Support effects on adsorption and catalytic activation of O2 in single atom iron catalysts with graphene-based substrates.

The adsorption and catalytic activation of O2 on single atom iron catalysts with graphene-based substrates were investigated systematically by density functional theory calculation. It is found that the support effects of graphene-based substrates have a significant influence on the stability of the single atom catalysts, the adsorption configuration, the electron transfer mechanism, the adsorption energy and the energy barrier. The differences in the stable adsorption configuration of O2 on single atom iron catalysts with different graphene-based substrates can be well understood by the symmetrical matching principle based on frontier molecular orbital analysis. There are two different mechanisms of electron transfer, in which the Fe atom acts as the electron donor in single vacancy graphene-based substrates while the Fe atom mainly acts as the bridge for electron transfer in double vacancy graphene-based substrates. The Fermi softness and work function are good descriptors of the adsorption energy and they can well reveal the relationship between electronic structure and adsorption energy. This single atom iron catalyst with single vacancy graphene modified by three nitrogen atoms is a promising non-noble metal single atom catalyst in the adsorption and catalytic oxidation of O2. Furthermore, the findings can lay the foundation for the further study of graphene-based support effects and provide a guideline for the development and design of new non-noble-metal single atom catalysts.

[Hydrophilic Surface Modification of Polydimethylsiloxane with UV/Ozone Treatment].

The UV/ozone surface treatment was a simple and low cost hydrophilic modification method. In this paper，UV/ozone treatment is utilized to hydrophilize the surface of PDMS and the results are compared. Contact angle is applied to estimate the effect and stability of the modified surfaces. The results show that the contact angle is around 60° on the PDMS surface with UV/ozone treatment after 12 hours, and it can maintain the surface hydrophilicity in two weeks under ambient atmosphere. The results of FTIR spectroscopy indicate that many chemical functional groups of PDMS surface have been changed with UV/ozone modification, ­CH3 hydrophobic group gradually decrease over time, ­OH and Si­OH hydrophilic groups increase obviously, and the characteristic peaks of SiO2 gradually appear. Through SEM/EDS analysis, it has been found that the major constituent of the surface of PDMS is SiO2 after the surface modification. These results demonstrate that the more hydrophilic groups and the glass-like SiOx layer are formed on the PDMS surface modified with UV/ozone, which enhance the surface hydrophilic and minimize the hydrophobic recovery.

[Reduced irradiation target volume of mediastinal lymph node drainage in conformal radiotherapy for patients with non-small cell lung cancer after thoracic surgery].

OBJECTIVE: To decrease lung and esophageal radiation injuries by reducing irradiation target volume of mediastinal lymph mode drainage in conformal radiotherapy (CRT) for patients with non-small cell lung cancer (NSCLC) after thoracic surgery. METHODS: Fifty-three patients with NSCLC were randomized into groups A and B to receive 3D-CRT after thoracic surgery. Patients in group A, according to conventional therapy, received preventive nodal irradiation (PNI) of the mediastinal lymph node drainage, and those in group B, according to pathological nodal staging after operation, did not have PNI of the metastasis-free area to reduce the clinical target volume (CTV). Patients in both groups were treated with conventional fractionated radiotherapy (CFRT) at 2 Gy in each fraction, and 5 fractions each week. All patients were followed up for two years to record their 2-year survival rate, local relapse of lymph node drainage and lung and esophageal radiation injuries. RESULTS: The total 2-year survival rate was 58.5%in these patients and comparable between the two groups. The rates of local regional relapse and recurrence out of the CTV were 13.8% and 3.4% in group A and 16.7% and 8.3% in group B, respectively (P=1 and P=0.571). The incidence of radiation pneumonia and lung fibrosis were 6.9% and 62.1% in group A and 0% and 58.3% in group B (P=0.459 and P=0.782), and that of radiation esogphagitis and esophagus stricture rates were 27.6% and 6.9% in group A and 12.5% and 4.2% in group B, respectively (P=0.039 and P=1). CONCLUSION: Reduced CTV does not warrant decrease in the local control but may lower the incidence of acute esophageal radiation injury in postoperative patients with NSCLC.

[Relationship between radiosensitivity of nasopharyngeal carcinoma and MDR1 gene polymorphism].

OBJECTIVE: To investigate the relationship between human multidrug resistancel gene (MDR1) polymorphisms and the radiosensitivity of nasopharyngeal carcinoma (NPC). METHODS: Blood samples were collected from 59 NPC patients, who were devided into radiosensitive or radioresistant groups according to their responses to radiation therapy. The genotypes for MDR1 polymorphisms (G2677T in exon 21 and C3435T in exon 26) and their haplotypes were determined by PCR and restriction fragment length polymorphism analysis. The results were further confirmed by sequencing. RESULTS: The 3435CC genotype was associated with a significantly better response to radiotherapy than combined 3435 CT and TT genotype (P=0.026). The 2677GG genotype was also associated with a better response in comparison with combined 2677 GT and TT genotype, but this relation was not statistically significant. Patients with 2677G-3435C haplotype had a significant better response to radiotherapy than those with the other haplotypes (P=0.017). CONCLUSION: The MDR1 G2677T and C3435T polymorphisms may help predict the response to radiotherapy in NPC patients.

Therapeutic effect of three-dimensional conformal radiotherapy on locally advanced pancreatic carcinoma.

OBJECTIVE: To evaluate the effects of the two conformal radiotherapy modalities in the treatment of locally advanced pancreatic carcinoma. METHODS: From October, 1998 to June, 2001, 67 patients with locally advanced pancreatic carcinoma received conformal radiotherapy (CRT). Vacuum cushions were applied to immobilize the patients before contrast CT scans, the treatment plans were simulated by three-dimensional treatment planning system. The patients were randomized into group A to receive a total dose of 45-54 Gy given in 8-12 fractions completed in 18-27 d and group B with a total dose of 45-54 Gy in 15-18 fractions within 20-25 d. RESULTS: The partial and complete pain relief rates of the two groups were 95.9% and 81.6%, respectively, one month after the completion of the radiotherapy, with a median survival of 12.5 months. The response rates of the patients and the 2-year overall survival rates in group A were 81.8% and 51.6%, respectively, and were 35.3% and 12.1% in group B. The low-dose fractionated CRT was superior than accelerated CRT. CONCLUSION: For patients with unresectable pancreatic cancer receiving low-dose fractionated CRT, a high dose targeted at the tumor can be given in a fraction and the normal surrounding tissues are exposed to low-dose radiation, to achieve good therapeutic effect with minimized adverse effects on normal tissues in relation to the exposure.

Etiological analysis of the sequelae of radiotherapy for nasopharyngeal carcinoma: a follow-up study of 112 cases.

OBJECTIVE: To explore the etiology of the sequelae of radiotherapy for nasopharyngeal carcinoma (NPC) so as to find the possible means for reducing or preventing its occurrence. METHODS: A total of 112 pathologically confirmed patients with nasopharyngeal carcinoma, who had survived for 5 years following the radiotherapy, were included in this study. Sixty-four patients with the primary carcinoma in the nasopharyngeal region received radiotherapy with the radiation field covering the bilateral anterior ear regions, and in the other 48 patients, adjuvent exposure of the anterior nasal region was administered. The metastases in the cervical lymph nodes were exposed to tangential radiation by 40 Gy X-ray followed by approximately 20 Gy vertical electron beam exposure. RESULTS: Limited mouth-opening and dry mouth occurred mostly during the first 2 years after radiotherapy, and hearing loss in the first year. Neck fibrosis tended to increase with the time elapse after the therapy, and posterior cranial nerve damages showed no signs of time-related occurrence. It was found that the occurrence of neck fibrosis, dry mouth and the nerve injuries did not obviously correlate with the dosage of X-ray exposure in the anterior ear regions, while limited mouth-opening and the hearing loss increased with the radiation dosage. The sequelae did not arise from different radiation field selection as adopted in this study. CONCLUSION: The radiation dose should be controlled at around 70 Gy for NPC treatment, and for carcinoma remnant in the nasopharyngeal region, additional dose in the cavity would be appropriate. When the X-ray dose of 65 Gy in the neck region fails to result in satisfactory recession of lymph node metastasis, comprehensive treatment involving multiple modalities should be considered.