bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanofibrillar surface structures of gel‐drawn UHMW‐polyethylene tapes
Authors: Sheiko S. S. , Möller M. , Kunz M. , Deckmann H.
Published: April 2003

The fibrillar structure of gel‐drawn ultrahigh molecular weight polyethylene was studied by scanning force microscopy (SFM), transmission electron microscopy (TEM) and 2H‐NMR. Periodically striped 20—50 nm wide nanofibrils were depicted at the surface of the ultradrawn tapes. A periodicity of about 25 nm was observed independently of the draw ratio in the range 10 ≤ λ ≤ 70. This is consistent with the long period derived from SAXS experiments. The stripes were more pronounced at low draw ratios and a short range interfibrillar correlation was detected in that case. Based on variations in the 2H‐NMR relaxation times and segment orientation, it is concluded that structural defects are concentrated within small domains inside the crystallites and that the striped structure originates from defect layers within the fibrillar crystallites.
Dynamic mechanical properties of interpenetrating polymer networks based on polyacrylates and epoxy
Authors: Tan S. , Zhang D. , Zhou E.
Published: April 2003

Interpenetrating polymer networks (IPNs) based on polyacrylate (poly(polyethylene glycol diacrylate), PEGDA) and epoxy(diglycidyl ether of bisphenol A, DGEBA) were prepared simultaneously. Dynamic mechanical properties of the SINs (simultaneous interpenetrating networks) with various compositions were studied. Enhanced mechanical properties were found in this case. From the point of view of pre‐swollen networks, all of the PEGDA/DGEBA IPNs were composed of the individual pre‐swollen networks. A micro‐phase segregation system was produced in the SIN. Glass transition temperatures shifted inward, which was attributed to molecular packing effects or mutual‐entanglements of molecular segments among the individual pre‐swollen networks. In accordance with the additivity of properties, namely the parallel model, the entanglement density between the two polymer networks reached its maximum at 50/50 PEGDA/DGEBA IPN.
Poly(P‐xylylene)s: Synthesis, polymer analogous reactions, and perspectives on structure–property relationships
Authors: Greiner A. , Mang S. , Schäfer O. , Simon P.
Published: April 2003

A critical overview of different synthetic approaches to poly(p‐xylylene)s (PPXs) is coupled with perspectives on particular structure–property relationships and challenging applications. An attempt is made to emphasize the potential of different synthetic approaches to PPXs focused on different applications. Additionally, the synthesis and polymer analogous reactions of PPXs without leaving groups and functionalized PPXs (with leaving groups in the a‐position) serving as processable precursors for non‐processable polymers are evaluated.
Alkynes bearing furan rings. 1. Synthesis and polymerization with Mo‐based catalysts
Authors: Méalares C. , Costa G. , Gandini A. , Valenti B.
Published: April 2003

This paper describes the preparation of new alkynes bearing furanic substituents and their polymerization by catalytic systems based on transition metal halides in order to obtain novel materials with original properties because of the presence of both furan moieties and alternate single and double bonds. However, difficulties arising from the specific reactivity of the heterocycle in our experimental conditions led us to envisage an indirect way to obtain well‐defined products, using an aromatic polymer as the precursor.
Novel fluorinated block copolymers for the construction of ultra‐low energy surfaces and as dispersion stabilizers in solvents with low cohesion energy
Authors: Antonietti M. , Förster S. , Micha M. A. , Oestreich S.
Published: April 2003

Block copolymers consisting of polystyrene and a block containing long fluorinated side chains are made by two very effective polymer analogous reactions from commercially available polystyrene‐b‐polybutadiene block copolymers. Since these polymers consist of two mutually immiscible blocks with hydrophobic and very hydrophobic character they form micelles in a wide range of media down to very hydrophobic solvents, e. g. toluene, tetrahydrofurane (THF), perfluorohexane, perfluoro(methylcyclohexane), hexafluorobenzene and 1,1,2‐trichlorotrifluoroethane (Freon 113). First indications that our polymers are useful as effective steric stabilizers in such solvents are given by characterization of some polymer dispersions made in the solvents via precipitation polymerization.

In the solid state, mesophase formation typical for block copolymers is observed and characterized by quantitative small angle X‐ray scattering (SAXS). The surface of such films is controlled by the fluorinated block and exhibits an ultra‐low surface energy of the order of γSV = 15 mN/m, below that of polytetrafluoroethylene (PTFE) or polydimethylsiloxanes (PDMS). Unlike PTFE, the blocky nature of the presented polymer enables thermoplastic processing and dissolution in standard solvents, which is of practical relevance. Gas‐permeability measurements on membranes coated with these copolymers exhibit some interesting selectivities.
X‐Ray investigation of the structure of polyurethane elastomers based on 1,5‐naphthalene diisocyanate
Authors: Androsch R. , Blackwell J. , Chvalun S. N. , Festel G. , Eisenbach C. D.
Published: April 2003

The structure of the crystalline hard domains of polyurethane elastomers based on 1,5‐naphthalene diisocyanate (NDI) has been investigated by X‐ray methods. The specimens were pressed films prepared from NDI and 1,4‐butanediol (chain extender), with poly(oxytetramethylene) as the soft segments. Small angle X‐ray data show that the hard domains are lamellae oriented preferentially with their planes parallel to the film surface. The corresponding wide angle data show that the hard domains are crystalline, and that the degree of crystallinity can be more than 60%. The hard segment chains are relatively extended and are oriented perpendicular to the film surface: they probably form a staggered array in which they are linked in sheets by hydrogen bonds. Molecular models suggest that the hydrogen bonds are shorter, and hence stronger, than those formed in the hard domains of equivalent elastomers based on diphenylmethane diisocyanate (MDI) or dicyclohexylmethane diisocyanate (HMDI). In addition, the stacking of the naphthylene units is unencumbered by the presence of the bridge methylene groups in the latter systems, and these structural features probably account for the higher melting temperature of the hard domains.
Polypropylene growth on silica‐supported metallocene catalysts: A microscopic study to explain kinetic behavior especially in early polymerization stages
Authors: Steinmetz B. , Tesche B. , Przybyla C. , Zechlin J. , Fink G.
Published: April 2003

The polypropylene growth on metallocene/MAO catalysts supported on a silica carrier has been examined by scanning electron microscopy. The kinetic induction period in early polymerization stages can be explained by the formation of a discrete polymer layer only on the outer surface of the catalyst particle. Differences in the fragmentation process at later stages are pointed out, depending on the supporting procedure of the catalyst system.
Comparison of polydipentylsilylenes and ‐siloxanes containing chiral groups
Authors: Schwegler L. A. , Molenberg A. , Möller M.
Published: April 2003

Polydipentylsilylene and ‐siloxane copolymers, containing bis[(S)‐(+)‐2‐methylbutyl]silane units have been synthesized. Thermal analysis demonstrated for both types of copolymers that crystallization was hindered on incorporation of the 2‐methylbutyl groups. Optical rotation measurements in various solvents yielded a much stronger optical activity of the polysilylene copolymers, compared to the polysiloxanes. This effect has been explained by the formation of a chiral supramolecular structure in the case of the polysilylenes. The measurements have indicated that the solvent quality can be employed to enhance the formation of this structure at relatively low 2‐methylbutyl contents.
Characterization of antigen processing machinery and Survivin expression in tonsillar squamous cell carcinoma
Authors: Weinman Eric C. , Roche Patrick C. , Kasperbauer Jan L. , Cha Steve S. , Sargent Dan J. , Cheville John , Murphy Linda M. , Chen Lieping , Wettstein Peter J. , Gostout Bobbie , Ferrone Soldano , Strome Scott E.
Published: April 2003

BACKGROUND

There is a statistically significant association between human leukocyte antigen (HLA) Class I antigen expression and improved prognosis for some patients. This association reflects the control of tumor growth by HLA Class I antigen‐restricted, tumor‐associated antigen‐specific cytolytic T cells. However, progression of other malignant diseases is not associated with the loss of HLA expression. These observations show that the poor prognosis of a subset of tumors, despite high HLA Class I antigen expression, may reflect the development of alternative mechanisms utilized by tumor cells to escape from immune recognition and destruction.

METHODS

The authors evaluated the possible correlation between the expression of the antiapoptosis gene, Survivin, HLA Class I, and progression of tonsillar squamous cell carcinomas (TSCC) lesions. Tissue microarrays were constructed from primary TSCC, metastatically involved lymph nodes, adjacent normal mucosa, and tonsillar parenchyma excised for nonmalignant conditions.

RESULTS

Immunoperoxidase staining of tissue sections demonstrated that Survivin expression is significantly higher (P < 0.001) in malignant tumors than in normal tissue samples. In addition, Survivin expression is significantly higher (P = 0.05) in metastatic than in primary lesions. Survivin expression in primary lesions correlated positively with delta (P = 0.025), tapasin (P = 0.028), and HLA Class I antigen (P = 0.006) expression. The expression patterns of delta, tapasin, HLA Class I antigen, β‐2‐microglobulin, and Survivin did not demonstrate any significant association with the clinical course of disease.

CONCLUSIONS

For TSCC that maintain the expression of HLA Class I antigen, overexpression of Survivin may provide an alternative explanation for tumor progression. Cancer 2003;97:2203–11. © 2003 American Cancer Society.

DOI 10.1002/cncr.11311
Weekly paclitaxel and gemcitabine chemotherapy for metastatic non‐small cell lung carcinoma (NSCLC)
Authors: Hirsh Vera , Whittom Renaud , Ofiara Linda , Desjardins Pierre , Ayoub Joseph , Charpentier Danielle , Small David , Pintos Javier , Langleben Adrian
Published: April 2003

BACKGROUND

The current dose‐optimizing Phase II study evaluated the effect of weekly paclitaxel and gemcitabine on the response rate and survival of patients with non‐small cell lung carcinoma (NSCLC) using dose modifications that permitted optimal treatment intensity.

METHODS

Forty‐five patients (40 with TNM Stage IV and 5 with TNM Stage IIIB NSCLC) were treated with gemcitabine at 1000 mg/m2 via a 30‐minute intravenous (i.v.) infusion and with paclitaxel at 100 mg/m2 via a 60‐minute i.v. infusion. The first 3 patients received chemotherapy on Days 1, 8, and 15 every 4 weeks; the next 42 patients, participating in the Phase II trial, received chemotherapy on Days 1 and 8 every 3 weeks.

RESULTS

The 3 patients who received paclitaxel and gemcitabine on Days 1, 8, and 15 every 4 weeks tolerated the treatment poorly. One patient died suddenly after Day 15 treatment during the first cycle, and the other 2 patients discontinued the treatment because of unacceptable toxicity before the third cycle of chemotherapy. The next 42 patients, 40 of whom were evaluable, entered this trial between May 2000 and April 2001. They received paclitaxel at 100 mg/m2 i.v. followed by gemcitabine at 1000 mg/m2 i.v. on Days 1 and 8 every 3 weeks. Two patients (5%) achieved complete response, 20 (50%) achieved partial response, and 8 (20%) had stable disease. Median survival (MS) was 9.8 months; and 1‐year survival was 35%. The 32 patients with performance status (PS) 0 or 1 had an MS of 11 months; the 8 patients with PS 2 had an MS of 3 months. Toxicity (especially hematologic toxicity, neuropathy, and alopecia) was minimal.

CONCLUSION

A weekly paclitaxel and gemcitabine regimen that incorporated the authors' dose modifications resulted in good efficacy with minimal toxicity. Cancer 2003;97:2242–7. © 2003 American Cancer Society.

DOI 10.1002/cncr.11319
Temozolomide as an alternative to irradiation for elderly patients with newly diagnosed malignant gliomas
Authors: Glantz Michael , Chamberlain Marc , Liu Qin , Litofsky N. Scott , Recht Lawrence D.
Published: April 2003

BACKGROUND

The optimal treatment for elderly patients (defined as patients 70 years of age or older) with malignant gliomas (MG) remains controversial. Some physicians advocate withholding therapy following diagnosis based on the observation that elderly patients do not tolerate adjuvant radiotherapy. The availability of temozolomide (TMZ), a new alkylating agent with antiglioma efficacy, offers another potential therapeutic option for these patients. The drug can be administered orally at home with minimal morbidity.

METHODS

The authors retrospectively reviewed a cohort of 86 consecutive elderly MG patients from three institutions, 32 of whom received monthly TMZ in lieu of radiation.

RESULTS

Initial Karnofsky performance score was the only predictor of survival in this cohort. No difference in survival was noted between these two groups. Toxicity was minimal in the chemotherapy‐treated group and a higher percentage of patients receiving chemotherapy died at home.

CONCLUSIONS

The authors concluded that TMZ is as effective as irradiation as a treatment of elderly patients with MG. It is an alternative and, perhaps, a superior therapeutic option to irradiation, based on its ease of administration and low morbidity. Cancer 2003;97:2262–6. © 2003 American Cancer Society.

DOI 10.1002/cncr.11323
Reduced expression of hMSH2 protein is correlated to poor survival for soft tissue sarcoma patients
Authors: Taubert Helge W. , Bartel Frank , Kappler Matthias , Schuster Katja , Meye Axel , Lautenschläger Christine , Thamm‐Mücke Barbara , Bache Matthias , Schmidt Hannelore , Holzhausen Hans‐Jürgen , Würl Peter
Published: April 2003

BACKGROUND

Deregulation of DNA mismatch repair is a common mechanism for the development of hereditary nonpolyposis colon carcinoma and related familiar cancers, but it also plays a role in the tumorigenesis of sporadic cancers. Although the protein expression of the two main components of DNA mismatch repair, hMSH2 and hMLH1, has been described in soft tissue sarcoma (STS) patients, its prognostic impact is yet to be determined.

METHODS

The authors investigated the expression of the DNA repair proteins hMSH2 and hMLH1 by Western blot analysis in tumor samples of 57 STS patients. The correlation between the expression of hMSH2/hMLH1 and survival was studied in a Cox proportional hazards regression model, which was adjusted for the prognostic effects of staging, tumor entity, and radicality of tumor resection.

RESULTS

Nine of 57 STS (16%) showed reduced expression of hMSH2 and reduced expression of hMLH1 was detected in seven STS patients (12%). In a Kaplan–Meier analysis, the median survival for patients with reduced expression of the hMSH2 protein was 18 months, whereas the patients with a normal expression of hMSH2 survived for an average of 68 months. A multivariate Cox proportional hazards regression model revealed a significant correlation between the reduced expression of the hMSH2 protein and poor survival (relative risk = 4.7; 95% confidence interval [CI]: 1.3–17.2; P = 0.019).

CONCLUSIONS

Reduced expression of the hMSH2 protein is an independent negative prognostic factor for STS patients. Cancer 2003;97:2273–8. © 2003 American Cancer Society.

DOI 10.1002/cncr.11326
Patients' willingness to participate in symptom‐related and disease‐modifying research
Authors: Crowley Roxane , Casarett David
Published: April 2003

BACKGROUND

The growth of cancer symptom management research has been limited by challenges of slow recruitment and underenrollment. One potential solution to this problem is the use of screening questions that identify patients who are interested in participating in research. The goal of this study was to evaluate this strategy in patients with cancer.

METHODS

Two screening questions (for symptom management research and disease‐modifying research) were integrated into the intake process of the palliative care clinic of an urban Veteran's Administration medical center. A chart review was conducted to extract patients' reported willingness to be recruited for research, explanations for their responses, demographic data, Memorial Symptom Assessment Scale Global Distress Index (GDI) subscale scores, and Eastern Cooperative Oncology Group performance score.

RESULTS

Charts were reviewed for the first 100 patients seen for a palliative care clinic visit, 86 of whom had cancer. Patients were less likely to be interested in symptom‐related research than in disease‐modifying research (32 of 86 [37%] vs. 46 of 86 [54%]; sign test, P = 0.009). Patients' interest in each type of research was associated moderately (kappa = 0.41; P < 0.001). Independent predictors of interest in symptom management research included younger age, white race, and a lower GDI symptom distress score. Independent predictors of interest in disease‐modifying research included only younger age and white race.

CONCLUSIONS

Screening questions may be useful in identifying patients who are willing to be recruited for research. However, further study is needed to evaluate this process in other populations, as well as to determine whether screening questions introduce selection bias in the recruitment process. Cancer 2003;97:2327–33. Published 2003 by the American Cancer Society.

DOI 10.1002/cncr.11329
Conservative management of Paget disease of the breast with radiotherapy
Authors: Marshall Jennifer K. , Griffith Kent A. , Haffty Bruce G. , Solin Lawrence J. , Vicini Frank A. , McCormick Beryl , Wazer David E. , Recht Abram , Pierce Lori J.
Published: April 2003

BACKGROUND

At 5‐year follow‐up, patients with Paget disease of the breast who were treated with breast‐conserving surgery (BCS) and radiotherapy (RT) had excellent results. The current report provides 10‐ and 15‐year rates of tumor control in the breast, as well as disease‐free and overall survival rates following BCS and RT in a cohort of patients with Paget disease presenting without a palpable mass or mammographic density.

METHODS

Through a collaborative review of patients treated with BCS and RT from seven institutions, 38 cases of Paget disease of the breast presenting without a palpable mass or mammographic density were identified. All patients had pathologic confirmation of typical Paget cells at time of diagnosis. Thirty‐six of 38 patients had a minimum follow‐up greater than 12 months and constitute the study cohort. Ninety‐four percent of patients underwent complete or partial excision of the nipple‐areola complex and all patients received a median external beam irradiation dose of 50 Gy (range, 45–54 Gy) to the whole breast. Ninety‐seven percent of patients also received a boost to the remaining nipple or tumor bed, a median total dose of 61.5 Gy (range, 50.4–70 Gy).

RESULTS

With median follow‐up of 113 months (range, 18–257 months), 4 of 36 patients (11%) developed a first recurrence of disease in the treated breast only. Two of the four recurrences in the breast were ductal carcinoma in situ (DCIS) only and two were invasive with DCIS. Two additional patients had a recurrence in the breast as a component of first failure. Actuarial local control rates for the breast as the only site of first recurrence were 91% at 5 years (95% confidence interval [CI], 80–100%) and 87% (95% CI, 75–99%) at both 10 and 15 years. Actuarial local control rates for breast recurrence, as a component of first failure, were 91% (95% CI, 80–100%), 83% (95% CI, 69–97%), and 76% (95% CI, 58–94%) at 5, 10, and 15 years, respectively. No clinical factors were identified as significant predictors for breast recurrence. Five‐, 10‐ and 15‐year actuarial rates for survival without disease of 97% (95% CI, 90–100%) and 5‐, 10‐, and 15‐year actuarial rates of overall survival of 93% (95% CI, 84–100%) at 5 years and 90% (95% CI, 78–100%) at 10 and 15 years were reported.

CONCLUSIONS

These data confirm excellent rates of local control, disease‐free survial, and overall survival at 10 and 15 years following BCS and RT for Paget disease of the breast. This study continues to support the recommendation of local excision and definitive breast irradiation as an alternative to mastectomy in the treatment of patients with Paget disease presenting without a palpable mass or mammographic density. Cancer 2003;97:2142–9. © 2003 American Cancer Society.

DOI 10.1002/cncr.11337
Neurologic complications of bladder carcinoma
Authors: Anderson Thomas S. , Regine William F. , Kryscio Richard , Patchell Roy A.
Published: April 2003

BACKGROUND

Carcinoma of the urinary bladder accounts for approximately 2% of all malignant tumors and usually spreads through both local invasion and hematogenous dissemination. In the current study, the authors reviewed a large series of patients to determine the nature and frequency of neurologic complications.

METHODS

In the current study, the authors reviewed the records of 359 patients with bladder carcinoma who were treated at the study institution between 1962–2001.

RESULTS

Fifty‐two patients (14%) were reported to have neurologic complications. Complications resulting from neurologic metastases were relatively infrequent (5%). Seven patients (2%) had lumbosacral plexopathies and 6 patients (2%) had metastatic epidural spinal cord compression. Brain metastases were present in only 4 patients (1%). Nonmetastatic complications were more common than metastatic complications and were comprised of metabolic encephalopathies in 24 patients (7%), peripheral neuropathies in 9 patients (2.5%), cerebral infarctions in 6 patients (2%), and seizures in 5 patients (1%). No cases of neurologic infection or carcinomatous meningitis were reported.

CONCLUSIONS

The results of the current study demonstrate that neurologic complications are relatively uncommon in patients with bladder carcinoma and that local extension into peripheral nerves or bone, rather than hematogenous dissemination, is the most common cause of neurologic complications resulting from bladder carcinoma. Cancer 2003;97:2267–72. © 2003 American Cancer Society.

DOI 10.1002/cncr.11354
The effects of diversity on business performance: Report of the diversity research network
Authors: Kochan Thomas , Bezrukova Katerina , Ely Robin , Jackson Susan , Joshi Aparna , Jehn Karen , Leonard Jonathan , Levine David , Thomas David
Published: April 2003

This article summarizes the results and conclusions reached in studies of the relationships between race and
gender diversity and business performance carried out in four large firms by a research consortium known as the
Diversity Research Network. These researchers were asked by the BOLD Initiative to conduct this research to test
arguments regarding the “business case” for diversity. Few positive or negative direct effects of
diversity on performance were observed. Instead a number of different aspects of the organizational context and
some group processes moderated diversity‐performance relationships. This suggests a more nuanced view of
the “business case” for diversity may be appropriate. © 2003 Wiley Periodicals, Inc.
Role of proliferation in HER2 status predicted response to doxorubicin
Authors: Campiglio Manuela , Somenzi Giulia , Olgiati Clelia , Beretta Giovanni , Balsari Andrea , Zaffaroni Nadia , Valagussa Pinuccia , Ménard Sylvie
Published: April 2003

The role of HER2 in predicting response to doxorubicin (DXR) therapy in breast cancer was evaluated in vivo in a series of breast carcinomas from 220 patients with tumors larger than 2.5 cm and treated with 3 cycles of DXR (75 mg/m2) as neoadjuvant chemotherapy. Patients with HER2‐positive tumors were more frequently responsive to DXR treatment compared with HER2‐negative patients (p = 0.05; Mantel‐Haenszel X2 = 0.009). Progesterone receptor (PgR) negativity, but not mutated p53, was also associated with response to DXR (p = 0.05; Mantel‐Haenszel X2 = 0.004). Further analysis of those correlations using breast carcinoma cell lines characterized for different biologic parameters revealed a trend between HER2 positivity/PgR negativity and greater DXR sensitivity, but the strongest direct correlation was found between the proliferation rate and sensitivity to DXR (r = 0.82, p = 0.00009). Neither p53 nor the DXR target molecule topoisomerase‐II‐α was significantly associated with in vitro sensitivity to DXR. Thus, whereas data showed that the major biologic parameter associated with in vitro response to DXR in breast cancer cells appears to be the tumor proliferation rate, HER2 expression together with PgR negativity may serve as the counterpart of the proliferation marker in predicting the in vivo response to DXR. © 2003 Wiley‐Liss, Inc.
Vaccination of fusion cells of rat dendritic and carcinoma cells prevents tumor growth in vivo
Authors: Kawada Masaya , Ikeda Hitoshi , Takahashi Toshiyuki , Ishizu Akihiro , Ishikura Hiroshi , Katoh Hiroyuki , Yoshiki Takashi
Published: April 2003

Several reports on immunotherapy using dendritic cells‐based vaccine have been published. We investigated findings using fusion cells (FCs) generated from rat dendritic cells and a syngeneic hepatic cancer cell line with regard to inducing anti‐tumor immunity. Vaccination of rats using FCs protected against growth of the subcutaneously implanted tumor in vivo and induced infiltration of CD8+ T cells into the tumor. At the site of CD8+ T cell infiltration, there were apoptotic tumor cells. T cells from spleen of FCs‐vaccinated rats with protective ability against tumor growth included tumor specific cytotoxic CD8+ T cells restricted to major histocompatibility complex Class I. In addition, adaptive transfer of in vitro re‐stimulated splenic T cells with FCs was effective in preventing tumor growth and in vivo vaccinations of rats with FCs after resection of the subcutaneous implanted tumor inhibited local tumor recurrences. Immunotherapy using FCs appears to be an effective method if used in combination with surgical or other anti‐cancer therapies. © 2003 Wiley‐Liss, Inc.
Efficient engraftment of human primary breast cancer transplants in nonconditioned NOD/Scid mice
Authors: Beckhove Philipp , Schütz Florian , Diel Ingo J. , Solomayer Erich‐Franz , Bastert Gunther , Foerster Joanna , Feuerer Markus , Bai Lianhua , Sinn Hans‐Peter , Umansky Viktor , Schirrmacher Volker
Published: April 2003

We describe a new human tumor xenotransplant animal model that is highly efficient for engraftment, does not need host conditioning and is suitable for in vivo studies of human tumors. Pieces of 61 freshly operated primary breast tumors were implanted into 172 irradiated and 228 nonconditioned NOD/Scid mice. A high mortality was observed in irradiated but not in nonconditioned recipients. More than 90% of analyzed implanted breast cancer specimens engrafted in the NOD/Scid mice irrespective of pretreatment. The tumors were vascularized within 3 days of implantation and maintained original histomorphology as well as expression patterns of tumor markers (cytokeratin and MUC1) and cytokines (tumor necrosis factor alpha (TNF‐α), interleukin‐4 (IL‐4) and IL‐10) released by adjacent stromal cells. A majority of tumors grew slowly, locally infiltrating host tissue, whereas some grew aggressively, developing large, fatal tumor masses and metastases within regional lymph nodes. Tumor progression in mice correlated with stage, grade, proliferation index and hormone receptor status of primary tumors. The reproducible growth behavior and preservation of characteristic features suggest that this new xenotransplant model is relevant and can be recommended for testing new anticancer therapies. © 2003 Wiley‐Liss, Inc.
Contractibility techniques as a closure concept
Authors: Ryjáček Zdeněk , Schelp R. H.
Published: April 2003

We introduce a closure concept in the class of line graphs and claw‐free graphs based on contractibility of certain subgraphs in the line graph preimage. The closure can be considered as a common generalization and strengthening of the reduction techniques of Catlin and Veldman and of the closure concept introduced by the first author. We show that the closure is uniquely determined and the closure operation preserves the circumference of the graph. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 37–48, 2003
Polymerization ofN‐vinylcarbazole with ziegler‐type catalyst systems
Authors: Heller Jorge , Tieszen D. O. , Parkinson D. B.
Published: April 2003

The polymerization ofN‐vinylcarbazole with the TiCl4–Al(i‐Bu)3, TiCl4–AlEt3, TiCl3–Al(i‐Bu)3, and the TiCl4–n‐BuLi systems was studied. It was found thatN‐vinylcarbazole undergoes a very facile cationic polymerization with TiCl4, or TiCl3, and that catalyst complexes which contain a low metal alkyl/transition metal halide ratio promote a very rapid cationic polymerization. When the catalyst components are mixed in the presence of monomer, considerable cationic polymerization due to the transition metal halide alone takes place before the reaction between the titanium halide and metal alkyl is complete. Experiments with catalyst components mixed in the absence of monomer have shown that the rate of the reaction is markedly dependent on the ratio of the catalyst components and that each system studied had a characteristic ratio at which the catalytic activity suffered a marked drop. With TiCl3–Al(i‐Bu)3this drop occurred at an Al/Ti ratio of 0.8, with TiCl4–Al(i‐Bu)3at an Al/Ti ratio of 3, and with TiCl4–n‐BuLi at a Li/Ti ratio of 1.5. This was interpreted as indicating that at these ratios the surface of the titanium halide becomes completely modified by the metal alkyl so that noN‐vinylcarbazole–titanium halide interaction could take place. The per cent reduction of TiCl4to lower valence states was studied with then‐BuLi–TiCl4system as a function of the Li/Ti ratio and it was found that the maximum per cent reduction takes place at a Li/Ti ratio of 2. The per cent reduction rapidly decreased to zero at higher Li/Ti ratios. The polymers ofN‐vinylcarbazole formed with Ziegler‐type catalyst systems were examined by x‐ray diffraction, by their appearance under a polarizing microscope, by infrared spectroscopy, and by nuclear magnetic resonance. These measurements indicated that only amorphous, atactic polymers were formed.
Tracer techniques for the determination of monomer reactivity ratios. IV. Copolymerization characteristics of some divinyl monomers
Authors: Wiley Richard H. , Mayberry Gerald L.
Published: April 2003

A series of divinyl monomers of the formula
\documentclass{article}\pagestyle{empty}\begin{document}$$ \left( {{\rm CH}_{\rm 2} = {\rm CHC}_{\rm 6} {\rm H}_{\rm 4} - } \right)_2 {\rm X} $$\end{document}
where × is CH2, CH2CH2, CH2CH2CH2, CH2CH2CH2CH2,O, and S have been prepared from the carbinols by dehydration and copolymerized with styrene. The kinetic data are consistent with a copolymerization in which the two vinyl groups react independently. The divinyl monomer behaves as two equivalents of a vinyl monomer to give solutions for the copolymerization equation in which r1 (for styrene) varies from 0.61 to 1.13 and r2 (for the divinyl compound) varies from 0.78 to 1.51.
Effect of polar and nonpolar solvents on the viscosity and the molecular weight of polymer solutions
Authors: Kalpagam V. , Rao M. Ramakrishna
Published: April 2003

Light‐scattering studies of well fractionated samples of poly(vinyl acetate) were carried out in four solvents, viz., acetonitrile, ethyl formate, methyl isobutyl ketone, and dioxane, in order to investigate the effect of the polar and nonpolar nature of the solvents on the molecular weight and the viscosity of the samples studied. The molecular weights thus obtained are found to be in good agreement in all the solvents except dioxane, in which the values are twice as high. This twofold increase in dioxane has been explained in terms of secondary bonding. The relation between [η] and Mw are established for the systems poly(vinyl acetate)–ethyl formate, poly(vinyl acetate)–acetonitrile, and poly(vinyl acetate)–methyl isobutyl ketone. The root‐mean‐square radii and the second virial coefficients are also determined.
Thermodynamics of crystalline linear high polymers. II. The influence of copolymer units on the thermodynamic properties of polyethylene
Authors: Wunderlich Bernhard , Poland Douglas
Published: April 2003

CO and CHCH3 copolymers with polyethylene have been investigated by means of DTA and X‐ray methods. The reproducibility of DTA was investigated for monomeric and polymeric standard compounds and found usable for maximum melting point determinations. The maximum melting point is discussed for copolymers, and an equation is given which corrects the influence of chain folding. CO was found to be a crystallizable defect unit, while CHCH3 causes a noncrystallizable amorphous defect.
Homogeneous anionic polymerization. III. Molecular weight of polyisoprene initiated by butyllithium
Authors: Morton Maurice , Bostick E. E. , Clarke R. G.
Published: April 2003

A study has been carried out on the molecular weights and their distribution for polyisoprene prepared with butyl lithium as initiator in n‐hexane and tetrahydrofuran solvents. A stoichiometry of one chain per initiator molecule was found to apply. As in the case of styrene, the initiation reaction in the hydrocarbon solvent was relatively slow compared to propagation, thus leading to a broadening of the molecular weight distribution. However, narrow distributions were obtained by using a preinitiation technique, whereby all chains had an opportunity of growing simultaneously. In the THF solvent, the molecular weight distribution waa somewhat broader (M̄v/M̄n, ∽ 1.3) presumably due to a slow competitive chain termination reaction between the growing anionic chains and the solvent, a t room temperature.
Rheology of polytetrafluoroethylene
Authors: Tobolsky A. V. , Katz D. , Takahashi M.
Published: April 2003

The rheology of polytetrafluoroethylene above its melting point was studied by the technique of stress relaxation. The temperature shift for the maximum relaxation time at various temperatures fits the WLF equation, if the value of Tg is taken to be 110°C. Degradation of the polymer becomes appreciable above 380°C. Master stress relaxation curves were constructed from the data between 336 and 380°C. The continuous distribution of relaxation times was obtained, and also the discrete distribution of relaxation times by procedure X. The contribution of the maximum relaxation time to the total flow viscosity indicates that the molecular weight distribution of the sample used was narrow.
Termination of the anionic polymerization of acrylonitrile at low catalyst concentrations
Authors: Ottolenghi Ariel , Zilkha Albert
Published: April 2003

The homogeneous anionic polymerization of acrylonitrile in dimethylformamide with n‐butyllithium was studied. Two different termination reactions were found to exist depending on catalyst concentration. At high catalyst concentrations termination was bimolecular by chain transfer to monomer, while at relatively low catalyst concentrations termination was monomolecular, by an inner cyclization reaction of the growing chain end. The existence of chain transfer only at high catalyst concentrations suggests the possibility of free catalyst molecules participating in the transfer reaction. At intermediate catalyst concentrations, both monomolecular and bimolecular terminations were found to occur side by side, and DP = Kp[M]/(Ktr[C][M] + Kt). Study of the dependence of molecular weight on per cent conversion at low catalyst concentrations showed that, up to about 30% conversion, there is a linear relationship between molecular weight and concentration of monomer consumed which is independent of temperature and monomer. After this degree of conversion, molecular weight stopped to increase and remained constant due to monomolecular termination. All over the wide range of catalyst concentrations investigated, the catalyst efficiency in initiating polymerization was found to be low. In the lowest range where there is a linear dependence of molecular weight on per cent conversion it was also found that the molecular weights are proportional to [M]/[C], which is a property of “living” systems.
Crystalline order in nylon 66
Authors: Starkweather Howard W. , Whitney John F. , Johnson Donald R.
Published: April 2003

The x‐ray diffraction patterns of nylon 66 at small and large angles have been correlated with the densities of samples prepared in various ways. Quenching from the melt to 0°C. produces structures which are less than 40% crystalline, as determined by density and have structures similar to nematic liquid crystals. More dense specimens have a triclinic structure and appear to contain lamellae 50–100 A. thick which consist of outer amorphous layers and a central portion which is about 80% crystalline. Thermodynamic and spectroscopic evidence indicates that the disorder on melting consists of rotations about the bonds connecting CH2groups.
Diffusion constants of a maltosaccharide series
Authors: Bourne M. C. , Chichester C. O. , Sterling C.
Published: April 2003

A series of maltosaccharides, from glucose through maltohexaose, was prepared from starch labeled with 14C. Self and integral diffusion coefficients were measured in dilute and in concentrated solvents. The coefficients were related more or less rectilinearly with the logarithm of degree of polymerization, presumably because of molecule asymmetry. A greater diminution in the coefficient occurred in 20% sucrose than in 20% corn syrup of approximately equal molarity but considerably greater viscosity.
Polymer NMR spectroscopy. IX. Polyacrylamide and polymethacrylamide in aqueous solution
Authors: Bovey F. A. , Tiers G. V. D.
Published: April 2003

The NMR spectrum of polyacrylamide in aqueous solution exhibits a doublet resonance in the amide proton region, in contrast to the broad singlet shown by most smallmolecule amides. This is attributed to the relatively slow reorientation rate of the polymer segments, permitting effective coupling of the electric quadrupole moment of the N14 nucleus to the motions of the molecular framework. This, in turn, narrows the amide resonance to such a degree that the two protons can be discriminated. By observation of the collapse of this doublet, the rate of rotation of the amide groups can be measured; at pH 4.5 this rotation requires an activation energy of 10.5 ± 1 kcal. and is more rapid than proton exchange between the amide group and water. Rotation is not catalyzed by acid or base, where as exchange is catalyzed by both and becomes more rapid than rotation at high and low pH. The two amide protons exchange at equal rates; if intramolecular hydrogen bonding of amide groups is present, it has no apparent retarding effect on proton exchange. These results are discussed in terms of possible protonated intermediates.
Crystal structure of a new form of polyoxymethylene
Authors: Carazzolo Gianalvise , Mammi Mario
Published: April 2003

A new crystalline form of polyoxymethylene is described with an orthorhombic unit cell, space group P212121, and lattice constants a = 4.77 A., b = 7.65 A., c = 3.56 A. The chains are helicoidal with the axis of the helix parallel to c. The period of identity of 3.56 A. comprises two monomeric units and one turn of the helix. The lattice of orthorhombic polyoxymethylene is made up of isomorphous helicoidal chains.
Fracture processes in polymeric materials. IV. Dependence of the fracture surface energy on temperature and molecular structure
Authors: Berry J. P.
Published: April 2003

The study of the influence of flaw size on the tensile strength of poly(methyl methacrylate) samples has been extended over the temperature range −190°C. to 50°C. The fracture surface energy increases with decreasing temperature, while the inherent flaw size of uncracked samples passes through a minimum at about −20°C. The fracture surface energy and inherent flaw size of a copolymer of methyl methacrylate and 10 mole‐% of ethylene glycol dimethacrylate have been obtained at room temperature, by a similar method. These results are examined in the light of the hypothesis already put forward concerning the factors which govern the strength and fracture properties of glassy polymers.
Light‐scattering studies on sugar beet arabans
Authors: Tomimatsu Yoshio , Palmer K. J.
Published: April 2003

The discrepancy in the light‐scattering molecular weight of sugar beet araban in two solvent systems, 2M NaCl and 1% (v/v) DMF, is explained as being due to a charge effect in the latter solvent. The previously reported explanation of a multicomponent effect in 1% (v/v) DMF, based on the assumption that araban is uncharged, is shown to be incorrect by equilibrium dialysis experiments. Titration and sodium analysis indicate a total charge of about 20 per araban molecule, while the limiting slope of the Debye plot of light‐scattering data in low ionic strength solvent indicate an effective charge of 10. Attempts to explain the observed curvature in the Debye plot for araban in low ionic strength buffer on the basis of the Stigter‐Hill method was unsatisfactory, probably due to the inadequacy of the solid sphere‐diffuse double layer model for araban and/or the inapplicability of the Stigter‐Hill virial expansion method at high ratios of macromolecule to salt in low ionic strength solvent. Molecular weight measurements on araban acetate prepared for purification purposes indicate considerable degradation during deacetylation but not during acetylation. This suggests that araban in situ has a molecular weight considerably greater than that observed for the purified araban.
Crystal structure studies on the polymorphic forms of nylons 6 and 8 and other even nylons
Authors: Vogelsong Donald C.
Published: April 2003

Polymorphism present in the even nylons has been accounted for in terms of parallel and antiparallel packing of the polyamide chains. Hydrogen bonding appears to play the most important part in governing chain packing. For example, in the antiparallel structure (alternate chains running in opposite directions), complete hydrogen bonding is possible for fully extended planar zigzag nylon chains. In the parallel structure (all chains running in the same direction) complete hydrogen bonding is not possible for the fully extended nylon chains. Hence, the nylon chains twist to satisfy this requirement. This has been shown by interpretation of the x‐ray diffraction pattern of γ‐phase nylon 6. Between nylons 6 and 8 there appears to be a transition between the thermodynamic stabilities of the polymorphic chain packings. Antiparallel chain packing appears to be the common form of nylons 4 and 6. Parallel chain packing appears to be the common form of nylons 8 and 10. Apparently, when sufficient flexibility is given to the even nylon chains by the addition of methylene groups, the twisted chain structure is favored.
Photolytic degradation of poly(methyl methacrylate)
Authors: Fox Robert B. , Isaacs Lawrence G. , Stokes Suzanne
Published: April 2003

Thin films of poly(methyl methacrylate) (PMMA) at about 25°C. irradiated with a medium‐pressure mercury lamp undergo random scission with a quantum yield of 0.039 and 0.017 scissions/quantum absorbed in vacuum and in air, respectively. Crosslinking in air was not observed. Quantum yields for scission were independent of intensity. Volatile products included methyl formate, methyl methacrylate, and methanol in quantum yields of 0.14, 0.20, and 0.48 molecules per quantum absorbed, respectively. During irradiation in either vacuum or air, the ultraviolet absorption of PMMA increases with a band at 285 mμ, attributed to carbonyl groups in the polymer itself. A mechanism for the photodegradation of PMMA is suggested.
Interfacial polycondensation. XIII. Viscosity–molecular weight relationship and some molecular characteristics of 6‐10 polyamide
Authors: Morgan Paul W. , Kwolek Stephanie L.
Published: April 2003

Number‐average molecular weights were estimated by determination of endgroups on 6‐10 polyamide samples prepared by stirred and unstirred interfacial polycondensation procedures under varying conditions. Polymers made by melt and interfacial polycondensation methods obeyed the same dilute solution viscosity relationships. However, polymers from interfacial polycondensation reactions deviated in molecular weight distribution from that found for polymers prepared by the melt method. The deviation, which presents the appearance of broader than random distribution, is believed to result to a considerable degree from the presence of an unusually large low molecular weight fraction rather than a continuous distortion of the distribution curve. The interfacially prepared polyamides having the highest viscosity numbers, obtained by adjusting the concentration ratios of the two reactants, showed the least deviation from random distributions. Evidence was found for branching and even network formation in 6‐10 polyamide prepared by interfacial polycondensation as the concentration of the diacid chloride phase was increased. Branching probably occurred through acylation of amide links along the polymer chain to yield imide groups. These groups were cleaved to amide groups in the molten polymer or upon solution in sulfuric acid. Melt‐prepared, unfractionated 6‐10 polyamide followed the relationship [η] = 1.35 × 10−4 M̄n0.96, and a κ′ factor of 0.43 was found in the equation relating solution viscosity to concentration, ηnp/c = [η] + κ′[η]2c, for dilute solution determinations in m‐cresol at 25°C.
Crystallite orientation in regenerated cellulose filaments. I. Measurement of orientation by x‐ray methods
Authors: Ellis K. C. , Warwicker J. O.
Published: April 2003

The theory of the fiber diagram has been considered, and it has been shown that Polanyi's theory can be rewritten in terms of the reciprocal lattice and Ewald's construction. By the use of this theory the opacity at a point of an x‐ray diffraction photograph of a fiber has been related to the density of reciprocal lattice points at a point in reciprocal space. The effect of imperfections in the experimental arrangement on the azimuthal intensity distribution in a fiber diagram has been considered and an arrangement has been described with which the distribution of orientation of the crystallites can be obtained from the azimuthal intensity distribution after the application of only two simple conversion factors.
Inhibition kinetics of polymerization of styrene. III. Investigations on the effect of substituted trinitrobenzenes
Authors: Tüdös Ferenc , Kende Imre , Azori Mária
Published: April 2003

In the present paper the effects of substituted derivatives, namely the NH2, OCH3, CH3, Cl, and CO2C2H5 derivatives of s‐trinitrobenzene are described on the initiated polymerization of styrene. The investigations were extended to the determination of the relative reactivity k5/k2 of the inhibitor as well as of the value of stoichiometric coefficient. It was shown by the values of k5/k2 that the Hammett equation can be considered valid within a factor of two. Corresponding to the electron‐donating properties of the employed substituents, the values of the stoichiometric coefficient in crease from 2.7 to 3.8. This fact as well as other data from literature lead to a mechanism by which these values, which are unexpected in the case of molecular inhibitors, can be interpreted.