Correlation of cell numbers with catalase activities of pure strains of bacteria

An attempt was made to correlate the catalase production with the actual number of aerobic bacterial cells generating the enzyme: bacteria were obtained from the surface of marine fish. A linear correlation was found between the log of catalase activity and log of bacterial count in single culture

Comparison of media and methods for the detection and enumeration of Clostridium perfringens in seafoods

Three direct plating methods and two most probable number (MPN) procedures were compared for the enumeration of Clostridium perfringens in seafoods the sulfitecycloserine (SC) agar, sulfite-polymyxin-sulfadiazine (SPS) agar, tryptone-sulfite- neomycin (TSN) agar, LS medium MPN procedure and iron milk MPN procedure. Isolates were confirmed as C. perfringens. The two MPN procedures compared very well with the three plating media tested with stock culture of C. perfringens from our laboratory collection and the reference strain NCIB 6125. But in fish samples, the two liquid media were found to be more sensitive and hence the MPN procedure using LS medium for the detection of C. perfringens in seafoods is suggested

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Constraints on cosmic strings using data from the first Advanced LIGO observing run

Cosmic strings are topological defects which can be formed in grand unified theory scale phase transitions in the early universe. They are also predicted to form in the context of string theory. The main mechanism for a network of Nambu-Goto cosmic strings to lose energy is through the production of loops and the subsequent emission of gravitational waves, thus offering an experimental signature for the existence of cosmic strings. Here we report on the analysis conducted to specifically search for gravitational-wave bursts from cosmic string loops in the data of Advanced LIGO 2015-2016 observing run (O1). No evidence of such signals was found in the data, and as a result we set upper limits on the cosmic string parameters for three recent loop distribution models. In this paper, we initially derive constraints on the string tension Gμ and the intercommutation probability, using not only the burst analysis performed on the O1 data set but also results from the previously published LIGO stochastic O1 analysis, pulsar timing arrays, cosmic microwave background and big-bang nucleosynthesis experiments. We show that these data sets are complementary in that they probe gravitational waves produced by cosmic string loops during very different epochs. Finally, we show that the data sets exclude large parts of the parameter space of the three loop distribution models we consider

Cost effective potentiostatic control unit for recovery of silver from photographic fixer solution

Photographic fixture solution originates from the processing of black and white photographic films and the silver concentration in the fixer is around 2 to 8 gl-1. Due to over increasing cost of silver and very stringent pollution regulations, it makes one to recover silver from the fixer solution which is a good secondary source for silver. Normally during the silver recovery from fixer in galvanostatic mode, current has to be decreased with respect to silver concentration in fixer for avoiding sulphide formation. In order to achieve this a cost effective potentiostatic control unit is employed for silver recovery which will make the current to decrease due to decreasing silver concentration in the fixer solution. In this paper the effect of cathode potential and the effect of silver concentration on silver recovery from fixer solution using the cost effective potentiostatic control unit are studied and the results are reporte

Evaluation of adjunctive tests for cervical cancer screening in low resource settings

Background: Visual inspection of cervix after application of acetic acid (VIA) is an effective screening tool for cervical cancer in low resource settings, but its low specificity leads to high referral rates. Adjunctive testing may overcome this drawback. Aims: This pilot study was aimed to assess test performances of VIA, human papillomavirus (HPV) testing and Pap smear, individually and in simulated combinations, to determine the probable best screening option. Setting and Design: Gynecology outpatient department (OPD); cross-sectional study. Materials and Methods: One hundred women with complaints of irregular vaginal bleeding or discharge, post coital bleeding or unhealthy cervix on examination underwent Pap smear, HPV testing, VIA, colposcopy and biopsy, if indicated, in this screening order. Statistical Analysis: Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each of the tests with a biopsy result of 65HSIL taken as the gold standard. Simulated parallel and sequential combinations for VIA/Pap, VIA/HPV and HPV/Pap were calculated and compared with individual test performance. Results: Prevalence of abnormal Pap smears was 5%, VIA positive 51% and HPV positive 16%. Sensitivity and specificity of VIA were 100% and 53.3% respectively. For HPV and Pap tests corresponding figures were 85.7%, 89.7% and 50%, 98.9% respectively. The best simulated combination with a balance of sensitivity and specificity was of VIA followed by HPV testing (sensitivity 85.7%, specificity 95.4%). Conclusion: Addition of HPV testing to VIA can increase the specificity of VIA, thereby reducing the referral rates without compromising the sensitivity of the test

Evaluation of adjunctive tests for cervical cancer screening in low resource settings

Background: Visual inspection of cervix after application of acetic acid (VIA) is an effective screening tool for cervical cancer in low resource settings, but its low specificity leads to high referral rates. Adjunctive testing may overcome this drawback. Aims: This pilot study was aimed to assess test performances of VIA, human papillomavirus (HPV) testing and Pap smear, individually and in simulated combinations, to determine the probable best screening option. Setting and Design: Gynecology outpatient department (OPD); cross-sectional study. Materials and Methods: One hundred women with complaints of irregular vaginal bleeding or discharge, post coital bleeding or unhealthy cervix on examination underwent Pap smear, HPV testing, VIA, colposcopy and biopsy, if indicated, in this screening order. Statistical Analysis: Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each of the tests with a biopsy result of ≥HSIL taken as the gold standard. Simulated parallel and sequential combinations for VIA/Pap, VIA/HPV and HPV/Pap were calculated and compared with individual test performance. Results: Prevalence of abnormal Pap smears was 5%, VIA positive 51% and HPV positive 16%. Sensitivity and specificity of VIA were 100% and 53.3% respectively. For HPV and Pap tests corresponding figures were 85.7%, 89.7% and 50%, 98.9% respectively. The best simulated combination with a balance of sensitivity and specificity was of VIA followed by HPV testing (sensitivity 85.7%, specificity 95.4%). Conclusion: Addition of HPV testing to VIA can increase the specificity of VIA, thereby reducing the referral rates without compromising the sensitivity of the test