Length-dependent extraction of single-walled carbon nanotubes

A two-phase liquid-liquid extraction process is presented which is capable of extracting water-soluble single-walled carbon nanotubes into an organic phase. The extraction utilizes electrostatic interactions between a common phase transfer agent and the sidewall functional groups on the nanotubes. Large length-dependent van der Waals forces for nanotubes allow the ability to control the length of nanotubes extracted into the organic phase as demonstrated by atomic force microscopy.     

Thermal Diffusivity of Palm Olein and Compounds Containing <Emphasis Type="Italic">β</Emphasis>-carotene

The effect of dissolving β-carotene into palm olein was experimentally investigated using time-resolved thermal lens spectroscopy. The thermal diffusivity of palm olein was measured, and the dependence on the concentration of the compounds was studied. The results show an enhancement in the thermal diffusivity by increasing the quantity of β-carotene in the compounds. This behavior was interpreted on the basis of the electronic structure of the β-carotene molecule.     

Synthesis, hydration and durability of rice hull cements doped with chromium

This work describes the synthesis, hydration and durability behavior of β-Ca(2)SiO(4) doped with chromium. β-Ca(2)SiO(4) is a component of commercial cement. Rice hull is an agricultural residue containing about 10% of silica as inorganic constituent. The controlled burning of rice hull was used to obtain this biogenic silica, used as starting material. In many situations chromium is added during cement preparation in order to promote encapsulation, at temperatures around 1500°C. The synthesis presented here is completed at 800°C, causing a substantial reduction in energy consumption. Moreover, chromium is chemically bonded to cement crystal, which is safer than simple physical encapsulation. Results show that chromium can be inserted into the structure of β-Ca(2)SiO(4) up to 1% (molar ratio). Hydration degree and durability studies show that insertion of chromium causes no deleterious effects on physical and chemical properties of these doped materials when compared to β-pure Ca(2)SiO(4).     

Effect of crystal orientation on lapping and polishing processes of natural quartz

Lapping and polishing processes of natural quartz are investigated in relation to crystallographic orientation and applied normal stress. Weight loss measurements and surface profilometry were carried out in X-, Y-, Z-, and AT-cut samples. The relationship found between material removal rate and stress depends on specimen orientation. Based on indentation fracture mechanics, this behavior is discussed in relation to fracture toughness and scratch hardness anisotropy of quartz crystals. Scanning electron microscopy (SEM) shows that brittle microcracking is the primary mechanism involved with material removal in the lapping process. Plastic deformation mechanisms begin to operate on lapped and polished surfaces above a certain value of stress. Surface profiles and SEM micrographs show that the roughness of lapped surfaces decreases with increasing normal stress, but an opposite behavior is observed in polished surfaces     

Nucleation Processes Close to the Spinodal

Using an analytical equation of state (EOS) which describes a system that can exist in a liquid or vapor phase, a generalized Landau free-energy expansion around any spinodal point is constructed. For this simple model, the critical exponents associated with the spinodal line are obtained, and the model reduces to the usual expansion around the critical point as a particular case. The approach may become an interesting starting point to study phase separation mechanisms, such as nucleation and spinodal decomposition, far from the critical point. The decay of deeply quenched metastable states close to the spinodal through a nucleation process is analyzed and their mean lifetime is obtained. The results are compared with those obtained through the use of the usual Landau free-energy expansion around the critical point.     

Studies on electrodeposition and corrosion behaviour of a Ni–W–Co amorphous alloy

A ternary alloy Ni–W–Co was electrodeposited and operational parameters in relation to its corrosion resistance and deposition efficiency were optimized. A 2² full factorial design was successfully employed for experimental design analysis of the results. By means of response surface analysis, the statistical model identified the following operating conditions for obtaining corrosion resistant alloy: 60 mA/cm² current density, 70 °C temperature, 20 rpm cathode rotation and 8.0 pH. The alloy was deposited at 36% current efficiency, with an average composition of 70% Ni, 8% Co, 22% W and traces of boron and with E _corr −0.508 V and R _p 4.56 × 10⁴ Ohm. The deposit obtained under these conditions had an amorphous character and showed good adherence, high corrosion resistance and presence of nodules on its surface. Electrochemical corrosion tests verified that the Ni–W–Co alloy had better corrosion resistance than similarly electrodeposited Co–W amorphous alloy.     

Transchoroidal approach to the third ventricle: an anatomic study of the choroidal fissure and its clinical application

OBJECTIVE: We review the anatomic features of the lateral ventricle, the foramen of Monro, the third ventricle, and the choroidal fissure, and we describe the transchoroidal approach to the third ventricle. This approach consists of opening the taenia fornicis of the choroidal fissure in the body of the lateral ventricle and approaching the third ventricle between the two internal cerebral veins. This route allows further posterior enlargement of the foramen of Monro without sacrificing any neural structures. When necessary, the anterior septal vein can be sacrificed. METHODS: Twenty adult cadaveric brains and four adult cadaveric heads were studied, using a magnification ranging from 3 times to 40 times, after perfusion of the arteries and veins with colored latex. RESULTS: The choroidal fissure is a natural cleft between the thalamus and the fornix, and it is identified by following the choroid plexus in the lateral ventricle. The choroid plexus in the body of the lateral ventricle originates from the tela choroidea of the roof of the third ventricle and is apparently attached to the fornix by the taenia fornicis and to the thalamus by the taenia choroidea. The taenia is actually the ependyma that covers the internal wall of the ventricular cavity and the choroid plexus. CONCLUSION: An understanding of the choroidal fissure is fundamental for use of the transchoroidal approach. Unlike transforaminal, subchoroidal, subforniceal, and interforniceal approaches to the third ventricle, which sacrifice some neural or vascular structures, the transchoroidal approach follows a natural route, and certainly it is one of the options to be considered when entry into the third ventricle is required.     

The complete amino acid sequence of a trypsin inhibitor from Bauhinia variegata var. candida seeds

Trypsin inhibitors of two varieties of Bauhinia variegata seeds have been isolated and characterized. Bauhinia variegata candida trypsin inhibitor (BvcTI) and B. variegata lilac trypsin inhibitor (BvlTI) are proteins with Mr of about 20,000 without free sulfhydryl groups. Amino acid analysis shows a high content of aspartic acid, glutamic acid, serine, and glycine, and a low content of histidine, tyrosine, methionine, and lysine in both inhibitors. Isoelectric focusing for both varieties detected three isoforms (pI 4.85, 5.00, and 5.15), which were resolved by HPLC procedure. The trypsin inhibitors show Ki values of 6.9 and 1.2 nM for BvcTI and BvlTI, respectively. The N-terminal sequences of the three trypsin inhibitor isoforms from both varieties of Bauhinia variegata and the complete amino acid sequence of B. variegata var. candida L. trypsin inhibitor isoform 3 (BvcTI-3) are presented. The sequences have been determined by automated Edman degradation of the reduced and carboxymethylated proteins of the peptides resulting from Staphylococcus aureus protease and trypsin digestion. BvcTI-3 is composed of 167 residues and has a calculated molecular mass of 18,529. Homology studies with other trypsin inhibitors show that BvcTI-3 belongs to the Kunitz family. The putative active site encompasses Arg (63)-Ile (64).     

Accelerated recovery of glycerol-induced acute renal failure in rats with previous partial hepatectomy

Recent primary prevention trials demonstrated that cardiovascular morbidity and mortality benefits are not accompanied by adverse effects on overall mortality and morbidity in cohorts representing plasma cholesterol concentrations observed in the bulk of coronary artery disease. During the past year, further analyses of the West of Scotland Coronary Prevention Study have indicated that benefit requires a 25% reduction of LDL cholesterol and that such treatment is not very expensive when focussed on selected high-risk individuals. The Air Force/Texas Coronary Artery Prevention Study indicated that benefit is seen in individuals with even lower plasma lipid concentration. Although current treatment with lifestyle and lipid modifying drug management is successful in primary prevention, the unpredictable nature of coronary artery disease and the cost of drugs mitigate against direct application of drug management in persons with relatively low risk, but selective treatment should be undertaken in very high-risk settings. Future studies need to examine more specific at risk cohorts, test better targeted lipoprotein modification, test more risk factors and also examine whether changes in vascular function or markers of inflammation will predict a better outcome.