Optical measurements of phase steps in segmented mirrors - fundamental precision limits

Phase steps are an important type of wavefront aberrations generated by large telescopes with segmented mirrors. In a closed-loop correction cycle these phase steps have to be measured with the highest possible precision using natural reference stars, that is with a small number of photons. In this paper the classical Fisher information of statistics is used for calculating the Cramer-Rao bound, which determines the limit to the precision with which the height of the steps can be estimated in an unbiased fashion with a given number of photons and a given measuring device. Four types of measurement devices are discussed: a Shack-Hartmann sensor with one small cylindrical lenslet covering a sub-aperture centred over a border, a modified Mach-Zehnder interferometer, a Foucault test, and a curvature sensor. The Cramer-Rao bound is calculated for all sensors under ideal conditions, that is narrowband measurements without additional noise or disturbances apart from the photon shot noise. This limit is compared with the ultimate quantum statistical limit for the estimate of such a step which is independent of the measuring device. For the Shack-Hartmann sensor, the effects on the Cramer-Rao bound of broadband measurements, finite sampling, and disturbances such as atmospheric seeing and detector readout noise are also investigated. The methods presented here can be used to compare the precision limits of various devices for measuring phase steps and for optimising the parameters of the devices. Under ideal conditions the Shack-Hartmann and the Foucault devices nearly attain the ultimate quantum statistical limits, whereas the Mach-Zehnder and the curvature devices each require approximately twenty times as many photons in order to reach the same precision.Comment: 23 pages, 19 figures, to be submitted to Journal of Modern Optic

On-sky multi-wavelength phasing of segmented telescopes with the Zernike phase contrast sensor

Future Extremely Large Telescopes will adopt segmented primary mirrors with several hundreds of segments. Cophasing of the segments together is essential to reach high wavefront quality. The phasing sensor must be able to maintain very high phasing accuracy during the observations, while being able to phase segments dephased by several micrometers. The Zernike phase contrast sensor has been demonstrated on-sky at the Very Large Telescope. We present the multi-wavelength scheme that has been implemented to extend the capture range from \pmlambda/2 on the wavefront to many micrometers, demonstrating that it is successful at phasing mirrors with piston errors up to \pm4.0 micron on the wavefront. We discuss the results at different levels and conclude with a phasing strategy for a future Extremely Large Telescope.Comment: 17 pages, 8 figures, 2 tables. Accepted for publication in Applied Optics; he final publised version is available on the OSA website: http://www.opticsinfobase.org/abstract.cfm?msid=13671

Conceptual study for a sub-pupil instrument having 4 high order adaptive optics paths for parallel multi-wavelength high contrast imaging, and medium resolution spectrometry

We present the concept of an instrument that will create 4 circular sub-pupils of 3 m in diameter. Each sub-pupil path will be corrected by a high order adaptive optics system (SR~80% in H) without spider and M2 obstruction. These four independent channels, obviously all pointed towards the same field, allows the possibility of covering totally different parts of the electromagnetic spectrum simultaneously without compromising Signal to Noise Ratio. Each channel can be dedicated to very specialized but complementary purposes: high contrast imaging, pseudo-wide field imaging, high precision multi-color photometry, medium-resolution spectroscopy, polarimetry and sparse-aperture masking

Extinction controlled Adaptive Mask Coronagraph Lyot and Phase Mask dual concept for wide extinction area

A dual coronagraph based on the Adaptive Mask concept is presented in this paper. A Lyot coronagraph with a variable diameter occulting disk and a nulling stellar coronagraph based on the Adaptive Phase Mask concept using polarization interferometry are presented in this work. Observations on sky and numerical simulations show the usefulness of the proposed method to optimize the nulling efficiency of the coronagraphs. In the case of the phase mask, the active control system will correct for the detrimental effects of image instabilities on the destructive interference (low-order aberrations such as tip-tilt and focus). The phase mask adaptability both in size, phase and amplitude also compensate for manufacturing errors of the mask itself, and potentially for chromatic effects. Liquid-crystal properties are used to provide variable transmission of an annulus around the phase mask, but also to achieve the achromatic π phase shift in the core of the PSF by rotating the polarization by 180°.A compressed mercury (Hg) drop is used as an occulting disk for the Lyot mask, its size control offers an adaptation to the seeing conditions and provides an optimization of the Tip-tilt correction

Assessment of the Knowledge Level of Pomegranate Production Technologies in Maharashtra, India

China is the world's top fruit grower, with India ranking in second. Maharashtra, Tamil Nadu, Karnataka, Andhra Pradesh, Gujrat, Bihar, and Uttar Pradesh are the main fruit-growing states in India. The present study was conducted in Maharashtra with the specific objective of determining “Knowledge Level of the Pomegranate Growers”. Nashik, Sholapur and Ahmednagar districts were purposively selected for the study, as they are some of the maximum pomegranates growing districts in Maharashtra state. A Total of 180 pomegranate growers were selected from six talukas of these districts. Descriptive statistics was used for data analysis. The study revealed that more than four fifth (83.34 %) of the pomegranate growers had medium level of knowledge about pomegranate production technologies, followed by 12.77 per cent and 03.89 per cent of the pomegranate growers having low and high level of knowledge, respectively

Single vs. Multiple Laparoscopies: Pain Status One Year Post-Hysterectomy for Chronic Pelvic Pain

Despite the prevalence of chronic pelvic pain (CPP)— affecting one in seven women in the U.S.— its cause is often unknown. As such, an evaluation of our current approaches to the work-up of CPP is warranted. Laparoscopy is considered a gold standard tool in the evaluation of CPP with 40% of all laparoscopies in the U.S. performed for this condition [1]. However, limited data exists portraying the clinical importance and outcomes for repeat diagnostic laparoscopies. This is a retrospective case-control study to determine the incidence of multiple laparoscopies for CPP over the past 10 years, and to compare outcomes between patients who underwent single (SL) vs multiple (ML) laparoscopies. We propose that patients who undergo multiple laparoscopies warrant discussion of hysterectomy as our results indicate that resolution of pain in patients who undergo multiple laparoscopies for the indication of CPP is similar to patients undergoing hysterectomy after single laparoscopy

E-Z Point: A New Safe and Reproducible Laparoscopic Entry in the Left Upper Quadrant Using a Veress Needle

BACKGROUND: Over half of all fatal complications occur during primary laparoscopic entry. In our practice, we developed a novel modification of closed LUQ entry at Palmer\u27s point and designated it E-Z entry. AIMS: To evaluate the risks and safety of left subcostal entry, a technique we have designated \u27E-Z\u27 entry at our institution. SETTINGS AND DESIGN: A retrospective chart review was conducted at a tertiary care medical centre of patients who underwent laparoscopic procedures by a single surgeon known to perform left subcostal entry for the last 10 years, using the E-Z entry technique. MATERIALS AND METHODS: Retrospective chart review and description of surgical technique. STATISTICAL ANALYSIS USED: Simple descriptive statistics and univariate two-group comparisons. RESULTS: One hundred ninety-eight laparoscopic cases were identified as performed by a single surgeon in the last 10 years: 149 underwent umbilical entry and 49 underwent E-Z entry. The average number of previous abdominal surgeries was higher in the E-Z entry group compared to the umbilical group, 1.3 versus 0.5, respectively (P = 0.003). The umbilical entry group had no complications. One complication was noted with the E‑Z entry technique, in which the Veress needle was noted to perforate the liver capsule but was managed expectantly. CONCLUSION: We propose the E-Z entry technique for Veress needle entry as an ergonomic and easily reproducible entry technique in the left upper quadrant in the setting of suspected intraperitoneal adhesions

Comparative Analysis of Integrated Marketing Communication Strategies in view point of Sales Promotion and Advertising in the Specialty Division of Pharmaceutical Sector: A Modern Perspective

The empirical study of sales and promotional strategies is one of the avenues through which each major organizational group tries to enter and grow in the era of fierce competition, impulsive markets, and the remarkable potentiality of the Indian pharmaceutical sector. As a result, current companies are attempting to survive while also being willing to increase their profitability. The aforementioned research, which is being conducted in Belagavi, aims to concentrate on two distinct product promotion strategies: advertising and sales promotion. The pharmaceutical industry uses these strategies to boost product sales and gain a competitive edge on other industries in the future. Using the concepts of the Four Pillars—Medical Representatives, Medical Practitioners (GPs, CPs, and CPs), Field Managers, and Chemists—this article aims to exemplify the advertising and sales promotion tactics of pharmaceutical companies. Having gone through this article, one would learn about the prevalent performance of the pharmaceutical industry based on a comparison of sales promotion and advertising. One would also be able to determine which approach would be best to gain a stronger hold on the market given the competition