no accurate method of dose calculation for these situations. Most calculations are performed considering only the effect of the attenuators on the primary radiation beam and can produce large errors in dosimetry. In the present study, the broad beam attenuation is investigated in homogeneous phantoms for various radiation field sizes, photon beam energies, and depths in phantom. A calculational method taking account of primary as well as first scatter radiation is developed. This method predicts reasonably well the transmission through lead attenuators for the various experimental conditions investigated.
Homogeneous Earthquake Faulting, Stress and Fault Strength on Kilometer Scales
Hardebeck, J. L.
2006-12-01
I investigate small-scale fault structure using three new high-quality focal mechanism datasets of small (MLoma Prieta earthquake. I quantify the degree of mechanism variability on a range of length scales, by comparing the hypocentral distance between every pair of events and the angular difference between their focal mechanisms. I explore the implications of focal mechanism variability for the heterogeneity or homogeneity of stress and fault strength on various length scales. Focal mechanisms are very similar, often identical to within the 1σ uncertainty of ~25°, on small length scales of effect of uncertainty in earthquake locations and focal mechanisms on the apparent mechanism variability. The result that fault geometry, stress and fault strength are generally homogeneous on ~10 km length scales is encouraging for understanding earthquake physics. It may be possible to measure these parameters with enough precision to be useful in studying and modeling large earthquakes and the behavior of major faults.
Role of Clustering Coefficient on Cooperation Dynamics in Homogeneous Networks
Institute of Scientific and Technical Information of China (English)
WU Gang; GAO Kun; YANG Han-Xin; WANG Bing-Hong
2008-01-01
Based on previous works, we give further investigations on the Prisoners' Dilemma Game (PDG) on two different types of homogeneous networks, i.e. the homogeneous small-world network (HSWN) and the regular ring graph. We find that the so-called resonance-like character can occur on both the networks. Different from the viewpoint in previous publications, we think the small-world effect may be unnecessary to produce this character. Therefore, over these two types of networks, we suggest a common understanding in the viewpoint of clustering coefficient. Detailed simulation results can sustain our viewpoint quite well. Furthermore, we investigate the Snowdrift Game (SG) on the same networks. The difference between the outputs of the PDG and the SG can also sustain our viewpoint.
Can photonic crystals be homogenized in higher bands?
Markel, Vadim A
2015-01-01
We consider the conditions under which photonic crystals (PCs) can be viewed as electromagnetically homogeneous at frequencies in the higher photonic bands and, in particular, near the higher-order $\\Gamma$-points. We show that the observation that a purely real isofrequency line of the PC is close to a mathematical circle is insufficient for establishing homogenizability. Complex dispersion points must be included into consideration even in the case of strictly non-absorbing materials. By applying a more careful analysis to the dispersion relations and complex isofrequency lines, we have found that two-dimensional PCs with $C_4$ and $C_6$ symmetries are not electromagnetically homogeneous in the higher photonic bands in spite of the fact that, at some particular frequencies, the real isofrequency lines of these PCs can be circular with high precision.
Self-formed waterfall plunge pools in homogeneous rock
Scheingross, Joel S.; Lo, Daniel Y.; Lamb, Michael P.
2017-01-01
Waterfalls are ubiquitous, and their upstream propagation can set the pace of landscape evolution, yet no experimental studies have examined waterfall plunge pool erosion in homogeneous rock. We performed laboratory experiments, using synthetic foam as a bedrock simulant, to produce self-formed waterfall plunge pools via particle impact abrasion. Plunge pool vertical incision exceeded lateral erosion by approximately tenfold until pools deepened to the point that the supplied sediment could not be evacuated and deposition armored the pool bedrock floor. Lateral erosion of plunge pool sidewalls continued after sediment deposition, but primarily at the downstream pool wall, which might lead to undermining of the plunge pool lip, sediment evacuation, and continued vertical pool floor incision in natural streams. Undercutting of the upstream pool wall was absent, and our results suggest that vertical drilling of successive plunge pools is a more efficient waterfall retreat mechanism than the classic model of headwall undercutting and collapse in homogeneous rock.
Physical librations and possible homogeneity of natural moons from astrometry
Lainey, Valery; Cooper, Nicholas; Murray, Carl; Noyelles, Benoît; Pasewladt, Andreas; Robert, Vincent; Rosenblatt, Pascal; Thuillot, William
2016-10-01
Astrometry is the discipline that aims to provide positions of celestial objects in space with the highest accuracy. Thanks to recent space missions like Mars Express and Cassini, astrometric measurements of moons have allowed the probing of the gravity environment of their systems with unprecedented resolution. Here we focus on the possible determination of physical librations on the rotation of the moons, by modelling their effects on the moons' orbits. Assuming a homogeneous density, a theoretical expectation of the main libration can be computed and compared with possible observed values obtained indirectly from the orbit. In this work, we obtain for Phobos a physical libration of 1.04 +/- 0.02 degrees, in agreement with a homogeneous interior. The case of some of the inner moons of Saturn will be addressed, also.
Lifting, restricting and sifting integral points on affine homogeneous varieties
Gorodnik, Alexander
2010-01-01
In a previous paper {GN2} an effective solution of the lattice point counting problem in general domains in semisimple S-algebraic groups and affine symmetric varieties was established. The method relies on the mean ergodic theorem for the action of G on G/Gamma, and implies uniformity in counting over families of lattice subgroups admitting a uniform spectral gap. In the present paper we extend some methods developed in {NS} and use them to establish several useful consequences of this property, including : Effective upper bounds on lifting for solutions of congruences in affine homogeneous varieties, effective upper bounds on the number of integral points on general subvarieties of semisimple group varieties, effective lower bounds on the number of almost prime points on symmetric varieties, and effective upper bounds on almost prime solutions of Linnik-type congruence problems in homogeneous varieties.
Homogenization of long fiber reinforced composites including fiber bending effects
Poulios, Konstantinos; Niordson, Christian F.
2016-09-01
This paper presents a homogenization method, which accounts for intrinsic size effects related to the fiber diameter in long fiber reinforced composite materials with two independent constitutive models for the matrix and fiber materials. A new choice of internal kinematic variables allows to maintain the kinematics of the two material phases independent from the assumed constitutive models, so that stress-deformation relationships, can be expressed in the framework of hyper-elasticity and hyper-elastoplasticity for the fiber and the matrix materials respectively. The bending stiffness of the reinforcing fibers is captured by higher order strain terms, resulting in an accurate representation of the micro-mechanical behavior of the composite. Numerical examples show that the accuracy of the proposed model is very close to a non-homogenized finite-element model with an explicit discretization of the matrix and the fibers.
Electrical model of dielectric barrier discharge homogenous and filamentary modes
López-Fernandez, J. A.; Peña-Eguiluz, R.; López-Callejas, R.; Mercado-Cabrera, A.; Valencia-Alvarado, R.; Muñoz-Castro, A.; Rodríguez-Méndez, B. G.
2017-01-01
This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results.
The IDSA and the homogeneous sphere: Issues and possible improvements
Michaud, Jérôme
2016-01-01
In this paper, we are concerned with the study of the Isotropic Diffusion Source Approximation (IDSA) (Baxter et al., Phys. Rev. E 73, 046118, 2006) of radiative transfer. After having recalled well-known limits of the radiative transfer equation, we present the IDSA and adapt it to the case of the homogeneous sphere. We then show that for this example the IDSA suffers from severe numerical difficulties. We argue that these difficulties originate in the min-max switch coupling mechanism used in the IDSA. To overcome this problem we reformulate the IDSA to avoid the problematic coupling. This allows us to access the modeling error of the IDSA for the homogeneous sphere test case. The IDSA is shown to overestimate the streaming component, hence we propose a new version of the IDSA which is numerically shown to be more accurate than the old one. Analytical results and numerical tests are provided to support the accuracy of the new proposed approximation.
Mixing and chemical reaction in sheared and nonsheared homogeneous turbulence
Leonard, Andy D.; Hill, James C.
1992-01-01
Direct numerical simulations were made to examine the local structure of the reaction zone for a moderately fast reaction between unmixed species in decaying, homogeneous turbulence and in a homogeneous turbulent shear flow. Pseudospectral techniques were used in domains of 64 exp 3 and higher wavenumbers. A finite-rate, single step reaction between non-premixed reactants was considered, and in one case temperature-dependent Arrhenius kinetics was assumed. Locally intense reaction rates that tend to persist throughout the simulations occur in locations where the reactant concentration gradients are large and are amplified by the local rate of strain. The reaction zones are more organized in the case of a uniform mean shear than in isotropic turbulence, and regions of intense reaction rate appear to be associated with vortex structures such as horseshoe vortices and fingers seen in mixing layers. Concentration gradients tend to align with the direction of the most compressive principal strain rate, more so in the isotropic case.
Effectiveness of layered stemming in comparison with homogeneous stemming
Energy Technology Data Exchange (ETDEWEB)
Pitts, J. H.
1976-04-01
Stemming materials utilized to fill emplacement holes at the Nevada Test Site must have a permeability small enough to prevent release of radioactive materials into the atmosphere following an experimental underground nuclear explosion. Ideal gas flow characteristic of a layered stemming column in comparison to a homogeneous stemming column when one end is exposed to a noncondensible gas source at constant pressure was examined. Although the analysis was completed in one-dimensional Cartesian coordinates, extension of the results is two-dimensional flow fields is approximated by considering parallel flow paths around the low permeability layers when the formation permeability is large. Application to cases where condensible gases are present, can be expected to give similar comparative results between layered and homogeneous stemming columns. (TFD)
Waveform relaxation for the computational homogenization of multiscale magnetoquasistatic problems
Niyonzima, I.; Geuzaine, C.; Schöps, S.
2016-12-01
This paper proposes the application of the waveform relaxation method to the homogenization of multiscale magnetoquasistatic problems. In the monolithic heterogeneous multiscale method, the nonlinear macroscale problem is solved using the Newton-Raphson scheme. The resolution of many mesoscale problems per Gauß point allows to compute the homogenized constitutive law and its derivative by finite differences. In the proposed approach, the macroscale problem and the mesoscale problems are weakly coupled and solved separately using the finite element method on time intervals for several waveform relaxation iterations. The exchange of information between both problems is still carried out using the heterogeneous multiscale method. However, the partial derivatives can now be evaluated exactly by solving only one mesoscale problem per Gauß point.
New method to quantitatively evaluate the homogeneity of asphalt mixtures
Institute of Scientific and Technical Information of China (English)
WU Wen-liang; ZHANG Xiao-ning; WANG Duan-yi; LI Zhi
2009-01-01
To evaluate the homogeneity of asphalt mixtures, the images of sections obtained by cutting the as-phah mixtures specimen horizontally or vertically were analyzed with digital image processing techniques, and the particle area ratio was achieved by applying sector scan for horizontal specimen and vertical scan for vertical one. The research result indicates that the influence of random distribution of aggregates in cutting the specimen can be eliminated by using colored aggregates to distinguish coarse and fine aggregates and using color threshold to segment the images. Choosing three typical gradations, proving particle area ratio obeying normal distribution and using the variability of particle area ratio as an index, it is feasible to quantitatively evaluate the homogenei-ty of asphalt mixtures.
Exploring the Kibble-Zurek mechanism with homogeneous Bose gases
Beugnon, J
2016-01-01
Out-of-equilibrium phenomena is a subject of considerable interest in many fields of physics. Ultracold quantum gases, which are extremely clean, well-isolated and highly controllable systems, offer ideal platforms to investigate this topic. The recent progress in tailoring trapping potentials now allows the experimental production of homogeneous samples in custom geometries, which is a key advance for studies of the emergence of coherence in interacting quantum systems. Here we review recent experiments in which temperature quenches have been performed across the Bose-Einstein condensation (BEC) phase transition in an annular geometry and in homogeneous 3D and quasi-2D gases. Combined, these experiments give a comprehensive picture of the Kibble-Zurek (KZ) scenario through complementary measurements of correlation functions and topological defects density. They also allow the measurement of KZ scaling laws, the direct confirmation of the "freeze-out" hypothesis that underlies the KZ theory, and the extractio...
Antioxidant effects of calcium antagonists in rat brain homogenates.
Yao, K; Ina, Y; Nagashima, K; Ohmori, K; Ohno, T
2000-06-01
We studied the antioxidant activities of calcium antagonists against autoxidation in rat brain homogenates. The homogenates were incubated for 30 min at 37 degrees C with or without a calcium antagonist and subsequently assayed for lipid peroxide content. Percent inhibition of the lipid peroxidation was used as an index of the antioxidant effect. Dihydropyridine calcium antagonists exhibited concentration-dependent (3-300 micromol/l) inhibitory effects against lipid peroxidation. The relative order of antioxidant potency and associated IC50 values (micromol/l) of the calcium antagonists for inhibition of the lipid peroxidation were as follows: nifedipine (51.5)>barnidipine (58.6)>benidipine (71.2)>nicardipine (129.3)>amlodipine (135.5)>nilvadipine (167.3)>nitrendipine (252.1)> diltiazem (>300)=verapamil (>300). These results suggest that some dihydropyridine calcium antagonists show antioxidant properties. The antioxidant effects of the calcium antagonists may contribute to their pharmacological actions.
Some variance reduction methods for numerical stochastic homogenization.
Blanc, X; Le Bris, C; Legoll, F
2016-04-28
We give an overview of a series of recent studies devoted to variance reduction techniques for numerical stochastic homogenization. Numerical homogenization requires that a set of problems is solved at the microscale, the so-called corrector problems. In a random environment, these problems are stochastic and therefore need to be repeatedly solved, for several configurations of the medium considered. An empirical average over all configurations is then performed using the Monte Carlo approach, so as to approximate the effective coefficients necessary to determine the macroscopic behaviour. Variance severely affects the accuracy and the cost of such computations. Variance reduction approaches, borrowed from other contexts in the engineering sciences, can be useful. Some of these variance reduction techniques are presented, studied and tested here.
Homogeneous Catalysis with Metal Complexes Fundamentals and Applications
Duca, Gheorghe
2012-01-01
The book about homogeneous catalysis with metal complexes deals with the description of the reductive-oxidative, metal complexes in a liquid phase (in polar solvents, mainly in water, and less in nonpolar solvents). The exceptional importance of the redox processes in chemical systems, in the reactions occuring in living organisms, the environmental processes, atmosphere, water, soil, and in industrial technologies (especially in food-processing industries) is discussed. The detailed practical aspects of the established regularities are explained for solving the specific practical tasks in various fields of industrial chemistry, biochemistry, medicine, analytical chemistry and ecological chemistry. The main scope of the book is the survey and systematization of the latest advances in homogeneous catalysis with metal complexes. It gives an overview of the research results and practical experience accumulated by the author during the last decade.
Desertification, salinization, and biotic homogenization in a dryland river ecosystem
Miyazono, S.; Patino, Reynaldo; Taylor, C.M.
2015-01-01
This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977-1989) and current (2010-2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t-test (variability). Trends in hydrological conditions (1970s-2010s) were examined by Kendall tau and quantile regression, and associations between streamfiow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was > 2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and
Studies of the Beetle 1.2 Pipeline Homogeneity
Agari, M; Blouw, J; Schmelling, M; Hofmann, W; Schwingenheuer, B; Pugatch, V; Volyanskyy, D; Jiménez-Otero, S; Tran, M T; Voss, H; Bernhard, R P; Köstner, S; Lehner, F; Lois, C; Needham, M; Steinkamp, O; Straumann, U; Vollhardt, A
2003-01-01
The pipeline homogeneity in general and the behaviour of the edge channels of the Beetle 1.2 readout chip [1] were studied with data taken during the Silicon Tracker test beam period in May 2003. A contribution of roughly 10\\% from pipeline inhomogeneities to the strip noise was observed. All channels including the first and the last one were found to be fully functional.
A Simple First-Principles Homogenization Theory for Chiral Metamaterials
Directory of Open Access Journals (Sweden)
Carlo Rizza
2015-04-01
Full Text Available We discuss a simple first-principles homogenization theory for describing, in the long-wavelength limit, the effective bianisotropic response of a periodic metamaterial composite without intrinsic chiral and magnetic inclusions. In the case where the dielectric contrast is low, we obtain a full analytical description which can be considered the extension of Landau-Lifshitz-Looyenga effective-medium formulation in the context of periodic metamaterials.
Research on homogeneous deformation of electromagnetic incremental tube bulging
Cui, Xiaohui; Mo, Jianhua; Li, Jianjun
2014-01-01
The electromagnetic incremental forming (EMIF) method is used for tube forming process. Suitable 2D FE models are designed to predict the forming process with a moving coil. In comparison with experimental values, simulation method can obtain accurate results. Then, effect factors named overlapping ration of adjacent discharge positions, discharge voltage, forming sequence and die dimension on tube homogeneous deformation are discussed. The result demonstrates that it is feasib...
Radiation Resistance and Gain of Homogeneous Ring Quasi-Array
DEFF Research Database (Denmark)
Knudsen, H. L.
1954-01-01
In a previous paper homogeneous ring quasi-arrays of tangential or radial dipoles were introduced, i.e. systems of dipoles arranged equidistantly along a circle, the dipoles being oriented in tangential or radial directions and carrying currents with the same amplitude, but with a phase......-arrays of an infinite number of tangential or radial dipoles, and from the results arrived at conclusions are drawn as to the applicability of such antenna systems...
Homogeneous Charge Compression Ignition Combustion of Dimethyl Ether
Pedersen, Troels Dyhr; Schramm, Jesper
2011-01-01
This thesis is based on experimental and numerical studies on the use of dimethyl ether (DME) in the homogeneous charge compression ignition (HCCI) combustion process. The first paper in this thesis was published in 2007 and describes HCCI combustion of pure DME in a small diesel engine. The tests were designed to investigate the effect of engine speed, compression ratio and equivalence ratio on the combustion timing and the engine performance. It was found that the required compression ratio...
On generalized Gaussian free fields and stochastic homogenization
Gu, Yu; Mourrat, Jean-Christophe
2016-01-01
We study a generalization of the notion of Gaussian free field (GFF). Although the extension seems minor, we first show that a generalized GFF does not satisfy the spatial Markov property, unless it is a classical GFF. In stochastic homogenization, the scaling limit of the corrector is a possibly generalized GFF described in terms of an "effective fluctuation tensor" that we denote by $\\mathsf{Q}$. We prove an expansion of $\\mathsf{Q}$ in the regime of small ellipticity ratio. This expansion ...
Electromagnetic Radiation in a Uniformly Moving, Homogeneous Medium
DEFF Research Database (Denmark)
Johannsen, Günther
1972-01-01
A new method of treating radiation problems in a uniformly moving, homogeneous medium is presented. A certain transformation technique in connection with the four-dimensional Green's function method makes it possible to elaborate the Green's functions of the governing differential equations in th...... in the rest system of the medium, whereas the final integrals determining the field may be calculated in the rest system of the source. ©1972 The American Institute of Physics...
Genetic background of clinical homogeneity of phenylketonuria in Poland.
Jaruzelska, J; Matuszak, R; Lyonnet, S; Rey, F; Rey, J; Filipowicz, J; Borski, K; Munnich, A.
1993-01-01
In order to elucidate the clinical homogeneity and severity of the hyperphenylalaninaemias in Poland, a total of 71 children with typical phenylketonuria (PKU) originating from western and northern Poland were screened for 13 mutations in the phenylalanine hydroxylase (PAH) gene. Eighty percent of all PKU alleles tested were found to carry an identified mutation. One mutation, namely the R408W mutation, accounted for more than 63% of mutant PAH alleles in Poland, the other 27% being accounted...
Optimal Layout of Transshipment Facilities on An Infinite Homogeneous Plane
Xie, Weijun; Ouyang, Yanfeng
2014-01-01
This paper studies optimal spatial layout of transshipment facilities and the corresponding service regions on an infinite homogeneous plane $\\mathbb{R}^2$ that minimize the total cost for facility set-up, outbound delivery and inbound replenishment transportation. The problem has strong implications in the context of freight logistics and transit system design. This paper first focuses on a Euclidean plane and presents a new proof for the known Gersho's conjecture, which states that the opti...
Generating and controlling homogeneous air turbulence using random jet arrays
Carter, Douglas; Petersen, Alec; Amili, Omid; Coletti, Filippo
2016-12-01
The use of random jet arrays, already employed in water tank facilities to generate zero-mean-flow homogeneous turbulence, is extended to air as a working fluid. A novel facility is introduced that uses two facing arrays of individually controlled jets (256 in total) to force steady homogeneous turbulence with negligible mean flow, shear, and strain. Quasi-synthetic jet pumps are created by expanding pressurized air through small straight nozzles and are actuated by fast-response low-voltage solenoid valves. Velocity fields, two-point correlations, energy spectra, and second-order structure functions are obtained from 2D PIV and are used to characterize the turbulence from the integral-to-the Kolmogorov scales. Several metrics are defined to quantify how well zero-mean-flow homogeneous turbulence is approximated for a wide range of forcing and geometric parameters. With increasing jet firing time duration, both the velocity fluctuations and the integral length scales are augmented and therefore the Reynolds number is increased. We reach a Taylor-microscale Reynolds number of 470, a large-scale Reynolds number of 74,000, and an integral-to-Kolmogorov length scale ratio of 680. The volume of the present homogeneous turbulence, the largest reported to date in a zero-mean-flow facility, is much larger than the integral length scale, allowing for the natural development of the energy cascade. The turbulence is found to be anisotropic irrespective of the distance between the jet arrays. Fine grids placed in front of the jets are effective at modulating the turbulence, reducing both velocity fluctuations and integral scales. Varying the jet-to-jet spacing within each array has no effect on the integral length scale, suggesting that this is dictated by the length scale of the jets.
POLYMERIZATION MECHANISM OF DIENES WITH HOMOGENEOUS RARE EARTH CATALYSTS
Institute of Scientific and Technical Information of China (English)
JIN Yingtai; ZHANG Xitian; PEI Fengkui; WU Yue
1990-01-01
The reaction mechanisms ofdiene polymerization with homogeneous rare earth catalyst are studied by means of the spectra of 1H- NM R, one- and two- dimensions 13C-NMR. Based on the data of above NMR spectra, it is proposed that the polymerization reaction proceeds according to the following mechanism: η4-diene (cis- (→)trans- )and η3-allyl (syn- (→)anti- ).
Homogenization of soil properties map by Principal Component Analysis
Valverde Arias, Omar; Garrido, Alberto; Villeta, Maria; Tarquis, Ana Maria
2016-04-01
It is widely known that extreme climatic phenomena occur with more intensity and frequency. This fact has put more pressure over farming, becoming very important to implement agriculture risk management policies by governments and institutions. One of the main strategies is transfer risk by agriculture insurance. Agriculture insurance based in indexes has gained importance in the last decade. And consist in a comparison between measured index values with a defined threshold that triggers damage losses. However, based index insurance could not be based on an isolated measurement. It is necessary to be integrated in a complete monitoring system that uses many sources of information and tools. For example, index influence areas, crop production risk maps, crop yields, claim statistics, and so on. To establish index influence area is necessary to have a secondary information that show us homogeneous climatic and soil areas, which inside of each homogeneous classes, index measurements on crops of interest are going to be similar, and in this way reduce basis risk. But it is necessary an efficient method to accomplish this aim, to get homogeneous areas that not depends on only in expert criteria and that could be widely used, for this reason this study asses two conventional agricultural and geographic methods (control and climatic maps) based in expert criteria, and one classical statistical method of multi-factorial analysis (factorial map), all of them to homogenize soil and climatic characteristics. Resulting maps were validated by agricultural and spatial analysis, obtaining very good results in statistical method (Factorial map) that proves to be an efficient and accuracy method that could be used for similar porpoises.
Homogeneity Property of Besov and Triebel-Lizorkin Spaces
Directory of Open Access Journals (Sweden)
Cornelia Schneider
2012-01-01
Full Text Available We consider the classical Besov and Triebel-Lizorkin spaces defined via differences and prove a homogeneity property for functions with bounded support in the frame of these spaces. As the proof is based on compact embeddings between the studied function spaces, we present also some results on the entropy numbers of these embeddings. Moreover, we derive some applications in terms of pointwise multipliers.
Quantum product and parabolic orbits in homogeneous spaces
Pech, Clélia
2012-01-01
Chaput, Manivel and Perrin proved a formula describing the quantum product by Schubert classes associated to cominuscule weights in a rational projective homogeneous space X. In the case where X has Picard rank one, we link this formula to the stratification of X by P-orbits, where P is the parabolic subgroup associated to the cominuscule weight. We deduce a decomposition of the Hasse diagram of X, i.e the diagram describing the cup-product with the hyperplane class.
On the transition between heterogeneous and homogeneous freezing
Directory of Open Access Journals (Sweden)
K. Gierens
2003-01-01
Full Text Available Box model simulations of an uplifting and adiabatically cooling cloud of aerosol have been performed in order to study the transition between cirrus formation dominated by homogeneous nucleation of ice to that dominated by heterogeneous nucleation. The aerosol was assumed to consist of an internal mixture of sulfuric acid solution droplets with inclusions of soot. The parametrisation of De Mott et al. (1997 was used to simulate the heterogeneous nucleation of ice in such droplets with soot inclusions. The simulations show that the transition from heterogeneous to homogeneous nucleation occurs over a narrow range of soot concentration. Thus it seems to be possible to fix critical concentrations of heterogeneous ice nuclei which must be exceeded if heterogeneous freezing dominates cirrus formation. A formula has been derived that allows to compute the critical concentrations of heterogeneous ice nuclei as a function of temperature, updraft speed, ambient pressure, and supersaturation at which heterogeneous freezing occurs. Generally, homogeneous nucleation dominates in regions with updrafts stronger than 20 cm s -1, with the exception of heavily polluted areas which could be common in the northern hemisphere due to air traffic, where updrafts of the order 1 m s-1 may be necessary to render heterogeneous nucleation unimportant. According to the present results it cannot be excluded that heterogeneous nucleation plays a more important role for cirrus formation in the northern midlatitudes than anywhere else. A possible consequence of these results is that air pollution may lead to a higher coverage of cirrus clouds, but then these clouds will be optically thinner than clouds formed by homogeneous freezing, with the exception of regions where condensation trails are frequent.
Comment on evidence for surface-initiated homogenous nucleation
Directory of Open Access Journals (Sweden)
J. E. Kay
2003-01-01
Full Text Available We investigate theoretical, laboratory, and atmospheric evidence for a recently proposed hypothesis: homogenous ice nucleation occurs at the surface, not in the volume, of supercooled water drops. Using existing thermodynamic arguments, laboratory experiments, and atmospheric data, we conclude that ice embryo formation at the surface cannot be confirmed or disregarded. Ice nucleation rates measured as a function of drop size in an air ambient could help distinguish between volume and surface nucleation rates.
Uniqueness of the differential Mueller matrix of uniform homogeneous media.
Devlaminck, Vincent; Ossikovski, Razvigor
2014-06-01
We show that the differential matrix of a uniform homogeneous medium containing birefringence may not be uniquely determined from its Mueller matrix, resulting in the potential existence of an infinite set of elementary polarization properties parameterized by an integer parameter. The uniqueness depends on the symmetry properties of a special differential matrix derived from the eigenvalue decomposition of the Mueller matrix. The conditions for the uniqueness of the differential matrix are identified, physically discussed, and illustrated in examples from the literature.
Upper Maxwellian bounds for the spatially homogeneous Boltzmann equation
Gamba, I. M.; Panferov, V.; Villani, C.
2007-01-01
For the spatially homogeneous Boltzmann equation with cutoff hard potentials it is shown that solutions remain bounded from above, uniformly in time, by a Maxwellian distribution, provided the initial data have a Maxwellian upper bound. The main technique is based on a comparison principle that uses a certain dissipative property of the linear Boltzmann equation. Implications of the technique to propagation of upper Maxwellian bounds in the spatially-inhomogeneous case are discussed.
Homogeneous CdTe quantum dots-carbon nanotubes heterostructures
Energy Technology Data Exchange (ETDEWEB)
Vieira, Kayo Oliveira [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Bettini, Jefferson [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, CEP 13083-970, Campinas, SP (Brazil); Ferrari, Jefferson Luis [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Schiavon, Marco Antonio, E-mail: schiavon@ufsj.edu.br [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil)
2015-01-15
The development of homogeneous CdTe quantum dots-carbon nanotubes heterostructures based on electrostatic interactions has been investigated. We report a simple and reproducible non-covalent functionalization route that can be accomplished at room temperature, to prepare colloidal composites consisting of CdTe nanocrystals deposited onto multi-walled carbon nanotubes (MWCNTs) functionalized with a thin layer of polyelectrolytes by layer-by-layer technique. Specifically, physical adsorption of polyelectrolytes such as poly (4-styrene sulfonate) and poly (diallyldimethylammonium chloride) was used to deagglomerate and disperse MWCNTs, onto which we deposited CdTe quantum dots coated with mercaptopropionic acid (MPA), as surface ligand, via electrostatic interactions. Confirmation of the CdTe quantum dots/carbon nanotubes heterostructures was done by transmission and scanning electron microscopies (TEM and SEM), dynamic-light scattering (DLS) together with absorption, emission, Raman and infrared spectroscopies (UV–vis, PL, Raman and FT-IR). Almost complete quenching of the PL band of the CdTe quantum dots was observed after adsorption on the MWCNTs, presumably through efficient energy transfer process from photoexcited CdTe to MWCNTs. - Highlights: • Highly homogeneous CdTe-carbon nanotubes heterostructures were prepared. • Simple and reproducible non-covalent functionalization route. • CdTe nanocrystals homogeneously deposited onto multi-walled carbon nanotubes. • Efficient energy transfer process from photoexcited CdTe to MWCNTs.
Mathematical Structure of Loop Quantum Cosmology: Homogeneous Models
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Martin Bojowald
2013-12-01
Full Text Available The mathematical structure of homogeneous loop quantum cosmology is analyzed, starting with and taking into account the general classification of homogeneous connections not restricted to be Abelian. As a first consequence, it is seen that the usual approach of quantizing Abelian models using spaces of functions on the Bohr compactification of the real line does not capture all properties of homogeneous connections. A new, more general quantization is introduced which applies to non-Abelian models and, in the Abelian case, can be mapped by an isometric, but not unitary, algebra morphism onto common representations making use of the Bohr compactification. Physically, the Bohr compactification of spaces of Abelian connections leads to a degeneracy of edge lengths and representations of holonomies. Lifting this degeneracy, the new quantization gives rise to several dynamical properties, including lattice refinement seen as a direct consequence of state-dependent regularizations of the Hamiltonian constraint of loop quantum gravity. The representation of basic operators - holonomies and fluxes - can be derived from the full theory specialized to lattices. With the new methods of this article, loop quantum cosmology comes closer to the full theory and is in a better position to produce reliable predictions when all quantum effects of the theory are taken into account.
How to determine composite material properties using numerical homogenization
DEFF Research Database (Denmark)
Andreassen, Erik; Andreasen, Casper Schousboe
2014-01-01
Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how t...... cell of the periodic material can take the shape of a square, rectangle, or parallelogram, allowing for all kinds of 2D periodicities. © 2013 Elsevier B.V. All rights reserved.......Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how...... the basic code, which computes the effective elasticity tensor of a two material composite, where one material could be void, is easily extended to include more materials. Furthermore, extensions to homogenization of conductivity, thermal expansion, and fluid permeability are described in detail. The unit...
Broken Ergodicity in Two-Dimensional Homogeneous Magnetohydrodynamic Turbulence
Shebalin, John V.
2010-01-01
Two-dimensional (2-D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3-D) homogeneous MHD turbulence.The se features include several ideal invariants, along with the phenomenon of broken ergodicity. Broken ergodicity appears when certain modes act like random variables with mean values that are large compared to their standard deviations, indicating a coherent structure or dynamo.Recently, the origin of broken ergodicity in 3-D MHD turbulence that is manifest in the lowest wavenumbers was explained. Here, a detailed description of the origins of broken ergodicity in 2-D MHD turbulence is presented. It will be seen that broken ergodicity in ideal 2-D MHD turbulence can be manifest in the lowest wavenumbers of a finite numerical model for certain initial conditions or in the highest wavenumbers for another set of initial conditions.T he origins of broken ergodicity in ideal 2-D homogeneous MHD turbulence are found through an eigen analysis of the covariance matrices of the modal probability density functions.It will also be shown that when the lowest wavenumber magnetic field becomes quasi-stationary, the higher wavenumber modes can propagate as Alfven waves on these almost static large-scale magnetic structures
Fourier-based strength homogenization of porous media
Bignonnet, François; Hassen, Ghazi; Dormieux, Luc
2016-11-01
An efficient numerical method is proposed to upscale the strength properties of heterogeneous media with periodic boundary conditions. The method relies on a formal analogy between strength homogenization and non-linear elasticity homogenization. The non-linear problems are solved on a regular discretization grid using the Augmented Lagrangian version of Fast Fourier Transform based schemes initially introduced for elasticity upscaling. The method is implemented for microstructures with local strength properties governed either by a Green criterion or a Von Mises criterion, including pores or rigid inclusions. A thorough comparison with available analytical results or finite element elasto-plastic simulations is proposed to validate the method on simple microstructures. As an application, the strength of complex microstructures such as the random Boolean model of spheres is then studied, including a comparison to closed-form Gurson and Eshelby based strength estimates. The effects of the microstructure morphology and the third invariant of the macroscopic stress tensor on the homogenized strength are quantitatively discussed.
Fourier-based strength homogenization of porous media
Bignonnet, François; Hassen, Ghazi; Dormieux, Luc
2016-07-01
An efficient numerical method is proposed to upscale the strength properties of heterogeneous media with periodic boundary conditions. The method relies on a formal analogy between strength homogenization and non-linear elasticity homogenization. The non-linear problems are solved on a regular discretization grid using the Augmented Lagrangian version of Fast Fourier Transform based schemes initially introduced for elasticity upscaling. The method is implemented for microstructures with local strength properties governed either by a Green criterion or a Von Mises criterion, including pores or rigid inclusions. A thorough comparison with available analytical results or finite element elasto-plastic simulations is proposed to validate the method on simple microstructures. As an application, the strength of complex microstructures such as the random Boolean model of spheres is then studied, including a comparison to closed-form Gurson and Eshelby based strength estimates. The effects of the microstructure morphology and the third invariant of the macroscopic stress tensor on the homogenized strength are quantitatively discussed.
Properties of subvisible cirrus clouds formed by homogeneous freezing
Directory of Open Access Journals (Sweden)
B. Kärcher
2002-04-01
Full Text Available Number concentrations and mean sizes of ice crystals and derived microphysical and optical properties of subvisible cirrus clouds (SVCs formed by homogeneous freezing of supercooled aerosols are investigated as a function of temperature and updraft speed of adiabatically ascending air parcels. The properties of such clouds are insensitive to variations of the aerosol number and size distribution. Based on criteria constraining the optical extinction, sedimentation time, and existence time of SVCs, longer-lived (>10 min clouds, capable of exerting a measurable radiative or chemical impact, are generated within a narrow range of updraft speeds below 1 - 2 cm s ^{-1} at temperatures below about 215K, with concentrations of ice crystals not exceeding 0.1 cm^{-3}. The clouds do not reach an equilibrium state because the ice crystals sediment out of the formation layer typically before the supersaturation is removed. Given these results, it seems likely that a limited number (<0.1 cm^{-3} of effective heterogeneous freezing nuclei that nucleate ice below the homogeneous freezing threshold can control the formation and properties of SVCs, although homogeneous freezing nuclei are far more abundant.
Surface modification of polycarbonate in homogeneous atmospheric pressure discharge
Energy Technology Data Exchange (ETDEWEB)
SIra, M; Trunec, D; St' ahel, P; BursIkova, V; Navratil, Z [Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic)
2008-01-07
A homogeneous atmospheric pressure dielectric barrier discharge was used for the surface modification of polycarbonate (PC). The discharge was generated between two planar metal electrodes, the top electrode was covered by glass and the bottom electrode was covered by a polymer sample. The discharge burned in pure nitrogen or in a mixture of nitrogen and hydrogen. The surface properties of both treated and untreated polymers were characterized by atomic force microscopy, surface free energy (SFE) measurements and x-ray photoelectron spectroscopy. The influence of the treatment time and power input to the discharge on the surface properties of polymers was studied. The ageing of treated samples was also investigated. The treatment of polymers in the homogeneous atmospheric pressure discharge was homogeneous and the polymer surfaces showed a smaller degree of roughness in comparison with the polymer surfaces treated in a filamentary discharge. The SFE of the treated PC obtained at optimum conditions was 53 mJ m{sup -2} and the corresponding contact angle of water was 38{sup 0}. The maximum decrease in the SFE during ageing was about 13%. The analysis of the chemical composition showed an increase in the nitrogen concentration in the surface layer, but almost a zero increase in the oxygen concentration. This result was discussed concerning the measured values of the SFE measurement.
Essential Medical Capabilities and Medical Readiness
2016-07-01
15-001098 Copy Essential Medical Capabilities and Medical Readiness John E. Whitley Joseph F. Adams Joseph J. Angello Jennifer T. Brooks Sarah K...other national challenges. Essential Medical Capabilities and Medical Readiness John E. Whitley Joseph F. Adams Joseph J. Angello Jennifer T. Brooks...noted that the ability of the Military Health System to provide operational healthcare is measured by the readiness of its medical personnel and
Ray, J.; Lee, B.; Baltrusaitis, J.; Jun, Y.
2012-12-01
Homogeneous and heterogeneous iron hydroxide nanoparticle nucleation can occur continuously in both natural and complex aqueous systems. Iron oxide nanoparticles can act as sinks and/or carriers for heavy metal contaminants; therefore, it is important to develop a better understanding of factors affecting their formation. Organic coatings are ubiquitous in aqueous environments where they can exist on mineral surfaces (e.g., biofilm), as nanoparticle surface coatings (e.g., natural organic matter), or be introduced as coagulants in water treatment systems. These surface coatings could influence the formation of iron oxide nanoparticles and thus, the mobility of aqueous contaminants. Therefore, to better understand the fate and transport of contaminants in complex aqueous environments, we need more accurate information about mechanisms governing heterogeneous and homogeneous nucleation and growth of iron(III) hydroxide nanoparticles in the presence of organic surface coatings. In this work, we used a unique measurement technique allowing for simultaneous small-angle X-ray scattering (SAXS) and grazing incidence (GISAXS) analysis to monitor nanoparticle nucleation in solution and at substrate surfaces. Clean quartz, and polyaspartate- and alginate-coated substrates were chosen as model substrates to represent mineral coatings, engineered organic coatings and natural organic coatings. Polyaspartate was determined to be the most negatively charged substrate and quartz to be the least negatively charged substrate; however, after 2 h of reaction, the total nanoparticle volume calculations—determined from GISAXS—indicate that precipitation of positively-charged iron(III) hydroxide nanoparticles is 10 times higher on the quartz substrate than on the polyaspartate substrate. This implies that electrostatics do not govern iron(III) hydroxide nucleation. Furthermore, homogeneous nucleation approximately 250 μm above the substrate surface was highest in the presence of the
Mars Aqueous Chemistry Experiment (MACE)
Benton, Clark C. (Editor)
1995-01-01
The concept of an aqueous-based chemical analyzer for Martian surface materials has been demonstrated to be feasible. During the processes of analysis, design, breadboarding, and most importantly, testing, it has become quite apparent that there are many challenges in implementing such a system. Nonetheless, excellent progress has been made and a number of problems which arose have been solved. The ability to conduct this work under a development environment which is separate and which precedes the project-level development has allowed us to find solutions to these implementation realities at low cost. If the instrument had been selected for a mission without this laboratory pre-project work, the costs of implementation would be much higher. In the four areas covered in Sections D, E, F, and G of this Final Report, outstanding progress has been made. There still remains the task of flight-qualifying certain of the components. This is traditionally done under the aegis of a Flight Project, but just as the concept development can be done at much lower cost when kept small and focused, so could the qualification program of critical parts benefit. We recommend, therefore, that NASA consider means of such qualifications and brass-boarding, in advance of final flight development. This is a generic recommendation, but hardware such as the Mars aqueous chemistry experiment (MACE) and other similarly-new concepts are particularly applicable. MACE now has wide versatility, in being able to reliably dispense both liquids and solids as chemical reagents to an entire suite of samples. The hardware and the experiment is much simpler than was developed for the Viking Biology instrument, yet can accomplish all the inorganic chemical measurements that the Viking desing was capable of. In addition, it is much more flexible and versatile to new experiment protocols (and reagents) than the Viking design ever could have been. MACE opens up the opportunity for many different scientific
Anarjan, Navideh; Jafarizadeh-Malmiri, Hoda; Nehdi, Imededdine Arbi; Sbihi, Hassen Mohamed; Al-Resayes, Saud Ibrahim; Tan, Chin Ping
2015-01-01
Nanodispersion systems allow incorporation of lipophilic bioactives, such as astaxanthin (a fat soluble carotenoid) into aqueous systems, which can improve their solubility, bioavailability, and stability, and widen their uses in water-based pharmaceutical and food products. In this study, response surface methodology was used to investigate the influences of homogenization time (0.5-20 minutes) and speed (1,000-9,000 rpm) in the formation of astaxanthin nanodispersions via the solvent-diffusion process. The product was characterized for particle size and astaxanthin concentration using laser diffraction particle size analysis and high performance liquid chromatography, respectively. Relatively high determination coefficients (ranging from 0.896 to 0.969) were obtained for all suggested polynomial regression models. The overall optimal homogenization conditions were determined by multiple response optimization analysis to be 6,000 rpm for 7 minutes. In vitro cellular uptake of astaxanthin from the suggested individual and multiple optimized astaxanthin nanodispersions was also evaluated. The cellular uptake of astaxanthin was found to be considerably increased (by more than five times) as it became incorporated into optimum nanodispersion systems. The lack of a significant difference between predicted and experimental values confirms the suitability of the regression equations connecting the response variables studied to the independent parameters.
Gartrell, Nanette
2014-01-01
Nanette Gartrell, MD, is a psychiatrist and researcher whose investigations have documented the mental health and psychological well-being of lesbian, gay, bisexual, and transgender (LGBT) people over the past four decades. Nanette is the principal investigator of an ongoing longitudinal study of lesbian families in which the children were conceived by donor insemination. Now in its 27th year, this project has been cited internationally in the debates over equality in marriage, foster care, and adoption. Previously on the faculty at Harvard Medical School and the University of California, San Francisco, Nanette is currently a Visiting Distinguished Scholar at the Williams Institute, UCLA School of Law. In 2013, Nanette received the Association of Women Psychiatrists Presidential Commendation Award for "selfless and enduring vision, leadership, wisdom, and mentorship in the fields of women's mental health, ethics, and gender research." At the age of 63, Nanette experienced a 3 ½ month period of intractable, incapacitating dizziness for which there was never a clear diagnosis.
Hydrophobic effect at aqueous interfaces
Pohorille, Andrew
2005-01-01
Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.
Turkish Medical Information System and Medical Librarianship
Directory of Open Access Journals (Sweden)
Huriye Çolaklar
2010-01-01
Full Text Available In Turkey, medical information is supported at state level according to national policies. However, although the history of medical libraries in Turkey goes back to the 13th century in Anatolia, modern medical library applications adopted since the 1950s have not received much state support. In the past thirteen years a few medical libraries joined forces under ÜNAK (the Association of University and Research Librarians to contribute to the organization and development of Turkish Medical Information through the establishment of a "Medical Working Group" in 2000.
Electrospinning of silk fibroin from all aqueous solution at low concentration.
Kishimoto, Yuki; Morikawa, Hideaki; Yamanaka, Shigeru; Tamada, Yasushi
2017-04-01
Non-woven mats of Bombyx mori silk fibroin were fabricated using electrospinning with an all aqueous solution at electrospinning at low concentrations of 5wt%. Evaluation of structural and mechanical properties of the non-woven mat fabricated with water solvent revealed that it is safe for use in the human body. It is anticipated for wider use in medical materials such as cellular scaffolds for tissue engineering.
Allelopathic Potential of Cucumber Tissues Aqueous Extracts
Institute of Scientific and Technical Information of China (English)
DONG Lin-lin; HAO Zhi-peng; ZUO Yuan-mei; LI Xiao-lin; WANG Qian
2011-01-01
[ Objective] The aim of this study was to explore allelopathic effects of the water-extracted crude of cucumber plant parts on seed germination and seedling growth of lettuce ( Lactuca sativa L. ), cabbage ( Brassica pekinensis L. ), radish ( Raphanus sativus L. ) and scallion ( Allium fistulosum L. ). [ Method] The allelopathic effects of different cucumber tissues aqueous extracts were investigated on lettuce, cabbage,radish and scallion using the water-soluble allelopathic principle by seedling bioassay tests. [ Result] The trends of inhibitory effects of different cucumber parts increased with increasing extract concentrations. The inhibition effects and the inhibition rate of three aqueous extracts were more significant on root growth than shoot length. Leaf aqueous extracts represented the most exhibited and root aqueous extracts representing the least inhibitory on seed germination, shoot length and root length of lettuce, cabbage, radish and scallion. [Conclusion] This study had provided basis for allelopathic character of different cucumber plant parts.
Calorimetric studies of macromolecular aqueous solutions
Blandamer, M.J; Cullis, P.M.; Engberts, J.B.F.N.
1996-01-01
Both titration and differential scanning microcalorimetric techniques are shown to yield important information concerning the properties of macromolecules in aqueous solution. Application of titration calorimetry is examined in me context of deaggregation of canonic micelles (e.g. hexadecyltrimethyl
Precipitation of neptunium dioxide from aqueous solution
Energy Technology Data Exchange (ETDEWEB)
Roberts, K E
1999-12-01
Tens of thousands of metric tons of highly radioactive, nuclear waste have been generated in the US. Currently, there is no treatment or disposal facility for these wastes. Of the radioactive elements in high-level nuclear waste, neptunium (Np) is of particular concern because it has a long half-life and may potentially be very mobile in groundwaters associated with a proposed underground disposal site at Yucca Mountain, Nevada. Aqueous Np concentrations observed in previous, short-term solubility experiments led to calculated potential doses exceeding proposed long-term regulatory limits. However, thermodynamic data for Np at 25 C showed that these observed aqueous Np concentrations were supersaturated with respect to crystalline NpO{sub 2}. It was hypothesized that NpO{sub 2} is the thermodynamically stable solid phase in aqueous solution, but it is slow to form in an aqueous solution of NpO{sub 2}{sup +} on the time scale of previous experiments. The precipitation of NpO{sub 2} would provide significantly lower aqueous Np concentrations leading to calculated doses below proposed regulatory limits. To test this hypothesis, solubility experiments were performed at elevated temperature to accelerate any slow precipitation kinetics. Ionic NpO{sub 2}{sup +} (aq) was introduced into very dilute aqueous solutions of NaCl with initial pH values ranging from 6 to 10. The reaction vessels were placed in an oven and allowed to react at 200 C until steady-state aqueous Np concentrations were observed. In all cases, aqueous Np concentrations decreased significantly from the initial value of 10{sup {minus}4} M. The solids that formed were analyzed by x-ray powder diffraction, x-ray absorption spectroscopy, and scanning electron microscopy. The solids were determined to be high-purity crystals of NpO{sub 2}. This is the first time that crystalline NpO{sub 2} has been observed to precipitate from NpO{sub 2}{sup +}(aq) in near-neutral aqueous solutions. The results obtained
Tidal spin down rates of homogeneous triaxial viscoelastic bodies
Quillen, Alice C.; Kueter-Young, Andrea; Frouard, Julien; Ragozzine, Darin
2016-12-01
We use numerical simulations to measure the sensitivity of the tidal spin-down rate of a homogeneous triaxial ellipsoid to its axis ratios by comparing the drift rate in orbital semimajor axis to that of a spherical body with the same mass, volume and simulated rheology. We use a mass-spring model approximating a viscoelastic body spinning around its shortest body axis, with spin aligned with orbital spin axis, and in circular orbit about a point mass. The torque or drift rate can be estimated from that predicted for a sphere with equivalent volume if multiplied by 0.5 (1 + b^4/a^4)(b/a)^{-4/3} (c/a)^{-α _c} where b/a and c/a are the body axis ratios and index αc ≈ 1.05 is consistent with the random lattice mass-spring model simulations but αc = 4/3 suggested by scaling estimates. A homogeneous body with axis ratios 0.5 and 0.8, like Haumea, has orbital semimajor axis drift rate about twice as fast as a spherical body with the same mass, volume and material properties. A simulation approximating a mostly rocky body but with 20 per cent of its mass as ice concentrated at its ends has a drift rate 10 times faster than the equivalent homogeneous rocky sphere. However, this increase in drift rate is not enough to allow Haumea's satellite, Hi'iaka, to have tidally drifted away from Haumea to its current orbital semimajor axis.
A brief introduction to homogenization and miscellaneous applications*
Directory of Open Access Journals (Sweden)
Allaire Grégoire
2012-09-01
Full Text Available This paper is a set of lecture notes for a short introductory course on homogenization. It covers the basic tools of periodic homogenization (two-scale asymptotic expansions, the oscillating test function method and two-scale convergence and briefly describes the main results of the more general theory of G− or H−convergence. Several applications of the method are given: derivation of Darcy’s law for flows in porous media, derivation of the porosity model and long time behavior of a diffusion equation. Numerical agorithms for homogenization are also discussed, including multiscale finite element methods. Cet article reprend des notes de cours, d’un niveau introductif, sur l’homogénéisation. Ces notes couvrent la théorie de l’homogénéisation périodique (développements asymptotiques à deux échelles, méthode de la fonction test oscillante, convergence à deux échelles et décrivent brièvement les principaux résultats de la théorie plus générale de la G− ou H− convergence. Plusieurs applications de la méthode sont données : dérivation de la loi de Darcy pour des écoulements en milieux poreux, dérivation du modèle de double porosité et comportement en temps grand d’une équation de diffusion. Des algorithmes numériques pour l’homogénéisation sont aussi présentés, dont, en particulier, les méthodes d’éléments finis multi-échelles.
High-temperature study of defects and homogeneity in glass
Yoon, Chang Hyun
Glass frit has many useful applications in the glass and ceramic industries. Several attempts were made in this study to understand the origin of problems that generally occur when using glass frit. The effect of water/glass interactions on the rheology of glass suspension and the final properties of glass and glaze were studied. The dissolution of refractory inclusions and its influence on the bubble evolution, glass structure, and homogeneity of the resulting melt were also studied. The effects of long-term interaction of water with various frit suspensions were considered. The change in suspension rheology is associated with the ion concentration of the frit suspension, which strongly depends on the frit composition, additives, and solid content of frit suspension. Physical property and compositional variations resulted from dealkalization reactions between the frit particles and water. New investigative techniques for continuous monitoring and quantitative analysis of the dissolution of refractory inclusions in glass have been developed utilizing high-temperature microscopy with computer image analysis. The dissolution rates of refractory oxides in glass frit were measured utilizing hot-stage microscopy in the temperature range from 1050°C to 1400°C. The effects of dissolution on the structure of the final glass, were monitored by infrared spectroscopy. Homogenization of the resulting melts was studied using a Christiansen filter. It was found that melting temperature and time strongly influence the dissolution of refractory batch materials and subsequent homogenization rates, leading to large differences in final structures for glass melts and glazes which have not attained equilibrium.
Aqueous lixiviants: Principle, types, and applications
Wang, Shijie
2007-10-01
Aqueous lixiviant is a leach liquour capable of dissolving all or part of ore or concentrate. It plays a critical role in the hydrometallurgical process. Although cyanide leaching of gold and silver has demonstrated success in the industry for 100 years, searching for innovative lixiviants to leach gold, copper, and other heavy metals effectively, economically, and environmentally has never stopped. This paper reviews the aqueous lixiviant’s principle, summarizes the types used in numerous sites, and presents its new applications.
Aqueous foam toxicology evaluation and hazard review
Energy Technology Data Exchange (ETDEWEB)
Archuleta, M.M.
1995-10-01
Aqueous foams are aggregates of bubbles mechanically generated by passing air or other gases through a net, screen, or other porous medium that is wetted by an aqueous solution of surface-active foaming agents (surfactants). Aqueous foams are important in modem fire-fighting technology, as well as for military uses for area denial and riot or crowd control. An aqueous foam is currently being developed and evaluated by Sandia National Laboratories (SNL) as a Less-Than-Lethal Weapon for the National Institute of Justice (NIJ). The purpose of this study is to evaluate the toxicity of the aqueous foam developed for the NIJ and to determine whether there are any significant adverse health effects associated with completely immersing individuals without protective equipment in the foam. The toxicity of the aqueous foam formulation developed for NIJ is determined by evaluating the toxicity of the individual components of the foam. The foam is made from a 2--5% solution of Steol CA-330 surfactant in water generated at expansion ratios ranging from 500:1 to 1000:1. SteoI CA-330 is a 35% ammonium laureth sulfate in water and is produced by Stepan Chemical Company and containing trace amounts (<0.1%) of 1,4-dioxane. The results of this study indicate that Steol CA-330 is a non-toxic, mildly irritating, surfactant that is used extensively in the cosmetics industry for hair care and bath products. Inhalation or dermal exposure to this material in aqueous foam is not expected to produce significant irritation or systemic toxicity to exposed individuals, even after prolonged exposure. The amount of 1,4-dioxane in the surfactant, and subsequently in the foam, is negligible and therefore, the toxicity associated with dioxane exposure is not significant. In general, immersion in similar aqueous foams has not resulted in acute, immediately life-threatening effects, or chronic, long-term, non-reversible effects following exposure.
Stabilized aqueous gels and uses thereof
Energy Technology Data Exchange (ETDEWEB)
Swanson, B.L.
1978-08-29
New improved aqueous gels, and methods of using same in contacting subterranean formations, are provided. The gels are prepared by gelling an aqueous brine having incorporated therein a water-soluble cellulose ether such as a carboxymethylcellulose (CMC), and are rendered more stable to decomposition by incorporating a sulfoalkylated tannin stabilizing agent, such as a sulfomethylated quebracho (SMQ), in the gel during the preparation thereof.
Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi
2013-08-19
Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions.
Elliptic elements in a Weyl group: a homogeneity property
Lusztig, G
2010-01-01
Let G be a reductive group over an algebraically closed field whose characteristic is not a bad prime for G. Let w be an elliptic element of the Weyl group which has minimal length in its conjugacy class. We show that there exists a unique unipotent class X in G such that the following holds: if V is the variety of pairs consisting of an element g in X and a Borel subgroup B such that B,gBg^{-1} are in relative position w, then V is a homogeneous G-space.
Non-Homogenous Moral Space (from Bentham toSen
Directory of Open Access Journals (Sweden)
Piotr (Peter Boltuc
2013-12-01
Full Text Available The notion of moral space covers all thin (universal and thick (particular characteristics that may plausibly be seen as morally relevant. In this paper, I investigate certain properties of moral space so defined. These properties are not easily visible if we analyze moral characteristics individually, but become clear once we consider them collectively. In particular, following Amartya Sen, I claim that the value of moral properties is, in part, a function of positional characteristics. I call this notion the non-homogeneity of moral space.
Nonlinear fast sausage waves in homogeneous magnetic flux tubes
Mikhalyaev, Badma B.; Ruderman, Michael S.
2015-12-01
> We consider fast sausage waves in straight homogeneous magnetic tubes. The plasma motion is described by the ideal magnetohydrodynamic equations in the cold plasma approximation. We derive the nonlinear Schrödinger equation describing the nonlinear evolution of an envelope of a carrier wave. The coefficients of this equation are expressed in terms Bessel and modified Bessel functions. They are calculated numerically for various values of parameters. In particular, we show that the criterion for the onset of the modulational or Benjamin-Fair instability is satisfied. The implication of the obtained results for solar physics is discussed.
Improved flexibility with grayscale fabrication of calcium fluoride homogenizers
Brown, Jeremiah; Brakhage, Peter; Simmons, Lamarr; Mueller, Ralf
2012-03-01
High quality and highly uniform illumination is a critical component for advanced lithography systems and wafer inspection tools. Homogenizer elements fabricated in calcium fluoride have demonstrated good performance for deep UV applications. Grayscale photolithography allows for the fabrication of single-sided micro lens array (MLA) elements with excellent optical performance. The MLA offers some significant advantages over crossed cylinders fabricated using grayscale photolithography processes, including the reduction in the number of fabrication steps and the added flexibility of manufacturing noncylindrical surface geometries. This research presentation reviews the fabrication process and compares grayscale crossed cylindrical arrays and MLAs in terms of their capabilities and performance.
Exhaust gas recirculation in a homogeneous charge compression ignition engine
Duffy, Kevin P.; Kieser, Andrew J.; Rodman, Anthony; Liechty, Michael P.; Hergart, Carl-Anders; Hardy, William L.
2008-05-27
A homogeneous charge compression ignition engine operates by injecting liquid fuel directly in a combustion chamber, and mixing the fuel with recirculated exhaust and fresh air through an auto ignition condition of the fuel. The engine includes at least one turbocharger for extracting energy from the engine exhaust and using that energy to boost intake pressure of recirculated exhaust gas and fresh air. Elevated proportions of exhaust gas recirculated to the engine are attained by throttling the fresh air inlet supply. These elevated exhaust gas recirculation rates allow the HCCI engine to be operated at higher speeds and loads rendering the HCCI engine a more viable alternative to a conventional diesel engine.
Polynomial solutions of quasi_homogeneous partial differential equations
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
By means of a method of analytic number theory the following theorem is proved. Let p be a quasi_homogeneous linear partial differential operator with degree m, m>0, w.r.t a dilation {δ-τ}-{τ<0} given by (a-1,…, a-n). Assume that either a1,…, an are positive rational numbers or m=∑nj=1α-jα-j for some α=(α-1, …, αn)∈I{}+n-+. Then the dimension of the space of polynomial solutions of the equation p[u]=0 on R+n must be infinite.
Homogeneous approximation property for continuous shearlet transforms in higher dimensions
Directory of Open Access Journals (Sweden)
Yu Su
2016-07-01
Full Text Available Abstract This paper is concerned with the generalization of the homogeneous approximation property (HAP for a continuous shearlet transform to higher dimensions. First, we give a pointwise convergence result on the inverse shearlet transform in higher dimensions. Second, we show that every pair of admissible shearlets possess the HAP in the sense of L 2 ( R d $L^{2}(R^{d}$ . Third, we give a sufficient condition for the pointwise HAP to hold, which depends on both shearlets and functions to be reconstructed.
The General Theory of Homogenization A Personalized Introduction
Tartar, Luc
2010-01-01
Homogenization is not about periodicity, or Gamma-convergence, but about understanding which effective equations to use at macroscopic level, knowing which partial differential equations govern mesoscopic levels, without using probabilities (which destroy physical reality); instead, one uses various topologies of weak type, the G-convergence of Sergio Spagnolo, the H-convergence of Francois Murat and the author, and some responsible for the appearance of nonlocal effects, which many theories in continuum mechanics or physics guessed wrongly. For a better understanding of 20th century science,
Homogenization of a double porosity model in deformable media
Directory of Open Access Journals (Sweden)
Abdelhamid Ainouz
2013-04-01
Full Text Available The article addresses the homogenization of a family of micro-models for the flow of a slightly compressible fluid in a poroelastic matrix containing periodically distributed poroelastic inclusions, with low permeabilities and with imperfect contact on the interface. The micro-models are based on Biot's system for consolidation processes in each phase, with interfacial barrier formulation. Using the two-scale convergence technique, it is shown that the derived system is a general model of that proposed by Aifantis, plus an extra memory term.
Homogeneity of Danish environmental and clinical isolates of Shewanella algae
DEFF Research Database (Denmark)
Vogel, Birte Fonnesbech; Holt, H.M.; Gerner-Smidt, P.;
2000-01-01
Danish isolates of Shewanella algae constituted by whole-cell protein profiling a very homogeneous group, and no clear distinction was seen between strains from the marine environment and strains of clinical origin. Although variation between all strains was observed by ribotyping and random...... amplified polymorphic DNA analysis, no clonal relationship between infective strains was found. From several patients, clonally identical strains of S. algae were reisolated up to 8 months after the primary isolation, indicating that the same strain may be able to maintain the infection....
Stochastic model of milk homogenization process using Markov's chain
A. A. Khvostov; R. S. Sumina; G. I. Kotov; Ivanov, A. V.
2016-01-01
The process of development of a mathematical model of the process of homogenization of dairy products is considered in the work. The theory of Markov's chains was used in the development of the mathematical model, Markov's chain with discrete states and continuous parameter for which the homogenisation pressure is taken, being the basis for the model structure. Machine realization of the model is implemented in the medium of structural modeling MathWorks Simulink™. Identification of the model...
Homogeneous Poisson Structures on Loop Spaces of Symmetric Spaces
Directory of Open Access Journals (Sweden)
Doug Pickrell
2008-10-01
Full Text Available This paper is a sequel to [Caine A., Pickrell D., Int. Math. Res. Not., to appear, arXiv:0710.4484], where we studied the Hamiltonian systems which arise from the Evens-Lu construction of homogeneous Poisson structures on both compact and noncompact type symmetric spaces. In this paper we consider loop space analogues. Many of the results extend in a relatively routine way to the loop space setting, but new issues emerge. The main point of this paper is to spell out the meaning of the results, especially in the SU(2 case. Applications include integral formulas and factorizations for Toeplitz determinants.
Lipase-catalyzed synthesis of monoacylglycerol in a homogeneous system.
Monteiro, Julieta B; Nascimento, Maria G; Ninow, Jorge L
2003-04-01
The 1,3-regiospecifique lipase, Lipozyme IM, catalyzed the esterification of lauric acid and glycerol in a homogeneous system. To overcome the drawback of the insolubility of glycerol in hexane, which is extensively used in enzymatic synthesis, a mixture of n-hexane/tert-butanol (1:1, v/v) was used leading to a monophasic system. The conversion of lauric acid into monolaurin was 65% in 8 h, when a molar ratio of glycerol to fatty acid (5:1) was used with the fatty acid at 0.1 M, and the phenomenon of acyl migration was minimized.
Homogenized Elastic Properties of Graphene for Small Deformations
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Jurica Sorić
2013-09-01
Full Text Available In this paper, we provide the quantification of the linear and non-linear elastic mechanical properties of graphene based upon the judicious combination of molecular mechanics simulation results and homogenization methods. We clarify the influence on computed results by the main model features, such as specimen size, chirality of microstructure, the effect of chosen boundary conditions (imposed displacement versus force and the corresponding plane stress transformation. The proposed approach is capable of explaining the scatter of the results for computed stresses, energy and stiffness and provides the bounds on graphene elastic properties, which are quite important in modeling and simulation of the virtual experiments on graphene-based devices.
HOMOGENIZATION OF SEMILINEAR PARABOLIC EQUATIONS IN PERFORATED DOMAINS
Institute of Scientific and Technical Information of China (English)
P.DONATO; A. NABIL
2004-01-01
This paper is devoted to the homogenization of a semilinear parabolic equation with rapidly oscillating coefficients in a domain periodically perforated by e-periodic holes of size ε. A Neumann condition is prescribed on the boundary of the holes.The presence of the holes does not allow to prove a compactness of the solutions in L2. To overcome this difficulty, the authors introduce a suitable auxiliary linear problem to which a corrector result is applied. Then, the asymptotic behaviour of the semilinear problem as e → 0 is described, and the limit equation is given.
Viscous tilting and production of vorticity in homogeneous turbulence
Holzner, M.; Guala, M.; Lüthi, B.; Liberzon, A.; Nikitin, N.; Kinzelbach, W.; Tsinober, A.
2010-06-01
Viscous depletion of vorticity is an essential and well known property of turbulent flows, balancing, in the mean, the net vorticity production associated with the vortex stretching mechanism. In this letter, we, however, demonstrate that viscous effects are not restricted to a mere destruction process, but play a more complex role in vorticity dynamics that is as important as vortex stretching. Based on the results from three dimensional particle tracking velocimetry experiments and direct numerical simulation of homogeneous and quasi-isotropic turbulence, we show that the viscous term in the vorticity equation can also locally induce production of vorticity and changes of the orientation of the vorticity vector (viscous tilting).
Viscous tilting and production of vorticity in homogeneous turbulence
Holzner, M; Lüthi, B; Liberzon, A; Nikitin, N; Kinzelbach, W; Tsinober, A
2010-01-01
Viscous depletion of vorticity is an essential and well known property of turbulent flows, balancing, in the mean, the net vorticity production associated with the vortex stretching mechanism. In this letter we however demonstrate that viscous effects are not restricted to a mere destruction process, but play a more complex role in vorticity dynamics that is as important as vortex stretching. Based on results from particle tracking experiments (3D-PTV) and direct numerical simulation (DNS) of homogeneous and quasi isotropic turbulence, we show that the viscous term in the vorticity equation can also locally induce production of vorticity and changes of its orientation (viscous tilting).
Are geological media homogeneous or heterogeneous for neutron investigations?
Woźnicka, U; Drozdowicz, K; Gabańska, B; Krynicka, E; Igielski, A
2003-01-01
The thermal neutron absorption cross section of a heterogeneous material is lower than that of the corresponding homogeneous one which contains the same components. When rock materials are investigated the sample usually contains grains which create heterogeneity. The heterogeneity effect depends on the mass contribution of highly and low-absorbing centers, on the ratio of their absorption cross sections, and on their sizes. An influence of the granulation of silicon and diabase samples on the absorption cross section measured with Czubek's method has been experimentally investigated. A 20% underestimation of the absorption cross section has been observed for diabase grains of sizes from 6.3 to 12.8 mm.
Scalar oscillatory integrals in smooth spaces of homogeneous type
Gressman, Philip T
2012-01-01
We consider a generalization of the notion of spaces of homogeneous type, inspired by recent work of Street [21] on the multi-parameter Carnot-Caratheodory geometry, which imbues such spaces with differentiability structure. The setting allows one to formulate estimates for scalar oscillatory integrals on these spaces which are uniform and respect the underlying geometry of both the space and the phase function. As a corollary we obtain a generalization of a theorem of Bruna, Nagel, and Wainger [1] on the asymptotic behavior of scalar oscillatory integrals with smooth, convex phase of finite type.
Biotic homogenization can decrease landscape-scale forest multifunctionality
DEFF Research Database (Denmark)
van der Plas, Fons; Manning, Pete; Soliveres, Santiago;
2016-01-01
-diversity and landscape-scale multifunctionality were always positive, because a high spatial turnover in species composition was closely related to a high spatial turnover in functions that were supported at high levels. Our findings have major implications for forest management and indicate that biotic homogenization...... a comprehensive pan-European dataset, including 16 ecosystem functions measured in 209 forest plots across six European countries, and performed simulations to investigate how local plot-scale richness of tree species (α-diversity) and their turnover between plots (β-diversity) are related to landscape...
Chaos Control on a Duopoly Game with Homogeneous Strategy
Directory of Open Access Journals (Sweden)
Manying Bai
2016-01-01
Full Text Available We study the dynamics of a nonlinear discrete-time duopoly game, where the players have homogenous knowledge on the market demand and decide their outputs based on adaptive expectation. The Nash equilibrium and its local stability are investigated. The numerical simulation results show that the model may exhibit chaotic phenomena. Quasiperiodicity is also found by setting the parameters at specific values. The system can be stabilized to a stable state by using delayed feedback control method. The discussion of control strategy shows that the effect of both firms taking control method is better than that of single firm taking control method.
Homogeneous cosmologies and the Maupertuis-Jacobi principle
Elias, L A; Elias, Luciana A.; Saa, Alberto
2007-01-01
A recent work showing that homogeneous and isotropic cosmologies involving scalar fields are equivalent to the geodesics of certain effective manifolds is generalized to the non-minimally coupled and anisotropic cases. As the Maupertuis-Jacobi principle in classical mechanics, such result permits us to infer some dynamical properties of cosmological models from the geometry of the associated effective manifolds, allowing us to go a step further in the study of cosmological dynamics. By means of some explicit examples, we show how the geometrical analysis can simplify considerably the dynamical analysis of cosmological models.
Nationwide Genomic Study in Denmark Reveals Remarkable Population Homogeneity
DEFF Research Database (Denmark)
Athanasiadis, Georgios; Cheng, Jade Y; Vilhjálmsson, Bjarni J;
2016-01-01
polygenic predictions of phenotypic traits in adolescents. We observed remarkable homogeneity across different geographic regions, although we could still detect weak signals of genetic structure reflecting the history of the country. Denmark presented genomic affinity with primarily neighboring countries...... with overall resemblance of decreasing weight from Britain, Sweden, Norway, Germany and France. A Polish admixture signal was detected in Zealand and Funen and our date estimates coincided with historical evidence of Wend settlements in the south of Denmark. We also observed considerably diverse demographic...
ASRM process development in aqueous cleaning
Swisher, Bill
1992-12-01
Viewgraphs are included on process development in aqueous cleaning which is taking place at the Aerojet Advanced Solid Rocket Motor (ASRM) Division under a NASA Marshall Space and Flight Center contract for design, development, test, and evaluation of the ASRM including new production facilities. The ASRM will utilize aqueous cleaning in several manufacturing process steps to clean case segments, nozzle metal components, and igniter closures. ASRM manufacturing process development is underway, including agent selection, agent characterization, subscale process optimization, bonding verification, and scale-up validation. Process parameters are currently being tested for optimization utilizing a Taguci Matrix, including agent concentration, cleaning solution temperature, agitation and immersion time, rinse water amount and temperature, and use/non-use of drying air. Based on results of process development testing to date, several observations are offered: aqueous cleaning appears effective for steels and SermeTel-coated metals in ASRM processing; aqueous cleaning agents may stain and/or attack bare aluminum metals to various extents; aqueous cleaning appears unsuitable for thermal sprayed aluminum-coated steel; aqueous cleaning appears to adequately remove a wide range of contaminants from flat metal surfaces, but supplementary assistance may be needed to remove clumps of tenacious contaminants embedded in holes, etc.; and hot rinse water appears to be beneficial to aid in drying of bare steel and retarding oxidation rate.
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Medication Use during Pregnancy
... What's this? Submit Button Past Emails CDC Features Medication Use During Pregnancy Recommend on Facebook Tweet Share ... are taking only medications that are necessary. What Medications Can Cause Birth Defects? We know that taking ...
A new framework for simulating forced homogeneous buoyant turbulent flows
Carroll, Phares L.; Blanquart, Guillaume
2015-06-01
This work proposes a new simulation methodology to study variable density turbulent buoyant flows. The mathematical framework, referred to as homogeneous buoyant turbulence, relies on a triply periodic domain and incorporates numerical forcing methods commonly used in simulation studies of homogeneous, isotropic flows. In order to separate the effects due to buoyancy from those due to large-scale gradients, the linear scalar forcing technique is used to maintain the scalar variance at a constant value. Two sources of kinetic energy production are considered in the momentum equation, namely shear via an isotropic forcing term and buoyancy via the gravity term. The simulation framework is designed such that the four dimensionless parameters of importance in buoyant mixing, namely the Reynolds, Richardson, Atwood, and Schmidt numbers, can be independently varied and controlled. The framework is used to interrogate fully non-buoyant, fully buoyant, and partially buoyant turbulent flows. The results show that the statistics of the scalar fields (mixture fraction and density) are not influenced by the energy production mechanism (shear vs. buoyancy). On the other hand, the velocity field exhibits anisotropy, namely a larger variance in the direction of gravity which is associated with a statistical dependence of the velocity component on the local fluid density.
Homogeneous and heterogeneous reactions of anthracene with selected atmospheric oxidants.
Zhang, Yang; Shu, Jinian; Zhang, Yuanxun; Yang, Bo
2013-09-01
The reactions of gas-phase anthracene and suspended anthracene particles with O3 and O3-NO were conducted in a 200-L reaction chamber, respectively. The secondary organic aerosol (SOA) formations from gas-phase reactions of anthracene with O3 and O3-NO were observed. Meanwhile, the size distributions and mass concentrations of SOA were monitored with a scanning mobility particle sizer (SMPS) during the formation processes. The rapid exponential growths of SOA reveal that the atmospheric lifetimes of gas-phase anthracene towards O3 and O3-NO are less than 20.5 and 4.34 hr, respectively. The particulate oxidation products from homogeneous and heterogeneous reactions were analyzed with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). Gas chromatograph/mass spectrometer (GC/MS) analyses of oxidation products of anthracene were carried out for assigning the time-of-flight (TOF) mass spectra of products from homogeneous and heterogeneous reactions. Anthrone, anthraquinone, 9,10-dihydroxyanthracene, and 1,9,10-trihydroxyanthracene were the ozonation products of anthracene, while anthrone, anthraquinone, 9-nitroanthracene, and 1,8-dihydroxyanthraquinone were the main products of anthracene with O3-NO.
Homogeneous and heterogeneous reactions of anthracene with selected atmospheric oxidants
Institute of Scientific and Technical Information of China (English)
Yang Zhang; Jinian Shu; Yuanxun Zhang; Bo Yang
2013-01-01
The reactions of gas-phase anthracene and suspended anthracene particles with O3 and O3-NO were conducted in a 200-L reaction chamber,respectively.The secondary organic aerosol (SOA) formations from gas-phase reactions of anthracene with O3 and O3-NO were observed.Meanwhile,the size distributions and mass concentrations of SOA were monitored with a scanning mobility particle sizer (SMPS) during the formation processes.The rapid exponential growths of SOA reveal that the atmospheric lifetimes of gas-phase anthracene towards O3 and O3-NO are less than 20.5 and 4.34 hr,respectively.The particulate oxidation products from homogeneous and heterogeneous reactions were analyzed with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUVATOFMS).Gas chromatograph/mass spectrometer (GC/MS) analyses of oxidation products of anthracene were carried out for assigning the time-of-flight (TOF) mass spectra of products from homogeneous and heterogeneous reactions.Anthrone,anthraquinone,9,10-dihydroxyanthracene,and 1,9,10-trihydroxyanthracene were the ozonation products of anthracene,while anthrone,anthraquinone,9-nitroanthracene,and 1,8-dihydroxyanthraquinone were the main products of anthracene with O3-NO.
Direction of unsaturated flow in a homogeneous and isotropic hillslope
Lu, Ning; Kaya, Basak Sener; Godt, Jonathan W.
2011-01-01
The distribution of soil moisture in a homogeneous and isotropic hillslope is a transient, variably saturated physical process controlled by rainfall characteristics, hillslope geometry, and the hydrological properties of the hillslope materials. The major driving mechanisms for moisture movement are gravity and gradients in matric potential. The latter is solely controlled by gradients of moisture content. In a homogeneous and isotropic saturated hillslope, absent a gradient in moisture content and under the driving force of gravity with a constant pressure boundary at the slope surface, flow is always in the lateral downslope direction, under either transient or steady state conditions. However, under variably saturated conditions, both gravity and moisture content gradients drive fluid motion, leading to complex flow patterns. In general, the flow field near the ground surface is variably saturated and transient, and the direction of flow could be laterally downslope, laterally upslope, or vertically downward. Previous work has suggested that prevailing rainfall conditions are sufficient to completely control these flow regimes. This work, however, shows that under time-varying rainfall conditions, vertical, downslope, and upslope lateral flow can concurrently occur at different depths and locations within the hillslope. More importantly, we show that the state of wetting or drying in a hillslope defines the temporal and spatial regimes of flow and when and where laterally downslope and/or laterally upslope flow occurs.
Experimental demonstration of a homogeneous two-scale dynamo
Stieglitz, R.; Muller, U.
2002-06-01
It has been shown theoretically in the past that homogeneous dynamos may occur for various velocity fields. G.O. Roberts investigated spatially periodic velocity fields, which Busse confined to a finite cylindrical domain. Using a mean field approach he derived an approximate condition for the onset of dynamo action. Based on Busse's idea at the Forschungszentrum Karlsruhe a conceptual design for an experimental homogeneous dynamo was developed, and a test facility was set up. The first experiments demonstrated that a permanent dynamo can exist in a cylindrical container filled with liquid sodium in which by means of guide vanes counter rotating and counter current spiral vortices are arranged. The dynamo is self-exciting at sufficiently high flow rates, and the magnetic field saturates at a mean value. The instantaneous magnetic field fluctuates around this mean value by about 5%. As predicted by theory the mode of the observed magnetic field is strongly non-axisymmetric. In a series of experiments a phase and a bifurcation diagramm for dynamo action was derived which depend on the spiral and axial flow rates. Figs 5, Refs 14.
All-sky homogeneity of precipitable water vapour over Paranal
Querel, Richard R
2014-01-01
A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (~10 {\\mu}m) for cloud detection. We present, for the first time, a statistical analysis of the homogeneity of all-sky PWV using 21 months of periodic (every 6 hours) all-sky scans from the radiometer. These data provide unique insight into the spatial and temporal variation of atmospheric conditions relevant for astronomical observations, particularly in the infrared. We find the PWV over Paranal to be remarkably homogeneous across the sky down to 27.5{\\deg} el...
Exploiting Homogeneity of Density in Incremental Hierarchical Clustering
Directory of Open Access Journals (Sweden)
Dwi H. Widiyantoro
2006-11-01
Full Text Available Hierarchical clustering is an important tool in many applications. As it involves a large data set that proliferates over time, reclustering the data set periodically is not an efficient process. Therefore, the ability to incorporate a new data set incrementally into an existing hierarchy becomes increasingly demanding. This article describes Homogen, a system that employs a new algorithm for generating a hierarchy of concepts and clusters incrementally from a stream of observations. The system aims to construct a hierarchy that satisfies the homogeneity and the monotonicity properties. Working in a bottom-up fashion, a new observation is placed in the hierarchy and a sequence of hierarchy restructuring processes is performed only in regions that have been affected by the presence of the new observation. Additionally, it combines multiple restructuring techniques that address different restructuring objectives to get a synergistic effect. The system has been tested on a variety of domains including structured and unstructured data sets. The experimental results reveal that the system is able to construct a concept hierarchy that is consistent regardless of the input data order and whose quality is comparable to the quality of those produced by non incremental clustering algorithms.
Pre-heating Fuel for Charge Homogeneity to Improve Combustion
Directory of Open Access Journals (Sweden)
Arjun Shanmukam
2013-06-01
Full Text Available The idea of the automobile engine that people have is of one that is bygone. The automobile engine today is the pinnacle of engineering expertise, implementing the best of technologies and undergoing the best of manufacturing processes to make the closest possible achievement to perfection, from design to combustion. The art of perfection though starts much before the process itself. In case of the automobile engine, the process is the 4-Stroke cycle that most engines go through and the art we are referring to is attaining homogeneity in charge. Homogeneous charge in an Internal Combustion Engine refers to the complete mixture of fuel (Petrol and air, entering the cylinder. Ideally this would mean the complete dispersion of the atomised fuel in air. This as a result reduces the overall efficiency of the engine. To help achieve the required atomisation, reducing the Surface Tension of the fuel is a potential solution. On reduction of Surface Tension the atomisation is enhanced, possibly reaching the ideal value. This can be achieved by heating the fuel to an operating temperature for which heat can be extracted from a potential source, namely the Exhaust Manifold.
Homogeneous gas phase models of relaxation kinetics in neon afterglow
Directory of Open Access Journals (Sweden)
Marković Vidosav Lj.
2007-01-01
Full Text Available The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time td (τ (memory curve is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect, because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2 + and nitrogen ions N2 + (present as impurities and the approximate value of N2 + ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.
Micromechanics and homogenization of inelastic composite materials with growing cracks
Costanzo, Francesco; Boyd, James G.; Allen, David H.
1996-03-01
A homogenization scheme is employed to derive the effective constitutive equations of an elastoplastic composite system with growing damage. The homogenization procedure followed herein is based on the thermodynamics of dissipative media. It is shown that when damage consists of sharps microcracks the macroscopic constitutive behavior is that of a so-called generalized standard material. The latter is a general dissipative medium whose constitutive equations are completely characterized by a single scalar convex potential function of the chosen state variables and whose evolution is completely characterized by a single convex dissipation potential function of the thermodynamic forces conjugate to the chosen internal state variables. The analysis presented is valid under the assumption that the evolution of the representative volume element at hand is unique and stable. The results of the theoretical analysis are then employed for formulating an approximate method for practically deriving the macroscopic constitutive equations. Computer software development for the application of said method is currently ongoing. A simple example of the numerical results obtained so far is presented.
Improvement of thermal homogenization using multiple swirling jets
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Braikia Mohamed
2012-01-01
Full Text Available The aim of this study is to examine different blowing configurations of multiple swirling jets for use it in terminal units of ventilation applications. The influence of several parameters such as the inclined vanes of diffuser and the sense of rotation of the single or multiple swirling jets, their number and their arrangement on the flow resulting dynamically and thermally is experimentally investigated. Flow rate was adjusted at Reynolds numbers, Re0, ranging from 104 to 30.103. The current study is carried out under uniform heat flux condition for each diffuser at Reynolds number of 30.103, the air being the working fluid. Experiences concerning the fusion of several jets show that the resulting jet is clearly more homogenized under swirling influence. The findings of this study show that the gap between the jets and their sense of rotation relative to the central jet, affects the quality of the homogenization of ambiance. Among the studied different configuration, the one which consists of a swirling central jet controlling the behavior of six swirling jets in counter-rotation is shown to be the most effective in terms of thermal destratification.
Numerical Studies of Homogenization under a Fast Cellular Flow
Iyer, Gautam
2012-09-13
We consider a two dimensional particle diffusing in the presence of a fast cellular flow confined to a finite domain. If the flow amplitude A is held fixed and the number of cells L 2 →∞, then the problem homogenizes; this has been well studied. Also well studied is the limit when L is fixed and A→∞. In this case the solution averages along stream lines. The double limit as both the flow amplitude A→∞and the number of cells L 2 →∞was recently studied [G. Iyer et al., preprint, arXiv:1108.0074]; one observes a sharp transition between the homogenization and averaging regimes occurring at A = L 2. This paper numerically studies a few theoretically unresolved aspects of this problem when both A and L are large that were left open in [G. Iyer et al., preprint, arXiv:1108.0074] using the numerical method devised in [G. A. Pavliotis, A. M. Stewart, and K. C. Zygalakis, J. Comput. Phys., 228 (2009), pp. 1030-1055]. Our treatment of the numerical method uses recent developments in the theory of modified equations for numerical integrators of stochastic differential equations [K. C. Zygalakis, SIAM J. Sci. Comput., 33 (2001), pp. 102-130]. © 2012 Society for Industrial and Applied Mathematics.
xPand: An algorithm for perturbing homogeneous cosmologies
Pitrou, Cyril; Umeh, Obinna
2013-01-01
In the present paper, we develop in detail a fully geometrical method for deriving perturbation equations about a spatially homogeneous background. This method relies on the 3+1 splitting of the background space-time and does not use any particular set of coordinates: it is implemented in terms of geometrical quantities only, using the tensor algebra package xTensor in the xAct distribution along with the extension for perturbations xPert. Our algorithm allows one to obtain the perturbation equations for all types of homogeneous cosmologies, up to any order and in all possible gauges. As applications, we recover the well-known perturbed Einstein equations for Friedmann--Lema\\^itre--Robertson--Walker cosmologies up to second order and for Bianchi I cosmologies at first order. This work opens the door to the study of these models at higher order and to that of any other perturbed Bianchi cosmologies, by circumventing the usually too cumbersome derivation of the perturbed equations.
Einstein-Cartan gravitational collapse of a homogeneous Weyssenhoff fluid
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Ziaie, Amir Hadi; Sepangi, Hamid Reza [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of); Vargas Moniz, Paulo [Universidade da Beira Interior, Departamento de Fisica, Covilha (Portugal); Universidade da Beira Interior, Centro de Matematica e Aplicacoes (CMA-UBI), Covilha (Portugal); Ranjbar, Arash [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of); Centro de Estudios Cientficos (CECs), Valdivia (Chile); Universidad Andres Bello, Santiago (Chile)
2014-11-15
We consider the gravitational collapse of a spherically symmetric homogeneous matter distribution consisting of a Weyssenhoff fluid in the presence of a negative cosmological constant. Our aim is to investigate the effects of torsion and spin averaged terms on the final outcome of the collapse. For a specific interior space-time setup, namely the homogeneous and isotropic FLRW metric, we obtain two classes of solutions to the field equations where depending on the relation between spin source parameters, (i) the collapse procedure culminates in a space-time singularity or (ii) it is replaced by a non-singular bounce. We show that, under certain conditions, for a specific subset of the former solutions, the formation of trapped surfaces is prevented and thus the resulted singularity could be naked. The curvature singularity that forms could be gravitationally strong in the sense of Tipler. Our numerical analysis for the latter solutions shows that the collapsing dynamical process experiences four phases, so that two of which occur at the pre-bounce and the other two at post-bounce regimes. We further observe that there can be found a minimum radius for the apparent horizon curve, such that the main outcome of which is that there exists an upper bound for the size of the collapsing body, below which no horizon forms throughout the whole scenario. (orig.)
To the theory of homogeneous nucleation: Cluster energy
Al'Tman, I. S.; Agranovskii, I. E.; Choi, M.; Zagainov, V. A.
2008-12-01
An attempt is made to critically analyze the modern state of the theory of homogeneous nucleation as concerns its ability to describe experiments with high accuracy. An analysis of the experimental data led us to conclude that the dependence of the nucleation rate on supersaturation and temperature T was not described by the theory, which underestimates the critical cluster size compared with the Gibbs-Thomson equation. The possibility of applying density functional theory (one of the latest achievements in the theory of homogeneous nucleation) was questioned. Within this theory, the Gibbs-Thomson equation remains valid even outside the classic capillary approximation. It is suggested that, to bring theory in consistency with experiment, certain fundamental propositions of the theory of nucleation should be revised. The inclusion of an additional contribution to the Gibbs energy of a cluster caused by the size dependence of the specific heat capacity of the cluster decreases the critical cluster size compared with the value calculated by the Gibbs-Thomson equation. The calculated dependence of nucleation rate on supersaturation was in agreement with the experimental results.
Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis
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Masahiko Arai
2015-05-01
Full Text Available Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species are leaching away into the liquid phases [2,3]. The metal leaching would make it difficult for the catalysts to maintain their desired initial performance for repeated batch reactions and during continuous ones. The metal leaching would also cause some undesired contamination of products by the metal species dissolved in the reaction mixture, and the separation of the metal contaminants would be required to purify the products. Therefore, various novel methods have been proposed so far to immobilize/stabilize the active metal species and to separate/collect/reuse the dissolved metal species [4]. In addition, knowledge on the heterogeneous and homogeneous natures of organic reactions using heterogeneous catalysts is important to discuss their reaction mechanisms and catalytically working active species. [...
Parahydrogen Induced polarization by homogeneous catalysis: theory and applications.
Buljubasich, Lisandro; Franzoni, María Belén; Münnemann, Kerstin
2013-01-01
The alignment of the nuclear spins in parahydrogen can be transferred to other molecules by a homogeneously catalyzed hydrogenation reaction resulting in dramatically enhanced NMR signals. In this chapter we introduce the involved theoretical concepts by two different approaches: the well known, intuitive population approach and the more complex but more complete density operator formalism. Furthermore, we present two interesting applications of PHIP employing homogeneous catalysis. The first demonstrates the feasibility of using PHIP hyperpolarized molecules as contrast agents in (1)H MRI. The contrast arises from the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via PHIP. It allows for the discrimination of a small amount of hyperpolarized molecules from a large background signal and may open up unprecedented opportunities to use the standard MRI nucleus (1)H for, e.g., metabolic imaging in the future. The second application shows the possibility of continuously producing hyperpolarization via PHIP by employing hollow fiber membranes. The continuous generation of hyperpolarization can overcome the problem of fast relaxation times inherent in all hyperpolarization techniques employed in liquid-state NMR. It allows, for instance, the recording of a reliable 2D spectrum much faster than performing the same experiment with thermally polarized protons. The membrane technique can be straightforwardly extended to produce a continuous flow of a hyperpolarized liquid for MRI enabling important applications in natural sciences and medicine.
Tidal spin down rates of homogeneous triaxial viscoelastic bodies
Quillen, Alice C; Frouard, Julien; Ragozzine, Darin
2016-01-01
We use simulations to measure the sensitivity of the tidal spin down rate of a homogeneous triaxial ellipsoid to its axis ratios by comparing the drift rate in orbital semi-major axis to that of a spherical body with the same mass, volume and simulated rheology. We use a mass-spring model approximating a viscoelastic body spinning around its shortest body axis, with spin aligned with orbital spin axis, and in circular orbit about a point mass. The torque or drift rate can be estimated from that predicted for a sphere with equivalent volume if multiplied by $0.5 (1 + b^4/a^4)(b/a)^{-4/3} (c/a)^{-\\alpha_c}$ where $b/a$ and $c/a$ are the body axis ratios and index $\\alpha_c \\approx 1.1$ is consistent with the random lattice mass spring model simulations but $\\alpha_c \\sim 4/3$ suggested by scaling estimates. A homogeneous body with axis ratios 0.5 and and 0.8, like Haumea, has orbital semi-major axis drift rate about twice as fast as a spherical body with the same mass, volume and material properties. A simulati...
Nonlinear ionic transport through microstructured solid electrolytes: homogenization estimates
Curto Sillamoni, Ignacio J.; Idiart, Martín I.
2016-10-01
We consider the transport of multiple ionic species by diffusion and migration through microstructured solid electrolytes in the presence of strong electric fields. The assumed constitutive relations for the constituent phases follow from convex energy and dissipation potentials which guarantee thermodynamic consistency. The effective response is heuristically deduced from a multi-scale convergence analysis of the relevant field equations. The resulting homogenized response involves an effective dissipation potential per species. Each potential is mathematically akin to that of a standard nonlinear heterogeneous conductor. A ‘linear-comparison’ homogenization technique is then used to generate estimates for these nonlinear potentials in terms of available estimates for corresponding linear conductors. By way of example, use is made of the Maxwell-Garnett and effective-medium linear approximations to generate estimates for two-phase systems with power-law dissipation. Explicit formulas are given for some limiting cases. In the case of threshold-type behavior, the estimates exhibit non-analytical dilute limits and seem to be consistent with fields localized in low energy paths.
IMPACT OF COOKING HOMOGENEITY ON PULP STRENGTH PROPERTIES
Institute of Scientific and Technical Information of China (English)
BofengMao
2004-01-01
Cooking homogeneity of kraft pulping can havesignificant impact on pulp strength properties. Wehave studied cooking homogeneity of two kraftdigesters within Stora Enso. One of the digesters is aone-vessel hydraulic continuous digester (digester A)and the other one is a two-vessel vapor/liquor phasecontinuous digester (digester B). They are located inthe same mill and use the same softwood chipquality. Due to the differences in chip pre-steamingand cooking facilities and conditions, significantdifferences in pulp strength properties, reject contentsand kappa variations have been found between thepulps produced in the two digesters. Digester A has amodem chip bin with efficient pre-heating and airremoval, whereas digester B has poor chippre-steaming conditions. Our strength deliverystudies show that although the two digesters producepulps with the same kappa number and viscosity, thepulp produced in digester A has about 20% higherstrength delivery, l%-unit (based on wood) lowerreject content and lower kappa variations based onFTIR spectra analysis on pulp sheet than the pulpproduced in digester B.Results of the studies indicate that morehomogeneous cooking,variation in the fibers,i.e., lower lignin/kappa leads to improved pulpstrength properties. Efficient chip pre-steaming isimportant/essential for achieving homogeneouscooking. Rebuilding the equipment for improvingchip pre-steaming conditions of digester B is to becarded out.
The Homogeneity Research of Urban Rail Transit Network Performance
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Wang Fu-jian
2016-01-01
Full Text Available Urban Rail Transit is an important part of the public transit, it is necessary to carry out the corresponding network function analysis. Previous studies mainly about network performance analysis of a single city rail transit, lacking of horizontal comparison between the multi-city, it is difficult to find inner unity of different Urban Rail Transit network functions. Taking into account the Urban Rail Transit network is a typical complex networks, so this paper proposes the application of complex network theory to research the homogeneity of Urban Rail Transit network performance. This paper selects rail networks of Beijing, Shanghai, Guangzhou as calculation case, gave them a complex network mapping through the L, P Space method and had a static topological analysis using complex network theory, Network characteristics in three cities were calculated and analyzed form node degree distribution and node connection preference. Finally, this paper studied the network efficiency changes of Urban Rail Transit system under different attack mode. The results showed that, although rail transport network size, model construction and construction planning of the three cities are different, but their network performance in many aspects showed high homogeneity.
Anomalous diffusion in strong cellular flows: Averaging and homogenization
Pajor-Gyulai, Zsolt
This thesis considers the possible limit behaviors of a strong Hamiltonian cellular flow that is subjected to a Brownian stochastic perturbation. Three possible limits are identified. When long timescales are considered, the limit behavior is described by classical homogenization theory. In the intermediate (finite) time case, it is shown that the limit behavior is anomalously diffusive. This means that the limit is given by a Brownian motion that is time changed by the local time of a process on the graph which is associated with the structure of the unperturbed flow lines (Reeb graph) that one obtains by Freidlin-Wentzell type averaging. Finally, we consider the case when the motion starts close to, or on, the cell boundary and derive a limit for the displacement on timescales of order proportional to some power of a small parameter with exponent between zero and one. (modulo a logarithmic correction to compensate for the slowdown of the flow near the saddle points of the Hamiltonian). The latter two cases are novel results obtained by the author and his collaborators. We also consider two applications of the above results to associated partial differential equation (PDE) problems. Namely, we study a two-parameter averaging-homogenization type elliptic boundary value problem and obtain a precise description of the limit behavior of the solution as a function of the parameters using the well-known stochastic representation. Additionally, we study a similar parabolic Cauchy problem.
Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation
Gasmi, Hatem; Hamdi, Essaïeb; Bouden Romdhane, Nejla
2014-07-01
Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young's modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young's modulus of equivalent medium for wave propagation analysis.
Array imaging of localized objects in homogeneous and heterogeneous media
Chai, Anwei; Moscoso, Miguel; Papanicolaou, George
2016-10-01
We present a comprehensive study of the resolution and stability properties of sparse promoting optimization theories applied to narrow band array imaging of localized scatterers. We consider homogeneous and heterogeneous media, and multiple and single scattering situations. When the media is homogeneous with strong multiple scattering between scatterers, we give a non-iterative formulation to find the locations and reflectivities of the scatterers from a nonlinear inverse problem in two steps, using either single or multiple illuminations. We further introduce an approach that uses the top singular vectors of the response matrix as optimal illuminations, which improves the robustness of sparse promoting optimization with respect to additive noise. When multiple scattering is negligible, the optimization problem becomes linear and can be reduced to a hybrid-{{\\ell }}1 method when optimal illuminations are used. When the media is random, and the interaction with the unknown inhomogeneities can be primarily modeled by wavefront distortions, we address the statistical stability of these methods. We analyze the fluctuations of the images obtained with the hybrid-{{\\ell }}1 method, and we show that it is stable with respect to different realizations of the random medium provided the imaging array is large enough. We compare the performance of the hybrid-{{\\ell }}1 method in random media to the widely used Kirchhoff migration and the multiple signal classification methods.
Changes of the Temperature and Precipitation Extremes on Homogenized Data
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LAKATOS, Mónika
2007-01-01
Full Text Available Climate indices to detect changes have been defined in several international projects onclimate change. Climate index calculations require at least daily resolution of time series withoutinhomogeneities, such as transfer of stations, changes in observation practice. In many cases thecharacteristics of the estimated linear trends, calculated from the original and from the homogenizedtime series are significantly different. The ECA&D (European Climate Assessment & Dataset indicesand some other special temperature and precipitation indices of own development were applied to theClimate Database of the Hungarian Meteorological Service. Long term daily maximum, minimum anddaily mean temperature data series and daily precipitation sums were examined. The climate indexcalculation processes were tested on original observations and on homogenized daily data fortemperature; in the case of precipitation a complementation process was performed to fill in the gapsof missing data. Experiences of comparing the climate index calculation results, based on original andcomplemented-homogenized data, are reported in this paper. We present the preliminary result ofclimate index calculations also on gridded (interpolated daily data.
Directory of Open Access Journals (Sweden)
Sethi M.
2016-05-01
Full Text Available The present paper discusses the dispersion equation for SH waves in a non-homogeneous monoclinic layer over a semi infinite isotropic medium. The wave velocity equation has been obtained. In the isotropic case, when non-homogeneity is absent, the dispersion equation reduces to the standard SH wave equation. The dispersion curves are depicted by means of graphs for different values of non-homogeneity parameters for the layer and semi-infinite medium.
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
@@ The interface between homogeneous catalysis and heterogeneous catalysis has great scope for the development of new catalytic materials[1～4]. Supported aqueous-phase (SAP) catalysis has been employed for the hydroformylation of olefins under mild conditions with high efficiency and convenient separation from the products[5,6].
Besov continuity for pseudo-differential operators on compact homogeneous manifolds
Cardona, Duván
2016-01-01
In this paper we study the Besov continuity of pseudo-differential operators on compact homogeneous manifolds $M=G/K.$ We use the global quantization of these operators in terms of the representation theory of compact homogeneous manifolds.
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Skals, Kasper; Burcharth, Hans F.
2008-01-01
The paper deals with homogeneous and multi-layer berm breakwaters designed to maximize the utilization of the quarry material. Two wide stone classes are typically used for berm breakwaters with a homogeneous berm....