983 research outputs found
Coarse wavelength division (de)multiplexer using an interleaved angled multimode interferometer structure
We have demonstrated a coarse wavelength (de)multiplexing structure on the silicon-on-insulator platform. It comprises two 4-channel angled multimode interferometers interleaved with an imbalanced Mach-Zehnder interferometer (MZI) leading to an 8-channel multiplexing device. The device requires only single lithography and etching steps for fabrication and has a good tolerance to fabrication errors in terms of waveguide width. The insertion loss and crosstalk achieved are 3-4 dB and -(15-20) dB, respectively. Potential is shown for achieving improved performance using larger waveguide bending radii in the MZI arms and/or (a) local heater(s) for refractive index tuning
Abundance and movements of caribou in the oilfield complex near Prudhoe Bay, Alaska
We examined the distribution and movements of 141 radiocollared female caribou (Rangifer tarandus granti) of the Central Arctic Herd during summer, 1980-1993. Numbers of caribou locations within each of 5 quadrats along the arctic coast were totalled separately for days during which insects were active and inactive, and numbers of east-west and west-east crossings of each quadrat mid-line were determined from sequential observations. Both abundance and lateral movements of radiocollared females in the quadrat encompassing the intensively-developed Prudhoe Bay oilfield complex were significantly lower than in other quadrats (P < 0.001 and P < 0.00001, respectively). Avoidance of, and fewer movements within, the complex by female caribou are ostensibly in response to the dense network of production and support facilities, roads, above-ground pipelines, and the associated vehicular and human activity. Impaired access to this area constitutes a functional loss of habitat
Locally erasable couplers for optical device testing in silicon on insulator
Wafer scale testing is critical to reducing production costs and increasing production yield. Here we report a method that allows testing of individual optical components within a complex optical integrated circuit. The method is based on diffractive grating couplers, fabricated using lattice damage induced by ion implantation of germanium. These gratings can be erased via localised laser annealing, which is shown to reduce the outcoupling efficiency by over 20 dB after the device testing is completed. Laser annealing was achieved by employing a CW laser, operating at visible wavelengths thus reducing equipment costs and allowing annealing through thick oxide claddings. The process used also retains CMOS compatibility
Noncommutative waves have infinite propagation speed
We prove the existence of global solutions to the Cauchy problem for
noncommutative nonlinear wave equations in arbitrary even spatial dimensions
where the noncommutativity is only in the spatial directions. We find that for
existence there are no conditions on the degree of the nonlinearity provided
the potential is positive. We furthermore prove that nonlinear noncommutative
waves have infinite propagation speed, i.e., if the initial conditions at time
0 have a compact support then for any positive time the support of the solution
can be arbitrarily large.Comment: 15 pages, references adde
Open String Star as a Continuous Moyal Product
We establish that the open string star product in the zero momentum sector
can be described as a continuous tensor product of mutually commuting two
dimensional Moyal star products. Let the continuous variable parametrize the eigenvalues of the Neumann matrices; then the
noncommutativity parameter is given by .
For each , the Moyal coordinates are a linear combination of even
position modes, and the Fourier transform of a linear combination of odd
position modes. The commuting coordinate at is identified as the
momentum carried by half the string. We discuss the relation to Bars' work, and
attempt to write the string field action as a noncommutative field theory.Comment: 30 pages, LaTeX. One reference adde
Evidence from the Skilled-Unskilled Canadian Wage Index
Les fluctuations des indices de salaires entre les ouvriers qualifies et la main-dâĆuvre non qualifiĂ©e tiennent depuis longtemps une place importante dans la littĂ©rature traitant du partage des revenus. Bien que les Ă©tudes contemporaines sur le sujet au Canada soient peu nombreuses, celles-ci ont Ă©tĂ© acceptĂ©es comme allant de soi et on les retrouve dans les manuels. Ces Ă©tudes dĂ©montrent que, au cours des dĂ©cennies rĂ©centes, il y aurait eu un mouvement significatif dans le sens de l'Ă©galisation des salaires entre les travailleurs canadiens qualifies et non qualifies. Dans cet article, nous nous efforcerons de rĂ©viser cette opinion en corrigeant les erreurs de mesure qui nous paraissent les plus manifestes. Notre propre apprĂ©ciation se fonde sur les corrections suivantes : nous opposons les salaires rĂ©els aux salaires nominaux, c'est-Ă -dire que des corrections sont faites en tenant compte des changements dans le cout de la vie entre les deux groupes; on utilise les ratios de salaires au lieu des diffĂ©rences pour mesurer les changements dans les taux de salaires relatifs des travailleurs qualifies et non qualifies; on remplace les comparaisons annuelles par l'analyse de rĂ©gression. L'utilisation des statistiques Les statistiques salariales sur lesquelles nous nous fondons â les taux de salaires urbains dans l'imprimerie, la construction, les municipalitĂ©s et les chemins de fer â sont un sous-ensemble des donnĂ©es utilisĂ©es par Peitchinis (1974, 1975) et Ostry et Zaidi (1972). Le choix de ces industries s'appuie sur les considĂ©rations suivantes : premiĂšrement, ces catĂ©gories d'emplois Ă©taient relativement homogĂšnes par rapport Ă la pĂ©riode Ă©tudiĂ©e si on tenait compte de la description de la tache; en second lieu, les donnĂ©es salariales Ă©taient disponibles rĂ©gionalement; troisiĂšmement, les travailleurs engages dans ces groupes d'emploi Ă©taient nombreux; enfin, ces groupes industriels Ă©taient conformes aux tendances normales des salaires nominaux parmi les travailleurs qualifies et non qualifies. Surtout, les tendances des salaires dans les industries choisies varient d'une convergence extrĂȘme du ratio du salaire nominal (les mĂ©tiers de la construction) Ă une divergence croissante (les employĂ©s municipaux). Les rĂ©sultats obtenusEn rĂ©sumĂ©, les constatations sont les suivantes. En ce qui concerne l'industrie des mĂ©tiers de la construction, l'indice nominal accentue substantiellement la baisse dans le ratio de salaires entre les travailleurs qualifies et non qualifies. En outre, les pĂ©riodes marquĂ©es de forte exagĂ©ration sont les dĂ©cennies 1940 Ă 1960. Ce sont ces pĂ©riodes qui ont Ă©tĂ© retenues dans les textes comme des pĂ©riodes d'inĂ©galitĂ© dĂ©clinante. Pour l'industrie des chemins de fer, l'abaissement du ratio dans le salaire rĂ©el se produit Ă deux reprises entre 1940 et 1944, puis entre 1960 et 1970. Dans le cas des employĂ©s municipaux, le ratio du salaire rĂ©el ne diminue pas, mais s'accroit de 19 pour cent pendant la pĂ©riode 1930-1973. L'exemple de l'industrie de l'imprimerie fait voir un affaissement substantiel Ă la fois dans le ratio du salaire rĂ©el et du salaire nominal de 1930 Ă 1972 (baisse de 19 et de 41 pour cent respectivement) cependant que, en 1978, l'un et l'autre ratios se sont Ă©levĂ© Ă leur niveau antĂ©rieur de 1930. Les rĂ©sultats de la rĂ©gression dĂ©montrent de façon succincte ces tendances complexes. En rĂ©sumĂ©, le paramĂštre temps note pour chaque rĂ©gression est le changement en pourcentage dans le ratio de salaire dĂ©valuĂ© pour la pĂ©riode s'y rapportant. Ce qu'il faut noter, c'est que, Ă l'exception importante de la rĂ©gression des mĂ©tiers du bĂątiment, le paramĂštre temps est faible (chemin de fer et imprimerie) ou nĂ©gatif (les employĂ©s municipaux). DiffĂ©rentes particularitĂ©s de la tendance de la rĂ©gression dans le temps furent calculĂ©es de façon Ă dĂ©couvrir la variation cyclique de mĂȘme que les problĂšmes de mesure pour l'avenir. L'hypothĂšse de Gunderson selon laquelle le chĂŽmage influencerait le taux de convergence est confirmĂ©e. Par la suite, l'Ă©tude a Ă©tĂ© divisĂ©e en plusieurs sous-pĂ©riodes de maniĂšre Ă vĂ©rifier deux hypothĂšses supplĂ©mentaires. En premier lieu, Peitchinis avait signale une convergence marquĂ©e entre 1930 et 1956. Par aprĂšs, il n'avait dĂ©couvert aucune telle convergence. Les rĂ©sultats obtenus indiquent le contraire. En outre, les consĂ©quences des taux galopants d'inflation aprĂšs 1972 sont dĂ©montrĂ©es dans les sous-pĂ©riodes de rĂ©gression dans l'industrie de l'imprimerie. Compte tenu de la pĂ©riode inflationniste rĂ©cente (1972-1978), l'Ă©valuation faite de la tendance du paramĂštre temps devient sans signification. Enfin, on a utilise les rĂ©sultats de la rĂ©gression pour tenter de dĂ©couvrir les dĂ©viations d'ensemble. Ă Toronto, dans l'industrie de l'imprimerie par exemple, le taux de convergence du salaire rĂ©el est en gĂ©nĂ©ral la moitiĂ© du taux pour l'ensemble du Canada, tandis qu'Ă Winnipeg, il Ă©tait en gĂ©nĂ©ral vingt pour cent plus Ă©levĂ©s. En consĂ©quence, si on pouvait calculer le ratio de salaire par le niveau d'emploi pour chaque ville, la tendance dans le temps serait mĂȘme plus basse. En somme, l'article dĂ©montre que, si l'on dĂ©value les indices des salaires et qu'on les fait rĂ©gresser dans le temps, il y a modification importante des opinions courantes sur les taux de convergence des ratios de salaires au Canada entre les travailleurs qualifies et non qualifies. L'industrie de la construction, dont le taux de convergence est le plus marque pour l'indice des salaires rĂ©els ne dĂ©cline que de trente-deux pour cent pendant la pĂ©riode 1930-1972, ce qui est loin du dĂ©clin de 72 pour cent calcule Ă partir de l'indice nominal. Dans les autres cas, chemins de fer et imprimerie, les taux de convergence bougent si lentement qu'il faudrait plus de 130 ans pour en arriver Ă une convergence moyenne de 50 pour cent qui, selon Peitchinis, se produirait en quarante ans.The authors critically reassess the standard view that Canada's skilled-unskilled wage differential has collapsed over the past four decades
InGaAs/AlGaAsSb avalanche photodiode with high gain - bandwidth product
Increasing reliance on the Internet places greater and greater demands for high -speed optical communication systems. Increasing their data transfer rate allows more data to be transferred over existing links. With optical receivers being essential to all optical links, bandwidth performance of key components in receivers, such as avalanche photodiodes (APDs), must be improved. The APDs rely on In0.53Ga0.47As (grown lattice-matched to InP substrates) to efficiently absorb and detect the optical signals with 1310 or 1550 nm wavelength, the optimal wavelengths of operation for these optical links. Thus developing InP -compatible APDs with high gain-bandwidth product (GBP) is important to the overall effort of increasing optical linksâ data transfer rate. Here we demonstrate a novel InGaAs/AlGaAsSb APD, grown on an InP substrate, with a GBP of 424 GHz, the highest value reported for InP -compatible APDs, which is clearly applicable to future optical communication systems at or above 10 Gb/s
Mental, behavioral and neurodevelopmental disorders in the ICD-11 : An international perspective on key changes and controversies
The Author(s). 2020Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.An update of the chapter on Mental, Behavioral and Neurodevelopmental Disorders in the International Classification of Diseases and Related Health Problems (ICD) is of great interest around the world. The recent approval of the 11th Revision of the ICD (ICD-11) by the World Health Organization (WHO) raises broad questions about the status of nosology of mental disorders as a whole as well as more focused questions regarding changes to the diagnostic guidelines for specific conditions and the implications of these changes for practice and research. This Forum brings together a broad range of experts to reflect on key changes and controversies in the ICD-11 classification of mental disorders. Taken together, there is consensus that the WHO's focus on global applicability and clinical utility in developing the diagnostic guidelines for this chapter will maximize the likelihood that it will be adopted by mental health professionals and administrators. This focus is also expected to enhance the application of the guidelines in non-specialist settings and their usefulness for scaling up evidence-based interventions. The new mental disorders classification in ICD-11 and its accompanying diagnostic guidelines therefore represent an important, albeit iterative, advance for the field.Peer reviewedFinal Published versio
Improving the efficiency of fibre-chip grating couplers near 1310 nm
We present our recent work on fibre-chip grating couplers operating around 1310 nm. For the first time, we demonstrated the combination of dual-etch and apodization design approaches which can offer state of the art performance. Initial tests from fabricated structures show a -2.2dB loss
On Blowup for time-dependent generalized Hartree-Fock equations
We prove finite-time blowup for spherically symmetric and negative energy
solutions of Hartree-Fock and Hartree-Fock-Bogoliubov type equations, which
describe the evolution of attractive fermionic systems (e. g. white dwarfs).
Our main results are twofold: First, we extend the recent blowup result of
[Hainzl and Schlein, Comm. Math. Phys. \textbf{287} (2009), 705--714] to
Hartree-Fock equations with infinite rank solutions and a general class of
Newtonian type interactions. Second, we show the existence of finite-time
blowup for spherically symmetric solutions of a Hartree-Fock-Bogoliubov model,
where an angular momentum cutoff is introduced. We also explain the key
difficulties encountered in the full Hartree-Fock-Bogoliubov theory.Comment: 24 page
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