A formation mechanism for catalytically grown helix-shaped graphite nanotubes

The concept of a spatial-velocity hodograph is introduced to describe quantitatively the extrusion of a carbon tubule from a catalytic particle. The conditions under which a continuous tubular surface can be generated are discussed in terms of this hodograph, the shape of which determines the geometry of the initial nanotube. The model is consistent with all observed tubular shapes and explains why the formation process induces stresses that may lead to "spontaneous" plastic deformation of the tubule. This result is due to the violation of the continuity condition, that is, to the mismatch between the extrusion velocity by the catalytic particle, required to generate a continuous tubular surface, and the rate of carbon deposition.     

Fibroleiomyoma in elephant uterus

The result of the histological diagnosis from postmortal investigation of the Indian elephant (Elephas maximus) uterus structure is presented in the current study. The rare anatomical finding showed altered nodular part from the uterus wall. Through conventional and histochemical staining neoplasmatic formations were determined and diagnosis Fibroleiomyoma was established, which should not be accepted as the prime cause for the animal's death.     

Gel structures in soils

The colloidal structures in soils were studied by scanning and transmission electron microscopy. Small-angle neutron scattering was used in the pioneering study of the colloidal soil structures and their rearrangements under the effect of different factors. It was found that colloidal particles are fixed apart in a gel matrix formed by organic molecules. The results obtained suggest that the organomineral gel is composed of soil humus occurring, at least in part, in a gel-like status and reinforced by organic and inorganic colloidal particles. In the interaction with water, the reinforced humus gel behaves as many polymers: it swells, absorbing water and increasing in volume; it shrinks under drying conditions. Different impacts on the soil affect the status of the reinforced humus gel, which results in the observed changes of the soil properties.     

Changes in Physical Properties of Chernozems under the Impact of No-Till Technology

Eurasian Soil Science - This article presents the results of research on the impact of no-till technology on the natural bulk density and macro- and microaggregate composition of the topsoil...     

Insect inhabitants of old larval galleries of<Emphasis Type="Italic"> Saperda populnea</Emphasis> (L.) (Coleoptera: Cerambycidae) in Bulgaria

The complex of insect inhabitants of old larval galleries of Saperda populnea (L.) (Coleoptera: Cerambycidae) was studied during the period 2000–2003 in 18 localities in Bulgaria. As a result, 32 insect species were reared from old S. populnea galls: Metopoplax origani (Kolenati) (Heteroptera: Lygaeidae), Malachius sp. (Coleoptera: Malachiidae), Agrilus pratensis pratensis (Ratzeburg) (Coleoptera: Buprestidae), Xylocleptes bispinus (Duftschmidt) (Coleoptera: Scolytidae), Crossocerus cetratus (Shuckard), Crossocerus megacephalus (Rossi), Crossocerus nigritus (Lepeletier & Brullé), Crossocerus acanthophorus (Kohl), Passaloecus brevilabris Wolf, Passaloecus gracilis (Curtis), Psenulus schencki (Tournier), Solierella compedita compedita (Piccioli), Trypoxylon figulus figulus (Linnaeus), Trypoxylon fronticorne fronticorne Gussakovskij (Hymenoptera: Crabronidae), Cleptes schmidti Linsenmaiser, Trichrysis cyanea (Linnaeus) (Hymenoptera: Chrysididae), Clistopyga incitator (Fabricius), Ctenochira sanguinatoria (Ratzeburg), Liotryphon crassisetus (Thomson), Nemeritis fallax (Gravenhorst), Mesochorus georgievi Schwenke, Campoletis sp. (Hymenoptera: Ichneumonidae), Charmon extensor (Linnaeus) (Hymenoptera: Braconidae), Eupelmus urozonus Dalman (Hymenoptera: Eupelmidae), Perilampus aeneus (Rossius) (Hymenoptera: Perilampidae), Trichiocampus grandis (Lepeletier) (Hymenoptera: Tenthredinidae), Janus luteipes (Lepeletier) (Hymenoptera: Cephidae), Cydia corollana (Hübner) (Lepidoptera: Tortricidae), Fiebrigella brevibucca (Duda) (Diptera: Chloropidae), Eustolomyia hilaris (Fallén) (Diptera: Anthomyiidae), Senotaina sp. (Diptera: Sarcophagidae) and Heringia vitripennis (Meigen) (Diptera: Syrphidae). Amongst them, 27 species were established as new inhabitants of old S. populnea galls. Five species (C. schmidti, N. fallax, M. georgievi, P. aeneus and J. luteipes) were recorded for the first time in Bulgaria. The dwellers of old S. populnea galls belong to the following ecological groups: insects using galls as a place to develop (3 species); insects nidificating in empty galls (10 species); insects using old galls as a pupating place (1 species); insects using empty galls as overwintering shelters (3 species); predators and parasites of primary dwellers of empty galls (13 species); or insects with uncertain ecological status (2 species).     

The Effect of Season on Spermatozoa Motility,Plasma Membrane and Acrosome Integrity in Fresh and Frozen–Thawed Semen from Xinong Saanen Bucks

The aim of this study was to evaluate whether the season of ejaculate collection influences seminal quality parameters of pre‐ and post‐freeze–thawing in Xinong Saanen bucks. Ejaculates were collected from eight bucks throughout the four seasons (spring, summer, autumn and winter) in a 12 months’ time period, identified in the Northern Hemisphere. Semen samples were evaluated by the combinations of conventional and Computer‐Assisted Sperm Analysis (CASA) when fresh and after frozen–thawed, respectively. The results clearly demonstrated that season of ejaculate collection influenced (p < 0.05) fresh semen quality. Highest semen quality was observed during autumn. On the contrary, undesirable indices (significantly lower, p < 0.05) were observed in winter as compared with the other remaining seasons. CASA has clearly shown the influences of seasonal variations on semen motility parameters. Furthermore, season of ejaculate collection was also found to influence sperm freezability. Semen characteristics after frozen–thawed followed a similar pattern with that of fresh ejaculate except in spring. The results revealed that sperm quality was higher (p < 0.01) in summer and autumn than in spring and winter. In conclusion, seasonal variation influences semen quality in Xinong Saanen bucks. In addition to summer and autumn, fresh ejaculates in spring can also be successfully used for AI. Sperm from ejaculates collected during summer and autumn are more suitable for cryopreservation. Hence, it is possible to increase the efficiency of goat breeding by manipulating the seasonal variations of semen quality for immediate AI and/or cryopreservation.