2,040 research outputs found
Spectroscopy of the odd-odd fp-shell nucleus 52Sc from secondary fragmentation
The odd-odd fp-shell nucleus 52Sc was investigated using in-beam gamma-ray
spectroscopy following secondary fragmentation of a 55V and 57Cr cocktail beam.
Aside from the known gamma-ray transition at 674(5)keV, a new decay at
E_gamma=212(3) keV was observed. It is attributed to the depopulation of a
low-lying excited level. This new state is discussed in the framework of
shell-model calculations with the GXPF1, GXPF1A, and KB3G effective
interactions. These calculations are found to be fairly robust for the
low-lying level scheme of 52Sc irrespective of the choice of the effective
interaction. In addition, the frequency of spin values predicted by the shell
model is successfully modeled by a spin distribution formulated in a
statistical approach with an empirical, energy-independent spin-cutoff
parameter.Comment: accepted for publication in PR
One-neutron knockout in the vicinity of the N=32 sub-shell closure: 9Be(57Cr,56Cr+ gamma)X
The one-neutron knockout reaction 9Be(57Cr,56Cr + gamma)X has been measured
in inverse kinematics with an intermediate-energy beam. Cross sections to
individual states in 56Cr were partially untangled through the detection of the
characteristic gamma-ray transitions in coincidence with the reaction residues.
The experimental inclusive longitudinal momentum distribution and the yields to
individual states are compared to calculations that combine spectroscopic
factors from the full fp shell model and nucleon-removal cross sections
computed in a few-body eikonal approach.Comment: PRC, in pres
Cross-shell excitation in two-proton knockout: Structure of Ca
The two-proton knockout reaction Be(Ti,Ca) has
been studied at 72 MeV/nucleon. Besides the strong feeding of the Ca
ground state, the only other sizeable cross section proceeds to a 3 level
at 3.9 MeV. There is no measurable direct yield to the first excited 2
state at 2.6 MeV. The results illustrate the potential of such direct reactions
for exploring cross-shell proton excitations in neutron-rich nuclei and
confirms the doubly-magic nature of Ca
Mapping SERS in CB:Au Plasmonic Nanoaggregates
In order to optimize surface-enhanced Raman scattering (SERS) of noble metal nanostructures for enabling chemical identification of analyte molecules, careful design of nanoparticle structures must be considered. We spatially map the local SERS enhancements across individual micro-aggregates comprised of monodisperse nanoparticles separated by rigid monodisperse 0.9 nm gaps and show the influence of depositing these onto different underlying substrates. Experiments and simulations show that the gaps between neighbouring nanoparticles dominate the SERS enhancement far more than the gaps between nanoparticles and substrate
Affective iconic words benefit from additional soundâmeaning integration in the left amygdala
Recent studies have shown that a similarity between sound and meaning of a word (i.e., iconicity) can help more readily access the meaning of that word, but the neural mechanisms underlying this beneficial role of iconicity in semantic processing remain largely unknown. In an fMRI study, we focused on the affective domain and examined whether affective iconic words (e.g., high arousal in both sound and meaning) activate additional brain regions that integrate emotional information from different domains (i.e., sound and meaning). In line with our hypothesis, affective iconic words, compared to their nonâiconic counterparts, elicited additional BOLD responses in the left amygdala known for its role in multimodal representation of emotions. Functional connectivity analyses revealed that the observed amygdalar activity was modulated by an interaction of iconic condition and activations in two hubs representative for processing sound (left superior temporal gyrus) and meaning (left inferior frontal gyrus) of words. These results provide a neural explanation for the facilitative role of iconicity in language processing and indicate that language users are sensitive to the interaction between sound and meaning aspect of words, suggesting the existence of iconicity as a general property of human language
Revealing the electronic structure of a carbon nanotube carrying a supercurrent
Carbon nanotubes (CNTs) are not intrinsically superconducting but they can
carry a supercurrent when connected to superconducting electrodes. This
supercurrent is mainly transmitted by discrete entangled electron-hole states
confined to the nanotube, called Andreev Bound States (ABS). These states are a
key concept in mesoscopic superconductivity as they provide a universal
description of Josephson-like effects in quantum-coherent nanostructures (e.g.
molecules, nanowires, magnetic or normal metallic layers) connected to
superconducting leads. We report here the first tunneling spectroscopy of
individually resolved ABS, in a nanotube-superconductor device. Analyzing the
evolution of the ABS spectrum with a gate voltage, we show that the ABS arise
from the discrete electronic levels of the molecule and that they reveal
detailed information about the energies of these levels, their relative spin
orientation and the coupling to the leads. Such measurements hence constitute a
powerful new spectroscopic technique capable of elucidating the electronic
structure of CNT-based devices, including those with well-coupled leads. This
is relevant for conventional applications (e.g. superconducting or normal
transistors, SQUIDs) and quantum information processing (e.g. entangled
electron pairs generation, ABS-based qubits). Finally, our device is a new type
of dc-measurable SQUID
Non-linear electromagnetic response of graphene
It is shown that the massless energy spectrum of electrons and holes in
graphene leads to the strongly non-linear electromagnetic response of this
system. We predict that the graphene layer, irradiated by electromagnetic
waves, emits radiation at higher frequency harmonics and can work as a
frequency multiplier. The operating frequency of the graphene frequency
multiplier can lie in a broad range from microwaves to the infrared.Comment: 5 pages, 3 figure
Application of DEN refinement and automated model building to a difficult case of molecular-replacement phasing: the structure of a putative succinyl-diaminopimelate desuccinylase from Corynebacterium glutamicum.
Phasing by molecular replacement remains difficult for targets that are far from the search model or in situations where the crystal diffracts only weakly or to low resolution. Here, the process of determining and refining the structure of Cgl1109, a putative succinyl-diaminopimelate desuccinylase from Corynebacterium glutamicum, at âŒ3â
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resolution is described using a combination of homology modeling with MODELLER, molecular-replacement phasing with Phaser, deformable elastic network (DEN) refinement and automated model building using AutoBuild in a semi-automated fashion, followed by final refinement cycles with phenix.refine and Coot. This difficult molecular-replacement case illustrates the power of including DEN restraints derived from a starting model to guide the movements of the model during refinement. The resulting improved model phases provide better starting points for automated model building and produce more significant difference peaks in anomalous difference Fourier maps to locate anomalous scatterers than does standard refinement. This example also illustrates a current limitation of automated procedures that require manual adjustment of local sequence misalignments between the homology model and the target sequence
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