Studies in bubble formation—I bubble formation under constant flow conditions

A model based on two step mechanism of bubble formation is proposed. The resulting equations are used to explain the discrepancies existing in the literature. Data have been collected over a wide range of variables to test the model.

Moment methods and "restricted variation" in kinetic theory

It is shown that there is a strict one-to-one correspondence between results obtained by the use of "restricted" variational principles and those obtained by a moment method of the Mott-Smith type for shock structure.

Charge distribution, dipole moment and molecular structure of silyl compounds

The formal charge distribution and hence the electric moments of a number of halosilanes and their methyl derivatives have been calculated by the method of Image and Image . The difference between the observed and the calculated values in simple halosilanes is attributed to a change in the hybridization of the terminal halogen atom and in methyl halosilanes to the enhanced electron release of the methyl group towards silicon compared with carbon.

Equivalence conditions for classes of linear and non-linear distributed parameter systems

Equivalence of certain classes of second-order non-linear distributed parameter systems and corresponding linear third-order systems is established through a differential transformation technique. As linear systems are amenable to analysis through existing techniques, this study is expected to offer a method of tackling certain classes of non-linear problems which may otherwise prove to be formidable in nature.

Improved Conditions For L2-Stability Of Nonstationary Feedback-Systems

Concerning the L2-stability of feedback systems containing a linear time-varying operator, some of the stringent restrictions imposed on the multiplier as well as the linear part of the system, in the criteria presented earlier, are relaxed.

Moment-Matched Lognormal Modeling of Uplink Interference with Power Control and Cell Selection

We develop an alternate characterization of the statistical distribution of the inter-cell interference power observed in the uplink of CDMA systems. We show that the lognormal distribution better matches the cumulative distribution and complementary cumulative distribution functions of the uplink interference than the conventionally assumed Gaussian distribution and variants based on it. This is in spite of the fact that many users together contribute to uplink interference, with the number of users and their locations both being random. Our observations hold even in the presence of power control and cell selection, which have hitherto been used to justify the Gaussian distribution approximation. The parameters of the lognormal are obtained by matching moments, for which detailed analytical expressions that incorporate wireless propagation, cellular layout, power control, and cell selection parameters are developed. The moment-matched lognormal model, while not perfect, is an order of magnitude better in modeling the interference power distribution.

The Critical Role of N- and C-Terminal Contact in Protein Stability and Folding of a Family 10 Xylanase under Extreme Conditions

Background: Stabilization strategies adopted by proteins under extreme conditions are very complex and involve various kinds of interactions. Recent studies have shown that a large proportion of proteins have their N- and C-terminal elements in close contact and suggested they play a role in protein folding and stability. However, the biological significance of this contact remains elusive. Methodology: In the present study, we investigate the role of N- and C-terminal residue interaction using a family 10 xylanase (BSX) with a TIM-barrel structure that shows stability under high temperature,alkali pH, and protease and SDS treatment. Based on crystal structure,an aromatic cluster was identified that involves Phe4, Trp6 and Tyr343 holding the Nand C-terminus together; this is a unique and important feature of this protein that might be crucial for folding and stabilityunder poly-extreme conditions. Conclusion: A series of mutants was created to disrupt this aromatic cluster formation and study the loss of stability and function under given conditions. While the deletions of Phe4 resulted in loss of stability, removal of Trp6 and Tyr343 affected in vivo folding and activity. Alanine substitution with Phe4, Trp6 and Tyr343 drastically decreased stability under all parameters studied. Importantly,substitution of Phe4 with Trp increased stability in SDS treatment.Mass spectrometry results of limited proteolysis further demonstrated that the Arg344 residue is highly susceptible to trypsin digestion in sensitive mutants such as DF4, W6A and Y343A, suggesting again that disruption of the Phe4-Trp6-Tyr343 (F-W-Y) cluster destabilizes the N-and C-terminal interaction. Our results underscore the importance of N- and C-terminal contact through aromatic interactions in protein folding and stability under extreme conditions, and these results may be useful to improve the stability of other proteins under suboptimal conditions.

Limit Analysis of Slabs with Free Edge

The general method earlier developed by the writers for obtaining valid lower bound solutions to slabs under uniformly distributed load and supported along all edges is extended to the slabs with a free edge. Lower bound solutions with normal moment criterion are presented for six cases of orthotropically reinforced slabs, with one of the short edges being free and the other three edges being any combination of fixed and simply supported conditions. The expressions for moment field and collapse load are given for each slab. The lower bounds have been compared with the corresponding upper bound values obtained from the yield line theory with simple straight yield line modes of failure. They are also compared with Nielsen’s solutions available for two cases with isotropic reinforcement.

Probabilistic Analysis of Cracking Moment of Reinforced Concrete Beams

Probabilistic analysis of cracking moment from 22 simply supported reinforced concrete beams is performed. When the basic variables follow the distribution considered in this study, the cracking moment of a beam is found to follow a normal distribution. An expression is derived, for characteristic cracking moment, which will be useful in examining reinforced concrete beams for a limit state of cracking.

Invariant-preserving Petri net reduction and conditions for invariant-existence

The use of invariants is an important tool for analysis of distributed and concurrent systems modeled by Petri nets. For a large practical system, the computation of desired invariants by the existing techniques is a time-consuming task. This paper proposes a theoretical foundation for simplified computation of desired invariants. We provide invariant-preserving Petri net reduction rules followed by the conditions for the existence of invariants in various well-structured nets. If an invariant exists, it can be found directly from the net structure using the formulas derived, or by applying the existing techniques on the reduced net.