Mild Cognitive Impairment is characterized by age-related decline in a variety of cognitive domains, including reference and working memory and olfactory function. Importantly, declining age-related mnemonic abilities is not inevitable; learning and memory deficits emerge in some people by middle-age while others remain largely cognitively-intact even at advanced chronological ages. The goal of this thesis is to establish a Fischer 344 (F344) rat model with some features of human cognitive aging which can then be utilized to undercover the neurobiological underpinnings of age-related cognitive deficits. Young (6 mo), middle-aged (11 mo), and aged (22 mo) F344 rats were behaviorally characterized in a well-established reference memory version of the Morris water maze task. Indeed, age-related impairments did occur across the lifespan. Moreover, the reference memory protocol used here was sufficiently sensitive to detect a difference in individual abilities among aged F344 rats such that approximately half of the rats performed on par with young while the other half performed outside this range, demonstrating impairment. These data mimic individual differences in declarative memory among aged humans. Subsequently, subsets of rats initially characterized on the reference memory version of the water maze were tested on either a spatial working memory water maze task or an olfactory discrimination task. Despite detecting an age-related delay-dependent decline in spatial working memory, this impairment was not correlated with spatial reference memory. In contrast, a strong and significant relationship was observed among aged rats in the odor discrimination task such that aged rats with the worst spatial reference memory were also the most impaired in their ability to discriminate odors for a food reward. Importantly, this subset of cognitively-impaired rats was not impaired on digging media discrimination problems with identical task demands, nor were they anosmic. These data are among the first to demonstrate a cross-domain cognitive deficit in a rodent model of human aging. Together, the current study both confirms the use of the naturalistic F344 rat model for the study of cognitive deficits within the context of aging and provides the most comprehensive cognitive profile of this rat population to date.

The effect of joint strength of PbSn and AuSn solder in aging test for laser module packaging has been studied experimentally. The thermal conditions were aged at 150 ¢J for 1,4,9,16,25 and 36 days. It was found that the joint strength decreased as aging test time increased. The joint strength of PbSn solder with the gold coating on SUS304 substrate of 2 µm and 10 µm decreased about 17% and 28% after aging test, respectively. The joint strength of PbSn solder with the gold coating on SUS304 substrate of 2 µm and 10 µm decreased about 16% and 9% after aging test, respectively. we also presented the microstructure of the intermetallic compound ¡]IMC ¡^growth under aging test. Results showed that the thickness of the IMC increased after aging test. The growth thickness of the IMC from 1 to 36 days for the PbSn and AuSn solder were measured to be 5.26 to 34.37 and 0.48 to 1.64 µm, respectively. The joint strength decreased under aging test may be due to the crack and void defects increased within the solder. The crack and void defects in solder were observed by metallographic photos.

Abstract The influence of thermal aging on joint strength and fracture surface of PbSn and AuSn solders in laser module packages has been studied experimentally and numerically. Al2O3-Solder-Substrate assembled samples were aged at 150oC for one, four, nine, sixteen, twenty-five, thirty-six, and forty-nine days. It was found that the joint strength decreased as the aging time increased. This joint strength decrease is due to the increase of void and crack formations in solder joints. There is a correlation between the intermetallic compound (IMC) growth and the joint strength for PbSn and AuSn solders under aging test. The fracture surface of PbSn specimen is gradually changed from the ductile dominated morphology of as-soldered status to the brittle dominated morphology. The section view indicates Kirkendall voids appeared around the interface of bulk solder and IMC layers after 49 days of aging. However, AuSn specimen still shows a ductile dominated morphology and no Kirkendall voids observed even after 49 days of aging. Through 49 days of aging, the shear force drops of 2£gm Au-coated PbSn and AuSn specimens are 9.48kg and 7.65kg, respectively; the shear force drops of 10£gm Au-coated PbSn and AuSn specimens are 9.42kg and 5.88kg,respectively. A finite-element method (FEM) analysis was performed on the calculation of joint strength variation of PbSn and AuSn solders in thermal aging tests. Simulation results were in good agreement with the experimental measurements that the solder joint strength decreased as the aging time increased. Another study is based on the well-known result of thermal induced fiber alignment shifts of fiber-solder-ferrule (FSF) joints in laser diode package. It indicates fiber alignment shift under temperature cycling tests can be reduced significantly if the fiber can be located closer to the center of the ferrule. An approach to make an FSF with the minimum eccentric offset is studied, an in-house design machine set is used for this purpose, which includes a hot plate, a fiber fix stage, an image capture camera, and a PC with offset analysis program. A preliminary target is set to achieve a maximum 20£gm offset FSF. It was believed that a less than 0.5£gm fiber shift could be measured after 500 temperature cycles. After the practical experiment trial, FSF with around 10 and 12£gm offset is available. However, the continuous improvement is necessary for process stability.

Many senescent individuals demonstrate an inability to regulate mean arterial pressure (MAP) in response to standing or head-up tilt; however, whether this aging effect is the result of depressed cardiac function or an inability to reduce peripheral vascular conductance remains unknown. Therefore, the purpose of this research was to investigate the effects of aging on MAP, heart rate (HR), regional blood flow (via radioactive-microspheres), and vascular conductance during head-up tilt in conscious young (4 mo; n=12) and old (24 mo; n=10) male Fischer-344 rats. Heart rate and MAP were measured continuously during normal posture and during 10 minutes of head-up tilt. Blood flow was determined during normal posture and at the end of 10 minutes of head-up tilt. Young rats increased MAP significantly at the onset of head-up tilt and generally maintained the increase in MAP for the duration of head-up tilt, while aged rats showed a significant reduction in MAP after 10 minutes of head-up tilt. In the normal posture, aged rats demonstrated lower blood flow to splanchnic, bone, renal, and skin tissues versus young rats. With tilt there were decreases in blood flow to skin, bone, and hind-limb in both age groups and in fat, splanchnic, reproductive, and renal tissues in the young. Bone blood flow was attenuated with age across both conditions in hind foot, distal femur, femur marrow, and proximal and distal tibia. Head-up tilt caused a decrease in blood flow across both age groups in all bones sampled with the exception of the hind foot. These results provide evidence that the initial maintenance of MAP in aged rats during head-up tilt occurs through decreased regional blood flow and vascular conductance, and that the fall in pressure is not attributable to an increase in tissue blood flow and vascular conductance. Therefore, reductions in arterial pressure during headup tilt are likely a result of an old age-induced reduction in cardiac performance. In addition, this is the first study to demonstrate a decreased bone vascular conductance in both young and old rats during head-up tilt.

This thesis presents a study made on erosion control blankets with respect to their aging and longevity. Erosion control blankets have been relied upon increasingly in recent times replacing the old and traditional methods for protecting areas from erosion by storm water and other factors. But what can be an estimated duration for which a given set of blankets can be functional in channel erosion control. This research is done with the ultimate aim of understanding whether these erosion control blankets can stay in place and be conducive to some vegetation growth, which is said to be the most reliable measure for long-lasting erosion control. Seven erosion control blankets, consisting of natural, synthetic and composite types, were put to actual use for erosion control for 3 years in a field. After 3 years these used materials were cut from the field for conducting the tests. Unused blankets of the same brands were obtained. Index tests were conducted on both used and unused material specimens to measure the erosion control properties. All materials experienced a significant amount of strength loss after use. The natural materials show 80% strength loss, while the composite and synthetic materials were tested to have around 50% strength losses after being put to use for 3 years. Thus it can be observed that the composite and synthetic materials have a decent amount of life where erosion control is concerned. Other tests also proved that composite materials can be relied upon for erosion control to a reasonable extent, and the research goal was achieved.

As life expectancy in the United States increases each year, the percentage of the population that is comprised of aged individuals rises also. Researchers expect the largest increase in population to occur in the segment consisting of individuals 85 and older. Thus, investigations of the aging process, with the goals of further extending average life expectancy and improving the quality of life for aged individuals, have become increasingly important to our society. To better understand the genetics of aging, we elected to utilize another model organism, the domestic dog. The benefit to this work is that breeds exhibit extreme, natural variation in life expectancies. Here I report my contributions towards establishing the dog as another model organism for investigations of the aging process. Multiple linear regression analysis was carried out to determine the association between life spans and breed size in the dog, based upon data derived from the American pet population. A negative correlation was observed between both height and longevity and between weight and longevity with weight being the significant predictor of life span. Fifty-four genes implicated in the aging process were mapped to the canine genome. These genes were selected because of their demonstrated contribution to longevity in other organisms or based upon their proximity to a marker, D4S1564, on human chromosome 4. Four genes that are associated with dwarf mice and extended life span were analyzed in nine dog breeds of varying sizes and life expectancies. Fifty-three polymorphisms were discovered in Ghr, Ghrhr, Pit1, and Prop1. Thirteen ancestral SNPs were discovered in which both alleles were found in every breed. In Ghrhr, a transition mutation was found that changes the amino acid sequence as well as the function of the protein and is statistically significant (p=4.8 x 10-6) when large dogs are compared to medium-sized breeds, but not when they are compared to small breeds (p=0.001). This SNP warrants further investigation in additional dogs and breeds.

Alzheimer'€™s disease (AD) is the fifth leading cause of death among the elderly. This study uses National Center for Health Statistics (NCHS) Multiple Cause of Death data for the United States for the years 1998 to 2002, examining the 9.5 million death records of all decedents of age 60 and over, and determines their incidence of AD. Seven independent variables are used: age, sex, race, ethnicity, marital status, education level and whether or not they lived in a metropolitan area. This study uses logistic regression, modeling five nested models, to determine the likelihood of mortality by AD and the direction of the relationship between AD and each of the variables. A Bayesian analysis, used to determine the best fit model, found that the full model was the best fit. The major findings of the study are that the incidence of AD increases significantly with increasing age in decedents aged 60-90. However, this peaks for decedents aged 85-89. Those who survive past age 90 begin to have a lesser likelihood of mortality by AD. With the exceptions of marital status and education, the hypotheses were supported. Females are more likely to die of AD than males. NonHispanic Whites are more likely to die of AD than Hispanics and NonHispanic Blacks. There is an increased risk of dying in a nursing home if one dies of AD. Future research as outlined above is needed to learn further about this fifth leading cause of mortality of those over age 60.

Thesis (M.S.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains : 89 p. Includes bibliographical references : p. 44-48.

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Pathology. Title from title-page of electronic thesis. Includes bibliographical references.

Thesis (doctoral)--University of Sheffield, 1991. / BLDSC reference no.: DX200396.