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In (1) R. G. Douglas says: “For a finite abelian group there exists a unique invariant mean which must be inversion invariant. For an infinite torsion abelian group it is not clear what the situation is.” It is not hard to see that if every element of an abelian group G is of order 2, then every invariant mean on G is also inversion invariant (see 1, remark 4). In this note we prove the following theorem (Theorem 1 below): An abelian torsion group G has an invariant mean which is not inverse invariant if, and only if, 2G is infinite. This result, together with the theorems of Douglas, answers completely the question of the existence (on an arbitrary abelian group) of invariant means which are not inverse invariant.
Cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a serious pest of several crops throughout the world, representing millions of United States of America dollars worth of damage. This pest can adapt to various cropping systems in a wide geographical range and has high migratory potential. It features high fecundity and can develop resistance to almost all insecticides used for its management. Several investigations to develop microsatellite markers for H. armigera have not been successful because of the paucity of microsatellites in the lepidopteran genome. As well, collections of H. armigera from cotton fields of southern and western India were not yet studied for molecular genetic diversity. The current study aimed to screen publicly available expressed sequence tag resources for simple sequence repeats and assess their potential as DNA markers for assessment of gene flow between collections of southern and western India. We identified 30 polymorphic microsatellites for potential use in diversity analysis of H. armigera collections. Genetic diversity analysis revealed that the collections were widely diverse with population differentiation index (Fst) of 0.17. Furthermore, gene flow analysis revealed a mean frequency of private alleles of 11% within the collections. The microsatellite resources we developed could be widely used for molecular diversity or population genetic research involving this important pest of cotton and food crops.
Hippocampal shrinkage is commonly reported in schizophrenia, but its role in the illness is still poorly understood. In particular, it is unclear how clinical and psychosocial variables relate to hippocampal volumes.
To investigate neuroanatomic differences in the hippocampus using three-dimensional (3D) computational image analysis.
We used high-resolution magnetic resonance imaging and surface-based modelling to map the 3D profile of hippocampal differences in adults with schizophrenia (n=67) and a healthy control group (n = 72). Manual tracings were used to create 3D parametric mesh models of the hippocampus. Regression models were used to relate diagnostic measures to maps of radial distance, and colour-coded maps were generated to show the profile of associations.
There was no detectable difference between the schizophrenia and control groups in hippocampal radial distance. In the schizophrenia group, however, bilateral shape deflation was associated with greater illness severity (length of illness, positive and negative symptoms) and with poorer social functioning (educational level, quality of life and health status), which survived Bonferroni correction.
Illness severity and poor social functioning may be associated with hippocampal deflation in schizophrenia. As a structural sign of poor outcome, imaging measures might help to identify a subgroup of patients who may need specific treatment to resist hippocampal shrinkage, such as cognitive rehabilitation or physical exercise.
Conventionally, mean grain size is considered the most critical microstructural parameter in determining the mechanical behavior of pure metals. By systematically controlling the distribution of grain orientations in aluminum films, we show that microstructural heterogeneity alone induces large variation in the mechanical behavior of nanocrystalline metal films. Aluminum films with relatively homogeneous microstructure (all grains with identical out-of-plane orientation) show substantially less early Bauschinger effect compared to films with heterogeneous microstructure, irrespective of film thickness or grain size. On the other hand, the films with homogeneous microstructure show relatively higher yield stresses. A direct correspondence is found between the nonuniformity of plastic deformation and early Bauschinger effect, which confirms the critical role of microstructural heterogeneity.
The film properties of two PECVD deposited dielectric copper barrier films
have been optimized to improve BEOL device reliability in terms of
electromigration. Two critical aspects that affect electromigration are the
dielectric barrier film hermeticity and adhesion to copper. We use a method
to quantify the barrier film hermeticity and have optimized the hermeticity
of the BLOκ™ low-κ dielectric barrier film to be similar to that of silicon
nitride. By using FT-IR we find that the film porosity has a much stronger
effect than the film stoichiometry on hermeticity. In addition, the
interfaces between Damascene Nitride™ with copper, as well as BLOκ with
copper have been engineered to improve the interfacial adhesion energy to
>10 J/m2 for both Damascene Nitride and BLOκ.
Supercritical fluids (SF) have been used in a wide variety of applications:
in industrial processes, analytical, waste detoxification, etc. Recently,
its usefulness extends to the semiconductor industry. Researches have shown
that supercritical CO2 (SCCO2) can be used to remove
photoresists and significantly reduce the amount of waste from solvents in
comparison to conventional stripping techniques. SF will also find its
usefulness in cleaning high aspect ratio vias and deep trenches as
semiconductor features shrink to submicron levels. We will report here the
use of supercritical CO2 treatments in extraction of porogens
from a nanohybrid film fabricated via templated-porogen approach. Its use as
a medium to repair the damage in porous films from plasma ashing will also
be presented. The ability to tune the solvation and diffusion power of
SCCO2 and to swell the film matrix make it a good medium for
silylation to restore hydrophobicity and functionalize the film.
Monolithic wafer-level three-dimensional (3D) ICs based upon bonding of processed wafers and die-to-wafer 3D ICs based upon bonding die to a host wafer require additional planarization considerations compared to conventional planar ICs and wafer-scale packaging. Various planarization issues are described, focusing on the more stringent technology requirements of monolithic wafer-level 3D ICs. The specific 3D IC technology approach considered here consists of wafer bonding with dielectric adhesives, a three-step thinning process of grinding, polishing and etching, and an inter-wafer interconnect process using copper damascene patterning. The use of a bonding adhesive to relax pre-bonding wafer planarization requirements is a key to process compatibility with standard IC processes. Minimizing edge chipping during wafer thinning requires understanding of the relationships between wafer bonding, thinning and pre-bonding IC processes. The advantage of silicon-on-insulator technology in alleviating planarization issues with wafer thinning for 3D ICs is described.
We have synthesized nanoporous carbon membranes that have monodisperse pores of 4–5 Å. These membranes have excellent size and shape selectivity that makes them an ideal candidate for use as separators in fuel cells. The selectivity of these membranes to gases such as N2, O2 and water gas [carbon monoxide and hydrogen] were measured using a permeation testing unit. These membranes were then tested as separators in fuel cells.
Nanoporous carbon materials with high surface area (1500 – 2000 m2/g) and narrow pore size distribution ranging from 1 – 3 nm were synthesized using polyfurfuryl alcohol/polyethylene glycol diacid and coal tar pitch/polymer blends. Electrical double layer capacitance of synthesized carbon was measured using cyclic voltammetry. There is a strong correlation between the surface area of the carbon and the specific capacitance. Carbon that had surface area smaller than 1000 m2/g had specific capacitance less than 50 F/g while the carbons having surface area from 1000 – 1500 m2/g showed specific capacitances in the order of 200 -250 F/g. It was shown that the mesoporosity and macroporosity in the parent carbon are critical for both activation and as well as the specific capacitance of the material. The use of these carbons in EDLCs was also demonstrated by fabricating a two-electrode ultracapacitor.
The electronic structure and high pressure structural phase transition in thorium antimonide have been investigated using the tight binding LMTO method. We have calculated the total energies by reducing the cell volume for NaCl as well as CsCl structures using TBLMTO method. The total energy calculations reveal that ThSb undergoes a structural transition from NaCl to CsCl structure at 78 kbar. The calculated value of equilibrium cell volume and the cell volume at which phase transition occurs are found to have a good agreement with the experimental results.
Platinum supported on nanoporous carbon (NPC) is promising candidate for using as electrodes in proton exchange membrane fuel cells. Performance of the anode of a fuel cell is markedly influenced by the efficiency of the splitting of hydrogen atoms by platinum and the transference of the produced protons to the carbon support (spillover process). Consequently a better understanding of these elemental processes could prompt the improvement of the materials used. With this aim, a series of Pt/NPC samples varying the metallic content were studied by electron spin resonance (ESR) under controlled gas environment. This spectroscopic tool is especially suitable for the investigation of processes that involve transference of electrons. In the present case, all materials studied, including bare carbon, showed a very narrow signal (Hpp=1.5–3 gauss) at g=2.0028±0.0002 after activation in vacuum at 500–C. In the case of the pure carbon and for the samples with lower platinum content (lower than 0.2 wt%) signals are significantly asymmetric, and their intensity is scarcely affected by the introduction of hydrogen up to 500°C. In contrast the spin concentration experiences a significant increment when the samples with platinum loading comes in contact with hydrogen at temperatures in the 300–500°C range. Although the centres originating these signals are located in the carbon matrix, the present results emphasize the importance of platinum for hydrogen activation and electron transference.
The present work is aimed at developing uniform nanoporous carbon membranes on porous stainless steel supports. Thin layers of polyfurfuryl alcohol are applied on the stainless steel supports using spin coating method. Nanoporous carbon is obtained by pyrolyzing polyfurfuryl alcohol films under inert atmosphere. Uniform nanoporous carbon membranes were obtained by repeated spin coating and pyrolysis of polyfurfuryl alcohol on the stainless steel supports. The morphology of the membranes was examined using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). It was shown that there is direct correlation between the morphology and the selectivity of the membranes. SEM and AFM show the presence of globular domains during the formation of carbon membranes. The selectivity increased with the decrease in the size of the globules. It was also shown that the annealing of the membrane affected both the morphology and the selectivity of the membrane.
A nanocomposite carbon composed with single wall carbon nanotube (SWNT) and nanoporous carbon (NPC) was prepared by grafting a carbonizable polymer, poly(furfuryl alcohol) (PFA) to a SWNT. The SWNT was first functionalized with arylsulfonic acid groups on sidewall (SA-SWNT) and then converted to PFA-functionalized SWNT (PFA-SWNT) by in situ polymerization of furfuryl alcohol (FA). SWNT/NPC nanocomposite carbon was generated by heating PFA-SWNT in argon at 600°C. A continuous phase was formed between SWNT and NPC. The deformation of the nanocomposite carbon at high temperature was studied by heating it at temperatures from 1200 to 2000 °C and characterized with HRTEM and Raman spectra. It was found that NPC tended to graphitize along the axis of neighboring nanotubes at temperature higher than 1400°C. Complete graphitization of NPC and SWNTs was obtained at 2000 °C, when the NPC transformed to graphitic nanoribbon (GNR) and SWNT or DWNT collapsed within the confines of the GNR. Nanocomposite polymer and carbon fibers were prepared by dispersing small amount of SA-SWNT in FA, followed with polymerization, thermosetting and pyrolysis. The composite polymer fibers' Young's modulus was lower than the pure PFA fibers prepared at the same conditions. However, after heated in argon at 300 °C, 400 °C, 500 °C and 600 °C respectively, the Young's modulus of the nanocomposite carbon fibers turned to be higher than the fibers derived from pure PFA and the enhancement by SWNT increase with increasing temperature. For the nanocomposite carbon fibers treated at 600 °C, the fibers had ∼20% increase of Young's modulus over the fibers from pure PFA with only 0.1wt% of SA-SWNT in FA.
Two first-step copper damascene slurries and one commercial second-step slurry are characterized in terms of their intrinsic properties and CMP performance. A prototype first-step slurry with high static etch rate (∼150 nm/min) yielded higher dishing in the copper lines (∼200 nm in 100 μm lines) compared to a commercial first-step slurry with negligible static etch rate. In both the cases, dishing in copper lines is observed to be a strong function of line width and radial position on the wafer. High static etch rate of the prototype slurry is believed to be responsible for the high dishing. Non-selective second-step polishing removes the liner layer while maintaining planarity.
A short term survey to quantify the number of marine mammals incidentally caught, and interviews to gain perceptions of local fishers towards issues of by-catch, were conducted. A total of 44 cetaceans was recorded as incidental catches at Chennai, Kakinada and Mangalore fishing harbours during 80 days of observation. Six species of dolphins and one species of porpoise were recorded. The spinner dolphin Stenella longirostris was the most frequently caught (38.6%), followed by the finless porpoise Neophocaena phocaenoides (31.8%). Gill-nets and purse seines operated from motorized boats accounted for the entire by-catch. It is estimated that 9000–10,000 cetaceans are killed by gill-nets every year along the Indian coast. The intricacies and possibilities of reducing cetacean kills by gill-nets are discussed in this paper.
A locally compact semilattice with open principal filters is a zero-dimensional scattered space. Cardinal invariants of locally compact and compact semilattices with open principal filters are investigated. Structure of topological semilattices on the one-point Alexandroff compactification of an uncountable discrete space and linearly ordered compact semilattices with open principal filters are researched.
Real-valued function spaces CoL
lack almost transitive
norms. If there is a complex-valued CoL
transitive norm then there is also one with transitive norm. We give fairly
topological conditions for the complex-valued CoL
to have transitive norm.
Transverse curvature effects in axi-symmetric flow on a circulai cylinder are discussed and it is deduced that for small δ/a, where δ is the boundary layer thickness and a is the cylinder radius, transverse curvature effects are small, for δ/a = 0(1) the effect is felt mainly in the outer region and for δ/a » 1, both the inner and the outer regions are affected. It is argued that the last case can only be achieved experimentally in the laboratory if the radius Reynolds number Ra= U1a/v is small and the streamwise Reynolds number Rx=U1xlv is large, implying x/a large. New experimental data are presented for this case. The data show that both the mean and turbulent flow field scale on outer variables throughout the layer and, for Ra≥455, exhibit Reynolds number independence. No logarithmic region is found in the mean profiles, a result which is echoed by the absence of a shoulder in the streamwise turbulence profiles which clearly evidence that the flow in the layer is fully turbulent. A flow model is suggested, in physical terms, to explain the very high turbulence levels found close to the cylinder at values of Ra which should, according to stability theory, be bordering on laminar flow.
One often encounters problems that are difficult as they are, but become manageable when translated to a different category. Thus very often, problems on Boolean algebras are answered by first transferring them to problems on Boolean spaces. (See, for example, ). It is with this spirit that we approach in this paper two problems on Boolean algebras. These problems are two decades old, and are considered to be outstanding problems in the field.