Search results for "buffer"
showing 10 items of 230 documents
Cooling and slowing of trapped antiprotons below 100 meV
1989
Electron cooling of trapped antiprotons allows their storage at energies 10 million times lower than is available in any antiproton storage ring. More than 60 000 antiprotons with energies from 0 to 3000 eV are stored in an ion trap from a single pulse of 5.9-MeV antiprotons from LEAR. Trapped antiprotons maintain their initial energy distribution over a storage lifetime exceeding 50 h unless allowed to collide with a cold buffer gas of trapped electrons, where- upon they cool dramatically to 1 eV in tens of seconds. The cooled antiprotons can be stacked into a harmonic potential well suited for long-term storage and precision measurements.
Trapped charged particles and fundamental interactions
2008
Low-Energy Precision Tests of Electroweak Theory.- Principles of Ion Traps.- Simulations for Ion Traps Methods and Numerical Implementation.- Simulations for Ion Traps Buffer Gas Cooling.- Highly-charged ions and high-resolution mass spectrometry in a Penning trap.- Fundamental tests with trapped antiprotons.
Persistent currents in a circular array of Bose-Einstein condensates
2002
A ring-shaped array of Bose-Einstein condensed atomic gases can display circular currents if the relative phase of neighboring condensates becomes locked to certain values. It is shown that, irrespective of the mechanism responsible for generating these states, only a restricted set of currents are stable, depending on the number of condensates, on the interaction and tunneling energies, and on the total number of particles. Different instabilities due to quasiparticle excitations are characterized and possible experimental setups for testing the stability prediction are also discussed.
Trapped ion density distribution in the presence of He-buffer gas
1981
The spatial density distribution of Ba+ ions, confined in a rf quadrupole trap, has been measured by laser scanning across the trap. This allows to determine the ion temperature, assuming thermal equilibrium. Under UHV conditions the average ion energy has been found to be one tenth of the trap potential well depth. Collisions with He at pressures up to 5×10−6 mbar reduce the ion temperature by a factor of 3.
Buffer strips can pre-empt extinction debt in boreal streamside habitats
2013
Background Conservation of biological diversity and economical utilization of natural resources form an almost inevitable confrontation between the two. In practice, however, a balance between the two ought to be found, and in managed boreal forests, preservation of woodland key habitats is increasingly used strategy to safeguard biological diversity. According to the Finnish Forests Act, certain Forest Act habitat (FAH) types must be safeguarded, provided they are clearly distinguishable from their surroundings. Furthermore, once the habitat has been identified as a FAH, its special characteristics must not be altered. Both of these aspects contain ambiguities that potentially undermine th…
Spectroscopic, radiochemical, and theoretical studies of the Ga3+-N-2-hydroxyethyl piperazine-N'-2-ethanesulfonic acid (HEPES buffer) system: evidenc…
2013
Recent reports have claimed a superior performance of HEPES buffer in comparison to alternative buffer systems for 67/68 Ga labeling in aqueous media. In this paper we report spectroscopic (1H and 71 Ga NMR), radiochemical, mass spectrometry and theoretical modeling studies on the Ga3+/HEPES system (HEPES = N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) performed with the aim of elucidating a potential contribution of HEPES in the 68/67 Ga radiolabeling process. Our results demonstrate that HEPES acts as a weakly but competitive chelator of Ga3+ and that this interaction depends on the relative Ga3+: HEPES concentration. A by-product formed in the labeling mixture has been identified …
Amphiphilic poly(hydroxyethylaspartamide) derivative-based micelles as drug delivery systems for ferulic acid
2008
Self-assembling micelles, potentially useful as drug delivery systems for ferulic acid (FA), were obtained in aqueous media from amphiphilic alpha,beta-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) copolymers bearing at the polyamino acidic backbone both poly(ethyleneglycol) (2000 or 5000 Da) and hexadecylamine (C(16)) moieties, at a concentration of 7 x 10(- 3) and 4 x 10(- 3) g/l, respectively, with nanometre size and negative zeta potential. These micelles were able to entrap FA and to release it in a prolonged way in phosphate buffer solution at pH 7.4 and human plasma. These systems were also stable in storage conditions and have no cytotoxic effects on Caco-2, 16 HBE, HuDe and K562 cel…
Analysis of post-harvest fungicides by micellar electrokinetic chromatography.
2001
A method based on solid-phase extraction (SPE) and micellar electrokinetic chromatography (MEKC) was developed for the simultaneous determination of carbendazim, imazalil, methylthiophanate, O-phenylphenol, prochloraz, procimidone, thiabendazole and triadimefon residues in grape, lettuce, orange and tomato. Selectivity and resolution were studied changing the pH and the concentration of the buffer, the type and concentration of surfactant and the methanol content in the mobile phase. A buffer consisting of 4 mM borate with 75 mM sodium cholate (pH 9.2) gave the best results. The recoveries of the fungicides in spiked fruit and vegetable samples ranged from 30 to 105%, and the limits of dete…
Micellar enhanced fluorimetric determination of carbendazim in natural waters
1994
Abstract A micellar enhanced flow-injection fluorimetric method was developed for the determination of carbendazim in natural water samples. The method is based on the direct injection of 500 μ1 of water into a three-channel flow manifold in which the samples are merged with a buffer solution and subsequently with a surfactant solution. Two alternative procedures were used: one based on the use of sodium dodecyl sulphate micelles in 0.1 M HCl, which permits a 2.6-fold enhancement of the sensitivity found in the absence of micelles to be obtained, and the other based on the use of cetyltrimethylammonium bromide in 0.1 M NaOH, which provides a 11.6-fold enhancement of sensitivity and a limit …
Pulsed EPR determination of water accessibility to spin-labeled amino acid residues in LHCIIb.
2009
Membrane proteins reside in a structured environment in which some of their residues are accessible to water, some are in contact with alkyl chains of lipid molecules, and some are buried in the protein. Water accessibility of residues may change during folding or function-related structural dynamics. Several techniques based on the combination of pulsed electron paramagnetic resonance (EPR) with site-directed spin labeling can be used to quantify such water accessibility. Accessibility parameters for different residues in major plant light-harvesting complex IIb are determined by electron spin echo envelope modulation spectroscopy in the presence of deuterated water, deuterium contrast in …