bluuebunny/crossref_metadata_2025 huggingface dataset:
3C-SiC Films on Si for MEMS Applications: Mechanical Properties
Authors: Locke Christopher , Kravchenko G. , Waters P. , Reddy J. D. , Du K. , Volinsky A.A. , Frewin Christopher L. , Saddow Stephen E.
Published: March 2009

Single crystal 3C-SiC films were grown on (100) and (111) Si substrate orientations in order to study the resulting mechanical properties of this material. In addition, poly-crystalline 3C-SiC was also grown on (100)Si so that a comparison with monocrystaline 3C-SiC, also grown on (100)Si, could be made. The mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates were measured by means of nanoindentation using a Berkovich diamond tip. These results indicate that polycrystalline SiC thin films are attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging. MEMS cantilevers and membranes fabricated from a 2 µm thick single crystal 3C-SiC grown on (100)Si under similar conditions resulted in a small degree of bow with only 9 µm of deflection for a cantilever of 700 µm length with an estimated tensile film stress of 300 MPa. Single crystal 3C-SiC films on (111)Si substrates have the highest elastic and plastic properties, although due to high residual stress they tend to crack and delaminate.
Avalanche Capability of Unipolar SiC Diodes: A Feature for Ruggedness and Reliability Improvement
Authors: Hilsenbeck Jochen , Treu Michael , Rupp Roland , Peters Dethard , Elpelt Rudolf
Published: March 2009

SiC Diodes in the 300 to 1200V range have steadily increased their market penetration in the last 7 years. Especially the 600V SiC diodes are a nearly mandatory device for further increase of power density in modern switch mode power supplies. Those devices entered the market from the high end side due to the still significant higher costs in comparison with conventional fast Si diodes. On the other hand, these high end markets like server or telecom power supplies also require very high reliability of the devices used. In previous papers we showed, that Merged-PN-Schottky (MPS) diodes can be designed for avalanche ruggedness [1,2].
In this paper we will describe, how this feature supports overall reliability improvement. Addditionally, we will show, how a conventional SiC Schottky diode without MPS structure can be modified in order to achieve stable avalanche breakdown in combination with strong reliability improvement.
Grayscale Junction Termination for High-Voltage SiC Devices
Authors: Imhoff Eugene A. , Kub Fritz J. , Hobart Karl D.
Published: March 2009

In silicon carbide devices used above around 2.4 kV, effective anode edge termination usually requires a high-resolution floating guard ring implant or multiple lithography/implant cycles to effect a multi-zone junction termination extension. In general the goal is to produce a smoothly tapered field profile to prevent high-voltage field-crowding that causes premature breakdown at the edge of the high voltage electrode. Using a much simpler grayscale photolithographic technique and a single termination implant, we directly produce the desired tapered doping profile. The effectiveness of this termination is shown by the near-ideal (6.1 kV) breakdown measured in PiN diodes made with a 38 µm intrinsic layer. The simple method is applicable to the fabrication of many high-voltage devices.
Lifetime Investigations of 4H-SiC PiN Power Diodes
Authors: Reshanov Sergey A. , Bartsch Wolfgang , Zippelius Bernd , Pensl Gerhard
Published: March 2009

Lifetime measurements are performed on 4H-SiC pin power diodes (6.5 kV). The lifetime values in the base range from 1.1 s to 2.1 s; these values demonstrate the high quality of the 4H-SiC epilayer and the optimized device processing. The observed lifetimes are correlated with deep defect centers detected by deep level transient spectroscopy. The role of the Z1/2-center as a lifetime killer is discussed.
Electrical Characterization of Large Area 800 V Enhancement-Mode SiC VJFETs for High Temperature Applications
Authors: Ritenour Andrew , Bondarenko Volodymyr , Kelley Robin L. , Sheridan David C.
Published: March 2009

Prototype 800 V, 47 A enhancement-mode SiC VJFETs have been developed for high temperature operation (250 °C). With an active area of 23 mm2 and target threshold voltage of +1.25 V, these devices exhibited a 28 m room temperature on-resistance and excellent blocking characteristics at elevated temperature. With improved device packaging, on-resistance and saturation current values of 15 m and 100 A, respectively, are achievable.
Performance of 60 A, 1200 V 4H-SiC DMOSFETs
Authors: Hull Brett A. , Jonas Charlotte , Ryu Sei Hyung , Das Mrinal K. , O'Loughlin Michael  J. , Husna Fatima , Callanan Robert , Richmond Jim , Agarwal Anant K. , Palmour John W. , Scozzie Charles
Published: March 2009

Large area (8 mm x 7 mm) 1200 V 4H-SiC DMOSFETs with a specific on-resistance as low as 9 m•cm2 (at VGS = 20 V) able to conduct 60 A at a power dissipation of 200 W/cm2 are presented. On-resistance is fairly stable with temperature, increasing from 11.5 m•cm2 (at VGS = 15 V) at 25°C to 14 m•cm2 at 150°C. The DMOSFETs exhibit avalanche breakdown at 1600 V with the gate shorted to the source, although sub-breakdown leakage currents up to 50 A are observed at 1200 V and 200°C due to the threshold voltage lowering with temperature. When switched with a clamped inductive load circuit from 65 A conducting to 750 V blocking, the turn-on and turn-off energies at 150°C were less than 4.5 mJ.
Improvements in SiC MOS Processing as Revealed by Studies of Fixed and Oxide Trap Charge
Authors: Habersat Daniel B. , Lelis Aivars J. , Potbhare Siddharth , Goldsman Neil
Published: March 2009

In order to improve Silicon Carbide MOSFET device performance, it is important to minimize the on-state losses by improving the effective channel mobility, which can be done by decreasing interfacial charge consisting of interface traps, fixed charge, and oxide traps, which degrade mobility due to Coulombic scattering. This paper considers a method for distinguishing between oxide traps and fixed charge, and discusses how this charge has varied with processing over the last several years. Our results show that, over the period of study, NF has trended downward. Also, the number of switching oxide traps, which gives a lower bound for Not, appears to have decreased considerably. The trends for improvement in NF and ΔNot are promising, but our data suggests that NF and Not remain much too high and need to be reduced further to realize significant gains in SiC MOSFET performance.
Effects of the Surface Condition of the Substrates on the Electrical Characteristics of 4H-SiC MOSFETs
Authors: Ohshima Takeshi , Onoda Shinobu , Kamada Toshiro , Hotta Kazutoshi , Kawata Kenji , Eryu Osamu
Published: March 2009

Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) were fabricated on p-type epitaxial 4H-SiC substrates with different surface conditions and these electrical characteristics were compared. The MOSFETs on Chemical Mechanical Polished substrates showed the drain current of the order of 10-12A at a gate voltage of 0 V, and the value of the drain current increased with increasing the surface roughness of substrates. With decreasing the surface roughness of substrates, the values of the threshold voltage decreased and the quality of gate oxide became better.
High Channel Mobility in P-Channel MOSFETs Fabricated on 4H-SiC (0001) and Non-Basal Faces
Authors: Noborio Masato , Suda Jun , Kimoto Tsunenobu
Published: March 2009

P-channel MOSFETs have been fabricated on 4H-SiC (0001) face as well as on 4H-SiC (03-38) and (11-20) faces. The gate oxides were formed by thermal oxidation in dry N2O ambient, which is widely accepted to improve the performance of n-channel SiC MOSFETs. The p-channel SiC MOSFETs with N2O-grown oxides on 4H-SiC (0001), (03-38), and (11-20) faces show a channel mobility of 7 cm2/Vs, 11 cm2/Vs, and 17 cm2/Vs, respectively. From the quasi-static C-V curves measured by using gate-controlled diodes, the interface state density was calculated by an original method. The interface state density was the lowest at the SiO2/4H-SiC (03-38) interface (about 1x1012 cm-2eV-1 at EV + 0.2 eV). The authors have applied deposited oxides to the 4H-SiC p-channel MOSFETs. The (0001), (03-38), and (11-20) MOSFETs with deposited oxides exhibit a channel mobility of 10 cm2/Vs, 13 cm2/Vs, and 17 cm2/Vs, respectively. The deposited oxides are one of effective approaches to improve both n-channel and p-channel 4H-SiC MOS devices.
Quasi-Charge-Sheet Model for Inversion Layer Mobility in 4H-SiC MOSFETs
Authors: Rao R. Ramakrishna , Matocha Kevin , Tilak Vinayak
Published: March 2009

The mobility of electrons in the inversion layer of 4H-Silicon Carbide (SiC) MOSFETs is lower than the ideal value due to the various scattering mechanisms that takes place at the surface. These scattering mechanisms are strong function of both the interface-trapped charge density and inversion-layer electron density. In this work, we develop a quasi-charge-sheet model to quantify coulomb scattering due to interface trapped-charge in SiC MOSFET inversion layers and calculate the inversion layer electron mobility.
Growth of 4H-SiC Epitaxial Layers on 4° Off-Axis Si-Face Substrates
Authors: Henry Anne , Leone Stefano , Pedersen Henrik , Kordina Olof , Janzén Erik
Published: March 2009

CVD growth of epitaxial layers with a mirror like surface grown on 75 mm diameter 4° off-axis 4H SiC substrates is demonstrated. The effect of the C/Si ratio, temperature and temperature ramp up conditions is studied in detail. A low C/Si ratio of 0.4 and a temperature of 1530 °C is the best combination to avoid step bunching and triangular defects on the epitaxial layers. Using a low growth rate (about 3 µm/h) 6 μm thick, n-type doped epilayers were grown on 75 mm diameter wafers resulting in an RMS value of 0.7 nm and good reproducibility. 20 μm thick epitaxial layers with a background doping in the low 1014 cm-3 were grown with a mirror-like, defect-free surface. Preliminary results when using higher Si/H2 ratio (up to 0.4 %) and HCl addition are also presented: growth rate of 28 μm/h is achieved while keeping a smooth morphology.
Channel Hot-Carrier Effect of 4H-SiC MOSFET
Authors: Yu Liang Chun , Cheung Kin P. , Suehle John S. , Campbell Jason P. , Sheng Kuang , Lelis Aivars J. , Ryu Sei Hyung
Published: March 2009

SiC MOSFET, as power device, can be expected to operate with high drain and high gate voltages, possibly leading to hot-carrier effect. However, hot-carrier degradation in a SiC MOSFET is difficult to detect because the as fabricated devices contain high level of defects. We report, for the first time, evidence of hot-carrier effect in 4H-SiC MOSFET. The result suggests that hot hole from impact ionization trapped in the oxide is the cause of the channel hot-carrier effect.
Assessment of High and Low Temperature Performance of SiC BJTs
Authors: Nawaz Muhammad , Zaring Carina , Bource J. , Schupbach Marcelo , Domeij Martin , Lee H.S. , Östling Mikael
Published: March 2009

This paper addresses the performance of SiC NPN Bipolar Junction Transistors (BJTs) at high and low temperature. A current gain of 50 at room temperature was obtained which decreases to 25 at 275 oC. A maximum current gain (β) of 111 has been reported at -86 oC. At low temperature (below -86 oC), the current gain drops rapidly because of carrier freezout effect. At room temperature, a minimum on-resistance of 7 mΩ-cm2 was obtained. This increases to 28 mΩ-cm2 at 275 oC. The on-resistance of BJTs is approximately unaffected by lowering the temperature down to -86 oC from room temperature. Below -86 oC, the on-resistance jumps up rapidly because of carrier freezeout. Electrical performance of BJTs have been fairly stable during stress measurement at high temperature (120 hours at 100 oC ) at a collector bias of 1000V (with open base) for devices with a breakdown voltage of 1200V.The devices have been stressed further at low (i.e., 6) and high gain (i.e., 15) at room temperature. Initial degradation within first hour of stress test has been reported and then degradation stabilizes out. Packaged devices were tested up to 550 oC and performed admirably well up to that temperature.
Ultra Low Noise Epitaxial 4H-SiC X-Ray Detectors
Authors: Bertuccio Giuseppe , Caccia S. , Nava Filippo , Foti Gaetano , Puglisi Donatella , Lanzieri Claudio , Lavanga S. , Abbondanza Giuseppe , Crippa Danilo , Preti F.
Published: March 2009

The design and the experimental results of some prototypes of SiC X-ray detectors are presented. The devices have been manufactured on a 2’’ 4H-SiC wafer with 115 m thick undoped high purity epitaxial layer, which constitutes the detection’s active volume. Pad and pixel detectors based on Ni-Schottky junctions have been tested. The residual doping of the epi-layer was found to be extremely low, 3.7 x 1013 cm-3, allowing to achieve the highest detection efficiency and the lower specific capacitance of the detectors. At +22°C and in operating bias condition, the reverse current densities of the detector’s Schottky junctions have been measured to be between J=0.3 pA/cm2 and J=4 pA/cm2; these values are more than two orders of magnitude lower than those of state of the art silicon detectors. With such low leakage currents, the equivalent electronic noise of SiC pixel detectors is as low as 0.5 electrons r.m.s at room temperature, which represents a new state of the art in the scenario of semiconductor radiation detectors.
Solar-Blind 4H-SiC Avalanche Photodiodes
Authors: Soloviev Stanislav I. , Vert Alexey V. , Fronheiser Jody , Sandvik Peter M.
Published: March 2009

In this work, solar-blind UV 4H-SiC avalanche photodetectors were fabricated and tested in linear and Geiger modes. APDs with both PIN and separate absorption and multiplication (SAM) structures were investigated. PIN structures demonstrated higher quantum efficiencies while the SAM structure exhibit lower leakage currents. Deposition of a thin film optical filter on top of the devices was used to provide a high photon rejection ratio of (Stas add value here). However, an external filter showed a better photon rejection ratio compared to the deposited one by about one order of magnitude.
High Temperature Characteristics for UV Responsivity of 3C-SiC pn Photodiode
Authors: Hirabayashi Yasuo , Akiyama Kensuke , Kaneko Satoru
Published: March 2009

The photo-response of 3C-SiC pn homojunction photodiodes was measured at high temperature up to 673K. At 473K, the response is hardly different from that at the room temperature. At 573K and 673K, the peak is red shift and lowering comparing that of 298K. The response increases on the long-wavelength region of the profile because of an increase in optical absorption coefficient on increase in temperature. Responsivities at various temperatures were calculated using one-dimensional diffusion model. The calculated profiles of response are qualitatively in agreement with the experimental results except for that of 473K.
Structural Characterization of GaN Epitaxial Layers Grown on 4H-SiC Substrates with Different Off-Cut
Authors: Caban Piotr , Kościewicz Kinga , Strupiński Wlodek , Szmidt Jan , Pagowska Karolina , Ratajczak Renata , Wojcik Marek , Gaca Jaroslaw , Turos Andrzej
Published: March 2009

The influence of surface preparation of 4H-SiC substrates on structural properties of GaN grown by low pressure metalorganic vapour phase epitaxy was studied. Substrate etching has an impact on the crystallographic structure of epilayers and improves its crystal quality. The GaN layers were characterized by RBS/channelling and HRXRD measurements. It was observed that on-axis 4H-SiC is most suitable for GaN epitaxy and that substrate etching improves the crystal quality of epilayer.
Comparative Study of 3C-GaN Grown on Semi-Insulating 3C-SiC/Si(100) Substrates
Authors: Tschumak Elena , Tonisch Katja , Pezoldt Joerg , As Donat J.
Published: March 2009

Cubic gallium nitride epitaxial layers grown on differently carbonized silicon substrates were studied by high resolution X-ray diffraction. In the case of cubic GaN layers with equal layer thickness an improvement of the layer quality in terms of full width of the half maximum can be achieved by using higher carbonization temperatures. The higher crystalline quality led to an in¬crease of the residual stress in the grown layer. An increase in the thickness of the cubic Gallium Nitride allows to improve the crystallinity and to reduce the residual stress.
High Voltage AlGaN/GaN HEMTs Employing a Tapered Field Plate
Authors: Choi Young Hwan , Lim Ji Yong , Cho Kyu Heon , Kim Young Shil , Han Min Koo
Published: March 2009

AlGaN/GaN HEMTs employing a tapered field plate, which decreases the gate leakage current and improves the breakdown voltage without any sacrifice of the forward electrical characteristics were proposed and fabricated. The tapered structure was fabricated by the wet etching process. The depletion region of the proposed structure expands toward the slope of the tapered field plate and the electric field concentration at the gate edge can be successfully suppressed. The gate leakage current of proposed device at VGS= -5 V and VDS= 100 V was decreased by 2-3 orders compared with that of the conventional one. The breakdown voltage of proposed device was 880 V while that of conventional one was 548 V.
Influence of the N/Al Ratio in the Gas Phase on the Growth of AlN by High Temperature Chemical Vapor Deposition (HTCVD)
Authors: Claudel Arnaud , Blanquet Elisabeth , Chaussende Didier , Pique D. , Pons Michel
Published: March 2009

In order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750°C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influences of N/Al ratio in the gas phase on growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 µm/h have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As-grown AlN layers were characterized by SEM and X-ray Diffraction. Surface morphology is studied by SEM and FEG-SEM and crystallographic orientations were obtained by X-ray diffraction on θ/2θ.
Large Single Crystal Diamond Plates Produced by Microwave Plasma CVD
Authors: Mokuno Yoshiaki , Chayahara Akiyoshi , Yamada Hideaki , Tsubouchi Nobuteru
Published: March 2009

Recent developments in producing large single crystal CVD diamond plates are reviewed. The developments consist of synthesis of large single crystal diamond and production of single crystal diamond plates from the bulk diamond by the lift-off process. Combining these developments, half-inch single crystal CVD diamond plates have been successfully produced.
First report of pupal parasitoids of filth-breeding flies (Diptera) from bovine manure in northeastern Mexico
Authors: Loera-Gallardo Jesus , Luna-Salas Juan F. , Gibson G.A.P.
Published: March 2009

A total of 2702 individuals representing nine species of Pteromalidae (Chalcidoidea) plus at least one species of Diapriidae, Trichopria haematobiae (Ashmead) (Diaprioidea), were reared as pupal parasitoids of filth-breeding flies in bovine manure during a 2-year study in northern Tamaulipas, Mexico. The Pteromalidae included two undescribed species of Spalangia Latreille plus Spalangia cameroni Perkins, S. drosophilae Ashmead, S. endius Walker, S. nigroaenea Curtis, Muscidifurax raptor Girault and Sanders, M. zaraptor Kogan and Legner, and Pachycrepoideus vindemiae (Rondani). Spalangia nigroaenea accounted for 71% of all the pupal parasitoids and all six Spalangia species for 94% of the parasitoids over the 2 years. Based on its preponderance, S. nigroaenea is recommended as a candidate for inundative releases within integrated pest management programs to help control fly pests of cattle in northeastern Mexico.
Lymantria dispar sex pheromone is a behavioral antagonist to pheromonal attraction of male Lymantria mathura
Authors: Gries Regine , Schaefer Paul W. , Nakamura Katsunori , Gries Gerhard
Published: March 2009

In a trapping study conducted in the experimental research forest of the Tohoku Research Center, Morioka, Honshu, Japan, we investigated the effect of heterospecific pheromone on pheromonal attraction of male Japanese gypsy moth, Lymantria disparjaponica (Motschulsky), and male pink gypsy moth, L. mathura Moore (Lepidoptera: Noctuidae: Lymantriinae). Traps baited with synthetic pheromone of L. d. japonica ((7R,8S)-cis-7,8-epoxy-2-methyloctadecane = (+)-disparlure (100 µg)) or L. mathura ((9R,10S,3Z,6Z)-cis-9,10-epoxynonadecadiene = (+)-mathuralure (20 µg) and (9S,10R,3Z,6Z)-cis-9,10-epoxynonadecadiene = (−)-mathuralure (80 µg)) attracted male L. d. japonica or L. mathura, respectively. Traps baited with synthetic pheromone of both species captured significantly fewer male L. mathura than traps baited solely with synthetic L. mathura pheromone. Numbers of male L. d. japonica captured in traps baited with (+)-disparlure were unaffected by the addition of L. mathura pheromone. (+)-Disparlure is a behavioral antagonist to pheromonal attraction of male L. mathura, whereas male L. d. japonica are indifferent to the presence of synthetic L. mathura pheromone.
The role of Bi3+‐complex ion as the stabilizer in electroless nickel plating process
Authors: Wang K. , Hong L. , Liu Z‐L.
Published: March 2009

Bi3+‐complex ion is presented here as a less toxic stabilizer for use in electroless nickel plating (ENP) to replace the existing Pb2+ ion stabilizer. The asymmetric derivatives of EDTA are identified to be a type of coordination ligands that can combine with Bi3+ ions to form soluble complexes in the acidic ENP solution. In the ENP system studied the Bi3+‐complex ion displays a critical stabilizer concentration of about 10−5 mol/L, that is, the percolation concentration over which the ENP rate drops sharply. Besides the experimental measurement, deposition rates of both Ni and P are also simulated by using a kinetic model that has been derived from the double electric layer theory. The Bi3+‐complex ion, behaving like conventional Pb2+ ion, stabilizes ENP bath through the chemical replacement reaction at the surface of Ni deposition layer and results in a passive plating surface. This investigation also verifies the properties of the EN deposit, which are insignificantly affected by the length of service time of the plating solution by employing Bi3+‐complex ion stabilizer. © 2009 American Institute of Chemical Engineers AIChE J, 2009
It ain't over till it's over: fashioning durable settlements
Authors: Berger Vivian
Published: March 2009

Vivian Berger, of New York, examines hard‐earned settlements that nearly evaporated. In order to better serve mediation participants' interests, she presents six problems that hinder or prevent a mediation agreement, and discusses precautions to avoid getting derailed.
Total Synthesis of Hopeahainol A and Hopeanol
Authors: Nicolaou K. C. , Wu T. Robert , Kang Qiang , Chen David Y.‐K.
Published: March 2009

Fast die gleichen, aber keine identischen Strukturen haben die beiden kürzlich entdeckten Naturstoffe Hopeahainol A (1) und Hopeanol (2), die wichtige unterschiedliche biologische Eigenschaften aufweisen (siehe Strukturen). Mithilfe einer Serie neuartiger Kaskadenreaktionen und Gerüstumlagerungen ist nun ihre erste Totalsynthese gelungen.

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Genetic polymorphisms in DNA repair genes as modulators of Hodgkin disease risk
Authors: El‐Zein Randa , Monroy Claudia M. , Etzel Carol J. , Cortes Andrea C. , Xing Yun , Collier Amanda L. , Strom Sara S.
Published: March 2009

BACKGROUND:

Although the pathogenesis of Hodgkin disease (HD) remains unknown, the results of epidemiologic studies suggest that heritable factors are important in terms of susceptibility. Polymorphisms in DNA repair genes may contribute to individual susceptibility for development of different cancers. However, to the authors' knowledge, few studies to date have investigated the role of such polymorphisms as risk factors for development of HD.

METHODS:

The authors evaluated the relation between polymorphisms in 3 nucleotide excision repair pathway genes (XPD [Lys751Gln], XPC [Lys939Gln], and XPG [Asp1104His]), the base excision repair XRCC1 (Arg399Gln), and double‐strand break repair XRCC3 (Thr241Met) in a population of 200 HD cases and 220 matched controls. Variants were investigated independently and in combination; odd ratios (OR) were calculated.

RESULTS:

A positive association was found for XRCC1 gene polymorphism Arg399Gln (OR, 1.77; 95% confidence interval [95% CI], 1.16‐2.71) and risk of HD. The combined analysis demonstrated that XRCC1/XRCC3 and XRCC1/XPC polymorphisms were associated with a significant increase in HD risk. XRCC1 Arg/Arg and XRCC3 Thr/Met genotypes combined were associated with an OR of 2.38 (95% CI, 1.24‐4.55). The XRCC1 Arg/Gln and XRCC3 Thr/Thr, Thr/Met, and Met/Met genotypes had ORs of 1.88 (95% CI, 1.02‐4.10), 1.97 (95% CI, 1.05‐3.73), and 4.13 (95% CI, 1.50‐11.33), respectively. XRCC1 Gln/Gln and XRCC3 Thr/Thr variant led to a significant increase in risk, with ORs of 3.00 (95% CI, 1.15‐7.80). Similarly, XRCC1 Arg/Gln together with XPC Lys/Lys was found to significantly increase the risk of HD (OR, 2.14; 95% CI, 1.09‐4.23).

CONCLUSIONS:

These data suggest that genetic polymorphisms in DNA repair genes may modify the risk of HD, especially when interactions between the pathways are considered. Cancer 2009. © 2009 American Cancer Society.
Negative Helicobacter pylori status is associated with poor prognosis in patients with gastric cancer
Authors: Marrelli Daniele , Pedrazzani Corrado , Berardi Anna , Corso Giovanni , Neri Alessandro , Garosi Lorenzo , Vindigni Carla , Santucci Annalisa , Figura Natale , Roviello Franco
Published: March 2009

BACKGROUND:

Recent studies have suggested that Helicobacter pylori (H. pylori) infection may be related to better prognosis in patients with gastric cancer, but to the authors' knowledge, this finding has not yet been validated. In the current study, the association between H. pylori status and clinical outcome was investigated in a large cohort of patients.

METHODS:

Frozen non‐neoplastic gastric mucosa and serum samples obtained from 297 patients who underwent surgery for primary gastric cancer between 1988 and 2004 were retrieved from the serum and tissue bank of the study department. H. pylori status was defined by means of polymerase chain reaction (PCR) analysis for the vacA gene in gastric mucosa and by serologic assay of H. pylori and CagA antibodies. Univariate and multivariate analyses were used for the association between clinicopathologic variables and long‐term outcome.

RESULTS:

Positivity for H. pylori infection was observed in 256 of 297 patients (86%), whereas in 41 patients (14%), PCR for vacA and both serologic tests were negative. Negative H. pylori status was found to be significantly associated with cardia location, advanced pT classification, noncurative surgery, and a lower 5‐year survival rate after R0 resection (24% vs 57%; P < .001). Multivariate survival analysis confirmed H. pylori status as a significant prognostic factor (hazards ratio, 2.47; 95% confidence interval, 1.40‐4.35 [P = .002]). The influence of H. pylori status on long‐term survival was observed in patients with early as well as advanced pT classifications.

CONCLUSIONS:

Negative H. pylori status appears to be an indicator of poor prognosis in patients with gastric cancer, and is independent of other well‒known clinical and pathologic prognostic variables. Cancer 2009. © 2009 American Cancer Society.
Properties of Co‐doped ZnO films prepared by electrochemical deposition
Authors: Wang Y. X. , Ding X. , Cheng Y. , Zhang Y. J. , Yang L. L. , Liu H. L. , Fan H. G. , Liu Y. , Yang J. H.
Published: March 2009

We prepared Co‐doped ZnO films by the electrochemical deposition. X‐ray diffraction (XRD), high resolution transmission microscopy (HRTEM), x‐ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), x‐ray absorption near‐edge structure (XANES), vibrating sample magnetometer (VSM), optical absorption, and photoluminescence (PL) measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Co‐doped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polymorphism in endostatin, an angiogenesis inhibitor, and prostate cancer risk and survival: A prospective study
Authors: Mucci Lorelei A. , Stark Jennifer R. , Figg William D. , Schumacher Fredrick , Li Haojie , Abe Miyako , Hennessy Kristen , Stampfer Meir J. , Gaziano John Michael , Ma Jing , Kantoff Philip W.
Published: March 2009

Endostatin inhibits endothelial cell proliferation and migration, prerequisites of angiogenesis. A functional missense mutation (D104N) in endostatin was associated with an increased prostate cancer risk in a small study. We undertook a larger, prospective study within the Physicians' Health Study to examine D104N and prostate cancer risk and progression among 544 incident prostate cancer cases (1982–1995) and 678 matched controls. The association between endostatin genotype and cancer risk was estimated using logistic regression models. Among cases, Cox models were used to assess D104N and lethal prostate cancer. Given the role of endostatin in neovascularization of adipose tissue, we cross classified individuals on D104N genotype and body mass index (BMI). The genotype frequency was 1.3% homozygous (NN), 14.5% heterozygous (DN) and 84.2% wildtype homozygous (DD). There was no overall association between carriage of the N allele and prostate cancer risk (RR = 1.2, 95% CI: 0.9–1.6) or cancer‐specific mortality (HR = 1.2, 0.7–1.8). Cases with the polymorphic allele were less likely to be overweight (BMI 25 kg/m2 or greater, 26%) compared to men wildtype homozygous (48%), p < 0.0001. Being overweight was associated with a 60% greater prostate cancer risk among those who were wildtype homozygous. In contrast, being overweight was associated with a 50% lower risk of cancer among those with the N allele. We did not confirm an earlier observation between the D104N polymorphism and prostate cancer. However, our data indicate that prostate cancer cases who carry the variant N allele are more likely to be overweight, and may be more susceptible to the angiogenic influences of obesity in prostate cancer pathogenesis. © 2009 UICC
Triggered release from peptide‐proteinoid microspheres
Authors: Quirk Stephen
Published: March 2009

Proteinoid microspheres (PM) are unusual polymers formed by the thermal condensation of amino acids. Although they have been studied for over 60 years, they are only now beginning to garner interest as controlled release agents. Although they are very biocompatible, it has been problematic to design useful triggers that release small molecules from PM interiors. This has severely limited their usefulness. In the present study, short peptides have been successfully incorporated into PMs during their formation. The resulting hybrid peptide‐PMs can release their interior content when hydrolyzed by a proteinase. Specifically, if a matrix metalloproteinase (MMP) cleavage site peptide is incorporated into a PM, the peptide‐PM will release interior contents only in the presence of the MMP recognizing the cleavage peptide. The release rate can be determined by the concentration of the peptide in the PM synthesis mixture. This potentially makes peptide‐PMs useful for delivering inhibitors or drugs into acute and chronic wounds, periodontal disease sites, and other disease states involving the fine‐tuned regulation of proteinases. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010
Reaction of 2‐carboxy‐1‐methylindole‐3‐acetic acid anhydride with amines and with S‐methylisothiosemicarbazide
Authors: Ali M. I. , Abdel‐Fattah A. M. , Hussain S. M. , El‐Reedy A. M.
Published: March 2009

2‐Carboxy‐1‐alkylindole‐3‐acetic acid anhydrides (I) condensed with S‐methylisothiosemicarbazide in DMF to form 5,11‐dihydro‐6‐methyl‐2‐methylthioindolo[3′,2′:4,5]pyrido[1,2‐b]‐s‐triazol‐5‐one (II). Compound II underwent ring opening on refluxing with sodium hydroxide solution to give IV. The anhydride I reacted with primary amines in benzene to give 2‐carboxy‐1‐alkylindole‐3‐acetanilide derivatives (VI) which yielded l‐methylindole‐3‐acetic acid by decarboxylation followed by hydrolysis. Compound II oxidised to the diketo compound X which could be prepared by the hydrolysis of the azomethine derivative IX with acetic acid‐hydrochloric acid mixture. Compound II reacted with benzyl chloride to yield the dibenzyl derivative XII, condensed with p‐chlorobenzaldehyde to form the 11‐p‐chlorobenzylidene derivative XI and coupled with arenediazonium salt to give the 11‐arylhydrazone derivatives XIII.
On triazoles. I. The reaction of N‐cyanocarbonimidodithioic acid diesters with hydrazines
Authors: Reiter J. , Somorai T. , Jerkovich Gy. , Dvortsák P.
Published: March 2009

The reaction of N‐cyanocarbonimidodithioic acid di(alkyl and aralkyl)esters with different alkyl‐, aralkyl‐ and arylhydrazines to yield 1‐substituted‐3‐R‐thio‐5‐amino‐1H‐1,2,4‐triazoles (3) and 2‐substituted‐3‐R‐thio‐5‐amino‐2H‐1,2,4‐triazoles (4) was studied. Isolation of the different types of isomeric pairs of 3 and 4 helped to prove the structure of products obtained which made possible correction of some confusion in the literature. The 3 (R = H) tautomeric structure of the non‐substituted derivatives was supported by comparison of their uv and cmr spectra with those of the alkylated and aralkylated derivatives 3 and 4, respectively, again correcting confusion in the literature. An hplc determination of the ratio of products 3 and 4 formed in the above reactions with different hydrazines made it possible to prove the mechanism of the reaction.
Total assignment of the 1H NMR spectra of 5H‐indolo[1,7‐ab] [1]benzazepine,6,7‐dihydro‐5H‐indolo[1,7‐ab][1]benzazepine and pyrrolo[3,2,1‐kl ] phenothiazine
Authors: Hallberg Anders , Dahlgren Torsten , Martin Arnold , Christiansen Kenner
Published: March 2009

The total assignment of the 1H nmr spectrum of the three tetracyclic compounds: 5H ‐indolo[1,7‐ab][1]benzazepine,6,7‐dihydro‐5H ‐indolo[1,7‐ab ][1]benzazepine and pyrrolo[3,2,1‐kl ]phenothiazine is described. Assignments were based on decoupling experiments and the spectrum of 1,10‐dideuteriopyrrolo[3,2,1‐kl]phenothiazine and the spectral parameters were verified by spin‐simulation techniques. A temperature study of 6,7‐dihydro‐5H ‐indolo[1,7‐ab][1]benzazepine was also performed.
The preparation of arylpropiolic acids via styrylisoxazoles
Authors: Chimichi S. , De Sio F. , Donati D. , Pepino R. , Rabatti L. , Sarti‐Fantoni P.
Published: March 2009

The vic‐dibromo derivatives obtained by bromine addition to 3‐methyl‐4‐nitro‐5‐styrylisoxazoles were used as starting materials for the preparation of arylpropiolic acids.
Derivatives of imidazo[5,1‐c][1,4]benzoxazin‐l‐ones and related analogs. Part I
Authors: Banzatti C. , Della Torre A. , Melloni P. , Pieraccioli D. , Salvadori P.
Published: March 2009

The bicyclic 2,3,3a,4‐tetrahydro‐1H‐imidazo[5,1‐c][1,4]benzoxazin‐1‐one system and the related 1,4‐benzo‐thiazine and 4,1]benzoxazepine analogs were synthesized. They were easily obtained by melting a suitable diamine derivative with urea. Some of them displayed very good reversible MAO‐I activity selective for type A. The preparation of the intermediate amines is also given.
Synthesis and chemistry of some pyridazine nucleosides related to certain 5‐substituted pyrimidine nucleosides
Authors: Katz David J. , Wise Dean S. , Townsend Leroy B.
Published: March 2009

Condensation of 3,4‐dichloro‐6‐[(trimethylsilyl)oxy] pyridazine (3) with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranose (4), by the stannic chloride catalyzed procedure, has furnished 3,4‐dichloro‐1‐(2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl) pyridazin‐6‐one (5). Nucleophilic displacement of the chloro groups and removal of the benzoyl blocking groups from 5 has furnished 3‐chloro‐4‐methoxy‐, 3,4‐dimethoxy‐, 4‐amino‐3‐chloro‐, 3‐chloro‐4‐methylamino‐, 3‐chloro‐4‐hydroxy‐, and 4‐hydroxy‐3‐methoxy‐1‐β‐D‐ribofuranosylpyridazin‐6‐one. An unusual reaction of 5 with dimethylamine is reported. Condensation of 4,5‐dichloro‐3‐nitro‐6‐[(trimethylsilyl)oxy]pyridazine with 4 yielded 4,5‐dichloro‐3‐nitro‐1‐(2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl)pyridazin‐6‐one (24). Nucleophilic displacement of the aromatic nitro groups from 24 is discussed. Condensation of 3 with 3,5‐di‐O‐p‐toluoyl 2‐deoxy‐D‐erythro‐pentofuranosyl chloride (28) afforded an α, β mixture of 2‐deoxy nucleosides. The synthesis of certain 3‐substituted pyridazine 2′‐deoxy necleosides are reported.
Pyrrolo[1,2‐a]thiéno[2,3‐e]pyrazine. Etude chimique de la dihydro‐4,5 oxo‐5 pyrrolo[1,2‐a]thiéno[2,3‐e]pyrazine
Authors: Effi Yamien , Lancelot Jean‐Charles , Rault Sylvain , Robba Max
Published: March 2009

La dihydro‐4, 5 oxo‐5 pyrrolo[1, 2‐a]thiéno[2, 3‐e]pyrazine 1 qui présente la tautomérie lactime‐lactame peut subir des réactions de substitution électrophile au niveau de l'atome d'azote lactamique. La chloro‐5 pyrazine 11 autorise les réactions de substitution nucléophile sur le cycle pyrazinique.

Les dérivés hydrazinés obtenus par cette voie peuvent exister sous la forme tautomère hydrazone. Cette tautomérie est étudiée par spectrométrie de 1H‐rmn. La réaction de thionation forme la thioxopyrazine 27 qui peut subir des réactions de S‐substitution.
The preparation of macrocyclic polyether‐diester compounds by transesterification including the preparation of two new nitrogen containing diester‐crown compounds
Authors: Bradshaw Jerald S. , Jones Brian A. , Nielsen Ralph B. , Spencer Neil O. , Thompson Patricia K.
Published: March 2009

Macrocyclic polyether‐diester compounds have been prepared by reacting oligoethylene glycols with the appropriate dimethyl esters in the presence of catalytic amounts of alkali metal methoxides. The methanol by‐product was removed by molecular sieves. Product yields were improved for the preparation of all macrocyclic compounds except a compound containing a furan subcyclic group (4). Six new macrocyclic diester compounds (7‐12) could only be prepared using the base catalyzed transesterification process since the acid chloride synthetic method failed or the acid chloride could not be made. The formation of compounds 5 and 6 from dimethyl 2, 6‐pyridine dicarboxylate (17) and the triethylene and tetraethylene glycols proceded by way of half‐transesterified intermediates. These intermediates were also observed for the base catalyzed decomposition of 5 and 6 in methanol to form the glycol and the diester 17.
Hydrazine‐hydrazone tautomerism in phenylhydrazinopyrimidones
Authors: Wright George E.
Published: March 2009

4‐Phenylhydrazino‐2‐pyrimidone and its 1‐methyl analog have been shown by 1H nmr to exist in intercon‐verting hydrazine and hydrazone tautomers in deuteriodimethylsulfoxide solution. Solvent effects indicate that increasing solvent polarity favors the hydrazine forms. In contrast, the 3‐methyl analog occurs exclusively as the hydrazone. The hydrazone forms of the parent and 1‐methyl derivatives appear to adopt the syn rotamers as a result of intramolecular hydrogen bonding. Variable temperature studies showed relatively high free energy barriers to tautomerization in these compounds, resulting both from solvation and intramolecular hydrogen bonding. The 1H nmr spectra of 1‐methyl‐4‐hydrazino‐2‐pyrimidone suggest that it exists predominately as the hydrazone in deuteriodimethylsulfoxiderdeuteriochloroform solution, although the barrier to tautomerization is similar to those for the phenylhydrazino compounds.
Preparation of new dihydrofuro[2,3‐f]indole derivatives
Authors: Plattner J. J. , Parks J. A.
Published: March 2009

The preparation of new dihydrofuro[2, 3‐f]indole derivatives and their fully aromatic counterparts is described. Key steps in the synthesis include a Claisen rearrangement/m‐chloroperoxybenzoic acid oxidation sequence to form a dihydrobenzofuran intermediate and an iron/acetic acid reductive cyclization to generate the dihydrofuro[2, 3‐f]indole nucleus. Introduction of a 5‐phenyl substituent on the indole nitrogen was effected by a modified Ullmann reaction. Fully aromatic furo[2, 3‐f]indoles were obtained from the dihydro congeners by dehydrogenation with 2, 3‐dichloro‐5, 6‐dicyano‐1, 4‐benzoquinone.
Synthesis of β‐lactams by the photolysis of cyclohexyl benzoylformate in the presence of imines
Authors: Aoyama Hiromu , Sakamoto Masami , Yoshida Katsuhiko , Omote Yoshimori
Published: March 2009

Reaction of imines with hydroxyphenylketene which was produced by photolysis of cyclohexyl benzoylformate gave β‐lactams in good yields.
Synthesis of 2‐(α‐hydroxyalkyl)‐1,3‐heterocyclic alcohols and aryl carbamates
Authors: Pridgen Lendon N. , Miller George
Published: March 2009

Several N‐(substituted phenyl)carbamoyloxylalkyl‐1,3‐heterocycles of the structure 3 were prepared from their respective α‐hydroxyalkyl‐1,3‐heterocyclic alcohols 1. Efficient syntheses of the prerequisite novel 1,3‐heterocyclic alcohols, such as 2‐(α‐hydroxyalkyl)‐2‐oxazolines, −5,6‐dihydro‐1H‐1,3‐oxazines, −1,4,5,6‐tetra‐hydropyrimidines, ‐imidazolines, and 4,5,6,7‐tetrahydro‐1H‐1,3‐diazepines were developed. Stannous octoate was found to effectively catalyze the formation of the carbamate 3 from heterocyclic alcohol 1 and aryl‐isocyanate 2.
Chromium trioxide oxidation products from 4‐spiro‐1‐phenylisochromans
Authors: Gatta Franco , Settimj Guido
Published: March 2009

Chromium trioxide oxidation of 1‐phenylisochroman‐4‐spiro‐1′‐cyclopentane (Ia) in acetic acid led to the expected 1‐(2‐benzoylphenyl)cyclopentanecarboxylic acid (IIa), while its 6,7‐dimethoxy analogue Ib and 6,7‐dimethoxy‐1‐phenylisochroman‐4‐spiro‐4′‐(1′‐methyl)piperidine (Ic) under the same conditions gave a mixture of their related 1‐hydroxy derivatives VIIIb and VIIIc and of the p‐benzoquinones, 1‐benzoyloxymethyl‐1‐(2,5‐dioxo‐4‐methoxyphenyl)cyclopentane (IXb) and 1‐benzoyloxymethyl‐1‐(2,5‐dioxo‐4‐methoxyphenyl)‐1‐methylpiperidine (IXc). Cyclization of Ila with hydrazine or monomethylhydrazine led to the 5‐spiro‐substituted 1‐phenyl‐3,5‐dihydro‐4H‐2,3‐benzodiazepin‐4‐ones IIIa or XIa.
Eight‐membered heterocycles. 12H‐dibenzo[d,g][1,3,2]dioxaphosphocin and 12H‐dibenzo[d,g][1,3,2]dioxaborocin derivatives
Authors: Pastor Stephen D. , Spivack John D.
Published: March 2009

The synthesis of phosphonite and thiophosphite derivatives of the 12H‐dibenzo[d,g][1,3,2]dioxaphosphocin ring system is described. The 'H nmr shows evidence for long‐range coupling of the C‐12 methine proton to phosphorus. The 1H nmr of the 12H‐dibenzo[d,g][1,3,2]dioxaborocin ring system is compared to that of the phosphorus analog. The nmr spectral data suggest that the phosphorus and boron containing ring systems have similar ring conformations.
Synthesis of 4‐(4‐Alkyl‐2‐morpholinyl)indoles
Authors: Clark Robin D.
Published: March 2009

N‐substituted 4‐(2‐morpholinyl)indoles were prepared from 1‐(t‐butoxycarbonyl)‐4‐acetylindole (7) which was itself prepared from 4‐cyanoindole. Bromination of ketone 7, followed by reaction with amines and subsequent sodium borohydride reduction, gave amino alcohols. These were converted to α‐chloro amides that were cyclized to lactams. Lithium aluminum hydride reduction served both to remove the t‐BOC protecting group and to reduce the lactams to the 4‐(2‐morpholinyl) indoles.
Synthesis of 1,3,4,14b‐tetrahydro‐2H,10H‐pyrazino[1,2‐α]‐ pyrrolo[2,1‐c][1,4]benzodiazepines
Authors: Ong‐Lee Avelina , Sylvester Leo , Wasley Jan W. F.
Published: March 2009

1,3,4,14b‐Tetrahydro‐2H,10H‐pyrazino[1,2‐α]pyrrolo[2,1‐c] [1,4]benzodiazepines (1a‐e) were synthesized to investigate their potential CNS activity. The key step in the synthesis was the formation of the 10,11‐dihydro‐5H‐pyrrolo[2,1‐c][1,4]benzodiazepine (13) by reduction and concomitant cyclization of the nitroketone (11). Biological evaluation of 1a‐e revealed interesting properties for 1b (CGS 7525A) [2].
Darstellung und isolierung isomerer phenoxaphosphinsäuren
Authors: Renger Bernd
Published: March 2009

In contrast to literature data, m‐chloro, bromo or methyl substituents on diphenyl ethers do not block attack ortho to them in the reaction with phosphorus trichloride and aluminium chloride. By reacting diphenyl ethers 3 and 6 mixtures of the isomeric phenoxaphosphinic acids 4/5 and 7/8 were obtained, which were easily separated by crystallisation.
Preparation of 5‐substituted benzylbarburituric acids and investigation of the effect of the benzyl and substituted benzyl groups on the acidity of barbituric acid
Authors: Tate John V. , Tinnerman William N. , Jurevics Vito , Jeskey Harold , Biehl Edward R.
Published: March 2009

The acidity of 5‐benzylbarbituric acid and a series of 5‐substituted benzylbarbituric acids has been determined in 50% ethanol/water and they were found to be more acidic than barbituric acid. The pKas of these derivatives obey Hammett's equation indicating that their acidity is affected by substituents in the same manner as the benzoic acid ionization constants. A synthesis of these acids is described.
New reactions of deoxyvasicinone. Part 4
Authors: Dunn A. D. , Kinnear K. I.
Published: March 2009

Analogues of deoxyvasicinone (1) in which the pyrrolo ring is substituted, enlarged, or attached to the a face of the quinazolone system were prepared and several reactions of these analogues with electrophilic reagents have been investigated.
Synthesis of pyrrolo[1,2‐a]naphtho[1,8‐ef][1,4]diazepines
Authors: Cheeseman G. W. H. , Eccleshall S. A.
Published: March 2009

The title compounds 9–12 were prepared from N‐(8‐nitronaphthyl)pyrrole (3).
Synthesis and reactions of sydnone oximes
Authors: Lowe James D. , Turnbull Kenneth
Published: March 2009

Oximino sydnones 1a,b have been prepared and subjected to reaction with a variety of electrophilic reagents. The aldoxime reacted with all of the latter (except acetic anhydride) to give 3‐(2‐cyanophenyl)sydnone 1h. With acetic anhydride, both sydnone oximes formed the corresponding O‐acetates li,m. Similarly, O‐sulfonates 1l,k,j, respectively, were obtained by reaction of the ketoxime with benzene‐, methane‐ and para‐toluenesulfonyl chloride. Thermolysis (on silica) of the O‐sulfonates and the O‐acetates has been examined.
Synthesis of pyrazolo[4,5‐d]‐ and pyrazolo[4,5‐c][1]benzazepine derivatives. IV
Authors: Melani Fabrizio , Cecchi Lucia , Palazzino Giovanna , Filacchioni Guido
Published: March 2009

Following our reports on synthetic tricyclic analogues of antitumor anthramycin the synthesis of some isomers pyrazolo[4,5‐d]‐ and pyrazolo[4,5‐c][1]benzazepine derivatives is reported.
Synthesis of NSC‐341,964: An unexpected study on the stability of 2‐aryl‐4H‐3,1‐benzoxazin‐4‐ones
Authors: Johnson Judith L. , Pattison Ian
Published: March 2009

Resynthesis of NSC 341,964, which had been assigned structure 1 (1‐[[3‐(7‐chloro‐4‐oxo‐4H‐3,1‐benzoxazin‐2‐yl)phenyl]methyl]pyridinium chloride) was approached via 7‐chloro‐2‐(3‐methylphenyl)‐4H‐3,1‐benzoxazin‐4‐one (5) obtained from 3‐methylbenzoyl chloride (2) and 2‐amino‐4‐chlorobenzoic acid (3) followed by dehydration in acetic anhydride. Radical bromination provided 6 which with pyridine afforded the bromide analog 7 of 1. Ion exchange, however, gave ring‐opened benzoic acid 8 rather than 1. The original sample of NSC 341,964 also proved to be ring‐opened material. However, 7 upon standing exhibited slow hydrolysis to 8 so that the structure of the original NSC 341,964 remains uncertain. A more direct route to compound 8 is also described.