False Signatures Research Articles

Infrared hyperspectral imaging polarimeter using birefringent prisms

A compact short-wavelength and middle-wavelength infrared hyperspectral imaging polarimeter (IHIP) is introduced. The sensor includes a pair of sapphire Wollaston prisms and several high-order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image. The IHIP operates over a ±5° field of view and implements a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. In this paper, the optical layout and operation of the IHIP sensor are presented in addition to the radiometric, spectral, and polarimetric calibration techniques used with the system. Spectral and spectropolarimetric results from the laboratory and outdoor tests with the instrument are also presented.

Diagnostic and prognostic value of alpha internexin expression in a series of 409 gliomas

The neuronal intermediate filament alpha internexin (INA) is expressed in most gliomas with 1p19q codeletion and could represent a valuable prognostic marker in clinical routine. INA expression was analysed on 409 gliomas and correlated with histology, progression free survival (PFS), overall survival (OS), genomic profile assessed by CGH-array, IDH1/ IDH2 mutation and p53 expression. INA was expressed in 59% of grade II oligodendrogliomas ( n = 73), 45% of grade III oligodendrogliomas ( n = 133), 15% of grade II oligoastrocytomas ( n = 61), 12% of grade III oligoastrocytomas ( n = 41), 23% of glioblastomas with oligodendroglial component ( n = 31), 0% of grade I astrocytomas ( n = 3), 0% of grade II astrocytomas ( n = 14), 6% of grade III astrocytomas ( n = 17) and 0% of glioblastomas ( n = 36). INA expression was detected in 85% of gliomas with complete 1p19q codeletion (‘true 1p19q signature’) ( n = 85) versus 15% of gliomas without 1p19q codeletion ( n = 245), including 14% of gliomas with variable/partial 1p19q deletion (‘false 1p19q signature’) ( n = 72) ( p < 0.0001). INA was expressed by 43% of gliomas with IDH1 mutation ( n = 197) versus 12% of gliomas without IDH1 mutation ( n = 156) ( p < 0.0001). In oligodendroglial gliomas ( n = 240), INA expression specificity for 1p19q codeletion was 80%, sensitivity 85%, positive predictive value 70%, and negative predictive value was 91%. Combining INA and p53 expressions improved INA predictive accuracy for 1p19q codeletion. In grade III gliomas, INA expression was associated with longer PFS (42.1 versus 10.2 months, p = 0.0007) and longer OS (124.6 versus 20.6 months, p = 0.0001). In conclusion, INA expression is a fast, cheap and reliable prognostic marker, and represents a surrogate marker for 1p19q complete codeletion.

Unmodified gravity

By relaxing the conventional assumption of a purely gravitational interaction between dark energy and dark matter, substantial alterations to the growth of cosmological structure can occur. In this work we focus on the homogeneous transfer of energy from a decaying form of dark energy. We present simple analytic solutions to the modified growth rates of matter fluctuations in these models, and demonstrate that neglecting physics within the dark sector may induce a significant bias in the inferred growth rate, potentially offering a false signature of modified gravity.

False EX1 signatures caused by sample carryover during HX MS analyses

Discovery of EX1 kinetics in hydrogen exchange (HX) mass spectrometry (MS) experiments is rare. Proteins follow the EX1 kinetic regime when cooperative unfolding events simultaneously expose multiple residues to solvent such that they all become deuterated together before the region is able to refold. A number of factors can contribute to what we call “false EX1” in which it appears as though EX1 occurs in a protein when it probably does not. One of the contributors to false EX1 is peptide carryover between chromatographic runs. In this work, we explore the origins of peptide carryover in HX MS, describe how carryover causes mass spectra to indicate false EX1 kinetics and then describe an optimized washing protocol that can be used to eliminate peptide carryover. A series of solvent injections was developed and found to efficiently eliminate carryover signatures such that analysis of deuterium incorporation could be reliably followed for two proteins prone to high carryover.

Absolute Probe of Surface Chirality Based on Focused Circularly Polarized Light

We present a new nonlinear optical technique to probe chirality, i.e., lack of reflection symmetry, of surfaces and thin molecular films. The technique is based on second-harmonic generation and focusing of circularly polarized light at normal incidence on the sample. Because of the high symmetry of the experimental arrangement, the technique provides an unambiguous probe of chirality in the sense that it avoids false chiral signatures arising from possible in-plane anisotropy of the sample. The technique is verified by using two Langmuir−Blodgett thin films, one chiral and anisotropic, the other achiral and anisotropic, where the latter acted as a reference. Due to the focusing condition, the technique is also naturally applicable to nonlinear chiral microscopy of surfaces and interfaces.

False signature reduction in channeled spectropolarimetry

Channeled spectropolarimetry measures the complete polarization state of light, using a single spectrum, by amplitude modulating the Stokes parameters onto spectral carrier frequencies. However, spectral features that are not band limited in the Fourier transform domain, such as narrow-band atomic absorption lines, can generate false polarimetric signatures. We present a false-signature (aliasing) reduction technique that reduces the error induced by these non-band-limited features. Additionally, the spectral resolution of the S0 Stokes parameter is improved, up to the maximum resolution offered by the spectrometer. A theoretical model for implementing the technique on a Fourier transform infrared spectrometer is presented, including an enhanced model that accounts for dichroism within the crystal. The approach is experimentally demonstrated in the middle-wavelength infrared (3-5 µm) with the use of two multiple-order yttrium vanadate retarders. Additional results demonstrating the technique for wavelengths spanning 2.5-15 µm are obtained using cadmium sulfide retarders. Reconstructions are compared to conventional channeled spectropolarimetric reconstructions from the same system.

Character Recognition Method by Time-Frequency Analyses Using Writing Pressure

With the development of information and communication technology, personal verification becomes more and more important. In the future ubiquitous society, the development of terminals handling personal information requires the personal verification technology. The signature is one of the personal verification methods; however, the number of characters is limited in the case of the signature and therefore false signature is used easily. Thus, personal identification is difficult from handwriting.This paper proposes a “haptic pen” that extracts the writing pressure, and shows a character recognition method by time-frequency analyses. Although the figures of characters written by different amanuenses are similar, the differences appear in the time-frequency domain. As a result, it is possible to use the proposed character recognition for personal identification more exactly. The experimental results showed the viability of the proposed method.

Total elimination of sampling errors in polarization imagery obtained with integrated microgrid polarimeters

Microgrid polarimeters operate by integrating a focal plane array with an array of micropolarizers. The Stokes parameters are estimated by comparing polarization measurements from pixels in a neighborhood around the point of interest. The main drawback is that the measurements used to estimate the Stokes vector are made at different locations, leading to a false polarization signature owing to instantaneous field-of-view (IFOV) errors. We demonstrate for the first time, to our knowledge, that spatially band limited polarization images can be ideally reconstructed with no IFOV error by using a linear system framework.

Evaluation of Precipitation Features in High-Frequency SSM/I Measurements Over Indian Land and Oceanic Regions

Evaluation of the Special Sensor Microwave Imager (SSM/I) precipitation features is presented from various passes over Indian oceanic and land regions under the framework of radiative transfer simulations for both emission and scattering atmospheres. There is considerable uncertainty in the interpretation of the SSM/I high-frequency scattering features for development of rainfall algorithms. Specifically large areas of very low emissivity regimes showing false rain signatures due to the presence of low brightness temperatures (TBs) that are often present in the vicinity of colder sea surface areas in the 85-GHz TB from SSM/I. In this connection, the Polarization Corrected Temperature (PCT) defined by Spencer using the 85-GHz channels, vertical (V) and horizontal (H), has been studied to delineate these surface effects. These false scattering signatures, once corrected using PCT as a suitable parameter, significantly improve the quality of the SSM/I-derived precipitation areas. These results are also confirmed with the cloud optical depth data from the Moderate Resolution Imaging Spectroradiometer sensor onboard the Aqua satellite and the standard merged rain product (geostationary infrared and Tropical Rainfall Measuring Mission (TRMM) microwave data) 3B42 from TRMM. This letter is aimed for selecting PCT as one of the suitable predictor variables for the development of operational rainfall retrieval algorithm for the Indo-French Megha-Tropiques satellite's microwave radiometer at high frequencies.

Comments on “Arc magmatism and subduction history beneath the Zagros Mountains, Iran: A new report of adakites and geodynamic consequences” by J. Omrani, P. Agard, H. Whitechurch, M. Bennoit, G. Prouteau, L. Jolivet

Based on the imprecise geochemical data for 62 samples from Qom, Anar and Baft regions in central Iranian magmatic arc Omrani et al. (Omrani, J., Agard, P., Witechurch, H., Benoit, M., Prouteau, G., Jolivet, L., 2008. Arc magmatism and subduction history beneath the Zagsros Mountains, Iran: A new report of adakites and geodynamic consequences. Lithos 106, 380–398.), suggested that all studied magmatic rocks display the geochemical affinity of subduction-related calc–alkalic rock suites. Here, we demonstrate that the incorrect altered and variable geochemical data (e.g., Al2O3, Sr, Y, Ni, Cr, SiO2, Na2O, La/Yb and Th/Ce), show that most of the samples actually display calc–alkaline, shoshonitic and calc–alkalic–adakitic affinities. Furthermore, as a result of alteration, rock samples of similar age (e.g., Qom) indicate both adakitic and non-adakitic compositional signatures, which is misleading. On the basis of more than 400 previously published geochemical analyses, we suggest that, after eliminating the false geochemical signatures, the calc–alkaline and adakitic affinities of the central Iranian magmatic arc are due to flat subduction and might be related to a second phase of Miocene- Pliocene porphyry copper mineralization, which is a considerable exploration target and thus merits further investigation.

Unpolarized calibration and nonuniformity correction for long-wave infrared microgrid imaging polarimeters

Recent developments for long-wave infrared (LWIR) imaging polarimeters include incorporating a microgrid polarizer array onto the focal plane array. Inherent advantages over other classes of polarimeters include rugged packaging, inherent alignment of the optomechanical system, and temporal synchronization that facilitates instantaneous acquisition of both thermal and polarimetric information. On the other hand, the pixel-to-pixel instantaneous field-of-view error that is inherent in the microgrid strategy leads to false polarization signatures. Because of this error, residual pixel-to-pixel variations in the gain-corrected responsivity, the noise-equivalent input, and variations in the pixel-to-pixel micropolarizer performance are extremely important. The degree of linear polarization is highly sensitive to these parameters and is consequently used as a metric to explore instrument sensitivities. We explore the unpolarized calibration issues associated with this class of LWIR polarimeters and discuss the resulting false polarization signature for thermally flat test scenes.

Reconciling the electron counterstreaming and dropout occurrence rates with the heliospheric flux budget

Counterstreaming electrons (CSEs) are treated as signatures of closed magnetic flux, i.e., loops connected to the Sun at both ends. However, CSEs at 1 AU likely fade as the apex of a closed loop passes beyond some distance R, owing to scattering of the sunward beam along its continually increasing path length. The remaining antisunward beam at 1 AU would then give a false signature of open flux. Subsequent opening of a loop at the Sun by interchange reconnection with an open field line would produce an electron dropout (ED) at 1 AU, as if two open field lines were reconnecting to completely disconnect from the Sun. Thus EDs can be signatures of interchange reconnection as well as the commonly attributed disconnection. We incorporate CSE fadeout into a model that matches time‐varying closed flux from interplanetary coronal mass ejections (ICMEs) to the solar cycle variation in heliospheric flux. Using the observed occurrence rate of CSEs at solar maximum, the model estimates R ∼ 8–10 AU. Hence we demonstrate that EDs should be much rarer than CSEs at 1 AU, as EDs can only be detected when the juncture points of reconnected field lines lie sunward of the detector, whereas CSEs continue to be detected in the legs of all loops that have expanded beyond the detector, out to R. We also demonstrate that if closed flux added to the heliosphere by ICMEs is instead balanced by disconnection elsewhere, then ED occurrence at 1 AU would still be rare, contrary to earlier expectations.

WormShield: Fast Worm Signature Generation with Distributed Fingerprint Aggregation

Fast and accurate generation of worm signatures is essential to contain zero-day worms at the Internet scale. Recent work has shown that signature generation can be automated by analyzing the repetition of worm substrings (that is, fingerprints) and their address dispersion. However, at the early stage of a worm outbreak, individual edge networks are often short of enough worm exploits for generating accurate signatures. This paper presents both theoretical and experimental results on a collaborative worm signature generation system (WormShield) that employs distributed fingerprint filtering and aggregation over multiple edge networks. By analyzing real-life Internet traces, we discovered that fingerprints in background traffic exhibit a Zipf-like distribution. Due to this property, a distributed fingerprint filtering reduces the amount of aggregation traffic significantly. WormShield monitors utilize a new distributed aggregation tree (DAT) to compute global fingerprint statistics in a scalable and load-balanced fashion. We simulated a spectrum of scanning worms including CodeRed and Slammer by using realistic Internet configurations of about 100,000 edge networks. On average, 256 collaborative monitors generate the signature of CodeRedl-v2 135 times faster than using the same number of isolated monitors. In addition to speed gains, we observed less than 100 false signatures out of 18.7-Gbyte Internet traces, yielding a very low false-positive rate. Each monitor only generates about 0.6 kilobit per second of aggregation traffic, which is 0.003 percent of the 18 megabits per second link traffic sniffed. These results demonstrate that the WormShield system offers distinct advantages in speed gains, signature accuracy, and scalability for large-scale worm containment.

Automatic removal of cosmic ray signatures in Deep Impact images

The results of recognition of cosmic ray (CR) signatures on single images made during the Deep Impact mission were analyzed for several codes written by several authors. For automatic removal of CR signatures on many images, we suggest using the code imgclean ( http://pdssbn.astro.umd.edu/volume/didoc_0001/document/calibration_software/dical_v5/) written by E. Deutsch as other codes considered do not work properly automatically with a large number of images and do not run to completion for some images; however, other codes can be better for analysis of certain specific images. Sometimes imgclean detects false CR signatures near the edge of a comet nucleus, and it often does not recognize all pixels of long CR signatures. Our code rmcr is the only code among those considered that allows one to work with raw images. For most visual images made during low solar activity at exposure time t > 4 s, the number of clusters of bright pixels on an image per second per sq. cm of CCD was about 2–4, both for dark and normal sky images. At high solar activity, it sometimes exceeded 10. The ratio of the number of CR signatures consisting of n pixels obtained at high solar activity to that at low solar activity was greater for greater n. The number of clusters detected as CR signatures on a single infrared image is by at least a factor of several greater than the actual number of CR signatures; the number of clusters based on analysis of two successive dark infrared frames is in agreement with an expected number of CR signatures. Some glitches of false CR signatures include bright pixels repeatedly present on different infrared images. Our interactive code imr allows a user to choose the regions on a considered image where glitches detected by imgclean as CR signatures are ignored. In other regions chosen by the user, the brightness of some pixels is replaced by the local median brightness if the brightness of these pixels is greater by some factor than the median brightness. The interactive code allows one to delete long CR signatures and prevents removal of false CR signatures near the edge of the nucleus of the comet. The interactive code can be applied to editing any digital images. Results obtained can be used for other missions to comets.

Point source detection and characterization for vehicle radiation portal monitors

Many international border crossings presently screen cargo for illicit nuclear material using radiation portal monitors (RPMs) that measure the gamma ray and/or neutron flux emitted by vehicles. The fact that many target sources have a point-like geometry can be exploited to detect subthreshold sources and filter out benign sources that frequently possess a distributed geometry. This report describes a two-step process, which has the potential to complement other alarm algorithms, for detecting and characterizing point sources. The first step applies a matched filter whereas step two uses a weighted nonlinear least squares method. In a base-case simulation, matched filtering detected a 250-cps source injected onto a white-noise background at a 95% detection probability and a 0.003 false alarm probability. For the same simulation, the maximum likelihood estimation technique performed well at source strengths of 250 and 400 cps. These simulations provided a best-case feasibility study for this technique, which will be extended to experimental data that possess false point-source signatures resulting from background shielding caused by vehicle design and cargo distribution

A Real-time Intrusion Prevention System for Commercial Enterprise Databases

Modern intrusion detection systems are comprised of three basically different approaches, host based, network based, and a third relatively recent addition called procedural based detection. The first two have been extremely popular in the commercial market for a number of years now because they are relatively simple to use, understand and maintain. However, they fall prey to a number of shortcomings such as scaling with increased traffic requirements, use of complex and false positive prone signature databases, and their inability to detect novel intrusive attempts. This intrusion detection systems represent a great leap forward over current security technologies by addressing these and other concerns. This paper presents an overview of our work in creating a true database intrusion detection system. Based on many years of Database Security Research, the proposed solution detects a wide range of specific and general forms of misuse, provides detailed reports, and has a low false-alarm rate. Traditional database security mechanisms are very limited in defending successful data attacks. Authorized but malicious transactions can make a database useless by impairing its integrity and availability. The proposed solution offers the ability to detect misuse and subversion through the direct monitoring of database operations inside the database host, providing an important complement to host-based and network-based surveillance. Suites of the proposed solution may be deployed throughout a network, and their alarms managed, correlated, and acted on by remote or local subscribing security services, thus helping to address issues of decentralized management.

On the Variable Nature of Galactic and Extragalactic Objects with Sources from the Faint Sky Variability Survey

The Faint Sky Variability Survey (FSVS) has cataloged approximately 23 deg in BVI filters from ∼16 to 25 mag to investigate variability in faint sources at moderate to high Galactic latitudes, encompassing a wide range of goals as is discussed in P. J. Groot et al. (2003, MNRAS, 339, 427). Multiepoch (10–30) observations were made in V spanning minutes to years. Amplitude sensitivity limits were determined from simulated variability tests to be ∼0.015–0.075 mag in V over 18–22 mag. The fraction of point sources from the survey found to be variable reaches 8% between 18 and 22.0 mag in V over both moderate and high Galactic latitudes of 30 and 90 . Overall, the dominant population of variable sources are bluer than a B V of 0.65 and have main-sequence colors, likely reflecting larger populations of RR Lyrae, SX Phe, g Doradus, and W UMa variables than expected. The population of ultracool dwarfs has been investigated using V I color selection to identify the potential for variability studies. An L2 dwarf is the coolest source thus far spectroscopically identified, with candidates roughly predicted to temperatures as cool as L8. Variability information for ultracool dwarfs is mostly lost as the cooler sources become exceedingly faint in V. Thus, variability information is found to be limited to an amplitude sensitivity of mag reaching only to DV ∼ 0.1 late M type dwarfs (M8–M9). Follow-up photometry in the I band has revealed variability in an M8–M9 and an L2 dwarf, with the M8–M9 dwarf showing a 3 hr periodicity likely attributable to rotational modulation of surface features. The population of cataclysmic variables (CVs) has been investigated using a B V, V I color and variability selection criteria to additionally search for a “missing” population of evolved, low mass transfer types as discussed in S. B. Howell, L. A. Nelson, & S. Rappaport (2001, ApJ, 550, 897). Two known CVs, GO Com and V394 Lyr, were observed in the FSVS and identified using the CV selection criteria in the survey. In conjunction with the FSVS photometry, two first possible periods are proposed for V394 Lyr of 2.2 and 5.7 hr. An estimate of the number of CVs expected has been made in comparison to the candidates found and shows an overabundance of candidates by a factor of 3–300 over the V magnitude range of the survey, making additional colors or spectroscopy necessary to identify candidates in a larger sample. An initial sample of eight candidates out of over 1000 had follow-up observations obtained and were identified to be pulsational variables (e.g., RR Lyrae, SX Phe), a W UMa binary, an M dwarf flare star, and a quasar, identifying a sample of the types of contaminating sources. As quasars overlap the color space of CVs and variability can provide limits on theoretical models for the unresolved interior processes, the population of quasars has been investigated for variability with a sample of known and newly discovered sources. The initial sample is predominately radioquiet—only one out of 27 is identified as radio-loud as determined from overlapping radio surveys—and potentially very large (∼700 to mag) given quasar space densities B ∼ 21 found in the 2dF redshift survey (S. M. Croom et al. 2001, MNRAS, 322, L29). Few quasars (∼10%) are found with intranight and day timescale variability, whereas the entire sample shows long month to year timescale variability at greater amplitudes (typically greater than 0.1 mag), not too dissimilar to that found in other studies (e.g., G. E. Romero, S. A. Cellone, & J. A. Combi 1999, AA G. Gopal-Krishna et al. 2000, MNRAS, 314, 815; M. R. S. Hawkins 2000, A&AS, 142, 465). The sample of radio-quiet, low-redshift, low-luminosity quasars classified as point sources are found to have brightness variations correlated with changes in the seeing FWHM of ∼0.03 mag arcsec , thus showing a false variability signature. Such a correlation is attributable to a detectable contribution of the host galaxy and provides a warning in studies of variability on a seemingly pointlike source at these amplitude levels. Overall, the FSVS provides a discovery survey data set with suggestions for future time-sampled, wide-field imaging surveys. In regards to other surveys, the FSVS provides a faint sample of variability to large-sky photometric surveys (e.g., SDSS) and extending brighter variability surveys (e.g., ROTSE, LONEOS, BSVS). Further detailed follow-up studies are in progress to extend the science results.

Discrimination of Signatures Using Euclid Distances (Application to Electrical Certification)

Handwriting has continued to persist as a means of communication and recording information every day. This paper describes a new discrimination of handwriting signatures with a new ball-point pen-based device. The piezoelectric element is constructed in the ball-point pen and the phase shift circuit is used for the measurement of the writing pressure. The time series data of the writing pressure is changed to the frequency spectrum using Maximum Entropy Method (MEM). MT (Mahalanobis-Taguchi) method is applied to the frequency spectrums of the handwriting signatures for the discrimination between the true signatures and the false signatures. The experimental results show the possibility of the discrimination of the signatures.

On the Security of Digital Signature Schemes Based on Error-Correcting Codes

In this paper we discuss the security of digital signature schemes based on error-correcting codes. Several attacks to the Xinmei scheme are surveyed, and some reasons given to explain why the Xinmei scheme failed, such as the linearity of the signature and the redundancy of public keys. Another weakness is found in the Alabbadi-Wicker scheme, which results in a universal forgery attack against it. This attack shows that the Alabbadi-Wicker scheme fails to implement the necessary property of a digital signature scheme: it is infeasible to find a false signature algorithm Ds from the public verification algorithm E such that E(Ds (\underline{m})) e \underline{m} for all messages \underline{m}. Further analysis shows that this new weakness also applies to the Xinmei scheme.

Voorlopige catalogus van de schilderijen van Pieter Veen

AbstractPieter Veen's name is virtually unmentioned in art-historical sources. Moreover, many of his paintings, some of them bearing false signatures, were sold under other names, which may partly account for his obscurity. Veen lived and worked in Rotterdam, where he was a dean of Saint Luke's guild in 1716, 1720, 1731 and 1736. Eighteenth-century auction catalogues list him as a pupil of Adriaen van der Werff, whose influence can certainly be seen in his work. Not, however, in his earliest extant painting, and the only one to be dated: a portrait of Geertruy van der Hey, a burgomaster's wife, done in 1686. In type, the portrait is closer to the work of Jan Verkolje, who was active in Delft. From a written source we know that Veen painted a portrait of Adriaen Boon in 1684. This justifies the cautious conclusion that he began his career as a portraitist. By far the greater part of his output consisted however of history paintings, most of them religious works. He also painted a few mythological pictures and especially allegories. An occasional link can be established with work by Adriaen van der Werff; Veen's Fall, for instance, is partly based on the latter's Adam and Eve after the Fall. Veen's style is less rigidly classicistic, though. His paintings have a narrative character. In that respect his work has more in common with the notions of classicism as expressed in Gerard Hoet's bible illustrations and Arnold Houbraken's paintings. Veen tends towards the decorative: graceful attitudes, elongated bodies and little parallel folds in garments are characteristic of his style. An eclectic painter, he was influenced by the art of both his own period and the past. Abraham Receiving the Three Angels, Susanna and the Elders and Apollo and Daphne, for instance, appear to derive from sixteenth-century exemplars. The Holy Family with Anna and Angels is actually a direct copy of a composition by Hans van Aken. The landscape in Shepherd Playing a Flute displays the influence of French classicists such as Poussin and Millet, many of whose works Veen could have seen in Rotterdam. Pieter Veen possessed only a modest talent, and there arc hardly any signs of a development in his work. Nonetheless, this forgotten Rotterdam painter deserves a place among the minor masters of the period.