Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles

We have studied the magnetic behavior of dextran-coated magnetite (Fe$_3$O$_4$) nanoparticles with median particle size \left=8 $nm$. Magnetization curves and in-field M\"ossbauer spectroscopy measurements showed that the magnetic moment $M_S$ of the particles was much smaller than the bulk material. However, we found no evidence of magnetic irreversibility or non-saturating behavior at high fields, usually associated to spin canting. The values of magnetic anisotropy $K_{eff}$ from different techniques indicate that surface or shape contributions are negligible. It is proposed that these particles have bulk-like ferrimagnetic structure with ordered A and B sublattices, but nearly compensated magnetic moments. The dependence of the blocking temperature with frequency and applied fields, $T_B(H,\omega)$, suggests that the observed non-monotonic behavior is governed by the strength of interparticle interactions.Comment: 11 pages, 7 figures, 3 Table

Ondernemingsredding en werknemers in die Suid- Afrikaanse reg: “Verlore siele” of nie?

In South Africa, business rescue is a procedure created by the Companies Act 71 of 2008, which aims to facilitate the rehabilitation of companies in financial distress. Not all companies in financial distress will fail; some only need care and guidance to keep the wolf from the door. The business rescue procedure grants a financially distressed company the opportunity to re-organize its affairs by allowing for a moratorium on legal proceedings and the implementation of a structured payment scheme with creditors or, alternatively, to provide the creditors and shareholders with a better return than in liquidation. In addition, it could also be argued that a further objective of the business rescue procedure is the retention of the company’s workforce, entirely or to some extent, at least. Despite their improved position in rescue proceedings, employees remain vulnerable and have subsequently been regarded as “lost souls” in corporate insolvency procedures. It is widely acknowledged that employees are now in a better position when it comes to protecting their rights during employment. In business rescue proceedings, the primary view held by many is that employees are in a much better position than they were during rescue proceedings in the past. The Companies Act makes extensive provision for the involvement of  employees who are affected by the business rescue process, in its undertaking or implementation, and creates a platform for them to contribute to an outcome that affects them. This article investigates the outcome of business rescue proceedings on employee rights during the phases of business rescue, both in their capacities as employees and creditors of the company, and over the course of various employment relationships. It will be concluded that employees are not as protected during business rescue proceedings as is generally believed

Run-time Spatial Mapping of Streaming Applications to Heterogeneous Multi-Processor Systems

In this paper, we define the problem of spatial mapping. We present reasons why performing spatial mappings at run-time is both necessary and desirable. We propose what is—to our knowledge—the first attempt at a formal description of spatial mappings for the embedded real-time streaming application domain. Thereby, we introduce criteria for a qualitative comparison of these spatial mappings. As an illustration of how our formalization relates to practice, we relate our own spatial mapping algorithm to the formal model

Investigation of the Domain Wall Fermion Approach to Chiral Gauge Theories on the Lattice

We investigate a recent proposal to construct chiral gauge theories on the lattice using domain wall fermions. We restrict ourselves to the finite volume case, in which two domain walls are present, with modes of opposite chirality on each of them. We couple the chiral fermions on only one of the domain walls to a gauge field. In order to preserve gauge invariance, we have to add a scalar field, which gives rise to additional light mirror fermion and scalar modes. We argue that in an anomaly free model these extra modes would decouple if our model possesses a so-called strong coupling symmetric phase. However, our numerical results indicate that such a phase most probably does not exist. ---- Note: 9 Postscript figures are appended as uuencoded compressed tar file.Comment: 27p. Latex; UCSD/PTH 93-28, Wash. U. HEP/93-6

Remote sensing and hydrologic models for performance assessment in Sirsa Irrigation Circle, India

Irrigation management / Irrigation systems / Irrigation canals / Performance evaluation / Remote sensing / GIS / Models / Irrigated farming / Hydrology / Satellite surveys / Irrigation scheduling / Evapotranspiration / India

Time scales in nuclear giant resonances

We propose a general approach to characterise fluctuations of measured cross sections of nuclear giant resonances. Simulated cross sections are obtained from a particular, yet representative self-energy which contains all information about fragmentations. Using a wavelet analysis, we demonstrate the extraction of time scales of cascading decays into configurations of different complexity of the resonance. We argue that the spreading widths of collective excitations in nuclei are determined by the number of fragmentations as seen in the power spectrum. An analytic treatment of the wavelet analysis using a Fourier expansion of the cross section confirms this principle. A simple rule for the relative life times of states associated with hierarchies of different complexity is given.Comment: 5 pages, 4 figure

The Bright End of the z~9 and z~10 UV Luminosity Functions using all five CANDELS Fields

The deep, wide-area (~800-900 arcmin**2) near-infrared/WFC3/IR + Spitzer/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of high redshift UV luminosity functions (LFs). However, the lack of HST 1.05-micron observations over the CANDELS fields has made it difficult to identify z~9-10 sources robustly, since such data are needed to confirm the presence of an abrupt Lyman break at 1.2 microns. We report here on the successful identification of many such z~9-10 sources from a new HST program (z9-CANDELS) that targets the highest-probability z~9-10 galaxy candidates with observations at 1.05 microns, to search for a robust Lyman-break at 1.2 microns. The potential z~9-10 candidates are preselected from the full HST, Spitzer/IRAC S-CANDELS observations, and the deepest-available ground-based optical+near-infrared observations. We identified 15 credible z~9-10 galaxies over the CANDELS fields. Nine of these galaxies lie at z~9 and 5 are new identifications. Our targeted follow-up strategy has proven to be very efficient in making use of scarce HST time to secure a reliable sample of z~9-10 galaxies. Through extensive simulations, we replicate the selection process for our sample (both the preselection and follow-up) and use it to improve current estimates for the volume density of bright z~9 and z~10 galaxies. The volume densities we find are 5(-2)(+3)x and 8(-3)(+9)x lower, respectively, than found at z~8. When compared with the best-fit evolution (i.e., dlog_{10} rho(UV)/dz=-0.29+/-0.02) in the UV luminosities densities from z~8 to z~4 integrated to 0.3L*(z=3) (-20 mag), these luminosity densities are 2.6(-0.9)(+1.5)x and 2.2(-1.1)(+2.0)x lower, respectively, than the extrapolated trends. Our new results are broadly consistent with the "accelerated evolution" scenario at z>8, as seen in many theoretical models.Comment: 23 pages, 15 figures, 7 tables, updated to match the version in press, including some minor textual corrections identified at the proof stag

Bubbling the False Vacuum Away

We investigate the role of nonperturbative, bubble-like inhomogeneities on the decay rate of false-vacuum states in two and three-dimensional scalar field theories. The inhomogeneities are induced by setting up large-amplitude oscillations of the field about the false vacuum as, for example, after a rapid quench or in certain models of cosmological inflation. We show that, for a wide range of parameters, the presence of large-amplitude bubble-like inhomogeneities greatly accelerates the decay rate, changing it from the well-known exponential suppression of homogeneous nucleation to a power-law suppression. It is argued that this fast, power-law vacuum decay -- known as resonant nucleation -- is promoted by the presence of long-lived oscillons among the nonperturbative fluctuations about the false vacuum. A phase diagram is obtained distinguishing three possible mechanisms for vacuum decay: homogeneous nucleation, resonant nucleation, and cross-over. Possible applications are briefly discussed.Comment: 13 Pages, 16 figures, revtex4, submitted to pr

The Chiral Condensate of Strongly Coupled QCD in the 't Hooft Limit

Using the recently proposed generalization to an arbitrary number of colors of the strong coupling approach to lattice gauge theories\cite{Grignani:2003uv}, we compute the chiral condensate of massless QCD in the 't Hooft limit.Comment: 12 pages, revtex