Strong accumulators from collision-resistant hashing

Accumulator schemes were introduced in order to represent a large set of values as one short value called the accumulator. These schemes allow one to generate membership proofs, that is, short witnesses that a certain value belongs to the set. In universal accumulator schemes, efficient proofs of non-membership can also be created. Li et?al. (Proceedings of applied cryptography and network security—ACNS ’07, LNCS, vol 4521, 2007), building on the work of Camenisch and Lysyanskaya (Advances in cryptology—proceedings of Crypto ’02, LNCS, vol 2442. Springer, Berlin, pp 61–76, 2002), proposed an efficient accumulator scheme, which relies on a trusted accumulator manager. Specifically, a manager that correctly performs accumulator updates. In this work, we introduce the notion of strong universal accumulator schemes, which are similar in functionality to universal accumulator schemes, but do not assume the accumulator manager is trusted. We also formalize the security requirements for such schemes. We then give a simple construction of a strong universal accumulator scheme, which is provably secure under the assumption that collision-resistant hash functions exist. The weaker requirement on the accumulator manager comes at a price; our scheme is less efficient than known universal accumulator schemes—the size of (non)membership witnesses is logarithmic in the size of the accumulated set in contrast to constant in the scheme of Camenisch and Lysyanskaya. Finally, we show how to use strong universal accumulators to solve a problem of practical relevance, the so-called e-Invoice Factoring Problem.     

Individual Assessments for Personnel Selection: An Update on a Rarely Researched But Avidly Practiced Practice.

To keep consulting psychologists up-to-date on research relevant to practice, a review was conducted of the recent literature written about individual assessment practices. This review on articles and books that were published in the past 10 years. Trends in individual assessment practices are discussed, and theoretical support for the use of individual assessment in personnel selection is provided despite the limited empirical support. A research agenda for individual assessment practices is also proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A simple empirical method for estimating surface water vapour pressure using MODIS near-infrared channels: applications to northern Spain's Asturias region

In this article, we present a simple methodology for obtaining algorithms to estimate surface water vapour pressure (e ₀) over cloud-free land areas using Moderate Resolution Imaging Spectroradiometer (MODIS) data. The algorithm obtained in this case is adapted to the particular climatic characteristics of the Asturias region, but the methodology can easily be extrapolated and used to obtain algorithms for other regions around the world. The proposed method estimates e ₀ from a simple linear combination of the radiances of the MODIS near-infrared (NIR) channels more commonly applied to total precipitable water (W) estimations. Comparison between the e ₀ data measured at the ground-based meteorological stations in Asturias (daily data from 2004) versus the values predicted using the proposed algorithm gives R ² = 0.76 and residual standard error (RSE) = 2.07 hPa (16%). The algorithm was tested using the data from 2008 obtained in Asturias and in two sites outside of Asturias with similar latitudes and radiosonde observations (La Coruña and Santander). The resulting validation demonstrates that the algorithm gives good results in Asturias (root-mean-square deviation (RMSD) = 2.50 hPa (19%) and bias = 1.26 hPa, with R ² = 0.65) and when La Coruña is included (R ² = 0.61), but that its validity is decreased when Santander is also included (R ² = 0.56).

The possibility of obtaining e ₀ from three global MODIS algorithms for W retrieval was also tested and compared to our algorithm. The results show that our algorithm gives better results than the International MODIS/Atmospheric InfraRed Sounder Processing Package (IMAPP) Water Vapour Near-Infrared (WVNIR) product and the Sobrino algorithm. The MODIS Total Precipitable Water (MOD05) product is worse than that obtained with our algorithm in Asturias (R ² = 0.61 vs. R ² = 0.65), but the two values are similar if the stations in La Coruña (R ² = 0.60) and Santander (R ² = 0.56) are included in the comparison. The dominant advantage of the novel algorithm proposed in this study is that it is simpler and can be produced quickly in real time.     

Specific detection and quantification of Aspergillus flavus and Aspergillus parasiticus in wheat flour by SYBR® Green quantitative PCR

Aflatoxins are important mycotoxins that represent a serious risk for human and animal health. These mycotoxins are mainly produced by Aspergillus flavus and Aspergillus parasiticus, two closely related species with different array of aflatoxins. In this work, two specific quantitative PCR (qPCR) assays were developed to detect and quantify both species in wheat flour using primers based on the multicopy ITS2 rDNA target sequence. The species specificity of the assays was tested in a wide range of strains of these species and others colonizing the same commodities. The sensitivity of the assay was estimated in 2.5 pg/reaction in both species. Discrimination capacity for detection and relative quantification of A. flavus and A. parasiticus DNA were analyzed using samples with DNA mixtures containing also other fungal species at different ratios. Both qPCR assays could detect spore concentrations equal or higher than 10⁶ spores/g in flour samples without prior incubation. These assays are valuable tools to improve diagnosis at an early stage and in all critical control points of food chain integrated in HACCP strategies.     

Indicating Surface of Natural Reflectance

Abstract

To study the behaviour of anisotropic media in reflection when illuminated by natural light, an ‘indicating surface of natural reflectance’ is defined. The use of such a surface is proposed, and its statistical parameters are given. The expressions that relate these parameters to the refractive indices of the incident medium and to the principal indices of the medium under observation have been deduced for the case of uniaxial media. Those corresponding to uniaxial transparent substances are presented here.     

Revision of ochratoxin a production capacity by the main species of Aspergillus section Circumdati. Aspergillus steynii revealed as the main risk of OTA contamination

Ochratoxin A (OTA) is a highly toxigenic mycotoxin commonly present in a number of diverse agroproducts. Aspergillus Section Circumdati includes some of the most important OTA-producing species: Aspergillus ochraceus, Aspergillus elegans and the recently described Aspergillus steynii and Aspergillus westerdijkiae. In this work, OTA production by several strains of these four species from diverse origins and food matrices was examined. Identification of all the strains was carried out by specific PCR assays. The strains were cultivated in CYA solid medium and OTA was measured by HLPC. This study demonstrated for the first time the high capacity of A. steynii strains to produce OTA at higher levels than A. westerdijkiae,A. ochraceus and A. elegans strains showed low levels or no production at all. In conclusion, the results of this study suggest that the occurrence of A. steynii and A. westerdijkiae might represent the major potential risk for OTA contamination due to their high production and the diversity of commodities that these species may contaminate.     

End-to-end security in the presence of intelligent data adapting proxies: the case of authenticating transcoded streaming media

We consider the problem of maintaining end-to-end security in the presence of intelligent proxies that may adaptively modify data being transmitted across a network. The video coding community considers this problem in the context of transcoding media streams, but their approaches either fail to address authentication or fail to provide meaningful security guarantees. We present two provably-secure schemes, LISSA and TRESSA, that allow an intelligent network intermediary to intercept a stream signed by a content provider, and adapt it dynamically, while preserving the ultimate receiver's ability to securely verify the content provider's signature (and, hence, authenticity and integrity of the data received). Our schemes allow the intermediary to selectively remove portions of the stream and, thus, permit common media transcoding techniques such as scalable compression and multiple file switching. Moreover, a content provider only has to encode and sign its entire data stream once, as opposed to nondynamically encoding and signing different versions for each anticipated combination of device, network configuration, and channel condition. Our implementation results demonstrate efficiency.     

Immunity and malnutrition in alcoholic liver diseases

Assessment of immunity was performed in 150 patients with alcoholic liver disease (15 steatosis, 30 hepatitis and 105 cirrhosis: 34 in grade A, 34 in grade B and 37 in grade C, according to Child-Pugh classification). This assessment was based on the total lymphocyte count and a delayed hypersensitivity skin multiple test. Likewise, nutritional status of patients was studied using anthropometric and biochemical parameters (triceps skinfold thickness, arm muscle circumference and serum albumin). The association between alcoholic liver disease, malnutrition and immunity was analyzed. The results show that lymphopenia and disorders in cell-mediate immunity were more common in those patients with cirrhosis, increasing the number of anergic patients while the degree of hepatocellular insufficiency worsens (8.8% in grade A, 11.8% in grade B and 32.4% in grade C). Although there where significantly more alterations of delayed cutaneous hypersensitivity in cirrhotics with malnutrition (hypoergy: 55.2% and anergy: 37.9%) than in those well nourished (hypoergy: 23.7% and anergy: 10.5%, p < 0.01), lymphopenia didn't show differences between these groups. We think that immunity mus'nt be considered a parameter in nutritional assessment.