bluuebunny/crossref_metadata_2025 huggingface dataset:
1.3
μ
m
InGaAs vertical-cavity surface-emitting lasers with mode filter for single mode operation
Authors: von Würtemberg R. Marcks , Sundgren P. , Berggren J. , Hammar M. , Ghisoni M. , Ödling E. , Oscarsson V. , Malmquist J.
Published: November 2004

We report on the performance and analysis of 1.3μm range InGaAs∕GaAs vertical-cavity surface-emitting lasers (VCSELs) with an integrated mode filter consisting of a patterned silicon layer on the top distributer Bragg reflector. In this way, 1mW of single mode power is obtained from a device with a wavelength of 1265nm and a threshold current of 2.6mA at room temperature. An effective index model is used to extract the internal and external losses of the VCSEL structure and to predict the modal losses with and without mode filter, thereby providing a useful design tool for single mode VCSELs.
Dramatic effects of hole transport layer on the efficiency of iridium-based organic light-emitting diodes
Authors: Wang Ying
Published: November 2004

Electroluminescent efficiency of organic light-emitting diodes with Ir-based emitter depends strongly on the nature of the hole transport layer used. The efficiency is not correlated with the oxidation potential of the hole transport material. Instead, we found that many of the hole transport materials used can quench the photoluminescence intensity of the Ir green emitter and the photoluminescent quenching efficiency correlates well with the device efficiency. Based on the pulse radiolysis energy transfer experiments, we established the origin of the photoluminescent quenching as due to energy transfer from the excited state of Ir green emitter to the triplet state of the hole transport material.
Nucleation and growth of deformation twins in nanocrystalline aluminum
Authors: Zhu Y. T. , Liao X. Z. , Srinivasan S. G. , Zhao Y. H. , Baskes M. I. , Zhou F. , Lavernia E. J.
Published: November 2004

Deformation twins (DTs) in nanocrystalline (nc) Al were both predicted by atomic simulations, and observed experimentally. However, despite encouraging preliminary results, their formation mechanism remains poorly understood. Here we present an analytical model, based on classical dislocation theory, to explain the nucleation and growth of DTs in nc Al. A 60° dislocation system consisting of a 90° leading partial and a 30° trailing partial is found to most readily nucleate and grow a DT. The model suggests that the stress for twin growth is much smaller than that for its nucleation. It also predicts an optimal grain size for twin nucleation. The model successfully explains DTs observed experimentally in nc Al and is also applicable to other nc metals.
Dynamics of magnetically retained supraparticle structures in a liquid flow
Authors: Rida A. , Gijs M. A. M.
Published: November 2004

We study the dynamic motion of magnetic structures composed of micron-size ferromagnetic particles. The supraparticle structures are retained in a microfluidic channel by a local oscillating magnetic field while subjected to a viscous liquid flow. We analyze the position of the magnetic structures as a function of the flow velocity and of the frequency and amplitude of the magnetic field. We also study the conditions for release of the magnetic structures from the localized magnetic field region.
Relativistic laser plasma from micron-sized argon clusters as a debris-free x-ray source for pulse x-ray diffraction
Authors: Fukuda Yuji , Akahane Yutaka , Aoyama Makoto , Inoue Norihiro , Ueda Hideki , Nakai Yoshiki , Tsuji Koichi , Yamakawa Koichi , Hironaka Yoichiro , Kishimura Hiroaki , Morishita Hiroto , Kondo Ken-ichi , Nakamura Kazutaka G.
Published: November 2004

We have demonstrated diffraction from Si(111) crystal using x rays from highly ionized Ar ions produced by laser irradiation with an intensity of 6×1018W∕cm2 and a pulse duration of 30 fs acting upon micron-sized Ar clusters. The measured total photon flux and linewidth in the Heα1 line (3.14 keV) were 4×107photons∕shot∕4πsr and 3.7 eV (full width at half maximum), respectively, which is sufficient to utilize as a debris-free light source for time-resolved x-ray diffraction studies.
Surface ordering of (In,Ga)As quantum dots controlled by GaAs substrate indexes
Authors: Wang Zh. M. , Seydmohamadi Sh. , Lee J. H. , Salamo G. J.
Published: November 2004

Self-organized surface ordering of (In,Ga)As quantum dots in a GaAs matrix was investigated using stacked multiple quantum dot layers prepared by molecular-beam epitaxy. While one-dimensional chain-like ordering is formed on singular and slightly misorientated GaAs(100) surfaces, we report on two-dimensional square-like ordering that appears on GaAs(n11)B, where n is 7, 5, 4, and 3. Using a technique to control surface diffusion, the different ordering patterns are found to result from the competition between anisotropic surface diffusion and anisotropic elastic matrix, a similar mechanism suggested before by Solomon [Appl. Phys. Lett. 84, 2073 (2004)].
Determination of composition and strain field of a III∕V quaternary quantum dot system
Authors: Otto R. , Kirmse H. , Häusler I. , Neumann W. , Rosenauer A. , Bimberg D. , Müller-Kirsch L.
Published: November 2004

A system composed of a double layer of stacked quantum dots (QDs) of (In,Ga)As and Ga(Sb,As) was investigated by quantitative high-resolution transmission electron microscopy. The layers were grown by metalorganic chemical vapor deposition on a GaAs substrate. The strain field of the lower quantum dots determines the nucleation in the subsequent layer. Investigating this effect, the strain field as well as the composition could be measured at high resolution. Local changes of lattice distances could be quantified with a precision of 0.003nm. The error in determining the local composition inside the InxGa1−xAs resp., GaSbyAs1−y QDs amounts to ΔxIn=0.02 and ΔySb=0.03.
Photoexcitation of excitons in self-assembled quantum dots
Authors: Pettersson H. , Landin L. , Liu R. , Seifert W. , Pistol M.-E. , Samuelson L.
Published: November 2004

Using an approach of combining Fourier transform infrared spectroscopy with resonant illumination from a secondary external light source, we have measured the photocurrent (PC) for multiple layers of self-assembled InAs dots embedded in a matrix of InP. Without external illumination, we observe photoexcitation of electrons from bound states in the dots to the InP barrier. By additional illumination from the external light source, a strong broadening of the PC signal is observed. We interpret this broadening in terms of photoexcitation of electrons in the presence of additional holes in the dots created by the external light source. We extract the spectral distribution of the photoexcitation process at 6 and 77K, respectively, and show by comparison with theoretical calculations that it is consistent with an exciton binding energy of 20meV.
Structural properties and bandgap bowing of ZnO1−xSx thin films deposited by reactive sputtering
Authors: Meyer B. K. , Polity A. , Farangis B. , He Y. , Hasselkamp D. , Krämer Th. , Wang C.
Published: November 2004

A series of ZnO1−xSx films with 0⩽x⩽1.0 was deposited by radio-frequency reactive sputtering on different substrates. The structural characterization by x-ray diffraction measurements revealed that the films have wurtzite symmetry and correlated investigations of the layer composition by photoelectron spectroscopy showed that the lattice constant varies linearly with x. The composition dependence of the band gap energy in the ternary system was determined by optical transmission and the optical bowing parameter was found to be about 3eV.
Metastable phase formation during α2(D19) to γ(L1) transformation in as-atomized γ-TiAl alloy powders
Authors: Karadge M. , Gouma P. I.
Published: November 2004

α 2 ( D 0 19 ) to γ(L10) transformation during heating of as-atomized γ-TiAl powder was investigated by differential scanning calorimetry and x-ray diffraction. The as-atomized coarse powder particles (γ-TiAl powder: Ti–45Al–2Nb–0.7Mo–0.1W–2Cr–0.27O–0.2Si) with large amounts of retained α2 are a perfect candidate to investigate this transformation. It was observed that α2 to γ transformation is a two-step process involving the formation of a disordered face-centered-cubic γ′TiAl [with a(γ′)=c(γ)] as an intermediate phase followed by ordering.
Changes in the leakage currents in Ba0.8Sr0.2TiO3∕ZrO2 multilayers due to modulations in oxygen concentration
Authors: Sahoo S. K. , Agrawal D. C. , Mohapatra Y. N. , Majumder Subhasish B. , Katiyar Ram S.
Published: November 2004

Use of multilayer dielectric thin films provides opportunities to optimize properties for different applications. In this work, the changes in the leakage current in Ba0.8Sr0.2TiO3 thin films upon introduction of ZrO2 layers of different thicknesses are studied. Unusual changes in the leakage current and the transition field with variation in the number and thickness of the ZrO2 layers are observed. Profile of the oxygen concentration across the sample, as determined by x-ray photoelectron spectroscopy, shows that the oxygen diffusion length controls the modulation in the concentration of the charged oxygen vacancies, and hence the depletion layer thicknesses, at the interfaces. A qualitative model for the observed behavior is provided.
Measuring electro-optic coefficients of poled polymers using fiber-optic Mach–Zehnder interferometer
Authors: Wang Yi-Ping , Chen Jian-Ping , Li Xin-Wan , Hong Jian-Xun , Zhang Xiao-Hong , Zhou Jun-He , Ye Ai-Lun
Published: November 2004

It is proposed and demonstrated that fiber-optic Mach–Zehnder interferometer measures accurately electro-optic coefficients of, not only poled polymer thin films, but also poled polymer waveguides. Furthermore, the tensor components, both r13 and r33, of electro-optic coefficient can be measured simultaneously.
Efficient p-type doping of GaN films by plasma-assisted molecular beam epitaxy
Authors: Bhattacharyya A. , Li W. , Cabalu J. , Moustakas T. D. , Smith David J. , Hervig R. L.
Published: November 2004

In this paper we report on the mechanism of efficient incorporation of Mg in GaN films during growth by plasma-assisted molecular beam epitaxy. It is found that Mg incorporates more efficiently during growth of GaN films at high temperatures (770 °C) under extreme Ga-rich conditions. We propose that this result is due to the dissolution of Mg in the excess Ga on the growth surface and its incorporation into the GaN film via liquid-phase processes. Transport measurements at 300K together with secondary-ion-mass-spectroscopy indicate that the Mg-doping efficiency of GaN under these conditions of growth is 10%. Using this method of doping, p-type GaN films free of Ga droplets, with hole concentrations varying from 2×1017 to 3×1018cm−3 and corresponding mobilities varying from 30 to 2cm2∕Vs, are obtained. The lowest resistivity achieved is 0.3 Ω cm.
Structure of pentacene thin films
Authors: Ruiz Ricardo , Mayer Alex C. , Malliaras George G. , Nickel Bert , Scoles Giacinto , Kazimirov Alexander , Kim Hyunjung , Headrick Randall L. , Islam Zahirul
Published: November 2004

Grazing incidence x-ray diffraction, x-ray reflectivity and atomic force microscopy have been performed to study the structure of pentacene thin films on oxidized Si substrates from submonolayer to multilayer coverages. The volume of the unit cell in the thin film phase is almost identical to that of the bulk phase, thus the molecular packing efficiency is effectively the same in both phases. The structure forming from the first monolayer remains the same for films at least 190Å thick. The in-plane structure of the submonolayer islands also remains unchanged within a substrate temperature range of 0<Tsub<45°C while the island size changes by more than a factor of 4.
Effects of polarized organosilane self-assembled monolayers on organic single-crystal field-effect transistors
Authors: Takeya J. , Nishikawa T. , Takenobu T. , Kobayashi S. , Iwasa Y. , Mitani T. , Goldmann C. , Krellner C. , Batlogg B.
Published: November 2004

The surface conductivity is measured by a four-probe technique for pentacene and rubrene single crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields. The polarization of the self-assembled monolayers (SAMs) shifts the threshold gate voltage, while maintaining a very low subthreshold swing of the single-crystal devices (0.11 V∕decade). The results, excluding influences of parasitic contacts and grain boundaries, demonstrate SAM-induced nanoscale charge injection up to ∼1012cm−2 at the surface of the organic single crystals.
Charging control of InP∕GaInP quantum dots by heterostructure design
Authors: Persson Jonas , Hessman Dan , Pistol Mats-Erik , Seifert Werner , Samuelson Lars
Published: November 2004

Semiconductor quantum dots are often charged due to accumulation from a doped host material. Using low-temperature photoluminescence, we have studied the charging of single self-assembled InP dots in structures designed to control the electron population in a weakly n-type environment. By using designed heterostructures to position the Fermi level of the structure, not requiring electric fields or currents, we show that the electron accumulation can be reduced from approximately 18 electrons in the dot to approximately 8 electrons. In particular, we show that the single quantum dot luminescence spectrum of the Fermi-level pinned structure perfectly matches the low-energy part of the highly charged reference spectrum, a phenomenon predicted by the model for multiple charging of quantum dots.
Hydrogen adsorption in mesoporous carbons
Authors: Pang Jiebin , Hampsey J. Eric , Wu Zhiwang , Hu Qingyuan , Lu Yunfeng
Published: November 2004

The hydrogen adsorption of mesoporous carbon materials with different mesostructures, surface areas, and pore volumes has been investigated. Experimental results indicate that the hydrogen adsorption capacities are dominantly related to their surface areas. A hydrogen adsorption capacity of 1.78 wt % was obtained at 77 K and ambient pressure of 850 mm Hg (0.11 MPa) for the mesoporous carbon with a surface area of 2314m2∕g.
Superhigh strength and good soft-magnetic properties of (Fe,Co)–B–Si–Nb bulk glassy alloys with high glass-forming ability
Authors: Shen Baolong , Inoue Akihisa , Chang Chuntao
Published: November 2004

Fe -based bulk ferromagnetic glassy alloys with diameters up to 5mm were formed in [(Fe1−xCox)0.75B0.2Si0.05]96Nb4 system by the copper mold casting method. The substitution of Co for Fe caused an increase of glass-forming ability as well as an improvement of mechanical and magnetic properties. The bulk glassy alloys exhibited superhigh fracture strength of 3900–4250MPa, Young’s modulus of 190–210GPa, elastic strain of 0.02, and plastic strain of 0.0025. The bulk glassy alloys also exhibited good soft magnetic properties, i.e., saturation magnetization of 0.84–1.13T, low coercive force of 1.5–2.7A∕m, high permeability exceeding 1.2×104, and Curie temperature of 600–690K.

At the request of the authors, this article is being retracted effective 29 March 2011.
Control of the growth orientation and electrical properties of polycrystalline Cu2O thin films by group-IV elements doping
Authors: Ishizuka Shogo , Akimoto Katsuhiro
Published: November 2004

The effects of group-IV element dopants on the structural and electrical properties of Cu2O thin films were studied. Similar dopant-induced behavior was found in the observed variations of the growth orientation and electrical properties of Si- and Ge-doped Cu2O thin films. Ge doping was found to induce electrically active acceptors with an activation energy of 0.18 eV, comparable to the 0.19 eV value of Si-doped Cu2O. These results suggest that locally formed silicate and germanate have the same effect on the structural and electrical properties of Cu2O. On the other hand, Sn and Pb likely act as donors when incorporated substitutionally onto Cu-lattice sites, although further study may be required to suppress self-compensation effects in Cu2O to achieve n-type conductivity.
Mask pattern transferred transient grating technique for molecular-dynamics study in solutions
Authors: Okamoto Koichi , Zhang Zhaoyu , Scherer Axel , Wei David T.
Published: November 2004

We have developed a mask pattern transferred transient grating (MPT-TG) technique by using metal grating films. Transient thermal grating is generated by an ultraviolet light pattern transfer to nitrobenzene in 2-propanol solution, and the subsequent effect is detected through its diffraction to a probe beam. The thermal diffusion coefficient is obtained by the relationship between the grating periods and the signal decay lifetime, and is well in agreement with the calculated value. This technique has many advantages, such as a simple setting, an easy alignment, accurate phase control, and high stability for molecular-dynamics study in solutions.
SRK2C, a SNF1-related protein kinase 2, improves drought tolerance by controlling stress-responsive gene expression in
Arabidopsis thaliana
Authors: Umezawa Taishi , Yoshida Riichiro , Maruyama Kyonoshin , Yamaguchi-Shinozaki Kazuko , Shinozaki Kazuo
Published: November 2004

Protein phosphorylation/dephosphorylation are major signaling events induced by osmotic stress in higher plants. Here, we showed that a SNF1-related protein kinase 2 (SnRK2), SRK2C, is an osmotic-stress-activated protein kinase in
Arabidopsis thaliana
that can significantly impact drought tolerance of
Arabidopsis
plants. Knockout mutants of SRK2C exhibited drought hypersensitivity in their roots, suggesting that SRK2C is a positive regulator of drought tolerance in
Arabidopsis
roots. Additionally, transgenic plants with
CaMV35S
promoter::
SRK2C
-
GFP
displayed higher overall drought tolerance than control plants. Whereas stomatal regulation in
35S
::
SRK2C
-
GFP
plants was not altered, microarray analysis revealed that their drought tolerance coincided with up-regulation of many stress-responsive genes, for example,
RD29A
,
COR15A
, and
DREB1A
/
CBF3
. From these results, we concluded that SRK2C is capable of mediating signals initiated during drought stress, resulting in appropriate gene expression. Our present study reveals new insights around signal output from osmotic-stress-activated SnRK2 protein kinase as well as supporting feasibility of manipulating SnRK2 toward improving plant osmotic-stress tolerance.
Acute vascular occlusion in horses: effects on skeletal muscle size and blood flow
Authors: Abe T , Kearns CF , Filho HC Manso , Sato Y , Sleeper M , McKeever KH
Published: November 2004

The purpose of this study was to demonstrate whether acute vascular occlusion was safe and if it would result in changes to limb muscle size in horses. Six healthy, unfit Standardbred mares were used. Horses (standing at rest) wore an occlusion cuff at the most proximal position of the left forelimb. The right forelimb was used as control. An occlusion pressure of 200 mmHg was set for 5 min followed by a 2 min recovery. Three sets of occlusions were given to each horse. Muscle thickness was measured using B-mode ultrasound. The circumference of the forelimb and first phalanx was measured using a flexible tape measure. Pulsed-wave Doppler was performed on the radialis artery with a 5–10 MHz mechanical transducer at baseline and at each occlusion. Peak flow velocity (PFV) and the flow velocity integral (FVI) were measured each time. Mid-forelimb, but not first phalanx, girth was increased (P<0.05) in the occluded but not in the control leg following occlusion. Extensor and flexor muscle thickness was increased (P<0.05) in the occluded but not in the control leg. There were no changes (P>0.05) in PFV or FVI at any measurement time point. Acute vascular occlusion may be a suitable and safe model for studying muscle hypertrophy in horses.
African athletic aptitude and the social sciences
Authors: Hoberman John
Published: November 2004

Scientific investigation of racial athletic aptitude has been preceded by a century of pseudo- and quasi-scientific speculations on this topic. For this reason, physiological and anatomical research on African runners is performed in a social context that is still permeated by folkloric ideas about racial differences, some of which pertain to athletic performance. A powerful stereotype of ‘tropical nature’ and its ‘superabundant’ vitality has influenced non-African thinking about African athletic potential. The idea that evolutionary adaptation in Africa is a particularly severe version of natural selection has had a similar effect on Western thinking about African runners. Romantic ideas about African athletic aptitude may, therefore, be understood as modern versions of the doctrine of black ‘hardiness’ that survives in contemporary biomedicine in various forms.
Angiotensin-converting enzyme and human physical performance
Authors: Payne John , Montgomery Hugh
Published: November 2004

Genes undoubtedly play a role in the development of a successful athlete. This view has flourished on anecdotes such as the observation of a child who displays the same aptitude for a particular sport as one of their parents, or a pair of sisters who both excel in the same discipline. However, the conclusions made from this type of observation have an obvious limitation: that similar environmental factors may be just as responsible as genetic inheritance in explaining the passage and sharing of talent between family members. Here, we review briefly the salient data showing that genes do play a role in athletic performance, and although the data examining the effect of specific genes are limited, we present data examining the role of the angiotensin-converting enzyme gene in human physical performance.
Estimation of the Plasma Effect Site Equilibration Rate Constant (ke0) of Propofol in Children Using the Time to Peak Effect
Authors: Muñoz Hernán R. , Cortínez Luis I. , Ibacache Mauricio E. , Altermatt Fernando R.
Published: November 2004

Background

Targeting the effect site concentration may offer advantages over the traditional forms of administrating intravenous anesthetics. Because the lack of the plasma effect site equilibration rate constant (ke0) for propofol in children precludes the use of this technique in this population, the authors estimated the value of ke0 for propofol in children using the time to peak effect (tpeak) method and two pharmacokinetic models of propofol for children.

Methods

: The tpeak after a submaximal bolus dose of propofol was measured by means of the Alaris A-Line auditory evoked potential monitor (Danmeter A/S, Odense, Denmark) in 25 children (aged 3-11 yr) and 25 adults (aged 35-48 yr). Using tpeak and two previously validated sets of pharmacokinetic parameters for propofol in children, Kataria's and that used in the Paedfusor (Graseby Medical Ltd., Hertfordshire, United Kingdom), the ke0 was estimated according to a method recently published.

Results

The mean tpeak was 80 +/- 20 s in adults and 132 +/- 49 s in children (P < 0.001). The median ke0 in children was 0.41 min(-1) with the model of Kataria and 0.91 min(-1) with the Paedfusor model (P < 0.01). The corresponding t1/2 ke0 values, in minutes, were 1.7 and 0.8, respectively (P < 0.01).

Conclusions

: Children have a significantly longer tpeak of propofol than adults. The values of ke0 of propofol calculated for children depend on the pharmacokinetic model used and also can only be used with the appropriate set of pharmacokinetic parameters to target effect site in this population.
Platelet Gene Polymorphisms and Cardiac Risk Assessment in Vascular Surgical Patients
Authors: Faraday Nauder , Martinez Elizabeth A. , Scharpf Robert B. , Kasch-Semenza Laura , Dorman Todd , Pronovost Peter J. , Perler Bruce , Gerstenblith Gary , Bray Paul F. , Fleisher Lee A.
Published: November 2004

Background

Current perioperative cardiac risk assessment tools use historic and surgical factors to stratify patient risk. Polymorphisms in platelet glycoprotein (GP) IIIa and GPIbalpha are associated with myocardial ischemic risk in nonsurgical settings, but their relation to perioperative ischemia is unclear. The authors hypothesized that platelet genotype would be an independent predictor of postoperative myocardial ischemia and would improve risk assessment when added to clinical factors.

Methods

One hundred ninety-six patients who underwent infrainguinal, abdominal aortic, or thoracoabdominal vascular surgery were evaluated for clinical and genetic factors that might predict the development of postoperative myocardial ischemia. Genomic DNA was genotyped for the Leu33Pro polymorphism of GPIIIa and the Thr145Met polymorphism of GPIbalpha. Myocardial ischemic outcome was determined by review of the medical record for cardiac death or myocardial infarction and by surveillance troponin I and automated continuous 12-lead electrocardiographic analysis.

Results

Sixty-five patients (33%) experienced one or more ischemic endpoints (2% death, 5% myocardial infarction, 20% troponin+, 22% electrocardiogram+). The Pro33 (adjusted odds ratio [OR], 2.4 [95% confidence interval, 1.2-6.2]) and Met145 (OR 3.4 [1.4-9.3]) genotypes were independent predictors of composite ischemic outcome by multivariate regression, as were diabetes mellitus (OR 4.0 [1.7-12.5]), abdominal aortic surgery (OR 4.1 [1.7-14.4]), and thoracoabdominal aortic surgery (OR 6.4 [2.7-23.8]). The addition of platelet gene polymorphisms to clinical factors improved fit (likelihood ratio testing chi-square = 13.5, P < 0.001) of an ischemia prediction model. The derived risk assessment tool had a receiver operator characteristic curve of 0.73 (0.65-0.81) compared with 0.64 (0.57-0.74) for a model excluding genetic factors (P = 0.04). A significant relation between the GPIbalpha polymorphism and ischemic outcome remained after excluding electrocardiographic ischemia from the composite endpoint.

Conclusions

Platelet polymorphisms are independent risk factors for postoperative myocardial ischemia and improve a risk prediction model when added to historic and surgical risk factors.
Differential Protective Effects of Volatile Anesthetics against Renal Ischemia–Reperfusion Injury In Vivo
Authors: Lee H Thomas , Ota-Setlik Ayuko , Fu Yulei , Nasr Samih H. , Emala Charles W.
Published: November 2004

Background

Volatile anesthetics protect against cardiac ischemia-reperfusion injury via adenosine triphosphate-dependent potassium channel activation. The authors questioned whether volatile anesthetics can also protect against renal ischemia-reperfusion injury and, if so, whether cellular adenosine triphosphate-dependent potassium channels, antiinflammatory effects of volatile anesthetics, or both are involved.

Methods

Rats were anesthetized with equipotent doses of volatile anesthetics (desflurane, halothane, isoflurane, or sevoflurane) or injectable anesthetics (pentobarbital or ketamine) and subjected to 45 min of renal ischemia and 3 h of reperfusion during anesthesia.

Results

Rats treated with volatile anesthetics had lower plasma creatinine and reduced renal necrosis 24-72 h after injury compared with rats anesthetized with pentobarbital or ketamine. Twenty-four hours after injury, sevoflurane-, isoflurane-, or halothane-treated rats had creatinine (+/- SD) of 2.3 +/- 0.7 mg/dl (n = 12), 1.8 +/- 0.5 mg/dl (n = 6), and 2.4 +/- 1.2 mg/dl (n = 6), respectively, compared with rats treated with pentobarbital (5.8 +/- 1.2 mg/dl, n = 9) or ketamine (4.6 +/- 1.2 mg/dl, n = 8). Among the volatile anesthetics, desflurane demonstrated the least reduction in plasma creatinine after 24 h (4.1 +/- 0.8 mg/dl, n = 12). Renal cortices from volatile anesthetic-treated rats demonstrated reduced expression of intercellular adhesion molecule 1 protein and messenger RNA as well as messenger RNAs encoding proinflammatory cytokines and chemokines. Volatile anesthetic treatment reduced renal cortex myeloperoxidase activity and reduced nuclear translocation of proinflammatory nuclear factor kappaB. Adenosine triphosphate-dependent potassium channels are not involved in sevoflurane-mediated renal protection because glibenclamide did not block renal protection (creatinine: 2.4 +/- 0.4 mg/dl, n = 3).

Conclusion

Some volatile anesthetics confer profound protection against renal ischemia-reperfusion injury compared with pentobarbital or ketamine anesthesia by attenuating inflammation. These findings may have significant clinical implications for anesthesiologists regarding the choice of volatile anesthetic agents in patients subjected to perioperative renal ischemia.
Propofol Attenuates Peroxynitrite-mediated DNA Damage and Apoptosis in Cultured Astrocytes
Authors: Acquaviva Rosaria , Campisi Agata , Murabito Paolo , Raciti Giuseppina , Avola Roberto , Mangiameli Salvatore , Musumeci Ilenia , Barcellona Maria Luisa , Vanella Angelo , Li Volti Giovanni
Published: November 2004

Background

The concentration of peroxynitrite in the brain increases after central nervous system injuries. The authors hypothesized that propofol, because of its particular chemical structure, mitigates the effects of peroxynitrite-mediated oxidative stress and apoptosis by the induction of heme oxygenase (HO)-1 in primary cultured astroglial cells.

Methods

Primary cultured astroglial cells were incubated for 18 h with a known peroxynitrite donor (3 mm SIN-1) in the presence or absence of propofol (40 microm, 80 microm, 160 microm, and 1 mm). The protective effects of propofol were evaluated by 3(4,5-dimethyl-thiazol-2-yl)2,5-diphenyl-tetrazolium bromide cytotoxicity assay, lactic dehydrogenase release, DNA ladderization by Comet assay, and caspase-3 activation by Western blot analysis.

Results

Appropriate propofol concentrations (ranging from 40 microm to 1 mm) significantly increased HO-1 expression and attenuated SIN-1-mediated DNA ladderization and caspase-3 activation. The protective effects of propofol were mitigated by the addition of tin mesoporphyrin, a potent inhibitor of HO activity. The addition of a specific synthetic inhibitor of nuclear factor kappaB abolished propofol-mediated HO-1 induction, suggesting a possible role of this nuclear transcriptional factor in our experimental conditions.

Conclusions

The antioxidant properties of propofol can be partially attributed to its scavenging effect on peroxynitrite as well as to its ability to increase HO-1 expression at higher concentrations, a property that might be relevant to neuroprotection during anesthesia.
Desflurane Preconditioning Induces Time-dependent Activation of Protein Kinase C Epsilon and Extracellular Signal-regulated Kinase 1 and 2 in the Rat Heart In Vivo
Authors: Toma Octavian , Weber Nina C. , Wolter Jessica I. , Obal Detlef , Preckel Benedikt , Schlack Wolfgang
Published: November 2004

Background

Activation of protein kinase C epsilon (PKC-epsilon) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) are important for cardioprotection by preconditioning. The present study investigated the time dependency of PKC-epsilon and ERK1/2 activation during desflurane-induced preconditioning in the rat heart.

Methods

Anesthetized rats were subjected to regional myocardial ischemia and reperfusion, and infarct size was measured by triphenyltetrazoliumchloride staining (percentage of area at risk). In three groups, desflurane-induced preconditioning was induced by two 5-min periods of desflurane inhalation (1 minimal alveolar concentration), interspersed with two 10-min periods of washout. Three groups did not undergo desflurane-induced preconditioning. The rats received 0.9% saline, the PKC blocker calphostin C, or the ERK1/2 inhibitor PD98059 with or without desflurane preconditioning (each group, n = 7). Additional hearts were excised at four different time points with or without PKC or ERK1/2 blockade: without further treatment, after the first or the second period of desflurane-induced preconditioning, or at the end of the last washout phase (each time point, n = 4). Phosphorylated cytosolic PKC-epsilon and ERK1/2, and membrane translocation of PKC-epsilon were determined by Western blot analysis (average light intensity).

Results

Desflurane significantly reduced infarct size from 57.2 +/- 4.7% in controls to 35.2 +/- 16.7% (desflurane-induced preconditioning, mean +/- SD, P < 0.05). Both calphostin C and PD98059 abolished this effect (58.8 +/- 13.2% and 64.2 +/- 15.4% respectively, both P < 0.05 versus desflurane-induced preconditioning). Cytosolic phosphorylated PKC-epsilon reached its maximum after the second desflurane-induced preconditioning and returned to baseline after the last washout period. Both calphostin C and PD98059 inhibited PKC-epsilon activation. ERK1/2 phosphorylation reached its maximum after the first desflurane-induced preconditioning and returned to baseline after the last washout period. Calphostin C had no effect on ERK1/2 phosphorylation.

Conclusions

Both, PKC and ERK1/2 mediate desflurane-induced preconditioning. PKC-epsilon and ERK1/2 are both activated in a time dependent manner during desflurane-induced preconditioning, but ERK1/2 activation during desflurane-induced preconditioning is not PKC dependent. Moreover, ERK1/2 blockade abolished PKC-epsilon activation, suggesting ERK-dependent activation of PKC-epsilon during desflurane-induced preconditioning.
Chronic Oral Gabapentin Reduces Elements of Central Sensitization in Human Experimental Hyperalgesia
Authors: Gottrup Hanne , Juhl Gitte , Kristensen Anders D. , Lai Robert , Chizh Boris A. , Brown John , Bach Flemming W. , Jensen Troels S.
Published: November 2004

Background

In chronic pain, increased activity from intact or damaged peripheral nerve endings results in an enhanced response in central pain transmission systems, a mechanism known as central sensitization. Central sensitization can also be invoked in human experimental models. Therefore, these models may be useful to characterize novel analgesics in humans. The anticonvulsant gabapentin has demonstrated efficacy in patients with neuropathic pain, but its mode of action remains unclear. This study examined the effects of gabapentin on signs of central sensitization (brush and pinprick hyperalgesia) in a human model of capsaicin-evoked pain, using a gabapentin dosing regimen similar to that used in the clinic. The aims were to determine whether gabapentin, dosed in a manner similar to that used in the clinic, affected the various components of central sensitization and to assess the utility of this model for characterizing novel analgesics.

Methods

Intradermal capsaicin (100 microg/20 microl) was administered in the volar forearm of 41 male human volunteers to induce pain and clinical signs of central sensitization. Gabapentin (titrated to 2,400 mg daily) or placebo was given orally for 15 days in a randomized, double-blind, parallel-group design. The capsaicin test was conducted at baseline and after gabapentin or placebo. Endpoints were the size of areas of brush-evoked allodynia (with cotton gauze) and pinprick hyperalgesia (with von Frey filament), and the intensity of ongoing brush- and pinprick-evoked pain.

Results

Gabapentin significantly reduced the area of brush allodynia compared with placebo (P </= 0.05) and insignificantly attenuated the area of pinprick hyperalgesia. Gabapentin had no significant effect on spontaneous and evoked pain intensity.

Conclusion

Oral gabapentin, administered to healthy volunteers in a regimen similar to that used in treating chronic neuropathic pain, reduces measures of central sensitization evoked by intradermal capsaicin. This suggests that the pain-relieving effect in chronic neuropathic pain condition is linked to the effect of gabapentin on central sensitization. The ability of the capsaicin model to detect the efficacy of this standard treatment of neuropathic pain suggests that it may have a predictive value for detection of efficacy in human subjects.
Effect of Pain and Audiovisual Stimulation on the Depression of Acute Hypoxic Ventilatory Response by Low-dose Halothane in Humans
Authors: Pandit Jaideep J. , Moreau Ben , Donoghue Simon , Robbins Peter A.
Published: November 2004

Background

The effects of different low-dose volatile agents in blunting the acute hypoxic ventilatory response (AHVR) are variable. Arousal (due to audiovisual stimulation) may prevent isoflurane-induced blunting of AHVR. The purpose of this study was to assess whether this was also the case for halothane. The authors also assessed the effects of pain on the interaction of halothane and AHVR.

Methods

Step decreases in end-tidal partial pressure of oxygen using dynamic end-tidal forcing were performed from normoxia to hypoxia (50 mmHg) in 10 healthy volunteers, with end-tidal partial pressure of carbon dioxide held 1-2 mmHg above normal, in six protocols: (1) control conditions (darkened, quiet room, eyes closed) without halothane and (2) with 0.1 minimum alveolar concentration (MAC) halothane; (3) audiovisual stimulation (bright room, loud television) without halothane and (4) with 0.1 MAC halothane; (5) pain (electrical stimulation of skin over the tibia to produce a visual analog pain score of 5-6 out of 10) without halothane and (6) with 0.1 MAC halothane. The Bispectral Index of the electroencephalogram was also monitored.

Results

Halothane did not affect normoxic minute ventilation in any arousal state but significantly reduced the magnitude of AHVR by 50% regardless of the background arousal state (P < 0.001). Bispectral Index values were reduced by halothane only in the absence of arousal (P < 0.003). Both pain and audiovisual stimulation modestly increased normoxic minute ventilation (P < 0.002) and AHVR (P < 0.003).

Conclusions

Audiovisual stimulation does not prevent the blunting of AHVR by low-dose halothane. This result with halothane differs from previous results with isoflurane. Therefore, different anesthetics interact in different ways with arousal states. This finding raises the possibility that different anesthetics might differentially affect the hypoxic chemoreflex loop or that they might act in the brain at sites separate from the chemoreflex loop, differently to influence the wakefulness drive to ventilation.
Is Low-dose Haloperidol a Useful Antiemetic?
Authors: Büttner Michael , Walder Bernhard , von Elm Erik , Tramèr Martin R.
Published: November 2004

The antiemetic efficacy of haloperidol was studied using data from 15 published (1962-1988) and 8 unpublished randomized trials; 1,397 adults received haloperidol, and 1,071 were controls. Settings were postoperative nausea or vomiting (1,994 patients), gastroenterology (261), chemotherapy (189), and radiation therapy (24). The relative benefit to prevent postoperative nausea or vomiting during 24 h with 0.5-4 mg haloperidol compared with placebo was 1.26-1.51 (number needed to treat, 3.2-5.1), without evidence of dose responsiveness; 0.25 mg was not antiemetic. With 1 mg haloperidol, the relative benefit to stop postoperative nausea or vomiting during 2-4 h compared with placebo was 1.53 (95% confidence interval, 1.17-2.00; number needed to treat, 6); with 2 mg, the relative benefit was 1.73 (1.11-2.68; number needed to treat, 4). In gastroenterology, 2 mg haloperidol was more effective than 1 mg. For chemotherapy and radiation therapy, no conclusions could be drawn. With 4 mg, one patient had extrapyramidal symptoms. With 5 mg, sedation was increased, with a relative risk of 2.09 (95% confidence interval, 1.73-2.52; number needed to treat, 4.4). There were no reports on cardiac toxicity. Postoperatively and in gastroenterology, haloperidol is antiemetic, with minimal toxicity. For other clinical settings and for children, valid data are unavailable.
DIATOM MINERALIZATION OF SILICIC ACID. VI. THE EFFECTS OF MICROTUBULE INHIBITORS ON SILICIC ACID METABOLISM IN NAVICULA SAPROPHILA1
Authors: Blank Gregory S. , Sullivan Cornelius W.
Published: November 2004

The role of microtubules in silicon metabolism leading to valve formation was investigated in the pennate diatom Navicula saprophila Lange‐Bertalot & Bonik. By using synchronized cells blocked after mitosis and cytokinesis but prior to cell wall formation, effects due to inhibition of mitosis were eliminated. Cells were treated with three anti‐microtubule drugs to assess the role of microtubules. Chemical analogs to two of the drugs provided controls for inhibition not related to microtubule disruption. Although all three anti‐microtubule drugs reduced cell separation at high concentrations (1 × 10−3 M), podophyllotoxin was the only drug which reduced cell separation at concentrations lower than 1 × 10−5 M. None of the drugs at any concentration tested affected cell viability. There was no differential inhibitory effect between the active and inactive drugs on silicic acid transport, total uptake, incorporation, or pool formation. There was no qualitative difference between silica incorporated in treated and untreated cells. A colchicine binding component was isolated from N. saprophila. The characteristics of colchicine binding suggest this component may be tubulin. Microtubules do not appear to be involved in any of the steps of silicon metabolism leading to valve formation and yet they have profound influence on the symmetry and pattern of the mineralized product, the siliceous valve.
ATRACTOMORPHA ECHINATA GEN. ET SP. NOV., A NEW ANISOGAMOUS MEMBER OF THE SPHAEROPLEACEAE (CHLOROPHYCEAE)1,2
Authors: Hoffman Larry R.
Published: November 2004

Atractomorpha echinata gen. et sp. nov. is described from isolates derived from zygotes present in a dry soil sample obtained from Texas. The new genus is distinguished from Sphaeroplea primarily by its pattern of vegetative growth. While Sphaeroplea is distinctly filamentous with numerous coenocytic cells uniseriately arranged, Atractomorpha grows as individual, multinucleate, spindle‐shaped cells with sharply pointed extremities. Such cells may vary considerably in length (25–6000 μm, or more) and normally lack septa. In young, rapidly growing cultures the cells often attain lengths of 300–500 μm, but rarely exceed 1800 μm. The new species is further characterized by: (1) the regular formation of biflagellate zoospores in asexual reproduction, (2)anisogamy (occasionally oogamy) and (3) the size and ornamentation of its zygotes. Variations in vegetative morphology are discussed as are conditions for obtaining gametogenesis.
A PHYSIOLOGICAL TEST OF THE THEORY OF COMPLEMENTARY CHROMATIC ADAPTATION. I. COLOR MUTANTS OF A RED SEAWEED1
Authors: Ramus J. , van, der Meer John P.
Published: November 2004

The physiological behavior of phycoerythrin‐deficient mutants of the red seaweed Gracilaria tikvahiae (Mc‐Lachlan 1979) is compared to that of their wild types. The mutants are phenotypically green while the wild types are red. Cloned scions were grown factorially at irradiances saturating and limiting to growth, and spectral distributions which were broadband (white) and narrowband (green). The green light field complements the absorptance spectrum of phycoerythrin. Experiments were performed in an outdoor continuous flow system. Physiological measurements included light‐harvesting pigment composition, instantaneous photosynthesis‐light relationships and growth. In all cases, the mutants performed as their wild type progenitors. Further, physiological responses occurring in no less than 8 days were dependent solely on irradiance (“intensity”), and were independent of spectral distribution (“color”). The data do not conform with the predictions of the theory of complementary chromatic adaptation for seaweeds.
EFFECTS OF EXTERNAL INORGANIC NITROGEN CONCENTRATION ON METABOLISM, GROWTH AND ACTIVITIES OF KEY CARBON AND NITROGEN ASSIMILATORY ENZYMES OF LAMINARIA SACCHARINA (PHAEOPHYCEAE) IN CULTURE1
Authors: Wheeler W. N. , Weidner M.
Published: November 2004

The growth rate of Laminaria saccharina (L.) Lamour. is dependent on inorganic nitrogen in culture. Growth rates were saturated between 5 and 10 μmol · L−1 nitrate. The activities of ribulose‐1,5 bisphosphate carboxylase, phosphoenolpyruvate carboxykinase, mannitol‐1‐phosphate dehydrogenase, nitrate reductase and glutamine synthetase also varied with the concentration of inorganic nitrogen in the medium. All enzyme activities were lowest at 2.5 μmol · L−1 nitrate (the lowest concentration used) increasing to a maximum activity between 10 and 30 μmol · L−1 nitrate. Most enzyme activities followed a hyperbolic curve resembling those described by the Michaelis‐Menten equation, with different half‐saturation constants.
COMPOSITION OF SIEVE TUBE SAP FROM MACROCYSTIS PYRIFERA (PHAEOPHYTA) WITH EMPHASIS ON THE INORGANIC CONSTITUENTS1
Authors: Manley Steven L.
Published: November 2004

A quantitative accounting of the solids in the sieve tube sap from Macrocystis pyrifera (L.) e. Ag. was performed. The major organic compounds (mannitol, amino acids, and protein) and inorganic cations (K+, Na+, Mg2+ and Ca2+) were present near previously reported levels. The anions, until now unreported (except for iodide), included chloride as the major inorganic ion, bromide, phosphate, nitrate, and bicarbonate as the major inorganic carbon species. Sulfate and ammonium were below the detection limits of 1.5 ppm and 2 ppm, respectively. The elements B and As were also present although their speciation was not determined.
COMMUNITY STRUCTURE DYNAMICS OF EPILITHIC AND EPIPHYTIC DIATOMS IN A MISSISSIPPI STREAM1
Authors: O'Quinn Ruth , Sullivan Michael J.
Published: November 2004

Epilithic and epiphytic diatoms were collected monthly from 18 June 1979 through 19 May 1980 from both shaded and unshaded sites of Sessums Creek, a shallow, oligotrophic and strongly alkaline stream in northeastern Mississippi. The dominant macroalgae were filamentous green algae belonging to the non‐mucilage producing genera Cladophora and Rhizoclonium. Ninety taxa were identified with Navicula minima Grun. and Nitzschia dissipata (Kütz.) Grun. accounting for 50% of all valves counted. Other important taxa were Navicula menisculus var. upsaliensis (Grun.) Grun., N. cryptocephala var. veneta (Kütz.) Rabh., Achnanthes minutissima Kütz. and Cymbella turgida (Greg.) Cl. With few exceptions, the more dominant taxa were equally abundant in the shaded and unshaded sites and also in the epilithon and epiphyton. Species diversity (H') and the number of taxa in a sample in all four habitats showed an identical pattern, being lowest in winter and highest in fall. No one pair of habitats was more structurally similar than any‐other pair when compared by a similarity index (SIMI). Apparently, differences in light intensity and substrate type had little effect on diatom distribution in Sessums Creek and it was concluded that the locality sampled supported a single, nearly homogeneous diatom community.
A PHYSIOLOGICAL TEST OF THE THEORY OF COMPLEMENTARY CHROMATIC ADAPTATION. II. BROWN, GREEN AND RED SEAWEEDS1
Authors: Ramus J.
Published: November 2004

The effect of light quantity (irradiance) on the photosynthetic physiology of seven seaweed species was distinguished from the effect of light quality (color). Plants were grown in outdoor, continuous‐flow tanks, at irradiances saturating and limiting to growth, and in spectral distributions that were either broadband (white) or narrowband (green). The green light field complemented the absorptance spectrum of phycoerythrin and approximated the spectral distribution of a submarine light field in turbid coastal water near the compensation depth. Physiological measurements, made after 6–15 days growth, included light‐harvesting pigment densities, instantaneous photosynthesis‐light relationships and growth rate. In all experiments, these photosynthetic properties were independent of spectral distribution (color) and in most experiments were dependent on irradiance. These data do not conform to the predictions of the theory of complementary chromatic adaptation for seaweeds.