Clustering in iron-doped magnesium oxide

The distribution of iron in single crystals of magnesium oxide has been investigated using electron paramagnetic resonance (EPR), ferrimagnetic resonance (FMR) and reflection electron diffraction (RED). The total iron content of the samples was in the range 100 - 13000 ppm by weight, the crystals being examined in the as-received state, after solution treatment, and following various aging treatments. The solution treatment involved the samples being held at 1400ºC for 24 hours in an oxygen atmosphere, and then quenched to room temperature. The samples were aged in oxygen at temperatures in the range 600 - 800ºC for various lengths of time. The EPR investigations were carried out at 9 GHz, over the temperature range from 4 - 300 K. Comparison of the integrated intensity of the EPR spectral lines with those of a standard suggested that in both the as-received and solution treated crystals very little (in some cases <0.1%) of the iron contributes to the Fe(^3+) isolated ion cubic site spectrum. Analysis of the experimental linewidths and shapes lends support to this suggestion. The experimental linewidths are in all cases broader than is expected on the basis of dipolar broadening theory, and it is suggested that this broadening is partly due to interactions with the undetected fraction of the iron. An unusual broad (1,3 kG wide) line which shows a complex structure at liquid helium temperatures was detected in two of the samples following solution treatment. Its appearance was accompanied by a complete absence of fine structure lines from the spectra in which it appeared. It is probable that the disappearance of the fine structure and the appearance of this broad line are related, but the relationship is not at present clear. Following aging treatments ferrimagnetic resonance was detected at 9 GHz, in the temperature range 4 - 500 K. This resonance arises out of the precipitation of magnesioferrite from the host lattice. In most of the samples which showed evidence of precipitation two quite different FMR lines were found - an isotropic line which appeared after short aging times, and an anisotropic line which apparently replaces the isotropic one as aging progresses. Analysis of the measured anpsotropy field of the particles precipitated at 800ºC indicated that the rate of growth of the volume of the precipitates is linear with time, after about one hour's aging. The chemical formula for these particular precipitates was determined to be Mg(_x)Fe(_3-x)O(_4-(x-1)/2')) where x = 1.29, the fraction of Mg ions on tetrahedral sites being taken to be 0.30. Analysis of the magnetic characteristics of the precipitates generally gave agreement with what published data are available. In addition the measured anisotropy field H(^sp)(_ɑ) in all samples was found to obey the empirical relationship where D = -0.045 + .004 G(^0.5) K(^-1), T is the temperature and C is a sample dependent constant. The widths of the FMR lines obtained from the high concentration samples aged at 800ºC were independent of sample, and after aging for one hour decreased monotonically with continued aging. This change in width is possibly a consequence of 'voids' of host material in the initial precipitates filling with aging. These linewidths were also remarkable in that they showed a marked decrease with increased recording temperature. Since this behaviour is quite at variance with the behaviour of bulk magnesioferrite it is probably a consequence of the superparamagnetic nature of the particles. Reflection electron diffraction studies of the etched surfaces of the crystals showed only one pattern - the standard spinel pattern - when ferrimagnetic precipitates were present, regardless of the type of FMR spectral line produced by the precipitates. This spinel had a lattice parameter almost exactly twice that of the host. Two other RED patterns were recorded from some of the samples - one possibly due to the calcium-stabilised zirconia discussed by Venables, and the other tentatively assigned to an aluminium spinel

Automated identification of neurons and their locations

Individual locations of many neuronal cell bodies (>10^4) are needed to enable statistically significant measurements of spatial organization within the brain such as nearest-neighbor and microcolumnarity measurements. In this paper, we introduce an Automated Neuron Recognition Algorithm (ANRA) which obtains the (x,y) location of individual neurons within digitized images of Nissl-stained, 30 micron thick, frozen sections of the cerebral cortex of the Rhesus monkey. Identification of neurons within such Nissl-stained sections is inherently difficult due to the variability in neuron staining, the overlap of neurons, the presence of partial or damaged neurons at tissue surfaces, and the presence of non-neuron objects, such as glial cells, blood vessels, and random artifacts. To overcome these challenges and identify neurons, ANRA applies a combination of image segmentation and machine learning. The steps involve active contour segmentation to find outlines of potential neuron cell bodies followed by artificial neural network training using the segmentation properties (size, optical density, gyration, etc.) to distinguish between neuron and non-neuron segmentations. ANRA positively identifies 86[5]% neurons with 15[8]% error (mean[st.dev.]) on a wide range of Nissl-stained images, whereas semi-automatic methods obtain 80[7]%/17[12]%. A further advantage of ANRA is that it affords an unlimited increase in speed from semi-automatic methods, and is computationally efficient, with the ability to recognize ~100 neurons per minute using a standard personal computer. ANRA is amenable to analysis of huge photo-montages of Nissl-stained tissue, thereby opening the door to fast, efficient and quantitative analysis of vast stores of archival material that exist in laboratories and research collections around the world.Comment: 38 pages. Formatted for two-sided printing. Supplemental material and software available at http://physics.bu.edu/~ainglis/ANRA

Analytical relationship for the cranking inertia

The wave function of a spheroidal harmonic oscillator without spin-orbit interaction is expressed in terms of associated Laguerre and Hermite polynomials. The pairing gap and Fermi energy are found by solving the BCS system of two equations. Analytical relationships for the matrix elements of inertia are obtained function of the main quantum numbers and potential derivative. They may be used to test complex computer codes one should develop in a realistic approach of the fission dynamics. The results given for the $^{240}$Pu nucleus are compared with a hydrodynamical model. The importance of taking into account the correction term due to the variation of the occupation number is stressed.Comment: 12 pages, 4 figure

Detection and Interpretation Of Long-Lived X-Ray Quasi-Periodic Pulsations in the X-Class Solar Flare On 2013 May 14

Quasi-periodic pulsations (QPP) seen in the time derivative of the GOES soft X-ray light curves are analyzed for the near-limb X3.2 event on 14 May 2013. The pulsations are apparent for a total of at least two hours from the impulsive phase to well into the decay phase, with a total of 163 distinct pulses evident to the naked eye. A wavelet analysis shows that the characteristic time scale of these pulsations increases systematically from $\sim$25 s at 01:10 UT, the time of the GOES peak, to $\sim$100 s at 02:00 UT. A second ridge in the wavelet power spectrum, most likely associated with flaring emission from a different active region, shows an increase from $\sim$40 s at 01:40 UT to $\sim$100 s at 03:10 UT. We assume that the QPP that produced the first ridge result from vertical kink-mode oscillations of the newly formed loops following magnetic reconnection in the coronal current sheet. This allows us to estimate the magnetic field strength as a function of altitude given the density, loop length, and QPP time scale as functions of time determined from the GOES light curves and RHESSI images. The calculated magnetic field strength of the newly formed loops ranges from about $\sim$500 G at an altitude of 24 Mm to a low value of $\sim$10 G at 60 Mm, in general agreement with the expected values at these altitudes. Fast sausage mode oscillations are also discussed and cannot be ruled out as an alternate mechanism for producing the QPP

HST Observations of the Serendipitous X-ray Companion to Mrk 273: Cluster at z=0.46?

We have used HST I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same field-of-view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST image. The luminosity of the galaxy and the properties of the surrounding environment suggest that Mrk 273X is the brightest galaxy in a relatively poor cluster at a redshift near 0.46. Its off-center location in the cluster and the presence of other galaxy groupings in the HST image may indicate that this is a dynamically young cluster on the verge of merging with its neighboring clusters. We find that Mrk 273X is a bright featureless elliptical galaxy with no evidence for a disk. It follows the de Vaucouleurs (r^{1/4}) surface brightness law very well over a range of 8 magnitudes. Though the surface brightness profile does not appear to be dominated by the AGN, the galaxy has very blue colors that do appear to be produced by the AGN. Mrk 273X is most similar to the IC 5063 class of active galaxies --- a hybrid Sy 2 / powerful radio galaxy.Comment: Accepted for publication in the Astrophysical Journal. 8 pages, including 4 postscript figures. Uses emulateapj.sty and psfig.sty. Higher quality version of Figure 1 is available at http://rings.gsfc.nasa.gov/~borne/fig1-markgals.gi

Meeting the challenges posed by an escalating diabetes healthcare burden: A mixed methods study

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Background: The ongoing escalation in the incidence of diabetes is contributing to a growing burden on health services because patients with diabetes as a co-morbidity are now spread throughout the hospital (rather than being located in specific areas). Thus, there is a need for expertise in diabetes care throughout services to ensure optimal care and reduce threats to patient safety. Aims and objectives: To identify new strategies to maintain optimal care for patients with diabetes while in hospital. Design: Mixed methods underpinned by Appreciative Inquiry. Methods: The Diabetes Knowledge Questionnaire Survey (DKQS) (n = 173); focus group interviews with nurses and midwives (n = 40), and individual interviews with recently discharged hospital patients (n = 6). Quantitative data were analysed using descriptive statistics and qualitative data by thematic analysis. Results: Highlight a need to enhance knowledge and confidence of diabetes management among nursing, midwifery, medical and ancillary staff through the introduction of focused education strategies. This, together with improved communication and team work, is required to relieve the burdens on frontline nursing staff and patients caused by delays in prescribing and reviewing insulin requirements and in accessing needed food for people with diabetes. Conclusions: In seeking solutions to the challenges in caring for hospitalised patients with diabetes there is a need to work across the entire hospital workforce and to develop effective and efficient methods for ensuring appropriate skills and knowledge of diabetes management for staff across complex and rapidly changing hospital systems. Relevance to clinical practice: The introduction and implementation of innovative educational and organisational strategies are needed to assist in meeting the challenges posed by an escalating diabetes healthcare burden. The safety of patients with diabetes can be optimised with the timely availability of appropriate meals and snacks, and enhanced coordination and communication between and within multidisciplinary teams

Spatially Resolved Far-Ultraviolet Spectroscopy of the Nuclear Region of NGC 1068

We carry out high-resolution FUSE spectroscopy of the nuclear region of NGC 1068. The first set of spectra was obtained with a 30" square aperture that collects all emission from the narrow-line region. The data reveal a strong broad OVI component of FWHM ~3500 kms-1 and two narrow OVI 1031/1037 components of ~350 kms-1. The CIII 977 and NIII 991 emission lines in this spectrum can be fitted with a narrow component of FWHM ~1000 kms-1 and a broad one of ~2500 kms-1. Another set of seven spatially resolved spectra were made using a long slit of 1.25" X 20", at steps of ~1" along the axis of the emission-line cone. We find that (1) Major emission lines in the FUSE wavelength range consist of a broad and a narrow component; (2) There is a gradient in the velocity field for the narrow OVI component of ~200 kms-1 from ~2" southwest of the nucleus to ~4" northeast. A similar pattern is also observed with the broad OVI component, with a gradient of ~3000 kms-1. These are consistent with the HST/STIS findings and suggest a biconical structure in which the velocity field is mainly radial outflow; (3) A major portion of the CIII and NIII line flux is produced in the compact core. They are therefore not effective temperature diagnostics for the conical region; and (4) The best-fitted UV continuum suggests virtually no reddening, and the HeII 1085/1640 ratio suggests a consistently low extinction factor across the cone.Comment: To appear in the Astrophysical Journal. 37 pages with 12 figure

ISO-SWS spectroscopy of NGC 1068

We present ISO-SWS spectroscopy of NGC 1068 for the wavelength range 2.4 to 45um, detecting a total of 36 emission lines. Most of the observed transitions are fine structure and recombination lines originating in the narrow line region. We compare the line profiles of optical lines and reddening-insensitive infrared lines to constrain the dynamical structure and extinction properties of the NLR. The considerable differences found are most likely explained by two effects. (1) The spatial structure of the NLR is a combination of a highly ionized outflow cone and lower excitation extended emission. (2) Parts of the NLR, mainly in the receding part at velocities above systemic, are subject to extinction that is significantly suppressing optical emission. Line asymmetries and net blueshifts remain, however, even for infrared fine structure lines suffering very little obscuration. This may be either due to an intrinsic asymmetry of the NLR, or due to a very high column density obscuring component which is hiding part of the NLR even from infrared view. Mid-infrared emission of molecular hydrogen in NGC 1068 arises in a dense molecular medium at temperatures of a few hundred Kelvin that is most likely closely related to the warm and dense components seen in the near-infrared H2 transitions, and in millimeter wave tracers of molecular gas. Any emission of the putative pc-scale molecular torus is likely overwhelmed by this larger scale emission.Comment: aastex (V4), 9 eps figures. Accepted by Ap

The Electron Scattering Region in Seyfert Nuclei

The electron scattering region (ESR) is one of important ingredients in Seyfert nuclei because it makes possible to observe the hidden broad line region (hereafter HBLR) in some type 2 Seyfert nuclei (hereafter S2s). However, little is known about its physical and geometrical properties. Using the number ratio of S2s with and without HBLR, we investigate statistically where the ESR is in Seyfert nuclei. Our analysis suggests that the ESR is located at radius between $\sim$ 0.01 pc and $\sim$ 0.1 pc from the central engine. We also discuss a possible origin of the ESR briefly.Comment: 5 pages and 1 figure. The Astrophysical Journal (Letters), in pres

Generalized Involution Models for Wreath Products

We prove that if a finite group $H$ has a generalized involution model, as defined by Bump and Ginzburg, then the wreath product $H \wr S_n$ also has a generalized involution model. This extends the work of Baddeley concerning involution models for wreath products. As an application, we construct a Gelfand model for wreath products of the form $A \wr S_n$ with $A$ abelian, and give an alternate proof of a recent result due to Adin, Postnikov, and Roichman describing a particularly elegant Gelfand model for the wreath product \ZZ_r \wr S_n. We conclude by discussing some notable properties of this representation and its decomposition into irreducible constituents, proving a conjecture of Adin, Roichman, and Postnikov's.Comment: 29 page