Conditions for free magnetic monopoles in nanoscale square arrays of dipolar spin ice

We study a modified frustrated dipolar array recently proposed by M\"{o}ller and Moessner [Phys. Rev. Lett. \textbf{96}, 237202 (2006)], which is based on an array manufactured lithographically by Wang \emph{et al.} [Nature (London) \textbf{439}, 303 (2006)] and consists of introducing a height offset $h$ between islands (dipoles) pointing along the two different lattice directions. The ground-states and excitations are studied as a function of $h$. We have found, in qualitative agreement with the results of M\"{o}ller and Moessner, that the ground-state changes for $h>h_{1}$, where $h_{1}= 0.444a$ ($a$ is the lattice parameter or distance between islands). In addition, the excitations above the ground-state behave like magnetic poles but confined by a string, whose tension decreases as $h$ increases, in such a way that for $h\approx h_1$ its value is around 20 times smaller than that for $h=0$. The system exhibits an anisotropy in the sense that the string tension and magnetic charge depends significantly on the directions in which the monopoles are separated. In turn, the intensity of the magnetic charge abruptly changes when the monopoles are separated along the direction of the longest axis of the islands. Such a gap is attributed to the transition from the anti to the ferromagnetic ground-state when $h=h_1$.Comment: 6 pages, 7 figures. Published versio

Partnering with Medicaid to Advance and Sustain the Goals of the Child Welfare System

The purpose of this paper is to serve as a practical guide for child welfare directors who are looking to expand or sustain services for the children and families that they serve. This paper focuses on ways to partner with Medicaid to leverage opportunities to provide high quality services for children in child welfare who have behavioral health needs. It also includes information that will provide a foundational understanding of the behavioral health needs of children involved with the child welfare system, with an emphasis on describing child behavior through the lens of child development, adaptive functioning, and trauma; the services that can effectively address those behavioral and trauma related responses that can disrupt a child's skills and abilities; and, examples from states and counties who are providing these services and supports

CALCOM'10 Sea Trial - field calibration data report

Rep 04/10 - SiPLAB November/2010The CALCOM'10 sea trial took place in a region SSE of Vilamoura from 22nd to 24th June to support WEAM & PHITOM projects. The rst day was devoted to equipment testing and calibration. The second and third days were devoted to eld calibration and underwater communications. This report refers to eld calibration data acquired 23rd June, Day 2, and 24th June, Day 3

Acoustic oceanographic buoy data report Makai Ex 2005

Rep 04/05 - SiPLAB 17/Nov/2005 UniversityIt is now well accepted in the underwater acoustic scientific community that below, say, 1 kHz acoustic propagation models are accurate enough to be able to predict the received acoustic field up to the point of allowing precise and reliable source tracking in range and depth with only limited environmental information. This results from a large number of studies both theoretical and with real data, carried out in the last 20 years. With the event of underwater communications and the necessity to increase the signal bandwidth for allowing higher communication rates, the frequency band of interest was raised to above 10 kHz. In this frequency band the detailed knowledge of the environment - acoustic signal interplay is reduced. The purpose of the MakaiEx sea trial is to acquire data in a complete range of frequencies from 500 Hz up to 50 kHz, for a variety of applications ranging from high-frequency tomography, coherent SISO and MIMO applications, vector - sensor, active and passive sonar, etc...The MakaiEx sea trial, that took place off Kauai I. from 15 September - 2 October, involved a large number of teams both from government and international laboratories, universities and private companies, from various countries. Each team focused on its specific set of objectives in relation with its equipment or scientific interest. The team from the University of Algarve (UALg) focused on the data acquired by their receiving Acoustic Oceanographic Buoy - version 2 (AOB2) during six deployments in the period 15 - 27 September. This report describes the AOB2 data set as well as all the related environmental and geometrical data relative to the AOB2 deployments. The material described herein represents a valuable data set for supporting the research objectives of projects NUACE1, namely to fulfill NUACE’s task 3 and 4 and RADAR2, namely its tasks 2 and 3 devoted to the developement and testing of a field of sonobuoys.This report presents the testing of the most recent version of the Acoustic Oceanographic Buoy (AOB) system and the results obtained during the Makai Ex sea trial. The MakaiEx sea trial took place off the west coast of Kauai I., Hawaii, USA, in the period September 15 - 27, 2005. The authors of this report would like to thank: • all the personnel involved, including R/V Kilo Moana crew • the scientist in charge Michael B. Porter • the University of Hawaii for its support • FCT (Portugal) for the funding provided under projects NUACE (POSI/CPS/47824/ 2002) and RADAR (POCTI/CTA/47719/2002). • ONR for the funding under ONR-IFO VSP grant # N00014-04-1-403

Magnetic domain fluctuations in an antiferromagnetic film observed with coherent resonant soft x-ray scattering

We report the direct observation of slow fluctuations of helical antiferromagnetic domains in an ultra-thin holmium film using coherent resonant magnetic x-ray scattering. We observe a gradual increase of the fluctuations in the speckle pattern with increasing temperature, while at the same time a static contribution to the speckle pattern remains. This finding indicates that domain-wall fluctuations occur over a large range of time scales. We ascribe this non-ergodic behavior to the strong dependence of the fluctuation rate on the local thickness of the film.Comment: to appear in Phys. Rev. Let

Proximity effect of vanadium on spin-density-wave magnetism in Cr films

The spin-density wave (SDW) state in thin chromium films is well known to be strongly affected by proximity effects from neighboring layers. To date the main attention has been given to effects arising from exchange interactions at interfaces. In the present work we report on combined neutron and synchrotron scattering studies of proximity effects in Cr/V films where the boundary condition is due to the hybridization of Cr with paramagnetic V at the interface. We find that the V/Cr interface has a strong and long-range effect on the polarization, period, and the N\'{e}el temperature of the SDW in rather thick Cr films. This unusually strong effect is unexpected and not predicted by theory.Comment: 7 figure

An environmental equalizer for underwater acoustic communications Tested at Hydralab III

It is known that small changes in source and receiver locations can cause significant changes in underwater acoustic channel impulse responses. At HYDRALAB III an underwater acoustic experiment was conducted to show that a source depth-shift causes a frequency-shift in the channel impulse response and that such behavior can be used to implement an environmental-based equalizer for underwater communications that compensates for the performance loss due to the source depth-shift

A Correlation between the Emission Intensity of Self-Assembled Germanium Islands and the Quality Factor of Silicon Photonic Crystal Nanocavities

We present a comparative micro-photoluminescence study of the emission intensity of self-assembled germanium islands coupled to the resonator mode of two-dimensional silicon photonic crystal defect nanocavities. The emission intensity is investigated for cavity modes of L3 and Hexapole cavities with different cavity quality factors. For each of these cavities many nominally identical samples are probed to obtain reliable statistics. As the quality factor increases we observe a clear decrease in the average mode emission intensity recorded under comparable optical pumping conditions. This clear experimentally observed trend is compared with simulations based on a dissipative master equation approach that describes a cavity weakly coupled to an ensemble of emitters. We obtain evidence that reabsorption of photons emitted into the cavity mode is responsible for the observed trend. In combination with the observation of cavity linewidth broadening in power dependent measurements, we conclude that free carrier absorption is the limiting effect for the cavity mediated light enhancement under conditions of strong pumping.Comment: 8 pages, 5 figure

Extended Source Diffraction Effects Near Gravitational Lens Fold Caustics

Calculations are presented detailing the gravitational lens diffraction due to the steep brightness gradient of the limb of a stellar source. The lensing case studied is the fold caustic crossing. The limb diffraction signal greatly exceeds that due to the disk as a whole and should be detectable for white dwarf sources in our Galaxy and it's satellites with existing telescopes. Detection of this diffraction signal would provide an additional mathematical constraint, reducing the degeneracy among models of the lensing geometry. The diffraction pattern provides pico-arcsecond resolution of the limb profile.Comment: 19 pages including 17 figures, Accepted for publication in ApJ, Minor conceptual change from previous versio