Magnetite oxidation in a traveling grate pellet plant: A computer model

A mathematical model of the packed bed of a traveling grate pelletizing machine has been written. This model allows simulation of the temperature profiles in the packed bed of the machine while magnetite oxidation occurs. Knowledge of kinetic data for magnetite oxidation of ore balls of the concentrate concerned is required for simulation. Temperatures measured during industrial pot tests compare well with those predicted by the model. Results for ore balls of two concentrates were compared. KARL D. LIBSCH, formerly Graduate Student, Lehigh University, Bethlehem, Pa. 18015     

X-ray diffraction study of a bulk,polycrystalline Ag-9 at. pct Sn alloy deformed in compression

An analysis was made of X-ray powder pattern peaks from a bulk, polycrystalline Ag-9at. pct Sn alloy that was plastically deformed by compression. The shapes and positions of all available (hkl) reflections were recorded using the focusing, Bragg-Brentano X-ray geometry. Fourier analysis of the profiles were carried out on (111)–(222), (200)–(400), and (220)–(440) pairs of reflections. The effective particle sizesD _e (hkl) decreased rapidly with increasing deformation and reached values ofD _e (111)=110Å,D _e (100)=40Å, andD _e (110)=90Å beyond 20 pct reduction in thickness. The anistropy of the particle sizes is interpreted as a consequence of faulting in the deformed alloy. The mean square strains in the [111] direction were of the order of 10^?5 after more than 20 pct reduction in thickness. Lattice parameter measurements yield the deformation fault probability (α≈0.02), and the residual stresses. The variation of the true lattice parametera _o with increasing deformation indicated that segregation occurred in the deformed alloy. From the ratio of 〈ε²〉/α (≈ 6 × 10^?4), a nominal stacking fault energy of 6 erg per sq cm was calculated.     

Streckgrenzenverhalten von a-Eisen im Grenzfall homogener Verformung

Ziel der Arbeit ist es, im Rahmen einer einfachen Modellvorstellung die plastische Verformung von a-Eisen zu beschreiben, soweit es sich um eine homogene Verformung handelt. Die homogene Verformung wird mit Hilfe der Multiplikationstheorie beschrieben. Die Gültigkeit der Ergebnisse beschränkt sich auf die direkte Streckgrenze und kleine Verformungsgrade.     

Cross-modal transfer and information processing by the sense of touch in infancy.

136 1-yr-old infants were tested on tasks of visual–tactual cross-modal transfer and tactual intramodal processing. In Exp I, Ss successfully differentiated novel from familiar objects by tactual exploration after 60 sec of either visual familiarization (V–T) or 60 sec of tactual familiarization (T–T); all testing that involved tactual exploration was carried out in total darkness, using infrared videotaping. In both tasks, Ss spent significantly more time manipulating novel than familiar shapes. In the T–T task they also engaged in more manipulatory episodes and exhibited more hand-to-hand transfers with the novel shapes. Neither type of transfer was shown with shorter (30-sec) familiarization periods. The finding of successful T–T transfer with 60-sec familiarization was confirmed in Exp II using different stimuli and a modified testing procedure. In both experiments there was evidence that T–T processing surpassed V–T transfer. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The development of the globally harmonized system (GHS) of classification and labelling of hazardous chemicals

The hazards of chemicals can be classified using classification criteria that are based on physical, chemical and ecotoxicological endpoints. These criteria may be developed be iteratively, based on scientific or regulatory processes. A number of national and international schemes have been developed over the past 50 years, and some, such as the UN Dangerous Goods system or the EC system for hazardous substances, are in widespread use. However, the unnecessarily complicated multiplicity of existing hazard classifications created much unnecessary confusion at the user level, and a recommendation was made at the 1992 Rio Earth summit to develop a globally harmonized chemical hazard classification and compatible labelling system, including material safety data sheets and easily understandable symbols, that could be used for manufacture, transport, use and disposal of chemical substances. This became the globally harmonized system for the Classification and Labelling of Chemicals (GHS). The developmental phase of the GHS is largely complete. Consistent criteria for categorising chemicals according to their toxic, physical, chemical and ecological hazards are now available. Consistent hazard communication tools such as labelling and material safety data sheets are also close to finalisation. The next phase is implementation of the GHS. The Intergovernmental Forum for Chemical Safety recommends that all countries implement the GHS as soon as possible with a view to have the system fully operational by 2008. When the GHS is in place, the world will finally have one system for classification of chemical hazards.     

Molecular depth profiling of multilayer polymer films using time-of-flight secondary ion mass spectrometry

The low penetration depth and high sputter rates obtained using polyatomic primary ions have facilitated their use for the molecular depth profiling of some spin-cast polymer films by secondary ion mass spectrometry (SIMS). In this study, dual-beam time-of-flight (TOF) SIMS (sputter ion, 5 keV SF(5)(+); analysis ion, 10 keV Ar(+)) was used to depth profile spin-cast multilayers of poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), and trifluoroacetic anhydride-derivatized poly(2-hydroxyethyl methacrylate) (TFAA-PHEMA) on silicon substrates. Characteristic positive and negative secondary ions were monitored as a function of depth using SF(5)(+) primary ion doses necessary to sputter through the polymer layer and uncover the silicon substrate (>5 x10(14) ions/cm(2)). The sputter rates of the polymers in the multilayers were typically less than for corresponding single-layer films, and the order of the polymers in the multilayer affected the sputter rates of the polymers. Multilayer samples with PHEMA as the outermost layer resulted in lowered sputter rates for the underlying polymer layer due to increased ion-induced damage accumulation rates in PHEMA. Additionally, the presence of a PMMA or PHEMA overlayer significantly decreased the sputter rate of TFAA-PHEMA underlayers due to ion-induced damage accumulation in the overlayer. Typical interface widths between adjacent polymer layers were 10-15 nm for bilayer films and increased with depth to approximately 35 nm for the trilayer films. The increase in interface width and observations using optical microscopy showed the formation of sputter-induced surface roughness during the depth profiles of the trilayer polymer films. This study shows that polyatomic primary ions can be used for the molecular depth profiling of some multilayer polymer films and presents new opportunities for the analysis of thin organic films using TOF-SIMS.     

Resonant laser ablation of metals detected by atomic emission in a microwave plasma and by inductively coupled plasma mass spectrometry

It has been shown that an increase in sensitivity and selectivity of detection of an analyte can be achieved by tuning the ablation laser wavelength to match that of a resonant gas-phase transition of that analyte. This has been termed resonant laser ablation (RLA). For a pulsed tunable nanosecond laser, the data presented here illustrate the resonant enhancement effect in pure copper and aluminum samples, chromium oxide thin films, and for trace molybdenum in stainless steel samples, and indicate two main characteristics of the RLA phenomenon. The first is that there is an increase in the number of atoms ablated from the surface. The second is that the bandwidth of the wavelength dependence of the ablation is on the order of 1 nm. The effect was found to be virtually identical whether the atoms were detected by use of a microwave-induced plasma with atomic emission detection, by an inductively coupled plasma with mass spectrometric detection, or by observation of the number of laser pulses required to penetrate through thin films. The data indicate that a distinct ablation laser wavelength dependence exists, probably initiated via resonant radiation trapping, and accompanied by collisional broadening. Desorption contributions through radiation trapping are substantiated by changes in crater morphology as a function of wavelength and by the relatively broad linewidth of the ablation laser wavelength scans, compared to gas-phase excitation spectra. Also, other experiments with thin films demonstrate the existence of a distinct laser-material interaction and suggest that a combination of desorption induced by electronic transition (DIET) with resonant radiation trapping could assist in the enhancement of desorption yields. These results were obtained by a detailed inspection of the effect of the wavelength of the ablation laser over a narrow range of energy densities that lie between the threshold of laser-induced desorption of species and the usual analytical ablation regime. Normal ablation employs high-power lasers in an attempt to create a vapor plume without selective vaporization, and with a stoichiometry that accurately represents the stoichiometry of species in the solid sample. RLA, as a method of selective vaporization, appears to provide an opportunity to exploit selective vaporization in new ways.     

Photocatalytic degradation-excitation-emission matrix fluorescence for increasing the selectivity of polycyclic aromatic hydrocarbon analyses

The application of photocatalysis enhancement to calibration of fluorescence excitation-emission matrixes (EEMs) with parallel factor (PARAFAC) analysis is described. In this study, three- and four-way PARAFAC analysis was employed to extract the fluorescent species' spectra from overlapping EEMs. Time-dependent photocatalysis degradation of the polycyclic aromatic hydrocarbons (PAHs) was employed to create an additional dimension for analysis. The consequent four-dimension degradation-EEM data cubes have greater selectivity for each PAH than do three-dimension EEM data cubes alone. On a scale of 0 to 1, with 0 being completely collinear spectra and 1 being orthogonal spectra, including the time-dependent measurements increased the selectivity an average of 21%, from 0.73 to 0.87.     

Quantification of cytokines involved in wound healing using surface plasmon resonance

Sensing of three cytokines related to chronic wound healing, interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha), with detection limits at or below 1 ng/mL in buffered saline solution and spiked cell culture medium (CCM) has been achieved. Fiber-optic surface plasmon resonance (SPR) sensors are coated with an antibody binding layer and antibodies specific to the cytokine of interest are covalently attached to this layer. To achieve such detection limits in a complex medium such as CCM, total protein content of 4 mg/mL, the use of a novel N-hydroxysuccinimide ester of 16-mercaptohexadecanoic acid (NHS-MHA) is necessary. A comparison of the detection limits for IL-6 using currently widely used CM-dextran and NHS-MHA shows an improvement by a factor of 3 using NHS-MHA. The detection limits for the monitoring of cytokines in spiked saline solutions and CCM were similar for TNF-alpha and slightly higher for IL-1 and IL-6. The detection of each cytokine in the presence of interfering agents resulted in concentration prediction well within the error of calibration. The SPR sensors are stable in CCM after 20 min of pretreatment in CCM, minimizing the reliance on a reference sensor to quantify the cytokines in complex media. This technique enables a major advancement in the field of real-time monitoring of biologically relevant molecules in complex biological fluids.