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The effects of fragmentation and overstorey tree diversity on tree regeneration were assessed in tropical rain forests of the Western Ghats, India. Ninety plots were sampled for saplings (1–5 cm diameter at breast height (dbh); 5×5-m plots) and overstorey trees (>9.55 cm dbh; 20×20-m plots) within two fragments (32 ha and 18 ha) and two continuous forests. We tested the hypotheses that fragmentation and expected seed-dispersal declines (1) reduce sapling densities and species richness of all species and old-growth species, and increase recruitment of early-successional species, (2) reduce the prevalence of dispersed recruits and (3) increase influence of local overstorey on sapling densities and richness. Continuous forests and fragments had similar sapling densities and species richness overall, but density and richness of old-growth species declined by 62% and 48%, respectively, in fragments. Fragments had 39% lower densities and 24% lower richness of immigrant saplings (presumed dispersed into sites as conspecific adults were absent nearby), and immigrant densities of old-growth bird-dispersed species declined by 79%. Sapling species richness (overall and old-growth) increased with overstorey species richness in fragments, but was unrelated to overstorey richness in continuous forests. Our results show that while forest fragments retain significant sapling diversity, losses of immigrant recruits and increased overstorey influence strengthen barriers to natural regeneration of old-growth tropical rain forests.
High resolution optical spectroscopy of V795 Herculis shows complex time- and phase-dependent behaviour of the disk emission. Separate low- and high-velocity fluctuations phased on the 2.6 hr orbital period are observed in the wings of the Balmer lines, prompting a gas stream overflow model.
To investigate the aetiology of rhinitis occurring in pregnancy, by (1) describing the relationship between pregnancy rhinitis and serum oestrogen, progesterone, placental growth hormone and insulin-like growth factor, and (2) assessing the prevalence of pregnancy rhinitis among Malaysian women.
Prospective study involving 30 pregnant women followed at an ante-natal clinic for 14 months. Hormone levels were analysed during pregnancy and the post-partum period.
Levels of all four hormones were elevated in the third trimester, compared with first trimester and post-partum values. Rhinitis patients had higher levels of oestrogen and insulin-like growth factor 1 in the third trimester than non-rhinitis patients, although these differences were not statistically significant. The prevalence of rhinitis was 53.3 per cent, with most cases occurring in the third trimester. Patients with pregnancy rhinitis had a higher prevalence of female babies, compared with non-rhinitis patients (p = 0.003).
Pregnancy rhinitis was significantly more common in women giving birth to female babies. Women with pregnancy rhinitis had a non-significant elevation in oestrogen and insulin-like growth factor 1 levels, compared with those without rhinitis.
To illustrate a case of an iatrogenic mucosal tear in the trachea which caused a one-way valve effect, obstructing the airway and manifesting as post-extubation stridor.
We report a case of iatrogenic tracheal mucosal tear secondary to violent movement during intubation. The patient presented with post-extubation stridor that worsened over three days. Initial evidence suggested tracheal stenosis. Computed tomography scans revealed a mucosal tear at the level of the seventh cervical to second thoracic vertebrae. The tear was caused by forceful inflow of air as breathing became more and more difficult, resulting in a false tract. A tracheostomy changed the direction of airflow, bypassing the tear. The inflated tracheostomy tube cuff acted as a stent to keep the flap in place as healing occurred.
Iatrogenic laryngotracheal injuries are common, especially when endotracheal intubation is performed under unfavourable emergency conditions. A tracheal mucosal tear is a rare entity which is almost always undiagnosed. However, a tracheal mucosal flap may be suspected when changes in patient position alter the nature and severity of the resultant stridor and/or respiratory distress. In such cases, an inflated tracheostomy tube cuff should be kept in place for an adequate period, to act as a stent and help keep the flap in place while healing occurs.
Vestibular schwannomas are the hallmark of neurofibromatosis type two. They are difficult to treat, due to their bilateral presentation and the quest for hearing preservation. Our report describes a new treatment approach in this clinical scenario.
We report two cases which confirm that bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor, causes regression of vestibular schwannomas in patients with a previous history of gamma knife radiosurgery or failed treatment with another form of vascular endothelial growth factor targeted therapy.
In 2009, Plotkin et al. reported the volumetric response of vestibular schwannomas to bevacizumab treatment, both in untreated patients and in patients previously treated with erlotinib, an epidermal growth factor receptor inhibitor. The presented cases support the use of bevacizumab to treat vestibular schwannomas. Given the extremely slow growth of these tumours, we note the rapidity of volume reduction following bevacizumab therapy.
A novel rapid densification technique for fabrication of bulk shape YBa2Cu307–xsuperconductor is presented. The Ceracon process is a one‐step, quasi‐isostatic consolidation route utilizing conventional P/M equipment and set‐up. The Ceracon technology has enabled successful fabrication of bulk, shapes such as discs, cylinders, hollow cylinders and spheres along with significant increases in the density up to 95‐98% of the theorertical. The superconducting volume fraction is preserved due to short hold times at the operating temperatures and avoidance of high processing temperatures. Results based on densities, microstructure, susceptibility measurements, X‐ray diffraction patterns and TGA measurements are discussed.
The phenomenon of plastic flow in alumina was previously [1 and 2] characterized using sintering models and transmission electron microscopy. Some of the findingsof the work were (a) near equality in the activation energy for volume diffusion and surface area reduction (82 kJ/mol), (b) a higher activation energy (440 kJ/mol) for Coble creep mechanism in the absence of gamma/alpha phase transformation and a lower activation energy (250 kJ/mol) when phase transformation was a part ofthe sintering process and, (c) presence of extended dislocations and deformed electron diffraction spots.
In view of these results it was of interest to follow the effect of solute addition on plastic flow [ 3 ]. The solutes were incorporated in alumina through gel synthesis route and formed solid—solution systems of Cr203— A1203 and MoO3 — A12O3 at 1000°C. In the course of sintering there is partiai vaporization of caromiaand reduction of MoO3. The chromiavacancy and Mo metal thus impart an impurity decoration to the lattice. The scanning electron micrographs seem to show that they are segregated along grain boundaries, sub—grain boundaries and dislocations. With increase in temperature the linear vacancy segregations and the scattered vacancy clusters annihilate to form pores. These pores transform to creep cavities that extend from grain boundary to volume. The clustered occurrence of Mo at grain boundaries and its extended spacing in the subgrain boundary is perhaps indicative of a dislocation pipe model for its segregation. On the basis of these modeling and microstructural results a heuristic argument is presented in favor of kinetic equality among self diffusion, dislocation pipe diffusion and dislocation climb, and in favor of the commencement of Coble and Nabarros—Herring creep with severance of these equalities.
Gas atomization is one of the key processes used for the production of rapidly solidified materials. The unique feature of the gas atomization process is its capability to form spherical powders of multicomponent alloys containing reactive elements. Spherically shaped powder is specified in the secondary processing operations used in a number of applications. This requirement has resulted from the higher flow rate, better packing density, and lower surface area obtained in spherical particles compared to irregularly shaped particles.
We have investigated the microstructure, electrical resistivity and mechanical behavior of DC magnetron sputtered A1-4wt%Cu films. The substrate temperatures were varied systematically from room temperature to 500 °C. Scanning and transmission electron microscopy of the sputtered films show that the top surface of the films sputtered at low temperatures (< 200 °C) exhibits a pure Al-like fine grain morphology. In contrast, sputter deposition at higher temperatures (> 300 °C) produces films that are characterized at the top surface by a distribution of θ’-A12Cu precipitates with a platelet morphology. The mechanical behavior of the sputtered films were investigated by performing indentation tests using a depth-sensing technique.
Implantation of nitrogen into steels is known to affect surface sensitive mechanical properties. Tensile properties of thin foils implanted with either nitrogen or helium at 300 K have been measured. Fluences greater than 1 × 1016 ions/cm2 raise the yield stress and fracture stress and reduce the plastic strain to failure. Both nitrogen and helium give comparable stress-strain responses for equal average concentrations of implanted ions. The mechanical response is discussed in terms of plastic flow of laminated structures and hardening mechanisms. Initial results of atom probe field ion microscopy examinations of nitrogen implanted Fe-15 wt.% Cr-12 wt.% Ni alloy are described.
Current hot isostatic consolidation methodology used for the fabrication of complex-shaped Si3N4-based components requires the use of an expensive glass encapsulation technique and extended thermal exposure (in hours) of the specimen. An alternative consolidation approach involving the use of solid pressure transmitting media under high pressure, has enabled the consolidation of Si3N4 alloys without the need for glass encapsulation.
Characterization of microstructures and mechanical properties of this (MOR, fracture toughness) material has been carried out and will be presented. It has been noted that in Si 3N4/8%Y2O3-4%Al2O3 composition, consolidated using this approach, a significantly larger volume fraction of α phase has been retained compared with typically observed conversion in α⇒ β in hot isostatically pressed material or sintered material.
Key issues for addressing densification and microstructure control using this process are presented. This rapid consolidation approach appears to be a promising alternative to hot isostatic pressing for the fabrication of complex-shaped Si3N4 components.
A variety of Inl-xGaxAs, Inl-yAlyAs and Inl-x-yGaxAlyAs films have been grown on InP by molecular beam epitaxy. A comprehensive characterization was performed using Raman scattering, photoluminescence (PL), Fourier transform infrared (FTIR) spectroscopy and double crystal X-ray diffraction on these ternary and quaternary heterostructures with different compositions and growth conditions. The lattice matched and mismatched structures are studied. Our analyses show that the interface mismatch exerts an important influence on the optical properties of these heterostructures, and conversely that Raman, PL and FTIR can be used to probe the interface mismatch nondestructively.
High resolution 29Si NMR has been used to study the extent of
cross condensation taking place in a hybrid organic/inorganic sol-gel
system. Tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) sol-gels
were chosen for this purpose. The sols were prepared by acid catalyzed
hydrolysis of TEOS and MTEOS with a H2O/Si ratio of 0.3.
29Si NMR shows signals due to both self-condensation and
cross-condensation between TEOS and MTEOS. Resonance assignments were made
by comparing the positions and intensities of peaks in the spectra of single
and multicomponent systems. It was found that, within experimental error,
the self- and cross-condensation rates are equal and that extensive
molecular level mixing takes place during the early stages of the
Tin films were deposited on silicon substrates by RF diode sputtering and the growth behavior of these films were characterized by scanning electron microscopy. The time dependent plastic flow behavior in these films were examined by performing indentation tests using a dcpth-scnsing hardness testing machine. Individual indentation experiments with different constant load segments were conducted and the creep characteristics of both sputtered films and bulk Sn were examined. The stress exponents determined from these tests were compared with those determined for bulk Sn from conventional creep tests. The influence of the substrate material on the creep properties of the film are described.
Laminated metal-metal and metal-semiconductor ribbons have been prepared by a modified melt-spinning technique. Characterization studies have been carried out on laminated Sn-Zn, Ge-Al, InSb-CuZr and some other materials. Characteristics of these ribbons and their potential applications will be described.
Investigations of the mechanical behavior of materials used in magnetic recording is of considerable practical importance in order to assure reliable file performance. With this objective, we have investigated the magnitude of the internal stresses observed in four sputtered thin film materials typically used in magnetic recording. First, the magnitude of the stresses observed in sputtered carbon films with and without hydrogen were measured and the nature of stress relaxation and thermal stability in different ambicnts were investigated. Second, the magnitude of the internal stress in CoPtCr magnetic media with and without a Cr-based sublayer that enhances magnetic performance was examined. Finally, the magnitude of stresses typically observed in thicker sputtered films of alumina were investigated both at room temperature and at elevated temperatures. The magnitude of the stresses observed in these sputtered films and their influence on mechanical performance are discussed.
In the Idaho Chemical Processing Plant (ICPP) waste streams, zirconia is often the waste load limiting species. It modifies the glass network, enhances durability, increases viscosity and induces crystallization. The limits of its dissolution in boroaluminosilicate glass, with magnesia and soda additions were experimentally determined. A ternary compositional surface is evolved to present the isothermal regimes of liquid, liquid+zircon, liquid+forsterite, and liquid phase sintered ceramic. The potential of partitioning the transuranics, transition elements and solutes in these regimes is discussed. The visible Raman spectroscopic results are presented to elucidate the dependence among glass composition, structure and chemical durability.