Recent progress in microspherical superlens nanoscopy raises a fundamental question about the transition from super-resolution properties of mesoscale microspheres, which can provide a subwavelength ...resolution Formula: see text, to macroscale ball lenses, for which the imaging quality degrades because of aberrations. To address this question, this work develops a theory describing the imaging by contact ball lenses with diameters Formula: see text covering this transition range and for a broad range of refractive indices Formula: see text. Starting from geometrical optics we subsequently proceed to an exact numerical solution of the Maxwell equations explaining virtual and real image formation as well as magnification M and resolution near the critical index Formula: see text which is of interest for applications demanding the highest M such as cellphone microscopy. The wave effects manifest themselves in a strong dependence of the image plane position and magnification on Formula: see text, for which a simple analytical formula is derived. It is demonstrated that a subwavelength resolution is achievable at Formula: see text. The theory explains the results of experimental contact-ball imaging. The understanding of the physical mechanisms of image formation revealed in this study creates a basis for developing applications of contact ball lenses in cellphone-based microscopy.
It is predicted that the optical force experienced by a dielectric particle excited resonantly by a surface wave can be directed opposite to the incident power flow when the exciting wave is a ...backward one. This is consistent with the electromagnetic momentum flow of the backward wave being directed opposite to the power flow. The magnitude of the force can be comparable to the momentum flow of the surface wave. Such forces bring a deeper understanding of the electromagnetics of backward surface waves and can be used in integrated photonic circuits and optofluidic devices.
The trace element systematics (Rb, Hf, Y, Zr, Nb, Yb, Ta, and other trace elements) is considered in sandstones and fine-grained clastic rocks (shales and argillaceous siltstones) of the Upper ...Riphean arkose complex of the Southern Urals (Biryan Subformation of the Zilmerdak Formation, Karatau Group). These rocks were formed during the first sedimentation cycle; therefore, it can be assumed that their lithogeochemical features largely reflect the petrogeochemical characteristics of source rocks, in this case, granitoids. An analysis of the distribution of data points of arkose and subarkose sandstones and fine-grained clastic rocks in different discriminant diagrams allows us to conclude that the main sources of clastics for the Upper Riphean arkose complex were volcanic-arc (VAG) and collisional (COLG) granites. The contribution of within-plate granites (WPG) is also possible, which is clearly seen in most of the Pearce diagrams and in the Hf–Rb–Ta and Zr–(Nb/Zr)
PM
diagrams. According to their petrogeochemical characteristics, these granites could belong to alkaline and magnesian varieties and were close to S-granites. This assumption is also supported by the wide spectrum of U–Th–U isotope ages of detrital zircons present in the arkose sandstones of the Biryan Subformation of the Zilmerdak Formation, which possibly reflect the age range of zircon xenocrysts inherited from the melt source(s). All these facts do not provide information on definite massifs and their distribution areas, but allows us to significantly specify information about the possible nature of granite sources for clastics of the Upper Riphean arkose complex of the Southern Urals.
The paper presents data on the lithochemistry of Upper Riphean and Vendian metapelites in the Bodaibo structural–facies zone of the Baikal–Patom foldbelt. The typical K
2
O/Na
2
O and SiO
2
/Al
2
O
3
...ratios of the metapelites indicate that they have not been affected by potassium metasomatism and silicification processes. The ratios in the metapelites of the TM and FM and of the NAM and HM modules of the rocks suggest that their protoliths consisted mostly of the material of the first sedimentation cycle. Its sources were most likely igneous rocks of intermediate and mafic composition. The composition of the protoliths is comparable to kaolinite, kaolinite–illite–smectite, and chlorite–smectite–illite clays, i.e., it did not principally differ from the composition of most “ordinary” clay rocks. The average values of the chemical index of alteration (CIA
correct
) exceed its threshold value that distinguishes between rocks formed in cold/arid and warm/humid climates, only for metapelites of the Kharlukhtakh, Khaiverga, Aunakit, and Vacha formations. The metapelites of the other levels of the Upper Riphean and Vendian of the Bodaibo zone are composed of thin-grained aluminosilicate clastic material relatively weakly altered by chemical weathering in the paleocatchment areas. The average values of the phosphorus enrichment coefficient in the formations give reason to believe that the paleoproductivity of the sedimentation areas of the Upper Riphean and Vendian was insignificant, despite the locally rather high content of TOC in the metapelites. The metapelites also show no evidence of the presence of “camouflaged” pyroclastics or products of underwater exhalations.
—
This paper presents a complex interpretation of structural–petrological studies and new geochemical and isotope–geochronological data on the Paleoarchean metamorphic and metaintrusive rocks of ...Mts. Rymill and Bloomfield in the northern part of the granite-greenstone Ruker terrane (Prince Charles Mountains, East Antarctica). The detailed sequence of changing Archean tectonomagmatic processes in the northern block of the Ruker area has been revealed and the main stages of tectonic deformations and metamorphism of Precambrian geodynamic evolution are shown, which is a key for the understanding of the geological evolution of the Archean metamorphic complexes of East Antarctica and ancient Earth’s regions. The northern part of the Ruker Terrane is composed of the Meso-Neoarchean granite–gneiss domes, which are tectonically framed by fragments of greenstone belt of the metavolcanosedimentary Meso-Neoarchean Menzies Series. The detached blocks or packages of sheets of metavolcanosedimentary sequences are a section of weakly metamorphosed intermediate–felsic sandstones, quartzites, and micaceous schists. An assemblage of rocks spans a significant period from 3.2 to 2.5 Ga. The composition of the Mesoarchean granite–gneiss domes of the Mawson Series (3.2–3.1 Ga) corresponds to those of ancient granitoids, is similar to tonalite–trondhjemite–granodiorite (TTG) complexes, and is comparable with similar associations of ancient cratons of Australia, Canada, and Fennoscandia. The rocks of the Mawson Series are polymetamorphic and a significant part of their recrystallization is related to the Mesoarchean stage of metamorphism, whose end is comparable with the formation of the Meso-Neoarchean blocks of the granite–gneiss association of the TTG dome of ~2.8 Ga identified by the author. The age of the striking tectonothermal event of ~2.7 Ga is determined by overgrowths of zircons from the TTG gneisses. The Mawson Orthogneiss and TTG gneisses are compared with intraplate A‑granitoids and are ascribed to low-Ti high-K Archean granitoids. The geochemistry of the rocks indicates that primary melts of the Meso-Archean Mawson Orthogneiss formed in crust at shallower depths (
P
< 8–10 kbar) in comparison with Meso-Archean TTG gneisses, whose formation is possibly caused by the increasing thickness of the crust followed by its extension and thinning at a boundary of ~2.5 Ga.
The article overviews concepts of the formation of sedimentary sequences of the Belt-Purcell Supergroup, a classical Upper Precambrian section of the Rocky Mountains (North America). Analysis of data ...on the bulk chemical composition of mudstones of the Belt-Purcell Supergroup (González-Álvarez, 2005; González-Álvarez and Kerrich, 2010) suggests that the overwhelming part of the fine-grained aluminosiliciclastic filling in the Belt Basin was delivered from complexes with non-Archean geochemical characteristics. During almost the entire period of sedimentary filling in the Belt Basin, the fine-grained aluminosiliciclastic material was delivered by large river arteries similar to modern rivers of category 1, i.e., major rivers draining large (>100 000 km
2
) continental areas (Bayon et al., 2015), and category 2 (rivers draining the “mixed/sedimentary” rocks). This fact confirms the concept of the formation of sedimentary sequences of the Belt-Purcell Supergroup inferred from both traditional geological methods and analysis of data on the U–Pb isotopic ages of detrital zircons and monazites from sandstones of various lithostratigraphic units.
We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. ...Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released in January 2009, and is available on the Web through
http://www-nds.iaea.org/RIPL-3/
. This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations.
The numerical data and computer codes included in RIPL-3 are arranged in seven segments:
MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi
et al. (2003).
DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic and
γ-ray decay probabilities available from ENSDF in October 2007.
NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab.
OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment.
LEVEL DENSITIES contains phenomenological parameterizations based on the modified Fermi gas and superfluid models and microscopic calculations which are based on a realistic microscopic single-particle level scheme. Partial level densities formulae are also recommended. All tabulated total level densities are consistent with both the recommended average neutron resonance parameters and discrete levels.
GAMMA contains parameters that quantify giant resonances, experimental gamma-ray strength functions and methods for calculating gamma emission in statistical model codes. The experimental GDR parameters are represented by Lorentzian fits to the photo-absorption cross sections for 102 nuclides ranging from
51V to
239Pu.
FISSION includes global prescriptions for fission barriers and nuclear level densities at fission saddle points based on microscopic HFB calculations constrained by experimental fission cross sections.
Quantum Coherence in an Optical Modulator Carter, S. G; Birkedal, V; Wang, C. S ...
Science (American Association for the Advancement of Science),
10/2005, Letnik:
310, Številka:
5748
Journal Article
Recenzirano
Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum ...wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications.
The distribution of composition fields of syn-rift and syncollisional sandstones and fine-grained clastic/clayey rocks of various structures and different ages are compared on the SiO
2
–K
2
O/Na
2
...O, F1–F2, and DF1–DF2 diagrams. Syn-rift sedimentary sequences fill intraplate rifts, rifts at divergent, conservative and convergent plate boundaries, as well as their triple junctions. Syncollisional sediments are referred to rocks of foredeep and intermontane troughs, which are made up of molasses proper, flysch and schliers, and volcanogenic and nonfolded (distal) molasses. Fields of syn-rift and syncollisional sandstones in the SiO
2
–K
2
O/Na
2
O diagram show significant overlap. In the F1–F2 and DF1–DF2 diagrams, the distribution of the fields of syn-rift and syncollisional fine-grained clastic/clayey rocks is also substantially similar. Hence, the above mentioned diagrams cannot be used for reliable discrimination between syn-rift and syncollisional terrigenous associations. Correspondingly, it is hardly possible to use these diagrams alone for determination of geodynamic nature of sediments.
Water-soluble nanocomposites based on CdSe/ZnS quantum dots (QDs) and hydrophobic tetraphenylporphyrin (TPP) molecules passivated by chitosan (CS) have been formed. Magnetic circular dichroism (MCD) ...spectra evidence TPP presence in both monomeric and agglomerated forms in the nanocomposites. The nanocomposites demonstrate more pronounced singlet oxygen generation compared to free TPP in CS at the same concentration due to the intracomplex Förster resonance energy transfer (FRET) with a 45% average efficiency.
A CdSe/ZnS QD-TPP nanocomposite and energy transfer from QDs to (i) TPP monomers to oxygen generating singlet oxygen (SO) and (ii) TPP aggregates cannot generate SO in chitosan solution.
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