Microorganisms linked to Neoproterozoic microspar carbonate sedimentation in the Jilin-Liaoning area

Molar-tooth carbonate refers to a sort of rock that has ptygmatical folded structure comparable to the ivory. This kind of carbonate exists in a special time range (from Middle to Neoproterozoic). Its origin and the possibility to use it in stratigraphic correlation of the paleocontinent is the key task of the IGCP447, a project on Proterozoic molar tooth carbonates and the evolution of the earth (2001-2005). The importance lies in that the molar-tooth structure is the key to solving problems related to Precambrian biological and global geochemical events. The molar-tooth structure is associated with microorganisms. Development and recession of such carbonates have relations with the evolution process of early lives and abrupt changes in sea carbonate geochemistry. In recent years, based on researches on petrology, geochemistry and Sr isotope of molar-tooth carbonate in the Jilin-Liaoning and Xuzhou-Huaiyang area, the authors hold that it can be used as a marker for stratigraphic sequence and sedimentary facies analyses.

Microorganisms linked to Neoproterozoic microspar carbonate sedimentation in the Jilin-Liaoning area

Molar-tooth carbonate refers to a sort of rock that has ptygmatical folded structure comparable to the ivory. This kind of carbonate exists in a special time range (from Middle to Neoproterozoic). Its origin and the possibility to use it in stratigraphic correlation of the paleocontinent is the key task of the IGCP447, a project on Proterozoic molar tooth carbonates and the evolution of the earth (2001-2005). The importance lies in that the molar-tooth structure is the key to solving problems related to Precambrian biological and global geochemical events. The molar-tooth structure is associated with microorganisms. Development and recession of such carbonates have relations with the evolution process of early lives and abrupt changes in sea carbonate geochemistry. In recent years, based on researches on petrology, geochemistry and Sr isotope of molar-tooth carbonate in the Jilin-Liaoning and Xuzhou-Huaiyang area, the authors hold that it can be used as a marker for stratigraphic sequence and sedimentary facies analyses.

Indigenous Australia is deadly – and Leah Purcell shows it (Documentary review)

Urban skyline, as seen from inside a medium-density apartment block, opens Australian director Leah Purcell’s Who We Are: Brave New Clan (2014), which was broadcast on Foxtel’s Bio Channel last night. The one-off documentary – which deserves another run – follows the lives of six Indigenous Australians (not connected in real life but our “clan” for the sake of the documentary). Does it work? Oh yes...

Emitter near an arbitrary body: Purcell effect, optical theorem and the Wheeler-Feynman absorber

The altered spontaneous emission of an emitter near an arbitrary body can be elucidated using an energy balance of the electromagnetic field. From a classical point of view it is trivial to show that the field scattered back from any body should alter the emission of the source. But it is not at all apparent that the total radiative and non-radiative decay in an arbitrary body can add to the vacuum decay rate of the emitter (i.e.) an increase of emission that is just as much as the body absorbs and radiates in all directions. This gives us an opportunity to revisit two other elegant classical ideas of the past, the optical theorem and the Wheeler-Feynman absorber theory of radiation. It also provides us alternative perspectives of Purcell effect and generalizes many of its manifestations, both enhancement and inhibition of emission. When the optical density of states of a body or a material is difficult to resolve (in a complex geometry or a highly inhomogeneous volume) such a generalization offers new directions to solutions. (c) 2012 Elsevier Ltd. All rights reserved.

Stable isotope evidence for ca. 2.7-Ga-old Archean cap carbonates from the Dharwar Supergroup, southern India

Carbon isotope compositions of carbonate rocks from similar to 2.7-Ga-old Neoarchean Vanivilas Formation of the Dharwar Supergroup presented earlier by us are re-evaluated in this study, besides oxygen isotope compositions of a few silica dolomite pairs. The purpose of such a revisit assumes significance in view of recent field evidences that suggest a glaciomarine origin for the matrix-supported conglomerate member, the Talya conglomerate, which underlies the carbonate rocks of the Vanivilas Formation. An in-depth analysis of carbon isotope data reveals preservation of their pristine character despite the rocks having been subjected to metamorphism to different degrees (from lower greenschist to lower amphibolite facies). The dolomitic member of Vanivilas Formation of Marikanive area is characterized by highly depleted delta C-13 value (up to -5 parts per thousand VPDB) and merits as the Indian example of ca. 2.7-Ga-old cap carbonate. This inference is further supported by estimated low temperature of equilibration documented by a few silica dolomite pairs from the Vanivilas Formation collected near Kalche area. These pairs show evidence for oxygen isotopic equilibrium at low temperatures (similar to 0-20 degrees C) with depleted water (delta O-18 = -21 parts per thousand to -15 parts per thousand VSMOW) of glacial origin. We propose that the mineral pairs were deposited during the deglaciation period when the ocean temperature was in its gradual restoration phase. The dolomite of Marikanive area is the first record of cap carbonates from the Indian subcontinent with Neoarchean antiquity.

Enhancement of room temperature sub-bandgap light emission from silicon photonic crystal nanocavity by Purcell effect

We report the enhancement of sub-bandgap photoluminescence from silicon via the Purcell effect. We couple the defect emission from silicon, which is believed to be due to hydrogen incorporation into the lattice, to a photonic crystal (PhC) nanocavity. We observe an up to 300-fold enhancement of the emission at room temperature at 1550 nm, as compared to an unpatterned sample, which is then comparable to the silicon band-edge emission. We discuss the possibility of enhancing this emission even further by introducing additional defects by ion implantation, or by treating the silicon PhC nanocavity with hydrogen plasma. © 2011 Elsevier B.V.

An extension of Purcell's vector method with applications to panel element equations

The classical Purcell's vector method, for the construction of solutions to dense systems of linear equations is extended to a flexible orthogonalisation procedure. Some properties are revealed of the orthogonalisation procedure in relation to the classical Gauss-Jordan elimination with or without pivoting. Additional properties that are not shared by the classical Gauss-Jordan elimination are exploited. Further properties related to distributed computing are discussed with applications to panel element equations in subsonic compressible aerodynamics. Using an orthogonalisation procedure within panel methods enables a functional decomposition of the sequential panel methods and leads to a two-level parallelism.

Parallel algorithms of the Purcell method for direct solution of linear systems

In this paper, we first demonstrate that the classical Purcell's vector method when combined with row pivoting yields a consistently small growth factor in comparison to the well-known Gauss elimination method, the Gauss–Jordan method and the Gauss–Huard method with partial pivoting. We then present six parallel algorithms of the Purcell method that may be used for direct solution of linear systems. The algorithms differ in ways of pivoting and load balancing. We recommend algorithms V and VI for their reliability and algorithms III and IV for good load balance if local pivoting is acceptable. Some numerical results are presented.

Interpretaciones desde la ventana del ático de la Casa Purcell (2008-2012).

Tesis (Maestría en Artes con Acentuación en Artes Visuales) UANL, 2012.

THE PYROCHLORE SUPERGROUP OF MINERALS: NOMENCLATURE

A new scheme of nomenclature for the pyrochlore supergroup, approved by the CNMNC-IMA, is based on the ions at the A, B and Y sites. What has been referred to until now as the pyrochlore group should be referred to as the pyrochlore supergroup, and the subgroups should be changed to groups. Five groups are recommended, based on the atomic proportions of the B atoms Nb, Ta, Sb, Ti, and W. The recommended groups are pyrochlore, microlite, romite, betafite, and elsmoreite, respectively. The new names are composed of two prefixes and one root name (identical to the name of the group). The first prefix refers to the dominant anion (or cation) of the dominant valence [or H(2)O or rectangle] at the Y site. The second prefix refers to the dominant cation of the dominant valence [or H(2)O or rectangle] at the A site. The prefix "" keno-"" represents "" vacancy"". Where the first and second prefixes are equal, then only one prefix is applied. Complete descriptions are missing for the majority of the pyrochlore-supergroup species. Only seven names refer to valid species on the grounds of their complete descriptions: oxycalciopyrochlore, hydropyrochlore, hydroxykenomicrolite, oxystannomicrolite, oxystibiomicrolite, hydroxycalcioromite, and hydrokenoelsmoreite. Fluornatromicrolite is an IMA-approved mineral, but the complete description has not yet been published. The following 20 names refer to minerals that need to be completely described in order to be approved as valid species: hydroxycalciopyrochlore, fluornatropyrochlore, fluorcalciopyrochlore, fluorstrontiopyrochlore, fluorkenopyrochlore, oxynatropyrochlore, oxyplumbopyrochlore, oxyyttropyrochlore-(Y), kenoplumbopyrochlore, fluorcalciomicrolite, oxycalciomicrolite, kenoplumbomicrolite, hydromicrolite, hydrokenomicrolite, oxycalciobetafite, oxyuranobetafite, fluornatroromite, fluorcalcioromte, oxycalcioromite, and oxyplumboromite. For these, there are only chemical or crystalstructure data. Type specimens need to be defined. Potential candidates for several other species exist, but are not sufficiently well characterized to grant them any official status. Ancient chemical data refer to wet-chemical analyses and commonly represent a mixture of minerals. These data were not used here. All data used represent results of electron-microprobe analyses or were obtained by crystal-structure refinement. We also verified the scarcity of crystal-chemical data in the literature. There are crystalstructure determinations published for only nine pyrochlore-supergroup minerals: hydropyrochlore, hydroxykenomicrolite, hydroxycalcioromite, hydrokenoelsmoreite, hydroxycalciopyrochlore, fluorcalciopyrochlore, kenoplumbomicrolite, oxycalciobetafite, and fluornatroromite. The following mineral names are now discarded: alumotungstite, bariomicrolite, bariopyrochlore, bindheimite, bismutomicrolite, bismutopyrochlore, bismutostibiconite, calciobetafite, ceriopyrochlore-(Ce), cesstibtantite, ferritungstite, jixianite, kalipyrochlore, monimolite, natrobistantite, partzite, plumbobetafite, plumbomicrolite, plumbopyrochlore, stannomicrolite, stetefeldtite, stibiconite, stibiobetafite, stibiomicrolite, strontiopyrochlore, uranmicrolite, uranpyrochlore, yttrobetafite-(Y), and yttropyrochlore-(Y).

Qualitative analysis by online nuclear magnetic resonance using Carr-Purcell-Meiboom-Gill sequence with low refocusing flip angles

The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence has been used in many applications of magnetic resonance imaging (MRI) and low-resolution NMR (LRNMR) spectroscopy. Recently. CPMG was used in online LRNMR measurements that use long RF pulse trains, causing an increase in probe temperature and, therefore, tuning and matching maladjustments. To minimize this problem, the use of a low-power CPMG sequence based on low refocusing pulse flip angles (LRFA) was studied experimentally and theoretically. This approach has been used in several MRI protocols to reduce incident RF power and meet the specific absorption rate. The results for CPMG with LRFA of 3 pi/4 (CPMG(135)), pi/2 (CPMG(90)) and pi/4 (CPMG(45)) were compared with conventional CPMG with refocusing pi pulses. For a homogeneous field, with linewidth equal to Delta nu = 15 Hz, the refocusing flip angles can be as low as pi/4 to obtain the transverse relaxation time (T(2)) value with errors below 5%. For a less homogeneous magnetic field. Delta nu = 100 Hz, the choice of the LRFA has to take into account the reduction in the intensity of the CPMG signal and the increase in the time constant of the CPMG decay that also becomes dependent on longitudinal relaxation time (T(1)). We have compared the T(2) values measured by conventional CPMG and CPMG(90) for 30 oilseed species, and a good correlation coefficient, r = 0.98, was obtained. Therefore, for oilseeds, the T(2) measurements performed with pi/2 refocusing pulses (CPMG(90)), with the same pulse width of conventional CPMG, use only 25% of the RF power. This reduces the heating problem in the probe and reduces the power deposition in the samples. (C) 2011 Elsevier B.V. All rights reserved.

Use of Carr-Purcell pulse sequence with low refocusing flip angle to measure T-1 and T-2 in a single experiment

The Carr-Purcell pulse sequence, with low refocusing flip angle, produces echoes midway between refocusing pulses that decay to a minimum value dependent on T*(2). When the refocusing flip angle was pi/2 (CP90) and tau > T*(2), the signal after the minimum value, increased to reach a steady-state free precession regime (SSFP), composed of a free induction decay signal after each pulse and an echo, before the next pulse. When tau < T*(2), the signal increased from the minimum value to the steady-state regime with a time constant (T*) = 2T(1)T(2)/(T-1 + T-2). identical to the time constant observed in the SSFP sequence, known as the continuous wave free precession (CWFP). The steady-state amplitude obtained with M-cp90 = M0T2/(T-1+T-2) was identical to CWFP. Therefore, this sequence was named CP-CWFP because it is a Carr-Purcell sequence that produces results similar to the CWFP. However, CP-CWFP is a better sequence for measuring the longitudinal and transverse relaxation times in single scan, when the sample exhibits T-1 similar to T-2. Therefore, this sequence can be a useful method in time domain NMR and can be widely used in the agriculture, food and petrochemical industries because those samples tend to have similar relaxation times in low magnetic fields. (C) 2011 Elsevier Inc. All rights reserved.

Untersuchung zum Entstehungsmechanismus von Smith-Purcell-Strahlung im Nahbereich mit einem 855 MeV Elektronenstrahl geringer Emittanz

Experimental investigations of visible Smith-Purcell-radiation with a micro-focused high relativistic electron beam (E=855 MeV) are presented in the near region, in which the electron beam grazes the surface of the grating. The radiation intensity was measured as a function of the angle of observation and of the distance between electron beam axis and the surface of the grating simultaneously for two different wavelengths (360 nm, 546 nm).In the experiments Smith-Purcell-radiation was identified by the measured angular distribution fulfilling the characteristic coherence condition. By the observed distance dependence of the intensity two components of Smith-Purcell-radiation could be separated: one component with the theoretical predicted interaction length hint, which is produced by electrons passing over the surface of the grating, and an additional component in the near region leading to a strong enhancement of the intensity, which is produced by electrons hitting the surface. To describe the intensity of the observed additional radiation component a simple model for optical grating transition radiation, caused by the electrons passing through the grating structure, is presented. Taking into account the simple scalar model, the results of a Monte-Carlo calculation show that the additional radiation component could be explained by optical grating transition radiation.