2,283 research outputs found
Measures of fine tuning
Fine-tuning criteria are frequently used to place upper limits on the masses
of superpartners in supersymmetric extensions of the standard model. However,
commonly used prescriptions for quantifying naturalness have some important
shortcomings. Motivated by this, we propose new criteria for quantifying fine
tuning that can be used to place upper limits on superpartner masses with
greater fidelity. In addition, our analysis attempts to make explicit the
assumptions implicit in quantifications of naturalness. We apply our criteria
to the minimal supersymmetric extension of the standard model, and we find that
the scale of supersymmetry breaking can be larger than previous methods
indicate.Comment: 15 pages, LaTex, 5 figures uuencoded, gz-compressed file. Minor
revisions bring the archived manuscript into agreement with published versio
Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes
In this work we numerically calculate the electric current through three
kinds of DNA sequences (telomeric, \lambda-DNA, and p53-DNA) described by
different heuristic models. A bias voltage is applied between two zig-zag edged
graphene contacts attached to the DNA segments, while a gate terminal modulates
the conductance of the molecule. The calculation of current is performed by
integrating the transmission function (calculated using the lattice Green's
function) over the range of energies allowed by the chemical potentials. We
show that a telomeric DNA sequence, when treated as a quantum wire in the fully
coherent low-temperature regime, works as an excellent semiconductor. Clear
steps are apparent in the current-voltage curves of telomeric sequences and are
present independent of lengths and sequence initialisation at the contacts. The
current-voltage curves suggest the existence of stepped structures independent
of length and sequencing initialisation at the contacts. We also find that the
molecule-electrode coupling can drastically influence the magnitude of the
current. The difference between telomeric DNA and other DNA, such as
\lambda-DNA and DNA for the tumour suppressor p53, is particularly visible in
the length dependence of the current
Marine Biodiversity in Juan Fernández and Desventuradas Islands, Chile: Global Endemism Hotspots
22 páginas, 6 tablas, 5 figurasThe Juan Fernández and Desventuradas islands are among the few oceanic islands
belonging to Chile. They possess a unique mix of tropical, subtropical, and temperate
marine species, and although close to continental South America, elements of the biota
have greater affinities with the central and south Pacific owing to the Humboldt Current,
which creates a strong biogeographic barrier between these islands and the continent. The
Juan Fernández Archipelago has ~700 people, with the major industry being the fishery for
the endemic lobster, Jasus frontalis. The Desventuradas Islands are uninhabited except for
a small Chilean military garrison on San Félix Island. We compared the marine biodiversity
of these islands across multiple taxonomic groups. At San Ambrosio Island (SA), in Desventuradas,
the laminarian kelp (Eisenia cokeri), which is limited to Desventuradas in Chile,
accounted for >50% of the benthic cover at wave exposed areas, while more sheltered sites
were dominated by sea urchin barrens. The benthos at Robinson Crusoe Island (RC), in the
Juan Fernández Archipelago, comprised a diverse mix of macroalgae and invertebrates, a
number of which are endemic to the region. The biomass of commercially targeted fishes
was >2 times higher in remote sites around RC compared to sheltered locations closest to
port, and overall biomass was 35% higher around SA compared to RC, likely reflecting fishing
effects around RC. The number of endemic fish species was extremely high at both
islands, with 87.5% of the species surveyed at RC and 72% at SA consisting of regional
endemics. Remarkably, endemics accounted for 99% of the numerical abundance of fishes
surveyed at RC and 96% at SA, which is the highest assemblage-level endemism known
for any individual marine ecosystem on earth. Our results highlight the uniqueness
and global significance of these biodiversity hotspots exposed to very different fishing
pressures.ES received funding from Blancpain,
Davidoff Cool Water and The National Geographic
Society. Oceana provided funding to ATP. CFG was
suported by Grant NC120030 from the Millennium
Scientific Initiative.Peer reviewe
Application of Renormalization to Potential Scattering
A recently proposed renormalization scheme can be used to deal with
nonrelativistic potential scattering exhibiting ultraviolet divergence in
momentum space. A numerical application of this scheme is made in the case of
potential scattering with divergence for small r, common in molecular
and nuclear physics, by the use of cut-offs in momentum and configuration
spaces. The cut-off is finally removed in terms of a physical observable and
model-independent result is obtained at low energies. The expected variation of
the off-shell behavior of the t matrix arising from the renormalization scheme
is also discussed.Comment: 15 pages plus 5 figure
Sugar cane tolerance to sequential application of nematicides and herbicides
Um experimento foi instalado em solo arenoso (85% de areia) na Usina Equipav, Promissão-SP, com o objetivo de estudar a possibilidade de ocorrência de interação entre nematicidas e herbicidas aplicados em seqüência, na cultura da canade- açúcar, variedade SP81-3250. O delineamento experimental adotado foi o de blocos ao acaso, com 4 repetições, no esquema fatorial, com 3 níveis da variável 1 (nematicidas) e 5 níveis da variável 2 (herbicidas). A aplicação dos nematicidas terbufós e carbofuran, ambos a 3000 g/ha, foi realizada manualmente, no fundo do sulco de plantio. Um outro tratamento foi utilizado, sem a aplicação de nematicida. Os herbicidas aplicados em pré-emergência da cultura e das plantas daninhas, foram: oxyfluorfen+ametryne (480+ 1500 g/ha), oxyfluorfen+diuron (480+2400 g/ha) e thiazopyr--arnetryne (360+ 1500 gI ha), além das testemunhas com e sem capina. As chuvas freqüentes ocorridas no primeiro mês do experimento proporcionaram uma situação interativa bastante drástica entre os produtos. Concluiu-se que não existiu interação significativa entre os nematicidas e herbicidas, que viesse a interferir na produtividade da cultura da cana-de-açúcar. O carbofuran conduziu a uma produtividade agrícola maior do que o terbufós, e este maior do que a testemunha; thiazopyr+arnetryne causou no início os maiores sintomas visuais de fitotoxicidade, os quais não foram responsáveis por quebra de produtividade agrícola; oxyfluorfen+arnetryne e oxyfluorfen+diuron, na ausência ou na presença de carbofuran ou terbufós, comportaram-se como os produtos mais seletivos para a cultura da cana-de-açúcar.A field experiment was carried out in a sandy soil (85 % of sand) aiming at studying herbicide/nematicide interaction in sugar cane. Terbufos and carbofuran, both applied at 3000 g/ha in the furrow at planting and the herbicides oxyfluorfen--ametryne (480+ 1500 g/ha), oxyfluorfen+diuron (480+2400 g/ha) and thiazopyr+ametryn (360+ 1500 g/ha) were studied. The herbicides were applied before emergence of the sugar cane plants, with a CO2 knapsack sprayer, equipped with 6 nozzles Teejet DO 80.02. The experimental design was a completely randomized block design in a factorial 3 x 5 arrangement, with four replications. The nematicides did not show any interaction with the herbicides. Carbofuran was better than terbufós, producing higher sugarcane yield. Thiazopyr + ametryn showed the most severe phytotoxic effects until 123 DAA (days after application). A tank mixture oxyfluorfen + ametryn and oxyfluorfen+diuron were the most selective products for the sugarcane plants. Sugarcane yield was not affected by any of the applied herbicides
The circularly permuted globin domain of androglobin exhibits atypical heme stabilization and nitric oxide interaction
In the decade since the discovery of androglobin, a multi-domain hemoglobin of metazoans associated with ciliogenesis and spermatogenesis, there has been little advance in the knowledge of the biochemical and structural properties of this unusual member of the hemoglobin superfamily. Using a method for aligning remote homologues, coupled with molecular modelling and molecular dynamics, we have identified a novel structural alignment to other hemoglobins. This has led to the first stable recombinant expression and characterization of the circularly permuted globin domain. Exceptional for eukaryotic globins is that a tyrosine takes the place of the highly conserved phenylalanine in the CD1 position, a critical point in stabilizing the heme. A disulfide bond, similar to that found in neuroglobin, forms a closed loop around the heme pocket, taking the place of androglobin's missing CD loop and further supporting the heme pocket structure. Highly unusual in the globin superfamily is that the heme iron binds nitric oxide as a five-coordinate complex similar to other heme proteins that have nitric oxide storage functions. With rapid autoxidation and high nitrite reductase activity, the globin appears to be more tailored toward nitric oxide homeostasis or buffering. The use of our multi-template profile alignment method to yield the first biochemical characterisation of the circularly permuted globin domain of androglobin expands our knowledge of the fundamental functioning of this elusive protein and provides a pathway to better define the link between the biochemical traits of androglobin with proposed physiological functions
Atomic photoionization experiment by harmonic-generation spectroscopy
Citation: Frolov, M. V., Sarantseva, T. S., Manakov, N. L., Fulfer, K. D., Wilson, B. P., Tross, J., . . . Trallero-Herrero, C. A. (2016). Atomic photoionization experiment by harmonic-generation spectroscopy. Physical Review A, 93(3), 5. doi:10.1103/PhysRevA.93.031403Measurements of the high-order-harmonic generation yield of the argon (Ar) atom driven by a strong elliptically polarized laser field are shown to completely determine the field-free differential photoionization cross section of Ar, i.e., the energy dependence of both the angle-integrated photoionization cross section and the angular distribution asymmetry parameter
A tutorial
PM003/2016.
Publisher Copyright:
© 2022 The Author(s)The capabilities of bioanalytical mass spectrometry to (i) detect and differentiate viruses at the peptide level whilst maintaining high sample throughput and (ii) to provide diagnosis and prognosis for infected patients are presented as a tutorial in this work to aid analytical chemists and physicians to gain insights into the possibilities offered by current high-resolution mass spectrometry technology and bioinformatics. From (i) sampling to sample treatment; (ii) Matrix-Assisted Laser Desorption Ionization- to Electrospray Ionization -based mass spectrometry; and (iii) from clustering to peptide sequencing; a detailed step-by-step guide is provided and exemplified using SARS-CoV-2 Spike Y839 variant and the variant of concern SARS-CoV-2 Alpha (B.1.1.7 lineage), Influenza B, and Influenza A subtypes AH1N1pdm09 and AH3N2.publishersversionpublishe
GUTs in Curved Spacetime: Running Gravitational Constants, Newtonian Potential and the Quantum Corrected Gravitational Equations
The running coupling constants (in particular, the gravitational one) are
studied in asymptotically free GUTs and in finite GUTs in curved spacetime,
with explicit examples. The running gravitational coupling is used to calculate
the leading quantum GUT corrections to the Newtonian potential, which turn out
to be of logarithmic form in asymptotically free GUTs. A comparison with the
effective theory for the conformal factor ---where leading quantum corrections
to the Newtonian potential are again logarithmic--- is made. A totally
asymptotically free GUT with quantum higher derivative gravity is then
constructed, using the technique of introducing renormalization group (RG)
potentials in the space of couplings. RG equations for the cosmological and
gravitational couplings in this theory are derived, and solved numerically,
showing the influence of higher-derivative quantum gravity on the Newtonian
potential. The RG-improved effective gravitational Lagrangian for
asymptotically free massive GUTs is calculated in the strong (almost constant)
curvature regime, and the non-singular De Sitter solution to the quantum
corrected gravitational equations is subsequently discussed. Finally, possible
extensions of the results here obtained are briefly outlined.Comment: LaTeX, 27 pages, 2 uu-figure
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