Thermoelectric performance enhancement of calcium cobaltite through barium grain boundary segregation.

We report the dramatic increase of the Seebeck coefficient S and thermoelectric performance of calcium cobaltite Ca3Co4O9+δ ceramics through non-stoichiometric addition of minute amount of Ba. The nominal chemistry of polycrystal pellets are Ca3BaxCo4O9+δ (x = 0, 0.01, 0.05, and 0.1). At 323 K, S of Ca3Co4O9+δ is 135 µV K(-1), whereas S of Ba incorporated Ca3Ba0.05Co4O9+δ is 162.5 µV·K(-1), which is the highest S value near room temperature regime reported for calcium cobaltite. The increase of S for Ca3Ba0.05Co4O9+δ sample is accompanied by the decrease of the electrical resistivity ρ, resulting in high power factor S(2)/ρ of 843 µW·m(-1) K(-2) at 1007 K. Moreover, the thermal conductivities κ of Ca3BaxCo4O9+δ decrease with the increase of the Ba addition. The figure-of-merit ZT for Ca3Ba0.05Co4O9+δ reaches 0.52 at 1073 K and a factor of 2.5 increment in comparison with undoped Ca3Co4O9+δ. Nanostructure examinations show that the added Ba segregated at the Ca3Co4O9+δ grain boundaries, while the Ca3Co4O9+δ grain interior is free of Ba. Performance enhancement is attributed to the carrier filtering effect caused by the Ba segregation. In addition, Ba segregation promotes the better crystal alignment and the development of crystal texture.

Comprehensive commissioning of a cone beam CT imaging ring for treatment of HDR GYN patients.

PURPOSE: A new mobile cone beam computed tomography (CBCT) imaging ring (IRm, Elekta, v2.10.6, Veenendaal, Netherlands) has recently been proposed for brachytherapy to improve procedure efficiency. We describe the commissioning process and end-to-end tests for GYN HDR brachytherapy employing IRm CBCT imaging. MATERIALS AND METHODS: Commissioning included imaging isocenter test, 3D image quality, 2D imaging quality, image dose, and tube characteristics. CIRS HDR GYN phantom and Venezia CT/MR gynecological applicator were used to perform end-to-end (E2E) tests and optimize workflow. Venezia applicator and four interstitial needles were inserted into the phantom and IRm CBCT images were acquired. Phantom and applicator were scanned with CT scanner (Siemens SOMATOM go.Open Pro) using department's pelvis imaging protocol. MR imaging was performed using 0.35T MR Linac TRUFI pulse sequence. CBCT images were registered to CT and MR using rigid registration to assess image quality and applicator geometry fidelity. RESULTS: All physics tests passed within acceptance tolerances. Registration of CBCT images to MR and CT scans was acceptable for applicator placement. Applicator registration of CBCT images to CT demonstrated excellent agreement of most distal source dwell position (<1 mm). Slice thickness was also measured to be 1.25 mm, within 0.5 mm of its nominal value. CONCLUSION: Based on E2E and commissioning results, IRm is an appropriate tool for brachytherapy treatment planning. This study demonstrated good image quality in GYN phantom and Venezia applicator using the IRm. Distal source dwell position agreement between CBCT and CT was acceptable for clinical use.

Prospective Trial of Functional Lung Avoidance Radiation Therapy for Lung Cancer: Quality of Life Report.

PURPOSE: A novel form of lung function imaging has been developed that uses 4-dimensional computed tomography (4DCT) data to generate lung ventilation images (4DCT-ventilation). Functional avoidance uses 4DCT-ventilation to reduce doses to functional lung with the aim of reducing pulmonary side effects. A phase 2, multicenter 4DCT-ventilation functional avoidance clinical trial was completed. The purpose of this work was to quantify changes in patient-reported outcomes (PROs) for patients treated with functional avoidance and determine which metrics are predictive of PRO changes. MATERIALS AND METHODS: Patients with locally advanced lung cancer receiving curative-intent radiation therapy were accrued. Each patient had a 4DCT-ventilation image generated using 4DCT data and image processing. PRO instruments included the Functional Assessment of Cancer Therapy-Lung (FACT-L) questionnaire administered pretreatment; at the end of treatment; and at 3, 6, and 12 months posttreatment. Using the FACT-Trial Outcome Index and the FACT-Lung Cancer Subscale results, the percentage of clinically meaningful declines (CMDs) were determined. A linear mixed-effects model was used to determine which patient, clinical, dose, and dose-function metrics were predictive of PRO decline. RESULTS: Of the 59 patients who completed baseline PRO surveys. 83% had non-small cell lung cancer, with 75% having stage 3 disease. The median dose was 60 Gy in 30 fractions. CMD FACT-Trial Outcome Index decline was 46.3%, 38.5%, and 26.8%, at 3, 6, and 12 months, respectively. CMD FACT-Lung Cancer Subscale decline was 33.3%, 33.3%, and 29.3%, at 3, 6, and 12 months, respectively. Although an increase in most dose and dose-function parameters was associated with a modest decline in PROs, none of the results were significant (all P > .053). CONCLUSIONS: The current work presents an innovative combination of use of functional avoidance and PRO assessment and is the first report of PROs for patients treated with prospective 4DCT-ventilation functional avoidance. Approximately 30% of patients had clinically significant decline in PROs at 12 months posttreatment. The study provides additional data on outcomes with 4DCT-ventilation functional avoidance.

Grain Boundary Phase Segregation for Dramatic Improvement of the Thermoelectric Performance of Oxide Ceramics.

This work presents a novel approach of dramatically increasing the energy conversion efficiency of thermoelectric CaMnO3-δ ceramics through the combination of lattice dopants substitution and secondary phase segregation at the grain boundaries. The oxide ceramic samples are with the nominal composition of Ca1- xBi xMnCu yO3-δ ( x = 0, 0.02, 0.03; y = 0.02, 0.04). When Cu is introduced into the Ca1- xBi xMnCu yO3-δ samples, the grain growth from Bi-doped CaMnO3-δ grains is accompanied by the limited solubility of Cu ions in the grain interior, whereas Cu mainly formed a CuO secondary phase at the grain boundaries. Cu nonstoichiometry addition subsequently resulted in the increase of the Seebeck coefficient and decrease of electrical resistivity simultaneously. The sample with designed chemistry of Ca2.97Bi0.03MnCu0.04O3-δ exhibits the power factor of 2.4 mW m-1 K-2 at 337 K and figure of merit ZT of 0.67 at 773 K. This ZT of 0.67 is by far the highest ZT reported for various perovskites oxide ceramics. Such enhancements in electrical power factor and the overall ZT are attributed to the synergistic effect of decreasing the carrier concentration to increase the Seebeck coefficient and simultaneously increasing the carrier mobility through the existence of CuO phase at the grain boundaries.