3,162 research outputs found
Is the fish-hook effect in hydrocyclones a real phenomenon?
Although the fish-hook effect has been reported by many for a very long time, scientists and practitioners
alike share contradictory opinions about this phenomenon. While some believe that it is of physical origin,
others opine that it is the result of measurement errors. This article investigates the possibility that the
fish-hook effect could indeed be measurement error related. Since all the experimental errors are embedded
in the raw size distribution measurements, the paper first lays down the steps that lead to estimation of the
partition function and confidence bounds, which are seldom reported in hydrocyclone literature, from the
errors associated with the experimental size distribution measurements. Using several data sets generated
using a 100 mm diameter hydrocyclone operating under controlled dilute to dense regimes, careful analysis
of the partition functions following the developed methodology yields unambiguous evidence that the
fish-hook effect is a real physical phenomenon. An attempt is also made to reunite some of the major contradictory
views behind the existence of the fish-hook based on sound statistical arguments
β-adrenergic-mediated dynamic augmentation of sarcolemmal CaV 1.2 clustering and co-operativity in ventricular myocytes.
Key pointsPrevailing dogma holds that activation of the β-adrenergic receptor/cAMP/protein kinase A signalling pathway leads to enhanced L-type CaV 1.2 channel activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. However, the full mechanistic and molecular details underlying this phenomenon are incompletely understood. CaV 1.2 channel clusters decorate T-tubule sarcolemmas of ventricular myocytes. Within clusters, nanometer proximity between channels permits Ca2+ -dependent co-operative gating behaviour mediated by physical interactions between adjacent channel C-terminal tails. We report that stimulation of cardiomyocytes with isoproterenol, evokes dynamic, protein kinase A-dependent augmentation of CaV 1.2 channel abundance along cardiomyocyte T-tubules, resulting in the appearance of channel 'super-clusters', and enhanced channel co-operativity that amplifies Ca2+ influx. On the basis of these data, we suggest a new model in which a sub-sarcolemmal pool of pre-synthesized CaV 1.2 channels resides in cardiomyocytes and can be mobilized to the membrane in times of high haemodynamic or metabolic demand, to tune excitation-contraction coupling.AbstractVoltage-dependent L-type CaV 1.2 channels play an indispensable role in cardiac excitation-contraction coupling. Activation of the β-adrenergic receptor (βAR)/cAMP/protein kinase A (PKA) signalling pathway leads to enhanced CaV 1.2 activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. CaV 1.2 channels exhibit a clustered distribution along the T-tubule sarcolemma of ventricular myocytes where nanometer proximity between channels permits Ca2+ -dependent co-operative gating behaviour mediated by dynamic, physical, allosteric interactions between adjacent channel C-terminal tails. This amplifies Ca2+ influx and augments myocyte Ca2+ transient and contraction amplitudes. We investigated whether βAR signalling could alter CaV 1.2 channel clustering to facilitate co-operative channel interactions and elevate Ca2+ influx in ventricular myocytes. Bimolecular fluorescence complementation experiments reveal that the βAR agonist, isoproterenol (ISO), promotes enhanced CaV 1.2-CaV 1.2 physical interactions. Super-resolution nanoscopy and dynamic channel tracking indicate that these interactions are expedited by enhanced spatial proximity between channels, resulting in the appearance of CaV 1.2 'super-clusters' along the z-lines of ISO-stimulated cardiomyocytes. The mechanism that leads to super-cluster formation involves rapid, dynamic augmentation of sarcolemmal CaV 1.2 channel abundance after ISO application. Optical and electrophysiological single channel recordings confirm that these newly inserted channels are functional and contribute to overt co-operative gating behaviour of CaV 1.2 channels in ISO stimulated myocytes. The results of the present study reveal a new facet of βAR-mediated regulation of CaV 1.2 channels in the heart and support the novel concept that a pre-synthesized pool of sub-sarcolemmal CaV 1.2 channel-containing vesicles/endosomes resides in cardiomyocytes and can be mobilized to the sarcolemma to tune excitation-contraction coupling to meet metabolic and/or haemodynamic demands
Cloning and functional characterisation of the duplicated RDL subunits from the pea aphid, Acyrthosiphon pisum
The insect GABA receptor, RDL (resistance to dieldrin), is a cys-loop ligand-gated ion channel (cysLGIC) that plays central roles in neuronal signaling and is the target of several classes of insecticides. Many insects studied to date possess one Rdl gene, however, there is evidence of two Rdls in aphids. To further characterize this insecticide target from pests that cause millions of dollars’ worth of crop damage each year, we identified the complete cysLGIC gene superfamily of the pea aphid, Acyrthosiphon pisum, using BLAST analysis. This confirmed the presence of two Rdl-like genes (RDL1 and RDL2) that likely arose from a recent gene duplication. When expressed individually in Xenopus laevis oocytes, both subunits formed functional ion channels gated by GABA. Alternative splicing of RDL1 influenced the potency of GABA and the potency of fipronil was different on the RDL1bd splice variant and RDL2. Imidacloprid and clothianidin showed no antagonistic activity on RDL1 whilst 100 M thiacloprid reduced the GABA responses of RDL1 and RDL2 to 55% and 62%, respectively. It is concluded that gene duplication of Rdl may have conferred increased tolerance to natural insecticides and played a role in the evolution of insect cysLGICs
Study of Neutron-Induced Fission Cross Sections of U, Am, and Cm at n_TOF
Neutron induced fission cross sections of several isotopes have been measured at the
CERN n_TOF spallation neutron facility. Between them some measurements involve isotopes
(233U, 241Am, 243Am, 245Cm) relevant for applications to nuclear technologies. The n_TOF
facility delivers neutrons with high instantaneous flux and in a wide energy range, from thermal
up to 250 MeV. The experimental apparatus consists of an ionization chamber that discriminates
fission fragments and α particles coming from natural radioactivity of the samples. All the
measurements were performed referring to the standard cross section of 235U.European Commission Joint Research Centre European Community (EC) FIKW-CT-2000-0010
Enhanced wheat yield by biochar addition under different mineral fertilization levels
Climate change and global warming have worldwide
adverse consequences. Biochar production and its use in
agriculture can play a key role in climate change mitigation
and help improve the quality and management of waste materials
coming from agriculture and forestry. Biochar is a carbonaceous
material obtained from thermal decomposition of
residual biomass at relatively low temperature and under
oxygen limited conditions (pyrolysis). Biochar is currently a
subject of active research worldwide because it can constitute
a viable option for sustainable agriculture due to its potential
as a long-term sink for carbon in soil and benefits for crops.
However, to date, the results of research studies on biochar
effects on crop production show great variability, depending
on the biochar type and experimental conditions. Therefore, it
is important to identify the beneficial aspects of biochar addition
to soil on crop yield in order to promote the adoption of
this practice in agriculture. In this study, the effects of two
types of biochar from agricultural wastes typical of Southern
Spain: wheat straw and olive tree pruning, combined with
different mineral fertilization levels on the growth and yield
of wheat (Triticum durum L. cv. Vitron) were evaluated.
Durum wheat was pot-grown for 2 months in a growth chamber
on a soil collected from an agricultural field near Córdoba,
Southern Spain. Soil properties and plant growth variables
were studied in order to assess the agronomic efficiency of
biochar. Our results show that biochar addition to a nutrientpoor,
slightly acidic loamy sand soil had little effect on wheat
yield in the absence of mineral fertilization. However, at the
highest mineral fertilizer rate, addition of biochar led to about
20–30 % increase in grain yield compared with the use of the
mineral fertilizer alone. Both biochars acted as a source of
available P, which led to beneficial effects on crop production.
In contrast, the addition of biochar resulted in decreases in
available N and Mn. A maximum reduction in plant nutrient
concentration of 25 and 80% compared to nonbiochar-treated
soils for N and Mn, respectively, was detected. This fact was
related to the own nature of biochar: low available nitrogen
content, high adsorption capacity, and low mineralization rate
for N; and alkaline pH and high carbonate content for Mn. Our
results indicate that biochar-based soil management strategies
can enhance wheat production with the environmental benefits
of global warming mitigation. This can contribute positively
to the viability and benefits of agricultural production
systems. However, the nutrient–biochar interactions should
receive special attention due to the great variability in the
properties of biochar-type materials
Podoplanin Associates with CD44 to Promote Directional Cell Migration
Podoplanin, a cancer-associated glycoprotein, interacts with CD44. Both glycoproteins are coordinately upregulated during tumor progression. Podoplanin–CD44 interaction in the cell membrane occurs mainly in migrating cells, and it seems to be required for podoplanin-mediated cell migration and directionality
Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts
We outline the scientific motivation behind a search for gravitational waves
associated with short gamma ray bursts detected by the InterPlanetary Network
(IPN) during LIGO's fifth science run and Virgo's first science run. The IPN
localisation of short gamma ray bursts is limited to extended error boxes of
different shapes and sizes and a search on these error boxes poses a series of
challenges for data analysis. We will discuss these challenges and outline the
methods to optimise the search over these error boxes.Comment: Methods paper; Proceedings for Eduardo Amaldi 9 Conference on
Gravitational Waves, July 2011, Cardiff, U
Swift follow-up observations of candidate gravitational-wave transient events
We present the first multi-wavelength follow-up observations of two candidate
gravitational-wave (GW) transient events recorded by LIGO and Virgo in their
2009-2010 science run. The events were selected with low latency by the network
of GW detectors and their candidate sky locations were observed by the Swift
observatory. Image transient detection was used to analyze the collected
electromagnetic data, which were found to be consistent with background.
Off-line analysis of the GW data alone has also established that the selected
GW events show no evidence of an astrophysical origin; one of them is
consistent with background and the other one was a test, part of a "blind
injection challenge". With this work we demonstrate the feasibility of rapid
follow-ups of GW transients and establish the sensitivity improvement joint
electromagnetic and GW observations could bring. This is a first step toward an
electromagnetic follow-up program in the regime of routine detections with the
advanced GW instruments expected within this decade. In that regime
multi-wavelength observations will play a significant role in completing the
astrophysical identification of GW sources. We present the methods and results
from this first combined analysis and discuss its implications in terms of
sensitivity for the present and future instruments.Comment: Submitted for publication 2012 May 25, accepted 2012 October 25,
published 2012 November 21, in ApJS, 203, 28 (
http://stacks.iop.org/0067-0049/203/28 ); 14 pages, 3 figures, 6 tables;
LIGO-P1100038; Science summary at
http://www.ligo.org/science/Publication-S6LVSwift/index.php ; Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p110003
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
Sensitivity to Gravitational Waves from Compact Binary Coalescences Achieved during LIGO's Fifth and Virgo's First Science Run
We summarize the sensitivity achieved by the LIGO and Virgo gravitational
wave detectors for compact binary coalescence (CBC) searches during LIGO's
fifth science run and Virgo's first science run. We present noise spectral
density curves for each of the four detectors that operated during these
science runs which are representative of the typical performance achieved by
the detectors for CBC searches. These spectra are intended for release to the
public as a summary of detector performance for CBC searches during these
science runs.Comment: 12 pages, 5 figure
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