Vibration Fatigue of FDM 3D Printed Structures: The Use of Frequency Domain Approach

Additive manufactured structures are replacing the corresponding ones realized with classical manufacturing technique. As for metallic structures, 3D printed components are generally subjected to dynamic loading conditions which can lead to fatigue failure. In this context, it is useful, and sometimes mandatory, to determine the fatigue life of such components through numerical simulation. The methods currently available in literature for the estimation of fatigue life were originally developed for metallic structures and, therefore, it is now necessary to verify their applicability also for components fabricated with different materials. To this end, in the current activity three of the most used spectral methods for the estimation of fatigue life were used to determine the fatigue life of a 3D printed Y-shaped specimen realized in polylactic acid subjected to random loads with the aim of determining their adaptability also for this kind of materials. To certify the accuracy of the numerical prediction, a set of experimental tests were conducted in order to obtain the real fatigue life of the component and to compare the experimental results with those numerically obtained. The obtained outcomes showed there is an excellent match between the numerical and the experimental data, thus certifying the possibility of using the investigated spectral methods to predict the fatigue life of additive manufactured components.     

Gender differences in the relation between comorbidity and mortality of patients with Alzheimer's disease. Systematic Assessment of Geriatric drug use via Epidemiology (SAGE) Study Group.

OBJECTIVE: To investigate whether differences in the number and type of comorbid conditions may help explain the gender gap in mortality among patients with AD. BACKGROUND: The prevalence and incidence of AD are higher among women, who also have more severe cognitive impairment and accelerated decline. However, men have an exceedingly higher mortality. METHODS: The authors conducted a retrospective cohort study on 5,831 men and 17,918 women with a diagnosis of AD. Data were from the Systematic Assessment of Geriatric drug use via Epidemiology (SAGE) database, which includes information on residents of 1,492 nursing homes in five US states (1992-1995). Men and women were compared with respect to demographic characteristics, dementia severity, psychiatric and behavioral symptoms, indicators of physical disability, and general health status. Also compared were age- and race-adjusted prevalence of all comorbid conditions at each level of cognitive impairment. In survival analyses, the risk of death and of hospitalization were determined by gender and level of cognitive impairment. Finally, gender-related differences in the intensity of pharmacologic treatment were examined. RESULTS: Women were older than men (83+/-7 versus 81+/-7 years) and were more likely to exhibit severe cognitive deterioration (27% versus 19% among men). Overall, there were no significant gender-related differences on several measures of physical disability (activities of daily living performance, gait and history of falls, incontinence, pressure sores), but significantly more women were underweight (45% versus 37% among men). However, the age- and race-adjusted 1-year mortality rate was 17% for women and 31% for men. The mortality rate of women at the highest degree of dementia severity was lower than the rate for men with minimal cognitive impairment. At any level of cognitive impairment, the prevalence of arrhythmia, chronic obstructive pulmonary disease, PD, and cancer was higher among men. Women were also less likely to be hospitalized, and they received fewer medications for each given disease. CONCLUSIONS: The survival advantage of women with AD relative to men may occur as a result of fewer comorbid clinical conditions associated with the diagnosis of dementia.     

Spontaneous and MNNG‐induced reversion of an EGFP construct in HeLa cells: An assay for observing mutations in living cells by fluorescent microscopy

A HeLa cell line stably expressing the enhanced green fluorescence protein (EGFP) gene, interrupted by the HBB IVS2‐654 intron, was studied without treatment and after treatment with a single standard dose of 15 μM of N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG). This assay was done in order to prove that such a construct can revert by a variety of mechanisms and that it produces a visible phenotype, i.e., green fluorescence. The system permits visual detection of living mutant cells among a background of non‐mutant cells and does not require a selective medium. The results show that the construct reverts by large deletions (–62, –100, and –162 bp), small insertions (+4 bp), small rearrangements (19 bp duplication), base substitutions at purines (G₆₅₂, G₆₅₃, A₆₅₅, G₅₇₉), and a pyrimidine (T₆₅₄) between nucleotide positions 579 and 837. Splice‐site mutations were recovered, and some of the mechanisms underlying these mutations are discussed. Because of the ease of detection of revertant cells under fluorescent light and the wide variety of mutations that can be recovered, further development of this system could make it a useful new mammalian cell mutagenicity assay. Hum Mutat 18:526–534, 2001. © 2001 Wiley‐Liss, Inc.     

A catalogue of polymorphisms related to xenobiotic metabolism and cancer susceptibility

High-throughput genotyping technology of multiple genes based on large samples of cases and controls are likely to be important in identifying common genes which have a moderate effect on the development of specific diseases. We present here a comprehensive list of 313 known experimentally confirmed polymorphisms in 54 genes which are particularly relevant for metabolism of drugs, alcohol, tobacco, and other potential carcinogens. We have compiled a catalog with a standardized format that summarizes the genetic and biochemical properties of the selected polymorphisms. We have also confirmed or redesigned experimental conditions for simplex or multiplex PCR amplification of a subset of 168 SNPs of particular interest, which will provide the basis for the design of assays compatible with high-throughput genotyping.