Cholesterol gallstone induction in hamsters reflects strain differences in plasma lipoproteins and bile acid profiles

Because different strains of hamsters vary in their susceptibility to gallstones, the relationship between plasma lipoproteins, hepatic cholesterol, bile lipids and bile acid profile was examined during gallstone induction in strains of male Syrian hamsters from Charles River Lakeview (CHR), Biobreeder F₁B (BIO) and Harlan Sprague-Dawley (HAR). Gallstones were induced by feeding a purified diet containing 0.4 or 0.8% cholesterol for 5 wk. Basal plasma total cholesterol was similar, but the hypercholesterolemia induced by dietary challenge was significantly lower in CHR than in HAR and BIO hamsters. Cholesterol-fed CHR hamsters transported cholesterol mainly in HDL (47%), whereas VLDL-C+IDL-C predominated in BIO and HAR hamsters, and their HDL transported only 28 and 38%, respectively. HAR hamsters accumulated the most hepatic cholesterol, revealed the highest cholate/cheno ratio, the lowest glycine/taurine ratio and hydrophobicity index. HAR also developed the fewest cholesterol gallstones (23%), while 64% of CHR and 58% of BIO hamsters had cholesterol gallstones and 34% of BIO hamsters developed pigment stones. Doubling dietary cholesterol from 0.4 to 0.8% doubled the incidence of cholesterol gallstones but exerted minimal impact on other parameters compared to strain differences. Thus, different strains of hamsters vary considerably with respect to biliary cholesterol, bile acid profile and formation of cholesterol gallstones associated with differences in plasma lipoprotein profiles.     

Evaluation of Color-Difference Equations: A New Approach*

Very many tests of color-difference formulas have been made and they have been applied generally to a broad range of samples. These tests have failed to lead to unequivocal conclusions regarding the optimum color-difference formula. This will always remain the case if the difference between formulas is no larger than the uncertainty of the visual observations. We have approached the problem of the evaluation of various color-difference equations from a different point of view. We have directed our attention to specific regions of color space, in which there are substantial anomalies in the differences predicted by several different formulas, to seek an answer to the question whether one or another of these is correct for a given individual.     

Advantages of using a node-oriented sparse-matrix solver in nuclear plant dynamic analyses

Nuclear plant dynamic analyses are commonly carried out by directly integrating the equations of motion of the model, or by using the free vibration characteristics with methods based on modal decomposition. In both approaches a large system of linear equations with little or no change in the coefficient matrix has to be solved repeatedly, either in the eigensolver or in the time integrator. The efficiency of the linear equation solver determines, to a large extent, the cost of the numerical production.The present linear equation solver has been designed to meet a number of objectives. The system matrices are assembled in terms of node-oriented submatrices instead of individual coefficients. Nodal quantities considered are not restricted to displacements. The Gauss elimination scheme is geared to sparseness rather than bandedness of the coefficient matrix. This eliminates trivial arithmetic and storage of zeroes. Matrix decomposition, and forward and backward substitutions, are separated. Thus, in an eigensolution iteration, or in a time integration, a sequence of right-hand-sides may be operated on with the coefficient matrix decomposed only once. Prescribed degrees of freedom are retained in the system of equations. Oblique excitations are treated directly through individual coordinate reference systems. Support forces are computed directly by multiplication of the unmodified coefficient matrix with the solution vector. Accuracy checks are conducted via comparison of total potential and kinetic energies.Application of the solution algorithm to a typical nuclear plant computer model is compared to other storage and solution schemes. The operation count of the present scheme indicates its performance advantage.     

Instantiability of RSA-OAEP Under Chosen-Plaintext Attack

We show that the widely deployed RSA-OAEP encryption scheme of Bellare and Rogaway (Eurocrypt 1994), which combines RSA with two rounds of an underlying Feistel network whose hash ( i.e., round) functions are modeled as random oracles, meets indistinguishability under chosen-plaintext attack (IND-CPA) in the standard model based on simple, non-interactive, and non-interdependent assumptions on RSA and the hash functions. To prove this, we first give a result on a more general notion called “padding-based” encryption, saying that such a scheme is IND-CPA if (1) its underlying padding transform satisfies a “fooling" condition against small-range distinguishers on a class of high-entropy input distributions, and (2) its trapdoor permutation is sufficiently lossy as defined by Peikert and Waters (STOC 2008). We then show that the first round of OAEP satisfies condition (1) if its hash function is t-wise independent for t roughly proportional to the allowed message length. We clarify that this result requires the hash function to be keyed, and for its key to be included in the public key of RSA-OAEP. We also show that RSA satisfies condition (2) under the \(\Phi \)-Hiding Assumption of Cachin et al. (Eurocrypt 1999). This is the first positive result about the instantiability of RSA-OAEP. In particular, it increases confidence that chosen-plaintext attacks are unlikely to be found against the scheme. In contrast, RSA-OAEP’s predecessor in PKCS #1 v1.5 was shown to be vulnerable to such attacks by Coron et al. (Eurocrypt 2000).