• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 121
  • 81
  • 37
  • 13
  • 6
  • 5
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 318
  • 68
  • 67
  • 60
  • 54
  • 48
  • 48
  • 47
  • 42
  • 40
  • 35
  • 30
  • 28
  • 27
  • 27
  • 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.
11

Randomization of recrystallization textures in an experimental Al-5%Mg alloy and AA6111

Chang, Sin-ting, Cynthia. January 2005 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
12

A novel thermomechanical treatment process for enhancing gamma fibre texture recrystallisation components

Lam, Kai-tung, George. January 2002 (has links)
Thesis (M.Phil.)--University of Hong Kong, 2002. / Includes bibliographical references. Also available in print.
13

Time resolved reflectivity studies of electron beam processing of semiconductors

Timans, P. J. January 1987 (has links)
This work describes methods for making dynamic observations of the effects of electron beam heating, in a range of applications to semiconductors. The studies were based on the use of the time resolved reflectivity (TRR) method, in which the reflectivity of the specimens surface is measured during the heating cycle. The best experimental conditions for this technique have been identified and several applications are described in detail. Studies were made of epitaxial regrowth of amorphous layers created by ion implantation into silicon. The TRR method was applied using red and infra-red wavelengths, to characterize the regrowth kinetics, paying special attention to the influence of electrically active dopants. The results demonstrate that doping has a large effect on the regrowth process, for reasons which are related to both electrical and structural factors. The use of isothermal electron beam heating for annealing silicon-on-sapphire (SOS) specimens was investigated. In these studies, the TRR technique was applied to measurement of the temperature of the specimens and to observation of epitaxial recrystallization of amorphous layers created by self-implantation. In SOS films the amorphous layers could be at the surface or buried beneath a thin single crystal layer, and these cases resulted in different regrowth behaviour. TRR methods using green and red probe wavelengths proved to be sensitive to the type of crystallization, as well as the rate at which it occurs. They should also help to identify the best conditions for improvement of the crystal quality of SOS films. TRR was also used to examine heating of silicon-on-insulator materials by swept line electron beams. Temperature distributions were evaluated by measuring the reflectivity of a small area as the electron beam passed through it and the effects of various changes in the heating conditions were explored. Studies were made of zone melting recrystallization by observing the abrupt reflectivity changes which occur when silicon melts or freezes. In future work, TRR techniques could be developed to allow detailed investigation of the recrystallization process in structures intended for seeded recrystallization.
14

Elucidating the Key Structural Features of Carbohydrates and Surfactants Necessary for Inhibiting Ice Recrystallization

Balcerzak, Anna January 2014 (has links)
Ice recrystallization during thawing after cryopreservation results in extensive cellular damage that ultimately leads to cell death and decreased cell viabilities. This is a significant problem particularly with cryopreserved cells utilized in various regenerative medicine therapies. Given the success of these therapies to treat spinal cord injury, cartilage lesions, and cardiacdisease, the development of new and improved cryprotectants that minimize cell damageduring freeze-thawing and improve cell viability post-cryopreservation are urgently required. The current cryopreservative dimethyl sulfoxide, DMSO, is associated with cytotoxicity in clinical settings and is not an optimal cryopreservative. Our laboratory is interested in synthesizing small molecules that possess the property of ice recrystallization inhibition (IRI) activity that can be utilized as cryopreservatives without the cytotoxic effects associated with DMSO. This thesis focuses on the development of small molecule ice recrystallization inhibitors and elucidating the structural features of disaccharides and surfactants that are responsible for potent IRI activity. The first part of this study examines simple disaccharide derivatives mimicking those found in the native AFGP to determine whether disaccharide structure influences IRI activity. Towards this end, the (1,6)-linked AFGP disaccharide analogue was synthesized, assessed for IRI activity using a splat-cooling assay, and compared to the native (1,3)- and (1,4)-linked AFGP disaccharide analogues. The change in linkage was found to have a profound affect on IRI activity. The second part of the study focuses on surfactants and gelators as ice recrystallization inhibitors. Our laboratory has demonstrated that carbohydrate-based hydrogelators can be potent inhibitors of ice recrystallization. While our studies have indicated that a delicate balance between hydrophobic and hydrophilic interactions is crucial for ice recrystallization inhibition (IRI) activity, the essential structural features necessary for potent IRI activity remain unknown. To address this issue, structurally diverse amino acid-based surfactants/gelators, anti-ice nucleating agents, and glycoconjugates were synthesized and assessed for IRI activity. The results indicate that long alkyl chains and increased hydrophobicity are important for potent IRI activity and iii that the position of these alkyl chains is essential. Also, the counterion of these compounds affects the IRI activity and is related to the counterion degree of hydration. These compounds were assessed for their ability to cryopreserve human liver cells (Hep G2) and human bone marrow cells (Tf-1α) in cell-based assays. Additionally, the best IRI assay solution was determined, which involved studying how the salts of the phosphate buffered saline (PBS) solution modulated IRI activity. Finally, small molecule ice recrystallization inhibitors were assessed for their ability to protect the viral vectors vaccinia virus, vesicular stomatitis virus, and herpes simplex-1 virus at various storage conditions. This will aid in developing improved preservation protocols for vaccines and viruses utilized in cancer therapy (oncolytic viruses).
15

The Rational Design and Use of Novel Small-Molecule Ice Recrystallization Inhibitors for the Cryopreservation of Hematopoietic Stem Cells and Red Blood Cells

Briard, Jennie Grace January 2016 (has links)
Over the past few decades, there has been an increase in the development of new cellular therapies used for the treatment of various conditions. Thus, the rapid development of therapies requiring transfusion and transplantation of cells has resulted in a need to preserve these cellular therapy products. Cryopreservation is the only currently used method for the long-term storage of cells. The most commonly used cryoprotectants are 10% dimethyl sulfoxide (DMSO) for hematopoietic stem cells (HSCs) and 40% glycerol for red blood cells (RBCs). DMSO fails to protect the functionality of HSCs after cryopreservation and therefore, up to 20% of HSC transplantations fail to engraft. The glycerol in thawed RBC units must be removed to <1% to prevent intravascular hemolysis which is time-consuming. Thus, there is an urgent need to develop improved cryoprotectants for HSCs and RBCs. DMSO and glycerol are unable to control ice recrystallization which is a major source of cellular injury during cryopreservation. Therefore, compounds with the ability to inhibit ice recrystallization could represent a new class of cryoprotectant with a novel mechanism of action. This thesis focuses on the rational design of small-molecule ice recrystallization inhibitors. The key structural attributes required for ice recrystallization inhibition (IRI) activity are investigated. The amphiphilic balance required for IRI activity is explored. Furthermore, two new classes of small-molecule IRIs containing aromatic rings were rationally designed. As a result, several very highly IRI active molecules were discovered. The use of IRIs to improve the cryopreservation of HSCs and RBCs was explored. A number of IRIs improved the post-thaw functionality of HSCs. Supplementation of the current cryoprotectant solution with IRIs resulted in an increase in CFU recovery and frequency of multipotent progenitors. This would reduce the percentage of engraftment failure and allow for a larger proportion of cord blood banks’ inventory to provide an adequate dose for patients requiring transplants. Several IRIs were found to be effective cryoprotectants for RBCs with reduced amounts of glycerol. This could reduce the deglycerolization time for RBCs. These results demonstrate the potential of small-molecule IRIs to improve the current cryopreservation procedures for important cellular therapy products.
16

Small Molecule Ice Recrystallization Inhibitors and Their Use in Methane Clathrate Inhibition

Tonelli, Devin L. 05 April 2013 (has links)
Inhibiting the formation of ice is an essential process commercially, industrially, and medically. Compounds that work to stop the formation of ice have historically possessed drawbacks such as toxicity or prohibitively high active concentrations. One class of molecules, ice recrystallization inhibitors, work to reduce the damage caused by the combination of small ice crystals into larger ones. Recent advances made by the Ben lab have identified small molecule carbohydrate analogues that are highly active in the field of ice recrystallization and have potential in the cryopreservation of living tissue. A similar class of molecules, kinetic hydrate inhibitors, work to prevent the formation of another type of ice – gas hydrate. Gas hydrates are formed by the encapsulation of a molecule of a hydrocarbon inside a growing ice crystal. These compounds become problematic in high pressure and low temperature areas where methane is present - such as an oil pipeline. A recent study has highlighted the effects of antifreeze glycoprotein, a biological ice recrystallization inhibitor, in the inhibition of methane clathrates. Connecting these two fields through the synthesis and testing of small molecule ice recrystallization inhibitors in the inhibition of methane hydrates is unprecedented and may lead to a novel class of compounds.
17

Small Molecule Ice Recrystallization Inhibitors and Their Use in Methane Clathrate Inhibition

Tonelli, Devin L. 05 April 2013 (has links)
Inhibiting the formation of ice is an essential process commercially, industrially, and medically. Compounds that work to stop the formation of ice have historically possessed drawbacks such as toxicity or prohibitively high active concentrations. One class of molecules, ice recrystallization inhibitors, work to reduce the damage caused by the combination of small ice crystals into larger ones. Recent advances made by the Ben lab have identified small molecule carbohydrate analogues that are highly active in the field of ice recrystallization and have potential in the cryopreservation of living tissue. A similar class of molecules, kinetic hydrate inhibitors, work to prevent the formation of another type of ice – gas hydrate. Gas hydrates are formed by the encapsulation of a molecule of a hydrocarbon inside a growing ice crystal. These compounds become problematic in high pressure and low temperature areas where methane is present - such as an oil pipeline. A recent study has highlighted the effects of antifreeze glycoprotein, a biological ice recrystallization inhibitor, in the inhibition of methane clathrates. Connecting these two fields through the synthesis and testing of small molecule ice recrystallization inhibitors in the inhibition of methane hydrates is unprecedented and may lead to a novel class of compounds.
18

Small Molecule Ice Recrystallization Inhibitors and Their Use in Methane Clathrate Inhibition

Tonelli, Devin L. January 2013 (has links)
Inhibiting the formation of ice is an essential process commercially, industrially, and medically. Compounds that work to stop the formation of ice have historically possessed drawbacks such as toxicity or prohibitively high active concentrations. One class of molecules, ice recrystallization inhibitors, work to reduce the damage caused by the combination of small ice crystals into larger ones. Recent advances made by the Ben lab have identified small molecule carbohydrate analogues that are highly active in the field of ice recrystallization and have potential in the cryopreservation of living tissue. A similar class of molecules, kinetic hydrate inhibitors, work to prevent the formation of another type of ice – gas hydrate. Gas hydrates are formed by the encapsulation of a molecule of a hydrocarbon inside a growing ice crystal. These compounds become problematic in high pressure and low temperature areas where methane is present - such as an oil pipeline. A recent study has highlighted the effects of antifreeze glycoprotein, a biological ice recrystallization inhibitor, in the inhibition of methane clathrates. Connecting these two fields through the synthesis and testing of small molecule ice recrystallization inhibitors in the inhibition of methane hydrates is unprecedented and may lead to a novel class of compounds.
19

none

Chou, Shih-Po 12 August 2002 (has links)
none
20

Hot working behavior of AZ31 Magnesium alloys

Suen, Der-Kai 12 August 2005 (has links)
none

Page generated in 0.1129 seconds