Fitting the frequency-dependent parameters in the Bergeron line model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nano-displacement measurements of a new piezoelectric flextensional actuator by using a high dynamic range interferometry homodyne method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Frequency upconversion involving triads and quartets of ions in a Pr3+/Nd3+ codoped fluoroindate glass

Frequency upconversion (UC) processes involving energy transfer (ET) among Nd 3+ and Pr 3+ ions in a fluoroindate glass are reported. In a first experiment, the excitation of Pr 3+ [transition 3H 4→ 1D 2] and of Nd 3+ [transition 4I 9/2→( 2G 7/2+ 4G 5/2)] was achieved with a dye laser operating in the 575-590 nm range. In a second experiment, the Nd 3+ ions were excited with the second harmonic of a Nd: YAG laser at 532 nm. The ET processes leading to UC in both experiments were studied by monitoring the blue fluorescence decay at 480 nm due to the transition 3P 0→ 3H 4 in Pr 3+. In the more relevant UC process, quartets of ions (Nd-Nd-Pr-Pr) are excited due to absorption of three laser photons by two Nd 3+ ions which transfer their energy to two Pr 3+ ions. Each Pr 3+ ion promoted to the 3P 0 level decays to the ground state emitting one photon in the blue region. This conclusion was achieved investigating the dependence of the UC fluorescence intensity as a function of laser intensity, samples concentrations, and temporal behavior of the UC signal. Other UC processes involving nonisoionic groups of three ions are also reported. © 2002 American Institute of Physics.

Reliable assessment of forearm photoageing by high-frequency ultrasound: a cross-sectional study

High-frequency ultrasound is a non-invasive tool used in skin ageing research to assess dermis thickness and echogenicity. This study evaluated the reliability of a range of high-frequency ultrasound parameters and tested their correlation with age and a validated clinical scale for the assessment of forearm skin photoageing; the difference between two body sites according to environmental exposition patterns was also investigated. Twenty-three volunteers aged 28-82 years were divided into three groups according to forearm photoageing degree. A 20 MHz ultrasound unit was used to obtain cross-sectional images of the skin by two trained investigators on two different sites: the dorsal forearm (chronically photoexposed skin) and the proximal medial arm (non-photoexposed skin). Several echogenicity parameters were studied for each skin compartment: total dermis, upper dermis and lower dermis, and the ratio between upper and lower dermis. The intraclass correlation coefficient (for complete agreement) between investigators was higher for upper and total dermis echogenicity measures compared with the lower dermis. At the non-photoexposed site, the upper and lower dermis parameter ratio was better correlated with age. At the photoexposed area, total dermis parameters demonstrated higher correlations with clinical score. The authors discuss the choice of parameters for forearm photoageing assessment using high-frequency ultrasound.

Synthesis Methodology Applied to a Tunable Patch Filter With Independent Frequency and Bandwidth Control

A new methodology for the synthesis of tunable patch filters is presented. The methodology helps the designer to perform a theoretical analysis of the filter through a coupling matrix that includes the effect of the tuning elements used to tune the filter. This general methodology accounts for any tuning parameter desired and was applied to the design of a tunable dual-mode patch filter with independent control of center frequency and bandwidth (BW). The bandpass filter uses a single triangular resonator with two etched slots that split the fundamental degenerate modes and form the filter passband. Varactor diodes assembled across the slots are used to vary the frequency of each degenerate fundamental mode independently, which is feasible due to the nature of the coupling scheme of the filter. The varactor diode model used in simulations, their assembling, the dc bias configuration, and measured results are presented. The theory results are compared to the simulations and to measurements showing a very good agreement and validating the proposed methodology. The fabricated filter presents an elliptic response with 20% of center frequency tuning range around 3.2 GHz and a fractional BW variation from 4% to 12% with low insertion loss and high power handling with a 1-dB compression point higher than +14.5 dB.

Anointing variation across wild capuchin populations: a review of material preferences, bout frequency and anointing sociality in Cebus and Sapajus

The frequency of anointing bouts and the materials used for self- and social anointing vary across capuchin species in captivity, but there is little published data on capuchin anointing in the wild. Here we present previously unpublished data on anointing behaviors from capuchin monkey populations at ten different field sites and incorporate these data into a review of the anointing literature for captive and wild capuchins. Using a comparative phylogenetic framework, we test four hypotheses derived primarily from captive literature for variation in anointing between wild untufted capuchins (Cebus) and tufted capuchins (Sapajus), including that (1) the frequency of anointing is higher in Cebus, (2) Cebus uses a higher proportion of plant species to insect species for anointing compared with Sapajus, (3) anointing material diversity is higher in Cebus, and (4) social indices of anointing are higher in Cebus. We found that wild Cebus anoints more with plant parts, including fruits, whereas wild Sapajus anoints more with ants and other arthropods. Cebus capucinus in particular uses more plant species per site for anointing compared with other capuchins and may specialize in anointing as an activity independent from foraging, whereas most other capuchin species tend to eat the substances they use for anointing. In agreement with captive studies, we found evidence that wild Cebus anoints at a significantly higher frequency than Sapajus. However, contrary to the captive literature, we found no difference in the range of sociality for anointing between Cebus and Sapajus in the wild. We review anointing in the context of other Neotropical primate rubbing behaviors and consider the evidence for anointing as self-medication; as a mechanism for enhanced sociality; and as a behavioral response to chemical stimuli. Am. J. Primatol. 74:299314, 2012. (c) 2011 Wiley Periodicals, Inc.

Dynamic symmetry loss of high-frequency hysteresis loops in single-domain particles with uniaxial anisotropy

Understanding how magnetic materials respond to rapidly varying magnetic fields, as in dynamic hysteresis loops, constitutes a complex and physically interesting problem. But in order to accomplish a thorough investigation, one must necessarily consider the effects of thermal fluctuations. Albeit being present in all real systems, these are seldom included in numerical studies. The notable exceptions are the Ising systems, which have been extensively studied in the past, but describe only one of the many mechanisms of magnetization reversal known to occur. In this paper we employ the Stochastic Landau-Lifshitz formalism to study high-frequency hysteresis loops of single-domain particles with uniaxial anisotropy at an arbitrary temperature. We show that in certain conditions the magnetic response may become predominantly out-of-phase and the loops may undergo a dynamic symmetry loss. This is found to be a direct consequence of the competing responses due to the thermal fluctuations and the gyroscopic motion of the magnetization. We have also found the magnetic behavior to be exceedingly sensitive to temperature variations, not only within the superparamagnetic-ferromagnetic transition range usually considered, but specially at even lower temperatures, where the bulk of interesting phenomena is seen to take place. (C) 2011 Elsevier B.V. All rights reserved.

Frequency and predictors of symptomatic intracranial hemorrhage after intravenous thrombolysis for acute ischemic stroke in a Brazilian public hospital

OBJECTIVE: Scarce data are available on the occurrence of symptomatic intracranial hemorrhage related to intravenous thrombolysis for acute stroke in South America. We aimed to address the frequency and clinical predictors of symptomatic intracranial hemorrhage after stroke thrombolysis at our tertiary emergency unit in Brazil. METHOD: We reviewed the clinical and radiological data of 117 consecutive acute ischemic stroke patients treated with intravenous thrombolysis in our hospital between May 2001 and April 2010. We compared our results with those of the Safe Implementation of Thrombolysis in Stroke registry. Univariate and multiple regression analyses were performed to identify factors associated with symptomatic intracranial transformation. RESULTS: In total, 113 cases from the initial sample were analyzed. The median National Institutes of Health Stroke Scale score was 16 (interquartile range: 10-20). The median onset-to-treatment time was 188 minutes (interquartile range: 155-227). There were seven symptomatic intracranial hemorrhages (6.2%; Safe Implementation of Thrombolysis in Stroke registry: 4.9%; p = 0.505). In the univariate analysis, current statin treatment and elevated National Institute of Health Stroke Scale scores were related to symptomatic intracranial hemorrhage. After the multivariate analysis, current statin treatment was the only factor independently associated with symptomatic intracranial hemorrhage. CONCLUSIONS: In this series of Brazilian patients with severe strokes treated with intravenous thrombolysis in a public university hospital at a late treatment window, we found no increase in the rate of symptomatic intracranial hemorrhage. Additional studies are necessary to clarify the possible association between statins and the risk of symptomatic intracranial hemorrhage after stroke thrombolysis.

High frequency acoustics in colloid-based meso- and nanostructures by spontaneous Brillouin light scattering

Materials that can mold the flow of elastic waves of certain energy in certain directions are called phononic materials. The present thesis deals essentially with such phononic systems, which are structured in the mesoscale (<1 µm), and with their individual components. Such systems show interesting phononic properties in the hypersonic region, i.e., at frequencies in the GHz range. It is shown that colloidal systems are excellent model systems for the realization of such phononic materials. Therefore, different structures and particle architectures are investigated by Brillouin light scattering, the inelastic scattering of light by phonons.rnThe experimental part of this work is divided into three chapters: Chapter 4 is concerned with the localized mechanical waves in the individual spherical colloidal particles, i.e., with their resonance- or eigenvibrations. The investigation of these vibrations with regard to the environment of the particles, their chemical composition, and the influence of temperature on nanoscopically structured colloids allows novel insights into the physical properties of colloids at small length scales. Furthermore, some general questions concerning light scattering on such systems, in dispute so far, are convincingly addressed.rnChapter 5 is a study of the traveling of mechanical waves in colloidal systems, consisting of ordered and disordered colloids in liquid or elastic matrix. Such systems show acoustic band gaps, which can be explained geometrically (Bragg gap) or by the interaction of the acoustic band with the eigenvibrations of the individual spheres (hybridization gap).rnWhile the latter has no analogue in photonics, the presence of strong phonon scatterers, when a large elastic mismatch between the composite components exists, can largely impact phonon propagation in analogy to strong multiple light scattering systems. The former is exemplified in silica based phononic structures that opens the door to new ways of sound propagation manipulation.rnChapter 6 describes the first measurement of the elastic moduli in newly fabricated by physical vapor deposition so-called ‘stable organic glasses’. rnIn brief, this thesis explores novel phenomena in colloid-based hypersonic phononic structures, utilizing a versatile microfabrication technique along with different colloid architectures provided by material science, and applying a non-destructive optical experimental tool to record dispersion diagrams.rn

Arbitrary Waveform Multilevel Generator for High Voltage High Frequency Plasma Actuators

This dissertation presents the theory and the conducted activity that lead to the construction of a high voltage high frequency arbitrary waveform voltage generator. The generator has been specifically designed to supply power to a wide range of plasma actuators. The system has been completely designed, manufactured and tested at the Department of Electrical, Electronic and Information Engineering of the University of Bologna. The generator structure is based on the single phase cascaded H-bridge multilevel topology and is comprised of 24 elementary units that are series connected in order to form the typical staircase output voltage waveform of a multilevel converter. The total number of voltage levels that can be produced by the generator is 49. Each level is 600 V making the output peak-to-peak voltage equal to 28.8 kV. The large number of levels provides high resolution with respect to the output voltage having thus the possibility to generate arbitrary waveforms. Maximum frequency of operation is 20 kHz. A study of the relevant literature shows that this is the first time that a cascaded multilevel converter of such dimensions has been constructed. Isolation and control challenges had to be solved for the realization of the system. The biggest problem of the current technology in power supplies for plasma actuators is load matching. Resonant converters are the most used power supplies and are seriously affected by this problem. The manufactured generator completely solves this issue providing consistent voltage output independently of the connected load. This fact is very important when executing tests and during the comparison of the results because all measures should be comparable and not dependent from matching issues. The use of the multilevel converter for power supplying a plasma actuator is a real technological breakthrough that has provided and will continue to provide very significant experimental results.

Search for a spin-dependent short-range force between nucleons with a 3 He, 129 Xe clock-comparison experiment

Light pseudoscalar bosons, such as the axion that was originally proposed as a solution of the strong CP problem, would cause a new spin-dependent short-range interaction. In this thesis, an experiment is presented to search for axion mediated short-range interaction between a nucleon and the spin of a polarized bound neutron. This interaction cause a shift in the precession frequency of nuclear spin-polarized gases in the presence of an unpolarized mass. To get rid of magnetic field drifts co-located, nuclear spin polarized 3He and 129Xe atoms were used. The free nuclear spin precession frequencies were measured in a homogeneous magnetic guiding field of about 350nT using LTc SQUID detectors. The whole setup was housed in a magnetically shielded room at the Physikalisch Technische Bundesanstalt (PTB) in Berlin. With this setup long nuclear spin-coherence times, respectively, transverse relaxation times of 5h for 129Xe and 53h for 3He could be achieved. The results of the last run in September 2010 are presented which give new upper limits on the scalar-pseudoscalar coupling of axion-like particles in the axion-mass window from 10^(-2) eV to 10^(-6) eV. The laboratory upper bounds were improved by up to 4 orders of magnitude.

Frequency-dependent response of snow in uniaxial compression and comparison with numerical simulation

La determinazione del modulo di Young è fondamentale nello studio della propagazione di fratture prima del rilascio di una valanga e per lo sviluppo di affidabili modelli di stabilità della neve. Il confronto tra simulazioni numeriche del modulo di Young e i valori sperimentali mostra che questi ultimi sono tre ordini di grandezza inferiori a quelli simulati (Reuter et al. 2013)⁠. Lo scopo di questo lavoro è stimare il modulo di elasticità studiando la dipendenza dalla frequenza della risposta di diversi tipi di neve a bassa densità, 140-280 kg m-3. Ciò è stato fatto applicando una compressione dinamica uniassiale a -15°C nel range 1-250 Hz utilizzando il Young's modulus device (YMD), prototipo di cycling loading device progettato all'Istituto per lo studio della neve e delle valanghe (SLF). Una risposta viscoelastica della neve è stata identificata a tutte le frequenze considerate, la teoria della viscoelasticità è stata applicata assumendo valida l'ipotesi di risposta lineare della neve. Il valore dello storage modulus, E', a 100 Hz è stato identificato come ragionevolmente rappresentativo del modulo di Young di ciascun campione neve. Il comportamento viscoso è stato valutato considerando la loss tangent e la viscosità ricavata dai modelli di Voigt e Maxwell. Il passaggio da un comportamento più viscoso ad uno più elastico è stato trovato a 40 Hz (~1.1•10-2 s-1). Il maggior contributo alla dissipazione è nel range 1-10 Hz. Infine, le simulazioni numeriche del modulo di Young sono state ottenute nello stesso modo di Reuter et al.. La differenza tra le simulazioni ed i valori sperimentali di E' sono, al massimo, di un fattore 5; invece, in Reuter et al.⁠, era di 3 ordini di grandezza. Pertanto, i nostri valori sperimentali e numerici corrispondono meglio, indicando che il metodo qui utilizzato ha portato ad un miglioramento significativo.

The effect of arts speech therapy on cerebral oxygenation and low frequency hemodynamic oscillations measured using functional near-infrared spectroscopy

Introduction: As a previous study revealed, arts speech therapy (AST) affects cardiorespiratory interaction [1]. The aim of the present study was to investigate whether AST also has effects on brain oxygenation and hemodynamics measured non-invasively using near-infrared spectroscopy (NIRS). Material and methods: NIRS measurements were performed on 17 subjects (8 men and 9 women, mean age: 35.6 ± 12.7 y) during AST. Each measurement lasted 35 min, comprising 8 min pre-baseline, 10 min recitation and 20 min post-baseline. For each subject, measurements were performed for three different AST recitation tasks (recitation of alliterative, hexameter and prose verse). Relative concentration changes of oxyhemoglobin (Δ[O2Hb]) and deoxyhemoglobin (Δ[HHb]) as well as the tissue oxygenation index (TOI) were measured using a Hamamatsu NIRO300 NIRS device and a sensor placed on the subjects forehead. Movement artifacts were removed using a novel method [2]. Statistical analysis (Wilcoxon test) was applied to the data to investigate (i) if the recitation causes changes in the median values and/or in the Mayer wave power spectral density (MW-PSD, range: 0.07–0.13 Hz) of Δ[O2Hb], Δ[HHb] or TOI, and (ii) if these changes vary between the 3 recitation forms. Results: For all three recitation styles a significant (p < 0.05) decrease in Δ[O2Hb] and TOI was found, indicating a decrease in blood flow. These decreases did not vary significantly between the three styles. MW-PSD increased significantly for Δ[O2Hb] when reciting the hexameter and prose verse, and for Δ[HHb] and TOI when reciting alliterations and hexameter, representing an increase in Mayer waves. The MW-PSD increase for Δ[O2Hb] was significantly larger for the hexameter verse compared to alliterative and prose verse Conclusion: The study showed that AST affects brain hemodynamics (oxygenation, blood flow and Mayer waves). Recitation caused a significant decrease in cerebral blood flow for all recitation styles as well as an increase in Mayer waves, particularly for the hexameter, which may indicate a sympathetic activation. References 1. D. Cysarz, D. von Bonin, H. Lackner, P. Heusser, M. Moser, H. Bettermann. Am J Physiol Heart Circ Physiol, 287 (2) (2004), pp. H579–H587 2. F. Scholkmann, S. Spichtig, T. Muehlemann, M. Wolf. Physiol Meas, 31 (5) (2010), pp. 649–662

Sensitivity Gains, Linearity, and Spectral Reproducibility in Nonuniformly Sampled Multidimensional MAS NMR Spectra of High Dynamic Range

Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear C-13-C-13 correlation spectra. We demonstrate on model compounds and on 1-73-(U-C-13,N-15)/74-108-(U-N-15) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7-2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear C-13-C-13 MAS correlation experiments that yield high-quality artifact-free datasets.

Myocardial infarction and post-traumatic stress disorder: frequency, outcome, and atherosclerotic mechanisms

BACKGROUND: Post-traumatic stress disorder (PTSD) may develop in the aftermath of an acute myocardial infarction (MI). Whether PTSD is a risk factor for cardiovascular disease (CVD) is elusive. The biological mechanisms linking PTSD with atherosclerosis are unclear. DESIGN: A critical review of 31 studies in the English language pursuing three aims: (i) to estimate the prevalence of PTSD in post-MI patients; (ii) to investigate the association of PTSD with cardiovascular endpoints; and (iii) to search for low-grade systemic inflammatory changes in PTSD pertinent to atherosclerosis. METHODS: We located studies by PubMed electronic library search and through checking the bibliographies of these sources. RESULTS: The weighted prevalence of PTSD after MI was 14.7% (range 0-25%; a total of 13 studies and 827 post-MI patients). Two studies reported a prospective association between PTSD and an increased risk of cardiovascular readmission in post-MI patients and of cardiovascular mortality in combat veterans, respectively. In a total of 11 studies, patients with PTSD had increased rates of physician-rated and self-reported cardiovascular diseases. Various cytokines and C-reactive protein were investigated in a total of seven studies suggesting that PTSD confers a pro-inflammatory state. CONCLUSIONS: Increasing evidence suggests that PTSD specifically related to MI develops considerably frequently in post-MI patients. More research is needed in larger cohorts applying a population design to substantiate findings suggesting PTSD is an atherogenic risk factor and to understand better the suspected behavioural and biological mechanisms involved.