919 research outputs found
A synergistic mixture of diatomaceous earth and deltamethrin to control stored grain insects
In order to mitigate the negative effect of diatomaceous earth (DE) on bulk density and grain flowability, DE was mixed with other insecticides. This paper investigates the efficacy of a mixture of DE and deltamethrin against Sitophilus zeamais, the maize weevil, Rhyzopertha dominica, the lesser grain borer, and Tribolium castaneum, the red flour beetle. Five mixtures of DE and deltamethrin were prepared in the laboratory containing the same quantity of DE and different concentrations of the active ingredient of deltamethrin. The ratio of DE and deltamethrin in formulations were: DE 1 part: deltamethrin 0.00025, 0.00050, 0.00075, 0.0010 and 0.00125 parts. Co-toxicity and Co-efficient values higher than 100 (S. zeamais 170–386, R. dominica 188–601, and T. castaneum 157–285) indicated synergism between DE and deltamethrin.Keywords: Diatomaceous earth, Deltamethrin, Ready to use mixture, Co-toxicity, Co-efficient, Synergism, Grain insect pest
Tunable linear and quadratic optomechanical coupling for a tilted membrane within an optical cavity: theory and experiment
We present an experimental study of an optomechanical system formed by a
vibrating thin semi-transparent membrane within a high-finesse optical cavity.
We show that the coupling between the optical cavity modes and the vibrational
modes of the membrane can be tuned by varying the membrane position and
orientation. In particular we demonstrate a large quadratic dispersive
optomechanical coupling in correspondence with avoided crossings between
optical cavity modes weakly coupled by scattering at the membrane surface. The
experimental results are well explained by a first order perturbation treatment
of the cavity eigenmodes.Comment: 10 pages, 6 figure
Time-Resolved Studies of Stick-Slip Friction in Sheared Granular Layers
Sensitive and fast force measurements are performed on sheared granular
layers undergoing stick-slip motion, along with simultaneous imaging. A full
study has been done for spherical particles with a +-20% size distribution.
Stick-slip motion due to repetitive fluidization of the layer occurs for low
driving velocities. Between major slip events, slight creep occurs that is
variable from one event to the next. The effects of changing the stiffness k
and velocity V of the driving system are studied in detail. The stick-slip
motion is almost periodic for spherical particles over a wide range of
parameters, but becomes irregular when k is large and V is relatively small. At
larger V, the motion becomes smoother and is affected by the inertia of the
upper plate bounding the layer. Measurements of the period T and amplitude A of
the relative motion are presented as a function of V. At a critical value Vc, a
transition to continuous sliding motion occurs that is discontinuous for k not
too large. The time dependence of the instantaneous velocity of the upper plate
and the frictional force produced by the granular layer are determined within
individual slipping events. The force is a multi-valued function of the
instantaneous velocity, with pronounced hysteresis and a sudden drop prior to
resticking. Measurements of vertical displacement reveal a small dilation of
the material (about one tenth of the mean particle size in a layer 20 particles
deep) associated with each slip event. Finally, optical imaging reveals that
localized microscopic rearrangements precede (and follow) each slip event. The
behavior of smooth particles is contrasted with that of rough particles.Comment: 20, pages, 17 figures, to appear in Phys. Rev.
The Generalized Star Product and the Factorization of Scattering Matrices on Graphs
In this article we continue our analysis of Schr\"odinger operators on
arbitrary graphs given as certain Laplace operators. In the present paper we
give the proof of the composition rule for the scattering matrices. This
composition rule gives the scattering matrix of a graph as a generalized star
product of the scattering matrices corresponding to its subgraphs. We perform a
detailed analysis of the generalized star product for arbitrary unitary
matrices. The relation to the theory of transfer matrices is also discussed
Surface Roughness and Effective Stick-Slip Motion
The effect of random surface roughness on hydrodynamics of viscous
incompressible liquid is discussed. Roughness-driven contributions to
hydrodynamic flows, energy dissipation, and friction force are calculated in a
wide range of parameters. When the hydrodynamic decay length (the viscous wave
penetration depth) is larger than the size of random surface inhomogeneities,
it is possible to replace a random rough surface by effective stick-slip
boundary conditions on a flat surface with two constants: the stick-slip length
and the renormalization of viscosity near the boundary. The stick-slip length
and the renormalization coefficient are expressed explicitly via the
correlation function of random surface inhomogeneities. The effective
stick-slip length is always negative signifying the effective slow-down of the
hydrodynamic flows by the rough surface (stick rather than slip motion). A
simple hydrodynamic model is presented as an illustration of these general
hydrodynamic results. The effective boundary parameters are analyzed
numerically for Gaussian, power-law and exponentially decaying correlators with
various indices. The maximum on the frequency dependence of the dissipation
allows one to extract the correlation radius (characteristic size) of the
surface inhomogeneities directly from, for example, experiments with torsional
quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure
Dynamic response of HTS composite tapes to pulsed currents
Dynamic voltage-current characteristics of an HTS Ag/BiSCCO composite tape
are studied both experimentally and theoretically. The tape is subjected by
pulsed currents with different shapes and magnitude and voltage traces are
measured using the four-point method with different location of potential taps
on the sample surface. Clockwise and anticlockwise hysteresis loops are
obtained for the same sample depending on location of the potential taps. The
dynamic characteristics deviate substantially from the DC characteristic,
especially in the range of low voltages where a criterion for the critical
current value is usually chosen (1-10 mkV/cm). The critical current determined
from dynamic characteristics and its change with the pulse magnitude depend on
location of the potential taps and on the curve branch chosen for the critical
current determination (ascending or descending). The theoretical analysis is
based on a model of the magnetic flux diffusion into a composite tape for a
superconductor described by the flux creep characteristic. Numerical simulation
based on this model gives the results in good agreement with the experimental
ones and explains the observed peculiarities of the dynamic characteristics of
HTS composite tapes. The difference between the magnetic diffusion into a tape
and a slab is discussed.Comment: 18 pages, 13 figure
Importing genetically altered animals : ensuring quality
The reproducibility of research using laboratory animals requires reliable management of their quality, in particular of their genetics, health and environment, all of which contribute to their phenotypes. The point at which these biological materials are transferred between researchers is particularly sensitive, as it may result in a loss of integrity of the animals and/or their documentation. Here, we describe the various aspects of laboratory animal quality that should be confirmed when sharing rodent research models. We also discuss how repositories of biological materials support the scientific community to ensure the continuity of the quality of laboratory animals. Both the concept of quality and the role of repositories themselves extend to all exchanges of biological materials and all networks that support the sharing of these reagents.Peer reviewe
Inhibition of cathepsin B by caspase-3 inhibitors blocks programmed cell death in <i>Arabidopsis</i>
Programmed cell death (PCD) is used by plants for development and survival to biotic and abiotic stresses. The role of caspases in PCD is well established in animal cells. Over the past 15 years, the importance of caspase-3-like enzymatic activity for plant PCD completion has been widely documented despite the absence of caspase orthologues. In particular, caspase-3 inhibitors blocked nearly all plant PCD tested. Here, we affinity-purified a plant caspase-3-like activity using a biotin-labelled caspase-3 inhibitor and identified Arabidopsis thaliana cathepsin B3 (AtCathB3) by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Consistent with this, recombinant AtCathB3 was found to have caspase-3-like activity and to be inhibited by caspase-3 inhibitors. AtCathepsin B triple-mutant lines showed reduced caspase-3-like enzymatic activity and reduced labelling with activity-based caspase-3 probes. Importantly, AtCathepsin B triple mutants showed a strong reduction in the PCD induced by ultraviolet (UV), oxidative stress (H2O2, methyl viologen) or endoplasmic reticulum stress. Our observations contribute to explain why caspase-3 inhibitors inhibit plant PCD and provide new tools to further plant PCD research. The fact that cathepsin B does regulate PCD in both animal and plant cells suggests that this protease may be part of an ancestral PCD pathway pre-existing the plant/animal divergence that needs further characterisation
The Role of Eif6 in Skeletal Muscle Homeostasis Revealed by Endurance Training Co-expression Networks
Regular endurance training improves muscle oxidative capacity and reduces the risk of age-related disorders. Understanding the molecular networks underlying this phenomenon is crucial. Here, by exploiting the power of computational modeling, we show that endurance training induces profound changes in gene regulatory networks linking signaling and selective control of translation to energy metabolism and tissue remodeling. We discovered that knockdown of the mTOR-independent factor Eif6, which we predicted to be a key regulator of this process, affects mitochondrial respiration efficiency, ROS production, and exercise performance. Our work demonstrates the validity of a data-driven approach to understanding muscle homeostasis
The role of CO2 variability and exposure time for biological impacts of ocean acidification
Biological impacts of ocean acidification have mostly been studied using future levels of CO without consideration of natural variability or how this modulates both duration and magnitude of CO exposure. Here we combine results from laboratory studies on coral reef fish with diurnal in situ CO data from a shallow coral reef, to demonstrate how natural variability alters exposure times for marine organisms under increasingly high-CO conditions. Large in situ CO variability already results in exposure of coral reef fish to short-term CO levels higher than laboratory-derived critical CO levels (∼600 μatm). However, we suggest that the in situ exposure time is presently insufficient to induce negative effects observed in laboratory studies. Our results suggest that both exposure time and the magnitude of CO levels will be important in determining the response of organisms to future ocean acidification, where both will increase markedly with future increases in CO. Key Points Seawater CO2 variability alters in situ CO2 exposure time and magnitude Fish are presently exposed to short-term CO2 levels above critical values Acidification experiments should consider both CO2 level and exposure time
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