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Advances in Photosynthesis and Respiration
Biophysical Techniques in Photosynthesis Volume II Advances in Photosynthesis and Respiration VOLUME 26 Series Editor: GOVINDJEE University of Illinois, Urbana, Illinois, U.S.A. Consulting Editors: Julian EATON-RYE, Dunedin, New Zealand Christine H. FOYER, Newcastle upon Tyne, U.K. David B. KNAFF, Lubbock, Texas, U.S.A. Anthony L. MOORE, Brighton, U.K. Sabeeha MERCHANT, Los Angeles, California, U.S.A. Krishna NIYOGI, Berkeley, California, U.S.A. William PARSON, Seatle, Washington, U.S.A. Agepati RAGHAVENDRA, Hyderabad, India Gernot RENGER, Berlin, Germany The scope of our series, beginning with volume 11, reflects the concept that photosynthesis and respiration are intertwined with respect to both the protein complexes involved and to the entire bioenergetic machinery of all life. Advances in Photosynthesis and Respiration is a book series that provides a comprehensive and state-of-the-art account of research in photo- synthesis and respiration. Photosynthesis is the process by which higher plants, algae, and certain species of bacteria transform and store solar energy in the form of energy-rich organic molecules. These compounds are in turn used as the energy source for all growth and reproduction in these and almost all other organisms. As such, virtually all life on the planet ultimately depends on photosynthetic energy conversion. Respiration, which occurs in mitochondrial and bacterial membranes, utilizes energy present in organic molecules to fuel a wide range of metabolic reactions critical for cell growth and development. In addition, many photosynthetic organisms engage in energetically wasteful photorespiration that begins in the chloroplast with an oxygenation reaction catalyzed by the same enzyme responsible for capturing carbon dioxide in photosynthesis. -
Simulation and Theory of Classical Spin Hopping on a Lattice
magnetochemistry Article Simulation and Theory of Classical Spin Hopping on a Lattice Richard Gerst , Rodrigo Becerra Silva and Nicholas J. Harmon * Department of Physics, University of Evansville, Evansville, IN 47722, USA; [email protected] (R.G.); [email protected] (R.B.S.) * Correspondence: [email protected] Abstract: The behavior of spin for incoherently hopping carriers is critical to understand in a variety of systems such as organic semiconductors, amorphous semiconductors, and muon-implanted materials. This work specifically examined the spin relaxation of hopping spin/charge carriers through a cubic lattice in the presence of varying degrees of energy disorder when the carrier spin is treated classically and random spin rotations are suffered during the hopping process (to mimic spin–orbit coupling effects) instead of during the wait time period (which would be more appropriate for hyperfine coupling). The problem was studied under a variety of different assumptions regarding the hopping rates and the random local fields. In some cases, analytic solutions for the spin relaxation rate were obtained. In all the models, we found that exponentially distributed energy disorder led to a drastic reduction in spin polarization losses that fell nonexponentially. Keywords: spintronics; organic semiconductors; hopping transport; spin transport 1. Introduction Citation: Gerst, R.; Becerra Silva, R.; Spin relaxation of carriers has garnered much interest in the past few decades due to Harmon, N.J. Simulation and Theory the prospect of spin electronic or spintronic devices that use spin functionality in addition to of Classical Spin Hopping on a charge functionality. However, most work has been concentrated on band transport [1–5]. -
Solar Thermochemical Hydrogen Production Research (STCH)
SANDIA REPORT SAND2011-3622 Unlimited Release Printed May 2011 Solar Thermochemical Hydrogen Production Research (STCH) Thermochemical Cycle Selection and Investment Priority Robert Perret Prepared by Sandia National Laboratories Albuquerque, New Mexico 87185 and Livermore, California 94550 Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. Approved for public release; further dissemination unlimited. Issued by Sandia National Laboratories, operated for the United States Department of Energy by Sandia Corporation. NOTICE: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government, nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, make any warranty, express or implied, or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represent that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government, any agency thereof, or any of their contractors or subcontractors. The views and opinions expressed herein do not necessarily state or reflect those of the United States Government, any agency thereof, or any of their contractors. Printed in the United States of America. This report has been reproduced directly from the best available copy. -
THE HYDROGEN ECONOMY. a Non-Technical Review
Hydrogen holds out the promise of a truly sustainable global energy future. As a clean energy carrier that can be produced from any primary energy source, hydrogen used in highly efficient fuel cells could prove to be the answer to our growing concerns about energy security, urban pollution and climate change. This prize surely warrants For more information, contact: THE HYDROGEN ECONOMY the attention and resources currently being UNEP DTIE directed at hydrogen – even if the Energy Branch prospects for widespread 39-43 Quai André Citroën commercialisation of hydrogen in the A non-technical review 75739 Paris Cedex 15, France foreseeable future are uncertain. Tel. : +33 1 44 37 14 50 Fax.: +33 1 44 37 14 74 E-mail: [email protected] www.unep.fr/energy/ ROGRAMME P NVIRONMENT E ATIONS N NITED DTI-0762-PA U Copyright © United Nations Environment Programme, 2006 This publication may be reproduced in whole or in part and in any form for educational or non-profit purposes without special permission from the copyright holder, provided acknowledgement of the source is made. UNEP would appreciate receiving a copy of any publication that uses this publication as a source. No use of this publication may be made for resale or for any other commercial purpose whatsoever without prior permission in writing from the United Nations Environment Programme. Disclaimer The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the United Nations Environment Programme concerning the legal status of any country, territory, city or area or of its authorities, or concerning delimitation of its frontiers or boundaries. -
Dirac Material Graphene
Dirac Material Graphene Elena Sheka Russian Peoples’ Friendship University of Russia Moscow, 117198 Russia [email protected] Abstract. The paper presents author’s view on spin-rooted properties of graphene supported by numerous experimental and calculation evidences. Correlation of odd pz electrons of the honeycomb lattice meets a strict demand “different orbitals for different spins”, which leads to spin polarization of electronic states, on the one hand, and generation of an impressive pool of local spins distributed over the lattice, on the other. These features characterize graphene as a peculiar semimetal with Dirac cone spectrum at particular points of Brillouin zone. However, spin-orbit coupling (SOC), though small but available, supplemented by dynamic SOC caused by electron correlation, transforms graphene-semimetal into graphene-topological insulator (TI). The consequent topological non-triviality and local spins are proposed to discuss such peculiar properties of graphene as high temperature ferromagnetism and outstanding chemical behavior. The connection of these new findings with difficulties met at attempting to convert graphene-TI into semiconductor one is discussed. Key words: graphene, Dirac fermions, quasi-relativistic description, hexagonal honeycomb structure, local spins, open-shell molecules, spin-orbital coupling, quantum spin Hall insulator, high temperature ferromagnetism, chemical activity. 1. Introduction Presented in the current paper concerns three main issues laying the foundation of spin features of graphene: (1) a significant correlation of pz odd electrons, exhibited in terms of spin peculiarities of the unrestricted Hartree-Fock (UHF) solutions, (2) spin-orbital coupling (SOC) and (3) the crucial role of the C=C bond length distribution over the body in exhibiting the spin- based features. -
HYDROGEN for HEATING: ATMOSPHERIC IMPACTS a Literature Review
HYDROGEN FOR HEATING: ATMOSPHERIC IMPACTS A literature review BEIS Research Paper Number 2018: no. 21 November 2018 7th October 2018 HYDROGEN FOR HEATING: ATMOSPHERIC IMPACTS – A LITERATURE REVIEW R.G. (Dick) Derwent OBE rdscientific, Newbury The preparation of this review and assessment was supported by the Department for Business, Energy and Industrial Strategy under Purchase Order No. 13070002913. BEIS Research Paper No. 21 1 HYDROGEN FOR HEATING: ATMOSPHERIC IMPACTS – A LITERATURE REVIEW Summary Introduction The Department for Business, Energy and Industrial Strategy (BEIS) is undertaking work to strengthen the evidence base on the potential long-term approaches for decarbonising heating. One approach being explored is whether hydrogen could be used in place of natural gas in the gas grid to provide a source of low-carbon heat in the future. BEIS commissioned rdscientific to carry out a literature review to assess the evidence on the potential atmospheric impacts of increased emissions to the atmosphere of hydrogen. Headline Findings This review summarises the present state of our understanding of the potential global atmospheric impacts of any future increased use of hydrogen through release of additional hydrogen into the atmosphere. This review has identified two global atmospheric dis- benefits from a future hydrogen economy: stratospheric ozone depletion through its moistening of the stratosphere, and contribution to climate change through increasing the growth rates of methane and tropospheric ozone. • The consensus from the limited number of studies using current stratospheric ozone models is that the impacts of hydrogen on the stratospheric ozone layer are small. • The best estimate of the carbon dioxide (CO2) equivalence of hydrogen is 4.3 megatonnes of carbon dioxide per 1 megatonne emission of hydrogen over a 100- year time horizon, the plausible range 0 – 9.8 expresses 95% confidence. -
The Effects of Weak Magnetic Fields on Radical Pairs
Bioelectromagnetics The Effects of Weak Magnetic Fields on Radical Pairs Frank S. Barnes1* and Ben Greenebaum2 1Department of Electricaland Computer Engineering, University of Colorado, Boulder, Colorado 2Department of Physics, University of Wisconsin-Parkside, Kenosha,Wisconsin It is proposed that radical concentrations can be modified by combinations of weak, steady and alternating magnetic fields that modify the population distribution of the nuclear and electronic spin state, the energy levels and the alignment of the magnetic moments of the components of the radical pairs. In low external magnetic fields, the electronic and nuclear angular momentum vectors are coupled by internal forces that outweigh the external fields’ interactions and are characterized in the Hamiltonian by the total quantum number F. Radical pairs form with their unpaired electrons in singlet (S) or triplet (T) states with respect to each other. At frequencies corresponding to the energy separation between the various states in the external magnetic fields, transitions can occur that change the populations of both electron and nuclear states. In addition, the coupling between the nuclei, nuclei and electrons, and Zeeman shifts in the electron and nuclear energy levels can lead to transitions with resonances spanning frequencies from a few Hertz into the megahertz region. For nuclear energy levels with narrow absorption line widths, this can lead to amplitude and frequency windows. Changes in the pair recombination rates can change radical concentrations and modify biological processes. The overall conclusion is that the application of magnetic fields at frequencies ranging from a few Hertz to microwaves at the absorption frequencies observed in electron and nuclear resonance spectroscopy for radicals can lead to changes in free radical concentrations and have the potential to lead to biologically significant changes. -
The Scientific Case 67 5
5. The Scientific Case 67 5. Chemistry 5.1 Introduction whereas, including cooperative Panel: magnetic interactions, the U.E. Steiner (Konstanz) In chemistry, the application of modern field of molecular (Chairman) magnetic fields has a long magnetism offers new possibilities R. Bittl (Berlin) tradition and has led to well for structural control by magnetic M. Ernst (Nijmegen) established disciplines and fields. In the following sections O. Kahn (Bordeaux) techniques. Two main purposes in these several areas are discussed using high magnetic fields may be from the point of view of the distinguished; the probing of likely impact of intense magnetic structural and dynamical fields. properties and the controlling of chemical processes and structures. 5.2 Molecular magnetism The ability of a magnetic field to function as a probe is usually based Molecular magnetism is a rather on the exploitation of the field new field of research which has dependence of some property of emerged during the last decade or the chemical substance or system, so. It deals with the physics and including its interaction with chemistry of open-shell radiation; i.e. various kinds of molecules and of molecular spectroscopies, of which NMR is assemblies involving open-shell the most vital and powerful one. units. What characterizes this field Thereby detailed qualitative and of research is its deeply quantitative information can be multidisciplinary character. It gained as to chemical composition brings together organic, inorganic, (chemical analysis) as well as and organometallic synthetic structural and dynamical chemists along with theoreticians, properties. Structural aspects solid state physicists, materials pertain to the characterization of and life scientists. -
Coherent Spin Dynamics of Radical Pairs in Weak Magnetic Fields
Coherent Spin Dynamics of Radical Pairs in Weak Magnetic Fields by Hannah J. Hogben A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Trinity Term 2011 University of Oxford Department of Chemistry Physical and Theoretical Chemistry Laboratory Oriel College Abstract Coherent Spin Dynamics of Radical Pairs in Weak Magnetic Fields Hannah J. Hogben Department of Chemistry Physical and Theoretical Chemistry Laboratory and Oriel College Abstract of a thesis submitted for the degree of Doctor of Philosophy Trinity Term 2011 The outcome of chemical reactions proceeding via radical pair (RP) intermediates can be in- fluenced by the magnitude and direction of applied magnetic fields, even for interaction strengths far smaller than the thermal energy. Sensitivity to Earth-strength magnetic fields has been sug- gested as a biophysical mechanism of animal magnetoreception and this thesis is concerned with simulations of the effects of such weak magnetic fields on RP reaction yields. State-space restriction techniques previously used in the simulation of NMR spectra are here applied to RPs. Methods for improving the efficiency of Liouville-space spin dynamics calculations are presented along with a procedure to form operators directly into a reduced state-space. These are implemented in the spin dynamics software Spinach. Entanglement is shown to be a crucial ingredient for the observation of a low field effect on RP reaction yields in some cases. It is also observed that many chemically plausible initial states possess an inherent directionality which may be a useful source of anisotropy in RP reactions. The nature of the radical species involved in magnetoreception is investigated theoretically. -
Biogeochemical Cycle
Biogeochemical cycle In ecology and Earth science, a biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical substance moves through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. There are biogeochemical cycles for the chemical elements calcium, carbon, hydrogen, mercury, nitrogen, oxygen, phosphorus, selenium, and sulfur; molecular cycles for water and silica; macroscopic cycles such as the rock cycle; as well as human-induced cycles for synthetic compounds such as An illustration of the oceanic whale pump polychlorinated biphenyl (PCB). In some showing how whales cycle nutrients cycles there are reservoirs where a through the water column substance remains for a long period of time. Contents Systems Reservoirs Important cycles See also References Further reading Systems Ecological systems (ecosystems) have many biogeochemical cycles operating as a part of the system, for example the water cycle, the carbon cycle, the nitrogen cycle, etc. All chemical elements occurring in organisms are part of biogeochemical cycles. In addition to being a part of living organisms, these chemical elements also cycle through abiotic factors of ecosystems such as water (hydrosphere), land (lithosphere), and/or the air (atmosphere).[1] The living factors of the planet can be referred to collectively as the biosphere. All the nutrients—such as carbon, nitrogen, oxygen, phosphorus, and sulfur—used in ecosystems by living organisms are a part of a closed system; therefore, these chemicals are recycled instead of being lost and replenished constantly such as in an open system.[1] The flow of energy in an ecosystem is an open system; the sun constantly gives the planet energy in the form of light while it is eventually used and lost in the form of heat throughout the trophic levels of a food web. -
The Resolution of the Diamond Problem After 200 Years
Treatise on the Resolution of the Diamond Problem After 200 Years Reginald B. Little* and Joseph Roache Florida A&M University Florida State University National High Magnetic Field Laboratory Tallahassee, Florida 32308 Abstract: The problem of the physicochemical synthesis of diamond spans more than 200 years, involving many giants of science. Many technologies have been discovered, realized and used to resolve this diamond problem. Here the origin, definition and cause of the diamond problem are presented. The Resolution of the diamond problem is then discussed on the basis of the Little Effect, involving novel roton-phonon driven (antisymmetrical) multi-spin induced orbital orientation, subshell rehybridization and valence shell rotation of radical complexes in quantum fluids under magnetization across thermal, pressure, compositional, and spinor gradients in both space and time. Some experimental evidence of this magnetic quantum Resolution is briefly reviewed and integrated with this recent fruitful discovery. Furthermore, the implications of the Little Effect in comparison to the Woodward-Hoffman Rule are considered. The distinction of the Little Effect from the prior radical pair effect is clarified. The better compatibility of radicals, dangling bonds and magnetism with the diamond lattice relative to the graphitic lattice is discussed. Finally, these novel physicochemical phenomena for the Little Effect are compared with the natural diamond genesis. * corresponding author; email : [email protected] Keywords: diamond, high pressure, plasma deposition, catalytic properties, magnetic properties. 1. Introduction – The Diamond Problem: A long history of giants of science has defined and contributed to the solution of the diamond problem. Section 2 considers the cause of the diamond problem. -
Hydrogen Storage Materials with Focus on Main Group I-II Elements Department: Materials Research Department
Ris0-PhD-21(EN) Hydrogen Storage Materials with Focus on Main Group l-ll Elements Anders Andreasen Ris0 National Laboratory Roskilde Denmark October 2005 Hydrogen storage materials with focus on main group I II elements Preparation and characterization Ph.D. thesis by Anders Andreasen Rise National Laboratory Roskilde, 2005 Author: Anders Andreasen Riso-PhD-21(EN) 2005 Title: Hydrogen Storage Materials with Focus on Main Group I-II Elements Department: Materials Research Department This thesis is submitted in partial fulfillment of the requirements for the Ph. D. degree at the Department of Chemical Engineering, Technical University of Demnark Abstract (max. 2000 char.): ISBN 87-550-3498-5 A future hydrogen based society, viz. a society in which hydrogen is the primary energy carrier, is viewed by many as a solution to many of the energy related problems of the world { the ultimate problem being the eventual depletion of fossil fuels. Although, for the hydrogen based society to become realizable, several technical difficulties must be dealt with. Especially, the transport sector relies on a cheap, safe and reliable way of storing hydrogen with high storage capacity, fast kinetics and favourable thermodynamics. No potential hydrogen storage candidate has been found yet, which meets all the criteria just summarized. The hydrogen storage solution showing the greatest potential in fulfilling the hydrogen storage criteria with respect to storage capacity, is solid state storage in Contract no.: light metal hydrides e.g. alkali metals and alkali earth metals. The remaining issues to be dealt with mainly concerns the kinetics of hydrogen uptake/release and the thermal stability of the formed hydride.