To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
denote the nth partial sum of the Fourier Legendre series of a function ƒ(x). The references available to us, except (5), prove only that Sn(ƒ, x) converges uniformly to ƒ(x) in [— 1, 1] if ƒ(x) has a continuous second derivative on [—1, 1]. Very recently Suetin (5) has shown by employing a theorem of A. F. Timan (7) (which is a stronger form of Jackson's theorem) that Sn(ƒ, x) converges uniformly to ƒ(x) ƒ(x) belongs to a Lipschitz class of order greater than 1/2 in [—1, 1]. More generally he has proved the following theorem.
Measurements of local plasma parameters in dusty plasma are crucial for understanding
the physics issues related to such systems. The Langmuir probe, a small electrode
immersed in the plasma, provides such measurements. However, designing of a Langmuir
probe system in a dusty plasma environment demands special consideration. First, the
probe has to be miniaturized enough so that its perturbation on the ambient dust
structure is minimal. At the same time, the probe dimensions must be such that a
well-defined theory exists for interpretation of its characteristics. The associated
instrumentation must also support the measurement of current collected by the probe
with high signal to noise ratio. The most important consideration, of course, comes
from the fact that the probes are prone to dust contamination, as the dust particles
tend to stick to the probe surface and alter the current collecting area in
unpredictable ways. This article describes the design and operation of a Langmuir
probe system that resolves these challenging issues in dusty plasma. In doing so,
first, different theories that are used to interpret the probe characteristics in
collisionless as well as in collisional regimes are discussed, with special emphasis
on application. The critical issues associated with the current–voltage
characteristics of Langmuir probe obtained in different operating regimes are
discussed. Then, an algorithm for processing these characteristics efficiently in
presence of ion-neutral collisions in the probe sheath is presented.
Various promising applications such as acoustic cloaking, sub-wavelength imaging, acoustic wave manipulation, transmission or reflection control etc. are feasible because of the ability of manipulating sounds and vibrations using artificially engineered “Acoustics meta-materials”. Recent works on space-coiling acoustic metamaterials show their extreme constitutive parameters like large refractive index, double negativity and zero mass density. Three dimensional structures have a wide application in sub-wavelength broadband acoustic wave suppression due to huge attenuation. Here we report the study of propagated and transmitted wave through 3D acoustic metamaterials structure using finite element method. Our simulations on 3D structure show a huge absorption/damping over few hundreds kilohertz frequency range.
In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n ⩽ 1%, Luniform ~ 120 cm at argon filling pressure of ~10−4 mbar and axial magnetic field of B = 1090 G.
We report on the effects of the frequency dispersion in light sensitive materials used in photoimpedance wireless sensors. An example of such a sensor is a gated semiconductor connecting two or more fixed capacitances. The impedance of the device under illumination is changed by the change in the photoresistance of the semiconductor layer and the change in the gate-semiconductor capacitance. We report on the design and simulation of the frequency dispersion of the impedance of this device in silicon and discuss the physics and device performance. We also evaluate the dynamic range and sensitivity of the wireless photoimpedance sensors and show their advantages for wireless sensing applications compared to more conventional light sensors.
Maximization of non-coking coal in coal blend is eloquent interest among researchers in
coke making throughout the world. To maximize the non-coking coals in coal blend with the
scarce and expensive coking coals is an essential practice in the iron and steel industry.
The fundamental aspect of the coal blending theory of low value coals to produce good
quality of metallurgical coke in non-recovery coke making process was investigated in this
study by using the composite coking potential technique. The implementation of the
technique has yielded use of up to 25% pulverized coal injection, 20% raw petroleum coke
as a component of coal blend. Results show that the coal blend having composite coking
potential value of
⩾4.8 is desired to achieve the targeted coke strength
after reaction of
The most abundant biopolymer, cellulose, occurs as a supra-molecular organisation of poly-glucan chains. The cellulose produced by bacteria has been characterised by various techniques including SEM, AFM, PXRD and SAXS, to elucidate the multi-level organisation. A model has been developed to relate this organisation to the cellulose biosynthetic machinery in bacteria.
A new technology to size nanoparticles in liquids is presented. The technique is based on aerosol technology coupled to a nanoparticle nebulizer. This allows number concentration measurements in the size range ca. 5 to 500 nm with high peak resolution.
Here we show that microtubular bundles bend flexibly under a hydrodynamic flow to form teardrop patterns. In a highly concentrated microtubular solution, patterns of same-sized teardrops form according to the maximum critical curvature, which is determined by the specific rigidity of the microtubules. Our understanding is that these micropatterns grow when microtubular bundles with hydrodynamic flow energy are converted into stable teardrop patterns as a higher structure. This conversion is generated by the combined effect of multiple kinds of energy, including heat and hydrodynamic flow, as well as life systems. These self-generating patterns in a spatio-temporal stream are reminiscent of what the artist Edward Munch called a scream of nature. We also envision that microtubular pattering with hierarchical structure will broaden the potential application of these geometrical structures and guide biomimetic material engineering towards areas such as integrated energy conversion, soft material patterning, and living signal transduction.
Nanoporous gold is a material with many possible applications e.g. in catalysts, sensors and electrode materials. We studied the functionalization of the nanoporous gold with TiO2 particles. Aiming at the low temperature oxidation of CO, the nanoporous gold can be coated with TiO2 in order to enhance catalytic activity. Structure and distribution of the TiO2 on the gold surface are important structural features, which were investigated by transmission electron microscopy. The preparation of the porous gold was tested with focused ion beam - preparation, conventional Ar+ ion beam preparation of nanoporous gold embedded in epoxy and ultramicrotome preparation of nanoporous gold embedded in epoxy. Considering the beam damage on the structure and the contamination of the surface, ultramicrotome preparation turned out to be the best solution. It was shown, that the gold ligaments are abundantly covered by approximately 5 nm TiO2 particles. The determination of the largest lattice fringe distance in high resolution mode revealed that the crystalline nanoparticles consist of the anatase phase. The spatial Ti distribution was measured with energy filtered transmission electron microscopy. Scanning transmission electron microscopy tomography was applied to reconstruct the three-dimensional structure of the gold coated with TiO2 particles.
Environmental concerns emphasize the urgent need for the development of biodegradable polymers. In this study, poly (lactic acid) (PLA), being a biodegradable polymer matrix, was used together with poly (ethylene glycol) (PEG) to enhance its low toughness. In addition, the deterioration in mechanical properties owing to plasticization was tried to be overcome by addition of nanofiller. As nanofiller, two nanotubular halloysite (HNT) types, one local (ESAN HNT) and an imported one (Nanoclay HNT) supplied by Aldrich, were used. As the first step, characterization and purification of local HNT was performed. In the second step, plasticized and unplasticized PLA matrix composites containing 3, 5 and 10 wt % were prepared and their morphological and mechanical analysis were performed. Upon the addition of both ESAN HNT (local HNT) and Nanoclay HNT (imported HNT) no improvement was observed in the basal spacing of the clay layers owing to poor interaction between the matrix and the surface of the nanotubes which should be modified for better dispersion.
The body and elytra of the diamond weevil, Entimus imperialis, is studded with numerous brightly colored scales. The scales exhibit brilliant reflections because they contain unusually large diamond-type photonic crystals. The scales are concentrated in pits on the otherwise black elytra. This framing enhances the color contrast when the weevil is observed from nearby. From a distance the diamond weevil looks green, alike green foliage. Another weevil, Eupholus cuvieri, has also scales with green reflective photonic crystals, but here the scales are arranged closely apposed on the planar elytra. Both weevils use photonic crystals for camouflage, but the display methods are different.
Pigeonpea is an important legume crop of the semi-arid tropics. In India, pigeonpea is mostly grown in areas prone to waterlogging, resulting in major production losses. It is imperative to identify genotypes that show tolerance at critical crop growth stages to prevent these losses. A selection of 272 diverse pigeonpea accessions was evaluated for seed submergence tolerance for different durations (0, 120, 144, 168 and 192 h) under in vitro conditions in the laboratory. All genotypes exhibited high (0·79–0·98) survival rates for up to 120 h of submergence. After 192 h of submergence, the hybrids as a group exhibited significantly higher survival rates (0·79) than the germplasm (0·71), elite breeding lines (0·68) and commercial varieties (0·58). Ninety-six genotypes representing the phenotypic variation observed during laboratory screening were further evaluated for waterlogging tolerance at the early seedling stage using pots, and survival rates were recorded for 8 days after completion of the stress treatment. Forty-nine of these 96 genotypes, representing the phenotypic variation for waterlogging tolerance, were chosen in order to evaluate their performance under natural field conditions. The following cultivated varieties and hybrids were identified as tolerant after three levels of testing (in vitro, in pots and in the field): ICPH 2431, ICPH 2740, ICPH 2671, ICPH 4187, MAL 9, LRG 30, Maruti, ICPL 20128, ICPL 332, ICPL 20237, ICPL 20238, Asha and MAL 15. These materials can be used as sources of waterlogging tolerance in breeding programmes.
Phosphoenolpyruvate carboxykinase (PEPCK, EC 22.214.171.124) is an essential regulatory enzyme of glycolysis in helminths in contrast to its role in gluconeogenesis in their host. Previously we have reported that phytochemicals from Flemingia vestita (Family: Fabaceae), genistein in particular, have vermifugal action and are known to affect carbohydrate metabolism in the cestode, Raillietina echinobothrida. In order to determine the functional differences of PEPCK from the parasite and its avian host (Gallus domesticus), we purified the parasite enzyme apparently to homogeneity, and characterized it. The native PEPCK is a monomer with a subunit molecular weight of 65 kDa. The purified enzyme displayed standard Michaelis-Menten kinetics with Km value of 42·52 μM for its substrate PEP. The Ki for the competitive inhibitors GTP, GMP, ITP and IMP for the carboxylation reaction were determined and discussed. In order to identify putative modulators from plant sources, phytochemicals from F. vestita and Stephania glabra were tested on the purified PEPCK, which resulted in alteration of its activity. From our results, we hypothesize that PEPCK may be a potential target site for anthelmintic action.
Abstract We compare for multiblock copolymers the results of mean field calculations with those from Monte Carlo simulations based on the bond uctuation method and experimental results from scattering data. The application of Leibler's  theory for copolymers and the results of Monte Carlo simulations indicate that the microphase separation transition occurs at larger xN as the number of blocks is increased beyond two (i.e., beyond diblock), and that the characteristic length scale of the emerging morphology decreases as the number of blocks increases. The latter is in qualitative agreement with published experimental results  for model multiblock poly(styrene-isoprene) systems and recent results  for a segmented poly(ester-urethane).
Motivated by recent experiments on filled polymer thin films, we study the effect of the presence of filler particles on phase separating mixtures. Using a generalized Cahn-Hillard-cook model, we show that the preferential wetting of one phase on the filler surface generates transient composition waves in the phase separating blends. The interference of the composition waves from different particles can stabilize the transient patterns, leading to desirable control of the morphology.
This work is aimed at understanding the nature of the interactions between
metal interconnects and nanoporous dielectrics in integrated circuits.
Electrical testing of MIS capacitors is used to assess Cu diffusion and
charge injection in the dielectric in the presence of an electric field. We
have found that surface modification of nanoporous silica reveals the
importance of chemically bound or adsorbed water species in the dielectric
and how they trigger metal diffusion. We propose that a combination of
moisture-related species in the dielectric and interfacial oxygen oxidize
Cu. The copper oxide acts as a source for Cu ions available for diffusion. A
quantitative analysis of Cu drift in nanoporous dielectrics that shows the
importance of surface chemistry is presented and the mechanism of metal
diffusion and charge injection in nanoporous dielectrics is discussed.
Polymerization occurring during fluorocarbon plasma treatment as a potential
method for pore sealing was investigated. CHF3 was used as a
reactant gas to expedite the rate of polymerization due to the presence of
hydrogen and the low C/F ratio. The reactor pressure was varied from 30mTorr
to 90mTorr to change the number of neutrals that act as the polymerizing
species. The films were exposed to the plasma for times of 1min, 3min, and 5
min to observe the penetration depth of neutrals and the thickness of
modified layer as a function of time. Dielectric constants were measured
before and after plasma treatment. The film morphology was investigated by
scanning electron microscopy before and after plasma treatment and a
featureless surface morphology was observed at 90mTorr on a 56% porosity
film. After plasma treatment, the average pore neck size decreases which may
help reduce metal precursor penetration during metallization.
Two particularly important reliability issues facing the integration of low-
κ dielectric films are the fracture energy of the barrier-dielectric
interface and the barrier layer integrity during processing. We have noticed
that the compressive stresses in the barrier layers on low- κ dielectrics
lead to spontaneous delamination and formation of telephone-cord like
morphologies. These morphologies allow the measurement of fracture energy
and are advantageous over artificially contrived features to yield realistic
debonding parameters. The fracture energy of common barrier films, TaN and
Ta, was determined using this method for varying porosity nanoporous silica
and MSQ. Detailed characterization of the telephone cord morphology using a
combination of Optical Microscopy, SEM and Profilometry was done. The
fracture energy for Ta on different low-κ dielectrics was evaluated using a
1-D model for straight buckles. The kinetic coefficient of buckling was also