bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and Reactions of a Stable 1,2‐Dichloro‐1,2‐diborolane and Aromatic Tetraboranes
Authors: Präsang Carsten , Sahin Yüksel , Hofmann Matthias , Geiseler Gertraud , Massa Werner , Berndt Armin 
Published: May 2004

AbstractThe 1,2‐dichloro‐1,2‐diborolane 1b was isolated in good yield after the reaction of the 1,2‐bis(dimethylamino)‐1,2‐diborolane 2c with BCl3. We prepared 2c from 1,2‐bis(dimethylamino)‐1,2‐dichlorodiborane(4) (3) and TMEDA‐free [1,3‐bis(trimethylsilyl)allyl]lithium (5a·Li), which is accessible by deprotonation of 1,3‐bis(trimethylsilyl)propene (4a) with n‐butyllithium in diethyl ether. Upon its reaction with lithium in THF, the 1‐allyl‐2‐chlorodiborane(4) 6a obtained in the first step undergoes an unprecedented ring closure with 1,2‐migration of a trimethylsilyl substituent to yield the boron‐stabilized carbanion 7a. Reaction of 7a with either chlorotrimethylsilane or HCl gives 2c or 2d, respectively. The latter compound cannot be transformed into an isolable 1,2‐dichloro‐1,2‐diborolane; this observation demonstrates that a trimethylsilyl substituent next to each boron atom is essential for the stability of 1,2‐dichloro‐1,2‐diborolanes. Compound 1b is a versatile starting material, inter alia for the syntheses of the aromatic tetraboranes(6) cis‐11 and trans‐13 and the aromatic tetraborane(4) cis‐12. The isomerization cis‐11 → trans‐13 can be explained on the basis of reactions occurring under the conservation of two‐electron aromaticity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Broadband wireless access based on VSF‐OFCDM and VSCRF‐CDMA and its experiments
Authors: Atarashi Hiroyuki , Maeda Noriyuki , Kishiyama Yoshihisa , Sawahashi Mamoru 
Published: May 2004

AbstractThis paper presents broadband packet wireless access schemes based on variable spreading factor (VSF)‐orthogonal frequency and code division multiplexing (OFCDM) in the downlink and variable spreading and chip repetition factors (VSCRF)‐CDMA in the uplink for the systems beyond IMT‐2000. In our design concept for wireless access in both links, radio parameters such as the spreading factor (SF) are optimally controlled so that the system capacity is maximized according to the cell configuration, channel load and radio channel conditions, based on the tradeoff between efficient suppression of other‐cell interference and the capacity increase in the target cell by exploiting orthogonality in the time and frequency domains. We demonstrate that the peak throughput of greater than 100 Mbps and 20 Mbps is achieved by the implemented base station and mobile station transceivers using the 100‐MHz and 40‐MHz bandwidths in the downlink and uplink respectively. Moreover, the simulation results show the possibility of the peak throughput of approximately 1 Gbps for short‐range area applications using the 100‐MHz bandwidth OFCDM downlink by applying four‐branch multiple input multiple output (MIMO) multiplexing with 16 QAM data modulation and punctured turbo coding. Copyright © 2004 AEI
Efficient packet data service in a spread spectrum OFDM cellular system with 2‐dimensional radio resource allocation
Authors: Novak Robert , Krzymien Witold A. 
Published: May 2004

AbstractThis paper describes and evaluates a novel 2‐dimensional radio resource allocation scheme for high‐throughput cellular packet data access. The proposed system employs spread spectrum orthogonal frequency division multiplexing with adaptive time and frequency allocation (SS‐OFDM‐F/TA) of radio resources. In order to achieve high spectral efficiency of downlink packet transmissions to multiple mobile users, multi‐user diversity available in the multi path fading environment is exploited through the use of adaptive modulation and coding, best serving sector selection, suitable scheduling of packet transmissions and hybrid ARQ employing soft‐packet combining and incremental redundancy. The data throughput, packet delay and fairness of the system with slow and fast best sector selection are examined. A method of grouping disjoint sub‐bands for use in highly frequency‐selective environments is described and evaluated. Packet re‐transmission options including a proposal of several asynchronous re‐transmission algorithms and constraining the maximum re‐transmission interval are also considered. It is demonstrated that the proposed spread spectrum OFDM system is capable of reaching a spectral efficiency of about 1.7 b/sec/Hz/sector with single receive and transmit antennas, and seems to provide a promising solution for high‐throughput best‐effort delay‐tolerant data services in future cellular radio systems. Copyright © 2004 AEI
Spreading sequences for multi‐carrier CDMA systems with nonlinear amplifier
Authors: Saito Masato , Hara Takao , Gima Tetsuhito , Okada Minoru , Yamamoto Heiichi 
Published: May 2004

AbstractMulti‐carrier CDMA (MC‐CDMA) system with a nonlinear amplifier is evaluated in this study. This paper proposes to use the amplifier at the saturation by minimizing the degradation of MC‐CDMA signal due to the nonlinearity. Peak‐to‐average power ratio (PAPR) of MC‐CDMA signals for various spreading sequences is also evaluated for both up‐ and down‐links. As spreading sequences, M‐sequences and their variations are considered in this study. As a result, Golay complementary sequences are suitable for the up‐link and low‐traffic down‐link. Meanwhile, Hadamard sequences provide the minimum PAPR in the down‐link with heavy traffic. Copyright © 2004 AEI
A novel soft handoff technique using STTD for MC‐CDMA in a frequency selective fading channel
Authors: Lee Kyesan , Nakagawa Masao 
Published: May 2004

AbstractAntennas are commonly located in close proximity to each other and there is high correlation between them. In such cases, there exists correlated fading among antennas. The correlated fading degrades the performance of this system. This paper presents an effective soft handoff technique using space time transmitter diversity (STTD) with two base stations for multi‐carrier (MC)‐CDMA to achieve high diversity gain in a wireless broadband channel. The proposed system is a dual step diversity scheme in frequency selective fading channel environments combining the frequency diversity effect achieved by the use of multi‐carriers and the antenna diversity gain afforded by STTD. This is an effective diversity scheme, which improves the signal quality at the receiver by simple processing across two transmit antennas. No feedback from the receiver to the transmitter is required in this system and the computation complexity is low. Copyright © 2004 AEI
Synchronization sensitivity of multicarrier systems
Authors: Steendam Heidi , Moeneclaey Marc 
Published: May 2004

AbstractIn this paper, we give an overview of the sensitivity of a number of multicarrier systems to carrier and clock synchronization errors. A comparison is made between orthogonal frequency division multiplexing/multiple access (OFDM(A)) and two combinations of the orthogonal multicarrier technique and the code‐division multiple access (CDMA) technique, i.e. multicarrier CDMA (MC‐CDMA), where the spreading is accomplished in the frequency domain and multicarrier direct‐sequence CDMA (MC‐DS‐CDMA), where the spreading is done in the time domain. We evaluate the effect of small synchronization errors on the BER performance by deriving simple analytical expressions for the BER degradation that are based upon truncated Taylor series expansions. To allow a fair comparison, all considered systems are able to accommodate the same number of users and each user operates at the same data rate. Under these conditions, we show that all multicarrier systems exhibit the same sensitivity to carrier phase jitter and timing jitter. Further, when the number of carriers is equal to the maximum number of users, the different multicarrier systems also are equally affected by a carrier frequency offset or a clock frequency offset. Copyright © 2004 AEI
A numerical‐variational procedure for laminar flow in curved square ducts
Authors: Hatzikonstantinou P. M. , Sakalis V. D. 
Published: May 2004

AbstractA new numerical method is presented for the solution of the Navier–Stokes and continuity equations governing the internal incompressible flows. The method denoted as the CVP method consists in the numerical solution of these equations in conjunction with three additional variational equations for the continuity, the vorticity and the pressure field, using a non‐staggered grid. The method is used for the study of the characteristics of the laminar fully developed flows in curved square ducts. Numerical results are presented for the effects of the flow parameters like the curvature, the Dean number and the stream pressure gradient on the velocity distributions, the friction factor and the appearance of a pair of vortices in addition to those of the familiar secondary flow. The accuracy of the method is discussed and the results are compared with those obtained by us, using a variation of the velocity–pressure linked equation methods denoted as the PLEM method and the results obtained by other methods. Copyright © 2004 John Wiley & Sons, Ltd.
Large eddy simulation of turbulent concentric annular channel flows
Authors: Liu Nan‐Sheng , Lu Xi‐Yun 
Published: May 2004

AbstractFully developed turbulent concentric annular channel flow has been investigated numerically by use of large eddy simulation (LES) technique coupled with a localized one‐equation dynamic subgrid‐scale (SGS) model. The objective of this study is to deal with the behaviour of turbulent flow near the inner and outer walls of the concentric annular channel and to examine the effectiveness of LES technique for predicting the turbulent flow influenced by the transverse curvature effect. The computations are performed for the Reynolds number Reτ=180, 395 and 640, based on an averaged friction velocity and the annular channel width with the inner and outer cylinder radius being Ri=1 and Ro=2. To validate the present approach, calculated results for turbulent pipe flow and concentric annular channel flow are compared with available experimental data and direct numerical simulation results, which confirms that the present approach can be used to study turbulent concentric annular channel flow satisfactorily. To elucidate turbulence characteristics in the concentric annular channel, some typical quantities, including the resolved velocity, turbulence intensity, turbulent eddy viscosity, SGS kinetic energy, SGS dissipation rate, Reynolds stress budgets, and turbulence structures based on the velocity fluctuations, are analysed. Copyright © 2004 John Wiley & Sons, Ltd.
Dll3 pudgy mutation differentially disrupts dynamic expression of somite genes
Authors: Kusumi Kenro , Mimoto Mizuho S. , Covello Kelly L. , Beddington Rosa S.P. , Krumlauf Robb , Dunwoodie Sally L. 
Published: May 2004

AbstractMutations in the notch ligand delta‐like 3 have been identified in both the pudgy mouse (Dll3pu; Kusumi et al.: Nat Genet 19:274–278, 1998) and the human disorder spondylocostal dysostosis (SCD; Bulman et al.: Nat Genet 24:438–441, 2000), and a targeted mutation has been generated (Dll3neo; Dunwoodie et al.: Development 129:1795–1806, 2002). Vertebral and rib malformations deriving from defects in somitic patterning are key features of these disorders. In the mouse, notch pathway genes such as Lfng, Hes1, Hes7, and Hey2 display dynamic patterns of expression in paraxial mesoderm, cycling in synchrony with somite formation (Aulehla and Johnson: Dev Biol 207:49–61, 1999; Forsberg et al.: Curr Biol 8:1027–1030, 1998; Jouve et al.: Development 127:1421–1429, 2000; McGrew et al.: Curr Biol 8:979–982, 1998; Nakagawa et al.: Dev Biol 216:72–84, 1999). We report here that the Dll3pu mutation has different effects on the expression of cycling (Lfng and Hes7) and stage‐specific genes (Hey3 and Mesp2). This suggests a more complex situation than a single oscillatory mechanism in somitogenesis and provides an explanation for the unique radiological features of the human DLL3‐type of SCD. genesis 39:115–121, 2004. © 2004 Wiley‐Liss, Inc.
Increased cytotoxic potential of microglia from ALS‐transgenic mice
Authors: Weydt Patrick , Yuen Eric C. , Ransom Bruce R. , Möller Thomas 
Published: May 2004

AbstractAmyotrophic lateral sclerosis is a fatal, adult‐onset motor neuron disease. A subset of cases is caused by mutations of superoxide dismutase 1 (SOD1) gene. The mechanisms how the mutations in this ubiquitous enzyme mediate the highly selective motor neuron degeneration, however, remain poorly understood. Recent results from transgenic animal models suggest a “non‐cell autonomous” mechanism; i.e., cells other than neurons play an active role in motor neuron death. To investigate a possible effect of mtSOD1 on microglial cells, we compared primary cultured microglia from mtSOD1‐transgenic mice and nontransgenic litter controls at neonatal (3 days) and adult (60 days) age. We found that mtSOD1 expression increases the production of TNF‐α and attenuates IL‐6‐release by LPS‐activated adult microglia. Neonatal microglia, however, showed no differences. Our findings suggest an increased cytotoxic potential of adult mtSOD1 microglia, which only becomes apparent after microglial activation. © 2004 Wiley‐Liss, Inc.
Resident microglia from adult mice are refractory to nitric oxide‐inducing stimuli due to impaired NOS2 gene expression
Authors: Brannan Courtney A. , Roberts Margo R. 
Published: May 2004

AbstractMicroglia are the immunoregulatory cells of the central nervous system (CNS) and share many characteristics with resident macrophages in extracerebral tissues. Nitric oxide (NO) is secreted by macrophages following induction of the NO synthase gene NOS2 by stimuli elicited during a T‐cell response and/or by microbial products. NO regulates both innate and adaptive immune responses, such as killing intracellular pathogens and inhibiting T‐cell proliferation. Regulation of NO production by microglia, however, is poorly understood. We find that microglia from healthy adult mice produce negligible amounts of NO compared with resident macrophages during restimulation of peptide‐specific CD8 T cells, and therefore cannot block T‐cell proliferation. The impaired NO response extends to exogenous NOS2‐inducing stimuli, including cytokines, CD40 ligation, and lipopolysaccharide. In contrast, microglia produce proinflammatory cytokines in response to these same stimuli, and therefore possess a relatively selective block in NO production. We go on to show that resident microglia fail to produce detectable levels of either the NOS2 enzyme or NOS2 RNA in response to NO‐inducing stimuli. We therefore propose that microglia in the healthy adult brain exist in an “NO‐incompetent” state in which NO production is blocked at the level of NOS2 RNA. The inability of resident microglia in the healthy CNS to produce NO may allow these immunoregulatory cells to modulate immune processes temporally, and may serve to protect the CNS from irreparable damage at the onset of infection or injury. © 2004 Wiley‐Liss, Inc.
Synthesis of Pederic Acid and Related Model Studies
Authors: Breitfelder Steffen , Schuemacher Anne C. , Rölle Thomas , Kikuchi Makoto , Hoffmann Reinhard W. 
Published: May 2004

Abstract{[2‐(Trimethylsilyl)ethoxy]methyl} (SEM)‐protected pederic acid 16 was prepared by deriving the stereogenic center at C(7) from mannitol and those at C(2) and C(3) (mycalamide numbering) from trans‐2,3‐dimethyloxirane. Routes to pederamides involving a late oxygenation at C(7) were explored.
Scanning electron microscopy of the tongue papillae in the pig (Sus scrofa)
Authors: Kumar Suraj , Bate Luis A. 
Published: May 2004

AbstractA clear understanding of the role of different papillae in the pig may permit the development of a more palatable diet, thus, better utilizing anatomical structures and morphological characteristics to enhance health and productivity in this domestic species. The study used ten healthy market‐size, mixed‐breed pigs to properly describe the surface structure of the tongue papillae using standard scanning electron microscopic techniques. Two types of sharp and blunt filiform papillae were identified. Fungiform papillae, located on the lateral side of the tongue, were circular and large with surface taste pores. The majority of oval papillae on the dorsal surface of the tongue contained multidirectional surface grooves and lacked taste pores. The foliate papillae, located principally on the caudal third and lateral part of the tongue, were comprised of four to five leaves and they had additional pseudopapillae. The two vallate papillae, found in the caudal third and dorsum of the tongue, had a well‐defined vallum and pseudopapillae on their surface. At the root of the tongue, two types of conical papillae with or without apex were observed. The entire area covered by conical papillae was deeply occupied by lingual tonsils. The lingual tonsils were scattered with varying sized lymph nodules in the propria mucosa of the conical papillae deep to epithelium. Functionally, the filiform and conical papillae appeared to have a mechanical role whereas fungiform, foliate, and vallate papillae apparently perform a gustatory role in the pig. The tonsillar location at the root of the tongue provides an ideal experimental model for immunohistological and immunological studies on the lymphoid tissue in man. Microsc. Res. Tech. 63:253–258, 2004. © 2004 Wiley‐Liss, Inc.
An EBSP study of isothermally‐annealed cold‐rolled nickel
Authors: Baker I. , Li J. 
Published: May 2004

AbstractScanning electron microscopy and electron backscattered patterns, EBSP, have been employed to reveal both the grain structure and texture of 90% cold‐rolled polycrystalline nickel after 1‐hour anneals at a variety of temperatures. After annealing at either 400° or 500°C, small, cube‐oriented, equi‐axed grains were produced via primary recrystallization. At 600°C, large {124}<211> oriented grains accounted for an increasing proportion of the microstructure, until at 1000°C only large grains (∼600 μm) and a sharp {124}<211> texture were present. Detailed EBSP analyses of the grain boundaries surrounding the large abnormally grown grains observed at 600°C demonstrated that formation of the secondary recrystallization texture was due to migration of high‐mobility, random high‐angle boundaries around grains that had a size advantage, consistent with the Abbruzzese‐Lücke model. Microsc. Res. Tech. 63:289–297, 2004. © 2004 Wiley‐Liss, Inc.
Total mesorectal excision for middle and lower rectal cancer: A single institution experience with 337 consecutive patients
Authors: Piso Pompiliu , Dahlke Marc‐Hendrik , Mirena Petrit , Schmidt Ursula , Aselmann Heiko , Schlitt Hans Juergen , Raab Rudolf , Klempnauer Juergen 
Published: May 2004

AbstractBackground and ObjectivesThere have been reports on improved prognosis after TME for middle and lower rectal cancer. No prospective randomized studies have yet been performed. This is a large single institution series evaluating its own results of TME.MethodsThis retrospective study analyses data of 337 patients with middle and lower rectal cancer, treated with either curative or palliative intention between 1990 and 1998.ResultsOf all patients, 212 had lower rectal and 125 middle rectal carcinomas. The rate of rectal resections with TME was 96%. A total of 223 patients were treated by anterior rectal resection; 92 patients had to undergo abdomino‐perineal resection. Ten patients were operated by a Hartmann resection. Postoperative morbidity was 35% with a leakage rate of 9%. Postoperative mortality was 4%. The rate of local recurrence was 8.6%. The 5‐year survival rate after curative resection was 69.3%. The multivariate analysis outlined the tumor stage as independent prognostic factor.ConclusionsIn our experience, TME is feasible with acceptable postoperative morbidity and low mortality. The local recurrence rate can be decreased to lower than 10%. The almost 70% 5‐year survival rate indicates a clear benefit for the patients. These findings recommend TME as standard procedure for middle and lower rectal cancer. J. Surg. Oncol. 2004;86:115–121. © 2004 Wiley‐Liss, Inc.
Social capital and nonprofit leaders
Authors: King Nancy K. 
Published: May 2004

AbstractThe concept of social capital seems to be a very compatible, useful, and important one for nonprofit organizations. Nonprofits must sustain and enhance the original social capital with which they were formed and broaden it into a variety of key areas. Nonprofits and their leaders must foster social capital in order to recruit and develop board members, raise philanthropic support, develop strategic partnerships, engage in advocacy, enhance community relations, and create a shared strategic vision and mission within the organization and its employees. Nonprofit executives have a pivotal role in carrying out these functions, but they do so through relationships and networks with others. These activities are time‐consuming and demanding, and they require planning.This article provides a focused literature analysis on the concept of social capital as it applies to nonprofit management and leadership. The author views the literature with respect to definitions of social capital and the way nonprofits generate and mobilize social capital in order to achieve organizational goals. The author also cites methods for measuring social capital.
Paediatric malignant tumours of the gastrointestinal tract in the West Midlands, UK, 1957–2000: A large population based survey
Authors: Hameed R. , Parkes Sheila , Davies P. , Morland B. J. 
Published: May 2004

AbstractBackgroundTo investigate the incidence, clinical characteristics and survival of malignant tumours of the gastrointestinal tract in children in the West Midlands in Britain over a 44‐year span time, to identify any change over this period and to compare the data with the world literature.ProcedureRetrospective population based study. Fifty‐seven patients were identified from the records of the West Midlands Regional Children's Tumour Registry. Age‐standardised incidence rates were calculated using the world standardised population method. Statistical tests used were the Log rank test and survival curves were produced using the Kaplan–Meier method.ResultsThe age‐standardised incidence of overall gut tumours during the period 1957–2000 was 1.10/million/year. The age standardised incidence of non‐Hodgkin lymphoma (NHL) was calculated as 0.9/million/year and for adenocarcinoma 0.14/million/year.ConclusionMalignant tumours of the gastrointestinal tract remain rare in children. No changing trends in incidence were observed over the 44‐year period. NHL was the commonest malignancy overall and of the small bowel while equal number of adenocarcinoma and NHL were identified in the large bowel. There was no significant difference in survival between sexes, site and age groups in both NHL and adenocarcinoma. Survival has improved over the last four decades for NHL patients but remains poor for the adenocarcinoma patients. © 2004 Wiley‐Liss, Inc.
Complementary therapies: considerations for diabetes care
Authors: Dunning T 
Published: May 2004

AbstractComplementary therapies (CTs) are receiving increasing attention in mainstream health care. Over 50% of the global population between 25% 30% of people with diabetes use CTs. In addition, health professionals are increasingly incorporating CT into their practice or referring patients to CT practitioners. This paper explores the philosophy underlying CT, gives an overview of the types of therapies used, outlines the reasons people use CTs the risks benefits for people with diabetes. Copyright © 2004 John Wiley & Sons, Ltd.