The effect of annealing on the elastoplastic and viscoelastic responses of isotactic polypropylene

Observations are reported on isotactic polypropylene (i) in a series of tensile tests with a constant strain rate on specimens annealed for 24 h at various temperatures in the range from 110 to 150 °C, (ii) in two series of creep tests in the subyield region of deformations on samples not subjected to thermal treatment and on specimens annealed at 140 °C, and (iii) in a series of tensile relaxation tests on non-annealed specimens. Constitutive equations are derived for the elastoplastic and non-linear viscoelastic responses of semicrystalline polymers. A polymer is treated as an equivalent transient network of macro-molecules bridged by junctions (physical cross-links, entanglements and lamellar blocks). The network is assumed to be highly heterogeneous, and it is thought of as an ensemble of meso-regions with different activation energies for separation of strands from temporary nodes. The elastoplastic behavior is modelled as sliding of junctions in meso-domains with respect to their reference positions driven by macro-deformation. The viscoelastic response is attributed to detachment of active strands from temporary junctions and attachment of dangling chains to the network. Constitutive equations for isothermal deformations with small strains are derived by using the laws of thermodynamics. Adjustable parameters in the stress–strain relations are found by fitting the experimental data.     

Thermally Induced Viscous Flow of Borophosphosilicate-Glass Thin Films on Stepped Surfaces,Part 2: Generalized Parameters for ULSI Glass Flow Characterization

New flow parameters termed flow effectiveness andthermal budgetare used for the characterization of the thermal flow of borophosphosilicate glass serving as a premetal dielectric in ULSI circuits. Their practical value is discussed. It is concluded that the approach proposed reduces the cost of measurement, facilitates the interpretation of measured data, works for both furnace and rapid thermal annealing, is applicable to ULSI gap filling as well as glass planarization, and enables one to optimize the annealing temperature for thin films of low-fusible multicomponent glasses.     

Controlled Elemental Depth Profile in Sol–Gel-Derived PZT Films

Elemental depth profiles of PZT films prepared by two sol–gel formulations, differing in the zirconium precursor stabilization, were investigated by SIMS analysis. Early decomposition of the zirconium precursor yielded opposing gradients of zirconium and titanium, while simultaneous late decomposition of zirconium and titanium precursors provided profile uniformity. The gradients formed during initial crystallization are irreversible. Both types of films showed excellent hysteresis; however, uniform films exhibited a much higher dielectric constant, indicating superior piezoelectric properties. Non-uniform films displayed a complex CV pattern, consistent with an inhomogeneous structure. Finally, thermal decomposition of the individual metal precursors is crucial for controlling film uniformity.     

Artificial abortions in Bulgaria and their prevention

Authors go into one extremely important problem for the family, woman, natality and family planning in Bulgaria. Scarcely during the last years it can be observed a slight reduction of the frequency of induced abortions. The average age of women having an abortion is high--about 30, which shows, that induced abortion is still a method of regulation fertility in intergenetic interval. The rate of those who have induced abortion under the age of 19 in Bulgaria is 7.8 to 53.3%, in Czechoslovakia, 6.7%, in DDR--50.0%, Greece--68%, Hungary--8.9%, Sweden--15.8%. The rate of done again induced abortion is higher, that is a result of bad preventing activities during the first abortion. Similar is the tendency of growing number of unmarried women having an induced abortion, as it is in the other countries: from 16.4% in 1980 to 21.7% in 1987. Bulgaria is on the third place in Europe according to the absolute number of dead cases after abortion (maternity death, after Rumania and USSR). It can be mentioned that in Bulgaria women do not use the most modern and safest devices, medicines for interruption of pregnancy.     

Improved activity and thermostability of Candida antarctica lipase B by DNA family shuffling

DNA family shuffling was used to create chimeric lipase B proteins with improved activity toward the hydrolysis of diethyl 3-(3',4'-dichlorophenyl)glutarate (DDG). Three homologous lipases from Candida antarctica ATCC 32657, Hyphozyma sp. CBS 648.91 and Crytococcus tsukubaensis ATCC 24555 were cloned and shuffled to generate a diverse gene library. A high-throughput screening assay was developed and used successfully to identify chimeric lipase B proteins having a 20-fold higher activity toward DDG than lipase B from C.antarctica ATCC 32657 and a 13-fold higher activity than the most active parent derived from C.tsukubaensis ATCC 24555. In addition, the stability characteristics of several highly active chimeric proteins were also improved as a result of family shuffling. For example, the half-life at 45 degrees C and melting point (T(m)) of one chimera exceeded those of lipase B from C.antarctica ATCC 32657 by 11-fold and 6.4 degrees C, respectively, which closely approached the stability characteristics of the most thermostable parent derived from Hyphozyma sp. CBS 648.91.     

Reduction of NOx by H2 on WOx-Promoted Pt/Al2O3/SiO2 Catalysts Under O2-Rich Conditions

This work addresses the reduction of NO_x by H₂ under O₂-rich conditions using Al₂O₃/SiO₂-supported Pt catalysts with different loads of WO_x promotor. The samples were thoroughly characterised by N₂ physisorption, temperature-programmed desorption of CO, scanning electron microscopy, X-ray diffraction, laser raman spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance infrared fourier transform spectroscopy with probe molecule CO. The catalytic studies of the samples without WO_x showed pronounced NO_x conversion below 200 °C, whereas highest efficiency was related to small Pt particles. The introduction of WO_x provided increasing deNO_x activity as well as N₂ selectivity. This promoting effect was referred to an additional reaction path at the Pt-WO_x/Al₂O₃/SiO₂ interface, whereas an electronic activation of Pt by strong metal support interaction was excluded.

Graphic Abstract

     

Life under ice in the perennial ice‐covered Lake Glubokoe in Summer (East Antarctica)

This study focuses on hydrological and biotic variables in Lake Glubokoe, which is located in Thala Hills of Enderby Land (East Antarctica). Water and sediment samples and physical measurements were collected once a week in the austral summer (19 December 2010 – 6 February 2011). This lake exhibits perennial ice cover that reached a thickness of 2.5–2.7 m during the study period. A very low concentration of planktonic chlorophyll‐a (0.06–0.45 μg L^?1) was measured in the lake, indicating its ultra‐oligotrophic status. The water was poorly populated by algae and metazoans, especially in upper waters below ice cover to a depth of 2 m. Small planktonic organisms (2–5 μm) were observed throughout the study period, but larger organisms (>8 μm) such as the cyanobacteria Planktolyngbya limnetica occurred only during the warmest period (January). Only few individuals of metazoans (rotifers) were found in planktonic samples. Due to deep light penetration (10–15% of incoming active solar radiation reached the depth of 30 m), thick cyanobacterial mats (30 cm) cover all the bottom surface (grey silts) in the lake. Abundant benthic biota associated with these mats was found (up to 1000 ind. m^?2). Among the benthic metazoans, bdelloid rotifers and tardigrades were the dominating taxa. The results of this study suggest a typical ecological feature of most subglacial lakes in East Antarctica is that metazoans are very poor in the pelagic zone, preferring instead to occupy an area near the lake bottom because of a favourable constant temperature of 4 °C, good level of dissolved oxygen and available food resources as the bacterial detritus.     

Consistent segmentation of 3D models

This paper proposes a method to segment a set of models consistently. The method simultaneously segments models and creates correspondences between segments. First, a graph is constructed whose nodes represent the faces of every mesh, and whose edges connect adjacent faces within a mesh and corresponding faces in different meshes. Second, a consistent segmentation is created by clustering this graph, allowing for outlier segments that are not present in every mesh. The method is demonstrated for several classes of objects and used for two applications: symmetric segmentation and segmentation transfer.