Novel Power Electronics Three-Dimensional Heat Exchanger: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, K.; Cousineau, J.; Lustbader, J.

2014-08-01

Electric drive systems for vehicle propulsion enable technologies critical to meeting challenges for energy, environmental, and economic security. Enabling cost-effective electric drive systems requires reductions in inverter power semiconductor area. As critical components of the electric drive system are made smaller, heat removal becomes an increasing challenge. In this paper, we demonstrate an integrated approach to the design of thermal management systems for power semiconductors that matches the passive thermal resistance of the packaging with the active convective cooling performance of the heat exchanger. The heat exchanger concept builds on existing semiconductor thermal management improvements described in literature and patents,more » which include improved bonded interface materials, direct cooling of the semiconductor packages, and double-sided cooling. The key difference in the described concept is the achievement of high heat transfer performance with less aggressive cooling techniques by optimizing the passive and active heat transfer paths. An extruded aluminum design was selected because of its lower tooling cost, higher performance, and scalability in comparison to cast aluminum. Results demonstrated a heat flux improvement of a factor of two, and a package heat density improvement over 30%, which achieved the thermal performance targets.« less

The Pulse Detonation Rocket Induced MHD Ejector (PDRIME) Concept (Preprint)

DTIC Science & Technology

2008-06-10

flight applications. Thrust augmentation , such as PDE- ejector configurations, can potentially alleviate this problem. Here, we study the potential...flow, to assist in augmentation of the thrust . Ejectors typically transfer energy between streams through shear stress between separate flow streams...and the ejector operates. This is one of several configurations in which the PDRIME concept could be used for thrust augmentation in advanced

New service of Earth Interactions offers sneak peek at work in progress

NASA Astrophysics Data System (ADS)

A new service of the all-electronic journal Earth Interactions (Web site http://EarthInter-actions.org) now provides online access to abstracts or preprints of selected papers being presented at various Earth system science conferences. The new service, “Earth Abstractions,” is separate from the peer-reviewed articles in Earth Interactions. The editors select the sessions that will be featured. AGU Spring Meeting abstracts are now highlighted on the site.The abstract titles in Earth Abstractions will link directly to online extended abstracts or preprints located on the authors' home servers if such abstracts are made available. As the author updates the preprint and posts it to the same URL, Earth Abstractions will continue to feature the most recent information from the author related to that work. Readers can preview an author's work as it evolves prior to the meeting as well as refer to it for a year after the meeting has ended. This exchange also provides a means for authors to receive positive feedback on their papers independent of the conference session, which may help those who plan to submit papers about their work to a peer-reviewed journal.

Mechanism of Hydrogen Production in [Fe-Fe]-Hydrogenase: A Density Functional Theory Study (Preprint)

DTIC Science & Technology

2007-03-01

of NiFe hydrogenases. Dalton Transactions 2003,4030-4038. (9) Armstrong, F. A., Hydrogenases: active site puzzles and progress. Current Opinion in...DFT Investigation of Structural, Electronic, and Catalytic Properties of Diiron Complexes Related to the [2Fe]H Subcluster of Fe-Only Hydrogenases...Hydrogenases: Effects of Redox State and Ligand Characteristics on Structural, Electronic, and Reactivity Properties of Complexes Related to the [2Fe]H

Stress Corrosion Cracking Facet Crystallography of Ti-8Al-1Mo-1V (Preprint)

DTIC Science & Technology

2011-05-01

fractography and electron backscatter diffraction. The results indicate that most facets are formed nearly perpendicular to the loading direction on...of Ti-8Al- 1Mo-1V have been characterized using quantitative fractography and electron backscatter diffraction. The results indicate that most facets...EBSD and quantitative tilt fractography [27;29] allow for determination of the crystallographic fracture plane to an accuracy between 1o [29] and

When are Overcomplete Topic Models Identifiable? Uniqueness of Tensor Tucker Decompositions with Structured Sparsity

DTIC Science & Technology

2013-08-14

Communications and Computing, Electrical Engineering and Computer Science Dept., University of California, Irvine, USA 92697. Email : a.anandkumar...uci.edu,mjanzami@uci.edu. Daniel Hsu and Sham Kakade are with Microsoft Research New England, 1 Memorial Drive, Cambridge, MA 02142. Email : dahsu...Andreas Maurer, Massimiliano Pontil, and Bernardino Romera-Paredes. Sparse coding for multitask and transfer learning. ArxXiv preprint, abs/1209.0738, 2012

Numerical and Analytical Modeling of Laser Deposition with Preheating (Preprint)

DTIC Science & Technology

2007-03-01

temperature materials, Numerical Heat Transfer 11 (1987) 477-491. [9] L. Han, F.W. Liou, K.M. Phatk, Modeling of laser cladding with powder injection... cladding process. This laser additive manufacturing technique allows quick fabrication of fully-dense metallic components directly from Computer...1, laser deposition uses a focused laser beam as a heat source to create a melt pool on an underlying substrate. Powder material is then injected

Magnetohydrodynamic Augmentation of Pulse Detonation Rocket Engines (Preprint)

DTIC Science & Technology

2010-09-28

augmentation of the thrust . Ejectors typically transfer energy between streams through shear stress between separate flow streams, where a portion of the...the opportunity to extract energy and apply it to a separate stream where the net thrust can be increased. With MHD augmentation , such as in the Pulse...with the PDRIME for separate or additional thrust augmentation . Results show potential performance gains under many flight and operating conditions

The preprint debate: What are the issues?

PubMed

da Silva, Jaime A Teixeira

2018-04-01

The debate surrounding preprints is increasing. Preprint proponents claim that preprints are a way to shore up trust in academic publishing, that they provide an additional 'quality' screen prior to traditional peer review, that they can assist with the replication crisis plaguing science in part by making negative or contradictory results public, and that they speed up the publishing process because fundamental results can be presented early, serving as timely reports for the purposes of tenure or grant funding. Preprint skeptics and critics claim that preprints may represent a risk and a danger to quality-based academic publishing because they are documents that have not been carefully and thoroughly vetted prior to their release into the public domain. Thus, academics who cite invalid, poorly vetted, or false facts could cause harm, not unlike the unscholarly 'predatory' open access movement. Feedback on work from lesser-known groups, or on less glamorous topics, may be null or worse than from traditional peer review, annulling an initial key objective of preprints. Although there is no widespread empirical evidence or data yet regarding some of these issues, academics should be aware of the ideological, financial, and political tug-of-war taking place before deciding if they wish to publish their important findings as a preprint prior or simultaneous to submitting to a regular journal for peer review.

When are Overcomplete Representations Identifiable? Uniqueness of Tensor Decompositions Under Expansion Constraints

DTIC Science & Technology

2013-06-16

Science Dept., University of California, Irvine, USA 92697. Email : a.anandkumar@uci.edu,mjanzami@uci.edu. Daniel Hsu and Sham Kakade are with...Microsoft Research New England, 1 Memorial Drive, Cambridge, MA 02142. Email : dahsu@microsoft.com, skakade@microsoft.com 1 a latent space dimensionality...Sparse coding for multitask and transfer learning. ArxXiv preprint, abs/1209.0738, 2012. [34] G.H. Golub and C.F. Van Loan. Matrix Computations. The

A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)

DTIC Science & Technology

2008-06-01

comprehensive model of capillary discharge is important to understand the physics and engineering aspects of the capillary discharge thruster. A schematic...investigators since the mid-1980s see 1-11 and references therein, satisfy both of these conditions well. These studies investigated the dynamics of high...is a comprehensive description of the radiative heat transfer in the capillary discharge. It is worth noting that in other types of capillary

Preprinting Microbiology

PubMed Central

2017-01-01

ABSTRACT The field of microbiology has experienced significant growth due to transformative advances in technology and the influx of scientists driven by a curiosity to understand how microbes sustain myriad biochemical processes that maintain Earth. With this explosion in scientific output, a significant bottleneck has been the ability to rapidly disseminate new knowledge to peers and the public. Preprints have emerged as a tool that a growing number of microbiologists are using to overcome this bottleneck. Posting preprints can help to transparently recruit a more diverse pool of reviewers prior to submitting to a journal for formal peer review. Although the use of preprints is still limited in the biological sciences, early indications are that preprints are a robust tool that can complement and enhance peer-reviewed publications. As publishing moves to embrace advances in Internet technology, there are many opportunities for preprints and peer-reviewed journals to coexist in the same ecosystem. PMID:28536284

Preprinting Microbiology.

PubMed

Schloss, Patrick D

2017-05-23

The field of microbiology has experienced significant growth due to transformative advances in technology and the influx of scientists driven by a curiosity to understand how microbes sustain myriad biochemical processes that maintain Earth. With this explosion in scientific output, a significant bottleneck has been the ability to rapidly disseminate new knowledge to peers and the public. Preprints have emerged as a tool that a growing number of microbiologists are using to overcome this bottleneck. Posting preprints can help to transparently recruit a more diverse pool of reviewers prior to submitting to a journal for formal peer review. Although the use of preprints is still limited in the biological sciences, early indications are that preprints are a robust tool that can complement and enhance peer-reviewed publications. As publishing moves to embrace advances in Internet technology, there are many opportunities for preprints and peer-reviewed journals to coexist in the same ecosystem. Copyright © 2017 Schloss.

Electronic Information Management for PfP Nations (La gestion electronique des informations pour les pays du PfP)

DTIC Science & Technology

2003-04-01

such repositories containing electronic information sources that can be used for academic research. The Los Alamos Physics Archive, providing access to...Pinfield, Gardner and MacColl. 2002). The first e-print server was the Los Alamos Physics Archive, presently known as arXiv.org, which was created in 1991...by Ginsparg (Ginsparg 1996; Luce 2001; McKiernan 2000) at the Los Alamos National Laboratory, to give access to pre-prints in the domain of high

Effects of eye-glasses, hair, headgear, and clothing on measured head-related transfer functions Part Ib

NASA Astrophysics Data System (ADS)

Riederer, Klaus A. J.

2003-10-01

Extensive head-related transfer function (HRTF) measurements show high HRTF repeatability, consequences of different measurement methods, and conditions covering the whole three-dimensional space [Riederer, J. Audio Eng. Soc. (Abstracts) 46, 1036 (1998), preprint 4846]. This study concentrates on specific effects on HRTFs carefully re-measured on the same Cortex dummy head applying Sennheiser KE4-211-2 microphones at its silicone putty blocked ear-canal entrances, employing 252 sound incidents including seven elevations. The effects of five different wigs (synthetic, natural, thick, thin, long and short hair) with varied hairstyles, four hats (cap, bicycle helmet, mens and womens trilby), clothes (alpaca pullover, bicycling drymax-jacket) and spectacles were investigated under 28 combinations. The influences are highly dependent on direction, frequency, and case. Clothes and eye-glasses affect minimally HRTF; hair has a stronger effect, depending on the actual hairdo (typically above 7 kHz). Hats alter intensively HRTFs (typically above 5 kHz), depending on the model. The measurements give deeper insight to the development of idiosyncratic features in binaural localization cues. The second part of the study addresses their perceptual effects [Riederer, J. Acoust. Soc. Am., this issue]. [Work supported by Graduate School of Electronics, Telecommunication and Automation; thanks to Finnish Broadcasting Company, Mr. Hellstrom; Mrs. Chen.

Load-Differential Imaging for Detection and Localization of Fatigue Cracks Using Lamb Waves (Preprint)

DTIC Science & Technology

2012-03-01

AFRL-RX-WP-TP-2012-0278 LOAD-DIFFERENTIAL IMAGING FOR DETECTION AND LOCALIZATION OF FATIGUE CRACKS USING LAMB WAVES (PREPRINT) X. Chen...OF FATIGUE CRACKS USING LAMB WAVES (PREPRINT) 5a. CONTRACT NUMBER FA8650-09-C-5206 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6...Jan 2012. Preprint journal article to be submitted to NDT & E. This document contains color. 14. ABSTRACT Fatigue cracks are common and

PRN: a preprint service for catalyzing R-fMRI and neuroscience related studies

PubMed Central

Yan, Chao-gan; Li, Qingyang; Gao, Lei

2015-01-01

Sharing drafts of scientific manuscripts on preprint hosting services for early exposure and pre-publication feedback is a well-accepted practice in fields such as physics, astronomy, or mathematics. The field of neuroscience, however, has yet to adopt the preprint model. A reason for this reluctance might partly be the lack of central preprint services for the field of neuroscience. To address this issue, we announce the launch of Preprints of the R-fMRI Network (PRN), a community funded preprint hosting service. PRN provides free-submission and free hosting of manuscripts for resting state functional magnetic resonance imaging (R-fMRI) and neuroscience related studies. Submitted articles are openly discussed and receive feedback from readers and a panel of invited consultants from the R-fMRI Network. All manuscripts and feedback are freely accessible online with citable permanent URL for open-access. The goal of PRN is to supplement the peer reviewed journal publication system – by more rapidly communicating the latest research achievements throughout the world. We hope PRN would help the field to embrace the preprint model and thus further accelerate R-fMRI and neuroscience related studies, eventually enhancing human mental health. PMID:25844159

Adaptive Distributed Intelligent Control Architecture for Future Propulsion Systems (Preprint)

DTIC Science & Technology

2007-04-01

weight will be reduced by replacing heavy harness assemblies and FADECs , with distributed processing elements interconnected. This paper reviews...Digital Electronic Controls ( FADECs ), with distributed processing elements interconnected through a serial bus. Efficient data flow throughout the...because intelligence is embedded in components while overall control is maintained in the FADEC . The need for Distributed Control Systems in

The prehistory of biology preprints: A forgotten experiment from the 1960s.

PubMed

Cobb, Matthew

2017-11-01

In 1961, the National Institutes of Health (NIH) began to circulate biological preprints in a forgotten experiment called the Information Exchange Groups (IEGs). This system eventually attracted over 3,600 participants and saw the production of over 2,500 different documents, but by 1967, it was effectively shut down following the refusal of journals to accept articles that had been circulated as preprints. This article charts the rise and fall of the IEGs and explores the parallels with the 1990s and the biomedical preprint movement of today.

Effect of Specimen Thickness on the Creep Response of a Ni-Based Single Crystal Superalloy (PREPRINT)

DTIC Science & Technology

2012-08-01

unlimited 3.1.2. Fractography Figure 5: SEM images of a 3.18mm thick sheet specimen tested at 760◦C/758MPa. (a) The region near the fracture surface... fractography using secondary electron imaging (SE) in a scanning electron microscope (SEM). No surface oxidation was observed at this temperature. The...ruptured after 210 hours. 3.2.3. Fractography The SEM image of the reconstructed creep ruptured specimen with thickness h = 3.18mm is shown in Fig. 18a

Paper-based silver-nanowire electronic circuits with outstanding electrical conductivity and extreme bending stability.

PubMed

Huang, Gui-Wen; Xiao, Hong-Mei; Fu, Shao-Yun

2014-08-07

Here a facile, green and efficient printing-filtration-press (PFP) technique is reported for room-temperature (RT) mass-production of low-cost, environmentally friendly, high performance paper-based electronic circuits. The as-prepared silver nanowires (Ag-NWs) are uniformly deposited at RT on a pre-printed paper substrate to form high quality circuits via vacuum filtration and pressing. The PFP circuit exhibits more excellent electrical property and bending stability compared with other flexible circuits made by existing techniques. Furthermore, practical applications of the PFP circuits are demonstrated.

Trajectory, Development, and Temperature of Spark Kernels Exiting into Quiescent Air (Preprint)

DTIC Science & Technology

2012-04-01

spark is an electrical discharge in which a portion of the energy is transferred to plasma and the surrounding fluid and the remaining portion is lost...integrated radiation intensity, λα λ λ λλλ dII ∫=∆ 2 1 . (1) αλ is the spectral absorption coefficient which accounts for variations...premixed hydrogen flame anchored to a Hencken burner. This flame has been well characterized by CARS measurements26,27. A temperature profile26 was assumed

Measurements of Ocean Surface Turbulence and Wave-Turbulence Interactions (PREPRINT)

DTIC Science & Technology

2008-02-19

measurements described here were obtained from a Þeld experiment conducted from R /P 1In the case of gas transfer, these molecular layers can also be at the...ßux data. The eddy covariance sys- tem included a three-axis anemometer/thermometer (Campbell CSAT 3), an open path infrared hygrometer/CO2 sensor...boom of R /P FLIP approximately 18 m from the hull at an elevation of 13 m above mean sea level (MSL). The infrared optical system was set-up with the

An Automated Multi-Modal Serial Sectioning System for Characterization of Grain-Scale Microstructures in Engineering Materials (Preprint)

DTIC Science & Technology

2012-03-01

the three main sub-systems. The Mitsubishi RV12SVL 6-axis robot arm has a 54’’ reach, which allows it to readily move a 2” diameter stainless ... steel sample holder, Figure 2A, between sample exchange points on the Robo-Met.3D, the Tescan SEM, and an additional sample transfer stand that enables...Rowenhorst DJ, et al. (2006) Crystallographic and morphological analysis of coarse martensite : Combining EBSD and serial sectioning. Scripta

Additive Manufacturing for Superalloys - Producibility and Cost Validation (Preprint)

DTIC Science & Technology

2011-03-01

evaluated in this study were: Shaped Metal Deposition (SMD, 3D Weld Deposition) Laser Powder Deposition (LPD) Electron Beam Wire Deposition (EBWD...envelope and would be removed during subsequent machining. Radiographic inspection also revealed fine random internal micro porosity in some of the...successfully fabricated the required deposition samples for Task 2 (see Figure 4). A surface examination revealed some surface cracks and porosity , but all

Exploring a New Model for Preprint Server: A Case Study of CSPO

ERIC Educational Resources Information Center

Hu, Changping; Zhang, Yaokun; Chen, Guo

2010-01-01

This paper describes the introduction of an open-access preprint server in China covering 43 disciplines. The system includes mandatory deposit for state-funded research and reports on the repository and its effectiveness and outlines a novel process of peer-review of preprints in the repository, which can be incorporated into the established…

A Real-Time Systems Symposium Preprint.

DTIC Science & Technology

1983-09-01

Real - Time Systems Symposium Preprint Interim Tech...estimate of the occurence of the error. Unclassii ledSECUqITY CLASSIF’ICA T" NO MI*IA If’ inDI /’rrd erter for~~ble. ’Corrputnqg A REAL - TIME SYSTEMS SYMPOSIUM...ABSTRACT This technical report contains a preprint of a paper accepted for presentation at the REAL - TIME SYSTEMS SYMPOSIUM, Arlington,

Optimizing the Design of Preprinted Orders for Ambulatory Chemotherapy: Combining Oncology, Human Factors, and Graphic Design

PubMed Central

Jeon, Jennifer; White, Rachel E.; Hunt, Richard G.; Cassano-Piché, Andrea L.; Easty, Anthony C.

2012-01-01

Purpose: To establish a set of guidelines for developing ambulatory chemotherapy preprinted orders. Methods: Multiple methods were used to develop the preprinted order guidelines. These included (A) a comprehensive literature review and an environmental scan; (B) analyses of field study observations and incident reports; (C) critical review of evidence from the literature and the field study observation analyses; (D) review of the draft guidelines by a clinical advisory group; and (E) collaboration with graphic designers to develop sample preprinted orders, refine the design guidelines, and format the resulting content. Results: The Guidelines for Developing Ambulatory Chemotherapy Preprinted Orders, which consist of guidance on the design process, content, and graphic design elements of ambulatory chemotherapy preprinted orders, have been established. Conclusion: Health care is a safety critical, dynamic, and complex sociotechnical system. Identifying safety risks in such a system and effectively addressing them often require the expertise of multiple disciplines. This study illustrates how human factors professionals, clinicians, and designers can leverage each other's expertise to uncover commonly overlooked patient safety hazards and to provide health care professionals with innovative, practical, and user-centered tools to minimize those hazards. PMID:23077436

Optimizing the design of preprinted orders for ambulatory chemotherapy: combining oncology, human factors, and graphic design.

PubMed

Jeon, Jennifer; White, Rachel E; Hunt, Richard G; Cassano-Piché, Andrea L; Easty, Anthony C

2012-03-01

To establish a set of guidelines for developing ambulatory chemotherapy preprinted orders. Multiple methods were used to develop the preprinted order guidelines. These included (A) a comprehensive literature review and an environmental scan; (B) analyses of field study observations and incident reports; (C) critical review of evidence from the literature and the field study observation analyses; (D) review of the draft guidelines by a clinical advisory group; and (E) collaboration with graphic designers to develop sample preprinted orders, refine the design guidelines, and format the resulting content. The Guidelines for Developing Ambulatory Chemotherapy Preprinted Orders, which consist of guidance on the design process, content, and graphic design elements of ambulatory chemotherapy preprinted orders, have been established. Health care is a safety critical, dynamic, and complex sociotechnical system. Identifying safety risks in such a system and effectively addressing them often require the expertise of multiple disciplines. This study illustrates how human factors professionals, clinicians, and designers can leverage each other's expertise to uncover commonly overlooked patient safety hazards and to provide health care professionals with innovative, practical, and user-centered tools to minimize those hazards.

Comparison of Communication Architectures and Network Topologies for Distributed Propulsion Controls (Preprint)

DTIC Science & Technology

2013-05-01

logic to perform control function computations and are connected to the full authority digital engine control ( FADEC ) via a high-speed data...Digital Engine Control ( FADEC ) via a high speed data communication bus. The short term distributed engine control configu- rations will be core...concen- trator; and high temperature electronics, high speed communication bus between the data concentrator and the control law processor master FADEC

Review: Microstructure Engineering of Titanium Alloys via Small Boron Additions (Preprint)

DTIC Science & Technology

2011-07-01

small amount of boron to γ titanium aluminides (TiAl) has been found to improve room temperature ductility [12]. The principal effect of boron...AFRL-RX-WP-TP-2011-4298 REVIEW: MICROSTRUCTURE ENGINEERING OF TITANIUM ALLOYS VIA SMALL BORON ADDITIONS (Preprint) D.B. Miracle...2011 Journal Article Preprint 01 July 2011 – 01 July 2011 4. TITLE AND SUBTITLE REVIEW: MICROSTRUCTURE ENGINEERING OF TITANIUM ALLOYS VIA SMALL

FAST TRACK COMMUNICATION: On the structure of k-Lie algebras

NASA Astrophysics Data System (ADS)

Papadopoulos, G.

2008-07-01

We show that the structure constants of k-Lie algebras, k > 3, with a positive definite metric are the sum of the volume forms of orthogonal k-planes. This generalizes the result for k = 3 in Papadopoulos (2008 Preprint arXiv:0804.2662) and Gauntlett and Gutowski (2008 Preprint arXiv:0804.3078), and confirms a conjecture in Figueroa-O'Farrill and Papadopoulos (2002 Preprint math/0211170).

The Role of Microtexture on Fatigue Lifetime Variability and Crack Initiation Mechanisms (Preprint)

DTIC Science & Technology

2011-10-01

October 2011 4 . TITLE AND SUBTITLE THE ROLE OF MICROTEXTURE OF FATIGUE LIFETIME VARIABILITY AND CRACK INITIATION MECHANISMS (PREPRINT) 5a...CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) Christopher J. Szczepanski (Universal Technology...Preprint journal article to be submitted to Titanium 2011 World Conference. This document contains color. 14. ABSTRACT Commercial titanium alloys

Quasiperiodic Strain Bursts and Self-Organization in Crystal Microplasticity (PREPRINT)

DTIC Science & Technology

2012-03-01

AFRL-RX-WP-TP-2012-0249 QUASIPERIODIC STRAIN BURSTS AND SELF- ORGANIZATION IN CRYSTAL MICROPLASTICITY (PREPRINT) D.M. Dimiduk Metals...2012 4. TITLE AND SUBTITLE QUASIPERIODIC STRAIN BURSTS AND SELF-ORGANIZATION IN CRYSTAL MICROPLASTICITY (PREPRINT) 5a. CONTRACT NUMBER In-house...18 Quasiperiodic strain bursts and self-organization in crystal microplasticity S. Papanikolaou,1,2∗ D. M. Dimiduk,3 W. Choi4, J. P. Sethna4, M. D

Preparation of Composite Fluoropolymers with Enhanced Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint)

DTIC Science & Technology

2010-02-17

Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Scott T... Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint) Scott T. Iacono, a,b Stephen M. Budy, a,c Dennis W. Smith, a and...nanometer-sized surface roughness due to POSS aggregation. 23 Likewise, similar dewetting behavior, 90 albeit modest, was observed utilizing partially

The Origins of Microtexture in Duplex Ti Alloys (Preprint)

DTIC Science & Technology

2008-06-01

To) June 2008 Journal Article Preprint 4 . TITLE AND SUBTITLE THE ORIGINS OF MICROTEXTURE IN DUPLEX Ti ALLOYS (PREPRINT) 5a. CONTRACT NUMBER In...house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) M.G. Glavic (UES, Inc.) B.B. Bartha (United Technologies Corporation...applicable to duplex alpha/beta titanium microstructures. The crystallographic coherency of the primary and secondary alpha phase with the prior beta

Load-Differential Features for Automated Detection of Fatigue Cracks Using Guided Waves (Preprint)

DTIC Science & Technology

2011-11-01

AFRL-RX-WP-TP-2011-4363 LOAD-DIFFERENTIAL FEATURES FOR AUTOMATED DETECTION OF FATIGUE CRACKS USING GUIDED WAVES (PREPRINT) Jennifer E...AUTOMATED DETECTION OF FATIGUE CRACKS USING GUIDED WAVES (PREPRINT) 5a. CONTRACT NUMBER FA8650-09-C-5206 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...tensile loads open fatigue cracks and thus enhance their detectability using ultrasonic methods. Here we introduce a class of load-differential methods

Preprints, Impact Factors, and Unethical Behavior, but also Lots of Good News.

PubMed

Gölitz, Peter

2016-10-24

Preprints as well? There is already the Accepted Article (published directly after refereeing and author revision), the Early-View/ASAP-Version (after refereeing, editing and proofing), and the final Version of Record. The problems with preprints are discussed in this Editorial along with the undeclared resubmission of previously rejected manuscripts: publication times, color costs, and Angewandte Symposia are further topics. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tailored Organometallic Polymers

DTIC Science & Technology

1993-01-31

2-4). These synthetic pathways provide access to a wide variety of new silicon compounds for use as reagents in organic syntheses and the electronics...34Si0 2 as a Source of Si Containing Compounds / Polymers", D.J. Ray, R.M. Laine, C. Viney and T.R. Robinson, ACS Polymer Preprints (1991) 32(3), 550...3) as precursors to orgar.osilicon compounds .[10-12] Pentacoordinate silicates are easily prepa’ed frotv tetrasubstituted Si centers containing

A View of Cyberterrorism Five Years Later (PREPRINT)

DTIC Science & Technology

2007-01-01

2006, http://www.zone-h.org/content/view/10/30/, accessed June 12, 2006. 17 Stephen Ulph, “Internet Mujahideen Refine Electronic Warfare Tactics...Jeffrey Pool, “Technology and Security Discussions on the Jihadist Forums,” Jamestown Foundation, October 11, 2005. 26 Stephen Ulph, “Internet...Domination Design,” The Age, August 24, 2005. 36 Dan Verton, Black Ice, Mc- Graw Hill, 2003, pp. 88-91. 37 Susan Schmidt, “Qatari Man Designated

Standardized Fault-Tolerant Sensing Nodes for an Intelligent Turbine Engine Control System (Preprint)

DTIC Science & Technology

2013-05-01

representation of a centralized control system on a turbine engine. All actuators and sensors are point-to-point cabled to the controller ( FADEC ) which...electronics themselves. Figure 1: Centralized Control System Each function resides within the FADEC and uses Unique Point-to-Point Analog...distributed control system on the same turbine engine. The actuators and sensors interface to Smart Nodes which, in turn communicate to the FADEC via

A Feasibility Study of Life-Extending Controls for Aircraft Turbine Engines Using a Generic Air Force Model (Preprint)

DTIC Science & Technology

2006-12-01

intelligent control algorithm embedded in the FADEC . This paper evaluates the LEC, based on critical components research, to demonstrate how an...control action, engine component life usage, and designing an intelligent control algorithm embedded in the FADEC . This paper evaluates the LEC, based on...simulation code for each simulator. One is typically configured to operate as a Full- Authority Digital Electronic Controller ( FADEC

Life Prediction of Fretting Fatigue with Advanced Surface Treatments (Preprint)

DTIC Science & Technology

2006-05-01

surfaces and not the fretting pads. The chosen coatings included DLC, Ni-B, Molybdenum, and Nitride. These 4 coatings, their application to the titanium ...Article Preprint 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 4 . TITLE AND SUBTITLE LIFE PREDICTION OF FRETTING FATIGUE WITH ADVANCED SURFACE...TREATMENTS (PREPRINT) 5c. PROGRAM ELEMENT NUMBER N/A 5d. PROJECT NUMBER M02R 5e. TASK NUMBER 30 6 . AUTHOR(S) Patrick J. Golden and Michael

3D printing and intraoperative neuronavigation tailoring for skull base reconstruction after extended endoscopic endonasal surgery: proof of concept.

PubMed

Essayed, Walid I; Unadkat, Prashin; Hosny, Ahmed; Frisken, Sarah; Rassi, Marcio S; Mukundan, Srinivasan; Weaver, James C; Al-Mefty, Ossama; Golby, Alexandra J; Dunn, Ian F

2018-03-02

OBJECTIVE Endoscopic endonasal approaches are increasingly performed for the surgical treatment of multiple skull base pathologies. Preventing postoperative CSF leaks remains a major challenge, particularly in extended approaches. In this study, the authors assessed the potential use of modern multimaterial 3D printing and neuronavigation to help model these extended defects and develop specifically tailored prostheses for reconstructive purposes. METHODS Extended endoscopic endonasal skull base approaches were performed on 3 human cadaveric heads. Preprocedure and intraprocedure CT scans were completed and were used to segment and design extended and tailored skull base models. Multimaterial models with different core/edge interfaces were 3D printed for implantation trials. A novel application of the intraoperative landmark acquisition method was used to transfer the navigation, helping to tailor the extended models. RESULTS Prostheses were created based on preoperative and intraoperative CT scans. The navigation transfer offered sufficiently accurate data to tailor the preprinted extended skull base defect prostheses. Successful implantation of the skull base prostheses was achieved in all specimens. The progressive flexibility gradient of the models' edges offered the best compromise for easy intranasal maneuverability, anchoring, and structural stability. Prostheses printed based on intraprocedure CT scans were accurate in shape but slightly undersized. CONCLUSIONS Preoperative 3D printing of patient-specific skull base models is achievable for extended endoscopic endonasal surgery. The careful spatial modeling and the use of a flexibility gradient in the design helped achieve the most stable reconstruction. Neuronavigation can help tailor preprinted prostheses.

Hot Deformation of Ti-6Al-4V Single-Colony Samples (Preprint)

DTIC Science & Technology

2008-02-01

Journal Article Preprint 4 . TITLE AND SUBTITLE HOT DEFORMATION OF Ti-6Al-4V SINGLE-COLONY SAMPLES (PREPRINT) 5a. CONTRACT NUMBER In-house 5b...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) A.A. Salem (Universal Technology Corp.) S.L. Semiatin (AFRL/RXLMP) 5d. PROJECT...strength, corrosion resistance, and low density, Ti-6Al-4V is the most commonly used alpha/beta titanium alloy. It accounts for approximately 80

GHz Modulation of GaAs-Based Bipolar Cascade VCSELs (Preprint)

DTIC Science & Technology

2006-11-01

VCSELs were grown on n+ GaAs substrates by molecular beam epitaxy . The laser cavities consist of 1-, 2-, or 3-stage 52λ microcavi- ties, each containing...AFRL-SN-WP-TP-2006-128 GHz MODULATION OF GaAs-BASED BIPOLAR CASCADE VCSELs (PREPRINT) W.J. Siskaninetz, R.G. Bedford, T.R. Nelson, Jr., J.E...TITLE AND SUBTITLE GHz MODULATION OF GaAs-BASED BIPOLAR CASCADE VCSELs (PREPRINT) 5c. PROGRAM ELEMENT NUMBER 69199F 5d. PROJECT NUMBER 2002 5e

Air-Cooled Heat Exchanger for High-Temperature Power Electronics: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waye, S. K.; Lustbader, J.; Musselman, M.

2015-05-06

This work demonstrates a direct air-cooled heat exchanger strategy for high-temperature power electronic devices with an application specific to automotive traction drive inverters. We present experimental heat dissipation and system pressure curves versus flow rate for baseline and optimized sub-module assemblies containing two ceramic resistance heaters that provide device heat fluxes. The maximum allowable junction temperature was set to 175 deg.C. Results were extrapolated to the inverter scale and combined with balance-of-inverter components to estimate inverter power density and specific power. The results exceeded the goal of 12 kW/L and 12 kW/kg for power density and specific power, respectively.

ArXives of Earth science

NASA Astrophysics Data System (ADS)

2018-03-01

Preprint servers afford a platform for sharing research before peer review. We are pleased that two dedicated preprint servers have opened for the Earth sciences and welcome submissions that have been posted there first.

Preliminary Study of Heat Transfer Correlation Development and Pressure Loss Behavior in Curved High Aspect Ratio Coolant Channels (Preprint)

DTIC Science & Technology

2008-06-19

be present in a straight channel (Seban and McLaughlin, 1963; McCormack, Welker, Kelleher, 1969; Sturgis and Mudawar , 1999). However, it is unclear...and downstream locations (i.e. mid-channel and exit locations). Sturgis and Mudawar (1999) and Sturgis and Nathman (2008) provide lists of curvature...Terms Author Curvature term, φcur Comments Ito (1959) 1. 05.Re          c cur d D  Limited to Re(D/dc)2>6 Sturgis and Mudawar (1999) 1

How the Scientific Community Reacts to Newly Submitted Preprints: Article Downloads, Twitter Mentions, and Citations

PubMed Central

Shuai, Xin; Pepe, Alberto; Bollen, Johan

2012-01-01

We analyze the online response to the preprint publication of a cohort of 4,606 scientific articles submitted to the preprint database arXiv.org between October 2010 and May 2011. We study three forms of responses to these preprints: downloads on the arXiv.org site, mentions on the social media site Twitter, and early citations in the scholarly record. We perform two analyses. First, we analyze the delay and time span of article downloads and Twitter mentions following submission, to understand the temporal configuration of these reactions and whether one precedes or follows the other. Second, we run regression and correlation tests to investigate the relationship between Twitter mentions, arXiv downloads, and article citations. We find that Twitter mentions and arXiv downloads of scholarly articles follow two distinct temporal patterns of activity, with Twitter mentions having shorter delays and narrower time spans than arXiv downloads. We also find that the volume of Twitter mentions is statistically correlated with arXiv downloads and early citations just months after the publication of a preprint, with a possible bias that favors highly mentioned articles. PMID:23133597

Building and Managing Electronic Resources in Digital Era in India with Special Reference to IUCAA and NIV, Pune: A Comparative Case Study

NASA Astrophysics Data System (ADS)

Sahu, H. K.; Singh, S. N.

2015-04-01

This paper discusses and presents a comparative case study of two libraries in Pune, India, Inter-University Centre for Astronomy and Astrophysics and Information Centre and Library of National Institute of Virology (Indian Council of Medical Research). It compares how both libraries have managed their e-resource collections, including acquisitions, subscriptions, and consortia arrangements, while also developing a collection of their own resources, including pre-prints and publications, video lectures, and other materials in an institutional repository. This study illustrates how difficult it is to manage electronic resources in a developing country like India, even though electronic resources are used more than print resources. Electronic resource management can be daunting, but with a systematic approach, various problems can be solved, and use of the materials will be enhanced.

A Weakest-Link Approach for Fatigue Limit of 30CrNiMo8 Steels (Preprint)

DTIC Science & Technology

2011-03-01

34Application of a Weakest-Link Concept to the Fatigue Limit of the Bearing Steel Sae 52100 in a Bainitic Condition," Fatigue and Fracture of...AFRL-RX-WP-TP-2011-4206 A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) S. Ekwaro-Osire and H.V. Kulkarni Texas...2011 4. TITLE AND SUBTITLE A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

Anisotropy of the Hot Plastic Deformation of Ti-6Al-4V Single-Colony Samples (Preprint)

DTIC Science & Technology

2009-04-01

April 2009 Journal Article Preprint 01 April 2009- 01 April 2009 4 . TITLE AND SUBTITLE ANISOTROPY OF THE HOT PLASTIC DEFORMATION OF Ti-6Al-4V SINGLE...COLONY SAMPLES (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) A.A. Salem and S.L...resistance, and low density, Ti-6Al-4V is the most commonly used alpha/beta titanium alloy. It accounts for approximately 80% of the total titanium used in

Microstructural Influences on Very High Cycle Fatigue Crack Initiation in Ti-6246 (PREPRINT)

DTIC Science & Technology

2008-04-01

surface (in degrees). Facet # 1 2 3 4 5a 5b 6 7 8 9 Angle 46 45 39 19 26 35 33 31 32 21 Table II. Orientation of facets (in degrees). Facet # 1* 2 3 4 ...TYPE 3. DATES COVERED (From - To) April 2008 Journal Article Preprint 4 . TITLE AND SUBTITLE MICROSTRUCTURAL INFLUENCES ON VERY HIGH CYCLE...FATIGUE CRACK INITIATION IN Ti-6246 (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S

The Mean vs Life-Limiting Fatigue Response of a Ni-Base Superalloy, Part 1: Mechanisms (Preprint)

DTIC Science & Technology

2008-09-01

34’"L’\\" ~~·~~~:~~~?~i.. ~ ~I~~~.~.’ ,~.- .":_~ ••-:;’~.:-- 10JJITl 3 4 S 6 Grain diameter (",m) Figure 1: Microstructure of the INIOO...DATES COVERED (From - To) September 2008 Journal Article Preprint 4 . TITLE AND SUBTITLE THE MEAN VS LIFE-LIMITING FATIGUE RESPONSE OF A Ni-BASE...SUPERALLOY, PART 1: MECHANISMS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S

Microstructural Evolution and Tensile Properties of SnAgCu Mixed with Sn-Pb Solder Alloys (Preprint)

DTIC Science & Technology

2009-03-01

AFRL-RX-WP-TP-2009-4132 MICROSTRUCTURAL EVOLUTION AND TENSILE PROPERTIES OF SnAgCu MIXED WITH Sn-Pb SOLDER ALLOYS (PREPRINT...PROPERTIES OF SnAgCu MIXED WITH Sn-Pb SOLDER ALLOYS (PREPRINT) 5a. CONTRACT NUMBER FA8650-04-C-5704 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...ANSI Std. Z39-18 Microstructural evolution and tensile properties of SnAgCu mixed with Sn-Pb solder alloys Fengjiang Wang,1 Matthew O’Keefe,1,2 and

A Coupled EBSD/EDS Method to Determine the Primary- and Secondary-Alpha Textures in Titanium Alloys With Duplex Microstructures (Preprint)

DTIC Science & Technology

2007-07-01

primary and secondary alpha in micrographs and thus to correlate microstructural features and texture data [3- 6 ]. For instance, Germain, et al. [3, 4 ...Following electropolishing , the sample was mounted 7/3/2007 6 on the tilting stage inside an XL30 field-emission-gun scanning-electron-microscope (FEG...AFRL-RX-WP-TP-2008-4338 A COUPLED EBSD/EDS METHOD TO DETERMINE THE PRIMARY–AND SECONDARY–ALPHA TEXTURES IN TITANIUM ALLOYS WITH DUPLEX

Synthesis and Properties of N7O+ (PREPRINT)

DTIC Science & Technology

2009-11-23

isolated by pumping off the solvent and gaseous products at low temperature. With an excess of HN3, replacement of the second fluorine atom started to...was analyzed and involves the electrophilic attack of the terminal gamma-N atom of one azide ligand on the electron rich alpha-N atom of the second...Chem. Soc. 1995, 117, 6136. (8) Christe, K. O., Wilson, W. W., Schack, C. J., J. Fluorine . Chem. 1978, 11, 71. (9) Moller, C., Plesset, M. S., Phys

Chaotic Motions in the Real Fuzzy Electronic Circuits (Preprint)

DTIC Science & Technology

2012-12-01

the research field of secure communications, the original source should be blended with other complex signals. Chaotic signals are one of the good... blending of the linear system models. Consider a continuous-time nonlinear dynamic system as follows: Rule i: IF )(1 tx is ...1iM and )(txn is...Chaos Solitons Fractals, vol. 21, no. 4, pp. 957–965, 2004. 29. L. M. Tam and W. M. SiTou, “Parametric study of the fractional order Chen–Lee

Probabilistic Sensitivity Analysis of Fretting Fatigue (Preprint)

DTIC Science & Technology

2009-04-01

AFRL-RX-WP-TP-2009-4091 PROBABILISTIC SENSITIVITY ANALYSIS OF FRETTING FATIGUE (Preprint) Patrick J. Golden, Harry R. Millwater , and...Sensitivity Analysis of Fretting Fatigue Patrick J. Golden * Air Force Research Laboratory, Wright-Patterson AFB, OH 45433 Harry R. Millwater † and

Research Studies on Advanced Optical Module/Head Designs for Optical Data Storage

NASA Technical Reports Server (NTRS)

1992-01-01

Preprints are presented from the recent 1992 Optical Data Storage meeting in San Jose. The papers are divided into the following topical areas: Magneto-optical media (Modeling/design and fabrication/characterization/testing); Optical heads (holographic optical elements); and Optical heads (integrated optics). Some representative titles are as follow: Diffraction analysis and evaluation of several focus and track error detection schemes for magneto-optical disk systems; Proposal for massively parallel data storage system; Transfer function characteristics of super resolving systems; Modeling and measurement of a micro-optic beam deflector; Oxidation processes in magneto-optic and related materials; and A modal analysis of lamellar diffraction gratings in conical mountings.

Proposed Reference Spectral Irradiance Standards to Improve Photovoltaic Concentrating System Design and Performance Evaluation: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, D. R.; Emery, K. E.; Gueymard, C.

2002-05-01

This conference paper describes the American Society for Testing and Materials (ASTM), the International Electrotechnical Commission (IEC), and the International Standards Organization (ISO) standard solar terrestrial spectra (ASTM G-159, IEC-904-3, ISO 9845-1) provide standard spectra for photovoltaic performance applications. Modern terrestrial spectral radiation models and knowledge of atmospheric physics are applied to develop suggested revisions to update the reference spectra. We use a moderately complex radiative transfer model (SMARTS2) to produce the revised spectra. SMARTS2 has been validated against the complex MODTRAN radiative transfer code and spectral measurements. The model is proposed as an adjunct standard to reproduce the referencemore » spectra. The proposed spectra represent typical clear sky spectral conditions associated with sites representing reasonable photovoltaic energy production and weathering and durability climates. The proposed spectra are under consideration by ASTM.« less

Toward Improved Modeling of Spectral Solar Irradiance for Solar Energy Applications: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit

This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to extend the capability of the Fast All-sky Radiation Model for Solar applications (FARMS) by computing spectral solar irradiances over both horizontal and inclined surfaces. A new model is developed by computing the optical thickness of the atmosphere using a spectral irradiance model for clear-sky conditions, SMARTS2. A comprehensive lookup table (LUT) of cloud bidirectional transmittance distribution functions (BTDFs) is precomputed for 2002 wavelength bands using an atmospheric radiative transfer model, libRadtran. The solar radiation transmitted through the atmosphere is given by considering all possible paths of photon transmissionmore » and the relevent scattering and absorption attenuation. Our results indicate that this new model has an accuracy that is similar to that of state-of-the-art radiative transfer models, but it is significantly more efficient.« less

High Performance Polymer Film Dielectrics for Air Force Wide-Temperature Power Electronics Applications (Preprint)

DTIC Science & Technology

2009-02-01

with a combination of a turbo pump and a scroll pump system. The sample probing is accomplished with 3-axis molybdenum probing rod test fixture...thin films were carefully isolated by the addition of a non- solvent such as de-ionized, distilled water. The films were dried at ~ 0.1 torr vacuum ...1000ºC. The test station has a 100V/10A power supply, a temperature controller as well as a vacuum controller. A vacuum of < 1 µ torr is achieved

Experimental and Numerical Examination of a Hall Thruster Plume (Preprint)

DTIC Science & Technology

2007-07-31

Hall thruster has been characterized through measurements from various plasma electrostatic probes. Ion current flux, plasma potential, plasma density, and electron temperatures were measured from the near-field plume to 60 cm downstream of the exit plane. These experimentally derived measurements were compared to numerical simulations run with the plasma plume code DRACO. A major goal of this study was to determine the fidelity of the DRACO numerical simulation. The effect of background pressure on the thruster plume was also examined using ion current flux measurements

A multifaceted knowledge translation strategy can increase compliance with guideline recommendations for mechanical bowel preparation.

PubMed

Eskicioglu, Cagla; Pearsall, Emily; Victor, J Charles; Aarts, Mary-Anne; Okrainec, Allan; McLeod, Robin S

2015-01-01

The successful transfer of evidence into clinical practice is a slow and haphazard process. We report the outcome of a 5-year knowledge translation (KT) strategy to increase adherence with a clinical practice guideline (CPG) for mechanical bowel preparation (MBP) for elective colorectal surgery patients. A locally tailored CPG recommending MBP practices was developed. Data on MBP practices were collected at six University of Toronto hospitals before CPG implementation as well as after two separate KT strategies. KT strategy #1 included development of the CPG, education by opinion leaders, reminder cards, and presentations of data. KT strategy #2 included selection of hospital champions, development of communities of practice, education, reminder cards, electronic updates, pre-printed standardized orders, and audit and feedback. A total of 744 patients (400 males, 344 females, mean age 57.0) were included. Compliance increased from 58.6 to 70.4% after KT strategy #1 and to 81.1% after KT strategy #2 (p < 0.001). Using a tailored KT strategy, increased compliance was observed with CPG recommendations over time suggesting that a longitudinal KT strategy is required to increase and sustain compliance with recommendations. Furthermore, different strategies may be required at different times (i.e., educational sessions initially and reminders and standardized orders to maintain adherence).

Comparing published scientific journal articles to their pre-print versions

DOE PAGES

Klein, Martin; Broadwell, Peter; Farb, Sharon E.; ...

2018-02-05

Academic publishers claim that they add value to scholarly communications by coordinating reviews and contributing and enhancing text during publication. These contributions come at a considerable cost: US academic libraries paid $1.7 billion for serial subscriptions in 2008 alone. Library budgets, in contrast, are flat and not able to keep pace with serial price inflation. Here, we have investigated the publishers’ value proposition by conducting a comparative study of pre-print papers from two distinct science, technology, and medicine corpora and their final published counterparts. This comparison had two working assumptions: (1) If the publishers’ argument is valid, the text ofmore » a pre-print paper should vary measurably from its corresponding final published version, and (2) by applying standard similarity measures, we should be able to detect and quantify such differences. Our analysis revealed that the text contents of the scientific papers generally changed very little from their pre-print to final published versions. These findings contribute empirical indicators to discussions of the added value of commercial publishers and therefore should influence libraries’ economic decisions regarding access to scholarly publications.« less

Comparing published scientific journal articles to their pre-print versions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, Martin; Broadwell, Peter; Farb, Sharon E.

Academic publishers claim that they add value to scholarly communications by coordinating reviews and contributing and enhancing text during publication. These contributions come at a considerable cost: US academic libraries paid $1.7 billion for serial subscriptions in 2008 alone. Library budgets, in contrast, are flat and not able to keep pace with serial price inflation. Here, we have investigated the publishers’ value proposition by conducting a comparative study of pre-print papers from two distinct science, technology, and medicine corpora and their final published counterparts. This comparison had two working assumptions: (1) If the publishers’ argument is valid, the text ofmore » a pre-print paper should vary measurably from its corresponding final published version, and (2) by applying standard similarity measures, we should be able to detect and quantify such differences. Our analysis revealed that the text contents of the scientific papers generally changed very little from their pre-print to final published versions. These findings contribute empirical indicators to discussions of the added value of commercial publishers and therefore should influence libraries’ economic decisions regarding access to scholarly publications.« less

Convective Heat Transfer Coefficients of Automatic Transmission Fluid Jets with Implications for Electric Machine Thermal Management: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, Kevin; Moreno, Gilberto

2015-09-29

Thermal management for electric machines (motors/ generators) is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. Cooling of the electric machine(s) in some electric vehicle traction drive applications is accomplished by impinging automatic transmission fluid (ATF) jets onto the machine's copper windings. In this study, we provide the results of experiments characterizing the thermal performance of ATF jets on surfaces representative of windings, using Ford's Mercon LV ATF. Experiments were carried out at various ATF temperatures and jet velocities to quantify the influence of these parameters on heat transfer coefficients. Fluid temperatures weremore » varied from 50 degrees C to 90 degrees C to encompass potential operating temperatures within an automotive transaxle environment. The jet nozzle velocities were varied from 0.5 to 10 m/s. The experimental ATF heat transfer coefficient results provided in this report are a useful resource for understanding factors that influence the performance of ATF-based cooling systems for electric machines.« less

Vital sign documentation in electronic records: The development of workarounds.

PubMed

Stevenson, Jean E; Israelsson, Johan; Nilsson, Gunilla; Petersson, Goran; Bath, Peter A

2018-06-01

Workarounds are commonplace in healthcare settings. An increase in the use of electronic health records has led to an escalation of workarounds as healthcare professionals cope with systems which are inadequate for their needs. Closely related to this, the documentation of vital signs in electronic health records has been problematic. The accuracy and completeness of vital sign documentation has a direct impact on the recognition of deterioration in a patient's condition. We examined workflow processes to identify workarounds related to vital signs in a 372-bed hospital in Sweden. In three clinical areas, a qualitative study was performed with data collected during observations and interviews and analysed through thematic content analysis. We identified paper workarounds in the form of handwritten notes and a total of eight pre-printed paper observation charts. Our results suggested that nurses created workarounds to allow a smooth workflow and ensure patients safety.

Superhydrophobic Superoleophobic Woven Fabrics (Preprint)

DTIC Science & Technology

2011-06-01

AFRL-RX-TY-TP-2011-0050 SUPERHYDROPHOBIC SUPEROLEOPHOBIC WOVEN FABRICS (PREPRINT) Hoonjoo Lee Department of Textile and Apparel...RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) JUN 2011 Book Chapter 20-JUN-2008 -- 30-APR-2011 Superhydrophobic Superoleophobic Woven Fabrics...roll-off angles are analyzed, and finally superhydrophobic , superoleophobic, woven fabric is designed and developed using chemical and geometrical

THE ROLE AND DISTRIBUTION OF WRITTEN INFORMAL COMMUNICATION IN THEORETICAL HIGH ENERGY PHYSICS.

ERIC Educational Resources Information Center

LIBBEY, MILES A.; ZALTMAN, GERALD

THIS STUDY OF "PREPRINT" DISTRIBUTION IN THEORECTICAL HIGH ENERGY PHYSICS USED A QUESTIONNAIRE CIRCULATED TO ALL KNOWN HIGH ENERGY THEORISTS. A SECOND QUESTIONNAIRE WAS SENT TO A REPRESENTATIVE SAMPLE OF "PREPRINT LIBRARIANS" AT VARIOUS INSTITUTIONS IN THE U.S. AND ABROAD. BASED ON THIS DATA, THE STUDY CONCLUDED THAT AN EXPERIMENT WITH CENTRALIZED…

49 CFR 40.14 - What collection information must employers provide to collectors?

Code of Federal Regulations, 2013 CFR

2013-10-01

... (the checkmark can pre-printed in the appropriate box on the CCF at Step 1-D). (h) Test reason, as appropriate: Pre-employment; Random; Reasonable Suspicion/Reasonable Cause; Post-Accident; Return-to-Duty; and... or ID number. (c) Laboratory name and address (can be pre-printed on the CCF). (d) Employer name...

49 CFR 40.14 - What collection information must employers provide to collectors?

Code of Federal Regulations, 2011 CFR

2011-10-01

... (the checkmark can pre-printed in the appropriate box on the CCF at Step 1-D). (h) Test reason, as appropriate: Pre-employment; Random; Reasonable Suspicion/Reasonable Cause; Post-Accident; Return-to-Duty; and... or ID number. (c) Laboratory name and address (can be pre-printed on the CCF). (d) Employer name...

49 CFR 40.14 - What collection information must employers provide to collectors?

Code of Federal Regulations, 2010 CFR

2010-10-01

... (the checkmark can pre-printed in the appropriate box on the CCF at Step 1-D). (h) Test reason, as appropriate: Pre-employment; Random; Reasonable Suspicion/Reasonable Cause; Post-Accident; Return-to-Duty; and... or ID number. (c) Laboratory name and address (can be pre-printed on the CCF). (d) Employer name...

49 CFR 40.14 - What collection information must employers provide to collectors?

Code of Federal Regulations, 2014 CFR

2014-10-01

... (the checkmark can pre-printed in the appropriate box on the CCF at Step 1-D). (h) Test reason, as appropriate: Pre-employment; Random; Reasonable Suspicion/Reasonable Cause; Post-Accident; Return-to-Duty; and... or ID number. (c) Laboratory name and address (can be pre-printed on the CCF). (d) Employer name...

49 CFR 40.14 - What collection information must employers provide to collectors?

Code of Federal Regulations, 2012 CFR

2012-10-01

... (the checkmark can pre-printed in the appropriate box on the CCF at Step 1-D). (h) Test reason, as appropriate: Pre-employment; Random; Reasonable Suspicion/Reasonable Cause; Post-Accident; Return-to-Duty; and... or ID number. (c) Laboratory name and address (can be pre-printed on the CCF). (d) Employer name...

Nanoscale Characterization of Elemental Partitioning Between Gamma and Gamma Prime Phases in Rene 88DT Nickel Base Superalloy (Preprint)

DTIC Science & Technology

2008-02-01

penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN...analysis "as condu,ted on a FEI Tecnai F20 field emission gun transmission electron microscope operaling at 200 KV. Imagcs were obtained using lhe Cr M...line marked AI3 in (a). The neck region exhibil’ an inlensity lying in t>etween lhal of lhe yand y’phases. (c) Inlensily prot1le aemS > lhe line CD in (a

Cross-Correlation for Automated Stitching of Two-Dimensional Multi-Tile Electron Backscatter Diffraction Data (Preprint)

DTIC Science & Technology

2012-08-01

270 350x 650 (25, 26) 2 20 Ni-15Al- 5Cr+C,B,Zr 187 x 187 500x 44 ( 4 , 11) 0.5 40 A. Coarse grain, single phase α- titanium The coarse grained... titanium alloy serves as an instructive example because, as evident in Figure 4 (a), only one triple point and one grain boundary appear in the search...wpafb.af.mil Figure 4 . Crystal orientation maps for the first (left) and second (current) tiles of (a) coarse grained α- Titanium , (b) a 2x2 array of a

Mergers, Acquisitions, and Access: STM Publishing Today

NASA Astrophysics Data System (ADS)

Robertson, Kathleen

Electronic publishing is changing the fundamentals of the entire printing/delivery/archive system that has served as the distribution mechanism for scientific research over the last century and a half. The merger-mania of the last 20 years, preprint pools, and publishers' licensing and journals-bundling plans are among the phenomena impacting the scientific information field. Science-Technology-Medical (STM) publishing is experiencing a period of intense consolidation and reorganization. This paper gives an overview of the economic factors fueling these trends, the major STM publishers, and the government regulatory bodies that referee this industry in Europe, Canada, and the USA.

Combination Antimicrobial Nanocomposite Materials for Neutralization of Biological Threat Agents (PREPRINT)

DTIC Science & Technology

2008-09-01

AFRL-RX-TY-TP-2008-4601 PREPRINT COMBINATION ANTIMICROBIAL NANOCOMPOSITE MATERIALS FOR NEUTRALIZATION OF BIOLOGICAL THREAT AGENTS...AIRBASE TECHNOLOGIES DIVISION MATERIALS AND MANUFACTURING DIRECTORATE AIR FORCE RESEARCH LABORATORY AIR FORCE MATERIEL COMMAND 139 BARNES DRIVE, SUITE 2...a composite material that combines the protein and inorganic components. The process can be mimicked in vitro to some degree, providing methods for

Preprints in biomedicine: alternative or complement to the traditional model of publication?

PubMed

Aquino-Jarquin, Guillermo; Valencia-Reyes, Josefina de Monserrat; Silva-Carmona, Abraham; Granados-Riverón, Javier Tadeo

2018-01-01

The peer-review system has allowed the quality control of the manuscripts submitted for publication to scientific journals for over three centuries. However, due to its relative slowness and other drawbacks, some researchers, mainly in the areas of Physics and Mathematics, started some decades ago to propagate, by electronic means, manuscripts not yet submitted to a journal for formal publication. The dissemination of this practice led to the establishment of permanent repositories like ArXiv, to which preprints can be sent to be published whitou charge, allowing also the search and download of the works they contain with no payment required from the reader. In biomedical sciences, the adoption of the system has been slower than in the exact sciences and previous attempts like e-biomed, Netprints, and Nature Precedings did not prosper. A new generation of repositories like bioRXiv, inspired by ArXiv, seems to enjoy an increasing acceptance among biomedical researchers. Here, we discuss the potential role of this emerging system to establish discovery priority in biomedicine and to improve manuscripts before they are submitted to scientific journals besides other applications which could be implemented in the extent that the model becomes more popular. Copyright: © 2018 SecretarÍa de Salud.

Rotating Detonation Engine Operation (Preprint)

DTIC Science & Technology

2012-01-01

MdotH2 = mass flow of hydrogen MdotAir = mass flow of air PCB = Piezoelectric Pressure Sensor PDE = Pulsed Detonation Engine RDE = Rotating ...and unsteady thrust output of PDEs . One of the new designs was the Rotating Detonation Engine (RDE). An RDE operates by exhausting an initial...AFRL-RZ-WP-TP-2012-0003 ROTATING DETONATION ENGINE OPERATION (PREPRINT) James A. Suchocki and Sheng-Tao John Yu The Ohio State

Fatigue Crack Detection via Load-Differential Guided Wave Methods (Preprint)

DTIC Science & Technology

2011-11-01

AFRL-RX-WP-TP-2011-4362 FATIGUE CRACK DETECTION VIA LOAD- DIFFERENTIAL GUIDED WAVE METHODS (PREPRINT) Jennifer E. Michaels, Sang Jun Lee...November 2011 Technical Paper 1 November 2011 – 1 November 2011 4. TITLE AND SUBTITLE FATIGUE CRACK DETECTION VIA LOAD-DIFFERENTIAL GUIDED WAVE...document contains color. 14. ABSTRACT Detection of fatigue cracks originating from fastener holes is an important application for structural health

An Opportunistic Wireless Charging System Design for an On-Demand Shuttle Service: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doubleday, Kate; Meintz, Andrew; Markel, Tony

System right-sizing is critical to implementation of in-motion wireless power transfer (WPT) for electric vehicles. This study introduces a modeling tool, WPTSim, which uses one-second speed, location, and road grade data from an on-demand employee shuttle in operation to simulate the incorporation of WPT at fine granularity. Vehicle power and state of charge are simulated over the drive cycle to evaluate potential system designs. The required battery capacity is determined based on the rated power at a variable number of charging locations. Adding just one WPT location can more than halve the battery capacity needed. Many configurations are capable ofmore » being self sustaining with WPT, while others benefit from supplemental stationary charging.« less

Nonlinear Wave Propagation

DTIC Science & Technology

1983-12-30

Transform for the Kadomtsev - Petviashvili Equation , M.J. Ablowitz , D. Bar Yaacov and A.S. Fokas, to appear in Stud. in Appl. Math. I.N.S. #21 preprint...Benjamin-Ono equation bears many similariti to the multidimensional problem, especially the Kadomtsev - Petviashvili equation . We discuss many of these...appear in Stud. in Appl. Math. I.N.S. #22 preprint, 1982. 67. On the Inverse Scattering Transform for the Kadomtsev - Petviashvili Equation , M.J. Ablowitz

Blast Injury: Translating Research Into Operational Medicine (Preprint)

DTIC Science & Technology

2008-05-20

i Blast Injury: Translating Research into Operational Medicine Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for...SUBTITLE Blast Injury: Translating Research Into Operational Medicine 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...Z39-18 iii Blast Injury: Translating Research into Operational Medicine Preprint BI-QP-JHS-CH10 Borden Institute This chapter was originally

Mobile access to virtual randomization for investigator-initiated trials.

PubMed

Deserno, Thomas M; Keszei, András P

2017-08-01

Background/aims Randomization is indispensable in clinical trials in order to provide unbiased treatment allocation and a valid statistical inference. Improper handling of allocation lists can be avoided using central systems, for example, human-based services. However, central systems are unaffordable for investigator-initiated trials and might be inaccessible from some places, where study subjects need allocations. We propose mobile access to virtual randomization, where the randomization lists are non-existent and the appropriate allocation is computed on demand. Methods The core of the system architecture is an electronic data capture system or a clinical trial management system, which is extended by an R interface connecting the R server using the Java R Interface. Mobile devices communicate via the representational state transfer web services. Furthermore, a simple web-based setup allows configuring the appropriate statistics by non-statisticians. Our comprehensive R script supports simple randomization, restricted randomization using a random allocation rule, block randomization, and stratified randomization for un-blinded, single-blinded, and double-blinded trials. For each trial, the electronic data capture system or the clinical trial management system stores the randomization parameters and the subject assignments. Results Apps are provided for iOS and Android and subjects are randomized using smartphones. After logging onto the system, the user selects the trial and the subject, and the allocation number and treatment arm are displayed instantaneously and stored in the core system. So far, 156 subjects have been allocated from mobile devices serving five investigator-initiated trials. Conclusion Transforming pre-printed allocation lists into virtual ones ensures the correct conduct of trials and guarantees a strictly sequential processing in all trial sites. Covering 88% of all randomization models that are used in recent trials, virtual randomization becomes available for investigator-initiated trials and potentially for large multi-center trials.

Post-Correlation Semi-Coherent Integration for High-Dynamic and Weak GPS Signal Acquisition (Preprint)

DTIC Science & Technology

2008-06-01

provide the coverage. To enable weak GPS signal acquisition , one known technique at the receiver end is to extend the signal integration time...Han, “Block Accumulating Coherent Integration Over Extended Interval (BACIX) for Weak GPS Signal Acquisition ,” Proc. of ION-GNSS’06, Ft. Worth, TX...AFRL-RY-WP-TP-2008-1158 POST-CORRELATION SEMI-COHERENT INTEGRATION FOR HIGH-DYNAMIC AND WEAK GPS SIGNAL ACQUISITION (PREPRINT) Chun Yang

Acoustoelastic Lamb Wave Propagation in Biaxially Stressed Plates (Preprint)

DTIC Science & Technology

2012-03-01

0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing...control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1 . REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3. DATES COVERED (From - To) March 2012...Journal Article 1 March 2012 – 1 March 2012 4. TITLE AND SUBTITLE ACOUSTOELASTIC LAMB WAVE PROPAGATION IN BIAXIALLY STRESSED PLATES (PREPRINT

Molecular Structure Analysis of Aminophenyl Silsesquioxane (Preprint)

DTIC Science & Technology

2006-10-31

Preprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) 5d. PROJECT NUMBER Andre Lee (Michigan State Univ.); Timothy S . Haddad (ERC...Joseph J. Schwab & 23030521 Yi Zhong An (Hybrid Plastics, Inc.) 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME( S ) AND...Edwards AFB CA 93524-7401 9. SPONSORING / MONITORING AGENCY NAME( S ) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM( S ) Air Force Research Laboratory

Probabilistic Sensitivity Analysis with Respect to Bounds of Truncated Distributions (PREPRINT)

DTIC Science & Technology

2010-04-01

AFRL-RX-WP-TP-2010-4147 PROBABILISTIC SENSITIVITY ANALYSIS WITH RESPECT TO BOUNDS OF TRUNCATED DISTRIBUTIONS (PREPRINT) H. Millwater and...5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR(S) H. Millwater and Y. Feng 5d. PROJECT...Z39-18 1 Probabilistic Sensitivity Analysis with respect to Bounds of Truncated Distributions H. Millwater and Y. Feng Department of Mechanical

New Insights into Structure-Property Relationships in Thermosetting Polymers from Studies of Co-Cured Polycyanurate Networks (Preprint)

DTIC Science & Technology

2011-12-19

have shown through positron annihilation studies that a substantial amount of free volume develops during the final stages of cyanate ester cure...Polymers from 5b. GRANT NUMBER Studies of Co-Cured Polycyanurate Networks (preprint) 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Andrew J. Guenthner...Macromolecules. 14. ABSTRACT Studies of the physical properties of the co-cured networks formed from three similar dicyanate ester monomers revealed a

Vacuum Levels Needed to Simulate Internal Fatigue Crack Growth in Titanium Alloys and Nickel-Base Superalloys Thermaodynamic Conditioners (Preprint)

DTIC Science & Technology

2012-08-01

AFRL-RX-WP-TP-2012-0412 VACUUM LEVELS NEEDED TO SIMULATE INTERNAL FATIGUE CRACK GROWTH IN TITANIUM ALLOYS AND NICKEL - BASE SUPERALLOYS...LEVELS NEEDED TO SIMULATE INTERNAL FATIGUE CRACK GROWTH IN TITANIUM ALLOYS AND NICKEL - BASE SUPERALLOYS: THERMAODYNAMIC CONSIDERATIONS (PREPRINT) 5a...have examined fatigue growth of surface cracks in vacuum to simulate sub-surface growth in Ti- alloys and Ni - base superalloys. Even with the highest

Thermal Decomposition Mechanism of 1-ethyl-3-methylimidazolium Bromide Ionic Liquid (Preprint)

DTIC Science & Technology

2011-09-14

TetraethylammoniumTrifluoromentanesulfonate Ionic Liquid and Neutralized Nafion 117 for High-Temperature Fuel Cells J. Am. Chem. Soc. 2010, 132, 2183-2195. (7) Kim, S. Y.; Kim, S...bromide 5b. GRANT NUMBER ionic liquid (Preprint) 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Steven D. Chambreau, Jerry A. Boatz, Ghanshyam L. Vaaghjiani...In order to better understand the volatilization process for ionic liquids , the vapor evolved from heating the ionic liquid 1-ethyl-3

A Study of Stress Distribution in Layered and Gradient Tribological Coatings (Preprint)

DTIC Science & Technology

2006-11-01

FG) Ti/TiC coating design. On the top of the 440C stainless steel substrate, α-Ti is added as a bond layer with 50nm thickness to improve the... stainless steel substrate and the rigid spherical indenter was performed. Figure 5 (a) shows the normalized Hertzian point contact pressure distribution...AFRL-ML-WP-TP-2007-402 A STUDY OF STRESS DISTRIBUTION IN LAYERED AND GRADIENT TRIBOLOGICAL COATINGS (PREPRINT) Young Sup Kang, Shashi K

Time-dependent multi-dimensional simulation studies of the electron output scheme for high power FELs

NASA Astrophysics Data System (ADS)

Hahn, S. J.; Fawley, W. M.; Kim, K.-J.; Edighoffer, J. A.

1995-04-01

We examine the performance of the so-called electron output scheme recently proposed by the Novosibirsk group [G.I. Erg et al., 15th Int. Free Electron Laser Conf., The Hague, The Netherlands, 1993, Book of Abstracts p. 50; Preprint Budker INP 93-75]. In this scheme, the key role of the FEL oscillator is to induce bunching, while an external undulator, called the radiator, then outcouples the bunched electron beam to optical energy via coherent emission. The level of the intracavity power in the oscillator is kept low by employing a transverse optical klystron (TOK) configuration, thus avoiding excessive thermal loading on the cavity mirrors. Time-dependent effects are important in the operation of the electron output scheme because high gain in the TOK oscillator leads to sideband instabilities and chaotic behavior. We have carried out an extensive simulation study by using 1D and 2D time-dependent codes and find that proper control of the oscillator cavity detuning and cavity loss results in high output bunching with a narrow spectral bandwidth. Large cavity detuning in the oscillator and tapering of the radiator undulator is necessary for the optimum output power.

Analysis of EUV/FUV dayglow and auroral measurements

NASA Technical Reports Server (NTRS)

Majeed, T.; Strickland, D. J.; Link, R.

1994-01-01

This report documents investigations carried out over the twelve month period which commenced in November 1992. The contract identifies the following three tasks: analysis of the O II 83.4 nm dayglow and comparison with incoherent scatter radar data, analysis of the EUV spectrum of an electron aurora, and analysis of the EUV spectrum of a proton-hydrogen-electron aurora. The analysis approach, data reduction methods, and results, including plots of O I 98.9 nm versus time and average spectra, are presented for the last two tasks. The appendices contain preprints of two papers written under the first task. The first paper examines the effect of new O(3P) photoionization cross sections, N2 photoabsorption cross sections, and O(+) oscillator strengths and transition probabilities on the O II 83.4 nm dayglow. The second addresses the problem of remotely sensing the dayside F2 region using limb O II 83.4 nm data.

Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys (Preprint)

DTIC Science & Technology

2012-08-01

materials and components designs Conclusions This paper used electropolished specimens of the high-strength titanium alloy Ti-6Al- 2Sn-4Zr-6Mo to...From - To) August 2012 Technical Paper 1 July 2012 – 1 August 2012 4 . TITLE AND SUBTITLE REDUCING UNCERTAINTY IN FATIGUE LIFE LIMITS OF TURBINE...ENGINE ALLOYS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) J.M. Larsen, C.J

Fatigue Variability of a Single Crystal Superalloy at Elevated Temperature (Preprint)

DTIC Science & Technology

2009-03-01

cast slabs of PWA 1484 with the primary longitudinal axis in the > direction (±5 °). The dogbone specimens had a 6 mm gage length and 4 mm...literature concerning the fatigue properties of PWA 1484. It has been reported that fatigue failures often start from eutectics and carbides [ 4 , 6 ...COVERED (From - To) March 2009 Journal Article Preprint 01 March 2009 – 01 March 2009 4 . TITLE AND SUBTITLE FATIGUE VARIABILITY OF A SINGLE CRYSTAL

Atomistic Simulations of Intersection Cross-Slip Nucleation in Ll2 Ni3Al (Preprint)

DTIC Science & Technology

2011-11-01

CROSS-SLIP NUCLEATION IN Ll2 Ni3Al (Preprint) 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR( S ...PROJECT NUMBER 4347 5e. TASK NUMBER 20 5f. WORK UNIT NUMBER LM121100 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) 8. PERFORMING...SPONSORING/MONITORING AGENCY NAME( S ) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY ACRONYM( S ) Air Force Research Laboratory Materials and

Industrial Technology Modernization Program. Phase 3 Proposal, Category 1 Project Countermeasures Assembly Improvements

DTIC Science & Technology

1985-05-24

Tracor INDUSTRIAL TECHNOLOGY MODERNIZATION PROGRAM DTICRt .1ECTE CDJUN07 1989 00 PHASE 3 PROPOSAL CATEGORY 1 PROJECT COUNTERMEASURES ASSEMBLY...package in bin C V_ Put-package back in bin C Put part in plastic bag 0CDV _7 _ ] Seal plastic bag with stapler CDDV _ _- 1 Mark paperwork CDV __ I Peel...part in plastic bag CDV7 Seal plastic bag with stapler C>CDV _ Mark paperwork ~CV_ _ Peel preprinted tag from sheet ~ D Put preprinted tag on plastic

Fully kinetic 3D simulations of the Hermean magnetosphere under realistic conditions: a new approach

NASA Astrophysics Data System (ADS)

Amaya, Jorge; Gonzalez-Herrero, Diego; Lembège, Bertrand; Lapenta, Giovanni

2017-04-01

Simulations of the magnetosphere of planets are usually performed using the MHD and the hybrid approaches. However, these two methods still rely on approximations for the computation of the pressure tensor, and require the neutrality of the plasma at every point of the domain by construction. These approximations undermine the role of electrons on the emergence of plasma features in the magnetosphere of planets. The high mobility of electrons, their characteristic time and space scales, and the lack of perfect neutrality, are the source of many observed phenomena in the magnetospheres, including the turbulence energy cascade, the magnetic reconnection, the particle acceleration in the shock front and the formation of current systems around the magnetosphere. Fully kinetic codes are extremely demanding of computing time, and have been unable to perform simulations of the full magnetosphere at the real scales of a planet with realistic plasma conditions. This is caused by two main reasons: 1) explicit codes must resolve the electron scales limiting the time and space discretisation, and 2) current versions of semi-implicit codes are unstable for cell sizes larger than a few Debye lengths. In this work we present new simulations performed with ECsim, an Energy Conserving semi-implicit method [1], that can overcome these two barriers. We compare the solutions obtained with ECsim with the solutions obtained by the classic semi-implicit code iPic3D [2]. The new simulations with ECsim demand a larger computational effort, but the time and space discretisations are larger than those in iPic3D allowing for a faster simulation time of the full planetary environment. The new code, ECsim, can reach a resolution allowing the capture of significant large scale physics without loosing kinetic electron information, such as wave-electron interaction and non-Maxwellian electron velocity distributions [3]. The code is able to better capture the thickness of the different boundary layers of the magnetosphere of Mercury. Electron kinetics are consistent with the spatial and temporal scale resolutions. Simulations are compared with measurements from the MESSENGER spacecraft showing a better fit when compared against the classic fully kinetic code iPic3D. These results show that the new generation of Energy Conserving semi-implicit codes can be used for an accurate analysis and interpretation of particle data from magnetospheric missions like BepiColombo and MMS, including electron velocity distributions and electron temperature anisotropies. [1] Lapenta, G. (2016). Exactly Energy Conserving Implicit Moment Particle in Cell Formulation. arXiv preprint arXiv:1602.06326. [2] Markidis, S., & Lapenta, G. (2010). Multi-scale simulations of plasma with iPIC3D. Mathematics and Computers in Simulation, 80(7), 1509-1519. [3] Lapenta, G., Gonzalez-Herrero, D., & Boella, E. (2016). Multiple scale kinetic simulations with the energy conserving semi implicit particle in cell (PIC) method. arXiv preprint arXiv:1612.08289.

Full Text Searching and Customization in the NASA ADS Abstract Service

NASA Technical Reports Server (NTRS)

Eichhorn, G.; Accomazzi, A.; Grant, C. S.; Kurtz, M. J.; Henneken, E. A.; Thompson, D. M.; Murray, S. S.

2004-01-01

The NASA-ADS Abstract Service provides a sophisticated search capability for the literature in Astronomy, Planetary Sciences, Physics/Geophysics, and Space Instrumentation. The ADS is funded by NASA and access to the ADS services is free to anybody worldwide without restrictions. It allows the user to search the literature by author, title, and abstract text. The ADS database contains over 3.6 million references, with 965,000 in the Astronomy/Planetary Sciences database, and 1.6 million in the Physics/Geophysics database. 2/3 of the records have full abstracts, the rest are table of contents entries (titles and author lists only). The coverage for the Astronomy literature is better than 95% from 1975. Before that we cover all major journals and many smaller ones. Most of the journal literature is covered back to volume 1. We now get abstracts on a regular basis from most journals. Over the last year we have entered basically all conference proceedings tables of contents that are available at the Harvard Smithsonian Center for Astrophysics library. This has greatly increased the coverage of conference proceedings in the ADS. The ADS also covers the ArXiv Preprints. We download these preprints every night and index all the preprints. They can be searched either together with the other abstracts or separately. There are currently about 260,000 preprints in that database. In January 2004 we have introduced two new services, full text searching and a personal notification service called "myADS". As all other ADS services, these are free to use for anybody.

Formation of Equiaxed Alpha and Titanium Nitride Precipitates in Spark Plasma Sintered TiB/Ti-6Al-4V Composites (Preprint)

DTIC Science & Technology

2012-08-01

AFRL-RX-WP-TP-2012-0372 FORMATION OF EQUIAXED ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES...ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES (PREPRINT) 5a. CONTRACT NUMBER FA8650-08-C-5226 5b...distribution of TiN precipitates, as revealed by TEM studies. 15. SUBJECT TERMS Ti-6Al-4V; TiB; TiN; Spark Plasma Sintering ; Composite; α/β phase

Net widens for funding of arXiv preprint server

NASA Astrophysics Data System (ADS)

Cartwright, Jon

2010-03-01

Librarians at Cornell University in the US want more external funding to support their popular arXiv preprint server because the running costs are now "beyond a single institution's resources". The open-access server, which received more than 60 000 new submissions last year and has about 400 000 registered users, is expanding so fast that the budget for staff and running costs is expected to rise by a fifth to 500 000 by 2012. Although most of the top 25 institutional users have already made financial commitments, Cornell now wants several hundred others to pledge support too.

12 CFR 1005.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 12 Banks and Banking 8 2012-01-01 2012-01-01 false Electronic fund transfer service provider not... PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) § 1005.14 Electronic fund transfer service provider not holding consumer's account. (a) Provider of electronic fund transfer service. A person that provides an...

12 CFR 1005.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 12 Banks and Banking 8 2013-01-01 2013-01-01 false Electronic fund transfer service provider not... PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) General § 1005.14 Electronic fund transfer service provider not holding consumer's account. (a) Provider of electronic fund transfer service. A person that...

12 CFR 1005.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 12 Banks and Banking 8 2014-01-01 2014-01-01 false Electronic fund transfer service provider not... PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) General § 1005.14 Electronic fund transfer service provider not holding consumer's account. (a) Provider of electronic fund transfer service. A person that...

Transport properties of coupled quantum dots in the presence of phonons

NASA Astrophysics Data System (ADS)

Martins, G.; Al-Hassanieh, K.

2005-03-01

Here is presented the numerical study of the effect of Holstein phonons in the transport properties of two coupled quantum dots (QDs) in the Kondo regime. For the QDs we use the Anderson impurity model and each QD is coupled to a different Holstein mode. At T=0, in the absence of phonons, and with 1 electron per dot, the usual splitting of the Kondo resonance is observed.^1 When the QDs are coupled to the phonons, there is a reduction of the effective Coulomb repulsion, which is explained through a canonical transformation. In addition, the conductance at the electron-hole symmetric gate potential is not affected by the phonons. This is caused by the modulation of the coupling factors.^2 The difference between the effects of phonons in lithographic QDs and in molecular conductors is also discussed. 1- C.A. Büsser et al, Phys. Rev. B 62, 9907 (2000). 2- K.A. Al-Hassanieh, C.A. Büsser, G.B. Martins, Adriana Moreo and Elbio Dagotto (preprint)

Stress Intensity of Delamination in a Sintered-Silver Interconnection: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, D. J.; Paret, P. P.; Wereszczak, A. A.

2014-08-01

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase-change materials pose bottlenecks to heat removal and are also associated with reliability concerns. The industry trend is toward high thermal performance bonded interfaces for large-area attachments. However, because of coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a reliability problem. These defects manifest themselves in increased thermal resistance. This research aims to investigate and improve the thermal performance and reliability of sintered-silver for power electronics packaging applications. This has been experimentally accomplished by the synthesismore » of large-area bonded interfaces between metalized substrates and copper base plates that have subsequently been subjected to thermal cycles. A finite element model of crack initiation and propagation in these bonded interfaces will allow for the interpretation of degradation rates by a crack-velocity (V)-stress intensity factor (K) analysis. A description of the experiment and the modeling approach are discussed.« less

Simulated Real-World Energy Impacts of a Thermally Sensitive Powertrain Considering Viscous Losses and Enrichment: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, E.; Gonder, J.; Lopp, S.

It is widely understood that cold ambient temperatures increase vehicle fuel consumption due to heat transfer losses, increased friction (increased viscosity lubricants), and enrichment strategies (accelerated catalyst heating). However, relatively little effort has been dedicated to thoroughly quantifying these impacts across a large set of real world drive cycle data and ambient conditions. This work leverages experimental dynamometer vehicle data collected under various drive cycles and ambient conditions to develop a simplified modeling framework for quantifying thermal effects on vehicle energy consumption. These models are applied over a wide array of real-world usage profiles and typical meteorological data to developmore » estimates of in-use fuel economy. The paper concludes with a discussion of how this integrated testing/modeling approach may be applied to quantify real-world, off-cycle fuel economy benefits of various technologies.« less

Potential-Induced Degradation-Delamination Mode in Crystalline Silicon Modules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hacke, Peter L; Kempe, Michael D; Wohlgemuth, John

A test sequence producing potential-induced degradation-delamination (PID-d) in crystalline silicon modules has been tested and found comparable under visual inspection to cell/encapsulant delamination seen in some fielded modules. Four commercial modules were put through this sequence, 85 degrees C, 85%, 1000 h damp heat, followed by an intensive PID stress sequence of 72 degrees C, 95% RH, and -1000 V, with the module face grounded using a metal foil. The 60 cell c-Si modules exhibiting the highest current transfer (4.4 center dot 10-4 A) exhibited PID-d at the first inspection after 156 h of PID stress. Effects promoting PID-d aremore » reduced adhesion caused by damp heat, sodium migration further reducing adhesion to the cells, and gaseous products of electrochemical reactions driven by the applied system voltage. A new work item proposal for an IEC test standard to evaluate for PID-d is anticipated.« less

Quantum tunneling resonant electron transfer process in Lorentzian plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Woo-Pyo; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791

The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunnelingmore » resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed.« less

Ultrafast direct electron transfer at organic semiconductor and metal interfaces.

PubMed

Xiang, Bo; Li, Yingmin; Pham, C Huy; Paesani, Francesco; Xiong, Wei

2017-11-01

The ability to control direct electron transfer can facilitate the development of new molecular electronics, light-harvesting materials, and photocatalysis. However, control of direct electron transfer has been rarely reported, and the molecular conformation-electron dynamics relationships remain unclear. We describe direct electron transfer at buried interfaces between an organic polymer semiconductor film and a gold substrate by observing the first dynamical electric field-induced vibrational sum frequency generation (VSFG). In transient electric field-induced VSFG measurements on this system, we observe dynamical responses (<150 fs) that depend on photon energy and polarization, demonstrating that electrons are directly transferred from the Fermi level of gold to the lowest unoccupied molecular orbital of organic semiconductor. Transient spectra further reveal that, although the interfaces are prepared without deliberate alignment control, a subensemble of surface molecules can adopt conformations for direct electron transfer. Density functional theory calculations support the experimental results and ascribe the observed electron transfer to a flat-lying polymer configuration in which electronic orbitals are found to be delocalized across the interface. The present observation of direct electron transfer at complex interfaces and the insights gained into the relationship between molecular conformations and electron dynamics will have implications for implementing novel direct electron transfer in energy materials.

Contribution of direct electron transfer mechanisms to overall electron transfer in microbial fuel cells utilising Shewanella oneidensis as biocatalyst.

PubMed

Fapetu, Segun; Keshavarz, Taj; Clements, Mark; Kyazze, Godfrey

2016-09-01

To investigate the contribution of direct electron transfer mechanisms to electricity production in microbial fuel cells by physically retaining Shewanella oneidensis cells close to or away from the anode electrode. A maximum power output of 114 ± 6 mWm(-2) was obtained when cells were retained close to the anode using a dialysis membrane. This was 3.5 times more than when the cells were separated away from the anode. Without the membrane the maximum power output was 129 ± 6 mWm(-2). The direct mechanisms of electron transfer contributed significantly to overall electron transfer from S. oneidensis to electrodes, a result that was corroborated by another experiment where S. oneidensis cells were entrapped in alginate gels. S. oneidensis transfers electrons primarily by direct electron transfer as opposed to mediated electron transfer.

Suppression of BRCA2 by Mutant Mitochondrial DNA in Prostate Cancer

DTIC Science & Technology

2011-05-01

Briefly, the electron transfer activities of complex I/III (NADH dehydrogenase/cytochrome bc1 complex: catalyzes the electron transfer from NADH to...ferricytochrome c) and complex II/III (succinate dehydrogenase/cytochrome bc1 complex: catalyzes the electron transfer from succinate to ferricytochrome...The electron transfer activity of complex IV (cytochrome c oxidase: catalyzes the final step of the respiratory chain by transferring electrons from

Electrochemical Measurement of Electron Transfer Kinetics by Shewanella oneidensis MR-1*

PubMed Central

Baron, Daniel; LaBelle, Edward; Coursolle, Dan; Gralnick, Jeffrey A.; Bond, Daniel R.

2009-01-01

Shewanella oneidensis strain MR-1 can respire using carbon electrodes and metal oxyhydroxides as electron acceptors, requiring mechanisms for transferring electrons from the cell interior to surfaces located beyond the cell. Although purified outer membrane cytochromes will reduce both electrodes and metals, S. oneidensis also secretes flavins, which accelerate electron transfer to metals and electrodes. We developed techniques for detecting direct electron transfer by intact cells, using turnover and single turnover voltammetry. Metabolically active cells attached to graphite electrodes produced thin (submonolayer) films that demonstrated both catalytic and reversible electron transfer in the presence and absence of flavins. In the absence of soluble flavins, electron transfer occurred in a broad potential window centered at ∼0 V (versus standard hydrogen electrode), and was altered in single (ΔomcA, ΔmtrC) and double deletion (ΔomcA/ΔmtrC) mutants of outer membrane cytochromes. The addition of soluble flavins at physiological concentrations significantly accelerated electron transfer and allowed catalytic electron transfer to occur at lower applied potentials (−0.2 V). Scan rate analysis indicated that rate constants for direct electron transfer were slower than those reported for pure cytochromes (∼1 s−1). These observations indicated that anodic current in the higher (>0 V) window is due to activation of a direct transfer mechanism, whereas electron transfer at lower potentials is enabled by flavins. The electrochemical dissection of these activities in living cells into two systems with characteristic midpoint potentials and kinetic behaviors explains prior observations and demonstrates the complementary nature of S. oneidensis electron transfer strategies. PMID:19661057

Hydrated Electron Transfer to Nucleobases in Aqueous Solutions Revealed by Ab Initio Molecular Dynamics Simulations.

PubMed

Zhao, Jing; Wang, Mei; Fu, Aiyun; Yang, Hongfang; Bu, Yuxiang

2015-08-03

We present an ab initio molecular dynamics (AIMD) simulation study into the transfer dynamics of an excess electron from its cavity-shaped hydrated electron state to a hydrated nucleobase (NB)-bound state. In contrast to the traditional view that electron localization at NBs (G/A/C/T), which is the first step for electron-induced DNA damage, is related only to dry or prehydrated electrons, and a fully hydrated electron no longer transfers to NBs, our AIMD simulations indicate that a fully hydrated electron can still transfer to NBs. We monitored the transfer dynamics of fully hydrated electrons towards hydrated NBs in aqueous solutions by using AIMD simulations and found that due to solution-structure fluctuation and attraction of NBs, a fully hydrated electron can transfer to a NB gradually over time. Concurrently, the hydrated electron cavity gradually reorganizes, distorts, and even breaks. The transfer could be completed in about 120-200 fs in four aqueous NB solutions, depending on the electron-binding ability of hydrated NBs and the structural fluctuation of the solution. The transferring electron resides in the π*-type lowest unoccupied molecular orbital of the NB, which leads to a hydrated NB anion. Clearly, the observed transfer of hydrated electrons can be attributed to the strong electron-binding ability of hydrated NBs over the hydrated electron cavity, which is the driving force, and the transfer dynamics is structure-fluctuation controlled. This work provides new insights into the evolution dynamics of hydrated electrons and provides some helpful information for understanding the DNA-damage mechanism in solution. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Slip Activity in Single Grains Extracted from Polycrystalline Specimen by X-Ray Line Broadening (Preprint)

DTIC Science & Technology

2010-01-01

4 6 8 0.005 0.010 -101-3 -110-2 1-10-2F W H M [ 1 /n m ] K [ 1/nm ] Gr #44 Gr #50 Gr #72 -101-1 1-101 (a...0 2 4 6 0.000 0.005 0.010 (b) K2Ccalc [ 1/nm ] FW H M [ 1 /n m ] Gr #44 Gr #50 Gr #72 17 Figure 5. The FWHM (in 1/nm scales) in...Preprint 01 January 2010 – 01 January 2010 4 . TITLE AND SUBTITLE SLIP ACTIVITY IN SINGLE GRAINS EXTRACTED FROM POLYCRYSTALLINE SPECIMEN BY X-RAY

Pilot evaluation of isolation patients' perceptions on ability to identify types of health care workers when wearing isolation gowns.

PubMed

Roderick, Mickey; Speroni, Karen Gabel; Stafford, Amy; Seibert, Dorothy J

2017-03-01

In a survey research study, perceptions of 50 hospitalized patients on contact isolation were evaluated regarding their ability to identify health care worker (HCW) type in isolation gowns with no hospital badge under or on the gown, in isolation gowns with the hospital badge partially visible through the gown, and in isolation gowns with a preprinted large font Registered Nurse and Nursing Technician sticker badge on the outside of the gown. Patients ranked their ability to identify HCWs when entering their hospital room as important (average ranking, 8.0, where 0 was not at all important and 10 was very important); 28 patients (56%) specified all HCWs entering their hospital room should wear a preprinted large font sticker badge on the outside of their isolation gowns. Patients found little difficulty identifying HCW type with the large font preprinted sticker badge (average difficulty ranking, 1.0, where 0 is not at all difficult and 10 is very difficult), a simplistic method to improve HCW type identification. Copyright © 2017 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Electron transfer and conformational change in complexes of trimethylamine dehydrogenase and electron transferring flavoprotein.

PubMed

Jones, Matthew; Talfournier, Francois; Bobrov, Anton; Grossmann, J Günter; Vekshin, Nikolai; Sutcliffe, Michael J; Scrutton, Nigel S

2002-03-08

The trimethylamine dehydrogenase-electron transferring flavoprotein (TMADH.ETF) electron transfer complex has been studied by fluorescence and absorption spectroscopies. These studies indicate that a series of conformational changes occur during the assembly of the TMADH.ETF electron transfer complex and that the kinetics of assembly observed with mutant TMADH (Y442F/L/G) or ETF (alpha R237A) complexes are much slower than are the corresponding rates of electron transfer in these complexes. This suggests that electron transfer does not occur in the thermodynamically most favorable state (which takes too long to form), but that one or more metastable states (which are formed more rapidly) are competent in transferring electrons from TMADH to ETF. Additionally, fluorescence spectroscopy studies of the TMADH.ETF complex indicate that ETF undergoes a stable conformational change (termed structural imprinting) when it interacts transiently with TMADH to form a second, distinct, structural form. The mutant complexes compromise imprinting of ETF, indicating a dependence on the native interactions present in the wild-type complex. The imprinted form of semiquinone ETF exhibits an enhanced rate of electron transfer to the artificial electron acceptor, ferricenium. Overall molecular conformations as probed by small-angle x-ray scattering studies are indistinguishable for imprinted and non-imprinted ETF, suggesting that changes in structure likely involve confined reorganizations within the vicinity of the FAD. Our results indicate a series of conformational events occur during the assembly of the TMADH.ETF electron transfer complex, and that the properties of electron transfer proteins can be affected lastingly by transient interaction with their physiological redox partners. This may have significant implications for our understanding of biological electron transfer reactions in vivo, because ETF encounters TMADH at all times in the cell. Our studies suggest that caution needs to be exercised in extrapolating the properties of in vitro interprotein electron transfer reactions to those occurring in vivo.

31 CFR 208.3 - Payment by electronic funds transfer.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 31 Money and Finance:Treasury 2 2011-07-01 2011-07-01 false Payment by electronic funds transfer... DISBURSEMENTS § 208.3 Payment by electronic funds transfer. Subject to § 208.4, and notwithstanding any other... electronic funds transfer. ...

48 CFR 18.124 - Electronic funds transfer.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Electronic funds transfer. 18.124 Section 18.124 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION... Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to support...

48 CFR 18.124 - Electronic funds transfer.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Electronic funds transfer. 18.124 Section 18.124 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION... Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to support...

31 CFR 208.3 - Payment by electronic funds transfer.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 31 Money and Finance:Treasury 2 2012-07-01 2012-07-01 false Payment by electronic funds transfer... DISBURSEMENTS § 208.3 Payment by electronic funds transfer. Subject to § 208.4, and notwithstanding any other... electronic funds transfer. ...

48 CFR 18.123 - Electronic funds transfer.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Electronic funds transfer. 18.123 Section 18.123 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION... Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to support...

48 CFR 18.124 - Electronic funds transfer.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Electronic funds transfer. 18.124 Section 18.124 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION... Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to support...

48 CFR 18.124 - Electronic funds transfer.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Electronic funds transfer. 18.124 Section 18.124 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION... Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to support...

Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticles

PubMed Central

Tvrdy, Kevin; Frantsuzov, Pavel A.; Kamat, Prashant V.

2011-01-01

Quantum dot-metal oxide junctions are an integral part of next-generation solar cells, light emitting diodes, and nanostructured electronic arrays. Here we present a comprehensive examination of electron transfer at these junctions, using a series of CdSe quantum dot donors (sizes 2.8, 3.3, 4.0, and 4.2 nm in diameter) and metal oxide nanoparticle acceptors (SnO2, TiO2, and ZnO). Apparent electron transfer rate constants showed strong dependence on change in system free energy, exhibiting a sharp rise at small driving forces followed by a modest rise further away from the characteristic reorganization energy. The observed trend mimics the predicted behavior of electron transfer from a single quantum state to a continuum of electron accepting states, such as those present in the conduction band of a metal oxide nanoparticle. In contrast with dye-sensitized metal oxide electron transfer studies, our systems did not exhibit unthermalized hot-electron injection due to relatively large ratios of electron cooling rate to electron transfer rate. To investigate the implications of these findings in photovoltaic cells, quantum dot-metal oxide working electrodes were constructed in an identical fashion to the films used for the electron transfer portion of the study. Interestingly, the films which exhibited the fastest electron transfer rates (SnO2) were not the same as those which showed the highest photocurrent (TiO2). These findings suggest that, in addition to electron transfer at the quantum dot-metal oxide interface, other electron transfer reactions play key roles in the determination of overall device efficiency. PMID:21149685

Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticles.

PubMed

Tvrdy, Kevin; Frantsuzov, Pavel A; Kamat, Prashant V

2011-01-04

Quantum dot-metal oxide junctions are an integral part of next-generation solar cells, light emitting diodes, and nanostructured electronic arrays. Here we present a comprehensive examination of electron transfer at these junctions, using a series of CdSe quantum dot donors (sizes 2.8, 3.3, 4.0, and 4.2 nm in diameter) and metal oxide nanoparticle acceptors (SnO(2), TiO(2), and ZnO). Apparent electron transfer rate constants showed strong dependence on change in system free energy, exhibiting a sharp rise at small driving forces followed by a modest rise further away from the characteristic reorganization energy. The observed trend mimics the predicted behavior of electron transfer from a single quantum state to a continuum of electron accepting states, such as those present in the conduction band of a metal oxide nanoparticle. In contrast with dye-sensitized metal oxide electron transfer studies, our systems did not exhibit unthermalized hot-electron injection due to relatively large ratios of electron cooling rate to electron transfer rate. To investigate the implications of these findings in photovoltaic cells, quantum dot-metal oxide working electrodes were constructed in an identical fashion to the films used for the electron transfer portion of the study. Interestingly, the films which exhibited the fastest electron transfer rates (SnO(2)) were not the same as those which showed the highest photocurrent (TiO(2)). These findings suggest that, in addition to electron transfer at the quantum dot-metal oxide interface, other electron transfer reactions play key roles in the determination of overall device efficiency.

Modular electron transfer circuits for synthetic biology

PubMed Central

Agapakis, Christina M

2010-01-01

Electron transfer is central to a wide range of essential metabolic pathways, from photosynthesis to fermentation. The evolutionary diversity and conservation of proteins that transfer electrons makes these pathways a valuable platform for engineered metabolic circuits in synthetic biology. Rational engineering of electron transfer pathways containing hydrogenases has the potential to lead to industrial scale production of hydrogen as an alternative source of clean fuel and experimental assays for understanding the complex interactions of multiple electron transfer proteins in vivo. We designed and implemented a synthetic hydrogen metabolism circuit in Escherichia coli that creates an electron transfer pathway both orthogonal to and integrated within existing metabolism. The design of such modular electron transfer circuits allows for facile characterization of in vivo system parameters with applications toward further engineering for alternative energy production. PMID:21468209

Electrochemical control over photoinduced electron transfer and trapping in CdSe-CdTe quantum-dot solids.

PubMed

Boehme, Simon C; Walvis, T Ardaan; Infante, Ivan; Grozema, Ferdinand C; Vanmaekelbergh, Daniël; Siebbeles, Laurens D A; Houtepen, Arjan J

2014-07-22

Understanding and controlling charge transfer between different kinds of colloidal quantum dots (QDs) is important for devices such as light-emitting diodes and solar cells and for thermoelectric applications. Here we study photoinduced electron transfer between CdTe and CdSe QDs in a QD film. We find that very efficient electron trapping in CdTe QDs obstructs electron transfer to CdSe QDs under most conditions. Only the use of thiol ligands results in somewhat slower electron trapping; in this case the competition between trapping and electron transfer results in a small fraction of electrons being transferred to CdSe. However, we demonstrate that electron trapping can be controlled and even avoided altogether by using the unique combination of electrochemistry and transient absorption spectroscopy. When the Fermi level is raised electrochemically, traps are filled with electrons and electron transfer from CdTe to CdSe QDs occurs with unity efficiency. These results show the great importance of knowing and controlling the Fermi level in QD films and open up the possibility of studying the density of trap states in QD films as well as the systematic investigation of the intrinsic electron transfer rates in donor-acceptor films.

Dinitrogen Difluoride Chemistry. Improved Synthesis of cis- and trans-N2F2, Synthesis and Characterization of N2F+Sn2F9 High-Level Electronic Structure Calculations of cis-N2F2, trans-N2F2, F2N=N, and N2F+, and Mechanism of the trans-cis Isomerization of N2F2 (Preprint)

DTIC Science & Technology

2010-05-01

measurements of Pankratov and Sokolov who found that within experimental error this value was close to zero.48 We note that the current calculations are...Z. Chem. Phys. Lett. 1977, 50, 418. 9. Christe, K. O.; Wilson, R. D.; Wilson, W. W.; Bau, R.; Sukumar, S.; Dixon, D. A. J. Am. Chem. Soc. 1991 , 113...Phys. Chem. Ref. Data, Mono. 9, Suppl. 1 (1998). 48. Pankratov , A. V.; Sokolov, O. M. Russ. J. Inorg. Chem. 1966, 11, 943. 49. Christe, K. O

Hot-electron transfer in quantum-dot heterojunction films.

PubMed

Grimaldi, Gianluca; Crisp, Ryan W; Ten Brinck, Stephanie; Zapata, Felipe; van Ouwendorp, Michiko; Renaud, Nicolas; Kirkwood, Nicholas; Evers, Wiel H; Kinge, Sachin; Infante, Ivan; Siebbeles, Laurens D A; Houtepen, Arjan J

2018-06-13

Thermalization losses limit the photon-to-power conversion of solar cells at the high-energy side of the solar spectrum, as electrons quickly lose their energy relaxing to the band edge. Hot-electron transfer could reduce these losses. Here, we demonstrate fast and efficient hot-electron transfer between lead selenide and cadmium selenide quantum dots assembled in a quantum-dot heterojunction solid. In this system, the energy structure of the absorber material and of the electron extracting material can be easily tuned via a variation of quantum-dot size, allowing us to tailor the energetics of the transfer process for device applications. The efficiency of the transfer process increases with excitation energy as a result of the more favorable competition between hot-electron transfer and electron cooling. The experimental picture is supported by time-domain density functional theory calculations, showing that electron density is transferred from lead selenide to cadmium selenide quantum dots on the sub-picosecond timescale.

Electron-transfer oxidation properties of DNA bases and DNA oligomers.

PubMed

Fukuzumi, Shunichi; Miyao, Hiroshi; Ohkubo, Kei; Suenobu, Tomoyoshi

2005-04-21

Kinetics for the thermal and photoinduced electron-transfer oxidation of a series of DNA bases with various oxidants having the known one-electron reduction potentials (E(red)) in an aqueous solution at 298 K were examined, and the resulting electron-transfer rate constants (k(et)) were evaluated in light of the free energy relationship of electron transfer to determine the one-electron oxidation potentials (E(ox)) of DNA bases and the intrinsic barrier of the electron transfer. Although the E(ox) value of GMP at pH 7 is the lowest (1.07 V vs SCE) among the four DNA bases, the highest E(ox) value (CMP) is only 0.19 V higher than that of GMP. The selective oxidation of GMP in the thermal electron-transfer oxidation of GMP results from a significant decrease in the pH dependent oxidation potential due to the deprotonation of GMP*+. The one-electron reduced species of the photosensitizer produced by photoinduced electron transfer are observed as the transient absorption spectra when the free energy change of electron transfer is negative. The rate constants of electron-transfer oxidation of the guanine moieties in DNA oligomers with Fe(bpy)3(3+) and Ru(bpy)3(3+) were also determined using DNA oligomers containing different guanine (G) sequences from 1 to 10 G. The rate constants of electron-transfer oxidation of the guanine moieties in single- and double-stranded DNA oligomers with Fe(bpy)3(2+) and Ru(bpy)3(3+) are dependent on the number of sequential guanine molecules as well as on pH.

14 CFR 1274.931 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS WITH COMMERCIAL FIRMS Other Provisions and Special Conditions § 1274.931 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods July 2002 Payments under this...

77 FR 40459 - Electronic Fund Transfers (Regulation E); Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-10

... Electronic Fund Transfers (Regulation E); Correction AGENCY: Bureau of Consumer Financial Protection. ACTION... published the Final Rule (77 FR 6194), which implements the Electronic Fund Transfer Act, and the official... Sec. 1005.3(a) in the interim final rule, Electronic Fund Transfers (Regulation E), published on...

14 CFR 1274.931 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS WITH COMMERCIAL FIRMS Other Provisions and Special Conditions § 1274.931 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods July 2002 Payments under this...

14 CFR § 1260.69 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Electronic funds transfer payment methods... GRANTS AND COOPERATIVE AGREEMENTS General Special Conditions § 1260.69 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods October 2000 (a) Payments under this grant will be made...

14 CFR 1260.69 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS General Special Conditions § 1260.69 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods October 2000 (a) Payments under this grant will be made by the...

14 CFR 1260.69 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS General Special Conditions § 1260.69 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods October 2000 (a) Payments under this grant will be made by the...

14 CFR 1260.69 - Electronic funds transfer payment methods.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS General Special Conditions § 1260.69 Electronic funds transfer payment methods. Electronic Funds Transfer Payment Methods October 2000 (a) Payments under this grant will be made by the...

The influence of dielectric relaxation on intramolecular electron transfer

NASA Astrophysics Data System (ADS)

Heitele, H.; Michel-Beyerle, M. E.; Finckh, P.

1987-07-01

An unusually strong temperature dependence on the intramolecular electron-transfer rate has been observed for bridged donor-acceptor compounds in propylene glycol solution. In the frame of recent electron-transfer theories this effect reflects the influence of dielectric relaxation dynamics on electron transfer. With increasing dielectric relaxation time a smooth transition from non-adiabatic to solvent-controlled adiabatic behaviour is observed. The electron transfer rate in the solvent-controlled adiabatic limit is dominated by an inhomogeneous distribution of relaxation times.

12 CFR 205.15 - Electronic fund transfer of government benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 12 Banks and Banking 2 2011-01-01 2011-01-01 false Electronic fund transfer of government benefits. 205.15 Section 205.15 Banks and Banking FEDERAL RESERVE SYSTEM BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.15 Electronic fund transfer of government...

12 CFR 1005.3 - Coverage.

Code of Federal Regulations, 2014 CFR

2014-01-01

...-time electronic fund transfer from a consumer's account. The consumer must authorize the transfer. (ii... one-time electronic fund transfer (in providing a check to a merchant or other payee for the MICR... transfer. A consumer authorizes a one-time electronic fund transfer from his or her account to pay the fee...

The sixth conference on satellite meteorology and oceanography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hauth, F.F.; Purdom, J.F.W.

The Sixth Conference on Satellite Meteorology and Oceanography was held in conjunction with the AMS Annual Meeting in Atlanta, Georgia, the week of 6 January 1992. Over 150 scientific papers were presented orally or in poster sessions. Joint sessions were held with the Symposium on Weather Forecasting and the Eighth International Conference on Interactive Information and Processing Systems for Meteorology, Oceanography, and Hydrology. The quality of the papers in the preprint volume, as well as in the presentations at both oral and poster sessions, reflects the robustness of national and international operational and research interests in satellite meteorology and oceanography.more » A preprint volume for this conference is available through the AMS.« less

12 CFR 205.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2010 CFR

2010-01-01

... consumer learns of the loss or theft; and extends the time periods for reporting unauthorized transfers or... 12 Banks and Banking 2 2010-01-01 2010-01-01 false Electronic fund transfer service provider not... GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.14 Electronic fund...

12 CFR 205.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2013 CFR

2013-01-01

... consumer learns of the loss or theft; and extends the time periods for reporting unauthorized transfers or... 12 Banks and Banking 2 2013-01-01 2013-01-01 false Electronic fund transfer service provider not... GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.14 Electronic fund...

12 CFR 205.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2014 CFR

2014-01-01

... consumer learns of the loss or theft; and extends the time periods for reporting unauthorized transfers or... 12 Banks and Banking 2 2014-01-01 2014-01-01 false Electronic fund transfer service provider not... GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.14 Electronic fund...

12 CFR 205.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2011 CFR

2011-01-01

... consumer learns of the loss or theft; and extends the time periods for reporting unauthorized transfers or... 12 Banks and Banking 2 2011-01-01 2011-01-01 false Electronic fund transfer service provider not... GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.14 Electronic fund...

12 CFR 205.14 - Electronic fund transfer service provider not holding consumer's account.

Code of Federal Regulations, 2012 CFR

2012-01-01

... consumer learns of the loss or theft; and extends the time periods for reporting unauthorized transfers or... 12 Banks and Banking 2 2012-01-01 2012-01-01 false Electronic fund transfer service provider not... GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.14 Electronic fund...

Anomalous single-electron transfer in common-gate quadruple-dot single-electron devices with asymmetric junction capacitances

NASA Astrophysics Data System (ADS)

Imai, Shigeru; Ito, Masato

2018-06-01

In this paper, anomalous single-electron transfer in common-gate quadruple-dot turnstile devices with asymmetric junction capacitances is revealed. That is, the islands have the same total number of excess electrons at high and low gate voltages of the swing that transfers a single electron. In another situation, two electrons enter the islands from the source and two electrons leave the islands for the source and drain during a gate voltage swing cycle. First, stability diagrams of the turnstile devices are presented. Then, sequences of single-electron tunneling events by gate voltage swings are investigated, which demonstrate the above-mentioned anomalous single-electron transfer between the source and the drain. The anomalous single-electron transfer can be understood by regarding the four islands as “three virtual islands and a virtual source or drain electrode of a virtual triple-dot device”. The anomalous behaviors of the four islands are explained by the normal behavior of the virtual islands transferring a single electron and the behavior of the virtual electrode.

Apparatus and method of direct water cooling several parallel circuit cards each containing several chip packages

DOEpatents

Cipolla, Thomas M [Katonah, NY; Colgan, Evan George [Chestnut Ridge, NY; Coteus, Paul W [Yorktown Heights, NY; Hall, Shawn Anthony [Pleasantville, NY; Tian, Shurong [Mount Kisco, NY

2011-12-20

A cooling apparatus, system and like method for an electronic device includes a plurality of heat producing electronic devices affixed to a wiring substrate. A plurality of heat transfer assemblies each include heat spreaders and thermally communicate with the heat producing electronic devices for transferring heat from the heat producing electronic devices to the heat transfer assemblies. The plurality of heat producing electronic devices and respective heat transfer assemblies are positioned on the wiring substrate having the regions overlapping. A heat conduit thermally communicates with the heat transfer assemblies. The heat conduit circulates thermally conductive fluid therethrough in a closed loop for transferring heat to the fluid from the heat transfer assemblies via the heat spreader. A thermally conductive support structure supports the heat conduit and thermally communicates with the heat transfer assemblies via the heat spreader transferring heat to the fluid of the heat conduit from the support structure.

Acid/base-regulated reversible electron transfer disproportionation of N–N linked bicarbazole and biacridine derivatives† †Electronic supplementary information (ESI) available: Experimental information, synthesis and characterization data, NMR spectra, solid state NMR data, X-ray data, ESR spectra, UV-Vis-NIR spectra, fluorescence spectra, kinetic experiments, theoretical calculations, Tables S1–S8, Scheme S1, Fig. S1–12, References. CCDC 1025063, 1038914, 1049677 and 1040722. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc00946d

PubMed Central

Pandit, Palash; Yamamoto, Koji; Nakamura, Toshikazu; Nishimura, Katsuyuki; Kurashige, Yuki; Yanai, Takeshi; Nakamura, Go; Masaoka, Shigeyuki; Furukawa, Ko; Yakiyama, Yumi; Kawano, Masaki

2015-01-01

Regulation of electron transfer on organic substances by external stimuli is a fundamental issue in science and technology, which affects organic materials, chemical synthesis, and biological metabolism. Nevertheless, acid/base-responsive organic materials that exhibit reversible electron transfer have not been well studied and developed, owing to the difficulty in inventing a mechanism to associate acid/base stimuli and electron transfer. We discovered a new phenomenon in which N–N linked bicarbazole (BC) and tetramethylbiacridine (TBA) derivatives undergo electron transfer disproportionation by acid stimulus, forming their stable radical cations and reduced species. The reaction occurs through a biradical intermediate generated by the acid-triggered N–N bond cleavage reaction of BC or TBA, which acts as a two electron acceptor to undergo electron transfer reactions with two equivalents of BC or TBA. In addition, in the case of TBA the disproportionation reaction is highly reversible through neutralization with NEt3, which recovers TBA through back electron transfer and N–N bond formation reactions. This highly reversible electron transfer reaction is possible due to the association between the acid stimulus and electron transfer via the acid-regulated N–N bond cleavage/formation reactions which provide an efficient switching mechanism, the ability of the organic molecules to act as multi-electron donors and acceptors, the extraordinary stability of the radical species, the highly selective reactivity, and the balance of the redox potentials. This discovery provides new design concepts for acid/base-regulated organic electron transfer systems, chemical reagents, or organic materials. PMID:29218181

Rate of Interfacial Electron Transfer through the 1,2,3-Triazole Linkage

PubMed Central

Devaraj, Neal K.; Decreau, Richard A.; Ebina, Wataru; Collman, James P.; Chidsey, Christopher E. D.

2012-01-01

The rate of electron transfer is measured to two ferrocene and one iron tetraphenylporphyrin redox species coupled through terminal acetylenes to azide-terminated thiol monolayers by the Cu(I)-catalyzed azide–alkyne cycloaddition (a Sharpless “click” reaction) to form the 1,2,3-triazole linkage. The high yield, chemoselectivity, convenience, and broad applicability of this triazole formation reaction make such a modular assembly strategy very attractive. Electron-transfer rate constants from greater than 60,000 to 1 s−1 are obtained by varying the length and conjugation of the electron-transfer bridge and by varying the surrounding diluent thiols in the monolayer. Triazole and the triazole carbonyl linkages provide similar electronic coupling for electron transfer as esters. The ability to vary the rate of electron transfer to many different redox species over many orders of magnitude by using modular coupling chemistry provides a convenient way to study and control the delivery of electrons to multielectron redox catalysts and similar interfacial systems that require controlled delivery of electrons. PMID:16898751

Passive Two-Phase Cooling of Automotive Power Electronics: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, G.; Jeffers, J. R.; Narumanchi, S.

2014-08-01

Experiments were conducted to evaluate the use of a passive two-phase cooling strategy as a means of cooling automotive power electronics. The proposed cooling approach utilizes an indirect cooling configuration to alleviate some reliability concerns and to allow the use of conventional power modules. An inverter-scale proof-of-concept cooling system was fabricated, and tests were conducted using the refrigerants hydrofluoroolefin HFO-1234yf and hydrofluorocarbon HFC-245fa. Results demonstrated that the system can dissipate at least 3.5 kW of heat with 250 cm3 of HFC-245fa. An advanced evaporator design that incorporates features to improve performance and reduce size was conceived. Simulation results indicate itsmore » thermal resistance can be 37% to 48% lower than automotive dual side cooled power modules. Tests were also conducted to measure the thermal performance of two air-cooled condensers--plain and rifled finned tube designs. The results combined with some analysis were then used to estimate the required condenser size per operating conditions and maximum allowable system (i.e., vapor and liquid) temperatures.« less

Laboratory Studies in UV and EUV Solar Physics

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Wagner, William J. (Technical Monitor)

2002-01-01

The Ion Beam Experiment at the Center for Astrophysics is dedicated to the study of ion-electron collision processes of importance in solar physics. The analysis of measurements of Electron Impact Excitation (EIE) from the 3s3p(exp 3)P(exp o) metastable state to the 3s3p(exp 1)P state of Si(2+) was completed during the past year and a paper describing the results is available as a preprint. Our current program is directed at measuring absolute cross sections for dielectronic recombination (DR) and EIE in Si(3+), one of the primary ions used for probing the solar transition region. Our study of DR is particularly concerned with the effects of electric and magnetic fields on the recombination rates. Measurements of silicon ions with charge greater than n=2 have necessitated upgrading the experiment with a new ion source. The new source is also suitable for producing C(2+) beams to be used for measurements of EIE and DR for that system. The source is expected to be capable of producing beams of more highly charged systems as well.

On the physics of electron transfer (drift) in the substance: about the reason of “abnormal” fast transfer of electrons in the plasma of tokamak and at known Bohm’s diffusion

NASA Astrophysics Data System (ADS)

Boriev, I. A.

2018-03-01

An analysis of the problem of so-called “abnormal” fast transfer of electrons in tokamak plasma, which turned out much faster than the result of accepted calculation, is given. Such transfer of hot electrons leads to unexpectedly fast destruction of the inner tokamak wall with ejection of its matter in plasma volume, what violates a condition of plasma confinement for controlled thermonuclear fusion. It is shown, taking into account real physics of electron drift in the gas (plasma) and using the conservation law for momentum of electron transfer (drift), that the drift velocity of elastically scattered electrons should be significantly greater than that of accepted calculation. The reason is that the relaxation time of the momentum of electron transfer, to which the electron drift velocity is proportional, is significantly greater (from 16 up to 4 times) than the electron free path time. Therefore, generally accepted replacement of the relaxation time, which is unknown a priori, by the electron free path time, leads to significant (16 times for thermal electrons) underestimation of electron drift velocity (mobility). This result means, that transfer of elastically (and isotropically) scattered electrons in the gas phase should be so fast, and corresponds to multiplying coefficient (16), introduced by D. Bohm to explain the observed by him “abnormal” fast diffusion of electrons.

Marcus equation

DOE R&D Accomplishments Database

1998-09-21

In the late 1950s to early 1960s Rudolph A. Marcus developed a theory for treating the rates of outer-sphere electron-transfer reactions. Outer-sphere reactions are reactions in which an electron is transferred from a donor to an acceptor without any chemical bonds being made or broken. (Electron-transfer reactions in which bonds are made or broken are referred to as inner-sphere reactions.) Marcus derived several very useful expressions, one of which has come to be known as the Marcus cross-relation or, more simply, as the Marcus equation. It is widely used for correlating and predicting electron-transfer rates. For his contributions to the understanding of electron-transfer reactions, Marcus received the 1992 Nobel Prize in Chemistry. This paper discusses the development and use of the Marcus equation. Topics include self-exchange reactions; net electron-transfer reactions; Marcus cross-relation; and proton, hydride, atom and group transfers.

Coupled sensitizer-catalyst dyads: electron-transfer reactions in a perylene-polyoxometalate conjugate.

PubMed

Odobel, Fabrice; Séverac, Marjorie; Pellegrin, Yann; Blart, Errol; Fosse, Céline; Cannizzo, Caroline; Mayer, Cédric R; Elliott, Kristopher J; Harriman, Anthony

2009-01-01

Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide.

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

NASA Astrophysics Data System (ADS)

Delor, Milan; Archer, Stuart A.; Keane, Theo; Meijer, Anthony J. H. M.; Sazanovich, Igor V.; Greetham, Gregory M.; Towrie, Michael; Weinstein, Julia A.

2017-11-01

Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer donor-bridge-acceptor-bridge-donor 'fork' system: asymmetric 13C isotopic labelling of one of the two -C≡C- bridges makes the two parallel and otherwise identical donor→acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UVpump(excitation)-IRpump(perturbation)-IRprobe(monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices.

Response Time Measurements of the NIF DANTE XRD-31 X-Ray Diodes (Pre-print)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Don Pellinen and Michael Griffin

2009-01-23

The XRD-31 is a fast, windowless X-ray vacuum photodiode developed by EG&G. It is currently the primary fast X-ray detector used to diagnose the X-rays on NIF and OMEGA on the multichannel DANTE spectrometer. The XRD-31 has a dynamic range of less than 1e-12 amps to more than 10 amps. A technique is described to measure the impulse response of the diodes to a 150 fs pulse of 200 nm laser light and a method to calculate the “risetime” for a square pulse and compare it with the computed electron transit time from the photocathode to the anode. Measured responsemore » time for 5 XRD-31s assembled in early 2004 was 149.7 ps +-2.75 ps.« less

Quantum liquids get thin

NASA Astrophysics Data System (ADS)

Ferrier-Barbut, Igor; Pfau, Tilman

2018-01-01

A liquid exists when interactions that attract its constituent particles to each other are counterbalanced by a repulsion acting at higher densities. Other characteristics of liquids are short-range correlations and the existence of surface tension (1). Ultracold atom experiments provide a privileged platform with which to observe exotic states of matter, but the densities are far too low to obtain a conventional liquid because the atoms are too far apart to create repulsive forces arising from the Pauli exclusion principle of the atoms' internal electrons. The observation of quantum liquid droplets in an ultracold mixture of two quantum fluids is now reported on page 301 of this issue by Cabrera et al. (2) and a recent preprint by Semeghini et al. (3). Unlike conventional liquids, these liquids arise from a weak attraction and repulsive many-body correlations in the mixtures.

Thermal transfer structures coupling electronics card(s) to coolant-cooled structure(s)

DOEpatents

David, Milnes P; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Parida, Pritish R; Schmidt, Roger R

2014-12-16

Cooling apparatuses and coolant-cooled electronic systems are provided which include thermal transfer structures configured to engage with a spring force one or more electronics cards with docking of the electronics card(s) within a respective socket(s) of the electronic system. A thermal transfer structure of the cooling apparatus includes a thermal spreader having a first thermal conduction surface, and a thermally conductive spring assembly coupled to the conduction surface of the thermal spreader and positioned and configured to reside between and physically couple a first surface of an electronics card to the first surface of the thermal spreader with docking of the electronics card within a socket of the electronic system. The thermal transfer structure is, in one embodiment, metallurgically bonded to a coolant-cooled structure and facilitates transfer of heat from the electronics card to coolant flowing through the coolant-cooled structure.

Radiation Belt Electron Dynamics: Modeling Atmospheric Losses

NASA Technical Reports Server (NTRS)

Selesnick, R. S.

2003-01-01

The first year of work on this project has been completed. This report provides a summary of the progress made and the plan for the coming year. Also included with this report is a preprint of an article that was accepted for publication in Journal of Geophysical Research and describes in detail most of the results from the first year of effort. The goal for the first year was to develop a radiation belt electron model for fitting to data from the SAMPEX and Polar satellites that would provide an empirical description of the electron losses into the upper atmosphere. This was largely accomplished according to the original plan (with one exception being that, for reasons described below, the inclusion of the loss cone electrons in the model was deferred). The main concerns at the start were to accurately represent the balance between pitch angle diffusion and eastward drift that determines the dominant features of the low altitude data, and then to accurately convert the model into simulated data based on the characteristics of the particular electron detectors. Considerable effort was devoted to achieving these ends. Once the model was providing accurate results it was applied to data sets selected from appropriate periods in 1997, 1998, and 1999. For each interval of -30 to 60 days, the model parameters were calculated daily, thus providing good short and long term temporal resolution, and for a range of radial locations from L = 2.7 to 3.9. .

FTP-Server for exchange, interpretation, and database-search of ion mobility spectra, literature, preprints and software

NASA Technical Reports Server (NTRS)

Baumbach, J. I.; Vonirmer, A.

1995-01-01

To assist current discussion in the field of ion mobility spectrometry, at the Institut fur Spectrochemie und angewandte Spektroskopie, Dortmund, start with 4th of December, 1994 work of an FTP-Server, available for all research groups at univerisities, institutes and research worker in industry. We support the exchange, interpretation, and database-search of ion mobility spectra through data format JCAMP-DS (Joint Committee on Atomic and Molecular Physical Data) as well as literature retrieval, pre-print, notice, and discussion board. We describe in general lines the entrance conditions, local addresses, and main code words. For further details, a monthly news report will be prepared for all common users. Internet email address for subscribing is included in document.

Ultrafast forward and backward electron transfer dynamics of coumarin 337 in hydrogen-bonded anilines as studied with femtosecond UV-pump/IR-probe spectroscopy.

PubMed

Ghosh, Hirendra N; Verma, Sandeep; Nibbering, Erik T J

2011-02-10

Femtosecond infrared spectroscopy is used to study both forward and backward electron transfer (ET) dynamics between coumarin 337 (C337) and the aromatic amine solvents aniline (AN), N-methylaniline (MAN), and N,N-dimethylaniline (DMAN), where all the aniline solvents can donate an electron but only AN and MAN can form hydrogen bonds with C337. The formation of a hydrogen bond with AN and MAN is confirmed with steady state FT-IR spectroscopy, where the C═O stretching vibration is a direct marker mode for hydrogen bond formation. Transient IR absorption measurements in all solvents show an absorption band at 2166 cm(-1), which has been attributed to the C≡N stretching vibration of the C337 radical anion formed after ET. Forward electron transfer dynamics is found to be biexponential with time constants τ(ET)(1) = 500 fs, τ(ET)(2) = 7 ps in all solvents. Despite the presence of hydrogen bonds of C337 with the solvents AN and MAN, no effect has been found on the forward electron transfer step. Because of the absence of an H/D isotope effect on the forward electron transfer reaction of C337 in AN, hydrogen bonds are understood to play a minor role in mediating electron transfer. In contrast, direct π-orbital overlap between C337 and the aromatic amine solvents causes ultrafast forward electron transfer dynamics. Backward electron transfer dynamics, in contrast, is dependent on the solvent used. Standard Marcus theory explains the observed backward electron transfer rates.

Photo-induced electron transfer method

DOEpatents

Wohlgemuth, R.; Calvin, M.

1984-01-24

The efficiency of photo-induced electron transfer reactions is increased and the back transfer of electrons in such reactions is greatly reduced when a photo-sensitizer zinc porphyrin-surfactant and an electron donor manganese porphyrin-surfactant are admixed into phospholipid membranes. The phospholipids comprising said membranes are selected from phospholipids whose head portions are negatively charged. Said membranes are contacted with an aqueous medium in which an essentially neutral viologen electron acceptor is admixed. Catalysts capable of transferring electrons from reduced viologen electron acceptor to hydrogen to produce elemental hydrogen are also included in the aqueous medium. An oxidizable olefin is also admixed in the phospholipid for the purpose of combining with oxygen that coordinates with oxidized electron donor manganese porphyrin-surfactant.

Allosteric control of internal electron transfer in cytochrome cd1 nitrite reductase

PubMed Central

Farver, Ole; Kroneck, Peter M. H.; Zumft, Walter G.; Pecht, Israel

2003-01-01

Cytochrome cd1 nitrite reductase is a bifunctional multiheme enzyme catalyzing the one-electron reduction of nitrite to nitric oxide and the four-electron reduction of dioxygen to water. Kinetics and thermodynamics of the internal electron transfer process in the Pseudomonas stutzeri enzyme have been studied and found to be dominated by pronounced interactions between the c and the d1 hemes. The interactions are expressed both in dramatic changes in the internal electron-transfer rates between these sites and in marked cooperativity in their electron affinity. The results constitute a prime example of intraprotein control of the electron-transfer rates by allosteric interactions. PMID:12802018

Dynamics driving function: new insights from electron transferring flavoproteins and partner complexes.

PubMed

Toogood, Helen S; Leys, David; Scrutton, Nigel S

2007-11-01

Electron transferring flavoproteins (ETFs) are soluble heterodimeric FAD-containing proteins that function primarily as soluble electron carriers between various flavoprotein dehydrogenases. ETF is positioned at a key metabolic branch point, responsible for transferring electrons from up to 10 primary dehydrogenases to the membrane-bound respiratory chain. Clinical mutations of ETF result in the often fatal disease glutaric aciduria type II. Structural and biophysical studies of ETF in complex with partner proteins have shown that ETF partitions the functions of partner binding and electron transfer between (a) a 'recognition loop', which acts as a static anchor at the ETF-partner interface, and (b) a highly mobile redox-active FAD domain. Together, this enables the FAD domain of ETF to sample a range of conformations, some compatible with fast interprotein electron transfer. This 'conformational sampling' enables ETF to recognize structurally distinct partners, whilst also maintaining a degree of specificity. Complex formation triggers mobility of the FAD domain, an 'induced disorder' mechanism contrasting with the more generally accepted models of protein-protein interaction by induced fit mechanisms. We discuss the implications of the highly dynamic nature of ETFs in biological interprotein electron transfer. ETF complexes point to mechanisms of electron transfer in which 'dynamics drive function', a feature that is probably widespread in biology given the modular assembly and flexible nature of biological electron transfer systems.

Parallel Large-scale Semidefinite Programming for Strong Electron Correlation: Using Correlation and Entanglement in the Design of Efficient Energy-Transfer Mechanisms

DTIC Science & Technology

2014-09-24

which nature uses strong electron correlation for efficient energy transfer, particularly in photosynthesis and bioluminescence, (ii) providing an...strong electron correlation for efficient energy transfer, particularly in photosynthesis and bioluminescence, (ii) providing an innovative paradigm...efficient energy transfer, particularly in photosynthesis and bioluminescence, (ii) providing an innovative paradigm for energy transfer in photovoltaic

Electron Tunneling in Lithium Ammonia Solutions Probed by Frequency-Dependent Electron-Spin Relaxation Studies

PubMed Central

Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.

2012-01-01

Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential of multi-frequency EPR measurements to interrogate the microscopic nature and dynamics of ultra fast electron transfer or quantum-tunneling processes in liquids. Our results also impact on the universal issue of the role of a host solvent (or host matrix, e.g. a semiconductor) in mediating long-range electron transfer processes and we discuss the implications of our results with a range of other materials and systems exhibiting the phenomenon of electron transfer. PMID:22568866

Opto-electronic conversion logic behaviour through dynamic modulation of electron/energy transfer states at the TiO2-carbon quantum dot interface.

PubMed

Wang, Fang; Zhang, Yonglai; Liu, Yang; Wang, Xuefeng; Shen, Mingrong; Lee, Shuit-Tong; Kang, Zhenhui

2013-03-07

Here we show a bias-mediated electron/energy transfer process at the CQDs-TiO(2) interface for the dynamic modulation of opto-electronic properties. Different energy and electron transfer states have been observed in the CQDs-TNTs system due to the up-conversion photoluminescence and the electron donation/acceptance properties of the CQDs decorated on TNTs.

Experimental insights on the electron transfer and energy transfer processes between Ce{sup 3+}-Yb{sup 3+} and Ce{sup 3+}-Tb{sup 3+} in borate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sontakke, Atul D., E-mail: sontakke.atul.55a@st.kyoto-u.ac.jp; Katayama, Yumiko; Tanabe, Setsuhisa

2015-03-30

A facile method to describe the electron transfer and energy transfer processes among lanthanide ions is presented based on the temperature dependent donor luminescence decay kinetics. The electron transfer process in Ce{sup 3+}-Yb{sup 3+} exhibits a steady rise with temperature, whereas the Ce{sup 3+}-Tb{sup 3+} energy transfer remains nearly unaffected. This feature has been investigated using the rate equation modeling and a methodology for the quantitative estimation of interaction parameters is presented. Moreover, the overall consequences of electron transfer and energy transfer process on donor-acceptor luminescence behavior, quantum efficiency, and donor luminescence decay kinetics are discussed in borate glass host.more » The results in this study propose a straight forward approach to distinguish the electron transfer and energy transfer processes between lanthanide ions in dielectric hosts, which is highly advantageous in view of the recent developments on lanthanide doped materials for spectral conversion, persistent luminescence, and related applications.« less

Verification of the electron/proton coupled mechanism for phenolic H-atom transfer using a triplet π,π ∗ carbonyl

NASA Astrophysics Data System (ADS)

Yamaji, Minoru; Oshima, Juro; Hidaka, Motohiko

2009-06-01

Evidence for the coupled electron/proton transfer mechanism of the phenolic H-atom transfer between triplet π,π ∗ 3,3'-carbonylbis(7-diethylaminocoumarin) and phenol derivatives is obtained by using laser photolysis techniques. It was confirmed that the quenching rate constants of triplet CBC by phenols having positive Hammett constants do not follow the Rehm-Weller equation for electron transfer while those by phenols with negative Hammett constants do it. From the viewpoint of thermodynamic parameters for electron transfer, the crucial factors for phenolic H-atom transfer to π,π ∗ triplet are discussed.

Bridge-mediated hopping or superexchange electron-transfer processes in bis(triarylamine) systems

NASA Astrophysics Data System (ADS)

Lambert, Christoph; Nöll, Gilbert; Schelter, Jürgen

2002-09-01

Hopping and superexchange are generally considered to be alternative electron-transfer mechanisms in molecular systems. In this work we used mixed-valence radical cations as model systems for the investigation of electron-transfer pathways. We show that substituents attached to a conjugated bridge connecting two triarylamine redox centres have a marked influence on the near-infrared absorption spectra of the corresponding cations. Spectral analysis, followed by evaluation of the electron-transfer parameters using the Generalized Mulliken-Hush theory and simulation of the potential energy surfaces, indicate that hopping and superexchange are not alternatives, but are both present in the radical cation with a dimethoxybenzene bridge. We found that the type of electron-transfer mechanism depends on the bridge-reorganization energy as well as on the bridge-state energy. Because superexchange and hopping follow different distance laws, our findings have implications for the design of new molecular and polymeric electron-transfer materials.

Direct Electron Transfer of Dehydrogenases for Development of 3rd Generation Biosensors and Enzymatic Fuel Cells.

PubMed

Bollella, Paolo; Gorton, Lo; Antiochia, Riccarda

2018-04-24

Dehydrogenase based bioelectrocatalysis has been increasingly exploited in recent years in order to develop new bioelectrochemical devices, such as biosensors and biofuel cells, with improved performances. In some cases, dehydrogeases are able to directly exchange electrons with an appropriately designed electrode surface, without the need for an added redox mediator, allowing bioelectrocatalysis based on a direct electron transfer process. In this review we briefly describe the electron transfer mechanism of dehydrogenase enzymes and some of the characteristics required for bioelectrocatalysis reactions via a direct electron transfer mechanism. Special attention is given to cellobiose dehydrogenase and fructose dehydrogenase, which showed efficient direct electron transfer reactions. An overview of the most recent biosensors and biofuel cells based on the two dehydrogenases will be presented. The various strategies to prepare modified electrodes in order to improve the electron transfer properties of the device will be carefully investigated and all analytical parameters will be presented, discussed and compared.

Study of ring influence and electronic response to proton transfer reactions. Reaction electronic flux analysis.

PubMed

Herrera, Barbara

2011-05-01

In this article, a theoretical study of 1-5 proton transfers is presented. Two model systems which represent 1-5 proton transfer, 3-hidroxy-2-propenimine and salicyldenaniline have been studied as shown in Fig. 1. For this purpose, a DFT/B3LYP/6-311+G**, reaction force and reaction electronic flux analysis is made. The obtained results indicate that both proton transfers exhibit energetic and electronic differences emphasizing the role of the neighbor ring and the impact of conjugation on electronic properties.

Coherent Electron Transfer at the Ag / Graphite Heterojunction Interface

NASA Astrophysics Data System (ADS)

Tan, Shijing; Dai, Yanan; Zhang, Shengmin; Liu, Liming; Zhao, Jin; Petek, Hrvoje

2018-03-01

Charge transfer in transduction of light to electrical or chemical energy at heterojunctions of metals with semiconductors or semimetals is believed to occur by photogenerated hot electrons in metal undergoing incoherent internal photoemission through the heterojunction interface. Charge transfer, however, can also occur coherently by dipole coupling of electronic bands at the heterojunction interface. Microscopic physical insights into how transfer occurs can be elucidated by following the coherent polarization of the donor and acceptor states on the time scale of electronic dephasing. By time-resolved multiphoton photoemission spectroscopy (MPP), we investigate the coherent electron transfer from an interface state that forms upon chemisorption of Ag nanoclusters onto graphite to a σ symmetry interlayer band of graphite. Multidimensional MPP spectroscopy reveals a resonant two-photon transition, which dephases within 10 fs completing the coherent transfer.

Food Antioxidants: Chemical Insights at the Molecular Level.

PubMed

Galano, Annia; Mazzone, Gloria; Alvarez-Diduk, Ruslán; Marino, Tiziana; Alvarez-Idaboy, J Raúl; Russo, Nino

2016-01-01

In this review, we briefly summarize the reliability of the density functional theory (DFT)-based methods to accurately predict the main antioxidant properties and the reaction mechanisms involved in the free radical-scavenging reactions of chemical compounds present in food. The analyzed properties are the bond dissociation energies, in particular those involving OH bonds, electron transfer enthalpies, adiabatic ionization potentials, and proton affinities. The reaction mechanisms are hydrogen-atom transfer, proton-coupled electron transfer, radical adduct formation, single electron transfer, sequential electron proton transfer, proton-loss electron transfer, and proton-loss hydrogen-atom transfer. Furthermore, the chelating ability of these compounds and its role in decreasing or inhibiting the oxidative stress induced by Fe(III) and Cu(II) are considered. Comparisons between theoretical and experimental data confirm that modern theoretical tools are not only able to explain controversial experimental facts but also to predict chemical behavior.

On generalized Mulliken-Hush approach of electronic transfer: Inclusion of non-zero off-diagonal diabatic dipole moment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kryachko, E.S.

1999-06-03

The electronic coupling between the initial and final diabatic states is the major factor that determines the rate of electron transfer. A general formula for the adiabatic-to-diabatic mixing angle in terms of the electronic dipole moments is derived within a two-state model. It expresses the electronic coupling determining the rate of electronic transfer in terms of the off-diagonal diabatic dipole moment.

Photo-induced electron transfer method

DOEpatents

Wohlgemuth, Roland; Calvin, Melvin

1984-01-01

The efficiency of photo-induced electron transfer reactions is increased and the back transfer of electrons in such reactions is greatly reduced when a photo-sensitizer zinc porphyrin-surfactant and an electron donor manganese porphyrin-surfactant are admixed into phospho-lipid membranes. The phospholipids comprising said membranes are selected from phospholipids whose head portions are negatively charged. Said membranes are contacted with an aqueous medium in which an essentially neutral viologen electron acceptor is admixed. Catalysts capable of transfering electrons from reduced viologen electron acceptor to hydrogen to produce elemental hydrogen are also included in the aqueous medium. An oxidizable olefin is also admixed in the phospholipid for the purpose of combining with oxygen that coordinates with oxidized electron donor manganese porphyrin-surfactant.

Improved Critical Eigenfunction Restriction Estimates on Riemannian Surfaces with Nonpositive Curvature

NASA Astrophysics Data System (ADS)

Xi, Yakun; Zhang, Cheng

2017-03-01

We show that one can obtain improved L 4 geodesic restriction estimates for eigenfunctions on compact Riemannian surfaces with nonpositive curvature. We achieve this by adapting Sogge's strategy in (Improved critical eigenfunction estimates on manifolds of nonpositive curvature, Preprint). We first combine the improved L 2 restriction estimate of Blair and Sogge (Concerning Toponogov's Theorem and logarithmic improvement of estimates of eigenfunctions, Preprint) and the classical improved {L^∞} estimate of Bérard to obtain an improved weak-type L 4 restriction estimate. We then upgrade this weak estimate to a strong one by using the improved Lorentz space estimate of Bak and Seeger (Math Res Lett 18(4):767-781, 2011). This estimate improves the L 4 restriction estimate of Burq et al. (Duke Math J 138:445-486, 2007) and Hu (Forum Math 6:1021-1052, 2009) by a power of {(log logλ)^{-1}}. Moreover, in the case of compact hyperbolic surfaces, we obtain further improvements in terms of {(logλ)^{-1}} by applying the ideas from (Chen and Sogge, Commun Math Phys 329(3):435-459, 2014) and (Blair and Sogge, Concerning Toponogov's Theorem and logarithmic improvement of estimates of eigenfunctions, Preprint). We are able to compute various constants that appeared in (Chen and Sogge, Commun Math Phys 329(3):435-459, 2014) explicitly, by proving detailed oscillatory integral estimates and lifting calculations to the universal cover H^2.

Application of Electron-Transfer Theory to Several Systems of Biological Interest

DOE R&D Accomplishments Database

Marcus, R. A.; Sutin, N.

1985-03-23

Electron-transfer reaction rates are compared with theoretically calculated values for several reactions in the bacterial photosynthetic reaction center. A second aspect of the theory, the cross-relation, is illustrated using protein-protein electron transfers.

Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit

Solar radiation can be computed using radiative transfer models, such as the Rapid Radiation Transfer Model (RRTM) and its general circulation model applications, and used for various energy applications. Due to the complexity of computing radiation fields in aerosol and cloudy atmospheres, simulating solar radiation can be extremely time-consuming, but many approximations--e.g., the two-stream approach and the delta-M truncation scheme--can be utilized. To provide a new fast option for computing solar radiation, we developed the Fast All-sky Radiation Model for Solar applications (FARMS) by parameterizing the simulated diffuse horizontal irradiance and direct normal irradiance for cloudy conditions from the RRTMmore » runs using a 16-stream discrete ordinates radiative transfer method. The solar irradiance at the surface was simulated by combining the cloud irradiance parameterizations with a fast clear-sky model, REST2. To understand the accuracy and efficiency of the newly developed fast model, we analyzed FARMS runs using cloud optical and microphysical properties retrieved using GOES data from 2009-2012. The global horizontal irradiance for cloudy conditions was simulated using FARMS and RRTM for global circulation modeling with a two-stream approximation and compared to measurements taken from the U.S. Department of Energy's Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains site. Our results indicate that the accuracy of FARMS is comparable to or better than the two-stream approach; however, FARMS is approximately 400 times more efficient because it does not explicitly solve the radiative transfer equation for each individual cloud condition. Radiative transfer model runs are computationally expensive, but this model is promising for broad applications in solar resource assessment and forecasting. It is currently being used in the National Solar Radiation Database, which is publicly available from the National Renewable Energy Laboratory at http://nsrdb.nrel.gov.« less

Synergistic electron transfer effect-based signal amplification strategy for the ultrasensitive detection of dopamine.

PubMed

Lu, Qiujun; Chen, Xiaogen; Liu, Dan; Wu, Cuiyan; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2018-05-15

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag + into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors. Copyright © 2018. Published by Elsevier B.V.

Quantifying electron transfer reactions in biological systems: what interactions play the major role?

NASA Astrophysics Data System (ADS)

Sjulstok, Emil; Olsen, Jógvan Magnus Haugaard; Solov'Yov, Ilia A.

2015-12-01

Various biological processes involve the conversion of energy into forms that are usable for chemical transformations and are quantum mechanical in nature. Such processes involve light absorption, excited electronic states formation, excitation energy transfer, electrons and protons tunnelling which for example occur in photosynthesis, cellular respiration, DNA repair, and possibly magnetic field sensing. Quantum biology uses computation to model biological interactions in light of quantum mechanical effects and has primarily developed over the past decade as a result of convergence between quantum physics and biology. In this paper we consider electron transfer in biological processes, from a theoretical view-point; namely in terms of quantum mechanical and semi-classical models. We systematically characterize the interactions between the moving electron and its biological environment to deduce the driving force for the electron transfer reaction and to establish those interactions that play the major role in propelling the electron. The suggested approach is seen as a general recipe to treat electron transfer events in biological systems computationally, and we utilize it to describe specifically the electron transfer reactions in Arabidopsis thaliana cryptochrome-a signaling photoreceptor protein that became attractive recently due to its possible function as a biological magnetoreceptor.

ELECTRON TRANSFER MECHANISM AT THE SOLID-LIQUID INTERFACE OF PHYLLOSILICATES

EPA Science Inventory

Interfacial electron transfer processes on clay minerals have significant impact in natural environments and geochemical systems. Nitrobenzene was used as molecular probes to study the electron transfer mechanism at the solid-water interfaces of Fe-containing phyllosicates. For...

Tunneling induced electron transfer between separated protons

NASA Astrophysics Data System (ADS)

Vindel-Zandbergen, Patricia; Meier, Christoph; Sola, Ignacio R.

2018-04-01

We study electron transfer between two separated protons using local control theory. In this symmetric system one can favour a slow transfer by biasing the algorithm, achieving high efficiencies for fixed nuclei. The solution can be parametrized using a sequence of a pump followed by a dump pulse that lead to tunneling-induced electron transfer. Finally, we study the effect of the nuclear kinetic energy on the efficiency. Even in the absence of relative motion between the protons, the spreading of the nuclear wave function is enough to reduce the yield of electronic transfer to less than one half.

X.400: The Standard for Message Handling Systems.

ERIC Educational Resources Information Center

Swain, Leigh; Tallim, Paula

1990-01-01

Profiles X.400, the Open Systems Interconnection (OSI) Application layer standard that supports interpersonal electronic mail services, facsimile transfer, electronic data interchange, electronic funds transfer, electronic publishing, and electronic invoicing. Also discussed are an electronic directory to support message handling, compatibility…

Application of Degenerately Doped Metal Oxides in the Study of Photoinduced Interfacial Electron Transfer.

PubMed

Farnum, Byron H; Morseth, Zachary A; Brennaman, M Kyle; Papanikolas, John M; Meyer, Thomas J

2015-06-18

Degenerately doped In2O3:Sn semiconductor nanoparticles (nanoITO) have been used to study the photoinduced interfacial electron-transfer reactivity of surface-bound [Ru(II)(bpy)2(4,4'-(PO3H2)2-bpy)](2+) (RuP(2+)) molecules as a function of driving force over a range of 1.8 eV. The metallic properties of the ITO nanoparticles, present within an interconnected mesoporous film, allowed for the driving force to be tuned by controlling their Fermi level with an external bias while their optical transparency allowed for transient absorption spectroscopy to be used to monitor electron-transfer kinetics. Photoinduced electron transfer from excited-state -RuP(2+*) molecules to nanoITO was found to be dependent on applied bias and competitive with nonradiative energy transfer to nanoITO. Back electron transfer from nanoITO to oxidized -RuP(3+) was also dependent on the applied bias but without complication from inter- or intraparticle electron diffusion in the oxide nanoparticles. Analysis of the electron injection kinetics as a function of driving force using Marcus-Gerischer theory resulted in an experimental estimate of the reorganization energy for the excited-state -RuP(3+/2+*) redox couple of λ* = 0.83 eV and an electronic coupling matrix element, arising from electronic wave function overlap between the donor orbital in the molecule and the acceptor orbital(s) in the nanoITO electrode, of Hab = 20-45 cm(-1). Similar analysis of the back electron-transfer kinetics yielded λ = 0.56 eV for the ground-state -RuP(3+/2+) redox couple and Hab = 2-4 cm(-1). The use of these wide band gap, degenerately doped materials provides a unique experimental approach for investigating single-site electron transfer at the surface of oxide nanoparticles.

Chemical and charge transfer studies on interfaces of a conjugated polymer and ITO

NASA Astrophysics Data System (ADS)

David, Tanya M. S.; Arasho, Wondwosson; Smith, O'Neil; Hong, Kunlun; Bonner, Carl; Sun, Sam-Shajing

2017-08-01

Conjugated oligomers and polymers are very attractive for potential future plastic electronic and opto-electronic device applications such as plastic photo detectors and solar cells, thermoelectric devices, field effect transistors, and light emitting diodes. Understanding and optimizing charge transport between an active polymer layer and conductive substrate is critical to the optimization of polymer based electronic and opto-electronic devices. This study focused on the design, synthesis, self-assembly, and electron transfers and transports of a phosphonic acid end-functionalized polyphenylenevinylene (PPV) that was covalently attached and self-assembled onto an Indium Tin Oxide (ITO) substrate. This study demonstrated how atomic force microscopy (AFM) can be an effective characterization technique in conjunction with conventional electron transfer methods, including cyclic voltammetry (CV), towards determining electron transfer rates in polymer and polymer/conductor interface systems. This study found that the electron transfer rates of covalently attached and self-assembled films were much faster than the spin coated films. The knowledge from this study can be very useful for designing potential polymer based electronic and opto-electronic thin film devices.

Electron transfer by excited benzoquinone anions: slow rates for two-electron transitions.

PubMed

Zamadar, Matibur; Cook, Andrew R; Lewandowska-Andralojc, Anna; Holroyd, Richard; Jiang, Yan; Bikalis, Jin; Miller, John R

2013-09-05

Electron transfer (ET) rate constants from the lowest excited state of the radical anion of benzoquinone, BQ(-•)*, were measured in THF solution. Rate constants for bimolecular electron transfer reactions typically reach the diffusion-controlled limit when the free-energy change, ΔG°, reaches -0.3 eV. The rate constants for ET from BQ(-•)* are one-to-two decades smaller at this energy and do not reach the diffusion-controlled limit until -ΔG° is 1.5-2.0 eV. The rates are so slow probably because a second electron must also undergo a transition to make use of the energy of the excited state. Similarly, ET, from solvated electrons to neutral BQ to form the lowest excited state, is slow, while fast ET is observed at a higher excited state, which can be populated in a transition involving only one electron. A simple picture based on perturbation theory can roughly account for the control of electron transfer by the need for transition of a second electron. The picture also explains how extra driving force (-ΔG°) can restore fast rates of electron transfer.

Evidence that Additions of Grignard Reagents to Aliphatic Aldehydes Do Not Involve Single-Electron-Transfer Processes.

PubMed

Otte, Douglas A L; Woerpel, K A

2015-08-07

Addition of allylmagnesium reagents to an aliphatic aldehyde bearing a radical clock gave only addition products and no evidence of ring-opened products that would suggest single-electron-transfer reactions. The analogous Barbier reaction also did not provide evidence for a single-electron-transfer mechanism in the addition step. Other Grignard reagents (methyl-, vinyl-, t-Bu-, and triphenylmethylmagnesium halides) also do not appear to add to an alkyl aldehyde by a single-electron-transfer mechanism.

Evidence for protein conformational change at a Au(110)/protein interface

NASA Astrophysics Data System (ADS)

Messiha, H. L.; Smith, C. I.; Scrutton, N. S.; Weightman, P.

2008-07-01

Evidence is presented that reflection anisotropy spectroscopy (RAS) can provide real-time measurements of conformational change in proteins induced by electron transfer reactions. A bacterial electron transferring flavoprotein (ETF) has been modified so as to adsorb on an Au(110) electrode and enable reversible electron transfer to the protein cofactor in the absence of mediators. Reversible changes are observed in the RAS of this protein that are interpreted as arising from conformational changes accompanying the transfer of electrons.

Enhanced electron transfer kinetics through hybrid graphene-carbon nanotube films.

PubMed

Henry, Philémon A; Raut, Akshay S; Ubnoske, Stephen M; Parker, Charles B; Glass, Jeffrey T

2014-11-01

We report the first study of the electrochemical reactivity of a graphenated carbon nanotube (g-CNT) film. The electron transfer kinetics of the ferri-ferrocyanide couple were examined for a g-CNT film and compared to the kinetics to standard carbon nanotubes (CNTs). The g-CNT film exhibited much higher catalytic activity, with a heterogeneous electron-transfer rate constant, k 0 , approximately two orders of magnitude higher than for standard CNTs. Scanning electron microscopy and Raman spectroscopy were used to correlate the higher electron transfer kinetics with the higher edge-density of the g-CNT film.

Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

PubMed Central

Westereng, Bjørge; Cannella, David; Wittrup Agger, Jane; Jørgensen, Henning; Larsen Andersen, Mogens; Eijsink, Vincent G.H.; Felby, Claus

2015-01-01

Enzymatic oxidation of cell wall polysaccharides by lytic polysaccharide monooxygenases (LPMOs) plays a pivotal role in the degradation of plant biomass. While experiments have shown that LPMOs are copper dependent enzymes requiring an electron donor, the mechanism and origin of the electron supply in biological systems are only partly understood. We show here that insoluble high molecular weight lignin functions as a reservoir of electrons facilitating LPMO activity. The electrons are donated to the enzyme by long-range electron transfer involving soluble low molecular weight lignins present in plant cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds new light on how oxidative enzymes present in plant degraders may act in concert. PMID:26686263

CymA and Exogenous Flavins Improve Extracellular Electron Transfer and Couple It to Cell Growth in Mtr-Expressing Escherichia coli

DOE PAGES

Jensen, Heather M.; TerAvest, Michaela A.; Kokish, Mark G.; ...

2016-03-22

Introducing extracellular electron transfer pathways into heterologous organisms offers the opportunity to explore fundamental biogeochemical processes and to biologically alter redox states of exogenous metals for various applications. While expression of the MtrCAB electron nanoconduit from Shewanella oneidensis MR-1 permits extracellular electron transfer in Escherichia coli, the low electron flux and absence of growth in these cells limits their practicality for such applications. In this paper, we investigate how the rate of electron transfer to extracellular Fe(III) and cell survival in engineered E. coli are affected by mimicking different features of the S. oneidensis pathway: the number of electron nanoconduits,more » the link between the quinol pool and MtrA, and the presence of flavin-dependent electron transfer. While increasing the number of pathways does not significantly improve the extracellular electron transfer rate or cell survival, using the native inner membrane component, CymA, significantly improves the reduction rate of extracellular acceptors and increases cell viability. Strikingly, introducing both CymA and riboflavin to Mtr-expressing E. coli also allowed these cells to couple metal reduction to growth, which is the first time an increase in biomass of an engineered E. coli has been observed under Fe 2O 3 (s) reducing conditions. Overall and finally, this work provides engineered E. coli strains for modulating extracellular metal reduction and elucidates critical factors for engineering extracellular electron transfer in heterologous organisms.« less

CymA and Exogenous Flavins Improve Extracellular Electron Transfer and Couple It to Cell Growth in Mtr-Expressing Escherichia coli

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Heather M.; TerAvest, Michaela A.; Kokish, Mark G.

Introducing extracellular electron transfer pathways into heterologous organisms offers the opportunity to explore fundamental biogeochemical processes and to biologically alter redox states of exogenous metals for various applications. While expression of the MtrCAB electron nanoconduit from Shewanella oneidensis MR-1 permits extracellular electron transfer in Escherichia coli, the low electron flux and absence of growth in these cells limits their practicality for such applications. In this paper, we investigate how the rate of electron transfer to extracellular Fe(III) and cell survival in engineered E. coli are affected by mimicking different features of the S. oneidensis pathway: the number of electron nanoconduits,more » the link between the quinol pool and MtrA, and the presence of flavin-dependent electron transfer. While increasing the number of pathways does not significantly improve the extracellular electron transfer rate or cell survival, using the native inner membrane component, CymA, significantly improves the reduction rate of extracellular acceptors and increases cell viability. Strikingly, introducing both CymA and riboflavin to Mtr-expressing E. coli also allowed these cells to couple metal reduction to growth, which is the first time an increase in biomass of an engineered E. coli has been observed under Fe 2O 3 (s) reducing conditions. Overall and finally, this work provides engineered E. coli strains for modulating extracellular metal reduction and elucidates critical factors for engineering extracellular electron transfer in heterologous organisms.« less

Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer

NASA Astrophysics Data System (ADS)

Skourtis, Spiros S.; Prytkova, Tatiana; Beratan, David N.

2007-12-01

This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH--containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH-, upon photo-excitation of FADH- with 350-450 nm light. We compute the lowest singlet excited states of FADH- in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH- that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron-acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH--thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green's function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH- causes a π→π* charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH--to-dimer electronic coupling, thus inducing rapid electron transfer.

Photoinduced electron transfer between benzyloxy dendrimer phthalocyanine and benzoquinone

NASA Astrophysics Data System (ADS)

Zhang, Tiantian; Ma, Dongdong; Pan, Sujuan; Wu, Shijun; Jiang, Yufeng; Zeng, Di; Yang, Hongqin; Peng, Yiru

2016-10-01

Photo-induced electron transfer (PET) is an important and fundamental process in natural photosynthesis. To mimic such interesting PET process, a suitable donor and acceptor couple were properly chosen. Dendrimer phthalocyanines and their derivatives have emerged as promising materials for artificial photosynthesis systems. In this paper, the electron transfer between the light harvest dendrimer phthalocyanine (donor) and the 1,4-benzoquinone (acceptor) was studied by UV/Vis and fluorescence spectroscopic methods. It was found that fluorescence of phthalocyanine was quenched by benzoquinone (BQ) via excited state electron transfer, from the phthalocyanine to the BQ upon excitation at 610 nm. The Stern-Volmer constant (KSV) of electron transfer was calculated. Our study suggests that this dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential artificial photosynthesis system.

Long-range electron transfer in porphyrin-containing [2]-rotaxanes: tuning the rate by metal cation coordination.

PubMed

Andersson, Mikael; Linke, Myriam; Chambron, Jean-Claude; Davidsson, Jan; Heitz, Valérie; Hammarström, Leif; Sauvage, Jean-Pierre

2002-04-24

A series of [2]-rotaxanes has been synthesized in which two Zn(II)-porphyrins (ZnP) electron donors were attached as stoppers on the rod. A macrocycle attached to a Au(III)-porphyrin (AuP+) acceptor was threaded on the rod. By selective excitation of either porphyrin, we could induce an electron transfer from the ZnP to the AuP+ unit that generated the same ZnP*+-AuP* charge-transfer state irrespective of which porphyrin was excited. Although the reactants were linked only by mechanical or coordination bonds, electron-transfer rate constants up to 1.2x10(10) x s(-1) were obtained over a 15-17 A edge-to-edge distance between the porphyrins. The resulting charge-transfer state had a relatively long lifetime of 10-40 ns and was formed in high yield (>80%) in most cases. By a simple variation of the link between the reactants, viz. a coordination of the phenanthroline units on the rotaxane rod and ring by either Ag+ or Cu+, we could enhance the electron-transfer rate from the ZnP to the excited 3AuP+. We interpret our data in terms of an enhanced superexchange mechanism with Ag+ and a change to a stepwise hopping mechanism with Cu+, involving the oxidized Cu(phen)22+ unit as a real intermediate. When the ZnP unit was excited instead, electron transfer from the excited 1ZnP to AuP+ was not affected, or even slowed, by Ag+ or Cu+. We discuss this asymmetry in terms of the different orbitals involved in mediating the reaction in an electron- and a hole-transfer mechanism. Our results show the possibility to tune the rates of electron transfer between noncovalently linked reactants by a convenient modification of the link. The different effect of Ag+ and Cu+ on the rate with ZnP and AuP+ excitation shows an additional possibility to control the electron-transfer reactions by selective excitation. We also found that coordination of the Cu+ introduced an energy-transfer reaction from 1ZnP to Cu(phen)2+ (k = 5.1x10(9) x s(-1)) that proceeded in competition with electron transfer to AuP+ and was followed by a quantitative energy transfer to give the 3ZnP state (k = 1.5x10(9) x s(-1)).

A molecular shift register based on electron transfer

NASA Technical Reports Server (NTRS)

Hopfield, J. J.; Onuchic, Josenelson; Beratan, David N.

1988-01-01

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a 'molecular electronic device' that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.

12 CFR 1005.6 - Liability of consumer for unauthorized transfers.

Code of Federal Regulations, 2012 CFR

2012-01-01

... transfers. 1005.6 Section 1005.6 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) § 1005.6 Liability of consumer for unauthorized transfers. (a) Conditions for..., for an unauthorized electronic fund transfer involving the consumer's account only if the financial...

Stabilization of non-productive conformations underpins rapid electron transfer to electron-transferring flavoprotein.

PubMed

Toogood, Helen S; van Thiel, Adam; Scrutton, Nigel S; Leys, David

2005-08-26

Crystal structures of protein complexes with electron-transferring flavoprotein (ETF) have revealed a dual protein-protein interface with one region serving as anchor while the ETF FAD domain samples available space within the complex. We show that mutation of the conserved Glu-165beta in human ETF leads to drastically modulated rates of interprotein electron transfer with both medium chain acyl-CoA dehydrogenase and dimethylglycine dehydrogenase. The crystal structure of free E165betaA ETF is essentially identical to that of wild-type ETF, but the crystal structure of the E165betaA ETF.medium chain acyl-CoA dehydrogenase complex reveals clear electron density for the FAD domain in a position optimal for fast interprotein electron transfer. Based on our observations, we present a dynamic multistate model for conformational sampling that for the wild-type ETF. medium chain acyl-CoA dehydrogenase complex involves random motion between three distinct positions for the ETF FAD domain. ETF Glu-165beta plays a key role in stabilizing positions incompatible with fast interprotein electron transfer, thus ensuring high rates of complex dissociation.

77 FR 34127 - Financial Management Service; Proposed Collection of Information: Electronic Transfer Account...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-08

... Information: Electronic Transfer Account (ETA) Financial Agency Agreement AGENCY: Financial Management Service... of information described below: Title: Electronic Transfer Account (ETA) Financial Agency Agreement... public and other Federal agencies to take this opportunity to comment on a continuing information...

31 CFR 208.4 - Waivers.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Payment by electronic funds transfer is not required in the following cases: (1) Where an individual: (i... are not required to be made by electronic funds transfer, unless and until such payments become... waiver request with Treasury certifying that payment by electronic funds transfer would impose a hardship...

12 CFR 1005.7 - Initial disclosures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... disclosures required by this section at the time a consumer contracts for an electronic fund transfer service or before the first electronic fund transfer is made involving the consumer's account. (b) Content of... Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E...

Solvent effects on the oxidation (electron transfer) reaction of [Fe(CN) 6] 4- by [Co(NH 3) 5pz] 3+

NASA Astrophysics Data System (ADS)

Muriel, F.; Jiménez, R.; López, M.; Prado-Gotor, R.; Sánchez, F.

2004-03-01

Solvent effects on the title reaction were studied in different reaction media constituted by water and organic cosolvents (methanol, tert-butyl alcohol, ethyleneglycol and glucose) at 298.2 K. The results are considered in light of the Marcus-Hush approach for electron transfer reactions. Variations of the electron transfer rate constant are shown to be mainly due to changes in the reaction free energy. On the other hand the energies of the MMCT band, corresponding to the optical electron transfer within the ion pair [Fe(CN) 6] 4-/[Co(NH 3) 5pz] 3+, in the different reaction media, have been obtained. The activation free energies of the thermal electron transfer process have been calculated from the band ( Eop) data, and compared with those obtained from the kinetic study. Quantitative agreement is found between the two series of data. This shows the possibility of estimating activation free energies for electron transfer reactions from static (optical) measurements.

Bidirectional Photoinduced Electron Transfer in Ruthenium(II)-Tris-bipyridyl-Modified PpcA, a Multi-heme c -Type Cytochrome from Geobacter sulfurreducens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kokhan, Oleksandr; Ponomarenko, Nina S.; Pokkuluri, P. Raj

PpcA, a tri-heme cytochrome c7 from Geobacter sulfurreducens was investigated as a model for photosensitizer-initiated electron transfer within a multi-heme "molecular wire" protein architecture. E. coli expression of PpcA was found to be tolerant of cysteine site-directed mutagenesis, demonstrated by the successful expression of natively folded proteins bearing cysteine mutations at a series of sites selected to vary characteristically with respect to the three -CXXCH- heme binding domains. A preliminary survey of 5 selected mutants found that the introduced cysteines can be readily covalently linked to a Ru(II)-(2,2'-bpy)2(4-bromomethyl-4’-methyl-2,2'-bpy) photosensitizer (where bpy = bipyridine), and that the linked constructs support bothmore » photo-oxidative and photo-reductive quenching of the photosensitizer excited-state, depending upon the initial heme redox state. For photo-oxidative electron transfer, apparent heme reduction risetimes were found to vary from 7 x 10-12 s to 5 x 10-8 s, depending upon the site of photosensitizer linking. The excited-state electron transfers are about 103-fold faster than any previously reported photosensitizer-redox protein covalently linked construct. Preliminary conformational analysis using molecular dynamics simulations shows that rates for electron transfer track both the distance and pathways for electron transfer. Two mutants with the fastest charge transfer rates, A23C and K29C, showed a significant role of specific paths for electron transfer. While K29C labeled mutant was expected to have approximately 0.8Å greater donor-acceptor distance, it showed 20-fold faster charge separation rate. Clear evidence for inter-heme electron transfer within the multi-heme protein is not detected within the lifetimes of the charge separated states. These results demonstrate an opportunity to develop multi-heme c-cytochromes for investigation of electron transfer in protein "molecular wires" and to serve as frameworks for metalloprotein designs that support multiple electron transfer redox chemistry.« less

Photoemission of Energetic Hot Electrons Produced via Up-Conversion in Doped Quantum Dots.

PubMed

Dong, Yitong; Parobek, David; Rossi, Daniel; Son, Dong Hee

2016-11-09

The benefits of the hot electrons from semiconductor nanostructures in photocatalysis or photovoltaics result from their higher energy compared to that of the band-edge electrons facilitating the electron-transfer process. The production of high-energy hot electrons usually requires short-wavelength UV or intense multiphoton visible excitation. Here, we show that highly energetic hot electrons capable of above-threshold ionization are produced via exciton-to-hot-carrier up-conversion in Mn-doped quantum dots under weak band gap excitation (∼10 W/cm 2 ) achievable with the concentrated solar radiation. The energy of hot electrons is as high as ∼0.4 eV above the vacuum level, much greater than those observed in other semiconductor or plasmonic metal nanostructures, which are capable of performing energetically and kinetically more-challenging electron transfer. Furthermore, the prospect of generating solvated electron is unique for the energetic hot electrons from up-conversion, which can open a new door for long-range electron transfer beyond short-range interfacial electron transfer.

Quantum Calculations of Electron Tunneling in Respiratory Complex III.

PubMed

Hagras, Muhammad A; Hayashi, Tomoyuki; Stuchebrukhov, Alexei A

2015-11-19

The most detailed and comprehensive to date study of electron transfer reactions in the respiratory complex III of aerobic cells, also known as bc1 complex, is reported. In the framework of the tunneling current theory, electron tunneling rates and atomistic tunneling pathways between different redox centers were investigated for all electron transfer reactions comprising different stages of the proton-motive Q-cycle. The calculations reveal that complex III is a smart nanomachine, which under certain conditions undergoes conformational changes gating electron transfer, or channeling electrons to specific pathways. One-electron tunneling approximation was adopted in the tunneling calculations, which were performed using hybrid Broken-Symmetry (BS) unrestricted DFT/ZINDO levels of theory. The tunneling orbitals were determined using an exact biorthogonalization scheme that uniquely separates pairs of tunneling orbitals with small overlaps out of the remaining Franck-Condon orbitals with significant overlap. Electron transfer rates in different redox pairs show exponential distance dependence, in agreement with the reported experimental data; some reactions involve coupled proton transfer. Proper treatment of a concerted two-electron bifurcated tunneling reaction at the Q(o) site is given.

Charge transfer from TiO2 into adsorbed benzene diazonium compounds

NASA Astrophysics Data System (ADS)

Merson, A.; Dittrich, Th.; Zidon, Y.; Rappich, J.; Shapira, Yoram

2004-08-01

Electron transfer from sol-gel-prepared TiO2 into adsorbed benzene diazonium compounds has been investigated using cyclic voltammetry, x-ray photoelectron spectroscopy, contact potential difference, and surface photovoltage spectroscopy. The results show that the potential of maximum electron transfer depends strongly on the dipole moment of the benzene compound. Two reactive surface sites at which electron transfer occurs have been identified.

Direct Observation of Excimer-Mediated Intramolecular Electron Transfer in a Cofacially-Stacked Perylene Bisimide Pair.

PubMed

Sung, Jooyoung; Nowak-Król, Agnieszka; Schlosser, Felix; Fimmel, Benjamin; Kim, Woojae; Kim, Dongho; Würthner, Frank

2016-07-27

We have elucidated excimer-mediated intramolecular electron transfer in cofacially stacked PBIs tethered by two phenylene-butadiynylene loops. The electron transfer between energetically equivalent PBIs is revealed by the simultaneous observation of the PBI radical anion and cation bands in the transient absorption spectra. The fluorescence decay time of the excimer states is in good agreement with the rise time of PBI radical bands in transient absorption spectra suggesting that the electron transfer dynamics proceed via the excimer state. We can conclude that the excimer state effectuates the efficient charge transfer in the cofacially stacked PBI dimer.

12 CFR 1005.6 - Liability of consumer for unauthorized transfers.

Code of Federal Regulations, 2014 CFR

2014-01-01

... transfers. 1005.6 Section 1005.6 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) General § 1005.6 Liability of consumer for unauthorized transfers. (a) Conditions... this section, for an unauthorized electronic fund transfer involving the consumer's account only if the...

12 CFR 1005.6 - Liability of consumer for unauthorized transfers.

Code of Federal Regulations, 2013 CFR

2013-01-01

... transfers. 1005.6 Section 1005.6 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION ELECTRONIC FUND TRANSFERS (REGULATION E) General § 1005.6 Liability of consumer for unauthorized transfers. (a) Conditions... this section, for an unauthorized electronic fund transfer involving the consumer's account only if the...

Single-Molecule Interfacial Electron Transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, H. Peter

This project is focused on the use of single-molecule high spatial and temporal resolved techniques to study molecular dynamics in condensed phase and at interfaces, especially, the complex reaction dynamics associated with electron and energy transfer rate processes. The complexity and inhomogeneity of the interfacial ET dynamics often present a major challenge for a molecular level comprehension of the intrinsically complex systems, which calls for both higher spatial and temporal resolutions at ultimate single-molecule and single-particle sensitivities. Combined single-molecule spectroscopy and electrochemical atomic force microscopy approaches are unique for heterogeneous and complex interfacial electron transfer systems because the static andmore » dynamic inhomogeneities can be identified and characterized by studying one molecule at a specific nanoscale surface site at a time. The goal of our project is to integrate and apply these spectroscopic imaging and topographic scanning techniques to measure the energy flow and electron flow between molecules and substrate surfaces as a function of surface site geometry and molecular structure. We have been primarily focusing on studying interfacial electron transfer under ambient condition and electrolyte solution involving both single crystal and colloidal TiO 2 and related substrates. The resulting molecular level understanding of the fundamental interfacial electron transfer processes will be important for developing efficient light harvesting systems and broadly applicable to problems in fundamental chemistry and physics. We have made significant advancement on deciphering the underlying mechanism of the complex and inhomogeneous interfacial electron transfer dynamics in dyesensitized TiO 2 nanoparticle systems that strongly involves with and regulated by molecule-surface interactions. We have studied interfacial electron transfer on TiO 2 nanoparticle surfaces by using ultrafast single-molecule spectroscopy and electrochemical AFM metal tip scanning microscopy, focusing on understanding the interfacial electron transfer dynamics at specific nanoscale electron transfer sites with high-spatially and temporally resolved topographic-and-spectroscopic characterization at individual molecule basis, characterizing single-molecule rate processes, reaction driving force, and molecule-substrate electronic coupling. One of the most significant characteristics of our new approach is that we are able to interrogate the complex interfacial electron transfer dynamics by actively pin-point energetic manipulation of the surface interaction and electronic couplings, beyond the conventional excitation and observation.« less

What Hinders Electron Transfer Dissociation (ETD) of DNA Cations?

NASA Astrophysics Data System (ADS)

Hari, Yvonne; Leumann, Christian J.; Schürch, Stefan

2017-12-01

Radical activation methods, such as electron transfer dissociation (ETD), produce structural information complementary to collision-induced dissociation. Herein, electron transfer dissociation of 3-fold protonated DNA hexamers was studied to gain insight into the fragmentation mechanism. The fragmentation patterns of a large set of DNA hexamers confirm cytosine as the primary target of electron transfer. The reported data reveal backbone cleavage by internal electron transfer from the nucleobase to the phosphate linker leading either to a•/ w or d/ z• ion pairs. This reaction pathway contrasts with previous findings on the dissociation processes after electron capture by DNA cations, suggesting multiple, parallel dissociation channels. However, all these channels merely result in partial fragmentation of the precursor ion because the charge-reduced DNA radical cations are quite stable. Two hypotheses are put forward to explain the low dissociation yield of DNA radical cations: it is either attributed to non-covalent interactions between complementary fragments or to the stabilization of the unpaired electron in stacked nucleobases. MS3 experiments suggest that the charge-reduced species is the intact oligonucleotide. Moreover, introducing abasic sites significantly increases the dissociation yield of DNA cations. Consequently, the stabilization of the unpaired electron by π-π-stacking provides an appropriate rationale for the high intensity of DNA radical cations after electron transfer. [Figure not available: see fulltext.

75 FR 33681 - Electronic Fund Transfers

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-15

... FEDERAL RESERVE SYSTEM 12 CFR Part 205 [Regulation E; Docket No. R-1343] Electronic Fund Transfers June 4, 2010. AGENCY: Board of Governors of the Federal Reserve System. ACTION: Final rule; correction..., published on June 4, 2010 (75 FR 31665) make the following correction: PART 205--ELECTRONIC FUND TRANSFERS...

Inner reorganization limiting electron transfer controlled hydrogen bonding: intra- vs. intermolecular effects.

PubMed

Martínez-González, Eduardo; Frontana, Carlos

2014-05-07

In this work, experimental evidence of the influence of the electron transfer kinetics during electron transfer controlled hydrogen bonding between anion radicals of metronidazole and ornidazole, derivatives of 5-nitro-imidazole, and 1,3-diethylurea as the hydrogen bond donor, is presented. Analysis of the variations of voltammetric EpIcvs. log KB[DH], where KB is the binding constant, allowed us to determine the values of the binding constant and also the electron transfer rate k, confirmed by experiments obtained at different scan rates. Electronic structure calculations at the BHandHLYP/6-311++G(2d,2p) level for metronidazole, including the solvent effect by the Cramer/Truhlar model, suggested that the minimum energy conformer is stabilized by intramolecular hydrogen bonding. In this structure, the inner reorganization energy, λi,j, contributes significantly (0.5 eV) to the total reorganization energy of electron transfer, thus leading to a diminishment of the experimental k.

Development of a Simple Electron Transfer and Polarization Model and Its Application to Biological Systems.

PubMed

Diller, David J

2017-01-10

Here we present a new method for point charge calculation which we call Q ET (charges by electron transfer). The intent of this work is to develop a method that can be useful for studying charge transfer in large biological systems. It is based on the intuitive framework of the Q EQ method with the key difference being that the Q ET method tracks all pairwise electron transfers by augmenting the Q EQ pseudoenergy function with a distance dependent cost function for each electron transfer. This approach solves the key limitation of the Q EQ method which is its handling of formally charged groups. First, we parametrize the Q ET method by fitting to electrostatic potentials calculated using ab initio quantum mechanics on over 11,000 small molecules. On an external test set of over 2500 small molecules the Q ET method achieves a mean absolute error of 1.37 kcal/mol/electron when compared to the ab initio electrostatic potentials. Second, we examine the conformational dependence of the charges on over 2700 tripeptides. With the tripeptide data set, we show that the conformational effects account for approximately 0.4 kcal/mol/electron on the electrostatic potentials. Third, we test the Q ET method for its ability to reproduce the effects of polarization and electron transfer on 1000 water clusters. For the water clusters, we show that the Q ET method captures about 50% of the polarization and electron transfer effects. Finally, we examine the effects of electron transfer and polarizability on the electrostatic interaction between p38 and 94 small molecule ligands. When used in conjunction with the Generalized-Born continuum solvent model, polarization and electron transfer with the Q ET model lead to an average change of 17 kcal/mol on the calculated electrostatic component of ΔG.

Phylogenetic analysis of proteins associated in the four major energy metabolism systems: photosynthesis, aerobic respiration, denitrification, and sulfur respiration.

PubMed

Tomiki, Takeshi; Saitou, Naruya

2004-08-01

The four electron transfer energy metabolism systems, photosynthesis, aerobic respiration, denitrification, and sulfur respiration, are thought to be evolutionarily related because of the similarity of electron transfer patterns and the existence of some homologous proteins. How these systems have evolved is elusive. We therefore conducted a comprehensive homology search using PSI-BLAST, and phylogenetic analyses were conducted for the three homologous groups (groups 1-3) based on multiple alignments of domains defined in the Pfam database. There are five electron transfer types important for catalytic reaction in group 1, and many proteins bind molybdenum. Deletions of two domains led to loss of the function of binding molybdenum and ferredoxin, and these deletions seem to be critical for the electron transfer pattern changes in group 1. Two types of electron transfer were found in group 2, and all its member proteins bind siroheme and ferredoxin. Insertion of the pyridine nucleotide disulfide oxidoreductase domain seemed to be the critical point for the electron transfer pattern change in this group. The proteins belonging to group 3 are all flavin enzymes, and they bind flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN). Types of electron transfer in this group are divergent, but there are two common characteristics. NAD(P)H works as an electron donor or acceptor, and FAD or FMN transfers electrons from/to NAD(P)H. Electron transfer functions might be added to these common characteristics by the addition of functional domains through the evolution of group 3 proteins. Based on the phylogenetic analyses in this study and previous studies, we inferred the phylogeny of the energy metabolism systems as follows: photosynthesis (and possibly aerobic respiration) and the sulfur/nitrogen assimilation system first diverged, then the sulfur/nitrogen dissimilation system was produced from the latter system.

Predicting the Rate Constant of Electron Tunneling Reactions at the CdSe-TiO2 Interface.

PubMed

Hines, Douglas A; Forrest, Ryan P; Corcelli, Steven A; Kamat, Prashant V

2015-06-18

Current interest in quantum dot solar cells (QDSCs) motivates an understanding of the electron transfer dynamics at the quantum dot (QD)-metal oxide (MO) interface. Employing transient absorption spectroscopy, we have monitored the electron transfer rate (ket) at this interface as a function of the bridge molecules that link QDs to TiO2. Using mercaptoacetic acid, 3-mercaptopropionic acid, 8-mercaptooctanoic acid, and 16-mercaptohexadecanoic acid, we observe an exponential attenuation of ket with increasing linker length, and attribute this to the tunneling of the electron through the insulating linker molecule. We model the electron transfer reaction using both rectangular and trapezoidal barrier models that have been discussed in the literature. The one-electron reduction potential (equivalent to the lowest unoccupied molecular orbital) of each molecule as determined by cyclic voltammetry (CV) was used to estimate the effective barrier height presented by each ligand at the CdSe-TiO2 interface. The electron transfer rate (ket) calculated for each CdSe-ligand-TiO2 interface using both models showed the results in agreement with the experimentally determined trend. This demonstrates that electron transfer between CdSe and TiO2 can be viewed as electron tunneling through a layer of linking molecules and provides a useful method for predicting electron transfer rate constants.

Proton-coupled electron transfer versus hydrogen atom transfer: generation of charge-localized diabatic states.

PubMed

Sirjoosingh, Andrew; Hammes-Schiffer, Sharon

2011-03-24

The distinction between proton-coupled electron transfer (PCET) and hydrogen atom transfer (HAT) mechanisms is important for the characterization of many chemical and biological processes. PCET and HAT mechanisms can be differentiated in terms of electronically nonadiabatic and adiabatic proton transfer, respectively. In this paper, quantitative diagnostics to evaluate the degree of electron-proton nonadiabaticity are presented. Moreover, the connection between the degree of electron-proton nonadiabaticity and the physical characteristics distinguishing PCET from HAT, namely, the extent of electronic charge redistribution, is clarified. In addition, a rigorous diabatization scheme for transforming the adiabatic electronic states into charge-localized diabatic states for PCET reactions is presented. These diabatic states are constructed to ensure that the first-order nonadiabatic couplings with respect to the one-dimensional transferring hydrogen coordinate vanish exactly. Application of these approaches to the phenoxyl-phenol and benzyl-toluene systems characterizes the former as PCET and the latter as HAT. The diabatic states generated for the phenoxyl-phenol system possess physically meaningful, localized electronic charge distributions that are relatively invariant along the hydrogen coordinate. These diabatic electronic states can be combined with the associated proton vibrational states to generate the reactant and product electron-proton vibronic states that form the basis of nonadiabatic PCET theories. Furthermore, these vibronic states and the corresponding vibronic couplings may be used to calculate rate constants and kinetic isotope effects of PCET reactions.

49 CFR 225.37 - Optical media transfer and electronic submission.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Optical media transfer and electronic submission..., AND INVESTIGATIONS § 225.37 Optical media transfer and electronic submission. (a) A railroad has the option of submitting the following reports, updates, and amendments by way of optical media (CD-ROM), or...

49 CFR 225.37 - Optical media transfer and electronic submission.

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2013-10-01

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49 CFR 225.37 - Optical media transfer and electronic submission.

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2011-10-01

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49 CFR 225.37 - Optical media transfer and electronic submission.

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76 FR 708 - Electronic Funds Transfer of Depository Taxes; Correction

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40 CFR Table I-2 to Subpart I - Examples of Fluorinated GHGs and Fluorinated Heat Transfer Fluids Used by the Electronics Industry

Code of Federal Regulations, 2012 CFR

2012-07-01

... Fluorinated Heat Transfer Fluids Used by the Electronics Industry I Table I-2 to Subpart I Protection of... REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-2 Table I-2 to Subpart I—Examples of Fluorinated GHGs and Fluorinated Heat Transfer Fluids Used by the Electronics Industry Product type...

On judgement of electron transfer between two regions divided by the separatrix of confronting divergent magnetic fields applied to an inductively coupled plasma

NASA Astrophysics Data System (ADS)

Sugawara, Hirotake; Yamamoto, Tappei

2016-09-01

In order to quantitatively evaluate the electron confinement effect of the confronting divergent magnetic fields (CDMFs) applied to an inductively coupled plasma, we analyzed the electron transfer between two regions divided by the separatrix of the CDMFs in Ar at 0.67 Pa at 300 K using a Monte Carlo method. A conventional transfer judgement was simply based on the electron passage across the separatrix from the upstream source region to the downstream diffusion region. An issue was an overestimation of the transfer due to temporary stay of electrons in the downstream region. Electrons may pass the downstream region during their gyration even in case they are effectively bound to the upstream region, where their guiding magnetic flux lines run. More than half of the transfers were temporary ones and such seeming transfers were relevantly excluded from the statistics by introducing a newly chosen criterion based on the passage of electron gyrocenters across the separatrix and collisional events in the downstream region. Simulation results showed a tendency that the ratio of the temporary transfers excluded was higher under stronger magnetic fields because of higher cyclotron frequency. Work supported by JSPS Kakenhi Grant Number 16K05626.

The role of defects in Fe(II) – goethite electron transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrade de Notini, Luiza; Latta, Drew; Neumann, Anke

Despite accumulating experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemical calculations suggest that oxidation of sorbed Fe(II) is not energetically feasible unless defects are present. Here we used isotope specific 57Fe Mössbauer spectroscopy to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, we heated the mineral to try to anneal the goethite surface and ground goethite to try to create defects. We found that heating goethite results in less oxidation of sorbed Fe(II) by goethite. When goethite was re-ground after heating, electron transfer was partially restored. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) ofmore » heated and ground goethite confirm that heating and grinding alter the surface structure of the goethite. We propose that the heating process annealed the surface and decreased the number of sites where electron transfer could occur. Our experimental findings suggest that surface defects play an important role in Fe(II)-goethite electron transfer as suggested by computational calculations. Our finding that defects influence heterogeneous Fe(II)-goethite electron transfer has important implications for Fe(II) driven recrystallization of Fe oxides, as well as X and Y.« less

Effect of group electronegativity on electron transfer in bis(hydrazine) radical cations.

PubMed

Qin, Haimei; Zhong, Xinxin; Si, Yubing; Zhang, Weiwei; Zhao, Yi

2011-04-14

The radical cation of 4,10-ditert-butyl-5,9-diisopropyl-4,5,9,10-tetraazatetracyclo[6.2.2.2]-tetradecane (sBI4T(+)), as well as its substituted bis(hydrazine) radical cations, is chosen for the investigation of the electronegativity dependence of its intramolecular electron transfer. To do so, two parameters, reorganization energy and electronic coupling, are calculated with several ab initio approaches. It is found that the electronic couplings decrease with the increase of the group electronegativity while the reorganization energies do not show an explicit dependency. Furthermore, Marcus formula is employed to reveal those effect on the electron transfer rates. The predicted rates of electron transfer generally decrease with increasing group electronegativity, although not monotonically.

Space Sciences Laboratory Publications and Presentations

NASA Technical Reports Server (NTRS)

Summers, F. G. (Compiler)

1998-01-01

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 - December 31, 1997. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by page number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publication in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature.

Dynamics and mechanism of UV-damaged DNA repair in indole-thymine dimer adduct: molecular origin of low repair quantum efficiency.

PubMed

Guo, Xunmin; Liu, Zheyun; Song, Qinhua; Wang, Lijuan; Zhong, Dongping

2015-02-26

Many biomimetic chemical systems for repair of UV-damaged DNA showed very low repair efficiency, and the molecular origin is still unknown. Here, we report our systematic characterization of the repair dynamics of a model compound of indole-thymine dimer adduct in three solvents with different polarity. By resolving all elementary steps including three electron-transfer processes and two bond-breaking and bond-formation dynamics with femtosecond resolution, we observed the slow electron injection in 580 ps in water, 4 ns in acetonitrile, and 1.38 ns in dioxane, the fast back electron transfer without repair in 120, 150, and 180 ps, and the slow bond splitting in 550 ps, 1.9 ns, and 4.5 ns, respectively. The dimer bond cleavage is clearly accelerated by the solvent polarity. By comparing with the biological repair machine photolyase with a slow back electron transfer (2.4 ns) and a fast bond cleavage (90 ps), the low repair efficiency in the biomimetic system is mainly determined by the fast back electron transfer and slow bond breakage. We also found that the model system exists in a dynamic heterogeneous C-clamped conformation, leading to a stretched dynamic behavior. In water, we even identified another stacked form with ultrafast cyclic electron transfer, significantly reducing the repair efficiency. Thus, the comparison of the repair efficiency in different solvents is complicated and should be cautious, and only the dynamics by resolving all elementary steps can finally determine the total repair efficiency. Finally, we use the Marcus electron-transfer theory to analyze all electron-transfer reactions and rationalize all observed electron-transfer dynamics.

Electron shuttles in biotechnology.

PubMed

Watanabe, Kazuya; Manefield, Mike; Lee, Matthew; Kouzuma, Atsushi

2009-12-01

Electron-shuttling compounds (electron shuttles [ESs], or redox mediators) are essential components in intracellular electron transfer, while microbes also utilize self-produced and naturally present ESs for extracellular electron transfer. These compounds assist in microbial energy metabolism by facilitating electron transfer between microbes, from electron-donating substances to microbes, and/or from microbes to electron-accepting substances. Artificially supplemented ESs can create new routes of electron flow in the microbial energy metabolism, thereby opening up new possibilities for the application of microbes to biotechnology processes. Typical examples of such processes include halogenated-organics bioremediation, azo-dye decolorization, and microbial fuel cells. Herein we suggest that ESs can be applied widely to create new microbial biotechnology processes.

Incorporation of charge transfer into the explicit polarization fragment method by grand canonical density functional theory.

PubMed

Isegawa, Miho; Gao, Jiali; Truhlar, Donald G

2011-08-28

Molecular fragmentation algorithms provide a powerful approach to extending electronic structure methods to very large systems. Here we present a method for including charge transfer between molecular fragments in the explicit polarization (X-Pol) fragment method for calculating potential energy surfaces. In the conventional X-Pol method, the total charge of each fragment is preserved, and charge transfer between fragments is not allowed. The description of charge transfer is made possible by treating each fragment as an open system with respect to the number of electrons. To achieve this, we applied Mermin's finite temperature method to the X-Pol wave function. In the application of this method to X-Pol, the fragments are open systems that partially equilibrate their number of electrons through a quasithermodynamics electron reservoir. The number of electrons in a given fragment can take a fractional value, and the electrons of each fragment obey the Fermi-Dirac distribution. The equilibrium state for the electrons is determined by electronegativity equalization with conservation of the total number of electrons. The amount of charge transfer is controlled by re-interpreting the temperature parameter in the Fermi-Dirac distribution function as a coupling strength parameter. We determined this coupling parameter so as to reproduce the charge transfer energy obtained by block localized energy decomposition analysis. We apply the new method to ten systems, and we show that it can yield reasonable approximations to potential energy profiles, to charge transfer stabilization energies, and to the direction and amount of charge transferred. © 2011 American Institute of Physics

Incorporation of charge transfer into the explicit polarization fragment method by grand canonical density functional theory

PubMed Central

Isegawa, Miho; Gao, Jiali; Truhlar, Donald G.

2011-01-01

Molecular fragmentation algorithms provide a powerful approach to extending electronic structure methods to very large systems. Here we present a method for including charge transfer between molecular fragments in the explicit polarization (X-Pol) fragment method for calculating potential energy surfaces. In the conventional X-Pol method, the total charge of each fragment is preserved, and charge transfer between fragments is not allowed. The description of charge transfer is made possible by treating each fragment as an open system with respect to the number of electrons. To achieve this, we applied Mermin's finite temperature method to the X-Pol wave function. In the application of this method to X-Pol, the fragments are open systems that partially equilibrate their number of electrons through a quasithermodynamics electron reservoir. The number of electrons in a given fragment can take a fractional value, and the electrons of each fragment obey the Fermi–Dirac distribution. The equilibrium state for the electrons is determined by electronegativity equalization with conservation of the total number of electrons. The amount of charge transfer is controlled by re-interpreting the temperature parameter in the Fermi–Dirac distribution function as a coupling strength parameter. We determined this coupling parameter so as to reproduce the charge transfer energy obtained by block localized energy decomposition analysis. We apply the new method to ten systems, and we show that it can yield reasonable approximations to potential energy profiles, to charge transfer stabilization energies, and to the direction and amount of charge transferred. PMID:21895159

Using the plasmon linewidth to calculate the time and efficiency of electron transfer between gold nanorods and graphene.

PubMed

Hoggard, Anneli; Wang, Lin-Yung; Ma, Lulu; Fang, Ying; You, Ge; Olson, Jana; Liu, Zheng; Chang, Wei-Shun; Ajayan, Pulickel M; Link, Stephan

2013-12-23

We present a quantitative analysis of the electron transfer between single gold nanorods and monolayer graphene under no electrical bias. Using single-particle dark-field scattering and photoluminescence spectroscopy to access the homogeneous linewidth, we observe broadening of the surface plasmon resonance for gold nanorods on graphene compared to nanorods on a quartz substrate. Because of the absence of spectral plasmon shifts, dielectric interactions between the gold nanorods and graphene are not important and we instead assign the plasmon damping to charge transfer between plasmon-generated hot electrons and the graphene that acts as an efficient acceptor. Analysis of the plasmon linewidth yields an average electron transfer time of 160 ± 30 fs, which is otherwise difficult to measure directly in the time domain with single-particle sensitivity. In comparison to intrinsic hot electron decay and radiative relaxation, we furthermore calculate from the plasmon linewidth that charge transfer between the gold nanorods and the graphene support occurs with an efficiency of ∼10%. Our results are important for future applications of light harvesting with metal nanoparticle plasmons and efficient hot electron acceptors as well as for understanding hot electron transfer in plasmon-assisted chemical reactions.

Sensitization of ultra-long-range excited-state electron transfer by energy transfer in a polymerized film

PubMed Central

Ito, Akitaka; Stewart, David J.; Fang, Zhen; Brennaman, M. Kyle; Meyer, Thomas J.

2012-01-01

Distance-dependent energy transfer occurs from the Metal-to-Ligand Charge Transfer (MLCT) excited state to an anthracene-acrylate derivative (Acr-An) incorporated into the polymer network of a semirigid poly(ethyleneglycol)dimethacrylate monolith. Following excitation, to Acr-An triplet energy transfer occurs followed by long-range, Acr-3An—Acr-An → Acr-An—Acr-3An, energy migration. With methyl viologen dication (MV2+) added as a trap, Acr-3An + MV2+ → Acr-An+ + MV+ electron transfer results in sensitized electron transfer quenching over a distance of approximately 90 Å. PMID:22949698

40 CFR Table I-2 to Subpart I of... - Examples of Fluorinated GHGs and Fluorinated Heat Transfer Fluids Used by the Electronics Industry

Code of Federal Regulations, 2013 CFR

2013-07-01

... Fluorinated Heat Transfer Fluids Used by the Electronics Industry I Table I-2 to Subpart I of Part 98... GREENHOUSE GAS REPORTING Electronics Manufacturing Pt. 98, Subpt. I, Table I-2 Table I-2 to Subpart I of Part 98—Examples of Fluorinated GHGs and Fluorinated Heat Transfer Fluids Used by the Electronics Industry...

48 CFR 252.232-7011 - Payments in Support of Emergencies and Contingency Operations.

Code of Federal Regulations, 2011 CFR

2011-10-01

.... Internal Revenue Code. (ix) Electronic funds transfer banking information. (A) The Contractor shall include electronic funds transfer banking information on the invoice only if required elsewhere in this contract. (B) If electronic funds transfer banking information is not required to be on the invoice, in order for...

76 FR 52862 - Time for Payment of Certain Excise Taxes, and Quarterly Excise Tax Payments for Small Alcohol...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-24

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Co-adsorption of water and oxygen on GaN: Effects of charge transfer and formation of electron depletion layer.

PubMed

Wang, Qi; Puntambekar, Ajinkya; Chakrapani, Vidhya

2017-09-14

Species from ambient atmosphere such as water and oxygen are known to affect electronic and optical properties of GaN, but the underlying mechanism is not clearly known. In this work, we show through careful measurement of electrical resistivity and photoluminescence intensity under various adsorbates that the presence of oxygen or water vapor alone is not sufficient to induce electron transfer to these species. Rather, the presence of both water and oxygen is necessary to induce electron transfer from GaN that leads to the formation of an electron depletion region on the surface. Exposure to acidic gases decreases n-type conductivity due to increased electron transfer from GaN, while basic gases increase n-type conductivity and PL intensity due to reduced charge transfer from GaN. These changes in the electrical and optical properties, as explained using a new electrochemical framework based on the phenomenon of surface transfer doping, suggest that gases interact with the semiconductor surface through electrochemical reactions occurring in an adsorbed water layer present on the surface.

The interaction of trimethylamine dehydrogenase and electron-transferring flavoprotein.

PubMed

Shi, Weiwei; Mersfelder, John; Hille, Russ

2005-05-27

The interaction between the physiological electron transfer partners trimethylamine dehydrogenase (TMADH) and electron-transferring flavoprotein (ETF) from Methylophilus methylotrophus has been examined with particular regard to the proposal that the former protein "imprints" a conformational change on the latter. The results indicate that the absorbance change previously attributed to changes in the environment of the FAD of ETF upon binding to TMADH is instead caused by electron transfer from partially reduced, as-isolated TMADH to ETF. Prior treatment of the as-isolated enzyme with the oxidant ferricenium essentially abolishes the observed spectral change. Further, when the semiquinone form of ETF is used instead of the oxidized form, the mirror image of the spectral change seen with as-isolated TMADH and oxidized ETF is observed. This is attributable to a small amount of electron transfer in the reverse of the physiological direction. Kinetic determination of the dissociation constant and limiting rate constant for electron transfer within the complex of (reduced) TMADH with (oxidized) ETF is reconfirmed and discussed in the context of a recently proposed model for the interaction between the two proteins that involves "structural imprinting" of ETF.

Protein electron transfer: Dynamics and statistics

NASA Astrophysics Data System (ADS)

Matyushov, Dmitry V.

2013-07-01

Electron transfer between redox proteins participating in energy chains of biology is required to proceed with high energetic efficiency, minimizing losses of redox energy to heat. Within the standard models of electron transfer, this requirement, combined with the need for unidirectional (preferably activationless) transitions, is translated into the need to minimize the reorganization energy of electron transfer. This design program is, however, unrealistic for proteins whose active sites are typically positioned close to the polar and flexible protein-water interface to allow inter-protein electron tunneling. The high flexibility of the interfacial region makes both the hydration water and the surface protein layer act as highly polar solvents. The reorganization energy, as measured by fluctuations, is not minimized, but rather maximized in this region. Natural systems in fact utilize the broad breadth of interfacial electrostatic fluctuations, but in the ways not anticipated by the standard models based on equilibrium thermodynamics. The combination of the broad spectrum of static fluctuations with their dispersive dynamics offers the mechanism of dynamical freezing (ergodicity breaking) of subsets of nuclear modes on the time of reaction/residence of the electron at a redox cofactor. The separation of time-scales of nuclear modes coupled to electron transfer allows dynamical freezing. In particular, the separation between the relaxation time of electro-elastic fluctuations of the interface and the time of conformational transitions of the protein caused by changing redox state results in dynamical freezing of the latter for sufficiently fast electron transfer. The observable consequence of this dynamical freezing is significantly different reorganization energies describing the curvature at the bottom of electron-transfer free energy surfaces (large) and the distance between their minima (Stokes shift, small). The ratio of the two reorganization energies establishes the parameter by which the energetic efficiency of protein electron transfer is increased relative to the standard expectations, thus minimizing losses of energy to heat. Energetically efficient electron transfer occurs in a chain of conformationally quenched cofactors and is characterized by flattened free energy surfaces, reminiscent of the flat and rugged landscape at the stability basin of a folded protein.

Protein electron transfer: Dynamics and statistics.

PubMed

Matyushov, Dmitry V

2013-07-14

Electron transfer between redox proteins participating in energy chains of biology is required to proceed with high energetic efficiency, minimizing losses of redox energy to heat. Within the standard models of electron transfer, this requirement, combined with the need for unidirectional (preferably activationless) transitions, is translated into the need to minimize the reorganization energy of electron transfer. This design program is, however, unrealistic for proteins whose active sites are typically positioned close to the polar and flexible protein-water interface to allow inter-protein electron tunneling. The high flexibility of the interfacial region makes both the hydration water and the surface protein layer act as highly polar solvents. The reorganization energy, as measured by fluctuations, is not minimized, but rather maximized in this region. Natural systems in fact utilize the broad breadth of interfacial electrostatic fluctuations, but in the ways not anticipated by the standard models based on equilibrium thermodynamics. The combination of the broad spectrum of static fluctuations with their dispersive dynamics offers the mechanism of dynamical freezing (ergodicity breaking) of subsets of nuclear modes on the time of reaction/residence of the electron at a redox cofactor. The separation of time-scales of nuclear modes coupled to electron transfer allows dynamical freezing. In particular, the separation between the relaxation time of electro-elastic fluctuations of the interface and the time of conformational transitions of the protein caused by changing redox state results in dynamical freezing of the latter for sufficiently fast electron transfer. The observable consequence of this dynamical freezing is significantly different reorganization energies describing the curvature at the bottom of electron-transfer free energy surfaces (large) and the distance between their minima (Stokes shift, small). The ratio of the two reorganization energies establishes the parameter by which the energetic efficiency of protein electron transfer is increased relative to the standard expectations, thus minimizing losses of energy to heat. Energetically efficient electron transfer occurs in a chain of conformationally quenched cofactors and is characterized by flattened free energy surfaces, reminiscent of the flat and rugged landscape at the stability basin of a folded protein.

Optical determination of charge transfer times from indoline dyes to ZnO in solid state dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Meyenburg, I.; Hofeditz, N.; Ruess, R.; Rudolph, M.; Schlettwein, D.; Heimbrodt, W.

2018-05-01

We studied the electron transfer at the interface of organic-inorganic hybrids consisting of indoline derivatives (D149 and D131) on ZnO substrates using a new optical method. We revealed the electron transfer times from the excited dye, e.g. the excitons formed in the dye aggregates to the ZnO substrate by analyzing the photoluminescence transients of the excitons after femtosecond excitation and applying kinetic model calculations. We reveal the changes of the electron transfer times by applying electrical bias. Pushing the Fermi energy of the ZnO substrate towards the excited dye level the transfer time gets longer and eventually the electron transfer is suppressed. The level alignment between the excited dye state and the ZnO Fermi-level is estimated. The excited state of D131 is about 100 meV higher than the respective state of D149 compared to the ZnO conduction band. This leads to shorter electron transfer times and eventually to higher quantum efficiencies of the solar cells.

Multiple electron injection dynamics in linearly-linked two dye co-sensitized nanocrystalline metal oxide electrodes for dye-sensitized solar cells.

PubMed

Shen, Qing; Ogomi, Yuhei; Park, Byung-wook; Inoue, Takafumi; Pandey, Shyam S; Miyamoto, Akari; Fujita, Shinsuke; Katayama, Kenji; Toyoda, Taro; Hayase, Shuzi

2012-04-07

Understanding the electron transfer dynamics at the interface between dye sensitizer and semiconductor nanoparticle is very important for both a fundamental study and development of dye-sensitized solar cells (DSCs), which are a potential candidate for next generation solar cells. In this study, we have characterized the ultrafast photoexcited electron dynamics in a newly produced linearly-linked two dye co-sensitized solar cell using both a transient absorption (TA) and an improved transient grating (TG) technique, in which tin(IV) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NcSn) and cis-diisothiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II) bis(tetrabutylammonium) (N719) are molecularly and linearly linked and are bonded to the surface of a nanocrystalline tin dioxide (SnO(2)) electrode by a metal-O-metal linkage (i.e. SnO(2)-NcSn-N719). By comparing the TA and TG kinetics of NcSn, N719, and hybrid NcSn-N719 molecules adsorbed onto both of the SnO(2) and zirconium dioxide (ZrO(2)) nanocrystalline films, the forward and backward electron transfer dynamics in SnO(2)-NcSn-N719 were clarified. We found that there are two pathways for electron injection from the linearly-linked two dye molecules (NcSn-N719) to SnO(2). The first is a stepwise electron injection, in which photoexcited electrons first transfer from N719 to NcSn with a transfer time of 0.95 ps and then transfer from NcSn to the conduction band (CB) of SnO(2) with two timescales of 1.6 ps and 4.2 ps. The second is direct photoexcited electron transfer from N719 to the CB of SnO(2) with a timescale of 20-30 ps. On the other hand, back electron transfer from SnO(2) to NcSn is on a timescale of about 2 ns, which is about three orders of magnitude slower compared to the forward electron transfer from NcSn to SnO(2). The back electron transfer from NcSn to N719 is on a timescale of about 40 ps, which is about one order slower compared to the forward electron transfer from N719 to NcSn. These results demonstrate that photoexcited electrons can be effectively injected into SnO(2) from both of the N719 and NcSn dyes.

12 CFR 205.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.9 Receipts at electronic terminals; periodic..., a financial institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following...

12 CFR 205.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.9 Receipts at electronic terminals; periodic..., a financial institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following...

12 CFR 205.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.9 Receipts at electronic terminals; periodic..., a financial institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following...

12 CFR 205.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.9 Receipts at electronic terminals; periodic..., a financial institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following...

12 CFR 205.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.9 Receipts at electronic terminals; periodic..., a financial institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following...

Ultrafast above-threshold dynamics of the radical anion of a prototypical quinone electron-acceptor.

PubMed

Horke, Daniel A; Li, Quansong; Blancafort, Lluís; Verlet, Jan R R

2013-08-01

Quinones feature prominently as electron acceptors in nature. Their electron-transfer reactions are often highly exergonic, for which Marcus theory predicts reduced electron-transfer rates because of a free-energy barrier that occurs in the inverted region. However, the electron-transfer kinetics that involve quinones can appear barrierless. Here, we consider the intrinsic properties of the para-benzoquinone radical anion, which serves as the prototypical electron-transfer reaction product involving a quinone-based acceptor. Using time-resolved photoelectron spectroscopy and ab initio calculations, we show that excitation at 400 and 480 nm yields excited states that are unbound with respect to electron loss. These excited states are shown to decay on a sub-40 fs timescale through a series of conical intersections with lower-lying excited states, ultimately to form the ground anionic state and avoid autodetachment. From an isolated electron-acceptor perspective, this ultrafast stabilization mechanism accounts for the ability of para-benzoquinone to capture and retain electrons.

For Your Phone Only: Custom Protocols for Efficient Secure Function Evaluation on Mobile Devices (Preprint)

DTIC Science & Technology

2012-11-01

that mobile application developers should reconsider implementing garbled circuits due to their extreme resource usage, and instead rely upon our equivalently secure and significantly more efficient alternative.

Cumulative reports and publications through December 31, 1985

NASA Technical Reports Server (NTRS)

1986-01-01

A complete list of ICASE Reports are contained. Since ICASE Reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

Operating Reserves and Wind Power Integration: An International Comparison; Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milligan, M.; Donohoo, P.; Lew, D.

2010-10-01

This paper provides a high-level international comparison of methods and key results from both operating practice and integration analysis, based on an informal International Energy Agency Task 25: Large-scale Wind Integration.

Interim Evaluation Results from New Flyer/Allison Hybrid Buses at King County Metro: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandler, K.; Eberts, E.; Eudy, L.

2005-05-01

This paper prepared for the 2005 American Public Transportation Association Bus & Paratransit Conference discusses NREL/DOE evaluation of hybrid electric articulated transit buses operated by King County Metro.

Photocatalytic Conversion of Nitrobenzene to Aniline through Sequential Proton-Coupled One-Electron Transfers from a Cadmium Sulfide Quantum Dot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Stephen C.; Bettis Homan, Stephanie; Weiss, Emily A.

2016-01-28

This paper describes the use of cadmium sulfide quantum dots (CdS QDs) as visible-light photocatalysts for the reduction of nitrobenzene to aniline through six sequential photoinduced, proton-coupled electron transfers. At pH 3.6–4.3, the internal quantum yield of photons-to-reducing electrons is 37.1% over 54 h of illumination, with no apparent decrease in catalyst activity. Monitoring of the QD exciton by transient absorption reveals that, for each step in the catalytic cycle, the sacrificial reductant, 3-mercaptopropionic acid, scavenges the excitonic hole in ~5 ps to form QD•–; electron transfer to nitrobenzene or the intermediates nitrosobenzene and phenylhydroxylamine then occurs on the nanosecondmore » time scale. The rate constants for the single-electron transfer reactions are correlated with the driving forces for the corresponding proton-coupled electron transfers. This result suggests, but does not prove, that electron transfer, not proton transfer, is rate-limiting for these reactions. Nuclear magnetic resonance analysis of the QD–molecule systems shows that the photoproduct aniline, left unprotonated, serves as a poison for the QD catalyst by adsorbing to its surface. Performing the reaction at an acidic pH not only encourages aniline to desorb but also increases the probability of protonated intermediates; the latter effect probably ensures that recruitment of protons is not rate-limiting.« less

Quantum state transfer in double-quantum-well devices

NASA Technical Reports Server (NTRS)

Jakumeit, Jurgen; Tutt, Marcel; Pavlidis, Dimitris

1994-01-01

A Monte Carlo simulation of double-quantum-well (DQW) devices is presented in view of analyzing the quantum state transfer (QST) effect. Different structures, based on the AlGaAs/GaAs system, were simulated at 77 and 300 K and optimized in terms of electron transfer and device speed. The analysis revealed the dominant role of the impurity scattering for the QST. Different approaches were used for the optimization of QST devices and basic physical limitations were found in the electron transfer between the QWs. The maximum transfer of electrons from a high to a low mobility well was at best 20%. Negative differential resistance is hampered by the almost linear rather than threshold dependent relation of electron transfer on electric field. By optimizing the doping profile the operation frequency limit could be extended to 260 GHz.

Dioxygen in Polyoxometalate Mediated Reactions.

PubMed

Weinstock, Ira A; Schreiber, Roy E; Neumann, Ronny

2018-03-14

In this review article, we consider the use of molecular oxygen in reactions mediated by polyoxometalates. Polyoxometalates are anionic metal oxide clusters of a variety of structures that are soluble in liquid phases and therefore amenable to homogeneous catalytic transformations. Often, they are active for electron transfer oxidations of a myriad of substrates and upon reduction can be reoxidized by molecular oxygen. For example, the phosphovanadomolybdate, H 5 PV 2 Mo 10 O 40 , can oxidize Pd(0) thereby enabling aerobic reactions catalyzed by Pd and H 5 PV 2 Mo 10 O 40 . In a similar vein, polyoxometalates can stabilize metal nanoparticles, leading to additional transformations. Furthermore, electron transfer oxidation of other substrates such as halides and sulfur-containing compounds is possible. More uniquely, H 5 PV 2 Mo 10 O 40 and its analogues can mediate electron transfer-oxygen transfer reactions where oxygen atoms are transferred from the polyoxometalate to the substrate. This unique property has enabled correspondingly unique transformations involving carbon-carbon, carbon-hydrogen, and carbon-metal bond activation. The pathway for the reoxidation of vanadomolybdates with O 2 appears to be an inner-sphere reaction, but the oxidation of one-electron reduced polyoxotungstates has been shown through intensive research to be an outer-sphere reaction. Beyond electron transfer and electron transfer-oxygen transfer aerobic transformations, there a few examples of apparent dioxygenase activity where both oxygen atoms are donated to a substrate.

Picture of the Week: Hacking the bio-nano interface for better biofuels

Science.gov Websites

) influence electron transfer between the enzyme and the electrode to determine the best placement of enzymes compounds) influence electron transfer between the enzyme and the electrode to determine the best placement studied how three quinones (a class of organic compounds) influence electron transfer between the enzyme

Intramolecular electron-transfer rates in mixed-valence triarylamines: measurement by variable-temperature ESR spectroscopy and comparison with optical data.

PubMed

Lancaster, Kelly; Odom, Susan A; Jones, Simon C; Thayumanavan, S; Marder, Seth R; Brédas, Jean-Luc; Coropceanu, Veaceslav; Barlow, Stephen

2009-02-11

The electron spin resonance spectra of the radical cations of 4,4'-bis[di(4-methoxyphenyl)amino]tolane, E-4,4'-bis[di(4-methoxyphenyl)amino]stilbene, and E,E-1,4-bis{4-[di(4-methoxyphenyl)amino]styryl}benzene in dichloromethane exhibit five lines over a wide temperature range due to equivalent coupling to two 14N nuclei, indicating either delocalization between both nitrogen atoms or rapid intramolecular electron transfer on the electron spin resonance time scale. In contrast, those of the radical cations of 1,4-bis{4-[di(4-methoxyphenyl)amino]phenylethynyl}benzene and E,E-1,4-bis{4-[di(4-n-butoxyphenyl)amino]styryl}-2,5-dicyanobenzene exhibit line shapes that vary strongly with temperature, displaying five lines at room temperature and only three lines at ca. 190 K, indicative of slow electron transfer on the electron spin resonance time scale at low temperatures. The rates of intramolecular electron transfer in the latter compounds were obtained by simulation of the electron spin resonance spectra and display an Arrhenius temperature dependence. The activation barriers obtained from Arrhenius plots are significantly less than anticipated from Hush analyses of the intervalence bands when the diabatic electron-transfer distance, R, is equated to the N[symbol: see text]N distance. Comparison of optical and electron spin resonance data suggests that R is in fact only ca. 40% of the N[symbol: see text]N distance, while the Arrhenius prefactor indicates that the electron transfer falls in the adiabatic regime.

Role of protein fluctuation correlations in electron transfer in photosynthetic complexes.

PubMed

Nesterov, Alexander I; Berman, Gennady P

2015-04-01

We consider the dependence of the electron transfer in photosynthetic complexes on correlation properties of random fluctuations of the protein environment. The electron subsystem is modeled by a finite network of connected electron (exciton) sites. The fluctuations of the protein environment are modeled by random telegraph processes, which act either collectively (correlated) or independently (uncorrelated) on the electron sites. We derived an exact closed system of first-order linear differential equations with constant coefficients, for the average density matrix elements and for their first moments. Under some conditions, we obtained analytic expressions for the electron transfer rates and found the range of parameters for their applicability by comparing with the exact numerical simulations. We also compared the correlated and uncorrelated regimes and demonstrated numerically that the uncorrelated fluctuations of the protein environment can, under some conditions, either increase or decrease the electron transfer rates.

Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

NASA Astrophysics Data System (ADS)

Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

2016-09-01

Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

Alternative ground states enable pathway switching in biological electron transfer

DOE PAGES

Abriata, Luciano A.; Alvarez-Paggi, Damian; Ledesma, Gabirela N.; ...

2012-10-10

Electron transfer is the simplest chemical reaction and constitutes the basis of a large variety of biological processes, such as photosynthesis and cellular respiration. Nature has evolved specific proteins and cofactors for these functions. The mechanisms optimizing biological electron transfer have been matter of intense debate, such as the role of the protein milieu between donor and acceptor sites. Here we propose a mechanism regulating long-range electron transfer in proteins. Specifically, we report a spectroscopic, electrochemical, and theoretical study on WT and single-mutant CuA redox centers from Thermus thermophilus, which shows that thermal fluctuations may populate two alternative ground-state electronicmore » wave functions optimized for electron entry and exit, respectively, through two different and nearly perpendicular pathways. In conclusion, these findings suggest a unique role for alternative or “invisible” electronic ground states in directional electron transfer. Moreover, it is shown that this energy gap and, therefore, the equilibrium between ground states can be fine-tuned by minor perturbations, suggesting alternative ways through which protein–protein interactions and membrane potential may optimize and regulate electron–proton energy transduction.« less

Ultrafast Electron Transfer Kinetics in the LM Dimer of Bacterial Photosynthetic Reaction Center from Rhodobacter sphaeroides.

PubMed

Sun, Chang; Carey, Anne-Marie; Gao, Bing-Rong; Wraight, Colin A; Woodbury, Neal W; Lin, Su

2016-06-23

It has become increasingly clear that dynamics plays a major role in the function of many protein systems. One system that has proven particularly facile for studying the effects of dynamics on protein-mediated chemistry is the bacterial photosynthetic reaction center from Rhodobacter sphaeroides. Previous experimental and computational analysis have suggested that the dynamics of the protein matrix surrounding the primary quinone acceptor, QA, may be particularly important in electron transfer involving this cofactor. One can substantially increase the flexibility of this region by removing one of the reaction center subunits, the H-subunit. Even with this large change in structure, photoinduced electron transfer to the quinone still takes place. To evaluate the effect of H-subunit removal on electron transfer to QA, we have compared the kinetics of electron transfer and associated spectral evolution for the LM dimer with that of the intact reaction center complex on picosecond to millisecond time scales. The transient absorption spectra associated with all measured electron transfer reactions are similar, with the exception of a broadening in the QX transition and a blue-shift in the QY transition bands of the special pair of bacteriochlorophylls (P) in the LM dimer. The kinetics of the electron transfer reactions not involving quinones are unaffected. There is, however, a 4-fold decrease in the electron transfer rate from the reduced bacteriopheophytin to QA in the LM dimer compared to the intact reaction center and a similar decrease in the recombination rate of the resulting charge-separated state (P(+)QA(-)). These results are consistent with the concept that the removal of the H-subunit results in increased flexibility in the region around the quinone and an associated shift in the reorganization energy associated with charge separation and recombination.

Photoinduced electron transfer in covalent ruthenium-anthraquinone dyads: relative importance of driving-force, solvent polarity, and donor-bridge energy gap.

PubMed

Hankache, Jihane; Wenger, Oliver S

2012-02-28

Four rigid rod-like molecules comprised of a Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) photosensitizer, a 9,10-anthraquinone electron acceptor, and a molecular bridge connecting the two redox partners were synthesized and investigated by optical spectroscopic and electrochemical means. An attempt was made to assess the relative importance of driving-force, solvent polarity, and bridge variation on the rates of photoinduced electron transfer in these molecules. Expectedly, introduction of tert-butyl substituents in the bipyridine ligands of the ruthenium complex and a change in solvent from dichloromethane to acetonitrile lead to a significant acceleration of charge transfer rates. In dichloromethane, photoinduced electron transfer is not competitive with the inherent excited-state deactivation processes of the photosensitizer. In acetonitrile, an increase in driving-force by 0.2 eV through attachment of tert-butyl substituents to the bpy ancillary ligands causes an increase in electron transfer rates by an order of magnitude. Replacement of a p-xylene bridge by a p-dimethoxybenzene spacer entails an acceleration of charge transfer rates by a factor of 3.5. In the dyads from this study, the relative order of importance of individual influences on electron transfer rates is therefore as follows: solvent polarity ≥ driving-force > donor-bridge energy gap.

CRADA Payment Options | NCI Technology Transfer Center | TTC

Cancer.gov

NCI TTC CRADA PAYMENT OPTIONS: Electronic Payments by Wire Transfer via Fedwire, Mail a check to the Institute or Center, or Automated Clearing House (ACH)/Electronic Funds Transfer (ETF) payments via Pay.gov (NCI ONLY).

Transfer coefficients in ultracold strongly coupled plasma

NASA Astrophysics Data System (ADS)

Bobrov, A. A.; Vorob'ev, V. S.; Zelener, B. V.

2018-03-01

We use both analytical and molecular dynamic methods for electron transfer coefficients in an ultracold plasma when its temperature is small and the coupling parameter characterizing the interaction of electrons and ions exceeds unity. For these conditions, we use the approach of nearest neighbor to determine the average electron (ion) diffusion coefficient and to calculate other electron transfer coefficients (viscosity and electrical and thermal conductivities). Molecular dynamics simulations produce electronic and ionic diffusion coefficients, confirming the reliability of these results. The results compare favorably with experimental and numerical data from earlier studies.

Theory for electron transfer from a mixed-valence dimer with paramagnetic sites to a mononuclear acceptor

NASA Astrophysics Data System (ADS)

Bominaar, E. L.; Achim, C.; Borshch, S. A.

1999-06-01

Polynuclear transition-metal complexes, such as Fe-S clusters, are the prosthetic groups in a large number of metalloproteins and serve as temporary electron storage units in a number of important redox-based biological processes. Polynuclearity distinguishes clusters from mononuclear centers and confers upon them unique properties, such as spin ordering and the presence of thermally accessible excited spin states in clusters with paramagnetic sites, and fractional valencies in clusters of the mixed-valence type. In an earlier study we presented an effective-mode (EM) analysis of electron transfer from a binuclear mixed-valence donor with paramagnetic sites to a mononuclear acceptor which revealed that the cluster-specific attributes have an important impact on the kinetics of long-range electron transfer. In the present study, the validity of these results is tested in the framework of more detailed theories which we have termed the multimode semiclassical (SC) model and the quantum-mechanical (QM) model. It is found that the qualitative trends in the rate constant are the same in all treatments and that the semiclassical models provide a good approximation of the more rigorous quantum-mechanical description of electron transfer under physiologically relevant conditions. In particular, the present results corroborate the importance of electron transfer via excited spin states in reactions with a low driving force and justify the use of semiclassical theory in cases in which the QM model is computationally too demanding. We consider cases in which either one or two donor sites of a dimer are electronically coupled to the acceptor. In the case of multiconnectivity, the rate constant for electron transfer from a valence-delocalized (class-III) donor is nonadditive with respect to transfer from individual metal sites of the donor and undergoes an order-of-magnitude change by reversing the sign of the intradimer metal-metal resonance parameter (β). In the case of single connectivity, the rate constant for electron transfer from a valence-localized (class-II) donor can readily be tuned over several orders of magnitude by introducing differences in the electronic potentials at the two metal sites of the donor. These results indicate that theories of cluster-based electron transfer, in order to be realistic, need to consider both intrinsic electronic structure and extrinsic interactions of the cluster with the protein environment.

Understanding the Charge Transfer at the Interface of Electron Donors and Acceptors: TTF–TCNQ as an Example

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Changwon; Atalla, Viktor; Smith, Sean

Charge transfer between an electron donor and an electron acceptor is widely accepted as being independent of their relative configurations if the interaction between them is weak; however, the limit of this concept for an interacting system has not yet been well established. Our study of prototypical electron donor–acceptor molecules, tetrathiafulvalene–tetracyanoquinodimethane, using density functional theory based on an advanced functional, clearly demonstrates that for interacting molecules, their configurational arrangement is as important as their individual electronic properties in the asymptotic limit to determine the charge transfer direction. For the first time, we demonstrate that by changing their relative orientation, onemore » can reverse the charge transfer direction of the pair, causing the molecules to exchange roles as donor and acceptor. In conclusion, our theory has important implications for understanding the interfacial charge-transfer mechanism of hybrid systems and related phenomena.« less

Sulfate-reducing bacteria: Microbiology and physiology

NASA Technical Reports Server (NTRS)

Peck, H. D.

1985-01-01

The sulfate reducing bacteria, the first nonphotosynthetic anaerobic bacteria demonstrated to contain c type cytochromes, perform electron transfer coupled to phosphorylation. A new bioenergetic scheme for the formation of a proton gradient for growth of Desulfovibrio on organic substrates and sulfate involving vectors electron transfer and consistent with the cellular localization of enzymes and electron transfer components was proposed. Hydrogen is produced in the cytoplasm from organic substrates and, as a permease molecule diffuses rapidly across the cytoplasmic membrane, it is oxidized to protons and electrons by the periplasmic hydrogenase. The electrons only are transferred across the cytoplasmic membrane to the cytoplasm where they are used to reduce sulfate to sulfide. The protons are used for transport or to drive a reversible ATPOSE. The net effect is the transfer of protons across the cytoplasmic membrane with the intervention of a proton pump. This type of H2 cycling is relevant to the bioenergetics of other types of anaerobic microorganisms.

Understanding the Charge Transfer at the Interface of Electron Donors and Acceptors: TTF–TCNQ as an Example

DOE PAGES

Park, Changwon; Atalla, Viktor; Smith, Sean; ...

2017-06-16

Charge transfer between an electron donor and an electron acceptor is widely accepted as being independent of their relative configurations if the interaction between them is weak; however, the limit of this concept for an interacting system has not yet been well established. Our study of prototypical electron donor–acceptor molecules, tetrathiafulvalene–tetracyanoquinodimethane, using density functional theory based on an advanced functional, clearly demonstrates that for interacting molecules, their configurational arrangement is as important as their individual electronic properties in the asymptotic limit to determine the charge transfer direction. For the first time, we demonstrate that by changing their relative orientation, onemore » can reverse the charge transfer direction of the pair, causing the molecules to exchange roles as donor and acceptor. In conclusion, our theory has important implications for understanding the interfacial charge-transfer mechanism of hybrid systems and related phenomena.« less

Nanoantioxidant-driven plasmon enhanced proton-coupled electron transfer

NASA Astrophysics Data System (ADS)

Sotiriou, Georgios A.; Blattmann, Christoph O.; Deligiannakis, Yiannis

2015-12-01

Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon-enhancement of PCET brings together the so far unrelated research domains of nanoplasmonics and electron/proton translocation with significant impact on applications based on interfacial electron/proton transfer.Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon-enhancement of PCET brings together the so far unrelated research domains of nanoplasmonics and electron/proton translocation with significant impact on applications based on interfacial electron/proton transfer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04942c

Electron energy distribution function, effective electron temperature, and dust charge in the temporal afterglow of a plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denysenko, I. B.; Azarenkov, N. A.; Kersten, H.

2016-05-15

Analytical expressions describing the variation of electron energy distribution function (EEDF) in an afterglow of a plasma are obtained. Especially, the case when the electron energy loss is mainly due to momentum-transfer electron-neutral collisions is considered. The study is carried out for different EEDFs in the steady state, including Maxwellian and Druyvesteyn distributions. The analytical results are not only obtained for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy but also for the case when the collisions are a power function of electron energy. Using analytical expressions for the EEDF, the effective electron temperaturemore » and charge of the dust particles, which are assumed to be present in plasma, are calculated for different afterglow durations. An analytical expression for the rate describing collection of electrons by dust particles for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy is also derived. The EEDF profile and, as a result, the effective electron temperature and dust charge are sufficiently different in the cases when the rate for momentum-transfer electron-neutral collisions is independent on electron energy and when the rate is a power function of electron energy.« less

Molecular dynamics simulations give insight into the conformational change, complex formation, and electron transfer pathway for cytochrome P450 reductase

PubMed Central

Sündermann, Axel; Oostenbrink, Chris

2013-01-01

Cytochrome P450 reductase (CYPOR) undergoes a large conformational change to allow for an electron transfer to a redox partner to take place. After an internal electron transfer over its cofactors, it opens up to facilitate the interaction and electron transfer with a cytochrome P450. The open conformation appears difficult to crystallize. Therefore, a model of a human CYPOR in the open conformation was constructed to be able to investigate the stability and conformational change of this protein by means of molecular dynamics simulations. Since the role of the protein is to provide electrons to a redox partner, the interactions with cytochrome P450 2D6 (2D6) were investigated and a possible complex structure is suggested. Additionally, electron pathway calculations with a newly written program were performed to investigate which amino acids relay the electrons from the FMN cofactor of CYPOR to the HEME of 2D6. Several possible interacting amino acids in the complex, as well as a possible electron transfer pathway were identified and open the way for further investigation by site directed mutagenesis studies. PMID:23832577

Electron transfer across a thermal gradient

PubMed Central

Craven, Galen T.

2016-01-01

Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor–acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures. PMID:27450086

Ultrafast Electron Transfer across a Nanocapsular Wall: Coumarins as Donors, Viologen as Acceptor, and Octa Acid Capsule as the Mediator.

PubMed

Chuang, Chi-Hung; Porel, Mintu; Choudhury, Rajib; Burda, Clemens; Ramamurthy, V

2018-01-11

Results of our study on ultrafast electron transfer (eT) dynamics from coumarins (coumarin-1, coumarin-480, and coumarin-153) incarcerated within octa acid (OA) capsules as electron donors to methyl viologen dissolved in water as acceptor are presented. Upon photoexcitation, coumarin inside the OA capsule transfers an electron to the acceptor electrostatically attached to the capsule leading to a long-lived radical-ion pair separated by the OA capsular wall. This charge-separated state returns to the neutral ground state via back electron transfer on the nanosecond time scale. This system allows for ultrafast electron transfer processes through a molecular wall from the apolar capsular interior to the highly polar (aqueous) environment on the femtosecond time scale. Employing femtosecond transient absorption spectroscopy, distinct rates of both forward (1-25 ps) and backward eT (700-1200 ps) processes were measured. Further understanding of the energetics is provided using Rehm-Weller analysis for the investigated photoinduced eT reactions. The results provide the rates of the eT across a molecular wall, akin to an isotropic solution, depending on the standard free energy of the reaction. The insights from this work could be utilized in the future design of efficient electron transfer processes across interfaces separating apolar and polar environments.

A unified diabatic description for electron transfer reactions, isomerization reactions, proton transfer reactions, and aromaticity.

PubMed

Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

2015-10-14

While diabatic approaches are ubiquitous for the understanding of electron-transfer reactions and have been mooted as being of general relevance, alternate applications have not been able to unify the same wide range of observed spectroscopic and kinetic properties. The cause of this is identified as the fundamentally different orbital configurations involved: charge-transfer phenomena involve typically either 1 or 3 electrons in two orbitals whereas most reactions are typically closed shell. As a result, two vibrationally coupled electronic states depict charge-transfer scenarios whereas three coupled states arise for closed-shell reactions of non-degenerate molecules and seven states for the reactions implicated in the aromaticity of benzene. Previous diabatic treatments of closed-shell processes have considered only two arbitrarily chosen states as being critical, mapping these states to those for electron transfer. We show that such effective two-state diabatic models are feasible but involve renormalized electronic coupling and vibrational coupling parameters, with this renormalization being property dependent. With this caveat, diabatic models are shown to provide excellent descriptions of the spectroscopy and kinetics of the ammonia inversion reaction, proton transfer in N2H7(+), and aromaticity in benzene. This allows for the development of a single simple theory that can semi-quantitatively describe all of these chemical phenomena, as well as of course electron-transfer reactions. It forms a basis for understanding many technologically relevant aspects of chemical reactions, condensed-matter physics, chemical quantum entanglement, nanotechnology, and natural or artificial solar energy capture and conversion.

Electronic Transfer of School Records.

ERIC Educational Resources Information Center

Yeagley, Raymond

2001-01-01

Describes the electronic transfer of student records, notably the use of a Web-server named CHARLOTTE sponsored by the National Forum on Education Statistics and an Electronic Data Exchange system named SPEEDE/ExPRESS. (PKP)

Ru–protein–Co biohybrids designed for solar hydrogen production: understanding electron transfer pathways related to photocatalytic function† †Electronic supplementary information (ESI) available: Time traces of photocatalysis, additional EPR spectra and parameters, UV-visible spectroscopy data, and kinetic fits of TA traces. See DOI: 10.1039/c6sc03121h Click here for additional data file.

PubMed Central

Soltau, Sarah R.; Dahlberg, Peter D.; Niklas, Jens; Poluektov, Oleg G.; Mulfort, Karen L.

2016-01-01

A series of Ru–protein–Co biohybrids have been prepared using the electron transfer proteins ferredoxin (Fd) and flavodoxin (Fld) as scaffolds for photocatalytic hydrogen production. The light-generated charge separation within these hybrids has been monitored by transient optical and electron paramagnetic resonance spectroscopies. Two distinct electron transfer pathways are observed. The Ru–Fd–Co biohybrid produces up to 650 turnovers of H2 utilizing an oxidative quenching mechanism for Ru(ii)* and a sequential electron transfer pathway via the native [2Fe–2S] cluster to generate a Ru(iii)–Fd–Co(i) charge separated state that lasts for ∼6 ms. In contrast, a direct electron transfer pathway occurs for the Ru–ApoFld–Co biohybrid, which lacks an internal electron relay, generating Ru(i)–ApoFld–Co(i) charge separated state that persists for ∼800 μs and produces 85 turnovers of H2 by a reductive quenching mechanism for Ru(ii)*. This work demonstrates the utility of protein architectures for linking donor and catalytic function via direct or sequential electron transfer pathways to enable stabilized charge separation which facilitates photocatalysis for solar fuel production. PMID:28451142

Cumulative reports and publications through December 31, 1990

NASA Technical Reports Server (NTRS)

1991-01-01

This document contains a complete list of ICASE reports. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

Cumulative reports and publications through December 31, 1986

NASA Technical Reports Server (NTRS)

1987-01-01

This document contains a complete list of ICASE Reports. Since ICASE Reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

Cumulative reports and publications through December 31, 1988

NASA Technical Reports Server (NTRS)

1989-01-01

This document contains a complete list of ICASE Reports. Since ICASE Reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

Oxygen equipment and rapid decompression studies.

DOT National Transportation Integrated Search

1979-03-01

This is a collection of reports of evaluations of the protective capability of various oxygen systems at high altitude and during rapid decompression. Results of these studies were presented at scientific meetings and/or published in preprints or pro...

Cumulative reports and publications through December 31, 1993

NASA Technical Reports Server (NTRS)

1994-01-01

This document contains a complete list of ICASE reports. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

Production of vibrationally excited N 2 by electron impact

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Cartwright, D. C.; Teubner, P. J. O.

2004-08-01

Energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N 2 in this is particularly significant. We report here the results from a new calculation of electron energy transfer rates ( Q) for vibrational excitation of N 2, as a function of the electron temperature Te. The present study was motivated by the development of a new cross-section compilation for vibrational excitation processes in N 2 which supercedes those used in the earlier calculations of the electron energy transfer rates. We show that the energy dependence and magnitude of these cross sections, particularly in the region of the well-known 2Π g resonance in N 2, significantly affect the calculated values of Q. A detailed comparison between the current and previous calculated electron energy transfer rates is made and coefficients are provided so that these rates for transitions from level 0 to levels 1-10 can be calculated for electron temperatures less than 6000 K.

Photogeneration of Charge Carriers in Bilayer Assemblies of Conjugated Rigid-Rod Polymers

DTIC Science & Technology

1994-07-08

photoinduced electron transfer and exciplex formation at the bilayer interface. Thus photocarrier generation on photoexcitation of the conjugated rigid...rod polymers in the bilayer occurs by photoinduced electron transfer, forming intermolecular exciplexes which dissociate efficiently in electric field...photogeneration, conjugated rigid-rod polymers, is. MACI COD bilayer assemblies, electron transfer, exciplexes . 11. SEOJUTY CLASUICA 10. 51(11MIE CLASSIMIAVION

Telematics and satellites. Part 1: Information systems

NASA Astrophysics Data System (ADS)

Burke, W. R.

1980-06-01

Telematic systems are identified and described. The applications are examined emphasizing the role played by satellite links. The discussion includes file transfer, examples of distributed processor systems, terminal communication, information retrieval systems, office information systems, electronic preparation and publishing of information, electronic systems for transfer of funds, electronic mail systems, record file transfer characteristics, intra-enterprise networks, and inter-enterprise networks.

Is back-electron transfer process in Betaine-30 coherent?

NASA Astrophysics Data System (ADS)

Rafiq, Shahnawaz; Scholes, Gregory D.

2017-09-01

The possible role of coherent vibrational motion in ultrafast photo-induced electron transfer remains unclear despite considerable experimental and theoretical advances. We revisited this problem by tracking the back-electron transfer (bET) process in Betaine-30 with broadband pump-probe spectroscopy. Dephasing time constant of certain high-frequency vibrations as a function of solvent shows a trend similar to the ET rates. In the purview of Bixon-Jortner model, high-frequency quantum vibrations bridge the reactant-product energy gap by providing activationless vibronic channels. Such interaction reduces the effective coupling significantly and thereby the coherence effects are eliminated due to energy gap fluctuations, making the back-electron transfer incoherent.

Modeling time-coincident ultrafast electron transfer and solvation processes at molecule-semiconductor interfaces

NASA Astrophysics Data System (ADS)

Li, Lesheng; Giokas, Paul G.; Kanai, Yosuke; Moran, Andrew M.

2014-06-01

Kinetic models based on Fermi's Golden Rule are commonly employed to understand photoinduced electron transfer dynamics at molecule-semiconductor interfaces. Implicit in such second-order perturbative descriptions is the assumption that nuclear relaxation of the photoexcited electron donor is fast compared to electron injection into the semiconductor. This approximation breaks down in systems where electron transfer transitions occur on 100-fs time scale. Here, we present a fourth-order perturbative model that captures the interplay between time-coincident electron transfer and nuclear relaxation processes initiated by light absorption. The model consists of a fairly small number of parameters, which can be derived from standard spectroscopic measurements (e.g., linear absorbance, fluorescence) and/or first-principles electronic structure calculations. Insights provided by the model are illustrated for a two-level donor molecule coupled to both (i) a single acceptor level and (ii) a density of states (DOS) calculated for TiO2 using a first-principles electronic structure theory. These numerical calculations show that second-order kinetic theories fail to capture basic physical effects when the DOS exhibits narrow maxima near the energy of the molecular excited state. Overall, we conclude that the present fourth-order rate formula constitutes a rigorous and intuitive framework for understanding photoinduced electron transfer dynamics that occur on the 100-fs time scale.

Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms▿ †

PubMed Central

Marsili, Enrico; Rollefson, Janet B.; Baron, Daniel B.; Hozalski, Raymond M.; Bond, Daniel R.

2008-01-01

While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 μm) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes. At low scan rates, cyclic voltammetry revealed catalytic electron transfer between cells and the electrode, similar to what has been observed for pure enzymes attached to electrodes under continuous turnover conditions. Differential pulse voltammetry and electrochemical impedance spectroscopy also revealed features that were consistent with electron transfer being mediated by an adsorbed catalyst. Multiple redox-active species were detected, revealing complexity at the outer surfaces of this bacterium. These techniques provide the basis for cataloging quantifiable, defined electron transfer phenotypes as a function of potential, electrode material, growth phase, and culture conditions and provide a framework for comparisons with other species or communities. PMID:18849456

Real-time electron transfer in respiratory complex I

PubMed Central

Verkhovskaya, Marina L.; Belevich, Nikolai; Euro, Liliya; Wikström, Mårten; Verkhovsky, Michael I.

2008-01-01

Electron transfer in complex I from Escherichia coli was investigated by an ultrafast freeze-quench approach. The reaction of complex I with NADH was stopped in the time domain from 90 μs to 8 ms and analyzed by electron paramagnetic resonance (EPR) spectroscopy at low temperatures. The data show that after binding of the first molecule of NADH, two electrons move via the FMN cofactor to the iron–sulfur (Fe/S) centers N1a and N2 with an apparent time constant of ≈90 μs, implying that these two centers should have the highest redox potential in the enzyme. The rate of reduction of center N2 (the last center in the electron transfer sequence) is close to that predicted by electron transfer theory, which argues for the absence of coupled proton transfer or conformational changes during electron transfer from FMN to N2. After fast reduction of N1a and N2, we observe a slow, ≈1-ms component of reduction of other Fe/S clusters. Because all elementary electron transfer rates between clusters are several orders of magnitude higher than this observed rate, we conclude that the millisecond component is limited by a single process corresponding to dissociation of the oxidized NAD+ molecule from its binding site, where it prevents entry of the next NADH molecule. Despite the presence of approximately one ubiquinone per enzyme molecule, no transient semiquinone formation was observed, which has mechanistic implications, suggesting a high thermodynamic barrier for ubiquinone reduction to the semiquinone radical. Possible consequences of these findings for the proton translocation mechanism are discussed. PMID:18316732

Dexter energy transfer pathways

PubMed Central

Skourtis, Spiros S.; Liu, Chaoren; Antoniou, Panayiotis; Virshup, Aaron M.; Beratan, David N.

2016-01-01

Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor–acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways. PMID:27382185

Dexter energy transfer pathways.

PubMed

Skourtis, Spiros S; Liu, Chaoren; Antoniou, Panayiotis; Virshup, Aaron M; Beratan, David N

2016-07-19

Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor-acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways.

Effect of proton transfer on the electronic coupling in DNA

NASA Astrophysics Data System (ADS)

Rak, Janusz; Makowska, Joanna; Voityuk, Alexander A.

2006-06-01

The effects of single and double proton transfer within Watson-Crick base pairs on donor-acceptor electronic couplings, Vda, in DNA are studied on the bases of quantum chemical calculations. Four dimers [AT,AT], [GC,GC], [GC,AT] and [GC,TA)] are considered. Three techniques - the generalized Mulliken-Hush scheme, the fragment charge method and the diabatic states method - are employed to estimate Vda for hole transfer between base pairs. We show that both single- and double proton transfer (PT) reactions may substantially affect the electronic coupling in DNA. The electronic coupling in [AT,AT] is predicted to be most sensitive to PT. Single PT within the first base pair in the dimer leads to increase in the hole transfer efficiency by a factor of 4, while proton transfer within the second pair should substantially, by 2.7 times, decrease the rate of charge transfer. Thus, directional asymmetry of the PT effects on the electronic coupling is predicted. The changes in the Vda matrix elements correlate with the topological properties of orbitals of donor and acceptor and can be qualitatively rationalized in terms of resonance structures of donor and acceptor. Atomic pair contributions to the Vda matrix elements are also analyzed.

Ultrafast electron and hole transfer dynamics of a solar cell dye containing hole acceptors on mesoporous TiO2 and Al2O3.

PubMed

Scholz, Mirko; Flender, Oliver; Boschloo, Gerrit; Oum, Kawon; Lenzer, Thomas

2017-03-08

The stability of dye cations against recombination with conduction band electrons in mesoporous TiO 2 electrodes is a key property for improving light harvesting in dye-sensitised solar cells. Using ultrafast transient broadband absorption spectroscopy, we monitor efficient intramolecular hole transfer in the solar cell dye E6 having two peripheral triarylamine acceptors. After photoexcitation, two hole transfer mechanisms are identified: a concerted mechanism for electron injection and hole transfer (2.4 ps) and a sequential mechanism with time constants of 3.9 ps and 30 ps. This way the dye retards unwanted recombination with a TiO 2 conduction band electron by quickly moving the hole further away from the surface. Contact of the E6/TiO 2 surface with the solvent acetonitrile has almost no influence on the electron injection and hole transfer kinetics. Fast hole transfer (2.8 ps) is also observed on a "non-injecting" Al 2 O 3 surface generating a radical cation-radical anion species with a lifetime of 530 ps. The findings confirm the good intramolecular hole transfer properties of this dye on both thin films. In contrast, intramolecular hole transfer does not occur in the mid-polar organic solvent methyl acetate. This is confirmed by TDDFT calculations suggesting a polarity-induced reduction of the driving force for hole transfer. In methyl acetate, only the relaxation of the initially photoexcited core chromophore is observed including solvent relaxation processes of the electronically excited state S 1 /ICT.

Electronic Data Interchange: Using Technology to Exchange Transcripts.

ERIC Educational Resources Information Center

Stewart, John T.

1994-01-01

Describes the Florida Automated System for Transferring Educational Records (FASTER) project, which permits the electronic exchange of student transcripts; uses of similar electronic data interchange (EDI) programs in other states; and the national SPEEDE/ExPRESS project, which uses a standard format for transferring electronic transcripts.…

Electronic coupling in long-range electron transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newton, M.D.

1996-12-31

One of the quantities crucial in controlling electron transfer (et) kinetics is the donor/acceptor electronic coupling integral (HDA). Recent theoretical models for HDA will be presented, and the results of ab initio computational implementation will be reported and analyzed for several metal-to-metal ligand charge transfer processes in complex molecular aggregates. New procedures for defining diabatic states, including a generalization of the Mulliken-Hush model, allow applications to optical and excited state as well as ground state et in a many-state framework.

Electron transfer statistics and thermal fluctuations in molecular junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goswami, Himangshu Prabal; Harbola, Upendra

2015-02-28

We derive analytical expressions for probability distribution function (PDF) for electron transport in a simple model of quantum junction in presence of thermal fluctuations. Our approach is based on the large deviation theory combined with the generating function method. For large number of electrons transferred, the PDF is found to decay exponentially in the tails with different rates due to applied bias. This asymmetry in the PDF is related to the fluctuation theorem. Statistics of fluctuations are analyzed in terms of the Fano factor. Thermal fluctuations play a quantitative role in determining the statistics of electron transfer; they tend tomore » suppress the average current while enhancing the fluctuations in particle transfer. This gives rise to both bunching and antibunching phenomena as determined by the Fano factor. The thermal fluctuations and shot noise compete with each other and determine the net (effective) statistics of particle transfer. Exact analytical expression is obtained for delay time distribution. The optimal values of the delay time between successive electron transfers can be lowered below the corresponding shot noise values by tuning the thermal effects.« less

Extracellular electron transfer mechanisms between microorganisms and minerals.

PubMed

Shi, Liang; Dong, Hailiang; Reguera, Gemma; Beyenal, Haluk; Lu, Anhuai; Liu, Juan; Yu, Han-Qing; Fredrickson, James K

2016-10-01

Electrons can be transferred from microorganisms to multivalent metal ions that are associated with minerals and vice versa. As the microbial cell envelope is neither physically permeable to minerals nor electrically conductive, microorganisms have evolved strategies to exchange electrons with extracellular minerals. In this Review, we discuss the molecular mechanisms that underlie the ability of microorganisms to exchange electrons, such as c-type cytochromes and microbial nanowires, with extracellular minerals and with microorganisms of the same or different species. Microorganisms that have extracellular electron transfer capability can be used for biotechnological applications, including bioremediation, biomining and the production of biofuels and nanomaterials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A; Gardel, EJ; Vidoudez, C

Oxidation-reduction reactions underlie energy generation in nearly all life forms. Although most organisms use soluble oxidants and reductants, some microbes can access solid-phase materials as electron-acceptors or -donors via extracellular electron transfer. Many studies have focused on the reduction of solid-phase oxidants. Far less is known about electron uptake via microbial extracellular electron transfer, and almost nothing is known about the associated mechanisms. Here we show that the iron-oxidizing photoautotroph Rhodopseudomonas palustris TIE-1 accepts electrons from a poised electrode, with carbon dioxide as the sole carbon source/electron acceptor. Both electron uptake and ruBisCo form I expression are stimulated by light.more » Electron uptake also occurs in the dark, uncoupled from photosynthesis. Notably, the pioABC operon, which encodes a protein system essential for photoautotrophic growth by ferrous iron oxidation, influences electron uptake. These data reveal a previously unknown metabolic versatility of photoferrotrophs to use extracellular electron transfer for electron uptake.« less

77 FR 10373 - Greenhouse Gas Reporting Program: Electronics Manufacturing: Revisions to Heat Transfer Fluid...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-22

... Greenhouse Gas Reporting Program: Electronics Manufacturing: Revisions to Heat Transfer Fluid Provisions... technical revisions to the electronics manufacturing source category of the Greenhouse Gas Reporting Rule... related to the electronics manufacturing source category. DATES: This rule will be effective on March 23...

12 CFR 1005.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... TRANSFERS (REGULATION E) General § 1005.9 Receipts at electronic terminals; periodic statements. (a... institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following information, as applicable...

12 CFR 1005.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... TRANSFERS (REGULATION E) General § 1005.9 Receipts at electronic terminals; periodic statements. (a... institution shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following information, as applicable...

12 CFR 1005.9 - Receipts at electronic terminals; periodic statements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... TRANSFERS (REGULATION E) § 1005.9 Receipts at electronic terminals; periodic statements. (a) Receipts at... shall make a receipt available to a consumer at the time the consumer initiates an electronic fund transfer at an electronic terminal. The receipt shall set forth the following information, as applicable...

78 FR 48913 - Agency Information Collection Activities: Submission to OMB for Reinstatement, Without Change, of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-12

... electronic funds transfer information to maintain its vendor (credit union) records to make electronic... maintain current electronic funds transfer data for its vendor (credit union) electronic routing and... the information on the respondents such as through the use of automated collection techniques or other...

Rapid electron transfer by the carbon matrix in natural pyrogenic carbon

PubMed Central

Sun, Tianran; Levin, Barnaby D. A.; Guzman, Juan J. L.; Enders, Akio; Muller, David A.; Angenent, Largus T.; Lehmann, Johannes

2017-01-01

Surface functional groups constitute major electroactive components in pyrogenic carbon. However, the electrochemical properties of pyrogenic carbon matrices and the kinetic preference of functional groups or carbon matrices for electron transfer remain unknown. Here we show that environmentally relevant pyrogenic carbon with average H/C and O/C ratios of less than 0.35 and 0.09 can directly transfer electrons more than three times faster than the charging and discharging cycles of surface functional groups and have a 1.5 V potential range for biogeochemical reactions that invoke electron transfer processes. Surface functional groups contribute to the overall electron flux of pyrogenic carbon to a lesser extent with greater pyrolysis temperature due to lower charging and discharging capacities, although the charging and discharging kinetics remain unchanged. This study could spur the development of a new generation of biogeochemical electron flux models that focus on the bacteria–carbon–mineral conductive network. PMID:28361882

Cumulative reports and publications through December 31, 1987

NASA Technical Reports Server (NTRS)

1988-01-01

This document contains a complete list of Institute for Computer Applications in Science and Engineering (ICASE) Reports. Since ICASE Reports are preprints of articles to be published in journals or conference proceeding, the published reference is included when available.

Hiding Crimes in Cyberspace (PREPRINT)

DTIC Science & Technology

1999-07-01

enforcement agencies have encountered encrypted e-mail and files in investigations of pedophiles and child pornography, including the FBI’s Innocent Images...for sexually assaulting minors and distributing child pornography (Akdeniz). The priest was part of an international pedophile ring that

Hybrid fusions show that inter-monomer electron transfer robustly supports cytochrome bc{sub 1} function in vivo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekiert, Robert; Czapla, Monika; Sarewicz, Marcin

2014-08-22

Highlights: • We used hybrid fusion bc{sub 1} complex to test inter-monomer electron transfer in vivo. • Cross-inactivated complexes were able to sustain photoheterotrophic growth. • Inter-monomer electron transfer supports catalytic cycle in vivo. • bc{sub 1} dimer is functional even when cytochrome b subunits come from different species. - Abstract: Electronic connection between Q{sub o} and Q{sub i} quinone catalytic sites of dimeric cytochrome bc{sub 1} is a central feature of the energy-conserving Q cycle. While both the intra- and inter-monomer electron transfers were shown to connect the sites in the enzyme, mechanistic and physiological significance of the lattermore » remains unclear. Here, using a series of mutated hybrid cytochrome bc{sub 1}-like complexes, we show that inter-monomer electron transfer robustly sustains the function of the enzyme in vivo, even when the two subunits in a dimer come from different species. This indicates that minimal requirement for bioenergetic efficiency is to provide a chain of cofactors for uncompromised electron flux between the catalytic sites, while the details of protein scaffold are secondary.« less

Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

PubMed Central

Petrenko, Alexander; Stein, Matthias

2017-01-01

Biohydrogen is a versatile energy carrier for the generation of electric energy from renewable sources. Hydrogenases can be used in enzymatic fuel cells to oxidize dihydrogen. The rate of electron transfer (ET) at the anodic side between the [NiFe]-hydrogenase enzyme distal iron–sulfur cluster and the electrode surface can be described by the Marcus equation. All parameters for the Marcus equation are accessible from Density Functional Theory (DFT) calculations. The distal cubane FeS-cluster has a three-cysteine and one-histidine coordination [Fe4S4](His)(Cys)3 first ligation sphere. The reorganization energy (inner- and outer-sphere) is almost unchanged upon a histidine-to-cysteine substitution. Differences in rates of electron transfer between the wild-type enzyme and an all-cysteine mutant can be rationalized by a diminished electronic coupling between the donor and acceptor molecules in the [Fe4S4](Cys)4 case. The fast and efficient electron transfer from the distal iron–sulfur cluster is realized by a fine-tuned protein environment, which facilitates the flow of electrons. This study enables the design and control of electron transfer rates and pathways by protein engineering. PMID:28067774

Electron transfer mediators accelerated the microbiologically influence corrosion against carbon steel by nitrate reducing Pseudomonas aeruginosa biofilm.

PubMed

Jia, Ru; Yang, Dongqing; Xu, Dake; Gu, Tingyue

2017-12-01

Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10ppm (w/w) (26.6μM) riboflavin or 10ppm (12.7μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5μm to 24.4μm and 25.0μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06mg/cm 2 to 2.34mg/cm 2 and 2.61mg/cm 2 , respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data. Copyright © 2017 Elsevier B.V. All rights reserved.

Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

NASA Technical Reports Server (NTRS)

Fischer, U.

1985-01-01

Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

Frenkel versus charge-transfer exciton dispersion in molecular crystals

NASA Astrophysics Data System (ADS)

Cudazzo, Pierluigi; Gatti, Matteo; Rubio, Angel; Sottile, Francesco

2013-11-01

By solving the many-body Bethe-Salpeter equation at finite momentum transfer, we characterize the exciton dispersion in two prototypical molecular crystals, picene and pentacene, in which localized Frenkel excitons compete with delocalized charge-transfer excitons. We explain the exciton dispersion on the basis of the interplay between electron and hole hopping and electron-hole exchange interaction, unraveling a simple microscopic description to distinguish Frenkel and charge-transfer excitons. This analysis is general and can be applied to other systems in which the electron wave functions are strongly localized, as in strongly correlated insulators.

Extracellular Electron Uptake: Among Autotrophs and Mediated by Surfaces.

PubMed

Tremblay, Pier-Luc; Angenent, Largus T; Zhang, Tian

2017-04-01

Autotrophic microbes can acquire electrons from solid donors such as steel, other microbial cells, or electrodes. Based on this feature, bioprocesses are being developed for the microbial electrosynthesis (MES) of useful products from the greenhouse gas CO 2 . Extracellular electron-transfer mechanisms involved in the acquisition of electrons from metals by electrical microbially influenced corrosion (EMIC), from other living cells by interspecies electron transfer (IET), or from an electrode during MES rely on: (i) mediators such as H 2 ; (ii) physical contact through electron-transfer proteins; or (iii) mediator-generating enzymes detached from cells. This review explores the interactions of autotrophs with solid electron donors and their importance in nature and for biosustainable technologies. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Electronic Flux in Chemical Reactions. Insights on the Mechanism of the Maillard Reaction

NASA Astrophysics Data System (ADS)

Flores, Patricio; Gutiérrez-Oliva, Soledad; Herrera, Bárbara; Silva, Eduardo; Toro-Labbé, Alejandro

2007-11-01

The electronic transfer that occurs during a chemical process is analysed in term of a new concept, the electronic flux, that allows characterizing the regions along the reaction coordinate where electron transfer is actually taking place. The electron flux is quantified through the variation of the electronic chemical potential with respect to the reaction coordinate and is used, together with the reaction force, to shed light on reaction mechanism of the Schiff base formation in the Maillard reaction. By partitioning the reaction coordinate in regions in which different process might be taking place, electronic reordering associated to polarization and transfer has been identified and found to be localized at specific transition state regions where most bond forming and breaking occur.

A molecular Debye-Hückel approach to the reorganization energy of electron transfer reactions in an electric cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Tiejun; Department of Chemistry, Iowa State University, Ames, Iowa 50011; Song, Xueyu

2014-10-07

Electron transfer near an electrode immersed in ionic fluids is studied using the linear response approximation, namely, mean value of the vertical energy gap can be used to evaluate the reorganization energy, and hence any linear response model that can treat Coulomb interactions successfully can be used for the reorganization energy calculation. Specifically, a molecular Debye-Hückel theory is used to calculate the reorganization energy of electron transfer reactions in an electric cell. Applications to electron transfer near an electrode in molten salts show that the reorganization energies from our molecular Debye-Hückel theory agree well with the results from MD simulations.

Studying electron transfer through alkanethiol self-assembled monolayers on a hanging mercury drop electrode using potentiometric measurements.

PubMed

Cohen-Atiya, Meirav; Mandler, Daniel

2006-10-14

A new approach based on measuring the change of the open-circuit potential (OCP) of a hanging mercury drop electrode (HMDE), modified with alkanethiols of different chain length conducted in a solution containing a mixture of Ru(NH3)6(2+) and Ru(NH3)6(3+) is used for studying electron transfer across the monolayer. Following the time dependence of the OCP allowed the extraction of the kinetic parameters, such as the charge transfer resistance (R(ct)) and the electron transfer rate constant (k(et)), for different alkanethiol monolayers. An electron tunneling coefficient, beta, of 0.9 A(-1) was calculated for the monolayers on Hg.

Photoinduced Bimolecular Electron Transfer in Ionic Liquids: Cationic Electron Donors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Boning; Liang, Min; Zmich, Nicole

Recently, we have reported a systematic study of photoinduced electron-transfer reactions in ionic liquid solvents using neutral and anionic electron donors and a series of cyano-substituted anthracene acceptors [Wu, B.; Maroncelli, M.; Castner, E. W., Jr.Photoinduced Bimolecular Electron Transfer in Ionic Liquids. J. Am. Chem. Soc.139, 2017, 14568]. In this paper, we report complementary results for a cationic class of 1-alkyl-4-dimethylaminopyridinium electron donors. Reductive quenching of cyano-substituted anthracene fluorophores by these cationic quenchers is studied in solutions of acetonitrile and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Varying the length of the alkyl chain permits tuning of the quencher diffusivities in solution.more » The observed quenching kinetics are interpreted using a diffusion-reaction analysis. Finally, together with results from the prior study, these results show that the intrinsic electron-transfer rate constant does not depend on the quencher charge in this family of reactions.« less

Photoinduced Bimolecular Electron Transfer in Ionic Liquids: Cationic Electron Donors

DOE PAGES

Wu, Boning; Liang, Min; Zmich, Nicole; ...

2018-01-29

Recently, we have reported a systematic study of photoinduced electron-transfer reactions in ionic liquid solvents using neutral and anionic electron donors and a series of cyano-substituted anthracene acceptors [Wu, B.; Maroncelli, M.; Castner, E. W., Jr.Photoinduced Bimolecular Electron Transfer in Ionic Liquids. J. Am. Chem. Soc.139, 2017, 14568]. In this paper, we report complementary results for a cationic class of 1-alkyl-4-dimethylaminopyridinium electron donors. Reductive quenching of cyano-substituted anthracene fluorophores by these cationic quenchers is studied in solutions of acetonitrile and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Varying the length of the alkyl chain permits tuning of the quencher diffusivities in solution.more » The observed quenching kinetics are interpreted using a diffusion-reaction analysis. Finally, together with results from the prior study, these results show that the intrinsic electron-transfer rate constant does not depend on the quencher charge in this family of reactions.« less

Feasibility study of electron transfer quantum well infrared photodetectors for spectral tuning in the long-wave infrared band

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jolley, Greg; Dehdashti Akhavan, Nima; Umana-Membreno, Gilberto

An electron transfer quantum well infrared photodetector (QWIP) consisting of repeating units of two coupled quantum wells (QWs) is capable of exhibiting a two color voltage dependent spectral response. However, significant electron transfer between the coupled QWs is required for spectral tuning, which may require the application of relatively high electric fields. Also, the band structure of coupled quantum wells is more complicated in comparison to a regular quantum well and, therefore, it is not always obvious if an electron transfer QWIP can be designed such that it meets specific performance characteristics. This paper presents a feasibility study of themore » electron transfer QWIP and its suitability for spectral tuning. Self consistent calculations have been performed of the bandstructure and the electric field that results from electron population within the quantum wells, from which the optical characteristics have been obtained. The band structure, spectral response, and the resonant final state energy locations have been compared with standard QWIPs. It is shown that spectral tuning in the long-wave infrared band can be achieved over a wide wavelength range of several microns while maintaining a relatively narrow spectral response FWHM. However, the total absorption strength is more limited in comparison to a standard QWIP, since the higher QW doping densities require much higher electric fields for electron transfer.« less

Toddlers' word learning and transfer from electronic and print books.

PubMed

Strouse, Gabrielle A; Ganea, Patricia A

2017-04-01

Transfer from symbolic media to the real world can be difficult for young children. A sample of 73 toddlers aged 17 to 23months were read either an electronic book displayed on a touchscreen device or a traditional print book in which a novel object was paired with a novel label. Toddlers in both conditions learned the label within the context of the book. However, only those who read the traditional format book generalized and transferred the label to other contexts. An older group of 28 toddlers aged 24 to 30months did generalize and transfer from the electronic book. Across ages, those children who primarily used screens to watch prerecorded video at home transferred less from the electronic book than those with more diverse home media experiences. Copyright © 2016 Elsevier Inc. All rights reserved.

Interplay between barrier width and height in electron tunneling: photoinduced electron transfer in porphyrin-based donor-bridge-acceptor systems.

PubMed

Pettersson, Karin; Wiberg, Joanna; Ljungdahl, Thomas; Mårtensson, Jerker; Albinsson, Bo

2006-01-12

The rate of electron tunneling in molecular donor-bridge-acceptor (D-B-A) systems is determined both by the tunneling barrier width and height, that is, both by the distance between the donor and acceptor as well as by the energy gap between the donor and bridge moieties. These factors are therefore important to control when designing functional electron transfer systems, such as constructs for photovoltaics, artificial photosynthesis, and molecular scale electronics. In this paper we have investigated a set of D-B-A systems in which the distance and the energy difference between the donor and bridge states (DeltaEDB) are systematically varied. Zinc(II) and gold(III) porphyrins were chosen as electron donor and acceptor because of their suitable driving force for photoinduced electron transfer (-0.9 eV in butyronitrile) and well-characterized photophysics. We have previously shown, in accordance with the superexchange mechanism for electron transfer, that the electron transfer rate is proportional to the inverse of DeltaEDB in a series of zinc/gold porphyrin D-B-A systems with bridges of constant edge to edge distance (19.6 A) and varying DeltaEDB (3900-17 600 cm(-1)). Here, we use the same donor and acceptor but the bridge is shortened or extended giving a set of oligo-p-phenyleneethynylene bridges (OPE) with four different edge to edge distances ranging from 12.7 to 33.4 A. These two sets of D-B-A systems-ZnP-RB-AuP+ and ZnP-nB-AuP+-have one bridge in common, and hence, for the first time both the distance and DeltaEDB dependence of electron transfer can be studied simultaneously in a systematic way.

Electron transfer dynamics and yield from gold nanoparticle to different semiconductors induced by plasmon band excitation

NASA Astrophysics Data System (ADS)

Du, L. C.; Xi, W. D.; Zhang, J. B.; Matsuzaki, H.; Furube, A.

2018-06-01

Photoinduced electron transfer from gold nanoparticles (NPs) to semiconductor under plasmon excitation is an important phenomenon in photocatalysis and solar cell applications. Femtosecond plasmon-induced electron transfer from gold NPs to the conduction band of different semiconductor like TiO2, SnO2, and ZnO was monitored at 3440 nm upon optical excitation of the surface plasmon band of gold NPs. It was found that electron injection was completed within 240 fs and the electron injection yield reached 10-30% under 570 nm excitation. It means TiO2 is not the only proper semiconductor as electron acceptors in such gold/semiconductor nanoparticle systems.

Probing the coupling between proton and electron transfer in Photosystem II core complexes containing a 3-fluorotyrosine

PubMed Central

Rappaport, Fabrice; Boussac, Alain; Force, Dee Ann; Peloquin, Jeffrey; Brynda, Marcin; Sugiura, Miwa; Un, Sun; Britt, R. David; Diner, Bruce A.

2009-01-01

The catalytic cycle of numerous enzymes involves the coupling between proton transfer and electron transfer. Yet, the understanding of this coordinated transfer in biological systems remains limited, likely because its characterization relies on the controlled but experimentally challenging modifications of the free energy changes associated with either the electron or proton transfer. We have performed such a study here in Photosystem II. The driving force for electron transfer from TyrZ to P680•+ has been decreased by ~ 80 meV by mutating the axial ligand of P680, and that for proton transfer upon oxidation of TyrZ by substituting a 3-fluorotyrosine (3F-TyrZ) for TyrZ. In Mn-depleted Photosystem II, the dependence upon pH of the oxidation rates of TyrZ and 3F-TyrZ were found to be similar. However, in the pH range where the phenolic hydroxyl of TyrZ is involved in a H-bond with a proton acceptor, the activation energy of the oxidation of 3F-TyrZ is decreased by 110 meV, a value which correlates with the in vitro finding of a 90 meV stabilization energy to the phenolate form of 3F-Tyr when compared to Tyr (Seyedsayamdost et al., 2006, JACS 128:1569–79). Thus, when the phenol of YZ acts as a H-bond-donor, its oxidation by P680•+ is controlled by its prior deprotonation. This contrasts with the situation prevailing at lower pH, where the proton acceptor is protonated and therefore unavailable, in which the oxidation-induced proton transfer from the phenolic hydroxyl of TyrZ has been proposed to occur concertedly with the electron transfer to P680•+. This suggests a switch between a concerted proton/electron transfer at pHs < 7.5 to a sequential one at pHs > 7.5 and illustrates the roles of the H-bond and of the likely salt-bridge existing between the phenolate and the nearby proton acceptor in determining the coupling between proton and electron transfer. PMID:19265377

ZnO-nanorods/graphene heterostructure: a direct electron transfer glucose biosensor

NASA Astrophysics Data System (ADS)

Zhao, Yu; Li, Wenbo; Pan, Lijia; Zhai, Dongyuan; Wang, Yu; Li, Lanlan; Cheng, Wen; Yin, Wei; Wang, Xinran; Xu, Jian-Bin; Shi, Yi

2016-08-01

ZnO-nanorods/graphene heterostructure was synthesized by hydrothermal growth of ZnO nanorods on chemically reduced graphene (CRG) film. The hybrid structure was demonstrated as a biosensor, where direct electron transfer between glucose oxidase (GOD) and electrode was observed. The charge transfer was attributed to the ZnO nanorod wiring between the redox center of GOD and electrode, and the ZnO/graphene heterostructure facilitated the transport of electrons on the hybride electrode. The glucose sensor based on the GOD-ZnO/CRG/Pt electrode had a high sensitivity of 17.64 μA mM-1, which is higher than most of the previously reported values for direct electron transfer based glucose biosensors. Moreover, this biosensor is linearly proportional to the concentration of glucose in the range of 0.2-1.6 mM. The study revealed that the band structure of electrode could affect the detection of direct electron transfer of GOD, which would be helpful for the design of the biosensor electrodes in the future.

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

DOE PAGES

Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; ...

2014-10-08

Here, the hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We concludemore » that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.« less

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

PubMed Central

Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; Roubelakis, Manolis M.; Maher, Andrew G.; Lee, Chang Hoon; Chambers, Matthew B.; Hammes-Schiffer, Sharon; Nocera, Daniel G.

2014-01-01

The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring. PMID:25298534

Energy gap law of electron transfer in nonpolar solvents.

PubMed

Tachiya, M; Seki, Kazuhiko

2007-09-27

We investigate the energy gap law of electron transfer in nonpolar solvents for charge separation and charge recombination reactions. In polar solvents, the reaction coordinate is given in terms of the electrostatic potentials from solvent permanent dipoles at solutes. In nonpolar solvents, the energy fluctuation due to solvent polarization is absent, but the energy of the ion pair state changes significantly with the distance between the ions as a result of the unscreened strong Coulomb potential. The electron transfer occurs when the final state energy coincides with the initial state energy. For charge separation reactions, the initial state is a neutral pair state, and its energy changes little with the distance between the reactants, whereas the final state is an ion pair state and its energy changes significantly with the mutual distance; for charge recombination reactions, vice versa. We show that the energy gap law of electron-transfer rates in nonpolar solvents significantly depends on the type of electron transfer.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Chemical dynamics of the first proton-coupled electron transfer of water oxidation on TiO2 anatase.

PubMed

Chen, Jia; Li, Ye-Fei; Sit, Patrick; Selloni, Annabella

2013-12-18

Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

Extracellular enzymes facilitate electron uptake in biocorrosion and bioelectrosynthesis.

PubMed

Deutzmann, Jörg S; Sahin, Merve; Spormann, Alfred M

2015-04-21

Direct, mediator-free transfer of electrons between a microbial cell and a solid phase in its surrounding environment has been suggested to be a widespread and ecologically significant process. The high rates of microbial electron uptake observed during microbially influenced corrosion of iron [Fe(0)] and during microbial electrosynthesis have been considered support for a direct electron uptake in these microbial processes. However, the underlying molecular mechanisms of direct electron uptake are unknown. We investigated the electron uptake characteristics of the Fe(0)-corroding and electromethanogenic archaeon Methanococcus maripaludis and discovered that free, surface-associated redox enzymes, such as hydrogenases and presumably formate dehydrogenases, are sufficient to mediate an apparent direct electron uptake. In genetic and biochemical experiments, we showed that these enzymes, which are released from cells during routine culturing, catalyze the formation of H2 or formate when sorbed to an appropriate redox-active surface. These low-molecular-weight products are rapidly consumed by M. maripaludis cells when present, thereby preventing their accumulation to any appreciable or even detectable level. Rates of H2 and formate formation by cell-free spent culture medium were sufficient to explain the observed rates of methane formation from Fe(0) and cathode-derived electrons by wild-type M. maripaludis as well as by a mutant strain carrying deletions in all catabolic hydrogenases. Our data collectively show that cell-derived free enzymes can mimic direct extracellular electron transfer during Fe(0) corrosion and microbial electrosynthesis and may represent an ecologically important but so far overlooked mechanism in biological electron transfer. The intriguing trait of some microbial organisms to engage in direct electron transfer is thought to be widespread in nature. Consequently, direct uptake of electrons into microbial cells from solid surfaces is assumed to have a significant impact not only on fundamental microbial and biogeochemical processes but also on applied bioelectrochemical systems, such as microbial electrosynthesis and biocorrosion. This study provides a simple mechanistic explanation for frequently observed fast electron uptake kinetics in microbiological systems without a direct transfer: free, cell-derived enzymes can interact with cathodic surfaces and catalyze the formation of intermediates that are rapidly consumed by microbial cells. This electron transfer mechanism likely plays a significant role in various microbial electron transfer reactions in the environment. Copyright © 2015 Deutzmann et al.

Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis

DTIC Science & Technology

2016-07-08

AFRL-AFOSR-VA-TR-2016-0244 Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis Jahan Dawlaty UNIVERSITY OF SOUTHERN...TITLE AND SUBTITLE Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550...298 Back (Rev. 8/98) DISTRIBUTION A: Distribution approved for public release. Final Report: AFOSR YIP Grant FA9550-13-1-0128: Ultrafast Spectroscopy

Stimulated Electron Desorption Studies from Microwave Vacuum Electronics / High Power Microwave Materials

DTIC Science & Technology

2010-02-11

purchase a new gun. Mr. Mike Ackeret ( Transfer Engineering Inc.) Transfer Engineering’s expertise in specialty UHV work and machining propelled...modifications they helped design for the test stand. With UNLV guidance, Transfer Engineering designed and built the original UNLV SEE Test Stand...Staib electron gun, an isolated beam drift tube, a hexanode delay line with a chevron microchannel plate (MCP) stack, an isolated grid, an isolated

Electron-transfer and acid-base properties of a two-electron oxidized form of quaterpyrrole that acts as both an electron donor and an acceptor.

PubMed

Zhang, Min; E, Wenbo; Ohkubo, Kei; Sanchez-Garcia, David; Yoon, Dae-Wi; Sessler, Jonathan L; Fukuzumi, Shunichi; Kadish, Karl M

2008-02-21

Electron-transfer interconversion between the four-electron oxidized form of a quaterpyrrole (abbreviated as P4 for four pyrroles) and the two-electron oxidized form (P4H2) as well as between P4H2 and its fully reduced form (P4H4) bearing analogous substituents in the alpha- and beta-pyrrolic positions was studied by means of cyclic voltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysis measurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor. The radical cation (P4H2*+) and radical anion (P4H2*-) are both produced by photoinduced electron transfer from dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound is also produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2*+ and P4H2*- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, the two-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous to those seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2*+ and disproportionation of P4H2 were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reduction of P4H2, respectively.

Dependence of intramolecular electron-transfer rates on driving force, pH, and temperature in ammineruthenium-modified ferrocytochromes c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wishart, J.F.; Sun, J.; Su, C.

1997-01-23

Several ruthenium ammine complexes were used to modify horse-heart cytochrome c at histidine-33, creating a series of (NH{sub 3}){sub 4}(L)Ru-Cyt c derivatives (L = H{sub 2}O/OH{sup -}, ammonia, 4-ethylpyridine, 3,5-lutidine, pyridine, isonicotinamide, N-methylpyrazinium) with a wide range of driving forces for Fe-to-Ru electron transfer (-{Delta}G{degree} = -0.125 to +0.46 eV). Electron-transfer rates and activation parameters were measured by pulse radiolysis using azide or carbonate radicals. The driving-force dependence of electron-transfer rates between redox centers of the same charge types obeys Marcus-Hush theory. The activationless rate limit for all of the ruthenium derivatives except the N-methylpyrazinium complex is 3.9x10{sup 5} s{supmore » -1}. Thermodynamic parameters obtained from nonisothermal differential pulse voltammetry show that the electron-transfer reactions are entropy-driven. The thermodynamic and kinetic effects of phosphate ion binding to the ruthenium center are examined. The rate of intramolecular electron transfer in (NH{sub 3}){sub 4}(isn)Ru{sup III}-Cyt c{sup II} decreases at high pH, with a midpoint at pH 9.1. 28 refs., 4 figs., 3 tabs.« less

Excitation energy transfer in the photosystem I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webber, Andrew N

2012-09-25

Photosystem I is a multimeric pigment protein complex in plants, green alage and cyanobacteria that functions in series with Photosystem II to use light energy to oxidize water and reduce carbon dioxide. The Photosystem I core complex contains 96 chlorophyll a molecules and 22 carotenoids that are involved in light harvesting and electron transfer. In eucaryotes, PSI also has a peripheral light harvesting complex I (LHCI). The role of specific chlorophylls in excitation and electron transfer are still unresolved. In particular, the role of so-called bridging chlorophylls, located between the bulk antenna and the core electron transfer chain, in themore » transfer of excitation energy to the reaction center are unknown. During the past funding period, site directed mutagenesis has been used to create mutants that effect the physical properties of these key chlorophylls, and to explore how this alters the function of the photosystem. Studying these mutants using ultrafast absorption spectroscopy has led to a better understanding of the process by which excitation energy is transferred from the antenna chlorophylls to the electron transfer chain chlorophylls, and what the role of connecting chlorophylls and A_0 chlorophylls is in this process. We have also used these mutants to investigate whch of the central group of six chlorophylls are involved in the primary steps of charge separation and electron transfer.« less

Dynamics of charge-transfer excitons in type-II semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Stein, M.; Lammers, C.; Richter, P.-H.; Fuchs, C.; Stolz, W.; Koch, M.; Vänskä, O.; Weseloh, M. J.; Kira, M.; Koch, S. W.

2018-03-01

The formation, decay, and coherence properties of charge-transfer excitons in semiconductor heterostructures are investigated by applying four-wave-mixing and terahertz spectroscopy in combination with a predictive microscopic theory. A charge-transfer process is identified where the optically induced coherences decay directly into a charge-transfer electron-hole plasma and exciton states. It is shown that charge-transfer excitons are more sensitive to the fermionic electron-hole substructure than regular excitons.

36 CFR § 1235.44 - What general transfer requirements apply to electronic records?

Code of Federal Regulations, 2013 CFR

2013-07-01

... requirements apply to electronic records? § 1235.44 Section § 1235.44 Parks, Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION RECORDS MANAGEMENT TRANSFER OF RECORDS TO THE NATIONAL... requirements apply to electronic records? (a) Each agency must retain a copy of permanent electronic records...

Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

NASA Astrophysics Data System (ADS)

Perlík, Václav; Seibt, Joachim; Cranston, Laura J.; Cogdell, Richard J.; Lincoln, Craig N.; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

2015-06-01

The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.

Electron transfer from plastocyanin to photosystem I.

PubMed Central

Haehnel, W; Jansen, T; Gause, K; Klösgen, R B; Stahl, B; Michl, D; Huvermann, B; Karas, M; Herrmann, R G

1994-01-01

Mutant plastocyanins with Leu at position 10, 90 or 83 (Gly, Ala and Tyr respectively in wildtype) were constructed by site-specific mutagenesis of the spinach gene, and expressed in transgenic potato plants under the control of the authentic plastocyanin promoter, as well as in Escherichia coli as truncated precursor intermediates carrying the C-terminal 22 amino acid residues of the transit peptide, i.e. the thylakoid-targeting domain that acts as a bacterial export signal. The identity of the purified plastocyanins was verified by matrix-assisted laser desorption/ionization mass spectrometry. The formation of a complex between authentic or mutant spinach plastocyanin and isolated photosystem I and the electron transfer has been studied from the biphasic reduction kinetics of P700+ after excitation with laser flashes. The formation of the complex was abolished by the bulky hydrophobic group of Leu at the respective position of G10 or A90 which are part of the conserved flat hydrophobic surface around the copper ligand H87. The rate of electron transfer decreased by both mutations to < 20% of that found with wildtype plastocyanin. We conclude that the conserved flat surface of plastocyanin represents one of two crucial structural elements for both the docking at photosystem I and the efficient electron transfer via H87 to P700+. The Y83L mutant exhibited faster electron transfer to P700+ than did authentic plastocyanin. This proves that Y83 is not involved in electron transfer to P700 and suggests that electron transfer from cytochrome f and to P700 follows different routes in the plastocyanin molecule. Plastocyanin (Y83L) expressed in either E. coli or potato exhibited different isoelectric points and binding constants to photosystem I indicative of differences in the folding of the protein. The structure of the binding site at photosystem I and the mechanism of electron transfer are discussed. Images PMID:8131737

Some New Hypotheses Concerning Word Families in Chinese

ERIC Educational Resources Information Center

Pulleyblank, E. G.

1973-01-01

Revised version of a paper entitled Word Families in Chinese: A Reconsideration'' presented at the 28th International Congress of Orientalists, Canberra, Australia, January 1971, and published in preprint form in Unicorn'' n9 p1-19 Jan 1972. (VM)

Wind Power Forecasting Error Distributions over Multiple Timescales: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodge, B. M.; Milligan, M.

2011-03-01

In this paper, we examine the shape of the persistence model error distribution for ten different wind plants in the ERCOT system over multiple timescales. Comparisons are made between the experimental distribution shape and that of the normal distribution.

Cogging Torque Reduction in a Permanent Magnet Wind Turbine Generator: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, E.; Green, J.

2002-01-01

In this paper, we investigate three design options to minimize cogging torque: uniformity of air gap, pole width, and skewing. Although the design improvement is intended for small wind turbines, it is also applicable to larger wind turbines.

12 CFR 205.7 - Initial disclosures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... TRANSFERS (REGULATION E) § 205.7 Initial disclosures. (a) Timing of disclosures. A financial institution shall make the disclosures required by this section at the time a consumer contracts for an electronic fund transfer service or before the first electronic fund transfer is made involving the consumer's...

12 CFR 205.7 - Initial disclosures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... TRANSFERS (REGULATION E) § 205.7 Initial disclosures. (a) Timing of disclosures. A financial institution shall make the disclosures required by this section at the time a consumer contracts for an electronic fund transfer service or before the first electronic fund transfer is made involving the consumer's...

Extracellular electron transfer mechanisms between microorganisms and minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Liang; Dong, Hailiang; Reguera, Gemma

Electrons can be transferred from microorganisms to multivalent metal ions that are associated with minerals and vice versa. As the microbial cell envelope is neither physically permeable to minerals nor electrically conductive, microorganisms have evolved strategies to exchange electrons with extracellular minerals. In this Review, we discuss the molecular mechanisms that underlie the ability of microorganisms to exchange electrons, such as c-type cytochromes and microbial nanowires, with extracellular minerals and with microorganisms of the same or different species. Microorganisms that have extracellular electron transfer capability can be used for biotechnological applications, including bioremediation, biomining and the production of biofuels andmore » nanomaterials.« less

Quantum dynamical simulation of photoinduced electron transfer processes in dye-semiconductor systems: theory and application to coumarin 343 at TiO₂.

PubMed

Li, Jingrui; Kondov, Ivan; Wang, Haobin; Thoss, Michael

2015-04-10

A recently developed methodology to simulate photoinduced electron transfer processes at dye-semiconductor interfaces is outlined. The methodology employs a first-principles-based model Hamiltonian and accurate quantum dynamics simulations using the multilayer multiconfiguration time-dependent Hartree approach. This method is applied to study electron injection in the dye-semiconductor system coumarin 343-TiO2. Specifically, the influence of electronic-vibrational coupling is analyzed. Extending previous work, we consider the influence of Dushinsky rotation of the normal modes as well as anharmonicities of the potential energy surfaces on the electron transfer dynamics.

Global fully kinetic models of planetary magnetospheres with iPic3D

NASA Astrophysics Data System (ADS)

Gonzalez, D.; Sanna, L.; Amaya, J.; Zitz, A.; Lembege, B.; Markidis, S.; Schriver, D.; Walker, R. J.; Berchem, J.; Peng, I. B.; Travnicek, P. M.; Lapenta, G.

2016-12-01

We report on the latest developments of our approach to model planetary magnetospheres, mini magnetospheres and the Earth's magnetosphere with the fully kinetic, electromagnetic particle in cell code iPic3D. The code treats electrons and multiple species of ions as full kinetic particles. We review: 1) Why a fully kinetic model and in particular why kinetic electrons are needed for capturing some of the most important aspects of the physics processes of planetary magnetospheres. 2) Why the energy conserving implicit method (ECIM) in its newest implementation [1] is the right approach to reach this goal. We consider the different electron scales and study how the new IECIM can be tuned to resolve only the electron scales of interest while averaging over the unresolved scales preserving their contribution to the evolution. 3) How with modern computing planetary magnetospheres, mini magnetosphere and eventually Earth's magnetosphere can be modeled with fully kinetic electrons. The path from petascale to exascale for iPiC3D is outlined based on the DEEP-ER project [2], using dynamic allocation of different processor architectures (Xeon and Xeon Phi) and innovative I/O technologies.Specifically results from models of Mercury are presented and compared with MESSENGER observations and with previous hybrid (fluid electrons and kinetic ions) simulations. The plasma convection around the planets includes the development of hydrodynamic instabilities at the flanks, the presence of the collisionless shocks, the magnetosheath, the magnetopause, reconnection zones, the formation of the plasma sheet and the magnetotail, and the variation of ion/electron plasma flows when crossing these frontiers. Given the full kinetic nature of our approach we focus on detailed particle dynamics and distribution at locations that can be used for comparison with satellite data. [1] Lapenta, G. (2016). Exactly Energy Conserving Implicit Moment Particle in Cell Formulation. arXiv preprint arXiv:1602.06326.[2] www.deep-er.eu

Thermomechanical Modeling of Sintered Silver - A Fracture Mechanics-based Approach: Extended Abstract: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paret, Paul P; DeVoto, Douglas J; Narumanchi, Sreekant V

Sintered silver has proven to be a promising candidate for use as a die-attach and substrate-attach material in automotive power electronics components. It holds promise of greater reliability than lead-based and lead-free solders, especially at higher temperatures (less than 200 degrees Celcius). Accurate predictive lifetime models of sintered silver need to be developed and its failure mechanisms thoroughly characterized before it can be deployed as a die-attach or substrate-attach material in wide-bandgap device-based packages. We present a finite element method (FEM) modeling methodology that can offer greater accuracy in predicting the failure of sintered silver under accelerated thermal cycling. Amore » fracture mechanics-based approach is adopted in the FEM model, and J-integral/thermal cycle values are computed. In this paper, we outline the procedures for obtaining the J-integral/thermal cycle values in a computational model and report on the possible advantage of using these values as modeling parameters in a predictive lifetime model.« less

Safe and successful implementation of CPOE for chemotherapy at a children's cancer center.

PubMed

Hoffman, James M; Baker, Donald K; Howard, Scott C; Laver, Joseph H; Shenep, Jerry L

2011-02-01

Computerized prescriber order entry (CPOE) for medications has been implemented in only approximately 1 in 6 United States hospitals, with CPOE for chemotherapy lagging behind that for nonchemotherapy medications. The high risks associated with chemotherapy combined with other aspects of cancer care present unique challenges for the safe and appropriate use of CPOE. This article describes the process for safe and successful implementation of CPOE for chemotherapy at a children's cancer center. A core principle throughout the development and implementation of this system was that it must be as safe (and eventually safer) as existing paper systems and processes. The history of requiring standardized, regimen-specific, preprinted paper order forms served as the foundation for safe implementation of CPOE for chemotherapy. Extensive use of electronic order sets with advanced functionality; formal process redesign and system analysis; automated clinical decision support; and a phased implementation approach were essential strategies for safe implementation of CPOE. With careful planning and adequate resources, CPOE for chemotherapy can be safely implemented.

On the origin of red and blue shifts of X-H and C-H stretching vibrations in formic acid (formate ion) and proton donor complexes.

PubMed

Tâme Parreira, Renato Luis; Galembeck, Sérgio Emanuel; Hobza, Pavel

2007-01-08

Complexes between formic acid or formate anion and various proton donors (HF, H(2)O, NH(3), and CH(4)) are studied by the MP2 and B3LYP methods with the 6-311++G(3df,3pd) basis set. Formation of a complex is characterized by electron-density transfer from electron donor to ligands. This transfer is much larger with the formate anion, for which it exceeds 0.1 e. Electron-density transfer from electron lone pairs of the electron donor is directed into sigma* antibonding orbitals of X--H bonds of the electron acceptor and leads to elongation of the bond and a red shift of the X--H stretching frequency (standard H-bonding). However, pronounced electron-density transfer from electron lone pairs of the electron donor also leads to reorganization of the electron density in the electron donor, which results in changes in geometry and vibrational frequency. These changes are largest for the C--H bonds of formic acid and formate anion, which do not participate in H-bonding. The resulting blue shift of this stretching frequency is substantial and amounts to almost 35 and 170 cm(-1), respectively.

Investigation of Thermal Interface Materials Using Phase-Sensitive Transient Thermoreflectance Technique: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, X.; King, C.; DeVoto, D.

2014-08-01

With increasing power density in electronics packages/modules, thermal resistances at multiple interfaces are a bottleneck to efficient heat removal from the package. In this work, the performance of thermal interface materials such as grease, thermoplastic adhesives and diffusion-bonded interfaces are characterized using the phase-sensitive transient thermoreflectance technique. A multi-layer heat conduction model was constructed and theoretical solutions were derived to obtain the relation between phase lag and the thermal/physical properties. This technique enables simultaneous extraction of the contact resistance and bulk thermal conductivity of the TIMs. With the measurements, the bulk thermal conductivity of Dow TC-5022 thermal grease (70 tomore » 75 um bondline thickness) was 3 to 5 W/(m-K) and the contact resistance was 5 to 10 mm2-K/W. For the Btech thermoplastic material (45 to 80 μm bondline thickness), the bulk thermal conductivity was 20 to 50 W/(m-K) and the contact resistance was 2 to 5 mm2-K/W. Measurements were also conducted to quantify the thermal performance of diffusion-bonded interface for power electronics applications. Results with the diffusion-bonded sample showed that the interfacial thermal resistance is more than one order of magnitude lower than those of traditional TIMs, suggesting potential pathways to efficient thermal management.« less

High-Resolution AES Mapping and TEM Study of Cu(In,Ga)Se2 Thin Film Growth: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, C. L.; Yan, Y.; Jones, K.

2001-10-01

Presented at 2001 NCPV Program Review Meeting: TEM and high-resolution AES mapping data on CIGS samples. The chalcopyrite Cu(In,Ga)Se{sub 2} (CIGS) shows promise as an absorber layer in thin polycrystalline solar cells, however, details of the PVD growth of this complicated material remain in a developing stage. Previous workers have postulated the existence of a thin film of liquid Cu{sub x}Se on the growing CIGS film, and that this layer acts as a reservoir of copper as well as a layer in which rapid mass transport is possible. In this paper we present transmission electron microscopy (TEM) and high resolutionmore » Auger electron spectroscopy (AES) mapping data taken on samples that had their growth interrupted at a stage when Cu{sub x}Se was expected to be present. The AES maps show CIGS grains which are highly enriched in copper relative to the rest of the CIGS film, and that these same areas contain almost no indium, results consistent with the presence of CuxSe. Small-area diffraction analysis and energy dispersive spectroscopy (EDS) performed on these same samples independently confirm the presence of Cu{sub x}Se at the surface of growing CIGS films.« less

USING MOLECULAR PROBES TO STUDY INTERFACIAL REDOX REACTION AT FE-BEARING SMECTITES

EPA Science Inventory

The interfacial electron transfer of clay-water systems has a wide range of significance in geochemical and biogeochernical environments. However the mechanism of interfacial electron transport is poorly understood. The electron transfer mechanism at the solid-water interfaces of...

Redox Modulation of Flavin and Tyrosine Determines Photoinduced Proton-coupled Electron Transfer and Photoactivation of BLUF Photoreceptors

PubMed Central

Mathes, Tilo; van Stokkum, Ivo H. M.; Stierl, Manuela; Kennis, John T. M.

2012-01-01

Photoinduced electron transfer in biological systems, especially in proteins, is a highly intriguing matter. Its mechanistic details cannot be addressed by structural data obtained by crystallography alone because this provides only static information on a given redox system. In combination with transient spectroscopy and site-directed manipulation of the protein, however, a dynamic molecular picture of the ET process may be obtained. In BLUF (blue light sensors using FAD) photoreceptors, proton-coupled electron transfer between a tyrosine and the flavin cofactor is the key reaction to switch from a dark-adapted to a light-adapted state, which corresponds to the biological signaling state. Particularly puzzling is the fact that, although the various naturally occurring BLUF domains show little difference in the amino acid composition of the flavin binding pocket, the reaction rates of the forward reaction differ quite largely from a few ps up to several hundred ps. In this study, we modified the redox potential of the flavin/tyrosine redox pair by site-directed mutagenesis close to the flavin C2 carbonyl and fluorination of the tyrosine, respectively. We provide information on how changes in the redox potential of either reaction partner significantly influence photoinduced proton-coupled electron transfer. The altered redox potentials allowed us furthermore to experimentally describe an excited state charge transfer intermediately prior to electron transfer in the BLUF photocycle. Additionally, we show that the electron transfer rate directly correlates with the quantum yield of signaling state formation. PMID:22833672

12 CFR 205.11 - Procedures for resolving errors.

Code of Federal Regulations, 2010 CFR

2010-01-01

... institution's findings and shall note the consumer's right to request the documents that the institution... transfer; (ii) An incorrect electronic fund transfer to or from the consumer's account; (iii) The omission... made by the financial institution relating to an electronic fund transfer; (v) The consumer's receipt...

Photoinduced electron transfer in a molecular dyad by nanosecond pump-pump-probe spectroscopy.

PubMed

Ha-Thi, M-H; Pham, V-T; Pino, T; Maslova, V; Quaranta, A; Lefumeux, C; Leibl, W; Aukauloo, A

2018-06-01

The design of robust and inexpensive molecular photocatalysts for the conversion of abundant stable molecules like H2O and CO2 into an energetic carrier is one of the major fundamental questions for scientists nowadays. The outstanding challenge is to couple single photoinduced charge separation events with the sequential accumulation of redox equivalents at the catalytic unit for performing multielectronic catalytic reactions. Herein, double excitation by nanosecond pump-pump-probe experiments was used to interrogate the photoinduced charge transfer and charge accumulation on a molecular dyad composed of a porphyrin chromophore and a ruthenium-based catalyst in the presence of a reversible electron acceptor. An accumulative charge transfer state is unattainable because of rapid reverse electron transfer to the photosensitizer upon the second excitation and the low driving force of the forward photodriven electron transfer reaction. Such a method allows the fundamental understanding of the relaxation mechanism after two sequential photon absorptions, deciphering the undesired electron transfer reactions that limit the charge accumulation efficiency. This study is a step toward the improvement of synthetic strategies of molecular photocatalysts for light-induced charge accumulation and more generally, for solar energy conversion.

Excited state electron transfer in systems with a well-defined geometry. [cyclophane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaufmann, K.J.

1980-12-01

The effect of temperature, dielectric strength and ligand on the structure of the mesopyropheophorbide cyclophanes will be studied. ESR, NMR, emission and absorption spectroscopy, as well as circular dichroism will be used. The changes in structure will be correlated with changes in the photochemical activity. Electron acceptors such as benzoquinone will be utilized to stabilize the charge separation. Charge separation in porphyrin quinone dimers will also be studied. It was found that electron transfer in the cyclophane system is relatively slow. This is presumably due to an orientation requirement for fast electron transfer. Solvent dielectric also is important in producingmore » a charge separation. Decreasing the temperature effects the yield of charge transfer, but not the kinetics.« less

Investigating molecule-semiconductor interfaces with nonlinear spectroscopies

NASA Astrophysics Data System (ADS)

Giokas, Paul George

Knowledge of electronic structures and transport mechanisms at molecule-semiconductor interfaces is motivated by their ubiquity in photoelectrochemical cells. In this dissertation, optical spectroscopies are used uncover the influence of electronic coupling, coherent vibrational motion, and molecular geometry, and other factors on dynamics initiated by light absorption at such interfaces. These are explored for a family of ruthenium bipyridyl chromophores bound to titanium dioxide. Transient absorption measurements show molecular singlet state electron injection in 100 fs or less. Resonance Raman intensity analysis suggests the electronic excitations possess very little charge transfer character. The connections drawn in this work between molecular structure and photophysical behavior contribute to the general understanding of photoelectrochemical cells. Knowledge of binding geometry in nanocrystalline films is challenged by heterogeneity of semiconductor surfaces. Polarized resonance Raman spectroscopy is used to characterize the ruthenium chromophore family on single crystal titanium dioxide . Chromophores display a broad distribution of molecular geometries at the interface, with increased variation in binding angle due to the presence of a methylene bridge, as well as additional phosphonate anchors. This result implies multiple binding configurations for chromophores which incorporate multiple phosphonate ligands, and indicates the need for careful consideration when developing surface-assembled chromophore-catalyst cells. Electron transfer transitions occurring on the 100 fs time scale challenge conventional second-order approximations made when modeling these reactions. A fourth-order perturbative model which includes the relationship between coincident electron transfer and nuclear relaxation processes is presented. Insights provided by the model are illustrated for a two-level donor molecule. The presented fourth-order rate formula constitutes a rigorous and intuitive framework for understanding sub-picosecond photoinduced electron transfer dynamics. Charge transfer systems fit by this model include catechol-sensitized titanium dioxide nanoparticles and a closely-related molecular complex. These systems exhibit vibrational coherence coincident with back-electron transfer in the first picosecond after excitation, which suggests that intramolecular nuclear motion strongly influences the electronic transfer process and plays an important role in the dynamics of interfacial systems following light absorption.

A Versatile High-Vacuum Cryo-transfer System for Cryo-microscopy and Analytics

PubMed Central

Tacke, Sebastian; Krzyzanek, Vladislav; Nüsse, Harald; Wepf, Roger Albert; Klingauf, Jürgen; Reichelt, Rudolf

2016-01-01

Cryogenic microscopy methods have gained increasing popularity, as they offer an unaltered view on the architecture of biological specimens. As a prerequisite, samples must be handled under cryogenic conditions below their recrystallization temperature, and contamination during sample transfer and handling must be prevented. We present a high-vacuum cryo-transfer system that streamlines the entire handling of frozen-hydrated samples from the vitrification process to low temperature imaging for scanning transmission electron microscopy and transmission electron microscopy. A template for cryo-electron microscopy and multimodal cryo-imaging approaches with numerous sample transfer steps is presented. PMID:26910419

Role of Surface-Capping Ligands in Photoexcited Electron Transfer between CdS Nanorods and [FeFe] Hydrogenase and the Subsequent H 2 Generation

DOE PAGES

Wilker, Molly B.; Utterback, James K.; Greene, Sophie; ...

2017-12-08

Complexes of CdS nanorods and [FeFe] hydrogenase from Clostridium acetobutylicum have been shown to photochemically produce H 2. This study examines the role of the ligands that passivate the nanocrystal surfaces in the electron transfer from photoexcited CdS to hydrogenase and the H 2 generation that follows. We functionalized CdS nanorods with a series of mercaptocarboxylate surface-capping ligands of varying lengths and measured their photoexcited electron relaxation by transient absorption (TA) spectroscopy before and after hydrogenase adsorption. Rate constants for electron transfer from the nanocrystals to the enzyme, extracted by modeling of TA kinetics, decrease exponentially with ligand length, suggestingmore » that the ligand layer acts as a barrier to charge transfer and controls the degree of electronic coupling. Relative light-driven H 2 production efficiencies follow the relative quantum efficiencies of electron transfer, revealing the critical role of surface-capping ligands in determining the photochemical activity of these nanocrystal-enzyme complexes. Our results suggest that the H 2 production in this system could be maximized with a choice of a surface-capping ligand that decreases the distance between the nanocrystal surface and the electron injection site of the enzyme.« less

Role of Surface-Capping Ligands in Photoexcited Electron Transfer between CdS Nanorods and [FeFe] Hydrogenase and the Subsequent H 2 Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilker, Molly B.; Utterback, James K.; Greene, Sophie

Complexes of CdS nanorods and [FeFe] hydrogenase from Clostridium acetobutylicum have been shown to photochemically produce H 2. This study examines the role of the ligands that passivate the nanocrystal surfaces in the electron transfer from photoexcited CdS to hydrogenase and the H 2 generation that follows. We functionalized CdS nanorods with a series of mercaptocarboxylate surface-capping ligands of varying lengths and measured their photoexcited electron relaxation by transient absorption (TA) spectroscopy before and after hydrogenase adsorption. Rate constants for electron transfer from the nanocrystals to the enzyme, extracted by modeling of TA kinetics, decrease exponentially with ligand length, suggestingmore » that the ligand layer acts as a barrier to charge transfer and controls the degree of electronic coupling. Relative light-driven H 2 production efficiencies follow the relative quantum efficiencies of electron transfer, revealing the critical role of surface-capping ligands in determining the photochemical activity of these nanocrystal-enzyme complexes. Our results suggest that the H 2 production in this system could be maximized with a choice of a surface-capping ligand that decreases the distance between the nanocrystal surface and the electron injection site of the enzyme.« less

Electron transfer between colloidal ZnO nanocrystals.

PubMed

Hayoun, Rebecca; Whitaker, Kelly M; Gamelin, Daniel R; Mayer, James M

2011-03-30

Colloidal ZnO nanocrystals capped with dodecylamine and dissolved in toluene can be charged photochemically to give stable solutions in which electrons are present in the conduction bands of the nanocrystals. These conduction-band electrons are readily monitored by EPR spectroscopy, with g* values that correlate with the nanocrystal sizes. Mixing a solution of charged small nanocrystals (e(-)(CB):ZnO-S) with a solution of uncharged large nanocrystals (ZnO-L) caused changes in the EPR spectrum indicative of quantitative electron transfer from small to large nanocrystals. EPR spectra of the reverse reaction, e(-)(CB):ZnO-L + ZnO-S, showed that electrons do not transfer from large to small nanocrystals. Stopped-flow kinetics studies monitoring the change in the UV band-edge absorption showed that reactions of 50 μM nanocrystals were complete within the 5 ms mixing time of the instrument. Similar results were obtained for the reaction of charged nanocrystals with methyl viologen (MV(2+)). These and related results indicate that the electron-transfer reactions of these colloidal nanocrystals are quantitative and very rapid, despite the presence of ~1.5 nm long dodecylamine capping ligands. These soluble ZnO nanocrystals are thus well-defined redox reagents suitable for studies of electron transfer involving semiconductor nanostructures.

Real Time Quantification of Ultrafast Photoinduced Bimolecular Electron Transfer Rate: Direct Probing of the Transient Intermediate.

PubMed

Mukherjee, Puspal; Biswas, Somnath; Sen, Pratik

2015-08-27

Fluorescence quenching studies through steady-state and time-resolved measurements are inadequate to quantify the bimolecular electron transfer rate in bulk homogeneous solution due to constraints from diffusion. To nullify the effect of diffusion, direct evaluation of the rate of formation of a transient intermediate produced upon the electron transfer is essential. Methyl viologen, a well-known electron acceptor, produces a radical cation after accepting an electron, which has a characteristic strong and broad absorption band centered at 600 nm. Hence it is a good choice to evaluate the rate of photoinduced electron transfer reaction employing femtosecond broadband transient absorption spectroscopy. The time constant of the aforementioned process between pyrene and methyl viologen in methanol has been estimated to be 2.5 ± 0.4 ps using the same technique. The time constant for the backward reaction was found to be 14 ± 1 ps. These values did not change with variation of concentration of quencher, i.e., methyl viologen. Hence, we can infer that diffusion has no contribution in the estimation of rate constants. However, on changing the solvent from methanol to ethanol, the time constant of the electron transfer reaction has been found to increase and has accounted for the change in solvent reorganization energy.

Supramolecular networks with electron transfer in two dimensions

DOEpatents

Stupp, Samuel I.; Stoddart, J. Fraser; Shveyd, Alexander K.; Tayi, Alok S.; Sue, Chi-Hau; Narayanan, Ashwin

2016-09-13

Organic charge-transfer (CT) co-crystals in a crossed stack system are disclosed. The co-crystals exhibit bidirectional charge transfer interactions where one donor molecule shares electrons with two different acceptors, one acceptor face-to-face and the other edge-to-face. The assembly and charge transfer interaction results in a pleochroic material whereby the optical absorption continuously changes depending on the polarization angle of incident light.

pH-dependent electron transfer reaction and direct bioelectrocatalysis of the quinohemoprotein pyranose dehydrogenase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeda, Kouta; Matsumura, Hirotoshi; Ishida, Takuya

A pyranose dehydrogenase from Coprinopsis cinerea (CcPDH) is an extracellular quinohemoeprotein, which consists a b-type cytochrome domain, a pyrroloquinoline-quinone (PQQ) domain, and a family 1-type carbohydrate-binding module. The electron transfer reaction of CcPDH was studied using some electron acceptors and a carbon electrode at various pH levels. Phenazine methosulfate (PMS) reacted directly at the PQQ domain, whereas cytochrome c (cyt c) reacted via the cytochrome domain of intact CcPDH. Thus, electrons are transferred from reduced PQQ in the catalytic domain of CcPDH to heme b in the N-terminal cytochrome domain, which acts as a built-in mediator and transfers electron tomore » a heterogenous electron transfer protein. The optimal pH values of the PMS reduction (pH 6.5) and the cyt c reduction (pH 8.5) differ. The catalytic currents for the oxidation of L-fucose were observed within a range of pH 4.5 to 11. Bioelectrocatalysis of CcPDH based on direct electron transfer demonstrated that the pH profile of the biocatalytic current was similar to the reduction activity of cyt c characters. - Highlights: • pH dependencies of activity were different for the reduction of cyt c and DCPIP. • DET-based bioelectrocatalysis of CcPDH was observed. • The similar pH-dependent profile was found with cyt c and electrode. • The present results suggested that IET reaction of CcPDH shows pH dependence.« less

Curvature Dependent Reactivity of Fullerenes and Nanotubes

NASA Technical Reports Server (NTRS)

Park, Seongjun; Cho, Kyeongjae; Srivastava, Deepak

2000-01-01

Dependence of pyramidalization angle, examples of nanotube surfaces, internal and external reactivity, and binding energies are some of the topics discussed in this conference presentation preprint. Final conclusions include the relationship between the pyramidal angle of the surface and its associated external reaction energy.

75 FR 57962 - Proposed Information Collection Activity; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-23

... DEPARTMENT OF HEALTH AND HUMAN SERVICES Administration for Children and Families Proposed Information Collection Activity; Comment Request Proposed Projects Title: Child Care and Development Fund Tribal Plan Preprint--ACF- 118-A. OMB No.: 0970-0198. Description: The Child Care and Development Fund...

New Development of Polymer-Based Cotton for Breathable Material

USDA-ARS?s Scientific Manuscript database

Recently, we converted the poly (ethylene oxide) dibromide to poly (ethylene oxide) diazides and reacted to study cycloaddition polymerization with bisphenol-A dipropargyl ether to produce elastomers compatible with cotton (Polymer Preprints, 2005, 46(1), 737-738). The reactants were characterized w...

Microstructure Instability in Cryogenically-Deformed Copper (Preprint)

DTIC Science & Technology

2011-03-01

prepared using conventional metallographic techniques followed by electropolishing in a solution of 70 pct. orthophosphoric acid in water at ambient...at room temperatu re on the microhardness profile across the sample diameter is shown in Fig. 1. After 15 minutes, the microhardness distribution was

Theory of Skin Depth Interaction of Lasers with Plasmas

DTIC Science & Technology

2003-07-20

laser plasma interaction, Czechoslovak J. Physics, 52, Suppl. D (CD No.7), (2002) D349 [6] J.L Nuckolls and L. Wood, Future of Inertial Fusion Energy , Preprint UCRL-JC-149860 (September 4, 2002) www.llnl.gov/tid/ Library..html 224

Photothermal Stability of an E-Beam Pre-Crosslinked EVA Encapsulant and Its Performance Degradation on a-Si Submodules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F. J.; Watson, G. L.; Glick, S. H.

2001-10-01

Presented at the 2001 NCPV Program Review Meeting: Study of photothermal stability of special EVA encapsulant by accelerated exposure testing and analysis of causes of performance degradation on a-Si modules.

Electron Transfer Strategies Regulate Carbonate Mineral and Micropore Formation.

PubMed

Zeng, Zhirui; Tice, Michael M

2018-01-01

Some microbial carbonates are robust biosignatures due to their distinct morphologies and compositions. However, whether carbonates induced by microbial iron reduction have such features is unknown. Iron-reducing bacteria use various strategies to transfer electrons to iron oxide minerals (e.g., membrane-bound enzymes, soluble electron shuttles, nanowires, as well as different mechanisms for moving over or attaching to mineral surfaces). This diversity has the potential to create mineral biosignatures through manipulating the microenvironments in which carbonate precipitation occurs. We used Shewanella oneidensis MR-1, Geothrix fermentans, and Geobacter metallireducens GS-15, representing three different strategies, to reduce solid ferric hydroxide in order to evaluate their influence on carbonate and micropore formation (micro-size porosity in mineral rocks). Our results indicate that electron transfer strategies determined the morphology (rhombohedral, spherical, or long-chained) of precipitated calcium-rich siderite by controlling the level of carbonate saturation and the location of carbonate formation. Remarkably, electron transfer strategies also produced distinctive cell-shaped micropores in both carbonate and hydroxide minerals, thus producing suites of features that could potentially serve as biosignatures recording information about the sizes, shapes, and physiologies of iron-reducing organisms. Key Words: Microbial iron reduction-Micropore-Electron transfer strategies-Microbial carbonate. Astrobiology 18, 28-36.

36 CFR § 1235.50 - What specifications and standards for transfer apply to electronic records?

Code of Federal Regulations, 2013 CFR

2013-07-01

... Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION RECORDS MANAGEMENT TRANSFER OF RECORDS TO THE... Records Administration, Electronic/Special Media Records Services Division (NWME), 8601 Adelphi Road... and Records Administration, Electronic/Special Media Records Services Division (NWME), 8601 Adelphi...

36 CFR 1235.50 - What specifications and standards for transfer apply to electronic records?

Code of Federal Regulations, 2014 CFR

2014-07-01

... Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION RECORDS MANAGEMENT TRANSFER OF REC- ORDS TO THE... Records Administration, Electronic/Special Media Records Services Division (NWME), 8601 Adelphi Road... and Records Administration, Electronic/Special Media Records Services Division (NWME), 8601 Adelphi...

Monte-Carlo modelling of nano-material photocatalysis: bridging photocatalytic activity and microscopic charge kinetics.

PubMed

Liu, Baoshun

2016-04-28

In photocatalysis, it is known that light intensity, organic concentration, and temperature affect the photocatalytic activity by changing the microscopic kinetics of holes and electrons. However, how the microscopic kinetics of holes and electrons relates to the photocatalytic activity was not well known. In the present research, we developed a Monte-Carlo random walking model that involved all of the charge kinetics, including the photo-generation, the recombination, the transport, and the interfacial transfer of holes and electrons, to simulate the overall photocatalytic reaction, which we called a "computer experiment" of photocatalysis. By using this model, we simulated the effect of light intensity, temperature, and organic surface coverage on the photocatalytic activity and the density of the free electrons that accumulate in the simulated system. It was seen that the increase of light intensity increases the electron density and its mobility, which increases the probability for a hole/electron to find an electron/hole for recombination, and consequently led to an apparent kinetics that the quantum yield (QY) decreases with the increase of light intensity. It was also seen that the increase of organic surface coverage could increase the rate of hole interfacial transfer and result in the decrease of the probability for an electron to recombine with a hole. Moreover, the increase of organic coverage on the nano-material surface can also increase the accumulation of electrons, which enhances the mobility for electrons to undergo interfacial transfer, and finally leads to the increase of photocatalytic activity. The simulation showed that the temperature had a more complicated effect, as it can simultaneously change the activation of electrons, the interfacial transfer of holes, and the interfacial transfer of electrons. It was shown that the interfacial transfer of holes might play a main role at low temperature, with the temperature-dependence of QY conforming to the Arrhenius model. The activation of electrons from the traps to the conduction band might become important at high temperature, which accelerates the electron movement for recombination and leads to a temperature dependence of QY that deviates from the Arrhenius model.

12 CFR 205.3 - Coverage.

Code of Federal Regulations, 2014 CFR

2014-01-01

... to initiate a one-time electronic fund transfer from a consumer's account. The consumer must...-time electronic fund transfer (in providing a check to a merchant or other payee for the MICR encoding... information for the transfer shall also provide a notice to the consumer at the same time it provides the...

12 CFR 205.3 - Coverage.

Code of Federal Regulations, 2011 CFR

2011-01-01

... to initiate a one-time electronic fund transfer from a consumer's account. The consumer must...-time electronic fund transfer (in providing a check to a merchant or other payee for the MICR encoding... information for the transfer shall also provide a notice to the consumer at the same time it provides the...

12 CFR 205.3 - Coverage.

Code of Federal Regulations, 2013 CFR

2013-01-01

... to initiate a one-time electronic fund transfer from a consumer's account. The consumer must...-time electronic fund transfer (in providing a check to a merchant or other payee for the MICR encoding... information for the transfer shall also provide a notice to the consumer at the same time it provides the...

Charge-transfer complexes and their role in exciplex emission and near-infrared photovoltaics.

PubMed

Ng, Tsz-Wai; Lo, Ming-Fai; Fung, Man-Keung; Zhang, Wen-Jun; Lee, Chun-Sing

2014-08-20

Charge transfer and interactions at organic heterojunctions (OHJs) are known to have critical influences on various properties of organic electronic devices. In this Research News article, a short review is given from the electronic viewpoint on how the local molecular interactions and interfacial energetics at P/N OHJs contribute to the recombination/dissociation of electron-hole pairs. Very often, the P-type materials donate electrons to the N-type materials, giving rise to charge-transfer complexes (CTCs) with a P(δ+) -N(δ-) configuration. A recently observed opposite charge-transfer direction in OHJs is also discussed (i.e., N-type material donates electrons to P-type material to form P(δ-) -N(δ+) ). Recent studies on the electronic structures of CTC-forming material pairs are also summarized. The formation of P(δ-) -N(δ+) -type CTCs and their correlations with exciplex emission are examined. Furthermore, the potential applications of CTCs in NIR photovoltaic devices are reviewed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

PubMed Central

Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; van Driel, Tim B.; Adachi, Shin-ichi; Bordage, Amélie; Bressler, Christian; Chabera, Pavel; Christensen, Morten; Dohn, Asmus O.; Galler, Andreas; Gawelda, Wojciech; Gosztola, David; Haldrup, Kristoffer; Harlang, Tobias; Liu, Yizhu; Møller, Klaus B.; Németh, Zoltán; Nozawa, Shunsuke; Pápai, Mátyás; Sato, Tokushi; Sato, Takahiro; Suarez-Alcantara, Karina; Togashi, Tadashi; Tono, Kensuke; Uhlig, Jens; Vithanage, Dimali A.; Wärnmark, Kenneth; Yabashi, Makina; Zhang, Jianxin; Sundström, Villy; Nielsen, Martin M.

2015-01-01

Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined. PMID:25727920

Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

DOE PAGES

Canton, Sophie E.; Kjær, Kasper S.; Vankó, György; ...

2015-03-02

Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor–acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances.more » Thus experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.« less

Photosensitizing Electron Transfer Processes of Fullerenes, Carbon Nanotubes, and Carbon Nanohorns.

PubMed

Ito, Osamu

2017-03-01

In this account, studies on the photosensitizing electron transfer of nanocarbons, such as fullerenes, single-walled carbon nanotubes (SWCNTs), and carbon nanohorns (CNH), performed in our laboratory for about 15 years in the early 21st century have been briefly reviewed. These novel nanocarbons act as excellent electron acceptors, when they are linked to light-absorbing electron donors, such as porphyrins or phthalocyanines. For such molecule-nanocarbon hybrids, the direct confirmation of fast, transient, electron-transfer phenomena must be performed with time-resolved spectroscopic methods, such as transient absorption spectral measurements, in addition to fluorescence time-profile measurements in the wide-wavelength regions. Careful use of these methods affords useful information to understand photoinduced electron-transfer mechanisms. In addition, kinetic data obtained by these methods can assist in the construction of light-active devices, such as photovoltaic cells and solar H 2 -generation systems. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental and Theoretical Demonstrations for the Mechanism behind Enhanced Microbial Electron Transfer by CNT Network

NASA Astrophysics Data System (ADS)

Liu, Xian-Wei; Chen, Jie-Jie; Huang, Yu-Xi; Sun, Xue-Fei; Sheng, Guo-Ping; Li, Dao-Bo; Xiong, Lu; Zhang, Yuan-Yuan; Zhao, Feng; Yu, Han-Qing

2014-01-01

Bioelectrochemical systems (BESs) share the principle of the microbially catalyzed anodic substrate oxidation. Creating an electrode interface to promote extracellular electron transfer from microbes to electrode and understanding such mechanisms are crucial for engineering BESs. In this study, significantly promoted electron transfer and a 10-times increase in current generation in a BES were achieved by the utilization of carbon nanotube (CNT) network, compared with carbon paper. The mechanisms for the enhanced current generation with the CNT network were elucidated with both experimental approach and molecular dynamic simulations. The fabricated CNT network was found to be able to substantially enhance the interaction between the c-type cytochromes and solid electron acceptor, indicating that the direct electron transfer from outer-membrane decaheme c-type cytochromes to electrode might occur. The results obtained in this study will benefit for the optimized design of new materials to target the outer membrane proteins for enhanced electron exchanges.

Phonon-electron coupling and tunneling effect on charge transport in organic semi-conductor crystals of Cn-BTBT.

PubMed

Zhou, Yecheng; Deng, Wei-Qiao; Zhang, Hao-Li

2016-09-14

Cn-[1]benzothieno[3,2-b][1]-benzothiophene (BTBT) crystals show very high hole mobilities in experiments. These high mobilities are beyond existing theory prediction. Here, we employed different quantum chemistry methods to investigate charge transfer in Cn-BTBT crystals and tried to find out the reasons for the underestimation in the theory. It was found that the hopping rate estimated by the Fermi Golden Rule is higher than that of the Marcus theory due to the high temperature approximation and failure at the classic limit. More importantly, molecular dynamics simulations revealed that the phonon induced fluctuation of electronic transfer integral is much larger than the average of the electronic transfer integral itself. Mobilities become higher if simulations implement the phonon-electron coupling. This conclusion indicates that the phonon-electron coupling promotes charge transfer in organic semi-conductors at room temperature.

Phonon-electron coupling and tunneling effect on charge transport in organic semi-conductor crystals of Cn-BTBT

NASA Astrophysics Data System (ADS)

Zhou, Yecheng; Deng, Wei-Qiao; Zhang, Hao-Li

2016-09-01

Cn-[1]benzothieno[3,2-b][1]-benzothiophene (BTBT) crystals show very high hole mobilities in experiments. These high mobilities are beyond existing theory prediction. Here, we employed different quantum chemistry methods to investigate charge transfer in Cn-BTBT crystals and tried to find out the reasons for the underestimation in the theory. It was found that the hopping rate estimated by the Fermi Golden Rule is higher than that of the Marcus theory due to the high temperature approximation and failure at the classic limit. More importantly, molecular dynamics simulations revealed that the phonon induced fluctuation of electronic transfer integral is much larger than the average of the electronic transfer integral itself. Mobilities become higher if simulations implement the phonon-electron coupling. This conclusion indicates that the phonon-electron coupling promotes charge transfer in organic semi-conductors at room temperature.

Electronic and Vibrational Coherence in Charge-Transfer Reactions

NASA Astrophysics Data System (ADS)

Scherer, Norbert

1996-03-01

The ultrafast dynamics associated with optically-induced intervalence charge-transfer reactions in solution and protein environments are reported. These studies include the Fe^(II)-Fe^(III) MMCT complex Prussian blue and the mixed valence dimer (CN)_5Ru^(II)CNRuRu^(III)(NH_3)_5. The protein systems include blue copper proteins and the bacterial photosynthetic reaction center. The experimental approaches include photon echo, wavelength-resolved pump-probe and anisotropy measurements performed with 12-16fs duration optical pulses. Complicated time-domain waveforms reflect the several different p[rocesses and time scales for relaxation of coherences (both electronic and vibrational) and populations within these systems. The photon echo and anisotropy results probe electronic coherence and dephasing prior to back electron transfer. Wavelength-resolved pump-probe results reveal vibrational modes coupled to the CT-coordinate as well as formation of new product states or vibrational cooling in the ground state following back electron transfer.

Electron Transfer Dissociation: Effects of Cation Charge State on Product Partitioning in Ion/Ion Electron Transfer to Multiply Protonated Polypeptides

PubMed Central

Liu, Jian; McLuckey, Scott A.

2012-01-01

The effect of cation charge state on product partitioning in the gas-phase ion/ion electron transfer reactions of multiply protonated tryptic peptides, model peptides, and relatively large peptides with singly charged radical anions has been examined. In particular, partitioning into various competing channels, such as proton transfer (PT) versus electron transfer (ET), electron transfer with subsequent dissociation (ETD) versus electron transfer with no dissociation (ET,noD), and fragmentation of backbone bonds versus fragmentation of side chains, was measured quantitatively as a function of peptide charge state to allow insights to be drawn about the fundamental aspects of ion/ion reactions that lead to ETD. The ET channel increases relative to the PT channel, ETD increases relative to ET,noD, and fragmentation at backbone bonds increases relative to side-chain cleavages as cation charge state increases. The increase in ET versus PT with charge state is consistent with a Landau-Zener based curve-crossing model. An optimum charge state for ET is predicted by the model for the ground state-to-ground state reaction. However, when the population of excited product ion states is considered, it is possible that a decrease in ET efficiency as charge state increases will not be observed due to the possibility of the population of excited electronic states of the products. Several factors can contribute to the increase in ETD versus ET,noD and backbone cleavage versus side-chain losses. These factors include an increase in reaction exothermicity and charge state dependent differences in precursor and product ion structures, stabilities, and sites of protonation. PMID:23264749

Copper-Containing Nitrite Reductase Employing Proton-Coupled Spin-Exchanged Electron-Transfer and Multiproton Synchronized Transfer to Reduce Nitrite.

PubMed

Qin, Xin; Deng, Li; Hu, Caihong; Li, Li; Chen, Xiaohua

2017-10-20

The possible catalytic mechanism of the reduction of nitrite by copper-containing nitrite reductases (CuNiRs) is examined by using the M06 function according to two copper models, which include type-one copper (T1Cu) and type-two copper (T2Cu) sites. Examinations confirm that the protonation of two residues, His255 and Asp98, near the T2Cu site, can modulate the redox states of T1Cu and T2Cu, but cannot directly cause electron transfer from T1Cu to T2Cu. The electron hole remains at the T2Cu site when only one residue, His255 or Asp98, is protonated. However, the hole resides at the T1Cu site when both His255 and Asp98 are protonated. Then, the first protonation of nitrite takes place through indirect proton transfer from protonated His255 through the bridging H 2 O and Asp98 with three protons moving together, which cannot cause the cleavage of the HO-NO bond. Subsequently, the substrate is required to obtain another proton from reprotonated His255 through the bridging H 2 O. The reprotonation of nitrite induces the generation of nitric oxide (NO) and H 2 O at the T2Cu site through a special double-proton-coupled spin-exchanged electron-transfer mechanism with indirect proton transfer from His255 to the substrate, a beta-electron of T2Cu I shift to the NO cation, and the remaining alpha-electron changing spin direction at the same time. These results may provide useful information to better understand detailed proton-/electron-transfer reactions for the catalytic processes of CuNiR. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Constraint-based modeling of carbon fixation and the energetics of electron transfer in Geobacter metallireducens.

PubMed

Feist, Adam M; Nagarajan, Harish; Rotaru, Amelia-Elena; Tremblay, Pier-Luc; Zhang, Tian; Nevin, Kelly P; Lovley, Derek R; Zengler, Karsten

2014-04-01

Geobacter species are of great interest for environmental and biotechnology applications as they can carry out direct electron transfer to insoluble metals or other microorganisms and have the ability to assimilate inorganic carbon. Here, we report on the capability and key enabling metabolic machinery of Geobacter metallireducens GS-15 to carry out CO2 fixation and direct electron transfer to iron. An updated metabolic reconstruction was generated, growth screens on targeted conditions of interest were performed, and constraint-based analysis was utilized to characterize and evaluate critical pathways and reactions in G. metallireducens. The novel capability of G. metallireducens to grow autotrophically with formate and Fe(III) was predicted and subsequently validated in vivo. Additionally, the energetic cost of transferring electrons to an external electron acceptor was determined through analysis of growth experiments carried out using three different electron acceptors (Fe(III), nitrate, and fumarate) by systematically isolating and examining different parts of the electron transport chain. The updated reconstruction will serve as a knowledgebase for understanding and engineering Geobacter and similar species.

Concerted electron-proton transfer in the optical excitation of hydrogen-bonded dyes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westlake, Brittany C.; Brennaman, Kyle M.; Concepcion, Javier J.

2011-05-24

The simultaneous, concerted transfer of electrons and protons—electron-proton transfer (EPT)—is an important mechanism utilized in chemistry and biology to avoid high energy intermediates. There are many examples of thermally activated EPT in ground-state reactions and in excited states following photoexcitation and thermal relaxation. Here we report application of ultrafast excitation with absorption and Raman monitoring to detect a photochemically driven EPT process (photo-EPT). In this process, both electrons and protons are transferred during the absorption of a photon. Photo-EPT is induced by intramolecular charge-transfer (ICT) excitation of hydrogen-bonded-base adducts with either a coumarin dye or 4-nitro-4'-biphenylphenol. Femtosecond transient absorption spectralmore » measurements following ICT excitation reveal the appearance of two spectroscopically distinct states having different dynamical signatures. One of these states corresponds to a conventional ICT excited state in which the transferring H⁺ is initially associated with the proton donor. Proton transfer to the base (B) then occurs on the picosecond time scale. The other state is an ICT-EPT photoproduct. Upon excitation it forms initially in the nuclear configuration of the ground state by application of the Franck–Condon principle. However, due to the change in electronic configuration induced by the transition, excitation is accompanied by proton transfer with the protonated base formed with a highly elongated ⁺H–B bond. Coherent Raman spectroscopy confirms the presence of a vibrational mode corresponding to the protonated base in the optically prepared state.« less

Concerted electron-proton transfer in the optical excitation of hydrogen-bonded dyes.

PubMed

Westlake, Brittany C; Brennaman, M Kyle; Concepcion, Javier J; Paul, Jared J; Bettis, Stephanie E; Hampton, Shaun D; Miller, Stephen A; Lebedeva, Natalia V; Forbes, Malcolm D E; Moran, Andrew M; Meyer, Thomas J; Papanikolas, John M

2011-05-24

The simultaneous, concerted transfer of electrons and protons--electron-proton transfer (EPT)--is an important mechanism utilized in chemistry and biology to avoid high energy intermediates. There are many examples of thermally activated EPT in ground-state reactions and in excited states following photoexcitation and thermal relaxation. Here we report application of ultrafast excitation with absorption and Raman monitoring to detect a photochemically driven EPT process (photo-EPT). In this process, both electrons and protons are transferred during the absorption of a photon. Photo-EPT is induced by intramolecular charge-transfer (ICT) excitation of hydrogen-bonded-base adducts with either a coumarin dye or 4-nitro-4'-biphenylphenol. Femtosecond transient absorption spectral measurements following ICT excitation reveal the appearance of two spectroscopically distinct states having different dynamical signatures. One of these states corresponds to a conventional ICT excited state in which the transferring H(+) is initially associated with the proton donor. Proton transfer to the base (B) then occurs on the picosecond time scale. The other state is an ICT-EPT photoproduct. Upon excitation it forms initially in the nuclear configuration of the ground state by application of the Franck-Condon principle. However, due to the change in electronic configuration induced by the transition, excitation is accompanied by proton transfer with the protonated base formed with a highly elongated (+)H ─ B bond. Coherent Raman spectroscopy confirms the presence of a vibrational mode corresponding to the protonated base in the optically prepared state.

Influence of naturally-occurring 5′-pyrophosphate-linked substituents on the binding of adenylic inhibitors to ribonuclease a: An X-ray crystallographic study

PubMed Central

Holloway, Daniel E; Chavali, Gayatri B; Leonidas, Demetres D; Baker, Matthew D; Acharya, K Ravi

2009-01-01

Ribonuclease A is the archetype of a functionally diverse superfamily of vertebrate-specific ribonucleases. Inhibitors of its action have potential use in the elucidation of the in vivo roles of these enzymes and in the treatment of pathologies associated therewith. Derivatives of adenosine 5′-pyrophosphate are the most potent nucleotide-based inhibitors known. Here, we use X-ray crystallography to visualize the binding of four naturally-occurring derivatives that contain 5′-pyrophosphate-linked extensions. 5′-ATP binds with the adenine occupying the B2 subsite in the manner of an RNA substrate but with the γ-phosphate at the P1 subsite. Diadenosine triphosphate (Ap3A) binds with the adenine in syn conformation, the β-phosphate as the principal P1 subsite ligand and without order beyond the γ-phosphate. NADPH and NADP+ bind with the adenine stacked against an alternative rotamer of His119, the 2′-phosphate at the P1 subsite, and without order beyond the 5′-α-phosphate. We also present the structure of the complex formed with pyrophosphate ion. The structural data enable existing kinetic data on the binding of these compounds to a variety of ribonucleases to be rationalized and suggest that as the complexity of the 5′-linked extension increases, the need to avoid unfavorable contacts places limitations on the number of possible binding modes. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 995–1008, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com PMID:19191310

Role of cation size in the energy of electron transfer to 1:1 polyoxometalate ion pairs {(M+)(Xn+VW11O40)}(8–n)–(M=Li, Na, K)

Treesearch

Vladimir A. Grigoriev; Craig L. Hill; Ira A. Weinstock

2000-01-01

The use of soluble salts of polyoxometalates (d0-early-transition metal oxygen-anion clusters or POMs) as selective oxidation or electron-transfer catalysts, as probes in physical-organic and biological chemistry, and in the study of electron-and energy-transfer phenomena constitutes a substantial and rapidly growing literature. While rarely addressed, however, POM...

Special Inspector General for Iraq Reconstruction. Quarterly Report and Semiannual Report to the United States Congress

DTIC Science & Technology

2008-01-30

Energy Fusion Cell, and allocations include $110 million for oil pipeline exclusion zones—which aim to prevent illegal tapping and sabotage of...sectors in Iraq. This quarter SIGIR highlights two of these programs: the electronic funds transfer ( EFT ) system and U.S. advisory support provided to...the Iraq Stock Exchange. eleCTroniC funds Transfer SIGIR noted last quarter that Iraq finally acti- vated an electronic funds transfer ( EFT ) system

Special Inspector General for Iraq Reconstruction: Quarterly Report and Semiannual Report to the United States Congress

DTIC Science & Technology

2008-01-30

Cell, and allocations include $110 million for oil pipeline exclusion zones—which aim to prevent illegal tapping and sabotage of pipelines—$51...This quarter SIGIR highlights two of these programs: the electronic funds transfer ( EFT ) system and U.S. advisory support provided to the Iraq Stock...Exchange. eleCTroniC funds Transfer SIGIR noted last quarter that Iraq finally acti- vated an electronic funds transfer ( EFT ) system. The United

Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex.

PubMed

Toogood, Helen S; van Thiel, Adam; Basran, Jaswir; Sutcliffe, Mike J; Scrutton, Nigel S; Leys, David

2004-07-30

The crystal structure of the human electron transferring flavoprotein (ETF).medium chain acyl-CoA dehydrogenase (MCAD) complex reveals a dual mode of protein-protein interaction, imparting both specificity and promiscuity in the interaction of ETF with a range of structurally distinct primary dehydrogenases. ETF partitions the functions of partner binding and electron transfer between (i) the recognition loop, which acts as a static anchor at the ETF.MCAD interface, and (ii) the highly mobile redox active FAD domain. Together, these enable the FAD domain of ETF to sample a range of conformations, some compatible with fast interprotein electron transfer. Disorders in amino acid or fatty acid catabolism can be attributed to mutations at the protein-protein interface. Crucially, complex formation triggers mobility of the FAD domain, an induced disorder that contrasts with general models of protein-protein interaction by induced fit mechanisms. The subsequent interfacial motion in the MCAD.ETF complex is the basis for the interaction of ETF with structurally diverse protein partners. Solution studies using ETF and MCAD with mutations at the protein-protein interface support this dynamic model and indicate ionic interactions between MCAD Glu(212) and ETF Arg alpha(249) are likely to transiently stabilize productive conformations of the FAD domain leading to enhanced electron transfer rates between both partners.

Molecular implementation of molecular shift register memories

NASA Technical Reports Server (NTRS)

Beratan, David N. (Inventor); Onuchic, Jose N. (Inventor)

1991-01-01

An electronic shift register memory (20) at the molecular level is described. The memory elements are based on a chain of electron transfer molecules (22) and the information is shifted by photoinduced (26) electron transfer reactions. Thus, multi-step sequences of charge transfer reactions are used to move charge with high efficiency down a molecular chain. The device integrates compositions of the invention onto a VLSI substrate (36), providing an example of a molecular electronic device which may be fabricated. Three energy level schemes, molecular implementation of these schemes, optical excitation strategies, charge amplification strategies, and error correction strategies are described.

Communication: Charge transfer dominates over proton transfer in the reaction of nitric acid with gas-phase hydrated electrons

NASA Astrophysics Data System (ADS)

Lengyel, Jozef; Med, Jakub; Slavíček, Petr; Beyer, Martin K.

2017-09-01

The reaction of HNO3 with hydrated electrons (H2O)n- (n = 35-65) in the gas phase was studied using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and ab initio molecular dynamics simulations. Kinetic analysis of the experimental data shows that OH-(H2O)m is formed primarily via a reaction of the hydrated electron with HNO3 inside the cluster, while proton transfer is not observed and NO3-(H2O)m is just a secondary product. The reaction enthalpy was determined using nanocalorimetry, revealing a quite exothermic charge transfer with -241 ± 69 kJ mol-1. Ab initio molecular dynamics simulations indicate that proton transfer is an allowed reaction pathway, but the overall thermochemistry favors charge transfer.

Robust and stretchable indium gallium zinc oxide-based electronic textiles formed by cilia-assisted transfer printing

PubMed Central

Yoon, Jongwon; Jeong, Yunkyung; Kim, Heeje; Yoo, Seonggwang; Jung, Hoon Sun; Kim, Yonghun; Hwang, Youngkyu; Hyun, Yujun; Hong, Woong-Ki; Lee, Byoung Hun; Choa, Sung-Hoon; Ko, Heung Cho

2016-01-01

Electronic textile (e-textile) allows for high-end wearable electronic devices that provide easy access for carrying, handling and using. However, the related technology does not seem to be mature because the woven fabric hampers not only the device fabrication process directly on the complex surface but also the transfer printing of ultrathin planar electronic devices. Here we report an indirect method that enables conformal wrapping of surface with arbitrary yet complex shapes. Artificial cilia are introduced in the periphery of electronic devices as adhesive elements. The cilia also play an important role in confining a small amount of glue and damping mechanical stress to maintain robust electronic performance under mechanical deformation. The example of electronic applications depicts the feasibility of cilia for ‘stick-&-play' systems, which provide electronic functions by transfer printing on unconventional complex surfaces. PMID:27248982

Nonadiabatic one-electron transfer mechanism for the O-O bond formation in the oxygen-evolving complex of photosystem II

NASA Astrophysics Data System (ADS)

Shoji, Mitsuo; Isobe, Hiroshi; Shigeta, Yasuteru; Nakajima, Takahito; Yamaguchi, Kizashi

2018-04-01

The reaction mechanism of the O2 formation in the S4 state of the oxygen-evolving complex of photosystem II was clarified at the quantum mechanics/molecular mechanics (QM/MM) level. After the Yz (Y161) oxidation and the following proton transfer in the S3 state, five reaction steps are required to produce the molecular dioxygen. The highest barrier step is the first proton transfer reaction (0 → 1). The following reactions involving electron transfers were precisely analyzed in terms of their energies, structures and spin densities. We found that the one-electron transfer from the Mn4Ca cluster to Y161 triggers the O-O sigma bond formation.

12 CFR 205.10 - Preauthorized transfers.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 12 Banks and Banking 2 2011-01-01 2011-01-01 false Preauthorized transfers. 205.10 Section 205.10 Banks and Banking FEDERAL RESERVE SYSTEM BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM ELECTRONIC...'s account—(1) Notice by financial institution. When a person initiates preauthorized electronic fund...

Heterogeneous Electron-Transfer Dynamics through Dipole-Bridge Groups.

PubMed

Nieto-Pescador, Jesus; Abraham, Baxter; Li, Jingjing; Batarseh, Alberto; Bartynski, Robert A; Galoppini, Elena; Gundlach, Lars

2016-01-14

Heterogeneous electron transfer (HET) between photoexcited molecules and colloidal TiO 2 has been investigated for a set of Zn-porphyrin chromophores attached to the semiconductor via linkers that allow to change level alignment by 200 meV by reorientation of the dipole moment. These unique dye molecules have been studied by femtosecond transient absorption spectroscopy in solution and adsorbed on the TiO 2 colloidal film in vacuum. In solution energy transfer from the excited chromophore to the dipole group has been identified as a slow relaxation pathway competing with S 2 -S 1 internal conversion. On the film heterogeneous electron transfer occurred in 80 fs, much faster compared to all intramolecular pathways. Despite a difference of 200 meV in level alignment of the excited state with respect to the semiconductor conduction band, identical electron transfer times were measured for different linkers. The measurements are compared to a quantum-mechanical model that accounts for electronic-vibronic coupling and finite band width for the acceptor states. We conclude that HET occurs into a distribution of transition states that differs from regular surface states or bridge mediated states.

Elucidating nitric oxide synthase domain interactions by molecular dynamics.

PubMed

Hollingsworth, Scott A; Holden, Jeffrey K; Li, Huiying; Poulos, Thomas L

2016-02-01

Nitric oxide synthase (NOS) is a multidomain enzyme that catalyzes the production of nitric oxide (NO) by oxidizing L-Arg to NO and L-citrulline. NO production requires multiple interdomain electron transfer steps between the flavin mononucleotide (FMN) and heme domain. Specifically, NADPH-derived electrons are transferred to the heme-containing oxygenase domain via the flavin adenine dinucleotide (FAD) and FMN containing reductase domains. While crystal structures are available for both the reductase and oxygenase domains of NOS, to date there is no atomic level structural information on domain interactions required for the final FMN-to-heme electron transfer step. Here, we evaluate a model of this final electron transfer step for the heme-FMN-calmodulin NOS complex based on the recent biophysical studies using a 105-ns molecular dynamics trajectory. The resulting equilibrated complex structure is very stable and provides a detailed prediction of interdomain contacts required for stabilizing the NOS output state. The resulting equilibrated complex model agrees well with previous experimental work and provides a detailed working model of the final NOS electron transfer step required for NO biosynthesis. © 2015 The Protein Society.

ZnO-nanorods/graphene heterostructure: a direct electron transfer glucose biosensor

PubMed Central

Zhao, Yu; Li, Wenbo; Pan, Lijia; Zhai, Dongyuan; Wang, Yu; Li, Lanlan; Cheng, Wen; Yin, Wei; Wang, Xinran; Xu, Jian-Bin; Shi, Yi

2016-01-01

ZnO-nanorods/graphene heterostructure was synthesized by hydrothermal growth of ZnO nanorods on chemically reduced graphene (CRG) film. The hybrid structure was demonstrated as a biosensor, where direct electron transfer between glucose oxidase (GOD) and electrode was observed. The charge transfer was attributed to the ZnO nanorod wiring between the redox center of GOD and electrode, and the ZnO/graphene heterostructure facilitated the transport of electrons on the hybride electrode. The glucose sensor based on the GOD-ZnO/CRG/Pt electrode had a high sensitivity of 17.64 μA mM−1, which is higher than most of the previously reported values for direct electron transfer based glucose biosensors. Moreover, this biosensor is linearly proportional to the concentration of glucose in the range of 0.2–1.6 mM. The study revealed that the band structure of electrode could affect the detection of direct electron transfer of GOD, which would be helpful for the design of the biosensor electrodes in the future. PMID:27572675

Ultrafast electronic dynamics driven by nuclear motion

NASA Astrophysics Data System (ADS)

Vendrell, Oriol

2016-05-01

The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

Effects of Charge-Transfer Excitons on the Photophysics of Organic Semiconductors

NASA Astrophysics Data System (ADS)

Hestand, Nicholas J.

The field of organic electronics has received considerable attention over the past several years due to the promise of novel electronic materials that are cheap, flexible and light weight. While some devices based on organic materials have already emerged on the market (e.g. organic light emitting diodes), a deeper understanding of the excited states within the condensed phase is necessary both to improve current commercial products and to develop new materials for applications that are currently in the commercial pipeline (e.g. organic photovoltaics, wearable displays, and field effect transistors). To this end, a model for pi-conjugated molecular aggregates and crystals is developed and analyzed. The model considers two types of electronic excitations, namely Frenkel and charge-transfer excitons, both of which play a prominent role in determining the nature of the excited states within tightly-packed organic systems. The former consist of an electron-hole pair bound to the same molecule while in the later the electron and hole are located on different molecules. The model also considers the important nuclear reorganization that occurs when the system switches between electronic states. This is achieved using a Holstein-style Hamiltonian that includes linear vibronic coupling of the electronic states to the nuclear motion associated with the high frequency vinyl-stretching and ring-breathing modes. Analysis of the model reveals spectroscopic signatures of charge-transfer mediated J- and H-aggregation in systems where the photophysical properties are determined primarily by charge-transfer interactions. Importantly, such signatures are found to be sensitive to the relative phase of the intermolecular electron and hole transfer integrals, and the relative energy of the Frenkel and charge-transfer states. When the charge-transfer integrals are in phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits J-aggregate characteristics including a positive band curvature, a red shifted main absorption peak, and an increase in the ratio of the first two vibronic peaks relative to the monomer. On the other hand, when the charge-transfer integrals are out of phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits H-aggregate characteristics including a negative band curvature, a blue shifted main absorption peak, and a decrease in the ratio of the first two vibronic peaks relative to the monomer. Notably, these signatures are consistent with those exhibited by Coulombically coupled J- and H-aggregates. Additional signatures of charge-transfer J- and H-aggregation are also discovered, the most notable of which is the appearance of a second absorption band when the charge-transfer integrals are in phase and the charge-transfer and Frenkel excitons are near resonance. In such instances, the peak-to-peak spacing is found to be proportional to the sum of the electron and hole transfer integrals. Further analysis of the charge-transfer interactions within the context of an effective Frenkel exciton coupling reveals that the charge-transfer interactions interfere directly with the intermolecular Coulombic coupling. The interference can be either constructive or destructive resulting in either enhanced or suppressed J- or H- aggregate behavior relative to what is expected based on Coulombic coupling alone. Such interferences result in four new aggregate types, namely HH-, HJ-, JH-, and JJ-aggregates, where the first letter indicates the nature of the Coulombic coupling and the second indicates the nature of the charge-transfer coupling. Vibronic signatures of such aggregates are developed and provide a means by which to rapidly screen materials for certain electronic characteristics. Notably, a large total (Coulombic plus charge-transfer) exciton coupling is associated with an absorption spectrum in which the ratio of the first two vibronic peaks deviates significantly from that of the unaggregated monomer. Hence, strongly coupled, high exciton mobility aggregates can be readily distinguished from low mobility aggregates by the ratio of their first two vibronic peaks. (Abstract shortened by ProQuest.).

Fast electron transfer through a single molecule natively structured redox protein

NASA Astrophysics Data System (ADS)

Della Pia, Eduardo Antonio; Chi, Qijin; MacDonald, J. Emyr; Ulstrup, Jens; Jones, D. Dafydd; Elliott, Martin

2012-10-01

The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conductance through single-molecules of the electron transfer protein cytochrome b562 in its native conformation, under pseudo-physiological conditions. This is achieved by thiol (SH) linker pairs at opposite ends of the molecule through protein engineering, resulting in defined covalent contact between a gold surface and a platinum-iridium STM tip. Two different orientations of the linkers were examined: a long-axis configuration (SH-LA) and a short-axis configuration (SH-SA). In each case, the molecular conductance could be `gated' through electrochemical control of the heme redox state. Reproducible and remarkably high conductance was observed in this relatively complex electron transfer system, with single-molecule conductance values peaking around 18 nS and 12 nS for the SH-SA and SH-LA cytochrome b562 molecules near zero electrochemical overpotential. This strongly points to the important role of the heme co-factor bound to the natively structured protein. We suggest that the two-step model of protein electron transfer in the STM geometry requires a multi-electron transfer to explain such a high conductance. The model also yields a low value for the reorganisation energy, implying that solvent reorganisation is largely absent.The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conductance through single-molecules of the electron transfer protein cytochrome b562 in its native conformation, under pseudo-physiological conditions. This is achieved by thiol (SH) linker pairs at opposite ends of the molecule through protein engineering, resulting in defined covalent contact between a gold surface and a platinum-iridium STM tip. Two different orientations of the linkers were examined: a long-axis configuration (SH-LA) and a short-axis configuration (SH-SA). In each case, the molecular conductance could be `gated' through electrochemical control of the heme redox state. Reproducible and remarkably high conductance was observed in this relatively complex electron transfer system, with single-molecule conductance values peaking around 18 nS and 12 nS for the SH-SA and SH-LA cytochrome b562 molecules near zero electrochemical overpotential. This strongly points to the important role of the heme co-factor bound to the natively structured protein. We suggest that the two-step model of protein electron transfer in the STM geometry requires a multi-electron transfer to explain such a high conductance. The model also yields a low value for the reorganisation energy, implying that solvent reorganisation is largely absent. Electronic supplementary information (ESI) available: Experimental methods, DNA and protein sequences, additional STM statistical analysis and images, electrochemical data and It-z data analysis. See DOI: 10.1039/c2nr32131a

2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCusker, James

The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perlík, Václav; Seibt, Joachim; Šanda, František

The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system’s Hamiltonian, reproduces all measuredmore » quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.« less

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family.

PubMed

Garcia Costas, Amaya M; Poudel, Saroj; Miller, Anne-Frances; Schut, Gerrit J; Ledbetter, Rhesa N; Fixen, Kathryn R; Seefeldt, Lance C; Adams, Michael W W; Harwood, Caroline S; Boyd, Eric S; Peters, John W

2017-11-01

Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes. IMPORTANCE Electron bifurcation has recently been recognized as an electron transfer mechanism used by microorganisms to maximize energy conservation. Bifurcating enzymes couple thermodynamically unfavorable reactions with thermodynamically favorable reactions in an overall spontaneous process. Here we show that the electron-transferring flavoprotein (Etf) enzyme family exhibits far greater diversity than previously recognized, and we provide a phylogenetic analysis that clearly delineates bifurcating versus nonbifurcating members of this family. Structural modeling of proteins within these groups reveals key differences between the bifurcating and nonbifurcating Etfs. Copyright © 2017 American Society for Microbiology.

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family

PubMed Central

Garcia Costas, Amaya M.; Poudel, Saroj; Miller, Anne-Frances; Schut, Gerrit J.; Ledbetter, Rhesa N.; Seefeldt, Lance C.; Adams, Michael W. W.

2017-01-01

ABSTRACT Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes. IMPORTANCE Electron bifurcation has recently been recognized as an electron transfer mechanism used by microorganisms to maximize energy conservation. Bifurcating enzymes couple thermodynamically unfavorable reactions with thermodynamically favorable reactions in an overall spontaneous process. Here we show that the electron-transferring flavoprotein (Etf) enzyme family exhibits far greater diversity than previously recognized, and we provide a phylogenetic analysis that clearly delineates bifurcating versus nonbifurcating members of this family. Structural modeling of proteins within these groups reveals key differences between the bifurcating and nonbifurcating Etfs. PMID:28808132

Screening of exciplex formation by distant electron transfer.

PubMed

Fedorenko, S G; Khokhlova, S S; Burshtein, A I

2012-01-12

The excitation quenching by reversible exciplex formation, combined with irreversible but distant electron transfer, is considered by means of the integral encounter theory (IET). Assuming that the quenchers are in great excess, the set of IET equations for the excitations, free ions, and exciplexes is derived. Solving these equations gives the Laplace images of all these populations, and these are used to specify the quantum yields of the corresponding reaction products. It appears that diffusion facilitates the exciplex production and the electron transfer. On the other hand the stronger the electron transfer is, the weaker is the exciplex production. At slow diffusion the distant quenching of excitations by ionization prevents their reaching the contact where they can turn into exciplexes. This is a screening effect that is most pronounced when the ionization rate is large.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, K.S.; Freilich, S.C.; Schaeffer, C.G.

Studies were initiated utilizing picosecond (ps) absorption spectroscopy, to directly monitor the dynamics of electron transfer from 1,4-diazabicyclo(2.2.2)octane (Dabco) to the excited states of benzophenone and fluorenone. These two systems were chosen because of their contrasting photochemistry. The quantum yield for photoreduction of benzophenone in polar solvents is generally greater than 0.1, while that of fluorenone is zero. In polar solvents, the proposed mechanism dictates that an electron is transferred to the excited singlet state fluorenone, which then back-transfers the electron, regenerating ground-state fluorenone and amine. Photolysis of benzophenone in the presence of an amine transfers an electron to anmore » excited triplet state, forming an ion pair that is stable relative to diffusional separation. The results of this study verify this proposal.« less

Experimental studies of fundamental issues in electron transfer through nanometer scale devices

NASA Astrophysics Data System (ADS)

Yamamoto, Hiromichi

Electron transfer reactions constitute many of the primary events in materials science, chemistry, physics, and biochemistry, e.g. the electron transport properties and photoexcited processes in solids and molecules, chemical reactions, corrosion, photosynthesis, respiration, and so forth. A self-assembled monolayer (SAM) film provides us with a unique environment not only to understand and manipulate the surface electronic properties of a solid, but also to control electron transfer processes at the interface. The first topic in this thesis describes the structure and electron tunneling characterization of alkanethiol SAMs on InP(100). Angle-resolved X-ray photoelectron spectroscopy was used to characterize the bonding of alkanethiols to n-InP surfaces and to measure the monolayer thickness. The results showed that the sulfur binds to In atoms on the surface, and provided film thicknesses of 6.4 A for C8H17SH, 11.1 A for C12H25SH, and 14.9 A for C16H 33SH, resulting in an average tilt angle of 55°. The analysis indicated that super-exchange coupling between the alkane chains plays an important role in defining electron tunneling barriers, especially for highly tilted chains. The second topic describes studies of cytochrome c bound to pure and mixed SAMs of o-terminated alkanethiol (terminated with pyridine, imidazole or nitrile groups) and alkanethiol on gold. Electrochemical methods are used to determine electron transfer rate constants of cytochrome c, and scanning tunneling microscopy to observe the cytochrome c on the SAM. Detailed analysis revealed direct association of the heme of cytochrome c with the terminal groups of the SAMs and a 'turning-over' of the electron transfer of cytochrome c from adiabatic to non-adiabatic regime. The third topic describes studies of oxidation and reduction of cytochrome c in solution through eleven different self-assembled monolayers (SAMs) on gold electrodes by cyclic voltammetry. Electron transfer rate constants of cytochrome c through the eleven SAMs ranged from ≤10-4 to ˜10-1 cm/sec. A strong correlation between the electron transfer rate constants and the hydrogen bonding ability of the SAM is identified. This correlation is discussed in terms of the dependence of the rate constant on the outer-sphere reorganization energy and the electronic coupling between the cytochrome and the differently terminated monolayer films.

Single-molecule interfacial electron transfer dynamics in solar energy conversion

NASA Astrophysics Data System (ADS)

Dhital, Bharat

This dissertation work investigated the parameters affecting the interfacial electron transfer (ET) dynamics in dye-semiconductor nanoparticles (NPs) system by using single-molecule fluorescence spectroscopy and imaging combined with electrochemistry. The influence of the molecule-substrate electronic coupling, the molecular structure, binding geometry on the surface and the molecule-attachment surface chemistry on interfacial charge transfer processes was studied on zinc porphyrin-TiO2 NP systems. The fluorescence blinking measurement on TiO2 NP demonstrated that electronic coupling regulates dynamics of charge transfer processes at the interface depending on the conformation of molecule on the surface. Moreover, semiconductor surface charge induced electronic coupling of molecule which is electrostatically adsorbed on the semiconductor surface also predominantly alters the ET dynamics. Furthermore, interfacial electric field and electron accepting state density dependent ET dynamics has been dissected in zinc porphyrin-TiO2 NP system by observing the single-molecule fluorescence blinking dynamics and fluorescence lifetime with and without applied bias. The significant difference in fluorescence fluctuation and lifetime suggested the modulation of charge transfer dynamics at the interface with external electric field perturbation. Quasi-continuous distribution of fluorescence intensity with applied negative potential was attributed to the faster charge recombination due to reduced density of electron accepting states. The driving force and electron accepting state density ET dependent dynamics has also been probed in zinc porphyrin-TiO2 NP and zinc porphyrin-indium tin oxide (ITO) systems. Study of a molecule adsorbed on two different semiconductors (ITO and TiO2), with large difference in electron densities and distinct driving forces, allows us to observe the changes in rates of back electron transfer process reflected by the suppressed fluorescence blinking of molecule on ITO surface. Finally, the electric field effect on the interface properties has been probed by using surface-enhanced Raman spectroscopy and supported by density functional theory calculations in alizarin-TiO2 system. The perturbation, created by the external potential, has been observed to cause a shift and/or splitting interfacial bond vibrational mode, typical indicator of the coupling energy changes between alizarin and TiO2. Such splitting provides evidence for electric field-dependent electronic coupling changes that have a significant impact on the interfacial electron transfer dynamics.

Cumulative reports and publications through December 31, 1994

NASA Technical Reports Server (NTRS)

1995-01-01

This document contains a complete list of Institute for Computer Applications in Science and Engineering (ICASE) reports. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

How Nano are Nanocomposites (Preprint)

DTIC Science & Technology

2007-02-01

with λ being the wavelength of the radiation . Based on this Fourier transform, r and q are conjugate variables. Although Eqs. (1) and (2) are...generation material is produced from porcellanite, a mineral rich in amorphous silica that is found in the Negev desert in southern Israel (Dimosil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beigi, Salman

Sandwiched (quantum) α-Rényi divergence has been recently defined in the independent works of Wilde et al. [“Strong converse for the classical capacity of entanglement-breaking channels,” preprint http://arxiv.org/abs/arXiv:1306.1586 (2013)] and Müller-Lennert et al. [“On quantum Rényi entropies: a new definition, some properties and several conjectures,” preprint http://arxiv.org/abs/arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo informationmore » defined in terms of sandwiched α-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.« less

Space Sciences Laboratory publications and presentations, 1 January - 31 December, 1993

NASA Technical Reports Server (NTRS)

Moorehead, T. W.

1994-01-01

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 to December 31, 1993. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by report number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Space Sciences Laboratory Publications and Presentations

NASA Technical Reports Server (NTRS)

Moorehead, T. W. (Compiler)

1995-01-01

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period Jan. 1 - Dec. 31, 1994. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an appendix (arranged by report number) listing preprints issued by the laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in referenced professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Towards an open science publishing platform.

PubMed

Tracz, Vitek; Lawrence, Rebecca

2016-01-01

The way science and research is done is rapidly becoming more open and collaborative. The traditional way of publishing new findings in journals is becoming increasingly outdated and no longer serves the needs of much of science. Whilst preprints can bring significant benefits of removing delay and selection, they do not go far enough if simply implemented alongside the existing journal system. We propose that we need a new approach, an Open Science Platform, that takes the benefits of preprints but adds formal, invited, and transparent post-publication peer review. This bypasses the problems of the current journal system and, in doing so, moves the evaluation of research and researchers away from the journal-based Impact Factor and towards a fairer system of article-based qualitative and quantitative indicators. In the long term, it should be irrelevant where a researcher publishes their findings. What is important is that research is shared and made available without delay within a framework that encourages quality standards and requires all players in the research community to work as collaborators.

Space Science Laboratory Publications and Presentations

NASA Technical Reports Server (NTRS)

Moorehead, T. W. (Compiler)

1993-01-01

This document lists the significant publications and presentations of the Space Science Laboratory during the period January 1 - December 31, 1992. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by report number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Protocols for Scholarly Communication

NASA Astrophysics Data System (ADS)

Pepe, A.; Yeomans, J.

2007-10-01

CERN, the European Organization for Nuclear Research, has operated an institutional preprint repository for more than 10 years. The repository contains over 850,000 records of which more than 450,000 are full-text OA preprints, mostly in the field of particle physics, and it is integrated with the library's holdings of books, conference proceedings, journals and other grey literature. In order to encourage effective propagation and open access to scholarly material, CERN is implementing a range of innovative library services into its document repository: automatic keywording, reference extraction, collaborative management tools and bibliometric tools. Some of these services, such as user reviewing and automatic metadata extraction, could make up an interesting testbed for future publishing solutions and certainly provide an exciting environment for e-science possibilities. The future protocol for scientific communication should guide authors naturally towards OA publication, and CERN wants to help reach a full open access publishing environment for the particle physics community and related sciences in the next few years.

Sandwiched Rényi divergence satisfies data processing inequality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beigi, Salman

2013-12-15

Sandwiched (quantum) α-Rényi divergence has been recently defined in the independent works of Wilde et al. [“Strong converse for the classical capacity of entanglement-breaking channels,” preprint http://arxiv.org/abs/arXiv:1306.1586 (2013)] and Müller-Lennert et al. [“On quantum Rényi entropies: a new definition, some properties and several conjectures,” preprint http://arxiv.org/abs/arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo informationmore » defined in terms of sandwiched α-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.« less

Laser photolysis studies of the phenolic H-atom transfer mechanism for a triplet π,π ∗ ketone in solution revisited

NASA Astrophysics Data System (ADS)

Yamaji, Minoru; Aoyama, Yutaka; Furukawa, Takashi; Itoh, Takao; Tobita, Seiji

2006-03-01

The mechanism of the H-atom transfer from phenols or thiophenols to triplet π,π ∗ 5,12-naphthacenequinone (5,12-NQ) has been examined by means of laser flash photolysis at 295 K. Based on the Hammett plots and the Rehm-Weller equation for the quenching rate constants, the phenolic H-atom transfer from phenols or thiophenols to triplet π,π ∗ 5,12-NQ is shown to proceed via the electron transfer followed by proton transfer. The previously proposed mechanism for H-atom transfer of π,π ∗ triplets, that proton transfer is followed by electron transfer, was not verified in the present systems.

Fragment-based Quantum Mechanical/Molecular Mechanical Simulations of Thermodynamic and Kinetic Process of the Ru2+-Ru3+ Self-Exchange Electron Transfer.

PubMed

Zeng, Xiancheng; Hu, Xiangqian; Yang, Weitao

2012-12-11

A fragment-based fractional number of electron (FNE) approach, is developed to study entire electron transfer (ET) processes from the electron donor region to the acceptor region in condensed phase. Both regions are described by the density-fragment interaction (DFI) method while FNE as an efficient ET order parameter is applied to simulate the electron transfer process. In association with the QM/MM energy expression, the DFI-FNE method is demonstrated to describe ET processes robustly with the Ru 2+ -Ru 3+ self-exchange ET as a proof-of-concept example. This method allows for systematic calculations of redox free energies, reorganization energies, and electronic couplings, and the absolute ET rate constants within the Marcus regime.

Efficient algorithms for the simulation of non-adiabatic electron transfer in complex molecular systems: application to DNA.

PubMed

Kubař, Tomáš; Elstner, Marcus

2013-04-28

In this work, a fragment-orbital density functional theory-based method is combined with two different non-adiabatic schemes for the propagation of the electronic degrees of freedom. This allows us to perform unbiased simulations of electron transfer processes in complex media, and the computational scheme is applied to the transfer of a hole in solvated DNA. It turns out that the mean-field approach, where the wave function of the hole is driven into a superposition of adiabatic states, leads to over-delocalization of the hole charge. This problem is avoided using a surface hopping scheme, resulting in a smaller rate of hole transfer. The method is highly efficient due to the on-the-fly computation of the coarse-grained DFT Hamiltonian for the nucleobases, which is coupled to the environment using a QM/MM approach. The computational efficiency and partial parallel character of the methodology make it possible to simulate electron transfer in systems of relevant biochemical size on a nanosecond time scale. Since standard non-polarizable force fields are applied in the molecular-mechanics part of the calculation, a simple scaling scheme was introduced into the electrostatic potential in order to simulate the effect of electronic polarization. It is shown that electronic polarization has an important effect on the features of charge transfer. The methodology is applied to two kinds of DNA sequences, illustrating the features of transfer along a flat energy landscape as well as over an energy barrier. The performance and relative merit of the mean-field scheme and the surface hopping for this application are discussed.

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2012-08-20

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Group transfer and electron transfer reactions of organometallic complexes

NASA Astrophysics Data System (ADS)

Atwood, Jim D.

During 1994, despite the disruptions, the authors have made progress in several aspects of their research on electron transfer reactions between organometallic complexes. This summary covers three areas that are relatively complete: (1) reactions between metal carbonyl anions and metal carbonyl halides, (2) reactions of hydrido- and alkyl-containing anions (RFe(CO)4(-) and RW(CO)5(-) with metal carbonyl cations; and (3) reactions of a seventeen-electron complex (Cp* Cr(CO)3*) with metal carbonyl derivatives. Two areas of examination that have just begun (possible carbene transfer and the possible role of metal carbonyl anions in carbon-hydrogen bond activation) will also be described.

Tuning of Hemes b Equilibrium Redox Potential Is Not Required for Cross-Membrane Electron Transfer.

PubMed

Pintscher, Sebastian; Kuleta, Patryk; Cieluch, Ewelina; Borek, Arkadiusz; Sarewicz, Marcin; Osyczka, Artur

2016-03-25

In biological energy conversion, cross-membrane electron transfer often involves an assembly of two hemesb The hemes display a large difference in redox midpoint potentials (ΔEm_b), which in several proteins is assumed to facilitate cross-membrane electron transfer and overcome a barrier of membrane potential. Here we challenge this assumption reporting on hemebligand mutants of cytochromebc1in which, for the first time in transmembrane cytochrome, one natural histidine has been replaced by lysine without loss of the native low spin type of heme iron. With these mutants we show that ΔEm_b can be markedly increased, and the redox potential of one of the hemes can stay above the level of quinone pool, or ΔEm_b can be markedly decreased to the point that two hemes are almost isopotential, yet the enzyme retains catalytically competent electron transfer between quinone binding sites and remains functionalin vivo This reveals that cytochromebc1can accommodate large changes in ΔEm_b without hampering catalysis, as long as these changes do not impose overly endergonic steps on downhill electron transfer from substrate to product. We propose that hemesbin this cytochrome and in other membranous cytochromesbact as electronic connectors for the catalytic sites with no fine tuning in ΔEm_b required for efficient cross-membrane electron transfer. We link this concept with a natural flexibility in occurrence of several thermodynamic configurations of the direction of electron flow and the direction of the gradient of potential in relation to the vector of the electric membrane potential. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Estimates of electronic coupling for excess electron transfer in DNA

NASA Astrophysics Data System (ADS)

Voityuk, Alexander A.

2005-07-01

Electronic coupling Vda is one of the key parameters that determine the rate of charge transfer through DNA. While there have been several computational studies of Vda for hole transfer, estimates of electronic couplings for excess electron transfer (ET) in DNA remain unavailable. In the paper, an efficient strategy is established for calculating the ET matrix elements between base pairs in a π stack. Two approaches are considered. First, we employ the diabatic-state (DS) method in which donor and acceptor are represented with radical anions of the canonical base pairs adenine-thymine (AT) and guanine-cytosine (GC). In this approach, similar values of Vda are obtained with the standard 6-31G* and extended 6-31++G** basis sets. Second, the electronic couplings are derived from lowest unoccupied molecular orbitals (LUMOs) of neutral systems by using the generalized Mulliken-Hush or fragment charge methods. Because the radical-anion states of AT and GC are well reproduced by LUMOs of the neutral base pairs calculated without diffuse functions, the estimated values of Vda are in good agreement with the couplings obtained for radical-anion states using the DS method. However, when the calculation of a neutral stack is carried out with diffuse functions, LUMOs of the system exhibit the dipole-bound character and cannot be used for estimating electronic couplings. Our calculations suggest that the ET matrix elements Vda for models containing intrastrand thymine and cytosine bases are essentially larger than the couplings in complexes with interstrand pyrimidine bases. The matrix elements for excess electron transfer are found to be considerably smaller than the corresponding values for hole transfer and to be very responsive to structural changes in a DNA stack.

Monitoring the Reaction Process During the S2 → S3 Transition in Photosynthetic Water Oxidation Using Time-Resolved Infrared Spectroscopy.

PubMed

Sakamoto, Hiroki; Shimizu, Tatsuki; Nagao, Ryo; Noguchi, Takumi

2017-02-08

Photosynthetic water oxidation performed at the Mn 4 CaO 5 cluster in photosystem II plays a crucial role in energy production as electron and proton sources necessary for CO 2 fixation. Molecular oxygen, a byproduct, is a source of the oxygenic atmosphere that sustains life on earth. However, the molecular mechanism of water oxidation is not yet well-understood. In the reaction cycle of intermediates called S states, the S 2 → S 3 transition is particularly important; it consists of multiple processes of electron transfer, proton release, and water insertion, and generates an intermediate leading to O-O bond formation. In this study, we monitored the reaction process during the S 2 → S 3 transition using time-resolved infrared spectroscopy to clarify its molecular mechanism. A change in the hydrogen-bond interaction of the oxidized Y Z • radical, an immediate electron acceptor of the Mn 4 CaO 5 cluster, was clearly observed as a ∼100 μs phase before the electron-transfer phase with a time constant of ∼350 μs. This observation provides strong experimental evidence that rearrangement of the hydrogen-bond network around Y Z • , possibly due to the movement of a water molecule located near Y Z • to the Mn site, takes place before the electron transfer. The electron transfer was coupled with proton release, as revealed by a relatively high deuterium kinetic isotope effect of 1.9. This proton release, which decreases the redox potential of the Mn 4 CaO 5 cluster to facilitate electron transfer to Y Z • , was proposed to determine, as a rate-limiting step, the relatively slow electron-transfer rate of the S 2 → S 3 transition.

New electron-energy transfer rates for vibrational excitation of O2

NASA Astrophysics Data System (ADS)

Jones, D. B.; Campbell, L.; Bottema, M. J.; Brunger, M. J.

2003-09-01

We report on our computation of electron-energy transfer rates for vibrational excitation of O2. This work was necessitated by inadequacies in the electron-impact cross section databases employed in previous studies and, in one case, an inaccurate approximate formulation to the rate equation. Both these inadequacies led to incorrect energy transfer rates being published in the literature. We also demonstrate the importance of using cross sections that encompass an energy range that is extended enough to appropriately describe the environment under investigation.

Transient alkylaminium radicals in n-hexane. Condensed-phase ion-molecule reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werst, D.W.; Trifunac, A.D.

Time-resolved fluorescence detected magnetic resonance (FDMR) is used to observe alkylaminium radicals formed in n-hexane solutions by electron pulse radiolysis. The ease of observation of aminium radical FDMR signals increases with increasing alkyl substitution of the amine solutes. The results are discussed in terms of the ion-molecule reactions, such as proton transfer, which compete with the electron-transfer processes, i.e, the electron transfer from solute molecules to n-hexane radical cations and geminate recombination.

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

NASA Astrophysics Data System (ADS)

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-01

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K -shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion.

PubMed

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-02

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Cascading electron and hole transfer dynamics in a CdS/CdTe core-shell sensitized with bromo-pyrogallol red (Br-PGR): slow charge recombination in type II regime.

PubMed

Maity, Partha; Debnath, Tushar; Chopra, Uday; Ghosh, Hirendra Nath

2015-02-14

Ultrafast cascading hole and electron transfer dynamics have been demonstrated in a CdS/CdTe type II core-shell sensitized with Br-PGR using transient absorption spectroscopy and the charge recombination dynamics have been compared with those of CdS/Br-PGR composite materials. Steady state optical absorption studies suggest that Br-PGR forms strong charge transfer (CT) complexes with both the CdS QD and CdS/CdTe core-shell. Hole transfer from the photo-excited QD and QD core-shell to Br-PGR was confirmed by both steady state and time-resolved emission spectroscopy. Charge separation was also confirmed by detecting electrons in the conduction band of the QD and the cation radical of Br-PGR as measured from femtosecond transient absorption spectroscopy. Charge separation in the CdS/Br-PGR composite materials was found to take place in three different pathways, by transferring the photo-excited hole of CdS to Br-PGR, electron injection from the photo-excited Br-PGR to the CdS QD, and direct electron transfer from the HOMO of Br-PGR to the conduction band of the CdS QD. However, in the CdS/CdTe/Br-PGR system hole transfer from the photo-excited CdS to Br-PGR and electron injection from the photo-excited Br-PGR to CdS take place after cascading through the CdTe shell QD. Charge separation also takes place via direct electron transfer from the Br-PGR HOMO to the conduction band of CdS/CdTe. Charge recombination (CR) dynamics between the electron in the conduction band of the CdS QD and the Br-PGR cation radical were determined by monitoring the bleach recovery kinetics. The CR dynamics were found to be much slower in the CdS/CdTe/Br-PGR system than in the CdS/Br-PGR system. The formation of the strong CT complex and the separation of charges cascading through the CdTe shell help to slow down charge recombination in the type II regime.

Time-resolved measurement of intramolecular photoinduced electron transfer processes in perylene diimides (Conference Presentation)

NASA Astrophysics Data System (ADS)

Döring, Robin Carl; Baal, Eduard; Sundermeyer, Jörg; Chatterjee, Sangam

2017-02-01

Perylene-3,4,9,10-tetracarboxylic acid (PTCDA) and respective derivatives (e.g. perylene diimide - PDI) are widely used as dyes but also for device applications such as organic field effect transistors or in organic photovoltaics. Due to their intrinsically high quantum efficiencies they are also used as spectroscopic standards. One major drawback of these materials is their low solubility in organic solvents which can be addressed by long alkyl substitutions. When introducing a tertiary amine into the molecule a mechanism known as photoinduced electron transfer (PET) can occur. Here, following an optically excited HOMO-LUMO transition of the core, an electron from the electron lone pair of the amine is transferred to the HOMO of the perylene core. Hence, radiative recombination is disallowed and photoluminescence effectively quenched. Here, we perform a systematic study of the distance dependence of the PET by introducing alkyle groups as spacer units between PDI core and the tertiary amine. Dynamics of the PET are extracted from ultrafast time-resolved photoluminescence measurement data. A rate equation model, simulating a three level system, reveals rate constant of the back electron transfer, otherwise not accessible with our experimental methods. Assuming a Marcus model of electron transfer, electronic coupling strength between the electronic states involved in the respective transitions can be calculated. In addition to the distance dependence, the effects of protonation and methylation of the the tertiary amine units are studied.

Near field wireless power transfer using curved relay resonators for extended transfer distance

NASA Astrophysics Data System (ADS)

Zhu, D.; Clare, L.; Stark, B. H.; Beeby, S. P.

2015-12-01

This paper investigates the performance of a near field wireless power transfer system that uses curved relay resonator to extend transfer distance. Near field wireless power transfer operates based on the near-field electromagnetic coupling of coils. Such a system can transfer energy over a relatively short distance which is of the same order of dimensions of the coupled coils. The energy transfer distance can be increased using flat relay resonators. Recent developments in printing electronics and e-textiles have seen increasing demand of embedding electronics into fabrics. Near field wireless power transfer is one of the most promising methods to power electronics on fabrics. The concept can be applied to body-worn textiles by, for example, integrating a transmitter coil into upholstery, and a flexible receiver coil into garments. Flexible textile coils take on the shape of the supporting materials such as garments, and therefore curved resonator and receiver coils are investigated in this work. Experimental results showed that using curved relay resonator can effectively extend the wireless power transfer distance. However, as the curvature of the coil increases, the performance of the wireless power transfer, especially the maximum received power, deteriorates.

Internal electron transfer between hemes and Cu(II) bound at cysteine beta93 promotes methemoglobin reduction by carbon monoxide.

PubMed

Bonaventura, C; Godette, G; Tesh, S; Holm, D E; Bonaventura, J; Crumbliss, A L; Pearce, L L; Peterson, J

1999-02-26

Previous studies showed that CO/H2O oxidation provides electrons to drive the reduction of oxidized hemoglobin (metHb). We report here that Cu(II) addition accelerates the rate of metHb beta chain reduction by CO by a factor of about 1000. A mechanism whereby electron transfer occurs via an internal pathway coupling CO/H2O oxidation to Fe(III) and Cu(II) reduction is suggested by the observation that the copper-induced rate enhancement is inhibited by blocking Cys-beta93 with N-ethylmaleimide. Furthermore, this internal electron-transfer pathway is more readily established at low Cu(II) concentrations in Hb Deer Lodge (beta2His --> Arg) and other species lacking His-beta2 than in Hb A0. This difference is consistent with preferential binding of Cu(II) in Hb A0 to a high affinity site involving His-beta2, which is ineffective in promoting electron exchange between Cu(II) and the beta heme iron. Effective electron transfer is thus affected by Hb type but is not governed by the R left arrow over right arrow T conformational equilibrium. The beta hemes in Cu(II)-metHb are reduced under CO at rates close to those observed for cytochrome c oxidase, where heme and copper are present together in the oxygen-binding site and where internal electron transfer also occurs.

Conversion and origin of normal and abnormal temperature dependences of kinetic isotope effect in hydride transfer reactions.

PubMed

Zhu, Xiao-Qing; Li, Xiu-Tao; Han, Su-Hui; Mei, Lian-Rui

2012-05-18

The effects of substituents on the temperature dependences of kinetic isotope effect (KIE) for the reactions of the hydride transfer from the substituted 5-methyl-6-phenyl-5,6-dihydrophenanthridine (G-PDH) to thioxanthylium (TX(+)) in acetonitrile were examined, and the results show that the temperature dependences of KIE for the hydride transfer reactions can be converted by adjusting the nature of the substituents in the molecule of the hydride donor. In general, electron-withdrawing groups can make the KIE to have normal temperature dependence, but electron-donating groups can make the KIE to have abnormal temperature dependence. Thermodynamic analysis on the possible pathways of the hydride transfer from G-PDH to TX(+) in acetonitrile suggests that the transfers of the hydride anion in the reactions are all carried out by the concerted one-step mechanism whether the substituent is an electron-withdrawing group or an electron-donating group. But the examination of Hammett-type free energy analysis on the hydride transfer reactions supports that the concerted one-step hydride transfer is not due to an elementary chemical reaction. The experimental values of KIE at different temperatures for the hydride transfer reactions were modeled by using a kinetic equation formed according to a multistage mechanism of the hydride transfer including a returnable charge-transfer complex as the reaction intermediate; the real mechanism of the hydride transfer and the root that why the temperature dependences of KIE can be converted as the nature of the substituents are changed were discovered.

Experimental exploration of the Mulliken-Hush relationship for intramolecular electron transfer reactions.

PubMed

Mukherjee, Tamal; Ito, Naoki; Gould, Ian R

2011-03-17

The Mulliken-Hush (M-H) relationship provides the critical link between optical and thermal electron transfer processes, and yet very little direct experimental support for its applicability has been provided. Dicyanovinylazaadamantane (DCVA) represents a simple two-state (neutral/charge-transfer) intramolecular electron transfer system that exhibits charge-transfer absorption and emission spectra that are readily measurable in solvents with a wide range of polarities. In this regard it represents an ideal model system for studying the factors that control both optical charge separation (absorption) and recombination (emission) processes in solution. Here we explore the applicability of the M-H relation to quantitative descriptions of the optical charge-transfer processes in DCVA. For DCVA, the measured radiative rate constants exhibit a linear dependence on transition energy, and transition dipole moments exhibit an inverse dependence on transition energy, consistent with the M-H relationship.

Proton-Coupled Electron Transfer in Artificial Photosynthetic Systems.

PubMed

Mora, S Jimena; Odella, Emmanuel; Moore, Gary F; Gust, Devens; Moore, Thomas A; Moore, Ana L

2018-02-20

Artificial photosynthetic constructs can in principle operate more efficiently than natural photosynthesis because they can be rationally designed to optimize solar energy conversion for meeting human demands rather than the multiple needs of an organism competing for growth and reproduction in a complex ecosystem. The artificial photosynthetic constructs described in this Account consist primarily of covalently linked synthetic chromophores, electron donors and acceptors, and proton donors and acceptors that carry out the light absorption, electron transfer, and proton-coupled electron transfer (PCET) processes characteristic of photosynthetic cells. PCET is the movement of an electron from one site to another accompanied by proton transfer. PCET and the transport of protons over tens of angstroms are important in all living cells because they are a fundamental link between redox processes and the establishment of transmembrane gradients of proton electrochemical potential, known as proton-motive force (PMF), which is the unifying concept in bioenergetics. We have chosen a benzimidazole phenol (BIP) system as a platform for the study of PCET because with appropriate substitutions it is possible to design assemblies in which one or multiple proton transfers can accompany oxidation of the phenol. In BIP, oxidation of the phenol increases its acidity by more than ten pK a units; thus, electrochemical oxidation of the phenol is associated with a proton transfer to the imidazole. This is an example of a PCET process involving transfer of one electron and one proton, known as electron-proton transfer (EPT). When the benzimidazole moiety of BIP is substituted at the 4-position with good proton acceptor groups such as aliphatic amines, experimental and theoretical results indicate that two proton transfers occur upon one-electron oxidation of the phenol. This phenomenon is described as a one-electron-two-proton transfer (E2PT) process and results in translocation of protons over ∼7 Å via a Grotthuss-type mechanism, where the protons traverse a network of internally H-bonded sites. In the case of the E2TP process involving BIP analogues with amino group substituents, the thermodynamic price paid in redox potential to move a proton to the final proton acceptor is ∼300 mV. In this example, the decrease in redox potential limits the oxidizing power of the resulting phenoxyl radical. Thus, unlike the biological counterpart, the artificial construct is thermodynamically incapable of effectively advancing the redox state of a water oxidation catalyst. The design of systems where multiple proton transfer events are coupled to an oxidation reaction while a relatively high redox potential is maintained remains an outstanding challenge. The ability to control proton transfer and activity at defined distances and times is key to achieving proton management in the vicinity of catalysts operating at low overpotential in myriad biochemically important processes. Artificial photosynthetic constructs with well-defined structures, such as the ones described in this Account, can provide the means for discovering design principles upon which efficient redox catalysts for electrolysis and fuel cells can be based.

Metabolic spatial variability in electrode-respiring Geobacter sulfurreducens biofilms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renslow, Ryan S.; Babauta, Jerome T.; Dohnalkova, Alice

2013-06-01

Certain bacteria are capable of transferring electrons derived from respiratory metabolism to solid extracellular electron-accepting materials1-4. This ability allows the organisms to use conductive substrata as their sole electron sink, generating electricity that is available for practical applications5-7. Geobacter is a biofilm-forming genus capable of this extracellular electron transfer8-11. Evidence in the literature suggests that Geobacter cells produce a conductive matrix to gain access to electron-accepting surfaces12,13. It has been hypothesized that cells that are more than tens of microns from the electron-accepting surface cannot respire because of electrical resistance in the matrix and thus remain metabolically inactive14-16. To testmore » this hypothesis, we sought to determine whether the entire biofilm remains metabolically active and able to respire on an electron-accepting surface as the biofilm thickness increases. We developed and used a novel electrochemical-nuclear magnetic resonance (EC-NMR) microimaging system capable of sustaining an electrochemically active biofilm on a polarized electrode inside a superconducting magnet, allowing for simultaneous NMR and electrochemical investigation of a biofilm for the first time. Here, we show that Geobacter biofilms can grow to several hundred microns thick while respiring on an electrode and that the top of the biofilm remains metabolically active. This is only possible if the cells near the top are able to transfer electrons through the initial biofilm matrix to the electrode. We used X-ray absorption spectroscopy to verify electron transfer to uranium ions by metabolically active cells near the top of the biofilm. Our results reveal that extracellular electron transfer is not prevented by electrical resistance, even when the biofilm is hundreds of microns thick. Furthermore, the electron donor may be the limiting factor for respiration and the base of the biofilm may be less active despite being in close proximity to the electrode. Long-range electron transfer across metabolically inactive regions within Geobacter biofilms adds a novel facet to our comprehension of electrochemically active biology.« less

Electron impact cross-sections and cooling rates for methane. [in thermal balance of electrons in atmospheres and ionospheres of planets and satellites in outer solar system

NASA Technical Reports Server (NTRS)

Gan, L.; Cravens, T. E.

1992-01-01

Energy transfer between electrons and methane gas by collisional processes plays an important role in the thermal balance of electrons in the atmospheres and ionospheres of planets and satellites in the outer solar system. The literature is reviewed for electron impact cross-sections for methane in this paper. Energy transfer rates are calculated for elastic and inelastic processes using a Maxwellian electron distribution. Vibrational, rotational, and electronic excitation and ionization are included. Results are presented for a wide range of electron temperatures and neutral temperatures.

Impact excitation and electron-hole multiplication in graphene and carbon nanotubes.

PubMed

Gabor, Nathaniel M

2013-06-18

In semiconductor photovoltaics, photoconversion efficiency is governed by a simple competition: the incident photon energy is either transferred to the crystal lattice (heat) or transferred to electrons. In conventional materials, energy loss to the lattice is more efficient than energy transferred to electrons, thus limiting the power conversion efficiency. Quantum electronic systems, such as quantum dots, nanowires, and two-dimensional electronic membranes, promise to tip the balance in this competition by simultaneously limiting energy transfer to the lattice and enhancing energy transfer to electrons. By exploring the optical, thermal, and electronic properties of quantum materials, we may perhaps find an ideal optoelectronic material that provides low cost fabrication, facile systems integration, and a means to surpass the standard limit for photoconversion efficiency. Nanoscale carbon materials, such as graphene and carbon nanotubes, provide ideal experimental quantum systems in which to explore optoelectronic behavior for applications in solar energy harvesting. Within essentially the same material, researchers can achieve a broad spectrum of energetic configurations, from a gapless semimetal to a large band-gap semiconducting nanowire. Owing to their nanoscale dimensions, graphene and carbon nanotubes exhibit electronic and optical properties that reflect strong electron-electron interactions. Such strong interactions may lead to exotic low-energy electron transport behavior and high-energy electron scattering processes such as impact excitation and the inverse process of Auger recombination. High-energy processes, which become very important under photoexcitation, may be particularly efficient in nanoscale carbon materials due to the relativistic-like, charged particle band structure and sensitivity to the dielectric environment. In addition, due to the covalently bonded carbon framework that makes up these materials, electron-phonon coupling is very weak. In carbon nanomaterials, strong electron-electron interactions combined with weak electron-phonon interactions results in excellent optical, thermal and electronic properties, the exploration of which promises to reveal fundamentally new physical processes and deliver advanced nanotechnologies. In this Account, we review the results of novel optoelectronic experiments that explore the intrinsic photoresponse of carbon nanomaterials integrated into nanoscale devices. By fabricating gate voltage-controlled photodetectors composed of atomically thin sheets of graphene and individual carbon nanotubes, we are able to fully explore electron transport in these systems under optical illumination. We find that strong electron-electron interactions play a key role in the intrinsic photoresponse of both materials, as evidenced by hot carrier transport in graphene and highly efficient multiple electron-hole pair generation in nanotubes. In both of these quantum systems, photoexcitation leads to high-energy electron-hole pairs that relax energy predominantly into the electronic system, rather than heating the lattice. Due to highly efficient energy transfer from photons into electrons, graphene and carbon nanotubes may be ideal materials for solar energy harvesting devices with efficiencies that could exceed the Shockley-Queisser limit.

Photoinduced triplet-triplet energy transfer in a 2-ureido-4(1H)-pyrimidinone-bridged, quadruply hydrogen-bonded ferrocene-fullerene assembly.

PubMed

Feng, Ke; Yu, Mao-Lin; Wang, Su-Min; Wang, Ge-Xia; Tung, Chen-Ho; Wu, Li-Zhu

2013-01-14

2-Ureido-4(1H)-pyrimidinone-bridged ferrocene-fullerene assembly I is designed and synthesized for elaborating the photoinduced electron-transfer processes in self-complementary quadruply hydrogen-bonded modules. Unexpectedly, steady-state and time-resolved spectroscopy reveal an inefficient electron-transfer process from the ferrocene to the singlet or triplet excited state of the fullerene, although the electron-transfer reactions are thermodynamically feasible. Instead, an effective intra-assembly triplet-triplet energy-transfer process is found to be operative in assembly I with a rate constant of 9.2×10(5) s(-1) and an efficiency of 73% in CH(2)Cl(2) at room temperature. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microelectrode voltammetry of multi-electron transfers complicated by coupled chemical equilibria: a general theory for the extended square scheme.

PubMed

Laborda, Eduardo; Gómez-Gil, José María; Molina, Angela

2017-06-28

A very general and simple theoretical solution is presented for the current-potential-time response of reversible multi-electron transfer processes complicated by homogeneous chemical equilibria (the so-called extended square scheme). The expressions presented here are applicable regardless of the number of electrons transferred and coupled chemical processes, and they are particularized for a wide variety of microelectrode geometries. The voltammetric response of very different systems presenting multi-electron transfers is considered for the most widely-used techniques (namely, cyclic voltammetry, square wave voltammetry, differential pulse voltammetry and steady state voltammetry), studying the influence of the microelectrode geometry and the number and thermodynamics of the (electro)chemical steps. Most appropriate techniques and procedures for the determination of the 'interaction' between successive transfers are discussed. Special attention is paid to those situations where homogeneous chemical processes, such as protonation, complexation or ion association, affect the electrochemical behaviour of the system by different stabilization of the oxidation states.

Tuning the driving force for exciton dissociation in single-walled carbon nanotube heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ihly, Rachelle; Mistry, Kevin S.; Ferguson, Andrew J.

2016-04-25

Understanding the kinetics and energetics of interfacial electron transfer in molecular systems is crucial for the development of a broad array of technologies, including photovoltaics, solar fuel systems and energy storage. The Marcus formulation for electron transfer relates the thermodynamic driving force and reorganization energy for charge transfer between a given donor/acceptor pair to the kinetics and yield of electron transfer. Here we investigated the influence of the thermodynamic driving force for photoinduced electron transfer (PET) between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives by employing time-resolved microwave conductivity as a sensitive probe of interfacial exciton dissociation. For the firstmore » time, we observed the Marcus inverted region (in which driving force exceeds reorganization energy) and quantified the reorganization energy for PET for a model SWCNT/acceptor system. The small reorganization energies (about 130 meV, most of which probably arises from the fullerene acceptors) are beneficial in minimizing energy loss in photoconversion schemes.« less

Photochromic molecules as building blocks for molecular electronics.

PubMed

Peter, Belser

2010-01-01

Energy and electron transfer processes can be easily induced by a photonic excitation of a donor metal complex ([Ru(bpy)3]2), which is connected via a wire-type molecular fragment to an acceptor metal complex ([Os(bpy)3]2+). The rate constant for the transfer process can be determined by emission measurements of the two connected metal complexes. The system can be modified by incorporation of a switching unit or an interrupter into the wire, influencing the transfer process. Such a molecular device corresponds to an interrupter, mimic the same function applied in molecular electronics. We have used organic switches, which show photochromic properties. By irradiation with light of different wavelengths, the switch changes its functionality by a photochemical reaction from an OFF- to an ON-state and vice versa. The ON- respectively OFF-state is manifested by a color change but also in different conductivity properties for energy and electron transfer processes. Therefore, the mentioned molecular device can work as a simple interrupter, controlling the rate of the transfer processes.

Outward electron transfer by Saccharomyces cerevisiae monitored with a bi-cathodic microbial fuel cell-type activity sensor.

PubMed

Ducommun, Raphaël; Favre, Marie-France; Carrard, Delphine; Fischer, Fabian

2010-03-01

A Janus head-like bi-cathodic microbial fuel cell was constructed to monitor the electron transfer from Saccharomyces cerevisiae to a woven carbon anode. The experiments were conducted during an ethanol cultivation of 170 g/l glucose in the presence and absence of yeast-peptone medium. First, using a basic fuel-cell type activity sensor, it was shown that yeast-peptone medium contains electroactive compounds. For this purpose, 1% solutions of soy peptone and yeast extract were subjected to oxidative conditions, using a microbial fuel cell set-up corresponding to a typical galvanic cell, consisting of culture medium in the anodic half-cell and 0.5 M K(3)Fe(CN)(6) in the cathodic half-cell. Second, using a bi-cathodic microbial fuel cell, it was shown that electrons were transferred from yeast cells to the carbon anode. The participation of electroactive compounds in the electron transport was separated as background current. This result was verified by applying medium-free conditions, where only glucose was fed, confirming that electrons are transferred from yeast cells to the woven carbon anode. Knowledge about the electron transfer through the cell membrane is of importance in amperometric online monitoring of yeast fermentations and for electricity production with microbial fuel cells. Copyright (c) 2009 John Wiley & Sons, Ltd.

Fractional conductance oscillations in quantum rings: wave packet picture of transport in a few-electron system.

PubMed

Chwiej, T; Szafran, B

2013-04-17

We study electron transfer across a two-terminal quantum ring using a time-dependent description of the scattering process. For the considered scattering event the quantum ring is initially charged with one or two electrons, with another electron incident to the ring from the input channel. We study the electron transfer probability (T) as a function of the external magnetic field. We determine the periodicity of T for a varied number of electrons confined within the ring. For that purpose we develop a method to describe the wave packet dynamics for a few electrons participating in the scattering process, taking into full account the electron-electron correlations. We find that electron transfer across the quantum ring initially charged by a single electron acquires a distinct periodicity of half of the magnetic flux quantum (Φ0/2), corresponding to the formation of a transient two-electron state inside the ring. In the case of a three-electron scattering problem with two electrons initially occupying the ring, a period of Φ0/3 for T is formed in the limit of thin channels. The effect of disorder present in the confinement potential of the ring is also discussed.

Linguistic Communications 1.

ERIC Educational Resources Information Center

Monash Univ., Clayton, Victoria (Australia).

The present compilation of papers on linguistics is the result of joint efforts by the Classical Studies, French, Japanese, Linguistics, and Russian Departments of Monash University. Selections in the Pre-Prints and Articles section include: "For/Arabic Bilingualism in the Zalingei Area," by B. Jernudd; "Prosodic Problems in a Generative Phonology…

Wind Energy-Related Atmospheric Boundary Layer Large-Eddy Simulation Using OpenFOAM: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Churchfield, M.J.; Vijayakumar, G.; Brasseur, J.G.

This paper develops and evaluates the performance of a large-eddy simulation (LES) solver in computing the atmospheric boundary layer (ABL) over flat terrain under a variety of stability conditions, ranging from shear driven (neutral stratification) to moderately convective (unstable stratification).

Automated Aerial Refueling Presentation to 2007 ARSAG Conference (Preprint)

DTIC Science & Technology

2007-04-01

this technology allows manned or unmanned platforms to fly formation in IFR conditions. 3 3Approved for public release; distribution is unlimited...conducted in conjunction with the DARPA TTNT China Lake test It was determine that TTNT needed slight modifications which have been incorporated. Station

Bio-Based Approaches to Inorganic Material Synthesis (Preprint)

DTIC Science & Technology

2007-03-01

involves the fungus and plant pathogen Fusarium oxysporum acting on amorphous silica in rice husks to transform it into crystalline silica...nanoparticles after 24 hrs at room temperature [3]. Specific cationic proteins from F. oxysporum were found to be associated with the crystalline silica 2 after

Modeling Human Performance in Restless Bandits with Particle Filters (Preprint)

DTIC Science & Technology

2009-01-01

respond to changes ( Gallistel , 2001). Here, we use a particle filter approach to finding solutions to the restless bandit problem. Particle...Experimental Psychology: Learning, Memory, and Cognition, 10(2), 258-270. Gallistel , C. R., Mark, T., King, A., & Latham, P. E. (2001). The rat

75 FR 55330 - Agency Information Collection Activities: Proposed Collection; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-10

... physician self-referral prohibition in section 1877 of the Social Security Act for certain arrangements in... providing services or furnishing items under Medicaid; conducting audits of claims submitted for payment... Information Collection: State Plan Preprint for Medicaid Recovery Audit Contractors (RACs); Use: Under section...

Non-Local Propagation of Correlations in Quantum Systems with Long-Range Interactions

DTIC Science & Technology

2014-07-10

interferencepathways13.Thisprocessdiffers substantially from local quenches21, where a single site emits quasiparticles thatmay travel ballistically3,13...Preprint at http://arxiv.org/abs/1401.6174 (2014). 21. Jurcevic, P. et al. Quasiparticle engineering and entanglement propagation in a quantummany-body

Amide Neighbouring-Group Effects in Peptides: Phenylalanine as Relay Amino Acid in Long-Distance Electron Transfer.

PubMed

Nathanael, Joses G; Gamon, Luke F; Cordes, Meike; Rablen, Paul R; Bally, Thomas; Fromm, Katharina M; Giese, Bernd; Wille, Uta

2018-05-04

In nature, proteins serve as media for long-distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single-step superexchange or through a multi-step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long-distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilise the Phe radical cation. This neighbouring-amide-group effect helps improve understanding of the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anion Photoelectron Spectroscopy of the Homogenous 2-Hydroxypyridine Dimer Electron Induced Proton Transfer System

NASA Astrophysics Data System (ADS)

Vlk, Alexandra; Stokes, Sarah; Wang, Yi; Hicks, Zachary; Zhang, Xinxing; Blando, Nicolas; Frock, Andrew; Marquez, Sara; Bowen, Kit; Bowen Lab JHU Team

Anion photoelectron spectroscopic (PES) and density functional theory (DFT) studies on the dimer anion of (2-hydroxypyridine)2-are reported. The experimentally measured vertical detachment energy (VDE) of 1.21eV compares well with the theoretically predicted values. The 2-hydroxypyridine anionic dimer system was investigated because of its resemblance to the nitrogenous heterocyclic pyrimidine nucleobases. Experimental and theoretical results show electron induced proton transfer (EIPT) in both the lactim and lactam homogeneous dimers. Upon electron attachment, the anion can serve as the intermediate between the two neutral dimers. A possible double proton transfer process can occur from the neutral (2-hydroxypyridine)2 to (2-pyridone)2 through the dimer anion. This potentially suggests an electron catalyzed double proton transfer mechanism of tautomerization. Research supported by the NSF Grant No. CHE-1360692.

Probe-based measurement of lateral single-electron transfer between individual molecules

PubMed Central

Steurer, Wolfram; Fatayer, Shadi; Gross, Leo; Meyer, Gerhard

2015-01-01

The field of molecular electronics aims at using single molecules as functional building blocks for electronics components, such as switches, rectifiers or transistors. A key challenge is to perform measurements with atomistic control over the alignment of the molecule and its contacting electrodes. Here we use atomic force microscopy to examine charge transfer between weakly coupled pentacene molecules on insulating films with single-electron sensitivity and control over the atomistic details. We show that, in addition to the imaging capability, the probe tip can be used to control the charge state of individual molecules and to detect charge transfers to/from the tip, as well as between individual molecules. Our approach represents a novel route for molecular charge transfer studies with a host of opportunities, especially in combination with single atom/molecule manipulation and nanopatterning techniques. PMID:26387533

12 CFR 205.16 - Disclosures at automated teller machines.

Code of Federal Regulations, 2010 CFR

2010-01-01

... which a consumer initiates an electronic fund transfer or a balance inquiry and that does not hold the account to or from which the transfer is made, or about which an inquiry is made. (b) General. An... transfer or a balance inquiry shall: (1) Provide notice that a fee will be imposed for providing electronic...

Ab initio study of charge transfer between lithium and aromatic hydrocarbons. Can the results be directly transferred to the lithium-graphene interaction?

PubMed

Sadlej-Sosnowska, N

2014-08-28

We have used electronic density calculations to study neutral complexes of Li with aromatic hydrocarbons. The charge transferred between a Li atom and benzene, coronene, circumcoronene, and circumcircumcoronene has been studied by ab initio methods (at the HF and MP2 level). Toward this aim, the method of integrating electron density in two cuboid fragments of space was applied. One of the fragments was constructed so that it enclosed the bulk of the electron density of lithium; the second, the bulk of the electron density of hydrocarbon. It was found that for each complex two conformations were identified: the most stable with a greater vertical Li-hydrocarbon distance, on the order of 2.5 Å, and another of higher energy with a corresponding distance less than 2 Å. In all cases the transfer of a fractional number, 0.1-0.3 electrons, between Li and hydrocarbon was found; however, the direction of the transfer was not the same in all complexes investigated. The structures of complexes of the first configuration could be represented as Li(σ-)···AH(σ+), whereas the opposite direction of charge transfer was found for complexes of the second configuration, with higher energy. The directions of the dipole moments in the complexes supported these conclusions because they directly measure the redistribution of electron density in a complex with respect to substrates.

78 FR 59375 - Agency Information Collection Activities: Submission to OMB for Reinstatement, Without Change, of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-26

... transfer information to maintain its vendor (credit union) records to make electronic payments to credit... current electronic funds transfer data for its vendor (credit union) electronic routing and transit data... such as through the use of automated collection techniques or other forms of information technology. It...

Mulliken Hush elucidation of the encounter (precursor) complex in intermolecular electron transfer via self-exchange of tetracyanoethylene anion-radical

NASA Astrophysics Data System (ADS)

Rosokha, S. V.; Newton, M. D.; Head-Gordon, M.; Kochi, J. K.

2006-05-01

The paramagnetic [1:1] encounter complex (TCNE)2-rad is established as the important precursor in the kinetics and mechanism of electron-transfer for the self-exchange between tetracyanoethylene acceptor ( TCNE) and its radical-anion as the donor. Spectroscopic observation of the dimeric complex (TCNE)2-rad by its intervalence absorption band at the solvent-dependent wavelength of λIV ˜ 1500 nm facilitates the application of Mulliken-Hush theory which reveals the significant electronic interaction extant between the pair of cofacial TCNE moieties with the sizable coupling of HDA = 1000 cm -1. The transient existence of such an encounter complex provides the critical link in the electron-transfer kinetics by lowering the classical Marcus reorganization barrier by the amount of HDA in this strongly adiabatic system. Ab initio quantum-mechanical methods as applied to independent theoretical computations of both the reorganization energy ( λ) and the electronic coupling element ( HDA) confirm the essential correctness of the Mulliken-Hush formalism for fast electron transfer via strongly coupled donor/acceptor encounter complexes.

Electrochemical performance and microbial community profiles in microbial fuel cells in relation to electron transfer mechanisms.

PubMed

Uria, Naroa; Ferrera, Isabel; Mas, Jordi

2017-10-18

Microbial fuel cells (MFCs) operating with complex microbial communities have been extensively reported in the past, and are commonly used in applications such as wastewater treatment, bioremediation or in-situ powering of environmental sensors. However, our knowledge on how the composition of the microbial community and the different types of electron transfer to the anode affect the performance of these bioelectrochemical systems is far from complete. To fill this gap of knowledge, we designed a set of three MFCs with different constrains limiting direct and mediated electron transfer to the anode. The results obtained indicate that MFCs with a naked anode on which a biofilm was allowed unrestricted development (MFC-A) had the most diverse archaeal and bacterial community, and offered the best performance. In this MFC both, direct and mediated electron transfer, occurred simultaneously, but direct electron transfer was the predominant mechanism. Microbial fuel cells in which the anode was enclosed in a dialysis membrane and biofilm was not allowed to develop (MFC-D), had a much lower power output (about 60% lower), and a prevalence of dissolved redox species that acted as putative electron shuttles. In the anolyte of this MFC, Arcobacter and Methanosaeta were the prevalent bacteria and archaea respectively. In the third MFC, in which the anode had been covered by a cation selective nafion membrane (MFC-N), power output decreased a further 5% (95% less than MFC-A). In this MFC, conventional organic electron shuttles could not operate and the low power output obtained was presumably attributed to fermentation end-products produced by some of the organisms present in the anolyte, probably Pseudomonas or Methanosaeta. Electron transfer mechanisms have an impact on the development of different microbial communities and in turn on MFC performance. Although a stable current was achieved in all cases, direct electron transfer MFC showed the best performance concluding that biofilms are the major contributors to current production in MFCs. Characterization of the complex microbial assemblages in these systems may help us to unveil new electrogenic microorganisms and improve our understanding on their role to the functioning of MFCs.

Electron Transport at the Microbe–Mineral Interface: A Synthesis of Current Research Challenges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richardson, David; Fredrickson, Jim K.; Zachara, John M.

2012-12-01

Many bacterial and archaeal species can couple growth to the respiratory reduction or oxidation of insoluble mineral oxides of transition metals. These solid substrates are abundant electron sinks and sources for life on Earth, but, since they are insoluble in water, they cannot enter the bacterial cells. So, to exploit these electron sinks and sources, specific respiratory electron-transfer mechanisms must overcome the physical limitations associated with electron transfer between a microbe and extracellular metal oxides. Recent microbiological, geochemical, biochemical, spectroscopic and structural work is beginning to shed light on the molecular mechanism and impacts of electron transfer at themicrobe–mineral interfacemore » from a nanometre to kilometre scale. The research field is attracting attention in applied quarters from those with interests in nanowires, microbial fuel cells, bioremediation and microbial cell factories.« less

Modelling magnetic reconnection events relevant for solar physics with the new Energy Conserving Moment Implicit Method

NASA Astrophysics Data System (ADS)

Boella, Elisabetta; Herrero-Gonzalez, Diego; Innocenti, Maria Elena; Bemporad, Alessandro; Lapenta, Giovanni

2017-04-01

Fully kinetic simulations of magnetic reconnection events in the solar environment are especially challenging due to the extreme range of spatial and temporal scales that characterises them. As one moves from the photosphere to the chromosphere and the corona, the temperature increases from sub eV to 10-100 eV, while the mass density decreases from 10-4 to 10-12 kg/m3 and further. The intrinsic scales of kinetic reconnection (inertial length and gyroradius) are tremendously smaller than the maximum resolution available in observations. Furthermore, no direct information is available on the size of reconnection regions, plasmoids and reconnection fronts, while observations suggest that the process can cascade down to very small scale te{Bemporad}. Resolving the electron and ion scales while simulating a sufficiently large domain is a great challenge facing solar modelling. An especially challenging aspect is the need to consider the Debye length. The very low temperature of the electrons and the large spatial and temporal scales make these simulations hard to implement within existing Particle in Cell (PIC) methods. The limit is the ratio of the grid spacing to the Debye length. PIC methods show good stability and energy conservation when the grid does not exceed the Debye length too much. Semi-implicit methods te{Brackbill, Langdon} improve on this point. Only the recently developed fully energy conserving implicit methods have solved the problem te{Markidis, Chen}, but at a high computational cost. Very recently, we have developed an efficient new semi-implicit algorithm, which has been proven to conserve energy exactly to machine precision te{Lapenta}. In this work, we illustrate the main steps that enabled this great breakthrough and report the implementation on a new massively parallel three dimensional PIC code, called ECsim te{Lapenta2}. The new approach is applied to the problem of reconnection in the solar environment. We compare results of a simple 2D configuration similar to the so-called GEM challenge for different ranges of electron temperature, density and magnetic field, relative to different distances from the photosphere, demonstrating the capability of the new code. Finally, we report on the first results (to the authors' knowledge) of realistic magnetic 3D reconnection simulations in the solar environment, considering a large domain sufficient to describe the interaction of large scale dynamics with the reconnection process. A. Bemporad, ApJ 689, 572 (2008). J.U. Brackbill and D.W. Forslund, J. Comput. Phys. 46, 271 (1982). A. Langdon et al., J. Comput. Phys. 51, 107 (1983). S. Markidis and G. Lapenta, J. Comput. Phys. 230, 7037 (2011). G. Chen et al., J. Comput. Phys. 230, 7018 (2011). G. Lapenta, arXiv preprint arXiv:1602.06326 (2016). G. Lapenta et al., arXiv preprint arXiv:1612.08289 (2016).

Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production

PubMed Central

Zhu, Nan; Zheng, Kaibo; Karki, Khadga J.; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E.; Pullerits, Tõnu; Chi, Qijin

2015-01-01

Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s−1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications. PMID:25996307