bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of cellulose derivatives prepared in NaOH/urea aqueous solutions
Authors: Zhou Jinping , Zhang Lina , Deng Qinghai , Wu Xiaojun 
Published: October 2004

AbstractWe successfully synthesized hydroxypropylcellulose (HPC) and methylcellulose (MC) in high yields from cellulose in 6 wt % NaOH/4 wt % urea aqueous solutions at 25 °C. The cellulose derivatives were characterized with NMR, size exclusion chromatography/laser light scattering, gas chromatography (GC), ultraviolet, and solubility measurements in different solvents. According to the results of solution13C NMR and GC, the individual degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the monomer unit) at C‐2 hydroxyl groups was slightly higher than the DS values at C‐3 and C‐6 hydroxyl groups for HPC and MC. In comparison with traditional systems, NaOH/urea aqueous solutions were proved to be a stable and more homogeneous reaction medium for preparing cellulose ether with a more uniform microstructure. The low limits for the average number of moles of the substituent groups per monomer unit and the DS value of water‐soluble HPC were 1.03 and 0.85, respectively. MC (DS = 1.48) had good solubility in both water and organic solvents, and the precipitation point occurred at about 67 °C for a 2% (w/v) aqueous solution. In this way, we could provide a simple, pollution‐free, and homogeneous aqueous solution system for synthesizing cellulose ethers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5911–5920, 2004
Polymers based on benzyl methacrylate: Synthesis via atom transfer radical polymerization, characterization, and thermal stabilities
Authors: Demirelli Kadir , Coskun Mehmet , Kaya Esin 
Published: October 2004

AbstractCopolymerization and homopolymerization of benzyl methacrylate (BMA) and ethyl methacrylate (EMA) by the atom transfer radical polymerization method (ATRP) were performed at 90 °C. ATRP of BMA was also carried out at 80, 100, and 110 °C. The number‐average molecular weight (Mn) and polydispersities decreased with temperature. When BMA units increased in the copolymer system, the Mn values and polydispersities decreased (1.63 < Mw/Mn < 1.13). The homopolymers and poly(BMA‐co‐EMA) were characterized by Fourier transform infrared (FTIR), 1H and 13C NMR, and gel permeation chromatography (GPC) techniques. The compositions of the copolymers were calculated from 1H NMR spectra. For the atom transfer radical copolymerization system, their monomer reactivity ratios were obtained by using the Kelen–Tüdös equation, as r1 = 0.812, r2 = 1.162 (r1 is the monomer reactivity ratio of BMA). The initial decomposition temperatures of the resultant copolymers decrease with an increasing mol fraction of BMA, which indicates that the heat resistance of the copolymer has been improved by decreasing the BMA units. Blends of poly(BMA) and poly(EMA) obtained via the ATRP method have been prepared by casting films from a dichlorormethane solution. The blends have been characterized by differential scanning calorimetry and thermogravimetry. The measurements were comparable with those of copolymers synthesized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5964–5973, 2004
Crystallization behavior and morphology of poly(ethylene‐co‐trimethylene terephthalate)s
Authors: Wu Tzong‐Ming , Lin Yen‐Wen 
Published: October 2004

AbstractThe melt crystallization behaviors and crystalline structures of poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate), and poly(ethylene‐co‐trimethylene terephthalate) (PETT) were investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction at various crystallization temperatures (Tcs). The PETT copolymers were synthesized via the polycondensation of terephthalate with ethylene glycol and trimethylene glycol (TG) in various compositions. The copolymers with 69.0 mol % or more TG or 31.0 mol % or less TG were crystallizable, but the other copolymers containing 34–56 mol % TG were amorphous. The DSC isothermal results revealed that the addition of a small amount of flexible TG (up to 21 mol %) to the PET structure slightly reduced the formation of three‐dimensional spherulites. A greater TG concentration (91–100%) in the copolyesters changed the crystal growth from two‐dimensional to three‐dimensional. The DSC heating scans after the completion of isothermal crystallization at various Tcs showed three melting endotherms for PET, PETT‐88, PETT‐84, and PETT‐79 and four melting endotherms for PETT‐9 and PETT. The presence of an additional melting endotherm could be attributed to the melting of thinner and imperfect copolyester crystallites. Analyses of the Lauritzen–Hoffman equation demonstrated that PETT‐88 had the highest values of the product of the lateral and folding surface free energies, and this suggested that the addition of small amounts of flexible trimethylene terephthalate segments to PET disturbed chain regularity, thus increasing molecular chain mobility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4255–4271, 2004
A density functional method for the calculation of the zero‐voltage conductance of molecular electronic devices
Authors: Ernzerhof Matthias , Zhuang Min 
Published: October 2004

AbstractMolecular electronics poses a new challenge to density functional theory. The key property of molecular electronic devices is their conductance g. Here we propose a new strategy for the calculation of g employing Kohn–Sham density functional theory. We illustrate our approach by studying the conductance of short gold wires that are one atom in diameter. In agreement with recent experiments, we obtain conductance variations with the number of atoms in the wire. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Rider's net moment estimation using control force of motion system for bicycle simulator
Authors: Shin Jae‐Cheol , Lee Chong‐Won 
Published: October 2004

AbstractOne of the challenging problems with bicycle simulators is to deal with the virtual bicycle dynamics that is coupled with rider's motion. For the virtual bicycle dynamics calculation and the real time simulation, it is necessary to identify the control inputs from the rider as well as the virtual environments. The steering, pedaling, and braking torques can be easily measured by using torque sensors and the virtual environments can be generated and provided by a visual system. However, direct measurement of the rider's net moment that significantly affects the bicycle motion is not practical. In this work, it is shown that six control forces of the Stewart platform‐based motion system can be used for effective estimation of the rider's net moment, incorporated with the sliding mode controller with perturbation estimation. © 2004 Wiley Periodicals, Inc.
CAD‐based automated robot programming in adhesive spray systems for shoe outsoles and uppers
Authors: Kim J. Y. 
Published: October 2004

AbstractMost shoe manufacturing processes are not yet automated; it puts restrictions on increasing productivity. Among them, adhesive application processes particularly are holding the most workers and working hours. In addition, the working environment is very poor due to the toxicity of adhesive agents. In the case of automating an adhesive application process by using a robot, robot teaching by playback is difficult to produce high productivity because the kinds of shoes to be taught mount up to several thousands. To cope with it, it is necessary to generate robot working paths automatically according to the kind, the size, or the right and the left of shoes, and also to teach the generated paths to a robot automatically. This paper presents a method to generate three‐dimensional robot working paths off‐line based on CAD data in an automatic adhesive spray system for shoe outsoles and uppers. First, this paper describes how to extract the three‐dimensional data of an outsole outline from a two‐dimensional CAD drawing file. Second, it describes how to extract the three‐dimensional data of an upper profiling line from the three‐dimensional scanning data that is opened in a three‐dimensional CAD program. Third, it describes how to generate robot working paths based on the extracted data and the nozzle setting parameters for adhesive spray. Also, a series of experiments for adhesive spray is performed to verify the effectiveness of the presented methods. This study will do much for increasing productivity in shoe manufacturing as a core work of a robotic adhesive spray system. © 2004 Wiley Periodicals, Inc.
Human capital and learning as a source of sustainable competitive advantage
Authors: Hatch Nile W. , Dyer Jeffrey H. 
Published: October 2004

AbstractThis paper seeks to identify the sources of wide and persistent variations in learning performance in the semiconductor manufacturing industry. In the resource‐based view of the firm, human capital is frequently assumed to contribute to competitive advantage due to its inimitability based on its intangible, firm‐specific, and socially complex nature. Consistent with this view, we find that investments in firm‐specific human capital have a significant impact on learning and firm performance. More specifically, human capital selection (education requirements and screening), development through training, and deployment significantly improve learning by doing, which in turn improves performance. However, we find that acquiring human capital with prior industry experience from external sources significantly reduces learning performance. We also find that firms with high turnover significantly underperform their rivals, revealing the time‐compression diseconomies that protect firm‐specific human capital from imitation. These results provide new empirical evidence of the inimitability of human capital. Copyright © 2004 John Wiley & Sons, Ltd.
Ownership structure and firm value: new evidence from Spain
Authors: de Miguel Alberto , Pindado Julio , de la Torre Chabela 
Published: October 2004

AbstractThis paper provides new evidence on the way in which ownership influences firm value. Unlike previous studies, the empirical evidence obtained from our ownership concentration model supports not only the monitoring but also the expropriation effects. Additionally, the insider ownership model provides results that confirm the convergence‐of‐interest and the entrenchment effects, even though Spanish insiders get entrenched at higher ownership levels than their U.S. and U.K. counterparts. Copyright © 2004 John Wiley & Sons, Ltd.
The impact of market cycle on the performance of Singapore acquirers
Authors: Pangarkar Nitin , Lie Junius R. 
Published: October 2004

AbstractIn this paper, we hypothesize that acquisitions undertaken during low market cycles will exhibit better performance than other acquisitions for two key reasons: lower likelihood of overpayment due to hubris and ease in implementing restructuring initiatives such as retrenchment. We define performance as the cumulative abnormal returns surrounding the acquisition event and deploy a trend‐based measure for market cycle. Based on an analysis of 115 acquisitions by Singapore firms between 1990 and 1999, we find strong support for the hypothesized relationship. Copyright © 2004 John Wiley & Sons, Ltd.
Optical Properties of Nanoparticle‐Based Metallodielectric Inverse Opals
Authors: Wang Dayang , Li Jensen , Chan C. T. , Salgueiriño‐Maceira Verónica , Liz‐Marzán Luis M. , Romanov Sergei , Caruso Frank 
Published: October 2004

AbstractMetallodielectric inverse opals were prepared by co‐crystallizing silica‐coated gold nanoparticles and polymer spheres, followed by removal of the crystal template. The inverse opals exhibit a distinct reflectance peak, which results from Bragg diffraction due to the highly ordered 3D macroporous structure. Photonic band‐structure calculations indicate that the characteristic reflectance peaks observed are signatures of the directional gap at the L point. It is demonstrated that the optical properties (the position and magnitude of the electromagnetic bandgaps) of the gold–silica nanocomposite inverse opals can be engineered by varying the nanoparticle morphology (core size and shell thickness) and/or the nanoparticle volume‐filling ratio of the composite. The use of metallodielectric nanoparticles to form inverse opals offers a versatile approach to prepare photonic materials that may exhibit absolute bandgaps.
Optimizing the Treatment of AMES High‐risk Papillary Thyroid Carcinoma
Authors: Lo Chung‐Yau , Chan Wai‐Fan , Lam King‐Yin , Wan Koon‐Yat 
Published: October 2004

AbstractA minority of patients with papillary thyroid carcinoma (PTC) is at high‐risk of developing recurrent disease and death. Risk group stratification as defined by age, metastases to distant site, extrathyroidal invasion, and tumor size (AMES) criteria is frequently employed to identify high‐risk patients for aggressive surgical and adjuvant treatments. The present study aimed at evaluating risk factors and the impact of treatment on cause‐specific mortality (CSM) in this group of high‐risk patients. From 1961 to 2000, 150 of 499 patients surgically treated for PTC were considered as high‐risk by AMES criteria. At 10‐years CSM was significantly higher in high‐risk patients (28%) than in low‐risk patients (2%) (p< 0.0001). The clinicopathologic features, treatment, and outcome of AMES high‐risk patients were retrospectively studied and risk factors for CSM were analyzed. There were 58 men and 92 women with a median age of 62 years (range: 18–87 years). Bilateral thyroidectomy was performed for 143 (95%) patients and concomitant neck dissection was performed for 82 patients (55%). Thirty‐six patients (24%) underwent incomplete tumor excision with residual disease. Radioactive iodine (I131) ablation and external‐beam irradiation were administered to 102 (68%) and 46 patients (31%), respectively. Over a median follow‐up of 7.6 years, the overall mortality was 23% and 44%, whereas the CSM was 14% and 28% at 5 and 10 years, respectively. Using the Cox proportional hazard model, distant metastasis at presentation, incomplete tumor excision, and no postoperative I131treatment were independent prognostic factors of poor survival. Patients who underwent an incomplete excision showed improved survival after I131ablation (p= 0.0008), external‐beam irradiation (p= 0.02), or both forms of treatment (p= 0.04). Within this high‐risk AMES group, International Union Against Cancer (UICC) pTNM staging and MACIS (Metastasis, Age, Completeness, Invasion, Size) scoring correlated significantly with CSM. AMES high‐risk PTC patients should undergo total thyroidectomy aiming at complete tumor resection followed by I131ablation. External‐beam irradiation should be added for patients with residual disease after an incomplete excision.
Long‐term Survival of Patients with Small Intestinal Carcinoid Tumors
Authors: Zar Niklas , Garmo Hans , Holmberg Lars , Rastad Jonas , Hellman Per 
Published: October 2004

AbstractMidgut carcinoid tumors are rare and have a markedly better prognosis than adenocarcinoma in the small intestine. New diagnostic methods and medical as well as surgical therapies have evolved during the last decades, leading to more active care of these patients. Patients with small intestinal carcinoids diagnosed from 1960 to 2000 in the duodenum (n= 89) and jejunum/ileum (n= 2437) were identified in the Swedish Cancer Registry. Cases without histologic verification and autopsy cases were excluded. Overall, cause‐specific and relative survival were calculated. The overall 5‐, 10‐, and 15 year survivals were, respectively, 60%, 46%, and 28% for duodenal tumors and 56%, 36%, and 23% for jejunal/ileal tumors. Cause‐specific 5‐, 10‐, and 15‐year survival was 94% for all three follow‐up periods for duodenal tumors and 87%, 80%, and 77% for those in the jejunum/ileum. The corresponding relative survivals were, respectively, 72%, 67%, and 51% for duodenal tumors and 67%, 54%, and 44% for those in the jejunum/ileum. Sex did not influence overall or cause‐specific survival. The age at diagnosis correlated inversely with overall and cause‐specific survival for tumors in the jejunum/ileum. For tumors in the jejunum/ileum, the overall and cause‐specific survival correlated with the time period of diagnosis, with a more favorable prognosis for those diagnosed in recent years. A multivariate Cox proportional hazards model showed similar results. We concluded that young age and diagnosis in recent years are positive predictors of survival for patients with midgut carcinoids. The divergence between cause‐specific and relative survival implies the need for a more detailed analysis of the causes of death of these patients.
Trends in Utilization of Adrenalectomy in the United States: Have Indications Changed?
Authors: Saunders Brian D. , Wainess Reid M. , Dimick Justin B. , Upchurch Gilbert R. , Doherty Gerard M. , Gauger Paul G. 
Published: October 2004

AbstractMinimally invasive approaches have dramatically reduced morbidity associated with adrenalectomy. There has been concern that an increased frequency of adrenal imaging along with the advantages of less morbidity could influence the indications for adrenalectomy. We tested the hypothesis that adrenalectomy has become more common over time and that benign diseases have been increasingly represented among procedural indications. The Nationwide Inpatient Sample (NIS) database was utilized to determine the incidence of adrenalectomy and the associated surgical indications in the United States between 1988 and 2000. All discharged patients were identified whose primary ICD‐9‐CM procedure code was for adrenalectomy, regardless of the specific surgical approach (laparoscopic adrenalectomy was not reliably coded). This subset was then queried for associated ICD‐9‐CM diagnostic codes. Linear regression and t‐tests were utilized to determine the significance of trends. The total number of adrenalectomies increased significantly, from 12.9 per 100,000 discharges in 1988 to 18.5 per 100,000 discharges in 2000 (p = 0.000003). The total number of adrenalectomies with a primary ICD‐9‐CM code for malignant adrenal neoplasm did not increase significantly: from 1.2 per 100,000 discharges in 1988 to 1.6 per 100,000 discharges in 2000 (p = 0.47). The total number of adrenalectomies with a primary ICD‐9‐CM diagnostic code for benign adrenal neoplasm increased significantly, from 2.8 per 100,000 discharges in 1988 to 4.8 per 100,000 discharges in 2000 (p = 0.00002). The average percentage of adrenalectomies performed for malignant neoplasm was significantly higher during the period 1988–1993 when compared to 1994–2000 (11% vs. 9%; p = 0.002). The average percentage of adrenalectomies performed for benign neoplasm was significantly lower during 1988–1993 when compared to 1994–2000 (25% vs. 28%; p = 0.015). Adrenalectomy is being performed with increasing frequency. This is associated with an increase in the proportion of adrenalectomies performed for benign neoplasms. Assuming no significant change in disease prevalence during the study period, these data suggest that indications for adrenalectomy may have changed somewhat over that period.
Depression and associated organic diseases: are there any specific depressive symptoms? Results from the dialogue-2 survey
Authors: Guelfi J.D. , Rousseau C. , Lancrenon S. 
Published: October 2004

AbstractThe objective of the survey was to compare depressive symptoms in depression with and without a concomitant organic disease. The results based on the HAD and CES-D scales showed that, compared to those with an isolated depression, the patients with an associated chronic organic disease have a higher score on two items on the HAD. Three variables on the CES-D scale also helped to differentiate the two groups of depressed patients. No significant difference was found between the two groups in terms of anxiety or cognitive symptoms, fatigue or feelings of disability. Our results do not indicate any symptom that is specific to a combination of depression and somatic diseases. Guilt and hostility showed a lower level in depression associated with a concomitant somatic disease than in isolated depression.
Spatial structure and geometry of schools of sardine (Sardinops sagax) in relation to abundance, fishing effort, and catch in northern Chile
Authors: Castillo Jorge , Robotham Hugo 
Published: October 2004

Abstract
We analysed the interrelationships of morphological, energetic, and relational descriptors of schools of sardines in the winter seasons of 1984–1990. A surface occupation index was used to measure the space covered by sardine. These descriptors were then related to catch, fishing effort, and catch per unit effort (cpue). We found that the greater the distance between the schools and the smaller the surface occupation index for schools, the smaller their size, biomass, and density. However, these descriptors were weakly related to the number of schools. The annual catch, fishing effort, and cpue were significantly and directly related to surface occupation index and inversely with the distance between schools. These fishery indices were weakly related to school area, school density, and school biomass. The change in the space occupied by sardine affected their catchability, as shown by the logarithmic relationship between the cpue and the acoustic biomass. The lack of linearity can be corrected by taking into consideration the index of surface occupation of the stock so as to produce a corrected cpue (cpue*) value, which is directly proportional to stock biomass.
Performance of precautionary reference points in providing management advice on North Sea fish stocks
Authors: Piet G.J. , Rice J.C. 
Published: October 2004

Abstract
For 17 stocks in the North Sea, the performance and effectiveness of management advice using precautionary reference points was evaluated. Three criteria were used to identify whether a stock was within safe biological limits: SSB < Bpa, F > Fpa, or SSB < Bpa and F > Fpa. Four scenarios were considered, comparing the advice in the assessment year with what is retrospectively (2002 assessment) known to be the status of the stock at that time: (1) stock outside safe biological limits, advice to reduce fishing; (2) stock outside safe biological limits, advice for status quo harvesting; (3) stock within safe biological limits, advice to reduce fishing; and (4) stock within safe biological limits, advice for status quo (or increased) harvesting. Signal Detection Theory was applied to these scenarios, and the proportion of Hits (1 and 4), Misses (2), and False Alarms (3) were determined for each year as the proportion of the stocks for which the respective scenarios applied. Using both Bpa and Fpa was deemed the approach with the lowest error rate, and it resulted in about the same proportion of Hits in management advice as when Bpa alone was used (62%), but the proportion of Misses was slightly lower (24% vs. 26%). Therefore, the suggested EcoQ element would be the proportion of commercial fish stocks within safe biological limits (i.e. SSB > Bpa, F < Fpa), and the Ecological Quality Objective (EcoQO) should be that this EcoQ should be at or above a desired level. This desired level is a societal/political decision relative to the EcoQ reference level (i.e. where the anthropogenic influence on the ecological system is minimal), which by definition is 100%. At present, probably <10% of North Sea fish stocks are within safe biological limits, despite the relatively high Hit rate of >60%. A possible explanation is that most of these stocks (e.g. flatfish and roundfish) are caught in a mixed fishery, for which TAC management is less effective.