Quantifying the computational capability of a nanomagnetic reservoir computing platform with emergent magnetisation dynamics.

Devices based on arrays of interconnected magnetic nano-rings with emergent magnetization dynamics have recently been proposed for use in reservoir computing applications, but for them to be computationally useful it must be possible to optimise their dynamical responses. Here, we use a phenomenological model to demonstrate that such reservoirs can be optimised for classification tasks by tuning hyperparameters that control the scaling and input-rate of data into the system using rotating magnetic fields. We use task-independent metrics to assess the rings' computational capabilities at each set of these hyperparameters and show how these metrics correlate directly to performance in spoken and written digit recognition tasks. We then show that these metrics, and performance in tasks, can be further improved by expanding the reservoir's output to include multiple, concurrent measures of the ring arrays' magnetic states.

Probing the Transfer of the Exchange Bias Effect by Polarized Neutron Reflectometry.

The magnetic reversal behavior of a ferromagnet (FM) coupled through an FeMn antiferromagnet (AF) to a pinned ferromagnet has been investigated by polarized neutron reflectivity measurements. With FeMn as the AF layer it is found that there exists 90° interlayer coupling through this layer and that this plays a key role in the transfer of the exchange bias (EB) effect from the FM/AF interface to the AF/pinned-FM interface. Combined with Monte Carlo simulations, we demonstrate that the competition between the interlayer coupling and the anisotropy of the AF layer results in a control of the EB effect which has potential for device applications.

Spin-echo small-angle neutron scattering (SESANS) studies of diblock copolymer nanoparticles.

Poly(glycerol monomethacrylate)-poly(benzyl methacrylate) (PGMA-PBzMA) diblock copolymer nanoparticles were synthesized via polymerization-induced self-assembly (PISA) using reversible addition-fragmentation chain-transfer (RAFT) aqueous emulsion polymerization in D2O. Such PISA syntheses produce sterically-stabilized nanoparticles in situ and can be performed at relatively high copolymer concentrations (up to 50 wt%). This PGMA-PBzMA formulation is known to form only spherical nanoparticles in water using aqueous emulsion polymerization (Macromolecules, 2014, 47, 5613-5623), which makes it an ideal model system for exploring new characterization methods. The polymer micelles were characterized using small-angle X-ray scattering (SAXS) and a recently developed form of neutron scattering, spin-echo small-angle neutron scattering (SESANS). As far as we are aware, this is the first report of a study of polymer micelles by SESANS, and the data agree well with reciprocal-space scattering. Using this technique enables characterization of the concentrated, as synthesized dispersions directly without dilution, and this will provide a method to study self-assembled polymer systems that have concentration dependent morphologies, while still maintaining the advantages of scattering techniques.

Interfacial Origin of the Magnetisation Suppression of Thin Film Yttrium Iron Garnet.

Yttrium iron garnet has a very high Verdet constant, is transparent in the infrared and is an insulating ferrimagnet leading to its use in optical and magneto-optical applications. Its high Q-factor has been exploited to make resonators and filters in microwave devices, but it also has the lowest magnetic damping of any known material. In this article we describe the structural and magnetic properties of single crystal thin-film YIG where the temperature dependence of the magnetisation reveals a decrease in the low temperature region. In order to understand this complex material we bring a large number of structural and magnetic techniques to bear on the same samples. Through a comprehensive analysis we show that at the substrate -YIG interface, an interdiffusion zone of only 4-6 nm exists. Due to the interdiffusion of Y from the YIG and Gd from the substrate, an addition magnetic layer is formed at the interface whose properties are crucially important in samples with a thickness of YIG less than 200 nm.

Probing the spiral magnetic phase in 6 nm textured erbium using polarised neutron reflectometry.

We characterise the magnetic state of highly-textured, sputter deposited erbium for a film of thickness 6 nm. Using polarised neutron reflectometry it is found that the film has a high degree of magnetic disorder, and we present some evidence that the film's local magnetic state is consistent with bulk-like spiral magnetism. This, combined with complementary characterisation techniques, show that thin film erbium is a strong candidate material for incorporation into device structures.

Magnetic Phases of Sputter Deposited Thin-Film Erbium.

We present a detailed structural and magnetic characterization of sputter deposited thin film erbium, determined by x-ray diffraction, transport measurements, magnetometry and neutron diffraction. This provides information on the onset and change of the magnetic state as a function of temperature and applied magnetic field. Many of the features of bulk material are reproduced. Also of interest is the identification of a conical magnetic state which repeats with a wavevector parallel to the c axis τc = 4/17 in units of the reciprocal lattice parameter c*, which is a state not observed in any other thin film or bulk measurements. The data from the various techniques are combined to construct magnetic field, temperature (H, T)-phase diagrams for the 200 nm-thick Er sample that serves as a foundation for future exploitation of this complex magnetic thin film system.

MeV proton flux predictions near Saturn's D ring.

Radiation belts of MeV protons have been observed just outward of Saturn's main rings. During the final stages of the mission, the Cassini spacecraft will pass through the gap between the main rings and the planet. Based on how the known radiation belts of Saturn are formed, it is expected that MeV protons will be present in this gap and also bounce through the tenuous D ring right outside the gap. At least one model has suggested that the intensity of MeV protons near the planet could be much larger than in the known belts. We model this inner radiation belt using a technique developed earlier to understand Saturn's known radiation belts. We find that the inner belt is very different from the outer belts in the sense that its intensity is limited by the densities of the D ring and Saturn's upper atmosphere, not by radial diffusion and satellite absorption. The atmospheric density is relatively well constrained by EUV occultations. Based on that we predict an intensity in the gap region that is well below that of the known belts. It is more difficult to do the same for the region magnetically connected to the D ring since its density is poorly constrained. We find that the intensity in this region can be comparable to the known belts. Such intensities pose no hazard to the mission since Cassini would only experience these fluxes on timescales of minutes but might affect scientific measurements by decreasing the signal-to-contamination ratio of instruments.

Methylmercuric chloride induces activation of neuronal stress circuitry and alters exploratory behavior in the mouse.

Methylmercury (MeHg) is a well-known neurotoxicant, responsible for neurological and cognitive alterations. However, there is very little information available on the effects of MeHg administration on activation of murine neuronal pathways involved in the stress response, and whether this is altered as a function of repeated exposure to MeHg. Moreover, interactions between MeHg and other psychogenic and inflammatory stressors have yet to be fully determined. Acute i.p. exposure of male C57BL/6J mice to MeHg (2-8 mg/kg) dose-dependently attenuated exploratory behavior in the open field in the presence and absence of a novel object. In addition, increased numbers of c-Fos immunoreactive cells appeared in response to acute i.p. and i.c.v. MeHg within thalamic (anterior paraventricular nucleus of the thalamus (PVA)/posterior paraventricular nucleus of the thalamus (PV)), hypothalamic (paraventricular nucleus of the hypothalamus (PVN)), central amygdaloid nucleus (CeC), septal and hippocampal (dentate gyrus) nuclei, medial bed nucleus (BSTm) and the locus coeruleus (Lc). The increase in c-Fos positive cells in response to acute i.p. and i.c.v. MeHg did not appear to be influenced further by open field exposure. Repeated administration of MeHg led to an attenuation of most parameters of open field behavior altered by acute MeHg. However, increased c-Fos was significant in the CeC, Dg, supracapsular bed nucleus (BSTs), and Lc. Moreover, open field exposure after repeated treatments resulted in significant c-Fos responses in similar areas. Interestingly, 3 days after the final repeated MeHg dose (2 or 4 mg/kg) c-Fos increases to an immunogenic stressor (LPS) were not affected by MeHg pretreatment. These results demonstrate that systemic exposure to acute and repeated MeHg serves to activate the brain's stress circuitry, and furthermore appears to engage normal neuronal habituation processes.

Kinetics of chemical degradation of isoxaflutole: influence of the nature of aqueous buffers (alkanoic acid/sodium salt vs phosphate).

A kinetic study of the chemical degradation of isoxaflutole (5-cyclopropyl-1,2-oxazol-4-yl alpha alpha alpha-trifluoro-2-mesyl-p-tolyl ketone) into its diketonitrile derivative (DKN), which is its active herbicide principle, in organic buffers at different pH values was carried out using a HPLC/UV detection method. The values of the pseudo-first-order rate constants Kobs for the reaction were calculated and compared with those previously obtained in inorganic buffers. In both cases, Kobs was found to be dependent on pH and temperature, but at pH 5.2 the degradation of isoxaflutole in CH3COOH/CH3COONa buffers was considerably faster than in KH2PO4/Na2HPO4 buffers, indicating that the compound was sensitive to the nature of the reagents used to prepare buffered solutions. The influence of phosphate and acetate concentrations and the influence of the R-substituent in RCOOH/RCOONa buffers were investigated. For the HA/A- buffers studied, the values of Kobs were linearly dependent on HA and A- concentrations, which meant that the degradation of isoxaflutole was subject to general catalysis. The values of Kobs were also found to be dependent on the number and the position of the CH3 groups of the R-substituent. The known degradation product of DKN (a benzoic acid derivative) was not detected throughout this study.

Fate of a phenylpyrazole in vegetation and soil under tropical field conditions.

The fate of fipronil, a phenylpyrazole insecticide, and its metabolites under tropical conditions was studied in soil and in vegetation after treatment for locust control. Two different plots were treated with a formulation of fipronil at doses of 5 and 10 g of active ingredient ha(-)(1), respectively. Vegetation and soil at depths of 0-5 and 5-20 cm were sampled for up to 2 months after treatment. After extraction and purification on fipronil immunoaffinity cartridges, residues were analyzed by gas chromatography using electron capture and mass detectors. In soil, a rapid initial decrease of fipronil was observed with a rapid formation of the sulfone and the photodegradate; the amide and the sulfide were not detected. In vegetation, a rapid initial decrease of fipronil was also observed with a rapid formation of mostly the sulfone; the photodegradate and the sulfide were also detected but at much lower concentrations. The metabolites resulting from the degradation of fipronil were similar in both soil and vegetation, but their relative concentrations were different.

Kinetics of abiotic hydrolysis of isoxaflutole: influence of pH and temperature in aqueous mineral buffered solutions.

A kinetic study of the chemical hydrolysis of isoxaflutole [5-cyclopropyl-4-(2-methanesulfonyl-4-trifluoromethylbenzoyl)is oxazol e (IFT)], a new herbicide recently developed by Rhône-Poulenc Agro, in buffered, sterile aqueous solutions was carried out in the dark at 295, 308, and 323 K and at nine pH values between 1.8 and 10.1. Samples were analyzed by HPLC-UV. The decrease in IFT concentration was accompanied by an increase in the concentration of its diketonitrile derivative (DKN). Obeying pseudo-first-order kinetics, isoxaflutole hydrolysis increased with increasing pH and temperature: for 295 K and pH 9.3 the rate of degradation was 100-fold faster than at pH 3.8. Using the Arrhenius equation, the rate constants K(obsd), activation energies E(a), and entropies DeltaS() were calculated, and plotting log(K(obsd)) against pH showed that the effect of pH varied with temperature. According to DeltaS() values the mechanism of the reaction was found to be different with respect to pH range. The benzoic acid derivative, known as a degradation product of DKN in plants, was not detected in the present study.

An investigation of the spatial variations of the energetic trapped electrons at low altitudes.

We have analyzed the trapped electron data (0.19-3.2 MeV) taken by the Japanese OHZORA satellite operated at 350-850 km altitude in polar orbit during 1984-1987 near solar minimum. The electron observations reveal all the global attributes of the quiet-time electron radiation belts, such is the South Atlantic Anomaly, the electron "slot", and the outer radiation belt regions. The electron data are in general agreement with the NASA AE-8 electron model, but there are differences, particularly with respect to distinctive local-time variations in the slot region. In this paper, we present results from analyses of variations of the electron pitch angle distributions with local time, L-shell and altitude.

The impact of non-endotoxin LAL-reactive materials on Limulus amebocyte lysate analyses.

Limulus amebocyte lysate (LAL) is activated by bacterial endotoxins and certain glucans (beta-D-glucan, LAL-RM). The potential for conflicting inter-laboratory results for LAL tests exists because commercial LAL reagents are highly variable in response to LAL-reactive glucans. The nature of beta-D-glucan activation of LAL and means for rendering LAL non-responsive to glucan are reviewed to provide a background for resolving conflicting data. Kinetic LAL methods are particularly useful for screening materials potentially contaminated with glucan. The presence of beta-D-glucan in parenterals is uncommon and is likely limited to products exposed to microbial or cellulosic materials. A scheme is suggested for identifying LAL-reactive glucans and for LAL release-testing without glucan interference.

Action of taurine, 3-aminopropanesulfonic acid, and GABA on the hindgut and heart of the cockroach, Leucophaea maderae.

Taurine, glycine, glutamate, and gamma-aminobutyric acid (GABA) were all present in concentrations of greater than 1% of the total free amino acid content in the brain, thoracic, and abdominal ganglia of Leucophaea maderae. Hemolymph, subesophageal ganglia, and hindgut had substantial amounts of glutamate and glycine, but less than 0.3% taurine or GABA. Taurine, 3-aminopropanesulfonic acid (3-APS), cysteine-sulfinic acid (CSA), and GABA each had myotropic activity on the isolated cockroach hindgut, with 3-APS having the most consistent effect (ED50 = 0.63 mM), while taurine and CSA activities were similar to that of GABA on the hindgut. Both taurine and 3-APS had anti-arrhythmic effects on semi-isolated heart preparations of L. maderae, while GABA was inhibitory and induced arrhythmia. Bicuculline was antagonistic to the effects of GABA, taurine, and 3-APS on the hindgut, and induced arrhythmia in heart preparations; this arrhythmia was reversible by taurine, but not by GABA or 3-APS.

Endogenous colonization by gentamicin-resistant gram-negative bacilli elaborating aminoglycoside (3)-5-acetyltransferase.

Members of the family Enterobacteriaceae that elaborate aminoglycoside 3-5-acetyltransferase [AAC(3)-5] caused a nosocomial outbreak at the Vanderbilt University Medical Center and have persisted. To see whether the gene for AAC(3)-5 was present in the community, stool cultures of newly admitted patients and ambulatory persons were examined with a specific gene probe. AAC(3)-5-positive strains were present in the intestinal flora examined.

Resolving LAL Test interferences.

A greater understanding of the nature of LAL-Test interferences and the use of permissible dilution have minimized inhibition problems. Common interference mechanisms include suboptimal pH, endotoxin aggregation or adsorption, container effects, unbalanced cation concentration, enzyme or protein modification, and non-specific LAL activation. Dilution is the best approach to resolving interferences because over 90% are concentration dependent and are solved by the 1:40 dilution with LAL Reagent Water. Other problems are approached by using dilution plus a specific pretreatment procedure designed to neutralize the offending mechanism.

Mycobacterium chelonae: a cause of nodular skin lesions with a proclivity for renal transplant recipients.

PURPOSE: Infections due to Mycobacterium chelonae are uncommon. Several renal transplant recipients at our medical center have developed M. chelonae infections during the past several years, so we decided to review our recent experience with M. chelonae infections. PATIENTS AND METHODS: The clinical microbiology laboratory records of four Vanderbilt University Affiliated Hospitals were reviewed. Ten patients with M. chelonae tissue or blood infections were identified between 1982 and July 1988. RESULTS: All infections involved the skin and subcutaneous tissue. Three infections developed at the sites of medical injections. The remaining seven infections occurred in renal transplant recipients and produced a clinically distinctive syndrome. All were indolent tender nodular lesions on the extremities, usually the lower legs. Systemic symptoms were absent, and white blood cell counts were within normal limits. Diagnosis required tissue biopsy and cultures that were incubated for a month. Therapy consisted of surgical excision combined with long-term antibiotics. Even so, some patients had a chronic, relapsing course. CONCLUSION: Although other diagnoses must be considered, the presumptive diagnosis of M. chelonae infection is suggested by the appearance of nodular erythematous lesions on the legs of a renal transplant recipient.

Recurrent meningitis in a black man.

A 43-year-old black man had recurrence of acute bacterial meningitis caused by Neisseria meningitidis. He had had three previous episodes of acute meningitis, starting at age 27 years. The patient's serum was found to have an undetectable level of the sixth component of complement. Congenital absence of one of the terminal proteins in the complement system impairs a patient's ability to eradicate bacteria, and increases susceptibility to recurring infections caused by meningococci and other Neisseria species. Though the serum of complement-deficient patients promotes normal opsonization of bacteria, it is unable to kill meningococci directly. The currently available meningococcal vaccine may augment type-specific antibody, but it does not correct the underlying complement deficiency. The role of self-administered antibiotics in preventing recurrent Neisseria infection remains uncertain.

Symptomatic sclerosing cholangitis in patients with a normal alkaline phosphatase: two case reports and a review of the literature.

The diagnosis of sclerosing cholangitis is usually not considered in the absence of an elevation of serum alkaline phosphatase. The purpose of this paper is to report two symptomatic cases of primary sclerosing cholangitis (PSC) which presented with a normal alkaline phosphatase, and to review the literature regarding alkaline phosphatase in PSC. A total of 172 patients with PSC were identified in the literature; six of these patients (3%) presented with a normal alkaline phosphatase. Patients with diseases known to be associated with primary sclerosing cholangitis and having a compatible clinical presentation should be considered for evaluation with endoscopic retrograde cholangiography, even in the presence of a normal level of serum alkaline phosphatase.