30 research outputs found
Energy spectra of the ocean's internal wave field: theory and observations
The high-frequency limit of the Garrett and Munk spectrum of internal waves
in the ocean and the observed deviations from it are shown to form a pattern
consistent with the predictions of wave turbulence theory. In particular, the
high frequency limit of the Garrett and Munk spectrum constitutes an {\it
exact} steady state solution of the corresponding kinetic equation.Comment: 4 pages, one color figur
Nonlinear surface waves in left-handed materials
We study both linear and nonlinear surface waves localized at the interface
separating a left-handed medium (i.e. the medium with both negative dielectric
permittivity and negative magnetic permeability) and a conventional (or
right-handed) dielectric medium. We demonstrate that the interface can support
both TE- and TM-polarized surface waves - surface polaritons, and we study
their properties. We describe the intensity-dependent properties of nonlinear
surface waves in three different cases, i.e. when both the LH and RH media are
nonlinear and when either of the media is nonlinear. In the case when both
media are nonlinear, we find two types of nonlinear surface waves, one with the
maximum amplitude at the interface, and the other one with two humps. In the
case when one medium is nonlinear, only one type of surface wave exists, which
has the maximum electric field at the interface, unlike waves in right-handed
materials where the surface-wave maximum is usually shifted into a
self-focussing nonlinear medium. We discus the possibility of tuning the wave
group velocity in both the linear and nonlinear cases, and show that
group-velocity dispersion, which leads to pulse broadening, can be balanced by
the nonlinearity of the media, so resulting in soliton propagation.Comment: 9 pages, 10 figure
On the energy transported by exact plane gravitational-wave solutions
The energy and momentum transported by exact plane gravitational-wave
solutions of Einstein equations are computed using the teleparallel equivalent
formulation of Einstein's theory. It is shown that these waves transport
neither energy nor momentum. A comparison with the usual linear plane
gravitational-waves solution of the linearized Einstein equation is presented.Comment: 15 pages, Revtex, no figures, to appear in Class. Quantum Gra
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Light scattering spectroscopy identifies the malignant potential of pancreatic cysts during endoscopy
Pancreatic cancers are usually detected at an advanced stage and have poor prognosis. About one fifth of these arise from pancreatic cystic lesions. Yet not all lesions are precancerous, and imaging tools lack adequate accuracy for distinguishing precancerous from benign cysts. Therefore, decisions on surgical resection usually rely on endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). Unfortunately, cyst fluid often contains few cells, and fluid chemical analysis lacks accuracy, resulting in dire consequences, including unnecessary pancreatic surgery for benign cysts and the development of cancer. Here, we report an optical spectroscopic technique, based on a spatial gating fibre-optic probe, that predicts the malignant potential of pancreatic cystic lesions during routine diagnostic EUS-FNA procedures. In a double-blind prospective study in 25 patients, with 14 cysts measured in vivo and 13 postoperatively, the technique achieved an overall accuracy of 95%, with a 95%confidence interval of 78–99%, in cysts with definitive diagnosis
Origin of the Ceratitida (Ammonoidea) inferred from the early internal shell features
Volume: 5Start Page: 201End Page: 21
Late Permian to Middle Triassic palaeogeographic differentiation of key ammonoid groups: evidence from the former USSR
Palaeontological characteristics of the Upper Permian and upper Olenekian to lowermost Anisian sequences in the Tethys and the Boreal realm are reviewed in the context of global correlation. Data from key Wuchiapingian and Changhsingian sections in Transcaucasia, Lower and Middle Triassic sections in the Verkhoyansk area, Arctic Siberia, the southern Far East (South Primorye and Kitakami) and Mangyshlak (Kazakhstan) are examined. Dominant groups of ammonoids are shown for these different regions. Through correlation, it is suggested that significant thermal maxima (recognized using geochemical, palaeozoogeographical and palaeoecological data) existed during the late Kungurian, early Wuchiapingian, latest Changhsingian, middle Olenekian and earliest Anisian periods. Successive expansions and reductions of the warm– temperate climatic zones into middle and high latitudes during the Late Permian and the Early and Middle Triassic are a result of strong climatic fluctuations
The Influence of Biomolecule Composition on Colloidal Beer Structure
Recent studies have revealed an interest in the composition of beer biomolecules as a colloidal system and their influence on the formation of beer taste. The purpose of this research was to establish biochemical interactions between the biomolecules of plant-based raw materials of beer in order to understand the overall structure of beer as a complex system of bound biomolecules. Generally accepted methods of analytical research in the field of brewing, biochemistry and proteomics were used to solve the research objectives. The studies allowed us to establish the relationship between the grain and plant-based raw materials used, as well as the processing technologies and biomolecular profiles of beer. The qualitative profile of the distribution of protein compounds as a framework for the formation of a colloidal system and the role of carbohydrate dextrins and phenol compounds are given. This article provides information about the presence of biogenic compounds in the structure of beer that positively affect the functioning of the body. A critical assessment of the influence of some parameters on the completeness of beer taste by biomolecules is given. Conclusion: the conducted analytical studies allowed us to confirm the hypothesis about the nitrogen structure of beer and the relationship of other biomolecules with protein substances, and to identify the main factors affecting the distribution of biomolecules by fractions