Neste trabalho, utilizando técnicas magneto-ópticas, estudamos tempos de relaxação spin-rede (T1) do estado fundamental de centros \'F\' e, cristais de halogenetos alcalinos (KCl-KBr). Descrevemos um sistema semi-automático para medidas ópticas de T1, capaz de medir tempos de relação curtos (~1mS), baseado na medida do Dicroísmo Circular magnético (DCM) que apresentam aqueles sais quando portadores de centros paramagnéticos. Obtivemos a dependência de T1 com o campo magnético H (até 65 Kgauss), bem como os espectros de DCM para diferentes concentrações nas matrizes mistas. Uma teoria desenvolvida por Panepucci e Mollenauer (1) para matrizes puras, foi adaptadas para explicar a relaxação spin-rede nos cristais mistos. Os resultados obtidos para o processo direto (T~2.0 K), confrontados com auqela teoria, mostram que o mecanismo de relaxação dominante até 25 KGauss continua sendo a modulação por fônons da interação hiperfins entre o elétron \'F\' e os núcleos vizinhos. / Using magneto-optic techniques we have studied the ground state spin- lattice relaxation times (T1) of \'F\' centers in mixed Alkali Halide cristals (KCl-KBr). We describe a computer assisted system to optically measure short relaxation times (~1mS). The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. We obtained the T1 magnetic field dependency at 2 K up to 65 kGauss), as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behavior of T1 in mixed cristais. The Direct Process results (T~2.0 K) compared against that theory shows that the main relaxation mecanism, Up to 25 kGauss, continues to be phonon modulation of the hyperfine interaction between \'F\' electrons and surrounding nuclei.

No description available.

Public school teachers face a great amount of stress, and that stress may lead to other adverse health outcomes. This study examined elementary public school teachers' stress levels before and after the use of guided imagery relaxation. Guided by the transactional model of stress and coping as the theoretical framework, the purpose of this research was to evaluate the use of guided imagery as an effective technique in the stress reduction of elementary public school teachers, thus enhancing the learning experience of students and creating healthier public school teachers. Eighty-one teachers (71 women, 10 men) participated in this study by completing the Classroom Appraisal of Resources and Demands Inventory Elementary Version. Several variables were examined including gender, years of experience, and adverse health as related to stress experiences. A repeated measures analysis of variance revealed that guided imagery relaxation was statistically significant in reducing stress levels of public school teachers. These results have implications for positive social change by illuminating the utility of a stress-reduction technique for public school teachers. School administrators and educators may find these results useful in their work to retain talented teachers.

The purpose of this study is to clarify the role of anxiety management techniques (cue-controlled relaxation, systematic desensitization) as components of an assertiveness training program. Volunteers from Utah State University and the surround ing community were randomly assigned to one of three treatment groups and a control group which were used in a pre-post change comparison design. Treatment groups consisted of: (1) cue-controlled relaxation plus assertiveness training, (2) systematic desensitization plus assertiveness training, and (3) assertiveness training extended. The control group was a delayed treatment control. All subjects were administered pre-tests with the following instruments: two self report inventories (the College Self-Expression Scale and the Rathus Assertiveness Scale) and a Behavioral Performance Test. The Behavioral Performance Test consisted of ten separate multiple stimulus role playing situations (five pre-test and five posttest) which were videotaped and rated on four performance variables: (1) verbal content, (2) percent of eye contact, (3) assertive affect, and (4) overall assertiveness. All treatment groups were exposed to four two-hour sessions of basic assertiveness training which consisted of shaping procedures (i.e. behavioral rehearsal, modeling, etc.). Treatment groups I and II were provided six additional hours of training in cue-controlled relaxation and systematic desensitization, respectively, while Group III was provided six additional hours of basic assertiveness instruction. Each of the treatment groups received equal amounts (14 hours) of training exposure over an eight-week period. At the conclusion of training, all subjects were posttested using the same measures used for pre-testing. The results of the study indicated (l) that no one treatment approach can be considered superior or inferior to the other in its effectiveness in increasing assertive behavior, and (2) that all treatment groups showed significantly greater ability to increase assertiveness than was evidenced with the control group.

The focus of this study was to explore the effects of training with Electromyogram (EMG) feedback relaxation on test anxiety and academic achievement. Subjects were 60 students from an Introductory Psychology Class who scored highest on the Suinn Test Anxiety Behavior Scale (STABS). Subjects were divided into three groups: (1) EMG training, (2) Attention, and (3) Control. Treatment was 12 sessions over a six-week period. A pretest and posttest of the STABS was used as a measure of anxiety with the measure of academic achievement being the first and fourth tests in the Psychology class. Analysis of covariance was used to evaluate the data. No significant difference was found between the adjusted posttest means for anxiety reduction or academic achievement.

Magnetic nanoparticles (MNPs) have found use in a wide variety of biomedical applications including hyperthermia, imaging and drug delivery. Certain physical properties, such as the ability to generate heat in response to an alternating magnetic field, make these structures ideal for such purposes. This study's objective was to elucidate the mechanisms primarily responsible for RF MNP heating and determine how such processes affect polymer solutions that might be useful in drug delivery. 15-20 nm magnetite (Fe3O4) nanoparticles at 0.2% and 0.5% concentrations were heated with RF fields of different strengths (200 Oe, 400 Oe and 600 Oe) in water and in 0.5% gellan gum solution. Mixing and fan cooling were used in an attempt to improve accuracy of data collection. Specific absorption rate (SAR) values were determined experimentally for each combination of solvent, concentration and field strength. Theoretical calculation of SAR was performed using a model based on linear response theory. Mixing yielded greater precision in experimental determination of SAR while the effects of cooling on this parameter were negligible. Solutions with gellan gum displayed smoother heating over time but no significant changes in SAR values. This was attributed to low polymer concentration and lack of structural phase transition. The LRT model was found to be adequate for calculating SAR at low polymer concentration and was useful in identifying Neel relaxation as the dominant heating process. Heating trials with MNPs in 2% agar confirmed Neel relaxation to be primarily responsible for heat generation in the particles studied.

A wide range of modern large-scale systems relies on recovering a signal from noisy linear measurements. In many applications, the useful signal has inherent properties, such as sparsity, low-rankness, or boundedness, and making use of these properties and structures allow a more efficient recovery. Hence, a significant amount of work has been dedicated to developing and analyzing algorithms that can take advantage of the signal structure. Especially, since the advent of Compressed Sensing (CS) there has been significant progress towards this direction. Generally speaking, the signal structure can be harnessed by solving an appropriate regularized or constrained M-estimator. In modern Multi-input Multi-output (MIMO) communication systems, all transmitted signals are drawn from finite constellations and are thus bounded. Besides, most recent modulation schemes such as Generalized Space Shift Keying (GSSK) or Generalized Spatial Modulation (GSM) yield signals that are inherently sparse. In the recovery procedure, boundedness and sparsity can be promoted by using the ℓ1 norm regularization and by imposing an ℓ∞ norm constraint respectively. In this thesis, we propose novel optimization algorithms to recover certain classes of structured signals with emphasis on MIMO communication systems. The exact analysis permits a clear characterization of how well these systems perform. Also, it allows an automatic tuning of the parameters. In each context, we define the appropriate performance metrics and we analyze them exactly in the High Dimentional Regime (HDR). The framework we use for the analysis is based on Gaussian process inequalities; in particular, on a new strong and tight version of a classical comparison inequality (due to Gordon, 1988) in the presence of additional convexity assumptions. The new framework that emerged from this inequality is coined as Convex Gaussian Min-max Theorem (CGMT).

No description available.

The primary objective of the studies described in this thesis was to improve the cryopreservation success of koala spermatozoa for the purpose of establishing a genome resource bank for this species. A defining feature of the studies in this thesis was the implementation of an organelle-specific approach to better understand the causes of koala sperm cryo-injury. The functional attributes of spermatozoa, such as mitochondrial function, plasma membrane fluidity, membrane lipid asymmetry and DNA integrity were assessed as an indication of cryo-injury. Sperm mitochondrial function and plasma membrane integrity were examined by cryomicroscopy using the fluorescent probes JC-1 and propidium iodide (PI) respectively in a dual staining technique. Cooling and re-warming koala spermatozoa were more detrimental to mitochondrial function than to plasma membrane integrity. Mitochondrial membrane potential (MMP) was suppressed by freezing and thawing treatments; after thawing, MMP declined significantly during rewarming (from 5ºC to 35ºC). The distribution of GM1 ganglioside was examined using fluorescent-labelled cholera toxin B. No significant redistribution of GM1 was observed after chilling or cryotreatment. The externalisation of phosphatidylserine (PS) was examined using fluorescent-labelled annexin V. There was no significant increase in translocation of PS after chilling or cryopreservation. These observations imply that cryotreatment had little effect on plasma membrane lipid asymmetry. Koala spermatozoa were incubated in a range of anisotonic media to investigate whether nuclear swelling was caused by osmotic flux during the cryopreservation process. Although the most hypotonic solution tested (64 mOsm/kg) induced the highest incidence of nuclear relaxation (mean ± SEM; 12 ± 3%), this was not as severe as that previously documented following cryopreservation. Chromatin relaxation is a phenomenon observed in koala spermatozoa, where the sperm nucleus expands due to the result of structural changes in the natural conformation of the sperm DNA/protamine complex. DNA fragmentation was not a primary cause of cryopreservation-induced sperm chromatin relaxation, although in situ nick translation of putative DNA breaks indicated that these increased as the sperm head became progressively more relaxed. Using a Sperm Chromatin Dispersion test (SCDt) specifically developed and validated for koala spermatozoa, a continuum of nuclear morphotypes was observed, ranging from no apparent DNA fragmentation to spermatozoa with highly dispersed and degraded chromatin. A double comet assay was also developed to investigate DNA fragmentation in the koala spermatozoa. Conducted under neutral followed by alkaline conditions, this assay was able to differentiate between single- (SSB) and double-stranded (DSB) DNA damage in an effort to refine the interpretation of DNA damage in mature koala spermatozoa; the majority of the koala spermatozoa had nuclei with DNA abasic-like residues. The ubiquity of these residues suggested that constitutive alkali-labile sites are part of the structural configuration of the koala sperm nucleus. Spermatozoa with “true” DNA fragmentation exhibited a continuum of comet morphologies, ranging from a more severe form of alkaline-susceptible DNA, to nuclei that exhibited both SSB and DSB. Swelling of koala sperm chromatin following cryopreservation has largely been attributed to the absence of inter-molecular disulphide cross-linkages in the marsupial sperm nucleus. Fish spermatozoa also lack disulphide bonds within their chromatin, but nevertheless, have been successfully cryopreserved. To examine the hypothesis that the cryoprotectants used for fish sperm cryopreservation will confer a similar degree of protection on koala spermatozoa, various concentrations of five cryoprotectants (dimethyl sulphoxide, methanol, propylene glycol, ethylene glycol and dimethylacetamide) were evaluated. Each treatment was compared against an established koala sperm cryopreservation protocol that uses 14% glycerol. Dimethylacetamide at a concentration of 12.5% (v/v) was found to be comparable to glycerol in the successful cryopreservation of koala spermatozoa although high inter-male variability was observed. However, when the new protocol was subsequently validated for a larger population of captive koalas (n = 22), glycerol emerged the better cryoprotectant with respect to all sperm viability parameters assessed except for that of the incidence of chromatin relaxation, which was not affected by the cryoprotectant. Significant difference was also observed in the post-thaw survival of spermatozoa from different animals, which was independent of pre-freeze semen quality. Based on post-thaw semen viability parameters, the koalas could be divided into two distinct groups, where one group had significantly higher sperm viability compared to the other group, regardless of cryoprotectant used. Positive correlation between motility and MMP was observed before and after cryopreservation. However, cryopreservation significantly reduced the dependency between these variables (P < 0.001), suggesting that cryopreservation reduced the dependency between mitochondrial function and motility.

The primary objective of the studies described in this thesis was to improve the cryopreservation success of koala spermatozoa for the purpose of establishing a genome resource bank for this species. A defining feature of the studies in this thesis was the implementation of an organelle-specific approach to better understand the causes of koala sperm cryo-injury. The functional attributes of spermatozoa, such as mitochondrial function, plasma membrane fluidity, membrane lipid asymmetry and DNA integrity were assessed as an indication of cryo-injury. Sperm mitochondrial function and plasma membrane integrity were examined by cryomicroscopy using the fluorescent probes JC-1 and propidium iodide (PI) respectively in a dual staining technique. Cooling and re-warming koala spermatozoa were more detrimental to mitochondrial function than to plasma membrane integrity. Mitochondrial membrane potential (MMP) was suppressed by freezing and thawing treatments; after thawing, MMP declined significantly during rewarming (from 5ºC to 35ºC). The distribution of GM1 ganglioside was examined using fluorescent-labelled cholera toxin B. No significant redistribution of GM1 was observed after chilling or cryotreatment. The externalisation of phosphatidylserine (PS) was examined using fluorescent-labelled annexin V. There was no significant increase in translocation of PS after chilling or cryopreservation. These observations imply that cryotreatment had little effect on plasma membrane lipid asymmetry. Koala spermatozoa were incubated in a range of anisotonic media to investigate whether nuclear swelling was caused by osmotic flux during the cryopreservation process. Although the most hypotonic solution tested (64 mOsm/kg) induced the highest incidence of nuclear relaxation (mean ± SEM; 12 ± 3%), this was not as severe as that previously documented following cryopreservation. Chromatin relaxation is a phenomenon observed in koala spermatozoa, where the sperm nucleus expands due to the result of structural changes in the natural conformation of the sperm DNA/protamine complex. DNA fragmentation was not a primary cause of cryopreservation-induced sperm chromatin relaxation, although in situ nick translation of putative DNA breaks indicated that these increased as the sperm head became progressively more relaxed. Using a Sperm Chromatin Dispersion test (SCDt) specifically developed and validated for koala spermatozoa, a continuum of nuclear morphotypes was observed, ranging from no apparent DNA fragmentation to spermatozoa with highly dispersed and degraded chromatin. A double comet assay was also developed to investigate DNA fragmentation in the koala spermatozoa. Conducted under neutral followed by alkaline conditions, this assay was able to differentiate between single- (SSB) and double-stranded (DSB) DNA damage in an effort to refine the interpretation of DNA damage in mature koala spermatozoa; the majority of the koala spermatozoa had nuclei with DNA abasic-like residues. The ubiquity of these residues suggested that constitutive alkali-labile sites are part of the structural configuration of the koala sperm nucleus. Spermatozoa with “true” DNA fragmentation exhibited a continuum of comet morphologies, ranging from a more severe form of alkaline-susceptible DNA, to nuclei that exhibited both SSB and DSB. Swelling of koala sperm chromatin following cryopreservation has largely been attributed to the absence of inter-molecular disulphide cross-linkages in the marsupial sperm nucleus. Fish spermatozoa also lack disulphide bonds within their chromatin, but nevertheless, have been successfully cryopreserved. To examine the hypothesis that the cryoprotectants used for fish sperm cryopreservation will confer a similar degree of protection on koala spermatozoa, various concentrations of five cryoprotectants (dimethyl sulphoxide, methanol, propylene glycol, ethylene glycol and dimethylacetamide) were evaluated. Each treatment was compared against an established koala sperm cryopreservation protocol that uses 14% glycerol. Dimethylacetamide at a concentration of 12.5% (v/v) was found to be comparable to glycerol in the successful cryopreservation of koala spermatozoa although high inter-male variability was observed. However, when the new protocol was subsequently validated for a larger population of captive koalas (n = 22), glycerol emerged the better cryoprotectant with respect to all sperm viability parameters assessed except for that of the incidence of chromatin relaxation, which was not affected by the cryoprotectant. Significant difference was also observed in the post-thaw survival of spermatozoa from different animals, which was independent of pre-freeze semen quality. Based on post-thaw semen viability parameters, the koalas could be divided into two distinct groups, where one group had significantly higher sperm viability compared to the other group, regardless of cryoprotectant used. Positive correlation between motility and MMP was observed before and after cryopreservation. However, cryopreservation significantly reduced the dependency between these variables (P < 0.001), suggesting that cryopreservation reduced the dependency between mitochondrial function and motility.