bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro and in vivo antitumor properties of the cyclin dependent kinase inhibitor CYC202 (R‐roscovitine)
Authors: McClue Steven J. , Blake David , Clarke Rosemary , Cowan Angela , Cummings Lorna , Fischer Peter M. , MacKenzie Mairi , Melville Jean , Stewart Kevin , Wang Shudong , Zhelev Nikolai , Zheleva Daniella , Lane David P.
Published: November 2002

CDK2 inhibitors have been proposed as effective anti‐cancer therapeutics. We show here that CYC202 (R‐roscovitine) is a potent inhibitor of recombinant CDK2/cyclin E kinase activity (IC50 = 0.10 μM) with an average cytotoxic IC50 of 15.2 μM in a panel of 19 human tumour cell lines, and we also demonstrate selectivity for rapidly proliferating cells over non‐proliferating cells. A study of the cell cycle effects of CYC202 in Lovo colorectal carcinoma cells showed that the major effect was not the predicted arrest in one part of the cycle, but rather an induction of cell death from all compartments of the cell cycle. The maximum tolerated dose given intravenously to mice was in excess of 20 mg/kg. Doses up to 2,000 mg/kg were tolerated when administered orally in mice. Following repeated intraperitoneal administration (3 times daily for 5 days) of 100 mg/kg to nude mice bearing the Lovo human colorectal tumour, CYC202 induced a significant antitumour effect with a 45% reduction in tumour growth compared to controls. A second experiment using the human uterine xenograft MESSA‐DX5 treated with orally administered CYC202 (500 mg/kg 3 times daily for 4 days) also exhibited a significant reduction in the rate of growth of the tumour (62%). These data, showing enzyme and cellular potency together with antitumour activity, confirm the potential of CDK2 inhibitors such as CYC202 as anticancer drugs. © 2002 Wiley‐Liss, Inc.
The copper chelator trientine has an antiangiogenic effect against hepatocellular carcinoma, possibly through inhibition of interleukin‐8 production
Authors: Moriguchi Michihisa , Nakajima Tomoki , Kimura Hiroyuki , Watanabe Tadashi , Takashima Hidetaka , Mitsumoto Yasuhide , Katagishi Tatsuo , Okanoue Takeshi , Kagawa Keizo
Published: November 2002

Recent studies have revealed that copper is an important cofactor for several angiogenic agents. We examined the antiangiogenic effect against hepatocellular carcinoma (HCC) of the copper chelator trientine, especially focusing on the relationship between copper and interleukin‐8 (IL‐8), a potent angiogenic factor produced by hepatoma cells. HuH‐7 hepatoma cells were transplanted into nude mice and the growth of xenograft tumors was compared to and without administration of trientine. Using the resected tumor, microvessel density, apoptotic potential and proliferative activity were analyzed histologically and IL‐8 mRNA was semiquantified by RT‐PCR. In addition, HuH‐7 cells were cultured in control medium, medium supplemented with copper, medium supplemented with trientine and medium supplemented with both copper and trientine. Human IL‐8 levels were measured in the supernatants by ELISA. Using the extracts from cultured cells, IL‐8 mRNA was semiquantified by RT‐PCR. Trientine suppressed the growth of xenograft tumors significantly. Histologically, apoptotic potential was increased significantly and microvessel density, decreased. The production of IL‐8 from the tumor was suppressed by trientine. In vitro, IL‐8 production by HuH‐7 cells in copper‐containing medium was significantly greater than that in copper‐free medium, and this effect was weakened when trientine was added. However, no significant change was apparent when trientine was added to the medium alone. In conclusion, the chelating effect of trientine prevented copper from functioning as a cofactor in angiogenesis, which resulted in reduced IL‐8 production from HuH‐7 cells. © 2002 Wiley‐Liss, Inc.
Cell‐free 27 kDa heat shock protein (hsp27) and hsp27–cytochrome c complexes in the cervix of women with ovarian or endometrial cancer
Authors: Korneeva Irina , Caputo Thomas A. , Witkin Steven S.
Published: November 2002

Antibodies to the 27 kDa heat shock protein (hsp27) are present in some women with ovarian and endometrial cancers but not in women with nonmalignant conditions or healthy women. The appearance of these antibodies suggests that the corresponding protein (hsp27) may be present in an extracellular form in gynecologic cancer patients. Synthesis of hsp27 is upregulated in gynecologic cancers and inhibits induction of apoptosis. We now report the detection of hsp27 as well as hsp27–cytochrome c complexes in cell‐free endocervical or posterior vaginal specimens from women with endometrial or ovarian cancer. Specimens were obtained with a cotton swab from 209 consecutive patients seen by a gynecologic oncologist. After removal of cellular components, aliquots of supernatants were assayed by ELISA for hsp27, using cytochrome c bound to microtiter plate wells, and for hsp27–cytochrome c complexes, using antibodies to cytochrome c and hsp27. Among 47 women with ovarian cancer, 38.3% were positive for hsp27 and 27.7% had hsp27–cytochrome c complexes. Similarly, among 52 women with endometrial cancer, 34.6% were hsp27‐positive and 30.8% had hsp27–cytochrome c complexes. In contrast to the women with ovarian or endometrial cancer, of the 86 women with benign diagnoses only, 10.5% had cervical hsp27 (p < 0.002) and 8.1% had hsp27–cytochrome c complexes (p < 0.004). Among ovarian cancer patients, hsp27 was identified in 44.0% of the 25 women with active disease as opposed to 17.6% of the 17 patients in remission (p < 0.05). In women with stage 1–2 active ovarian cancer, 8 of 10 (80.0%) were hsp27‐positive as opposed to 3 of 14 (21.4%) stage 3–4 patients (p < 0.01). For hsp27–cytochrome c complexes, 50% of ovarian cancer patients with active stage 1–2 disease as opposed to 21.4% with stage 3–4 disease were positive. Among women with endometrial cancer, only 10 of the 52 patients had active disease and 44 were in stage 1–2. For this malignancy, there was no relation between detection of hsp27 or hsp27–cytochrome c and active disease or cancer stage. Our results suggest that cell‐free hsp27 and hsp27–cytochrome c complexes can be detected in the lower genital tract of women with ovarian and endometrial cancers. Identification of these biomarkers may be beneficial in the early diagnosis of these malignancies. © 2002 Wiley‐Liss, Inc.
Association of functional polymorphisms of matrix metalloproteinase (MMP)‐1 and MMP‐3 genes with colorectal cancer
Authors: Hinoda Yuji , Okayama Naoko , Takano Naofumi , Fujimura Kozue , Suehiro Yutaka , Hamanaka Yuichiro , Hazama Shoichi , Kitamura Yutaka , Kamatani Naoyuki , Oka Masaaki
Published: November 2002

Matrix metalloproteinase (MMP)‐1 and MMP‐3 genes are associated with tumor cell invasion and metastasis with their promoter polymorphisms influencing the level of transcription. Our study explored the association of these polymorphisms with colorectal cancer risk in a Japanese population. DNA was extracted from peripheral blood of 101 patients with colorectal cancer and 127 age‐ and gender‐matched healthy volunteers. Genotyping was carried out using PCR‐RFLP and direct sequencing. In the MMP‐1 gene polymorphism, the frequency of the 2G/2G genotype that is associated with higher enzyme activity was significantly increased in colorectal cancer patients when compared to controls (p = 0.0067; OR = 2.077; 95% CI = 1.221–3.534). With regard to the MMP‐3 polymorphism, unexpectedly, the frequency of the 6A/6A genotype causing lower enzyme activity was significantly increased in patients (p = 0.0129; OR = 2.110; 95% CI = 1.165–3.822). Because the loci for the 2 MMP genes are closely linked, we examined linkage disequilibrium between the 2 loci using expectation‐maximization algorithm. We found that the 2 loci were in linkage disequilibrium and that 2G‐6A haplotype was significantly increased in patients compared to controls (p = 0.0010; OR = 1.949; 95% CI = 1.305–2.911). Our present data suggest that the MMP‐1 and MMP‐3 promoter polymorphisms may be associated with a colorectal cancer susceptibility in Japanese. © 2002 Wiley‐Liss, Inc.
Evidence of benefit from centralised treatment of ovarian cancer: A nationwide population‐based survival analysis in Finland
Authors: Kumpulainen Salla , Grénman Seija , Kyyrönen Pentti , Pukkala Eero , Sankila Risto
Published: November 2002

To assess the effect of different hospital types or surgical volume on the survival of ovarian cancer patients, a nationwide and population‐based analysis was carried out in Finland. The study included all 3,851 ovarian cancer patients operated from 1983–94. The patients were classified according to the hospital of the first surgery. The hospitals were categorized by type (university, central or other hospital) and, separately, into quartiles by the number of operated patients (surgical volume). The patients operated at university hospitals had better survival than those operated in central hospitals, the 5‐year relative survival rates (RSR) being 45% (95% CI = 42–48%) and 37% (34–40%), respectively. RSR in the ‘other hospital’ category was 45% (42–48%). The RSR for the patients operated in the highest volume hospitals was 47% (43–50%), and by decreasing volume (quartile) the RSR was 40% (36–43%), 40% (36–43%) and 42% (38–45%), respectively. After controlling for potential confounding by stage and age using regression models, the results remained practically the same. The results indicate that further centralizing of operative treatment of ovarian cancer may still improve survival rates on a population level in Finland. © 2002 Wiley‐Liss, Inc.
Myeloperoxidase (MPO) genotype and lung cancer histologic types: The MPO −463 A allele is associated with reduced risk for small cell lung cancer in smokers
Authors: Dally Heike , Gassner Kai , Jäger Birgit , Schmezer Peter , Spiegelhalder Bertold , Edler Lutz , Drings Peter , Dienemann Hendrik , Schulz Volker , Kayser Klaus , Bartsch Helmut , Risch Angela
Published: November 2002

MPO participates in the metabolic activation of tobacco carcinogens such as PAHs. A frequent MPO −463 G→A polymorphism in the promoter region reduces MPO transcription and has been correlated with >4‐fold lower benzo[a]pyrene–DNA adduct levels in the skin of coal tar–treated patients. Four of 7 case‐control studies found significantly reduced lung cancer risk associated with the A allele. Due to their different etiologies, we examined whether the MPO genotype affects histologic lung cancer types differentially. A case‐control study was conducted in 625 ever‐smoking lung cancer patients, including 228 adenocarcinomas, 224 SCCs, 135 SCLCs and 340 ever‐smoking hospital controls. MPO genotyping was performed by capillary PCR followed by fluorescence‐based melting curve analysis. Combining the MPO −463 (G/A+A/A) genotypes, a protective effect approaching significance (OR = 0.75, 95% CI 0.55–1.01) was observed when comparing all lung cancer cases to controls. Among histologic types of lung cancer, a weak protective effect was found for both adenocarcinoma (OR = 0.81, CI 0.55–1.19) and SCC (OR = 0.82, CI 0.56–1.21); a stronger and significant effect was found for SCLC (OR = 0.58, CI 0.36–0.95; p = 0.029). Our results also suggest that the MPO genotype varies among inflammatory nonmalignant lung diseases. In conclusion, our results emphasize the need for a separate analysis of lung cancer histologic types and an adjustment for inflammatory nonmalignant lung diseases in future MPO‐related studies. We confirm that the MPO −463 A variant affords a protective effect against lung cancer risk in smokers, which was strongest for SCLC patients. © 2002 Wiley‐Liss, Inc.
A case‐control analysis of lymphocytic chromosome 9 aberrations in lung cancer
Authors: Zhu Yong , Spitz Margaret R. , Strom Sara , Tomlinson Gail E. , Amos Christopher I. , Minna John D. , Wu Xifeng
Published: November 2002

Cytogenetic aberrations on chromosome 9 have been reported to be one of the most frequent genetic changes in lung tumorigenesis. Although many of these changes have been detected in lung carcinoma specimens, there is growing evidence showing the concordance between chromosomal alterations in primary lung tumors and peripheral blood lymphocytes (PBLs). We investigated whether spontaneous aberrations on chromosome 9 in PBLs are associated with the presence of lung cancer and with a family history of cancer. A personal interview, to construct a detailed epidemiologic profile including family history of cancer, was conducted on 174 lung cancer cases and 162 matched controls. One hundred metaphases from PBLs of each subject were analyzed for chromosome 9 aberrations using the whole chromosome painting technique. Overall, the mean proportion of individuals with chromosome 9 abnormalities in their PBLs was significantly higher in cases (96.0%) than in controls (60.5%) (p < 0.05). After adjustment by age, gender, ethnicity, family size, and pack‐years, there was a 16.63‐fold significantly elevated odds ratio (OR) for lung cancer associated with chromosome 9 aberrations. When subjects were categorized by frequencies of the chromosome 9 lesions, we observed significantly increased odds ratios of 11.13 (4.66, 26.58) and 27.45 (11.15, 67.54) for individuals with 1 chromosome 9 aberration and ≥2 chromosome 9 aberrations, respectively. By performing family history analyses, we further observed that control individuals with chromosome 9 aberrations were more likely to report a family history of any cancer (OR = 1.67 [0.84, 3.32]) and lung cancer (OR = 2.49 [0.81, 7.67]). Our findings suggest that chromosome 9 aberrations in PBLs might be considered a marker of lung cancer predisposition and may be associated with familial aggregation of cancer. © 2002 Wiley‐Liss, Inc.
Generation of monoclonal antibodies against Hong Kong nasopharyngeal carcinoma‐associated Epstein‐Barr virus latent membrane protein 1 (LMP1)
Authors: Chan Ben Chung Lap , To Ka Fai , Pang Jesse Chung Sean , Chung Yuk Fei , Lo Kwok Wai , Tong Joanna Hung Man , Huang Dolly Wai Sin , Lim Pak Leong , Chui Yiu Loon
Published: November 2002

A panel of monoclonal antibodies specific to Hong Kong Chinese nasopharyngeal carcinoma (NPC)‐associated Epstein‐Barr virus (EBV) latent membrane protein 1 (LMP1) variants has been generated. These monoclonal antibodies not only differentiate the Hong Kong Chinese NPC‐associated LMP1 variants from the prototype B95‐8 LMP1, derived from Caucasian infectious mononucleosis, but also differentiate the 2 highly homologous LMP1 deletion variants commonly found in Hong Kong primary NPC. The predominant deletion type variant, DV‐Asp335, is characterized by an aspartic acid at residue 335 located in the cytoplasmic C‐terminal region, whereas the other minor deletion variant, DV‐Gly335, has a glycine in the same residue position. 335D is hitherto found predominantly in LMP1 of the China 1 strain in association with NPC in the Chinese populations located in southern China and Malaysia. These antibodies, which are applicable in ELISA, immunofluorescence, immunoprecipitation, immunoblotting and immunohistochemistry on paraffin sections, are the first variant‐specific anti‐LMP1 monoclonal antibodies produced, and will be useful in investigating the functional significance of 335D in NPC. © 2002 Wiley‐Liss, Inc.
Design of tracking photovoltaic systems with a single vertical axis
Authors: Lorenzo E. , Pérez M. , Ezpeleta A. , Acedo J.
Published: November 2002

Solar tracking is used in large grid‐connected photovoltaic plants to maximise solar radiation collection and, hence, to reduce the cost of delivered electricity. In particular, single vertical axis tracking, also called azimuth tracking, allows for energy gains up to 40%, compared with optimally tilted fully static arrays. This paper examines the theoretical aspects associated with the design of azimuth tracking, taking into account shadowing between different trackers and back‐tracking features. Then, the practical design of the trackers installed at the 1.4 MW Tudela PV plant is presented and discussed. Finally, this tracking alternative is compared with the more conventional fully stationary approach. Copyright © 2002 John Wiley & Sons, Ltd.
Shape and size dependence of the anti‐reflective and light‐trapping action of periodic grooves
Authors: Abouelsaood Ahmed A. , El‐Naggar S. A. , Ghannam M. Y.
Published: November 2002

The shape and size dependence of the anti‐reflective and light‐diffusing properties of surfaces with linear periodic grooves is studied. Grooves of triangular or rectangular cross‐sections on the front or back surface of a crystalline silicon layer are considered. Our method is an extension of the rigorous, two‐dimensional, coupled‐wave, electromagnetic analysis of TE modes in dielectric relief gratings to the case of multilayer systems with both TE and TM modes through the use of a generalized transfer matrix formalism. Surfaces with shallow, sub‐micrometre rectangular grooves have substantial anti‐reflective and light‐diffusing actions contrary to geometric optics results. Surfaces with sub‐micrometre triangular grooves are less efficient anti‐reflectors and light diffusers than we expect from geometric optics predictions, which are slowly approached as the period increases. Light diffusion is totally absent for grooves of either types with a period Λ < 0.2 μm. Front‐surface rectangular grooves of period 0ċ65 μm and height 0ċ2 μm lead to an absorbance enhancement in the infrared part of the solar spectrum comparable to that achieved with practical 70ċ5° triangular grooves. Back‐surface rectangular grooves lead to some improvement compared with flat surfaces, but are somewhat inferior to back‐surface triangular grooves. Copyright © 2002 John Wiley & Sons, Ltd.
A simplified model based on clearness index for estimating yearly performance of hybrid PV energy systems
Authors: Celik Ali Naci
Published: November 2002

A simplified model for estimating the energy contribution of PV converter in a hybrid PV–wind system is presented. The simplified model determines the yearly solar fraction, that is the fraction of energy demand provided by PV, and the remaining loss of load (LOL) is assumed to be provided by wind turbines. The novel model is based on simulation results derived from 8 years of measured hour‐by‐hour solar irradiation data from five different locations in the world. The system performance is simulated by the PV–wind energy simulation program of the Cardiff School of Engineering (ARES). An hourly constant load profile is assumed.

The performance of a PV system is primarily dependent on the solar irradiation distribution in a given location for the period of time in question. The new model correlates the location dependence observed in the yearly solar fraction curves of different data sets with one of the most characteristic solar irradiation distribution parameters, the yearly clearness index of the respective solar irradiation data. The new model requires the yearly clearness index value, which is commonly available for most locations throughout the world, as input. As the novel model is validated with solar irradiation data from different locations in the world, it could be used for predicting the solar fraction in a hybrid PV system with a very high level of accuracy, for a wide range of climates. Copyright © 2002 John Wiley & Sons, Ltd.
Concerning the relationship between clear‐sky, global and direct‐beam, solar spectra
Authors: Faiman David , Jacob Sareet , Karnieli Arnon
Published: November 2002

Clear‐sky direct‐beam and normal global solar spectra were measured with a spectroradiometer with and without a collimating tube. The ratio of the two spectra was found to be well approximated by a simple two‐parameter formula suggested by Rayleigh scattering. Copyright © 2002 John Wiley & Sons, Ltd.
Tools for the profitability analysis of grid‐connected photovoltaics
Authors: Nofuentes G. , Aguilera J. , Muñoz F. J.
Published: November 2002

Three key geographical zones—the Euro area, Japan and the USA—are promoting the use of grid‐connected PV through attractive financial support programmes. After a short introduction to the financial analysis of PV grid‐connected systems, this paper presents some time‐saving charts and tables intended to assess the profitability of such PV systems in respect of some of the economic measures of these programmes. These easy‐to‐use tools are addressed to PV designers and investors to help them assess their investment from an exclusively economic point of view. Decision‐makers in the developed countries may also find them of value in planning their PV support measures. Some examples demonstrate how to use these tools, taking into account different available incentives and economic forecasts. Copyright © 2002 John Wiley & Sons, Ltd.
Comments on experience curves for PV modules
Authors: Parente Virginia , Goldemberg José , Zilles Roberto
Published: November 2002

Learning through market experience reduces prices for various energy technologies. This phenomenon can be captured by experience curves. In this short communication we update and analyze the experience curve trend for one of these technologies: photovoltaic modules for electricity generation. The results reinforce the importance of energy technology policy on contributing towards making new technologies commercially competitive. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis and characterization of block copolymers from 2‐vinylnaphthalene by anionic polymerization
Authors: Zeng Faquan , Yang Mu , Zhang Jianxin , Varshney Sunil K.
Published: November 2002

The anionic polymerization of 2‐vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at −78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec‐butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at −78 °C initiated by an adduct of sBuLi–LiCl. The crossover propagation from poly(2‐vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight‐average molecular/number‐average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo‐PDMS. Poly(2VN‐b‐nBA) (where nBA is n‐butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN‐b‐tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and 1H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN‐b‐AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert‐butyl from the poly(2VN‐b‐tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387–4397, 2002
Preparation of a copolymer of methyl methacrylate with a new monomer, 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate, and its initiation of the graft copolymerization of styrene with a controlled radical mechanism
Authors: Zhang Haitao , Guo Zhenrong , Huang Junlian
Published: November 2002

A copolymer [P(MMA‐co‐TBPM)] was prepared by the radical polymerization of methyl methacrylate (MMA) and 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate (TBPM) with azobisisobutyronitrile as an initiator. TBPM was a new monomer containing an activated ester. Both the copolymer and TBPM were characterized with NMR, IR, and gel permeation chromatography in detail. It was confirmed that P(MMA‐co‐TBPM) could initiate the graft polymerization of styrene by the cleavage of the activated ester of the TBPM segment. This process was controllable, and the molecular weight of the graft chain of polystyrene increased with the increment of conversion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4398–4403, 2002
Synthesis of a novel block copolymer poly(ethylene oxide)‐block‐poly(4‐vinylpyridine) by combination of anionic ring‐opening and controllable free‐radical polymerization
Authors: Lu Guangqiang , Jia Zhongfan , Yi Wen , Huang Junlian
Published: November 2002

The block copolymer poly(ethylene oxide)‐b‐poly(4‐vinylpyridine) was synthesized by a combination of living anionic ring‐opening polymerization and a controllable radical mechanism. The poly(ethylene oxide) prepolymer with the 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end group (PEOT) was first obtained by anionic ring‐opening polymerization of ethylene oxide with sodium 4‐oxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy as the initiator in a homogeneous process. In the polymerization UV and electron spin resonance spectroscopy determined the 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy moiety was left intact. The copolymers were then obtained by radical polymerization of 4‐vinylpyridine in the presence of PEOT. The polymerization showed a controllable radical mechanism. The desired block copolymers were characterized by gel permeation chromatography, Fourier transform infrared, and NMR spectroscopy in detail. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4404–4409, 2002
SEC‐MALDI‐TOF mass spectral characterization of a hyperbranched polyether prepared via melt transetherification
Authors: Jayakannan M. , Van Dongen Joost L. J. , Behera Girish Ch. , Ramakrishnan S.
Published: November 2002

An AB2 monomer, 1‐(2‐hydroxyethoxy)‐3,5‐bis‐(methoxymethyl)‐2,4,6‐trimethylbenzene, was synthesized from mesitol and melt‐polycondensed in the presence of an acid catalyst via a transetherification process at 145–150 °C to yield a soluble, moderately high molecular weight hyperbranched polyether. The degree of branching in the polymer was calculated to be 0.78 by a comparison of its NMR spectrum with that of an appropriately designed model compound. The weight‐average molecular weight of the hyperbranched polymer was determined to be 64,600 (weight‐average molecular weight/number‐average molecular weight = 5.2) by size exclusion chromatography (SEC) in CHCl3 with polystyrene standards. The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by SEC and by the subjection of each fraction to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4463–4476, 2002
Substituent effects on the chain‐transfer behavior of 7‐methylene‐2‐methyl‐1,5‐dithiacyclooctane in the presence of disulfides and thiols
Authors: Harrisson Simon , Davis Thomas P. , Evans Richard A. , Rizzardo Ezio
Published: November 2002

The chain‐transfer behavior of 7‐methylene‐2‐methyl‐1,5‐dithiacyclooctane was investigated in the presence of four chain‐transfer agents: thiophenol (PhSH), thiobenzoic acid (BzSH), diphenyl disulfide (PhSSPh), and dibenzoyl disulfide (BzSSBz). The chain‐transfer constants for these compounds at 60 °C were 0.38 (PhSH), 0.76 (BzSH), 0.24 (PhSSPh), and 0.05 (BzSSBz). The variations in the thiol chain‐transfer constants could be explained in terms of the stability of the resulting radicals. The chain transfer to the disulfides, however, appeared to be determined by the electronic character of the disulfide bond, and this suggests that the transfer took place via an addition–fragmentation mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4421–4425, 2002
Synthesis and characterization of novel luminescent polymers with alternate phenothiazine and divinylbenzene units
Authors: Wu Tzi‐Yi , Chen Yun
Published: November 2002

Novel luminescent polymers (P1 and P2) carrying alternate phenothiazine and divinylbenzene units were synthesized via the Wittig reaction. Absorption, fluorescence, and cyclic voltammetric methods were applied to investigate their optical and electrochemical properties. The photoluminescence (PL) maxima of P1 and P2 were 559 and 568 nm, respectively. Compared with reported hole‐transport groups such as carbazole, alkyldiphenylamine, triphenylamine, and iminodibenzyl chromophores, phenothiazine moieties in P1 and P2 bathochromically shift the PL maxima and narrow the band gaps. Their relative PL efficiencies were about 0.5 and 0.3 in solution and in the film state, respectively. Moreover, highest occupied molecular orbitals of P1 (4.78 eV) and P2 (4.74 eV) were even higher than the work function of ITO electrode (4.8 eV). The threshold electric fields of the Al/P1 (or P2)/ITO device were about 1.52–1.63 · 106 V/cm, which were smaller than 1.73 · 106 V/cm of P3, consisting of alternate iminodibenzyl and divinylbenzene units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4452–4462, 2002
Kinetic study of the nitroxide‐mediated controlled free‐radical polymerization of n‐butyl acrylate in aqueous miniemulsions
Authors: Farcet Céline , Nicolas Julien , Charleux Bernadette
Published: November 2002

The controlled free‐radical homopolymerization of n‐butyl acrylate was studied in aqueous miniemulsions at 112 and 125 °C with a low molar mass alkoxyamine unimolecular initiator and an acyclic β‐phosphonylated nitroxide mediator, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. The polymerizations led to stable latices with 20 wt % solids and were obtained with neither coagulation during synthesis nor destabilization over time. However, in contrast to latices obtained via classical free‐radical polymerization, the average particle size of the final latices was large, with broad particle size distributions. The initial [SG1]0/[alkoxyamine]0 molar ratio was shown to control the rate of polymerization. The fraction of SG1 released upon macroradical self‐termination was small with respect to the initial alkoxyamine concentration, indicating a very low fraction of dead chains. Average molar masses were controlled by the initial concentration of alkoxyamine and increased linearly with monomer conversion. The molar mass distribution was narrow, depending on the initial concentration of free nitroxide in the system. The initiator efficiency was lower than 1 at 112 °C but was very significantly improved when either a macroinitiator was used at 112 °C or the polymerization temperature was raised to 125 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4410–4420, 2002
Star polymer synthesis using trithiocarbonate functional β‐cyclodextrin cores (reversible addition–fragmentation chain‐transfer polymerization)
Authors: Stenzel Martina H. , Davis Thomas P.
Published: November 2002

Polystyrene stars were synthesized with reversible addition–fragmentation chain‐transfer (RAFT) polymerization. The core of the stars comprised a trithiocarbonate heptafunctional β‐cyclodextrin ring. Polymerizations were performed at 100 and 120 °C in the absence of an extraneous initiator and at 60 °C in the presence of a radical initiator. Monofunctional trithiocarbonate was also synthesized and used to make linear polystyrene to allow direct a comparison with the star synthesis. In all cases, the polymerization kinetics conformed to pseudo‐first‐order behavior. The measured molecular weights of the stars were found to deviate from those predicted on the basis of the monomer/trithiocarbonate group ratio. The extent of this deviation was dependent on the polymerization temperature, RAFT agent concentration, and conversion. Despite the low radical concentrations, termination reactions are suggested to play a significant role in the seven‐arm polystyrene star syntheses. The synthetic method was found to be suitable for generating star block structures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4498–4512, 2002
Telomerization of vinylidene fluoride with alkyl (or aryl) trifluoromethanethiosulfonates
Authors: Ameduri Bruno , Billard Thierry , Langlois Bernard
Published: November 2002

The photochemical‐induced telomerization of vinylidene fluoride (VDF) with cyclohexyl (or phenyl) trifluoromethanethiosulfonate (CF3SO2SR), leading to CF3(VDF)nSR telomers, where R stands for cyclohexyl or phenyl, is presented. These sulfurated transfer agents were synthesized by the reaction between sodium triflinate (CF3SO2Na) and disulfide in the presence of bromine. 19F NMR spectroscopy enabled an assessment of the average degrees of telomerization (DPn) of these telomers with a neat CF3 end group as the label. These DPn values increased for higher [VDF]0/[CF3SO2SR]0 initial molar ratios. Interestingly, the normal/reversed ratio of VDF units in these telomers was low. Finally, the cotelomerization of VDF and hexafluoropropylene with these transfer agents was successfully achieved, leading to original ω‐CF3 fluoroelastomers, the thermal properties of which were investigated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4538–4549, 2002
Micellar polymerization of amphiphilic poly(vinyl alcohol) macromonomer having a methacrylate end group prepared by aldol‐type group‐transfer polymerization
Authors: Takasu Akinori , Ohmori Shigeki , Yamauchi Yutaka , Hirabayashi Tadamichi
Published: November 2002

Amphiphilic and heterotactic‐rich poly(vinyl alcohol) (PVA) macromonomer, that is, PVA having a phenyl or phenoxyethyl methacrylate unit as the polymerizable end group, was synthesized via the aldol‐type group‐transfer polymerization (aldol‐GTP) technique. Aldol‐GTPs of vinyloxytriethylsilane (VOTES) were carried out in dichloromethane with 4‐methacryloylbenzaldehyde and 4‐(2‐methacryloylethoxy)benzaldehyde as the initiators with various Lewis acids. The polymerizations proceeded smoothly to give silylated PVA macromonomers (number‐average molecular weights: 1.3 × 103–1.96 × 104). Poly(VOTES) was easily desilylated to give heterotactic‐rich PVA macromonomer in good yield. The critical micelle concentration of the PVA macromonomer was determined by surface‐tension measurement. Micellar polymerization of the amphiphilic macromonomer gave comb‐shaped (graft) polymer having PVA side chains effectively (conversion: 80–82%), whereas polymerization in dimethyl sulfoxide (homogeneous state) did not. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4477–4484, 2002
Biodegradable network elastomeric polyesters from multifunctional aromatic carboxylic acids and poly(ϵ‐caprolactone) diols
Authors: Nagata Minoru , Kanechika Masao , Sakai Wataru , Tsutsumi Naoto
Published: November 2002

Novel biodegradable network polyesters were prepared from multifunctional aromatic carboxylic acids [trimesic acid (Y), pyromellic acid (X), and mellic acid (YM)] and poly(ϵ‐caprolactone) (PCL) diols with molecular weights of 530, 1250, and 2000. Prepolymers prepared by a melt polycondensation method were cast from dimethylformamide solutions and postpolymerized at 220 °C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density measurements, differential scanning calorimetry, thermomechanical analysis, and tensile testing. Some network polyester films, including YPCL1250, XPCL1250, and YMPCL2000, showed elastomeric properties with high ultimate elongation and low tensile modulus. The enzymatic degradation was measured by the weight loss of the network polyester films in a buffer solution with Rhizopus delemar lipase at 37 °C. The degree and rate of degradation increased with the increasing molecular weight of the PCL diols, but they decreased in the order of YPCL > XPCL > YMPCL because of the increase in the crosslinking densities of the network films. The degraded products after enzymatic degradation showed that the ester linkage of the PCL component and the aromatic ester linkage between Y and PCL diols were hydrolyzed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4523–4529, 2002
Attempt to investigate the temperature effect on polycondensation from the solution copolyesterification of preformed oligomers and bisphenols with tosyl chloride/dimethylformamide/pyridine
Authors: Higashi Fukuji , Hayashi Ryohsuke , Ohno Harumi
Published: November 2002

Two‐stage copolycondensations of isophthalic acid/terephthalic acid (50/50) and a bisphenol (BP) first and then a comonomer BP were carried at 80 and 120 °C. BPs were divided into two groups: those with polar substituents and those without polar substituents. The copolycondensation with any combination of BPs proceeded nearly equally well at 80 °C. However, the reaction at 120 °C was retarded differently by the groups of comonomers. For the preformed oligomers from BPs without polar substituents, the temperature did not affect the reaction very much, but the reaction was significantly retarded with BPs containing polar groups. All of the reactions of the oligomers from BPs having polar groups with comonomer BPs, regardless of their substituents, were greatly disturbed by the temperature rising. The results were attributed to the temperature effect on the way in which the oligomers reacted with comonomers due to the interactions between them, and they were examined in terms of the distributions of comonomers determined by 1H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4556–4562, 2002
Synthesis and optical and electrochemical properties of novel copolymers containing alternating 2,3‐divinylquinoxaline and hole‐transporting units
Authors: Wu Tzi‐Yi , Chen Yun
Published: November 2002

For the enhancement of charge affinity, electron‐affinitive 2,3‐divinylquinoxaline and a series of hole‐transporting chromophores (iminodibenzyl, phenothiazine, dihexyloxybenzene, and didodecyloxydistyrylbenzene) were incorporated alternately into the polymeric main chain. The resulting copolymers (P1–P4) were basically amorphous materials and were thermally stable below 300 °C. The electronic structures, photoluminescence, and electrochemical properties of these copolymers were mainly determined by the electron‐donating chromophores in the backbone. They showed significant positive solvatochromism in formic acid. An electrochemical study revealed that they exhibited lower band gaps (<2.3 eV) due to alternating donor and acceptor conjugated units (push–pull structure). Single‐layer light‐emitting diodes of aluminum, P1–P4, and indium tin oxide glass were fabricated, and preliminary electroluminescence spectra showed that P1, P3, and P4 were orange‐emitting materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4570–4580, 2002
Alternating copolymerization of propylene oxide with carbon monoxide catalyzed by Co complex and Co/Ru complexes
Authors: Takeuchi Daisuke , Sakaguchi Yoshihiko , Osakada Kohtaro
Published: November 2002

Co2(CO)8 catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8–3‐hydroxypyridine catalyst, show the following structure [CH2CH(CH3)OCO]n. The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the RuCo mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002
Synthesis and characterization of novel biodegradable poly(ester amide) with ether linkage in the backbone chain
Authors: Li Ming Xia , Zhuo Ren Xi , Qu Fan Qi
Published: November 2002

A series of biodegradable poly(ester amide)s having ether linkages in the main chain were synthesized by ring‐opening copolymerization of 3‐morpholinone (M) and ε‐caprolactone (CL) in bulk with stannous octoate, aluminium isopropoxide, or aluminium isobutoxide as an initiator. The influence of reaction conditions such as polymerization temperature, polymerization time, initiator, and initiator concentration on the monomer conversion and molecular weight are investigated. The comonomer reactivity ratios were determined (M 0.74 and CL 1.28). The water absorption of the polymers increased with increasing M content. In vitro degradation data and the release profiles of 5‐Fluorouracil showed that both the degradation rate and drug‐release rate increase with an enhanced M content in the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4550–4555, 2002
Displaying images on mobile devices: capabilities, issues, and solutions
Authors: Luo Jiebo , Singhal Amit , Braun Gustav , Gray Robert T. , Touchard Nicolas , Seignol Olivier
Published: November 2002

Wireless imaging is enabling visual communication ‘anytime anywhere’ to become a reality. Apart from wireless communication issues, a key technical challenge is how to achieve the best‐perceived image quality given the limited screen size and display bit‐depth of the mobile devices. In this paper, we give an overview of the current capabilities of various mobile devices, highlight some of the technical issues, and present potential solutions. In addition, we present a review of some of the software products on the market and look ahead to the trend toward more capable devices. Copyright © 2002 John Wiley & Sons, Ltd.
Second‐generation error concealment for video transport over error‐prone channels
Authors: Chen Trista Pei‐chun , Chen Tsuhan
Published: November 2002

Video transport over error‐prone channels may result in loss or erroneous decoding of the video data. Error concealment is an effective mechanism to reconstruct the video data. In this paper, we review error‐concealment methods and introduce a new framework, which we refer to assecond‐generation error concealment. All the error‐concealment methods reconstruct the lost video data by making use of certaina prioriknowledge about the video content.First‐generation error concealmentbuilds sucha prioriin a heuristic manner. The proposed second‐generation error concealment builds thea prioriby modeling the statistics of the video content explicitly, typically in the region of interest (ROI). Context‐based models are trained with the correctly received video data and then used to replenish the lost video data. Trained models capture the statistics of the video content and thus reconstruct the lost video data better than reconstruction by heuristics. A new dynamic model ‘updating principal components’ (UPC) is proposed as a model for second‐generation error concealment. UPC can be applied to pixel values to conceal loss of pixel data. In addition, UPC can be applied to motion vectors, which results in ‘updating eigenflows’ (U‐Eigenflow), to conceal loss of motion vectors. With UPC applied to both pixel values and motion vectors, hybrid temporal/spatial error concealment can be achieved. The proposed second‐generation error‐concealment method provides superior performances to first‐generation error‐concealment methods. Copyright © 2002 John Wiley & Sons, Ltd.
3G wireless multimedia: technologies and practical issues
Authors: Zeng Wenjun , Wen Jiangtao
Published: November 2002

This paper provides overviews of the emerging wireless communication standards, end‐to‐end wireless streaming systems, and relevant wireless multimedia technologies. It highlights some of the challenges in the deployment of 3G wireless multimedia services, using PacketVideo's solutions as an example. Copyright © 2002 John Wiley & Sons, Ltd.
IEEE 802.11 FHSS receiver design for cluster‐based multihop video communications
Authors: Ban Koichiro , Gharavi Hamid
Published: November 2002

Recently, we proposed an ad hoc, cluster‐based, multihop network architecture for video communications using IEEE 802.11 FHSS (Frequency Hopping Spread Spectrum) wireless LAN (WLAN) technology with 2GFSK (2‐level Gaussian Frequency Shift Keying) modulation capable of 1 Mb s−1 transmission. To increase the transmission rate to 2 Mb s−1 for higher‐quality video communications, we evaluated the performance of the IEEE 802.11 FHSS system when a 4GFSK modulation option is selected. Since the 2 Mb s−1 system utilizing 4GFSK modulation is not very efficient in terms of Radio Frequency (RF) range, to improve its performance for multihop applications a combination of diversity and noncoherent Viterbi equalizer are considered. For video transmission, we employed a bitstream‐splitting technique together with a packet‐based error‐protection strategy to combat packet drops under multipath fading conditions. The real‐time transport protocol (RTP), user datagram protocol (UDP), and Internet protocol (IP) are used for video streaming. This includes an RTP packetization scheme to control the packet size and to improve the error‐resilient decoding of the partitioned video signal. The paper includes the simulation results showing the effects of the receiver design and diversity on the quality of the received video signals. Copyright © 2002 John Wiley & Sons, Ltd.
Combined hidden Markov source estimation and low‐density parity‐check coding: a novel joint source–channel coding scheme for multimedia communications
Authors: Yin Liuguo , Lu Jianhua , Wu Youshou
Published: November 2002

Joint source–channel coding schemes have been proven to be very effective for reliable multimedia communications. In this paper, we develop a joint source–channel coding scheme that combines the hidden Markov source (HMS) estimation and the low‐density parity‐check (LDPC) codes with an iterative estimation/decoding scheme. With this innovative combination, multimedia source redundancy could be accurately extracted by the hidden Markov estimation without any a priori information about the source. Moreover, the interleaver that is usually used to separate the source coding and channel coding can be avoided by exploiting the randomizing property of the LDPC codes. Furthermore, the channel decoding procedure may be implemented in parallel, resulting in good performance with a fairly low decoding complexity and delay. Simulation results have shown that the proposed scheme can achieve much better performance than the standard coding scheme over the binary input additive white Gaussian noise (BIAWGN) channels. Copyright © 2002 John Wiley & Sons, Ltd.