Cyanate Research Articles

Gelam Tree-Derived Carbon Nanosheets as Thick and Free-Standing Electrode for Supercapacitor

Most electrodes for supercapacitors are prepared as thick layer electrodes. Compact, thick and free-standing electrodes are needed for supercapacitor with high volumetric capacitance and energy density. Carbon nanosheets were obtained from treating the bark of the Gelam tree (Melaleuca cajuput Powell) via hydrothermal and microwave processes. The XRD results showed the presence of graphitic carbon in the Gelam tree-derived carbon nanosheet. The carbon nanosheet (the thickness of 0.01 cm) was mixed with graphite and poly(aniline) as conducting binder to fabricate a supercapacitor electrode. Conductivity as high as 3.67 x 10-2 S cm-1 were obtained from the electrode using the carbon nanosheet to graphite the ratio of 3:7. The electrode with this composition had a porous structure. The electrode with a carbon nanosheet to graphite the ratio of 7:3 had a granular morphology with a low conductivity of 0.8 x 10-3 S cm-1. Cyclic voltammetry tests were conducted in lithium chloride and ammonium cyanate-based electrolytes. Both types of electrodes (ratio 3:7 and 7:3) had the same trend of capacitance and voltage window in lithium chloride and ammonium cyanate-based electrolytes. Capacitance as high as 0.0618 F was obtained from the electrode using the 7:3 ratios nanosheet in 10 % ammonium cyanate electrolyte. A novel supercapacitor with high capacitance designed using a thick layer electrode can readily be prepared from the carbon nanosheets derived from the agricultural wood waste.

Radio-sensitivity of Human Colorectal Cancer Cell is Regulated by Potassium Cyanate

Radio-sensitivity of Human Colorectal Cancer Cell is Regulated by Potassium Cyanate

Effect of thermosetting resin matrix on resistance-temperature stability of carbon fiber conductive composites

Carbon fiber conductive composites have been widely used as various electronic components due to their incomparable advantages compared with metal materials in lightweight, easy processing and especially the wide tunability of conductivity. However, negative temperature coefficient (NTC) effect or positive temperature coefficient (PTC) effect produced under the service temperature leads to the fluctuation of their resistance, thus making great effect on precision and limiting extensive applications. In this paper, mainly focusing on the effect of resin matrix on the conductive property and developing the resistance-temperature stable conductive composites, the various conductive composites were prepared by compounding thermoset resin with the hybrid fibers consisting of short carbon fiber (SCF) and short glass fiber (SGF) via changing the content and type of resin matrix respectively. The optical microscope and scanning electron microscope (SEM) images indicated SCF and SGF co-constructed the conductive nets. The temperature cycling testing results from the unsaturated polyester resin (UPR)-based composites showed that all the samples with different content of UPR exhibited the almost unchanged resistance when temperature was below glass transition temperature (Tg) of pure resin matrix, while exhibited the PTC effect as well as hysteresis loop when temperature was above Tg. In addition, the hysteresis loop became smaller and shifted to a higher temperature with the decrease of resin content in composite, meaning that lower resin content is responsible for the high resistance stability. More importantly, it reveals that there is a strong correlation between the resistance stability of composite and thermal property of resin matrix such as Tg. When bisphenol E cyanate (CE) with an over 200 °C Tg value is used as the resin matrix, the higher stability of conductive composite is achieved than that based on UPR and EP, and the average change in resistance is less than 1% during the heating-cooling test at 20 °C–180 °C.

Chemistry of Phosphorus Ylides: Part 45 Synthesis of Phosphoranylidene Thietane, Azetidine and Thiazinane Derivatives as Potent Chemo Preventative Agents

Reactions of nucleophilic active phosphacumulenes with iso(thio)cyanate compounds were performed. The reaction products depend on the nature of the reagent, substrate and the condition of the reaction used. New heterocyclic 4-membered or 6-membered sulfur and nitrogen compounds such as phosphoranylidene thietane, azetidine and thiazinane were obtained. On the other hand, the stable phosphonium ylides with the iso(thio)cyanate afforded phosphoranylidene thiocarbamoyl derivatives. Possible reaction mechanisms are considered and the structural assignments are based on compatible analytical and spectroscopic data.

Research progress on the relationship between plasma protein carbamylation and chronic kidney disease

Plasma protein carbamylation may change the structure of protein, thus influencing its function. Carbamylation is mainly through combination of cyanate with protein, which is elevated in patients with chronic kidney disease mainly because cyanate level is raised due to decomposition of the increasing urea in this population. Carbamylated plasma protein may influence the kidney directly, and has potential value in evaluation of complications, prognosis, and therapy of chronic kidney disease patients. This review introduced plasma protein carbamylation and summarized its value as a biomarker in chronic kidney disease, and promising therapy focusing on lowering plasma protein carbamylation based on recent advances. Key words: Chronic kidney disease; Plasma protein; Carbamylation

Tough epoxy/cyanate ester resins with improved thermal stability, lower dielectric constant and loss based on unique hyperbranched polysiloxane liquid crystalline

Toughening thermally resistant resin without sacrificing outstanding performances of original resin is still a big challenge. Herein, a novel liquid crystalline hyperbranched polysiloxane (LCPSi) with wide transition temperature range and terminal amino groups was facilely synthesized, which was then used to toughen epoxy (EP)/cyanate (CE) ester (the weight ratio of EP to CE is 1:9, coded as eCE). Results show that a small addition of LCPSi can remarkably improve the integrated performances of eCE resin including toughness, stiffness, thermal and dielectric properties. For example, the impact strength and flexural modulus of 1.5LCPSi/eCE resin (with 1.5 wt% LCPSi) are 2.3 and 1.5 times of those of eCE resin, respectively; meanwhile the initial thermal decomposition temperature (Tdi) at which the weight loss of the sample reaches 5 wt% of the former is 18.9°C higher than that of the latter; moreover, both dielectric constant and loss decrease. Those attractive performances demonstrate that LCPSi is a multi‐functional modifier of eCE resin. The origin behind was intensively discussed through the structure–property relationship. Copyright © 2015 John Wiley & Sons, Ltd.

Preparation and characterization of cyanate/epoxy foam

A new type of cyanate (CE)/epoxy (EP) foam with bisphenol-A dicyanate ester prepolymer and diglycidyl ether of bisphenol-A (BADCy/DGEBA) has been successfully prepared through a two-step process. The structure and properties of CE/EP foam were studied. The results reveal that the CE/EP foams, with relatively uniform cell structure, were composed of closed cells as confirmed by scanning electron microscopy. The compressive strength increased from 0.507 MPa to 3.021 MPa, and the compressive modulus ( E) increased from 15 MPa to 123 MPa as the density increased from 0.103 g cm−3 to 0.305 g cm−3. Dynamic mechanical analysis revealed that the CE/EP foams possessed a high glass transition temperature ( Tg) (203°C) and that density had only a little impact on Tg. Moreover, the excellent thermal stability presented with the onset of weight loss taken at 5% value was above 320°C, and the residual weight of the foam was more than 21.6% at 800°C. With increase in the density of CE/EP foams, the dielectric constants (ε) gradually decreased. For the foam with density of ρ = 0.162 g cm−3, the value of ε was as low as 2.28 at the frequency of 10 kHz.

Mechanical Properties of Cyanate Ester/Epoxy Resins Reinforced with Functionalized Multi-wall Carbon Nanotubes

Mechanical Properties of Cyanate Ester/Epoxy Resins Reinforced with Functionalized Multi-wall Carbon Nanotubes

Long Chain Bismaleimide Modified Cyanate Ester Resin and Its Composites

A kind of long chain bismaleimide-modified cyanate ester resin and the relevant composites were prepared and characterized. The results indicate that when the resin content of the long chain maleimide-terminated thioetherimide(MIMTI) reached 37.5% (mass fraction), the T-5% of the modified cyanate ester resin (MTI/T-3) was 414 degrees C. Tensile strength and flexural strength of the MTI/T-3 composite were 431.2 and 331.0 MPa, 631.5 and 278.4 MPa at room temperature and 200 degrees C, respectively. And its coefficient of thermal expansion(CTE) in X-Y axis and the moisture absorption were 18.1x10(-6) degrees C-1 and 1.4%, respectively. Compared to the common bismaleimide-modified cyanate ester resins, and the 20% and 30% MIMTI-modified cyanate ester resin MTI/T-1 and MTI/T-2, respectively, the obtained cyanate ester resin MTI/T-3 exhibited good processing, excellent heat resistance and mechanical properties, low moisture absorption and low CTE.

Study of SiO 2/PMMA/CE tri-component interpenetrating polymer network composites

A technology of conjugated tri-component interpenetrating polymer networks was applied to synthesize a nano-SiO 2/polymethylmethacrylate (PMMA)/cyanate (CE) composite through an asynchronous synthesis way. The microstructure of the composite was characterized using infrared spectroscopy (IR) and transmission electron microscopy (TEM). The mechanical properties were measured in German-made DL-1000B and XCL-40 universal material test machines, respectively. Results showed that both the impact strength and the flexural strength were in the optimum status when 3% SiO 2/PMMA/CE was chosen as a sample with the PMMA/CE ratio of 20/80. Compared with the strengths of pure cyanate, those of the composite were raised by 137.28% and 31.29%, respectively. When 3% nano-SiO 2 was added, the impact strength was increased by 29.96% and the flexural strength by 20.05%, compared with the strengths of polymers without SiO 2. Analysis and measurements by IR and TEM indicated that no chemical reactions took place among components in the composite. The interpenetration of the conjugated tri-component improved the loading capacity of the polymer, hence the toughness enhancement of cyanate.

New composites with high thermal conductivity and low dielectric constant for microelectronic packaging

AbstractThree composites based on cyanate (CE) resin, aluminum nitride (AlN), surface‐treated aluminum nitride [AlN(KH560)], and silicon dioxide (SiO2) for microelectronic packaging, coded as AlN/CE, AlN(KH560)‐SiO2(KH560)/CE, and AlN‐SiO2/CE composite, respectively, were developed for the first time. The thermal conductivity and dielectric constant of all composites were investigated in detail. Results show that properties of fillers in composites have great influence on the thermal conductivity and dielectric constant of composites. Surface treatment of fillers is beneficial to increase the thermal conductivity or reduce dielectric constant of the composites. Comparing with binary composite, when the filler content is high, ternary composites possess lower thermal conductivity and dielectric constant. The reasons leading to these outcomes are discussed intensively. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Reactivity of [Cp*Rh(η2-NO3)(CF3SO3)] toward Organic Thiols and Cyanate: Preparation and Structures of [Cp*Rh(μ-R)3Cp*Rh](CF3SO3)(R = Ph, i-Bu, or Allyl) and [Cp*Rh(η1-NO3)(μ-NCO)

Reactivity of [Cp*Rh(η2-NO3)(CF3SO3)] toward Organic Thiols and Cyanate: Preparation and Structures of [Cp*Rh(μ-R)3Cp*Rh](CF3SO3)(R = Ph, i-Bu, or Allyl) and [Cp*Rh(η1-NO3)(μ-NCO)

Tyrosine and N-carbamoyl-tyrosine in end-stage renal disease during continuous ambulatory peritoneal dialysis.

Lower-than-normal tyrosine concentrations of unexplained pathogenesis in plasma and intracellular body water have been reported in patients with chronic renal failure. We found a derivative of tyrosine that is not measured by the usual methods of amino-acid analysis because its alpha-amino group is blocked and cannot react to form other derivatives. An in vivo covalent reaction with urea-derived cyanate forms alpha-amino-carbamoyl-tyrosine (N-C-Tyr) in patients with end-stage renal disease. A longitudinal study of patients with end-stage renal disease who were treated with continuous ambulatory peritoneal dialysis shows that plasma that is obtained within 4 hours of the morning meal contains 70.1 +/- 6 mumol/L of tyrosine (mean +/- SEM) and 77.2 +/- 12 mumol/L of N-C-Tyr (mean +/- SEM). Thus there is a molecule of N-C-Tyr for each molecule of tyrosine present. The carbamoylation index or ratio of N-C-Tyr to tyrosine, blood urea nitrogen, episodes of peritonitis, and changes in dialysis protocol were compared. A reduction in the number of peritoneal dialysis exchanges resulted in parallel increases in carbamoylation index and blood urea nitrogen. Altering dialysis by increasing the number of exchanges or adding supplemental hemodialysis resulted in a decrease in the carbamoylation index with a delayed decrease in blood urea nitrogen. We found a significant increase of N-C-Tyr (p = 0.005) and of the carbamoylation index (p = 0.004) during six episodes of peritonitis compared with 10 periods of no peritonitis in two patients who had multiple episodes of peritonitis.(ABSTRACT TRUNCATED AT 250 WORDS)

ChemInform Abstract: O‐Carbamoylsalicylates: Agents for Modification of Hemoglobins.

To combine the attractive features of cyanate and of O-acetylsalicylate as hemoglobin-modifying agents we have prepared carbamoylsalicylate. This compound is a close analogue of aspirin and also resembles a masked cyanate. O-Carbamoylsalicylate and some related carbamates modify hemoglobin substantially, even at 5 mM concentration.

Acquisition of resistance to 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride in V79 cells through increased removal of O6-alkylguanine.

The molecular mechanism of acquisition of resistance to 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitroso ure a hydrochloride (ACNU) was investigated using ACNU-resistant clones (ACNUr-1-4) isolated from the V79 cell line. The binding level of alkyl cyanate, a decomposition product of ACNU, to protein in ACNUr-1 cells was not less than that in the parental V79 cells, indicating that the acquired resistance was not due to a reduced intracellular concentration of ACNU. Because O6-chloroethylguanine, an intermediate in cytotoxic interstrand cross-link formation by ACNU, is known to be repaired by the same mechanism as O6-ethyldeoxyguanosine (O6-EtdGuo), we quantitated O6-EtdGuo by radioimmunoassay at various times after exposure of cells to 100 micrograms/ml N-ethyl-N-nitrosourea for 20 min. In V79 cells, elimination of O6-EtdGuo was negligible, but in all four resistant clones, 30 to 59% of the O6-EtdGuo was removed within 24 hr after exposure. This increased removal of O6-EtdGuo among the resistant clones was associated with the activity of O6-alkylguanine DNA alkyltransferase (O6-AGT) determined using cell extracts. The present results indicate that increased removal of O6-chloroethylguanine in ACNU-resistant clones by O6-AGT is mechanistically linked to the acquisition of resistance to ACNU.

Does Elevated Blood Urea Participate in the Pathogenesis of the Uremic Syndrome

REA is quantitatively the most abundant of the various products of protein catabolism in mammals, accounting for 85% of the excreted urinary nitrogen. It is not surprising, therefore, that it was one of the earliest chemical substances to be identified and measured specifically in the blood and urine. By 1823, Prevost and Dumasi reported that bilateral nephrectomy in dogs caused a rise in blood urea. Shortly afterward, Christison2.3 recognized that in patients with renal failure, the urea concentration increased in the blood and decreased in the urine. The term “uremia,” meaning literally “urine in the blood,” was introduced by Piorry and L’heritier4 in 1840 to describe the clinical syndrome resulting from renal failure severe enough to result in retention in the blood of nitrogen products of protein metabolism. In 1836, Richard Bright5 raised the question of the possible role of urea as a uremic toxin, but evidence implicating urea specifically was not forthcoming until the early 1900s when attempts were made to produce uremic symptoms in nephrectomized dogs and cats and normal human subjects by rapid administration of large quantities of urea. The designs of many of these experiments are open to criticism, as pointed out in the monograph by Schreiner and Maher. In normal human subjects and animals with normal renal function, the blood concentrations of urea found in uremic patients are difficult to attain because of the rapid excretion of urea. Large doses, therefore, must be given in a short time to overcome the osmotic diuretic effects of urea. Although urea diffuses rapidly across most cell membranes, it is possible by rapid parenteral administration to create osmotic gradients between, for example, blood and brain or blood and intraocular fluids. These osmotic gradients in themselves could lead to symptoms, such as headache and nausea. Oral administration is unpleasant because of the large bulk of urea needed to raise the blood urea in subjects with normal renal function. In longer-term experiments, other products may be formed from urea, such as cyanate and ammonia, which may lead to

Mechanism of inhibition of hemoglobin S polymerization by cyanate.

We have studied the effect of carbamylation on hemoglobin S (HbS) polymerization with the use of a new quantitative gelling technique. HbS gels fromed in the presence of nitrogen and dithionite (with or without carbon monoxide) at pH 7 in 0.15M phosphate were separated into sol and gel phases by centrifugation at 130,000 g. Hb concentration to the sol phase ([Hb]sol) of nonligated HbS was found to be constant (10.5 +/- 092 mM heme) over a range of original Hb concentrations from 11 to 17 mM at 24degrees C. This suggests that the HbS sol-gel equilibrium behaves as simple two-phase system. Increasing levels of total carbamylation from 0.65 to 3.65 moles CNO-/mole Hb tetramer (0.36 to 2.2 moles N-terminal/mole Hb4) progressively increases [Hb]sol. Specific activity of 14CNO-HbS was similar in the sol and gel phases, whereas COHbS appeared to be completely excluded from polymer structure of the gel. A comparison of the solubility of uncarbamylated and heavily carbamylated HbS at Co saturations ranging from 3 to 61 percent showed that the larges difference in [Hb]sol occured at the lowest ligand saturation rather than at intermediate states of ligation. Inhibition of HbS polymerization by carbamylation under these conditions, therefore, is not primarily the result of an effect on the T in equilibrium R comformational equilibrium. Our findings indicate that cyanate can interfere with HbS polymerization directly, possibly by alteration of surface binding sit(s) which are critical to aggregation. This direct action of cyanate may contribute significantly to the hematologic improvement achieved by cyanate treatment in sickle cell disease.

Determination of the blood concentrations of cyanate after intravenous administration to patients with sickle-cell disease.

Abstract A method for the determination of free cyanate in micromolar concentrations in blood is described. Cyanate is converted quantitatively to S-carbamylcysteine in the presence of excess cysteine and dithionite at pH 7.4; the amount of S-carbamylcysteine formed is measured by amino-acid analysis. For standard solutions, the accuracy and precision of the method is within 4 per cent. With this procedure we have been able to determine that a single pharmacologically effective dose of cyanate disappears from the circulation of sickle-cell anemia patients with a half-time in the range of 30 to 40 minutes after intravenous administration.

Gas chromatographic determination of the carbamylation of hemoglobin S by cyanate.

Gas chromatographic determination of the carbamylation of hemoglobin S by cyanate.

Treatment of acute leukemia.

Treatment of acute leukemia.