Articles de revues : « Densità energetica »

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Yang, Junqing, Xuedong Gong et Guixiang Wang. « Design of new aliphatic azido nitro compounds as plasticizer : an initial exploration on AFCTEE (1-azido-formic acid 1,1,1-trinitro-ethyl ester) ». Canadian Journal of Chemistry 93, n^o 7 (juillet 2015) : 690–95. http://dx.doi.org/10.1139/cjc-2014-0565.

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To explore new high-energy azido nitro compounds as plasticizers for propellants, AFCTEE (1-azido-formic acid 1,1,1-trinitro-ethyl ester) was designed and studied using density functional theory. The predicted density of AFCTEE, 1.90 gcm−3, is comparable to that of HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane) and much higher than that of general organic azido compounds. AFCTEE possesses higher energetic properties and chemical stability than the promising azido nitro plasticizer DAMNP (1,3-diazido-2-methyl-2-nitropropane) and the conventional plasticizer NG (nitroglycerine), and it has a moderate thermal stability. The pyrolysis of AFCTEE starts from the rupture of C–NO2 and then the breakage of N–N2 via Curtius rearrangement. This work is the initial exploration for AFCTEE, aiming at the energetics, spectra (IR, NMR, and UV), stability, and decomposition mechanism. Compared with DAMNP, the advantages of superior energetic properties and chemical stability suggest AFCTEE is a promising energetic azido nitro compound and is worth further investigation.

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Sivy, Kelly J., Anne W. Nolin, Christopher L. Cosgrove et Laura R. Prugh. « Critical snow density threshold for Dall’s sheep (Ovis dalli dalli) ». Canadian Journal of Zoology 96, n^o 10 (octobre 2018) : 1170–77. http://dx.doi.org/10.1139/cjz-2017-0259.

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Snow cover can significantly impact animal movement and energetics, yet few studies have investigated the link between physical properties of snow and energetic costs. Quantification of thresholds in snow properties that influence animal movement are needed to help address this knowledge gap. Recent population declines of Dall’s sheep (Ovis dalli dalli Nelson, 1884) could be due in part to changing snow conditions. We examined the effect of snow density, snow depth, and snow hardness on sinking depths of Dall’s sheep tracks encountered in Wrangell–St. Elias National Park and Preserve, Alaska. Snow depth was a poor predictor of sinking depths of sheep tracks (R2 = 0.02, p = 0.38), as was mean weighted hardness (R2 = 0.09, p = 0.07). Across competing models, top layer snow density (0–10 cm) and sheep age class were the best predictors of track sink depths (R2 = 0.58). Track sink depth decreased with increasing snow density, and the snowpack supported the mass of a sheep above a density threshold of 329 ± 18 kg/m3 (mean ± SE). This threshold could aid interpretation of winter movement and energetic costs by animals, thus improving our ability to predict consequences of changing snowpack conditions on wildlife.

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Kingsley, Michael C. S. « The numbers of ringed seals (Phoca hispida) in Baffin Bay and associated waters ». NAMMCO Scientific Publications 1 (12 juin 1998) : 181. http://dx.doi.org/10.7557/3.2988.

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The size of the population of ringed seals (Phoca hispida) inhabiting Baffin Bay and associated waters was estimated by two methods. An approximate model of the energetics of the polar bear (Ursus maritimus) estimated an energetic need of about 16,000 MJ/bear per year. Modelled estimates of the energetic yield of a ringed seal population showed that a stable standing population of 140-170 ringed seals per bear would be needed to provide that much energy, assuming that all mortalities were due to polar bear predation. This result was sensitive to assumptions about the Field Metabolic Rate (FMR) of the bears and the energetic yield of individual ringed seals, but less sensitive to assumptions about relative incidence of predation on different age classes of seal or the age structure of the polar bear population. Estimated sizes of polar bear populations in Baffin Bay and associated waters (total about 4,025), and of the standing population needed to support an estimated hunter kill of 100,000 yielded a population estimate of, very roughly, 1.2 million ringed seals. Estimates of ice areas and of the density of hauled out seals from aerial surveys were used to generate another approximate figure for the ringed seal population, which was about the same. The density of seals in the pack-ice area of Baffin Bay, which is imperfectly known, has a large influence on the latter estimate.

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Tesema, Fasil, Noora Partamies, Daniel K. Whiter et Yasunobu Ogawa. « Types of pulsating aurora : comparison of model and EISCAT electron density observations ». Annales Geophysicae 40, n^o 1 (4 janvier 2022) : 1–10. http://dx.doi.org/10.5194/angeo-40-1-2022.

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Abstract. Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitudes and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such an underestimation. One way to do this is to test and validate the existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average or typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from the EISCAT (European Incoherent Scatter scientific radar system) radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from the Polar Operational Environmental Satellite (POES) as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

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Sączewski, Jarosław, Joanna Fedorowicz, Paulina Wiśniewska et Maria Gdaniec. « Theoretical and Experimental Insights into the Tandem Mannich—Electrophilic Amination Reaction : Synthesis of Safirinium Dyes ». Applied Sciences 11, n^o 12 (14 juin 2021) : 5498. http://dx.doi.org/10.3390/app11125498.

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Isoxazolo[3,4-b]pyridin-3(1H)-ones are ‘spring-loaded’ compounds that quantitatively react with iminium salts derived from formaldehyde and secondary amines to yield fluorescent Safirinium dyes. The mechanism and energetics of the above tandem Mannich–electrophilic amination reaction have been investigated experimentally and using theoretical methods. The hybrid B3LYP functional with GD3 empirical dispersion and range-separated hybrid functional ωB97XD, both combined with a PCM model, were applied to acquire the energetic profiles of the studied reaction with respect to the structure of secondary amine and isoxazolone used. Diastereoselectivity of the tandem reactions involving iminium salt derived from L-proline has been rationalized theoretically by means of density functional theory calculations.

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Dewar, Roderick C. « Plant energetics and population density ». Nature 398, n^o 6728 (avril 1999) : 572. http://dx.doi.org/10.1038/19215.

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Magnani, Federico. « Plant energetics and population density” ». Nature 398, n^o 6728 (avril 1999) : 572. http://dx.doi.org/10.1038/19217.

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Enquist, Brian J., James H. Brown et Geoffrey B. West. « Plant energetics and population density ». Nature 398, n^o 6728 (avril 1999) : 573. http://dx.doi.org/10.1038/19219.

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Liu, Y., S. Consta, F. Ogeer, Y. J. Shi et R. H. Lipson. « Geometries and energetics of methanol–ethanol clusters : a VUV laser/time-of-flight mass spectrometry and density functional theory study ». Canadian Journal of Chemistry 85, n^o 10 (1 octobre 2007) : 843–52. http://dx.doi.org/10.1139/v07-104.

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Hydrogen-bonded clusters, formed above liquid methanol (Me) and ethanol (Et) mixtures of various compositions, were entrained in a supersonic jet and probed using 118 nm vacuum ultraviolet (VUV) laser single-photon ionization/time-of-flight mass spectrometry. The spectra are dominated by protonated cluster ions, formed by ionizing hydrogen-bonded MemEtn neutrals, m = 0–4, n = 0–3, and m + n = 2–5. The structures and energetics of the neutral and ionic species were investigated using both the all-atom optimized potential for liquid state, OPLS-AA, and the density functional (DFT) calculations. The energetic factors affecting the observed cluster distributions were examined. Calculations indicate that the large change in binding energy going from trimer to tetramer can be attributed more to pair-wise interactions than to cooperativity effects.Key words: alcohol clusters, cluster formation, DFT calculations, mass spectrometry, vacuum ultraviolet laser.

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Zhao, Dongbo, Shubin Liu et Dahua Chen. « A Density Functional Theory and Information-Theoretic Approach Study of Interaction Energy and Polarizability for Base Pairs and Peptides ». Pharmaceuticals 15, n^o 8 (28 juillet 2022) : 938. http://dx.doi.org/10.3390/ph15080938.

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Using density functional theory (DFT) and the information-theoretic approach (ITA) quantities to appreciate the energetics and properties of biopolymers is still an unaccomplished and ongoing task. To this end, we studied the building blocks of nucleic acid base pairs and small peptides. For base pairs, we have dissected the relative importance of energetic components by using two energy partition schemes in DFT. Our results convincingly show that the exchange-correlation effect predominantly governs the molecular stability of base pairs while the electrostatic potential plays a minor but indispensable role, and the steric effect is trivial. Furthermore, we have revealed that simple density-based ITA functions are in good relationships with molecular polarizabilities for a series of 30 hydrogen-bonded base pairs and all 20 natural α-amino acids, 400 dipeptides, and 8000 tripeptides. Based on these lines, one can easily predict the molecular polarizabilities of larger peptides, even proteins as long as the total molecular wavefunction is available, rather than solving the computationally demanding coupled-perturbed Hartree–Fock (CPHF) equation or its DFT counterpart coupled-perturbed Kohn–Sham (CPKS) equation.

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Ward, Darren M., Keith H. Nislow et Carol L. Folt. « Seasonal shift in the effects of predators on juvenile Atlantic salmon (Salmo salar) energetics ». Canadian Journal of Fisheries and Aquatic Sciences 68, n^o 12 (décembre 2011) : 2080–89. http://dx.doi.org/10.1139/f2011-123.

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Predator effects on prey populations are determined by the number of prey consumed and effects on the traits of surviving prey. Yet the effects of predators on prey traits are rarely evaluated in field studies. We measured the effects of predators on energetic traits (consumption and growth rates) of juvenile Atlantic salmon ( Salmo salar ) in a large-scale field study. Salmon fry were released at 18 sites that encompassed a wide range of predatory slimy sculpin ( Cottus cognatus ) abundance. We sampled salmon after 21 and 140 days to measure salmon growth and estimate consumption using a mass-balance model of methylmercury accumulation. Salmon population density was reduced fivefold at sites with abundant sculpin. Over the early season, salmon consumed less where sculpin were abundant, suggesting that reduced foraging under predation risk contributed to predator-caused mortality. In contrast, over the late season, salmon grew more where sculpin were abundant, suggesting that compensatory growth at reduced salmon population density moderated predator-caused mortality. Predator effects on prey energetics can drive variation in survival and growth, with important consequences for population dynamics.

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Burrage, Matthew K., Moritz Hundertmark, Ladislav Valkovič, William D. Watson, Jennifer Rayner, Nikant Sabharwal, Vanessa M. Ferreira et al. « Energetic Basis for Exercise-Induced Pulmonary Congestion in Heart Failure With Preserved Ejection Fraction ». Circulation 144, n^o 21 (23 novembre 2021) : 1664–78. http://dx.doi.org/10.1161/circulationaha.121.054858.

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Background: Transient pulmonary congestion during exercise is emerging as an important determinant of reduced exercise capacity in heart failure with preserved ejection fraction (HFpEF). We sought to determine whether an abnormal cardiac energetic state underpins this process. Methods: We recruited patients across the spectrum of diastolic dysfunction and HFpEF (controls, n=11; type 2 diabetes, n=9; HFpEF, n=14; and severe diastolic dysfunction attributable to cardiac amyloidosis, n=9). Cardiac energetics were measured using phosphorus spectroscopy to define the myocardial phosphocreatine to ATP ratio. Cardiac function was assessed by cardiovascular magnetic resonance cine imaging and echocardiography and lung water using magnetic resonance proton density mapping. Studies were performed at rest and during submaximal exercise using a magnetic resonance imaging ergometer. Results: Paralleling the stepwise decline in diastolic function across the groups (E/e′ ratio; P <0.001) was an increase in NT-proBNP (N-terminal pro-brain natriuretic peptide; P <0.001) and a reduction in phosphocreatine/ATP ratio (control, 2.15 [2.09, 2.29]; type 2 diabetes, 1.71 [1.61, 1.91]; HFpEF, 1.66 [1.44, 1.89]; cardiac amyloidosis, 1.30 [1.16, 1.53]; P <0.001). During 20-W exercise, lower left ventricular diastolic filling rates (r=0.58; P <0.001), lower left ventricular diastolic reserve (r=0.55; P <0.001), left atrial dilatation (r=–0.52; P <0.001), lower right ventricular contractile reserve (right ventricular ejection fraction change, r=0.57; P <0.001), and right atrial dilation (r=–0.71; P <0.001) were all linked to lower phosphocreatine/ATP ratio. Along with these changes, pulmonary proton density mapping revealed transient pulmonary congestion in patients with HFpEF (+4.4% [0.5, 6.4]; P =0.002) and cardiac amyloidosis (+6.4% [3.3, 10.0]; P =0.004), which was not seen in healthy controls (–0.1% [–1.9, 2.1]; P =0.89) or type 2 diabetes without HFpEF (+0.8% [–1.7, 1.9]; P =0.82). The development of exercise-induced pulmonary congestion was associated with lower phosphocreatine/ATP ratio (r=–0.43; P =0.004). Conclusions: A gradient of myocardial energetic deficit exists across the spectrum of HFpEF. Even at low workload, this energetic deficit is related to markedly abnormal exercise responses in all 4 cardiac chambers, which is associated with detectable pulmonary congestion. The findings support an energetic basis for transient pulmonary congestion in HFpEF.

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Hosseinnejad, Tayebeh, et Marzieh Omrani-Pachin. « Quantum chemistry study on the promoted reactivity of substituted cyclooctynes in bioorthogonal cycloaddition reactions ». Heterocyclic Communications 27, n^o 1 (1 janvier 2021) : 142–54. http://dx.doi.org/10.1515/hc-2020-0129.

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Abstract In the present research, we focus on the energetics and electronic aspects of enhanced reactivity in the regioselective bioorthogonal 1,3-dipolar cycloaddition reaction of various substituted cyclooctynes with methyl azide, applying quantum chemistry approaches. In this respect, we assessed the structural and energetic properties of regioisomeric products and their corresponded transition states and calculated the reaction electronic energy changes and energy barriers through the cycloaddition pathways. The obtained results revealed that the trifluoromethyl substitution and fluorination of cyclooctynes lead to improved reactivity, in conjunction with increased exothermicity and decreased activation energy values. On the other hand, quantum theory of atoms in molecules computations were performed on some key bond and ring critical points that demonstrated the stabilizing topological properties of electron density and its derivatives upon trifluoromethyl substitution and fluorination of propargylic carbon of cyclooctynes which can be regarded as the essential origin of enhanced reactivity.

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Xia, Min, Qifa Yao, Huilian Yang, Tao Guo, Xiuxin Du, Yanjie Zhang, Guoping Li et Yunjun Luo. « Preparation of Bi2O3/Al Core-Shell Energetic Composite by Two-Step Ball Milling Method and Its Application in Solid Propellant ». Materials 12, n^o 11 (11 juin 2019) : 1879. http://dx.doi.org/10.3390/ma12111879.

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In this article, Bi2O3/Al high-density energetic composites with a core-shell structure were prepared by a two-step ball milling method using a common planetary ball milling instrument, and their morphology, structure, and properties were characterized in detail. Through a reasonable ratio design and optimization of the ball milling conditions, the density of the Bi2O3/Al core-shell energetic composite is increased by about 11.3% compared to that of the physical mixed sample under the same conditions. The DSC (Differential Scanning Calorimetry) test also showed that the exothermic quantity of the thermite reaction of the energetic composite reached 2112.21 J/g, which is very close to the theoretical exothermic quantity. The effect of Bi2O3/Al core-shell energetic composite on the energy performance of insensitive HTPE propellant was further studied. The theoretical calculation results showed that replacing the partial Al with Bi2O3/Al core-shell energetic composite can make the density of propellant reach 2.056 g/cm3, and the density specific impulse reach 502.3 s·g/cm3, which is significantly higher than the density and density specific impulse of the conventional composite solid propellant. The thermal test showed that the explosive heat of the HTPE (Hydroxyl terminated polyether) propellant also increased with the increase of the content of Bi2O3/Al core-shell energetic composite.

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Ranjbarvaziri, Sara, Kristina B. Kooiker, Mathew Ellenberger, Giovanni Fajardo, Mingming Zhao, Alison Schroer Vander Roest, Rahel A. Woldeyes et al. « Altered Cardiac Energetics and Mitochondrial Dysfunction in Hypertrophic Cardiomyopathy ». Circulation 144, n^o 21 (23 novembre 2021) : 1714–31. http://dx.doi.org/10.1161/circulationaha.121.053575.

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Background: Hypertrophic cardiomyopathy (HCM) is a complex disease partly explained by the effects of individual gene variants on sarcomeric protein biomechanics. At the cellular level, HCM mutations most commonly enhance force production, leading to higher energy demands. Despite significant advances in elucidating sarcomeric structure–function relationships, there is still much to be learned about the mechanisms that link altered cardiac energetics to HCM phenotypes. In this work, we test the hypothesis that changes in cardiac energetics represent a common pathophysiologic pathway in HCM. Methods: We performed a comprehensive multiomics profile of the molecular (transcripts, metabolites, and complex lipids), ultrastructural, and functional components of HCM energetics using myocardial samples from 27 HCM patients and 13 normal controls (donor hearts). Results: Integrated omics analysis revealed alterations in a wide array of biochemical pathways with major dysregulation in fatty acid metabolism, reduction of acylcarnitines, and accumulation of free fatty acids. HCM hearts showed evidence of global energetic decompensation manifested by a decrease in high energy phosphate metabolites (ATP, ADP, and phosphocreatine) and a reduction in mitochondrial genes involved in creatine kinase and ATP synthesis. Accompanying these metabolic derangements, electron microscopy showed an increased fraction of severely damaged mitochondria with reduced cristae density, coinciding with reduced citrate synthase activity and mitochondrial oxidative respiration. These mitochondrial abnormalities were associated with elevated reactive oxygen species and reduced antioxidant defenses. However, despite significant mitochondrial injury, HCM hearts failed to upregulate mitophagic clearance. Conclusions: Overall, our findings suggest that perturbed metabolic signaling and mitochondrial dysfunction are common pathogenic mechanisms in patients with HCM. These results highlight potential new drug targets for attenuation of the clinical disease through improving metabolic function and reducing mitochondrial injury.

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A, David Stephen, Asthana S.N, Rajesh. B. Pawar et Kumuradhas P. « Charge density studies of energetic material : RDX ». Frontiers in Advanced Materials Research 2, n^o 1 (26 mai 2020) : 1–14. http://dx.doi.org/10.34256/famr2011.

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Experimental charge density study has been carried out for Cyclotrimethylene-trinitramine (space group Pbca), an explosive material from a low temperature X-ray diffraction experiment. The electron density was modeled using the Hansen-Coppens multipole model and refined to R=0.032 for 6226 unique observed reflections. The electron density, laplacian and electrostatic potential distributions are reported and discussed, especially, the properties of the bond (3,-1) critical points, which are thought to play a key role in the decomposition of the molecule. From the bond topological analysis of all the bonds, it is observed that the N–N bond is the weakest. The dominating nature of the oxygen atoms was clearly well understood from isosurface electrostatic potential of isolated and symmetrically sitting molecules in the crystal.

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Hunt, Emily M., et Matt Jackson. « Coating and Characterization of Mock and Explosive Materials ». Advances in Materials Science and Engineering 2012 (2012) : 1–5. http://dx.doi.org/10.1155/2012/468032.

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This project develops a method of manufacturing plastic-bonded explosives by using use precision control of agglomeration and coating of energetic powders. The energetic material coating process entails suspending either wet or dry energetic powders in a stream of inert gas and contacting the energetic powder with atomized droplets of a lacquer composed of binder and organic solvent. By using a high-velocity air stream to pneumatically convey the energetic powders and droplets of lacquer, the energetic powders are efficiently wetted while agglomerate drying begins almost immediately. The result is an energetic powder uniformly coated with binder, that is, a PBX, with a high bulk density suitable for pressing. Experiments have been conducted using mock explosive materials to examine coating effectiveness and density. Energetic materials are now being coated and will be tested both mechanically and thermally. This allows for a comprehensive comparison of the morphology and reactivity of the newly coated materials to previously manufactured materials.

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Arabnejad, Saeid, Koichi Yamashita et Sergei Manzhos. « Defects in crystalline PVDF : a density functional theory-density functional tight binding study ». Physical Chemistry Chemical Physics 19, n^o 11 (2017) : 7560–67. http://dx.doi.org/10.1039/c7cp00510e.

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We present a comparative density functional theory (DFT) and density functional tight binding (DFTB) study of structures, energetics, vibrational properties as well as electronic structures of the four crystalline phases of polyvinylidene fluoride (PVDF) with different types of defects.

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Seino, Kaori, et Atsushi Oshiyama. « Microscopic Identification of Surface Steps on SiC by Density-Functional Calculations ». Materials Science Forum 1004 (juillet 2020) : 145–52. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.145.

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We have performed density-functional calculations in order to clarify atomic structures and energetics of surface steps on SiC. The obtained energetics of distinct step types on vicinal 3C-SiC(111) surfaces which correspond to 4H- and 6H-SiC(0001) surfaces reveals the atom-scale reason for the experimental observation in the past that the step morphology is straight for the SiC(0001) surfaces inclined toward the 〈1-100〉 direction while it is meandering for the 〈11-20〉 inclined surfaces. The calculations clarify the rebonding between upper- and lower-terrace edge atoms, which is decisive for the energetics of the atomic steps.

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Laskar, Tanmoy, Alicia Rouco Escorial, Genevieve Schroeder, Wen-fai Fong, Edo Berger, Péter Veres, Shivani Bhandari et al. « The First Short GRB Millimeter Afterglow : The Wide-angled Jet of the Extremely Energetic SGRB 211106A ». Astrophysical Journal Letters 935, n^o 1 (1 août 2022) : L11. http://dx.doi.org/10.3847/2041-8213/ac8421.

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Abstract We present the discovery of the first millimeter afterglow of a short-duration γ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲ z ≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction, A V ≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at t jet = 29.2 − 4.0 + 4.5 days. For a presumed redshift of z = 1, we infer an opening angle, θ jet = (15.°5 ± 1.°4), and beaming-corrected kinetic energy of log ( E K / erg ) = 51.8 ± 0.3 , making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%–40% on timescales of ≳2 days at rates of ≈0.8–1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows.

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Ziegler, Tom. « The 1994 Alcan Award Lecture Density functional theory as a practical tool in studies of organometallic energetics and kinetics. Beating the heavy metal blues with DFT ». Canadian Journal of Chemistry 73, n^o 6 (1 juin 1995) : 743–61. http://dx.doi.org/10.1139/v95-095.

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An evaluation is given of approximate density functional theory as a practical tool in studies on organometallic energetics and kinetics. The evaluation covers electronic excitations and ionizations, electron capture, conformational changes, molecular vibrations, and bond energies, as well as reaction profiles. Keywords: density functional theory, energetics, kinetics, organometallic, catalysis.

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Liu, Yang, Yuangang Xu, Qi Sun et Ming Lu. « Modification of crystalline energetic salts through polymorphic transition : enhanced crystal density and energy performance ». CrystEngComm 22, n^o 24 (2020) : 4130–35. http://dx.doi.org/10.1039/d0ce00056f.

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Taylor, Christopher R., Peter J. Bygrave, Judy N. Hart, Neil L. Allan et Frederick R. Manby. « Improving density functional theory for crystal polymorph energetics ». Physical Chemistry Chemical Physics 14, n^o 21 (2012) : 7739. http://dx.doi.org/10.1039/c2cp24090d.

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Enquist, Brian J., James H. Brown et Geoffrey B. West. « Allometric scaling of plant energetics and population density ». Nature 395, n^o 6698 (septembre 1998) : 163–65. http://dx.doi.org/10.1038/25977.

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Xu, Chuanhao, Chongwei An, Yanling Long, Qianbing Li, Hao Guo, Shuang Wang et Jingyu Wang. « Inkjet printing of energetic composites with high density ». RSC Advances 8, n^o 63 (2018) : 35863–69. http://dx.doi.org/10.1039/c8ra06610h.

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To explore a new manufacturing method in preparing energetic composites, an inkjet printing device possessing the ability of high precision and flexibility was utilized to deposit six 3,4-dinitrofurazanofuroxan and hexogen based explosive inks.

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Denton, M. H., et T. E. Cayton. « Density and temperature of energetic electrons in the Earth's magnetotail derived from high-latitude GPS observations during the declining phase of the solar cycle ». Annales Geophysicae 29, n^o 10 (7 octobre 2011) : 1755–63. http://dx.doi.org/10.5194/angeo-29-1755-2011.

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Abstract. Single relativistic-Maxwellian fits are made to high-latitude GPS-satellite observations of energetic electrons for the period January 2006–November 2010; a constellation of 12 GPS space vehicles provides the observations. The derived fit parameters (for energies ~0.1–1.0 MeV), in combination with field-line mapping on the nightside of the magnetosphere, provide a survey of the energetic electron density and temperature distribution in the magnetotail between McIlwain L-values of L=6 and L=22. Analysis reveals the characteristics of the density-temperature distribution of energetic electrons and its variation as a function of solar wind speed and the Kp index. The density-temperature characteristics of the magnetotail energetic electrons are very similar to those found in the outer electron radiation belt as measured at geosynchronous orbit. The energetic electron density in the magnetotail is much greater during increased geomagnetic activity and during fast solar wind. The total electron density in the magnetotail is found to be strongly correlated with solar wind speed and is at least a factor of two greater for high-speed solar wind (VSW=500–1000 km s−1) compared to low-speed solar wind (VSW=100–400 km s−1). These results have important implications for understanding (a) how the solar wind may modulate entry into the magnetosphere during fast and slow solar wind, and (b) if the magnetotail is a source or a sink for the outer electron radiation belt.

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Myrvold, Knut Marius, et Brian Patrick Kennedy. « Increasing water temperatures exacerbate the potential for density dependence in juvenile steelhead ». Canadian Journal of Fisheries and Aquatic Sciences 75, n^o 6 (juin 2018) : 897–907. http://dx.doi.org/10.1139/cjfas-2016-0497.

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We studied the potential effects of predicted climate change on the energetic demands of juvenile steelhead (Oncorhynchus mykiss) and their consequences for local population size and structure in Idaho, USA. Projected increases in water temperature incurred on average a 10% higher energetic cost by 2040 (range 7.0%–12.5% among study reaches in the watershed) and a 16% increase (range 8.5%–21.3%) by 2080 following the A1B scenario. The predicted increase in energetic cost was largest in the coolest stream reaches, where the proportional increases in energetic cost exceed that of temperature. Energetically, and in absence of increases in food supply, local densities were consequently expected to decline. We examined which factors best described the shape of current size distributions to explore future size distributions as temperatures increase. Mass distribution skewness was best explained by local biomass (positive relationship) and water temperature (negative relationship). The results suggest that local steelhead cohorts will approach a platykurtic, slightly negatively skewed distribution with increasing temperatures and demonstrate that temperature can exacerbate demographic density dependence in fish populations.

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Gonzalez Carmona, Juan Manuel, Alexander Ruden Muñoz, Christian Barbosa, Carolina Ortega Portilla et Federico Sequeda Osorio. « Computational Study of Allotropic Structures of Carbon by Density Functional Theory (DTF) ». Ingeniería y Ciencia 10, n^o 19 (janvier 2014) : 145–62. http://dx.doi.org/10.17230/ingciencia.10.19.7.

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In this paper using Density Functional Theory (DFT), the principal carbonallo tropic crystalline structures (Diamond, graphite, nanotube y fullerene-C60) were simulated. The results shows diamond sp3 bonds formation between carbon atomsand low reactivity, indicating low probability of lateral compound formation and high mechanical properties. Interplanar weakness was evidentin graphite structure, which is related to solid lubrication process. Carbon-Carbon metallic bonds and polarizations at the edges of the structure were observed in Armchair Carbon Nanotube, stabilizing the system which allows the nanotube continuous growth. In fullerene C60structureaFaraday nano-gauge behavior was confirmed, together withlowprobability of interatomic polarization, indicating high structural stability. Besides Total Energy (TE) and Nuclear Repulsion Energy (NRE) values were used to perform energetic comparisons between different structures, allowing the study of electronic stability and their relationship to mechanical properties.

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Tabaru, Y., Y. Nakao, H. Nakashima et K. Kudo. « Areal density diagnostics using suprathermal fusion reaction for laser-imploded D-T pellets ». Laser and Particle Beams 16, n^o 1 (mars 1998) : 153–76. http://dx.doi.org/10.1017/s0263034600011848.

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Detecting highly energetic neutrons produced by suprathermal fusion reactions is expected as a useful method for the areal density diagnosis in future ICF experiments. This paper examines the possibility of ρR diagnosis using suprathermal fusions, on the basis of transport calculations for neutrons and charged particles. Not only neutron elastic scattering but also nuclear elastic scattering of α-particles are considered as the processes producing energetic recoil ions. Since the suprathermal fusion reaction is affected by the plasma temperature through the slowing-down process of energetic α-particles and recoil ions, the yield ratio of highly energetic neutrons emitted from suprathermal fusions to total ones depends considerably on tne temperature. An areal density diagnostic method based on neutron spectroscopy is proposed here that can eliminate the influence of the plasma temperature on the determination of the areal density. Moreover, on the basis of coupled transport/hydrodynamic calculation, we derive a more realistic energy spectrum of neutrons escaping from laser-imploded D-T pellet and examine the usefulness of the diagnosis method proposed in this paper. It is shown that the Method proposed here may be useful for the areal density diagnosis in the ignition-grade ICF Pellets.

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Liang, Y. L., L. G. Wang, C. G. Wang, G. C. Wang et L. Zhang. « Carrier Density Dependence of the Mobility in Disordered Organic Semiconductors with Gaussian Disorder ». Journal of Nanoelectronics and Optoelectronics 17, n^o 7 (1 juillet 2022) : 1098–103. http://dx.doi.org/10.1166/jno.2022.3284.

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In this paper, the charge transport properties and energetic disorder are studied for pristine Si-PCPDTBT, mono-PCBM, bis-PCBM, and their blends of Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM. We show that the current density versus voltage curves of electron-only devices for mono-PCBM, bis-PCBM, Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM, and hole-only devices for Si-PCPDTBT, Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM cannot be accurately described using a conventional mobility model within which the mobility depends only on the electric field, but that a fully consistent description of all curves can be obtained using the improved extended Gaussian disorder model (IEGDM). Within the IEGDM, the presence of energetic disorder is described by a Gaussian density of states, and the mobility depends on the electric field and carrier density. Furthermore, we found that the mobility increases as the width of the Gaussian density of states decreases for both electron-only and hole-only devices, and the mobility is closely related to the energetic disorder. We view this as an indication that the energetic disorder appears to govern the charge transport in disordered organic semiconductors.

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FU, G. Y. « On nonlinear self-interaction of geodesic acoustic mode driven by energetic particles ». Journal of Plasma Physics 77, n^o 4 (22 octobre 2010) : 457–67. http://dx.doi.org/10.1017/s0022377810000619.

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AbstractIt is shown that nonlinear self-interaction of energetic particle-driven geodesic acoustic mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second-order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and energetic particles. Near the midplane of a tokamak, the second-order plasma density perturbation (the sum of second harmonic and zero frequency sideband) is negative on the low field side with its size comparable to the main harmonic at low fluctuation level. These analytic predictions are consistent with the recent experimental observation in DIII-D.

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Knouft, Jason H. « Regional analysis of body size and population density in stream fish assemblages : testing predictions of the energetic equivalence rule ». Canadian Journal of Fisheries and Aquatic Sciences 59, n^o 8 (1 août 2002) : 1350–60. http://dx.doi.org/10.1139/f02-110.

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The energetic equivalence rule predicts that body mass (W) and population density (β) within an assemblage are negatively correlated and will exhibit a W0.75 = β relationship. Bergmann's rule predicts that body size among species will increase with increasing latitude. If species body size increases with latitude, the shape of the body size population density distribution among assemblages may also vary. This change in the body size population density distribution, when viewed in the context of the energetic equivalence rule, may indicate an alteration in the use of available energy by individuals of different sizes within an assemblage. Twenty-eight streams were sampled across four geographically distinct regions to determine if stream fish assemblages conform to the prediction of the energetic equivalence rule. Body size in stream fish assemblages did not support the pattern predicted by Bergmann's rule, but rather was negatively correlated with latitude. Stream fish assemblages generally did not conform to the relationship predicted by the energetic equivalence rule. Moreover, these results, coupled with the predictions of the energetic equivalence rule, suggest that larger individuals tended to control a disproportionately greater amount of energy than smaller individuals in stream fish assemblages, which may be partially due to predation pressure on smaller individuals.

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Zhao, X. X., S. H. Li, Y. Wang, Y. C. Li, F. Q. Zhao et S. P. Pang. « Design and synthesis of energetic materials towards high density and positive oxygen balance by N-dinitromethyl functionalization of nitroazoles ». Journal of Materials Chemistry A 4, n^o 15 (2016) : 5495–504. http://dx.doi.org/10.1039/c6ta01501h.

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The top of the pyramid of tetrazole-based CHNO energetic materials for density and OB: N-dinitromethyl functionalization is a new N-functionalized strategy for the synthesis of highly dense and oxygen-rich energetic materials.

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Giles, Ian D., Alan J. DeHope, Nathaniel B. Zuckerman, Damon A. Parrish et Philip F. Pagoria. « Effect of counter-ion on packing and crystal density of 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1H-tetrazol-1-olate) with five different cations ». Acta Crystallographica Section E Crystallographic Communications 74, n^o 4 (9 mars 2018) : 505–13. http://dx.doi.org/10.1107/s205698901800364x.

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In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1H-tetrazol-1-olate), with the following cations: hydrazinium (1) (2N2H5 +·C6N12O4 2−), hydroxylammonium (2) 2NH4O+·C6N12O4 2− [Pagoria et al.. (2017). Chem. Heterocycl. Compd, 53, 760–778; included for comparison], dimethylammonium (3) (2C2H8N+·C6N12O4 2−), 5-amino-1H-tetrazol-4-ium (4) (2CH4N5 +·C6N12O4 2−·4H2O), and aminoguanidinium (5) (2CH7N4 +·C6N12O4 2−). Both the supramolecular interactions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m−1. In 5, the tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.

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Persic, Massimo, et Yoel Rephaeli. « Non-thermal emission in the lobes of Fornax A ». Monthly Notices of the Royal Astronomical Society 485, n^o 2 (20 février 2019) : 2001–9. http://dx.doi.org/10.1093/mnras/stz511.

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Abstract Current measurements of the spectral energy distribution in radio, X-ray and γ-ray provide a sufficiently wide basis for determining basic properties of energetic electrons and protons in the extended lobes of the radio galaxy Fornax A. Of particular interest is establishing observationally, for the first time, the level of contribution of energetic protons to the extended emission observed by the Fermi satellite. Two recent studies concluded that the observed γ-ray emission is unlikely to result from Compton scattering of energetic electrons off the optical radiation field in the lobes, and therefore that the emission originates from decays of neutral pions produced in interactions of energetic protons with protons in the lobe plasma, implying an uncomfortably high-proton energy density. However, our exact calculation of the emission by energetic electrons in the magnetized lobe plasma leads to the conclusion that all the observed emission can, in fact, be accounted for by energetic electrons scattering off the ambient optical radiation field, whose energy density (which, based on recent observations, is dominated by emission from the central galaxy NGC 1316) we calculate to be higher than previously estimated.

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Ding, Qing Yun, Dan Ma, Yu Tang, Xi Li, Chao Qun Ma et Peng Shen. « Effect of Secondary Treatment on the Exothermic and Tensile Properties of Vacuum Hot-Pressed Ni/Al Energetic Structural Composites ». Materials Science Forum 1071 (18 octobre 2022) : 74–79. http://dx.doi.org/10.4028/p-o0f39g.

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Ni/Al energetic structural materials were prepared by vacuum hot-pressing method and then treated by secondary treatment of cold rolling or cold isostatic pressing. The effects of secondary treatment on the surface morphology, the phase composition, density, exothermic properties and tensile properties of Ni/Al energetic structural materials were investigated. The results showed that the density, the reaction energy density and the sensitivity of energetic materials improved significantly by the secondary treatment of cold rolling or cold isostatic pressing. It was also found that, after cold rolling and cold isostatic pressing, the energy density increased from 780 J/g to 1089 J/g and 993 J/g, respectively, and the initial reaction temperature was advanced by 46 °C and 14°C simultaneously. This is related to the increased in the contact area between Al particles and Ni particles. Meanwhile, the tensile strength increased from 166.7 MPa to 254.8 MPa and 211.3 MPa, respectively.

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ELLIS, JOHN, NICK E. MAVROMATOS et DIMITRI V. NANOPOULOS. « D-FOAM PHENOMENOLOGY : DARK ENERGY, THE VELOCITY OF LIGHT AND A POSSIBLE D-VOID ». International Journal of Modern Physics A 26, n^o 13 (20 mai 2011) : 2243–62. http://dx.doi.org/10.1142/s0217751x11053353.

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In a D-brane model of cosmology and space–time foam, there are contributions to the dark energy that depend on the D-brane 10-velocities and on the density of D-particle defects in the ten-dimensional bulk. The latter may also reduce the speeds of energetic photons, establishing a phenomenological connection with astrophysical probes of the universality of the velocity of light. Specifically, the cosmological dark energy density measured at the present epoch may be linked to the apparent retardation of energetic photons propagating from nearby AGN's. However, this nascent field of "D-foam phenomenology" may be complicated by variations in the D-particle density encountered at different cosmological epochs. A reduced density of D-particles encountered at redshifts z ~ 1 — a "D-void" — would increase the dark energy while suppressing the vacuum refractive index, and thereby might reconcile the AGN measurements with the relatively small retardation seen for the energetic photons propagating from GRB 090510, as measured by the Fermi satellite.

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Wang, Hao-Ran, Chong Zhang, Bing-Cheng Hu et Xue-Hai Ju. « Theoretical Investigation of Energetic Salts with Pentazolate Anion ». Molecules 25, n^o 8 (13 avril 2020) : 1783. http://dx.doi.org/10.3390/molecules25081783.

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Energetic salts based on pentazolate anion (cyclo-N5−) have attracted much attention due to their high nitrogen contents. However, it is an enormous challenge to efficiently screen out an appropriate cation that can match well with cyclo-N5−. The vertical electron affinity (VEA) of the cations and vertical ionization potential (VIP) of the anions for 135 energetic salts and some cyclo-N5− salts were calculated by the density functional theory (DFT). The magnitudes of VEA and VIP, and their matchability were analyzed. The results based on the calculations at the B3LYP/6-311++G(d,p) and B3LYP/aug-cc-pVTZ levels indicate that there is an excellent compatibility between cyclo-N5− and cation when the difference between the VEA of cation and the VIP of cyclo-N5− anion is −2.8 to −1.0 eV. The densities of the salts were predicted by the DFT method. Relationship between the calculated density and the experimental density was established as ρExpt = 1.111ρcal − 0.06067 with a correlation coefficient of 0.905. This regression equation could be in turn used to calibrate the calculated density of the cyclo-N5− energetic salts accurately. This work provides a favorable way to explore the energetic salts with excellent performance based on cyclo-N5−.

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Ma, Yuguang, et Peter Politzer. « Electronic Density Approaches to the Energetics of Noncovalent Interactions ». International Journal of Molecular Sciences 5, n^o 4 (1 avril 2004) : 130–40. http://dx.doi.org/10.3390/i5040130.

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Zeng, Chen, Suping Duan, Chi Wang, Lei Dai, Stephen Fuselier, James Burch, Roy Torbert, Barbara Giles et Christopher Russell. « Magnetospheric Multiscale observations of energetic oxygen ions at the duskside magnetopause during intense substorms ». Annales Geophysicae 38, n^o 1 (29 janvier 2020) : 123–35. http://dx.doi.org/10.5194/angeo-38-123-2020.

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Abstract. Energetic oxygen ions (1–40 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the duskside magnetopause boundary layer during phase 1 are investigated. There are 57 duskside magnetopause crossing events identified during intense substorms (AE>500 nT). These 57 events of energetic O+ at the duskside magnetopause include 26 events during the expansion phase and 31 events during the recovery phase of intense substorms. It is found that the O+ density in the duskside magnetopause boundary layer during the recovery phase (0.081 cm−3) is larger than that during the expansion phase (0.069 cm−3). The 26 events of energetic O+ ions at the duskside magnetopause during intense substorm expansion phase are all under the southward interplanetary magnetic field (IMF). There are only seven events under northward IMF, and they all occurred during the intense substorm recovery phase. The density of energetic O+ at the duskside magnetopause ranges from 0.007 to 0.599 cm−3. The maximum density of O+ occurred during the intense substorm recovery phase and under southward IMF. When the IMF is southward, the O+ density shows an exponential increase with the IMF Bz absolute value. Meanwhile, the O+/H+ density ratio shows an exponential growth with the IMF By. These results agree with previous studies in the near-Earth magnetosphere during intense substorm. It is suggested that O+ abundance in the duskside magnetopause boundary layer has a close relation to O+ variations in the near-Earth magnetosphere during intense substorms.

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Sibeck, D. G., K. Kudela, T. Mukai, Z. Nemecek et J. Safrankova. « Radial dependence of foreshock cavities : a case study ». Annales Geophysicae 22, n^o 12 (22 décembre 2004) : 4143–51. http://dx.doi.org/10.5194/angeo-22-4143-2004.

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Abstract. We present a case study of Geotail, Interball-1, IMP-8, and Wind observations of density and magnetic field strength cavities excavated by the enhanced pressures associated with bursts of energetic ions in the foreshock. Consistent with theoretical predictions, the pressure of the energetic ions diminishes rapidly with upstream distance due to a decrease in the flux of energetic ions and a transition from near-isotropic to streaming pitch angle distributions. Consequently, the cavities can only be observed immediately upstream from the bow shock. A comparison of conditions upstream from the pre- and post-noon bow shock demonstrates that foreshock cavities introduce perturbations into the oncoming solar wind flow with dimensions smaller than those of the magnetosphere. Dayside geosynchronous magnetic field strength variations observed by GOES-8 do not track the density variations seen by any of the spacecraft upstream from the bow shock in a one-to-one manner, indicating that none of these spacecraft observed the precise sequence of density variations that actually struck the subsolar magnetopause. Key words. Interplanetary physics (energetic particles; planetary bow shocks) – Magnetospheric physics (solar wind-magnetosphere interactions)

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Xu, Luping, Juan Qiao, Siyu Xu, Xiaoyu Zhao, Wanjun Gong et Taizhong Huang. « Constructing Strategies and Applications of Nitrogen-Rich Energetic Metal–Organic Framework Materials ». Catalysts 10, n^o 6 (19 juin 2020) : 690. http://dx.doi.org/10.3390/catal10060690.

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The synthesis of energetic metal–organic frameworks (EMOFs) with one-dimensional, two-dimensional and three-dimensional structures is an effective strategy for developing new-generation high-energy-density and insensitive materials. The basic properties, models, synthetic strategies and applications of EMOF materials with nitrogen-rich energetic groups as ligands are reviewed. In contrast with traditional energetic materials, EMOFs exhibit some interesting characteristics, like tunable structure, diverse pores, high-density, high-detonation heat and so on. The traditional strategies to design EMOF materials with ideal properties are just to change the types and the size of energetic ligands and to select different metal ions. Recently, some new design concepts have come forth to produce more EMOFs materials with excellent properties, by modifying the energetic groups on the ligands and introducing highly energetic anion into skeleton, encapsulating metastable anions, introducing templates and so on. The paper points out that appropriate constructing strategy should be adopted according to the inherent characteristics of different EMOFs, by combining with functional requirements and considering the difficulties and the cost of production. To promote the development and application of EMOF materials, the more accurate and comprehensive synthesis, systematic performance measurement methods, theoretical calculation and structure simulation should be reinforced.

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Marquet, Pablo A., Sergio A. Navarrete et Juan C. Castilla. « Body Size, Population Density, and the Energetic Equivalence Rule ». Journal of Animal Ecology 64, n^o 3 (mai 1995) : 325. http://dx.doi.org/10.2307/5894.

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Woinska, Magdalena, Monika Nowakowska, Przemyslaw Taciak, Paulina M. Dominiak et Krzysztof Wozniak. « Structure, charge density and energetic features of quinoline derivatives ». Acta Crystallographica Section A Foundations and Advances 73, a2 (1 décembre 2017) : C699—C700. http://dx.doi.org/10.1107/s205327331708874x.

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Chi, Weijie, Butong Li et Haishun Wu. « Density function theory study on energetic nitro-triaziridine derivatives ». Structural Chemistry 24, n^o 2 (3 juillet 2012) : 375–81. http://dx.doi.org/10.1007/s11224-012-0083-2.

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Hobosyan, Mkhitar A., et Karen S. Martirosyan. « Iodine Pentoxide Nano-rods for High Density Energetic Materials ». Propellants, Explosives, Pyrotechnics 42, n^o 5 (20 février 2017) : 506–13. http://dx.doi.org/10.1002/prep.201600220.

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Hou, Tianjiao, Hongwei Ruan, Guixiang Wang et Jun Luo. « 2,4,4,8,8-Pentanitro-2-Azaadamantane : A High-Density Energetic Compound ». European Journal of Organic Chemistry 2017, n^o 46 (14 décembre 2017) : 6957–60. http://dx.doi.org/10.1002/ejoc.201701403.

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Joo, Young-Hyuk, et Jean'ne M. Shreeve. « High-Density Energetic Mono- or Bis(Oxy)-5-Nitroiminotetrazoles ». Angewandte Chemie International Edition 49, n^o 40 (25 août 2010) : 7320–23. http://dx.doi.org/10.1002/anie.201003866.

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Joo, Young-Hyuk, et Jean'ne M. Shreeve. « High-Density Energetic Mono- or Bis(Oxy)-5-Nitroiminotetrazoles ». Angewandte Chemie 122, n^o 40 (25 août 2010) : 7478–81. http://dx.doi.org/10.1002/ange.201003866.

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Gettins, Peter G. W., et Klavs Dolmer. « A proximal pair of positive charges provides the dominant ligand-binding contribution to complement-like domains from the LRP (low-density lipoprotein receptor-related protein) ». Biochemical Journal 443, n^o 1 (14 mars 2012) : 65–73. http://dx.doi.org/10.1042/bj20111867.

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The LRP (low-density lipoprotein receptor-related protein) can bind a wide range of structurally diverse ligands to regions composed of clusters of ~40 residue Ca2+-dependent, disulfide-rich, CRs (complement-like repeats). Whereas lysine residues from the ligands have been implicated in binding, there has been no quantification of the energetic contributions of such interactions and hence of their relative importance in overall affinity, or of the ability of arginine or histidine residues to bind. We have used four representative CR domains from the principal ligand-binding cluster of LRP to determine the energetics of interaction with well-defined small ligands that include methyl esters of lysine, arginine, histidine and aspartate, as well as N-terminally blocked lysine methyl ester. We found that not only lysine but also arginine and histidine bound well, and when present with an additional proximal positive charge, accounted for about half of the total binding energy of a protein ligand such as PAI-1 (plasminogen activator inhibitor-1). Two such sets of interactions, one to each of two CR domains could thus account for almost all of the necessary binding energy of a real ligand such as PAI-1. For the CR domains, a central aspartate residue in the sequence DxDxD tightens the Kd by ~20-fold, whereas DxDDD is no more effective. Together these findings establish the rules for determining the binding specificity of protein ligands to LRP and to other LDLR (low-density lipoprotein receptor) family members.

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