10,668 research outputs found
Challenges for Water Researchers in Alberta in a Climate of Policy Uncertainty
A safe and plentiful supply of surface water is crucial to the well-being of every resident of Alberta. The effective and efficient use of surface water is central to economic growth and environmental sustainability. As the necessary but competing demands on surface water intensify, the awareness of its limited supply increases. This is particularly evident in southern Alberta, which has experienced significant agricultural, industrial and population growth. In addition to its use for extensive irrigation, surface water in the South Saskatchewan River basin is vital to meet drinking and sanitation needs in rural and urban communities. Management of this key resource involves many researchable issues– water supply, water treatment, water distribution, wastewater collection and processing, flood control, navigation, hydropower production, aquatic recreation – which interact with each other and with government policies. The purpose of this article is to outline the priorities for socio-economic research on surface water resource issues in light of the ever-changing legal and policy frameworks in Alberta.Resource /Energy Economics and Policy,
Maximum-likelihood estimation prevents unphysical Mueller matrices
We show that the method of maximum-likelihood estimation, recently introduced
in the context of quantum process tomography, can be applied to the
determination of Mueller matrices characterizing the polarization properties of
classical optical systems. Contrary to linear reconstruction algorithms, the
proposed method yields physically acceptable Mueller matrices even in presence
of uncontrolled experimental errors. We illustrate the method on the case of an
unphysical measured Mueller matrix taken from the literature.Comment: 3 pages, 1 figur
Hiperuricemia y componentes del síndrome metabólico en niños y adolescentes obesos
ResumenIntroducciónLa hiperuricemia se ha observado como una alteración metabólica adicional en pacientes adultos obesos, pero es poco conocida su magnitud en pacientes pediátricos.ObjetivosAnalizar la asociación entre ácido úrico sérico (AUS) con magnitud de la obesidad general y visceral y con otras mediciones bioquímicas en niños y adolescentes obesos de Santiago, Chile.Sujetos y métodoEn un estudio transversal se evaluaron 770 niños (edades: 6-15 años) de un colegio público de Santiago, Chile, encontrando 227 obesos (29%) (IMC>2 DE, estándares OMS). Se seleccionaron aleatoriamente 90 niños y aceptaron participar 77, sin otras enfermedades crónicas. Se evaluó: peso, talla, perímetro abdominal, adiposidad visceral con ultrasonografía abdominal y mediciones metabólicas: insulinemia, glucemia (HOMA), lípidos séricos, aspartato aminotransferasa, alanina aminotransferasa (ALT) y AUS.ResultadosLas concentraciones de AUS fueron 0,200±0,065mmol/l. El AUS fue mayor en niños con valores de hiperinsulinismo (ajustado según edad): 0,221±0,075 vs 0,183±0,054mmol/l (p<0,01), sin diferencias según HOMA; las diferencias también se observaron según ALT (>vs<26 U/ml): 0,238±0,070 vs 0,178±0,054mmol/l, p<0,001; la regresión logística controlando por sexo, edad e intensidad de la obesidad mostró solo las ALT asociadas a aumento de AUS. No hubo asociación de mayor AUS con magnitud de IMC, adiposidad visceral o hígado graso.ConclusionesLos niños y adolescentes obesos de Santiago, Chile, tienen una uricemia mayor en asociación a un aumento de la actividad de la enzima ALT e hiperinsulinismo. Se justifica analizar uricemia en el estudio de niños obesos y en su seguimiento.AbstractIntroductionHyperuricaemia has been suggested as an additional metabolic factor in adult obese patients, but it has not been sufficiently studied in paediatric.ObjectivesTo assess the relationship between serum uric acid levels (SUAL) with the level of general and visceral obesity, and other biochemical parameters in children and adolescents of Santiago, Chile.Subjects and methodA cross sectional study was conducted on 770 children and adolescents (ages: 6-15 y.) from a public school in Santiago, Chile, of whom 227 (29%) were obese (BMI>2 SD, WHO growth standards). Ninety subjects were randomly selected and 77 with no other chronic disease (41 males) accepted to participate. Data was collected on weight, stature, abdominal circumference (AC), visceral adiposity using ultrasound, and other biochemical measurements including fasting glucose, insulin, serum lipids, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and SUAL.ResultsThe mean SUAL was 0.200±0.065mmol/L, and was increased in children with hyperinsulinism (adjusted by age: 0.221±0.075 vs 0.183±0.054mmol/L; P<.01), with no significant differences according to HOMA. Differences were also found between children with ALT>or<26 U/mL: 0.238±0.070 vs 0.178±0.054mmol/L, P<.001. The logistic regression showed the increased SUAL was only associated with increased ALT. No significant differences were found in general or visceral adiposity measurements or fatty liver.ConclusionsChildren and adolescents from Santiago, Chile have higher uric acid serum uric acid levels as well as an association with increased ALT and insulin. It is demonstrated in this study that uric acid should be measured in obese children and adolescents, and in their follow up
Synchronous Behavior of Two Coupled Electronic Neurons
We report on experimental studies of synchronization phenomena in a pair of
analog electronic neurons (ENs). The ENs were designed to reproduce the
observed membrane voltage oscillations of isolated biological neurons from the
stomatogastric ganglion of the California spiny lobster Panulirus interruptus.
The ENs are simple analog circuits which integrate four dimensional
differential equations representing fast and slow subcellular mechanisms that
produce the characteristic regular/chaotic spiking-bursting behavior of these
cells. In this paper we study their dynamical behavior as we couple them in the
same configurations as we have done for their counterpart biological neurons.
The interconnections we use for these neural oscillators are both direct
electrical connections and excitatory and inhibitory chemical connections: each
realized by analog circuitry and suggested by biological examples. We provide
here quantitative evidence that the ENs and the biological neurons behave
similarly when coupled in the same manner. They each display well defined
bifurcations in their mutual synchronization and regularization. We report
briefly on an experiment on coupled biological neurons and four dimensional ENs
which provides further ground for testing the validity of our numerical and
electronic models of individual neural behavior. Our experiments as a whole
present interesting new examples of regularization and synchronization in
coupled nonlinear oscillators.Comment: 26 pages, 10 figure
Percolation model for structural phase transitions in LiHIO mixed crystals
A percolation model is proposed to explain the structural phase transitions
found in LiHIO mixed crystals as a function of the
concentration parameter . The percolation thresholds are obtained from Monte
Carlo simulations on the specific lattices occupied by lithium atoms and
hydrogen bonds. The theoretical results strongly suggest that percolating
lithium vacancies and hydrogen bonds are indeed responsible for the solid
solution observed in the experimental range .Comment: 4 pages, 2 figure
Interaction potentials, spectroscopy and transport properties of C+(2PJ) and C+(4PJ) with helium
We calculate accurate interatomic potentials for the interaction of a singly-charged carbon cation with a helium atom. We employ the RCCSD(T) method, and basis sets of quadruple-zeta and quintuple-zeta quality; each point is counterpoise corrected and extrapolated to the basis set limit. We consider the two lowest C+(2P) and C+(4P) electronic states of the carbon cation, and calculate the interatomic potentials for the terms that arise from these: 2-PI and 2-SIG+, and 4-PI and 4-SIG- , respectively. We additionally calculate the interatomic potentials for the respective spin-orbit levels, and examine the effect on the spectroscopic parameters. Finally, we employ each set of potentials to calculate transport coefficients, and compare these to available data. Critical comments are made in the cases where there are discrepancies between the calculated values and measured data
The cubic chessboard
We present a survey of recent results, scattered in a series of papers that
appeared during past five years, whose common denominator is the use of cubic
relations in various algebraic structures. Cubic (or ternary) relations can
represent different symmetries with respect to the permutation group S_3, or
its cyclic subgroup Z_3. Also ordinary or ternary algebras can be divided in
different classes with respect to their symmetry properties. We pay special
attention to the non-associative ternary algebra of 3-forms (or ``cubic
matrices''), and Z_3-graded matrix algebras. We also discuss the Z_3-graded
generalization of Grassmann algebras and their realization in generalized
exterior differential forms. A new type of gauge theory based on this
differential calculus is presented. Finally, a ternary generalization of
Clifford algebras is introduced, and an analog of Dirac's equation is
discussed, which can be diagonalized only after taking the cube of the
Z_3-graded generalization of Dirac's operator. A possibility of using these
ideas for the description of quark fields is suggested and discussed in the
last Section.Comment: 23 pages, dedicated to A. Trautman on the occasion of his 64th
birthda
Bottom-up strategies for the assembling of magnetic systems using nanoclusters
International audienceIn the frame of the 20th Anniversary of the Journal of Nanoparticle Research (JNR), our aim is to start from the historical context twenty, years ago and to give some recent results and perspectives concerning nanomagnets prepared from clusters preformed in the gas phase using the Low Energy Cluster Beam Deposition (LECBD) technique. In this paper, we focus our attention on the typical case of Co clusters embedded in various matrices to study interface magnetic anisotropy and magnetic interactions as a function of volume concentrations, and on still current and perspectives through two examples of binary metallic 3d-5d TM (namely CoPt and FeAu) clusters assemblies to illustrate size-related and nanoalloy phenomena on magnetic properties in well-defined mass-selected clusters. The structural and magnetic properties of these cluster assemblies were investigated using various experimental techniques that include High Resolution Transmission Electron Microscopy (HRTEM), Superconducting Quantum Interference Device (SQUID) magnetometry, as well as synchrotron techniques such as Extended X-Ray Absorption Fine Structure (EXAFS) and X-Ray Magnetic Circular Dichroism (XMCD). Depending on the chemical nature of both NPs and matrix, we observe different magnetic responses compared to their bulk counterparts. In particular, we show how finite size effects (size reduction) enhance their magnetic moment and how specific relaxation in nanoalloys can impact their magnetic anisotropy
An insulating grid spacer for large-area MICROMEGAS chambers
We present an original design for large area gaseous detectors based on the MICROMEGAS technology. This technology incorporates an insulating grid, sandwiched between the micro-mesh and the anode-pad plane, which provides an uniform 200 m amplification gap. The uniformity of the amplification gap thickness has been verified under several experimental conditions. The gain performances of the detector are presented and compared to the values obtained with detectors using cylindrical micro spacers. The new design presents several technical and financial advantages
The STAR Silicon Strip Detector (SSD)
The STAR Silicon Strip Detector (SSD) completes the three layers of the
Silicon Vertex Tracker (SVT) to make an inner tracking system located inside
the Time Projection Chamber (TPC). This additional fourth layer provides two
dimensional hit position and energy loss measurements for charged particles,
improving the extrapolation of TPC tracks through SVT hits. To match the high
multiplicity of central Au+Au collisions at RHIC the double sided silicon strip
technology was chosen which makes the SSD a half million channels detector.
Dedicated electronics have been designed for both readout and control. Also a
novel technique of bonding, the Tape Automated Bonding (TAB), was used to
fullfill the large number of bounds to be done. All aspects of the SSD are
shortly described here and test performances of produced detection modules as
well as simulated results on hit reconstruction are given.Comment: 11 pages, 8 figures, 1 tabl
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