475 research outputs found
Effect of Sucrose and Growth Regulator's Level on Ginger Micropropagation
Ginger is most important cash crop of the hilly region of Nepal. However, availability of disease free planting material (rhizome) is the major problem faced by Nepalese farmers. Tissue culture is the only option to produce disease free rhizome of ginger. Suitable culture media combination is most important for the production of planting material in ginger through tissue culture. Therefore, effect of different level of sucrose and growth regulators on micro-propagation of ginger was studied using local collection ‘Kaski Local'. Early stage bud was used as explant. MS basal media with different level of sucrose and growth regulators was used as tissue culture media. 30 g/L sucrose, 30 g/L sucrose+5mg/L BA, 30 g/L sucrose+5 mg/L BA+0.5 mg/L NAA, 60 g/L sucrose+5mg/L BA, 60 g/L sucrose+5 mg/L BA+0.5mg/L NAA, 90 g/L sucrose+5 mg/L BA was used in this study. The explants were surface sterilized, cultured and incubated at 25±2°C, 90-95% relative humidity and 14:10 hours light:dark photoperiod for 8 weeks. Increased level of the sucrose increased the rhizome weight, however, addition of NAA produced more positive effect for this. MS basal media with 60 g/L sucrose+5 mg/L BA+0.5 mg/L NAA produced higher rhizome weight.Journal of Nepal Agricultural Research Council Vol.3 2017: 45-4
Magnetic-field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4
Anisotropic low-temperature properties of the cubic spinel helimagnet
ZnCr2Se4 in the single-domain spin-spiral state are investigated by a
combination of neutron scattering, thermal conductivity, ultrasound velocity,
and dilatometry measurements. In an applied magnetic field, neutron
spectroscopy shows a complex and nonmonotonic evolution of the spin-wave
spectrum across the quantum-critical point that separates the spin-spiral phase
from the field-polarized ferromagnetic phase at high fields. A tiny spin gap of
the pseudo-Goldstone magnon mode, observed at wave vectors that are
structurally equivalent but orthogonal to the propagation vector of the spin
helix, vanishes at this quantum critical point, restoring the cubic symmetry in
the magnetic subsystem. The anisotropy imposed by the spin helix has only a
minor influence on the lattice structure and sound velocity but has a much
stronger effect on the heat conductivities measured parallel and perpendicular
to the magnetic propagation vector. The thermal transport is anisotropic at T <
2 K, highly sensitive to an external magnetic field, and likely results
directly from magnonic heat conduction. We also report long-time thermal
relaxation phenomena, revealed by capacitive dilatometry, which are due to
magnetic domain motion related to the destruction of the single-domain magnetic
state, initially stabilized in the sample by the application and removal of
magnetic field. Our results can be generalized to a broad class of helimagnetic
materials in which a discrete lattice symmetry is spontaneously broken by the
magnetic order.Comment: 13 pages, 8 figures + Supplemental Materia
DXL: a sounding rocket mission for the study of solar wind charge exchange and local hot bubble X-ray emission
The Diffuse X-rays from the Local galaxy (DXL) mission is an approved
sounding rocket project with a first launch scheduled around December 2012. Its
goal is to identify and separate the X-ray emission generated by solar wind
charge exchange from that of the local hot bubble to improve our understanding
of both. With 1,000 cm2 proportional counters and grasp of about 10 cm2 sr both
in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-minute flight what cannot
be achieved by current and future X-ray satellites.Comment: 15 Pages, 5 figures. Accepted for publication on Experimental
Astronom
Graphene Transistor as a Probe for Streaming Potential
We explore the dependence of electrical transport in a graphene field effect
transistor (GraFET) on the flow of the liquid within the immediate vicinity of
that transistor. We find large and reproducible shifts in the charge neutrality
point of GraFETs that are dependent on the fluid velocity and the ionic
concentration. We show that these shifts are consistent with the variation of
the local electrochemical potential of the liquid next to graphene that are
caused by the fluid flow (streaming potential). Furthermore, we utilize the
sensitivity of electrical transport in GraFETs to the parameters of the fluid
flow to demonstrate graphene-based mass flow and ionic concentration sensing.
We successfully detect a flow as small as~70nL/min, and detect a change in the
ionic concentration as small as ~40nM.Comment: 6 pages, 4 figure
Population of Merging Compact Binaries Inferred Using Gravitational Waves through GWTC-3
We report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star-black hole mergers. We infer the binary neutron star merger rate to be between 10 and 1700 Gpc-3 yr-1 and the neutron star-black hole merger rate to be between 7.8 and 140 Gpc-3 yr-1, assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and 44 Gpc-3 yr-1 at a fiducial redshift (z=0.2). The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to (1+z)κ with κ=2.9-1.8+1.7 for z≲1. Using both binary neutron star and neutron star-black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from 1.2-0.2+0.1 to 2.0-0.3+0.3M⊙. We confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. We also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of 8.3-0.5+0.3 and 27.9-1.8+1.9M⊙. While we continue to find that the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately 60M⊙, which would indicate the presence of a upper mass gap. Observed black hole spins are small, with half of spin magnitudes below χi≈0.25. While the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also observe evidence of misalignment of spins relative to the orbital angular momentum
The population of merging compact binaries inferred using gravitational waves through GWTC-3
We report on the population properties of 76 compact binary mergers detected with gravitational waves below a false alarm rate of 1 per year through GWTC-3. The catalog contains three classes of binary mergers: BBH, BNS, and NSBH mergers. We infer the BNS merger rate to be between 10 and 1700 and the NSBH merger rate to be between 7.8 and 140 , assuming a constant rate density versus comoving volume and taking the union of 90% credible intervals for methods used in this work. Accounting for the BBH merger rate to evolve with redshift, we find the BBH merger rate to be between 17.9 and 44 at a fiducial redshift (z=0.2). We obtain a broad neutron star mass distribution extending from to . We can confidently identify a rapid decrease in merger rate versus component mass between neutron star-like masses and black-hole-like masses, but there is no evidence that the merger rate increases again before 10 . We also find the BBH mass distribution has localized over- and under-densities relative to a power law distribution. While we continue to find the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above . The rate of BBH mergers is observed to increase with redshift at a rate proportional to with for . Observed black hole spins are small, with half of spin magnitudes below . We observe evidence of negative aligned spins in the population, and an increase in spin magnitude for systems with more unequal mass ratio
All-sky search for long-duration gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run
After the detection of gravitational waves from compact binary coalescences, the search for transient gravitational-wave signals with less well-defined waveforms for which matched filtering is not well suited is one of the frontiers for gravitational-wave astronomy. Broadly classified into “short” ≲1 s and “long” ≳1 s duration signals, these signals are expected from a variety of astrophysical processes, including non-axisymmetric deformations in magnetars or eccentric binary black hole coalescences. In this work, we present a search for long-duration gravitational-wave transients from Advanced LIGO and Advanced Virgo’s third observing run from April 2019 to March 2020. For this search, we use minimal assumptions for the sky location, event time, waveform morphology, and duration of the source. The search covers the range of 2–500 s in duration and a frequency band of 24–2048 Hz. We find no significant triggers within this parameter space; we report sensitivity limits on the signal strength of gravitational waves characterized by the root-sum-square amplitude hrss as a function of waveform morphology. These hrss limits improve upon the results from the second observing run by an average factor of 1.8
Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run
We present a search for dark photon dark matter that could couple to
gravitational-wave interferometers using data from Advanced LIGO and Virgo's
third observing run. To perform this analysis, we use two methods, one based on
cross-correlation of the strain channels in the two nearly aligned LIGO
detectors, and one that looks for excess power in the strain channels of the
LIGO and Virgo detectors. The excess power method optimizes the Fourier
Transform coherence time as a function of frequency, to account for the
expected signal width due to Doppler modulations. We do not find any evidence
of dark photon dark matter with a mass between eV/, which corresponds to frequencies between 10-2000
Hz, and therefore provide upper limits on the square of the minimum coupling of
dark photons to baryons, i.e. dark matter. For the
cross-correlation method, the best median constraint on the squared coupling is
at eV/; for the
other analysis, the best constraint is at eV/. These limits improve upon those obtained
in direct dark matter detection experiments by a factor of for
eV/, and are, in absolute terms, the
most stringent constraint so far in a large mass range eV/.Comment: 20 pages, 7 figure
Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs
We report results from searches for anisotropic stochastic gravitational-wave
backgrounds using data from the first three observing runs of the Advanced LIGO
and Advanced Virgo detectors. For the first time, we include Virgo data in our
analysis and run our search with a new efficient pipeline called {\tt PyStoch}
on data folded over one sidereal day. We use gravitational-wave radiometry
(broadband and narrow band) to produce sky maps of stochastic
gravitational-wave backgrounds and to search for gravitational waves from point
sources. A spherical harmonic decomposition method is employed to look for
gravitational-wave emission from spatially-extended sources. Neither technique
found evidence of gravitational-wave signals. Hence we derive 95\%
confidence-level upper limit sky maps on the gravitational-wave energy flux
from broadband point sources, ranging from and on the
(normalized) gravitational-wave energy density spectrum from extended sources,
ranging from , depending on direction () and spectral index
(). These limits improve upon previous limits by factors of . We also set 95\% confidence level upper limits on the frequency-dependent
strain amplitudes of quasimonochromatic gravitational waves coming from three
interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best
upper limits range from a factor of
improvement compared to previous stochastic radiometer searches.Comment: 23 Pages, 9 Figure
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