First measurement of the |t|-dependence of coherent J/ψ photonuclear production

The first measurement of the cross section for coherent J/ψ photoproduction as a function of |t|, the square of the momentum transferred between the incoming and outgoing target nucleus, is presented. The data were measured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV with the J/ψ produced in the central rapidity region |y|<0.8, which corresponds to the small Bjorken-x range (0.3−1.4)×10−3. The measured |t|-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according to the leading-twist approximation, or gluon-saturation effects from the impact-parameter dependent Balitsky–Kovchegov equation. These new results are therefore a valid tool to constrain the relevant model parameters and to investigate the transverse gluonic structure at very low Bjorken-x.publishedVersio

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Resolving the strange behavior of extraterrestrial potassium in the upper atmosphere

It has been known since the 1960s that the layers of Na and K atoms, which occur between 80 and 105 km in the Earth's atmosphere as a result of meteoric ablation, exhibit completely different seasonal behavior. In the extratropics Na varies annually, with a pronounced wintertime maximum and summertime minimum. However, K varies semiannually with a small summertime maximum and minima at the equinoxes. This contrasting behavior has never been satisfactorily explained. Here we use a combination of electronic structure and chemical kinetic rate theory to determine two key differences in the chemistries of K and Na. First, the neutralization of K+ ions is only favored at low temperatures during summer. Second, cycling between K and its major neutral reservoir KHCO3 is essentially temperature independent. A whole atmosphere model incorporating this new chemistry, together with a meteor input function, now correctly predicts the seasonal behavior of the K layer

Bacteriorhodopsin analogue from indolic chromophores

A new analogue of bacteriorhodopsin (bR) was prepared by allowing bacterioopsin (bOP), the apo-protein of bR to interact with (2Z,4E)-3-chloro-5-(1H-indol-3-yl)-2,4-pentadienal as chromophore. It was characterised for its opsin shift, stability, light-induced pH change and fluorescence emission. Indolic aldehydes viz. 1H-indole-3-carboxaldehyde and (2Z,4E)-3-chloro-5-[1-(phenylsulfonyl)-1H-indol-3-yl]-2,4-pentadienal did not bind bOP

Donor-Acceptor Conjugated Linear Polyenes: A Study of Excited State Intramolecular Charge Transfer, Photoisomerization and Fluorescence Probe Properties

Numerous studies of donor-acceptor conjugated linear polyenes have been carried out with the goal to understand the exact nature of the excited state electronic structure and dynamics. In this article we discuss our endeavours with regard to the excited state intramolecular charge transfer, photoisomerization and fluorescence probe properties of various donor-acceptor substituted compounds of diphenylpolyene [Ar(CH = CH) (n) Ar] series and ethenylindoles

Ethenyl indoles as neutral hydrophobic fluorescence probes

3-(4-Nitrophenylethenyl-E)-NH-indole (1), 3-(4-nitrophenyl ethenyl-E)-N-acetylindole (2), and 3-(4-nitrophenylethenyl-E)-N-benzenesulfonylindole (3) are relatively less fluorescent in organic solvents, with fluorescence quantum yield (Phi(f)) in the range of 0.002 to 0.066 depending on the solvent polarity. However, in bovine serum albumin (BSA)-phosphate buffer, the fluorescence of these compounds gets drastically enhanced with Phi(f) in the range of 0.21 to 0.67, depending on the substituent on the indolic nitrogen atom. Additionally, linear increase in the fluorescence intensity of 2 and 3 occurs on increasing the BSA concentration. These fluorescence properties together with the neutral, hydrophobic nature of these compounds make these fluorophores good fluorescence probe for studying the micropolarity of proteins like BSA and in general the ligand-protein interactions. Copyright (c) 2007 , Ltd

Substituent directed distal photoisomerisation of > C=C < in indolic dienyl chromophores

Methyl-3-methyl-5-(3-N-benzenesulphonylindole)-2E,4E-pentadienoate and methyl-3-methyl-5-(3-N-H indole)-2E,4E-pentadienoate are synthesized and their photoisomerisation behaviour in 1.4-dioxane and methanol are examined. The photoisomerisation of these compounds is highly dependent upon the substituent present at the indolic nitrogen atom