On non-negligible bias of the first output byte of RC4 towards the first three bytes of the secret key

In this paper, we show that the first byte of the keystream output of RC4 has non-negligible bias towards the sum of the first three bytes of the secret key. This result is based on our observation that the index, where the first byte of the keystream output is chosen from, is approximately twice more likely to be 2 than any other value. Our technique is further used to theoretically prove Roos’s experimental observation (A class of weak keys in the RC4 stream cipher, 1995) related to weak keys.     

New mesogens with a fluoro-substituted bent core

Ferroelectric properties in liquid crystals are no longer restricted to materials with a chiral molecular structure; ferroelectricity has been observed in a smectic phase formed by bent achiral molecules. Accordingly, two homologous series possessing a central biphenyl methane core have been synthesized, the central core having two lateral fluoro substituents. Both the series have six-ring structures and exhibit smectic mesophases of high thermal stability. The flexible biphenyl methane core imparts a slight curve to the molecules, giving them a bent shape.     

Synthesis and Crystal Structure of 2-Amino-4,6,6-trimethyl-cyclohex-2-en-1,1,3,4(S)-tetracarbonitrile

Abstract  

Crystal structure analysis of the novel 2-amino-4,6,6-trimethyl-cyclohex-2-en-1,1,3,4(S)-tetracarbonitrile, obtained in 70% yield, by the Bi(OTf)₃ catalyzed reaction of acetone and malononitrile, at room temperature, is described. For the first time Bi(OTf)₃–Et₃N has been used in this inverse electron demand Diels–Alder cycloaddition reaction involving the participation of carbonitrile π-bond. The structure of the molecule was established by spectral analysis and X-ray diffraction studies. The compound crystallizes in the monoclinic space group P2₁/n with unit cell parameters: a = 8.0580 (17), b = 13.038 (3), c = 12.641 (3) ?, β = 101.883 (4)°, Z = 4. The crystal structure was solved by direct methods and refined to R = 0.0506 for 2,456 observed reflections. The cyclohexene ring of the molecule adopts a distorted sofa conformation. The molecules in the unit cell are arranged in layers. The crystal structure in stabilized by C–H⋯N and N–H⋯N interactions.     

Phase Separation of Triblock Polymers and Tritons in the Presence of Biomolecules

Surfactant?Cbiomolecule interactions have been investigated by studying the additive effect of various kinds of biomolecules such as amino acids, dipeptides, amino alcohols, sugars, hydroxy acids and dicarboxylic acids on the cloud point behavior of nonionic surfactants including triblock polymers (L64, P84) and tritons (TX100, TX114). In most cases, addition of biomolecules has been found to cause a depression in the cloud point of the triblock polymers and tritons. The presence of biomolecules in the solution of a nonionic surfactant causes drastic changes to the clouding behavior of the surfactant, especially at high biomolecule concentrations. The results reveal that both hydrophobicity and structural aspects play important roles in the observed cloud point variation of the nonionic surfactants.     

Tandem Michael addition–Fries rearrangement of sorbylanilides: a convenient one pot synthesis of novel benzo[b]azocin-6-ones

The Letter pertains to an unprecedented tandem Michael addition–Fries rearrangement of sorbyl anilides resulting in a convenient one pot synthesis of novel benzo[b]azocin-6-ones. The reaction is thought to proceed via a δ-lactam intermediate, earlier considered un-reactive for Fries rearrangement. The proposed mechanism was further supported by examining the reactions of α,β-unsaturated anilides. Their inability to undergo any transformation under similar reaction conditions, especially the Fries–Michael rearrangement, indirectly validated the mechanism.     

Results on rotation symmetric bent functions

In this paper we analyze the combinatorial properties related to the Walsh spectra of rotation symmetric Boolean functions on even number of variables. These results are then applied in studying rotation symmetric bent functions. For the first time we could present an enumeration strategy for all the 10-variable rotation symmetric bent functions.     

Magnetic behavior of Ba3Cu3Sc4O12

The chain-like system Ba(3)Cu(3)Sc(4)O(12) has potentially interesting magnetic properties due to the presence of Cu(2+) and a structure-suggested low dimensionality. We present magnetization M versus magnetic field H and temperature T, T- and H-dependent heat-capacity C(p), (45)Sc nuclear magnetic resonance (NMR), muon spin rotation (μSR), neutron diffraction measurements and electronic structure calculations for Ba(3)Cu(3)Sc(4)O(12). The onset of magnetic long-range antiferromagnetic (AF) order at T(N) ～ 16 K is consistently evidenced from the whole gamut of our data. A significant sensitivity of T(N) to the applied magnetic field H (T(N) ～ 0 K for H = 70 kOe) is also reported. Coupled with a ferromagnetic Curie-Weiss temperature (θ(CW) ～ 65 K) in the susceptibility (from a 100 to 300 K fit), it is indicative of competing ferromagnetic and antiferromagnetic interactions. These indications are corroborated by our density functional theory based electronic structure calculations, where we find the presence of significant ferromagnetic couplings between some copper ions whereas AF couplings were present between some others. Our experimental data, backed by our theoretical calculations, rule out the one-dimensional magnetic behavior suggested by the structure and the observed long-range order is due to the presence of non-negligible magnetic interactions between adjacent as well as next-nearest chains.     

Optimization of bivalent glutathione S-transferase inhibitors by combinatorial linker design

Dimeric glutathione S-transferases (GSTs) are pharmacological targets for several diseases, including cancer. Isoform specificity has been difficult to achieve due to their overlapping substrate selectivity. Here we demonstrate the utility of bivalent GST inhibitors and their optimization via combinatorial linker design. A combinatorial library with dipeptide linkers emanating symmetrically from a central scaffold (bis-3,5-aminomethyl benzoic acid, AMAB) to connect two ethacrynic acid moieties was prepared and decoded via iterative deconvolution, against the isoforms GSTA1-1 and GSTP1-1. The library yielded high affinity GSTA1-1 selective inhibitors (70-120-fold selectivity) and with stoichiometry of one inhibitor: one GSTA1-1 dimer. Saturation Transfer Difference (STD) NMR with one of these inhibitors, with linker structure (Asp-Gly-AMAB-Gly-Asp) and K(D) = 42 nM for GSTA1-1, demonstrates that the Asp-Gly linker interacts tightly with GSTA1-1, but not P1-1. H/D exchange mass spectrometry was used to map the protein binding site and indicates that peptides within the intersubunit cleft and in the substrate binding site are protected by inhibitor from solvent exchange. A model is proposed for the binding orientation of the inhibitor, which is consistent with electrostatic complementarity between the protein cleft and inhibitor linker as the source of isoform selectivity and high affinity. The results demonstrate the utility of combinatorial, or "irrational", linker design for optimizing bivalent inhibitors.     

On sorting by 3-bounded transpositions

Heath and Vergara [Sorting by short block moves, Algorithmica 28 (2000) 323-352] proved the equivalence between sorting by 3-bounded transpositions and sorting by correcting skips and correcting hops. This paper explores various algorithmic as well as combinatorial aspects of correcting skips/hops, with the aim of understanding 3-bounded transpositions better.We show that to sort any permutation via correcting hops and skips, ⌊n/2⌋ correcting skips suffice. We also present a tighter analysis of the approximation algorithm of Heath and Vergara, and a possible simplification. Along the way, we study the class H_n of those permutations of S_n which can be sorted using correcting hops alone, and characterize large subsets of this class. We obtain a combinatorial characterization of the set G_n⊆S_n of all correcting-hop-free permutations, and describe a linear-time algorithm to optimally sort such permutations. We also show how to efficiently sort a permutation with a minimum number of correcting moves.