Experimental study of main rotor tip geometry and tail rotor interactions in hover. Volume 1. Text and figures

A model scale hover test was conducted in the Sikorsky Aircraft Model rotor hover Facility to identify and quantify the impact of the tail rotor on the demonstrated advantages of advanced geometry tip configurations. The test was conducted using the Basic Model Test Rig and two scaled main rotor systems, one representing a 1/5.727 scale UH-60A BLACK HAWK and the others a 1/4.71 scale S-76. Eight alternate rotor tip configurations were tested, 3 on the BLACK HAWK rotor and 6 on the S-76 rotor. Four of these tips were then selected for testing in close proximity to an operating tail rotor (operating in both tractor and pusher modes) to determine if the performance advantages that could be obtained from the use of advanced geometry tips in a main rotor only environment would still exist in the more complex flow field involving a tail rotor. The test showed that overall the tail rotor effects on the advanced tip configurations tested are not substantially different from the effects on conventional tips

Scattering induced dynamical entanglement and the quantum-classical correspondence

The generation of entanglement produced by a local potential interaction in a bipartite system is investigated. The degree of entanglement is contrasted with the underlying classical dynamics for a Rydberg molecule (a charged particle colliding on a kicked top). Entanglement is seen to depend on the structure of classical phase-space rather than on the global dynamical regime. As a consequence regular classical dynamics can in certain circumstances be associated with higher entanglement generation than chaotic dynamics. In addition quantum effects also come into play: for example partial revivals, which are expected to persist in the semiclassical limit, affect the long time behaviour of the reduced linear entropy. These results suggest that entanglement may not be a pertinent universal signature of chaos.Comment: Published versio

Medial opening wedge high tibial osteotomy: A retrospective review of patient outcomes over 10 years

Objectives: High tibial osteotomy (HTO) has become a well-established treatment for unicompartmental osteoarthritis of the knee. Over the last 30 years, various techniques have been introduced to advance this procedure. The purpose of this study is to review the outcomes of patients who received medial opening wedge HTO over the last ten years (2002-2012) using a modern, low profile, medially based fixation device. In addition, we sought to determine if obese patients had a less favorable outcome than their non-obese counterparts. Methods: Ninety-three patients were identified from a surgical database as having undergone a HTO for medial compartment osteoarthritis of the knee with varus mal-alignment. All procedures were performed by one of two fellowship trained orthopedic surgeons from 2002-2012 utilizing a low profile fixation device and identical surgical technique. Minimum follow-up was one year for inclusion in the study. Outcomes were measured using Lysholm and WOMAC scores. Radiographs were evaluated to determine delayed union or non-union at the osteotomy site and surveillance was undertaken to evaluate post operative complications. Results: 93 patients were identified from the database, 63 (70%) were available for follow-up and are included in this analysis. Average follow-up time was 48 months (range 17 to 137). There were 44 males and 19 females. The average age was 45 years old. The average final Lysholm and WOMAC scores were 66.4 (range: 13-100) and 18.6 (range: 0-86) respectively. There was no significant difference in reported Lysholm or WOMAC scores between obese (BMI \u3e30) and non-obese patients (p=.31;p=.69). Complications were as follows: 3 patients required a surgical lysis of adhesions, 2 patients developed an infection, and 1 patient experienced a delayed union. At final follow-up, 18 patients received additional treatment on the affected knee: 11 required removal of symptomatic hardware, 5 received viscosupplementation, 2 underwent a total knee replacement. Conclusion: Low profile, medial based devices used in the setting of HTO is an accepted treatment for unicompartmental osteoarthritis of the knee. At final follow-up, a majority of patients reported positive outcomes and few complications. 18 patients required additional treatment for osteoarthritis. In our analysis, obese patients faired equally as well as their non-obese counterparts, with no significant difference in outcomes scores or complication rate. Survivorship of high tibial osteotomy was excellent in this series, with only 2 patients having undergone total knee replacement at last follow-up. © The Author(s) 2015

Arthroscopic transosseous rotator cuff repair: A prospective study on cost savings, surgical time, and outcomes

Objectives: Health expenditures in the United States are outpacing national income, and affordability has become a major policy issue. Over 500,000 rotator cuff repairs (RCR) are performed annually in the United States making RCR a potential source of cost savings. Arthroscopic trans-osseous equivalent (TOE) repair using a double row of anchors has shown superior biomechanical strength compared to other techniques, but at a higher cost. The arthroscopic transosseous (TO) repair is a novel technique allowing arthroscopic rotator cuff repair to be performed without suture anchors. Arthroscopic TO repair may be a means to provide similarly excellent patient outcomes while lowering the cost of care. The primary purpose is to compare the price differential and time of surgery for an arthroscopic rotator cuff repair using anchorless TO repair verses an anchor trans-osseous equivalent (TOE) repair. A secondary purpose of the study was to evaluate outcomes at 6 months postoperatively. Methods: A prospective, case-controlled study evaluating arthroscopic rotator cuff repair using two techniques was performed. The study group consisting of 21 patients undergoing TO repair was compared to a control group consisting of 22 patients undergoing TOE repair. The groups were controlled for size of tear, biceps treatment, acromioplasty, distal clavicle excision, and labral pathology. The primary outcome measures were surgical time as well as total cost of implants and equipment for each surgery, determined by an independent third party, Atlanticare Hospital. Secondary outcomes were changes in the SST, VAS, and SANE scores. Results: Mean total surgical implant/equipment cost per procedure for TOE repair was $2348.03 (SD 490.30) and for TO repair was$1204.97 (SD 330.69; p\u3c0.0001). Mean cut to close time for TOE repair was 85 minutes (95% CI is 77-90) verses 74 (95% CI = 71-98) for TO repair. A log rank test revealed no difference in time (p =0.95). A linear regression model was developed to evaluate the change in SST, VAS, and SANE scores from pre-op to 6 months follow-up. Our study was underpowered but no difference in outcome was observed. Conclusion: Arthroscopic TO rotator cuff repair is a cost savings and time neutral technique compared to TOE repair. A mean of $1100 can be saved in surgical cost per case. In a country that performs over 500,000 RCRs annually, utilizing a TO repair technique can provide substantial cost savings to the healthcare system. © The Author(s) 2015

Double lenses

The analysis of the shear induced by a single cluster on the images of a large number of background galaxies is all centered around the curl-free character of a well-known vector field that can be derived from the data. Such basic property breaks down when the source galaxies happen to be observed through two clusters at different redshifts, partially aligned along the line of sight. In this paper we address the study of double lenses and obtain five main results. (i) First we generalize the procedure to extract the available information, contained in the observed shear field, from the case of a single lens to that of a double lens. (ii) Then we evaluate the possibility of detecting the signature of double lensing given the known properties of the distribution of clusters of galaxies. (iii) As a different astrophysical application, we demonstrate how the method can be used to detect the presence of a dark cluster that might happen to be partially aligned with a bright cluster studied in terms of statistical lensing. (iv) In addition, we show that the redshift distribution of the source galaxies, which in principle might also contribute to break the curl-free character of the shear field, actually produces systematic effects typically two orders of magnitude smaller than the double lensing effects we are focusing on. (v) Remarkably, a discussion of relevant contributions to the noise of the shear measurement has brought up an intrinsic limitation of weak lensing analyses, since one specific contribution, associated with the presence of a non-vanishing two-galaxy correlation function, turns out not to decrease with the density of source galaxies (and thus with the depth of the observations).Comment: 40 pages, 15 figures. Accepted for publication in ApJ main journa

Soft X-ray Absorption by High-Redshift Intergalactic Helium

The Lyman alpha absorption from intergalactic, once-ionized helium (HeII) has been measured with HST in four quasars over the last few years, over the redshift range 2.4 < z < 3.2. These observations have indicated that the HeII reionization may not have been completed until z\simeq 2.8, and that large fluctuations in the intensity of the HeII-ionizing background were present before this epoch. The detailed history of HeII reionization at higher redshifts is, however, model-dependent and difficult to determine from these observations, because the IGM can be completely optically thick to Lya photons when only a small fraction of the helium remains as HeII. In addition, finding quasars in which the HeII Lya absorption can be observed becomes increasingly difficult at higher redshift, owing to the large abundance of hydrogen Lyman limit systems. It is pointed out here that HeII in the IGM should also cause detectable continuum absorption in the soft X-rays. The spectrum of a high-redshift source seen behind the IGM when most of the helium was HeII should recover from the HeII Lyman continuum absorption at an observed energy \sim 0.1 keV. Galactic absorption will generally be stronger, but not by a large factor; the intergalactic HeII absorption can be detected as an excess over the expected Galactic absorption from the 21cm HI column density. In principle, this method allows a direct determination of the fraction of helium that was singly ionized as a function of redshift, if the measurement is done on a large sample of high-redshift sources over a range of redshift.Comment: accepted to The Astrophysical Journal Letter

Surface integral equation method for sharp edge structures with junctions

Complex scattering targets contain metallic structures with junctions and sharp edges that require a special procedure to be analyzed by the Method of Moments. Singular basis functions to mdel junctions with edge profile connected together are considered. At the Conference, we will show how to handle the different geometrical cases together with numerical results that validate the proposed metho

HST/ACS weak lensing analysis of the galaxy cluster RDCS 1252.9-2927 at z=1.24

We present a weak lensing analysis of one of the most distant massive galaxy cluster known, RDCS 1252.9-2927 at z=1.24, using deep images from the Advanced Camera for Survey (ACS) on board the Hubble Space Telescope (HST). By taking advantage of the depth and of the angular resolution of the ACS images, we detect for the first time at z>1 a clear weak lensing signal in both the i (F775W) and z (F850LP) filters. We measure a 5-\sigma signal in the i band and a 3-\sigma signal in the shallower z band image. The two radial mass profiles are found to be in very good agreement with each other, and provide a measurement of the total mass of the cluster inside a 1Mpc radius of M(<1Mpc) = (8.0 +/- 1.3) x 10^14 M_\odot in the current cosmological concordance model h =0.70, \Omega_m=0.3, \Omega_\Lambda=0.7, assuming a redshift distribution of background galaxies as inferred from the Hubble Deep Fields surveys. A weak lensing signal is detected out to the boundary of our field (3' radius, corresponding to 1.5Mpc at the cluster redshift). We detect a small offset between the centroid of the weak lensing mass map and the brightest cluster galaxy, and we discuss the possible origin of this discrepancy. The cumulative weak lensing radial mass profile is found to be in good agreement with the X-ray mass estimate based on Chandr and XMM-Newton observations, at least out to R_500=0.5Mpc.Comment: 38 pages, ApJ in press. Full resolution images available at http://www.eso.org/~prosati/RDCS1252/Lombardi_etal_accepted.pd