Ad hoc file system

Ad hoc File System (AFS) is middleware for peers wishing to share and access data in ad hoc fashion. AFS permits processes to export local files and import files shared by other processes. Communication between hosts is facilitated by the M2MI Framework, a novel paradigm for building collaborative systems. The API provided by AFS allows for data to be exported to the middleware, which become accessible to hosts running AFS. Interested peers can import exported data to their local system, allowing uniform access to local and remote files. Peers can also unexport and unimport data undoing effects of export and import operations. To illustrate functionalities of Ad hoc File System, two user applications have been developed. The first is a character based console application similar to shells, such as the K shell, and the second is a visual application that demonstrates how the file system in AFS changes due to different operations

Constraining Quasar and IGM Properties Through Bubble Detection in Redshifted 21-cm Maps

The infrared detection of a z>7 quasar has opened up a new window to directly probe the IGM during the epoch of reionization. In this paper we theoretically consider the possibility of detecting the ionized bubble around a z=8 quasar using targeted redshifted 21-cm observations with the GMRT. The apparent shape and size of the ionized bubble, as seen by a distant observer, depends on the parameters \dot{N}_{phs}/C, x_HI/C and \tau_Q where \dot{N}_{phs}, \tau_Q, x_HI and C are respectively the photon emission rate, age of the quasar, the neutral fraction and clumping factor of the IGM.Here we have analytically estimated the shape and size of a quasar's ionized bubble assuming an uniform IGM and ignoring other ionizing sources besides the quasar, and used this as a template for matched filter bubble search with the GMRT visibility data. We have assumed that \dot{N}_{phs} is known from the infrared spectrum and C from theoretical considerations, which gives us two free parameters x_HI and \tau_Q for bubble. Considering 1,000 hr of observation, we find that there is a reasonably large region of parameter space where a 3\sigma detection is possible. We also find that it will be possible to place lower limits on x_HI and \tau_Q with this observation. Deeper follow up observations can place upper limits on \tau_Q and x_HI. Value of C affect the estimation of x_HI but the estimation of \tau_Q remains unaffected.We have used a semi-numerical technique to simulate the apparent shape and size of quasar ionized bubbles considering the presence of other ionizing sources and inhomogeneities in the IGM. The presence of other sources increase the size of the quasar bubble, leading to underestimation of x_HI. Clustering of other ionizing sources around the quasar can produce severe distortions in bubble's shape. However, this does not severely affect parameter estimation in the bubbles that are large.Comment: 18 pages, 16 figures, 3 tables. Minor change in text. Accepted for publication in MNRA

A comparative study on sedative and cardiorespiratory effects of clonidine and dexmedetomidine added to ropivacaine in supraclavicular brachial plexus block in upper extremity surgery

Background: Supraclavicular brachial plexus block is widely used peripheral nerve block technique used for surgery of the upper extremity. Several drugs have been used with local anesthetic as adjuvants for rapid, dense, and prolonged analgesia. Aims and Objectives: The aims and objectives of the study are to compare the degree of sedation and cardiorespiratory effects of clonidine and dexmedetomidine added to ropivacaine in supraclavicular brachial plexus block. Materials and Methods: A double-blinded comparative study was done on eighty patients who were randomly allocated equally into two groups and received clonidine and dexmedetomidine added to ropivacaine 0.5%. Intraoperative degree of sedation and cardiorespiratory parameters were monitored in regular intervals and compared to find difference. Results: Heart rate was consistently lower with dexmedetomidine. Systolic, diastolic, and mean arterial pressures (MAPs) were comparable in both groups at all time points except at 45 min when diastolic and MAP were lower with dexmedetomidine and it was statistically significant. Sedation score in Group D was higher except at 5 min and difference was statistically significant. All patients in both groups were sedated and easily arousable. There was statistically significant difference in peroperative oxygen saturation between the groups although it was clinically not significant. Conclusion: There was more hemodynamic effect of dexmedetomidine than clonidine but these effects can be managed by medication easily. In addition to this, it was found that dexmedetomidine provides conscious sedation without any respiratory depression. Comparing the risk and benefit dexmedetomidine can be used with local anesthetic in supraclavicular brachial plexus block in upper extremity surgery

Speed Binning Aware Design Methodology to Improve Profit under Parameter Variations

Abstract-Designin

Power law scaling in Universal Extra Dimension scenarios

We study the power law running of gauge, Yukawa and quartic scalar couplings in the universal extra dimension scenario where the extra dimension is accessed by all the standard model fields. After compactifying on an $S_1 /Z_2$ orbifold, we compute one-loop contributions of the relevant Kaluza-Klein (KK) towers to the above couplings up to a cutoff scale $\Lambda$. Beyond the scale of inverse radius, once the KK states are excited, these couplings exhibit power law dependence on $\Lambda$. As a result of faster running, the gauge couplings tend to unify at a relatively low scale, and we choose our cutoff also around that scale. For example, for a radius $R \sim 1 TeV^{-1}$, the cutoff is around 30 TeV. We then examine the consequences of power law running on the triviality and vacuum stability bounds on the Higgs mass. We also comment that the supersymmetric extension of the scenario requires $R^{-1}$ to be larger than $\sim 10^{10}$ GeV in order that the gauge couplings remain perturbative up to the scale where they tend to unify.Comment: Latex, 12 pages, 5 figures; v2: minor changes, to appear in Nucl. Phys.

Comparison of efficacy between intravenous clonidine and dexmedetomidine as pre-medication in attenuating hemodynamic stress responses during laparoscopic cholecystectomy

Background: Laparoscopic cholecystectomy is a commonly performed surgery and stable intraoperative hemodynamic status is desirable during pneumoperitonium. Clonidine and dexmedetomidine (alpha-2 adrenergic agonist) were used in this study to attenuate the stress response of pneumoperitoneum because alpha-2 adrenergic agonists help in the attenuation of neuroendocrine and hemodynamic responses to surgery and anesthesia, due to its sympatholytic action. Aims and Objectives: The aims and objectives of the study are to conduct a comparative evaluation of clonidine and dexmedetomidine as pre-anesthetic medication for the attenuation of hemodynamic changes during laparoscopic cholecystectomy surgeries. Materials and Methods: Eighty patients of either sex, aged 20–50 years, complying to the American Society of Anesthesiologists physical status I-II, scheduled for elective laparoscopic cholecystectomy under general anesthesia were divided into two equal groups to receive either clonidine 1 mg/kg (Group-C, n=40) or dexmedetomidine 1 mg/kg (Group-D, n=40), both injected through intravenous route as 15 mL volume with normal saline. Heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and SpO2 were measured before and after giving the study drugs, before and immediately after pneumoperitoneum, and then, at 10, 20, 30, 40, and 50 min of pneumoperitoneum. Results: Statistically significant difference was observed in heart rate in the dexmedetomidine group constantly since giving study drug, immediately after the creation of pneumoperitoneum, and then, 10, 20, 30, 40, and 50 min after pneumoperitoneum. Systolic, diastolic, and mean blood pressures were found to be significantly lower in Group D (except after administering study drug), immediately after creating pneumoperitoneum, and 10, 20, 30, 40, and 50 min after pneumoperitoneum. Conclusion: Dexmedetomidine as pre-medication is more efficacious in attenuating hemodynamic stress responses in laparoscopic cholecystectomy surgeries compared to clonidine as pre-medication

Simulating the impact of HI fluctuations on matched filter search for ionized bubbles in redshifted 21 cm maps

Extending the formalism of Datta, Bharadwaj & Choudhury (2007) for detecting ionized bubbles in redshifted 21 cm maps using a matched-filtering technique, we use different simulations to analyze the impact of HI fluctuations outside the bubble on the detectability of the bubble. In the first three kinds of simulations there is a spherical bubble of comoving radius R_b, the one that we are trying to detect, located at the center, and the neutral hydrogen (HI) outside the bubble traces the underlying dark matter distribution. We consider three different possible scenarios of reionization, i.e., (i) there is a single bubble (SB) in the field of view (FoV) and the hydrogen neutral fraction is constant outside this bubble (ii) patchy reionization with many small ionized bubbles in the FoV (PR1) and (iii) many spherical ionized bubbles of the same radius $R_b$ (PR2). The fourth kind of simulation uses more realistic maps based on semi-numeric modelling (SM) of ionized regions. We find that for both the SB and PR1 scenarios the fluctuating IGM restricts bubble detection to size R_b<= 6 Mpc and R_b<= 12 Mpc for the GMRT and the MWA respectively, however large be the integration time. These results are well explained by analytical predictions. Large uncertainty due to the HI fluctuations restricts bubble detection in the PR2 scenario for neutral fraction x_HI<0.6. The matched-filter technique works well even when the targeted ionized bubble is non-spherical due to surrounding bubbles and inhomogeneous recombination (SM). We find that determining the size and positions of the bubbles is not limited by the HI fluctuations in the SB and PR1 scenario but limited by the instrument's angular resolution instead, and this can be done more precisely for larger bubble (abridged).Comment: 14 pages, 15 Postscript figures, Revised to incorporate ionization maps produced by the semi-numeric approach. Accepted for publication in MNRA

Cross-correlation of the HI 21-cm Signal and Lyman-alpha Forest: A Probe Of Cosmology

Separating the cosmological redshifted 21-cm signal from foregrounds is a major challenge. We present the cross-correlation of the redshifted 21-cm emission from neutral hydrogen (HI) in the post-reionization era with the Ly-alpha forest as a new probe of the large scale matter distribution in the redshift range z=2 to 3 without the problem of foreground contamination. Though the 21-cm and the Ly-alpha forest signals originate from different astrophysical systems, they are both expected to trace the underlying dark matter distribution on large scales. The multi-frequency angular cross-correlation power spectrum estimator is found to be unaffected by the discrete quasar sampling, which only affects the noise in the estimate. We consider a hypothetical redshifted 21-cm observation in a single field of view 1.3 degrees (FWHM) centered at z=2.2 where the binned 21-cm angular power spectrum can be measured at an SNR of 3 sigma or better across the range 500 < l < 4000 . Keeping the parameters of the 21-cm observation fixed, we have estimated the SNR for the cross-correlation signal varying the quasar angular number density n of the Ly-alpha forest survey. Assuming that the spectra have SNR ~5 in pixels of length 44 km/s, we find that a 5 sigma detection of the cross-correlation signal is possible at 600 < l < 2000 with n=4 deg^{-2}. This value of n is well within the reach of upcoming Ly-alpha forest surveys. The cross-correlation signal will be a new, independent probe of the astrophysics of the diffuse IGM, the growth of structure and the expansion history of the Universe.Comment: Revised paper, accepted to MNRA

GMRT observation towards detecting the Post-reionization 21-cm signal

We have analyzed 610 MHz GMRT observations towards detecting the redshifted 21-cm signal from z=1.32. The multi-frequency angular power spectrum C_l(Delta nu) is used to characterize the statistical properties of the background radiation across angular scales ~20" to 10', and a frequency bandwidth of 7.5 MHz with resolution 125 kHz. The measured C_l(Delta nu) which ranges from 7 mK^2 to 18 mK^2 is dominated by foregrounds, the expected HI signal C_l^HI(Delta nu) ~10^{-6}- 10^{-7} mK^2 is several orders of magnitude smaller. The foregrounds, believed to originate from continuum sources, is expected to vary smoothly with Delta nu whereas the HI signal decorrelates within ~0.5 MHz and this holds the promise of separating the two. For each l, we use the interval 0.5 < Delta nu < 7.5 MHz to fit a fourth order polynomial which is subtracted from the measured C_l(Delta nu) to remove any smoothly varying component across the entire bandwidth Delta nu < 7.5 MHz. The residual C_l(Delta nu), we find, has an oscillatory pattern with amplitude and period respectively ~0.1 mK^2 and Delta nu = 3 MHz at the smallest l value of 1476, and the amplitude and period decreasing with increasing l. Applying a suitably chosen high pass filter, we are able to remove the residual oscillatory pattern for l=1476 where the residual C_l(Delta nu) is now consistent with zero at the 3-sigma noise level. We conclude that we have successfully removed the foregrounds at l=1476 and the residuals are consistent with noise. We use this to place an upper limit on the HI signal whose amplitude is determined by x_HI b where x_HI and b are the HI neutral fraction and the HI bias respectively. A value of x_HI b greater than 7.95 would have been detected in our observation, and is therefore ruled out at the 3-sigma level. (abridged)Comment: 29 pages, 13 figures, Accepted to MNRA