1,384 research outputs found
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Lifespan map creation enhances stream restoration design.
Research and engineering efforts are establishing a vast number of stream restoration planning approaches, design testing frameworks, construction techniques, and performance evaluation methods. A primary question arises as to the lifespan of stream restoration features. This study develops a framework to identify relevant parameters, design criteria and survival thresholds for ten multidisciplinary restoration techniques: âąParameterize relevant features, notably, (1) bar and floodplain grading; (2) berm setback; (3) vegetation plantings; (4) riprap placement; (5) sediment replenishment; (6) side cavities; (7) side channel and anabranches; (8) streambed reshaping; (9) structure removal; and (10) placement of wood in the shape of engineered logjams and rootstocks.âąIdentify survival thresholds for parameters, where the feature life ends when the threshold value is exceeded.âąCompare parameter thresholds with spatial data of topographic change and hydrodynamic forces as a result of hydrodynamic modelling of multiple discharges. The discharge or topographic change rate that is related to the lowest (flood) return period spatially determines the feature's lifespan in years
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River Architect
© 2020 The Authors River design is often conceptually approached aiming at either physical channel stability or ecological functionality. We present a novel concept within an open-source software called River Architect that addresses both these goals and estimates costs. River Architect is flexible for site- and application-specific characteristics, with modules for the analysis and design of habitat-enhancing and channel-stabilising feature groups. Ecological assets are assessed as a function of a novel metric that incorporates the seasonal and discharge-dependent preferred habitat area of target species. Calculations of cost estimates and ecological efficiency are illustrated by an example in a gravel-cobble-bed river
Measuring a photonic qubit without destroying it
Measuring the polarisation of a single photon typically results in its
destruction. We propose, demonstrate, and completely characterise a
\emph{quantum non-demolition} (QND) scheme for realising such a measurement
non-destructively. This scheme uses only linear optics and photo-detection of
ancillary modes to induce a strong non-linearity at the single photon level,
non-deterministically. We vary this QND measurement continuously into the weak
regime, and use it to perform a non-destructive test of complementarity in
quantum mechanics. Our scheme realises the most advanced general measurement of
a qubit: it is non-destructive, can be made in any basis, and with arbitrary
strength.Comment: 4 pages, 3 figure
Internet e Direitos Fundamentais
Book notes:
Clara-Luz Ălvarez. Internet y Derechos Fundamentales. MĂ©xico: Editorial Porrua, 2011, 283p.Book notes:
Clara-Luz Ălvarez. Internet y Derechos Fundamentales. MĂ©xico: Editorial Porrua, 2011, 283p.Resenha do livro:
Clara-Luz Ălvarez. Internet y Derechos Fundamentales. MĂ©xico: Editorial Porrua, 2011, 283p
Quality of a Which-Way Detector
We introduce a measure Q of the "quality" of a quantum which-way detector,
which characterizes its intrinsic ability to extract which-way information in
an asymmetric two-way interferometer. The "quality" Q allows one to separate
the contribution to the distinguishability of the ways arising from the quantum
properties of the detector from the contribution stemming from a-priori
which-way knowledge available to the experimenter, which can be quantified by a
predictability parameter P. We provide an inequality relating these two sources
of which-way information to the value of the fringe visibility displayed by the
interferometer. We show that this inequality is an expression of duality,
allowing one to trace the loss of coherence to the two reservoirs of which-way
information represented by Q and P. Finally, we illustrate the formalism with
the use of a quantum logic gate: the Symmetric Quanton-Detecton System (SQDS).
The SQDS can be regarded as two qubits trying to acquire which way information
about each other. The SQDS will provide an illustrating example of the
reciprocal effects induced by duality between system and which-way detector.Comment: 10 pages, 5 figure
Internet e Direitos Fundamentais
Resenha do livro:
Clara-Luz Ălvarez. Internet y Derechos Fundamentales. MĂ©xico: Editorial Porrua, 2011, 283p
Comparison of 87Rb N-resonances for D1 and D2 transitions
We report an experimental comparison of three-photon-absorption resonances
(known as "N-resonances") for the D_1 and D_2 optical transitions of thermal
87Rb vapor. We find that the D_2 N-resonance has better contrast, a broader
linewidth, and a more symmetric lineshape than the D_1 N-resonance. Taken
together, these factors imply superior performance for frequency standards
operating on alkali D_2 N-resonances, in contrast to coherent population
trapping (CPT) resonances for which the D_2 transition provides poorer
frequency standard performance than the D_1 transition.Comment: 3 pages, 4 figure
On the unique possibility to increase significantly the contrast of dark resonances on D1 line of Rb
We propose and study, theoretically and experimentally, a new scheme of
excitation of a coherent population trapping resonance for D1 line of alakli
atoms with nuclear spin by bichromatic linearly polarized light ({\em
lin}{\em lin} field) at the conditions of spectral resolution of the
excited state. The unique properties of this scheme result in a high contrast
of dark resonance for D1 line of Rb.Comment: 9 pages, 7 figures. This material has been partially presented on
ICONO-2005, 14 May 2005, St. Petersburg, Russia. v2 references added; text is
changed a bi
Dual channel self-oscillating optical magnetometer
We report on a two-channel magnetometer based on nonlinear magneto-optical
rotation in a Cs glass cell with buffer gas. The Cs atoms are optically pumped
and probed by free running diode lasers tuned to the D line. A wide
frequency modulation of the pump laser is used to produce both synchronous
Zeeman optical pumping and hyperfine repumping. The magnetometer works in an
unshielded environment and spurious signal from distant magnetic sources is
rejected by means of differential measurement. In this regime the magnetometer
simultaneously gives the magnetic field modulus and the field difference.
Rejection of the common-mode noise allows for high-resolution magnetometry
with a sensitivity of \pthz{2}. This sensitivity, in conjunction with long-term
stability and a large bandwidth, makes possible to detect water proton
magnetization and its free induction decay in a measurement volume of 5 cmComment: 13 pages, 9 figures. Improved version (v2). Accepted for publicatio
Reactive oxygen species-linked regulation of the multidrug resistance transporter P-glycoprotein in Nox-1 overexpressing prostate tumor spheroids
AbstractExpression of the multidrug resistance (MDR) transporter P-glycoprotein (P-gp) has been demonstrated to be regulated by hypoxia-inducible factor-1α (HIF-1α) and inhibited by intracellular reactive oxygen species (ROS). Herein, P-gp and HIF-1α expression were investigated in multicellular prostate tumor spheroids overexpressing the ROS-generating enzyme Nox-1 in comparison to the mother cell line DU-145. In Nox-1-overexpressing tumor spheroids (DU-145Nox1) generation of ROS as well as expression of Nox-1 was significantly increased as compared to DU-145 tumor spheroids. ROS generation was significantly inhibited in the presence of the NADPH-oxidase antagonists diphenylen-iodonium chloride (DPI) and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). Albeit growth kinetic of DU-145Nox1 tumor spheroids was decreased as compared to DU-145 spheroids, elevated expression of Ki-67 was observed indicating increased cell cycle activity. In DU-145Nox1 tumor spheroids, expression of HIF-1α as well as P-gp was significantly decreased as compared to DU-145 spheroids, which resulted in an increased retention of the anticancer agent doxorubicin. Pretreatment with the free radical scavengers vitamin E and vitamin C increased the expression of P-gp as well as HIF-1α in Nox-1-overexpressing cells, whereas no effect of free radical scavengers was observed on mdr-1 mRNA expression. In summary, the data of the present study demonstrate that the development of P-gp-mediated MDR is abolished under conditions of elevated ROS levels, suggesting that the MDR phenotype can be circumvented by modest increase of intracellular ROS generation
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