Invariance of waveguide grating mirrors to lateral displacement phase shifts

We present a method to analyse the coupling of lateral displacements in nanoscale structures, in particular waveguide grating mirrors (WGM), into the phase of a reflected Gaussian beam using a finite-difference time-domain simulation. Such phase noise is of interest for using WGMs in high-precision interferometry. We show that WGMs do not couple lateral displacements into the phase of a reflected beam to a precision of 10^{-7} rad and that WGMs are therefore not subject to the same stringent alignment requirements as previously proposed layouts using diffraction gratings.Comment: 3 Pages, 4 figure

Phase effects due to beam misalignment on diffraction gratings

All-reflective interferometer configurations have been proposed for the next generation of gravitational wave detectors, with diffractive elements replacing transmissive optics. However, an additional phase noise creates more stringent conditions for alignment stability. A framework for alignment stability with the use of diffractive elements was required using a Gaussian model. We successfully create such a framework involving modal decomposition to replicate small displacements of the beam (or grating) and show that the modal model does not contain the phase changes seen in an otherwise geometric planewave approach. The modal decomposition description is justified by verifying experimentally that the phase of a diffracted Gaussian beam is independent of the beam shape, achieved by comparing the phase change between a zero-order and first-order mode beam. To interpret our findings we employ a rigorous time-domain simulation to demonstrate that the phase changes resulting from a modal decomposition are correct, provided that the coordinate system which measures the phase is moved simultaneously with the effective beam displacement. This indeed corresponds to the phase change observed in the geometric planewave model. The change in the coordinate system does not instinctively occur within the analytical framework, and therefore requires either a manual change in the coordinate system or an addition of the geometric planewave phase factor.Comment: 14 pages, 8 figures, submitted to Optics Expres

Upper limits to surface force disturbances on LISA proof masses and the possibility of observing galactic binaries

We report on the measurement of parasitic surface force noise on a hollow replica of a LISA (Laser Interferometer Space Antenna for the observation of gravitational waves) proof mass surrounded by a faithful representation of its in flight surroundings, namely the capacitive sensor used to detect proof-mass motion. Parasitic forces are detected through the corresponding torque exerted on the proof mass and measured with a torsion pendulum in the frequency range 0.1 30 mHz. The sensor electrodes, electrode housing and associated readout electronics have the same nominal design as for the flight hardware, including 4 mm gaps around the proof mass along the sensitive laser interferometry axis. We show that the measured upper limit for surface forces would allow detection of a number of galactic binaries signals with signal to noise ratio up to approximately 40 for 1 year integration. We also discuss how the flight test under development, LISA Pathfinder, will substantially improve this limit, approaching the performance required for LISA.Comment: 3 Figures. Submitted to Physical Review Letter

Lower urinary tract symptoms and benign prostatic hyperplasia and their impact on quality of life

LUTS is an acronym that refers to symptoms affecting the lower urinary tract, which are very common in elderly subjects (between 60 and 70%), and often associated with, but not always caused by, benign prostatic hypertrophy (BPH). BPH is a chronic condition characterized by an increase in the number of cells, particularly in the transition area of the prostate. BPH involves a compression of the surrounding tissues, consequently obstructing vescical voiding. Nycturia and urgency represent the most prevalent symptoms and those with the greatest impact on quality of life measured as urinary-specific health-related quality. The prevalence of BPH is directly proportional to age; therefore, the absolute number of subjects affected is growing throughout the world. BPH is one of the most common medical conditions affecting those over 50. The overall cost for the diagnosis and treatment of BPH-related LUTS, in the US, has been estimated at approximately 1.1 billion US$/year, compared to total annual expenditure for urological conditions of some 9 billion and this cost continues to increase. The quick prostate test, which was developed by the Italian Urology Society (SIU), is an easy to use instrument that can be utilized in first-level screening for evaluation of the male population with LUTS. This test can be used both in patients not on pharmacological treatment and as a therapy-monitoring instrument. A positive response to one of the questions is sufficient for requesting a more in-depth investigation, which may provide indications on the therapeutic strategy to be taken

Thermal noise limit in the Virgo mirror suspension

Abstract The expected current limit to the Virgo sensitivity is presented. New materials to realize a low thermal noise suspension for the Virgo optics are investigated. A promising fused silica suspension for the Virgo mirrors is presented

Higher order Laguerre-Gauss mode degeneracy in realistic, high finesse cavities

Higher order Laguerre-Gauss (LG) beams have been proposed for use in future gravitational wave detectors, such as upgrades to the Advanced LIGO detectors and the Einstein Telescope, for their potential to reduce the effects of the thermal noise of the test masses. This paper details the theoretical analysis and simulation work carried out to investigate the behaviour of LG beams in realistic optical setups, in particular the coupling between different LG modes in a linear cavity. We present a new analytical approximation to compute the coupling between modes, using Zernike polynomials to describe mirror surface distortions. We apply this method in a study of the behaviour of the LG33 mode within realistic arm cavities, using measured mirror surface maps from the Advanced LIGO project. We show mode distortions that can be expected to arise due to the degeneracy of higher order spatial modes within such cavities and relate this to the theoretical analysis. Finally we identify the mirror distortions which cause significant coupling from the LG33 mode into other order 9 modes and derive requirements for the mirror surfaces.Comment: 12 pages Submitted to PRD 19/07/201

Realistic polarizing Sagnac topology with DC readout for the Einstein Telescope

The Einstein Telescope (ET) is a proposed future gravitational wave detector. Its design is original, using a triangular orientation of three detectors and a xylophone configuration, splitting each detector into one high-frequency and one low-frequency system. In other aspects the current design retains the dual-recycled Michelson interferometer typical of current detectors, such as Advanced LIGO. In this paper, we investigate the feasibility of replacing the low-frequency part of the ET detectors with a Sagnac interferometer. We show that a Sagnac interferometer, using realistic optical parameters based on the ET design, could provide a similar level of radiation pressure noise suppression without the need for a signal recycling mirror and the extensive filter cavities. We consider the practical issues of a realistic, power-recycled Sagnac, using linear arm cavities and polarizing optics. In particular, we investigate the effects of nonperfect polarizing optics and propose a new method for the generation of a local oscillator field similar to the DC readout scheme of current detectors.Comment: 15 pages, 15 figure

Validations of new cut-offs for surgical drains management and use of computerized tomography scan after pancreatoduodenectomy: The DALCUT trial

BACKGROUND Postoperative pancreatic fistula (POPF) is the most fearful complication after pancreatic surgery and can lead to severe postoperative complications such as surgical site infections, sepsis and bleeding. A previous study which identified cut-offs of drains amylase levels (DALs) determined on postoperative day (POD) 1 and POD3, was able to significantly predict POPF, abdominal collections and biliary fistulas, when related to specific findings detected at the abdominal computerized tomography (CT) scan routinely performed on POD3. AIM To validate the cut-offs of DALs in POD1 and POD3, established during the previous study, to assess the risk of clinically relevant POPF and confirm the usefulness of abdominal CT scan on POD3 in patients at increased risk of abdominal collection. METHODS The DALCUT trial is an interventional prospective study. All patients who will undergo pancreatoduodenectomy (PD) for periampullary neoplasms will be considered eligible. All patients will receive clinical staging and, if eligible for surgery, will undergo routine preoperative evaluation. After the PD, daily DALs will be evaluated from POD1. Drains removal and possible requirement of abdominal CT scans in POD3 will be managed on the basis of the outcome of DALs in the first three postoperative days. RESULTS This prospective study could validate the role of DALs in the management of surgical drains and in assessing the risk or relevant complications after PD. Drains could be removed in POD3 in case of POD1 DALs < 666 U/L and POD3 DALs < 207 U/L. In case of POD3 DALs & GE; 252, abdominal CT scan will be performed in POD3 to identify abdominal collections & GE; 5 cm. In this latter category of patients, drains could be maintained beyond POD3. CONCLUSION The results of this trial will contribute to a better knowledge of POPF and management of surgical drains

Utility of preoperative systemic inflammatory biomarkers in predicting postoperative complications after pancreaticoduodenectomy: Literature review and single center experience

BACKGROUNDThe role of preoperative inflammatory biomarkers (PIBs) in predicting postoperative morbidity has been assessed in colorectal and otorhinolaryngeal surgery. However, data regarding the role that preoperative inflammatory biomarkers have on morbidity after pancreaticoduodenectomiy (PD) are less consistent.AIMTo assess the utility of PIBs in predicting postoperative complications after pancreaticoduodenectomy.METHODSA database of 317 consecutive pancreaticoduodenectomies performed from April 2003 to November 2018 has been retrospectively analyzed. Data regarding preoperative neutrophil-to-lymphocyte ratio (NLR), derived NLR and C-reactive protein (CRP), and postoperative complications of 238 cases have been evaluated. Exclusion criteria were: age < 18-years-old, previous neoadjuvant treatment, absence of data about PIBs, concomitant hematological disorders, and presence of active infections at the moment of the surgery. PIBs were compared using Mann-Whitney's test and receiver operating characteristic (ROC) analysis was performed to define the cutoffs. The positive predictive value (PPV) was computed to evaluate the probability to develop complication. P-values < 0.05 were considered statistically significant.RESULTSAccording to the literature findings, only four papers have been published reporting the relation between the inflammatory biomarkers and PD postoperative morbidity. A combination of preoperative and postoperative inflammatory biomarkers in predicting complications after PD and the utility of preoperative NLR in the development of postoperative pancreatic fistula (POPF) have been reported. The combination of PIBs and postoperative day-1 drains amylase has been reported to predict the incidence of POPF. According to our results, CRP values were significantly different between patients who had/did not have postoperative complications and abdominal collections (P < 0.05). Notably, patients with preoperative CRP > 8.81 mg/dL were at higher risk of both overall complications and abdominal collections (respectively P = 0.0037, PPV = 0.95, negative predictive value [NPV] = 0.27 and P = 0.016, PPV = 0.59, NPV = 0.68). Preoperative derived neutrophil-to-lymphocyte ratio (dNLR) (cut off > 1.47) was also a predictor of abdominal collection (P = 0.021, PPV = 0.48, NPV = 0.71). Combining CRP and dNLR, PPV increased to 0.67. NLR (cut off > 1.65) was significantly associated with postoperative hemorrhage (P = 0.016, PPV = 0.17, NPV = 0.98).CONCLUSIONPIBs may predict complications after PD. During postoperative care, PIB levels could influence decisions regarding the timing of drains removal and the selection of patients who might benefit from second level diagnostic exams

Prospects for detecting gravitational waves at 5 Hz with ground-based detectors

We propose an upgrade to Advanced LIGO (aLIGO), named LIGO-LF, that focuses on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore the upgrade's astrophysical applications. We present a comprehensive study of the detector's technical noises and show that with technologies currently under development, such as interferometrically sensed seismometers and balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by quantum and thermal noises down to 5 Hz. These technologies are also directly applicable to the future generation of detectors. We go on to consider this upgrade's implications for the astrophysical output of an aLIGO-like detector. A single LIGO-LF can detect mergers of stellar-mass black holes (BHs) out to a redshift of z~6 and would be sensitive to intermediate-mass black holes up to 2000 M_\odot. The detection rate of merging BHs will increase by a factor of 18 compared to aLIGO. Additionally, for a given source the chirp mass and total mass can be constrained 2 times better than aLIGO and the effective spin 3-5 times better than aLIGO. Furthermore, LIGO-LF enables the localization of coalescing binary neutron stars with an uncertainty solid angle 10 times smaller than that of aLIGO at 30 Hz, and 4 times smaller when the entire signal is used. LIGO-LF also significantly enhances the probability of detecting other astrophysical phenomena including the tidal excitation of neutron star r-modes and the gravitational memory effects.Comment: 5 pages, 6 figures, published in PR