Plastisol Foaming Process. Decomposition of the Foaming Agent, Polymer Behavior in the Corresponding Temperature Range and Resulting Foam Properties

The decomposition of azodicarbonamide, used as foaming agent in PVC - plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min-1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g -1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol-1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse

Mean-field transport theory for the two-flavour NJL model

By making decomposition of the Wigner function simultaneously in both the spinor and the isospin spaces we derive a set of kinetic equations for the quark distribution functions and the spin densities. A detailed analysis of the consequences imposed by the chiral invariance on the form of the transport equations is presented.Comment: Revtex, 25 pages, no figure

Expression of P-glycoprotein, a multidrug-resistance gene product, is induced by radiotherapy in patients with oral squamous cell carcinoma

BACKGROUND. It has been observed that patients who have previously undergone radiotherapy have a lower rate of response to chemotherapy. METHODS. The authors investigated the effects of radiation on the expression of P-glycoprotein (Pgp), a multidrug-resistance gene product, in 56 patients with primary oral cancer. No patients received prior or concurrent chemotherapy. The 56 patients consisted of 3 groups: 1) 20 patients with preradiation or pretreatment specimens only, 2) 18 patients with both pre- and postradiation specimens, and 3) 18 patients with postradiation specimens only. Pgp expression was determined by immunohistochemistry with two monoclonal antibodies, C219 and C494. RESULTS. Among patients in Groups 1 and 2, only 1 (2.6%) and 2 (5.3%) patients had Pgp expression in their tumors before treatment with C219 and C494, respectively. For Group 2 patients, 66.7% and 72.2% had tumors that expressed Pgp with the two antibodies, respectively, only after and not prior to radiation. When patients in Groups 2 and 3 were combined, 63.9% and 72.2% had Pgp expression with the two antibodies, respectively, after radiation. Pgp expression was significantly induced after radiation compared with expression before treatment (P < 0.001). Overexpression of p53 protein, detected by immunohistochemistry with DO-7 antibody, was seen in the tumors of 40 patients (71.4%), and the status was quite consistent throughout radiotherapy. Pgp expression had no significant association with p53 protein expression. CONCLUSIONS. Pgp expression was significantly induced by radiation in human oral cancers. This induction of Pgp expression likely confers multidrug resistance to the cancer cells and may affect the efficacy of subsequent or concurrent chemotherapy. It may explain the lower rate of response to chemotherapy among patients who have previously had radiotherapy.link_to_subscribed_fulltex

Ten years research on NPC in Hong Kong University Hospital

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Nasopharyngeal carcinoma research in Hong Kong in the past decade

Objective: To review the research carried out in Hong Kong on nasopharyngeal carcinoma (NPC) over the past 10 years. Methods: The literature published in Hong Kong over the past 10 years on nasopharyngeal carcinoma were reviewed in the light of other important international publications on the same subject. Results: The research carried out in Hong Kong covers etiology, natural behavior, treatment and prognosis of NPC. These studies not only elucidated the different aspects of NPC, many of these new findings will also guide future directions of research. Conclusions: Major efforts have been made to research into the various aspects of PC with important findings which will translate into better treatment results. As this tumor is uncommon in other parts of the world, continued efforts to improve the prevention, early diagnosis, treatment and care of this tumor are required in China.link_to_OA_fulltex

Can intensity-modulated radiotherapy preserve oral health-related quality of life of nasopharyngeal carcinoma patients?

Purpose: To investigate the changes in salivary function and oral health-related quality of life for patients with nasopharyngeal carcinoma treated by intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 57 patients with early-stage nasopharyngeal carcinoma received IMRT. The parotid and whole saliva flow was measured, and the Medical Outcomes Study 36-item short form, European Organization for Research and Treatment of Cancer Quality of Life questionnaire-C30, European Organization for Research and Treatment of Cancer Quality of Life questionnaire 35-item head-and-neck module, and Oral Health Impact Profile questionnaires were completed at baseline and 2, 6, 12, 18, and 24 months after IMRT. Results: Parotid saliva flow recovered fully after 1 year and maintained. Whole saliva flow recovered partially to 40% of baseline. A general trend of deterioration in most quality of life scales was observed after IMRT, followed by gradual recovery. Persistent oral-related symptoms were found 2 years after treatment. Conclusion: IMRT for early-stage nasopharyngeal carcinoma could only partially preserve the whole salivary function and oral health-related quality of life. © 2012 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

The efficacy of fiberoptic endoscopic examination and biopsy in the detection of early nasopharyngeal carcinoma

Fiberoptic endoscopic examination and biopsy of the nasopharynx was done in 130 patients as a prospective study. They all had elevated titers of antibodies against the viral capsid antigen of Epstein-Barr virus but no symptoms or signs of nasopharyngeal carcinoma. Each underwent a biopsy from six fixed sites in the nasopharynx. Of the 780 biopsy specimens taken from seven patients, 11 showed the presence of nasopharyngeal carcinoma. Techniques to improve the yields of such biopsies with fiberoptic endoscopy are discussed. The presence of tumor was unrelated to the macroscopic endoscopic findings. The highest incidence of subclinical tumor is in the pharyngeal recess.link_to_subscribed_fulltex

Nasopharyngeal carcinoma research in Hong Kong in the past decade

Objective: To review the research carried out in Hong Kong on nasopharyngeal carcinoma (NPC) over the past 10 years. Methods: The literature published in Hong Kong over the past 10 years on nasopharyngeal carcinoma were reviewed in the light of other important international publications on the same subject. Results: The research carried out in Hong Kong covers etiology, natural behavior, treatment and prognosis of NPC. These studies not only elucidated the different aspects of NPC, many of these new findings will also guide future directions of research. Conclusions: Major efforts have been made to research into the various aspects of PC with important findings which will translate into better treatment results. As this tumor is uncommon in other parts of the world, continued efforts to improve the prevention, early diagnosis, treatment and care of this tumor are required in China.link_to_OA_fulltex