New results in cosmology

From an observational perspective cosmology is today in excellent shape - advances in instrumentation and data processing have enabled us to study the universe in detail back to when the first galaxies formed, map the fluctuations in the cosmic microwave background which provide a measure of the overall geometry, and reconstruct the thermal history reliably back to at least the primordial nucleosynthesis era. However recent deep studies of the Hubble expansion rate have suggested that the universe is accelerating, driven by some form of `dark' (vacuum) energy. If true, this implies a new energy scale in Nature of order 0.001 eV, well below any known scale of fundamental physics. This has refocussed attention on the notorious cosmological constant problem at the interface of general relativity and quantum field theory. It is possible that the resolution of this situation will require fundamental modifications to our ideas about gravity.Comment: 15 pages (JHEP LaTeX), 12 figures; Plenary talk at EPS-HEP 2001, Budapest, 12-18 July 2001; Revisions: refs updated, typos fixe

Successful Supersymmetric Inflation

The temperature fluctuations in the cosmic microwave background observed by COBE provide strong support for an inflationary phase in the early universe, below the GUT scale. We argue that a singlet field in a hidden sector of an effective supergravity theory yields the required inflationary potential without fine tuning. Reheating occurs to a temperature low enough to avoid the gravitino problem, but high enough to allow subsequent baryogenesis. Two observational consequences are that gravitational waves contribute negligibly to the microwave background anisotropy, and the spectrum of scalar density perturbations is `tilted', improving the fit to large-scale structure in an universe dominated by cold dark matter.Comment: 4 pages, uuencoded PostScript (3 figures incl.), to appear in Proc. International EPS Conf. on High Energy Physics, Brussels, 199

Hybrid Scenario Based Performance Analysis of DSDV and DSR

The area of mobile ad hoc networking has received considerable attention of the research community in recent years. These networks have gained immense popularity primarily due to their infrastructure-less mode of operation which makes them a suitable candidate for deployment in emergency scenarios like relief operation, battlefield etc., where either the pre-existing infrastructure is totally damaged or it is not possible to establish a new infrastructure quickly. However, MANETs are constrained due to the limited transmission range of the mobile nodes which reduces the total coverage area. Sometimes the infrastructure-less ad hoc network may be combined with a fixed network to form a hybrid network which can cover a wider area with the advantage of having less fixed infrastructure. In such a combined network, for transferring data, we need base stations which act as gateways between the wired and wireless domains. Due to the hybrid nature of these networks, routing is considered a challenging task. Several routing protocols have been proposed and tested under various traffic conditions. However, the simulations of such routing protocols usually do not consider the hybrid network scenario. In this work we have carried out a systematic performance study of the two prominent routing protocols: Destination Sequenced Distance Vector Routing (DSDV) and Dynamic Source Routing (DSR) protocols in the hybrid networking environment. We have analyzed the performance differentials on the basis of three metrics - packet delivery fraction, average end-to-end delay and normalized routing load under varying pause time with different number of sources using NS2 based simulation.Comment: 15 Page

The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy for Gas Sensing Applications

In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate using three different heating elements use as separately are presented. Three different materials (viz. DilverP1, Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 µm. CoventorWareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating element are 13.06 mW, 190 MPa and 0.028 µm which are less in comparison to those with Poly Silicon heater and Platinum heater at moderate temperature (150-200 °C) over the sensing material (ZnO). When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3431

The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy for Gas Sensing Applications

In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate using three different heating elements use as separately are presented. Three different materials (viz. DilverP1, Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 m. Coventor- WareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating element are 13.06 mW, 190 MPa and 0.028 m which are less in comparison to those with Poly Silicon heater and Platinum heater at moderate temperature (150-200 C) over the sensing material (ZnO). When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3581

Analytical Modeling of SON MOSFET and Realization Inverter Circuit for High Speed and Ultra Dense Low Power Circuits

In the recent years, there has been considerable interest in the realization of high speed, small-size and low-power consuming devices and systems. As a consequence, the search for new principle of operation of the small-size, high speed and low-power device is becoming more and more important. In our earlier paper, it has been established that SON technology, not only improve the dc performance with reduce a short-channel effect and threshold voltage, it also improves the frequency response due to improvement in conductance and reduced parasitic effect. Further, it is already in our knowledge that SCEs are suppressed in dual material gate MOSFETs because of the perceivable step in the surface-potential profile, which screens the drain potential. The concept of dual material gate has been applied to SON MOSFETs structure and the features exhibited by resulting new SON structure has been examined for the first time by developing an analytical model and the result agree well with the MEDICI simulation values. In order to substantiate the merits of the proposed SON MOSFETs, a MOS Inverter is realized using the SON MOSFETs and its performance is investigated as an aid to the high-speed, ultra-dense and low-power circuit related work. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2779

Tricho-dento-osseous syndrome and precocious eruption

Tricho-dento-osseous syndrome (TDO), an uncommon form of ectodermal dysplasia is an autosomal dominant genetic disorder which is characterized by inherited defects in tissues arising from epithelial-mesenchymal interaction. Genetic studies have revealed that it is caused by mutation in the DLX3 gene. TDO presents with a great phenotypic heterogeneity and studies have suggested that this heterogeneity is the result of environmental factors or other genetic modifiers. In this article, we report a case of TDO in which the child had typical clinical features of hair, teeth and bone defects, as seen in TDO. Parents of the child were unaffected. Genetic analysis of the child revealed mutation in DLX3 gene. The child also showed precocious eruption of the permanent molars, a clinical feature which has been rarely reported. We suggest that the precocious eruption seen in TDO is probably due to a markedly increased osteoblastic activity