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Reversing entanglement change by a weak measurement

Reversing entanglement change by a weak measurement

Entanglement of a system changes due to interactions with the environment. A typical type of interaction is amplitude damping. If we add a detector to monitor the environment and only select the no-damping outcome, this amplitude damping is modified into a weak measurement. Here we show that the entanglement change of a two-qubit state due to amplitude damping or weak measurement can be probabilistically reversed. For the amplitude-damping case, the entanglement partially recovers under most conditions. For the weak-measurement case, the recovery of the initial entangled state is exact. The reversal procedure involves another weak measurement, preceded and followed by bit flips applied to both qubits. We propose a linear optics scheme for the experimental demonstration of these procedures.
Ca(2+) signaling, genes and the cell cycle

Ca(2+) signaling, genes and the cell cycle

Changes in the concentration and spatial distribution of Ca2+ ions in the cytoplasm constitute a ubiquitous intracellular signaling module in cellular physiology. With the advent of Ca2+ dyes that allow direct visualization of Ca2+ transients, combined with powerful experimental tools such as electrophysiological recordings, intracellular Ca2+ transients have been implicated in practically every aspect of cellular physiology, including cellular proliferation.
Quantum state engineering by a coherent superposition of photon subtraction and addition

Quantum state engineering by a coherent superposition of photon subtraction and addition

We study a coherent superposition t (a) over cap + r (a) over cap dagger of field annihilation and creation operators acting on continuous variable systems and propose its application for quantum state engineering. Specifically, it is investigated how the superposed operation transforms a classical state to a nonclassical one, together with emerging nonclassical effects. We also propose an experimental scheme to implement this elementary coherent operation and discuss its usefulness to produce an arbitrary superposition of number states involving up to two photons.
Quantum interference due to energy shifts and its effect on spontaneous emission

Quantum interference due to energy shifts and its effect on spontaneous emission

We study the quantum interference in spontaneous emission with the inclusion of counterrotating terms and energy shifts. The energy shifts come from the emission and then reabsorption of virtual photons as well as the real photon emission. We show that the quantum interference resulting from the energy shifts has significant influence on the effective decay rates of the two levels, even when the transition dipole elements are the same and the energy separation of the two levels is small. We also show that the energy shift has substantial influence on the spectrum emitted by the atom. The result is valid in the long time limit. The effect of the energy shift can be observed at the time scale of 1 over the atomic decay rate. We suggest an experiment to test the effect of quantum interference because of energy shifts on the emission spectrum.
Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis

Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis

The egg's competency to activate at fertilization and transition to embryogenesis is dependent on its ability to generate a fertilization-specific Ca2+ transient To endow the egg with this capacity, Ca2+ signals remodel during oocyte maturation, including inactivation of the primary Ca2+ influx pathway store operated Ca2+ entry (SOCE) SOCE inactivation is coupled to internalization of the SOCE channel, rail In this study, we show that Orai1 internalizes during meiosis through a caveolin (Cav) and dynamin-dependent endocytic pathway Cav binds to Orai1, and we map a Cav consensus binding site in the rail N terminus, which is required for rail internalization Furthermore, at rest, Orai1 actively recycles between an endosomal compartment and the cell membrane through a Rho dependent endocytic pathway A significant percentage of total Orai1 is intracellular at steady state Store depletion completely shifts endosomal Orai1 to the cell membrane These results define vesicular trafficking mechanisms in the oocyte that control Orai1 subcellular localization at steady state, during meiosis, and after store depletion.
Risk factors contributing to road traffic crashes in a fast-developing country: the neglected health problem

Risk factors contributing to road traffic crashes in a fast-developing country: the neglected health problem

BACKGROUND
The main objective of this study was to explore the patterns of road traffic crashes (RTCs) among drivers in Qatar and to examine the contributing factors involved.
METHODS
This study was a cross-sectional survey conducted from February to June 2009 at the Primary Health Care Centers in the State of Qatar. A random sample of 1675 Qatari drivers were approached, and 1228 of them responded and agreed to participate in this study, with a response rate of 74.6%. Face to face interview was conducted by well-trained research assistants based on a questionnaire covering sociodemographic information, driving history, type of vehicle, driver behavior, details of crashes, and accident pattern.
RESULTS
The study revealed that 26.6% of the studied Qatari drivers were involved in RTCs. 69.4% of the drivers with a history of RTCs were male. Drivers in the age group 25-34 years showed a higher risk of having a crash (31.2%). Drivers of cars (45.6%) and 4WD/SUVs (23.5%) were more frequently involved in RTCs. 23.5% of drivers who had RTC did not always wear their seat belt while driving. 37.9% of the drivers with RTC were engaged in eating and drinking and 41.9% were using their mobile phones while driving. More than half of the drivers with RTCs had traffic violations (57.2%), with 25.7% exceeding the speed limit. A highly significant difference was observed between the two groups (drivers with and without RTC) in terms of presence of traffic violation (<0.001) and exceeding the speed limit (<0.001). Most of the crashes happened during sunny days (84.7%) with fewer crashes on holidays (5.5%) and weekends (12.5%). Overturn skid (17.7%), angle collision (14.3%) and rear-end hit (10.7%) were the most frequently reported patterns of RTCs.
Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis

Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis

The egg's competency to activate at fertilization and transition to embryogenesis is dependent on its ability to generate a fertilization-specific Ca2+ transient To endow the egg with this capacity, Ca2+ signals remodel during oocyte maturation, including inactivation of the primary Ca2+ influx pathway store operated Ca2+ entry (SOCE) SOCE inactivation is coupled to internalization of the SOCE channel, rail In this study,
Mitigating Error Propagation in Two-Way Relay Channels with Network Coding

Mitigating Error Propagation in Two-Way Relay Channels with Network Coding

In relay networks, error propagation at the relay nodes degrades the performance of the system. To combat that effect, it has been suggested to implement a reliability threshold at the relay to control error propagation. Specifically, the relay calculates log-likelihood ratio (LLR) values for the bits sent from the source. These values are subjected to a threshold to selectively forward bits that are most reliable and discard bits that are less so, resulting in less errors propagating to the destination. We investigate the application of this technique to a network-coded two-way relay channel where the relay is assisting two sources simultaneously. We first consider network-coded systems without channel coding, and then consider network-channel coded systems. We examine two modes of thresholding, one based on the individual bits, and the other based on the combined bits. We provide the full analysis for the bit-error rate (BER) performance of both thresholding modes and optimize the thresholds accordingly. We demonstrate that the optimum thresholds based on both modes give similar performances and are far better than the case of no thresholding. We also consider the performance of the proposed thresholding techniques for network-channel coded systems. We present several numerical examples that illustrate the efficacy of employing thresholding at the relay nodes (for networks with and without channel coding).
On the Viscosity of Natural Gases from Qatari North Field Reservoir

On the Viscosity of Natural Gases from Qatari North Field Reservoir

New viscosity measurements of three natural gas-like mixtures with compositions resembling those of the Qatari North Field reservoir are reported in this work. The viscosity measurements were performed with an electromagnetic piston viscometer for temperatures from (250 to 450) K and pressure between (10 and 65) MPa. The apparatus was calibrated by use of nitrogen and propane as viscosity reference data. Uncertainties of reported data are +/- 2.5 % for pressure less than 30 MPa and +/- 4 % for higher pressures. The predictive ability of several models was analyzed in relation to the experimental reported viscosity data, leading to large deviations from the reported measurements. The effects of mixtures' composition on viscosity were also studied.
Dynamic Model of PEM Fuel Cell Using Real-time Simulation Techniques

Dynamic Model of PEM Fuel Cell Using Real-time Simulation Techniques

The increased integration of fuel cells with power electronics critical loads and control systems has prompted recent interest in accurate electrical terminal models of the polymer electrolyte membrane (PEM) fuel cell Advancement in computing technologies, particularly parallel computation techniques and various real-time simulation tools have allowed the prototyping of novel apparatus to be investigated in a virtual system under a wide range of realistic conditions repeatedly safely and economically This paper builds upon both advancements and provides a means of optimized model construction boosting computation speeds for a fuel cell model on a real-time simulator which can be used in a power hardware-In-the-loop (PHIL) application Significant improvement in computation time has been achieved The effectiveness of the proposed model developed on Opal RT s RT Lab Matlab/Simulink based real-time engineering simulator is verified using experimental results from a Ballard Nexa fuel cell system. 
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DeSIGN: Guided Practice for Sign Language

DeSIGN: Guided Practice for Sign Language

Children learn and practice their vocabulary through interaction with parents and friends as well as through formal instruction at school. However, for deaf children, sign language is the main...
Calcium channels determine how life begins, and ends
Calcium channels determine how life begins, and ends

Calcium channels determine how life begins, and ends

Ongoing work at Weill Cornell Medical College in Qatar (WCMC-Q) is investigating how intracellular calcium (Ca2+) signaling pathways are involved in the very beginning of life as they prepare the...
Taking gas-to-liquid technology to the next level
Taking gas-to-liquid technology to the next level

Taking gas-to-liquid technology to the next level

In the 1920s, two German scientists—Franz Fischer and Hans Tropsch—developed revolutionary chemical reactions that could transform gas into liquid. These reactions proved particularly...
Researchers build the case for wind and wave studies in Qatar
Researchers build the case for wind and wave studies in Qatar

Researchers build the case for wind and wave studies in Qatar

For the first time, fine detail about the wind and wave conditions around the coast of Qatar has been recorded. By arranging the most sophisticated equipment available on the edge of a 500-meter...
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