Experimental study of the FemtoTalbot effect

Experimental investigation of Talbot self-imaging effect of an amplitude grating under illumination of femtosecond laser pulse -- the FemtoTalbot effect is reported. Theoretical analyzed results show that Talbot images under illumination of femtosecond laser pulses are not the same as that under continuous wave illumination. Experimental results are in good agreement with the theoretical analysis. We believe that the experimental investigation of the FemtoTalbot effect is highly interesting for the enormous potential applications of Talbot effect.

An experimental study of a stellar neutron source: ^(13)C(α, n)^(16)O

Described in this thesis are measurements made of the thick-target neutron yield from the reaction ¹³C(α, n)¹⁶O. The yield was determined for laboratory bombarding energies between 0.475 and 0.700 MeV, using a stilbene crystal neutron detector and pulse-shape discrimination to eliminate gamma rays. Stellar temperatures between 2.5 and 4.5 x 10^{8 o}K are involved in this energy region. From the neutron yield was extracted the astrophysical cross-section factor S(E), which was found to fit a linear function: S(E) = [(5.48 ± 1.77) + (12.05 ± 3.91)E] x 10⁵ MeV-barns, center-of-mass system. The stellar rate of the ¹³C(α, n)¹⁶O reaction if calculated, and discussed with reference to helium burning and neutron production in the core of a giant star.

Results are also presented of measurements carried out on the reaction ⁹Be(α, n)¹²C, taken with a thin Be target. The bombarding energy-range covered was from 0.340 to 0.680 MeV, with excitation curves for the ground- and first excited-state neutrons being reported. Some angular distributions were also measured. Resonances were found at bombarding energies of E_LAB = 0.520 MeV (E_CM = 0.360 MeV, Γ ~ 55 keV CM, ωγ = 3.79 eV CM) and E_LAB = 0.600 MeV (E_CM = 0.415 MeV, Γ ˂ 4 keV CM, ωγ = 0.88 eV CM). The astrophysical rate of the ⁹Be(α, n)¹²C reaction due to these resonances is calculated.

Experimental and theoretical studies of the electrothermal instability in a nonequilibrium plasma

Experimental and theoretical studies have been made of the electrothermal waves occurring in a nonequilibrium MHD plasma. These waves are caused by an instability that occurs when a plasma having a dependence of conductivity on current density is subjected to crossed electric and magnetic fields. Theoretically, these waves were studied by developing and solving the equations of a steady, one-dimensional nonuniformity in electron density. From these nonlinear equations, predictions of the maximum amplitude and of the half width of steady waves could be obtained. Experimentally, the waves were studied in a nonequilibrium discharge produced in a potassium-seeded argon plasma at 2000°K and 1 atm. pressure. The behavior of such a discharge with four different configurations of electrodes was determined from photographs, photomultiplier measurements, and voltage probes. These four configurations were chosen to produce steady waves, to check the stability of steady waves, and to observe the manifestation of the waves in a MHD generator or accelerator configuration.

Steady, one-dimensional waves were found to exist in a number of situations, and where they existed, their characteristics agreed with the predictions of the steady theory. Some extensions of this theory were necessary, however, to describe the transient phenomena occurring in the inlet region of a discharge transverse to the gas flow. It was also found that in a discharge away from the stabilizing effect of the electrodes, steady waves became unstable for large Hall parameters. Methods of prediction of the effective electrical conductivity and Hall parameter of a plasma with nonuniformities caused by the electrothermal waves were also studied. Using these methods and the values of amplitude predicted by the steady theory, it was found that the measured decrease in transverse conductivity of a MHD device, 50 per cent at a Hall parameter of 5, could be accounted for in terms of the electrothermal instability.

Experimental study study of antiproton-proton annihilation into a pair of charged Pi-Mesons or K-Mesons for incident antiproton mementa in the range from 0.72 GeV/c to 2.62 GeV/c

The cross sections for the two antiproton-proton annihilation-in-flight modes,

ˉp + p → π⁺ + π^-

ˉp + p → k⁺ + k^-

were measured for fifteen laboratory antiproton beam momenta ranging from 0.72 to 2.62 GeV/c. No magnets were used to determine the charges in the final state. As a result, the angular distributions were obtained in the form [dσ/dΩ (Θ_C.M.) + dσ/dΩ (π – Θ_C.M.)] for 45 ≲ Θ_C.M. ≲ 135°.

A hodoscope-counter system was used to discriminate against events with final states having more than two particles and antiproton-proton elastic scattering events. One spark chamber was used to record the track of each of the two charged final particles. A total of about 40,000 pictures were taken. The events were analyzed by measuring the laboratory angle of the track in each chamber. The value of the square of the mass of the final particles was calculated for each event assuming the reaction

ˉp + p → a pair of particles with equal masses.

About 20,000 events were found to be either annihilation into π ^±-pair or k ^±-pair events. The two different charged meson pair modes were also distinctly separated.

The average differential cross section of ˉp + p → π⁺ + π^- varied from ~ 25 µb/sr at antiproton beam momentum 0.72 GeV/c (total energy in center-of-mass system, √s = 2.0 GeV) to ~ 2 µb/sr at beam momentum 2.62 GeV/c (√s = 2.64 GeV). The most striking feature in the angular distribution was a peak at Θ_C.M. = 90° (cos Θ_C.M. = 0) which increased with √s and reached a maximum at √s ~ 2.1 GeV (beam momentum ~ 1.1 GeV/c). Then it diminished and seemed to disappear completely at √s ~ 2.5 GeV (beam momentum ~ 2.13 GeV/c). A valley in the angular distribution occurred at cos Θ_C.M. ≈ 0.4. The differential cross section then increased as cos Θ_C.M. approached 1.

The average differential cross section for ˉp + p → k⁺ + k^- was about one third of that of the π^±-pair mode throughout the energy range of this experiment. At the lower energies, the angular distribution, unlike that of the π^±-pair mode, was quite isotropic. However, a peak at Θ_C.M. = 90° seemed to develop at √s ~ 2.37 GeV (antiproton beam momentum ~ 1.82 GeV/c). No observable change was seen at that energy in the π^±-pair cross section.

The possible connection of these features with the observed meson resonances at 2.2 GeV and 2.38 GeV, and its implications, were discussed.

Experimental investigation of optical beam deflection based on PLZT electro-optic ceramic

Based on the optical characteristics of PLZT electro-optic ceramic, two kinds of electro-optic deflectors, triangular electrode structure and optical phased array technology, are studied in detail by using transverse electro-optic effect. Theoretically, the electro-optic deflection characteristics and mechanisms of the deflectors are analyzed. Experimentally, the optical characteristics of ceramic wafer, such as the phase modulation, the hysteresis and the electro-induced loss characteristics, are measured firstly, and then the beam deflection experiments are designed to verify the theoretical results. Moreover, the effect of temperature on the performance of triangular electrode deflector is investigated. The characteristics of both deflectors are also compared and illuminated. (c) 2007 Optical Society of America.

Experimental design in fluvial ichthyology: getting the most for your money

In field biology, cost efficiency is an essential element of experimental design, with ramifications extending well beyond the basic monetary considerations associated with labour and equipment acquisition. Current economic constraints often require scientists to undertake many technical, secretarial and managerial tasks in addition to those associated with data collection, analysis, interpretation and publication. Because the time spent to process material in the laboratory can rarely be shortened without compromising the integrity of the results, it is imperative that field experiments be well-organised, addressing as many aspects of the problem as possible during the same sampling excursion. The sampling strategy employed should provide a maximum of good field data with a minimum cost of time and effort.

Diálogo institucional e direito à saúde

O trabalho busca analisar os problemas envolvendo a efetivação do direito à saúde no Brasil, os conflitos alocativos subjacentes à temática e o papel das instituições representativas, do Judiciário e da sociedade civil neste processo. Pretende-se reafirmar a importância da proteção do direito à saúde e, ao mesmo tempo, criticar uma certa euforia doutrinária e jurisprudencial que se instalou nos últimos anos e passou a compreender o Judiciário como o último guardião das promessas constitucionais não cumpridas pelos ramos representativos. O trabalho analisa as experiências constitucionais de países que não apostam no dogma da supremacia judicial e tentam conciliar a revisão judicial com mecanismos mais democráticos. A partir daí propõe o marco teórico das teorias do diálogo institucional como uma alternativa menos unilateral para enfrentar os desafios desencadeados no campo sanitário. No trabalho enfatiza-se a importância pelas preocupações com a efetividade da constituição, mas propõe-se uma reflexão sobre qual seria a melhor alternativa para tanto, chegando-se à conclusão contra-intuitiva de que talvez o caminho mais eficaz passe por um controle judicial fraco, que não despreze as potencialidades do Direito, mas que aposte mais na democracia e na interação sinérgica entre os ramos representativos e a sociedade civil.

Theoretical investigations of experimental gravitation

This thesis has two basic themes: the investigation of new experiments which can be used to test relativistic gravity, and the investigation of new technologies and new experimental techniques which can be applied to make gravitational wave astronomy a reality.

Advancing technology will soon make possible a new class of gravitation experiments: pure laboratory experiments with laboratory sources of non-Newtonian gravity and laboratory detectors. The key advance in techno1ogy is the development of resonant sensing systems with very low levels of dissipation. Chapter 1 considers three such systems (torque balances, dielectric monocrystals, and superconducting microwave resonators), and it proposes eight laboratory experiments which use these systems as detectors. For each experiment it describes the dominant sources of noise and the technology required.

The coupled electro-mechanical system consisting of a microwave cavity and its walls can serve as a gravitational radiation detector. A gravitational wave interacts with the walls, and the resulting motion induces transitions from a highly excited cavity mode to a nearly unexcited mode. Chapter 2 describes briefly a formalism for analyzing such a detector, and it proposes a particular design.

The monitoring of a quantum mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. Chapter 3 reviews the standard techniques for monitoring the oscillator; and it introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator.

The standard method for monitoring the oscillator is the "amplitude- and-phase" method (position or momentum transducer with output fed through a linear amplifier). The accuracy obtainable by this method is limited by the uncertainty principle. To do better requires a measurement of the type which Braginsky has called "quantum nondemolition." A well-known quantum nondemolition technique is "quantum counting," which can detect an arbitrarily weak force, but which cannot provide good accuracy in determining its precise time-dependence. Chapter 3 considers extensively a new type of quantum nondemolition measurement - a "back-action-evading" measurement of the real part X₁ (or the imaginary part X₂) of the oscillator's complex amplitude. In principle X₁ can be measured arbitrarily quickly and arbitrarily accurately, and a sequence of such measurements can lead to an arbitrarily accurate monitoring of the classical force.

Chapter 3 describes explicit gedanken experiments which demonstrate that X₁ can be measured arbitrarily quickly and arbitrarily accurately, it considers approximate back-action-evading measurements, and it develops a theory of quantum nondemolition measurement for arbitrary quantum mechanical systems.

In Rosen's "bimetric" theory of gravity the (local) speed of gravitational radiation v_g is determined by the combined effects of cosmological boundary values and nearby concentrations of matter. It is possible for v_g to be less than the speed of light. Chapter 4 shows that emission of gravitational radiation prevents particles of nonzero rest mass from exceeding the speed of gravitational radiation. Observations of relativistic particles place limits on v_g and the cosmological boundary values today, and observations of synchrotron radiation from compact radio sources place limits on the cosmological boundary values in the past.

A mathematical and experimental investigation of microcycle spectral estimates of semiconductor flicker noise

The experimental portion of this thesis tries to estimate the density of the power spectrum of very low frequency semiconductor noise, from 10^-6.3 cps to 1. cps with a greater accuracy than that achieved in previous similar attempts: it is concluded that the spectrum is 1/f^α with α approximately 1.3 over most of the frequency range, but appearing to have a value of about 1 in the lowest decade. The noise sources are, among others, the first stage circuits of a grounded input silicon epitaxial operational amplifier. This thesis also investigates a peculiar form of stationarity which seems to distinguish flicker noise from other semiconductor noise.

In order to decrease by an order of magnitude the pernicious effects of temperature drifts, semiconductor "aging", and possible mechanical failures associated with prolonged periods of data taking, 10 independent noise sources were time-multiplexed and their spectral estimates were subsequently averaged. If the sources have similar spectra, it is demonstrated that this reduces the necessary data-taking time by a factor of 10 for a given accuracy.

In view of the measured high temperature sensitivity of the noise sources, it was necessary to combine the passive attenuation of a special-material container with active control. The noise sources were placed in a copper-epoxy container of high heat capacity and medium heat conductivity, and that container was immersed in a temperature controlled circulating ethylene-glycol bath.

Other spectra of interest, estimated from data taken concurrently with the semiconductor noise data were the spectra of the bath's controlled temperature, the semiconductor surface temperature, and the power supply voltage amplitude fluctuations. A brief description of the equipment constructed to obtain the aforementioned data is included.

The analytical portion of this work is concerned with the following questions: what is the best final spectral density estimate given 10 statistically independent ones of varying quality and magnitude? How can the Blackman and Tukey algorithm which is used for spectral estimation in this work be improved upon? How can non-equidistant sampling reduce data processing cost? Should one try to remove common trands shared by supposedly statistically independent noise sources and, if so, what are the mathematical difficulties involved? What is a physically plausible mathematical model that can account for flicker noise and what are the mathematical implications on its statistical properties? Finally, the variance of the spectral estimate obtained through the Blackman/Tukey algorithm is analyzed in greater detail; the variance is shown to diverge for α ≥ 1 in an assumed power spectrum of k/|f|^α, unless the assumed spectrum is "truncated".

Experimental studies of weak superconductivity

Experimental investigations were made of the nature of weak superconductivity in a structure having well-defined, controllable characteristics and geometry. Controlled experiments were made possible by using a thin-film structure which was entirely metallic and consisted of a superconducting film with a localized section that was weak in the sense that its transition temperature was depressed relative to the rest of the film. The depression of transition temperature was brought about by underlaying the superconductor with a normal metal.

The DC and AC electrical characteristics of this structure were studied. It was found that this structure exhibited a non-zero, time-average supercurrent at finite voltage to at least .2 mV, and generated an oscillating electric potential at a frequency given by the Josephson relation. The DC V-I characteristic and the amplitude of the AC oscillation were found to be consistent with a two- fluid (normal current-supercurrent) model of weak super-conductivity based on e thermodynamically irreversible process of repetitive phase-slip, and featuring a periodic time dependence in the amplitude of the superconducting order parameter.

The observed linewidth of the AC oscillation could be accounted for by incorporating Johnson noise in the two-fluid model.

Experimentally it was found that the behavior of a short (length on the order of the coherence distance) weak superconductor could be characterized by its critical current and normal-state resistance, and an empirical expression was obtained for the time dependence of the super-current and voltage.

It was found that the results could not be explained on the basis of the theory of the Josephson junction.

Efeitos macrovasculares, microvasculares e interação leucócito-endotélio, na endotoxemia experimental após o uso de Dobutamina com e sem ressuscitação volêmica

Na sepse, o mecanismo desencadeador de morte é a disfunção múltipla de órgãos e sistemas. Com isso a microcirculação é considerada o motor na patogênese da sepse. A perfusão microcirculatória representa um dos principais objetivos para melhorar as taxas de sobrevida. Uma vez reconhecida a síndrome séptica, o protocolo clínico estabelece o uso de fluidoterapia com salina, de forma vigorosa na primeira hora e seguida de suporte inotrópico com Dobutamina. A partir daí foi levantada a hipótese das drogas β-agonistas serem relevantes na recuperação da microcirculação, antes mesmo de seu conhecido papel na recuperação do choque cardiogênico. Assim, estudar o papel da Dobutamina, um β-agonista, na resposta adrenérgica em situação de sepse se faz necessário e urgente e o entendimento de sua ação, associada à reposição volêmica, foi objeto deste estudo. Foram usados no presente estudo, 78 hamsters, induzida a endotoxemia com LPS (2mg/kg/de massa de peso corporal) e divididos em 9 grupos: controle (n=10), endotóxico(n=10), endotóxico tratados com Dobutamina na dose de 5 e 15 μg /kg/min (n=10), Isoproterenol(n=10), ressuscitação volêmica (n=10) e ressuscitação volêmica associada à Dobutamina 5 (n=10) e 15 μg/kg/min (n=4) e Isoproterenol (n=4). Foram comparados os resultados de recuperação da densidade capilar funcional ao longo do tempo entre os grupos, e obteve-se resultado estatisticamente significativo no grupo em que se usa Dobutamina de 5μg/kg/min associada à ressuscitação volêmica p< 0,05. Em conclusão este estudo mostra que o papel da ressuscitação volêmica é crucial na resposta da microcirculação para melhorar a densidade capilar funcional, que a velocidade da hemácia capilar tem relação direta com a melhora na perfusão tecidual e que a associação de recuperação volêmica com solução salina e Dobutamina na dose de 5 μg /kg /min melhora significativamente sua resposta e melhora a perfusão.

Estudo das alterações cardiovasculares e metabólicas em modelo experimental de programação metabólica: efeito de extrato da casca de uva Vitis vinífera

Estudos epidemiológicos e experimentais têm sugerido que fatores de risco cardiovasculares podem ser parcialmente atribuídos às influências do ambiente em que vive o indivíduo, e que a nutrição materna influencia na programação de alterações metabólicas e cardiovasculares no indivíduo adulto e que caracterizam a síndrome metabólica (SM). Em contrapartida, estudos prévios de nosso laboratório demonstram que o extrato da casca de uva Vitis labrusca (GSE) possui efeito vasodilatador, antihipertensivo e antioxidante. Desta forma, o objetivo deste estudo foi avaliar o efeito do tratamento oral com GSE (200mg/kg/dia), sobre as alterações cardiovasculares e metabólicas e estresse oxidativo observados na prole adulta (fêmea e machos) com 3 e 6 meses, cujas mães foram submetidas a uma dieta rica em gordura (hiperlipídica) durante a lactação. Quatro grupos de ratas foram alimentados com dietas experimentais: controle (7% de gordura); controle + GSE (7% de gordura + GSE), hiperlipídica (24% de gordura); hiperlipídica + GSE (24% de gordura + GSE) durante a lactação. Após o desmame, todos os filhotes passaram a ser alimentados com uma dieta controle e foram sacrificados aos 3 ou 6 meses de idade. A pressão arterial sistólica (PAS) foi medida por pletismografia de cauda e o efeito vasodilatador da acetilcolina (ACh) foi avaliado em leito arterial mesentérico (LAM) perfundido. Foram avaliados o peso corporal, adiposidade (intra-abdominal e gonadal), níveis plasmáticos de colesterol total, triglicerídeos, glicose e insulina, e a resistência à insulina (RI) foi calculada pelo índice de HOMA IR. As expressões do IRS-1, Akt e GLUT-4 foram determinadas em músculo soleus. O dano oxidativo, níveis de nitritos e a atividade das enzimas antioxidantes: superóxido dismutase, catalase e glutationa peroxidase foram dosados no plasma e homogenato de LAM. A PAS e tecido adiposo foram aumentados nas proles adultas de ambos os sexos e idades do grupo hiperlipídico e revertidos pelo tratamento com o GSE. A resposta vasodilatadora à ACh em LAM não foi diferente entre os grupos de ambos os sexos, mas foram reduzidas com o envelhecimento. Nas proles fêmeas e machos do grupo hiperlipídico também foram observados o aumento dos níveis de triglicerídeos, de glicose e RI em ambas as idades e foram reduzidos pelo GSE. No grupo hiperlipídico houve redução nas expressões de IRS-1, Akt e GLUT-4 e o GSE reverteu estas expressões. Os níveis plasmáticos de malondialdeído estavam aumentados e os níveis de nitrito diminuídos no grupo hiperlipídico, de ambos os sexos e idades e foram revertidos pelo GSE. As atividades das enzimas antioxidantes no plasma e no mesentério foram reduzidas no grupo hiperlipídico e restauradas pelo GSE. Em conclusão, O GSE parece proteger as proles fêmeas e machos, cujas mães foram expostas a uma dieta hiperlipídica durante a lactação, dos fatores de riscos cardiovasculares, proporcionando uma fonte alternativa nutricional para a prevenção da SM.