Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO_3 with R = La, Pr, Nd and Eu

We present a combined study of the thermal expansion and the thermal conductivity of the perovskite series RCoO_3 with R = La, Nd, Pr and Eu. The well-known spin-state transition in LaCoO_3 is strongly affected by the exchange of the R ions due to their different ionic radii, i.e. chemical pressure. This can be monitored in detail by measurements of the thermal expansion, which is a highly sensitive probe for detecting spin-state transitions. The Co ions in the higher spin state act as additional scattering centers for phonons, therefore suppressing the phonon thermal conductivity. Based on the analysis of the interplay between spin-state transition and heat transport, we present a quantitative model of the thermal conductivity for the entire series. In PrCoO_3, an additional scattering effect is active at low temperatures. This effect arises from the crystal field splitting of the 4f multiplet, which allows for resonant scattering of phonons between the various 4f levels.Comment: 15 pages including 5 figure

Thermal Conductivity, Thermopower, and Figure of Merit of La_{1-x}Sr_xCoO_3

We present a study of the thermal conductivity k and the thermopower S of single crystals of La_{1-x}Sr_xCoO_3 with 0<= x <= 0.3. For all Sr concentrations La_{1-x}Sr_xCoO_3 has rather low k values, whereas S strongly changes as a function of x. We discuss the influence of the temperature- and the doping-induced spin-state transitions of the Co ions on both, S and k. From S, k, and the electrical resistivity rho we derive the thermoelectric figure of merit Z=S^2/(k*rho). For intermediate Sr concentrations we find notably large values of Z indicating that Co-based materials could be promising candidates for thermoelectric cooling.Comment: 7 pages, 5 figures included, submitted to Phys. Rev.

Spin-State Transition and Metal-Insulator Transition in La1−x_{1-x}Eux_xCoO3_3}

We present a study of the structure, the electric resistivity, the magnetic susceptibility, and the thermal expansion of La$_{1-x}$Eu$_x$CoO$_3$. LaCoO$_3$ shows a temperature-induced spin-state transition around 100 K and a metal-insulator transition around 500 K. Partial substitution of La$^{3+}$ by the smaller Eu$^{3+}$ causes chemical pressure and leads to a drastic increase of the spin gap from about 190 K in LaCoO$_3$ to about 2000 K in EuCoO$_3$, so that the spin-state transition is shifted to much higher temperatures. A combined analysis of thermal expansion and susceptibility gives evidence that the spin-state transition has to be attributed to a population of an intermediate-spin state with orbital order for $x<0.5$ and without orbital order for larger $x$. In contrast to the spin-state transition, the metal-insulator transition is shifted only moderately to higher temperatures with increasing Eu content, showing that the metal-insulator transition occurs independently from the spin-state distribution of the Co$^{3+}$ ions. Around the metal-insulator transition the magnetic susceptibility shows a similar increase for all $x$ and approaches a doping-independent value around 1000 K indicating that well above the metal-insulator transition the same spin state is approached for all $x$.Comment: 10 pages, 6 figure

МЕТОДИКА ПРОВЕДЕННЯ ІСТОРИКО-КРАЄЗНАВЧИХ ЕКСПЕДИЦІЙ НА ПІВДНІ УКРАЇНИ ІНСТИТУТОМ ЕТНОГРАФІЇ АН СРСР у 50-60-ті рр. ХХ ст.

Український народ у своїй історії має великий досвід духовного життя, бо з покоління в покоління передає набуті навички, що стали невід’ємною части-ною нашої національності. Але з кожним роком наше покоління, на жаль, втра-чає зв’язок з попередніми поколіннями. Тому, щоб зберегти традиції, націона-льні особливості, в різні часи різноманітні інститути, товариства, окремі дослі-дники намагались створити найоптимальнішу методику організації та прове-дення історико-краєзнавчих експедицій

Structural and chemical investigations of adapted Siemens feed rods for an optimized float zone process

The optimization of the float zone process for industrial application is a promising way to crystallize high purity silicon for high efficiency solar cells with reduced process costs. We investigated two differently produced Siemens rods which should be used as feed material for the float zone process. The aim is to identify and to improve material properties of the feed rods which have a high impact to the float zone process. We show here microstructural and chemical analysis comparing feed rods manufactured under standard conditions and under float zone adapted conditions. To resolve the growth behavior of the grains SEM/EBSD mappings are performed at different positions. TEM analyses are used to investigate the interface region between the mono- and the multicrystalline silicon within the Siemens feed rod. Additionally, drilled cores are cut out from the feed rods containing the region of the slim rod. Afterwards, the drilled cores are crystallized with the float zone process. Finally, carbon and oxygen measurements with FT-IR spectrometry on different positions of the crystallized drilled cores of the Siemens feed rods show the influence of the slim rod material to the float zone process

Influence of slim rod material properties to the Siemens feed rod and the float zone process

The identification and understanding of material properties influencing the float zone process is important to crystallize high purity silicon for high efficiency solar cells. Also the knowledge of minimal requirements to crystallize monocrystalline silicon with the float zone process is of interest from an economic point of view. In the present study, feed rods for the float zone process composed of a central slim rod and the deposited silicon from the Siemens process are investigated. Previous studies have shown that the slim rod has a significant impact on the purity and suitability for further crystallization processes. In particular, contaminations like substitutional carbon and the presence of precipitates as well as the formation of oxide layers play an important role and are investigated in detail. For this purpose different slim rod materials were used in deposition and float zone crystallization experiments. Samples were prepared by cross sectioning and core drilling of Siemens rods, which were recrystallized with the float zone process. Recrystallized drilled cores are analyzed with FT-IR spectrometry concerning the carbon and oxygen content. To estimate the grain growth behavior on the slim rod surface in dependence of the used slim rod material, EBSD mappings inside a SEM are performed on squared and circular slim rods. TEM analysis was used to investigate the presence of an oxide layer at the interface between slim rod and deposited polycrystalline silicon. Additionally the influence of a nitrogen-containing gas atmosphere during the slim rod pulling is investigated by IR microscopy and ToF-SIMS regarding Si3N4 precipitation

Bevacizumab in association with de Gramont 5-fluorouracil/folinic acid in patients with oxaliplatin-, irinotecan-, and cetuximab-refractory colorectal cancer: a single-center phase 2 trial.

BACKGROUND: The aim of the current study was the investigation of the value of bevacizumab+5-fluorouracil(5-FU)/folinic acid in patients with advanced colorectal cancers who have exhausted standard chemotherapy options. METHODS: The authors included 48 heavily pretreated patients (colon:rectum, 33:15; men:women, 23:25; median age, 63 years; range, 27-79 years) whose disease had progressed during or within an oxaliplatin-based first-line chemotherapy, an irinotecan-based second-line regimen, and a third-line treatment with cetuximab plus weekly irinotecan. Bevacizumab was given at a dose of 5 mg/kg. 5-FU/folinic acid was administered according to the de Gramont schedule. RESULTS: The response rate was 6.25%, and 30.4% of patients demonstrated stable disease as the best response. The median time to disease progression was 3.5 months (95% confidence interval [95% CI], 2.3-6.9 months), and the median survival time was 7.7 months (95% CI, 3.9-11.9 months). The most common grade 3 to 4 side toxicities (graded according to the National Cancer Institute Common Toxicity Criteria [version 2.0]) were: diarrhea (20.8%), fatigue (14.5%), and stomatitis (12.5%). Grade 3 to 4 hemorrhage occurred in 8 patients (16.6%), including 4 cases of bleeding in the gastrointestinal tract. Other relatively common adverse events such as hypertension, thrombosis, and bowel perforation were reported in 50%, 18.7%, and 4.16%, of patients respectively. CONCLUSIONS: The data from the current study suggest a modest but significant clinical benefit of bevacizumab+de Gramont schedule in heavily pretreated colorectal cancer patients. Copyright (c) 2009 American Cancer Society

Multipoint temperature monitoring of microwave thermal ablation in bones through fiber bragg grating sensor arrays

Bones are a frequent site of metastases that cause intolerable cancer-related pain in 90% of patients, making their quality of life poor. In this scenario, being able to treat bone oncology patients by means of minimally invasive techniques can be crucial to avoid surgery-related risks and decrease hospitalization times. The use of microwave ablation (MWA) is gaining broad clinical acceptance to treat bone tumors. It is worth investigating temperature variations in bone tissue undergoing MWA because the clinical outcomes can be inferred from this parameter. Several feasibility studies have been performed, but an experimental analysis of the temperature trends reached into the bone during the MWA has not yet been assessed. In this work, a multi-point temperature study along the bone structure during such treatment is presented. The study has been carried out on ex vivo bovine femur and tibia, subjected to MWA. An overall of 40 measurement points covering a large sensing area was obtained for each configuration. Temperature monitoring was performed by using 40 fiber Bragg grating (FBGs) sensors (four arrays each housing 10 FBGs), inserted into the bones at specific distances to the microwave antenna. As result, the ability of this experimental multi-point monitoring approach in tracking temperature variations within bone tissue during MWA treatments was shown. This study lays the foundations for the design of a novel approach to study the effects of MWA on bone tumors. As consequence, the MWA treatment settings could be optimized in order to maximize the treatment effects of such a promising clinical application, but also customized for the specific tumor and patient

Gut microbiota-derived propionate reduces cancer cell proliferation in the liver

Peer reviewedPublisher PD