bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Ca doping on the optical properties of La1.2Sr1.8Mn2O7
Authors: Her J. L. , Liu H. L. , Shen C. H. , Liu R. S. , Sheu H. S.
Published: January 2006

We present x-ray-diffraction, infrared reflectivity, and Raman-scattering measurements of La1.2(Sr1.8−xCax)Mn2O7 as a function of temperature and doping (x=0.0, 0.4, 0.6, and 0.8). At room temperature, x-ray-diffraction data show that the replacement of Sr ions with smaller Ca ions causes a shrinkage of the unit-cell volume. The far-infrared conductivity spectra of all doped samples are typical of an insulator, showing only phonons. When doped with Ca on Sr and a corresponding systematic reduction in Curie temperature (Tc), there is a suppression of the low-frequency optical spectral weight. For the x=0.0 compound, the Raman-active phonon associated with the internal stretching of the oxygen atoms in MnO6 octahedra shows a noticeable hardening below Tc. A polaron transport can be attributed to the observed frequency shifts. Interestingly, this hardening is reduced as the Ca content increases. These observations suggest that Ca doping disrupts the effects of the double-exchange interaction on the lattice degree of freedom, thereby accounting for the characteristic changes in the phase diagram.
Studies of the plume emission during the femtosecond and nanosecond ablation of graphite in nitrogen
Authors: Fuge Gareth M. , Ashfold Michael N. R. , Henley Simon J.
Published: January 2006

Comparative studies of the pulsed laser ablation of graphite in 20mTorr of N2 using both 15ns and 450fs pulses at a wavelength of 248nm are reported. Emissions from the resulting ablation plumes, and from collisions with ablated material and the background N2 gas molecules, have been investigated by wavelength-, space-, and time-resolved optical emission spectroscopy (OES), and the observations correlated with the results of the analyses of films formed when such material is incident on a silicon substrate. Wavelength-dispersed spectra of the plume arising in nanosecond ablation reveal CI, CII, and C2 emissions—concentrated close to the target—and, at greater distances, strong CN and weak N2+ emissions. N2+(B–X) emission dominates in the case of femtosecond ablation. Time-gated imaging studies have allowed estimation of propagation velocities for these various emissions. Possible production routes for secondary emitters such as CN and N2+ are discussed, and arguments presented to show that measurements of the apparent propagation “velocities” of such emissions are unlikely to provide meaningful measures of the velocities (or energies) with which these carriers impact on a substrate surface. Laser Raman spectroscopy confirms nitrogen incorporation within the films grown by both nanosecond and femtosecond ablations; the former films are deduced to be both thicker and to have higher N content—findings that accord with the OES analyses.
Size-dependent band gap of colloidal quantum dots
Authors: Baskoutas Sotirios , Terzis Andreas F.
Published: January 2006

The size-dependent band gap of semiconductor quantum dots is a well-known and widely studied quantum confinement effect. In order to understand the size-dependent band gap, different theoretical approaches have been adopted, including the effective-mass approximation with infinite or finite confinement potentials, the tight-binding method, the linear combination of atomic orbitals method, and the empirical pseudopotential method. In the present work we calculate the size-dependent band gap of colloidal quantum dots using a recently developed method that predicts accurately the eigenstates and eigenenergies of nanostructures by utilizing the adiabatic theorem of quantum mechanics. We have studied various semiconductor (CdS, CdSe, CdTe, PbSe, InP, and InAs) quantum dots in different matrices. The theoretical predictions are, in most cases, in good agreement with the corresponding experimental data. In addition, our results indicate that the height of the finite-depth well confining potential is independent of the specific semiconductor of the quantum dot and exclusively depends on the matrix energy-band gap by a simple linear relation.
Effect of metal-ion doping on the optical properties of nanocrystalline ZnO thin films
Authors: Mendoza-Galván A. , Trejo-Cruz C. , Lee J. , Bhattacharyya D. , Metson J. , Evans P. J. , Pal U.
Published: January 2006

Optical properties of metal (Al, Ag, Sb, and Sn)-ion-implanted ZnO films have been studied by ultraviolet-visible spectroscopy and spectroscopic ellipsometric techniques. The effects of metal-ion doping on the optical band gap (Eg), refractive index (n), and extinction coefficient (k) of nanocrystalline ZnO films have been studied for the similar implantation dose of all the metal ions. The ellipsometric spectra of the ion-implanted samples could be well described by considering an air/roughness/ZnO–M (layer 1)/ZnO (layer 2)/glass model. The band gap of ZnO films increases with Al ion doping and decreases with doping of Ag, Sb, and Sn ions. The refractive index of ZnO films in the visible spectral region increases substantially on Sb and Sn ion doping, while it decreases to some extent with Al ion doping.
The ion cyclotron resonance frequency of short, single-species plasmas in Penning traps
Authors: Barlow S. E. , Tinkle Mark D.
Published: January 2006

We present here models that allow us to calculate the effects of various linear and low-order nonlinear terms on the E×B drift frequency in a cylindrical Penning trap mass spectrometer. These effects translate directly to shifts in the observed ion cyclotron resonance frequency. We show that nonlinearities in the external electrostatic potential interact with the space charge to affect the observations. Similarly, image charge effects are readily incorporated. The model is then used to describe experimental observations and found to largely account for our observations.
Ab initio investigations of the radical-radical reaction of O(P3)+C3H3
Authors: Lee Hohjai , Nam Mi-Ja , Choi Jong-Ho
Published: January 2006

We present ab initio calculations of the reaction of ground-state atomic oxygen [O(P3)] with a propargyl (C3H3) radical based on the application of the density-functional method and the complete basis-set model. It has been predicted that the barrierless addition of O(P3) to C3H3 on the lowest doublet potential-energy surface produces several energy-rich intermediates, which undergo subsequent isomerization and decomposition steps to generate various exothermic reaction products: C2H3+CO, C3H2O+H, C3H2+OH, C2H2+CHO, C2H2O+CH, C2HO+CH2, and CH2O+C2H. The respective reaction pathways are examined extensively with the aid of statistical Rice-Ramsperger-Kassel-Marcus calculations, suggesting that the primary reaction channel is the formation of propynal (CHCCHO)+H. For the minor C3H2+OH channel, which has been reported in recent gas-phase crossed-beam experiments [H. Lee et al., J. Chem. Phys. 119, 9337 (2003); 120, 2215 (2004)], a comparison on the basis of prior statistical calculations is made with the nascent rotational state distributions of the OH products to elucidate the mechanistic and dynamic characteristics at the molecular level.
Adhesion hysteresis and friction at nanometer and micrometer lengths
Authors: Szoszkiewicz Robert , Bhushan Bharat , Huey Bryan D. , Kulik Andrzej J. , Gremaud Gerard
Published: January 2006

Comparisons between adhesion hysteresis and friction at nanometer and micrometer length scales were investigated experimentally and theoretically. Nanoscale adhesion hysteresis was measured using the ultrasonic force microscopy (UFM) on mica, calcite, and a few metallic samples (Pt, Au, Cu, Zn, Ti, and Fe). Obtained adhesion hysteresis ranged between 4×10−19 and 4×10−18J. At the microscale a similar setup with a nanoindenter was used and the same samples were investigated. Adhesion hysteresis measured at the microscale ranged between 8×10−17 and 14×10−17J. Friction was investigated via lateral force microscopy, as well as by scratch tests done with the nanoindenter. Numerical simulations based on the UFM model as well as established theories of contact mechanics studied qualitative dependencies of adhesion hysteresis on experimental parameters. Quantitative relations between adhesion hysteresis and friction were obtained through an analytic model relying on elastic and adhesive properties of the contact. The model agreed with measurements and simulations.
Exploring hyperpolarized Kr83 by remotely detected NMR relaxometry
Authors: Cleveland Zackary I. , Pavlovskaya Galina E. , Stupic Karl F. , LeNoir Catherine F. , Meersmann Thomas
Published: January 2006

For the first time, a hyperpolarized (hp) noble gas with a nuclear electric quadrupole moment is available for high-field nuclear-magnetic-resonance (NMR) spectroscopy and magnetic-resonance imaging. Hp Kr83 (I=9∕2) is generated by spin-exchange optical pumping and separated from the rubidium vapor used in the pumping process. Optical pumping occurs under the previously unstudied condition of high krypton gas densities. Signal enhancements of more than three orders of magnitude compared to the thermal equilibrium Kr83 signal at 9.4T magnetic-field strength are obtained. The spin-lattice relaxation of Kr83 is caused primarly by quadrupolar couplings during the brief adsorption periods of the krypton atoms on the surrounding container walls and significantly limits the currently obtained spin polarization. Measurements in macroscopic glass containers and in desiccated canine lung tissue at field strengths between 0.05 and 3T using remotely detected hp Kr83 NMR spectroscopy reveal that the longitudinal relaxation dramatically accelerates as the magnetic-field strength decreases.
Influence of pulse duration on the plasma characteristics in high-power pulsed magnetron discharges
Authors: Konstantinidis S. , Dauchot J. P. , Ganciu M. , Ricard A. , Hecq M.
Published: January 2006

High-power pulsed magnetron discharges have drawn an increasing interest as an approach to produce highly ionized metallic vapor. In this paper we propose to study how the plasma composition and the deposition rate are influenced by the pulse duration. The plasma is studied by time-resolved optical emission and absorption spectroscopies and the deposition rate is controlled thanks to a quartz microbalance. The pulse length is varied between 2.5 and 20μs at 2 and 10mTorr in pure argon. The sputtered material is titanium. For a constant discharge power, the deposition rate increases as the pulse length decreases. With 5μs pulse, for an average power of 300W, the deposition rate is ∼70% of the deposition rate obtained in direct current magnetron sputtering at the same power. The increase of deposition rate can be related to the sputtering regime. For long pulses, self-sputtering seems to occur as demonstrated by time-resolved optical emission diagnostic of the discharge. In contrary, the metallic vapor ionization rate, as determined by absorption measurements, diminishes as the pulses are shortened. Nevertheless, the ionization rate is in the range of 50% for 5μs pulses while it lies below 10% in the case of a classical continuous magnetron discharge.
Characterization of the magnetization vortex state in magnetic tunnel junctions patterned into nanometer-scale arrays
Authors: Girgis E. , Pogossian S. P. , Gbordzoe M.
Published: January 2006

The aim of this work is to investigate the switching characteristics of magnetic tunnel junctions (MTJs) that contain two ferromagnetic layers in a magnetization vortex state as a function of the aspect ratio (length/width). Magnetic tunnel junctions NiFe30nm∕AlOx1.3nm∕Co15nm have been patterned into arrays of dots with identical geometries as in a single layer having a vortex state at low aspect (width/length) dots. The switching characteristics were studied using a vibrating sample magnetometer and magneto-optic Kerr effect techniques. The results show the relation between the switching fields and the sizes of the MTJ dots in which the switching of the two ferromagnetic layers is indistinguishable at low aspect ratio. It was found that as the aspect ratio increases, the switching becomes more distinguishable. This can be attributed to the magnetization vortices in the two ferromagnetic layers and the magnetostatic coupling (dipole-dipole interaction), which are size-dependent.
Potential-energy surface, van der Waals energy spectrum, and vibronic transitions in s-tetrazine-argon complex
Authors: Makarewicz Jan
Published: January 2006

The van der Waals vibrational states and the structure of the vibronic spectrum of s-tetrazine-argon complex have been studied by the ab initio methods. The potential-energy surface of the ground S0 electronic state of the complex has been constructed by fitting the analytical many-body expansion to a large set of the interaction energy values computed using the second-order Møller-Plesset perturbation theory combined with the standard aug-cc-pVDZ basis set. The equilibrium structure of the complex found is that with argon located above the tetrazine ring at a distance of 3.394 Å. The calculated dissociation energy of 354cm−1 is compatible with the experiment. The van der Waals energy spectrum calculated from the potential-energy surface is explained analyzing a correlation with a simpler energy spectrum of benzene-argon. A new assignment of the S0–S1 vibronic spectrum is proposed on the basis of the rigorous selection rules, vibrational energy levels in S0 and S1 states and vibronic transition intensities calculated from the electronic transition dipole moment surfaces.
Ultralow threshold field emission from a single multipod structure of ZnO
Authors: Ramgir Niranjan S. , Mulla Imtiaz S. , Vijayamohanan K. , Late Dattatray J. , Bhise Ashok B. , More Mahendra A. , Joag Dilip S.
Published: January 2006

The field emission of individual ZnO multipods and a single arm of a multipod structure grown by a vapor deposition were carried out. A current of 1 nA with an ultralow onset voltage of 40 V was observed repeatedly for the single multipod as well as for the arm. The nonlinearity observed in the Fowler–Nordheim plots have been interpreted on the basis of the theory of electron emission from semiconductors and a scheme explaining the field emission behavior in both the high- and low-field regions owing to the very high geometrical factor has been picturized.
Room-temperature continuous-wave operation of quantum-cascade lasers at λ∼4μm
Authors: Yu J. S. , Darvish S. R. , Evans A. , Nguyen J. , Slivken S. , Razeghi M.
Published: January 2006

High-power cw λ∼4μm quantum-cascade lasers (QCLs) are demonstrated. The effect of different cavity length and laser die bonding is also investigated. For a high-reflectivity-coated 11-μm-wide and 4-mm-long epilayer-down bonded QCL, cw output powers as high as 1.6W at 80K and 160mW at 298K are obtained, and the cw operation is achieved up to 313K with 12mW. The laser exhibits a threshold current density of 1.96kA∕cm2, a slope efficiency of 737mW∕A, and a maximum wall-plug efficiency of 0.9% under cw mode at 298K. In pulsed mode, a maximum average power of 552mW at 298K is achieved at 45% duty cycle and a characteristic temperature is 176K from 80to393K.
Ultraviolet band-pass Schottky barrier photodetectors formed by Al-doped ZnO contacts to n-GaN
Authors: Sheu J. K. , Lee M. L. , Tun C. J. , Lin S. W.
Published: January 2006

This work prepared Al-doped ZnO(AZO) films using dc sputtering to form Schottky contacts onto GaN films with low-temperature-grown GaN cap layer. Application of ultraviolet photodetector showed that spectral responsivity exhibits a narrow bandpass characteristic ranging from 345to375nm. Moreover, unbiased peak responsivity was estimated to be around 0.12A∕W at 365nm, which corresponds to a quantum efficiency of around 40%. In our study, relatively low responsivity can be explained by the marked absorption of the AZO contact layer. When the reverse biases were below 5V, the study revealed that dark currents were well below 5×10−12A even though the samples were annealed at increased temperatures.
A Finemet-type alloy as a low-cost candidate for high-temperature magnetic refrigeration
Authors: Franco V. , Blázquez J. S. , Conde C. F. , Conde A.
Published: January 2006

The refrigerant capacity (RC) of Fe68.5Mo5Si13.5B9Cu1Nb3 alloy is studied. For the amorphous sample, RC=63Jkg−1 for an optimal reversible cycle with cold and hot ends at 328K and 520K, respectively, for a maximum applied field H=15kOe. Nanocrystallization diminishes both the peak entropy change and RC of the material. Although the measured RC is smaller than for Gd5Ge1.9Si2Fe0.1 (240Jkg−1 for H=50kOe), the Mo-Finemet alloy is more than 20 times cheaper, the applied field employed is smaller, and the temperature span of the optimal cycle is increased. This makes this alloy a promising material for high-temperature refrigeration.
Reflection-type pulsed terahertz imaging with a phase-retrieval algorithm
Authors: Ino Y. , Héroux J. B. , Mukaiyama T. , Kuwata-Gonokami M.
Published: January 2006

We propose and demonstrate a scheme for two-dimensional terahertz reflection imaging using a time-domain phase-retrieval algorithm based on the dispersion relations of complex reflection coefficients. With this scheme, topographic images—as well as the dielectric functions of a structured sample—can be obtained. A composite sample made of a semiconductor and metals is characterized within depth and lateral errors of 50μm and 100μm.
Correlation of growth stress and structural evolution during metalorganic chemical vapor deposition of GaN on (111) Si
Authors: Raghavan Srinivasan , Weng Xiaojun , Dickey Elizabeth , Redwing Joan M.
Published: January 2006

Compositionally graded AlGaN buffer layers enable the growth of thicker crack free layers of GaN on (111) Si than is possible with an AlN buffer layer. Using cross sectional transmission electron microscopy and in situ stress measurements, it is shown that a compressive growth stress is incorporated in the GaN layer when the graded AlGaN buffer layer is thick enough to accommodate all microstructural evolution, which is primarily a reduction in threading dislocation density with thickness during growth. Most of the dislocation density reduction is observed to occur when the film is growing under a compressive stress. This compressive stress arises from the changing lattice parameter due to grading and helps to offset the tensile stress generated by microstructural evolution. It also helps to decrease the tensile thermal expansion mismatch stress during cooling and thus reduces film cracking.
Effects of a thin Al layer insertion between AlGaN and Schottky gate on the AlGaN∕GaN high electron mobility transistor characteristics
Authors: Nanjo Takuma , Oishi Toshiyuki , Suita Muneyoshi , Abe Yuji , Tokuda Yasunori
Published: January 2006

To improve an AlGaN∕GaN high electron mobility transistor, an Al layer as thin as 3 nm was inserted between the AlGaN barrier layer and the gate contact. At our preceded experiments on Schottky diodes, we confirmed significant improvement in capacitance-gate voltage characteristics especially at a low frequency as well as drastic reduction in gate leakage current, which should be interpreted in terms of decrease in oxygen-related trap density at the AlGaN surface. As a result of the trap reduction, the transistor indicates marked improvement of current collapse with no degradation in transconductance.
Ab initio calculation of hydrostatic absolute deformation potential of semiconductors
Authors: Li Yong-Hua , Gong X. G. , Wei Su-Huai
Published: January 2006

The hydrostatic absolute deformation potential (ADP) of the valence-band maximum state is one of the most important properties of semiconductors. Yet, it has been calculated in the past only using assumptions that have not been rigorously approved. In this letter, we present an approach to calculate the hydrostatic ADP of Si, GaAs, and ZnSe using an ab initio all-electron method and lattice harmonic expansions. We show that the calculated ADP is independent of the selection of the reference energy levels. The calculated ADPs are all positive for the three systems. However, as the p-d coupling increases in the II-VI compounds, the ADP decreases.
Lightwand Tracheal Intubation with and without Muscle Relaxation
Authors: Massó Eva , Sabaté Sergi , Hinojosa Marta , Vila Pere , Canet Jaume , Langeron Olivier
Published: January 2006

Background

Lightwand tracheal intubation is a suitable technique for patients who are difficult to intubate but who are receiving effective ventilation. The effect of muscle relaxants on the efficacy of lightwand intubation has not yet been evaluated. The authors conducted a prospective, double-blind, placebo-controlled study to assess the effectiveness and incidence of complications of lightwand tracheal intubation performed during general anesthesia with and without the use of a muscle relaxant in patients with apparently normal airway anatomy.

Methods

One hundred seventy-six patients who required orotracheal intubation were prospectively included. Anesthesia was administered using propofol (2 mg/kg, then 3 mg . kg (-1). h(-1)) and remifentanil (1 microg/kg, then 0.3 microg . kg(-1) . min(-1)). Patients were randomly assigned to one of two groups (n = 88 for each) to receive rocuronium 0.6 mg/kg or saline intravenously. Lightwand orotracheal intubation (Trachlight; Laerdal Medical Inc., Armonk, NY) was attempted after 3 min. The authors recorded the number of successful intubations, the number of attempts and their duration, and events during the procedure.

Results

The failure rate of lightwand intubation was 12% in the placebo group and 2% in the rocuronium group (P = 0.021). Patients in the placebo group received more multiple intubation attempts (P < 0.001), required a greater intubation time (77 +/- 65 vs. 52 +/- 31 s; P = 0.002) and experienced a greater incidence of events during intubation (61 vs. 0%; P < 0.001) than patients in the rocuronium group.

Conclusions

The use of muscle relaxants in patients with apparently normal airways is associated with a lower failure rate, decreased intubation time, and fewer attempts when performing lightwand orotracheal intubation.
Devices for Lung Isolation Used by Anesthesiologists with Limited Thoracic Experience
Authors: Campos Javier H. , Hallam Ezra A. , Van Natta Timothy , Kernstine Kemp H.
Published: January 2006

Background

Lung isolation is accomplished with a double-lumen tube or a bronchial blocker. Previous studies comparing lung isolation methods were performed by experienced anesthesiologists in thoracic anesthesia. Therefore, the results of these studies may not be relevant to the anesthesiologist with limited experience. This study compared the success rates of lung isolation devices among anesthesiologists with limited experience in thoracic anesthesia.

Methods

A prospective, randomized trial was designed to determine the success and time required for proper placement of the left-sided double-lumen tube (n = 22), the Univent tube (Vitaid Ltd., Lewiston, NY; n = 22), and the Arndt Blocker (Cook Critical Care, Bloomington, IN; n = 22). Anesthesiologists with less than two lung isolation cases per month were included (faculty n = 17 and senior residents n = 11). Variables recorded included (1) successful placement (as determined by an independent observer), (2) time of placement, and (3) the number of times the fiberoptic bronchoscope was used.

Results

Participants failed to place or position their assigned device in 25 of 66 patients (failure was 39% among faculty and 36% among senior residents). The failure rate did not differ among the three devices (P = 0.65). The median (25th-75th percentile) times to complete the placement procedures were as follows: (1) double-lumen tube: 6.1 min (4.6-9.5 min), (2) Univent tube: 6.7 min (4.9-8.8 min), and (3) Arndt Blocker: 8.6 min (5.8-17.5 min) (P = 0.45 comparing all devices). After device malposition was identified, it took 1 min or less for the investigating anesthesiologist to achieve optimal position.

Conclusions

Anesthesiologists with limited experience in thoracic anesthesia frequently fail to successfully place lung isolation devices. Rapid successful device placement by an experienced anesthesiologist excluded any contribution of uniquely difficult anatomy. The nature of the malpositions suggests that the most critical factor in successful placement was the anesthesiologist's knowledge of endoscopic bronchial anatomy.
Impact of Postoperative Unwashed Shed Blood Retrieved after Total Knee Arthroplasty on Endotoxin-stimulated Tumor Necrosis Factor α Release In Vitro
Authors: Muñoz Manuel , Muñoz Encarnación , Navajas Ana , Campos Arturo , Rius Francisca , Gómez Aurelio
Published: January 2006

Background

: Allogeneic or autologous blood seems to have an immunosuppressive effect that is largely attributable to storage-dependent factors. However, transfusion of postoperative unwashed shed blood (USB) after elective total knee replacement does not undergo storage. Therefore, the authors explored the effects of USB on the mitogen-driven cytokine synthesis by the patient's peripheral blood mononuclear cells.

Methods

: Perioperative blood samples were obtained from 12 total knee replacement patients with and 5 without reinfusion of leukoreduced USB, and from USB reinfusion line, before and after leukoreduction. Venous blood obtained at 4-6 postoperative hours was coincubated with USB. Endotoxin-stimulated release of tumor necrosis factor alpha and interleukin 10 was measured after 24 h of culture by solid-phase enzyme-labeled chemiluminescent immunometric assay.

Results

: Coincubation of postoperative venous blood with USB, USB cells, or USB plasma resulted in a significant depression of tumor necrosis factor-alpha synthesis, without significant effects on interleukin-10 synthesis. However, no differences were observed for endotoxin-stimulated cytokine release in perioperative blood samples from patients receiving or not receiving USB.

Conclusion

: These data suggest that USB seemed to contain an antiinflammatory agent. However, at the actual retransfusion rate, USB does not seem to further enhance the immunosuppression that follows knee replacement surgery.
Cerebral Blood Flow Affects Dose Requirements of Intracarotid Propofol for Electrocerebral Silence
Authors: Joshi Shailendra , Wang Mei , Etu Joshua J. , Nishanian Ervant V. , Pile-Spellman John
Published: January 2006

Background

The authors hypothesized that cerebral blood flow (CBF) changes will affect the dose of intracarotid propofol required to produce electrocerebral silence.

Methods

The authors tested their hypothesis on New Zealand White rabbits. The first group of 9 animals received intracarotid propofol during (1) normoventilation, (2) hyperventilation, and (3) hypoventilation. The second group of 14 animals received intracarotid propofol with or without concurrent intraarterial verapamil, a potent cerebral vasodilator. The third group of 8 animals received bolus injection of propofol during normotension, during severe cerebral hypoperfusion, and after hemodynamic recovery.

Results

In the first group, there was a linear correlation between the dose of intracarotid propofol and percent change (%Delta) in CBF from the baseline due to changes in the minute ventilation, Total Dose (y) = 0.17 + 0.012 * %Delta CBF (x), n = 27, r = 0.76. In the second group, the dose of propofol was also a function of CBF change after verapamil, Total Dose (y) = 0.98 + 0.1 * %Delta CBF (x), n = 14, r = 0.75. In the third group, the duration of electrocerebral silence after intracarotid propofol (3 mg) was significantly increased with concurrent cerebral hypoperfusion compared with prehypoperfusion and posthypoperfusion values (141 +/- 38 vs. 19 +/- 24 and 16 +/- 12 s, respectively, P < 0.0001).

Conclusions

The authors conclude that CBF affects the dose requirements of intracarotid propofol required to produce electrocerebral silence. Furthermore, the manipulation of CBF might be a useful tool to enhance the efficacy of intracarotid drugs.
Age-dependent Responses to Nerve Injury– induced Mechanical Allodynia
Authors: Ririe Douglas G. , Eisenach James C.
Published: January 2006

Background

Developmental differences in responses to acute and chronic nerve injury have received minimal attention. This study examines developmental differences in behavioral responses to a proximal (closer to the spinal cord) (L5 and L6 spinal nerve root ligation) or to a more distal (closer to peripheral innervation) (partial sciatic nerve ligation) nerve injury in rats paralleling the infant to young adult human.

Methods

Withdrawal thresholds to von Frey filament testing in the hind paw were determined before and various times after either spinal nerve root ligation or partial sciatic nerve ligation in rats aged 2, 4, and 16 weeks. Control rats of these ages were observed serially without surgery. Times for withdrawal thresholds to mechanical stimuli to return to 80% of that of the hind paw in the control animals were compared among the different ages in the two models.

Results

Baseline withdrawal thresholds in younger rats were lower (P < 0.05). In the 2-week-old animals, distal injury partial sciatic nerve ligation did not cause a reduction in withdrawal threshold from baseline. This was different from the spinal nerve root ligation group and the older animals in the partial sciatic nerve ligation group. However, when compared with age-matched control animals, both nerve injuries resulted in reduced withdrawal thresholds (P < 0.05). The resolution of hypersensitivity to mechanical stimulation, as measured by return of threshold to 80% of controls, occurred more quickly in 2-week-old than in 4- and 16-week-old animals in both injury models (P < 0.05).

Conclusion

These data suggest that resolution of sensitization to A-fiber input occurs more rapidly in young animals. In addition, distal injury has less of a sensitizing effect on A-fiber input than proximal injury in the younger animals. The authors speculate that neuroimmune responses, especially at the site of injury, are developmentally regulated and less likely to produce chronic pain when injury occurs at a young age.
Perioperative Abstinence from Cigarettes
Authors: Warner David O. , Warltier David C.
Published: January 2006

Chronic exposure to cigarette smoke produces profound changes in physiology that may alter responses to perioperative interventions and contribute to perioperative morbidity. Because of smoke-free policies in healthcare facilities, all smokers undergoing surgery are abstinent from cigarettes for at least some period of time so that all are in various stages of recovery from the effects of smoke. Understanding this recovery process will help perioperative physicians better treat these patients. This review examines current knowledge regarding how both short-term (duration ranging from hours to weeks) and long-term smoking cessation affects selected physiology and pathophysiology of particular relevance to perioperative outcomes and how these changes affect perioperative risk. It will also consider current evidence regarding how nicotine replacement therapy, a valuable adjunct to help patients maintain abstinence, may affect perioperative physiology.
Non-structural proteins of dengue 2 virus offer limited protection to interferon-deficient mice after dengue 2 virus challenge
Authors: Calvert Amanda E. , Huang Claire Y.-H. , Kinney Richard M. , Roehrig John T.
Published: January 2006

Chimeric (D2/WN) viruses containing the pre-membrane (prM) and envelope (E) proteins ofWest Nile virus(WN virus) and the capsid (C) and non-structural proteins of dengue 2 (DEN2) virus were used to evaluate the protective immunity elicited by either the flaviviral E protein or non-structural proteins. AG129 interferon-deficient mice, previously shown to be protected against lethal DEN1 or DEN2 viral infection after vaccination with a wild-type or candidate vaccine strain of DEN1 or DEN2 virus, respectively, were immunized with chimeric D2/WN virus and then challenged with DEN2 virus. D2/WN chimeric viruses were non-pathogenic in AG129 mice. These viruses elicited little anti-DEN E antibody, high levels of anti-DEN NS1 antibody and no or very low levels of DEN2 virus-neutralizing antibodies. Only 15 % of D2/WN-immunized mice survived challenge with DEN2 virus. However, their mean survival time increased by 11–14 days over non-immunized controls. These results suggest that, whilst the non-structural proteins were able to enhance mean survival times of AG129 mice, this protection was not as effective as protection mediated by the E protein.
Molecular-based reclassification of the bovine enteroviruses
Authors: Zell Roland , Krumbholz Andi , Dauber Malte , Hoey Elizabeth , Wutzler Peter
Published: January 2006

Bovine enteroviruses are currently classified into two serotypes within the speciesBovine enterovirus(BEV). Comparison of the sequences of six American and eleven German BEV isolates with published BEV sequences revealed the necessity to revise the taxonomy of these viruses. Molecular data indicate that the bovine enteroviruses are composed of two clusters (designated BEV-A and -B) each with two and three geno-/serotypes, respectively. Whereas low amino acid identity of the capsid proteins 1C (VP3) and 1D (VP1) is the main criterion for the discrimination of geno-/serotypes, the BEV clusters, presumably representing species, differ in sequence identity of all viral proteins. In addition, characteristic lengths of (i) the capsid proteins 1B, 1C and 1D, (ii) the 2C protein, and (iii) the 3′-non-translated region are observed. The BEVs can be distinguished from the other enteroviruses by sequence identity and unique features of the 5′-non-translated region, i.e. a conserved second cloverleaf and characteristic RNA structures of the internal ribosome entry site. Phylogenetically, the closest relatives of the bovine enteroviruses are the porcine enteroviruses. Incongruent phylogenies of the 5′-non-translated region, the capsid proteins and the 3D polymerase indicate frequent intraserotypic and interserotypic recombination within the non-capsid and the capsid region of the BEV genome.
Design and preclinical evaluation of a multigene human immunodeficiency virus type 1 subtype C DNA vaccine for clinical trial
Authors: Burgers Wendy A. , van Harmelen Joanne H. , Shephard Enid , Adams Craig , Mgwebi Thandiswa , Bourn William , Hanke Tomáš , Williamson Anna-Lise , Williamson Carolyn
Published: January 2006

In this study, the design and preclinical development of a multigene human immunodeficiency virus type 1 (HIV-1) subtype C DNA vaccine are described, developed as part of the South African AIDS Vaccine Initiative (SAAVI). Genetic variation remains a major obstacle in the development of an HIV-1 vaccine and recent strategies have focused on constructing vaccines based on the subtypes dominant in the developing world, where the epidemic is most severe. The vaccine, SAAVI DNA-C, contains an equimolar mixture of two plasmids, pTHr.grttnC and pTHr.gp150CT, which express a polyprotein derived from Gag, reverse transcriptase (RT), Tat and Nef, and a truncated Env, respectively. Genes included in the vaccine were obtained from individuals within 3 months of infection and selection was based on closeness to a South African subtype C consensus sequence. All genes were codon-optimized for increased expression in humans. The genes have been modified for safety, stability and immunogenicity. Tat was inactivated through shuffling of gene fragments, whilst maintaining all potential epitopes; the active site of RT was mutated; 124 aa were removed from the cytoplasmic tail of gp160; and Nef and Gag myristylation sites were inactivated. Following vaccination of BALB/c mice, high levels of cytotoxic T lymphocytes were induced against multiple epitopes and the vaccine stimulated strong CD8+gamma interferon responses. In addition, high titres of antibodies to gp120 were induced in guinea pigs. This vaccine is the first component of a prime–boost regimen that is scheduled for clinical trials in humans in the USA and South Africa.
Pns12 protein of Rice dwarf virus is essential for formation of viroplasms and nucleation of viral-assembly complexes
Authors: Wei Taiyun , Shimizu Takumi , Hagiwara Kyoji , Kikuchi Akira , Moriyasu Yusuke , Suzuki Nobuhiro , Chen Hongyan , Omura Toshihiro
Published: January 2006

Cytoplasmic inclusion bodies, known as viroplasms or viral factories, are assumed to be the sites of replication of members of the family Reoviridae. Immunocytochemical and biochemical analyses were carried out to characterize the poorly understood viroplasms of the phytoreovirus Rice dwarf virus (RDV). Within 6 h of inoculation of cells, viroplasms, namely discrete cytoplasmic inclusions, were formed that contained the non-structural proteins Pns6, Pns11 and Pns12 of RDV, which appeared to be the constituents of the inclusions. Formation of similar inclusions in non-host insect cells upon expression of Pns12 in a baculovirus system and the association of molecules of Pns12 in vitro suggested that the inclusions observed in RDV-infected cells were composed basically of Pns12. Core proteins P1, P3, P5 and P7 and core virus particles were identified in the interior region of the inclusions. In contrast, accumulation of the outer capsid proteins P2, P8 and P9 and of intact virus particles was evident in the peripheral regions of the inclusions. These observations suggest that core particles were constructed inside the inclusions, whereas outer capsid proteins were assembled at the periphery of the inclusions. Viral inclusions were shown to be the sites of viral RNA synthesis by labelling infected cells with 5-bromouridine 5′-triphosphate. The number of viroplasms decreased with time post-inoculation as their sizes increased, suggesting that inclusions might fuse with one another during the virus-propagation process. Our results are consistent with a model, proposed for vertebrate reoviruses, in which viroplasms play a pivotal role in virus assembly.
Zygocactus virus X-based expression vectors and formation of rod-shaped virus-like particles in plants by the expressed coat proteins of Beet necrotic yellow vein virus and Soil-borne cereal mosaic virus
Authors: Koenig R. , Lesemann D.-E. , Loss S. , Engelmann J. , Commandeur U. , Deml G. , Schiemann J. , Aust H. , Burgermeister W.
Published: January 2006

Expression vectors were constructed from 35S promoter-containing full-length cDNA clones of Zygocactus virus X (ZVX). The expression of foreign genes was driven by the ZVX coat protein (cp) subgenomic promoter. It was successful only when the variable region downstream of the conserved putative promoter region GSTTAAGTT(X12–13)GAA was retained. Most of the ZVX cp gene, except for a short 3′ part, was replaced by the corresponding sequence of the related Schlumbergera virus X (SVX) and its cp subgenomic promoter to enable encapsidation of the transcribed RNA by an SVX/ZVX hybrid cp. Vector-expressed cp of Beet necrotic yellow vein virus (BNYVV) assembled in Chenopodium quinoa, Tetragonia expansa and Beta vulgaris leaves into particles resembling true BNYVV particles. The virus produced from these constructs retained its ability to express BNYVV cp in local infections during successive passages on C. quinoa. This ability was lost, however, in the rarely occurring systemic infections.
Atypical prion protein in sheep brain collected during the British scrapie-surveillance programme
Authors: Everest S. J. , Thorne L. , Barnicle D. A. , Edwards J. C. , Elliott H. , Jackman R. , Hope J.
Published: January 2006

Scrapie of sheep and goats is the most common prion disease (or transmissible spongiform encephalopathy, TSE) of mammals and aggregates of abnormal, proteinase-resistant prion protein (PrPSc) are found in all naturally occurring prion diseases. During active surveillance of British sheep for TSEs, 29 201 sheep brain stem samples were collected from abattoirs and analysed for the presence of PrPSc. Of these samples, 54 were found to be positive by using an ELISA screening test, but 28 of these could not be confirmed initially by immunohistochemistry. These unconfirmed or atypical cases were generally found in PrP genotypes normally associated with relative resistance to clinical scrapie and further biochemical analysis revealed that they contained forms of PrPSc with a relatively protease-sensitive amyloid core, some resembling those of Nor98 scrapie. The presence of these atypical forms of protease-resistant PrP raises concerns that some TSE disorders of PrP metabolism previously may have escaped identification in the British sheep population.
Novel mutation in Hepatitis B virus preventing HBeAg production and resembling primate strains
Authors: Ingman M. , Lindqvist B. , Kidd-Ljunggren K.
Published: January 2006

Chronic carriers of hepatitis B infection often harbour virus strains with mutations in the precore region. These mutations are temporally associated with the development of HBeAg loss and seroconversion to anti-HBe. The most common precore mutation is a stop codon at position 1896, but other mutations leading to abolished HBeAg secretion have been described. Here, a novel precore mutation introducing a lysine in the precore position 28, a sequence shared by non-human primates but not by other human isolates, is described. However, the insertion causes a frame-shift preventing the expression of HBeAg by introducing a stop codon 5 aa downstream of the mutation. Analysis of the predicted RNA secondary structure indicates that the insertion could occur without fatally affecting the stability of the stem–loop encapsidation signal.
Public information and patch estimation for group foragers: a re‐evaluation of patch‐quitting strategies in a patchy environment
Authors: P. Fraser Chris , D. Ruxton Graeme , Broom Mark
Published: January 2006

Classical foraging theory states that animals feeding in a patchy environment can maximise their long term prey capture rates by quitting food patches when they have depleted prey to a certain threshold level. Theory suggests that social foragers may be better able to do this if all individuals in a group have access to the prey capture information of all other group members. This will allow all foragers to make a more accurate estimation of the patch quality over time and hence enable them to quit patches closer to the optimal prey threshold level. We develop a model to examine the foraging efficiency of three strategies that could be used by a cohesive foraging group to initiate quitting a patch, where foragers do not use such information, and compare these with a fourth strategy in which foragers use public information of all prey capture events made by the group. We carried out simulations in six different prey environments, in which we varied the mean number of prey per patch and the variance of prey number between patches. Groups sharing public information were able to consistently quit patches close to the optimal prey threshold level, and obtained constant prey capture rates, in groups of all sizes. In contrast all groups not sharing public information quit patches progressively earlier than the optimal prey threshold value, and experienced decreasing prey capture rates, as group size increased. This is more apparent as the variance in prey number between patches increases. Thus in a patchy environment, where uncertainty is high, although public information use does not increase the foraging efficiency of groups over that of a lone forager, it certainly offers benefits over groups which do not, and particularly where group size is large.
Are animals capable of Bayesian updating? An empirical review
Authors: J. Valone Thomas
Published: January 2006

Numerous behavioral models assume individuals combine knowledge in the form of a prior distribution with current sample information using Bayesian updating to estimate the quality of environmental parameters. I examine this assumption by reviewing 11 empirical studies. Six studies compared observed behavior to predictions of Bayesian and non‐Bayesian models, while five studies manipulated prior distributions directly and observed how such manipulations altered behavior. Eight species of birds, three mammals, one fish and one insect exhibited behavior consistent with Bayesian updating models; one studied bird species failed to show evidence of Bayesian updating. Most studies examined how individuals estimated food patch quality but two investigated mating decisions. These studies suggest a variety of animals in different ecological contexts behave in manners consistent with predictions of Bayesian updating models. Future work on decision‐making should focus on understanding how animals learn prior distributions and on decision‐making in additional ecological contexts.
Population dynamics of a host‐specific root‐feeding cyst nematode and resource quantity in the root zone of a clonal grass
Authors: Van der Stoel C. D. , Duyts H. , Van der Putten W. H.
Published: January 2006

Recent studies have suggested that root‐feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding‐specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and greenhouse studies pointed at bottom‐up control by their host plant. Here we examine the population dynamics of H. arenaria in the field in relation to resource quantity in the root zone of Ammophila arenaria (marram grass).

Ammophila arenaria is a pioneer grass in mobile coastal foredunes of northwestern and Mediterranean Europe. Every year, the plant expands clonally into freshly deposited layers of wind‐blown sand, followed by dispersal and build‐up of the nematode population into the new root zone. In a newly developing root zone the first H. arenaria cysts were observed one month after the first new roots were detected, indicating that nematode dispersal is not limiting the initial establishment of new populations. Throughout the growth season, the numbers of cysts, as well as the numbers of eggs and juveniles within cysts, were related to the quantity of roots. However, cyst density varied between years. Therefore, we conclude that in new root layers of A. arenaria cyst nematodes are bottom‐up controlled by resource quantity, but that other factors, for example resource quality, influence the relation between nematode abundance and resource quantity.

In deeper root zones the nematode abundance declines over time. Here, numbers of cysts were not related to root biomass, while numbers of eggs and juveniles inside the cysts were weakly related. This points at other factors than resource quantity, for example the quality of the roots or unsuitable abiotic environmental conditions that have a stronger influence on cyst numbers than resource quantity. We discuss how bottom‐up control of cyst nematodes may indirectly protect the plant against harmful root knot nematodes.