Results 1 - 10 of 280
Results 1 - 10 of 280. Search took: 0.022 seconds
|Sort by: date | relevance|
[en] The High Rigidity Spectrometer (HRS) is being developed to make optimum use of the fast rare-isotope beams that will be available at the Facility for Rare-Isotope Beams (FRIB) and will be the key experimental tool to study the most exotic, neutron-rich nuclei. The HRS will accommodate detector systems for charged particles, neutrons, and gamma rays. This will enable coincidence measurements of reaction products that stem from a variety of reactions such as knockout, breakup, charge exchange or Coulomb excitation. First-order ion optical studies are under way and this paper will offer some details on the current design ideas.
[en] The development of NMR methods for the characterization of structure and dynamics in mesophase composite systems was originally proposed in this LDRD. Mesophase systems are organic/inorganic hybrid materials whose size and motional properties span the definition of liquids and solids, such as highly viscous gels or colloidal suspensions. They are often composite, ill defined, macromolecular structures that prove difficult to characterize. Mesophase materials are of broad scientific and programmatic interest and include composite load bearing foams, aerogels, optical coatings, silicate oligomers, porous heterogeneous catalysts, and nanostructured materials such as semiconductor quantum dot superlattices. Since mesophased materials and precursors generally lack long-range order they have proven to be difficult to characterize beyond local, shortrange order. NMR methods are optimal for such a task since NMR observables are sensitive to wide ranges of length (0-30(angstrom)) and time (10-9-100sec) scales. We have developed a suit of NMR methods to measure local, intermediate, and long range structure in a series of mesophase systems and have constructed correlations between NMR observables and molecular size, topology, and network structure. The goal of this research was the development of a strong LLNL capability in the characterization of mesophased materials by NMR spectroscopy that will lead to a capability in rational synthesis of such materials and a fundamental understanding of their structure-property relationships. We demonstrate our progress towards attaining this goal by presenting NMR results on four mesophased model systems
[en] The ground state of proton-unbound 11N is thought to consist of a broad s-wave state, but this has not been experimentally verified. Due to recent interest in this system, the authors have studied 11N using the neutron-stripping reaction 9Be(12N,11N) at E(12N)= 40 MeV/A. The radioactive 12N beam was produced by projectile fragmentation of 80 MeV/A 16O using the NSCL A1200 fragment separator. Coincident proton and 10C particles from the inflight decay of 11N were detected and the decay energy of the composite system was determined from the measured energies and angles. Results from this study and model calculations will be present
[en] High energy γ rays were measured in coincidence with inelastically scattered α particles at beam energies of 40 MeV/nucleon (on 120Sn and 20Pb targets) and 50 MeV/nucleon (on 120Sn). High energy target excitations were observed and the giant dipole resonance (GDR) built on these excited states was measured by its γ ray decay. The width of the GDR increases with excitation energy. This increase is not as strong as in the corresponding fusion-evaporation reactions. 26 refs
[en] This paper discusses how clean technologies can get returns from greenhouse gases credits. Businesses recognize that climate change opportunity is bigger than information technology. Clean technologies and climate change will transform the economy. Clean technologies will bring business opportunities, revitalize industry and the economy, bring jobs and increase exports.
[en] This paper discusses the program to train and develop a community of experts with the highest standards of professional practice in measuring, accounting, auditing and managing greenhouse gas emissions. Experts should operate with a common code of conduct and ethics, and provide the high levels of professional competency.
[en] Magnetic resonance imaging (MRI) with a continuously moving table (CMT) represents a novel method allowing for the seamless acquisition of an extended field-of-view in the z-direction. One option to realize CMT MRI from a technical point of view is based on very fast sequences like echo planar imaging (EPI). Consequently, table translation for signal sampling and image reconstruction can be neglected. The acquisition of different contrasts, however, necessitates table motion correction, either during acquisition or via post-processing. First clinical studies applying fast steady-state imaging already yielded promising results with respect to metastasis detection. Nevertheless, additional equipment has to be installed for table motion and position tracking. In contrast, the subsequently developed sliding multislice (SMS) technique can be implemented without any additional hardware. In clinical studies, the achievable image quality corresponds to stationary sequences. Additionally, the use of SMS for the detection of pulmonary and abdominal metastases appears to be comparable to computed tomography (CT). Due to the relatively short examination times, CMT MRI can be integrated into highly specialized stationary imaging protocols, thus increasing the possibility to combine local staging with thoracoabdominal metastasis screening within one examination. New contrasts like diffusion-weighted imaging (DWI) or Dixon techniques as well as improved workflow including breathing motion compensation and intuitive scout acquisition have already been proposed and will further expand the clinical applications of this technique. (orig.)
[en] MRI is accepted as one of the major diagnostic tools for the detection of anorectal fistulas and abscesses. Noninvasiveness and high accuracy are advantageous hallmarks of this technique. In general, the purpose of imaging anal fistulas is to reduce the risk of recurrence, incontinence and non-healing. To achieve these goals, the applied method must provide the proctologist with detailed information. In this context, MRI acts as a guide for surgeons to accurately plan fistula operations. Another aspect is the follow-up of conservatively treated patients with fistulizing Crohn's disease. In 2000, subtraction MR fistulography was introduced as new imaging technique. This review provides an overview of the entire spectrum of diagnostic modalities for anorectal fistulas with emphasis on subtraction MR fistulography. (orig.)
[en] Many metallic superlattices are known to exhibit dramatic anomalous elastic properties as a function of modulation wavelength. All measurements to date measure either a shear modulus or a longitudinal modulus in the superlattice plane. Here they present a method which also probes longitudinal elastic behavior perpendicular to the layers using a nano-hardness tester. In this method, a diamond tip is indented into the material and both the indentation depth and applied force are constantly monitored during loading and unloading. The elastic properties are extracted from the unloading part of the force versus displacement curve. Contrary to the anomaly found in a shear modulus, no anomaly in Young's modulus was found in the present study on Mo/Ni superlattices