Underwater localization of pure tones by harbor seals (Phoca vitulina)

The underwater sound localization acuity of harbor seals (Phoca vitulina) was measured in the horizontal plane. Minimum audible angles (MAAs) of pure tones were determined as a function of frequency from 0.2 to 16 kHz for two seals. Testing was conducted in a 10-m-diam underwater half circle using a right/left psychophysical procedure. The results indicate that for both harbor seals, MAAs were large at high frequencies (13.5 degrees and 17.4 degrees at 16 kHz), transitional at intermediate frequencies (9.6 degrees and 10.1 degrees at 4 kHz), and particularly small at low frequencies (3.2 degrees and 3.1 degrees at 0.2 kHz). Harbor seals seem to be able to utilize both binaural cues, interaural time differences (ITDs) and interaural intensity differences (IIDs), but a significant decrease in the sound localization acuity with increasing frequency suggests that IID cues may not be as robust as ITD cues under water. These results suggest that the harbor seal can be regarded as a low-frequency specialist. Additionally, to obtain a MAA more representative of the species, the horizontal underwater MAA of six adult harbor seals was measured at 2 kHz under identical conditions. The MAAs of the six animals ranged from 8.8 degrees to 11.7 degrees , resulting in a mean MAA of 10.3 degrees .     

Underwater auditory localization by a swimming harbor seal (Phoca vitulina)

The underwater sound localization acuity of a swimming harbor seal (Phoca vitulina) was measured in the horizontal plane at 13 different positions. The stimulus was either a double sound (two 6-kHz pure tones lasting 0.5 s separated by an interval of 0.2 s) or a single continuous sound of 1.2 s. Testing was conducted in a 10-m-diam underwater half circle arena with hidden loudspeakers installed at the exterior perimeter. The animal was trained to swim along the diameter of the half circle and to change its course towards the sound source as soon as the signal was given. The seal indicated the sound source by touching its assumed position at the board of the half circle. The deviation of the seals choice from the actual sound source was measured by means of video analysis. In trials with the double sound the seal localized the sound sources with a mean deviation of 2.8 degrees and in trials with the single sound with a mean deviation of 4.5 degrees. In a second experiment minimum audible angles of the stationary animal were found to be 9.8 degrees in front and 9.7 degrees in the back of the seal's head.     

Measuring hearing in the harbor seal (Phoca vitulina): comparison of behavioral and auditory brainstem response techniques

Auditory brainstem response (ABR) and standard behavioral methods were compared by measuring in-air audiograms for an adult female harbor seal (Phoca vitulina). Behavioral audiograms were obtained using two techniques: the method of constant stimuli and the staircase method. Sensitivity was tested from 0.250 to 30 kHz. The seal showed good sensitivity from 6 to 12 kHz [best sensitivity 8.1 dB (re 20 microPa2 x s) RMS at 8 kHz]. The staircase method yielded thresholds that were lower by 10 dB on average than the method of constant stimuli. ABRs were recorded at 2, 4, 8, 16, and 22 kHz and showed a similar best range (8-16 kHz). ABR thresholds averaged 5.7 dB higher than behavioral thresholds at 2, 4, and 8 kHz. ABRs were at least 7 dB lower at 16 kHz, and approximately 3 dB higher at 22 kHz. The better sensitivity of ABRs at higher frequencies could have reflected differences in the seal's behavior during ABR testing and/or bandwidth characteristics of test stimuli. These results agree with comparisons of ABR and behavioral methods performed in other recent studies and indicate that ABR methods represent a good alternative for estimating hearing range and sensitivity in pinnipeds, particularly when time is a critical factor and animals are untrained.     

Single particle excitations in Ba from a ( , t) reaction study

The ¹³⁰Ba( ¹²⁹Ba reaction was studied with 25 MeV deuterons and excellent energy resolution. About 50 excited states have been observed up to E_x = 2.0 MeV and for 42 of them transferred ℓ values and/or J^π values were assigned on the basis of the measured angular distributions and asymmetries. The level scheme of ¹²⁹Ba, the neutron pickup strength distribution and the known electromagnetic decay scheme are compared with results of calculations with the interacting boson-fermion model. These simple multi-shell IBFM-1 calculations describe well the main features of the experimental data.     

The effect of signal duration on the underwater detection thresholds of a harbor porpoise (Phocoena phocoena) for single frequency-modulated tonal signals between 0.25 and 160 kHz

The underwater hearing sensitivity of a young male harbor porpoise for tonal signals of various signal durations was quantified by using a behavioral psychophysical technique. The animal was trained to respond only when it detected an acoustic signal. Fifty percent detection thresholds were obtained for tonal signals (15 frequencies between 0.25-160 kHz, durations 0.5-5000 ms depending on the frequency; 134 frequency-duration combinations in total). Detection thresholds were quantified by varying signal amplitude by the 1-up 1-down staircase method. The hearing thresholds increased when the signal duration fell below the time constant of integration. The time constants, derived from an exponential model of integration [Plomp and Bouman, J. Acoust. Soc. Am. 31, 749-758 (1959)], varied from 629 ms at 2 kHz to 39 ms at 64 kHz. The integration times of the porpoises were similar to those of other mammals including humans, even though the porpoise is a marine mammal and a hearing specialist. The results enable more accurate estimations of the distances at which porpoises can detect short-duration environmental tonal signals. The audiogram thresholds presented by Kastelein et al. [J. Acoust. Soc. Am. 112, 334-344 (2002)], after correction for the frequency bandwidth of the FM signals, are similar to the results of the present study for signals of 1500 ms duration. Harbor porpoise hearing is more sensitive between 2 and 10 kHz, and less sensitive above 10 kHz, than formerly believed.     

Copper(I)‐catalyzed reaction of unsymmetrical alkyne with HB(pin): a density functional theory study

With the aid of density functional theory calculations, we have investigated the mechanism of copper(I)‐catalyzed reaction between unsymmetrical alkyne 1‐phenyl‐1‐butyne and HB(pin). The results of the density functional theory calculations show that the reaction mechanism involves syn‐addition of catalyst ([NHC]CuH) (NHC = N‐heterocyclic carbene) to 1‐phenyl‐1‐butyne to form the alkenyl copper intermediates 2a and 5a , and then intermediates 2a and 5a react with HB(pin) to give intermediates 3 ( 3a , 3b ) and 6 ( 6a , 6b ), and finally elimination of catalyst completes the catalytic cycle and yields the α‐product P₁ and β‐product P₂ . We found that α‐product should be more favored than β‐product. The calculated results are consistent with the experimental findings. The present paper may provide a useful guide for understanding other analogous copper‐catalyzed hydroboration of unsymmetrical alkynes.     

Switching ability of nitro-spiropyran on Au(111): electronic structure changes as a sensitive probe during a ring-opening reaction

Spiropyran is a prototype molecular switch which undergoes a reversible ring-opening reaction by photoinduced cleavage of a C-O bond in the spiropyran (SP) to the merocyanine (MC) isomer. While the electronic states and switching behavior are well characterized in solution, adsorption on metal surfaces crucially affects these properties. Using two-photon photoemission and scanning tunneling spectroscopy, we resolve the molecular energy levels on a Au(111) surface of both isomeric forms. Illumination at various wavelengths does not yield any observable switching rate, thus evidencing a very small upper limit of the quantum efficiency. Electron-induced switching from the SP to the MC isomer via generation of a negative ion resonance can be detected with a quantum yield of (2.2 ± 0.2) × 10(-10) events/electron in tunneling spectroscopy. In contrast, the back reaction could not be observed. This study reveals that the switching properties of surface-bound molecular switches can be very different compared with free molecules, reflecting the strong influence of the interaction with the metal substrate.     

Diagnostic analysis of stone materials from underwater excavations: the case study of the Roman archaeological site of Baia (Naples,Italy)

This work belongs to the framework of the national research project “COMAS” (Planned COnservation, “in situ”, of underwater archaeological artifacts), funded by the Italian Ministry of Education, Universities and Research (MIUR), concerning the submarine archaeological area of Baia (Naples, Italy). The site includes remains of the ancient cities of Baiae and Portus Iulius, which, since the 4th century AD, started to be submerged because of the bradyseism phenomenon. The work aims to the characterization of four different types of stone materials collected from the site, specifically marbles, limestones, ignimbrites, and bricks, in order to investigate their state of conservation. In particular, specimens were sampled from some masonry structures and pavement slabs (opus sectile) in a specific area of the submerged site, called “Villa a Protiro”. In order to characterize archaeological samples from a mineralogical-petrographic point of view, polarized optical microscopy and X-ray diffraction analyses were carried out, while to assess their conservation state, the surface colonization by biodeteriogen agents and their interaction with the substrate were studied through observations under a stereomicroscope, scanning electron microscopy and Fourier transform infrared spectroscopy. Marble and limestone samples revealed an intense bioerosion phenomena, attributable to epilithic and endolithic forms, particularly boring sponges. On the contrary, ignimbrites suffer a lower degree of biological colonization related to the activity of other species, such as serpulids and bryozoans. In bricks, biocolonisation is correlated to the type of temper used in the artifact, the quartz pastes having a greater susceptibility to biological attack than the volcanic ones.     

The effect of antifreeze proteins and poly(vinyl alcohol) on the nucleation of ice: a preliminary study

Three substances have been tested for ice nucleation inhibition. These were an antifreeze protein AFP III from the fish Macrozoarces americanus, an antifreeze glycoprotein AFGP from the fish Dissostichus mawsoni, and an 80% hydrolysed poly(vinyl alcohol) with a molecular weight of 9 to 10 kD. A nucleation spectrometer was used to test nucleation inhibition at a range of concentrations against two types of ice nuclei: those present in tap water and a bacterial nucleator from Pseudomonas syringae. The PVA reduced the nucleation temperature of tap water and the bacterial dispersions at all the concentrations which were tested. The AFGP reduced the nucleation temperature of tap water but enhanced the nucleation activity of the bacterial nucleators. At low concentrations the AFP III reduced the nucleation temperature of both tap water and the bacterial nucleator. At high concentrations the AFP III enhanced the nucleation temperature of the bacterial nucleator and broadened the nucleation spectrum of the tap water to encompass the nucleation spread of the control. The possible mechanisms of nucleation suppression and enhancement are discussed.     

Equations of motion for a (non‐linear) scalar field model as derived from the field equations

The problem of derivation of the equations of motion from the field equations is considered. Einstein's field equations have a specific analytical form: They are linear in the second order derivatives and quadratic in the first order derivatives of the field variables. We utilize this particular form and propose a novel algorithm for the derivation of the equations of motion from the field equations. It is based on the condition of the balance between the singular terms of the field equation. We apply the algorithm to a non‐linear Lorentz invariant scalar field model. We show that it results in the Newton law of attraction between the singularities of the field moved on approximately geodesic curves. The algorithm is applicable to the N‐body problem of the Lorentz invariant field equations.     

Diffraction of helium from a stepped surface: Cu(117) — An experimental study

The scattering of an helium nozzle beam (incident energy 21 and 63 meV) from a copper (117) stepped surface has been studied for crystal temperature ranging from 70 to 773 K. The diffraction pattern from the step array is readily seen. The influence of residual impurity on the surface is carefully discussed. Special attention has been paid to the influence of experimental factors upon peak shapes. True peak amplitudes are deduced. The peak intensities versus temperature and versus incidence angle has been measured. Extrapolation of the intensities to 0 K allows a direct comparison of the data with the prediction of a hard corrugated wall model. A corrugation profile is given which fits quite well the data. Clear evidence for resonances with bound states has been found. Three energy levels of the potential well are thus determined (5.9,4.0, 2.1 meV) which agrees with a Morse or a 3–9 potential.     

Evidence for F(-) formation by simultaneous double-electron capture during scattering of F(+) from a LiF(001) surface

Slow F(+) ions (v<0.1 a.u.) scattered from a clean and flat LiF(001) surface under a grazing angle of incidence exhibit a high probability for forming F(-) ions in the reflected beam, whereas no negative ions are found for neutral F(0) projectiles. From detailed studies of projectile energy loss and charge transfer, we find evidence for a correlated double-electron capture process in the formation of the F(-) ions.     

Rotation of hydrogen molecules during the dissociative adsorption on the Mg(0001) surface: a first-principles study

Using first-principles calculations,we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg(0001) surface.It is found that during the dissociative adsorption process with the minimum energy barrier,the hydrogen molecule first orients perpendicularly,and then rotates tobecome parallel to the surface.It is also found that the orientation of the hydrogen molecule in the transition state is neither perpendicular nor parallel to the surface.Most importantly,we find that the rotation causes a reduction of the calculated dissociation energy barrier for the hydrogen molecule.The underlying electronic mechanism for the rotation of the hydrogen molecule is also discussed in the paper.     

Silicon carbide nanotubes (SiCNTs) serving for catalytic decomposition of toxic diazomethane (DAZM) gas: a DFT study

In the present study, the adsorption and decomposition of diazomethane (DAZM) on the surface of (6,0) zigzag silicon carbide nanotube (SiCNT) are investigated using density functional theory calculations. The geometry structures of the three stable configurations, adsorption energies and electronic properties of DAZM adsorption on the surface of SiCNT are investigated. It was found that the DAZM molecule is decomposed over the surface of (6,0) SiCNT with activation energy (E_act) of 0.523 eV. The curvature effect on the adsorption energies of the DAZM molecule is also considered by studying (5,0) and (7,0) SiCNTs. The results display that DAZM adsorption over smaller diameter of SiCNT is thermodynamically more favourable than larger one.     

Interaction of atomic oxygen (N2O) with a clean Si(001) surface: O adsorption geometries as derived from the O KVV Auger lineshape

The room temperature adsorption of N₂O on the clean Si(001)2 × 1 surface was used as a model system in an Auger electron spectroscopy (AES) study presented in this paper. Earlier experimental and recent theoretical work have provided evidence that this reaction evolves in discernible stages each exhibiting different adsorption geometries for the oxygen atom. In this AES study the intensity ratio of the KL₁L₁ and KL_2,3L_2,3 O Auger transitions, , was measured as a function of the fractional oxygen coverage, θ, and compared with our calculated intensity ratios and binding energy measurements of the O 1s photoelectron from literature. As a result we have found, for the first time, that (θ) can be related to a specific adsorption geometry in the submonolayer range. Moreover, we have found experimental evidence for an intermediate stable O adsorption state on the dimer at low coverage (θ 0.2 monolayer), as proposed earlier from theoretical studies.     

Effect of radiative transfer of heat released from combustion reaction on temperature distribution: A numerical study for a 2-D system

Both light and heat are produced during a chemical reaction in a combustion process, but traditionally all the energy released is taken as to be transformed into the internal energy of the combustion medium. So the temperature of the medium increases, and then the thermal radiation emitted from it increases too. Chemiluminescence is generated during a chemical reaction and independent of the temperature, and has been used widely for combustion diagnostics. It was assumed in this paper that the total energy released in a combustion reaction is divided into two parts, one part is a self-absorbed heat, and the other is a directly emitted heat. The former is absorbed immediately by the products, becomes the internal energy and then increases the temperature of the products as treated in the traditional way. The latter is emitted directly as radiation into the combustion domain and should be included in the radiation transfer equation (RTE) as a part of radiation source. For a simple, 2-D, gray, emitting-absorbing, rectangular system, the numerical study showed that the temperatures in reaction zones depended on the fraction of the directly emitted energy, and the smaller the gas absorption coefficient was, the more strong the dependence appeared. Because the effect of the fraction of the directly emitted heat on the temperature distribution in the reacting zones for gas combustion is significant, it is required to conduct experimental measurements to determine the fraction of self-absorbed heat for different combustion processes.     

Direct extraction of the Eliashberg function for electron-phonon coupling: a case study of Be(10(-)10)

We propose a systematic procedure to directly extract the Eliashberg function for electron-phonon coupling from high-resolution angle-resolved photoemission measurement. The procedure is successfully applied to the Be(10(-)10) surface, providing new insights into electron-phonon coupling at this surface. The method is shown to be robust against imperfections in experimental data and suitable for wider applications.     

Energy exchange in structure scattering: a molecular dynamics study for Cs from Pt(1 1 1)

We have employed a classical molecular dynamics simulation to investigate the energy transfer of a heavy projectile ion to a surface, i.e. Cs⁺ impacting onto Pt(1 1 1), for incidence energies between 25 and 100 eV and an incidence angle of 45°. The in-plane scattering results show a continuous increase of the final energy with increasing scattering angle. All scattering intensities have a main supraspecular peak and scattering into subspecular angles increases with increasing incidence energy. The large projectile/target mass ratio causes a high energy loss and a strong angular dependence of the final energy distribution. The trends of the energy transfer and its angular dependence can be understood in terms of a binary collision model, augmented with double collisions and an the image charge correction. Backscattering at high incidence energies leads to a distribution of very low final energies, indicating the onset of surface sputtering. Peaks in the energy spectra arise from impact site dependent scattering and can be assigned to single, double, triple or sputtering type collisions.     

A reaction cell for time‐resolved in situ XAS studies during wet chemical synthesis: the Cu2(OH)3Cl case

The use of in situ time‐resolved dispersive X‐ray absorption spectroscopy (DXAS) to monitor the formation of Cu₂(OH)₃Cl particles in an aqueous solution is reported. The measurements were performed using a dedicated reaction cell, which enabled the evolution of the Cu K‐edge X‐ray absorption near‐edge spectroscopy to be followed during mild chemical synthesis. The formed Cu₂(OH)₃Cl particles were also characterized by synchrotron‐radiation‐excited X‐ray photoelectron spectroscopy, X‐ray diffraction and scanning electron microscopy. The influence of polyvinylpyrrolidone (PVP) on the electronic and structural properties of the formed particles was investigated. The results indicate clearly the formation of Cu₂(OH)₃Cl, with or without the use of PVP, which presents very similar crystalline structures in the long‐range order. However, depending on the reaction, dramatic differences were observed by in situ DXAS in the vicinities of the Cu atoms.