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The Debreu–Farrell measure of technical efficiency is widely used to benchmark firm performance. A limitation of this measure is that it is orientation restricted and evaluates the performance of a decision-making unit in an explicit direction relative to the best-practice frontier and not the most productive point on the frontier. Therefore, the measure does not provide policy insight on how to direct decision-making units to achieve the best possible productivity level. Taking a departure from conventional nonparametric benchmarking studies, this study benchmarks the performance of commercial farm businesses in the Western Australia’s wheatbelt region using total factor productivity efficiency (‘TFP efficiency’) and compares the results to those when the conventional technical efficiency measures are applied. We find that the two measures of firm performance differ and are influenced by different sources of firm heterogeneity. Therefore, derived policy insights and prescriptions also differ. This is an important insight that policymakers and practitioners need to be aware of.

Background Cobicistat (COBI), a CYP3A inhibitor, is a pharmacokinetic enhancer that increases exposures of the HIV protease inhibitors (PIs) atazanavir (ATV) and darunavir (DRV). The potential drug interaction between COBI-boosted PIs and hormonal contraceptives, which are substrates of intestinal efflux transporters and extensively metabolized by CYP enzymes, glucuronidation and sulfation, was evaluated. Methods This was a Phase I, open-label, two cohort ( n=18/cohort), fixed-sequence study in healthy females that evaluated the drug–drug interaction (DDI) between multiple-dose ATV+COBI or DRV+COBI and single-dose drospirenone/ethinyl estradiol (EE). DDIs were evaluated using 90% confidence intervals of the geometric least-squares mean ratios of the test (drospirenone/EE+boosted PI) versus reference (drospirenone/EE) using lack of DDI boundaries of 70–143%. Safety was assessed throughout the study. Results 29/36 participants completed the study. Relative to drospirenone/EE alone, drospirenone area under the plasma concentration versus time curve extrapolated to infinity (AUCinf) was 1.6-fold and 2.3-fold higher, and maximum observed plasma concentration (Cmax) was unaltered, upon coadministration with DRV+COBI and ATV+COBI, respectively. EE AUCinf decreased 30% with drospirenone/EE + DRV+COBI and was unchanged with ATV+COBI + drospirenone/EE, relative to drospirenone/EE alone. Study treatments were generally well tolerated. The majority of adverse events were mild and consistent with known safety profiles of the compounds. Conclusions Consistent with COBI-mediated CYP3A inhibition, drospirenone exposure increased following coadministration with COBI-containing regimens, with a greater increase with ATV+COBI. Thus, clinical monitoring for drospirenone-associated hyperkalaemia is recommended with DRV+COBI and ATV+COBI should not be used with drospirenone. Lower EE exposure with DRV+COBI may be attributed to inductive effects of DRV on CYP enzymes and/or intestinal efflux transporters (that is, P-gp) involved in EE disposition.

The Richard F. Caris Mirror Lab at the University of Arizona continues the production of 8.4 m lightweight honeycomb segments for the primary mirror of the Giant Magellan Telescope. GMT will have a center segment surrounded by six identical off-axis segments, plus an additional off-axis segment to allow continuous operation as segments are removed for coating. Production highlights of the last two years include the spin-casting of Segment 5, preliminary polishing of Segment 2, and completion of the rear surface processing for Segments 3 and 4. We completed a preliminary design of the significant modifications of the test systems required for Segment 4, the center segment. We finished an upgrade of the 8.4 m polishing machine; both the upgrade and experience gained with Segment 1 have contributed to much faster polishing convergence for Segment 2. Prior to polishing Segment 2, we verified the stability and accuracy of the measurement systems by re-measuring Segment 1, achieving good agreement among multiple independent tests as well as good agreement with the original acceptance tests of Segment 1.

The diverse design space of freeform and deformable optics allows the design of innovative optical system concepts. A manufacturing technology is the remaining piece that prevents full realization of a freeform and adaptable optics age.

At the core of the Large Synoptic Survey Telescope (LSST) three-mirror optical design is the primary/tertiary (M1M3) mirror that combines these two large mirrors onto one monolithic substrate. The M1M3 mirror was spin cast and polished at the Steward Observatory Mirror Lab at The University of Arizona (formerly SOML, now the Richard F. Caris Mirror Lab at the University of Arizona (RFCML)). Final acceptance of the mirror occurred during the year 2015 and the mirror is now in storage while the mirror cell assembly is being fabricated. The M1M3 mirror will be tested at RFCML after integration with its mirror cell before being shipped to Chile.

The Richard F. Caris Mirror Lab at the University of Arizona is responsible for production of the eight 8.4 m segments for the primary mirror of the Giant Magellan Telescope, including one spare off-axis segment. We report on the successful casting of Segment 4, the center segment. Prior to generating the optical surface of Segment 2, we carried out a major upgrade of our 8.4 m Large Optical Generator. The upgrade includes new hardware and software to improve accuracy, safety, reliability and ease of use. We are currently carrying out an upgrade of our 8.4 m polishing machine that includes improved orbital polishing capabilities. We added and modified several components of the optical tests during the manufacture of Segment 1, and we have continued to improve the systems in preparation for Segments 2-8. We completed two projects that were prior commitments before GMT Segment 2: casting and polishing the combined primary and tertiary mirrors for the LSST, and casting and generating a 6.5 m mirror for the Tokyo Atacama Observatory.

The Giant Magellan Telescope (GMT) primary mirror consists of seven 8.4 m light-weight honeycomb mirrors that are being manufactured at the Richard F. Caris Mirror Lab (RFCML), University of Arizona. In order to manufacture the largest and most aspheric astronomical mirrors various high precision fabrication technologies have been developed, researched and implemented at the RFCML. The unique 8.4 m (in mirror diameter) capacity fabrication facilities are fully equipped with large optical generator (LOG), large polishing machine (LPM), stressed lap, rigid conformal lap (RC lap) and their process simulation/optimization intelligence called MATRIX. While the core capability and key manufacturing technologies have been well demonstrated by completing the first GMT off-axis segment, there have been significant hardware and software level improvements in order to improve and enhance the GMT primary mirror manufacturing efficiency. The new and improved manufacturing technology plays a key role to realize GMT, the next generation extremely large telescope enabling new science and discoveries, with high fabrication efficiency and confidence.

The LSST M1/M3 combines an 8.4 m primary mirror and a 5.1 m tertiary mirror on one glass substrate. The combined mirror was completed at the Richard F. Caris Mirror Lab at the University of Arizona in October 2014. Interferometric measurements show that both mirrors have surface accuracy better than 20 nm rms over their clear apertures, in nearsimultaneous tests, and that both mirrors meet their stringent structure function specifications. Acceptance tests showed that the radii of curvature, conic constants, and alignment of the 2 optical axes are within the specified tolerances. The mirror figures are obtained by combining the lab measurements with a model of the telescope’s active optics system that uses the 156 support actuators to bend the glass substrate. This correction affects both mirror surfaces simultaneously. We showed that both mirrors have excellent figures and meet their specifications with a single bending of the substrate and correction forces that are well within the allowed magnitude. The interferometers do not resolve some small surface features with high slope errors. We used a new instrument based on deflectometry to measure many of these features with sub-millimeter spatial resolution, and nanometer accuracy for small features, over 12.5 cm apertures. Mirror Lab and LSST staff created synthetic models of both mirrors by combining the interferometric maps and the small highresolution maps, and used these to show the impact of the small features on images is acceptably small.

Background BIC is a novel integrase inhibitor coformulated with emtricitabine (F) and tenofovir alafenamide (TAF) for treatment of HIV. MET is first-line therapy in diabetic HIV patients. In vitro, BIC inhibits renal transporters OCT2 and MATE1, which affect MET disposition. This study evaluated the effect of BIC on the PK and PD of MET following coadministration with the B/F/TAF. Methods This was a Phase 1, blinded, placebo-controlled, crossover study in 32 healthy subjects randomized 1:1 to either B/F/TAF or placebo QD for 9 days followed by a 3-day washout. Following 4 days of B/F/TAF or placebo, subjects received 850 mg MET at 12 hours postdose of B/F/TAF or placebo, and 500 mg BID for 4 additional days. Plasma and urine PK of MET were assessed on the last treatment day (Days 9 and 21 for B/F/TAF or placebo). Oral glucose tolerance test was performed before (Days 5 and 17) and after MET (Days 9 and 21). MET PD endpoints including plasma glucose, active Glucagon-Like Peptide 1 (GLP-1) and lactate were assessed after glucose intake. Geometric mean ratios (GMR) and 90% confidence intervals (CIs) for MET PK were calculated for B/F/TAF vs. placebo. Comparisons of PD responses within treatments (before vs. after MET) and comparisons between treatments (B/F/TAF vs. placebo) were done via nonparametric Wilcoxon signed-rank test (P > 0.05 denotes non-significance). Results MET plasma AUCtau was increased 39% (%GMR [90% CI]: 139 [131, 148]) with B/F/TAF vs. placebo, with no change in median plasma t1/2 (B/F/TAF: 6.4 hours; placebo: 7.1 hours). MET renal clearance decreased 31% with B/F/TAF vs. placebo. Following MET administration, statistically significant reduction of plasma glucose, and increase of plasma active GLP-1 and lactate levels relative to baseline were observed (P < 0.001) confirming their utility as PD endpoints. Importantly, PD responses were not statistically different when MET was administered with B/F/TAF vs. placebo (p >0.05). Conclusion Inhibition of renal transporters OCT2/MATE1 by BIC led to a modest increase of MET plasma exposure upon coadministration with B/F/TAF; however, the PD characteristics of MET were not significantly affected by B/F/TAF relative to placebo. Based on these findings, prospective dose adjustment/restriction of MET is not required upon coadministration with B/F/TAF. Disclosures J. Custodio, Gilead Sciences: Employee and Shareholder, Salary; S. West, Gilead Sciences: Employee and Shareholder, Salary; A. Yu, Gilead Science: Employee, Salary; H. Martin, Gilead Sciences: Employee, Salary; H. Graham, Gilead Sciences: Employee and Shareholder, Salary; E. Quirk, Gilead: Employee and Shareholder, Salary; B. Kearney, Gilead: Employee and Shareholder, Salary

Segment production for the Giant Magellan Telescope is well underway, with the off-axis Segment 1 completed, off-axis Segments 2 and 3 already cast, and mold construction in progress for the casting of Segment 4, the center segment. All equipment and techniques required for segment fabrication and testing have been demonstrated in the manufacture of Segment 1. The equipment includes a 28 m test tower that incorporates four independent measurements of the segment's figure and geometry. The interferometric test uses a large asymmetric null corrector with three elements including a 3.75 m spherical mirror and a computer-generated hologram. For independent verification of the large-scale segment shape, we use a scanning pentaprism test that exploits the natural geometry of the telescope to focus collimated light to a point. The Software Configurable Optical Test System, loosely based on the Hartmann test, measures slope errors to submicroradian accuracy at high resolution over the full aperture. An enhanced laser tracker system guides the figuring through grinding and initial polishing. All measurements agree within the expected uncertainties, including three independent measurements of radius of curvature that agree within 0.3 mm. Segment 1 was polished using a 1.2 m stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital polisher for deterministic small-scale figuring. For the remaining segments, the Mirror Lab is building a smaller, orbital stressed lap to combine the smoothing capability with deterministic figuring.

The Steward Observatory Mirror Lab is nearing completion of the combined primary and tertiary mirrors of the Large Synoptic Survey Telescope. Fabrication of the combined mirror requires simulation of an active-optics correction that affects both mirror surfaces in a coordinated way. As is common for large mirrors, the specification allows correction of large-scale figure errors by a simulated bending of the substrate with the 156 mirror support actuators. Any bending affects both mirrors, so this active-optics correction is constrained by the requirement of bending the substrate so both mirrors meet their figure specifications simultaneously. The starting point of the simulated correction must be measurements of both mirrors with the substrate in the same shape, i. e. the same state of mechanical and thermal stress. Polishing was carried out using a 1.2 m stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital polisher for deterministic small-scale figuring. The primary mirror is accurate to about 25 nm rms surface after the active-optics correction, while work continues toward completion of the tertiary.

The University of Arizona Mirror Laboratory polishing program relies on the stressed-lap tool. Its implementation is discussed for recent mirrors including the off-axis Giant Magellan Telescope and Large Synoptic Survey Telescope mirrors.

We present an overview of the engineering design and empirical performance of four stressed-lap polishing tools developed at the University of Arizona. Descriptions of the electromechanical actuators, servo systems, computer interfacing, and attachment of the lap to the polishing machine are provided. The empirical performance of a representative tool is discussed in terms of accuracy, repeatability, and hysteresis. Finally, we estimate the statistical likelihood of aluminum lap-plate failure through a metal-fatigue analysis for a worst-case stress-cycling situation.

We describe a relatively simple, but highly effective, approach to the system design and alignment of an all-refractive Offner null corrector and phase-measuring Shack cube interferometer. In addition we outline procedures for fabricating and testing the optical components. Allowable errors for all parameters are determined by a tolerance analysis that separates axisymmetric and residual figure errors. An open construction optics frame provides a high degree of metering flexibility by incorporating simple kinematic mounts that provide adjustment of each lens while also allowing the lens to be removed and replaced with2microm absolute repeatability. Nonaxisymmetric alignment errors are removed by rotating the optics on a high-precision bearing. Axial spacings are measured with contact transducers attached to both ends of an Invar metering rod. Two completed systems have guided the stressed-lap polishing of 1.8-m f/ 1.0 and 3.5-m f/ 1.5 aspheric mirrors.

The Giant Magellan Telescope has a 25 meter f/0.7 near-parabolic primary mirror constructed from seven 8.4 meter diameter segments. Several aspects of the interferometric optical test used to guide polishing of the six off-axis segments go beyond the demonstrated state of the art in optical testing. The null corrector is created from two obliquelyilluminated spherical mirrors combined with a computer-generated hologram (the measurement hologram). The larger mirror is 3.75 m in diameter and is supported at the top of a test tower, 23.5 m above the GMT segment. Its size rules out a direct validation of the wavefront produced by the null corrector. We can, however, use a reference hologram placed at an intermediate focus between the two spherical mirrors to measure the wavefront produced by the measurement hologram and the first mirror. This reference hologram is aligned to match the wavefront and thereby becomes the alignment reference for the rest of the system. The position and orientation of the reference hologram, the 3.75 m mirror and the GMT segment are measured with a dedicated laser tracker, leading to an alignment accuracy of about 100 microns over the 24 m dimensions of the test. In addition to the interferometer that measures the GMT segment, a separate interferometer at the center of curvature of the 3.75 m sphere monitors its figure simultaneously with the GMT measurement, allowing active correction and compensation for residual errors. We describe the details of the design, alignment, and use of this unique off-axis optical test.

Lockheed Martin Corporation (LMC) tasked The University of Arizona Steward Observatory (UASO) to conduct an engineering study to examine the feasibility of creating a 4m space telescope based on mature borosilicate technology developed at the UASO for ground-based telescopes. UASO has completed this study and concluded that existing launch vehicles can deliver a 4m monolithic telescope system to a 500 km circular orbit and provide reliable imagery at NIIRS 7-8. An analysis of such an imager based on a lightweight, high-performance, structured 4m primary mirror cast from borosilicate glass is described. The relatively high CTE of this glass is used to advantage by maintaining mirror shape quality with a thermal figuring method. Placed in a 290 K thermal shroud (similar to the Hubble Space Telescope), the orbit averaged figure surface error is 6nm rms when earth-looking. Space-looking optical performance shows that a similar thermal conditioning scheme combined with a 270 K shroud achieves primary mirror distortion of 10 nm rms surface. Analysis shows that a 3-point bipod mount will provide launch survivability with ample margin. The primary mirror naturally maintains its shape at 1g allowing excellent end-to-end pre-launch testing with e.g. the LOTIS 6.5m Collimator. The telescope includes simple systems to measure and correct mirror shape and alignment errors incorporating technologies already proven on the LOTIS Collimator. We have sketched a notional earth-looking 4m telescope concept combined with a wide field TMA concept into a DELTA IV or ATLAS 552 EELV fairing. We have combined an initial analysis of launch and space performance of a special light-weighted honeycomb borosilicate mirror (areal density 95 kg/m 2 ) with public domain information on the existing launch vehicles.

The primary mirror of the Giant Magellan Telescope consists of seven 8.4 m segments which are borosilicate honeycomb sandwich mirrors. Fabrication and testing of the off-axis segments is challenging and has led to a number of innovations in manufacturing technology. The polishing system includes an actively stressed lap that follows the shape of the aspheric surface, used for large-scale figuring and smoothing, and a passive "rigid conformal lap" for small-scale figuring and smoothing. Four independent measurement systems support all stages of fabrication and provide redundant measurements of all critical parameters including mirror figure, radius of curvature, off-axis distance and clocking. The first measurement uses a laser tracker to scan the surface, with external references to compensate for rigid body displacements and refractive index variations. The main optical test is a full-aperture interferometric measurement, but it requires an asymmetric null corrector with three elements, including a 3.75 m mirror and a computer-generated hologram, to compensate for the surface's 14 mm departure from the best-fit sphere. Two additional optical tests measure large-scale and small-scale structure, with some overlap. Together these measurements provide high confidence that the segments meet all requirements.

The Large Optical Test and Integration Site (LOTIS) at the Lockheed Martin Space Systems Company in Sunnyvale, CA is designed for the verification and testing of optical systems. The facility consists of a large, temperature stabilized vacuum chamber that also functions as a class 10k cleanroom. Within this chamber and atop an advanced vibration-isolation bench are the 6.5 meter diameter LOTIS Collimator and Scene Generator, LOTIS alignment and support equipment. The optical payloads are also placed on the vibration bench in the chamber for testing. The Scene Generator is attached to the Collimator forming the Scene Projection System (SPS) and this system is designed to operate in both air and vacuum, providing test imagery in an adaptable suite of visible/near infrared (VNIR) and midwave infrared (MWIR) point sources, and combined bandwidth visible-through-MWIR point sources, for testing of large aperture optical payloads. The heart of the SPS is the LOTIS Collimator, a 6.5m f/15 telescope, which projects scenes with wavefront errors

The proposed science missions of the LSST require a telescope with an optical etendue of greater than 250 meters square degrees square. The current LSST Baseline Configuration has a field of view of 3.5 degrees and an optical etendue of 302 m 2 d 2 . The etendue calculation includes the effect of gradual vignetting by the camera as the field angle increases. A current optical point design includes spun cast light-weighted borosilicate mirrors (primary and tertiary) of 8.4 and 5 m diameter respectively. Thermal control systems are needed to optimize telescope seeing and to minimize the thermal distortion of the mirrors. The goals of this study are to determine the airflow requirements for the specified ambient temperature rate of change, to identify thermal time constants and to predict the magnitude and form of thermal distortions that can be developed by environmental conditions. Operational data taken at the 6.5 m MMT (Multi-Mirror Telescope Observatory) and at the Magellan Observatory are presented for comparison with this study. Finally, the results from the thermal analysis were used to simulate the LSST focus control over one night of observation and to estimate the effect on the image quality for different correction frequencies.

The Mycobacterium leprae RuvA homologue (MlRuvA) was over-expressed in Escherichia coli and purified to homogeneity. The DNA-binding specificity and the functional interactions of MlRuvA with E. coli RuvB and RuvC (EcRuvB and EcRuvC) were examined using synthetic Holliday junctions. MlRuvA bound specifically to Holliday junctions and produced similar band-shift patterns as EcRuvA. Moreover, MlRuvA formed functional DNA helicase and branch-migration enzymes with EcRuvB, although the heterologous enzyme had a lower efficiency. These results demonstrate that the RuvA homologue of M. leprae is a functional branch-migration subunit. Whereas MlRuvA promoted branch-migration in combination with EcRuvB, it was unable to stimulate branch-migration-dependent resolution in a RuvABC complex. The inability to stimulate RuvC was not due to its failure to form heterologous RuvABC complexes on junctions, since such complexes were detected by co-immunoprecipitation. Most likely, the stability of the heterologous RuvABC complex and, possibly, the interactions between RuvA and RuvC were impaired, as gel-shift experiments failed to show mixed MlRuvA-EcRuvC-junction complexes. These results demonstrate that branch-migration per se and the assembly of a RuvABC complex on the Holliday junction are insufficient for RuvAB-dependent resolution of the junction by RuvC, suggesting that specific and intimate interactions between all three proteins are required for the function of a RuvABC "resolvasome".

In Escherichia coli, the RuvA and RuvB proteins interact at Holliday junctions to promote branch migration leading to the formation of heteroduplex DNA. RuvA provides junction-binding specificity and RuvB drives ATP-dependent branch migration. Since RuvB contains sequence motifs characteristic of a DNA helicase and RuvAB exhibit helicase activity in vitro, we have analysed the role of DNA unwinding in relation to branch migration. A mutant RuvB protein, RuvB(D113E), mutated in helicase motif II (the DExx box), has been purified to homogeneity. The mutant protein forms hexameric rings on DNA similar to those formed by wild-type protein and promotes branch migration in the presence of RuvA. However, RuvB(D113E) exhibits reduced ATPase activity and is severely compromised in its DNA helicase activity. Models for RuvAB-mediated branch migration that invoke only limited DNA unwinding activity are proposed.

We describe the fabrication of the 6.5 m f/1.25 primary mirrors for the Multiple Mirror Telescope Conversion and the first Magellan telescope. Figuring was performed with a 1.2 m stressed lap-which bends under active control to match the local curvature of the optical surface-and small passive tools. The figure was measured with IR and visible interferometers, using refractive null correctors to compensate 810 microns of aspheric departure. We present the final measurements as surface maps, synthetic interferograms and synthetic images.

The RuvA, RuvB and RuvC proteins of Escherichia coli process Holliday junctions during genetic recombination and DNA repair. Biochemical studies have shown that RuvA and RuvB promote branch migration whereas RuvC resolves junctions by endonucleolytic cleavage. Here we show that RuvAB stimulate Holliday junction resolution by RuvC. Elevated RuvC activity was dependent upon RuvAB-mediated ATP-hydrolysis. These results show that the three Ruv proteins work in a coordinated manner to promote Holliday junction resolution, and account for the resolvase-defective phenotype exhibited by ruvA, ruvB or ruvC mutant strains.

The primary mirror for the Multiple Mirror Telescope Conversion is the first 6.5 m honeycomb sandwich mirror cast and polished by the Steward Observatory Mirror Lab. We describe the optical fabrication and testing of the f/1.25 paraboloid, and present the final measurements of figure accuracy and inferred image quality. Figuring was performed with a 1.2 m stressed lap--which bends under active control to match the local curvature of the optical surface--and a variety of small passive tools. The mirror was pressurized to compensate for polishing loads and thereby eliminate print-through of the honeycomb structure. The net result is a smoother surface on scales of 5 - 20 cm than has been achieved on previous honeycomb sandwich mirrors. The figure was measured with IR and visible interferometers, using refractive null correctors to compensate 810 microns of aspheric departure. The final measurements were used to calculate synthetic stellar images in a variety of seeing conditions.

We describe the active support system and optimization of support forces for the 6.5 m primary mirror for the Multiple Mirror Telescope Conversion. The mirror was figured to an accuracy of 26 nm rms surface error, excluding certain flexible bending modes that will be controlled by support forces in the telescope. On installation of the mirror into its telescope support cell, an initial optimization of support forces is needed because of minor differences between the support used during fabrication and that in the telescope cell. The optimization is based on figure measurements made interferometrically in the vibration- isolated test tower of the Steward Observatory Mirror Lab. Actuator influence functions were determined by finite- element analysis and verified by measurement. The optimization is performed by singular value decomposition of the influence functions into normal modes. Preliminary results give a wavefront accuracy better than that of the atmosphere in 0.11 arcsecond seeing.

The Steward Observatory Mirror Lab is in the process of fabricating the 6.5 m mirror for the conversion of the multiple mirror telescope (MMT) to a single primary mirror. For this purpose the lab has developed a versatile polishing system built around the stressed lap polishing tool. The system must produce an f/1.25 parabolic surface with an accuracy corresponding to 0.09 arcsecond FWHM seeing and 1.5% scattering loss at 500 nm wavelength.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The 6.5 m upgrade of the multiple mirror telescope (MMT) will include a number of new secondary mirrors. For first light, there will be an f/9 Cassegrain secondary manufactured from a 1.0 m diameter Hextek borosilicate honeycomb meniscus blank. This f-ratio is designed to match that of the present MMT to allow the use of existing instrumentation for first light. This will be followed by the wide field f/5 secondary combined with a refractive corrector which includes an atmospheric dispersion corrector (ADC) to give a 1 degree unvignetted Cassegrain field. The f/5 mirror is made from a 1.7 m diameter lightweighted machined Zerodur blank. Two f/15 0.64 m diameter secondaries are being designed. The first of these is an adaptive secondary consisting of a thin 2 mm thick shell faceplate with 300 voice coil actuators and associated capacitive displacement sensors. A chopping f/15 secondary is planned using a rigid lightweight blank such as silicon carbide. The 8.4 m large binocular telescope (LBT) will have two secondaries for each of the two primaries. For first light, 0.87 m diameter f/15 Gregorian adaptive secondaries are planned. These concave mirrors will use the same thin shell faceplate, voice coil actuator and capacitive sensor technology currently being developed for the MMT f/15 adaptive secondary. A pair of 1.25 m diameter f/4 Cassegrain secondaries will be built next. These will be used together with refractive corrector optics to give a 1 degree field. These mirrors are being polished and tested at the Steward Observatory Mirror Laboratory (SOML) using the recently completed Secondary Fabrication and Test Facility. Stressed lap polishing is used to achieve the fast, highly aspheric surfaces and testing is done with the computer generated hologram (CGH) test plate technique. Each of these secondaries requires a support system, five axis actuation and thermal environmental control. The in-house development of this number of secondaries enables an integrated design approach. As much as possible of the development, design and hardware costs will be shared between secondaries. This paper describes the designs which are being developed for the support, actuation and thermal control for each of these secondaries.

The Vatican Advanced Technology Telescope incorporates a fast (f/1.0) borosilicate honeycomb primary mirror and an f/0.9 secondary in an aplanatic Gregorian optical configuration. We provide a brief technical and performance overview by describing the optical layout, the primary and secondary mirror systems, and the telescope drive and control system. Results from a high resolution wavefront sensor and a current wide-field image taken at the f/9 focus demonstrates the overall fine performance of the telescope.

Operated by the Multiple Mirror Telescope Observatory (MMTO), the multiple mirror telescope (MMT) is funded jointly by the Smithsonian Institution (SAO) and the University of Arizona (UA). The two organizations equally share observing time on the telescope. The MMT was dedicated in May 1979, and is located on the summit of Mt. Hopkins (at an altitude of 2.6 km), 64 km south of Tucson, Arizona, at the Smithsonian Institution's Fred Lawrence Whipple Observatory (FLWO). As a result of advances in the technology at the Steward Observatory Mirror Laboratory for the casting of large and fast borosilicate honeycomb astronomical primary mirrors, in 1987 it was decided to convert the MMT from its six 1.8 m mirror array (effective aperture of 4.5 m) to a single 6.5 m diameter primary mirror telescope. This conversion will more than double the light gathering capacity, and will by design, increase the angular field of view by a factor of 15. Because the site is already developed and the existing building and mount will be used with some modification, the conversion will be accomplished for only about $20 million. During 1995, several major technical milestones were reached: (1) the existing building was modified, (2) the major steel telescope structures were fabricated, and (3) the mirror blank was diamond wheel ground (generated). All major mechanical hardware required to affect the conversion is now nearly in hand. Once the primary mirror is polished and lab-tested on its support system, the six-mirror MMT will be taken out of service and the conversion process begun. We anticipate that a 6 - 12 month period will be required to rebuild the telescope, install its optics and achieve f/9 first light, now projected to occur in early 1998. The f/5.4 and f/15 implementation will then follow. We provide a qualitative and brief update of project progress.

The E. coli RuvA and RuvB proteins, which are involved in the late stages of recombination and the recombinational repair of damaged DNA, bind to Holliday junctions and promote branch migration. We have used electron microscopy and image analysis to examine RuvA and RuvB bound to model Holliday structures. The two hexameric rings of RuvB are oriented in a bipolar manner, so that the large end of each faces the junction. The results suggest a model for branch migration in which DNA is pumped out of the small end of each ring as ATP is hydrolyzed. The same structural polarity has been established for the bacteriophage T7 gp4 replicative helicase. Mass and image analysis of the RuvAB-junction complex suggests that two tetramers of RuvA form a symmetrical sandwich about the plane of the junction.

The instruments used to interferometrically measure the optical surfaces of the 6.5-m f/1.25 primary mirrors for the University of Arizona telescope projects must compensate over 800 μm surface departure from the best fitting sphere. The errors in the optical test must not contribute more than 0.04 arc seconds FWHM to the final image and the conic constant must be held to 0.01%. This paper presents an overview of the instruments used to measure these giant mirrors to such high accuracy.

The RuvA and RuvB proteins of Escherichia coli promote the branch migration of Holliday junctions in vitro. To understand the relationship between branch migration and the intrinsic 5'--3' DNA helicase activity of RuvAB, the requirements and substrate specificity of the helicase reaction have been studied in more detail. We find that RuvAB-mediated DNA unwinding and branch migration reactions show similar requirements for Mg2+ and ATP and are inhibited to a similar extent by ADP and ATP gamma S (adenosine 5'-O-(3-thiotriphosphate)). The helicase activity, measured by the dissociation of a short fragment from circular single-stranded DNA, requires both RuvA and RuvB and is stimulated by subsaturating concentrations of single-strand binding protein (SSB). In contrast, saturating concentrations of SSB are inhibitory. Using substrates that contain a DNA junction, which permits the specific binding of RuvA, we find that the RuvA and RuvB proteins promote two types of helicase reactions: nonspecific reactions, which are sensitive to inhibition by stoichiometric amounts of SSB, and junction-targeted reactions, which are not inhibited by SSB. Using three-armed structures, we observe that junction-targeted reactions display a polarity and result in asymmetric product formation. Junction-specific binding and the subsequent initiation of DNA unwinding are likely to represent early steps in the process of branch migration.

The Escherichia coli RuvA and RuvB proteins mediate ATP-dependent branch migration of Holliday junctions during homologous genetic recombination. RuvA is a DNA-binding protein with high affinity for Holliday junctions, to which it directs RuvB (a DNA-dependent ATPase). Electron microscopic studies have shown that RuvB forms double hexameric rings on duplex DNA. To determine whether the rings are biologically active, the conditions required for their formation and activity have been analysed. The quaternary structure of RuvB appears to be dependent upon the binding of ATP, magnesium ions, and the presence of RuvA. In the presence of Mg2+ and ATP, RuvB forms hexamers; however, in the presence of Mg2+ alone, dodecamers were observed. Both forms of the protein are stable and have been isolated by gel filtration. Performed dodecamers and, to a lesser extent, hexamers assembled in the absence of DNA lack ATPase activity. Maximal ATPase activity was observed when RuvB assembled directly on DNA in the presence of Mg2+ and ATP. Moreover, under these conditions, a direct interaction between RuvB hexamers and tetramers of RuvA was observed.

The instruments used to interferometrically measure the optical surfaces of the 6.5-m f/1.25 primary mirrors for the MMT conversion and Magellan Telescopes must compensate over 800 micrometers surface departure from the best fitting sphere. The errors in the optical test must not contribute more than 0.04 arc seconds FWHM to the final image and the conic constant must be held to 0.01%. This paper presents the design, analysis, fabrication, and certification of the instruments used to measure these giant mirrors to such high accuracy.

The specificity of the Escherichia coli RuvC Holliday junction resolvase has been investigated in vitro. RuvC protein cleaves synthetic DNA substrates that model three- or four-stranded recombination intermediates but fails to act upon Y junctions, G/A mismatches, heterologous loop structures, or two-stranded branched junctions. RuvC therefore differs from endonuclease VII of bacteriophage T4 which exhibits broad range specificity. Using related three- and four-stranded synthetic DNA junctions, we show that RuvC cleaves both junctions at the same DNA sequence and requires a region of homology at the junction point. The action of RuvC on three- and four-stranded recombination intermediates made by RecA was also investigated. We found that RuvC fails to resolve three-stranded intermediates in the presence of RecA, although four-stranded intermediates are resolved under the same conditions. However, both three- and four-stranded intermediates are substrates for the nuclease after removal of RecA. We interpret these differences in terms of the contiguity of the RecA nucleoprotein filament which may, under certain conditions, limit access to the Holliday junction resolvase.

D. Anderson, J. Burge, D. Ketelsen, B. Martin, S. WestSteward Observatory Mirror LaboratoryUniversity of ArizonaTucson, Arizona 8572].G. Poczulp, J. Richardson, W. WongNational Optical Astronomy ObservatoriesP.O. Box 26732, Tucson, Arizona 85726—67321. Abstract.The continuing development of rapid fabrication methods for large optics atthe Steward Observatory Mirror Lab has resulted in the completion of the WIYN 3.5m primary mirror in only five months. The use of these methods, though rapid,also resulted in one of the best surface figures we have produced (16 rim rms),excellent microroughness (8 angstroms rms), and very smooth small—scale figureerror as determined by the structure function of the surface errors. In thispaper, we review the important techniques in the grinding, polishing, and testingof the mirror used to achieve these results.2. Introduction.

The stressed-lap polishing technique has been developed to meet the challenge of polishing 8- m-class mirrors with highly aspheric figures to an accuracy consistent with the best ground- based telescope sites. The method is currently being demonstrated in the polishing of two primary mirrors, a 1.8-m f/1.0 ellipsoid and a 3.5-m f/1.5 paraboloid. The figure accuracies achieved at the time of writing are 43 nm rms surface error for the 1.8-m mirror, and 190 nm rms surface error for the 3.5-m mirror. Polishing is proceedings on both mirrors. In this paper we describe the process used for the 3.5-m mirror and the progress through the early stages of fabrication. We also summarize progress on the 1.8-m mirror.

Stressed-lap polishing has been used to complete three fast borosilicate honeycomb-sandwich mirrors. The 1.8-m f/1 primary mirror for the Lennon Telescope being built by the Vatican Observatory and the University of Arizona has been figured to an accuracy of 17 nm rms surface error, the 3.5-m f/1.5 primary mirror for the Starfire Optical Range of the U. S. Air Force Phillips Laboratory to 21 nm rms, and the 3.5-m f/1.75 primary mirror for the Astrophysical Research Consortium to 19 nm rms. The 3.5-m mirrors were figured in a new polishing facility, using a computer-controlled polishing machine and vibration-isolated test tower both sized for 8-m mirrors.

The contact hypothesis predicts that cooperative interaction with members of a disliked group results in increased liking for those members and generalizes to more positive attitudes toward the group. The authors sought to provide evidence consistent with the hypothesis that contact affects attitude in part by eliciting a more positive portrait of the typical group member. Undergraduates participated in a 1-hr dyadic learning session (scripted cooperative learning, jigsaw cooperative learning, or individual study) with a confederate portrayed as a former mental patient. Students initially expected the confederate to display traits similar to those of a typical former mental patient. After the sessions, initially prejudiced students in the 2 cooperative conditions described the typical mental patient more positively and adopted more positive attitudes and wider latitudes of acceptance toward the group. Connections between intergroup attitudes and impression formation are discussed.

Fabricating very large (up to 8.4 m) and very fast (down to f/1) aspherics is one of the principal goals of the Steward Observatory Mirror Laboratory. As a first step toward this goal we have been fabricating the 1.8-m f/1 primary mirror for the Vatican Advanced Technology Telescope. Using a novel stressed-lap polishing tool we have been able to achieve a smooth, high quality figure on the mirror that departs from the best-fit sphere by >700 waves. The tool is 60 cm in diameter, faced with pitch, and is actively bent under computer control to fit the asphere as it is stroked across the surface in conventional fashion. Initially, the mirror was polished as a sphere to the final aspheric specifications with a rigid lap of the same size to establish techniques for figuring the mirror with a tool of this size. The asphere was then diamond generated into the surface on the large optical generator to ~4 μm rms. Stressed-lap polishing then commenced without any further grinding. Both speed and pressure variation of the lap were used to achieve rotational symmetry.

The stressed-lap polishing technique has been developed to figure large, highly aspheric mirrors for optical and infrared telescopes. The Steward Observatory Mirror Laboratory plans to cast and polish lightweight honeycomb sandwich mirrors up to 8.4-m diameter, with focal ratios as fast as 1.14. These mirrors must be figured to an accuracy corresponding to better than 0.1 arcsec FWHM image quality. Three primary mirrors have been cast at 1.8-m diameter and three at 3.5-m diameter, and two of these are being polished with stressed laps: a 1.8-m f/1.0 ellipsoid for the Vatican Advanced Technology Telescope, and a 3.5-m f/1.5 paraboloid for a telescope at the Air Force Phillips Laboratory. Both mirrors are far more aspheric than any existing astronomical telescope mirror, with peak-to-valley departures of 445μm and 253μm from the best-fitting sphere. Through active control of the shape of the polishing tool, the stressed lap combines the natural smoothing and corrective effect of a large, stiff, rapidly moving tool with the ability to maintain an accurate fit to a severely aspheric surface.

We are in the process of polishing a 1.8-rn f/i ellipsoid with an actively stressed lap. As a preliminary exercise, we have polished the mirror as a sphere using a rigid subdiameter lap. The overall surface error was 25 nm rms, and the surface met a specification corresponding to i/8-arcsec image quality. A stressed lap 600 mm in diameter was designed and built to polish the mirror as an f/i ellipsoid. It consists of an aluminum disk which changes shape continuously under the influence of 12 moment-generating actuators. These actuators are programmed to produce the shape changes necessary to make the lap fit the mirror surface as it moves across that surface and rotates. In this paper we describe the principles and design of the lap, test results, and progress to date in polishing the 1.8-rn mirror.

Homologous pairing between gapped circular and partially homologous form I DNA, catalyzed by Escherichia coli RecA protein, leads to the formation of nascent synaptic joints between regions of duplex DNA. These duplex-duplex interactions result in underwinding of the form I DNA, as detected by a topoisomerase assay. Underwound DNA species have been studied with regard to their formation, stability, and topological requirements. The synaptic joints are short-lived and of low frequency compared with those formed between single-stranded and duplex DNA. Measurement of the degree of underwinding indicates joints 300-400 base pairs in length, in which the two DNA molecules are presumed to be interwound within the RecA-nucleoprotein filament. Underwound DNA was not detected in reactions between gapped DNA and partially homologous nicked circular or relaxed covalently closed DNA. We have also investigated the requirements for the initiation of strand exchange. Previous results have shown that strand exchange requires a homologous 3'-terminus complementary to the gapped region. We now show that the minimum length of overlap required for efficient initiation of strand exchange is one to two turns of DNA within the RecA-DNA nucleoprotein filament.

The optical, mechanical, and electronic designs of a multi-purpose near-infrared (1.1 - 2.5 microns) camera built for Las Campanas Observatory are described. The camera is used on both the 2.5-m duPont and 1-m Swope telescopes. A refractive all-spherical achromatic reimager incorporates three confocal discrete-zooms which image onto a Rockwell HgCdTe (NICMOS2) 128 x 128 detector array. Although the instrument was designed primarily for imaging, we have included two experimental modes for future use--a low-resolution grism (R 400) and a cooronagraph. The optical design choices and procedures are described in some detail. The entire 0.6m optical path resides at 77 degrees Kelvin and is folded onto a 25.4 cm diameter dewar work surface. The instrument is remotely controlled by a Sun 386i graphics workstation via serial links to microprocessor-controlled motor-encoder packages and the array control electronics. Electronic designs suitable for use with a NICMOS2 array are given. The data are acquired and inspected using IRAF routines running under the UNIX multitasking environment. Initial performance results on camera optical quality and system sensitivity are given.

We report the results of infrared imaging photometry of four radio galaxies with redshifts greater than 2. The infrared images show a wide range of morphologies when compared to the optical images. Two objects are quite compact in the IR while one is significantly extended and is closely aligned with its radio source axis and follows the optical morphology. The spectral energy distributions of each galaxy are determined and these too show a wide range of colors, with the more compact objects redder

The development of an astronomical polarimeter for the spectral region 1-2.6 microns is reported. The instrument incorporates a fused silica stress-birefringent modulator capable of producing square-wave polarimetric modulation of over 95 percent efficiency from dc to 2 Hz and quarter-wave retardation at wavelengths up to the K photometric bands. Possible applications of this instrument are examined, including the search for comparatively weak magnetic fields in white dwarf accretion binaries, the study of the nature of polarization in faint active galactic nuclei, and near-IR survey of isolated magnetic white dwarfs.