115 research outputs found
Inelastic Coulomb scattering rates due to acoustic and optical plasmon modes in coupled quantum wires
We report a theoretical study on the inelastic Coulomb scattering rate of an
injected electron in two coupled quantum wires in quasi-one-dimensional doped
semiconductors. Two peaks appear in the scattering spectrum due to the optical
and the acoustic plasmon scattering in the system. We find that the scattering
rate due to the optical plasmon mode is similar to that in a single wire but
the acoustic plasmon scattering depends crucially on its dispersion relation at
small . Furthermore, the effects of tunneling between the two wires are
studied on the inelastic Coulomb scattering rate. We show that a weak tunneling
can strongly affect the acoustic plasmon scattering.Comment: 6 Postscript figure
Cloning of the maoA gene that encodes aromatic amine oxidase of Escherichia coli W3350 and characterization of the overexpressed enzyme
Cloning of the maoA gene that encodes aromatic amine oxidase of Escherichia coli W3350 and characterization of the overexpressed enzyme
Pauli blocking of stimulated emission in a degenerate Fermi gas
The Pauli exclusion principle in quantum mechanics has a profound influence
on the structure of matter and on interactions between fermions. Almost 30
years ago it was predicted that the Pauli exclusion principle could lead to a
suppression of spontaneous emission, and only recently several experiments
confirmed this phenomenon. Here we report that this so-called Pauli blockade
not only affects incoherent processes but also, more generally, coherently
driven systems. It manifests itself as an intriguing sub-Doppler narrowing of a
doubly-forbidden transition profile in an optically trapped Fermi gas of
. By actively pumping atoms out of the excited state, we break
the coherence of the excitation and lift the narrowing effect, confirming the
influence of Pauli blockade on the transition profile. This new insight into
the interplay between quantum statistics and coherent driving is a promising
development for future applications involving fermionic systems.Comment: 36 pages, 8 figure
The alpha and helion particle charge radius difference from spectroscopy of quantum-degenerate helium
Accurate spectroscopic measurements of calculable systems provide a powerful
method for testing the Standard Model and extracting fundamental constants.
Recently, spectroscopic measurements of finite nuclear size effects in normal
and muonic hydrogen resulted in unexpectedly large adjustments of the proton
charge radius and the Rydberg constant. We measured the
transition frequency in a Fermi gas of
He with an order of magnitude higher accuracy than before. Together with a
previous measurement in a He Bose-Einstein condensate, a squared charge
radius difference is
determined between the helion and alpha particle. This measurement provides a
benchmark with unprecedented accuracy for nuclear structure calculations. A
deviation of 3.6 is found with a determination (arXiv:2305.11679) based
on spectroscopy of muonic helium ions.Comment: Paper and supplementary in total 13 pages and 5 figure
Barriers and Facilitators of Safe Communication in Obstetrics: Results from Qualitative Interviews with Physicians, Midwives and Nurses.
Patient safety is an important objective in health care. Preventable adverse events (pAEs) as the counterpart to patient safety are harmful incidents that fell behind health care standards and have led to temporary or permanent harm or death. As safe communication and mutual understanding are of crucial importance for providing a high quality of care under everyday conditions, we aimed to identify barriers and facilitators that impact safe communication in obstetrics from the subjective perspective of health care workers. A qualitative study with 20 semi-structured interviews at two university hospitals in Germany was conducted to explore everyday perceptions from a subjective perspective (subjective theories). Physicians, midwives, and nurses in a wide span of professional experience and positions were enrolled. We identified a structural area of conflict at the professional interface between midwives and physicians. Mandatory interprofessional meetings, acceptance of subjective mistakes, mutual understanding, and debriefings of conflict situations are reported to improve collaboration. Additionally, emergency trainings, trainings in precise communication, and handovers are proposed to reduce risks for pAEs. Furthermore, the participants reported time-constraints and understaffing as a huge burden that hinders safe communication. Concluding, safety culture and organizational management are closely entwined and strategies should address various levels of which communication trainings are promising
Resonant Raman scattering off neutral quantum dots
Resonant inelastic (Raman) light scattering off neutral GaAs quantum dots
which contain a mean number, N=42, of electron-hole pairs is computed. We find
Raman amplitudes corresponding to strongly collective final states
(charge-density excitations) of similar magnitude as the amplitudes related to
weakly collective or single-particle excitations. As a function of the incident
laser frequency or the magnetic field, they are rapidly varying amplitudes. It
is argued that strong Raman peaks should come out in the spin-density channels,
not related to valence-band mixing effects in the intermediate states.Comment: Accepted in Physical Review
Coulomb correlation effects in semiconductor quantum dots: The role of dimensionality
We study the energy spectra of small three-dimensional (3D) and
two-dimensional (2D) semiconductor quantum dots through different theoretical
approaches (single-site Hubbard and Hartree-Fock hamiltonians); in the smallest
dots we also compare with exact results. We find that purely 2D models often
lead to an inadequate description of the Coulomb interaction existing in
realistic structures, as a consequence of the overestimated carrier
localization. We show that the dimensionality of the dots has a crucial impact
on (i) the accuracy of the predicted addition spectra; (ii) the range of
validity of approximate theoretical schemes. When applied to realistic 3D
geometries, the latter are found to be much more accurate than in the
corresponding 2D cases for a large class of quantum dots; the single-site
Hubbard hamiltonian is shown to provide a very effective and accurate scheme to
describe quantum dot spectra, leading to good agreement with experiments.Comment: LaTeX 2.09, RevTeX, 25 pages, 9 Encapsulated Postscript figures. To
be published in Physical Review
A novel copper complex induces ROS generation in doxorubicin resistant Ehrlich ascitis carcinoma cells and increases activity of antioxidant enzymes in vital organs in vivo
BACKGROUND: In search of a suitable GSH-depleting agent, a novel copper complex viz., copper N-(2-hydroxyacetophenone) glycinate (CuNG) has been synthesized, which was initially found to be a potential resistance modifying agent and later found to be an immunomodulator in mice model in different doses. The objective of the present work was to decipher the effect of CuNG on reactive oxygen species (ROS) generation and antioxidant enzymes in normal and doxorubicin-resistant Ehrlich ascites carcinoma (EAC/Dox)-bearing Swiss albino mice. METHODS: The effect of CuNG has been studied on ROS generation, multidrug resistance-associated protein1 (MRP1) expression and on activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). RESULTS: CuNG increased ROS generation and reduced MRP1 expression in EAC/Dox cells while only temporarily depleted glutathione (GSH) within 2 h in heart, kidney, liver and lung of EAC/Dox bearing mice, which were restored within 24 h. The level of liver Cu was observed to be inversely proportional to the level of GSH. Moreover, CuNG modulated SOD, CAT and GPx in different organs and thereby reduced oxidative stress. Thus nontoxic dose of CuNG may be utilized to reduce MRP1 expression and thus sensitize EAC/Dox cells to standard chemotherapy. Moreover, CuNG modulated SOD, CAT and and GPx activities to reduce oxidative stress in some vital organs of EAC/Dox bearing mice. CuNG treatment also helped to recover liver and renal function in EAC/Dox bearing mice. CONCLUSION: Based on our studies, we conclude that CuNG may be a promising candidate to sensitize drug resistant cancers in the clinic
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