High intensity anthropogenic sound damages fish ears

Marine petroleum exploration involves the repetitive use of high-energy noise sources, air-guns, that produce a short, sharp, low-frequency sound. Despite reports of behavioral responses of fishes and marine mammals to such noise, it is not known whether exposure to air-guns has the potential to damage the ears of aquatic vertebrates. It is shown here that the ears of fish exposed to an operating air-gun sustained extensive damage to their sensory epithelia that was apparent as ablated hair cells. The damage was regionally severe, with no evidence of repair or replacement of damaged sensory cells up to 58 days after air-gun exposure.     

Direct measurement of the thermal rate coefficient for electron attachment to ozone in the gas phase, 300-550 K: implications for the ionosphere

Attachment of thermal electrons to O3 was studied in 133 Pa He between 300-550 K; the process is extremely inefficient. The rate coefficient increases sharply with temperature from 0.9 to 5 x 10(-11) cm(3) s(-1) (+/-30%) and comparison to kinetic energy measurements suggests internal energy can drive the reaction. These determinations account for competing processes of diffusion, recombination, and electron detachment reactions, and imply that no significant zero-energy resonance cross section exists, contradicting recent electron-beam results that call for substantial revision of ionospheric models.     

A solid-phase synthetic strategy for labeled peptides: synthesis of a biotinylated derivative of the delta opioid receptor antagonist TIPP (Tyr-Tic-Phe-Phe-OH)

A general solid-phase synthetic strategy for labeled peptides was developed and used to prepare a biotinylated derivative of the delta opioid receptor antagonist TIPP (Tyr-Tic-Phe-Phe-OH). A monoprotected hydrophilic diamine linker was attached to an aldehyde-containing solid-phase resin by reductive amination, followed by introduction of biotin and peptide synthesis to yield Tyr-Tic-Phe-Phe-Asp-NH(CH(2)CH(2)O)(2)CH(2)CH(2)NH-biotin (2). The high delta receptor affinity and selectivity of 2 demonstrate the applicability of this design approach for labeled peptide derivatives.     

Temperature Dependence for the Relative Raman Cross Section of the Ammonia/Water Complex

The Raman spectra of aqueous ammonia solutions have been obtained between -40 and 25 degrees C. The Raman spectrum of neat water was also obtained at 25 degrees C and is characterized by two broad peaks observed at 3200 and 3400 cm(-1). The spectrum due to water is subtracted to determine the NH(3) spectrum at all temperatures. In ammonia-water solutions, the spectrum shows three features at measured displacements of 3250, 3316, and 3400 cm(-1). The feature at 3316 cm(-1) is assigned to the Q branch of the symmetric stretch. The broad, weak features at 3250 and 3400 cm(-1), previously assigned to rotational bands, are assigned to combination bands. The NH(3) combination bands are assigned by comparing with sum frequency generation (SFG) experiments, monitoring changes with temperature, and analyzing the polarization data. The rotational structure of the Q band is also discussed. As the temperature is lowered from 25 to -40 degrees C, an increase in the Raman intensity is observed for all bands. The relative Raman scattering cross section is determined from the numerically integrated area of the NH(3) Q branch at each temperature. Copyright 2001 Academic Press.     

Optimal distillation of a greenberger-horne-zeilinger state

We present the optimal local protocol to distill a Greenberger-Horne-Zeilinger state from a single copy of any pure state of three qubits.     

Enhanced detonation sensitivities of silicon analogs of PETN: reaction force analysis and the role of σ–hole interactions

Si-pentaerythritol tetranitrate (PETN), Si[CH₂ONO₂]₄, is a silicon analog of the widely used explosive PETN, C[CH₂ONO₂]₄. Si-PETN is extremely sensitive to impact, much more so than PETN. This was attributed by Liu et al. to Si-PETN having a much lower activation barrier to decomposition, via a facile rearrangement that is not as readily available to PETN, and which releases considerable energy that can promote further steps. We have investigated computationally why the barrier to the rearrangement is so much lower for Si-PETN than for PETN, using 5, (H₃C)₃C–CH₂ONO₂, and 6, (H₃C)₃Si–CH₂ONO₂, as models for PETN and Si-PETN. Reaction force analysis shows that most of the difference between the rearrangement barriers for 5 and 6 comes about in the initial (reactant) stages of the processes, in which 6 benefits from a 1,3 electrostatic interaction involving a positive σ–hole on the silicon and the negative linking oxygen. The analogous interaction is weaker in 5, since the central carbon does not have positive σ–holes; furthermore, this carbon is less able than silicon to temporarily expand its coordination sphere. A similar explanation involving a positive silicon σ–hole and a linking oxygen is proposed for Si-PETN. The greater exothermicity of the rearrangement of 6 (and also Si-PETN) can be rationalized, following Liu et al., in terms of the formation of the strong Si–O bond.     

A C2-symmetric analogue of dppf: synthesis and structures of the indenyl-diphosphine complex 1,3-(Ph2PSe)2(C9H6) and the racemic and meso isomers of the heterobimetallic complex Mo(CO)4(1-PPh2-η-C9H6)2Fe

The preparation, isolation and characterisation of 1,3-bis(diphenylphosphino)indene (1) from indene and chlorodiphenylphosphine is described. The reaction of 1 with selenium gives the diselenide adduct 1,3-bis(diphenylselenophosphino)indene (2) which was characterised crystallographically. Deprotonation of 1 and treatment with ferrous chloride gives the unstable tetraphosphine complex bis(1,3-bis(diphenylphosphino)indenyl)iron(II) (3). Complex 3 decomposes to the diphosphine complex bis(1-diphenylphosphinoindenyl)iron(II) (4) via replacement of one diphenylphosphine substituent per indenyl ligand by a hydrogen atom. Complex 4 was also prepared by treatment of two equivalents of 1-diphenylphosphinoindenide with ferrous chloride. The heterobimetallic complex tetracarbonyl(bis(1-diphenylphosphinoindenyl)iron(II))molybdenum(0) (5) was also prepared and crystal structures of both the meso (5a) and C₂-symmetric racemic (5b) isomers are reported.