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

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

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

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

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

Radiated Immediate Prepectoral Direct to Implant Reconstruction: A Retrospective Cohort Study

Purpose: Increasing use of prepectoral plane in post mastectomy implant-based reconstruction has made immediate direct to implant (DTI) reconstruction more achievable. There has been increased incidence of post mastectomy radiation therapy (PMRT) making it important to understand the complication profile of immediate DTI reconstruction in patients who may require adjuvant radiation therapy. Methods: A retrospective cohort study of consecutive patients undergoing prepectoral DTI reconstruction with and without PMRT was performed. Patient and treatment level factors, operative, and post-operative outcomes were extracted on both the patient and breast level for the prepectoral radiated and nonradiated patients. The presence of at least one minor complication (superficial or full-thickness necrosis, cellulitis requiring oral antibiotics, hematoma, or seroma) or major complication (cellulitis requiring intravenous antibiotics, hospital readmission, explanation, or unplanned return to the operating room) was compared. We also evaluated how radiation affects outcomes of prepectoral DTI vs subpectoral DTI. Univariate analysis was performed to evaluate differences in outcomes between groups. Results: 242 patients underwent DTI reconstruction.148 patients underwent prepectoral DTI reconstruction. 54 patients underwent subpectoral DTI reconstruction. Patients who underwent PMRT had higher rates of neoadjuvant chemotherapy and axillary lymph node dissection. Univariate analysis did not demonstrate any significant differences in minor or major complications between the radiated and non-radiated prepectoral DTI breasts. Radiated prepectoral patients had a higher rate of capsular contracture and explant for capsular contracture. Conclusion: Immediate prepectoral DTI reconstruction in patients who will have PMRT has an improved complication profile compared to subpectoral placement

Preferências estabelecidas e personalidade: uma abordagem comportamental

TCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.Este estudo tem o objetivo de contribuir para o entendimento da dissonância cognitiva que surge quando preferências estabelecidas com relação a produtos são alteradas à medida em que os consumidores se deparam com informação mais completa do que a existente na escolha inicial. Buscou-se verificar a probabilidade de abandono da escolha preliminar na amostra de consumidores analisada. A contribuição se refere à mediação da habilidade cognitiva e da personalidade nessas decisões. No experimento, os participantes com fraca preferência na escolha inicial – e baixa habilidade cognitiva, além de baixos escores em traços de honestidade-humildade, extroversão e conscienciosidade – tendem a abandonar a escolha inicial. Já os participantes com escores mais altos em todas essas características tendem a não abandonar a sua escolha preliminar