On the pitting corrosion of tin in aqueous solutions

Four independent techniques were employed to prove that Sn undergoes pitting corrosion. The first was based on the measurement of the variation of the open circuit potential of the Sn electrode in aerated Cl^? solutions of various concentrations. Steady-state potentials were attained slowly and erratically from negative values, and were more positive the higher the dilution. Sn electrodes prepassivated in CrO₄^2? solutions responded readily to additions of Cl^? ion. The potentials developed were more noble than those measured in presence of the passivator alone, and changed to positive values with the increase of the concentration of the pitting corrosion agent. Attack was under cathodic control.Galvanostatic polarization of the Sri electrode was carried out in 0.005 to 0.1M NaOH, in the presence of various additions of Cl^?. Above a certain Cl^? content, contingent upon the alkali concentration, the aggressive anion prevented the evolution of Oa on the electrode, and oscillations in the E?t curves were recorded. Competitive adsorption of Cl^? and OH^? is assumed to occur, which affected both the quantity of electricity, Q_p, consumed along the oxide formation steps, and the rate of potential increase, dE/dt, following oxidation. Plots of the two variables as a function of the Cl^? ion concentration exhibited a definite break at the value characteristic for the initiation of pitting attack. Potentiodynamic polarization showed that the pitting corrosion potential progressively shifts towards negative values as the concentration of the aggressive agent in solution was increased. The pitting corrosion currents resulting from the addition of Cl^? to Sn electrodes prepassivated in CrO₄^2? solutions were measured. The dependence of the maximum currents on solution composition is explained on the basis of competitive adsorption.     

Reactions with the arylhydrazones of some α,β-diketoesters

Treatment of the α, β-diketo-ester-α-arylhydrazones 1a–e and 2a–d with GRIGNARD reagents results in the formation of the ketocarbinols 3a–h and 4a–g , respectively. The arylhydrazones of ethyl mesoxalate 5a–e react with phenylmagnesium bromide to yield compounds 3a–e . A novel synthesis of α-arylazo-β-arylchalcones 6a–e and their reaction with hydrazines are reported. Whereas the arylhydrazones 10a, b, 2a, b, d, 13a–c and 14a–c react with piperidine and formaldehyde to yield the MANNICH bases 11a, b, 12a–c and 15a–c , compound 5a was recovered unchanged.     

Regulation of Molecular Targets in Osteosarcoma Treatment

The most prevalent malignant bone tumor, osteosarcoma, affects the growth plates of long bones in adolescents and young adults. Standard chemotherapeutic methods showed poor response rates in patients with recurrent and metastatic phases. Therefore, it is critical to develop novel and efficient targeted therapies to address relapse cases. In this regard, RNA interference technologies are encouraging options in cancer treatment, in which small interfering RNAs regulate the gene expression following RNA interference pathways. The determination of target tissue is as important as the selection of tissue-specific promoters. Moreover, small interfering RNAs should be delivered effectively into the cytoplasm. Lentiviral vectors could encapsulate and deliver the desired gene into the cell and integrate it into the genome, providing long-term regulation of targeted genes. Silencing overexpressed genes promote the tumor cells to lose invasiveness, prevents their proliferation, and triggers their apoptosis. The uniqueness of cancer cells among patients requires novel therapeutic methods that treat patients based on their unique mutations. Several studies showed the effectiveness of different approaches such as microRNA, drug- or chemotherapy-related methods in treating the disease; however, identifying various targets was challenging to understanding disease progression. In this regard, the patient-specific abnormal gene might be targeted using genomics and molecular advancements such as RNA interference approaches. Here, we review potential therapeutic targets for the RNA interference approach, which is applicable as a therapeutic option for osteosarcoma patients, and we point out how the small interfering RNA method becomes a promising approach for the unmet challenge.     

Surface‐confined electropolymerization of pyronin Y in the graphene composite paper structure for the amperometric determination of dopamine

Surface‐confined electropolymerization allowed us to easily prepare homogeneous polymer composite paper structures. The fabrication of freestanding graphene (Gr)‐based composite electrodes is very important for many modular approaches in electrochemical applications, such as fuel cells, supercapacitors, and sensors. A Gr composite paper electrode doped with polymeric films of pyronin Y was fabricated by two repetitive simple applications: vacuum filtration and surface‐confined electropolymerization. The characterization of this composite paper was done with scanning tunneling microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, powder X‐ray diffraction spectroscopy, Raman spectroscopy, UV–visible absorption spectroscopy, four‐point probe conductivity measurement, cyclic voltammetry, and electrochemical impedance spectroscopy. The freestanding composite paper demonstrated good electrocatalytic activity for the electrooxidation of dopamine; this indicated that this composite paper could be used for the amperometric quantification of dopamine in real samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45139.     

Comparison of acid and enzymatic hydrolysis of tobacco stalk xylan for preparation of xylooligosaccharides

Tobacco stalk (TS), a major agricultural waste in the Black Sea region of Turkey, was used for the production of xylooligosaccharides (XOs). It contains about 22 g/100 g xylan whose composition was determined as 93.5 g/100 g xylose, 6.54 g/100 g glucose and 11.2 g/100 g uronic acid after complete acid hydrolysis. XO production was performed by enzymatic and acid hydrolysis of xylan which was obtained by alkali extraction from tobacco stalk. In enzyme hydrolysis, xylan was hydrolyzed using a xylanase preparation and the effects of pH, temperature, hydrolysis period, substrate and enzyme concentrations on the xylooligosaccharide yield and degree of polymerization were investigated. For enzymatic hydrolysis under optimum conditions XO yield with respect to tobacco stalk xylan (TSX) was 8.2 g/100 g after 8 h and 11.4 g/100 g after 24 h reaction period. In the acid hydrolysis, sulfuric acid was used and the hydrolyzate contained different amount of oligosaccharides and monosaccharides. For acid hydrolysis under optimum conditions, XO yield with respect to TSX was 13.0 g/100 g. Enzymatically obtained oligosaccharides were purified via ultrafiltration by using 10 and 3 kDa membranes. After a two-step membrane processing, the permeate containing mostly oligosaccharides was obtained.     

Evidence for adaptive autoregulatory displacement in hypotensive cortical territories adjacent to arteriovenous malformations. Columbia University AVM Study Project

We hypothesized that chronic hypotension in normal vascular territories fed by arteriovenous malformation pedicles may reset the lower limit of autoregulation and allow flow to remain constant over a lower pressure range. We studied the effect of increasing systemic mean arterial pressure (SMAP) with phenylephrine on cerebral blood flow using a novel technique. Fourteen patients undergoing 15 procedures were studied before endovascular embolization of arteriovenous malformations under neuroleptic conscious sedation. Mean pressures were transduced via a 1.5-F intracranial microcatheter, which was passed under fluoroscopic guidance into the target feeding artery. The microcatheter was positioned (unwedged) at a point that was relatively hypotensive to systemic pressure but that irrigated normal cortex on angiography; feeding mean arterial pressure (FMAP) and SMAP were recorded. A bolus of 133Xe in saline was injected into the microcatheter, and washout was recorded for 3 minutes by a scintillation detector placed over the vascular territory of the injected pedicle. SMAP was then increased approximately 25 mm Hg by phenylephrine infusion, a second bolus was given, and washout was recorded. After exclusion of the shunt spike, initial slope was calculated. The SMAP (mean +/- standard error) increased from 65 +/- 3 to 89 +/- 2 mm Hg (P < 0.0001), and FMAP increased from 46 +/- 3 to 63 +/- 3 mm Hg (P < 0.0001); cerebral blood flow did not change (40 +/- 2 to 40 +/- 2 ml/100 g per min, P = 0.9199). Dividing the cases on the basis of the baseline FMAP into a "severe" hypotensive group (FMAP = 38 +/- 2; n = 7) and a "moderate" hypotensive group (FMAP = 54 +/- 3; n = 8), cerebral blood flow did not change in either group during phenylephrine challenge. Chronic hypotension does not necessarily result in "vasomotor paralysis" with loss of the ability to vasoconstrict to acute increases in perfusion pressure. Instead, it appears to displace adaptively the lower limit of autoregulation in affected vascular territories by a shift of the autoregulatory curve to the left, conceptually analogous to the adaptive displacement seen with chronic hypertension and its treatment.     

Spectroscopic behavior of poly(vinyl alcohol) films with different molecular weights after UV irradiation,thermal annealing,and double treatment with UV irradiation and thermal annealing

Pure poly(vinyl alcohol) (PVA) films with molecular weights 5,000, 72,000, and 125,000 g/mole were prepared by casting technique. The thickness of prepared samples was 0.21 mm. Xenon arc lamp was used to irradiate two samples from each molecular weight at 400 W for 5 min. One from each irradiated PVA samples was heated at 423 K for 2 h. An additional PVA sample unirradiated from each molecular weight was heated at 423 K for 2 h. Optical absorption measurements have been carried out in the wavelength range of 190–900 nm for untreated, UV‐irradiated, heated, and double‐treated samples by UV irradiation and heat. The double‐treated PVA samples with molecular weights 5,000 and 72,000 g/mole showed approximately zero transmission in comparison with untreated PVA sample in the wavelength range of 190–320 nm. PVA sample with 125,000 g/mole was irradiated with 600 W for 5 min to obtain the zero transmission in the same wavelength range. Identification of the structure and assignments of energy bands were studied also by using FTIR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 589–594, 2003     

The Autoxidation of Tensides I: The Autoxidation,Toxicity and Reclamation of Dianhydro Mannitol Mono-Oleate

Dianhydro mannitol mono-oleate, a surfactant used in the preparation of water-in-oil injectable pharmaceutical preparations was found to autoxidize on storing, with the formation of free acidity and labile peroxides. The autoxidized substance was found to cause peritoneal adhesions when injected intraperitoneally in mice. The autoxidized material could be reclaimed by chromatography through alumina. The eluate was comparable to normal saline in toxicity and the adsorbate was found to be more toxic.