41 research outputs found
Massive CP theory from a microscopic model for doped antiferromagnets
A path-integral for the t-J model in two dimensions is constructed based on
Dirac quantization, with an action found originally by Wiegmann (Phys. Rev.
Lett. {\bf 60}, 821 (1988); Nucl. Phys. B323, 311 (1989)). Concentrating on the
low doping limit, we assume short range antiferromagnetic order of the spin
degrees of freedom. Going over to a local spin quantization axis of the dopant
fermions, that follows the spin degree of freedom, staggered CP fields
result and the constraint against double occupancy can be resolved. The
staggered CP fields are split into slow and fast modes, such that after a
gradient expansion, and after integrating out the fast modes and the dopant
fermions, a CP field-theory with a massive gauge field is obtained that
describes generically incommensurate coplanar magnetic structures, as discussed
previously in the context of frustrated quantum antiferromagnets. Hence, the
possibility of deconfined spinons is opened by doping a colinear
antiferromagnet.Comment: 24 pages, no figure
The , interaction in finite volume and the resonance
In this work the interaction of the coupled channels and
in an SU(4) extrapolation of the chiral unitary theory, where the
resonance appears as dynamically generated from that
interaction, is extended to produce results in finite volume. Energy levels in
the finite box are evaluated and, assuming that they would correspond to
lattice results, the inverse problem of determining the phase shifts in the
infinite volume from the lattice results is solved. We observe that it is
possible to obtain accurate phase shifts and the position of the
resonance, but it requires the explicit consideration of the
two coupled channels. We also observe that some of the energy levels in the box
are attached to the closed channel, such that their use to induce the phase shifts via L\"uscher's formula leads to incorrect results.Comment: 10 pages, 13 figures, accepted for publication in Eur. Phys. J.
Scalar mesons moving in a finite volume and the role of partial wave mixing
Phase shifts and resonance parameters can be obtained from finite-volume
lattice spectra for interacting pairs of particles, moving with nonzero total
momentum. We present a simple derivation of the method that is subsequently
applied to obtain the pi pi and pi K phase shifts in the sectors with total
isospin I=0 and I=1/2, respectively. Considering different total momenta, one
obtains extra data points for a given volume that allow for a very efficient
extraction of the resonance parameters in the infinite-volume limit.
Corrections due to the mixing of partial waves are provided. We expect that our
results will help to optimize the strategies in lattice simulations, which aim
at an accurate determination of the scattering and resonance properties.Comment: 19 pages, 12 figure
Characterization of the adaptive response of grapevine (cv. Tempranillo) to UV-B radiation under water deficit conditions
This work aims to characterize the physiological response of grapevine (Vitis vinifera L.) cv. Tempranillo to UV-B radiation under water deficit conditions. Grapevine fruit-bearing cuttings were exposed to three levels of supplemental biologically effective UV-B radiation (0, 5.98 and 9.66 kJ mâ2 dayâ1) and two water regimes (well watered and water deficit), in a factorial design, from fruit-set to maturity under glasshouse-controlled conditions. UV-B induced a transient decrease in net photosynthesis (Anet), actual and maximum potential efficiency of photosystem II, particularly on well watered plants. Methanol extractable UV-B absorbing compounds (MEUVAC) concentration and superoxide dismutase activity increased with UV-B. Water deficit effected decrease in Anet and stomatal conductance, and did not change non-photochemical quenching and the de-epoxidation state of xanthophylls, dark respiration and photorespiration being alternative ways to dissipate the excess of energy. Little interactive effects between UV-B and drought were detected on photosynthesis performance, where the impact of UV-B was overshadowed by the effects of water deficit. Grape berry ripening was strongly delayed when UV-B and water deficit were applied in combination. In summary, deficit irrigation did not modify the adaptive response of grapevine to UV-B, through the accumulation of MEUVAC. However, combined treatments caused additive effects on berry ripening
Matrix elements of unstable states
Using the language of non-relativistic effective Lagrangians, we formulate a
systematic framework for the calculation of resonance matrix elements in
lattice QCD. The generalization of the L\"uscher-Lellouch formula for these
matrix elements is derived. We further discuss in detail the procedure of the
analytic continuation of the resonance matrix elements into the complex energy
plane and investigate the infinite-volume limit
The relevance of tissue angiotensin-converting enzyme: manifestations in mechanistic and endpoint data
Angiotensin-converting enzyme (ACE) is primarily localized (>90%) in various tissues and organs, most notably on the endothelium but also within parenchyma and inflammatory cells. Tissue ACE is now recognized as a key factor in cardiovascular and renal diseases. Endothelial dysfunction, in response to a number of risk factors or injury such as hypertension, diabetes mellitus, hypercholesteremia, and cigarette smoking, disrupts the balance of vasodilation and vasoconstriction, vascular smooth muscle cell growth, the inflammatory and oxidative state of the vessel wall, and is associated with activation of tissue ACE. Pathologic activation of local ACE can have deleterious effects on the heart, vasculature, and the kidneys. The imbalance resulting from increased local formation of angiotensin II and increased bradykinin degradation favors cardiovascular disease. Indeed, ACE inhibitors effectively reduce high blood pressure and exert cardio- and renoprotective actions. Recent evidence suggests that a principal target of ACE inhibitor action is at the tissue sites. Pharmacokinetic properties of various ACE inhibitors indicate that there are differences in their binding characteristics for tissue ACE. Clinical studies comparing the effects of antihypertensives (especially ACE inhibitors) on endothelial function suggest differences. More comparative experimental and clinical studies should address the significance of these drug differences and their impact on clinical events
Finite volume treatment of pi pi scattering and limits to phase shifts extraction from lattice QCD
We study theoretically the effects of finite volume for pipi scattering in
order to extract physical observables for infinite volume from lattice QCD. We
compare three different approaches for pipi scattering (lowest order
Bethe-Salpeter approach, N/D and inverse amplitude methods) with the aim to
study the effects of the finite size of the box in the potential of the
different theories, specially the left-hand cut contribution through loops in
the crossed t,u-channels. We quantify the error made by neglecting these
effects in usual extractions of physical observables from lattice QCD spectra.
We conclude that for pipi phase-shifts in the scalar-isoscalar channel up to
800 MeV this effect is negligible for box sizes bigger than 2.5m_pi^-1 and of
the order of 5% at around 1.5-2m_pi^-1. For isospin 2 the finite size effects
can reach up to 10% for that energy. We also quantify the error made when using
the standard Luscher method to extract physical observables from lattice QCD,
which is widely used in the literature but is an approximation of the one used
in the present work.Comment: 10 pages, 8 figure
Serum levels of mitochondrial inhibitory factor 1 are independently associated with long-term prognosis in coronary artery disease: the GENES Study
Background
Epidemiological and observational studies have established that high-density lipoprotein cholesterol (HDL-C) is an independent negative cardiovascular risk factor. However, simple measurement of HDL-C levels is no longer sufficient for cardiovascular risk assessment. Therefore, there is a critical need for novel non-invasive biomarkers that would display prognostic superiority over HDL-C. Cell surface ecto-F1-ATPase contributes to several athero-protective properties of HDL, including reverse cholesterol transport and vascular endothelial protection. Serum inhibitory factor 1 (IF1), an endogenous inhibitor of ecto-F1-ATPase, is an independent determinant of HDL-C associated with low risk of coronary artery disease (CAD). This work aimed to examine the predictive value of serum IF1 for long-term mortality in CAD patients. Its informative value was compared to that of HDL-C.
Method
Serum IF1 levels were measured in 577 male participants with stable CAD (age 45â74 years) from the GENES (Genetique et ENvironnement en Europe du Sud) study. Vital status was yearly assessed, with a median follow-up of 11 years and a 29.5 % mortality rate. Cardiovascular mortality accounted for the majority (62.4 %) of deaths.
Results
IF1 levels were positively correlated with HDL-C (rsâ=â0.40; Pâ<â0.001) and negatively with triglycerides (rsâ=ââ0.21, Pâ<â0.001) and CAD severity documented by the Gensini score (rsâ=ââ0.13; Pâ<â0.01). Total and cardiovascular mortality were lower at the highest quartiles of IF1 (HRâ=â0.55; 95 % CI, 0.38â0.89 and 0.50 (0.28â0.89), respectively) but not according to HDL-C. Inverse associations of IF1 with mortality remained significant, after multivariate adjustments for classical cardiovascular risk factors (age, smoking, physical activity, waist circumference, HDL-C, dyslipidemia, hypertension, and diabetes) and for powerful biological and clinical variables of prognosis, including heart rate, ankle-brachial index and biomarkers of cardiac diseases. The 10-year mortality was 28.5 % in patients with low IF1 (<0.42 mg/L) and 21.4 % in those with high IF1 (â„0.42 mg/L, Pâ<â0.02).
Conclusions
We investigated for the first time the relation between IF1 levels and long-term prognosis in CAD patients, and found an independent negative association. IF1 measurement might be used as a novel HDL-related biomarker to better stratify risk in populations at high risk or in the setting of pharmacotherapy
Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field
Effects of UV-B radiation on grapevine (Vitis vinifera cv. Tempranillo) leaf physiology and berry composition, framed within the climate change scenario (water deficit, elevated CO2 and elevated temperature)
The aim of the thesis was to assess the effect of UV-B radiation on grapevine Vitis vinifera cv. Tempranillo leaf physiology and grape berry composition, framed within the climate change scenario. Grapevine fruit-bearing cuttings were exposed to three UV-B doses (0, 5.98, 9.66 kJ m-2 d-1) under greenhouse conditions. The combined effects of UV-B and water deficit, as well as, UV-B and elevated CO2-temperature (700 ppm, +4ÂșC), applied from fruit set to maturity were also tested. The results show that initial down-regulation of photosynthesis was followed by an acclimation, mediated by the accumulation of UV-B absorbing compounds and antioxidant response elicitation (flavonoids and antioxidant enzymes). Berry ripeness was delayed by UV-B exposure and water deficit, especially when they were applied in combination, whereas it was hastened by elevated CO2-temperature. In the last case, UV-B attenuated the effect of elevated CO2 and temperature. Changes in berry ripening rates were associated with changes in photosynthetic performance. Grape berry skin flavonol and anthocyanin concentration was increased by UV-B, mainly due to the up-regulation of the structural (CHS, F3ÂżH, FLS, UFGT and GST) and regulatory genes (MYBF1 and MYBA1) committed to their synthesis. Quantitative changes in flavonol concentration induced by UV-B were always associated with qualitative changes in flavonol profile (i.e. increased relative abundance of mono- and disubstituted flavonols), as a result of the competition of FLS with flavonoid hydroxylases (F3ÂżH and F3Âż5ÂżH) for the same substrates. The up-regulation of FLS and F3Âż5ÂżH by UV-B radiation and water deficit, respectively, resulted in an interactive effect on the flavonol B ring hydroxylation pattern. Under elevated CO2-temperature anthocyanin-sugar accumulation was decoupled. However, UV-B partially alleviated this uncoupling by up-regulating anthocyanin biosynthesis and modulating berry ripening rates