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Since the work of Semon was rediscovered by Schacter in 1978, there has been a renewed interest is searching for the “engram” as the locus of memory in the brain and Hebb’s cell assembly has been equated with Semon’s engram. There have been many theories of memory involving some concept of synaptic change, culminating in the “Hebb Synapse” theory in 1949. However, Hebb said that the idea that any two cells or systems of cells that are repeatedly active at the same time will tend to become “associated,” was not his idea, but an old one. In this manuscript we give an overview of some of the theories of the neural basis of learning and memory before Hebb and describe the synaptic theory of William McDougall, which appears to have been an idea ahead of its time; so far ahead of its time that it was completely ignored by his contemporaries. We conclude by examining some critiques of McDougall’s theory of inhibition and with a short discussion on the fate of neuroscientists whose ideas were neglected when first presented but were accepted as important many decades later.

Understanding 3D genome structure requires high throughput, genome-wide approaches. However, assays for all vs. all chromatin interaction mapping are expensive and time consuming, which severely restricts their usage for large-scale mutagenesis screens or for mapping the impact of sequence variants. Computational models sophisticated enough to grasp the determinants of chromatin folding provide a unique window into the functional determinants of 3D genome structure as well as the effects of genome variation.A chromatin interaction predictor should work at the base pair level but also incorporate large-scale genomic context to simultaneously capture the large scale and intricate structures of chromatin architecture. Similarly, to be a flexible and generalisable approach it should also be applicable to data it has not been explicitly trained on. To develop a model with these properties, we designed a deep neuronal network (deepC) that utilizes transfer learning to accurately predict chromatin interactions from DNA sequence at megabase scale. The model generalizes well to unseen chromosomes and works across cell types, Hi-C data resolutions and a range of sequencing depths. DeepC integrates DNA sequence context on an unprecedented scale, bridging the different levels of resolution from base pairs to TADs. We demonstrate how this model allows us to investigate sequence determinants of chromatin folding at genome-wide scale and to predict the importance of regulatory elements and the impact of sequence variations.

Spatial navigation is a universal behavior that varies depending on goals, experience and available sensory stimuli. Spatial navigational tasks are routinely used to study learning, memory and goal-directed behavior, in both animals and humans. One popular paradigm for testing spatial memory is the Morris water maze, where subjects learn the location of a hidden platform that offers escape from a pool of water. Researchers typically express learning as a function of the latency to escape, though this reveals little about the underlying navigational strategies. Recently, a number of studies have begun to classify water maze search strategies in order to clarify the precise spatial and mnemonic functions of different brain regions, and to identify which aspects of spatial memory are disrupted in disease models. However, despite their usefulness, strategy analyses have not been widely adopted due to the lack of software to automate analyses. To address this need we developed Pathfinder, an open source application for analyzing spatial navigation behaviors. In a representative dataset, we show that Pathfinder effectively characterizes the development of highly-specific spatial search strategies as male and female mice learn a standard spatial water maze. Pathfinder can read data files from commercially- and freely-available software packages, is optimized for classifying search strategies in water maze paradigms, but can also be used to analyze 2D navigation by other species, and in other tasks, as long as timestamped xy coordinates are available. Pathfinder is simple to use, can automatically determine pool and platform geometry, generates heat maps, analyzes navigation with respect to multiple goal locations, and can be updated to accommodate future developments in spatial behavioral analyses. Given these features, Pathfinder may be a useful tool for studying how navigational strategies are regulated by the environment, depend on specific neural circuits, and are altered by pathology.

MotivationConvolutional neural networks (CNNs) have been trememdously successful in many contexts, particularly where training data is abundant and signal-to-noise ratios are large. However, when predicting noisily observed biological phenotypes from DNA sequence, each training instance is only weakly informative, and the amount of training data is often fundamentally limited, emphasizing the need for methods that make optimal use of training data and any structure inherent in the model.ResultsHere we show how to combine equivariant networks, a general mathematical framework for handling exact symmetries in CNNs, with Bayesian dropout, a version of MC dropout suggested by a reinterpretation of dropout as a variational Bayesian approximation, to develop a model that exhibits exact reverse-complement symmetry and is more resistant to overtraining. We find that this model has increased power and generalizability, resulting in significantly better predictive accuracy compared to standard CNN implementations and state-of-art deep-learning-based motif finders. We use our network to predict recombination hotspots from sequence, and identify high-resolution binding motifs for the recombination-initiation protein PRDM9, which were recently validated by high-resolution assays. The network achieves a predictive accuracy comparable to that attainable by a direct assay of the H3K4me3 histone mark, a proxy for PRDM9 binding.Availabilityhttps://github.com/luntergroup/EquivariantNetworksContactrichard.brown@well.ox.ac.uk, gerton.lunter@well.ox.ac.ukSupplementary informationSupplementary data are available at Bioinformatics online.

Active whisking in mice and rats is one of the fastest behaviours known in mammals and is used to guide complex behaviours such as exploration and navigation. During object contact, whisker movements are actively controlled and undergo robust changes in timing, speed and position. This study quantifies whisker movements in 6- to 7-month old male and female 5xFAD mice, and their C57/SJL F1 wild-type (WT) controls. As well as genotype, we examined sex differences and the effects of retinal degeneration (rd). Mice were filmed using a high-speed video camera at 500 frames per second (fps), under infrared light while behaving freely in three tasks: object exploration, sequential object exploration and tunnel running. Measures of whisker position, amplitude, speed and asymmetry were extracted and analysed for each task. The 5xFAD mice had significantly altered whisker angular positions, amplitude and asymmetry during object contacts and female 5xFAD mice with rd had lower mean angular positions during object contact. There were no significant effects of genotype on sequential object exploration or on tunnel running but differences due to sex and rd were found in both tasks, with female mice making larger and faster whisker movements overall, and mice with rd making larger and faster whisker movements during object contact. There were sex differences in whisker movements during sequential object exploration and females with rd had higher whisker retraction speeds in tunnel running. These data show that measuring whisker movements can quantify genotype and sex differences and the effects of rd during exploratory behaviour in these mice.

Increased evidence suggests that marine unsaturated fatty acids (FAs) can protect neurons from amyloid-β (Aβ)-induced neurodegeneration. Nuclear magnetic resonance (NMR), high performance liquid chromatography (HPLC) and gas chromatography (GC) assays showed that the acetone extract 4-2A obtained from shrimp Pandalus borealis industry processing wastes contained 67.19% monounsaturated FAs and 16.84% polyunsaturated FAs. The present study evaluated the anti-oxidative and anti-inflammatory effects of 4-2A in Aβ25–35-insulted differentiated SH-SY5Y cells. Cell viability and cytotoxicity were measured by using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Quantitative PCR and Western blotting were used to study the expression of neurotrophins, pro-inflammatory cytokines and apoptosis-related genes. Administration of 20 μM Aβ25–35 significantly reduced SH-SY5Y cell viability, the expression of nerve growth factor (NGF) and its tyrosine kinase TrkA receptor, as well as the level of glutathione, while increased reactive oxygen species (ROS), nitric oxide, tumor necrosis factor (TNF)-α, brain derived neurotrophic factor (BDNF) and its TrkB receptor. Aβ25–35 also increased the Bax/Bcl-2 ratio and Caspase-3 expression. Treatment with 4-2A significantly attenuated the Aβ25–35-induced changes in cell viability, ROS, GSH, NGF, TrkA, TNF-α, the Bax/Bcl-2 ratio and Caspase-3, except for nitric oxide, BDNF and TrKB. In conclusion, 4-2A effectively protected SH-SY5Y cells against Aβ-induced neuronal apoptosis/death by suppressing inflammation and oxidative stress and up-regulating NGF and TrKA expression.

Brain glucose hypometabolism has been observed in Alzheimer’s disease (AD) patients, and is detected with 18 F radiolabelled glucose, using positron emission tomography. A pathological hallmark of AD is deposition of brain β - amyloid plaques that may influence cerebral glucose metabolism. The five times familial AD (5XFAD) mouse is a model of brain amyloidosis exhibiting AD-like phenotypes. This study examines brain β -amyloid plaque deposition and 18 FDG uptake, to search for an early biomarker distinguishing 5XFAD from wild-type mice. Thus, brain 18 FDG uptake and plaque deposition was studied in these mice at age 2, 5 and 13 months. The 5XFAD mice demonstrated significantly reduced brain 18 FDG uptake at 13 months relative to wild-type controls but not in younger mice, despite substantial β - amyloid plaque deposition. However, by comparing the ratio of uptake values for glucose in different regions in the same brain, 5XFAD mice could be distinguished from controls at age 2 months. This method of measuring altered glucose metabolism may represent an early biomarker for the progression of amyloid deposition in the brain. We conclude that brain 18 FDG uptake can be a sensitive biomarker for early detection of abnormal metabolism in the 5XFAD mouse when alternative relative uptake values are utilized.

Hypersonic hybrid hydrodynamic-molecular gas flow solvers are required to satisfy the two essential requirements of any high-speed reacting code, these being physical accuracy and computational efficiency. The James Weir Fluids Laboratory at the University of Strathclyde is currently developing an open-source hybrid code which will eventually reconcile the direct simulation Monte-Carlo method, making use of the OpenFOAM application called dsmcFoam, and the newly coded open-source two-temperature computational fluid dynamics solver named hy2Foam. In conjunction with employing the CVDV chemistry-vibration model in hy2Foam, novel use is made of the QK rates in a CFD solver. In this paper, further testing is performed, in particular with the CFD solver, to ensure its efficacy before considering more advanced test cases. The hy2Foam and dsmcFoam codes have shown to compare reasonably well, thus providing a useful basis for other codes to compare against.

During re-entry, a spacecraft will experience flow conditions ranging from highly rarefied to continuum. To simulate regions in between, a hydrodynamic-molecular gas hybrid solver should be used to provide accuracy and effciency. Currently available hybrid codes are in-house codes or do not provide the capabilities to simulate all of the phenomena a spacecraft will experience during re-entry. An open-source CFD-DSMC hybrid code is being developed within the OpenFOAM framework, coupling the solvers dsmcFoam and hy2Foam. In this paper, comparison between the CFD, DSMC and hybrid codes have been performed for simple cases. The dsmcFoam and the hybrid code have shown to compare satisfactorily.

Much of the original historical data behind the greatest discoveries in neuroscience are now lost. However, a recently rediscovered box of histological slides belonging to Sir Charles Sherrington, a pioneer in spinal cord and motor control research, has survived at the University of Oxford since 1936. Sherrington coined the term 'synapse', developed the concept of inhibition in neuronal function, demonstrated the integration of sensory and motor actions of the nervous system, and examined the synaptic activity of single neurons and their integration into neuronal circuits. Here, we explore Sherrington's lifetime of discoveries, with reference to histological specimens from his box of slides.

To decrease the need for fossil fuels, the alternative energy resources must be not only economically viable but also sustainable in the long term. One of the most promising alternatives is the marine renewable energy resource. The relatively young marine energy industry is presented with two challenges: first, to deliver a continuous reliable power supply, and second, to minimize potentially harmful effects of the power extraction on the marine environment. The requirement to understand the interactions between a tidal turbine and the surrounding flow environment motivated this work. A tidal turbine mounted on the seabed induces a wake that extends far downstream of the device. As the direction of tidal flow changes, so does the position of the wake with respect to the device. The detailed study of the turbine wake has been conducted by means of computer simulations. An existing finite-volume computer model called the vorticity transport model has been modified to suit the purpose of simulating the wake of a horizontal axis tidal turbine subjected to a nonuniform flow typical of that close to the seabed. High-resolution computer simulations suggest that a progressive fragmentation of the vortical structure occurs during the development of the wake of a tidal turbine. The predicted fragmentation generates small-scale unsteady flow phenomena beyond five rotor diameters downstream of the device in the area previously thought unaffected by the presence of a tidal turbine. The effects of nonuniform flow on the vorticity structure downstream of a tidal turbine and the fragmentation process are analyzed in this work.

Numerical meshes of both cork and carbon fiber ablative materials in their virgin and pyrolized states, with realistic porosity and tortuosity, have been created from microcomputed tomography scans. The porosity of each material has been calculated from the microcomputed scans and used to extract smaller representative sample volumes to perform numerical simulations on. Direct simulation Monte Carlo simulations of rarefied gas flow through these materials have been performed to find the permeability of each material to argon gas and to a gas mixture. The method has been validated by comparing the measured permeability for a Berea sandstone material with previously published experimental values. For the specific pressure conditions investigated here, the cork-phenolic material becomes around 10 times more permeable after being pyrolized, whereas the carbon-phenolic material only becomes five times more permeable than its virgin form. The permeability to the gas mixture is found to be greater than to argon for most of the samples, showing the importance of choosing the correct gas for rarefied permeability studies. The form of the pressure and Mach number profiles through the materials is independent of the applied pressure gradient.

Validation and verification represent an important element in the development of a computational code. The aim is establish both confidence in the algorithm and its suitability for the intended purpose. In this paper, a direct simulation Monte Carlo solver, called dsmcFoam, is carefully investigated for its ability to solve low and high speed non-reacting gas flows in simple and complex geometries. The test cases are: flow over sharp and truncated flat plates, the Mars Pathfinder probe, a micro-channel with heated internal steps, and a simple micro-channel. For all the cases investigated, dsmcFoam demonstrates very good agreement with experimental and numerical data available in the literature.

Local time stepping (LTS) and adaptive mesh refinement (AMR) have been implemented into rhoCentralFoam, a compressible solver within the open source computational fluid dynamics (CFD) code OpenFOAM. The LTS solver has been validated using a compressible Couette channel with heat transfer and a supersonic at plate. An excellent concurrence is found for these cases in comparison with the solutions with the obtained results being, respectively, 2.56 and 8.96 times faster compared to the unmodified solver. The AMR solver was employed to simulate hypersonic flow over a 30° wedge, and the Sod shock tube test case, and has also achieved satisfactory agreement with the analytical solutions. These results highlight the potentially significant computational cost savings that may be achieved when solving high-speed, compressible flows using this approach.

The highly complex flow physics that characterise re-entry conditions have to be reproduced by means of numerical simulations with both an acceptable level of accuracy and within reasonable timescales. In this respect, a new CFD solver, hyFoam, has been developed within the framework of the open-source CFD platform OpenFOAM for modelling hypersonic reacting flows. hyFoam has been successfully validated for two 0-degree adiabatic heat bath test cases and the limitations of a one-temperature CFD model have been highlighted. To cope with high-temperature gas chemistry, the internal energy has been decomposed into its elementary energy modes, thus introducing the translational-rotational and the vibrational temperatures. A two-temperature CFD model is being implemented in order to attain a better agreement between CFD and DSMC results. Validation of the code for a single species has been executed while mixture-related libraries are currently being developed. The vibrational-translational relaxation time formulation has also been presented and discussed.

An open-source implementation of chemistry modeling for the direct simulation Monte Carlo method is presented. Following the recent work of Bird (BirdG. A., “The Q-K Model for Gas Phase Chemical Reaction Rates,” Physics of Fluids, Vol. 23, No. 10, 2011, Paper 106101), an approach known as the quantum-kinetic method has been adopted to describe chemical reactions in a five-species air model using direct simulation Monte Carlo procedures based on microscopic gas information. The quantum-kinetic technique has been implemented within the framework of the dsmcFoam code, a derivative of the open-source computational-fluid-dynamics code OpenFOAM. Results for vibrational relaxation, dissociation, and exchange reaction rates for an adiabatic bath demonstrate the success of the quantum-kinetic model implementation in dsmcFoam when compared with analytical solutions for both inert and reacting conditions. A comparison is also made between the quantum-kinetic and total collision energy chemistry approaches for a hype...

Accurate aerodynamic modelling of vertical-axis wind turbines poses a significant challenge. The rotation of the turbine induces large variations in the angle of attack of its blades that can manifest as dynamic stall. In addition, interactions between the blades of the turbine and the wake that they produce can result in impulsive changes to the aerodynamic loading. The Vorticity Transport Model has been used to simulate the aerodynamic performance and wake dynamics of three different vertical-axis wind turbine configurations. It is known that vertical-axis turbines with either straight or curved blades deliver torque to their shaft that fluctuates at the blade passage frequency of the rotor. In contrast, a turbine with helically twisted blades delivers a relatively steady torque to the shaft. In this article, the interactions between helically twisted blades and the vortices within their wake are shown to result in localized perturbations to the aerodynamic loading on the rotor that can disrupt the otherwise relatively smooth power output that is predicted by simplistic aerodynamic tools that do not model the wake to sufficient fidelity. Furthermore, vertical-axis wind turbines with curved blades are shown to be somewhat more susceptible to local dynamic stall than turbines with straight blades.

Brown’s vorticity transport model has been used to investigate how the local blade aerodynamic model influences the quality of the prediction of the high-frequency airloads associated with blade–vortex interactions, and thus the accuracy with which the acoustic signature of a helicopter rotor can be predicted. The vorticity transport model can accurately resolve the structure of the wake of the rotor and allows significant flexibility in the way that the blade loading can be represented. The Second Higher-Harmonic Control Aeroacoustics Rotor Test was initiated to provide experimental insight into the acoustic signature of a rotor in cases of strong blade–vortex interaction. Predictions of two models for the local blade aerodynamics are compared with the test data. A marked improvement in accuracy of the predicted high-frequency airloads and acoustic signature is obtained when a lifting-chord model for the blade aerodynamics is used instead of a lifting-line-type approach. Errors in the amplitude and phase of the acoustic peaks are reduced, and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake, with the lifting-chord model producing the best representation of the distribution of sound pressure below the rotor.

Brown’s vorticity transport model has been used to investigate the influence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter blade–vortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows significant flexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to blade–vortex interactions as the computational grid is refined, exposing the fundamental deficiencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach.

The aerodynamic interactions that can occur within a wind farm can result in the constituent turbines generating a lower power output than would be possible if each of the turbines were operated in isolation. Tightening of the constraints on the siting of wind farms is likely to increase the scale of the problem in the future. The aerodynamic performance of turbine rotors and the mechanisms that couple the fluid dynamics of multiple rotors can be most readily understood by simplifying the problem and considering the interaction between only two rotors. The aerodynamic interaction between two rotors in both co-axial and offset configurations has been simulated using the Vorticity Transport Model. The aerodynamic interaction is a function of the tip speed ratio, and both the streamwise and crosswind separation between the rotors. The simulations show that the momentum deficit at a turbine operating within the wake developed by the rotor of a second turbine is governed by the development of instabilities within the wake of the upwind rotor, and the ensuing structure of the wake as it impinges on the downwind rotor. If the wind farm configuration or wind conditions are such that a turbine rotor is subject to partial impingement by the wake produced by an upstream turbine, then significant unsteadiness in the aerodynamic loading on the rotor blades of the downwind turbine can result, and this unsteadiness can have considerable implications for the fatigue life of the blade structure and rotor hub.

The growing investment by governments and electric utilities in energy efficiency programs highlights the need for simple tools to help assess and explain the size of the potential resource. One technique that is commonly used in this effort is to characterize electricity savings in terms of avoided power plants, because it is easier for people to visualize a power plant than it is to understand an abstraction such as billions of kilowatt-hours. Unfortunately, there is no standardization around the characteristics of such power plants. In this letter we define parameters for a standard avoided power plant that have physical meaning and intuitive plausibility, for use in back-of-the-envelope calculations. For the prototypical plant this article settles on a 500 MW existing coal plant operating at a 70% capacity factor with 7% T&D losses. Displacing such a plant for one year would save 3 billion kWh/year at the meter and reduce emissions by 3 million metric tons of CO2 per year. The proposed name for this metric is the Rosenfeld, in keeping with the tradition among scientists of naming units in honor of the person most responsible for the discovery and widespread adoption of the underlying scientific principle in question—Dr Arthur H. Rosenfeld.

The performance of a coaxial rotor in hover, in steady forward flight, and in level, coordinated turns is contrasted with that of an equivalent, conventional rotor with the same overall solidity, number of blades, and blade aerodynamic properties. Brown's vorticity transport model is used to calculate the profile, induced, and parasite contributions to the overall power consumed by the two systems, and the highly resolved representation of the rotor wake that is produced by the model is used to relate the observed differences in the performance of the two systems to the structures of their respective wakes. In all flight conditions, all else being equal, the coaxial system requires less induced power than the conventional system. In hover, the conventional rotor consumes increasingly more induced power than the coaxial rotor as thrust is increased. In forward flight, the relative advantage of the coaxial configuration is particularly evident at pretransitional advance ratios. In turning flight, the benefits of the coaxial rotor are seen at all load factors. The beneficial properties of the coaxial rotor in forward flight and maneuver, as far as induced power is concerned, are a subtle effect of rotor-wake interaction and result principally from differences between the two types of rotor in the character and strength of the localized interaction between the developing supervortices and the highly loaded blade-tips at the lateral extremities of the rotor. In hover, the increased axial convection rate of the tip vortices appears to result in a favorable redistribution of the loading slightly inboard of the tip of the upper rotor of the coaxial system.

The unsteady loads experienced by a helicopter are known to be strongly influenced by aerodynamic interactions between the rotor and fuselage; these unsteady loads can lead to deficiencies in handling qualities and unacceptable vibratory characteristics of the rotorcraft. This work uses a vorticity-based computational model to study the governing processes that underpin this aerodynamic interaction and aims to provide greater understanding of the wake dynamics in the presence of a fuselage, as well as an appreciation of how the geometry of the wake affects the loading on the fuselage. The well-known experiments using NASA's ROBIN fuselage are used to assess the accuracy of the computations. Comparisons of calculations against results from smoke visualization experiments are used to demonstrate the ability of the model to reproduce accurately the geometry of the rotor wake, and comparisons with inflow data from the experiments show the method to capture well the velocity field near to the rotor. The fuselage model is able to predict accurately the unsteady fuselage loading that is induced by blade passage and also by the inviscid interaction between the main rotor wake and fuselage.

Aerodynamic interference between the main and tail rotor can have a strong negative influence on the flight mechanics of a conventional helicopter. Significant unsteadiness in the tail rotor loading is encountered under certain flight conditions, but the character of the unsteadiness can depend on the direction of rotation of the tail rotor. Numerical simulations, using Brown's vorticity transport model, of the aerodynamic interaction between the main and tail rotors of a helicopter are presented for a range of forward and lateral flight trajectories. Distinct differences are predicted in the behavior of the system in left and right sideward flight that are consistent with flight experience that the greatest fluctuations in loading or control input are required in left sideways flight (for a counterclockwise rotating main rotor). These fluctuations are generally more extreme for a system with tail rotor rotating top-forward than top-aft. Differences are also exposed in the character of the lateral excitation of the system as forward flight speed is varied. The observed behavior appears to originate in the disruption of the tail rotor wake that is induced by its entrainment into the wake of the main rotor. The extent of the disruption is dependent on flight condition, and the unsteadiness of the process depends on the direction of rotation of the tail rotor. In intermediate-speed forward flight and right sideward flight, the free stream delays the entrainment of the tail rotor wake far enough downstream for the perturbations to the rotor loading to be slight. Conversely, in left sideward and quartering flight, the free stream confines the entrainment process close to the rotors, where it causes significant unsteadiness in the loads produced by the system.

Office equipment is expected to be the fastest-growing segment of commercial energy use over the next 20 years, yet many aspects of office equipment energy use are poorly understood. User behavior, such as turning off devices at night or enabling power management, influences energy use to a great extent. The computing environment also plays a role both in influencing user behavior and in the success of power management. Information about turn-off rates and power management rates for office equipment was collected through a series of after-hours audits in commercial buildings. Sixteen businesses were recruited, including offices (small, medium and large offices in a variety of industries), schools, and medical buildings in California, Georgia, and Pennsylvania. The types and power states of office equipment found in these buildings were recorded and analyzed. This article presents these data for computers, monitors, printers, copiers, fax machines, scanners and multi-function devices. These data can be used to improve estimates of both energy consumption for these devices and savings from energy conservation efforts.

This paper provides a general overview of electricity consumption and peak load in California, by both sector and end use. We examine the growth in electricity demand between 1980 and 2000, as well as the composition of electricity end uses in 1999. One of the main conclusions from this analysis is that electricity use in California in the 1990s did not grow explosively, nor was the amount of growth unanticipated. In both absolute and relative terms, growth in electricity use was greater in the 1980s than the 1990s. During the 1990s, most of the growth in electricity use has been in the buildings sector, particularly commercial buildings. In 2000, the building sector accounted for 2/3 of annual electricity consumption and 3/4 of the summer peak load.