Search results for "PUMP"
showing 10 items of 471 documents
On block pumpable languages
2016
Ehrenfeucht, Parikh and Rozenberg gave an interesting characterisation of the regular languages called the block pumping property. When requiring this property only with respect to members of the language but not with respect to nonmembers, one gets the notion of block pumpable languages. It is shown that these block pumpable are a more general concept than regular languages and that they are an interesting notion of their own: they are closed under intersection, union and homomorphism by transducers; they admit multiple pumping; they have either polynomial or exponential growth.
A distributed model for continuous-wave erbium-doped fiber laser
2011
Abstract A distributed model of a continuous-wave erbium-doped fiber laser is discussed. The model is based on two contra-propagated traveling laser waves, and includes inhomogeneous pumping, excited state absorption at the pump and the laser wavelengths, amplified spontaneous emission and radial distribution of populations of erbium levels. It is shown that excited state absorption is a main limiting factor to the laser's efficiency. Moreover, consideration of radial distributions of erbium levels' populations in the model reduces laser efficiency and decreases optimal reflection of the laser output coupler. The modeling results are in excellent agreement with the experimental study on the…
High-efficiency Q-switched erbium fiber laser using a Bragg grating-based modulator
2002
Abstract In this work we analyze the behavior of an erbium-doped fiber laser which is based on a simple scheme. Excitation of the active medium is performed in the 980 nm pump band with a CW semiconductor laser source. Two fiber Bragg gratings acting as mirrors of the Fabry–Perot laser cavity were used. One of these gratings was mounted over a piezoelectric (PZT) element. By applying voltage pulses to the piezoelectric, the laser cavity was temporally modulated and Q-switched laser pulses up to 530 mW peak powers at 3 kHz were obtained. Typical laser emission of 2–3 μs temporal widths and 0.1 nm of optical bandwidth have been achieved when the system was operated at 18.5 kHz repetition rate…
Dual-kind Q-switching of erbium fiber laser
2014
Two different regimes of Q-switching in the same implementation of an actively Q-switched erbium-doped fiber laser are demonstrated. Depending on the active fiber length and repetition rate of an intracavity Q-cell (acousto-optic modulator), the laser operates either in the regime of common, rather long and low-power, pulses composed of several sub-pulses or in the one of very short and powerful stimulated Brillouin scattering-induced pulses. The basic physical reason of the laser system to oscillate in one of these two regimes is the existence or absence of CW narrow-line “bad-cavity” lasing in the intervals when the Q-cell is blocked.
Uso degli inibitori di pompa protonica in un Policlinico Universitario
2012
Summary Introduction Proton pump inhibitors (PPIs) are highly prescribed drugs in Italy and in particular in the Sicilian region but little is known about their use in the hospital setting. Materials and methods PPI utilization and related costs were reviewed retrospectively by examining the pharmaceutical records of drug dispensation to the various wards of the Policlinico Universitario P. Giaccone of Palermo in 2010. Differences in the prescribing rates and drug preferences among the different clinical wards were analyzed. Results A total of 20,420 patients were hospitalized at the Policlinico of Palermo in 2010. Overall, the consumption of PPIs was 120 DDD/100 bed-days for the year 2010 …
Interaction risk with proton pump inhibitors in general practice: significant disagreement between different drug-related information sources.
2006
Aims To compare information on drug–drug interactions (DDIs) reported on two standard drug-related information sources (Summary of Product Characteristics and Drugdex system by Micromedex), by assessing the prevalence and predictors of potential DDI with proton pump inhibitors (PPIs) in general practice. Methods From the ‘Caserta-1’ Local Health-Service database, 156 general practitioners (GPs) were recruited. From more than 180 000 individuals registered on their lists, we selected patients receiving co-prescription of PPI and medications at interaction risk, according to the Italian Summary of Product Characteristics (SPC) of PPI and Drugdex information, during the year 2003. Thereafter, …
Clinical pharmacology and safety profile of esomeprazole, the first enantiomerically pure proton pump inhibitor
2001
Awareness of important differences in the pharmacological profile of individual optical isomers of chiral drugs led to the development of esomeprazole, the S-isomer of omeprazole, a new pharmacological entity designed to improve the clinical outcome of available proton pump inhibitors in the management of acid-related disorders. The superior acid control achieved by esomeprazole is mainly due to an advantageous metabolism compared with racemate omeprazole, leading to improved bioavailability and to enhanced delivery of the drug to the gastric proton pump.
Vibrational relaxation of Na2 molecules in a triplet state: collisional transfer from a mixed A 1Σu+ − b3Πu gateway level to long-lived levels of b 3…
1997
Abstract Collision-induced vibrational transitions of Na2 within the b 3Π1u state have been observed in a free jet expansion, using two CW dye lasers for the pump and probe steps. The b-state is entered by the pump laser using a low mixed ( A 1 Σ u + − b 3 Π u ) level as a gateway. The occupations of various v′,J′-levels are studied as functions of the position in the flowing gas. The radiative lifetimes of Na2 in levels which had been populated by vibrational relaxation are found to be very long (> 4 μs). Cross-sections are estimated for vibrationally inelastic collisions with Na and Ar atoms.
The multixenobiotic resistance mechanism in the marine sponge Suberites domuncula: its potential applicability for the evaluation of environmental po…
1996
Experiments were carried out with the marine sponge Suberites domuncala to determine whether sponges may express - like mammalian tumor cells a multidrug-like transporter system. The results demonstrate that sponge cells possess such a protective system termed multixenobiotic resistance (MXR) pump or P-glycoprotein-like pump, The protein was identified by antisera for the mammalian P170 multidrug resistance protein as a 130 kDa molecule, Binding studies were performed with H-3-vincristine (H-3-VCR) and membrane vesicles ; this process is ATP-dependent and inhibited by verapamil, which is known to reverse the multidrug-resistance phenotype in mammalian systems, Accumulation experiments were …
Gigahertz Single-Electron Pumping Mediated by Parasitic States
2018
In quantum metrology, semiconductor single-electron pumps are used to generate accurate electric currents with the ultimate goal of implementing the emerging quantum standard of the ampere. Pumps based on electrostatically defined tunable quantum dots (QDs) have thus far shown the most promising performance in combining fast and accurate charge transfer. However, at frequencies exceeding approximately 1 GHz, the accuracy typically decreases. Recently, hybrid pumps based on QDs coupled to trap states have led to increased transfer rates due to tighter electrostatic confinement. Here, we operate a hybrid electron pump in silicon obtained by coupling a QD to multiple parasitic states, and achi…