Hidrogeochemical study in South Amazon region using Photoacoustic Spectroscopy

In this study we demonstrate the usefulness of the Photoacoustic Spectroscopy (PAS) in the investigation of water collected from a natural site located within the Amazon region, Brazil, during the wet to dry seasons transition (May/2006). The water samples were collected from different stages along a hydrologic pathway including precipitation water (Prec), groundwater (GW), through flow water (TF), overland flow water (OF), and stream flow water (SW). The observed photoacoustic spectral features, in the 0.3 to 1.0 μm wavelength region, fall within three distinct bands (C, S, and L). We found band-C, band-S and band-L occurring in the spectral range of 0.30 to 0.40 μm, 0.40 to 0.45 μm and 0.45 to 1.0 μm regions, respectively. The photoacoustic features shift peak positions and change intensities for all samples investigated, thus supporting the proposal of PAS as a useful technique to investigate water samples from natural environments.     

Babassu mesocarp (Orbignya phalerata Mart) nanoparticle-based biosensors for indirect sulfite detection in industrial juices

Journal of Solid State Electrochemistry - The present work proposes a new electrochemical sulfite biosensor based on babassu mesocarp nanoparticles (BMNPs) immobilized on the surface of a pyrolytic...     

Lie point symmetries and some group invariant solutions of the quasilinear equation involving the infinity Laplacian

Using the classical Lie method we obtain the full Lie point symmetry group of the Aronsson equation in two independent variables. Some group invariant solutions of this equation are found and a conjecture on the Lie point symmetry group of the Aronsson equation in Rⁿ is presented.     

Catechins: Therapeutic Perspectives in COVID-19-Associated Acute Kidney Injury

Data obtained from several intensive care units around the world have provided substantial evidence of the strong association between impairment of the renal function and in-hospital deaths of critically ill COVID-19 patients, especially those with comorbidities and requiring renal replacement therapy (RRT). Acute kidney injury (AKI) is a common renal disorder of various etiologies characterized by a sudden and sustained decrease of renal function. Studies have shown that 5–46% of COVID-19 patients develop AKI during hospital stay, and the mortality of those patients may reach up to 100% depending on various factors, such as organ failures and RRT requirement. Catechins are natural products that have multiple pharmacological activities, including anti-coronavirus and reno-protective activities against kidney injury induced by nephrotoxic agents, obstructive nephropathies and AKI accompanying metabolic and cardiovascular disorders. Therefore, in this review, we discuss the anti-SARS-CoV-2 and reno-protective effects of catechins from a mechanistic perspective. We believe that catechins may serve as promising therapeutics in COVID-19-associated AKI due to their well-recognized anti-SARS-CoV-2, and antioxidant and anti-inflammatory properties that mediate their reno-protective activities.     

Synthesis and Cytotoxic Activity of 4-Substituted 3-Cyano-6,6-dimethyl-5,6-dihydro-2-pyranones

The respective 4-(arylvinyl)lactones and compounds of the Michael adduct type were synthesized by the condensation of substituted benzaldehydes with 3-cyano-4,6,6-trimethyl-5,6-dihydro-2-pyranone in the presence of catalytic amounts of sodium hydroxide. It was shown by the semiempirical AM1 method that the indicated products can be formed through one and the same intermediate compound. Some of the synthesized phenylvinyl-5,6-dihydro-2-pyranones have a cytotoxic effect, and this corresponds to the prognosis of the OREX expert system.     

Effects of X-ray absorption in the analysis of thick target samples by XRF

The accuracy of the quantitative analysis of thick targets by XRF is impaired by effects due to the absorption of X-rays in the matrix associated with the non-uniformity of the X-ray beam and the lack of knowledge of the actual distribution of trace elements in the target. The uncertainty in the elemental mass associated to a definite number X-rays detected is discussed in the paper. A correction factor is derived to account specifically for the effect of the absorption of X-rays and the non-uniformity of the X-ray beam. Work partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico, Financiadora de Estudos e Projetos and International Atomic Energy Agency.     

Multiple scattering mass operator method for molecular orbital calculations

An exchange-correlation potential model to be used in connection with the multiple scattering method is presented. Retaining the main advantages of the multiple scattering method with the Xα potential, particularly its low computational requirements, this new formalism does not require any adjustable parameter. Test calculations on the NiF₆^4? system are reported and compared with experimental and ab initio results.