bluuebunny/crossref_metadata_2025 huggingface dataset:
All-epitaxial, lithographically defined, current- and mode-confined vertical-cavity surface-emitting laser based on selective interfacial fermi-level pinning
Authors: Ahn J. , Lu D. , Deppe D. G.
Published: January 2005

An approach is presented to fabricate a current- and mode-confined vertical-cavity surface-emitting laser that is all-epitaxial and lithographically defined. The device uses selective Fermi level pinning to self-align the electrical injection to a mode-confining intracavity phase-shifting mesa.
Imaging surface-acoustic fields in a longitudinal leaky wave resonator
Authors: Holmgren O. , Knuuttila J. V. , Makkonen T. , Kokkonen K. , Plessky V. P. , Steichen W. , Solal M. , Salomaa M. M.
Published: January 2005

Acoustic wave fields in a surface-acoustic-wave resonator employing the longitudinal leaky wave mode have been imaged using a scanning Michelson laser interferometer. The synchronous one-port resonator is fabricated on YZ-cut lithium niobate. The vibration amplitude component perpendicular to the surface has been measured at several frequencies around the fundamental-mode resonance frequency of 1.54 GHz and around the Rayleigh-wave resonance frequency of 0.82 GHz. The longitudinal beating pattern, typically observed in the resonators utilizing Rayleigh waves, is not observed in the longitudinal leaky surface acoustic-wave resonator within the measured frequency range.
Reduction of the threading dislocation density in GaN films grown on vicinal sapphire (0001) substrates
Authors: Shen X. Q. , Matsuhata H. , Okumura H.
Published: January 2005

Structural properties of GaN films grown on vicinal sapphire (0001) substrates with various vicinal angles by plasma-assisted molecular beam epitaxy are investigated. High-resolution x-ray diffraction (HRXRD) results reveal the dramatic improvement of both tilting and twisting grain features of the GaN films when the vicinal angle is larger than 0.5° with the formation of multilayer macro-steps on the surface. The threading dislocation density reduces by over an order of magnitude estimated from the HRXRD results. Cross-sectional transmission electron microscopy observations clearly show that the formation and lateral propagation of macro-steps on the GaN surface play an important role in this dislocation reduction. A method for the reduction of threading dislocation density in GaN epilayers is proposed.
Effect of Cu deficiency on the defect levels of Cu0.86In1.09Se2.05 determined by spectroscopic ellipsometry
Authors: Han Sung-Ho , Hasoon Falah S. , Al-Thani Hamda A. , Hermann Allen M. , Levi Dean H.
Published: January 2005

Room temperature spectroscopic ellipsometry measurement of Cu0.86In1.09Se2.05 reveals that shallow defect states are found in the sub-band-gap region. The energies of these defect levels are in quantitative agreement with those calculated and measured by photoluminescence, electrical conductivity, optical absorption, and deep level transient spectroscopy at low temperatures. The results can be explained in terms of the defect physics of this material and suggest that the defect levels are due to Cu deficiency. This work opens up the possibility of measuring defect levels of off-stoichiometric or heavily doped semiconductors by spectroscopic ellipsometry at room temperature.
Radiotracer measurements as a sensitive tool for the detection of metal penetration in molecular-based organic electronics
Authors: Scharnberg M. , Hu J. , Kanzow J. , Rätzke K. , Adelung R. , Faupel F. , Pannemann C. , Hilleringmann U. , Meyer S. , Pflaum J.
Published: January 2005

The metallization of organic thin films is a crucial point in the development of molecular electronics. However, there is no method established yet to detect trace amounts of metal atoms in those thin films. Radiotracer measurements can quantify even very small amounts of material penetrating into the bulk, in our case less than 0.01% of a monolayer. Here, the application of this technique on two different well-characterized organic thin film systems (diindenoperylene and pentacene) is demonstrated. The results show that Ag is mainly adsorbed on the surface, but indicate that already at moderate deposition temperatures Ag can penetrate into the organic thin films and agglomerate at the film/substrate interface.
Evaluation of nickel and molybdenum silicides for dual gate complementary metal-oxide semiconductor application
Authors: Biswas Nivedita , Gurganus Jason , Misra Veena , Yang Yan , Stemmer Susanne
Published: January 2005

Characteristics of NiSi and MoSi via full consumption of undoped silicon layers have been studied. Interaction of nickel (Ni) and molybdenum (Mo) silicides with SiO2 was evaluated in terms of work function and thermal stability. For nickel silicide, the work function values were low for samples annealed at 400 °C even after full consumption of silicon. The work function increased with the anneal temperature and stabilized at 600 °C to close to midgap values. Dielectric interaction as a result of silicide formation was studied using current–voltage characteristics. Low leakage currents in these stacks indicated minimum dielectric damage due to silicided gates. Silicidation of Mo was found to be incomplete as the capacitance–voltage curves were marked with larger EOT values and negative shifts in the flatband voltages even at 700 °C. Auger depth profiling, high resolution transmission electron microscopy (HRTEM) and x-ray diffraction (XRD) were used for material analysis of the silicided gate stacks.
Microfluidic devices with tunable microtopographies
Authors: Hsu Chia-Hsien , Folch Albert
Published: January 2005

Microfluidic devices are critical components of many biomedical and bioanalytical instruments and allow for probing chemical and physical phenomena at the micron scale. Most current microfluidic devices, however, have the inherent functional limitation that the cross-sectional channel geometry, which determines the fluid flow patterns, is essentially constant at any given point in the channel. We present microfluidic channels that contain topographical features whose size can be tuned by the user in real time. We demonstrate that the topographical changes can be used to alter the laminar flow patterns in microfluidic mixers and to physically trap small fluid volumes.
The effective electromechanical coupling coefficient of piezoelectric thin-film resonators
Authors: Chen Qingming , Wang Qing-Ming
Published: January 2005

The input electric impedance Zin for a three-layer thin-film bulk acoustic wave resonator is derived by transfer matrix method to describe the resonator behavior. Based on the impedance spectra, the effective coupling coefficient keff2 of a thin-film resonator can be evaluated with respect to the resonator structure and thin-film properties. The results for both AlN and lead zirconate titanate thin-film resonators reveal that the mechanical Q factor of the thin-film piezoelectric material has a significant effect on the effective coupling coefficient keff2 of the device. keff2 decreases with theincrease of the mechanical quality factor Q. A maximum keff2 value can be obtained at an appropriate thickness ratio of electrode/piezoelectric layers.
Thermoreflectance based thermal microscope
Authors: Christofferson James , Shakouri Ali
Published: January 2005

Thermal images of active semiconductor devices are acquired and processed in real time using visible light thermoreflectance imaging with 34mK sensitivity. By using a 16×16 alternating current coupled photodiode array with synchronous frequency domain filtering a dynamic range of 123dB is achieved for 1s averaging. Thus with a stable and higher power light source, fundamentally the camera can reach 6mK sensitivity over a submicron area. The number of pixels in the image is increased to 160×160 by multiple frame image enhancement and submicron spatial resolution is achieved. The photodiode array system has a maximum 40kHz frame rate and generates a synchronous trigger for recovery of the phase signal. Amplitude and phase images of the thermoreflectance signal for 50×50 micron square active SiGe based microcoolers are presented.
Combining singular value decomposition and a non-negative constraint in a hybrid method for photothermal depth profiling
Authors: Verkruysse Wim , Majaron Boris , Choi Bernard , Nelson J. Stuart
Published: January 2005

We present a method to solve the inverse problem in pulsed photothermal radiometry (PPTR) that exploits advantages of truncated singular value decomposition (T-SVD) while imposing a non-negativity constraint to the solution. The presented method is a hybrid in the sense that it expresses the solution vector as a linear superposition of right singular vectors, but with a non-negative constraint applied to it. The weights for the superposition are determined using an optimization algorithm. In one-dimensional PPTR simulation examples, the best reconstruction results are of comparable quality to those of the conjugate gradient method. Furthermore, the hybrid method exhibits a sharper knee in the L-curve and small susceptibility to over-iteration in presence of experimental noise, thus facilitating the regularization process. As a result, the reconstructed temperature profiles are more likely to be closer to the original initial profiles.
A concept to determine the true temperature of opaque materials using a tricolor pyroreflectometer
Authors: Hernandez D.
Published: January 2005

Despite the existence of several possible optical pyrometric methodologies, the determination of the true temperature has still not received a universal and perfect solution. We present here an analysis of our theoretical simulations and experimental measurements that have been carried out in order to validate a three-color method. Our goal is to test a pyroreflectometer (working wavelengths 0.84, 1.3, and 1.55μm) equipped with an optical fiber probe. This apparatus has been developed for in situ measurements in severe conditions (high temperature, difficult accessibility, controlled atmosphere, vacuum,…) to determine the true temperature of opaque materials. The method is based on three monochromatic measurements proportional to the emitted radiance; three monochromatic measurements proportional to normal reflectivities; the hypothesis of the same bidirectional reflectivity distribution function (BRDF) for the instrumented sample at the three working wavelengths. Using the six simultaneous measurements, the diffuse factor η and the apparent diffuse factor η∗ are introduced to determine the convergence temperature T∗ that is assumed to be equal to the true temperature T. After theoretical simulation, the method has been experimentally verified on several materials and an analysis of the causes of errors and their impact on the method accuracy and the operator modus, is discussed. The quality of the results obtained demonstrates the utility of the tricolor pyroreflectometer in a situation where fundamental parameters, such as the temperature and radiative properties, are difficult to measure.
Synthesis of well-aligned ZnO nanowires by simple physical vapor deposition on c-oriented ZnO thin films without catalysts or additives
Authors: Wang Lisheng , Zhang Xiaozhong , Zhao Songqing , Zhou Guoyuan , Zhou Yueliang , Qi Junjie
Published: January 2005

Well-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrates without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60nm in majority and 120nm in minority. They are about 4μm in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices.
High-voltage operation with high current gain of pnp AlGaN∕GaN heterojunction bipolar transistors with thin n-type GaN base
Authors: Kumakura Kazuhide , Makimoto Toshiki
Published: January 2005

A pnp AlGaN∕GaN heterojunction bipolar transistor (HBT) with a thin n-GaN base shows high-voltage operation with high current gain in the common-emitter configuration at room temperature. The device structure was grown by metalorganic vapor phase epitaxy on a sapphire substrate. The emitter area is 30μm×50μm. The HBT can operate at high voltage of 70V with the maximum current gain of 40 at the collector current of 10mA. The maximum output power density is 172kW∕cm2. Transport characteristics in the HBT were also investigated. At small collector current, the current gain is dominated by the recombination current at the emitter-base heterojunction. At moderate collector current, the calculated minority hole diffusion length well agreed with that determined from electron beam induced current measurements, indicating the current gain is dominated by the minority carrier diffusion. At large collector current, a high injection effect was observed in the current gain characteristics.
Orientation-dependent x-ray absorption fine structure of ZnO nanorods
Authors: Han S.-W. , Yoo H.-J. , An Sung Jin , Yoo Jinkyoung , Yi Gyu-Chul
Published: January 2005

The local structure of two samples of vertically well-aligned ZnO nanorods with average diameters of 13 and 37nm were studied using orientation-dependent x-ray absorption fine structure (XAFS) at the Zn K edge. The aligned ZnO nanorod samples were fabricated on sapphire (0001) substrates with a catalyst-free metalorganic vapor-phase epitaxy method. The XAFS measurements showed that both nanorod samples have a well-ordered wurtzite structure and that no vacancy was observed at either site of zinc or oxygen atoms. However, we found that in both samples the lattice constants of a and b were shrunken by ∼0.04Å while c was elongated by ∼0.1Å, compared with those of their bulk counterparts. Furthermore, there was a substantial amount of disorder in the bond length of the only Zn–O pairs located near the ab plane. This may suggest that the terminating atoms at the boundaries of the nanorods are oxygen atoms.
Laser bending for high-precision curvature adjustment of microcantilevers
Authors: Zhang X. Richard , Xu Xianfan
Published: January 2005

This work describes a laser based technique to adjust curvatures of silicon microcantilevers used for chemical and biological detection. In batch fabricated silicon cantilever arrays used for parallel sensing, it is often desirable that all cantilevers have nearly identical curvatures or flatness. We demonstrate that using the laser technique, it is possible to adjust curvatures by an amount as small as 3.5μrad, for cantilevers with a typical dimension of 110×13×0.6μm (length×width×thickness). Different laser parameters can be applied in order to achieve the required curvature adjustment. A two-dimensional finite element model of laser curvature adjustment is presented which enables the prediction of the laser processing parameters.
Limiting factors of room-temperature nonradiative photoluminescence lifetime in polar and nonpolar GaN studied by time-resolved photoluminescence and slow positron annihilation techniques
Authors: Chichibu S. F. , Uedono A. , Onuma T. , Sota T. , Haskell B. A. , DenBaars S. P. , Speck J. S. , Nakamura S.
Published: January 2005

Room-temperature nonradiative lifetime (τnr) of the near-band-edge excitonic photoluminescence (PL) peak in {0001} polar, (112¯0), (11¯00), and (001) nonpolar GaN was shown to increase with the decrease in density or size of Ga vacancies (VGa) and with the decrease in gross density of point defects including complexes, leading to the increase in the PL intensity. As the edge threading dislocation density decreased, density or size of VGa tended to decrease and τnr tended to increase. However, there existed remarkable exceptions. The results indicate that nonradiative recombination process is governed not by single point defects, but by certain defects introduced with the incorporation of VGa, such as VGa-defect complexes.
Analytical investigation of spin-transfer dynamics using a perpendicular-to-plane polarizer
Authors: Lee K. J. , Redon O. , Dieny B.
Published: January 2005

We studied current-induced magnetic switching and excitations in structures comprising a free layer with in-plane magnetization traversed by a current with perpendicular-to-plane spin polarization. We derived analytical solutions from the Landau–Lifshitz–Gilbert equation including the spin-torque term, and compared them to numerical simulations within the single domain assumption. Taking into account the criterion of thermal stability, the magnetization switching in nanostructures of typical size below 100nm comprising a perpendicular polarizer is found to require larger current density but to be much faster than with a longitudinal polarizer. Furthermore, a steady precession of magnetization can be generated in this geometry; those frequencies can be tuned from about 1 to 20GHz by only changing the current without applying any external field. This opens a promising application as microwave sources.
Luminescence from stacking faults in gallium nitride
Authors: Liu R. , Bell A. , Ponce F. A. , Chen C. Q. , Yang J. W. , Khan M. A.
Published: January 2005

A direct correlation has been established between stacking faults in a-plane GaN epilayers and luminescence peaks in the 3.29–3.41 eV range. The structural features of the stacking faults were determined by diffraction-contrast transmission electron microscopy, while the optical emission characteristics were observed by highly spatially resolved monochromatic cathodoluminescence. The studies were performed in the exact same regions of thinned foils. We find that stacking faults on the basal plane are responsible for the strong emission at ∼3.14eV. Luminescence peaks at ∼3.33 and ∼3.29eV are associated with the presence of stacking faults on prismatic a planes and partial dislocations at the stacking fault boundaries, respectively.
Lead barium zirconate perovskite films for electrically tunable applications
Authors: Wu Mei-Hai , Wu Jenn-Ming
Published: January 2005

Lead barium zirconate (PBZ) thin films were deposited on Pt∕Ti∕SiO2∕Si substrates by spincoating sol-gel precursor solutions to fabricate films for electrically tunable device applications. Randomly oriented (Pb1−xBax)ZrO3 cubic perovskite films with x=0.4, 0.6, and 0.8 were formed after heat treating at 600 °C–750 °C. The results demonstrated that the (Pb0.6Ba0.4)ZrO3 film possessed promising tunable dielectric properties as measured at 1 MHz. The (Pb0.6Ba0.4)ZrO3 film heat treated at 750 °C has a dielectric dissipation factor (tanδ) of 0.007 and a dielectric tunability of 43%. The figure of merit of the (Pb0.6Ba0.4)ZrO3 film is 61.43, which is comparable with the foremost investigated (BaSr)TiO3 films.
Formation and structure of ramified charge transportation networks in an electromechanical system
Authors: Jun Joseph K. , Hübler Alfred H.
Published: January 2005

We present findings in an experiment where we obtain stationary ramified transportation networks in a macroscopic nonbiological system. Our purpose here is to introduce the phenomenology of the experiment. We describe the dynamical formation of the network which consists of three growth stages: (I) strand formation, (II) boundary formation, and (III) geometric expansion. We find that the system forms statistically robust network features, like the number of termini and the number of branch points. We also find that the networks are usually trees, meaning that they lack closed loops; indeed, we find that loops are unstable in the network. Finally, we find that the final topology of the network is sensitive to the initial conditions of the particles, in particular to its geometry.
Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein
Authors: Weichsel Andrzej , Maes Estelle M. , Andersen John F. , Valenzuela Jesus G. , Shokhireva Tatjana Kh. , Walker F. Ann , Montfort William R.
Published: January 2005

Certain bloodsucking insects deliver nitric oxide (NO) while feeding, to induce vasodilation and inhibit blood coagulation. We have expressed, characterized, and determined the crystal structure of the
Cimex lectularius
(bedbug) nitrophorin, the protein responsible for NO storage and delivery, to understand how the insect successfully handles this reactive molecule. Surprisingly, NO binds not only to the ferric nitrophorin heme, but it can also be stored as an
S
-nitroso (SNO) conjugate of the proximal heme cysteine (Cys-60) when present at higher concentrations. EPR- and UV-visible spectroscopies, and a crystallographic structure determination to 1.75-Å resolution, reveal SNO formation to proceed with reduction of the heme iron, yielding an Fe-NO complex. Stopped-flow kinetic measurements indicate that an ordered reaction mechanism takes place: initial NO binding occurs at the ferric heme and is followed by heme reduction, Cys-60 release from the heme iron, and SNO formation. Release of NO occurs through a reversal of these steps. These data provide, to our knowledge, the first view of reversible metal-assisted SNO formation in a protein and suggest a mechanism for its role in NO release from ferrous heme. This mechanism and
Cimex
nitrophorin structure are completely unlike those of the nitrophorins from
Rhodnius prolixus
, where NO protection is provided by a large conformational change that buries the heme nitrosyl complex, highlighting the remarkable evolution of proteins that assist insects in bloodfeeding.
Active site restructuring regulates ligand recognition in class A penicillin-binding proteins
Authors: Macheboeuf Pauline , Di Guilmi Anne Marie , Job Viviana , Vernet Thierry , Dideberg Otto , Dessen Andréa
Published: January 2005

Bacterial cell division is a complex, multimolecular process that requires biosynthesis of new peptidoglycan by penicillin-binding proteins (PBPs) during cell wall elongation and septum formation steps.
Streptococcus pneumoniae
has three bifunctional (class A) PBPs that catalyze both polymerization of glycan chains (glycosyltransfer) and cross-linking of pentapeptidic bridges (transpeptidation) during the peptidoglycan biosynthetic process. In addition to playing important roles in cell division, PBPs are also the targets for β-lactam antibiotics and thus play key roles in drug-resistance mechanisms. The crystal structure of a soluble form of pneumococcal PBP1b (PBP1b
*
) has been solved to 1.9 Å, thus providing previously undescribed structural information regarding a class A PBP from any organism. PBP1b
*
is a three-domain molecule harboring a short peptide from the glycosyltransferase domain bound to an interdomain linker region, the transpeptidase domain, and a C-terminal region. The structure of PBP1b
*
complexed with β-lactam antibiotics reveals that ligand recognition requires a conformational modification involving conserved elements within the cleft. The open and closed structures of PBP1b
*
suggest how class A PBPs may become activated as novel peptidoglycan synthesis becomes necessary during the cell division process. In addition, this structure provides an initial framework for the understanding of the role of class A PBPs in the development of antibiotic resistance.
Hypertension in mice lacking the proatrial natriuretic peptide convertase corin
Authors: Chan Joyce C. Y. , Knudson Ole , Wu Faye , Morser John , Dole William P. , Wu Qingyu
Published: January 2005

Atrial natriuretic peptide (ANP) is a cardiac hormone that regulates blood pressure. In cardiomyocytes, the hormone is synthesized as a precursor, proatrial natriuretic peptide (pro-ANP), which is proteolytically converted to active ANP. Corin is a cardiac transmembrane serine protease that has been shown to process pro-ANP
in vitro
, but its physiological importance had not been established. Here, we show that corin-deficient (
Cor
-/-
) mice develop normally during embryogenesis and survive to postnatal life.
Cor
-/-
mice have elevated levels of pro-ANP but no detectable levels of ANP as compared with WT littermates. Infusion of an active recombinant soluble corin transiently restores pro-ANP conversion, resulting in the release of circulating biologically active ANP. Using radiotelemetry to assess blood pressure, we find that
Cor
-/-
mice have spontaneous hypertension as compared with WT mice, and it is enhanced after dietary salt loading. Pregnant
Cor
-/-
mice demonstrate late-gestation proteinuria and enhanced high blood pressure during pregnancy. In addition,
Cor
-/-
mice exhibit cardiac hypertrophy resulting in a mild decline in cardiac function later in life. Thus, our data establish corin as the physiological pro-ANP convertase and indicate that corin deficiency may contribute to hypertensive heart disease.
Solution NMR-derived global fold of a monomeric 82-kDa enzyme
Authors: Tugarinov Vitali , Choy Wing-Yiu , Orekhov Vladislav Yu. , Kay Lewis E.
Published: January 2005

The size of proteins that can be studied by solution NMR spectroscopy has increased significantly because of recent developments in methodology. Important experiments include those that make use of approaches that increase the lifetimes of NMR signals or that define the orientation of internuclear bond vectors with respect to a common molecular frame. The advances in NMR techniques are strongly coupled to isotope labeling methods that increase sensitivity and reduce the complexity of NMR spectra. We show that these developments can be exploited in structural studies of high-molecular-weight, single-polypeptide proteins, and we present the solution global fold of the monomeric 723-residue (82-kDa) enzyme malate synthase G from
Escherichia coli
, which has been extensively characterized by NMR in the past several years.
Fluorescent imaging of Cl
-
in
Amphiuma
red blood cells: How the nuclear exclusion of Cl
-
affects the plasma membrane potential
Authors: Hoffman Joseph F. , Geibel John P.
Published: January 2005

In this work, we test the idea that most, if not all, cellular Cl
-
of
Amphiuma
red blood cells is contained in the cytoplasm. If true, this could resolve the difference between the measured plasma membrane potential (
E
m
) and that expected from the Donnan equilibrium distribution of Cl
-
. We studied the changes in the fluorescence intensity of the Cl
-
-sensitive dye, MQAE, entrapped in red cells that occurred when intracellular Cl
-
was exchanged with

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. We could thus monitor the distribution of Cl
-
between the nuclear and cytoplasmic compartments. We found that essentially all of the cell's Cl
-
resides in the cytoplasm. Knowing the volume of the cell occupied by the nucleus, we could accordingly correct the measured values of cell Cl
-
. This resulted in establishing a concordance between the measured values of
E
m
and those calculated from the corrected values of the Cl
-
ratio, thus explaining the discrepancy. The exclusion of Cl
-
from the nucleus may result from its unusually high content of “excess” DNA that imposes an imbalance of net negative charge.
Lipid peroxidation and protein oxidation in patients affected by Hodgkin′s lymphoma
Authors: Morabito F. , Cristani M. , Saija A. , Stelitano C. , Callea V. , Tomaino A. , Minciullo P. L. , Gangemi S.
Published: January 2005

A dysregulation of the redox homoeostasis has been reported in various neoplastic disorders. Malondialdehyde/4‐hydroxy‐2,3‐nonenal (MDA/HNE) and protein carbonyl groups represent in vivo indexes of lipid peroxidation and protein oxidation, respectively, suitable to investigate radical‐mediated physio‐pathological conditions.

We evaluated MDA/HNE and protein carbonyl groups in sera of untreated Hodgkin′s lymphoma (HL) patients in advanced disease stages, in order to quantify the oxidative stress.

HL patients displayed significantly higher levels of both MDA/HNE and protein carbonyl groups as compared with healthy controls.

This is the first evidence that a strong increase in HL is one of the most common haematological malignancies, representing approximately 30% of all lymphomas in the circulating protein carbonyl content in HL. These findings may contribute to a better definition of the redox homoeostasis dysregulation in HL.
Production of interferon‐γ by natural killer cells and aging in chronic human schistosomiasis
Authors: Speziali E. , Bethony J. , Martins-Filho O. , Fraga L. A. O. , Lemos D. S. , Souza L. J. , Correa-Oliveira R. , Faria A. M. C.
Published: January 2005

BACKGROUNG: Aging is associated with several alterations in the phenotype, repertoire and activation status of lymphocytes as well as in the cytokine profile produced by these cells. As a lifelong condition, chronic parasitic diseases such as human schistosomiasis overlaps with the aging process and no systematic study has yet addressed the changes in immune response during infection with Schistosoma mansoni in older individuals.

Aim: Herein we study the influence of immunological alterations brought about by senescence in the course of schistosomiasis.

Materials and methods: Individuals 10‐95 years of age, from both sexes, from an endemic area for S. mansoni infection were matched by intensity of infection as measured by egg counts. We analyzed, as a parameter, cytokine expression by lymphocytes and natural killer cells after in vitro stimulation with soluble egg antigen and soluble worm antigen using flow cytometry.

Results: We demonstrated that the frequency of CD16+ interferon‐γ (IFN‐γ)+ natural killer cells in negative individuals over the age of 70 years is significantly higher than in positive individuals after in vitro stimulation with S. mansoni antigen extracts. The frequency of these cells is increased in all individuals over the age of 50 years and only declines in positive individuals after 70 years of age. Analysis of either CD4? or CD8? cells after antigen stimulation show no significant increase in frequency of IFN‐γ in negative or in positive individuals of this age group, suggesting that the effect on CD16+ cells is not T‐cell dependent.

Conclusion: Since production of IFN‐γ has been related to resistance to schistosome infection, our data suggest that age‐associated changes in CD16+ cells may play a role in controlling infection intensity in the elderly in S. mansoni endemic areas of Brazil.
Role of type I interferon in the bacillus Calmette‐Guérin‐induced expression of CXCL10 from human monocytes
Authors: Samperio Patricia Méndez , Trejo Artemisa , Miranda Elena
Published: January 2005

BACKGROUND: The proinflammatory chemokine CXCL10, in addition to its chemotactic properties, is also involved in the stimulation of natural killer and T‐cell migration in Mycobacterium tuberculosis infection. In this study, our experiments were designed to determine the role of interferon (IFN)‐αβ in the production of CXCL10 by human monocytes infected with Mycobacterium bovis bacillus Calmette‐Guérin (BCG).

Methods: The concentrations of CXCL10 in culture supernatants of monocytes infected with M. bovis BCG were determined by enzyme‐linked immunosorbent assay. CXCL10 mRNA levels were determined by the reverse transcription‐polymerase chain reaction method.

Results: We have shown the induction of CXCL10 following infection with M. bovis BCG in a dose‐dependent and time‐dependent manner. Importantly, the secretion of CXCL10 in response to M. bovis was increased by IFN‐α. These results were further confirmed by the fact that the addition of an anti‐IFN‐αβ neutralizing antibody completely reversed the stimulatory effect, whereas an isotype‐matched control antibody had no significant effect on CXCL10 secretion. It is important to note that no significant effect of type I IFN on CXCL8 production in M. bovis‐infected monocytes was observed. This was consistent with the finding by the reverse transcription‐polymerase chain reaction method that treatment with anti‐IFN‐α/β antibodies potentially inhibited CXCL10 mRNA levels, whereas no significant effect was observed on CXCL8 mRNA. Moreover, in THP‐1 monocytes and THP‐1 macrophages, the addition of exogenous IFN‐α stimulated CXCL10 secretion.

Conclusions: Collectively, these results indicate that the type I IFN may play an important role to modulate the expression of CXCL10 in M. bovis BCG infection. Studies on M. bovis‐induced chemokine secretion could provide important insight into the regulation of the immune response against tuberculosis.
No effects of ozonated autohemotherapy on inflammation response in hemodialyzed patients
Authors: Tylicki Leszek , Biedunkiewicz Bogdan , Rachon Dominik , Nieweglowski Tomasz , Hak Lukasz , Chamienia Andrzej , Debska-Slizien Alicja , Aleksandrowicz Ewa , Mysliwska Jolanta , Rutkowski Boleslaw
Published: January 2005

BACKGROUND: Ozone as a strong oxidant may induce an inflammatory response.

Aim: The hypothesis was verified as to whether ozonated autohemotherapy using an ozone dose in therapeutic range changes the plasma concentration of C‐reactive protein and interleukin‐6, markers of inflammation.

Methods: In a controlled, single‐blind, cross‐over study, 12 chronically hemodialyzed patients with peripheral arterial disease were exposed to nine sessions of autohemotherapy with blood exposure to oxygen as a control followed by nine sessions of ozonated autohemotherapy with an ozone concentration of 50 μg/ml.

Results: There was no statistical difference between C‐reactive protein levels at baseline (1.53±1.01 mg/l), after nine sessions of control autohemotherapy (1.48±0.96 mg/l), and after nine sessions of ozonated autohemotherapy (1.55±0.84 mg/l). There was also no statistical difference between the interleukin‐6 serum concentration at baseline (438±118 pg/ml), after nine sessions of control autohemotherapy (444±120 pg/ml), and after nine sessions of ozonated autohemotherapy (466±152 pg/ml).

Conclusion: The results of this study suggest that ozonated autohemotherapy using an ozone concentration of 50 μg/ml does not induce an inflammatory response.
Role of CC chemokine CCL6/C10 as a monocyte chemoattractant in a murine acute peritonitis
Authors: LaFleur Andrew M. , Lukacs Nicholas W. , Kunkel Steven L. , Matsukawa Akihiro
Published: January 2005

THE aim of this study was to determine the role of CC chemokine CCL6/C10 in acute inflammation. Intraperitoneal injection of thioglycollate increased peritoneal CCL6, which peaked at 4 h and remained elevated at 48 h. Neutralization of CCL6 significantly inhibited the macrophage infiltration (34‐48% reduction), but not other cell types, without decreasing the other CC chemokines known to attract monocytes/macrophages. CCL6 was expressed in peripheral eosinophils and elicited macrophages, but not in elicited neutrophils. Peritoneal CCL6 level was not decreased in granulocyte‐depleted mice where eosinophil influx was significantly impaired. Thus, CCL6 appears to contribute to the macrophage infiltration that is independent of other CC chemokines. Eosinophils pre‐store CCL6, but do not release CCL6 in the peritoneum in this model of inflammation.
Plant Origin of Green Propolis: Bee Behavior, Plant Anatomy and Chemistry
Authors: Teixeira Érica Weinstein , Negri Giuseppina , Meira Renata M. S. A. , Message Dejair , Salatino Antonio
Published: January 2005

Propolis, a honeybee product, has gained popularity as a food and alternative medicine. Its constituents have been shown to exert pharmacological effects, such as anti‐microbial, anti‐inflammatory and anticancer. Shoot apices of Baccharis dracunculifolia (alecrim plant, Asteraceae) have been pointed out as sources of resin for green propolis. The present work aimed (i) to observe the collecting behavior of bees, (ii) to test the efficacy of histological analysis in studies of propolis botanical origin and (iii) to compare the chemistries of alecrim apices, resin masses and green propolis. Bee behavior was observed, and resin and propolis were microscopically analyzed by inclusion in methacrylate. Ethanol extracts of shoot apices, resin and propolis were analyzed by gas chromatography/mass spectroscopy. Bees cut small fragments from alecrim apices, manipulate and place the resulting mass in the corbiculae. Fragments were detected in propolis and identified as alecrim vestiges by detection of alecrim structures. Prenylated and non‐prenylated phenylpropanoids, terpenoids and compounds from other classes were identified. Compounds so far unreported for propolis were identified, including anthracene derivatives. Some compounds were found in propolis and resin mass, but not in shoot apices. Differences were detected between male and female apices and, among apices, resin and propolis. Alecrim apices are resin sources for green propolis. Chemical composition of alecrim apices seems to vary independently of season and phenology. Probably, green propolis composition is more complex and unpredictable than previously assumed.
Theta oscillations by synaptic excitation in a neocortical circuit model
Authors: Budd Julian M. L.
Published: January 2005

Neocortical theta-band oscillatory activity is associated with cognitive tasks involving learning and memory. This oscillatory activity is proposed to originate from the synchronization of interconnected layer V intrinsic bursting (IB) neurons by recurrent excitation. To test this hypothesis, a sparsely connected spiking circuit model based on empirical data was simulated using Hodgkin-Huxley-type bursting neurons and use-dependent depressing synaptic connections. In response to a heterogeneous tonic current stimulus, the model generated coherent and robust oscillatory activity throughout the theta-band (4-12 Hz). These oscillations were not, however, self-sustaining without a driving current, and not dependent on
N
-methyl-D-aspartate receptor synaptic currents. At realistic connection strengths, synaptic depression was necessary to avoid instability and expanded the basin of attraction for theta oscillations by controlling the gain of recurrent excitation. These results support the hypothesis that IB neuron networks can generate robust and coherent theta-band oscillations in neocortex.
Recent X–ray diffraction studies of muscle contraction and their implications
Authors: Holmes K. C. , Trentham D. R. , Simmons R. , Huxley Hugh E.
Published: January 2005

Recent studies on the interference fringes in the myosin meridional reflections provide a new source of structural information on cross–bridge movement during mechanical transients and steady shortening. Many observations can be interpreted satisfactorily by
the tilting lever–arm model, with some assumptions, including the presence of fixed repeating structures contributing to the M3 and higher–order meridional reflections. In isometric contraction, the lever arms are oriented near the start of the working stroke, with a dispersion of
ca
+−20–25°. Upon a rapid release
of 10–12 nm, they move to the end of the stroke, with a well–known T2 delay of 1–2 ms. This delay must represent additional processes, which have to occur even in
tension–generating heads, or activation of attached heads, which initially do not develop force. Surprisingly, in muscles shortening at moderate loads (0.5–0.6 P
0
), the mean position of the heads moves only 2–3 nm closer to the M–line than in the isometric case, reminiscent of the Piazzesi–Lombardi model.
A model of stereocilia adaptation based on single molecule mechanical studies of myosin I
Authors: Holmes K. C. , Trentham D. R. , Simmons R. , Batters Christopher , Wallace Mark I. , Coluccio Lynne M. , Molloy Justin E.
Published: January 2005

We have used an optical tweezers–based apparatus to perform single molecule mechanical experiments using the unconventional myosins, Myo1b and Myo1c. The single–headed nature and slow ATPase kinetics of these myosins make them ideal for detailed studies of the molecular mechanism of force generation by acto–myosin. Myo1c exhibits several features that have not been seen using fast skeletal muscle myosin II. (i) The working stroke occurs in two, distinct phases, producing an initial 3 nm and then a further 1.5 nm of movement. (ii) Two types of binding interaction were observed: short–lived ATP–independent binding events that produced no movement and longer–lived, ATP–dependent events that produced a full working stroke. The stiffness of both types of interaction was similar. (iii) In a new type of experiment, using feedback to apply controlled displacements to a single acto–myosin cross–bridge, we found abrupt changes in force during attachment of the acto–Myo1b cross–bridge, a result that is consistent with the classical ‘
T
2
’ behaviour of single muscle fibres. Given that these myosins might exhibit the classical
T
2
behaviour, we propose a new model to explain the slow phase of sensory adaptation of the hair cells of the inner ear.
Adenosine diphosphate and strain sensitivity in myosin motors
Authors: Holmes K. C. , Trentham D. R. , Simmons R. , Nyitrai Miklós , Geeves Michael A.
Published: January 2005

The release of adenosine diphosphate (ADP) from the actomyosin cross–bridge plays an important role in the adenosine–triphosphate–driven cross–bridge cycle. In fast contracting muscle fibres, the rate at which ADP is released from the cross–bridge correlates with the maximum shortening velocity of the muscle fibre, and in some models the rate of ADP release defines the maximum shortening velocity. In addition, it has long been thought that the rate of ADP release could be sensitive to the load on the cross–bridge and thereby provide a molecular explanation of the Fenn effect. However, direct evidence of a strain–sensitive ADP–release mechanism has been hard to come by for fast muscle myosins. The recently published evidence for a strain–sensing mechanism involving ADP release for slower muscle myosins, and in particular non–muscle myosins, is more compelling and can provide the mechanism of processivity for motors such as myosin V. It is therefore timely to examine the evidence for this strain–sensing mechanism. The evidence presented here will argue that a strain–sensitive mechanism of ADP release is universal for all myosins but the basic mechanism has evolved in different ways for different types of myosin. Furthermore, this strain–sensing mechanism provides a way of coordinating the action of multiple myosin motor domains in a single myosin molecule, or in complex assemblies of myosins over long distances without invoking a classic direct allosteric or cooperative communication between motors.
The motor mechanism of myosin V: insights for muscle contraction
Authors: Holmes K. C. , Trentham D. R. , Simmons R. , Sweeney H. Lee , Houdusse Anne
Published: January 2005

It is 50 years since the sliding of actin and myosin filaments was proposed as the basis of force generation and shortening in striated muscle. Although this is now generally accepted, the detailed molecular mechanism of how myosin uses adenosine triphosphate to generate force during its cyclic interaction with actin is only now being unravelled. New insights have come from the unconventional myosins, especially myosin V. Myosin V is kinetically tuned to allow movement on actin filaments as a single molecule, which has led to new kinetic, mechanical and structural data that have filled in missing pieces of the actomyosin–chemo–mechanical transduction puzzle.
Relatives’ experiences of critical care
Authors: Hughes Felicity , Bryan Karen , Robbins Ian
Published: January 2005

• This exploratory study investigates relatives’ overall experiences of the critical care environment and how staff perceived these experiences

• Traditionally, research in Critical Care concentrated on patients’ psychological well‐being or relatives’ immediate needs. There is little research that addresses the relative's overall experience of events

• Critical Care Units are possibly the most daunting units in hospitals. Having a family member admitted to a Critical Care Unit could qualify as a traumatic‐enough stressor to induce post‐traumatic stress symptoms in relatives

• A convenience sample of eight relatives and five staff participated in the study. The study used qualitative methods and drew on techniques of grounded theory

• While staff perceived relatives’ experiences accurately; issues arose, from both staff and relatives perspective, with regard to accurate dissemination of information

• Further research into the communication processes used within Critical Care Units is required in addition to developing best practice in this area
When the unreal becomes real: family members’ experiences of cardiac arrest
Authors: Weslien Marita , Nilstun Tore , Lundqvist Anita , Fridlund Bengt
Published: January 2005

• The aim of this study was to provide insight into family members’ experiences related to cardiac arrest

• Data were collected through semi‐structured interviews with 17 family members approximately 5–34 months after the cardiac arrest of a relative. As the focus was on the family members’ experiences seen from a holistic perspective, content analysis was chosen for the study

• When the event occurred to the patient, family members realized the need for assistance and managed to initiate first actions

• When the emergency medical service arrived, family members responded to stress and forgot their own needs

• When the staff took over at the hospital, family members not only received sympathy but also encountered professional distancing

• Because their experiences vary widely, the encounter has to be developed through a comforting, sympathetic and respectful dialogue in consideration for individuals’ preferences
Kinetic therapy positively influences oxygenation in patients with ALI/ARDS
Authors: Rance Martine
Published: January 2005

• Acute respiratory distress syndrome (ARDS) is a fulminant form of respiratory failure, with diverse aetiology, despite technological advances in intensive care medicine; mortality rates remain 50–70%

• Costs associated with the management of patients in intensive therapy unit (ITU) are very high; therefore, the requirement for those working in critical care to provide evidence‐based practice is mandatory

• One area of investigation is that kinetic therapy improves pulmonary complications in critically ill patients by positively influencing oxygenation and gaseous exchange

• Whilst kinetic therapy does appear to be an effective therapy in ITU, there are inconsistencies in reported findings, and thus, clearly a need for further research into this innovative therapy to maximize its potential
Simulating the East African wildebeest migration patterns using GIS and remote sensing
Authors: Musiega Douglas E. , Kazadi Sanga‐Ngoie
Published: January 2005

The Serengeti–Mara ecosystem in East Africa is a spectacular natural heritage endowed with diverse fauna and flora. The presence of the seasonally migrating wildebeest (Connochaetes taurinus) is a major boost for tourism. This migration however has enormous impacts to the ecosystem. Consequently efforts at monitoring the herd's migration trends and patterns remain a challenge to wildlife managers and ecologists in the region. In this paper, the relative influence of vegetation (normalized difference vegetation index), landscape and relief on herds migration routes are investigated and the migration routes simulated using GIS and remote sensing techniques. The results are compared with the annual mean route taken by the herds, as determined by radio tracking over the 1995–1997 period. Green vegetation availability is shown to be the major criterion in route choice. It is also shown that during the dry season phases of the migration (western trek, western corridor), the herd endures complex relief (complexity quantified based on slope and inter‐visibility) in the search for greener grass. During the season of abundance (southern trek), relief becomes critical in making route choices, with herds avoiding difficult terrain, notwithstanding their relatively more abundant vegetation. The method proposed in this paper is viable for rapid prediction of approximate routes for the migrating wildebeest in different climatic conditions.