Miracle-dz/UniFAR-FTUs huggingface dataset:
Stability of Similarity Solutions for a Gravitationally Contracting Isothermal Sphere: Convergence to the Larson-Penston Solution

We investigated the stability of similarity solutions for a gravitationally contracting isothermal sphere by means of a normal mode analysis. We found that a normal mode grows in proportion to (t0 - t)-σ, where t denotes the time. The symbol, t0, denotes an epoch at which the central density increases infinitely [ρ ∝ (t0 - t)-2]. The Hunter-b and -d solutions are very unstable against spherical perturbations; the growth rates of the unstable perturbations are as large as σ = 56.2 and 6.48 × 103 for the Hunter-b and -d solutions, respectively. The Hunter solutions are unlikely to be realized in astrophysical situations and even in numerical simulations. The Larson-Penston solution is less unstable. Even if an unstable spherical perturbation exists, the growth rate should be lower than σ ≤ 1. We have found an unstable mode in which the angular velocity increases as Ω ∝ (t0 - t)-4/3. Since this mode grows slowly, the Larson-Penston solution will be realized approximately when the initial rotation is very small.
The x-ray camera of the EXIST/SXI telescope

The Energetic X-ray Imaging Survey Telescope (EXIST) mission, submitted to the Decadal Survey, is a multiwavelength observatory mainly devoted to the study of Super Massive Black Holes, Gamma Ray Bursts and other transient sources. The set of instruments foreseen for EXIST includes a soft x-ray telescope (SXI), proposed as a contribution of the Italian Space Agency (ASI). We present the baseline design of the X-Ray camera for SXI telescope, that we have finalized under ASI contract. The camera is based on a focal plane detector consisting of a 450 μm thick silicon pixel sensor sensitive, with high QE, in the full SXI range (0.1-10 KeV), and capable of high energy resolution when operated in photon counting mode (E/dE ~ 47 at 6 keV), frame rate ~ 100-200 frames/s (enabling timing in the ms range), and spatial resolution matching the optical characteristics of the mirror module. We provide an overview of the mechanical, thermal and electrical concept of the camera.
Model choice and squared prediction errors in PLS regression

Squared prediction errors (SPE) in ${\bf X}$ are discussed in relation to the conventional PLSR versus bidiagonalization model and algorithm issue concerning residual and prediction consistency, with focus on process monitoring and fault detection. Our analysis leads to the conclusion that conventional PLSR based on the NIPALS algorithm is ambiguous in SPE values caused by process faults. The basic reason for this is that the sample residuals are not found as projections onto the orthogonal complement of the space where the scores and regression solution are located, and where also the statistical ${\it T}^{\rm 2}$ limit is defined. The alternative non‐orthogonalized PLSR and bidiagonalization (Bidiag2) algorithms, as well as a simple re‐formulation of the NIPALS algorithm (RE‐PLSR), give unambiguous SPE values, and the last two of these also retain orthogonal score vectors. While prediction results from all of these methods in theory are identical, our conclusion is that methods where the ${\it T}^{\rm 2}$ and SPE values for process faults are uncorrelated should be preferred. Tests with added ${\bf y}$ errors on real data do not indicate that this conclusion should be altered because of such errors. Copyright © 2011 John Wiley & Sons, Ltd.
Fast threshold selection algorithm for segmentation of synthetic aperture radar images

Automatic detection of disjoint regions in synthetic aperture radar (SAR) images for applications requiring localisation and identification of objects is complicated by the nature of the speckle. A multi-level ratio of exponential weighted averages (MROEWA) together with a fast algorithm for optimal threshold selection is proposed for SAR segmentation. A non-parametric and unsupervised principle using the grey level histogram is utilised for producing the regions that are homogenous. An optimal threshold is automatically selected by maximising the separability of the classes in grey level by incorporating a simple search strategy. Experimental results on both synthetic and real images verify the effectiveness of the proposed method. It is validated that the proposed method outperforms greatly by reducing the number of arithmetic operations required for computing the optimal threshold.
Properties of high birefringence chalcogenide glass holey fibre for mid-infrared transparency

At present, it is desirable to find a preferable medium for mid-infrared transparency. In this paper, a kind of birefringence holey fibre (HF) is proposed. Its background is the gallium lanthanum chalcogenide glass (GLS) which remains highly transparent from 0.5 to 10 µm, has high refractive index n and high nonlinear refractive index n2. In the HF, high birefringence, high nonlinear coefficient and low confinement loss are simultaneously achieved in the wavelength region from visible light to mid-infrared. Meanwhile the waveguide dispersion can be adjusted flexibly. The birefringence comes up to 0.088, and at 1.55 µm the nonlinear coefficient runs up to 3.80 m − 1 W − 1.
Testing Against Ordered Alternatives for Censored Survival Data

In animal carcinogenesis experiments or comparative clinical trials where the r groups correspond to increasing dosages of an agent or an increasing number of additional modalities and the primary outcome is time to a certain event (e.g., tumor occurrence, death) T, ordered alternatives of the form H1 : S1 ≤ S2 ≤ · · · ≤ Sr , where Si(t) = Pr (Ti > t) is the survival function for group are of special interest. Using the counting process formulation of the problem and generalizing earlier results, we show that the class of all two-sample weighted logrank statistics can be extended to test specifically for ordered alternatives. Ordered versions of the Gehan-Wilcoxon, unweighted logrank, and Peto–Prentice–Wilcoxon tests are investigated in detail. Asymptotic relative efficiencies under Lehmann and scale alternatives are evaluated analytically and numerically among these three tests and against Tarone's trend test (1975) for Weibull, gamma, and lognormal survival distributions. Effects of censoring and unequa.
An adaptive edge preserving variational method for color image regularization

In this paper, an adaptive edge preserving variational framework for color image regularization is proposed. Unlike previous methods that emphasize only on image regularization term or use constant image fidelity term, in this framework, the balance between image regularization term and fidelity term is elegantly reached by adaptively assigning edge regions higher fidelity weight than homogenous regions. The adaptive fidelity weight is decided by the proposed edge indicator function together with the estimated noise variance. The proposed approach achieves both good noise removal and edge preserving. Experimental results show the improved performance of our framework compared to other existing methods even in highly noised conditions.
Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives—including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)—and the CPs is usually governed by non-covalent functionalization through π–π interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of π orbitals.
The Las Campanas/AAT Rich Cluster Survey

Abstract Some unsolved cosmological questions remain in relation to the formation of structure in the universe. One way of addressing such questions is to use rich galaxy clusters as tracers of the growth of large-scale structure. To date, studies of rich clusters of galaxies have concentrated on systems generally at either high redshift or in the local universe. The properties of clusters and their constituent galaxies at these extrema are becoming well understood. In particular, it is becoming clear that rich clusters have undergone considerable evolution both dynamically and in their galaxy populations over the last 5–8 Gyr. We are undertaking a detailed study of rich clusters of galaxies in the range 0·05 ≲ z ≲ 0·15. Our results will be directly comparable to those of previous studies both at high and low redshift and, for the first time, provide continuous coverage across this important and unexplored transitory epoch in terms of galaxy evolution and structure growth.
Using the Score Test to Identify the Longitudinal Biomarker Considering Accelerate Failure Time Model with the Frailty in Survival Analysis

Quality of life (QOL) is looked upon as a multidimensional entity comprising physical, psychological, social, and medical parameters. QOL is a good prognostic factor for the cancer patients. In this article, we want to determine if QOL is a good biomarker as a surrogate to indicate the survival time of gastric cancer patients. We conducted a single institutional trial and examines QOL of gastric cancer patients receiving the different surgery. In this trial, QOL is a longitudinal measurement. The accelerated failure time model can be used to deal with survival data when the proportionality assumption fails to capture the relationship between the survival time and covariates. In this article, similar to Henderson et al. (2000, 2002), a joint likelihood function combines the likelihood functions of the longitudinal biomarkers and the survival times under the accelerated failure time assumption. We introduce a method employing a frailty model to identify longitudinal biomarkers or surrogates for a time to event outcome. We allow random effects to be present in both the longitudinal biomarker and underlying survival function. The random effects in the biomarker are introduced via an explicit term while the random effect in the underlying survival function is introduced by the inclusion of frailty into the model. We will introduce a method to identify longitudinal biomarkers or surrogates for a time to event outcome based on the accelerated failure time assumption.
Atmospheric Circulation Associated with Persistent Generalized Frosts in Central-Southern South America

Abstract This paper describes the large-scale atmospheric circulation associated with persistent generalized frosts (GFs; at least 75% of the stations report frosts) in the east-central region of Argentina known as the Wet Pampa. The GF events are grouped according to their persistence, and NCEP–NCAR reanalysis data are used to create daily composites of mass and wind field anomalies during the 1961–90 winters. The GFs are caused by an anticyclonic anomaly that enters South America, generating southerly wind anomalies and cold air advection that are strengthened by the meridional layout of a cyclonic anomaly over the South Atlantic Ocean. In the case of the more persistent events the wind anomaly grows during the previous days and becomes quasi-stationary. Also, the study identifies at 250 hPa a double train of eastward-moving Rossby waves along the subtropical and subpolar latitudes, respectively, of the Southern Hemisphere. The layout of both wave trains favors the development of an intense southerly wi.
Classes of recursively enumerable sets and their decision problems

1. Introduction. In this paper we consider classes whose elements are re-cursively enumerable sets of non-negative integers. No discussion of recur-sively enumerable sets can avoid the use of such classes, so that it seems desirable to know some of their properties. We give our attention here to the properties of complete recursive enumerability and complete recursiveness (which may be intuitively interpreted as decidability). Perhaps our most interesting result (and the one which gives this paper its name) is the fact that no nontrivial class is completely recursive. We assume familiarity with a paper of Kleene [5](2), and with ideas which are well summarized in the first sections of a paper of Post Í7].
TU-E-210A-01: Dual-Energy CT with Fast-KVp Switch

Purpose: Dual‐energy (DE) CT has received much attention in recent years. There are various approaches to the data acquisition, differing in terms of the simultaneity, geometric alignment, data collection efficiency and completeness, and flexibility. We present a fast‐kVp switching (FKS) method in combination with advanced imagegeneration process, and demonstrate the efficacy of our approach with phantom and clinical results. Methods and Materials: In FKS, the input to the x‐ray tube is rapidly changed between two kVp‐settings in adjacent views. To ensure the signal fidelity, x‐ray generator was redesigned to minimize its input impedance, new scintillating material was developed to reduce the primary speed to a small fraction of a millisecond, and the data acquisition system was designed to sample up to 7Hz frequency. To take full advantage of the co‐registered dual‐energy projections, advanced algorithms were developed to enable projection‐space pre‐processing, calibration,reconstruction, and spectral image displays. These techniques allow the production of mono‐energetic CTimages, as well as different material decomposed images.Results: Phantom experiments and computer simulations show that because of the near simultaneous data acquisition in terms of timing and orientation, mis‐registration due to patient motion is kept to a minimized. FKS also allows the projection‐space processing of the dual‐energy signals and results in a significant improvement in terms of beam‐hardening artifacts. Advanced algorithms allow superb noise suppression in the mono‐energetic images as well as material‐decomposed images. Clinical studies demonstrate the importance of beam‐hardening reduction, metal artifact reduction, and the accuracy of material decomposition. Conclusion: We present a fast‐kVp switching approach to the dual‐energy data acquisition and advanced algorithms to the dual‐energy reconstruction. Phantom and clinical experiments have demonstrated that such approach provides superior image quality and clinical utility.
VIBRATION AND WAVE LOCALIZATION IN A NEARLY PERIODIC BEADED STRING

The dynamics of an exact, linear model of a string with attached beads are examined. A study of the perfectly periodic system is performed using a transfer matrix formulation. A closed-form solution for the natural frequencies of the finite system is obtained. The relationship between natural frequencies and the passbands and stop bands of propagating waves is studied. The effect of random disorder of (a) bead spacing and (b) bead mass is examined and interesting, fundamental differences are observed. In the case of bead-spacing disorder both weak and strong localization occur, whereas bead-mass disorder only causes weak localization. Localization, the spatial confinement of vibration energy due to periodicity breaking disorder, is quantified by the localization factor. Analytical approximations of the localization factor are derived, in the limits of large and small coupling to disorder ratios. The results are verified through Monte Carlo simulations. The natural frequencies and modes of the disordered s.
Formation of Ge nanocrystals embedded in aSiO2matrix: Transmission electron microscopy, x-ray absorption, and optical studies

The structure of Ge nanocrystals embedded into a SiO 2 matrix on either Si(100) or quartz-glass substrates has been studied by transmission electron microscopy, x-ray absorption fine structure, and Raman scattering. The size of the nanocrystals (5-20 nm) is found to strongly depend on the substrate material, while their shape-either spherical nanocrystals with multiple twinning defects or faceted single crystals-depends on the location of the nanocrystals in the matrix. We found that Ge nanocrystals are predominantly formed from the amorphous Ge phase, preexisting in the samples with higher Ge concentration, the formed nanocrystals are randomly oriented and have a Ge-Ge bond length of 2.45′0.01 A, i.e., are relaxed.
Measurement of the impulse produced by a pulsed surface discharge actuator in air

The pulsed surface discharge in atmospheric pressure air generates a shock wave, thereby transferring an impulse to the surrounding gas. The aim of this work is to measure this impulse, using implementation of a plasma actuator based on linear surface discharges of length up to 10 cm, and of linear energy in a range 0.1–0.5 J cm−1. The shock wave generated by the discharge is visualized using a pulsed schlieren system and the impulse is measured with a dedicated balance. These measurements are correlated with 1D numerical simulations of pulsed energy depositions in a perfect gas. Experiments show that the discharge generates a cylindrical shock wave that travels at sonic speed after a few tens of microseconds, and produces an impulse that varies from 1 to 4 mN s m−1 and scales linearly with the linear energy density. This linearity agrees with the numerical simulations when 9.5% of the energy dissipated in the discharge is assumed to heat the gas. Overall, to produce a time-averaged force similar to the one achieved by dielectric barrier discharge (DBD) actuators, 2 to 3 times more power is required. However, surface discharge actuators do not saturate, and thus can induce time-averaged forces one or two orders of magnitude above DBD when pulsed at several hundreds of hertz.
Determination of local optical properties of the rat barrel cortex during neural activation: Monte-Carlo approach to light propagation

Spatially-spectrally-resolved reflectance measurements allow in vivo measuring the optical coefficients of absorption and scattering within the cortical tissue. This method, if applied to neural tissue during enhanced activity, could allow a straightforward monitoring of the blood oxygen saturation changes occurring in the brain cortex during hemodynamic responses. Furthermore, it may provide valuable information on possible absorption and scattering changes occurring during stimulation. The feasibility of such measurements was investigated by carrying a preliminary numerical study using a Monte-Carlo light propagation routine. Experimental parameters such as the geometry of the optical probe, baseline cortex optical coefficients retrieved from the literature and anatomical characteristics of the rat barrel cortex were used as an input for the simulations. The sensitivity of the probe to the local variations of optical coefficients was investigated with this numerical approach. Additionally, the influence of the barrel cortex dimensions and the probe positioning relatively to the activated region were studied for instrumental optimization purpose. It was found that typical variations of optical coefficients can be detected if the activated region of barrel cortex has a volume of typically 1 mm3 or larger. The decay of the probe sensitivity to changes was studied as a function of the depth of the activated region. The results showed that the best sensitivity is achieved by placing the light injection fiber of the optical probe aligned onto the center of the cylindrical barrel.
Subsampling and model selection in time series analysis

In this paper the subsampling method of Carlstein (1986) is used to estimate the risk of prediction for time series data. We extend Carlstein's result by proving strong consistency of the subsampling estimator and we propose a procedure for selecting a time series model empirically from a set of possibly nonnested and misspecified models by using estimated risk of prediction as a selection criterion. When this procedure is applied to the selection of the order of an autoregressive model, it is shown to be a consistent order selector if an appropriate subsample size is chosen. We propose a practical model selection procedure with a common subsample size chosen by Hall & Jing's (1996) procedure.
A new CT system architecture for high temporal resolution with applications to improved geometric dose efficiency and sparse sampling

A new scalable CT system architecture is introduced with the potential to achieve much higher temporal resolution than is possible with current CT designs while maintaining the flux per rotation near today’s levels. Higher effective rotation speeds can be achieved leveraging today’s x-ray tube designs and capabilities. The new CT architecture comprises the following elements: (1) decoupling of the source rotation from the detector rotation through the provision of two independent, coaxial and coplanar rotating gantries (drums); (2) observation of a source at a range of azimuthal angles with respect to a given detector cell; (3) utilization of a multiplicity of x-ray sources; (4) use of a wide-angle iso-centered detector mounted on the independent detector drum; (5) the detector drum presents a wide angular aperture allowing x-rays from the various sources to pass through, with the active detector cells occupying about 240-degrees in one configuration, and the wide aperture the complementary 120-degrees; (6) anti-scatter grids with absorbing lamellas oriented substantially parallel to the main gantry plane; (7) optional sparse view acquisition in “bunches,” a unique sparse sampling pattern potentially enabling further data acquisition speed-up for specific applications. Temporal resolution gains are achieved when multiple sources are simultaneously in view of the extended detector. Accurate data acquisition then relies on multiplexing in space, time, or spectra. Thus the use of an energy-discriminating detector, such as a photon-counting detector, and of tube pulsing will be advantageous. Volume-based scatter correction methods have the potential to apply when space multiplexing is used.
A complete digital optics applied to digital holographic microscopy: application to chromatic aberration compensation

In optics, optical elements are used to transform, to filter or to process physical wavefronts in order to magnify images, compensate for aberration or to suppress unwanted diffracted order for example. Because digital holography provides numerical wavefronts, we developed a digital optics, involving numerical elements such as numerical lenses and pinholes, to mimic numerically what is usually done physically, with the advantage to be able to define any shape for these elements and to place them everywhere without obstruction problems. We demonstrate that automatic and non-automatic procedures allow diffracted order or parasitic interferences filtering, compensation for aberration and image distortion, and control of position and magnification of reconstructed wavefront. We apply this digital optics to compensate for chromatic aberration in multi-wavelength holography in order to have perfect superposition between wavefronts reconstructed from digital hologram recorded with different wavelengths. This has a great importance for synthetic wavelength digital holography or tomographic digital holography that use multiple wavelengths.