Astrometric Methods and Instrumentation to Identify and Characterize Extrasolar Planets: A Review

I present a review of astrometric techniques and instrumentation utilized to search for, detect, and characterize extra-solar planets. First, I briefly summarize the properties of the present-day sample of extrasolar planets, in connection with predictions from theoretical models of planet formation and evolution. Next, the generic approach to planet detection with astrometry is described, with significant discussion of a variety of technical, statistical, and astrophysical issues to be faced by future ground-based as well as space-borne efforts in order to achieve the required degree of measurement precision. After a brief summary of past and present efforts to detect planets via milli-arcsecond astrometry, I then discuss the planet-finding capabilities of future astrometric observatories aiming at micro-arcsecond precision. Lastly, I outline a number experiments that can be conducted by means of high-precision astrometry during the next decade, to illustrate its potential for important contributions to planetary science, in comparison with other indirect and direct methods for the detection and characterization of planetary systems.Comment: 61 pages, 8 figures, PASP, accepted (October 2005 issue

Dorsal subthalamic deep brain stimulation improves pain in Parkinson's disease

IntroductionInconsistent effects of subthalamic deep brain stimulation (STN DBS) on pain, a common non-motor symptom of Parkinson's disease (PD), may be due to variations in active contact location relative to some pain-reducing locus of stimulation. This study models and compares the loci of maximal effect for pain reduction and motor improvement in STN DBS.MethodsWe measured Movement Disorder Society Unified PD Rating Scale (MDS-UPDRS) Part I pain score (item-9), and MDS-UPDRS Part III motor score, preoperatively and 6–12 months after STN DBS. An ordinary least-squares regression model was used to examine active contact location as a predictor of follow-up pain score while controlling for baseline pain, age, dopaminergic medication, and motor improvement. An atlas-independent isotropic electric field model was applied to distinguish sites of maximally effective stimulation for pain and motor improvement.ResultsIn 74 PD patients, mean pain score significantly improved after STN DBS (p = 0.01). In a regression model, more dorsal active contact location was the only significant predictor of pain improvement (R2 = 0.17, p = 0.03). The stimulation locus for maximal pain improvement was lateral, anterior, and dorsal to that for maximal motor improvement.ConclusionSTN stimulation, dorsal to the site of optimal motor improvement, improves pain. This region contains the zona incerta, which is known to modulate pain in humans, and may explain this observation

The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific

The Preliminary VOCALS Model Assessment (PreVOCA) aims to assess contemporary atmospheric modeling of the subtropical South East Pacific, with a particular focus on the clouds and the marine boundary layer (MBL). Models results from fourteen modeling centers were collected including operational forecast models, regional models, and global climate models for the month of October 2006. Forecast models and global climate models produced daily forecasts, while most regional models were run continuously during the study period, initialized and forced at the boundaries with global model analyses. Results are compared in the region from 40° S to the equator and from 110° W to 70° W, corresponding to the Pacific coast of South America. Mean-monthly model surface winds agree well with QuikSCAT observed winds and models agree fairly well on mean weak large-scale subsidence in the region next to the coast. However they have greatly differing geographic patterns of mean cloud fraction with only a few models agreeing well with MODIS observations. Most models also underestimate the MBL depth by several hundred meters in the eastern part of the study region. The diurnal cycle of liquid water path is underestimated by most models at the 85° W 20° S stratus buoy site compared with satellite, consistent with previous modeling studies. The low cloud fraction is also underestimated during all parts of the diurnal cycle compared to surface-based climatologies. Most models qualitatively capture the MBL deepening around 15 October 2006 at the stratus buoy, associated with colder air at 700 hPa

Submillimetric GPS distance measurement over short baselines: case study in inner consistency

Distance determination in the open air with submillimetric accuracy is a challenging task usually carried out with the use of submillimetric distancemeters and costly observation campaigns. The present paper represents a first step in the research of the potential use of GPS for submillimetric distance determination for distances up to a few hundred metres consisting in the evaluation of GPS distance determination reproducibility. As will be concluded, reliable submillimetric precision is attainable after some hours of observation if the same equipment in both baseline ends is used, even considering that there still remain some long-term systematic effects of a few tenths of a millimetre. The need for precise absolute antenna calibration values is also shown to be critical for submillimetric distance reproducibility.This research is funded by the Spanish Ministry of Science and Innovation (AYA2011-23232). The authors are grateful to the editor and the anonymous reviewers for their valuable suggestions, corrections and comments that helped improve the original manuscript.Baselga Moreno, S.; García-Asenjo Villamayor, L.; Garrigues Talens, P. (2013). Submillimetric GPS distance measurement over short baselines: case study in inner consistency. Measurement Science and Technology. 24(7):750011-750018. https://doi.org/10.1088/0957-0233/24/7/075001S750011750018247Amiri-Simkooei, A. R., & Tiberius, C. C. J. M. (2006). Assessing receiver noise using GPS short baseline time series. GPS Solutions, 11(1), 21-35. doi:10.1007/s10291-006-0026-8Bruyninx, C., Altamimi, Z., Boucher, C., Brockmann, E., Caporali, A., Gurtner, W., … Weber, G. (2009). The European Reference Frame: Maintenance and Products. International Association of Geodesy Symposia, 131-136. doi:10.1007/978-3-642-00860-3_20Doloca, N. R., Meiners-Hagen, K., Wedde, M., Pollinger, F., & Abou-Zeid, A. (2010). Absolute distance measurement system using a femtosecond laser as a modulator. Measurement Science and Technology, 21(11), 115302. doi:10.1088/0957-0233/21/11/115302Dow, J. M., Neilan, R. E., & Rizos, C. (2009). The International GNSS Service in a changing landscape of Global Navigation Satellite Systems. Journal of Geodesy, 83(3-4), 191-198. doi:10.1007/s00190-008-0300-3Firuzabadì, D., & King, R. W. (2011). GPS precision as a function of session duration and reference frame using multi-point software. GPS Solutions, 16(2), 191-196. doi:10.1007/s10291-011-0218-8Hyun, S., Kim, Y.-J., Kim, Y., Jin, J., & Kim, S.-W. (2009). Absolute length measurement with the frequency comb of a femtosecond laser. Measurement Science and Technology, 20(9), 095302. doi:10.1088/0957-0233/20/9/095302Koivula, H., Häkli, P., Jokela, J., Buga, A., & Putrimas, R. (2011). GPS Metrology: Bringing Traceable Scale to a Local Crustal Deformation GPS Network. International Association of Geodesy Symposia, 105-112. doi:10.1007/978-3-642-20338-1_13Ray, J., Altamimi, Z., Collilieux, X., & van Dam, T. (2007). Anomalous harmonics in the spectra of GPS position estimates. GPS Solutions, 12(1), 55-64. doi:10.1007/s10291-007-0067-7Schuhler, N., Salvadé, Y., Lévêque, S., Dändliker, R., & Holzwarth, R. (2006). Frequency-comb-referenced two-wavelength source for absolute distance measurement. Optics Letters, 31(21), 3101. doi:10.1364/ol.31.003101Snay, R. A., & Soler, T. (2008). Continuously Operating Reference Station (CORS): History, Applications, and Future Enhancements. Journal of Surveying Engineering, 134(4), 95-104. doi:10.1061/(asce)0733-9453(2008)134:4(95

Manipulation of Costimulatory Molecules by Intracellular Pathogens: Veni, Vidi, Vici!!

Some of the most successful pathogens of human, such as Mycobacterium tuberculosis (Mtb), HIV, and Leishmania donovani not only establish chronic infections but also remain a grave global threat. These pathogens have developed innovative strategies to evade immune responses such as antigenic shift and drift, interference with antigen processing/presentation, subversion of phagocytosis, induction of immune regulatory pathways, and manipulation of the costimulatory molecules. Costimulatory molecules expressed on the surface of various cells play a decisive role in the initiation and sustenance of immunity. Exploitation of the “code of conduct” of costimulation pathways provides evolutionary incentive to the pathogens and thereby abates the functioning of the immune system. Here we review how Mtb, HIV, Leishmania sp., and other pathogens manipulate costimulatory molecules to establish chronic infection. Impairment by pathogens in the signaling events delivered by costimulatory molecules may be responsible for defective T-cell responses; consequently organisms grow unhindered in the host cells. This review summarizes the convergent devices that pathogens employ to tune and tame the immune system using costimulatory molecules. Studying host-pathogen interaction in context with costimulatory signals may unveil the molecular mechanism that will help in understanding the survival/death of the pathogens. We emphasize that the very same pathways can potentially be exploited to develop immunotherapeutic strategies to eliminate intracellular pathogens