Centrifugation of stallion semen is an integral part of the cryopreservation procedure, primarily allowing for the concentration of sperm and removal of seminal plasma. In addition, centrifugation is required for maximizing spermatozoal quality in semen from some stallions subjected to cooled transport, because of the detrimental effects of long-term exposure to high levels of seminal plasma. The centrifugation process, however, has potential deleterious effects, including reduction in sperm quality as well as loss of sperm numbers. Since centrifugation plays such a crucial role in semen processing, two experiments were designed to evaluate more efficient centrifugation methods to meet the demands of the equine industry. In Experiment 1, semen was centrifuged in two different tube types (nipple- or conical-bottom), using a cushioned technique (Eqcellsire® Component B) with two different extenders (opaque-INRA96 or clear-HGLL). For Experiment 2, nipple-tube centrifugation was conducted at two different g forces (400 or 600) for 20 min, using three different iodixanol cushion media, Eqcellsire® Component B, OptiPrep™, or Cushion Fluid™. Regardless of tube or extender types, centrifugation of semen resulted in sperm recovery rates ≥ 90%; however, centrifugation in INRA 96 extender yielded higher sperm motility values than did centrifugation in HGLL extender (P < 0.05). Cushion type or g force did not impact post-centrifugation semen quality, based on the laboratory values measured (P > 0.05). These results indicate that cushioned centrifugation of stallion semen in either conical-bottom or nipple-bottom tubes can yield a high sperm harvest, while maintaining sperm function. An optically opaque extender, as is typically used in the equine breeding industry, can be used to achieve this goal. The fertility rate (94%; 131/140) following cushioned semen centrifugation in a commercial program this past year indicates that these laboratory results are transferable to the clinical setting.

Centrifugation of stallion semen is an integral part of the cryopreservation procedure, primarily allowing for the concentration of sperm and removal of seminal plasma. In addition, centrifugation is required for maximizing spermatozoal quality in semen from some stallions subjected to cooled transport, because of the detrimental effects of long-term exposure to high levels of seminal plasma. The centrifugation process, however, has potential deleterious effects, including reduction in sperm quality as well as loss of sperm numbers. Since centrifugation plays such a crucial role in semen processing, two experiments were designed to evaluate more efficient centrifugation methods to meet the demands of the equine industry. In Experiment 1, semen was centrifuged in two different tube types (nipple- or conical-bottom), using a cushioned technique (Eqcellsire® Component B) with two different extenders (opaque-INRA96 or clear-HGLL). For Experiment 2, nipple-tube centrifugation was conducted at two different g forces (400 or 600) for 20 min, using three different iodixanol cushion media, Eqcellsire® Component B, OptiPrep™, or Cushion Fluid™. Regardless of tube or extender types, centrifugation of semen resulted in sperm recovery rates ≥ 90%; however, centrifugation in INRA 96 extender yielded higher sperm motility values than did centrifugation in HGLL extender (P < 0.05). Cushion type or g force did not impact post-centrifugation semen quality, based on the laboratory values measured (P > 0.05). These results indicate that cushioned centrifugation of stallion semen in either conical-bottom or nipple-bottom tubes can yield a high sperm harvest, while maintaining sperm function. An optically opaque extender, as is typically used in the equine breeding industry, can be used to achieve this goal. The fertility rate (94%; 131/140) following cushioned semen centrifugation in a commercial program this past year indicates that these laboratory results are transferable to the clinical setting.

The objective of this research is to develop a new and efficient method of absorbing a vehicle??s kinetic energy for highway safety crash cushions. A vehicle that makes a direct impact with a rigid highway structure traveling at highway speeds can be fatal for its occupants. Crash cushions are implemented on roadways in front of these rigid structures with the intent to ??soften?? the impact. The cushion will bring a vehicle to a stop at safe rates before it impacts the rigid structure. The energy absorbing component of the crash cushion must meet four main requirements. The cushion must reduce the vehicles speed at a rate that does not allow the occupant to impact the vehicle interior at velocities greater than 12 m/s. The cushion must then bring the vehicle to a complete stop with deceleration rates below 20 g??s. A crash cushion must satisfy these requirements for an 820 kg vehicle and a 2000 kg vehicle traveling at 100 km/hr. Advanced design methodologies were applied to enable multiple, innovative design concepts. These concepts made use of the deformation of steel in structural pipe, structural angle, and structural plate to reduce the velocity of a vehicle at a safe rate. Critical design parameters were identified which allowed for efficient and effective numerical experiments to be conducted. The data collected from these experiments were then validated when compared to physical test data. After the data had been collected, each of the designs was compared to one another in order to decide upon the best design. The design selected was the deforming plate concept which makes use of steel plate mounted in a fashion that created two arms that acted similar to two cantilever beams. A wedge was forced beneath these arms deforming them upward. This design is effective because the deformation can be easily controlled by the thickness of the plate, the moment arm created by the wedge, and the geometry of the wedge. Steel plate is a readily available material that requires minimal manufacturing for installation preparation making it cost-effective, and easy to install. In the event of impact with the cushion, new parts will be inexpensive and readily available. Being reusable, easy to repair and low in cost, the energy absorbing concept presented herein is a cost effective alternative to existing energy absorbing technology. Due to replaceable parts being readily available, repair time and cost will be reduced compared to other designs that require new parts to be fabricated for replacement. This will make for a competitive design.

Centrifugation of stallion semen is an integral part of the cryopreservation procedure, primarily allowing for the concentration of sperm and removal of seminal plasma. In addition, centrifugation is required for maximizing spermatozoal quality in semen from some stallions subjected to cooled transport, because of the detrimental effects of long-term exposure to high levels of seminal plasma. The centrifugation process, however, has potential deleterious effects, including reduction in sperm quality as well as loss of sperm numbers. Since centrifugation plays such a crucial role in semen processing, two experiments were designed to evaluate more efficient centrifugation methods to meet the demands of the equine industry. In Experiment 1, semen was centrifuged in two different tube types (nipple- or conical-bottom), using a cushioned technique (Eqcellsire® Component B) with two different extenders (opaque-INRA96 or clear-HGLL). For Experiment 2, nipple-tube centrifugation was conducted at two different g forces (400 or 600) for 20 min, using three different iodixanol cushion media, Eqcellsire® Component B, OptiPrep[TM], or Cushion Fluid[TM]. Regardless of tube or extender types, centrifugation of semen resulted in sperm recovery rates ≥90%; however, centrifugation in INRA 96 extender yielded higher sperm motility values than did centrifugation in HGLL extender (P < 0.05). Cushion type or g force did not impact post-centrifugation semen quality, based on the laboratory values measured (P > 0.05). These results indicate that cushioned centrifugation of stallion semen in either conical-bottom or nipple-bottom tubes can yield a high sperm harvest, while maintaining sperm function. An optically opaque extender, as is typically used in the equine breeding industry, can be used to achieve this goal. The fertility rate (94%; 131/140) following cushioned semen centrifugation in a commercial program this past year indicates that these laboratory results are transferable to the clinical setting.

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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 183-190). Also available via the Internet.

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This study conducted a series of road tests in the regular fleet operations of a revenue service to better understand the relationship between vehicle seat design and driver fatigue, improve two newly proposed objective methods for evaluating driver fatigue, and provide design guidelines for evaluating and improving vehicle seat characteristics in terms of driver fatigue. Each driver completed a test session on two seat cushions - one a polyurethane foam cushion and one an air-inflated cushion. Objective measurements of pressure distribution were taken throughout each test session, while subjective measurements were collected using surveys taken at one-hour intervals. Based on these results, we find that the air-inflated seat cushion has advantages in terms of subjective measures of comfort, support, and fatigue. We show that the objective measure aPcrms highlights characteristic differences between seat cushions, as the air-inflated seat cushion provides less area in high pressure regions, thus occluding less blood flow to tissue in the seated area. While we were unable to effectively assess the validity of the proposed measures or improve them further, the characteristic difference between seat cushions is not highlighted by using previously existing objective measures. This implies that aPcrms is a more useful measure and should be considered when evaluating the subjective quality of seat cushion designs under dynamic conditions, such as those existing in commercial truck driving. / Master of Science

Devido a forte concorrência dentro do mercado automobilístico, aspectos como qualidade e custo tornam-se prioritários na busca de competitividade. Diversas empresas trabalham em propostas visando a redução de custo sem perda de qualidade. Diversos veículos dentro do mercado brasileiro usam o coxim hidráulico no sistema de apoio do motor. A proposta inicial visa substituição deste coxim por um coxim elastomérico. Seguindo esta proposta, tem-se esta pesquisa que visa apresentar comparativamente o comportamento entre o coxim hidráulico e o coxim elastomérico. Além da revisão bibliográfica, realizamos o estudo comparativo experimental com peças físicas avaliadas conforme especificações utilizadas pela indústria automobilística. Observamos que o coxim elastomérico apresentou substancial melhoria desde os anos 70, oferecendo bom compromisso entre rigidez estática e isolação de vibração. O coxim hidráulico, por sua vez, apresenta alto amortecimento na faixa de baixa freqüência e sua rigidez dinâmica ainda é maior na faixa de alta freqüência, porém seu desempenho quanto a isolação de vibração irá depender da rigidez dinâmica, da constante de amortecimento e da faixa de freqüência em estará submetido. Devido ao custo do coxim elastomérico ser cerca de três vezes menor que o custo do coxim hidráulico, o mesmo torna-se grande atrativo para compor o sistema de apoio do motor. Ainda acrescentamos que se deve avaliar o veículo como um todo em laboratórios especializados para avaliação do desempenho quanto ao conforto do usuário. / Due to strong competition inside of the automotive market, aspects as quality and cost become priority in the search of competitiveness. Several companies work in proposals seeking the cost reduction without quality loss. Several vehicles inside of Brazilian market use the hydraulic mount at their engine mount system. The initial proposal seeks the substitution of this type of mount by an elastomeric mount. Based on this proposal, we have this research that intends to present comparatively the behavior between the hydraulic mount and the elastomeric mount. Besides the researched bibliography, we accomplished the practical comparative study with physical parts evaluating as specifications used by automotive industries. We observed that the elastomeric mount presented substantial improvements since the seventies, offering good compromising between static stiffness and isolation vibration performance. The hydraulic mount presents high damping at low frequency range but its dynamic stiffness at high frequency is larger than elastomeric mount, but its performance at vibration isolation will depend of dynamic stiffness, damping coefficient and of the frequency range that it will be submitted. Due to the cost of the elastomeric mount to be about three times smaller than hydraulic mount cost, the elastomeric mount becomes great attraction to compose the engine mount system. Besides the cost, is evident that should be also evaluate the performance for the users comfort and new studies in specialized laboratories shall be accomplished.