6,401 research outputs found

    Federal Reserve Information During the Great Moderation

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    Using data from the period 1970-1991, Romer and Romer (2000) showed that Federal Reserve forecasts of inflation and output were superior to those provided by commercial forecasters. In this paper, we show that this superior forecasting performance deteriorated after 1991. Over the decade 1992-2001, the superior forecast accuracy of the Fed held only over a very short time horizon and was limited to its forecasts of inflation. In addition, the performance of both the Fed and the commercial forecasters in predicting inflation and output, relative to that of "naive" benchmark models, dropped remarkably during this period.

    Efficient generic calibration method for general cameras with single centre of projection

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    Generic camera calibration is a non-parametric calibration technique that is applicable to any type of vision sensor. However, the standard generic calibration method was developed with the goal of generality and it is therefore sub-optimal for the common case of cameras with a single centre of projection (e.g. pinhole, fisheye, hyperboloidal catadioptric). This paper proposes novel improvements to the standard generic calibration method for central cameras that reduce its complexity, and improve its accuracy and robustness. Improvements are achieved by taking advantage of the geometric constraints resulting from a single centre of projection. Input data for the algorithm is acquired using active grids, the performance of which is characterised. A new linear estimation stage to the generic algorithm is proposed incorporating classical pinhole calibration techniques, and it is shown to be significantly more accurate than the linear estimation stage of the standard method. A linear method for pose estimation is also proposed and evaluated against the existing polynomial method. Distortion correction and motion reconstruction experiments are conducted with real data for a hyperboloidal catadioptric sensor for both the standard and proposed methods. Results show the accuracy and robustness of the proposed method to be superior to those of the standard method

    Towards dynamic camera calibration for constrained flexible mirror imaging

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    Flexible mirror imaging systems consisting of a perspective camera viewing a scene reflected in a flexible mirror can provide direct control over image field-of-view and resolution. However, calibration of such systems is difficult due to the vast range of possible mirror shapes and the flexible nature of the system. This paper proposes the fundamentals of a dynamic calibration approach for flexible mirror imaging systems by examining the constrained case of single dimensional flexing. The calibration process consists of an initial primary calibration stage followed by in-service dynamic calibration. Dynamic calibration uses a linear approximation to initialise a non-linear minimisation step, the result of which is the estimate of the mirror surface shape. The method is easier to implement than existing calibration methods for flexible mirror imagers, requiring only two images of a calibration grid for each dynamic calibration update. Experimental results with both simulated and real data are presented that demonstrate the capabilities of the proposed approach

    The End of the Home Affordable Modification Program and the Start of a New Problem

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    The mortgage crisis hit the United States hard, leaving millions of homeowners facing hardship and foreclosure. One of many programs enacted during the mortgage crisis was the Home Affordable Modification Program (HAMP). The Obama Administration set out to assist three to four million struggling homeowners in modifying their mortgages and avoiding foreclosure. This note examines HAMP, focusing on the years of litigation that shaped HAMP, giving life to a program that was built on a foundation ready to crack. HAMP provided homeowners with modified mortgage payments, typically beginning with a trial period plan. Once completed, homeowners were routinely denied, resulting in a vast number of lawsuits filling the courts with claims ranging from contractual to constitutional. Borrowers that did receive permanent modification often re-defaulted, placing them in the same position they were prior to the modification. This note proposes a solution founded in five core principles: efficiency, affordability, accessibility, accountability, and enforceability. It further recommends utilizing the remaining funds of the since expired HAMP to revamp the program, focusing on each principle both individually and collectively, to ultimately assist the homeowners that are still rearing from the mortgage crisis

    Searching for Galactic White Dwarf Binaries in Mock LISA Data using an F-Statistic Template Bank

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    We describe an F-statistic search for continuous gravitational waves from galactic white-dwarf binaries in simulated LISA Data. Our search method employs a hierarchical template-grid based exploration of the parameter space. In the first stage, candidate sources are identified in searches using different simulated laser signal combinations (known as TDI variables). Since each source generates a primary maximum near its true "Doppler parameters" (intrinsic frequency and sky position) as well as numerous secondary maxima of the F-statistic in Doppler parameter space, a search for multiple sources needs to distinguish between true signals and secondary maxima associated with other, "louder" signals. Our method does this by applying a coincidence test to reject candidates which are not found at nearby parameter space positions in searches using each of the three TDI variables. For signals surviving the coincidence test, we perform a fully coherent search over a refined parameter grid to provide an accurate parameter estimation for the final candidates. Suitably tuned, the pipeline is able to extract 1989 true signals with only 5 false alarms. The use of the rigid adiabatic approximation allows recovery of signal parameters with errors comparable to statistical expectations, although there is still some systematic excess with respect to statistical errors expected from Gaussian noise. An experimental iterative pipeline with seven rounds of signal subtraction and re-analysis of the residuals allows us to increase the number of signals recovered to a total of 3419 with 29 false alarms.Comment: 29 pages, 11 figures; submitted to Classical and Quantum Gravit

    A survey of Chronic Pneumonia and Polyarthritis Syndrome (CPPS)- associated Mycoplasma bovis in western Canadian feedlots

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    Mycoplasma bovis is generally considered the causative pathogen associated with Chronic Pneumonia and Polyarthritis Syndrome (CPPS) in feedlot cattle. However, M. bovis virulence may vary between strains as it is also isolated from asympytomatic cattle. The following study aims to determine the prevalence of M. bovis in the respiratory tract of western Canadian cattle using two sampling methods and at two time points following feedlot entry. Three study groups were sampled. In the first group nasal swabs (NS) and bronchoalveolar lavages (BAL) were taken from 36 clincally healthy cattle at the University of Saskatchewan feedlot at both 14 and 90 days on feed (DOF). In a second experiment, NS were taken from 56 animals upon arrival at a commercial feedlot and one week to three months later upon treatment for respiratory disease. Lung and joint tissue swabs were collected at necropsy from a third group of 19 animals with CPPS clinical pathology originating in 10 different western Canadian feedlots. All samples were selectively cultured for Mycoplasma spp. DNA was extracted from isolated putative Mycoplasma colonies and amplified with universal 16S rRNA gene primers for identification. Amplified Fragment Length Polymorphism (AFLP) was used to genetically differentiate M. bovis positive isolates. More M. bovis was isolated from NS than BAL and M. bovis prevalence increased with DOF in the feedlot in both the University of Saskatchewan and commercial feedlot trials. Three genetically distinct clusters (A, B, and C) were isolated from the necropsy group. Two of these clusters were primarily associated with isolates collected from feedlot cattle and one strain was exclusively found in CPPS-associated mortalities. No significance difference in the prevalence of M. bovis strains was observed between different days on feed or sampling methods. It was concluded that either the difference in disease state is a host dependent outcome, due to a multi-factorial disease complex, or the AFLP assay was not sensitive enough to differentiate strains based on virulence

    Application of the Nicoya OpenSPR to Studies of Biomolecular Binding: A Review of the Literature from 2016 to 2022

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    The Nicoya OpenSPR is a benchtop surface plasmon resonance (SPR) instrument. As with other optical biosensor instruments, it is suitable for the label-free interaction analysis of a diverse set of biomolecules, including proteins, peptides, antibodies, nucleic acids, lipids, viruses, and hormones/cytokines. Supported assays include affinity/kinetics characterization, concentration analysis, yes/no assessment of binding, competition studies, and epitope mapping. OpenSPR exploits localized SPR detection in a benchtop platform and can be connected with an autosampler (XT) to perform automated analysis over an extended time period. In this review article, we provide a comprehensive survey of the 200 peer-reviewed papers published between 2016 and 2022 that use the OpenSPR platform. We highlight the range of biomolecular analytes and interactions that have been investigated using the platform, provide an overview on the most common applications for the instrument, and point out some representative research that highlights the flexibility and utility of the instrument

    Republicanism in Georgia: A Contemporary Perspective

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    Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

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    As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates (M˙out\dot{M}_{out}/M˙acc\dot{M}_{acc}). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of \sim 20^{\circ}. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain (M˙out\dot{M}_{out}/M˙acc\dot{M}_{acc}). The outflow is spatially resolved in the [SII]λλ6716,6731[SII]\lambda \lambda 6716,6731 lines and is detected out to \sim 1\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log(M˙acc\dot{M}_{acc}) [Msun_{sun}/yr]= -10.6 ±\pm 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow M˙out\dot{M}_{out} was derived for a range of values of Av_{v}, up to a value of Av_{v} = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow (M˙out\dot{M}_{out}) was estimated in the range -11.7 to -11.1 for both jets combined. Thus M˙out\dot{M}_{out}/M˙acc\dot{M}_{acc} [\Msun/yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the Hα\alpha line show that the bulk of the H I emission comes from the accretion flow.Comment: accepted by Astronomy & Astrophysic
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