Analysis facility infrastructure (Tier-3) for ATLAS experiment

In the ATLAS computing model the tiered hierarchy ranged from the Tier-0 (CERN) down to desktops or workstations (Tier-3). The focus on defining the roles of each tiered component has evolved with the initial emphasis on the Tier-0 and Tier-1 definition and roles. The various LHC (Large Hadron Collider) projects, including ATLAS, then evolved the tiered hierarchy to include Tier-2’s (Regional centers) as part of their projects. Tier-3 centres, on the other hand, have been defined as whatever an institution could construct to support their Physics goals using institutional and otherwise leveraged resources and therefore have not been considered to be part of the official ATLAS computing resources. However, Tier-3 centres are going to exist and will have implications on how the computing model should support ATLAS physicists. Tier-3 users will want to access LHC data and simulations and will want to enable their resources to support their analysis and simulation work. This document will define how IFIC (Instituto de Física Corpuscular de Valencia), after discussing with the ATLAS Tier-3 task force, should interact with the ATLAS computing model, detail the conditions under which Tier-3 centres can expect some level of support and set reasonable expectations for the scope and support of ATLAS Tier-3 sites.     

Synthesis of 2-nitro- and 2,2'-dinitrobiphenyls by means of the suzuki cross-coupling reaction

[Reaction: see text]. Mechanistic investigations and protocols for the synthesis of 2-nitrobiphenyls and 2,2'-dinitrobiphenyls are disclosed. It is revealed that obstacles appear during the transmetalation step when the phenylboronic acid is substituted with a nitro group in the 2-position, whereas when substituted in the 3- or 4-positions, the reaction follows similar patterns as found in the electrophilic substitution of nitrobenzenes, an observation that may be attributed to the elimination step of the catalytic cycle.     

Multicomponent domino processes based on the organocatalytic generation of conjugated acetylides: efficient synthetic manifolds for diversity-oriented molecular construction

The organocatalytic generation of a strong base by the action of a good nucleophile is the base for the in situ catalytic generation of conjugated acetylides in the presence of aldehydes or activated ketones. The method is affordable in a multicomponent, domino format able to generate a chemically diverse set of multifunctionalized adducts that are very well suited for diversity-oriented molecular construction. The domino process involves a nucleophile as catalyst and a terminal conjugated alkyne (H-C[triple chemical bond]C-Z) and an aldehyde or activated ketone as building blocks. The chemical outcome of this process changes dramatically as a function of the nucleophile (tertiary amine or phosphine), temperature, stoichiometry, and solvent. These multicomponent domino processes achieve molecular construction with good atom economy and, very importantly, with an exquisite chemo-differentiating incorporation of identical starting units into the products (nondegenerated chemical output). These properties convert the H-C[triple chemical bond]C-Z unit into a specific building block for diversity-oriented molecular construction. Applications to the modular and diversity-oriented synthesis of relevant heterocycles are discussed. A protocol involving two coupled domino processes linked in a one-pot manner will be discussed as an efficient synthetic manifold for the modular and diversity-oriented construction of multisubstituted nitrogen-containing heterocycles.     

A concise and diastereoselective total synthesis of cis and trans-pterocarpans

A new strategy for the diastereoselective and convergent synthesis of pterocarpans which is able to control the relative stereochemistry of the molecule through allylation of aromatic aldehydes with cyclic allylsiloxanes is described.     

An improved cryopreservation protocol for pineapple apices using encapsulation-vitrification

Several modifications to the cryogenic protocols previously described for pineapple apices were performed using vitrification and encapsulation-vitrification. Pregrowth of apices in sucrose-proline before loading significantly reduced the exposure duration to PVS2 and PVS3 required for successful cryopreservation. Encapsulation and treatments with PVS3 at 0 degree C gave the highest survival before and after cooling. Optimal conditions involved the encapsulation of pineapple apices in calcium alginate (3 percent) followed by a 2-d preculture in liquid medium with 0.16 M sucrose + 0.3 M proline for 24 h and then transfer to 0.3 M sucrose + 0.3 M proline for an additional 24 h. After preculture, samples were loaded in 0.75 M sucrose + 1 M glycerol solution at room temperature (25 min) and dehydrated with PVS3 at 0 degree C for 60 min before immersion into liquid nitrogen. Following this procedure 54 percent and 83 percent of apices from MD-2 and Puerto Rico varieties respectively survived.     

Large quantum nonlinear dynamic susceptibility of single-molecule magnets

The nonlinear dynamical response of Mn12 single-molecule magnets is experimentally found to be very large, quite insensitive to the spin-lattice coupling constant, and displaying peaks reversed with respect to classical superparamagnets. It is shown that these features are caused by the strong field dependence of the relaxation rate due to the detuning of energy levels between which tunneling takes place. The nonlinear susceptibility technique, previously overlooked, is thus proposed as a privileged probe to ascertain the occurrence of quantum effects in mesoscopic magnetic systems.     

Novel magnetic supports for small molecule affinity capture of proteins for use in proteomics

Magnetic supports are tested for use in batch affinity capture of proteins. Two types of magnetic polymer composites were used for solid phase synthesis and for the batch affinity chromatography of folate binding protein from a protein mixture. Gly-Gly-L-Methotrexate as well as other analogs were synthesized on magnetic supports consisting of either polyoxyalkyleneamine grafted onto polystyrene beads or a copolymer of polyethylene glycol dimethylacrylamide (PEGA). Both supports incorporated within their matrix sub-micron particles of paramagnetic magnetite. The peptide-methotrexate analogs were attached to the magnetic supports via a photocleavable linker. The bound methotrexate-peptide analogs were equilibrated with a protein mixture consisting of bovine albumin, chicken albumin, folate binding protein, lysozyme, lactoferrin and lactoperoxidase precursor in phosphate buffered saline (PBS) and then after magnetically separating and washing the supports of any unbound components the bound protein was removed either through the photocleavage of the tethered methotrexate-peptide ligand or via exchange with soluble methotrexate. In all cases, the photocleavage or exchange with soluble methotrexate released folate binding protein as the major affinity captured protein. Of the two magnetic supports tested, the PEGA based support was found to be superior to the polyoxyalkyleneamine grafted polystyrene support and comparable to beaded agarose in releasing bound folate binding protein. Of the two methods for removing bound protein, photocleavage of the covalently attached ligand was found to release exclusively folate binding protein as opposed to exchange with soluble methotrexate which released residual amounts of the non-specifically bound proteins bovine and chicken albumin, in addition to folate binding protein. Thus, use of the PEGA based magnetic support in conjunction with a photocleavable linker should help facilitate the automation of multiple parallel affinity chromatography for proteomics applications.     

Laser-induced control of (multichannel) intracluster reactions

An experimental and theoretical study on the excited Ba FCH₃(A) photodissociation yield as a function of the excitation laser fluence is reported. Experimentally, it was found that the two-photodissociation channel yields, i.e. the reactive BaF and non-reactive Ba^* products, increased exhibiting a similar behaviour, as the laser fluence changed from 0.2 up to ca. 4 mJ/cm². Beyond this value the BaF yield levels off and the Ba^* decreases over the 4-7 mJ/cm² range. The theoretical simulation of the excited state electron-ion dynamics within the time-dependent density functional theory revealed that the reactive channel dominated the photofragmentation dynamics as it occurs within a femtosecond time scale and became accelerated as the photodissociation laser fluence increased. By contrast, the non-reactive channel only manifested for low laser fluences at the nano/picosecond time regime resulted inactive as the laser fluence increased. A simple scheme to control the dynamics of the intracluster multichannel reaction is suggested in which the slowest the channel the easiest to close it as the excitation laser power increases.Received: 3 July 2003PACS: 36.40.Jn Reactivity of clusters - 36.40.Qv Stability and fragmentation of clusters - 34.50.Rk Laser-modified scattering and reactions     

Selection rules and superconducting correlations in carbon nanotubes

We carry out a detailed analysis of the effective interaction arising from electron-phonon scattering and its capability to produce the superconducting correlations observed in the carbon nanotubes. It is shown that certain selection rules prevent the exchange of phonons in some of the interaction channels, depending on the geometry of the nanotubes and on whether they are doped or not. In addition, we discuss the mechanism working in nanotube ropes by which the electrostatic coupling among a large number of metallic nanotubes leads to a substantial reduction in the strength of the Coulomb interaction. The scaling equation for the superconducting response function is then improved nonperturbatively, by including the exact contribution from forward-scattering processes. This allows us to estimate the boundary between superconducting and nonsuperconducting phases in the ropes, as well as to constrain the actual values of the strength of the effective attractive interaction.Received: 13 August 2003, Published online: 23 December 2003PACS: 71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.) - 73.63.Fg Nanotubes - 74.78.Na Mesoscopic and nanoscale systems     

Molecular beam electric resonance without A- and B-fields

We report on a novel phenomenon observed during the passage of a pulsed NO beam seeded in He through a combined homogeneous, static electric and RF field, denoted as C-field in a standard molecular beam electric resonance (MBER) experiment. Although we refrain from the state selective A- and B-fields, which are considered crucial for a MBER experiment, the transmitted intensity exhibits as a function of the RF frequency conspicuous dips at resonance frequencies that depend strictly linearly on the static field strength E ₀. Their spectral width is by a factor of 4 smaller than the time of flight broadening. Both, the resonance frequencies and their linear field dependence can be precisely predicted applying a simple expression for the Stark effect to a transition of a single rotational state (J = 3/2) of the electronic ground state . However, this formula is valid only in the high field limit (E ₀ > 1000 kV/m) while the employed field (E ₀ = 1.47 kV/m) was in the extreme low field domain where the large type doubling and hyperfine coupling lead to a purely quadratic Stark effect. We assume that the phenomenon is due to a yet unknown collective rather than to an isolated particle process.Received: 9 May 2003, Published online: 12 August 2003PACS: 33.20.Bx Radio-frequency and microwave spectra - 32.60. + i Zeeman and Stark effects Author for correspondence: A. González Ureña