Search results for "Pumps"
showing 9 items of 29 documents
The cost of an action potential.
2000
Neuronal modules, or 'cell-assemblies', comprising millions of mutually interconnected cells have been postulated to form the basis of many functions of the brain, such as mood, sleep, hunger, vigilance, and more. Depending on the extent of the module, neurocommunication in cell-assemblies might exceed metabolic resources. A medium-size (10000 neurons) module would require at least 10 J per l of brain, based on a calculated cost of an isolated action potential (AP) of 10(11)-10(12) molecules of ATP per cm(2) of cell membrane, with an absolute minimum of 10(6) ATP at a node of Ranvier. The figure matches the cost of depolarizing the unmyelinated axon of the large monopolar cell in the blowfl…
Comparison between the energy performance of a ground coupled water to water heat pump system and an air to water heat pump system for heating and co…
2008
Abstract The investigation presented in this article was aimed at demonstrating the technical and economical feasibility of using ground source heat pump systems in mixed climate applications, where cooling requirements are dominant. We show an experimental comparison between a ground coupled heat pump system and a conventional air to water heat pump system, focussing at the heating and cooling energy performance. A direct comparison could be made as both systems are linked, in parallel, to the same building with exactly the same loads and climatic conditions. For a whole climatic season the results obtained show that the geothermal system saves, in terms of primary energy consumption, a 43…
Kinetics of proton release and uptake by channelrhodopsin-2
2012
Electrophysiological experiments showed that the light-activated cation channel channelrhodopsin-2 (ChR2) pumps protons in the absence of a membrane potential. We determined here the kinetics of transient pH change using a water-soluble pH-indicator. It is shown that ChR2 released protons prior to uptake with a stoichiometry of 0.3 protons per ChR2. Comparison to the photocycle kinetics revealed that proton release and uptake match rise and decay of the View the MathML sourceP3520 intermediate. As the View the MathML sourceP3520 state also represents the conductive state of cation channeling, the concurrence of proton pumping and channel gating implies an intimate mechanistic link of the tw…
Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications
2011
Single-track, asymmetric nanopores can currently be functionalised with a spatially inhomogeneous distribution of fixed charges and a variety of pore tip shapes. Optimising the asymmetric nanopore characteristics is crucial for practical applications in nanofluidics. We have addressed here this question for three cases based on different input/output chemical and electrical signals: (i) ion pumping up a concentration gradient by means of a periodic, time-dependent bias potential, (ii) information processing with a single nanopore acting as the nanofluidic diode of a logic gate, and (iii) electrical energy harvesting using a nanopore that separates two solutions of different salt concentrati…
Electrical hybrid heat pumps assisted by natural gas boilers: a review
2022
In this paper, a comprehensive review is performed on hybrid systems using electrical Heat Pumps for Heating, Ventilation & Air Conditioning systems and Domestic Hot Water production using case studies from 2016 to 2022. This work particularly focuses on studies that investigated systems with electrical Heat Pumps assisted by a gas boiler. Some studies that considered the exploitation of renewable energy sources, but not as a whole sub-stitute for fossil sources, have also been included. In particular, the analysis investigated the layouts of the systems by considering the type and the size of the components, the control methods applied (by distinguishing rule-based control methods and …
Urban Energy Hubs Economic Optimization and Environmental Comparison in Italy and Vietnam
2018
This paper aims to perform the minimization of the yearly energy supply cost from the main electricity and natural gas grids related to an energy district, considering the installation of different equipments. The case study refers to energy consumption of a medium density urban district and involves the exploitation of different energy sources and devices (photovoltaic systems, electrical energy storage, heat pumps and cogenerators). The analysis of the district energy supply is accomplished through an energy hub model. After a cost analysis related to the considered energy systems, a MILP algorithm was used for the optimization of a cost function and the simulation of various scenarios. M…
Pumps as turbines regulation study through a decision-support algorithm
2022
The water distribution network (WDN) is subject to water leakages due to pipes breaking, which induces a wastage of water and overconsumption of power for pumps. Leakages are directly related to pressure in the pipes. To reduce leakages, pressure reducing valves (PRV) are installed in water distribution networks to reduce pressure in the pipes. However, pressure reduction induces a loss of energy which is wasted within the PRV. To recover a part of this energy, pressure reducing valves can be replaced by using pumps as turbines (PATs). Since head and flow rates are variable in the WDN, it is necessary to regulate the PAT, which does not function properly under variable upstream conditions. …
On the Impact of Heat Pumps Electric Load on the Power Consumption of Lampedusa
2020
The present paper reports the results of a simulation study regarding the impact of the adoption of heat pumps for domestic hot water production in the island of Lampedusa (Italy). In the study, it has been assumed to replace electric storage water heaters with heat pumps at every dwelling of the about four thousand domestic end-users of the island and, in addition, to control the heat pump operation in order to enhance some parameters that characterize the quality of the generation and distribution system of the island (power peak, energy losses and voltage drop). According to the results of the simulations, while the replacement of electric storage water heaters with heat pumps is able to…
Continuous subcutaneous Insulin infusion leads to immediate, table, and long-term changes in metabolic control
2008
Background: Evaluations of continuous subcutaneous insulin infusion (CSII) usually focus on one pre- and one post-CSII measurement to assess metabolic therapy outcome. Aim: Extending this research, the aim of the present study was to provide a more fine-grained analysis of achieved glycaemic control. Methods: In 52 patients with type 1 diabetes (mean age of 37.85 years at CSII begin; s.d. ± 12.41), haemoglobin A1c (HbA1c) levels were assessed every 3 months over a period of 5 years (1 year before and 4 years after the introduction of CSII). Mixed models were utilized to describe changes in glycaemic control. Results: The pre–post course showed that already in the first quarter, a statis…