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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
841

Föräldrar separerar, men inte från barnen : en studie om socialtjänstens handläggning enligt Föräldrabalken 6:20

Fredholm, Karin, Kulin, Helena January 2005 (has links)
Denna studie är en beskrivning av två socialtjänsters olika handläggningsstrategier i samband med att de lämnar upplysningar till domstolen i mål om vårdnad, boende och umgänge och motiven till de olika strategierna. Vårdnadstvister som tas upp i domstol är en lång process och kan vara påfrestande både för barnet och föräldrarna. Om föräldrarna i en vårdnadstvist vänder sig till domstolen involveras även socialtjänsten. Detta då domstolen enligt Föräldrabalken ska begära in upplysningar om barnet och föräldrarna från socialtjänsten. Inför dessa upplysningar väljer vissa kommuner att samtala med föräldrarna medan andra kommuner inte gör det. I två fokusgruppsintervjuer med socialsekreterare delges synsättet på vilken betydelse detta samtal kan ha utifrån ett konfliklösningsperspektiv samt synen på deras handläggningsstrategier. Resultatet visade att de olika kommunerna hade olika synsätt på samtal med föräldrarna i detta skede och om samtalet har någon påverkan ur ett konfliklösningsperspektiv. Vidare framkom det att de var medvetna om innehållet
842

Familjehemsplacering för barn i asylsökande familjer

Nordesjö, Ylva January 2007 (has links)
Asylsökande föräldrar lever under stark social och ekonomisk press. De har ofta sviktande psykisk och fysisk hälsa till följd av tidigare traumatisering och den belastning som asylprocessen innebär. Om föräldrarna under dessa omständigheter inte längre klarar att ta hand om sina barn kan barnen bli placerade i familjehem. Sex socialsekreterare med erfarenhet av sådana placeringar djupintervjuades med syfte att undersöka hur barn och föräldrar från asylsökande familjer reagerar när barn placeras i familjehem utan sina föräldrar. Syftet var också att undersöka hur socialsekreterarna resonerar kring och påverkas av att arbeta med placering av barn från asylsökande familjer. Tematisk analys utfördes enligt Hayes. Resultaten tyder på att omsorgssvikten har varit akut och att socialsekreterarna då beslut har fattats endast haft begränsad information om barn-föräldraanknytningens kvalitet. Socialsekreterarna har inte heller uppmärksammat barns och föräldrars separationsreaktioner vid och under placering. Det är tydligt att socialsekreterare som placerar barn från asylsökande familjer i familjehem påverkas av den asylprocess som familjen genomgår. Det finns inte någon praxis eller fast uppfattning om hur socialsekreterare ska resonera och besluta i dessa ärenden.
843

Nanoporous Materials for Carbon Dioxide Separation and Storage

Varela Guerrero, Victor 2011 May 1900 (has links)
Global climate change is one of the most challenging problems that human beings are facing. The large anthropogenic emission of CO2 in the atmosphere is one of the major causes for the climate change. Coal-fired power plants are the single-largest anthropogenic emission sources globally, accounting for approximately one third of the total CO2 emissions. It is therefore necessary to reduce CO2 emission from coal-fired power plants. Current technologies for the post-combustion CO2 capture from flue gas streams can be broadly classified into the three categories: absorption, adsorption, and membrane processes. Despite challenges, CO2 capture by adsorption using solid sorbents and membranes offers opportunities for energy-efficient capture and storage of CO2. Nanoporous materials have attracted tremendous interest in research and development due to their potential in conventional applications such as catalysis, ion-exchange, and gas separation as well as in advanced applications such as sensors, delivery, and micro-devices. In the first part of this dissertation, we will study the synthesis of membranes using an emerging class of nanoporous materials, metal-organic frameworks (MOFs) for carbon dioxide (CO2) separations. Due to the unique chemistry of MOFs which is very different from that of zeolites, the techniques developed for the synthesis of zeolite membranes cannot be used directly. In order to overcome this challenge, a couple of novel techniques were developed: 1) "thermal seeding" for the secondary growth and 2) "surface modification" for the in situ growth. Membranes of HKUST-1 and ZIF-8, two of the most important MOFs, were prepared on porous α-alumina supports using thermal seeding and the surface modification techniques, respectively. The second part of this dissertation demonstrates a simple and commercially viable application of nanoporous materials (zeolite 5A and amine-functionalized mesoporus silica), storing CO2 as a micro-fire extinguishers in polymers. Materialist is observed that by dispersing these highly CO2-philic nanoporous materials in polymer matrices, the propagation of flame was greatly retarded and extinguished. This flame retarding behavior is attributed to the fact that CO2 released from the sorbents (zeolite 5A and mesoporous silica), blocks the flow of oxygen, therefore causing the fire to be effectively extinguished. Our results suggest that the binding strength of CO2 on sorbents play an important role. If the binding strength of CO2 is too low, CO2 releases too early, thereby ineffective in retarding the flame.
844

OMAKA FÖRÄLDRAR : En kvalitativ studie om separerade föräldrars konflikter

Laitinen, Erja January 2008 (has links)
En kvalitativ studie om konflikter mellan separerade föräldrar och samhällsförändringar som har bidragit till att konflikter mellan dessa föräldrar har ökat. De frågeställningar som har använts är: Går det att urskilja några specifika målgrupper som nyttjar erbjudandet om samarbetssamtal? Vilka orsaker kan det finnas till att föräldrar uppsöker hjälp i form av samarbetssamtal? Finns det några specifika samhällsförändringar som har bidragit till att konflikter mellan separerade föräldrar har ökat? En semistrukturerad intervjumetod har använts för att intervjua familjerättsekreterare i deras roll som samtalsledare. Litteraturstudier har utförts om samhällsutvecklingen. En narrativ analysmetod har använts för redovisning av resultatet. Resultatet visar bl.a. att föräldrarna befinner sig i kris samt att föräldrarna tänker olika om vad som är barns bästa efter separationen vilket kan leda till svårare konflikter. Resultatet visar även att antalet småbarnsföräldrar i konflikt har ökat. Utvecklingen av gemensam vårdnad, växelvis boende och jämställdhet är några samhällsförändringar som har bidragit till att öka konflikter mellan separerade föräldrar. Slutsatsen visar på att individualismens inträde och ökning i samhället är den främsta samhällsförändringen som har påverkat konflikterna mellan separerade föräldrar.
845

Supercritical Fluid Assisted Recovery of Organometallic Catalysts from Polymers

Yang, Lijuan 17 May 2012 (has links)
The recovery of organometallic catalysts from polymer matrices is of great importance in promoting the application of homogeneous catalysts in industry. Such a green recovery technique will not only popularize the techniques of green catalytic hydrogenation of polymers by Rempel’s group, but also consummates the technique of heterogenization of organometallic catalysts. The high value product of hydrogenated nitrile butadiene rubber (HNBR) with dissolution of Wilkinson’s catalyst [RhCl(TPP)3] was selected as the model polymer matrix for developing a green separation technique. The supercritical carbon dioxide (scCO2) soluble fluorous Wilkinson’s catalyst [RhCl(P(p-CF3C6H4)3)3] was synthesized and shown exhibit a very limited activity in the catalytic hydrogenation of bulk HNBR. Its recovery from a HNBR matrix using scCO2 however failed. In spite of the assistance of the scCO2 dissolvable chelating ligand thenoyltrifluoroacetone (TTA), the weak compatibility of scCO2 with rhodium complexes failed again as an extraction solvent for the HNBR matrix. Inspired by the merits of CO2-expanded liquids (CXLs) and the versatility of CO2 in changing the physical properties of polymer melts, CXLs were tested as extracting solvents for separation of Wilkinson’s catalyst from bulk HNBR. CO2-expanded water (CXW) and CO2-expanded alcohols including methanol and ethanol (CXM and CXE) were examined with the assistance of a variety of chelating agents. The investigated chelating agents include ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), diethylenetriamine (DETA), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA), and N,N,N’,N’-tetramethylethylenediamine (TMEDA). CXM and PMDETA were recognized as the optimal combination of extracting solvent and chelating agent for recovery of Wilkinson’s catalyst from HNBR. An extraction system consisting of CXM and PMDETA was carefully investigated with respect to the effects of temperature and pressure on the extraction performance over the temperature range of 40 to 100 °C and the pressure range of 20 to 200 bar. Increasing temperature effectively increased the extraction rate and became less influential when the temperature was above 80 °C. Increasing pressure at a fixed temperature was found to improve the extraction rate followed by suppressing it. Nevertheless, further increasing the pressure to an extreme high value above the respective critical point was able to promote the extraction rate again. The complex effects of pressure were thoroughly investigated by the means of analyzing the dissolution behavior of CO2 in HNBR and the variation of the extraction phase composition at different operational conditions. 0.14 g/mL was determined as the CO2 density by which the optimal pressure at a fixed temperature can be estimated. Based on a careful interpretation of the experimental results, an extraction mechanism was illustrated for interpreting the present extraction system. Additionally, the reactions involved in the extraction process were illustrated to reveal the principal challenges present in the extraction process and pointed out the potential solution for eliminating the obstacles. Two special operations-sequential operation and pressure varying procedure were tested for their effectiveness in enhancing the extraction ratio. A pressure varying procedure was found to be beneficial in further improving the extraction ratio, while sequential operation did not show any promise in enhancing the recovery. At last, the developed technique was shown to be highly efficient in applying it to HNBR particles coagulated from the HNBR latex. A residue of 59 ppm rhodium was obtained after 9 hours of operation. This study establishes a technology platform for separating the expensive catalyst from the polymer matrix, using “green” CO2-expanded liquids.
846

The Effect of Surfactant and Compatibilizer on Inorganic Loading and Properties of PPO-based EPMM Membranes

Bissadi, Golnaz 07 December 2012 (has links)
Hybrid membranes represent a promising alternative to the limitations of organic and inorganic materials for high productivity and selectivity gas separation membranes. In this study, the previously developed concept of emulsion-polymerized mixed matrix (EPMM) membranes was further advanced by investigating the effects of surfactant and compatibilizer on inorganic loading in poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based EPMM membranes, in which inorganic part of the membranes originated from tetraethylorthosilicate (TEOS). The polymerization of TEOS, which consists of hydrolysis of TEOS and condensation of the hydrolyzed TEOS, was carried out as (i) one- and (ii) two-step processes. In the one-step process, the hydrolysis and condensation take place in the same environment of a weak acid provided by the aqueous solution of aluminum hydroxonitrate and sodium carbonate. In the two-step process, the hydrolysis takes place in the environment of a strong acid (solution of hydrochloric acid), whereas the condensation takes place in weak base environment obtained by adding excess of the ammonium hydroxide solution to the acidic solution of the hydrolyzed TEOS. For both one- and two-step processes, the emulsion polymerization of TEOS was carried out in two types of emulsions made of (i) pure trichloroethylene (TCE) solvent, and (ii) 10 w/v% solution of PPO in TCE, using different combinations of the compatibilizer (ethanol) and the surfactant (n-octanol). The experiments with pure TCE, which are referred to as a gravimetric powder method (GPM) allowed assessing the effect of different experimental parameters on the conversion of TEOS. The GPM tests also provided a guide for the synthesis of casting emulsions containing PPO, from which the EPMM membranes were prepared using a spin coating technique. The synthesized EPMM membranes were characterized using 29Si nuclear magnetic resonance (29Si NMR), differential scanning calorimetry (DSC), inductively coupled plasma mass spectrometry (ICP-MS), and gas permeation measurements carried out in a constant pressure (CP) system. The 29Si NMR analysis verified polymerization of TEOS in the emulsions made of pure TCE, and the PPO solution in TCE. The conversions of TEOS in the two-step process in the two types of emulsions were very close to each other. In the case of the one-step process, the conversions in the TCE emulsion were significantly greater than those in the emulsion of the PPO solution in TCE. Consequently, the conversions of TEOS in the EPMM membranes made in the two-step process were greater than those in the EPMM membranes made in the one-step process. The latter ranged between 10 - 20%, while the highest conversion in the two-step process was 74% in the presence of pure compatibilizer with no surfactant. Despite greater conversions and hence the greater inorganic loadings, the EPMM membranes prepared in the two-step process had glass transition temperatures (Tg) only slightly greater than the reference PPO membranes. In contrast, despite relatively low inorganic loadings, the EPMM membranes prepared in the one-step process had Tgs markedly greater than PPO, and showed the expected trend of an increase in Tg with the inorganic loading. These results indicate that in the case of the one-step process the polymerized TEOS was well integrated with the PPO chains and the interactions between the two phases lead to high Tgs. On the other hand, this was not the case for the EPMM membranes prepared in the two-step process, suggesting possible phase separation between the polymerized TEOS and the organic phase. The latter was confirmed by detecting no selectivity in the EPMM membranes prepared by the two-step process. In contrast, the EPMM membranes prepared in the one-step process in the presence of the compatibilizer and no surfactant showed 50% greater O2 permeability coefficient and a slightly greater O2/N2 permeability ratio compared to the reference PPO membranes.
847

<i>Schizosaccharomyces pombe </i> Phosphatidylinositol 4-kinase, Pik1p, in cell cycle control

Park, Jae-Sook 15 May 2007
Pik1p, one of three phosphatidylinositol 4-kinases in the fission yeast, <i>Schizosaccharomyces pombe</i>, was found previously to interact with Cdc4p, a myosin essential light chain that is required for cytokinesis. The involvement of pik1 in cell cycle control was investigated. A fluorescently tagged Pik1p fusion protein was associated with Golgi throughout the cycle, and was found at the medial division plane of the cell during late cytokinesis. This latter distribution has not been reported previously. Gene deletion in diploid cells and tetrad analysis revealed that pik1 is essential for cell viability and is required for spore germination. The terminal phenotype of a temperature-sensitive, loss-of-function allele (pik1-td) indicated that pik1 is involved in cytokinesis: particularly for suppression of secondary septum material deposition, for suppression of initiation of supernumerary septa, and for cell separation. Contractile ring formation was normal in pik1-td cells at the restrictive temperature although the pattern of F-actin patches was disrupted. The F-actin patches were dispersed throughout the cytoplasm. Accumulation of extra inner membranous or vesicle-like structures was observed in these cells. The <i>S. pombe</i> nmt1 promoter and attenuated versions of it were found to be useful for complementation studies in <i>S. cerevisiae</i>. Heterologous expression of <i>S. pombe</i> pik1 complemented the essential functions of a temperature-sensitive allele (pik1﷓101) of its orthologue in <i>Saccharomyces cerevisiae</i> that were lost at the restrictive temperature. A residue required for <i>S. pombe</i> Pik1p lipid kinase activity, D709, was also required for this complementation. A residue, R838, which is required for interactions between Pik1p and Cdc4p was not required for this complementation. The timing and localization of Pik1p to the division plane of the cell late in cytokinesis combined with analysis of the terminal phenotype of a loss-of-function allele, indicate that Pik1p and/or its derived phosphoinositides are required for regulation of septation and cell separation. Pik1p may be involved in the transport, possibly via vesicular transport, of enzymes required for hydrolysis of the primary septum. It may be involved in signaling pathways that lead to the initiation of septation and to the cessation of the deposition of secondary septum material.
848

A Numerical Model for Oil/Water Separation from a Solid Particle

Fan, Eric Sheung-Chi 26 July 2010 (has links)
A computational fluid dynamics model has been developed to study an oil-coated particle immersed in a uniform aqueous flow, to determine the conditions that favour oil separation. The governing flow equations are discretized using a finite volume approach, and the oil/water interface is captured using the Volume-of-Fluid (VOF) method in a 2D spherical coordinate system. The model predicts different mechanisms for oil separation. At a Reynolds number, Re, equal to 1, and at a low capillary number, Ca << 1, the high interfacial tension can induce rapid contact line motion, to the extent that the oil film can advance past its equilibrium position and separate from the particle. This mechanism requires that the contact angle measured through the oil phase is large. On the other hand, as Ca approaches 1, the shear exerted by the external flow stretches the oil into a thread that will eventually rupture and separate.
849

A Numerical Model for Oil/Water Separation from a Solid Particle

Fan, Eric Sheung-Chi 26 July 2010 (has links)
A computational fluid dynamics model has been developed to study an oil-coated particle immersed in a uniform aqueous flow, to determine the conditions that favour oil separation. The governing flow equations are discretized using a finite volume approach, and the oil/water interface is captured using the Volume-of-Fluid (VOF) method in a 2D spherical coordinate system. The model predicts different mechanisms for oil separation. At a Reynolds number, Re, equal to 1, and at a low capillary number, Ca << 1, the high interfacial tension can induce rapid contact line motion, to the extent that the oil film can advance past its equilibrium position and separate from the particle. This mechanism requires that the contact angle measured through the oil phase is large. On the other hand, as Ca approaches 1, the shear exerted by the external flow stretches the oil into a thread that will eventually rupture and separate.
850

Effect Of Compatibilizers On The Gas Separation Performance Of Polycarbonate Membranes

Sen, Deser 01 September 2003 (has links) (PDF)
In this study, the effect of compatibilizers on the gas separation performance of polycarbonate (PC) membranes was investigated. Membranes were prepared by solvent evaporation method. They were characterized by single gas permeability measurements of O2, N2, H2 and CO2 as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR). Membranes containing 0.5 to 10 w% p-nitroaniline (pNA) were prepared to study the effect of compatibilizer concentration on the membrane performance. Permeabilities of all gases decreased but selectivities increased with pNA concentration. The membranes with 5 w% pNA showed a selectivity of 114.5 for H2 over N2, 53.9 for CO2 over N2 and 13.4 for O2 over N2 at room temperature, whereas, the H2/N2, CO2/N2 and O2/N2 selectivities for pure PC membranes were 43.5, 20.6 and 5.6, respectively. The N2 permeabilities through pure PC membrane and 5 w% pNA/PC membrane were 0.265 and 0.064 barrer, respectively. The glass transition temperature of the membranes decreased with increasing pNA concentration. FTIR spectra showed that the peaks assigned to nitro and amine groups of pNA shifted and/or broadened. The DSC and FTIR results suggested an interaction between PC and pNA. The effect of type of compatibilizer was also studied. The compatibilizers were 4-amino 3-nitro phenol (ANP), Catechol and 2-hydroxy 5-methyl aniline (HMA). Similar to membranes prepared with pNA, membranes prepared with these compatibilizers had a lower permeability and glass transition temperature but higher selectivity than pure PC membranes. Their FTIR spectra were also indicated a possible interaction between PC and compatibilizer. In conclusion, PC/compatibilizer blend membranes for successful gas separation were prepared. Low molecular weight compounds with multifunctional groups were found to effect membrane properties at low concentration range, 0.5-5 w%.

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