Hippocampal subfields and limbic white matter jointly predict learning rate in older adults

First published online: 04 December 2019Age-related memory impairments have been linked to differences in structural brain parameters, including cerebral white matter (WM) microstructure and hippocampal (HC) volume, but their combined influences are rarely investigated. In a population-based sample of 337 older participants aged 61-82 years (Mage = 69.66, SDage = 3.92 years), we modeled the independent and joint effects of limbic WM microstructure and HC subfield volumes on verbal learning. Participants completed a verbal learning task of recall over five repeated trials and underwent magnetic resonance imaging (MRI), including structural and diffusion scans. We segmented three HC subregions on high-resolution MRI data and sampled mean fractional anisotropy (FA) from bilateral limbic WM tracts identified via deterministic fiber tractography. Using structural equation modeling, we evaluated the associations between learning rate and latent factors representing FA sampled from limbic WM tracts, and HC subfield volumes, and their latent interaction. Results showed limbic WM and the interaction of HC and WM-but not HC volume alone-predicted verbal learning rates. Model decomposition revealed HC volume is only positively associated with learning rate in individuals with higher WM anisotropy. We conclude that the structural characteristics of limbic WM regions and HC volume jointly contribute to verbal learning in older adults

Cutting forces in gear machining by disk milling cutters

Подані результати експериментальних досліджень силових характеристик процесу нарізання зубчастих коліс дисковими фрезами. Проведено обробку зубчастого колеса із використанням 4-х стратегій, що відрізняються схемами зняття припуску. Встановлено відмінності та закономірності змін силових характеристик процесу обробки за різними стратегіями. Встановлено переваги і недоліки різних стратегій стосовно якості і продуктивності обробки, а також стійкості інструменту. Сформульовано проблеми, що потребують вирішення при виборі оптимальної стратегії обробки.Purpose. Experimental study of cutting force components in gear machining by disk milling cutter and taking into account the different machining strategies as well as determination of advantages and disadvantages of these strategies based on obtained experimental results. Design/methodology/approach. This paper is dedicated to the experimental study of cutting force components and their variation in gear machining by disk milling cutter with different machining strategies as well as to the subsequent diskussion of obtained experimental results. Findings. It was found that the known strategies for material removal, tool movement (its running-in or running-out) and tool engagement in gear machining by disk milling cutter have different force characteristics. This can lead to the different roughness and surface quality of the tooth flanks as well as to different tool wear rates and manufacturing costs. Thus, the consideration of the radial, axial and tangential forces is very important for a correct selection of an optimal machining strategy and optimal cutting parameters for each manufacturing task. Originality/value. The experimental results show that the known strategies for gear machining by disk milling cutter have different force characteristics. This can influence machining quality and tool wear rate as well as lead to increase in manufacturing costs. It means that, in order to select a perfectly suitable machining method with the optimal process parameters for each individual manufacturing task and thereby to increase the efficiency of the gear manufacturing, the profound knowledge about achievable quality parameters and tool life are required.Представлены результаты экспериментальных исследований силовых характеристик процесса нарезания зубчатых колес дисковыми фрезами. Проведена обработка зубчатого колеса с использованием 4-х стратегий, отличающихся схемами снятия припуска. Установлены отличия и закономерности изменения силовых характеристик процесса обработки по разным стратегиям. Установлены преимущества и недостатки разных стратегий по качеству и производительности обработки, а также стойкости инструмента. Сформулированы проблемы, требующие решения при выборе оптимальной стратегии обработки

本邦人大腿骨傾斜角度ノレントゲン的測定ニ就テ(第一囘報告)

Once every menstrual cycle, eggs are ovulated into the oviduct where they await fertilization. The ovulated eggs are arrested in metaphase of the second meiotic division, and only complete meiosis upon fertilization. It is crucial that the maintenance of metaphase arrest is tightly controlled, because the spontaneous activation of the egg would preclude the development of a viable embryo (Zhang et al. 2015 J. Genet. Genomics 42, 477-485. (doi:10.1016/j.jgg.2015.07.004); Combelles et al. 2011 Hum. Reprod. 26, 545-552. (doi:10.1093/humrep/deq363); Escrich et al. 2011 J. Assist. Reprod. Genet. 28, 111-117. (doi:10.1007/s10815-010-9493-5)). However, the mechanisms that control the meiotic arrest in mammalian eggs are only poorly understood. Here, we report that a complex of BTG4 and CAF1 safeguards metaphase II arrest in mammalian eggs by deadenylating maternal mRNAs. As a follow-up of our recent high content RNAi screen for meiotic genes (Pfender et al. 2015 Nature 524, 239-242. (doi:10.1038/nature14568)), we identified Btg4 as an essential regulator of metaphase II arrest. Btg4-depleted eggs progress into anaphase II spontaneously before fertilization. BTG4 prevents the progression into anaphase by ensuring that the anaphase-promoting complex/cyclosome (APC/C) is completely inhibited during the arrest. The inhibition of the APC/C relies on EMI2 (Tang et al. 2010 Mol. Biol. Cell 21, 2589-2597. (doi:10.1091/mbc.E09-08-0708); Ohe et al. 2010 Mol. Biol. Cell 21, 905-913. (doi:10.1091/mbc.E09-11-0974)), whose expression is perturbed in the absence of BTG4. BTG4 controls protein expression during metaphase II arrest by forming a complex with the CAF1 deadenylase and we hypothesize that this complex is recruited to the mRNA via interactions between BTG4 and poly(A)-binding proteins. The BTG4-CAF1 complex drives the shortening of the poly(A) tails of a large number of transcripts at the MI-MII transition, and this wave of deadenylation is essential for the arrest in metaphase II. These findings establish a BTG4-dependent pathway for controlling poly(A) tail length during meiosis and identify an unexpected role for mRNA deadenylation in preventing the spontaneous activation of eggs

Variations in Cholesterol Management Practices of U.S. Physicians

AbstractObjectives. This study sought to evaluate national cholesterol management practices of U.S. physicians.Background. Past studies show that nonclinical factors affect physician practices. We tested the hypothesis that physician and patient characteristics influence cholesterol management.Methods. We used a stratified, random sample of 2,332 office-based physicians providing 56,215 visits to adults in the 1991–1992 National Ambulatory Medical Care Surveys. We investigated physicians’ reporting of cholesterol-related screening, counseling or medications during office visits and used multiple logistic regression to assess independent predictors.Results. An estimated 1.12 billion adult office visits occurred in 1991 and 1992 (95% confidence interval 1.06 to 1.18 billion). For the 1.03 billion visits by patients without reported hyperlipidemia, cholesterol screening (2.8% of visits) and counseling (1.2%) were not frequent. The likelihood of screening increased with older age, cardiovascular disease risk factors, white race and private insurance. We estimate that only 1 in 12 adults received cholesterol screening annually. In the 85 million visits by patients with hyperlipidemia, cholesterol testing was reported in 22.9%, cholesterol counseling in 34.4% and lipid-lowering medications in 23.1%. Testing was more likely in diabetic and nonobese patients. Counseling was more likely with younger age, cardiovascular disease and private insurance. Medications use was associated with cardiovascular disease, Northeast region of the United States, nonobese patients and visits to internists. Physician practices did not differ by patient gender.Conclusions. Although clinical conditions strongly influence cholesterol management, the appropriateness of variations noted by payment source, geographic region and physician specialty deserve further evaluation. These variations and the low estimated volume of services suggest that physicians have not fully adopted recommended cholesterol management practices.(J Am Coll Cardiol 1997;29:139–46)

On supersymmetry breaking vacua from D-branes at orientifold singularities

We present a large class of models of D-branes at (orientifold) Calabi-Yau sin- gularities which enjoy dynamical supersymmetry breaking at low energy, by means of either the SU(5) or 3\u20132 supersymmetry breaking models. Once embedded in a warped throat or, equivalently, in a large N theory, all models display an instability along a Coulomb branch direction towards supersymmetry preserving vacua. Interestingly, the nature of the run- away mechanism is model-independent and has a precise geometrical interpretation. This naturally suggests the properties a Calabi-Yau singularity should have in order for such instability not to occur

Modulation of three-dimensional structure and research of folding-analoges of AMB A 6 allergen of Ambrosia artemisiifolia

Amb A 6 allergen of Ambrosia artemisiifolia is a ragweed allergen (a principle cause of late summer hayfever in North America and Europe) (Hiller et al. 1998). The weed has recently become spreading as a neophyte in Europe, while climate change may also affect the growth of the plant and additionally may also influence pollen allergenicity (Kelish et al. 2014). In Ukraine, the number of diseases caused by this allergen has recently increases. The three-dimensional structure of Amb A 6 allergen is undescribed. The aim of our study was to modulate of three-dimensional structure and search of folding-analoges of AMB A 6 allergen of A. artemisiifolia