214 research outputs found
Characterisation of bacteriocins produced by Lactobacillus spp. isolated from the traditional Pakistani yoghurt and their antimicrobial activity against common foodborne pathogens
Lactic acid bacteria (LAB) are widely known for their probiotic activities for centuries. These bacteria synthesise some secretory proteinaceous toxins, bacteriocins, which help destroy similar or interrelated bacterial strains. This study was aimed at characterising bacteriocins extracted from Lactobacillus spp. found in yoghurt and assessing their bactericidal effect on foodborne bacteria. Twelve isolated Lactobacillus spp. were examined to produce bacteriocins by the organic solvent extraction method. Bacteriocins produced by two of these strains, Lactobacillus helveticus (BLh) and Lactobacillus plantarum (BLp), showed the most significant antimicrobial activity, especially against Staphylococcus aureus and Acinetobacter baumannii. Analysis of SDS-PAGE showed that L. plantarum and L. helveticus bacteriocins have a molecular weight of ~10âkDa and ~15âkDa, respectively. L. plantarum (BLp) bacteriocin was heat stable while L. helveticus (BLh) bacteriocin was heat labile. Both bacteriocins have shown activity at acidic pH. Exposure to a UV light enhances the activity of the BLh; however, it had negligible effects on the BLp. Different proteolytic enzymes confirmed the proteinaceous nature of both the bacteriocins. From this study, it was concluded that bacteriocin extracts from L. helveticus (BLh) can be considered a preferable candidate against foodborne pathogens as compared to L. plantarum (BLp). These partially purified bacteriocins should be further processed to attain purified product that could be useful for food spoilage and preservation purposes
Conditional dependence structure and risk spillovers between Bitcoin and fiat currencies
This paper investigates the extreme dependence and risk spillovers between Bitcoin and the currencies of the BRICS and G7 economies. We find time-varying dependence between Bitcoin and all currencies. Moreover, when analysing risk spillovers from Bitcoin to currencies, we find that Bitcoin exercises significant power over most currencies, with the South African rand and Brazilian real holding both the highest downside and upside risk before and during the COVID-19 pandemic period, respectively. When considering risk spillovers from currencies towards Bitcoin, the Japanese yen exhibits the highest downside spillovers. Importantly, we find asymmetric spillovers between extreme upward and downward movements
Study of the role of dysprosium substitution in tuning structural, optical, electrical, dielectric, ferroelectric, and magnetic properties of bismuth ferrite multiferroic
Magnetoelectric multiferroics, which combine ferroelectric and magnetic characteristics, have potential use in a variety of electronic devices. In this work, Dy3+ substituted bismuth ferrites with the chemical formula Bi1âxDyxFeO3 (x = 0.0, 0.15, 0.30, 0.45, and 0.60) were synthesized using the sol-gel auto combustion process. The effect of Dysprosium substitution in BiFeO3 (BFO), on its structural, surface morphology, optical, electrical, dielectric, ferroelectric, and magnetic properties were studied. The rhombohedral perovskite structure of the space group (R3c) was confirmed via X-ray diffraction (XRD) analysis. Moreover, the crystallite size had a maximum value of 59.57 nm for x = 0.30. XRD and FTIR confirmed the substitution of Dy3+ into BFO ferrite. Further, the structural change and absorption bands confirmed the substitution of Dy3+ ions into the lattice. For x = 0.30, the energy bandgap of 2.81 eV was found. The resistivity and activation energy were minimum and drift mobility was maximum at x = 0.30 as compared to Dy3+ doped BFO samples. At low frequency, the dielectric loss was reduced, while at high frequency, the dielectric loss increased with increasing frequency. The saturated polarization (PS), electric polarization (EC), and remnant polarization (Pr) have values of 6.95 ”C/cm2, 3.49 ”C/cm2, and 1.53 kV/cm for x = 0.30, respectively. The maximum saturation magnetization and microwave frequencies were 10.89 emu/g and 2.41 GHz, respectively at Dy3+ concentration x = 0.30. These materials are suitable for electronic and microwave devices
Spectral Index and Non-Gaussianity in Supersymmetric Hybrid Inflation
We consider a supersymmetric hybrid inflation model with two inflaton fields.
The superpotential during inflation is dominated by W=(\kappa S+\kappa' S')M^2,
where S, S' are inflatons carrying the same U(1)_R charge, \kappa, \kappa' are
dimensionless couplings, and M (\sim 10^{15-16} GeV) is a dimensionful
parameter associated with a symmetry breaking scale. One light mass eigenstate
drives inflation, while the other heavier mass eigenstate is stuck to the
origin. The smallness of the lighter inflaton mass for the scalar spectral
index n_s\approx 0.96, which is the center value of WMAP7, can be controlled by
the ratio \kappa'/\kappa through the supergravity corrections. We also discuss
the possibility of the two field inflation and large non-Gaussianity in this
setup.Comment: 17 pages, 2 figures, version published in Eur. Phys. J.
Kaehler Potentials for Hilltop F-term Hybrid Inflation
We consider the basic supersymmetric (SUSY) models of F-term hybrid inflation
(FHI). We show that a simple class of Kaehler potentials ensures a resolution
to the \eta problem and allows for inflation of hilltop type. As a consequence,
observationally acceptable values for the spectral index, ns, can be achieved
constraining the coefficient c4k of the quartic supergravity correction to the
inflationary potential. For about the central value of ns, in the case of
standard FHI, the grand unification (GUT) scale turns out to be well below its
SUSY value with the relevant coupling constant \kappa in the range
(0.0006-0.15) and c4k=-(1100-0.05). In the case of shifted [smooth] FHI, the
GUT scale can be identified with its SUSY value for c4k=-16 [c4k=-1/16].Comment: 12 pages, 3 figures; Several amends have been realize
Constrained Supersymmetric Flipped SU(5) GUT Phenomenology
We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT
model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are
constrained to be universal at some input scale, , above the GUT scale,
. We analyze the parameter space of CFSU(5) assuming that the lightest
supersymmetric particle (LSP) provides the cosmological cold dark matter,
paying careful attention to the matching of parameters at the GUT scale. We
first display some specific examples of the evolutions of the SSB parameters
that exhibit some generic features. Specifically, we note that the relationship
between the masses of the lightest neutralino and the lighter stau is sensitive
to , as is the relationship between the neutralino mass and the masses
of the heavier Higgs bosons. For these reasons, prominent features in generic
planes such as coannihilation strips and rapid-annihilation
funnels are also sensitive to , as we illustrate for several cases with
tan(beta)=10 and 55. However, these features do not necessarily disappear at
large , unlike the case in the minimal conventional SU(5) GUT. Our
results are relatively insensitive to neutrino masses.Comment: 23 pages, 8 figures; (v2) added explanations and corrected typos,
version to appear in EPJ
A muon-track reconstruction exploiting stochastic losses for large-scale Cherenkov detectors
IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole. The main goal of IceCube is the detection of astrophysical neutrinos and the identification of their sources. High-energy muon neutrinos are observed via the secondary muons produced in charge current interactions with nuclei in the ice. Currently, the best performing muon track directional reconstruction is based on a maximum likelihood method using the arrival time distribution of Cherenkov photons registered by the experiment\u27s photomultipliers. A known systematic shortcoming of the prevailing method is to assume a continuous energy loss along the muon track. However at energies >1 TeV the light yield from muons is dominated by stochastic showers. This paper discusses a generalized ansatz where the expected arrival time distribution is parametrized by a stochastic muon energy loss pattern. This more realistic parametrization of the loss profile leads to an improvement of the muon angular resolution of up to 20% for through-going tracks and up to a factor 2 for starting tracks over existing algorithms. Additionally, the procedure to estimate the directional reconstruction uncertainty has been improved to be more robust against numerical errors
Ï production in pâPb collisions at âsNN=8.16 TeV
Ï production in pâPb interactions is studied at the centre-of-mass energy per nucleonânucleon collision âsNN = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and â4.46 < ycms < â2.96, down to zero transverse momentum. In this work, results on the Ï(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the Ï(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the Ï(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the Ï(1S). A first measurement of the Ï(3S) has also been performed. Finally, results are compared with previous ALICE measurements in pâPb collisions at âsNN = 5.02 TeV and with theoretical calculations.publishedVersio
(Anti-)deuteron production in pp collisions at 1as=13TeV
The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at s=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity (d Nch/ d \u3b7 3c 26) as measured in p\u2013Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p\u2013Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM)
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