Intermediate Spectra Research Articles

Complex F,Cl Apatite Solid Solution Investigated Using Multinuclear Solid-State NMR Methods

A series of synthetic F,Cl apatites with low hydroxyl content was investigated using 31P, 19F, and 35Cl solid-state magic angle spinning (MAS) NMR spectroscopic methods. 31P single-pulse (SP) NMR spectra show that for each composition the phosphate 31P chemical shift depends on occupancy of the nearest anion site for each composition. Overall the average chemical shift deviates from linear across the F/Cl series. For intermediate compositions 19F SP NMR spectra reveal complex, broadened spectral profiles that are not correlated to composition. 19F{35Cl} TRAPDOR results indicate that the spectral profiles do not reflect occupancy of F and Cl in adjacent column anion sites. We propose that the complex 19F lineshapes are principally due to broad distributions of 19F–Ca distances arising from displacement of F along the anion channel. Approximate fluorine atomic positions are estimated based on 19F chemical shifts of alkaline earth fluoride salts, and the results are in good accord with those proposed for int...

Reaction kinetics and mechanisms of organosilicon fungicide flusilazole with sulfate and hydroxyl radicals

Flusilazole is an organosilane fungicide used for treatments in agriculture and horticulture for control of diseases. The reaction kinetics and mechanism of flusilazole with sulfate and hydroxyl radicals were studied. The rate constant of the radicals with the fungicide were determined by laser flash photolysis of peroxodisulfate and hydrogen peroxide. The results were 2.0 × 109 s−1M−1 for the reaction of the fungicide with HO and 4.6 × 108 s−1 M−1 for the same reaction with SO4– radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S2O82− with flusilazole, were identified as α-aminoalkyl and siloxyl radicals and agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. In the continuous photolysis experiments, performed by photo-Fenton reaction of the fungicide, the main degradation products were: (bis(4-fluorophenyl)-hydroxy-methylsilane) and the non-toxic silicic acid, diethyl bis(trimethylsilyl) ester, in ten and twenty minutes of reaction, respectively.

Excitation of photosystem I by 760 nm femtosecond laser pulses: transient absorption spectra and intermediates

Excitation of photosystem I (PS I) by a femtosecond 760 nm pump leads to one- and two-photon absorption. The one-photon excitation produces intermediates with transient absorption spectra similar to the spectra of the primary and secondary ion-radical pairs in the PS I reaction center. The two-photon absorption generates the upper level excited states of chlorophyll (Chl) and carotenoid molecules in the antenna. These excited states are converted into the long-lived intermediates and can be tentatively attributed to the excited and charge–transfer ion-radical states of Chl molecules and to the excited states of carotenoids in the antenna. The transient spectra of intermediates generated by two-photon excitation differ from the transient one-photon spectra of the primary and secondary ion-radical pairs.

Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx atz= 1.4

The light from distant supernovae (SNe) can be magnified through gravitational lensing when a foreground galaxy is located along the line of sight. This line-up allows for detailed studies of SNe at high redshift that otherwise would not be possible. Spectroscopic observations of lensed high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they can be used to test for evolution of their intrinsic properties. The use of SNe Ia for probing the cosmic expansion history has proven to be an extremely powerful method for measuring cosmological parameters. However, if systematic redshift-dependent properties are found, their usefulness for future surveys could be challenged. We investigate whether the spectroscopic properties of the strongly lensed and very distant SN Ia PS1-10afx at $z=1.4$ deviates from the well-studied populations of normal SNe Ia at nearby or intermediate distance. We created median spectra from nearby and intermediate-redshift spectroscopically normal SNe Ia from the literature at -5 and +1 days from light-curve maximum. We then compared these median spectra to those of PS1-10afx. We do not find signs of spectral evolution in PS1-10afx. The observed deviation between PS1-10afx and the median templates are within what is found for SNe at low- and intermediate-redshift. There is a noticeable broad feature centred at $\rm \lambda\sim 3500$~\AA{}, which is present only to a lesser extent in individual low and intermediate redshift SN Ia spectra. From a comparison with a recently developed explosion model, we find this feature to be dominated by iron peak elements, in particular, singly ionized cobalt and chromium.

Relative Thom spectra via operadic Kan extensions

We show that a large number of Thom spectra, i.e. colimits of morphisms $BG\to BGL_1(\mathbb{S})$, can be obtained as iterated Thom spectra, i.e. colimits of morphisms $BG\to BGL_1(Mf)$ for some Thom spectrum $Mf$. This leads to a number of new relative Thom isomorphisms, e.g. $MU[6,\infty)\wedge_{MString} MU[6,\infty)\simeq MU[6,\infty)\wedge\mathbb{S}[B^3Spin]$. As an example of interest to chromatic homotopy theorists, we also show that Ravenel's $X(n)$ filtration of $MU$ is a tower of intermediate Thom spectra determined by a natural filtration of $BU$ by sub-bialagebras.

Analyses with latest major nuclear data libraries of the fission rate ratios for several TRU nuclides in the FCA-IX experiments

ABSTRACTIn the 1980s, a series of integral experiments was conducted in FCA-IX assemblies with systematically changed neutron spectra covering from the intermediate to fast ones. The experiments provide systematic data of central fission rates for TRU nuclides containing minor actinides, 237Np, 238Pu, 239Pu, 242Pu, 241Am, 243Am, and 244Cm. Regarding the fission rate ratios relative to 239Pu, benchmark models had been recently developed for validation of nuclear data for the TRU's fission cross sections. In this paper, the latest major nuclear data libraries, JENDL-4.0, ENDF/B-VII.1, and JEFF-3.2, are compared on the benchmark models. For the libraries, the analyses by a Monte Carlo calculation code show obvious overestimations particularly for the fission rate ratios of 244Cm to 239Pu. Additionally, a large discrepancy about by 20% between the libraries is revealed for the fission rate ratio of 238Pu to 239Pu measured in the intermediate neutron spectrum. The causes of discrepancies are furthermore clarified by sensitivity analyses.

A new L5 brown dwarf member of the Hyades cluster with chromospheric activity

Our aim is to identify brown dwarf members of the nearby Hyades open star cluster to determine the photometric and spectroscopic properties of brown dwarfs at moderately old ages and extend the knowledge of the substellar mass function of the cluster. We cross-matched the 2MASS and AllWISE public catalogues and measured proper motions to identify low-mass stars and brown dwarf candidates in an area of radius eight degrees around the central region of the Hyades cluster. We identified objects with photometry and proper motions consistent with cluster membership. For the faintest ($J$\,=\,17.2 mag) most promising astrometric and photometric low-mass candidate 2MASS\,J04183483$+$2131275\@, with a membership probability of 94.5\%, we obtained low-resolution (R\,=\,300--1000) and intermediate-resolution (R\,=\,2500) spectroscopy with the 10.4m Gran Telescopio Canarias. From the low-resolution spectra we determined a L5.0$\pm$0.5 spectral type, consistent with the available photometry. In the intermediate dispersion spectrum we detected H$\alpha$ in emission (marginally resolved with a full width half maximum of $\sim$2.8 \AA{}) and determined a $\log ($L$_{\rm{H}\alpha}$/L$_{\rm bol})=-6.0$ dex. From H$\alpha$ we obtained a radial velocity of 38.0$\pm$2.9 km$\cdot$s$^{-1}$, which combined with the proper motion leads to space velocities which are fully consistent with membership in the Hyades cluster.

Combined Method for the Synthesis of Ultrafine Powder Carbides of W, Ti, V

In this work we propose a new method for synthesis of ultrafine powders of tungsten, titanium and vanadium carbides combining two methods – liquid-phase precipitation on carbon substrate and low-temperature microwave heat treatment in argon stream. An entire spectrum of intermediates obtained by thermolysis, reduction and carbonization of precursors, as well as the final products has been presented. As a result of sample assessment, the phase composition, structure, morphology and particle size, as well as the size of specific surface areas have been determined.

Coordinating Role of IQGAP1 in the Regulation of Multivesicular Endosomal Compartment Dynamics

IQGAP1 is a large, multi-domain scaffold that helps orchestrate cell signaling and cytoskeletal mechanics by controlling interactions among a spectrum of receptors, signaling intermediates, and cytoskeletal proteins. While this coordination is known to impact cell morphology, motility, cell adhesion, and vesicular traffic, among other functions, the spatiotemporal properties and regulatory mechanisms of IQGAP1 have not been fully resolved. Herein, we describe a series of super-resolution and live-cell imaging analyses that identified a role for IQGAP1 in the regulation of an actin cytoskeletal shell surrounding a novel membranous compartment that localizes selectively to the basal cortex of polarized epithelial cells (MCF-10A). These largely immotile yet highly dynamic structures are identified as multivesicular membrane processing stations that participate in adherens junction protein traffic. We also show that IQGAP1 appears to both stabilize the actin coating and constrain its growth. Loss of compartmental IQGAP1 initiates a disassembly mechanism involving rapid and unconstrained actin polymerization around the compartment and dispersal of its vesicle contents. Together, these findings suggest IQGAP1 achieves this control over compartment dynamics by harnessing both stabilizing and antagonistic interactions with actin.

Synoptic environments and characteristics of cold air outbreaks in the Irminger Sea

ABSTRACTCold air outbreaks (CAOs) are the dominant cause of intense wintertime upward heat fluxes in the Irminger Sea. In this study, the climatological pathways of Irminger Sea CAO airmasses and the evolution of airmass properties, as well as the large‐scale synoptic environments leading to CAO formation are examined for winter. To that end, a comprehensive, multi‐decadal climatology of Irminger Sea CAO airmasses using kinematic trajectories is presented, complemented by a composite analysis of the large‐scale synoptic environment for intense CAO events.The following three synoptic environments conducive for CAO formation are identified: (1) The westerly environment is characterized by an upper‐level trough crossing Greenland and inducing strong westerly winds at crest level, accompanied by either cyclogenesis or the intensification of an existing cyclone in the lee of Greenland. The associated CAO airmasses originate in the Canadian Arctic, overflow southern Greenland, and descend into the Irminger Sea with an according imprint in their thermodynamic evolution. (2) In the easterly cyclonic environment, one or multiple cyclones in the Nordic Seas induce northerly winds along Greenland's eastern coast that transport Arctic airmasses from Fram Strait to Denmark Strait. (3) The easterly anti‐cyclonic environment, finally, is dominated by an anti‐cyclone over Greenland with similar airmass origins and pathways as in the easterly cyclonic environment. The two easterly environments represent the limiting cases of an intermediate spectrum, whereas in contrast the westerly environment is clearly distinct. Katabatic drainage from northern Greenland contributes to the CAO airmasses in both easterly environments, whereas in the easterly cyclonic environment also marine airmasses from the Nordic Seas are involved. An important conclusion of this study is that the amount of heat extracted from the ocean by a CAO airmass depends critically on its pathway, and thus on the synoptic environment.

The coordinating role of IQGAP1 in the regulation of local, endosome-specific actin networks.

ABSTRACTIQGAP1 is a large, multi-domain scaffold that helps orchestrate cell signaling and cytoskeletal mechanics by controlling interactions among a spectrum of receptors, signaling intermediates, and cytoskeletal proteins. While this coordination is known to impact cell morphology, motility, cell adhesion, and vesicular traffic, among other functions, the spatiotemporal properties and regulatory mechanisms of IQGAP1 have not been fully resolved. Herein, we describe a series of super-resolution and live-cell imaging analyses that identified a role for IQGAP1 in the regulation of an actin cytoskeletal shell surrounding a novel membranous compartment that localizes selectively to the basal cortex of polarized epithelial cells (MCF-10A). We also show that IQGAP1 appears to both stabilize the actin coating and constrain its growth. Loss of compartmental IQGAP1 initiates a disassembly mechanism involving rapid and unconstrained actin polymerization around the compartment and dispersal of its vesicle contents. Together, these findings suggest IQGAP1 achieves this control by harnessing both stabilizing and antagonistic interactions with actin. They also demonstrate the utility of these compartments for image-based investigations of the spatial and temporal dynamics of IQGAP1 within endosome-specific actin networks.

Young stellar populations in type II quasars: timing the onset of star formation and nuclear activity

Despite the emerging morphological evidence that luminous quasar-like AGN are triggered in galaxy mergers, the natures of the triggering mergers and the order of events in the triggering sequence remain uncertain. In this work, we present a detailed study of the stellar populations of the host galaxies of 21 type II quasars, with the aim of understanding the sequence of events between the onset of the merger, the triggering of the associated starburst and the initiation of the quasar activity. To this end, we model high quality, wide spectral coverage, intermediate resolution optical spectra of the type II quasars. We find that of the 21 objects, the higher-order Balmer absorption lines, characteristic of young stellar populations (YSP) , are directly detected in ~62% of the sample. We also fit these spectra using a number of combinations of stellar and/or power-law components, representative of viable formation histories, as well as including the possibility of scattered AGN light. We find that 90 % of the type II quasar host galaxies require the inclusion of a YSP to adequately model their spectra, whilst 71 % of the sample require the inclusion of a YSP with age < 100 Myr. Since the ages of the YSP in most type II quasar host galaxies are comparable with the expected lifetimes of the AGN activity, these results provide strong evidence that the quasars are triggered close to the peaks of the merger-induced starbursts.

Physical particularities of nuclear reactors using heavy moderators of neutrons

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using 233U as a fissile nuclide and 232Th and 231Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.

Effective conditions for the neutron flux density at axial boundaries of the core

Analytical expressions for elements of the triangular matrix of effective conditions at the boundary of the core with a multiregion reflector are derived in the few-group diffusion approximation. The developed technique is verified using the example of fuel assemblies of a light-water reactor with an intermediate neutron spectrum.

Two-stage method of synthesis of ultrafine powder of α-phase metallic cobalt

AbstractIn this article a new method of synthesizing ultrafine powder of α-phase metallic cobalt is proposed, synthesis by a combination of two methods, liquid-phase precipitation on a carbon support and low-temperature microwave heat treatment in the stream of argon. An entire spectrum of intermediates obtained during thermolysis and reduction of cobalt precursors during heat treatment by electromagnetic field to the final product is presented. Sample structure, morphology and particle size as well as phase composition and the size of specific surface areas are shown.

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

UVO0825+15 is a hot bright helium-rich subdwarf which lies in {\it K2} Field 5 and in a sample of intermediate helium-rich subdwarfs observed with {\it Subaru/HDS}. The {\it K2} light curve shows low-amplitude variations, whilst the {\it Subaru} spectrum shows Pb{\sc iv} absorption lines, indicative of a very high lead overabundance. UVO0825+15 also has a high proper motion with kinematics typical for a thick disk star. Analyses of ultraviolet and intermediate dispersion optical spectra rule out a short-period binary companion, and provide fundamental atmospheric parameters of $T_{\rm off}=38\,900\pm270$\,K, $\log g/{\rm cm\,s^{-2}}=5.97\pm0.11$, $\log n_{\rm He}/n_{\rm H}=-0.57\pm0.01$, $E_{B-V}\approx0.03$, and angular radius $\theta = 1.062\pm0.006\times10^{-11}$ radians (formal errors). The high-resolution spectrum shows that carbon is $>2$ dex subsolar, iron is approximately solar and all other elements heavier than argon are at least 2 -- 4 dex overabundant, including germanium, yttrium and lead. Approximately 150 lines in the blue-optical spectrum remain unidentified. The chemical structure of the photosphere is presumed to be determined by radiatively-dominated diffusion. The {\it K2} light curve shows a dominant period around 10.8\,h, with a variable amplitude, its first harmonic, and another period at 13.3\,h. The preferred explanation is multi-periodic non-radial oscillation due to g-modes with very high radial order, although this presents difficulties for pulsation theory. Alternative explanations fail for lack of radial-velocity evidence. UVO0825+15 represents the fourth member of a group of hot subdwarfs having helium-enriched photospheres and 3--4 dex overabundances of trans-iron elements, and is the first lead-rich subdwarf to show evidence of pulsations.

Dramatic Effect of Carboxylic Acid on the Electronic Structure of the Active Species in Fe(PDP)-Catalyzed Asymmetric Epoxidation

The electronic structure of the iron–oxygen intermediates responsible for catalytic transformations in the biomimetic catalyst systems [((S,S)-PDP)FeII(OTf)2]/H2O2/RCOOH has been found to be strongly dependent on the structure of the carboxylic acid RCOOH. For carboxylic acids with primary and secondary α-carbon atoms (acetic acid, butyric acid, caproic acid), the active species exhibit electron paramagnetic resonance (EPR) spectra with large g-factor anisotropy (g1 = 2.7, g2 = 2.4, g3 = 1.7), whereas for those with tertiary α-carbon atoms (2-ethylhexanoic acid, valproic acid, 2-ethylbutyric acid), the active species display EPR spectra with small g-factor anisotropy (g1 = 2.07, g2 = 2.01, g3 = 1.96). The EPR spectra of the latter intermediates are very similar to those of the intermediates previously assigned to oxoiron(V) species. The systems featuring intermediates of the second type ensure higher enantioselection in the epoxidation of electron-deficient olefins.

Nonoxido V(IV) Complexes: Prediction of the EPR Spectrum and Electronic Structure of Simple Coordination Compounds and Amavadin.

Density functional theory (DFT) calculations of the (51)V hyperfine coupling (HFC) tensor A have been completed for 20 "bare" V(IV) complexes with different donor sets, electric charges, and coordination geometries. Calculations were performed with ORCA and Gaussian software, using functionals BP86, TPSS0, B1LYP, PBE0, B3LYP, B3P, B3PW, O3LYP, BHandHLYP, BHandH, and B2PLYP. Among the basis sets, 6-311g(d,p), 6-311++g(d,p), VTZ, cc-pVTZ, def2-TZVPP, and the "core properties" CP(PPP) were tested. The experimental Aiso and Ai (where i = x or z, depending on the geometry and electronic structure of V(IV) complex) were compared with the values calculated by DFT methods. The results indicated that, based on the mean absolute percentage deviation (MAPD), the best functional to predict Aiso or Ai is the double hybrid B2PLYP. With this functional and the basis set VTZ, it is possible to predict the Aiso and Az of the EPR spectrum of amavadin with deviations of -1.1% and -2.0% from the experimental values. The results allowed us to divide the spectra of nonoxido V(IV) compounds in three types-called "type 1", "type 2", and "type 3", characterized by different composition of the singly occupied molecular orbital (SOMO) and relationship between the values of Ax, Ay, and Az. For "type 1" spectra, Az ≫ Ax ≈ Ay and Az is in the range of (135-155) × 10(-4) cm(-1); for "type 2" spectra, Ax ≈ Ay ≫ Az and Ax ≈ Ay are in the range of (90-120) × 10(-4) cm(-1); and for the intermediate spectra of "type 3", Az > Ay > Ax or Ax > Ay > Az, with Az or Ax values in the range of (120-135) × 10(-4) cm(-1). The electronic structure of the V(IV) species was also discussed, and the results showed that the values of Ax or Az are correlated with the percent contribution of V-dxy orbital in the SOMO. Similarly to V(IV)O species, for amavadin the SOMO is based mainly on the V-dxy orbital, and this accounts for the large experimental value of Az (153 × 10(-4) cm(-1)).

Taxonomy of Individual Variations in Aesthetic Responses to Fractal Patterns.

In two experiments, we investigate group and individual preferences in a range of different types of patterns with varying fractal-like scaling characteristics. In Experiment 1, we used 1/f filtered grayscale images as well as their thresholded (black and white) and edges only counterparts. Separate groups of observers viewed different types of images varying in slope of their amplitude spectra. Although with each image type, the groups exhibited the “universal” pattern of preference for intermediate amplitude spectrum slopes, we identified 4 distinct sub-groups in each case. Sub-group 1 exhibited a typical peak preference for intermediate amplitude spectrum slopes (“intermediate”; approx. 50%); sub-group 2 exhibited a linear increase in preference with increasing amplitude spectrum slope (“smooth”; approx. 20%), while sub-group 3 exhibited a linear decrease in preference as a function of the amplitude spectrum slope (“sharp”; approx. 20%). Sub-group 4 revealed no significant preference (“other”; approx. 10%). In Experiment 2, we extended the range of different image types and investigated preferences within the same observers. We replicate the results of our first experiment and show that individual participants exhibit stable patterns of preference across a wide range of image types. In both experiments, Q-mode factor analysis identified two principal factors that were able to explain more than 80% of interindividual variations in preference across all types of images, suggesting a highly similar dimensional structure of interindividual variations in preference for fractal-like scaling characteristics.

Equations for a Heterogeneous Reactor with Effective Conditions on the Axial Boundaries of the Core

The equations of a heterogeneous reactor with effective conditions at the core boundary and end reflectors are derived. The numerical solution of these equations gives significant reduction of the axial harmonics and the computational time for calculation of reactors with a large spike in the thermal neutron flux in the end reflectors. The efficacy of the method is illustrated by an example of a calculation of a reactor with an intermediate neutron spectrum.