Um fotômetro de fluxo para análises clínicas a base de um diodo emissor de luz bicolor

The construction and evaluation of an inexpensive flow photometer for clinical analysis, using a bicolour LED and a phototransistor adapted for tubular flow cell, are described. The instrument presents some new features such as: automatic zero, electronic calibration and peak-hold signal. When compared with a classical photometer, it is simpler and has the advantages of a flow analysis system: lower volumes of reagents and samples, lower levels of contamination, shorter time for analysis and lower analysis costs. The instrument was used in the determination of the constituents in blood samples. The results obtained agree with those obtained by a classical photometer and the precision was better.

Compósitos colágeno aniônico: fosfato de cálcio. Preparação e caracterização

Anionic collagen: calcium phosphate composite was obtained by controlled mixing of collagen and calcium phosphate until the consistence of a past. Material was characterized by a Ca/P ratio of 1.55, with a X-ray diffraction pattern similar to that for hydroxyapatite. Differential Scanning Calorimetry showed that the protein is not denatured under the processing conditions. Scanning Electronic Microscopy showed that the mineral phase are regularly covered with collagen fibers, indicating that anionic collagen is efficient in the preparation of stable form of calcium phosphate ceramic paste.

Estudo das propriedades ópticas em vidros 0,3La2S3-0,7Ga2S 3

In this work we describe the synthesis and characterization of chalcogenide glass (0.3La2S3-0.7Ga2S 3) with low phonons frequencies. Several properties were measured like Sellmeier parameters, linear refractive index dispersion and material dispersion. Samples with the composition above were doped with Dy2S3. The absorption and emission characteristics were measured by electronic spectroscopy and fluorescence spectrum respectively. Raman and infrared spectroscopy shows that these glasses present low phonons frequencies and strucuture composed by GaS4 tetrahedrals. The Lines model was used for calculate the coefficients values of the non linear refractive index.

Estudo do comportamento ácido-base da 4,4'-ditiodipiridina

Despite the importance of the 4,4'-dithiodipyridine as an electrode modifier on the protein electrochemical studies and as a remarkable bridged-ligand on conducting electronic density in binuclear mixed valence complexes, there is no data available in the literature concerning acid-base behavior of this compound. Aiming to afford such information we undertook the ionization equilibrium study of this ligand. Although two acid species, DTDPH+ and DTDPH2+ have been detected in solution, only the diacid-form was possible to be isolated as a perclorate salt DTDPH2(ClO4)2. The ionization constants for the two step equilibrium processes (pKa1=2.70 and pKa2=4.80) were determined by using the spectrophotometric technique and aqueous solutions of CF3COONa, mu=0,1 mol.L-1 .

Isolamento e caracterização de acil-tiossemicarbazidas como intermediários na síntese de compostos mesoiônicos

1,3,4-thiadiazolium-2-aminides and their isomers 1,3,4-triazolium-2-thiolates have been synthesized via anhydroacylation reactions. This work presents a study by infrared monitoring of the reaction between substituted aroyl acid chlorides and 1,4-diphenylthiosemcarbazide. The intermediates and products were isolated, purified and charaterized by IR and 13C NMR spectroscopy. The increasing or decreasing in intensity of characteristic stretching bands indicated the rate dependence on the electronic nature of substituents. The results also demonstrate that 1,3,4-triazolium-2-thiolates are obtained in anhydrous conditions whereas presence of water leads to a mixture of the isomers.

Les Sentències catòliques del diví poeta Dant (1545) d’en Jaume Ferrer de Blanes: edició crítica del text

Procurador reial i nobiliari, cosmògraf, joier, lapidari, mercader i escriptor, i al capdavall, un ciutadà català honrat, en Ferrer (Vidreres, ~1445 – Blanes, 1529) va marxar de ben jove, primer, a la cort de Nàpols, al servei del rei en Ferran I, i després a la cort de Sicília, al servei de la reina na Joana de Sicília. Acabada aquesta peripècia italiana va tornar a Blanes al servei del vescomte de Cabrera i de Bas fins que va morir a la mateixa vila al 1529. Un seu criat, disset anys més tard, va editar uns papers esparsos que havia trobat a can Ferrer, les (sic) Sentèncias cathòlicas del diví poeta Dant florentí, compilades per lo prudentíssim mossèn Jaume Ferrer de Blanes, incloent-hi tres parts. La primera, Conclusions, és un sumari destinat a mostrar (sic) «Entre totas las cosas necessàries a l’home per aconseguir lo seu fi y beatitut eterna principalment són tres»; la segona, Meditació, és una reflexió a fi d’il•luminar els misteris sobre la passió i mort de Jesucrist a (sic) «lo santíssim loch de Calvari»; la tercera, Letras, és un conjunt de dotze documents, entre cartes i d’altres textos, «fetas a mossèn Jaume Ferrer, respostes e regles per ell ordenades en cosmographia y en art de navegar». En Ferrer, home de grans recursos, fa un recorregut per tots els coneixements que havia acumulat al llarg de la seva vida, de Dant Alighieri a Ptolemeu i del marquès de Santillana a Albert Gran o a Aristòtil, fent servir fragments de la Commedia, dels Proverbios, de la Bíblia i de moltes altres autoritats científiques i filosòfiques, en català, italià, espanyol, llatí i, també, set mots en arameu

Estudo químico-computacional da reatividade de aziridinona e diaziridinona através de cálculos semi-empíricos

The results of semiempirical molecular orbital calculations performed on aziridinone and diaziridinone employing the MNDO, AM1, and PM3 molecular models are presented. The AM1 method, which best reproduces ground-state molecular properties, is used to calculate electronic parameters and the use of these parameters for the evaluation of reactivity is discussed.

The 21st century chemistry journal

Internet publication will radically alter how chemists will publish their research in the next century. In this article, we describe two fundamental changes: enhanced chemical publication which allows chemists to publish materials that cannot be published on paper and end-user customization which allows readers to read articles prepared to meet their specifications. These concepts have been implemented within the Internet Journal of Chemistry, a new journal designed to employ the latest technologies for chemical publications.

Elementos da dinâmica química ao nível da teoria variacional do estado de transição com correções interpoladas

In this article are presented some fundamental elements of the conventional and of the variational transition state theories which are needed to carried out calculations of semi-classical chemical dynamics. Some important bottlenecks in building reliable potential energy surfaces using electronic structure calculations are also discussed. It is put emphasis on the methodology of the variational transition state theory with interpolated corrections (VTST-IC), and its application in the calculations of the rate constants and of the kinetic isotope effect (KIE) of CH4 + Cl « CH3 + HCl reaction.

Investigação espectroscópica dos carbonilos heterobimetálicos cis-[Fe(CO)4(HgX)2], X = Cl, Br,I

The series of compounds cis-[Fe(CO)4(HgX)2], X=Cl,Br,I shows an octahedral geometry around the iron atom with the two HgX groups cis to each other. In this paper the assignment for the carbonyl stretching modes and the calculation of their force constants were performed on the basis of the Cotton-Krainhanzel model. Taking into account all the data from the IR, 199Hg NMR and UV-vis spectra it is possible to verify the influence of X on the electronic densities at the metallic centers.

Síntese de poli(p-xililenos)

Poly(p-xylylenes), PPX, are a class of high performance insulating materials with many applications in the electronic component industry. We review herewith the most important synthetic routes to these polymers, described in the literature, since 1904.

Entendendo estrutura molecular com a molécula de hidrogênio ionizada

In this paper a general view about the modern molecular structure theory is developed discussing the ionized hydrogen molecule. We introduce some necessary approximation methods for the electronic and nuclear spectra study adopting a systematic approach. In addition though, we have performed calculations in order to illustrate these methods.

O ensino de aspectos históricos e filosóficos da Química e as teorias ácido-base do século XX

In this paper, an overview about philosophy of science, the concept of "theory" and some characteristics of a"good"theory (1- ordination and explanation of the facts, 2- proposal of problems, and 3- simplicity and funcionality) are initialy introduced. Following, some historical landmarks of acidity and basicity and a summary of the main acid-base theories of the XX century (Arrhenius, solvent systems, protonic, electronic, Lux, Usanovich and ionotropic) are presented. Historical and conceptual relations between these theories are discussed and the three characteristics of a "good" theory are applied. The results showed that the protonic and eletronic theories are the "best". Some discussion of the implications to chemical education are presented too.