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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Marked Consequences of Systematic Oligothiophene Catenation in Thieno[3,4- c ]pyrrole-4,6-dione and Bithiopheneimide Photovoltaic Copolymers
As effective building blocks for high-mobility transistor polymers, oligothiophenes are receiving attention for polymer solar cells (PSCs) because the resulting polymers can effectively suppress charge recombination. In this work we investigate two series of in-chain donor–acceptor copolymers, PTPDnT and PBTInT, based on thieno[3,4-c]pyrrole-4,6-dione (TPD) or bithiopheneimide (BTI) as electron acceptor units, respectively, and oligothiophenes (nTs) as donor counits, for high-performance PSCs. Intramolecular S···O interaction leads to more planar TPD polymer backbones, however backbone torsion yields greater open-circuit voltages for BTI polymers. Thiophene addition progressively raises polymer HOMOs but marginally affects their band gaps. FT-Raman spectra indicate that PTPDnT and PBTInT conjugation lengths scale with nT catenation up to $n$ = 3 and then saturate for longer oligomer. Furthermore, the effects of oligothiophene alkylation position are explored, revealing that the alkylation pattern greatly affects film morphology and PSC performance. The 3T with “outward” alkylation in PTPD3T and PBTI3T affords optimal $π$-conjugation, close stacking, long-range order, and high hole mobilities (0.1 cm 2 /(V s)). These characteristics contribute to the exceptional ~80% fill factors for PTPD3T-based PSCs with PCE = 7.7%. The results demonstrate that 3T is the optimal donor unit among nTs ($n$ = 1–4) for photovoltaic polymers. Grazing incidence wide-angle X-ray scattering, transmission electron microscopy, and time-resolved microwave conductivity measurements reveal that the terthiophene-based PTPD3T blend maintains high crystallinity with appreciable local mobility and long charge carrier lifetime. These results provide fundamental materials structure-device performance correlations and suggest guidelines for designing oligothiophene-based polymers with optimal thiophene catenation and appropriate alkylation pattern to maximize PSC performance.
Interfacial Chemistry in Solid-State Batteries: Formation of Interphase and Its Consequences
Benefitting from extremely high shear modulus and high ionic transference number, solid electrolytes are promising candidates to address both the dendrite growth and electrolyte consumption problems inherent to the widely adopted liquid-phase electrolyte batteries. However, solid electrolyte/electrode interfaces present high resistance and complicated morphology, hampering the development of solid-state battery systems, while requiring advanced analysis for rational improvement. Here, we employ an ultra-sensitive three-dimensional (3D) chemical analysis to uncover the dynamic formation of interphases at the solid electrolyte/electrode interface. While the formation of interphases widens the electrochemical window, their electronic and ionic conductivities determine the electrochemical performance and has a large influence on dendrite growth. Our results suggest that, contrary to the general understanding, highly stable solid electrolytes with metal anodes in fact promote fast dendritic formation, as a result of less Li consumption and much larger curvature of dendrite tips that leads to an enhanced electric driving force. Detailed thermodynamic analysis shows an interphase with low electronic conductivity, high ionic conductivity, chemically stable yet having a dynamic thickness and uniform coverage is needed to prevent dendrite growth. Finally, this work provides a paradigm for interphase design to address the dendrite challenge, paving the way for the development of robust, fully operational solid-state batteries.
Surface charge dynamics in photosynthetic membranes and the structural consequences
The strict stacking of plant photosynthetic membranes into granal structures plays a vital role in energy conversion. The molecular forces that lead to grana stacking, however, are poorly understood. Here we evaluate the interplay between repulsive electrostatic (F el ) and attractive van der Waals (F vdWaals ) forces in grana stacking. In contrast to previous reports, we find that the physicochemical balance between attractive and repulsive forces fully explains grana stacking. Extending the force balance analysis to lateral interactions within the oxygen-evolving photosystem II (PSII)–light harvesting complex II (LHCII) supercomplex reveals that supercomplex stability is very sensitive to F el changes. F el is highly dynamic, increasing up to 1.7-fold on addition of negative charges by phosphorylation of grana-hosted proteins. We show that this leads to specific destabilization of the supercomplex, and that changes in F el have contrasting effects on vertical stacking and lateral intramembrane organization. Lastly, this enables discrete biological control of these central structural features.
Thermodynamic consequences of Tyr to Trp mutations in the cation–π-mediated binding of trimethyllysine by the HP1 chromodomain
Evolution has converged on cation–p interactions for recognition of quaternary alkyl ammonium groups such as trimethyllysine (Kme3). While computational modelling indicates that Trp provides the strongest cation–p interaction of the native aromatic amino acids, there is limited corroborative data from measurements within proteins. Herein we investigate a Tyr to Trp mutation in the binding pocket of the HP1 chromodomain, a reader protein that recognizes Kme3. Binding studies demonstrate that the Trpmediated cation–p interaction is about -5 kcal mol -1 stronger, and the Y24W crystal structure shows that the mutation is not perturbing. Quantum mechanical calculations indicate that greater enthalpic binding is predominantly due to increased cation–π interactions. NMR studies indicate that differences in the unbound state of the Y24W mutation lead to enthalpy–entropy compensation. These results provide direct experimental quantification of Trp versus Tyr in a cation–π interaction and afford insight into the conservation of aromatic cage residues in Kme3 reader domains.
Host galaxy spectra and consequences for supernova typing from the SDSS SN survey
We present the spectroscopy from 5254 galaxies that hosted supernovae (SNe) or other transient events in the Sloan Digital Sky Survey II (SDSS-II). Obtained during SDSS-I, SDSS-II, and the Baryon Oscillation Spectroscopic Survey, this sample represents the largest systematic, unbiased, magnitude limited spectroscopic survey of SN host galaxies. Using the host galaxy redshifts, we test the impact of photometric SN classification based on SDSS imaging data with and without using spectroscopic redshifts of the host galaxies. Following our suggested scheme, there are a total of 1166 photometrically classified SNe Ia when using a flat redshift prior and 1126 SNe Ia when the host spectroscopic redshift is assumed. For 1024 (87.8%) candidates classified as likely SNe Ia without redshift information, we find that the classification is unchanged when adding the host galaxy redshift. Using photometry from SDSS imaging data and the host galaxy spectra, we also report host galaxy properties for use in future analysis of SN astrophysics. Finally, we investigate the differences in the interpretation of the light curve properties with and without knowledge of the redshift. Without host galaxy redshifts, we find that SALT2 light curve fits are systematically biased toward lower photometric redshift estimates and redder colors in the limit of low signal-to-noise data. The general improvements in performance of the light curve fitter and the increased diversity of the host galaxy sample highlights the importance of host galaxy spectroscopy for current photometric SN surveys such as the Dark Energy Survey and future surveys such as the Large Synoptic Survey Telescope.
Some cosmological consequences of Weyl invariance
We examine some Weyl invariant cosmological models in the framework of generalized dilaton gravity, in which the action is made of a set of N conformally coupled scalar fields. It will be shown that when the FRW ansatz for the spacetime metric is assumed, the Ward identity for conformal invariance guarantees that the gravitational equations hold whenever the scalar fields EM do so. It follows that any scale factor can solve the theory provided a non-trivial profile for a dilaton field. In particular, accelerated expansion is a natural solution to the full set of equations.
Dry and hot: the hydraulic consequences of a climate change-type drought for Amazonian trees
How plants respond physiologically to leaf warming and low water availability may determine how they will perform under future climate change. In 2015-2016 an unprecedented drought occurred across Amazonia with record-breaking high temperatures and low soil moisture, offering a unique opportunity to evaluate the performances of Amazonian trees to a severe climatic event. We quantified the responses of leaf water potential, sap velocity, whole-tree hydraulic conductance (Kwt), turgor loss and xylem embolism, during and after the 2015-2016 El Niño for five canopy-tree species. Leaf/xylem safety margins (SM), sap velocity and Kwt showed a sharp drop during warm periods. SMs were negatively correlated with vapor pressure deficit but had no significant relationship with soil water storage. Based on our calculations of canopy stomatal and xylem resistances, the decrease in sap velocity and Kwt was due to a combination of xylem cavitation, and stomatal closure. Our results suggest extremely warm droughts greatly amplify the degree of trees’ physiological stress and can lead to mortality. Given the extreme nature of the 2015-2016 El Niño and that temperatures are predicted to increase, this work can serve as a case study of the possible impact climate warming can have on tropical trees.
Atomic structure of the i- R -Cd quasicrystals and consequences for magnetism
Not Available
Consequences of Femtosecond Laser Filament Generation Conditions in Standoff Laser Induced Breakdown Spectroscopy
We investigate the role of femtosecond laser focusing conditions on ablation properties and its implications on analytical merits and standoff detection applications. Femtosecond laser pulses can be used for ablation either by tightly focusing or by using filaments generated during its propagation. We evaluated the persistence of atomic, and molecular emission features as well as time evolution of the fundamental properties (temperature and density) of ablation plumes generated using different methods.
Consequences of Decreased Light Harvesting on Photosystem II Function in Synechocystic sp. PCC 6803
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Consequences of CCD imperfections for cosmology determined by weak lensing surveys: from laboratory measurements to cosmological parameter bias
Weak gravitational lensing causes subtle changes in the apparent shapes of galaxies due to the bending of light by the gravity of foreground masses. By measuring the shapes of large numbers of galaxies (millions in recent surveys, up to tens of billions in future surveys) we can infer the parameters that determine cosmology. Imperfections in the detectors used to record images of the sky can introduce changes in the apparent shapes of galaxies, which in turn can bias the inferred cosmological parameters. In this paper we consider the effect of two widely discussed sensor imperfections: tree rings, due to impurity gradients that cause transverse electric fields in the charge-coupled devices (CCDs), and pixel size variation, due to periodic CCD fabrication errors. These imperfections can be observed when the detectors are subject to uniform illumination (flat-field images). We develop methods to determine the spurious shear and convergence (due to the imperfections) from the flat-field images. We calculate how the spurious shear when added to the lensing shear will bias the determination of cosmological parameters. We apply our methods to candidate sensors of the Large Synoptic Survey Telescope (LSST) as a timely and important example, analyzing flat-field images recorded with LSST prototype CCDs in the laboratory. We find that tree rings and periodic pixel size variation present in the LSST CCDs will introduce negligible bias to cosmological parameters determined from the lensing power spectrum, specifically w, Ω{sub m}, and σ{sub 8}.
State-of-the-Art Reactor Consequence Analysis Project Uncertainty Analysis: Insights on Offsite Consequences.
Abstract not provided.
Examining the Effect of Plume Rise on Radiological Consequences of Nuclear Accidents
A nuclear accident could cause release of radioactive material outside containment. This material will eventually disperse into the surrounding environment, and could pose a serious threat to public safety, and environment. Mitigation of radiological consequences of such an accident is highly desirable, and since Fukushima accident, there has been a growing focus on nuclear utilities to develop capabilities for this purpose. Undoubtedly, suppression of radioactive material release and dispersion is the primary mean for mitigating radiological consequences nevertheless alternative methods should also be explored to broaden the spectrum of choices for actual circumstances. As we know that, dispersion of radioactive material and subsequent radiological consequences are affected by plume rise. Plume rise is an important factor in determining ground level contamination since it can increase effective release height appreciably provided that effluent discharge speed and temperature is high enough. Under most circumstances, one can expect reduction in radiological consequences due to lower levels of radiation dose and ground contamination in the presence of adequate plume rise. Nevertheless, the effect of plume rise is usually ignored in radiological consequence studies for the sake of conservatism, and lack of information. However, this particular attribute of plume rise interested us to investigate the effect of plume rise in the scope of consequence mitigation and how this advantage could be utilized during an accident progression to minimize the impact of radioactivity release to the environment. In this work, we examine the effect of plume rise on radiological consequences of a nuclear accident for plume rise contributions much larger ({approx}500 m) than usually achievable in normal circumstances. The effect of plume rise on radiological consequences is quantified in this study as decontamination credit (DCC) achievable corresponding to maximum annual dose. This analysis is performed for a number of release heights and atmospheric conditions. We discuss available results in the scope of radiological consequence mitigation, devising a strategy for utilizing plume rise phenomenon with the help of an external propelling device like a jet engine for radiological consequence management. This study is continuation of our efforts for devising systems and strategies to mitigate consequences of radioactivity release accidents like Fukushima. We have proposed several ideas for suppressing/preventing the dispersion of released radioactive material to the environment using offsite equipment.
A whole wilderness of warning: Assessing economic consequences of nuclear releases - 15494
The consequences of the Fukushima Dai-ichi disaster may provide a useful analogue for assessing the consequences of an accident involving the transport of spent nuclear fuel in the United States. An unexamined, to date, aspect of the Fukushima Dai-ichi disaster is the wide disagreement about the economic consequences of the release. There exist a variety of different estimates and different models and methods for performing these estimates, but not a systematic way to address the range of issues such a disaster generated. This paper examines the sources, methods, data, and assumptions used to prepare economic consequence estimates of the disaster. This paper compares and contrasts these estimates and evaluates them for their reliability. The wide dispersion of consequence assessments as defined by various media and agency impact reports in the post-Fukushima era are evidence that such variability does not serve the industry, regulators, government or researchers well. While a protocol exists to gauge the intensity of an incident (INES Scale) no pre-existing methodology exists to measure the various socioeconomic impacts associated with a radiological disaster, be it induced by a natural disaster incident or human initiated. This paper argues that an improved method will be necessary and suggests some parameters for such a method. Nevada has started the dialogue on such a comprehensive methodology (Ballard 2012, Ballard 2014). Despite this effort by a stakeholder, the regulatory agencies involved in nuclear waste shipments in the United States appear reluctant to begin a dialogue about how to address the full range and scope of issues. Resolution of this problem will be a necessary prerequisite to any large scale shipping program. It will be necessary to adopt a standardized methodology to assess consequences of a radiological emergency and incorporate this into the environmental impact statement process for the shipping program. This analytical deficiency should be addressed by these agencies/regulators and in preparation for the potential movement of nuclear waste in the quantities necessary to service the nuclear power industry and to address the existing spent nuclear fuel (SNF) stockpiles across the United States. It will be necessary to demonstrate to stakeholders that the benefits of shipping radioactive substances this dangerous outweigh the costs of a possible accident or terrorist incident. The nuclear energy industry should support funding for these assessment studies in order to provide a basis for discussions about the costs and benefits of the shipments. The studies would provide stakeholders with clarity about the possible consequences of the program. The studies will also assist Japan in its efforts to understand what their disaster means for that country. This paper will begin the dialogue on how such analytical protocols could be constructed to pre-stage the research necessary to assess such consequences. (authors)
Concept for Cyber-Physical Consequence Process
The Department of Homeland Security’s Office of Cyber and Infrastructure Analysis (DHS/OCIA) has a mission and vision that promotes innovation as central to expanding the organization’s capability to conduct consequence analysis. To pursue such innovation, OCIA is sponsoring a seedling effort with Idaho National Laboratory (INL) to leverage data from the proposed Automated Vulnerability Assessment (AVA) capability, which the DHS Science and Technology (S&T) Directorate is developing through a separate INL effort. The first phase of this effort is to develop a process by which recognized vulnerabilities can be scored relative to importance, reflected primarily in the ability to initiate high consequence and potentially cascading events. This report documents a cyber-physical metrics process (CPMP) to tie physical impact to the malicious exploitation of cyber vulnerabilities in industrial control systems (ICS) with the potential for initiating consequence in the critical infrastructure. The scale of achieving any particular physical consequence is dependent upon the ICS Component the vulnerability exists on, the Level of Access that the exploit would allow to component function and the Physical Impact (CLAPI) to the power system that the component is tied. A modified common vulnerability scoring system (CVSS) was detailed and demonstrated for the power sector with three case studies associated with a recognized vulnerability, with significant consequence detail provided to apply the process across the power sector. A detailed table that provides background on the power system components, ICS-enabled monitoring and control, potential consequence effects, and CVSS scoring is provided. To demonstrate the applicability of the CPMP, tables are provided as examples for other sectors that include chemical, water/wastewater and oil/gas.
Criticality Analysis of a Water Distribution System Considering Both Economic Consequences and Hydraulic Loss Using Modern Portfolio Theory
This study introduces an approach using Modern Portfolio Theory (MPT) to consider hydraulic resilience and economic consequence resilience of a water distribution system (WDS) to identify critical assets. ECLIPS (Economic Consequence Linked to Interruption in Providing Service), a way to represent loss of water provision as economic loss, is used to measure economic consequence following a reduction of WDS functionality. The approach is demonstrated using a hypothetical WDS and tested for pipe breakage and replacement scenarios using EPANET hydraulic simulations. First, the correlation between hydraulic resilience and economic consequence resilience was investigated to assess differences between two resilience measures for identifying pipe’s criticality for replacement. The results confirmed the two resilience measures exhibited differing responses (covariance = 0.2), suggesting that use of both would provide complementary insight. Results of the MPT analysis identified the benefits of balancing hydraulic and economic consequence resilience measures to yield lower risk. This study provides a practical approach to incorporate economic consequence into planning, design, and research applications identifying critical WDS assets.