Functional approach to quantum friction: effective action and dissipative force

We study the Casimir friction due to the relative, uniform, lateral motion of two parallel semitransparent mirrors coupled to a vacuum real scalar field, $\phi$. We follow a functional approach, whereby nonlocal terms in the action for $\phi$, concentrated on the mirrors' locii, appear after functional integration of the microscopic degrees of freedom. This action for $\phi$, which incorporates the relevant properties of the mirrors, is then used as the starting point for two complementary evaluations: Firstly, we calculate the { in-out} effective action for the system, which develops an imaginary part, hence a non-vanishing probability for the decay (because of friction) of the initial vacuum state. Secondly, we evaluate another observable: the vacuum expectation value of the frictional force, using the { in-in} or Closed Time Path formalism. Explicit results are presented for zero-width mirrors and half-spaces, in a model where the microscopic degrees of freedom at the mirrors are a set of identical quantum harmonic oscillators, linearly coupled to $\phi

Diacritical study of light, electrons, and sound scattering by particles and holes

We discuss the differences and similarities in the interaction of scalar and vector wave-fields with particles and holes. Analytical results are provided for the transmission of isolated and arrayed small holes as well as surface modes in hole arrays for light, electrons, and sound. In contrast to the optical case, small-hole arrays in perforated perfect screens cannot produce acoustic or electronic surface-bound states. However, unlike electrons and light, sound is transmitted through individual holes approximately in proportion to their area, regardless their size. We discuss these issues with a systematic analysis that allows exploring both common properties and unique behavior in wave phenomena for different material realizations.Comment: 3 figure

Gas Exchange Relations of Ungrafted Grapevines (cv. Carménère) Growing Under Irrigated Field Conditions

A study was carried out to evaluate the leaf gas exchange relations and water-use efficiency (WUE) of ungrafted Carménère (Vitis vinifera L.) grapevines growing under field conditions and different levels of water stress. Stomatal conductance (gs), transpiration (E), net CO2 assimilation (AN) and stem water potential (Ψs) were measured at midday in a drip-irrigated commercial vineyard located in the Maule Valley (Chile) during three growing seasons (2005 to 2009). In addition, the instantaneous (AN/E) and intrinsic (AN/gs) water-use efficiencies and stomatal sensitivity factor (k) were estimated for the own-rooted grapevines. In this study a significant non-linear relationship was observed between AN and gs (r2 = 0.82), with values of AN decreasing from 14.9 to 3.5 μmol/m2/sec as gs diminished from 0.5 to 0.05 mol/m2/sec. This resulted in a progressive increase in WUEi (intrinsic water use efficiency). A significant linear relationship was observed between Ψs and gs (r2 = 0.39) for measurements taken before and after véraison, with an increasing scattering from -1.6 to -0.4 MPa. Finally, k decreased as water stress increased, with values of 234 and 120 for no and severe water stress respectively, while k ranged from 264 to 480 and 255 to 297 for the measurements taken before and after véraison respectively. Based on the results obtained in the present study, the cultivar Carménère could be classified as drought tolerant at low water potentials, with a large range of physiological parameters changing in response to water stress

Axon micro-dissection and transcriptome profiling reveals the in vivo RNA content of fully differentiated myelinated motor axons

Axonal protein synthesis has been shown to play a role in developmental and regenerative growth, as well as in the maintenance of the axoplasm in steady state. Recent studies have begun to identify the mRNAs localized in axons, which could be translated locally under different conditions. Despite that now hundreds or thousands of mRNAs have been shown to be localized into the axonal compartment of cultured neurons in vitro, knowledge of which mRNAs are localized in mature myelinated axons is quite limited. With the purpose of characterizing the transcriptome of mature myelinated motor axons of peripheral nervous system, we modified the axon micro-dissection method devised by Koenig, enabling the isolation of the axoplasm RNA to perform RNA-seq analysis. The transcriptome analysis indicates that the number of RNAs detected in mature axons is lower in comparison with in vitro data, is depleted of glial markers and enriched in neuronal markers. The mature myelinated axons are enriched for mRNAs related to cytoskeleton, translation and oxidative phosphorylation. Moreover, it was possible to define core genes present in axons when comparing our data with transcriptomic data of axons grown in different conditions. This work provides evidence that axon micro-dissection is a valuable method to obtain data at genome-wide levels of mature and myelinated axons of the peripheral nervous system, and could be especially useful for the study of axonal involvement in neurodegenerative pathologies of motor neurons such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophies (SMA). Faria

Cute hypotensor effect of the vascular occlusion exercise on elderly adults

Objetivo: El objetivo de este estudio fue evaluar la respuesta cardíaca aguda después de realizar una sesión de ejercicio con oclusión vascular en adultos mayores (AM). Sujetos y método: 22 participantes voluntarios, fueron sometidos al protocolo experimental de ejercicio dinámico de prensión manual con un 30% de presión de oclusión (PO), después de registrar los valores basales y en reposo de presión arterial sistólica (PAS), presión arterial diastólica (PAD) y frecuencia cardíaca (FC). Evaluadas en condiciones basales y entre los 5 y 30 minutos post-oclusión. Resultados: Al finalizar el protocolo se observó una reducción significativa en la PAS y FC a los 15’, 20’ y 25’ (p<0,05) y para la PAD a los 10’ y 20’ (p<0,05). Conclusión: El efecto agudo del ejercicio con oclusión vascular genera una reducción significativa de PAS, PAD y FC hasta 25 minutos post-oclusión, en los AM analizadosThe objective of this study was to evaluate the acute cardiac response after performing an exercise session with vascular occlusion in elderly adults (EA). Twenty-two volunteer participants underwent the experimental protocol of dynamic manual grip exercise with 30% occlusion pressure (OP), after recording the baseline values and resting systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). All measures were taken in basal conditions and between 5 and 30 minutes’ post-occlusion. At the end of the protocol, there was a significant reduction in SBP and HR at 15 ', 20' and 25 '(p <0.05) and for DBP at 10' and 20 '(p <0.05).). The acute effect of exercise with vascular occlusion generates a significant reduction of SBP, Basal Diastolic Pressure (BDP) and HR up to 25 minutes’ post-occlusion, in the EA analyze

Water and Flamingo Feces Bacterial Communities from High- Altitude Andean Lakes under Selective Antibiotic Pressure Studied by PCR-DGGE Analyses

High-altitude Andean lakes are exposed to extreme environmental factors like high salinity, ultraviolet radiation, heavy metals, among others. As it was previously shown, these lakes are not only the habitat of a high diversity of bacteria with multiple resistances; they also support an enormous population of flamingos, which migrate among these wetlands, and they could play a role as disseminators and/or reservoirs of pathogenic bacteria

Emergence of the pointer basis through the dynamics of correlations

We use the classical correlation between a quantum system being measured and its measurement apparatus to analyze the amount of information being retrieved in a quantum measurement process. Accounting for decoherence of the apparatus, we show that these correlations may have a sudden transition from a decay regime to a constant level. This transition characterizes a non-asymptotic emergence of the pointer basis, while the system-apparatus can still be quantum correlated. We provide a formalization of the concept of emergence of a pointer basis in an apparatus subject to decoherence. This contrast of the pointer basis emergence to the quantum to classical transition is demonstrated in an experiment with polarization entangled photon pairs.Comment: 4+2 pgs, 3 figures. Title changed. Revised version to appear on PR