bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport by an intrusion generated by boundary mixing in a lake
Authors: Wain Danielle J. , Rehmann Chris R.
Published: August 2010

A dye study was conducted to track an intrusion generated at the boundary of a small lake. Persistent turbid layers offshore presented evidence of possible intrusions from boundary mixing. After high winds, a streak of Rhodamine WT was injected at the boundary of the lake where the slope was between 5% and 10%. Both vertical profiles and longitudinal transects of the dye concentration were measured. The three‐dimensional dye mapping showed a distinct dye intrusion, ranging between 0.5 and 1 m thick, over 200 m in horizontal extent offshore, 1 day after the injection. Profiles of temperature microstructure measured soon after the injection both at the injection site and offshore showed an elevated eddy diffusivity near the boundary where the dye was injected, indicating that the intrusion resulted from boundary mixing. Because the dominant internal waves are subcritical, the mixing is most likely due to seiching currents interacting with the boundary. The propagation characteristics of the intrusion were predicted most closely by a formulation for a radially spreading intrusion governed by a balance between buoyancy and inertia. These results show that intrusion generation and propagation may be a significant process for mass transport in stratified lakes and reservoirs.
Combined role of advective pumping and mechanical dispersion on time scales of bed form–induced hyporheic exchange
Authors: Bottacin‐Busolin A. , Marion A.
Published: August 2010

This study analyzes the effect of advective pumping and pore scale dispersion on bed form–induced hyporheic exchange. Advection and dispersion play a competitive role in the exchange dynamics between the porous medium and the overlying stream: Advective fluxes first lead solutes deep into the bed and then back to the stream water, whereas dispersive fluxes favor the transfer of solutes deep into the bed leading to a permanent mass retention. The combined effect of advective exchange and dispersive fluxes produces complexity in the shape of the tails of the residence time distributions (RTDs), which follow at various stages of the process either a power law or an exponential decay. The seepage velocity induced by the stream gradient and, in case of a moving bed, the celerity of the translating bed forms limit the thickness of the advective hyporheic zone, inducing the RTDs to decrease rapidly at late time. This rapid decay can be preceded by a temporal region where the probability density functions (pdf's) tend to be inversely proportional to the square of time, and is followed by a region dominated by dispersion where the pdf's tend to be inversely proportional to the 3/2 power of time. The process shows distinct temporal ranges identified here by appropriate dimensionless parameters. Because of this complex exchange dynamics, models considering pure advection in the porous medium can significantly underestimate solute transfer at long time scales, whereas purely diffusive models of hyporheic exchange appear inadequate to represent the physical processes at an intermediate stage.
A generalized reactive force field for nonlinear hydrogen bonds: Hydrogen dynamics and transfer in malonaldehyde
Authors: Yang Yonggang , Meuwly Markus
Published: August 2010

Using molecular dynamics (MD) simulations, the spectroscopy and dynamics of malonaldehyde is investigated. To this end, the recently proposed molecular mechanics with proton transfer (MMPT) potential is generalized to nonlinear hydrogen bonds. The calculated properties for malonaldehyde in both gas and condensed phases, including equilibrium geometries, infrared spectra, tunneling splittings, and hydrogen transfer rates, compare well with previous experimental and computational works. In particular, by using a harmonic bath averaged (HBA) Hamiltonian, which is based on a reaction path Hamiltonian, it is possible to estimate the tunneling splitting in an efficient manner. It is found that a zero point corrected barrier of 6.7 kcal/mol and effective masses of 1.234 (i.e., 23.4% larger than the mass of a physical H-atom) and 1.117 (for the physical D-atom) are consistent with the measured splittings of 21.6 and 2.9 cm−1, respectively. The HBA Hamiltonian also yields a pair of hydrogen transfer fundamentals at 1573 and 1267 cm−1, similar to results obtained with a reaction surface Hamiltonian on a MP2/6-31G∗∗ potential energy surface. This amounts to a substantial redshift of more than 1000 cm−1 which can be rationalized by comparison with weakly (HCO+: rare gas) and strongly (H2OH+OH2) proton-bound systems. Hydrogen transfer rates in vacuum and water were determined from the validated MMPT potential and it is found that the solvent enhances the rate by a factor of 5 at 300 K. The rates of 2.4/ns and 10/ns are commensurate with previous density functional tight binding ab initio MD studies.
The distorted close-packed crystal structure of methane A
Authors: Maynard-Casely H. E. , Bull C. L. , Guthrie M. , Loa I. , McMahon M. I. , Gregoryanz E. , Nelmes R. J. , Loveday J. S.
Published: August 2010

We have determined the full crystal structure of the high-pressure phase methane A. X-ray single-crystal diffraction data were used to determine the carbon-atom arrangement, and neutron powder diffraction data from a deuterated sample allowed the deuterium atoms to be located. It was then possible to refine all the hydrogen positions from the single-crystal x-ray data. The structure has 21 molecules in a rhombohedral unit cell, and is quite strongly distorted from the cubic close-packed structure of methane I, although some structural similarities remain. Full knowledge of this structure is important for modeling of methane at higher pressures, including in relation to the mineralogy of the outer solar system. We discuss interesting structural parallels with the carbon tetrahalides.
Magnetostriction under high prestress in Fe81Ga19 crystal
Authors: Liu Jinghua , Wang Zhibin , Jiang Chengbao , Xu Huibin
Published: August 2010

Seeking high precision actuator and transducer materials potentially applied under high load remains active in recent years. Magnetostrictive property, magnetostriction saturation field HS, and pizeomagnetic coefficient d33 are investigated in Fe81Ga19 alloy under high compressive prestress. The measured saturation magnetostriction remains above 300 ppm in the ⟨001⟩ oriented Fe81Ga19 polycrystalline rod under high compressive prestress up to 431 MPa. Two-stage phenomenon was observed in curves plotted for HS and d33 against compressive prestress σ. The domain rotation path and magnetostriction under different compressive prestress are simulated, and this helps to deeply understand the tested magnetostriction. Based on the simulation, the mathematical equations of HS-σ and d33-σ were established for Fe–Ga ⟨001⟩ oriented crystal revealed two mechanisms, which satisfy proposed functions of experimental data. The high magnetostriction and low saturation field under high prestress indicate that Fe–Ga alloy is possible to be a sound candidate for high load application.
Linear and nonlinear optical properties of a two-subband system in a symmetric semiconductor quantum well
Authors: Kosionis Spyridon G. , Terzis Andreas F. , Simserides Constantinos , Paspalakis Emmanuel
Published: August 2010

We study the linear and nonlinear optical response of intersubband transitions in a semiconductor quantum well. We describe the coupling of the quantum well structure with the electromagnetic field by using the nonlinear density matrix equations, in the two-subband approximation. We provide proper approximate analytical solutions to these equations that are used for the closed-form determination of the optical susceptibilities χ(1), χ(3), and χ(5). We also explore the dependence of χ(1), χ(3), and χ(5) on the electron sheet density for a specific double GaAs/AlGaAs quantum well.
Role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films
Authors: Jie Jin , Morita Aya , Shirai Hajime
Published: August 2010

The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied by alternating the deposition of a several-nanometer-thick ZnO layer and the O2/Ar mixture plasma exposure, i.e., layer-by-layer technique. The film crystallization promoted with suppressing the oxygen vacancy and interstitial defects by adjusting the exposure condition of O2/Ar plasma. These findings suggest that the chemical potential of oxygen atom determine the film crystallization as well as the electronic state. The diffusion and effusion of oxygen atoms at the growing surface play a role of thermal annealing, promoted the film crystallization as well as the creation and the annihilation of oxygen and zinc related defects. The role of oxygen atoms reaching at the film-growing surface is discussed in term of chemical annealing. The possible oxygen diffusion mechanism is proposed.
Resonant two-photon ionization spectroscopy of jet-cooled tantalum carbide, TaC
Authors: Krechkivska Olha , Morse Michael D.
Published: August 2010

The optical spectrum of diatomic TaC has been investigated for the first time, with transitions recorded in the range from 17 850 to 20 000 cm−1. Six bands were rotationally resolved and analyzed to obtain ground and excited state parameters, including band origins, upper and lower state rotational constants and bond lengths, Fermi contact parameter bF for the ground state, and lambda doubling parameters for the excited states. The ground state of TaC was found to be X Σ2+, originating from the 1σ22σ21π43σ1 electronic configuration, in which only the valence orbitals arising from the Ta(5d+6s) and C(2s+2p) orbitals are listed. All of the rotationally resolved and analyzed bands were found to originate from the ground state, giving B0″=0.489 683(83) cm−1, r0″=1.749 01(15) Å, and bF″=0.131 20(36) cm−1 (1σ error limits) for T181a C12. Comparison of the Fermi contact parameter to the atomic value shows that the 3σ orbital is approximately 75% Ta 6s in character. The other group 5 transition metal carbides, VC and NbC, have long been known to have 1σ22σ21π41δ1, Δ2 ground states, with low-lying 1σ22σ21π43σ1, Σ2+ excited states. The emergence of a different ground state in TaC, as compared to VC and NbC, is due to the relativistic stabilization of the 6s orbital in Ta. This lowers the energy of the 6s-like 3σ orbital in TaC, causing the 1σ22σ21π43σ1, Σ2+ state to fall below the 1σ22σ21π41δ1, Δ2 state.
Rovibronically selected and resolved two-color laser photoionization and photoelectron study of nickel carbide cation
Authors: Chang Yih Chung , Shi Xiaoyu , Lau Kai-Chung , Yin Qing-Zhu , Liou H. T. , Ng C. Y.
Published: August 2010

We have performed a two-color laser photoionization and photoelectron study of nickel carbide (NiC) and its cation (NiC+). By preparing NiC in a single rovibronic level of an intermediate vibronic state via visible laser excitation prior to ultraviolet laser photoionization, we have measured the photoionization efficiency spectrum of NiC near its ionization threshold, covering the formation of NiC+(X Σ2+;v+=0–3). We have also obtained well-resolved rotational transitions for the v+=0 and 1 vibrational bands of the NiC+(X Σ2+) ground state. The assignment of rotational transitions observed between the neutral NiC intermediate state and the NiC+ ion ground state has allowed the direct determination of a highly precise value for the ionization energy of NiC, IE(NiC)=67 525.1±0.5 cm−1 (8.372 05±0.000 06 eV). This experiment also provides reliable values for the vibrational spacing [ΔG(1/2)=859.5±0.5 cm−1], rotational constants (Be+=0.6395±0.0018 cm−1 and αe+=0.0097±0.0009 cm−1), and equilibrium bond distance (re+=1.628 Å) for the NiC+(X Σ2+) ground state. The experimental results presented here are valuable for benchmarking the development of more reliable ab initio quantum computation procedures for energetic and spectroscopic calculations of transition metal-containing molecules.
Steady-state current transfer and scattering theory
Authors: Ben-Moshe Vered , Rai Dhurba , Skourtis Spiros S. , Nitzan Abraham
Published: August 2010

The correspondence between the steady-state theory of current transfer and scattering theory in a system of coupled tight-binding models of one-dimensional wires is explored. For weak interwire coupling both calculations give nearly identical results, except at singular points associated with band edges. The effect of decoherence in each of these models is studied using a generalization of the Liouville–von Neuman equation suitable for steady-state situations. An example of a single impurity model is studied in detail, leading to a lattice model of scattering off target that affects both potential scattering and decoherence. For an impurity level lying inside the energy band, the transmission coefficient diminishes with increasing dephasing rate, while the opposite holds for impurity energy outside the band. The efficiency of current transfer in the coupled wire system decreases with increasing dephasing.
Portable high pressure sapphire anvil cell for gas hydrates research
Authors: Wang Zhao , He Duanwei , Zhang Wei , Li Wenqiang , Li Wenyong , Qin Jiaqian , Lei Li , Zou Yongtao , Yang Xiangdong
Published: August 2010

A sapphire anvil cell, a portable system having a sample volume of about 400 mm3 (Φ8×8 mm), has been developed for gas hydrates research under high pressure. As both pressure and temperature of the sample can be precisely monitored in real time, the system has significant advantages for gas hydrates research at the pressure range of 1–40 MPa and temperature range of 250–350 K. We have applied this sapphire anvil cell system to carry out experiments for investigating the formation and dissociation of CO2 hydrate. In addition, the developed sapphire anvil cell can be used for in situ thermal, electric, ultrasonic, visible light, Raman, and IR measurements.
Vibrational characterization of ethylene adsorption and its thermal evolution on Si(001)-(2×1): Identification of majority and minority species
Authors: Kostov Krassimir L. , Nathaniel Rachel , Mineva Tzonka , Widdra Wolf
Published: August 2010

The vibrational and structural properties of a single-domain Si(001)-(2×1) surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority species consist of ethylene molecules which are di-σ bonded to the two Si atoms of a single SiSi dimer. The local symmetry of this adsorption complex is reduced to C2 for ethylene saturation coverage as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the CC bond around the surface normal and the twist of the methylene groups around the CC axis. Experimentally, 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14% of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules di-σ bonded to two adjacent SiSi dimers (in an end-bridge configuration). One part of the minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter, a di-σ end-bridge like bonding configuration is proposed based on a comparison with vibrational data for adsorbed acetylene on Si(100)-(2×1).
Optimal design strategies for electrostatic energy storage in quantum multiwell heterostructures
Authors: Grigorenko Ilya , Rabitz Herschel
Published: August 2010

We study physical principles of optimal design of a nanoscale multiwell heterostructure functioning as an electrostatic energy storage device. We performed numerical optimization of the multiwell trapping potential for electrons in the nanostructure with the goal to obtain the maximum possible static polarizability of the system. The response of the heterostructure is modeled microscopically using nonlocal linear response theory within the random phase approximation. Three main design strategies are identified which lead to the maximization of the stored energy. We found that the efficiency of each strategy crucially depends on the temperature and the broadening of electron levels. The stored energy for optimized heterostructures can exceed the nonoptimized ones by a factor of 450. These findings provide a theoretical basis for the development of new nanoscale capacitors with high energy density storage capabilities.
The effect of dopant at the Zr site on the proton conduction pathways of SrZrO3: An orthorhombic perovskite
Authors: Gomez Maria A. , Chunduru Mythili , Chigweshe Lorencia , Fletcher Katharyn M.
Published: August 2010

Doping orthorhombic SrZrO3 at 12.5% of the Zr sites with Al3+ leads to a local squaring of the lattice, while doping with larger Y3+ increases local octahedral distortions. Proton activation energy barriers and transition state theory prefactors are calculated. The wide range of intra-, inter-, and rotational barriers suggest that a comprehensive pathway analysis is needed to find the limiting conduction barriers. Simple seven to ten step periodic pathways leading to system wide conduction are enumerated using vertex coding. At 900–1300 K, the average limiting barriers to long range conduction are 0.6 and 0.4 eV in Al/SrZrO3 and Y/SrZrO3, respectively, in reasonable agreement with the experiment. Path analysis gives the added insight that conduction pathways in Al/SrZrO3 avoid doped regions, while conduction pathways in Y/SrZrO3 traverse them.
Structural and electrical analysis of the atomic layer deposition of HfO2/n-In0.53Ga0.47As capacitors with and without an Al2O3 interface control layer
Authors: O’Mahony A. , Monaghan S. , Provenzano G. , Povey I. M. , Nolan M. G. , O’Connor É. , Cherkaoui K. , Newcomb S. B. , Crupi F. , Hurley P. K. , Pemble M. E.
Published: August 2010

High mobility III-V substrates with high-k oxides are required for device scaling without loss of channel mobility. Interest has focused on the self-cleaning effect on selected III-V substrates during atomic layer deposition of Al2O3. A thin (∼1 nm) Al2O3 interface control layer is deposited on In0.53Ga0.47As prior to HfO2 growth, providing the benefit of self-cleaning and improving the interface quality by reducing interface state defect densities by ∼50% while maintaining scaling trends. Significant reductions in leakage current density and increased breakdown voltage are found, indicative of a band structure improvement due to the reduction/removal of the In0.53Ga0.47As native oxides.
Subgrain size inhomogeneities in the luminescence spectra of thin film chalcopyrites
Authors: Gütay Levent , Lienau Christoph , Bauer Gottfried Heinrich
Published: August 2010

We report near-field photoluminescence (PL) spectra of Cu(InGa)Se2 thin films recorded with a lateral optical resolution of ≈200 nm and simultaneous detection of the sample topography. Our results reveal significant local variations in the PL spectra, specifically the PL yield, on length scales of 0.2–1.5 μm. Local variations in both the splitting of quasi-Fermi levels μ and the band gap energy are quantitatively extracted from the PL spectra by applying Planck’s generalized law. We show pronounced fluctuations of μ and the band gap on length scales below the grain size. These fluctuations are only weakly correlated with the topographic film structure.
Exchange bias in GeMn nanocolumns: The role of surface oxidation
Authors: Tardif S. , Cherifi S. , Jamet M. , Devillers T. , Barski A. , Schmitz D. , Darowski N. , Thakur P. , Cezar J. C. , Brookes N. B. , Mattana R. , Cibert J.
Published: August 2010

We report on the exchange biasing of self-assembled ferromagnetic GeMn nanocolumns by GeMn-oxide caps. The x-ray absorption spectroscopy analysis of this surface oxide shows a multiplet fine structure that is typical of the Mn2+ valence state in MnO. A magnetization hysteresis shift |HE|∼100 Oe and a coercivity enhancement ΔHc∼70 Oe have been obtained upon cooling (300–5 K) in a magnetic field as low as 0.25 T. This exchange bias is attributed to the interface coupling between the ferromagnetic nanocolumns and the antiferromagnetic MnO-like caps. The effect enhancement is achieved by depositing a MnO layer on the GeMn nanocolumns.
High quantum efficiency of depth grade doping negative-electron-affinity GaN photocathode
Authors: Guo Xiangyang , Wang Xiaohui , Chang Benkang , Zhang Yijun , Gao Pin
Published: August 2010

A depth grade doping sample gallium nitride (GaN) photocathode was designed to obtain an extremely high quantum efficiency (QE). Two other uniform doping samples were prepared in the same procedure as contrast. The calibrated QE curves were achieved; by comparing theoretical calculated values with the experimental QE plots, the escape probability and diffusion length were fitted. The QE value of gradient doping sample is as high as 68.7% at 5.17 eV; the diffusion length of gradient doping sample is fitted to be 250 nm which is much higher than uniform doping samples. That explains why depth-grade-doping can improve the QE of GaN photocathode significantly.

At the request of the authors, this article is being retracted effective 13 January 2011.
Three-dimensional hole gas induced by polarization in (0001)-oriented metal-face III-nitride structure
Authors: Zhang L. , Ding K. , Yan J. C. , Wang J. X. , Zeng Y. P. , Wei T. B. , Li Y. Y. , Sun B. J. , Duan R. F. , Li J. M.
Published: August 2010

Polarization-doping via graded AlGaN layer on N-face (0001¯) GaN has been demonstrated as an inspiring p-type doping method for wide-band-gap nitrides. However, the polarity of III-nitrides grown by metal organic chemical vapor deposition is metal-face typically. In this paper, we show that three-dimensional mobile hole gas induced by polarization can be formed in (0001)-oriented metal-face III-nitride structure. The hole concentration of a Mg-doped AlxGa1−xN layer with graded Al composition from x=0.3 to 0 grown on AlN buffer layer is remarkably enhanced, compared with that of a Mg-doped GaN layer grown under the same conditions. In addition, the hole concentration in the graded AlGaN layer is absence of freezeout as the temperature decreases, indicating that the hole is induced by polarization. This p-type doping method paves a way for achieving high-efficiency in wide-band-gap semiconductor light-emitting devices with p-type doping problem.
Long-term post-fire succession of Pinus brutia forest in the east Mediterranean
Authors: Kavgacı Ali , Čarni Andraž , Başaran Saime , Başaran Mehmet Ali , Košir Petra , Marinšek Aleksander , Šilc Urban
Published: August 2010

We studied post-fire long-term regeneration of a south-western Turkey (Antalya region) forest using the synchronical approach. We analysed species richness patterns and vegetation diversity. Species were grouped according to plant functional types and special emphasis was given to seeders and resprouters. We recorded two plant species richness peaks, with the highest richness immediately following the fire and with the second peak 7 years after disturbance. Beta diversity decreased over time but also showed two peaks. The results of our floristic survey show that the majority of species are present from the beginning of the succession and suggest that Pinus brutia forests of the east Mediterranean basin recover through autosuccession. However, changes in species richness and β diversity indicate successional changes and thus we cannot completely support the model of direct recovery.
Paired Eucalyptus forest catchment study of prescribed fire effects on suspended sediment and nutrient exports in south-eastern Australia
Authors: Smith Hugh G. , Sheridan Gary J. , Lane Patrick N. J. , Sherwin Christopher B.
Published: August 2010

The effect of prescribed fire on suspended sediment and nutrient exports was investigated in two small Eucalyptus forest catchments in south-eastern Australia. In 2005, a patchy, mostly low-severity prescribed fire was applied to both catchments, followed in 2006 by a second burn applied to riparian areas of one catchment, with the other catchment utilised as a control for this burn. Historic pre-fire weekly stream water sampling was combined with post-fire weekly and storm-based sampling to quantify the effect of the fires. The 2005 fire resulted in a significant difference (P = 0.000) in suspended sediment concentrations compared to pre-fire data and generated peak study period suspended sediment (11.5 kg ha–1 year–1) and total phosphorous (0.016 kg ha–1 year–1) exports under near-average rainfall. However, peak suspended sediment exports only slightly exceeded the average annual load from a nearby undisturbed catchment. Well-below-average rainfall in 2006 resulted in lower exports after this burn compared with the 2005 fire. The results highlighted the importance of hydrological conditions for suspended sediment and nutrient exports within the first 12–18 months after prescribed fires, beyond which generally rapid surface vegetation recovery is likely to mitigate any burns effects.
Linear model for spread rate and mass loss rate for mixed-size fuel beds
Authors: Viegas Domingos X. , Almeida Miguel , Miranda Ana I. , Ribeiro Luis M.
Published: August 2010

A linearised model to estimate the properties of composite fuel beds based on the mass fraction of each fuel component is proposed. Laboratory experiments to determine combustibility properties of fuel beds composed of two, three and four components were performed under no-slope and no-wind conditions. Results of the rate of spread and mass loss rate compared favourably with model predictions. Results from tests with wind-induced fire fronts were also compared with the present model. The linear model provides a simple method to estimate of the rate of spread of composite fuels.
Economic optimisation of wildfire intervention activities
Authors: Butry David T. , Prestemon Jeffrey P. , Abt Karen L. , Sutphen Ronda
Published: August 2010

We describe how two important tools of wildfire management, wildfire prevention education and prescribed fire for fuels management, can be coordinated to minimise the combination of management costs and expected societal losses resulting from wildland fire. We present a long-run model that accounts for the dynamics of wildfire, the effects of fuels management on wildfire ignition risk and area burned, and the effects of wildfire prevention education on the ignition risk of human-caused, unintentional wildfires. Based on wildfire management activities in Florida from 2002 to 2007, we find that although wildfire prevention education and prescribed fire have different effects on timing and types of fires, the optimal solution is to increase both interventions. Prescribed fire affects whole landscapes and therefore reduces losses from all wildfire types (including lightning), whereas wildfire prevention education reduces only human-caused ignitions. However, prescribed fire offers a longer-term solution with little short-term flexibility. Wildfire prevention education programs, by comparison, are more flexible, both in time and space, and can respond to unexpected outbreaks, but with limited mitigation longevity. Only when used together in a coordinated effort do we find the costs and losses from unintentional wildfires are minimised.
Yukiko Goda: Memories are made of this
Authors: Short Ben
Published: August 2010

Goda investigates how neurons fine-tune their signals.
Isohalic sorption isotherms.
Authors: POULTER R. G. , DOE P. E. , OLLEY JUNE
Published: August 2010

Isohalic sorption isotherms of cod (Gadus morrhua) are used, in conjunction with growth data for dun mould (Wallemia sebi), to predict the shelf life of dried salted fish in tropical climates. Measured shelf‐lives of several fish species processed and stored by traditional methods are in agreement with the predictions.
AN INSOLUBILISED PEPSIN
Authors: Ryle A. P.
Published: August 2010

A highly active insoluble form of pepsin has been prepared for use in isolation of pepsin C inhibitor, a purpose for which it eventually proved ineffective. The preparation may be of interest to others.
STRUCTURE OF A HYPOTHALAMIC PEPTIDE POSSESSING GONADOTROPIN‐RELEASING ACTIVITY
Authors: Nair R. M. G. , Schally Andrew V.
Published: August 2010

A second batch of porcine gonadotropin‐releasing hormone, isolated by a new procedure, gave an amino acid composition: Trp 1, His 1, Arg 1, Ser 1, Glu 1, Pro 1, Gly 2, Leu 1, and Tyr 1, with 67% amino acid recovery. Edman‐dansyl degradation of the intact hormone did not give a positive result, suggesting a blocked N‐terminus. Esterification of the peptide with [14C]diazomethane failed to yield any [14C]methylester, indicating the absence of any free carboxyl‐group in the molecule. This suggested that the C‐terminus of the hormone is also blocked. High and low resolution mass spectral fragmentation of the hormonal peptide gave intense bands due to (pyro)‐glutamyl residue which occupies the N‐terminus. The main diketopiperazine bands from the mass spectral data were due to (pyro)Glu‐His, Trp‐Ser, Tyr‐Gly, Leu‐Arg, Arg‐Pro, Pro‐Gly, and their decomposition. Mass spectral fragmentation of the hormone and its chymotryptic fragments after acetylation and permethylation, before and after methanolysis, yielded orderly patterns, indicating the sequence of the deca‐peptide and also confirming the (pyro)glutamyl N‐terminus and the glycylamide C‐terminus. These studies, in agreement with the conventional chemical sequencing of the hypothalamic peptide after enzymic cleavage, proved that the structure of the hormone is: Glu‐His‐Trp‐Ser‐Tyr‐Gly‐Leu‐Arg‐Pro‐Gly‐NH2
CARBOXYLIC TERMINAL DETERMINATION IN SIMPLER PEPTIDES BY SELECTIVE REDUCTION OF CARBOXYLIC GROUP BY SODIUM DIHYDRO BIS‐(2‐METHOXYETHOXY) ALUMINATE
Authors: Saund A. K. , Prashad Bhagwati , Koul A. K. , Bachhawat J. M. , Mathur N. K.
Published: August 2010

The terminal carboxylic group in acylamino acids and peptides is selectively reduced by sodium dihydro bis‐(2‐methoxyethoxy) aluminate to alcoholic group. On hydrolysing the reduced acylamino acids or peptides, the original carboxy terminal amino acid is liberated as amino alcohol which can be easily identified. The reaction of reduced N‐acylamino alcohol with carbonyl diimidazole yields an N‐acyl‐2‐oxazolidone derivative from which the N‐acyl group is easily removed producing 2‐oxazolidone. The possibility of selective cleavage of the terminal amino alcohol and its characterisation as 2‐oxazolidone derivative has been investigated.
CONFORMATION OF ANTIBIOTIC PROTEIN, NEOCARZINOSTATIN, STUDIED BY PLANE POLARIZED INFRARED SPECTROSCOPY, CIRCULAR DICHROISM AND OPTICAL ROTATORY DISPERSION
Authors: Maeda Hiroshi , Shiraishi Hiroyuki , Onodera Shinji , Ishida Nakao
Published: August 2010

The peptide backbone and aromatic side chain conformations of antitumour antibiotic protein, neocarzinostatin and its derivative tetra‐S‐carboxymethyl neocarzinostatin, have been studied using the ultraviolet circular dichroism (CD), optical rotatory dispersion (ORD) and plane polarized infrared spectroscopy.

The near ultraviolet CD and ORD indicated multiple contributions from side chain chromophores (π → π*) suggesting buried state (resulting asymmetric property) of phenylalanyl and tyrosyl and perhaps cystine residues in neocarzinostatin. These results are quite accordant with that of chemical inactivity of the tyrosyl and cystinyl residues in the antibiotic. No clear band was assigned for contribution of tryptophyl residue.

The results of the infrared spectroscopy at amide I and II have been found more useful in the present study for the analysis of peptide backbone conformations, which indicated the presence of cross β‐conformation, while the far ultraviolet CD and ORD spectra were atypical and unable to be interpreted.

The results of the examination of amino acid sequence and composition support the finding of infrared studies.

The assumption that neocarzinostatin possesses a rigid overall conformation can be explained by the above results and by our separate findings of its peculiar resistances to disulfide bond reductions in aqueous system and hydrolyses by proteolytic enzymes.
SYNTHESIS OF A CHELATED CORE RELATED TO RUBREDOXIN: Amino Acids and Peptides. XXXV*
Authors: Ali Akhtar , Fahrenholz Falk , Garing John C. , Weinstein Boris
Published: August 2010

Two protected pentapeptides corresponding to the amino acid sequences 6–10 and 38–42 of rubredoxin were synthesized and coupled to yield a decapeptide. This hybrid compound, as well as the corresponding deblocked derivative, formed soluble iron complexes, whose visual absorption colors were similar to the native protein.
PROTEIN CATABOLISM: III. Proteolytic Enzymes of Guinea Pig Cerebral Cortex and Synaptosomal Localization
Authors: Bosmann H. Bruce
Published: August 2010

Two proteinases of guinea pig cerebral cortex, one of pH optimum 3.4, the other of pH optimum 7.6, were purified 130‐ and 900‐fold by centrifugation and Sephadex G‐100 and G‐200 gel chromatography. Both proteinases were assayed for utilizing [3H]acetyl hemoglobin as substrate. The purified pH 3.4 proteinase had two bands on sodium dodecyl sulfate polyacrylamide gel electrophoresis while the purified pH 7.6 proteinase gave three bands when stained for protein; none of the purified material stained for glycoprotein. The purified pH 3.4 proteinase had pI of 4.0 to 5.0 and a Km of 1 ± 10‐4 M hemoglobin. This acid proteinase showed no cofactor requirements, was inhibited 51% by 0.1 M HgCl2, and was relatively inactive against low molecular weight synthetic substrates. The purified pH 7.6 proteinase had pI of 6.7 to 7.4 and a Km of 1 ± 10‐5 M. This neutral proteinase showed no cofactor requirements, was severely inhibited by HgCl2 and diisopropylphosphofluoridate, and was also relatively inactive against low molecular weight synthetic substrates. On fractionation of the guinea pig cerebral cortex into ‘myelin’, ‘purified synaptosomes’ and ‘mitochondria’ fractions proteinase activity was found in each fraction. Highest activity of both pH 3.4 and pH 7.6 enzymes was in the ‘mitochondrial’ fraction. Fractionation of synaptosomes indicated highest pH 7.6 and pH 3.4 proteolytic activity in the fraction D ‘synaptic vesicle’ fraction. This activity was further purified on continuous sucrose gradients and separation of the pH 3.4 and pH 7.6 enzymes achieved. The purified pH 7.6 proteinase was found to be capable of releasing peptides and glycopeptides from isolated synaptosome surface electrokinetically in a manner similar to trypsin.
A STUDY OF THE CYSTINE RESIDUES IN BOMBYX MORI AND OTHER SILKS
Authors: Earland Christopher , Robins Simon P.
Published: August 2010

Silks representative of the three subfamilies of Bombycidae have been studied and it has been found that they all contain cystine residues. The amount present varies, but irrespective of the country of origin is constant for a given species. In all cases the cystine content of the sericin was found to be at least twice that of the fibroin, which suggests that disulphide cross‐linking does not contribute to the insolubility of the latter.

The cystine content of Bombyx mori fibroin is 10.0 μ mole/g and this work has shown that at least one third of this cystine is present in the sequence

Arg‐Ala‐Leu‐Pro‐Cys‐Asn‐Val‐Cys

Although such a small cystine‐containing ring has not previously been reported as occurring in proteins, it is concluded that on stereochemical grounds the structure is sound.
BOVINE SERUM ALBUMIN IN LITHIUM CHLORIDE SOLUTIONS. ASSOCIATION BEHAVIOR AT NEUTRAL pH
Authors: Sun S. F. , del Rosario N. O. , Goldstein L. A.
Published: August 2010

Measurements of light scattering at 546 nm were carried out on bovine serum albumin in LiCl solutions at neutral pH (ca. 5.2) and room temperature. The concentration of LiCl varied from 0.1 to 7.0 M. There was a relatively small increase in the molecular weight of the protein when the concentration of LiCl in aqueous solutions was in the range between 0.1 M and 3.0 M. A major increase occurred when the concentration of LiCl exceeded 3.0 M. Preferential binding of LiCl to the protein varied in the same direction: negative when the concentration of LiCl was below 3.0 M and positive when the concentration was above 3.0 M. A reaction pattern suggested that the aggregation is preceded by a reversible conformational change of the monomer and the aggregation is a combination of denatured monomers.
β‐LYTIC PROTEASE, A NEUTRAL SORANGIOPEPTIDASE*
Authors: Oza Narendra B.
Published: August 2010

The specificity of β‐lytic protease of Sorangium is found to be similar to neutral proteases of bacterial origin. The β‐enzyme did not hydrolyze any of the common esters of pancreopeptidases; however, an affinity for the peptide bond between R and R1 in the molecular arrangement X‐R‐R1‐NH2 was shown. The substitution occurred at the N‐terminal of a hydrophobic amino acid whose carboxyl end was not terminal. 3‐(2‐furyl‐acryloyl)‐glycyl‐L‐leucine amide was the substrate of choice since accurate spectrophotometric rate assays could be accomplished with this substrate.

A close relationship existed between the mammalian proteases and Sorangium proteases. The β‐enzyme was similar to carboxypeptidase (non‐serine protease) in some respects, and the α, δ, enzymes of Sorangium were, to some extent, similar to serine proteases of mammalian origin. In agreement with the nomenclature of other neutral proteases, a more specific name of ‘Neutral Sorangiopeptidase’ has been suggested.
ISOBUTANE CHEMICAL IONIZATION MASS SPECTROMETRY OF DIPEPTIDES
Authors: Bowen D. V. , Field F. H.
Published: August 2010

The isobutane chemical ionization mass spectra of 25 dipeptides have been determined. All of the peptides gave spectra useful for identification and sequencing. The spectra of most peptides showed two or three sequence ions (an N‐amide, an N‐imine, and/or a (C‐amino acid +1)+ ion) and every spectrum showed at least one sequence ion. Peptides containing Ile or Leu could not be differentiated by this method. Peptides containing Ser or Thr gave ions at (M+l)+ and useful sequence ions. Peptides containing Asp or Glu generally did not produce (M+l)+ ions, but the spectra of these peptides were still useful for sequencing.
CHEMICAL MODIFICATION OF NEUTRAL SUBTILOPEPTIDASE BY AROMATIC DIAZO COMPOUNDS
Authors: Fujiwara Kunio , Tsuru Daisuke
Published: August 2010

Effect of several aromatic diazo compounds on the activity of neutral protease of Bacillus subtilis var. amylosacchariticus (neutral subtilopeptidase) was investigated. Treatment of the enzyme with a 50‐fold molar excess of p‐nitrobenzene diazonium fluoroborate at pH 6.5 for 15 min reduced the caseinolytic activity, whereas it increased the activity toward synthetic substrate, Z‐Gly‐L‐Leu. NH2, to 180 to 250% of that of the native enzyme. Almost the same result was obtained by incubating the enzyme with a 50‐fold molar excess of β‐diazonaphthalene fluoroborate at pH 8.5–10.0 for 15 min. Spectrophotometric and amino acid analyses indicated that the azocoupling occurred exclusively at the tyrosyl residue(s) of the enzyme. Another diazo compound, 3‐diazoquinoline fluoroborate, however, seemed to react with lysyl residue(s) of the enzyme, without significantly affecting the enzyme activity.
SYNTHESIS AND BIOLOGICAL STUDIES OF NOVEL BRADYKININ ANALOGUES
Authors: Felix Arthur M. , Jimenez Manuel H. , Vergona Ronald , Cohen Michael R.
Published: August 2010

Ten new nonapeptide and decapeptide analogues of bradykinin were prepared by solid phase synthesis. Analogues of proline (3,4‐dehydroproline; azetidine‐2‐carboxylic acid; cis,trans‐4‐methylproline; thiazolidine‐4‐carboxylic acid and trans‐4‐hydroxyproline) were successfully incorporated into the peptides in place of proline at position 3. In vivo and in vitro pharmacological studies revealed that the analogues were in general less active than bradykinin. Several structure‐activity relationships were postulated from rat blood pressure, rat uterus and guinea pig ileum studies.
THE CRYSTAL AND MOLECULAR STRUCTURE OF YEAST L‐LACTATE DEHYDROGENASE (CYTOCHROME b2):
Authors: Olive J. , Barbotin J. N. , Risler J. L.
Published: August 2010

An electron microscopy study of yeast cytochrome b2 has been performed on two different crystalline forms by negative staining and freeze‐etching.

The overall dimensions of the tetrameric molecule were deduced from the study of the trigonal (DNA‐free) crystals, and were found to be 97 × 60× 56 Å. These dimensions impose some restrictions to the possible packings of the molecules in the tetragonal (DNA‐containing) crystals. Together with the optical diffraction pattern of the micrographs and results of earlier X‐ray diffraction studies, these data permit the conclusion that, at 20 Å resolution, cytochrome b2 is a true tetramer with molecular symmetry 222.
CONFORMATIONS OF OILSEED STORAGE PROTEINS (GLOBULINS) DETERMINED BY CIRCULAR DICHROISM
Authors: Jacks T. J. , Barker R. H. , Weigang O. E.
Published: August 2010

Conformations of seed globulins from cucurbit, hemp, peanut, and soy, determined by circular dichroism, consisted of 8% α‐helical, 31 % pleated sheet, and 61% unordered structures (mean values).
IMMUNOCHEMICAL IDENTIFICATION OF NEUTRAL PEPTIDE HYDROLASES IN DORMANT AND GERMINATING BARLEY GRAINS
Authors: Tronier Bente , Ory Robert L. , Djurtoft Robert J.
Published: August 2010

The chromogenic substrate, N‐acetyl‐DL‐phenylalanine‐β‐naphthyl ester (APNE), used in trypsin or chymotrypsin studies, has been employed to identify neutral peptide hydrolases in barley by immunoelectrophoretic analysis. Enzyme activity was observed in proximal (embryo part) and distal (endosperm part) portions of barley grains before and after germination. The proximal portion contained all detectable activity in the ungerminated seed. This enzyme migrates strongly towards the anode. During germination a new enzyme is formed which hydrolyzes the same substrate but is electrophoretically different from the enzyme found in dormant grains (it is more neutral or cathodic). The newly‐formed enzyme appears in the proximal part of the seed after 34 hours of germination and in the distal part after 96 hours. This enzyme does not appear to be a carboxypeptidase but may be related to one (or more) of the reported barley aminopeptidases.
SHORT DIGESTION OF BOVINE SERUM ALBUMIN WITH PEPSIN. ISOLATION AND CHARACTERIZATION OF FRAGMENTS AND THEIR LOCATION IN THE ALBUMIN MOLECULE
Authors: Braam W. G. M. , Hilar M. C. , Harmsen B. J. M. , van Os G. A. J.
Published: August 2010

After short peptic digestion of bovine serum albumin between pH 3.6 and 3.9, a limited number of well defined fragments are found. The isolation and characterization of some fragments, probably placed in the C‐terminal part of albumin, have been given in a previous paper. This paper describes the isolation, characterization and localization of a number of N‐terminal fragments of bovine serum albumin. The investigation comprises molecular weight determination, amino acid analysis, N‐terminal amino acid determination, copper binding studies and SH‐group determination. It is concluded that cleavage of albumin by pepsin between pH 3.6 and 3.9 preferentially occurs in the C‐terminal moiety of albumin. This leads to the appearance of large fragments with the same N‐terminal end as albumin. The mechanism of the digestion by pepsin is discussed in relation to the structural model of albumin and the conformational change at low pH (N‐F transition).
A STUDY OF THE ACTIVE CENTER OF TRYPSINOGEN BY COMPARATIVE AFFINITY CHROMATOGRAPHY OF TRYPSINOGEN, α‐, β‐, ψ‐TRYPSINS, DIP‐TRYPSIN, CHYMOTRYPSINOGEN, α‐CHYMOTRYPSIN AND ELASTASE
Authors: Chauvet Jacqueline , Acher Roger
Published: August 2010

Affinity chromatography of α‐, β‐, ψ‐trypsins, chymotrypsin and elastase on trypsin inhibitor (bovine Kunitz inhibitor) coupled with Sepharose has shown that, despite the conformational similarity, elastase is not adsorbed in contrast to trypsins and chymotrypsin. This result might suggest that the specificity site is involved in the binding. On the other hand, because inactive DFP‐treated trypsin is not adsorbed, the catalytic site and especially Ser‐195 might also be necessary for the association.

Chrymotrypsinogen is not adsorbed on the inhibitor‐Sepharose, but trypsinogen is retarded at pH 7.0 and the delay is increased at pH 8.1. The behaviour of trypsinogen on inhibitor‐Sepharose, in contrast to those of DIP‐trypsin and chymotrypsinogen, suggests that both catalytic and specificity sites are necessary for the binding and that these sites are partially pre‐existent in trypsinogen.
THE EFFECTS OF COMBINING TWO DIFFERENT ALCOHOLS ON THE HEAT‐INDUCED REVERSIBLE DENATURATION OF RIBONUCLEASE
Authors: Gerlsma Sicco Y. , Stuur Elzo R.
Published: August 2010

The effects of combining two different alcohols on the transition temperature of ribonuclease were investigated.

It appears that at 60°C the combined effects on the transition temperature of ribonuclease of two different alcohols are equal to the algebraic sum of the effects of each individual alcohol. This holds true for a combination of two monohydric alcohols, two polyhydric alcohols and a combination of a monohydric and a polyhydric alcohol.

At lower temperatures only the effects of the combinations of two polyhydric alcohols show additivity. The combined effect of a polyvalent alcohol and a monovalent alcohol at low temperature is surprisingly higher than the algebraic sum of the effects of the individual alcohols.

The polyhydric alcohol enhances the hydrophobic effect of the monovalent alcohol for temperatures up to 50°C. Obviously the polyhydric alcohol perturbs the water structure at these low temperatures, which leads to the intensifying of the interhydrophobic interactions.

Furthermore, the combined effect of two different monovalent alcohols with different hydrophobic effects does not show additivity at low temperatures. The single (OH) group of the weakest hydrophobic alcohol enhances the hydrophobic effect of the potentially strongest hydrophobic alcohol.
ADRENOCORTICOTROPIN. 46.
Authors: Blake James , Li Choh Hao
Published: August 2010

Four biologically active peptides have been synthesized by the solid‐phase method: [2‐δ‐aminovaleric acid]‐adrenocorticotropin‐(2–19), [3‐ω‐aminocaprylic acid]‐adrenocortitropin‐(3–19), [3‐δ‐aminovaleric acid]‐adrenocorticotropin‐(3–19), and [3,4‐δ‐aminovaleric acid]‐adrenocorticotropin‐(3–19). The in vivo steroidogenic activity and the in vitro lipolytic activity of the above peptides relative to that of adrenocorticotropin‐(1–19) are reported.
MALEYLATION OF ALKALINE MESENTERICOPEPTIDASE
Authors: Genov Nicolay , Shopova Maria
Published: August 2010

Seven of the eight e‐amino groups of the lysyl residues in alkaline mesentericopeptidase were modified when the enzyme was treated with maleic anhydride. Some conclusions about the degree of exposure to the solvent of these amino acid side chains were made. The results are discussed in relation to the X‐ray crystallographic model of subtilisin type BPN.

The maleylation of alkaline mesentericopeptidase caused a loss of its elastolytic activity while the rate of cleavage of casein was slightly increased. Maleyl‐enzyme has the same activity as the native mesentericopeptidase with the synthetic ester substrates Nα‐tosyl‐L‐arginine methyl ester and N‐acetyl‐L‐tyrosine ethyl ester. It was concluded that the additional negatively charged groups were introduced outside the primary binding sites for small substrates.

The effects of varying the salt concentration on mesentericopeptidase activities were studied and conclusions about the forces responsible for the formation of the enzyme‐substrate complexes were drawn.