Feedback regulation of the heat shock response in E. coli

Survival of organisms in extreme conditions has necessitated the evolution of stress response networks that detect and respond to environmental changes. Among the extreme conditions that cells must face is the exposure to higher than normal temperatures. In this paper, we propose a detailed biochemical model that captures the dynamical nature of the heat-shock response in Escherichia coli. Using this model, we show that both feedback and feedforward control are utilized to achieve robustness, performance, and efficiency of the response to the heat stress. We discuss the evolutionary advantages that feedback confers to the system, as compared to other strategies that could have been implemented to get the same performance

A review of compressors for high temperature heat pumps

Data availability: No data was used for the research described in the article.The development of high temperature heat pumps for waste heat recovery benefits industrial processes by meeting demand, increasing energy efficiency, and reducing emissions. The aim of such systems is to upgrade waste heat streams, typically around 50 °C to 100 °C, to higher temperatures ranging from 100 °C to around 200 °C. A primary challenge in getting the required high temperatures is the compression system. There is a plethora of recently published research papers including reviews that address high temperature heat pumps. However, there has been no comprehensive review addressing compression systems, despite their major influence in the successful development of high temperature heat pumps; this paper provides a comprehensive review of such compressors. Firstly, an overview of heat pump systems is provided, which covers cycle arrangements and working fluid selection. This is followed by a review of the different compressor technologies used, and the development of relevant modelling and design tools. Finally, suggestions for future directions in research for high temperature heat pump compressors are provided. It was found that screw compressors have been the obvious choice for heat pumps due to the experience gained from the refrigeration industry. However, the temperatures they can handle are constrained by the maximum possible limitation to avoid oil degradation. For higher temperatures, better efficiency, and larger capacity, it seems that the alternative is turbo-compressors. Nevertheless, there is a lack of experience in this area and more research and development efforts are required to enable these machines to achieve their potential in high temperature heat pumps

Performance Assessment of a Recuperated Turboshaft Engine: A Multifuel Case

Paper No: GT2022-80455, V004T06A007.The low cycle efficiency of simple cycle micro gas turbines is typically raised by the use of recuperators. The recuperated cycle allows for improved efficiency at low power-to-weight ratio, mainly due to the weight of the added heat exchanger. As weight is considered to be a key parameter for aeroengines, an analysis that addresses benefits and drawbacks of a more efficient, but heavier propulsion system design is required to be carried out. This paper assesses propulsion systems based on simple and recuperated cycle small gas turbine configurations, unusual in aviation, running with conventional jet fuel or hydrogen. An analytical model capable of modelling a turboshaft engine steady state design and off-design operation is developed. The specific fuel consumption of different engine arrangements is therefore calculated to evaluate the performance trade-off between the improved power plant fuel economy and its larger weight under a generic reference mission for a light helicopter. To enable a consistent mission analysis study of the hydrogen fueled rotorcraft, the weight of the tanks for liquid hydrogen storage is estimated according to a preliminary design model. The results obtained suggest that a hydrogen-fueled recuperated powerplant can shorten the flight time to reach the breakeven point, compared to a recuperated jet fuel powerplant of the same power rating.Europea n Union’s Horizon 2020 research and innovation programme under Marie Skłodowska Curie grant a greement No 861079 “NextMGT – Next Generation of Micro Gas Turbines for High Efficiency, Low Emissions and Fuel Flexibility

A techno-economic assessment of waste oil biodiesel blends for automotive applications in urban areas: Case of India

The effects of greenhouse gas emissions, urban air pollution, and rising transport fuel prices, on the low-income capita in India, necessitate appropriate measures to ensure commodities are sustainably available. This paper presents a study whereby biodiesel blends produced from waste cooking oil are optimised for use in urban medium-duty commercial vehicles, accounting for factors of production capacity, economics, and approximated engine characteristics. An artificial neural network model, trained with experimental data, is used to predict performance, combustion, and emission parameters. The results for various biodiesel blends are applied to a standard driving cycle to obtain variations in key factors. A multi objective optimisation is carried out with engine operation parameters to arrive at optimised biodiesel blends varying between 25% and 81% based on different criteria such as minimising fuel cost, enhancing engine efficiency, and reducing emissions. Considerations when choosing blend concentration are discussed in light of different governmental targets

A review of compressors for high temperature heat pumps

The development of high temperature heat pumps for waste heat recovery benefits industrial processes by meeting demand, increasing energy efficiency, and reducing emissions. The aim of such systems is to upgrade waste heat streams, typically around 50 °C to 100 °C, to higher temperatures ranging from 100 °C to around 200 °C. A primary challenge in getting the required high temperatures is the compression system. There is a plethora of recently published research papers including reviews that address high temperature heat pumps. However, there has been no comprehensive review addressing compression systems, despite their major influence in the successful development of high temperature heat pumps; this paper provides a comprehensive review of such compressors. Firstly, an overview of heat pump systems is provided, which covers cycle arrangements and working fluid selection. This is followed by a review of the different compressor technologies used, and the development of relevant modelling and design tools. Finally, suggestions for future directions in research for high temperature heat pump compressors are provided. It was found that screw compressors have been the obvious choice for heat pumps due to the experience gained from the refrigeration industry. However, the temperatures they can handle are constrained by the maximum possible limitation to avoid oil degradation. For higher temperatures, better efficiency, and larger capacity, it seems that the alternative is turbo-compressors. Nevertheless, there is a lack of experience in this area and more research and development efforts are required to enable these machines to achieve their potential in high temperature heat pumps

On the Production of π+π+\pi^+\pi^+ Pairs in pp Collisions at 0.8 GeV

Data accumulated recently for the exclusive measurement of the $pp\to pp\pi^+\pi^-$ reaction at a beam energy of 0.793 GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the $pp \to nn\pi^+\pi^+$ reaction channel. The latter is expected to be the only $\pi\pi$ production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the $\pi\pi$ production process. No single event has been found, which meets all conditions for being a candidate for the $pp \to nn \pi^+\pi^+$ reaction. This gives an upper limit for the cross section of 0.16 $\mu$b (90% C.L.), which is more than an order of magnitude smaller than the cross sections of the other two-pion production channels at the same incident energy

On the SigmaN cusp in the pp -> pK+Lambda reaction

Measurements of the $pp \to pK^+\Lambda$ reaction at $T_p$ = 2.28 GeV have been carried out at COSY-TOF. In addition to the $\Lambda p$ FSI and $N^*$ resonance excitation effects a pronounced narrow structure is observed in the Dalitz plot and in its projection on the $p\Lambda$-invariant mass. The structure appears at the $pp \to$N$K^+\Sigma$ threshold and is interpreted as $\Sigma$N cusp effect. The observed width of 20 MeV/$c^2$ is substantially broader than anticipated from previous inclusive measurements. Angular distributions of this cusp structure are shown to be dissimilar to those in the residual $pK^+\Lambda$ channel, but similar to those observed in the $pK^+\Sigma^0$ channel

A Study on the Market Potential of Biomass-Based Micro Gas Turbines in SubSaharan Africa

Selection and peer-review under responsibility of the scientific committee of the 13th Int. Conf. on Applied Energy (ICAE2021).Biomass can be used as an alternative fuel in micro gas turbines to produce electricity, heat and/ or cooling. This is an affordable carbon-neutral renewable energy source which is widely available in most African countries. In this project the main aim is to gather information and data to evaluate the feasibility and the market potential of this technology in three sub-Saharan African countries. This includes data about the energy market, information on feedstock availability in different regions, statistics on the electricity grid, the demand profiles of different consumers, as well as insight on the national policies and regulation. The information is used to help understand the needs of the energy market in the partner countries and the potential of the proposed technology.Global Challenges Research Fund (GCRF), provided by Research England

The study of the negative pion production in neutron-proton collisions at beam momenta below 1.8 GeV/c

A detailed investigation of the reaction np -> pp\pi^{-} has been carried out using the data obtained with the continuous neutron beam produced by charge exchange scattering of protons off a deuterium target. A partial wave event-by-event based maximum likelihood analysis was applied to determine contributions of different partial waves to the pion production process. The combined analysis of the np -> pp\pi^{-} and pp -> pp\pi^{0} data measured in the same energy region allows us to determine the contribution of isoscalar partial waves (I=0) in the momentum range from 1.1 up to 1.8 GeV/c. The decay of isoscalar partial waves into (^1S_0)_{pp}\pi$ channel provides a good tool for a determination of the pp S-wave scalar scattering length in the final state which was found to be a_{pp}=-7.5\pm 0.3 fm.Comment: 6 pages, 6 figure

Strong negative self regulation of Prokaryotic transcription factors increases the intrinsic noise of protein expression

Background Many prokaryotic transcription factors repress their own transcription. It is often asserted that such regulation enables a cell to homeostatically maintain protein abundance. We explore the role of negative self regulation of transcription in regulating the variability of protein abundance using a variety of stochastic modeling techniques. Results We undertake a novel analysis of a classic model for negative self regulation. We demonstrate that, with standard approximations, protein variance relative to its mean should be independent of repressor strength in a physiological range. Consequently, in that range, the coefficient of variation would increase with repressor strength. However, stochastic computer simulations demonstrate that there is a greater increase in noise associated with strong repressors than predicted by theory. The discrepancies between the mathematical analysis and computer simulations arise because with strong repressors the approximation that leads to Michaelis-Menten-like hyperbolic repression terms ceases to be valid. Because we observe that strong negative feedback increases variability and so is unlikely to be a mechanism for noise control, we suggest instead that negative feedback is evolutionarily favoured because it allows the cell to minimize mRNA usage. To test this, we used in silico evolution to demonstrate that while negative feedback can achieve only a modest improvement in protein noise reduction compared with the unregulated system, it can achieve good improvement in protein response times and very substantial improvement in reducing mRNA levels. Conclusions Strong negative self regulation of transcription may not always be a mechanism for homeostatic control of protein abundance, but instead might be evolutionarily favoured as a mechanism to limit the use of mRNA. The use of hyperbolic terms derived from quasi-steady-state approximation should also be avoided in the analysis of stochastic models with strong repressors