Loss Of Energy Production Research Articles

Protective Measures to Enhance Human Longevity and Aging: A Review of Strategies to Minimize Cellular Damage

Aging is a universal process in all life forms. The most current and widely accepted definition of human aging is a progressive loss of function and energy production that is accompanied by decreased fertility and increased mortality with advancing age. The most obvious and commonly recognized consequence of aging and energy decline is a decrease in skeletal muscle function, which affects every aspect of human life from the ability to walk and run, to chew, and swallow and digest food. Some crucial factors responsible for aging and longevity include genetics, environment, and nutrition, serious disease disorders such as cancer and cardio-vascular diseases, sarcoma and cell senescence. Oxidative damage caused due to the accumulation of molecular waste-by-products of the body’s metabolic processes, which our bodies are unable to break down or excrete, is chiefly responsible for aging and diseases. Regular physical activity, consumption of foods rich in phytochemicals and anti-oxidants, cessation of smoking, avoiding foods high in saturated and hydrogenated fats are some of the strategies that should be taken into account to delay aging and prolong longevity.

Massive tree mortality from flood pulse disturbances in Amazonian floodplain forests: The collateral effects of hydropower production

Large dams built for hydroelectric power generation alter the hydrology of rivers, attenuating the flood pulse downstream of the dam and impacting riparian and floodplain ecosystems. The present work mapped black-water floodplain forests (igapó) downstream of the Balbina Reservoir, which was created between 1983 and 1987 by damming the Uatumã River in the Central Amazon basin. We apply remote sensing methods to detect tree mortality resulting from hydrological changes, based on analysis of 56 ALOS/PALSAR synthetic aperture radar images acquired at different flood levels between 2006 and 2011. Our application of object-based image analysis (OBIA) methods and the random forests supervised classification algorithm yielded an overall accuracy of 87.2%. A total of 9800 km2 of igapó forests were mapped along the entire river downstream of the dam, but forest mortality was only observed below the first 49 km downstream, after the Morena rapids, along an 80-km river stretch. In total, 12% of the floodplain forest died within this stretch. We also detected that 29% of the remaining living igapó forest may be presently undergoing mortality. Furthermore, this large loss does not include the entirety of lost igapó forests downstream of the dam; areas which are now above current maximum flooding heights are no longer floodable and do not show on our mapping but will likely transition over time to upland forest species composition and dynamics, also characteristic of igapó loss. Our results show that floodplain forests are extremely sensitive to long-term downstream hydrological changes and disturbances resulting from the disruption of the natural flood pulse. Brazilian hydropower regulations should require that Amazon dam operations ensure the simulation of the natural flood-pulse, despite losses in energy production, to preserve the integrity of floodplain forest ecosystems and to mitigate impacts for the riverine populations.

Process resilience analysis based data-driven maintenance optimization: Application to cooling tower operations

In a process plant system, safe and reliable operations are highly sensitive to utilities such as power, steam, cooling water, nitrogen, and instrument air. These play an important role or act as safety barriers. This is because a disturbance in their supply is likely to affect process operations downstream, may reduce the production efficiency, and may lead to a sudden shutdown or contribute to an unsafe condition. The focus of this paper is to introduce and evaluate a model for survival of a process system under upset conditions using the Process Resilience Analysis Framework (PRAF). Resilience metrics within a data-driven and model-based optimization approach using Bayesian regression are employed integrating both technical (process parameter variations) and social (human and organizational) factors. Based on an optimization objective function accounting for the overall system performance in terms of energy consumption, maintenance costs, safety impact, environmental impact, asset damage, and production loss, the proposed methodology aims to determine the optimal maintenance policy for optimal and safer plant operations. The implementation of the survival model within the PRAF is demonstrated on a cooling tower operation example problem, where optimal operation and maintenance (preventive, corrective, and predictive) strategies are determined based on trade-off analysis of process revenue, safety impact, and maintenance costs.

Expert System Based on Fuzzy Logic: Application on Faults Detection and Diagnosis of DFIG

<p>Electrical energy production based on wind power is gaining area as renewable resources in the recent years because it gets clean energy with minimum cost. The major challenge for wind turbines is the electrical and the mechanical failures which can occur at any time causing damages and therefore it leads to machine downtimes and to energy production loss. To avoid this problem, several methods have been developed and used. In this paper, we proposed an expert system based on fuzzy logic which can detect and diagnosis DFIG’s faults via the Stator current’s signatures. The fuzzy inference system exploits the root mean square values of the stator’s currents according to expert’s rules to diagnosis the DFIG’s state. The smart proposed expert system is verified using simulations done under Matlab/Simulink. The obtained results are very interesting and show the efficiency of the proposed strategy.</p>

A cascading power sharing control for microgrid embedded with wind and solar generation

Abstract Traditionally, wind power and solar photovoltaic (PV) power generation is non-dispatchable and their normal operation relies on Maximum Power Point Tracking (MPPT) control. Therefore, it can be of highly disturbance to the system dispatch in particularly context of microgrids. To effectively fulfill dispatch command or market schedule, a novel cascading power sharing control (PSC) scheme is proposed to coordinate wind and solar PV power productions in microgrids while reducing the loss of renewable energy production involved. Considering different properties of wind and solar PV power generation systems, the discrepancies between dispatch command (market schedule) and actual renewable generation is firstly counterbalanced by adjusting wind power output via temperately storing or releasing kinetic energy of turbine rotors. Only when rotors of wind generator reach their limitations, should solar PVs begin to reduce their generation. The proposed PSC scheme is fully simulated in a microgrid with wind and solar PV, and the simulation results clearly indicate it can be more energy efficient than the traditional dispatch method while fulfilling the dispatch demand.

State-of-art review of the optimization methods to design the configuration of hybrid renewable energy systems (HRESs)

The current research aims to present an inclusive review of latest research works performed with the aim of improving the efficiency of the hybrid renewable energy systems (HRESs) by employing diverse ranges of the optimization techniques, which aid the designers to achieve the minimum expected total cost, while satisfying the power demand and the reliability. For this purpose, a detailed analysis of the different classification drivers considering the design factors such as the optimization goals, utilized optimization methods, grid type as well as the investigated technology has been conducted. Initial results have indicated that among all optimization goals, load demand parameters including loss of power supply probability (LPSP) and loss of load probability (LLP), cost, sizing (configuration), energy production, and environmental emissions are the most frequent design variables which have been cited the most. Another result of this paper indicates that almost 70% of the research projects have been dedicated towards the optimization of the off-grid applications of the HRESs. Furthermore, it has been demonstrated that, integration of the PV, wind and battery is the most frequent configuration. In the next stage of the paper, a review concerning the sizing methods is also carried out to outline the most common techniques which are used to configure the components of the HRESs. In this regard, an analysis covering the optimized indicators such as the cost drivers, energy index parameters, load indicators, battery’s state of charge, PV generator area, design parameters such as the LPSP, and the wind power generation to load ratio, is also performed.

Multidisciplinary design analysis and optimisation of a reference offshore wind plant

Motivated by the need to develop reference wind energy systems for optimisation and technology assessment studies, the International Energy Agency Wind Task 37 on Wind Energy Systems Engineering is developing a reference offshore wind power plant at the Dutch offshore wind energy areas Borssele III and IV. This paper presents a comparison between two approaches for developing the preliminary design of an offshore wind plant turbine layout, electrical collection system, and support structures. The first is a sequential approach, where components of the wind farm are optimised sequentially, each with its own objective function, thus neglecting potential interactions between them. The second approach uses Multidisciplinary Design Analysis and Optimisation (MDAO), where all components are jointly optimised with the overall system levelised cost of energy (LCOE) as a global objective function. Studying the cases of regular and irregular layouts, the integrated approach always shows a greater improvement in the LCOE of the final design compared to the design resulting from the traditional sequential approach. The most significant trade-off exploited by the MDAO approach used in this study is between losses in energy production due to turbine wake effects and the costs of electrical cable infrastructure.

Variable Utilization-Level Scheme for Load-Sharing Control of Wind Farm

Under maximum power point tracking control, wind power is not dispatchable and can be highly disturbing to the supply–demand balance control in the context of microgrid particularly. To effectively dispatch wind power according to, e.g., operator command or market schedule, a variable utilization level (UL) scheme is proposed for a wind power plant (WPP) to fulfill the dispatch order while reducing the loss of total energy production. Considering different wind conditions, the proposed scheme directs the power output for each wind turbine (WT) according to a specific UL, which is adaptively adjusted according to WT rotor speed so that less reduction of energy production can be ensured. Meanwhile, more rotational kinetic energy stored can be stored in WPP, which can be later released for system support when needed. The proposed variable UL scheme is fully investigated in a doubly fed induction generator-based WPP and the results clearly indicate the proposed scheme can harvest more energy than the conventional same UL one while fulfilling the dispatch demand.

The effect of silage type on animal performance, energy utilisation and enteric methane emission in lactating dairy cows

The present study aimed to investigate the effect of silage type on dry matter (DM) intake, nutrient digestibility, energy utilisation and methane (CH4) emission. Six late lactating Holstein dairy cows were used in a replicated 3 × 3 Latin square design study with three treatments (grass silage (GS), maize silage (MS) and whole-crop wheat silage (WCWS)) and three periods (3 weeks/period). All animals were offered forage ad libitum and 5.55 kg/day of a concentrate supplement, which contained (DM basis) 66.0% rapeseed meal, 28.3% soyabean meal and 5.7% a mineral/vitamin supplement. During each period, animals were subject to digestibility, CH4 and heat production measurements during the final 6 days using calorimeter chambers. The results demonstrated that total DM intake for MS and WCWS diets were higher (P < 0.001) than for the GS diet. Faecal energy and heat production loss for the GS diet were lower (P < 0.01) than for MS and WCWS diets. In contrast, cows fed the GS diet had higher (P < 0.05) urine energy loss compared with MS and WCWS diets. In comparison with the GS and MS diets, WCWS diet produced a lower CH4 loss per kg DM and organic matter intake (P < 0.01), and CH4 energy output as a proportion of gross energy and metabolisable energy intake (P < 0.05). The present study demonstrates that choice of forage types affects energy utilisation and CH4 emission in dairy cows.

Mitigating the negative impacts of tall wind turbines on bats: Vertical activity profiles and relationships to wind speed.

Wind turbines represent a source of hazard for bats, especially through collision with rotor blades. With increasing technical development, tall turbines (rotor-swept zone 50–150 m above ground level) are becoming widespread, yet we lack quantitative information about species active at these heights, which impedes proposing targeted mitigation recommendations for bat-friendly turbine operation. We investigated vertical activity profiles of a bat assemblage, and their relationships to wind speed, within a major valley of the European Alps where tall wind turbines are being deployed. To monitor bat activity we installed automatic recorders at sequentially increasing heights from ground level up to 65 m, with the goal to determine species-specific vertical activity profiles and to link them to wind speed. Bat call sequences were analysed with an automatic algorithm, paying particular attention to mouse-eared bats (Myotis myotis and Myotis blythii) and the European free-tailed bat (Tadarida teniotis), three locally rare species. The most often recorded bats were the Common pipistrelle (Pipistrellus pipistrellus) and Savi’s pipistrelle (Hypsugo savii). Mouse-eared bats were rarely recorded, and mostly just above ground, appearing out of risk of collision. T. teniotis had a more evenly distributed vertical activity profile, often being active at rotor level, but its activity at that height ceased above 5 ms-1 wind speed. Overall bat activity in the rotor-swept zone declined with increasing wind speed, dropping below 5% above 5.4 ms-1. Collision risk could be drastically reduced if nocturnal operation of tall wind turbines would be restricted to wind speeds above 5 ms-1. Such measure should be implemented year-round because T. teniotis remains active in winter. This operational restriction is likely to cause only small energy production losses at these tall wind turbines, although further analyses are needed to assess these losses precisely.

Hydropower Infrastructure Performance after the 2015 Gorkha, Nepal, Earthquake Sequence

Hydropower infrastructure, the primary source of electricity in Nepal, experienced severe damage following the 2015 Gorkha earthquake sequence, resulting in a 15% loss in the country's energy production. The performance of hydropower infrastructure during and after the sequence was one of the unique focuses of the Geotechnical Extreme Events Reconnaissance (GEER) study. The GEER team visited damaged hydropower projects along the Trishuli and Sunkoshi rivers by road and on foot, along with the ongoing 465-MW Upper Tamakoshi hydropower project by helicopter. The primary cause of damage to the hydropower infrastructure was landslide and rockfall debris falling on powerhouses, penstocks, and dam structures. Moreover, landslides blocked road access to many sites, delaying necessary repairs to damaged structures and resumption of power generation. Power production in Nepal before and after the 2015 Gorkha earthquake sequence, seismic performance of visited hydropower projects, and short- and long-term effects, together with residual risks for Nepal's hydro-power infrastructure, are discussed in this paper.

An analysis of offshore wind farm SCADA measurements to identify key parameters influencing the magnitude of wake effects

Abstract. For offshore wind farms, wake effects are among the largest sources of losses in energy production. At the same time, wake modelling is still associated with very high uncertainties. Therefore current research focusses on improving wake model predictions. It is known that atmospheric conditions, especially atmospheric stability, crucially influence the magnitude of those wake effects. The classification of atmospheric stability is usually based on measurements from met masts, buoys or lidar (light detection and ranging). In offshore conditions these measurements are expensive and scarce. However, every wind farm permanently produces SCADA (supervisory control and data acquisition) measurements. The objective of this study is to establish a classification for the magnitude of wake effects based on SCADA data. This delivers a basis to fit engineering wake models better to the ambient conditions in an offshore wind farm. The method is established with data from two offshore wind farms which each have a met mast nearby. A correlation is established between the stability classification from the met mast and signals within the SCADA data from the wind farm. The significance of these new signals on power production is demonstrated with data from two wind farms with met mast and long-range lidar measurements. Additionally, the method is validated with data from another wind farm without a met mast. The proposed signal consists of a good correlation between the standard deviation of active power divided by the average power of wind turbines in free flow with the ambient turbulence intensity (TI) when the wind turbines were operating in partial load. It allows us to distinguish between conditions with different magnitudes of wake effects. The proposed signal is very sensitive to increased turbulence induced by neighbouring turbines and wind farms, even at a distance of more than 38 rotor diameters.

A mitochondrial proteomics view of complex I deficiency in Candida albicans

Proteomic analyses were carried out on isolated mitochondrial samples of C. albicans from gene-deleted mutants (nuo1Δ, nuo2Δ and goa1Δ) as well as the parental strain in order to better understand the contribution of these three fungal-specific mitochondrial ETC complex I (CI) subunits to cellular activities. Herein, we identify 2333 putative proteins from four strains, in which a total of 663 proteins (28.5%) are putatively located in mitochondria. Comparison of protein abundances between mutants and the parental strain reveal 146 differentially-expressed proteins, of which 78 are decreased and 68 are increased in at least one mutant. The common changes across the three mutants include the down-regulation of nuclear-encoded CI subunit proteins as well as phospholipid, ergosterol and cell wall mannan synthesis, and up-regulated proteins in CIV and the alternative oxidase (AOX2). As for gene-specific functions, we find that NUO1 participates in nucleotide synthesis and ribosomal biogenesis; NUO2 is involved in vesicle trafficking; and GOA1 appears to regulate membrane transporter proteins, ROS removal, and substrates trafficking between peroxisomes and mitochondria. The proteomic view of general as well as mutant-specific proteins further extends our understanding of the functional roles of non-mammalian CI-specific subunit proteins in cell processes. Particularly intriguing is the confirmation of a regulatory role for GOA1 on ETC function, a protein found almost exclusively in Candida species. SignificanceFungal mitochondria are critical for fungal pathogenesis. The absence of any of the three fungal specific CI subunits in mitochondria causes an avirulence phenotype of C. albicans in a murine model of invasive disease. As model yeast (Saccharomyces cerevisiae) lacks a CI and is rarely a pathogen of humans, C. albicans is a better choice for establishing a link between mitochondrial CI and pathogenesis. Apart from the general effects of CI mutants on respiration, previous phenotyping of these mutants were quite similar to each other or to CI conservative subunit. By comparison to transcriptional data, the proteomic data obtained in this study indicate that biosynthetic events in each mutant such as cell wall and cell membrane phospholipids and ergosterol are generally decreased in both transcriptomal and translational levels. However, in the case of mitochondrial function, glycolysis/gluconeogenesis, and ROS scavengers, often gene changes are opposite that of proteomic data in mutants. We hypothesize that the loss of energy production in mutants is compensated by increases in protein levels of glycolysis, gluconeogenesis, and anti-ROS scavengers that at least extend mutant survival.

Therapeutic targeting of the pathological triad of extrasynaptic NMDA receptor signaling in neurodegenerations.

Activation of extrasynaptic N-methyl-d-aspartate (NMDA) receptors causes neurodegeneration and cell death. The disease mechanism involves a pathological triad consisting of mitochondrial dysfunction, loss of integrity of neuronal structures and connectivity, and disruption of excitation-transcription coupling caused by CREB (cyclic adenosine monophosphate-responsive element-binding protein) shut-off and nuclear accumulation of class IIa histone deacetylases. Interdependency within the triad fuels an accelerating disease progression that culminates in failure of mitochondrial energy production and cell loss. Both acute and slowly progressive neurodegenerative conditions, including stroke, Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's disease, share increased death signaling by extrasynaptic NMDA receptors caused by elevated extracellular glutamate concentrations or relocalization of NMDA receptors to extrasynaptic sites. Six areas of therapeutic objectives are defined, based on which a broadly applicable combination therapy is proposed to combat the pathological triad of extrasynaptic NMDA receptor signaling that is common to many neurodegenerative diseases.

Technical and Economic Feasibility study on Repowering of Wind Farms

Objectives: The main objective of the paper is to perform a repowering assessment of an old wind farm consisting of 2 bladed turbines located at Gudimangalam near Coimbatore in Tamil Nadu which is a good wind potential site. Methods/Statistical Analysis: Repowering refers to the replacement of first generation small capacity wind turbines with modern multi megawatt wind turbines that can produce more energy than before from the same site. Technical analysis of the site is done using WAsP software with the help of wind data collected from a met mast at the site and includes the calculation of Net Annual Energy Production and Wake losses. Net Annual Energy Production and Wake losses are the primary indicators for selecting the best options for repowering. The option selected is further supported by calculating the economic performance indices. The total repowering has been accomplished through partial repowering executed in three stages. Partial repowering refers to the replacement of only few of the turbines from the existing wind farm rather than replacing the whole farm. The economic feasibility of every repowering option has been studied based on the calculation of the economic performance indices like ALCoG, Payback Period and IRR. Findings: The study mainly results in framing a procedure for performing total repowering for any site through the optimization of best possible partial repowering options. The existing site comprises 18 turbines of 450 kW rating and is having a net AEP of 14.5 GWh with a wake loss of 3.82%. The Plant Load Factor (PLF) is obtained to be 20.44%. The best possible total repowering option is found to be producing a net AEP of 65.287 GWh with a wake loss of 2.36% and included 9 Suzlon S95 2.1 MW turbines which are four times the AEP of the existing farm. The three stages of partial repowering also include replacement of 6 old turbines by 3 new turbines in each stage. Finally the total repowering is reached through the execution of partial repowering options in three stages and it results in close proximity to the best possible total repowering option in both technical and economic aspects. The final repowering eventually attained results in a net AEP of 65.28 GWh with a wake loss of 2.36% which is the exact match of the best possible total repowering option found in the beginning. The total repowering also leads to an improvement in PLF i.e. almost doubles the PLF to 39.42%. Application/Improvements: This procedure can be very useful where the initial investment is an important factor. The study infers that performing total repowering through optimization process is more beneficial than performing partial repowering randomly.

Dark matter constraints from stellar evolution

The study of dark matter constraints from its effect on star evolution has been discussed in recent years. We propose a star evolution simulation approach to determine those costraints from properties related to star evolutionary stages and propose globular cluster observables in order to check those constraints. My work in progress (my PhD project research) employs FRANEC code to simulate complete star evolution from pre-main sequence to AGB phase, and regards several DM candidates like axions or WIMPs, motivated by different unsolved physical problems. Detailed energy production or energy loss due to DM particles are included, taking into account the expected interaction between dark matter particles and stellar plasma within different models.

Reactor Reactivity Excess Optimization for Xenon Poisoning Compensation Taking Account of Force-Majeure Circumstances

The energy-production losses versus the reserved reactivity excess as a function of the probability of accidental shutdown of the reactor are presented. A formulation of the optimization problem of power control during the period of threat under force-majeure circumstances is examined. The efficacy of optimization and the character of the optimal regimes as a function of the duration of the period of threat are presented.

Enteric Methane Emission, Energetic Efficiency and Energy Requirements for the Maintenance of Beef Cattle in the Tropics

This study was conducted to determine the energy balance of beef cattle by indirect animal calorimetry utilizing a ventilated head box respiration system. Fifteen native Thai bulls were randomly allocated to one of three dietary metabolizable energy intake (MEI) levels (1.1 × maintenance, 1.5 × maintenance and 1.9 × maintenance) in a completely randomized design for a 116 day feeding trial. Animals were allocated to individual metabolic cages for the determination of digestibility and energy balance. Heat production was determined from oxygen consumption, carbon dioxide and methane production. The results showed that dry matter, organic matter and crude protein intake were increased (P 0.05) by MEI levels. The energy loss in feces and urine (% of gross energy intake) were not different (P > 0.05); however, enteric methane conversion rate (% of methane energy loss per gross energy intake) and heat energy production loss (% gross energy intake) were linearly decreased (P < 0.01) with increasing MEI levels. Methane conversion rates ranged from 8.4 to 10.0% and appeared to have been underestimated by the Intergovernmental Panel on Climate Change 6.5% default values set for cattle fed low quality crop residues and by-products. The estimate of metabolizable energy requirements for maintenance was measured using linear regression analysis derived for native Thai cattle was 520 kilojoules per kilogram of metabolic body weight per day. Increased dietary intake levels reduced enteric methane emissions in beef cattle fed on tropical feedstuffs. The results of the present study indicated that greater dietary intake feeding strategy in cattle fed above the maintenance level resulted in improved energetic efficiency utilization, and thus improved energy retention because of the reduction of enteric methane energy emission and heat production. Discipline: Animal industry Additional key words: cattle, energy requirements, enteric methane, tropical This paper reports results obtained in the international project on “Establishment of feeding standard of beef cattle and feedstuff database in Indochina.” The Japan International Research Center for Agricultural Sciences, Department of Livestock Development, Ministry of Agriculture and Cooperatives, Thailand, and Khon Kaen University took responsibility for all subjects picked up in the project, implemented main subjects jointly and managed the project. Since it is essential to construct a regional research cooperation network for the efficient achievement of the targets, other research organizations such as Mahasarakham University, Ubon Ratchatanee University, Rajamangala University of Technology-Isan, Suranaree University of Technology, Chiang Mai University, Maejo University, Prince of Songkla University, National University of Laos, Lao PDR, and Royal University of Agriculture, Cambodia were also involved in the project. The project was implemented during the five-year period from 2006 to March 2011. Present address: 4 Division of Animal Sccience, Faculty of Technology, Mahasarakham University (Mahasarakham 44150, Thailand) 5 NARO Institute of Livestock and Grassland Science (Tsukuba, Ibaraki 305-0901, Japan) *Corresponding author: e-mail: kritapon@kku.ac.th Received 2 December 2014; accepted 31 March 2015.

Choosing co-substrates to supplement biogas production from animal slurry – A life cycle assessment of the environmental consequences

Biogas production from animal slurry can provide substantial contributions to reach renewable energy targets, yet due to the low methane potential of slurry, biogas plants depend on the addition of co-substrates to make operations profitable. The environmental performance of three underexploited co-substrates, straw, organic household waste and the solid fraction of separated slurry, were assessed against slurry management without biogas production, using LCA methodology. The analysis showed straw, which would have been left on arable fields, to be an environmentally superior co-substrate. Due to its low nutrient content and high methane potential, straw yields the lowest impacts for eutrophication and the highest climate change and fossil depletion savings. Co-substrates diverted from incineration to biogas production had fewer environmental benefits, due to the loss of energy production, which is then produced from conventional fossil fuels. The scenarios can often provide benefits for one impact category while causing impacts in another.

Glucose metabolism is inhibited by caspases upon the induction of apoptosis.

Rapidly proliferating cells, such as cancer cells, have adopted aerobic glycolysis rather than oxidative phosphorylation to supply their energy demand; this phenomenon is known as ‘the Warburg effect'. It is now widely accepted that during apoptosis the loss of energy production, orchestrated by caspases, contributes to the dismantling of the dying cell. However, how this loss of energy production occurs is still only partially known. In the present work, we established that during apoptosis the level of cellular ATP decreased in a caspase-dependent manner. We demonstrated that this decrease in ATP content was independent of any caspase modification of glucose uptake, ATP consumption or reactive oxygen species production but was dependent on a caspase-dependent inhibition of glycolysis. We found that the activity of the two glycolysis-limiting enzymes, phosphofructokinase and pyruvate kinase, were affected by caspases, whereas the activity of phosphoglycerate kinase was not, suggesting specificity of the effect. Finally, using a metabolomic analysis, we observed that caspases led to a decrease in several key metabolites, including phosphoserine, which is a major regulator of pyruvate kinase muscle isozyme activity. Thus, we have established that during apoptosis, caspases can shut down the main energy production pathway in cancer cells, leading to the impairment in the activity of the two enzymes controlling limiting steps of glycolysis.