2,676 research outputs found
Finite-temperature critical point of a glass transition
We generalize the simplest kinetically constrained model of a glass-forming
liquid by softening kinetic constraints, allowing them to be violated with a
small finite rate. We demonstrate that this model supports a first-order
dynamical (space-time) phase transition, similar to those observed with hard
constraints. In addition, we find that the first-order phase boundary in this
softened model ends in a finite-temperature dynamical critical point, which we
expect to be present in natural systems. We discuss links between this critical
point and quantum phase transitions, showing that dynamical phase transitions
in dimensions map to quantum transitions in the same dimension, and hence
to classical thermodynamic phase transitions in dimensions. We make these
links explicit through exact mappings between master operators, transfer
matrices, and Hamiltonians for quantum spin chains.Comment: 10 pages, 5 figure
Natural and projectively equivariant quantizations by means of Cartan Connections
The existence of a natural and projectively equivariant quantization in the
sense of Lecomte [20] was proved recently by M. Bordemann [4], using the
framework of Thomas-Whitehead connections. We give a new proof of existence
using the notion of Cartan projective connections and we obtain an explicit
formula in terms of these connections. Our method yields the existence of a
projectively equivariant quantization if and only if an \sl(m+1,\R)-equivariant
quantization exists in the flat situation in the sense of [18], thus solving
one of the problems left open by M. Bordemann.Comment: 13 page
Генетический полиморфизм клонов и их семенного потомства в архивно-клоновой плантации плюсовых деревьев сосны обыкновенной
Изучена генетическая изменчивость по 12 аллозимным локусам (10 полиморфных) архивно-клоновой плантации 23 плюсовых деревьев Pinus sylvestris L. и их семенного потомства на юго-востоке Украины. Более половины клонов имели 4–8 гетерозиготных локусов, а их семенное потомство отличалось меньшим уровнем изменчивости, чем материнские растения. Семенное потомство получено от высокой доли ауткроссинга (tm = = 95 %). Для потомства клонов характерна повышенная доля нарушений сегрегации аллелей в мегагаметофитах и высокая встречаемость существенных отклонений в распределении генотипов зародышей семян от теоретически ожидаемого согласно закону Харди Вайнберга.Досліджено генетичну мінливість за 12 алозимними локусами (10 поліморфних) архівно-клонової плантації 23 плюсових дерев Pinus sylvestris L. та їх насіннєвого потомства на південному сході України. Понад половина клонів мали 4–8 гетерозиготних локусів, а їх насіннєве потомство відрізнялося нижчим рівнем мінливості, ніж материнські рослини. Насіннєве потомство отримано від високої частки ауткросинга (tm = 95 %). Для потомства клонів характерна підвищена частка порушень сегрегації алелів у мегагаметофітах і висока частота відхилень розподілу генотипів зародків насіння від очікуваного згідно з законом Харді-Вайнберга.Genetic variation at 12 allozyme loci (10 of them being polymorphic ones) has been studied in the archive-clone plantation of 23 Pinus sylvestris plus-trees and their seed progeny in the south-east of Ukraine. More than a half of clones had 4–8 heterozygous loci, whereas their seed progeny was marked by a lower variation than maternal trees. Seed progeny was obtained at a high outcrossing rate (tm= 95 %). The clone progeny was characterized by a high percentage of abnormal allele segregation in megagametophytes. There was also a high frequency of significant deviation in distribution of seed embryo genotypes from the theoretically expected one according to the Hardy-Weinberg law
Forest productivity decline caused by successional paludification of boreal soils
Long-term forest productivity decline in boreal forests has been extensively studied in the last decades, yet its causes are still unclear. Soil conditions associated with soil organic matter accumulation are thought to be responsible for site productivity decline. The objectives of this study were to determine if paludification of boreal soils resulted in reduced forest productivity, and to identify changes in the physical and chemical properties of soils associated with reduction in productivity. We used a chronosequence of 23 black spruce stands ranging in postfire age from 50 to 2350 years and calculated three different stand productivity indices, including site index. We assessed changes in forest productivity with time using two complementary approaches: (1) by comparing productivity among the chronosequence stands and (2) by comparing the productivity of successive cohorts of trees within the same stands to determine the influence of time independently of other site factors. Charcoal stratigraphy indicates that the forest stands differ in their fire history and originated either from high- or low-severity soil burns. Both chronosequence and cohort approaches demonstrate declines in black spruce productivity of 50-80% with increased paludification, particularly during the first centuries after fire. Paludification alters bryophyte abundance and succession, increases soil moisture, reduces soil temperature and nutrient availability, and alters the vertical distribution of roots. Low-severity soil burns significantly accelerate rates of paludification and productivity decline compared with high-severity fires and ultimately reduce nutrient content in black spruce needles. The two combined approaches indicate that paludification can be driven by forest succession only, independently of site factors such as position on slope. This successional paludification contrasts with edaphic paludification, where topography and drainage primarily control the extent and rate of paludification. At the landscape scale, the fire regime (frequency and severity) controls paludification and forest productivity through its effect on soil organic layers. Implications for global carbon budgets and sustainable forestry are discussed
Observation of resonance trapping in an open microwave cavity
The coupling of a quantum mechanical system to open decay channels has been
theoretically studied in numerous works, mainly in the context of nuclear
physics but also in atomic, molecular and mesoscopic physics. Theory predicts
that with increasing coupling strength to the channels the resonance widths of
all states should first increase but finally decrease again for most of the
states. In this letter, the first direct experimental verification of this
effect, known as resonance trapping, is presented. In the experiment a
microwave Sinai cavity with an attached waveguide with variable slit width was
used.Comment: to be published in Phys. Rev. Let
Mobile Intervention for Individuals With Psychosis, Dual Disorders, and Their Common Comorbidities: A Literature Review.
Over 50% of people diagnosed with a severe mental illness, such as schizophrenia or bipolar disorder, will meet criteria for a substance use disorder in their lifetime. This dual disorder often starts during youth and leads to significant societal costs, including lower employability rates, more hospitalizations, and higher risk of homelessness and of suicide attempts when compared to those with a serious mental illness without substance misuse. Moreover, many individuals presenting with comorbid disorders also present with other psychological difficulties as well, such as personality disorders or anxiety and depression, also known as complex comorbid disorders. Transdiagnostic treatments that focus on core difficulties found in people with complex dual disorders, such as emotional regulation, are direly needed. Emotional regulation skills can help reduce distress related to psychotic symptoms and maintain abstinence in substance use disorders. New technologies in the field of communications have developed considerably over the past decade and have the potential to improve access to such treatments, a major problem in many health care settings. As such, this paper aims at: presenting core difficulties present in many individuals with dual disorders, reviewing the scientific literature pertaining to the use of mobile applications in mental health and addictions, and presenting the development and potential of a new application for emotional regulation for people with dual disorders
Resonance trapping and saturation of decay widths
Resonance trapping appears in open many-particle quantum systems at high
level density when the coupling to the continuum of decay channels reaches a
critical strength. Here a reorganization of the system takes place and a
separation of different time scales appears. We investigate it under the
influence of additional weakly coupled channels as well as by taking into
account the real part of the coupling term between system and continuum. We
observe a saturation of the mean width of the trapped states. Also the decay
rates saturate as a function of the coupling strength. The mechanism of the
saturation is studied in detail. In any case, the critical region of
reorganization is enlarged. When the transmission coefficients for the
different channels are different, the width distribution is broadened as
compared to a chi_K^2 distribution where K is the number of channels. Resonance
trapping takes place before the broad state overlaps regions beyond the
extension of the spectrum of the closed system.Comment: 18 pages, 8 figures, accepted by Phys. Rev.
Not gate in a cis-trans photoisomerization model
We numerically study the implementation of a NOT gate by laser pulses in a
model molecular system presenting two electronic surfaces coupled by non
adiabatic interactions. The two states of the bit are the fundamental states of
the cis-trans isomers of the molecule. The gate is classical in the sense that
it involves a one-qubit flip so that the encoding of the outputs is based on
population analysis which does not take the phases into account. This gate can
also be viewed as a double photo-switch process with the property that the same
electric field controls the two isomerizations. As an example, we consider
one-dimensional cuts in a model of the retinal in rhodopsin already proposed in
the literature. The laser pulses are computed by the Multi Target Optimal
Control Theory with chirped pulses as trial fields. Very high fidelities are
obtained. We also examine the stability of the control when the system is
coupled to a bath of oscillators modelled by an Ohmic spectral density. The
bath correlation time scale being smaller than the pulse duration the dynamics
is carried out in the Markovian approximation.Comment: 29 pages, 7 figure
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