Half-life of the doubly magic r-process nucleus 78Ni

Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r process). 78Ni is the only doubly magic nucleus that is also an important waiting point in the r process, and serves as a major bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been experimentally deduced for the first time at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University, and was found to be 110(+100)(-60) ms. In the same experiment, a first half-life was deduced for 77Ni of 128(+27)(-33) ms, and more precise half-lives were deduced for 75Ni and 76Ni of 344(+20)(-24) ms and 238(+15)(-18) ms, respectively.     

The rotator cuff tear: MR evaluation

Magnetic resonance imaging (MRI) is evolving as a particularly valuable diagnostic procedure in the evaluation of musculoskeletal pathology. To assess the role of MRI as applied to the shoulder, we examined eight normal volunteers, six patients with seven arthrographically proven rotator cuff tears and two patients with impingement symptomatology but with negative double contrast conventional and computed tomographic arthrography. The studies were performed on a 1-Tesla magnet operating at 0.5 Tesla. Coronal T1-weighted images were obtained in all cases and coronal spin density and T2-weighted pulse sequences were employed in two cases. In the normal individuals, the supraspinatus muscle and tendon could be consistently demonstrated. The proximal humeral marrow, the superior glenoid labrum, and the acromioclavicular joint could also be examined. Findings in patients with rotator cuff tears included: (1) hypointense gap within the supraspinatus muscle-tendon complex on T1-weighted sequences, (2) absence of a demonstrable supraspinatus tendon with narrowing of the subacromial space secondary to elevation of the humeral head, and (3) increased signal within the supraspinatus tendon on T2-weighted images. In the patients with impingement syndrome and negative arthrography, MR demonstrated elevation of the supraspinatus tendon with subacromial impingement in one case and a normal supraspinatus tendon in the other. Impingement on the coracoacroaminal arch causes progressive fibrosis, atrophy, and eventual tear of the rotator cuff. The potential applications of MRI relative to the shoulder include assessment of tendon retraction in patients with supraspinatus tears and noninvasive evaluation of patients with impingement syndrome, permitting etiologic determinations, hopefully before irreversible tendon injury has occurred.     

Molecular weight and long-chain branching distributions of some polybutadienes and styrene–butadiene rubbers. Determination by GPC and dilute solution viscometry

A method described for the determination of molecular weight and long-chain branching distributions of polymers requires no prior knowledge of the functional relation between branching frequency and molecular weight. It is based on preparative fractionation and viscometric and gel-permeation chromatographic measurements on both fractions and whole polymer. The technique is applied to several polybutadienes and butadiene-styrene copolymers differing widely in method of synthesis and pattern of long-chain branching.     

Trends in bioanalytical methods for the determination and quantification of club drugs: 2000-2010

The term 'club drug' can be loosely defined as any substance used to enhance social settings. Such drugs are commonly found at raves or similar all-night dance parties and include methamphetamine, 3,4-methylenedioxymethamphetamine, gamma-hydroxybutyrate (GHB), ketamine (KET), and flunitrazepam (FLU). These drugs have potentially dangerous side effects including hallucinations, paranoia, amnesia and hyperthermia. In addition, GHB, KET and FLU are considered predatory drugs due to their roles in drug-facilitated sexual assault. Forensic and regulatory agencies routinely have the need for determination and accurate quantification of these drugs in biological fluids, especially in cases of mortality or criminal investigations. This review presents the chromatographic and spectroscopic methods published for such analyses over the last decade, including sample preparation techniques and validation data.     

Identification of “Known Unknowns” Utilizing Accurate Mass Data and Chemical Abstracts Service Databases

In many cases, an unknown to an investigator is actually known in the chemical literature. We refer to these types of compounds as “known unknowns.” Chemical Abstracts Service (CAS) Registry is a particularly good source of these substances as it contains over 54 million entries. Accurate mass measurements can be used to query the CAS Registry by either molecular formulae or average molecular weights. Searching the database by the web-based version of SciFinder is the preferred approach when molecular formulae are available. However, if a definitive molecular formula cannot be ascertained, searching the database with STN Express by average molecular weights is a viable alternative. The results from either approach are refined by employing the number of associated references or minimal sample history as orthogonal filters. These approaches were shown to be successful in identifying “known unknowns” noted in LC-MS and even GC-MS analyses in our laboratory. In addition, they were demonstrated in the identification of a variety of compounds of interest to others.     

Field testing of collection and measurement of radioxenon for the Comprehensive Test Ban Treaty

Pacific Northwest National Laboratory, with guidance and support from the U.S. Department of Energy's NN-20 Comprehensive Test Ban Treaty (CTBT) Research and Development program, has developed and demonstrated a fully automatic sampler-analyzer (ARSA) for the collection and quantitative measurement of the four xenon radionuclides,^131mXe (11.9 d),^133mXe (2.19 d),¹³³Xe (5.24 d), and¹³⁵Xe (9.10 h), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a CTBT, and may have applications in stack monitoring and other areas where xenon radionuclides are present. The activity ratios between certain of these radionuclides permit discrimination between radioxenon originating from nuclear detonations and that from nuclear reactor operations, nuclear fuel reprocessing, or from medical isotope production and usage. With the ARSA system, xenon is continuously and automatically separated from the atmosphere at flow rates of about 100 lpm by sorption-bed techniques. Samples collected in 8 hours are automatically analyzed by electron-photon coincidence spectrometry to provide detection sensitivities as low as 100 μBq/m³ of air. This sensitivity is about 10-fold better than achieved with reported laboratory-based procedures¹ for the short time collection intervals of interest. Gamma-ray energy spectra and gas analysis data are automatically collected.