1,625 research outputs found
The Noncommutative Geometry of the Quantum Projective Plane
We study the spectral geometry of the quantum projective plane CP^2_q, a
deformation of the complex projective plane CP^2, the simplest example of a
spin^c manifold which is not spin. In particular, we construct a Dirac operator
D which gives a 0^+ summable spectral triple, equivariant under U_q(su(3)). The
square of D is a central element for which left and right actions on spinors
coincide, a fact that is exploited to compute explicitly its spectrum.Comment: v2: 26 pages. Paper completely reorganized; no major change, several
minor one
Mechanical characteristics of graphene nanoplatelets-modified asphalt mixes. A comparison with polymer-and not-modified asphalt mixes
In recent years, nanotechnology has sparked an interest in nanomodification of bituminous materials to increase the viscosity of asphalt binders and improves the rutting and fatigue resistance of asphalt mixtures. This paper presents the experimental results of laboratory tests on bituminous mixtures laid on a 1052 m-long test section built in Rome, Italy. Four asphalt mixtures for wearing and binder layer were considered: two polymer modified asphalt concretes (the former modified with the additive Superplast and the latter modified with styrene-butadiene-styrene), a "hard" graphene nanoplatelets (GNPs) modified asphalt concrete and a not-modified mixture. The indirect tensile strength, water sensitivity, stiffness modulus, and fatigue resistance of the mixtures were tested and compared. A statistical analysis based on the results has shown that the mixtures with GNPs have higher mechanical performances than the others: GNP could significantly improve the tested mechanical performances; further studies will be carried out to investigate its effect on rutting and skid resistance
Prognostic significance of primary-tumor extension, stage and grade of nuclear differentiation in patients with renal cell carcinoma
Surgery remains the preferred therapy for renal cell carcinoma. The various adjunctive or complementary therapies currently yield disappointing results. Identifying reliable prognostic factors could help in selecting patients most likely to benefit from postoperative adjuvant therapies. We reviewed the surgical records of 78 patients who had undergone radical nephrectomy with lymphadenectomy for renal cell carcinoma, matched for type of operation and histology. According to staging (TNM), 5.1% of the patients were classified as stage I, 51.3% as stage II, 29.5% as stage III and 14.5% as stage IV. Of the 78 patients 40 were T2N0 and 21 T3aN0. Tumor grading showed that 39.7% of the patients had well-differentiated tumors(G1), 41.1% moderately-differentiated (G2), and 19.2% poorly-differentiated tumors (G3). Overall actuarial survival at 5 and 10 years was 100% for stage 1; 91.3% at 5 years and 83.1% at 10 years for stage II; 45.5% and 34.1% for stage III; and 29.1% and nil for stage IV (stage II vs stage III p = 0.0001). Patients with tumors confined to the kidney (pT2N0) had better 5- and 10-year survival rates than patients with tumors infiltrating the perirenal fat (pT3aN0) (p = 0.000006). Survival differed according to nuclear grading (G1 vs G3 ; p = 0.000005; G2 vs G3; p = 0.0009). In conclusion our review identified tumor stage, primary-tumor extension, and the grade of nuclear differentiation as reliable prognostic factors in patients with renal cell carcinomas
Endotracheal intubation to reduce aspiration events in acutely comatose patients: a systematic review
Background: It is customary to believe that a patient with a Glasgow Coma Scale (GCS) score less than or equal to 8 should be intubated to avoid aspiration. We conducted a systematic review to establish if patients with GCS 64 8 for trauma or non-traumatic emergencies and treated in the acute care setting (e.g., Emergency Department or Pre-hospital environment) should be intubated to avoid aspiration or aspiration pneumonia/pneumonitis, and consequently, reduce mortality. Methods: We searched six databases, Pubmed, Embase, Scopus, SpringerLink, Cochrane Library, and Ovid Emcare, from April 15th to October 14th, 2020, for studies involving low GCS score patients of whom the risk of aspiration and related complications was assessed. Results: Thirteen studies were included in the final analysis (7 on non-traumatic population, 4 on trauma population, 1 pediatric and 1 adult mixed case studies). For the non-traumatic cases, two prospective studies and one retrospective study found no difference in aspiration risk between intubated and non-intubated patients. Two retrospective studies reported a reduction in the risk of aspiration in the intubated patient group. For traumatic cases, the study that considered the risk of aspiration did not show any differences between the two groups. A study on adult mixed cases found no difference in the incidence of aspiration among intubated and non-intubated patients. A study on pediatric patients found increased mortality for intubated versus non-intubated non-traumatic patients with a low GCS score. Conclusion: Whether intubation results in a reduction in the incidence of aspiration events and whether these are more frequent in patients with low GCS scores are not yet established. The paucity of evidence on this topic makes clinical trials justifiable and necessary. Trial registration: Prospero registration number: CRD42020136987
Effets de frontière, migrations et redistribution du peuplement en Bolivie : les dynamiques territoriales dans le départament du Tarija
Behavior evaluation of bituminous mixtures reinforced with nano-sized additives. A review
This article presents a comparative review of the most commonly used nano-additives for bituminous mixtures: nanoclays (NC), nanosilicates, carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), nano-calcium oxide (CaO), and nano-titanium dioxide (TiO2). In this study, the mechanical behavior of the obtained additive mixture is evaluated. According to the revised literature, the results strongly depend on type, concentration, and dispersal of used nano-additive. In fact, it has been seen that simple shear mixing followed by sonication homogenizes the distribution of the nanoparticles within the bituminous matrix and favors the bonds’ formation. The viscosity of the mixture of bitumen with nanoparticles improves with the increase of the percentage of additive added: it indicates a potential improvement to permanent deformation and rutting. Another benefit is an increased resistance of the binder to aging. Furthermore, it has been shown that the nanoparticles are able to prolong the service life of a bituminous mixture by means of various interdependent chemical–physical mechanisms that can influence the resistance to fatigue failure or the ability to self-heal. However, the effectiveness of these improvements depends on the particle type, added quantity and mixing technique, and the tests carried out
Excitonic Effects in Quantum Wires
We review the effects of Coulomb correlation on the linear and non-linear
optical properties of semiconductor quantum wires, with emphasis on recent
results for the bound excitonic states. Our theoretical approach is based on
generalized semiconductor Bloch equations, and allows full three-dimensional
multisubband description of electron-hole correlation for arbitrary confinement
profiles. In particular, we consider V- and T-shaped structures for which
significant experimental advances were obtained recently. Above band gap, a
very general result obtained by this approach is that electron-hole Coulomb
correlation removes the inverse-square-root single-particle singularity in the
optical spectra at band edge, in agreement with previous reports from purely
one-dimensional models. Strong correlation effects on transitions in the
continuum are found to persist also at high densities of photoexcited carriers.
Below bandgap, we find that the same potential- (Coulomb) to kinetic-energy
ratio holds for quite different wire cross sections and compositions. As a
consequence, we identify a shape- and barrier-independent parameter that
governs a universal scaling law for exciton binding energy with size. Previous
indications that the shape of the wire cross-section may have important effects
on exciton binding are discussed in the light of the present results.Comment: Proc. OECS-5 Conference, G\"ottingen, 1997 (To appear in Phys. Stat.
Sol. (b)
Optimum Filter Synthesis with DPLMS Method for Energy Reconstruction
Optimum filters are granted increasing recognition as valuable tools for
parametric estimation in many scientific and technical fields. The DPLMS
method, introduced some twenty years ago, is effective among the synthesis
algorithms since it derives the optimum filters directly from the experimental
signal and noise waveforms. Two new extensions of the DPLMS method are here
presented. The first one speeds up the synthesis phase and improves the energy
estimation by synthesizing optimum filters with automatically designed flat-top
length. The second one improves the quality of parameter estimation in
multi-channel systems by taking advantage of the inter-channel noise
correlation properties. The theoretical and functional aspects behind the DPLMS
method for optimum filter synthesis are first recalled and illustrated in more
detail. The two new DPLMS extensions are subsequently introduced from the
theoretical viewpoint and more thoroughly considered from the applicative
perspective. The DPLMS optimum filters have been applied first to simulated
signals with various amounts and characteristics of superimposed noise and then
to the experimental waveforms acquired from a solid-state Ge detector. The
results obtained are considered from both the absolute viewpoint and in
comparison with those of more traditional, suboptimal filters. The results
demonstrate the effectiveness of the two new DPLMS extensions. For
single-channel energy estimations, the optimum filters provide comparatively
better results than the other filters. The DPLMS multi-channel optimum filters
further enhance the quality of the estimations, compared to single-channel
optimum filters, with non-negligible inter-channel noise correlation. The
effectiveness and robustness of the DPLMS method in synthesizing high-quality
filters for energy estimation will be tested soon within leading-edge
multi-channel physics experiments.Comment: 15 pages, 13 figure
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