Effect of the radiolitic sterilization in polyethylene/starch blends

Samples of LDPE/modified starch blends 80/20 m/m before and after exposure to gamma rays were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. The effect of gamma radiation is clearly seen in the samples irradiated at a dose of 25 kGy. The main alteration in the polymeric material after exposure at the radiation range was a decrease in the mechanical properties, alterations in the chemical structure of the blend with an increase in the carbonyl and vinyl indices and the appearance of new crystalline symmetry generating a crystalline domain not existing before in the blend.

Microencapsulação do agente quelante sulfoxina em microesferas de quitosana preparadas por spray drying como novo adsorvente para íons metálicos

In this work, a new adsorbent was prepared by microencapsulation of sulfoxine into chitosan microspheres by the spray drying technique. The new adsorbent was characterized by Raman spectroscopy, scanning electron microscopy and microanalysis of energy dispersive X-rays. The Cu(II) adsorption was studied as a function of pH, time and concentration. The optimum pH was found to be 6.0. The kinetic and equilibrium data showed that the adsorption process followed the pseudo second-order kinetic model and the Langmuir isotherm model over the entire concentration range. An increase of 8.0% in the maximum adsorption capacity of the adsorbent (53.8 mg g-1) was observed as compared to chitosan glutaraldehyde cross-linked microspheres.

Raios-x: fascinação, medo e ciência

This work presents the discovery and the use of x-rays at the end of the XIXth and the beginning of the XXth century. X-rays greatly impacted science and everyday life. Their existence broke the idea that knowledge had reached a limiting step. In general, people regarded x-rays as a marvel of science, but reactions against their use were also found. Several applications were proposed, especially in medicine. However, little or no attention was paid to security measures, leading to health damages and even death. The development of the radiological protection took into account the accidents with the x-rays.

Double-bilayer: a new phase formed by lysophospholipids and the corresponding fatty acid

The product of catalytic activity of the enzyme phospholipase A2, which resembles the core unit of animal toxins, on phospholipids is a 1:1 mixture of lysolipid and fatty acid. This mixture was studied by time-resolved simultaneous small- and wide angle x-ray diffraction over the temperature range from 23 to 53.5ºC. An unusually large lamellar structure was observed, with d = 11 nm, contradicting the complex functional dimer model between lysolipid and fatty acid. It can be explained by formation of a "double-bilayer", a new phase consisting of two different bilayers, one formed by lysophospholipid and other by fatty acid, bound together by head group interactions. Its strucutre was confirmed by simulations of the X-ray scattering pattern.

Estudo das interações entre o complexo polieletrolítico trimetilquitosana/carboximetilcelulose e Cu+2, ácido húmico e atrazina em solução aquosa

The polyelectrolyte complex (PEC) resulting from the reaction of sodium carboxymethylcellulose (CMC) and N,N,N-trimethylchitosan hydrochloride (TMQ) was prepared and then characterized by infrared spectroscopy and energy dispersive X rays analysis. The interactions involving the PEC and Cu2+ ions, humic acid and atrazine in aqueous medium were studied. From the adsorption isotherms the maximum amount adsorbed (Xmax) was determined as 61 mg Cu2+/g PEC, 171 mg humic acid/g PEC and 5 mg atrazine/g PEC. The results show that the CMC/TMQ complex has a high affinity for the studied species, indicating its potential application to remove them from aqueous media.

Encapsulation of naproxen in nanostructured system: structural characterization and in vitro release studies

Nanoparticles were produced by solvent emulsification evaporation method with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process (73 ± 1.5%), excellent encapsulation efficiency (81.3 ± 4.2%) and spherical shape. X-rays diffraction demonstrated the loss of drug crystallinity after encapsulation; however, the profile of the diffractograms of the poly-ε-caprolactone (PCL) nanoparticles was kept. Differential scanning calorimetry thermograms, correspondingly, exhibited the loss of drug melting peak and the increasing of the melting point of the PCL nanoparticles, evidencing an interaction drug-polymer. Naproxen release was low and sustained obeying the Higuchi´s kinetic. The results show that nanoparticles are promising sustained release system to the naproxen.

Sistema para realização de medidas de luminescência com excitação por Raios X

In this work is presented a versatile system for X-ray excited optical luminescence (XEOL) measurements. The apparatus was assembled from a sample holder connected to an optical fiber responsibly for the acquisition of the scintillation signal. The spectrum is registered with a CCD coupled in a spectrograph provided with diffraction gratings. The system performance was analyzed by exciting GdAlO3:Eu3+ 3.0 at.% with X-rays from a diffractometer and measuring the emission spectra. The system can be used to obtain precise and reliable spectroscopic properties of samples with various conformations without the loss of the required safety when dealing with ionizing radiations.

Desenvolvimento de um algoritmo para identificação e correção de spikes em espectroscopia Raman de imagem

Raman imaging spectroscopy is a highly useful analytical tool that provides spatial and spectral information on a sample. However, CCD detectors used in dispersive instruments present the drawback of being sensitive to cosmic rays, giving rise to spikes in Raman spectra. Spikes influence variance structures and must be removed prior to the use of multivariate techniques. A new algorithm for correction of spikes in Raman imaging was developed using an approach based on comparison of nearest neighbor pixels. The algorithm showed characteristics including simplicity, rapidity, selectivity and high quality in spike removal from hyperspectral images.

MATERIAIS VÍTREOS E LUZ: PARTE 1

2015 is the Year of Light, according to UNESCO. Chemistry has a close relationship with light and one of the materials that allows such synergy is glass. Depending on the chemical composition of the glass, it is possible to achieve technological applications for the whole range of wavelengths extending from the region of the microwave to gamma rays. This diversity of applications opens a large range of research where chemistry, as a central science, overlaps the fields of physics, engineering, medicine, etc., generating a huge amount of knowledge and technological products used for humanity. This review article aimed at discussing some families of glasses, illustrating some applications. Due to the extension of the theme, and all points raised, we thought it would be good to divide the article into two parts. In the first part we focus on the properties of heavy metal oxide glasses, fluoride glasses and chalcogenide glasses. In the second part we emphasize the properties of glassy thin films prepared by sol-gel methodology and some applications, of both glasses as the films in photonics, and more attention was given to the nonlinear properties and uses of photonic fibers.

Peritonite por bário

We report a case of a 49 years-old man who underwent a barium meal examination for an epigastric pain. A perforated gastric ulcer with barium extravasation into peritoneal cavity was seen on X-rays. During an emergency laparotomy, a perforated pyloric ulcer was noted, along with barium contamination in the peritoneal cavity. The ulcer was closed with an omental patch and an extensive peritoneal lavage with saline was performed. During the postoperative period, the patient developed signs of peritonitis and underwent a new laparotomy was at the 9th day showing a subfrenic abscess with a large barium contamination. The patient presented septic shock and multiple organ failure. dying on the 21th day.

Osteocondromatose múltipla hereditária com envolvimento costal

This is a case report on Hereditary Multiple Osteochondromatosis (HMO) with rib involvement. The authors present aspects of thoracic surface anatomy, and thoracic images (X-rays, computed tomography, magnetic nuclear resonance), as well as the operating procedure.

Origin of successive cambia on stem in three species of Menispermaceae

The lianas observed in this study, Abuta convexa (Vell.) Diels, Abuta imene (Mart.) Eichler, and Chondrodendron platiphyllum (A. St.-Hil.) Miers, all have successive cambia in their stems. The terminology applied to stem histology in species with successive cambia is as diverse as the interpretations of the origins of this cambial variant. Therefore, this study specifically investigates the origin of successive cambia through a developmental analysis of the above-mentioned species, including an analysis of the terminology used to describe this cambial variation. For the first time, we have identified several developmental stages giving rise to the origins of successive cambia in this family. First, the pericycle originates in 1-3 layers of conjunctive tissue. After the differentiation of the first ring, the conjunctive tissue undergoes new divisions, developing approximately 10 rows of parenchyma cells. In the middle portion, a layer of sclereids is formed, again subdividing the conjunctive tissue into two parts: internal and external. New cambia originate in the internal part, from which new secondary vascular strands will originate, giving rise to the second successive vascular ring of the stem. The external part remains parenchymatous during the installation of the second ring and will undergo new periclinal division, repeating the entire process. New cambia will originate from the neoformed strands, which will form only rays. In the literature, successive cambia are formed by a meristem called "diffuse lateral meristem."However, based on the species of Menispermaceae studied in this report, it is demonstrated that the diffuse lateral meristem is the pericycle itself.

The radioprotective effect of a new aminothiol (20-PRA)

We examined the radioprotective effect of aminothiol 2-N-propylamine-cyclo-hexanethiol (20-PRA) on a human leukemic cell line (K562) following various radiation doses (5, 7.5 and 20 Gy) using a source of 60Co g-rays. At 5 Gy and 1 nM 20-PRA, a substantial protective effect (58%) was seen 24 h after irradiation, followed by a decrease at 48 h (11%). At the high radiation dose (20 Gy) a low protective effect was also seen (35%). In addition, the antitumorigenic potential of 10 nM 20-PRA was shown by the inhibition of crown gall formation induced by Agrobacterium tumefaciens. The radioprotective potency of 20-PRA is 105-106 times higher than that of the aminothiol WR-1065 (N-(2-mercaptoethyl)-1,3-diaminopropane) whose protective effect is in the 0.1 to 1.0 mM range.

Structural, functional and immunological studies on a polymeric bacterial protein

The characterization of proteins from Brucella spp, the causative agent of brucellosis, has been the subject of intensive research. We have described an 18-kDa cytoplasmic protein of Brucella abortus and shown the potential usefulness of this protein as an antigen for the serologic diagnosis of brucellosis. The amino acid sequence of the protein showed a low but significant homology with that of lumazine synthases. Lumazine is an intermediate product in bacterial riboflavin biosynthesis. The recombinant form of the 18-kDa protein (expressed in E. coli) folds like the native Brucella protein and has lumazine-synthase enzymatic activity. Three-dimensional analysis by X-ray crystallography of the homolog Bacillus subtilis lumazine synthase has revealed that the enzyme forms an icosahedral capsid. Recombinant lumazine synthase from B. abortus was crystallized, diffracted X rays to 2.7-Å resolution at room temperature, and the structure successfully solved by molecular replacement procedures. The macromolecular assembly of the enzyme differs from that of the enzyme from B. subtilis. The Brucella enzyme remains pentameric (90 kDa) in its crystallographic form. Nonetheless, the active sites of the two enzymes are virtually identical at the structural level, indicating that inhibitors of these enzymes could be viable pharmaceuticals across a broad species range. We describe the structural reasons for the differences in their quaternary arrangement and also discuss the potential use of this protein as a target for the development of acellular vaccines.

Aurapten, a coumarin with growth inhibition against Leishmania major promastigotes

Several natural compounds have been identified for the treatment of leishmaniasis. Among them are some alkaloids, chalcones, lactones, tetralones, and saponins. The new compound reported here, 7-geranyloxycoumarin, called aurapten, belongs to the chemical class of the coumarins and has a molecular weight of 298.37. The compund was extracted from the Rutaceae species Esenbeckia febrifuga and was purified from a hexane extract starting from 407.7 g of dried leaves and followed by four silica gel chromatographic fractionation steps using different solvents as the mobile phase. The resulting compound (47 mg) of shows significant growth inhibition with an LD50 of 30 µM against the tropical parasite Leishmania major, which causes severe clinical manifestations in humans and is endemic in the tropical and subtropical regions. In the present study, we investigated the atomic structure of aurapten in order to determine the existence of common structural motifs that might be related to other coumarins and potentially to other identified inhibitors of Leishmania growth and viability. This compound has a comparable inhibitory activity of other isolated molecules. The aurapten is a planar molecule constituted of an aromatic system with electron delocalization. A hydrophobic side chain consisting of ten carbon atoms with two double bonds and negative density has been identified and may be relevant for further compound synthesis.