3,083 research outputs found
Genome-inspired molecular identification in organic matter via Raman spectroscopy
Rapid, non-destructive characterization of molecular level chemistry for
organic matter (OM) is experimentally challenging. Raman spectroscopy is one of
the most widely used techniques for non-destructive chemical characterization,
although it currently does not provide detailed identification of molecular
components in OM, due to the combination of diffraction-limited spatial
resolution and poor applicability of peak-fitting algorithms. Here, we develop
a genome-inspired collective molecular structure fingerprinting approach, which
utilizes ab initio calculations and data mining techniques to extract molecular
level chemistry from the Raman spectra of OM. We illustrate the power of such
an approach by identifying representative molecular fingerprints in OM, for
which the molecular chemistry is to date inaccessible using non-destructive
characterization techniques. Chemical properties such as aromatic cluster size
distribution and H/C ratio can now be quantified directly using the identified
molecular fingerprints. Our approach will enable non-destructive identification
of chemical signatures with their correlation to the preservation of
biosignatures in OM, accurate detection and quantification of environmental
contamination, as well as objective assessment of OM with respect to their
chemical contents
Dynamic properties of the spin-1/2 XY chain with three-site interactions
We consider a spin-1/2 XY chain in a transverse (z) field with multi-site
interactions. The additional terms introduced into the Hamiltonian involve
products of spin components related to three adjacent sites. A Jordan-Wigner
transformation leads to a simple bilinear Fermi form for the resulting
Hamiltonian and hence the spin model admits a rigorous analysis. We point out
the close relationships between several variants of the model which were
discussed separately in previous studies. The ground-state phases (ferromagnet
and two kinds of spin liquid) of the model are reflected in the dynamic
structure factors of the spin chains, which are the main focus in this study.
First we consider the zz dynamic structure factor reporting for this quantity a
closed-form expression and analyzing the properties of the two-fermion
(particle-hole) excitation continuum which governs the dynamics of transverse
spin component fluctuations and of some other local operator fluctuations. Then
we examine the xx dynamic structure factor which is governed by many-fermion
excitations, reporting both analytical and numerical results. We discuss some
easily recognized features of the dynamic structure factors which are
signatures for the presence of the three-site interactions.Comment: 28 pages, 10 fugure
Backarc Lithospheric Thickness and Serpentine Stability Control Slab-Mantle Coupling Depths in Subduction Zones
A key feature of subduction zone geodynamics and thermal structure is the point at which the slab and mantle mechanically couple. This point defines the depth at which traction between slab and mantle begins to drive mantle wedge circulation and also corresponds with a rapid increase in temperature along the slab-mantle interface. Here, we consider the effects of the backarc thermal structure and slab thermal parameter on coupling depth using two-dimensional thermomechanical models of oceanic-continental convergent margins. Coupling depth is strongly correlated with backarc lithospheric thickness, and weakly correlated with slab thermal parameter. Slab-mantle coupling becomes significant where weak, hydrous antigorite reacts to form strong, anhydrous olivine and pyroxene along the slab-mantle interface. Highly efficient (predominantly advective) heat transfer in the asthenospheric mantle wedge and inefficient (predominantly conductive) heat transfer in the lithospheric mantle wedge results in competing feedbacks that stabilize the antigorite-out reaction at depths determined primarily by the mechanical thickness of the backarc lithosphere. For subduction zone segments where backarc lithospheric thickness can be inverted from surface heat flow, our results provide a regression model that can be applied with slab thermal parameter to predict coupling depth. Consistently high backarc heat flow in circum-Pacific subduction zones suggests uniformly thin overriding plates likely regulated by lithospheric erosion caused by hydration and melting processes under volcanic arcs. This may also explain a common depth of slab-mantle coupling globally
Current correlations and quantum localization in 2D disordered systems with broken time-reversal invariance
We study long-range correlations of equilibrium current densities in a
two-dimensional mesoscopic system with the time reversal invariance broken by a
random or homogeneous magnetic field. Our result is universal, i.e. it does not
depend on the type (random potential or random magnetic field) or correlation
length of disorder. This contradicts recent sigma-model calculations of
Taras-Semchuk and Efetov (TS&E) for the current correlation function, as well
as for the renormalization of the conductivity. We show explicitly that the new
term in the sigma-model derived by TS&E and claimed to lead to delocalization
does not exist. The error in the derivation of TS&E is traced to an incorrect
ultraviolet regularization procedure violating current conservation and gauge
invariance.Comment: 8 pages, 3 figure
Switching properties of ferromagnetic nanoparticles driven by a circularly polarized magnetic field
We present a comprehensive study of the magnetization switching of a uniaxial nanoparticle
driven by a circularly polarized magnetic field rotated in the plane perpendicular to the easy
axis. The conditions for the existence of the uniform and non-uniform precessions of the
nanoparticle magnetic moment are derived. In addition, the differences between switchings via
uniform and non-uniform precession are determined, and the essential role of field polarization
is demonstrated. The dependence of the switching time on the field amplitude and frequency are
calculated numerically. We show that a permanent magnetic field can reduce the amplitude and
frequency of the switching rotating field, and that the combined action of these field is
characterized by an extremely strong dependence of the switching time on the field parameters.
We also demonstrate that the transition process caused by an external magnetic field pulse can
decrease the switching amplitude in comparison with the value predicted from analysis of the
stability criterion. We discuss the advantages of switching the magnetization by means of the
action of a rotating field over the magnetization switching using a steady field applied
perpendicular to the easy axis.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/261
Emergent Ising degrees of freedom in frustrated two-leg ladder and bilayer Heisenberg antiferromagnets
Based on exact diagonalization data for finite quantum Heisenberg
antiferromagnets on two frustrated lattices (two-leg ladder and bilayer) and
analytical arguments we map low-energy degrees of freedom of the spin models in
a magnetic field on classical lattice-gas models. Further we use
transfer-matrix calculations and classical Monte Carlo simulations to give a
quantitative description of low-temperature thermodynamics of the quantum spin
models. The classical lattice-gas model yields an excellent description of the
quantum spin models up to quite large temperatures. The main peculiarity of the
considered frustrated bilayer is a phase transition which occurs at low
temperatures for a wide range of magnetic fields below the saturation magnetic
field and belongs to the two-dimensional Ising model universality class.Comment: 17 pages, 8 figure
Where attention goes, energy flows : enhancing individual sustainability in software engineering
Software engineers are plagued by the same troubles as many others in highly skilled jobs and digitized environments: Ever-expanding to-do lists, time to market pressure from management, deadline- driven development, continuous interruption during working tasks, and the juggle of balancing that with other areas of life (physical, mental and emotional health, family, household, finance, friends, hobbies and community service). These demands of life in combina- tion with a seemingly ever-increasing pace wear or burn out many people in the long run. Specifically, as software engineers, this also leads to decreased creativity and less efficiency in problem-solving. Generally offered solutions are reducing screen time and spending more time outdoors, both of which are hard to do within the work of a software engineer. On a meta level, if the developers of the systems that run most of our world do not develop individual sus- tainability with a balanced pace of life, that imbalance propagates into the systems we develop (similar to Conway’s Law). We argue that mindfulness practices like yoga poses (asanas), breathing prac- tices, and meditation exercises can help individually, and even more effectively in combination. In this exploratory paper, we discuss related work that explores the application of these mitigations in other application domains and propose a research agenda to explore their use within software engineering education and practice.Engaging with mindfulness practices in the context of software engineering promises to enhance creativity and cognitive problem- solving skills, leading to more efficiency and effectiveness during software development and increased individual sustainability. This, in turn, leads to better team spirit as well as increased economic profit, both in terms of maintaining human capital and customer contract deliverables
Excision of a Rare Triquetral Body Fracture Nonunion
Aside from the more common dorsal avulsion fractures, isolated triquetral body fractures are a rare injury and often missed. When they are identified, conservative treatment via immobilization is often the standard of care for initial treatment. Rarely, triquetral body fractures can develop into symptomatic nonunions, causing considerable pain and disability. Multiple classification schemes have been described to categorize triquetrum fractures; however, distal triquetrum fractures fit into none of the established models. There is scarce literature describing treatment of triquetral body fracture nonunions. The few reports that exist often use a variation of open reduction internal fixation with or without grafting as treatment. We present the case of an unusual triquetral body fracture nonunion that was successfully treated via surgical excision of the ununited distal fragment
Exact evidence for the spontaneous antiferromagnetic long-range order in the two-dimensional hybrid model of localized Ising spins and itinerant electrons
The generalized decoration-iteration transformation is adopted to treat
exactly a hybrid model of doubly decorated two-dimensional lattices, which have
localized Ising spins at their nodal lattice sites and itinerant electrons
delocalized over pairs of decorating sites. Under the assumption of a half
filling of each couple of the decorating sites, the investigated model system
exhibits a remarkable spontaneous antiferromagnetic long-range order with an
obvious quantum reduction of the staggered magnetization. It is shown that the
critical temperature of the spontaneously long-range ordered quantum
antiferromagnet displays an outstanding non-monotonic dependence on a ratio
between the kinetic term and the Ising-type exchange interaction.Comment: 8 pages, 6 figure
The role of karyopherins in the regulated sumoylation of septins
In the yeast Saccharomyces cerevisiae, several components of the septin ring are sumoylated during anaphase and then abruptly desumoylated at cytokinesis. We show that septin sumoylation is controlled by the interactions of two enzymes of the sumoylation pathway, Siz1p and Ulp1p, with the nuclear transport machinery. The E3 ligase Siz1p is imported into the nucleus by the karyopherin Kap95p during interphase. In M phase, Siz1p is exported from the nucleus by the karyopherin Kap142p/Msn5p and subsequently targeted to the septin ring, where it participates in septin sumoylation. We also show that the accumulation of sumoylated septins during mitosis is dependent on the interactions of the SUMO isopeptidase Ulp1p with Kap121p and Kap95p–Kap60p and the nuclear pore complex (NPC). In addition to sequestering Ulp1 at the NPC, Kap121p is required for targeting Ulp1p to the septin ring during mitosis. We present a model in which Ulp1p is maintained at the NPC during interphase and transiently interacts with the septin ring during mitosis
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