Modifications in stability and structure of whey protein-coated o/w emulsions by interacting chitosan and gum arabic mixed dispersions

The influence of chitosan and gum arabic mixtures on the behaviour of o/w emulsions has been investigated at pH = 3.0. The emulsion behaviour, properties and microstructure were found to be greatly dependent on the precise gum arabic to chitosan ratio. Mixing of gum arabic with chitosan leads to the formation of coacervates of a size dependent on their ratio. Incorporation of low gum arabic to chitosan weight ratios into whey protein-coated emulsions causes depletion flocculation and gravity-induced phase separation. Increasing the polysaccharide weight ratio further, a droplet network with a rather high viscosity (at low shear stress) is generated, which prevents or even inhibits phase separation. At even higher gum arabic to chitosan ratios, the emulsion droplets were immobilised into clusters of an insoluble ternary matrix. Although the emulsion droplet charge had the same sign as that of the coacervates, clusters of oil droplets in a ternary matrix were generated. A mechanism to explain the behaviour of the whey protein-stabilised o/w emulsions is described on the basis of confocal and phase contrast microscopic observations, rheological data, zeta potential measurements, particle size analysis and visual assessment of the macroscopic phase separation events.     

Contact Resistance Measurements for Observation of Fluid Film Effects in Journal Bearings

Wear studies of material combinations, sliding or rolling in contact, frequently produce very inconsistent results. Thin film effects are often cited as the cause of these disparities. One means of detecting the presence of these films is by the use of electrical contact measurements to determine the degree of metal-to-metal contact.

This paper describes an experimental study of the wear behavior of grease-lubricated, cast bronze sleeve bearings running against steel, shafts at high loads, to 24.8 megapascals and a low sliding velocity of 1.6 m/min. The effects of the casting method, shaft speed and shaft finish were investigated.

Bearing torques, temperatures, contact resistances, and wear rates were monitored, during the tests. Neither the torque nor the temperature measurements could be related consistently to the wear data. On the other hand, the electrical contact resistance measurements correlated very well. Changes in wear rates were accompanied by corresponding changes in contact resistance. A region in the contact resistance measurements was identified which corresponded to a transition from low wear to high wear.     

Between-cue associations influence searching for a hidden goal in an environment with a distinctive shape.

In Experiment 1 rats had to escape from a kite-shaped pool by swimming to a submerged escape platform in a right-angled corner. The two walls creating this corner were white and the two walls creating the opposite, incorrect, right-angled corner were black. The rats were then trained in a square pool with two white walls forming one corner and two black walls forming the opposite corner. The platform was in the white corner for a consistent group and the black corner for an inconsistent group. A test in an entirely white kite revealed a stronger preference for the correct than the incorrect corner in the consistent but not the inconsistent group. This outcome is attributed to the formation of associations between geometric cues, provided by the shape of the pool, and the color of the walls. The results were replicated in a second experiment in which the walls of the test pool were the same color as the incorrect corner during initial training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two potential energetic compounds: Ammonium superoxide and ammonium ozonide

Abstract

Two proposed ionic compounds, NH₄O₂ and NH₄O₃, are discussed in terms of several properties related to energetic performance. These include oxygen content, moles of gas produced and heat released upon decomposition, and specific impulse. The heat release was calculated in each instance using the predicted lattice energy, which was obtained from the computed electrostatic potential on the surface of the negative ion. NH₄O₂ is found to be superior to HMX in each property considered, while NH₄O₃ is better than HMX in some and comparable in the others.     

High Speed Particle Beam Generation: A Dynamic Focusing Mechanism for Selecting Ultrafine Particles

RSMS-II is a unique characterization technique for analyzing the chemical content of individual airborne ultrafine particles in real time. Although based on earlier versions, the newest implementation offers crucial enhancements including a smart data acquisition system and a completely redesigned particle inlet. The particle inlet is based on a dynamic focusing mechanism that selectively transmits a narrow particle size range in the form of a high speed particle beam. The mean particle size that is optimally transmitted is dynamically altered by changing the nozzle source pressure, thus particles over a wide size range may be selected. Inherent in the design of dynamic focusing mechanisms is the ability to size-select particles based on their aerodynamic characteristics, thus obviating the need for additional sizing components. The principle, design, and calibration of a variable pressure inlet is presented in the current work. Characteristics are estimated employing a theoretical approach based on the Stokes number definition and supported with numerical simulations using CFD tools. Results from a preliminary effort in calibrating the inlet using monodisperse aerosol are presented. Results indicate that the size resolving capability of the inlet may be enhanced at the expense of lowered transmission rates. Finally, the capability of RSMS-II as a characterization technique is demonstrated by analyzing ultrafine atmospheric particles from a moderately polluted episode.     

Oligomer Content of α-Pinene Secondary Organic Aerosol

The quantity, extraction efficiency, and molecular composition of non-volatile oligomeric species in SOA generated by the reaction of α-pinene with ozone were studied. Two different methods of determining the total particulate mass in the reaction chamber were compared and found to be in good agreement when changes in the partitioning of semi-volatile compounds to the particle phase during measurement were properly handled. Almost all of the non-volatile organic carbon formed by the reaction was collected and recovered by extraction with organic solvents; recoveries with water extraction were somewhat lower. The identities of compounds extracted by the various solvents were determined using electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. Over 80% of the peaks weighted by mass and intensity were the same in the spectra of samples obtained from different extraction solvents. Standard addition plots were used to determine the amounts of two commercially available monomer compounds in the SOA extracts. When the response factors for those compounds were applied to other monomers detected in the mass spectra, the weight percent of monomers was estimated to be slightly less than 50%, with the remaining mass (over 50%) assigned to oligomers. The oligomer content is sufficiently large that it should be taken into account when modeling the formation and properties of laboratory SOA.     

DNA binding of an ethidium intercalator attached to a monolayer-protected gold cluster

Ethidium intercalation has been investigated as a means of inducing binding of Au nanoparticles to DNA. The ethidium sites are attached to the nanoparticles as thiolate ligands, using 3,8-diamino-5-mercaptododecyl-6-phenylphenanthridinium (ethidium thiolate). Each nanoparticle bears only one or two ethidium thiolate ligands. The rest of the thiolate monolayer ligands on the monolayer-protected Au clusters (MPCs) were either N-(2-mercaptopropionyl)glycine (tiopronin/ethidium MPC) or trimethyl(mercaptoundecyl)ammonium (TMA/ethidium MPC). In solution mixtures of DNA and MPCs, the energy-transfer quenching of the ethidium ligands by the metal-like MPC core is partially released by ethidium binding to DNA, as observed by an increase in the intensity of ethidium fluorescence. Binding of the cationic TMA/ethidium MPC to DNA was efficient and rapid. The negatively charged tiopronin/ethidium MPC, in contrast, exhibits slow intercalation kinetics, relative to ethidium cation not attached to an MPC. The slow kinetics were analyzed as two competing binding interactions. The tiopronin/ethidium MPC binding to DNA was imaged by AFM.     

Retrospective dose assessment: the measurement of the dose in quartz in dating and accident dosimetry

In retrospective dosimetry using luminescence it is never possible to obtain a sample of the unaltered phosphor as it was at somc time in the past and before radiation exposure. This prevents direct calibration using conventional personnel dosimetry techniques, and so measurement protocols must be devised which allow accurate estimation of the dose using only the exposed phosphor. This has led to the use of complex protocols, requiring many tens of notionally identical subsamples, to obtain one estimate of the unknown dose. More recently, considerable effort has gone into devising protocols which provide an estimate of the unknown dose from only one subsample. These avoid the need to assume homogeneity in the sample. These protocols also allow faster measurement, which for the first time makes it practical to obtain multiple estimates of the unknown dose and thus externally calculated random errors. This paper discusses the development of single-aliquot protocols, with particular reference to those devised for use with quartz, and finally reviews some of their applications in the retrospective assessment of dose.     

Optically stimulated luminescence in retrospective dosimetry

Since the beginning of the 1990s the exploration of optically stimulated luminescence (OSL) in retrospective accident dosimetry has driven an intensive investigation and development programme at Ris? into measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including the evaluation of the single-aliquot regenerative-dose (SAR) measurement protocol with brick quartz and the determination of dose-depth profiles in building materials as a guide to determining the mean energy of the incident radiation. Investigations into heated materials are most advanced, and a lower detection limit for quartz extracted from Chernobyl bricks was determined to be <10 mGy. The first results from the measurement of doses in unheated building materials such as mortar and concrete are also discussed. Both small-aliquot and single-grain techniques have been used to assess accident doses in these cement based building materials more commonly found in workplaces. Finally some results of a preliminary investigation of the OSL properties of household chemicals are discussed with reference to their potential as accident dosemeters.