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A modified mixing and casting procedure was used for the preparation of Al-1.2 Si-0.8 Fe–Gr composite (wt.%). Graphite and gray cast iron powders were blended and dispersed in Al-1.2 Si matrix alloy melt and poured in a cast iron mould. Gray cast iron powder worked as carrier for graphite particles. The presence of graphite improves the ultimate tensile strength, tensile and compressive stress but beyond 1 % of graphite all properties deteriorate. However, hardness continuously increases and percentage elongation reduces with graphite. In wear studies, different mechanisms: mild-oxidative, oxidative-metallic and severe-metallic, are operative in the different combinations of sliding velocities and applied loads.

Dry-sliding wear behaviour of bainitic structure (BS) and tempered martensitic structure (TMS) of Ni–Cr–Mo–V steels have been investigated at room temperature, using a pin-on-disc wear testing rig. These two microstructures reveal the rising trend of wear rate with normal applied load and sliding velocities in the initial stages; but once a maxima is attained in wear rate, then wear rate decreases with further increase in applied load or sliding velocity. It is also observed that wear resistance of TMS steel is superior to BS steel, but the difference in wear rate is not significant. The stereo-micrographs of debris generated show the oxidative and metallic modes of wear for both the microstructures. The study of worn surface clearly highlights the oxide formation, smearing of surface and distortion associated with straining and plastic deformation. The micro-ploughing, spalling and subsequent detachment of oxides and metallic surface layers from the worn-out surface of the pin specimen are the dominant mechanisms of the wear under different conditions of applied loads and sliding velocities. The wear rate is very much influenced by the yield strength and hardness of the bainitic and tempered martensitic steels.

Two compositions of aluminium alloys Al-1.2 wt.% Cu-0.9 wt.% Ni-0.7 wt.% Si and Al-1.1 wt.% Cu were chosen to produce conventional bearing alloys with about 6 & 20 wt.% of tin respectively and other two alloys with same basic compositions were produced using lead as dispersoid in same amount instead of tin. The alloys were prepared by impeller mixing and bottom discharge chill casting technique. Their density, microstructure, mechanical properties were evaluated at room temperature. Sliding wear characteristics of these alloys under lubrication were studied in detail. Debris and worn surface analysis was also done. Tin and lead decreased tensile and compression strength of aluminium matrix alloys, percentage elongation was increased in both the cases. Strength properties of aluminium-tin alloys are slightly more than the equivalent experimental aluminium-lead alloys. Wear rate of leaded alloys is lower than the aluminium-tin alloys. Leaded aluminium bearing alloys exhibit superior wear resistance with slightly lower mechanical properties, to that of aluminium-tin alloys.

Costus pictus, belonging to the family Costaceae, is one of the valuable medicinal plants with its anti-diabetic property. Despite ever-increasing demand from the pharmaceutical industry, this species is being less exploited at molecular level. Hence, an effort has been made in the present study to characterize the 15 accessions of C. pictuscollected from different geographical regions of India through random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers. A total of 25 RAPD and 20 ISSR primers were used in the present study. The RAPD analysis generated 343 loci, of which 124 were polymorphic with an average of 4.96 loci per primer. While, ISSR primers produced 177 loci, of which 77 were polymorphic with an average of 3.85 loci per primer. The similarity coefficients ranged from 0.86–0.99, 0.84–0.95 and 0.86–0.96 for RAPD, ISSR and combined RAPD-ISSR, respectively. The UPGMA dendrogram generated using these data showed low level of divergence among the accessions from South and West regions. Further, accession-specific bands were also revealed by RAPD and ISSR markers which might be contributed to specific trait. This investigation was an understanding of genetic variation within the C. pictusaccessions. The present finding indicates that both the marker tools RAPD and ISSR combined or individually can be used in determining the genetic relationship between the accessions. It may be concluded that data of hereditary differences appeared among the C. pictusaccessions could be utilized for their conservation and reproducing programs.

Segmental dynamics are measured in pure polyisobutylene (PIB), pure deuterium-labeled head-to-head poly(propylene) (hhPP), and a blend containing 70% PIB/30% hhPP by mass using ¹³C spin−lattice relaxation, ²H spin−lattice relaxation, and dielectric spectroscopy (DS). The NMR measurements are made between 313 K and 413 K (spin−lattice relaxation measurements are sensitive to motions in the nanosecond range), while the DS measurements (which span the second to microsecond range) are made between 225 K and 325 K. While NMR and DS monitor local dynamics over a wide range of temperature and time, NMR has the additional advantage of being able to determine the local motion of each component in the blend through isotopic labeling. The spin−lattice relaxation data are interpreted using a modified Kohlrausch−Williams−Watts (KWW) correlation function with a Vogel−Fulcher−Tammann−Hesse (VFTH) temperature dependence of relaxation time, giving temperature-dependent segmental correlation times from NMR in the short time (high temperature) range that are compared to dielectric segmental correlation times at lower temperatures. Because of the small PIB dipole moment, DS on hhPP/PIB blends is dominated by the dynamics of hhPP. NMR measurements show very little shift in the component dynamics upon blending, but the shift becomes larger at lower temperatures. One factor in the variation of the separation between the dynamics of the two polymers with temperature is the unusual VFTH parameters for pure PIB, which signify its small fragility. The Lodge−McLeish model is unsuccessful in predicting the changes in component dynamics upon blending for hhPP, while it describes the temperature-dependent dynamics of PIB over the limited temperature range studied by NMR.

Predictions of the linear viscoelastic complex shear modulus in model miscible blends of polyisoprene (PI) and poly(vinyl ethylene) (PVE) are compared with literature data. Using ideas of chain connectivity, the effective monomer relaxation times of PI and PVE in the blend were calculated using PI self-composition φPI,s = 0.40 and PVE self-composition φPVE,s = 0.80, determined in our earlier analysis of segmental dynamics in PI/PVE blends. The reptation times of PI and PVE were then determined from their effective monomer relaxation times in the blend, assuming a common tube for both components (thus specifying the blend plateau modulus). The component reptation times and effective terminal dispersion widths from fits to the pure component polymers were input along with the blend plateau modulus to the des Cloizeaux “double reptation” model of polymer dynamics to make predictions of blend linear viscoelasticity with no adjustable parameters. The calculated frequency dependence of the complex modulus of PI/PVE blends was found to be in near quantitative agreement with experimental data, including the experimentally observed thermorheological complexity.

We have performed experiments on model emulsions of polyisobutylene (PIB) and poly(dimethylsiloxane) (PDMS) to quantify the effect of confinement on deformation and stability under flow of droplets and strings (threads). It is known from earlier work from our group that, under confinement, droplets in concentrated emulsions can coalesce with each other and elongate in the flow direction to form stable strings. In the present context, strings can be simply viewed as droplets having a large aspect ratio whereas, in the bulk case, there are two known states of a droplet (stable and unstable), as determined by the droplet Capillary number (Ca). We find that confinement effects induce three additional states:  squashed drops, stable strings, and unstable strings. For strings, deformation under confinement is a very strong function of Ca:  the aspect ratio of a string scales nearly as Ca³. This scaling relationship is unique to confinement, and it sets strings apart from transiently stretched droplets in the bulk. Confinement not only promotes deformation but also allows larger stable droplets to exist under flow than what is predicted by the critical Ca. Strings are stabilized by a combination of the shear flow field and wall effects arising from confinement.

We investigate the transfer of the Cohen–Macaulay property from a commutative ring to a subring of invariants under the action of a finite group. Our point of view is ring theoretic and not a priori tailored to a particular type of group action. As an illustration, we discuss the special case of multiplicative actions, that is, actions on group algebras k[Zn] via an action on Zn.

We report results on the linear viscoelasticity (oscillatory shear in the temperature range Tg (glass-transition temperature) ≤ T ≤ Tg + 90 K) of miscible blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) and segmental relaxations, measured by dielectric spectroscopy. The Flory−Huggins interaction parameter of this blend is weakly negative, and the glass transitions of the pure components are quite disparate (ΔTg = 125 K). PS/PVME blends have been found to be consistently thermorheologically complex at both the segmental and terminal levels:  the empirical time−temperature superposition (tTS) principle applies to neither their oscillatory shear response nor their dielectric response. Using the tube model, we quantitatively compare dielectric and mechanical results. At low temperatures, the effective time scale for motion of a Kuhn segment (the shortest Rouse mode) is near the long-time end of the distribution of segmental relaxation times of PVME, in both the pure and blended states. The slowest relaxing segments thus control the longer-time relaxation processes of the chains. Miscible blends with weak interactions and large ΔTg have concentration fluctuations that broaden the distribution of segmental relaxation times. This distribution narrows as the temperature is raised in the blend, leading to the failure of tTS for terminal dynamics.

The linear viscoelasticity of miscible blends of a random copolymer of 80% styrene and 20% acrylonitrile and poly(methyl methacrylate) has been investigated using oscillatory shear. The Flory−Huggins interaction parameter of this blend is weakly negative. The glass transitions of the pure components are very close (ΔTg = 20 K). The blends are thermorheologically simple, in that the oscillatory shear response at different temperatures can be superimposed with the empirical time−temperature superposition principle with a precision similar to that for the pure component polymers. These results are anticipated by a theory of concentration-fluctuation-induced dynamic heterogeneities in miscible polymer blends. While sizable concentration fluctuations are present in this blend system, they do not complicate the dynamics, because all compositions have similar local dynamics. We suggest a simple phase diagram based on this model, that should be useful for deciding whether time−temperature superposition will be valid for a given blend with weak energetic interactions. Regions of thermorheological complexity are separated from regions of thermorheological simplicity on a plot of the range of blend free volume studied against the glass transition contrast of the components (ΔTg).

Abstract: LetA andB be two reduced commutative rings with finitely many minimal prime ideals. If the polynomial algebrasA[X 1 …X n ]=B[Y 1 …Y n ] whereX i ,Y iF are variables overA andB respectively, then there exists an injective ring homomorphism ϕ:A→B such thatB is finitely generated over ϕ(A).

The antifriction and antiseizure characteristics of a number of aluminium bearing alloys varying in lead content from 10 to 50 wt-% have been studied under different lubrication conditions using a bearing test machine designed for the investigation. With continuous oil lubrication, bearings of all the leaded alloys are able to run without seizure up to the regimes of boundary and mixed lubrication, whereas the base alloys seize under conditions in which the leaded alloys are under hydrodynamic lubrication. The load at which bearing seizure takes place is primarily determined by the frictional state of the bearing. In general, the addition of lead to aluminium alloys is found to reduce interface friction and to improve their ability to resist seizure only for concentrations in the range 10–25 wt-%. Lead–containing aluminium alloys also show a capacity to absorb and to store a lubricating oil and to use it to diminish friction in the event of failure of the oil supply.MST/121

Groundwater samples from Moradabad city were analyzed for chemical parameters. For present study 58 water samples were collected from different localities on the basis of various land use patterns. The higher values of most of the parameters were found in the area of old settlement, while lower values observed in new settlements. This shows clear impact of land use on groundwater. Water quality data collected from different localities are used in conjunction with multivariate statistical technique to identify key variables. The first four components were chosen for interpretation of the data, which accounts for 77.38% of the total variance in the data set. The maximum number of variables, i.e. Cl, Na, TH, TDS, EC and salinity were characterized by first component, while second component is characterized by DO and Mg. The third and fourth components were characterized by Ca, SiO2 HCO3 and K respectively. This shows that hydrochemical constituents of the groundwater are mainly controlled by TDS and EC. For cluster analysis single linkage method was used. The findings of the cluster analysis are presented in the form of dendrogram of the sampling stations (cases) as well as hydrochemical variables, which produced four major groupings, suggests that groundwater monitoring can be consolidated.