bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Multiplication Factor of Avalanche Photodiode
Authors: Nishida Katsuhiko
Published: November 2005

General formulas for the photomultiplication factor M

p
are derived by considering the dark current injected into the avalanche region and the space charge effect due to the avalanche current. The numerical calculations were carried out in case of the silicon PN junction.
The optimum impurity concentration to maximize M

p
in the avalanche region is derived for a given junction area and a given load resistance. The analyses also indicate M

p
is much improved with decreasing the dark current.
The analytical results are well confirmed in the silicon P+ PNN+ diode with an engraved guard ring. The junction uniformity was improved by gallium diffusion ( P) preceding boron diffusion ( P+). Both the spatial variation of M

p
in the junction plane and the avalanche noise were reduced to one tenth of those of the conventional P+ N junction diodes.
Nonlinear Effects of Surface Charge Waves in a n-InSb MOS Structure in a Transverse Magnetic Field
Authors: Toda Minoru
Published: November 2005

Nonlinear effects resulting from a modulation of the propagation velocity of the surface charge wave in a n-InSb MOS structure in a transverse magnetic field have been investigated. It is found that the propagation velocity is a function of the MOS capacitance which can be modulated by a voltage across the structure. When the peak value of an input signal level exceeds several tenths of a millivolt, a distortion of the output waveform is observed. In order to observe parametric amplification, both the input signal and the pumping signal, with twice the frequency of the input signal, are applied, and a decrease in the propagation loss was observed. A theory has been developed to explain the above nonlinear phenomena. The theoretical curve agrees fairly well with experimental plots. It is concluded that if a larger modulation of the capacitance could be obtained, the device quality would be greatly improved.
Effect of Average Stress in Films on Uniaxial Magnetic Anisotropy in Electrodeposited Nickel-Iron Thin Films
Authors: Satō Masayoshi , Tokuda Masamitsu , Maeda Masao
Published: November 2005

To study the effect of average stress in films on uniaxial magnetic anisotropy in nickel-iron thin films electrodeposited on a surface scratched in one direction, measurements of average stress σ, uniaxial magnetic anisotropy constant K

u
, magnetization I

s
, film thickness and weight of films were carried out on films of various composition covering a range from 50% nickel to 100% nickel. These measurements were also carried out on films prepared from a plating bath containing 0.8 g/liter of saccharin.
The measured values of σ were found to depend on the composition of films and on saccharin in the plating bath, and the effect of σ on K

u
is found to be well explained by the expression K

u
=1/2(N

t
-N

p
)I

s

2+3/2λσsin
2θ.
Ensemble-Averaged Coherence Function of Light Reflected from Rough Surface: Determination of Its Correlation Length
Authors: Nagata Ken-ichi , Yoshida Nobuaki , Nishiwaki Jien
Published: November 2005

The ensemble-averaged coherence function of light reflected from the Gaussian rough surface having irregularities of gentle slope is derived on the basis of Kirchhoff's diffraction integral and with quasi-monochromatic approximation. The ensemble-averaged coherence function of light reflected at the rough surface depends on the roughness constants, σ andΔ, through the factorD(σ,Δ)=exp [-g2{1-ρ02(τ0)}], and the factor possesses spatial dependence through the Gaussian correlation function ρ0(τ0) of surface heights at two singular points of interval τ0. The ensemble-averaged coherence function takes the similar form to the averaged correlation between two geometrical beams reflected at the two points in specular direction referred to the mean surface of rough surface. The degree of coherence degradates on ensemble-averaging by the factorD(σ,Δ). This degradation factor is measured with the interferometer consisting of two diffracting apertures. The correlation lengthΔof the rough surface is estimated from measured values ofD(σ,Δ) by using rms roughness values σ obtained from reflectance for infrared light.
Improved Ta Level Indicator for Liquid He
Authors: Takiguchi Katsumi , Kawate Yoshio , Shigi Toyoichiro
Published: November 2005

In this paper are described improvements of the level indicator fixed in a cryostat by using combination of Ta short coils and a Ta long solenoid wound together with insulated heater wire. The short coil indicates accurately whether liquid surface is above or below it even when liquid He is being transferred. Its response time is a few tenths of a second. The long solenoid indicates liquid level continuously and with much less response time, but its indication is always about 5 mm more than actual depth in static condition and 10∼20 mm more during liquid transfer. Total power consumption in the probe is less than 20 milliwatts.
Dielectric Properties of SbSI at Microwave Frequencies
Authors: Hosoya Masahiko , Nakamura Eiji
Published: November 2005

The complex dielectric constants κ=κ'-iκ'' along the c axis of SbSI at 3.3 and 9.8 GHz have been measured between 0°C and 50°C. The value of κ' in paraelectric phase is found to show as high value as 3×104 even in this frequency range. No remarkable dielectric dispersion was observed below 9.8 GHz. No essential difference was found between 3.3 and 9.8 GHz. The values of tan
δ at 3.3 and 9.8 GHz are about 0.1 and 0.3, respectively, near the Curie temperature. To ascertain the accuracy of the cavity perturbation method, a new expression is proposed.
The Effects of Lubricant Inertia on Soueeze Films in Journal Bearings
Authors: Agrawal V. K.
Published: November 2005

A theoretical investigation of inertia effects on squeeze films in full and half journal bearings of infinite length are presented. It is found that the time of approach is increased due to inertia forces. Further it is seen that inertia forces make a significant contribution to the time of approach at large value of ⊼.
Unit for the Precise Measurement of Electron Diffraction Intensities by Gas Molecules
Authors: Murata Yoshitada , Kuchitsu Kozo , Kimura Masao
Published: November 2005

An apparatus for the precise measurement of electron intensity diffracted from gas molecules has been constructed. Care has been taken to define camera distances precisely by installing a table, to which the nozzle and the photographic plate can be fixed firmly, and to eliminate extraneous scattering by designing a suitable electron-optical system and by inserting a brass ring with a folded wall covered with soot into the sector race. A critical examination by the use of carbon dioxide has shown that the structure can be determined with the accuracy of one thousandth of an angstrom with the present apparatus.
Magnetic Properties of (Cr1-xFex)O2
Authors: Hirota Eiichi , Mihara Toshihiro , Kawamata Tadashi , Asanuma Mitsuru
Published: November 2005

The solubility limit of Fe-ion in CrO2 and the properties of (Cr1-x
Fe
x
)O2 were examined. Added Fe-ions dissolve into CrO2 and form an oxide of (Cr1-2x

4+Cr
x

5+Fe
x

3+)O2, up to the x-value of about 0.06. The T
c
increases from 116°C for the pure CrO2 to about 155°C with an Fe-addition of x=0.06. The magnetic moments of Fe3+ and Cr5+ couple in anti-parallel way to that of Cr4+.
Far-Field Diffraction by Various Sector Apertures
Authors: Asakura Toshimitsu
Published: November 2005

Equations are derived for computing the form of the aberration-free far-field diffraction patterns by various sector apertures. These equations have been used to compute the log-irradiance distribution in the focal plane and the three-dimensional irradiance distribution in meridional planes of a far-field diffraction pattern. The results are discussed and shown graphically. Some experiments were conducted to verify the results of irradiance distribution in the focal plane.
The Response of the Gamma-Ray Density Gauge to the Boundary between Two Materials
Authors: Uemura Teiji
Published: November 2005

The calculations for the single scattering of gamma-rays were made on the case where the surface density gauge was placed on the boundary between two materials of different densities. The calculations and experiments were performed for the boundary perpendicular to the gauge axis and for that perallel to the gauge axis under various gauge configurations.
The manner of response to the boundary varied with the source-detector separations µ0ρD which is expressed in mean free path of incident rays and with the solid angle of incidence of the gamma-rays. When the value of µ0ρD and the difference between the densities of two materials were small, the response to the boundary nearly took the shape of a took step function.
Electron Acceleration by an Alternating Periodic Structure
Authors: Kikuchi Takuo , Takata Koji
Published: November 2005

The design and some experimental results of a 30 cm long standing wave electron linac are described. The accelerating tube is an alternating periodic structure (APS) and fed with 2856 MHz rf power in 2 µsec pulses by a tunable magnetron (Toshiba M4543). With a peak power of 3 MW, 4 MeV 100 mA beam pulses are produced. Peak accelerated currents of 400 mA with 1 µsec duration are obtained for 50 KeV 1A injection currents. This linac will be used for radiation therapy.
Low Frequency Dielectric Dispersion of Sodium Thiosulfate Pentahydrate
Authors: Tsunekawa Shin , Takagi Yutaka , Ishibashi Yoshihiro
Published: November 2005

The low frequency dielectric dispersions of sodium thiosulfate pentahydrates were measured. Data obtained support the hypothesis that there are continuous chains of hydrogen bonds along the b axis as well as along both the a and c axes in this material.
Double Injection in GaP Electroluminescent Diodes
Authors: Maeda Keiji
Published: November 2005

Electrical and optical properties accompanied with double injection and negative resistance in GaP electroluminescent diodes were investigated at 77°K. A region, where current is proportional to the square of the applied voltage and marked changes occurs in luminescence spectra, was observed. By pulse measurements, switching time to the negative resistance was found to be an order of msec. The double injection is caused by hole injection into the high resistivity n-region. A new theory of double injection is formulated, taking into account charge neutrality and boundary condition of carrier injection. The square-law is associated with densities of recombination centers larger than the injected carrier density. This theory explains the experimental results satisfactorily. Immediate cause of the negative resistance is considered to be a rise of sample temperature.
Temperature Dependence of Hyperfine Spectrum of Rb D1Line
Authors: Fukuyo Hitohiro , Iga Ken-ichi , Kuramochi Naimu , Tanigawa Hiroshi
Published: November 2005

This paper deals with the experimental studies of the rubidium (Rb) spectral lamp for the purpose of getting an excellent pumping light source for a Rb gas cell type frequency standard, or for a Rb microwave maser. Some of Rb lamps containing Ne, Ar, Kr, and Ne-Ar as a carrier gas were made by way of experiment. In order to observe the hyperfine spectrum of D1line, the Fabry-Perot type scanning interferometer was made, which is driven electrostrictively. The hyperfine components of D1line were resolved successfully. It was observed that the line which is used as a pumping source became intense as the lamp temperature was raised, and it began to be dipped and decrease, however, over the definite temperature. Also observed was that this optimum temperature differs from the temperature at which the integrated intensity of D1line shows a maximum.
Frequency and Temperature Dependence of C-V Characteristics at Ge-SiO2 Interface and BT Treatments
Authors: Yashiro Takehisa
Published: November 2005

The silicon dioxide films were formed on germanium surfaces by the SiBr4–H2O reaction. SiO2 passivated Ge surfaces showed a definite “step” or “plateau” in the C-V curves at 1MHz and room temperature. The plateau disappeared with the increase of measuring frequency or the decrease of temperature. The plateau is supposed to be due to interface states of a single level, lying 0.12 or 0.09eV above the valence band, depending on a specimen used. Using these MOS diodes, the effect of the BT treatment was investigated. The C-V curves after the BT treatment measured at -70°C to eliminate the effect of interface states showed that N

F
B
pg would saturate after positive bias treatments and that it wouldn't after negative bias treatments. These results can be explained by the electrochemical reaction at the Ge-SiO2 interface. By the heat-treatment for the various lengths of time after the negative BT treatment, another new “step” in C-V curves was ovserved at -70°C.
The Nernst Effect of Bi-Sb Alloys
Authors: Aono Tomoyoshi
Published: November 2005

Temperature dependence of the transverse and longitudinal Nernst effect has been measured on Bi-Sb alloys containing 3-12 at% Sb in weak magnetic field. Nernst coefficient was found to differ for the heat flow along the binary and bisectrix axis. The influence of Sb admixture on the transverse coefficient appears for the binary axis at first and then for the bisectrix axis. When the temperature is made lower the transverse Nernst coefficient increases its magnitude monotonically without changing its sign. The longitudinal coefficient was found to have a sign opposite to the longitudinal coefficient. The results of these observations are shown to be explained by taking into account the fact that these alloys are intrinsic but the mobility ratio changes with Sb concentration.
Self-Isolated Transistor Structures of Bipolar Integrated Circuits
Authors: Makimoto Tsugio , Sugawara Katsuro , Maki Michiyoshi
Published: November 2005

Self-isolated transistor structures for bipolar integrated circuits are proposed. Some of the advantageous features of the proposed structures are; negligible minority carrier storage in collector region, low collector series resistance and large current handling capability, high packing density, and ease of processing.
Cutoff frequency of about 600 MHz was observed for the graded base structure, and about 400 MHz for the uniform base structure. It is also shown that the current handling capability is improved.
Epitaxial growth is one of the critical steps in producing self-isolated bipolar integrated circuits. A discussion is given for the specification of the epitaxial layer. In order to minimize the back diffusion from the buried layer to the base, a new possible way of processing is proposed which makes use of the simultaneous diffusion of Ga, As, and P.
Pattern Classification with an Optical PAPA Device
Authors: Kato Hisatoyo , Tanaka Shun-ichi
Published: November 2005

An optical PAPA (Automatic Programmer and Analyzer of Probabilities) device using a coherent optical system was made. Each random mask used for the classification of the input patterns consists of the several elements of the matrix pattern of diffraction gratings with particular azimuthal orientation theta of grating lines. Therefore, the transmitted light through the input pattern and random masks is theta modulated and is used to make the filter for classification. Horizontal and vertical line patterns and Japanese characters were classified with proper accuracy. Problems of the selection of random masks, characteristics of a photographic emulsion and errors of classification are also discussed.
Tunable Parametric Oscillator Using a Guided Wave Structure
Authors: Suematsu Yasuharu
Published: November 2005

A proposed tunable optical parametric oscillator in a guided wave structure consisting of a thin nonlinear slab asymmetrically sandwiched by two linear dielectrics is treated theoretically. The two linear dielectrics have smaller indices of refraction than the nonlinear dielectric, and the oscillator frequency is tunable by changing the refractive index of one of the linear dielectrics. For a GaAs nonlinear film sandwiched by Irtran 3 or Sapphire and liquid, calculations show that the oscillation frequency can be tuned over ±35% of the subharmonic frequency of a 1.06µ pump as the refractive index of the liquid is varied from 1.25 to 1.6. For reasonable parameters, the threshold power is estimated to be 7 milliwatts.
The phase matching conditions and oscillation characteristics for parametric interaction in a guided wave structure are derived and discussed.
On Determination of Gold Trap Concentration in Diffused Silicon pn Junctions
Authors: Ogawa Takuzō , Yatsuo Tsutomu , Kamei Tatsuya , Morita Keiichi
Published: November 2005

On diffused silicon p
n junctions doped with gold, junction capacitance for very low and high frequencies was analyzed and gold trap concentration was determined by measurement of junction capacitance on the basis of the analysis. It is concluded that the gold trap concentration gives reasonable value, because the gold trap concentration in the diffused diodes quenched after gold diffusion agrees with the gold concentration determined by the tracer analysis with Au198. The values of the gold trap concentration in the diffused diodes quenched after gold diffusion are almost equal to the solubility of the interstitial gold, but they are less for more slowly cooled diodes and the diodes alloyed after gold diffusion.
Direct Measurement of RF Field Using Diode
Authors: Hirakawa Hiromasa , Okumura Shoji
Published: November 2005

A direct measurement method of RF field using diode is described. The measurement consists in inserting a diode into RF field with the aid of two resistive strings, and reading the detected DC voltage by an electrometer outside the field. Analysis of operation principle and results of experiment at 400 MHz are presented.
The Resolution Function of a Twin-Rotor Neutron Time-of-Flight Spectrometer
Authors: Komura S. , Cooper M. J.
Published: November 2005

An analytic expression is derived for the resolution of a twin-rotor neutron time-of-flight spectrometer, assuming Gaussian time delay and collimation functions. A formulation is used which is similar to that used by Cooper and Nathans (Acta. cryst. 23 (1967) 357) in the derivation of the resolution function of a three-crystal neutron diffractometer, so that a direct comparison of the results in the two cases is possible. The results of example calculations are also presented and discussed.
The Structure of Cobalt Films Formed on Rocksalt and Mica by Vacuum Evaporation
Authors: Kato Teruo , Ogawa Shiro
Published: November 2005

The structure and orientation of cobalt films several hundred Å thick formed on cleavage faces of rocksalt and mica by vacuum evaporation under the pressure of 10-7–10-6 Torr have been studied by transmission electron diffraction in relation to the substrate temperature. When the temperature is low, the h.c.p. and f.c.c. phases co-exist in cobalt films formed on both the substrates, but as the temperature is elevated, the h.c.p. phase becomes predominant on mica and the f.c.c. phase does on rocksalt, resulting in the films consisting purely of the single phases at temperatures above 300°C. Even films formed on rocksalt at the temperature at which only the single phase is formed at a large thickness have been observed to consist of the two phases at a small thickness.
Flux Instabilities in High Field Superconducting Wires
Authors: Kobayashi Hisayasu , Yasukōchi Kō , Ogasawara Takeshi
Published: November 2005

The magnetic flux instability is investigated in Nb-25% Zr wires, 0.25 mm in diameter, and the low field instability is found to be an intrinsic phenomenon of high field superconducting wires. The flux Jump is induced artificially by an application of the heat pulse and the magnetic field pulse. The stability is represented quantitatively by a minimum power of the pulse P

c
at which the superconductor quenches into a normal state. The critical power
P

c
reduces discontinuously above a certain current, the threshold current
I

t
. Threshold current
I

t
and P

c
depend on the history of the field-current application. The stability at the current above I

t
increases with increasing ambient magnetic field and with decreasing critical current. Partial flux jump is induced above a certain current I

f
below I

t
. The detailed structure of the distribution of the magnetic induction in the sample plays an important rote in the stability.
Anomalous Capacitance in Gallium Phosphide Electroluminescent p-n Junctions
Authors: Toyama Masaharu
Published: November 2005

Anomalous capacitance-voltage and current-voltage characteristics have been observed in GaP p-n junctions. Capacitance in these diodes abruptly decreases in the forward direction when the applied voltage exceeds 1.5 V, and is largely frequency-dependent above 100 kHz. Moreover, both capacitance and parallel conductance are temperature-dependent above 100 kHz. The observed anomalies have quantitatively been explained by a model in which deep centers take part in space charges in the depletion layer. The deep centers are considered to be acceptors due to Ga vacancies produced by zinc diffusion which occurs during junction formation by liquid phase epitaxy or during heat treatment, and to be distributed in the p-side. Analyses of experimental data have revealed that the junction has a p-π-i-n structure and that, in the π-layer, the deep acceptor concentration is predominantly high as compared with the net shallow acceptor concentration. Voltage dependence of diode current and red electroluminescence has also been interpreted in terms of this junction structure.
Effects of Silicon Surface Conditions on Nickel-Silicon Contacts
Authors: Itoh Yokichi
Published: November 2005

The effect of residual damage or strain, induced by mirror polishing of silicon surface, on the height of Schottky barrier formed between Ni and n-type (111) Si was investigated. If a layer of one micron or greater was removed from the silicon surface, the barrier height decreased from about 0.56 eV to about 0.53 eV. This observation shows that an effect, detectable by Schottky barrier height, exists in the layer of about one micron thick on the mirror polished surface.
In addition, by heat treatment at high temperatures, the effect of gas desorption from the silicon surface on the barrier height was investigated. The barrier height was found to increase with increasing temperature of the heat treatment. By heating at 1000°C for 30 minutes, the barrier height of up to about 0.66 eV was observed.
Dye Sensitization of Photoconductivity of Poly-N-Vinylcarbazole II. Fluorescence Quenching and Charge Transfer
Authors: Ikeda Mitsusuke , Murakami Yoshinobu , Morimoto Kazuhisa , Sato Hisanao
Published: November 2005

Fluorescence and excitation spectra of poly-N-vinylcarbazole (PNVC) and dyes were measured. The fluorescence of dyes decreased with the addition of PNVC and that of PNVC also decreased with the addition of dyes, with a peak at about 425 mµ. The quenching of PNVC fluorescence was found to be more remarkable for dyes having larger sensitization effects on the photocurrent in PNVC films. These results suggest that both the fluorescence quenching and the sensitization of the photocurrent are due to the electron transfer from PNVC to dyes under illumination.
Electrical Characteristics of an MHD Channel Using Arc Cathodes in a Potassium-Seeded Argon Plasma
Authors: Shirakata Hirofumi , Yano Syukuro
Published: November 2005

The effects of the arc cathode on electrical characteristics of the MHD channel were investigated. Two experiments using a potassium-seeded argon gas were made: one was the applied field experiment at 1790°K and 1 atm, and the other was the preliminary generator experiment at 1850°K and 1 atm. In the applied field experiment, it was found that the cathode sheath resistance was decreased by two figures when the arc cathode was operated. In the generator experiment, the increment of the true generator current induced by the MHD effect became evident from the results of analysis by the use of an equivalent circuit.
A High-Sensitive, Simple Calorimeter for Phase-Change Detection
Authors: Hirakawa Kinshiro , Furukawa Minoru
Published: November 2005

A high-sensitive but very simple calorimeter has been designed for the purpose of phase change detection. The key point is in use of styrofoam in construction of the conduction type calorimeter. The sensitivity is so high that the sample whose size is about 2 cc is enough for the most of purposes. For instance the well defined anomalous heat capacities in Rochelle-salt have been detected by this method.
Some Properties of Silica Film Made by RF Glow Discharge Sputtering
Authors: Kozuma Taisaku , Kobayashi Takao , Hamaguchi Chihiro , Nakai Junkichi , Fujioka Toshiaki , Matsuzawa Akio
Published: November 2005

Electrical and optical properties of silica films obtained by RF sputtering both with and without oxygen ambient have been investigated. The resistivity of a typical film without oxygen ambient is found to be about 2×1016Ω cm at room temperature and the activation energy is estimated to be 1.6 eV in the temperature range from 200°C to 400°C. Small quantity of oxygen gas results in an appreciable reduction of deposition rate. With increasing the oxygen partial pressure, the values of ε' and tan
δ are found to increase and the absorption peak near 9.3µ shifts to longer wave lengths. These results are considered to be explained in terms of a change in film composition caused by oxygen ambient.
Magnetohydrodynamic Channel Flow of Suspension
Authors: Yang Wen-Jei , Ou Jenn-Wuu
Published: November 2005

An analytical method is developed to determine the flow and heat transfer characteristics of suspensions in a parallel-plate channel under the influence of electric and magnetic fields. The flow is fully developed to Hartmann profile and the rheological behavior of the suspensions obeys the power-law model. Two cases of wall thermal condition are considered: the prescribed wall heat flux and the prescribed wall temperature. Numerical results show considerable deviations in the Hartmann profile, viscous and Joule heating, and heat transfer rate when the rheological characteristics of the suspension deviates from a Newtonian one.
Terrestrial laser scanning for monitoring the process of hard rock coastal cliff erosion
Authors: Rosser N.J. , Petley D.N. , Lim M. , Dunning S.A. , Allison R.J.
Published: November 2005

Hard rock cliffs represent approximately 75% of the world's coastline. The rate and nature of the mechanisms that govern the retreat of these cliffs remain poorly constrained, primarily because conventional approaches employed to monitor these processes are generally inadequate for describing cliff erosion processes directly. These techniques are usually centred upon the interpretation of data collected periodically from aerial sensors, including stereographic aerial photographs and more recently air-borne LIDAR. These methods are generally not capable of assessing the pattern of erosion on the cliff face due to the oblique viewing angles, and hence tend to concentrate upon the resultant recession of the cliff top rather than change on the cliff face. Thus, processes of undercutting and small scale iterative failures of localized sections of the cliff face are generally not recorded. It is only when a failure affects the cliff top that any retreat is recorded. It is therefore unsurprising that cliff erosion is commonly deemed to be episodic.

This paper presents a new approach to detailed cliff process monitoring using terrestrial laser scanning (TLS), which directly monitors changes on coastal cliff faces. The method allows the quantification of failures ranging in scale from the detachment of blocks of a few centimetres in dimension through to large rock, debris or soil, falls, slides and flows over 1000 m
3
. The collection of data is on-site and rapid and hence cost effective, providing a detailed description of the nature of coastal cliff erosion.

This paper describes the methodological approach and demonstrates the range of results which can be generated, here shown for 16 months of monitoring data collected for a near-vertical cliff section on the coast of North Yorkshire, UK. The results demonstrate that terrestrial laser scanning can be used to quantify cliff failures to a previously unobtainable precision. The results reveal a strong spatial and temporal pattern of cliff collapse which contradicts commonly held perceptions of the nature of coastal cliff development.
Hydrogeological investigation in the Channel Islands: the important role of German military geologists during World War II
Authors: Robins N.S. , Rose E.P.F.
Published: November 2005

Investigation of groundwater resources in Jersey and Guernsey has been driven by different needs in three phases: the first, an intensive phase, took place between 1940 and 1945, when the islands were occupied by German armed forces; the second in the 1970s, in response to increasing reliance on, and demand for groundwater; and the third between 1991 and 1998, in response to a drought between 1989 and 1991. First phase investigation in Alderney was followed directly by third phase work. Maps and reports from the first phase studies for all three islands have only recently been rediscovered: second and third phase investigations were all carried out in ignorance of the German work. The surviving German documents have revealed studies on crystalline basement aquifers with thin Quaternary cover far in advance of work elsewhere in the British Isles at that time. German work on Jersey centred on a map portraying the different hydraulic properties of the various rock types as a two-dimensional model, whereas that on Guernsey concentrated on availability of potable water and depth to water in the coastal areas of the island. Both investigations depended on well and borehole inventories as primary data sources. The modern third phase studies also used well inventories, but were supported with hydrochemical evidence to determine groundwater provenance. These studies considered the groundwater flow systems as three-dimensional models using conceptualized flow systems and island-wide water balances to understand the hydrogeology of the islands. Nevertheless, the work carried out by the German geologists showed a comprehensive and advanced understanding of the hydrogeology of the islands which would, in hindsight, have been of great benefit to the second and third phase studies if it had been available when they were carried out.
Reduction of experimental necrotizing enterocolitis with anti-TNF-α
Authors: Halpern Melissa D. , Clark Jessica A. , Saunders Tara A. , Doelle Sarah M. , Hosseini Dania Molla , Stagner Anna M. , Dvorak Bohuslav
Published: November 2005

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of premature infants. However, despite significant morbidity and mortality, the etiology and pathogenesis of NEC are poorly understood. Evidence suggests that ileal proinflammatory mediators such as IL-18 contribute to the pathology associated with this disease. In addition, we have previously shown that upregulation of TNF-α in the liver is correlated with ileal disease severity in a neonatal rat model of NEC. With the use of a neonatal rat model of NEC, we evaluated the incidence and severity of ileal damage along with the production of both hepatic and ileal proinflammatory cytokines in animals injected with (anti-TNF-α; n = 23) or without (NEC; n = 25) a monoclonal anti-TNF-α antibody. In addition, we assessed changes in apoptosis and ileal permeability in the NEC and anti-TNF-α groups. Ileal damage was significantly decreased, and the incidence of NEC was reduced from 80% to 17% in animals receiving anti-TNF-α. Hepatic TNF-α and hepatic and ileal IL-18 were significantly decreased in pups given anti-TNF-α compared with those sham injected. In addition, ileal luminal levels of both TNF-α and IL-18 were significantly decreased in the anti-TNF-α-injected group. Ileal paracellular permeability and the proapoptotic markers Bax and cleaved caspase-3 were significantly decreased in the anti-TNF-α group. These data show that hepatic TNF-α is an important component for the development of NEC in the neonatal rat model and suggest that anti-TNF-α could be used as a potential therapy for human NEC.
The nuclear receptor for bile acids, FXR, transactivates human organic solute transporter-α and -β genes
Authors: Landrier Jean-François , Eloranta Jyrki J. , Vavricka Stephan R. , Kullak-Ublick Gerd A.
Published: November 2005

Bile acids are synthesized from cholesterol in the liver and are excreted into bile via the hepatocyte canalicular bile salt export pump. After their passage into the intestine, bile acids are reabsorbed in the ileum by sodium-dependent uptake across the apical membrane of enterocytes. At the basolateral domain of ileal enterocytes, bile acids are extruded into portal blood by the heterodimeric organic solute transporter OSTα/OSTβ. Although the transport function of OSTα/OSTβ has been characterized, little is known about the regulation of its expression. We show here that human OSTα/OSTβ expression is induced by bile acids through ligand-dependent transactivation of both OST genes by the nuclear bile acid receptor/farnesoid X receptor (FXR). FXR agonists induced endogenous mRNA levels of OSTα and OSTβ in cultured cells, an effect that was not discernible upon inhibition of FXR expression by small interfering RNAs. Furthermore, OST mRNAs were induced in human ileal biopsies exposed to the bile acid chenodeoxycholic acid. Reporter constructs containing OSTα or OSTβ promoters were transactivated by FXR in the presence of its ligand. Two functional FXR binding motifs were identified in the OSTα gene and one in the OSTβ gene. Targeted mutation of these elements led to reduced inducibility of both OST promoters by FXR. In conclusion, the genes encoding the human OSTα/OSTβ complex are induced by bile acids and FXR. By coordinated control of OSTα/OSTβ expression, bile acids may adjust the rate of their own efflux from enterocytes in response to changes in intracellular bile acid levels.
Increased natriuretic peptide receptor A and C gene expression in rats with pressure-overload cardiac hypertrophy
Authors: Christoffersen Tue E. H. , Aplin Mark , Strom Claes C. , Sheikh Soren P. , Skott Ole , Busk Peter K. , Haunso Stig , Nielsen Lars B.
Published: November 2005

Both atrial (ANP) and brain (BNP) natriuretic peptide affect development of cardiac hypertrophy and fibrosis via binding to natriuretic peptide receptor (NPR)-A in the heart. A putative clearance receptor, NPR-C, is believed to regulate cardiac levels of ANP and BNP. The renin-angiotensin system also affects cardiac hypertrophy and fibrosis. In this study we examined the expression of genes for the NPRs in rats with pressure-overload cardiac hypertrophy. The ANG II type 1 receptor was blocked with losartan (10 mg·kg−1·day−1) to investigate a possible role of the renin-angiotensin system in regulation of natriuretic peptide and NPR gene expression. The ascending aorta was banded in 84 rats during Hypnorm/Dormicum-isoflurane anesthesia; after 4 wk the rats were randomized to treatment with losartan or placebo. The left ventricle of the heart was removed 1, 2, or 4 wk later. Aortic banding increased left ventricular expression of NPR-A and NPR-C mRNA by 110% ( P < 0.001) and 520% ( P < 0.01), respectively, after 8 wk; as expected, it also increased the expression of ANP and BNP mRNAs. Losartan induced a slight reduction of left ventricular weight but did not affect the expression of mRNAs for the natriuretic peptides or their receptors. Although increased gene expression does not necessarily convey a higher concentration of the protein, the data suggest that pressure overload is accompanied by upregulation of not only ANP and BNP but also their receptors NPR-A and NPR-C in the left ventricle.
NO-dependent blood pressure regulation in RGS2-deficient mice
Authors: Obst Michael , Tank Jens , Plehm Ralph , Blumer Kendall J. , Diedrich Andrè , Jordan Jens , Luft Friedrich C. , Gross Volkmar
Published: November 2005

The regulator of G protein signaling (RGS) 2, a GTPase-activating protein, is activated via the nitric oxide (NO)-cGMP pathway and thereby may influence blood pressure regulation. To test that notion, we measured mean arterial blood pressure (MAP) and heart rate (HR) with telemetry in Nω-nitro-l-arginine methyl ester (l-NAME, 5 mg l-NAME/10 ml tap water)-treated RGS2-deficient (RGS2−/−) and RGS2-sufficient (RGS2+/+) mice and assessed autonomic function. Without l-NAME, RGS2−/−mice showed during day and night a similar increase of MAP compared with controls. l-NAME treatment increased MAP in both strains. nNOS is involved in this l-NAME-dependent blood pressure increase, since 7-nitroindazole increased MAP by 8 and 9 mmHg ( P < 0.05) in both strains. The l-NAME-induced MAP increase of 14–15 mmHg during night was similar in both strains. However, the l-NAME-induced MAP increase during the day was smaller in RGS2−/−than in RGS2+/+(11 ± 1 vs. 17 ± 2 mmHg; P < 0.05). Urinary norepinephrine and epinephrine excretion was higher in RGS2−/−than in RGS2+/+mice. The MAP decrease after prazosin was more pronounced in l-NAME-RGS2−/−. HR variability parameters [root mean square of successive differences (RMSSD), low-frequency (LF) power, and high-frequency (HF) power] and baroreflex sensitivity were increased in RGS2−/−. Atropine and atropine plus metoprolol markedly reduced RMSSD, LF, and HF. Our data suggest an interaction between RGS2 and the NO-cGMP pathway. The blunted l-NAME response in RGS2−/−during the day suggests impaired NO signaling. The MAP increases during the active phase in RGS2−/−mice may be related to central sympathetic activation and increased vascular adrenergic responsiveness.
Glucocorticoids act in the dorsal hindbrain to modulate baroreflex control of heart rate
Authors: Bechtold Andrea G. , Scheuer Deborah A.
Published: November 2005

Systemic corticosterone (Cort) modulates arterial baroreflex control of both heart rate and renal sympathetic nerve activity. Because baroreceptor afferents terminate in the dorsal hindbrain (DHB), an area with dense corticosteroid receptor expression, we tested the hypothesis that prolonged activation of DHB Cort receptors increases the midpoint and reduces the gain of arterial baroreflex control of heart rate in conscious rats. Small (3–4 mg) pellets of Cort (DHB Cort) or Silastic (DHB Sham) were placed on the surface of the DHB, or Cort was administered systemically by placing a Cort pellet on the surface of the dura (Dura Cort). Baroreflex control of heart rate was determined in conscious male Sprague Dawley rats on each of 4 days after initiation of treatment. Plots of arterial pressure vs. heart rate were analyzed using a four-parameter logistic function. After 3 days of treatment, the arterial pressure midpoint for baroreflex control of heart rate was increased in DHB Cort rats (123 ± 2 mmHg) relative to both DHB Sham (108 ± 3 mmHg) and Dura Cort rats (109 ± 2 mmHg, P < 0.05). On day 4, baseline arterial pressure was greater in DHB Cort (112 ± 2 mmHg) compared with DHB Sham (105 ± 2 mmHg) and Dura Cort animals (106 ± 2 mmHg, P < 0.05), and the arterial pressure midpoint was significantly greater than mean arterial pressure in the DHB Cort group only. Also on day 4, maximum baroreflex gain was reduced in DHB Cort (2.72 ± 0.12 beats·min−1·mmHg−1) relative to DHB Sham and Dura Cort rats (3.51 ± 0.28 and 3.37 ± 0.27 beats·min−1·mmHg−1, P < 0.05). We conclude that Cort acts in the DHB to increase the midpoint and reduce the gain of the heart rate baroreflex function.
Recovery of phrenic activity and ventilation after cervical spinal hemisection in rats
Authors: Fuller David D. , Golder Francis J. , Olson E. B. , Mitchell Gordon S.
Published: November 2005

We tested two hypotheses: 1) that the spontaneous enhancement of phrenic motor output below a C2spinal hemisection (C2HS) is associated with plasticity in ventrolateral spinal inputs to phrenic motoneurons; and 2) that phrenic motor recovery in anesthetized rats after C2HS correlates with increased capacity to generate inspiratory volume during hypercapnia in unanesthetized rats. At 2 and 4 wk post-C2HS, ipsilateral phrenic nerve activity was recorded in anesthetized, paralyzed, vagotomized, and ventilated rats. Electrical stimulation of the ventrolateral funiculus contralateral to C2HS was used to activate crossed spinal synaptic pathway phrenic motoneurons. Inspiratory phrenic burst amplitudes ipsilateral to C2HS were larger in the 4- vs. 2-wk groups ( P < 0.05); however, no differences in spinally evoked compound phrenic action potentials could be detected. In unanesthetized rats, inspiratory volume and frequency were quantified using barometric plethysmography at inspired CO2fractions between 0.0 and 0.07 (inspired O2fraction 0.21, balance N2) before and 2, 3, and 5 wk post-C2HS. Inspiratory volume was diminished, and frequency enhanced, at 0.0 inspired CO2fraction ( P < 0.05) 2-wk post-C2HS; further changes were not observed in the 3- and 5-wk groups. Inspiratory frequency during hypercapnia was unaffected by C2HS. Hypercapnic inspiratory volumes were similarly attenuated at all time points post-C2HS ( P < 0.05), thereby decreasing hypercapnic minute ventilation ( P < 0.05). Thus increases in ipsilateral phrenic activity during 4 wk post-C2HS have little impact on the capacity to generate inspiratory volume in unanesthetized rats. Enhanced crossed phrenic activity post-C2HS may reflect plasticity associated with spinal axons not activated by our ventrolateral spinal stimulation.
Inconsistencies between human genetic cytolocations and those derived using genomic sequence
Authors: Cuticchia A.J. , Kulkarni R.D. , Parris W.E. , Cooley P.C. , Hall R.D. , Silk G.W.
Published: November 2005

One result of the publishing of the human genome sequence is the ability to define objects through their position on the consensus sequence. While this has simplified the process of creating order maps for genes on a chromosome, it has created discrepancies between the published cytolocations of human genes, as presented through genetic references, and those locations derived computationally from the genomic sequence. For the 6,830 records with HUGO gene symbols shared between the online version of Mendelian Inheritance in Man and Ensembl, 18% of the records have a discrepancy of at least one cytogenetic band between the datasets. Discordance between data sets at this frequency would have a significant impact on the utility of datasets created by the amalgamation of numerous biological databases.
7E olfactory receptor gene clusters and evolutionary chromosome rearrangements
Authors: Yue Y. , Haaf T.
Published: November 2005

Olfactory receptor (OR) genes of the 7E subfamily have been duplicated to multiple regions throughout the human genome. Segmental duplications containing 7E OR genes have been associated with both pathological and evolutionary chromosome rearrangements. Many of these breakpoint regions coincide with breaks of chromosomal synteny in the mouse, rat and/or chicken genomes. Collectively, these data suggest that 7E OR-containing regions represent hot spots of genomic instability.
Histone H3 lysine 4 dimethylation is enriched on the inactive sex chromosomes in male meiosis but absent on the inactive X in female somatic cells
Authors: Khalil A.M. , Driscoll D.J.
Published: November 2005

Inactivation of the X chromosome occurs in female somatic cells and in male meiosis. In both cases, the inactive X chromosome undergoes changes in histone modifications including deacetylation of core histone proteins and enrichment with histone H3 lysine 9 (H3-K9) dimethylation. In this study we show that while the inactive X in female somatic cells is largely devoid of H3-K4 dimethylation, the inactive X in male meiosis is enriched with this modification. However, the inactive X chromosome in female somatic cells and the inactive X and Y in male meiosis are devoid of H3-K4 trimethylation. Further, trimethylation of H3-K4 is present at discrete regions along most of the autosomes, while H3-K4 dimethylation shows a more homogenous staining. Also, the Y chromosome is largely devoid of H3-K4 di- and trimethylation in somatic cells of both humans and mice, however, the Y chromosome is enriched with H3-K4 di- but not trimethylation throughout spermatogenesis. Our results provide insights into the differences between female somatic cells and male germ cells in inactivating the X chromosome, and suggest that trimethylation, and not dimethylation, of H3-K4 is a more robust indicator of the active regions of the genome.
In silico comparison of gene expression levels in ten human tumor types reveals candidate genes associated with carcinogenesis
Authors: Chen S. , Zhu B. , Yu L.
Published: November 2005

Most human cancers are characterized by genomic instability. Changes associated with such may result in altered expression of numerous genes. The sequence information available in the public databases can be used to identify transcripts differentially expressed in cancers. Determining cancer-related genes that are commonly deregulated in different tumor types may facilitate identification of targets for cancer diagnoses and therapeutic treatments. Using a data-mining tool named Digital Differential Display (DDD) from the UniGene database at the NCBI web site, gene expression levels of ten different tumor types and their counterpart normal tissues were analyzed. Unigenes which showed transcriptional regulation in more than five tumor types with ≧2-fold differences from normal tissues were identified. The expression data of selected Unigenes were subjected to clustering analysis. 127 commonly up-regulated genes and 92 commonly down-regulated genes were identified. Clustering analysis using these genes showed that most tumor types can be clustered into a separate branch from most normal tissues. Nineteen genes that have been shown to be involved in carcinogenesis by experimental evidence were also identified. Present computational analyses revealed 219 candidate cancer-related genes that are commonly deregulated in ten human tumor types which may contribute to the progress of carcinogenesis.
Trisomy of chromosome 18 in the baboon (Papio hamadryas anubis)
Authors: Howell K.H. , Hubbard G.B. , Moore C.M. , Dunn B.G. , von Kap-Herr C. , Raveendran M. , Rogers J.A. , Leland M.M. , Brasky K.M. , Nathanielsz P.W. , Schlabritz-Loutsevitch N.E.
Published: November 2005

Trisomy 18 is usually a lethal chromosomal abnormality and is the second most common autosomal trisomy in humans, with an incidence of 1:8000 live births. It is commonly associated with abnormalities of the lower and upper extremities, having the frequency of 95% and 65%, respectively. A newborn female olive baboon (Papio hamadryas anubis) was diagnosed with intrauterine growth retardation and severe arthrogryposis-like congenital joint deformities. Cytogenetic analysis including G-banding and fluorescence in situ hybridization (FISH) revealed that the congenital abnormalities were associated with chromosomal mosaicism for trisomy 18. Genetic analysis with microsatellites from chromosome 18 confirmed the maternal origin of the extra chromosome 18. This is the first report of trisomy 18 in the baboon, which may be a promising animal model of human disease.