Towards absolute calibration of optical tweezers

Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous (MD) model, taking account of spherical aberration at the glass/water interface. This first-principles theory is formulated entirely in terms of experimentally accessible parameters (none adjustable). Careful experimental tests of the MDSA theory, undertaken at two laboratories, with very different setups, are described. A detailed description is given of the procedures employed to measure laser beam waist, local beam power at the transparent microspheres trapped by the tweezers, microsphere radius and the trap transverse stiffness, as a function of radius and height in the (inverted microscope) sample chamber. We find generally very good agreement with MDSA theory predictions, for a wide size range, from the Rayleigh domain to large radii, including the values most often employed in practice, and at different chamber heights, both with objective overfilling and underfilling. The results asymptotically approach geometrical optics in the mean over size intervals, as they should, and this already happens for size parameters not much larger than unity. MDSA predictions for the trapping threshold, position of stiffness peak, stiffness variation with height, multiple equilibrium points and `hopping' effects among them are verified. Remaining discrepancies are ascribed to focus degradation, possibly arising from objective aberrations in the infrared, not yet included in MDSA theory.Comment: 15 pages, 20 figure

EFFECT OF SUPERHEATING DEGREE AND PRESSURE ON EFFICIENCY OF AN ORES (ORGANIC RANKINE ENERGY STORAGE) SYSTEM

The increased share of intermittent renewable energy sources has led to the development of new energy storage solutions to mitigate the effects of the variability of energy supply. CAES (Compressed Air Energy Storage) and LAES (Liquid Air Energy Storage) are two of the main solutions for medium to large-scale systems for long-term energy storage. However, both are limited; the first requires the availability of suitable geological formations and the second requires considerable investment because of the required liquefaction process. This work aims to evaluate the thermodynamic performance of an energy storage system, called Organic Rankine Energy Storage (ORES), with a focus on the effects of pressure and superheating degree at the expander inlet on the round-trip efficiency (i.e. ratio of generated energy during energy discharge over consumed energy during energy storage) of the system. The system was evaluated for six organic fluids which were selected based on commercial maturity, environmental impacts, and safety conditions, namely R-134a, R-152a, R-142b, R-236ea, R-365mfc, and R-141b. The efficiency of the system was obtained for each of those fluids using a steady-state model approximation of the operation of the system and for pressures at the expander inlet varying from 675 kPa up to 4,300 kPa (or 95% of the critical pressure, if lower) and for superheating degrees from 0 up to 40 K. The evaluation of the system for six organic fluids as working fluid resulted in round-trip efficiencies around 70 % (comparable to both CAES and LAES when subject to similar methodologies) with higher sensitivity to pressure than to superheating degree. For all fluids, an increase of 5 K in the superheating degree resulted in an absolute decrease of 2-5% in the round-trip efficiency. Effects of pressure were more diverse, R-152b, R-134a and R-142b showed an average reduction of 10% in efficiency for each reduction of 500 kPa in pressure (in the high efficiency operation region, while R-365mfc and R-141b were much less affected, around 5% decrease in efficiency for each reduction of 500 kPa. The fluids that had the highest efficiencies and that also presented a high efficiency for a wider range of pressures were the R141b and R365mfc, which are also the fluids with the highest critical temperatures

Wood characterization using the power spectral density and phase velocity of ultrasonic signals.

The application of non-destructive testing (NDT) in the analysis of trees in forest plantations permits the evaluation of the wood quality, the internal defects in development or pest attack and its characterization for application as solid wood and its products. These techniques have been constantly improved with the use of computers, electronics and agricultural control levels in order to provide tools to the specialists in integrated management. The ultrasound has been used in agriculture as NDT to determine the elasticity modulus of juvenile and mature wood of pinus and other species. This study aimed to the evaluation of new techniques for characterization of wood using parameters such as the power spectral density (PSD) and phase velocity of ultrasonic signals propagating in wood. The tests were performed using a pair of ultrasonic transducers with central frequency of 50 kHz (083-067-038, GE) which were connected to an ultrasonic pulser/receiver (5077PR, Olympus). The transmitting transducer was coupled to the samples of pinus using ultrasound gel and excited with negative pulses of short duration (5 μs) and high amplitude (-400 V) to generate longitudinal and shear waves. The ultrasound signals that propagated through the samples were received by the receiving transducer, amplified (20 to 40 dB), acquired in a digital scope (MSO4104B, Tektronix) and then transferred to a microcomputer. The tests have been done with 10 reference samples (healthy) and 10 attacked by wood wasps, with small holes in the bark. The transducers were placed on the samples in the axial, radial and inclined modes. The data were processed using the Matlab (Mathworks Inc.) to determine the power spectral density (PSD), the root mean square deviation index (cRMSDdB) and the phase velocity between the reference and attacked samples. The cRMSDdB calculated between the PSD of the reference and the attacked samples were generally higher for samples with higher degree of damage, however, in some cases, they were lower due to the presence of wood knots. The phase velocities were calculated in the frequency range 1-200 kHz and generally show higher values for the reference samples. The group velocities were also calculated and the results were in the range 1200-3000 m/s, indicating that these parameters can be used for wood characterization

Radiation Pressure as a Source of Decoherence

We consider the interaction of an harmonic oscillator with the quantum field via radiation pressure. We show that a `Schrodinger cat' state decoheres in a time scale that depends on the degree of `classicality' of the state components, and which may be much shorter than the relaxation time scale associated to the dynamical Casimir effect. We also show that decoherence is a consequence of the entanglement between the quantum states of the oscillator and field two-photon states. With the help of the fluctuation-dissipation theorem, we derive a relation between decoherence and damping rates valid for arbitrary values of the temperature of the field. Coherent states are selected by the interaction as pointer states.Comment: 14 pages, 3 figures, RevTex fil

MHSP in reversed-biased operation mode for ion blocking in gas-avalanche multipliers

We present recent results on the operation of gas-avalanche detectors comprising a cascade of gas electron multipliers (GEMs) and Micro-Hole and Strip Plates (MHSPs) multiplier operated in reversed-bias (R-MHSP) mode. The operation mechanism of the R-MHSP is explained and its potential contribution to ion-backflow (IBF) reduction is demonstrated. IBF values of 4E-3 were obtained in cascaded R-MHSP and GEM multipliers at gains of about 1E+4, though at the expense of reduced effective gain in the first R- MHSP multiplier in the cascade.Comment: 23 pages, 8 figure

Typology of sugarcane production in Brazil: the use of multivariate statistics on municipal data.

Abstract: Given the large territorial extension and the high social and economic diversity, Brazil has a remarkable variability in agricultural cropping systems. The description and the understanding of this variability is fundamental for proposing research gaps, technology transfer and appropriate public policies for the sector. Sugarcane is used for several purposes on farms, such as household consumption, energy and sugar production, and forage production. Data collected during the 2006 agricultural census, accomplished by the Brazilian Institute of Geography and Statistics (IBGE), shows that 192,931 farms (3.7% of Brazilian farms) reported having grown sugarcane in 2006. This paper addresses the classification and characterization of the sugarcane producing municipalities in Brazil, using techniques of multivariate statistical analysis (factor and cluster analysis). The 41 variables used were created from the data collected by the 2006 agricultural census, covering 3,576 municipalities. Data went through a sugarcane filter, and was then regrouped by municipality. Those variables gather socioeconomic and technological information on the farms, such as land usage, harvested area, production goal, productivity, input usage, use of industrial wastes, irrigation, source of producer?s income, percentage of the income that comes from sugarcane, family or conventional farming, size of herds, distance from the farms to sugar mills, among the most important. Analyses identified 9 different groups of sugarcane production in the municipalities, remarking large variability of sugarcane sector in Brazil, and the clear spatial differences of production and technology use in the territory. The results of the statistical analysis and the characteristics of the groups were discussed among scholars specialized in sugarcane research and were considered coherent with Brazilian reality.ICAS VI

Decoherence via Dynamical Casimir Effect

We derive a master equation for a mirror interacting with the vacuum field via radiation pressure. The dynamical Casimir effect leads to decoherence of a 'Schroedinger cat' state in a time scale that depends on the degree of 'macroscopicity' of the state components, and which may be much shorter than the relaxation time scale. Coherent states are selected by the interaction as pointer states.Comment: 4 pages, 2 figure

Análise qualitativa de lipídios-ligado em solo de plantação de eucalipto.

EVINCI. Resumo

Fatores de risco para mortalidade em idosos

OBJECTIVE: The risk factors for diseases and premature deaths are important in drawing up preventive measures. This study had the aim of analyzing the risk factors for death among elderly people. METHODS: This study was carried out among participants in the SABE (Health, Wellbeing and Aging) study, in the city of São Paulo in 2000. Interviews were conducted with 2,143 elderly people (60 years old or over), using a standardized questionnaire for the SABE study. The sample was obtained from census tracts, in two stages, with replacements and with probability proportional to the population, and with supplementation of the sample of people aged 75 years or over. The final data were weighted so that they could be expanded. Between the two data collection times, there were 38 deaths which comprised study sample. Logistic regression was utilized for the data analysis, with a significance level of 5%. RESULTS: The risk factors found were: locomotion difficulty, advanced age, male gender, self-assessment of health as "bad" and difficulty in going to the bathroom, OR=3.15; 2.93; 2.90; 2.69 and 2.51, respectively. CONCLUSIONS: The results may contribute towards the adoption of preventive measures for elderly people, with the aim of diminishing the expected number of fatal outcomes.OBJETIVO: Os fatores de risco para as doenças e mortes prematuras são importantes para a elaboração de condutas preventivas. O objetivo do trabalho foi analisar os fatores de risco para óbito entre idosos. MÉTODOS: O estudo foi realizado no Município de São Paulo, em participantes do estudo SABE (Saúde, Bem-estar e Envelhecimento), em 2000. Foram entrevistados 2.143 indivíduos com 60 anos ou mais, utilizando-se o questionário padronizado do estudo SABE. A amostra foi obtida de setores censitários em dois estágios, com reposição e com probabilidade proporcional à população, com complementação da amostra de pessoas de 75 anos ou mais. Os dados finais foram ponderados para poderem ser expandidos. Entre os dois períodos de coleta de dados ocorreram 38 óbitos que compuseram a amostra do estudo. Para a análise dos dados, utilizou-se regressão logística, com nível de significância de 5%. RESULTADOS: Os fatores de risco encontrados foram: dificuldade de locomoção, idade avançada, gênero masculino, auto-avaliação de saúde como "má" e dificuldade para ir ao banheiro, OR=3,15; 2,93; 2,90; 2,69 e 2,51, respectivamente. CONCLUSÕES: Os resultados podem contribuir para a adoção de medidas preventivas para os idosos, visando à diminuição de desfechos fatais antecipados

Efecto del bioplaguicida Bacillus thuringiensis (Berliner, 1911), cepa 344, en organismos indicadores del compartimiento acuático.

Resumen: El Bacillus thuringiensis (Berliner, 1911) (Bt) es una bacteria que contiene endotoxinas con acción insecticida para varias especies. A pesar de la conocida inocuidad de la utilización de Bt y otros bioplaguicidas utilizados en la lucha contra las plagas, ha habido algunos informes acerca de las infecciones y los efectos adversos sobre los organismos no blanco, entre estos, especies acuáticas. En este estudio, se evaluó los efectos derivados de la exposición a la cepa 344 del Bt (Bt344) en algunos organismos de diferentes niveles tróficos de la cadena alimentaria acuática. Los organismos de prueba estuvieron expuestos a concentraciones correspondientes a más de 1.000 veces la tasa de aplicación efectiva para controlar el gusano cogollero del maíz (Spodoptera frugiperda). El Bt344 no alteró los patrones de crecimiento de las algas Pseudokirchneriella subcapitata. Una tasa de mortalidad significativa equivalente a 8,9%, pero menor que el límite aceptable para el control (10%), se registró para el pez Hyphessobrycon scholzei. Sin embargo, la exposición al agente biológico disminuyó la supervivencia de Daphnia similis en 44,8%, en comparación con el control. Esto sugiere un riesgo para algunas especies acuáticas de invertebrados