Design of single peptides for self-assembled conduction channels

Self-assembly of peptides provides the possibility of achieving relatively long range order on surfaces. These ordered peptides can also form channels that can be used as conduction channels. In the past, studies were focused on electron conduction through the secondary structure and amine bond of peptides and these restrict conduction of electrons over a short range (a few nanometers). In this work, we demonstrate the realization of electron conduction over a longer range of a few hundred nanometers via π-π stacking of the phenyl groups in the tyrosine residue of a single peptide. The peptide used in this work was designed with a phenyl ring for π-π stacking at one end and a carboxylic group at the other end for binding to aminopropyltriethoxysilane (APTES) treated silicon wafer. The distance between the peptides is controlled by a disulfide bond formed between neighboring cysteine residue and also by the amine groups of aminopropyltriethoxysilane. We demonstrate that the self-assembled peptide is conducting in the dry state over hundreds of nanometers, realizing the possibility of using peptide as a molecular wire.     

Techno-economic performance analysis of solar cooling systems

Vapour absorption cooling systems, powered by solar thermal energy, are now commercially manufactured in sizes ranging from 1.5 to over 20 RT (one refrigeration ton = 3.51 kW of cooling). The needed thermal energy at appropriate temperature potential can either be provided by solar thermal collectors or else from a solar pond. The paper gives the assessment criteria and results for technical and economic evaluation of the performance of absorption chiller using a solar pond. These results, based on Kuwait's environmental data and costs, have been compared with three alternate cooling systems, namely:

• 1 Solar thermal collector absorption cooling system.
• 2 Solar photovoltaic cooling system.
• 3 Standard vapour compression cooling system.

The criteria, used for performance evaluation of the solar cooling systems on a technical basis, consists of assessing the extent to which such systems can make a positive contribution in a conserving fossil fuel. This is done by first estimating the total electrical energy needed by the standard system (defined in para. 3 above) to produce one unit of cooling output. Solar cooling systems are then analysed and compared with a standard system to establish their electrical energy saving or generation capability, after accounting for the parasitic electrical energy used in pump/fan motors and equivalent energy needed for the production of soft water (used-up in the cooling tower) from seawater desalination. The economic analysis considers the cost and life of subsystems and that of the electrical and water desalination plants to arrive at the unit cooling cost. The unit cooling is defined as the ratio of amortized capital investments plus operation and maintenance costs over the year and the total yearly cooling production by the system. The results show that the solar pond absorption cooling system is the closest competitor to the conventional cooling system.     

Evaluation Metrics for the Rating and Optimization of Snap-fits

Current snap-fit design guides recommend sizing snap-fit features on the basis of insertion force and allowable strain during assembly. Retention force information in such guides is often inaccurate, although this is considered to be the primary attribute of the snap-fit after assembly. The authors contend that these (insertion force, allowable strain, retention force) are not the only critical performance criteria for snap-fit features. Designers have to contend with several other constraints and design requirements. Additional performance metrics for snap-fit features are proposed by drawing upon considerable experience with plastic part design issues. Locking ratio, dimensional and volumetric retention force, consideration of the characteristic dimension of the joint and snap-fit, feature stiffness, required over-insertion and consideration of snap-fit strength relative to part strength are proposed to supplement currently used metrics for evaluating and rating snap-fit designs. The applicability of these metrics is illustrated with real-life examples, and their merits and demerits discussed. A chart of achievable locking ratios for different snap-fit topologies is presented for use as a design tool for the initial selection of snap-fit topologies. Its use as a rational basis for selection and optimization of snap-fits is suggested. Adoption of proposed metrics will allow designers to better quantify, and thereby optimize the performance of, snap-fit features. These ideas will be built upon in the future, and used as a basis for a comprehensive snap-fit selection and detailed design tool.     

A precedence-constrained asymmetric traveling salesman model for disassembly optimization

In this paper, we address a product-disassembly optimization problem, which aims at minimizing the costs associated with the disassembly process (namely, the cost of breaking the joints and the sequence-dependent set-up cost associated with the disassembly operations), while maximizing the benefits resulting from the recovery of components and subassemblies that constitute the product. A method able to capture the mating relationships among the parts and joints of the product through a network representation scheme is developed. The disassembly optimization problem is formulated as a precedence-constrained asymmetric traveling salesman problem. A three-stage iterative procedure is designed to obtain optimal or near-optimal solutions to the problem. The results demonstrate that our procedure generates solutions that are within 2% of optimality for all test cases, while only requiring a reasonable computational effort.     

The use of benzyl alcohol and amyl-m-cresol (Strepsils) in the oral cavity. (Review of the literature and first clinical experiences)

The authors summarised the literature data of benzylalcohol and amyl-m-cresol. In the clinical practice they used Strepsils in the treatment of 22 patients suffered from oral inflammatic diseases and in the 20 prophylactic cases of oral surgical interventions. The preliminary clinical report shows that, the Strepsils seems to be very effective in the treatment of oral inflammations and in the prophylaxis too.     

On the Consequences of Information Delays in the Scheduling of Semi-Automated Flexible Machines

Manufacturing systems with varying levels and types of flexibility employ alternative scheduling strategies to exploit flexibility for performance enhancement. Scheduling decisions in manufacturing systems are influenced by time delays due to information handling activities such as information collection, transfer, and processing. More specifically, scheduling strategies implicitly involve information intensive activities that may entail significant time delays for implementation, depending on the extant shop floor automation and integration within a flexible system. These are information delays and we believe that most contemporary flexible systems must inherently cope with some level of information delay when implementing on-line scheduling strategies. This paper conceptualizes the manifestation of information delays in the context of scheduling decisions within flexible systems through the definition of three key delay modes: (i) Mode 1 information-transfer delay; (ii) Mode 2 decision-implementation delay; and (iii) Mode 3 status-review delay. We then stress the need and importance of devising suitable on-line scheduling strategies for countering the effect of information delays by demonstrating the efficacy of a novel scheduling strategy on a single machine. While opening a new scheduling dimension with potential research ramifications, this paper highlights the fact that the concept of information delay can effectively capture the synergism issues related with flexibility, integration, and automation in the context of scheduling decisions within semi-automated flexible systems.     

Nanolubrication: Characterization of patterned lubricant films on magnetic hard disks

Patterned lubricant films on magnetic hard disks offer potential advantages in controlled bonding sites, higher average shear strength, and longer durability. However, since the lubricant film thickness is at 1 or 2 nm, characterization of the pattern is difficult. Normal atomic force microscopic techniques can only image very small area in the nanometer range and the sharp tip can potentially modify the pattern. A wide area optical technique is needed to characterize the patterns. This paper examines patterned lubricant film using an optical surface analyzer (OSA) to image the bonded phase and mobile phase of an alcohol functionalized perfluoropolyether (PFPE) on magnetic hard disks. The phase shift signal and reflectivity intensity of the polarized light spectra provide clear optical images of the lubricant film at nanometer thickness. Optical images were successfully obtained before and after the buffing process and the ramp load and unload (L/UL) testing. Results of 100% bonded, 100% mobile, and 20% zigzag patterned lubricant films confirm that the patterned lubricant films can control the bonded/mobile ratio of such films better.     

Finite element analysis of fluid-structure interaction effect on liquid retaining structures due to sloshing

Fluid-structure interaction problems, which may be categorized into different types, have attracted the attention of engineers because of their numerous practical applications. Sloshing of liquid in a liquid filled container subjected to external excitations and coupled interaction between the liquid and container wall due to sloshing is one such problem. The focus of the present paper is on the development of a numerical scheme using finite element technique to calculate the sloshing displacement of liquid and pressure developed due to such sloshing. The scheme is extended to study the coupled effect of sloshing and container wall movement due to change in the liquid pressure.