Dieterici gas as a Unified Model for Dark Matter and Dark Energy

The dominance of dark energy in the universe has necessitated the introduction of a repulsive gravity source to make q0 negative. The models for dark energy range from a simple lambda-term to quintessence, Chaplygin gas, etc. We look at the possibility of how change of behaviour of missing energy density, from DM to DE, may be determined by the change in the equation of state of a background fluid instead of a form of potential. The question of cosmic acceleration can be discussed within the framework of theories which do not necessarily include scalar fields.Comment: 9 pages, 38 equation

Synthesis and characterization of polyurethane microspheres

A novel particle forming polymerization technique for the preparation of polyurethane microspheres with particle size in the range 0.1-100 micron is described. The method is general, applicable to wide variety of diols and isocyanates and is very simple. The key to successful particle forming polymerization is the use of novel steric stabilizers, such as, a reactive diol containing two primary hydroxyl groups with a long hydrophobic acrylate ester moiety and an amphiphilic block copolymer. The effect of various reactiorr variables on the particle forming polymerization process will be discussed

Crystallisation behaviour of composites of HDPE and MWCNTs: The effect of nanotube dispersion, orientation and polymer deformation

Multi-walled carbon nanotubes (MWCNTs) were readily dispersed and distributed in the high density polyethylene (HDPE) matrix and a very low (<0.3 wt%, 0.17 vol%) rheological percolation threshold obtained. The polymer is seen to coat the MWCNTs, which act as a nucleating agent and induce an oriented nanohybrid shish-kebab (NHSK) crystalline structure, in part an artefact of the injection moulding process. The elastic modulus and yield stress of HDPE increased on addition, but the polymer strain at break increased sharply below percolation before decreasing again above percolation. Addition of MWCNTs, above the percolation threshold, hindered orientation of the polymer chains such that failure occurred before necking during tensile testing, the inclusion of MWCNTs altered the uniaxial deformation behaviour of HDPE. SAXS/WAXS studies on samples post uniaxial drawing revealed that the HDPE and composites of HDPE and MWCNTs developed a highly oriented sheared herringbone lamellar structure. The drawing process also caused surface cavitation and voiding in the composites

Cemented hemi arthroplasty for unstable intertrochanteric fractures in elderly

Background: The incidence of the intertrochanteric fractures is increasing in recent times. It is found that more and more of these fractures are seen in elderly. The treatment of these fractures was historically non surgical. The use of dynamic hip screw and angled blade plate in the surgical management of these fractures is a recent practice. The objective of the study was to analyse the role of cemented hemi-arthroplasty in the treatment of unstable inter trochanteric fractures in elderly.Methods: This study was conducted between June 2014 to June 2016. Results were analysed prospectively. From a total 94 inter trochanteric fractures admitted during this period 20 patients were chosen who fulfilled our inclusion criteria. All the patients were treated in Malla Reddy Institute of Medical Sciences. Primary cemented hemiarthroplasty was done in the entire patient by a senior faculty member. The results were assessed according to Harris hip score.Results: There were 13 females and 7 males in our study. The average age was 69.2 years. There was Evan’s type 1-c 11, 1-d 7 and 1-e 2 in numbers all the patients were followed up for a period of 18 months.Conclusions: In our short study, it is concluded that the primary cemented hemi arthroplasty is a good option in unstable inter trochanteric fractures in elderly

Routing in heterogeneous wireless ad hoc networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.Includes bibliographical references (p. 135-146).Wireless ad hoc networks are used in several applications ranging from infrastructure monitoring to providing Internet connectivity to remote locations. A common assumption about these networks is that the devices that form the network are homogeneous in their capabilities. However in reality, the networks can be heterogeneous in the capabilities of the devices. The main contribution of this thesis is the identification of issues for efficient communication in heterogeneous networks and the proposed solutions to these issues. The first part of the thesis deals with the issues of unambiguous classification of devices and device identification in ad hoc networks. A taxonomical approach is developed, which allows devices with wide range of capabilities to be classified on the basis of their functionality. Once classified, devices are characterized on the basis of different attributes. An IPv6 identification scheme and two routing services based on this scheme that allow object-object communication are developed. The identification scheme is extended to a multi-addressing scheme for wireless ad hoc networks. These two issues and the developed solutions are applicable to a broad range of heterogeneous networks. The second part of the thesis deals with heterogeneous networks consisting of omnidirectional and directional antennas. A new MAC protocol for directional antennas, request-to-pause-directional-MAC (RTP-DMAC) protocol is developed that solves the deafness issue, which is common in networks with directional antennas. Three new routing metrics, which are extensions to the expected number of transmissions (ETX) metric are developed. The first metric, ETX1, reduces the route length by increasing the transmission power. The routing and MAC layers assume the presence of bidirectional links for their proper operation. However networks with omnidirectional and directional antennas have unidirectional links. The other two metrics, unidirectional-ETX (U-ETX) and unidirectional-ETX1 (U-ETX1), increase the transmission power of the directional nodes so that the unidirectional links appear as bidirectional links at the MAC and the routing layers. The performance of these metrics in different scenarios is evaluated.by Sivaram M.S.L. Cheekiralla.Ph.D

The Unique Origin of Colors of Armchair Carbon Nanotubes

The colors of suspended metallic colloidal particles are determined by their size-dependent plasma resonance, while those of semiconducting colloidal particles are determined by their size-dependent band gap. Here, we present a novel case for armchair carbon nanotubes, suspended in aqueous medium, for which the color depends on their size-dependent excitonic resonance, even though the individual particles are metallic. We observe distinct colors of a series of armchair-enriched nanotube suspensions, highlighting the unique coloration mechanism of these one-dimensional metals.Comment: 4 pages, 3 figure

Running coupling in electroweak interactions of leptons from f(R)-gravity with torsion

The f(R)-gravitational theory with torsion is considered for one family of leptons; it is found that the torsion tensor gives rise to interactions having the structure of the weak forces while the intrinsic non-linearity of the f(R) function provides an energy-dependent coupling: in this way, torsional f(R) gravity naturally generates both structure and strength of the electroweak interactions among leptons. This implies that the weak interactions among the lepton fields could be addressed as a geometric effect due to the interactions among spinors induced by the presence of torsion in the most general f(R) gravity. Phenomenological considerations are addressed.Comment: 9 pages. arXiv admin note: text overlap with arXiv:1012.5529 by other author