937 research outputs found
QCD corrections to the electric dipole moment of the neutron in the MSSM
We consider the QCD corrections to the electric dipole moment of the neutron
in the Minimal Supersymmetric Standard Model. We provide a master formula for
the Wilson coefficients at the low energy scale including for the first time
the mixing between the electric and chromoelectric operators and correcting
widely used previous LO estimates. We show that, because of the mixing between
the electric and chromoelectric operators, the neutralino contribution is
always strongly suppressed. We find that, in general, the effect of the QCD
corrections is to reduce the amount of CP violation generated at the high
scale. We discuss the perturbative uncertainties of the LO computation, which
are particularly large for the gluino-mediated contribution. This motivates our
Next-to-Leading order analysis. We compute for the first time the order alpha_s
corrections to the Wilson coefficients for the gluino contributions, and
recompute the two-loop anomalous dimension for the dipole operators. We show
that the large LO uncertainty disappears once NLO corrections are taken into
account.Comment: 23 pages, 5 figures, added references, corrected typo
Irreversible and reversible modes of operation of deterministic ratchets
We discuss a problem of optimization of the energetic efficiency of a simple
rocked ratchet. We concentrate on a low-temperature case in which the
particle's motion in a ratchet potential is deterministic. We show that the
energetic efficiency of a ratchet working adiabatically is bounded from above
by a value depending on the form of ratchet potential. The ratchets with
strongly asymmetric potentials can achieve ideal efficiency of unity without
approaching reversibility. On the other hand we show that for any form of the
ratchet potential a set of time-protocols of the outer force exist under which
the operation is reversible and the ideal value of efficiency is also achieved.
The mode of operation of the ratchet is still quasistatic but not adiabatic.
The high values of efficiency can be preserved even under elevated
temperatures
Subjective and objective assessment of physical activity in multiple sclerosis and their relation to health-related quality of life
Background Physical activity (PA) is frequently restricted in people with
multiple sclerosis (PwMS) and aiming to enhance PA is considered beneficial in
this population. We here aimed to explore two standard methods (subjective
plus objective) to assess PA reduction in PwMS and to describe the relation of
PA to health-related quality of life (hrQoL). Methods PA was objectively
measured over a 7-day period in 26 PwMS (EDSS 1.5–6.0) and 30 matched healthy
controls (HC) using SenseWear mini® armband (SWAmini) and reported as step
count, mean total and activity related energy expenditure (EE) as well as time
spent in PA of different intensities. Measures of EE were also derived from
self-assessment with IPAQ (International Physical Activity Questionnaire) long
version, which additionally yielded information on the context of PA and a
classification into subjects’ PA levels. To explore the convergence between
both types of assessment, IPAQ categories (low, moderate, high) were related
to selected PA parameters from objective assessment using ANOVA. Group
differences and associated effect sizes for all PA parameters as well as their
relation to clinical and hrQoL measures were determined. Results Both, SWAmini
and IPAQ assessment, captured differences in PA between PwMS and HC. IPAQ
categories fit well with common cut-offs for step count (p = 0.002) and mean
METs (p = 0.004) to determine PA levels with objective devices. Correlations
between specifically matched pairs of IPAQ and SWAmini parameters ranged
between r .288 and r .507. Concerning hrQoL, the lower limb mobility subscore
was related to four PA measures, while a relation with patients’ report of
general contentment was only seen for one. Conclusions Both methods of
assessment seem applicable in PwMS and able to describe reductions in daily PA
at group level. Whether they can be used to track individual effects of
interventions to enhance PA levels needs further exploration. The relation of
PA measures with hrQoL seen with lower limb mobility suggests lower limb
function not only as a major target for intervention to increase PA but also
as a possible surrogate for PA changes
Generalized stochastic Schroedinger equations for state vector collapse
A number of authors have proposed stochastic versions of the Schr\"odinger
equation, either as effective evolution equations for open quantum systems or
as alternative theories with an intrinsic collapse mechanism. We discuss here
two directions for generalization of these equations. First, we study a general
class of norm preserving stochastic evolution equations, and show that even
after making several specializations, there is an infinity of possible
stochastic Schr\"odinger equations for which state vector collapse is provable.
Second, we explore the problem of formulating a relativistic stochastic
Schr\"odinger equation, using a manifestly covariant equation for a quantum
field system based on the interaction picture of Tomonaga and Schwinger. The
stochastic noise term in this equation can couple to any local scalar density
that commutes with the interaction energy density, and leads to collapse onto
spatially localized eigenstates. However, as found in a similar model by
Pearle, the equation predicts an infinite rate of energy nonconservation
proportional to , arising from the local double commutator in
the drift term.Comment: 24 pages Plain TeX. Minor changes, some new references. To appear in
Journal of Physics
Climate change and water resources in arid regions : uncertainty of the baseline time period
Recent climate change studies have given a lot of attention to the uncertainty that stems from general circulation models (GCM), greenhouse gas emission scenarios, hydrological models and downscaling approaches. Yet, the uncertainty that stems from the selection of the baseline period has not been studied. Accordingly, the main research question is as follows: What would be the differences and/or the similarities in the evaluation of climate change impacts between the GCM and the delta perturbation scenarios using different baseline periods? This article addresses this issue through comparison of the results of two different baseline periods, investigating the uncertainties in evaluating climate change impact on the hydrological characteristics of arid regions. The Lower Zab River Basin (Northern Iraq) has been selected as a representative case study. The research outcomes show that the considered baseline periods suggest increases and decreases in the temperature and precipitation (P), respectively, over the 2020, 2050 and 2080 periods. The two climatic scenarios are likely to lead to similar reductions in the reservoir mean monthly flows, and subsequently, their maximum discharge is approximately identical. The predicted reduction in the inflow for the 2080–2099 time period fluctuates between 31 and 49% based on SRA1B and SRA2 scenarios, respectively. The delta perturbation scenario permits the sensitivity of the climatic models to be clearly determined compared to the GCM. The former allows for a wide variety of likely climate change scenarios at the regional level and are easier to generate and apply so that they could complement the latter
KK Parity in Warped Extra Dimension
We construct models with a Kaluza-Klein (KK) parity in a five- dimensional
warped geometry, in an attempt to address the little hierarchy problem present
in setups with bulk Standard Model fields. The lightest KK particle (LKP) is
stable and can play the role of dark matter. We consider the possibilities of
gluing two identical slices of 5D AdS in either the UV (IR-UV-IR model) or the
IR region (UV-IR-UV model) and discuss the model-building issues as well as
phenomenological properties in both cases. In particular, we find that the
UV-IR-UV model is not gravitationally stable and that additional mechanisms
might be required in the IR-UV-IR model in order to address flavor issues.
Collider signals of the warped KK parity are different from either the
conventional warped extra dimension without KK parity, in which the new
particles are not necessarily pair-produced, or the KK parity in flat universal
extra dimensions, where each KK level is nearly degenerate in mass. Dark matter
and collider properties of a TeV mass KK Z gauge boson as the LKP are
discussed.Comment: 35 pages, 11 figure
Sheehan's like syndrome in a man
An 84-year-old physician self-diagnosed that he had a pituitary tumour when he was found to have a bilateral upper quadrantanopia on routine eye testing. Magnetic resonance imaging (MRI) confirmed a large non-functioning pituitary macroadenoma associated with chiasmal compression. Investigation showed partial hypopituitarism with disconnection hyperprolactinaemia [prolactin 1095 mU/L (60–300)]. He was treated with hormonal replacement consisting of thyroxin 100 µg and prednisolone 3 mg and was offered transphenoidal hypophysectomy, but chose a conservative approach. Two years later, his visual fields worsened (Figure 1A) corresponding to an increase in macrodenoma size. Subsequently, he fell and fractured his left shoulder, which became infected, requiring surgery. Immediately after the shoulder surgery, he became hypotensive and vomited several times, and his visual fields became restricted. MRI showed pituitary infarction (Figure 1B), and he did not require surgical intervention. A few weeks later, he noticed dramatic improvement in his vision. His prolactin level dropped from a peak level of 1095 to 48 mU/L (60–300), suggesting lactotroph infarction. Repeated pituitary MRI showed dramatic reduction in the height of the pituitary macroadenoma consistent with the improvement in his visual fields (Figure 1C)
The importance of interocean exchange south of Africa in a numerical model
A fine resolution numerical model of the Southern Ocean (the Fine Resolution Antarctic Model (FRAM)) has been used to investigate the way in which heat is supplied to the South Atlantic. The heat budget in the model is compared with other estimates and is found to be broadly realistic. The temperature structure in the Atlantic, and therefore the meridional heat transport, depend heavily on the input of heat from the Indian Ocean via the Agulhas Retroflection region. FRAM is compared with three models which do not exhibit a significant input of heat from the Indian Ocean. These models also have a lower equatorward heat transport in the South Atlantic. Horizontal resolution affects the amount of Agulhas transfer with coarser resolution leading to lower heat transport in the Atlantic, a result which has implications for ocean models used in climate simulations
Housework by Husbands Determinants and Implications
WOMEN continue to carry disproportionate responsibility for household tasks. A study of 650 Detroit women reveals that attitudes, employment status, life cycle, and husband's income all contribute to husband's housework effort. Some evidence is presented that the greater the earnings differential of husband over wife, the less he contributes in help at home.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67012/2/10.1177_0192513X8100200207.pd
Association between objectively measured physical activity and opioid, hypnotic, or anticholinergic medication use in older people – data from the Physical Activity Cohort Scotland study
Background: Centrally acting medications cause cognitive slowing and incoordination, which could reduce older people’s physical activity levels. This association has not been studied previously.Objectives: To examine the association between opioid, hypnotic and anticholinergic medication, and objectively measured physical activity, in a cohort of older people.Methods: We used data from the Physical Activity Cohort Scotland, a representative cohort of community-dwelling older people aged 65 and over who were assessed at baseline and again 2-3 years later. Objective physical activity was measured using Stayhealthy RT3 accelerometers over 7 days. Baseline medication use (opioid use, hypnotic use, modified anticholinergic risk score [mARS]) was obtained from linked, routinely collected community prescribing records. Cross-sectional and longitudinal associations between baseline medication use and both baseline activity and change in activity over time were analysed using unadjusted and adjusted linear regression models.Results: 310 participants were included in the analysis; mean age 77 (SD 7) years. No association was seen between baseline use of any medication class and baseline physical activity levels in unadjusted or adjusted models. For change in activity over time, there was no difference between users and non-users of hypnotics or opioids. Higher anticholinergic burden was associated with a steeper decline in activity over the follow up period (mARS=0: -7051 counts/24h/yr; mARS=1-2 -15942 counts/24h/yr; mARS>=3 -19544 counts/24h/yr; p=0.03) and this remained robust to multiple adjustments.Conclusion: Anticholinergic burden is associated with greater decline in objectively measured physical activity over time in older people, a finding not seen with hypnotic or opioid use
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