Stream Of Nitrogen Research Articles

Improvement of the mechanical and oxidation resistance of pyrolytic carbon coatings by co-deposition synthesis of pyrolytic carbon-silicon carbide nanocomposite

In this work, pyrolytic carbon- silicon carbide (PyC-SiC) nanocomposites were prepared via pyrolysis of Trimethylsilyl chloride (TMSCl) as precursor using chemical vapor deposition method at high temperature (1100 ºC). The nanocomposite of PyC-SiC was synthesized by the deposition of SiC and PyC components from the stream of nitrogen as carrier gas by the co-deposition method. The effect of substrate type and TMSCl concentration on microstructure, composition, thermal properties, and mechanical behavior were investigated. The formation of PyC-SiC nanocomposites was followed by Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Scanning electron microscopy was used to study of nanocomposite morphology. Additionally, the amount and distribution of Si element in the PyC-SiC nanocomposites was determined by energy dispersive X-ray mapping. The results showed that the nanocomposite containing higher SiC content was synthesized by TMSCl at 2.5 vol% on graphite. Furthermore, the results of thermogravimetric analysis and wear resistance (via tribometer) showed that the oxidation and wear resistance of nanocomposites increased with an increase in the amount of embedded silicon in the nanocomposites. Oxidation temperature and wear resistance of prepared nanocomposites in comparison with PyC increased to about 100 ºC and 300%, respectively. The tribology results showed that the friction coefficient of nanocomposites increases about 25–300% with increasing TMSCl concentration. Finally, the results of the nanoindentation test showed that increasing the amount of SiC embedded in nanocomposites improved the elastic modulus and hardness of nanocomposites about 180% and 100%, respectively.

Experimental investigation of the thermal loads upon electrodynamic modification of supersonic flow around axisymmetrical body

The results of experimental studies of the magnetohydrodynamic (MHD) effect on the flow around an axisymmetric model of a supersonic nitrogen stream are presented. The magnetic field was created by a solenoid located on the cylindrical part of the model under the influence of a pulsed electric current flowing through the solenoid. A pulsed gas discharge was ignited on the conical surface of the model, acquiring rotation in the solenoidal magnetic field around the model axis. The effect of the magnetic field on the gas-dynamic structure of the flow near the model and the heat flux to its surface were investigated. In the experiments, schlieren pictures,fast photographic scans of the discharge glow were recorded, and heat flux was measured. The effect of a magnetic field on the gasdynamic structure of the flow near the model and the heat load to its surface were found. Also, the dependence of MHD effects on the polarity of external voltage source connecting was found.

Simultaneous Determination and Validation of 5F-ADBICA and 5F-NPB-22 in Whole Blood and Urine by LC/MS–MS

Synthetic cannabinoids (SCs) are the most rapidly growing class of recreational designer drugs. The rapid growth in popularity of SC use among teens and adults is of serious in our country as all of the world. These products are saturated in various plants crumb in order to make herbal appearence. They are not for human consumption and also their chemical structures are rapidly evolving. They are known as “Bonsai” in Turkey. 5F-ADBICA and 5F-NPB-22 are the two most commonly detected compounds in seized herbal products by police forces. The aim of this study was to determine and validate 5F-ADBICA and 5F-NPB-22 in whole blood and urine by LC/MS–MS. No method exists in the literature for the simultaneous determination of these new-generation SCs. 250 µL blank blood was transferred to 16 × 100-mm test tubes. Extraction was performed with 2 mL acetonitrile:ethyl acetate (25:75). The tubes were capped and rotated for 15 min. The samples were then centrifuged for 10 min at 3500 rpm. The organic layer was transferred to other tube and was evaporated to dryness at 45 °C under a stream of nitrogen. 0.5 mL of urine samples, 1.5 mL ice-cold acetonitrile and 0.5 mL of a 10 M ammonium formate solution were added. The mixture was shaken, centrifuged, and 1 mL of the organic layer was transferred into a separate vial and evaporated to dryness under a stream of nitrogen. The dried extracts were reconstituted with mobile phase A. The chromatographic separation was performed with a pentafluorophenylpropyl (PFPP) column (Allure 50 × 2.150 mm i.d., 5 μm, Restek, Bellefonte, PA, USA) using a gradient binary with 10 mM ammonium formate (A) in ultrapure water and methanol (B). The run time is 20 min. The method was validated in terms of limits of detection (LODs) (0.01–0.12 ng/mL) and quantification (LOQs) (0.03–0.36 ng/mL), extraction recovery (ER) (77.4–97.3%), matrix effect (ME) (63.3–83.6%), linearity, intra- and interday precision (CV ˂ 20%) and carryover. A simple, cost-effective, and accurate LC/MS–MS method has been developed for the simultaneous quantification of 5F-ADBICA and 5F-NPB-22 in whole blood and urine. The newly developed analytical methods allow the analysis of new-generation synthetic cannabinoids.

Characterization of structural and chemical modifications during the steam activation of activated carbons

An anthracite-based material of low porosity was activated in a nitrogen stream enriched with water vapor to produce four activated carbons, which differ systematically in their structural and chemical properties. Characterization of the structural properties of the base and the activated materials was carried out by volumetric measurements and mercury porosimetry. A general classification of chemical composition was done by ultimate analysis. The surface chemistry was analyzed by Boehm titration. The adsorption performance was investigated by measuring excess isotherms and load-dependent adsorption enthalpies of selected probe molecules: acetone (polar), n-heptane (non-polar) and toluene (aromatic). Assuming distribution rules for selective adsorption, the molar ratios of the surface groups were estimated from the excess isotherms. The combination of these methods enables the observation and differentiation of structural and surface chemical changes of the carbons during activation. For example, it could be shown that the broader pore width distribution with an increasing proportion of mesopores occurring in the course of activation leads to a more pronounced energetic heterogeneity. It was also found that an increase in surface area with increasing activation time is accompanied by an increase in aromatic surface groups and a reduction of polar and non-polar surface groups. Especially the adsorption of the polar probe molecule acetone revealed the heterogeneity of the surface chemistry, which together with the heterogeneous structural composition resulted in a distinct decrease of the adsorption enthalpy with increasing loading.

Fixing the Broken Phosphorus Cycle: Wastewater Remediation by Microalgal Polyphosphates.

Phosphorus (P), in the form of phosphate derived from either inorganic (Pi) or organic (Po) forms is an essential macronutrient for all life. P undergoes a biogeochemical cycle within the environment, but anthropogenic redistribution through inefficient agricultural practice and inadequate nutrient recovery at wastewater treatment works have resulted in a sustained transfer of P from rock deposits to land and aquatic environments. Our present and near future supply of P is primarily mined from rock P reserves in a limited number of geographical regions. To help ensure that this resource is adequate for humanity’s food security, an energy-efficient means of recovering P from waste and recycling it for agriculture is required. This will also help to address excess discharge to water bodies and the resulting eutrophication. Microalgae possess the advantage of polymeric inorganic polyphosphate (PolyP) storage which can potentially operate simultaneously with remediation of waste nitrogen and phosphorus streams and flue gases (CO2, SOx, and NOx). Having high productivity in photoautotrophic, mixotrophic or heterotrophic growth modes, they can be harnessed in wastewater remediation strategies for biofuel production either directly (biodiesel) or in conjunction with anaerobic digestion (biogas) or dark fermentation (biohydrogen). Regulation of algal P uptake, storage, and mobilization is intertwined with the cellular status of other macronutrients (e.g., nitrogen and sulphur) in addition to the manufacture of other storage products (e.g., carbohydrate and lipids) or macromolecules (e.g., cell wall). A greater understanding of controlling factors in this complex interaction is required to facilitate and improve P control, recovery, and reuse from waste streams. The best understood algal genetic model is Chlamydomonas reinhardtii in terms of utility and shared resources. It also displays mixotrophic growth and advantageously, species of this genus are often found growing in wastewater treatment plants. In this review, we focus primarily on the molecular and genetic aspects of PolyP production or turnover and place this knowledge in the context of wastewater remediation and highlight developments and challenges in this field.

Adsorption of carbon dioxide on CuxMgy(BTC)2 MOFs: influence of Cu/Mg ratio

A series of bimetallic metal-organic frameworks (CuxMgy(BTC)2 MOFs) was synthesized. The as-produced MOFs were described utilizing different characterizations techniques. The dynamic adsorption efficiencies of the prepared MOFs toward the carbon dioxide (CO2) from the nitrogen stream at separate temperatures and various total levels of flow were achieved including the evaluation of the suitable kinetic model. The results showed that copper ions could be substituted successfully by magnesium ions up to molar ratio 1:1 (Cu1.5Mg1.5(BTC)2 MOF), without obvious deformation in the crystalline structure of the parent Cu3(BTC)2.3H2O (HKUST-1). In all of the as-synthesized MOFs, the introduction of magnesium ions to the context of Cu-BTC had accompanied changes in the morphological structure, porosity, and thermal behavior. The Cu1.5Mg1.5(BTC)2 MOF showed significant enhancing on its CO2 adsorption capacity (23.85 mmol/g) compared with Cu-BTC MOF (5.95 mmol/g) and Mg-BTC MOF (4.57 mmol/g), which indicated the key-role of the central metals in the MOF in CO2 adsorption. The second-order kinetic studies suited the experimental work with more precise than pseudo-first-order. Also, the reusability of the bimetallic adsorbent under the optimum temperature and flow rate was evaluated for 5 cycles.

A new type of hydrothermal diamond-anvil cell with cooling system.

A new type of hydrothermal diamond-anvil cell (HDAC-VII) and its accompanied cooling system were designed. The design of HDAC-VII in which the three posts work simultaneously as guideposts and screw posts greatly shortened the horizontal size of HDAC compared with older types. It provides more open space and shorter distance to analyze and observe the sample chamber from side access. Moreover, four ports were used to connect the upper and lower spaces between windows and anvils, so mixed gas (Ar + H2) can pass through both of them. In the heating experiments, the mixed gas prevents diamond anvils and other parts from being oxidized as well as cooling the observing windows. Dry gas can be passed through those spaces during cooling, preventing condensation on the table faces of anvils and the observing windows. The cooling system can cool the sample chamber to -170 °C with an accuracy of ±0.5 °C by using a nitrogen stream cooled through a stainless steel coil immersed in a liquid nitrogen Dewar. The heating rates while reheating a frozen sample can be controlled to be 0.1 °C/min with a temperature fluctuation of 0.1 °C. These improvements extend the HDAC applications especially in low temperature conditions. For example, (1) we measured the salinities of NaCl-H2O loaded in the sample chamber, (2) we observed the ice I and VI-melting process and correspondingly calculated the density of water in the sample chamber, and (3) we performed lepidolite crystallization in an aqueous solution with 10 wt. % NaCl to simulate its natural forming conditions.

Comparative pharmacokinetic study of five flavonoids in normal rats and rats with gastric ulcer following oral administration of Mongolian medicine, Shudage - 4 by UPLC – ESI – MS/MS

Purpose: To develop a simple, rapid and sensitive ultra-performance liquid chromatography - electrospray ionization-mass spectrometry (UPLC–ESI–MS/MS) method was developed and fully validated for the simultaneous determination of galangin, kaempferide, galangin-3-methylether, kaempferol and quercetin in rat plasma after oral administration of Mongolian Medicine, Shudage-4 extracts.
 Methods: The galangin, kaempferide, galangin-3-methylether, kaempferol and quercetin were separated on a C18 column using 0.1 % formic acid at a flow rate of 0.4 mL / min and detected by a mass spectrometer in negative-ion mode with selected reaction monitoring (SRM) mode. Plasma samples were processed with a simple deproteinization technique using ethyl acetate and acetonitrile. Following the protein precipitation, the plasma samples were evaporated under gentle stream of nitrogen and analyzed by above method. Naringin was used as an internal standard (IS). Method validation was performed according to the Chinese Food and Drug Administration guidelines.
 Results: A good linearity (r2 ≥ 0.9990) was showed by the UPLC – ESI – MS / MS method, the low limits of quantification for galangin, kaempferide, galangin-3-methylether, kaempferol and quercetin were 229.8, 78.8, 32.0, 123.7 and 137.8 ng / mL, respectively. The results of inter-day and intra-day precisions met the experimental requirement (< 7.8 %). The matrix effect and recovery efficiency of the five analytes were more than 72.9 and 88.7 % respectively. The stability of the analytes were satisfactory. The UPLC – ESI – MS / MS method has been used for the five analytes’ pharmacokinetics study successfully after gastrointestinal route of the Mongolian Medicine Shudage-4. The pharmacokinetic parameters showed significant differences (P < 0.05) between the normal and gastric ulcer groups. The metabolism and transport of the five analytes in gastric ulcer rates were faster than in normal rats after administration of Shudage - 4 extract. Double-peak phenomenon appeared in galangin, galangin – 3 - methylether and quercetin.
 Conclusion: The results suggest that the metabolism and transport of Mongolian Medicine Shudage-4 in gastric ulcer rats is faster than in normal rats and may be enriched and acted on at the lesion site.
 Keywords: UPLC – ESI – MS / MS; Mongolian medicine; Shudage - 4; pharmacokinetics; gastric ulcer

Analysis and optimization of the liquid nitrogen pre-cooling stage for the EAST helium refrigerator

Pre-cooling of helium with liquid nitrogen is a good alternative to large scale helium refrigerators for initial cool-down from room temperature to about 80 K due to high exergy efficiency, high cooling capacity, and low demand of heat exchanger area. However, during the initial cool-down, two problems have to be faced for an improper liquid nitrogen pre-cooling stage arrangement. The temperature difference between helium and nitrogen at the cold end of the first heat exchanger became very large, which leaded to high thermal stress and potential damage. The outlet temperature of the nitrogen stream of the heat exchanger is lower than room temperature, thus the efficiency decreases and more liquid nitrogen is consumed. In this paper, the performance of a liquid nitrogen pre-cooling stage for the EAST 2kW/4.5K helium refrigerator during cool-down phase will be analyzed. Then a new arrangement will be sought to avoid a larger temperature difference and underutilization of nitrogen cold energy. The current work may help to design, optimize and operate the liquid nitrogen pre-cooling stage for large scale helium refrigerators.

Application of QuEChERS-EMR-Lipid-DLLME method for the determination of polycyclic aromatic hydrocarbons in smoked food of animal origin

The aim of this study was to develop an effective sample preparation procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in smoked fatty products of animal origin (fish, cheese and sausage). Two different approaches were tested: classical QuEChERS and procedure with the use of Enhanced Matrix Removal (EMR)-Lipid material. Two techniques of extract preconcentration: under nitrogen stream and with the use of dispersive liquid-liquid microextraction (DLLME), were also taken into consideration. All samples were analysed using gas chromatography-mass spectrometry. The results showed the optimised sample preparation procedure was composed of three steps: 1) QuEChERS extraction, 2) clean-up by EMR-Lipid material and 3) extract preconcentration by DLLME. The obtained recovery rates within the range of 50–120% were received for all compounds with relative standard deviation (RSD) values lower than 16.7%. The proposed method is fast and effective and can be successfully applied for PAHs determination in difficult matrices such as heat-treated food of animal origin with high fat content. The research also discovered the significance of the quality of the laboratory disposables. Contaminants present in plastic consumables can be transferred to the sample extract contributing to its contamination and can also lead to failure of analytical equipment.

Recovery of vinyl chloride from by‐streams of polyvinyl chloride production by TPSA in a multitubular adsorber

AbstractThis work aims at developing an efficient and feasible adsorption‐based separation process for the separation of vinyl chloride and nitrogen, on activated carbon, by employing a multitubular packed bed geometry, with adsorbent material inside the tubes. Using this geometry, a 2‐dimensional mathematical model of a temperature pressure swing adsorption process was used to developed a 6‐step three multitubular adsorbers system capable of separating and purifying an industrial scale gas stream of a 40:60% (v/v) vinyl chloride/nitrogen mixture into a 95% (v/v) vinyl chloride stream and a nitrogen stream with a vinyl chloride limit concentration of 8 ppm (w/w). The process reported energy consumption of 4.88 × 106 J/kgVCM and recovery capacity of 24.35 kgVCM/(m3unit h). The multitubular geometry enabled the use of lower adsorbent loads, shorter cycle times, and lower regeneration temperatures. An equivalent 1‐dimensional model has also shown to satisfactorily estimate the performance of the current equipment.

Numerical investigation of coal self-heating in longwall goaf considering airflow leakage from mining induced crack

Self-heating of coal is a long-standing hazard and pollution source in longwall goaf and abnormal air leakage into goaf is a key yet complex drive to the hazard. To investigate such a problem with more insights, a numerical model without considering coal moisture is established based on a Shendong longwall. Abnormal air leakage into goaf mainly sources from the edge cracks resulting in presence of high level oxygen (8 %∼13 %) in start-off area of the longwall. Two heating liable regimes were identified: one is behind longwall face and another one locates in the start-off zone. Heating in the start-off zone develops more quickly than that in heating regime one. On day 25 the maximum temperature of regime two can rise to 500K while it can only increase to approximately 340K in regime one. The heating spot behind longwall face tends to be self-suppressed with longwall advancing while the heating in the start-off zone can develop to a spontaneous combustion incident due to constant airflow leakage from the mining induced cracks. A wide range of inertisation plans including different locations, strategies, and flowrates of nitrogen injection were conducted. An optimum inertisation plan is to proactively inject inert gas with a low flowrate (e.g. 122m3/h) from a seal along the start-off line. A high flowrate of nitrogen stream is preferable to suppress an on-going heating and the reactive inertisation should be maintained for a long run otherwise the heating is very likely to re-develop.

Measurement of the times for pyrolysis and the thermal diffusivity of a pyrolysing particle of wood and also of the resulting char

Cubes and spheres of spruce wood have been prepared, with a fine thermocouple inserted to measure the temperature at their centre. Individual particles were immersed rapidly in a bed of sand (mean size ∼0.2 mm), which was fluidised by nitrogen and held at a fixed temperature up to 700 °C. The rising temperature measured at a particle's centre yielded the effective value of the particle's thermal diffusivity. The temperature response showed evidence of at least two endothermic decomposition reactions, which corresponded to the pyrolysis of fine particles of the wood in a thermogravimetric analyser (TGA). However, the wood undergoing thermal decomposition in a fluidised bed at 500 °C revealed at least one exothermic step at the very end of heating. After being heated this way in a hot bed fluidised by nitrogen, the particles of char formed by spruce wood had very much the same size and shape as the original piece of wood before being heated. These new particles of “char”, formed whilst being heated in a hot fluidised bed, were cooled in a stream of nitrogen and returned to the fluidised bed for re-heating without any complications from pyrolysis. The rise in the char's central temperature with time gave an unambiguous value for the thermal diffusivity of the char. It is clear that volatile matter leaving a particle of wood reduced the rate of heat transfer between a hot fluidised bed and the centre of a devolatilising particle. Also, the time for complete pyrolysis was proportional to the square of the characteristic size (r0) of the spruce being heated. In addition, the time for pyrolysis was proportional to Tbed3±1, so that for a cube of spruce tpyr = 2.9 ± 0.3 × 1015r02/Tbed3 in seconds. Photographic evidence confirmed that devolatilisation of particles of spruce larger than ≈ 2 mm in a fluidised bed follows a shrinking core model and is accordingly controlled by internal heat transfer.

The productivity of spring wheat, the streams of nitrogen and agroecosystem stability with the application of fertilizers and biopreparation

To form spring wheat grain at the insufficient bringing of nitric fertilizers the additional sources of nitric feed are necessary. They can be filled in due to the inoculation of seeds with microbial preparation of Rhizoagrin (RA) created on the basis of associative bacteria. The inoculation of seeds of RA provided the increase of grain mass by 15 %. Biomass of spring wheat on sod-podzolic soil largely forms due to soil nitrogen, the share of which reaches four-fifths of the total removal of the element when using mineral fertilizers. Inoculation increases the fertilizer nitrogen use efficiency by 4.5% and reduces losses by 7%; there is a trend to increase the immobilization of N fertilizers. Stability of an agroecosystem is characterized by nitrogen flows. The amount of mineralized nitrogen depending on the fertilizer amounts to 17.4-18.0 g/m2, while the amount of reimmobilized nitrogen is 4.4-4.9g/m2 and net-mineralization (N-M) is 13.1 g/m2. The inoculation of seeds with Rhizoagrin does not significantly affect the processes of mineralization (M) and reimmobilization (RI) in anything of nitrogen in the soil. The use of nitrogen fertilizer brings the agroecosystem into a state of resistance (the maximum threshold limit of exposure (RI : M = 25% and N-M : RI = 3)). On average, over the years of research, inoculation of seeds with Rhizoagrin did not change the indicators of an agroecosystem’s stability with the application of the fertilizers.

Nitriding of Molten Chromium-Manganese Steels

Theoretical and experimental studies are conducted in the field of nitriding high strength nonmagnetic steels. Temperature-time correlation of the degree nitrogen assimilation and nitrogen content in steel 04Cr20Ni6Mn11Mo2NVNb in the case of alloying with nitrogencontaining manganese and chromium ferroalloys in air and during purging with nitrogen are determined by experiment. Gas phase nitriding of this steel is possible at 1450 °C during 30 min reaching a nitrogen content of 0.42%. A twostage process for lowcost nitriding is developed. In the first stage melts are purged with highpurity nitrogen to reach a nitrogen content of 0.25–0.30%. In the second stage powder alloying additions are injected into a stream of nitrogen with a melt temperature as low as possible.

CHARGE COMPENSATION IN POTASSIUM POLYFERRITE AT DOPING WITH FOUR-CHARGED IONS

In order to clarify the mechanism of charge compensation with the introduction of additives of four-charged ions ions into the composition of catalytically active potassium polyferrites, mixtures with different molar ratios KFeO2: Fe: Fe2O3: MeO2, where Me is Ce, Ti, Zr, were calcined in a muffle furnace in a stream of nitrogen for 4 - 6 h at a temperature of 970 K. As a result, single-phase potassium polyferrites with the β˝-alumina-type structure were obtained, which was confirmed by X-ray diffractometry. Based on the measurement of the electronic conductivity of doped polyferrites, the determination of the content of two-charged and three- charged iron, it has been established that the introduction of four-charged ions into the structure of a β˝-alumina type polyferrite occurs in accordance with the charge compensation mechanism described by the formula K2FeII1+qFeIII10-2qMeqIVO17, where q is a coefficient characterizing the content of the additive of four-charged ion. The above mechanism is implemented by reducing part of the three- charged iron while maintaining the initial content of alkali metal. The effect of the nature of the alloying ion on the composition and the electronic conductivity of the obtained polyferrite is shown. The destabilizing effect of four-charged ions, which is expressed in facilitating the emission of alkali metal from the crystal lattice of polyferrite, has been revealed. It is shown that the ratio of various charge forms of iron can be controlled within wide limits not only by changing the redox properties of the atmosphere, but also by introducing various additives into the potassium polyferrite structure. A violation of single-phase cerium-doped polyferrites was noted when reaching a value of q of more than 0.6. For polyferrites doped with titanium or zirconium, the structure was maintained throughout the entire range of q values studied.

Fabricating copper and copper/nickel alloy single crystal bead electrodes with a hydrogen–oxygen torch in ambient air

The use of copper single-crystal electrodes (CSCEs) has revealed the crucial role of electrode structure in electrocatalysis and corrosion. CSCEs, although commercially available, can be prepared in-house by melting the end of a Cu wire to form a single crystal bead (SCB) in ambient air. Unlike the conventional torch used for making Pt and Au SCBs, the torch used in this study allows the Cu bead to cool down to room temperature in a nitrogen stream. The resulting Cu bead is subsequently fabricated into a CSCE with a desired orientation. Copper’s propensity for oxidation does not pose a problem for our method as long as the H2 and O2 fluxes to the flame are well-controlled. The bulk oxide in the Cu SCB prepared as above is below the detection limit of our X-ray photoelectron spectrometer. The devised method opens up an avenue toward the study of electrochemistry at well-defined Cu and possibly other non-noble transition metal electrodes. Moreover, this method can also be used to make alloyed SCBs, as illustrated by the successful fabrication of a Cu/Ni (98.5/1.5) bead. The resulting Cu(1 1 1) and Cu98.5Ni1.5(1 1 1) electrodes are examined by cyclic voltammetry and in situ scanning tunneling microscopy in 0.1 M sulfuric acid. The trace amount of Ni in the Cu(1 1 1) electrode affects the potential, but not the structure, of specific adsorption of the (bi)sulfate anion. A (√3 × √7)–HSO4− structure and the Cu(1 1 1) lattice are imaged by STM at positive and negative potentials.

Differential Pulse Voltammetric Determination of 2‐Methyl‐4,6‐Dinitrophenol using Bismuth Bulk Electrode

AbstractThis work reports the application of bismuth bulk electrode (BiBE) for the determination of 2‐methyl‐4,6‐dinitrophenol (MDNP) by differential pulse voltammetry (DPV) in Britton‐Robinson buffer of pH 12.0 as an optimal medium. BiBE was prepared by transferring molten bismuth into a glass tube under constant stream of nitrogen. The linear concentration dependences were measured from 1 to 10 μmol ⋅ L−1 and from 10 to 100 μmol ⋅ L−1 by using optimum accumulation potential of −0.7 V and optimum accumulation time 30 s. Under these conditions limit of determination and limit of quantification was 0.45 and 1.5 μmol ⋅ L−1, respectively. The developed method was successfully applied for the analysis of tap water as a model sample.

Low-Temperature Synthesis of Aluminum Nitride by Addition of Ammonium Chloride.

Aluminum nitride (AlN) is highly insulating and has a high thermal conductivity. AlN also has the advantages of being nontoxic and chemically stable. Therefore, it is a suitable sealing material for electric devices. Previous studies have shown that the addition of NH4Cl has a large influence on the formation of AlN and can effectively be used in its low-temperature synthesis without the use of special equipment. However, it has not been clarified whether NH4Cl simply promotes the reaction between Al and nitrogen or directly contributes to the nitridation reaction. In this study, which was part of a series of studies on the development of low-temperature synthesis methods for AlN, the nitridation behaviors of Al in Al–N2, Al–NH4Cl–N2, and Al–NH4Cl–He systems were determined, and the effects of the heating temperature and amount of NH4Cl on the nitridation behavior were examined in detail. When NH4Cl was added, AlN began to form at 600 °C, a formation temperature that was approximately 200 °C lower than that when only Al powder was heated under a nitrogen stream. The fact that the formation of AlN was also observed when the NH4Cl-added Al powder was heated under a helium gas stream confirmed that nitrogen derived from NH4Cl contributed to the formation of the AlN. Furthermore, based on the experimental results, the reaction mechanism was clarified, and the kinetic parameters for the nitridation of Al were determined.

192 Terpenes as antinutritive chemicals in red cedar

Abstract At some research sites goats aggressively consumed red cedar (Juniperus virginiana) throughout the year, while at other sites goats consumed little cedar, although they consumed more cedar in winter. It was hypothesized that differences in red cedar intake may be caused by terpenes. The purpose of this study was to measure terpenes in cedar needles at different locations and times of the year. Ninety-one samples of red cedar needles were obtained from four locations (Langston, OK; Midwest City, OK; Mannford, OK; Neosho, MO) at monthly intervals over a 2-yr period. Needles were manually stripped from branches at approximately 1.5 m high from at least 25 plants at each location. Sixty grams of cedar needles were extracted by steam distillation for 2 h. Some samples were exhaustively extracted for a further 6 h to calculate recovery (45.7%). Two mL of diethyl ether were added, containing 1 mg/mL of methyl decanoate (internal standard), samples were vortexed and the ether was dried with a stream of nitrogen. Samples were subjected to gas chromatography for terpenes. The total amount of terpenes (mg/g DM) was calculated as the sum of peak areas/peak area of the internal standard x 2 mg internal standard/ 0.457/ dried weight of cedar needles. Months were categorized as season. Data were analyzed using the SAS GLM procedure with factors of season, year, and location. Neither season (P > 0.8) nor location (P > 0.25) nor the interaction (P > .9) were significant factors determining total terpene content of red cedar. Concentration of total terpenes for Langston was 20.8, Mannford 18.4, Neosho 15.2, and OKC 18.6 mg/g DM. Concentration by season was Fall 17.1, Spring 18.6, Summer 17.5, and Winter 19.7 mg/g DM. Total terpene concentration does not seem to be a factor affecting red cedar consumption by goats.