2,225 research outputs found
Reflection coefficient for superresonant scattering
We investigate superresonant scattering of acoustic disturbances from a
rotating acoustic black hole in the low frequency range. We derive an
expression for the reflection coefficient, exhibiting its frequency dependence
in this regime.Comment: 7 page
Chiral Gauge Theory on Lattice with Domain Wall Fermions
We investigate a U(1) lattice chiral gauge theory with domain wall fermions
and compact gauge fixing. In the reduced model limit, our perturbative and
numerical investigations show that there exist no extra mirror chiral modes.
The longitudinal gauge degrees of freedom have no effect on the free domain
wall fermion spectrum consisting of opposite chiral modes at the domain wall
and at the anti-domain wall which have an exponentially damped overlap.Comment: 16 pages revtex, 5 postscript figures, PRD versio
Superradiant scattering from a hydrodynamic vortex
We show that sound waves scattered from a hydrodynamic vortex may be
amplified. Such superradiant scattering follows from the physical analogy
between spinning black holes and hydrodynamic vortices. However a sonic horizon
analogous to the black hole event horizon does not exist unless the vortex
possesses a central drain, which is challenging to produce experimentally. In
the astrophysical domain, superradiance can occur even in the absence of an
event horizon: we show that in the hydrodynamic analogue, a drain is not
required and a vortex scatters sound superradiantly. Possible experimental
realization in dilute gas Bose-Einstein condensates is discussed.Comment: 10 pages, 1 figur
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Two-component fluorescent-semiconducting hydrogel from Naphthalene Diimide-Appended peptide with long-chain amines: variation in thermal and mechanical strengths of gels
wo-component fluorescent hydrogels have been discovered, containing the mixtures of naphthalene diimide (NDI)-conjugated peptide-functionalized bola-amphiphile and primary amines with long alkyl chains at physiological pH 7.46. The aggregation-induced enhanced emission associated with an NDI-appended peptide in aqueous medium is rare, as water is known to be a good quencher of fluorescence. In this study, an NDI-containing gelator peptide forms a highly fluorescent aggregate in aqueous medium. Absorption and emission spectroscopic techniques reveal the formation of J-aggregates among the chromophoric moieties in their aggregated state in aqueous medium. However, this NDI-containing peptide does not form any gel in aqueous medium. In the presence of the primary amines with long alkyl chains in the buffer solution, it forms two-component fluorescent hydrogels exhibiting bright yellow fluorescence under a UV lamp (365 nm). Probably, the acid–amine interaction between the amines and the bola-amphiphile triggers the gel formation, as evident from Fourier transform infrared data, indicating the presence of a carboxylate group (−COO–) and an ammonium species (NH3+) in the coassembled two-component gel system. Low- and wide-angle powder X-ray diffraction and small-angle X-ray scattering further support the fact that the coassembled state in the gel form is produced by the supramolecular interaction between the NDI-based bola-amphiphile and the long-chain amines. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy images reveal that the π-conjugated coassembled hydrogels exhibit nanofibrillar network morphologies. Interestingly, the coassembled hydrogels exhibit an enhanced fluorescence emission, excited-state lifetime, and quantum yield when compared with those of the NDI-containing amphiphile alone in its self-assembled state in aqueous medium. Moreover, the thermal stability and mechanical strength of these gels have been successfully tuned by varying the alkyl chain length of the corresponding amine. Moreover, these NDI–peptide-conjugated soft materials exhibit semiconducting behavior in their respective coassembled states. This holds future promise to use these peptide-appended NDI-based coassembled soft materials for applications in optoelectronic and other devices
Mobilizacja krwiotwórczych komórek macierzystych — wczoraj i dziś
The method of hematopoietic stem cells (HSC) mobilization to peripheral blood enabled theirefficient collection from peripheral blood instead of bone marrow, for the purpose of autologousor allogeneic transplantation. Depending on the activity of the disease and on the need ofchemotherapeutic treatment, the current protocols of mobilization consist of granulocyte-colonystimulating factor (G-CSF) alone, or in combination with chemotherapy. The mobilizationsthat use these protocols are usually efficient, as it has been documented for the last 15 years oftheir use. Recently, the new mobilization strategy arose based on the discovery of plerixafor —a specific antagonist of the CXCR4 receptor. The numerous studies revealed its high efficacy ofHSC mobilization, especially when used in combination with G-CSF, and eventually chemotherapy.The current review presents the historical perspective of HSC mobilization, focusingon the last observations regarding the use of plerixafor.Metoda mobilizacji krwiotwórczych komórek macierzystych (HSC) do krwi obwodowej umożliwiłaich efektywne pobieranie z krwi, zamiast ze szpiku, w celu autologicznego lub allogenicznegoprzeszczepienia. Zależnie od aktywności choroby, a także od potrzeby stosowania leczeniachemioterapeutycznego, obecnie stosuje się protokoły mobilizacji oparte na podawaniu czynnikastymulującego wzrost kolonii granulocytów (G-CSF) — samego lub w skojarzeniu z chemioterapią.Mobilizacje według tych protokołów są na ogół skuteczne, co udowodniono w ciąguostatnich 15 lat. Ostatnio pojawiła się kolejna możliwość terapeutyczna, wynikająca z zastosowaniapleryksaforu — swoistego antagonisty receptora chemokinowego CXCR4. Wyniki licznychbadań wykazały jego wysoką skuteczność w mobilizacji HSC, szczególnie jeśli jest stosowanyw skojarzeniu z G-CSF, a niekiedy także z chemioterapią. W niniejszym artykuleprzedstawiono rys historyczny strategii mobilizacji HSC oraz najnowsze obserwacje dotyczącezastosowania pleryksaforu
Improving Reversible Capacities of High-Surface Lithium Insertion Materials – The Case of Amorphous TiO2
Chemisorbed water and solvent molecules and their reactivity with components from the electrolyte in high-surface nanostructured electrodes remains a contributing factor towards capacity diminishment on cycling in lithium ion batteries due to the limit in maximum annealing temperature. Here we report a marked improvement in the capacity retention of amorphous TiO2 by the choice of preparation solvent, control of annealing temperature and the presence of surface functional groups. Careful heating of the amorphous TiO2 sample prepared in acetone under vacuum lead to complete removal of all molecular solvent and an improved capacity retention of 220 mAh/g over 50 cycles at a C/10 rate. Amorphous TiO2 when prepared in ethanol and heated under vacuum showed an even better capacity retention of 240 mAh/g. From FTIR Spectroscopy and Electron Energy Loss Spectroscopy measurements, the improved capacity is attributed to the complete removal of ethanol and the presence of very small fractions of residual functional groups coordinated to oxygen-deficient surface titanium sites. These displace the more reactive chemisorbed hydroxyl groups, limiting reaction with components from the electrolyte and possibly enhancing the integrity of the solid electrolyte interface (SEI). The present research provides a facile strategy to improve the capacity retention of nanostructured electrode materials
Bulk Fermi surface and momentum density in heavily doped LaSrCuO using high resolution Compton scattering and positron annihilation spectroscopies
We have observed the bulk Fermi surface (FS) in an overdoped (=0.3) single
crystal of LaSrCuO by using Compton scattering. A
two-dimensional (2D) momentum density reconstruction from measured Compton
profiles yields a clear FS signature in the third Brillouin zone along [100].
The quantitative agreement between density functional theory (DFT) calculations
and momentum density experiment suggests that Fermi-liquid physics is restored
in the overdoped regime. In particular the predicted FS topology is found to be
in good accord with the corresponding experimental data. We find similar
quantitative agreement between the measured 2D angular correlation of positron
annihilation radiation (2D-ACAR) spectra and the DFT based computations.
However, 2D-ACAR does not give such a clear signature of the FS in the extended
momentum space in either the theory or the experiment.Comment: 9 pages, 8 figure
QCD equation of state at non-zero chemical potential
We present our new results for the QCD equation of state at nonzero chemical
potential at N_t=6 and compare them with N_t=4. We use the Taylor expansion
method with terms up to sixth order in simulations with 2+1 flavors of improved
asqtad quarks along a line of constant physics with m_l=0.1 m_s and
approximately physical strange quark mass m_s.Comment: 7 pages, 10 figures, presented at Lattice 2008 (Nonzero Temperature
and Density), College of William and Mary, Williamsburg, V
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