Characterizing the relative role of low-frequency and turbulent processes in the nocturnal boundary layer through the analysis of two-point correlations of the wind components

The study presents an analysis of two-point correlations between time series of nocturnal atmospheric wind, obtained from two micrometeorological towers, 45 m horizontally apart, each equipped with two sonic anemometers, 2.5 m vertically apart. It focuses on the scale dependence of the two-point correlations obtained from sensors vertically and horizontally separated. In particular, the role of low-frequency non-turbulent processes in the correlations is assessed, and compared to that of the turbulent scales of motion. The vertical correlations of the streamwise and vertical wind components show little dependence on the turbulence intensity, but those of the spanwise component decrease appreciably as it gets more turbulent. Multiresolution decomposition shows that the two-point correlations become increasingly dominated by low-frequency scales as it gets less turbulent, and that such large-scale processes are largely reduced in fully turbulent conditions. It is also shown that the vertical correlations of the spanwise wind component is negative for very small time scales. Horizontal two-point correlations obtained at the 45 m separation distance between the towers are almost entirely dominated by low-frequency motions, regardless of the turbulence intensity, but the magnitude of such correlations decreases with increasing turbulence intensity for any wind components. A comparison between the horizontal two-point correlations and autocorrelations taken with a time lag given by the ratio of the horizontal separation to the mean wind component in the direction that connects the two towers leads to the conclusion that the statistical properties of turbulence are often preserved over the horizontal distance, despite the lack of turbulence correlations for that separation.     

Scaling laws in the dynamics of crime growth rate

The increasing number of crimes in areas with large concentrations of people have made cities one of the main sources of violence. Understanding characteristics of how crime rate expands and its relations with the cities size goes beyond an academic question, being a central issue for contemporary society. Here, we characterize and analyze quantitative aspects of murders in the period from 1980 to 2009 in Brazilian cities. We find that the distribution of the annual, biannual and triannual logarithmic homicide growth rates exhibit the same functional form for distinct scales, that is, a scale invariant behavior. We also identify asymptotic power-law decay relations between the standard deviations of these three growth rates and the initial size. Further, we discuss similarities with complex organizations.     

Structural,electronic, and magnetic entropy contributions of the orbital order–disorder transition in LaMnO3

Measurements of X-ray diffraction, electrical resistivity, and magnetization are reported across the Jahn–Teller phase transition in LaMnO₃. Using a thermodynamic equation, we obtained the pressure derivative of the critical temperature (T _JT ), dT _JT /dP?=??28.3?K?GPa^?1. This approach also reveals that 5.7(3)J?(mol?K)^?1 comes from the volume change and 0.8(2)?J?(mol?K)^?1 from the magnetic exchange interaction change across the phase transition. Around T _JT , a robust increase in the electrical conductivity takes place and the electronic entropy change, which is assumed to be negligible for the majority of electronic systems, was found to be 1.8(3)?J?(mol?K)^?1.     

NO Fluorescence Sensing by Europium Tetracyclines Complexes in the Presence of H2O2

The effect on the fluorescence of the europium:tetracycline (Eu:Tc), europium:oxytetracycline (Eu:OxyTc) and europium:chlortetracycline (Eu:ClTc) complexes in approximately 2:1 ratio of nitric oxide (NO), peroxynitrite (ONOO^?), hydrogen peroxide (H₂O₂) and superoxide (O₂ ^·?) was assessed at three ROS/RNS concentrations levels, 30 °C and pH 6.00, 7.00 and 8.00. Except for the NO, an enhancement of fluorescence intensity was observed at pH 7.00 for all the europium tetracyclines complexes—the high enhancement was observed for H₂O₂. The quenching of the fluorescence of the Tc complexes, without and with the presence of other ROS/RNS species, provoked by NO constituted the bases for an analytical strategy for NO detection. The quantification capability was evaluated in a NO donor and in a standard solution. Good quantification results were obtained with the Eu:Tc (3:1) and Eu:OxyTc (4:1) complexes in the presence of H₂O₂ 200 μM with a detection limit of about 3 μM (Eu:OxyTc).     

Repeated Richardson extrapolation applied to the two-dimensional Laplace equation using triangular and square grids

The focus of this work is to verify the efficiency of the Repeated Richardson Extrapolation (RRE) to reduce the discretization error in a triangular grid and to compare the result to the one obtained for a square grid for the two-dimensional Laplace equation. Two different geometries were employed: the first one, a unitary square domain, was discretized into a square or triangular grid; and the second, a half square triangle, was discretized into a triangular grid. The methodology employed used the following conditions: the finite volume method, uniform grids, second-order accurate approximations, several variables of interest, Dirichlet boundary conditions, grids with up to 16,777,216 nodes for the square domain and up to 2097,152 nodes for the half square triangle domain, multigrid method, double precision, up to eleven Richardson extrapolations for the first domain and up to ten Richardson extrapolations for the second domain. It was verified that (1) RRE is efficient in reducing the discretization error in a triangular grid, achieving an effective order of approximately 11 for all the variables of interest for the first geometry; (2) for the same number of nodes and with or without RRE, the discretization error is smaller in a square grid than in a triangular grid; and (3) the magnitude of the numerical error reduction depends on, among other factors, the variable of interest and the domain geometry.     

Preparation and Characterization of New Biodegradable Films Made from Poly(L-Lactic Acid) and Chitosan Blends Using a Common Solvent

Poly-(L-lactic acid) (PLLA) has been widely used for various biomedical applications due to its interesting properties such as its mechanical behavior, processability, biocompatibility, and biodegradability. Blending this polymer with chitosan that, besides being biodegradable and hydrophilic, can interact with anionic glycosaminoglycans, proteoglycans, and other negatively charged molecules of the extracellular matrix, could constitute an excellent way to improve the biological performance of PLLA in these kinds of applications. Such blends could also be used in environmental applications. In this work a new and simple method of preparing biodegradable blends of chitosan and PLLA at room temperature was developed. To the best of our knowledge, this is the first time that a common solvent for the two polymers has been used, hexafluor-2-propanol (HFIP), to produce a homogeneous solution containing both PLLA and chitosan. We also anticipate that this solvent can also be used to compatibilize other combinations of natural and synthetic polymers. Membranes were then obtained by solvent casting. Films with different fractions of each component were successfully prepared and didn't show visible phase separation. The prepared films were characterized by differential scanning calorimetry (DSC) in order to analyze the miscibility of the two components as a function of the composition of the film.     

Source of slow lithium atoms from Ne or H2 matrix isolation sublimation

We have studied, via laser absorption spectroscopy, the velocity distribution of (7)Li atoms released from cryogenic matrices of solid neon or molecular hydrogen. The Li atoms are implanted into the Ne or H(2) matrices--grown onto a sapphire substrate--by laser ablation of a solid Li or LiH precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms. With a NiCr film resistor deposited directly onto the sapphire substrate we are able to transfer high instantaneous power to the matrix, thus reaching a fast sublimation regime. In this regime the Li atoms can get entrained in the released matrix gas, and we were also able to achieve matrix sublimation times down to 10 μs for both H(2) or Ne matrix, enabling us to proceed with the trapping of the species of our interest such as atomic hydrogen, lithium, and molecules. The sublimation of the H(2) matrix, with its large center-of-mass velocity, provides evidence for a new regime of one-dimensional thermalization. The laser ablated Li seems to penetrate the H(2) matrix deeper than it does in Ne.     

Effects of low-level laser therapy at wavelengths of 660 and 808 nm in experimental model of osteoarthritis

The aim of the present study was to analyze the influence of low-level laser radiation at wavelengths of 660 and 808 nm in an experimental model of osteoarthritis (OA). The sample was composed of 36 male adult Wistar rats divided into three groups (G1, G2 and G3). For the induction of cartilage injury, three injections of 4% papain and 10 μL of a cysteine solution were performed at right knee of the hind leg. Two weeks after the last injection, group G1 was treated with InGaAlP (660 nm, 100 mW, 3.57 W cm(-2), 40 s) and G2 was treated with AsGaAl (808 nm, 100 mW, 3.57 W cm(-2), 40 s) both with energy of 4 J. There were significant differences in the type of squamous epithelium between days 7 and 14 in G2 (P < 0.05) and on day 14 between G1 and G2 (P < 0.05). Moreover, statistically significant differences were found in the formation of new blood vessels between G1 and G3 on days 7 and 21 as well as between G2 and G3 on day 21. The formation of fibrotic tissue was greater in G3 (P < 0.05). In conclusion, laser therapy, especially at a wavelength of 808 nm, stimulated angiogenesis and reduced the formation of fibrosis in an experimental model of OA.     

Synthesis of novel selenium and tellurium-containing tetrazoles: a class of chalcogen compounds with antifungal activity

We describe herein the synthesis and antifungal activity of new 5-arylchalcogenoalkyl-1H-tetrazoles 4. Arylchalcogenoalkyl-1H-tetrazoles 4 have been synthesized in high yields by reaction of arylchalcogenolate anions with chloronitriles 2, and subsequent [2+3] cycloaddition of resulting arylchalcogenoalkylnitriles 3 with sodium azide by zinc catalysis in aqueous solution. The obtained compound 4a was screened for antifungal activity and presented inhibitory property against seven fungal strains. This protocol is an efficient method to produce new selenium–nitrogen compounds with antifungal activity.     

Highly stereoselective method to prepare bis-phenylchalcogen alkenes via addition of chalcogenolate to phenylseleno alkynes

The preparation of bis-phenylchalcogen alkenes starting from phenylseleno alkynes is described. The nucleophilic species of selenium, tellurium and sulfur were generated in situ from the reaction of the respective diphenyl dichalcogenide with NaBH₄ in PEG-400 as solvent. The chalcogenolate anions were efficiently and selectively added to a variety of phenylselenoalkynes at mild conditions, furnishing the respective (Z)-1,2-bis-phenylchalcogen alkenes in good yields.