Crystal growth of FeCO3 in mixed monoethylene glycol and water solvent

The transportation of natural gas in long subsea pipelines is a challenge when it comes to hydrate prevention, corrosion and mineral scaling. When monoethylene glycol (MEG) is injected into carbon steel pipelines to prevent formation of gas hydrates, the solubility of the corrosion products is altered. Understanding the kinetics of FeCO₃ precipitation may make it possible to avoid deposition in the gas liquid separation process and improve solids removal in MEG recovery units. In this work, the growth kinetics of iron carbonate (siderite) has been studied in seeded batch experiments in MEG‐water solutions with 0 and 40 wt% MEG at 50 and 70 °C. Precautions were taken to keep anaerobic conditions and avoid oxidation of ferrous ions. The growth rate (G) was measured as function of supersaturation (S) and fitted to the equation: G = k_r(S‐1)^g. The growth order (g) was approximately 2 independent of the MEG concentration at the two temperatures. The growth rate constant (k_r) was in the range of 6 × 10⁻¹¹ to 1 × 10⁻¹⁰ m/s. Temperature increase from 50 to 70°C had no measurable effect on the growth rate while in the presence of 40 wt% MEG the growth rate constant decreased.     

One-step separation of terpenoids from leaves extracts of Solanum cernuum by high-performance countercurrent chromatography

Solanum cernuum is a native shrub from Brazil that has been used as medicine since the nineteenth century. Although it has been utilized for a long time, there are few studies regarding its chemical composition and it motivated us to investigate this species. The dried leaves of S. cernuum were extracted with methanol and the obtained extract was further partitioned with different organic solvents. As part of our investigation, the n-hexane fraction was submitted to CCC with a nonaqueous solvent system composed of hexane, acetonitrile, and ethyl acetate (5:5:1, v/v/v). Three terpenoids were obtained by one-step separation and identified as 24-oxo-31-norcycloartanone (22.8 mg), lupeol (9.4 mg), and cycloeucalenone (13.4 mg). Complementarily, the solvents system used on the separation have had their compositions determined by gas chromotography–flame ionization detector (GC-FID).     

Density, excess volume, and excess coefficient of thermal expansion of the binary systems of dimethyl carbonate with butyl methacrylate, allyl methacrylate, styrene, and vinyl acetate at T = (293.15, 303.15, and 313.15) K

Densities of the binary systems of dimethyl carbonate with butyl methacrylate, allyl methacrylate, styrene, and vinyl acetate have been measured as a function of the composition at (293.15, 303.15, and 313.15) K at atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The excess molar volumes are negative for the (dimethyl carbonate + vinyl acetate) system and positive for the three other binaries, and become more so as the temperature increases from (293.15 to 313.15) K. The apparent volumes were used to calculate the values of the partial excess molar volumes at infinite dilution. The excess coefficient of thermal expansion is positive for the four binary systems. The calculated excess molar volumes were correlated with the Redlich-Kister equation and with a series of Legendre polynomials. An explanation of the results is offered based on the FT-IR (ATR) spectra of several mixtures of the different systems.     

Synthesis and spectral data of new 1,2‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)ethanes and 1,4‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)butanes

New αω‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)alkanes were prepared via a common two step procedure using N,N‐bis‐hetarylidenamines condensation with α‐mercaptoacetic acid. The used bis‐aldimines were obtained from reaction between ethylenediamine or putrescine and benzaldehyde or the isomeric pyridinecarboxyaldehydes. The bis‐(2‐phenyl‐4‐oxothiazolidin‐3‐yl)alkanes were prepared by one‐pot three component reaction of diamine, aldehyde and α‐mercaptoacetic acid under very mild conditions.     

Volumetric Properties of the Ternary System Dimethyl Carbonate + Butyl Methacrylate + Allyl Methacrylate and Its Binary Butyl Methacrylate + Allyl Methacrylate at 293.15 K and p=101.325 kPa

Densities of the ternary system dimethyl carbonate + butyl methacrylate + allyl methacrylate and its binary subsystem butyl methacrylate + allyl methacrylate have been measured in the whole composition range, at 293.15 K and atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The calculated excess molar volumes of the binary system are positive and were correlated with the Redlich?CKister equation and with a series of Legendre polynomials. Several models were used to correlate ternary behavior from the excess molar volume data of their constituent binaries and found to fit the data equally well. The best fit was based on a direct approach, without information on the component binary systems.     

Field performance test of PASS,an instrument for the rapid assay of plutonium and other γ-ray emitting radionuclides

A field performance test was conducted at the INEL with the mobile Rapid Transuranic Monitoring Laboratory (RTML) that was developed for the analysis of samples from sites or facilities potentially contaminated with plutonium, other actinides, and -ray emitting activation and fission-product radionuclides. The performance test and results are described for the Photon Analysis Spectrometer System (PASS), one of three RTML assay systems. This system consists of a thin-window, n-type Ge spectrometer, that automatically analyzes soil, smear, and air particulate-filter samples for actinides emitting L x rays, and for activation and fission products that emit rays. The measurements were blind and performed with 11-g soil samples gathered from the Cold Test Pit and with spiked samples containing known mixtures of²³⁹Pu,²⁴¹Am⁶⁰Co, and¹³⁷Cs. In the spiked samples the plutonium activity concentrations ranged from 75 to 500 pCi/g while the other radionuclides ranged from 10 to 130 pCi/g. Lower limits of detection (LLDs) were verified to be 1, 5, 5, and 40 pCi/g for²⁴¹Am,⁶⁰Co,¹³⁷Cs, and²³⁹Pu, respectively. Results from the performance test are presented.     

Momentum distribution of relativistic nuclei with Hartree-Fock mesonic correlations

The impact of Hartree-Fock correlations on the nuclear momentum distribution is studied in a fully relativistic one-boson-exchange model. Hartree-Fock equations are exactly solved to first order in the coupling constants. The renormalization of the Dirac spinors in the medium is shown to affect the momentum distribution, as opposed to what happens in the non-relativistic case. The unitarity of the model is shown to be preserved by the present renormalization procedure. Received: 7 June 2002 / Accepted: 24 September 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: juan@nucle.us.es Communicated by G. Orlandini     

Effect of the lectin of Bauhinia variegata and its recombinant isoform on surgically induced skin wounds in a murine model

Lectins are a structurally heterogeneous group of highly specific carbohydrate-binding proteins. Due to their great biotechnological potential, lectins are widely used in biomedical research. The purpose of the present study was to evaluate the healing potential of the lectin of Bauhinia variegata (nBVL) and its recombinant isoform (rBVL-1). Following surgical creation of dorsal skin wounds, seven groups of mice were submitted to topical treatment for 12 days with lectin, D-galactose, BSA and saline. The animals were anesthetized and euthanized on POD 2, 7 and 12 in order to evaluate the healing potential of each treatment. The parameters considered included wound size, contraction rate, epithelialization rate and histopathological findings. Wound closure was fastest in animals treated with rBVL-1 (POD 7). nBVL was more effective than the controls. All skin layers were reconstructed and keratin deposition increased. Our findings indicate that the lectin of Bauhinia variegata possesses pro-healing properties and may be employed in the treatment of acute skin wounds.     

Modification of composites of block copolymers–gold nanoparticles with enzymes and their characterization by electrochemical techniques

In this work, the poly(styrene-vynil pyridine) block copolymer was used as a porous pattern to study the electrodeposition of gold inside the pores, as a new method to obtain gold nanoparticles. The porous pattern left by the copolymer film onto a conductive glass surface was characterized by atomic force microscopy (AFM), evidencing pores of 30 nm diameter. After the electrodeposition, 30 nm diameter gold nanoparticles were obtained and they were characterized by cyclic voltammetry (CV) and AFM, and then used to study the adsorption of glucose oxidase enzyme. The adsorption process of glucose oxidase on gold nanowires was investigated by CV and electrochemical impedance spectroscopy. The morphological and capacitance results indicate that the block copolymer–gold nanoparticle composite seems to be a good candidate to design biosensors and immunosensors.