The purpose of this thesis has been to design and develop a practical apparatus for determining the residual strength of clay soils. To provide background for the study, current knowledge regarding residual strength is reviewed, including the following points. 1. Residual strength, defined as the lowest drained strength a soil can exhibit, is attained at large shear displacements. 2. Residual conditions result when particles located in shear bands within the failure zone become aligned in the direction of shear. 3. Residual strength, derived from interparticle bonding, is influenced by crystal structure and, in active clay minerals, by pore water chemistry. The ring shear test, performed by applying a torsional shear load to an annular shaped specimen, is particularly suited for residual strength determinations because of unlimited uni-directional strain capabilities. The UBC Ring Shear Device was designed to combine versatility with uncomplicated operation. Features of the design are as follows. 1. Variable sample height up to 0.75 inches. 2. Smoothly variable normal stress up to 200 psi delivered through an air piston. 3. Smoothly variable rate of shear from 3-2 inches per year to 9 inches per hour. 4. A non-tilting loading platen which reduces required machine tolerances and improves control of sample losses during testing. 5. Automatic data acquisition. 6. A simple method of sample placement. Residual strength determinations obtained with the UBC Ring Shear Device demonstrate its efficient and effective operation. Minimal supervision is required and test results are easily interpreted. Multi-reversal direct shear tests for residual strength were undertaken for comparison with the ring shear results, but no satisfactory results were obtained due to excess pore pressures within the test specimens. Recommendations for improvements to both ring shear and direct shear devices are given. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Power and strength training, using conventional techniques, has been studied by several researchers. Investigations into the use of different training methods and their effect on power and strength development are continually being studied and re-assessed. Recently, the use of faradic or electrical stimulation has become an interesting alternative method, although much controversy surrounds this technique. It has been reported by Johnson et al. (1977) and Kots (1977) that faradic stimulation is used with success as part of a strengthening program by elite Soviet athletes. The combined effects of a program consisting of exercise as well as electrical stimulation was undertaken to determine the muscular power and strength potentials. The main objective of this study was to compare power and strength changes between equated groups employing the following training techniques: electrical stimulation plus isokinetic exercise, isokinetic exercise and electrical stimulation, respectively. Twenty-seven, moderately trained, female subjects, nine per group, were tested on three separate occasions. During the first session, height, weight, left and right quadriceps power evaluation, time to peak tension of the muscle contraction at the four velocities :(30, 100, 180 and 0 degrees per second) and two thigh girth measurements were determined. The three groups were equated for power after the pretest was conducted. The second and third testing sessions assessed the power and time to peak tension of the non-dominant leg at the four velocities and patellar and gluteal thigh girths. A significant difference for power was found between the pre and post tests and the pre and mid tests for the combined groups during the six week period of training. Although no difference was found between each of the three groups, the results indicated that programs involving electrical stimulation and isokinetic exercise, isokinetic exercise and electrical stimulation only, are potentially effective in improving muscular power and strength in normal subjects. The study revealed that one method was not superior to another after six weeks of training. There was significant power differences between the pre and post tests and pre and mid tests at the slow isokinetic speeds of 30° and 0° per second. Since the training was conducted at the speeds of 30° and 0° (isometric) per second, the slow testing speeds reflected neural adaptation and muscular recruitment when the specificity of training theory is considered. These findings imply that power and strength training benefits are limited to speeds used during training. During the six week training period, time to peak maximal torque and hypertrophy of the quadriceps muscle group did not alter significantly when examining the means of all three groups. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

After knee surgery, the development of leg strength and size to its original levels are important requirements in the recovery. The major aim in the rehabilitation of a meniscectomy is to return the injured limb to its original size by a program of active exercises. Failure to do this may result in limited activity and re-injury to the knee joint A program of electrical stimulation has been found to be effective in controlling muscle atrophy during the time of denervation in animals and humans (in animals - Schimrizk et a 1976; Herbison et al, 1973, 1971; Stillwell et al, 1962 and Guttman and Guttman, 1942; in humans - Osbourne, 1951 and Jackson and Seddon, 1945). At the present time no studies have been done to determine if electrical stimulation will be effective in controlling muscle atrophy in normally innervated muscles during the period of immobilization. The purpose of this investigation was to determine the effects of a 10-12 day program of electrical stimulation on the control of muscle atrophy and strength loss during the period of immobilization. A subproblem of this investigation was to determine the relationship between muscle atrophy and strength loss. The subjects for this study were eighteen patients undergoing a meniscectomy operation (mean age 22.7 yrs.). Subjects were rated according to strength per body weight and assigned to a control or an experimental group. The experimental group participated in a five session program of electrical stimulation in addition to a standard physiotherapy program. The control group participated only in the standard physiotherapy program. The electrical stimulation consisted of five sessions each lasting ten minutes. Ninety muscle contractions were made during the ten minute session. The sessions were held on weekdays within a 10-12 day period of the operation. The first session was held 48 hours after the operation. In the first two sessions the leg was stimulated at the immobilized angle and in the remaining three sessions the leg was stimulated at 115 degrees of extention. All subjects were tested one day prior to the operation and at the end of the 10-12 day period for thigh volume and maximal isometric leg strength. The following hypotheses were tested for significance at the .05 level. 1. The use of electrical stimulation in addition to the standard physiotherapy program will show less muscle atrophy as compared to the standard physiotherapy program. 2. The use of electrical stimulation in addition to the standard physiotherapy program will maintain a higher level of original isometric strength as compared to the standard physiotherapy program. 3. There is a positive linear relationship between muscle atrophy and strength loss. Analysis of variance revealed that hypothesis #1 is supported at the .01 level and hypothesis #2 is not supported at the .05 level of significance. The Pearson Product Moment Correlation showed that hypothesis #3 is supported when the two groups were combined and for the control group only at the .01 level of significance, but not for the treatment group only, at the .05 level. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Magister Scientiae - MSc / The purpose of this in vitro study is to compare the relative retentive strength of conventional amalgam restorations and bonded amalgam restorations using resin adhesive, glass ionomer cements and resin cements.

archives@tulane.edu / Previous work has revealed a presynaptic cytosolic Na+-dependent regulation on vesicular glutamate content and mEPSC amplitude via activating vacuolar Na+/H+ exchangers (NHEs) expressed on the synaptic vesicles, suggesting a presynaptic determinant of quantal size for synaptic strength. However, it remains unknown how spike activities control intracellular Na+ at the axon terminals and how the fluctuation of presynaptic Na+ during activities modulates quantal content and contributes to synaptic strength. I studied these questions using the calyx of Held, a giant glutamatergic synapse. With two-photon Na+ imaging, I found that presynaptic Na+ substantially accumulated during spike firing in a frequency and duration-dependent manner. This spike-induced elevation of presynaptic Na+ gradually increased EPSC amplitude by solely affecting vesicular glutamate filling, which was further confirmed as increased amplitude of asynchronous released vesicles, but without affecting the size of readily releasable pool or neurotransmitter release probability. This Na+-dependent modulation of EPSC amplitude resulted in a change of the reliability of transferring presynaptic spike to postsynaptic firing. Finally, blockade of NHEs reduced both EPSC amplitude and reliability of synaptic signaling, suggesting that NHEs are required for presynaptic Na+ regulation of synaptic transmission. Recent studies demonstrated that a non-inactivation cation channel NALCN (Na+ leak channel, non-selective), characterized as a major Na+ leak channel, is widely expressed in the central nervous system. Immunostaining revealed the expression of NALCN channel at the calyceal terminals. In line with a role of NALCN in controlling the cell excitability, calyces with conditional knockout (cKO) of NALCN exhibited a more hyperpolarized resting membrane potential compared with the wildtype (WT) calyces. Blockade of NALCN with a non-specific blocker gadolinium (Gd3+) induced a reduction of basal Na+ level and mEPSC amplitude in the WT but not in cKO group, suggesting the involvement of presynaptic NALCN channels in regulating the vesicular glutamate content. More importantly, two-photon Ca2+ imaging showed that NALCN channels were permeable to Ca2+, and Gd3+ decreased the basal Ca2+ level in WT but not cKO calyces. The Ca2+ permeability was further confirmed by reduced sensitivity of mEPSC frequency in response to increased extracellular Ca2+ concentration in cKO and reduced initial release probability in response to application of Gd3+ to block NALCN channels in WT group. Finally, Gd3+ induced a stronger reduction of EPSC amplitude in WT group compared to cKO group. Overall, these data indicate that NALCN channels regulate glutamate transmission through modulation of both quantal size and initial release probability. / 1 / Dainan Li

Southern pine (SP) lumber is the primary softwood material in the United States. The main procedure during lumber grading process is the identification of the strength reducing characteristics that impacts the modulus of rupture (MOR). Non-destructive evaluation technology can be used to identify higher-stiffness material. This study investigated the use of vibration methods to evaluate the mechanical properties of southern pine lumber. Significant correlations between the properties determined by non-destructive techniques and the static MOE were found. No strong correlations were found for MOR because it is related to the ultimate strength of material, often associated with the existence of localized defects, such as a knot. Non-destructive measurements, visual characteristics, and lumber density were used as independent variables. Linear models were constructed to indirectly estimate the MOE and MOR. The variables selected was dynamic modulus of elasticity (dMOE) to predict MOE. Adding density and knot diameter ratio to the model it was possible to develop a prediction model for MOR. It was possible to improve predictability of strength (MOR) with a combination of non-destructive and knot evaluation.

No description available.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / This study evaluated the feasibility of bonding brackets to porcelain for orthodontic purposes by measuring and comparing tensile strengths of five silane-based adhesive systems. Each adhesive system bonded mesh pad brackets to 10 glazed and 10 deglazed metal-ceramic crowns and the specimens were then thermocycled between 16 degrees and 56 degrees for 2500 cycles. Clinically relevant bond strengths, comparable to those of adhesives bonding brackets to enamel, were recorded for four of the systems compared. System l+ and Porcelain Primer had the highest mean values followed by Lee's Enamelite 500, then Vivadent's Silanit, Contact-Resin and Isopast, then 3M's Concise and Scotchprime. Most, if not all, failure sites for the four were at the bracket-resin interface. Two-way factorial analysis of variance demonstrated significant differences at P<.001 among the four adhesives but no contribution of surface effect, whether glazed or deglazed, was suggested statistically. Neuman-Keul sequential range tests showed significant differences between System l+ and the three other systems but no significant differences among the three were detected. Den-Mat's Ultrabond recorded extremely low tensile strength values and was of dubious clinical value. A t-test suggested that deglazing porcelain contributed no significant difference in strength compared with intact, glazed porcelain. All failure sites were at the porcelain-resin interface for this product. Since resin may remain bonded to porcelain following debonding, George Taub's diamond polishing paste and Shofu porcelain polishing wheels were compared as to their ability in restoring the porcelain to its original state. Because of the great adhesive bond of the resin to porcelain, craters, pits or tears may be created when resin is cleaned from porcelain with conventional scalers and pliers. The diamond paste gave a better restorative finish than the stones but the end result depended on the extent of original damage following cleaning. Orthodontists should take this point into account when considering bonding to porcelain crowns or veneers for esthetics sake where final risks may outweigh initial benefits. In a limited survey of 100 orthodontists responding to a questionnaire, 89% indicated that they have bonded or contemplated bonding to composite restored teeth, and 83% indicated that they have bonded or contemplated bonding to porcelain.

Attachment strength of Listeria spp. and their InlA expression was assessed. Listeria monocytogenes 19111 exhibited the strongest attachment strength with L. monocytogenes 19115, L. grayi, L. innocua, and L. monocytogenes 7644 being the weakest. InlA expression was not detected in silver stained SDS gels but was detected in Western blotting images. Internalin A was only detected in protein extracts of L. monocytogenes 19111 and 7644 with band intensities of 50.1 and 2.5 pixels, respectively. Greater InlA expression was correlated with higher attachment strength in L. monocytogenes 19111. Listeria monocytogenes 19115 did not express InlA but it had a stronger attachment than L. monocytogenes 7644 which demonstrated InlA expression. Intensity of InlA expressed in L. monocytogenes 19111 increased when temperature increased from 10 to 40 oC, and L. monocytogenes 7644 only expressed InlA at 40 oC. It was also determined that InlA was more expressed in nutrient-rich media than in nutrient-poor media.