407 research outputs found
Nonintegrability of the two-body problem in constant curvature spaces
We consider the reduced two-body problem with the Newton and the oscillator
potentials on the sphere and the hyperbolic plane .
For both types of interaction we prove the nonexistence of an additional
meromorphic integral for the complexified dynamic systems.Comment: 20 pages, typos correcte
Adrenergic/Cholinergic Immunomodulation in the Rat ModelâIn Vivo Veritas?
For several years, our group has been studying the in vivo role of adrenergic and cholinergic
mechanisms in the immune-neuroendocrine dialogue in the rat model. The main results of these studies can be
summarized as follows: (1) exogenous or endogenous catecholamines suppress PBL functions through alpha-2-receptor-mediated
mechanisms, lymphocytes of the spleen are resistant to adrenergic in vivo stimulation,
(2) direct or indirect cholinergic treatment leads to enhanced ex vivo functions of splenic and thymic lymphocytes
leaving PBL unaffected, (3) cholinergic pathways play a critical role in the âtalking backâ of the immune system to the brain,
(4) acetylcholine inhibits apoptosis of thymocytes possibly via direct effects on thymic epithelial cells, and may
thereby influence T-cell maturation, (5) lymphocytes of the various immunological compartments were found to be
equipped with the key enzymes for the synthesis of both acetylcholine and norepinephrine, and to secrete these
neurotransmitters in culture supernatant
Two-body quantum mechanical problem on spheres
The quantum mechanical two-body problem with a central interaction on the
sphere is considered. Using recent results in representation
theory an ordinary differential equation for some energy levels is found. For
several interactive potentials these energy levels are calculated in explicit
form.Comment: 41 pages, no figures, typos corrected; appendix D was adde
Recommended from our members
Association of severity of primary open-angle glaucoma with serum vitamin D levels in patients of African descent.
PurposeTo study the relationship between primary open-angle glaucoma (POAG) in a cohort of patients of African descent (AD) and serum vitamin D levels.MethodsA subset of the AD and glaucoma evaluation study III (ADAGES III) cohort, consisting of 357 patients with a diagnosis of POAG and 178 normal controls of self-reported AD, were included in this analysis. Demographic information, family history, and blood samples were collected from all the participants. All the subjects underwent clinical evaluation, including visual field (VF) mean deviation (MD), central cornea thickness (CCT), intraocular pressure (IOP), and height and weight measurements. POAG patients were classified into early and advanced phenotypes based on the severity of their visual field damage, and they were matched for age, gender, and history of hypertension and diabetes. Serum 25-Hydroxy (25-OH) vitamin D levels were measured by enzyme-linked immunosorbent assay (ELISA). The association of serum vitamin D levels with the development and severity of POAG was tested by analysis of variance (ANOVA) and the paired t-test.ResultsThe 178 early POAG subjects had a visual field MD of better than -4.0 dB, and the 179 advanced glaucoma subjects had a visual field MD of worse than -10 dB. The mean (95% confidence interval [CI]) levels of vitamin D of the subjects in the control (8.02 ± 6.19 pg/ml) and early phenotype (7.56 ± 5.74 pg/ml) groups were significantly or marginally significantly different from the levels observed in subjects with the advanced phenotype (6.35 ± 4.76 pg/ml; p = 0.0117 and 0.0543, respectively). In contrast, the mean serum vitamin D level in controls was not significantly different from that of the subjects with the early glaucoma phenotype (p = 0.8508).ConclusionsIn this AD cohort, patients with advanced glaucoma had lower serum levels of vitamin D compared with early glaucoma and normal subjects
Exact results of the mixed-spin Ising model on a decorated square lattice with two different decorating spins of integer magnitudes
The mixed-spin Ising model on a decorated square lattice with two different
decorating spins of the integer magnitudes S_B = 1 and S_C = 2 placed on
horizontal and vertical bonds of the lattice, respectively, is examined within
an exact analytical approach based on the generalized decoration-iteration
mapping transformation. Besides the ground-state analysis, finite-temperature
properties of the system are also investigated in detail. The most interesting
numerical result to emerge from our study relates to a striking critical
behaviour of the spontaneously ordered 'quasi-1D' spin system. It was found
that this quite remarkable spontaneous order arises when one sub-lattice of the
decorating spins (either S_B or S_C) tends towards their 'non-magnetic' spin
state S = 0 and the system becomes disordered only upon further single-ion
anisotropy strengthening. The effect of single-ion anisotropy upon the
temperature dependence of the total and sub-lattice magnetization is also
particularly investigated.Comment: 17 pages, 6 figure
Power-law spin correlations in pyrochlore antiferromagnets
The ground state ensemble of the highly frustrated pyrochlore-lattice
antiferromagnet can be mapped to a coarse-grained ``polarization'' field
satisfying a zero-divergence condition From this it follows that the
correlations of this field, as well as the actual spin correlations, decay with
separation like a dipole-dipole interaction (). Furthermore, a lattice
version of the derivation gives an approximate formula for spin correlations,
with several features that agree well with simulations and neutron-diffraction
measurements of diffuse scattering, in particular the pinch-point
(pseudo-dipolar) singularities at reciprocal lattice vectors. This system is
compared to others in which constraints also imply diffraction singularities,
and other possible applications of the coarse-grained polarization are
discussed.Comment: 13 pp, revtex, two figure
Fire Suppression Impacts on Fuels and Fire Intensity in the Western U.S.: Insights from Archaeological Luminescence Dating in Northern New Mexico
Here, we show that the last century of fire suppression in the western U.S. has resulted in fire intensities that are unique over more than 900 years of record in ponderosa pine forests (Pinus ponderosa). Specifically, we use the heat-sensitive luminescence signal of archaeological ceramics and tree-ring fire histories to show that a recent fire during mild weather conditions was more intense than anything experienced in centuries of frequent wildfires. We support this with a particularly robust set of optically stimulated luminescence measurements on pottery from an archaeological site in northern New Mexico. The heating effects of an October 2012 CE prescribed fire reset the luminescence signal in all 12 surface samples of archaeological ceramics, whereas none of the 10 samples exposed to at least 14 previous fires (1696â1893 CE) revealed any evidence of past thermal impact. This was true regardless of the fire behavior contexts of the 2012 CE samples (crown, surface, and smoldering fires). It suggests that the fuel characteristics from fire suppression at this site have no analog during the 550 years since the depopulation of this site or the 350 years of preceding occupation of the forested landscape of this region
Tuning the pseudospin polarization of graphene by a pseudo-magnetic field
One of the intriguing characteristics of honeycomb lattices is the appearance
of a pseudo-magnetic field as a result of mechanical deformation. In the case
of graphene, the Landau quantization resulting from this pseudo-magnetic field
has been measured using scanning tunneling microscopy. Here we show that a
signature of the pseudo-magnetic field is a local sublattice symmetry breaking
observable as a redistribution of the local density of states. This can be
interpreted as a polarization of graphene's pseudospin due to a strain induced
pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic
field. We reveal this sublattice symmetry breaking by tunably straining
graphene using the tip of a scanning tunneling microscope. The tip locally
lifts the graphene membrane from a SiO support, as visible by an increased
slope of the curves. The amount of lifting is consistent with molecular
dynamics calculations, which reveal a deformed graphene area under the tip in
the shape of a Gaussian. The pseudo-magnetic field induced by the deformation
becomes visible as a sublattice symmetry breaking which scales with the lifting
height of the strained deformation and therefore with the pseudo-magnetic field
strength. Its magnitude is quantitatively reproduced by analytic and
tight-binding models, revealing fields of 1000 T. These results might be the
starting point for an effective THz valley filter, as a basic element of
valleytronics.Comment: Revised manuscript: streamlined the abstract and introduction, added
methods to supplement, Nano Letters, 201
Intraoperative hyperspectral label-free imaging: from system design to first-in-patient translation.
Despite advances in intraoperative surgical imaging, reliable discrimination of critical tissue during surgery remains challenging. As a result, decisions with potentially life-changing consequences for patients are still based on the surgeon's subjective visual assessment. Hyperspectral imaging (HSI) provides a promising solution for objective intraoperative tissue characterisation, with the advantages of being non-contact, non-ionising and non-invasive. However, while its potential to aid surgical decision-making has been investigated for a range of applications, to date no real-time intraoperative HSI (iHSI) system has been presented that follows critical design considerations to ensure a satisfactory integration into the surgical workflow. By establishing functional and technical requirements of an intraoperative system for surgery, we present an iHSI system design that allows for real-time wide-field HSI and responsive surgical guidance in a highly constrained operating theatre. Two systems exploiting state-of-the-art industrial HSI cameras, respectively using linescan and snapshot imaging technology, were designed and investigated by performing assessments against established design criteria and ex vivo tissue experiments. Finally, we report the use of our real-time iHSI system in a clinical feasibility case study as part of a spinal fusion surgery. Our results demonstrate seamless integration into existing surgical workflows
BEST PRACTICE GUIDE: USE OF THERMAL IMAGERS TO PERFORM TRACEABLE NON-CONTACT SCREENING OF HUMAN BODY TEMPERATURE
- âŠ