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Search Results: 1 - 10 of 537063 matches for " P. M. Adam "
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Nanoplasmonics: From biochemical sensors to surface enhanced spectroscopies
P. M. Adam
Atti della Accademia Peloritana dei Pericolanti : Classe di Scienze Fisiche, Matematiche e Naturali , 2011, DOI: 10.1478/c1v89s1p015
Abstract: Plasmonics is a field connected to optics dealing with the properties and applications of surface plasmons which are modes of metal dielectric interfaces. Nanoplasmonics concerns the excitation, manipulation and detection of the surface plasmons at the nanometric scale. It has highly potential applications for ultrasensitive biochemical sensing. Surface enhanced spectroscopies are the ultimate sensor tools as they can reach single molecule sensitivity. We will present in this paper our results towards the realization of highly controllable and reproducible nanoplasmonics substrates.
Application of the Veneziano Model in Charmonium Dalitz Plot Analysis
Adam P. Szczepaniak,M. R. Pennington
Physics , 2014,
Abstract: We adapt the Veneziano model to the analysis of vector charmonium decays. Starting from a set of covariant Veneziano terms we show how to construct partial waves amplitudes that receive contributions from selected Regge trajectories. The amplitudes, nevertheless retain the proper asymptotic limit. This arises from duality between directly produced resonances and cross-channel Reggeon and in practical applications helps remove uncertainties in the parametrization of backgrounds.
Equatorial superrotation on tidally locked exoplanets
Adam P. Showman,Lorenzo M. Polvani
Physics , 2011, DOI: 10.1088/0004-637X/738/1/71
Abstract: The increasing richness of exoplanet observations has motivated a variety of three-dimensional atmospheric circulation models of these planets. Under strongly irradiated conditions, models of tidally locked, short-period planets (both hot Jupiters and terrestrial planets) tend to exhibit a circulation dominated by a fast eastward, or "superrotating," jet stream at the equator. Under appropriate conditions, this phenomenon can cause the hottest regions to be displaced eastward from the substellar point by tens of degrees longitude. Such an offset has been observed on HD 189733b, supporting the possibility of equatorial jets on short-period exoplanets. Despite its relevance, however, the dynamical mechanisms responsible for generating the equatorial superrotation in such models have not been identified. Here, we show that the equatorial jet results from the interaction of the mean flow with standing, planetary-scale Rossby and Kelvin waves induced by the day-night thermal forcing. The Rossby waves develop phase tilts that pump eastward momentum from high latitudes to the equator, thereby inducing equatorial superrotation. We present an analytic theory demonstrating this mechanism and explore its properties in a hierarchy of one-layer (shallow-water) calculations and fully 3D models. The wave-mean-flow interaction produces an equatorial jet whose latitudinal width is comparable to that of the Rossby waves, namely the equatorial Rossby deformation radius modified by radiative and frictional effects. For conditions typical of synchronously rotating hot Jupiters, this length is comparable to a planetary radius, explaining the broad scale of the equatorial jet obtained in most hot Jupiter models. Our theory illuminates the dependence of the equatorial jet speed on forcing amplitude, strength of friction, and other parameters, as well as the conditions under which jets can form at all.
Loop models with crossings
Adam Nahum,P. Serna,A. M. Somoza,M. Ortu?o
Physics , 2013, DOI: 10.1103/PhysRevB.87.184204
Abstract: The universal behaviour of two-dimensional loop models can change dramatically when loops are allowed to cross. We study models with crossings both analytically and with extensive Monte Carlo simulations. Our main focus (the 'completely packed loop model with crossings') is a simple generalisation of well-known models which shows an interesting phase diagram with continuous phase transitions of a new kind. These separate the unusual 'Goldstone' phase observed previously from phases with short loops. Using mappings to Z_2 lattice gauge theory, we show that the continuum description of the model is a replica limit of the sigma model on real projective space (RP^{n-1}). This field theory sustains Z_2 point defects which proliferate at the transition. In addition to studying the new critical points, we characterise the universal properties of the Goldstone phase in detail, comparing renormalisation group (RG) calculations with numerical data on systems of linear size up to L=10^6 at loop fugacity n=1. (Very large sizes are necessary because of the logarithmic form of correlation functions and other observables.) The model is relevant to polymers on the verge of collapse, and a particular point in parameter space maps to self-avoiding trails at their \Theta-point; we use the RG treatment of a perturbed sigma model to resolve some perplexing features in the previous literature on trails. Finally, one of the phase transitions considered here is a close analogue of those in disordered electronic systems --- specifically, Anderson metal-insulator transitions --- and provides a simpler context in which to study the properties of these poorly-understood (central-charge-zero) critical points.
The effect of a dietary supplement (N-oleyl-phosphatidyl-ethanolamine and epigallocatechin gallate) on dietary compliance and body fat loss in adults who are overweight: A double-blind, randomized control trial
Mangine Gerald T,Gonzalez Adam M,Wells Adam J,McCormack William P
Lipids in Health and Disease , 2012, DOI: 10.1186/1476-511x-11-127
Abstract: Background A dietary supplement containing a blend of 170 mg of N-oleyl-phosphatidylethanolamine (NOPE) and 100 mg of epigallocatechin-3-gallate (EGCG) has been shown to improve compliance to low caloric diets. Considering the cost of dietary ingredients, many manufacturers attempt to determine the lowest efficacious dose. Thus, the purpose of this study was to evaluate the efficacy of 8-weeks of supplementation with a daily intake of 120 mg of NOPE and 105 mg of EGCG in conjunction with a low caloric diet and regular, moderate exercise on dietary compliance in healthy, overweight adults. An additional purpose was to examine the effect of this supplement/diet/exercise paradigm on changes in body composition, sensation of appetite, mood and severity of binge eating. Methods Fifty healthy, overweight (BMI > 25 m·kg2) men (15) and women (35) (SUP; n = 25; 32.7 ± 13.75 y; BMI = 33.4 ± 6.2; PLA; n = 25, 34.3 ± 12.7 years; BMI = 33.2 ± 6.8) were recruited for a double-blind, placebo controlled study. Each volunteer was randomly assigned to either the supplement (SUP; n = 25) or placebo group (PLA; n = 25). Based upon a self-reported 3-day dietary recall all volunteers were recommended a 500 kcal or 30% (maximum of 1000 kcal) reduction in caloric intake. Volunteers were also encouraged to exercise 30 minutes per day, three times per week. Results Subjects in SUP were significantly more compliant (x2 = 3.86, p = 0.049) in maintaining a low caloric diet at week 4, but this was not able to be maintained through the 8-week study. In addition, a significant difference in mood, feelings of fatigue and confusion were noted between the groups at week 4, but again not maintained by week 8 where only feelings of tension were improved. No differences between groups (p > 0.05) were observed for body mass, body composition, feelings of hunger, and binge eating after eight weeks. Conclusion Supplementing with a combination of 120 mg of NOPE and 105 mg of EGCG does appear to enhance compliance to a low caloric diet and improve mood for 4 –weeks, but loses its effectiveness by week 8.
The genetic basis of energy conservation in the sulfate-reducing bacterium Desulfovibrio alaskensis G20
Morgan N. Price,Jayashree Ray,Jennifer V. Kuehl,Stefan Bauer,Adam M. Deutschbauer,Adam P. Arkin
Frontiers in Microbiology , 2014, DOI: 10.3389/fmicb.2014.00577
Abstract: Sulfate-reducing bacteria play major roles in the global carbon and sulfur cycles, but it remains unclear how reducing sulfate yields energy. To determine the genetic basis of energy conservation, we measured the fitness of thousands of pooled mutants of Desulfovibrio alaskensis G20 during growth in 12 different combinations of electron donors and acceptors. We show that ion pumping by the ferredoxin:NADH oxidoreductase Rnf is required whenever substrate-level phosphorylation is not possible. The uncharacterized complex Hdr/flox-1 (Dde_1207:13) is sometimes important alongside Rnf and may perform an electron bifurcation to generate more reduced ferredoxin from NADH to allow further ion pumping. Similarly, during the oxidation of malate or fumarate, the electron-bifurcating transhydrogenase NfnAB-2 (Dde_1250:1) is important and may generate reduced ferredoxin to allow additional ion pumping by Rnf. During formate oxidation, the periplasmic [NiFeSe] hydrogenase HysAB is required, which suggests that hydrogen forms in the periplasm, diffuses to the cytoplasm, and is used to reduce ferredoxin, thus providing a substrate for Rnf. During hydrogen utilization, the transmembrane electron transport complex Tmc is important and may move electrons from the periplasm into the cytoplasmic sulfite reduction pathway. Finally, mutants of many other putative electron carriers have no clear phenotype, which suggests that they are not important under our growth conditions, although we cannot rule out genetic redundancy.
Using polymer electrolyte gates to set-and-freeze threshold voltage and local potential in nanowire-based devices and thermoelectrics
Sofia Fahlvik Svensson,Adam M. Burke,Damon J. Carrad,Martin Leijnse,Heiner Linke,Adam P. Micolich
Physics , 2014, DOI: 10.1002/adfm.201402921
Abstract: We use the strongly temperature-dependent ionic mobility in polymer electrolytes to 'freeze in' specific ionic charge environments around a nanowire using a local wrap-gate geometry. This enables us to set both the threshold voltage for a conventional doped substrate gate and the local disorder potential at temperatures below 200 Kelvin, which we characterize in detail by combining conductance and thermovoltage measurements with modeling. Our results demonstrate that local polymer electrolyte gates are compatible with nanowire thermoelectrics, where they offer the advantage of a very low thermal conductivity, and hold great potential towards setting the optimal operating point for solid-state cooling applications.
The Earliest Post-Paleozoic Freshwater Bivalves Preserved in Coprolites from the Karoo Basin, South Africa
Adam M. Yates, Frank H. Neumann, P. John Hancox
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030228
Abstract: Background Several clades of bivalve molluscs have invaded freshwaters at various times throughout Phanerozoic history. The most successful freshwater clade in the modern world is the Unionoida. Unionoids arose in the Triassic Period, sometime after the major extinction event at the End-Permian boundary and are now widely distributed across all continents except Antarctica. Until now, no freshwater bivalves of any kind were known to exist in the Early Triassic. Principal Findings Here we report on a faunule of two small freshwater bivalve species preserved in vertebrate coprolites from the Olenekian (Lower Triassic) of the Burgersdorp Formation of the Karoo Basin, South Africa. Positive identification of these bivalves is not possible due to the limited material. Nevertheless they do show similarities with Unionoida although they fall below the size range of extant unionoids. Phylogenetic analysis is not possible with such limited material and consequently the assignment remains somewhat speculative. Conclusions Bivalve molluscs re-invaded freshwaters soon after the End-Permian extinction event, during the earliest part of the recovery phase during the Olenekian Stage of the Early Triassic. If the specimens do represent unionoids then these Early Triassic examples may be an example of the Lilliput effect. Since the oldest incontrovertible freshwater unionoids are also from sub-Saharan Africa, it is possible that this subcontinent hosted the initial freshwater radiation of the Unionoida. This find also demonstrates the importance of coprolites as microenvironments of exceptional preservation that contain fossils of organisms that would otherwise have left no trace.
Evolution, ecology and the engineered organism: lessons for synthetic biology
Jeffrey M Skerker, Julius B Lucks, Adam P Arkin
Genome Biology , 2009, DOI: 10.1186/gb-2009-10-11-114
Abstract: One of the most powerful and controversial aspects of engineering living organisms is that they reproduce, evolve, and interact with their environment. Humans have been engineering plants and animals since the advent of agriculture approximately 12,000 years ago through breeding and artificial selection for their domestication [1]. The evolution of corn from the small grass teosinte [2], or the transformation of the wolf into 'man's best friend' (the dog) [1] are testaments to the success of this approach. We have even 'domesticated' microorganisms, using yeast and bacteria for the production of beer, wine, cheese and yogurt as well as numerous other products we consume every day [3,4].Although powerful, genetic engineering by classical breeding and selection is slow, and results in a large number of unknown genetic changes that are hard to reconcile and may have unintended secondary effects. What we need is a rational approach to the engineering of biological systems that makes the process fast, cheap and safe, to solve problems in energy, health, agriculture and the environment. First steps towards realizing this aim began with the advent of recombinant DNA technology in the latter half of the 20th century, which created visions of a new era of 'synthetic biology' where novel genes could be designed and constructed for useful purposes [5-7]. Since then we have made incredible advances in our ability to manipulate genes, genomes and organisms, and this has led to a renewed interest in making synthetic biology a reality [8].A number of recent reviews have been written on the principles and practice of synthetic biology [8-11], but here we focus on the interplay between synthetic biology, evolution and ecology. Evolution teaches us about what solutions nature has evolved for biological problems, how to evolve them further, and how robust they are to change. Ecology gives us information on how our engineered systems will perform once they leave the laboratory and ente
Disruption of the maxi-K-caveolin-1 interaction alters current expression in human myometrial cells
Adam M Brainard, Victoria P Korovkina, Sarah K England
Reproductive Biology and Endocrinology , 2009, DOI: 10.1186/1477-7827-7-131
Abstract: Myometrial biopsies were collected from women undergoing elective C-sections. From these samples, myometrial cells were isolated, cultured, infected with a virus containing either caveolin-1 (cav-1) siRNA or scrambled cav-1 siRNA, and finally subjected to patch-clamp analysis. Mutant caveolin-binding site maxi-K channel constructs were generated and transfected into mouse Ltk- fibroblasts. Channel activity, expression, association, and localization were examined by patch-clamping, Western blot, immunoprecipitation, and immunofluorescence, respectively.The caveolin-1 siRNA suppressed the total K+ current in human myometrial smooth muscle cells (hMSMC), as evident from comparison to the currents generated by both non-infected cells and cells infected with scrambled siRNA controls. The interaction between the maxi-K channel and caveolin depends on a region in the channel's C-terminal caveolin-binding site. Mutations of aromatic residues in this site (mutant F1012A, mutant Y1007A, F1012A and mutant Y1007A, F1012A, Y1015A) resulted in a decrease in K+ current compared to that produced by wild-type channels transfected into mouse Ltk- fibroblasts. However, mutation of all three aromatic amino acids (mutant Y1007A, F1012A, Y1015A) was necessary to disrupt the association between caveolin and the maxi-K channel, as visualized by immunofluorescence and immunoprecipitation.Our results suggest that disruption of the caveolin-binding site interferes with the cav-1/maxi-K channel interaction, and that lack of the cav-1/maxi-K channel interaction in MSMCs attenuates the total K+ channel current of the cell.Potassium efflux from myometrial cells results in membrane repolarization. This potassium efflux constitutes the primary ionic current responsible for maintaining resting membrane potential, and contributes significantly to uterine quiescence during pregnancy. In myometrial smooth muscle cells (MSMCs), changes in the expression or activity of K+ channels can translate into inad
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