3,061 research outputs found

    TMCalc - A fast code to derive Teff and [Fe/H] for FGK stars

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    We present a new direct spectroscopic calibration for a fast estimation of the stellar metallicity [Fe/H]. These calibrations were computed using a large sample of 451 solar-type stars for which we have precise spectroscopic parameters derived from high quality spectra. The new [Fe/H] calibration is based on weak Fe I lines, which are expected to be less dependent on surface gravity and microturbulence, and require only a pre-determination of the effective temperature. This temperature can be obtained using a previously presented line-ratio calibration. We also present a simple code that uses the calibrations and procedures presented in these works to obtain both the effective temperature and the [Fe/H] estimate. The code, written in C, is freely available for the community and may be used as an extension of the ARES code. We test these calibrations for 582 independent FGK stars. We show that the code can be used as a precise and fast indicator of the spectroscopic temperature and metallicity for dwarf FKG stars with effective temperatures ranging from 4500 K to 6500 K and with [Fe/H] ranging from -0.8 dex to 0.4 dex.Comment: 10 pages, 8 Figures, published in A&

    Efecto de las características del biorreactor y de su manejo sobre el desarrollo de cultivos embriogénicos de alcornoque

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    En el marco del proyecto SEFEAL-2, liderado por TRAGSA, se aplican protocolos de embriogénesis somática (ES) para desarrollar variedades de alcornoque de alta calidad y productividad. Al mismo tiempo se mejora la técnica de ES para abaratar los costes y permitir su aplicación a escala comercial. En el alcornoque, como en otras especies, el desarrollo comercial de la embriogénesis como técnica de multiplicación masiva se basa en el uso de biorreactores y medios líquidos agitados. El diseño del biorreactor, su sistema de cierre y el nivel de agitación determinan el grado de mezclado, el estrés hidrodinámico y el intercambio gaseoso, y por ello afectan tanto al crecimiento como al desarrollo de los cultivos embriogénicos. Mediante un ensayo factorial se testaron 3 tipos de envase y tres niveles de agitación. Los efectos sobre el intercambio gaseoso se estimaron a través de la tasa de transferencia de O2 (OTR) y su coeficiente volumétrico de transferencia de masa (KLa), y los efectos sobre el nivel de mezclado mediante el “shear force index” (SFI), un indicador de estrés hidrodinámico. El tipo de envase afectó básicamente al número total de agregados embriogénicos y a la frecuencia de formación de los agregados de mayor tamaño. El nivel de agitación tuvo mayores efectos que el tipo de envase tanto sobre el número como sobre el tamaño de los agregados. Para las condiciones ensayadas, que dieron lugar a valores de KLa comprendidos entre 0,11 h-1 y 1,47 h-1, la disponibilidad de oxígeno no pareció limitante. En cualquier caso, los efectos del tipo de envase y del nivel de agitación sobre los procesos de crecimiento y desarrollo de los materiales embriogénicos de alcornoque fueron complejos resultando muy significativa la interacción tipo de envase por nivel de agitación

    Circulating vitamin D levels and colorectal cancer risk: a meta-analysis and systematic review of case-control and prospective cohort studies

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    The associations between circulating vitamin D concentrations and total and site-specific colorectal cancer (CRC) incidence have been examined in several epidemiological studies with overall inconclusive findings. The aim of this systematic review and meta-analysis of both case-control and prospective cohort studies was to evaluate the association between CRC and circulating levels of vitamin D. The main exposure and outcome were circulating total 25(OH)D and CRC, respectively, in the overall population (i.e., all subjects). Two reviewers, working independently, screened all the literature available to identify studies that met the inclusion criteria (e.g., case-control or prospective cohort studies, published in English, and excluding non-original papers). Data were pooled by the generic inverse variance method using a random or fixed effect model, as approriate. Heterogeneity was identified using the Cochran's Q-test and quantified by the I2 statistic. Results were stratified by study design, sex, and metabolite of vitamin D. Sensitivity and subgroup analyses were also performed. A total of 28 original studies were included for the quantitative meta-analysis. Meta-analyses comparing the highest vs lowest categories, showed a 39% lower risk between levels of total 25(OH)D and CRC risk (OR (95% CI): 0.61 (0.52; 0.71); 11 studies) in case-control studies; whereas a 20% reduced CRC risk in prospective cohort studies (HR (95% CI): 0.80 (0.66; 0.97); 6 studies). Results in women mirrored main results, whereas results in men were non-significant in both analyses. Our findings support an inverse association between circulating vitamin D levels and CRC risk

    Cyano-and ketone-containing selenoesters as multi-target compounds against resistant cancers

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    Fifteen selenocompounds, comprising of eight ketone-containing selenoesters (K1–K8, also known as oxoselenoesters) and seven cyano-containing selenoesters (N1–N7, known also as cyanoselenoesters), have been designed, synthesized, and evaluated as novel anticancer agents. These compounds are derivatives of previously reported active selenoesters and were prepared following a three-step one-pot synthetic route. The following evaluations were performed in their biological assessment: cytotoxicity determination, selectivity towards cancer cells in respect to non-cancer cells, checkerboard combination assay, ABCB1 inhibition and inhibition of ABCB1 ATPase activity, apoptosis induction, and wound healing assay. As key results, all the compounds showed cytotoxicity against cancer cells at low micromolar concentrations, with cyanoselenoesters being strongly selective. All of the oxoselenoesters, except K4, were potent ABCB1 inhibitors, and two of them, namely K5 and K6, enhanced the activity of doxorubicin in a synergistic manner. The majority of these ketone derivatives modulated the ATPase activity, showed wound healing activity, and induced apoptosis, with K3 being the most potent, with a potency close to that of the reference compound. To summarize, these novel derivatives have promising multi-target activity, and are worthy to be studied more in-depth in future works to gain a greater understanding of their potential applications against cancer.The study was supported by the projects SZTE ÁOK-KKA 2018/270-62-2 of the University of Szeged, Faculty of Medicine and GINOP-2.3.2-15-2016-00038 (Hungary); and Consejo Superior de Investigaciones Científicas (CSIC, Spain, project LINKA20285). This research was funded by VISEGRAD FUND, grant number 22010090; and by the mobility project from the Czech Ministry of Education, Youth and Sports INTER-COST, grant number LTC19007. This article is based upon work from COST Action 17104 , supported by COST (European Cooperation in Science and Technology), (http://www.cost.eu, accessed on 17 September 2021). The study was supported also by two cultural associations: “Trevinca” and “Iniciativas Ropelanas”

    Genome-wide profiling of methylation identifies novel targets with aberrant hyper-methylation and reduced expression in low-risk myelodysplastic syndromes

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    Gene expression profiling signatures may be used to classify the subtypes of Myelodysplastic syndrome (MDS) patients. However, there are few reports on the global methylation status in MDS. The integration of genome-wide epigenetic regulatory marks with gene expression levels would provide additional information regarding the biological differences between MDS and healthy controls. Gene expression and methylation status were measured using high-density microarrays. A total of 552 differentially methylated CpG loci were identified as being present in low-risk MDS; hypermethylated genes were more frequent than hypomethylated genes. In addition, mRNA expression profiling identified 1005 genes that significantly differed between low-risk MDS and the control group. Integrative analysis of the epigenetic and expression profiles revealed that 66.7% of the hypermethylated genes were underexpressed in low-risk MDS cases. Gene network analysis revealed molecular mechanisms associated with the low-risk MDS group, including altered apoptosis pathways. The two key apoptotic genes BCL2 and ETS1 were identified as silenced genes. In addition, the immune response and micro RNA biogenesis were affected by the hypermethylation and underexpression of IL27RA and DICER1. Our integrative analysis revealed that aberrant epigenetic regulation is a hallmark of low-risk MDS patients and could have a central role in these diseases. © 2013 Macmillan Publishers Limited All rights reserved

    Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations

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    Order-disorder phase transitions induced by thermal annealing have been studied in the ordered-vacancy compound ZnGa2Se4 by means of Raman scattering and optical absorption measurements. The partially disordered as-grown sample with tetragonal defect stannite (DS) structure and I (4) over bar 2m space group has been subjected to controlled heating and cooling cycles. In situ Raman scattering measurements carried out during the whole annealing cycle show that annealing the sample to 400 degrees C results in a cation ordering in the sample, leading to the crystallization of the ordered tetragonal defect chalcopyrite (DC) structure with I (4) over bar space group. On decreasing temperature the ordered cation scheme of the DC phase can be retained at ambient conditions. The symmetry of the Raman-active modes in both DS and DC phases is discussed and the similarities and differences between the Raman spectra of the two phases emphasized. The ordered structure of annealed samples is confirmed by optical absorption measurements and ab initio calculations, that show that the direct bandgap of DC-ZnGa2Se4 is larger than that of DS-ZnGa2Se4.This study was supported by the Spanish government MEC under grants MAT2010-21270-C04-01/03/04 and MAT2010-19837-C06-06, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). EP-G, AM, and PR-H acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster. Finally, the authors would also like to acknowledge M C Moron for stimulating discussions and revision of the present manuscript.Vilaplana Cerda, RI.; Gomis Hilario, O.; Pérez-González, E.; Ortiz, HM.; Manjón Herrera, FJ.; Rodríguez-Hernández, P.; Muñoz, A.... (2013). Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations. Journal of Physics: Condensed Matter. 25(16):165802-1-165802-11. https://doi.org/10.1088/0953-8984/25/16/165802S165802-1165802-112516Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Yahia, I. S., Fadel, M., Sakr, G. B., & Shenouda, S. S. (2010). Memory switching of ZnGa2Se4 thin films as a new material for phase change memories (PCMs). Journal of Alloys and Compounds, 507(2), 551-556. doi:10.1016/j.jallcom.2010.08.021Yahia, I. S., Fadel, M., Sakr, G. B., Yakuphanoglu, F., Shenouda, S. S., & Farooq, W. A. (2011). Analysis of current–voltage characteristics of Al/p-ZnGa2Se4/n-Si nanocrystalline heterojunction diode. Journal of Alloys and Compounds, 509(12), 4414-4419. doi:10.1016/j.jallcom.2011.01.068Hahn, H., Frank, G., Klingler, W., St�rger, A. D., & St�rger, G. (1955). Untersuchungen �ber tern�re Chalkogenide. VI. �ber Tern�re Chalkogenide des Aluminiums, Galliums und Indiums mit Zink, Cadmium und Quecksilber. Zeitschrift f�r anorganische und allgemeine Chemie, 279(5-6), 241-270. doi:10.1002/zaac.19552790502Errandonea, D., Kumar, R. S., Manjón, F. J., Ursaki, V. V., & Tiginyanu, I. M. (2008). High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4. Journal of Applied Physics, 104(6), 063524. doi:10.1063/1.2981089Morón, M. C., & Hull, S. (2003). Order-disorder phase transition inZn1−xMnxGa2Se4: Long-range order parameter versusx. Physical Review B, 67(12). doi:10.1103/physrevb.67.125208Morón, M. C., & Hull, S. (2005). Effect of magnetic dilution in Zn1−xMnxGa2Se4 (0<x<0.5). Journal of Applied Physics, 98(1), 013904. doi:10.1063/1.1944220Morón, M. C., & Hull, S. (2007). The influence of magnetic dilution in the Zn1−xMnxGa2Se4 series with 0.5<x⩽1. Journal of Applied Physics, 102(3), 033919. doi:10.1063/1.2767273Antonioli, G., Lottici, P. P., & Razzetti, C. (1989). The structure of the defect chalcopyrite ZnGa2Se4 studied by EXAFS. physica status solidi (b), 152(1), 39-49. doi:10.1002/pssb.2221520104Haeuseler, H. (1978). FIR- und Ramanspektren von ternären Chalkogeniden des Galliums und Indiums mit Zink, Cadmium und Quecksilber. Journal of Solid State Chemistry, 26(4), 367-376. doi:10.1016/0022-4596(78)90171-8Eifler, A., Krauss, G., Riede, V., Krämer, V., & Grill, W. (2005). Optical phonon modes and structure of ZnGa2Se4 and ZnGa2S4. Journal of Physics and Chemistry of Solids, 66(11), 2052-2057. doi:10.1016/j.jpcs.2005.09.049Lottici, P. P., & Razzetti, C. (1983). A comparison of the raman spectra of ZnGa2Se4 and other gallium defect chalcopyrites. Solid State Communications, 46(9), 681-684. doi:10.1016/0038-1098(83)90506-9Razzetti, C., Lottici, P. P., & Antonioli, G. (1987). Structure and lattice dynamics of nonmagnetic defective AIIBIII2XIV4 compounds and alloys. Progress in Crystal Growth and Characterization, 15(1), 43-73. doi:10.1016/0146-3535(87)90009-8Attolini, G., Bini, S., Lottici, P. P., & Razzetti, C. (1992). Effects of Group III Cation Substitution in the Raman Spectra of Some Defective Chalcopyrites. Crystal Research and Technology, 27(5), 685-690. doi:10.1002/crat.2170270519Takahashi, Y., Namatsu, H., Machida, K., & Minegishi, K. (1993). Measurements of Diffusion Coefficiens of Water in Electron Cryclotron Resonance Plasma SiO2. Japanese Journal of Applied Physics, 32(Part 2, No. 3B), L431-L433. doi:10.1143/jjap.32.l431Ursaki, V. V., Burlakov, I. I., Tiginyanu, I. M., Raptis, Y. S., Anastassakis, E., & Anedda, A. (1999). Phase transitions in defect chalcopyrite compounds under hydrostatic pressure. Physical Review B, 59(1), 257-268. doi:10.1103/physrevb.59.257Allakhverdiev, K., Gashimzade, F., Kerimova, T., Mitani, T., Naitou, T., Matsuishi, K., & Onari, S. (2003). Raman scattering under pressure in ZnGa2Se4. Journal of Physics and Chemistry of Solids, 64(9-10), 1597-1601. doi:10.1016/s0022-3697(03)00077-5Alonso-Gutiérrez, P., Sanjuán, M. L., & Morón, M. C. (2009). Thermally activated cation ordering in Zn0.5Mn0.5Ga2Se4single crystals studied by Raman scattering. physica status solidi (c), 6(5), 1182-1186. doi:10.1002/pssc.200881218Caldera, D., Morocoima, M., Quintero, M., Rincon, C., Casanova, R., & Grima, P. (2011). On the crystal structure of the defective ternary compound. Solid State Communications, 151(3), 212-215. doi:10.1016/j.ssc.2010.11.031Gomis, O., Vilaplana, R., Manjón, F. J., Pérez-González, E., López-Solano, J., Rodríguez-Hernández, P., … Ursaki, V. V. (2012). High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds. Journal of Applied Physics, 111(1), 013518. doi:10.1063/1.3675162Eifler, A., Hecht, J.-D., Lippold, G., Riede, V., Grill, W., Krauß, G., & Krämer, V. (1999). Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals. Physica B: Condensed Matter, 263-264, 806-808. doi:10.1016/s0921-4526(98)01292-7Sanjuán, M. L., & Morón, M. C. (2002). Raman study of Zn1−xMnxGa2Se4 diluted magnetic semiconductors: disorder and resonance effects. Physica B: Condensed Matter, 316-317, 565-567. doi:10.1016/s0921-4526(02)00574-4Letoullec, R., Pinceaux, J. P., & Loubeyre, P. (1988). The membrane diamond anvil cell: A new device for generating continuous pressure and temperature variations. High Pressure Research, 1(1), 77-90. doi:10.1080/08957958808202482Perdew, J. P., Burke, K., & Ernzerhof, M. (1997). Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)]. Physical Review Letters, 78(7), 1396-1396. doi:10.1103/physrevlett.78.1396Manjón, F. J., Gomis, O., Rodríguez-Hernández, P., Pérez-González, E., Muñoz, A., Errandonea, D., … Ursaki, V. V. (2010). Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds. Physical Review B, 81(19). doi:10.1103/physrevb.81.195201Santamaría-Pérez, D., Amboage, M., Manjón, F. J., Errandonea, D., Muñoz, A., Rodríguez-Hernández, P., … Tiginyanu, I. M. (2012). Crystal Chemistry of CdIn2S4, MgIn2S4, and MnIn2S4 Thiospinels under High Pressure. The Journal of Physical Chemistry C, 116(26), 14078-14087. doi:10.1021/jp303164kBaroni, S., de Gironcoli, S., Dal Corso, A., & Giannozzi, P. (2001). Phonons and related crystal properties from density-functional perturbation theory. Reviews of Modern Physics, 73(2), 515-562. doi:10.1103/revmodphys.73.515Giannozzi, P., Baroni, S., Bonini, N., Calandra, M., Car, R., Cavazzoni, C., … Wentzcovitch, R. M. (2009). QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. Journal of Physics: Condensed Matter, 21(39), 395502. doi:10.1088/0953-8984/21/39/395502Kroumova, E., Aroyo, M. I., Perez-Mato, J. M., Kirov, A., Capillas, C., Ivantchev, S., & Wondratschek, H. (2003). Bilbao Crystallographic Server : Useful Databases and Tools for Phase-Transition Studies. Phase Transitions, 76(1-2), 155-170. doi:10.1080/0141159031000076110Loudon, R. (1964). The Raman effect in crystals. Advances in Physics, 13(52), 423-482. doi:10.1080/00018736400101051Alonso-Gutiérrez, P., & Sanjuán, M. L. (2008). Ordinary and extraordinary phonons and photons: Raman study of anisotropy effects in the polar modes ofMnGa2Se4. Physical Review B, 78(4). doi:10.1103/physrevb.78.045212Manjón, F. J., Marí, B., Serrano, J., & Romero, A. H. (2005). Silent Raman modes in zinc oxide and related nitrides. Journal of Applied Physics, 97(5), 053516. doi:10.1063/1.1856222Garbato, L., Ledda, F., & Rucci, A. (1987). Structural distortions and polymorphic behaviour in ABC2 and AB2C4 tetrahedral compounds. Progress in Crystal Growth and Characterization, 15(1), 1-41. doi:10.1016/0146-3535(87)90008-6Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Marquina, J., Power, C., Grima, P., Morocoima, M., Quintero, M., Couzinet, B., … González, J. (2006). Crystallographic properties of the MnGa2Se4 compound under high pressure. Journal of Applied Physics, 100(9), 093513. doi:10.1063/1.2358826Meenakshi, S., Vijayakumar, V., Eifler, A., & Hochheimer, H. D. (2010). Pressure-induced phase transition in defect Chalcopyrites HgAl2Se4 and CdAl2S4. 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    Altered corticostriatal functional connectivity in obsessive-compulsive disorder

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    Context: neurobiological models of obsessive-compulsive disorder (OCD) emphasize disturbances in the function and connectivity of brain corticostriatal networks, or 'loops.' Although neuroimaging studies of patients have supported this network model of OCD, very few have applied measurements that are sensitive to brain connectivity features. Objective: using resting-state functional magnetic resonance imaging, we tested the hypothesis that OCD is associated with disturbances in the functional connectivity of primarily ventral corticostriatal regions, measured from coherent spontaneous fluctuations in the blood oxygenation level-dependent (BOLD) signal. Design: case-control cross-sectional study. Setting: hospital referral OCD unit and magnetic resonance imaging facility. Participants: a total of 21 patients with OCD (10 men, 11 women) and 21 healthy control subjects matched for age, sex, and estimated intelligence. Main outcome measures: voxelwise statistical parametric maps testing the strength of functional connectivity of 4 striatal seed regions of interest (dorsal caudate nucleus, ventral caudate/nucleus accumbens, dorsal putamen, and ventral putamen) with remaining brain areas. Results: for both groups, there was a clear distinction in the pattern of cortical connectivity of dorsal and ventral striatal regions, consistent with the notion of segregated motor, associative, and limbic corticostriatal networks. Between groups, patients with OCD had significantly increased functional connectivity along a ventral corticostriatal axis, implicating the orbitofrontal cortex and surrounding areas. The specific strength of connectivity between the ventral caudate/nucleus accumbens and the anterior orbitofrontal cortex predicted patients' overall symptom severity (r(2) = 0.57; P < .001). Additionally, patients with OCD showed evidence of reduced functional connectivity of the dorsal striatum and lateral prefrontal cortex, and of the ventral striatum with the region of the midbrain ventral tegmental area. Conclusions: this study directly supports the hypothesis that OCD is associated with functional alterations of brain corticostriatal networks. Specifically, our findings emphasize abnormal and heightened functional connectivity of ventrolimbic corticostriatal regions in patients with OCD

    Experiences of water immersion during childbirth: a qualitative thematic synthesis

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    Background The increasing demand for childbirth care based on physiological principles has led official bodies to encourage health centers to provide evidence‑based care aimed at promoting women’s participation in informed decision‑making and avoiding excessive medical intervention during childbirth. One of the goals is to reduce pain and find alternative measures to epidural anesthesia to enhance women’s autonomy and well‑being during child‑ birth. Currently, water immersion is used as a non‑pharmacological method for pain relief. This review aimed to identify and synthesize evidence on women’s and midwives’ experiences, values, and prefer‑ ences regarding water immersion during childbirth. Methods A systematic review and thematic synthesis of qualitative evidence were conducted. Databases were searched and references were checked according to specific criteria. Studies that used qualitative data collection and analysis methods to examine the opinions of women or midwives in the hospital setting were included. Non‑qualita‑ tive studies, mixed‑methods studies that did not separately report qualitative results, and studies in languages other than English or Spanish were excluded. The Critical Appraisal Skills Program Qualitative Research Checklist was used to assess study quality, and results were synthesized using thematic synthesis. Results Thirteen studies met the inclusion criteria and were included in this review. The qualitative studies yielded three key themes: 1) reasons identified by women and midwives for choosing a water birth, 2) benefits experienced in water births, and 3) barriers and facilitators of water immersion during childbirth. Conclusions The evidence from qualitative studies indicates that women report benefits associated with water birth. From the perspective of midwives, ensuring safe water births requires adequate resources, midwives training, and rig‑ orous standardized protocols to ensure that all pregnant women can safely opt for water immersion during childbirth with satisfactory results

    Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations

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    We have determined the angular diameters of two metal-poor stars, HD 122563 and Gmb 1830, using CHARA and Palomar Testbed Interferometer observations. For the giant star HD 122563, we derive an angular diameter theta_3D = 0.940 +- 0.011 milliarcseconds (mas) using limb-darkening from 3D convection simulations and for the dwarf star Gmb 1830 (HD 103095) we obtain a 1D limb-darkened angular diameter theta_1D = 0.679 +- 0.007 mas. Coupling the angular diameters with photometry yields effective temperatures with precisions better than 55 K (Teff = 4598 +- 41 K and 4818 +- 54 K --- for the giant and the dwarf star, respectively). Including their distances results in very well-determined luminosities and radii (L = 230 +- 6 L_sun, R = 23.9 +- 1.9 R_sun and L = 0.213 +- 0.002 L_sun, R = 0.664 +- 0.015 R_sun, respectively). We used the CESAM2k stellar structure and evolution code in order to produce models that fit the observational data. We found values of the mixing-length parameter alpha (which describes 1D convection) that depend on the mass of the star. The masses were determined from the models with precisions of <3% and with the well-measured radii excellent constraints on the surface gravity are obtained (log g = 1.60 +- 0.04, 4.59 +- 0.02, respectively). The very small errors on both log g and Teff provide stringent constraints for spectroscopic analyses given the sensitivity of abundances to both of these values. The precise determination of Teff for the two stars brings into question the photometric scales for metal-poor stars.Comment: accepted A&A, 8 dbl-column pages, incl. 7 tables and 4 figure
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