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PubMed2004

Efficient method for the reduction of large piston errors in segmented-mirror telescopes.

Phase discontinuity sensing (PDS) is one of two successful approaches to segment phasing that are currently in use at the Keck telescopes, but it has only a limited capture range. We describe and present numerical simulations of a broadband version of the current (narrowband) PDS algorithm that can extend the capture range from 0.4 to 40 microns. Like the original algorithm, the new broadband PDS algorithm requires no special-purpose hardware but only a high-resolution area detector operating in the 2-3-microns range. The potential application of this algorithm to extremely large telescopes is also discussed.

Journal Article↗

PubMed2004

Comparison of conoscopic, telescopic, and goniometric methods for measuring angular emissions from medical liquid-crystal displays.

Although emissive displays exhibit a quasi-Lambertian emission, the anisotropy of the electro-optic effect that controls light transmission in liquid-crystal displays (LCDs) causes the pixel luminance to vary, sometimes strongly, with the viewing angle. These variations are not identical for all gray levels and can eventually cause gray-scale inversions. We compare methods currently used to measure angular luminance variations in the LCDs: the goniometric method, the telescopic method, and the conoscopic or Fourier-optics method. We show that, although they are the same at the high end of the gray scale, the results of the three methods differ significantly at lower gray levels. In some cases the measured luminance was as much as 38% higher for the conoscopic system, and 26% higher for the telescopic method, than the value obtained with the goniometric approach. This shift in the minimum luminance measurement translates directly into the contrast ratio, affecting the reporting of technical specifications of display systems.

Computer Peripherals↗

PubMed2004

Effects of misalignment errors on the optical transfer functions of synthetic aperture telescopes.

A segmented or diluted aperture optical system will undergo phase errors as a result of errors in the positioning of the segments. The errors associated with a segmented primary mirror limit the image quality obtainable with synthetic aperture telescopes. Here we study the effects of segmentation errors on image quality, considering both the phase angle and the amplitude of the optical transfer function (OTF). We show that, in these kinds of telescope, phasing and alignment errors among segments reduce the amplitude and distort the phase angle of the OTF.

Journal Article↗

PubMed2005

Holographic correction and phasing of large sparse-array telescopes.

I have constructed a 1-m-diameter telescope using separate, low-quality spherical primary mirror segments. A single hologram of the mirrors is used to correct the random surface distortions as well as spherical aberration, while simultaneously phasing the individual apertures together. I present experimental results of the removal of an error of thousands of waves to produce a diffraction-limited instrument operating over a narrow bandwidth. This technique promises to have many benefits in future space-based telescopes for imaging, lidar, and optical communications.

Journal Article↗

PubMed2005

Optimal defocus distance for testing the 2.1 m telescope at San Pedro Mártir.

Within the preliminary development of a low-cost active optics system (AOS), computer simulations have been performed. The general purpose of simulations is to find an optimal scheme for the wavefront control of the primary mirror. We present results for the wavefront sensor of the AOS proposed for the 2.1 m telescope at San Pedro Mártir. The method presented here can be used for any other telescopes as well.

Journal Article↗

PubMed2006

Apochromatic telescope without anomalous dispersion glasses.

In order to correct secondary longitudinal chromatic aberration in conventional refracting optical systems, it is necessary to use at least one optical material having anomalous partial dispersion. A novel lens system with correction of the secondary spectrum by using only normal glasses is presented. The lens system comprises three widely separated lens components; both second and third components are subaperture. The presented example of an apochromatic telescope demonstrates secondary spectrum correction with the use of only crown BK7 and flint F2, which are among the most inexpensive optical glasses available at the market. Two more similar designs are presented, both with the use of low-cost slightly anomalous dispersion glasses. These telescopes have a higher relative aperture and a smaller tertiary spectrum.

Journal Article↗

PubMed2006

Optical control of the Advanced Technology Solar Telescope.

The Advanced Technology Solar Telescope (ATST) is an off-axis Gregorian astronomical telescope design. The ATST is expected to be subject to thermal and gravitational effects that result in misalignments of its mirrors and warping of its primary mirror. These effects require active, closed-loop correction to maintain its as-designed diffraction-limited optical performance. The simulation and modeling of the ATST with a closed-loop correction strategy are presented. The correction strategy is derived from the linear mathematical properties of two Jacobian, or influence, matrices that map the ATST rigid-body (RB) misalignments and primary mirror figure errors to wavefront sensor (WFS) measurements. The two Jacobian matrices also quantify the sensitivities of the ATST to RB and primary mirror figure perturbations. The modeled active correction strategy results in a decrease of the rms wavefront error averaged over the field of view (FOV) from 500 to 19 nm, subject to 10 nm rms WFS noise. This result is obtained utilizing nine WFSs distributed in the FOV with a 300 nm rms astigmatism figure error on the primary mirror. Correction of the ATST RB perturbations is demonstrated for an optimum subset of three WFSs with corrections improving the ATST rms wavefront error from 340 to 17.8 nm. In addition to the active correction of the ATST, an analytically robust sensitivity analysis that can be generally extended to a wider class of optical systems is presented.

Journal Article↗

PubMed2006

Adaptive optics sky coverage modeling for extremely large telescopes.

A Monte Carlo sky coverage model for laser guide star adaptive optics systems was proposed by Clare and Ellerbroek [J. Opt. Soc. Am. A 23, 418 (2006)]. We refine the model to include (i) natural guide star (NGS) statistics using published star count models, (ii) noise on the NGS measurements, (iii) the effect of telescope wind shake, (iv) a model for how the Strehl and hence NGS wavefront sensor measurement noise varies across the field, (v) the focus error due to imperfectly tracking the range to the sodium layer, (vi) the mechanical bandwidths of the tip-tilt (TT) stage and deformable mirror actuators, and (vii) temporal filtering of the NGS measurements to balance errors due to noise and servo lag. From this model, we are able to generate a TT error budget for the Thirty Meter Telescope facility narrow-field infrared adaptive optics system (NFIRAOS) and perform several design trade studies. With the current NFIRAOS design, the median TT error at the galactic pole with median seeing is calculated to be 65 nm or 1.8 mas rms.

Journal Article↗

PubMed1993

Comparative efficacy of bronchoalveolar lavage and telescoping plugged catheter in the diagnosis of pneumonia in mechanically ventilated patients.

The relative efficacy of telescoping plugged catheter (TPC) and bronchoalveolar lavage (BAL) in the diagnosis of pneumonia in mechanically ventilated patients has been compared in 45 subjects suspected of having pneumonia because of the presence of clinical and radiographic criteria. Diagnosis of pneumonia was strongly suggested in 25 of the 45 patients, and definitely confirmed in 10 of them. The diagnostic threshold to assess a quantitative bacterial culture as positive was a growth on BAL of > or = 10(5) cfu/ml and on TPC of > or = 10(3) cfu/ml. The BAL specimen cultures established the diagnosis in 19 cases (76 percent). In the remaining six patients, this technique did not permit the assessment of the diagnosis, which was established by other procedures (TPC, blood cultures, clinical outcome, or autopsy). False-positive results were not found. Sensitivity and specificity for BAL cultures were 76 percent and 100 percent, respectively. Telescoping plugged catheter established the presence of pneumonia in 16 patients (64 percent). Combining both techniques, the sensitivity increased up to 88 percent, maintaining specificity of 100 percent. In summary, BAL has a greater sensitivity than TPC in the diagnosis of pneumonias in mechanically ventilated patients. However, they are procedures that can complement each other.

Adolescent↗

PubMed1980

Oral telescoping orthosis: an aid to functional rehabilitation of quadriplegic patients.

The possibility of periodontal disease, chipping of various teeth, or extrusion from use of a mouthstick is minimized with a mouthpiece that covers the complete dentition. Even the simplest of these devices permits increased function for the quadriplegic patient. A case is reported of a young man for whom the oral telescoping orthosis was fitted with a mouthpiece that covered the complete dentition. Damage to the hard or soft tissue structures has not been apparent in eight years of use. Furthermore, the functional capability of the patient has been enhanced. The oral telescoping orthosis is recommended for motivated quadriplegic patients who retain sufficient control of the head and oral and pharyngeal muscles.

Adult↗

PubMedDate not supplied

[Development of a periodontium-approximated specimen holder for attrition studies of telescopic crowns].

To enable attritional studies on telescopic crowns, a specimen holder has been constructed that is intended to simulate, in zero approximation, the biomechanical properties of abutments bearing telescopic crowns. The specimen holder consists essentially of a system with two metal "concertinas" with different elasticity constants reflecting the different biomechanical parameters for periodontium and bone. The biomechanical processes in the periodontium are too complex to be simulated accurately in vitro. Nevertheless, the specimen holder described here enables the forces acting during insertion and removal of a partial denture to be accommodated elastically in the angular and axial directions, to simulate the possible degrees of freedom of the abutments in situ. In this way, the unavoidable errors of specimen fixation are rendered tolerable, so that local preferential wear is decisively reduced.

Alveolar Process↗

PubMed1999

Telescoping of landmark events associated with drinking: a gender comparison.

OBJECTIVE: The literature suggests that women exhibit "telescoped" development of (i.e., faster progression to) alcoholism, with fewer years drinking than men. The purpose of this study was to use data gathered in the course of a large clinical trial to further examine this issue. METHOD: Subjects in this retrospective study were from a pool of 1,307 men and 419 women enrolled in Project MATCH, a multisite alcohol treatment matching study. MATCH subjects were recruited from both outpatient and aftercare settings over a 2-year period. Age-of-onset for landmark events in the development of alcoholism were determined from self-report and clinical interviews given at baseline entry into the study. Gender differences in age-of-onset variables were assessed within both outpatient and aftercare settings. Gender differences in progression times between successive landmarks were also examined. Differences were tested with both multivariate and univariate ANOVA techniques. RESULTS: Women generally began getting drunk regularly at a later average age than men (26.6 versus 22.7 years, p< or =.001), began experiencing their first drinking problems at a later average age than men (27.5 versus 25.0 years, p< or =.001) and exhibited loss of control over their drinking at a later average age than men (29.8 versus 27.2 years, p< or =.001). However, these gender differences were most pronounced for older individuals and attenuated for younger subjects. Women also progressed faster than men, on average, between first getting drunk regularly and first encountering drinking problems (0.9 versus 2.3 years, p< or =.001) and between first loss of drinking control and onset of worst drinking problems (5.5 versus 7.8 years, p< or =.001). Women also exhibited shorter average progression times between first getting drunk regularly and first seeking treatment (11.6 versus 15.8 years, p< or =.001), although this effect was negligible for younger subjects. CONCLUSIONS: Telescoping is a relatively robust phenomenon in treatment-seeking alcoholics and indicates that women are more likely to progress faster through the landmark events in the development of alcoholism than are men.

Adult↗

PubMed1999

Treatment of molar furcation involvement using root separation and a crown and sleeve-coping telescopic denture. A longitudinal study.

Because of the inconsistent results of periodontal and prosthetic therapy, periodontists may choose to treat maxillary molar furcation involvements (FI) with poor root morphology utilizing a root resection technique (RRT). In addition, poor root morphology of the remaining root following RRT is usually considered a high risk factor for long-term periodontal and prosthetic success. The purpose of this retrospective study was to investigate the differences in the clinical periodontal parameters between molar abutments with and without molar root separation and/or resection (RSR) before and after periodontal and prosthetic therapy, using a crown and sleeve-coping telescopic denture (CSCTD). A total of 85 molars (47 maxillary and 38 mandibular) were treated in 25 subjects. There were 33 abutments without root separation/resection and 52 abutments with RSR. Forty-three CSCTD were placed, 23 in the maxillary arch and 20 in the mandibular arch. The mean observation period was 6.7+/-1.9 years (range, 5 to 13 years). The plaque index, gingival index, probing depth, clinical attachment level, and alveolar bone change were recorded. The differences in these parameters before and after periodontal and prosthetic therapy between the advanced furcation-involved molars with and without RSR were evaluated. The results revealed a remarkable improvement in the periodontal parameters in advanced Class II and Class III FI in molars with RSR as compared to those without RSR. It was, therefore, concluded that molar abutments with RSR in conjunction with a specifically designed telescopic device provide a modified approach for treating molars with advanced Class II and III FI.

Adult↗

PubMed1989

[Prosthetic rehabilitation with the removable partial dentures using telescopic crowns after removal of unsuccessful dental implants].

It is well-known that unsuccessful dental implants sometimes give rise to pronounced inflammatory bone resorption of the upper and lower jaw, and that in such cases it is practically much difficult to attain adequate prosthodontic rehabilitation after removal of the implants. On this study it is completely reported that two patients suffering from implant-induced osteomyelitis could be finely compensated for with the removable partial dentures using telescopic crowns after removal of the implants, and then the results are shortly discussed from the view of pathology, oral surgery and prosthodontics. In the first case a 52-year-old woman had been suffering from osteomyelitis of the right mandible due to the both bladevent and endodontic-endosseous implant, and in another case a 43-year-old woman had been suffering from osteomyelitis of the right maxilla due to the endosseous subperiosteal implant, and they had borne insufficient mastication on the affected side of the jaws. Several months after removal of the unsuccessful dental implants, they were rehabilitated with the removable partial dentures using telescopic crowns to recover and maintain good functions such as occlusion, mastication, cosmetics and speech, and oral and general health.

Adult↗

PubMed1989

[Electromyographic study on masticatory function of the telescope denture wearers in the Kennedy Class II mandible].

Masticatory function of 10 telescope denture wearers in the Kennedy class II mandible patients was evaluated with electromyography. Electromyographic activity during mastication with kamaboko and peeled raw carrot was recorded from bilateral masseter and the anterior part of temporal muscles at each interval: Before treatment, immediately after denture insertion and 2, 4, 6, 8 weeks after respectively. Mean of duration, interval and cycle of EMG activities, coefficient of variation and average variation were calculated. The results were as follows: 1. Means of duration and cycle times decreased immediately to 2 weeks after denture insertion. 2. EMG activities during raw carrot chewing became regular immediately to 2 weeks after denture insertion, and within 4 weeks in kamaboko chewing. These results suggest that telescope dentures would be adapted to stomatognathic system within short period after denture insertion.

Denture, Overlay↗

PubMed1988

[Follow-up study of periodontal tissues around the abutment teeth in Konus telescope denture].

The purpose of this study was to evaluate the periodontal tissues around the 47 abutment teeth in patients with advanced periodontitis for 5 years maintenance periods. The periodontal and prosthetic treatment were carried out and 16 Konus telescope dentures were applied for 11 patients. During 5 years maintenance therapy, periodontal conditions were observed once a year assessing probing depth, attachment level, tooth mobility index, gingival index, marginal alveolar bone height, width of periodontal ligament and loss of lamina dura. The results showed that increase of probing depth in 0.61 mm and attachment loss in 0.78 mm were observed for 5 years. A slight gingival inflammation occurred and tooth mobility increased in some extent. Enlargement of periodontal ligament space and loss of lamina dura in 40% of abutment teeth were observed for 5 years. There were six decayed teeth, six teeth, from which a intracoronal crown was removed, and two extracted teeth in 47 abutment teeth. In conclusion, the periodontal tissues around abutment teeth in Konus telescope denture changed slightly at one year after denture placement, after which, the periodontal tissues were well maintained.

Dental Abutments↗

PubMed1989

[Maintenance and the clinical evaluation of periodontal patients in Konus-Telescope denture].

In order to assess by periodontal evaluation the changes that might occur with time in the abutment teeth and periodontal tissues when Konus-Telescope dentures are used as that final treatment of periodontal disease, the dentures (15 units) were placed in 13 patients with missing tooth and periodontal disease and findings at the time of denture placement and 30 months after the placement were compared. The number of cases that exhibited significant changes in hygiene level, tissue inflammation and periodontal pocket depth of the abutment teeth after 30 months was very small, while as many as 85.2% of the abutment teeth showed decrease in tooth mobility. Increase in tooth mobility was not detected in any of the cases. In addition, X-ray examination revealed tendencies toward improvement of the periodontal ligament and remission of alveolar bone resorption in many of the cases. These results suggest that Konus-Telescope denture is highly offers protection of the residual periodontal tissues through its secondary splint action.

Bone Resorption↗

PubMed1989

Telescoping of alcoholism in women alcoholics.

The accelerated progression of alcoholism, or telescoping, was examined among women alcoholics. Three aspects of telescoping in women were examined: the age of onset of four landmark symptoms, the number of years between landmark symptoms, and the number of symptoms occurring within each interval between landmarks. Women alcoholics were found to report a significantly shorter interval between the age at which they first began experiencing alcohol-related problems and the time they sought treatment than did male alcoholics.

Adult↗