Net Energy Input Research Articles

Obesity--What Is To Be Done?

The word epidemic conjures up alarming images: plague, pestilence, destruction, and death. We are not used to lumping obesity in with such disasters, but the recent increase in the global prevalence of obesity qualifies as an epidemic. Obesity claims an increasing number of lives worldwide; discouraging statistics abound in both the medical and popular press. This issue of Science also reports some of this bad news. We learn, for starters, that the obesity epidemic is recognized by the World Health Organization as one of the top 10 global health problems. Multiple social forces work against maintenance of a healthy weight, such as food availability, declines in traditional lifestyles, and sedentary living. The medical profession is reported to lack both the knowledge and the incentives (financial and otherwise) to combat this threat to health. All of us, particularly certain populations, have powerful genetic predispositions to retain excess calories in preparation for famine. The biological systems that manage our food intake—controlling how often and how much we eat and making corrections when the long-term equilibrium is disrupted—are extraordinarily complex and not yet well understood. Powerful biological control mechanisms spur calorie intake, but less powerful ones limit it. As-yet-unknown players are probably confounding researchers' efforts to untangle this system. Clinicians have few tools with which to fight this epidemic; current antiobesity drugs are not highly effective and are fraught with side effects. But the articles in this issue also point to areas where we can expect to make real progress against this epidemic. The tools of molecular genetics have yielded a rush of new information about molecular signals that guide short-term decisions, such as whether to eat now or push away from the table. Other molecules take a longer view, monitoring fat balance (see the News story by Marx, p. 846). Information from basic research has identified numerous drug targets, as Gura's News story (p. 849) points out. Several compounds are in human clinical trials now, and more are in development. Although Friedman (p. [856][1]) outlines the enormity of the obesity problem in his Viewpoint, likening it to that of cancer, he suggests that new molecular knowledge coupled with an evolutionary view may give us enough information to fight obesity productively. Science clearly has the potential to inform and perhaps help solve some aspects of this intricate problem. What about social forces? Hill et al. (p. 853) argue in their Viewpoint that it will take only a small reduction in daily net energy input to prevent further increases in obesity rates—an attainable goal, they believe. Social change can also occur in the medical profession as physicians and other health care professionals learn more about how to treat obesity, as argued by Pi-Sunyer (p. [859][2]). Perhaps the biggest challenge is outlined by Nestle in her editorial (p. 781). When the interests of corporate institutions that control the distribution of food and its advertisement (with the goal of maximizing food consumption) conflict with the public good, who is to intervene and how? [1]: /lookup/doi/10.1126/science.1079856 [2]: /lookup/doi/10.1126/science.1082319

Laser Forming with Constant Line Energy

This paper investigates the condition of constant line energy, that is, the ratio of laser power to scanning velocity is kept constant. Under the condition, the effects of velocity change on temperature, net energy input, strain rate and material flow stress are studied. Their collective effects on dimension, residual stress, hardness and microstructure are also presented. Numerical results are experimentally validated and used to study process transiency, and aid understanding the complex and often conflicting effects of the condition.

Biomass energy transport: Analysis of bioenergy transport chains using life cycle inventory method

Biomass for energy conversion is usually considered as a local resource. With appropriate logistic systems, access to biomass can be improved over a large geographical area. In this study, life cycle inventory (LCI) has been used as a method to investigate the environmental load of selected bioenergy transport chains. As a case study, chains starting in Sweden and ending in Holland have been investigated. Biomass originates from tree sections or forest residues, the latter upgraded to bales or pellets. The study is concentrated on production of electricity, hot cooling water is considered as a loss. Electricity is, in the case study, produced from solid biomass in the importing country. Electricity can also be produced in the country of origin and exported via the transnational grid as transportation medium. The results show that emissions from long range transportation, 1200 km, performed with ships, is of minor importance compared to emissions from local bioenergy systems in a local market. In bioenergy systems the use of fuels and electricity for operating machines and transportation carriers requires a net energy input which amounts to typically 7–9% of delivered electrical energy from the system. Emissions of key substances such as NO x , CO, S, hydrocarbons, and particles are low in a perspective of sustainability. Emissions of CO 2 from bio-combustion are considered to be zero since there is approximately no net contribution of carbon to the biosphere in an energy system based on biomass. The results indicate that biomass for energy can be transported from Scandinavia to Holland without losing its environmental benefits.

Determination of Time Span for the Appearance of Flutes on the Track Surface of Rolling-Element Bearings Under the Influence of Electric Current

A theoretical approach is developed to determine the time span for the development of flutes after the appearance of slip bands on the track surface of rolling-element bearings operating under the influence of electric current. A theoretical model has been developed using the continuum theory of Griffith to determine the energy per unit area required for the development of corrugations after the appearance of slip bands on the track surfaces. Also, an expression is deduced for the net energy input per unit area on the track surfaces by the amount of electric current passed through the bearing at the measured shaft voltage in a given span of operation. By the formulation of pitch of corrugations derived using bearing dimensional and operational parameters, along with developed model and expressions, the time span for the development of corrugations has been determined. A similar time span has also been ascertained experimentally. Theoretical and experimental values of time span, thus determined, have been compared and found to match closely. The analysis can also be used for the determination of the shaft voltage or bearing current if the time for the formation of corrugation is known. Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

Growth of swimming muscles and its metabolic cost in larvae of whitefish at different temperatures

The temperature relationship of routine metabolic rate (Rr) of non‐feeding, non‐growing Coregonus lavaretus larvae between 2 and 15°C is characterized by Q10‐values ranging from l.8‐2.45. The rate of growth, based on weight determinations, of first‐feeding larvae amounted to 3.5, 7.6 and 9.4% day‐1 at 5, 10 and 12°C respectively, from which Q10‐values between 4.0 and 4.8 can be calculated. The rate of increase of muscle mass between 5 and 10°C, based on the determination of the cross‐sectional area of inner muscle fibres, resulted in a Q10‐value of 4.5. Water temperature influenced the pattern of growth of the inner muscle fibres. At hatching, after 360 day degrees, total muscle mass of larvae reared at 4 and 8°C was independent of temperature, but at 4°C the rate of mass increase owed more to hyperplasia (increase in fibre number) than to hypertrophy (increase in fibre mass), whereas at 8°C the opposite was the case. The calculation of power budgets (including the metabolic cost of growth) of first‐feeding larvae yielded net conversion efficiencies (K2) increasing with temperature from 46.3% at 5°C to 54.7% at 12°C. Comparing our data with literature data two general conclusions can be drawn. (1) In first‐feeding larvae the net, but not the gross, conversion efficiency of food energy increases with temperature. This is due to net energy input being characterized by a much higher Q10‐value than energy expenditures. (2) In embryos of freshwater fish so far investigated hyperplasia plays a greater role in the increase of fibre mass than hypertrophy at the lower temperature, whereas in embryos of marine fish hyperplasia prevails at the higher temperature. It is suggested that this discrepancy correlates with the high concentration of free amino acids in the eggs of marine species which provide an additional, easily available, source of metabolic energy absent in freshwater species.

Dynamics and Energy Balance of the Hadley Circulation and the Tropical Precipitation Zones. Part II: Sensitivity to Meridional SST Distribution

A series of GCM experiments is performed in order to examine the dynamics of the time-averaged distribution of precipitation and Hadley circulation in low-latitude areas. As an extension to Part I of this study, the sensitivity to the latitudinal distribution of the globally prescribed sea surface temperature (SST) is examined. When the peak of SST is not at the equator but nearby, a single precipitation peak appears on the opposite side of the equator. When the latitude of the SST peak becomes high enough (about 15°), an abrupt jump of the precipitation peak is observed. This behavior is completely different if the evaporation from the ocean is estimated independent of the surface wind speed. Factors controlling the latitude of the precipitation zone are discussed. It is found that one essential component is the convergent flow in the planetary boundary layer, which is driven by the SST gradient. Another important factor is the net moist static energy input into the atmosphere, which is the difference between the energy input from the surface and the radiative loss. The near-neutral stratification of the atmosphere, which may be partially determined by the distribution of the SST, is also considered to be important because it controls the moist static energy balance of the atmosphere.

Optically thin cirrus clouds: Radiative impact on the warm pool

Over the convectively active tropical ocean regions, measurements made from space in the infrared (i.r.) and visible have revealed the presence of optically thin cirrus clouds which are quite transparent in the visible and nearly opaque in the infrared. The Nimbus 4 Infrared Interferometer Spectrometer (IRIS), which has a field of view (FOV) of ≈ 100 km, has been utilized to examine the i.r. optical characteristics of these cirrus clouds. From the IRIS data it has been observed that these optically thin cirrus clouds prevail extensively over the “warm pool” region of the equatorial western Pacific surrounding Indonesia. It is found that the seasonal cloud cover produced by these thin cirrus exceeds 50% near the central regions of the “warm pool”. For most of these clouds, optical thickness in the infrared is < 2. It is deduced that dense cold anvil clouds associated with deep convection spread extensively and are responsible for the formation of the thin cirrus. This is supported by the observation that the coverage of the dense anvil clouds is an order of magnitude less than that of the thin cirrus. Observations made by the Earth Radiation Budget Experiment (ERBE) reveal that the “warm pool” region constitutes a local maximum in net input of radiative energy. From these observations, together with a simple radiative energy balance model, we have inferred that the greenhouse effect produced by the optically thin cirrus clouds can be a significant factor in maintaining the “warm pool”.

The influence of bovine oocyte type on in vitro-fertilization and subsequent development in vitro

Microalgae technology is attractive for simultaneously treating wastewater and producing valuable biomass. However, biofuel application demands a very low net-energy input that can hardly be fulfilled. Therefore, exploration of a more direct-use of microalgae biomass and selection of appropriate microalgae species are necessary to fine-tune viable applications. This study assesses performance of sequencing batch membrane photobioreactors (SB-MPBRs) for simultaneously polishing secondary effluent by cultivating Staurastrum sp., a species suitable as aquaculture feed. The effect of feed composition (high and low phosphorous, P) on microalgae growth, membrane fouling propensity, nutrient removal, as well as oxygen enrichment capacity were evaluated. Overall results demonstrate the effectiveness of SB-MPBR to cultivate Staurastrum sp. in secondary effluent by achieving biomass concentration of 0.45 and 0.6 g/L and very low nutrients concentrations in the effluents (≈ 0, 10 and 2 mg/L, for chemical oxygen demand (COD), TN and TP respectively). The actual biomass productivity of the SM-MPBRS are 40.0 and 30.0 g/(day m3) for the low-P and high-P feeds, corresponding to production costs of 11.3 and 15.1 $/kg biomass, respectively. Low-P feed results in a slightly higher biomass productivity of 33% compare to high-P feed, but slightly higher fouling propensity. The growth in both SB-MPBRS seems to be limited by the inorganic carbon supply. Too-short HRT leads to nutrients accumulation of the nutrients and eventually reduced their removal efficiencies. Overall results show a new cultivation method for aquaculture feed while at the same time polish secondary effluent and enrich its oxygen concentration.

Generation of the dynamic input profile to solar collection systems

A method is established for extracting the net energy input to a solar collector as a continuous explicit function of time by processing discrete, instantaneous, direct, and diffuse measurements on a horizontal surface. The dynamics of the energy input are analysed. A computer program is coded to yield the effective input as a polynomial in time. Both the analysis and the program are presented in general form.

Nitrogen Accretion and Its Energetics in the Himalayan Alder

Energetics of nitrogen accretion was studied in five different ages of Alnus nepalensis D. Don (alder) plantations in the Kalimpong forest division of the Eastern Himalayas. The percentage contributions of biological N2 fixation to annual total nitrogen uptake were 33%, 19%, 15%, 13% and 11% in 7-, 17-, 30-, 46and 56-year-old plantations, respectively. Nitrogen accretion through fixation reduced with the decrease in nitrogen demand as trees aged (117kg ha-1 yr-1 in 7-year stand to 29kg ha-1 yr-1 in 56-year stand). Low N2 fixation efficiency and low net energy allocation in root nodules with increase in tree age caused sharp reduction in nitrogen accretion through fixation in older stands, while nitrogen uptake from soil remained nearly the same in young to old plantations. Nitrogen build up strategy is based on sound energy conservation dynamics and the alder replenishes nitrogen in erosion prone hill slopes of the Himalayas. Key-words: Alnus nepalensis, N2-fixation-efficiency, energy cost, net energy input, nitrogen replenishment

Optimization of Extrusion Rice Bran Stabilization Process

ABSTRACTEffects of processing variables, production rate, number of die openings and initial moisture content on the discharge temperature and power input during rice bran extrusion with an autogenous single‐screw extruder were analyzed. At extrusion temperatures above 128°C, all lipase activity in the bran was lost regardless of moisture content of the bran fed. Net specific energy input (NSE) varied with changes in die opening and moisture contents and total power efficiency was increased with increasing production rate without change in NSE value. Percolation rate through the extruded bran bed was increased to nine times over that of raw bran; the extraction time to reach 1% residual oil in extruded bran was reduced to 10 min from 100 min for the raw bran.

Calibration of the NBS Calibrated Hot Box

Abstract A series of calibration tests were conducted in the laboratory in order to determine the overall experimental error and uncertainty for the NBS calibrated hot box. For these tests, 10 cm (4 in.) and 20 cm (8 in.) thick polystyrene wall specimens having independently measured thermal resistances were installed in a support frame and sandwiched between the metering and climatic chambers. The metering chamber was operated at a typical indoor condition for a residence, while the climatic chamber was operated at selected steady outdoor winter conditions. For each of the tests, an energy balance was performed on the metering chamber. The heat transfer that flanks the wall specimen and passes through the support frame was predicted using a finite-difference model. The other heat losses and gains for the energy balance were measured. The residual energy loss for the energy balance of the metering chamber represents the overall experimental error and uncertainty. The maximum observed residual energy loss for all of the calibration tests without the metering chamber cooling coil operated was 1.9 W. This value occurred when the 10 cm (4 in.) wall specimen was exposed to a 23 K (41°F) temperature difference. This value, however, comprised only 1.8% of the net energy input to the metering chamber.

Heavy oil processing in steam and hydrogen plasmas

AbstractHeavy oil in the form of finely divided spray was reacted with steam and hydrogen plasmas respectively. The heavy oil was preheated to 473 K at a pressure of 2 MPa and fed through pressure atomizers at flow rates between 0.002 and 0.08 m3/h into a dc plasma jet contained in a reactor 20 cm in diameter and 1.5 m long. The hydrogen and steam plasmas had maximum initial temperatures of 6000 K and 3450 K respectively and specific net energy inputs between 0.4 and 12.6 kWh/kg oil were used. With a hydrogen plasma, the heavy oil reacted to form acetylene, ethylene, methane, soot, and pitches, while with a steam plasma, carbon monoxide and dioxide were formed as well. Light liquid hydrocarbons were not in evidence. Increases in the hydrogen (or steam)‐to‐oil ratio and specific energy consumption increased the oil‐to‐gas conversions.

Energetics of earthworm populations in tropical pastures from India

This paper reports our results of studies connected with the energy flow in earthworm populations in an upland and a lowland pasture where grazing by large herbivores were not allowed. The net annual energy input was more than double in the lowand pasture. Flooding during the rainy season caused heavy mortality and migration of worms in lowland pasture. Higher energy consumption through respiration in the upland pasture was due to difference in environmental conditions. Lower amount of secondary production (P) and higher amount of energy utilized in respiration (R) cause an increased R:P ratio in upland pasture. Energy channelization in both the sites has been represented in box type energy flow models. Management of these pasture lands depends on the understanding of the dynamics of energy flow in these systems.

The Southwest and the Plains: Ecology and Economics

The ecological concept of niche is used to provide a better understanding of prehistoric interactions between the Plains and the Puebloan Southwest. A diachronic model is presented based on concepts of energy flow and regional microvariation in net energy input. At a general level, such use of ecological models and principles enables changes in human systems to be seen as an example of a general increase in ecosystem complexity. The application of more powerful theoretic and methodological concepts and constructs can then lead to a more powerful theory of human cultural evolution.

On the Steady-State Energy Balance of Short Gravity Wave Systems

Steady-state energy balances of short gravity wave systems generated in a wave tank with and without airflow have been measured and compared with the predictions of perturbation theory. Wind-wave spectra were found to fit a JONSWAP form to a good approximation if a wind-dependent equilibrium range coefficient was used. Mechanically generated waves were produced which had frequency spectra similar to wind-generated wave spectra and which exhibited nonlinear effects through a decrease in the spectral peak frequency with fetch. In the wind-wave case, perturbation theory well predicted the difference between the net source function and energy input from the wind for a wide range of fetch and wind speed conditions provided that surface tension was properly taken into account. In the case of waves generated without airflow, perturbation theory predicted energy transfer rates much smaller than the measured values.

Climate and thermodynamic systems of maximum dissipation

THE Earth–atmosphere is a classic example of a closed, dissipative and nonlinear thermodynamic system which is subject to both regular and irregular impulses causing significant departure from steady state. It is closed because it exchanges energy (solar and thermal radiant energy) but not mass with its environment. It is dissipative because the net input of radiant energy occurs mainly in regions of high temperature towards the Equator and the net output occurs mainly in regions of low temperature towards the poles. It is nonlinear basically because of the multiplicity of internal feedbacks and because of the importance of advective processes. It has steady-state character in the sense that the annual mean radiant energy input is very close to the annual mean output, and parameters such as the annual mean temperature do not vary significantly from one period to another. The regular seasonal variation in solar position ensures significant departure from the steady state so defined, and there are also significant irregular departures arising (for instance) from variations of solar input and IR output caused by variations in the amount and distribution of cloud. Recently I have shown1 that the overall Earth–atmosphere climate system seems to have adopted a format whereby the total thermodynamic dissipation associated with the horizontal energy flows in the atmosphere and ocean is a maximum. ‘Format’ in this context refers to the annual average geographic distribution of cloud, surface temperature and the horizontal energy flows. The practical significance of this is that, if one could accept it as a general principle governing climate behaviour, one could use it directly as a means of a priori prediction of climate and climate change without needing detailed analysis of the internal workings of the system. I could not explain previously why the Earth–atmosphere system should be so constrained. This note points out that the Earth–atmosphere has characteristics such that it might be expected to obey such a constraint. Furthermore, these characteristics are sufficiently general that the same principle of selection of steady-state mode of maximum dissipation may apply to a broad class of non-linear systems.

The steady‐state format of global climate

AbstractIt can be proved for certain small‐scale convective heat transfer processes that the preferred steady‐state mode is one of maximum entropy production. The constraint is more or less equivalent to one of maximum kinetic energy dissipation or of maximum convective heat transport. Evidence is accumulating that the same constraint may apply on the much larger scale of the earth‐atmosphere system. The concept is accepted as the basis of a purely thermodynamic model of the mean annual global climate. The model allows a prieri calculation of the broad‐scale geographic distributions of cloud, surface temperature, horizontal energy fluxes in the ocean and in the atmosphere, net radiant energy inputs, etc. The agreement with observation strongly supports the basic concept. It suggests also that, to the extent allowed by the degrees of freedom in the dynamics, the partition of atmospheric and oceanic energy flow is determined by a requirement to equalize the local dissipations in the two media.

The local climate of the Øvre Heimdalen valley

Owing to the high altitude of Øvre Heimdalen and the complex topography within the valley, climatic conditions are complicated. The valley is situated in a mountain region with a subarctic or tundra macroclimate, which exists over the lake itself and on the SSW‐valley side. However, the favourable combination of slope angle and exposure of the NNE‐valley side gives a radiation or continental type of local climate on this side.The large net input of radiant energy onto the NNE‐valley side during the summer results in higher air temperatures, greater precipitation and higher air humidity than elsewhere in the valley. This is clearly reflected in the luxuriant vegetation on this side. Thus, the climate of the Øvre Heimdalsvatn area is strongly influenced by terrain irregularities and shows how fundamentally different growth possibilities due to local climates may be over short distances in the uppermost valleys on the eastern side of the central mountain chain.

Energy flow and closure of current systems in the magnetosphere

The result of an attempt to express the net energy input to the magnetosphere‐ionosphere system in terms of upstream solar wind parameters is presented. Seven types of electric current system within the magnetosphere are defined and discussed, and it is found that only three of these systematically transfer energy into the magnetosphere from the solar wind. One of these is the magnetotail current system, and the other two form the field‐aligned current observed at the northern edge of the auroral oval. In order to calculate energy input, reasonable models are developed for each of a number of magnetospheric processes. These include (1) flow through the shock, flow in the magnetosheath, and merging; (2) reconnection and the neutral line in the magnetotail; and (3) Alfven layer shielding of the inner magnetosphere from convective flow, nightside pressure balances, and precipitation, and hence from these the width and conductance of the nightside auroral oval. The use of these models permits the development of explicit equations for the total energy input to the magnetosphere‐ionosphere system in terms of upstream solar wind parameters. The interplanetary magnetic field strength and orientation and the solar wind velocity dominate energy input via the nightside plasma sheet. The density of the solar wind is also an important variable for the energy input by the high‐latitude current systems.