Heat shock protein 90 (Hsp90) is an ATP-dependent molecular chaperone which is essential in eukaryotes. It is required for the activation and stabilization of a wide variety of client proteins and ...many of them are involved in important cellular pathways. Since Hsp90 affects numerous physiological processes such as signal transduction, intracellular transport, and protein degradation, it became an interesting target for cancer therapy. Structurally, Hsp90 is a flexible dimeric protein composed of three different domains which adopt structurally distinct conformations. ATP binding triggers directionality in these conformational changes and leads to a more compact state. To achieve its function, Hsp90 works together with a large group of cofactors, termed co-chaperones. Co-chaperones form defined binary or ternary complexes with Hsp90, which facilitate the maturation of client proteins. In addition, posttranslational modifications of Hsp90, such as phosphorylation and acetylation, provide another level of regulation. They influence the conformational cycle, co-chaperone interaction, and inter-domain communications. In this review, we discuss the recent progress made in understanding the Hsp90 machinery.
The aim of this article is to survey the huge literature that has emerged in the last four decades following Nordhaus’s (Rev Econ Stud 42(2):169–190, 1975) publication on political business cycles ...(PBCs). I first propose some developments in history of thought to examine the context in which this ground-breaking contribution saw the light of the day. I also present a simplified version of Nordhaus’s model to highlight his key results. I detail some early critiques of this model and the fields of investigations to which they gave birth. I then focus on the institutional context and examine its influence on PBCs, the actual research agenda. Finally, I derive some paths for future research.
•A novel CO2 based combined cooling, heating and power system is proposed.•The CO2 based refrigeration cycle driven by the bottoming tCO2 power cycle is developed.•Parametric analyses are performed ...to study effects of key parameters on CCHP system performances.•Optimizations on the thermodynamic and economic performances of the CCHP system are conducted.
In this paper, a novel combined cooling, heating and power (CCHP) system consisting of a supercritical carbon dioxide (sCO2) power cycle, a transcritical carbon dioxide (tCO2) power cycle with a carbon dioxide based refrigeration cycle, and a direct heating (DH) system is proposed. In the novel system, the waste heat from sCO2 power cycle is recovered by the tCO2 power cycle to generate additional power and drive the CO2 based refrigeration cycle to provide cooling for users, and the DH system further recovers the waste heat from the sCO2/tCO2 power cycle and the refrigeration compressor outflow to feed heat for users. Mathematical models are developed to conduct the thermodynamic and exergoeconomic analysis of the proposed CCHP system, and parametric studies on the effects of different key parameters on the system performance are carried out. Besides that, the optimization and comparative researches are performed to find out and compare the maximum system exergy efficiency and minimum total product unit cost for the proposed CCHP system and the stand-alone sCO2 system. The results indicate that for different users’ demands, the proposed CCHP system can obtain the best improvement by 12.01% for the system exergy efficiency and 5.14% for the total product unit cost, and the worst improvement by 10.83% for the system exergy efficiency and 4.12% for the total product unit cost, compared with the stand-alone sCO2 power cycle. These results confirm the obvious superiority in thermodynamic and economic performance of the proposed CCHP system under different users’ demands.
Cell cycles, essential for biological function, have been investigated extensively. However, enabling a global understanding and defining a physical quantification of the stability and function of ...the cell cycle remains challenging. Based upon a mammalian cell cycle gene network, we uncovered the underlying Mexican hat landscape of the cell cycle. We found the emergence of three local basins of attraction and two major potential barriers along the cell cycle trajectory. The three local basins of attraction characterize the G1, S/G2, and M phases. The barriers characterize the G1 and S/G2 checkpoints, respectively, of the cell cycle, thus providing an explanation of the checkpoint mechanism for the cell cycle from the physical perspective. We found that the progression of a cell cycle is determined by two driving forces: curl flux for acceleration and potential barriers for deceleration along the cycle path. Therefore, the cell cycle can be promoted (suppressed), either by enhancing (suppressing) the flux (representing the energy input) or by lowering (increasing) the barrier along the cell cycle path. We found that both the entropy production rate and energy per cell cycle increase as the growth factor increases. This reflects that cell growth and division are driven by energy or nutrition supply. More energy input increases flux and decreases barrier along the cell cycle path, leading to faster oscillations. We also identified certain key genes and regulations for stability and progression of the cell cycle. Some of these findings were evidenced from experiments whereas others lead to predictions and potential anticancer strategies.
Supercritical carbon dioxide (S-CO2) cycle is proven to be one promising alternative to provide high efficiency and has been developed for a wide range of energy conversion applications. Thermal ...efficiency of the S-CO2 cycle can be further improved by incorporating an appropriate bottoming cycle utilizing the residual heat. In this paper, an Organic Rankine Cycle (ORC) is added to the S-CO2 cycle for heat recovery. Different recuperative ratios of the topping S-CO2 cycle are considered and the influence of heat source initial temperature and total heat load on the bottoming ORC is evaluated. Two configurations of the S-CO2-ORC combined cycle system are presented, one without a pre-cooler and the other still with a pre-cooler, corresponding to total and partial residual heat recovery respectively. Though the entire residual heat recovery by the bottoming cycle could definitely increase the system thermal efficiency, the low ORC evaporation temperature and mediocre ORC performance leads to a limited improvement. While in the combined cycle system with a pre-cooler, higher ORC evaporation temperature could be attained and it has a remarkable effect on the ORC performance, even though part of the topping cycle residual heat is discharged to the ambient. The simulation results reveal that the S-CO2-ORC combined cycle system performance could be significantly improved through this parametric optimization. The recompression S-CO2 cycle with bottoming ORC is then analyzed and thermal performance is improved based on the previous optimization results. The bottoming ORC could effectively recover the residual heat of the topping S-CO2 cycle and increase the system thermal efficiency, thus it can be considered and applied in similar practical cases.
•An ORC is added to the S-CO2 cycle for residual heat recovery.•Different recuperative ratios of the topping cycle is considered.•Influence of the heat source conditions on the bottoming ORC is evaluated.•Parametric optimization of the combined cycle system is conducted.
•A combined-cycle S-CO2/ORC system is presented for ICE waste-heat recovery.•Comparisons are shown with a standalone S-CO2 cycle system for a 1170 kW ICE.•The combined-cycle system has a 58% higher ...maximum net power output.•The combined-cycle system has a 4% higher minimum specific investment cost (4670 $/kW)•Significant performance improvements can be achieved for a range of ICEs of different sizes.
Supercritical CO2 (S-CO2) power-cycle systems are a promising technology for waste-heat recovery from internal combustion engines (ICEs). However, the effective utilisation of the heat from both the exhaust gases and cooling circuit by a standalone S-CO2 cycle system remains a challenge due to the unmatched thermal load of these heat sources, while a large amount of unexploited heat is directly rejected in the system’s pre-cooler. In this paper, a combined-cycle system for ICE waste-heat recovery is presented that couples an S-CO2 cycle to a bottoming organic Rankine cycle (ORC), which recovers heat rejected from the S-CO2 cycle system, as well as thermal energy available from the jacket-water and exhaust-gas streams that have not been utilised by the S-CO2 cycle system. Parametric optimisation is implemented to determine operating conditions for both cycles from thermodynamic and economic perspectives. With a baseline case using a standalone S-CO2 cycle system for an ICE with a rated power output of 1170 kW, our investigation reveals that the combined-cycle system can deliver a maximum net power output of 215 kW at a minimum specific investment cost (SIC) of 4670 $/kW, which are 58% and 4% higher than those of the standalone S-CO2 cycle system, respectively. A range of ICEs of different sizes are also considered, with significant performance improvements indicating a promising potential of exploiting such combined-cycle systems. This work motivates the pursuit of further performance improvements to waste-heat recovery systems from ICEs and other similar applications.
Most of Earth's terrestrial surface is made up of sloping landscapes. The lateral distribution of topsoil by erosion controls the availability, stock, and persistence of essential elements in the ...terrestrial ecosystem. Over the last two decades, the role of soil erosion in biogeochemical cycling of essential elements has gained considerable interest from the climate, global change, and biogeochemistry communities after soil erosion and terrestrial sedimentation were found to induce a previously unaccounted terrestrial sink for atmospheric carbon dioxide. More recent studies have highlighted the role of erosion in the persistence of organic matter in soil and in the biogeochemical cycling of elements beyond carbon
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Here we synthesize available knowledge and data on how erosion serves as a major driver of biogeochemical cycling of essential elements. We address implications of erosion-driven changes in biogeochemical cycles on the availability of essential elements for primary production, on the magnitude of elemental exports downstream, and on the exchange of greenhouse gases from the terrestrial ecosystem to the atmosphere. Furthermore, we explore fates of eroded material and how terrestrial mass movement events play major roles in modifying Earth's climate.
•A novel triple power cycle is proposed and evaluated using thermoeconomic analysis.•A gas turbine cycle is combined with an s-CO2 recompression cycle and ORC.•The triple cycle is optimized using a ...particle swarm optimization algorithm.•The optimum efficiency and LCOE are 0.521 and $52.819/MWh, respectively.•The proposed cycle has superiority over a very efficient cycle from the literature.
In this study, a novel triple power cycle is proposed where waste heat from a gas turbine cycle is utilized to drive a supercritical carbon dioxide (s-CO2) recompression cycle and a recuperative organic Rankine cycle (ORC) in sequence. A detailed thermoeconomic model is developed and implemented in MATLAB to evaluate the performance of the proposed cycle under different operating conditions. Optimization using a particle swarm optimization (PSO) algorithm is performed to minimize the levelized cost of electricity (LCOE) and determine the optimum design conditions of the cycle. The optimization results show that for a 100 MW cycle, the overall thermal efficiency and LCOE are 0.521 and $52.819/MWh, respectively. The turbine inlet temperature of the gas turbine and s-CO2 cycles are found as the most influential parameters on the thermoeconomic performance of the triple cycle. The proposed triple cycle shows an excellent waste energy recovery potential and superiority over a very thermodynamically efficient cycle from the literature, which included a gas turbine topping cycle and a complex cascade s-CO2 power cycle used a bottoming cycle. The proposed triple cycle shows up to 0.9% points higher efficiency while it has fewer heat exchangers and turbomachinery than the cycle from the literature.
Life Cycle Assessment (LCA) has developed in Australia over the last 20 years into a technique for systematically identifying the resource flows and environmental impacts associated with the ...provision of products and services. Interest in LCA has accelerated alongside growing demand to assess and reduce greenhouse gas emissions across different manufacturing and service sectors. This book focuses on the reflective practice of LCA, and provides critical insight into the technique and how it can be used as a problem-solving tool. It describes the distinctive strengths and limitations of LCA, with an emphasis on practice in Australia, as well as in waste management, the built environment, water and agriculture. Supported by examples and case studies, each chapter investigates contemporary challenges for environmental assessment and performance improvement in these key sectors. Students, environmental managers and CEOs, consultants, and government and policy decision-makers will benefit from this book.
Quiescent neural stem cells (NSCs) in the adult mouse brain are the source of neurogenesis that regulates innate and adaptive behaviors. Adult NSCs in the subventricular zone are derived from a ...subpopulation of embryonic neural stem-progenitor cells (NPCs) that is characterized by a slower cell cycle relative to the more abundant rapid cycling NPCs that build the brain. Yet, how slow cell cycle can cause the establishment of adult NSCs remains largely unknown. Here, we demonstrate that Notch and an effector Hey1 form a module that is upregulated by cell cycle arrest in slowly dividing NPCs. In contrast to the oscillatory expression of the Notch effectors Hes1 and Hes5 in fast cycling progenitors, Hey1 displays a non-oscillatory stationary expression pattern and contributes to the long-term maintenance of NSCs. These findings reveal a novel division of labor in Notch effectors where cell cycle rate biases effector selection and cell fate.
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