bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear evolution of Tayler unstable equilibrium states
Authors: Elstner D. , Bonanno A. , Rüdiger G.
Published: September 2008

We investigate the nonlinear evolution of Tayler unstable toroidal fields in a disk geometry, by numerical simulations. We consider non‐rotating and rigid rotating disks, with different radial field profiles. The initial configuration is in equilibrium, which is achieved by a pressure gradient or an external potential force. The nonlinear evolution of the system leads to a stable equilibrium with a current free toroidal field. Only for the fast rotating case we could preserve a ring type structure of the toroidal field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aluminum Compounds Containing η1‐ and/or η5‐Bidentate Dianionic Pyrrolyl–Methylamide Ligands
Authors: Chen Ya‐Chi , Lin Che‐Yu , Li Chun‐Yin , Huang Jui‐Hsien , Chang Ling‐Chueh , Lee Ting‐Yu
Published: September 2008

A series of dialuminum compounds have been synthesized and their reactivity and application for lactide polymerization have been studied. The reaction of AlH3⋅NMe3 with [C4H3NH(2‐CH2NHtBu)] in diethyl ether generated a dimeric aluminum hydride compound, [{[C4H3N(2‐CH2NtBu)]AlH}2] (1). The structure of 1 was confirmed by spectroscopy of a deuterated analogue of 1 with an AlD function. Direct treatment of [C4H3NH(2‐CH2NHtBu)] with LiAlH4 in diethyl ether resulted in colorless crystals of [{Li[μ‐η1:η5‐C4H3N(2‐CH2NtBu)]2Al}2] (2) in 80 % yield after recrystallization from a toluene solution. The μ‐η1:η5‐pyrrolyl protons exhibit high‐field shifts at δ=5.73, 6.15, and 6.72 comparable to a similar η5‐bonding mode in the literature. Treatment of 1 with 1 equiv acetone oxime or acetone in dichloromethane gave [{[C4H3N(2‐CH2NtBu)]Al[ϰO,ϰN‐(ONCMe2)]}2] (3) and [{[C4H3N(2‐CH2NtBu)]Al(OCHMe2)}2] (4) in 67 % and 60 % yield, respectively. Compounds 1–4 have been characterized by X‐ray diffractometry and were used as catalysts for ε‐caprolactone polymerization.
Tetraethylenepentamine‐Directed Controllable Synthesis of Wurtzite ZnSe Nanostructures with Tunable Morphology
Authors: Xi Baojuan , Xiong Shenglin , Xu Dechen , Li Jingfa , Zhou Hongyang , Pan Jun , Li Jiangying , Qian Yitai
Published: September 2008

A novel tetraethylenepentamine (TEPA)‐directed method has been successfully developed for the controlled synthesis of ZnSe particles with distinctive morphologies, including nanobelts, nanowires, and hierarchically solid/hollow spheres. These structures, self‐assembled from nanobelts and nanorods, have been synthesized by adjusting the reaction parameters, such as the solvent composition, reaction temperature, and the aging time. Results reveal that the volume ratio of H2O and TEPA plays a crucial role in the final morphology of ZnSe products. The mechanisms of phase formation and morphology control of ZnSe particles are proposed and discussed in detail. The products have been characterized by means of X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy (TEM), selected area electron diffraction, high‐resolution TEM, Raman spectra and luminescence spectroscopy. The as‐prepared ZnSe nanoparticles display shape‐ and size‐dependent photoluminescent optical properties. This is the first time to report preparation of complex hollow structures of ZnSe crystals with hierarchy through a simple solution‐based route. This synthetic route is designed to exploit a new H2O/TEPA/N2H4⋅H2O system possibly for the preparation of other semiconductor nanomaterials.
Interfacial Behavior and Film Patterning of Redox‐Active Cationic Copper(II)‐Containing Surfactants
Authors: Driscoll Jeffery A. , Allard Marco M. , Wu Libo , Heeg Mary Jane , da Rocha Sandro R. P. , Verani Cláudio N.
Published: September 2008

Herein, we describe the synthesis and characterization of a novel series of single‐tail amphiphiles L (Py=pyridine, Cn=C18, C16, C14, C10) and their copper(II)‐containing complexes, which are of relevance for patterned films. The N‐(pyridine‐2‐ylmethyl)alkyl‐1‐amine ligands and their complexes [CuIICl2(L)] (1), [CuIICl2(L)] (2), [CuIICl2(L)] (3), [CuIIBr2(L)] (4), [CuIIBr2(L)] (5), and [CuIIBr2(L)] (6) were synthesized, isolated, and characterized by means of mass spectrometry, IR and NMR spectroscopies, and elemental analysis. Complexes 1, 2, 3, and 6 had their molecular structure solved by X‐ray diffraction methods, which showed that the local geometry around the metal center is distorted square planar. With the aim of using these species as precursors for redox‐responsive films, an assessment of their electrochemical properties involved cyclic voltammetry in different solvents, with different supporting electrolytes and scan rates. Density functional theory calculations of relevant species in bulk and at interfaces were used to evaluate their electronic structure and dipole moments. The morphology and order of the resulting films at the air/water interface were studied by isothermal compression and Brewster angle microscopy. Biphasic patterned Langmuir films were observed for all complexes except 3 and 6, and dependence on the chain length and the nature of the halogen coligand determine the characteristics of the isotherms and their intricate topology. Complexes 3 and 6, which have shorter chain lengths, failed to exhibit organization. These results exemplify the first comprehensive study of the behavior of single‐tail metallosurfactants, which are likely to lead to high‐end technological applications based on their patterned films.
The ability to survive mitosis in the presence of microtubule poisons differs significantly between human nontransformed (RPE‐1) and cancer (U2OS, HeLa) cells
Authors: Brito Daniela A. , Rieder Conly L.
Published: September 2008

We used live cell imaging to compare the fate of human nontransformed (RPE‐1) and cancer (HeLa, U2OS) cells as they entered mitosis in nocodazole or taxol. In the same field, and in either drug, a cell in all lines could die in mitosis, exit mitosis and die within 10 h, or exit mitosis and survive ≥10 h. Relative to RPE‐1 cells, significantly fewer HeLa or U2OS cells survived mitosis or remained viable after mitosis: in nocodazole concentrations that inhibit spindle microtubule assembly, or in 500 nM taxol, 30% and 27% of RPE‐1 cells, respectively, died in or within 10 h of exiting mitosis while 90% and 49% of U2OS and 78% and 81% of HeLa died. This was even true for clinically relevant taxol concentrations (5 nM) which killed 93% and 46%, respectively, of HeLa and U2OS cells in mitosis or within 10 h of escaping mitosis, compared to 1% of RPE‐1 cells. Together these data imply that studies using HeLa or U2OS cells, harvested after a prolonged block in mitosis with nocodazole or taxol, are significantly contaminated with dead or dying cells. We also found that the relationship between the duration of mitosis and survival is drug and cell type specific and that lethality is related to the cell type and drug used to prevent satisfaction of the kinetochore attachment checkpoint. Finally, work with a pan‐caspase inhibitor suggests that the primary apoptotic pathway triggered by nocodazole during mitosis in RPE‐1 cells is not active in U2OS cells. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.
New DNA Polymerase IIIC Inhibitors: 3‐Subtituted Anilinouracils with Potent Antibacterial Activity in vitro and in vivo
Authors: Svenstrup Niels , Ehlert Kerstin , Ladel Christoph , Kuhl Alexander , Häbich Dieter
Published: September 2008

The development of resistance has rendered several antibiotics clinically ineffective, and there is an urgent medical need for potent and safe antibacterials with a novel and valid mode of action. To avoid cross‐resistance, they should preferably inhibit targets that are not addressed by established antibiotics. In this respect, 6‐anilinouracils represent a promising lead structure. They target the Gram‐positive DNA polymerase IIIC, a target that is associated with a bactericidal mode of action. Moreover, they have no cross‐resistance to marketed antibiotics. This paper describes the synthesis and biological characterization of structurally novel anilinouracils, some of which display potent in vivo efficacy in murine models of bacterial septicemia.
Decreasing disparity in liver transplantation among white and Asian patients with hepatocellular carcinoma
Authors: Robbins Anthony S. , Daily Michael F. , Aoki Christopher A. , Chen Moon S. , Troppmann Christoph , Perez Richard V.
Published: September 2008

BACKGROUND.

A preliminary study using national cancer surveillance data from 1998 through 2002 suggested that there were significant differences between non‐Hispanic whites (‘whites’) and Asian/Pacific Islanders (APIs) in the use of liver transplantation as a treatment for hepatocellular carcinoma (HCC).

METHODS.

The objective of the current study was to examine whether differences in liver transplantation between whites and APIs with HCC were changing over time. By using a population‐based, statewide cancer registry, data were obtained on all HCC cases diagnosed in California between 1998 and 2005, and the study was limited to white and API patients with nonmetastatic HCC who had tumors that measured ≤5 cm in greatest dimension (n = 1728 patients).

RESULTS.

From 1998 through 2003 (n = 1051 patients), the odds of undergoing liver transplantation were 2.56 times greater for white patients than for API patients (95% confidence interval [CI], 1.72–3.80 times higher), even after adjusting for age, sex, marital status, year of diagnosis, TNM stage, and tumor grade. In contrast, during 2004 and 2005 (n = 677 patients), there were no significant differences in the odds of undergoing liver transplantation. Between 2002 and 2004, changes in liver transplantation policy assigned priority points to patients with HCC (initially to stage I and II, then to stage II only). After the policy changes, API patients with HCC experienced a significant increase in stage II diagnoses, whereas white patients did not.

CONCLUSIONS.

In California, there was a large and significant disparity in the rate of liver transplantation among white and API patients with HCC from 1998 through 2003 but not during 2004 and 2005. Changes in liver transplantation policy from 2002 through 2004 may have played a role in decreasing this difference. Cancer 2008. © 2008 American Cancer Society.
Expression of neuronal nicotinic acetylcholine receptor subunit mRNAs in rat hippocampal GABAergic interneurons
Authors: Son Jong‐Hyun , Winzer‐Serhan Ursula H.
Published: September 2008

Hippocampal inhibitory interneurons are a diverse population of cells widely scattered in the hippocampus, where they regulate hippocampal circuit activity. The hippocampus receives cholinergic projections from the basal forebrain, and functional studies have suggested the presence of different subtypes of nicotinic acetylcholine receptors (AChRs) on γ‐aminobutyric acid (GABA)ergic interneurons. Single‐cell polymerase chain reaction analysis had confirmed that several nAChR subunit mRNAs are co‐expressed with glutamate decarboxylase 67 (GAD67), the marker for GABAergic interneurons. In this anatomical study, we systematically investigated the co‐expression of GAD67 with different nAChR subunits by using double in situ hybridization with a digoxigenin‐labeled GAD67 probe and35S‐labeled probes for nAChR subunits (α2, α3, α4, α5, α6, α7, β2, β3, and β4). The results revealed that most GAD67‐positive interneurons expressed β2, and 67 % also expressed α7 mRNA. In contrast, mRNA expression of other subunits was limited; only 13 % of GAD67‐positive neurons co‐expressed α4, and less than 10% expressed transcripts for α2, α3, α5, or β4. Most GAD67/α2 co‐expression was located in CA1/CA3 stratum oriens, and GAD67/α5 co‐expression was predominantly detected in CA1/CA3 stratum radiatum/lacunosum moleculare and the dentate gyrus. Expression of α6 and β3 mRNAs was rarely detected in the hippocampus, and mRNAs were not co‐expressed with GAD67. These findings suggest that the majority of nicotinic responses in GABAergic interneurons should be mediated by a homomeric α7 or heteromeric α7*‐containing nAChRs. Other possible combinations such as α2β2*, α4β2*, or α5β2* heteromeric nAChRs could contribute to functional nicotinic response in subsets of GABAergic interneurons but overall would have a minor role. J. Comp. Neurol. 511:286–299, 2008. © 2008 Wiley‐Liss, Inc.
Pleiotropic function of FGF‐4: Its role in development and stem cells
Authors: Kosaka Nobuyoshi , Sakamoto Hiromi , Terada Masaaki , Ochiya Takahiro
Published: September 2008

Fibroblast growth factors (FGFs) were initially recognized as fibroblast‐specific growth factor, and it is now apparent that these growth factors regulate multiple biological functions. The diversity of FGFs function is paralleled by the emerging diversity of interactions between FGF ligands and their receptors. FGF‐4 is a member of the FGF superfamily and is a mitogen exhibiting strong action on numerous different cell types. It plays a role in various stages of development and morphogenesis, as well as in a variety of biological processes. Recent studies reveal the molecular mechanisms of FGF‐4 gene regulation in mammalian cells, which is involved in the developmental process. Furthermore, FGF‐4 also acts on the regulation of proliferation and differentiation in embryonic stem cells and tissue stem cells. In this review, we focus on the diverse biological functions of FGF‐4 in the developmental process and also discuss its putative roles in stem cell biology. Developmental Dynamics 238:265–276, 2009. © 2008 Wiley‐Liss, Inc.
Hypoxia controls CD4+CD25+ regulatory T‐cell homeostasis via hypoxia‐inducible factor‐1α
Authors: Ben‐Shoshan Jeremy , Maysel‐Auslender Sophia , Mor Adi , Keren Gad , George Jacob
Published: September 2008

Recent data suggest that hypoxia and its principal molecular signature HIF‐1 (hypoxia‐inducing factor‐1) may tune down inflammation by dictating anti‐inflammatory programs. We tested the effects of hypoxia and HIF‐1α on the homeostasis of naturally occurring regulatory T cells (Treg) and their transcriptional activator Foxp3. Hypoxia induced a time‐dependent increase in HIF‐1α in mouse and human T cells. Hypoxia upregulated the expression of Foxp3 in Jurkat T cells, human and murine mononuclear cells. The effects of hypoxia on Foxp3 expression were HIF‐1α‐dependent as they were abolished upon transfection with short‐interfering RNAs for HIF‐1α and promoted by HIF‐1α overexpression. Hypoxia increased the potency of Treg, as hypoxic CD4+CD25+ lymphocytes were more effective than normoxic cells in suppressing the proliferation of CD4+CD25− effectors. In vivo expression of HIF‐1α achieved by hydrodynamic injection of the respective naked DNA similarly induced an increase in Foxp3 expression and an increase in the number of functionally active Foxp3+CD4+CD25+ Treg. Thus, hypoxia dictates an anti‐inflammatory program by driving expression of HIF‐1α that acts to increase the number and suppressive properties of naturally occurring CD4+CD25+ Treg.
Insights into Langerhans cell function from Langerhans cell ablation models
Authors: Kaplan Daniel H. , Kissenpfennig Adrien , Clausen Björn E.
Published: September 2008

Langerhans cells (LC) are the principal dendritic cell (DC) population in the epidermis of the skin. Owing to their prominent position at the environmental barrier, LC have long been considered to be prototypic sentinel DC. More recently, the precise role of LC in the initiation and control of cutaneous immune responses has become debatable. To elucidate their contribution to immune regulation in the skin, our laboratories have generated genetically modified mice in which LC can be followed in situ by expression of enhanced green fluorescent protein and can be either inducibly or constitutively depleted in vivo. This review highlights the similarities and differences between these mouse models, discusses the discovery and functional significance of Langerin+ dermal DC, and examines some recent data that help to shed light on LC function.
Langerhans cells and viral immunity
Authors: Cunningham Anthony L. , Carbone Francis , Geijtenbeek Teunis B. H.
Published: September 2008

Langerhans cells (LC) are a unique dendritic cell subset that are located in mucosal stratified squamous epithelium and skin epidermis. Their location is ideally suited for their function as antigen presenting cells that capture invading viruses and induce anti‐viral immunity. However, it is becoming evident that the interaction between LC and viruses can result in different responses, depending on the virus and the receptors involved. Here we will discuss the recent data on the similarities and differences in roles of LC in viral immunity to and infection with HIV, herpes simplex and varicella–zoster virus. Although all three viruses interact with LC during initial infection, the effects can be quite different, reflecting differences in biology and pathogenesis.
E‐box protein E2‐2 is a crucial regulator of plasmacytoid DC development
Authors: Esashi Eiji , Liu Yong‐Jun
Published: September 2008

DC play central roles in priming both innate and adaptive immune responses. Multiple DC subsets have been identified on the basis of their phenotype and function. Plasmacytoid DC (pDC) are professional IFN‐producing cells that play an essential role in anti‐viral immunity. A series of recent studies demonstrates that the regulation of pDC development is different from other types of DC. In this issue of the European Journal of Immunology, new insight is provided into how human pDC development is regulated by various transcription factors, in particular by the Ets family protein Spi‐B and E‐box protein E2‐2.
Cover Picture: Science is multidimensional and very complex. – Eur. J. Immunol. 9/2008
Authors: Minguet Susana , Dopfer Elaine P. , Pollmer Careen , Freudenberg Marina A. , Galanos Chris , Reth Michael , Huber Michael , Schamel Wolfgang W.
Published: September 2008

The cover image was specifically designed based on an illustration provided by Minguet et al., the authors of Enhanced B‐cell activation mediated by TLR4 and BCR crosstalk (pp. 2475–2487). The authors demonstrate that while simultaneous stimulation of TLR4 and BCR activates B cells in an additive manner, antigen‐coupled LPS activates B cells synergistically. The authors proposed this image based on the idea that “science is multidimensional and will never be finished or completely understood”. The
illustration was further enhanced with images taken from various studies published in this issue of the European Journal of Immunology.
Synthesis, Resolution, and Application of Cyclobutyl‐ and Adamantyl‐Quinazolinap Ligands
Authors: Fekner Tomasz , Müller‐Bunz Helge , Guiry Patrick J.
Published: September 2008

An expedient, seven‐step synthesis of two new members of the Quinazolinap ligand family, 2‐cyclobutyl‐ and 2‐(1‐adamantyl)‐Quinazolinaps, has been developed. The racemic ligands have been efficiently resolved by fractional crystallization of their diastereomeric palladacycle complexes. The enantioenriched ligands provide good levels of enantioselection (ee's up to 89 %) in a prototypical PdII‐catalyzed allylic alkylation reaction. 2‐Cyclobutyl‐Quinazolinap has been further functionalized at the 2‐position via metalation with a superbase followed by reaction with a range of electrophiles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Some characteristics of oogenesis in the female Turkish hamster subjected to modified environments
Authors: Jagiello Georgiana M. , Fang Jye‐Siung , Hembree Wylie C. , Ducayen‐Knowles Mercedes B.
Published: September 2008

The hibernating female Turkish hamster (Mesocricetus brandti) was utilized for a study of possible in vivo effects of cold on oocyte maturation. Such a physiologic model offered an opportunity to analyze the ability of oocytes exposed to prolonged periods of reduced core temperature and/or light to subsequently mature to Metaphase II. Detailed observations of core temperatures, torpor/arousal, serum estradiol, and ovarian histology were made. An average incidence of 37.7% binuclearity was found in the germinal vesicle, metaphase I and II occytes of this species. Maturation to Metaphase II of total chromosome complements did not vary significantly in the experimental groups compared with the control, but aneuploidy was detected in the oocytes of animals exposed to reduced temperature or light. An effect of in vivo reduced core temperatures on oocyte chromosome complements validates many of the published in vitro studies with temperature reduction. The model presents an excellent physiologic system for perturbing and analyzing many aspects of mammalian oocyte development.
Time diversity: A solution for 900 MHz trunking systems
Authors: Velasco Jaime Bustillo , Pliego Miguel Rodriguez‐Palanca
Published: September 2008

The interest into PMR trunking systems is due to the increase of spectral efficiency that can be obtained sharing frequencies between more users. The British DTI protocol specification MPT 1327, intended to be used on this kind of systems, has been recently released, and it is now being accepted as a standard on some european countries.

This protocol is based on the MPT 1317 signaling format specification, designed to work at frequencies of 50–500 MHz, and for this reason, it presents some problems when working with RF frequencies of 900 MHz and moving vehicles.

The problem comes out from the low bit rate used (1200 bit/s, and the block length (64 bit). If we consider a vehicle that is running at a speed of 100 km/h, we will have a mean of two fades into each information block, while the code (BCH 63, 48) has only a good capacity of error detection/correction for single error bursts.

The paper, proposes a solution to this problem, that consists on raising the bit rate to 2400 bit/s, using indirect PSK modulation, with coherect demodulation, instead of FFSK with incoherent demodulation, as it is usual. With this method, we obtain the same BER. Added to this bit rate increase, that allows us to lower the mean number of fades into each block to one, we apply time diversity [2], sending two times each block into the forward control channel, and sending also two times each return control channel or traffic channel message. This diversity system can be implemented bitwise, using channel information to select the most likely value of each bit [4], or block to block, using the error detection capabilities of the code [6].

The system has been simulated for 900 MHz and 100 km/h, and measured into a laboratory test setup, using a fading simulator.

The results show that proposed method gives the same quality working at 900 MHz that the classic approach working at 150 MHz, showing an improvement of 6 dB over the standard approach working at 900 MHz.
Improved performance in a local area network integrating voice and data
Authors: Marini Michele
Published: September 2008

The performances of a Local Area Network (LAN) integrating voice and data are improved changing the 2 register management in the Reserved Virtual Time CSMA protocol adopted for vocal packets, and using a new exponential backoff algorithm for voice, that introduces a maximum backoff time equal to the vocal packet size involved in the retransmission. In addition, a dynamic priority assignment is used between voice and data, that permits to consider a finite number of buffers for data packets.

Simulation results are presented to evaluate LAN performances.
Feasibility of 3D integration
Authors: Sasaki Nohuo
Published: September 2008

Laser‐recrystatiization is the best way to fabricate SOI for 3D IC's. Low source‐to‐drain leakage current as small as 3fA/μm is obtained for the SOI MOSFET's with the simple unseeded recrystallization containing grain boundaries. For the 3D CMOS static RAM's, packing density ratio to the conventional 2D CMOS static RAM's is given by 2n/3. and process steps ratio is given by n/3, where n is the device stacking number. The yield and cost OF 3D 1C's are analyzed. The cost of 3D IC's is less than that of 2D IC's at least by a factor of two for static CMOS RAM's, if the yield is determined by such random defects as accidental fine particles. The reason of this is that 3D 1C's do not require some process steps, which are necessary for 2D 1C's to differentiate between n‐ and p‐channel MOSFET's in a single device level.
Modeling of electron beam scattering in high resolution lithography for the fabrication of X‐Ray masks
Authors: Gentili M. , Lucchesini A. , Scopa L. , Lugli P. , Paoletti A. , Messina G. , Santangelo S. , Tucciarone A.
Published: September 2008

A single‐layer resist process for X‐ray master mask fabrication by electron beam lithography is theoretically and experimentally investigated. In the mask fabrication process boron nitride membranes are utilized and final absorber structures are obtained by Au electroplating after e‐beam patterning at different primary beam energies, on a single PMMA layer of 10000 A. The e‐beam energies experimentally utilized are 20 and 30 keV. Detailed Monte Carlo analysis of the rnultilayer structure is carried out at 10, 20, 30 and 40 keV, the corresponding proximity function calculated and compared to experiment. It is found that an important source of backscattering is constituted by the thin metal layer as plating base, while the ultimate limit for resolution seems to be determined by forward scattering. Finally, it is demonstrated that by proper selection of the e‐beam energy it is possible to obtain high contrast absorbers down to 0.3 μm lines and spaces.
Charge trapping and interface trap generation in thin nitrided silicon dioxide films for VLSI
Authors: Severi Maurizio , Irnpronta Maurizio , Negrini Paolo , Vassura Stefano
Published: September 2008

This paper presents an extensive review of our work on the charge trapping characterization of thin (10–30 nm) nitrided SiO2 films. Trapping of both electrons and holes, along with generation of interface traps, was studied as a function of the process conditions using the avalanche injection technique. Electron trap generation and time dependent breakdown were also investigated by injecting electrons at high fields. Our results show that, due to the high electron trapping induced by nitridation, interface‐trap generation under electron injection remains higher than that in the reference oxide for all the nitridation conditions experienced. Nitridation also reduces the maximum charge to breakdown, QBD However, after a postnitridation annealing at 1000°C, the electron traps in the oxide nitrided at 900°C can be reduced to such a level that interface trap generation becomes lower than that in the reference oxide. QBD is also greatly improved. Furthermore, hole trapping and interface‐state generation under hole avalanche injection can be reduced by nitridation itself provided it is carried out at relatively high temperatures (>900°C) and for relatively long times (>15 min.). It is thus found that with a careful optimization of the nitridation and postnitridation treatment conditions, a more reliable gate dielectric can be obtained.
Gate oxide thinning as related to doping effects
Authors: Bellutti P. , Claeys C. , Debusschere I. , Corticelli F. , Govoni D.
Published: September 2008

Gate oxide thinning induced by selective oxidation process has been studied. Tests on samples having both high and low boron doping concentration after wet oxidation of 9 and 50 h, have shown that gate thinning phenomenon is related to substrate doping concentration for p‐type silicon. The chemical resistivity of the nitride or oxynitride layer, which is assumed to be responsible for the gate thinning, has been tested and it also results to be related to the substrate boron concentration. A possible interpretation of the occurrence of the doping effect is given.
Interconnections in application specific VLSI
Authors: Pramanik Dipankar , Spadini Gianpaolo
Published: September 2008

Process technologies developed for the fabrication of Application Specific Integrated Circuits must satisfy some unusual demands imposed by design automation and by fast turn around manufacturing.

In this paper we will discuss some of the problems that constrain the selection of a suitable interconnection technology for ASIC's VLSI.

Design automation (a tool necessary for ASIC designs) demands a simple set of design rules and very large current carrying capability metal Lines. On the other hand fast turnaround manufacturing requires the use of simple and proven technologies so that the product will be easily manufacturable, possibly in more than one foundry.

Some of the available technologies to implement mutilevel interconnections will be reviewed and the one chosen by VLSI Technology for their 1 μm ASIC process will be briefly described.
Multi‐level metallization: Future prospects
Authors: Crannernan E. H. A.
Published: September 2008

Chemical vapour deposition of tungsten and aluminium films is discussed as alternative to sputtering of aluminium in future multilevel metallization schemes. Because CVD generally offers a very good step coverage it is an attractive technology for filling sub‐micron via's and contact holes. In this paper three CVD‐based metallization scenaria are discussed. The first one is filling of via's with selective (CVD) W followed by sputtering of A1 on the planarized surface. Secondly, blanket deposition of W is discussed and thirdly blanket deposition of (CVD) aluminium.

The many problems plaguing selective W such as selectivity loss, encroachment, creep up, etc. are discussed. Selectivity loss is shown to be linked with the presence of reaction by‐products.

Aluminium CVD, carried out in a novel type multi‐chamber reactor system is presented as a potentially attractive alternative to tungsten.
Performance analysis of a new network access flow control method in computer communication networks
Authors: Uhl Tadeusz , Müller‐Clostermann Bruno
Published: September 2008

A new flow control rule for the network access level is introduced and its performance is investigated., The rule is based on measurements of the temporal changes of the traffic intensity. The admission of arriving local packets to a node is regulated dependent on the variations of local and transit traffic and the load in the neighbouring nodes. The objective of the new rule is to maximize the power (defined as the ratio of throughput and delay) for transit packets under consideration of a threshold value for local packets. This threshold serves to limit the unfairness for the local packets. A model for the node has been developed and evaluated by approximate analytical techniques. The performance results obtained enable the construction of a very efficient algorithm for the new flow control rule.
A mathematical model for the evaluation of spurious response interference in a superheterodyne receiver
Authors: De Franco Giuseppe
Published: September 2008

The Spurious Response phenomenon in a typical superheterodyne receiver, caused by one or more interfering transmitters, is analyzed. Particularly, a suitable model of superheterodyne receiver and the algorithm for the interference level computation is presented. The new approach to the Electromagnetic Interference (EMI) problem, above mentioned, is given by the algorithm for the evaluation of the spurious response rejection parameter: βst. In this way it is possible to evaluate the interference level of a victim receiver without using complex measurement procedures.
BICMOS technologies
Authors: Roche Marcel
Published: September 2008

This paper describes why and how BICMOS technology will be one of the top three technology stars of the next decade. After a presentation of the specific advantages and drawback5 of Bipolar and CMOS technologies, the exploitation of characteristics of both components. realized on the same chip, is discussed. A brief description of BICMOS process architectures is given and the performances currently achieved are presented. Finally present and future applicarions are considered for Memories, Gate arrays, Telecommunications IC's, Analog IC's etc.
Simulation of silicon semiconductor processing
Authors: Pichler Peter , Ryssel Heiner
Published: September 2008

In VLSI development process simulation is needed to understand the interaction between successive process steps and to give input data for device simulation. The goal of this paper is to sketch the present state of process simulation and to give the reader a feeling of the difficulties but also of what can be gained by using such tools. Due to their importance, most attention will be given to the simulation of ion implantation, diffusion, and oxidation.
Three‐dimensional simulation of VLSI structures
Authors: Ciampolini Paolo , Pierantoni Anna , Rudan Massimo , Baccarani Giorgio
Published: September 2008

Recent VLSI technologies allow for increasingly small and complex devices, this calling for three‐dimensional device simulation. In this paper, a 3D simulator is presented: the most relevant problems in its development were found in geometry management and computational efficiency. The adoption of suitable linear solvers enhances the overall computational performance, wihile the prism‐based discretization scheme greatly simplifies most of the geometry‐related algorithms, as demonstrated by the proposed examples, in which complex EPROM‐cell structures are easily handled.
Carrier transport modelling in the inversion layer of submicron semiconductor devices
Authors: Sala Cristiano , Magnus Wim , De Meyer Kristin
Published: September 2008

State of‐the‐art semiconductor devices are characterized nowadays by dimensions which are well into the submicron range. As a result, the physical models describing carrier transport in these devices need to be modified to be able to account for phenomena such as hot electron or quantum effects, which are intrinsic to this size regime. In this paper we present a formalism which, starting from a self‐consistent solution of Schrodinger's and Poisson's equations in terms. of semi‐analytical wavefunctions, leads to a system of quantum balance equations. It is expected that, as well as supplying a more accurate description of the abovementioned effects, the resulting models will not be computationally expensive and therefore amenable to implementation in a device simulator.
Modeling and control of VLSI circuit yield
Authors: Traversini Renzo , Lisio Aurelio De , Barbuscia Giuseppe
Published: September 2008

Due to the increasingly critical role played by yield performance in VLSI device market competition, the development of yield models for product design and production control and improvement is nowadays a very active field of research and development. The overall manufacturing yield can be decomposed in several yield contributions related to different phases of the production process or to different degradation mechanisms. Defect yield losses are related to local device deformations usually due to spot defects and particles. Parametric yield losses are linked 10 global device deformations related to limited control on process conditions. In the paper several state‐of‐the‐art modeling approaches to these yield terms will be presented. Moreover, the issue of yield control and monitoring for each of these loss contributions will be reviewed.
An extended majority‐carrier approach for the DC and small‐signal simulation of ion‐implanted mesfets on compensated and p‐type substrates
Authors: Ghione Giovanni , Benvenuti Augusto , Pirola Marco , Naldi Carlo
Published: September 2008

The paper proposes an extended majority‐carrier dc and ac two‐dimensional physical model for the simulation of ion‐implanted MESFETs on semi‐insulating andp‐type substrates, including the static and dynamic treatment of partly ionized impurity levels. The numerical implementation of the model is discussed, and it is shown how numerical ill‐conditioning problems suggest the implementation of a full two‐carrier model for the simulation of devices with un‐depletedp‐type substrates. A discussion is presented on the interpretation of rate‐dependent anomalies related to the frequency behaviour of the small‐signal parameters, and the importance of simulating a backgate electrode is stressed. Finally, comparisons are given with ac and dc data measured onp‐buried layer Siemens devices.
Modelling of pseudomorphic AlGaAs/GaInAs/AlGaAs layers using selfconsistent approach
Authors: Alamkan Jocelyn , Happy Henri , Cordier Yvon , Cappy Alain
Published: September 2008

A study of pseudomorphic layers properties using a selfconsistent approach is presented. The strain effects are taken into account. Sheet carrier density and capacitance voltage characteristics are related to technological layer parameters. Simple expressions of subband energy well suited for CAD are then deduced.
AlGaAs/GaAs: High electron mobility transistor simulations with PRISM
Authors: Jansen Philippe , Maene N. , Raedt Walter De , Naten S. , Stubbe D. , Schoenmaker Wim , Van Rossum M. , De Meyer K.
Published: September 2008

The two‐dimensional device simulator PRISM (PRogram for Investigating Semiconductor Models) [1], which is a general purpose device simulator, has been adapted to simulate III‐V heterojunction FET's [2]. PRISM can now simulate silicon devices (as MOSFET's, bipolar transistors, SO1 structures, etc.,), GaAs MESFET's, Schottky diodes and AIGaAsl GaAs HEMT's.

The program makes use of the finite element method to solve the Poisson equation and the finite boxes method to solve the continuity equations for electrons and holes. There is also an ongoing effort to implement the heat transport equation [3]. The finite element method has rarely been used in HEMT‐simulations. The main advantages of this method are the flexibility in defining sloped device contours and the possibilic to refine the mesh only locally, so that the number of nodes only increases moderately, as opposed to the situation with finite difference simulators. This advantage is very usefull for HEMT's were the thin AlGaAs/GaAs heterojunction region ( 40 nm) has to be simulated accurately compared to the bulk region.

Simulations of AlGaAslGaAs HEMT's have been performed, and comparisons with measurements on HEMT's [4] processed in IMEC have been made. The simulated I‐V characteristics and the transconductance curves agree very well. Also sheet concentrations and band diagrams can be extracted from the simulation results.
Monte carlo particle study of transport along the hetero interface in a field‐effect transistor
Authors: Moglestue Canute
Published: September 2008

An inverse heterojunction field‐effect transistor has been simulated by means of the Monte Carlo particle model, which represents a self‐consistent solution of Boltzmann's transport and Poisson's field equation. It was found that a quantum well forms between the source and the drain, which, only at the drain end of gate, gets sufficiently narrow that the lowest subband gets lifted more than the average thermal energy during practical operating conditions of the device. Nowhere is the intersubband separation large enough that multiple subband transport need to be considered. This represents a considerable saving in computer time as the scattering rates can be stored in tables which reside in their entirity in the central memory.

The simulated device was found to be a Gunn oscillator with a frequency of 110 GHz. The temporal evolution of the Gunn domains from nucleation to absorption in the drain has been studied.
Physical models for heterostructure FET simulation
Authors: Lugli Paolo , Neviani Andrea , Saraniti Marco
Published: September 2008

Field effect transistors (FET) based on heterostructures between III‐V binary and ternary compounds have been demonstrated as outstanding semiconductor devices for microwave applications. This paper will present a critical discussion of the physical models that are used to study the prototype of heterostructure devices, that is the High Electron Mobility Transistor (HEMT). The main technological features involved in the fabrication of HEMT are outlined and their incorporation into theoretical models discussed.
Analysis of the effect of irregularities on the electrodes of the calculable cross‐capacitor
Authors: Pogliano Umberto
Published: September 2008

A sensitivity function of the cross‐capacitance to the orthogonal displacements is. introduced to analyze the capacitance errors due to surface irregularities on the electrodes of a Lampard‐Thompson calculable cross‐capacitor.

A numerical evaluation of the sensitivity function far from the terminal guard electrodes, which defines the active length of the capacitor, has been done.

The method allows the evaluation of the errors in real cases, where the surface is not the exactly cylindrical and it can be a possible approach to the study of the two regions near the terminal guard electrodes, where the electrical field is strongly distorted, in order to compute corrective terms or to establish optimum criteria for the shape of these electrodes.
Simplified crosstalk measurements in medium length polarization maintaining fibers
Authors: Galtarossa Andrea , Pavan Antonio , Someda Carlo G. , Zanineilo Ruggiero , Srl. Saifo
Published: September 2008

A method has been recently proposed by Sasaoka and Tanaka for rapid crosstalk measurements, and demonstrated for short (10 m) polarization maintaining (PM) fibers. We introduce further simplification and successfully apply the method to medium‐length (100 m) fibers, e.g. for measuring crosstalk vs. fiber length. An accuracy of the order of 0.5 dB is easily achieved when measuring crosstalk around ‐ 30 dB.
A flexible FFT algorithm to process serial data signals using personal computer
Authors: Clemente Fabrizio , Cesarelli Mario , Bracale Marcello
Published: September 2008

The aim of the paper is to demonstrate the possibility of using Personal Computer PC‐DOS (or generally MS‐DOS) for real time (or quasi real time) signal processing of serial data adding a simple A/D conversion card and the mathematical co‐processor XXX87.

We have realized an assembly written FFT routine derived from a radix‐4 algorithm by Morris (1979). This algorithm is an autogenerated algorithm. This means that it is modified by another running off‐line algorithm according to the number of FFT points. The program is organized as subroutine to be called by high level language in different procedures.

This approach reduces the computational time which is particularly useful when many Fourier transforms on different data array are required.

Here reported are two biomedical applications of the routine for the spectral analysis of Doppler ultrasound velocimetry and for the surface electromiography (E.M.G.).
Diffraction of plane waves by a two‐part metal‐backed thin dielectric plane
Authors: Buyukaksoy Alinur , Erdoan Eren , Uzgoren Gökhan
Published: September 2008

Diffraction of a H,‐polarized plane wave by the discontinuties occurring in the material properties as well as in the thicknesses of a thin dielectric layer with a perfectly conducting backing is investigated. The effect of the dielectrics are simulated by second order generalized impedance boundary conditions which allow the structure to be treated as an infinitely thin two‐part plane.

Then the solution is accomplished by the standard Wiener‐Hopf technique.
From R&D laboratories: Design and realization by MCVD of optical fibres with zero dispersion wavelength around 1550 nm
Authors: Gnazzo Angelantonio , Modone Eros , Cognolato Livio , Cocito Giuseppe
Published: September 2008

Parameters of optical fibres with zero dispersion at 1550 nm have been designed.

In order to realize the critical core radius of 2.16 μm, some adjustments in pressurized MCVD process have been needed. A strict control of the process parameters during deposition, collapse and etching cycles allows to achieve the dispersion‐shifted fibre structure by MCVD as well.
Evolution of wireless information networks
Authors: Goodman David J.
Published: September 2008

Consumer and business demands for cellular mobile telephones and residential cordless phones are growing rapidly throughout the world. Both are relatively new and still function with their original, first generation technologies. In response to various pressures second generation systems and services are scheduled for introduction over the next three years. Meanwhile researches are formulating a vision of the third generation, when cordless, cellular, and other wireless networks will merge in a unified means of wireless access to advanced information services.

This paper traces the evolution of wireless information networks by examining goals, network architecture, transmission technologies, and control channels. In each instance, we describe, in a general way, first generation systems. We then discuss details of four different second generation systems: Pan‐European Digital Cellular (GSM), North American Digital Cellular (IS‐54), Second Generation Cordless Telecommunications (CT2), and Digital European Cordless Telecommunications (DECT). Finally, we provide a glimpse into the future by presenting work in progress on third generation technology, based on packet transmission and switching.
Telecommunication project overview: Introduction to the seminar
Authors: Roveri Aldo
Published: September 2008

The framework of the Telecommunication Project is firstly considered, by a snapshot on the evolution of public telecommunication networks towards broadband capabilities. Then, the objectives and the activities of the Project are illustred. Finally the papers of the Seminar are shortly presented.
Access and switching techniques for the broadband network
Authors: Dècina Maurizio , Chiarottino Wolmer , Melen Riccardo , Listanti Marco
Published: September 2008

The objectives and the early technical results of a project for the realization of an ATM local network testbed are described. The aim of the project is to realize a flexible experimentation environment to investigate the critical issues related to the introduction of ATM techniques in the network, including signalling, interworking and service support, in addition to the basic switching technology. After presenting the general structure and the solutions adopted for the testbed, the paper describes the main characteristics of its building blocks currently under development: the switching node with its ATM switching fabric and control units, the access network with the related interfaces and protocols, the customer equipment composed by ATM workstations, ATM terminal adaptors and LAN gateways, the interworking unit connecting the testbed to the telephone network. Finally the resources allocation and policing functions adopted are also discussed.
A fast coefficient computation algorithm for transversal and decision‐feedback equalizers
Authors: Buné Paul A. M.
Published: September 2008

Digital transmission is often inflicted by inter‐symbol interference (ISI), which increases the noise sensitivity of the transmission system and eventually causes symbol detection errors on itself. For ISI suppression, a variety of equalizer structures exists, among which transversal and decision‐feedback equalizers are very popular because of their simple primary structure and high degree of flexibility. The paper describes a fast coefficient computation algorithm for these equalizer types starting from a known or estimated channel impulse response, avoiding matrix inversion or iterative coefficient updates by feedback. It has especially been developed for high‐rate TDMA digital mobile radio systems, such as the pan‐European GSM system. Extensive simulations have shown that the performance of the decision‐feedback equalizer (DFE) with this algorithm is fairly comparable with the MLSE/Viterbi equalizer under typical conditions.