Modelling and Performance Analysis of New Coolstreaming for P2P IPTV

Peer to peer networks are becoming increasingly popular among Internet users as the downloading peers share the storage and upload bandwidth load of the system. This makes it possible for a large number of users to share a data file available at a server without the server upload bandwidth becoming a bottleneck. The P2P technology is being widely used not only for file sharing but also for video on demand, live streaming and IPTV. The delay deadlines are more stringent in live streaming and IPTV than those in file sharing as the traffic is real time. The performance perceived by a user depends upon whether the video stream is being downloaded at the streaming rate. Coolstreaming is the first large scale P2P IPTV system. We model the multi-channel Coolstreaming system via an open queueing network. The peer dynamics at a channel is modelled by a closed queueing network working at a faster rate. We compute the expected number of substreams in the overlay of New Coolstreaming which are not being received at the proper rate. The computation of the Markov chain with a very large state space is handled using the two time scale decomposition. Further we characterize the end to end delay encountered by a video stream originating from the server and received at a user of New Coolstreaming. Three factors contribute towards the delay. The first factor is the mean path length in terms of overlay hops of the partnership graph. The second factor is the mean number of routers between any two overlay peers in the network layer and the third factor is the queueing delay at a router in the Internet. The mean shortest path length in terms of overlay peers in the New Coolstreaming graph is shown to be O(logn)where nis the number of peers in the overlay. This is done by modelling the overlay by a random graph. The mean shortest path in terms of routers in the Internet’s router level topology is seen to be at most O(logNI)where NIis the number of routers in the Internet. We also discuss a method by which we can get the mean delay at a router in the Internet. Thus, the mean end to end delay in New Coolstreaming is shown to be upper bounded by O(lognlogNIE[W])where E[W]is the mean delay at a router in the Internet

On Gosper's Pi(q) and Lambert series identities

In an interesting article entitled `Experiments and discoveries in q-trigonometry'', R. W. Gosper conjectured few beautiful Pi(q) and Lambert series identities. Many people have attempted confirming some of those identities in the Gosper's list, mainly by using Gosper's q-trigonometric identities. In this paper we either prove or disprove all the Pi(q) and Lambert series identities in the Gosper's list by mainly using S. Ramanujan's theta function identities and W. N. Bailey's summation formula. In the process, we obtain three new Gosper kind of identities

Sequence-Specific Gene Correction of Cystic Fibrosis Airway Basal Cells

Cystic fibrosis (CF) is a lethal monogenic disease resulting from mutations in the CFTR gene which encodes a protein involved in regulating anion trans-epithelial transport. A three-base deletion in CFTR (termed as ΔF508 mutation), wherein CFTR protein is misfolded leading to its pre-mature degradation in the endoplasmic reticulum (ER), is the most common cause of this debilitating disease. Since CFTR is expressed in multiple body systems, CF affects different organs, but lung pathology is the greatest cause of death in affected patients. We achieved site-specific gene correction with an efficiency of ~10 % in CF airway basal cells homozygous for the ΔF508 mutation. Basal cells are a multipotent stem cell population of the respiratory epithelium and therefore, their gene correction could provide a long-term, permanent remedy for CF. Delivery of engineered sequence-specific zinc finger nucleases (ZFNs) and single-stranded oligo DNA (ssODN) carrying the correcting sequence via electroporation facilitated the correction. The gene-corrected cells upon in vitro differentiation using air-liquid interface showed presence of fully-glycosylated mature CFTR protein as opposed to differentiated mutant cells which synthesized only the core-glycosylated immature form. Most importantly, we demonstrated CFTR ion channel activity in the gene-corrected cells by Ussing chamber electrophysiology

Mimicking a Kerrlike medium in the dispersive regime of second-harmonic generation

We find an effective Hamiltonian describing the process of second-harmonic generation in the far-off resonant limit. We show that the dynamics of the fundamental mode is governed by a Kerrlike Hamiltonian. Some dynamical consequences are examined.Comment: 12 pages, 4 figures Submitted to Optics Communication

Vacuum Induced Coherences in Radiatively Coupled Multilevel Systems

We show that radiative coupling between two multilevel atoms having near-degenerate states can produce new interference effects in spontaneous emission. We explicitly demonstrate this possibility by considering two identical V systems each having a pair of transition dipole matrix elements which are orthogonal to each other. We discuss in detail the origin of the new interference terms and their consequences. Such terms lead to the evolution of certain coherences and excitations which would not occur otherwise. The special choice of the orientation of the transition dipole matrix elements enables us to illustrate the significance of vacuum induced coherence in multi-atom multilevel systems. These coherences can be significant in energy transfer studies.Comment: 13 pages including 8 figures in Revtex; submitted to PR

East African hydroclimatic variability: 1950-1999

The interannual variability in precipitation over East Africa is well-understood. Many studies have identified the factors influencing the interannual variability of precipitation such as El Niño – Southern Oscillation (ENSO), the Indian Ocean Dipole Mode (IODM), and Atlantic Ocean sea surface temperature and pressure variations. The relatively arid conditions in much of the East African region are not understood fully. The objective of present study is to determine the meteorological association of aridity over East Africa with regional hydroclimatic variables as well as to find global teleconnections affecting spatial distribution of aridity over East Africa. The East Africa Aridity index is calculated as the ratio of the mean seasonal precipitation to the mean seasonal potential evapotranspiration (after Budyko, 1974), and is used as a measure of aridity over East Africa. Principal components analysis was performed on the aridity index to identify characteristic modes of the temporal variability of the aridity index across East Africa. Correlation analysis was performed to identify the meteorological association in the interannual variability of aridity over East Africa and to find the global teleconnections, such as with ENSO, IODM, North Atlantic Oscillations (NAO), Tropical Atlantic SST Dipole (TASD), and Quasi Biennial Oscillations (QBO) in it. The first principal component of the aridity index was used for the correlation analysis. Correlations of the normalized difference vegetation index (NDVI) and Palmer Drought Severity Index (PDSI) with the first principal component of aridity index were calculated. The aridity index over East Africa is driven by precipitation rather than potential evapotranspiration (PET). The PET over East Africa is driven by precipitation rather than temperature. Aridity over East Africa is well correlated with the NDVI and PDSI. The ENSO influence on interannual variability of precipitation and hence on aridity is very much evident in all the seasons, while IODM influence is evident in the June – September season, the driest season for East Africa. Influence of NAO, TASD, and QBO was observed to be very small compared to that of ENSO and IODM. The teleconnections influencing the rainfall variability of East Africa also influenced variability in aridity

Observation of squeezed light from one atom excited with two photons

Single quantum emitters like atoms are well-known as non-classical light sources which can produce photons one by one at given times, with reduced intensity noise. However, the light field emitted by a single atom can exhibit much richer dynamics. A prominent example is the predicted ability for a single atom to produce quadrature-squeezed light, with sub-shot-noise amplitude or phase fluctuations. It has long been foreseen, though, that such squeezing would be "at least an order of magnitude more difficult" to observe than the emission of single photons. Squeezed beams have been generated using macroscopic and mesoscopic media down to a few tens of atoms, but despite experimental efforts, single-atom squeezing has so far escaped observation. Here we generate squeezed light with a single atom in a high-finesse optical resonator. The strong coupling of the atom to the cavity field induces a genuine quantum mechanical nonlinearity, several orders of magnitude larger than for usual macroscopic media. This produces observable quadrature squeezing with an excitation beam containing on average only two photons per system lifetime. In sharp contrast to the emission of single photons, the squeezed light stems from the quantum coherence of photon pairs emitted from the system. The ability of a single atom to induce strong coherent interactions between propagating photons opens up new perspectives for photonic quantum logic with single emittersComment: Main paper (4 pages, 3 figures) + Supplementary information (5 pages, 2 figures). Revised versio

Engineering Ionomer Materials for Addressing Ohmic Resistances in Electrochemical Desalination and Waste Heat Recovery

Water scarcity and energy availability present important challenges that need to be addressed in the coming centuries. In the front of water technologies, desalting brackish water is of extreme importance for thermal electric power plants, chemical manufacturing plants, and other industrial operations that treat and reuse their water utilities. Membrane capacitive deionization (MCDI) is an energy efficient desalination technique that has drawn attention from commercial entities. Most material research studies on MCDI focus on enhancing electrode performance while little emphasis is given to rationale design of ion-exchange membranes (IEMs). In this work, the ionic conductivity, permselectivity, and thickness for three different IEM chemistries (polyaliphatic, poly (arylene ether), and perfluorinated) were correlated to MCDI performance attributes. A 5-10-fold reduction in area specific resistance (ASR), with unconventional perfluorinated and poly (arylene ether) IEMs reduced the energy expended per ion removed in MCDI by a factor of two, compared to conventional electrodialysis IEMs. For further advancement in energy efficiency of operation, ohmic resistance of the spacer channel needs to be addressed for which, ion-exchange resins bound by a polymeric binder termed resin wafers were explored. A new class of ion-exchange resin wafers (RWs) fabricated with ion-conductive binders were developed that exhibit exceptional ionic conductivities - a 3-5-fold improvement over conventional RWs containing a non-ionic polyethylene binder. Incorporation into a resin-wafer electrodeionization stack (RW-EDI) resulted in an increased desalination rate and reduced energy expenditure. Overall, this work demonstrates that ohmic resistances can be substantially curtailed with ionomer binder RWs at dilute salt concentrations. With respect to energy, thermally regenerative ammonia flow batteries (TRBs) are an emerging platform for extracting electrical energy from low-grade waste heat (T \u3c 130 °C). Previous TRB demonstrations suffered from poor heat to electrical energy conversion efficiency when benchmarked against state-of-the-art thermoelectric generators. This work reports the highest power density to date for a TRB (280 W m-2 at 55 °C) with a 5.7× improvement in power density over conventional designs and thermal efficiency (ηth) values as high as 2.99 % and 37.9 % relative to the Carnot efficiency (ηth/C). The gains made in TRB performance was ascribed to the zero gap design and deploying a low-resistant, inexpensive anion exchange membrane (AEM) separator and implementing a copper ion selective ionomer coating on the copper mesh electrodes. The improved TRB power density and the use of a low-cost materials represent significant milestones in low-grade waste heat recovery using electrochemical platforms

A Review of Security Mechanisms for Detection of Malicious Transactions in Database

Insider attacks formed the biggest threaten against database management systems. There are many mechanisms have been developed to detect and prevent the insider attacks called Detection of Malicious Activities in Database Systems DEMIDS. The DEMIDS consider as one of the last defenses mechanism of the database security system. There are many mechanisms that have been developed to detect and prevent the misuse activities like delete, and update data on the database systems. These mechanisms utilize auditing and profiling methods to detect and prevent the malicious activities. However these mechanisms still have problems to detect the misuse activities such as limit to detect the malicious data on authorized commands. This study will address these problems by propose a mechanism that utilizes dependency relationship among items to detect and prevent the malicious data by calculate a number of relations among data items. If the number of relations among items is not allowed any modification or deletion then the mechanism will detect activity as malicious activity. The evaluation parameters such as detect, false positive and false negative rate use to evaluate the accuracy of proposed mechanism