A Stretchable and Flexible Cardiac Tissue–Electronics Hybrid Enabling Multiple Drug Release,Sensing, and Stimulation

Replacement of the damaged scar tissue created by a myocardial infarction is the goal of cardiac tissue engineering. However, once the implanted tissue is in place, monitoring its function is difficult and involves indirect methods, while intervention necessarily requires an invasive procedure and available medical attention. To overcome this, methods of integrating electronic components into engineered tissues have been recently presented. These allow for remote monitoring of tissue function as well as intervention through stimulation and controlled drug release. Here, an improved hybrid microelectronic tissue construct capable of withstanding the dynamic environment of the beating heart without compromising electronic or mechanical functionality is reported. While the reported system is enabled to sense the function of the engineered tissue and provide stimulation for pacing, an electroactive polymer on the electronics enables it to release multiple drugs in parallel. It is envisioned that the integration of microelectronic devices into engineered tissues will provide a better way to monitor patient health from afar, as well as provide facile, more exact methods to control the healing process.     

Experimental investigation of fracture under controlled stress triaxiality using shear-compression disk specimen

Experimental investigation of the effect of stress triaxiality on fracture strain has been performed using the shear-compression disk (SCD) specimen. A series of experiments was carried out under quasi-static loading conditions at triaxiality levels in the range of \(-\,0.7\) to \(+\,0.05\). The experiments were designed to generate relatively uniform strain and triaxiality in the sheared zone of the specimen, and a constant level of triaxiality along the entire loading path. The results obtained for SAE 1045 steel are compared to previous studies on the same material which revealed considerable differences. Discussion on possible contributing factors to the differences, and the potential of the SCD specimen for fracture investigations are discussed.     

The effect of gas bubbles on flash evaporation

The effect on evaporation rates of air content in flashing water was investigated experimentally in a scaled-down open-channel flash evaporator. The water was at 97°C–98°C, the flash-down temperature differences were up to about 2°C, and air content was up to 6.32 ppm. The ratio (ΔT_s/R_c), of the local liquid superheat to the equilibrium radius of bubbles was proposed as the correlating parameter for the flash-evaporation heat transfer Stanton Number, and a correlation was developed. The presence of air in the water was found to have an important influence on the process: both the Stanton Number and the approach to equilibrium of the flashing water were seen to improve with air concentration.     

Characterization of Secure Multiparty Computation Without Broadcast

A major challenge in the study of cryptography is characterizing the necessary and sufficient assumptions required to carry out a given cryptographic task. The focus of this work is the necessity of a broadcast channel for securely computing symmetric functionalities (where all the parties receive the same output) when one third of the parties, or more, might be corrupted. Assuming all parties are connected via a point-to-point network, but no broadcast channel (nor a secure setup phase) is available, we prove the following characterization:

• A symmetric n-party functionality can be securely computed facing \(n/3\le t<n/2\) corruptions (i.e., honest majority), if and only if it is \((n-2t)\) -dominated; a functionality is k-dominated, if any k-size subset of its input variables can be set to determine its output to some predetermined value.
• Assuming the existence of one-way functions, a symmetric n-party functionality can be securely computed facing \(t\ge n/2\) corruptions (i.e., no honest majority), if and only if it is 1-dominated and can be securely computed with broadcast.

It follows that, in case a third of the parties might be corrupted, broadcast is necessary for securely computing non-dominated functionalities (in which “small” subsets of the inputs cannot determine the output), including, as interesting special cases, the Boolean XOR and coin-flipping functionalities.

     

Fabrication of very high aspect ratio metal nanowires by a self-propulsion mechanism

A novel synthesis method of very high aspect ratio metal nanowires is described. The synthesis utilizes a nanoporous membrane as a template and self-electrophoresis as a directed force that continuously push formed nanowires out of the pores in a rate that is identical to the rate of their elongation. As a result, while the pores of membranes are only 6 microm long, the formed nanowires could be more than 100 microm long.     

Methodology for thermal design of novel combined refrigeration/power binary fluid systems

Refrigeration cogeneration systems which generate power alongside with cooling improve energy utilization significantly, because such systems offer a more reasonable arrangement of energy and exergy “flows” within the system, which results in lower fuel consumption as compared to the separate generation of power and cooling or heating. This paper proposes several novel systems of that type, based on ammonia–water working fluid. Importantly, general principles for integration of refrigeration and power systems to produce better energy and exergy efficiencies are summarized, based primarily on the reduction of exergy destruction. The proposed plants analyzed here operate in a fully-integrated combined cycle mode with ammonia–water Rankine cycle(s) and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. It was found that the cogeneration systems have good performance, with energy and exergy efficiencies of 28% and 55–60%, respectively, for the base-case studied (at maximum heat input temperature of 450 °C). That efficiency is, by itself, excellent for cogeneration cycles using heat sources at these temperatures, with the exergy efficiency comparable to that of nuclear power plants. When using exhaust heat from topping gas turbine power plants, the total plant energy efficiency can rise to the remarkable value of about 57%. The hardware proposed for use is conventional and commercially available; no hardware additional to that needed in conventional power and absorption cycles is needed.     

In silico design of small RNA switches

The discovery of natural RNA sensors that respond to a change in the environment by a conformational switch can be utilized for various biotechnological and nanobiotechnological advances. One class of RNA sensors is the riboswitch: an RNA genetic control element that is capable of sensing small molecules, responding to a deviation in ligand concentration with a structural change. Riboswitches are modularly built from smaller components. Computational methods can potentially be utilized in assembling these building block components and offering improvements in the biochemical design process. We describe a computational procedure to design RNA switches from building blocks with favorable properties. To achieve maximal throughput for genetic control purposes, future designer RNA switches can be assembled based on a computerized preprocessing buildup of the constituent domains, namely the aptamer and the expression platform in the case of a synthetic riboswitch. Conformational switching is enabled by the RNA versatility to possess two highly stable states that are energetically close to each other but topologically distinct, separated by an energy barrier between them. Initially, computer simulations can produce a list of short sequences that switch between two conformers when trigerred by point mutations or temperature. The short sequences should possess an additional desirable property; when these selected small RNA switch segments are attached to various aptamers, the ligand binding mechanism should replace the aforementioned event triggers, which will no longer be effective for crossing the energy barrier. In the assembled RNA sequence, energy minimization folding predictions should then show no difference between the folded structure of the entire sequence relative to the folded structure of each of its constituents. Moreover, energy minimization methods applied on the entire sequence could aid at this preprocessing stage by exhibiting high mutational robustness to capture the stability of the formed hairpin in the expression platform. The above computer-assisted assembly procedure together with application specific considerations may further be tailored for therapeutic gene regulation. Index Terms-Design of RNA switches, energy minimization methods, RNA folding predictions.     

Sustainable energy development: The present (2009) situation and possible paths to the future

Recent estimates and forecasts of the oil, gas, coal resources and their reserve/production ratio, nuclear and renewable energy potential, and energy uses are surveyed. A brief discussion of the status, sustainability (economic, environmental and social impact), and prospects of fossil, nuclear and renewable energy use, and of power generation (including hydrogen, fuel cells, micropower systems, and the futuristic concept of generating power in space for terrestrial use), is presented. Comments about energy use in general, with more detailed focus on insufficiently considered areas of transportation and buildings are brought up. Ways to resolve the problem of the availability, cost, and sustainability of energy resources alongside the rapidly rising demand are discussed. The author’s view of the promising energy R&D areas, their potential, foreseen improvements and their time scale, and last year’s trends in government funding are presented.     

COOLCEP (cool clean efficient power): A novel CO2-capturing oxy-fuel power system with LNG (liquefied natural gas) coldness energy utilization

A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO₂ and other emissions and a high efficiency. The plant operates as a subcritical CO₂ Rankine-like cycle. Beside the power generation, the system provides refrigeration in the CO₂ subcritical evaporation process, thus it is a cogeneration system with two valued products. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO₂ can be withdrawn from the cycle without consuming additional power. Two system variants are analyzed and compared, COOLCEP-S and COOLCEP-C. In the COOLCEP-S cycle configuration, the working fluid in the main turbine expands only to the CO₂ condensation pressure; in the COOLCEP-C cycle configuration, the turbine working fluid expands to a much lower pressure (near-ambient) to produce more power. The effects of some key parameters, the turbine inlet temperature and the backpressure, on the systems' performance are investigated. It was found that at the turbine inlet temperature of 900 °C, the energy efficiency of the COOLCEP-S system reaches 59%, which is higher than the 52% of the COOLCEP-C one. The capital investment cost of the economically optimized plant is estimated to be about 750 EUR/kWe and the payback period is about 8–9 years including the construction period, and the cost of electricity is estimated to be 0.031–0.034 EUR/kWh.