Disparity-defined objects moving in depth do not elicit three-dimensional shape constancy

Observers generally fail to recover three-dimensional shape accurately from binocular disparity. Typically, depth is overestimated at near distances and underestimated at far distances [Johnston, E. B. (1991). Systematic distortions of shape from stereopsis. Vision Research, 31, 1351-1360]. A simple prediction from this is that disparity-defined objects should appear to expand in depth when moving towards the observer, and compress in depth when moving away. However, additional information is provided when an object moves from which 3D Euclidean shape can be recovered, be this through the addition of structure from motion information [Richards, W. (1985). Structure from stereo and motion. Journal of the Optical Society of America A, 2, 343-349], or the use of non-generic strategies [Todd, J. T., & Norman, J. F. (2003). The visual perception of 3-D shape from multiple cues: Are observers capable of perceiving metric structure? Perception and Psychophysics, 65, 31-47]. Here, we investigated shape constancy for objects moving in depth. We found that to be perceived as constant in shape, objects needed to contract in depth when moving toward the observer, and expand in depth when moving away, countering the effects of incorrect distance scaling (Johnston, 1991). This is a striking example of the failure of shape constancy, but one that is predicted if observers neither accurately estimate object distance in order to recover Euclidean shape, nor are able to base their responses on a simpler processing strategy. © 2005 Elsevier Ltd. All rights reserved

Size and shape constancy in consumer virtual reality

With the increase in popularity of consumer virtual reality headsets, for research and other applications, it is important to understand the accuracy of 3D perception in VR. We investigated the perceptual accuracy of near-field virtual distances using a size and shape constancy task, in two commercially available devices. Participants wore either the HTC Vive or the Oculus Rift and adjusted the size of a virtual stimulus to match the geometric qualities (size and depth) of a physical stimulus they were able to refer to haptically. The judgments participants made allowed for an indirect measure of their perception of the egocentric, virtual distance to the stimuli. The data show under-constancy and are consistent with research from carefully calibrated psychophysical techniques. There was no difference in the degree of constancy found in the two headsets. We conclude that consumer virtual reality headsets provide a sufficiently high degree of accuracy in distance perception, to allow them to be used confidently in future experimental vision science, and other research applications in psychology

Planetary systems around close binary stars: the case of the very dusty, Sun-like, spectroscopic binary BD+20 307

Field star BD+20 307 is the dustiest known main sequence star, based on the fraction of its bolometric luminosity, 4%, that is emitted at infrared wavelengths. The particles that carry this large IR luminosity are unusually warm, comparable to the temperature of the zodiacal dust in the solar system, and their existence is likely to be a consequence of a fairly recent collision of large objects such as planets or planetary embryos. Thus, the age of BD+20 307 is potentially of interest in constraining the era of terrestrial planet formation. The present project was initiated with an attempt to derive this age using the Chandra X-ray Observatory to measure the X-ray flux of BD+20 307 in conjunction with extensive photometric and spectroscopic monitoring observations from Fairborn Observatory. However, the recent realization that BD+20 307 is a short period, double-line, spectroscopic binary whose components have very different lithium abundances, vitiates standard methods of age determination. We find the system to be metal-poor; this, combined with its measured lithium abundances, indicates that BD+20 307 may be several to many Gyr old. BD+20 307 affords astronomy a rare peek into a mature planetary system in orbit around a close binary star (because such systems are not amenable to study by the precision radial velocity technique).Comment: accepted for ApJ, December 10, 200

4D Emittance Measurements Using Multiple Wire and Waist Scan Methods in the ATF Extraction Line.

TUPC087International audienceEmittance measurements performed in the diagnostic section of the ATF extraction line since 1998 lead to ver- tical emittances three times larger than the expected ones, with a strong dependence on intensity. An experimental program is pursued to investigate potential sources of emit- tance growth and find possible remedies. This requires ef- ficient and reliable emittance measurement techniques. In the past, several phase-space reconstruction methods devel- oped at SLAC and KEK have been used to estimate the ver- tical emittance, based on multiple location beam size mea- surements and dedicated quadrupole scans. These methods have been shown to be very sensitive to measurement er- rors and other fluctuations in the beam conditions. In this context new emittance measurements have been performed revisiting these methods and newly developed ones with a systematic approach to compare and characterise their per- formance in the ATF extraction line

Određivanje dužine korijenskog kanala: procjena CDR® intraoralnog radiografskog sustava in vivo

The Computed Dental Radiolography System® (CDR: Schick Technologies, Long Island City, NY) is a CCD-based digital intraoral radiographic device which possesses a measurement software algorithm that can be adjusted with respect to an object of known dimension. This “calibration ” algorithm was compared to the CDR® preset mode and analog film using 30 root canals in vivo. The three measurement methods differed significantly from each other for 40% o f the canals sampled. Two o f the three differed significantly for 50% o f canals. No difference existed between the methods for 10% o f the canals. Estimates of tooth length using the calibrated mode differed from those obtained using a conventional radiographic technique by an average o f 1.2 mm, while those using the calibrated mode differed by 1.9 mm. The 1.2 mm average for the calibrated CDR® was judged to be an acceptable degree o f clinical error for most root canal procedures and indicates that the calibration function of the CDR® system should be used when measuring endodontic working lengths. The results demonstrated that calibration to a 15 mm probe when using the Schick CDR® system is more consistent with a comparable measurement, if film is used as the “gold standard”, than are measurements of the tooth length using the CDR® without calibration.Sustav "Kompjuterizirane dentalne radiografije" (CDR: Schick Technologies. Long Island City. NY) je na CDD-u zasnovan uređaj za digitalnu intraoralnu radio grafiju koji posjeduje "Software-ski algoritam" za mjerenja koji se može prilagoditi prema objektu poznate veličine. Ovaj "kalibracijski" algoritam uspoređen je sa sustavom CDR (kompjutorizirane dentalne radiografije) bez mjernog algoritma i analognim filmom rabeći 30 korijenskih kanala in vivo. Tri postupka mjerenja značajno su se razlikovali u 40% mjerenih korijenskih kanala. Dva od tri postupka razlikovala su se u 50% mjerenih kanala. Nikakve razlike između postupaka nije bilo u 10% mjerenih korijenskih kanala. Procjena duljine zuba korištenjem kalibriranog načina razlikovala se od procjene dobivene konvencionalnom (analognom) radio grafskom tehnikom za otprilike 1,2 mm, dok se od digitalnog sustava bez mjernog algoritma razlikovala za prosječno 1,9 mm. Razlika od 1,2 mm za "kalibrirani CDR" se procjenjuje kao prihvatljiva klinička greška za većinu endodontskih postupaka i ukazuje da bi se "kalibracijski sustav CDRa" trebao rabiti pri mjerenju radne duljine korijenskog kanala. Rezultati ukazuju da je kalibracija sonde do 15 mm kad se rabi Schch-ov CDR sustav postojanija s usporednim mjerenjem ako se film koji se mjeri uzme kao "zlatni standard", nego je mjerenje duljine CDR sustavom bez kalibracije

Infrared Spectroscopy of Symbiotic Stars. IV. V2116 Ophiuchi/GX 1+4, The Neutron Star Symbiotic

We have computed, based on 17 infrared radial velocities, the first set of orbital elements for the M giant in the symbiotic binary V2116 Ophiuchi. The giant's companion is a neutron star, the bright X-ray source GX 1+4. We find an orbital period of 1161 days by far the longest of any known X-ray binary. The orbit has a modest eccentricity of 0.10 with an orbital circularization time of less than 10^6 years. The large mass function of the orbit significantly restricts the mass of the M giant. Adopting a neutron-star mass of 1.35M(Sun), the maximum mass of the M giant is 1.22M(Sun), making it the less massive star. Derived abundances indicate a slightly subsolar metallicity. Carbon and nitrogen are in the expected ratio resulting from the red-giant first dredge-up phase. The lack of O-17 suggests that the M-giant has a mass less than 1.3M(Sun), consistent with our maximum mass. The red giant radius is 103R(Sun), much smaller than the estimated Roche lobe radius. Thus, the mass loss of the red giant is via a stellar wind. Although the M giant companion to the neutron star has a mass similar to the late-type star in low-mass X-ray binaries, its near-solar abundances and apparent runaway velocity are not fully consistent with the properties of this class of stars.Comment: In press to The Astrophysical Journal (10 April 2006 issue). 23 page

The orbits of the quadruple star system 88 Tau A from PHASES differential astrometry and radial velocity

We have used high precision differential astrometry from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) project and radial velocity measurements covering a time-span of 20 years to determine the orbital parameters of the 88 Tau A system. 88 Tau is a complex hierarchical multiple system comprising a total of six stars; we have studied the brightest 4, consisting of two short-period pairs orbiting each other with an 18-year period. We present the first orbital solution for one of the short-period pairs, and determine the masses of the components and distance to the system to the level of a few percent. In addition, our astrometric measurements allow us to make the first determination of the mutual inclinations of the orbits. We find that the sub-systems are not coplanar.Comment: Corrected Author Ordering; 12 Pages, Accepted for publication in Ap

The Zeta Herculis binary system revisited. Calibration and seismology

We have revisited the calibration of the visual binary system Zeta Herculis with the goal to give the seismological properties of the G0 IV sub-giant Zeta Her A. We have used the most recent physical and observational data. For the age we have obtained 3387 Myr, for the masses respectively 1.45 and 0.98 solar mass, for the initial helium mass fraction 0.243, for the initial mass ratio of heavy elements to hydrogen 0.0269 and for the mixing-length parameters respectively 0.92 and 0.90 using the Canuto & Mazitelli (1991, 1992) convection theory. Our results do not exclude that Zeta Her A is itself a binary sub-system; the mass of the hypothetical unseen companion would be smaller than 0.05 solar mass. The adiabatic oscillation spectrum of Zeta Her A is found to be a complicated superposition of acoustic and gravity modes; some of them have a dual character. This greatly complicates the classification of the non-radial modes. The echelle diagram used by the observers to extract the frequencies will work for ell=0, 2, 3. The large difference is found to be of the order of 42 mu Hz, in agreement with the Martic et al. (2001) seismic observations.Comment: 12 pages, A&A in pres

Experimental studies and analysis of the vertical emittance growth in the ATF extraction line in 2007-2008

The Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line. Since several years, the vertical beam emittance measured in the EXT line is significantly larger than that measured in the DR itself, and there are observations that the growth increases with beam intensity. A possible contribution is the non-linearity in the magnetic fields experienced by the beam when passing off-axis through several magnets shared by the DR and the EXT beam line in the initial part of the extraction process. Tracking simulations including non-linear field errors in these magnets predict significant emittance growth when the beam is displaced vertically with respect to the nominal trajectory. An experimental program has been carried out during 2007-2008 to study the relation between the extraction trajectory and the anomalous emittance growth. This note reports on the results of this program

Određivanje dužine korijenskog kanala: procjena CDR® intraoralnog radiografskog sustava in vivo

The Computed Dental Radiolography System® (CDR: Schick Technologies, Long Island City, NY) is a CCD-based digital intraoral radiographic device which possesses a measurement software algorithm that can be adjusted with respect to an object of known dimension. This “calibration ” algorithm was compared to the CDR® preset mode and analog film using 30 root canals in vivo. The three measurement methods differed significantly from each other for 40% o f the canals sampled. Two o f the three differed significantly for 50% o f canals. No difference existed between the methods for 10% o f the canals. Estimates of tooth length using the calibrated mode differed from those obtained using a conventional radiographic technique by an average o f 1.2 mm, while those using the calibrated mode differed by 1.9 mm. The 1.2 mm average for the calibrated CDR® was judged to be an acceptable degree o f clinical error for most root canal procedures and indicates that the calibration function of the CDR® system should be used when measuring endodontic working lengths. The results demonstrated that calibration to a 15 mm probe when using the Schick CDR® system is more consistent with a comparable measurement, if film is used as the “gold standard”, than are measurements of the tooth length using the CDR® without calibration.Sustav "Kompjuterizirane dentalne radiografije" (CDR: Schick Technologies. Long Island City. NY) je na CDD-u zasnovan uređaj za digitalnu intraoralnu radio grafiju koji posjeduje "Software-ski algoritam" za mjerenja koji se može prilagoditi prema objektu poznate veličine. Ovaj "kalibracijski" algoritam uspoređen je sa sustavom CDR (kompjutorizirane dentalne radiografije) bez mjernog algoritma i analognim filmom rabeći 30 korijenskih kanala in vivo. Tri postupka mjerenja značajno su se razlikovali u 40% mjerenih korijenskih kanala. Dva od tri postupka razlikovala su se u 50% mjerenih kanala. Nikakve razlike između postupaka nije bilo u 10% mjerenih korijenskih kanala. Procjena duljine zuba korištenjem kalibriranog načina razlikovala se od procjene dobivene konvencionalnom (analognom) radio grafskom tehnikom za otprilike 1,2 mm, dok se od digitalnog sustava bez mjernog algoritma razlikovala za prosječno 1,9 mm. Razlika od 1,2 mm za "kalibrirani CDR" se procjenjuje kao prihvatljiva klinička greška za većinu endodontskih postupaka i ukazuje da bi se "kalibracijski sustav CDRa" trebao rabiti pri mjerenju radne duljine korijenskog kanala. Rezultati ukazuju da je kalibracija sonde do 15 mm kad se rabi Schch-ov CDR sustav postojanija s usporednim mjerenjem ako se film koji se mjeri uzme kao "zlatni standard", nego je mjerenje duljine CDR sustavom bez kalibracije