2,082 research outputs found
Partial inhibition of ABA-induced stomatal closure by calcium-channel blockers.
ABA-induced increases in [Ca2+]cyt (cytosolic free Ca2+) may result from Ca2+ influx from the apoplast and/or release from intracellular stores. In this paper, Ca2+-channel blockers have been used to investigate this question in the detached epidermis of Commelina communis. Examples from the benzothiazepine, dihydropyridine and phenylalkylamine series all inhibited ABA-induced stomatal closure: (+/-) verapamil > nifedipine > diltiazem. Inhibition was partial, the magnitude of the effect being dependent on both the concentration of ABA and that of the channel blocker. The maximum inhibition observed in the presence of 100 nM ABA was approximately 66% at high (100 nM) concentrations of (+/-) verapamil or nifedipine. In the near absence of extracellular Ca2+ (2 mM EGTA) ABA-induced stomatal closure was reduced by approximately 22% and the inhibition by Ca2+-channel blockers abolished. Inhibition by (+/-) verapamil was totally reversible and exhibited signs of stereospecificity, the s(-) enantiomer being a more potent inhibitor of ABA-induced stomatal closure than the R(+) enantiomer. Bay K 8644 (a fluorinated analogue of nifedipine) exhibited biphasic action on 500 uM Ca2+-induced stomatal closure, i.e. agonistic at low concentrations (10 nM), antagonistic at high concentrations (> 10 nM to 100 uM), but did not affect ABA-induced stomatal closure. These results suggest that Ca2+ release from intracellular stores may be important in the ABA-induced increase in [Ca2+]cyt associated with stomatal closure. They do not, however, exclude a contribution of Ca2+ influx from the apoplast
Characterization of the glass transition in vitreous silica by temperature scanning small-angle X-ray scattering
The temperature dependence of the x-ray scattering in the region below the
first sharp diffraction peak was measured for silica glasses with low and high
OH content (GE-124 and Corning 7980). Data were obtained upon scanning the
temperature at 10, 40 and 80 K/min between 400 K and 1820 K. The measurements
resolve, for the first time, the hysteresis between heating and cooling through
the glass transition for silica glass, and the data have a better signal to
noise ratio than previous light scattering and differential thermal analysis
data. For the glass with the higher hydroxyl concentration the glass transition
is broader and at a lower temperature. Fits of the data to the
Adam-Gibbs-Fulcher equation provide updated kinetic parameters for this very
strong glass. The temperature derivative of the observed X-ray scattering
matches that of light scattering to within 14%.Comment: EurophysicsLetters, in pres
Three-Body approach to the K^- d Scattering Length in Particle Basis
We report on the first calculation of the scattering length A_{K^-d} based on
a relativistic three-body approach where the two-body input amplitudes coupled
to the Kbar N channels have been obtained with the chiral SU(3) constraint, but
with isospin symmetry breaking effects taken into account. Results are compared
with a recent calculation applying a similar set of two-body amplitudes,based
on the fixed center approximation, considered as a good approximation for a
loosely bound target, and for which we find significant deviations from the
exact three-body results. Effects of the hyperon-nucleon interaction, and
deuteron -wave component are also evaluated.Comment: 5 pages, Submitted to Phys. Rev.
Communicating Hunger and Satiation in the First Two Years of Life: A Systematic Review
Responsive feeding has been identified as important in preventing overconsumption by infants. However, this is predicated on an assumption that parents recognise and respond to infant feeding cues. Despite this, relatively little is understood about how infants engage parental feeding responses. Therefore the aim of this systematic review was to identify what is known about infant communication of hunger and satiation and what issues impact on the expression and perception of these states. A search of Medline, CINAHL, Web of Science, PsycINFO, Science Direct and Maternal and Infant care produced 27 papers. Eligibility criteria included: peer reviewed qualitative and/or quantitative publications on feeding behaviours, hunger, satiation/satiety cues of typically developing children in the first two years of life. Papers published between 1966 and 2013 were included in the review. The review revealed that feeding cues and behaviours are shaped by numerous issues, such as infants’ physical attributes, individual psychological factors and environmental factors. Meanwhile, infant characteristics, external cues and mothers’ own characteristics affect how feeding cues are perceived. The existing literature provides insights into many aspects of hunger and satiation in infancy; however, there are significant gaps in our knowledge. There is a lack of validated tools for measuring hunger and satiation, a need to understand how different infant characteristics impact on feeding behaviour and a need to extricate the respective contributions of infant and maternal characteristics to perceptions of hunger and satiation. Further research is also recommended to differentiate between feeding driven by liking and that driven by hunger
In situ measurements of density fluctuations and compressibility in silica glass as a function of temperature and thermal history
In this paper, small-angle X-ray scattering measurements are used to
determine the different compressibility contributions, as well as the
isothermal compressibility, in thermal equilibrium in silica glasses having
different thermal histories. Using two different methods of analysis, in the
supercooled liquid and in the glassy state, we obtain respectively the
temperature and fictive temperature dependences of the isotheraml
compressibility. The values obtained in the glass and supercooled liquid states
are very close to each other. They agree with previous determinations of the
literature. The compressibility in the glass state slightly decreases with
increasing fictive temperature. The relaxational part of the compressibility is
also calculated and compared to previous determinations. We discussed the small
differences between the different determinations
Statistical Mechanics in the Extended Gaussian Ensemble
The extended gaussian ensemble (EGE) is introduced as a generalization of the
canonical ensemble. The new ensemble is a further extension of the Gaussian
ensemble introduced by J. H. Hetherington [J. Low Temp. Phys. {\bf 66}, 145
(1987)]. The statistical mechanical formalism is derived both from the analysis
of the system attached to a finite reservoir and from the Maximum Statistical
Entropy Principle. The probability of each microstate depends on two parameters
and which allow to fix, independently, the mean energy of the
system and the energy fluctuations respectively. We establish the Legendre
transform structure for the generalized thermodynamic potential and propose a
stability criterion. We also compare the EGE probability distribution with the
-exponential distribution. As an example, an application to a system with
few independent spins is presented.Comment: Revtex 4, 8 pages, 8 figure
Evaluation of flight foods under hypokinetic conditions, part 2, chapters 4 and 5
Effects of weightlessness on body temperature and heart rate determined by 56 day bed rest stud
Carbon Foot-print Analysis and Life Cycle Assessment of Mayonnaise production. A comparison of their results and messages
Carbon Foot-print Analysis and Life Cycle Assessment of Mayonnaise production. A comparison of their results and messages
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