Raman satellites in optical scattering from a laser-ablated Mg plume

Raman satellites have been observed in the scattering of a Nd:YAG laser (532 nm) from a laser-ablated Mg plasma plume. We identify them as originating from transitions between the fine-structure components of the metastable 3s3p P-3(0,1,2) level of Mg. We have calculated the cross sections for Raman and Rayleigh scattering from the metastable state. Comparison of the expected ratio of the satellites to the Rayleigh peak indicates the changing population fraction of the metastable states in the plume.

Functionalised ionic liquids: synthesis of ionic liquids with tethered basic groups and their use in Heck and Knoevenagel reactions

A simple and efficient synthesis of a novel series of ionic liquids bearing nucleophilic (Me2N) and non-nucleophilic base ((Pr2N)-Pr-i) functionalities is described. The non-nucleophilic base functionality resembles the structure of the Hunig's base (N, N-diisopropylethylamine), which has been used widely in organic synthesis. A qualitative measure of the basicity of these ionic liquids is presented by utilising their interaction with universal indicator. The basicity of these ionic liquids was found to be dependent on the amine tether and choice of linker between the two nitrogen centres. The relative base strength of these ionic liquids was also probed by using them as catalysts in the Heck and Knoevenagel reactions.

Examination of the Silver Colloid Binding Behavior of Disulfide-Tethered Bipyridine Ligands and Their fac-Tricarbonylrhenium(I) Complexes

The syntheses of 2,2'-bipyridin-5-ylmethyl-5-(1,2-dithiolan-3-yl)pentanoate (L1) and N-(2,2'-bipyridin-5-ylmethyl)-5-(1,2-dithiolan-3-yl)pentanamide (L2) and their neutral fac carbonylrhenium(I) complexes [Re(L1)(CO)(3)Br] and [Re(L2)(CO)(3)Br] are reported. The. electronic absorption and emission spectra of the complexes are similar to the spectrum of the reference compound [Re(bipy)(CO)(3)Br] and correlate well with the density functional theory calculations undertaken. The surface-enhanced Raman spectroscopy (SERS) spectra (excited at both 532 and 785 nm) of the ligands and complexes were examined and compared to the spectrum of ethyl 5-(1,2-dithiolan-3-yl)pentanoate (L3), revealing that there is very little contribution to the spectra of these species from the dithiolated alkyl chains. The spectra are dominated by the characteristic peaks of a metalated 2,2'-bipyridyl group,arising from the silver colloid/ion complexation, and the rhenium center. The rhenium complexes show weak SERS bands related to the CO stretches and a broad band at 510 cm(-1) assigned to Re-CO stretching. Concentration dependent studies, measured by the relative intensity of several assigned peaks, indicate that, as the surface coverage increases, the bipyridine moiety lifts off the surface In the case of L1 and L2, this gives rise to complexes with silver at low concentration, enhancing the signals observed, while for the tricarbonylbromorhenium complexes of these ligands, the presence of the disulfide tether allows an enhancement in the limits of detection of these surface-borne species of 20 times in the case of [ReL2(CO)(3)Br] over [Re(bipy)(CO)(3)Br].

Specific role of neuronal nitric-oxide synthase when tethered to the plasma membrane calcium pump in regulating the beta-adrenergic signal in the myocardium

The cardiac neuronal nitric-oxide synthase (nNOS) has been described as a modulator of cardiac contractility. We have demonstrated previously that isoform 4b of the sarcolemmal calcium pump (PMCA4b) binds to nNOS in the heart and that this complex regulates beta-adrenergic signal transmission in vivo. Here, we investigated whether the nNOS-PMCA4b complex serves as a specific signaling modulator in the heart. PMCA4b transgenic mice (PMCA4b-TG) showed a significant reduction in nNOS and total NOS activities as well as in cGMP levels in the heart compared with their wild type (WT) littermates. In contrast, PMCA4b-TG hearts showed an elevation in cAMP levels compared with the WT. Adult cardiomyocytes isolated from PMCA4b-TG mice demonstrated a 3-fold increase in Ser(16) phospholamban (PLB) phosphorylation as well as Ser(22) and Ser(23) cardiac troponin I (cTnI) phosphorylation at base line compared with the WT. In addition, the relative induction of PLB phosphorylation and cTnI phosphorylation following isoproterenol treatment was severely reduced in PMCA4b-TG myocytes, explaining the blunted physiological response to the beta-adrenergic stimulation. In keeping with the data from the transgenic animals, neonatal rat cardiomyocytes overexpressing PMCA4b showed a significant reduction in nitric oxide and cGMP levels. This was accompanied by an increase in cAMP levels, which led to an increase in both PLB and cTnI phosphorylation at base line. Elevated cAMP levels were likely due to the modulation of cardiac phosphodiesterase, which determined the balance between cGMP and cAMP following PMCA4b overexpression. In conclusion, these results showed that the nNOS-PMCA4b complex regulates contractility via cAMP and phosphorylation of both PLB and cTnI.

Emission-line ratios for [N II] in gaseous nebulae and a comparison between theory and observation

R-matrix calculations of electron impact excitation rates among the 2s(2)2p(2) P-3, D-1, S-1, and 2s2p(3) S-5 levels of N II are presented. These results are used in conjunction with other recent calculations of electron impact excitation rates and Einstein A-coefficients for N II to derive the emission-line ratio: ratio diagrams and where (R-1, R-2) (R-1, R-3), where R-1 = I(5756.2 Angstrom)/I(6549.9 + 6585.2 Angstrom), R-2 = I(2143.5 Angstrom)/I(6549.9 + 6585.2 Angstrom), and R-3 = I(2139.7 Angstrom)/I(6549.9 + 658.2 Angstrom), for a range of electron temperatures (T-e = 5000-20,000 K) and electron densities (N-e = 10(2)-10(7) cm(-3)) appropriate to gaseous nebulae. These diagrams should, in principle, allow the simultaneous determination of T-e and N-e from measurements of the [N II] lines in a spectrum. Plasma parameters deduced for a sample of gaseous nebulae, using observational data obtained from ground-based telescopes plus the International Ultraviolet Explorer and Hubble Space Telescope satellites, are found to show generally excellent internal consistency and to be in good agreement with the values of T-e and N-e estimated from other line ratios. These results provide observational support for the accuracy of the theoretical ratios and hence the atomic data adopted in their derivation. Theoretical ratios are also presented for the infrared line pair R-4 = I(122 mum)/I(205 mum), and the usefulness of R-4 as an electron density diagnostic is briefly discussed.

X-ray emission from charge exchange of highly-charged ions in atoms and molecules

Charge exchange followed by radiative stabilization are the main processes responsible for the recent observations of X-ray emission from comets in their approach to the Sun. A new apparatus was constructed at JPL to measure, in collisions of HCIs with atoms and molecules, (a) absolute cross sections for single and multiple charge exchange, and (b) normalized X-ray emission cross sections. The ions are produced by the JPL HCI Facility and passed through a neutral-gas target cell. The product charge states are analyzed by a retarding potential difference technique. Results are made absolute by measuring target pressure, and incident and product ion currents. X-rays emitted from the product ions are detected with a Ge solid-state detector having a resolution of approximately 100 eV. X-ray astronomy has taken major steps forward with the recent launch of the high-resolution satellites Chandra and Newton. The cross sections reported herein are essential for the development of the solar wind comet interaction models inspired by these observations.

Synthesis of Piano Stool Complexes Employing the Pentafluorophenyl Substituted Diphosphine (C6F5)2PCH2P(C6F5)2 and the Effect of Phosphine Modifiers on Hydrogen Transfer Catalysis.

Ruthenium, rhodium, and iridium piano stool complexes of the pentafluorophenyl-substituted diphosphine (C6F5)2PCH2P(C6F5)2 (2) have been prepared and structurally characterized by single-crystal X-ray diffraction. The Cp-P tethered complex [{(C5Me4CH2C6F4(C6F5)CH2P(C6F5)2}RhCl2] (9), in which only one phosphorus is coordinated to the rhodium, was prepared by thermolysis of a slurry of [Cp*RhCl(-Cl)]2 and 2 and was structurally characterized by single-crystal X-ray diffraction. The tethering occurs by intramolecular dehydrofluorinative coupling of the pentamethylcyclopentadienyl ligand and P,P-coordinated 2. The geometric changes that occur on tethering force dissociation of one of the phosphorus atoms. The effects of introducing phosphine ligands to the coordination sphere of piano stool hydrogen transfer catalysts have been studied. The complexes of fluorinated phosphine complexes are found to transfer hydrogen at rates that compare favorably with leading catalysts, particularly when the phosphine and cyclopentadienyl functionalities are tethered. The highly chelating Cp-PP complex [(C5Me4CH2-2-C5F3N-4-PPhCH2CH2PPh2)RhCl]BF4 (1) was found to outperform all other complexes tested. The mechanism of hydrogen transfer catalyzed by piano stool phosphine complexes is discussed with reference to the trends in activity observed.

Optical Thomson scatter from laser-ablated plumes

We have obtained density and temperature informations on an expanding KrF laser-ablated magnesium plume via optical Thomson scatter with a frequency doubled Nd:YAG laser. The electron temperature was found to decay with the expected Te t-1 dependence. However, we have found the electron density to have a time dependence ne t-4.95 which can be explained by strong recombination processes. We also observed atomic Raman satellites originating from transitions between the different angular momentum levels of the metastable 3P0 term in Mg I.

Supported and liquid phase task specific ionic liquids for base catalysed Knoevenagel reactions

A series of Hunig's base tethered ammonium ionic liquids have been used to catalyse the Knoevenagel condensation of aldehydes/ketones with malononitrile and ethyl cyanoacetate. The reactions were performed under homogeneous and under biphasic, liquid-liquid and liquid-silica supported ionic liquid, conditions with the biphasic systems employing cyclohexene as the second phase. By increasing the distance between the ammonium head group and Hunig's base the activity of the catalyst was found to increase. Higher activity, in general, was found under homogeneous reaction conditions; however, the recyclability of the catalyst was improved by supporting the BIL under biphasic conditions. (c) 2007 Elsevier B.V. All rights reserved.

A Concise Approach to a Gelsemine Core Structure using an Oxygen to Carbon Bridge Swapping Strategy

A tricyclic core structure related to gelsemine was synthesized from an oxabicyclo[3.2.1]octanone by a three-step bridge swapping strategy involving elimination of the bridging ether oxygen and intramolecular Michael addition of a tethered cyanoacetamide unit.

On the function of the internal cavity of histone deacetylase protein 8: R37 is a crucial residue for catalysis

Biochemical studies reveal that a conserved arginine residue (R37) at the centre of the 14 angstrom internal cavity of histone deacetylase (HDAC) 8 is important for catalysis and acetate affinity. Computational studies indicate that R37 forms multiple hydrogen bonding interactions with the backbone carbonyl oxygen atoms of two conserved glycine residues, G303 and G305, resulting in a 'closed' form of the channel. One possible rationale for these data is that water or product (acetate) transit through the catalytically crucial internal channel of HDAC8 is regulated by a gating interaction between G139 and G303 tethered in position by the conserved R37. (C) 2011 Elsevier Ltd. All rights reserved.

Biosynthetic Chlorination of the Piperazate Residue in Kutzneride Biosynthesis by KthP

Kutznerides 2 and 8 of the cyclic hexadepsipeptide family of antifungal natural products from the soil actinomycete Kutzneria sp. 744 contain two sets of chlorinated residues, a 6,7-dichlorohexahydropyrroloindole moiety derived from dichlorotryptophan and a 5-chloropiperazate moiety, as well as a methylcyclopropylglycine residue that may arise from isoleucine via a cryptic chlorination pathway. Previous studies identified KtzD, KtzQ and KtzR as three halogenases in the kutzneride pathway but left no candidate for installing the CS chlorine on piperazate. On the basis of analysis of the complete genome sequence of Kutzneria, we now identify a fourth halogenase in the pathway whose gene is separated from the defined kutzneride cluster by 12 open reading frames. KthP (kutzneride halogenase for piperazate) is a mononuclear nonheme iron halogenase that acts on the piperazyl ring tethered by a thioester linkage to the holo forms of thiolation domains. MS analysis of the protein-bound product confirmed chlorination of the piperazate framework from the (3S)- but not the (3R)-piperazyl-S-pantetheinyl thiolation proteins. After thioesterase-mediated release, nuclear magnetic resonance was used to assign the free imino acid as (3S,5S)-5-chloropiperazate, distinct from the 3S,5R stereoisomer reported in the mature kutznerides. These results demonstrate that a fourth halogenase, KthP, is active in the kutzneride biosynthetic pathway and suggest further processing of the (3S,5S)-5-chloropiperazate during subsequent incorporation into the kutzneride depsipeptide frameworks.

Thomson Scattering as a Diagnostic of Second-Harmonic Nd:YAG-Laser-Ablated Mg Plasma Plume

Thomson scattering is one of the most powerful diagnostic tools for plasma characterization, and it has been applied to a variety of plasmas. It is a nonintrusive technique, and the interpretation of the signal is relatively simple. However, this method has not been widely applied to low-temperature laser-ablated plasmas. Raman satellites have been observed in the scattering spectrum from a Mg laser-ablated plasma, giving this diagnostic the potential to be also used in density quantification of metastable states in plasmas.

Finite Element Application to Analysis, Testing, and Manufacturing of Satellite Structures

Designing satellite structures poses an ongoing challenge as the interaction between analysis, experimental testing, and manufacturing phases is underdeveloped. Finite Element Analysis for Satellite Structures: Applications to Their Design, Manufacture and Testing explains the theoretical and practical knowledge needed to perform design of satellite structures. By layering detailed practical discussions with fully developed examples, Finite Element Analysis for Satellite Structures: Applications to Their Design, Manufacture and Testing provides the missing link between theory and implementation.
Computational examples cover all the major aspects of advanced analysis; including modal analysis, harmonic analysis, mechanical and thermal fatigue analysis using finite element method. Test cases are included to support explanations an a range of different manufacturing simulation techniques are described from riveting to shot peening to material cutting. Mechanical design of a satellites structures are covered in three steps: analysis step under design loads, experimental testing to verify design, and manufacturing.
Stress engineers, lecturers, researchers and students will find Finite Element Analysis for Satellite Structures: Applications to Their Design, Manufacture and Testing a key guide on with practical instruction on applying manufacturing simulations to improve their design and reduce project cost, how to prepare static and dynamic test specifications, and how to use finite element method to investigate in more details any component that may fail during testing.

Remote Sensing and GIScience in Geomorphological Mapping

The rapid proliferation of remote sensing and geographic information systems (GIS) into geomorphologic mapping has increased the objectivity and efficiency of landform segmentation, measurement, and classification. The near ubiquitous presence of Earth-observing satellites provides an array of perspectives to visualize the biophysical characteristics of landscapes, access inhospitable terrain on a predictable schedule, and study landscape processes when conditions are hazardous. GIS technology has altered the analysis, visualization, and dissemination of landform data due to the shared theoretical concepts that are fundamental to geomorphology and GIScience. The authors review geospatial technology applications in landform mapping (including emerging issues) within glacial, volcanic, landslide, and fluvial research.