672 research outputs found
Die Metallographie im Dienste der Hüttenkunde
No full textСканировала Верещак Т. Б.RUS: RUS: Содержание этой книжки было предметом доклада, сделанного Фридрихом Эмилем Гейном (Emil Heyn) в Берлине на V международном съезде прикладной химии, по секции металлургии. Благоприятный прием, оказанный докладу, побудил автора сделать его доступным в форме книги для более широких кругов. Автор надеялся, что эта книжка будет полезна при преподавании в высших технических училищах. Он не претендовал на то, чтобы дать полный обзор металлографии, а лишь хотел пробудить интерес к ней.UKR: Зміст цієї книжки був предметом доповіді, зробленої Фрідріхом Емілєм Гейном (Emil Heyn) у Берліні на V міжнародному з'їзді прикладної хімії, по секції металургії. Сприятливий прийом, наданий доповіді, спонукав автора зробити її доступною у формі книжки для ширших кіл. Автор сподівався, що ця книжка буде корисна під час викладання у вищих технічних училищах. Він не претендував на те, щоб дати повний огляд металографії, а лише хотів пробудити інтерес до неї.ENG: The contents of this book were the subject of a paper delivered by Fridrich Emil Heyn in Berlin at the Fifth International Congress of Applied Chemistry, Metallurgy Section. The favourable reception given to the paper prompted the author to make it available in book form to a wider audience. The author hoped that this little book would be useful in teaching at higher technical schools. He did not pretend to give a complete review of metallography, but only wanted to arouse interest in it
X-Ray Diffraction Studies of the Crystalline Structure of the Avian Egg Shell
No full textFrom x-ray studies, it is concluded that the avian egg shell is composed of calcium carbonate in the calcite modification. In the main portion (crystalline layer) the calcite occurs in large crystalline areas oriented with the hexagonal axis (17.6 A) inclined at 28 to 16° from the normal of the shell surface. With respect to the other areas, orientation is present over limited areas. The mammilla layer contains crystallites in entirely random orientation.The findings agree with the electron microscope observations by the second author (Heyn, 1936 a and b) according to whom large oriented crystals, spherulites, or dendrites would compose the main layer and small unoriented crystals the mammilla layer
Ultrastructural characteristics of human granulosa cells in a coculture system for in vitro fertilization
No full textThe use of somatic cells for cocultures during in vitro fertilization (IVF) is
currently finalized to obtain a higher number of healthy and viable embryos with
a high potential of implantation. Among the different cell lines that can be used
as feeder cells for cocultures, granulosa cells (GCs) are autologous cells, safe
and easy to recover. The aim of the present study was to analyze the fine
structure of human GCs used in a coculture system to evaluate, from a
morphodynamic point of view, their role in supporting embryo development. GCs
were collected during oocyte pick-up, 36 h after human chorionic gonadotropin
administration, from patients undergoing IVF procedures, who had given their
informed consent to be included in this protocol. After coculture, GCs were fixed
and processed for light microscopy (LM) and transmission electron microscopy
(TEM). By LM, GCs appeared as clusters of loosely packed cells, irregularly
rounded or polyhedral in shape, varying in diameter from 18 to 25 microm. Mitotic
cells, as well as regressing elements (with pyknotic nuclei or dense cytoplasm)
and cell fragments were occasionally observed. By TEM, the plasma membrane was
irregular due to the presence of cytoplasmic evaginations. Linear and annular gap
junctions between neighboring GCs were found. GC nuclei, rounded and
eccentrically located, contained finely dispersed chromatin, one (often two)
prominent nucleoli and, infrequently, peripheral patches of heterochromatin.
Numerous organelles populated the GC cytoplasm, among them, mitochondria were
rod-shaped or elongated, usually provided with tubular-vesicular cristae but
occasionally showing atypical, longitudinally oriented cristae. Membranes of
smooth endoplasmic reticulum, Golgi stacks and vesicles, secretory-like granules,
cisternae of rough endoplasmic reticulum (RER), free ribosomes and polysomes,
lysosomal-like bodies, microfilaments, and lipid droplets were also seen in the
GC cytoplasm. In most cells, RER was scarcely represented and numerous lipid
droplets filled the perinuclear space. On the contrary, some GCs contained an
abundant RER and rare lipid droplets scattered in the cytoplasm. In conclusion,
our data demonstrated the presence, in a coculture system, of GCs provided with
ultrastructural characteristics typical of healthy, metabolically active, mostly
steroidogenic cells. Protein-synthetic cells have also been detected. These data,
evaluated at the light of biochemical and clinical studies, sustain the
capability of human GCs cocultures to positively affect early embryo development
in vitro by the secretion of steroids and proteins, putative "embryotrophic"
factor
Morphodynamics of human endometrium during menopause and postmenopause (aging) as seen by scanning electron microscopy
No full textThe ultrastructural characteristics of the uterine mucosa have been evaluated in menopause and postmenopause by using integrated data of transmission and scanning electron microscopy. Although the surface epithelium is always present, a continuous process of flattening, deciliation as well as a reduction in microvilli number and density is evident as age proceeds. An outstanding and original finding is the formation of complex lamellar structures, the microplicae, on the apical surface of uterine epithelial cells. These may represent a sort of "vaginalization" not only increasing surface area but acting as a protective cushion against eventual injuries due to decreasing estrogen levels. These data may complement ordinary gynecologic procedures when evaluating reproductive function in aging women
An Atlas of Menopausal Aging. The Encyclopedia of Visual Medicine Series. The Parthenon Publishing Group, Londra.
No full textThis original and unique book includes a series of electron micrographs illustrating the morphodynamics of woman's reproductive life, from embryogenesis to ovulation, fertilization and postmenopause & aging
The collagen skeleton of the human umbilical cord at term. A scanning electron microscopy study after 2N-NaOH maceration
No full textThe organization of the collagen fibrils in the human umbilical cord at term is directly visualized by means of a scanning electron microscopy cell maceration method. This technique clearly reveals that there is a much more extensive collagen fibrillar architecture within the umbilical cord than that reported in the classical histological descriptions. The Wharton's jelly, in fact, appears as a spongy network of interlacing collagen fibres and small woven bundles apparently arranged at random and forming a continuous soft skeleton that encases the umbilical vessels, The collagen fibrillar network shows the presence of a wide system of interconnected cavities consisting of canalicular-like structures as well as cavernous and perivascular spaces. This system of cavities might play a mechanical role allowing the storing of the ground substance of the jelly and its diffusion during twisting or compression. Furthermore, it may have an important role facilitating the diffusion throughout the jelly of diffused materials (i.e. water and trophic metabolites) either from or to the umbilical vessels and the amniotic cavity, thus overcoming the lack of a proper vasculature within the jelly
Stootspanningen op transformatoren
No full textElectrical Engineering, Mathematics and Computer Scienc
Detection and location of discharges: In partuicular in plastic-insulated high-voltage cables
No full textElectrical Engineering, Mathematics and Computer Scienc
“Morphodynamics of Cells and Tissues. A Book in Memory of Pietro M. Motta”. Marcello Malpighi Symposia Series, Volume 9.
No full text3-D ultrastructural distribution of collagen in human placental villi at term in relation to vascular tree
No full textIn order to understand the 3-D distribution of collagen in relation to
vascularization, chorionic villi of human placentae, belonging to normal
pregnancies at term, were studied by scanning electron microscopy (SEM) after
alkali maceration techniques, and by transmission electron microscopy (TEM). The
villous tree appeared made of an uninterrupted structure of collagen fibres. The
collagen fibres connected the chorionic villi axis with their basal plates and
organised differently according to the various levels of villous branching. The
collagen of stem villi showed copious fibres. The external fibres (facing the
villous surface) were arranged mainly longitudinally. The central core of the
villi (inner fibres) were arranged concentrically around the wall of the fetal
vessels. Both external and internal fibres formed stratified lamellae or small
parallel bundles. The inner core of stem villi showed small holes housing
capillary spaces. Mature intermediate and terminal villi showed a scarce amount
of collagen arranged in thin concentric layer within the villous core,
surrounding numerous dilated capillary and sinusoid spaces.These observations
demonstrated that the extracellular matrix of human chorionic villi is highly
compartmentalised and shows a variable structural 3-D distribution depending on
the branching level of the villous tree, such a distribution ensures the most
favourable microenvironment for feto-maternal exchanges and it is likely able to
provide a modulated support to the developing chorionic fetal vessels and
trophoblastic layer as wel
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