Results 1 - 10 of 11
Results 1 - 10 of 11. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] Purpose: To determine the effect of cellular proliferation and cell cycle stage on the ability of postirradiation 5-fluorouracil (5-FU) to radiosensitize cultured human colon adenocarcinoma Clone A cells. Methods and Materials: Cell survival curves were generated for irradiated: (a) log- and plateau-phase Clone A cells; and (b) Clone A cells separated by centrifugal elutriation into the various phases of the cell cycle; with and without postirradiation treatment with 100 μg/ml 5-FU. Results: Postirradiation treatment with 5-FU sensitized proliferating cells to a greater degree than it sensitized cells growing in plateau phase. The β component of cell kill in log-phase cells was increased by a factor of 1.5 with a sensitizer enhancement ratio of 1.21 at the 0.01 survival level. Plateau-phase cells showed less radiosensitization (sensitizer enhancement ratio of 1.13 at the 0.01 survival level); however, there was a mild increase in both α and β kill in plateau-phase cells. Elutriated G1 cells were the most radiosensitive, independent of treatment with 5-FU. The phase of the cell cycle had little effect on the ability of fluorouracil to radiosensitize Clone A cells. Conclusion: Proliferating cells are more susceptible to radiosensitization with 5-FU than plateau-phase cells are, but this effect appears to be independent of the phase of the cell cycle
[en] Herein, a new and facile synthesis of a tin-carbon nanocomposite and its electrochemical characterization is presented. Tin nanoparticles were embedded in micron-sized carbonaceous particles, thus successfully preventing the aggregation of tin nanoparticles and buffering the occurring volume strain, which accompanies the reversible (de-)alloying process. Such active material presents specific capacities of around 440 and 390 mAh g−1 for applied specific currents of 0.1 and 0.2 A g−1, respectively, as lithium-ion anode using environmentally friendly and cost-efficient carboxymethyl cellulose as binder. Even more remarkably, at very high specific currents of 2, 5, and 10 A g−1, electrodes based on this composite still offer specific capacities of about 280, 240, and 187 mAh g−1, respectively. In addition, this tin-carbon nanocomposite appears highly promising as anode material for sodium-ion batteries, showing very stable cycling performance in a suitable potential range, and specific capacities of more than 180, 150, 130, and 90 mAh g−1 for an applied specific current of 12.2, 122, 244, and 610 mA g−1, respectively, thus highlighting the high versatility of this composite active material for both Li-ion and Na-ion battery technologies
[en] The multiterminal transport of electrons through a lattice of coupled quantum dots is studied in terms of the array topology and geometry, the internal features of its nodes, and an applied magnetic flux. The scattering properties of individual dots are addressed through separation of interfering lead-coupled states, boundary guiding and magnetic deflection. By assembling the dots into a lattice of variable spacing, connectivity and terminal positioning, the possibility of mode-resolved control of scattering between input and output lead states is investigated.
[en] Purpose: To evaluate preoperative infusional chemoradiation for patients with operable rectal cancer. Methods and Materials: Preoperative chemoradiation therapy using infusional 5-fluorouracil (5-FU), (300 mg/m2/day) together with daily irradiation (45 Gy/25 fractions/5 weeks) was administered to 77 patients with clinically Stage T3 rectal cancer. Endoscopic ultrasound confirmed the digital rectal exam in 63 patients. Surgery was performed approximately 6 weeks after the completion of chemoradiation therapy and included 25 abdominoperineal resections and 52 anal-sphincter-preserving procedures. Results: Posttreatment tumor stages were T1-2, N0 in 35%, T3 N0 in 25%, and T1-3, N1 in 11%; 29% had no evidence of tumor. Local tumor control after chemoradiation was seen in 96% (74 out of 77); 2 patients had recurrent disease at the anastomosis site and were treated successfully with abdominoperineal resection. Overall, pelvic control was obtained in 99% (76 out of 77). The survival after chemoradiation was higher in patients without node involvement than in those having node involvement (p = n.s.). More patients with pathologic complete responses or only microscopic foci survived than did patients who had gross residual tumor (p = 0.07). The actuarial survival rate was 83% at 3 years; the median follow-up was 27 months, with a range of 3 to 68 months. Acute, perioperative, and late complications were not more numerous or more severe with chemoradiation therapy than with traditional radiation therapy (XRT) alone. Conclusions: Excellent treatment response allowed two-thirds of the patients to have an anal-sphincter-sparing procedure. Gross residual disease in the resected specimen indicates a poor prognosis, and therapies specifically targeting these patients may improve survival further
[en] X-ray absorption spectroscopy (XAS) is applied to study the local geometry of Co, Ni, and Mn sites in a new high voltage cathode for lithium batteries. The material is a solid solution between Li2MnO3 and Li(x)Mn0.4Ni0.4Co0.2O2. The XAS technique has permitted to check the local atomic structure and charge associated with the metals in a series of electrodes with different lithium concentration x, obtained during the first charge operation, and compared to the first discharge and a successive charge. The ex-situ XAS investigation on the initial activation of the cathode material (first charge) can be described by two separated reaction of LiMO2 (M = Ni and Co) and Li2MnO3. The strength and limitations of the ExAFS approach in these materials is underlined. (paper)
[en] Highlights: ► Layered P2-Na0.45Ni0.22Co0.11Mn0.66O2 reversibly uptakes and releases Li and Na cations. ► Electrochemical performance of sodium intercalation is better than that of lithium. ► Na0.45Ni0.22Co0.11Mn0.66O2 shows good Na-ion intercalation capacity (125 mAh g−1). ► Na0.45Ni0.22Co0.11Mn0.66O2 shows high average discharge voltage (>3.3 V). ► Na-ion insertion in Na0.45Ni0.22Co0.11Mn0.66O2 offers high charge efficiency (≥99.5%). -- Abstract: Herein is reported the electrochemical performance of Na0.45Ni0.22Co0.11Mn0.66O2 as cathode material for lithium and sodium batteries. The material is able to reversibly accommodate both cation species but reveals a much better electrochemical performance towards Na-ion intercalation. Upon galvanostatic cycling for 100 cycles a much higher capacity retention (82% vs. Na, 61% vs. Li) and higher coulombic efficiency (99.5% vs. Na, 98.5% vs. Li) are shown by the sodium-based system. The worse electrochemical performance of the lithium-based system can be explained by the much higher irreversibility of the Mn3+/Mn4+ redox process
[en] Purpose: To determine the precision of megavoltage computed tomography (MVCT)-based alignment of the seroma cavity for patients undergoing partial breast irradiation; and to determine whether accelerated partial breast irradiation (APBI) plans can be generated for TomoTherapy deliveries that meet the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/Radiation Therapy Oncology Group (RTOG) 0413 protocol guidelines for target coverage and normal tissue dose limitations. Methods and Materials: We obtained 50 MVCT images from 10 patients. An interuser study was designed to assess the alignment precision. Using a standard helical and a fixed beam prototype ('topotherapy') optimizer, two APBI plans for each patient were developed. Results: The precision of the MVCT-based seroma cavity alignment was better than 2 mm if averaged over the patient population. Both treatment techniques could be used to generate acceptable APBI plans for patients that fulfilled the recommended NSABP B-39/RTOG-0413 selection criteria. For plans of comparable treatment time, the conformation of the prescription dose to the target was greater for helical deliveries, while the ipsilateral lung dose was significantly reduced for the topotherapy plans. Conclusions: The inherent volumetric imaging capabilities of a TomoTherapy Hi-Art unit allow for alignment of patients undergoing partial breast irradiation that is determined from the visibility of the seroma cavity on the MVCT image. The precision of the MVCT-based alignment was better than 2 mm (± standard deviation) when averaged over the patient population. Using the NSABP B-39/RTOG-0413 guidelines, acceptable APBI treatment plans can be generated using helical- or topotherapy-based delivery techniques
[en] In an attempt to realize sodium-ion batteries with enhanced safety, we report herein the utilization of ionic liquid (IL)-based electrolytes for cycling nanoparticulate anatase TiO_2 as sodium-ion anode material. The use of the IL-based electrolyte results in the highly stable cycling performance of anatase TiO_2-based electrodes, providing an initial specific capacity of 159 mAh g"−"1 when applying a specific current of 33.5 mA g"−"1, and still 155 mAh g"−"1 after 80 full (dis-)charge cycles. Moreover, a very promising rate performance is obtained with specific capacities of 108 and 78 mAh g"−"1 for specific currents of 335 and 670 mA g"−"1, respectively. Indeed, the excellent electrochemical performance, and high coulombic efficiency, as well as the electrochemical impedance spectroscopy results indicate the highly beneficial impact of the IL-based electrolyte on the formation of a stabilized solid electrolyte interphase (SEI).
[en] Purpose: To report on the initial clinical use of a commercially available system to deliver gated treatment using implanted fiducials, in-room kV X-rays, and an infrared camera tracking system. Methods and Materials: ExacTrac Adaptive Gating from BrainLab is a localization system using infrared cameras and X-rays. Gating signals are the patient's breathing pattern obtained from infrared reflectors on the patient. kV X-rays of an implanted fiducial are synchronized to the breathing pattern. After localization and shift of the patient to isocenter, the breathing pattern is used to gate Radiation. Feasibility tests included localization accuracy, radiation output constancy, and dose distributions with gating. Clinical experience is reported on treatment of patients with small lung lesions. Results: Localization accuracy of a moving target with gating was 1.7 mm. Dose constancy measurements showed insignificant change in output with gating. Improvements of dose distributions on moving targets improved with gating. Eleven patients with lung lesions were implanted with 20 mm x 0.7 mm gold coil (Visicoil). The implanted fiducial was used to localize and treat the patients with gating. Treatment planning and repeat computed tomographic scans showed that the change in center of gross target volume (GTV) to implanted marker averaged 2.47 mm due in part to asymmetric tumor shrinkage. Conclusion: ExacTrac Adaptive Gating has been used to treat lung lesions. Initial system evaluation verified its accuracy and usability. Implanted fiducials are visible in X-rays and did not migrate