Одноколейные тракторно-ледяные дороги: учебное пособие для лесотехнических вузов

Книга содержит описание конструкций однополозных тракторных саней, расчет основных деталей саней, краткие технические условия проектирования одноколейных тракторно-ледяных дорог, правила постройки и эксплуатации ледяных дорог и основы организации тракторного хозяйства на базе одноколейных ледяных дорог. Книга предназначена в качестве учебного пособия для лесотехнических вузов, но может также служить практическим пособием и для высшего технического персонала лесозаготовительных предприятий Наркомлеса СССР.0|7|Предисловие [c. 7]0|8|Введение [c. 8]0|11|Возникновение и развитие конструкции однополозных саней [c. 11]1|11|Первые опыты [c. 11]1|12|Принцип работы одноколейной ледяной дороги и теоретические основания проектирования однополозных саней [c. 12]1|17|Конструкция первых однополозных саней [c. 17]1|17|Однополозные сани Востокостальлеса [c. 17]1|19|Одкополозные сани ЦНИИМЭ, модель Б [c. 19]1|21|Однополозные сани на базе поковок тракторных двухполозных саней модели Д [c. 21]1|22|Однополозные сани Я. И. Гинзбурга модели 1939 г. [c. 22]1|33|Однополозные сани ГЗЯ-2 [c. 33]1|39|Варианты соединения коника с полозом [c. 39]1|39|Модернизированные однополозные сани на базе поковок саней модели Свердлеса и Востокостальлеса [c. 39]1|44|Бескониковые однополозные сани конструкции СибНИИЛХЭ [c. 44]1|46|Буферно-прицепные устройства трактора конструкции УЛТИ, Сотринского мехлесопункта и Стройлеспроекта [c. 46]1|48|Автоматическая сцепка тракторных саней [c. 48]1|49|Рама для перевозки коротья на однополозных санях [c. 49]1|51|Расчет саней [c. 51]1|51|Расчет полоза [c. 51]1|58|О форме подрезов [c. 58]0|61|Постройка одноколейных ледяных дорог [c. 61]1|61|Условия применения, сырьевая база и порядок оформления строительства [c. 61]1|62|Технические условия проектирования одноколейных ледяных дорог [c. 62]1|72|Изыскания трасс одноколейных ледяных дорог [c. 72]1|73|Строительные работы на одноколейных ледяных дорогах [c. 73]1|85|Дорожные орудия для строительства одноколейных ледяных дорог [c. 85]1|91|Цистерны для поливки ледяной дороги [c. 91]1|91|Насосные станции [c. 91]0|95|Эксплуатация ледяных дорог [c. 95]1|95|Техническая характеристика тяговых машин [c. 95]1|107|Эксплуатация газогенераторных тракторов на лесовывозке по ледяным дорогам [c. 107]1|115|Правила вождения поездов [c. 115]1|117|Формирование состава и маневры [c. 117]1|117|Содержание и ремонт пути ледяной дороги [c. 117]1|119|Техника безопасности при вывозке леса по тракторным ледяным дорогам [c. 119]1|121|Основные правила по технике безопасности для тракторного лесотранспорта [c. 121]0|123|Приложения [c. 123]1|123|Детали однополозных саней ГЗЯ-1 [c. 123]1|136|Детали модернизированных однополозных саней на базе поковок саней Свердллеса [c. 136]1|141|Краткая техническая характеристика гусеничных тракторов Челябинского тракторного завода [c. 141]0|143|Оглавление [c. 143

Magnetic resonance imaging indicators of blood-brain barrier and brain water changes in young rats with kaolin-induced hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Hydrocephalus is associated with enlargement of cerebral ventricles. We hypothesized that magnetic resonance (MR) imaging parameters known to be influenced by tissue water content would change in parallel with ventricle size in young rats and that changes in blood-brain barrier (BBB) permeability would be detected.</p> <p>Methods</p> <p>Hydrocephalus was induced by injection of kaolin into the cisterna magna of 4-week-old rats, which were studied 1 or 3 weeks later. MR was used to measure longitudinal and transverse relaxation times (T1 and T2) and apparent diffusion coefficients in several regions. Brain tissue water content was measured by the wet-dry weight method, and tissue density was measured in Percoll gradient columns. BBB permeability was measured by quantitative imaging of changes on T1-weighted images following injection of gadolinium diethylenetriamine penta-acetate (Gd-DTPA) tracer and microscopically by detection of fluorescent dextran conjugates.</p> <p>Results</p> <p>In nonhydrocephalic rats, water content decreased progressively from age 3 to 7 weeks. T1 and T2 and apparent diffusion coefficients did not exhibit parallel changes and there was no evidence of BBB permeability to tracers. The cerebral ventricles enlarged progressively in the weeks following kaolin injection. In hydrocephalic rats, the dorsal cortex was more dense and the white matter less so, indicating that the increased water content was largely confined to white matter. Hydrocephalus was associated with transient elevation of T1 in gray and white matter and persistent elevation of T2 in white matter. Changes in the apparent diffusion coefficients were significant only in white matter. Ventricle size correlated significantly with dorsal water content, T1, T2, and apparent diffusion coefficients. MR imaging showed evidence of Gd-DTPA leakage in periventricular tissue foci but not diffusely. These correlated with microscopic leak of larger dextran tracers.</p> <p>Conclusions</p> <p>MR characteristics cannot be used as direct surrogates for water content in the immature rat model of hydrocephalus, probably because they are also influenced by other changes in tissue composition that occur during brain maturation. There is no evidence for widespread persistent opening of BBB as a consequence of hydrocephalus in young rats. However, increase in focal BBB permeability suggests that periventricular blood vessels may be disrupted.</p

Newborn Genetic Screening for Hearing Impairment: A Preliminary Study at a Tertiary Center

Universal newborn hearing screening (UNHS) is of paramount importance for early identification and management of hearing impairment in children. However, infants with slight/mild, progressive, or late-onset hearing impairment might be missed in conventional UNHS. To investigate whether genetic screening for common deafness-associated mutations could assist in identifying these infants, 1017 consecutive newborns in a tertiary hospital were subjected to both newborn hearing screening using a two-step distortion-product otoacoustic emissions (DPOAE) screening and newborn genetic screening (NGS) for deafness. The NGS targeted 4 deafness-associated mutations commonly found in the Taiwanese population, including p.V37I (c.109G>A) and c.235delC of the GJB2 gene, c.919-2A>G of the SLC26A4 gene, and mitochondrial m.1555A>G of the 12S rRNA gene. The results of the NGS were then correlated to the results of the NHS. Of the 1017 newborns, 16 (1.6%) had unilateral DPOAE screening failure, and 22 (2.2%) had bilateral DPOAE screening failure. A total of 199 (19.6%) babies were found to have at least 1 mutated allele on the NGS for deafness, 11 (1.1%) of whom were homozygous for GJB2 p.V37I, 6 (0.6%) compound heterozygous for GJB2 p.V37I and c.235delC, and 1 (0.1%) homoplasmic for m.1555A>G, who may potentially have hearing loss. Among them, 3 babies, 5 babies, and 1 baby, respectively, passed the NHS at birth. Comprehensive audiological assessments in the 9 babies at 3 months identified 1 with slight hearing loss and 2 with mild hearing loss. NGS for common deafness-associated mutations may identify infants with slight/mild or potentially progressive hearing impairment, thus compensating for the inherent limitations of the conventional UNHS

Changing Bee and Hoverfly Pollinator Assemblages along an Urban-Rural Gradient

The potential for reduced pollination ecosystem service due to global declines of bees and other pollinators is cause for considerable concern. Habitat degradation, destruction and fragmentation due to agricultural intensification have historically been the main causes of this pollinator decline. However, despite increasing and accelerating levels of global urbanization, very little research has investigated the effects of urbanization on pollinator assemblages. We assessed changes in the diversity, abundance and species composition of bee and hoverfly pollinator assemblages in urban, suburban, and rural sites across a UK city.Bees and hoverflies were trapped and netted at 24 sites of similar habitat character (churchyards and cemeteries) that varied in position along a gradient of urbanization. Local habitat quality (altitude, shelter from wind, diversity and abundance of flowers), and the broader-scale degree of urbanization (e.g. percentage of built landscape and gardens within 100 m, 250 m, 500 m, 1 km, and 2.5 km of the site) were assessed for each study site. The diversity and abundance of pollinators were both significantly negatively associated with higher levels of urbanization. Assemblage composition changed along the urbanization gradient with some species positively associated with urban and suburban land-use, but more species negatively so. Pollinator assemblages were positively affected by good site habitat quality, in particular the availability of flowering plants.Our results show that urban areas can support diverse pollinator assemblages, but that this capacity is strongly affected by local habitat quality. Nonetheless, in both urban and suburban areas of the city the assemblages had fewer individuals and lower diversity than similar rural habitats. The unique development histories of different urban areas, and the difficulty of assessing mobile pollinator assemblages in just part of their range, mean that complementary studies in different cities and urban habitats are required to discover if these findings are more widely applicable