Photochemically induced nuclear spin polarization in reaction centers of photosystem II observed by 13C-solid-state NMR reveals a strongly asymmetric electronic structure of the P680.+ primary donor chlorophyll

We report 13C magic angle spinning NMR observation of photochemically induced dynamic nuclear spin polarization (photo- CIDNP) in the reaction center (RC) of photosystem II (PS2). The light-enhanced NMR signals of the natural abundance 13C provide information on the electronic structure of the primary electron donor P680 (chlorophyll a molecules absorbing around 680 nm) and on the pz spin density pattern in its oxidized form, P680⨥. Most centerband signals can be attributed to a single chlorophyll a (Chl a) cofactor that has little interaction with other pigments. The chemical shift anisotropy of the most intense signals is characteristic for aromatic carbon atoms. The data reveal a pronounced asymmetry of the electronic spin density distribution within the P680⨥. PS2 shows only a single broad and intense emissive signal, which is assigned to both the C-10 and C-15 methine carbon atoms. The spin density appears shifted toward ring III. This shift is remarkable, because, for monomeric Chl a radical cations in solution, the region of highest spin density is around ring II. It leads to a first hypothesis as to how the planet can provide itself with the chemical potential to split water and generate an oxygen atmosphere using the Chl a macroaromatic cycle. A local electrostatic field close to ring III can polarize the electronic charge and associated spin density and increase the redox potential of P680 by stabilizing the highest occupied molecular orbital, without a major change of color. This field could be produced, e.g., by protonation of the keto group of ring V. Finally, the radical cation electronic structure in PS2 is different from that in the bacterial RC, which shows at least four emissive centerbands, indicating a symmetric spin density distribution over the entire bacteriochlorophyll macrocycle.

A Cross-Polarization, Magic-Angle-Spinning, 13C-Nuclear-Magnetic-Resonance Study of Polysaccharides in Sugar Beet Cell Walls1

Solid-state nuclear magnetic resonance relaxation experiments were used to study the rigidity and spatial proximity of polymers in sugar beet (Beta vulgaris) cell walls. Proton T1ρ decay and cross-polarization patterns were consistent with the presence of rigid, crystalline cellulose microfibrils with a diameter of approximately 3 nm, mobile pectic galacturonans, and highly mobile arabinans. A direct-polarization, magic-angle-spinning spectrum recorded under conditions adapted to mobile polymers showed only the arabinans, which had a conformation similar to that of beet arabinans in solution. These cell walls contained very small amounts of hemicellulosic polymers such as xyloglucan, xylan, and mannan, and no arabinan or galacturonan fraction closely associated with cellulose microfibrils, as would be expected of hemicelluloses. Cellulose microfibrils in the beet cell walls were stable in the absence of any polysaccharide coating.

Symmetry and the energy landscapes of biomolecules

The role of symmetry in the folding of proteins is discussed using energy landscape theory. An analytical argument shows it is much easier to find sequences with funneled energy landscape capable of fast folding if the structure is symmetric. The analogy with phase transitions of small clusters with magic numbers is discussed.

Molecular organization of the postsynaptic specialization

A specific set of molecules including glutamate receptors is targeted to the postsynaptic specialization of excitatory synapses in the brain, gathering in a structure known as the postsynaptic density (PSD). Synaptic targeting of glutamate receptors depends on interactions between the C-terminal tails of receptor subunits and specific PDZ domain-containing scaffold proteins in the PSD. These scaffold proteins assemble a specialized protein complex around each class of glutamate receptor that functions in signal transduction, cytoskeletal anchoring, and trafficking of the receptors. Among the glutamate receptor subtypes, the N-methyl-d-aspartate receptor is relatively stably integrated in the PSD, whereas the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor moves in and out of the postsynaptic membrane in highly dynamic fashion. The distinctive cell biological behaviors of N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors can be explained by their differential interactions with cytoplasmic proteins.

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV – the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.

What We Are Learning About the Diverse Backgrounds of Academic Library Users: An Overview of Research Designs and Methods in Information Behaviour Studies

Academic libraries increasingly serve a more diverse population of users not only in regard to race and ethnicity, but also to age, gender, language, sexual orientation, and national and cultural backgrounds. This papers reports the findings of the study that explored information behaviour research as a potential source of information about diversity of academic library users and examined the relationship between the use of different research designs and data collection methods and the information gathered about users’ diverse backgrounds. The study found that information behaviour research offers limited insight into the diversity of academic library users. The choice of a research design was not critical but the use of multiple data collection played a role in gathering information about culturally diverse users.

A Watershed Approach to Managing the Natural Resources in South Carolina

Environmental degradation from point and non-point source pollution in the past ten years has made it increasingly clear that threats to aquatic resources cannot adequately be addressed without a more integrated watershed approach to the management. Through comprehensive, qualitative interviews of experts in the watershed approach in South Carolina, recommendations will be made to improve this holistic process. Conducting interviews to compile institutional knowledge on the incentives and barriers from professionals working within the watershed approach will show how managing the natural resources in South Carolina could be more effective and efficient. By gathering experiences of lessons learned, best approach techniques, and suggestions for future watershed planning, several recommendations were made to further the use of the watershed approach in South Carolina.

Unifying the observational diversity of isolated neutron stars via magneto-thermal evolution models

Observations of magnetars and some of the high magnetic field pulsars have shown that their thermal luminosity is systematically higher than that of classical radio-pulsars, thus confirming the idea that magnetic fields are involved in their X-ray emission. Here we present the results of 2D simulations of the fully coupled evolution of temperature and magnetic field in neutron stars, including the state-of-the-art kinetic coefficients and, for the first time, the important effect of the Hall term. After gathering and thoroughly re-analysing in a consistent way all the best available data on isolated, thermally emitting neutron stars, we compare our theoretical models to a data sample of 40 sources. We find that our evolutionary models can explain the phenomenological diversity of magnetars, high-B radio-pulsars, and isolated nearby neutron stars by only varying their initial magnetic field, mass and envelope composition. Nearly all sources appear to follow the expectations of the standard theoretical models. Finally, we discuss the expected outburst rates and the evolutionary links between different classes. Our results constitute a major step towards the grand unification of the isolated neutron star zoo.

X-Ray Imaging of SAPO-34 Molecular Sieves at the Nanoscale: Influence of Steaming on the Methanol-to-Hydrocarbons Reaction

The effect of a severe steaming treatment on the physicochemical properties and catalytic performance of H-SAPO-34 molecular sieves during the methanol-to-hydrocarbons (MTH) reaction has been investigated with a combination of scanning transmission X-ray microscopy (STXM), catalytic testing, and bulk characterization techniques, including ammonia temperature programmed desorption and 27Al and 29Si magic angle spinning nuclear magnetic resonance. For this purpose, two samples, namely a calcined and a steamed H-SAPO-34 catalyst powder, have been compared. It has been found that calcined H-SAPO-34 displays a high selectivity towards light olefins, yet shows a poor stability as compared to a zeolite H-ZSM-5 catalyst. Moreover, in situ STXM at the carbon K-edge during the MTH reaction allows construction of nanoscale chemical maps of the hydrocarbon species formed within the H-SAPO-34 aggregates as a function of reaction time and steam post-treatment. It was found that there is an initial preferential formation of coke precursor species within the core of the H-SAPO-34 aggregates. For longer times on stream the formation of the coke precursor species is extended to the outer regions, progressively filling the entire H-SAPO-34 catalyst particle. In contrast, the hydrothermally treated H-SAPO-34 showed similar reaction selectivity, but decreased activity and catalyst stability with respect to its calcined counterpart. These variations in MTH performance are related to a faster and more homogeneous formation of coke precursor species filling up the entire steamed H-SAPO-34 catalyst particle. Finally, the chemical imaging capabilities of the STXM method at the Al and Si K-edge are illustrated by visualizing the silicon islands at the nanoscale before and after steaming H-SAPO-34.

A GIS-based methodology to quantitatively define an Adjacent Protected Area in a shallow karst cavity: The case of Altamira cave

Different types of land use are usually present in the areas adjacent to many shallow karst cavities. Over time, the increasing amount of potentially harmful matter and energy, of mainly anthropic origin or influence, that reaches the interior of a shallow karst cavity can modify the hypogeal ecosystem and increase the risk of damage to the Palaeolithic rock art often preserved within the cavity. This study proposes a new Protected Area status based on the geological processes that control these matter and energy fluxes into the Altamira cave karst system. Analysis of the geological characteristics of the shallow karst system shows that direct and lateral infiltration, internal water circulation, ventilation, gas exchange and transmission of vibrations are the processes that control these matter and energy fluxes into the cave. This study applies a comprehensive methodological approach based on Geographic Information Systems (GIS) to establish the area of influence of each transfer process. The stratigraphic and structural characteristics of the interior of the cave were determined using 3D Laser Scanning topography combined with classical field work, data gathering, cartography and a porosity–permeability analysis of host rock samples. As a result, it was possible to determine the hydrogeological behavior of the cave. In addition, by mapping and modeling the surface parameters it was possible to identify the main features restricting hydrological behavior and hence direct and lateral infiltration into the cave. These surface parameters included the shape of the drainage network and a geomorphological and structural characterization via digital terrain models. Geological and geomorphological maps and models integrated into the GIS environment defined the areas involved in gas exchange and ventilation processes. Likewise, areas that could potentially transmit vibrations directly into the cave were identified. This study shows that it is possible to define a Protected Area by quantifying the area of influence related to each transfer process. The combined maximum area of influence of all the processes will result in the new Protected Area. This area will thus encompass all the processes that account for most of the matter and energy carried into the cave and will fulfill the criteria used to define the Protected Area. This methodology is based on the spatial quantification of processes and entities of geological origin and can therefore be applied to any shallow karst system that requires protection.

The invention of letters annotated by Charles Pinckney Sumner, ca. 1795-1796

Interleaved second-edition copy of Robert Treat Paine's poem "The Invention of Letters" with handwritten excerpts of 18th century poetry copied by Charles Pinckney Sumner. The excerpts appear to be verses alluded to, or emulated, by Paine in the poem. For example, Paine's verse includes "Beneath the shade, which Freedom's oak displays" and Sumner on the opposite page quoted Alexander Pope's poetry, "Beneath the shade a spreading beech displays." The excerpts include poetry by Alexander Pope, James Thompson, Robert Dodsley, William Falconer, William Hayley, Samuel Rogers, Richard Brinsley Sheridan, Thomas Gray, and John Denham.

Everyday Enchantments and Secular Magic in Montréal

In this thesis I argue that dominant ways of imagining modernity constitute a modern imaginary that carries with it particular expectations concerning modern places, spaces, emotions, and affects as well as expectations concerning the place of religion and enchantment in the modern world. I argue that this modern imaginary and the expectations it entails works to conceal and trivialize supra-rational beliefs and behaviours in scholarship but also in the lives of individuals. I focus on one particular subset of the supra-rational beliefs and behaviours that modern imaginary conceals and trivializes, namely beliefs and behaviours associated with lucky and protective objects. I also focus on the ways the modern imaginary conceals the presence and prevalence of these objects and the beliefs and behaviours they entail in one particular context, namely Montréal, Québec. I argue that these supra-rational beliefs and behaviours constitute a subjunctive mode for understanding and experiencing daily life and describe how the modern imaginary works to discredit this subjunctive register. Finally, I argue that scholars must begin to recognize and examine this subjunctive mode and the playful engagement with half-belief it involves.

The Common Security and Defence Policy: National Perspectives. Egmont Paper No. 79, May 2015

FOREWORD. When one looks at the present state of the CSDP, one cannot help but look on with disenchantment at the energy that appears to have abandoned both institutions and Member States. Commentators increasingly take for granted that nothing much should be expected from this field of EU policy. The reasons for this state of mind are well known: the recent economic and financial strains, which have impacted all EU action since 2008, means that most of the Member States will struggle to keep their defence budgets at their present level in the future, and we may even see reductions. Furthermore, and to put it mildly, most of the recent CSDP operations have also experienced a lack of enthusiasm. Adding to this overall trend, the EU is far from presenting a common vision of what security and defence should really mean. Many of the Member States do not want to be involved in all of today’s international turmoils, and they rarely share the strategic culture which inspires those Member States who see themselves as having special responsibilities in dealing with these crises. In the end it may be that Member States diverge fundamentally on the simple question of whether it is relevant for the EU to engage in most of the ‘hot’ crises Europe faces; many prefer to see Europe as a soft power, mostly dedicated to intervening on less dramatic fronts and more inclined to mend than to fight. For whatever reason given, it remains that if there is a lack of common understanding on what CSDP should really be about, it should not come as a surprise if this policy is presently in stalemate. As an additional blow, the Ukrainian crisis, which dragged on for the whole of last year, could only add to the downward spiral the EU has been experiencing, with a new Russia aggressively confronting Europe in a manner not too distant from the Cold War days. This attitude has triggered the natural reaction among EU Member States to seek reassurances from NATO about their own national security. Coupled with the return of France a few years ago into the integrated military command, NATO’s renewed relevance has sent a strong message to Europe about the military organisation’s credibility with regard to collective defence. Surprisingly, this overall trend was gathering momentum at the same time as other more positive developments. The European Council of December 2013 dedicated its main session to CSDP: it underlined Europe’s role as a ‘security provider’ while adopting a very ambitious road map for Europe in all possible dimensions of the security sector. Hence the impression of a genuine boost to all EU institutions, which have been invited to join efforts and give CSDP a reinvigorated efficiency. In the same way, the increasing instability in Europe’s neighbourhood has also called for more EU operations: most recently in Iraq, Libya, Northern Nigeria or South Sudan. Pressure for further EU engagement has been one of the most constant features of the discussions taking place around these crises. Moreover, a growing number of EU partners in Asia, Latin America or Eastern Europe have shown a renewed eagerness to join CSDP missions in what sounds like a vote of confidence for EU capacities. What kind of conclusion should be drawn from this contradictory situation? Probably that the EU has much more potential than it can sometimes figure out itself, if only it would be ready to adapt to the new global realities. But, more than anything else, an enhanced CSDP needs from all Member States strong political will and a clear vision of what they want this policy to be. Without this indispensable ingredient CSDP may continue to run its course, as it does today. It may even grow in efficiency but it will keep lacking the one resource that would definitely help it overcome all the present shortcomings that have prevented Europe from finding its true role and mission through the CSDP. Member States remain central to EU security and defence policy. This is why this collection of essays is so valuable for assessing in no uncertain way the long road that lies ahead for any progress to be made. Pierre VIMONT Senior Associate at Carnegie Europe Former Executive Secretary-General of the European External Action Service

spotlight europe #2015/04—October 2015: A Fiscal Union for Europe – Building Block and Not a Magic Bullet

The dramatic negotiations with Greece in the past few months have been a telling reminder of the weaknesses of the euro area. Most of the commentators are of the opinion that if the monetary union is going to be crisis-resistant and stable in the long term, certain very important elements will have to be changed. However, there is little or no agreement when it comes to specifying the "what" and the "how". In particular there are heated debates about the right steps to further integration in the area of fiscal policy. "Fiscal union can create stability only if it includes both credible budgetary rules and some kind of risk sharing", argue Katharina Gnath and Jörg Haas in the latest spotlight europe. However, "whilst it is an important and effective way of stabilizing the euro area, it should not exclude the use of other instruments."

Diplomatic parade or last struggle against fatalism? - Making sense of the Paris ministerial meeting on the Middle East Peace Process. EPC Commentary, 16 June 2016

On 3 June, the French government convened an international meeting in Paris, gathering 28 high-level delegations from all around the world, from Norway to Japan, in order to discuss the state of play and future prospects of the enduring Israel-Palestine conflict. The first ministerial meeting of the “Initiative for the Peace in the Middle East”, as it was labelled by the Quai d’Orsay, provided an important political signal, and a potential diplomatic format, to help revive the long-stalled peace process. Yet, its concrete deliverables remain beset by considerable uncertainty.