Resistance Minimum in Dilute Magnetic Alloys in the Absence of Impurity Moments

A possible mechanism for the resistance minimum in dilute alloys in which the localized impurity states are non-magnetic is suggested. The fact is considered that what is essential to the Kondo-like behaviour is the interaction of the conduction electron spin s with the internal dynamical degrees of freedom of the impurity centre. The necessary internal dynamical degrees of freedom are provided by the dynamical Jahn-Teller effect associated with the degenerate 3d-orbitals of the transition-metal impurities interacting with the surrounding (octahedral) complex of the nearest-neighbour atoms. The fictitious spin I characterizing certain low-lying vibronic states of the system is shown to couple with the conduction electron spin s via s-d mixing and spin-orbit coupling, giving rise to a singular temperature-dependent exchange-like interaction. The resistivity so calculated is in fair agreement with the experimental results of Cape and Hake for Ti containing 0.2 at% of Fe.

Dipole moments and structure of organophosphine and organoarsine compounds

The formal charge distributions in and the dipole moments of some organophosphines and arsines have been calculated, and the dipole moments of (p-chlorophenyl)dichlorophosphine (2.28 D) and (p-bromophenyl)dichlorophosphine (2.04 D) have been determined in benzene at 35° C. The differences between the observed and the calculated moments are explained in terms of dπ---pπ back-bonding and hyperconjugative effects in alkylhaloarsines. The mesomeric effects operating in the aromatic systems are evaluated by comparing the moments with those for the corresponding aliphatic systems. In unsaturated compounds the differences are attributed to mesomeric effects involving the expansion of arsenic valence shell.

A new mode of ring cleavage of 2,3-dihydroxybenzoic acid in Tecoma stans (L.). Partial purification and properties of 2,3-dihydroxybenzoate 2,3-oxygenase.

2,3-Dihydroxybenzoic acid has been shown to be oxidized via the 3-oxoadipate pathway in the leaves of Tecoma stans. The formation of 2-carboxy-cis,cis-muconic acid, a muconolactone, 3-oxoadipic acid and carbon dioxide during its metabolism has been demonstrated using an extract of Tecoma leaves. The first reaction of the pathway, viz., the conversion of 2,3-dihydroxybenzoate to 2-carboxy-cis,cis-muconic acid has been shown to be catalysed by an enzyme designated as 2,3-dihydroxybenzoate 2,3-oxygenase. The enzyme has been partially purified and a few of its properties studied. The enzyme is very labile with a half-life of 3--4 h. It is maximally active with 2,3-dihydroxybenzoate as the substrate and does not exhibit any activity with catechol, 4-methyl catechol, 3,4-dihydroxybenzoic acid, etc. However, 2,3-dihydroxy-p-toluate and 2,3-dihydroxy-p-cumate are also oxidized by the enzyme by about 38% and 28% respectively, compared to 2,3-dihydroxybenzoate. Sulfhydryl reagents inhibit the enzyme reaction and the inhibition can be prevented by preincubation of the enzyme with the substrate. Substrate also affords protection to the enzyme against thermal inactivation. Sulfhydryl compounds strongly inhibit the reaction and the inhibition cannot be prevented by preincubation of the enzyme with its substrates. Data on the effect of metal ions as well as metal chelating agents suggest that copper is the metal cofactor of the enzyme. Evidence is presented which suggests that iron may not be participating in the overall catalytic mechanism.

Measurements of partial discharges-corrections to erroneous counts occurring in a cumulative pulse-counting system

The discharge pulse rates at different magnitude levels are often used as criteria for monitoring the partial-discharge aging of insulation systems. Use of suggested corrections for errors in cumulative probability counting leads to better use of available counters.

Partial Integrated Guidance and Control of Surface-to-Air Interceptors for High Speed Targets

An important limitation of the existing IGC algorithms, is that they do not explicitly exploit the inherent time scale separation that exist in aerospace vehicles between rotational and translational motions and hence can be ineffective. To address this issue, a two-loop partial integrated guidance and control (PIGC) scheme has been proposed in this paper. In this design, the outer loop uses a recently developed, computationally efficient, optimal control formulation named as model predictive static programming. It gives the commanded pitch and yaw rates whereas necessary roll-rate command is generated from a roll-stabilization loop. The inner loop tracks the outer loop commands using the Dynamic inversion philosophy. Uncommonly, Six-Degree of freedom (Six-DOF) model is used directly in both the loops. This intelligent manipulation preserves the inherent time scale separation property between the translational and rotational dynamics, and hence overcomes the deficiency of current IGC designs, while preserving its benefits. Comparative studies of PIGC with one loop IGC and conventional three loop design were carried out for engaging incoming high speed target. Simulation studies demonstrate the usefulness of this method.

Scar outcome of children with partial thickness burns: A 3 and 6 month follow up

INTRODUCTION There is a paucity of research investigating the scar outcome of children with partial thickness burns. The aim of this study was to assess the scar outcome of children with partial thickness burns who received a silver dressing acutely. METHOD Children aged 0-15 years with an acute partial thickness burn, ≤10% TBSA were included. Children were originally recruited for an RCT investigating three dressings for partial thickness burns. Children were assessed at 3 and 6 months after re-epithelialization. 3D photographs were taken of the burn site, POSAS was completed and skin thickness was measured using ultrasound imaging. RESULTS Forty-three children returned for 3 and 6 month follow-ups or returned a photo. Days to re-epithelialization was a significant predictor of skin/scar quality at 3 and 6 months (p<0.01). Patient-rated color and observer-rated vascularity and pigmentation POSAS scores were comparable at 3 months (color vs. vascularity 0.88, p<0.001; color vs. pigmentation 0.64, p<0.001), but patients scored higher than the observer at 6 months (color vs. vascularity 0.57, p<0.05; color vs. pigmentation 0.15, p=0.60). Burn depth was significantly correlated with skin thickness (r=0.51, p<0.01). Hypopigmentation of the burn site was present in 25.8% of children who re-epithelialized in ≤2 weeks. CONCLUSION This study has provided information on outcomes for children with partial thickness burns and highlighted a need for further education of this population.

Randomised controlled trial of three burns dressings for partial thickness burns in children

BACKGROUND This study compared the effects of three silver dressing combinations on small to medium size acute partial thickness burns in children, focusing on re-epithelialization time, pain and distress during dressing changes. METHOD Children (0-15 years) with clean, ≤ 10% total body surface area (TBSA) partial thickness burns who met the inclusion criteria were included in the study. Children received either (1) Acticoat™; (2) Acticoat™ with Mepitel™; or (3) Mepilex Ag™ dressings. Measures of burn re-epithelialization, pain, and distress were recorded at dressing changes every 3-5 days until full re-epithelialization occurred. RESULTS One hundred and three children were recruited with 96 children included for analysis. No infections were detected for the course of the study. When adjusted for burn depth, Acticoat™ significantly increased the expected days to full re-epithelialization by 40% (IRR = 1.40; 95% CI: 1.14-1.73, p < 0.01) and Acticoat™ with Mepitel™ significantly increased the expected days to full re-epithelialization by 33% (IRR = 1.33; 95% CI: 1.08-1.63, p ≤ 0.01) when compared to Mepilex Ag™. Expected FLACC scores in the Mepilex Ag™ group were 32% lower at dressing removal (p = 0.01) and 37% lower at new dressing application (p = 0.04); and scores in the Acticoat™ with Mepitel™ group were 23% lower at dressing removal (p = 0.04) and 40% lower at new dressing application (p < 0.01), in comparison to the Acticoat™ group. Expected Visual Analog Scale-Pain (VAS-P) scores were 25% lower in the Mepilex Ag™ group at dressing removal (p = 0.04) and 34% lower in the Acticoat™ with Mepitel™ group (p = 0.02) at new dressing application in comparison to the Acticoat™ group. There was no significant difference between the Mepilex Ag™ and the Acticoat™ with Mepitel™ groups at all timepoints and with any pain measure. CONCLUSION Mepilex Ag™ is an effective silver dressing, in terms of accelerated wound re-epithelialization time (compared to Acticoat™ and Acticoat™ with Mepitel™) and decreased pain during dressing changes (compared to Acticoat™), for clean, < 10% TBSA partial thickness burns in children.

Effect of oxygen partial pressure on the growth of zinc micro and nanostructures

Zinc micro and nanostructures were synthesized in vacuum by condensing evaporated zinc on Si substrate at different gas pressures. The morphology of the grown Zn structures was found to be dependent on the oxygen partial pressure. Depending on oxygen partial pressure it varied from two-dimensional microdisks to one-dimensional nanowire. The morphology and structural properties of the grown micro and nanostructures were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Transmission electron microscopy (TEM) studies on the grown Zn nanowires have shown that they exhibit core/shell-like structures, where a thin ZnO layer forms the shell. A possible growth mechanism behind the formation of different micro and nanostructures has been proposed. In addition, we have synthesized ZnO nanocanal-like structures by annealing Zn nanowires in vacuum at 350 °C for 30 min.

Effect of oxygen partial pressure on the structural and optical properties of dc reactive magnetron sputtered molybdenum oxide films

Molybdenum oxide films (MoO3) were deposited on glass and crystalline silicon substrates by sputtering of molybdenum target under various oxygen partial pressures in the range 8 × 10−5–8 × 10−4 mbar and at a fixed substrate temperature of 473 K employing dc magnetron sputtering technique. The influence of oxygen partial pressure on the composition stoichiometry, chemical binding configuration, crystallographic structure and electrical and optical properties was systematically studied. X-ray photoelectron spectra of the films formed at 8 × 10−5 mbar showed the presence of Mo6+ and Mo5+ oxidation states of MoO3 and MoO3−x. The films deposited at oxygen partial pressure of 2 × 10−4 mbar showed Mo6+ oxidation state indicating the films were nearly stoichiometric. It was also confirmed by the Fourier transform infrared spectroscopic studies. X-ray diffraction studies revealed that the films formed at oxygen partial pressure of 2 × 10−4 mbar showed the presence of (0 k 0) reflections indicated the layered structure of α-phase MoO3. The electrical conductivity of the films decreased from 3.6 × 10−5 to 1.6 × 10−6 Ω−1 cm−1, the optical band gap of the films increased from 2.93 to 3.26 eV and the refractive index increased from 2.02 to 2.13 with the increase of oxygen partial pressure from 8 × 10−5 to 8 × 10−4 mbar, respectively.

On the Structure of Contractible Edges in k-connected Partial k-trees

Contraction of an edge e merges its end points into a new single vertex, and each neighbor of one of the end points of e is a neighbor of the new vertex. An edge in a k-connected graph is contractible if its contraction does not result in a graph with lesser connectivity; otherwise the edge is called non-contractible. In this paper, we present results on the structure of contractible edges in k-trees and k-connected partial k-trees. Firstly, we show that an edge e in a k-tree is contractible if and only if e belongs to exactly one (k + 1) clique. We use this characterization to show that the graph formed by contractible edges is a 2-connected graph. We also show that there are at least |V(G)| + k - 2 contractible edges in a k-tree. Secondly, we show that if an edge e in a partial k-tree is contractible then e is contractible in any k-tree which contains the partial k-tree as an edge subgraph. We also construct a class of contraction critical 2k-connected partial 2k-trees.

Partial foot amputations may not always be worth the risk of complications

To the Editor: Dillon and colleagues present a challenging perspective on the evidence comparing partial foot amputation (PFA) and below-knee amputation (BKA) outcomes.1,2 Australia's diabetes-related major amputation rates have only recently reduced to international levels3 and we fear that any oversimplistic perspectives may be detrimental to these improved rates and, importantly, to our patients. Thus, we believe these articles1,2 should be read cognisant of some important points...

Distributed space-time codes for cooperative networks with partial CSI

Design criteria and full-diversity Distributed Space Time Codes (DSTCs) for the two phase transmission based cooperative diversity protocol of Jing-Hassibi and the Generalized Nonorthogonal Amplify and Forward (GNAF) protocol are reported, when the relay nodes are assumed to have knowledge of the phase component of the source to relay channel gains. It is shown that this under this partial channel state information (CSI), several well known space time codes for the colocated MIMO (Multiple Input Multiple Output) channel become amenable for use as DSTCs. In particular, the well known complex orthogonal designs, generalized coordinate interleaved orthogonal designs (GCIODs) and unitary weight single symbol decodable (UW-SSD) codes are shown to satisfy the required design constraints for DSTCs. Exploiting the relaxed code design constraints, we propose DSTCs obtained from Clifford Algebras which have low ML decoding complexity.

Investigation of the local Fe magnetic moments at the grain boundaries of the Ca2FeReO6 double perovskite

The local Fe ferromagnetic (FM) moment at the grain boundaries of a ceramic sample of Ca2FeReO6 double perovskite was investigated by means of x-ray magnetic circular dichroism spectroscopy at the Fe L-2,L-3 edges and compared to the overall bulk magnetization. We found that, at the grain boundaries, the Fe FM moments at H=5 T are much smaller than expected and that the MxH curve is harder than in the bulk magnetization. These results suggest a larger degree of Fe/Re antisite disorder at the grain boundaries of this sample, shedding light into the intriguing nonmetallic resistivity behavior despite the reported presence of free carriers. (c) 2007 American Institute of Physics.

Low PAPR STBCs from Complex Partial-Orthogonal Designs (CPODs)

Space-time codes from complex orthogonal designs (CODs) with no zero entries offer low Peak to Average power ratio (PAPR) and avoid the problem of turning off antennas. But CODs for 2(a) antennas with a + 1 complex variables, with no zero entries are not known in the literature for a >= 4. In this paper, a method of obtaining no zero entry (NZE) codes, called Complex Partial-Orthogonal Designs (CPODs), for 2(a+1) antennas whenever a certain type of NZE code exists for 2(a) antennas is presented. This is achieved with slight increase in the ML decoding complexity for regular QAM constellations and no increase for other complex constellations. Since NZE CODs have been constructed recently for 8 antennas our method leads to NZE CPODs for 16 antennas. Moreover, starting from certain NZE CPODs for n antennas, a construction procedure is given to obtain NZE CPODs for 2n antennas. The class of CPODs do not offer full-diversity for all complex constellations. For the NZE CPODs presented in the paper, conditions on the signal sets which will guarantee full-diversity are identified. Simulations results show that bit error performance of our codes under average power constraint is same as that of the CODs and superior to CODs under peak power constraint.

Comparison of partial extraction reagents for assessing potential bioavailability of heavy metals in sediments

Assessment of heavy metal bioavailability in sediments is complex because of the number of partial extraction methods available for the assessment and the general lack of certified reference materials. This study evaluates five different extraction methodologies to ascertain the relative strengths and weaknesses of each method. The results are then compared to previously published work to ascertain the most effective partial extraction technique, which was established to be dilute (0.75 – 1 M) nitric acid solutions. These results imply that single reagent; weak acid extractions provide a better assessment of potentially bioavailable metals than the chelating agents used in sequential extraction methods.