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VLBA Scientific Memorandum n. 31: Astrometric calibration of mm-VLBI using "Source/Frequency Phase Referenced" observations
Richard Dodson,Maria J. Rioja
Physics , 2009,
Abstract: In this document we layout a new method to achieve "bona fide" high precision Very-Long-Baseline-Interferometry (VLBI) astrometric measurements of frequency-dependent positions of celestial sources (even) in the high (mm-wavelength) frequency range, where conventional phase referencing techniques fail. Our method, dubbed "Source/Frequency Phase Referencing" (SFPR) combines fast frequency-switching (or dual-frequency observations) with the source switching of conventional phase referencing techniques. The former is used to calibrate the dominant highly unpredictable rapid atmospheric fluctuations, which arise from variations of the water vapor content in the troposphere, and ultimately limit the application of conventional phase referencing techniques; the latter compensates the slower time scale remaining ionospheric/instrumental, non-negligible, phase variations. For cm-VLBI, the SFPR method is equivalent to conventional phase referencing applied to the measurement of frequency-dependent source positions changes ("core-shifts"). For mm-VLBI, the SFPR method stands as the only approach which will provide astrometry. In this memo we layout the scope and basis of our new method, along with a description of the strategy and a successful demonstration of the application of this new astrometric analysis technique to the highest frequency VLBA observations, at 86 GHz. Our previous comparative astrometric analysis of cm-VLBI observations, presented elsewhere, produced equivalent results using both methods.
VLBA Scientific Memorandum n. 32 - Multi-frequency Astrometry with VSOP-2: An application of Source/Frequency Phase Referencing techniques
Maria J. Rioja,Richard Dodson
Physics , 2009,
Abstract: This document describes the advantages of applying "Source/Frequency Phase Referencing" (SFPR) techniques to the analysis of VLBI observations with VSOP-2, for high precision astrometric measurements and/or increased sensitivity. The SFPR calibration technique basics and a demonstration of the method applied to highest frequency VLBA observations are described in detail in VLBA Scientific Memo n. 31. Here we outline its importance in the context of space VLBI astrometry with VSOP-2, where errors in the satellite orbit determination and rapid tropospheric phase fluctuations set extreme challenges for the successful application of conventional phase referencing techniques, specially at the higher frequencies. SFPR is ideally suited for full calibration of those - regardless of the orbit determination accuracy - and, in general, of any non-dispersive terms. The requirements for application of SFPR techniques are fully compatible with current technical specifications of VSOP-2. Hence we foresee that SFPR will play an important role in helping expanding the scientific outcome of the space VLBI mission.
High Precision Astrometric Millimeter VLBI Using a New Method for Atmospheric Calibration
Maria J. Rioja,Richard Dodson
Physics , 2011, DOI: 10.1088/0004-6256/141/4/114
Abstract: We describe a new method which achieves high precision Very Long Baseline Interferometry (VLBI) astrometry in observations at millimeter wavelengths. It combines fast frequency-switching observations, to correct for the dominant non-dispersive tropospheric fluctuations, with slow source-switching observations, for the remaining ionospheric dispersive terms. We call this method Source-Frequency Phase Referencing. Provided that the switching cycles match the properties of the propagation media, one can recover the source astrometry. We present an analytic description of the two-step calibration strategy, along with an error analysis to characterize its performance. Also, we provide observational demonstrations of a successful application with observations using the Very Long Baseline Array at 86 GHz of the pairs of sources 3C274 & 3C273 and 1308+326 & 1308+328, under various conditions. We conclude that this method is widely applicable to millimeter VLBI observations of many target sources, and unique in providing bona-fide astrometrically registered images and high precision relative astrometric measurements in mm-VLBI using existing and newly built instruments.
A phase-reference study of the quasar pair 1038+528A,B
Maria J. Rioja,Richard W. Porcas
Physics , 2000,
Abstract: We present results from 3.6 cm observations of the quasar pair 1038+528 A and B, made in 1995 using the VLBA together with the Effelsberg 100m telescope. We describe the use of a phase-referencing technique to measure the astrometric separation between the quasars. We also introduce a new data analysis method -"hybrid double mapping"- which preserves the relative astrometric information in a single VLBI hybrid map for close source pairs. We combine our measurements with those from three previous epochs, the earliest in 1981. Our new observations confirm the evolution within the structure of quasar B, previously proposed to explain the measured change in the relative separation of the pair. Our upper bound for any systematic proper motion between the mass centres of quasars A and B is 10 micro-arcsec/year. This is set by the limited precision in defining the reference points in the quasars at different epochs and by possible instabilities of the source "core" locations. A separate analysis enables us to put more stringent upper limits to any core motions along the two source axes.
Cáncer de próstata localizado de alto riesgo tratado mediante prostatectomía radical: Pronóstico y estudio de variables influyentes Radical prostatectomy for high risk localized prostate cancer: Prognosis and study of influential variables
A. Rincón Mayans,B. Zudaire,J. Brugarolas,J. Rioja
Anales del Sistema Sanitario de Navarra , 2012,
Abstract: Fundamento. Estudiar la supervivencia libre de progresión bioquímica (SLPB) que ha obtenido un grupo de pacientes de alto riesgo de acuerdo con la clasificación de D′Amico mediante prostatectomía radical. Identificar las variables clínico-patológicas influyentes en la supervivencia libre de progresión bioquímica y dise ar con ellas, si es posible, un modelo pronóstico. Material y métodos. Se estudian 232 pacientes, de una serie de 1.054, diagnosticados de cáncer de próstata clínicamente localizado y calificados de alto riesgo en la clasificación de D′Amico (PSA >20 ng/ml ó Gleason 8-10 ó T3) tratados mediante prostatectomía radical. Se estudia la SLPB y se analizan las variables clínico-patológicas recogidas (PSA, Gleason de la biopsia y de la pieza, estadio clínico y patológico, afectación unilateral o bilateral, márgenes de la pieza de prostatectomía, expresión de Ki-67) para identificar si influyen en la SLPB. Se ha utilizado para el estudio estadístico: tablas de contingencia y para el análisis de la supervivencia: Kaplan-Meyer, Log-rank y modelos de Cox. Resultados. Estudio descriptivo: PSA: 23,3 ng/ml (mediana); cGleason 2-6: 33%; 7: 13%; 8-10: 54%; T2: 58%; Afectación bilateral en la biopsia diagnóstica: 59%; RNM T2: 60%; RNM T3: 40%. pGleason 2-6: 24%; 7: 28%; 8-10: 48%; pT2: 43%; pT3a: 30%; pT3b: 27%; Margen afectado: 51%; N1:13%. Supervivencia libre de progresión: con una media y mediana de seguimiento de 64 meses; el 53% evidencia progresión bioquímica. La mediana hasta progresión: 42 meses. La supervivencia libre de progresión a 5 y 10 a os es 43±3% y 26±7%. El estudio multivariado (modelos de Cox) evidencia que las variables influyentes de forma independiente en la SLPB son la afectación de márgenes (HR: 3,5; 95% IC.1,9-6,7; p>0001); y Ki67 >10% (HR: 2,3; 95% IC: 1,2-4,3; P: 0,009). Grupos de riesgo: utilizando las dos variables influyentes y utilizando modelos de Cox se dise an tres grupos de riesgo como mejor modelo: Grupo 1 (0 variables presentes); Grupo 2 (1 variable); Grupo 3 (2 variables). La supervivencia libre de progresión es de 69±8%; 27±6% y 18±11% a los 5 a os. Las diferencias son significativas entre los tres grupos. Conclusión. El grupo de alto riesgo de la clasificación de D′Amico es heterogéneo en relación con la progresión bioquímica y puede ser desglosado en tres grupos de riesgo utilizando las dos variables de influencia independiente (márgenes afectados y porcentaje de Ki67). Background. To study the biochemical progression-free survival (BPFS) achieved by a group of high risk patients in accordance with D′Amico′s classif
Crioterapia de tumores renales: estado actual y desarrollos contemporáneos
Rioja,J.; Tzortzis,V.; Mamoulakis,C.; Laguna,M.P.;
Actas Urológicas Espa？olas , 2010, DOI: 10.4321/S0210-48062010000400002
Abstract: the proportion of renal tumors found incidentally dramatically increased in the past decade. more than half of them were diagnosed in patients over 70 years of age, a population with high associated comorbidity. nephron-sparing minimally invasive surgical procedures are aimed at treating patients with small renal tumors and multiple comorbidities. cryotherapy stands out among all other ablative procedures because of its better mid-term oncological outcome. a non-systematic review of the literature on cryotherapy as a treatment for renal tumors was made, analyzing its indications, actual and future application techniques, results, and complications.
Exploration of SFPR techniques for astrometry and observations of weak sources with high frequency Space VLBI
M. Rioja,R. Dodson,J. Malarecki,Y. Asaki
Physics , 2011, DOI: 10.1088/0004-6256/142/5/157
Abstract: Space Very-Long-Baseline-Interferometry (S-VLBI) observations at high frequencies hold the prospect of achieving the highest angular resolutions and astrometric accuracies, resulting from the long baselines between ground and satellite telescopes. Nevertheless, space-specific issues, such as limited accuracy in the satellite orbit reconstruction and constraints on the satellite antenna pointing operations, limit the application of conventional phase referencing. We investigate the feasibility of an alternative technique, source frequency phase referencing (SFPR), to the S-VLBI domain. With these investigations we aim to contribute to the design of the next-generation of S-VLBI missions. We have used both analytical and simulation studies to characterize the performance of SFPR in S-VLBI observations, applied to astrometry and increased coherence time, and compared these to results obtained using conventional phase referencing. The observing configurations use the specifications of the ASTRO-G mission for their starting point. Our results show that the SFPR technique enables astrometry at 43 GHz, using alternating observations with 22 GHz, regardless of the orbit errors, for most weathers and under a wide variety of conditions. The same applies to the increased coherence time for the detection of weak sources. Our studies show that the capability to carry out simultaneous dual frequency observations enables the application to higher frequencies, and a general improvement of the performance in all cases, hence we recommend its consideration for S-VLBI programs.
The Impact of Frequency Standards on Coherence in VLBI at the Highest Frequencies
M. Rioja,R. Dodson,Y. Asaki,J. Hartnett,S. Tingay
Physics , 2012, DOI: 10.1088/0004-6256/144/4/121
Abstract: We have carried out full imaging simulation studies to explore the impact of frequency standards in millimeter and sub-millimeter Very Long Baseline Interferometry (VLBI), focusing on the coherence time and sensitivity. In particular, we compare the performance of the H-maser, traditionally used in VLBI, to that of ultra-stable cryocooled sapphire oscillators over a range of observing frequencies, weather conditions and analysis strategies. Our simulations show that at the highest frequencies, the losses induced by H-maser instabilities are comparable to those from high quality tropospheric conditions. We find significant benefits in replacing H-masers with cryocooled sapphire oscillator based frequency references in VLBI observations at frequencies above 175 GHz in sites which have the best weather conditions; at 350 GHz we estimate a 20-40% increase in sensitivity, over that obtained when the sites have H-masers, for coherence losses of 20-10%, respectively. Maximum benefits are to be expected by using colocated Water Vapour Radiometers for atmospheric correction. In this case, we estimate a 60-120% increase in sensitivity over the H-maser at 350 GHz.
The Power of Simultaneous Multi-Frequency Observations for mm-VLBI: Astrometry up to 130 GHz with the KVN
Maria J. Rioja,Richard Dodson,Taehyun Jung,Bong Won Sohn
Physics , 2015, DOI: 10.1088/0004-6256/150/6/202
Abstract: Simultaneous observations at multiple frequency bands have the potential to overcome the fundamental limitation imposed by the atmospheric propagation in mm-VLBI observations. The propagation effects place a severe limit in the sensitivity achievable in mm-VLBI, reducing the time over which the signals can be coherently combined, and preventing the use of phase referencing and astrometric measurements. We carried out simultaneous observations at 22, 43, 87 and 130 GHz of a group of five AGNs, the weakest of which is ca. 200 mJy at 130 GHz, with angular separations ranging from 3.6 to 11 degrees, using the KVN. We analysed this data using the Frequency Phase Transfer (FPT) and the Source Frequency Phase Referencing (SFPR) techniques, which use the observations at a lower frequency to correct those at a higher frequency. The results of the analysis provide an empirical demonstration of the increase in the coherence times at 130 GHz from a few tens of seconds to about twenty minutes, with FPT, and up to many hours with SFPR. Moreover the astrometric analysis provides high precision relative position measurements between two frequencies, including, for the first time, astrometry at 130 GHz. Finally we demonstrate a method for the generalised decomposition of the relative position measurements into absolute position shifts for bona fide astrometric registration of the maps of the individual sources at multiple frequencies, up to 130 GHz.
ENGLISH-SPANISH TRANSLATIONS OF NARRATIVE TEXTS UNDER FRANCO. FINDINGS FROM CORPUS TRACEni (1962-1969)
Marta Rioja
Revista de Lingüística y Lenguas Aplicadas , 2010, DOI: 10.4995/rlyla.2010.768
Abstract: The paper explores the most relevant conclusions obtained after a quantitative and qualitative analysis of the corpus 0 TRACEni (1962-1969)(TRAducciones CEnsuradas narrativa inglés), which at present contains 9090 entries of English narrative texts translated into Castilian Spanish and published under those years. The aim of this paper is to examine the most relevant results from the initial Corpus TRACEni, obtained after a quantitative and qualitative analysis, with no recourse to the books themselves, with the ultimate purpose of exploiting some of those texts in the foreseeable future. The study of paratextual information of the translated texts into Castilian from 1962-1969 might give us an overview of the kind of literature that was imported in the country, undoubtedly affected as any other artistic productions by the constraint of official censorship. The paper explores the most relevant conclusions obtained after a quantitative and qualitative analysis of the corpus 0 TRACEni (1962-1969)(TRAducciones CEnsuradas narrativa inglés), which at present contains 9090 entries of English narrative texts translated into Castilian Spanish and published under those years. The aim of this paper is to examine the most relevant results from the initial Corpus TRACEni, obtained after a quantitative and qualitative analysis, with no recourse to the books themselves, with the ultimate purpose of exploiting some of those texts in the foreseeable future. The study of paratextual information of the translated texts into Castilian from 1962-1969 might give us an overview of the kind of literature that was imported in the country, undoubtedly affected as any other artistic productions by the constraint of official censorship.
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