683 research outputs found

    Interhemispheric differences in the HF radar signature of the cusp region: A review through the study of a case example

    Get PDF
    This paper aims to provide a review of our understanding of the HF radar signatures of the cusp and transient magnetopause reconnection phenomena through the study of a case example. Two Super DARN radars observe the conjugate cusp regions during an interval of southward IMF. These observations allow us to determine several parameters relating to the electrodynamics of the magnetopause reconnection process, including the mean reconnection voltage and the reconnection electric fields and X-line lengths in the two hemispheres. In addition, we identify several differences between the radar and flow signatures observed in the two hemispheres, specifically that flux transfer event signatures are observed in the Northern Hemisphere but not the Southern Hemisphere, and that the azimuthal component of the flow excited by reconnection is much greater in the Southern Hemisphere than in the Northern Hemisphere. We finish our discussion by identifying remaining questions regarding the interpretation of HF radar observations of the cusp

    Evidence for partial quenching of orbital angular momentum upon complex formation in the infrared spectrum of OH-acetylene

    Get PDF
    The entrance channel leading to the addition reaction between the hydroxyl radical and acetylene has been examined by spectroscopic characterization of the asymmetric CH stretching band of the π-hydrogen bonded OH-acetylene reactant complex. The infrared action spectrum observed at 3278.6 cm−1 (origin) consists of seven peaks of various intensities and widths, and is very different from those previously reported for closed-shell HF/HCl-acetylene complexes. The unusual spectrum arises from a partial quenching of the OH orbital angular momentum in the complex, which in turn is caused by a significant splitting of the OH monomer orbital degeneracy into 2A′ and 2A″ electronic states. The magnitude of the 2A′−2A″ splitting as well as the A rotational constant for the OH-acetylene complex are determined from the analysis of this b-type infrared band. The most populated OH product rotational state, jOH = 9/2, is consistent with intramolecular vibrational energy transfer to the ν2 C≡C stretching mode of the departing acetylene fragment. The lifting of the OH orbital degeneracy and partial quenching of its electronic orbital angular momentum indicate that the electronic changes accompanying the evolution of reactants into products have begun to occur in the reactant complex

    Infrared spectrum and stability of a π-type hydrogen-bonded complex between the OH and C2H2 reactants

    Get PDF
    A hydrogen-bonded complex between the hydroxyl radical and acetylene has been stabilized in the reactant channel well leading to the addition reaction and characterized by infrared action spectroscopy in the OH overtone region. Analysis of the rotational band structure associated with the a-type transition observed at 6885.53(1) cm−1 (origin) reveals a T-shaped structure with a 3.327(5) Å separation between the centers of mass of the monomer constituents. The OH (v = 1) product states populated following vibrational predissociation show that dissociation proceeds by two mechanisms: intramolecular vibrational to rotational energy transfer and intermolecular vibrational energy transfer. The highest observed OH product state establishes an upper limit of 956 cm−1 for the stability of the π-type hydrogen-bonded complex. The experimental results are in good accord with the intermolecular distance and well depth at the T-shaped minimum energy configuration obtained from complementary ab initio calculations, which were carried out at the restricted coupled cluster singles, doubles, noniterative triples level of theory with extrapolation to the complete basis set limit

    Condensed and Updated Version of the Systematic Approach Meteorological Knowledge Base Southern Hemisphere

    Get PDF
    The meteorological knowledge base for the Systematic and Integrated Approach to Tropical Cyclone Track Forecasting proposed by Carr and Elsberry has evolved as additional research has been completed. As this Systematic Approach has been applied in the Southern Hemisphere, a number of conceptual models have been refined and new terminology has been adopted to reflect global applicability. As a knowledge-based expert system is being developed, it was convenient to condense and update the meteorological knowledge base for the Southern Hemisphere. Thus, the material is presented with text on the left page and the corresponding figure on the facing page as it will appear on the computer screen.Prepared for: Office of Naval Research, Code 322MM, Arlington, VA 22217 SPAWARSYSCOM, Code PMW 185, San Diego, CA 92110http://archive.org/details/condensedupdated00carrSponsored by: Office of Naval Research and SPAWARSYSCOM.Approved for public release; distribution is unlimited

    An engineered Tetrahymena tRNA(Gln) for in vivo incorporation of unnatural amino acids into proteins by nonsense suppression

    Get PDF
    A new tRNA, THG73, has been designed and evaluated as a vehicle for incorporating unnatural amino acids site-specifically into proteins expressed in vivo using the stop codon suppression technique. The construct is a modification of tRNAGln(CUA) from Tetrahymena thermophila, which naturally recognizes the stop codon UAG. Using electrophysiological studies of mutations at several sites of the nicotinic acetylcholine receptor, it is established that THG73 represents a major improvement over previous nonsense suppressors both in terms of efficiency and fidelity of unnatural amino acid incorporation. Compared with a previous tRNA used for in vivo suppression, THG73 is as much as 100-fold less likely to be acylated by endogenous synthetases of the Xenopus oocyte. This effectively eliminates a major concern of the in vivo suppression methodology, the undesirable incorporation of natural amino acids at the suppression site. In addition, THG73 is 4-10-fold more efficient at incorporating unnatural amino acids in the oocyte system. Taken together, these two advances should greatly expand the range of applicability of the in vivo nonsense suppression methodology

    Observations of large flow shears around small-scale auroral beads observed at substorm onset

    Get PDF
    第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月16日(水) 統計数理研究所 3階リフレッシュフロ

    Identifying acne treatment uncertainties via a James Lind Alliance Priority Setting Partnership

    Get PDF
    Objectives: The Acne Priority Setting Partnership (PSP) was set up to identify and rank treatment uncertainties by bringing together people with acne, and professionals providing care within and beyond the National Health Service (NHS). Setting: The UK with international participation. Participants: Teenagers and adults with acne, parents, partners, nurses, clinicians, pharmacists, private practitioners. Methods: Treatment uncertainties were collected via separate online harvesting surveys, embedded within the PSP website, for patients and professionals. A wide variety of approaches were used to promote the surveys to stakeholder groups with a particular emphasis on teenagers and young adults. Survey submissions were collated using keywords and verified as uncertainties by appraising existing evidence. The 30 most popular themes were ranked via weighted scores from an online vote. At a priority setting workshop, patients and professionals discussed the 18 highest-scoring questions from the vote, and reached consensus on the top 10. Results: In the harvesting survey, 2310 people, including 652 professionals and 1456 patients (58% aged 24 y or younger), made submissions containing at least one research question. After checking for relevance and rephrasing, a total of 6255 questions were collated into themes. Valid votes ranking the 30 most common themes were obtained from 2807 participants. The top 10 uncertainties prioritised at the workshop were largely focused on management strategies, optimum use of common prescription medications and the role of nondrug based interventions. More female than male patients took part in the harvesting surveys and vote. A wider range of uncertainties were provided by patients compared to professionals. Conclusions: Engaging teenagers and young adults in priority setting is achievable using a variety of promotional methods. The top 10 uncertainties reveal an extensive knowledge gap about widely used interventions and the relative merits of drug versus non-drug based treatments in acne management

    Assembly of α4β2 Nicotinic Acetylcholine Receptors Assessed with Functional Fluorescently Labeled Subunits: Effects of Localization, Trafficking, and Nicotine-Induced Upregulation in Clonal Mammalian Cells and in Cultured Midbrain Neurons

    Get PDF
    Fura-2 recording of Ca^(2+) influx was used to show that incubation in 1 μM nicotine (2-6 d) upregulates several pharmacological components of acetylcholine (ACh) responses in ventral midbrain cultures, including a MLA-resistant, DHβE-sensitive component that presumably corresponds to α4β2 receptors. To study changes in α4β2 receptor levels and assembly during this upregulation, we incorporated yellow and cyan fluorescent proteins (YFPs and CFPs) into the α4 or β2 M3-M4 intracellular loops, and these subunits were coexpressed in human embryonic kidney (HEK) 293T cells and cultured ventral midbrain neurons. The fluorescent receptors resembled wild-type receptors in maximal responses to ACh, dose-response relations, ACh-induced Ca^(2+) influx, and somatic and dendritic distribution. Transfected midbrain neurons that were exposed to nicotine (1 d) displayed greater levels of fluorescent α4 and β2 nicotinic ACh receptor (nAChR) subunits. As expected from the hetero-multimeric nature of α4β2 receptors, coexpression of the α4-YFP and β2-CFP subunits resulted in robust fluorescence resonance energy transfer (FRET), with a FRET efficiency of 22%. In midbrain neurons, dendritic α4β2 nAChRs displayed greater FRET than receptors inside the soma, and in HEK293T cells, a similar increase was noted for receptors that were translocated to the surface during PKC stimulation. When cultured transfected midbrain neurons were incubated in 1 μMnicotine, there was increased FRET in the cell body, denoting increased assembly of α4β2 receptors. Thus, changes in α4β2 receptor assembly play a role in the regulation of α4β2 levels and responses in both clonal cell lines and midbrain neurons, and the regulation may result from Ca^(2+)-stimulated pathways

    Photodissociation of the OD radical at 226 and 243 nm

    Get PDF
    The photodissociation dynamics of state selected OD radicals has been examined at 243 and 226 nm using velocity map imaging to probe the angle–speed distributions of theD(2S) and O(3P2) products. Both experiment and complementary first principle calculations demonstrate that photodissociation occurs by promotion of OD from high vibrational levels of the ground X 2Π state to the repulsive 1 2Σ− state
    corecore