Spectroscopy of 26^{26}F

The structure of the weakly-bound $^{26}_{\;\;9}$F$_{17}$ odd-odd nucleus, produced from $^{27,28}$Na nuclei, has been investigated at GANIL by means of the in-beam $\gamma$-ray spectroscopy technique. A single $\gamma$-line is observed at 657(7) keV in $^{26}_{9}$F which has been ascribed to the decay of the excited J=$2^+$ state to the J=1$^+$ ground state. The possible presence of intruder negative parity states in $^{26}$F is also discussed.Comment: 3 pages, 1 figure, accepted for publication in Physical Review

Proton capture cross section of Sr isotopes and their importance for nucleosynthesis of proton-rich nuclides

The (p,$\gamma$) cross sections of three stable Sr isotopes have been measured in the astrophysically relevant energy range. These reactions are important for the $p$-process in stellar nucleosynthesis and, in addition, the reaction cross sections in the mass region up to 100 are also of importance concerning the $rp$-process associated with explosive hydrogen and helium burning. It is speculated that this $rp$-process could be responsible for a certain amount of $p$-nuclei in this mass region. The (p,$\gamma$) cross sections of $^{84,86,87}$Sr isotopes were determined using an activation technique. The measurements were carried out at the 5 MV Van de Graaff accelerator of the ATOMKI, Debrecen. The resulting cross sections are compared with the predictions of statistical model calculations. The predictions are in good agreement with the experimental results for $^{84}$Sr(p,$\gamma$)$^{85}$Y whereas the other two reactions exhibit differences that increase with mass number. The corresponding astrophysical reaction rates have also been computed.Comment: Phys. Rev. C in pres

Kondo Insulators Modeled by the One Dimensional Anderson Lattice: A Numerical Renormalization Group Study

In order to better understand Kondo insulators, we have studied both the symmetric and asymmetric Anderson lattices at half-filling in one dimension using the density matrix formulation of the numerical renormalization group. We have calculated the charge gap, spin gap and quasiparticle gap as a function of the repulsive interaction U using open boundary conditions for lattices as large as 24 sites. We find that the charge gap is larger than the spin gap for all U for both the symmetric and asymmetric cases. RKKY interactions are evident in the f-spin-f-spin correlation functions at large U in the symmetric case, but are suppressed in the asymmetric case as the f-level approaches the Fermi energy. This suppression can also be seen in the staggered susceptibility and it is consistent with neutron scattering measurements in CeNiSn.Comment: 32 pages, Latex file with Postcript figures

Geometric phase outside a Schwarzschild black hole and the Hawking effect

We study the Hawking effect in terms of the geometric phase acquired by a two-level atom as a result of coupling to vacuum fluctuations outside a Schwarzschild black hole in a gedanken experiment. We treat the atom in interaction with a bath of fluctuating quantized massless scalar fields as an open quantum system, whose dynamics is governed by a master equation obtained by tracing over the field degrees of freedom. The nonunitary effects of this system are examined by analyzing the geometric phase for the Boulware, Unruh and Hartle-Hawking vacua respectively. We find, for all the three cases, that the geometric phase of the atom turns out to be affected by the space-time curvature which backscatters the vacuum field modes. In both the Unruh and Hartle-Hawking vacua, the geometric phase exhibits similar behaviors as if there were thermal radiation at the Hawking temperature from the black hole. So, a measurement of the change of the geometric phase as opposed to that in a flat space-time can in principle reveal the existence of the Hawking radiation.Comment: 14 pages, no figures, a typo in the References corrected, version to appear in JHEP. arXiv admin note: text overlap with arXiv:1109.033

Influence of adding multiwalled carbon nanotubes on the adhesive strength of composite epoxy/sol–gel materials

The tensile shear strength of a composite epoxy/sol–gel system modified with different ratios of multiwall carbon nanotubes (MWCNTs) was evaluated using a mechanical testing machine. The experimental results showed that the shear strength increased when lower than ~0.07 wt% of MWCNTs were added in the composite solution. The increase of the shear strength was attributed to both the mechanical load transfer from the matrix to the MWCNTs and the high specific surface area of this material that increased the degree of crosslinking with other inorganic fillers in the formulation. However, a decrease in the adhesive shear strength was observed after more than ~0.07 wt% MWCNTs were added to the composite. The reason for this may be related to the high concentration of MWCNTs within the matrix leading to excessively high viscosity, dewetting of the substrate surfaces, and reduced bonding of MWCNTs with the matrix, thereby limiting the strength. SEM observation of the fracture surfaces for composite epoxy/sol–gel adhesive materials with 0.01 wt% MWCNTs showed a mixed interfacial/cohesive fracture mode. This fracture mode indicated strong links at the adhesive/substrate interface, and interaction between CNTs and the matrix was achieved; therefore, adhesion performance of the composite epoxy/sol–gel material to the substrate was improved. An increase of a strong peak related to the C–O bond at ~1733 cm-1 in the FTIR spectra was observed. This peak represented crosslinking between the CNT surface and the organosilica nanoparticles in the MWCNTs-doped composite adhesive. Raman spectroscopy was also used to identify MWCNTs within the adhesive material. The Raman spectra exhibit peaks at ~1275 cm-1 and in the range of ~1549–1590 cm-1. The former is the graphite G-band, while the latter is the diamond D-band. The D-band and G-band represent the C–C single bond and C=C double bond in carbon nanotubes, respectively

Direct observation of long-lived isomers in 212^{212}Bi

Long-lived isomers in 212Bi have been studied following 238U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into the GSI storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of 212Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring halflife >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognised, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer de-excitation studies.Comment: published in PRL 110, 12250

Neuronal circuitry for pain processing in the dorsal horn

Neurons in the spinal dorsal horn process sensory information, which is then transmitted to several brain regions, including those responsible for pain perception. The dorsal horn provides numerous potential targets for the development of novel analgesics and is thought to undergo changes that contribute to the exaggerated pain felt after nerve injury and inflammation. Despite its obvious importance, we still know little about the neuronal circuits that process sensory information, mainly because of the heterogeneity of the various neuronal components that make up these circuits. Recent studies have begun to shed light on the neuronal organization and circuitry of this complex region

Using jasmonates and salicylates to reduce losses within the fruit supply chain

The fresh produce industry is constantly growing, due to increasing consumer demand. The shelf-life of some fruit, however, is relatively short, limited by microbial contamination or visual, textural and nutritional quality loss. Thus, techniques for reducing undesired microbial contamination, spoilage and decay, as well as maintaining product’s visual, textural and nutritional quality are in high demand at all steps within the supply chain. The postharvest use of signalling molecules, i.e. jasmonates and salicylates seems to have unexplored potential. The focus of this review is on the effects of treatment with jasmonates and salicylates on the fresh produce quality, defined by decay incidence and severity, chilling injury, maintenance of texture, visual quality, taste and aroma, and nutritional content. Postharvest treatments with jasmonates and salicylates have the ability to reduce decay by increasing fruit resistance to diseases and reducing chilling injury in numerous products. These treatments also possess the ability to improve other quality characteristics, i.e. appearance, texture maintenance and nutritional content. Furthermore, they can easily be combined with other treatments, e.g. heat treatment, ultrasound treatment. A good understanding of all the benefits and limitations related to the postharvest use of jasmonates and salicylates is needed, and relevant information has been reviewed in this paper

Review of risk factors for human echinococcosis prevalence on the Qinghai-Tibet Plateau, China: a prospective for control options

Objective: Echinococcosis is a major parasitic zoonosis of public health importance in western China. In 2004, the Chinese Ministry of Health estimated that 380,000 people had the disease in the region. The Qinghai-Tibet Plateau is highly co-endemic with both alveolar echinococcosis (AE) and cystic echinococcosis (CE). In the past years, the Chinese government has been increasing the financial support to control the diseases in this region. Therefore, it is very important to identify the significant risk factors of the diseases by reviewing studies done in the region in the past decade to help policymakers design appropriate control strategies. Review: Selection criteria for which literature to review were firstly defined. Medline, CNKI (China National Knowledge Infrastructure), and Google Scholar were systematically searched for literature published between January 2000 and July 2011. Significant risk factors found by single factor and/or multiple factors analysis were listed, counted, and summarized. Literature was examined to check the comparability of the data; age and sex specific prevalence with same data structures were merged and used for further analysis. A variety of assumed social, economical, behavioral, and ecological risk factors were studied on the Plateau. Those most at risk were Tibetan herdsmen, the old and female in particular. By analyzing merged comparable data, it was found that females had a significant higher prevalence, and a positive linearity relationship existed between echinococcosis prevalence and increasing age. In terms of behavioral risk factors, playing with dogs was mostly correlated with CE and/or AE prevalence. In terms of hygiene, employing ground water as the drinking water source was significantly correlated with CE and AE prevalence. For definitive hosts, dog related factors were most frequently identified with prevalence of CE or/and AE; fox was a potential risk factor for AE prevalence only. Overgrazing and deforestation were significant for AE prevalence only. Conclusion: Tibetan herdsmen communities were at the highest risk of echinococcosis prevalence and should be the focus of echinococcosis control. Deworming both owned and stray dogs should be a major measure for controlling echinococcosis; treatment of wild definitive hosts should also be considered for AE endemic areas. Health education activities should be in concert with the local people's education backgrounds and languages in order to be able to improve behaviors. Further researches are needed to clarify the importance of wild hosts for AE/CE prevalence, the extent and range of the impacts of ecologic changes (overgrazing and deforestation) on the AE prevalence, and risk factors in Tibet