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Nitrogen Gas (nitrogen + gas)

Distribution by Scientific Domains

Chemistry	50%
Life Sciences	21%
Polymers and Materials Science	14%

Selected Abstracts

The Effect of Edible Coatings and Pressure Frying Using Nitrogen Gas on the Quality of Breaded Fried Chicken Nuggets

JOURNAL OF FOOD SCIENCE, Issue 3 2006
Tameshia S. Ballard
ABSTRACT: The effects of 2 edible coatings, methylcellulose (MC) and whey protein isolate (WPI), and 2 pressure sources (nitrogen gas and steam) on the quality attributes (crispness, moisture and fat content, juiciness, color, and texture) of breaded fried chicken nuggets were evaluated. MC or WPI was incorporated into either the pre-dust or the batter before frying. Chicken nuggets were fried in a modified restaurant-type pressure fryer under a constant pressure of 163 kPa at 175°C for 240 s. Samples were held under a heat lamp at 60°C for 0-, 10-, 20-, and 30-min time intervals. Crispness was evaluated using a nondestructive ultrasonic technique. Coating type and pressure source had a significant effect (P < 0.05) on all quality attributes. Chicken nuggets fried using nitrogen gas were crispier (P < 0.05) than those fried with steam. The treatment combination of MC incorporated into the pre-dust and frying with nitrogen gas was the most effective at maintaining product crispness. [source]

Treatment of Skim Latex Serum Using Gas Sparged Ultrafiltration

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005
Harunsyah
Abstract The major pollutants from a natural rubber processing factory have high organic content and emit an offensive smell due to the biodegradation of the organic matter. In latex concentrate factories, the main sources of effluent are the skim latex serum and washings from all process equipment. This paper presents an application of membrane technology that involves gas sparging for the treatment of skim latex serum. A semi-pilot-scale system using a PVDF vertical tubular membrane (MWCO 100,000) was installed as the experimental setup. Nitrogen gas was bubbled vertically upwards at flowrates ranging from 300 to 500 ml/min. Results obtained thus far show that gas sparging has increased the permeate flux between 1.37% and 146.34% compared to non-gas sparged conditions. In terms of permeate quality, the reductions achieved for suspended solids, total solids, COD, BOD, total nitrogen and ammoniacal nitrogen were 83%, 95%, 67%, 77%, 51%, 74%, respectively, for the gas-sparged condition. Under non gas-sparging conditions, reductions achieved for suspended solids, total solids, COD, BOD, total nitrogen and ammoniacal nitrogen were 92%, 96%, 67%, 72%, 60%, 75%, respectively. [source]

Oxidation chemistry of acid-volatile sulfide during analysis

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002
Adrian M. Gonzalez
Abstract The susceptibility of some components of sediment acid-volatile sulfide (AVS) to chemical oxidation is a critical factor impacting accurate measurement of AVS in sediment samples. This well-documented susceptibility to oxidation led to the requirement for oxygen-free conditions in the analytical method developed for AVS. In light of this acute potential to oxidize, the serendipitous finding that air can be used in the analysis of sediment AVS is counterintuitive and unexpected. To demonstrate and investigate this interesting observation, extraction experiments were performed using aqueous and solid-phase sulfide species. Experiments using air as the carrier gas showed a mean percentage recovery of sulfide matching that of traditional (nitrogen gas) analysis (i.e., >91%) and a time to completion of less than 30 min for aqueous sulfide and less than 60 min for sediment samples. These results are consistent with those of sulfide oxidation studies reported in the literature. Using air as the analytical carrier gas can provide an interesting alternative for developing an analytical method to determine AVS parameters in the field. [source]

Empirical slip and viscosity model performance for microscale gas flow

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2005
Matthew J. McNenly
Abstract For the simple geometries of Couette and Poiseuille flows, the velocity profile maintains a similar shape from continuum to free molecular flow. Therefore, modifications to the fluid viscosity and slip boundary conditions can improve the continuum based Navier,Stokes solution in the non-continuum non-equilibrium regime. In this investigation, the optimal modifications are found by a linear least-squares fit of the Navier,Stokes solution to the non-equilibrium solution obtained using the direct simulation Monte Carlo (DSMC) method. Models are then constructed for the Knudsen number dependence of the viscosity correction and the slip model from a database of DSMC solutions for Couette and Poiseuille flows of argon and nitrogen gas, with Knudsen numbers ranging from 0.01 to 10. Finally, the accuracy of the models is measured for non-equilibrium cases both in and outside the DSMC database. Flows outside the database include: combined Couette and Poiseuille flow, partial wall accommodation, helium gas, and non-zero convective acceleration. The models reproduce the velocity profiles in the DSMC database within an L2 error norm of 3% for Couette flows and 7% for Poiseuille flows. However, the errors in the model predictions outside the database are up to five times larger. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Inhibition of sulfide on the simultaneous removal of nitrate and p -cresol by a denitrifying sludge

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2008
Edna R Meza-Escalante
Abstract BACKGROUND: Many industrial discharges, such as those generated from petrochemical refineries, contain large amounts of sulfurous, nitrogenous and organic contaminants. Denitrification has emerged as a suitable technology for the simultaneous removal of these pollutants in a single reactor unit; however, more evidence is demanded to clarify the limitations of denitrification on the simultaneous removal of sulfide and phenolic contaminants and to optimize the biological process. The aim of this study was to evaluate the capacity of a denitrifying sludge to simultaneously convert sulfide and p -cresol via denitrification. RESULTS: Sulfide was the preferred electron donor over p -cresol, imposing a 5 h lag phase (required for complete sulfide removal) on organotrophic denitrification. Addition of sulfide (20 mg S2, L,1) to p -cresol-amended denitrifying cultures also decreased the reduction rate of nitrate and nitrite, as well as the production rate of nitrogen gas. Nitrite reduction rate was the most affected step by sulfide, decreasing from 35 to 21 mg N (g VSS d),1. A synergistic inhibitory effect of nitrate and sulfide was also observed on nitrite reduction. Despite the effects of sulfide on the respiratory rates monitored, complete removal of nitrate, sulfide and p -cresol could be achieved after 48 h of incubation. CONCLUSION: Our results suggest that simultaneous removal of sulfide and p -cresol could be achieved in denitrifying reactors, but a large hydraulic residence time may be required to sustain an efficient process due to inhibitory effects of sulfide. Copyright © 2008 Society of Chemical Industry [source]

The Effect of Edible Coatings and Pressure Frying Using Nitrogen Gas on the Quality of Breaded Fried Chicken Nuggets

Preparation and characterization of monodisperse superparamagnetic poly(vinyl alcohol) beads by reverse spray suspension crosslinking

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008
Chengli Yang
Abstract A novel protocol for preparing magnetic poly(vinyl alcohol) (PVA) beads by reverse spray suspension crosslinking was reported. The hydrophilic Fe3O4 nanoparticles were mixed with PVA, glutaraldehyde, and water to form aqueous phase. Then the aqueous phase was sprayed into vegetable oil by a pressure of nitrogen gas to form water in oil (W/O) suspension. The magnetic PVA beads were obtained in the presence of hydrochloric acid catalyst. It was found that the magnetic PVA beads obtained good properties when the PVA concentration was 10%, and the oil phase temperature was controlled at 40 °C. The mechanical stirring has little impact on the size of magnetic PVA beads in the process of reverse spray suspension crosslinking. The Cibacron Blue (CB) was coupled on the surface of magnetic PVA beads by surface chemical reaction. The morphology, size, and magnetic properties of the magnetic PVA beads were examined by scanning electron microscopy, laser diffraction, and vibrating sample magnetometer, respectively. Compared with the stirring method, it was found that the size of magnetic PVA beads was monodisperse and their saturation magnetization was much higher. Fourier transform infrared and X-ray photoelectron spectroscopy experimental results proved that CB molecules were covalently immobilized onto the surface of the magnetic PVA beads. Meanwhile, the protein affinity separation experiments demonstrated that the magnetic PVA beads can potentially be used as a carrier for large-scale protein separation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 203,210, 2008 [source]

Growth, clustering and morphology of intermetallic alloy core-shell nanodroplets

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008
A. C. Cefalas
Abstract Sm,Fe,Ta,N core-shell (CS) nanospheroids were fabricated from hot liquefied nanodroplets by 157 nm pulse laser deposition in nitrogen gas. The Sm13.8Fe82.2Ta4.0 intermetallic alloy was used as the target. At low laser energy (20 mJ), spherical CS of 1,35 nm radius were fabricated on a Si/Ta substrate forming uniform films. The small nanodroplets were grown in the plume from the gas phase, and the larger ones (>50 nm radius) from the target's hydrodynamic ejection. The critical radius of the droplets and their surface energy per unit area was found to be 7.5 nm and 3.8 ,J/cm2 respectively. A number of CS solidified in the plume and consist of 2.5,5 nm radius crystalline nucleus surrounded by a <35 nm radius amorphous spherical shell. This structure prevents the oxidization of the crystalline nucleus because oxidization is confined on the surface of the CS. Furthermore, multi-crystalline nanodomains (embryos) were identified in a single CS from both homogeneous and heterogeneous nucleation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The spatial pattern of air seeding thresholds in mature sugar maple trees

PLANT CELL & ENVIRONMENT, Issue 9 2005
BRENDAN CHOAT
ABSTRACT Air seeding threshold (Pa) of xylem vessels from current year growth rings were measured along the vertical axis of mature sugar maple trees (Acer saccharum Marsh.), with sampling points in primary leaf veins, petioles, 1-, 3-, and 7-year-old branches, large branches, the trunk and roots. The air seeding threshold was taken as the pressure required to force nitrogen gas through intervessel pit membranes. Although all measurements were made on wood produced in the same year, Pa varied between different regions of A. saccharum, with distal organs such as leaves and petioles having lower Pa than basal regions. Mean (SE) Pa ranged from 1.0 (± 0.1) MPa in primary leaf veins to 4.8 (± 0.1) MPa in the main trunk. Roots exhibited a Pa of 2.8 (± 0.2) MPa, lower than all other regions of the tree except leaf veins and petioles. Mean xylem vessel diameter increased basipetally, with the widest vessels occurring in the trunk and roots. Within the shoot, wider vessels had greater air seeding thresholds, contrasting with trends previously reported. However, further experimentation revealed that differences in Pa between regions of the stem were driven by the presence of primary xylem conduits, rather than differences in vessel diameter. In 1-year-old branches, Pa was significantly lower in primary xylem vessels than in adjacent secondary xylem vessels. This explained the lower values of Pa measured in petioles and leaf veins, which possessed a greater ratio of primary xylem to secondary xylem than other regions. The difference in Pa between primary and secondary xylem was attributed to the greater area of primary cell wall (pit membrane) exposed in primary xylem conduits with helical or annular thickening. [source]

Surface Modification of Carbon Electrode for Electric Double Layer Capacitor

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Daisuke Tashima
Abstract In this research, spatio-temporal profiles of positive and negative charges in an electric double layer capacitor (EDLC) which consists of activated carbon, treated by plasma discharges were measured. The plasma type was a high frequency glow discharge and the sample of activated carbon is set in the center of glow discharge. Optimal conditions for plasma surface treatment of activated carbon was examined from 0 to 60 min at 150,°C in nitrogen gas. As a result, nitrogen atom was doped onto the surface layer of the activated carbon. In addition, electron spectroscopy for chemical analysis (ESCA) spectra of nitrogen in the activated carbon was examined. By etching the surface layer of carbon electrode exposed to the plasma, the doped nitrogen atom penetrated about 3 nm of the surface layer of carbon electrode after 60 min of plasma surface treatment. [source]

Crystallization and preliminary crystallographic analysis of endonuclease VIII in its uncomplexed form

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2004
Gali Golan
The Escherichia coli DNA repair enzyme endonuclease VIII (EndoVIII or Nei) excises oxidized pyrimidines from damaged DNA substrates. It overlaps in substrate specificity with endonuclease III and may serve as a back-up for this enzyme in E. coli. The three-dimensional structure of Nei covalently complexed with DNA has been recently determined, revealing the critical amino-acid residues required for DNA binding and catalytic activity. Based on this information, several site-specific mutants of the enzyme have been tested for activity against various substrates. Although the crystal structure of the DNA-bound enzyme has been fully determined, the important structure of the free enzyme has not previously been analyzed. In this report, the crystallization and preliminary crystallographic characterization of DNA-free Nei are described. Four different crystal habits are reported for wild-type Nei and two of its catalytic mutants. Despite being crystallized under different conditions, all habits belong to the same crystal form, with the same space group (I222) and a similar crystallographic unit cell (average parameters a = 57.7, b = 80.2, c = 169.7,Å). Two of these crystal habits, I and IV, appear to be suitable for full crystallographic analysis. Crystal habit I was obtained by vapour diffusion using PEG 8000, glycerol and calcium acetate. Crystal habit IV was obtained by a similar method using PEG 400 and magnesium chloride. Both crystals are mechanically strong and stable in the X-ray beam once frozen under cold nitrogen gas. A full diffraction data set has recently been collected from a wild-type Nei crystal of habit I (2.6,Å resolution, 85.2% completeness, Rmerge = 9.8%). Additional diffraction data were collected from an Nei-R252A crystal of habit IV (2.05,Å resolution, 99.9% completeness, Rmerge = 6.0%) and an Nei-E2A crystal of habit IV (2.25,Å resolution, 91.7% completeness, Rmerge = 6.2%). These diffraction data were collected at 95,100 K using a synchrotron X-ray source and a CCD area detector. All three data sets are currently being used to obtain crystallographic phasing via molecular-replacement techniques. [source]

A new crystal form of XT6 enables a significant improvement of its diffraction quality and resolution

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004
Maya Bar
Xylanases (1,4-,- d -xylan xylanhydrolases; EC 3.2.1.8) hydrolyze the 1,4-,- d -xylopyranosyl linkage of xylans. The detailed structural characterization of these enzymes is of interest for the elucidation of their catalytic mechanism and for their rational modification toward improved stability and specificity. An extracellular xylanase from Geobacillus stearothermophilus T-6 (XT6) has recently been cloned, overexpressed, purified and biochemically characterized. Previous crystallographic efforts resulted in a hexagonal crystal form, which subsequently proved to be of limited use for structural analysis, mainly because of its relatively poor diffraction quality and resolution. A systematic search for more suitable crystals of XT6 recently resulted in a new crystal form of this enzyme with significantly improved diffraction characteristics. The new crystals belong to a C -centred monoclinic crystal system (space group C2), with unit-cell parameters a = 121.5, b = 61.7, c = 89.1,Å, , = 119.7°. These crystals diffract X-rays to better than 1.5,Å resolution, showing a very clear diffraction pattern of relatively high quality. The crystals are mechanically strong and exhibit excellent radiation-stability when frozen under cold nitrogen gas. A full diffraction data set to 1.45,Å resolution (94.1% completeness, Rmerge = 7.0%) has been collected from flash-frozen crystals of the native enzyme at 95,K using synchrotron radiation. Crystals of the E159A/E265A catalytic double mutant of XT6 were found to be isomorphous to those of native XT6. They were used for a full measurement of 1.8,Å resolution diffraction data at 100,K (90.9% completeness; Rmerge = 5.0%). These data are currently being used for the high-resolution structure determination of XT6 and its mutant for mechanistic interpretations and rational introduction of thermostability. [source]

Performance and population analysis of a non-sterile trickle bed reactor inoculated with Caldicellulosiruptor saccharolyticus, a thermophilic hydrogen producer

BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009
J.W. van Groenestijn
Abstract Non-axenic operation of a 400 L trickle bed reactor inoculated with the thermophile Caldicellulosiruptor saccharolyticus, yielded 2.8 mol,H2/mol hexose converted. The reactor was fed with a complex medium with sucrose as the main substrate, continuously flushed with nitrogen gas, and operated at 73°C. The volumetric productivity was 22 mmol,H2/(L,filterbed,h). Acetic acid and lactic acid were the main by-products in the liquid phase. Production of lactic acid occurred when hydrogen partial pressure was elevated above 2% and during suboptimal fermentation conditions that also resulted in the presence of mono- and disaccharides in the effluent. Methane production was negligible. The microbial community was analyzed at two different time points during operation. Initially, other species related to members of the genera Thermoanaerobacterium and Caldicellulosiruptor were present in the reactor. However, these were out-competed by C. saccharolyticus during a period when sucrose was completely used and no saccharides were discharged with the effluent. In general, the use of pure cultures in non-sterile industrial applications is known to be less useful because of contamination. However, our results show that the applied fermentation conditions resulted in a culture of a single dominant organism with excellent hydrogen production characteristics. Biotechnol. Bioeng. 2009;102: 1361,1367. © 2008 Wiley Periodicals, Inc. [source]

Effective Diffusivities and Convective Coefficients for CaO-CaSO4 and CaO-CaCl2 Pellets

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2004
C. Akosman
Abstract Diffusion and convective flow in the pores of pellets formed by compressing mixtures of calcined limestone and CaSO4/CaCl2 powders have been studied experimentally by using the single pellet moment technique. The experiments were conducted in a diffusion cell by flowing nitrogen gas (carrier) through both faces of the pellet. Limestone powder was calcined in an atmosphere of N2 at 800,°C and mixed with CaSO4/CaCl2 for diffusion experiments. Effective diffusivity of helium has been estimated by exposing the upper face of the pellet to a pulse of and matching the response peak on the lower face of the pellet with theoretical expressions. The values of the effective diffusivities increased with temperature, but decreased with increasing CaSO4/CaCl2 content in the pellet. The convective flow contribution to the diffusion flux was found to increase with increasing pressure drop across the pellet. [source]