On the direct construction of recursive MDS matrices

MDS matrices allow to build optimal linear diffusion layers in the design of block ciphers and hash functions. There has been a lot of study in designing efficient MDS matrices suitable for software and/or hardware implementations. In particular recursive MDS matrices are considered for resource constrained environments. Such matrices can be expressed as a power of simple companion matrices, i.e., an MDS matrix \(M = C_g^k\) for some companion matrix corresponding to a monic polynomial \(g(X) \in \mathbb {F}_q[X]\) of degree k. In this paper, we first show that for a monic polynomial g(X) of degree \(k\ge 2\), the matrix \(M = C_g^k\) is MDS if and only if g(X) has no nonzero multiple of degree \(\le 2k-1\) and weight \(\le k\). This characterization answers the issues raised by Augot et al. in FSE-2014 paper to some extent. We then revisit the algorithm given by Augot et al. to find all recursive MDS matrices that can be obtained from a class of BCH codes (which are also MDS) and propose an improved algorithm. We identify exactly what candidates in this class of BCH codes yield recursive MDS matrices. So the computation can be confined to only those potential candidate polynomials, and thus greatly reducing the complexity. As a consequence we are able to provide formulae for the number of such recursive MDS matrices, whereas in FSE-2014 paper, the same numbers are provided by exhaustively searching for some small parameter choices. We also present a few ideas making the search faster for finding efficient recursive MDS matrices in this class. Using our approach, it is possible to exhaustively search this class for larger parameter choices which was not possible earlier. We also present our search results for the case \(k=8\) and \(q=2^{16}\).     

A novel hybrid macrocyclic receptor based on bile acid and calix[4]arene frameworks for metal ion recognition

A novel hybrid macrocyclic receptor based on bile acid and calix[4]arene has been synthesized using the α-face of the bile acid and cone-conformation of calix[4]arene. Metal recognition properties of receptor were investigated. The receptor showed the strongest affinity for Hg²⁺ in acetonitrile. The stoichiometry of the Receptor:Hg²⁺ was 1:1.     

Asymmetric total synthesis of phomonol

An efficient asymmetric total synthesis of phomonol 1 is presented, starting from (S)-1,2-epoxypentane. The synthesis features Sharpless asymmetric dihydroxylation (AD), diastereoselective reductive etherification and Wacker oxidation as key steps.     

Determination of E. coli by a Graphene Oxide-Modified Quartz Crystal Microbalance

A biosensor for the determination of Escherichia coli using graphene oxide on the crystal (gold) surface was fabricated by the drop cast method. The E. coli sensing characteristics of the biosensor, such as a change in frequency, were examined by exposing the graphene oxide-coated crystal to various functionalization steps at room temperature. Graphene oxide was functionalized by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride–N-hydroxysuccinimide to covalently conjugate β-galactosidase antibodies to recognize microorganisms that produce this material. Frequency changes in the quartz crystal microbalance are dependent on the absorbed/desorbed masses of the analytes on the functional surface of the crystal. In addition, various characterization techniques were optimized for the morphological elemental analysis of the nanocoating that included field emission scanning electron microscopy, scanning electron microscopy, and electron diffraction spectroscopy. This surface was used in a quartz crystal microbalance nanoplatform for the rapid, sensitive, and label-free detection of E. coli. Under optimal conditions, the frequency of quartz crystal microbalance biosensor was directly proportional to the concentration of antigen with a dynamic range from 0.5?mg?mL^?1 to 5?ng?mL^?1 and a minimum detection limit of 5?ng?mL^?1, and a sensitivity of 0.037?Hz?g?ml^?1?cm^?1. These results show that the graphene oxide-coated crystal had excellent performance for E. coli. This research reports a simple, inexpensive, and effective highly stable biosensor using graphene oxide as the sensing medium.     

Detailed Hydrocarbon Class Composition Analysis and Trace Level BTEX Estimation in Raffinate Column Bottom (RCB) Using GC×GC–TOFMS

A two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) method was developed for the hydrocarbon class composition analysis and benzene, toluene, ethylbenzene, and xylene (BTEX) estimation of raffinate column bottom (RCB), which is generated as a by-product from linear alkyl benzene (LAB) plants. The molecular level characterization of RCB is important to generate value-added products for the petrochemical industry. GC×GC–TOFMS was found to be an excellent tool for estimation of hydrocarbon class composition (paraffins, naphthenes, monoaromatics, diaromatics, and polyaromatic hydrocarbons) and trace level BTEX in a single run. The hydrocarbon class composition was validated with the standard method based on HPLC (ASTM D6591) and good correlation was obtained. Finally, RCB is anticipated to be a useful nonhazardous safe by-product which could be used further for generating added value.     

Toward resistance‐compromised DHFR inhibitors part 1: Combined structure/ligand‐based virtual screenings and ADME‐Tox profiling

The front‐line antimalarial drugs, for example, chloroquine, mefloquine, sulfadoxine, pyrimethamine, atovaquone, and artemether, are often failing because of the worldwide spread of drug‐resistant parasites. There has been significant recent interest in virtual screening to drive innovative drug discovery and to combat resistance efforts for a wide range of diseases. In fact, virtual screening has become the “gold standard” for major pharmaceutical industries and some university groups. Therefore, we present herein a structure‐based LibDock/CHARMM modeling and a set of appropriate scoring function evaluation criteria: correlation, consensus score, correlation‐based score, generally applicable replacement for root‐mean‐square deviation using a training set of 38 phenylthiazolyl‐1,3,5‐triazines from our previous reports and followed by a ligand‐based model to identify molecular features like hydrogen‐bond acceptor, hydrogen‐bond donor, hydrophobicity, and ring aromatic (RA) using Catalyst HipHop/HypoGen module. Next, TOPKAT module was applied to predict ADME‐Tox properties. The combined structure/ligand‐based approaches inadvertently arrived at a conserved Arg122 binding site from reliable LigScore1_dreiding top scoring function and are subsequently attributed to reserve important interactions and combat mutational drug resistance. The best pharmacophore model suggested that 1 hydrogen‐bond acceptor, 2 hydrophobicities, and 1 ring aromatic feature with good sensitivity at 0.50, specificity at 0.66, enrichment at 1.60, and accuracy at 0.50. Finally, good pharmacokinetics, metabolic stability, and toxicity endpoints were predicted in the comparison of proguanil and cycloguanil. These druggability insights are useful for researchers to deliver more effective, safer, both wild‐type and resistance‐compromised, and more economical dihydrofolate reductase inhibitors in the near future.     

Magnetic resonance angiographic demonstration of carotid-cavernous fistula using elliptical centric time resolved imaging of contrast kinetics (EC-TRICKS)

Magnetic resonance angiographic evaluation of the intracranial vasculature has been predominantly carried out using conventional angiographic techniques such as time of flight and phase contrast sequences. These techniques have good spatial resolution but lack temporal resolution. Newer faster angiographic techniques have been developed to circumvent this limitation. Elliptical centric time-resolved imaging of contrast kinetics (EC-TRICKS) is one such technique which has combined the use of elliptical centric ordering of the k-space with multiphase 3D digital subtraction MR angiogram (MRA) to achieve excellent temporal resolution of the arterial and venous circulations. Its applications have been mainly in the peripheral vasculature. We report the use of this technique in a case of a high-flow, direct carotid-cavernous fistula to demonstrate its potential in intracranial MR angiography.     

Monte Carlo simulation of a film growth with reactive hydrophobic, polar, and aqueous components by a covalent bond fluctuating model

Using a bond fluctuating model (BFM), Monte Carlo simulations are performed to study the film growth in a mixture of reactive hydrophobic (H) and hydrophilic (P) groups in a simultaneous reactive and evaporating aqueous (A) solution on a simple three dimensional lattice. In addition to the excluded volume, short range phenomenological interactions among each constituents and kinetic functionalities are used to capture their major characteristics. The simulation involves thermodynamic equilibration via stochastic movement of each constituent by Metropolis algorithm as well as cross-linking reaction among constituents with evaporating aqueous component. The film thickness (h) and its interface width (W) are examined with a reactive aqueous solvent for a range of temperatures (T). Results are compared with a previous study [Yang et al. Macromol. Theory Simul. 15, 263 (2006)] with an effective bond fluctuation model (EBFM). Simulation data show a much slower power-law growth for h and W with BFM than that with EBFM. With BFM, growth of the film thickness can be described by h proportionaltgamma, with a typical value gamma1 approximately 0.97 in initial time regime followed by gamma2 approximately 0.77 at T=5, for example. Growth of the interface width can also be described by a power law, W proportionaltbeta, with beta1 approximately 0.40 initially and beta2 approximately 0.25 in later stage. Corresponding values of the exponents with EBFM are much higher, i.e., gamma1 approximately 1.84, gamma2 approximately 1.34 and beta1 approximately 1.05, beta2 approximately 0.60 at T=5. Correct restrictions on the bond length with the excluded volume used with BFM are found to have a greater effect on steady-state film thickness (hs) and the interface width (Ws) at low temperatures than that at high temperatures. The relaxation patterns of the interface width with BFM seem to change noticeably from those with EBFM. A better relaxed film with a smoother surface is thus achieved by the improved cross-linking covalent bond fluctuation model which is more realistic in capturing appropriate details of systems such as polyurethane film. The steady-state film thickness increases monotonically with the temperature possibly with two logarithmic dependences. The equilibrium interface width shows a nonmonotonic dependence: on increasing the temperature, Ws seems to increase slowly before it begins to decay Ws=4.12-1.39 ln(T).     

Electron transfer studies on cholesterol LB films assembled on thiophenol and 2-naphthalenethiol self-assembled monolayers

We have formed the cholesterol monolayer and multilayer LB films on the self-assembled monolayers of 2-naphthalenethiol (2-NT) and thiophenol (TP) and studied the electrochemical barrier properties of these composite films using cyclic voltammetry and electrochemical impedance spectroscopy. We have also characterized the cholesterol monolayer film using grazing angle FTIR, scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Cholesterol has a long hydrophobic steroid chain, which makes it a suitable candidate to assemble on the hydrophobic surfaces. We find that the highly hydrophobic surface formed by the self-assembled monolayers (SAM) of 2-NT and TP act as effective platforms for the fabrication of cholesterol monolayer and multilayer films. The STM studies show that the cholesterol monolayer films on 2-NT form striped patterns with a separation of 1.0 nm between them. The area per cholesterol molecule is observed to be 0.64 nm2 with a tilt angle of about 28.96 degrees from the surface normal. The electrochemical studies show a large increase in charge transfer resistance and lowering of interfacial capacitance due to the formation of the LB film of cholesterol. We have compared the behavior of this system with that of cholesterol monolayer and multilayers formed on the self-assembled monolayer of thiophenol.     

Polypyrrole-polyvinyl sulphonate film based disposable nucleic acid biosensor

Double stranded calf thymus deoxyribonucleic acid entrapped polypyrrole-polyvinyl sulphonate (dsCT-DNA-PPy-PVS) films fabricated onto indium-tin-oxide (ITO) coated glass plates have been used to detect organophosphates such as chlorpyrifos and malathion. These disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes have been characterized using cyclic voltammetry, Fourier-transform-infra-red (FTIR) spectroscopy and atomic force microscopy (AFM), respectively. These biosensing electrodes have a response time of 30 s, are stable for about 5 months when stored in desiccated conditions at 25 °C and can be used to amperometrically detect chlorpyrifos (0.0016-0.025 ppm) and malathion (0.17-5.0), respectively. The additive effect of these pesticides on the amperometric response of the disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes has also been investigated.