11,663 research outputs found
Defect-dependent colossal negative thermal expansion in UiO-66(Hf) metal-organic framework
Thermally-densified hafnium terephthalate UiO-66(Hf) is shown to exhibit the
strongest isotropic negative thermal expansion (NTE) effect yet reported for a
metal-organic framework (MOF). Incorporation of correlated vacancy defects
within the framework affects both the extent of thermal densification and the
magnitude of NTE observed in the densified product. We thus demonstrate that
defect inclusion can be used to tune systematically the physical behaviour of a
MOF.Comment: 8 pages, 4 figures, revise
Ratio control in a cascade model of cell differentiation
We propose a kind of reaction-diffusion equations for cell differentiation,
which exhibits the Turing instability. If the diffusivity of some variables is
set to be infinity, we get coupled competitive reaction-diffusion equations
with a global feedback term. The size ratio of each cell type is controlled by
a system parameter in the model. Finally, we extend the model to a cascade
model of cell differentiation. A hierarchical spatial structure appears as a
result of the cell differentiation. The size ratio of each cell type is also
controlled by the system parameter.Comment: 13 pages, 7 figure
The effect of seed moisture content and hot water treatment on carrot seed viability and Alternaria radicina control
Hot water treatment of seeds to control seedborne pathogens is an important tool for organic seed
production. Reducing seed moisture content may have the potential to increase carrot (Daucus carota L. var. sativus D.C.) seed tolerance to treatment. Two hot water seed treatment experiments were conducted
The effect of seed moisture content and the duration and temperature of hot water treatment on carrot seed viability and the control of Alternaria Radicina
Hot water treatment of seeds to control seedborne pathogens is an important tool for organic seed
production. Reducing seed moisture content may have the potential to increase carrot (Daucus carota
L. var. sativus D.C.) seed tolerance to treatment. Two hot water seed treatment experiments were
conducted. The first studied the effect of seed moisture content (SMC), treatment temperature and
treatment duration on germination. Maximum safe treatment temperature and durations were
established at 50°C and 30-40 min. Germination decreased slightly from 68% at 5% SMC to 63% at
20% SMC (LSD 1.2) for all durations. The second experiment studied the effect of initial SMC and
treatment durations on infestation of seed by Alternaria radicina and seed germination. Treatment at
50°C for 30 min for all SMC compared to the control resulted in a decrease in A. radicina infestation
from 69.2 to 1.7%. Reducing SMC from 20 to 5% for all durations resulted in a small decrease in
infestation from 25% to 18% (LSD 1.5). Reducing SMC to 5% prior to hot water treatment may be a
commercially viable means of minimising reductions in seed viability and decreasing fungal
infestation levels
Counselling in primary care : a systematic review of the evidence
Primary objective: To undertake a systematic review which aimed to locate, appraise and synthesise evidence to obtain a reliable overview of the clinical effectiveness, cost-effectiveness and user perspectives regarding counselling in primary care.
Main results: Evidence from 26 studies was presented as a narrative synthesis and demonstrated that counselling is effective in the short term, is as effective as CBT with typical heterogeneous primary care populations and more effective than routine primary care for the treatment of non-specific generic psychological problems, anxiety and depression. Counselling may reduce levels of referrals to psychiatric services, but does not appear to reduce medication, the number of GP consultations or overall
costs. Patients are highly satisfied with the counselling they have received in primary care and prefer counselling to medication for depression.
Conclusions and implications for future research: This review demonstrates the value of counselling as a valid
choice for primary care patients and as a broadly effective therapeutic intervention for a wide range of generic psychological conditions presenting in the primary care setting. More rigorous clinical and cost-effectiveness trials are needed together with surveys of more typical users of primary care services
Mapping the Secular Resonance for Retrograde Irregular Satellites
Constructing dynamical maps from the filtered output of numerical
integrations, we analyze the structure of the secular resonance for
fictitious irregular satellites in retrograde orbits. This commensurability is
associated to the secular angle , where
is the longitude of pericenter of the satellite and
corresponds to the (fixed) planetocentric orbit of the Sun. Our study is
performed in the restricted three-body problem, where the satellites are
considered as massless particles around a massive planet and perturbed by the
Sun. Depending on the initial conditions, the resonance presents a diversity of
possible resonant modes, including librations of around zero (as found
for Sinope and Pasiphae) or 180 degrees, as well as asymmetric librations (e.g.
Narvi). Symmetric modes are present in all giant planets, although each regime
appears restricted to certain values of the satellite inclination. Asymmetric
solutions, on the other hand, seem absent around Neptune due to its almost
circular heliocentric orbit. Simulating the effects of a smooth orbital
migration on the satellite, we find that the resonance lock is preserved as
long as the induced change in semimajor axis is much slower compared to the
period of the resonant angle (adiabatic limit). However, the librational mode
may vary during the process, switching between symmetric and asymmetric
oscillations. Finally, we present a simple scaling transformation that allows
to estimate the resonant structure around any giant planet from the results
calculated around a single primary mass.Comment: 11 pages, 13 figure
A long-lived horseshoe companion to the Earth
We present a dynamical investigation of a newly found asteroid, 2010 SO16,
and the discovery that it is a horseshoe companion of the Earth. The object's
absolute magnitude (H=20.7) makes this the largest object of its type known
to-date. By carrying out numerical integrations of dynamical clones, we find
that (a) its status as a horseshoe is secure given the current accuracy of its
ephemeris, and (b) the time spent in horseshoe libration with the Earth is
several times 10^5 yr, two orders of magnitude longer than determined for other
horseshoe asteroids of the Earth. Further, using a model based on Hill's
approximation to the three-body problem, we show that, apart from the low
eccentricity which prevents close encounters with other planets or the Earth
itself, its stability can be attributed to the value of its Jacobi constant far
from the regime that allows transitions into other coorbital modes or escape
from the resonance altogether. We provide evidence that the eventual escape of
the asteroid from horseshoe libration is caused by the action of planetary
secular perturbations and the stochastic evolution of the eccentricity. The
questions of its origin and the existence of as-yet-undiscovered co-orbital
companions of the Earth are discussed.Comment: Accepted in MNRAS; 6 pages, 3 figures, 2 table
What Can We Conclude from Death Registration? Improved Methods for Evaluating Completeness
Julie Rajaratnam and colleagues evaluate the performance of a suite of demographic methods that estimate the fraction of deaths registered and counted by civil registration systems, and identify three variants that generally perform the best
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