The universe in a soap film

The value of the cosmological constant is one of the major puzzles of modern cosmology: it is tiny but nonzero. Sorkin predicted, from the Causet approach to quantum gravity, that the cosmological constant has quantum fluctuations. The predicted order of magnitude of the fluctuations agrees with the subsequently observed value of the cosmological constant. We had earlier developed an analogy between the cosmological constant of the universe and the surface tension of fluid membranes. Here we demonstrate by computer simulations that the surface tension of a fluid membrane has statistical fluctuations stemming from its discrete molecular structure. Our analogy enables us to view these numerical experiments as probing a small and fluctuating cosmological constant. Deriving insights from our analogy, we show that a fluctuating cosmological constant is a generic feature of quantum gravity models and is far more general than the specific context in which it was originally proposed. We pursue and refine the idea of a fluctuating cosmological constant and work towards making further testable predictions. © 2009 IOP Publishing Ltd

In Situ Swelling Behavior of Chitosan-Polygalacturonic Acid/Hydroxyapatite Nanocomposites in Cell Culture Media

The molecular and mechanical characteristics of in situ degradation behavior of chitosan-polygalacturonic acid/hydroxyapatite (Chi-PgA-HAP) nanocomposite films is investigated using Fourier Transform Infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), and modulus mapping techniques for up to 48 days of soaking in cell culture media. The surface molecular structure of media-soaked samples changes over the course of 48 days of soaking, as indicated by significant changes in phosphate vibrations (1200–900 cm−1) indicating apatite formation. Chitosan-Polygalacturonic acid polyelectrolyte complexes (PECs) govern structural integrity of Chi-PgA-HAP nanocomposites and FTIR spectra indicate that PECs remain intact until 48 days of soaking. In situ AFM experiments on media-soaked samples indicate that soaking results in a change in topography and swelling proceeds differently at the initial soaking periods of about 8 days than for longer soaking. In situ modulus mapping experiments are done on soaked samples by probing ∼1–3 nm of surface indicating elastic moduli of ∼4 GPa resulting from proteins adsorbed on Chi-PgA-HAP nanocomposites. The elastic modulus decreases by ∼2 GPa over a long exposure to cell culture media (48 days). Thus, as water enters the Chi-PgA-HAP sample, surface molecular interactions in Chi-PgA-HAP structure occur that result in swelling, causing small changes in nanoscale mechanical properties

Stability of Hill Slopes and Foundation Condition at Radio Astronomy Centre Ootacamand

Stability aspects of hill slopes and foundation considerations of Radio Astronomy Centre at Ootacamand are described. The analysis of slopes indicated that if joints are not covered, the material in joints may lose strength and the slopes may enter a state of instability. Footings with inclined legs were found to resist the horizontal forces, pull and overturning movements. Lime piles adopted for strengthening soft material at one of the tower locations were found to be effective

Study of the immediate short term clinical and radiological outcome of intertrochanteric neck of femur fractures treated with primary bipolar hemiarthroplasty in geriatric population in a tertiary care centre

Background: Intertrochanteric fracture in elderly patient is a frequent problem and is becoming more common as the proportion of elderly people in the population increases. Unstable intertrochanteric fracture in the elderly patient is associated with a high rate of mortality as much as 20 percent during the first postoperative year. The treatment of such unstable intertrochanteric fracture is still controversial. So as to allow for earlier postoperative weight-bearing, primary hemiarthroplasty was proposed by some authors. The purpose of this study is to evaluate the functional and clinical outcomes of cemented bipolar arthroplasty as a primary treatment for unstable intertrochanteric fracture in the elderly patient.Methods: It was an observational retrospective plus prospective study design over a period of 18 months in a tertiary care setting with a sample size of 41. Patients fulfilling the inclusion criteria were assessed clinically using Harris hip score and radiologically were operated for bipolar hemiarthroplasty. They were assessed intraoperatively, immediate postoperatively and after 4 weeks for functional outcome using Harris hip score and assessed radiologically. Patients were also be evaluated for intraoperative and postoperative complications if any. The outcome was analysed statistically to comment on functional outcome of bipolar hemiarthroplasty.Results: In our study majority of the patients 70% (29) had excellent and good outcomes at the end of 1 month. Out of the rest 22% more had fair outcome at the end of month. Thus 93% patients had favorable outcomes at the end of 1 month while 7% (3 cases) had poor outcome when measured using Harris hip score.Conclusions: Primary cemented bipolar hemiarthroplasty is a viable option that leads to good functional outcomes and allows early mobilization and weight bearing

Agarose-stabilized gold nanoparticles for surface-enhanced Raman spectroscopic detection of DNA nucleosides

doi:10.1063/1.2192573 http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=APPLAB000088000015153114000001&idtype=cvips&prog=normal&doi=10.1063/1.2192573We present surface-enhanced Raman scattering (SERS) studies of DNA nucleosides using biologically benign agarose-stabilized gold nanoparticles (AAuNP). We compare the SERS activity of nucleosides with AAuNP to that of commercially obtained citrate-stabilized gold nanoparticles and find the SERS activity to be an order of magnitude higher with AAuNP. The higher SERS activity is explained in terms of the agarose matrix, which provides pathways for the gold nanoparticles to have distinct arrangements that result in stronger internal plasmon resonances.This work was supported through the University of Missouri Research Board grants URB04-023 (S.G.) and URB03-080 (M.C. and K.V.K.), NSF under Grant No. DMR-0413601and the NCI under Grant No. IR0ICA119412-01. The gold nanoparticles were produced and supplied by the University of Missouri Nanoparticle Production Core Facility

Multi-user video streaming using unequal error protection network coding in wireless networks

In this paper, we investigate a multi-user video streaming system applying unequal error protection (UEP) network coding (NC) for simultaneous real-time exchange of scalable video streams among multiple users. We focus on a simple wireless scenario where users exchange encoded data packets over a common central network node (e.g., a base station or an access point) that aims to capture the fundamental system behaviour. Our goal is to present analytical tools that provide both the decoding probability analysis and the expected delay guarantees for different importance layers of scalable video streams. Using the proposed tools, we offer a simple framework for design and analysis of UEP NC based multi-user video streaming systems and provide examples of system design for video conferencing scenario in broadband wireless cellular networks