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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.
151

Length Polymorphism in the Threonine-Glycine Repeat Region of the Period Gene in Drosophila melanogaster / Polymorphism in the THR-GLY Region of the Period Gene

Alladina, Fayaz 07 1900 (has links)
The period gene determines biological rhythmicity in Drosophila melanogaster. The X-linked gene is 7.4kb, containing 8 exons and 7 introns from which a 4.5kb message is translated. A striking feature of the protein encoded by per is a series of alternating threonine-glycine residues in the fifth exon. Moreover, this string of residues is polymorphic for length variation in natural populations, the most frequent variants having 17, 20 or 23 Thr-Gly pairs. In the present study, a geographic analysis of this polymorphism within North American populations was conducted, the results of which indicate significant variation of allele frequency with latitude. The use of spatial autocorrelation analysis and Mantel tests clearly show that the most common variant, encoding 17 Thr-Gly pairs, exhibits a clinal pattern in its distribution along a north-south axis. Furthermore, DNA sequence analysis of several variants has uncovered a novel new variant which encodes 22 Thr-Gly pairs whose nucleotide sequence differs from any published data. Similar statistical analysis conducted on seven allozymes for populations collected along the same transect shows that several have monotonic clinal patterns in their allele frequency distributions which also show correlation with latitude. A previous study of morphological traits on the same populations showed the existence of a non-monotonic clinal pattern. Comparison of the results observed for the molecular and morphological markers indicates that they are subject to different evolutionary forces. The results highlight the importance of comparing patterns of geographic variation using different genetic elements. / Thesis / Master of Science (MS)
152

Biosystematics of the genus Chionaspis (Homoptera, Coccoidea, Diaspididae) of North America, with emphasis on polymorphism

Liu, Tong-Xian January 1987 (has links)
The scurfy scales in the genus Chionaspis comprise a unique taxon among the armored scale insect genera in North America. The taxonomic reviews of the species belonging to the genus by Cooley (1899) and Ferris (1937, 1942) are far outdated. The present research is a comprehensive review of all the species in this genus in North America, with special emphasis on polymorphism associated with feeding sites which has been discovered in some species. Seventeen species have been redescribed and illustrated in detail, each with a discussion of their morphological affinities and relationships. Their host habits and zoogeography are summarized. The five species having typical bark and leaf forms, as well as intermediate forms, are discussed in more detail. A separate chapter deals with polymorphism, including a historical literature review of the subject. A hypothesis is given on the modes of transfer from the bark form to the leaf form and vice versa, that results in different morphs in first or second generations. Two keys were prepared: one for the genera related to Chionaspis and another for the determination of the species of this genus in North America. The three species that have been recently redescribed, C. americana and C. kosztarabi and C. nyssae are also discussed, and the most important morphological characters and the plates prepared by the original authors for each of these three species are given in order to better utilize the key to the species in North America. As a direct result of this research, two new species have been discovered: Chionaspis gilli Liu and Kosztarab, and C. hamoni Liu and Kosztarab. In addition new morphs were found for C. platani and C. wistariae. This thesis also includes many new distribution and host records for several species. The phylogenetic relationship of all the species in this study has been discussed, and as a result of the Ward's Minimum Variance Cluster Analysis (1985 version, SAS), a dendrogram has been provided based on 23 numerical characters. / Master of Science
153

Thermodynamic investigation of carbamazepine-saccharin co-crystal polymorphs

Pagire, Sudhir K., Jadav, Niten B., Vangala, Venu R., Whiteside, Benjamin R., Paradkar, Anant R 21 April 2017 (has links)
Yes / Polymorphism in active pharmaceutical ingredients (APIs) can be regarded as critical for the potential that crystal form can have on the quality, efficacy and safety of the final drug product. The current contribution aims to characterize thermodynamic interrelationship of a dimorphic co-crystal, FI and FII, involving carbamazepine (CBZ) and saccharin (SAC) molecules. Supramolecular synthesis of CBZ-SAC FI and FII have been performed using thermo-kinetic methods and systematically characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), solubility and slurry measurements. According to Berger and Ramberger’s heat of fusion rule, FI (ΔHfus = 121.1 J/g, mp 172.5 °C) and FII (ΔHfus= 110.3 J/g, mp 164.7 °C) are monotropically related. The solubility and van’t Hoff plot results suggest that FI stable and FII metastable forms. This study reveals that CBZ-SAC co-crystal phases, FI or FII, could be stable to heat induced stresses, however, FII converts to FI during solution mediated transformation. / Authors would like to acknowledge UKIERI (TPR 26), EPSRC (EP/J003360/1, EP/L027011/1) for the support. Open Access funded by Engineering and Physical Sciences Research Council
154

Candidate Gene Expression and SNP Analyses of Toxin-Induced Dilated Cardiomyopathy in the Turkey(Meleagris gallopavo)

Lin, Kuan-chin 17 May 2006 (has links)
Dilated cardiomyopathy (DCM), a heart disease, affects many vertebrates including humans and poultry. The disease can be either idiopathic (IDCM) or toxin-induced. Idiopathic DCM often occurs without a consensus cause. Though genetic and other studies of IDCM are extensive, the specific etiology of toxin-induced is still unknown. Here, our objective was to compare the level of mRNA expression of two candidate genes including troponin T (cTnT) and phospholamban (PLN) using quantitative reverse transcription polymerase chain reaction (RT-PCR) in toxin-induced DCM affected and unaffected turkeys. Cardiac TnT and PLN were chosen because their spontaneous expression has been reported to be associated with IDCM. We also scanned these genes for single nucleotide polymorphisms (SNPs) that could be useful in evaluating their functions in the incidence and severity of toxin-induced DCM in turkeys. There were no significant differences between affected and unaffected birds in the expression of both cTnT and PLN. A total of 12 SNPs were detected in cTnT and PLN DNA sequences. One of the seven haplotypes detected in cTnT was the most frequent. Linkage analysis showed that cTnT gene was unlinked on the current turkey genetic map. Resources developed here, including SNPs, haplotypes, cDNA sequences, and the PCR-RFLP genotype procedure will be used for future investigations involving cTnT and PLN and toxin-induced DCM. / Master of Science
155

Isomorphism: 'Molecular similarity to crystal structure similarity' in multicomponent forms of analgesic drugs tolfenamic and mefenamic acid

Ranjan, S., Devarapalli, R., Kundu, S., Saha, S., Deolka, S., Vangala, Venu R., Reddy, C.M. 22 April 2020 (has links)
Yes / The non-steroidal anti-inflammatory drugs mefenamic acid (MFA) and tolfenamic acid (TFA) have a close resemblance in their molecular scaffold, whereby a methyl group in MFA is substituted by a chloro group in TFA. The present study demonstrates the isomorphous nature of these compounds in a series of their multicomponent solids. Furthermore, the unique nature of MFA and TFA has been demonstrated while excavating their alternate solid forms in that, by varying the drug (MFA or TFA) to coformer [4-dimethylaminopyridine (DMAP)] stoichiometric ratio, both drugs have produced three different types of multicomponent crystals, viz. salt (1:1; API to coformer ratio), salt hydrate (1:1:1) and cocrystal salt (2:1). Interestingly, as anticipated from the close similarity of TFA and MFA structures, these multicomponent solids have shown an isomorphous relation. A thorough characterization and structural investigation of the new multicomponent forms of MFA and TFA revealed their similarity in terms of space group and structural packing with isomorphic nature among the pairs. Herein, the experimental results are generalized in a broader perspective for predictably identifying any possible new forms of comparable compounds by mapping their crystal structure landscapes. The utility of such an approach is evident from the identification of polymorph VI of TFA from hetero-seeding with isomorphous MFA form I from acetone–methanol (1:1) solution. That aside, a pseudopolymorph of TFA with dimethylformamide (DMF) was obtained, which also has some structural similarity to that of the solvate MFA:DMF. These new isostructural pairs are discussed in the context of solid form screening using structural landscape similarity / Department of Science and Technology (DST/SJF/CSA-02/2014–15); Royal Pharmaceutical Society of Great Britain for seed corn funding (2018–19); INSPIRE fellowship from Department of Science and Technology, Government of India; IISER-Kolkata (instrumental facilities and fellowships)
156

The investigation of the optical properties of polytypic minerals

Cooper, Brian J. January 1988 (has links)
A new approach to the investigation of the optical properties of polytypic minerals that combines spindle stage techniques, X-ray diffraction methods, electron microprobe analysis, and dielectric tensor calculations has been developed and applied to zinc sulfides and chloritoids. For the first time, X—ray diffraction studies of natural anisotropic zinc sulfides have documented the simultaneous occurrence of twinning and stacking disorder along more than one of the four symmetry equivalent <111> directions of sphalerite. Precession photographs of optically anisotropic zinc sulfides are characterized by twin—equivalent diffraction maxima and diffuse diffraction streaking along lattice rows with (h-k) ≠ 3n (equivalent hexagonal indices) in one or two <111> directions. A system of linear equations has been used to calculate the approximate volume fractions of each twin domain and the sphalerite host domain. Dielectric tensor calculations have been performed to illustrate that mixtures of cubic and hexagonal zinc sulfide may be optically biaxial if the intergrowth occurs along more than one of the symmetry equivalent <111> directions of sphalerite (cubic). The dependence of the optical properties upon the chemical variation and polytypic intergrowth in the Hg-Fe chloritoids has been investigated. The effects of the variation in chemical composition of specific polytypic compositions were analyzed first. The refractive indices of 10 approximately pure 2M₂ Hg-Fe chloritoids show strong correlations (R² ≥ 0.094) to the proportion of Hg cations in the H(1B) site, Hg/(Hg + Fe + Hn) - HGN. Correlations between the optical orientation angles and HGN were weaker (R² ≤ 0.87). The optical orientation is very sensitive to small variations in the polytypic composition, especially orientation angles that have fixed values in 2M₂ chloritoid. The parameter showing the most sensitivity is ∠ X ⋀ b, which is 0° in an ideal 2M₂ chloritoid, but increases to about 6° for a chloritoid containing 10% by volume 1Tc polytype. The sum of ∠ Y ⋀ c* and ∠ Z ⋀ c* for an ideal 2M₂ chloritoid has a value of 90°, whereas a chloritoid with 10% 1Tc has a sum of 92°. Although not as sensitive as ∠ X ⋀ b, this parameter can be determined with only a spindle stage or universal stage. The observed dependence of the optical properties on polytypic intergrowth and chemical variation has been modeled using dielectric tensor calculations based on the properties of a 1Tc layer and assuming that the 2M₂ polytype is derived by twinning the 1Tc polytype about [010] with an (001) composition plane. / Ph. D.
157

Novel formulations of a poorly soluble drug using the extrusion process.

Kulkarni, Chaitrali S. January 2013 (has links)
Hot melt extrusion has attracted recent interest from the pharmaceutical industry and academia as an innovative drug delivery technology. This novel technique has been shown to be a viable and robust method for preparing different drug delivery systems including pellets, implants, tablets, capsules and granules. The aim of this research was to understand hot melt extrusion processing and explore its pharmaceutical applications. Two applications of hot melt extrusion (HME) have been investigated to improve the properties of poorly soluble thermolabile drugs; polymeric solid dispersions and solid state polymorphic transformation. HME is a solvent free, continuous and readily scalable technique which is increasingly being considered as a viable alternative to conventionally used batch techniques. However, the high temperature and shear forces imparted by the extrusion process can limit its applications with heat sensitive active pharmaceutical ingredients (APIs). Artemisinin was selected as a model drug which being thermolabile in nature and possesses processing challenges to processing HME. A low Tg amphiphillic copolymer, Soluplus® was selected as a matrix material. Drug-polymer compatibility was studied using rotational rheometry and thermal characterisation. The drug was found to be completely dissolved within the polymer, although some discolouration of the mixture was observed, indicating degradation of the API. The addition of a small percentage of citric acid to the formulation was found to prevent this degradation by increasing the pH. The dissolution profile of the formulation was approximately five times higher compared to that of the pure drug. The pharmacokinetic study was carried out using Albino rats to calculate bioavailability. The area under plasma concentration time curve (AUC0-24hr) and peak plasma concentration (Cmax) were four times higher for the prepared solid dispersion compared to that of pure artemisinin. Extruded solid dispersions were found to be amorphous in nature and maintained stability for 2 years. A second route to improving the solubility of poorly soluble APIs was also investigated. It was found that under carefully controlled conditions, high temperature extrusion (HTE) could be used to achieve polymorphic transformation with a number of APIs. This solvent-free continuous process was demonstrated with artemisinin, piracetam, carbamazepine and chlorpropamide. Artemisinin was used as a detailed case study of stability, solvent mediated transformation and mechanism of polymrophic transformation during extrusion, using computational modelling and model shear flows. At high temperature, phase transformation from orthorhombic to triclinic crystals was found to occur via the vapour phase. Under mechanical stress the crystalline structure was disrupted, leading to new surfaces being continuously formed and exposed to high temperatures; thus accelerating the transformation process. Polymorphic transformation during HTE was found to comprise three stages; i) preheating and conveying; ii) vapour phase transformation and size reduction and iii) continuous transformation and agglomeration. The triclinic form showed four times greater dissolution rate as compared to the orthorhombic form. The triclinic form showed two fold increase in bioavailability in Albino rats.
158

POLIMORFISMOS GENÉTICOS ASSOCIADOS À PRÉ-ECLÂMPSIA: TENDÊNCIAS NA PRODUÇÃO CIENTÍFICA

Oliveira, Túlio Sérgio de 24 June 2016 (has links)
Submitted by admin tede (tede@pucgoias.edu.br) on 2016-10-07T13:33:46Z No. of bitstreams: 1 TÚLIO SÉRGIO DE OLIVEIRA.pdf: 820156 bytes, checksum: 904d8a04a1677fa8754a3159741cd43a (MD5) / Made available in DSpace on 2016-10-07T13:33:46Z (GMT). No. of bitstreams: 1 TÚLIO SÉRGIO DE OLIVEIRA.pdf: 820156 bytes, checksum: 904d8a04a1677fa8754a3159741cd43a (MD5) Previous issue date: 2016-06-24 / Preeclampsia is an exclusive pathology of pregnancy, characterized by hypertension associated with proteinuria. It occurs after 20 weeks of pregnancy. Its prevalence is 8% in singleton pregnancies and 14% in twin pregnancies. It has an unknown etiology up to date. It is currently accepted that genetic factors are important in the development of preeclampsia due to the increased risk in women with family history of preeclampsia, with a history of preeclampsia in a previous pregnancy and on those with partners whose mothers or previous partner have a history of preeclampsia. Preeclampsia figures as the main cause of maternal mortality in Brazil and for this reason, its study is of great interest to public health. The objective of this study was to identify the scientific publications about on preeclampsia and possible associations with genetic alterations during the period of 2005-2015, in the Scopus platform. Different approaches were carried out to evaluate the articles, using as a method, scientometrics. As a result, we observed a significant increase in research and publications on polymorphism in preeclampsia, with a prevalence of authors, publications and institutions of developed countries and a significant association of 45 polymorphisms of genes with preeclampsia. We observed that polymorphisms of genes and the relationship between them is not clear and needs further studies to obtain more results that are consistent. / Pré-eclâmpsia é uma patologia exclusiva da gravidez, caracterizada por hipertensão arterial e proteinúria após 20 semanas de gestação. Sua prevalência é de 8% em gestações únicas e 14% em gestações gemelares. Possui etiopatogenia desconhecida até o momento. Atualmente é aceito que fatores genéticos são importantes no desenvolvimento da doença, devido ao aumento do risco em gestantes com histórico familiar, pré-eclâmpsia em gestação anterior e em parceiro cujas mães ou parceiras anteriores possuem histórico de pré-eclâmpsia. A pré-eclâmpsia figura como principal causa de mortalidade materna no Brasil e por essa razão, seu estudo é de grande interesse em saúde pública. O objetivo deste estudo foi identificar as publicações cientificas, durante o período de 2005 a 2015, presentes na plataforma SCOPUS sobre pré-eclâmpsia e possíveis associações com alterações genéticas. Foram realizadas diferentes abordagens de avaliação sobre os artigos, utilizando como método, a cienciometria. Como resultados, observamos um aumento significativo de pesquisas e publicações sobre polimorfismo na pré-eclâmpsia, com prevalência de autores, publicações e instituições de países desenvolvidos e uma associação significativa de 45 polimorfismos de genes com a pré-eclâmpsia. Observamos que os polimorfismos de genes e a relação entre eles, ainda não está esclarecido, necessitando estudos complementares para se obter resultados mais consistentes.
159

Disease association and functional studies of apolipoprotein E non-coding single nucleotide polymorphisms (SNPs). / CUHK electronic theses & dissertations collection

January 2007 (has links)
Apolipoprotein E (apoE) is a lipid transport protein which plays a key role in lipid metabolism. In addition to the well known polymorphic coding alleles epsilon2, epsilon3 and epsilon4, APOE promoter single nucleotide polymorphisms (SNPs) have also been reported to modify disease susceptibilities in humans. / In a case-control study involving 710 Chinese type 2 diabetes and 198 non-diabetic subjects, genotyping of three SNPs (-491A/T, -219G/T and +113G/C) within the APOE proximal promoter identified that -491A was associated with increased risk for type 2 diabetes in women (OR=2.44, 95%CI=1.15-5.19, p=0.017). However, the three tested SNPs were not associated with the risk of diabetic nephropathy (DN). Yeast one-hybrid screening of the human brain cDNA library using the polymorphic DNA sequences spanning the APOE promoter -491 site as the 'baits' identified one of the interacting transcription factors being the activating transcription factor 4 (ATF4). Electrophoretic-mobility-shift assay confirmed the physical interaction of the purified recombinant ATF4 protein and APOE promoter -491 A/T spanning region (-521 to -461). The binding of ATF4 to the -491T-containing sequence was stronger than that of the -491A-containing sequence. Chromatin immunoprecipitation (ChIP) assay further confirmed the interaction between ATF4 and APOE promoter -491-spanning region in vivo. The functional significance of APOE -491A/T polymorphism was supported by the dual-luciferase reporter assay showing that -491 A to T single nucleotide substitution significantly decreased the activity of the cloned APOE promoter (-1019 to +407) in human kidney (293), liver (WRL-68) and astrocyte (U-87) cell lines. Further analysis showed that ATF4 over-expression significantly down-regulated the activities of the cloned APOE promoter. The suppression of ATF4 on APOE promoter with -491A allelic form was significantly stronger than that with -491T allelic form in 293 cells (p&lt;0.05). Interestingly, overexpression of recombinant ATF4 stimulated endogenous APOE transcription by about 10% in WRL-68 cells. / In conclusion, APOE promoter -491A/T polymorphism modifies the risk of type 2 diabetes in Hong Kong Chinese women. The -491A/T polymorphism controls APOE promoter activity and is interactive with transcription factor ATF4. / My thesis project aimed at testing two hypotheses: (1) APOE promoter SNPs associate with the risks of type 2 diabetes and diabetic nephropathy, (2) APOE promoter SNPs modify transcriptional control of the gene. / Geng, Hua. / "September 2007." / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4559. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 140-151). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
160

Investigation and modeling of the mechanisms involved in batch cooling crystallization and polymorphism through efficient use of the FBRM

Barthe, Stephanie Cecile 07 July 2008 (has links)
Batch crystallization is used widely in the production of high-value added species. It is widely recognized that product properties, some of which may be related directly to the utility of the drug, and downstream processes, such as tableting, are influenced by crystal morphology, size, and shape. The ability to observe on-line the evolution of the population density and detect a polymorphic transformation would constitute a major asset in understanding crystallizer operation and the phenomena that influence product quality. Focused-beam reflectance measurement (FBRM) is among the process analytical technologies (PAT) that hold promise for enhanced monitoring of pharmaceutical crystallization. It is based on scattering of laser light and provides a methodology for on-line monitoring of a representation of the crystal population in either batch or continuous crystallization systems. Properly installed, the FBRM allows on-line determination of the chord-length density, which is a complex function of crystal geometry and is statistically related to the population density. A model based on the geometry of the crystal was therefore established to relate both densities and thus enable computation of the population density from a measured chord length density. The evolution of the population density as a function of time leads to the estimation of the supersaturation and therefore allows the determination of the systems kinetics. From there, the population balance can be solved. Paracetamol is a common substance which exhibit polymorphism and is mainly used as an analgesic and antipyretic drug. The developed model was here applied to batch cooling crystallization of paracetamol from ethanol solutions; this system was used to explore the utility of FBRM data in detection of the polymorphic transformations. As different shapes generate different chord length densities, a transition from one polymorphic form with one specific crystal habit to another can be tracked through the FBRM. The purpose of the present study is to use the FBRM to monitor the evolution of the crystallization process, develop a model describing the evolution of the process, and monitor polymorphic transformation. The end results would be the possibility to implement a better control of the crystallization process that would ensure that downstream processing and product quality meet expectations.

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