bluuebunny/crossref_metadata_2025 huggingface dataset:
Carrier Lifetimes in GaN Revealed by Studying Photoluminescence Decay in Time and Frequency Domains
Authors: Tamulaitis Gintautas , Mickevicius Juras , Vitta Pranciskus , Zukauskas Arturas , Shur M. , Liu Kai , Fareed Qhalid , Zhang Jianping , Gaska Remis
Published: November 2006

The carrier dynamics in GaN epilayer, grown using migration enhanced metalorganic chemical vapor deposition (MEMOCVD), is investigated in a wide range of photoexcitation power density of twelve orders of magnitude. Study of photoluminescence decay lifetimes at extremely low excitation power densities of 0.5 mW/cm2 was performed using frequency-domain lifetime measurements with a UV LED (280 nm) as an excitation source. The carrier lifetimes at high excitation power densities was studied using time-resolved photoluminescence (TR PL) spectroscopy and light-induced transient grating (LITG) technique. The measurements were carried out in the temperature range from 10 to 300 K. At high carrier densities, which are typical for device applications, the room- temperature carrier lifetime of 2 ns was obtained, while a variety of decay components was revealed at low excitation intensities. Trapping and detrapping of the carriers/excitons is shown to play an important role in the carrier dynamics at low carrier densities.
Development of Yellow and White LED's Using InGaN-based Multi-Quantum well Structures
Authors: Bedair Salah M. , Barletta Phillip , Berkman Acar , Emara Ahmed , Reed Mason , El-Masry Nadia A. , Moody Baxter
Published: November 2006

In recent years, InGaN-based LED's emitting in the blue and green spectral regions have emerged into widespread use. However, due to fundamental material issues, achieving yellow and red emission from InGaN-based structures has presented a unique challenge. We have developed conditions for the MOCVD growth of a series of InGaN-based MQW devices that emit over a wide spectral range (420nm - 600nm). It has been found that the emission properties of these monochromatic devices depend critically on the growth rate, growth temperature, QW width, barrier growth conditions, and p-type capping layer growth conditions. Additionally, we have demonstrated white electroluminescence through the proper mixing of complementary colors.
Properties of CdZnO/ZnO Heterostructures for UV Light Emitters
Authors: Osinsky Andrei V. , Dong Jianwei , Hertog Brian , Dabiran Amir M. , Chow Peter , Schoenfeld Winston , Pearton Steve J. , Look David , Cartwright Alexander
Published: November 2006

In the paper we present band-gap alignment diagrams for type-II/type-I heterostructures incorporating the strong piezoelectric and spontaneous polarization fields in ZnCdMgO and AlGaN-based materials and interfaces. The paper describes some of the recent progress made in the development of high quality ZnCdO layers and CdZnO/ZnO heterostructures grown epitaxially by RF-plasma molecular beam epitaxy (MBE). We summarize optical and electrical properties of high quality CdxZn1-xO alloys with Cd mole fraction from 0.02 to 0.78 and discuss phase separation phenomenon, which may be present in ternary alloys. A single-crystal wurtzite structure of CdZnO alloys has been confirmed. We achieved a strong optical emission at RT in the 380 nm to 574 nm spectral range from CdxZn1-xO with various compositions. Dependence of the fundamental optical band gap on the composition of CdxZn1- xO alloys, band gap bowing, and the possible effect of composition micro-fluctuations in ternary CdxZn1-xO alloys on the optical bandgap is also discussed. Time resolved photoluminescence shows multi-exponential decay with 21 psec. and 49{plus minus}3 psec. lifetimes, suggesting that composition micro- fluctuations may be present in Cd0.16Zn0.84O film. We also report on crystallographic and optical properties of CdZnO/ZnO multiple quantum wells.
GaN-Based Devices for Reliable Operation at Very High Temperatures
Authors: Dabiran Amir M. , Osinsky Andrei V. , Peter Peter P. , Fitch Robert C. , Moser Neil , Crespo A , Anderson T J. , Ren F. , Khanna Rohit , Stafford L. , Pearton Steve J.
Published: November 2006

One of the main issues for high-temperature operation of GaN- based devices is the development of reliable metal contacts. We have investigated the thermal stability and device performance of AlGaN/GaN high-electron mobility transistors (HEMTs) with both conventional (Ti/Al/Ni/Au) and Ir-based (Ti/Al/Ir/Au) Ohmic contacts. Both dc and rf measurements showed better performance with Ir-based contacts, from room temperature up to 500{degree sign}C. We also fabricated AlGaN/GaN HEMTs with Ti/Al/TiB2/Ti/Au source/drain Ohmic contacts and a variety of gate metal schemes (Pt/Au, Ni/Au, Pt/TiB2/Au or Ni/TiB2/Au) and subjected them to long-term annealing at 350{degree sign}C. By comparison with companion devices with conventional Ti/Al/Pt/Au Ohmic contacts and Pt/Au gate contacts, the HEMTs with boride- based Ohmic metal and either Pt/Au, Ni/Au or Ni/TiB2/Au gate metal showed superior stability of both source-drain current and transconductance after 25 days aging at 350{degree sign}C.
CdS Roughness by Anti-Stokes Raman Spectroscopy
Authors: Molina-Contreras J. Rafael , Frausto-Reyes Claudio , Medina-Gutierrrez Cirilo , Calixto Sergio
Published: November 2006

A Raman system, with the 514.5 and 632.8 nm excitations wavelengths, was used to qualitatively detect the surface roughness of a CdS wafer sample. Anti-Stokes Raman spectra were obtained from several sample zones with different mean roughness levels, previously measured with Atomic Force Microscopy. Our results show that there is a spectrum profile which can be related to the sample roughness, which shows a better definition with the 514.5 nm excitation wavelength.
Ferromagnetic Properties of GaGdN Co-Doped with Si
Authors: Hite Jennifer , Frazier Rachel M. , Davies Ryan P. , Thaler Gerald T. , Abernathy Cammy R. , Pearton Steve J. , Zavada John M.
Published: November 2006

Single phase GaGdN and GaGdN:Si thin films were grown by gas source molecular beam epitaxy using solid Gd, Ga, and Si sources along with a RF nitrogen plasma. SQUID magnetometry indicated room temperature ferromagnetism in both materials. Defects played a large role in the magnetic ordering of the material, as seen in a drastic reduction of magnetic signal with degrading crystallinity. Highly resistive films became conductive with the addition of Si. Magnetization of the co-doped film increased with Si content, reaching levels higher than that of the singly-doped material.
Direction Dependent Electrical and Optical Properties of Gallium Nitride Nanowires
Authors: Sunkara Mahendra K. , Makkena Rahul , Li Hongwei , Alphenaar Bruce
Published: November 2006

Gallium Nitride (GaN) nanowires are synthesized in two distinct directions the <10-10> a-direction and the <0001> c- direction using a direct nitridation scheme. Field effect transistors are then fabricated using the as-synthesized 'a' and 'c' direction nanowires. Gate dependent electrical transport measurements performed on the a-direction nanowires showed an increase in conductivity with the applied gate bias while no gate dependent conductivity is observed in the case of 'c' direction nanowires. The electron mobility for the a- direction GaN nanowire FETs is estimated to be 170 cm2/V- s .Photo luminescence (PL) and UV-Vis absorption spectroscopy measurements show that the band gap of nanowires grown in a- direction blue shifts by about 50-70 meV when compared to the wires grown in c- direction.
Boron Carbide Heterojunction Diodes: Temperature Effects, Band Offsets, and Intrinsic and Extrinsic Carriers
Authors: Barrios Flores Oscar , Brand Jennifer I.
Published: November 2006

The I(V) characteristics of semiconducting boron carbide heterojunction diodes on silicon were measured at temperatures ranging from room temperature to 300 C (570 K). The precursor molecules for the plasma enhanced chemical vapor depositions of p-type and n-type films were the isoelectronic isomers, orthocarborane (1,2-C2B10H12) and metacarborane (1,7-C2B10H12), respectively. The qualitative behavior was similar that of previously reported boron carbide homojunctions and heteroisomeric diodes. Metacarborane is the more resistive of the two materials at all temperatures measured. The resistivity curves of the heterojunctions as a function of temperature reveal the difference in band offsets to be important, with the extrinsicintrinsic carrier transition occurring below room temperature for the p-type material from orthocarborane and at about 87 C (360 K) for the n-type material from metacarborane.
Electrochemical Detection of Polyphenolic Compounds Using Carbon Composite Electrodes
Authors: Davila Martin Marino Martin M. , Ahuatl Fortino , Elizalde Maria , Mattusch Juergen , Wennrich Rainer
Published: November 2006

Carbon - Polyvinylchloride composite electrodes were used to study ascorbic acid, (+)-catechin, (-)-epicatechin, gallic acid and (-)-epigallocatechin in phosphate buffer solutions (pH 5.0 and 7.0) and in a model wine solution pH 3.6 by cyclic, differential and square wave voltammetry. Excellent linearity was obtained for these antioxidant compounds by differential pulse voltammetry and the detection limits at carbon composites ranged from 29 µg/l to 0.45 mg/l for (+)- catechin and were 0.16, 0.15, 0.10 mg/l for gallic acid, (-)- epicatechin and (-)-epigallocatechin, respectively in model wine solution pH 3.6. Differential and square wave voltammetry were employed to determine their electrochemical parameters and to quantify antioxidants at a carbon composite in a model wine solution prepared from the dilution 0.13 % (v/v) of a commercial red wine.
Electrochemical pH-Stat for Microliter Fluid Specimens
Authors: Kao Linus T. , Hsu Hung-Yi , Shetty Gautam , Gratzl Miklos
Published: November 2006

pH-stating is a widely used technique for monitoring various (bio)chemical reactions involving generation or consumption of hydrogen/hydroxide ions. In this work a reagentless pH-stat has been developed where acid or base are generated by water electrolysis. Since the current that generates the reagents can be precisely measured even at low levels, very small sample volumes, in the 10-20 μL range, become accessible for pH-stating: a reduction of several orders of magnitude in specimen size. With proper current control the scheme may be calibration free by virtue of Faraday's law. Simplicity of reagent delivery and miniaturization of the accessible sample size render this approach advantageous with respect to conventional pH-stats, especially in the biomedical area. The electrochemical micro pH-stat is a derivative of the Rotating Sample System that has been conceived for a number of applications in very small samples.
A Field Effect Based Hydrogen Sensor for Low and High Concentrations
Authors: Moritz Werner , Fillipov Vladimir , Vasiliev Alexey , Cherkashinin Gennady , Szeponik Jan
Published: November 2006

A silicon based semiconductor sensor structure Pd/LaF3/Si3N4/SiO2/Si was prepared using thin layer technology. The sensor can be used for hydrogen detection at room temperature. Therefore, the power consumption is reduced by a factor 106 compared to the best low power consumption hydrogen sensors. In contrast to other sensors it can be used for measurements at very low and high hydrogen partial pressure. The limit of detection was determined to be 0.5 ppm. Measurements at high concentrations near to and above the Lower Explosion Level (LEL) of 4 % hydrogen in air are demonstrated. A method to achieve long lifetime of the sensor was developed.
A Proto-type Hydrogen Sensor using Palladium Nanowire Array
Authors: Cho Sung Min , Kim Moon Jung
Published: November 2006

Hydrogen gas is a non-polluting, abundant and useful fuel but highly flammable gas over 4% concentration in the air. In order to use the gas safely, the hydrogen safety sensor is required wherever using the hydrogen gas. Conventionally, Palladium (Pd) metal has long been used for the safety sensors because of its high hydrogen sensitivity1. In this study we demonstrated a hydrogen sensor using Pd nanowire array for the first time. Specially we focused on fabricating a proto-type hydrogen safety sensor and evaluating the Hydrogen sensing performance of the sensor
Use of Silica Nanowires on a Microfluidics Platform for the detection of IL-10
Authors: Bhansali S. , Sekhar Praveen Kumar , Ramgir Niranjan S. , Zhukov Tatyana , Zajac Aleksandra , Lee Latasha
Published: November 2006

This study permits label free real-time detection of the desired analyte, Interleukin-10 (IL-10), using localized silica nanowires as dendrimers, through optical recognition. QD-655 label was conjugated to antibody for IL-10 to evaluate the sensitivity of the sensor for detection of low concentrations of the target analyte. The tests show that the nanowire based sensor is capable of detecting the target analyte at a concentration under 100 μg/ml, which is better than 500 μg/ml used in protein microarrays (PMA).
Non-Volatile Solid-Electrolyte Memory Devices: Electronic versus Optical Latent Image Formation in Silver and Copper Halides
Authors: Tabib-Azar Massood , Xie Yan
Published: November 2006

We explore the possibility of using solid-electrolytes as active materials for non-volatile memory devices. We show that large ionic concentrations can be reversibly induced and then depleted using field effect in Cu2S thin films. Conditions needed to grow/etch nanowires in solid-electrolytes are also discussed. The field-induced ionic conductivities does not involve oxidation/reduction of Cu++ while nanowire growth/etch does. We discuss retention issues, write/erase speed and other related parameters in Cu2S and other SE such as Ag2S and CuI. Interestingly, it is easier to grow/etch nanowires in Ag2S than in Cu2S. Similarities and differences between electronic and optical reduction/oxidation in SE and silver halides are also discussed.
Scalable Microfabricated High Torque Mechanical Micromotors
Authors: Tabib-Azar Massood , You Liang
Published: November 2006

A new excitation technique based on the rectification of the oscillatory motion was used in surface micromachined 2-5 µm- thick LPCVD polysilicon micromotors with large torques. The 160 µm - 1600 µm diameter rotors consisted of a pivoted circular disk with perimeter cantilevers that bend and generate a twisting force upon actuation by a vibrating stator. The vibrations can be generated and harvested by and from many different sources. Here comb drives were used for feasibility studies. In comparison to electrostatic side-drive micromotors, the torques were larger and the maximum torque of up to 46 nanoN-m was observed and measured. The micromotors generated these large torques with relatively thin (<5 µm) rotors, they are fully compatible with IC processing, they can be scaled over a large range of diameters while requiring nearly constant excitation voltages, and there are no voltages applied directly to their rotors.
Complimentary Nano-Electromechanical Carbon Nanotube Switches
Authors: Tabib-Azar Massood , Bhunia Swarup , Saab Daniel
Published: November 2006

As an alternative to conventional CMOS devices, we are developing a new family of devices called Complementary Nano Electro-Mechanical Switches (CNEMS) using carbon nanotubes as active switching/latching elements. The basic structure of these devices consists of three co-planar carbon nanotubes arranged so that the central nanotube can touch the two side carbon nanotubes upon application of a voltage pulse between them. These devices have very low leakage current, low operation voltages, and they possess built-in energy storage to reduce computation power, resulting in very low overall power dissipation. Additionally, the presence of van der Waals forces endow these devices with latching mechanism for non- volatile memory-mode operation. The devices can also be readily integrated with CMOS allowing easy manufacturability and hybridization with conventional CMOS circuits. The architecture discussed here can dynamically adapt to application workload for optimized performance and reconfigure around defects / variations for reliable operation.
Design and Testing of a Wireless Portable Carbon Nanotube-Based Chemical Sensor System
Authors: Li J. , Lu Yijiang , Calusdian James , Yun Xiaoping , Meyyappan Meyya
Published: November 2006

The design and preliminary testing results of a wireless portable carbon nanotube-based chemical sensor system are presented in this paper. The overall sensor system consists of a chemical sensor module, a microcontroller-based data acquisition module, a multiplexer and constant current source module, and a wireless communication module. The chemical sensor module is based on use of an interdigited electrode (IDE) configuration. A layer of single-walled carbon nanotubes (SWNTs) is laid on the IDE electrodes. Chemical sensing is based on detection of changes in the conductivity of the SWNT network. The system has 32 channels of chemical sensing elements. It is self-contained and portable, and wirelessly transmits measurement data to a PC via an 802.11b wireless LAN. Preliminary results on chemical detection and chemical selectivity are described.
Arrayed Nanostructured Titania Functionalized For Hydrogen Detection
Authors: Monkowski Adam J. , Morrill Andrew R. , MacDonald Noel
Published: November 2006

Arrays of nanostructured titania (NST) sensing elements have been fabricated on the wafer scale using standard microfabrication techniques. Sensing elements are 20 µm on a side and formed by the oxidation of titanium thin films in aqueous hydrogen peroxide. NST elements as formed are highly sensitive to oxygen, but only slightly sensitive to hydrogen. Improved sensitivity to hydrogen is achieved by modification of the elements with platinum. A platinum salt solution is introduced to the NST sensor elements and subsequently thermally decomposed. When exposed to 10mT of hydrogen, the functionalized devices exhibit a one order of magnitude resistance decrease with a response time of approximately 4 sec; conversely as grown NST exhibit a resistance increase with a response time of 600 sec under the same conditions. Proposed sensing mechanisms of the NST elements are briefly discussed.
Formation of and Light Emission from Si Nanocrystals Embedded in Amorphous Silicon Oxides
Authors: Comedi David M. , Zalloum Othman , Blakie Darren , Wojcik Jacek , Mascher Peter
Published: November 2006

The formation of Si-nc embedded in amorphous Si oxides promoted by thermal annealing of SiyO1-y films (y=0.34-0.45) fabricated by plasma enhanced chemical vapor deposition is examined by X- ray diffraction and electron microscopy. UV and synchrotron radiation excited photoluminescence from the obtained structures is also studied and its origin elucidated
Silicon Microphotonic Waveguide Technology for Sensing, Spectroscopy and Communications
Authors: Janz Siegfried , Cheben P. , Delage A. , Densmore A. , Lamontagne B. , Post E. , Schmid J. , Waldon P. , Xu Dan-Xia , Yap K. P. , Ye W.N.
Published: November 2006

The high index contrast of the silicon-on-insulator waveguide system gives the optical device designer a new ability to manipulate light at the nanometer scale, tailor the interaction of light with the local environment, and reduce overall device size. This paper describes some of the unique features of the Si microphotonic waveguide system, and some of the resulting applications and challenges encountered in working with this platform. The work of our group in addressing some of the more promising application in sensing, spectroscopy and communications is reviewed, along with our solutions to challenges encountered in making devices on the Si waveguide platform.
Rearrangeable Nonblocking 8×8 Matrix Optical Switch based on Silica Waveguides and Extended Banyan Network
Authors: Sun De-Gui , Zha Ying , Zhang Ying , Li Xiaoqi , Deng Wenyuan , Fu Xiuhua
Published: November 2006

Based on the CROSSBAR network (CN) and the BANYAN network (BN), two new rearrangeable nonblocking constructions of extended BANYAN network (EBN) were proposed for implementing 8×8 optical matrix switch. The interconnection characteristics of these two types of rearrangeable nonblocking EBN were studied, and the driver logic program of switching units was provided. The calculated insertion loss is 3.3 dB for 8×8 optical matrix switch. Silica waveguide 8×8 matrix optical switch was designed and fabricated according to the calculated results. The silica waveguide propagation loss of 0.1dB/cm and waveguide- fiber coupling loss of 0.5dB/point were measured out. With the fabricated 8×8 matrix optical switch, optical insertion loss of 4.6 dB, cross-talk of -38 dB, polarization dependent loss of 0.4 dB, averaged switching power of 1.6 W, and switching time of 1 ms were achieved. A basic agreement between experimental results and theoretical calculated values was achieved.
Low Drive-Voltage and High-Bandwidth Electro-Optic Modulators Based on BaTiO3 Thin-Film Waveguides
Authors: Sun De-Gui , Fu Xiuhua , Liu Zhifu , Ho Seng-Tiong , Wessels Bruce
Published: November 2006

We investigated electro-optic modulator structures to target low drive voltage, high-speed modulation, and small device size with c-axis grown BaTiO3/MgO ferro-electric thin films. In this study, the calculations are focused on the ideal thin film with a quadratic relation between the half-wave drive voltage and the interaction length in the electro-optic modulation case we obtained in previous work. With the quadratic electro-optic modulating relation and the optimal rib waveguide structure of BaTiO3/MgO thin films, the frequency-voltage-size performances for 2.5GHz, 10GHz, 40GHz, and 100GHz modulation bandwidths have been obtained under half- wave drive voltages of 0.8V, 1.6V, 3.0V and 4.8V, respectively, for the ideal film with r51=730 pm/V at 1550nm wavelength, where both the phase velocity matching condition and the conductor induced microwave attenuation are considered. The required device lengths to achieve these four typical values of modulation bandwidth are 3.3 mm, 0.8 mm, 0.4 mm and 0.2 mm, respectively. With the c-axis grown BaTiO3/MgO crystal thin films and the quadratic electro-optic modulating relation, an electro-optic coefficient of reff=180 pm/V for the c-axis grown BaTiO3/MgO ferro-electric thin films was measured, which is relatively far from the ideal value of r51=560 pm/V.
Preparation of Carbon-Fiber Electrodes Modified with Platinum Nanoparticles Encapsulated in PAMAM Dendrimers
Authors: Ledesma Janet G. , Escalante Garcia Ismailia L. , Chapman Thomas W. , Rodríguez Francisco J. , Godínez Luis A.
Published: November 2006

This work examines the effect of the degree of surface oxidation of carbon fibers on the anchoring of hydroxyl- terminated dendrimers that encapsulate platinum nanoparticles. Several methods of electrochemical pretreatment were investigated for the preparation of the carbon-fiber surfaces to obtain electrodes with functional groups of varying characteristics. The resulting carbon-fiber surfaces were modified with platinum-encapsulating dendrimers by means of ether linkages. The coverage of active groups on the oxidized carbon surfaces as well as the active area of the dendrimer-encapsulated platinum (G4OHPt) were evaluated with respect to the pretreatment method. The results showed that cyclic voltammetry as the pretreatment method immobilizes a significant amount of dendrimer- encapsulated platinum on the carbon-fiber surface. Accordingly, kinetic parameters obtained for the oxygen-reduction reaction on this surface indicate acceptable catalytic activity.
PtCl62- and PtCl42- Reduction in Polyaniline: Methanol Oxidation at Morphologically Different Composites.
Authors: Hatchett David W. , Kinyanjui John
Published: November 2006

The electrochemical reduction of PtCl62- and PtCl42- in polyaniline (PANI) membranes is examined. The reduction of these species is energetically similar in the polymer membrane. The process results in morphologically distinct PANI/Pt composite materials with very different catalytic activities. The highest rate of methanol oxidation is observed for PANI/Pt composite produced from PtCl42-.
Monoclonal antibody antagonists of hypothalamic FGFR1 cause potent but reversible hypophagia and weight loss in rodents and monkeys
Authors: Sun Haijun D. , Malabunga Maria , Tonra James R. , DiRenzo Roberto , Carrick Francine E. , Zheng Huiyuan , Berthoud Hans-Rudolf , McGuinness Owen P. , Shen Juqun , Bohlen Peter , Leibel Rudolph L. , Kussie Paul
Published: November 2006

We generated three fully human monoclonal antibody antagonists against fibroblast growth factor receptor-1 (FGFR1) that potently block FGF signaling. We found that antibodies targeting the c-splice form of the receptor (FGFR1c) were anorexigenic when administered intraperitoneally three times weekly to mice, resulting in rapid, dose-dependent weight loss that plateaued (for doses >4 mg/kg) at 35–40% in 2 wk. Animals appeared healthy during treatment and regained their normal body weights and growth trajectories upon clearance of the antibodies from the bloodstream. Measurements of food consumption and energy expenditure indicated that the rapid weight loss was induced primarily by decreased energy intake and not by increased energy expenditure or cachexia and was accompanied by a greater reduction in fat than lean body mass. Hypophagia was not caused through malaise or illness, as indicated by absence of conditioned taste aversion, pica behavior, and decreased need-induced salt intake in rats. In support of a hypothalamic site of action, we found that, after intraperitoneal injections, anti-FGFR1c (IMC-A1), but not a control antibody, accumulated in the median eminence and adjacent mediobasal hypothalamus and that FGFR1c is enriched in the hypothalamus of mice. Furthermore, a single intracerebroventricular administration of 3 μg of IMC-A1 via the 3rd ventricle to mice caused an ∼36% reduction in food intake and an ∼6% weight loss within the ensuing 24 h. Our data suggest that FGF signaling through FGFR1c may play a physiological role in hypothalamic feeding circuit and that blocking it leads to hypophagia and weight loss.
Hypothalamic mapping of orexigenic action and Fos-like immunoreactivity following relaxin-3 administration in male Wistar rats
Authors: McGowan B. M. , Stanley S. A. , White N. E. , Spangeus A. , Patterson M. , Thompson E. L. , Smith K. L. , Donovan J. , Gardiner J. V. , Ghatei M. A. , Bloom S. R.
Published: November 2006

The insulin superfamily, characterized by common disulphide bonds, includes not only insulin but also insulin-like peptides such as relaxin-1 and relaxin-3. The actions of relaxin-3 are largely unknown, but recent work suggests a role in regulation of food intake. Relaxin-3 mRNA is highly expressed in the nucleus incertus, which has extensive projections to the hypothalamus, and relaxin immunoreactivity is present in several hypothalamic nuclei. In the rat, relaxin-3 binds and activates both relaxin family peptide receptor 1, which also binds relaxin-1, and a previously orphaned G protein-coupled receptor, RXFP3. These receptors are extensively expressed in the hypothalamus. The aims of these studies were twofold: 1) map the hypothalamic site(s) of the orexigenic action of relaxin-3 and 2) examine the site(s) of neuronal activation following central relaxin-3 administration. After microinjection into hypothalamic sites, human relaxin-3 (H3; 180 pmol) significantly stimulated 0- to 1-h food intake in the supraoptic nucleus (SON), arcuate nucleus (ARC), and the anterior preoptic area (APOA) [SON 0.4 ± 0.2 (vehicle) vs. 2.9 ± 0.5 g (H3), P < 0.001; ARC 0.7 ± 0.3 (vehicle) vs. 2.7 ± 0.2 g (H3), P < 0.05; and APOA 0.8 ± 0.1 (vehicle) vs. 2.2 ± 0.2 g (H3), P < 0.05]. Cumulative food intake was significantly increased ≤8 h following administration into the SON and 4 h into the APOA. A significant increase in Fos-like immunoreactivity was seen in the SON following central relaxin-3 administration. Relaxin-3 stimulates feeding in several hypothalamic nuclei, and these studies provide additional support for relaxin-3 as an important peptide in appetite regulation.
Growth hormone-induced insulin resistance is associated with increased intramyocellular triglyceride content but unaltered VLDL-triglyceride kinetics
Authors: Krag Morten B. , Gormsen Lars C. , Guo ZengKui , Christiansen Jens S. , Jensen Michael D. , Nielsen Søren , Jørgensen Jens O. L.
Published: November 2006

The ability of growth hormone (GH) to stimulate lipolysis and cause insulin resistance in skeletal muscle may be causally linked, but the mechanisms remain obscure. We investigated the impact of GH on the turnover of FFA and VLDL-TG, intramuscular triglyceride content (IMTG), and insulin sensitivity (euglycemic clamp) in nine healthy men in a randomized double-blind placebo-controlled crossover study after 8 days treatment with (A) Placebo + Placebo, (B) GH (2 mg daily) + Placebo, and (C) GH (2 mg daily) + Acipimox (250 mg × 3 daily). In the basal state, GH (B) increased FFA levels ( P < 0.05), palmitate turnover ( P < 0.05), and lipid oxidation ( P = 0.05), but VLDL-TG kinetics were unaffected. Administration of acipimox (C) suppressed basal lipolysis but did not influence VLDL-TG kinetics. In the basal state, IMTG content increased after GH (B; P = 0.03). Insulin resistance was induced by GH irrespective of concomitant acipimox ( P < 0.001). The turnover of FFA and VLDL-TG was suppressed by hyperinsulinemia during placebo and GH, whereas coadministration of acipimox induced a rebound increase FFA turnover and VLDL-TG clearance. We conclude that these results show that GH-induced insulin resistance is associated with increased IMTG and unaltered VLDL-TG kinetics; we hypothesize that fat oxidation in muscle tissue is an important primary effect of GH and that circulating FFA rather than VLDL-TG constitute the major source for this process; and the role of IMTG in the development of GH-induced insulin resistance merits future research.
Human brain glycogen content and metabolism: implications on its role in brain energy metabolism
Authors: Öz Gülin , Seaquist Elizabeth R. , Kumar Anjali , Criego Amy B. , Benedict Luke E. , Rao Jyothi P. , Henry Pierre-Gilles , Van De Moortele Pierre-Francois , Gruetter Rolf
Published: November 2006

The adult brain relies on glucose for its energy needs and stores it in the form of glycogen, primarily in astrocytes. Animal and culture studies indicate that brain glycogen may support neuronal function when the glucose supply from the blood is inadequate and/or during neuronal activation. However, the concentration of glycogen and rates of its metabolism in the human brain are unknown. We used in vivo localized 13C-NMR spectroscopy to measure glycogen content and turnover in the human brain. Nine healthy volunteers received intravenous infusions of [1-13C]glucose for durations ranging from 6 to 50 h, and brain glycogen labeling and washout were measured in the occipital lobe for up to 84 h. The labeling kinetics suggest that turnover is the main mechanism of label incorporation into brain glycogen. Upon fitting a model of glycogen metabolism to the time courses of newly synthesized glycogen, human brain glycogen content was estimated at ∼3.5 μmol/g, i.e., three- to fourfold higher than free glucose at euglycemia. Turnover of bulk brain glycogen occurred at a rate of 0.16 μmol·g−1·h−1, implying that complete turnover requires 3–5 days. Twenty minutes of visual stimulation ( n = 5) did not result in detectable glycogen utilization in the visual cortex, as judged from similar [13C]glycogen levels before and after stimulation. We conclude that the brain stores a substantial amount of glycogen relative to free glucose and metabolizes this store very slowly under normal physiology.
Transgenic overexpression of protein targeting to glycogen markedly increases adipocytic glycogen storage in mice
Authors: Jurczak Michael J. , Danos Arpad M. , Rehrmann Victoria R. , Allison Margaret B. , Greenberg Cynthia C. , Brady Matthew J.
Published: November 2006

Adipocytes express the rate-limiting enzymes required for glycogen metabolism and increase glycogen synthesis in response to insulin. However, the physiological function of adipocytic glycogen in vivo is unclear, due in part to the low absolute levels and the apparent biophysical constraints of adipocyte morphology on glycogen accumulation. To further study the regulation of glycogen metabolism in adipose tissue, transgenic mice were generated that overexpressed the protein phosphatase-1 (PP1) glycogen-targeting subunit (PTG) driven by the adipocyte fatty acid binding protein (aP2) promoter. Exogenous PTG was detected in gonadal, perirenal, and brown fat depots, but it was not detected in any other tissue examined. PTG overexpression resulted in a modest redistribution of PP1 to glycogen particles, corresponding to a threefold increase in the glycogen synthase activity ratio. Glycogen synthase protein levels were also increased twofold, resulting in a combined greater than sixfold enhancement of basal glycogen synthase specific activity. Adipocytic glycogen levels were increased 200- to 400-fold in transgenic animals, and this increase was maintained to 1 yr of age. In contrast, lipid metabolism in transgenic adipose tissue was not significantly altered, as assessed by lipogenic rates, weight gain on normal or high-fat diets, or circulating free fatty acid levels after a fast. However, circulating and adipocytic leptin levels were doubled in transgenic animals, whereas adiponectin expression was unchanged. Cumulatively, these data indicate that murine adipocytes are capable of storing far higher levels of glycogen than previously reported. Furthermore, these results were obtained by overexpression of an endogenous adipocytic protein, suggesting that mechanisms may exist in vivo to maintain adipocytic glycogen storage at a physiological set point.
Glomerular and tubular function during AT1 receptor blockade in pigs with neonatal induced partial ureteropelvic obstruction
Authors: Eskild-Jensen Anni , Thomsen Klaus , Rungø Christine , Ferreira Luis S. , Paulsen Lene Fogt , Rawashdeh Yazan F. , Nyengaard Jens Randel , Nielsen Søren , Djurhuus Jens Christian , Frøkiær Jørgen
Published: November 2006

Previously, we showed that neonatal induced chronic partial unilateral ureteral obstruction (PUUO) of the multipapillary pig kidney decreased glomerular filtration rate (GFR) of the obstructed kidney. We hypothesized that ANG II and nitric oxide (NO) are important for the changes in renal function and in the present study we examined the effects of chronic AT1 receptor blockade using CV-11974 (0.12 mg/h candesartan from age 23 to 30 days) on kidney function development after PUUO was induced in 2-day-old piglets. Moreover, the effect of superimposed acute NO inhibition using NG-nitro-l-arginine methyl ester (l-NAME; 15 mg/kg) was examined to identify if this has diagnostic potential. PUUO significantly increased GFR in the nonobstructed contralateral kidney independent of candesartan. In candesartan-treated piglets, the l-NAME-induced GFR reduction seen in normal and nonobstructed kidneys was absent in the partial obstructed kidneys. Urine output and fractional excretion of water were increased from the partial obstructed kidneys. Consistent with this immunohistochemical analyses showed a reduced aquaporin-2 labeling in the collecting duct principal cells. Moreover, renal sodium handling was compromised by PUUO evidenced by an increased fractional excretion of sodium which was enhanced by candesartan treatment. In conclusion, our findings suggest that the counterbalance between AT1 receptor-mediated vasoconstriction and NO-mediated vasodilatation which maintain GFR in normal young porcine kidneys is changed by neonatal induced chronic PUUO. This may have diagnostic potential in children with suspected congenital obstruction. Our results also demonstrate compromised tubular functions in response to chronic PUUO despite preservation of glomerular function.
Intrinsically Bursting Olfactory Receptor Neurons
Authors: Bobkov Y. V. , Ache B. W.
Published: November 2006

Rhythmically bursting neurons are fundamental to neuronal network function but typically are not considered in the context of primary sensory signaling. We now report intrinsically bursting lobster primary olfactory receptor neurons that respond to odors with a phase-dependent burst of action potentials. Rhythmic odor input as might be generated by sniffing entrains the intrinsic bursting rhythm in a concentration-dependent manner and presumably synchronizes the ensemble of bursting cells. We suggest such intrinsically bursting olfactory receptor cells provide a novel way for encoding odor information.
Copy number variation in the genome; the human DMD gene as an example
Authors: White S.J. , den Dunnen J.T.
Published: November 2006

Recent developments have yielded new technologies that have greatly simplified the detection of deletions and duplications, i.e., copy number variants (CNVs). These technologies can be used to screen for CNVs in and around specific genomic regions, as well as genome-wide. Several genome-wide studies have demonstrated that CNV in the human genome is widespread and may include millions of nucleotides. One of the questions that emerge is which sequences, structures and/or processes are involved in their generation. Using as an example the human DMD gene, mutations in which cause Duchenne and Becker muscular dystrophy, we review the current data, determine the deletion and duplication profile across the gene and summarize the information that has been collected regarding their origin. In addition we discuss the methods most frequently used for their detection, in particular MAPH and MLPA.
Genome wide measurement of DNA copy number changes in neuroblastoma: dissecting amplicons and mapping losses, gains and breakpoints
Authors: Michels E. , Vandesompele J. , Hoebeeck J. , Menten B. , De Preter K. , Laureys G. , Van Roy N. , Speleman F.
Published: November 2006

In the past few years high throughput methods for assessment of DNA copy number alterations have witnessed rapid progress. Both ‘in house’ developed BAC, cDNA, oligonucleotide and commercial arrays are now available and widely applied in the study of the human genome, particularly in the context of disease. Cancer cells are known to exhibit DNA losses, gains and amplifications affecting tumor suppressor genes and proto-oncogenes. Moreover, these patterns of genomic imbalances may be associated with particular tumor types or subtypes and may have prognostic value. Here we summarize recent array CGH findings in neuroblastoma, a pediatric tumor of the sympathetic nervous system. A total of 176 primary tumors and 53 cell lines have been analyzed on different platforms. Through these studies the genomic content and boundaries of deletions, gains and amplifications were characterized with unprecedented accuracy. Furthermore, in conjunction with cytogenetic findings, array CGH allows the mapping of breakpoints of unbalanced translocations at a very high resolution.
Efficacy Results of a 52-Week, Randomised, Double-Blind, Safety Study of a Calcipotriol/Betamethasone Dipropionate Two-Compound Product (Daivobet®/Dovobet®/Taclonex®) in the Treatment of Psoriasis Vulgaris
Authors: Kragballe K. , Austad J. , Barnes L. , Bibby A. , de la Brassinne M. , Cambazard F. , Fleming C. , Heikkilä H. , Williams Z. , Peyri Rey J. , Svensson Å. , Toole J. , Wozel G.
Published: November 2006

Background: The calcipotriol/betamethasone dipropionate two-compound product is safe and effective in the short-term treatment of psoriasis. Objective: The primary objective was to investigate the safety of two treatment regimens involving use of the two-compound product over 52 weeks. The efficacy results are presented here. Methods: Six hundred and thirty-four patients were randomised double-blind to treatment (once daily, when required) with either: 52 weeks of two-compound product (two-compound group), 52 weeks of alternating 4-week periods of two-compound product and calcipotriol (alternating group), or 4 weeks of two-compound product followed by 48 weeks of calcipotriol (calcipotriol group). Results: There was a trend towards a difference between treatments from the overall treatment effect for the percentage of satisfactory responses for each patient during the study (p = 0.071). This appeared to be due to the comparison of the two-compound and calcipotriol groups (p = 0.025). Conclusion: There was a trend towards the efficacy of the two-compound product used for up to 52 weeks being better than that of 4 weeks of the two-compound product followed by 48 weeks of calcipotriol.
Psoriasis Therapy in Real Life: The Need for Registries
Authors: Schmitt-Egenolf Marcus
Published: November 2006

The introduction of new therapeutic options for the management of psoriasis is a challenge for the dermatology community, and new tools are needed to face this challenge. This article argues for the establishment of profession-based registries to collect solid, long-term data on the safety and effectiveness of different psoriasis treatment regimens. Managed by health care professionals, registries will be most successful if they enroll patients based on indications for treatment rather than on drugs given. This protects the evaluation process from commercial influences and allows a fair comparison of old- versus new-generation psoriasis treatments. In contrast to the patients in a registry who receive care in the natural clinical setting, subjects in randomized clinical trials (RCTs) are selected according to study criteria and may therefore not reflect the experience of patients in clinical practice. It is possible that particular risks and opportunities in the real patient population may therefore go undetected in RCTs.
A Case of Primary Cutaneous Nasal Type NK/T-Cell Lymphoma and Review of the Literature
Authors: Stokkermans-Dubois J. , Jouary T. , Vergier B. , Delaunay M.M. , Taieb A.
Published: November 2006

Introduction: Cutaneous T-cell lymphoma subtypes are now better identified thanks to progress in immunohistochemistry. This article describes a new case of primary cutaneous natural killer/T-cell lymphoma of nasal type (NKTL-NT) and reviews 18 other cases of this rare neoplasm. Case Report: A 79-year-old man presented with a 3-cm nodular tumor of the left leg occurring on a primary chronic lymphedema of the legs. The lesion was CD56+, CD3 intracytoplasmic+, CD45+ and Epstein-Barr virus+. A comprehensive workup including CT scan and bone marrow biopsy was negative and a diagnosis of NKTL-NT with a primary cutaneous involvement was made. The patient was free of disease under multi-agent chemotherapy after 24 months of follow-up. Discussion: After reviewing 18 other cases of primary cutaneous NKTL-NT, we conclude that the prognosis of these lymphomas is usually poor. However, limited cutaneous forms have a longer median survival than extracutaneous variants.
Gonadotropins and Prostate Cancer – Revisited
Authors: Thwaini Ali , Naase Mahmoud , Chinegwundoh Frank , Baithun Suhail , Ghali Lucy , Shergill Iqbal , Iles Ray
Published: November 2006

Luteinizing hormone and follicle-stimulating hormone are called gonadotropins, because they stimulate the gonads – in males the testes and in females the ovaries. They are not necessary for life, but are essential for reproduction. In addition, the association of these hormones with prostate cancer has been the interest of many researchers. Their detection in the human prostate has been investigated using different methods, including immunologic and RT-PCR techniques. In addition, the increasing evidence of paracrine/autocrine functions of the gonadotropic glycoprotein hormones, their allocation to the superfamily of cystine knot growth factors, and luteinizing hormone/chorionic gonadotropin receptor gene expression in non-gonadal tissues led many researchers to investigate intraprostatic glycoprotein hormones and their receptor gene expression. We aim in this review to shed light on the physiology of the gonadotropins and their association with prostate cancer and highlight the future possibilities of their use as targets in treating this disease.
Repositioning and Removal of an Intra-Renal Migrated Ureteric Memokath® Stent
Authors: Siddique K.A. , Zammit P. , Bafaloukas N. , Albanis S. , Buchholz N.P.N.
Published: November 2006

The increasing use of ureteric stents including permanent ones is not without their own set of problems[.] The authors describe the difficulties encountered and a novel technique to reposition a permanent ureteric stent migrated into the kidney with an illustrated case. The same technique can also be applied to a-traumatically remove the stent if required.
Should Prostate Cancer Status Be Determined in Patients Undergoing Radical Cystoprostatectomy?
Authors: Sanli Oner , Acar Omer , Celtik Murad , Oktar Tayfun , Kılıcaraslan Isın , Ozcan Faruk , Tunc Murat , Esen Tarik
Published: November 2006

Introduction: We estimate the frequency of prostate cancers detected incidentally in radical cystoprostatectomy specimens and discuss whether the prostate cancer status should be determined in patients undergoing radical cystoprostatectomy. Materials and Methods: A total of 97 radical cystoprostatectomies without evidence of prostate cancer on digital rectal examination were performed for transitional cell carcinomas of the bladder between January 2001 and May 2004. The mean patient age at the time of surgery was 66.9 ± 9.52 (range 49–75) years. Results: The overall incidence of prostate cancer detected in radical cystoprostatectomy specimens was 21.6% (21/97 specimens). The mean tumor volume was found to be 0.93 ± 0.81 ml. The tumor volume was >0.5 ml in 12 cases (57.1%). The surgical margin was negative in all cases, and the disease was organ confined in 20 patients (95.2%). Capsular invasion was evident in 2 patients (9.5%), 1 of whom had lymph-node-positive disease. Conclusions: Despite the high prevalence of incidental prostate carcinomas among patients with bladder cancer undergoing cystoprostatectomy, the vast majority of the cancers are organ confined. However, the prostate cancer status should be determined on the basis of digital rectal examination and prostate-specific antigen in patients undergoing radical cystoprostatectomy – especially if prostate-sparing cystectomy is planned.