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Sample records for iv gel matrices

  1. Semihumid gels as matrices for laser media

    NASA Astrophysics Data System (ADS)

    Larrue, Denis; Zarzycki, J.; Canva, Michael; Georges, Patrick M.; Brun, Alain

    1992-12-01

    Laser dyes were trapped in SiO2 xerogel host matrices to obtain a solid state dye laser. The evolution of the mechanical properties of two kinds of matrices, 'classic' and 'sono' gels, was followed during drying. A new impregnation process was performed on these xerogels: impregnation with a 'sono' sol. The influence of this treatment on certain physical and mechanical properties of the resulting impregnated gels was studied. The results indicate that impregnation substantially improves hardness, elastic modulus and fracture stress. The samples can then be easily polished to obtain optical quality surfaces and be used in a laser cavity. Moreover, optical properties related to laser emission of these materials such as efficiency, lifetime and longevity are better when the laser dye doped xerogels are impregnated. The organic dye molecule used was sulforhodamine 640, and results were obtained six months after their synthesis, with a pump beam working at a 5 Hz repetition rate with 450 (mu) J/pulse energy level. With the first pump shot on a fixed point of the samples, tunability from 600 to 650 nm, 60 (mu) J threshold, 2600 pump shots lifetime and a 10.5% slope efficiency were achieved using an impregnated 'sono' gel matrix.

  2. Optical detection of parasitic protozoa in sol-gel matrices

    NASA Astrophysics Data System (ADS)

    Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

    1994-10-01

    Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

  3. Gels from soft hairy nanoparticles in polymeric matrices

    NASA Astrophysics Data System (ADS)

    Vlassopoulos, Dimitris

    2013-03-01

    Hairy particles represent a huge class of soft colloids with tunable interactions and properties. Advances in synthetic chemistry have enabled obtaining well-characterized such systems for specific needs. In this talk we present two model hairy soft particles with diameters of the order of tens of nanometers, star polymers and polymerically grafted spherical particles. In particular, we discuss design strategies for dispersing them in polymeric matrices and eventually creating and breaking gels. Control parameters are the matrix molar mass, the grafting density (or functionality) and the size of the grafts (or arms). The linear viscoelastic properties and slow time evolution of the gels are examined in view of the existing knowledge from colloidal gels consisting of micron-sized particles, and compared. In the case of stars we start from a concentrated glassy suspension in molecular solvent and add homopolymer at increasing concentration, and as a result of the induced osmotic pressure the stars shrink and a depletion gel is formed. For the grafted colloidal particles, they are added at low concentration to a polymer matrix, and it has been shown that under certain conditions the anisotropy of interactions gives rise to network formation. We then focus on the nonlinear rheological response and in particular the effect of shear flow in inducing a solid to liquid transition. Our studies show that the yielding process is gradual and shares many common features with that of flocculated colloidal suspensions, irrespectively of the shape of the building block of the gel. Whereas shear can melt such a gel, it cannot break it into its constituent blocks and hence fully disperse the hairy nanoparticles. On the other hand, the hairy particles are intrinsically hybrid. We show how this important feature is reflected on the heating of the gels. In that case, the mismatch of thermal expansion coefficients of core and shell appears to play a role on the particle response as it

  4. Slow Release Of Reagent Chemicals From Gel Matrices

    NASA Technical Reports Server (NTRS)

    Debnam, William J.; Barber, Patrick G.; Coleman, James

    1988-01-01

    Procedure developed for slow release of reagent chemicals into solutions. Simple and inexpensive and not subject to failure of equipment. Use of toothpaste-type tube or pump dispenser conceivably provides more controlled technique for storage and dispensation of gel matrix. Possible uses include controlled, slow release of reagents in chemical reactions, crystal growth, space-flight experiments, and preformed gel medications from packets.

  5. Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    2002-11-26

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  6. Sol-gel matrices for direct colorimetric detection of analytes

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    2000-01-01

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  7. Characterization of collagen gel solutions and collagen matrices for cell culture.

    PubMed

    Sheu, M T; Huang, J C; Yeh, G C; Ho, H O

    2001-07-01

    The influence of glutaraldehyde as a crosslinking agent to increase the strength of collagen matrices for cell culture was examined in this study. Collagen solutions of 1% were treated with different concentrations (0-0.2%) of glutaraldehyde for 24 h. The viscoelasticity of the resulting collagen gel solution was measured using dynamic mechanical analysis (DMA), which demonstrated that all collagen gel solutions examined followed the same model pattern. The creep compliance model of Voigt-Kelvin satisfactorily described the change of viscoelasticity expressed by these collagen gel solutions. These crosslinked collagen gel solutions were freeze-dried to form a matrix with a thickness of about 0.2-0.3 mm. The break modulus of these collagen matrices measured by DMA revealed that the higher the degree of crosslinking. the higher the break modulus. The compatibility of fibroblasts isolated from nude mouse skin with these collagen matrices was found to be acceptable at a cell density of 3 x 10(5) cells/cm2 with no contraction, even when using a concentration of glutaraldehyde of up to 0.2%. PMID:11396874

  8. Reducing bloodstream infection with a chlorhexidine gel IV dressing.

    PubMed

    Jeanes, Annette; Bitmead, James

    The use of vascular access devices (VAD) is common in healthcare provision but there is a significant risk of acquiring an infection. Central venous catheters (CVC) are associated with the highest risk of intravenous catheter-related bloodstream infection (CRBSI). 3M™ Tegaderm™ CHG IV dressing is a semi-permeable transparent adhesive dressing with an integrated gel pad containing chlorhexidine gluconate 2%. This product was reviewed by the National Institute for Health and Care Excellence (NICE) in 2015, recommending that Tegaderm CHG could be used for CVC and arterial line dressings in high-dependency and intensive-care settings. This article discusses issues around CRBSI, interventions to reduce the risk of CRBSI, and the use of Tegaderm CHG dressing. PMID:26496869

  9. Synthesis of Sol-Gel Matrices for Encapsulation of Enzymes Using an Aqueous Route

    SciTech Connect

    Ashley, C.S.; Bhatia, R.B.; Brinker, C.J.; Harris, T.M.

    1998-11-23

    Sol-gel matrices are promising host materials for potential chemical and biosensor applications. Previous studies have focused on modified sol-gel routes using alkoxides for encapsulation of enzymes. However the formation of alcohol as a byproduct during hydrolysis and condensation reactions poses limitations. We report the immobilization of glucose oxidase and peroxidase in silica prepared by an aqueous route which may provide a more favorable environment for the biomolecules. A two step aqueous sol-gel procedure using sodium silicate as the precursor was developed to encapsulate the enzymes and the dye precursor, o-dianisidine. Glucose oxidase catalyzes the oxidation of glucose to give gluconic acid and hydrogen peroxide. Peroxidase then catalyzes the reaction of the dye precursor with hydrogen peroxide to produce a colored product. The kinetics of the coupled enzymatic reactions were monitored by optical spectroscopy and compared to those occurring in tetramethyl orthosilicate (TMOS) derived silica matrices developed by Yamanaka. Enhanced kinetics in the aqueous silicate matrices were related to differences in the host microstructure as elucidated by microstructural comparisons of the corresponding aerogels.

  10. Titanium (IV) sol-gel chemistry in varied gravity environments

    NASA Astrophysics Data System (ADS)

    Hales, Matthew; Martens, Wayde; Steinberg, Theodore

    Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time

  11. Spectroscopic studies of chemical reactions and dynamics in sol-gel matrices

    SciTech Connect

    Akbarian, F.; Dunn, B.; Fuqua, P.D.; McKiernan, J.; Simoni, E.; Zink, J.I.

    1994-12-31

    The synthesis of sol-gel glasses containing organic and organometallic molecular dopants has been well established as an approach for creating new optical materials. Some of these properties are dependent upon chemical reactions which occur in porous xerogel matrices during the sol-gel process or when encapsulated molecules are exposed to other molecules in solution. In this paper, the study of two different types of chemical reactions in the pores of xerogel matrices is reported. In one case copper phthalocyanine is used to characterize dimerization within the pores. The results show that dimer formation is most likely to occur towards the end of the drying stage as the dye concentration in the pores increases from solvent evaporation. A second example involves the use of a pump-probe technique to determine the rate of proton recombination inside the pores of silica monoliths. The behavior of sols and gels is similar to aqueous solution while recombination of protons in the xerogel seems to be affected by the walls of the pores.

  12. Permeability of starch gel matrices and select films to solvent vapors.

    PubMed

    Glenn, Gregory M; Klamczynski, Artur P; Ludvik, Charles; Shey, Justin; Imam, Syed H; Chiou, Bor-Sen; McHugh, Tara; DeGrandi-Hoffman, Gloria; Orts, William; Wood, Delilah; Offeman, Rick

    2006-05-01

    Volatile agrochemicals such as 2-heptanone have potential in safely and effectively controlling important agricultural pests provided that they are properly delivered. The present study reports the permeability of starch gel matrices and various coatings, some of which are agricultural-based, that could be used in controlled release devices. Low-density, microcellular starch foam was made from wheat, Dent corn, and high amylose corn starches. The foam density ranged from 0.14 to 0.34 g/cm3, the pore volume ranged from 74 to 89%, and the loading capacity ranged from 2.3 to 7.2 times the foam weight. The compressive properties of the foam were not markedly affected by saturating the pore volume with silicone oil. The vapor transmission rate (VTR) and vapor permeability (VP) were measured in dry, porous starch foam and silicone-saturated starch gels. VTR values were highest in foam samples containing solvents with high vapor pressures. Silicone oil-saturated gels had lower VTR and VP values as compared to the dry foam. However, the silicone oil gel did not markedly reduce the VP for 2-heptanone and an additional vapor barrier or coating was needed to adequately reduce the evaporation rate. The VP of films of beeswax, paraffin, ethylene vinyl alcohol, a fruit film, and a laminate comprised of beeswax and fruit film was measured. The fruit film had a relatively high VP for polar solvents and a very low VP for nonpolar solvents. The laminate film provided a low VP for polar and nonpolar solvents. Perforating the fruit film portion of the laminate provided a method of attaining the target flux rate of 2-heptanone. The results demonstrate that the vapor flux rate of biologically active solvents can be controlled using agricultural materials. PMID:16637688

  13. Encapsulation of ruthenium nitrosylnitrate and DNA purines in nanostructured sol-gel silica matrices.

    PubMed

    Lopes, Luís M F; Garcia, Ana R; Fidalgo, Alexandra; Ilharco, Laura M

    2009-09-01

    The interactions between DNA purines (guanine and adenine) and the ruthenium complex Ru(NO)(NO(3))(3) were studied within nanostructured silica matrices prepared by a two-step sol-gel process. By infrared analysis in diffuse reflectance mode, it was proved that encapsulation induces a profound modification on the complex, whereas guanine and adenine preserve their structural integrity. The complex undergoes nitrate ligand exchange and co-condenses with the silica oligomers, but the nitrosyl groups remain stable, which is an unusual behavior in Ru nitrosyl complexes. In turn, the doping molecules affect the sol-gel reactions and eventually the silica structure as it forms: the complex yields a microporous structure, and the purine bases are responsible for the creation of macropores due to hydrogen bonding with the silanol groups of the matrix. In a confined environment, the interactions are much stronger for the coencapsulated pair guanine complex. While adenine only establishes hydrogen bonds or van der Waals interactions with the complex, guanine bonds covalently to Ru by one N atom of the imidazole ring, which becomes strongly perturbed, resulting in a deformation of the complex geometry. PMID:19499946

  14. HPMC-based gastroretentive dual working matrices coated with Ca(+2) ion crosslinked alginate-fenugreek gum gel membrane.

    PubMed

    Bera, Hriday; Gaini, Chakravarthy; Kumar, Sanoj; Sarkar, Srimanta; Boddupalli, Shashank; Ippagunta, Sohitha Reddy

    2016-10-01

    Novel alginate-fenugreek gum (FG) gel membrane coated hydroxypropylmethylcellulose (HPMC) based matrix tablets were developed for intragastric quetiapine fumarate (QF) delivery by combining floating and swelling mechanisms. The effects of polymer blend ratios [HPMC K4M:HPMC E15] and citric acid contents on time taken for 50% drug release (t50%, min) and drug release at 8h (Q8h, %) were studied to optimize the core tablets by 3(2) factorial design. The optimized tablets (F-O) exhibited t50% of 247.67±3.51min and Q8h of 71.11±0.32% with minimum errors in prediction. The optimized tablets were coated with Ca(+2) ions crosslinked alginate-FG gel membrane by diffusion-controlled interfacial complexation technique. The biopolymeric-coated optimized matrices exhibited superior buoyancy, preferred swelling characteristics and slower drug release rate. The drug release profiles of the QF-loaded uncoated and coated optimized matrices were best fitted in Korsmeyer-Peppas model with anomalous diffusion driven mechanism. The uncoated and coated tablets containing QF were also characterized for drug-excipients compatibility, thermal behaviour and surface morphology by FTIR, DSC and SEM analyses, respectively. Thus, the newly developed alginate-FG gel membrane coated HPMC matrices are appropriate for intragastric delivery of QF over a prolonged period of time with greater therapeutic benefits. PMID:27287111

  15. MRI-based polymer gel dosimetry for validating plans with multiple matrices in Gamma Knife stereotactic radiosurgery.

    PubMed

    Gopishankar, N; Watanabe, Yoichi; Subbiah, Vivekanandhan

    2011-01-01

    One of treatment planning techniques with Leksell GammaPlan (LGP) for Gamma Knife stereotactic radiosurgery (GKSRS) uses multiple matrices with multiple dose prescriptions. Computational complexity increases when shots are placed in multiple matrices with different grid sizes. Hence, the experimental validation of LGP calculated dose distributions is needed for those cases. For the current study, we used BANG3 polymer gel contained in a head-sized glass bottle to simulate the entire treatment process of GKSRS. A treatment plan with three 18 mm shots and one 8 mm shot in separate matrices was created with LGP. The prescribed maximum dose was 8 Gy to three shots and 16 Gy to one of the 18 mm shots. The 3D dose distribution recorded in the gel dosimeter was read using a Siemens 3T MRI scanner. The scanning parameters of a CPMG pulse sequence with 32 equidistant echoes were as follows: TR = 7 s, echo step = 13.6 ms, field-of-view = 256 mm × 256 mm, and pixel size = 1 mm × 1 mm. Interleaved acquisition mode was used to obtain 15 to 45 2-mm-thick slices. Using a calibration relationship between absorbed dose and the spin-spin relaxation rate (R2), we converted R2 images to dose images. MATLAB-based in-house programs were used for R2 estimation and dose comparison. Gamma-index analysis for the 3D data showed gamma values less than unity for 86% of the voxels. Through this study we accomplished the first application of polymer gel dosimetry for a true comparison between measured 3D dose distributions and LGP calculations for plans using multiple matrices for multiple targets. PMID:21587176

  16. Encapsulation of protein molecules in transparent porous silica matrices via an aqueous colloidal sol-gel process

    SciTech Connect

    Liu, D.M.; Chen, I.W.

    1999-12-10

    Encapsulation of several biologically important proteins, cytochrome c, catalase, myoglobin, and hemoglobin, into transparent porous silica matrices by an aqueous colloidal sol-gel process that requires no alcohol is reported. Optical characterization indicates a successful retention of protein conformation after encapsulation. The conformation retention is strongly correlated to both the rate of gelation and the subsequent drying speed. Using hemoglobin as a model protein, a higher colloidal solid concentration and a lower synthesis pH were found, both causing faster gelation, resulting in a better retention of conformation. Hemoglobin encapsulated in a thin film, which dries faster, also showed a better retention than in the bulk. This is attributed to the fact that when a protein is isolated, and especially when it is confined to a space close to its own dimensions, conformational changes are sterically hindered, hence the structural stability. Enzymatic activity of bovine liver catalase was also monitored and showed a remarkable improvement when encapsulated using the aqueous colloidal process, compared to using the conventional alkoxide-based process. Thus, the aqueous colloidal sol-gel process offers a promising alternative to the conventional sol-gel process for encapsulating biomolecules into transparent, porous matrices.

  17. Strength of interactions between immobilized dye molecules and sol-gel matrices.

    PubMed

    Ismail, Fanya; Schoenleber, Monika; Mansour, Rolan; Bastani, Behnam; Fielden, Peter; Goddard, Nicholas J

    2011-02-21

    In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel. PMID:21120245

  18. 29Si NMR investigation of ORMOSIL layers used as luminophores' sol-gel matrices in a UV optical fibre sensor

    NASA Astrophysics Data System (ADS)

    Chodkowska, Eliza M.; Rayss, Jan

    2007-07-01

    The paper concerns the results of ORMOSIL layer's applied in an optical fibre ultraviolet sensor Nuclear Magnetic Resonance investigation. The layer which substituted for optical fibre's cladding in device's sensing part acted as a matrix for a coumarin's derivative. The dye is able to convert ultraviolet into visible radiation which could be easily detected. Thanks to the fact that the refractive indices of ORMOSIL layers may be controlled and reach a value characteristic for the fused silica glass a satisfying sensitivity of the device can be achieved. However it may be expected that both the structure and the composition of ORMOSIL matrices could influence the organic dye's behaviour. The aim of the experiment presented in the paper was to prove a relation between the sol's condensation time and a composition of the obtained gel's structure. The obtained NMR spectra gave the evidence of non-condensed -Si-O-C IIH 5(H) moieties existence in the solid gels. Moreover, even a 42-days-long process does not lead to the total condensation of ethoxysilanes' molecules. It is probable that the remaining ethoxy or silanol groups interact with transducer's molecules as well as influence the refractive index of the gel layer.

  19. The influence of polymer content on early gel-layer formation in HPMC matrices: The use of CLSM visualisation to identify the percolation threshold.

    PubMed

    Mason, Laura Michelle; Campiñez, María Dolores; Pygall, Samuel R; Burley, Jonathan C; Gupta, Pranav; Storey, David E; Caraballo, Isidoro; Melia, Colin D

    2015-08-01

    Percolation theory has been used for several years in the design of HPMC hydrophilic matrices. This theory predicts that a minimum threshold content of polymer is required to provide extended release of drug, and that matrices with a lower polymer content will exhibit more rapid drug release as a result of percolation pathways facilitating the faster penetration of the aqueous medium. At present, percolation thresholds in HPMC matrices have been estimated solely through the mathematical modelling of dissolution data. This paper examines whether they can be also identified in a novel way: through the use of confocal laser scanning fluorescence microscopy (CLSM) to observe the morphology of the emerging gel layer during the initial period of polymer hydration and early gel formation at the matrix surface. In this study, matrices have been prepared with a polymer content of 5-30% w/w HPMC 2208 (Methocel K4M), with a mix of other excipients (a soluble drug (caffeine), lactose, microcrystalline cellulose and magnesium stearate) to provide a typical industrially realistic formulation. Dissolution studies, undertaken in water using USP apparatus 2 (paddle) at 50rpm, provided data for the calculation of the percolation threshold through relating dissolution kinetic parameters to the excipient volumetric fraction of the dry matrix. The HPMC percolation threshold estimated this way was found to be 12.8% v/v, which was equivalent to a matrix polymer content of 11.5% w/w. The pattern of polymer hydration and gel layer growth during early gel layer formation was examined by confocal laser scanning fluorescence microscopy (CLSM). Clear differences in gel layer formation were observed. At polymer contents above the estimated threshold a continuous gel layer was formed within 15min, whereas matrices with polymer contents below the threshold were characterised by irregular gel layer formation with little evidence of HPMC particle coalescence. According to percolation theory, this

  20. Comparison of spectroscopic and lasing properties of different types of sol-gel glass matrices containing Rh-6G.

    PubMed

    Deshpande, Aparna V; Rane, Jayraj R; Jathar, Laxman V

    2009-11-01

    Rhodamine-6G (Rh-6G) is embedded in sol-gel glass samples which have been prepared by three different methods namely: 1) using HCl as catalyst and glycerol as Drying Control Chemical Additive (DCCA), 2) using HCl as catalyst at 60 degrees C and drying at room temperature and 3) using HCl as catalyst at 60 degrees C and heated at 600 degrees C for 3 h. Comparative studies of spectroscopic and lasing properties of the three types of Rh-6G containing samples were carried out with the lapse of time upto 8 months. Photostability of Rh-6G containing sol-gel samples is measured in terms of half life under Nitrogen laser pumping as number of pulses of N2 laser necessary to reduce the dye laser intensity to 50% of the original value and value is 7500 pulses at 1.67 Hz rate. The best performance of Rh-6G, as far as its spectroscopic and lasing properties are concerned was found in third type of host matrices using HCl as catalyst at 60 degrees C and heated at 600 degrees C for 3 h. PMID:19562470

  1. Modular Injectable Matrices Based on Alginate Solution/Microsphere Mixtures That Gel in situ and Co-Deliver Immunomodulatory Factors

    PubMed Central

    Hori, Yuki; Winans, Amy M.; Irvine, Darrell J.

    2011-01-01

    Biocompatible polymer solutions that can crosslink in situ following injection to form stable hydrogels are of interest as depots for sustained delivery of therapeutic factors or cells, and as scaffolds for regenerative medicine. Here, injectable self-gelling alginate formulations obtained by mixing alginate microspheres (as calcium reservoirs) with soluble alginate solutions were characterized for potential use in immunotherapy. Rapid redistribution of calcium ions from microspheres into the surrounding alginate solution led to rapid crosslinking and formation of stable hydrogels. The mechanical properties of the resulting gels correlated with the concentration of calcium reservoir microspheres added to the solution. Soluble factors such as the cytokine interleukin-2 were readily incorporated into self-gelling alginate matrices by simply mixing them with the formulation prior to gelation. Using alginate microspheres as modular components, strategies for binding immunostimulatory CpG oligonucleotides onto the surface of microspheres were also demonstrated. When injected subcutaneously in the flanks of mice, self-gelling alginate formed soft macroporous gels supporting cellular infiltration and allowing ready access to microspheres carrying therapeutic factors embedded in the matrix. This in-situ gelling formulation may thus be useful for stimulating immune cells at a desired locale such as solid tumors or infection sites as well as for other soft tissue regeneration applications. PMID:19117820

  2. Fiber-optic dissolved oxygen and dissolved carbon dioxide sensors using fluorophores encapsulated in sol gel matrices

    NASA Astrophysics Data System (ADS)

    Kwon, Hyeog-Chan

    Fiber optic chemical sensors (FOCS) for oxygen, dissolved oxygen (DO), and dissolved CO2 sensing using thin films of fluorophores encapsulated in sol-gel matrices were made and tested. The DO/O2 sensor used ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) perchlorate (Ru(Ph 2Phen)Cl2) as the oxygen sensitive fluorophore and methyltrimethoxysilane (MTMS) sol-gel as the encapsulating matrix material. For the DCO2 sensor, 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) co-doped with sodium bicarbonate was used as the DCO2 sensitive fluorophore-chemical system and diisobutoxy-alumino triethoxysilane (ASE) sol-gel was used as the encapsulating matrix material. It was found that oxygen quenches the excited state Ru(Ph2Phen)Cl 2 by diffusing through the MTMS matrix. Continuous excitation of Ru(Ph 2Phen)Cl2 during MTMS drying resulted in long, single exponential lifetimes of the metal complex and increased sensor sensitivity. When the sensor was field tested, it was found to have an excellent match compared to conventional titration method for determining dissolved oxygen concentrations and had fast response times. It was determined that this sensor measured the vapor pressure of oxygen rather than the absolute concentration of dissolved oxygen. For DCO2 sensing, it was found that the dynamic response of the senor could be tuned by varying the HPTS to NaHCO3 ratios. The sensor had fast response times compared to other fiber optic DCO 2 sensors reported which typically have response times of minutes.

  3. Contrasting roles of layered structures in the molecular assembly of liquid crystal matrices on the viscoelastic properties of microparticle/liquid crystal composite gels leading to rigidification and destabilization.

    PubMed

    Yamamoto, Takahiro; Kawata, Yuki; Yoshida, Masaru

    2013-05-01

    We investigated the effects of the nematic and smectic A (SmA) phase structures of liquid crystalline matrices on the viscoelastic properties of microparticle/liquid-crystal composite gels. The storage (G') and loss (G″) moduli of the gels were largely increased in gels containing SmA matrices with a layered molecular assembly. However, the critical strain at which the gel state transformed into the sol state by the application of mechanical strain showed no significant changes with variation in the liquid crystal phase of the matrix. These results indicate that the introduction of a layered molecular assembly could be effective for rigidification of composite gels, while maintaining their critical strains. However, the composite gels tended to show a metastable state when SmA matrices were used because G' and G″ of the gels were close to each other in the entire frequency region. This behavior was in contrast to the gels with nematic matrices, which showed a larger value in G' than that in G″. The metastable state of gels with SmA matrices was also reflected in the frequency dependence of G' and in the deterioration of the recovery of the gel state after mechanical breakdown. PMID:23465188

  4. Nonlinear optical and electrical conductivity properties of Carbon Nanotubes (CNT) doped in Sol-Gel matrices

    NASA Astrophysics Data System (ADS)

    Pokrass, Mariana; Burshtein, Zeev; Bar, Galit; Gvishi, Raz

    2014-09-01

    Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large π-π* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was σ ≍10-3 (Ωcm)-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, φc = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

  5. Encapsulation of biomaterials in porous glass-like matrices prepared via an aqueous colloidal sol-gel process

    DOEpatents

    Liu, Dean-Mo; Chen, I-Wei

    2001-01-01

    The present invention provides a process for the encapsulation of biologically important proteins into transparent, porous silica matrices by an alcohol-free, aqueous, colloidal sol-gel process, and to the biological materials encapsulated thereby. The process is exemplified by studies involving encapsulated cytochrome c, catalase, myoglobin, and hemoglobin, although non-proteinaceous biomaterials, such as active DNA or RNA fragments, cells or even tissues, may also be encapsulated in accordance with the present methods. Conformation, and hence activity of the biomaterial, is successfully retained after encapsulation as demonstrated by optical characterization of the molecules, even after long-term storage. The retained conformation of the biomaterial is strongly correlated to both the rate of gelation and the subsequent drying speed of the encapsulatng matrix. Moreover, in accordance with this process, gelation is accelerated by the use of a higher colloidal solid concentration and a lower synthesis pH than conventional methods, thereby enhancing structural stability and retained conformation of the biomaterials. Thus, the invention also provides a remarkable improvement in retaining the biological activity of the encapsulated biomaterial, as compared with those involved in conventional alkoxide-based processes. It further provides new methods for the quantitative and qualitative detection of test substances that are reactive to, or catalyzed by, the active, encapsulated biological materials.

  6. Photo-responsive properties of azobenzene small molecules in sol-gel hybrid TiO2/ormosil organic-inorganic matrices

    NASA Astrophysics Data System (ADS)

    Que, Wenxiu; Hu, X.; Xia, X. L.; Zhao, L.

    2007-01-01

    Azodye-doped TiO2/ormosil hybrid materials for photonic applications were prepared by a low temperature sol-gel process from an organic-inorganic hybrid system. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane mixed with tetrapropyl orthotitanate were used as hybrid matrix precursors. The trans-cis-trans photoisomerization of azobenzene small molecules in sol-gel hybrid organic-inorganic matrices was induced by a photoirradiation with UV light and subsequent visible light. It was found that the hybrid film doped with azodyes and heated at a lower temperature was much better for applications in optical storage or optical switch. The planar waveguide properties of the hybrid films were also investigated by using a prism coupling technique. These results indicates that it is possible for the as prepared hybrid films to allow directly integrating on the same chip the optical storage or optical switch devices with the pump source.

  7. Photophysical, photochemical and laser behavior of some diolefinic laser dyes in sol-gel and methyl methacrylate/2-hydroxyethyl methacrylate copolymer matrices

    NASA Astrophysics Data System (ADS)

    Sakr, Mahmoud A. S.; Abdel Gawad, El-Sayed A.; Abou Kana, Maram T. H.; Ebeid, El-Zeiny M.

    2015-08-01

    The photophysical properties such as singlet absorption, molar absorptivity, fluorescence spectra, dipole moment, fluorescence quantum yields, fluorescence lifetimes and laser activity of 1,4-bis (β-Pyridyl-2-Vinyl) Benzene (P2VB), 2,5-distyryl-pyrazine (DSP) and 1,4-bis(2-methylstyryl)benzene(MSB) diolefineic laser dyes have been measured in different restricted hosts. (P2VB), (DSP) and (MSB) are embedded in transparent sol-gel glass and a copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) media. The absorption and fluorescence properties of these laser dyes in sol-gel glass matrices are compared with their respective properties in copolymer host. The photostability of these laser dyes in sol-gel glass and (MMA/HEMA) copolymer samples are measured in terms of half-life method (using nitrogen laser 337.1 nm in pumping), as the number of pulses necessary to reduce the dye laser intensity to 50% of its original value. The gel laser materials show improved photostability upon pumping by nitrogen laser compared with those in organic polymeric host matrix.

  8. Silica-gel Particles Loaded with an Ionic Liquid for Separation of Zr(IV) Prior to Its Determination by ICP-OES.

    PubMed

    Marwani, Hadi M; Alsafrani, Amjad E; Asiri, Abdullah M; Rahman, Mohammed M

    2016-01-01

    A new ionic liquid loaded silica gel amine (SG-APTMS-N,N-EPANTf₂) was developed, as an adsorptive material, for selective adsorption and determination of zirconium, Zr(IV), without the need for a chelating intermediate. Based on a selectivity study, the SG-APTMS-N,N-EPANTf₂ phase showed a perfect selectivity towards Zr(IV) at pH 4 as compared to other metallic ions, including gold [Au(III)], copper [Cu(II)], cobalt [Co(II)], chromium [Cr(III)], lead [Pb(II)], selenium [Se(IV)] and mercury [Hg(II)] ions. The influence of pH, Zr(IV) concentration, contact time and interfering ions on SG-APTMS-N,N-EPANTf₂ uptake for Zr(IV) was evaluated. The presence of incorporated donor atoms in newly synthesized SG-APTMS-N,N-EPANTf₂ phase played a significant role in enhancing its uptake capacity of Zr(IV) by 78.64% in contrast to silica gel (activated). The equilibrium and kinetic information of Zr(IV) adsorption onto SG-APTMS-N,N-EPANTf₂ were best expressed by Langmuir and pseudo second-order kinetic models, respectively. General co-existing cations did not interfere with the extraction and detection of Zr(IV). Finally, the analytical efficiency of the newly developed method was also confirmed by implementing it for the determination of Zr(IV) in several water samples. PMID:27367692

  9. Silica-gel Particles Loaded with an Ionic Liquid for Separation of Zr(IV) Prior to Its Determination by ICP-OES

    PubMed Central

    Marwani, Hadi M.; Alsafrani, Amjad E.; Asiri, Abdullah M.; Rahman, Mohammed M.

    2016-01-01

    A new ionic liquid loaded silica gel amine (SG-APTMS-N,N-EPANTf2) was developed, as an adsorptive material, for selective adsorption and determination of zirconium, Zr(IV), without the need for a chelating intermediate. Based on a selectivity study, the SG-APTMS-N,N-EPANTf2 phase showed a perfect selectivity towards Zr(IV) at pH 4 as compared to other metallic ions, including gold [Au(III)], copper [Cu(II)], cobalt [Co(II)], chromium [Cr(III)], lead [Pb(II)], selenium [Se(IV)] and mercury [Hg(II)] ions. The influence of pH, Zr(IV) concentration, contact time and interfering ions on SG-APTMS-N,N-EPANTf2 uptake for Zr(IV) was evaluated. The presence of incorporated donor atoms in newly synthesized SG-APTMS-N,N-EPANTf2 phase played a significant role in enhancing its uptake capacity of Zr(IV) by 78.64% in contrast to silica gel (activated). The equilibrium and kinetic information of Zr(IV) adsorption onto SG-APTMS-N,N-EPANTf2 were best expressed by Langmuir and pseudo second-order kinetic models, respectively. General co-existing cations did not interfere with the extraction and detection of Zr(IV). Finally, the analytical efficiency of the newly developed method was also confirmed by implementing it for the determination of Zr(IV) in several water samples. PMID:27367692

  10. Pressure-induced changes on the optical properties and microstructure of silica-gel matrices doped with rhodamine 6G

    NASA Astrophysics Data System (ADS)

    Costa, Tania Maria Haas; Hoffmann, Helena Sofia; Benvenutti, Edilson Valmir; Stefani, Valter; Gallas, Marcia Russman

    2005-12-01

    Sol-gel method and high-pressure technique were associated to produce silica compacts with low porosity and doped with rhodamine 6G (R6G). Acid catalyzed solutions of tetraethyl orthosilicate mixed with dye previously dissolved in ethanol were used for the synthesis of doped silica gel. The monolith obtained was comminuted and the powder was compacted between 3.0 and 7.7 GPa, at room temperature, using a toroidal-type high-pressure chamber. Excitation-emission fluorescence spectroscopy was used to investigate the optical properties of R6G embedded in the closed pores of the silica matrix. Measurements of surface areas and pore size distribution for the powders and compacts, using the N2 isotherms were performed, showing a great reduction in surface area and porosity, after compaction. The dye entrapped in the compacted silica maintains its optical properties similar to that in ethanolic solutions, meaning that the dye is dispersed in a molecular level. Additionally, these samples are optically transparent, hard and resistant to dye leaching and to chemical attacks, being a promising material to be used in optical devices.

  11. Spectroscopy in Sol-Gel Matrices: An Open-Ended Laboratory Experience for Upper-Level Undergraduates

    NASA Astrophysics Data System (ADS)

    Higginbotham, Catrena; Pike, Charles F.; Rice, Jeanette K.

    1998-04-01

    Guided-inquiry/cooperative learning laboratory experiences encourage critical thinking, problem- solving and teamwork skills in students, and have been proposed for many undergraduate laboratories, particularly general and organic. Fewer reports have appeared for upper level courses such as instrumental analysis. In this report, we discuss our recent conversion of our Instrumental Analysis:Spectroscopy course to guided-inquiry format, and describe an appropriate novel experiment. Sol-gel technology is incorporated as a means to investigate spectral properties of various organic molecules. Students are exposed to silicate glass synthesis as well as modern spectroscopic techniques. Experimental details are researched, designed and executed by the students, and the results presented in both written format as well as oral presentation/examination.

  12. Improved separation of palladium species in biological matrices by using a combination of gel permeation chromatography and isotachophoresis.

    PubMed

    Weber, Günther; Messerschmidt, Jürgen; von Bohlen, Alex; Kastenholz, Bernd; Günther, Klaus

    2004-06-01

    The binding of palladium to high-molecular-mass compounds in palladium-treated lettuce is investigated as an example for a biological matrix. The total palladium concentration in lettuce leaves is 10.3 ng/g wet weight. After homogenization, high-molecular-mass compounds (> 10 kDa) are isolated by ultrafiltration. For separation of these palladium species a combination of preparative gel permeation chromatography (GPC) and preparative isotachophoresis (ITP) is used. Palladium is determined in separated fractions by using a highly sensitive total reflection X-ray fluorescence (TXRF) method after preconcentration. After GPC separation, four main fractions of palladium species are collected, each containing palladium in ng quantities (3-10 ng). Two of these fractions are further separated by ITP, yielding at least three main peaks per GPC fraction, each containing palladium in the range of 0.3-3 ng. These palladium containing peaks are characterized by high-performance size exclusion chromatography (HPSEC) and capillary isotachophoresis (cITP) in parallel. HPSEC enables the estimation of the molecular mass of six main palladium peaks, covering a molecular mass range of 69-200 kDa. It is also shown that the estimation of molecular mass after separation is more reliable than the respective estimation directly in the first GPC run. However, cITP reveals that each of the separated peaks is still a mixture of at least five different compounds. PMID:15213973

  13. The use of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) polymers as spacers for isotachophoresis in sieving gel matrices.

    PubMed

    Bellini, M P; Manchester, K L

    1999-03-01

    The electric field strength gradients generated in isotachophoresis (ITP) may be used for the separation of biomolecules. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (polyAMPS) polymers of a uniform distribution of molecular mass were synthesized and used as novel spacers in ITP. Since these polymeric spacers are strongly acidic species, their ionic charges remain constant over a wide pH range, so that their ionic mobilities are governed solely by their molecular masses and not by the pH of the milieu. A modification of ITP known as telescope electrophoresis was used to separate a number of acidic dyes of varying ionic mobility, using polyAMPS polymers as spacers. The resolution obtained was superior to that obtained by polyacrylamide gel electrophoresis (PAGE), due to the focusing effect of the electric field strength gradient. Since these novel polymeric spacers are designed to operate within sieving medium, it was decided to test their suitability for the separation of DNA molecules. DNA molecules up to 1000 bp long were successfully resolved, with a similar resolution to that obtained with conventional PAGE. PMID:10036157

  14. Tretinoin Nanogel 0.025% Versus Conventional Gel 0.025% in Patients with Acne Vulgaris: A Randomized, Active Controlled, Multicentre, Parallel Group, Phase IV Clinical Trial

    PubMed Central

    Chandrashekhar, B S; Anitha, M.; Ruparelia, Mukesh; Vaidya, Pradyumna; Aamir, Riyaz; Shah, Sunil; Thilak, S; Aurangabadkar, Sanjeev; Pal, Sandeep; Saraswat, Abir

    2015-01-01

    Background: Conventional topical tretinoin formulation is often associated with local adverse events. Nanogel formulation of tretinoin has good physical stability and enables good penetration of tretinoin into the pilo-sebaceous glands. Aim: The present study was conducted to assess the efficacy and safety of a nanogel formulation of tretinoin as compared to its conventional gel formulation in the treatment of acne vulgaris of the face. Materials and Methods: This randomized, active controlled, multicentric, phase IV clinical trial evaluated the treatment of patients with acne vulgaris of the face by the two gel formulations locally applied once daily at night for 12 wk. Acne lesion counts (inflammatory, non-inflammatory & total) and severity grading were carried out on the monthly scheduled visits along with the tolerability assessments. Results: A total of 207 patients were randomized in the study. Reductions in the total (72.9% vs. 65.0%; p = 0.03) and inflammatory (78.1% vs. 66.9%; p = 0.02) acne lesions were reported to be significantly greater with the nanogel formulation as compared to the conventional gel formulation. Local adverse events were significantly less (p = 0.04) in the nanogel group (13.3%) as compared to the conventional gel group (24.7%). Dryness was the most common adverse event reported in both the treatment groups while peeling of skin, burning sensation and photosensitivity were reported in patients using the conventional gel only. Conclusion: In the treatment of acne vulgaris of the face, tretinoin nanogel formulation appears to be more effective and better tolerated than the conventional gel formulation. PMID:25738069

  15. Compound matrices

    NASA Astrophysics Data System (ADS)

    Kravvaritis, Christos; Mitrouli, Marilena

    2009-02-01

    This paper studies the possibility to calculate efficiently compounds of real matrices which have a special form or structure. The usefulness of such an effort lies in the fact that the computation of compound matrices, which is generally noneffective due to its high complexity, is encountered in several applications. A new approach for computing the Singular Value Decompositions (SVD's) of the compounds of a matrix is proposed by establishing the equality (up to a permutation) between the compounds of the SVD of a matrix and the SVD's of the compounds of the matrix. The superiority of the new idea over the standard method is demonstrated. Similar approaches with some limitations can be adopted for other matrix factorizations, too. Furthermore, formulas for the n - 1 compounds of Hadamard matrices are derived, which dodge the strenuous computations of the respective numerous large determinants. Finally, a combinatorial counting technique for finding the compounds of diagonal matrices is illustrated.

  16. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. IV. The automatic implementation of the Hessian based VBSCF method.

    PubMed

    Chen, Xun; Chen, Zhenhua; Wu, Wei

    2014-11-21

    In this paper, the Hessian matrix of valence bond (VB) self-consistent field (VBSCF) energy with respect to orbitals are evaluated by applying the nonorthogonal orbital based N-body reduced density matrices, which was presented in Paper I. To this end, an automatic formula/code generator (AFCG) is developed; with which the matrix elements between internally contracted excited configurations of VB wave function and the corresponding codes are generated automatically. Compared to the tedious manual formula deducing and implementing, AFCG is much more convenient and efficient, and enables us to avoid troublesome debugging. With the help of AFCG, the Hessian-based Newton-Raphson algorithm is implemented for the VBSCF orbital optimization. Test calculations indicate that the Newton-Raphson algorithm converges quadratically and has much better convergence behavior than the gradient-based LBFGS algorithms. Furthermore, a combined approach with LBFGS and Newton-Raphson algorithms is applied to reduce the total CPU time of the calculation. PMID:25416880

  17. Mechanisms of drug release in citrate buffered HPMC matrices.

    PubMed

    Pygall, Samuel R; Kujawinski, Sarah; Timmins, Peter; Melia, Colin D

    2009-03-31

    Few studies report the effects of alkalizing buffers in HPMC matrices. These agents are incorporated to provide micro-environmental buffering, protection of acid-labile ingredients, or pH-independent release of weak acid drugs. In this study, the influence of sodium citrate on the release kinetics, gel layer formation, internal gel pH and drug release mechanism was investigated in HPMC 2910 and 2208 (Methocel E4M and K4M) matrices containing 10% felbinac 39% HPMC, dextrose and sodium citrate. Matrix dissolution at pH 1.2 and pH 7.5 resulted in complex release profiles. HPMC 2910 matrices exhibited biphasic release, with citrate increasing the immediate release phase (<60min) and reducing the extended release. HPMC 2208 matrices were accelerated, but without the loss of extended release characteristics. Studies of early gel layer formation suggested gel barrier disruption and enhanced liquid penetration. pH modification of the gel layer was transitory (<2h) and corresponded temporally with the immediate release phase. Results suggest that in HPMC 2910 matrices, high initial citrate concentrations within the gel layer suppress particle swelling, interfere with diffusion barrier integrity, but are lost rapidly whereupon drug solubility reduces and the diffusion barrier recovers. These Hofmeister or osmotic-mediated effects are better resisted by the less methoxylated HPMC 2208. PMID:19100822

  18. On-line spectroscopic studies of group IV alkoxides and their interactions with organic additives during the sol-gel process

    SciTech Connect

    Wettling, D.; Truchet, S.; Guilment, J.; Poncelet, O.

    1996-12-31

    The potential of vibrational spectroscopy for the study of group 4 alkoxides M(OR){sub 4} has been demonstrated in several papers, but only a few of these papers have presented results from online measurements. The monitoring of different reactions such as the stabilization of the alkoxides with organic additives, the exchange processes between different metal alkoxides (R exchange or M exchange) and the hydrolysis process can be of great importance for the development of new synthetic routes leading to materials which are easier to process. NIR spectroscopy is a very versatile technique but lacks specificity while IR and Raman give more interpretive results but are not always easy during processing. The authors used both techniques along with chemometric tools to extract relevant information on their processes. The 2D correlation allowed benefits from the specificity of IR and Raman to develop robust NIR methods which are able to be used on line to monitor the different steps of the sol-gel process.

  19. Solid phase extraction, separation and preconcentration of rare elements thorium(IV), uranium(VI), zirconium(IV), cerium(IV) and chromium(III) amid several other foreign ions with eriochrome black T anchored to 3-D networking silica gel.

    PubMed

    Srivastava, Bhavya; Barman, Milan K; Chatterjee, Mousumi; Roy, Dipika; Mandal, Bhabatosh

    2016-06-17

    The present work reports the systematic studies on extraction, separation and preconcentration of Th(IV), U(VI), Zr(IV), Ce(IV) and Cr(III) amid several other foreign ions using EBT anchored {SiO2}n3-D microarray. The effect of various sorption parameters, such as pH, concentration, temperature, sample volume, flow-rate and co-existing foreign ions were investigated. Quantitative sorption was ensured at solution pH: 6.0-6.5 for Th(IV), Ce(IV), Cr(III) and pH: 2.75-3.0 for Zr(IV), U(VI) couple. Analysis on extracted species and extraction sites reveals that [Th4(μ(2)-OH)8(H2O)4](8+), [Ce6(μ(2)-OH)12(H2O)5](12+), [Cr3(μ(2)-OH)4(H2O)](5+), [(UO2)3(μ(2)-OH)5(H2O)3](+) and [Zr4(μ(2)-OH)8(H2O)0.5](8+) for the respective metal ions gets extracted at HOMO of the extractor. HOMO-{metal ion species} was found to be 1:1 complexation. Sorption was endothermic, entropy-gaining, instantaneous and spontaneous in nature. A density functional theory (DFT) calculation has been performed to analyze the 3-D structure and electronic distribution of the synthesized extractor. PMID:27185054

  20. Higher dimensional Hadamard matrices

    NASA Technical Reports Server (NTRS)

    Schlichta, P. J.

    1979-01-01

    The paper defines higher dimensional Hadamard matrices and enumerates on some of the simplest three-, four-, and five-dimensional cases and procedures for generating them. Special emphasis is given to proper matrices that have a dimensional hierarchy of orthogonalities. It is determined that this property lends itself primarily to the application of higher dimensional Hadamard matrices to error-correcting codes. A list of derived statements for n-dimensional Hadamard matrices are given, as well as a definition of Hadamard matrix families, such as minimal, Petrie polygon, antipodal (n-2)-dimensional sections, and double proximity shells.

  1. Regulation of migratory activity of human keratinocytes by topography of multiscale collagen-containing nanofibrous matrices.

    PubMed

    Fu, Xiaoling; Xu, Meng; Liu, Jie; Qi, Yanmei; Li, Shaohua; Wang, Hongjun

    2014-02-01

    Nanofibrous matrices hold great promise in skin wound repair partially due to their capability of recapturing the essential attributes of native extracellular matrix (ECM). With regard to limited studies on the effect of nanofibrous matrices on keratinocytes, the present study was aimed to understand how the topographical feature of nanofibrous matrices regulates keratinocyte motility by culturing keratinocytes on polycaprolactone (PCL)/collagen nanofibrous matrices (rough surface with fiber diameters of 331 ± 112 nm) or the matrices coated with a thin layer of collagen gel to form a secondary ultrafine fibrous network (smooth surface with ultrafine fiber diameters of 55 ± 26 nm). It was found that the PCL/collagen nanofibrous matrices alone did not stimulate cell migration, while collagen gel coating could significantly increase cell motility. Further studies demonstrated that the ultrafine fibrous network of collagen gel coating significantly activated integrin β1, Rac1 and Cdc42, facilitated the deposition of laminin-332 (formerly called laminin-5), and promoted the expression of active matrix metalloproteinases (MMPs) (i.e., MMP-2 and 9). Neutralization of integrin β1 activity abrogated the gel coating-induced keratinocyte migration. These findings provide important evidence on the role of topographical features of nanofibrous matrices in regulating the phenotypic alteration of keratinocytes and suggest the possible utility of collagen-containing nanofibrous matrices for skin regeneration especially in re-epithelialization. PMID:24268197

  2. Immobilization of plutonium from solutions on porous matrices by the method of high temperature sorption

    SciTech Connect

    Nardova, A.K.; Filippov, E.A.; Glagolenko, Y.B.

    1996-05-01

    This report presents the results of investigations of plutonium immobilization from solutions on inorganic matrices with the purpose of producing a solid waste form. High-temperature sorption is described which entails the adsorption of radionuclides from solutions on porous, inorganic matrices, as for example silica gel. The solution is brought to a boil with additional thermal process (calcination) of the saturated granules.

  3. Testing of novel desiccant materials and dehumidifier matrices for desiccant cooling applications

    SciTech Connect

    Pesaran, A.A.; Bingham, C.E.

    1989-03-01

    This paper presents the results of testing of desiccant materials and dehumidifier matrices for desiccant cooling and dehumidification applications. In testing desiccant materials, we used a gravimetric technique to measure the moisture capacity of four desiccant materials. These materials were microporous silica gel powder, macroporous silica gel powder, polystyrene sulfonic acid sodium salt, and a silica-gel/epoxy composite. The microporous silica gel powder had the most desirable moisture capacity properties of the four materials tested for desiccant cooling applications. The polystyrene sulfonic acid sodium salt showed some promise. Our testing of dehumidifier matrices included measuring the pressure drop and heat- and mass-transfer rate characteristics of a silica-gel/corrugated dehumidifier matrix under conditions typical of desiccant cooling systems. The matrix is a section of a commercial dehumidifier. The transient dehumidification capacity of the matrix was calculated from the tests and compared with previously tested matrices. 9 refs., 10 figs., 2 tabs.

  4. Polyelectrolyte gels

    SciTech Connect

    Segalman, D.J.; Witkowski, W.R.

    1995-06-01

    Polyelectrolyte (PE) gels are swollen polymer/solvent networks that undergo a reversible volume collapse/expansion through various types of stimulation. Applications that could exploit this large deformation and solvent expulsion/absorption characteristics include robotic {open_quotes}fingers{close_quotes} and drug delivery systems. The goals of the research were to first explore the feasibility of using the PE gels as {open_quotes}smart materials{close_quotes} - materials whose response can be controlled by an external stimulus through a feedback mechanism. Then develop a predictive capability to simulate the dynamic behavior of these gels. This involved experimentally characterizing the response of well-characterized gels to an applied electric field and other stimuli to develop an understanding of the underlying mechanisms which cause the volume collapse. Lastly, the numerical analysis tool was used to simulate various potential engineering devices based on PE gels. This report discusses the pursuit of those goals through experimental and computational means.

  5. Singular Mueller matrices

    NASA Astrophysics Data System (ADS)

    Gil, José J.; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance, or because its associated canonical depolarizer has the property of fully randomizing, the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, of potential usefulness to experimentalists dealing with such media.

  6. Singular Mueller matrices.

    PubMed

    Gil, José J; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance or because its associated canonical depolarizer has the property of fully randomizing the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed, and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, which are of potential usefulness to experimentalists dealing with such media. PMID:27140769

  7. Welding IV.

    ERIC Educational Resources Information Center

    Allegheny County Community Coll., Pittsburgh, PA.

    Instructional objectives and performance requirements are outlined in this course guide for Welding IV, a competency-based course in advanced arc welding offered at the Community College of Allegheny County to provide students with proficiency in: (1) single vee groove welding using code specifications established by the American Welding Society…

  8. Intermittency and random matrices

    NASA Astrophysics Data System (ADS)

    Sokoloff, Dmitry; Illarionov, E. A.

    2015-08-01

    A spectacular phenomenon of intermittency, i.e. a progressive growth of higher statistical moments of a physical field excited by an instability in a random medium, attracted the attention of Zeldovich in the last years of his life. At that time, the mathematical aspects underlying the physical description of this phenomenon were still under development and relations between various findings in the field remained obscure. Contemporary results from the theory of the product of independent random matrices (the Furstenberg theory) allowed the elaboration of the phenomenon of intermittency in a systematic way. We consider applications of the Furstenberg theory to some problems in cosmology and dynamo theory.

  9. IVS Organization

    NASA Technical Reports Server (NTRS)

    2004-01-01

    International VLBI Service (IVS) is an international collaboration of organizations which operate or support Very Long Baseline Interferometry (VLBI) components. The goals are: To provide a service to support geodetic, geophysical and astrometric research and operational activities. To promote research and development activities in all aspects of the geodetic and astrometric VLBI technique. To interact with the community of users of VLBI products and to integrate VLBI into a global Earth observing system.

  10. Adiabatic air dehumidification in laminar flow desiccant matrices

    SciTech Connect

    Pesaran, A A

    1987-07-01

    Adiabatic step transient heat- and mass-transfer and pressure drop experimental data were obtained for a dehumidifier test matrix that contained microbead-silica-gel desiccant in a parallel-plate geometry. The data were analyzed and compared with the results of two other test dehumidifiers: a parallel-plate matrix using crushed silica gel, and a staggered, parallel-strip matrix using microbead silica gel. The analysis showed that the overall heat- and mass-transfer Nusselt numbers of the staggered, parallel-strip matrix were about 70% to 80% larger than those of the parallel-plate matrices. It also showed that the solid-side resistance to moisture diffusion in the smaller microbead silica gel was about 45% less than that of crushed silica gel because the particle size was 60% smaller. The ratio of heat- or mass-transfer coefficient to pressure drop of the microbead-silica-gel staggered, parallel-strip matrix was higher than the other two test dehumidifiers. Based on these findings, a dehumidifier using microbead silica-gel in a staggered, parallel-strip geometry can be made more compact than the other combinations. 15 refs., 9 figs., 5 tabs.

  11. Effect of gel matrix confinement on the solvent dynamics in supramolecular gels.

    PubMed

    Kowalczuk, Joanna; Rachocki, Adam; Bielejewski, Michał; Tritt-Goc, Jadwiga

    2016-06-15

    Supramolecular gels formed by the sugar gelator of methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside (1) with 1,3-propanediol (PG) and 1-butanol (BU) were prepared with different gelator concentrations. The solvent dynamics within gels, characterized by the diffusion coefficient (D) and the spin-lattice relaxation time (T1), was the subject of NMR diffusometry and relaxometry studies. The diffusion was studied as a function of diffusion time and gelator concentrations. The relaxation time was measured as a function of Larmor frequency. The decrease of the diffusion coefficient was observed as a function of diffusion time for both gels and for all studied gelator concentrations. It is indicative of the confinement effect due to the geometrical restrictions of the gel matrix. The relaxation data for PG solvent confined in 1/PG gel revealed the low frequency dispersion (in kHz region) which is a fingerprint of a specific interaction experienced by PG solvents in the presence of the rigid structure of gelator 1 aggregates. The relaxation model, well known from the interpretation of liquid confined in nanopores as reorientations mediated by translational displacements (RMTD), was successfully applied to analyze the data of studied solvents confined in matrices of supramolecular gels. The microstructures of gel matrices were imaged by Polarized Microscopy. PMID:27003500

  12. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  13. Enhancing Understanding of Transformation Matrices

    ERIC Educational Resources Information Center

    Dick, Jonathan; Childrey, Maria

    2012-01-01

    With the Common Core State Standards' emphasis on transformations, teachers need a variety of approaches to increase student understanding. Teaching matrix transformations by focusing on row vectors gives students tools to create matrices to perform transformations. This empowerment opens many doors: Students are able to create the matrices for…

  14. Aerosol gels

    NASA Technical Reports Server (NTRS)

    Sorensen, Christopher M. (Inventor); Chakrabarti, Amitabha (Inventor); Dhaubhadel, Rajan (Inventor); Gerving, Corey (Inventor)

    2010-01-01

    An improved process for the production of ultralow density, high specific surface area gel products is provided which comprises providing, in an enclosed chamber, a mixture made up of small particles of material suspended in gas; the particles are then caused to aggregate in the chamber to form ramified fractal aggregate gels. The particles should have a radius (a) of up to about 50 nm and the aerosol should have a volume fraction (f.sub.v) of at least 10.sup.-4. In preferred practice, the mixture is created by a spark-induced explosion of a precursor material (e.g., a hydrocarbon) and oxygen within the chamber. New compositions of matter are disclosed having densities below 3.0 mg/cc.

  15. Mechanical and optical characterization of gelled matrices during storage.

    PubMed

    Lorenzo, Gabriel; Zaritzky, Noemí; Califano, Alicia

    2015-03-01

    The effect of composition and storage time on the rheological and optical attributes of multi-component gels containing locust bean gum (LBG), low acyl (LAG) and high acyl (HAG) gellan gums, was determined using three-component mixture design. The generalized Maxwell model was used to fit experimental rheological data. Mechanical and relaxation spectra of gelled systems were determined by the type of gellan gum used, except LBG alone which behaved as a diluted gum dispersion. Storage time dependence of the gels was analyzed using the rubber elasticity theory and to determine changes in network mesh size the equivalent network approach was applied. Destabilization kinetic was obtained from light scattering results; increasing LAG content improved the long-term stability of the matrices. Almost every formulation exhibited an increment in both moduli during the first 10 days remaining practically constant thereafter or until they broke (binary mixtures with LBG); gels with HAG/LBG mixtures were the least stable. PMID:25498706

  16. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/sqrt{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/sqrt{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  17. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-05-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  18. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  19. Numerical inversion of finite Toeplitz matrices and vector Toeplitz matrices

    NASA Technical Reports Server (NTRS)

    Bareiss, E. H.

    1969-01-01

    Numerical technique increases the efficiencies of the numerical methods involving Toeplitz matrices by reducing the number of multiplications required by an N-order Toeplitz matrix from N-cubed to N-squared multiplications. Some efficient algorithms are given.

  20. Innovative Immobilization Matrices.

    PubMed

    Alvarez, Gisela S; Echazu, Maria I A; Bertinatto, Jessica A; Catalano, Paolo N; Copello, Guillermo J; Foglia, Maria L; Gonzalez, Joaquin A; Giorgieri, Sergio A; Iglesias, Silvia L; Mebert, Andrea M; Santo-Orihuela, Pablo L; Tuttolomondo, Maria V; Villanueva, Emilia E; Desimone, Martín F

    2016-01-01

    We present a brief survey of some of the recent work of Professor Luis E. Díaz, performed together with his students and collaborators at the University of Buenos Aires. Dr Luis E. Díaz has been involved in research on biochemical and pharmaceutical sciences solving scientific and industry problems for over 40 years until he passed away. Prof. Díaz scientific interests included various topics from NMR spectroscopy to biomedicine but fundamentally he focused in various aspects of chemistry (analytical, organic, inorganic and environmental). This is not a complete survey but a sampling of prominent projects related to sol-gel chemistry with a focus on some of his recent publications. PMID:26956109

  1. Asteroids IV

    NASA Astrophysics Data System (ADS)

    Michel, Patrick; DeMeo, Francesca E.; Bottke, William F.

    . Asteroids, like planets, are driven by a great variety of both dynamical and physical mechanisms. In fact, images sent back by space missions show a collection of small worlds whose characteristics seem designed to overthrow our preconceived notions. Given their wide range of sizes and surface compositions, it is clear that many formed in very different places and at different times within the solar nebula. These characteristics make them an exciting challenge for researchers who crave complex problems. The return of samples from these bodies may ultimately be needed to provide us with solutions. In the book Asteroids IV, the editors and authors have taken major strides in the long journey toward a much deeper understanding of our fascinating planetary ancestors. This book reviews major advances in 43 chapters that have been written and reviewed by a team of more than 200 international authorities in asteroids. It is aimed to be as comprehensive as possible while also remaining accessible to students and researchers who are interested in learning about these small but nonetheless important worlds. We hope this volume will serve as a leading reference on the topic of asteroids for the decade to come. We are deeply indebted to the many authors and referees for their tremendous efforts in helping us create Asteroids IV. We also thank the members of the Asteroids IV scientific organizing committee for helping us shape the structure and content of the book. The conference associated with the book, "Asteroids Comets Meteors 2014" held June 30-July 4, 2014, in Helsinki, Finland, did an outstanding job of demonstrating how much progress we have made in the field over the last decade. We are extremely grateful to our host Karri Muinonnen and his team. The editors are also grateful to the Asteroids IV production staff, namely Renée Dotson and her colleagues at the Lunar and Planetary Institute, for their efforts, their invaluable assistance, and their enthusiasm; they made life as

  2. Asteroids IV

    NASA Astrophysics Data System (ADS)

    Michel, Patrick; DeMeo, Francesca E.; Bottke, William F.

    . Asteroids, like planets, are driven by a great variety of both dynamical and physical mechanisms. In fact, images sent back by space missions show a collection of small worlds whose characteristics seem designed to overthrow our preconceived notions. Given their wide range of sizes and surface compositions, it is clear that many formed in very different places and at different times within the solar nebula. These characteristics make them an exciting challenge for researchers who crave complex problems. The return of samples from these bodies may ultimately be needed to provide us with solutions. In the book Asteroids IV, the editors and authors have taken major strides in the long journey toward a much deeper understanding of our fascinating planetary ancestors. This book reviews major advances in 43 chapters that have been written and reviewed by a team of more than 200 international authorities in asteroids. It is aimed to be as comprehensive as possible while also remaining accessible to students and researchers who are interested in learning about these small but nonetheless important worlds. We hope this volume will serve as a leading reference on the topic of asteroids for the decade to come. We are deeply indebted to the many authors and referees for their tremendous efforts in helping us create Asteroids IV. We also thank the members of the Asteroids IV scientific organizing committee for helping us shape the structure and content of the book. The conference associated with the book, "Asteroids Comets Meteors 2014" held June 30-July 4, 2014, in Helsinki, Finland, did an outstanding job of demonstrating how much progress we have made in the field over the last decade. We are extremely grateful to our host Karri Muinonnen and his team. The editors are also grateful to the Asteroids IV production staff, namely Renée Dotson and her colleagues at the Lunar and Planetary Institute, for their efforts, their invaluable assistance, and their enthusiasm; they made life as

  3. What's wrong with risk matrices?

    PubMed

    Cox, Louis Anthony

    2008-04-01

    Risk matrices-tables mapping "frequency" and "severity" ratings to corresponding risk priority levels-are popular in applications as diverse as terrorism risk analysis, highway construction project management, office building risk analysis, climate change risk management, and enterprise risk management (ERM). National and international standards (e.g., Military Standard 882C and AS/NZS 4360:1999) have stimulated adoption of risk matrices by many organizations and risk consultants. However, little research rigorously validates their performance in actually improving risk management decisions. This article examines some mathematical properties of risk matrices and shows that they have the following limitations. (a) Poor Resolution. Typical risk matrices can correctly and unambiguously compare only a small fraction (e.g., less than 10%) of randomly selected pairs of hazards. They can assign identical ratings to quantitatively very different risks ("range compression"). (b) Errors. Risk matrices can mistakenly assign higher qualitative ratings to quantitatively smaller risks. For risks with negatively correlated frequencies and severities, they can be "worse than useless," leading to worse-than-random decisions. (c) Suboptimal Resource Allocation. Effective allocation of resources to risk-reducing countermeasures cannot be based on the categories provided by risk matrices. (d) Ambiguous Inputs and Outputs. Categorizations of severity cannot be made objectively for uncertain consequences. Inputs to risk matrices (e.g., frequency and severity categorizations) and resulting outputs (i.e., risk ratings) require subjective interpretation, and different users may obtain opposite ratings of the same quantitative risks. These limitations suggest that risk matrices should be used with caution, and only with careful explanations of embedded judgments. PMID:18419665

  4. Computer-Access-Code Matrices

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1990-01-01

    Authorized users respond to changing challenges with changing passwords. Scheme for controlling access to computers defeats eavesdroppers and "hackers". Based on password system of challenge and password or sign, challenge, and countersign correlated with random alphanumeric codes in matrices of two or more dimensions. Codes stored on floppy disk or plug-in card and changed frequently. For even higher security, matrices of four or more dimensions used, just as cubes compounded into hypercubes in concurrent processing.

  5. Ultrasound-mediated gene transfer (sonoporation) in fibrin-based matrices: potential for use in tissue regeneration.

    PubMed

    Nomikou, Nikolitsa; Feichtinger, Georg A; Redl, Heinz; McHale, Anthony P

    2016-01-01

    It has been suggested that gene transfer into donor cells is an efficient and practical means of locally supplying requisite growth factors for applications in tissue regeneration. Here we describe, for the first time, an ultrasound-mediated system that can non-invasively facilitate gene transfer into cells entrapped within fibrin-based matrices. Since ultrasound-mediated gene transfer is enhanced using microbubbles, we compared the efficacy of neutral and cationic forms of these reagents on the ultrasound-stimulated gene transfer process in gel matrices. In doing so we demonstrated the beneficial effects associated with the use of cationic microbubble preparations that interact directly with cells and nucleic acid within matrices. In some cases, gene expression was increased two-fold in gel matrices when cationic microbubbles were compared with neutral microbubbles. In addition, incorporating collagen into fibrin gels yielded a 25-fold increase in gene expression after application of ultrasound to microbubble-containing matrices. We suggest that this novel system may facilitate non-invasive temporal and spatial control of gene transfer in gel-based matrices for the purposes of tissue regeneration. PMID:23596105

  6. Constructions of Factorizable Multilevel Hadamard Matrices

    NASA Astrophysics Data System (ADS)

    Matsufuji, Shinya; Fan, Pingzhi

    Factorization of Hadamard matrices can provide fast algorithm and facilitate efficient hardware realization. In this letter, constructions of factorizable multilevel Hadamard matrices, which can be considered as special case of unitary matrices, are inverstigated. In particular, a class of ternary Hadamard matrices, together with its application, is presented.

  7. Pasting and extrusion properties of mixed carbohydrates and whey protein isolate matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mixed systems of whey protein isolate (WPI) or texturized WPI (tWPI) and different starches may form weak or strong gel pastes or rigid matrices depending on interactions. The paste viscoelasticity of starches from amioca, barley, corn starch, Hylon VII, plantain, and pea starch, mixed with whey pro...

  8. Development of sol-gel formulations for slow release of phermones

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new type of dispenser for slow-release of semiochemicals and sex pheromones was developed based on sol-gel polymers that can be useful in monitoring, mass trapping, and mating disruption in integrated pest management (IPM). Sol-gel matrices exhibit glass characteristics and allow control of the de...

  9. In Vitro release from reverse poloxamine/α-cyclodextrin matrices: modelling and comparison of dissolution profiles.

    PubMed

    Larrañeta, Eneko; Martínez-Ohárriz, Cristina; Vélaz, Itziar; Zornoza, Arantza; Machín, Rubén; Isasi, José Ramón

    2014-01-01

    Gels obtained by complexation of octablock star polyethylene oxide/polypropylene oxide copolymers (Tetronic 90R4) with α-cyclodextrin (α-CD) were evaluated as matrices for drug release. Both molecules are biocompatible so they can be potentially applied to drug delivery systems. Two different types of matrices of Tetronic 90R4 and α-CD were evaluated: gels and tablets. These gels are capable to gelifying in situ and show sustained erosion kinetics in aqueous media. Tablets were prepared by freeze-drying and comprising the gels. Using these two different matrices, the release of two model molecules, L-tryptophan (Trp), and a protein, bovine serum albumin (BSA), was evaluated. The release profiles of these molecules from gels and tablets prove that they are suitable for sustained delivery. Mathematical models were applied to the release curves from tablets to elucidate the drug delivery mechanism. Good correlations were found for the fittings of the release curves to different equations. The results point that the release of Trp from different tablets is always governed by Fickian diffusion, whereas the release of BSA is governed by a combination of diffusion and tablet erosion. PMID:24338752

  10. Iterative methods for Toeplitz-like matrices

    SciTech Connect

    Huckle, T.

    1994-12-31

    In this paper the author will give a survey on iterative methods for solving linear equations with Toeplitz matrices, Block Toeplitz matrices, Toeplitz plus Hankel matrices, and matrices with low displacement rank. He will treat the following subjects: (1) optimal (w)-circulant preconditioners is a generalization of circulant preconditioners; (2) Optimal implementation of circulant-like preconditioners in the complex and real case; (3) preconditioning of near-singular matrices; what kind of preconditioners can be used in this case; (4) circulant preconditioning for more general classes of Toeplitz matrices; what can be said about matrices with coefficients that are not l{sub 1}-sequences; (5) preconditioners for Toeplitz least squares problems, for block Toeplitz matrices, and for Toeplitz plus Hankel matrices.

  11. Microemulsion-based organogels as matrices for lipase immobilization.

    PubMed

    Zoumpanioti, Maria; Stamatis, Haralambos; Xenakis, Aristotelis

    2010-01-01

    Organogels based on water-in-oil microemulsions can be formed using various natural polymers such as gelatin, agar or cellulose derivatives. Enzymes entrapped in the water core of the microemulsion can keep their activity and enhance their stability within the gel matrix. The importance of the microemulsion based organogels (MBGs) leans on their numerous potential biotechnological applications. An important example is the use of various lipase microemulsion systems for hydrolytic or synthetic reactions. In this review, several MBGs are being evaluated as immobilization matrices for various enzymes. The main subject focuses on the parameters that affect the use of MBGs as media for bioorganic reactions using lipases as catalysts. PMID:20156546

  12. Outstanding properties of bistochastic matrices

    NASA Astrophysics Data System (ADS)

    Brugia, O.; Wolfowicz, W.

    1981-10-01

    The statistical properties of many devices used in communication systems, such as scramblers and line coding and decoding devices, are described by mathematical models in which the transition probability matrix is bistochastic. To facilitate the analysis of systems response, the specific properties of the bistochastic matrices are described in six theorems which are demonstrated.

  13. Fibonacci Identities, Matrices, and Graphs

    ERIC Educational Resources Information Center

    Huang, Danrun

    2005-01-01

    General strategies used to help discover, prove, and generalize identities for Fibonacci numbers are described along with some properties about the determinants of square matrices. A matrix proof for identity (2) that has received immense attention from many branches of mathematics, like linear algebra, dynamical systems, graph theory and others…

  14. Making almost commuting matrices commute

    SciTech Connect

    Hastings, Matthew B

    2008-01-01

    Suppose two Hermitian matrices A, B almost commute ({parallel}[A,B]{parallel} {<=} {delta}). Are they close to a commuting pair of Hermitian matrices, A', B', with {parallel}A-A'{parallel},{parallel}B-B'{parallel} {<=} {epsilon}? A theorem of H. Lin shows that this is uniformly true, in that for every {epsilon} > 0 there exists a {delta} > 0, independent of the size N of the matrices, for which almost commuting implies being close to a commuting pair. However, this theorem does not specifiy how {delta} depends on {epsilon}. We give uniform bounds relating {delta} and {epsilon}. The proof is constructive, giving an explicit algorithm to construct A' and B'. We provide tighter bounds in the case of block tridiagonal and tridiagnonal matrices. Within the context of quantum measurement, this implies an algorithm to construct a basis in which we can make a projective measurement that approximately measures two approximately commuting operators simultaneously. Finally, we comment briefly on the case of approximately measuring three or more approximately commuting operators using POVMs (positive operator-valued measures) instead of projective measurements.

  15. Inorganic Nanoparticle Nucleation on Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Kosteleski, Adrian John

    dressing applications. PAA's ability to nucleate nanoparticles in a solid matrix was displayed. Interestingly enough PAA retains its ability to nucleate nanoparticle even when its reactive functional groups are used in the crosslinking process. Silver nanoparticle composition and size on the solid polymer matrices was controlled by varying the composition of PAA. PAA and silver nanoparticles effect on the mechanical properties of the calcium alginate hydrogels were also studied. Physically crosslinking PAA with calcium alginate gels enables the development of intricate gel structures that are decorated with nucleated silver; yielding a composite biomaterial with improved and enhanced antimicrobial properties.

  16. Fundamentals of gel dosimeters

    NASA Astrophysics Data System (ADS)

    McAuley, K. B.; Nasr, A. T.

    2013-06-01

    Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

  17. S-matrices and integrability

    NASA Astrophysics Data System (ADS)

    Bombardelli, Diego

    2016-08-01

    In these notes we review the S-matrix theory in (1+1)-dimensional integrable models, focusing mainly on the relativistic case. Once the main definitions and physical properties are introduced, we discuss the factorization of scattering processes due to integrability. We then focus on the analytic properties of the two-particle scattering amplitude and illustrate the derivation of the S-matrices for all the possible bound states using the so-called bootstrap principle. General algebraic structures underlying the S-matrix theory and its relation with the form factors axioms are briefly mentioned. Finally, we discuss the S-matrices of sine-Gordon and SU(2), SU(3) chiral Gross–Neveu models. In loving memory of Lilia Grandi.

  18. Householder factorizations of unitary matrices

    NASA Astrophysics Data System (ADS)

    Urías, Jesús

    2010-07-01

    A method to construct all representations of finite dimensional unitary matrices as the product of Householder reflections is given. By arbitrarily severing the state space into orthogonal subspaces, the method may, e.g., identify the entangling and single-component quantum operations that are required in the engineering of quantum states of composite (multipartite) systems. Earlier constructions are shown to be extreme cases of the unifying scheme that is presented here.

  19. Threaded Operations on Sparse Matrices

    SciTech Connect

    Sneed, Brett

    2015-09-01

    We investigate the use of sparse matrices and OpenMP multi-threading on linear algebra operations involving them. Several sparse matrix data structures are presented. Implementation of the multi- threading primarily occurs in the level one and two BLAS functions used within the four algorithms investigated{the Power Method, Conjugate Gradient, Biconjugate Gradient, and Jacobi's Method. The bene ts of launching threads once per high level algorithm are explored.

  20. Compliance matrices for cracked bodies

    NASA Technical Reports Server (NTRS)

    Ballarini, R.

    1986-01-01

    An algorithm is presented which can be used to develop compliance matrices for cracked bodies. The method relies on the numerical solution of singular integral equations with Cauchy-type kernels and provides an efficient and accurate procedure for relating applied loadings to crack opening displacements. The algorithm should be of interest to those performing repetitive calculations in the analysis of experimental results obtained from fracture specimens.

  1. Intelligent Virtual Station (IVS)

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Intelligent Virtual Station (IVS) is enabling the integration of design, training, and operations capabilities into an intelligent virtual station for the International Space Station (ISS). A viewgraph of the IVS Remote Server is presented.

  2. Ovarian Cancer Stage IV

    MedlinePlus

    ... hyphen, e.g. -historical Searches are case-insensitive Ovarian Cancer Stage IV Add to My Pictures View /Download : ... 1200x1335 View Download Large: 2400x2670 View Download Title: Ovarian Cancer Stage IV Description: Drawing of stage IV shows ...

  3. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Yuzbashyan, Emil A.; Shastry, B. Sriram; Scaramazza, Jasen A.

    2016-05-01

    We construct ensembles of random integrable matrices with any prescribed number of nontrivial integrals and formulate integrable matrix theory (IMT)—a counterpart of random matrix theory (RMT) for quantum integrable models. A type-M family of integrable matrices consists of exactly N -M independent commuting N ×N matrices linear in a real parameter. We first develop a rotationally invariant parametrization of such matrices, previously only constructed in a preferred basis. For example, an arbitrary choice of a vector and two commuting Hermitian matrices defines a type-1 family and vice versa. Higher types similarly involve a random vector and two matrices. The basis-independent formulation allows us to derive the joint probability density for integrable matrices, similar to the construction of Gaussian ensembles in the RMT.

  4. Nonblocking optical planar switching matrices of short length

    NASA Astrophysics Data System (ADS)

    Giglmayr, Josef

    2001-05-01

    Planar switching matrices of parallel waveguides (WGs) have reduced loss due to the absence of tapering but require some confinement of wave propagation reported from Kerr nonlinearities (NL). Parallel switching matrices are fed by the multiple splitting of the input WGs, an appropriate network model is the parallel version of the Spanke-Benes (PSB) network and the reduction of the number of stages (NSs) below N (for N i/o) is analyzed. However, in the parallel case, regarding WGs and SB networks, the location of switches can no longer be fixed but must be a moving location (ML). From the several parallel paths through the PSB network the shortest path is chosen either at the end by path selection switches (PS-SWs) or at the beginning of the switching matrix, respectively. It turns out that the reduction of NS of the switching matrix and in turn the saving of the number of switches (NSWs) is compensated by the number of PS-SWs at the end or at the beginning of the matrix. The replacement of the PS-SWs by combiners at the output (i) restores the energy balance but (ii) causes phase mismatch (iii) provides redundant paths (iv) restricts the overall NS to the NS of the SB network for each copy but (v) improves the nonblocking (NB) characteristic. The routing of the switching matrices and their optical implementation is also briefly discussed.

  5. Testosterone Nasal Gel

    MedlinePlus

    Testosterone nasal gel is used to treat symptoms of low testosterone in men who have hypogonadism (a condition in which the body does not produce enough natural testosterone). Testosterone nasal gel is used only for men ...

  6. Effect Terthiophenes Units on the Microstructure and Birefringence of SiO2 Gels Prepared via Sol-Gels Processing

    SciTech Connect

    Kancono; Senin, H. B.

    2007-05-09

    Materials ceramics products based on SiO2 gels have been produced via sol-gels processing in present of 1% NH4F/H2O as catalyst. Alkoxysilane from tetraethoxysilane (TEOS) are chose as a matrices or template sources, than the product's of syntheses precursor: 2,5-bis(trimethoxysilyl)terthiophene (BTS3T) used as a motif organic compound: That product formed matrices as silicate backbone of terthiophene-briged silsesquioxane net-work; [O1.5Si-(C4H2S)n-SiO1.5]n. The structure silsesquioxane terthiophene-briged formed have layer distance of 4.6and 8.6 angstroms. So, that terthiophenes units in their structure give an effect on the characteristic pattern as an ordered micro lamellar structure. Electron microscopy analyses in matrices -Si-O-Si- there spheres formed by diameter about 10 {mu}m which are rich in silicon. The effect of terthiophenes unites on SiO2 gels formed shown that birefringence phenomenas are strong in presence of higher quantity oligothiophenes units, and will decrease with increase quantity of alkoxysilane, with anisotropic values differences decrease every 1.125 x 10-3 per mole SiO2, whereas the optical transparency of SiO2 gels formed are increase.

  7. Superalgebraic representation of Dirac matrices

    NASA Astrophysics Data System (ADS)

    Monakhov, V. V.

    2016-01-01

    We consider a Clifford extension of the Grassmann algebra in which operators are constructed from products of Grassmann variables and derivatives with respect to them. We show that this algebra contains a subalgebra isomorphic to a matrix algebra and that it additionally contains operators of a generalized matrix algebra that mix states with different numbers of Grassmann variables. We show that these operators are extensions of spin-tensors to the case of superspace. We construct a representation of Dirac matrices in the form of operators of a generalized matrix algebra.

  8. Dye energy transfer in xerogel matrices and application to solid-state dye lasers

    NASA Astrophysics Data System (ADS)

    Nhung, Tran Hong; Canva, Michael; Chaput, Frédéric; Goudket, Hélène; Roger, Gisèle; Brun, Alain; Manh, Dang Duc; Hung, Nguyen Dai; Boilot, Jean-Pierre

    2004-03-01

    Laser dyes Rhodamine B and Perylene Red were incorporated at different relative concentrations into hybrid matrices synthesized using the sol-gel process. Energy transfer from Rhodamine B-donor to Perylene Red-acceptor molecules was observed. Using the different co-doped samples, solid-state dye laser systems were achieved with tuning band position control and increased efficiency with respect to the materials using solely one type of dye.

  9. Structural evolution and stability of sol gel biocatalysts

    NASA Astrophysics Data System (ADS)

    Rodgers, L. E.; Knott, R. B.; Holden, P. J.; Pike, K. J.; Hanna, J. V.; Foster, L. J. R.; Bartlett, J. R.

    2006-11-01

    Immobilisation strategies for catalytic enzymes are important as they allow recovery and reuse of the biocatalysts. In this work, sol-gel matrices have been used to immobilise Candida antarctica lipase B (CALB), a commonly used industrial enzyme. The sol-gel bioencapsulate is produced through fluoride-catalysed hydrolysis of mixtures of tetramethylorthosilicate (TMOS) and methyltrimethoxysilane (MTMS) in the presence of CALB, yielding materials with controlled pore sizes and surface chemistries. Sol-gel matrices prolong the catalytic life and enhance the activity of CALB, although the molecular basis for this effect has yet to be elucidated due to the limitations of analytical techniques applied to date. Small angle neutron scattering (SANS) allows such multi-component systems to be characterised through contrast matching. In the sol-gel bioencapsulate system at the contrast match point for silica, residual scattering intensity is due to the CALB and density fluctuations in the matrix. A SANS contrast variation series found the match point for the silica matrix, both with and without enzyme present, to be around 35%. The model presented here proposes a mechanism for the interaction between CALB and the surrounding sol-gel matrix, and the observed improvement in enzyme activity and matrix strength. Essentially, the inclusion of CALB modulates silicate speciation during evolution of the inorganic network, leading to associated variations in SANS contrast. The SANS protocol developed here may be applied more generally to other encapsulated enzyme systems.

  10. Apparatus for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, Charles D.; Scott, Timothy C.; Davison, Brian H.

    1998-01-01

    An apparatus for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column.

  11. Apparatus for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, C.D.; Scott, T.C.; Davison, B.H.

    1998-03-19

    An apparatus is described for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column. 1 fig.

  12. Sol-Gel Glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  13. Energy levels and lifetimes of Nd IV, Pm IV, Sm IV, and Eu IV

    SciTech Connect

    Dzuba, V. A.; Safronova, U. I.; Johnson, W. R.

    2003-09-01

    To address the shortage of experimental data for electron spectra of triply ionized rare-earth elements we have calculated energy levels and lifetimes of 4f{sup n+1} and 4f{sup n}5d configurations of Nd IV (n=2), Pm IV (n=3), Sm IV (n=4), and Eu IV (n=5) using Hartree-Fock and configuration-interaction methods. To control the accuracy of our calculations we also performed similar calculations for Pr III, Nd III, and Sm III, for which experimental data are available. The results are important, in particular, for physics of magnetic garnets.

  14. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  15. Quasiperiodic tilings generated by matrices

    NASA Astrophysics Data System (ADS)

    Rao, Nagaraja S.; Suryanarayan, E. R.

    1994-02-01

    Using the inflation method, Watanabe, Ito and Soma [3], Clark and Suryanarayan [4] and Balagurusamy, Ramesh and Gopal [5] have obtained nonperiodic tilings of the plane with n-fold rotational symmetry, n = 2, 3, 4, 5, 8, using two unit prototiles. Fortunately, there is an easier way to generate a more general class of nonperiodic tilings which contains the above-mentioned tilings as special cases. We do this by specifying two matrices of order two which define the two classes of tilings; thus, our approach uses the basic techniques from linear algebra in the study of quasiperiodic tilings and the method can be generalized to obtain tilings that have more than two prototiles. The tilings generated are fractals and their dimensions and the rate of growth are determined.

  16. Shrinkage estimators for covariance matrices.

    PubMed

    Daniels, M J; Kass, R E

    2001-12-01

    Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically

  17. Using PLATO IV.

    ERIC Educational Resources Information Center

    Meller, David V.

    This beginning reference manual describes PLATO IV hardware for prospective users and provides an introduction to PLATO for new authors. The PLATO terminal is described in detail in Chapter 1. Chapter 2 provides a block diagram of the PLATO IV system. Procedures for getting on line are described in Chapter 3, and Chapter 4 provides references to…

  18. IV treatment at home

    MedlinePlus

    ... 24 hours a day. If there is a problem with the IV, you can call your home health care agency for help. If the IV comes out of ... bleeding stops. Then call the home health care agency or the doctor right away.

  19. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2003-09-01

    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of

  20. Astragaloside IV-loaded nanoparticle-enriched hydrogel induces wound healing and anti-scar activity through topical delivery.

    PubMed

    Chen, Xi; Peng, Li-Hua; Shan, Ying-Hui; Li, Ni; Wei, Wei; Yu, Lian; Li, Qi-Mei; Liang, Wen-Quan; Gao, Jian-Qing

    2013-04-15

    This study aims to investigate the novel preparation of solid lipid nanoparticle-enriched hydrogel (SLN-gel) for the topical delivery of astragaloside IV and to determine the effects of astragaloside IV-based SLN-gel on wound healing and anti-scar formation. Solid lipid nanoparticles (SLNs) were prepared through the solvent evaporation method. The particle size, polydispersity index (PDI), zeta potential (ZP), encapsulation efficiency (EE), drug release, and morphological properties of the SLNs were characterized. The optimized SLNs were incorporated in carbomer hydrogel to form an SLN-enriched gel (SLN-gel) carrier. The effects of astragaloside IV-enriched SLNs on wound healing were determined using the wound scratch test, and their uptake by skin cells was tested in vitro. With the rat full-skin excision model, the in vivo regulation of astragaloside IV-based SLN-gel in the wound stages of re-epithelization, angiogenesis, and extracellular matrix remodeling was investigated. The best formulation of astragaloside IV-based SLNs had high EE (93% ± 5%) and ZP (-23.6 mV ± 1.5 mV), with a PDI of 0.18 ± 0.03 and a drug loading percentage of 9%. Astragaloside IV-based SLNs and SLN-gel could release drug sustainably. Astragaloside IV-based SLNs enhanced the migration and proliferation of keratinocytes and increased drug uptake on fibroblasts in vitro (P<0.01) through the caveolae endocytosis pathway, which was inhibited by methyl-β-cyclodextrin. Astragaloside IV-based SLN-gel strengthened wound healing and inhibited scar formation in vivo by increasing wound closure rate (P<0.05) and by contributing to angiogenesis and collagen regular organization. SLN-enriched gel is a promising topical drug delivery system. Astragaloside IV-loaded SLN-enriched gel was proven as an excellent topical preparation with wound healing and anti-scar effects. PMID:23500766

  1. Comparative evaluation of rate of hydration and matrix erosion of HEC and HPC and study of drug release from their matrices.

    PubMed

    Sinha Roy, Dipasree; Rohera, Bhagwan D

    2002-08-01

    Hydrophilic polymers, in contact with the dissolution medium, may swell and make a continuous gel layer, erode or undergo combination of the two. The swelling action of these polymers is controlled by the rate of their hydration in the dissolution medium. The extent of polymer swelling, relative mobilities of dissolution medium and drug, and matrix erosion dictate the kinetics as well as mechanism of drug release from the polymeric matrices. The objective of the present investigations was to study the rate of hydration and the rate of matrix erosion of two hydrophilic, non-ionic cellulose ethers, i.e., hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC), and to compare the kinetics and mechanism of drug release from their matrices. Chlorpheniramine maleate was used as the model drug. Matrix tablets containing chlorpheniramine maleate, HEC or HPC and dicalcium phosphate were compressed at 156 MPa pressure. The rate of hydration of the polymer, rate of erosion of the matrices and in vitro drug release studies were carried out in phosphate buffer (pH 7.4). The hydration studies of the two polymers demonstrated that due to relatively larger water uptake, the degree of swelling of HEC matrices was considerably higher as compared to the HPC matrices. Also, HEC matrices exhibited relatively higher erosion as compared to HPC matrices. The drug release from HEC matrices occurred by non-Fickian transport, i.e., combination of drug diffusion and polymer swelling, while drug release from HPC matrices was controlled primarily by diffusion through pores and channels in the structure. The t(50%), time to reach 50% drug release, for HEC matrices was 4.8 h and that for HPC matrices was 6.5 h which indicates that a higher polymer level was needed in the case of HEC matrices to sustain the drug release for up to 12 h of dissolution as compared to HPC matrices due to relatively higher hydrophilicity of HEC. PMID:12128174

  2. Isolation of long-lived technetium-99 in confinement matrices

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Yudintsev, S. V.; Omel'Yanenko, B. I.

    2009-08-01

    Amongst fission products formed in atomic reactors, 99Tc is the most hazardous for the environment because of its long half-life (213000 yr), high content in spent nuclear fuel (SNF) (0.8-1.0 kg per ton of SNF), low sorption ability, and high mobility under aerobic conditions. The bulk of 99Tc (˜200 t) is incorporated into SNF. In the course of SNF reprocessing, this radioisotope is released as a separate fraction or along with actinides. More than 60 t of highly concentrated 99Tc have been accumulated to date. It is evident that isolation of 99Tc from the environment is a matter of great urgency. The immobilization of technetium in a highly stable and poorly soluble matrix is a necessary element in settling this problem. Ceramics composed of titanates with pyrochlore, perovskite, and rutile structures are proposed as matrices able to retain technetium along with actinides. The high chemical stability of these compounds has been corroborated by experiments. The difficulties in production of such matrices are related to the fugacity of Tc and the necessity of converting it into Tc(IV). To overcome this obstacle, self-propagating high-temperature synthesis (SHS), characterized by reductive conditions and a high reaction rate, is proposed. The charge for matrix synthesis consists of reducing agents (metallic powders with a strong affinity to oxygen, e.g., Ti and Zr), oxidants (MoO3, Fe2O3, CuO), and additives (TiO2, ZrO2, Y2O3, CaO, etc.), which taken together with other elements form target phases. Instead of Tc, Mo, close in chemical properties, is used in matrix synthesis as a simulator. Samples of Mo-bearing matrices have been synthesized with SHS; their phase compositions and Mo distribution therein are characterized. It has been shown that up to 40 wt % Mo can be incorporated into the synthesized matrices in the form of metal or structural admixtures in titanates. The titanate-zirconate pyrochlore-based matrices are the most appropriate for the joint

  3. Proper Values of Matrices and Some Applications.

    ERIC Educational Resources Information Center

    Amir-Moez, Ali R.

    1992-01-01

    Presents a short study of proper values of two-by-two matrices with real entries. Gives examples of symmetric matrices and applications to systems of linear equations of perpendicular lines intersecting at the origin and central conics rotated about the origin to eliminate the xy term from its equation. (MDH)

  4. Biocompatibility of Experimental Polymeric Tracheal Matrices.

    PubMed

    Kiselevskii, M V; Chikileva, I O; Vlasenko, R Ya; Sitdikova, S M; Tenchurin, T Kh; Mamagulashvili, V G; Shepelev, A D; Grigoriev, T A; Chvalun, S N

    2016-08-01

    Biocompatibility of a new tracheal matrix is studied. The new matrix is based on polymeric ultra-fiber material colonized by mesenchymal multipotent stromal cells. The experiments demonstrate cytoconductivity of the synthetic matrices and no signs of their degradation within 2 months after their implantation to recipient mice. These data suggest further studies of the synthetic tracheal matrices on large laboratory animals. PMID:27591876

  5. Harmonic balance calculations by using matrices

    NASA Astrophysics Data System (ADS)

    Fergusson, N. J.; Leung, A. Y. T.

    1995-05-01

    The computation of the total and tangential stiffness matrices associated with the harmonic balance method for non-linear ordinary differential equations requires some complicated calculations involving double sums. Some matrix results are presented here that ease the associated book-keeping and allow the matrices to be programmed easily.

  6. Products of Independent Elliptic Random Matrices

    NASA Astrophysics Data System (ADS)

    O'Rourke, Sean; Renfrew, David; Soshnikov, Alexander; Vu, Van

    2015-07-01

    For fixed , we study the product of independent elliptic random matrices as tends to infinity. Our main result shows that the empirical spectral distribution of the product converges, with probability , to the -th power of the circular law, regardless of the joint distribution of the mirror entries in each matrix. This leads to a new kind of universality phenomenon: the limit law for the product of independent random matrices is independent of the limit laws for the individual matrices themselves. Our result also generalizes earlier results of Götze-Tikhomirov (On the asymptotic spectrum of products of independent random matrices, available at http://arxiv.org/abs/1012.2710) and O'Rourke-Soshnikov (J Probab 16(81):2219-2245, 2011) concerning the product of independent iid random matrices.

  7. Solid-state tunable lasers based on dye-doped sol-gel materials

    SciTech Connect

    Dunn, B.; Mackenzie, J.D.; Zink, J.I.; Stafsudd, O.M.

    1992-03-01

    The sol-gel process is a solution synthesis technique which provides a low temperature chemical route for the preparation of rigid transparent matrix materials. The luminescent organic dye molecules, rhodamine 6G and coumarin 540A have been incorporated, via the sol-gel method, into aluminosilicate and organically modified silicate host matrices. Synthesis, laser oscillation and photostability for these systems are reported. The improved photostability of these materials with respect to comparable polymeric host materials is discussed.

  8. The detection of hexavalent chromium by organically doped sol-gels

    SciTech Connect

    Wong, P.W.; Mackenzie, J.D.

    1994-12-31

    The sol-gel process can be used to produce porous inorganic matrices that are doped with organic molecules. These doped gels can be used as a quantitative method for the spectrophotometric determination of trace concentrations of metallic ions. For the detection of hexavalent chromium, malachite green was used as the dopant. Preliminary results indicate concentrations on the order of 5 ppb are detectable using this method.

  9. Co-assembling peptides as defined matrices for endothelial cells

    PubMed Central

    Jung, Jangwook P.; Nagaraj, Arun K.; Fox, Emily K.; Rudra, Jai S.; Devgun, Jason M.; Collier, Joel H.

    2009-01-01

    Self-assembling peptides and peptide derivatives bearing cell-binding ligands are increasingly being investigated as defined cell culture matrices and as scaffolds for regenerative medicine. In order to systematically refine such scaffolds to elicit specific desired cell behaviors, ligand display should ideally be achieved without inadvertently altering other physicochemical properties such as viscoelasticity. Moreover, for in vivo applications, self-assembled biomaterials must exhibit low immunogenicity. In the present study, multi-peptide co-assembling hydrogels based on the beta-sheet fibrillizing peptide Q11 (QQKFQFQFEQQ) were designed such that they presented RGDS or IKVAV ligands on their fibril surfaces. In co-assemblies of the ligand-bearing peptides with Q11, ligand incorporation levels capable of influencing the attachment, spreading, morphology, and growth of human umbilical vein endothelial cells (HUVECs) did not significantly alter the materials’ fibrillization, beta-turn secondary structure, or stiffness. RGDS-Q11 specifically increased HUVEC attachment, spreading, and growth when co-assembled into Q11 gels, whereas IKVAV-Q11 exerted a more subtle influence on attachment and morphology. Additionally, Q11 and RGDS-Q11 were minimally immunogenic in mice, making Q11-based biomaterials attractive candidates for further investigation as defined, modular extracellular matrices for applications in vitro and in vivo. PMID:19203790

  10. Effect of additives on physicochemical properties in amorphous starch matrices.

    PubMed

    Liang, Jun; Wang, Simon; Ludescher, Richard D

    2015-03-15

    The effect of the addition of non-reducing sugars or methylcellulose on the matrix physical properties and rate of non-enzymatic browning (NBR) between exogenous glucose+lysine in a starch-based glassy matrix were studied, using the methods of luminescence and FTIR. Amorphous starch-based matrices were formulated by rapidly dehydrating potato starch gel mixed with additives at weight ratios of 7:93 (additive:starch). Data on the phosphorescence emission energy and lifetime from erythrosin B dispersed in the matrices indicated that sugars decreased starch matrix mobility in a Tg-dependent manner, except for trehalose that interacted with starch in a unique mode, while methylcellulose, the additive with the highest Tg, increased the molecular mobility. Using FTIR, we found that methylcellulose decreased the strength of hydrogen bond network and sugars enhanced the hydrogen bond strength in the order: trehalose>maltitol>sucrose. Comparing those changes with the rate of NBR between exogenous glucose+lysine, we suggest that NBR rates are primarily influenced by matrix mobility, which is modulated by the hydrogen bond network, and interactions among components. PMID:25308673

  11. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-09-30

    This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4

  12. Rheological properties of binary and ternary protein-polysaccharide co-hydrogels and comparative release kinetics of salbutamol sulphate from their matrices.

    PubMed

    Saxena, Anita; Kaloti, Mandeep; Bohidar, H B

    2011-03-01

    Rheological properties of binary (AgarGelA and AgarGelB) and ternary (AgarGelAB and GelABAgar) co-hydrogels of agar (polysaccharide) with gelatin A and gelatin B (proteins) were studied to investigate their differential viscoelastic behavior. Two sets of rheological experiments, isochronal temperature and isothermal frequency sweep, were performed and the storage modulii, G' was measured which could be correlated to the gel strengths. Two separate peaks at 70°C and 35°C, corresponding to melting temperatures of agar and gelatin gels respectively, were obtained when derivative of G' with respect to temperature, dG'/dT was plotted against temperature which clearly showed the presence of two separate networks of gelatin and agar interconnected to each other. The results revealed that AgarGelAB was the strongest and AgarGelA was the weakest gel among all the gels studied. In order to see the effect of gel microstructure on drug encapsulation and release behavior, a model drug salbutamol was encapsulated in various gel matrices and the release of the same was seen in phosphate buffer pH 7.4, in simulated gastric fluid pH 1.2 (SGF) and in simulated intestinal fluid pH 6.8 (SIF) media. The drug release behavior universally followed sigmoidal kinetics invariant of gel composition. It is concluded that the hydrogel microstructure influenced the release behavior and best release, in all the three media, could be found with binary gel, AgarGelB, and ternary gel, AgarGelAB. Finally, microstructure of these gels is proposed. PMID:21108963

  13. Characterizing the inverses of block tridiagonal, block Toeplitz matrices

    NASA Astrophysics Data System (ADS)

    Boffi, Nicholas M.; Hill, Judith C.; Reuter, Matthew G.

    2015-01-01

    We consider the inversion of block tridiagonal, block Toeplitz matrices and comment on the behaviour of these inverses as one moves away from the diagonal. Using matrix Möbius transformations, we first present an O(1) representation (with respect to the number of block rows and block columns) for the inverse matrix and subsequently use this representation to characterize the inverse matrix. There are four symmetry-distinct cases where the blocks of the inverse matrix (i) decay to zero on both sides of the diagonal, (ii) oscillate on both sides, (iii) decay on one side and oscillate on the other and (iv) decay on one side and grow on the other. This characterization exposes the necessary conditions for the inverse matrix to be numerically banded and may also aid in the design of preconditioners and fast algorithms. Finally, we present numerical examples of these matrix types.

  14. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-03-01

    This technical progress report describes work performed from September 1, 2003, through February 29, 2004, for the project, ''Conformance Improvement Using Gels.'' We examined the properties of several ''partially formed'' gels that were formulated with a combination of high and low molecular weight HPAM polymers. After placement in 4-mm-wide fractures, these gels required about 25 psi/ft for brine to breach the gel (the best performance to date in fractures this wide). After this breach, stabilized residual resistance factors decreased significantly with increased flow rate. Also, residual resistance factors were up to 9 times greater for water than for oil. Nevertheless, permeability reduction factors were substantial for both water and oil flow. Gel with 2.5% chopped fiberglass effectively plugged 4-mm-wide fractures if a 0.5-mm-wide constriction was present. The ability to screen-out at a constriction appears crucial for particulate incorporation to be useful in plugging fractures. In addition to fiberglass, we examined incorporation of polypropylene fibers into gels. Once dispersed in brine or gelant, the polypropylene fibers exhibited the least gravity segregation of any particulate that we have tested to date. In fractures with widths of at least 2 mm, 24-hr-old gels (0.5% high molecular weight HPAM) with 0.5% fiber did not exhibit progressive plugging during placement and showed extrusion pressure gradients similar to those of gels without the fiber. The presence of the fiber roughly doubled the gel's resistance to first breach by brine flow. The breaching pressure gradients were not as large as for gels made with high and low molecular weight polymers (mentioned above). However, their material requirements and costs (i.e., polymer and/or particulate concentrations) were substantially lower than for those gels. A partially formed gel made with 0.5% HPAM did not enter a 0.052-mm-wide fracture when applying a pressure gradient of 65 psi/ft. This result

  15. Digestion of Termiticide Bait Matrices by the Pest Termite Reticulitermes flavipes (Isoptera: Rhinotermitidae).

    PubMed

    Sethi, Amit; Karl, Zachary J; Scharf, Michael E

    2016-04-01

    Termites are highly effective digesters of wood lignocellulose, which is a central factor contributing to their global status as pests of wooden structures. For the same reason, termite baits that combine cellulosic matrices with slow-acting insecticides are both effective and popular as a reduced-risk approach for termite control. This study took a novel approach for assessing digestibility of termite bait matrices and matrix components to gain potentially new insights into bait attractiveness and efficacy. The rationale behind this study is that termite baits that are more digestible should have more nutritional value to termites and thus encourage maximal feeding and trophallactic transfer of active ingredients through termite colonies. Studies were done using in vitro digestion assays with termite gut protein extracts followed by colorimetric detection of released glucose and pentose monosaccharides from test substrates. The substrates tested included two commercial bait matrices (Recruit IV and Recruit II HD), two matrix components (compressed and toasted compressed cellulose), and two natural pine woods as positive controls (southern yellow and northern pine). Overall results show equal or greater monosaccharide availability for some commercial matrices than standard pine lignocelluloses, suggesting sufficient nutritional value for the proprietary matrices. Another more prominent trend was significant intercolony variation in digestibility across substrates, possibly resulting from differences in microbiota composition, long-term diet adaptation, or both. These findings thus illuminate new nutrition-based factors that can potentially impact bait feeding, trophallactic exchange, and efficacy. PMID:26896534

  16. Modeling chemoresponsive polymer gels.

    PubMed

    Kuksenok, Olga; Deb, Debabrata; Dayal, Pratyush; Balazs, Anna C

    2014-01-01

    Stimuli-responsive gels are vital components in the next generation of smart devices, which can sense and dynamically respond to changes in the local environment and thereby exhibit more autonomous functionality. We describe recently developed computational methods for simulating the properties of such stimuli-responsive gels in the presence of optical, chemical, and thermal gradients. Using these models, we determine how to harness light to drive shape changes and directed motion in spirobenzopyran-containing gels. Focusing on oscillating gels undergoing the Belousov-Zhabotinksy reaction, we demonstrate that these materials can spontaneously form self-rotating assemblies, or pinwheels. Finally, we model temperature-sensitive gels that encompass chemically reactive filaments to optimize the performance of this system as a homeostatic device for regulating temperature. These studies could facilitate the development of soft robots that autonomously interconvert chemical and mechanical energy and thus perform vital functions without the continuous need of external power sources. PMID:24498954

  17. Fibrillar peptide gels in biotechnology and biomedicine

    PubMed Central

    Jung, Jangwook P.; Gasiorowski, Joshua Z.; Collier, Joel H.

    2012-01-01

    Peptides, peptidomimetics, and peptide derivatives that self-assemble into fibrillar gels have received increasing interest as synthetic extracellular matrices for applications in 3D cell culture and regenerative medicine. Recently, several of these fibrillizing molecules have been functionalized with bioactive components such as cell-binding ligands, degradable sequences, drug-eluting compounds, and chemical modifications for cross-linking, producing gels that can reliably display multiple factors simultaneously. This capacity for incorporating precise levels of many different biological and chemical factors is advantageous given the natural complexity of cell-matrix interactions that many current biomaterial strategies seek to mimic. In this review, recent efforts in the area of fibril-forming peptide materials are described, and advantages of biomaterials containing multiple modular elements are outlined. In addition, a few hurdles and open questions surrounding fibrillar peptide gels are discussed, including issues of the materials’ structural heterogeneity, challenges in fully characterizing the diversity of their self-assembled structures, and incomplete knowledge of how the materials are processed in vivo. PMID:20091870

  18. The surface molecular functionality of decellularized extracellular matrices

    PubMed Central

    Barnes, Christopher A.; Brison, Jeremy; Michel, Roger; Brown, Bryan N.; Castner, David G.; Badylak, Stephen F.

    2010-01-01

    Decellularization of tissues and organs is a successful platform technology for creating scaffolding materials for tissue engineering and regenerative medicine. It has been suggested that the success of these materials upon implantation is due to the molecular signals provided by the remaining scaffold extracellular matrix (ECM) components presented to probing cells in vivo as they repopulate the surface. For this study, decellularized matrices were created from esophagus, bladder, and small intestine harvested from adult male Fischer 344 rats. The three decellularized matrices (each originating from source tissues which included an epithelial lining on their luminal surfaces) were immunostained for collagen IV and laminin to determine basement membrane retention. Scanning electron micrographs of the surfaces were used to provide insight into the surface topography of each of the decellularized tissues. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to generate high-resolution mass spectra for the surfaces of each scaffold. This surface sensitive technique allows for detailed molecular analysis of the outermost 1–2 nm of a material and has been applied previously to thin protein films and secreted ECM proteins on poly(N-isopropyl acrylamide) (polyNIPAAM) surfaces. To extract trends from within the complex ToF-SIMS dataset, a multivariate analysis technique, principal component analysis (PCA), was employed. Using this method, a molecular fingerprint of each surface was created and separation was seen in the PCA scores between the decellularized esophagus and the decellularized small intestine samples. The PCA scores for the decellularized bladder sample fell between the previous two decellularized samples. Protein films of common extracellular matrix constituents (collagen IV, collagen I, laminin, and Matrigel ) were also investigated. The PCA results from these protein films were used to develop qualitative hypotheses for the relationship of

  19. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Scaramazza, Jasen; Yuzbashyan, Emil; Shastry, Sriram

    We construct ensembles of random integrable matrices with any prescribed number of nontrivial integrals and formulate integrable matrix theory (IMT) - a counterpart of random matrix theory (RMT) for quantum integrable models. A type- M family of integrable matrices consists of exactly N - M independent commuting N × N matrices linear in a real parameter. We first develop a rotationally invariant parameterization of such matrices, previously only constructed in a preferred basis. For example, an arbitrary choice of a vector and two commuting Hermitian matrices defines a type-1 family and vice-versa. Higher types similarly involve a random vector and two matrices. The basis-independent formulation allows us to derive the joint probability density for integrable matrices, in a manner similar to the construction of Gaussian ensembles in the RMT. This work was supported in part by the David and Lucille Packard Foundation. The work at UCSC was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award # FG02-06ER46319.

  20. Hierarchically structured, hyaluronic acid-based hydrogel matrices via the covalent integration of microgels into macroscopic networks$

    PubMed Central

    Jha, Amit K.; Malik, Manisha S.; Farach-Carson, Mary C.; Duncan, Randall L.; Jia, Xinqiao

    2010-01-01

    We aimed to develop biomimetic hydrogel matrices that not only exhibit structural hierarchy and mechanical integrity, but also present biological cues in a controlled fashion. To this end, photocrosslinkable, hyaluronic acid (HA)-based hydrogel particles (HGPs) were synthesized via an inverse emulsion crosslinking process followed by chemical modification with glycidyl methacrylate (GMA). HA modified with GMA (HA-GMA) was employed as the soluble macromer. Macroscopic hydrogels containing covalently integrated hydrogel particles (HA-c-HGP) were prepared by radical polymerization of HA-GMA in the presence of crosslinkable HGPs. The covalent linkages between the hydrogel particles and the secondary HA matrix resulted in the formation of a diffuse, fibrilar interface around the particles. Compared to the traditional bulk gels synthesized by photocrosslinking of HA-GMA, these hydrogels exhibited a reduced sol fraction and a lower equilibrium swelling ratio. When tested under uniaxial compression, the HA-c-HGP gels were more pliable than the HA-p-HGP gels and fractured at higher strain than the HA-GMA gels. Primary bovine chondrocytes were photoencapsulated in the HA matrices with minimal cell damage. The 3D microenvironment created by HA-GMA and HA HGPs not only maintained the chondrocyte phenotype but also fostered the production of cartilage specific extracellular matrix. To further improve the biological activities of the HA-c-HGP gels, bone morphogenetic protein 2 (BMP-2) was loaded into the immobilized HGPs. BMP-2 was released from the HA-c-HGP gels in a controlled manner with reduced initial burst over prolonged periods of time. The HA-c-HGP gels are promising candidates for use as bioactive matrices for cartilage tissue engineering. PMID:20936090

  1. Community Detection for Correlation Matrices

    NASA Astrophysics Data System (ADS)

    MacMahon, Mel; Garlaschelli, Diego

    2015-04-01

    A challenging problem in the study of complex systems is that of resolving, without prior information, the emergent, mesoscopic organization determined by groups of units whose dynamical activity is more strongly correlated internally than with the rest of the system. The existing techniques to filter correlations are not explicitly oriented towards identifying such modules and can suffer from an unavoidable information loss. A promising alternative is that of employing community detection techniques developed in network theory. Unfortunately, this approach has focused predominantly on replacing network data with correlation matrices, a procedure that we show to be intrinsically biased because of its inconsistency with the null hypotheses underlying the existing algorithms. Here, we introduce, via a consistent redefinition of null models based on random matrix theory, the appropriate correlation-based counterparts of the most popular community detection techniques. Our methods can filter out both unit-specific noise and system-wide dependencies, and the resulting communities are internally correlated and mutually anticorrelated. We also implement multiresolution and multifrequency approaches revealing hierarchically nested subcommunities with "hard" cores and "soft" peripheries. We apply our techniques to several financial time series and identify mesoscopic groups of stocks which are irreducible to a standard, sectorial taxonomy; detect "soft stocks" that alternate between communities; and discuss implications for portfolio optimization and risk management.

  2. IV treatment at home

    MedlinePlus

    ... home; PICC line - home; Infusion therapy - home; Home health care - IV treatment ... Often, home health care nurses will come to your home to give you the medicine. Sometimes, a family member, a friend, or ...

  3. LU decompositions of generalized diagonally dominant matrices

    SciTech Connect

    Funderlic, R.E.; Neumann, M.; Plemmons, R.J.

    1982-02-01

    Using the simple vehicle of M-matrices, the existence and stability of LU decompositions of matrices A which can be scaled to diagonally dominant (possibly singular) matrices are investigated. Bounds on the growth factor for Gaussian elimination on A are derived. Motivation for this study is provided in part by applications to solving homogeneous systems of linear equations Ax = 0, arising in Markov queuing networks, input-output models in economics and compartmental systems, where A or -A is an irreducible, singular M-matrix.

  4. Kerov's interlacing sequences and random matrices

    NASA Astrophysics Data System (ADS)

    Bufetov, Alexey

    2013-11-01

    To a N × N real symmetric matrix Kerov assigns a piecewise linear function whose local minima are the eigenvalues of this matrix and whose local maxima are the eigenvalues of its (N - 1) × (N - 1) submatrix. We study the scaling limit of Kerov's piecewise linear functions for Wigner and Wishart matrices. For Wigner matrices the scaling limit is given by the Verhik-Kerov-Logan-Shepp curve which is known from asymptotic representation theory. For Wishart matrices the scaling limit is also explicitly found, and we explain its relation to the Marchenko-Pastur limit spectral law.

  5. Kerov's interlacing sequences and random matrices

    SciTech Connect

    Bufetov, Alexey

    2013-11-15

    To a N × N real symmetric matrix Kerov assigns a piecewise linear function whose local minima are the eigenvalues of this matrix and whose local maxima are the eigenvalues of its (N − 1) × (N − 1) submatrix. We study the scaling limit of Kerov's piecewise linear functions for Wigner and Wishart matrices. For Wigner matrices the scaling limit is given by the Verhik-Kerov-Logan-Shepp curve which is known from asymptotic representation theory. For Wishart matrices the scaling limit is also explicitly found, and we explain its relation to the Marchenko-Pastur limit spectral law.

  6. GCF Mark IV development

    NASA Technical Reports Server (NTRS)

    Mortensen, L. O.

    1982-01-01

    The Mark IV ground communication facility (GCF) as it is implemented to support the network consolidation program is reviewed. Changes in the GCF are made in the area of increased capacity. Common carrier circuits are the medium for data transfer. The message multiplexing in the Mark IV era differs from the Mark III era, in that all multiplexing is done in a GCF computer under GCF software control, which is similar to the multiplexing currently done in the high speed data subsystem.

  7. Exploring the synthesis and characterization of nanoenergetic materials from sol-gel chemistry

    NASA Astrophysics Data System (ADS)

    Walker, Jeremy D.

    Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed 'proton scavenging' mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. Gelation mechanisms for the formation of FeIIIxOyHz from THF and pyridine have been presented and confirmed through pH, XPS, and IR studies. THF follows a similar mechanism as PO, where the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide, which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening. Energetic properties for the Fe2O3/Al and RuO 2/Al sol-gel synthesized systems are also presented. Sol-gel chemistry synthesizes x-ray amorphous oxide matrices which contain substantial quantities of residual water and organic species. The iron (III) matrix, formed from the addition of a weak base epoxide molecule to a hydrated iron (III) nitrate solution, consists of stoichiometric Fe2O3, FeO(OH), and Fe(OH)3 and can only definitely be described as of Fe IIIxOyHz. XPS characterization of the metal oxide matrix synthesized from the addition of the weak base propylene oxide to a hydrated ruthenium (III) chloride solution corresponds to that of hydrous ruthenium (IV) oxide. Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Energetic

  8. Formation and properties of gels based on lipo-plexes.

    PubMed

    Pucci, Carlotta; Tardani, Franco; La Mesa, Camillo

    2014-06-12

    Aqueous systems containing sodium taurodeoxycholate and, eventually, soybean lecithin were investigated. Depending on the relative amounts of two such species, molecular, micellar, vesicular, liquid crystalline, and solid phases were formed. In the presence of bovine serum albumin, micellar and vesicular systems form lipo-plexes. The latter self-organize into gels, depending on composition and thermal treatments. According to scanning electron microscopy, vesicle-based gels obtained from lipo-plexes form sponge-like entities, whereas micelle-based ones self-arrange in fibrous organizations. Gels are characterized by a significant viscoelasticity in a wide temperature and frequency range. Rheological data were interpreted by assuming strict relations between the system response and the self-organization of the lipo-plexes into gels. It was inferred that differences in the gel properties depend on the different self-assembly modes of the aggregates formed by the mentioned lipo-plexes. Use of the above systems in biomedical applications, mostly in the preparation of matrices requiring the use of smart and biocompatible gels, is suggested. PMID:24836923

  9. ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES

    PubMed Central

    Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

    2016-01-01

    High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓr norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics. PMID:26806986

  10. A Computer Program for Clustering Large Matrices

    ERIC Educational Resources Information Center

    Koch, Valerie L.

    1976-01-01

    A Fortran V program is described derived for the Univac 1100 Series Computer for clustering into hierarchical structures large matrices, up to 1000 x 1000 and larger, of interassociations between objects. (RC)

  11. Synchronous correlation matrices and Connes' embedding conjecture

    NASA Astrophysics Data System (ADS)

    Dykema, Kenneth J.; Paulsen, Vern

    2016-01-01

    In the work of Paulsen et al. [J. Funct. Anal. (in press); preprint arXiv:1407.6918], the concept of synchronous quantum correlation matrices was introduced and these were shown to correspond to traces on certain C*-algebras. In particular, synchronous correlation matrices arose in their study of various versions of quantum chromatic numbers of graphs and other quantum versions of graph theoretic parameters. In this paper, we develop these ideas further, focusing on the relations between synchronous correlation matrices and microstates. We prove that Connes' embedding conjecture is equivalent to the equality of two families of synchronous quantum correlation matrices. We prove that if Connes' embedding conjecture has a positive answer, then the tracial rank and projective rank are equal for every graph. We then apply these results to more general non-local games.

  12. Examination of light distribution from sol-gel based applicators for interstitial laser therapy

    NASA Astrophysics Data System (ADS)

    Hołowacz, I.; Ulatowska-Jarża, A.; Podbielska, H.; Garbaczewska, I.

    2006-02-01

    We describe here the construction of sol-gel based applicators for interstitial thermotheraphy. The silica sol-gel coatings were prepared from silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The matrices were produced with various ratios R=5, 10, 20, 32, 50, whereas R denotes the number of solvent molds (here ethanol) to the number of TEOS moles. The spatial light intensity distribution was examined in order to find out the influence of R factor on the light distribution shape. It was shows that the most homogeneous patterns are observed for sol-gel coatings with R factors equal 10 and 20.

  13. Fermion masses from SO(10) Hermitian matrices

    SciTech Connect

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126 scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  14. Fermion masses from SO(10) Hermitian matrices

    NASA Astrophysics Data System (ADS)

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126¯ scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  15. Viscoelasticity of silica gels

    SciTech Connect

    Scherer, G.W.

    1995-12-01

    The response of silica gels to mechanical loads depends on the properties of the solid phase and the permeability of the network. Understanding this behavior is essential for modeling of stresses developed during drying or heating of gels. The permeability and the mechanical properties are readily determined from a simple beam-bending experiment, by measuring the load relaxation that occurs at constant deflection. Load decay results from movement of the liquid within the network; in addition, there may be viscoelastic relaxation of the network itself. Silica gel is viscoelastic in chemically aggressive media, but in inert liquids (such as ethanol or acetone) it is elastic. Experiments show that the viscoelastic relaxation time decreases as the concentration and pH of the water in the pore liquid increase. During drying, the permeability decreases and the viscosity increases, both exhibiting a power-law dependence on density of the gel network.

  16. Testosterone Nasal Gel

    MedlinePlus

    ... enough natural testosterone). Testosterone nasal gel is used only for men with low testosterone levels caused by ... is a controlled substance. Prescriptions may be refilled only a limited number of times; ask your pharmacist ...

  17. Microfluidics with Gel Emulsions

    NASA Astrophysics Data System (ADS)

    Priest, Craig; Surenjav, Enkhtuul; Herminghaus, Stephan; Seemann, Ralf

    2006-03-01

    Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodisperse emulsions to compartment liquids within microchannel geometries. At low continuous phase volume fractions, droplets self-organize to form well-defined arrangements, analogous to foam. While it is well-known that confined geometries can induce rearrangement of foam compartments at the millimeter-scale, similar dynamics are also expected for gel emulsions. We have studied online generation, organization and manipulation of gel emulsions using a variety of microchannel geometries. ``Passive'' reorganization, based on fixed channel geometries, can be supplemented by ``active'' manipulation by incorporating a ferrofluid phase. A ferromagnetic phase facilitates reorganization of liquid compartments on demand using an electromagnetic trigger. Moreover, coalescence between adjacent compartments within a gel emulsion can be induced using electrical potential. Microfluidics using gel emulsions will be well-suited for combinatorial chemistry, DNA sequencing, drug screening and protein crystallizations.

  18. Preparation of chitosan gel

    NASA Astrophysics Data System (ADS)

    Moussaoui, Y.; Mnasri, N.; Elaloui, E.; Ben Salem, R.; Lagerge, S.; de Menorval, L. C.

    2012-06-01

    Aerogel conditioning of the chitosan makes it possible to prepare porous solids of significant specific surface. The increase in the chitosan concentration or the degree of acetylation decreases the specific surface of the synthesized chitosan gel. Whereas drying with supercritical CO2 more effectively makes it possible to preserve the volume of the spheres of gel and to have a more significant specific surface in comparison with evaporative drying.

  19. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone

  20. Conformance Improvement Using Gels

    SciTech Connect

    Seright, Randall S.; Schrader, Richard; II Hagstrom, John; Wang, Ying; Al-Dahfeeri, Abdullah; Gary, Raven; Marin; Amaury; Lindquist, Brent

    2002-09-26

    This research project had two objectives. The first objective was to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective was to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

  1. Interplanetary Type IV Bursts

    NASA Astrophysics Data System (ADS)

    Hillaris, A.; Bouratzis, C.; Nindos, A.

    2016-08-01

    We study the characteristics of moving type IV radio bursts that extend to hectometric wavelengths (interplanetary type IV or type {IV}_{{IP}} bursts) and their relationship with energetic phenomena on the Sun. Our dataset comprises 48 interplanetary type IV bursts observed with the Radio and Plasma Wave Investigation (WAVES) instrument onboard Wind in the 13.825 MHz - 20 kHz frequency range. The dynamic spectra of the Radio Solar Telescope Network (RSTN), the Nançay Decametric Array (DAM), the Appareil de Routine pour le Traitement et l' Enregistrement Magnetique de l' Information Spectral (ARTEMIS-IV), the Culgoora, Hiraso, and the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) Radio Spectrographs were used to track the evolution of the events in the low corona. These were supplemented with soft X-ray (SXR) flux-measurements from the Geostationary Operational Environmental Satellite (GOES) and coronal mass ejections (CME) data from the Large Angle and Spectroscopic Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Positional information of the coronal bursts was obtained by the Nançay Radioheliograph (NRH). We examined the relationship of the type IV events with coronal radio bursts, CMEs, and SXR flares. The majority of the events (45) were characterized as compact, their duration was on average 106 minutes. This type of events was, mostly, associated with M- and X-class flares (40 out of 45) and fast CMEs, 32 of these events had CMEs faster than 1000 km s^{-1}. Furthermore, in 43 compact events the CME was possibly subjected to reduced aerodynamic drag as it was propagating in the wake of a previous CME. A minority (three) of long-lived type {IV}_{{IP}} bursts was detected, with durations from 960 minutes to 115 hours. These events are referred to as extended or long duration and appear to replenish their energetic electron content, possibly from electrons escaping from the corresponding coronal

  2. Polyacrylamide gel electrophoresis.

    PubMed

    Chrambach, A; Rodbard, D

    1971-04-30

    Polyacrylamide gel electrophoresis (PAGE) provides a versatile, gentle, high resolution method for fractionation and physical-chemical characterization of molecules on the basis of size, conformation, and net charge. The polymerization reaction can be rigorously controlled to provide uniform gels of reproducible, measurable pore size over a wide range. This makes it possible to obtain reproducible relative mobility (Rf) values as physical-chemical constants. Application and extension of Ogston's (random fiber) model for a gel allows for calculation of molecular volume, surface area, or radius, free mobility, and valence from RJ measurements at several gel concentrations, to calculate gel concentration for optimal resolution, and to predict behavior of macromolecules on gel gradients by computerized methods. Extension of classical moving boundary theory has been used to generate multiphasic buffer systems (providing selective stacking, unstacking, restacking, and preparative steady-state-stacking) with known operating characteristics for any pH at 0 degrees and 25 degrees C. A general strategy for isolation of macromolecules and for macromolecular mapping has been developed. Preparative scale PAGE is operational for milligram loads and feasible for gram quantities. PMID:4927678

  3. A Brief Historical Introduction to Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the ancient origin of matrices, and the system of linear equations. Included are algebraic properties of matrices, determinants, linear transformations, and Cramer's Rule for solving the system of algebraic equations. Special attention is given to some special matrices, including matrices in graph theory and electrical…

  4. Developmental Differences in Strategies for Solving Figural Matrices.

    ERIC Educational Resources Information Center

    Foorman, Barbara R.; And Others

    In order to study children's strategies for solving geometric matrices similar to those in the Raven's Progressive Matrices, ninety 7-, 10-, and 13-year-old boys and girls were administered tests of auditory and visual memory, the Raven's, and geometric matrices. The matrices varied in number of elements (1 to 3) and number of transformations (0…

  5. Condition number estimation of preconditioned matrices.

    PubMed

    Kushida, Noriyuki

    2015-01-01

    The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager's method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei's matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei's matrix, and matrices generated with the finite element method. PMID:25816331

  6. Condition Number Estimation of Preconditioned Matrices

    PubMed Central

    Kushida, Noriyuki

    2015-01-01

    The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager’s method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei’s matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei’s matrix, and matrices generated with the finite element method. PMID:25816331

  7. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2002-02-28

    This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.

  8. Small Titanium Oxo Clusters: Primary Structures of Titanium(IV) in Water.

    PubMed

    Zhang, Guanyun; Hou, Jie; Tung, Chen-Ho; Wang, Yifeng

    2016-04-01

    For sol-gel synthesis of titanium oxide, the titanium(IV) precursors are dissolved in water to form clear solutions. However, the solution status of titanium(IV) remains unclear. Herein three new and rare types of titanium oxo clusters are isolated from aqueous solutions of TiOSO4 and TiCl4 without using organic ligands. Our results indicate that titanium(IV) is readily hydrolyzed into oxo oligomers even in highly acidic solutions. The present clusters provide precise structural information for future characterization of the solution species and structural evolution of titanium(IV) in water and, meanwhile, are new molecular materials for photocatalysis. PMID:26990885

  9. PLATO IV Accountancy Index.

    ERIC Educational Resources Information Center

    Pondy, Dorothy, Comp.

    The catalog was compiled to assist instructors in planning community college and university curricula using the 48 computer-assisted accountancy lessons available on PLATO IV (Programmed Logic for Automatic Teaching Operation) for first semester accounting courses. It contains information on lesson access, lists of acceptable abbreviations for…

  10. IVS Technology Coordinator Report

    NASA Technical Reports Server (NTRS)

    Whitney, Alan

    2013-01-01

    This report of the Technology Coordinator includes the following: 1) continued work to implement the new VLBI2010 system, 2) the 1st International VLBI Technology Workshop, 3) a VLBI Digital- Backend Intercomparison Workshop, 4) DiFX software correlator development for geodetic VLBI, 5) a review of progress towards global VLBI standards, and 6) a welcome to new IVS Technology Coordinator Bill Petrachenko.

  11. The PLATO IV Architecture.

    ERIC Educational Resources Information Center

    Stifle, Jack

    The PLATO IV computer-based instructional system consists of a large scale centrally located CDC 6400 computer and a large number of remote student terminals. This is a brief and general description of the proposed input/output hardware necessary to interface the student terminals with the computer's central processing unit (CPU) using available…

  12. Bayesian Nonparametric Clustering for Positive Definite Matrices.

    PubMed

    Cherian, Anoop; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2016-05-01

    Symmetric Positive Definite (SPD) matrices emerge as data descriptors in several applications of computer vision such as object tracking, texture recognition, and diffusion tensor imaging. Clustering these data matrices forms an integral part of these applications, for which soft-clustering algorithms (K-Means, expectation maximization, etc.) are generally used. As is well-known, these algorithms need the number of clusters to be specified, which is difficult when the dataset scales. To address this issue, we resort to the classical nonparametric Bayesian framework by modeling the data as a mixture model using the Dirichlet process (DP) prior. Since these matrices do not conform to the Euclidean geometry, rather belongs to a curved Riemannian manifold,existing DP models cannot be directly applied. Thus, in this paper, we propose a novel DP mixture model framework for SPD matrices. Using the log-determinant divergence as the underlying dissimilarity measure to compare these matrices, and further using the connection between this measure and the Wishart distribution, we derive a novel DPM model based on the Wishart-Inverse-Wishart conjugate pair. We apply this model to several applications in computer vision. Our experiments demonstrate that our model is scalable to the dataset size and at the same time achieves superior accuracy compared to several state-of-the-art parametric and nonparametric clustering algorithms. PMID:27046838

  13. Compartmentalization of metals within the diverse colloidal matrices comprising activated sludge microbial flocs.

    PubMed

    Leppard, Gary G; Droppo, Ian G; West, M Marcia; Liss, Steven N

    2003-01-01

    Activated sludge floc from a wastewater treatment system was characterized, with regard to principal structural, chemical, and microbiological components and properties, in relation to contaminant-colloid associations and settling. Multiscale analytical microscopies, in conjunction with multimethod sample preparations, were used correlatively to characterize diverse colloidal matrices within microbial floc. Transmission electron microscopy, in conjunction with energy dispersive spectroscopy (EDS), revealed specific associations of contaminant heavy metals with individual bacterial cells and with extracellular polymeric substances (EPS). Floc structure was mapped from the level of gross morphology down to the nano-scale, and flocs were described with respect to settling properties, size, shape, density, porosity, bound water content, and EPS chemical composition; gross surface properties were also measured for correlation with principal floc features. Compartmentalization results based on 171 EDS analyses and representative high-resolution images showed that nano-scale agglomerations of (i) silver (100%) and (ii) zinc (91%) were confined almost entirely to EPS matrices while (iii) Pb (100%) was confined to intracellular granules and (iv) aluminum was partitioned between EPS matrices (41%) and intracellular matrices (59%). The results suggest that engineered changes in microbial physiology and/or in macromolecular EPS composition may influence metal removal efficiencies. PMID:14674532

  14. Kefiran-alginate gel microspheres for oral delivery of ciprofloxacin.

    PubMed

    Blandón, Lina M; Islan, German A; Castro, Guillermo R; Noseda, Miguel D; Thomaz-Soccol, Vanete; Soccol, Carlos R

    2016-09-01

    Ciprofloxacin is a broad-spectrum antibiotic associated with gastric and intestinal side effects after extended oral administration. Alginate is a biopolymer commonly employed in gel synthesis by ionotropic gelation, but unstable in the presence of biological metal-chelating compounds and/or under dried conditions. Kefiran is a microbial biopolymer able to form gels with the advantage of displaying antimicrobial activity. In the present study, kefiran-alginate gel microspheres were developed to encapsulate ciprofloxacin for antimicrobial controlled release and enhanced bactericidal effect against common pathogens. Scanning electron microscopy (SEM) analysis of the hybrid gel microspheres showed a spherical structure with a smoother surface compared to alginate gel matrices. In vitro release of ciprofloxacin from kefiran-alginate microspheres was less than 3.0% and 5.0% at pH 1.2 (stomach), and 5.0% and 25.0% at pH 7.4 (intestine) in 3 and 21h, respectively. Fourier transform infrared spectroscopy (FTIR) of ciprofloxacin-kefiran showed the displacement of typical bands of ciprofloxacin and kefiran, suggesting a cooperative interaction by hydrogen bridges between both molecules. Additionally, the thermal analysis of ciprofloxacin-kefiran showed a protective effect of the biopolymer against ciprofloxacin degradation at high temperatures. Finally, antimicrobial assays of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhymurium, and Staphylococcus aureus demonstrated the synergic effect between ciprofloxacin and kefiran against the tested microorganisms. PMID:27289312

  15. Advanced incomplete factorization algorithms for Stiltijes matrices

    SciTech Connect

    Il`in, V.P.

    1996-12-31

    The modern numerical methods for solving the linear algebraic systems Au = f with high order sparse matrices A, which arise in grid approximations of multidimensional boundary value problems, are based mainly on accelerated iterative processes with easily invertible preconditioning matrices presented in the form of approximate (incomplete) factorization of the original matrix A. We consider some recent algorithmic approaches, theoretical foundations, experimental data and open questions for incomplete factorization of Stiltijes matrices which are {open_quotes}the best{close_quotes} ones in the sense that they have the most advanced results. Special attention is given to solving the elliptic differential equations with strongly variable coefficients, singular perturbated diffusion-convection and parabolic equations.

  16. Origin of symmetric PMNS and CKM matrices

    NASA Astrophysics Data System (ADS)

    Rodejohann, Werner; Xu, Xun-Jie

    2015-03-01

    The Pontecorvo-Maki-Nakagawa-Sakata and Cabibbo-Kobayashi-Maskawa matrices are phenomenologically close to symmetric, and a symmetric form could be used as zeroth-order approximation for both matrices. We study the possible theoretical origin of this feature in flavor symmetry models. We identify necessary geometric properties of discrete flavor symmetry groups that can lead to symmetric mixing matrices. Those properties are actually very common in discrete groups such as A4 , S4 , or Δ (96 ) . As an application of our theorem, we generate a symmetric lepton mixing scheme with θ12=θ23=36.21 ° ; θ13=12.20 ° , and δ =0 , realized with the group Δ (96 ) .

  17. Octonion generalization of Pauli and Dirac matrices

    NASA Astrophysics Data System (ADS)

    Chanyal, B. C.

    2015-10-01

    Starting with octonion algebra and its 4 × 4 matrix representation, we have made an attempt to write the extension of Pauli's matrices in terms of division algebra (octonion). The octonion generalization of Pauli's matrices shows the counterpart of Pauli's spin and isospin matrices. In this paper, we also have obtained the relationship between Clifford algebras and the division algebras, i.e. a relation between octonion basis elements with Dirac (gamma), Weyl and Majorana representations. The division algebra structure leads to nice representations of the corresponding Clifford algebras. We have made an attempt to investigate the octonion formulation of Dirac wave equations, conserved current and weak isospin in simple, compact, consistent and manifestly covariant manner.

  18. Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

    Lang, M.; Fischer, J.; Werner, M.; Sommer, J.-U.

    2014-06-01

    The swelling equilibrium of Olympic gels, which are composed of entangled cyclic polymers, is studied by Monte Carlo simulations. In contrast to chemically cross-linked polymer networks, we observe that Olympic gels made of chains with a larger degree of polymerization, N, exhibit a smaller equilibrium swelling degree, Q∝N-0.28ϕ0-0.72, at the same polymer volume fraction ϕ0 at network preparation. This observation is explained by a desinterspersion (reorganization with release of nontrapped entanglements) process of overlapping nonconcatenated rings upon swelling.

  19. The suitability of tris(hydroxylmethyl) aminomethane (THAM) as a buffering system for hydroxypropyl methylcellulose (HPMC) hydrophilic matrices containing a weak acid drug.

    PubMed

    Pygall, Samuel R; Kujawinski, Sarah; Timmins, Peter; Melia, Colin D

    2010-03-15

    There are few studies of alkalising pH-modifiers in HPMC hydrophilic matrices. These agents may be incorporated to provide microenvironmental buffering and facilitate pH-independent release of weak acid drugs. This study compared tris(hydroxylmethyl) aminomethane (THAM, TRIS, tromethamine, trometamol) with sodium citrate as internal buffering agents for HPMC (4000 cps) 2208 and 2910 matrices containing felbinac, a weak acid drug which exhibits pH-dependent solubility. Drug release at pH 1.2 and 7.5 was accelerated by both buffers, but THAM-buffered matrices provided extended, diffusion-based release kinetics, without loss of matrix integrity at high buffer concentrations. Release kinetics appeared to be independent of media pH. THAM did not depress the sol-gel transition temperature or suppress HPMC particle swelling, and had minimal effects on gel layer formation. Sodium citrate promoted greater thickness of the early gel layer than THAM. Measurements of internal gel layer pH showed that both buffers produced a rapid alkalisation of the gel layer which was progressively lost. As result of its higher pK(a) and molar ratio on a percent weight basis, THAM provided a higher internal pH and a greater longevity of pH modification. It is concluded that THAM offers a useful buffering option for weak acid drugs in HPMC-based systems. PMID:20005935

  20. Complete primary structure of the triple-helical region and the carboxyl-terminal domain of a new type IV collagen chain, alpha 5(IV).

    PubMed

    Pihlajaniemi, T; Pohjolainen, E R; Myers, J C

    1990-08-15

    We have isolated and characterized overlapping cDNA clones which code for a previously unidentified human collagen chain. Although the cDNA-derived primary structure of this new polypeptide is very similar to the basement membrane collagen alpha 1(IV) and alpha 2(IV) chains, the carboxyl-terminal collagenous/non-collagenous junction sequence does not correspond to the junction sequence in either of the newly described alpha 3(IV) or alpha 4(IV) chains (Butkowski, R.J., Langeveld, J.P.M., Wieslander, J., Hamilton, J., and Hudson, B. G. (1987) J. Biol. Chem. 262, 7874-7877). Thus the protein presented here has been designated the alpha 5 chain of type IV collagen. Four clones encode an open reading frame of 1602 amino acids that cover about 95% of the entire chain including half of the amino-terminal 7S domain and all of the central triple-helical region and carboxyl-terminal NC1 domain. The collagenous region of the alpha 5(IV) chain contains 22 interruptions which are in most cases identical in distribution to those in both the alpha 1(IV) and alpha 2(IV) chains. Despite the relatively low degree of conservation among the amino acids in the triple-helical region of the three type IV collagen chains, analysis of the sequences clearly showed that alpha 5(IV) is more related to alpha 1(IV) than to alpha 2(IV). This similarity between the alpha 5(IV) and alpha 1(IV) chains is particularly evident in the NC1 domains where the two polypeptides are 83% identical in contrast to the alpha 5(IV) and alpha 2(IV) identity of 63%. In addition to greatly increasing the complexity of basement membranes, the alpha 5 chain of type IV collagen may be responsible for specialized functions of some of these extracellular matrices. In this regard, it is important to note that we have recently assigned the alpha 5(IV) gene to the region of the X chromosome containing the locus for a familial type of hereditary nephritis known as Alport syndrome (Myers, J.C., Jones, T.A., Pohjalainen, E

  1. Fast transforms: Banded matrices with banded inverses

    PubMed Central

    Strang, Gilbert

    2010-01-01

    It is unusual for both A and A-1 to be banded—but this can be a valuable property in applications. Block-diagonal matrices F are the simplest examples; wavelet transforms are more subtle. We show that every example can be factored into A = F1…FN where N is controlled by the bandwidths of A and A-1 (but not by their size, so this extends to infinite matrices and leads to new matrix groups). PMID:20615937

  2. Sparse Matrices in MATLAB: Design and Implementation

    NASA Technical Reports Server (NTRS)

    Gilbert, John R.; Moler, Cleve; Schreiber, Robert

    1992-01-01

    The matrix computation language and environment MATLAB is extended to include sparse matrix storage and operations. The only change to the outward appearance of the MATLAB language is a pair of commands to create full or sparse matrices. Nearly all the operations of MATLAB now apply equally to full or sparse matrices, without any explicit action by the user. The sparse data structure represents a matrix in space proportional to the number of nonzero entries, and most of the operations compute sparse results in time proportional to the number of arithmetic operations on nonzeros.

  3. Spectral properties of ghost Neumann matrices

    SciTech Connect

    Bonora, L.; Santos, R. J. Scherer; Tolla, D. D.

    2008-05-15

    We continue the analysis of the ghost wedge states in the oscillator formalism by studying the spectral properties of the ghost matrices of Neumann coefficients. We show that the traditional spectral representation is not valid for these matrices and propose a new heuristic formula that allows one to reconstruct them from the knowledge of their eigenvalues and eigenvectors. It turns out that additional data, which we call boundary data, are needed in order to actually implement the reconstruction. In particular our result lends support to the conjecture that there exists a ghost three strings vertex with properties parallel to those of the matter three strings vertex.

  4. Does WISC-IV Underestimate the Intelligence of Autistic Children?

    PubMed

    Nader, Anne-Marie; Courchesne, Valérie; Dawson, Michelle; Soulières, Isabelle

    2016-05-01

    Wechsler Intelligence Scale for Children (WISC) is widely used to estimate autistic intelligence (Joseph in The neuropsychology of autism. Oxford University Press, Oxford, 2011; Goldstein et al. in Assessment of autism spectrum disorders. Guilford Press, New York, 2008; Mottron in J Autism Dev Disord 34(1):19-27, 2004). However, previous studies suggest that while WISC-III and Raven's Progressive Matrices (RPM) provide similar estimates of non-autistic intelligence, autistic children perform significantly better on RPM (Dawson et al. in Psychol Sci 18(8):657-662, doi: 10.1111/j.1467-9280.2007.01954.x , 2007). The latest WISC version introduces substantial changes in subtests and index scores; thus, we asked whether WISC-IV still underestimates autistic intelligence. Twenty-five autistic and 22 typical children completed WISC-IV and RPM. Autistic children's RPM scores were significantly higher than their WISC-IV FSIQ, but there was no significant difference in typical children. Further, autistic children showed a distinctively uneven WISC-IV index profile, with a "peak" in the new Perceptual Reasoning Index. In spite of major changes, WISC-IV FSIQ continues to underestimate autistic intelligence. PMID:25308198

  5. Rheology of Active Gels

    NASA Astrophysics Data System (ADS)

    Chen, Daniel

    2015-03-01

    Active networks drive a diverse range of critical processes ranging from motility to division in living cells, yet a full picture of their rheological capabilities in non-cellular contexts is still emerging, e.g., How does the rheological response of a network capable of remodeling under internally-generated stresses differ from that of a passive biopolymer network? In order to address this and other basic questions, we have engineered an active gel composed of microtubules, bidirectional kinesin motors, and molecular depletant that self-organizes into a highly dynamic network of active bundles. The network continually remodels itself under ATP-tunable cycles of extension, buckling, fracturing, and self-healing. Using confocal rheometry we have simultaneously characterized the network's linear and non-linear rheological responses to shear deformation along with its dynamic morphology. We find several surprising and unique material properties for these active gels; most notably, rheological cloaking, the ability of the active gel to drive large-scale fluid mixing over several orders of flow magnitude while maintaining an invariant, solid-like rheological profile and spontaneous flow under confinement, the ability to exert micro-Newton forces to drive persistent directed motion of the rheometer tool. Taken together, these results and others to be discussed highlight the rich stress-structure-dynamics relationships in this class of biologically-derived active gels.

  6. Controlling the Localization of Liquid Droplets in Polymer Matrices by Evaporative Lithography.

    PubMed

    Zhao, Huaixia; Xu, Jiajia; Jing, Guangyin; Prieto-López, Lizbeth Ofelia; Deng, Xu; Cui, Jiaxi

    2016-08-26

    Localized inclusions of liquids provide solid materials with many functions, such as self-healing, secretion, and tunable mechanical properties, in a spatially controlled mode. However, a strategy to control the distribution of liquid droplets in solid matrices directly obtained from a homogeneous solution has not been reported thus far. Herein, we describe an approach to selectively localize liquid droplets in a supramolecular gel directly obtained from its solution by using evaporative lithography. In this process, the formation of droplet-embedded domains occurs in regions of free evaporation where the non-volatile liquid is concentrated and undergoes a phase separation to create liquid droplets prior to gelation, while a homogeneous gel matrix is formed in the regions of hindered evaporation. The different regions of a coating with droplet embedment patterns display different secretion abilities, enabling the control of the directional movement of water droplets. PMID:27460600

  7. A sputnik IV saga

    NASA Astrophysics Data System (ADS)

    Lundquist, Charles A.

    2009-12-01

    The Sputnik IV launch occurred on May 15, 1960. On May 19, an attempt to deorbit a 'space cabin' failed and the cabin went into a higher orbit. The orbit of the cabin was monitored and Moonwatch volunteer satellite tracking teams were alerted to watch for the vehicle demise. On September 5, 1962, several team members from Milwaukee, Wisconsin made observations starting at 4:49 a.m. of a fireball following the predicted orbit of Sputnik IV. Requests went out to report any objects found under the fireball path. An early morning police patrol in Manitowoc had noticed a metal object on a street and had moved it to the curb. Later the officers recovered the object and had it dropped off at the Milwaukee Journal. The Moonwarch team got the object and reported the situation to Moonwatch Headquarters at the Smithsonian Astrophysical Observatory. A team member flew to Cambridge with the object. It was a solid, 9.49 kg piece of steel with a slag-like layer attached to it. Subsequent analyses showed that it contained radioactive nuclei produced by cosmic ray exposure in space. The scientists at the Observatory quickly recognized that measurements of its induced radioactivity could serve as a calibration for similar measurements of recently fallen nickel-iron meteorites. Concurrently, the Observatory directorate informed government agencies that a fragment from Sputnik IV had been recovered. Coincidently, a debate in the UN Committee on Peaceful Uses of Outer Space involved the issue of liability for damage caused by falling satellite fragments. On September 12, the Observatory delivered the bulk of the fragment to the US Delegation to the UN. Two days later, the fragment was used by US Ambassador Francis Plimpton as an exhibit that the time had come to agree on liability for damage from satellite debris. He offered the Sputnik IV fragment to USSR Ambassador P.D. Morozov, who refused the offer. On October 23, Drs. Alla Massevitch and E.K. Federov of the USSR visited the

  8. Parameterized BLOSUM Matrices for Protein Alignment.

    PubMed

    Song, Dandan; Chen, Jiaxing; Chen, Guang; Li, Ning; Li, Jin; Fan, Jun; Bu, Dongbo; Li, Shuai Cheng

    2015-01-01

    Protein alignment is a basic step for many molecular biology researches. The BLOSUM matrices, especially BLOSUM62, are the de facto standard matrices for protein alignments. However, after widely utilization of the matrices for 15 years, programming errors were surprisingly found in the initial version of source codes for their generation. And amazingly, after bug correction, the "intended" BLOSUM62 matrix performs consistently worse than the "miscalculated" one. In this paper, we find linear relationships among the eigenvalues of the matrices and propose an algorithm to find optimal unified eigenvectors. With them, we can parameterize matrix BLOSUMx for any given variable x that could change continuously. We compare the effectiveness of our parameterized isentropic matrix with BLOSUM62. Furthermore, an iterative alignment and matrix selection process is proposed to adaptively find the best parameter and globally align two sequences. Experiments are conducted on aligning 13,667 families of Pfam database and on clustering MHC II protein sequences, whose improved accuracy demonstrates the effectiveness of our proposed method. PMID:26357279

  9. Malware Analysis Using Visualized Image Matrices

    PubMed Central

    Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  10. Malware analysis using visualized image matrices.

    PubMed

    Han, KyoungSoo; Kang, BooJoong; Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  11. Spectral averaging techniques for Jacobi matrices

    SciTech Connect

    Rio, Rafael del; Martinez, Carmen; Schulz-Baldes, Hermann

    2008-02-15

    Spectral averaging techniques for one-dimensional discrete Schroedinger operators are revisited and extended. In particular, simultaneous averaging over several parameters is discussed. Special focus is put on proving lower bounds on the density of the averaged spectral measures. These Wegner-type estimates are used to analyze stability properties for the spectral types of Jacobi matrices under local perturbations.

  12. Multifunctional matrices for oral peptide delivery.

    PubMed

    Bernkop-Schnürch, A; Walker, G

    2001-01-01

    The oral administration of peptide drugs represents one of the greatest challenges in pharmaceutical technology. To gain a sufficient bioavailability of these therapeutic agents, various barriers including the mucus-layer barrier, the enzymatic barrier, and the membrane barrier have to be overcome. A promising strategy for achieving this goal is the use of multifunctional matrices. These matrices are based on polymers that display mucoadhesive properties, a permeation-enhancing effect, enzyme-inhibiting properties, and/or a high buffer capacity. Moreover, a sustained or delayed drug release can be provided by delivery systems that contain such polymers. Among them, polyacrylates, cellulose derivatives, and chitosan are promising excipients that can also be customized by chemical modification to improve certain properties. For example, the covalent attachment of thiol moieties on these polymers leads to improved mucoadhesive and permeation-enhancing properties, and the conjugation of enzyme inhibitors enables the matrices to provide protection for peptide drugs against enzymatic degradation. The efficacy of multifunctional matrices in oral peptide delivery has been verified by various in vivo studies that could pave the way for the development of commercially viable formulations. PMID:11763498

  13. SPECIATION OF ARSENIC IN EXPOSURE ASSESSMENT MATRICES

    EPA Science Inventory

    The speciaton of arsenic in water, food and urine are analytical capabilities which are an essential part in arsenic risk assessment. The cancer risk associated with arsenic has been the driving force in generating the analytical research in each of these matrices. This presentat...

  14. Constructing random matrices to represent real ecosystems.

    PubMed

    James, Alex; Plank, Michael J; Rossberg, Axel G; Beecham, Jonathan; Emmerson, Mark; Pitchford, Jonathan W

    2015-05-01

    Models of complex systems with n components typically have order n(2) parameters because each component can potentially interact with every other. When it is impractical to measure these parameters, one may choose random parameter values and study the emergent statistical properties at the system level. Many influential results in theoretical ecology have been derived from two key assumptions: that species interact with random partners at random intensities and that intraspecific competition is comparable between species. Under these assumptions, community dynamics can be described by a community matrix that is often amenable to mathematical analysis. We combine empirical data with mathematical theory to show that both of these assumptions lead to results that must be interpreted with caution. We examine 21 empirically derived community matrices constructed using three established, independent methods. The empirically derived systems are more stable by orders of magnitude than results from random matrices. This consistent disparity is not explained by existing results on predator-prey interactions. We investigate the key properties of empirical community matrices that distinguish them from random matrices. We show that network topology is less important than the relationship between a species' trophic position within the food web and its interaction strengths. We identify key features of empirical networks that must be preserved if random matrix models are to capture the features of real ecosystems. PMID:25905510

  15. Noisy covariance matrices and portfolio optimization

    NASA Astrophysics Data System (ADS)

    Pafka, S.; Kondor, I.

    2002-05-01

    According to recent findings [#!bouchaud!#,#!stanley!#], empirical covariance matrices deduced from financial return series contain such a high amount of noise that, apart from a few large eigenvalues and the corresponding eigenvectors, their structure can essentially be regarded as random. In [#!bouchaud!#], e.g., it is reported that about 94% of the spectrum of these matrices can be fitted by that of a random matrix drawn from an appropriately chosen ensemble. In view of the fundamental role of covariance matrices in the theory of portfolio optimization as well as in industry-wide risk management practices, we analyze the possible implications of this effect. Simulation experiments with matrices having a structure such as described in [#!bouchaud!#,#!stanley!#] lead us to the conclusion that in the context of the classical portfolio problem (minimizing the portfolio variance under linear constraints) noise has relatively little effect. To leading order the solutions are determined by the stable, large eigenvalues, and the displacement of the solution (measured in variance) due to noise is rather small: depending on the size of the portfolio and on the length of the time series, it is of the order of 5 to 15%. The picture is completely different, however, if we attempt to minimize the variance under non-linear constraints, like those that arise e.g. in the problem of margin accounts or in international capital adequacy regulation. In these problems the presence of noise leads to a serious instability and a high degree of degeneracy of the solutions.

  16. On reduced density matrices for disjoint subsystems

    NASA Astrophysics Data System (ADS)

    Iglói, F.; Peschel, I.

    2010-02-01

    We show that spin and fermion representations for solvable quantum chains lead in general to different reduced density matrices if the subsystem is not singly connected. We study the effect for two sites in XX and XY chains as well as for sublattices in XX and transverse Ising chains.

  17. Platinum(IV)-chlorotoxin (CTX) conjugates for targeting cancer cells.

    PubMed

    Graf, Nora; Mokhtari, Tara E; Papayannopoulos, Ioannis A; Lippard, Stephen J

    2012-05-01

    Cisplatin is one of the most widely used anticancer drugs. Its side effects, however, have motivated researchers to search for equally effective analogs that are better tolerated. Selectively targeting cancer tissue is one promising strategy. For this purpose, a platinum(IV) complex was conjugated to the cancer-targeting peptide chlorotoxin (CTX, TM601) in order to deliver cisplatin selectively to cancer cells. The 1:1 Pt-CTX conjugate was characterized by mass spectrometry and gel electrophoresis. Like most platinum(IV) derivatives, the cytotoxicity of the conjugate was lower in cell culture than that of cisplatin, but greater than those of its Pt(IV) precursor and CTX in several cancer cell lines. PMID:22465700

  18. PMD IVS Analysis Center

    NASA Technical Reports Server (NTRS)

    Tornatore, Vincenza

    2013-01-01

    The main activities carried out at the PMD (Politecnico di Milano DIIAR) IVS Analysis Center during 2012 are briefly higlighted, and future plans for 2013 are sketched out. We principally continued to process European VLBI sessions using different approaches to evaluate possible differences due to various processing choices. Then VLBI solutions were also compared to the GPS ones as well as the ones calculated at co-located sites. Concerning the observational aspect, several tests were performed to identify the most suitable method to achieve the highest possible accuracy in the determination of GNSS (GLOBAL NAVIGATION SATELLITE SYSTEM) satellite positions using the VLBI technique.

  19. Permeability of starch gel matrices and select films to solvent vapors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The controlled release of volatile, agrochemicals is critical in developing approaches to pest control that are economically viable and environmentally sound. Dispensing systems that are made of materials that degrade in agricultural environments when they are spent offer distinct advantages over no...

  20. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  1. Improved Separability Criteria Based on Bloch Representation of Density Matrices.

    PubMed

    Shen, Shu-Qian; Yu, Juan; Li, Ming; Fei, Shao-Ming

    2016-01-01

    The correlation matrices or tensors in the Bloch representation of density matrices are encoded with entanglement properties. In this paper, based on the Bloch representation of density matrices, we give some new separability criteria for bipartite and multipartite quantum states. Theoretical analysis and some examples show that the proposed criteria can be more efficient than the previous related criteria. PMID:27350031

  2. Stiffness and mass matrices for shells of revolution (SAMMSOR II)

    NASA Technical Reports Server (NTRS)

    Tillerson, J. R.; Haisler, W. E.

    1974-01-01

    Utilizing element properties, structural stiffness and mass matrices are generated for as many as twenty harmonics and stored on magnetic tape. Matrices generated constitute input data to be used by other stiffness of revolution programs. Variety of boundary and loading conditions can be employed without having to create new mass and stiffness matrices for each case.

  3. Improved Separability Criteria Based on Bloch Representation of Density Matrices

    PubMed Central

    Shen, Shu-Qian; Yu, Juan; Li, Ming; Fei, Shao-Ming

    2016-01-01

    The correlation matrices or tensors in the Bloch representation of density matrices are encoded with entanglement properties. In this paper, based on the Bloch representation of density matrices, we give some new separability criteria for bipartite and multipartite quantum states. Theoretical analysis and some examples show that the proposed criteria can be more efficient than the previous related criteria. PMID:27350031

  4. Modulating the Rigidity and Mineralization of Collagen Gels Using Poly(Lactic-Co-Glycolic Acid) Microparticles

    PubMed Central

    DeVolder, Ross J.; Kim, Il Won; Kim, Eun-Suk

    2012-01-01

    Extensive efforts have been made to prepare osteoconductive collagen gels for the regeneration of normal bone and the pathological examination of diseased bone; however, collagen gels are often plagued by limited controllability of their rigidity and mineral deposition. This study reports a simple but efficient strategy that tunes the mechanical properties of, and apatite formation in, collagen gels by incorporating hydrolyzable poly(lactic-co-glycolic acid) (PLGA) microparticles within the gels. The PLGA microparticles are associated with the collagen fibrils and increased both the gel's elasticity and rigidity while minimally influencing its permeability. As compared with pure collagen gels, the PLGA microparticle-filled collagen gels, termed PLGA-Col hydrogels, significantly enhanced the deposition of apatite-like minerals within the gels when incubated in simulated body fluid or encapsulated with mesenchymal stem cells (MSCs) undergoing osteogenic differentiation. Finally, PLGA-Col hydrogels mineralized by differentiated MSCs led to an enhanced formation of bone-like tissues within the hydrogels. Overall, the PLGA-Col hydrogel system developed in this study will serve to improve the quality of osteoconductive matrices for both fundamental and clinical studies that are relevant to bone repair, regeneration, and pathogenesis. PMID:22480235

  5. Bacteria immobilised in Gels: Improved methodologies for antifouling and biocontrol applications.

    PubMed

    Holmström, C; Steinberg, P; Christov, V; Christie, G; Kjelleberg, S

    2000-01-01

    A range of bacteria, including the marine bacterium Pseudoalteromonas tunicata which produces antifouling compounds, and Escherichia coli were used to investigate methods for immobilising bacteria in gels. Different types of matrices were screened using the survival of barnacle nauplii as a bioassay. A Dupont® polyvinylalcohol (PVOH) 10% gel was found to be the optimal matrix. This non-toxic gel remained stable in seawater while allowing for an outflux of active biological compounds from the bacterial cells. The presence of active bacterial cells in the matrix was tested by CTC-staining, green fluorescent protein (GFP) expressing bacteria and a barnacle larvae bioassay. The Dupont® PVOH 10% gels containing P. tunicata cells were inhibitory against larvae for a period of up to 2 weeks. In further studies using gels containing immobilised bacteria, the E. coli strain C600 was employed based on its cell size, stress resistance and the fact that a plasmid for the expression of GFP could be transferred and maintained in the cells. Immobilised E. Coli cells maintained their viability in the Dupont® PVOH 10% gels for as long as 2 months, and the life-span of these "biologically active"; gels was increased to more than 2 months by the incorporation of small beads into the gels. The results indicate that bacteria can be immobilised in coatings for periods of time consistent with the needs of some antifouling and antibacterial applications. PMID:22115296

  6. Photochromic organic-inorganic composite materials prepared by sol-gel processing: Properties and potentials

    SciTech Connect

    Hou, L. |; Mennig, M.; Schmidt, H.

    1994-12-31

    The sol-gel method which features a low-temperature wet-chemical process opens vast possibilities to incorporating organic dyes into solid matrices for various optical applications. In this paper the authors present their experimental results on the sol-gel derived photochromic organic-inorganic composite (Ormocer) materials following an introductory description of the sol-gel process and a brief review on the state of the art of the photochromic solids prepared using this method. Their photochromic spirooxazine-Ormocer gels and coatings possess better photochromic response and color-change speed than the corresponding photochromic polymer coatings and similar photochemical stability to the latter. Further developments are proposed as to tackle the temperature dependence problem and further tap the potentialities of the photochromic dye-Ormocer material for practical applications.

  7. 78 FR 2390 - CSOLAR IV South, LLC, Wistaria Ranch Solar, LLC, CSOLAR IV West, LLC, CSOLAR IV North, LLC v...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-11

    ... Energy Regulatory Commission CSOLAR IV South, LLC, Wistaria Ranch Solar, LLC, CSOLAR IV West, LLC, CSOLAR IV North, LLC v. California Independent System Operator Corporation; Notice of Complaint Take notice... IV South, LLC, Wistaria Ranch Solar, LLC, CSOLAR IV West, LLC and CSOLAR IV North, LLC...

  8. Bioisosteric matrices for ligands of serotonin receptors.

    PubMed

    Warszycki, Dawid; Mordalski, Stefan; Staroń, Jakub; Bojarski, Andrzej J

    2015-04-01

    The concept of bioisosteric replacement matrices is applied to explore the chemical space of serotonin receptor ligands, aiming to determine the most efficient ways of manipulating the affinity for all 5-HT receptor subtypes. Analysis of a collection of over 1 million bioisosteres of compounds with measured activity towards serotonin receptors revealed that an average of 31 % of the ligands for each target are mutual bioisosteres. In addition, the collected dataset allowed the development of bioisosteric matrices-qualitative and quantitative descriptions of the biological effects of each predefined type of bioisosteric substitution, providing favored paths of modifying the compounds. The concept exemplified here for serotonin receptor ligands can likely be more broadly applied to other target classes, thus representing a useful guide for medicinal chemists designing novel ligands. PMID:25772514

  9. Evolutionary Games with Randomly Changing Payoff Matrices

    NASA Astrophysics Data System (ADS)

    Yakushkina, Tatiana; Saakian, David B.; Bratus, Alexander; Hu, Chin-Kun

    2015-06-01

    Evolutionary games are used in various fields stretching from economics to biology. In most of these games a constant payoff matrix is assumed, although some works also consider dynamic payoff matrices. In this article we assume a possibility of switching the system between two regimes with different sets of payoff matrices. Potentially such a model can qualitatively describe the development of bacterial or cancer cells with a mutator gene present. A finite population evolutionary game is studied. The model describes the simplest version of annealed disorder in the payoff matrix and is exactly solvable at the large population limit. We analyze the dynamics of the model, and derive the equations for both the maximum and the variance of the distribution using the Hamilton-Jacobi equation formalism.

  10. Approximate inverse preconditioners for general sparse matrices

    SciTech Connect

    Chow, E.; Saad, Y.

    1994-12-31

    Preconditioned Krylov subspace methods are often very efficient in solving sparse linear matrices that arise from the discretization of elliptic partial differential equations. However, for general sparse indifinite matrices, the usual ILU preconditioners fail, often because of the fact that the resulting factors L and U give rise to unstable forward and backward sweeps. In such cases, alternative preconditioners based on approximate inverses may be attractive. We are currently developing a number of such preconditioners based on iterating on each column to get the approximate inverse. For this approach to be efficient, the iteration must be done in sparse mode, i.e., we must use sparse-matrix by sparse-vector type operatoins. We will discuss a few options and compare their performance on standard problems from the Harwell-Boeing collection.

  11. Some physical applications of random hierarchical matrices

    SciTech Connect

    Avetisov, V. A.; Bikulov, A. Kh.; Vasilyev, O. A.; Nechaev, S. K.; Chertovich, A. V.

    2009-09-15

    The investigation of spectral properties of random block-hierarchical matrices as applied to dynamic and structural characteristics of complex hierarchical systems with disorder is proposed for the first time. Peculiarities of dynamics on random ultrametric energy landscapes are discussed and the statistical properties of scale-free and polyscale (depending on the topological characteristics under investigation) random hierarchical networks (graphs) obtained by multiple mapping are considered.

  12. Analysis of thematic map classification error matrices.

    USGS Publications Warehouse

    Rosenfield, G.H.

    1986-01-01

    The classification error matrix expresses the counts of agreement and disagreement between the classified categories and their verification. Thematic mapping experiments compare variables such as multiple photointerpretation or scales of mapping, and produce one or more classification error matrices. This paper presents a tutorial to implement a typical problem of a remotely sensed data experiment for solution by the linear model method.-from Author

  13. Photochromic Behavior of Spiropyran in Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Boudreault, Francois; Roberge, Mathieu; Ritcey, Anna M.; Lessard, Roger A.; Galstian, Tigran V.

    2001-03-01

    The photoexcitation, relaxation, and optical erasure regimes of spiropyran- (SP-) doped polymer films were studied. Cellulose acetate, poly(vinyl acetate), and poly(methyl methacrylate) (PMMA) were used as host polymer matrices. We studied the character of the photoreaction for both coloring and bleaching processes. Reversible holographic recording in SP -PMMA films and the origin of the photochemical fatigue was studied upon repeated UV -visible irradiation cycles.

  14. Preconditioning matrices for Chebyshev derivative operators

    NASA Technical Reports Server (NTRS)

    Rothman, Ernest E.

    1986-01-01

    The problem of preconditioning the matrices arising from pseudo-spectral Chebyshev approximations of first order operators is considered in both one and two dimensions. In one dimension a preconditioner represented by a full matrix which leads to preconditioned eigenvalues that are real, positive, and lie between 1 and pi/2, is already available. Since there are cases in which it is not computationally convenient to work with such a preconditioner, a large number of preconditioners were studied which were more sparse (in particular three and four diagonal matrices). The eigenvalues of such preconditioned matrices are compared. The results were applied to the problem of finding the steady state solution to an equation of the type u sub t = u sub x + f, where the Chebyshev collocation is used for the spatial variable and time discretization is performed by the Richardson method. In two dimensions different preconditioners are proposed for the matrix which arises from the pseudo-spectral discretization of the steady state problem. Results are given for the CPU time and the number of iterations using a Richardson iteration method for the unpreconditioned and preconditioned cases.

  15. Quark flavor mixings from hierarchical mass matrices

    NASA Astrophysics Data System (ADS)

    Verma, Rohit; Zhou, Shun

    2016-05-01

    In this paper, we extend the Fritzsch ansatz of quark mass matrices while retaining their hierarchical structures and show that the main features of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V, including |V^{}_{us}| ˜eq |V^{}_{cd}|, |V^{}_{cb}| ˜eq |V^{}_{ts}| and |V^{}_{ub}|/|V^{}_{cb}| < |V^{}_{td}|/|V^{}_{ts}|, can be well understood. This agreement is observed especially when the mass matrices have non-vanishing (1, 3) and (3, 1) off-diagonal elements. The phenomenological consequences of these for the allowed texture content and gross structural features of `hierarchical' quark mass matrices are addressed from a model-independent prospective under the assumption of factorizable phases in these. The approximate and analytical expressions of the CKM matrix elements are derived and a detailed analysis reveals that such structures are in good agreement with the observed quark flavor mixing angles and the CP-violating phase at the 1σ level and call upon a further investigation of the realization of these structures from a top-down prospective.

  16. Apparatus and method for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, C.D.; Scott, T.C.; Davison, B.H.

    1998-01-27

    An apparatus and method are disclosed for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column. 1 fig.

  17. Apparatus and method for the production of gel beads containing a biocatalyst

    DOEpatents

    Scott, Charles D.; Scott, Timothy C.; Davison, Brian H.

    1998-01-01

    An apparatus and method for the large-scale and continuous production of gel beads containing a biocatalyst. The apparatus is a columnar system based on the chemical cross-linking of hydrocolloidal gels that contain and immobilize a biocatalyst, the biocatalyst being a microorganism or an enzyme. Hydrocolloidal gels, such as alginate, carrageenan, and a mixture of bone gelatin and modified alginate, provide immobilization matrices that can be used to entrap and retain the biocatalyst while allowing effective contact with substrates and release of products. Such immobilized biocatalysts are generally formulated into small spheres or beads that have high concentrations of the biocatalyst within the gel matrix. The columnar system includes a gel dispersion nozzle submerged in a heated non-interacting liquid, typically an organic liquid, that is immiscible with water to allow efficient formation of spherical gel droplets, the non-interacting liquid having a specific gravity that is less than water so that the gel droplets will fall through the liquid by the force of gravity. The heated non-interacting liquid is in direct contact with a chilled upflowing non-interacting liquid that will provide sufficient residence time for the gel droplets as they fall through the liquid so that they will be cooled below the gelling temperature and form solid spheres. The upflowing non-interacting liquid is in direct contact with an upflowing temperature-controlled aqueous solution containing the necessary chemicals for cross-linking or fixing of the gel beads to add the necessary stability. The flow rates of the two liquid streams can be varied to control the proper residence time in each liquid section to accommodate the production of gel beads of differing settling velocities. A valve is provided for continuous removal of the stabilized gel beads from the bottom of the column.

  18. The Illiac IV

    SciTech Connect

    Hord, M.

    1982-01-01

    The story of the Illiac IV is also in part the story of the Institute for Advanced Computation. This is the government organization formed in 1971 by the Defense Advanced Research Projects Agency and the National Aeronautics and Space Administration Ames Research Center to develop and operate this computer. The Institute provides access to the Illiac through a connection to the ARPANET, a national communication network. The Institute also performs software development, maintenance, and research in various advanced computation topics. Considerable effort has been invested by the Institute in documenting the evolution of the Illiac system and providing those publications to the user community. This material has experienced quite limited circulation and to most of the computer world the Illiac remains mysterious. This attitude is fostered by the lack of a thorough summary of the Illiac's environment, design and capabilities. It is in response to that information gap that this book is addressed.

  19. Special paraunitary matrices, Cayley transform, and multidimensional orthogonal filter banks.

    PubMed

    Zhou, Jianping; Do, Minh N; Kovaĉević, Jelena

    2006-02-01

    We characterize and design multidimensional (MD) orthogonal filter banks using special paraunitary matrices and the Cayley transform. Orthogonal filter banks are represented by paraunitary matrices in the polyphase domain. We define special paraunitary matrices as paraunitary matrices with unit determinant. We show that every paraunitary matrix can be characterized by a special paraunitary matrix and a phase factor. Therefore, the design of paraunitary matrices (and thus of orthogonal filter banks) becomes the design of special paraunitary matrices, which requires a smaller set of nonlinear equations. Moreover, we provide a complete characterization of special paraunitary matrices in the Cayley domain, which converts nonlinear constraints into linear constraints. Our method greatly simplifies the design of MD orthogonal filter banks and leads to complete characterizations of such filter banks. PMID:16479821

  20. Flavonoids as matrices for MALDI-TOF mass spectrometric analysis of transition metal complexes

    NASA Astrophysics Data System (ADS)

    Petkovic, Marijana; Petrovic, Biljana; Savic, Jasmina; Bugarcic, Zivadin D.; Dimitric-Markovic, Jasmina; Momic, Tatjana; Vasic, Vesna

    2010-02-01

    Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a suitable method for the analysis of inorganic and organic compounds and biomolecules. This makes MALDI-TOF MS convenient for monitoring the interaction of metallo-drugs with biomolecules. Results presented in this manuscript demonstrate that flavonoids such as apigenin, kaempferol and luteolin are suitable for MALDI-TOF MS analysis of Pt(II), Pd(II), Pt(IV) and Ru(III) complexes, giving different signal-to-noise ratios of the analyte peak. The MALDI-TOF mass spectra of inorganic complexes acquired with these flavonoid matrices are easy to interpret and have some advantages over the application of other commonly used matrices: a low number of matrix peaks are detectable and the coordinative metal-ligand bond is, in most cases, preserved. On the other hand, flavonoids do not act as typical matrices, as their excess is not required for the acquisition of MALDI-TOF mass spectra of inorganic complexes.

  1. Deterministic matrices matching the compressed sensing phase transitions of Gaussian random matrices

    PubMed Central

    Monajemi, Hatef; Jafarpour, Sina; Gavish, Matan; Donoho, David L.; Ambikasaran, Sivaram; Bacallado, Sergio; Bharadia, Dinesh; Chen, Yuxin; Choi, Young; Chowdhury, Mainak; Chowdhury, Soham; Damle, Anil; Fithian, Will; Goetz, Georges; Grosenick, Logan; Gross, Sam; Hills, Gage; Hornstein, Michael; Lakkam, Milinda; Lee, Jason; Li, Jian; Liu, Linxi; Sing-Long, Carlos; Marx, Mike; Mittal, Akshay; Monajemi, Hatef; No, Albert; Omrani, Reza; Pekelis, Leonid; Qin, Junjie; Raines, Kevin; Ryu, Ernest; Saxe, Andrew; Shi, Dai; Siilats, Keith; Strauss, David; Tang, Gary; Wang, Chaojun; Zhou, Zoey; Zhu, Zhen

    2013-01-01

    In compressed sensing, one takes samples of an N-dimensional vector using an matrix A, obtaining undersampled measurements . For random matrices with independent standard Gaussian entries, it is known that, when is k-sparse, there is a precisely determined phase transition: for a certain region in the (,)-phase diagram, convex optimization typically finds the sparsest solution, whereas outside that region, it typically fails. It has been shown empirically that the same property—with the same phase transition location—holds for a wide range of non-Gaussian random matrix ensembles. We report extensive experiments showing that the Gaussian phase transition also describes numerous deterministic matrices, including Spikes and Sines, Spikes and Noiselets, Paley Frames, Delsarte-Goethals Frames, Chirp Sensing Matrices, and Grassmannian Frames. Namely, for each of these deterministic matrices in turn, for a typical k-sparse object, we observe that convex optimization is successful over a region of the phase diagram that coincides with the region known for Gaussian random matrices. Our experiments considered coefficients constrained to for four different sets , and the results establish our finding for each of the four associated phase transitions. PMID:23277588

  2. Clarification Procedure for Gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.; Simpson, Norman R.

    1987-01-01

    Procedure developed to obtain transparent gels with consistencies suitable for crystal growth, by replacing sodium ions in silicate solution with potassium ions. Clarification process uses cation-exchange resin to replace sodium ions in stock solution with potassium ions, placed in 1M solution of soluble potassium salt. Slurry stirred for several hours to allow potassium ions to replace all other cations on resin. Supernatant solution decanted through filter, and beads rinsed with distilled water. Rinsing removes excess salt but leaves cation-exchange beads fully charged with potassium ions.

  3. Confirmatory Factor Analysis of the WAIS-IV/WMS-IV

    ERIC Educational Resources Information Center

    Holdnack, James A.; Zhou, Xiaobin; Larrabee, Glenn J.; Millis, Scott R.; Salthouse, Timothy A.

    2011-01-01

    The Wechsler Adult Intelligence Scale-fourth edition (WAIS-IV) and the Wechsler Memory Scale-fourth edition (WMS-IV) were co-developed to be used individually or as a combined battery of tests. The independent factor structure of each of the tests has been identified; however, the combined factor structure has yet to be determined. Confirmatory…

  4. High transparent shape memory gel

    NASA Astrophysics Data System (ADS)

    Gong, Jin; Arai, Masanori; Kabir, M. H.; Makino, Masato; Furukawa, Hidemitsu

    2014-03-01

    Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals, and the functional groups of thermoreversible Diels-Alder reaction were introduced into soft gels as crosslinkable pendent chains. The functionalization and strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals and thermoreversible pendent chains. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

  5. Foam and gel decontamination techniques

    SciTech Connect

    McGlynn, J.F.; Rankin, W.N.

    1989-01-01

    The Savannah River Site is investigating decontamination technology to improve current decontamination techniques, and thereby reduce radiation exposure to plant personnel, reduce uptake of radioactive material, and improve safety during decontamination and decommissioning activities. When decontamination chemicals are applied as foam and gels, the contact time and cleaning ability of the chemical increases. Foam and gel applicators apply foam or gel that adheres to the surface being decontaminated for periods ranging from fifteen minutes (foam) to infinite contact (gel). This equipment was started up in a cold environment. The desired foam and gel consistency was achieved, operators were trained in its proper maintenance and operation, and the foam and gel were applied to walls, ceilings, and hard to reach surfaces. 17 figs.

  6. Polyoxometalate-based Supramolecular Gel

    NASA Astrophysics Data System (ADS)

    He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

    2013-05-01

    Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing.

  7. Collagen-IV supported embryoid bodies formation and differentiation from buffalo (Bubalus bubalis) embryonic stem cells

    SciTech Connect

    Taru Sharma, G.; Dubey, Pawan K.; Verma, Om Prakash; Pratheesh, M.D.; Nath, Amar; Sai Kumar, G.

    2012-08-03

    Graphical abstract: EBs formation, characterization and expression of germinal layers marker genes of in vivo developed teratoma using four different types of extracellular matrices. Highlights: Black-Right-Pointing-Pointer Collagen-IV matrix is found cytocompatible for EBs formation and differentiation. Black-Right-Pointing-Pointer Established 3D microenvironment for ES cells development and differentiation into three germ layers. Black-Right-Pointing-Pointer Collagen-IV may be useful as promising candidate for ES cells based therapeutic applications. -- Abstract: Embryoid bodies (EBs) are used as in vitro model to study early extraembryonic tissue formation and differentiation. In this study, a novel method using three dimensional extracellular matrices for in vitro generation of EBs from buffalo embryonic stem (ES) cells and its differentiation potential by teratoma formation was successfully established. In vitro derived inner cell masses (ICMs) of hatched buffalo blastocyst were cultured on buffalo fetal fibroblast feeder layer for primary cell colony formation. For generation of EBs, pluripotent ES cells were seeded onto four different types of extracellular matrices viz; collagen-IV, laminin, fibronectin and matrigel using undifferentiating ES cell culture medium. After 5 days of culture, ESCs gradually grew into aggregates and formed simple EBs having circular structures. Twenty-six days later, they formed cystic EBs over collagen matrix with higher EBs formation and greater proliferation rate as compared to other extracellular matrices. Studies involving histological observations, fluorescence microscopy and RT-PCR analysis of the in vivo developed teratoma revealed that presence of all the three germ layer derivatives viz. ectoderm (NCAM), mesoderm (Flk-1) and endoderm (AFP). In conclusion, the method described here demonstrates a simple and cost-effective way of generating EBs from buffalo ES cells. Collagen-IV matrix was found cytocompatible as it

  8. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, Douglas B.; Shahinpoor, Mohsen; Segalman, Daniel J.; Witkowski, Walter R.

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

  9. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  10. Gel polymer electrolytes for batteries

    DOEpatents

    Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

    2014-11-18

    Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

  11. Colloidal thermoresponsive gel forming hybrids.

    PubMed

    Liu, Ruixue; Tirelli, Nicola; Cellesi, Francesco; Saunders, Brian R

    2010-09-15

    Colloidal hybrids comprise organic and inorganic components and are attracting considerable attention in the literature. Recently, we reported hybrid anisotropic microsheets that formed thermoresponsive gels in polymer solutions [Liu et al., Langmuir, 25, 490, 2009]. Here, we investigate the composition and properties of these hybrid colloids themselves in detail for the first time. Three different cationic PNIPAm (N-isopropylacrylamide) graft copolymers and two inorganic nanoparticle types (laponite and Ludox silica) were used to prepare a range of hybrids. Anisotropic microsheets only formed when laponite particles were added to the copolymer implying directed self-assembly. Aqueous dispersions of the microsheets spontaneously formed gels at room temperature and these gels were thermoresponsive. They represent a new class of gel forming colloid and are termed thermoresponsive gel forming hybrids. The compositions of the hybrids were determined from thermogravimetric analysis and those that gave gel forming behaviour identified. Variable-temperature rheology experiments showed that the elasticity of the gels increased linearly with temperature. The reversibility of the thermally-triggered changes in gel elasticity was investigated. The concentration dependence of the rheology data was well described by elastic percolation scaling theory and the data could be collapsed onto a master curve. The concentration exponent for the elastic modulus was 2.5. The strong attractive interactions that exist between the dispersed gel forming hybrids was demonstrated by the formation of stable thermoresponsive hybrid hydrogels through casting of hybrid dispersions. PMID:20561633

  12. NATIONAL COASTAL CONDITION REPORT IV

    EPA Science Inventory

    The National Coastal Condition Report IV (NCCR IV) is the fourth in a series of environmental assessments of U.S. coastal waters and the Great Lakes. The report includes assessments of all the nation’s estuaries in the contiguous 48 states and Puerto Rico, south-eastern Alaska, ...

  13. Homogeneity of gels and gel-derived glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1984-01-01

    The significance and implications of gel preparation procedures in controlling the homogeneity of multicomponent oxide gels are discussed. The role of physicochemical factors such as the structure and chemical reactivities of alkoxides, the formation of double-metal alkoxides, and the nature of solvent(s) are critically analyzed in the context of homogeneity of gels during gelation. Three procedures for preparing gels in the SiO2-B2O3-Na2O system are examined in the context of cation distribution. Light scattering results for glasses in the SiO2-B2O3-Na2O system prepared by both the gel technique and the conventional technique are examined.

  14. Quantum groups, braiding matrices and coset models

    SciTech Connect

    Itoyama, H.

    1989-07-01

    We discuss a few results on quantum groups in the context of rational conformal field theory with underlying affine Lie algebras. A vertex-height correspondence - a well-known procedure in solvable lattice models - is introduced in the WZW theory. This leads to a new definition of chiral vertex operator in which the zero mode is given by the q-Clebsch Gordan coefficients. Braiding matrices of coset models are found to factorize into those of the WZW theories. We briefly discuss the construction of the generators of the universal enveloping algebra in Toda field theories. 21 refs., 2 figs.

  15. Decontamination of matrices containing actinide oxides

    SciTech Connect

    Villarreal, Robert

    1997-12-01

    There is provided a method for removing actinides and actinide oxides, particularly fired actinides, from soil and other contaminated matrices, comprising: (a) contacting a contaminated material with a solution of at least one inhibited fluoride and an acid to form a mixture; (b) heating the mixture of contaminated material and solution to a temperature in the range from about 30 C to about 90 C while stirring; (c) separating the solution from any undissolved matrix material in the mixture; (d) washing the undissolved matrix material to remove any residual materials; and (e) drying and returning the treated matrix material to the environment.

  16. Shear representations of beam transfer matrices.

    PubMed

    Başkal, S; Kim, Y S

    2001-05-01

    The beam transfer matrix, often called the ABCD matrix, is one of the essential mathematical instruments in optics. It is a unimodular matrix whose determinant is 1. If all the elements are real with three independent parameters, this matrix is a 2 x 2 representation of the group Sp(2). It is shown that a real ABCD matrix can be generated by two shear transformations. It is then noted that, in para-axial lens optics, the lens and translation matrices constitute two shear transformations. It is shown that a system with an arbitrary number of lenses can be reduced to a system consisting of three lenses. PMID:11415030

  17. Removal of selenite and chromate using iron(III)-doped alginate gels

    SciTech Connect

    Min, J.H.; Hering, J.G.

    1999-03-01

    Oxyanionic contaminants, specifically selenium and chromium(VI), were removed from solution by sorption onto gel beads formed by pretreating the biopolymer alginic acid with calcium and iron(III). The calcium-iron gel beads were found to be effective at removing selenium(IV) from solution. Chromium(VI) removal was less effective and the rate of sorption was slower than that of selenium(IV). At an initial selenium(IV) concentration of 400 {micro}g/L (5.1 {micro}M), up to approximately 94% removal of selenium from solution was achieved by a 120-hour equilibration with 20 calcium-iron beads (10 mg/L or 180 {micro}M total iron). Optimal selenium(IV) removal and stability of the calcium-iron beads were achieved at pH 4. Selenium(IV) sorption and kinetics data were comparable with those observed previously for arsenic(V). Selenium(IV) sorption data, as a function of dissolved concentration and iron content, were modeled. As calcium-iron beads became saturated, the extent of sorption of selenium(IV) or arsenic(V) was decreased by the presence of competing contaminant oxyanions or nonhazardous inorganic anions such as phosphate.

  18. Antimicrobial Graft Copolymer Gels.

    PubMed

    Harvey, Amanda C; Madsen, Jeppe; Douglas, C W Ian; MacNeil, Sheila; Armes, Steven P

    2016-08-01

    In view of the growing worldwide rise in microbial resistance, there is considerable interest in designing new antimicrobial copolymers. The aim of the current study was to investigate the relationship between antimicrobial activity and copolymer composition/architecture to gain a better understanding of their mechanism of action. Specifically, the antibacterial activity of several copolymers based on 2-(methacryloyloxy)ethyl phosphorylcholine [MPC] and 2-hydroxypropyl methacrylate (HPMA) toward Staphylococcus aureus was examined. Both block and graft copolymers were synthesized using either atom transfer radical polymerization or reversible addition-fragmentation chain transfer polymerization and characterized via (1)H NMR, gel permeation chromatography, rheology, and surface tensiometry. Antimicrobial activity was assessed using a range of well-known assays, including direct contact, live/dead staining, and the release of lactate dehydrogenase (LDH), while transmission electron microscopy was used to study the morphology of the bacteria before and after the addition of various copolymers. As expected, PMPC homopolymer was biocompatible but possessed no discernible antimicrobial activity. PMPC-based graft copolymers comprising PHPMA side chains (i.e. PMPC-g-PHPMA) significantly reduced both bacterial growth and viability. In contrast, a PMPC-PHPMA diblock copolymer comprising a PMPC stabilizer block and a hydrophobic core-forming PHPMA block did not exhibit any antimicrobial activity, although it did form a biocompatible worm gel. Surface tensiometry studies and LDH release assays suggest that the PMPC-g-PHPMA graft copolymer exhibits surfactant-like activity. Thus, the observed antimicrobial activity is likely to be the result of the weakly hydrophobic PHPMA chains penetrating (and hence rupturing) the bacterial membrane. PMID:27409712

  19. The Approximation of Two-Mode Proximity Matrices by Sums of Order-Constrained Matrices.

    ERIC Educational Resources Information Center

    Hubert, Lawrence; Arabie, Phipps

    1995-01-01

    A least-squares strategy is proposed for representing a two-mode proximity matrix as an approximate sum of a small number of matrices that satisfy certain simple order constraints on their entries. The primary class of constraints considered defines Q-forms for particular conditions in a two-mode matrix. (SLD)

  20. Frequency filtering decompositions for unsymmetric matrices and matrices with strongly varying coefficients

    SciTech Connect

    Wagner, C.

    1996-12-31

    In 1992, Wittum introduced the frequency filtering decompositions (FFD), which yield a fast method for the iterative solution of large systems of linear equations. Based on this method, the tangential frequency filtering decompositions (TFFD) have been developed. The TFFD allow the robust and efficient treatment of matrices with strongly varying coefficients. The existence and the convergence of the TFFD can be shown for symmetric and positive definite matrices. For a large class of matrices, it is possible to prove that the convergence rate of the TFFD and of the FFD is independent of the number of unknowns. For both methods, schemes for the construction of frequency filtering decompositions for unsymmetric matrices have been developed. Since, in contrast to Wittums`s FFD, the TFFD needs only one test vector, an adaptive test vector can be used. The TFFD with respect to the adaptive test vector can be combined with other iterative methods, e.g. multi-grid methods, in order to improve the robustness of these methods. The frequency filtering decompositions have been successfully applied to the problem of the decontamination of a heterogeneous porous medium by flushing.

  1. Compressed Sampling of Spectrally Sparse Signals Using Sparse Circulant Matrices

    NASA Astrophysics Data System (ADS)

    Xu, Guangjie; Wang, Huali; Sun, Lei; Zeng, Weijun; Wang, Qingguo

    2014-11-01

    Circulant measurement matrices constructed by partial cyclically shifts of one generating sequence, are easier to be implemented in hardware than widely used random measurement matrices; however, the diminishment of randomness makes it more sensitive to signal noise. Selecting a deterministic sequence with optimal periodic autocorrelation property (PACP) as generating sequence, would enhance the noise robustness of circulant measurement matrix, but this kind of deterministic circulant matrices only exists in the fixed periodic length. Actually, the selection of generating sequence doesn't affect the compressive performance of circulant measurement matrix but the subspace energy in spectrally sparse signals. Sparse circulant matrices, whose generating sequence is a sparse sequence, could keep the energy balance of subspaces and have similar noise robustness to deterministic circulant matrices. In addition, sparse circulant matrices have no restriction on length and are more suitable for the compressed sampling of spectrally sparse signals at arbitrary dimensionality.

  2. Crystallization of steroids in gels

    NASA Astrophysics Data System (ADS)

    Kalkura, S. Narayana; Devanarayanan, S.

    1991-03-01

    The crystal growth and characterization of certain steriods, viz., cholesterol, cholesteryl acetate, β-sitosterol, progesterone and testosterone, in a silica gel medium is discussed. The present study shows that the single test tube diffusion method can be used to grow crystals of steroids in a silica gel medium by the reduction of steroid solubility.

  3. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    2012-06-12

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

  4. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  5. Median Approximations for Genomes Modeled as Matrices.

    PubMed

    Zanetti, Joao Paulo Pereira; Biller, Priscila; Meidanis, Joao

    2016-04-01

    The genome median problem is an important problem in phylogenetic reconstruction under rearrangement models. It can be stated as follows: Given three genomes, find a fourth that minimizes the sum of the pairwise rearrangement distances between it and the three input genomes. In this paper, we model genomes as matrices and study the matrix median problem using the rank distance. It is known that, for any metric distance, at least one of the corners is a [Formula: see text]-approximation of the median. Our results allow us to compute up to three additional matrix median candidates, all of them with approximation ratios at least as good as the best corner, when the input matrices come from genomes. We also show a class of instances where our candidates are optimal. From the application point of view, it is usually more interesting to locate medians farther from the corners, and therefore, these new candidates are potentially more useful. In addition to the approximation algorithm, we suggest a heuristic to get a genome from an arbitrary square matrix. This is useful to translate the results of our median approximation algorithm back to genomes, and it has good results in our tests. To assess the relevance of our approach in the biological context, we ran simulated evolution tests and compared our solutions to those of an exact DCJ median solver. The results show that our method is capable of producing very good candidates. PMID:27072561

  6. Cl2 deposition on soil matrices.

    PubMed

    Hearn, John; Eichler, Jeffery; Hare, Christopher; Henley, Michael

    2012-10-30

    Deposition of chlorine gas, Cl(2), on synthetic soil sample matrices was examined in a small chamber to ascertain its potential significance as a chemical sink during large-scale releases. The effects of organic matter, clay and sand mass fractions of the soil matrix, soil packing, and exposure to ultraviolet (UV) light on the observed Cl(2) deposition were examined. Organic matter content was found to be the dominant soil variable investigated that affected Cl(2) deposition; all other variables exhibited no measurable effect. Analytical results from the top 8.5mm of soil columns exposed to Cl(2) were fit to a simple kinetic model with six adjustable parameters. The kinetic model included two reactive bins to account for fast- and slow-reacting material in the soil matrices. The resulting empirical equation agreed with the data to within a factor of two and accurately predicted results from soil mixes not used to optimize the adjustable parameters. Total Cl(2) deposition, assuming a penetration depth of 8.5mm, was calculated to be as high as 160 metric tons per square kilometer for soil with an organic content of 10%, and inferred deposition velocities were as high as 0.5 cm/s for organically rich soil. PMID:22975257

  7. Hydrodynamical spectral evolution for random matrices

    NASA Astrophysics Data System (ADS)

    Forrester, Peter J.; Grela, Jacek

    2016-02-01

    The eigenvalues of the matrix structure X+{X}(0), where X is a random Gaussian Hermitian matrix and {X}(0) is non-random or random independent of X, are closely related to Dyson Brownian motion. Previous works have shown how an infinite hierarchy of equations satisfied by the dynamical correlations become triangular in the infinite density limit, and give rise to the complex Burgers equation for the Green’s function of the corresponding one-point density function. We show how this and analogous partial differential equations, for chiral, circular and Jacobi versions of Dyson Brownian motion follow from a macroscopic hydrodynamical description involving the current density and continuity equation. The method of characteristics gives a systematic approach to solving the PDEs, and in the chiral case we show how this efficiently reclaims the characterization of the global eigenvalue density for non-central Wishart matrices due to Dozier and Silverstein. Collective variables provide another approach to deriving the complex Burgers equation in the Gaussian case, and we show that this approach applies equally as well to chiral matrices. We relate both the Gaussian and chiral cases to the asymptotics of matrix integrals.

  8. Tensor Dictionary Learning for Positive Definite Matrices.

    PubMed

    Sivalingam, Ravishankar; Boley, Daniel; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2015-11-01

    Sparse models have proven to be extremely successful in image processing and computer vision. However, a majority of the effort has been focused on sparse representation of vectors and low-rank models for general matrices. The success of sparse modeling, along with popularity of region covariances, has inspired the development of sparse coding approaches for these positive definite descriptors. While in earlier work, the dictionary was formed from all, or a random subset of, the training signals, it is clearly advantageous to learn a concise dictionary from the entire training set. In this paper, we propose a novel approach for dictionary learning over positive definite matrices. The dictionary is learned by alternating minimization between sparse coding and dictionary update stages, and different atom update methods are described. A discriminative version of the dictionary learning approach is also proposed, which simultaneously learns dictionaries for different classes in classification or clustering. Experimental results demonstrate the advantage of learning dictionaries from data both from reconstruction and classification viewpoints. Finally, a software library is presented comprising C++ binaries for all the positive definite sparse coding and dictionary learning approaches presented here. PMID:26054070

  9. FIBROBLAST MECHANICS IN 3D COLLAGEN MATRICES

    PubMed Central

    Rhee, Sangmyung; Grinnell, Frederick

    2007-01-01

    Connective tissues provide mechanical support and frameworks for the other tissues of the body. Type 1 collagen is the major protein component of ordinary connective tissue, and fibroblasts are the cell type primarily responsible for its biosynthesis and remodeling. Research on fibroblasts interacting with collagen matrices explores all four quadrants of cell mechanics: pro-migratory vs. pro-contractile growth factor environments on one axis; high tension vs. low tension cell-matrix interactions on the other. The dendritic fibroblast – probably equivalent to the resting tissue fibroblast – can be observed only in the low tension quadrant and generally has not been appreciated from research on cells incubated with planar culture surfaces. Fibroblasts in the low tension quadrant require microtubules for formation of dendritic extensions, whereas fibroblasts in the high tension quadrant require microtubules for polarization but not for spreading. Ruffling of dendritic extensions rather than their overall protrusion or retraction provides the mechanism for remodeling of floating collagen matrices, and floating matrix remodeling likely reflects a model of tissue mechanical homeostasis. PMID:17825456

  10. Bromination of selected pharmaceuticals in water matrices.

    PubMed

    Benitez, F Javier; Acero, Juan L; Real, Francisco J; Roldan, Gloria; Casas, Francisco

    2011-11-01

    The bromination of five selected pharmaceuticals (metoprolol, naproxen, amoxicillin, phenacetin, and hydrochlorothiazide) was studied with these compounds individually dissolved in ultra-pure water. The apparent rate constants for the bromination reaction were determined as a function of the pH, obtaining the sequence amoxicillin>naproxen>hydrochlorothiazide≈phenacetin≈metoprolol. A kinetic mechanism specifying the dissociation reactions and the species formed for each compound according to its pK(a) value and the pH allowed the intrinsic rate constants to be determined for each elementary reaction. There was fairly good agreement between the experimental and calculated values of the apparent rate constants, confirming the goodness of the proposed reaction mechanism. In a second stage, the bromination of the selected pharmaceuticals simultaneously dissolved in three water matrices (a groundwater, a surface water from a public reservoir, and a secondary effluent from a WWTP) was investigated. The pharmaceutical elimination trend agreed with the previously determined rate constants. The influence of the main operating conditions (pH, initial bromine dose, and characteristics of the water matrix) on the degradation of the pharmaceuticals was established. An elimination concentration profile for each pharmaceutical in the water matrices was proposed based on the use of the previously evaluated apparent rate constants, and the theoretical results agreed satisfactorily with experiment. Finally, chlorination experiments performed in the presence of bromide showed that low bromide concentrations slightly accelerate the oxidation of the selected pharmaceuticals during chlorine disinfection. PMID:21906777

  11. Electron-transfer reactions in polymer matrices

    NASA Astrophysics Data System (ADS)

    Vannikov, Anatolii V.; Grishina, Antonina D.

    1989-12-01

    This paper discusses the dark reactions and photoreactions that occur with transfer of an electron from a donor to an acceptor in polymer matrices under electron tunnelling conditions and when forming change-transfer complexes. The main emphasis is on an analysis of the factors that determine the rate of electron transfer, which, in accordance with the advanced theory of electron transfer, are the magnitude of the exchange interaction, the free energy of the process, and the reorganisation energies of the medium and the reacting donor and acceptor molecules. The existing models for the movement of charge carriers between single-type transport sites are discussed. The limits of applicability of the different models have been determined. The reorganisation energy of a polymer matrix is shown to have a considerable effect on the rate of movement of charge carriers on introduced transport molecules. The effect of the dielectric properties and free volume of polymer matrices on the characteristics of electron phototransfer in donor-acceptor complexes is discussed. The bibliography includes 126 references.

  12. Sucrose release from polysaccharide gels.

    PubMed

    Nishinari, Katsuyoshi; Fang, Yapeng

    2016-05-18

    Sucrose release from polysaccharide gels has been studied extensively because it is expected to be useful in understanding flavour release from solid foods and to find a new processing method which produces more palatable and healthier foods. We provide an overview of the release of sucrose and other sugars from gels of agar and related polysaccharides. The addition of sucrose to agar solutions leads to the increase in transparency of the resulting gels and the decrease in syneresis, which is attributed to the decrease in mesh size in gels. The syneresis occurring in the quiescent condition and fluid release induced by compression is discussed. The relationship between the sugar release and the structural, rheological and thermal properties of gels is also discussed. Finally, the future research direction is proposed. PMID:26952168

  13. Aqueous complexation of thorium(IV), uranium(IV), neptunium(IV), plutonium(III/IV), and cerium(III/IV) with DTPA.

    PubMed

    Brown, M Alex; Paulenova, Alena; Gelis, Artem V

    2012-07-16

    Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal. PMID:22738207

  14. Racah matrices and hidden integrability in evolution of knots

    NASA Astrophysics Data System (ADS)

    Mironov, A.; Morozov, A.; Morozov, An.; Sleptsov, A.

    2016-09-01

    We construct a general procedure to extract the exclusive Racah matrices S and S bar from the inclusive 3-strand mixing matrices by the evolution method and apply it to the first simple representations R = [ 1 ], [2], [3] and [ 2 , 2 ]. The matrices S and S bar relate respectively the maps (R ⊗ R) ⊗ R bar ⟶ R with R ⊗ (R ⊗ R bar) ⟶ R and (R ⊗ R bar) ⊗ R ⟶ R with R ⊗ (R bar ⊗ R) ⟶ R. They are building blocks for the colored HOMFLY polynomials of arbitrary arborescent (double fat) knots. Remarkably, the calculation realizes an unexpected integrability property underlying the evolution matrices.

  15. Bouncing gel balls: Impact of soft gels onto rigid surface

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Yamazaki, Y.; Okumura, K.

    2003-07-01

    After being thrown onto a solid substrate, very soft spherical gels bounce repeatedly. Separate rheological measurements suggest that these balls can be treated as nearly elastic. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, the gel ball deformed into flattened forms like a pancake. We measured the size of the gel balls at the maximal deformation and the contact time as a function of velocities for samples different in the original spherical radius and the Young modulus. The experimental results revealed a number of scaling relations. To interpret these relations, we developed scaling arguments to propose a physical picture.

  16. Impact of microbial Mn oxidation on the remobilization of bioreduced U(IV).

    PubMed

    Plathe, Kelly L; Lee, Sung-Woo; Tebo, Bradley M; Bargar, John R; Bernier-Latmani, Rizlan

    2013-04-16

    Effects of Mn redox cycling on the stability of bioreduced U(IV) are evaluated here. U(VI) can be biologically reduced to less soluble U(IV) species and the stimulation of biological activity to that end is a salient remediation strategy; however, the stability of these materials in the subsurface environments where they form remains unproven. Manganese oxides are capable of rapidly oxidizing U(IV) to U(VI) in mixed batch systems where the two solid phases are in direct contact. However, it is unknown whether the same oxidation would take place in a porous medium. To probe that question, U(IV) immobilized in agarose gels was exposed to conditions allowing biological Mn(II) oxidation (HEPES buffer, Mn(II), 5% O2 and Bacillus sp. SG-1 spores). Results show the oxidation of U(IV) to U(VI) is due primarily to O2 rather than to MnO2. U(VI) produced is retained within the gel to a greater extent when Mn oxides are present, suggesting the formation of strong surface complexes. The implication for the long-term stability of U in a bioremediated site is that, in the absence of competing ligands, biological Mn(II) oxidation may promote the immobilization of U(VI) produced by the oxidation of U(IV). PMID:23484504

  17. Electrospun ion gel nanofibers for flexible triboelectric nanogenerator: electrochemical effect on output power

    NASA Astrophysics Data System (ADS)

    Ye, Byeong Uk; Kim, Byoung-Joon; Ryu, Jungho; Lee, Joo Yul; Baik, Jeong Min; Hong, Kihyon

    2015-10-01

    A simple fabrication route for ion gel nanofibers in a triboelectric nanogenerator was demonstrated. Using an electrospinning technique, we could fabricate a large-area ion gel nanofiber mat. The triboelectric nanogenerator was demonstrated by employing an ion gel nanofiber and the device exhibited an output power of 0.37 mW and good stability under continuous operation.A simple fabrication route for ion gel nanofibers in a triboelectric nanogenerator was demonstrated. Using an electrospinning technique, we could fabricate a large-area ion gel nanofiber mat. The triboelectric nanogenerator was demonstrated by employing an ion gel nanofiber and the device exhibited an output power of 0.37 mW and good stability under continuous operation. Electronic supplementary information (ESI) available: I. Experimental section. II. FTIR and XRD spectra of ion gel nanofiber. III. Output voltage of TENG with various polymer nanofibers. IV. Output voltage of TENG under different connection types. V. Output voltage of TENG with 20 wt% ion gel nanofibers. See DOI: 10.1039/c5nr02602d

  18. EVALUATION OF THE PILLS IV

    EPA Science Inventory

    The report gives results of theoretical and experimental investigations of the operating characteristics of the PILLS IV (Particulate Instrumentation by Laser Light Scattering) in situ particle sizing instrument. Results of both investigations show large errors in sizing particle...

  19. Mechanical Failure in Colloidal Gels

    NASA Astrophysics Data System (ADS)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form

  20. Polyoxometalate-based Supramolecular Gel

    PubMed Central

    He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

    2013-01-01

    Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing. PMID:23666013

  1. Adhesive, elastomeric gel impregnating composition

    DOEpatents

    Shaw, David Glenn; Pollard, John Randolph; Brooks, Robert Aubrey

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  2. Photochromic reaction of spiropyran in polymer matrices

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Boudreault, Francois; Roberge, Mathieu; Galstian, Tigran V.; Lessard, Roger A.; Ritcey, Anna-Marie R.

    2000-12-01

    The photo excitations of Spiropyran-doped polymer films were studied. Cellulose acetate (CA), commercial ploy(methyl methacrylate) (PMMA) and PMMA prepared by radical polymerisation of MMA, were used as host polymer matrices. The open form of SP presents a maximum of absorption cantered at about 600 nm upon UV irradiation. We have determined the photoreaction rate constants, kuv and k15, for the coloring and bleaching processes. Reversible holographic recording in SPIPMMA films was studied and photochemical fatigue resistance was evaluated upon repeated UVfVisible irradiation cycles. We found a loss of 42, 53 and 74% respectively in PMMA by gravity deposition, PMMA (by polymerisation of MMA) and cellulose acetate films.

  3. Investigation of degradation mechanisms in composite matrices

    NASA Technical Reports Server (NTRS)

    Giori, C.; Yamauchi, T.

    1982-01-01

    Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

  4. Association of scattering matrices in quantum networks

    SciTech Connect

    Almeida, F.A.G.; Macêdo, A.M.S.

    2013-06-15

    Algorithms based on operations that associate scattering matrices in series or in parallel (analogous to impedance association in a classical circuit) are developed here. We exemplify their application by calculating the total scattering matrix of several types of quantum networks, such as star graphs and a chain of chaotic quantum dots, obtaining results with good agreement with the literature. Through a computational-time analysis we compare the efficiency of two algorithms for the simulation of a chain of chaotic quantum dots based on series association operations of (i) two-by-two centers and (ii) three-by-three ones. Empirical results point out that the algorithm (ii) is more efficient than (i) for small number of open scattering channels. A direct counting of floating point operations justifies quantitatively the superiority of the algorithm (i) for large number of open scattering channels.

  5. Plutonium(IV) precipitates formed in alkaline media in the presence of various anions

    SciTech Connect

    Krot, N.N.; Shilov, V.P.; Yusov, A.B.; Tananaev, I.G.; Grigoriev, M.S.; Garnov, A.Yu.; Perminov, V.P.; Astafurova, L.N.

    1998-09-01

    The tendency of Pu(IV) to hydrolyze and form true solutions, colloid solutions, or insoluble precipitates has been known since the Manhattan Project. Since then, specific studies have been performed to examine in detail the equilibria of Pu(IV) hydrolytic reactions in various media. Great attention also has been paid to the preparation, structure, and properties of Pu(IV) polymers or colloids. These compounds found an important application in sol-gel technology for the preparation of nuclear fuel materials. A most important result of these works was the conclusion that Pu(IV) hydroxide, after some aging, consists of very small PuO{sub 2} crystallites and should therefore be considered to be Pu(IV) hydrous oxide. However, studies of the properties and behavior of solid Pu(IV) hydroxide in complex heterogeneous systems are rare. The primary goal of this investigation was to obtain data on the composition and properties of Pu(IV) hydrous oxide or other compounds formed in alkaline media under different conditions. Such information is important to understand Pu(IV) behavior and the forms of its existence in the Hanford Site alkaline tank waste sludge. This knowledge then may be applied in assessing plutonium criticality hazards in the storage, retrieval, and treatment of Hanford Site tank wastes as well as in understanding its contribution to the transuranic waste inventory (threshold at 100 nCi/g or about 5 {times} 10{sup {minus}6} M) of the separate solution and solid phases.

  6. Robust Generalized Low Rank Approximations of Matrices

    PubMed Central

    Shi, Jiarong; Yang, Wei; Zheng, Xiuyun

    2015-01-01

    In recent years, the intrinsic low rank structure of some datasets has been extensively exploited to reduce dimensionality, remove noise and complete the missing entries. As a well-known technique for dimensionality reduction and data compression, Generalized Low Rank Approximations of Matrices (GLRAM) claims its superiority on computation time and compression ratio over the SVD. However, GLRAM is very sensitive to sparse large noise or outliers and its robust version does not have been explored or solved yet. To address this problem, this paper proposes a robust method for GLRAM, named Robust GLRAM (RGLRAM). We first formulate RGLRAM as an l1-norm optimization problem which minimizes the l1-norm of the approximation errors. Secondly, we apply the technique of Augmented Lagrange Multipliers (ALM) to solve this l1-norm minimization problem and derive a corresponding iterative scheme. Then the weak convergence of the proposed algorithm is discussed under mild conditions. Next, we investigate a special case of RGLRAM and extend RGLRAM to a general tensor case. Finally, the extensive experiments on synthetic data show that it is possible for RGLRAM to exactly recover both the low rank and the sparse components while it may be difficult for previous state-of-the-art algorithms. We also discuss three issues on RGLRAM: the sensitivity to initialization, the generalization ability and the relationship between the running time and the size/number of matrices. Moreover, the experimental results on images of faces with large corruptions illustrate that RGLRAM obtains the best denoising and compression performance than other methods. PMID:26367116

  7. Dirac matrices for Chern-Simons gravity

    SciTech Connect

    Izaurieta, Fernando; Ramirez, Ricardo; Rodriguez, Eduardo

    2012-10-06

    A genuine gauge theory for the Poincare, de Sitter or anti-de Sitter algebras can be constructed in (2n- 1)-dimensional spacetime by means of the Chern-Simons form, yielding a gravitational theory that differs from General Relativity but shares many of its properties, such as second order field equations for the metric. The particular form of the Lagrangian is determined by a rank n, symmetric tensor invariant under the relevant algebra. In practice, the calculation of this invariant tensor can be reduced to the computation of the trace of the symmetrized product of n Dirac Gamma matrices {Gamma}{sub ab} in 2n-dimensional spacetime. While straightforward in principle, this calculation can become extremely cumbersome in practice. For large enough n, existing computer algebra packages take an inordinate long time to produce the answer or plainly fail having used up all available memory. In this talk we show that the general formula for the trace of the symmetrized product of 2n Gamma matrices {Gamma}{sub ab} can be written as a certain sum over the integer partitions s of n, with every term being multiplied by a numerical cofficient {alpha}{sub s}. We then give a general algorithm that computes the {alpha}-coefficients as the solution of a linear system of equations generated by evaluating the general formula for different sets of tensors B{sup ab} with random numerical entries. A recurrence relation between different coefficients is shown to hold and is used in a second, 'minimal' algorithm to greatly speed up the computations. Runtime of the minimal algorithm stays below 1 min on a typical desktop computer for up to n = 25, which easily covers all foreseeable applications of the trace formula.

  8. Photoisomerization of azobenzenes isolated in cryogenic matrices.

    PubMed

    Duarte, Luís; Khriachtchev, Leonid; Fausto, Rui; Reva, Igor

    2016-06-22

    2,2'-Dihydroxyazobenzene (DAB), 2,2'-azotoluene (AT) and azobenzene (AB) were isolated in argon and xenon matrices and their molecular structures and photochemical transformations were characterized by infrared spectroscopy and theoretical calculations. All these compounds can adopt the E and Z isomeric forms around the central CNNC moiety, which can be enriched by several conformational and tautomeric modifications for DAB and AT. A number of DAB and AT isomeric forms were identified for the first time. For DAB, the E azo-enol isomer with two intramolecular six-membered quasi-rings formed via OHN hydrogen bonds was found after deposition. Irradiation with UV light generated a different E azo-enol form with two intramolecular H-bonded five-membered quasi-rings. Phototransformation was shown to be reversible and the forms could be interconverted by irradiation at different wavelengths. The isomerization between these two forms constitutes a direct experimental observation of an E → E isomerization in azobenzene-type molecules. Further irradiation generated a form(s) bearing both OH and NH groups. For AT, two E isomers with the CH3 groups forming five-membered and five/six-membered quasi-rings with the azo group were observed in the as-deposited matrices. Irradiation of AT with UV light generated a Z form that can be converted back to the E form at different irradiation wavelengths. E-AB was deposited in a xenon matrix and both E → Z and Z → E phototransformations were observed (contrary to what was previously reported in an argon matrix where only the Z → E conversion occurred). AB photoisomerization becomes more pronounced at elevated temperatures, thus indicating that the matrix effects responsible for hindering the AB photoisomerization are essentially due to steric restrictions. The different photoisomerization channels observed for these compounds are discussed in terms of a small-amplitude pedal motion. PMID:27279432

  9. Novel Factor-loaded Polyphosphazene Matrices

    PubMed Central

    Oredein-McCoy, Olugbemisola; Krogman, Nicholas R.; Weikel, Arlin L.; Hindenlang, Mark D.; Allcock, Harry R.; Laurencin, Cato T.

    2009-01-01

    Currently employed bone tissue engineered scaffolds often lack the potential for vascularization, which may be enhanced through the incorporation of and regulated release of angiogenic factors. For this reason, our objective was to fabricate and characterize protein-loaded amino acid ester polyphosphazene (Pphos)-based scaffolds and evaluate the novel sintering method used for protein incorporation, a method which will ultimately allow for the incorporation of proangiogenic agents. To test the hypothesis, Pphos and their composite microspheres with nanocrystalline hydroxyapatite (Pphos-HAp) were fabricated via the emulsion solvent evaporation method. Next, bovine serum albumin (BSA)-containing microsphere matrices were created using a novel solvent-non solvent approach for protein loading. The resulting protein (BSA) loaded-circular porous microsphere based scaffolds were characterized for morphology, porosity, protein structure, protein distribution, and subsequent protein release pattern. Scanning electron microscopy revealed porous microsphere scaffolds with a smooth surface and sufficient level of sintering, illustrated by fusion of adjacent microspheres. The porosity measured for the PNPhGly and PNPhGly-HAp scaffolds were 23 +/- 0.11% and 18+/- 4.02%, respectively, and within the range of trabecular bone. Circular dichroism confirmed an intact secondary protein structure for BSA following the solvent sintering method used for loading, and confocal microscopy verified that FITC-BSA was successfully entrapped both between adjacent microspheres and within the surface of the microspheres while sintering. For both Pphos and their composite microsphere scaffolds, BSA was released at a steady rate over a 21day time period, following a zero order release profile. HAp particles in the composite scaffolds served to improve the release profile pattern, underscoring the potential of HAp for growth factor delivery. Moreover, the results of this work suggests that the

  10. Cross-linked high amylose starch derivatives as matrices for controlled release of high drug loadings.

    PubMed

    Mulhbacher, J; Ispas-Szabo, P; Lenaerts, V; Mateescu, M A

    2001-09-11

    Selection of hydrogels as excipients in controlled drug release systems depends on the characteristics of the gel and of the drug. Three types of derivatives were synthesized from cross-linked high amylose starch (HASCL-6) by substitution of hydroxylic groups with cationic (carboxymethyl: CM), anionic (aminoethyl: AE) and acetate (Ac) groups. These new polymeric excipients are able to control the release over 20 h from monolithic tablets loaded with 20 to 60% drug. Three drugs were used as model tracer: acetaminophen (uncharged), acetylsalicylic acid (having an acidic group) and metformin (having a basic group). It was found that the release of ionic drugs from CM-HASCL-6 and AE-HASCL-6 matrices can be partially controlled by ionic interaction between pendant groups of polymer and drugs. The substitution degree of HASCL-6 derivatives can also be varied to modulate the drug's release time. These derivatives represent a novel generation of pharmaceutical excipients, recommended for high loading dosage formulations. PMID:11532312

  11. ABCD matrices as similarity transformations of Wigner matrices and periodic systems in optics.

    PubMed

    Başkal, S; Kim, Y S

    2009-09-01

    It is shown that every ray transfer matrix, often called the ABCD matrix, can be written as a similarity transformation of one of the Wigner matrices that dictate the internal space-time symmetries of relativistic particles, while the transformation matrix is a rotation preceded by a squeeze. The implementation of this mathematical procedure is described, and how it facilitates the calculations for scattering processes in periodic systems is explained. Multilayer optics and resonators such as laser cavities are discussed in detail. For both cases, the one-cycle transfer matrix is written as a similarity transformation of one of the Wigner matrices, rendering the computation of the ABCD matrix for an arbitrary number of cycles tractable. PMID:19721691

  12. The Modern Origin of Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the modern development of matrices, linear transformations, quadratic forms and their applications to geometry and mechanics, eigenvalues, eigenvectors and characteristic equations with applications. Included are the representations of real and complex numbers, and quaternions by matrices, and isomorphism in order to show…

  13. Some Interesting Characteristics of Markov Chain Transition Matrices.

    ERIC Educational Resources Information Center

    Egelston, Richard L.

    A Monte Carlo investigation of Markov chain matrices was conducted to create empirical distributions for two statistics created from the transition matrices. Curve fitting techniques developed by Karl Pearson were used to deduce if theoretical equations could be fit to the two sets of distributions. The set of distributions which describe the…

  14. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Master records and metal matrices. 10.90 Section 10.90 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. General Provisions Master Records, and Metal Matrices § 10.90...

  15. Introduction to the QIAT Self-Evaluation Matrices

    ERIC Educational Resources Information Center

    Zabala, Joy Smiley; Carl, Diana F.

    2004-01-01

    The QIAT Self-Evaluation Matrices (QILT, 2001) were developed in response to formative evaluation data indicating a need for a model that could assist in the application of the Quality Indicators for Assistive Technology Services in Schools (Zabala, et al, 2000). The QIAT Matrices are based on the idea that change does not happen immediately, but…

  16. Component Identification and Item Difficulty of Raven's Matrices Items.

    ERIC Educational Resources Information Center

    Green, Kathy E.; Kluever, Raymond C.

    Item components that might contribute to the difficulty of items on the Raven Colored Progressive Matrices (CPM) and the Standard Progressive Matrices (SPM) were studied. Subjects providing responses to CPM items were 269 children aged 2 years 9 months to 11 years 8 months, most of whom were referred for testing as potentially gifted. A second…

  17. Efficient quantum circuits for Toeplitz and Hankel matrices

    NASA Astrophysics Data System (ADS)

    Mahasinghe, A.; Wang, J. B.

    2016-07-01

    Toeplitz and Hankel matrices have been a subject of intense interest in a wide range of science and engineering related applications. In this paper, we show that quantum circuits can efficiently implement sparse or Fourier-sparse Toeplitz and Hankel matrices. This provides an essential ingredient for solving many physical problems with Toeplitz or Hankel symmetry in the quantum setting with deterministic queries.

  18. A Real Quaternion Spherical Ensemble of Random Matrices

    NASA Astrophysics Data System (ADS)

    Mays, Anthony

    2013-10-01

    One can identify a tripartite classification of random matrix ensembles into geometrical universality classes corresponding to the plane, the sphere and the anti-sphere. The plane is identified with Ginibre-type (iid) matrices and the anti-sphere with truncations of unitary matrices. This paper focusses on an ensemble corresponding to the sphere: matrices of the form Y= A -1 B, where A and B are independent N× N matrices with iid standard Gaussian real quaternion entries. By applying techniques similar to those used for the analogous complex and real spherical ensembles, the eigenvalue joint probability density function and correlation functions are calculated. This completes the exploration of spherical matrices using the traditional Dyson indices β=1,2,4. We find that the eigenvalue density (after stereographic projection onto the sphere) has a depletion of eigenvalues along a ring corresponding to the real axis, with reflective symmetry about this ring. However, in the limit of large matrix dimension, this eigenvalue density approaches that of the corresponding complex ensemble, a density which is uniform on the sphere. This result is in keeping with the spherical law (analogous to the circular law for iid matrices), which states that for matrices having the spherical structure Y= A -1 B, where A and B are independent, iid matrices the (stereographically projected) eigenvalue density tends to uniformity on the sphere.

  19. Calcium Alginate Gels as Stem Cell Matrix – Making Paracrine Stem Cell Activity Available for Enhanced Healing after Surgery

    PubMed Central

    Schmitt, Andreas; Rödel, Philipp; Anamur, Cihad; Seeliger, Claudine; Imhoff, Andreas B.; Herbst, Elmar; Vogt, Stephan; van Griensven, Martijn; Winter, Gerhard; Engert, Julia

    2015-01-01

    Regeneration after surgery can be improved by the administration of anabolic growth factors. However, to locally maintain these factors at the site of regeneration is problematic. The aim of this study was to develop a matrix system containing human mesenchymal stem cells (MSCs) which can be applied to the surgical site and allows the secretion of endogenous healing factors from the cells. Calcium alginate gels were prepared by a combination of internal and external gelation. The gelling behaviour, mechanical stability, surface adhesive properties and injectability of the gels were investigated. The permeability of the gels for growth factors was analysed using bovine serum albumin and lysozyme as model proteins. Human MSCs were isolated, cultivated and seeded into the alginate gels. Cell viability was determined by AlamarBlue assay and fluorescence microscopy. The release of human VEGF and bFGF from the cells was determined using an enzyme-linked immunoassay. Gels with sufficient mechanical properties were prepared which remained injectable through a syringe and solidified in a sufficient time frame after application. Surface adhesion was improved by the addition of polyethylene glycol 300,000 and hyaluronic acid. Humans MSCs remained viable for the duration of 6 weeks within the gels. Human VEGF and bFGF was found in quantifiable concentrations in cell culture supernatants of gels loaded with MSCs and incubated for a period of 6 weeks. This work shows that calcium alginate gels can function as immobilization matrices for human MSCs. PMID:25793885

  20. FY 2002 Report on Software Visualization Techniques for IV and V

    NASA Technical Reports Server (NTRS)

    Fotta, Michael E.

    2002-01-01

    One of the major challenges software engineers often face in performing IV&V is developing an understanding of a system created by a development team they have not been part of. As budgets shrink and software increases in complexity, this challenge will become even greater as these software engineers face increased time and resource constraints. This research will determine which current aspects of providing this understanding (e.g., code inspections, use of control graphs, use of adjacency matrices, requirements traceability) are critical to the performing IV&V and amenable to visualization techniques. We will then develop state-of-the-art software visualization techniques to facilitate the use of these aspects to understand software and perform IV&V.

  1. Dynamics of a DNA Gel

    NASA Astrophysics Data System (ADS)

    Adhikari, Ramesh; Bhattacharya, Aniket; Dogariu, Aristide

    We study in silico the properties of a gel consisting of DNA strands (modeled as semi-flexible chains) and linkers of varying flexibility, length, and topology. These linkers are envisioned and modeled as active components with additional attributes so as to mimic properties of a synthetic DNA gel containing motor proteins. We use Brownian dynamics to directly obtain frequency dependent complex shear moduli of the gel. We further carry out force spectroscopy on these computer generated gels and study the relaxation properties as a function of the important parameters of the model, e.g., densities and relative ratios of the DNAs and the linkers, the average life time of a link, etc. Our studies are relevant for designing synthetic bio-materials for both materials and medical applications.

  2. Time series, correlation matrices and random matrix models

    SciTech Connect

    Vinayak; Seligman, Thomas H.

    2014-01-08

    In this set of five lectures the authors have presented techniques to analyze open classical and quantum systems using correlation matrices. For diverse reasons we shall see that random matrices play an important role to describe a null hypothesis or a minimum information hypothesis for the description of a quantum system or subsystem. In the former case various forms of correlation matrices of time series associated with the classical observables of some system. The fact that such series are necessarily finite, inevitably introduces noise and this finite time influence lead to a random or stochastic component in these time series. By consequence random correlation matrices have a random component, and corresponding ensembles are used. In the latter we use random matrices to describe high temperature environment or uncontrolled perturbations, ensembles of differing chaotic systems etc. The common theme of the lectures is thus the importance of random matrix theory in a wide range of fields in and around physics.

  3. Almost Commuting Unitary Matrices Related to Time Reversal

    NASA Astrophysics Data System (ADS)

    Loring, Terry A.; Sørensen, Adam P. W.

    2013-11-01

    The behavior of fermionic systems depends on the geometry of the system and the symmetry class of the Hamiltonian and observables. Almost commuting matrices arise from band-projected position observables in such systems. One expects the mathematical behavior of almost commuting Hermitian matrices to depend on two factors. One factor will be the approximate polynomial relations satisfied by the matrices. The other factor is what algebra the matrices are in, either for , or , the algebra of quaternions. There are potential obstructions keeping k-tuples of almost commuting operators from being close to a commuting k-tuple.We consider two-dimensional geometries and so this obstruction lives in . This obstruction corresponds to either the Chern number or spin Chern number in physics. We show that if this obstruction is the trivial element in K-theory then the approximation by commuting matrices is possible.

  4. [Sample pretreatment for the measurement of phthalate esters in complex matrices].

    PubMed

    Liang, Jing; Zhuang, Wan'e; Lin, Fang; Yao, Wensong

    2014-11-01

    Sample pretreatment methods for the measurement of phthalate esters (PAEs) by gas chromatography-mass spectrometry (GC-MS) in various complex matrices, including sediment, soil, suspended particle matter, urban surface dust, Sinonovacula Constricta, cosmet- ic, leather, plastic and coastal/estuarine seawater, were proposed. The pretreatment which was appropriate for GC-MS detection was focused on the investigation and optimization of oper- ating parameters for the extraction and purification, such as the extraction solvent, the eluant and the adsorbent of solid phase extraction. The results of the study of pretreatment for various complex matrices showed that methylene chloride was the best solvent for the ultrasonic extraction when solid-liquid extraction was used; silica gel was the economical and practical adsorbent for solid-phase extraction for purification; C18 was the most commonly adsorbent for preconcentration of PAE in coastal/estuarine seawater sample; the mixed solution of n-hexane and ethyl acetate with a certain proportion was the suitable SPE eluent. Under the optimized conditions, the spiked recoveries were above 58% and the relative standard deviations (RSDs) were less than 10.5% (n = 6). The detection limits (DL, 3σ) were in the range of 0.3 μg/kg (dibutyl phthalate)--5.2 μg/kg ( diisononyl phthalate) for sediment, and 6 ng/L (dipropyl phthalate)--67 ng/L (diisodecyl phthalate) for costal/estuarine seawater. The pretreatment meth- od for various complex matrices is prominent for the measurement of the 16 PAEs with GC-MS. PMID:25764660

  5. Sample treatment and determination of pesticide residues in fatty vegetable matrices: a review.

    PubMed

    Gilbert-López, Bienvenida; García-Reyes, Juan F; Molina-Díaz, Antonio

    2009-07-15

    A demanding task in pesticide residue analysis is yet the development of multi-residue methods for the determination of pesticides in vegetables with relatively high fat content (i.e. edible oils and fatty vegetables). The separation of pesticides and other chemical contaminants from high-fat food samples prior to subsequent steps in the analytical process is yet a challenging issue to which much effort in method development has being applied. This review addresses the main sample treatment methodologies for pesticide residue analysis in fatty vegetable matrices. Even with the advent of advanced hyphenated techniques based on mass spectrometry these complex fatty matrices usually require extensive sample extraction and purification. Current methods involve the use of one or the combination of some of the following techniques for both the sample extraction and clean-up steps: liquid-liquid partitioning, solid-phase extraction (SPE), gel-permeation chromatography (GPC), matrix solid-phase dispersion (MSPD), etc. An overview of methods developed for these contaminants in fatty vegetables matrices is presented. Sample extraction and purification techniques are discussed and their most recent applications are highlighted. This review emphasizes that sample preparation is a critical step, but also the determination method is, and cannot be treated separately from sample treatment. In recent years, the appearance and use of new, more polar pesticides has fostered the development of liquid chromatography/mass spectrometry (LC-MS) besides gas chromatography. The main features of LC-MS for the analysis of multi-class pesticides in fatty vegetable samples will be also underlined, with an emphasis on the multi-class, multi-residue strategy and the difficulties associated. PMID:19559852

  6. Validation of analytical methods for ethyl carbamate in nine food matrices.

    PubMed

    Ryu, Dayeon; Choi, Bogyoung; Kim, Nayoung; Koh, Eunmi

    2016-11-15

    Ethyl carbamate (EC) is formed through a reaction between ethanol and either cyanate or N-carbamyl compounds. This study aimed to develop and validate analytical methods for EC determination in nine food matrices: apple juice, soju, milk, corn oil, rice porridge, peanut butter, beef, flat fish, and sea mustard. Differences from AOAC procedure were use of d5-EC as internal standard, dilution of alcohol content, removal of lipophilic compounds by hexane, and removal of hydrophilic polysaccharides by gel-forming. Standard curves had a good linearity (R(2)>0.997) in all matrices tested. LOD and LOQ were in the range of 0.69-6.08μg/kg and 2.10-18.43μg/kg, respectively. Recovery rates ranged from 80.75 to 121.82% for intra-day and ranged from 78.84 to 116.98% for inter-day. The relative standard deviations (RSDs) were below 14%. These results indicate that the established methods can be applied to determine EC in a variety of foods. PMID:27283695

  7. Starch-free grewia gum matrices: Compaction, swelling, erosion and drug release behaviour.

    PubMed

    Nep, E I; Asare-Addo, K; Ghori, M U; Conway, B R; Smith, A M

    2015-12-30

    Polysaccharides are suitable for application as hydrophilic matrices because of their ability to hydrate and swell upon contact with fluids, forming a gel layer which controls drug release. When extracted from plants, polysaccharides often contain significant quantities of starch that impacts upon their functional properties. This study aimed to evaluate differences in swelling, erosion and drug release from matrix tablets prepared from grewia gum (GG) and starch-free grewia gum (GDS) extracted from the stems of Grewia mollis. HPMC was used as a control polymer with theophylline as a model drug. Swelling, erosion, and in-vitro release were performed in deionized water, pH 1.2 and pH 6.8 media. The Vergnaud and Krosmeyer-Peppas model were used for swelling and drug release kinetics, respectively. However, linear regression technique was used to determine the erosion rate. GDS compacts were significantly harder than the native GG and HPMC compacts. GDS matrices exhibited the fastest erosion and drug release in deionised water and phosphate buffer compared with the GG and HPMC. At pH 1.2, GDS exhibited greater swelling than erosion, and drug release was similar to GG and HPMC. This highlights the potential of GDS as a matrix for controlled release similar to HPMC and GG at pH 1.2 but with a more rapid release at pH 6.8. GDS may have wider application in reinforcing compacts with relatively low mechanical strength. PMID:26536530

  8. In situ cross-linking of sodium alginate with calcium and aluminum ions to sustain the release of theophylline from polymeric matrices.

    PubMed

    Nokhodchi, Ali; Tailor, Anish

    2004-12-01

    Small matrices of calcium alginate or aluminium alginate have been investigated as possible controlled release systems for drugs. The objective of the present study was to sustain the release of theophylline from alginate matrices using different concentrations of aluminium chloride and calcium chloride in presence and absence of HPMC. Tablets containing differing concentrations of aluminium and calcium chloride were produced and the release rate of theophylline was tested using the basket dissolution apparatus over 8 h. Increasing amounts of aluminium chloride from 0.0001 to 0.00068 moles decreased the release of theophylline from 95.1 +/- 0.27 to 29.5 +/- 1.5, indicating a significant effect of aluminium ions on a reduction in the release rate of theophylline from sodium alginate matrices. In the case of matrices containing different concentrations of calcium ions, as the concentration of calcium chloride increased, the release rate increased to an optimum then declined after this. This was due to insufficient calcium ions being available to cross-link with the sodium alginate to form an insoluble gel. The effect of aluminium ions, as this is a trivalent ion compared to calcium, which is a divalent ion, aluminium ions are able to decrease the release rate with a smaller concentration compared to calcium ions. The results also showed that the presence of HPMC caused a reduction in release rate of theophylline from alginate matrices containing calcium chloride. Whereas, in the case of alginate matrices containing aluminium chloride the release rate of theophylline increased in presence of HPMC. For comparing the dissolution data, dissolution efficiency (DE) was used. The values of DE are consistent with the dissolution data. The results show that within a formulation series, DE values generally decrease when the cation concentration increases and this criterion can be used to describe the effect of calcium and aluminium ions on the release behaviour of theophylline

  9. TOPICAL REVIEW: Polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Baldock, C.; De Deene, Y.; Doran, S.; Ibbott, G.; Jirasek, A.; Lepage, M.; McAuley, K. B.; Oldham, M.; Schreiner, L. J.

    2010-03-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.

  10. Topical Review: Polymer gel dosimetry

    PubMed Central

    Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

    2010-01-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

  11. Protein Separation by Capillary Gel Electrophoresis: A Review

    PubMed Central

    Zhu, Zaifang; Lu, Joann J.; Liu, Shaorong

    2011-01-01

    Capillary gel electrophoresis (CGE) has been used for protein separation for more than two decades. Due to the technology advancement, current CGE methods are becoming more and more robust and reliable for protein analysis, and some of the methods have been routinely used for the analysis of protein-based pharmaceuticals and quality controls. In light of this progress, we survey 147 papers related to CGE separations of proteins and present an overview of this technology. We first introduce briefly the early development of CGE. We then review the methodology, in which we specifically describe the matrices, coatings, and detection strategies used in CGE. CGE using microfabricated channels and incorporation of CGE with two-dimensional protein separations are also discussed in this section. We finally present a few representative applications of CGE for separating proteins in real-world samples. PMID:22122927

  12. Hopping Diffusion of Nanoparticles in Polymer Matrices

    PubMed Central

    2016-01-01

    We propose a hopping mechanism for diffusion of large nonsticky nanoparticles subjected to topological constraints in both unentangled and entangled polymer solids (networks and gels) and entangled polymer liquids (melts and solutions). Probe particles with size larger than the mesh size ax of unentangled polymer networks or tube diameter ae of entangled polymer liquids are trapped by the network or entanglement cells. At long time scales, however, these particles can diffuse by overcoming free energy barrier between neighboring confinement cells. The terminal particle diffusion coefficient dominated by this hopping diffusion is appreciable for particles with size moderately larger than the network mesh size ax or tube diameter ae. Much larger particles in polymer solids will be permanently trapped by local network cells, whereas they can still move in polymer liquids by waiting for entanglement cells to rearrange on the relaxation time scales of these liquids. Hopping diffusion in entangled polymer liquids and networks has a weaker dependence on particle size than that in unentangled networks as entanglements can slide along chains under polymer deformation. The proposed novel hopping model enables understanding the motion of large nanoparticles in polymeric nanocomposites and the transport of nano drug carriers in complex biological gels such as mucus. PMID:25691803

  13. Characterization of Caramel Colour IV.

    PubMed

    Licht, B H; Shaw, K; Smith, C; Mendoza, M; Orr, J; Myers, D V

    1992-05-01

    A large number of commercial Caramel Colour IV samples were characterized in order to assess the uniformity of the class and to provide data to be used in specifications development. Owing to the chemical and physical complexity of caramel colour it was not feasible to perform detailed analysis of all constituents for assessment of uniformity. Instead, selected parameters were evaluated and judgements were made with respect to compositional uniformity based on the similarities of these parameters among the various samples. As Caramel Colour IV is required by the food industry in a range of colour intensities, there must be a range of properties that differ from sample to sample, but that are sufficiently similar for the material to still be considered as part of the Caramel Colour IV class. Fractions as well as whole caramel were analysed using selected spectrophotometric, chromatographic and chemical techniques. Samples were fractionated based on molecular weight and polarity. The data presented here provide evidence for the uniformity in composition of Caramel Colour IV with respect to molecular weight distribution, to nitrogen and sulphur content and their distribution throughout the fractions, to absorbance properties and to specific low molecular weight compounds. Thus, it can be concluded that Caramel Colour IV exhibits compositional uniformity within the range of colour intensity required by the food industry worldwide. PMID:1644377

  14. Alternative imaging modalities for polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Jirasek, Andrew

    2010-11-01

    This review summarizes recent work in the area of imaging polymer gel dosimeters using x-ray CT imaging, ultrasound, and radiation-induced changes in gel mechanical properties. In addition, recent work in the area of Raman tomographic imaging of canine bone, in conjunction with past efforts in Raman imaging of polymer gel dosimeters, raises new possibilities for new polymer gel imaging techniques.

  15. Rheological behavior of Slide Ring Gels.

    NASA Astrophysics Data System (ADS)

    Sharma, Vivek; Park, Jong Seung; Park, Jung O.; Srinivasarao, Mohan

    2006-03-01

    Slide ring gels were synthesized by chemically crosslinking, sparsely populated α-cyclodextrin (α-CD) present on the polyrotaxanes consisting of α-CD and polyethylene glycol (PEG). [1] Unlike physically or chemically crosslinked gels, slide ring gels are topological gels where crosslinks can slide along the chain. [2] We investigate the rheological behavior of these gels swollen in water and compare their viscoelastic properties to those of physical and chemical gels. We also study the equilibrium swelling behavior of these gels. [1] Okumura and Ito, Adv. Mater. 2001, 13, 485 [2] C. Zhao et al, J. Phys. Cond. Mat. 2005, 17, S2841

  16. Standard Missile Block IV battery

    SciTech Connect

    Martin, J.

    1996-11-01

    During the 1980`s a trend in automatic primary battery technologies was the replacement of silver-zinc batteries by thermal battery designs. The Standard missile (SM 2) Block IV development is a noteworthy reversal of this trend. The SM2, Block IV battery was originally attempted as a thermal battery with multiple companies attempting to develop a thermal battery design. These attempts resulted in failure to obtain a production thermal battery. A decision to pursue a silver-zinc battery design resulted in the development of a battery to supply the SM 2, Block IV (thermal battery design goal) and also the projected power requirements of the evolving SM 2, Block IVA in a single silver-zinc battery design. Several advancements in silver-zinc battery technology were utilized in this design that improve the producibility and extend the boundaries of silver-zinc batteries.

  17. Mechanically implementable accommodation matrices for passive force control

    SciTech Connect

    Goswami, A.; Peshkin, M.

    1999-08-01

    Robot force control implemented by means of passive mechanical devices has inherent advantages over active implementations with regard to stability, response rapidity, and physical robustness. The class of devices considered in this paper consists of a Stewart platform-type mechanism interconnected with a network of adjustable mechanical elements such as springs and dampers. The control law repertoire of such a device, imagined as a robot wrist, is given by the range of admittance matrices that it may be programmed to possess. This paper focuses on wrists incorporating damper networks for which the admittance matrices reduce to accommodation or inverse-damping matrices. The authors show that a hydraulic network of fully adjustable damper elements may attain any diagonally dominant accommodation matrix. They describe the technique of selecting the individual damping coefficients to design a desired matrix. They identify the set of dominant matrices as a polyhedral convex cone in the space of matrix entries, and show that each dominant matrix can be composed of a positive linear combination of a fixed set of basis matrices. The overall wrist-accommodation matrix is obtained by projecting the accommodation matrix of the damper network through the wrist kinematics. The linear combination of the dominant basis matrices projected through the wrist kinematics generates the entire space of mechanically implementable force-control laws. The authors quantify the versatility of mechanically implementable force-control laws by comparing this space to the space of all matrices.

  18. User`s guide and documentation manual for ``PC-Gel`` simulator

    SciTech Connect

    Chang, Ming-Ming; Gao, Hong W.

    1993-10-01

    PC-GEL is a three-dimensional, three-phase (oil, water, and gas) permeability modification simulator developed by incorporating an in-situ gelation model into a black oil simulator (BOAST) for personal computer application. The features included in the simulator are: transport of each chemical species of the polymer/crosslinker system in porous media, gelation reaction kinetics of the polymer with crosslinking agents, rheology of the polymer and gel, inaccessible pore volume to macromolecules, adsorption of chemical species on rock surfaces, retention of gel on the rock matrix, and permeability reduction caused by the adsorption of polymer and gel. The in-situ gelation model and simulator were validated against data reported in the literature. The simulator PC-GEL is useful for simulating and optimizing any combination of primary production, waterflooding, polymer flooding, and permeability modification treatments. A general background of permeability modification using crosslinked polymer gels is given in Section I and the governing equations, mechanisms, and numerical solutions of PC-GEL are given in Section II. Steps for preparing an input data file with reservoir and gel-chemical transport data, and recurrent data are described in Sections III and IV, respectively. Example data inputs are enclosed after explanations of each input line to help the user prepare data files. Major items of the output files are reviewed in Section V. Finally, three sample problems for running PC-GEL are described in Section VI, and input files and part of the output files of these problems are listed in the appendices. For the user`s reference a copy of the source code of PC-GEL computer program is attached in Appendix A.

  19. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.

    2012-07-03

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  20. Thixotropic gel for vadose zone remediation

    DOEpatents

    Rhia, Brian D.

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  1. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  2. Novel gels and their dispersions--oral drug delivery systems for ciclosporin.

    PubMed

    Murdan, Sudaxshina; Andrýsek, Tomas; Son, Delphine

    2005-08-26

    Amphiphilogels (gels that consist solely of surfactants) and gel-based emulsion (GEM) formulations (solutions that gel upon incorporation of small amounts of water) were investigated as oral delivery vehicles for ciclosporin A, in in vivo experiments in Beagle dogs. Both systems represent essentially self-dispersing non-lipidic drug delivery systems based on amphiphilic surfactants. Three different amphiphilogels (hydrophobic, hydrophilic and hydrophilic gel containing ethanol), the aqueous dispersions of the latter two amphiphilogels and of two GEM formulations were tested to determine the influence of (i) gel hydrophilicity/hydrophobicity, (ii) presence of ethanol, (iii) pre-dispersion of gels into aqueous medium prior to oral administration and (iv) size of dispersions, on drug absorption. It was found that all the formulations tested, except for the hydrophilic amphiphilogel and its aqueous dispersion, were bioequivalent to Neoral, the commercially available preparation. High drug absorption from the bioequivalent formulations was thought to be due to the fact that following oral administration, ciclosporin remained in a soluble form, hence was available for absorption, despite relatively large droplet sizes of the formulations. The hydrophilic gel and its dispersion allowed less drug absorption; this was assigned to the fact that, when the hydrophilic amphiphilogel contacted an aqueous medium, there were no lipophilic domains in which the drug could remain soluble. It is possible that some drug precipitated out and was unavailable for absorption. PMID:16009515

  3. Decellularized matrices for cardiovascular tissue engineering

    PubMed Central

    Moroni, Francesco; Mirabella, Teodelinda

    2014-01-01

    Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950’s. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to “biointegration”. Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption. PMID:24660110

  4. On polynomial preconditioning for indefinite Hermitian matrices

    NASA Technical Reports Server (NTRS)

    Freund, Roland W.

    1989-01-01

    The minimal residual method is studied combined with polynomial preconditioning for solving large linear systems (Ax = b) with indefinite Hermitian coefficient matrices (A). The standard approach for choosing the polynomial preconditioners leads to preconditioned systems which are positive definite. Here, a different strategy is studied which leaves the preconditioned coefficient matrix indefinite. More precisely, the polynomial preconditioner is designed to cluster the positive, resp. negative eigenvalues of A around 1, resp. around some negative constant. In particular, it is shown that such indefinite polynomial preconditioners can be obtained as the optimal solutions of a certain two parameter family of Chebyshev approximation problems. Some basic results are established for these approximation problems and a Remez type algorithm is sketched for their numerical solution. The problem of selecting the parameters such that the resulting indefinite polynomial preconditioners speeds up the convergence of minimal residual method optimally is also addressed. An approach is proposed based on the concept of asymptotic convergence factors. Finally, some numerical examples of indefinite polynomial preconditioners are given.

  5. Osteogenic signaling on silk-based matrices.

    PubMed

    Midha, Swati; Murab, Sumit; Ghosh, Sourabh

    2016-08-01

    Bone tissue engineering has mainly focused on generating 3D grafts to repair bone defects. However, the underlying signaling mechanisms responsible for development of such 3D bone equivalents have largely been ignored. Here we describe the crucial aspects of embryonic osteogenesis and bone development including cell sources and general signaling cascades that guide mesenchymal progenitors towards osteogenic lineage. Drawing from the knowledge of developmental biology, we then review how silk biomaterial can regulate osteogenic signaling by focusing on the expression of cell surface markers, functional genomic information (mRNA) of stem cells cultured on silk matrices. In an attempt to recapitulate exact in vivo microenvironment of osteogenesis, role of scaffold architecture and material chemistry in regulating cellular differentiation is elaborated. The generated knowledge will not only improve our understanding of cell-material interactions but reveal newer strategies beyond a conventional tissue engineering paradigm and open new prospects for developing silk-based therapies against clinically relevant bone disorders. PMID:27163625

  6. Substituted amylose matrices for oral drug delivery

    NASA Astrophysics Data System (ADS)

    Moghadam, S. H.; Wang, H. W.; Saddar El-Leithy, E.; Chebli, C.; Cartilier, L.

    2007-03-01

    High amylose corn starch was used to obtain substituted amylose (SA) polymers by chemically modifying hydroxyl groups by an etherification process using 1,2-epoxypropanol. Tablets for drug-controlled release were prepared by direct compression and their release properties assessed by an in vitro dissolution test (USP XXIII no 2). The polymer swelling was characterized by measuring gravimetrically the water uptake ability of polymer tablets. SA hydrophilic matrix tablets present sequentially a burst effect, typical of hydrophilic matrices, and a near constant release, typical of reservoir systems. After the burst effect, surface pores disappear progressively by molecular association of amylose chains; this allows the creation of a polymer layer acting as a diffusion barrier and explains the peculiar behaviour of SA polymers. Several formulation parameters such as compression force, drug loading, tablet weight and insoluble diluent concentration were investigated. On the other hand, tablet thickness, scanning electron microscope analysis and mercury intrusion porosimetry showed that the high crushing strength values observed for SA tablets were due to an unusual melting process occurring during tabletting although the tablet external layer went only through densification, deformation and partial melting. In contrast, HPMC tablets did not show any traces of a melting process.

  7. Occam's razor in quark mass matrices

    NASA Astrophysics Data System (ADS)

    Tanimoto, Morimitsu; Yanagida, Tsutomu T.

    2016-04-01

    From the standpoint of the Occam's razor approach, we consider the minimum number of parameters in the quark mass matrices needed for successful CKM mixing and CP violation. We impose three zeros in the down-quark mass matrix while taking the diagonal up-quark mass matrix to reduce the number of free parameters. The three zeros are maximal zeros in order to have a CP-violating phase in the quark mass matrix. Then, there remain six real parameters and one CP-violating phase, which is the minimal number needed to reproduce the observed data of the down-quark masses and the CKM parameters. Twenty textures with three zeros are examined. Among these, thirteen textures are viable for the down-quark mass matrix. As a representative of these textures, we discuss a texture Md^{(1)} in detail. By using the experimental data on sin 2β , θ _{13}, and θ _{23}, together with the observed quark masses, the Cabibbo angle is predicted to be close to the experimental data. It is found that this surprising result remains unchanged in all other viable textures. We also investigate the correlations between |V_{ub}/V_{cb}|, sin 2β , and J_CP. For all textures, the maximal value of the ratio |V_{ub}/V_{cb}| is 0.09, which is smaller than the upper bound of the experimental data, 0.094. We hope that this prediction will be tested in future experiments.

  8. Generalized graph states based on Hadamard matrices

    SciTech Connect

    Cui, Shawn X.; Yu, Nengkun; Zeng, Bei

    2015-07-15

    Graph states are widely used in quantum information theory, including entanglement theory, quantum error correction, and one-way quantum computing. Graph states have a nice structure related to a certain graph, which is given by either a stabilizer group or an encoding circuit, both can be directly given by the graph. To generalize graph states, whose stabilizer groups are abelian subgroups of the Pauli group, one approach taken is to study non-abelian stabilizers. In this work, we propose to generalize graph states based on the encoding circuit, which is completely determined by the graph and a Hadamard matrix. We study the entanglement structures of these generalized graph states and show that they are all maximally mixed locally. We also explore the relationship between the equivalence of Hadamard matrices and local equivalence of the corresponding generalized graph states. This leads to a natural generalization of the Pauli (X, Z) pairs, which characterizes the local symmetries of these generalized graph states. Our approach is also naturally generalized to construct graph quantum codes which are beyond stabilizer codes.

  9. The Representation and Parametrization of Orthogonal Matrices.

    PubMed

    Shepard, Ron; Brozell, Scott R; Gidofalvi, Gergely

    2015-07-16

    Four representations and parametrizations of orthogonal matrices Q ∈ R(m×n) in terms of the minimal number of essential parameters {φ} are discussed: the exponential representation, the Householder reflector representation, the Givens rotation representation, and the rational Cayley transform representation. Both square n = m and rectangular n < m situations are considered. Two separate kinds of parametrizations are considered: one in which the individual columns of Q are distinct, the Stiefel manifold, and the other in which only span(Q) is significant, the Grassmann manifold. The practical issues of numerical stability, continuity, and uniqueness are discussed. The computation of Q in terms of the essential parameters {φ}, and also the extraction of {φ} for a given Q are considered for all of the parametrizations. The transformation of gradient arrays between the Q and {φ} variables is discussed for all representations. It is our hope that developers of new methods will benefit from this comparative presentation of an important but rarely analyzed subject. PMID:25946418

  10. Photochemistry of glycolaldehyde in cryogenic matrices.

    PubMed

    Chin, W; Chevalier, M; Thon, R; Pollet, R; Ceponkus, J; Crépin, C

    2014-06-14

    The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S0, S1, and T1 states--to analyse the torsional deformations which are involved in the isomerization process--and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase. PMID:24929400

  11. Partitioning sparse matrices with eigenvectors of graphs

    NASA Technical Reports Server (NTRS)

    Pothen, Alex; Simon, Horst D.; Liou, Kang-Pu

    1990-01-01

    The problem of computing a small vertex separator in a graph arises in the context of computing a good ordering for the parallel factorization of sparse, symmetric matrices. An algebraic approach for computing vertex separators is considered in this paper. It is shown that lower bounds on separator sizes can be obtained in terms of the eigenvalues of the Laplacian matrix associated with a graph. The Laplacian eigenvectors of grid graphs can be computed from Kronecker products involving the eigenvectors of path graphs, and these eigenvectors can be used to compute good separators in grid graphs. A heuristic algorithm is designed to compute a vertex separator in a general graph by first computing an edge separator in the graph from an eigenvector of the Laplacian matrix, and then using a maximum matching in a subgraph to compute the vertex separator. Results on the quality of the separators computed by the spectral algorithm are presented, and these are compared with separators obtained from other algorithms for computing separators. Finally, the time required to compute the Laplacian eigenvector is reported, and the accuracy with which the eigenvector must be computed to obtain good separators is considered. The spectral algorithm has the advantage that it can be implemented on a medium-size multiprocessor in a straightforward manner.

  12. Photochemistry of glycolaldehyde in cryogenic matrices

    SciTech Connect

    Chin, W. Chevalier, M.; Thon, R.; Crépin, C.; Pollet, R.

    2014-06-14

    The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH{sub 3}OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H{sub 2}CO and HCO fragments are seen. Calculations of the potential energy surfaces of S{sub 0}, S{sub 1}, and T{sub 1} states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH{sub 3}OH molecular channel is a minor process, as in the gas phase.

  13. Non-viral gene-activated matrices

    PubMed Central

    Tierney, Erica G.; Duffy, Garry P.; Cryan, Sally-Ann; Curtin, Caroline M.; O’Brien, Fergal J.

    2013-01-01

    In the context of producing enhanced therapeutics for regenerative medicine, our laboratory develops gene-activated matrices (GAMs) using non-viral gene therapy (GT) in combination with collagen-based scaffolds engineered specifically for tissue repair. Non-viral vectors have been referred to as a minority pursuit in GT but considering the concerns associated with viral vectors and as transient gene expression is such a key consideration, further research is clearly warranted for tissue engineering (TE) applications. Mesenchymal stem cells (MSCs) are well regarded for their capability in bone regeneration but as primary cells, they are difficult to transfect. We have recently optimised the non-viral vector, polyethyleneimine (PEI), to achieve high transfection efficiencies in MSCs. Subsequently, a series of PEI-based GAMs were developed using collagen, collagen-glycosaminoglycan and collagen-nanohydroxyapatite (collagen-nHa) scaffolds whereby transgene expression was detected up to 21 d with the collagen-nHa scaffold providing the most prolonged expression. Moreover, all PEI-based GAMs contained a low plasmid DNA dose of 2 µg which is far below doses often required in previous GAMs. Having successfully developed these GAMs, the ephrinB2 gene has recently been incorporated to produce a novel therapeutic GAM for bone repair. Herein, we discuss our recent investigations in the development and application of non-viral GAMs. PMID:23538777

  14. Automated building extraction using dense elevation matrices

    NASA Astrophysics Data System (ADS)

    Bendett, A. A.; Rauhala, Urho A.; Pearson, James J.

    1997-02-01

    The identification and measurement of buildings in imagery is important to a number of applications including cartography, modeling and simulation, and weapon targeting. Extracting large numbers of buildings manually can be time- consuming and expensive, so the automation of the process is highly desirable. This paper describes and demonstrates such an automated process for extracting rectilinear buildings from stereo imagery. The first step is the generation of a dense elevation matrix registered to the imagery. In the examples shown, this was accomplished using global minimum residual matching (GMRM). GMRM automatically removes y- parallax from the stereo imagery and produces a dense matrix of x-parallax values which are proportional to the local elevation, and, of course, registered to the imagery. The second step is to form a joint probability distribution of the image gray levels and the corresponding height values from the elevation matrix. Based on the peaks of that distribution, the area of interest is segmented into feature and non-feature areas. The feature areas are further refined using length, width and height constraints to yield promising building hypotheses with their corresponding vertices. The gray shade image is used in the third step to verify the hypotheses and to determine precise edge locations corresponding to the approximate vertices and satisfying appropriate orthogonality constraints. Examples of successful application of this process to imagery are presented, and extensions involving the use of dense elevation matrices from other sources are possible.

  15. CLSM method for the dynamic observation of pH change within polymer matrices for oral delivery.

    PubMed

    Cook, Michael T; Saratoon, Teedah; Tzortzis, George; Edwards, Alexander; Charalampopoulos, Dimitris; Khutoryanskiy, Vitaliy V

    2013-02-11

    If acid-sensitive drugs or cells are administered orally, there is often a reduction in efficacy associated with gastric passage. Formulation into a polymer matrix is a potential method to improve their stability. The visualization of pH within these materials may help better understand the action of these polymer systems and allow comparison of different formulations. We herein describe the development of a novel confocal laser-scanning microscopy (CLSM) method for visualizing pH changes within polymer matrices and demonstrate its applicability to an enteric formulation based on chitosan-coated alginate gels. The system in question is first shown to protect an acid-sensitive bacterial strain to low pH, before being studied by our technique. Prior to this study, it has been claimed that protection by these materials is a result of buffering, but this has not been demonstrated. The visualization of pH within these matrices during exposure to a pH 2.0 simulated gastric solution showed an encroachment of acid from the periphery of the capsule, and a persistence of pHs above 2.0 within the matrix. This implies that the protective effect of the alginate-chitosan matrices is most likely due to a combination of buffering of acid as it enters the polymer matrix and the slowing of acid penetration. PMID:23301617

  16. Collaboration between HPMC and NaCMC in order to Reach the Polymer Critical Point in Theophylline Hydrophilic Matrices

    PubMed Central

    Contreras, L.; Melgoza, L. M.; Aguilar-de-Leyva, A.; Caraballo, I.

    2012-01-01

    Percolation theory has been applied in order to study the existence of critical points as well as the possibility to find a “combined percolation threshold” for ternary hydrophilic matrices prepared with HPMC, NaCMC, and theophylline. For this purpose, different batches of ternary as well as binary hydrophilic matrices have been prepared. Critical points have been found for binary hydrophilic matrices between 21.5 and 31.3% (v/v) of HPMC and between 39 and 54% (v/v) of NaCMC, respectively. In a previous work carried out with the same polymers but a much more soluble drug (KCl), it was demonstrated the existence of a partial collaboration between the polymers in order to establish the gel layer. In this work, it has been observed for the first time the need of a minimum concentration of one of the matrix-forming polymer (between 10 and 20% v/v, approximately) for establishing an effective collaboration. PMID:22919292

  17. Granulation and infiltration processes for the fabrication of minor actinide fuels, targets and conditioning matrices

    NASA Astrophysics Data System (ADS)

    Nästren, C.; Fernandez, A.; Haas, D.; Somers, J.; Walter, M.

    2007-05-01

    The impact of Pu and Am, two elements that potentially pose a long term hazard for the disposal of spent nuclear fuel, can be abated by their reintroduction into the fuel cycle for transmutation. Such transmutation targets can be fabricated by a sol gel method for the production of porous inactive beads, which are then infiltrated by Am solutions. Following calcination, compaction into pellets and sintering, the product is obtained. At its heart, the sol gel process relies on an ammonia precipitation, so that it is not universally applicable. Therefore, an alternative is sought not just to overcome this chemical limitation, but also to simplify the process and reduce waste streams. The new concept utilises powder metallurgy routes (compaction, crushing and sieving) to produce porous, almost, dust free granules, which are infiltrated with the actinide nitrate. The method has been developed using yttria stabilised zirconia and alumina, and has been demonstrated for the production of Al2O3-AmO2 targets for neutron capture investigations. The results are very promising and meet light water reactor fuel specifications. In addition, the process is ideally suited for the production of ceramic matrices for conditioning actinides for geological disposal.

  18. Interrogating erosion-based drug liberation phenomena from hydrophilic matrices using near infrared (NIR) spectroscopy.

    PubMed

    Avalle, Paolo; Pygall, Samuel R; Pritchard, Jonathan; Jastrzemska, Agnieszka

    2013-01-23

    The present work explores the application of in situ near infrared (NIR) imaging to determine the drug release mechanisms from hydrophilic matrices containing a low solubility model drug (Compound A, with aqueous solubility at 37°C ∼0.05 mg/mL). Correlation maps generated from the NIR data determined the extent drug and HPMC co-localisation. Judicious thresholding facilitated band separation of low drug/HPMC ratio and high drug/HPMC ratio. A pseudo-image time-series confirmed the dominant erosion release mechanisms. The gel layer region showed low drug concentration with progressive dissolution. However, large drug aggregates remained unchanged even when fully "immersed" within the gel layer. From the correlation maps, further discrimination was possible for the pure drug signal, generating a highly contrasted image that enabled individual particle tracking. These contrasted images also revealed the evolution of single or clusters of drug particles. Initially, an aggregative process involving the drug particles occurred, with a subsequent migration process of such particles. This second process dominated the subsequent 90 min before significant erosion. In summary, this study has provided tentative confirmation that NIR imaging has the potential to afford insights into drug liberation phenomena where erosion is the predominant release mechanism. PMID:23059372

  19. Introduction of organic/hydro-organic matrices in inductively coupled plasma optical emission spectrometry and mass spectrometry: a tutorial review. Part I. Theoretical considerations.

    PubMed

    Leclercq, Amélie; Nonell, Anthony; Todolí Torró, José Luis; Bresson, Carole; Vio, Laurent; Vercouter, Thomas; Chartier, Frédéric

    2015-07-23

    Due to their outstanding analytical performances, inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS) are widely used for multi-elemental measurements and also for isotopic characterization in the case of ICP-MS. While most studies are carried out in aqueous matrices, applications involving organic/hydro-organic matrices become increasingly widespread. This kind of matrices is introduced in ICP based instruments when classical "matrix removal" approaches such as acid digestion or extraction procedures cannot be implemented. Due to the physico-chemical properties of organic/hydro-organic matrices and their associated effects on instrumentation and analytical performances, their introduction into ICP sources is particularly challenging and has become a full topic. In this framework, numerous theoretical and phenomenological studies of these effects have been performed in the past, mainly by ICP-OES, while recent literature is more focused on applications and associated instrumental developments. This tutorial review, divided in two parts, explores the rich literature related to the introduction of organic/hydro-organic matrices in ICP-OES and ICP-MS. The present Part I, provides theoretical considerations in connection with the physico-chemical properties of organic/hydro-organic matrices, in order to better understand the induced phenomena. This focal point is divided in four chapters highlighting: (i) the impact of organic/hydro-organic matrices from aerosol generation to atomization/excitation/ionization processes; (ii) the production of carbon molecular constituents and their spatial distribution in the plasma with respect to analytes repartition; (iii) the subsequent modifications of plasma fundamental properties; and (iv) the resulting spectroscopic and non spectroscopic interferences. This first part of this tutorial review is addressed either to beginners or to more experienced scientists who are interested in the

  20. Bunch-Kaufman factorization for real symmetric indefinite banded matrices

    NASA Technical Reports Server (NTRS)

    Jones, Mark T.; Patrick, Merrell L.

    1989-01-01

    The Bunch-Kaufman algorithm for factoring symmetric indefinite matrices was rejected for banded matrices because it destroys the banded structure of the matrix. Herein, it is shown that for a subclass of real symmetric matrices which arise in solving the generalized eigenvalue problem using Lanczos's method, the Bunch-Kaufman algorithm does not result in major destruction of the bandwidth. Space time complexities of the algorithm are given and used to show that the Bunch-Kaufman algorithm is a significant improvement over LU factorization.

  1. On the asymptotic distribution of block-modified random matrices

    NASA Astrophysics Data System (ADS)

    Arizmendi, Octavio; Nechita, Ion; Vargas, Carlos

    2016-01-01

    We study random matrices acting on tensor product spaces which have been transformed by a linear block operation. Using operator-valued free probability theory, under some mild assumptions on the linear map acting on the blocks, we compute the asymptotic eigenvalue distribution of the modified matrices in terms of the initial asymptotic distribution. Moreover, using recent results on operator-valued subordination, we present an algorithm that computes, numerically but in full generality, the limiting eigenvalue distribution of the modified matrices. Our analytical results cover many cases of interest in quantum information theory: we unify some known results and we obtain new distributions and various generalizations.

  2. Phase direct CP violations and general mixing matrices

    NASA Astrophysics Data System (ADS)

    Chau, Ling-Lie

    2007-08-01

    I formulate expressions for amplitudes suitable for quantifying both modulus and phase direct CP violations. They result in Möbius transformation (MT) relations, which provide encouraging information for the search of direct CP violations in general. I apply the formulation to calculate the measurements of phase direct CP violations and strong amplitudes in B∓ →K∓π±π∓ by the Belle Collaboration. For the formulation, I show a versatile construction procedure for N × N Cabibbo-Kobayashi-Maskawa (CKM) matrices, Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrices, and general unitary matrices. It clarifies the 3 × 3 cases and is useful for the beyond.

  3. Random transition-rate matrices for the master equation.

    PubMed

    Timm, Carsten

    2009-08-01

    Random-matrix theory is applied to transition-rate matrices in the Pauli master equation. We study the distribution and correlations of eigenvalues, which govern the dynamics of complex stochastic systems. Both the cases of identical and of independent rates of forward and backward transitions are considered. The first case leads to symmetric transition-rate matrices, whereas the second corresponds to general asymmetric matrices. The resulting matrix ensembles are different from the standard ensembles and show different eigenvalue distributions. For example, the fraction of real eigenvalues scales anomalously with matrix dimension in the asymmetric case. PMID:19792110

  4. Coulometric Titrations in Wine Samples: Studies on the Determination of S(IV) and the Formation of Adducts

    NASA Astrophysics Data System (ADS)

    Lowinsohn, Denise; Bertotti, Mauro

    2002-01-01

    In this experiment, the sulfite in white wine samples is quantified by coulometric titration with iodine, using a procedure that minimizes errors due to air oxidation. Some aspects of the distinction of S(IV) forms in such matrices are discussed on the basis of the formation of adducts between sulfite and carbonyl compounds present in the wine. The reactivity of these S(IV)-bound compounds toward the reaction with iodine is addressed and the stability of the adducts as the sample pH is changed is discussed.

    See Letter re: this article.

  5. Gel placement in fractured systems

    SciTech Connect

    Seright, R.S.

    1995-11-01

    This paper examines several factors that can have an important effect on gel placement in fractured systems, including gelant viscosity, degree of gelation, and gravity. For an effective gel treatment, the conductivity of the fracture must be reduced and a viable flow path must remain open between the wellbore and mobile oil in the reservoir. During placement, the gelant that``leaks off`` from the fracture into the rock plays an important role in determining how well a gel treatment will reduce channeling. For a given volume of gelant injected the distance of gelant leakoff is greater for a viscous gelant than for a low-viscosity gelant. In one method to minimize gelant leakoff, sufficient gelation is designed to occur before the gelant leaves the wellbore. The authors investigated this approach in numerous experiments with both fractured and unfractured cores. They studied Cr(III)/acetate/hydrolyzed polyacrylamide (HPAM), resorcinol/formaldehyde, Cr(III)/xanthan, aluminum/citrate/HPAM, and other gelants and gels with various delay times between gelant preparation and injection. Their results suggest both hope and caution concerning the injection of gels into fractured systems.

  6. The PLATO IV Communications System.

    ERIC Educational Resources Information Center

    Sherwood, Bruce Arne; Stifle, Jack

    The PLATO IV computer-based educational system contains its own communications hardware and software for operating plasma-panel graphics terminals. Key echoing is performed by the central processing unit: every key pressed at a terminal passes through the entire system before anything appears on the terminal's screen. Each terminal is guaranteed…

  7. Title IV: Improving Indian Education.

    ERIC Educational Resources Information Center

    Barker, Kipp A.

    The Indian Education Act of 1972, Title IV, has improved Native American education by emphasizing Native American control; it comes after 400 years of Euro-American involvement in Indian education during which assimilation was the primary goal. In 1568 Jesuit priests began "civilizing" and Christianizing the "savage" Indians; in 1794 the first…

  8. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  9. Fundamentals of Polymer Gel Dosimeters

    NASA Astrophysics Data System (ADS)

    McAuley, Kim B.

    2006-12-01

    The recent literature on polymer gel dosimetry contains application papers and basic experimental studies involving polymethacrylic-acid-based and polyacrylamide-based gel dosimeters. The basic studies assess the relative merits of these two most commonly used dosimeters, and explore the effects of tetrakis hydroxymethyl phosphonium chloride (THPC) antioxidant on dosimeter performance. Polymer gel dosimeters that contain THPC or other oxygen scavengers are called normoxic dosimeters, because they can be prepared under normal atmospheric conditions, rather than in a glove box that excludes oxygen. In this review, an effort is made to explain some of the underlying chemical phenomena that affect dosimeter performance using THPC, and that lead to differences in behaviour between dosimeters made using the two types of monomer systems. Progress on the development of new more effective and less toxic dosimeters is also reported.

  10. Sol-gel derived sorbents

    DOEpatents

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  11. Physico-chemical properties of organically modified silicates' sol-gel layers for optical fibre sensors

    NASA Astrophysics Data System (ADS)

    Chodkowska, Eliza; Rayss, Jan

    2006-10-01

    The paper concerns the investigation of modified silica gel materials applied in optical fibre sensors. These materials are products of a sol-gel process in which three kinds of alkoxysilanes undergo hydrolysis and condensation and may play a role of the matrices containing transducer's molecules in the active layer of the sensor. In the experiment presented below three different compositions comprising tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PhTES) were used. The alkoxysilanes underwent hydrolysis and condensation and the obtained gels were investigated in order to determine their texture, strucuture, composition and chemical properties as far as the dependence of those characteristics on the hydrolysis time and the molar ratio of the ingredients in the initial sols. The methods employed in the experiment were: Atomic Force Microscopy (AFM) which delivered vital information about the gels' textures, contact angles' and surface charge's measurements serving to estimate chemical properties of the gels' surfaces, Nuclear Magnetic Resonance (NMR) which helped to evaluate the hydrolysis' rate and porosimetric measurements enabling a determination of BET surface area and average diametres of the pores. The results may occur important for improving the construction of optical fibre sensors in which organically modified silicates (ORMOSILs)-TEOS layes are used.

  12. Influence of the gel thickness on in vivo hyaline cartilage regeneration induced by double-network gel implanted at the bottom of a large osteochondral defect: Short-term results

    PubMed Central

    2013-01-01

    Background A double-network (DN) gel, which is composed of poly(2-acrylamido-2-methylpropanesulfonic acid) and poly(N,N’-dimethyl acrylamide), can induce hyaline cartilage regeneration in vivo in a large osteochondral defect. The purpose of this study was to clarify the influence of the thickness of the implanted DN gel on the induction ability of hyaline cartilage regeneration. Methods Thirty-eight mature rabbits were used in this study. We created an osteochondral defect having a diameter of 4.3-mm in the patellofemoral joint. The knees were randomly divided into 4 groups (Group I: 0.5-mm thick gel, Group II: 1.0-mm thick gel, Group III: 5.0-mm thick gel, and Group IV: untreated control). Animals in each group were further divided into 3 sub-groups depending on the gel implant position (2.0-, 3.0-, or 4.0-mm depth from the articular surface) in the defect. The regenerated tissues were evaluated with the Wayne’s gross and histological grading scales and real time PCR analysis of the cartilage marker genes at 4 weeks. Results According to the total Wayne’s score, when the depth of the final vacant space was set at 2.0 mm, the scores in Groups I, II, and III were significantly greater than that Group IV (p < 0.05), although there were no significant differences between Groups I and IV at a 3.0-mm deep vacant space. The expression levels of type-2 collagen in Groups II and III were significantly higher (p < 0.05) than that in Group IV. Conclusions The 1.0-mm thick DN gel sheet had the same ability to induce hyaline cartilage regeneration as the 5.0-mm thick DN gel plug. However, the induction ability of the 0.5-mm thick sheet was significantly lower when compared with the 1.0-mm thick gel sheet. The 1.0-mm DN gel sheet is a promising device to establish a cell-free cartilage regeneration strategy that minimizes bone loss from the gel implantation. PMID:23369101

  13. Soft fibrin gels promote selection and growth of tumorigenic cells

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Tan, Youhua; Zhang, Huafeng; Zhang, Yi; Xu, Pingwei; Chen, Junwei; Poh, Yeh-Chuin; Tang, Ke; Wang, Ning; Huang, Bo

    2012-08-01

    The identification of stem-cell-like cancer cells through conventional methods that depend on stem cell markers is often unreliable. We developed a mechanical method for selecting tumorigenic cells by culturing single cancer cells in fibrin matrices of ~100 Pa in stiffness. When cultured within these gels, primary human cancer cells or single cancer cells from mouse or human cancer cell lines grew within a few days into individual round colonies that resembled embryonic stem cell colonies. Subcutaneous or intravenous injection of 10 or 100 fibrin-cultured cells in syngeneic or severe combined immunodeficiency mice led to the formation of solid tumours at the site of injection or at the distant lung organ much more efficiently than control cancer cells selected using conventional surface marker methods or cultured on conventional rigid dishes or on soft gels. Remarkably, as few as ten such cells were able to survive and form tumours in the lungs of wild-type non-syngeneic mice.

  14. NMR relaxometry measurements of Fricke gel dosimeters exposed to neutrons

    NASA Astrophysics Data System (ADS)

    Marrale, Maurizio; Brai, Maria; Longo, Anna; Gallo, Salvatore; Tomarchio, Elio; Tranchina, Luigi; Gagliardo, Cesare; D'Errico, Francesco

    2014-11-01

    Fricke infused gel matrices offer several features making them suitable for dosimetric applications; among these there are tissue equivalence, low cost and ease of preparation. Their nuclear magnetic resonance (NMR) relaxation properties can be used as a radiation detector for the dosimetry of beams used in cancer therapy. In recent years neutron capture therapy has been resumed for the treatment of various types of cancer and it requires three-dimensional mapping of the neutron fields. In this work, we investigated this particular application through NMR relaxometry and MR imaging of Fricke gels exposed to neutrons. We analyzed both the R1 and R2 relaxation rates, which relate to the longitudinal T1 and transversal T2 relaxation times. In particular, we found that the relaxation rate R2 does not depend on the neutron fluence, whereas the relaxation rate R1 increases linearly with the fluence. The magnetic resonance imaging acquisitions showed that T1-weighted images allow the characterization of samples exposed to different neutron fluences.

  15. Statistical physics of polymer gels

    NASA Astrophysics Data System (ADS)

    Panyukov, Sergei; Rabin, Yitzhak

    1996-05-01

    This work presents a comprehensive analysis of the statistical mechanics of randomly cross-linked polymer gels, starting from a microscopic model of a network made of instantaneously cross-linked Gaussian chains with excluded volume, and ending with the derivation of explicit expressions for the thermodynamic functions and for the density correlation functions which can be tested by experiments. Using replica field theory we calculate the mean field density in replica space and show that this solution contains statistical information about the behavior of individual chains in the network. The average monomer positions change affinely with macroscopic deformation and fluctuations about these positions are limited to length scales of the order of the mesh size. We prove that a given gel has a unique state of microscopic equilibrium which depends on the temperature, the solvent, the average monomer density and the imposed deformation. This state is characterized by the set of the average positions of all the monomers or, equivalently, by a unique inhomogeneous monomer density profile. Gels are thus the only known example of equilibrium solids with no long-range order. We calculate the RPA density correlation functions that describe the statistical properties of small deviations from the average density, due to both static spatial heterogeneities (which characterize the inhomogeneous equilibrium state) and thermal fluctuations (about this equilibrium). We explain how the deformation-induced anisotropy of the inhomogeneous equilibrium density profile is revealed by small angle neutron scattering and light scattering experiments, through the observation of the butterfly effect. We show that all the statistical information about the structure of polymer networks is contained in two parameters whose values are determined by the conditions of synthesis: the density of cross-links and the heterogeneity parameter. We find that the structure of instantaneously cross

  16. Separation of traces of metal ions from sodium matrices

    NASA Technical Reports Server (NTRS)

    Korkisch, J.; Orlandini, K. A.

    1969-01-01

    Method for isolating metal ion traces from sodium matrices consists of two extractions and an ion exchange step. Extraction is accomplished by using 2-thenoyltrifluoracetone and dithizone followed by cation exchange.

  17. ALGORITHM FOR THE EVALUATION OF REDUCED WIGNER MATRICES

    SciTech Connect

    Prezeau, G.; Reinecke, M.

    2010-10-15

    Algorithms for the fast and exact computation of Wigner matrices are described and their application to a fast and massively parallel 4{pi} convolution code between a beam and a sky is also presented.

  18. Morphic images of binary words and Parikh matrices

    NASA Astrophysics Data System (ADS)

    Isawasan, Pradeep; Venkat, Ibrahim; Subramanian, K. G.; Sarmin, Nor Haniza

    2014-07-01

    A word is a finite sequence of symbols. Parikh matrix of a word, introduced by Mateescu et al (2000), has become an effective tool in the study of certain numerical properties of words based on subwords. There have been several investigations on various properties of Parikh matrices such as M-ambiguity, M-equivalence, subword equalities and inequalities, commutativity and so on. Recently, Parikh matrices of words that are images under certain morphisms have been studied for their properties. On the other hand, Parikh matrices of words involving a certain ratio property called weak-ratio property have been investigated by Subramanian et al (2009). Here we consider two special morphisms called Fibonacci and Tribonacci morphisms and obtain properties of Parikh matrices of images of binary words under these morphisms, utilizing the notion of weak-ratio property.

  19. Spectral density of a Wishart model for nonsymmetric correlation matrices

    NASA Astrophysics Data System (ADS)

    Vinayak

    2013-10-01

    The Wishart model for real symmetric correlation matrices is defined as W=AAt, where matrix A is usually a rectangular Gaussian random matrix and At is the transpose of A. Analogously, for nonsymmetric correlation matrices, a model may be defined for two statistically equivalent but different matrices A and B as ABt. The corresponding Wishart model, thus, is defined as C=ABtBAt. We study the spectral density of C for the case when A and B are not statistically independent. The ensemble average of such nonsymmetric matrices, therefore, does not simply vanishes to a null matrix. In this paper we derive a Pastur self-consistent equation which describes spectral density of C at large matrix dimension. We complement our analytic results with numerics.

  20. Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices

    ERIC Educational Resources Information Center

    Glaister, P.

    2008-01-01

    The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.

  1. Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A.

    1980-01-01

    This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

  2. Synbiotic matrices derived from plant oligosaccharides and polysaccharides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A porous synbiotic matrix was prepared by lyophilization of alginate and pectin or fructan oligosaccharides and polysaccharides cross-linked with calcium. These synbiotic matrices were excellent physical structures to support the growth of Lactobacillus acidophilus (1426) and Lactobacillus reuteri (...

  3. P03-based precession-nutation matrices

    NASA Astrophysics Data System (ADS)

    Wallace, P.; Capitaine, N.

    2006-10-01

    The IAU WG on precession and the ecliptic has recommended the adoption of the P03 models of Capitaine et al. (2003). We discuss methods for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. The equinox based NPB transformation can be formed using various sequences of rotations, while the CIO based transformation can be formed using series for the X, Y coordinates of the celestial intermediate pole (CIP) and for the CIO locator s; also, either matrix can be computing using series for the x, y, z components of the "rotation vector". Common to both methods is the CIP, which forms the bottom row of the transformation matrix. In the case of the CIO based transformation, the CIO is the top row of the NPB matrix, whereas in the equinox based case it enters via the GST formulation in the form of the equation of the origins (EO). The EO is the difference between ERA and GST and equivalently the distance between the CIO and equinox. The choice of method is dictated by considerations of internal consistency, flexibility and ease of use; the different ways agree at the level of a few microarcseconds over several centuries, and consume similar computing resources.

  4. Comparison of eigensolvers for symmetric band matrices

    PubMed Central

    Moldaschl, Michael; Gansterer, Wilfried N.

    2014-01-01

    We compare different algorithms for computing eigenvalues and eigenvectors of a symmetric band matrix across a wide range of synthetic test problems. Of particular interest is a comparison of state-of-the-art tridiagonalization-based methods as implemented in Lapack or Plasma on the one hand, and the block divide-and-conquer (BD&C) algorithm as well as the block twisted factorization (BTF) method on the other hand. The BD&C algorithm does not require tridiagonalization of the original band matrix at all, and the current version of the BTF method tridiagonalizes the original band matrix only for computing the eigenvalues. Avoiding the tridiagonalization process sidesteps the cost of backtransformation of the eigenvectors. Beyond that, we discovered another disadvantage of the backtransformation process for band matrices: In several scenarios, a lot of gradual underflow is observed in the (optional) accumulation of the transformation matrix and in the (obligatory) backtransformation step. According to the IEEE 754 standard for floating-point arithmetic, this implies many operations with subnormal (denormalized) numbers, which causes severe slowdowns compared to the other algorithms without backtransformation of the eigenvectors. We illustrate that in these cases the performance of existing methods from Lapack and Plasma reaches a competitive level only if subnormal numbers are disabled (and thus the IEEE standard is violated). Overall, our performance studies illustrate that if the problem size is large enough relative to the bandwidth, BD&C tends to achieve the highest performance of all methods if the spectrum to be computed is clustered. For test problems with well separated eigenvalues, the BTF method tends to become the fastest algorithm with growing problem size. PMID:26594079

  5. Radiative Properties of Silica Nanoporous Matrices

    NASA Astrophysics Data System (ADS)

    Lallich, Sylvain; Enguehard, Franck; Baillis, Dominique

    2008-08-01

    Superinsulating materials are currently of much interest because of the price of energy on the one hand and CO2 emissions attributed to offices and houses cooling and heating on the other hand. In this work, we aim at understanding and modeling the radiative transfer within silica nanoporous matrices that are the principal components of nanoporous superinsulating materials. We first elaborate samples of various thicknesses from a pyrogenic silica powder. These samples are characterized using two spectrophotometers on the whole wavelength range [250 nm; 20 μm]. Using a parameter identification technique, we compute the radiative properties of the various samples. Then, our samples being made of packed quasi-spherical particles, we use the Mie theory to model the radiative properties of these materials. Due to the observed discrepancies between the experimental radiative properties and those computed from the Mie theory with a uniform value of 10 nm for the scatterer diameter (value derived from TEM images), we determine an effective scatterer diameter that allows a good agreement between the experimental radiative properties and the Mie results. Nevertheless, in the short wavelength range, the Mie theory gives results that significantly differ from the experimental radiative properties. This behavior is attributed to structure effects as the wavelength is of the same order of magnitude as the diameter of the scatterer that is now regarded as an aggregate of nanoparticles. Hence, to take into account these effects, we use the discrete dipole approximation (DDA). The DDA extinction coefficient spectra appear to be much closer to the experimental results than the Mie spectra, and these first results are quite encouraging.

  6. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, R.F.; Welch, M.R.; Groeneveld, D.P.; Branson, F.A.

    1988-01-01

    Much of the floor of the Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first was the filter-paper method, which uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base 10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1 m depths derived by using the hand auger and filter paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter paper method could be obtained 90 to 95% of the time in soils where water content was less than field capacity. The greatest errors occurred at depths where there was a distinct transition between soils of different textures. (Lantz-PTT)

  7. Boundary transfer matrices and boundary quantum KZ equations

    SciTech Connect

    Vlaar, Bart

    2015-07-15

    A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.

  8. Facile Routes to Th(IV), U(IV), and Np(IV) Phosphites and Phosphates

    SciTech Connect

    Villa, Eric M.; Wang, Shuao; Alekseev, Evgeny V.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2011-08-05

    Three actinide(IV) phosphites and a NpIV phosphate, AnIV(HPO₃)₂(H₂O)₂ (An = Th, U, Np) and Cs[Np(H1.5PO₄)(PO₄)]₂, respectively, were synthesized using mild hydrothermal conditions. The first three phases are isotypic and were obtained using similar reaction conditions. Cs[Np(H1.5PO₄)(PO₄)]₂ was synthesized using an analogous method to that of Np(HPO₃)₂(H₂O)₂. However, this fourth phase is quite different in comparison to the other phases in both composition and structure. The structure of Cs[Np(H1.5PO₄)(PO₄)]₂ is constructed from double layers of neptunium(IV) phosphate with caesium cations in the interlayer region. In contrast, An(HPO₃)₂(H₂O)₂ (An = Th, U, Np) form dense 3D networks. The actinide contraction is detected in variety of metrics obtained from single-crystal X-ray diffraction data. Changes in the oxidation state of the neptunium starting materials yield different products.

  9. On Fluctuations of Eigenvalues of Random Band Matrices

    NASA Astrophysics Data System (ADS)

    Shcherbina, M.

    2015-10-01

    We consider the fluctuations of linear eigenvalue statistics of random band matrices whose entries have the form with i.i.d. possessing the th moment, where the function u has a finite support , so that M has only nonzero diagonals. The parameter b (called the bandwidth) is assumed to grow with n in a way such that . Without any additional assumptions on the growth of b we prove CLT for linear eigenvalue statistics for a rather wide class of test functions. Thus we improve and generalize the results of the previous papers (Jana et al., arXiv:1412.2445; Li et al. Random Matrices 2:04, 2013), where CLT was proven under the assumption . Moreover, we develop a method which allows to prove automatically the CLT for linear eigenvalue statistics of the smooth test functions for almost all classical models of random matrix theory: deformed Wigner and sample covariance matrices, sparse matrices, diluted random matrices, matrices with heavy tales etc.

  10. Binary matrices, decomposition and multiply-add architectures

    NASA Astrophysics Data System (ADS)

    Sarukhanian, Hakob; Agaian, Sos S.; Astola, Jaakko T.; Egiazarian, Karen O.

    2003-05-01

    Binary matrices or (+/-1)-matrices have found numerous applications in coding, signal processing, and communications. In this paper, a general and efficient algorithm of decomposition of binary matrices is developed. As a special case, Hadamard matrices are considered. The proposed scheme requires no zero padding of the input data. The problem of the construction of 4n-point Hadamard transform is related to the Hadamard problem: the question of existence of Hadamard matrices. (It is not proved whether for every integer n, there exists an orthogonal 4n×4n matrix with elements +/-1). The number of real operation in developed algorithms is reduced from 0(N2) to 0(Nlog2N). Comparisons revealing the efficiency of the proposed algorithms with respect to the known ones are given. In particular, it is demonstrated that, in typical applications, the proposed algorithm I s more efficient than the conventional Walsh Hadamard transform. Note that for Hadamard matrices of orders >=96 the general algorithm is more efficient than the classical Walsh-Hadamard transform whose order is a power of two. The algorithm has a simple and symmetric structure. The results of numerical examples are presented.

  11. Action recognition from video using feature covariance matrices.

    PubMed

    Guo, Kai; Ishwar, Prakash; Konrad, Janusz

    2013-06-01

    We propose a general framework for fast and accurate recognition of actions in video using empirical covariance matrices of features. A dense set of spatio-temporal feature vectors are computed from video to provide a localized description of the action, and subsequently aggregated in an empirical covariance matrix to compactly represent the action. Two supervised learning methods for action recognition are developed using feature covariance matrices. Common to both methods is the transformation of the classification problem in the closed convex cone of covariance matrices into an equivalent problem in the vector space of symmetric matrices via the matrix logarithm. The first method applies nearest-neighbor classification using a suitable Riemannian metric for covariance matrices. The second method approximates the logarithm of a query covariance matrix by a sparse linear combination of the logarithms of training covariance matrices. The action label is then determined from the sparse coefficients. Both methods achieve state-of-the-art classification performance on several datasets, and are robust to action variability, viewpoint changes, and low object resolution. The proposed framework is conceptually simple and has low storage and computational requirements making it attractive for real-time implementation. PMID:23508265

  12. Quantitative Analysis of Microbicide Concentrations in Fluids, Gels and Tissues Using Confocal Raman Spectroscopy

    PubMed Central

    Chuchuen, Oranat; Henderson, Marcus H.; Sykes, Craig; Kim, Min Sung; Kashuba, Angela D. M.; Katz, David F.

    2013-01-01

    Topical vaginal anti-HIV microbicides are an important focus in female-based strategies to prevent the sexual transmission of HIV. Understanding microbicide pharmacokinetics is essential to development, characterization and implementation of efficacious microbicide drug delivery formulations. Current methods to measure drug concentrations in tissue (e.g., LC-MS/MS, liquid chromatography coupled with tandem mass spectrometry) are highly sensitive, but destructive and complex. This project explored the use of confocal Raman spectroscopy to detect microbicide drugs and to measure their local concentrations in fluids, drug delivery gels, and tissues. We evaluated three candidate microbicide drugs: tenofovir, Dapivirine and IQP-0528. Measurements were performed in freshly excised porcine buccal tissue specimens, gel vehicles and fluids using two Horiba Raman microscopes, one of which is confocal. Characteristic spectral peak calibrations for each drug were obtained using serial dilutions in the three matrices. These specific Raman bands demonstrated strong linear concentration dependences in the matrices and were characterized with respect to their unique vibrational signatures. At least one specific Raman feature was identified for each drug as a marker band for detection in tissue. Sensitivity of detection was evaluated in the three matrices. A specific peak was also identified for tenofovir diphosphate, the anti-HIV bioactive product of tenofovir after phosphorylation in host cells. Z-scans of drug concentrations vs. depth in excised tissue specimens, incubated under layers of tenofovir solution in a Transwell assay, showed decreasing concentration with depth from the surface into the tissue. Time-dependent concentration profiles were obtained from tissue samples incubated in the Transwell assay, for times ranging 30 minutes - 6 hours. Calibrations and measurements from tissue permeation studies for tenofovir showed good correlation with gold standard LC-MS/MS data

  13. Intrarectal Lidocaine-Diltiazem-Meperidine Gel for Transrectal Ultrasound Guided Prostate Biopsy

    PubMed Central

    Imani, Farsad; Moghaddam, Yasaman; Shariat Moharari, Reza; Etezadi, Farhad; Khajavi, Mohammad Reza; Hosseini, Seyed Reza

    2015-01-01

    Background: TRUS-guided needle biopsy of the prostate gland is the current standard method used for diagnosis of prostate cancer. Pain control during this procedure is through the use of i.v. sedation or local anaesthetic (LA), depending on clinician preference. Objectives: The aim of this study was to evaluate the effectiveness of intrarectal lidocaine, lidocaine-diltiazem and lidocaine-meperidine-diltiazem gel for anesthetizing transrectal ultrasound guided prostate biopsy. Patients and Methods: In a randomized double-blind clinical trial, 100 consecutive patients were divided into three groups. The patients received one of the gels before transrectal ultrasound guided prostate needle biopsy: group A, intrarectal and perianal lidocaine, gel 1 g; group B, intrarectal lidocaine gel, 1 g, + perianal diltiazem, 1 g; group C, intrarectal lidocaine gel, 1 g, + meperidine, 25 mg, and perianal diltiazem, 1 g. Visual analog pain scale was used to estimate pain during probe insertion and biopsy. Heart rate and blood pressure during probe insertion and biopsy were recorded too. Results: The mean of visual analog pain scale was 4.5 in group A, 3.5 in group B, and 2.0 in group C during probe insertion (P value = 0.01). The mean of visual analog pain scale was 5.1 in group A, 3.5 group B, and 2.5 in group C during biopsy (P value = 0.001). The groups were comparable for patients' age, weight, serum prostate-specific antigen (PSA), and prostate size (P > 0.05). No side effects of meperidine and lidocaine including drowsiness, dizziness, tinnitus and light-headedness or requiring assistance for activity were noted. Conclusions: Lidocaine-meperidine-diltiazem gel provides significantly better pain control than lidocaine-diltiazem gel and lidocaine gel alone during transrectal ultrasound guided prostate biopsy and probe insertion. This mixture gel is safe, easy to administer and well accepted by patients. PMID:26161317

  14. Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest

    NASA Astrophysics Data System (ADS)

    Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T.

    2014-05-01

    The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of

  15. Nonlinear elasticity of alginate gels

    NASA Astrophysics Data System (ADS)

    Hashemnejad, Seyed Meysam; Kundu, Santanu

    Alginate is a naturally occurring anionic polysaccharide extracted from brown algae. Because of biocompatibility, low toxicity, and simple gelation process, alginate gels are used in biomedical and food applications. Here, we report the rheological behavior of ionically crosslinked alginate gels, which are obtained by in situ gelation of alginates with calcium salts, in between two parallel plates of a rheometer. Strain stiffening behavior was captured using large amplitude oscillatory shear (LAOS) experiments. In addition, negative normal stress was observed for these gels, which has not been reported earlier for any polysaccharide networks. The magnitude of negative normal stress increases with applied strain and can exceed that of the shear stress at large strain. Rheological results fitted with a constitutive model that considers both stretching and bending of chains indicate that nonlinearity is likely related to the stretching of the chains between the crosslink junctions. The results provide an improved understanding of the deformation mechanism of ionically crosslinked alginate gel and the results will be important in developing synthetic extracellular matrix (ECM) from these materials.

  16. Controlling the porosity of microporous silica by sol-gel processing using an organic template approach

    SciTech Connect

    Lu, Y.; Cao, G.Z.; Kale, R.P.; Delattre, L.; Lopez, G.P.; Brinker, C.J. |

    1996-12-31

    The authors use an organic template approach to prepare microporous silica with controlled pore size and narrow pore size distributions. This was accomplished by fabricating relatively dense hybrid silica matrices incorporating organic template ligands by sol-gel synthesis and then removing the organic ligands to create a microporous silica network. Comparison of computer simulation results and experimental data indicated that using this fugitive template approach, pore volume can be controlled by the amount of organic template added to the system, and pore size can be controlled by the size of the organic ligands.

  17. Excitation of heliumlike B IV

    NASA Astrophysics Data System (ADS)

    Kolk, K.-H.; Koenig, R.; Kunze, H.-J.

    1986-01-01

    Measurements are reported for line-intensity ratios emitted from heliumlike B IV ions in a plasma with electron density, N(e) = 1.5 x 10 to the 16th/cu cm and electron temperature, kT(e) = 175 eV. The plasma was produced in a theta-pinch discharge. The analysis supports theoretical excitation rates calculated in the distorted-wave approximation, which include the effect of resonances.

  18. Crystalline Colloidal Arrays in Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Sunkara, Hari B.; Penn, B. G.; Frazier, D. O.; Ramachandran, N.

    1997-01-01

    matrices, the factors which affect the optical diffraction qualities of resulting polymer films, and methods to improve the efficiencies of solid optical filters. Before this, we also present the experimental demonstration, of controlling the optical diffraction intensities from aqueous CCA dispersions by varying the temperature, which establishes the feasibility of fabricating all-optical switching devices with nonlinear periodic array structures.

  19. Calculating Percent Gel For Process Control

    NASA Technical Reports Server (NTRS)

    Webster, Charles Neal; Scott, Robert O.

    1988-01-01

    Reaction state of thermosetting resin tracked to assure desired properties. Rate of gel determined as function of temperature by measuring time to gel of part of graphite fabric impregnated with Hexcel R120 (or equivalent) phenolic resin.

  20. The influence of surfactants on the roughness of titania sol-gel films

    SciTech Connect

    Medina-Valtierra, Jorge . E-mail: jormeval@yahoo.com; Frausto-Reyes, Claudio . E-mail: cfraus@cio.mx; Calixto, Sergio . E-mail: scalixto@cio.mx; Bosch, Pedro . E-mail: lacv@xanum.uam.mx

    2007-03-15

    Substrate dipping in a composite sol-gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO{sub 2}) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol-gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV-vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO{sub 2} film was obtained with a short immersion of fiberglass into the sol-gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 deg. C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO{sub 2} films prepared from the sol-gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 {mu}m. Smooth TiO{sub 2} films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO{sub 2} films can enhance the inherent photocatalytic activity.

  1. Effect of a gel containing pilocarpine on vaginal atrophy in castrated rats

    PubMed Central

    de Sousa-Lages, Cristina A.; de Deus-Lages, Lívio P.; de Sousa, Gabriela V.; de Moura-Leal, Adinaide C.; Conde, Airton Mendes; Costa-Silva, Danylo Rafhael; da Conceição Barros-Oliveira, Maria; Borges, Carine Soares; Escórcio-Dourado, Carla Solange; Sampaio, Fabiane A.; Cunha-Nunes, Lívio C.; da-Silva, Benedito B.

    2016-01-01

    OBJECTIVES: To evaluate the effect of Carbopol gel formulations containing pilocarpine on the morphology and morphometry of the vaginal epithelium of castrated rats. METHODS: Thirty-one female Wistar-Hannover rats were randomly divided into four groups: the control Groups I (n=7, rats in persistent estrus; positive controls) and II (n=7, castrated rats, negative controls) and the experimental Groups, III (n=8) and IV (n=9). Persistent estrus (Group I) was achieved with a subcutaneous injection of testosterone propionate on the second postnatal day. At 90 days postnatal, rats in Groups II, III and IV were castrated and treated vaginally for 14 days with Carbopol gel (vehicle alone) or Carbopol gel containing 5% and 15% pilocarpine, respectively. Next, all of the animals were euthanized and their vaginas were removed for histological evaluation. A non-parametric test with a weighted linear regression model was used for data analysis (p<0.05). RESULTS: The morphological evaluation showed maturation of the vaginal epithelium with keratinization in Group I, whereas signs of vaginal atrophy were present in the rats of the other groups. Morphometric examinations showed mean thickness values of the vaginal epithelium of 195.10±12.23 μm, 30.90±1.14 μm, 28.16±2.98 μm and 29.84±2.30 μm in Groups I, II, III and IV, respectively, with statistically significant differences between Group I and the other three groups (p<0.0001) and no differences between Groups II, III and IV (p=0.0809). CONCLUSION: Topical gel formulations containing pilocarpine had no effect on atrophy of the vaginal epithelium in the castrated female rats. PMID:27276400

  2. Characteristics of platelet gels combined with silk

    PubMed Central

    Pallotta, Isabella; Kluge, Jonathan A.; Moreau, Jodie; Calabrese, Rossella

    2014-01-01

    Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact. PMID:24480538

  3. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  4. A clarified gel for crystal growth

    NASA Technical Reports Server (NTRS)

    Barber, P. G.; Simpson, N. R.

    1985-01-01

    A procedure for preparing clarified sodium silicate gels suitable for crystal growth is described. In the method described here, the silicate stock is clarified by pretreating it with cation exchange resins before preparing the gels. Also, a modified recipe is proposed for preparing gels to achieve improved transparency.

  5. Characteristics of platelet gels combined with silk.

    PubMed

    Pallotta, Isabella; Kluge, Jonathan A; Moreau, Jodie; Calabrese, Rossella; Kaplan, David L; Balduini, Alessandra

    2014-04-01

    Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel-forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact. PMID:24480538

  6. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen

    1995-01-01

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

  7. Role of alkyl alcohol on viscosity of silica-based chemical gels for decontamination of highly radioactive nuclear facilities

    SciTech Connect

    Choi, B. S.; Yoon, S. B.; Jung, C. H.; Lee, K. W.; Moon, J. K.

    2012-07-01

    Silica-based chemical gel for the decontamination of nuclear facilities was prepared by using fumed silica as a viscosifier, a 0.5 M Ce (IV) solution dissolved in concentrated nitric acid as a chemical decontamination agent, and tripropylene glycol butyl ether (TPGBE) as a co-viscosifier. A new effective strategy for the preparation of the chemical gel was investigated by introducing the alkyl alcohols as organic solvents to effectively dissolve the co-viscosifier. The mixture solution of the co-viscosifier and alkyl alcohols was more effective in the control of viscosity than that of the co-viscosifier only in gel. Here, the alkyl alcohols played a key role as an effective dissolution solvent for the co-viscosifier in the preparation of the chemical gel, resulting in a reducing of the amount of the co-viscosifier and gel time compared with that of the chemical gel prepared without the alkyl alcohols. It was considered that the alkyl alcohols contributed to the effective dissolution of the co-viscosifier as well as the homogeneous mixing in the formation of the gel, while the co-viscosifier in an aqueous media of the chemical decontamination agent solution showed a lower solubility. The decontamination efficiency of the chemical gels prepared in this work using a multi-channel analyzer (MCA) showed a high decontamination efficiency of over ca. 94% and ca. 92% for Co-60 and Cs-137 contaminated on surface of the stainless steel 304, respectively. (authors)

  8. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, Reuben F.; Welch, Michael R.; Groeneveld, David P.; Branson, Farrel A.

    1989-01-01

    Much of the floor of Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first, the filter-paper method, uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The previously published calibration relations used to estimate soil matric potential from the water content of the filter papers were modified on the basis of current laboratory data. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base-10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. The slope and intercepts of this function vary with the texture and saturation capacity of the soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1-m depth intervals derived by using the hand auger and filter-paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter-paper method could be obtained 90 to 95 percent of the

  9. Test Review: Advanced Clinical Solutions for WAIS-IV and WMS-IV

    ERIC Educational Resources Information Center

    Chu, Yiting; Lai, Mark H. C.; Xu, Yining; Zhou, Yuanyuan

    2012-01-01

    The authors review the "Advanced Clinical Solutions for WAIS-IV and WMS-IV". The "Advanced Clinical Solutions (ACS) for the Wechsler Adult Intelligence Scale-Fourth Edition" (WAIS-IV; Wechsler, 2008) and the "Wechsler Memory Scale-Fourth Edition" (WMS-IV; Wechsler, 2009) was published by Pearson in 2009. It is a clinical tool for extending the…

  10. Randomized Algorithms for Matrices and Data

    NASA Astrophysics Data System (ADS)

    Mahoney, Michael W.

    2012-03-01

    This chapter reviews recent work on randomized matrix algorithms. By “randomized matrix algorithms,” we refer to a class of recently developed random sampling and random projection algorithms for ubiquitous linear algebra problems such as least-squares (LS) regression and low-rank matrix approximation. These developments have been driven by applications in large-scale data analysis—applications which place very different demands on matrices than traditional scientific computing applications. Thus, in this review, we will focus on highlighting the simplicity and generality of several core ideas that underlie the usefulness of these randomized algorithms in scientific applications such as genetics (where these algorithms have already been applied) and astronomy (where, hopefully, in part due to this review they will soon be applied). The work we will review here had its origins within theoretical computer science (TCS). An important feature in the use of randomized algorithms in TCS more generally is that one must identify and then algorithmically deal with relevant “nonuniformity structure” in the data. For the randomized matrix algorithms to be reviewed here and that have proven useful recently in numerical linear algebra (NLA) and large-scale data analysis applications, the relevant nonuniformity structure is defined by the so-called statistical leverage scores. Defined more precisely below, these leverage scores are basically the diagonal elements of the projection matrix onto the dominant part of the spectrum of the input matrix. As such, they have a long history in statistical data analysis, where they have been used for outlier detection in regression diagnostics. More generally, these scores often have a very natural interpretation in terms of the data and processes generating the data. For example, they can be interpreted in terms of the leverage or influence that a given data point has on, say, the best low-rank matrix approximation; and this

  11. Calibration and temperature correction of heat dissipation matric potential sensors

    USGS Publications Warehouse

    Flint, A.L.; Campbell, G.S.; Ellett, K.M.; Calissendorff, C.

    2002-01-01

    This paper describes how heat dissipation sensors, used to measure soil water matric potential, were analyzed to develop a normalized calibration equation and a temperature correction method. Inference of soil matric potential depends on a correlation between the variable thermal conductance of the sensor's porous ceramic and matric poten-tial. Although this correlation varies among sensors, we demonstrate a normalizing procedure that produces a single calibration relationship. Using sensors from three sources and different calibration methods, the normalized calibration resulted in a mean absolute error of 23% over a matric potential range of -0.01 to -35 MPa. Because the thermal conductivity of variably saturated porous media is temperature dependent, a temperature correction is required for application of heat dissipation sensors in field soils. A temperature correction procedure is outlined that reduces temperature dependent errors by 10 times, which reduces the matric potential measurement errors by more than 30%. The temperature dependence is well described by a thermal conductivity model that allows for the correction of measurements at any temperature to measurements at the calibration temperature.

  12. On pseudo-stochastic matrices and pseudo-positive maps

    NASA Astrophysics Data System (ADS)

    Chruściński, D.; Man'ko, V. I.; Marmo, G.; Ventriglia, F.

    2015-11-01

    Stochastic matrices and positive maps in matrix algebras have proved to be very important tools for analysing classical and quantum systems. In particular they represent a natural set of transformations for classical and quantum states, respectively. Here we introduce the notion of pseudo-stochastic matrices and consider their semigroup property. Unlike stochastic matrices, pseudo-stochastic matrices are permitted to have matrix elements which are negative while respecting the requirement that the sum of the elements of each column is one. They also allow for convex combinations, and carry a Lie group structure which permits the introduction of Lie algebra generators. The quantum analog of a pseudo-stochastic matrix exists and is called a pseudo-positive map. They have the property of transforming a subset of quantum states (characterized by maximal purity or minimal von Neumann entropy requirements) into quantum states. Examples of qubit dynamics connected with ‘diamond’ sets of stochastic matrices and pseudo-positive maps are dealt with.

  13. Efficient computer algebra algorithms for polynomial matrices in control design

    NASA Technical Reports Server (NTRS)

    Baras, J. S.; Macenany, D. C.; Munach, R.

    1989-01-01

    The theory of polynomial matrices plays a key role in the design and analysis of multi-input multi-output control and communications systems using frequency domain methods. Examples include coprime factorizations of transfer functions, cannonical realizations from matrix fraction descriptions, and the transfer function design of feedback compensators. Typically, such problems abstract in a natural way to the need to solve systems of Diophantine equations or systems of linear equations over polynomials. These and other problems involving polynomial matrices can in turn be reduced to polynomial matrix triangularization procedures, a result which is not surprising given the importance of matrix triangularization techniques in numerical linear algebra. Matrices with entries from a field and Gaussian elimination play a fundamental role in understanding the triangularization process. In the case of polynomial matrices, matrices with entries from a ring for which Gaussian elimination is not defined and triangularization is accomplished by what is quite properly called Euclidean elimination. Unfortunately, the numerical stability and sensitivity issues which accompany floating point approaches to Euclidean elimination are not very well understood. New algorithms are presented which circumvent entirely such numerical issues through the use of exact, symbolic methods in computer algebra. The use of such error-free algorithms guarantees that the results are accurate to within the precision of the model data--the best that can be hoped for. Care must be taken in the design of such algorithms due to the phenomenon of intermediate expressions swell.

  14. An alternative clean-up column for the determination of polychlorinated biphenyls in solid matrices.

    PubMed

    Ndunda, Elizabeth N; Madadi, Vincent O; Mizaikoff, Boris

    2015-12-01

    The need for continuous monitoring of polychlorinated biphenyls (PCBs) has necessitated the development of analytical techniques that are sensitive and selective with minimal reagent requirement. In light of this, we developed a column for clean-up of soil and sediment extracts, which is less demanding in terms of the amount of solvent and sorbent. The dual-layer column consists of acidified silica gel and molecularly imprinted polymers (MIPs). MIPs were synthesized via aqueous suspension polymerization using PCB 15 as the dummy template, 4-vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linker and the obtained particles characterized via SEM, BET, and batch rebinding assays. Pre-concentration of the spiked real-world water sample using MISPE gave recoveries between 85.2 and 104.4% (RSD < 8.69). On the other hand, the specific dual-layer column designed for clean-up of extracts from complex matrices provided recoveries of 91.6-102.5% (RSD < 4%) for spiked soil, which was comparable to clean-up using acidified silica (70.4-90.5%; RSD < 3.72%) and sulfoxide modified silica (89.7-103.0%; RSD < 13.0%). However, the polymers were reusable maintaining recoveries of 79.8-111.8% after 30 cycles of regeneration and re-use, thereby availing a cost-effective clean-up procedure for continuous monitoring of PCBs. Method detection limits were 0.01-0.08 ng g(-1) and 0.002-0.01 ng mL(-1) for solid matrices and water, respectively. PMID:26560633

  15. An improved mechanically durable electrophoresis gel matrix that is fully compatible with fluorescence-based protein detection technologies.

    PubMed

    Schulenberg, Birte; Arnold, Brad; Patton, Wayne F

    2003-07-01

    Unfortunately, conventional large-format polyacrylamide gels are mechanically fragile, often tearing during the subsequent manipulations required for visualization of the proteins. This problem is compounded when large-format two-dimensional gels are subjected to multiple staining procedures in order to detect different classes of proteins, such as total protein, phosphoproteins, and glycoproteins. A mechanically durable liquid polyacrylamide-based matrix has been developed that, upon polymerization, facilitates the handling of one-dimensional and two-dimensional gels. The matrix, referred to as Rhinohide liquid acrylamide, is stable as a refrigerated solution for up to one year, and forms a polymer-reinforced polyacrylamide gel suitable for electrophoresis, upon addition of catalysts. The matrix is superior to previously reported durable gel matrices in that it does not cause distortion of high-molecular-weight bands and does not suffer from other spot morphology artifacts, such as doubling of protein spots in the molecular weight dimension. The matrix is particularly valuable for the analysis of proteins applying multiple applications of fluorescent dyes, as required with serial staining of proteins for phosphorylation, glycosylation, and total protein expression, using Pro-Q Diamond phosphoprotein stain, Pro-Q Emerald glycoprotein stain and SYPRO Ruby protein gel stain, respectively. PMID:12872220

  16. The Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

    Lang, Michael; Fischer, Jakob; Werner, Marco; Sommer, Jens-Uwe

    2014-03-01

    The swelling equilibrium of Olympic gels is studied by Monte Carlo Simulations. We observe that gels consisting of flexible cyclic molecules of a higher degree of polymerization N show a smaller equilibrium swelling degree Q ~N - 0 . 28φ0- 0 . 72 for the same monomer volume fraction φ0 at network preparation. This observation is explained by a disinterpenetration process of overlapping non-concatenated polymers upon swelling. In the limit of a sufficiently large number of concatenations per cyclic molecule we expect that the equilibrium degree of swelling becomes proportional to φ0- 1 / 2 independent of N. Our results challenge current textbook models for the equilibrium degree of swelling of entangled polymer networks. Now at: Bio Systems Analysis Group, Jena Centre for Bioinformatics (JCB) and Department for Mathematics and Computer Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany.

  17. Supercoiling transformation of chemical gels.

    PubMed

    Asai, Makoto; Katashima, Takuya; Sakai, Takamasa; Shibayama, Mitsuhiro

    2015-09-28

    The swelling/deswelling behavior of chemical gels has been an unsolved problem disputed over for a long time. The Obukhov-Rubinstein-Colby model depicts the influence that swelling/deswelling has on elasticity, but its physical picture is too complicated to be sufficiently validated by experiment. In this study, we use molecular dynamics simulation to verify the validity of the molecular picture of network strands predicted by the Obukhov-Rubinstein-Colby model. We conclude that the physical picture of the Obukhov-Rubinstein-Colby model is reasonable, and furthermore the simulation can reveal the details of conformational changes in network strands during the supercoiling transformation. Our findings not only reveal the validity, but also give a better understanding of the dynamics of the swelling/deswelling behavior of chemical gels. PMID:26279149

  18. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

    The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

  19. Stage IV-S neuroblastoma. Results with definitive therapy

    SciTech Connect

    Stokes, S.H.; Thomas, P.R.; Perez, C.A.; Vietti, T.J.

    1984-05-15

    The results of management of 14 patients with Stage IV-S neuroblastoma are reported. The treatment policy, although not consistent over this time span, in general used a combination of radiotherapy and chemotherapy or infrequently one modality alone. Twelve of 14 (86%) survived more than 6 years. One patient, with a solitary mediastinal primary tumor, died of rapidly progressive disease at three months. The other death occurred in a 4.5-year-old presenting with hepatomegaly at diagnosis followed by skeletal dissemination 2.5 years later. Thirteen of the patients were younger than 1 year of age. Of the 11 patients that received radiotherapy, 4 experienced mild asymptomatic scoliosis or kyphoscoliosis at 3 to 12 years after initial therapy. A review of the literature indicates that spontaneous regression in this tumor is very frequent; therefore, it is recommended that for the common presentation of massive hepatomegaly in an infant, close observation is warranted, unless life threatening complications occur. However, initial therapeutic intervention may be indicated in those patients with life threatening presentations. This data did not substantiate the necessity for complete surgical excision of the primary tumor, as has been suggested by others.

  20. Multiscale modeling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Wallmersperger, Thomas; Wittel, Falk K.; Kröplin, Bernd H.

    2006-03-01

    Electrolyte polymer gels are a very attractive class of actuation materials with remarkable electronic and mechanical properties having a great similarity to biological contractile tissues. They consist of a polymer network with ionizable groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. Due to this capability, they can be used as actuators for technical applications, where large swelling and shrinkage is desired. In the present work chemically and electrically stimulated polymer gels in a solution bath are investigated. To describe the different complicated phenomena occurring in these gels adequately, the modeling can be conducted on different scales. Therefore, models based on the statistical theory and porous media theory, as well as a multi-field model and a discrete element formulation are derived. A refinement of the different theories from global macroscopic to microscopic are presented in this paper: The statistical theory is a macroscopic theory capable to describe the global swelling or bending e.g. of a gel film, while the general theory of porous media (TPM) is a macroscopic continuum theory which is based on the theory of mixtures extended by the concept of volume fractions. The TPM is a homogenized model, i.e. all geometrical and physical quantities can be seen as statistical averages of the real quantities. The presented chemo-electro-mechanical multi-field formulation is a mesoscopic theory. It is capable of giving the concentrations and the electric potential in the whole domain. Finally the (micromechanical) discrete element (DE) theory is employed. In this case, the continuum is represented by distributed particles with local interaction relations combined with balance equations for the chemical field. This method is predestined for problems involving large displacements, strains and discontinuities. The presented formulations are compared and conclusions on their

  1. Effect of propolis gel on the in vitro reduction of dentin permeability

    PubMed Central

    SALES-PERES, Silvia Helena de Carvalho; de CARVALHO, Flávia Negreiros; MARSICANO, Juliane Avansini; MATTOS, Maria Cecília; PEREIRA, José Carlos; FORIM, Moacir Rossi; da SILVA, Maria Fatima das Graças Fernandes

    2011-01-01

    Objective The aim of this study was to evaluate the capacity of potassium oxalate, fluoride gel and two kinds of propolis gel to reduce the hydraulic conductance of dentin, in vitro. Material and Methods The methodology used for the measurement of hydraulic conductance of dentin in the present study was based on a model proposed in literature. Thirty-six 1-mm-thick dentin discs, obtained from extracted human third molars were divided into 4 groups (n=9). The groups corresponded to the following experimental materials: GI-10% propolis gel, pH 4.1; GII-30% propolis gel; GIII-3% potassium oxalate gel, pH 4,1; and GIV-1.23% fluoride gel, pH 4.1, applied to the dentin under the following surface conditions: after 37% phosphoric acid and before 6% citric acid application. The occluding capacity of the dentin tubules was evaluated using scanning electron microscopy (SEM) at ×500, ×1,000 and ×2,000 magnifications. Data were analyzed statistically by two-way ANOVA and Tukey's test at 5% significance level. Results Groups I, II, III, IV did not differ significantly from the others in any conditions by reducing in hydraulic conductance. The active agents reduced dentin permeability; however they produced the smallest reduction in hydraulic conductance when compared to the presence of smear layer (P<0.05). The effectiveness in reducing dentin permeability did not differ significantly from 10% or 30% propolis gels. SEM micrographs revealed that dentin tubules were partially occluded after treatment with propolis. Conclusions Under the conditions of this study, the application of 10% and 30% propolis gels did not seem to reduce the hydraulic conductance of dentin in vitro, but it showed capacity of partially obliterating the dentin tubules. Propolis is used in the treatment of different oral problems without causing significant great collateral effects, and can be a good option in the treatment of patients with dentin sensitivity. PMID:21956588

  2. Large N matrices from a nonlocal spin system

    NASA Astrophysics Data System (ADS)

    Anninos, Dionysios; Hartnoll, Sean A.; Huijse, Liza; Martin, Victoria L.

    2015-10-01

    Large N matrices underpin the best understood models of emergent spacetime. We suggest that large N matrices can themselves be emergent from simple quantum mechanical spin models with finite dimensional Hilbert spaces. We exhibit the emergence of large N matrices in a nonlocal statistical physics model of order N2 Ising spins. The spin partition function is shown to admit a large N saddle described by a matrix integral, which we solve. The matrix saddle is dominant at high temperatures, metastable at intermediate temperatures and ceases to exist below a critical order one temperature. The matrix saddle is disordered in a sense we make precise and competes with ordered low energy states. We verify our analytic results by Monte Carlo simulation of the spin system.

  3. Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

  4. Stable viscosity matrices for systems of conservation laws

    NASA Astrophysics Data System (ADS)

    Majda, Andrew; Pego, Robert L.

    A natural class of appropriate viscosity matrices for strictly hyperbolic systems of conservation laws in one space dimension, u1 + f( u) x = 0, uɛRm, is studied. These matrices are admissible in the sense that small-amplitude shock wave solutions of the hyperbolic system are shown to be limits of smooth traveling wave solutions of the parabolic system ut + f( u) x = v( Dux) x as ifv → 0 if D is in this class. The class is determined by a linearized stability requirement: The Cauchy problem for the equation u1 + f'( u0) ux = vDuxx should be well posed in L2 uniformly in v as v → 0. Previous examples of inadmissible viscosity matrices are accounted for through violation of the stability criterion.

  5. Parikh matrices of words under a generalized Thue morphism

    NASA Astrophysics Data System (ADS)

    Subramanian, K. G.; Isawasan, Pradeep; Venkat, Ibrahim; Khader, Ahamad Tajudin

    2013-10-01

    Parikh matrix of a word w, which is a sequence of symbols from an alphabet, was introduced by Mateescu et al. (2001) to count certain subwords in the word w. Subsequently, several investigations on various properties of Parikh matrices have been done. Parikh matrices of words that involve certain weak ratio-property are investigated by Subramanian et al (2009). On the other hand a morphism f is a mapping on words u,v whose images f(u), f(v) are also words with the property that f(uv) = f(u)f(v). Thue morphism on a binary alphabet is a special kind of morphism. Here we consider a generalization of Thue morphism, introduced by Seebold (2003) but restricting it to three symbols. We obtain certain properties of images of binary words under this generalized Thue morphism and also of their Parikh matrices, in the context of the weak ratio-property.

  6. Selective gel system for permeability profile control

    SciTech Connect

    Shu, P.

    1990-02-27

    This patent describes a process for closing pores in a more permeable zone of a formation. It comprises: placing into an aqueous solution a first composition sufficient to form ex-situ a size selective, shear thinning first gel which comprises a xanthan biopolymer, and a transitional metal ion; placing into the aqueous solution a second composition sufficient to form thermally a second in-situ gel which is substantially more resistant to formation conditions than the first gel. The composition comprises an aldehyde, and a phenolic compound; allowing the aqueous solution sufficient time to form the ex-situ gel; and injecting the aqueous solution containing the gel into the permeable zone where it reheals, is heated by the formation and thereafter forms a solid gel substantially more resistant to formation conditions than the first gel.

  7. Full-ionic liquid gel electrolytes: Enhanced photovoltaic performances in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Li, Qinghua; Tang, Qunwei; He, Benlin; Yang, Peizhi

    2014-10-01

    Liquid electrolytes containing redox species have been widely used in dye-sensitized solar cells (DSSCs), whereas the volatility of organic solvents has been a tremendous obstacle for their commercial application. To assemble durable DSSCs, here we report the synthesis of full-ionic liquid electrolyte, in which 1-butyl-3-methylimidazolium nitrate is employed as solvent and 1-methyl-3-propylimidazolium iodide is iodide source. Using the imbibition performance of amphiphilic poly(acrylic acid/gelatin) [poly(AA/GR)] and poly(acrylic acid/cetyltrimethyl ammonium bromide) [poly(AA/CTAB)] matrices, full-ionic liquid electrolytes are imbibed into three-dimensional framework of poly(AA/GR) or poly(AA/CTAB) to form stable gel electrolytes. Room-temperature ionic conductivities as high as 17.82 and 18.44 mS cm-1 are recorded from full-ionic liquid imbibed poly(AA/GR) and poly(AA/CTAB) gel electrolytes, respectively. Promising power conversion efficiencies of 7.19% and 7.15% are determined from their DSSC devices in comparison with 6.55% and 6.12% from traditional acetonitrile-based poly(AA/GR) and poly(AA/CTAB) gel electrolytes, respectively. The new concept along with easy fabrication demonstrates the full-ionic liquid electrolytes to be good alternatives for robust gel electrolytes in quasi-solid-state DSSCs.

  8. Arrowheaded enhanced multivariance products representation for matrices (AEMPRM): Specifically focusing on infinite matrices and converting arrowheadedness to tridiagonality

    NASA Astrophysics Data System (ADS)

    Özdemir, Gizem; Demiralp, Metin

    2015-12-01

    In this work, Enhanced Multivariance Products Representation (EMPR) approach which is a Demiralp-and-his- group extension to the Sobol's High Dimensional Model Representation (HDMR) has been used as the basic tool. Their discrete form have also been developed and used in practice by Demiralp and his group in addition to some other authors for the decomposition of the arrays like vectors, matrices, or multiway arrays. This work specifically focuses on the decomposition of infinite matrices involving denumerable infinitely many rows and columns. To this end the target matrix is first decomposed to the sum of certain outer products and then each outer product is treated by Tridiagonal Matrix Enhanced Multivariance Products Representation (TMEMPR) which has been developed by Demiralp and his group. The result is a three-matrix- factor-product whose kernel (the middle factor) is an arrowheaded matrix while the pre and post factors are invertable matrices decomposed of the support vectors of TMEMPR. This new method is called as Arrowheaded Enhanced Multivariance Products Representation for Matrices. The general purpose is approximation of denumerably infinite matrices with the new method.

  9. Commutative law for products of infinitely large isotropic random matrices.

    PubMed

    Burda, Zdzislaw; Livan, Giacomo; Swiech, Artur

    2013-08-01

    Ensembles of isotropic random matrices are defined by the invariance of the probability measure under the left (and right) multiplication by an arbitrary unitary matrix. We show that the multiplication of large isotropic random matrices is spectrally commutative and self-averaging in the limit of infinite matrix size N→∞. The notion of spectral commutativity means that the eigenvalue density of a product ABC... of such matrices is independent of the order of matrix multiplication, for example, the matrix ABCD has the same eigenvalue density as ADCB. In turn, the notion of self-averaging means that the product of n independent but identically distributed random matrices, which we symbolically denote by AAA..., has the same eigenvalue density as the corresponding power A(n) of a single matrix drawn from the underlying matrix ensemble. For example, the eigenvalue density of ABCCABC is the same as that of A(2)B(2)C(3). We also discuss the singular behavior of the eigenvalue and singular value densities of isotropic matrices and their products for small eigenvalues λ→0. We show that the singularities at the origin of the eigenvalue density and of the singular value density are in one-to-one correspondence in the limit N→∞: The eigenvalue density of an isotropic random matrix has a power-law singularity at the origin ~|λ|(-s) with a power sε(0,2) when and only when the density of its singular values has a power-law singularity ~λ(-σ) with a power σ=s/(4-s). These results are obtained analytically in the limit N→∞. We supplement these results with numerical simulations for large but finite N and discuss finite-size effects for the most common ensembles of isotropic random matrices. PMID:24032775

  10. Universal microscopic correlation functions for products of truncated unitary matrices

    NASA Astrophysics Data System (ADS)

    Akemann, Gernot; Burda, Zdzislaw; Kieburg, Mario; Nagao, Taro

    2014-06-01

    We investigate the spectral properties of the product of M complex non-Hermitian random matrices that are obtained by removing L rows and columns of larger unitary random matrices uniformly distributed on the group U(N + L). Such matrices are called truncated unitary matrices or random contractions. We first derive the joint probability distribution for the complex eigenvalues of the product matrix for fixed N, L, and M, given by a standard determinantal point process in the complex plane. The weight however is non-standard and can be expressed in terms of the Meijer G-function. The explicit knowledge of all eigenvalue correlation functions and the corresponding kernel allows us to take various large N (and L) limits at fixed M. At strong non-unitarity, with L/N finite, the eigenvalues condense on a domain inside the unit circle. At the edge and in the bulk we find the same universal microscopic kernel as for a single complex non-Hermitian matrix from the Ginibre ensemble. At the origin we find the same new universality classes labeled by M as for the product of M matrices from the Ginibre ensemble. Keeping a fixed size of truncation, L, when N goes to infinity leads to weak non-unitarity, with most eigenvalues on the unit circle as for unitary matrices. Here we find a new microscopic edge kernel that generalizes the known results for M = 1. We briefly comment on the case when each product matrix results from a truncation of different size Lj.

  11. Antibacterial Peptide-Based Gel for Prevention of Medical Implanted-Device Infection

    PubMed Central

    Mateescu, Mihaela; Baixe, Sébastien; Garnier, Tony; Jierry, Loic; Ball, Vincent; Haikel, Youssef; Metz-Boutigue, Marie Hélène; Nardin, Michel; Schaaf, Pierre; Etienne, Olivier; Lavalle, Philippe

    2015-01-01

    Implanted medical devices are prone to infection. Designing new strategies to reduce infection and implant rejection are an important challenge for modern medicine. To this end, in the last few years many hydrogels have been designed as matrices for antimicrobial molecules destined to fight frequent infection found in moist environments like the oral cavity. In this study, two types of original hydrogels containing the antimicrobial peptide Cateslytin have been designed. The first hydrogel is based on alginate modified with catechol moieties (AC gel). The choice of these catechol functional groups which derive from mussel’s catechol originates from their strong adhesion properties on various surfaces. The second type of gel we tested is a mixture of alginate catechol and thiol-terminated Pluronic (AC/PlubisSH), a polymer derived from Pluronic, a well-known biocompatible polymer. This PlubisSH polymer has been chosen for its capacity to enhance the cohesion of the composition. These two gels offer new clinical uses, as they can be injected and jellify in a few minutes. Moreover, we show these gels strongly adhere to implant surfaces and gingiva. Once gelled, they demonstrate a high level of rheological properties and stability. In particular, the dissipative energy of the (AC/PlubisSH) gel detachment reaches a high value on gingiva (10 J.m-2) and on titanium alloys (4 J.m-2), conferring a strong mechanical barrier. Moreover, the Cateslytin peptide in hydrogels exhibited potent antimicrobial activities against P. gingivalis, where a strong inhibition of bacterial metabolic activity and viability was observed, indicating reduced virulence. Gel biocompatibility tests indicate no signs of toxicity. In conclusion, these new hydrogels could be ideal candidates in the prevention and/or management of periimplant diseases. PMID:26659616

  12. Antibacterial Peptide-Based Gel for Prevention of Medical Implanted-Device Infection.

    PubMed

    Mateescu, Mihaela; Baixe, Sébastien; Garnier, Tony; Jierry, Loic; Ball, Vincent; Haikel, Youssef; Metz-Boutigue, Marie Hélène; Nardin, Michel; Schaaf, Pierre; Etienne, Olivier; Lavalle, Philippe

    2015-01-01

    Implanted medical devices are prone to infection. Designing new strategies to reduce infection and implant rejection are an important challenge for modern medicine. To this end, in the last few years many hydrogels have been designed as matrices for antimicrobial molecules destined to fight frequent infection found in moist environments like the oral cavity. In this study, two types of original hydrogels containing the antimicrobial peptide Cateslytin have been designed. The first hydrogel is based on alginate modified with catechol moieties (AC gel). The choice of these catechol functional groups which derive from mussel's catechol originates from their strong adhesion properties on various surfaces. The second type of gel we tested is a mixture of alginate catechol and thiol-terminated Pluronic (AC/PlubisSH), a polymer derived from Pluronic, a well-known biocompatible polymer. This PlubisSH polymer has been chosen for its capacity to enhance the cohesion of the composition. These two gels offer new clinical uses, as they can be injected and jellify in a few minutes. Moreover, we show these gels strongly adhere to implant surfaces and gingiva. Once gelled, they demonstrate a high level of rheological properties and stability. In particular, the dissipative energy of the (AC/PlubisSH) gel detachment reaches a high value on gingiva (10 J.m-2) and on titanium alloys (4 J.m-2), conferring a strong mechanical barrier. Moreover, the Cateslytin peptide in hydrogels exhibited potent antimicrobial activities against P. gingivalis, where a strong inhibition of bacterial metabolic activity and viability was observed, indicating reduced virulence. Gel biocompatibility tests indicate no signs of toxicity. In conclusion, these new hydrogels could be ideal candidates in the prevention and/or management of periimplant diseases. PMID:26659616

  13. Taming Tin(IV) Polyazides.

    PubMed

    Campbell, Rory; Davis, Martin F; Fazakerley, Mathew; Portius, Peter

    2015-12-14

    The first charge-neutral Lewis base adducts of tin(IV) tetraazide, [Sn(N3)4(bpy)], [Sn(N3)4(phen)] and [Sn(N3)4(py)2], and the salt bis{bis(triphenylphosphine)iminium} hexa(azido)stannate [(PPN)2Sn(N3)6] (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; py = pyridine; PPN = N(PPh3)2) have been prepared using covalent or ionic azide-transfer reagents and ligand-exchange reactions. The azides were isolated on the 0.3 to 1 g scale and characterized by IR and NMR spectroscopies, microanalytical and thermal methods and their molecular structures determined by single-crystal XRD. All complexes have a distorted octahedral Sn[N]6 coordination geometry and possess greater thermal stability than their Si and Ge homologues. The nitrogen content of the adducts of up to 44% exceed any Sn(IV) compound known hitherto. PMID:26767331

  14. MECHANISM OF CHEMICAL MUTAGENESIS IV.

    PubMed Central

    Lorkiewicz, Z.; Szybalski, Waclaw

    1961-01-01

    Lorkiewicz, Z. (University of Wisconsin, Madison), and Waclaw Szybalski. Mechanism of chemical mutagenesis. IV. Reaction between triethylene melamine and nucleic acid components. J. Bacteriol. 82: 195–201. 1961.—Triethylene melamine interacts primarily with phosphorylated intracellular deoxyribonucleic acid (DNA) precursors and not with DNA. It was found by direct chemical and chromatographic analysis that only pyrimidine precursors of nucleic acids are attacked by triethylene melamine. In the course of the triethylene melamine-deoxycytidine reaction the mutagenicity of the reaction mixture is lost, but the mutagenicity of the triethylene melamine-thymidine reaction products significantly increases above that of the reaction substrates. Several steps are postulated to explain the mechanism of the triethylene melamine-initiated mutagenic reaction: (i) Reaction I, semireversible uptake of triethylene melamine; (ii) reaction II, chemical interaction between triethylene melamine and intracellular thymidine mono- or triphosphate with the production of a functional analogue of the latter; (iii) incorporation of this fraudulent analogue into the newly formed DNA strand; (iv) occurrence of self-perpetuating errors in the sequence of natural bases during subsequent rounds of replication of the analogue-containing DNA strand. It is postulated that the mechanism of mutagenic responses to different types of mutagens can fit either a simplified (mutagenic base analogues) or extended version (radiation) of this schema. PMID:16561917

  15. SAXS study on myoglobin embedded in amorphous saccharide matrices.

    PubMed

    Giuffrida, S; Panzica, M; Giordano, F M; Longo, A

    2011-09-01

    We report on Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin and met-myoglobin embedded in low hydrated matrices of four different saccharides (trehalose, sucrose, maltose and lactose). Results confirm the already reported occurrence of inhomogeneities, which are not peculiar of trehalose samples, but appear also in maltose and lactose, and in some cases also sucrose, being dependent on the sample hydration and on the presence of sodium dithionite. This behaviour confirms our previous interpretation about the nature of the inhomogeneities, and prompt it as a possible general behaviour for highly concentrated sugar matrices. PMID:21938613

  16. Computation of Dioptric and Magnification Matrices in Ophthalmic Lenses

    NASA Astrophysics Data System (ADS)

    Barbero, S.

    2014-06-01

    The diopter power and magnification matrices characterize the first-order properties of ophthalmic lenses for different gaze directions. Therefore an efficient method to compute them is highly valuable in ophthalmic lens design and optical performance simulations. I present a novel method to numerically compute these matrices in ophthalmic lenses comprising any set of arbitrary surfaces. The method is based on computing one base ray, along the gaze direction, and two rays close to it. These two rays are obtained varying a small parameter that indicates their separation from the base ray. The method was validated comparing the results with a single refractive surface where exact solutions are directly obtained.

  17. Random reverse-cyclic matrices and screened harmonic oscillator.

    PubMed

    Srivastava, Shashi C L; Jain, Sudhir R

    2012-04-01

    We have calculated the joint probability distribution function for random reverse-cyclic matrices and shown that it is related to an N-body exactly solvable model. We refer to this well-known model potential as a screened harmonic oscillator. The connection enables us to obtain all the correlations among the particle positions moving in a screened harmonic potential. The density of nontrivial eigenvalues of this ensemble is found to be of the Wigner form and admits a hole at the origin, in contrast to the semicircle law of the Gaussian orthogonal ensemble of random matrices. The spacing distributions assume different forms ranging from Gaussian-like to Wigner. PMID:22680453

  18. Synthesis of stiffness and mass matrices from experimental vibration modes.

    NASA Technical Reports Server (NTRS)

    Ross, R. G., Jr.

    1971-01-01

    With highly complex structures, it is sometimes desirable to derive a dynamic model of the system from experimental vibration data. This paper presents algorithms for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way which preserves the physical significance of the individual mass and stiffness elements. The synthesizing procedures allow for the incorporation of other mass and stiffness data, whether empirical or based on the analyst's insight. The mass and stiffness matrices are derived for a cantilever beam example and are compared with those obtained using earlier techniques.

  19. Derivation of mass and stiffness matrices from dynamic test data.

    NASA Technical Reports Server (NTRS)

    Thoren, A. R.

    1972-01-01

    A technique is described by which orthonormal modal vectors, computed from dynamic test response data, are used to derive mass, stiffness, and damping matrices for a discrete model of the distributed elastic system. Matrices thus computed from subsystems tests may be readily incorporated into larger system models. The method has been applied to a test of the Saturn V S-II stage LOX tank-engine support system. The dynamic responses of the discrete model are shown to correlate well with test data throughout the frequency range tested.

  20. Model updating based on sensitivities of system matrices

    NASA Technical Reports Server (NTRS)

    Huang, Hsin-Hsen; Craig, Roy R., Jr.

    1993-01-01

    A new approach, which allows the physical parameters to be adjusted and preserves the structural connectivity condition, is developed in this paper. This approach is based on the sensitivities of the mass and stiffness matrices with respect to physical parameters in an attempt to use test data to correct the analytical model. The analytical mass and stiffness matrices can be corrected simultaneously. The modal data of the updated model dramatically converges to that of the test model. A numerical example is presented to illustrate the feasibility of this approach. Comparisons with the other methods are also given.

  1. Wavelet Multifractal Detrended Fluctuation Analysis of Encryption and Decryption Matrices

    NASA Astrophysics Data System (ADS)

    Murguía, J. S.; Mejía Carlos, M.; Vargas-Olmos, C.; Ramírez-Torres, M. T.; Rosu, H. C.

    2013-09-01

    In this paper, we study in detail the multifractal features of the main matrices of an encryption system based on a rule-90 cellular automaton. For this purpose, we consider the scaling method known as the wavelet transform multifractal detrended fluctuation analysis (WT-MFDFA). In addition, we analyze the multifractal structure of the matrices of different dimensions, and find that there are minimal differences in all the examined multifractal quantities such as the multifractal support, the most frequent singularity exponent, and the generalized Hurst exponent.

  2. NMR of molecules trapped in sol-gel glasses: Progressive closure of the nanoporosity during drying

    NASA Astrophysics Data System (ADS)

    Cros, F.; Malier, L.; Korb, J.-P.; Chaput, F.

    1998-02-01

    We characterize the closed porosity of porous hybrid organic-inorganic sol-gel matrices. 2H-nuclear relaxation of d16-adamantane confined in these pores evidences a molecular translational motion inside the porous network. The pores are shown to be interconnected at the submicrometric scale. By modelling the effect of interpore molecular jumps on the lineshape, we characterize the progressive closure of the nanoporosity during drying. Nous avons caractérisé la porosité de matrices hybrides organique-inorganiques poreuse, à porosité fermée, préparées par voie sol-gel. La relaxation nucléaire du deuterium de l'adamantane d16 confinée dans les pores de ces matériaux a mis en évidence un mouvement de translation de cette molécule à l'intérieur du système de pores, qui est en fait connexe à l'échelle sub-micrométrique. L'influence des sauts, d'un pore à un autre, sur la forme de raie nous a permis de caractériser la fermeture de ces pores au cours du séchage.

  3. "G.P.S Matrices" programme: A method to improve the mastery level of social science students in matrices operations

    NASA Astrophysics Data System (ADS)

    Lee, Ken Voon

    2013-04-01

    The purpose of this action research was to increase the mastery level of Form Five Social Science students in Tawau II National Secondary School in the operations of addition, subtraction and multiplication of matrices in Mathematics. A total of 30 students were involved. Preliminary findings through the analysis of pre-test results and questionnaire had identified the main problem faced in which the students felt confused with the application of principles of the operations of matrices when performing these operations. Therefore, an action research was conducted using an intervention programme called "G.P.S Matrices" to overcome the problem. This programme was divided into three phases. 'Gift of Matrices' phase aimed at forming matrix teaching aids. The second and third phases were 'Positioning the Elements of Matrices' and 'Strenghtening the Concept of Matrices'. These two phases were aimed at increasing the level of understanding and memory of the students towards the principles of matrix operations. Besides, this third phase was also aimed at creating an interesting learning environment. A comparison between the results of pre-test and post-test had shown a remarkable improvement in students' performances after implementing the programme. In addition, the analysis of interview findings also indicated a positive feedback on the changes in students' attitude, particularly in the aspect of students' understanding level. Moreover, the level of students' memory also increased following the use of the concrete matrix teaching aids created in phase one. Besides, teachers felt encouraging when conducive learning environment was created through students' presentation activity held in third phase. Furthermore, students were voluntarily involved in these student-centred activities. In conclusion, this research findings showed an increase in the mastery level of students in these three matrix operations and thus the objective of the research had been achieved.

  4. Sol–gel immobilization as a suitable technique for enhancement of α-amylase activity of Aspergillus oryzae PP

    PubMed Central

    Evstatieva, Yana; Yordanova, Mariya; Chernev, Georgi; Ruseva, Yanislava; Nikolova, Dilyana

    2014-01-01

    Bioencapsulation of microbial cells in silica-based matrices has proved to be a good strategy to enhance the biosynthetic capabilities and viability of bioproducers. In the present study, mycelium and pellet cultures of strain Aspergillus oryzae PP were successfully immobilized in sol–gel hybrid matrices composed of tetraethylorthosilicate as an inorganic precursor, 5% (w/v) starch and 10 or 15% (w/v) polyethylene oxide, or 10% (w/v) calcium alginate as organic compounds. Biosynthetic activity of immobilized cultures was investigated by batch and fed-batch cultivation and the obtained results of 3042.04 IU cm−3 were comparable with the enzyme activity of the free cell culture. Immobilized cultures retained their viability and biosynthetic capabilities up to the 744th h during fed-batch fermentation processes. Consequently, sol–gel encapsulation in hybrid matrices could be considered as a promising technique for immobilization of Aspergillus oryzae PP in order to increase the α-amylase production. PMID:26740773

  5. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  6. IVS contribution to ITRF2014

    NASA Astrophysics Data System (ADS)

    Bachmann, Sabine; Thaller, Daniela; Roggenbuck, Ole; Lösler, Michael; Messerschmitt, Linda

    2016-07-01

    Every few years the International Terrestrial Reference System (ITRS) Center of the International Earth Rotation and Reference Systems Service (IERS) decides to generate a new version of the International Terrestrial Reference Frame (ITRF). For the upcoming ITRF2014 the official contribution of the International VLBI Service for Geodesy and Astrometry (IVS) comprises 5796 combined sessions in SINEX file format from 1979.6 to 2015.0 containing 158 stations, overall. Nine AC contributions were included in the combination process, using five different software packages. Station coordinate time series of the combined solution show an overall repeatability of 3.3 mm for the north, 4.3 mm for the east and 7.5 mm for the height component over all stations. The minimum repeatabilities are 1.5 mm for north, 2.1 mm for east and 2.9 mm for height. One of the important differences between the IVS contribution to the ITRF2014 and the routine IVS combination is the omission of the correction for non-tidal atmospheric pressure loading (NTAL). Comparisons between the amplitudes of the annual signals derived by the VLBI observations and the annual signals from an NTAL model show that for some stations, NTAL has a high impact on station height variation. For other stations, the effect of NTAL is low. Occasionally other loading effects have a higher influence (e.g. continental water storage loading). External comparisons of the scale parameter between the VTRF2014 (a TRF based on combined VLBI solutions), DTRF2008 (DGFI-TUM realization of ITRS) and ITRF2008 revealed a significant difference in the scale. A scale difference of 0.11 ppb (i.e. 0.7 mm on the Earth's surface) has been detected between the VTRF2014 and the DTRF2008, and a scale difference of 0.44 ppb (i.e. 2.8 mm on the Earth's surface) between the VTRF2014 and ITRF2008. Internal comparisons between the EOP of the combined solution and the individual solutions from the AC contributions show a WRMS in X- and Y-Pole between

  7. IVS contribution to ITRF2014

    NASA Astrophysics Data System (ADS)

    Bachmann, Sabine; Thaller, Daniela; Roggenbuck, Ole; Lösler, Michael; Messerschmitt, Linda

    2016-04-01

    Every few years the International Terrestrial Reference System (ITRS) Center of the International Earth Rotation and Reference Systems Service (IERS) decides to generate a new version of the International Terrestrial Reference Frame (ITRF). For the upcoming ITRF2014 the official contribution of the International VLBI Service for Geodesy and Astrometry (IVS) comprises 5796 combined sessions in SINEX file format from 1979.6 to 2015.0 containing 158 stations, overall. Nine AC contributions were included in the combination process, using five different software packages. Station coordinate time series of the combined solution show an overall repeatability of 3.3 mm for the north, 4.3 mm for the east and 7.5 mm for the height component over all stations. The minimum repeatabilities are 1.5 mm for north, 2.1 mm for east and 2.9 mm for height. One of the important differences between the IVS contribution to the ITRF2014 and the routine IVS combination is the omission of the correction for non-tidal atmospheric pressure loading (NTAL). Comparisons between the amplitudes of the annual signals derived by the VLBI observations and the annual signals from an NTAL model show that for some stations, NTAL has a high impact on station height variation. For other stations, the effect of NTAL is low. Occasionally other loading effects have a higher influence (e.g. continental water storage loading). External comparisons of the scale parameter between the VTRF2014 (a TRF based on combined VLBI solutions), DTRF2008 (DGFI-TUM realization of ITRS) and ITRF2008 revealed a significant difference in the scale. A scale difference of 0.11 ppb (i.e. 0.7 mm on the Earth's surface) has been detected between the VTRF2014 and the DTRF2008, and a scale difference of 0.44 ppb (i.e. 2.8 mm on the Earth's surface) between the VTRF2014 and ITRF2008. Internal comparisons between the EOP of the combined solution and the individual solutions from the AC contributions show a WRMS in X- and Y-Pole between

  8. Transparent gel and xerogel of thorium phosphate: optical spectroscopy with: Nd3+,Eu3+,Cr3+ and Rhodamine 6G

    SciTech Connect

    Genet, M.; Brandel, V.; Lahalle, M.P.; Simoni, E.

    1992-03-01

    Chemical conditions for thorium phosphate gel preparation have been determined. The transparency is of good optical quality and the gel is very stable for a long time. Under drying condition, this gel can give rise to the xerogel which is still transparent. We can also prepare this xerogel by simple evaporation at room temperature of a very concentrated solution of thorium phosphate. From this viscous medium, the xerogel can be obtained in various kinds of shapes : threads, slabs and blocks. Solidification time depends on the final volume desired and spreads from few minutes to several weeks. Absorption spectrum of pure gel and xerogel have been recorded. Gel and xerogel doped with very well known probes like Nd3+ and Er3+ were examined to compare their optical properties with aqueous medium of the same chemical composition. Eu3+ doped gel and xerogel were also studied using their fluorescence properties. The optical properties of Cr3+ in doped gel and xerogel allowed us to determine the kinetics of hydration sphere modification during the drying period. Finally, as xerogel synthesis takes place at room temperature, fragile organic dye can be used as dopant, so Rhodamine 6G absorption and emission spectra have been studied in these conditions. When, at that time, the xerogel is doped with Coumarin 460 and Tb3+ an energy transfer is observed between dye and Tb3+ ions, which contributes to enhance the fluorescence of Tb3+ ions. Eu3+ behaves similarly. In conclusion, gel and xerogel of thorium phosphate tested with usual probes such as 3d, 4f ions and dyes seem to be very promising matrices.

  9. Dilithium hexaorganostannate(IV) compounds.

    PubMed

    Schrader, Ireen; Zeckert, Kornelia; Zahn, Stefan

    2014-12-01

    Hypercoordination of main-group elements such as the heavier Group 14 elements (silicon, germanium, tin, and lead) usually requires strong electron-withdrawing ligands and/or donating groups. Herein, we present the synthesis and characterization of two hexaaryltin(IV) dianions in form of their dilithium salts [Li2(thf)2{Sn(2-py(Me))6}] (py(Me)=C5H3N-5-Me) (2) and [Li2{Sn(2-py(OtBu))6}] (py(OtBu)=C5H3N-6-OtBu) (3). Both complexes are stable in the solid state and solution under inert conditions. Theoretical investigations of compound 2 reveal a significant valence 5s-orbital contribution of the tin atom forming six strongly polarized tin-carbon bonds. PMID:25314245

  10. Group-IV semiconductor compounds

    SciTech Connect

    Berding, M.A.; Sher, A.; van Schilfgaarde, M.

    1997-08-01

    Properties of ordered group-IV compounds containing carbon, silicon, and germanium are calculated within the local density approximation. Twenty-seven fully relaxed compounds represented by seven different compound structures are compared and, with the exception of SiC, all compounds are found to be metastable. Two trends emerge: carbon-germanium bonds are disfavored, and compounds that have carbon on a common sublattice are the least unbound because of their relatively low strain. When carbon shares a sublattice with silicon or germanium, the large strain results in a narrowing of the band gap, and in some cases the compound is metallic. The most promising structures with the lowest excess energy contain carbon on one sublattice and although they do not lattice match to silicon, they match rather well to silicon carbide. {copyright} {ital 1997} {ital The American Physical Society}

  11. Optical and Infrared Interferometry IV

    NASA Astrophysics Data System (ADS)

    Rajagopal, Jayadev K.; Creech-Eakman, Michelle J.; Malbet, Fabien

    2014-08-01

    Optical and IR Interferometry IV at the SPIE 2014 symposium in Montreal had a strong and vibrant program. After initial fears about budget cuts and travel-funding constraints, the Program Committee had to work hard to accommodate as many quality submissions as possible. Innovative, creative and visionary work ensured that the field has progressed well, despite the bleak funding climate felt in the US, Europe and elsewhere. Montreal proved an excellent venue for this, the largest of Interferometry conferences and the only one that brings together practitioners from the world over. Let us summarize a few highlights to convey a glimpse of the excitement that is detailed in the rest of these Proceedings.

  12. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  13. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  14. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  15. Extremal Positive Maps on M3(ℂ) and Idempotent Matrices

    NASA Astrophysics Data System (ADS)

    Miller, Marek; Olkiewicz, Robert

    2016-03-01

    A new method of analysing positive bistochastic maps on the algebra of complex matrices M3 has been proposed. By identifying the set of such maps with a convex set of linear operators on ℝ8, one can employ techniques from the theory of compact semigroups to obtain results concerning asymptotic properties of positive maps. It turns out that the idempotent elements play a crucial role in classifying the convex set into subsets, in which representations of extremal positive maps are to be found. It has been shown that all positive bistochastic maps, extremal in the set of all positive maps of M3, that are not Jordan isomorphisms of M3 are represented by matrices that fall into two possible categories, determined by the simplest idempotent matrices: one by the zero matrix, and the other by a one-dimensional orthogonal projection. Some norm conditions for matrices representing possible extremal maps have been specified and examples of maps from both categories have been brought up, based on the results published previously.

  16. DESI-MS Analysis of Mycotoxins from Grain Matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction – Determination of mycotoxins in grain matrices is a frequent need of growers and processors of cereal grains. Sample preparation for mycotoxin analysis is often laborious and time consuming. Here we demonstrate the application of desorption electrospray ionization – mass spectrometry...

  17. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

    Adopting a discrete-time cohort-type model to represent the dynamics of a population, the problem of achieving a desired total size of the population under a balanced growth (contraction) and the problem of maintaining the desired size, once achieved, are studied. Properties of positive-time systems and M-matrices are used to develop the results,…

  18. Controlled growth factor release from synthetic extracellular matrices

    NASA Astrophysics Data System (ADS)

    Lee, Kuen Yong; Peters, Martin C.; Anderson, Kenneth W.; Mooney, David J.

    2000-12-01

    Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.

  19. Technological optimization of manufacture of probiotic whey cheese matrices.

    PubMed

    Madureira, Ana R; Brandão, Teresa; Gomes, Ana M; Pintado, Manuela E; Malcata, F Xavier

    2011-03-01

    In attempts to optimize their manufacture, whey cheese matrices obtained via thermal processing of whey (leading to protein precipitation) and inoculated with probiotic cultures were tested. A central composite, face-centered design was followed, so a total of 16 experiments were run using fractional addition of bovine milk to feedstock whey, homogenization time, and storage time of whey cheese as processing parameters. Probiotic whey cheese matrices were inoculated with Lactobacillus casei LAFTIL26 at 10% (v/v), whereas control whey cheese matrices were added with skim milk previously acidified with lactic acid to the same level. All whey cheeses were stored at 7 °C up to 14 d. Chemical and sensory analyses were carried out for all samples, as well as rheological characterization by oscillatory viscometry and textural profiling. As expected, differences were found between control and probiotic matrices: fractional addition of milk and storage time were the factors accounting for the most important effects. Estimation of the best operating parameters was via response surface analysis: milk addition at a rate of 10% to 15% (v/v), and homogenization for 5 min led to the best probiotic whey cheeses in terms of texture and organoleptic properties, whereas the best time for consumption was found to be by 9 d of storage following manufacture. PMID:21535760

  20. Dimensionality of Data Matrices with Applications to Gene Expression Profiles

    ERIC Educational Resources Information Center

    Feng, Xingdong

    2009-01-01

    Probe-level microarray data are usually stored in matrices. Take a given probe set (gene), for example, each row of the matrix corresponds to an array, and each column corresponds to a probe. Often, people summarize each array by the gene expression level. Is one number sufficient to summarize a whole probe set for a specific gene in an array?…

  1. Technologies for detecting botulinum neurotoxins in biological and environmental matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomonitoring of food and environmental matrices is critical for the rapid and sensitive diagnosis, treatment, and prevention of diseases caused by toxins. The United States Centers for Disease Control and Prevention (CDC) has noted that toxins from bacteria, fungi, algae, and plants present an ongo...

  2. Variation in Raven's Progressive Matrices Scores across Time and Place

    ERIC Educational Resources Information Center

    Brouwers, Symen A.; Van de Vijver, Fons J. R.; Van Hemert, Dianne A.

    2009-01-01

    The paper describes a cross-cultural and historical meta-analysis of Raven's Progressive Matrices. Data were analyzed of 798 samples from 45 countries (N = 244,316), which were published between 1944 and 2003. Country-level indicators of educational permeation (which involves a broad set of interrelated educational input and output factors that…

  3. Current technologies for detection of ricin in different matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ricin is a convenient, potent, and available toxin for terrorist acts. The importance of detecting it in various matrices is obvious. This chapter reviews methods for ricin detection based on the mechanisms used for assay development. Five detection approaches are reviewed: 1. Antibody-based metho...

  4. Validating Alternative Modes of Scoring for Coloured Progressive Matrices.

    ERIC Educational Resources Information Center

    Razel, Micha; Eylon, Bat-Sheva

    Conventional scoring of the Coloured Progressive Matrices (CPM) was compared with three methods of multiple weight scoring. The methods include: (1) theoretical weighting in which the weights were based on a theory of cognitive processing; (2) judged weighting in which the weights were given by a group of nine adult expert judges; and (3)…

  5. A minimax approach to spatial estimation using affinity matrices

    NASA Technical Reports Server (NTRS)

    Morris, C. N.

    1983-01-01

    Estimates made in the plane to improve on noisy unbiased estimates were combined. Only a small fraction of points in a giant grid were used to do this, those that are most like a given point. A component of this process defining an affinity matrix of values, indicating which points are relevant to others. Minimax rules are shown to be based on affinity matrices.

  6. Cluster Matrices for Health Occupations. Education for Employment Task Lists.

    ERIC Educational Resources Information Center

    Lathrop, Janice

    These cluster matrices provide duties and tasks that form the basis of instructional content for secondary, postsecondary, and adult training programs for health occupations. The eight clusters (and the job titles included in each cluster) are as follows: (1) dental assisting (dental assistant); (2) dental laboratory technology (dental laboratory…

  7. Automorphisms of semigroups of invertible matrices with nonnegative integer elements

    SciTech Connect

    Semenov, Pavel P

    2012-09-30

    Let G{sub n}(Z) be the subsemigroup of GL{sub n}(Z) consisting of the matrices with nonnegative integer coefficients. In the paper, the automorphisms of this semigroup are described for n{>=}2. Bibliography: 5 titles.

  8. Effect of an Interactive Courseware in the Learning of Matrices

    ERIC Educational Resources Information Center

    Hoon, Teoh Sian; Chong, Toh Seong; Binti Ngah, Nor Azilah

    2010-01-01

    The main aim of this study is to integrate cooperative learning strategies, mastery learning and interactive multimedia to improve students' performance in Mathematics, specifically in the topic of matrices. It involved a quasi-experimental design with gain scores and time-on-task as dependent variables. The independent variables were three…

  9. Inverse of polynomial matrices in the irreducible form

    NASA Technical Reports Server (NTRS)

    Chang, Fan R.; Shieh, Leang S.; Mcinnis, Bayliss C.

    1987-01-01

    An algorithm is developed for finding the inverse of polynomial matrices in the irreducible form. The computational method involves the use of the left (right) matrix division method and the determination of linearly dependent vectors of the remainders. The obtained transfer function matrix has no nontrivial common factor between the elements of the numerator polynomial matrix and the denominator polynomial.

  10. Displacement properties of the product of two finite recursive matrices

    NASA Astrophysics Data System (ADS)

    Barnabei, Marilena; Montefusco, Laura B.

    2002-12-01

    We study the displacement properties, with respect to a suitable displacement operator, of the product of two finite sections of recursive matrices, and we give an explicit evaluation of the displacement rank of such a product in the case when the second matrix is a finite Toeplitz or Hankel matrix.

  11. Influence of gel/LED-laser application on cervical microleakage of two barrier materials used for endodontically treated teeth whitening

    NASA Astrophysics Data System (ADS)

    Marchesan, Melissa Andréia; Barros, Felipe; Porto, Saulo; Zaitter, Suellen; Brugnera, Aldo, Jr.; Sousa-Neto, Manoel D.

    2007-02-01

    This study evaluated ex vivo the influence of the number of gel/LED-laser applications/activations on cervical microleakage of two different barrier materials used for protection during whitening of endodontically treated teeth. Eighty-four canines were instrumented and obturated with epoxy resin sealer. The seal was removed 2 mm beyond the cemento-enamel junction for barrier placement and the teeth were divided into two groups of 40 teeth each: G1, zinc phosphate cement; G2, glass ionomer cement. The two groups were subdivided into 4 subgroups (n=10 each): I) no gel or LED-laser application; II) one gel application and two LED-laser activations; III) two gel applications and four LED-laser activations; IV) three gel applications and six LED-laser activations. The teeth were immersed in India ink for 7 days, decalcified and cleared. Cervical microleakage was quantified with a measurement microscope. Statistical analysis showed that zinc phosphate caused significantly lower microleakage than glass ionomer cement (presented microleakage in all subgroups). However, after two (p<0.01) and three (p<0.001) applications of gel, there was statistially significant microleakage in zinc phosphate barriers. Based on the present results, it can be concluded that cervical barriers with zinc phosphate cement show less cervical microleakage and that two or more applications/activations of gel/LED-laser significantly increase microleakage.

  12. Biosynthesis of Indole-3-Acetic Acid by New Klebsiella oxytoca Free and Immobilized Cells on Inorganic Matrices

    PubMed Central

    Celloto, Valéria R.; Oliveira, Arildo J. B.; Gonçalves, José E.; Watanabe, Cecília S. F.; Matioli, Graciette; Gonçalves, Regina A. C.

    2012-01-01

    While many natural and synthetic compounds exhibit auxin-like activity in bioassays, indole-3-acetic acid (IAA) is recognized as the key auxin in most plants. IAA has been implicated in almost all aspects of plant growth and development and a large array of bacteria have been reported to enhance plant growth. Cells of Klebsiella oxytoca isolated from the rhizosphere of Aspidosperma polyneuron and immobilized by adsorption on different inorganic matrices were used for IAA production. The matrices were prepared by the sol-gel method and the silica-titanium was the most suitable matrix for effective immobilization. In operational stability assays, IAA production was maintained after four cycles of production, obtaining 42.80 ± 2.03 μg mL−1 of IAA in the third cycle, which corresponds to a 54% increase in production in relation to the first cycle, whereas free cells began losing activity after the first cycle. After 90 days of storage at 4°C the immobilized cells showed the slight reduction of IAA production without significant loss of activity. PMID:22623901

  13. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, Norman L.

    1986-01-01

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  14. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, N.L.

    1983-11-10

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  15. Selective gel system for permeability profile control

    SciTech Connect

    Shu, P.

    1990-10-16

    This patent describes a selective gel for closing pores in a more permeable zone of a formation. It comprises: an aqueous solution of a first composition sufficient to form ex-situ a size selective, shear thinning first gel which comprises a xanthan biopolymer, and a transitional metal ion; and an aqueous solution of a second composition sufficient to form thermally a second in-situ gel that which comprises and aldehyde, and a phenolic compound which solutions are combined and allowed to form a shearable, rehealable ex-situ gel which can be injected into the permeable zone where it reheals when heated by the formation and thereafter forms a solid gel substantially more resistant to formation conditions than the first gel.

  16. GEM printer: 3D gel printer for free shaping of functional gel engineering materials

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Muroi, Hisato; Yamamoto, Kouki; Serizawa, Ryo; Gong, Jin

    2013-04-01

    In the past decade, several high-strength gels have been developed. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. The gels have both low surface friction and well permeability due to a large amount of water absorbed in the gels, which are superiority of the gels compering to the polyester fibers. It is, however, difficult for gels to be forked structure or cavity structure by using cutting or mold. Consequently, it is necessary to develop the additive manufacturing device to synthesize and mode freely gels at the same time. Here we try to develop an optical 3D gel printer that enables gels to be shaped precisely and freely. For the free forming of high-strength gels, the 1st gels are ground to particles and mixed with 2nd pregel solution, and the mixed solution is gelled by the irradiation of UV laser beam through an optical fiber. The use of the optical fiber makes one-point UV irradiation possible. Since the optical fiber is controlled by 3D-CAD, the precise and free molding in XYZ directions is easily realized. We successfully synthesized tough gels using the gel printer.

  17. Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography

    NASA Astrophysics Data System (ADS)

    Pilařová (Vávrů), Kateřina; Kozubíková, Petra; Šolc, Jaroslav; Spěváček, Václav

    2014-11-01

    The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios β and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

  18. Breast cancer cells mechanosensing in engineered matrices: Correlation with aggressive phenotype.

    PubMed

    Li, Ji; Wu, Yang; Schimmel, Nicholas; Al-Ameen, Mohammad Ali; Ghosh, Gargi

    2016-08-01

    The pathogenesis of cancer is often driven by the modulation of the tumor microenvironment. Recent reports have highlighted that the progressive stiffening of tumor matrix is crucial for malignant transformation. Though extensive work has been done analyzing the mechanotransductive signals involved in tumor progression, it is still not clear whether the stiffness induced changes in cancer cell behavior is conserved across the invasive/aggressive phenotype of cells. Here, we used synthetic hydrogel based cell culture platform to correlate the aggressive potential of the breast cancer cells to the responses to matrix stiffness. The cellular functions such as proliferation, migration, and angiogenic capability were characterized. We report that the proliferation and motility of the highly aggressive cell line MDA-MB-231 increased with increase in matrix rigidity. We also demonstrated for the first time that the change in matrix stiffness stimulated the angiogenic activity of these cells as manifested from enhanced expression of vascular endothelial growth factor (VEGF). Inhibition of actomyosin contractility attenuated proliferation of MDA-MB-231 cells on stiff matrices while promoted the growth on soft gels. In addition, the release of VEGF was reduced upon inhibition of contractility. The less and non-aggressive breast cancer cells, SKBr3 and MCF-7 respectively displayed less dependency on matrix stiffness. PMID:26874251

  19. Experimental investigation of the Ogston model for electrophoresis using calibrated matrices

    NASA Astrophysics Data System (ADS)

    McCormick, Laurette; Slater, Gary; Tinland, Bernard

    2002-03-01

    The Ogston regime of electrophoresis, which applies to analytes that are smaller than the pore size of the sieving medium, is highly relevant to many current and emerging separation technologies. The mean-field Ogston model assumes that the electrophoretic mobility is proportional to the fractional volume available to the analyte in the medium. However, our recent lattice model of this regime showed that this assumption is not founded. It is generally impossible to test the models because of our inability at measuring the mobility and the available volume separately. We present a novel approach that allows us to investigate this regime by means of a well-defined experimental artificial "gel" made of monodisperse silica spheres. The pore size and the disorder can be controlled via the sphere size or their packing arrangement. We will present a method for constructing well-ordered matrices, as well as preliminary measurements of the electrophoretic mobility and diffusion coefficients of objects differing in morphology (DNA fragments - soft coil; latex beads - hard spheres) in these media as a function of the relevant parameters (pore size, radius of gyration, electric field) and discuss the observed behavior in terms of the current theories.

  20. GPU implementations for fast factorizations of STAP covariance matrices

    NASA Astrophysics Data System (ADS)

    Roeder, Michael; Davis, Nolan; Furtek, Jeremy; Braunreiter, Dennis; Healy, Dennis

    2008-08-01

    One of the main goals of the STAP-BOY program has been the implementation of a space-time adaptive processing (STAP) algorithm on graphics processing units (GPUs) with the goal of reducing the processing time. Within the context of GPU implementation, we have further developed algorithms that exploit data redundancy inherent in particular STAP applications. Integration of these algorithms with GPU architecture is of primary importance for fast algorithmic processing times. STAP algorithms involve solving a linear system in which the transformation matrix is a covariance matrix. A standard method involves estimating a covariance matrix from a data matrix, computing its Cholesky factors by one of several methods, and then solving the system by substitution. Some STAP applications have redundancy in successive data matrices from which the covariance matrices are formed. For STAP applications in which a data matrix is updated with the addition of a new data row at the bottom and the elimination of the oldest data in the top of the matrix, a sequence of data matrices have multiple rows in common. Two methods have been developed for exploiting this type of data redundancy when computing Cholesky factors. These two methods are referred to as 1) Fast QR factorizations of successive data matrices 2) Fast Cholesky factorizations of successive covariance matrices. We have developed GPU implementations of these two methods. We show that these two algorithms exhibit reduced computational complexity when compared to benchmark algorithms that do not exploit data redundancy. More importantly, we show that when these algorithmic improvements are optimized for the GPU architecture, the processing times of a GPU implementation of these matrix factorization algorithms may be greatly improved.

  1. Microfluidics of soft granular gels

    NASA Astrophysics Data System (ADS)

    Nixon, Ryan; Bhattacharjee, Tapomoy; Sawyer, W. Gregory; Angelini, Thomas E.

    Microfluidic methods for encapsulating cells and particles typically involve drop making with two immiscible fluids. The main materials constraint in this approach is surface tension, creating inherent instability between the two fluids. We can eliminate this instability by using miscible inner and outer phases. This is achieved by using granular micro gels which are chemically miscible but physically do not mix. These microgels are yield stress materials, so they flow as solid plugs far from shear gradients, and fluidize where gradients are generated - near an injection nozzle for example. We have found that tuning the yield stress of the material by varying polymer concentration, device performance can be controlled. The solid like behavior of the gel allows us to produces infinitely stable jets that maintain their integrity and configuration over long distances and times. These properties can be combined and manipulated to produce discrete particulate bunches of an inner phase, flowing inside of an outer phase, well enough even to print a Morse code message suspended within flow chambers about a millimeter in diameter moving at millimeters a second.

  2. Self-Pumping Active Gel

    NASA Astrophysics Data System (ADS)

    Wu, Kun-Ta; Hishamunda, Jean Bernard; Fraden, Seth; Dogic, Zvonimir

    Isotropic active gels are the network which is consist of cross-linked building blocks and the structure of which changes randomly and isotropically with time. Dogic et. al. show that pairs of anti-parallel microtubules form extensile bundles, which merge, extend, and buckle. In an unconfined system, the dynamics of these bundles causes spontaneous turbulent-like flow driven by motion of microscopic molecular motors. We found that confining these active gels in a millimeter sized toroids causes a transition into a new dynamical state characterized by circulation currents persisting for hours until ATP is depleted. We show how toroid dimensions impact the properties of self-organized circular currents, how directions of circulation can be designed by engineering ratchet-shaped boundaries, and how circulations of connected toroids can be either synchronized or antisynchronized. Furthermore, we demonstrate that the flow rate in the circulation is independent of curvature and length of flow path. The flow rate persists for centimeters without decay, disregarding conventional pipe flow resistance. Such findings pave the path to self-pumping pipe transport and performing physical work with biological system.

  3. [Electron microscopy study of artificial vitreous gel].

    PubMed

    Ehgartner, E M; Schmut, O; Hofmann, H

    1986-04-01

    Artificial gels prepared from Cu2+-ions and hyaluronic acid were studied in the electron microscope and compared with the native vitreous body. Additionally, the authors attempted to produce transparent gels from the native constituents of the vitreous body, namely collagen and hyaluronic acid. Mixing of solutions of these constituents formed no gels but white precipitates. The ultrastructure of these precipitates was also studied in the electron microscope. PMID:3723971

  4. Gel time of calcium acrylate grouting material.

    PubMed

    Han, Tong-Chun

    2004-08-01

    Calcium acrylate is a polymerized grout, and can polymerize in an aqueous solution. The polymerization reaction utilizes ammonium persulfate as a catalyst and sodium thiosulfate as the activator. Based on the theory of reaction kinetics, this study on the relation between gel time and concentration of activator and catalyst showed that gel time of calcium acrylate is inversely proportional to activator and catalyst concentration. A formula of gel time is proposed, and an example is provided to verify the proposed formula. PMID:15236477

  5. Co-immobilization of glucose oxidase and hexokinase on silicate hybrid sol-gel membrane for glucose and ATP detections.

    PubMed

    Liu, Songqin; Sun, Yueming

    2007-01-15

    The co-immobilization of glucose oxidase (GOD) and hexokinase/glucose-6-phosphate dehydrogenase (HEX) in the silica hybrid sol-gel film for development of amperometric biosensors was investigated. The silica hybrid film fabricated by hydrolysis of the mixture of tetraethyl orthosilicate and 3-(trimethoxysiyl)propyl methacrylate possessed a three-dimension vesicle structure and good uniformity and conformability, and was ready for enzyme immobilization. The electrochemical and spectroscopic measurements showed that the silica hybrid sol-gel provided excellent matrice for the enzyme immobilization and that the immobilized enzyme retained its bioactivity effectively. The immobilized GOD could catalyze the oxidation of glucose, which could be used to determine glucose at +1.0 V without help of any mediator. The competition between GOD and HEX for the substrate glucose involving ATP as a co-substrate led to a decrease of the glucose response, which allowed us to develop an ATP sensor with a good stability. The fabricated silica hybrid sol-gel matrice offered a stage for further study of immobilization and electrochemistry of proteins. PMID:16687247

  6. Characterization of titanium and zirconium valerate sol-gel films

    SciTech Connect

    Severin, K.G.; Ledford, J.S.; Torgerson, B.A.; Berglund, K.A. )

    1994-07-01

    FTIR and XPS have been used to characterize titanium and zirconium valerate thin films prepared using sol-gel techniques. Films were prepared by hydrolysis of titanium(IV) isopropoxide or zirconium(IV) n-propoxide in excess valeric acid at room temperature. Film solution chemistry, from precursors to cast films, was followed with FTIR. The structure and chemical composition of films spin cast from fresh and day-old solutions were determined. Results of these studies suggest that all films consist of a metal-oxygen polymer backbone coordinated with bidentate valerate ligands. No evidence for the presence of alkoxide ligands has been found. A small amount of water is present in all cast films. While solution aging experiments indicate that the zirconium film structure does not change with solution reaction time, carboxylate ligand concentrations are higher in titanium films made from aged solutions. Titanium films made from aged solutions contain slightly less than 1.5 valerate ligands/titanium atom. Zirconium films are more highly carboxylated with almost two valerate groups per metal center. 57 refs., 6 figs., 1 tab.

  7. Conducting Polymer Electrodes for Gel Electrophoresis

    PubMed Central

    Bengtsson, Katarina; Nilsson, Sara; Robinson, Nathaniel D.

    2014-01-01

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that π-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation. PMID:24586761

  8. Functional behavior of isotropic magnetorheological gels

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, P.; Maniprakash, S.; Srinivasan, S. M.; Srinivasa, A. R.

    2010-08-01

    Magnetorheological (MR) gels are a new class of soft polymers whose properties can be controlled using a magnetic field. The functional effectiveness of these gels depends on their magnetic controllability. In this paper, an experimental investigation on the functional behavior of a particular type of magnetorheological gels under dynamic and static shear conditions in the presence of a magnetic field is studied. MR gels are prepared with micron sized polarizable carbonyl iron particles interspersed in a polymer matrix gel. The compliance of this magnetic gel can be varied under the influence of an external magnetic field. Since dynamical mechanical analysis tests are difficult to conduct in the presence of large deformations of the order of 50% and strong magnetic fields, a free decay test apparatus is designed and fabricated for obtaining the magnetic field dependent shearing response under dynamic conditions at room temperature. It is observed that a significant change in the elastic modulus occurs in the gels under a magnetic field in the range of 0.1-0.4 T. However, no significant change in the damping ratio is observed under various magnitudes of magnetic field. It is shown that the increase in shear modulus of this kind of magnetic composite gel could be as high as 59% of the zero field value for a gel prepared with 50% by weight of carbonyl iron particles.

  9. Tissue simulating gel for medical research

    NASA Technical Reports Server (NTRS)

    Companion, John A. (Inventor)

    1991-01-01

    A tissue simulating gel and a method for preparing the tissue simulating gel are disclosed. The tissue simulating gel is prepared by a process using water, gelatin, ethylene glycol, and a cross-linking agent. In order to closely approximate the characteristics of the type of tissue being simulated, other material has been added to change the electrical, sound conducting, and wave scattering properties of the tissue simulating gel. The result of the entire process is a formulation that will not melt at the elevated temperatures involved in hyperthermia medical research. Furthermore, the tissue simulating gel will not support mold or bacterial growth, is of a sufficient mechanical strength to maintain a desired shape without a supporting shell, and is non-hardening and non-drying. Substances have been injected into the tissue simulating gel prior to the setting-up thereof just as they could be injected into actual tissue, and the tissue simulating gel is translucent so as to permit visual inspection of its interior. A polyurethane spray often used for coating circuit boards can be applied to the surface of the tissue simulating gel to give a texture similar to human skin, making the tissue simulating gel easier to handle and contributing to its longevity.

  10. Ionic liquid based multifunctional double network gel

    NASA Astrophysics Data System (ADS)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu

    2015-04-01

    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  11. Structure of chitosan gels mineralized by sorption

    NASA Astrophysics Data System (ADS)

    Modrzejewska, Z.; Skwarczyńska, A.; Douglas, T. E. L.; Biniaś, D.; Maniukiewicz, W.; Sielski, J.

    2015-10-01

    The paper presents the structural studies of mineralized chitosan hydrogels. Hydrogels produced by using sodium beta-glycerophosphate (Na-β-GP) as a neutralizing agent. Mineralization was performed method "post loading", which consisted in sorption to the gels structure Ca ions. In order to obtain - in the structure of gels - compounds similar to the hydroxyapatites present naturally in bone tissue, gels after sorption were modified in: pH 7 buffer and sodium hydrogen phosphate. In order to determine the structural properties of the gels, the following methods were used: infrared spectroscopy with Fourier transformation, FTIR, X-ray diffractometry, XRD, scanning electron microscopy, SEM.

  12. Graph-Theoretic Representations for Proximity Matrices through Strongly-Anti-Robinson or Circular Strongly-Anti-Robinson Matrices.

    ERIC Educational Resources Information Center

    Hubert, Lawrence; Arabie, Phipps; Meulman, Jacqueline

    1998-01-01

    Introduces a method for fitting order-constrained matrices that satisfy the strongly anti-Robinson restrictions (SAR). The method permits a representation of the fitted values in a (least-squares) SAR approximating matrix as lengths of paths in a graph. The approach is illustrated with a published proximity matrix. (SLD)

  13. Qubit representations of the braid groups from generalized Yang-Baxter matrices

    NASA Astrophysics Data System (ADS)

    Vasquez, Jennifer F.; Wang, Zhenghan; Wong, Helen M.

    2016-04-01

    Generalized Yang-Baxter matrices sometimes give rise to braid group representations. We identify the exact images of some qubit representations of the braid groups from generalized Yang-Baxter matrices obtained from anyons in the metaplectic modular categories.

  14. Qubit representations of the braid groups from generalized Yang-Baxter matrices

    NASA Astrophysics Data System (ADS)

    Vasquez, Jennifer F.; Wang, Zhenghan; Wong, Helen M.

    2016-07-01

    Generalized Yang-Baxter matrices sometimes give rise to braid group representations. We identify the exact images of some qubit representations of the braid groups from generalized Yang-Baxter matrices obtained from anyons in the metaplectic modular categories.

  15. Novel core-shell cerium(IV)-immobilized magnetic polymeric microspheres for selective enrichment and rapid separation of phosphopeptides.

    PubMed

    Wang, Zhi-Gang; Cheng, Gong; Liu, Yan-Lin; Zhang, Ji-Lin; Sun, De-Hui; Ni, Jia-Zuan

    2014-03-01

    In this work, novel magnetic polymeric core-shell structured microspheres with immobilized Ce(IV), Fe3O4@SiO2@PVPA-Ce(IV), were designed rationally and synthesized successfully via a facile route for the first time. Magnetic Fe3O4@SiO2 microspheres were first prepared by directly coating a thin layer of silica onto Fe3O4 magnetic particles using a sol-gel method, a poly(vinylphosphonic acid) (PVPA) shell was then coated on the Fe3O4@SiO2 microspheres to form Fe3O4@SiO2@PVPA microspheres through a radical polymerization reaction, and finally Ce(IV) ions were robustly immobilized onto the Fe3O4@SiO2@PVPA microspheres through strong chelation between Ce(IV) ions and phosphate moieties in the PVPA. The applicability of the Fe3O4@SiO2@PVPA-Ce(IV) microspheres for selective enrichment and rapid separation of phosphopeptides from proteolytic digests of standard and real protein samples was investigated. The results demonstrated that the core-shell structured Fe3O4@SiO2@PVPA-Ce(IV) microspheres with abundant Ce(IV) affinity sites and excellent magnetic responsiveness can effectively purify phosphopeptides from complex biosamples for MS detection taking advantage of the rapid magnetic separation and the selective affinity between Ce(IV) ions and phosphate moieties of the phosphopeptides. Furthermore, they can be effectively recycled and show good reusability, and have better performance than commercial TiO2 beads and homemade Fe3O4@PMAA-Ce(IV) microspheres. Thus the Fe3O4@SiO2@PVPA-Ce(IV) microspheres can benefit greatly the mass spectrometric qualitative analysis of phosphopeptides in phosphoproteome research. PMID:24407680

  16. Molecular structural differences between low methoxy pectins induced by pectin methyl esterase II: effects on texture, release and perception of aroma in gels of similar modulus of elasticity.

    PubMed

    Kim, Yang; Kim, Young-Suk; Yoo, Sang-Ho; Kim, Kwang-Ok

    2014-02-15

    Six low-methoxy pectins with different degrees of methylesterification and amidation, and molecular weights were used to prepare gels with similar moduli of elasticity by varying the concentrations of pectin and calcium phosphate. Five aroma compounds were added to the gels and their sensory textural properties, release and perception of aromas were investigated. Sensory firmness, springiness, adhesiveness, chewiness and cohesiveness differed according to the gel type, even though the moduli of elasticity were not significantly different (p<0.05). Release and perception of aromas also displayed significant difference according to the gel type (p<0.05). Low-methoxy amidated pectin exhibited the lowest release and perception for all the aroma compounds, while pectin-methylesterase-treated pectin gels exhibited relatively higher aroma release and perception. These results showed that the structural properties of pectins and gelling factors that increase the non-polar character of the gel matrices could decrease the release and perception of aromas in pectin gel systems. PMID:24128568

  17. Stacking gels: A method for maximising output for pulsed-field gel electrophoresis.

    PubMed

    Heng, See Kah; Heng, Chua Kek; Puthucheary, S D

    2009-01-01

    Pulsed field gel electrophoresis (PFGE), the gold standard of molecular typing methods, has a major disadvantage of an unusually long electrophoretic time. From the original protocol of 6 days, it was modified to 3 days and subsequently to a single day. We describe the procedure of stacking five to six gels one on top of another in order to increase and maximize the output in a shorter time without compromising the resolution and reproducibility. All the variables that affect pulsed field gels during electrophoresis were taken into consideration. We firstly optimized the parameters to be used and secondly determined whether stacking of five to six gels had any effect on the molecular separation during electrophoresis in comparison with a single gel run. DNA preparation, restriction, electrophoresis, staining and gel documentation was carried out based on previously published methods. Gels were analysed using BioNumerics and dice coefficient and unweighted pair group methods were used to generate dendrograms based on 1.5% tolerance values. Identical band profiles and band resolution-separation were seen in the PFGE patterns with single gel and multiple stacking gels. Cluster analysis further strengthened the fact that results from stacking gels were reproducible and comparable with a single gel run. This method of stacking gels saves time and maximizes the output at the same time. The run time for a single gel was about 28 hours, but with six stacked gels the run time was 54 hours compared with 28 x 6 = 168 hours if they were run separately as single gels thus saving time of 67.86%. Beside the big factor of saving time, stacking gels save resources (electricity, reagents, water, chemicals and working time) by increasing the sample throughput in a shorter time without compromising on quality of data. But optimization of working parameters is vital depending on the PFGE system used. PMID:19384038

  18. Composite alginate gels for tunable cellular microenvironment mechanics

    NASA Astrophysics Data System (ADS)

    Khavari, Adele; Nydén, Magnus; Weitz, David A.; Ehrlicher, Allen J.

    2016-08-01

    The mechanics of the cellular microenvironment can be as critical as biochemistry in directing cell behavior. Many commonly utilized materials derived from extra-cellular-matrix create excellent scaffolds for cell growth, however, evaluating the relative mechanical and biochemical effects independently in 3D environments has been difficult in frequently used biopolymer matrices. Here we present 3D sodium alginate hydrogel microenvironments over a physiological range of stiffness (E = 1.85 to 5.29 kPa), with and without RGD binding sites or collagen fibers. We use confocal microscopy to measure the growth of multi-cellular aggregates (MCAs), of increasing metastatic potential in different elastic moduli of hydrogels, with and without binding factors. We find that the hydrogel stiffness regulates the growth and morphology of these cell clusters; MCAs grow larger and faster in the more rigid environments similar to cancerous breast tissue (E = 4–12 kPa) as compared to healthy tissue (E = 0.4–2 kpa). Adding binding factors from collagen and RGD peptides increases growth rates, and change maximum MCA sizes. These findings demonstrate the utility of these independently tunable mechanical/biochemistry gels, and that mechanical confinement in stiffer microenvironments may increase cell proliferation.

  19. Composite alginate gels for tunable cellular microenvironment mechanics.

    PubMed

    Khavari, Adele; Nydén, Magnus; Weitz, David A; Ehrlicher, Allen J

    2016-01-01

    The mechanics of the cellular microenvironment can be as critical as biochemistry in directing cell behavior. Many commonly utilized materials derived from extra-cellular-matrix create excellent scaffolds for cell growth, however, evaluating the relative mechanical and biochemical effects independently in 3D environments has been difficult in frequently used biopolymer matrices. Here we present 3D sodium alginate hydrogel microenvironments over a physiological range of stiffness (E = 1.85 to 5.29 kPa), with and without RGD binding sites or collagen fibers. We use confocal microscopy to measure the growth of multi-cellular aggregates (MCAs), of increasing metastatic potential in different elastic moduli of hydrogels, with and without binding factors. We find that the hydrogel stiffness regulates the growth and morphology of these cell clusters; MCAs grow larger and faster in the more rigid environments similar to cancerous breast tissue (E = 4-12 kPa) as compared to healthy tissue (E = 0.4-2 kpa). Adding binding factors from collagen and RGD peptides increases growth rates, and change maximum MCA sizes. These findings demonstrate the utility of these independently tunable mechanical/biochemistry gels, and that mechanical confinement in stiffer microenvironments may increase cell proliferation. PMID:27484403

  20. Composite alginate gels for tunable cellular microenvironment mechanics

    PubMed Central

    Khavari, Adele; Nydén, Magnus; Weitz, David A.; Ehrlicher, Allen J.

    2016-01-01

    The mechanics of the cellular microenvironment can be as critical as biochemistry in directing cell behavior. Many commonly utilized materials derived from extra-cellular-matrix create excellent scaffolds for cell growth, however, evaluating the relative mechanical and biochemical effects independently in 3D environments has been difficult in frequently used biopolymer matrices. Here we present 3D sodium alginate hydrogel microenvironments over a physiological range of stiffness (E = 1.85 to 5.29 kPa), with and without RGD binding sites or collagen fibers. We use confocal microscopy to measure the growth of multi-cellular aggregates (MCAs), of increasing metastatic potential in different elastic moduli of hydrogels, with and without binding factors. We find that the hydrogel stiffness regulates the growth and morphology of these cell clusters; MCAs grow larger and faster in the more rigid environments similar to cancerous breast tissue (E = 4–12 kPa) as compared to healthy tissue (E = 0.4–2 kpa). Adding binding factors from collagen and RGD peptides increases growth rates, and change maximum MCA sizes. These findings demonstrate the utility of these independently tunable mechanical/biochemistry gels, and that mechanical confinement in stiffer microenvironments may increase cell proliferation. PMID:27484403

  1. Stark broadening of B IV spectral lines

    NASA Astrophysics Data System (ADS)

    Dimitrijević, Milan S.; Christova, Magdalena; Simić, Zoran; Kovačević, Andjelka; Sahal-Bréchot, Sylvie

    2016-08-01

    Stark broadening parameters for 157 multiplets of helium-like boron (B IV) have been calculated using the impact semiclassical perturbation formalism. Obtained results have been used to investigate the regularities within spectral series. An example of the influence of Stark broadening on B IV lines in DO white dwarfs is given.

  2. Stark broadening of B IV spectral lines

    NASA Astrophysics Data System (ADS)

    Dimitrijević, Milan S.; Christova, Magdalena; Simić, Zoran; Kovačević, Andjelka; Sahal-Bréchot, Sylvie

    2016-05-01

    Stark broadening parameters for 157 multiplets of helium like boron (B IV) have been calculated using the impact semiclassical perturbation formalism. Obtained results have been used to investigate the regularities within spectral series. An example of the influence of Stark broadening on B IV lines in DO white dwarfs is given.

  3. CHLORINE ABSORPTION IN S(IV) SOLUTIONS

    EPA Science Inventory

    The rate of chlorine (Cl2) absorption into aqueous sulfite/bisulfite [S(IV)] solutions was measured at ambient temperature using a highly characterized stirred cell reactor. The reactor media were 0 to 10 mM S(IV) with pH ranging from 3.5 to 8.5. Experiments were performed using ...

  4. Metsahovi Radio Observatory - IVS Network Station

    NASA Technical Reports Server (NTRS)

    Uunila, Minttu; Zubko, Nataliya; Poutanen, Markku; Kallunki, Juha; Kallio, Ulla

    2013-01-01

    In 2012, Metsahovi Radio Observatory together with Finnish Geodetic Institute officially became an IVS Network Station. Eight IVS sessions were observed during the year. Two spacecraft tracking and one EVN X-band experiment were also performed. In 2012, the Metsahovi VLBI equipment was upgraded with a Digital Base Band Converter, a Mark 5B+, a FILA10G, and a FlexBuff.

  5. IVS Working Group 4: VLBI Data Structures

    NASA Technical Reports Server (NTRS)

    Gipson, John

    2010-01-01

    In 2007 the IVS Directing Board established IVS Working Group 4 on VLBI Data Structures. This note discusses the current VLBI data format, goals for a new format, the history and formation of the Working Group, and a timeline for the development of a new VLBI data format.

  6. CHLORINE ABSORPTION IN S(IV) SOLUTIONS

    EPA Science Inventory

    The report gives results of measurements of the rate of Chlorine (Cl2) absorption into aqueous sulfite/bisulfite -- S(IV) -- solutions at ambient temperature using a highly characterized stirred-cell reactor. The reactor media were 0 to 10 mM S(IV) with pHs of 3.5-8.5. Experiment...

  7. Terpolymer smart gels: synthesis and characterizations

    NASA Astrophysics Data System (ADS)

    Bag, Dibyendu S.; Alam, Sarfaraz; Mathur, G. N.

    2004-10-01

    Two smart terpolymer gels, MS-1 and MS-2, were synthesized such that the same gel can respond to more than one external environmental condition, such as pH, temperature, solvent composition, electric field. So two terpolymers gels of vinyl monomers such as sodium acrylate, acrylamide and N-isopropyl acrylamide were synthesized by using ammonium persulfate (APS) as an initiator, N,N,N',N'-tetramethyl ethylene diamine (TMEDA) as an accelerator and methylene bisacrylamide as a cross-linker. These terpolymers were characterized by elemental and Fourier transform infrared analysis. The swelling behavior of these terpolymer smart gels was evaluated by changing the pH, temperature and solvent composition. The variation of the swelling behavior with time was evaluated in an aqueous medium at room temperature. The time taken for maximum swelling (tm) was about 20 min for the gel MS-2. However the tm value for the gel MS-1 is higher than that of MS-2. The swelling behavior remains almost unchanged over a temperature range of 22-50 °C for both the gels. The discontinuous volume transitions were observed at pH 7.6 and 8.2 for the two gels, MS-1 and MS-2, respectively. The gel MS-1 suddenly shrinks below and swells above pH 7.6. Correspondingly, the pH is 8.2 for the case of MS-2. Volume transitions in an acetone-water mixture were also observed for these gels. The swelling behaviors of these two smart gels are almost parallel above the 40% acetone concentration.

  8. Pyrene-based fluorescent ambidextrous gelators: scaffolds for mechanically robust SWNT-gel nanocomposites.

    PubMed

    Mandal, Deep; Kar, Tanmoy; Das, Prasanta Kumar

    2014-01-27

    With the rapid progress in the development of supramolecular soft materials, examples of low-molecular-weight gelators (LMWGs) with the ability to immobilise both water and organic solvents by the same structural scaffold are very limited. In this paper, we report the development of pyrene-containing peptide-based ambidextrous gelators (AGs) with the ability to efficiently gelate both organic and aqueous solvents. The organo- and hydrogelation efficiencies of these gelators are in the range 0.7-1.1% w/v in various organic solvents and 0.5-5% w/v in water at certain acidic pH values (pH 2.0-4.0). Moreover, for the first time, AGs have been utilised to prepare single-walled carbon-nanotube (SWNT)-included soft nanocomposites in both hydro- and organogel matrices. The influence of different non-covalent interactions such as hydrogen bonding, hydrophobic, π-π and van der Waals interactions in self-assembled gelation has been studied in detail by circular dichroism, FTIR, variable-temperature NMR, 2D NOESY and luminescence spectroscopy. Interestingly, the presence of the pyrene moiety in the structure rendered these AGs intrinsically fluorescent, which was quenched upon successful integration of the SWNTs within the gel. The prepared hydro- and organogels along with their SWNT-integrated nanocomposites are thermoreversible in nature. The supramolecular morphologies of the dried gels and SWNT-gel nanocomposites have been studied by transmission electron microscopy, fluorescence microscopy and polarising optical microscopy, which confirmed the presence of three-dimensional self-assembled fibrillar networks (SAFINs) as well as the integrated SWNTs. Importantly, rheological studies revealed that the inclusion of SWNTs within the ambidextrous gels improved the mechanical rigidity of the resulting soft nanocomposites up to 3.8-fold relative to the native gels. PMID:24339266

  9. Mucolipidosis Type IV: an Update

    PubMed Central

    Wakabayashi, Kazuyo; Gustafson, Ann Marie; Sidransky, Ellen; Goldin, Ehud

    2011-01-01

    Mucolipidosis type IV (MLIV) is a neurodevelopmental as well as neurodegenerative disorder with severe psychomotor developmental delay, progressive visual impairment, and achlorydria. It is characterized by the presence of lysosomal inclusions in many cell types in patients. MLIV is an autosomal recessive disease caused by mutations in MCOLN1, which encodes for mucolipin-1, a member of the transient receptor potential (TRP) cation channel family. Although approximately 70-80% of patients identified are Ashkenazi Jewish, MLIV is a pan-ethnic disorder. Importantly, while MLIV is thought to be a rare disease, its frequency may be greater than currently appreciated, for its common presentation as a cerebral palsy-like encephalopathy can lead to misdiagnosis. Moreover, patients with milder variants are often not recognized as having MLIV. This review provides an update on the ethnic distribution, clinical manifestations, laboratory findings, methods of diagnosis, molecular genetics, differential diagnosis, and treatment of patients with MLIV. An enhanced awareness of the manifestations of this disorder may help to elucidate the true frequency and range of symptoms associated with MLIV, providing insight into the pathogenesis of this multi-system disease. PMID:21763169

  10. Viscoelastic Properties of Vitreous Gel

    NASA Astrophysics Data System (ADS)

    Pirouz Kavehpour, H.; Sharif-Kashani, Pooria

    2010-11-01

    We studied the rheological properties of porcine vitreous humor using a stressed-control shear rheometer. All experiments were performed in a closed environment at body temperature to mimic in-vivo conditions. We modeled the creep deformation using a two-element retardation spectrum model. By associating each element of the model to an individual biopolymeric system in the vitreous gel, a separate response to the applied stress was obtained from each component. The short time scale was associated with the collagen structure, while the longer time scale was related to the microfibrilis and hyaluronan network. We were able to distinguish the role of each main component from the overall rheological properties. Knowledge of this correlation enables us to relate the physical properties of vitreous to its pathology, as well as optimize surgical procedures such as vitrectomy.

  11. Gel transitions in colloidal suspensions

    NASA Astrophysics Data System (ADS)

    Bergenholtz, J.; Fuchs, M.

    1999-12-01

    The idealized mode-coupling theory (MCT) is applied to colloidal systems interacting via short-range attractive interactions of Yukawa form. At low temperatures, MCT predicts a slowing down of the local dynamics and ergodicity-breaking transitions. The non-ergodicity transitions share many features with the colloidal gel transition, and are proposed to be the source of gelation in colloidal systems. Previous calculations of the phase diagram are complemented with additional data for shorter ranges of the attractive interaction, showing that the path of the non-ergodicity transition line is then unimpeded by the gas-liquid critical curve at low temperatures. Particular attention is given to the critical non-ergodicity parameters; this is motivated by recent experimental measurements. An asymptotic model is developed, valid for dilute systems of spheres interacting via strong short-range attractions, and is shown to capture all aspects of the low-temperature MCT non-ergodicity transitions.

  12. Ethanol fermentation of sugarcane molasses by Zymomonas mobilis MTCC 92 immobilized in Luffa cylindrica L. sponge discs and Ca-alginate matrices.

    PubMed

    Behera, Shuvashish; Mohanty, Rama C; Ray, Ramesh C

    2012-10-01

    Bio-ethanol production from cane molasses (diluted to 15 % sugar w/v) was studied using the bacterium, Zymomonas mobilis MTCC 92 entrapped in luffa (Luffa cylindrica L.) sponge discs and Ca-alginate gel beads as the immobilizing matrices. At the end of 96 h fermentation, the final ethanol concentrations were 58.7 ± 0.09 and 59.1 ± 0.08 g/l molasses with luffa and Ca-alginate entrapped Z. mobilis cells, respectively exhibiting 83.25 ± 0.03 and 84.6 ± 0.02 % sugar conversion. There was no statistical significant difference (Fischer's LSD) in sugar utilization (t = 0.254, p<0.801) and ethanol production (t =-0.663, p<0.513) between the two immobilization matrices used. Further, the immobilized cells in both the matrices were physiologically active for three more cycles of operation with less than 15 % decrease in ethanol yield in the 4(th) cycle, which was due to some leakage of cells. In conclusion, luffa sponge was found to be equally good as Ca-alginate as a carrier material for bacterial (Z. mobilis) cell immobilization for ethanol production. Further, it has added advantages such as it is cheap, non-corrosive and has no environmental hazard. PMID:24031981

  13. Ethanol fermentation of sugarcane molasses by Zymomonas mobilis MTCC 92 immobilized in Luffa cylindrica L. sponge discs and Ca-alginate matrices

    PubMed Central

    Behera, Shuvashish; Mohanty, Rama C.; Ray, Ramesh C.

    2012-01-01

    Bio-ethanol production from cane molasses (diluted to 15 % sugar w/v) was studied using the bacterium, Zymomonas mobilis MTCC 92 entrapped in luffa (Luffa cylindrica L.) sponge discs and Ca-alginate gel beads as the immobilizing matrices. At the end of 96 h fermentation, the final ethanol concentrations were 58.7 ± 0.09 and 59.1 ± 0.08 g/l molasses with luffa and Ca-alginate entrapped Z. mobilis cells, respectively exhibiting 83.25 ± 0.03 and 84.6 ± 0.02 % sugar conversion. There was no statistical significant difference (Fischer’s LSD) in sugar utilization (t = 0.254, p<0.801) and ethanol production (t =-0.663, p<0.513) between the two immobilization matrices used. Further, the immobilized cells in both the matrices were physiologically active for three more cycles of operation with less than 15 % decrease in ethanol yield in the 4th cycle, which was due to some leakage of cells. In conclusion, luffa sponge was found to be equally good as Ca-alginate as a carrier material for bacterial (Z. mobilis) cell immobilization for ethanol production. Further, it has added advantages such as it is cheap, non-corrosive and has no environmental hazard. PMID:24031981

  14. A method by homemade OH/TSO-PMHS fibre solid-phase microextraction coupling with gas chromatography-mass spectrometry for analysis of antiestrogens in biological matrices.

    PubMed

    Liu, Wei; Zhang, Lan; Chen, Shengping; Duan, Hongbin; Chen, Xi; Wei, Zhenyi; Chen, Guonan

    2009-01-01

    A kind of homemade solid-phase microextraction fibre coupled with gas chromatography-mass spectrometry (GC-MS) was developed for trace analysis of antiestrogens (tamoxifen, cis- and trans-clomiphene) in biological matrices. In this method, derivatization was unnecessary and sample solution could be injected directly after very simple deproteinization operation. The conditions of influencing adsorption of the solid-phase microextraction (SPME) fibre and desorption of the analytes were investigated in details. Matrix effects were studied in different background. Under optimum conditions, the proposed method was further validated by spiking analytes into rabbit liver solutions. Linear ranges of tamoxifen, cis- and trans-clomiphene were 0.02-2.56, 0.08-2.56 and 0.16-2.56 ng mL(-1), respectively. The limits of quantitation were in the range of 0.02-0.16 ng mL(-1). The intra-day accuracy was ranged 96.2-106.2% and precision were in the range of 5.1-8.7%. The extraction recoveries of the antiestrogens in rabbit liver solution were between 73.8% and 113.1%, and R.S.D.s were from 3.6% to 14.1%. The results show that the homemade sol-gel coating is suitable for determination of trace antiestrogens in complex matrices. The proposed approach was proved to be rapid, simple, easy, sensitive and reproducible for trace analysis of antiestrogens in biological matrices. PMID:19046677

  15. Synthesis of phthalocyanine doped sol-gel materials

    NASA Technical Reports Server (NTRS)

    Dunn, Bruce

    1993-01-01

    The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross

  16. Dissemination of methicillin-resistant Staphylococcus aureus SCCmec type IV and SCCmec type V epidemic clones in a tertiary hospital: challenge to infection control.

    PubMed

    Dhawan, B; Rao, C; Udo, E E; Gadepalli, R; Vishnubhatla, S; Kapil, A

    2015-01-01

    Two-hundred MRSA strains from inpatients with healthcare-associated (HA) and 100 MRSA strains from outpatients with community-associated (CA) skin and soft tissue infections (SSTIs) were tested for antimicrobial susceptibility, staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) toxin, seh and arcA genes. Based on SCCmec typing, HA-MRSA isolates were further divided into HA-SCCmec I/II/III MRSA and HA-SCCmec IV/V MRSA, and CA-MRSA isolates into CA-SCCmec I/II/III MRSA and CA-SCCmec IV/V MRSA. SCCmec types were further characterized by pulsed-field gel electrophoresis, spa typing and multi-locus sequence typing. Seventy-five (37·5%) HA-MRSA isolates and 83/100 CA-MRSA isolates were SCCmec IV/V genotype. HA-SCCmec IV/V MRSA was associated with malignancy (P = 0·03) and bone fractures (P = 0·02) compared to CA-SCCmec IV/V MRSA. HA-SCCmec IV/V MRSA was associated with PVL gene carriage compared to HA-SCCmec I/II/III MRSA (P < 0·001). ST22-MRSA-IV (EMRSA-15), ST772-MRSA-V, and ST36-MRSA-IV and ST239:EMRSA-I:III were the major clones identified. Our study documents the emergence of SCCmec IV and SCCmec V MRSA clones in an Indian hospital. PMID:24690229

  17. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  18. Chain Release Behavior of Gellan Gels

    NASA Astrophysics Data System (ADS)

    Hossain, Khandker S.; Nishinari, Katsuyoshi

    The chain release behavior from gellan gels was studied by immersing the gel into water and monitoring the mass loss as a function of time. Concentration of released gellan in the external solution was determined for gels of different sizes using phenol-sulfuric acid method. The chain release process became faster with increasing total surface area and volume. However the concentration of released chain normalized by surface area and volume suggests that the chain release itself is governed not only by the ionic effect and the amount of unassociated chains in gel but other factors such as osmotic pressure may play an important role on the chain release from the gels. The diffusion coefficient was estimated from the chain release process which is in the same order of magnitude reported for an isolated gellan chain by light scattering. Rheological measurements also suggest that the unassociated gellan chains are released out when immersed in pure water while unassociated chains are restricted to release out when immersed in salt solution due to the intrusion of cations which is responsible for further association of the unassociated gellan chains being in agreement with the previously published results. The elastic modulus of gels was increased by immersion of gels in water and in salt solutions, which can be attributed as the stiffening of network chains due to gel swelling and the conversion from free and unassociated chains into network chains, respectively, leading to an increase in elastic modulus with time.

  19. Sol-gel kinetics by NMR

    SciTech Connect

    Assink, R.A.; Kay, B.D.

    1991-01-01

    The chemical synthesis of advanced ceramic and glass materials by the sol-gel process has become an area of increasing activity in the field of material science. The sol-gel process provides a means to prepare homogeneous, high purity materials with tailored chemical and physical properties. This paper surveyed the nuclear magnetic resonance (NMR) studies of silicon-based sol-gel kinetics. A review of the various models which have been used to analyze the chemical kinetics of various sol-gel systems was presented. The utility of NMR spectroscopy was demonstrated in investigating the influence that various reaction conditions have on the reaction pathways by which sol-gel derived materials are synthesized. By observing in a direct fashion the chemical pathway of the sol-gel, it is often possible to relate the final properties of the material to the formulation and reaction conditions of the sol-gel. The study of reaction kinetics by NMR is expected to play an increasingly important role in understanding sol-gel processing and material properties. 15 refs. (DP)

  20. A Short-Duration Gel Diffusion Experiment.

    ERIC Educational Resources Information Center

    Mulcahy, D. E.

    1980-01-01

    Described is a gel diffusion experiment that permits the completion of duplicate diffusion runs within a three-hour laboratory session. Information included for the short-duration gel diffusion experiment is the diffusion cell, the experiment, data treatment, and the expected results of the experiment. (Author/DS)

  1. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  2. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  3. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  4. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  5. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  6. Fluorescence detection for gel and capillary electrophoresis

    SciTech Connect

    Hogan, B.

    1992-07-21

    First, an indirect fluorescence detection system for the separation of proteins via gel electrophoresis. Quantities as low as 50 nanograms of bovine serum albumin and soybean trypsin inhibitor are separated and detected visually without the need for staining of the analytes. This is very similar to levels of protein commonly separated with gel electrophoresis.

  7. Anomalous C IV and Si IV resonance lines in 36 Lyncis

    SciTech Connect

    Sadakane, K.

    1984-03-01

    Of the anomalously strong C IV and Si IV resonance lines found in the UV spectrum of the chemically peculiar star 36 Lyncis, the C IV lines near 1550 A are noted to be absent in about 40 other middle or late B-type main sequence stars. Also found is a peculiar intensity ratio between C IV and Si IV lines, where the former are stronger. The continuous energy distribution of 36 Lyn in the UV region fits with those of late B-type stars, and the presence of a hot, chromospheric or coronal gas is suggested. 14 references.

  8. HiCPlotter integrates genomic data with interaction matrices.

    PubMed

    Akdemir, Kadir Caner; Chin, Lynda

    2015-01-01

    Metazoan genomic material is folded into stable non-randomly arranged chromosomal structures that are tightly associated with transcriptional regulation and DNA replication. Various factors including regulators of pluripotency, long non-coding RNAs, or the presence of architectural proteins have been implicated in regulation and assembly of the chromatin architecture. Therefore, comprehensive visualization of this multi-faceted structure is important to unravel the connections between nuclear architecture and transcriptional regulation. Here, we present an easy-to-use open-source visualization tool, HiCPlotter, to facilitate juxtaposition of Hi-C matrices with diverse genomic assay outputs, as well as to compare interaction matrices between various conditions. https://github.com/kcakdemir/HiCPlotter. PMID:26392354

  9. Chemical stability of titanium diboride reinforcement in nickel aluminide matrices

    NASA Technical Reports Server (NTRS)

    Rigney, J. D.; Lewandowski, J. J.

    1993-01-01

    Chemical stability of TiB2 reinforcement in NiAl (45 at percent Al) and Ni3Al (24 at percent Al) matrices has been theoretically and experimentally investigated. Calculations were made using thermodynamic properties of the systems to predict behavior at temperatures between 1173 and 1573 K. Experimental investigation of hot-press consolidated TiB2 particulate/prealloyed matrix powder blends were conducted using energy dispersive X-ray analysis, XRD, AES, and TEM. The theoretical and experimental analyses suggest that TiB2 is chemically stable in both matrices up to 1573 K; however, TiB2 was found to be less active in NiAl than in Ni3Al due to lower nickel activity in NiAl.

  10. Pseudounitary symmetry and the Gaussian pseudounitary ensemble of random matrices.

    PubMed

    Ahmed, Zafar; Jain, Sudhir R

    2003-04-01

    Employing the currently discussed notion of pseudo-Hermiticity, we define a pseudounitary group. Further, we develop a random matrix theory that is invariant under such a group and call this ensemble of pseudo-Hermitian random matrices the pseudounitary ensemble. We obtain exact results for the nearest-neighbor level-spacing distribution for (2 x 2) PT-invariant Hamiltonian matrices that have forms, approximately Sln(1/S) near zero spacing for three independent elements and approximately S for four independent elements. This shows a level repulsion in a marked distinction with an algebraic form S(beta) in the Wigner surmise. We believe that this paves the way for a description of varied phenomena in two-dimensional statistical mechanics, quantum chromodynamics, and so on. PMID:12786422

  11. Properties of Zero-Free Transfer Function Matrices

    NASA Astrophysics Data System (ADS)

    D. O. Anderson, Brian; Deistler, Manfred

    Transfer functions of linear, time-invariant finite-dimensional systems with more outputs than inputs, as arise in factor analysis (for example in econometrics), have, for state-variable descriptions with generic entries in the relevant matrices, no finite zeros. This paper gives a number of characterizations of such systems (and indeed square discrete-time systems with no zeros), using state-variable, impulse response, and matrix-fraction descriptions. Key properties include the ability to recover the input values at any time from a bounded interval of output values, without any knowledge of an initial state, and an ability to verify the no-zero property in terms of a property of the impulse response coefficient matrices. Results are particularized to cases where the transfer function matrix in question may or may not have a zero at infinity or a zero at zero.

  12. Fractal kinetics in drug release from finite fractal matrices

    NASA Astrophysics Data System (ADS)

    Kosmidis, Kosmas; Argyrakis, Panos; Macheras, Panos

    2003-09-01

    We have re-examined the random release of particles from fractal polymer matrices using Monte Carlo simulations, a problem originally studied by Bunde et al. [J. Chem. Phys. 83, 5909 (1985)]. A certain population of particles diffuses on a fractal structure, and as particles reach the boundaries of the structure they are removed from the system. We find that the number of particles that escape from the matrix as a function of time can be approximated by a Weibull (stretched exponential) function, similar to the case of release from Euclidean matrices. The earlier result that fractal release rates are described by power laws is correct only at the initial stage of the release, but it has to be modified if one is to describe in one picture the entire process for a finite system. These results pertain to the release of drugs, chemicals, agrochemicals, etc., from delivery systems.

  13. Crystalline matrices for immobilization of actinides: Corrosion resistance in water

    NASA Astrophysics Data System (ADS)

    Yudintsev, S. V.; Aleksandrova, E. V.; Livshits, T. S.; Mal'kovskii, V. I.; Bychkova, Ya. V.; Tagirov, B. R.

    2014-10-01

    The rate of leaching of actinide-simulating rare-earth elements from two types of crystalline matrices consisting of titanate and titanozirconate phases was examined. The experiments were carried out at 95°C in distilled water. The rates of REE leaching from the samples were below 10-3 g/m2 day, which satisfied the requirements for the characteristics of matrices for immobilization of actinides. After passing the treated solutions through filters of 450 to 25 nm pore sizes, the REE content was changed slightly or not at all. This fact points to the minor role or to the absence of the colloidal form of REE in the solutions after the experiments.

  14. Transformation matrices between non-linear and linear differential equations

    NASA Technical Reports Server (NTRS)

    Sartain, R. L.

    1983-01-01

    In the linearization of systems of non-linear differential equations, those systems which can be exactly transformed into the second order linear differential equation Y"-AY'-BY=0 where Y, Y', and Y" are n x 1 vectors and A and B are constant n x n matrices of real numbers were considered. The 2n x 2n matrix was used to transform the above matrix equation into the first order matrix equation X' = MX. Specially the matrix M and the conditions which will diagonalize or triangularize M were studied. Transformation matrices P and P sub -1 were used to accomplish this diagonalization or triangularization to return to the solution of the second order matrix differential equation system from the first order system.

  15. Optimal Estimation and Rank Detection for Sparse Spiked Covariance Matrices

    PubMed Central

    Cai, Tony; Ma, Zongming; Wu, Yihong

    2014-01-01

    This paper considers a sparse spiked covariancematrix model in the high-dimensional setting and studies the minimax estimation of the covariance matrix and the principal subspace as well as the minimax rank detection. The optimal rate of convergence for estimating the spiked covariance matrix under the spectral norm is established, which requires significantly different techniques from those for estimating other structured covariance matrices such as bandable or sparse covariance matrices. We also establish the minimax rate under the spectral norm for estimating the principal subspace, the primary object of interest in principal component analysis. In addition, the optimal rate for the rank detection boundary is obtained. This result also resolves the gap in a recent paper by Berthet and Rigollet [2] where the special case of rank one is considered. PMID:26257453

  16. Novel Organotin(IV)-Schiff Base Complexes: Synthesis, Characterization, Antimicrobial Activity, and DNA Interaction Studies

    PubMed Central

    Prasad, K. Shiva; Kumar, L. Shiva; Prasad, Melvin; Revanasiddappa, Hosakere D.

    2010-01-01

    Four organotin(IV) complexes with 2-(2-hydroxybenzylideneamino)isoindoline-1,3-dione (L1), and 4-(4-hydroxy-3-methoxybenzylideneamino-N-(pyrimidin-2-yl)benzenesulfonamide (L2) were synthesized and well characterized by analytical and spectral studies. The synthesized compounds were tested for antimicrobial activity by disc diffusion method. The DNA binding of the complexes 1 and 3 with CT-DNA has been performed with absorption spectroscopy, which showed that both the complexes are avid binders of CT-DNA. Also the nuclease activity of complexes 1 and 3 with plasmid DNA (pUC19) was studied using agarose gel electrophoresis. The complex 1 can act as effective DNA cleaving agent when compared to complex 3 resulting in the nicked form of DNA under physiological conditions. The gel was run both in the absence and presence of the oxidizing agent. PMID:21253533

  17. Transparent poly(vinyl acetate)-silica gels by a sol-gel process

    NASA Astrophysics Data System (ADS)

    Wojcik, Anna B.; Klein, Lisa C.

    1993-12-01

    Rod shaped silica-poly(vinyl acetate) (PVAc) gels have been prepared by a sol gel process. In situ polymerization of tetraethoxysilane (TEOS) was accomplished in the presence of low molecular weight PVAc by dissolving various amounts of PVAc in a mixture of TEOS, ethanol, water and hydrochloric acid (HCl). Gelation of this mixture was carried out between room temperature and slightly above. Silica-PVAc rods recovered from cylindrical molds were homogeneous and transparent. Gels with weight percents of PVAc ranging from 2% to 50% were prepared. Silica-PVAc gels have higher flexure strengths, less brittle character and improved water durability in comparison with pure sol- gel silica.

  18. Thermotropic nanostructured "gel in gel" systems for improved oil recovery and water shutoff

    NASA Astrophysics Data System (ADS)

    Altunina, L. K.; Kuvshinov, V. A.; Stasyeva, L. A.

    2015-10-01

    Thermotropic nanostructured system with two gel-forming components has been created based on inorganic hydroxypolymer and organic polymer with a lower critical solution temperature of "aluminum salt-cellulose ether-carbamide-water", forming at heating a bound-dispersed nano-sized "gel in gel" structure. The studies on the kinetics of gelation and rheological properties of solutions and gels in this system have shown that the gels have a higher viscosity and elasticity and thereby are promising for creating deflecting screens in oil reservoirs, redistribution of filtration flows, improved oil recovery and for water shutoff.

  19. Drop spreading and resorbtion on gel surfaces

    NASA Astrophysics Data System (ADS)

    Banaha, Mehdi; Daerr, Adrian; Limat, Laurent

    2008-03-01

    We have studied the dynamics of liquid drops on agar gels, using a visualisation method which captures the evolution of the free surface. A first remarquable observation is that drops of water deposited on the surface do not spread, although the gel consists of up to 99.7% water and as low as 0.3% agarose. Instead, the drop slowly de-wets and resorbs into the gel which swells locally. If the deposited drop contains surfactants, the dynamics is very different. A sharp circular swelling front develops and progressively invades the whole surface. We study the propagation of this front as a function of surfactant and agarose concentration, and compare its typical properties to similar fronts appearing during mass swarming events of bacterial colonies under the same conditions. The observations reveal the complex nature of gel surface physico-chemistry and its aging, and may be related to recent friction measurements at gel interfaces.

  20. Photoswitchable gel assembly based on molecular recognition.

    PubMed

    Yamaguchi, Hiroyasu; Kobayashi, Yuichiro; Kobayashi, Ryosuke; Takashima, Yoshinori; Hashidzume, Akihito; Harada, Akira

    2012-01-01

    The formation of effective and precise linkages in bottom-up or top-down processes is important for the development of self-assembled materials. Self-assembly through molecular recognition events is a powerful tool for producing functionalized materials. Photoresponsive molecular recognition systems can permit the creation of photoregulated self-assembled macroscopic objects. Here we demonstrate that macroscopic gel assembly can be highly regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules. A photoregulated gel assembly system is developed using polyacrylamide-based hydrogels functionalized with azobenzene (guest) or cyclodextrin (host) moieties. Reversible adhesion and dissociation of the host gel from the guest gel may be controlled by photoirradiation. The differential affinities of α-cyclodextrin or β-cyclodextrin for the trans-azobenzene and cis-azobenzene are employed in the construction of a photoswitchable gel assembly system. PMID:22215078

  1. Photoswitchable gel assembly based on molecular recognition

    PubMed Central

    Yamaguchi, Hiroyasu; Kobayashi, Yuichiro; Kobayashi, Ryosuke; Takashima, Yoshinori; Hashidzume, Akihito; Harada, Akira

    2012-01-01

    The formation of effective and precise linkages in bottom-up or top-down processes is important for the development of self-assembled materials. Self-assembly through molecular recognition events is a powerful tool for producing functionalized materials. Photoresponsive molecular recognition systems can permit the creation of photoregulated self-assembled macroscopic objects. Here we demonstrate that macroscopic gel assembly can be highly regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules. A photoregulated gel assembly system is developed using polyacrylamide-based hydrogels functionalized with azobenzene (guest) or cyclodextrin (host) moieties. Reversible adhesion and dissociation of the host gel from the guest gel may be controlled by photoirradiation. The differential affinities of α-cyclodextrin or β-cyclodextrin for the trans-azobenzene and cis-azobenzene are employed in the construction of a photoswitchable gel assembly system. PMID:22215078

  2. Improving immobilized biocatalysts by gel phase polymerization

    SciTech Connect

    Kuu, W.Y.; Polack, J.A.

    1983-08-01

    A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar or carrageenan gel with polyacrylamide to form a rigid support which retains the high catalytic activity characteristic of the untreated biocatalysts. The size and shape of the biocatalyst is unaffected by this treatment. The method involves the diffusion of acrylamide, N,N'-methylenebisacrylamide and BETA-dimethylaminopropionitrile (or N,N,N',N'-tetramethylethylenediamine) into the preformed biocatalyst beads followed by the addition of an initiator to cause polymerization within the beads. Treated gels have been used for the continuous fermentation of glucose to ethanol in a packed column for over two months.

  3. Generation of inkjet drop of particulate gel

    NASA Astrophysics Data System (ADS)

    Yoo, Hansol; Kim, Chongyoup

    2015-08-01

    The generation of inkjet drops of colloidal gels is studied experimentally. Particle suspensions are prepared by dispersing spherical polystyrene particles of 620 nm in the 1:1 mixture of deionized water and ethylene glycol. The gels are prepared by adding polyethylene oxide to the suspensions by inducing the depletion interaction between particles. It is demonstrated that inkjet drops can be generated by using the colloidal gels. It is found that the ligament extended from the inkjet nozzle is stabilized so that the drop can be generated without satellite droplets behind the main drop and the velocity of the gel drop is faster than that of the polymer solution at the same concentration. The gel drop generation characteristics are found to be sensitive to input voltage.

  4. Development of biodegradable aluminium carboxymethylcellulose matrices for mosquito larvicides.

    PubMed

    Mathew, Nisha; Kalyanasundaram, Muthuswami

    2004-07-01

    The use of ecofriendly biodegradable controlled-release formulations of mosquito larvicides could reduce the frequency of application and losses due to degradation of the insecticide compared with conventional formulations. Among the 20 matrices developed by entrapping the organophosphorus mosquito larvicide, fenthion, in carboxymethylcellulose ionotropically cross-linked with aluminium ions which were studied for release profiles, two matrices, CRF3b and CRF5b, were found to be stable for 16 and 14 weeks under simulated field conditions. The average concentration of fenthion released per week ranged from 0.06 to 3.5 mg litre(-1) for CRF3b and 0.09 to 2.72 mg litre(-1) for CRF5b. Of these two formulations, CRF3b was the more stable, maintaining the concentration of the active ingredient at the level required to effect mosquito control. The cumulative release of fenthion per pellet was 80% from CRF3b and 72% from CRF5b. Based on the study with fenthion, two similar matrices for triflumuron, a benzoylphenylurea insect growth regulator, STAR3b and STAR5b were developed. These matrices were stable up to 16 weeks with the average concentration of triflumuron released per week ranging from 0.05 to 3.44 mg litre(-1) for STAR3b and 0.07 to 2.71 mg litre(-1) for STARSb. The cumulative release of triflumuron per pellet was 75% from STAR3b and 76% from STAR5b. From the results of this study under simulated conditions, it is estimated that the application of four pellets of either fenthion or triflumuron per square metre of the breeding surface may play a useful role in controlling Culex quinquefasciatus Say in larval habitats for about 4 months. PMID:15260300

  5. Spectrum of Lebesgue Measure Zero for Jacobi Matrices of Quasicrystals

    NASA Astrophysics Data System (ADS)

    Beckus, Siegfried; Pogorzelski, Felix

    2013-09-01

    We study one-dimensional random Jacobi operators corresponding to strictly ergodic dynamical systems. We characterize the spectrum of these operators via non-uniformity of the transfer matrices and vanishing of the Lyapunov exponent. For aperiodic, minimal subshifts satisfying the so-called Boshernitzan condition this gives that the spectrum is supported on a Cantor set with Lebesgue measure zero. This generalizes earlier results for Schrödinger operators.

  6. Full-counting statistics of random transition-rate matrices.

    PubMed

    Mordovina, Uliana; Emary, Clive

    2013-12-01

    We study the full-counting statistics of current of large open systems through the application of random-matrix theory to transition-rate matrices. We develop a method for calculating the ensemble-averaged current-cumulant generating functions based on an expansion in terms of the inverse system size. We investigate how different symmetry properties and different counting schemes affect the results. PMID:24483426

  7. Partitioning Rectangular and Structurally Nonsymmetric Sparse Matrices for Parallel Processing

    SciTech Connect

    B. Hendrickson; T.G. Kolda

    1998-09-01

    A common operation in scientific computing is the multiplication of a sparse, rectangular or structurally nonsymmetric matrix and a vector. In many applications the matrix- transpose-vector product is also required. This paper addresses the efficient parallelization of these operations. We show that the problem can be expressed in terms of partitioning bipartite graphs. We then introduce several algorithms for this partitioning problem and compare their performance on a set of test matrices.

  8. Spectral properties of sums of Hermitian matrices and algebraic geometry

    NASA Astrophysics Data System (ADS)

    Chau Huu-Tai, P.; Van Isacker, P.

    2016-04-01

    It is shown that all the eigenvectors of a sum of Hermitian matrices belong to the same algebraic variety. A polynomial system characterizing this variety is given and a set of nonlinear equations is derived which allows the construction of the variety. Moreover, in some specific cases, explicit expressions for the eigenvectors and eigenvalues can be obtained. Explicit solutions of selected models are also derived.

  9. Solution of the determinantal assignment problem using the Grassmann matrices

    NASA Astrophysics Data System (ADS)

    Karcanias, Nicos; Leventides, John

    2016-02-01

    The paper provides a direct solution to the determinantal assignment problem (DAP) which unifies all frequency assignment problems of the linear control theory. The current approach is based on the solvability of the exterior equation ? where ? is an n -dimensional vector space over ? which is an integral part of the solution of DAP. New criteria for existence of solution and their computation based on the properties of structured matrices are referred to as Grassmann matrices. The solvability of this exterior equation is referred to as decomposability of ?, and it is in turn characterised by the set of quadratic Plücker relations (QPRs) describing the Grassmann variety of the corresponding projective space. Alternative new tests for decomposability of the multi-vector ? are given in terms of the rank properties of the Grassmann matrix, ? of the vector ?, which is constructed by the coordinates of ?. It is shown that the exterior equation is solvable (? is decomposable), if and only if ? where ?; the solution space for a decomposable ?, is the space ?. This provides an alternative linear algebra characterisation of the decomposability problem and of the Grassmann variety to that defined by the QPRs. Further properties of the Grassmann matrices are explored by defining the Hodge-Grassmann matrix as the dual of the Grassmann matrix. The connections of the Hodge-Grassmann matrix to the solution of exterior equations are examined, and an alternative new characterisation of decomposability is given in terms of the dimension of its image space. The framework based on the Grassmann matrices provides the means for the development of a new computational method for the solutions of the exact DAP (when such solutions exist), as well as computing approximate solutions, when exact solutions do not exist.

  10. Shuttle Program. Euler angles, quaternions, and transformation matrices working relationships

    NASA Technical Reports Server (NTRS)

    Henderson, D. M.

    1977-01-01

    A brief mathematical development of the relationship between the Euler angles and the transformation matrix, the quaternion and the transformation matrix, and the Euler angles and the quaternion is presented. The analysis and equations presented apply directly to current space shuttle problems. The twelve three-axis Euler transformation matrices are given as functions of the Euler angles, the equations for the quaternion as a funtion of the Euler angles, and the Euler angles as a function of the transformation matrix elements.

  11. Tan's Epsilon-Determinant and Ranks of Matrices over Semirings

    PubMed Central

    Mohindru, Preeti; Pereira, Rajesh

    2015-01-01

    We use the ϵ-determinant introduced by Ya-Jia Tan to define a family of ranks of matrices over certain semirings. We show that these ranks generalize some known rank functions over semirings such as the determinantal rank. We also show that this family of ranks satisfies the rank-sum and Sylvester inequalities. We classify all bijective linear maps which preserve these ranks.

  12. Approximating the largest eigenvalue of network adjacency matrices

    NASA Astrophysics Data System (ADS)

    Restrepo, Juan G.; Ott, Edward; Hunt, Brian R.

    2007-11-01

    The largest eigenvalue of the adjacency matrix of a network plays an important role in several network processes (e.g., synchronization of oscillators, percolation on directed networks, and linear stability of equilibria of network coupled systems). In this paper we develop approximations to the largest eigenvalue of adjacency matrices and discuss the relationships between these approximations. Numerical experiments on simulated networks are used to test our results.

  13. Higher order matrix differential equations with singular coefficient matrices

    SciTech Connect

    Fragkoulis, V. C.; Kougioumtzoglou, I. A.; Pantelous, A. A.; Pirrotta, A.

    2015-03-10

    In this article, the class of higher order linear matrix differential equations with constant coefficient matrices and stochastic process terms is studied. The coefficient of the highest order is considered to be singular; thus, rendering the response determination of such systems in a straightforward manner a difficult task. In this regard, the notion of the generalized inverse of a singular matrix is used for determining response statistics. Further, an application relevant to engineering dynamics problems is included.

  14. Challenges of Detecting Bioterrorism Agents in Complex Matrices

    NASA Astrophysics Data System (ADS)

    Hartmann, Erica M.; Halden, Rolf U.

    This chapter offers an overview of the shift from the use of mass ­spectrometry for studying purified bioterrorism agents to the development of methods for rapid detection thereof in environmental and clinical samples. We discuss the difficulties of working with such complex matrices and present methods for quickly and effectively reducing complexity through sample preparation. Finally, we examine a success story wherein the common pathogen and potential bioterrorism agent norovirus is detected at clinically relevant levels in human stool.

  15. Optical properties of graphene simulated in MATLAB using scattering matrices

    NASA Astrophysics Data System (ADS)

    Cariappa K., S.; Kumar, Anil

    2016-04-01

    Transmittance and absorbance spectrum of monolayer and bilayer graphene are simulated, in wavelength range 400-900nm, using scattering matrices of graphene and air. MATLAB is used for simulations studies and the results are in good agreement with the experimental values reported in the literature. The high transmittance values exhibited by graphene along with its electrical properties make it a potential alternative to conventional transparent conducting oxides.

  16. Supercritical Fluid Infusion of Iron Additives in Polymeric Matrices

    NASA Technical Reports Server (NTRS)

    Nazem, Negin; Taylor, Larry T.

    1999-01-01

    The objective of this project was the experimentation to measure preparation of iron nanophases within polymeric matrices via supercritical fluid infusion of iron precursors followed by thermal reduction. Another objective was to determine if supercritical CO2 could infuse into the polymer. The experiment is described along with the materials, and the supercritical fluid infusion and cure procedures. X-ray photoelectron spectra and transmission electron micrographs were obtained. The results are summarized in charts, and tables.

  17. Surprising Coordination Geometry Differences in Ce(IV)- and Pu(IV)-Maltol Complexes

    SciTech Connect

    Lawrence Berkeley National Laboratory; Raymond, Kenneth; Szigethy, Geza; Xu, Jide; Gorden, Anne E.V.; Teat, Simon J.; Shuh, David K.; Raymond, Kenneth N.

    2008-02-12

    As part of a study to characterize the detailed coordination behavior of Pu(IV), single crystal X-ray diffraction structures have been determined for Pu(IV) and Ce(IV) complexes with the naturally-occurring ligand maltol (3-hydroxy-2-methyl-pyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methyl-pyran-4-one). Although Ce(IV) is generally accepted as a structural analog for Pu(IV), and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the Ce(IV)-bromomaltol complex displays an uncommon ligand arrangement not mirrored in the Pu(IV) complex, although the two metal species are generally accepted to be structural analogs.

  18. Radiological properties of normoxic polymer gel dosimeters

    SciTech Connect

    Venning, A.J.; Nitschke, K.N.; Keall, P.J.; Baldock, C.

    2005-04-01

    The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m{sup -3}) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.

  19. Dewatering fine coal slurries by gel extraction

    SciTech Connect

    Gehrke, S.H.; Lyu, Lii-Hurng.

    1990-01-01

    A new technology called gel extraction has been evaluated to determine its economic viability in dewatering the fine and ultrafine coal slurries generated upon separation of sulfur and ash from clean coal during the physical coal cleaning process. Water must be removed from such slurries prior to transportation and combustion but the dewatering costs are substantial, especially for the fine particles below 28 mesh (0.6 mm). Gel extraction is a potential breakthrough in slurry dewatering technology. The goal of this project was to acquire the qualitative and quantitative data needed to estimate the potential of gel extraction for dewatering coal slurries. The specific objectives were to determine the maximum extents of dewatering (minimum surface moisture in the coal product), the clarity of the water removed (minimum solids content), the speed of the dewatering cycles, the service lifetime of the gels, and the factors which influence all of these. With the results obtained, an economic analysis of Ohio coal cleaning plant dewatering technologies was carried out. The polymer gel at the heart of this project, poly (N-isopropylacrylamide) (PNIPA), can swell several times its shrunken weight at 32[degrees]C by absorbing water at 25[degrees]C. In gel extraction, a shrunken NIPA gel is contacted with a slurry at ambient temperature or cooler; the gel swells by absorbing water from the slurry. The gel is then removed from the dewatered slurry and warmed above its critical temperature of 33[degrees]C, which returns it to the shrunken state by releasing the absorbed water. The facts that the gel is reusable and the process is simple and driven by low-grade energy (warm temperatures), and not inherently limited by particle size, made the process an attractive possible alternative to centrifugation, screening, filtration, etc. for slurry dewatering.

  20. Low-temperature sol-gel-derived nanosilver-embedded silane coating as biofilm inhibitor

    NASA Astrophysics Data System (ADS)

    Babapour, A.; Yang, B.; Bahang, S.; Cao, W.

    2011-04-01

    Silver nanocomposite coatings are prepared by the sol-gel method for the prevention of biofilm formation on the surface of medical implanted devices. High-temperature processing of such coatings can lead to diffusion of nanosilver and reduce the amount of available silver particles for long-term effects. Using a low-temperature sol-gel method, we have successfully prepared silane-based matrices, phenyltriethoxysilane (PhTEOS), containing different amounts of Ag nanoparticles. The incorporation of a silver salt into the sol-gel matrix resulted in a desired silver release rate, i.e. high initial release rate followed by a lower sustained release for more than 15 days, as determined by inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM) has been employed to investigate the morphology of the film surfaces before and after immersion in a nutrient-rich bacterial suspension of approximately 108 CFU ml - 1, which was incubated for up to 30 days at 37 °C. It was found that thin films containing 35 nm particles could prevent the formation of biofilm for over 30 days. The presence of surface silver before and after 3, 9 and 15 days immersion was confirmed by x-ray photoelectron spectroscopy (XPS).