The reflection and transmission properties of a triple band dichroic surface

The development of a triple-band dichroic surface design is detailed that is reflective in the Ka-band from 22.5 to 27.3 GHz and the Ku-band from 13.7 to 15.1 GHz, yet transparent in the S-band from 2.0 to 2.3 GHz, for all planes of incidence, and for all angles of incidence out to eta = 45 deg. The design is comprised of two gangbuster whole-surfaces separated by a distance, d, that is comparable to a fraction of a wavelength in S-band, and enhanced by the addition of a dielectric matching plate. The gangbuster array is comprised of tightly packed straight skewed dipole elements referred to as half-surfaces. Two of these half-surfaces are oriented orthogonal to each other and placed an array separation distance, s, apart to form the gangbuster whole-surface which allows any arbitrary plane of incidence. Results are given for the triple-band design with and without dielectric and conduction losses. The cross polarization properties of the dichroic surface was further investigated. It is shown that the reflection cross polarized component is dominated by the geometry of the front whole surface of the design (particularly the array separation s) and is never more than -22.5 dB in the frequency band 0 to 30 GHz. The transmission cross polarization component is dependent on both whole-surfaces and is never more than -30 dB in the same frequency band

Optical bistability involving planar metamaterial with broken structural symmetry

We report on a bistable light transmission through a planar metamaterial composed of a metal pattern of weakly asymmetric elements placed on a nonlinear substrate. Such structure bears the Fano-like sharp resonance response of a trapped-mode excitation. The feedback required for bistability is provided by the coupling between the strong antiphased trapped-mode-resonance currents excited on the metal elements and the intensity of inner field in the nonlinear substrate.Comment: 4 pages, 4 figure

Ptychographic X-ray computed tomography of extended colloidal networks in food emulsions

As a main structural level in colloidal food materials, extended colloidal networks are important for texture and rheology. By obtaining the 3D microstructure of the network, macroscopic mechanical properties of the material can be inferred. However, this approach is hampered by the lack of suitable non-destructive 3D imaging techniques with submicron resolution. We present results of quantitative ptychographic X-ray computed tomography applied to a palm kernel oil based oil-in-water emulsion. The measurements were carried out at ambient pressure and temperature. The 3D structure of the extended colloidal network of fat globules was obtained with a resolution of around 300 nm. Through image analysis of the network structure, the fat globule size distribution was computed and compared to previous findings. In further support, the reconstructed electron density values were within 4% of reference values.Comment: 19 pages, 4 figures, to be published in Food Structur

Design, theory, and measurement of a polarization insensitive absorber for terahertz imaging

We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. We derive geometrical-independent conditions for effective medium absorbers in general, and for resonant metamaterials specically. Our fabricated design reaches and absorptivity of 78% at 1.145 ThzComment: 6 Pages, 5 figures; figures update

Squeezing millimeter waves into microns

Alastair P. Hibbins, J. Roy Sambles, Christopher R. Lawrence and James R. Brown, Physical Review Letters, Vol. 92, article 143904 (2004). "Copyright © 2004 by the American Physical Society."Microstructured metallic devices will play a vital role in the continuing search to manipulate the passage of electromagnetic radiation relevant to optical, microwave, and communication technologies. Here, we investigate the electromagnetic response of a completely novel and ultrathin (≪wavelength) structure within which is buried a metal-clad waveguiding layer (“core”) of subwavelength width. By removing metal from the core cladding to form a periodic array of slits, radiation is coupled into a standing wave within the layer and the structure resonantly absorbs or transmits radiation of wavelength more than 100 times its thickness. Additionally, such structures display the truly remarkable capability of compressing half of the standing-wave wavelength into a fraction of the expected distance

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations : shallow-water environments

Author Posting. © Acoustical Society 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1749-1761, doi:10.1121/1.3666002.Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.This work was supported by the Office of Naval Research and the Naval Undersea Warfare Center’s Under- Sea Warfare chair at the Naval Postgraduate School

Clinical decision making and outcome in the routine care of people with severe mental illness across Europe (CEDAR)

Aims. There is a lack of knowledge on clinical decision making and its relation to outcome in the routine treatment of people with severe mental illness. This study examined preferred and experienced clinical decision making from the perspectives of patients and staff, and how these affect treatment outcome. Methods. CEDAR (ISRCTN75841675) is a naturalistic prospective observational study with bimonthly assessments during a 12-month observation period. 588 adults with severe mental illness were consecutively recruited from caseloads of community mental health services at the six study sites (Germany, UK, Italy, Hungary, Denmark, and Switzerland). Clinical decision making was measured using two instruments (Clinical Decision Making Style Scale. CDMS;Clinical Decision Making Involvement and Satisfaction Scale, CDIS) from patient and staff perspectives. Outcomes assessed were unmet needs (Camberwell Assessment of Need Short Appraisal Schedule, CANSAS). Mixed-effects multinomial regression was used to examine differences in involvement in and satisfaction with actual decision making. The effect of clinical decision making on outcome was examined using hierarchical linear modelling controlling for covariates. Results. Shared decision making was preferred by patients (2=135.08; p<0.001) and staff (2=368.17; p<0.001). Decision making style of staff significantly affected unmet needs over time, with unmet needs decreasing more in patients whose clinicians preferred active to passive (-0.406 unmet needs per two months, p=0.007) or shared (-0.303 unmet needs per two months, p=0.015) decision making. Conclusions. A shift from shared to active involvement of patients is indicated, including the development and rigorous test of targeted interventions

Perinatal psychiatric episodes: a population-based study on treatment incidence and prevalence

Perinatal psychiatric episodes comprise various disorders and symptom severity, which are diagnosed and treated in multiple treatment settings. To date, no studies have quantified the incidence and prevalence of perinatal psychiatric episodes treated in primary and secondary care, which we aimed to do in the present study. We designed a descriptive prospective study and included information from Danish population registers to study first-time ever and recurrent psychiatric episodes during the perinatal period, including treatment at psychiatric facilities and general practitioners (GPs). This was done for all women who had records of one or more singleton births from 1998 until 2012. In total, we had information on 822 439 children born to 491 242 unique mothers. Results showed first-time psychiatric episodes treated at inpatient facilities were rare during pregnancy, but increased significantly shortly following childbirth (0.02 vs 0.25 per 1000 births). In comparison, first-time psychiatric episodes treated at outpatient facilities were more common, and showed little variation across pregnancy and postpartum. For every single birth resulting in postpartum episodes treated at inpatient psychiatric facilities, 2.5 births were followed by an episode treated at outpatient psychiatric facility and 12 births by GP-provided pharmacological treatment. We interpret our results the following way: treated severe and moderate psychiatric disorders have different risk patterns in relation to pregnancy and childbirth, which suggests differences in the underlying etiology. We further speculate varying treatment incidence and prevalence in pregnancy vs postpartum may indicate that the current Diagnostic and Statistical Manual of Mental Disorders-5 peripartum specifier not adequately describes at-risk periods across moderate and severe perinatal psychiatric episodes

Perturbation Theory for Path Integrals of Stiff Polymers

The wormlike chain model of stiff polymers is a nonlinear $\sigma$-model in one spacetime dimension in which the ends are fluctuating freely. This causes important differences with respect to the presently available theory which exists only for periodic and Dirichlet boundary conditions. We modify this theory appropriately and show how to perform a systematic large-stiffness expansions for all physically interesting quantities in powers of $L/\xi$, where $L$ is the length and $\xi$ the persistence length of the polymer. This requires special procedures for regularizing highly divergent Feynman integrals which we have developed in previous work. We show that by adding to the unperturbed action a correction term ${\cal A}^{\rm corr}$, we can calculate all Feynman diagrams with Green functions satisfying Neumann boundary conditions. Our expansions yield, order by order, properly normalized end-to-end distribution function in arbitrary dimensions $d$, its even and odd moments, and the two-point correlation function

A decade of acoustic thermometry in the North Pacific Ocean

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94643/1/jgrc11250.pd