Enzymes immobilized on montmorillonite: comparison of performance in batch and packed-bed reactors

Summary The enzymes a-amylase, invertase and glucoamylase were immobilized on acid activated montmorillonite using two techniques, viz. adsorption and covalent binding, and their activities were tested in a batch and packed-bed reactor and were compared. The packed-bed reactor showed an improved performance for all immobilized enzymes, which was attributed to lowering of diffusional restrictions to mass transfer. Lower activity in case of batch reactor for immobilized invertase was due to a combined effect of loss of native conformation of enzyme on account of immobilization and mass transfer resistances due to improper diffusion of substrate to the active site of enzyme. For immobilized glucoamylase, the packed-bed reactor demonstrated exceptionally high activity that was very close to the free enzyme. Covalently bound glucoamylase showed higher activity than the free enzyme.     

On finding the nucleolus of an n-person cooperative game

Kohlberg (1972) has shown how the nucleolus for ann-person game with side-payments may be found by solving a single minimization LP in case the imputation space is a polytope. However the coefficients in the LP have a very wide range even for problems with 3 or 4 players. Therefore the method is computationally viable only for small problems on machines with finite precision. Maschler et al. (1979) find the nucleolus by solving a sequence of minimization LPs with constraint coefficients of either –1, 0 or 1. However the number of LPs to be solved is o(4 ⁿ ). In this paper, we show how to find the nucleolus by solving a sequence of o(2 ⁿ ) LPs whose constraint coefficients are –1, 0 or 1.     

Inequivalent quantizations for non-linear σ model

We compute the homotopy groups ₀ and ₁ of the classical configuration space of anO(3) invariant field theory on ×, where is a compact two dimensional manifold for arbitrary genusg and- denotes the time coordinate. We also present the finite dimensional, unitary, irreducible, inequivalent representations of the appropriate fundamental groups and comment on some of their implications.     

The utility of Bacillus subtilis as a bioflocculant for fine coal

The application of Bacillus subtilis as a flocculant for fine coal has been reported here. Zeta-potential measurements showed that both the coal and bacteria had similar surface charge as a function of pH. Surface free energy calculations showed that the coal was hydrophobic while the bacterium was hydrophilic. The adhesion of the bacteria to coal and subsequent settling was studied in detail. Adhesion of bacteria to coal surface and subsequent settling of coal was found to be quick. Both adhesion and settling were found to be independent of pH, which makes the process very attractive for field applications. The presence of an electrolyte along with the bacterium was found to not only enhance adhesion of bacteria, but also produce a clear supernatant. Further, the settled fraction was more compact than with bacteria alone. Interaction energy calculations using the extended DLVO theory showed that the electrical forces along with the acid–base interaction energy play a dominant role in the lower pH range. Above pH 7, the acid–base interaction energy is the predominant attractive force and is sufficient enough to overcome the repulsive forces due to electrical charges to bring about adhesion and thus settling of fine coal. With increase in electrolyte concentration, the change in total interaction energy with pH is minimal which probably leads to better adhesion and hence settling.     

Design of high-speed data transfer turbo code for body channel communication transceivers

In this work, a digital differential transmitter based on low-power wireless compensation transceiver for body channel communication (BCC) is proposed. Further, the proposed transceiver is composed of Touch Status Detection Unit (TSDU), Wireless Status Compensation Unit (WSCU), and a reconfigurable preamplifier. Initially, the human body channel environment for wireless communication is investigated based on properties from 1 to 100 MHz. Further, the turbo code-based encoding scheme is used to encode the data before transferring the data on the transmitter side. Also, the proposed error-correcting parallel turbo decoder using a modified step-by-step algorithm is presented. The turbo code-based decoding scheme is used to recover the error-free transmitted data at the receiver side. Results demonstrate that the proposed BCC transceiver is designed using 90 nm CMOS technology and it is observed that the proposed BCC transceiver has utilized an area of 600mm². Also, the maximum data rate achieved by a proposed BCC transceiver was 100 Mbps, and the overall transceiver power consumption is 0.42 mW, and energy for communication is 0.02 nj/b.     

A post quantum secure construction of an authentication protocol for satellite communication

Satellite's communication system is used to communicate under significant distance and circumstances where the other communication systems are not comfortable. Since all the data are exchanged over a public channel, so the security of the data is an essential component for the communicating parties. Both key exchange and authentication are two cryptographic tools to establish a secure communication between two parties. Currently, various kinds of authentication protocols are available to establish a secure network, but all of them depend on number–theoretical (discrete logarithm problem/factorization assumption) hard assumptions. Due to Shor's and Grover's computing algorithm number theoretic assumptions are breakable by quantum computers. Although Kumar and Garg have proposed a quantum attack-resistant protocol for satellite communication, it cannot resist stolen smart card attack. We have analyzed that how Kumar and Garg is vulnerable to the stolen smart card attack using differential power analysis attack described in He et al and Chen and Chen. We have also analyzed the modified version of signal leakage attack and sometimes called improved signal leakage attack on Kumar and Garg's protocol. We have tried to construct a secure and efficient authentication protocol for satellites communication that is secure against quantum computing. This is more efficient as it requires only three messages of exchange. This paper includes security proof and performance of the proposed authentication and key agreement protocol.