Ultrafast exciton dynamics and light-driven H2 evolution in colloidal semiconductor nanorods and Pt-tipped nanorods.

PubMed

Wu, Kaifeng; Zhu, Haiming; Lian, Tianquan

2015-03-17

distributions. The effect of the exciton dynamics on photoreduction reactions is illustrated using methyl viologen (MV(2+)) as a model electron acceptor. The steady-state MV(2+) photoreduction quantum yield of CdSe/CdS dot-in-rod NRs approaches unity under rod excitation, much larger than CdSe QDs and CdSe/CdS core/shell QDs. Detailed time-resolved studies show that in quasi-type II CdSe/CdS NRs and type II ZnSe/CdS NRs strong quantum confinement in the radial direction facilitates fast electron transfer and hole removal, whereas the fast carrier mobility along the axial direction enables long distance charge separation and slow charge recombination, which is essential for efficient MV(2+) photoreduction. The NR/MV(2+) relay system can be coupled to Pt nanoparticles in solution for light-driven H2 generation. Alternatively, Pt-tipped CdS and CdSe/CdS NRs provide fully integrated all inorganic systems for light-driven H2 generation. In CdS-Pt and CdSe/CdS-Pt hetero-NRs, ultrafast hole trapping on the CdS rod surface or in CdSe core enables efficient electron transfer from NRs to Pt tips by suppressing hole and energy transfer. It is shown that the quantum yields of photodriven H2 generation using these heterostructures correlate well with measured hole transfer rates from NRs to sacrificial donors, revealing that hole removal is the key efficiency-limiting step. These findings provide important insights for designing more efficient quantum confined NR and NR-Pt based systems for solar-to-fuel conversion.

Ultrafast core-loss spectroscopy in four-dimensional electron microscopy

PubMed Central

van der Veen, Renske M.; Penfold, Thomas J.; Zewail, Ahmed H.

2015-01-01

We demonstrate ultrafast core-electron energy-loss spectroscopy in four-dimensional electron microscopy as an element-specific probe of nanoscale dynamics. We apply it to the study of photoexcited graphite with femtosecond and nanosecond resolutions. The transient core-loss spectra, in combination with ab initio molecular dynamics simulations, reveal the elongation of the carbon-carbon bonds, even though the overall behavior is a contraction of the crystal lattice. A prompt energy-gap shrinkage is observed on the picosecond time scale, which is caused by local bond length elongation and the direct renormalization of band energies due to temperature-dependent electron–phonon interactions. PMID:26798793

Ultrafast Molecular Three-Electron Auger Decay.

PubMed

Feifel, Raimund; Eland, John H D; Squibb, Richard J; Mucke, Melanie; Zagorodskikh, Sergey; Linusson, Per; Tarantelli, Francesco; Kolorenč, Přemysl; Averbukh, Vitali

2016-02-19

Three-electron Auger decay is an exotic and elusive process, in which two outer-shell electrons simultaneously refill an inner-shell double vacancy with emission of a single Auger electron. Such transitions are forbidden by the many-electron selection rules, normally making their decay lifetimes orders of magnitude longer than the few-femtosecond lifetimes of normal (two-electron) Auger decay. Here we present theoretical predictions and direct experimental evidence for a few-femtosecond three-electron Auger decay of a double inner-valence-hole state in CH_{3}F. Our analysis shows that in contrast to double core holes, double inner-valence vacancies in molecules can decay exclusively by this ultrafast three-electron Auger process, and we predict that this phenomenon occurs widely.

Use of interfacial layers to prolong hole lifetimes in hematite probed by ultrafast transient absorption spectroscopy

NASA Astrophysics Data System (ADS)

Paradzah, Alexander T.; Diale, Mmantsae; Maabong, Kelebogile; Krüger, Tjaart P. J.

2018-04-01

Hematite is a widely investigated material for applications in solar water oxidation due primarily to its small bandgap. However, full realization of the material continues to be hampered by fast electron-hole recombination rates among other weaknesses such as low hole mobility, short hole diffusion length and low conductivity. To address the problem of fast electron-hole recombination, researchers have resorted to growth of nano-structured hematite, doping and use of under-layers. Under-layer materials enhance the photo-current by minimising electron-hole recombination through suppressing of back electron flow from the substrate, such as fluorine-doped tin oxide (FTO), to hematite. We have carried out ultrafast transient absorption spectroscopy on hematite in which Nb2O5 and SnO2 materials were used as interfacial layers to enhance hole lifetimes. The transient absorption data was fit with four different lifetimes ranging from a few hundred femtoseconds to a few nanoseconds. We show that the electron-hole recombination is slower in samples where interfacial layers are used than in pristine hematite. We also develop a model through target analysis to illustrate the effect of under-layers on electron-hole recombination rates in hematite thin films.

Core-core and core-valence correlation

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1988-01-01

The effect of (1s) core correlation on properties and energy separations was analyzed using full configuration-interaction (FCI) calculations. The Be 1 S - 1 P, the C 3 P - 5 S and CH+ 1 Sigma + or - 1 Pi separations, and CH+ spectroscopic constants, dipole moment and 1 Sigma + - 1 Pi transition dipole moment were studied. The results of the FCI calculations are compared to those obtained using approximate methods. In addition, the generation of atomic natural orbital (ANO) basis sets, as a method for contracting a primitive basis set for both valence and core correlation, is discussed. When both core-core and core-valence correlation are included in the calculation, no suitable truncated CI approach consistently reproduces the FCI, and contraction of the basis set is very difficult. If the (nearly constant) core-core correlation is eliminated, and only the core-valence correlation is included, CASSCF/MRCI approached reproduce the FCI results and basis set contraction is significantly easier.

Core logs from five holes near Kramer, in the Mojave Desert, California

USGS Publications Warehouse

Benda, William K.; Erd, Richard C.; Smith, Ward C.

1958-01-01

In 1957, five test holes were drilled near Kramer, California, in =he western Mojave Desert. The drill sites are in topographic basins where gravimetric and geologic surveys indicated the presence, beneath alluvium, of a thick section of Quaternary and Tertiary sedimentary and volcanic rocks. Two holes which were deeper tests at sites drilled in 1954 cored only silts, sands and gravels: Four Corners test hole No. 1 was drilled in sec. 20, T. I0 N., R. 6 W., to a depth of 3,500 feet. Four Corners No. 2, in sec. 5, T. I0 N., R. 8 W., was drilled to 2,328 feet. Three holes which were drilled at new sites north of the intersection of U. S. Highways 395 and 466, locally known as Four Corners, encountered colemanite-bearing sediments. The locations and total depths of these holes are as follows: Four Corners No. 3, sec. T. 11 N., R. 6 W., depth 2,568 feet; Four Corners No. 4, near northern edge of sec. 30, T. ll N., R. 6 W., depth 3,500 feet; Four Corners No. 5, near southern edge of sec. 30, depth 1,604 feet. The sections of rocks encountered in these three holes are similar. In each, the colemanite is in fine-grained sediments that lie below sands and gravels, which are about 600 to 800 feet thick, and are underlain by sandstones and conglomerates. Colemanite is most abundant in the cores from Four Corners to hole No. 5, particularly in the 76 feet of core recovered between depths of 1,051 and 1,131 feet. Chemical analysis shows that in this section of core the average content of B203 is above 14 percent. In addition to colemanite, the cores contain sulfides of arsenic, an unusual iron sulfide, and zeolites. This mineralogy of the colemanite-bearing sediments north of Four Corners, together with the general lake bed lithology and the occurrence as a tilted section of beds below sands and gravels, supports correlation with the upper or marginal parts of the borate-bearin8 sediments at the Kramer borate mining district, which have similar features. There is, however, no

Constraints on core collapse from the black hole mass function

NASA Astrophysics Data System (ADS)

Kochanek, C. S.

2015-01-01

We model the observed black hole mass function under the assumption that black hole formation is controlled by the compactness of the stellar core at the time of collapse. Low-compactness stars are more likely to explode as supernovae and produce neutron stars, while high-compactness stars are more likely to be failed supernovae that produce black holes with the mass of the helium core of the star. Using three sequences of stellar models and marginalizing over a model for the completeness of the black hole mass function, we find that the compactness ξ2.5 above which 50% of core collapses produce black holes is ξ _{2.5}^{50%}=0.24 (0.15 < ξ _{2.5}^{50%} < 0.37 at 90% confidence). The models also predict that f = 0.18 (0.09 < f < 0.39) of core collapses fail. We tested four other criteria for black hole formation based on ξ2.0 and ξ3.0, the compactnesses at enclosed masses of 2.0 or 3.0 rather than 2.5 M⊙, the mass of the iron core MFe, and the mass inside the oxygen burning shell MO. We found that ξ2.0 works as well as ξ2.5, while ξ3.0, MFe and MO are significantly worse. As expected from the high compactness of 20-25 M⊙ stars, black hole formation in this mass range provides a natural explanation of the red supergiant problem.

Disentangling formation of multiple-core holes in aminophenol molecules exposed to bright X-FEL radiation

NASA Astrophysics Data System (ADS)

Zhaunerchyk, V.; Kamińska, M.; Mucke, M.; Squibb, R. J.; Eland, J. H. D.; Piancastelli, M. N.; Frasinski, L. J.; Grilj, J.; Koch, M.; McFarland, B. K.; Sistrunk, E.; Gühr, M.; Coffee, R. N.; Bostedt, C.; Bozek, J. D.; Salén, P.; Meulen, P. v. d.; Linusson, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Richter, R.; Prince, K. C.; Takahashi, O.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Feifel, R.

2015-12-01

Competing multi-photon ionization processes, some leading to the formation of double core hole states, have been examined in 4-aminophenol. The experiments used the linac coherent light source (LCLS) x-ray free electron laser, in combination with a time-of-flight magnetic bottle electron spectrometer and the correlation analysis method of covariance mapping. The results imply that 4-aminophenol molecules exposed to the focused x-ray pulses of the LCLS sequentially absorb more than two x-ray photons, resulting in the formation of multiple core holes as well as in the sequential removal of photoelectrons and Auger electrons (so-called PAPA sequences).

Photonic crystal fiber technology for high-performance all-fiber monolithic ultrafast fiber amplifiers

NASA Astrophysics Data System (ADS)

Papior, Sidsel R.; Weirich, Johannes; Johansen, Mette M.; Jakobsen, Christian; Michieletto, Mattia; Triches, Marco; Kristensen, Torben; Olesen, Anders S.; Petersen, Christian; Andersen, Thomas V.; Maack, Martin D.; Alkeskjold, Thomas T.

2018-02-01

Photonic crystal fiber (PCF) technology for ultrafast fiber amplifiers traditionally uses air holes as key elements for large mode area (LMA) fiber designs. These air holes are crucial for the performance of high-end LMA PCFs, but makes splicing and interfacing more complex. To reduce this complexity in mid-range amplifiers, we present single-mode polarization-maintaining Yb-doped LMA PCFs without air holes for easier splicing into monolithic all-fiber amplifier designs. A 30 μm core all-solid spliceable PCF is presented, and amplification of 1064 nm light above 50 W with an optical to optical efficiency of 80 % is demonstrated. Furthermore, to demonstrate the excellent reliability of PCF based monolithic amplifiers, we demonstrate ultra-longterm performance data of > 35 khrs on a 14 μm core step-index type PCF amplifier with low long-term power degradation slope of < 1.5 % / 10,000 h.

Disentangling formation of multiple-core holes in aminophenol molecules exposed to bright X-FEL radiation

DOE PAGES

Zhaunerchyk, V.; Kaminska, M.; Mucke, M.; ...

2015-10-28

Competing multi-photon ionization processes, some leading to the formation of double core hole states, have been examined in 4-aminophenol. The experiments used the linac coherent light source (LCLS) x-ray free electron laser, in combination with a time-of-flight magnetic bottle electron spectrometer and the correlation analysis method of covariance mapping. Furthermore, the results imply that 4-aminophenol molecules exposed to the focused x-ray pulses of the LCLS sequentially absorb more than two x-ray photons, resulting in the formation of multiple core holes as well as in the sequential removal of photoelectrons and Auger electrons (so-called PAPA sequences).

Charge and spin control of ultrafast electron and hole dynamics in single CdSe/ZnSe quantum dots

NASA Astrophysics Data System (ADS)

Hinz, C.; Gumbsheimer, P.; Traum, C.; Holtkemper, M.; Bauer, B.; Haase, J.; Mahapatra, S.; Frey, A.; Brunner, K.; Reiter, D. E.; Kuhn, T.; Seletskiy, D. V.; Leitenstorfer, A.

2018-01-01

We study the dynamics of photoexcited electrons and holes in single negatively charged CdSe/ZnSe quantum dots with two-color femtosecond pump-probe spectroscopy. An initial characterization of the energy level structure is performed at low temperatures and magnetic fields of up to 5 T. Emission and absorption resonances are assigned to specific transitions between few-fermion states by a theoretical model based on a configuration interaction approach. To analyze the dynamics of individual charge carriers, we initialize the quantum system into excited trion states with defined energy and spin. Subsequently, the time-dependent occupation of the trion ground state is monitored by spectrally resolved differential transmission measurements. We observe subpicosecond dynamics for a hole excited to the D shell. The energy dependence of this D -to-S shell intraband transition is investigated in quantum dots of varying size. Excitation of an electron-hole pair in the respective p shells leads to the formation of singlet and triplet spin configurations. Relaxation of the p -shell singlet is observed to occur on a time scale of a few picoseconds. Pumping of p -shell triplet transitions opens up two pathways with distinctly different scattering times. These processes are shown to be governed by the mixing of singlet and triplet states due to exchange interactions enabling simultaneous electron and hole spin flips. To isolate the relaxation channels, we align the spin of the residual electron by a magnetic field and employ laser pulses of defined helicity. This step provides ultrafast preparation of a fully inverted trion ground state of the quantum dot with near unity probability, enabling deterministic addition of a single photon to the probe pulse. Therefore our experiments represent a significant step towards using single quantum emitters with well-controled inversion to manipulate the photon statistics of ultrafast light pulses.

Ultrafast Time-Resolved Photoluminescence Studies of Gallium-Arsenide

NASA Astrophysics Data System (ADS)

Johnson, Matthew Bruce

This thesis concerns the study of ultrafast phenomena in GaAs using time-resolved photoluminescence (PL). The thesis consists of five chapters. Chapter one is an introduction, which discusses the study of ultrafast phenomena in semiconductors. Chapter two is a description of the colliding-pulse mode-locked (CPM) ring dye laser, which is at the heart of the experimental apparatus used in this thesis. Chapter three presents a detailed experimental and theoretical investigation of photoluminescence excitation correlation spectroscopy (PECS), the novel technique which is used to time-resolve ultrafast PL phenomena. Chapters 4 and 5 discuss two applications of the PECS technique. In Chapter 4 the variation of PL intensity in In-alloyed GaAs substrate material is studied, while Chapter 5 discusses the variation of carrier lifetimes in ion-damaged GaAs used in photo-conductive circuit elements (PCEs). PECS is a pulse-probe technique that measures the cross correlation of photo-excited carrier populations. The theoretical model employed in this thesis is based upon the rate equation for a simple three-level system consisting of valence and conduction bands and a single trap level. In the limit of radiative band-to-band dominated recombination, no PECS signal should be observed; while in the capture -dominated recombination limit, the PECS signal from the band-to-band PL measures the cross correlation of the excited electron and hole populations and thus, the electron and hole lifetimes. PECS is experimentally investigated using a case study of PL in semi-insulating (SI) GaAs and In -alloyed GaAs. At 77 K, the PECS signal is characteristic of a capture-dominated system, yielding an electron-hole lifetime of about 200 ps. However, at 5 K the behavior is more complicated and shows saturation effects due to the C acceptor level, which is un-ionized at 5 K. As a first application, PECS is used to investigate the large band-to-band PL contrast observed near dislocations in In

Ultrafast X-ray Auger probing of photoexcited molecular dynamics

DOE PAGES

McFarland, B. K.; Farrell, J. P.; Miyabe, S.; ...

2014-06-23

Here, molecules can efficiently and selectively convert light energy into other degrees of freedom. Disentangling the underlying ultrafast motion of electrons and nuclei of the photoexcited molecule presents a challenge to current spectroscopic approaches. Here we explore the photoexcited dynamics of molecules by an interaction with an ultrafast X-ray pulse creating a highly localized core hole that decays via Auger emission. We discover that the Auger spectrum as a function of photoexcitation—X-ray-probe delay contains valuable information about the nuclear and electronic degrees of freedom from an element-specific point of view. For the nucleobase thymine, the oxygen Auger spectrum shifts towardsmore » high kinetic energies, resulting from a particular C–O bond stretch in the ππ* photoexcited state. A subsequent shift of the Auger spectrum towards lower kinetic energies displays the electronic relaxation of the initial photoexcited state within 200 fs. Ab-initio simulations reinforce our interpretation and indicate an electronic decay to the nπ* state.« less

Theoretical insights into the effect of a conjugated core on the hole transport properties of hole-transporting materials for perovskite solar cells.

PubMed

Zhang, Zemin; Hu, Weixia; Cui, Jianyu; He, Rongxing; Shen, Wei; Li, Ming

2017-09-20

Conjugated bifluorenylidene and naphthalene central cores are introduced into hole-transporting materials DT1 and DT2 to replace the spiro-core of the reported, highly efficient FDT. The effects of the conjugated core on the geometrics, electronic properties and hole transport properties are investigated by using density functional theory coupled with Marcus theory and the Einstein relation. The calculated results show that DT1 (-5.21 eV) and DT2 (-5.23 eV) have lower HOMO levels than FDT (-5.15 eV), which indicates that the perovskite solar cells with conjugated hole-transporting materials can have higher open-circuit voltages. The introduction of the conjugated core is beneficial to the more efficient face-to-face packing pattern of the dimer, resulting in a larger intermolecular electronic coupling. Importantly, it is found that DT1 (1.6 × 10 -3 cm 2 V -1 s -1 ) and DT2 (2.7 × 10 -2 cm 2 V -1 s -1 ) exhibit relatively higher hole mobilities than FDT (1.3 × 10 -4 cm 2 V -1 s -1 ) owing to the larger electronic coupling. Therefore, enhanced hole transport ability can be achieved by switching from the spiro-core to the conjugated core. The present work provides a new strategy to improve the hole transport properties of hole-transporting materials, which will contribute to the development of conjugated small molecules as hole-transporting materials in efficient perovskite solar cells.

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

NASA Astrophysics Data System (ADS)

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-01

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K -shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion.

PubMed

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-02

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Multiple core-hole formation by free-electron laser radiation in molecular nitrogen

NASA Astrophysics Data System (ADS)

Banks, H. I. B.; Little, D. A.; Emmanouilidou, A.

2018-05-01

We investigate the formation of multiple-core-hole states of molecular nitrogen interacting with a free-electron laser pulse. In previous work, we obtained bound and continuum molecular orbitals in the single-center expansion scheme and used these orbitals to calculate photo-ionization and auger decay rates. We extend our formulation to track the proportion of the population that accesses single-site versus two-site double-core-hole (TSDCH) states, before the formation of the final atomic ions. We investigate the pulse parameters that favor the formation of the single-site and TSDCH as well as triple-core-hole states for 525 and 1100 eV photons.

Nonlinear performance of asymmetric coupler based on dual-core photonic crystal fiber: Towards sub-nanojoule solitonic ultrafast all-optical switching

NASA Astrophysics Data System (ADS)

Curilla, L.; Astrauskas, I.; Pugzlys, A.; Stajanca, P.; Pysz, D.; Uherek, F.; Baltuska, A.; Bugar, I.

2018-05-01

We demonstrate ultrafast soliton-based nonlinear balancing of dual-core asymmetry in highly nonlinear photonic crystal fiber at sub-nanojoule pulse energy level. The effect of fiber asymmetry was studied experimentally by selective excitation and monitoring of individual fiber cores at different wavelengths between 1500 nm and 1800 nm. Higher energy transfer rate to non-excited core was observed in the case of fast core excitation due to nonlinear asymmetry balancing of temporal solitons, which was confirmed by the dedicated numerical simulations based on the coupled generalized nonlinear Schrödinger equations. Moreover, the simulation results correspond qualitatively with the experimentally acquired dependences of the output dual-core extinction ratio on excitation energy and wavelength. In the case of 1800 nm fast core excitation, narrow band spectral intensity switching between the output channels was registered with contrast of 23 dB. The switching was achieved by the change of the excitation pulse energy in sub-nanojoule region. The performed detailed analysis of the nonlinear balancing of dual-core asymmetry in solitonic propagation regime opens new perspectives for the development of ultrafast nonlinear all-optical switching devices.

Highly non-linear solid core photonic crystal fiber with one nano hole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangwar, Rahul Kumar, E-mail: rahul0889@gmail.com; Bhardwaj, Vanita, E-mail: bhardwajphy12@gmail.com; Singh, Vinod Kumar, E-mail: singh.vk.ap@ismdhanbad.co.in

2015-08-28

The numerical study of newly designed solid core photonic crystal fiber (SCPCF) having three hexagonal air hole rings in cladding region and one small nano hole at the center are presented. By using full vectorial finite element method (FV-FEM), we analyses the optical properties like effective area, nonlinearity and confinement loss of the proposed PCF. Results show that the change in core diameter controls the effective area, nonlinearity and confinement loss. A low effective area (3.34 µm{sup 2}), high nonlinearity (36.34 W{sup −1}km{sup −1}) and low confinement loss (0.00106 dB/km) are achieved at the communication wavelength 1.55 µm for themore » SCPCF having core air hole diameter 0.10 µm, cladding air holes diameter 1.00 µm and pitch 2.50 µm. This type of PCF is very useful in non-linear applications such as supercontinuum generation, four wave mixing, second harmonic generation etc.« less

Spin polarization and magnetic dichroism in photoemission from core and valence states in localized magnetic systems. IV. Core-hole polarization in resonant photoemission

NASA Astrophysics Data System (ADS)

van der Laan, Gerrit; Thole, B. T.

1995-12-01

A simple theory is presented for core-hole polarization probed by resonant photoemission in a two-steps approximation. After excitation from a core level to the valence shell, the core hole decays into two shallower core holes under emission of an electron. The nonspherical core hole and the final state selected cause a specific angle and spin distribution of the emitted electron. The experiment is characterized by the ground-state moments, the polarization of the light, and the spin and angular distribution of the emitted electron. The intensity is a sum over ground-state expectation values of tensor operators times the probability to create a polarized core hole using polarized light, times the probability for decay of such a core hole into the final state. We give general expressions for the angle- and spin-dependent intensities in various regimes of Coulomb and spin-orbit interaction: LS, LSJ, and jjJ coupling. The core-polarization analysis, which generalizes the use of sum rules in x-ray absorption spectroscopy where the integrated peak intensities give ground-state expectation values of the spin and orbital moment operators, makes it possible to measure different linear combinations of these operators. As an application the 2p3/23p3p decay in ferromagnetic nickel is calculated using Hartree-Fock values for the radial matrix elements and phase factors, and compared with experiment, the dichroism is smaller in the 3P final state but stronger in the 1D, 1S peak.

Phonon-Assisted Ultrafast Charge Transfer at van der Waals Heterostructure Interface.

PubMed

Zheng, Qijing; Saidi, Wissam A; Xie, Yu; Lan, Zhenggang; Prezhdo, Oleg V; Petek, Hrvoje; Zhao, Jin

2017-10-11

The van der Waals (vdW) interfaces of two-dimensional (2D) semiconductor are central to new device concepts and emerging technologies in light-electricity transduction where the efficient charge separation is a key factor. Contrary to general expectation, efficient electron-hole separation can occur in vertically stacked transition-metal dichalcogenide heterostructure bilayers through ultrafast charge transfer between the neighboring layers despite their weak vdW bonding. In this report, we show by ab initio nonadiabatic molecular dynamics calculations, that instead of direct tunneling, the ultrafast interlayer hole transfer is strongly promoted by an adiabatic mechanism through phonon excitation occurring on 20 fs, which is in good agreement with the experiment. The atomic level picture of the phonon-assisted ultrafast mechanism revealed in our study is valuable both for the fundamental understanding of ultrafast charge carrier dynamics at vdW heterointerfaces as well as for the design of novel quasi-2D devices for optoelectronic and photovoltaic applications.

Material processing with fiber based ultrafast pulse delivery

NASA Astrophysics Data System (ADS)

Baumbach, S.; Stockburger, R.; Führa, B.; Zoller, S.; Thum, S.; Moosmann, J.; Maier, D.; Kanal, F.; Russ, S.; Kaiser, E.; Budnicki, A.; Sutter, D. H.; Pricking, S.; Killi, A.

2018-02-01

We report on TRUMPF's ultrafast laser systems equipped with industrialized hollow core fiber laser light cables. Beam guidance in general by means of optical fibers, e.g. for multi kilowatt cw laser systems, has become an integral part of laser-based material processing. One advantage of fiber delivery, among others, is the mechanical separation between laser and processing head. An equally important benefit is given by the fact that the fiber end acts as an opto-mechanical fix-point close to successive optical elements in the processing head. Components like lenses, diffractive optical elements etc. can thus be designed towards higher efficiency which results in better material processing. These aspects gain increasing significance when the laser system operates in fundamental mode which is usually the case for ultrafast lasers. Through the last years beam guidance of ultrafast laser pulses by means of hollow core fiber technology established very rapidly. The combination of TRUMPF's long-term stable ultrafast laser sources, passive fiber coupling, connector and packaging forms a flexible and powerful system for laser based material processing well suited for an industrial environment. In this article we demonstrate common material processing applications with ultrafast lasers realized with TRUMPF's hollow core fiber delivery. The experimental results are contrasted and evaluated against conventional free space propagation in order to illustrate the performance of flexible ultrafast beam delivery.

Shell effect on the electron and hole reorganization energy of core-shell II-VI nanoclusters

NASA Astrophysics Data System (ADS)

Cui, Xianhui; Wang, Xinqin; Yang, Fang; Cui, Yingqi; Yang, Mingli

2017-09-01

Density functional theory calculations were performed to study the effect of shell encapsulation on the geometrical and electronic properties of pure and hybrid core-shell CdSe nanoclusters. The CdSe cores are distorted by the shells, and the shells exhibit distinct surface activity from the cores, which leads to remarkable changes in their electron transition behaviors. Although the electron and hole reorganization energies, which are related to the formation and recombination of electron-hole pairs, vary in a complicated way, their itemized contributions, potentials of electron extraction, ionization and affinity, and hole extraction (HEP), are dependent on the cluster size, shell composition and/or solvent. Our calculations suggest that the behaviors of charge carriers, free electrons and holes, in the semiconductor core-shell nanoclusters can be modulated by selecting appropriate cluster size and controlling the chemical composition of the shells.

Influence of heat treatment on hole transfer dynamics in core-shell quantum dot/organic hole conductor hybrid films

NASA Astrophysics Data System (ADS)

Sun, Mingye; Zheng, Youjin; Zhang, Lei; Zhao, Liping; Zhang, Bing

2017-08-01

The influence of heat treatment on hole transfer (HT) processes from the CdSe/ZnS and CdSe/CdS/ZnS quantum dots (QDs) to 4,4‧,4″-Tris(carbazol-9-yl)-triphenylamine (TCTA) in QD/TCTA hybrid films has been researched with time-resolved photoluminescence (PL) spectroscopy. The PL dynamic results demonstrated a heat-treatment-temperature-dependent HT process from the core-shell CdSe QDs to TCTA. The HT rates and efficiencies can be effectively increased due to reduced distance between core-shell CdSe QDs and TCTA after heat treatment. The CdS shell exhibited a more obvious effect on HT from the core-shell CdSe QDs to TCTA than on electron transfer to TiO2, due to higher barrier for holes to tunnel through CdS shell and larger effective mass of holes in CdS than electrons. These results indicate that heat treatment would be an effective means to further optimize solid-state QD sensitized solar cells and rational design of CdS shell is significant.

The Core-Collapse Supernova-Black Hole Connection

NASA Astrophysics Data System (ADS)

O'Connor, Evan

The death of a massive star is typically associated with a bright optical transient known as a core-collapse supernova. However, there is growing evidence that not all massive stars end their lives with a brillant optical display, but rather in a whimper. These failed supernovae, or unnovae, result from the central engine failing to turn the initial implosion of the iron core into an explosion that launches the supernova shock wave, unbinds the majority of the star, and creates the supernova as we know it. In these unnovae, the failure of the central engine is soon followed by the collapse of the would-be neutron star into a stellar mass black hole. Instead of the bright optical display following successful supernovae, little to no optical emission is expected from typical failed supernovae as most of the material quietly accretes onto the black hole. This makes the hunt for failed supernovae difficult. In this chapter for the Handbook of Supernovae, I present the growing observational evidence for failed supernovae and discuss the current theoretical understanding of how and in what stars the supernova central engine fails.

Observation of hole accumulation in Ge/Si core/shell nanowires using off-axis electron holography.

PubMed

Li, Luying; Smith, David J; Dailey, Eric; Madras, Prashanth; Drucker, Jeff; McCartney, Martha R

2011-02-09

Hole accumulation in Ge/Si core/shell nanowires (NWs) has been observed and quantified using off-axis electron holography and other electron microscopy techniques. The epitaxial [110]-oriented Ge/Si core/shell NWs were grown on Si (111) substrates by chemical vapor deposition through the vapor-liquid-solid growth mechanism. High-angle annular-dark-field scanning transmission electron microscopy images and off-axis electron holograms were obtained from specific NWs. The excess phase shifts measured by electron holography across the NWs indicated the presence of holes inside the Ge cores. Calculations based on a simplified coaxial cylindrical model gave hole densities of (0.4 ± 0.2) /nm(3) in the core regions.

Supermassive black holes do not correlate with galaxy disks or pseudobulges.

PubMed

Kormendy, John; Bender, R; Cornell, M E

2011-01-20

The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they seem not to correlate with galaxy disks. Disk-grown 'pseudobulges' are intermediate in properties between bulges and disks; it has been unclear whether they do or do not correlate with black holes in the same way that bulges do. At stake in this issue are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black-hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and in galaxies with pseudobulges grow as low-level Seyfert galaxies. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.

'Micro-hole' optical dating of quartz from HOTRAX-05 Arctic Ocean cores

NASA Astrophysics Data System (ADS)

Berger, G. W.; Polyak, L. V.

2011-12-01

For Quaternary Arctic Ocean cores, numeric dating methods are needed spanning and exceeding the age range of the widely used radiocarbon (C-14) method. Previously, luminescence sediment dating of 4-11 μm diameter quartz and feldspar grains from core tops has often produced large burial-age overestimates (e.g., by >7 kyr) due to failure to resolve mixed-age histories. However, application of micro-focused-laser ('micro-hole') photon-stimulated-luminescence (PSL) applied to quartz grains of 11-90 μm diameters from the tops (upper 2 cm) of high-sedimentation- rate HOTRAX-05 multi-cores at the Alaska margin provides expected near zero ages (0-200 a), thus overcoming the earlier problem of large PSL age over-estimation. This micro-hole PSL dating approach has also been applied to >11 μm quartz grains from multi-cores at two sites on the central Lomonosov Ridge. For a core top within a perched basin, a burial-age estimate of ~2 ka for 11-62 μm quartz was obtained, in accord with published C-14 age estimates from foraminifera, demonstrating the efficacy of the micro-hole approach to this ridge area. At a nearby 'erosive' ridge-top site, the micro-hole PSL approach paradoxically produces two different burial-age estimates from the same core-top horizon. The >90 μm quartz grains yield a burial age of ~25 ka, in accord with a C-14 age estimate of ~26 ka from >250 μm foraminifers from the same horizon. However, the 11-90 μm quartz produces a burial-age estimate of ~9 ka, indicating a differently preserved burial history for the medium silt grains than for the sand grains within a single horizon. This unexpected result provides a unique insight into past, complicated, depositional processes on this ridge top over a time range spanning the LGM. These results from the micro-hole PSL approach thus indicate a clear potential for dating times of detrital quartz deposition at other ridge tops in the Arctic Ocean, and for providing perhaps new insights into local preservation

Time-dependent Schrödinger equation for molecular core-hole dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Picón, A.

2017-02-01

X-ray spectroscopy is an important tool for the investigation of matter. X rays primarily interact with inner-shell electrons, creating core (inner-shell) holes that will decay on the time scale of attoseconds to a few femtoseconds through electron relaxations involving the emission of a photon or an electron. Furthermore, the advent of femtosecond x-ray pulses expands x-ray spectroscopy to the time domain and will eventually allow the control of core-hole population on time scales comparable to core-vacancy lifetimes. For both cases, a theoretical approach that accounts for the x-ray interaction while the electron relaxations occur is required. We describe a time-dependentmore » framework, based on solving the time-dependent Schrödinger equation, that is suitable for describing the induced electron and nuclear dynamics.« less

A 32-bit Ultrafast Parallel Correlator using Resonant Tunneling Devices

NASA Technical Reports Server (NTRS)

Kulkarni, Shriram; Mazumder, Pinaki; Haddad, George I.

1995-01-01

An ultrafast 32-bit pipeline correlator has been implemented using resonant tunneling diodes (RTD) and hetero-junction bipolar transistors (HBT). The negative differential resistance (NDR) characteristics of RTD's is the basis of logic gates with the self-latching property that eliminates pipeline area and delay overheads which limit throughput in conventional technologies. The circuit topology also allows threshold logic functions such as minority/majority to be implemented in a compact manner resulting in reduction of the overall complexity and delay of arbitrary logic circuits. The parallel correlator is an essential component in code division multi-access (CDMA) transceivers used for the continuous calculation of correlation between an incoming data stream and a PN sequence. Simulation results show that a nano-pipelined correlator can provide and effective throughput of one 32-bit correlation every 100 picoseconds, using minimal hardware, with a power dissipation of 1.5 watts. RTD plus HBT based logic gates have been fabricated and the RTD plus HBT based correlator is compared with state of the art complementary metal oxide semiconductor (CMOS) implementations.

Ultrafast electronic dynamics driven by nuclear motion

NASA Astrophysics Data System (ADS)

Vendrell, Oriol

2016-05-01

The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

Ultrafast Photodetection in the Quantum Wells of Single AlGaAs/GaAs-Based Nanowires.

PubMed

Erhard, N; Zenger, S; Morkötter, S; Rudolph, D; Weiss, M; Krenner, H J; Karl, H; Abstreiter, G; Finley, J J; Koblmüller, G; Holleitner, A W

2015-10-14

We investigate the ultrafast optoelectronic properties of single Al0.3Ga0.7As/GaAs core-shell nanowires. The nanowires contain GaAs-based quantum wells. For a resonant excitation of the quantum wells, we find a picosecond photocurrent which is consistent with an ultrafast lateral expansion of the photogenerated charge carriers. This Dember-effect does not occur for an excitation of the GaAs-based core of the nanowires. Instead, the core exhibits an ultrafast displacement current and a photothermoelectric current at the metal Schottky contacts. Our results uncover the optoelectronic dynamics in semiconductor core-shell nanowires comprising quantum wells, and they demonstrate the possibility to use the low-dimensional quantum well states therein for ultrafast photoswitches and photodetectors.

Supermassive black holes do not correlate with dark matter haloes of galaxies.

PubMed

Kormendy, John; Bender, Ralf

2011-01-20

Supermassive black holes have been detected in all galaxies that contain bulge components when the galaxies observed were close enough that the searches were feasible. Together with the observation that bigger black holes live in bigger bulges, this has led to the belief that black-hole growth and bulge formation regulate each other. That is, black holes and bulges coevolve. Therefore, reports of a similar correlation between black holes and the dark matter haloes in which visible galaxies are embedded have profound implications. Dark matter is likely to be non-baryonic, so these reports suggest that unknown, exotic physics controls black-hole growth. Here we show, in part on the basis of recent measurements of bulgeless galaxies, that there is almost no correlation between dark matter and parameters that measure black holes unless the galaxy also contains a bulge. We conclude that black holes do not correlate directly with dark matter. They do not correlate with galaxy disks, either. Therefore, black holes coevolve only with bulges. This simplifies the puzzle of their coevolution by focusing attention on purely baryonic processes in the galaxy mergers that make bulges.

In-fiber refractive index sensor based on single eccentric hole-assisted dual-core fiber.

PubMed

Yang, Jing; Guan, Chunying; Tian, Peixuan; Yuan, Tingting; Zhu, Zheng; Li, Ping; Shi, Jinhui; Yang, Jun; Yuan, Libo

2017-11-01

We propose a novel and simple in-fiber refractive index sensor based on resonant coupling, constructed by a short section of single eccentric hole-assisted dual-core fiber (SEHADCF) spliced between two single-mode fibers. The coupling characteristics of the SEHADCF are calculated numerically. The strong resonant coupling occurs when the fundamental mode of the center core phase-matches to that of the suspended core in the air hole. The effective refractive index of the fundamental mode of the suspended core can be obviously changed by injecting solution into the air hole. The responses of the proposed devices to the refractive index and temperature are experimentally measured. The refractive index sensitivity is 627.5 nm/refractive index unit in the refractive index range of 1.335-1.385. The sensor without solution filling is insensitive to temperature in the range of 30-90°C. The proposed refractive index sensor has outstanding advantages, such as simple fabrication, good mechanical strength, and excellent microfluidic channel, and will be of importance in biological detection, chemical analysis, and environment monitoring.

Supplemental materials for the ICDP-USGS Eyreville A, B, and C core holes, Chesapeake Bay impact structure: Core-box photographs, coring-run tables, and depth-conversion files

USGS Publications Warehouse

Durand, C.T.; Edwards, L.E.; Malinconico, M.L.; Powars, D.S.

2009-01-01

During 2005-2006, the International Continental Scientific Drilling Program and the U.S. Geological Survey drilled three continuous core holes into the Chesapeake Bay impact structure to a total depth of 1766.3 m. A collection of supplemental materials that presents a record of the core recovery and measurement data for the Eyreville cores is available on CD-ROM at the end of this volume and in the GSA Data Repository. The supplemental materials on the CD-ROM include digital photographs of each core box from the three core holes, tables of the three coring-run logs, as recorded on site, and a set of depth-conversion programs. In this chapter, the contents, purposes, and basic applications of the supplemental materials are briefly described. With this information, users can quickly decide if the materials will apply to their specific research needs. ?? 2009 The Geological Society of America.

Cascading electron and hole transfer dynamics in a CdS/CdTe core-shell sensitized with bromo-pyrogallol red (Br-PGR): slow charge recombination in type II regime.

PubMed

Maity, Partha; Debnath, Tushar; Chopra, Uday; Ghosh, Hirendra Nath

2015-02-14

Ultrafast cascading hole and electron transfer dynamics have been demonstrated in a CdS/CdTe type II core-shell sensitized with Br-PGR using transient absorption spectroscopy and the charge recombination dynamics have been compared with those of CdS/Br-PGR composite materials. Steady state optical absorption studies suggest that Br-PGR forms strong charge transfer (CT) complexes with both the CdS QD and CdS/CdTe core-shell. Hole transfer from the photo-excited QD and QD core-shell to Br-PGR was confirmed by both steady state and time-resolved emission spectroscopy. Charge separation was also confirmed by detecting electrons in the conduction band of the QD and the cation radical of Br-PGR as measured from femtosecond transient absorption spectroscopy. Charge separation in the CdS/Br-PGR composite materials was found to take place in three different pathways, by transferring the photo-excited hole of CdS to Br-PGR, electron injection from the photo-excited Br-PGR to the CdS QD, and direct electron transfer from the HOMO of Br-PGR to the conduction band of the CdS QD. However, in the CdS/CdTe/Br-PGR system hole transfer from the photo-excited CdS to Br-PGR and electron injection from the photo-excited Br-PGR to CdS take place after cascading through the CdTe shell QD. Charge separation also takes place via direct electron transfer from the Br-PGR HOMO to the conduction band of CdS/CdTe. Charge recombination (CR) dynamics between the electron in the conduction band of the CdS QD and the Br-PGR cation radical were determined by monitoring the bleach recovery kinetics. The CR dynamics were found to be much slower in the CdS/CdTe/Br-PGR system than in the CdS/Br-PGR system. The formation of the strong CT complex and the separation of charges cascading through the CdTe shell help to slow down charge recombination in the type II regime.

Drastic difference between hole and electron injection through the gradient shell of CdxSeyZn1-xS1-y quantum dots.

PubMed

Abdellah, Mohamed; Poulsen, Felipe; Zhu, Qiushi; Zhu, Nan; Žídek, Karel; Chábera, Pavel; Corti, Annamaria; Hansen, Thorsten; Chi, Qijin; Canton, Sophie E; Zheng, Kaibo; Pullerits, Tõnu

2017-08-31

Ultrafast fluorescence spectroscopy was used to investigate the hole injection in Cd x Se y Zn 1-x S 1-y gradient core-shell quantum dot (CSQD) sensitized p-type NiO photocathodes. A series of CSQDs with a wide range of shell thicknesses was studied. Complementary photoelectrochemical cell measurements were carried out to confirm that the hole injection from the active core through the gradient shell to NiO takes place. The hole injection from the valence band of the QDs to NiO depends much less on the shell thickness when compared to the corresponding electron injection to n-type semiconductor (ZnO). We simulate the charge carrier tunneling through the potential barrier due to the gradient shell by numerically solving the Schrödinger equation. The details of the band alignment determining the potential barrier are obtained from X-ray spectroscopy measurements. The observed drastic differences between the hole and electron injection are consistent with a model where the hole effective mass decreases, while the gradient shell thickness increases.

Ultrafast photoinduced charge separation in metal-semiconductor nanohybrids.

PubMed

Mongin, Denis; Shaviv, Ehud; Maioli, Paolo; Crut, Aurélien; Banin, Uri; Del Fatti, Natalia; Vallée, Fabrice

2012-08-28

Hybrid nano-objects formed by two or more disparate materials are among the most promising and versatile nanosystems. A key parameter in their properties is interaction between their components. In this context we have investigated ultrafast charge separation in semiconductor-metal nanohybrids using a model system of gold-tipped CdS nanorods in a matchstick architecture. Experiments are performed using an optical time-resolved pump-probe technique, exciting either the semiconductor or the metal component of the particles, and probing the light-induced change of their optical response. Electron-hole pairs photoexcited in the semiconductor part of the nanohybrids are shown to undergo rapid charge separation with the electron transferred to the metal part on a sub-20 fs time scale. This ultrafast gold charging leads to a transient red-shift and broadening of the metal surface plasmon resonance, in agreement with results for free clusters but in contrast to observation for static charging of gold nanoparticles in liquid environments. Quantitative comparison with a theoretical model is in excellent agreement with the experimental results, confirming photoexcitation of one electron-hole pair per nanohybrid followed by ultrafast charge separation. The results also point to the utilization of such metal-semiconductor nanohybrids in light-harvesting applications and in photocatalysis.

Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

NASA Astrophysics Data System (ADS)

Hu, Hao; Ding, Hepeng; Liu, Feng

2014-03-01

We investigate the ultrafast crystal-to-amorphous phase transition induced by femtosecond pulse laser excitation by exploiting the property of quantum electronic stress (QES) induced by the electron-hole plasma, which follows quantum Hooke's law. We demonstrates that two types of crystal-to-amorphous transitions occur in two distinct material classes: the faster nonthermal process, having a time scale shorter than one picosecond (ps), must occur in materials like ice having an anomalous phase diagram characterized with dTm/dP <0, where Tm is the melting temperature and P is pressure; while the slower thermal process, having a time scale of several ps, occurs preferably in other materials. The nonthermal process is driven by the QES acting like a negative internal pressure, which is generated predominantly by the holes in the electron-hole plasma that increases linearly with hole density. These findings significantly advance our fundamental understanding of physics underlying the ultrafast crystal-to-amorphous phase transitions, enabling quantitative a priori prediction. The work was supported by DOE-BES (Grant # DE-FG02-04ER46148), NSF MRSEC (Grant No. DMR-1121252) and DOE EFRC (Grant Number DE-SC0001061).

Hot-hole extraction from quantum dot to molecular adsorbate.

PubMed

Singhal, Pallavi; Ghosh, Hirendra N

2015-03-09

Ultrafast thermalized and hot-hole-transfer processes have been investigated in CdSe quantum dot (QD)/catechol composite systems in which hole transfer from photoexcited QDs to the catechols is thermodynamically favorable. A series of catechol derivatives were selected with different electron-donating and -withdrawing groups, and the effect of these groups on hole transfer and charge recombination (CR) dynamics has been investigated. The hole-transfer time was determined using the fluorescence upconversion technique and found to be 2-10 ps depending on the molecular structure of the catechol derivatives. The hot-hole-transfer process was followed after monitoring 2S luminescence of CdSe QDs. Interestingly, hot-hole extraction was observed only in the CdSe/3-methoxycatechol (3-OCH3) composite system owing to the higher electron-donating property of the 3-methoxy group. To confirm the extraction of the hot hole and to monitor the CR reaction in CdSe QD/catechol composite systems, ultrafast transient absorption studies have been carried out. Ultrafast transient-absorption studies show that the bleach recovery kinetics of CdSe QD at the 2S excitonic position is much faster in the presence of 3-OCH3. This faster bleach recovery at the 2S position in CdSe/3-OCH3 suggests hot-hole transfer from CdSe QD to 3-OCH3. CR dynamics in CdSe QD/catechol composite systems was followed by monitoring the excitonic bleach at the 1S position and was found to decrease with free energy of the CR reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

EFFECT OF PILOT HOLE TAPPING ON PULLOUT STRENGTH AND INSERTION TORQUE OF DUAL CORE PEDICLE SCREWS.

PubMed

Rosa, Rodrigo César; Silva, Patrícia; Falcai, Maurício José; Shimano, Antônio Carlos; Defino, Helton Luiz Aparecido

2010-01-01

To evaluate the influence of pilot hole tapping on pullout resistance and insertion torque of pedicle screws with a conical core. Mechanical tests using a universal testing machine were performed on pedicle screws with a conical core that were inserted into pedicles in the fifth lumbar vertebra of calves. The insertion torque was measured using a torque meter with a capacity of 10 Nm, which was considered to be the highest torque value. The pilot holes were prepared using a probe of external diameter 3.8 mm and tapping of the same dimensions and thread characteristics as the screw. Decreased insertion torque and pullout resistance were observed in the group with prior tapping of the pilot hole. Pilot hole tapping reduced the insertion torque and pullout resistance of pedicle screws with a conical core that had been inserted into the pedicle of the fifth lumbar vertebra of calves.

Coulomb drag in electron-hole bilayer: Mass-asymmetry and exchange correlation effects

NASA Astrophysics Data System (ADS)

Arora, Priya; Singh, Gurvinder; Moudgil, R. K.

2018-04-01

Motivated by a recent experiment by Zheng et al. [App. Phys. Lett. 108, 062102 (2016)] on coulomb drag in electron-hole and hole-hole bilayers based on GaAs/AlGaAs semiconductor heterostructure, we investigate theoretically the influence of mass-asymmetry and temperature-dependence of correlations on the drag rate. The correlation effects are dealt with using the Vignale-Singwi effective inter-layer interaction model which includes correlations through local-field corrections to the bare coulomb interactions. However, in this work, we have incorporated only the intra-layer correlations using the temperature-dependent Hubbard approximation. Our results display a reasonably good agreement with the experimental data. However, it is crucial to include both the electron-hole mass-asymmetry and temperature-dependence of correlations. Mass-asymmetry and correlations are found to result in a substantial enhancement of drag resistivity.

Strong core hole in resonant inelastic x-ray scattering (RIXS)

NASA Astrophysics Data System (ADS)

Markiewicz, Robert; Rehr, John; Bansil, Arun

2014-03-01

We apply a lattice version of Mahan, Nozières, and de Dominicis theory1 to RIXS calculations to understand the role of the core hole. The model reproduces the decomposition of the RIXS spectrum into well- and poorly-screened components. While the calculation can reproduce the full multiband spectrum, single pair excitations contribute the dominant part to the RIXS spectrum, and they can be described as the dynamic structure function S(q , ω) dressed by matrix element effects. We find evidence for an edge singularity at the RIXS threshold, similar to that found in x-ray absorption. We will discuss comparisons with long core hole lifetime calculations, and extensions to a system with antiferromagnetic order. 1. G.D. Mahan, Phys. Rev. 163, 612 (1967); P. Nozières and C.T. De Dominicis, ibid. 178, 1097 (1969). Supported by DOE Grants DE-FG02-07ER46352 and DE-FG03-97ER45623 and facilitated by the DOE CMCSN, under grant number DE-SC0007091.

Evaluation of core data, physical properties, and oil yield USBM/AEC Colorado Core Hole no. 3 (Bronco BR-1)

USGS Publications Warehouse

Ege, John R.; Carroll, R.D.; Way, R.J.; Magner, J.E.

1969-01-01

USBM/AEC Colorado Core Hole No. 3 (Bronco BR-1) is located in the SW1/4SW1/4SW1/4 sec. 14, T. 1 N., R. 98 W., Rio Blanco County, Colorado. The collar is at a ground elevation of 6,356 feet. The hole was core drilled between depths of 964 and 3,325 feet with a total depth of 3,797 feet. The hole was drilled to investigate geologic, geophysical and hydrological conditions at a possible in situ oil-shale retorting experiment site. The drill hole passed through 1,157 feet of alluvium and the Evacuation Creek Member of the Green River Formation, 1,603 feet of the Parachute Creek Member and penetrated into the Garden Gulch Member of the Green River Formation. In-bole density log/oil yield ratio interpretation indicates that two oil-shale zones exist which yield more than 20 gallons of shale oil per ton of rock; an upper zone lying between 1,271 and 1,750 feet in depth and a lower zone lying between 1,900 and 2,964 feet. Halite (sodium chloride salt) is found between 2,140 and 2,185 feet and nahcolite (sodium bicarbonate salt) between 2,195 and 2,700 feet. Nahcolite was present at one time above 2,195 feet but has been subsequently dissolved out by ground water. The core can be divided into six structural units based upon degree of fracturing. A highly fractured interval is found between 1,646 and 1,899 feet, which coincides with the dissolution or leached nahcolite zone. Physical property tests made on core samples between 1,356 and 3,253 feet give average values of 11,988 psi for uniaxial compressive strength, 1.38 X 10[superscript]6[superscript] psi for static Young's modulus and 11,809 fps for compressional velocity.

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures.

PubMed

Cherukara, Mathew J; Sasikumar, Kiran; DiChiara, Anthony; Leake, Steven J; Cha, Wonsuk; Dufresne, Eric M; Peterka, Tom; McNulty, Ian; Walko, Donald A; Wen, Haidan; Sankaranarayanan, Subramanian K R S; Harder, Ross J

2017-12-13

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. In this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplay of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.

Topics in Core-Collapse Supernova Theory: The Formation of Black Holes and the Transport of Neutrinos

NASA Astrophysics Data System (ADS)

O'Connor, Evan Patrick

Core-Collapse Supernovae are one of the most complex astrophysical systems in the universe. They deeply entwine aspects of physics and astrophysics that are rarely side by side in nature. To accurately model core-collapse supernovae one must self-consistently combine general relativity, nuclear physics, neutrino physics, and magneto-hydrodynamics in a symmetry-free computational environment. This is a challenging task, as each one of these aspects on its own is an area of great study. We take an open approach in an effort to encourage collaboration in the core-collapse supernovae community. In this thesis, we develop a new open-source general-relativistic spherically-symmetric Eulerian hydrodynamics code for studying stellar collapse, protoneutron star formation, and evolution until black hole formation. GR1D includes support for finite temperature equations of state and an efficient and qualitatively accurate treatment of neutrino leakage. GR1D implements spherically-symmetric rotation, allowing for the study of slowly rotating stellar collapse. GR1D is available at http://www.stellarcollapse.org. We use GR1D to perform an extensive study of black hole formation in failing core-collapse supernovae. Over 100 presupernova models from various sources are used in over 700 total simulations. We systematically explore the dependence of black hole formation on the input physics: initial zero-age main sequence (ZAMS) mass and metallicity, nuclear equation of state, rotation, and stellar mass loss rates. Assuming the core-collapse supernova mechanism fails and a black hole forms, we find that the outcome, for a given equation of state, can be estimated, to first order, by a single parameter, the compactness of the stellar core at bounce. By comparing the protoneutron star structure at the onset of gravitational instability with solutions of the Tolman-Oppenheimer-Volkof equations, we find that thermal pressure support in the outer protoneutron star core is responsible for

High-harmonic spectroscopy of ultrafast many-body dynamics in strongly correlated systems

NASA Astrophysics Data System (ADS)

Silva, R. E. F.; Blinov, Igor V.; Rubtsov, Alexey N.; Smirnova, O.; Ivanov, M.

2018-05-01

We bring together two topics that, until now, have been the focus of intense but non-overlapping research efforts. The first concerns high-harmonic generation in solids, which occurs when an intense light field excites a highly non-equilibrium electronic response in a semiconductor or a dielectric. The second concerns many-body dynamics in strongly correlated systems such as the Mott insulator. We show that high-harmonic generation can be used to time-resolve ultrafast many-body dynamics associated with an optically driven phase transition, with accuracy far exceeding one cycle of the driving light field. Our work paves the way for time-resolving highly non-equilibrium many-body dynamics in strongly correlated systems, with few femtosecond accuracy.

Coherent electron{endash}hole correlations in quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joensson, L.; Steiner, M.M.; Wilkins, J.W.

1997-03-01

Using numerical time propagation of the electron{endash}hole wave function, we demonstrate how various coherent correlation effects can be observed by laser excitation of a nanoscale semiconductor quantum dot. The lowest-lying states of an electron{endash}hole pair, when appropriately excited by a laser pulse, give rise to charge oscillations that are manifested by beatings in the optical or intraband polarizations. A GaAs 5{times}25{times}25 nm{sup 3} dot in the effective-mass approximation, including the screened Coulomb interaction between the electron and a heavy or light hole, is simulated. {copyright} {ital 1997 American Institute of Physics.}

Initial report of the physical property measurement, ChikyuOman core description Phase I: sheeted dike and gabbro boundary from ICDP Holes GT1A, GT2A and GT3A

NASA Astrophysics Data System (ADS)

Abe, N.; Okazaki, K.; Hatakeyama, K.; Ildefonse, B.; Leong, J. A. M.; Tateishi, Y.; Teagle, D. A. H.; Takazawa, E.; Kelemen, P. B.; Michibayashi, K.; Coggon, J. A.; Harris, M.; de Obeso, J. C.

2017-12-01

We report results on the physical property measurements of the core samples from ICDP Holes GT1A, GT2A and GT3A drilled at Samail Ophiolite, Sultanate of Oman. Cores from Holes GT1A and GT2A in the lower crust section are mainly composed of gabbros (gabbro and olivine gabbro), and small amounts of ultramafic rocks (wehrlite and dunite), while cores from Hole GT3A at the boundary between sheeted dikes and gabbro are mainly composed of basalt and diabase, followed by gabbros (gabbro, olivine gabbro and oxide gabbro), and less common felsic dikes, trondhjemite and tonalite, intrude the mafic rocks. Measurements of physical properties were undertaken to characterize recovered core material. Onboard the Drilling Vessel Chikyu, whole-round measurements included X-ray CT image, natural gamma radiation, and magnetic susceptibility for Leg 1, and additional P-wave velocity, gamma ray attenuation density, and electrical resistivity during Leg 2. Split-core point magnetic susceptibility and color spectroscopy were measured for all core sections. P-wave velocity, bulk/grain density and porosity of more than 500 discrete cube samples, and thermal conductivity on more than 240 pieces from the working half of the split core sections were also measured. Physical Properties of gabbroic rocks from Holes GT1A and GT2A are similar to typical oceanic gabbros from ODP and IODP expeditions at Atlantis Bank, Southwestern Indian Ridge (ODP Legs 118, 176 and 179; IODP Exp 360) and at Hess Deep, Eastern Pacific (ODP Leg 147 and IODP Exp. 345). Average P-wave velocity, bulk density, grain density, porosity and thermal conductivity are 6.7 km/s, 2.92 g/cm^3, 2.93 g/cm^3, 0.98% and 2.46 W/m/K, respectively. P-wave velocity of samples from all three holes is inversely correlated with porosity. No clear correlation between the original lithology and physical properties is observed. GT3A cores show a wider range (e.g., Vp from 2.2 to 7.1 km/s) of values for the measured physical properties

Modeling of blob-hole correlations in GPI edge turbulence data

NASA Astrophysics Data System (ADS)

Myra, J. R.; Russell, D. A.; Zweben, S. J.

2017-10-01

Gas-puff imaging (GPI) observations made on NSTX have revealed two-point spatial correlation patterns in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this work, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlation patterns that are qualitatively similar to the GPI data in many respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored. The possibility of using the model to ascertain new information about edge turbulence is discussed. Work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences under Award Number DE-FG02-02ER54678.

Direct Correlation of Excitonics with Efficiency in a Core-Shell Quantum Dot Solar Cell.

PubMed

Dana, Jayanta; Maiti, Sourav; Tripathi, Vaidehi S; Ghosh, Hirendra N

2018-02-16

Shell thickness dependent band-gap engineering of quasi type II core-shell material with higher carrier cooling time, lower interfacial defect states, and longer charge carrier recombination time can be a promising candidate for both photocatalysis and solar cell. In the present investigation, colloidal CdSe@CdS core-shells with different shell thickness (2, 4 and 6 monolayer CdS) were synthesized through hot injection method and have been characterized by high resolution transmission electron microscope (HRTEM) followed by steady state absorption and luminescence techniques. Ultrafast transient absorption (TA) studies suggest longer carrier cooling, lower interfacial surface states, and slower carrier recombination time in CdSe@CdS core-shell with increasing shell thickness. By TA spectroscopy, the role of CdS shell in power conversion efficiency (PCE) has been explained in detail. The measured PCE was found to initially increase and then decrease with increasing shell thickness. Shell thickness has been optimized to maximize the efficiency after correlating the shell controlled carrier cooling and recombination with PCE values and a maximum PCE of 3.88 % was obtained with 4 monolayers of CdS shell, which is found to be 57 % higher than compared to bare CdSe QDs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Core-core and core-valence correlation energy atomic and molecular benchmarks for Li through Ar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranasinghe, Duminda S.; Frisch, Michael J.; Petersson, George A., E-mail: gpetersson@wesleyan.edu

2015-12-07

We have established benchmark core-core, core-valence, and valence-valence absolute coupled-cluster single double (triple) correlation energies (±0.1%) for 210 species covering the first- and second-rows of the periodic table. These species provide 194 energy differences (±0.03 mE{sub h}) including ionization potentials, electron affinities, and total atomization energies. These results can be used for calibration of less expensive methodologies for practical routine determination of core-core and core-valence correlation energies.

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures

DOE PAGES

Cherukara, Mathew J.; Sasikumar, Kiran; DiChiara, Anthony; ...

2017-11-07

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. Here in this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplaymore » of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.« less

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherukara, Mathew J.; Sasikumar, Kiran; DiChiara, Anthony

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. Here in this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplaymore » of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.« less

Preliminary report on the geology, geophysics and hydrology of USBM/AEC Colorado core hole No. 2, Piceance Creek Basin, Rio Blanco County, Colorado

USGS Publications Warehouse

Ege, J.R.; Carroll, R.D.; Welder, F.A.

1967-01-01

Approximately 1,400 feet of continuous core was taken .between 800-2,214 feet in depth from USBM/AEC Colorado core hole No. 2. The drill, site is located in the Piceance Creek basin, Rio Blanco County, Colorado. From ground surface the drill hole penetrated 1,120 feet of the Evacuation Creek Member and 1,094 feet of oil shale in the Parachute Creek Member of the Green River Formation. Oil shale yielding more than 20 gallons per ton occurs between 1,260-2,214 feet in depth. A gas explosion near the bottom of the hole resulted in abandonment of the exploratory hole which was still in oil shale. The top of the nahcolite zone is at 1,693 feet. Below this depth the core contains common to abundant amounts of sodium bicarbonate salt intermixed with oil shale. The core is divided into seven structural zones that reflect changes in joint intensity, core loss and broken core due to natural causes. The zone of poor core recovery is in the Interval between 1,300-1,450 feet. Results of preliminary geophysical log analyses indicate that oil yields determined by Fischer assay compare favorably with yields determined by geophysical log analyses. There is strong evidence that analyses of complete core data from Colorado core holes No. 1 and No. 2 reveal a reliable relationship between geophysical log response and oil yield. The quality of the logs is poor in the rich shale section and the possibility of repeating the logging program should be considered. Observations during drilling, coring, and hydrologic testing of USBM/AEC Colorado core hole No. 2 reveal that the Parachute Creek Member of the Green River Formation is the principal aquifer water in the Parachute Creek Member is under artesian pressure. The upper part of the aquifer has a higher hydrostatic head than, and is hydrologically separated from the lower part of the aquifer. The transmissibility of the aquifer is about 3500 gpd per foot. The maximum water yield of the core hole during testing was about 500 gpm. Chemical

Plasma Heating and Ultrafast Semiconductor Laser Modulation Through a Terahertz Heating Field

NASA Technical Reports Server (NTRS)

Li, Jian-Zhong; Ning, C. Z.

2000-01-01

Electron-hole plasma heating and ultrafast modulation in a semiconductor laser under a terahertz electrical field are investigated using a set of hydrodynamic equations derived from the semiconductor Bloch equations. The self-consistent treatment of lasing and heating processes leads to the prediction of a strong saturation and degradation of modulation depth even at moderate terahertz field intensity. This saturation places a severe limit to bandwidth achievable with such scheme in ultrafast modulation. Strategies for increasing modulation depth are discussed.

Ultrafast Nonlinear Microscopy in III-V Semiconductor Nanostructures

DTIC Science & Technology

2016-01-20

SECURITY CLASSIFICATION OF: This project involved the investigation of the photoluminescence properties of individual ZnO nano-rods, characterization ...13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 15. SUBJECT TERMS b...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 ultrafast imaging, strained nanomaterials , electron-hole plasma dynamics, microscopy

Core-core and core-valence correlation

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1988-01-01

The effect of 1s core correlation on properties and energy separations are analyzed using full configuration-interaction (FCI) calculations. The Be1S - 1P, the C 3P - 5S,m and CH(+) 1Sigma(+) - 1Pi separations, and CH(+) spectroscopic constants, dipole moment, and 1Sigma(+) - 1Pi transition dipole moment have been studied. The results of the FCI calculations are compared to those obtained using approximate methods.

Absorption spectrum and ultrafast response of monolayer and bilayer transition-metal dichalcogenides

NASA Astrophysics Data System (ADS)

Turkowski, Volodymyr; Ramirez-Torres, Alfredo; Rahman, Talat S.

2015-03-01

We apply a combined time-dependent density functional theory and many-body theory approach to examine the absorption spectrum and nonequilibrium response of monolayer and bilayer MoS2, MoSe2, WS2 and WSe2 systems. In particular, we evaluate the possibility of existence of bound states - excitons and trions in the undoped systems. In a previous work we have already demonstrated that the binding energies of these states in the monolayer systems are large which makes them available for room temperature applications. We analyze the possibility of ultrafast electron-hole separation in bilayer systems through inter-layer hole transfer, and show that such a possibility exists, in agreement with experimental observations. For doped systems we consider the possibility of Mahan excitonic states in monolayers and show that the binding energy for these states is of the order of 10 meV. We perform a detailed analysis of the relaxation of doped monolayers excited by ultrafast laser pulse by taking into account electron-phonon scattering effects, and demonstrate that ultrafast (10-100fs) processes, including luminescence, may be relevant for these materials. Work supported in part by DOE Grant No. DOE-DE-FG02-07ER46354.

Hydrogeologic data from a 2,000-foot deep core hole at Polk City, Green Swamp area, central Florida

USGS Publications Warehouse

Navoy, A.S.

1986-01-01

Two core holes were drilled to depths of 906 and 1,996 feet, respectively, within the Tertiary limestone (Floridan) aquifers, at Polk City, central Florida. Data from the two holes revealed that the bottom of the zone of vigorous groundwater circulation is confined by carbonate rocks at a depth of about 1,000 feet (863 feet below sea level). The zone of circulation is divided into two high-permeability zones. The dissolved solids of the water within the high-permeability zones is approximately 150 milligrams per liter. Within the carbonate rocks, the dissolved solids content of the water reaches about 2,000 milligrams per liter at the bottom of the core hole. Water levels in the core holes declined a total of about 16 feet as the hole was drilled; most of the head loss occurred at depths below 1,800 feet. The porosities of selected cores ranged from 1.6 to 45.3 percent; the hydraulic conductivities ranged from less than 0.000024 to 19.0786 feet per day in the horizontal direction and from less than 0.000024 to 2.99 feet per day in the vertical direction; and the ratio of vertical to horizontal permeability ranged from 0.03 to 1.98. Due to drilling problems, packer tests and geophysical logging could not be accomplished. (USGS)

Correlating structural dynamics and catalytic activity of AgAu nanoparticles with ultrafast spectroscopy and all-atom molecular dynamics simulations.

PubMed

Ferbonink, G F; Rodrigues, T S; Dos Santos, D P; Camargo, P H C; Albuquerque, R Q; Nome, R A

2018-05-29

In this study, we investigated hollow AgAu nanoparticles with the goal of improving our understanding of the composition-dependent catalytic activity of these nanoparticles. AgAu nanoparticles were synthesized via the galvanic replacement method with controlled size and nanoparticle compositions. We studied extinction spectra with UV-Vis spectroscopy and simulations based on Mie theory and the boundary element method, and ultrafast spectroscopy measurements to characterize decay constants and the overall energy transfer dynamics as a function of AgAu composition. Electron-phonon coupling times for each composition were obtained from pump-power dependent pump-probe transients. These spectroscopic studies showed how nanoscale surface segregation, hollow interiors and porosity affect the surface plasmon resonance wavelength and fundamental electron-phonon coupling times. Analysis of the spectroscopic data was used to correlate electron-phonon coupling times to AgAu composition, and thus to surface segregation and catalytic activity. We have performed all-atom molecular dynamics simulations of model hollow AgAu core-shell nanoparticles to characterize nanoparticle stability and equilibrium structures, besides providing atomic level views of nanoparticle surface segregation. Overall, the basic atomistic and electron-lattice dynamics of core-shell AgAu nanoparticles characterized here thus aid the mechanistic understanding and performance optimization of AgAu nanoparticle catalysts.

X-ray Fluorescence Core Scanning of Oman Drilling Project Holes BT1B and GT3A Cores on D/V CHIKYU

NASA Astrophysics Data System (ADS)

Johnson, K. T. M.; Kelemen, P. B.; Michibayashi, K.; Greenberger, R. N.; Koepke, J.; Beinlich, A.; Morishita, T.; Jesus, A. P. M.; Lefay, R.

2017-12-01

The JEOL JSX-3600CA1 energy dispersive X-ray fluorescence core logger (XRF-CL) on the D/V Chikyu provides quantitative element concentrations of scanned cores. Scans of selected intervals are made on an x-y grid with point spacing of 5 mm. Element concentrations for Si, Al, Ti, Ca, Mg, Mn, Fe, Na, K, Cr, Ni, S and Zn are collected for each point on the grid. Accuracy of element concentrations provided by the instrument software is improved by applying empirical correction algorithms. Element concentrations were collected for 9,289 points from twenty-seven core intervals in Hole BT1B (basal thrust) and for 6,389 points from forty core intervals in Hole GT3A (sheeted dike-gabbro transition) of the Oman Drilling Project on the D/V Chikyu XRF-CL during Leg 2 of the Oman Drilling Project in August-September, 2017. The geochemical data are used for evaluating downhole compositional details associated with lithological changes, unit contacts and mineralogical variations and are particularly informative when plotted as concentration contour maps or downhole concentration diagrams. On Leg 2 additional core scans were made with X-ray Computed Tomography (X-ray CT) and infrared images from the visible-shortwave infrared imaging spectroscopy (IR) systems on board. XRF-CL, X-ray CT and IR imaging plots used together provide detailed information on rock compositions, textures and mineralogy that assist naked eye visual observations. Examples of some uses of XRF-CL geochemical maps and downhole data are shown. XRF-CL and IR scans of listvenite clearly show zones of magnesite, dolomite and the Cr-rich mica, fuchsite that are subdued in visual observation, and these scans can be used to calculate variations in proportions of these minerals in Hole BT1B cores. In Hole GT3A XRF-CL data can be used to distinguish compositional changes in different generations of sheeted dikes and gabbros and when combined with visual observations of intrusive relationships the detailed geochemical

The Quest for the Largest Depleted Galaxy Core: Supermassive Black Hole Binaries and Stalled Infalling Satellites

NASA Astrophysics Data System (ADS)

Bonfini, Paolo; Graham, Alister W.

2016-10-01

Partially depleted cores are practically ubiquitous in luminous early-type galaxies (M B ≲ -20.5 mag) and are typically smaller than 1 kpc. In one popular scenario, supermassive black hole (SMBH) binaries—established during dry (I.e., gas-poor) galaxy mergers—kick out the stars from a galaxy’s central region via three-body interactions. Here, this “binary black hole scouring scenario” is probed at its extremes by investigating the two galaxies reported to have the largest partially depleted cores found to date: 2MASX J09194427+5622012 and 2MASX J17222717+3207571 (the brightest galaxy in Abell 2261). We have fit these galaxy’s two-dimensional light distribution using the core-Sérsic model and found that the former galaxy has a core-Sérsic break radius {R}b,{cS}=0.55 {{kpc}}, which is three times smaller than the published value. We use this galaxy to caution that other reportedly large break radii may too have been overestimated if they were derived using the “sharp-transition” (inner core)-to-(outer Sérsic) model. In the case of 2MASX J17222717+3207571, we obtain R b,cS = 3.6 kpc. While we confirm that this is the biggest known partially depleted core of any galaxy, we stress that it is larger than expected from the evolution of SMBH binaries—unless one invokes substantial gravitational-wave-induced (black hole-)recoil events. Given the presence of multiple nuclei located (in projection) within the core radius of this galaxy, we explored and found support for the alternative “stalled infalling perturber” core-formation scenario, in which this galaxy’s core could have been excavated by the action of an infalling massive perturber.

Correlation induced electron-hole asymmetry in quasi- two-dimensional iridates.

PubMed

Pärschke, Ekaterina M; Wohlfeld, Krzysztof; Foyevtsova, Kateryna; van den Brink, Jeroen

2017-09-25

The resemblance of crystallographic and magnetic structures of the quasi-two-dimensional iridates Ba 2 IrO 4 and Sr 2 IrO 4 to La 2 CuO 4 points at an analogy to cuprate high-Tc superconductors, even if spin-orbit coupling is very strong in iridates. Here we examine this analogy for the motion of a charge (hole or electron) added to the antiferromagnetic ground state. We show that correlation effects render the hole and electron case in iridates very different. An added electron forms a spin polaron, similar to the cuprates, but the situation of a removed electron is far more complex. Many-body 5d 4 configurations form which can be singlet and triplet states of total angular momentum that strongly affect the hole motion. This not only has ramifications for the interpretation of (inverse-)photoemission experiments but also demonstrates that correlation physics renders electron- and hole-doped iridates fundamentally different.Some iridate compounds such as Sr 2 IrO 4 have electronic and atomic structures similar to quasi-2D copper oxides, raising the prospect of high temperature superconductivity. Here, the authors show that there is significant electron-hole asymmetry in iridates, contrary to expectations from the cuprates.

Particle-hole symmetry in many-body theories of electron correlation

NASA Astrophysics Data System (ADS)

Kats, Daniel; Usvyat, Denis; Manby, Frederick R.

2018-06-01

Second-quantised creation and annihilation operators for fermionic particles anticommute, but the same is true for the creation and annihilation operators for holes. This introduces a symmetry into the quantum theory of fermions that is absent for bosons. In ab initio electronic structure theory, it is common to classify methods by the number of electrons for which the method returns exact results: for example Hartree-Fock theory is exact for one-electron systems, whereas coupled-cluster theory with single and double excitations is exact for two-electron systems. Here, we discuss the generalisation: methods based on approximate wavefunctions that are exact for n-particle systems are also exact for n-hole systems. Novel electron correlation methods that attempt to improve on the coupled-cluster framework sometimes retain this property, and sometimes lose it. Here, we argue for retaining particle-hole symmetry as a desirable design criterion of approximate electron correlation methods. Dispensing with it might lead to loss of n-representability of density matrices, and this in turn can lead to spurious long-range behaviour in the correlation energy.

Ultrafast laser ablation for targeted atherosclerotic plaque removal

NASA Astrophysics Data System (ADS)

Lanvin, Thomas; Conkey, Donald B.; Descloux, Laurent; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

2015-07-01

Coronary artery disease, the main cause of heart disease, develops as immune cells and lipids accumulate into plaques within the coronary arterial wall. As a plaque grows, the tissue layer (fibrous cap) separating it from the blood flow becomes thinner and increasingly susceptible to rupturing and causing a potentially lethal thrombosis. The stabilization and/or treatment of atherosclerotic plaque is required to prevent rupturing and remains an unsolved medical problem. Here we show for the first time targeted, subsurface ablation of atherosclerotic plaque using ultrafast laser pulses. Excised atherosclerotic mouse aortas were ablated with ultrafast near-infrared (NIR) laser pulses. The physical damage was characterized with histological sections of the ablated atherosclerotic arteries from six different mice. The ultrafast ablation system was integrated with optical coherence tomography (OCT) imaging for plaque-specific targeting and monitoring of the resulting ablation volume. We find that ultrafast ablation of plaque just below the surface is possible without causing damage to the fibrous cap, which indicates the potential use of ultrafast ablation for subsurface atherosclerotic plaque removal. We further demonstrate ex vivo subsurface ablation of a plaque volume through a catheter device with the high-energy ultrafast pulse delivered via hollow-core photonic crystal fiber.

Influence of Nonfused Cores on the Photovoltaic Performance of Linear Triphenylamine-Based Hole-Transporting Materials for Perovskite Solar Cells.

PubMed

Wu, Yungen; Wang, Zhihui; Liang, Mao; Cheng, Hua; Li, Mengyuan; Liu, Liyuan; Wang, Baiyue; Wu, Jinhua; Prasad Ghimire, Raju; Wang, Xuda; Sun, Zhe; Xue, Song; Qiao, Qiquan

2018-05-30

The core plays a crucial role in achieving high performance of linear hole transport materials (HTMs) toward the perovskite solar cells (PSCs). Most studies focused on the development of fused heterocycles as cores for HTMs. Nevertheless, nonfused heterocycles deserve to be studied since they can be easily synthesized. In this work, we reported a series of low-cost triphenylamine HTMs (M101-M106) with different nonfused cores. Results concluded that the introduced core has a significant influence on conductivity, hole mobility, energy level, and solubility of linear HTMs. M103 and M104 with nonfused oligothiophene cores are superior to other HTMs in terms of conductivity, hole mobility, and surface morphology. PSCs based on M104 exhibited the highest power conversion efficiency of 16.50% under AM 1.5 sun, which is comparable to that of spiro-OMeTAD (16.67%) under the same conditions. Importantly, the employment of M104 is highly economical in terms of the cost of synthesis as compared to that of spiro-OMeTAD. This work demonstrated that nonfused heterocycles, such as oligothiophene, are promising cores for high performance of linear HTMs toward PSCs.

Engineering model for ultrafast laser microprocessing

NASA Astrophysics Data System (ADS)

Audouard, E.; Mottay, E.

2016-03-01

Ultrafast laser micro-machining relies on complex laser-matter interaction processes, leading to a virtually athermal laser ablation. The development of industrial ultrafast laser applications benefits from a better understanding of these processes. To this end, a number of sophisticated scientific models have been developed, providing valuable insights in the physics of the interaction. Yet, from an engineering point of view, they are often difficult to use, and require a number of adjustable parameters. We present a simple engineering model for ultrafast laser processing, applied in various real life applications: percussion drilling, line engraving, and non normal incidence trepanning. The model requires only two global parameters. Analytical results are derived for single pulse percussion drilling or simple pass engraving. Simple assumptions allow to predict the effect of non normal incident beams to obtain key parameters for trepanning drilling. The model is compared to experimental data on stainless steel with a wide range of laser characteristics (time duration, repetition rate, pulse energy) and machining conditions (sample or beam speed). Ablation depth and volume ablation rate are modeled for pulse durations from 100 fs to 1 ps. Trepanning time of 5.4 s with a conicity of 0.15° is obtained for a hole of 900 μm depth and 100 μm diameter.

Black Hole Formation in Failing Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

O'Connor, Evan; Ott, Christian D.

2011-04-01

We present results of a systematic study of failing core-collapse supernovae and the formation of stellar-mass black holes (BHs). Using our open-source general-relativistic 1.5D code GR1D equipped with a three-species neutrino leakage/heating scheme and over 100 presupernova models, we study the effects of the choice of nuclear equation of state (EOS), zero-age main sequence (ZAMS) mass and metallicity, rotation, and mass-loss prescription on BH formation. We find that the outcome, for a given EOS, can be estimated, to first order, by a single parameter, the compactness of the stellar core at bounce. By comparing protoneutron star (PNS) structure at the onset of gravitational instability with solutions of the Tolman-Oppenheimer-Volkof equations, we find that thermal pressure support in the outer PNS core is responsible for raising the maximum PNS mass by up to 25% above the cold NS value. By artificially increasing neutrino heating, we find the critical neutrino heating efficiency required for exploding a given progenitor structure and connect these findings with ZAMS conditions, establishing, albeit approximately, for the first time based on actual collapse simulations, the mapping between ZAMS parameters and the outcome of core collapse. We also study the effect of progenitor rotation and find that the dimensionless spin of nascent BHs may be robustly limited below a* = Jc/GM 2 = 1 by the appearance of nonaxisymmetric rotational instabilities.

Ultrafast Transient Absorption Spectroscopy Investigation of Photoinduced Dynamics in Novel Donor-Acceptor Core-Shell Nanostructures for Organic Photovoltaics

NASA Astrophysics Data System (ADS)

Strain, Jacob; Jamhawi, Abdelqader; Abeywickrama, Thulitha M.; Loomis, Wendy; Rathnayake, Hemali; Liu, Jinjun

2016-06-01

Novel donor-acceptor nanostructures were synthesized via covalent synthesis and/or UV cross-linking method. Their photoinduced dynamics were investigated with ultrafast transient absorption (TA) spectroscopy. These new nanostructures are made with the strategy in mind to reduce manufacturing steps in the process of fabricating an organic photovoltaic cell. By imitating the heterojunction interface within a fixed particle domain, several fabrication steps can be bypassed reducing cost and giving more applicability to other film deposition methods. Such applications include aerosol deposition and ink-jet printing. The systems that were studied by TA spectroscopy include PDIB core, PDIB-P3HT core-shell, and PDIB-PANT core-shell which range in size from 60 to 130 nm. Within the experimentally accessible spectra range there resides a region of ground state bleaching, stimulated emission, and excited-state absorption of both neutrals and anions. Control experiments have been carried out to assign these features. At high pump fluences the TA spectra of PDIB core alone also indicate an intramolecular charge separation. The TA spectroscopy results thus far suggest that the core-shells resemble the photoinduced dynamics of a standard film although the particles are dispersed in solution, which indicates the desired outcome of the work.

On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandra, Sankhabrata; Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in; Periyasamy, Ganga

2015-06-28

In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation- and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH{sub 2}, CF{sub 3}, and COOH substituents) molecules paired with NH{sub 3} (referred as ACl:NH{sub 3} complex): these complexes exhibit halogen bonds. To the best of our knowledge, this ismore » the first report on purely electron correlation- and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31 + G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl⋯NH{sub 3} complex, the hole is predicted to migrate from the NH{sub 3}-end to the ClCN-end of the NCCl⋯NH{sub 3} complex in approximately 0.5 fs on the D{sub 0} cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H{sub 2}NCl:NH{sub 3}, F{sub 3}CCl:NH{sub 3}, and HOOCCl:NH{sub 3}, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH{sub 3} and HOCl:NH{sub 3} complexes do not exhibit any charge migration following vertical ionization to the D{sub 0} cation state, pointing to interesting halogen bond strength-dependent charge migration.« less

Unambiguous observation of F-atom core-hole localization in CF 4 through body-frame photoelectron angular distributions

DOE PAGES

McCurdy, C. W.; Rescigno, T. N.; Trevisan, C. S.; ...

2017-01-17

A dramatic symmetry breaking in K-shell photoionization of the CF 4 molecule in which a core-hole vacancy is created in one of four equivalent fluorine atoms is displayed in the molecular frame angular distribution of the photoelectrons. In observing the photoejected electron in coincidence with an F + atomic ion after Auger decay we see how selecting the dissociation path where the core hole was localized was almost exclusively on that atom. A combination of measurements and ab initio calculations of the photoelectron angular distribution in the frame of the recoiling CF 3 + and F + atoms elucidates themore » underlying physics that derives from the Ne-like valence structure of the F(1s -1) core-excited atom.« less

I-cored Coil Probe Located Above a Conductive Plate with a Surface Hole

NASA Astrophysics Data System (ADS)

Tytko, Grzegorz; Dziczkowski, Leszek

2018-02-01

This work presents an axially symmetric mathematical model of an I-cored coil placed over a two-layered conductive material with a cylindrical surface hole. The problem was divided into regions for which the magnetic vector potential of a filamentary coil was established applying the truncated region eigenfunction expansion method. Then the final formula was developed to calculate impedance changes for a cylindrical coil with reference to both the air and to a material with no hole. The influence of a surface flaw in the conductive material on the components of coil impedance was examined. Calculations were made in Matlab for a hole with various radii and the results thereof were verified with the finite element method in COMSOL Multiphysics package. Very good consistency was achieved in all cases.

Evidence for Weakly Correlated Oxygen Holes in the Highest-Tc Cuprate Superconductor HgBa2 Ca2 Cu3 O8 +δ

NASA Astrophysics Data System (ADS)

Chainani, A.; Sicot, M.; Fagot-Revurat, Y.; Vasseur, G.; Granet, J.; Kierren, B.; Moreau, L.; Oura, M.; Yamamoto, A.; Tokura, Y.; Malterre, D.

2017-08-01

We study the electronic structure of HgBa2 Ca2 Cu3 O8 +δ (Hg1223; Tc=134 K ) using photoemission spectroscopy (PES) and x -ray absorption spectroscopy (XAS). Resonant valence band PES across the O K edge and Cu L edge identifies correlation satellites originating in O 2 p and Cu 3 d two-hole final states, respectively. Analyses using the experimental O 2 p and Cu 3 d partial density of states show quantitatively different on-site Coulomb energy for the Cu site (Ud d=6.5 ±0.5 eV ) and O site (Up p=1.0 ±0.5 eV ). Cu2 O7 -cluster calculations with nonlocal screening explain the Cu 2 p core level PES and Cu L -edge XAS spectra, confirm the Ud d and Up p values, and provide evidence for the Zhang-Rice singlet state in Hg1223. In contrast to other hole-doped cuprates and 3 d -transition metal oxides, the present results indicate weakly correlated oxygen holes in Hg1223.

Kinetic energy as functional of the correlation hole

NASA Astrophysics Data System (ADS)

Nalewajski, Roman F.

2003-01-01

Using the marginal decomposition of the many-body probability distribution the electronic kinetic energy is expressed as the functional of the electron density and correlation hole. The analysis covers both the molecule as a whole and its constituent subsystems. The importance of the Fisher information for locality is emphasized.

Towards ultrafast dynamics with split-pulse X-ray photon correlation spectroscopy at free electron laser sources

DOE PAGES

Roseker, W.; Hruszkewycz, S. O.; Lehmkuhler, F.; ...

2018-04-27

One of the important challenges in condensed matter science is to understand ultrafast, atomic-scale fluctuations that dictate dynamic processes in equilibrium and non-equilibrium materials. Here, we report an important step towards reaching that goal by using a state-of-the-art perfect crystal based split-and-delay system, capable of splitting individual X-ray pulses and introducing femtosecond to nanosecond time delays. We show the results of an ultrafast hard X-ray photon correlation spectroscopy experiment at LCLS where split X-ray pulses were used to measure the dynamics of gold nanoparticles suspended in hexane. We show how reliable speckle contrast values can be extracted even from verymore » low intensity free electron laser (FEL) speckle patterns by applying maximum likelihood fitting, thus demonstrating the potential of a split-and-delay approach for dynamics measurements at FEL sources. This will enable the characterization of equilibrium and, importantly also reversible non-equilibrium processes in atomically disordered materials.« less

Towards ultrafast dynamics with split-pulse X-ray photon correlation spectroscopy at free electron laser sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roseker, W.; Hruszkewycz, S. O.; Lehmkuhler, F.

One of the important challenges in condensed matter science is to understand ultrafast, atomic-scale fluctuations that dictate dynamic processes in equilibrium and non-equilibrium materials. Here, we report an important step towards reaching that goal by using a state-of-the-art perfect crystal based split-and-delay system, capable of splitting individual X-ray pulses and introducing femtosecond to nanosecond time delays. We show the results of an ultrafast hard X-ray photon correlation spectroscopy experiment at LCLS where split X-ray pulses were used to measure the dynamics of gold nanoparticles suspended in hexane. We show how reliable speckle contrast values can be extracted even from verymore » low intensity free electron laser (FEL) speckle patterns by applying maximum likelihood fitting, thus demonstrating the potential of a split-and-delay approach for dynamics measurements at FEL sources. This will enable the characterization of equilibrium and, importantly also reversible non-equilibrium processes in atomically disordered materials.« less

IODP Exp 362T: Additional Coring and Remediation in Hole U1473A - Continuing the Journey to the Moho

NASA Astrophysics Data System (ADS)

Blum, P.; Dick, H. J.; MacLeod, C. J.; Expedition 360 Scientists, I.

2016-12-01

IODP Hole U1473A, located at 32°42.362'S, 057°16.688'E in the central part of the Atlantis Bank, SW Indian Ridge, at 710.2 m water depth, was drilled to a depth of 789.7 m below seafloor during Exp. 360 (11/30/15 - 1/30/16) and recovered 469.2 m of gabbroic rocks. Following successful wireline logging, a mechanical bit release retainer sleeve (MBR-RS) appeared to have been lost in the hole, raising question about the feasibility of deepening the hole in the future.. We are here reporting the successful remediation operation carried out 12 - 21 Jul, which left the hole ready for deepening on a future expedition. Hole U1473A is serendipitously located on the scheduled Transit 362T from Cape Town to Colombo (4 Jul - 6 Aug) and had 14 days of redundant time and a nearly full technical contingent on board. This led to a request and approval to use the time to "fish" for the MBR-RS, cement the hole to stabilize fault zones, and recover up to 20 m of core to establish the feasibility for future deep drilling. An initial attempt at taking a temperature log in the hole was terminated at 277 m due an obstruction. Subsequent reaming successfully reached the bottom of the hole and removed all cuttings. To our surprise, deployment of the fishing tool recovered an 18-cm dia., 36-cm long rock core but no MBR-RS. The latter must have fallen to the seafloor unnoticed at the end of Exp. 360. Given the immaculate hole conditions, we went on to recover four additional cores with excellent recovery (86%), deepening the hole to 809.4 m. The new cores from 789.7 to 809.5 m consist mostly of medium to coarse-grained subophitic olivine gabbro with a weak magmatic fabric and irregular contacts between medium and coarse-grained size domains. From 795 - 797 m, a zone of Fe-Ti oxide gabbro results in high magnetic susceptibility (MS) and significant natural gamma radiation (NGR) with sheared contacts and an associated porphyroclastic interval. The interval below 797 m is more isotropic with

Blob-hole correlation model for edge turbulence and comparisons with NSTX gas puff imaging data

NASA Astrophysics Data System (ADS)

Myra, J. R.; Zweben, S. J.; Russell, D. A.

2018-07-01

Gas puff imaging (GPI) observations made in NSTX (Zweben et al 2017 Phys. Plasmas 24 102509) have revealed two-point spatial correlations of edge and scrape-off layer (SOL) turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlation patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or SOL), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracking of the highest and lowest values (extrema) of the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Other properties of the experimentally observed extrema are discussed.

Application of drilling, coring, and sampling techniques to test holes and wells

USGS Publications Warehouse

Shuter, Eugene; Teasdale, Warren E.

1989-01-01

The purpose of this manual is to provide ground-water hydrologists with a working knowledge of the techniques of test drilling, auger drilling, coring and sampling, and the related drilling and sampling equipment. For the most part, the techniques discussed deal with drilling, sampling, and completion of test holes in unconsolidated sediments because a hydrologist is interested primarily in shallow-aquifer data in this type of lithology. Successful drilling and coring of these materials usually is difficult, and published research information on the subject is not readily available. The authors emphasize in-situ sampling of unconsolidated sediments to obtain virtually undisturbed samples. Particular attention is given to auger drilling and hydraulic-rotary methods of drilling because these are the principal means of test drilling performed by the U.S. Geological Survey during hydrologic studies. Techniques for sampling areas contaminated by solid or liquid waste are discussed. Basic concepts of well development and a detailed discussion of drilling muds, as related to hole conditioning, also are included in the report. The information contained in this manual is intended to help ground-water hydrologists obtain useful subsurface data and samples from their drilling programs.

Ultrafast Phenomena XIV

NASA Astrophysics Data System (ADS)

Kobayashi, Takayoshi; Okada, Tadashi; Kobayashi, Tetsuro; Nelson, Keith A.; de Silvestri, Sandro

Ultrafast Phenomena XIV presents the latest advances in ultrafast science, including ultrafast laser and measurement technology as well as studies of ultrafast phenomena. Pico-, femto-, and atosecond processes relevant in physics, chemistry, biology, and engineering are presented. Ultrafast technology is now having a profound impact within a wide range of applications, among them imaging, material diagnostics, and transformation and high-speed optoelectronics . This book summarizes results presented at the 14th Ultrafast Phenomena Conference and reviews the state of the art in this important and rapidly advancing field.

THE SUPERMASSIVE BLACK HOLE MASS-SPHEROID STELLAR MASS RELATION FOR SERSIC AND CORE-SERSIC GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, Nicholas; Graham, Alister W; Schombert, James

2013-05-01

We have examined the relationship between supermassive black hole mass (M{sub BH}) and the stellar mass of the host spheroid (M{sub sph,*}) for a sample of 75 nearby galaxies. To derive the spheroid stellar masses we used improved Two Micron All Sky Survey K{sub s}-band photometry from the ARCHANGEL photometry pipeline. Dividing our sample into core-Sersic and Sersic galaxies, we find that they are described by very different M{sub BH}-M{sub sph,*} relations. For core-Sersic galaxies-which are typically massive and luminous, with M{sub BH} {approx}> 2 Multiplication-Sign 10{sup 8} M{sub Sun }-we find M{sub BH}{proportional_to} M{sub sph,*}{sup 0.97{+-}0.14}, consistent with othermore » literature relations. However, for the Sersic galaxies-with typically lower masses, M{sub sph,*} {approx}< 3 Multiplication-Sign 10{sup 10} M{sub Sun }-we find M{sub BH}{proportional_to}M{sub sph,*}{sup 2.22{+-}0.58}, a dramatically steeper slope that differs by more than 2 standard deviations. This relation confirms that, for Sersic galaxies, M{sub BH} is not a constant fraction of M{sub sph,*}. Sersic galaxies can grow via the accretion of gas which fuels both star formation and the central black hole, as well as through merging. Their black hole grows significantly more rapidly than their host spheroid, prior to growth by dry merging events that produce core-Sersic galaxies, where the black hole and spheroid grow in lockstep. We have additionally compared our Sersic M{sub BH}-M{sub sph,*} relation with the corresponding relation for nuclear star clusters, confirming that the two classes of central massive object follow significantly different scaling relations.« less

Selected data fron continental scientific drilling core holes VC-1 and VC-2a, Valles Caldera, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musgrave, J.A.; Goff, F.; Shevenell, L.

1989-02-01

This report presents geochemical and isotopic data on rocks and water and wellbore geophysical data from the Continental Scientific Drilling Program core holes VC-1 and VC-2a, Valles Caldera, New Mexico. These core holes were drilled as a portion of a broader program that seeks to answer fundamental questions about magma, water/rock interactions, ore deposits, and volcanology. The data in this report will assist the interpretation of the hydrothermal system in the Jemez Mountains and will stimulate further research in magmatic processes, hydrothermal alteration, ore deposits, hydrology, structural geology, and hydrothermal solution chemistry. 37 refs., 36 figs., 28 tabs.

Residual stress measurement of PMMA by combining drilling-hole with digital speckle correlation method

NASA Astrophysics Data System (ADS)

Yao, X. F.; Xiong, T. C.; Xu, H. M.; Wan, J. P.; Long, G. R.

2008-11-01

The residual stresses of the PMMA (polymethyl methacrylate) specimens after being drilled, reamed and polished respectively are investigated using the digital speckle correlation experimental method,. According to the displacement fields around the correlated calculated region, the polynomial curve fitting method is used to obtain the continuous displacement fields, and the strain fields can be obtained from the derivative of the displacement fields. Considering the constitutive equation of the material, the expression of the residual stress can be presented. During the data processing, according to the fitting effect of the data, the calculation region of the correlated speckles and the degree of the polynomial fitting curve is decided. These results show that the maximum stress is at the hole-wall of the drilling hole specimen and with the increasing of the diameter of the drilled hole, the residual stress resulting from the hole drilling increases, whereas the process of reaming and polishing hole can reduce the residual stress. The relative large discrete degree of the residual stress is due to the chip removal ability of the drill bit, the cutting feed of the drill and other various reasons.

Correlation between postoperative area of high autofluorescence in macula and visual acuity after macular hole closure.

PubMed

Zhang, Peng; Shang, Qingli; Ma, Jingxue; Hao, Yuhua; Ye, Cunxi

2017-03-20

To determine the correlation between the preoperative basal diameter of macular hole, the postoperative area of high autofluorescence (AF) in macula, and visual acuity in full-thickness macular hole. Forty-nine patients with full-thickness macular hole who underwent vitrectomy and C3F8 filling were reviewed. The preoperative diameter of macular hole, the 6 months postoperative area of high AF in macula if it existed, the length of inner segment/outer segment (IS/OS) defect, and visual acuity were obtained. The correlation between them was determined. At postoperative 6 months, the rate of high AF in macula was 63.3%. There were statistical differences between with and without high AF groups in postoperative best-corrected visual acuity (BCVA) (t = -2.751, p = 0.008), preoperative basal diameter of macular hole (t = -4.946, p = 0.00001), and postoperative length of IS/OS defect (t = -8.351, p<0.00001). Simple linear regression analysis showed high positive correlations between preoperative basal diameter of macular hole and area of high AF (p<0.00001, r = 0.893), postoperative length of IS/OS defect and area of high fundus AF (FAF) (p<0.00001, r = 0.779), and negative correlations between area of high AF and postoperative BCVA (p = 0.037, r = 0.375). There was low correlation between diameter of macular hole and postoperative BCVA (p = 0.112). The preoperative basal diameter of macular hole and postoperative length of IS/OS defect decides the postoperative area of high AF in macula to some degree, and the postoperative area of high AF in macula can be an evaluating indicator for poor macular function recovery.

Blob-hole correlation model for edge turbulence and comparisons with NSTX gas puff imaging data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myra, J. R.; Zweben, S. J.; Russell, D. A.

We report that gas puff imaging (GPI) observations made in NSTX [Zweben S J, et al., 2017 Phys. Plasmas 24 102509] have revealed two-point spatial correlations of edge and scrape-off layer turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlationmore » patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracking of the highest and lowest values (extrema) of the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Finally, other properties of the experimentally observed extrema are discussed.« less

Blob-hole correlation model for edge turbulence and comparisons with NSTX gas puff imaging data

DOE PAGES

Myra, J. R.; Zweben, S. J.; Russell, D. A.

2018-05-15

We report that gas puff imaging (GPI) observations made in NSTX [Zweben S J, et al., 2017 Phys. Plasmas 24 102509] have revealed two-point spatial correlations of edge and scrape-off layer turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlationmore » patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracking of the highest and lowest values (extrema) of the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Finally, other properties of the experimentally observed extrema are discussed.« less

Ultrafast photophysics of transition metal complexes.

PubMed

Chergui, Majed

2015-03-17

The properties of transition metal complexes are interesting not only for their potential applications in solar energy conversion, OLEDs, molecular electronics, biology, photochemistry, etc. but also for their fascinating photophysical properties that call for a rethinking of fundamental concepts. With the advent of ultrafast spectroscopy over 25 years ago and, more particularly, with improvements in the past 10-15 years, a new area of study was opened that has led to insightful observations of the intramolecular relaxation processes such as internal conversion (IC), intersystem crossing (ISC), and intramolecular vibrational redistribution (IVR). Indeed, ultrafast optical spectroscopic tools, such as fluorescence up-conversion, show that in many cases, intramolecular relaxation processes can be extremely fast and even shorter than time scales of vibrations. In addition, more and more examples are appearing showing that ultrafast ISC rates do not scale with the magnitude of the metal spin-orbit coupling constant, that is, that there is no heavy-atom effect on ultrafast time scales. It appears that the structural dynamics of the system and the density of states play a crucial role therein. While optical spectroscopy delivers an insightful picture of electronic relaxation processes involving valence orbitals, the photophysics of metal complexes involves excitations that may be centered on the metal (called metal-centered or MC) or the ligand (called ligand-centered or LC) or involve a transition from one to the other or vice versa (called MLCT or LMCT). These excitations call for an element-specific probe of the photophysics, which is achieved by X-ray absorption spectroscopy. In this case, transitions from core orbitals to valence orbitals or higher allow probing the electronic structure changes induced by the optical excitation of the valence orbitals, while also delivering information about the geometrical rearrangement of the neighbor atoms around the atom of

Primordial black holes in globular clusters

NASA Technical Reports Server (NTRS)

Sigurdsson, Steinn; Hernquist, Lars

1993-01-01

It has recently been recognized that significant numbers of medium-mass back holes (of order 10 solar masses) should form in globular clusters during the early stages of their evolution. Here we explore the dynamical and observational consequences of the presence of such a primordial black-hole population in a globular cluster. The holes initially segregate to the cluster cores, where they form binary and multiple black-hole systems. The subsequent dynamical evolution of the black-hole population ejects most of the holes on a relatively short timescale: a typical cluster will retain between zero and four black holes in its core, and possibly a few black holes in its halo. The presence of binary, triple, and quadruple black-hole systems in cluster cores will disrupt main-sequence and giant stellar binaries; this may account for the observed anomalies in the distribution of binaries in globular clusters. Furthermore, tidal interactions between a multiple black-hole system and a red giant star can remove much of the red giant's stellar envelope, which may explain the puzzling absence of larger red giants in the cores of some very dense clusters.

Ultrafast Hot Carrier Dynamics in GaN and Its Impact on the Efficiency Droop.

PubMed

Jhalani, Vatsal A; Zhou, Jin-Jian; Bernardi, Marco

2017-08-09

GaN is a key material for lighting technology. Yet, the carrier transport and ultrafast dynamics that are central in GaN light-emitting devices are not completely understood. We present first-principles calculations of carrier dynamics in GaN, focusing on electron-phonon (e-ph) scattering and the cooling and nanoscale dynamics of hot carriers. We find that e-ph scattering is significantly faster for holes compared to electrons and that for hot carriers with an initial 0.5-1 eV excess energy, holes take a significantly shorter time (∼0.1 ps) to relax to the band edge compared to electrons, which take ∼1 ps. The asymmetry in the hot carrier dynamics is shown to originate from the valence band degeneracy, the heavier effective mass of holes compared to electrons, and the details of the coupling to different phonon modes in the valence and conduction bands. We show that the slow cooling of hot electrons and their long ballistic mean free paths (over 3 nm at room temperature) are a possible cause of efficiency droop in GaN light-emitting diodes. Taken together, our work sheds light on the ultrafast dynamics of hot carriers in GaN and the nanoscale origin of efficiency droop.

Photonic crystal fiber technology for compact fiber-delivered high-power ultrafast fiber lasers

NASA Astrophysics Data System (ADS)

Triches, Marco; Michieletto, Mattia; Johansen, Mette M.; Jakobsen, Christian; Olesen, Anders S.; Papior, Sidsel R.; Kristensen, Torben; Bondue, Magalie; Weirich, Johannes; Alkeskjold, Thomas T.

2018-02-01

Photonic crystal fiber (PCF) technology has radically impacted the scientific and industrial ultrafast laser market. Reducing platform dimensions are important to decrease cost and footprint while maintaining high optical efficiency. We present our recent work on short 85 μm core ROD-type fiber amplifiers that maintain single-mode performance and excellent beam quality. Robust long-term performance at 100 W average power and 250 kW peak power in 20 ps pulses at 1030 nm wavelength is presented, exceeding 500 h with stable performance in terms of both polarization and power. In addition, we present our recent results on hollow-core ultrafast fiber delivery maintaining high beam quality and polarization purity.

RosettaHoles: rapid assessment of protein core packing for structure prediction, refinement, design, and validation.

PubMed

Sheffler, Will; Baker, David

2009-01-01

We present a novel method called RosettaHoles for visual and quantitative assessment of underpacking in the protein core. RosettaHoles generates a set of spherical cavity balls that fill the empty volume between atoms in the protein interior. For visualization, the cavity balls are aggregated into contiguous overlapping clusters and small cavities are discarded, leaving an uncluttered representation of the unfilled regions of space in a structure. For quantitative analysis, the cavity ball data are used to estimate the probability of observing a given cavity in a high-resolution crystal structure. RosettaHoles provides excellent discrimination between real and computationally generated structures, is predictive of incorrect regions in models, identifies problematic structures in the Protein Data Bank, and promises to be a useful validation tool for newly solved experimental structures.

RosettaHoles: Rapid assessment of protein core packing for structure prediction, refinement, design, and validation

PubMed Central

Sheffler, Will; Baker, David

2009-01-01

We present a novel method called RosettaHoles for visual and quantitative assessment of underpacking in the protein core. RosettaHoles generates a set of spherical cavity balls that fill the empty volume between atoms in the protein interior. For visualization, the cavity balls are aggregated into contiguous overlapping clusters and small cavities are discarded, leaving an uncluttered representation of the unfilled regions of space in a structure. For quantitative analysis, the cavity ball data are used to estimate the probability of observing a given cavity in a high-resolution crystal structure. RosettaHoles provides excellent discrimination between real and computationally generated structures, is predictive of incorrect regions in models, identifies problematic structures in the Protein Data Bank, and promises to be a useful validation tool for newly solved experimental structures. PMID:19177366

Integrated sequence stratigraphy of the postimpact sediments from the Eyreville core holes, Chesapeake Bay impact structure inner basin

USGS Publications Warehouse

Browning, J.V.; Miller, K.G.; McLaughlin, P.P.; Edwards, L.E.; Kulpecz, A.A.; Powars, D.S.; Wade, B.S.; Feigenson, M.D.; Wright, J.D.

2009-01-01

The Eyreville core holes provide the first continuously cored record of postimpact sequences from within the deepest part of the central Chesapeake Bay impact crater. We analyzed the upper Eocene to Pliocene postimpact sediments from the Eyreville A and C core holes for lithology (semiquantitative measurements of grain size and composition), sequence stratigraphy, and chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, and planktonic foraminifers); age resolution is approximately ??0.5 Ma for early Miocene sequences and approximately ??1.0 Ma for younger and older sequences. Eocene-lower Miocene sequences are subtle, upper middle to lower upper Miocene sequences are more clearly distinguished, and upper Miocene- Pliocene sequences display a distinct facies pattern within sequences. We recognize two upper Eocene, two Oligocene, nine Miocene, three Pliocene, and one Pleistocene sequence and correlate them with those in New Jersey and Delaware. The upper Eocene through Pleistocene strata at Eyreville record changes from: (1) rapidly deposited, extremely fi ne-grained Eocene strata that probably represent two sequences deposited in a deep (>200 m) basin; to (2) highly dissected Oligocene (two very thin sequences) to lower Miocene (three thin sequences) with a long hiatus; to (3) a thick, rapidly deposited (43-73 m/Ma), very fi ne-grained, biosiliceous middle Miocene (16.5-14 Ma) section divided into three sequences (V5-V3) deposited in middle neritic paleoenvironments; to (4) a 4.5-Ma-long hiatus (12.8-8.3 Ma); to (5) sandy, shelly upper Miocene to Pliocene strata (8.3-2.0 Ma) divided into six sequences deposited in shelf and shoreface environments; and, last, to (6) a sandy middle Pleistocene paralic sequence (~400 ka). The Eyreville cores thus record the fi lling of a deep impact-generated basin where the timing of sequence boundaries is heavily infl uenced by eustasy. ?? 2009 The Geological

Tuning ultrafast electron injection dynamics at organic-graphene/metal interfaces.

PubMed

Ravikumar, Abhilash; Kladnik, Gregor; Müller, Moritz; Cossaro, Albano; Bavdek, Gregor; Patera, Laerte L; Sánchez-Portal, Daniel; Venkataraman, Latha; Morgante, Alberto; Brivio, Gian Paolo; Cvetko, Dean; Fratesi, Guido

2018-05-03

We compare the ultrafast charge transfer dynamics of molecules on epitaxial graphene and bilayer graphene grown on Ni(111) interfaces through first principles calculations and X-ray resonant photoemission spectroscopy. We use 4,4'-bipyridine as a prototypical molecule for these explorations as the energy level alignment of core-excited molecular orbitals allows ultrafast injection of electrons from a substrate to a molecule on a femtosecond timescale. We show that the ultrafast injection of electrons from the substrate to the molecule is ∼4 times slower on weakly coupled bilayer graphene than on epitaxial graphene. Through our experiments and calculations, we can attribute this to a difference in the density of states close to the Fermi level between graphene and bilayer graphene. We therefore show how graphene coupling with the substrate influences charge transfer dynamics between organic molecules and graphene interfaces.

Dating the Vostok ice core record by importing the Devils Hole chronology

USGS Publications Warehouse

Landwehr, J.M.; Winograd, I.J.

2001-01-01

The development of an accurate chronology for the Vostok record continues to be an open research question because these invaluable ice cores cannot be dated directly. Depth-to-age relationships have been developed using many different approaches, but published age estimates are inconsistent, even for major paleoclimatic events. We have developed a chronology for the Vostok deuterium paleotemperature record using a simple and objective algorithm to transfer ages of major paleoclimatic events from the radiometrically dated 500,000-year ??18O-paleotemperature record from Devils Hole, Nevada. The method is based only on a strong inference that major shifts in paleotemperature recorded at both locations occurred synchronously, consistent with an atmospheric teleconnection. The derived depth-to-age relationship conforms with the physics of ice compaction, and internally produces ages for climatic events 5.4 and 11.24 which are consistent with the externally assigned ages that the Vostok team needed to assume in order to derive their most recent chronology, GT4. Indeed, the resulting V-DH chronology is highly correlated with GT4 because of the unexpected correspondence even in the timing of second-order climatic events that were not constrained by the algorithm. Furthermore, the algorithm developed herein is not specific to this problem; rather, the procedure can be used whenever two paleoclimate records are proxies for the same physical phenomenon, and paleoclimatic conditions forcing the two records can be considered to have occurred contemporaneously. The ability of the algorithm to date the East Antarctic Dome Fuji core is also demonstrated.

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE PAGES

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua; ...

2017-11-30

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Resolving ultrafast exciton migration in organic solids at the nanoscale

NASA Astrophysics Data System (ADS)

Ginsberg, Naomi

The migration of Frenkel excitons, tightly-bound electron-hole pairs, in photosynthesis and in organic semiconducting films is critical to the efficiency of natural and artificial light harvesting. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton migration lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore. By combining the ultrafast super-resolved measurements with exciton hopping simulations we furthermore specify the nature (in addition to the extent) of exciton migration as a function of the intrinsic and ensemble chromophore energy scales that determine a spatio-energetic landscape for migration. In collaboration with: Samuel Penwell, Lucas Ginsberg, University of California, Berkeley and Rodrigo Noriega University of Utah.

Improving the clinical correlation of multiple sclerosis black hole volume change by paired-scan analysis.

PubMed

Tam, Roger C; Traboulsee, Anthony; Riddehough, Andrew; Li, David K B

2012-01-01

The change in T 1-hypointense lesion ("black hole") volume is an important marker of pathological progression in multiple sclerosis (MS). Black hole boundaries often have low contrast and are difficult to determine accurately and most (semi-)automated segmentation methods first compute the T 2-hyperintense lesions, which are a superset of the black holes and are typically more distinct, to form a search space for the T 1w lesions. Two main potential sources of measurement noise in longitudinal black hole volume computation are partial volume and variability in the T 2w lesion segmentation. A paired analysis approach is proposed herein that uses registration to equalize partial volume and lesion mask processing to combine T 2w lesion segmentations across time. The scans of 247 MS patients are used to compare a selected black hole computation method with an enhanced version incorporating paired analysis, using rank correlation to a clinical variable (MS functional composite) as the primary outcome measure. The comparison is done at nine different levels of intensity as a previous study suggests that darker black holes may yield stronger correlations. The results demonstrate that paired analysis can strongly improve longitudinal correlation (from -0.148 to -0.303 in this sample) and may produce segmentations that are more sensitive to clinically relevant changes.

The ultrafast dynamics and conductivity of photoexcited graphene at different Fermi energies

PubMed Central

Turchinovich, Dmitry; Kläui, Mathias; Hendry, Euan; Polini, Marco

2018-01-01

For many of the envisioned optoelectronic applications of graphene, it is crucial to understand the subpicosecond carrier dynamics immediately following photoexcitation and the effect of photoexcitation on the electrical conductivity—the photoconductivity. Whereas these topics have been studied using various ultrafast experiments and theoretical approaches, controversial and incomplete explanations concerning the sign of the photoconductivity, the occurrence and significance of the creation of additional electron-hole pairs, and, in particular, how the relevant processes depend on Fermi energy have been put forward. We present a unified and intuitive physical picture of the ultrafast carrier dynamics and the photoconductivity, combining optical pump–terahertz probe measurements on a gate-tunable graphene device, with numerical calculations using the Boltzmann equation. We distinguish two types of ultrafast photo-induced carrier heating processes: At low (equilibrium) Fermi energy (EF ≲ 0.1 eV for our experiments), broadening of the carrier distribution involves interband transitions (interband heating). At higher Fermi energy (EF ≳ 0.15 eV), broadening of the carrier distribution involves intraband transitions (intraband heating). Under certain conditions, additional electron-hole pairs can be created [carrier multiplication (CM)] for low EF, and hot carriers (hot-CM) for higher EF. The resultant photoconductivity is positive (negative) for low (high) EF, which in our physical picture, is explained using solely electronic effects: It follows from the effect of the heated carrier distributions on the screening of impurities, consistent with the DC conductivity being mostly due to impurity scattering. The importance of these insights is highlighted by a discussion of the implications for graphene photodetector applications. PMID:29756035

PREFACE: Ultrafast biophotonics Ultrafast biophotonics

NASA Astrophysics Data System (ADS)

Gu, Min; Reid, Derryck; Ben-Yakar, Adela

2010-08-01

The use of light to explore biology can be traced to the first observations of tissue made with early microscopes in the mid-seventeenth century, and has today evolved into the discipline which we now know as biophotonics. This field encompasses a diverse range of activities, each of which shares the common theme of exploiting the interaction of light with biological material. With the rapid advancement of ultrafast optical technologies over the last few decades, ultrafast lasers have increasingly found applications in biophotonics, to the extent that the distinctive new field of ultrafast biophotonics has now emerged, where robust turnkey ultrafast laser systems are facilitating cutting-edge studies in the life sciences to take place in everyday laboratories. The broad spectral bandwidths, precision timing resolution, low coherence and high peak powers of ultrafast optical pulses provide unique opportunities for imaging and manipulating biological systems. Time-resolved studies of bio-molecular dynamics exploit the short pulse durations from such lasers, while other applications such as optical coherence tomography benefit from the broad optical bandwidths possible by using super-continuum generation and additionally allowing for high speed imaging with speeds as high as 47 000 scans per second. Continuing progress in laser-system technology is accelerating the adoption of ultrafast techniques across the life sciences, both in research laboratories and in clinical applications, such as laser-assisted in situ keratomileusis (LASIK) eye surgery. Revolutionizing the field of optical microscopy, two-photon excitation fluorescence (TPEF) microscopy has enabled higher spatial resolution with improved depth penetration into biological specimens. Advantages of this nonlinear optical process include: reduced photo-interactions, allowing for extensive imaging time periods; simultaneously exciting multiple fluorescent molecules with only one excitation wavelength; and

Elucidating ultrafast electron dynamics at surfaces using extreme ultraviolet (XUV) reflection-absorption spectroscopy.

PubMed

Biswas, Somnath; Husek, Jakub; Baker, L Robert

2018-04-24

Here we review the recent development of extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy. This method combines the benefits of X-ray absorption spectroscopy, such as element, oxidation, and spin state specificity, with surface sensitivity and ultrafast time resolution, having a probe depth of only a few nm and an instrument response less than 100 fs. Using this technique we investigated the ultrafast electron dynamics at a hematite (α-Fe2O3) surface. Surface electron trapping and small polaron formation both occur in 660 fs following photoexcitation. These kinetics are independent of surface morphology indicating that electron trapping is not mediated by defects. Instead, small polaron formation is proposed as the likely driving force for surface electron trapping. We also show that in Fe2O3, Co3O4, and NiO, band gap excitation promotes electron transfer from O 2p valence band states to metal 3d conduction band states. In addition to detecting the photoexcited electron at the metal M2,3-edge, the valence band hole is directly observed as transient signal at the O L1-edge. The size of the resulting charge transfer exciton is on the order of a single metal-oxygen bond length. Spectral shifts at the O L1-edge correlate with metal-oxygen bond covalency, confirming the relationship between valence band hybridization and the overpotential for water oxidation. These examples demonstrate the unique ability to measure ultrafast electron dynamics with element and chemical state resolution using XUV-RA spectroscopy. Accordingly, this method is poised to play an important role to reveal chemical details of previously unseen surface electron dynamics.

Quantum information cannot be completely hidden in correlations: implications for the black-hole information paradox.

PubMed

Braunstein, Samuel L; Pati, Arun K

2007-02-23

Can quantum-information theory shed light on black-hole evaporation? By entangling the in-fallen matter with an external system we show that the black-hole information paradox becomes more severe, even for cosmologically sized black holes. We rule out the possibility that the information about the in-fallen matter might hide in correlations between the Hawking radiation and the internal states of the black hole. As a consequence, either unitarity or Hawking's semiclassical predictions must break down. Any resolution of the black-hole information crisis must elucidate one of these possibilities.

Feasibility of UltraFast Doppler in Post-operative Evaluation of Hepatic Artery in Recipients following Liver Transplantation.

PubMed

Kim, Se-Young; Kim, Kyoung Won; Choi, Sang Hyun; Kwon, Jae Hyun; Song, Gi-Won; Kwon, Heon-Ju; Yun, Young Ju; Lee, Jeongjin; Lee, Sung-Gyu

2017-11-01

To determine the feasibility of using UltraFast Doppler in post-operative evaluation of the hepatic artery (HA) after liver transplantation (LT), we evaluated 283 simultaneous conventional and UltraFast Doppler sessions in 126 recipients over a 2-mo period after LT, using an Aixplorer scanner The Doppler indexes of the HA (peak systolic velocity [PSV], end-diastolic velocity [EDV], resistive index [RI] and systolic acceleration time [SAT]) by retrospective analysis of retrieved waves from UltraFast Doppler clips were compared with those obtained by conventional spectral Doppler. Correlation, performance in diagnosing the pathologic wave, examination time and reproducibility were evaluated. The PSV, EDV, RI and SAT of spectral and UltraFast Doppler measurements exhibited excellent correlation with favorable diagnostic performance. During the bedside examination, the mean time spent for UltraFast clip storing was significantly shorter than that for conventional Doppler US measurements. Both conventional and UltraFast Doppler exhibited good to excellent inter-analysis consistency. In conclusion, compared with conventional spectral Doppler, UltraFast Doppler values correlated excellently and yielded acceptable pathologic wave diagnostic performance with reduced examination time at the bedside and excellent reproducibility. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Sediment cores from kettle holes in NE Germany reveal recent impacts of agriculture.

PubMed

Kleeberg, Andreas; Neyen, Marielle; Schkade, Uwe-Karsten; Kalettka, Thomas; Lischeid, Gunnar

2016-04-01

Glacial kettle holes in young moraine regions receive abundant terrigenous material from their closed catchments. Core chronology and sediment accumulation were determined for two semi-permanent kettle holes, designated RG and KR, on arable land close to the villages of Rittgarten and Kraatz, respectively, in Uckermark, NE Germany. Core dating ((210)Pb, (137)Cs) revealed variable sediment accretion rates through time (RG 0.4-23.1 mm a(-1); KR 0.2-35.5 mm a(-1)), with periods of high accumulation corresponding to periods of intensive agricultural activity and consequent erosional inputs from catchments. Sediment composition (C, N, P, S, K, Ca, Fe, Mn, Zn, Cu, Mo, Pb, Cd, Zr) was used to determine sediment source and input processes. At RG, annual P input increased from 0.65 kg ha(-1) in the early nineteenth century to 1.67 kg ha(-1) by 2013. At KR, P input increased from 0.6 to 4.1 kg ha(-1) over the last century. There was a concurrent increase in Fe input in both water bodies. Thus, Fe/P ratios showed no temporal trend and did not differ between RG (18.5) and KR (18.4), indicating similar P mobility. At RG, the S/Fe ratio increased from 0.4 to 2.3, indicating more iron sulphides and thus higher P availability, coinciding with high coverage of duckweed (Spirodela polyrhiza (L.)) and soft hornwort (Ceratophyllum submersum L.). At KR, however, this ratio remained low and relatively unchanged (0.3 ± 0.4), indicating more efficient Fe-P binding and lower hydrophyte productivity. Trends in sediment composition indicate a shift towards eutrophication in both kettle holes, but with differences in timing and magnitude. Other morphologically similar kettle holes in NE Germany that are prone to erosion could have been similarly impacted but may differ in the extent of sediment infilling and degradation of their ecological functions.

Ultrafast Hole Trapping and Relaxation Dynamics in p-Type CuS Nanodisks

DOE PAGES

Ludwig, John; An, Li; Pattengale, Brian; ...

2015-06-22

CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of transient optical (OTA) and X-ray (XTA) absorption spectroscopy. OTA results show that the broad transient absorption in the visible region is attributed to the photoinduced hot and trapped holes. The hole trapping process occurs on a subpicosecond time scale, followed by carrier recombination (~100 ps). The nature of the hole trapping sites,more » revealed by XTA, is characteristic of S or organic ligands on the surface of CuS NDs. Lastly, these results not only suggest the possibility to control the hole dynamics by tuning the surface chemistry of CuS but also represent the first time observation of hole dynamics in semiconductor nanocrystals using XTA.« less

Size-Independent Exciton Localization Efficiency in Colloidal CdSe/CdS Core/Crown Nanosheet Type-I Heterostructures.

PubMed

Li, Qiuyang; Wu, Kaifeng; Chen, Jinquan; Chen, Zheyuan; McBride, James R; Lian, Tianquan

2016-03-22

CdSe/CdS core/crown nanoplatelet type I heterostructures are a class of two-dimensional materials with atomically precise thickness and many potential optoelectronic applications. It remains unclear how the precise thickness and lack of energy disorder affect the properties of exciton transport in these materials. By steady-state photoluminescence excitation spectroscopy and ultrafast transient absorption spectroscopy, we show that in five CdSe/CdS core/crown structures with the same core and increasing crown size (with thickness of ∼1.8 nm, width of ∼11 nm, and length from 20 to 40 nm), the crown-to-core exciton localization efficiency is independent of crown size and increases with photon energy above the band edge (from 70% at 400 nm to ∼100% at 370 nm), while the localization time increases with the crown size. These observations can be understood by a model that accounts for the competition of in-plane exciton diffusion and selective hole trapping at the core/crown interface. Our findings suggest that the exciton localization efficiency can be further improved by reducing interfacial defects.

Core-Cutoff Tool

NASA Technical Reports Server (NTRS)

Gheen, Darrell

2007-01-01

A tool makes a cut perpendicular to the cylindrical axis of a core hole at a predetermined depth to free the core at that depth. The tool does not damage the surrounding material from which the core was cut, and it operates within the core-hole kerf. Coring usually begins with use of a hole saw or a hollow cylindrical abrasive cutting tool to make an annular hole that leaves the core (sometimes called the plug ) in place. In this approach to coring as practiced heretofore, the core is removed forcibly in a manner chosen to shear the core, preferably at or near the greatest depth of the core hole. Unfortunately, such forcible removal often damages both the core and the surrounding material (see Figure 1). In an alternative prior approach, especially applicable to toxic or fragile material, a core is formed and freed by means of milling operations that generate much material waste. In contrast, the present tool eliminates the damage associated with the hole-saw approach and reduces the extent of milling operations (and, hence, reduces the waste) associated with the milling approach. The present tool (see Figure 2) includes an inner sleeve and an outer sleeve and resembles the hollow cylindrical tool used to cut the core hole. The sleeves are thin enough that this tool fits within the kerf of the core hole. The inner sleeve is attached to a shaft that, in turn, can be attached to a drill motor or handle for turning the tool. This tool also includes a cutting wire attached to the distal ends of both sleeves. The cutting wire is long enough that with sufficient relative rotation of the inner and outer sleeves, the wire can cut all the way to the center of the core. The tool is inserted in the kerf until its distal end is seated at the full depth. The inner sleeve is then turned. During turning, frictional drag on the outer core pulls the cutting wire into contact with the core. The cutting force of the wire against the core increases with the tension in the wire and

A 17-billion-solar-mass black hole in a group galaxy with a diffuse core.

PubMed

Thomas, Jens; Ma, Chung-Pei; McConnell, Nicholas J; Greene, Jenny E; Blakeslee, John P; Janish, Ryan

2016-04-21

Quasars are associated with and powered by the accretion of material onto massive black holes; the detection of highly luminous quasars with redshifts greater than z = 6 suggests that black holes of up to ten billion solar masses already existed 13 billion years ago. Two possible present-day 'dormant' descendants of this population of 'active' black holes have been found in the galaxies NGC 3842 and NGC 4889 at the centres of the Leo and Coma galaxy clusters, which together form the central region of the Great Wall--the largest local structure of galaxies. The most luminous quasars, however, are not confined to such high-density regions of the early Universe; yet dormant black holes of this high mass have not yet been found outside of modern-day rich clusters. Here we report observations of the stellar velocity distribution in the galaxy NGC 1600--a relatively isolated elliptical galaxy near the centre of a galaxy group at a distance of 64 megaparsecs from Earth. We use orbit superposition models to determine that the black hole at the centre of NGC 1600 has a mass of 17 billion solar masses. The spatial distribution of stars near the centre of NGC 1600 is rather diffuse. We find that the region of depleted stellar density in the cores of massive elliptical galaxies extends over the same radius as the gravitational sphere of influence of the central black holes, and interpret this as the dynamical imprint of the black holes.

Direct Characterization of Ultrafast Energy-Time Entangled Photon Pairs.

PubMed

MacLean, Jean-Philippe W; Donohue, John M; Resch, Kevin J

2018-02-02

Energy-time entangled photons are critical in many quantum optical phenomena and have emerged as important elements in quantum information protocols. Entanglement in this degree of freedom often manifests itself on ultrafast time scales, making it very difficult to detect, whether one employs direct or interferometric techniques, as photon-counting detectors have insufficient time resolution. Here, we implement ultrafast photon counters based on nonlinear interactions and strong femtosecond laser pulses to probe energy-time entanglement in this important regime. Using this technique and single-photon spectrometers, we characterize all the spectral and temporal correlations of two entangled photons with femtosecond resolution. This enables the witnessing of energy-time entanglement using uncertainty relations and the direct observation of nonlocal dispersion cancellation on ultrafast time scales. These techniques are essential to understand and control the energy-time degree of freedom of light for ultrafast quantum optics.

Core sample extractor

NASA Technical Reports Server (NTRS)

Akins, James; Cobb, Billy; Hart, Steve; Leaptrotte, Jeff; Milhollin, James; Pernik, Mark

1989-01-01

The problem of retrieving and storing core samples from a hole drilled on the lunar surface is addressed. The total depth of the hole in question is 50 meters with a maximum diameter of 100 millimeters. The core sample itself has a diameter of 60 millimeters and will be two meters in length. It is therefore necessary to retrieve and store 25 core samples per hole. The design utilizes a control system that will stop the mechanism at a certain depth, a cam-linkage system that will fracture the core, and a storage system that will save and catalogue the cores to be extracted. The Rod Changer and Storage Design Group will provide the necessary tooling to get into the hole as well as to the core. The mechanical design for the cam-linkage system as well as the conceptual design of the storage device are described.

Ultrafast Charge Transfer in Nickel Phthalocyanine Probed by Femtosecond Raman-Induced Kerr Effect Spectroscopy

PubMed Central

2015-01-01

The recently developed technique of femtosecond stimulated Raman spectroscopy, and its variant, femtosecond Raman-induced Kerr effect spectroscopy (FRIKES), offer access to ultrafast excited-state dynamics via structurally specific vibrational spectra. We have used FRIKES to study the photoexcitation dynamics of nickel(II) phthalocyanine with eight butoxy substituents, NiPc(OBu)8. NiPc(OBu)8 is reported to have a relatively long-lived ligand-to-metal charge-transfer (LMCT) state, an essential characteristic for efficient electron transfer in photocatalysis. Following photoexcitation, vibrational transitions in the FRIKES spectra, assignable to phthalocyanine ring modes, evolve on the femtosecond to picosecond time scales. Correlation of ring core size with the frequency of the ν10 (asymmetric C–N stretching) mode confirms the identity of the LMCT state, which has a ∼500 ps lifetime, as well as that of a precursor d-d excited state. An even earlier (∼0.2 ps) transient is observed and tentatively assigned to a higher-lying Jahn–Teller-active LMCT state. This study illustrates the power of FRIKES spectroscopy in elucidating ultrafast molecular dynamics. PMID:24841906

Stabilized soliton self-frequency shift and 0.1- PHz sideband generation in a photonic-crystal fiber with an air-hole-modified core.

PubMed

Liu, Bo-Wen; Hu, Ming-Lie; Fang, Xiao-Hui; Li, Yan-Feng; Chai, Lu; Wang, Ching-Yue; Tong, Weijun; Luo, Jie; Voronin, Aleksandr A; Zheltikov, Aleksei M

2008-09-15

Fiber dispersion and nonlinearity management strategy based on a modification of a photonic-crystal fiber (PCF) core with an air hole is shown to facilitate optimization of PCF components for a stable soliton frequency shift and subpetahertz sideband generation through four-wave mixing. Spectral recoil of an optical soliton by a red-shifted dispersive wave, generated through a soliton instability induced by high-order fiber dispersion, is shown to stabilize the soliton self-frequency shift in a highly nonlinear PCF with an air-hole-modified core relative to pump power variations. A fiber with a 2.3-microm-diameter core modified with a 0.9-microm-diameter air hole is used to demonstrate a robust soliton self-frequency shift of unamplified 50-fs Ti: sapphire laser pulses to a central wavelength of about 960 nm, which remains insensitive to variations in the pump pulse energy within the range from 60 to at least 100 pJ. In this regime of frequency shifting, intense high- and low-frequency branches of dispersive wave radiation are simultaneously observed in the spectrum of PCF output. An air-hole-modified-core PCF with appropriate dispersion and nonlinearity parameters is shown to provide efficient four-wave mixing, giving rise to Stokes and anti-Stokes sidebands whose frequency shift relative to the pump wavelength falls within the subpetahertz range, thus offering an attractive source for nonlinear Raman microspectroscopy.

Density of basalt core from Hilo drill hole, Hawaii

USGS Publications Warehouse

Moore, J.G.

2001-01-01

Density measurements of 1600 samples of core from 889 to 3097 m depth below sea level in the Hawaii Scientific Drilling Program hole near Hilo, Hawaii show marked differences between the basaltic rock types and help define stratigraphy in the hole. Water-saturated densities of subaerial lava flows (occurring above 1079 m depth) have the broadest range because of the large density variation within a single lava flow. Water-saturated densities commonly range from 2.0 to 3.0 with an average of 2.55 ?? 0.24 g/cc. Dikes and sills range from 2.8 to 3.1 g/cc). Densities of hyaloclastite commonly range from 2.3 to 2.7, with an overall average of about 2.5 g/cc. The low-density of most hyaloclastite is due primarily to palagonitization of abundant glass and presence of secondary minerals in the interstices between fragments. Four principal zones of pillow lava, separated by hyaloclastite, occur in the drill core. The shallowest (1983-2136 m) is paradoxically the densest, averaging 3.01 ?? 0.10 g/cc. The second (2234-2470 m) is decidedly the lightest, averaging 2.67 ?? 0.13 g/cc. The third (2640-2790 m) and fourth (2918-bottom at 3097 m) are high, averaging 2.89 ?? 0.17 and 2.97 ?? 0.08 g/cc, respectively. The first pillow zone includes degassed pillows i.e. lava erupted on land that flowed into the sea. These pillows are poor in vesicles, because the subaerial, one-atmosphere vesicles were compressed when the flow descended to deeper water and higher pressure. The second (low-density, non-degassed) pillow zone is the most vesicle-rich, apparently because it was erupted subaqueously at a shallow depth. The higher densities of the third and fourth zones result from a low vesicularity of only a few percent and an olivine content averaging more than 5% for the third zone and about 10% for the fourth zone. The uppermost hyaloclastite extending about 400 m below the bottom of the subaerial basalt is poorly cemented and absorbs up to 6 wt% of water when immersed. Progressing

Carotid Artery Stiffness Assessment by Ultrafast Ultrasound Imaging: Feasibility and Potential Influencing Factors.

PubMed

Pan, Fu-Shun; Yu, Liang; Luo, Jia; Wu, Ri-Dong; Xu, Ming; Liang, Jin-Yu; Zheng, Yan-Ling; Xie, Xiao-Yan

2018-04-19

To evaluate the feasibility of the ultrafast ultrasound pulsed wave velocity (PWV) for carotid stiffness assessment and potential influencing factors. Ultrafast PWV measurements of 442 carotid arteries in 162 consecutive patients (patient group) and 66 healthy volunteers (control group) were performed. High- and very high-frequency transducers were used in 110 carotid segments. The ultrafast PWVs at the beginning and end of systole were automatically measured. The correlations between the intima-media thickness (IMT) and ultrafast PWV and the equipment and carotid factors influencing the utility of ultrafast PWV were analyzed. Each ultrafast PWV acquisition was completed within 1 minute. The intraobserver variability showed mean differences ± SD of 0.12 ± 1.28 m/s for the PWV before systole and 0.06 ± 1.30 m/s for the PWV at the end of systole. Ultrafast PWV measurements were more likely obtained with the very high- frequency transducer when the IMT was less than 1.5 mm (P < .05). A generalized linear mixed-effects model analysis showed that the very high-frequency transducer had a greater ability to obtain a valid carotid ultrafast PWV measurement with an IMT of less than 1.5 mm (P < .05). The IMT was positively correlated with the PWV before systole and at the end of systole (r = 0.207-0.771; all P < .05) in the control group, patient group, and carotid subgroup with an IMT of less than 1.5 mm. A multiple regression analysis showed that the IMT and plaque were important independent factors in predicting failure of the ultrafast PWV (P < .001). The ultrafast PWV is an effective and user-friendly method for evaluating carotid stiffness. The IMT and transducer type are factors influencing the ability to obtain an ultrafast PWV measurement. © 2018 by the American Institute of Ultrasound in Medicine.

4-D ultrafast shear-wave imaging.

PubMed

Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael

2015-06-01

Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE.

Gravitational Wave Signatures in Black Hole Forming Core Collapse

NASA Astrophysics Data System (ADS)

Cerdá-Durán, Pablo; DeBrye, Nicolas; Aloy, Miguel A.; Font, José A.; Obergaulinger, Martin

2013-12-01

We present general relativistic numerical simulations of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). By analyzing the spectrogram of our simulations we are able to identify the frequencies associated with the presence of g-modes and with the SASI motions at the PNS surface. We note that the gravitational waves emitted reach large enough amplitudes to be detected with third-generation detectors such as the Einstein Telescope within a Virgo Cluster volume at rates <~ 0.1 yr-1.

Static Holes in Geometrically Frustrated Bow Tie Ladder

NASA Astrophysics Data System (ADS)

Martins, George; Brenig, Wolfram

2007-03-01

Doping of the geometrically frustrated bow-tie spin ladder with static holes is investigated by a complementary approach using exact diagonalization and hard-core quantum dimers. Results for the thermodynamics in the undoped case, the singlet density of states, the hole-binding energy, and the spin correlations will be presented. We find that the static holes polarize their vicinity by a localization of singlets in order to reduce the frustration. As a consequence the singlet polarization cloud induces short range repulsive forces between the holes with oscillatory longer range behavior. For those systems we have studied, most results for the quantum dimer approach are found to be qualitatively if not quantitatively in agreement with exact diagonalization. The ground state of the undoped system is non-degenerate with translationally invariant nearest-neighbor spin correlations up to a few unit cells, which is consistent with a spin liquid state or a valence bond crystal with very large unit cell. C. Waldtmann, A. Kreutzmann, U. Schollwock, K. Maisinger, and H.-U. Everts, Phys. Rev. B 62, 9472 (2000).

Dynamical manifestations of quantum chaos: correlation hole and bulge

NASA Astrophysics Data System (ADS)

Torres-Herrera, E. J.; Santos, Lea F.

2017-10-01

A main feature of a chaotic quantum system is a rigid spectrum where the levels do not cross. We discuss how the presence of level repulsion in lattice many-body quantum systems can be detected from the analysis of their time evolution instead of their energy spectra. This approach is advantageous to experiments that deal with dynamics, but have limited or no direct access to spectroscopy. Dynamical manifestations of avoided crossings occur at long times. They correspond to a drop, referred to as correlation hole, below the asymptotic value of the survival probability and to a bulge above the saturation point of the von Neumann entanglement entropy and the Shannon information entropy. By contrast, the evolution of these quantities at shorter times reflects the level of delocalization of the initial state, but not necessarily a rigid spectrum. The correlation hole is a general indicator of the integrable-chaos transition in disordered and clean models and as such can be used to detect the transition to the many-body localized phase in disordered interacting systems. This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

Preliminary report on Bureau of Mines Yellow Creek core hole No. 1, Rio Blanco County, Colorado

USGS Publications Warehouse

Carroll, R.D.; Coffin, D.L.; Ege, J.R.; Welder, F.A.

1967-01-01

Analysis of geologic, hydrologic , and geophysical data obtained in and around Yellow Creek core hole No. 1, Rio Blanco County, Colorado, indicate a 1,615-foot section of oil shale was penetrated by the hole. Geophysical log data indicate the presence of 25 gallons per ton shale for a thickness of 500 feet my be marginal. The richest section of oil shale is indicated to be centered around a depth of 2,260 feet. Within the oil shale the interval 1,182 to 1,737 feet is indicated to be relatively structurally incompetent and probably permeable. Extension of available regional hydrologic data indicate the oil shale section is probably water bearing and may yield as much as 1,000 gallons per minute. Hydrologic testing in the hole is recommended.

Ultrafast Spectral Diffusion of the First Subband Exciton in Single-Wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Schilling, Daniel; Hertel, Tobias

2013-03-01

The width of optical transitions in semiconductors is determined by homogeneous and inhomogeneous contributions. Here, we report on the determination of homogeneous linewidths for the first exciton subband transition and the dynamics of spectral diffusion in single-wall carbon nanotubes (SWNTs) using one- and two-dimensional time resolved spectral hole burning spectroscopy. Our investigation of highly purified semiconducting (6,5)-SWNTs suggests that room temperature homogeneous linewidths are on the order of 4 meV and are rapidly broadened by an ultrafast sub-ps spectral diffusion process. These findings are supported by our off-resonant excitation experiments where we observe sub-ps population transfer reflecting the thermal distribution of energy levels around the first subband exciton transition. The results of temperature-dependent spectral hole burning experiments between 17 K and 293 K suggest that homogeneous linewidths are due to exciton interaction with low energy optical phonons, most likely of the radial breathing mode type. In contrast, we find that inhomogeneous broadening is determined by an electronic degree of freedom such as ultrafast intra-tube exciton diffusion which is characteristic and unique for excitons in these one-dimensional semiconductors.

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells studied by transient circular dichromatic absorption spectroscopy at room temperature.

PubMed

Fang, Shaoyin; Zhu, Ruidan; Lai, Tianshu

2017-03-21

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells is studied using time-resolved circular dichromatic absorption spectroscopy at room temperature. It is found that ultrafast dynamics is dominated by the cooperative contributions of band filling and many-body effects. The relative contribution of the two effects is opposite in strength for electrons and holes. As a result, transient circular dichromatic differential transmission (TCD-DT) with co- and cross-circularly polarized pump and probe presents different strength at several picosecond delay time. Ultrafast spin relaxation dynamics of excited holes is sensitively reflected in TCD-DT with cross-circularly polarized pump and probe. A model, including coherent artifact, thermalization of nonthermal carriers and the cooperative contribution of band filling and many-body effects, is developed, and used to fit TCD-DT with cross-circularly polarized pump and probe. Spin relaxation time of holes is achieved as a function of excited hole density for the first time at room temperature, and increases with hole density, which disagrees with a theoretical prediction based on EY spin relaxation mechanism, implying that EY mechanism may be not dominant hole spin relaxation mechanism at room temperature, but DP mechanism is dominant possibly.

Direct observation of ultrafast many-body electron dynamics in an ultracold Rydberg gas

PubMed Central

Takei, Nobuyuki; Sommer, Christian; Genes, Claudiu; Pupillo, Guido; Goto, Haruka; Koyasu, Kuniaki; Chiba, Hisashi; Weidemüller, Matthias; Ohmori, Kenji

2016-01-01

Many-body correlations govern a variety of important quantum phenomena such as the emergence of superconductivity and magnetism. Understanding quantum many-body systems is thus one of the central goals of modern sciences. Here we demonstrate an experimental approach towards this goal by utilizing an ultracold Rydberg gas generated with a broadband picosecond laser pulse. We follow the ultrafast evolution of its electronic coherence by time-domain Ramsey interferometry with attosecond precision. The observed electronic coherence shows an ultrafast oscillation with a period of 1 femtosecond, whose phase shift on the attosecond timescale is consistent with many-body correlations among Rydberg atoms beyond mean-field approximations. This coherent and ultrafast many-body dynamics is actively controlled by tuning the orbital size and population of the Rydberg state, as well as the mean atomic distance. Our approach will offer a versatile platform to observe and manipulate non-equilibrium dynamics of quantum many-body systems on the ultrafast timescale. PMID:27849054

Fusion splicing small-core photonic crystal fibers and single-mode fibers by controlled air hole collapse

NASA Astrophysics Data System (ADS)

Zhou, Xuanfeng; Chen, Zilun; Chen, Haihuan; Hou, Jing

2012-11-01

A method based on controlled air hole collapse for low-loss fusion splicing small-core photonic crystal fibers (PCFs) and single-mode fibers (SMFs) was demonstrated. A taper rig was used to control air hole collapse accurately to enlarge the MFDs of PCFs which was then spliced with SMFs using a fusion splicer. An optimum mode field match at the interface of PCF-SMF was achieved and a low-loss with 0.64 dB was obtained from 3.57 dB for a PCF with 4 μm MFD and a SMF with 10.4 μm MFD experimentally.

Geologic, geotechnical, and geophysical properties of core from the Acme Fire-Pit-1 drill hole, Sheridan County, Wyoming

USGS Publications Warehouse

Collins, Donley S.

1983-01-01

A preliminary core study from the Acme Fire-Pit-1 drill hole, Sheridan County, Wyoming, revealed that the upper portion of the core had been baked by a fire confined to the underlying Monarch coal bed. The baked (clinkered) sediment above the Monarch coal bed was determined to have higher point-load strength values (greater than 2 MPa) than the sediment under the burned coal

Capturing local structure modulations of photoexcited BiVO4 by ultrafast transient XAFS.

PubMed

Uemura, Yohei; Kido, Daiki; Koide, Akihiro; Wakisaka, Yuki; Niwa, Yasuhiro; Nozawa, Shunsuke; Ichiyanagi, Kohei; Fukaya, Ryo; Adachi, Shin-Ichi; Katayama, Tetsuo; Togashi, Tadashi; Owada, Shigeki; Yabashi, Makina; Hatada, Keisuke; Iwase, Akihide; Kudo, Akihiko; Takakusagi, Satoru; Yokoyama, Toshihiko; Asakura, Kiyotaka

2017-06-29

Ultrafast excitation of photocatalytically active BiVO 4 was characterized by femto- and picosecond transient X-ray absorption fine structure spectroscopy. An initial photoexcited state (≪500 fs) changed to a metastable state accompanied by a structural change with a time constant of ∼14 ps. The structural change might stabilize holes on oxygen atoms since the interaction between Bi and O increases.

Observation of a cavitation cloud in tissue using correlation between ultrafast ultrasound images.

PubMed

Prieur, Fabrice; Zorgani, Ali; Catheline, Stefan; Souchon, Rémi; Mestas, Jean-Louis; Lafond, Maxime; Lafon, Cyril

2015-07-01

The local application of ultrasound is known to improve drug intake by tumors. Cavitating bubbles are one of the contributing effects. A setup in which two ultrasound transducers are placed confocally is used to generate cavitation in ex vivo tissue. As the transducers emit a series of short excitation bursts, the evolution of the cavitation activity is monitored using an ultrafast ultrasound imaging system. The frame rate of the system is several thousands of images per second, which provides several tens of images between consecutive excitation bursts. Using the correlation between consecutive images for speckle tracking, a decorrelation of the imaging signal appears due to the creation, fast movement, and dissolution of the bubbles in the cavitation cloud. By analyzing this area of decorrelation, the cavitation cloud can be localized and the spatial extent of the cavitation activity characterized.

Role of macular hole angle in macular hole closure.

PubMed

Chhablani, Jay; Khodani, Mitali; Hussein, Abdullah; Bondalapati, Sailaja; Rao, Harsha B; Narayanan, Raja; Sudhalkar, Aditya

2015-12-01

To evaluate correlation of various spectral-domain optical coherence tomography (SD-OCT) parameters including macular hole angle as well as various indices with anatomical and visual outcomes after idiopathic macular hole repair surgery. Retrospective study of 137 eyes of 137 patients who underwent idiopathic macular hole repair surgery between January 2008 and January 2014 was performed. Various qualitative parameters such as presence of vitreomacular traction, epiretinal membrane and cystic edges at the macular hole as well as quantitative parameters such as maximum diameter on the apex of the hole, minimum diameter between edges, nasal and temporal vertical height, longest base diameter and macular hole angle between the retinal edge and the retinal pigment epithelium were noted. Indices including hole form factor, Macular Hole Index (MHI), Diameter Hole Index and Tractional Hole Index (THI) were calculated. Univariate and multivariate regression analysis was performed separately for final visual acuity (VA) and type of closure as dependent variable in relation to SD-OCT parameters as independent variables. On multivariate regression only minimum diameter between edges (p≤0.01) and longest base diameter (p≤0.03) were correlated significantly with both, type 1 closure and final VA. Among the indices, significant correlation of MHI (p=0.009) was noted with type of closure and that of THI with final VA (p=0.017). Our study shows no significant correlation between macular hole angle and hole closure. Minimum diameter between the edges and longest diameter of the hole are best predictors of hole closure and postoperative VA. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Physical-Property Measurements on Core samples from Drill-Holes DB-1 and DB-2, Blue Mountain Geothermal Prospect, North-Central Nevada

USGS Publications Warehouse

Ponce, David A.; Watt, Janet T.; Casteel, John; Logsdon, Grant

2009-01-01

From May to June 2008, the U.S. Geological Survey (USGS) collected and measured physical properties on 36 core samples from drill-hole Deep Blue No. 1 (DB-1) and 46 samples from drill-hole Deep Blue No. 2 (DB-2) along the west side of Blue Mountain about 40 km west of Winnemucca, Nev. These data were collected as part of an effort to determine the geophysical setting of the Blue Mountain geothermal prospect as an aid to understanding the geologic framework of geothermal systems throughout the Great Basin. The physical properties of these rocks and other rock types in the area create a distinguishable pattern of gravity and magnetic anomalies that can be used to infer their subsurface geologic structure. Drill-holes DB-1 and DB-2 were spudded in alluvium on the western flank of Blue Mountain in 2002 and 2004, respectively, and are about 1 km apart. Drill-hole DB-1 is at a ground elevation of 1,325 m and was drilled to a depth of 672 m and drill-hole DB-2 is at a ground elevation of 1,392 m and was drilled to a depth of 1522 m. Diameter of the core samples is 6.4 cm. These drill holes penetrate Jurassic and Triassic metasedimentary rocks predominantly consisting of argillite, mudstone, and sandstone; Tertiary diorite and gabbro; and younger Tertiary felsic dikes.

Radio transients from newborn black holes

NASA Astrophysics Data System (ADS)

Kashiyama, Kazumi; Hotokezaka, Kenta; Murase, Kohta

2018-05-01

We consider radio emission from a newborn black hole (BH), which is accompanied by a mini-disk with a mass of ≲ M⊙. Such a disk can be formed from an outer edge of the progenitor's envelope, especially for metal-poor massive stars and/or massive stars in close binaries. The disk accretion rate is typically super-Eddington and an ultrafast outflow with a velocity of ˜0.1-0.3 c will be launched into the circumstellar medium. The outflow forms a collisionless shock, and electrons are accelerated and emit synchrotron emission in radio bands with a flux of ˜ 10^{26-30} erg s^{-1} Hz^{-1} days to decades after the BH formation. The model predicts not only a fast UV/optical transient but also quasi-simultaneous inverse-Compton X-ray emission ˜ a few days after the BH formation, and the discovery of the radio counterpart with coordinated searches will enable us to identify this type of transients. The occurrence rate can be 0.1 - 10 % of the core-collapse supernova rate, which makes them a promising target of dedicated radio observations such as the Jansky VLA Sky Survey.

Supermassive Black Holes and their Host Spheroids III. The Mbh-nsph Correlation

NASA Astrophysics Data System (ADS)

Savorgnan, Giulia A. D.

2016-04-01

The Sérsic {R}1/n model is the best approximation known to date for describing the light distribution of stellar spheroidal and disk components, with the Sérsic index n providing a direct measure of the central radial concentration of stars. The Sérsic index of a galaxy’s spheroidal component, nsph, has been shown to tightly correlate with the mass of the central supermassive black hole, MBH. The {M}{BH}{--}{n}{sph} correlation is also expected from other two well known scaling relations involving the spheroid luminosity, Lsph: the {L}{sph}{--}{n}{sph} and the {M}{BH}{--}{L}{sph}. Obtaining an accurate estimate of the spheroid Sérsic index requires a careful modeling of a galaxy’s light distribution and some studies have failed to recover a statistically significant {M}{BH}{--}{n}{sph} correlation. With the aim of re-investigating the {M}{BH}{--}{n}{sph} and other black hole mass scaling relations, we performed a detailed (I.e., bulge, disks, bars, spiral arms, rings, halo, nucleus, etc.) decomposition of 66 galaxies, with directly measured black hole masses, that had been imaged at 3.6 μm with Spitzer. In this paper, the third of this series, we present an analysis of the {L}{sph}{--}{n}{sph} and {M}{BH}{--}{n}{sph} diagrams. While early-type (elliptical+lenticular) and late-type (spiral) galaxies split into two separate relations in the {L}{sph}{--}{n}{sph} and {M}{BH}{--}{L}{sph} diagrams, they reunite into a single {M}{BH}\\propto {n}{sph}3.39+/- 0.15 sequence with relatively small intrinsic scatter (ɛ ≃ 0.25 {dex}). The black hole mass appears to be closely related to the spheroid central concentration of stars, which mirrors the inner gradient of the spheroid gravitational potential.

Ultrafast Multi-Level Logic Gates with Spin-Valley Coupled Polarization Anisotropy in Monolayer MoS2

PubMed Central

Wang, Yu-Ting; Luo, Chih-Wei; Yabushita, Atsushi; Wu, Kaung-Hsiung; Kobayashi, Takayoshi; Chen, Chang-Hsiao; Li, Lain-Jong

2015-01-01

The inherent valley-contrasting optical selection rules for interband transitions at the K and K′ valleys in monolayer MoS2 have attracted extensive interest. Carriers in these two valleys can be selectively excited by circularly polarized optical fields. The comprehensive dynamics of spin valley coupled polarization and polarized exciton are completely resolved in this work. Here, we present a systematic study of the ultrafast dynamics of monolayer MoS2 including spin randomization, exciton dissociation, free carrier relaxation, and electron-hole recombination by helicity- and photon energy-resolved transient spectroscopy. The time constants for these processes are 60 fs, 1 ps, 25 ps, and ~300 ps, respectively. The ultrafast dynamics of spin polarization, valley population, and exciton dissociation provides the desired information about the mechanism of radiationless transitions in various applications of 2D transition metal dichalcogenides. For example, spin valley coupled polarization provides a promising way to build optically selective-driven ultrafast valleytronics at room temperature. Therefore, a full understanding of the ultrafast dynamics in MoS2 is expected to provide important fundamental and technological perspectives. PMID:25656222

Ultrafast Silicon Photonics with Visible to Mid-Infrared Pumping of Silicon Nanocrystals.

PubMed

Diroll, Benjamin T; Schramke, Katelyn S; Guo, Peijun; Kortshagen, Uwe R; Schaller, Richard D

2017-10-11

Dynamic optical control of infrared (IR) transparency and refractive index is achieved using boron-doped silicon nanocrystals excited with mid-IR optical pulses. Unlike previous silicon-based optical switches, large changes in transmittance are achieved without a fabricated structure by exploiting strong light coupling of the localized surface plasmon resonance (LSPR) produced from free holes of p-type silicon nanocrystals. The choice of optical excitation wavelength allows for selectivity between hole heating and carrier generation through intraband or interband photoexcitation, respectively. Mid-IR optical pumping heats the free holes of p-Si nanocrystals to effective temperatures greater than 3500 K. Increases of the hole effective mass at high effective hole temperatures lead to a subpicosecond change of the dielectric function, resulting in a redshift of the LSPR, modulating mid-IR transmission by as much as 27%, and increasing the index of refraction by more than 0.1 in the mid-IR. Low hole heat capacity dictates subpicosecond hole cooling, substantially faster than carrier recombination, and negligible heating of the Si lattice, permitting mid-IR optical switching at terahertz repetition frequencies. Further, the energetic distribution of holes at high effective temperatures partially reverses the Burstein-Moss effect, permitting the modulation of transmittance at telecommunications wavelengths. The results presented here show that doped silicon, particularly in micro- or nanostructures, is a promising dynamic metamaterial for ultrafast IR photonics.

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides

NASA Astrophysics Data System (ADS)

Gu, Mingqiang; Rondinelli, James M.

2016-04-01

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides.

PubMed

Gu, Mingqiang; Rondinelli, James M

2016-04-29

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.

Ultrafast band engineering and transient spin currents in antiferromagnetic oxides

DOE PAGES

Gu, Mingqiang; Rondinelli, James M.

2016-04-29

Here, we report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO 3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observedmore » in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO 3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.« less

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides

PubMed Central

Gu, Mingqiang; Rondinelli, James M.

2016-01-01

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices. PMID:27126354

A New Black Hole Mass Estimate for Obscured Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Minezaki, Takeo; Matsushita, Kyoko

2015-04-01

We propose a new method for estimating the mass of a supermassive black hole, applicable to obscured active galactic nuclei (AGNs). This method estimates the black hole mass using the width of the narrow core of the neutral FeKα emission line in X-rays and the distance of its emitting region from the black hole based on the isotropic luminosity indicator via the luminosity scaling relation. Assuming the virial relation between the locations and the velocity widths of the neutral FeKα line core and the broad Hβ emission line, the luminosity scaling relation of the neutral FeKα line core emitting region is estimated. We find that the velocity width of the neutral FeKα line core falls between that of the broad Balmer emission lines and the corresponding value at the dust reverberation radius for most of the target AGNs. The black hole mass {{M}BH,FeKα } estimated with this method is then compared with other black hole mass estimates, such as the broad emission-line reverberation mass {{M}BH,rev} for type 1 AGNs, the mass {{M}BH,{{H2}O}} based on the H2O maser, and the single-epoch mass estimate {{M}BH,pol} based on the polarized broad Balmer lines for type 2 AGNs. We find that {{M}BH,FeKα } is consistent with {{M}BH,rev} and {{M}BH,pol}, and find that {{M}BH,FeKα } correlates well with {{M}BH,{{H2}O}}. These results suggest that {{M}BH,FeKα } is a potential indicator of the black hole mass for obscured AGNs. In contrast, {{M}BH,FeKα } is systematically larger than {{M}BH,{{H2}O}} by about a factor of 5, and the possible origins are discussed.

NGC 4051: Black hole mass and photon index-mass accretion rate correlation

NASA Astrophysics Data System (ADS)

Seifina, Elena; Chekhtman, Alexandre; Titarchuk, Lev

2018-05-01

We present a discovery of the correlation between the X-ray spectral (photon) index and mass accretion rate observed in an active galactic nucleus, NGC 4051. We analyzed spectral transition episodes observed in NGC 4051 using XMM-Newton, Suzaku and RXTE. We applied a scaling technique for a black hole (BH) mass evaluation which uses a correlation between the photon index and normalization of the seed (disk) component, which is proportional to a mass accretion rate. We developed an analytical model that shows the spectral (photon) index of the BH emergent spectrum undergoes an evolution from lower to higher values depending on a mass accretion rate in the accretion disk. We considered Cygnus X-1 and GRO J1550-564 as reference sources for which distances, inclination angles and the BH masses are evaluated by dynamical measurements. Application of the scaling technique for the photon index-mass accretion rate correlation provides an estimate of the black hole mass in NGC 4051 to be more than 6 × 105 solar masses.

Proton-hole and core-excited states in the semi-magic nucleus 131In82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taprogge, J.; Jungclaus, A.; Grawe, H.

2016-11-01

The decay of the N = 83 nucleus Cd-131 has been studied at the RIBF facility at the RIKEN Nishina Center. The main purpose of the study was to identify the position of the and proton-hole states and the energies of core-excited configurations in the semi-magic nucleus In-131. From the radiation emitted following the decay, a level scheme of In-131 was established and the feeding to each excited state determined. Similarities between the single-particle transitions observed in the decays of the N = 83 isotones In-132 and Cd-131 are discussed. Finally the excitation energies of several core-excited configurations in In-131more » are compared to QRPA and shell-model calculations.« less

Nondestructive continuous physical property measurements of core samples recovered from hole B, Taiwan Chelungpu-Fault Drilling Project

NASA Astrophysics Data System (ADS)

Hirono, Tetsuro; Yeh, En-Chao; Lin, Weiren; Sone, Hiroki; Mishima, Toshiaki; Soh, Wonn; Hashimoto, Yoshitaka; Matsubayashi, Osamu; Aoike, Kan; Ito, Hisao; Kinoshita, Masataka; Murayama, Masafumi; Song, Sheng-Rong; Ma, Kuo-Fong; Hung, Jih-Hao; Wang, Chien-Ying; Tsai, Yi-Ben; Kondo, Tomomi; Nishimura, Masahiro; Moriya, Soichi; Tanaka, Tomoyuki; Fujiki, Toru; Maeda, Lena; Muraki, Hiroaki; Kuramoto, Toshikatsu; Sugiyama, Kazuhiro; Sugawara, Toshikatsu

2007-07-01

The Taiwan Chelungpu-Fault Drilling Project was undertaken in 2002 to investigate the faulting mechanism of the 1999 Mw 7.6 Taiwan Chi-Chi earthquake. Hole B penetrated the Chelungpu fault, and core samples were recovered from between 948.42- and 1352.60-m depth. Three major zones, designated FZB1136 (fault zone at 1136-m depth in hole B), FZB1194, and FZB1243, were recognized in the core samples as active fault zones within the Chelungpu fault. Nondestructive continuous physical property measurements, conducted on all core samples, revealed that the three major fault zones were characterized by low gamma ray attenuation (GRA) densities and high magnetic susceptibilities. Extensive fracturing and cracks within the fault zones and/or loss of atoms with high atomic number, but not a measurement artifact, might have caused the low GRA densities, whereas the high magnetic susceptibility values might have resulted from the formation of magnetic minerals from paramagnetic minerals by frictional heating. Minor fault zones were characterized by low GRA densities and no change in magnetic susceptibility, and the latter may indicate that these minor zones experienced relatively low frictional heating. Magnetic susceptibility in a fault zone may be key to the determination that frictional heating occurred during an earthquake on the fault.

Exchange-Correlation Hole in Polarized Insulators: Implications for the Microscopic Functional Theory of Dielectrics

NASA Astrophysics Data System (ADS)

Ortiz, Gerardo; Souza, Ivo; Martin, Richard M.

1998-01-01

We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is uniquely characterized by the density and the macroscopic electric polarization of the dielectric medium.

Effectively Single-Mode Self-Recovering Ultrafast Nonlinear Nanowire Surface Plasmons

NASA Astrophysics Data System (ADS)

Tuniz, Alessandro; Weidlich, Stefan; Schmidt, Markus A.

2018-04-01

We report on a regime for surface-plasmon propagation, which is robust to defects and effectively single mode, and we exploit it for accessing the ultrafast nonlinear response of gold on centimeter-long subwavelength-diameter cylindrical nanowires. The hybrid plasmonic-photonic platform is formed by a gold nanowire, monolithically integrated into the core of an optical fiber. We show that, despite the dual-waveguide nature of this structure, the long-range surface plasmon is the only effectively propagating mode in the near infrared, which self-recovers in the presence of gaps via a light-recapturing effect. This self-recovery overcomes detrimental effects of wire discontinuities and enables measurements of the ultrafast nonlinearity of gold, which we perform for a 28-fs pulse duration.

Ultrafast Silicon Photonics with Visible to Mid-Infrared Pumping of Silicon Nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diroll, Benjamin T.; Schramke, Katelyn S.; Guo, Peijun

Dynamic optical control of infrared (IR) transparency and refractive index is achieved using boron-doped silicon nanocrystals excited with mid-IR optical pulses. Also, unlike previous silicon-based optical switches, large changes in transmittance are achieved without a fabricated structure by exploiting strong light coupling of the localized surface plasmon resonance (LSPR) produced from free holes of p-type silicon nanocrystals. The choice of optical excitation wavelength allows selectivity between hole heating and carrier generation through intraband or interband photoexcitation, respectively. Mid-IR optical pumping heats the free holes of p-Si nanocrystals to effective temperatures greater than 3500 K. Increases of the hole effective massmore » at high effective hole temperatures lead to a sub-picosecond change of the dielectric function resulting in a redshift of the LSPR, modulating mid-IR transmission by as much as 27% and increasing the index of refraction by more than 0.1 in the mid-IR. Low hole heat capacity dictates sub-picosecond hole cooling, substantially faster than carrier recombination, and negligible heating of the Si lattice, permitting mid-IR optical switching at terahertz repetition frequencies. Further, the energetic distribution of holes at high effective temperatures partially reverses the Burstein-Moss effect, permitting modulation of transmittance at telecommunications wavelengths. Lastly, the results presented here show that doped silicon, particularly in micro- or nanostructures, is a promising dynamic metamaterial for ultrafast IR photonics.« less

Ultrafast Silicon Photonics with Visible to Mid-Infrared Pumping of Silicon Nanocrystals

DOE PAGES

Diroll, Benjamin T.; Schramke, Katelyn S.; Guo, Peijun; ...

2017-09-11

Dynamic optical control of infrared (IR) transparency and refractive index is achieved using boron-doped silicon nanocrystals excited with mid-IR optical pulses. Also, unlike previous silicon-based optical switches, large changes in transmittance are achieved without a fabricated structure by exploiting strong light coupling of the localized surface plasmon resonance (LSPR) produced from free holes of p-type silicon nanocrystals. The choice of optical excitation wavelength allows selectivity between hole heating and carrier generation through intraband or interband photoexcitation, respectively. Mid-IR optical pumping heats the free holes of p-Si nanocrystals to effective temperatures greater than 3500 K. Increases of the hole effective massmore » at high effective hole temperatures lead to a sub-picosecond change of the dielectric function resulting in a redshift of the LSPR, modulating mid-IR transmission by as much as 27% and increasing the index of refraction by more than 0.1 in the mid-IR. Low hole heat capacity dictates sub-picosecond hole cooling, substantially faster than carrier recombination, and negligible heating of the Si lattice, permitting mid-IR optical switching at terahertz repetition frequencies. Further, the energetic distribution of holes at high effective temperatures partially reverses the Burstein-Moss effect, permitting modulation of transmittance at telecommunications wavelengths. Lastly, the results presented here show that doped silicon, particularly in micro- or nanostructures, is a promising dynamic metamaterial for ultrafast IR photonics.« less

Ultrafast Nanoimaging of the Photoinduced Phase Transition Dynamics in VO2.

PubMed

Dönges, Sven A; Khatib, Omar; O'Callahan, Brian T; Atkin, Joanna M; Park, Jae Hyung; Cobden, David; Raschke, Markus B

2016-05-11

Many phase transitions in correlated matter exhibit spatial inhomogeneities with expected yet unexplored effects on the associated ultrafast dynamics. Here we demonstrate the combination of ultrafast nondegenerate pump-probe spectroscopy with far from equilibrium excitation, and scattering scanning near-field optical microscopy (s-SNOM) for ultrafast nanoimaging. In a femtosecond near-field near-IR (NIR) pump and mid-IR (MIR) probe study, we investigate the photoinduced insulator-to-metal (IMT) transition in nominally homogeneous VO2 microcrystals. With pump fluences as high as 5 mJ/cm(2), we can reach three distinct excitation regimes. We observe a spatial heterogeneity on ∼50-100 nm length scales in the fluence-dependent IMT dynamics ranging from <100 fs to ∼1 ps. These results suggest a high sensitivity of the IMT with respect to small local variations in strain, doping, or defects that are difficult to discern microscopically. We provide a perspective with the distinct requirements and considerations of ultrafast spatiotemporal nanoimaging of phase transitions in quantum materials.

Single and double core-hole ion emission spectroscopy of transient neon plasmas produced by ultraintense x-ray laser pulses

NASA Astrophysics Data System (ADS)

Gao, Cheng; Zeng, Jiaolong; Yuan, Jianmin

2016-05-01

Single core-hole (SCH) and double core-hole (DCH) spectroscopy is investigated systematically for neon gas in the interaction with ultraintense x-ray pulses with photon energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in the detailed level accounting approximation, is utilized to study the dynamical evolution of the level population and emission properties of the laser-produced highly transient plasmas. The plasma density effects on level populations are demonstrated with an x-ray photon energy of 2000 eV. For laser photon energy in the range of 937 - 1360 eV, resonant absorptions (RA) of 1s-np (n> = 2) transitions play important roles in time evolution of the population and DCH emission spectroscopy. For x-ray photon energy larger than 1360 eV, no RA exist and transient plasmas show different features in the DCH spectroscopy.

Petrology of deep drill hole, Kilauea Volcano

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grose, L.T.; Keller, G.V.

1976-12-01

The first deep drill hole (1262 m TD) at the summit of an active volcano (1102 m elev) was drilled in 1973 at Kilauea volcano, Hawaii with support from NSF and USGS. The hole is located within southern margin of Kilauea caldera in northern part of a 15 km/sup 2/ triangular block bounded by east rift zone, Koae fault zone, and southwest rift zone-a summit area relatively free of faults, rifts, and extrusions. Nearest eruptions are from fissures 1.2 km away which are active in 1974 and which do not trend toward the drill hole. Core recovery totals 47 mmore » from 29 core runs at rather evenly spaced intervals to total depth. Megascopic, thin-section, and X-ray examination reveals: (1) Recovered core is essentially vesicular, intergranular, nonporphyritic to porphyritic olivine basalt with minor olivine diabase, picrite diabase, and basalt, (2) Hyaloclastite and pillow basalt are absent, (3) Below water table (614 m elev) with increasing depth, vesicularity decreases, and density, crystallinity, competence, vesicle fill, and alteration irregularly increase, (4) Alteration first occurs at water table where calcite and silica partially fill vesticles and olivine is partially serpentinized, (5) At about 570 m elev massive serpentinization of olivine and deposition of montmorillonite-nontronite occur; at about 210 m elev truscottite and tobermorite occur in vesicles; at about 35 m elev mordenite occurs in vesicles, (6) Bottom-hole cores have complete filling of vesicles with silica, minor silica replacement, and complete alteration of olivine, and (7) Plagioclase is unaltered. Chemical analyses of bottom-hole cores are similar to those of modern summit lavas. Alteration and low porosity in bottom-hole cores plus abrupt temperature increase suggest the drill hole penetrated a self-sealed ''cap rock'' to a hydrothermal convection cell and possibly a magma body.« less

Electron-mediated relaxation following ultrafast pumping of strongly correlated materials: model evidence of a correlation-tuned crossover between thermal and nonthermal states.

PubMed

Moritz, B; Kemper, A F; Sentef, M; Devereaux, T P; Freericks, J K

2013-08-16

We examine electron-electron mediated relaxation following ultrafast electric field pump excitation of the fermionic degrees of freedom in the Falicov-Kimball model for correlated electrons. The results reveal a dichotomy in the temporal evolution of the system as one tunes through the Mott metal-to-insulator transition: in the metallic regime relaxation can be characterized by evolution toward a steady state well described by Fermi-Dirac statistics with an increased effective temperature; however, in the insulating regime this quasithermal paradigm breaks down with relaxation toward a nonthermal state with a complicated electronic distribution as a function of momentum. We characterize the behavior by studying changes in the energy, photoemission response, and electronic distribution as functions of time. This relaxation may be observable qualitatively on short enough time scales that the electrons behave like an isolated system not in contact with additional degrees of freedom which would act as a thermal bath, especially when using strong driving fields and studying materials whose physics may manifest the effects of correlations.

Long-period fiber gratings as ultrafast optical differentiators.

PubMed

Kulishov, Mykola; Azaña, José

2005-10-15

It is demonstrated that a single, uniform long-period fiber grating (LPFG) working in the linear regime inherently behaves as an ultrafast optical temporal differentiator. Specifically, we show that the output temporal waveform in the core mode of a LPFG providing full energy coupling into the cladding mode is proportional to the first derivative of the optical temporal signal (e.g., optical pulse) launched at the input of the LPFG. Moreover, a LPFG providing full energy recoupling back from the cladding mode into the core mode inherently implements second-order temporal differentiation. Our numerical results have confirmed the feasibility of this simple, all-fiber approach to processing optical signals with temporal features in the picosecond and subpicosecond ranges.

Ab Initio Theory of Dynamical Core-Hole Screening in Graphite from X-Ray Absorption Spectra

NASA Astrophysics Data System (ADS)

Wessely, O.; Katsnelson, M. I.; Eriksson, O.

2005-04-01

We have implemented the effect of dynamical core-hole screening, as given by Mahan, Nozières, and De Dominicis, in a first-principles based method and applied the theory to the x-ray absorption (XA) spectrum of graphite. It turns out that two of the conspicuous peaks of graphite are well described, both regarding the position, shape, and relative intensity, whereas one peak is absent in the theory. Only by incorporation of both excitonic and delocalized processes can a full account of the experimental spectrum be obtained theoretically, and we interpret the XA spectrum in graphite to be the result of a well screened and a poor screened process, much in the same way as is done for core level x-ray photoelectron spectroscopy.

Development of ZnO:Ga as an Ultrafast Scintillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourret-Courchesne, E.D.; Derenzo, S.E.; Weber, M.J.

We report on several methods for synthesizing the ultra-fast scintillator ZnO(Ga), and measurements of the resulting products. This material has characteristics that make it an excellent alpha detector for tagging the time and direction of individual neutrons produced by t-d and d-d neutron generators (associated particle imaging). The intensity and decay time are strongly dependent on the method used for dopant incorporation. We compare samples made by diffusion of Ga metal to samples made by solid state reaction between ZnO and Ga2O3 followed by reduction in hydrogen. The latter is much more successful and has a pure, strong near-band-edge fluorescencemore » and an ultra-fast decay time of the x-ray-excited luminescence. The luminescence increases dramatically as the temperature is reduced to 10K. We also present results of an alternate low-temperature synthesis that produces luminescent particles with a more uniform size distribution. We examine possible mechanisms for the bright near-band-edge scintillation and favor the explanation that it is due to the recombination of Ga3+ donor electrons with ionization holes trapped on H+ ion acceptors.« less

Electron theory of fast and ultrafast dissipative magnetization dynamics.

PubMed

Fähnle, M; Illg, C

2011-12-14

For metallic magnets we review the experimental and electron-theoretical investigations of fast magnetization dynamics (on a timescale of ns to 100 ps) and of laser-pulse-induced ultrafast dynamics (few hundred fs). It is argued that for both situations the dominant contributions to the dissipative part of the dynamics arise from the excitation of electron-hole pairs and from the subsequent relaxation of these pairs by spin-dependent scattering processes, which transfer angular momentum to the lattice. By effective field theories (generalized breathing and bubbling Fermi-surface models) it is shown that the Gilbert equation of motion, which is often used to describe the fast dissipative magnetization dynamics, must be extended in several aspects. The basic assumptions of the Elliott-Yafet theory, which is often used to describe the ultrafast spin relaxation after laser-pulse irradiation, are discussed very critically. However, it is shown that for Ni this theory probably yields a value for the spin-relaxation time T(1) in good agreement with the experimental value. A relation between the quantity α characterizing the damping of the fast dynamics in simple situations and the time T(1) is derived. © 2011 IOP Publishing Ltd

Ultrafast time measurements by time-correlated single photon counting coupled with superconducting single photon detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shcheslavskiy, V., E-mail: vis@becker-hickl.de; Becker, W.; Morozov, P.

Time resolution is one of the main characteristics of the single photon detectors besides quantum efficiency and dark count rate. We demonstrate here an ultrafast time-correlated single photon counting (TCSPC) setup consisting of a newly developed single photon counting board SPC-150NX and a superconducting NbN single photon detector with a sensitive area of 7 × 7 μm. The combination delivers a record instrument response function with a full width at half maximum of 17.8 ps and system quantum efficiency ∼15% at wavelength of 1560 nm. A calculation of the root mean square value of the timing jitter for channels withmore » counts more than 1% of the peak value yielded about 7.6 ps. The setup has also good timing stability of the detector–TCSPC board.« less

Correlation of Pliocene and Pleistocene tephra layers between the Turkana Basin of East Africa and the Gulf of Aden

USGS Publications Warehouse

Brown, F.H.; Sarna-Wojcicki, A. M.; Meyer, C.E.; Haileab, B.

1992-01-01

Electron-microprobe analyses of glass shards from volcanic ash in Pliocene and Pleistocene deep-sea sediments in the Gulf of Aden and the Somali Basin demonstrate that most of the tephra layers correlate with tephra layers known on land in the Turkana Basin of northern Kenya and southern Ethiopia. Previous correlations are reviewed, and new correlations proposed. Together these data provide correlations between the deep-sea cores, and to the land-based sections at eight levels ranging in age from about 4 to 0.7 Ma. Specifically, we correlate the Moiti Tuff (???4.1 Ma) with a tephra layer at 188.6 m depth in DSDP hole 231 and with a tephra layer at 150 m depth in DSDP hole 241, the Wargolo Tuff with a tephra layer at 179.7 m in DSDP Hole 231 and with a tephra layer at 155.3 m depth in DSDP Hole 232, the Lomogol Tuff (defined here) with a tephra layer at 165 m in DSDP Hole 232A, the Lokochot Tuff with a tephra layer at 140.1 m depth in DSDP Hole 232, the Tulu Bor Tuff with a tephra layer at 160.8 m depth in DSDP Hole 231, the Kokiselei Tuff with a tephra layer at 120 m depth in DSDP Hole 231 and with a tephra layer at 90.3 m depth in DSDP Hole 232, the Silbo Tuff (0.74 Ma) with a tephra layer at 35.5 m depth in DSDP Hole 231 and possibly with a tephra layer at 10.9 m depth in DSDP Hole 241. We also present analyses of other tephra from the deep sea cores for which correlative units on land are not yet known. The correlated tephra layers provide eight chronostratigraphic horizons that make it possible to temporally correlate paleoecological and paleoclimatic data between the terrestrial and deep-sea sites. Such correlations may make it possible to interpret faunal evolution in the Lake Turkana basin and other sites in East Africa within a broader regional or global paleoclimatic context. ?? 1992.

Basic data from five core holes in the Raft River geothermal area, Cassia County, Idaho

USGS Publications Warehouse

Crosthwaite, E. G.

1976-01-01

meters) were completed in the area (Crosthwaite, 1974), and the Aerojet Nuclear Company, under the auspices of the U.S. Energy Research and Development Administration, was planning some deep drilling 4,000 to 6,000 feet (1,200 to 1,800 meters) (fig. 1). The purpose of the core drilling was to provide information to test geophysical interpretations of the subsurface structure and lithology and to provide hydrologic and geologic data on the shallow part of the geothermal system. Samples of the core were made available to several divisions and branches of the Geological Survey and to people and agencies outside the Survey. This report presents the basic data from the core holes that had been collected to September 1, 1975, and includes lithologic and geophysical well logs, chemical analyses of water (table 1), and laboratory analyses of cores (table 2) that were completed as of the above date. The data were collected by the Idaho District office, Hydrologic Laboratory, Borehole Geophysics Research Project, and Drilling, Sampling, and Testing Section, all of the Water Resources Division, and the Branch of Central Environmental Geology of the Geologic Divison.

Ice Core Depth-Age Relation for Vostok delta-D and Dome Fuji delta-18O Records Based on the Devils Hole Paleotemperature Chronology

USGS Publications Warehouse

Landwehr, Jurate Maciunas

2002-01-01

This report presents the data for the Vostok - Devils Hole chronology, termed V-DH chronology, for the Antarctic Vostok ice core record. This depth - age relation is based on a join between the Vostok deuterium profile (D) and the stable oxygen isotope ratio (18O) record of paleotemperature from a calcitic core at Devils Hole, Nevada, using the algorithm developed by Landwehr and Winograd (2001). Both the control points defining the V-DH chronology and the numeric values for the chronology are given. In addition, a plausible chronology for a deformed bottom portion of the Vostok core developed with this algorithm is presented. Landwehr and Winograd (2001) demonstrated the broader utility of their algorithm by applying it to another appropriate Antarctic paleotemperature record, the Antarctic Dome Fuji ice core 18O record. Control points for this chronology are also presented in this report but deemed preliminary because, to date, investigators have published only the visual trace and not the numeric values for the Dome Fuji 18O record. The total uncertainty that can be associated with the assigned ages is also given.

Ultrafast magnetic vortex core switching driven by the topological inverse Faraday effect.

PubMed

Taguchi, Katsuhisa; Ohe, Jun-ichiro; Tatara, Gen

2012-09-21

We present a theoretical discovery of an unconventional mechanism of inverse Faraday effect which acts selectively on topological magnetic structures. The effect, topological inverse Faraday effect, is induced by the spin Berry's phase of the magnetic structure when a circularly polarized light is applied. Thus a spin-orbit interaction is not necessary unlike that in the conventional inverse Faraday effect. We demonstrate by numerical simulation that topological inverse Faraday effect realizes ultrafast switching of a magnetic vortex within a switching time of 150 ps without magnetic field.

Recent advances in multidimensional ultrafast spectroscopy

NASA Astrophysics Data System (ADS)

Oliver, Thomas A. A.

2018-01-01

Multidimensional ultrafast spectroscopies are one of the premier tools to investigate condensed phase dynamics of biological, chemical and functional nanomaterial systems. As they reach maturity, the variety of frequency domains that can be explored has vastly increased, with experimental techniques capable of correlating excitation and emission frequencies from the terahertz through to the ultraviolet. Some of the most recent innovations also include extreme cross-peak spectroscopies that directly correlate the dynamics of electronic and vibrational states. This review article summarizes the key technological advances that have permitted these recent advances, and the insights gained from new multidimensional spectroscopic probes.

Recent advances in multidimensional ultrafast spectroscopy

PubMed Central

2018-01-01

Multidimensional ultrafast spectroscopies are one of the premier tools to investigate condensed phase dynamics of biological, chemical and functional nanomaterial systems. As they reach maturity, the variety of frequency domains that can be explored has vastly increased, with experimental techniques capable of correlating excitation and emission frequencies from the terahertz through to the ultraviolet. Some of the most recent innovations also include extreme cross-peak spectroscopies that directly correlate the dynamics of electronic and vibrational states. This review article summarizes the key technological advances that have permitted these recent advances, and the insights gained from new multidimensional spectroscopic probes. PMID:29410844

Tracking Hole Transport in DNA Hairpins Using a Phenylethynylguanine Nucleobase.

PubMed

Brown, Kristen E; Singh, Arunoday P N; Wu, Yi-Lin; Mishra, Ashutosh Kumar; Zhou, Jiawang; Lewis, Frederick D; Young, Ryan M; Wasielewski, Michael R

2017-08-30

The hole transport dynamics of DNA hairpins possessing a stilbene electron acceptor and donor along with a modified guanine (G) nucleobase, specifically 8-(4'-phenylethynyl)deoxyguanosine, or EG, have been investigated. The nearly indistinguishable oxidation potentials of EG and G and unique spectroscopic characteristics of EG +• make it well-suited for directly observing transient hole occupation during charge transport between a stilbene electron donor and acceptor. In contrast to the cation radical G +• , EG +• possesses a strong absorption near 460 nm and has a distinct Raman-active ethynyl stretch. Both spectroscopic characteristics are easily distinguished from those of the stilbene donor/acceptor radical ion chromophores. Employing EG, we observe its role as a shallow hole trap, or as an intermediate hole transport site when a deeper trap state is present. Using a combination of ultrafast absorption and stimulated Raman spectroscopies, the hole-transport dynamics are observed to be similar in systems having EG vs G bases, with small perturbations to the charge transport rates and yields. These results show EG can be deployed at specified locations throughout the sequence to report on hole occupancy, thereby enabling detailed monitoring of the hole transport dynamics with base-site specificity.

A new generation of effective core potentials for correlated calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Michael Chandler; Melton, Cody A.; Annaberdiyev, Abdulgani

Here, we outline ideas on desired properties for a new generation of effective core potentials (ECPs) that will allow valence-only calculations to reach the full potential offered by recent advances in many-body wave function methods. The key improvements include consistent use of correlated methods throughout ECP constructions and improved transferability as required for an accurate description of molecular systems over a range of geometries. The guiding principle is the isospectrality of all-electron and ECP Hamiltonians for a subset of valence states. We illustrate these concepts on a few first- and second-row atoms (B, C, N, O, S), and we obtainmore » higher accuracy in transferability than previous constructions while using semi-local ECPs with a small number of parameters. In addition, the constructed ECPs enable many-body calculations of valence properties with higher (or same) accuracy than their all-electron counterparts with uncorrelated cores. This implies that the ECPs include also some of the impacts of core-core and core-valence correlations on valence properties. The results open further prospects for ECP improvements and refinements.« less

A new generation of effective core potentials for correlated calculations

DOE PAGES

Bennett, Michael Chandler; Melton, Cody A.; Annaberdiyev, Abdulgani; ...

2017-12-12

Here, we outline ideas on desired properties for a new generation of effective core potentials (ECPs) that will allow valence-only calculations to reach the full potential offered by recent advances in many-body wave function methods. The key improvements include consistent use of correlated methods throughout ECP constructions and improved transferability as required for an accurate description of molecular systems over a range of geometries. The guiding principle is the isospectrality of all-electron and ECP Hamiltonians for a subset of valence states. We illustrate these concepts on a few first- and second-row atoms (B, C, N, O, S), and we obtainmore » higher accuracy in transferability than previous constructions while using semi-local ECPs with a small number of parameters. In addition, the constructed ECPs enable many-body calculations of valence properties with higher (or same) accuracy than their all-electron counterparts with uncorrelated cores. This implies that the ECPs include also some of the impacts of core-core and core-valence correlations on valence properties. The results open further prospects for ECP improvements and refinements.« less

A comparative theoretical study on core-hole excitation spectra of azafullerene and its derivatives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Yunfeng; Department of Physics, Guizhou University, Guiyang 550025; Gao, Bin, E-mail: bin.gao@uit.no

2014-03-28

The core-hole excitation spectra—near-edge x-ray absorption spectroscopy (NEXAFS), x-ray emission spectroscopy (XES), and x-ray photoelectron spectroscopy (XPS) shake-up satellites have been simulated at the level of density functional theory for the azafullerene C{sub 59}N and its derivatives (C{sub 59}N){sup +}, C{sub 59}HN, (C{sub 59}N){sub 2}, and C{sub 59}N–C{sub 60}, in which the XPS shake-up satellites were simulated using our developed equivalent core hole Kohn-Sham (ECH-KS) density functional theory approach [B. Gao, Z. Wu, and Y. Luo, J. Chem. Phys. 128, 234704 (2008)] which aims for the study of XPS shake-up satellites of large-scale molecules. Our calculated spectra are generally inmore » good agreement with available experimental results that validates the use of the ECH-KS method in the present work. The nitrogen K-edge NEXAFS, XES, and XPS shake-up satellites spectra in general can be used as fingerprints to distinguish the azafullerene C{sub 59}N and its different derivatives. Meanwhile, different carbon K-edge spectra could also provide detailed information of (local) electronic structures of different molecules. In particular, a peak (at around 284.5 eV) in the carbon K-edge NEXAFS spectrum of the heterodimer C{sub 59}N–C{sub 60} is confirmed to be related to the electron transfer from the C{sub 59}N part to the C{sub 60} part in this charge-transfer complex.« less

Ultra-Fast Outflows in Radio-Loud AGN: New Constraints on Jet-Disk Connection

NASA Astrophysics Data System (ADS)

Sambruna, Rita

There is strong observational and theoretical evidence that outflows/jets are coupled to accretion disks in black hole accreting systems, from Galactic to extragalactic sizes. While in radio-quiet AGN there is ample evidence for the presence of Ultra-Fast Outflows (UFOs) from the presence of blue-shifted absorption features in their 4-10~keV spectra, sub-relativistic winds are expected on theoretical basis in radio-loud AGN but have not been observed until now. Our recent Suzaku observations of 5 bright Broad- Line Radio Galaxies (BLRGs, the radio-loud counterparts of Seyferts) has started to change this picture. We found strong evidence for UFOs in 3 out of 5 BLRGs, with ionization parameters, column densities, and velocities of the absorber similar to Seyferts. Moreover, the outflows in BLRGs are likely to be energetically very significant: from the Suzaku data of the three sources, outflow masses similar to the accretion masses and kinetic energies of the wind similar to the X-ray luminosity and radio power of the jet are inferred. Clearly, UFOs in radio-loud AGN represent a new key ingredient to understand their central engines and in particular, the jet-disk linkage. Our discovery of UFOs in a handful of BLRGs raises the questions of how common disk winds are in radio-loud AGN, what the absorber physical and dynamical characteristics are, and what is the outflow role in broader picture of galaxy-black hole connection for radio sources, i.e., for large-scale feedback models. To address these and other issues, we propose to use archival XMM-Newton and Suzaku spectra to search for Ultra-Fast Outflows in a large number of radio sources. Over a period of two years, we will conduct a systematic, uniform analysis of the archival X-ray data, building on our extensive experience with a similar previous project for Seyferts, and using robust analysis and statistical methodologies. As an important side product, we will also obtain accurate, self- consistent measurements

Measurement of carotid pulse wave velocity using ultrafast ultrasound imaging in hypertensive patients.

PubMed

Li, Xiaopeng; Jiang, Jue; Zhang, Hong; Wang, Hua; Han, Donggang; Zhou, Qi; Gao, Ya; Yu, Shanshan; Qi, Yanhua

2017-04-01

The study aimed to assess the utility of ultrafast ultrasound imaging for evaluation of carotid pulse wave velocity (PWV) in newly diagnosed hypertension patients. This prospective non-randomized study enrolled 90 hypertensive patients in our hospital from September to December 2013 as a hypertension group. An age- and sex-matched cohort of 50 healthy adults in our hospital from September to December 2013 was also included in the study as a control group. Carotid PWV at the beginning and at the end of systole (PWV-BS and PWV-ES, respectively) and intima-media thickness (IMT) were measured by ultrafast ultrasound imaging technology. The associations of PWV-BS, PWV-ES, and IMT with hypertension stage were evaluated by Spearman correlation analysis. PWV-BS and PWV-ES in the hypertension group were significantly elevated compared with those in control group. Different hypertension stages significantly differed in PWV-BS and PWV-ES. PWV-BS and PWV-ES appeared to increase with the hypertension stage. Moreover, IMT, PWV-BS, and PWV-ES were positively correlated with the hypertension stage in hypertensive patients. Ultrafast ultrasound imaging was a valid and convenient method for the measurement of carotid PWV in hypertensive patients. Ultrafast ultrasound imaging might be recommended as a promising alternative method for early detection of arterial abnormality in clinical practice.

Ultrafast Graphene Light Emitters.

PubMed

Kim, Young Duck; Gao, Yuanda; Shiue, Ren-Jye; Wang, Lei; Aslan, Ozgur Burak; Bae, Myung-Ho; Kim, Hyungsik; Seo, Dongjea; Choi, Heon-Jin; Kim, Suk Hyun; Nemilentsau, Andrei; Low, Tony; Tan, Cheng; Efetov, Dmitri K; Taniguchi, Takashi; Watanabe, Kenji; Shepard, Kenneth L; Heinz, Tony F; Englund, Dirk; Hone, James

2018-02-14

Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge. Here, we demonstrate electrically driven ultrafast graphene light emitters that achieve light pulse generation with up to 10 GHz bandwidth across a broad spectral range from the visible to the near-infrared. The fast response results from ultrafast charge-carrier dynamics in graphene and weak electron-acoustic phonon-mediated coupling between the electronic and lattice degrees of freedom. We also find that encapsulating graphene with hexagonal boron nitride (hBN) layers strongly modifies the emission spectrum by changing the local optical density of states, thus providing up to 460% enhancement compared to the gray-body thermal radiation for a broad peak centered at 720 nm. Furthermore, the hBN encapsulation layers permit stable and bright visible thermal radiation with electronic temperatures up to 2000 K under ambient conditions as well as efficient ultrafast electronic cooling via near-field coupling to hybrid polaritonic modes under electrical excitation. These high-speed graphene light emitters provide a promising path for on-chip light sources for optical communications and other optoelectronic applications.

Ultrafast photoelectron spectroscopy of small molecule organic films

NASA Astrophysics Data System (ADS)

Read, Kendall Laine

As research in the field of ultrafast optics has produced shorter and shorter pulses, at an ever-widening range of frequencies, ultrafast spectroscopy has grown correspondingly. In particular, ultrafast photoelectron spectroscopy allows direct observation of electrons in transient or excited states, regardless of the eventual relaxation mechanisms. High-harmonic conversion of 800nm, femtosecond, Ti:sapphire laser pulses allows excite/probe spectroscopy down into atomic core level states. To this end, an ultrafast, X-UV photoelectron spectroscopic system is described, including design considerations for the high-harmonic generation line, the time of flight detector, and the subsequent data collection electronics. Using a similar experimental setup, I have performed several ultrafast, photoelectron excited state decay studies at the IBM, T. J. Watson Research Center. All of the observed materials were electroluminescent thin film organics, which have applications as the emitter layer in organic light emitting devices. The specific materials discussed are: Alq, BAlq, DPVBi, and Alq doped with DCM or DMQA. Alq:DCM is also known to lase at low photoexcitation thresholds. A detailed understanding of the involved relaxation mechanisms is beneficial to both applications. Using 3.14 eV excite, and 26.7 eV probe, 90 fs laser pulses, we have observed the lowest unoccupied molecular orbital (LUMO) decay rate over the first 200 picoseconds. During this time, diffusion is insignificant, and all dynamics occur in the absence of electron transport. With excitation intensities in the range of 100μJ/cm2, we have modeled the Alq, BAlq, and DPVBi decays via bimolecular singlet-singlet annihilation. At similar excitations, we have modeled the Alq:DCM decay via Förster transfer, stimulated emission, and excimeric formation. Furthermore, the Alq:DCM occupied to unoccupied molecular orbital energy gap was seen to shrink as a function of excite-to-probe delay, in accordance with the

Ultrafast switching of valence and generation of coherent acoustic phonons in semiconducting rare-earth monosulfides

NASA Astrophysics Data System (ADS)

Punpongjareorn, Napat; He, Xing; Tang, Zhongjia; Guloy, Arnold M.; Yang, Ding-Shyue

2017-08-01

We report on the ultrafast carrier dynamics and generation of coherent acoustic phonons in YbS, a semiconducting rare-earth monochalcogenide, using two-color pump-probe reflectivity. Compared to the carrier relaxation processes and lifetimes of conventional semiconductors, recombination of photoexcited electrons with holes in localized f orbitals is found to take place rapidly with a density-independent time constant of <500 fs in YbS. Such carrier annihilation signifies the unique and ultrafast nature of valence restoration of ytterbium ions after femtosecond photoexcitation switching. Following transfer of the absorbed energy to the lattice, coherent acoustic phonons emerge on the picosecond timescale as a result of the thermal strain in the photoexcited region. By analyzing the electronic and structural dynamics, we obtain the physical properties of YbS including its two-photon absorption and thermooptic coefficients, the period and decay time of the coherent oscillation, and the sound velocity.

Photon-trapping micro/nanostructures for high linearity in ultra-fast photodiodes

NASA Astrophysics Data System (ADS)

Cansizoglu, Hilal; Gao, Yang; Perez, Cesar Bartolo; Ghandiparsi, Soroush; Ponizovskaya Devine, Ekaterina; Cansizoglu, Mehmet F.; Yamada, Toshishige; Elrefaie, Aly F.; Wang, Shih-Yuan; Islam, M. Saif

2017-08-01

Photodetectors (PDs) in datacom and computer networks where the link length is up to 300 m, need to handle higher than typical input power used in other communication links. Also, to reduce power consumption due to equalization at high speed (>25Gb/s), the datacom links will use PAM-4 signaling instead of NRZ with stringent receiver linearity requirements. Si PDs with photon-trapping micro/nanostructures are shown to have high linearity in output current verses input optical power. Though there is less silicon material due to the holes, the micro-/nanostructured holes collectively reradiate the light to an in-plane direction of the PD surface and can avoid current crowding in the PD. Consequently, the photocurrent per unit volume remains at a low level contributing to high linearity in the photocurrent. We present the effect of design and lattice patterns of micro/nanostructures on the linearity of ultra-fast silicon PDs designed for high speed multi gigabit data networks.

Distributed ultrafast fibre laser

PubMed Central

Liu, Xueming; Cui, Yudong; Han, Dongdong; Yao, Xiankun; Sun, Zhipei

2015-01-01

A traditional ultrafast fibre laser has a constant cavity length that is independent of the pulse wavelength. The investigation of distributed ultrafast (DUF) lasers is conceptually and technically challenging and of great interest because the laser cavity length and fundamental cavity frequency are changeable based on the wavelength. Here, we propose and demonstrate a DUF fibre laser based on a linearly chirped fibre Bragg grating, where the total cavity length is linearly changeable as a function of the pulse wavelength. The spectral sidebands in DUF lasers are enhanced greatly, including the continuous-wave (CW) and pulse components. We observe that all sidebands of the pulse experience the same round-trip time although they have different round-trip distances and refractive indices. The pulse-shaping of the DUF laser is dominated by the dissipative processes in addition to the phase modulations, which makes our ultrafast laser simple and stable. This laser provides a simple, stable, low-cost, ultrafast-pulsed source with controllable and changeable cavity frequency. PMID:25765454

ANSYS-based birefringence property analysis of side-hole fiber induced by pressure and temperature

NASA Astrophysics Data System (ADS)

Zhou, Xinbang; Gong, Zhenfeng

2018-03-01

In this paper, we theoretically investigate the influences of pressure and temperature on the birefringence property of side-hole fibers with different shapes of holes using the finite element analysis method. A physical mechanism of the birefringence of the side-hole fiber is discussed with the presence of different external pressures and temperatures. The strain field distribution and birefringence values of circular-core, rectangular-core, and triangular-core side-hole fibers are presented. Our analysis shows the triangular-core side-hole fiber has low temperature sensitivity which weakens the cross sensitivity of temperature and strain. Additionally, an optimized structure design of the side-hole fiber is presented which can be used for the sensing application.

Guiding properties and dispersion control of kagome lattice hollow-core photonic crystal fibers.

PubMed

Im, Song-Jin; Husakou, Anton; Herrmann, Joachim

2009-07-20

Dispersion properties, loss and optimum design of kagome lattice hollow-core photonic crystal fibers filled with argon are studied for the purpose of possible applications in ultrafast nonlinear optics. As will be shown numerically and by using an approximate analytical formula these fibers exhibit anomalous dispersion for visible or UV wavelengths both for a 1-cell-core as well for a 3-ring-core which can be controlled by the gas pressure and do not suffer from high loss. It is shown that while the loss is mainly influenced by the strut thickness of the kagome lattice the group velocity dispersion is almost independently controlled by the core size. These results demonstrate that kagome lattice hollow fibers have a promising potential in ultrashort pulse delivering of high-energy pulses and in several interesting applications in ultrafast nonlinear optics.

Roadmap on ultrafast optics

NASA Astrophysics Data System (ADS)

Reid, Derryck T.; Heyl, Christoph M.; Thomson, Robert R.; Trebino, Rick; Steinmeyer, Günter; Fielding, Helen H.; Holzwarth, Ronald; Zhang, Zhigang; Del'Haye, Pascal; Südmeyer, Thomas; Mourou, Gérard; Tajima, Toshiki; Faccio, Daniele; Harren, Frans J. M.; Cerullo, Giulio

2016-09-01

The year 2015 marked the 25th anniversary of modern ultrafast optics, since the demonstration of the first Kerr lens modelocked Ti:sapphire laser in 1990 (Spence et al 1990 Conf. on Lasers and Electro-Optics, CLEO, pp 619-20) heralded an explosion of scientific and engineering innovation. The impact of this disruptive technology extended well beyond the previous discipline boundaries of lasers, reaching into biology labs, manufacturing facilities, and even consumer healthcare and electronics. In recognition of such a milestone, this roadmap on Ultrafast Optics draws together articles from some of the key opinion leaders in the field to provide a freeze-frame of the state-of-the-art, while also attempting to forecast the technical and scientific paradigms which will define the field over the next 25 years. While no roadmap can be fully comprehensive, the thirteen articles here reflect the most exciting technical opportunities presented at the current time in Ultrafast Optics. Several articles examine the future landscape for ultrafast light sources, from practical solid-state/fiber lasers and Raman microresonators to exotic attosecond extreme ultraviolet and possibly even zeptosecond x-ray pulses. Others address the control and measurement challenges, requiring radical approaches to harness nonlinear effects such as filamentation and parametric generation, coupled with the question of how to most accurately characterise the field of ultrafast pulses simultaneously in space and time. Applications of ultrafast sources in materials processing, spectroscopy and time-resolved chemistry are also discussed, highlighting the improvements in performance possible by using lasers of higher peak power and repetition rate, or by exploiting the phase stability of emerging new frequency comb sources.

Variable depth core sampler

DOEpatents

Bourgeois, Peter M.; Reger, Robert J.

1996-01-01

A variable depth core sampler apparatus comprising a first circular hole saw member, having longitudinal sections that collapses to form a point and capture a sample, and a second circular hole saw member residing inside said first hole saw member to support the longitudinal sections of said first hole saw member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside said first hole saw member.

Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Rongchun; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu; Nishiyama, Yusuke

2015-10-28

A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protonsmore » and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.« less

Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4.

PubMed

Dean, M P M; Cao, Y; Liu, X; Wall, S; Zhu, D; Mankowsky, R; Thampy, V; Chen, X M; Vale, J G; Casa, D; Kim, Jungho; Said, A H; Juhas, P; Alonso-Mori, R; Glownia, J M; Robert, A; Robinson, J; Sikorski, M; Song, S; Kozina, M; Lemke, H; Patthey, L; Owada, S; Katayama, T; Yabashi, M; Tanaka, Yoshikazu; Togashi, T; Liu, J; Rayan Serrao, C; Kim, B J; Huber, L; Chang, C-L; McMorrow, D F; Först, M; Hill, J P

2016-06-01

Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr 2IrO 4

DOE PAGES

Dean, M. P. M.; Cao, Y.; Liu, X.; ...

2016-05-09

Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity 1, 2, 3, 4. Recently, photo-excitation has been used to induce similarly exotic states transiently 5, 6, 7. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr 2IrO 4. We find that the non-equilibrium state, 2more » ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. In conclusion, the marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.« less

Scenarios for Ultrafast Gamma-Ray Variability in AGN

NASA Astrophysics Data System (ADS)

Aharonian, F. A.; Barkov, M. V.; Khangulyan, D.

2017-05-01

We analyze three scenarios to address the challenge of ultrafast gamma-ray variability reported from active galactic nuclei. We focus on the energy requirements imposed by these scenarios: (I) external cloud in the jet, (II) relativistic blob propagating through the jet material, and (III) production of high-energy gamma-rays in the magnetosphere gaps. We show that while the first two scenarios are not constrained by the flare luminosity, there is a robust upper limit on the luminosity of flares generated in the black hole magnetosphere. This limit depends weakly on the mass of the central black hole and is determined by the accretion disk magnetization, viewing angle, and the pair multiplicity. For the most favorable values of these parameters, the luminosity for 5-minute flares is limited by 2× {10}43 {erg} {{{s}}}-1, which excludes a black hole magnetosphere origin of the flare detected from IC 310. In the scopes of scenarios (I) and (II), the jet power, which is required to explain the IC 310 flare, exceeds the jet power estimated based on the radio data. To resolve this discrepancy in the framework of scenario (II), it is sufficient to assume that the relativistic blobs are not distributed isotropically in the jet reference frame. A realization of scenario (I) demands that the jet power during the flare exceeds by a factor 102 the power of the radio jet relevant to a timescale of 108 years.

Fluid inclusions and preliminary studies of hydrothermal alteration in core hole PLTG-1, Platanares geothermal area, Honduras

USGS Publications Warehouse

Bargar, K.E.

1991-01-01

The Platanares geothermal area in western Honduras consists of more than 100 hot springs that issue from numerous hot-spring groups along the banks or within the streambed of the Quebrada de Agua Caliente (brook of hot water). Evaluation of this geothermal area included drilling a 650-m deep PLTG-1 drill hole which penetrated a surface mantling of stream terrace deposits, about 550 m of Tertiary andesitic lava flows, and Cretaceous to lower Tertiary sedimentary rocks in the lower 90 m of the drill core. Fractures and cavities in the drill core are partly to completely filled by hydrothermal minerals that include quartz, kaolinite, mixed-layer illite-smectite, barite, fluorite, chlorite, calcite, laumontite, biotite, hematite, marcasite, pyrite, arsenopyrite, stibnite, and sphalerite; the most common open-space fillings are calcite and quartz. Biotite from 138.9-m depth, dated at 37.41 Ma by replicate 40Ar/39 Ar analyses using a continuous laser system, is the earliest hydrothermal mineral deposited in the PLTG-1 drill core. This mid-Tertiary age indicates that at least some of the hydrothermal alteration encountered in the PLTG-1 drill core occured in the distant past and is unrelated to the present geothermal system. Furthermore, homogenization temperatures (Th) and melting-point temperatures (Tm) for fluid inclusions in two of the later-formed hydrothermal minerals, calcite and barite, suggest that the temperatures and concentration of dissolved solids of the fluids present at the time these fluid inclusions formed were very different from the present temperatures and fluid chemistry measured in the drill hole. Liquid-rich secondary fluid inclusions in barite and caicite from drill hole PLTG-1 have Th values that range from about 20??C less than the present measured temperature curve at 590.1-m depth to as much as 90??C higher than the temperature curve at 46.75-m depth. Many of the barite Th measurements (ranging between 114?? and 265??C) plot above the

Jet Power vs. Black Hole Mass in Blazars: Exploring the Relationship in the Context of the B-Z Mechanism

NASA Astrophysics Data System (ADS)

Fernandes, Sunil; Schlegel, E.

2012-01-01

Recently, a tentative negative correlation between jet power and BH mass in a sample of GeV-TeV BL Lac objects(Zhang et al 2011). It was suggested that spin energy extraction could play a significant role in producing the jets and the jets are not purely accretion driven. Broderick et al (2011) recently explored the relationship between jet power and radio core luminosity building on Blanford et al (1979) theoretical work. Using this work we have studied the relationship between radio core luminosity (as a stand in for jet power) and black hole mass and have found a possible positive correlation in a sample of nearby BL Lac objects. The present poster attempts to explore this relationship in the context of the Blanford-Znajek mechanism which predicts jet power increases with black hole mass, spin rate, and accretion rate.

Ultrafast Dephasing and Incoherent Light Photon Echoes in Organic Amorphous Systems

NASA Astrophysics Data System (ADS)

Yano, Ryuzi; Matsumoto, Yoshinori; Tani, Toshiro; Nakatsuka, Hiroki

1989-10-01

Incoherent light photon echoes were observed in organic amorphous systems (cresyl violet in polyvinyl alcohol and 1,4-dihydroxyanthraquinone in polymethacrylic acid) by using temporally-incoherent nanosecond laser pulses. It was found that an echo decay curve of an organic amorphous system is composed of a sharp peak which decays very rapidly and a slowly decaying wing at the tail. We show that the persistent hole burning (PHB) spectra were reproduced by the Fourier-cosine transforms of the echo decay curves. We claim that in general, we must take into account the multi-level feature of the system in order to explain ultrafast dephasing at very low temperatures.

Testing ultrafast mode-locking at microhertz relative optical linewidth.

PubMed

Martin, Michael J; Foreman, Seth M; Schibli, T R; Ye, Jun

2009-01-19

We report new limits on the phase coherence of the ultrafast mode-locking process in an octave-spanning Ti:sapphire comb.We find that the mode-locking mechanism correlates optical phase across a full optical octave with less than 2.5 microHZ relative linewidth. This result is at least two orders of magnitude below recent predictions for quantum-limited individual comb-mode linewidths, verifying that the mode-locking mechanism strongly correlates quantum noise across the comb spectrum.

Variable depth core sampler

DOEpatents

Bourgeois, P.M.; Reger, R.J.

1996-02-20

A variable depth core sampler apparatus is described comprising a first circular hole saw member, having longitudinal sections that collapses to form a point and capture a sample, and a second circular hole saw member residing inside said first hole saw member to support the longitudinal sections of said first hole saw member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside said first hole saw member. 7 figs.

Selective isolation of the electron or hole in photocatalysis: ZnO-TiO2 and TiO2-ZnO core-shell structured heterojunction nanofibers via electrospinning and atomic layer deposition.

PubMed

Kayaci, Fatma; Vempati, Sesha; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

2014-06-07

Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ∼1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.

Unification of X-ray Winds in Seyfert Galaxies: From Ultra-fast Outflows to Warm Absorbers

NASA Astrophysics Data System (ADS)

Tombesi, Francesco; Cappi, M.; Reeves, J.; Nemmen, R.; Braito, V.; Gaspari, M.; Reynolds, C. S.

2013-04-01

The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is >60%, consistent with previous studies. The fraction of sources with UFOs is >34%, >67% of which also show WAs. The large dynamic range obtained when considering all the absorbers together allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. The absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. This strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The observed parameters and correlations are consistent with both radiation pressure through Compton scattering and MHD processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, have a sufficiently high mechanical power to significantly contribute to the AGN feedback.

Ultrafast and nonlinear surface-enhanced Raman spectroscopy.

PubMed

Gruenke, Natalie L; Cardinal, M Fernanda; McAnally, Michael O; Frontiera, Renee R; Schatz, George C; Van Duyne, Richard P

2016-04-21

Ultrafast surface-enhanced Raman spectroscopy (SERS) has the potential to study molecular dynamics near plasmonic surfaces to better understand plasmon-mediated chemical reactions such as plasmonically-enhanced photocatalytic or photovoltaic processes. This review discusses the combination of ultrafast Raman spectroscopic techniques with plasmonic substrates for high temporal resolution, high sensitivity, and high spatial resolution vibrational spectroscopy. First, we introduce background information relevant to ultrafast SERS: the mechanisms of surface enhancement in Raman scattering, the characterization of plasmonic materials with ultrafast techniques, and early complementary techniques to study molecule-plasmon interactions. We then discuss recent advances in surface-enhanced Raman spectroscopies with ultrafast pulses with a focus on the study of molecule-plasmon coupling and molecular dynamics with high sensitivity. We also highlight the challenges faced by this field by the potential damage caused by concentrated, highly energetic pulsed fields in plasmonic hotspots, and finally the potential for future ultrafast SERS studies.

Ultrafast Science Opportunities with Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durr, Hermann

X-rays and electrons are two of the most fundamental probes of matter. When the Linac Coherent Light Source (LCLS), the world’s first x-ray free electron laser, began operation in 2009, it transformed ultrafast science with the ability to generate laser-like x-ray pulses from the manipulation of relativistic electron beams. This document describes a similar future transformation. In Transmission Electron Microscopy, ultrafast relativistic (MeV energy) electron pulses can achieve unsurpassed spatial and temporal resolution. Ultrafast temporal resolution will be the next frontier in electron microscopy and can ideally complement ultrafast x-ray science done with free electron lasers. This document describes themore » Grand Challenge science opportunities in chemistry, material science, physics and biology that arise from an MeV ultrafast electron diffraction & microscopy facility, especially when coupled with linac-based intense THz and X-ray pump capabilities.« less

The correlation between the amplitude of Osborn wave and core body temperature.

PubMed

Omar, Hesham R; Camporesi, Enrico M

2015-08-01

Several reports illustrate an inverse correlation between the Osborn wave (J wave) amplitude and core body temperature. We attempted to study the strength of this correlation. We reviewed all articles reporting hypothermic J waves from 1950-2014 for patient demographics, core body temperature in Celsius (°C), amplitude of the J wave in millimeters (mm), lead with the highest amplitude of J wave, presence of acidosis, PO2, electrolytes and outcome. In cases with more than one electrocardiogram (ECG), the respective core body temperature and J wave amplitude of each ECG were recorded. The main study outcome is to evaluate the correlation between the J wave amplitude and core body temperature in the admission ECG. We have also examined the strength of this relationship in cases with more than one ECG. We attempted to find the most frequent lead that recorded the highest amplitude of the J wave in addition to the correlation between the amplitude of J wave and pH. We found 64 articles comprising a total of 68 cases. When analyzing only cases with more than one reported ECG, there was a strong inverse correlation (r = - 0.682, p<0.001) between J wave amplitude and body temperature: however, when analyzing admission ECG of all cases, the correlation was only moderate (r = - 0.410, p<0.001). The lead with the highest amplitude of the J wave was V4 (44% of the cases, p<0.001) followed by V3 (23.7% of the cases, p<0.001). The amplitude of the J wave in the admission ECG of hypothermic patients may not accurately predict the core body temperature. © The European Society of Cardiology 2014.

Interfacial charge separation and recombination in InP and quasi-type II InP/CdS core/shell quantum dot-molecular acceptor complexes.

PubMed

Wu, Kaifeng; Song, Nianhui; Liu, Zheng; Zhu, Haiming; Rodríguez-Córdoba, William; Lian, Tianquan

2013-08-15

Recent studies of group II-VI colloidal semiconductor heterostuctures, such as CdSe/CdS core/shell quantum dots (QDs) or dot-in-rod nanorods, show that type II and quasi-type II band alignment can facilitate electron transfer and slow down charge recombination in QD-molecular electron acceptor complexes. To explore the general applicability of this wave function engineering approach for controlling charge transfer properties, we investigate exciton relaxation and dissociation dynamics in InP (a group III-V semiconductor) and InP/CdS core/shell (a heterostructure beween group III-V and II-VI semiconductors) QDs by transient absorption spectroscopy. We show that InP/CdS QDs exhibit a quasi-type II band alignment with the 1S electron delocalized throughout the core and shell and the 1S hole confined in the InP core. In InP-methylviologen (MV(2+)) complexes, excitons in the QD can be dissociated by ultrafast electron transfer to MV(2+) from the 1S electron level (with an average time constant of 11.4 ps) as well as 1P and higher electron levels (with a time constant of 0.39 ps), which is followed by charge recombination to regenerate the complex in its ground state (with an average time constant of 47.1 ns). In comparison, InP/CdS-MV(2+) complexes show similar ultrafast charge separation and 5-fold slower charge recombination rates, consistent with the quasi-type II band alignment in these heterostructures. This result demonstrates that wave function engineering in nanoheterostructures of group III-V and II-VI semiconductors provides a promising approach for optimizing their light harvesting and charge separation for solar energy conversion applications.

Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

NASA Astrophysics Data System (ADS)

Hu, Hao; Ding, Hepeng; Liu, Feng

2015-02-01

Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a ``super pressing'' state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

PubMed Central

Hu, Hao; Ding, Hepeng; Liu, Feng

2015-01-01

Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions. PMID:25645258

Quantum Hooke's law to classify pulse laser induced ultrafast melting.

PubMed

Hu, Hao; Ding, Hepeng; Liu, Feng

2015-02-03

Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a "super pressing" state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

The 40Ar/39Ar and K/Ar dating of lavas from the Hilo 1-km core hole, Hawaii Scientific Drilling Project

USGS Publications Warehouse

Sharp, W.D.; Turrin, B.D.; Renne, P.R.; Lanphere, M.A.

1996-01-01

Mauna Kea lava flows cored in the HilIo hole range in age from <200 ka to about 400 ka based on 40Ar/39Ar incremental heating and K-Ar analyses of 16 groundmass samples and one coexisting plagioclase. The lavas, all subaerially deposited, include a lower section consisting only of tholeiitic basalts and an upper section of interbedded alkalic, transitional tholeiitic, and tholeiitic basalts. The lower section has yielded predominantly complex, discordant 40Ar/39Ar age spectra that result from mobility of 40Ar and perhaps K, the presence of excess 40Ar, and redistribution of 39Ar by recoil. Comparison of K-Ar ages with 40Ar/39Ar integrated ages indicates that some of these samples have also lost 39Ar. Nevertheless, two plateau ages of 391 ?? 40 and 400 ?? 26 ka from deep in the hole, combined with data from the upper section, show that the tholeiitic section accumulated at an average rate of about 7 to 8 m/kyr and has an mean recurrence interval of 0.5 kyr/flow unit. Samples from the upper section yield relatively precise 40Ar/39Ar plateau and isotope correlation ages of 326 ?? 23, 241 ?? 5, 232 ?? 4, and 199 ?? 9 ka for depths of -415.7 m to -299.2 m. Within their uncertainty, these ages define a linear relationship with depth, with an average accumulation rate of 0.9 m/kyr and an average recurrence interval of 4.8 kyr/flow unit. The top of the Mauna Kea sequence at -280 m must be older than the plateau age of 132 ?? 32 ka, obtained for the basal Mauna Loa flow in the corehole. The upward decrease in lava accumulation rate is a consequence of the decreasing magma supply available to Mauna Kea as it rode the Pacific plate away from its magma source, the Hawaiian mantle plume. The age-depth relation in the core hole may be used to test and refine models that relate the growth of Mauna Kea to the thermal and compositional structure of the mantle plume.

Double core-hole emissivity of transient aluminum plasmas produced in the interaction with ultra-intense x-ray laser pulse

NASA Astrophysics Data System (ADS)

Gao, Cheng; Zeng, Jiaolong; Yuan, Jianmin

2015-11-01

Emissivity of single core-hole (SCH) and double core-hole (DCH) states of aluminum plasmas produced in the interaction with ultra-intense x-ray laser pulse interaction are investigated systematically by solving the time-dependent rate equation implemented in the detailed level accounting approximation. We first demonstrated the plasma density effects on level populations and charge state distribution. Compared with recent experiments, it is shown that the plasma density effects play important roles in the evolution dynamics. Then we systematically investigated the emissivity of the transient aluminum plasmas produced by the x-ray laser pulses with a few photon energies above the threshold photon energy to create DCH states. For the laser photon energy where there are resonant absorptions (RA), 1s-np transitions with both full 1s and SCH 1s states play important roles in time evolution of the population and DCH emission spectroscopy. The significant RA effects are illustrated in detail for x-ray pulses, which creates the 1s-2p resonant absorption from the SCH states of Al VII. With the increase of the photon energy, the emissions from lower charge states become larger.

Coronal holes, large-scale magnetic field, and activity complexes in solar cycle 23

NASA Astrophysics Data System (ADS)

Tavastsherna, K. S.; Polyakow, E. V.

2014-12-01

A correlation among coronal holes (CH), a large-scale magnetic field (LMF), and activity complexes (AC) is studied in this work for 1997-2007 with the use of a coronal hole series obtained from observations at the Kitt Peak Observatory in the HeI 10830 Å line in 1975-2003 and SOHO/EIT-195 Å in 1996-2012 (Tlatov et al., 2014), synoptic Hα charts from Kislovodsk Mountain Astonomical Station, and the catalog of AC cores (Yazev, 2012). From the imposition of CH boundaries on Hα charts, which characterize the positions of neutral lines of the radial components of a large-scale solar magnetic field, it turns out that 70% of CH are located in unipolar regions of their sign during the above period, 10% are in the region of an opposite sign, and 20% are mainly very large CH, which are often crossed by the neutral lines of several unipolar regions. Data on mutual arrangement of CH and AC cores were obtained. It was shown that only some activity comples cores have genetic relationships with CH.

Tempo-spatially resolved dynamics of elec- trons and holes in bilayer MoS2 -WS2

NASA Astrophysics Data System (ADS)

Galicia-Hernandez, J. M.; Turkowski, V.; Hernandez-Cocoletzi, G.; Rahman, T. S.

We have performed a Density-Matrix Time-Dependent Density-Functional Theory analysis of the response of bilayer MoS2-WS2 to external laser-pulse perturbations. Time-resolved study of the dynamics of electrons and holes, including formation and dissociation of strongly-bound intra- and inter-layer excitonic states, shows that the experimentally observed ultrafast inter-layer MoS2 to WS2 migration of holes may be attributed to unusually large delocalization of the hole state which extends far into the inter-layer region. We also argue that the velocity of the hole transfer may be further enhanced by its interaction with transfer phonon modes. We analyze other possible consequences of the hole delocalization in the system, including reduction of the effects of the electron-electron and hole-hole repulsion in the trions and biexcitons as compared to that in the monolayers Work supported in part by DOE Grant No. DOE-DE-FG02-07ER46354 and by CONACYT Scholarship No. 23210 (J.M.G.H.).

Edge turbulence effect on ultra-fast swept reflectometry core measurements in tokamak plasmas

NASA Astrophysics Data System (ADS)

Zadvitskiy, G. V.; Heuraux, S.; Lechte, C.; Hacquin, S.; Sabot, R.

2018-02-01

Ultra-fast frequency-swept reflectometry (UFSR) enables one to provide information about the turbulence radial wave-number spectrum and perturbation amplitude with good spatial and temporal resolutions. However, a data interpretation of USFR is quiet tricky. An iterative algorithm to solve this inverse problem was used in past works, Gerbaud (2006 Rev. Sci. Instrum. 77 10E928). For a direct solution, a fast 1D Helmholtz solver was used. Two-dimensional effects are strong and should be taken into account during data interpretation. As 2D full-wave codes are still too time consuming for systematic application, fast 2D approaches based on the Born approximation are of prime interest. Such methods gives good results in the case of small turbulence levels. However in tokamak plasmas, edge turbulence is usually very strong and can distort and broaden the probing beam Sysoeva et al (2015 Nucl. Fusion 55 033016). It was shown that this can change reflectometer phase response from the plasma core. Comparison between 2D full wave computation and the simplified Born approximation was done. The approximated method can provide a right spectral shape, but it is unable to describe a change of the spectral amplitude with an edge turbulence level. Computation for the O-mode wave with the linear density profile in the slab geometry and for realistic Tore-Supra density profile, based on the experimental data turbulence amplitude and spectrum, were performed to investigate the role of strong edge turbulence. It is shown that the spectral peak in the signal amplitude variation spectrum which rises with edge turbulence can be a signature of strong edge turbulence. Moreover, computations for misaligned receiving and emitting antennas were performed. It was found that the signal amplitude variation peak changes its position with a receiving antenna poloidal displacement.

Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy

PubMed Central

Ghadiri, Elham; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E.

2016-01-01

Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded. PMID:27095505

Core drilling provides information about Santa Fe Group aquifer system beneath Albuquerque's West Mesa

USGS Publications Warehouse

Allen, B.D.; Connell, S.D.; Hawley, J.W.; Stone, B.D.

1998-01-01

Core samples from the upper ???1500 ft of the Santa Fe Group in the Albuquerque West Mesa area provide a first-hand look at the sediments and at subsurface stratigraphic relationships in this important part of the basin-fill aquifer system. Two major hydrostratigraphic subunits consisting of a lower coarse-grained, sandy interval and an overlying fine-grained, interbedded silty sand and clay interval lie beneath the water table at the 98th St core hole. Borehole electrical conductivity measurements reproduce major textural changes observed in the recovered cores and support subsurface correlations of hydrostratigraphic units in the Santa Fe Group aquifer system based on geophysical logs. Comparison of electrical logs from the core hole and from nearby city wells reveals laterally consistent lithostratigraphic patterns over much of the metropolitan area west of the Rio Grande that may be used to delineate structural and related stratigraphic features that have a direct bearing on the availability of ground water.

Recovery and Lithologic Analysis of Sediment from Hole UT-GOM2-1-H002, Green Canyon 955, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Kinash, N.; Cook, A.; Sawyer, D.; Heber, R.

2017-12-01

In May 2017 the University of Texas led a drilling and pressure coring expedition in the northern Gulf of Mexico, UT-GOM2-01. The holes were located in Green Canyon Block 955, where the Gulf of Mexico Joint Industry Project Leg II identified an approximately 100m thick hydrate-filled course-grained levee unit in 2009. Two separate wells were drilled into this unit: Holes H002 and H005. In Hole H002, a cutting shoe drill bit was used to collect the pressure cores, and only 1 of the 8 cores collected was pressurized during recovery. The core recovery in Hole H002 was generally poor, about 34%, while the only pressurized core had 45% recovery. In Hole H005, a face bit was used during pressure coring where 13 cores were collected and 9 cores remained pressurized. Core recovery in Hole H005 was much higher, at about 75%. The type of bit was not the only difference between the holes, however. Drilling mud was used throughout the drilling and pressure coring of Hole H002, while only seawater was used during the first 80m of pressure cores collected in Hole H005. Herein we focus on lithologic analysis of Hole H002 with the goal of documenting and understanding core recovery in Hole H002 to compare with Hole H005. X-ray Computed Tomography (XCT) images were collected by Geotek on pressurized cores, mostly from Hole H005, and at Ohio State on unpressurized cores, mostly from Hole H002. The XCT images of unpressurized cores show minimal sedimentary structures and layering, unlike the XCT images acquired on the pressurized, hydrate-bearing cores. Only small sections of the unpressurized cores remained intact. The unpressurized cores appear to have two prominent facies: 1) silt that did not retain original sedimentary fabric and often was loose within the core barrel, and 2) dense mud sections with some sedimentary structures and layering present. On the XCT images, drilling mud appears to be concentrated on the sides of cores, but also appears in layers and fractures within

A disc corona-jet model for the radio/X-ray correlation in black hole X-ray binaries

NASA Astrophysics Data System (ADS)

Qiao, Erlin; Liu, B. F.

2015-04-01

The observed tight radio/X-ray correlation in the low spectral state of some black hole X-ray binaries implies the strong coupling of the accretion and jet. The correlation of L_R ∝ L_X^{˜ 0.5-0.7} was well explained by the coupling of a radiatively inefficient accretion flow and a jet. Recently, however, a growing number of sources show more complicated radio/X-ray correlations, e.g. L_R ∝ L_X^{˜ 1.4} for LX/LEdd ≳ 10-3, which is suggested to be explained by the coupling of a radiatively efficient accretion flow and a jet. In this work, we interpret the deviation from the initial radio/X-ray correlation for LX/LEdd ≳ 10-3 with a detailed disc corona-jet model. In this model, the disc and corona are radiatively and dynamically coupled. Assuming a fraction of the matter in the accretion flow, η ≡ dot{M}_jet/dot{M}, is ejected to form the jet, we can calculate the emergent spectrum of the disc corona-jet system. We calculate LR and LX at different dot{M}, adjusting η to fit the observed radio/X-ray correlation of the black hole X-ray transient H1743-322 for LX/LEdd > 10-3. It is found that always the X-ray emission is dominated by the disc corona and the radio emission is dominated by the jet. We noted that the value of η for the deviated radio/X-ray correlation for LX/LEdd > 10-3 is systematically less than that of the case for LX/LEdd < 10-3, which is consistent with the general idea that the jet is often relatively suppressed at the high-luminosity phase in black hole X-ray binaries.

Ultrafast dynamics during the photoinduced phase transition in VO2

NASA Astrophysics Data System (ADS)

Wegkamp, Daniel; Stähler, Julia

2015-12-01

The phase transition of VO2 from a monoclinic insulator to a rutile metal, which occurs thermally at TC = 340 K, can also be driven by strong photoexcitation. The ultrafast dynamics during this photoinduced phase transition (PIPT) have attracted great scientific attention for decades, as this approach promises to answer the question of whether the insulator-to-metal (IMT) transition is caused by electronic or crystallographic processes through disentanglement of the different contributions in the time domain. We review our recent results achieved by femtosecond time-resolved photoelectron, optical, and coherent phonon spectroscopy and discuss them within the framework of a selection of latest, complementary studies of the ultrafast PIPT in VO2. We show that the population change of electrons and holes caused by photoexcitation launches a highly non-equilibrium plasma phase characterized by enhanced screening due to quasi-free carriers and followed by two branches of non-equilibrium dynamics: (i) an instantaneous (within the time resolution) collapse of the insulating gap that precedes charge carrier relaxation and significant ionic motion and (ii) an instantaneous lattice potential symmetry change that represents the onset of the crystallographic phase transition through ionic motion on longer timescales. We discuss the interconnection between these two non-thermal pathways with particular focus on the meaning of the critical fluence of the PIPT in different types of experiments. Based on this, we conclude that the PIPT threshold identified in optical experiments is most probably determined by the excitation density required to drive the lattice potential change rather than the IMT. These considerations suggest that the IMT can be driven by weaker excitation, predicting a transiently metallic, monoclinic state of VO2 that is not stabilized by the non-thermal structural transition and, thus, decays on ultrafast timescales.

Artist Concept: Active Black Hole Squashes Star Formation

NASA Image and Video Library

2012-05-09

Herschel Space Observatory has shown that galaxies with the most powerful, active, supermassive black holes at their cores produce fewer stars than galaxies with less active black holes in this artist concept.

Near infrared light induced plasmonic hot hole transfer at a nano-heterointerface.

PubMed

Lian, Zichao; Sakamoto, Masanori; Matsunaga, Hironori; Vequizo, Junie Jhon M; Yamakata, Akira; Haruta, Mitsutaka; Kurata, Hiroki; Ota, Wataru; Sato, Tohru; Teranishi, Toshiharu

2018-06-13

Localized surface plasmon resonance (LSPR)-induced hot-carrier transfer is a key mechanism for achieving artificial photosynthesis using the whole solar spectrum, even including the infrared (IR) region. In contrast to the explosive development of photocatalysts based on the plasmon-induced hot electron transfer, the hole transfer system is still quite immature regardless of its importance, because the mechanism of plasmon-induced hole transfer has remained unclear. Herein, we elucidate LSPR-induced hot hole transfer in CdS/CuS heterostructured nanocrystals (HNCs) using time-resolved IR (TR-IR) spectroscopy. TR-IR spectroscopy enables the direct observation of carrier in a LSPR-excited CdS/CuS HNC. The spectroscopic results provide insight into the novel hole transfer mechanism, named plasmon-induced transit carrier transfer (PITCT), with high quantum yields (19%) and long-lived charge separations (9.2 μs). As an ultrafast charge recombination is a major drawback of all plasmonic energy conversion systems, we anticipate that PITCT will break the limit of conventional plasmon-induced energy conversion.

Intermediate-Mass Black Holes

NASA Astrophysics Data System (ADS)

Miller, M. Coleman; Colbert, E. J. M.

2004-01-01

The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3 20 M⊙), which are produced by the core collapse of massive stars, and supermassive (M~106 1010 M⊙), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~102 104 M⊙. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.

Intermediate-Mass Black Holes

NASA Astrophysics Data System (ADS)

Coleman Miller, M.; Colbert, E. J. M.

The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3-20 M⊙), which are produced by the core collapse of massive stars, and supermassive (M~106-1010 M⊙), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~102-104 M⊙. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.

Neogene and Quaternary geology of a stratigraphic test hole on Horn Island, Mississippi Sound

USGS Publications Warehouse

Gohn, Gregory S.; Brewster-Wingard, G. Lynn; Cronin, Thomas M.; Edwards, Lucy E.; Gibson, Thomas G.; Rubin, Meyer; Willard, Debra A.

1996-01-01

During April and May, 1991, the U.S. Geological Survey (USGS) drilled a 510-ft-deep, continuously cored, stratigraphic test hole on Horn Island, Mississippi Sound, as part of a field study of the Neogene and Quaternary geology of the Mississippi coastal area. The USGS drilled two new holes at the Horn Island site. The first hole was continuously cored to a depth of 510 ft; coring stopped at this depth due to mechanical problems. To facilitate geophysical logging, an unsampled second hole was drilled to a depth of 519 ft at the same location.

The response of relativistic outflowing gas to the inner accretion disk of a black hole.

PubMed

Parker, Michael L; Pinto, Ciro; Fabian, Andrew C; Lohfink, Anne; Buisson, Douglas J K; Alston, William N; Kara, Erin; Cackett, Edward M; Chiang, Chia-Ying; Dauser, Thomas; De Marco, Barbara; Gallo, Luigi C; Garcia, Javier; Harrison, Fiona A; King, Ashley L; Middleton, Matthew J; Miller, Jon M; Miniutti, Giovanni; Reynolds, Christopher S; Uttley, Phil; Vasudevan, Ranjan; Walton, Dominic J; Wilkins, Daniel R; Zoghbi, Abderahmen

2017-03-01

The brightness of an active galactic nucleus is set by the gas falling onto it from the galaxy, and the gas infall rate is regulated by the brightness of the active galactic nucleus; this feedback loop is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts. Gas outflows (in the form of disk winds) release huge quantities of energy into the interstellar medium, potentially clearing the surrounding gas. The most extreme (in terms of speed and energy) of these-the ultrafast outflows-are the subset of X-ray-detected outflows with velocities higher than 10,000 kilometres per second, believed to originate in relativistic (that is, near the speed of light) disk winds a few hundred gravitational radii from the black hole. The absorption features produced by these outflows are variable, but no clear link has been found between the behaviour of the X-ray continuum and the velocity or optical depth of the outflows, owing to the long timescales of quasar variability. Here we report the observation of multiple absorption lines from an extreme ultrafast gas flow in the X-ray spectrum of the active galactic nucleus IRAS 13224-3809, at 0.236 ± 0.006 times the speed of light (71,000 kilometres per second), where the absorption is strongly anti-correlated with the emission of X-rays from the inner regions of the accretion disk. If the gas flow is identified as a genuine outflow then it is in the fastest five per cent of such winds, and its variability is hundreds of times faster than in other variable winds, allowing us to observe in hours what would take months in a quasar. We find X-ray spectral signatures of the wind simultaneously in both low- and high-energy detectors, suggesting a single ionized outflow, linking the low- and high-energy absorption lines. That this disk wind is responding to the emission from the inner accretion disk demonstrates a connection between accretion processes occurring on very different

Discovery of the correlation between peak episodic jet power and X-ray peak luminosity of the soft state in black hole transients

NASA Astrophysics Data System (ADS)

Zhang, H.; Yu, W.

2015-08-01

Episodic jets are usually observed in the intermediate state of black hole transients during their X-ray outbursts. Here we report the discovery of a strong positive correlation between the peak radio power of the episodic jet Pjet and the corresponding peak X-ray luminosity Lx of the soft state (in Eddington units) in a complete sample of the outbursts of black hole transients observed during the RXTE era of which data are available, which follows the relation log Pjet = (2.2 ± 0.3) + (1.6 ± 0.2) × log Lx. The transient ultraluminous X-ray source in M31 and HLX-1 in EXO 243-49 fall on the relation if they contain stellar-mass black hole and either stellar-mass black hole or intermediate-mass black hole, respectively. Besides, a significant correlation between the peak power of the episodic jet and the rate of increase of the X-ray luminosity dLx/dt during the rising phase of those outbursts is also found, following log Pjet = (2.0 ± 0.4) + (0.7 ± 0.2) × log dLx/dt. In GX 339-4 and H 1743-322 in which data for two outbursts are available, measurements of the peak radio power of the episodic jet and the X-ray peak luminosity (and its rate of change) shows similar positive correlations between outbursts, which demonstrate the dominant role of accretion over black hole spin in generating episodic jet power. On the other hand, no significant difference is seen among the systems with different measured black hole spin in current sample. This implies that the power of the episodic jet is strongly affected by non-stationary accretion instead of black hole spin characterized primarily by the rate of change of the mass accretion rate.

Physical Properties of Gabbroic Rock Exposed in Oceanic Core Complexes- New Borehole Data From IODP Hole U1473A in the Indian Ocean and Prior Mid-Atlantic Ridge Results

NASA Astrophysics Data System (ADS)

Blackman, D. K.; Ildefonse, B.; Abe, N.; Harding, A. J.; Guerin, G.

2016-12-01

IODP Expedition 360 to Atlantis Bank on the Southwest Indian Ridge obtained physical property measurements of the 800 m section drilled into the footwall of the oceanic core complex. Compressional velocity (Vp) of core samples range from 5.9-7.2 km/s throughout the hole, with no simple relation to either basic rock type or alteration. Some intervals show a local trend, for example a general increase from 6.7-7.1 km/s over the interval 280-400 mbsf, above a major fault zone at 411-462 mbsf. Below the fault zone, core sample Vp is lower on average (6.6 km/s) than it is in the upper part of the hole (6.8 km/s). Some of this decrease is due to locally greater alteration, but higher oxide content also contributes. Borehole logs show lower Vp shallower than 400 m (6.3-6.4 km/s) and close match to olivine gabbro values below the fault zone, due to higher alteration levels and greater shallow fracturing. Local trends of decreasing Vp, over 10's of m correspond to increasing sample porosity within veined or fractured intervals. Porosities of core in Hole U1473A are low overall (<4.5%) and more variable above 570 mbsf than below. Electrical resistivity of the wallrock tracks logged velocity pattern, dropping below 100 ohm-m in altered or fractured intervals 20-50 m thick and rising over 1000 ohm-m where fresher rock was recovered. The range of velocity, density, and resistivity at Hole U1473A are similar to those in the other deep boreholes from Atlantis Bank (ODP Hole 735B, 1105A) and slightly higher than Vp in the gabbroic core of Atlantis Massif in the Atlantic, Hole U1309D. This may reflect erosion of the detachment zone when the bank was exposed at sealevel. Atlantis Massif displays an increase in Vp from the seafloor to a fault zone at 750 mbsf ( 4.0-6.2 km/s), followed by fairly constant values ( 6.7 km/s) at greater depths, interrupted by a highly altered olivine-rich troctolite interval 1080-1200 mbsf where velocity is up to 1 km/s slower. New analysis of seismic

NEAR-EXTREMAL BLACK HOLES AS INITIAL CONDITIONS OF LONG GRB SUPERNOVAE AND PROBES OF THEIR GRAVITATIONAL WAVE EMISSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Putten, Maurice H. P. M.

2015-09-01

Long gamma-ray bursts (GRBs) associated with supernovae and short GRBs with extended emission (SGRBEE) from mergers are probably powered by black holes as a common inner engine, as their prompt GRB emission satisfies the same Amati correlation in the E{sub p,i}–E{sub iso} plane. We introduce modified Bardeen equations to identify hyper-accretion driving newly formed black holes in core-collapse supernovae to near-extremal spin as a precursor to prompt GRB emission. Subsequent spin-down is observed in the BATSE catalog of long GRBs. Spin-down provides a natural unification of long durations associated with the lifetime of black hole spin for normal long GRBsmore » and SGRBEEs, given the absence of major fallback matter in mergers. The results point to major emissions unseen in high frequency gravitational waves. A novel matched filtering method is described for LIGO–Virgo and KAGRA broadband probes of nearby core-collapse supernovae at essentially maximal sensitivity.« less

Individual and family environment correlates differ for consumption of core and non-core foods in children.

PubMed

Johnson, Laura; van Jaarsveld, Cornelia H M; Wardle, Jane

2011-03-01

Children's diets contain too few fruits and vegetables and too many foods high in saturated fat. Food intake is affected by multiple individual and family factors, which may differ for core foods (that are important to a healthy diet) and non-core foods (that are eaten more for pleasure than health). Data came from a sample of twins aged 11 years (n 342) and their parents from the Twins Early Development Study. Foods were categorised into two types: core (e.g. cereals, vegetables and dairy) and non-core (e.g. fats, crisps and biscuits). Parents' and children's intake was assessed by an FFQ. Mothers' and children's preference ratings and home availability were assessed for each food type. Parental feeding practices were assessed with the child feeding questionnaire and child television (TV) watching was maternally reported. Physical activity was measured using accelerometers. Correlates of the child's consumption of each food type were examined using a complex samples general linear model adjusted for potential confounders. Children's non-core food intake was associated with more TV watching, higher availability and greater maternal intake of non-core foods. Children's core food intake was associated with higher preferences for core foods and greater maternal intake of core foods. These results suggest that maternal intake influences both food types, while preferences affect intake of core foods but not of non-core foods, and availability and TV exposure were only important for non-core food intake. Cross-sectional studies cannot determine causality, but the present results suggest that different approaches may be needed to change the balance of core and non-core foods in children's diets.

Binary black holes in nuclei of extragalactic radio sources

NASA Astrophysics Data System (ADS)

Roland, J.; Britzen, S.

If we assume that nuclei of extragalactic radio sources contain a Binary Black Hole system, the 2 black holes can eject VLBI components and in that case 2 families of different VLBI trajectories will be observed. An important consequence of the presence of a Binary Black Hole system is the following: the VLBI core is associated with one black hole and if a VLBI component is ejected by the second black hole, one expects to be able to detect the offset of the origin of the VLBI component ejected by the black hole not associated with the VLBI core. The ejection of VLBI components is perturbed by the precession of the accretion disk and the motion of the black holes around the gravity center of the BBH system. We modeled the ejection of the component taking into account the 2 perturbations and we obtained a method to fit the coordinates of a VLBI component and to deduce the characteristics of the BBH system, i.e. the ratio Tp/Tb where Tp is the precession period of the accretion disk and Tb the orbital period of the BBH system, the mass ratio M1/M2, the radius of the BBH system Rbin. We applied the method to component S1 of 1823+568 and to component C5 of 3C 279 which presents a large offset of the space origin from the VLBI core. We found that 1823+568 contains a BBH system which size is Rbin ≈ 60 mu as and 3C 279 contains a BBH system which size is Rbin ≈ 378 mu as. We were able to deduce the separation of the 2 black holes and the coordinates of the second black hole from the VLBI core, this information will be important to make the link between the radio reference frame system deduced from VLBI observations and the optical reference frame system deduced from GAIA.

The coupling of a disk corona and a jet for the radio/X-ray correlation in black hole X-ray binaries

NASA Astrophysics Data System (ADS)

Qiao, Erlin

2015-08-01

We interpret the radio/X-ray correlation of LR ∝ LX1.4 for LX/LEdd >10-3 in black hole X-ray binaries with a detailed disk corona-jet model, in which the accretion flow and the jet are connected by a parameter, ‘η’, describing the fraction of the matter in the accretion flow ejected outward to form the jet. We calculate LR and LX at different mass accretion rates, adjusting η to fit the observed radio/X-ray correlation of the black hole X-ray transient H1743-322 for LX/LEdd > 10-3. It is found that the value of η for this radio/X-ray correlation for LX/LEdd > 10-3, is systematically less than that of the case for LX/LEdd < 10-3, which is consistent with the general idea that the jet is often relatively suppressed at the high luminosity phase in black hole X-ray binaries.

Numeric simulation of relativistic stellar core collapse and the formation of Reissner-Nordstroem black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghezzi, Cristian R.; Letelier, Patricio S.

2007-01-15

The time evolution of a set of 22M{sub {center_dot}} unstable charged stars that collapse is computed integrating the Einstein-Maxwell equations. The model simulates the collapse of a spherical star that had exhausted its nuclear fuel and has or acquires a net electric charge in its core while collapsing. When the charge-to-mass ratio is Q/{radical}(G)M{>=}1, the star does not collapse but spreads. On the other hand, a different physical behavior is observed with a charge-to-mass ratio of 1>Q/{radical}(G)M>0.1. In this case, the collapsing matter forms a bubble enclosing a lower density core. We discuss an immediate astrophysical consequence of these resultsmore » that is a more efficient neutrino trapping during the stellar collapse and an alternative mechanism for powerful supernova explosions. The outer space-time of the star is the Reissner-Nordstroem solution that matches smoothly with our interior numerical solution; thus the collapsing models form Reissner-Nordstroem black holes.« less

Quantum Hooke's Law to classify pulse laser induced ultrafast melting

DOE PAGES

Hu, Hao; Ding, Hepeng; Liu, Feng

2015-02-03

Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes ofmore » materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dT m/dP < 0, where T m is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.« less

Correlation between core ion energization, suprathermal electron bursts, and broadband ELF plasma waves

NASA Astrophysics Data System (ADS)

Knudsen, David J.; Clemmons, James H.; Wahlund, Jan-Erik

1998-03-01

Observations of the lowest energy or core ions provide a particularly sensitive measure of the early stages of auroral ion energization. Freja satellite observations of 0-20 eV core ions in the topside auroral ionosphere and cusp/cleft show signs of heating within both regions of VLF hiss and broadband ELF plasma waves. However, heating to several eV or more is associated predominantly with the ELF waves. A correlation analysis of wave and core ion data formed from orbital segments shows that, on average, correlations are highest for wave frequencies below several hundred Hz, and less at VLF hiss frequencies. A similar analysis shows a higher correlation between electron precipitation and ion heating for electron energies below several hundred eV (i.e., the energies associated with suprathermal electron bursts) and a lower correlation above the 1 keV energies associated with auroral inverted-V's. Signs of core ion heating begin to appear when wave power at the O+ gyrofrequency exceeds about 10-3(mVm-1)2/Hz, and when the integrated field-aligned electron flux exceeds a few times 107cm-2s-1sr-1. This electron energy flux threshold is at least an order of magnitude lower than previously inferred from earlier studies comparing suprathermal electron fluxes and energetic ions. Almost all observed heating events occur during enhanced or active geomagnetic conditions; i.e., Kp>=4. While the most intense core ion heating is correlated with broadband ELF waves, we also present one example of weak ion heating of a few eV in a region of VLF auroral hiss.

Relativistic many-body XMCD theory including core degenerate effects

NASA Astrophysics Data System (ADS)

Fujikawa, Takashi

2009-11-01

A many-body relativistic theory to analyze X-ray Magnetic Circular Dichroism (XMCD) spectra has been developed on the basis of relativistic quantum electrodynamic (QED) Keldysh Green's function approach. This theoretical framework enables us to handle relativistic many-body effects in terms of correlated nonrelativistic Green's function and relativistic correction operator Q, which naturally incorporates radiation field screening and other optical field effects in addition to electron-electron interactions. The former can describe the intensity ratio of L2/L3 which deviates from the statistical weight (branching ratio) 1/2. In addition to these effects, we consider the degenerate or nearly degenerate effects of core levels from which photoelectrons are excited. In XPS spectra, for example in Rh 3d sub level excitations, their peak shapes are quite different: This interesting behavior is explained by core-hole moving after the core excitation. We discuss similar problems in X-ray absorption spectra in particular excitation from deep 2p sub levels which are degenerate in each sub levels and nearly degenerate to each other in light elements: The hole left behind is not frozen there. We derive practical multiple scattering formulas which incorporate all those effects.

Experimental Identification of Ultrafast Reverse Hole Transfer at the Interface of the Photoexcited Methanol/Graphitic Carbon Nitride System.

PubMed

Chen, Zongwei; Zhang, Qun; Luo, Yi

2018-05-04

An experimental scrutiny of the photoexcited hole dynamics in a prototypical system is presented in which hole-scavenging methanol molecules are chemisorbed on a graphitic carbon nitride (g-C 3 N 4 ) substrate. A set of comparison and control experiments by means of femtosecond time-resolved transient absorption (fs-TA) spectroscopy were conducted. The elusive reverse hole transfer (RHT) process was identified, which occurs on a timescale of a few hundred picoseconds. The critical role of interfacially chemisorbed methoxy (instead of methanol) as the dominant species responsible for hole scavenging was confirmed by a control experiment using protonated g-C 3 N 4 as the substrate. A hot-hole transfer effect was revealed by implementing different interband photoexcitation scenarios. The RHT rate is the key factor governing the hole-scavenging ability of different hole scavengers. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of three-dimensional stress orientations in the Wenchuan earthquake Fault Scientific Drilling (WFSD) hole-1: A preliminary result by anelastic strain recovery measurements of core samples

NASA Astrophysics Data System (ADS)

Cui, J.; Lin, W.; Wang, L.; Tang, Z.; Sun, D.; Gao, L.; Wang, W.

2010-12-01

A great and destructive earthquake (Ms 8.0; Mw 7.9), Wunchuan earthquake struck on the Longmen Shan foreland trust zone in Sichuan province, China on 12 May 2008 (Xu et al., 2008; Episodes, Vol.31, pp.291-301). As a rapid response scientific drilling project, Wenchuan earthquake Fault Scientific Drilling (WFSD) started on 6 November 2008 shorter than a half of year from the date of earthquake main shock. The first pilot borehole (hole-1) has been drilled to the target depth (measured depth 1201 m MD, vertical depth 1179 m) at Hongkou, Dujianyan, Sichuan and passed through the main fault of the earthquake around 589 m MD. We are trying to determine three dimensional in-situ stress states in the WFSD boreholes by a core-based method, anelastic strain recovery (ASR) method (Lin et al., 2006; Tectonophysics, Vol4.26, pp.221-238). This method has been applied in several scientific drilling projects (TCDP: Lin et al., 2007; TAO, Vol.18, pp.379-393; NanTtoSEIZE: Byrne et al., 2009; GRL, Vol.36, L23310). These applications confirm the validity of using the ASR technique in determining in situ stresses by using drilled cores. We collected total 15 core samples in a depth range from 340 m MD to 1180 m MD, approximately for ASR measurements. Anelastic normal strains, measured every ten minutes in nine directions, including six independent directions, were used to calculate the anelastic strain tensors. The data of the ASR tests conducted at hole-1 is still undergoing analysis. As a tentative perspective, more than 10 core samples showed coherent strain recovery over one - two weeks. However, 2 or 3 core samples cannot be re-orientated to the global system. It means that we cannot rink the stress orientation determined by the core samples to geological structure. Unfortunately, a few core samples showed irregular strain recovery and were not analyzed further. The preliminary results of ASR tests at hole-1 show the stress orientations and stress regime changes a lot with the

Harmonium: An Ultrafast Vacuum Ultraviolet Facility.

PubMed

Arrell, Christopher A; Ojeda, José; Longetti, Luca; Crepaldi, Alberto; Roth, Silvan; Gatti, Gianmarco; Clark, Andrew; van Mourik, Frank; Drabbels, Marcel; Grioni, Marco; Chergui, Majed

2017-05-31

Harmonium is a vacuum ultraviolet (VUV) photon source built within the Lausanne Centre for Ultrafast Science (LACUS). Utilising high harmonic generation, photons from 20-110 eV are available to conduct steady-state or ultrafast photoelectron and photoion spectroscopies (PES and PIS). A pulse preserving monochromator provides either high energy resolution (70 meV) or high temporal resolution (40 fs). Three endstations have been commissioned for: a) PES of liquids; b) angular resolved PES (ARPES) of solids and; c) coincidence PES and PIS of gas phase molecules or clusters. The source has several key advantages: high repetition rate (up to 15 kHz) and high photon flux (1011 photons per second at 38 eV). The capabilities of the facility complement the Swiss ultrafast and X-ray community (SwissFEL, SLS, NCCR MUST, etc.) helping to maintain Switzerland's leading role in ultrafast science in the world.

Ultra-fast movies of thin-film laser ablation

NASA Astrophysics Data System (ADS)

Domke, Matthias; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2012-11-01

Ultra-short-pulse laser irradiation of thin molybdenum films from the glass substrate side initiates an intact Mo disk lift off free from thermal effects. For the investigation of the underlying physical effects, ultra-fast pump-probe microscopy is used to produce stop-motion movies of the single-pulse ablation process, initiated by a 660-fs laser pulse. The ultra-fast dynamics in the femtosecond and picosecond ranges are captured by stroboscopic illumination of the sample with an optically delayed probe pulse of 510-fs duration. The nanosecond and microsecond delay ranges of the probe pulse are covered by an electronically triggered 600-ps laser. Thus, the setup enables an observation of general laser ablation processes from the femtosecond delay range up to the final state. A comparison of time- and space-resolved observations of film and glass substrate side irradiation of a 470-nm molybdenum layer reveals the driving mechanisms of the Mo disk lift off initiated by glass-side irradiation. Observations suggest that a phase explosion generates a liquid-gas mixture in the molybdenum/glass interface about 10 ps after the impact of the pump laser pulse. Then, a shock wave and gas expansion cause the molybdenum layer to bulge, while the enclosed liquid-gas mixture cools and condenses at delay times in the 100-ps range. The bulging continues for approximately 20 ns, when an intact Mo disk shears and lifts off at a velocity of above 70 m/s. As a result, the remaining hole is free from thermal effects.

Ultrabroadband polarization splitter based on three-core photonic crystal fiber with a modulation core.

PubMed

Zhao, Tongtong; Lou, Shuqin; Wang, Xin; Zhou, Min; Lian, Zhenggang

2016-08-10

We design an ultrabroadband polarization splitter based on three-core photonic crystal fiber (PCF). A modulation core and two fluorine-doped cores are introduced to achieve an ultrawide bandwidth. The properties of three-core PCF are modeled by using the full-vector finite element method along with the full-vector beam propagation method. Numerical results demonstrate that an ultrabroadband splitter with 320 nm bandwidth with an extinction ratio as low as -20  dB can be achieved by using 52.8 mm long three-core PCF. This splitter also has high compatibility with standard single-mode fibers as the input and output ports due to low splicing loss of 0.02 dB. All the air holes in the proposed structure are circular holes and arranged in a triangular lattice that makes it easy to fabricate.

Correlation between electron spin resonance spectra and oil yield in eastern oil shales

USGS Publications Warehouse

Choudhury, M.; Rheams, K.F.; Harrell, J.W.

1986-01-01

Organic free radical spin concentrations were measured in 60 raw oil shale samples from north Alabama and south Tennessee and compared with Fischer assays and uranium concentrations. No correlation was found between spin concentration and oil yield for the complete set of samples. However, for a 13 sample set taken from a single core hole, a linear correlation was obtained. No correlation between spin concentration and uranium concentration was found. ?? 1986.

Regular black holes: Electrically charged solutions, Reissner-Nordstroem outside a de Sitter core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemos, Jose P. S.; Zanchin, Vilson T.; Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170, Santo Andre, Sao Paulo

2011-06-15

To have the correct picture of a black hole as a whole, it is of crucial importance to understand its interior. The singularities that lurk inside the horizon of the usual Kerr-Newman family of black hole solutions signal an endpoint to the physical laws and, as such, should be substituted in one way or another. A proposal that has been around for sometime is to replace the singular region of the spacetime by a region containing some form of matter or false vacuum configuration that can also cohabit with the black hole interior. Black holes without singularities are called regularmore » black holes. In the present work, regular black hole solutions are found within general relativity coupled to Maxwell's electromagnetism and charged matter. We show that there are objects which correspond to regular charged black holes, whose interior region is de Sitter, whose exterior region is Reissner-Nordstroem, and the boundary between both regions is made of an electrically charged spherically symmetric coat. There are several types of solutions: regular nonextremal black holes with a null matter boundary, regular nonextremal black holes with a timelike matter boundary, regular extremal black holes with a timelike matter boundary, and regular overcharged stars with a timelike matter boundary. The main physical and geometrical properties of such charged regular solutions are analyzed.« less

Effect of Vortex Circulation on Injectant from a Single Film-Cooling Hole and a Row of Film-Cooling Holes in a Turbulent Boundary Layer. Part 1. Injection Beneath the Vortex Downwash

DTIC Science & Technology

1989-06-01

coefficients vortex circulation, symbols used in vorticity plots representing circulation values derived from different vortex core models injection...derived from different vortex core models dimensionless core size parameter: t wice the a verage core radius divided by t h e i n jection hole...Wall Heating, xjd=109.2, m=0.5, Single Injection Hole Vortex w, Temp. Difference Range (.5- 2.5) degree s 91. Local Temperature Distribution

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wavemore » trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.« less

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

DOE PAGES

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

2017-12-05

We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wavemore » trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.« less

Ultrafast terahertz electrodynamics of photonic and electronic nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Liang

This thesis summarizes my work on using ultrafast laser pulses to study Terahertz (THz) electrodynamics of photonic and electronic nanostructures and microstructures. Ultrafast timeresolved (optical, NIR, MIR, THz) pump-probe spectroscopy setup has been successfully built, which enables me to perform a series of relevant experiments. Firstly, a novel high e ciency and compact THz wave emitter based on split-ring-resonators has been developed and characterized. The emitter can be pumped at any wavelength by tailoring the magnetic resonance and could generate gapless THz waves covering the entire THz band. Secondly, two kinds of new photonic structures for THz wave manipulation havemore » been successfully designed and characterized. One is based on the 1D and 2D photo-imprinted di ractive elements. The other is based on the photoexcited double-split-ring-resonator metamaterials. Both structures are exible and can modulate THz waves with large tunability. Thirdly, the dark excitons in semiconducting singlewalled carbon nanotubes are studied by optical pump and THz probe spectroscopy, which provides the rst insights into the THz responses of nonequilibrium excitonic correlations and dynamics from the dark ground states in carbon nanotubes. Next, several on-going projects are brie y presented such as the study of ultrafast THz dynamics of Dirac fermions in topological insulator Bi 2Se 3 with Mid-infrared excitation. Finally, the thesis ends with a summary of the completed experiments and an outlook of the future plan.« less

Exploring the electrochemical properties of hole transport materials with spiro-cores for efficient perovskite solar cells from first-principles.

PubMed

Chi, Wei-Jie; Li, Quan-Song; Li, Ze-Sheng

2016-03-21

Perovskite solar cells (PSCs) with organic small molecules as hole transport materials (HTMs) have attracted considerable attention due to their power conversion efficiencies as high as 20%. In the present work, three new spiro-type hole transport materials with spiro-cores, i.e. Spiro-F1, Spiro-F2 and Spiro-F3, are investigated by using density functional theory combined with the Marcus theory and Einstein relation. Based on the calculated and experimental highest occupied molecular orbital (HOMO) levels of 30 reference molecules, an empirical equation, which can predict the HOMO levels of hole transport materials accurately, is proposed. Moreover, a simplified method, in which the hole transport pathways are simplified to be one-dimensional, is presented and adopted to qualitatively compare the molecular hole mobilities. The calculated results show that the perovskite solar cells with the new hole transport materials can have higher open-circuit voltages due to the lower HOMO levels of Spiro-F1 (-5.31 eV), Spiro-F2 (-5.42 eV) and Spiro-F3 (-5.10 eV) compared with that of Spiro-OMeTAD (-5.09 eV). Furthermore, the hole mobilities of Spiro-F1 (1.75 × 10(-2) cm(2) V(-1) s(-1)) and Spiro-F3 (7.59 × 10(-3) cm(2) V(-1) s(-1)) are 3.1 and 1.4 times that of Spiro-OMeTAD (5.65 × 10(-3) cm(2) V(-1) s(-1)) respectively, due to small reorganization energies and large transfer integrals. Interestingly, the stability properties of Spiro-F1 and Spiro-F2 are shown to be comparable to that of Spiro-OMeTAD, and the dimers of Spiro-F2 and Spiro-F3 possess better stability than that of Spiro-OMeTAD. Taking into consideration the appropriate HOMO level, improved hole mobility and enhanced stability, Spiro-F1 and Spiro-F3 may become the most promising alternatives to Spiro-OMeTAD. The present work offers a new design strategy and reliable calculation methods towards the development of excellent organic small molecules as HTMs for highly efficient and stable PSCs.

Ultrafast and nanoscale diodes

NASA Astrophysics Data System (ADS)

Zhang, Peng; Lau, Y. Y.

2016-10-01

Charge carrier transport across interfaces of dissimilar materials (including vacuum) is the essence of all electronic devices. Ultrafast charge transport across a nanometre length scale is of fundamental importance in the miniaturization of vacuum and plasma electronics. With the combination of recent advances in electronics, photonics and nanotechnology, these miniature devices may integrate with solid-state platforms, achieving superior performance. This paper reviews recent modelling efforts on quantum tunnelling, ultrafast electron emission and transport, and electrical contact resistance. Unsolved problems and challenges in these areas are addressed.

A 5-mm piezo-scanning fiber device for high speed ultrafast laser microsurgery

PubMed Central

Ferhanoglu, Onur; Yildirim, Murat; Subramanian, Kaushik; Ben-Yakar, Adela

2014-01-01

Towards developing precise microsurgery tools for the clinic, we previously developed image-guided miniaturized devices using low repetition rate amplified ultrafast lasers for surgery. To improve the speed of tissue removal while reducing device diameter, here we present a new 5-mm diameter device that delivers high-repetition rate laser pulses for high speed ultrafast laser microsurgery. The device consists of an air-core photonic bandgap fiber (PBF) for the delivery of high energy pulses, a piezoelectric tube actuator for fiber scanning, and two aspheric lenses for focusing the light. Its inline optical architecture provides easy alignment and substantial size reduction to 5 mm diameter as compared to our previous MEMS-scanning devices while realizing improved intensity squared (two-photon) lateral and axial resolutions of 1.16 μm and 11.46 μm, respectively. Our study also sheds light on the maximum pulse energies that can be delivered through the air-core PBF and identifies cladding damage at the input facet of the fiber as the limiting factor. We have achieved a maximum energy delivery larger than 700 nJ at 92% coupling efficiency. An in depth analysis reveals how this value is greatly affected by possible slight misalignments of the beam during coupling and the measured small beam pointing fluctuations. In the absence of these imperfections, self-phase modulation becomes the limiting factor for the maximum energy delivery, setting the theoretical upper bound to near 2 μJ for a 1-m long, 7-μm, air-core PBF. Finally, the use of a 300 kHz repetition rate fiber laser enabled rapid ablation of 150 µm x 150 µm area within only 50 ms. Such ablation speeds can now allow the surgeons to translate the surgery device as fast as ~4 mm/s to continuously remove a thin layer of a 150 µm wide tissue. Thanks to a high optical transmission efficiency of the in-line optical architecture of the device and improved resolution, we could successfully perform ablation of

Low-loss polarization-maintaining terahertz fiber based on central air hole movements

NASA Astrophysics Data System (ADS)

Wu, Zhiqing; Li, Qingzhi; Xia, Handing; Shi, Zhaohua; Zhou, Xiaoyan; Deng, Qinghua; Wu, Weidong

2018-04-01

We report a type of single-hole core photonic crystal fiber for low-loss polarization-maintaining terahertz (THz) wave guidance. Simulation results show that high birefringence at a level of 10 - 2 can be obtained by a design of minor position adjustment of the central air hole. Low effective material loss can be achieved because of the introduced central air hole. The strategy of the central air hole movements is also applicable for the three-hole core THz photonic crystal fibers. Other transmission characteristics including single-mode condition, power fraction, confinement loss, and dispersion were discussed in detail. It is quite clear that the proposal facilitates the fabrication process due to the simple structure.

Effect of verification cores on tip capacity of drilled shafts.

DOT National Transportation Integrated Search

2009-02-01

This research addressed two key issues: : 1) Will verification cores holes fill during concrete backfilling? If so, what are the mechanical properties of the : filling material? In dry conditions, verification core holes always completely fill with c...

Magnetic field induced mixing of light hole excitonic states in (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires

NASA Astrophysics Data System (ADS)

Płachta, Jakub; Grodzicka, Emma; Kaleta, Anna; Kret, Sławomir; Baczewski, Lech T.; Pietruczik, Aleksiej; Wiater, Maciej; Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr; Karczewski, Grzegorz; Wojtowicz, Tomasz; Wojnar, Piotr

2018-05-01

A detailed magneto-photoluminescence study of individual (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires grown by molecular beam epitaxy is performed. First of all, an enhancement of the Zeeman splitting due to sp-d exchange interaction between band carriers and Mn-spins is evidenced in these nanostructures. Then, it is found that the value of this splitting depends strongly on the magnetic field direction with respect to the nanowire axis. The largest splitting is observed when the magnetic field is applied perpendicular and the smallest when it is applied parallel to the nanowire axis. This effect is explained in terms of magnetic field induced valence band mixing and evidences the light hole character of the excitonic emission. The values of the light and heavy hole splitting are determined for several individual nanowires based on the comparison of experimental results to theoretical calculations.

Magnetic field induced mixing of light hole excitonic states in (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires.

PubMed

Płachta, Jakub; Grodzicka, Emma; Kaleta, Anna; Kret, Sławomir; Baczewski, Lech T; Pietruczik, Aleksiej; Wiater, Maciej; Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr; Karczewski, Grzegorz; Wojtowicz, Tomasz; Wojnar, Piotr

2018-05-18

A detailed magneto-photoluminescence study of individual (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires grown by molecular beam epitaxy is performed. First of all, an enhancement of the Zeeman splitting due to sp-d exchange interaction between band carriers and Mn-spins is evidenced in these nanostructures. Then, it is found that the value of this splitting depends strongly on the magnetic field direction with respect to the nanowire axis. The largest splitting is observed when the magnetic field is applied perpendicular and the smallest when it is applied parallel to the nanowire axis. This effect is explained in terms of magnetic field induced valence band mixing and evidences the light hole character of the excitonic emission. The values of the light and heavy hole splitting are determined for several individual nanowires based on the comparison of experimental results to theoretical calculations.

Ultrafast demagnetization at high temperatures

NASA Astrophysics Data System (ADS)

Hoveyda, F.; Hohenstein, E.; Judge, R.; Smadici, S.

2018-05-01

Time-resolved pump-probe measurements were made at variable heat accumulation in Co/Pd superlattices. Heat accumulation increases the baseline temperature and decreases the equilibrium magnetization. Transient ultrafast demagnetization first develops with higher fluence in parallel with strong equilibrium thermal spin fluctuations. The ultrafast demagnetization is then gradually removed as the equilibrium temperature approaches the Curie temperature. The transient magnetization time-dependence is well fit with the spin-flip scattering model.

Staggered Multiple-PRF Ultrafast Color Doppler.

PubMed

Posada, Daniel; Poree, Jonathan; Pellissier, Arnaud; Chayer, Boris; Tournoux, Francois; Cloutier, Guy; Garcia, Damien

2016-06-01

Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity folding (aliasing) for large depths and/or large velocities. We investigated multiple pulse-repetition-frequency (PRF) emissions arranged in a series of staggered intervals to remove aliasing in ultrafast color Doppler. Staggered PRF is an emission process where time delays between successive pulse transmissions change in an alternating way. We tested staggered dual- and triple-PRF ultrafast color Doppler, 1) in vitro in a spinning disc and a free jet flow, and 2) in vivo in a human left ventricle. The in vitro results showed that the Nyquist velocity could be extended to up to 6 times the conventional limit. We found coefficients of determination r(2) ≥ 0.98 between the de-aliased and ground-truth velocities. Consistent de-aliased Doppler images were also obtained in the human left heart. Our results demonstrate that staggered multiple-PRF ultrafast color Doppler is efficient for high-velocity high-frame-rate blood flow imaging. This is particularly relevant for new developments in ultrasound imaging relying on accurate velocity measurements.

Spin-vibronic quantum dynamics for ultrafast excited-state processes.

PubMed

Eng, Julien; Gourlaouen, Christophe; Gindensperger, Etienne; Daniel, Chantal

2015-03-17

Ultrafast intersystem crossing (ISC) processes coupled to nuclear relaxation and solvation dynamics play a central role in the photophysics and photochemistry of a wide range of transition metal complexes. These phenomena occurring within a few hundred femtoseconds are investigated experimentally by ultrafast picosecond and femtosecond transient absorption or luminescence spectroscopies, and optical laser pump-X-ray probe techniques using picosecond and femtosecond X-ray pulses. The interpretation of ultrafast structural changes, time-resolved spectra, quantum yields, and time scales of elementary processes or transient lifetimes needs robust theoretical tools combining state-of-the-art quantum chemistry and developments in quantum dynamics for solving the electronic and nuclear problems. Multimode molecular dynamics beyond the Born-Oppenheimer approximation has been successfully applied to many small polyatomic systems. Its application to large molecules containing a transition metal atom is still a challenge because of the nuclear dimensionality of the problem, the high density of electronic excited states, and the spin-orbit coupling effects. Rhenium(I) α-diimine carbonyl complexes, [Re(L)(CO)3(N,N)](n+) are thermally and photochemically robust and highly flexible synthetically. Structural variations of the N,N and L ligands affect the spectroscopy, the photophysics, and the photochemistry of these chromophores easily incorporated into a complex environment. Visible light absorption opens the route to a wide range of applications such as sensors, probes, or emissive labels for imaging biomolecules. Halide complexes [Re(X)(CO)3(bpy)] (X = Cl, Br, or I; bpy = 2,2'-bipyridine) exhibit complex electronic structure and large spin-orbit effects that do not correlate with the heavy atom effects. Indeed, the (1)MLCT → (3)MLCT intersystem crossing (ISC) kinetics is slower than in [Ru(bpy)3](2+) or [Fe(bpy)3](2+) despite the presence of a third-row transition metal

The most massive black holes on the Fundamental Plane of black hole accretion

NASA Astrophysics Data System (ADS)

Mezcua, M.; Hlavacek-Larrondo, J.; Lucey, J. R.; Hogan, M. T.; Edge, A. C.; McNamara, B. R.

2018-02-01

We perform a detailed study of the location of brightest cluster galaxies (BCGs) on the Fundamental Plane of black hole (BH) accretion, which is an empirical correlation between a BH X-ray and radio luminosity and mass supported by theoretical models of accretion. The sample comprises 72 BCGs out to z ˜ 0.3 and with reliable nuclear X-ray and radio luminosities. These are found to correlate as L_X ∝ L_R^{0.75 ± 0.08}, favouring an advection-dominated accretion flow as the origin of the X-ray emission. BCGs are found to be on average offset from the Fundamental Plane such that their BH masses seem to be underestimated by the MBH-MK relation a factor ˜10. The offset is not explained by jet synchrotron cooling and is independent of emission process or amount of cluster gas cooling. Those core-dominated BCGs are found to be more significantly offset than those with weak core radio emission. For BCGs to on average follow the Fundamental Plane, a large fraction ( ˜ 40 per cent) should have BH masses >1010 M⊙ and thus host ultramassive BHs. The local BH-galaxy scaling relations would not hold for these extreme objects. The possible explanations for their formation, either via a two-phase process (the BH formed first, the galaxy grows later) or as descendants of high-z seed BHs, challenge the current paradigm of a synchronized galaxy-BH growth.

FIREWORKS NEAR A BLACK HOLE IN THE CORE OF SEYFERT GALAXY NGC 4151

NASA Technical Reports Server (NTRS)

2002-01-01

The Space Telescope Imaging Spectrograph (STIS) simultaneously records, in unprecedented detail, the velocities of hundreds of gas knots streaming at hundreds of thousands of miles per hour from the nucleus of NGC 4151, thought to house a supermassive black hole. This is the first time the velocity structure in the heart of this object, or similar objects, has been mapped so vividly this close to its central black hole. The twin cones of gas emission are powered by the energy released from the supermassive black hole believed to reside at the heart of this Seyfert galaxy. The STIS data clearly show that the gas knots illuminated by one of these cones is rapidly moving towards us, while the gas knots illuminated by the other cone are rapidly receding. The images have been rotated to show the same orientation of NGC 4151. The figures show: WFPC2 (upper left) -- A Hubble Wide Field Planetary Camera 2 image of the oxygen emission (5007 Angstroms) from the gas at the heart of NGC 4151. Though the twin cone structure can be seen, the image does not provide any information about the motion of the oxygen gas. STIS OPTICAL (upper right) -- In this STIS spectral image of the oxygen gas, the velocities of the knots are determined by comparing the knots of gas in the stationary WFPC2 image to the horizontal location of the knots in the STIS image. STIS OPTICAL (lower right) -- In this false color image the two emission lines of oxygen gas (the weaker one at 4959 Angstroms and the stronger one at 5007 Angstroms) are clearly visible. The horizontal line passing through the image is from the light generated by the powerful black hole at the center of NGC 4151. STIS ULTRAVIOLET (lower left) -- This STIS spectral image shows the velocity distribution of the carbon emission from the gas in the core of NGC 4151. It requires more energy to make the carbon gas glow (CIV at 1549 Angstroms) than it does to ionize the oxygen gas seen in the other images. This means we expect that the

Electron and hole relaxation pathways in semiconductor quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimov, V.I.; McBranch, D.W.; Leatherdale, C.A.

1999-11-01

Femtosecond (fs) broad-band transient absorption (TA) is used to study the intraband relaxation and depopulation dynamics of electron and hole quantized states in CdSe nanocrystals (NC{close_quote}s) with a range of surface properties. Instead of the drastic reduction in the energy relaxation rate expected due to a {open_quotes}phonon bottleneck,{close_quotes} we observe a fast subpicosecond 1P-to-1S electron relaxation, with the rate exceeding that due to phonon emission in bulk semiconductors. The energy relaxation is enhanced with reducing the NC{close_quote}s radius, and does not show any dependence on the NC surface properties (quality of the surface passivation). These data indicate that electron energymore » relaxation occurs by neither multiphonon emission nor by coupling to surface defects, but is likely meditated by Auger-type electron-hole energy transfer. We use fs infrared TA to probe electron and hole intraband transitions, which allows us to distinguish between electron and hole relaxation pathways leading to the depopulation of NC quantized states. In contrast to the electron relaxation, which is controlled by NC surface passivation, the depopulation of hole quantized states is extremely fast (sub-ps-to-ps time scales) in all types of samples, independent of NC surface treatment (including NC{close_quote}s overcoated with a ZnS layer). Our results indicate that ultrafast hole dynamics are not due to trapping at localized surface defects such as a vacancy, but rather arise from relaxation into intrinsic NC states or intrinsically unpassivated interface states. {copyright} {ital 1999} {ital The American Physical Society}« less

Ultrafast Charge Transfer and Hybrid Exciton Formation in 2D/0D Heterostructures

DOE PAGES

Boulesbaa, Abdelaziz; Wang, Kai; Mahjouri-Samani, Masoud; ...

2016-10-18

We report that photoinduced interfacial charge transfer is at the heart of many applications, including photovoltaics, photocatalysis, and photodetection. With the emergence of a new class of semiconductors such as monolayer two-dimensional transition metal dichalcogenides (2D-TMDs), charge transfer at the 2D/2D heterojunctions attracted several efforts due to the remarkable optical and electrical properties of 2D-TMDs. Unfortunately, in 2D/2D heterojunctions, for a given combination of two materials, the relative energy band alignment and the charge transfer efficiency are locked. Due to their large variety and broad size tunability, semiconductor quantum dots (0D-QDs) interfaced with 2D-TMDs may become an attractive heterostructure formore » optoelectronic applications. Here, we incorporate femtosecond pump-probe spectroscopy to reveal the sub-45 fs charge transfer at a 2D/0D heterostructure composed of tungsten disulfide monolayers (2D-WS 2) and a single layer of cadmium selenide (CdSe)/zinc sulfide (ZnS) core/shell 0D-QDs. Furthermore, ultrafast dynamics and steady-state measurements suggested that following electron transfer from the 2D to the 0D, hybrid excitons (HXs), wherein the electron resides in the 0D and hole resides in the 2D-TMD monolayer, are formed with a binding energy on the order of ~140 meV, which is several times lower than that of tightly bound excitons in 2D-TMDs.« less

Ultrafast Charge Transfer and Hybrid Exciton Formation in 2D/0D Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boulesbaa, Abdelaziz; Wang, Kai; Mahjouri-Samani, Masoud

We report that photoinduced interfacial charge transfer is at the heart of many applications, including photovoltaics, photocatalysis, and photodetection. With the emergence of a new class of semiconductors such as monolayer two-dimensional transition metal dichalcogenides (2D-TMDs), charge transfer at the 2D/2D heterojunctions attracted several efforts due to the remarkable optical and electrical properties of 2D-TMDs. Unfortunately, in 2D/2D heterojunctions, for a given combination of two materials, the relative energy band alignment and the charge transfer efficiency are locked. Due to their large variety and broad size tunability, semiconductor quantum dots (0D-QDs) interfaced with 2D-TMDs may become an attractive heterostructure formore » optoelectronic applications. Here, we incorporate femtosecond pump-probe spectroscopy to reveal the sub-45 fs charge transfer at a 2D/0D heterostructure composed of tungsten disulfide monolayers (2D-WS 2) and a single layer of cadmium selenide (CdSe)/zinc sulfide (ZnS) core/shell 0D-QDs. Furthermore, ultrafast dynamics and steady-state measurements suggested that following electron transfer from the 2D to the 0D, hybrid excitons (HXs), wherein the electron resides in the 0D and hole resides in the 2D-TMD monolayer, are formed with a binding energy on the order of ~140 meV, which is several times lower than that of tightly bound excitons in 2D-TMDs.« less

Drilling side holes from a borehole

NASA Technical Reports Server (NTRS)

Collins, E. R., Jr.

1980-01-01

Machine takes long horizontal stratum samples from confines of 21 cm bore hole. Stacked interlocking half cylindrical shells mate to form rigid thrust tube. Drive shaft and core storage device is flexible and retractable. Entire machine fits in 10 meter length of steel tube. Machine could drill drainage or ventilation holes in coal mines, or provide important information for geological, oil, and geothermal surveys.

EDITORIAL: Ultrafast magnetization processes

NASA Astrophysics Data System (ADS)

Hillebrands, Burkard

2008-09-01

fields can be used to induce a local demagnetization of the sample following femtosecond laser excitation. A B Schmidt et al [164003] report a new access to the surface electronic structure of fcc Co films combining spin-resolved one- and two-photon photoemission. The knowledge of surface states is important for interpreting time-resolved measurements of ultrafast magnetization dynamics in this material. An extension of ultrafast dynamics has been made by several groups. A Melnikov et al [164004] report on the ultrafast dynamics at lanthanide surfaces such as Gd(0001) and Tb(0001) using time-resolved second-harmonic generation and photoelectron spectroscopy. These surfaces exhibit a rich dynamics including a collective response of the crystal lattice and the magnetization. Effects of phonon-magnon scattering are discussed. M Fiebig et al [164005] report on experiments of ultrafast magnetization dynamics in antiferromagnetic compounds, and show that the magnetization dynamics in these systems differs noticeably from that of ferromagnetic compounds. They use optical second-harmonic generation and linear reflection to monitor the evolution of the antiferromagnetic order parameter subsequent to an intense optical excitation. In a theory paper, the local light-induced spin manipulation in two-magnetic-centre metallic chains is studied by T Hardenstein et al [164006] using highly correlational ab initio calculations. They show that, as an example of local spin manipulation, the spin on the iron side of a Co-Na-Fe cluster can be switched. S Halm et al [164007] present evidence to manipulate spin states in a diluted magnetic semiconductor on a submicrometer length scale via the magnetic fringe fields of micro-structured magnets. By optically switching the magnetization of the ferromagnet, the magnetization in the semiconductor is manipulated and the limits of a dynamical interaction between the spin states in the ferromagnet and the magnetic semiconductor are discussed. A second

Force-feeding Black Holes

NASA Astrophysics Data System (ADS)

Begelman, Mitchell C.

2012-04-01

We propose that the growth of supermassive black holes is associated mainly with brief episodes of highly super-Eddington infall of gas ("hyperaccretion"). This gas is not swallowed in real time, but forms an envelope of matter around the black hole that can be swallowed gradually, over a much longer timescale. However, only a small fraction of the black hole mass can be stored in the envelope at any one time. We argue that any infalling matter above a few percent of the hole's mass is ejected as a result of the plunge in opacity at temperatures below a few thousand degrees kelvin, corresponding to the Hayashi track. The speed of ejection of this matter, compared to the velocity dispersion σ of the host galaxy's core, determines whether the ejected matter is lost forever or returns eventually to rejoin the envelope, from which it can be ultimately accreted. The threshold between matter recycling and permanent loss defines a relationship between the maximum black hole mass and σ that resembles the empirical M BH-σ relation.

Ultrafast carrier dynamics in the large-magnetoresistance material WTe 2

DOE PAGES

Dai, Y. M.; Bowlan, J.; Li, H.; ...

2015-10-07

In this study, ultrafast optical pump-probe spectroscopy is used to track carrier dynamics in the large-magnetoresistance material WTe 2. Our experiments reveal a fast relaxation process occurring on a subpicosecond time scale that is caused by electron-phonon thermalization, allowing us to extract the electron-phonon coupling constant. An additional slower relaxation process, occurring on a time scale of ~5–15 ps, is attributed to phonon-assisted electron-hole recombination. As the temperature decreases from 300 K, the time scale governing this process increases due to the reduction of the phonon population. However, below ~50 K, an unusual decrease of the recombination time sets in,more » most likely due to a change in the electronic structure that has been linked to the large magnetoresistance observed in this material.« less

Design of exchange-correlation functionals through the correlation factor approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavlíková Přecechtělová, Jana, E-mail: j.precechtelova@gmail.com, E-mail: Matthias.Ernzerhof@UMontreal.ca; Institut für Chemie, Theoretische Chemie / Quantenchemie, Sekr. C7, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin; Bahmann, Hilke

The correlation factor model is developed in which the spherically averaged exchange-correlation hole of Kohn-Sham theory is factorized into an exchange hole model and a correlation factor. The exchange hole model reproduces the exact exchange energy per particle. The correlation factor is constructed in such a manner that the exchange-correlation energy correctly reduces to exact exchange in the high density and rapidly varying limits. Four different correlation factor models are presented which satisfy varying sets of physical constraints. Three models are free from empirical adjustments to experimental data, while one correlation factor model draws on one empirical parameter. The correlationmore » factor models are derived in detail and the resulting exchange-correlation holes are analyzed. Furthermore, the exchange-correlation energies obtained from the correlation factor models are employed to calculate total energies, atomization energies, and barrier heights. It is shown that accurate, non-empirical functionals can be constructed building on exact exchange. Avenues for further improvements are outlined as well.« less

Black hole feedback in a multiphase interstellar medium

NASA Astrophysics Data System (ADS)

Bourne, Martin A.; Nayakshin, Sergei; Hobbs, Alexander

2014-07-01

Ultrafast outflows (UFOs) from supermassive black holes (SMBHs) are thought to regulate the growth of SMBHs and host galaxies, resulting in a number of observational correlations. We present high-resolution numerical simulations of the impact of a thermalized UFO on the ambient gas in the inner part of the host galaxy. Our results depend strongly on whether the gas is homogeneous or clumpy. In the former case all of the ambient gas is driven outward rapidly as expected based on commonly used energy budget arguments, while in the latter the flows of mass and energy de-couple. Carrying most of the energy, the shocked UFO escapes from the bulge via paths of least resistance, taking with it only the low-density phase of the host. Most of the mass is however in the high-density phase, and is affected by the UFO much less strongly, and may even continue to flow inwards. We suggest that the UFO energy leakage through the pores in the multiphase interstellar medium (ISM) may explain why observed SMBHs are so massive despite their overwhelmingly large energy production rates. The multiphase ISM effects reported here are probably under-resolved in cosmological simulations but may be included in prescriptions for active galactic nuclei feedback in future simulations and in semi-analytical models.

NuSTAR REVEALS RELATIVISTIC REFLECTION BUT NO ULTRA-FAST OUTFLOW IN THE QUASAR PG 1211+143

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zoghbi, A.; Miller, J. M.; Walton, D. J.

We report on four epochs of observations of the quasar PG 1211+143 using NuSTAR. The net exposure time is 300 ks. Prior work on this source found suggestive evidence of an ultra-fast outflow (UFO) in the Fe K band with a velocity of approximately 0.1c. The putative flow would carry away a high-mass flux and kinetic power, with broad implications for feedback and black hole--galaxy co-evolution. NuSTAR detects PG 1211+143 out to 30 keV, meaning that the continuum is well-defined both through and above the Fe K band. A characteristic relativistic disk reflection spectrum is clearly revealed via a broadmore » Fe K emission line and Compton back-scattering curvature. The data offer only weak constraints on the spin of the black hole. A careful search for UFOs shows no significant absorption feature above 90% confidence. The limits are particularly tight when relativistic reflection is included. We discuss the statistics and the implications of these results in terms of connections between accretion onto quasars, Seyferts, and stellar-mass black holes, and feedback into their host environments.« less

NuSTAR Reveals Relativistic Reflection But No Ultra-Fast Outflow in the Quasar Pg∼1211+143

NASA Astrophysics Data System (ADS)

Zoghbi, A.; Miller, J. M.; Walton, D. J.; Harrison, F. A.; Fabian, A. C.; Reynolds, C. S.; Boggs, S. E.; Christensen, F. E.; Craig, W.; Hailey, C. J.; Stern, D.; Zhang, W. W.

2015-01-01

We report on four epochs of observations of the quasar PG 1211+143 using NuSTAR. The net exposure time is 300 ks. Prior work on this source found suggestive evidence of an ultra-fast outflow (UFO) in the Fe K band with a velocity of approximately 0.1c. The putative flow would carry away a high-mass flux and kinetic power, with broad implications for feedback and black hole--galaxy co-evolution. NuSTAR detects PG 1211+143 out to 30 keV, meaning that the continuum is well-defined both through and above the Fe K band. A characteristic relativistic disk reflection spectrum is clearly revealed via a broad Fe K emission line and Compton back-scattering curvature. The data offer only weak constraints on the spin of the black hole. A careful search for UFOs shows no significant absorption feature above 90% confidence. The limits are particularly tight when relativistic reflection is included. We discuss the statistics and the implications of these results in terms of connections between accretion onto quasars, Seyferts, and stellar-mass black holes, and feedback into their host environments.

Excitation and doping dependence of hole-spin relaxation in bulk GaAs

NASA Astrophysics Data System (ADS)

Krauss, Michael; Hilton, David; Schneider, Hans Christian

2009-03-01

We present theoretical and experimental results on ultrafast hole-spin dynamics in bulk GaAs. By combining a sufficiently realistic bandstructure at the level of an 8x8 k .p theory and a dynamical treatment of the relevant scattering mechanisms [1], we obtain quantitative agreement between the microscopic theoretical results and differential transmission measurements [2] for different excitation conditions. In particular, we examine the dependence of the hole-spin relaxation time on the optically excited carrier density, lattice temperature, and doping concentration. Although the spin relaxation is rather insensitive to changes in the optically excited density and temperature, strong p-doping causes a significantly faster relaxation. [1] M. Krauss, M. Aeschlimann, and H. C. Schneider, Phys.Rev.Lett. 100, 256601 (2008)[2] D. J. Hilton and C. L. Tang, Phys. Rev. Lett. 89, 146601 (2002)

Tuning a Schottky Barrier in a Photoexcited Topological Insulator with Transient Dirac Cone Electron-Hole Asymmetry

DTIC Science & Technology

2014-01-06

S. Jia9, H.W. Ji9, R.J. Cava9 & M. Marsi1 The advent of Dirac materials has made it possible to realize two-dimensional gases of relativistic...ultrafast light pulses a relativistic nanoscale Schottky barrier, in a way that is impossible with conventional optoelectronic materials . DOI : 10.1038...topological insulator with transient Dirac cone electron-hole asymmetry. Nat. Commun. 5:3003 doi : 10.1038/ncomms4003 (2014). ARTICLE NATURE

Wavelength-dependent ultrafast charge carrier separation in the WO 3/BiVO 4 coupled system

DOE PAGES

Grigioni, Ivan; Stamplecoskie, Kevin G.; Jara, Danilo H.; ...

2017-05-08

Due to its ~2.4 eV band gap, BiVO 4 is a very promising photoanode material for harvesting the blue portion of the solar light for photoelectrochemical (PEC) water splitting applications. In WO 3/BiVO 4 heterojunction films, the electrons photoexcited in BiVO 4 are injected into WO 3, overcoming the lower charge carriers’ diffusion properties limiting the PEC performance of BiVO 4 photoanodes. Here, we investigate by ultrafast transient absorption spectroscopy the charge carrier interactions occurring at the interface between the two oxides in heterojunction systems to directly unveil their wavelength dependence. Under selective BiVO 4 excitation, a favorable electron transfermore » from photoexcited BiVO 4 to WO 3 occurs immediately after excitation and leads to an increase of the trapped holes’ lifetime in BiVO4. However, a recombination channel opens when both oxides are simultaneously excited, evidenced by a shorter lifetime of trapped holes in BiVO 4. As a result, PEC measurements reveal the implication of these wavelength-dependent ultrafast interactions on the performances of the WO 3/BiVO 4 heterojunction.« less

Wavelength-dependent ultrafast charge carrier separation in the WO 3/BiVO 4 coupled system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigioni, Ivan; Stamplecoskie, Kevin G.; Jara, Danilo H.

Due to its ~2.4 eV band gap, BiVO 4 is a very promising photoanode material for harvesting the blue portion of the solar light for photoelectrochemical (PEC) water splitting applications. In WO 3/BiVO 4 heterojunction films, the electrons photoexcited in BiVO 4 are injected into WO 3, overcoming the lower charge carriers’ diffusion properties limiting the PEC performance of BiVO 4 photoanodes. Here, we investigate by ultrafast transient absorption spectroscopy the charge carrier interactions occurring at the interface between the two oxides in heterojunction systems to directly unveil their wavelength dependence. Under selective BiVO 4 excitation, a favorable electron transfermore » from photoexcited BiVO 4 to WO 3 occurs immediately after excitation and leads to an increase of the trapped holes’ lifetime in BiVO4. However, a recombination channel opens when both oxides are simultaneously excited, evidenced by a shorter lifetime of trapped holes in BiVO 4. As a result, PEC measurements reveal the implication of these wavelength-dependent ultrafast interactions on the performances of the WO 3/BiVO 4 heterojunction.« less

Protomagnetar and black hole formation in high-mass stars

NASA Astrophysics Data System (ADS)

Obergaulinger, M.; Aloy, M. Á.

2017-07-01

Using axisymmetric simulations coupling special relativistic magnetohydrodynamics (MHD), an approximate post-Newtonian gravitational potential and two-moment neutrino transport, we show different paths for the formation of either protomagnetars or stellar mass black holes. The fraction of prototypical stellar cores which should result in collapsars depends on a combination of several factors, among which the structure of the progenitor star and the profile of specific angular momentum are probably the foremost. Along with the implosion of the stellar core, we also obtain supernova-like explosions driven by neutrino heating and hydrodynamic instabilities or by magneto-rotational effects in cores of high-mass stars. In the latter case, highly collimated, mildly relativistic outflows are generated. We find that after a rather long post-collapse phase (lasting ≳1 s) black holes may form in cases both of successful and failed supernova-like explosions. A basic trend is that cores with a specific angular momentum smaller than that obtained by standard, one-dimensional stellar evolution calculations form black holes (and eventually collapsars). Complementary, protomagnetars result from stellar cores with the standard distribution of specific angular momentum obtained from prototypical stellar evolution calculations including magnetic torques and moderate to large mass-loss rates.

Ultrafast fiber lasers: practical applications

NASA Astrophysics Data System (ADS)

Pastirk, Igor; Sell, Alexander; Herda, Robert; Brodschelm, Andreas; Zach, Armin

2015-05-01

Over past three decades ultrafast lasers have come a long way from the bulky, demanding and very sensitive scientific research projects to widely available commercial products. For the majority of this period the titanium-sapphire-based ultrafast systems were the workhorse for scientific and emerging industrial and biomedical applications. However the complexity and intrinsic bulkiness of solid state lasers have prevented even larger penetration into wider array of practical applications. With emergence of femtosecond fiber lasers, based primarily on Er-doped and Yb-doped fibers that provide compact, inexpensive and dependable fs and ps pulses, new practical applications have become a reality. The overview of current state of the art ultrafast fiber sources, their basic principles and most prominent applications will be presented, including micromachining and biomedical implementations (ophthalmology) on one end of the pulse energy spectrum and 3D lithography and THz applications on the other.

Do Nuclear Star Clusters and Supermassive Black Holes Follow the Same Host-Galaxy Correlations?

DOE PAGES

Erwin, Peter; Gadotti, Dimitri Alexei

2012-01-01

Smore » tudies have suggested that there is a strong correlation between the masses of nuclear star clusters (NCs) and their host galaxies, a correlation which is said to be an extension of the well-known correlations between supermassive black holes (MBHs) and their host galaxies. But careful analysis of disk galaxies—including 2D bulge/disk/bar decompositions—shows that while MBHs correlate with the stellar mass of the bulge component of galaxies, the masses of NCs correlate much better with the total galaxy stellar mass. In addition, the mass ratio M NC / M ⋆ ,  tot for NCs in spirals (at least those with Hubble types c and later) is typically an order of magnitude smaller than the mass ratio M BH / M ⋆ ,  bul of MBHs. The absence of a universal “central massive object” correlation argues against common formation and growth mechanisms for both MBHs and NCs. We also discuss evidence for a break in the NC-host galaxy correlation, galaxies with Hubble types earlier than bc appear to host systematically more massive NCs than do types c and later.« less

Dynamically important magnetic fields near supermassive black holes in radio-loud AGN

NASA Astrophysics Data System (ADS)

Savolainen, Tuomas; Zamaninasab, Mohammad; Clausen-Brown, Eric; Tchekhovskoy, Alexander

The powerful radio jets ejected from the vicinity of accreting supermassive black holes in active galactic nuclei are thought to be formed by magnetic forces. However, there is little observational evidence of the actual strength of the magnetic fields in the jet-launching region, and in the accretion disks, of AGN. We have collected from the literature jet magnetic field estimates determined by very long baseline interferometry observations of the opacity-driven core-shift effect for 76 blazars and radio galaxies. We show that the jet magnetic flux of these radio-loud AGN tightly correlates with their accretion disk luminosity -- over seven orders of magnitude in accretion power. Moreover, the estimated magnetic flux threading the black hole quantitatively agrees with the saturation value expected in the magnetically arrested disk scenario. This implies that black holes in many, if not most, of the radio-loud AGN are surrounded by accretion disks that have dynamically important magnetic fields. Such disks behave very differently from the standard model disks with sub-equipartition magnetic fields, which may have important consequences for attempts to interpret disk spectral energy distributions or signatures of the possible black hole shadow in mm-VLBI images.

Short-Range Correlated Magnetic Core-Shell CrO₂/Cr₂O₃ Nanorods: Experimental Observations and Theoretical Considerations.

PubMed

Gandhi, Ashish C; Li, Tai-Yue; Chan, Ting Shan; Wu, Sheng Yun

2018-05-09

With the evolution of synthesis and the critical characterization of core-shell nanostructures, short-range magnetic correlation is of prime interest in employing their properties to develop novel devices and widespread applications. In this regard, a novel approach of the magnetic core-shell saturated magnetization (CSSM) cylinder model solely based on the contribution of saturated magnetization in one-dimensional CrO₂/Cr₂O₃ core-shell nanorods (NRs) has been developed and applied for the determination of core-diameter and shell-thickness. The nanosized effect leads to a short-range magnetic correlation of ferromagnetic core-CrO₂ extracted from CSSM, which can be explained using finite size scaling method. The outcome of this study is important in terms of utilizing magnetic properties for the critical characterization of core-shell nanomagnetic materials.

Lateral access to the holes of photonic crystal fibers selective filling and sensing applications

NASA Astrophysics Data System (ADS)

Cordeiro, Cristiano M. B.; Dos Santos, Eliane M.; Brito Cruz, C. H.; de Matos, Christiano J.; Ferreiira, Daniel S.

2006-09-01

A new, simple, technique is demonstrated to laterally access the cladding holes of solid-core photonic crystal fibers (PCFs) or the central hole of hollow-core PCFs by blowing a hole through the fiber wall (using a fusion splicer and the application of pressure). For both fiber types material was subsequently and successfully inserted into the holes. The proposed method compares favorably with other reported selective filling techniques in terms of simplicity and reproducibility. Also, since the holes are laterally filled, simultaneous optical access to the PCFs is possible, which can prove useful for practical sensing applications. As a proof-of-concept experiment, Rhodamine fluorescence measurements are shown.

Plasmonic antennas as design elements for coherent ultrafast nanophotonics.

PubMed

Brinks, Daan; Castro-Lopez, Marta; Hildner, Richard; van Hulst, Niek F

2013-11-12

Broadband excitation of plasmons allows control of light-matter interaction with nanometric precision at femtosecond timescales. Research in the field has spiked in the past decade in an effort to turn ultrafast plasmonics into a diagnostic, microscopy, computational, and engineering tool for this novel nanometric-femtosecond regime. Despite great developments, this goal has yet to materialize. Previous work failed to provide the ability to engineer and control the ultrafast response of a plasmonic system at will, needed to fully realize the potential of ultrafast nanophotonics in physical, biological, and chemical applications. Here, we perform systematic measurements of the coherent response of plasmonic nanoantennas at femtosecond timescales and use them as building blocks in ultrafast plasmonic structures. We determine the coherent response of individual nanoantennas to femtosecond excitation. By mixing localized resonances of characterized antennas, we design coupled plasmonic structures to achieve well-defined ultrafast and phase-stable field dynamics in a predetermined nanoscale hotspot. We present two examples of the application of such structures: control of the spectral amplitude and phase of a pulse in the near field, and ultrafast switching of mutually coherent hotspots. This simple, reproducible and scalable approach transforms ultrafast plasmonics into a straightforward tool for use in fields as diverse as room temperature quantum optics, nanoscale solid-state physics, and quantum biology.

Spatial Correlation in the Ambient Core Noise Field of a Turbofan Engine

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

2012-01-01

An acoustic transfer function relating combustion noise and turbine exit noise in the presence of enclosed ambient core noise is investigated using a dynamic system model and an acoustic system model for the particular turbofan engine studied and for a range of operating conditions. Measurements of cross-spectra magnitude and phase between the combustor and turbine exit and auto-spectra at the turbine exit and combustor are used to show the presence of indirect and direct combustion noise over the frequency range of 0 400 Hz. The procedure used evaluates the ratio of direct to indirect combustion noise. The procedure used also evaluates the post-combustion residence time in the combustor which is a factor in the formation of thermal NOx and soot in this region. These measurements are masked by the ambient core noise sound field in this frequency range which is observable since the transducers are situated within an acoustic wavelength of one another. An ambient core noise field model based on one and two dimensional spatial correlation functions is used to replicate the spatially correlated response of the pair of transducers. The spatial correlation function increases measured attenuation due to destructive interference and masks the true attenuation of the turbine.

Spatial correlation in the ambient core noise field of a turbofan engine.

PubMed

Miles, Jeffrey Hilton

2012-06-01

An acoustic transfer function relating combustion noise and turbine exit noise in the presence of enclosed ambient core noise is investigated using a dynamic system model and an acoustic system model for the particular turbofan engine studied and for a range of operating conditions. Measurements of cross-spectra magnitude and phase between the combustor and turbine exit and auto-spectra at the turbine exit and combustor are used to show the presence of indirect and direct combustion noise over the frequency range of 0-400 Hz. The procedure used evaluates the ratio of direct to indirect combustion noise. The procedure used also evaluates the post-combustion residence time in the combustor which is a factor in the formation of thermal NO(x) and soot in this region. These measurements are masked by the ambient core noise sound field in this frequency range which is observable since the transducers are situated within an acoustic wavelength of one another. An ambient core noise field model based on one and two dimensional spatial correlation functions is used to replicate the spatially correlated response of the pair of transducers. The spatial correlation function increases measured attenuation due to destructive interference and masks the true attenuation of the turbine.

On the interpretation of domain averaged Fermi hole analyses of correlated wavefunctions.

PubMed

Francisco, E; Martín Pendás, A; Costales, Aurora

2014-03-14

Few methods allow for a physically sound analysis of chemical bonds in cases where electron correlation may be a relevant factor. The domain averaged Fermi hole (DAFH) analysis, a tool firstly proposed by Robert Ponec in the 1990's to provide interpretations of the chemical bonding existing between two fragments Ω and Ω' that divide the real space exhaustively, is one of them. This method allows for a partition of the delocalization index or bond order between Ω and Ω' into one electron contributions, but the chemical interpretation of its parameters has been firmly established only for single determinant wavefunctions. In this paper we report a general interpretation based on the concept of excluded density that is also valid for correlated descriptions. Both analytical models and actual computations on a set of simple molecules (H2, N2, LiH, and CO) are discussed, and a classification of the possible DAFH situations is presented. Our results show that this kind of analysis may reveal several correlated assisted bonding patterns that might be difficult to detect using other methods. In agreement with previous knowledge, we find that the effective bond order in covalent links decreases due to localization of electrons driven by Coulomb correlation.

Multiple cores of Gleason score 6 correlate with favourable findings at radical prostatectomy

PubMed Central

Ellis, Carla L.; Walsh, Patrick C.; Partin, Alan W.; Epstein, Jonathan I.

2014-01-01

Objective To establish whether the good prognosis of Gleason score 6 (GS6) is maintained in the setting of multiple involved cores. Patients and Methods In total, 6156 men (from 1 April 2000 to 30 April 2007) with GS6 on biopsy underwent radical prostatectomy (RP) at our institution. The number of positive cores was correlated with the outcome at RP. Results More positive cores correlated with less organ-confined disease (P < 0.001), positive margins (P < 0.012), increasing RP grade (P < 0.001) and increased seminal vesicles/lymph node involvement (P = 0.012). For men with data available, the actuarial risk of being biochemically free of disease at 5 years was 93.2% when ≤6 cores were positive (812 men followed to 5 years) vs 89.1% if >6 cores were positive (41 men followed to 2 years) (P = 0.6). Although the predicted ‘cure rate’ of >75% probability of a tumour showing no evidence of biochemical recurrence at 10 years after RP was statistically different between cases with ≤6 vs >6 positive cores (P < 0.0001), the outcome in both groups was still favourable (90.5% vs 84%). Partin-like tables were generated factoring in the number of positive cores to predict organ-confined disease as a guide for urologists to perform nerve-sparing surgery. For example, with T1c disease, there was a ≥75% probability of organ-confined disease with one to three positive cores regardless of prostate-specific antigen (PSA) level, and the same probability was present with four to six positive cores and a PSA level of 0–4 ng/mL. Conclusion A low Gleason score on biopsy is a powerful prognostic finding, such that this favourable outcome is maintained even in the setting of multiple positive cores with GS6. PMID:23350787

Multiple cores of Gleason score 6 correlate with favourable findings at radical prostatectomy.

PubMed

Ellis, Carla L; Walsh, Patrick C; Partin, Alan W; Epstein, Jonathan I

2013-06-01

To establish whether the good prognosis of Gleason score 6 (GS6) is maintained in the setting of multiple involved cores. In total, 6156 men (from 1 April 2000 to 30 April 2007) with GS6 on biopsy underwent radical prostatectomy (RP) at our institution. The number of positive cores was correlated with the outcome at RP. More positive cores correlated with less organ-confined disease (P < 0.001), positive margins (P < 0.012), increasing RP grade (P < 0.001) and increased seminal vesicles/lymph node involvement (P = 0.012). For men with data available, the actuarial risk of being biochemically free of disease at 5 years was 93.2% when ≤6 cores were positive (812 men followed to 5 years) vs 89.1% if >6 cores were positive (41 men followed to 2 years) (P = 0.6). Although the predicted 'cure rate' of >75% probability of a tumour showing no evidence of biochemical recurrence at 10 years after RP was statistically different between cases with ≤6 vs >6 positive cores (P < 0.0001), the outcome in both groups was still favourable (90.5% vs 84%). Partin-like tables were generated factoring in the number of positive cores to predict organ-confined disease as a guide for urologists to perform nerve-sparing surgery. For example, with T1c disease, there was a ≥75% probability of organ-confined disease with one to three positive cores regardless of prostate-specific antigen (PSA) level, and the same probability was present with four to six positive cores and a PSA level of 0-4 ng/mL. A low Gleason score on biopsy is a powerful prognostic finding, such that this favourable outcome is maintained even in the setting of multiple positive cores with GS6. © 2013 BJU International.

Ultrafast optical switching in three-dimensional photonic crystals

NASA Astrophysics Data System (ADS)

Mazurenko, D. A.

2004-09-01

The rapidly expanding research on photonic crystals is driven by potential applications in all-optical switches, optical computers, low-threshold lasers, and holographic data storage. The performance of such devices might surpass the speed of traditional electronics by several orders of magnitude and may result in a true revolution in nanotechnology. The heart of such devices would likely be an optical switching element. This thesis analyzes different regimes of ultrafast all-optical switching in various three-dimensional photonic crystals, in particular opals filled with silicon or vanadium dioxide and periodic arrays of silica-gold core-shell spherical particles with silica outer shell. In the experiment an ultrashort optical pulse is used to excite a photonic crystal and change its complex effective dielectric constant. The change in the imaginary part of the dielectric constant corresponds to the change in absorption that suppresses interference inside the photonic crystal and modifies the amplitude of the reflectivity, while the change in the real part of the dielectric constant accounts for a shift in a spectral position of the photonic stop band. The first type of switching is shown on an example of an opal filled with silicon. In this crystal, switching is induced by photo-excited carriers in silicon that act as an electron plasma and increase the absorption in silicon. Within 30 fs constructive interference inside the opal vanishes and Bragg reflectivity drops down. Changes in reflectivity reach values as high as 46% at maximum excitation power. The experimental results are in a good agreement with calculations. The second type of switching is demonstrated in opal filled with vanadium dioxide. Here, the optical switching is driven by a photoinduced phase transition of vanadium dioxide. The phase transition takes place on a subpicosecond time scale and changes the effective dielectric constant of the opal. As a result, the spectral position of the photonic

What is an Oceanic Core Complex?

NASA Astrophysics Data System (ADS)

Schroeder, T.; Cheadle, M. J.

2007-12-01

The Mid-Atlantic Ridge (MAR) 75km north and south of the 15-20 Fracture Zone (FZ) has produced upper oceanic lithosphere composed dominantly of mantle peridotite with gabbro intrusions. In the absence of diapirism, mantle peridotite can only be exposed on the seafloor by extensional faulting, thus the sea floor geology and bathymetry provide widespread evidence for extensive low-angle faulting. However, only 3% of the seafloor in this region has the domal morphology characteristic of features that have been termed oceanic core complexes; suggesting that other processes, in addition to low-angle faulting, are responsible for the generation of domal core complexes. Most low-angle faults near the 15-20 FZ form gently dipping (10-15°), 10-15km-wide dip slopes on the flanks of 2000m relief bathymetric ridges that are up to 15-40km long (parallel to the MAR). Core recovered from ODP Leg 209 drill holes in these ridges is dominantly peridotite with small (<50m thick) gabbro intrusions. The peridotite is cut by a very high density of brittle faults dipping at both steep and gentle angles. Several holes also contain long-lived shear zones/faults in their upper reaches in which strain was localized at granulite facies, indicated by mylonitic olivine and cpx, and remained active during cooling to sub-greenschist grade, indicated by cross-cutting of progressively lower-grade syn-deformation mineral assemblages. These observations suggest that seafloor spreading is largely accommodated here by slip on low-angle faults, and that these faults are correctly termed detachment faults. Holes drilled into a domal oceanic core complex north of the 15-20 FZ during Leg 209 (ODP Site 1275) recovered dominantly gabbro and not mantle peridotite. This hole is cut by significantly fewer brittle and ductile faults than the peridotite drilled at the non-core-complex detachment fault sites. The detachment fault in the upper reaches (50m) of Site 1275 was localized at temperatures near feldspar

Density matrix-based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

NASA Astrophysics Data System (ADS)

Wang, Huihui; Bokarev, Sergey I.; Aziz, Saadullah G.; Kühn, Oliver

2017-08-01

Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic timescales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core-hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter timescale. Using density matrix-based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p→3d) excited states of a prototypical Fe(II) complex. This process occurs on a timescale, which is faster than that of Auger decay (∼4 fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its control by soft X-ray light.

Middleweight black holes found at last

NASA Astrophysics Data System (ADS)

Clery, Daniel

2018-06-01

How did giant black holes grow so big? Astronomers have long had evidence of baby black holes with masses of no more than tens of suns, and of million- or billion-solar-mass behemoths lurking at the centers of galaxies. But middle-size ones, weighing thousands or tens of thousands of suns, seemed to be missing. Their absence forced theorists to propose that supermassive black holes didn't grow gradually by slowly consuming matter, but somehow emerged as ready-made giants. Now, astronomers appear to have located some missing middleweights. An international team has scoured an archive of galaxy spectra and found more than 300 small galaxies that have the signature of intermediate mass black holes in their cores, opening new questions for theorists.

Ultrafast surface carrier dynamics in the topological insulator Bi₂Te₃.

PubMed

Hajlaoui, M; Papalazarou, E; Mauchain, J; Lantz, G; Moisan, N; Boschetto, D; Jiang, Z; Miotkowski, I; Chen, Y P; Taleb-Ibrahimi, A; Perfetti, L; Marsi, M

2012-07-11

We discuss the ultrafast evolution of the surface electronic structure of the topological insulator Bi(2)Te(3) following a femtosecond laser excitation. Using time and angle-resolved photoelectron spectroscopy, we provide a direct real-time visualization of the transient carrier population of both the surface states and the bulk conduction band. We find that the thermalization of the surface states is initially determined by interband scattering from the bulk conduction band, lasting for about 0.5 ps; subsequently, few picoseconds are necessary for the Dirac cone nonequilibrium electrons to recover a Fermi-Dirac distribution, while their relaxation extends over more than 10 ps. The surface sensitivity of our measurements makes it possible to estimate the range of the bulk-surface interband scattering channel, indicating that the process is effective over a distance of 5 nm or less. This establishes a correlation between the nanoscale thickness of the bulk charge reservoir and the evolution of the ultrafast carrier dynamics in the surface Dirac cone.

Effect of Osteonecrosis Intervention Rod Versus Core Decompression Using Multiple Small Drill Holes on Early Stages of Necrosis of the Femoral Head: A Prospective Study on a Series of 60 Patients with a Minimum 1-Year-Follow-Up.

PubMed

Miao, Haixiong; Ye, Dongping; Liang, Weiguo; Yao, Yicun

2015-01-01

The conventional CD used 10 mm drill holes associated with a lack of structural support. Thus, alternative methods such as a tantalum implant, small drill holes, and biological treatment were developed to prevent deterioration of the joint. The treatment of CD by multiple 3.2 mm drill holes could reduce the femoral neck fracture and partial weight bearing was allowed. This study was aimed to evaluate the effect of osteonecrosis intervention rod versus core decompression using multiple small drill holes on early stages of necrosis of the femoral head. From January 2011 to January 2012, 60 patients undergoing surgery for osteonecrosis with core decompression were randomly assigned into 2 groups based on the type of core decompression used: (1) a total of 30 osteonecrosis patients (with 16 hips on Steinburg stageⅠ,20 hips on Steinburg stageⅡ) were treated with a porous tantalum rod insertion. The diameter of the drill hole for the intervention rod was 10mm.(2) a total of 30 osteonecrosis patients (with 14 hips on Steinburg stageⅠ,20 hips on Steinburg stageⅡ) were treated with core decompression using five drill holes on the lateral femur, the diameter of the hole was 3.2 mm. The average age of the patient was 32.6 years (20-45 years) and the average time of follow-up was 25.6 months (12- 28 months) in the rod implanted group. The average age of the patient was 35.2 years (22- 43 years) and the average time of follow-up was 26.3 months (12-28 months) in the small drill holes group. The average of surgical time was 40 min, and the mean volume of blood loss was 30 ml in both surgical groups. The average of Harris score was improved from 56.2 ± 7.1 preoperative to 80.2 ± 11.4 at the last follow-up in the rod implanted group (p < 0.05). The mean Harris score was improved from 53.8 ± 6.6 preoperative to 79.7 ± 13.2 at the last follow-up in the small drill holes group (p<0. 05). No significant difference was observed in Harris score between the two groups. At the

Planet Traps and Planetary Cores: Origins of the Planet-Metallicity Correlation

NASA Astrophysics Data System (ADS)

Hasegawa, Yasuhiro; Pudritz, Ralph E.

2014-10-01

Massive exoplanets are observed preferentially around high metallicity ([Fe/H]) stars while low-mass exoplanets do not show such an effect. This so-called planet-metallicity correlation generally favors the idea that most observed gas giants at r < 10 AU are formed via a core accretion process. We investigate the origin of this phenomenon using a semi-analytical model, wherein the standard core accretion takes place at planet traps in protostellar disks where rapid type I migrators are halted. We focus on the three major exoplanetary populations—hot Jupiters, exo-Jupiters located at r ~= 1 AU, and the low-mass planets. We show using a statistical approach that the planet-metallicity correlations are well reproduced in these models. We find that there are specific transition metallicities with values [Fe/H] = -0.2 to -0.4, below which the low-mass population dominates, and above which the Jovian populations take over. The exo-Jupiters significantly exceed the hot Jupiter population at all observed metallicities. The low-mass planets formed via the core accretion are insensitive to metallicity, which may account for a large fraction of the observed super-Earths and hot-Neptunes. Finally, a controlling factor in building massive planets is the critical mass of planetary cores (M c, crit) that regulates the onset of rapid gas accretion. Assuming the current data is roughly complete at [Fe/H] > -0.6, our models predict that the most likely value of the "mean" critical core mass of Jovian planets is langM c, critrang ~= 5 M ⊕ rather than 10 M ⊕. This implies that grain opacities in accreting envelopes should be reduced in order to lower M c, crit.

Black Hole Safari: Tracking Populations and Hunting Big Game

NASA Astrophysics Data System (ADS)

McConnell, N. J.

2013-10-01

Understanding the physical connection, or lack thereof, between the growth of galaxies and supermassive black holes is a key challenge in extragalactic astronomy. Dynamical studies of nearby galaxies are building a census of black hole masses across a broad range of galaxy types and uncovering statistical correlations between galaxy bulge properties and black hole masses. These local correlations provide a baseline for studying galaxies and black holes at higher redshifts. Recent measurements have probed the extremes of the supermassive black hole population and introduced surprises that challenge simple models of black hole and galaxy co-evolution. Future advances in the quality and quantity of dynamical black hole mass measurements will shed light upon the growth of massive galaxies and black holes in different cosmic environments.

Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy

NASA Astrophysics Data System (ADS)

Mehl, Brian Peter

The polydispersity intrinsic to nanoscale and microscale semiconductor materials poses a major challenge to using individual objects as building blocks for device applications. The ability to manipulate the shape of ZnO structures is enormous, making it an ideal material for studying shape-dependent phenomena. We have built a nonlinear microscope used to directly image optical cavity modes in ZnO rods using second-harmonic generation. Images of second-harmonic generation in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second-harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second-harmonic condition that cannot be achieved in bulk ZnO. A more complicated second-harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. Additionally, the nonlinear microscope was combined with transient absorption pump-probe to follow the electron-hole recombination dynamics at different points within individual needle-shaped ZnO rods to characterize spatial differences in dynamical behavior. The results from pump-probe experiments are correlated with spatially resolved ultrafast emission measurements, and scanning electron microscopy provides structural details. Dramatically different electron-hole recombination dynamics are observed in the narrow tips compared to the interior, with the ends exhibiting a greater propensity for electron-hole plasma formation and faster recombination of carriers across the band gap that stem from a physical confinement of the charge carriers. In the interior of the rod, a greater fraction of the electron-hole recombination is trap-mediated and occurs on a significantly longer time

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

DOE PAGES

Zhou, Meng; Tian, Shubo; Zeng, Chenjie; ...

2016-12-22

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Meng; Tian, Shubo; Zeng, Chenjie

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

ULTRAFAST OUTFLOWS FROM BLACK HOLE MERGERS WITH A MINIDISK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murase, Kohta; Mészáros, Peter; Shoemaker, Ian

2016-05-01

Recently, the direct detection of gravitational waves from black hole (BH) mergers was announced by the Advanced LIGO Collaboration. Multi-messenger counterparts of stellar-mass BH mergers are of interest, and it had been suggested that a small disk or celestial body may be involved in the binary of two BHs. To test such possibilities, we consider the fate of a wind powered by an active minidisk in a relatively short, super-Eddington accretion episode onto a BH with ∼10–100 solar masses. We show that its thermal emission could be seen as a fast optical transient with the duration from hours to days.more » We also find that the coasting outflow forms external shocks due to interaction with the interstellar medium, whose synchrotron emission might be expected in the radio band on a timescale of years. Finally, we also discuss a possible jet component and the associated high-energy neutrino emission as well as ultra-high-energy cosmic-ray acceleration.« less

Structural and Functional Characterization of a Hole-Hole Homodimer Variant in a "Knob-Into-Hole" Bispecific Antibody.

PubMed

Zhang, Hui-Min; Li, Charlene; Lei, Ming; Lundin, Victor; Lee, Ho Young; Ninonuevo, Milady; Lin, Kevin; Han, Guanghui; Sandoval, Wendy; Lei, Dongsheng; Ren, Gang; Zhang, Jennifer; Liu, Hongbin

2017-12-19

Bispecific antibodies have great potential to be the next-generation biotherapeutics due to their ability to simultaneously recognize two different targets. Compared to conventional monoclonal antibodies, knob-into-hole bispecific antibodies face unique challenges in production and characterization due to the increase in variant possibilities, such as homodimerization in covalent and noncovalent forms. In this study, a storage- and pH-sensitive hydrophobic interaction chromatography (HIC) profile change was observed for the hole-hole homodimer, and the multiple HIC peaks were explored and shown to be conformational isomers. We combined traditional analytical methods with hydrogen/deuterium exchange mass spectrometry (HDX MS), native mass spectrometry, and negative-staining electron microscopy to comprehensively characterize the hole-hole homodimer. HDX MS revealed conformational changes at the resolution of a few amino acids overlapping the C H 2-C H 3 domain interface. Conformational heterogeneity was also assessed by HDX MS isotopic distribution. The hole-hole homodimer was demonstrated to adopt a more homogeneous conformational distribution during storage. This conformational change is likely caused by a lack of C H 3 domain dimerization (due to the three "hole" point mutations), resulting in a unique storage- and pH-dependent conformational destabilization and refolding of the hole-hole homodimer Fc. Compared with the hole-hole homodimer under different storage conditions, the bispecific heterodimer, guided by the knob-into-hole assembly, proved to be a stable conformation with homogeneous distribution, confirming its high quality as a desired therapeutic. Functional studies by antigen binding and neonatal Fc receptor (FcRn) binding correlated very well with the structural characterization. Comprehensive interpretation of the results has provided a better understanding of both the homodimer variant and the bispecific molecule.

Developing Topological Insulator Fiber Based Photon Pairs Source for Ultrafast Optoelectronic Applications

DTIC Science & Technology

2016-04-01

DEVELOPING TOPOLOGICAL INSULATOR FIBER BASED PHOTON PAIRS SOURCE FOR ULTRAFAST OPTOELECTRONIC APPLICATIONS NORTHWESTERN UNIVERSITY...REPORT TYPE FINAL TECHNICAL REPORT 3. DATES COVERED (From - To) APRIL 2015 – DEC 2015 4. TITLE AND SUBTITLE DEVELOPING TOPOLOGICAL INSULATOR FIBER BASED...in developing a new source for the production of correlated/entangled photon pairs based on the unique nanolayer properties of topological insulator

FORCE-FEEDING BLACK HOLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begelman, Mitchell C., E-mail: mitch@jila.colorado.edu

2012-04-10

We propose that the growth of supermassive black holes is associated mainly with brief episodes of highly super-Eddington infall of gas ({sup h}yperaccretion{sup )}. This gas is not swallowed in real time, but forms an envelope of matter around the black hole that can be swallowed gradually, over a much longer timescale. However, only a small fraction of the black hole mass can be stored in the envelope at any one time. We argue that any infalling matter above a few percent of the hole's mass is ejected as a result of the plunge in opacity at temperatures below amore » few thousand degrees kelvin, corresponding to the Hayashi track. The speed of ejection of this matter, compared to the velocity dispersion {sigma} of the host galaxy's core, determines whether the ejected matter is lost forever or returns eventually to rejoin the envelope, from which it can be ultimately accreted. The threshold between matter recycling and permanent loss defines a relationship between the maximum black hole mass and {sigma} that resembles the empirical M{sub BH}-{sigma} relation.« less

Data for four geologic test holes in the Sacramento Valley, California

USGS Publications Warehouse

Berkstresser, C.F.; French, J.J.; Schaal, M.E.

1985-01-01

The report provides geological and geophysical data for four of seven test holes drilled as a part of the Central Valley Aquifer Project, which is part of the Regional Aquifer Systems Analysis. The holes were drilled with a rotary well drilling machine to depths of 900 feet in the southwestern part of the Sacramento Valley in Solano and Yolo Counties. Geologic data for each well include lithology, texture, color, character of the contact, sorting, rounding, and cementation, determined from cuttings, cores, and sidewall covers. Fifty cores, 3 feet long, were obtained from each hole, and from eight to fourteen sidewall cores were collected. Geophysical data include a dual-induction log, spherically focused log (SFL), compensated neutron-formation density log, gamma-ray log, and a caliper log. These data are presented in four tables and on four plates. (USGS)

Quantum simulation of ultrafast dynamics using trapped ultracold atoms.

PubMed

Senaratne, Ruwan; Rajagopal, Shankari V; Shimasaki, Toshihiko; Dotti, Peter E; Fujiwara, Kurt M; Singh, Kevin; Geiger, Zachary A; Weld, David M

2018-05-25

Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.

Ultra-fast Object Recognition from Few Spikes

DTIC Science & Technology

2005-07-06

Computer Science and Artificial Intelligence Laboratory Ultra-fast Object Recognition from Few Spikes Chou Hung, Gabriel Kreiman , Tomaso Poggio...neural code for different kinds of object-related information. *The authors, Chou Hung and Gabriel Kreiman , contributed equally to this work...Supplementary Material is available at http://ramonycajal.mit.edu/ kreiman /resources/ultrafast

Progress in ultrafast laser processing and future prospects

NASA Astrophysics Data System (ADS)

Sugioka, Koji

2017-03-01

The unique characteristics of ultrafast lasers have rapidly revolutionized materials processing after their first demonstration in 1987. The ultrashort pulse width of the laser suppresses heat diffusion to the surroundings of the processed region, which minimizes the formation of a heat-affected zone and thereby enables ultrahigh precision micro- and nanofabrication of various materials. In addition, the extremely high peak intensity can induce nonlinear multiphoton absorption, which extends the diversity of materials that can be processed to transparent materials such as glass. Nonlinear multiphoton absorption enables three-dimensional (3D) micro- and nanofabrication by irradiation with tightly focused femtosecond laser pulses inside transparent materials. Thus, ultrafast lasers are currently widely used for both fundamental research and practical applications. This review presents progress in ultrafast laser processing, including micromachining, surface micro- and nanostructuring, nanoablation, and 3D and volume processing. Advanced technologies that promise to enhance the performance of ultrafast laser processing, such as hybrid additive and subtractive processing, and shaped beam processing are discussed. Commercial and industrial applications of ultrafast laser processing are also introduced. Finally, future prospects of the technology are given with a summary.

Detailed lithologic log of the Dow Chemical #1 B.L. Garrigan Drill Hole, Mississippi County, Arkansas

USGS Publications Warehouse

Collins, Donley S.; Skipp, Gary L.

1995-01-01

arch and is an important source of core from the Reelfoot basin (Collins and others, 1992). Therefore, this drill hole is important for understanding structure and Paleozoic stratigraphy in a basin where stratigraphic and structural data are sparse. Rocks in the Garrigan were originally logged and described by J.R. Howe (personal communication to D.S. Collins, 1990) and published as a composite stratigraphic section along with the rock description for the Dow Chemical #1 Wilson drill hole (Howe, 1984). F.A. McKeown later relogged the rocks in the Garrigan and presented a generalized log in McKeown and others (1990). Swolfs (1991) presented another version of the Garrigan drill-hole geologic section (fig. 2). Aided by new biostratigraphic information, Taylor and others (1991) corrected major errors in the characterization and correlation of rocks in the Garrigan (fig. 2). Collins (1991) described the insoluble residues from the cuttings of the Garrigan, but could not correlate them with the insoluble resides from rocks of the carbonate platform west of the basin. However Taylor and others (1991), Collins and others (1992), and Collins and Bohm (1993) did correlate fossils from the Garrigan to other drill holes in the Reelfoot basin and adjacent areas. Using these correlated data, Collins and Bohm (1993) provided information on the structural relief across a part of the Reelfoot basin. Collins and others (1992) also interpreted the depositional setting for the Paleozoic rocks of the Garrigan. This report presents a detailed lithologic log of the Paleozoic rocks penetrated by the Garrigan that differs from the lithologic logs of previous workers (Howe, 1984; McKeown and others, 1990; see also Dart, 1992, p. 18-19). The lithologic descriptions of the Garrigan are derived from observations of well cuttings and core. Cored intervals used were 11,426-11,402 ft, 10,229-10,200 ft, and 8,002-7,979 ft. These intervals were the only intervals cored during the Garrigan drill

Galaxies of all Shapes Host Black Holes

NASA Technical Reports Server (NTRS)

2008-01-01

This artist's concept illustrates the two types of spiral galaxies that populate our universe: those with plump middles, or central bulges (upper left), and those lacking the bulge (foreground).

New observations from NASA's Spitzer Space Telescope provide strong evidence that the slender, bulgeless galaxies can, like their chubbier counterparts, harbor supermassive black holes at their cores. Previously, astronomers thought that a galaxy without a bulge could not have a supermassive black hole. In this illustration, jets shooting away from the black holes are depicted as thin streams.

The findings are reshaping theories of galaxy formation, suggesting that a galaxy's 'waistline' does not determine whether it will be home to a big black hole.

Cerebellar gray matter and lobular volumes correlate with core autism symptoms

PubMed Central

D'Mello, Anila M.; Crocetti, Deana; Mostofsky, Stewart H.; Stoodley, Catherine J.

2015-01-01

Neuroanatomical differences in the cerebellum are among the most consistent findings in autism spectrum disorder (ASD), but little is known about the relationship between cerebellar dysfunction and core ASD symptoms. The newly-emerging existence of cerebellar sensorimotor and cognitive subregions provides a new framework for interpreting the functional significance of cerebellar findings in ASD. Here we use two complementary analyses — whole-brain voxel-based morphometry (VBM) and the SUIT cerebellar atlas — to investigate cerebellar regional gray matter (GM) and volumetric lobular measurements in 35 children with ASD and 35 typically-developing (TD) children (mean age 10.4 ± 1.6 years; range 8–13 years). To examine the relationships between cerebellar structure and core ASD symptoms, correlations were calculated between scores on the Autism Diagnostic Observation Schedule (ADOS) and Autism Diagnostic Interview (ADI) and the VBM and volumetric data. Both VBM and the SUIT analyses revealed reduced GM in ASD children in cerebellar lobule VII (Crus I/II). The degree of regional and lobular gray matter reductions in different cerebellar subregions correlated with the severity of symptoms in social interaction, communication, and repetitive behaviors. Structural differences and behavioral correlations converged on right cerebellar Crus I/II, a region which shows structural and functional connectivity with fronto-parietal and default mode networks. These results emphasize the importance of the location within the cerebellum to the potential functional impact of structural differences in ASD, and suggest that GM differences in cerebellar right Crus I/II are associated with the core ASD profile. PMID:25844317

3D ultrafast ultrasound imaging in vivo.

PubMed

Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

2014-10-07

Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra--and inter-observer variability.

Perspective: Ultrafast magnetism and THz spintronics

NASA Astrophysics Data System (ADS)

Walowski, Jakob; Münzenberg, Markus

2016-10-01

This year the discovery of femtosecond demagnetization by laser pulses is 20 years old. For the first time, this milestone work by Bigot and coworkers gave insight directly into the time scales of microscopic interactions that connect the spin and electron system. While intense discussions in the field were fueled by the complexity of the processes in the past, it now became evident that it is a puzzle of many different parts. Rather than providing an overview that has been presented in previous reviews on ultrafast processes in ferromagnets, this perspective will show that with our current depth of knowledge the first applications are developed: THz spintronics and all-optical spin manipulation are becoming more and more feasible. The aim of this perspective is to point out where we can connect the different puzzle pieces of understanding gathered over 20 years to develop novel applications. Based on many observations in a large number of experiments. Differences in the theoretical models arise from the localized and delocalized nature of ferromagnetism. Transport effects are intrinsically non-local in spintronic devices and at interfaces. We review the need for multiscale modeling to address the processes starting from electronic excitation of the spin system on the picometer length scale and sub-femtosecond time scale, to spin wave generation, and towards the modeling of ultrafast phase transitions that altogether determine the response time of the ferromagnetic system. Today, our current understanding gives rise to the first usage of ultrafast spin physics for ultrafast magnetism control: THz spintronic devices. This makes the field of ultrafast spin-dynamics an emerging topic open for many researchers right now.

Perspective: Ultrafast magnetism and THz spintronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walowski, Jakob; Münzenberg, Markus

This year the discovery of femtosecond demagnetization by laser pulses is 20 years old. For the first time, this milestone work by Bigot and coworkers gave insight directly into the time scales of microscopic interactions that connect the spin and electron system. While intense discussions in the field were fueled by the complexity of the processes in the past, it now became evident that it is a puzzle of many different parts. Rather than providing an overview that has been presented in previous reviews on ultrafast processes in ferromagnets, this perspective will show that with our current depth of knowledgemore » the first applications are developed: THz spintronics and all-optical spin manipulation are becoming more and more feasible. The aim of this perspective is to point out where we can connect the different puzzle pieces of understanding gathered over 20 years to develop novel applications. Based on many observations in a large number of experiments. Differences in the theoretical models arise from the localized and delocalized nature of ferromagnetism. Transport effects are intrinsically non-local in spintronic devices and at interfaces. We review the need for multiscale modeling to address the processes starting from electronic excitation of the spin system on the picometer length scale and sub-femtosecond time scale, to spin wave generation, and towards the modeling of ultrafast phase transitions that altogether determine the response time of the ferromagnetic system. Today, our current understanding gives rise to the first usage of ultrafast spin physics for ultrafast magnetism control: THz spintronic devices. This makes the field of ultrafast spin-dynamics an emerging topic open for many researchers right now.« less

An Integrated Finite Element-based Simulation Framework: From Hole Piercing to Hole Expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Xiaohua; Sun, Xin; Golovashchenko, Segey F.

An integrated finite element-based modeling framework is developed to predict the hole expansion ratio (HER) of AA6111-T4 sheet by considering the piercing-induced damages around the hole edge. Using damage models and parameters calibrated from previously reported tensile stretchability studies, the predicted HER correlates well with experimentally measured HER values for different hole piercing clearances. The hole piercing model shows burrs are not generated on the sheared surface for clearances less than 20%, which corresponds well with the experimental data on pierced holes cross-sections. Finite-element-calculated HER also is not especially sensitive to piercing clearances less than this value. However, as clearancesmore » increase to 30% and further to 40%, the HER values are predicted to be considerably smaller, also consistent with experimental measurements. Upon validation, the integrated modeling framework is used to examine the effects of different hole piercing and hole expansion conditions on the critical HERs for AA6111-T4.« less

Ultrafast FADC multiplexer

NASA Astrophysics Data System (ADS)

Mirzoyan, R.; Cortina, J.; Lorenz, E.; Martinez, M.; Ostankov, A.; Paneque, D.

2002-10-01

Ultrafast Flash amplitude-to-digital converters (FADCs) are still very expensive. Here we propose a multiplexing scheme allowing one in common trigger mode to read out multiple signal sources by using a single FADC channel. Usual coaxial cables can be used in the multiplexer as analog signal delay elements. The limited bandwidth of the coaxial cable, depending on its type and length will set an upper limit to the number of multiplexed channels. Better bandwidth and the correspondingly higher number of multiplexed channels one can obtain when using the technique of transmission of analog signals via optical fibers. Low-cost vertical cavity surface emitting laser (VCSEL) diodes can be used as converters of fast electrical signals into near infrared light. Multiplexing can be an economically priced solution when one needs ultrafast digitization of hundreds of fast signal channels.

4D multiple-cathode ultrafast electron microscopy

PubMed Central

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H.

2014-01-01

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging. PMID:25006261

4D multiple-cathode ultrafast electron microscopy.

PubMed

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H

2014-07-22

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging.

The host galaxy/AGN connection in nearby early-type galaxies. Is there a miniature radio-galaxy in every "core" galaxy?

NASA Astrophysics Data System (ADS)

Balmaverde, B.; Capetti, A.

2006-02-01

This is the second of a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. We selected two samples with 5 GHz VLA radio flux measurements down to 1 mJy, reaching levels of radio luminosity as low as 1036 erg s-1. In Paper I we presented a study of the surface brightness profiles for the 65 objects with available archival HST images out of the 116 radio-detected galaxies. We classified early-type galaxies into "core" and "power-law" galaxies, discriminating on the basis of the slope of their nuclear brightness profiles, following the Nukers scheme. Here we focus on the 29 core galaxies (hereafter CoreG). We used HST and Chandra data to isolate their optical and X-ray nuclear emission. The CoreG invariably host radio-loud nuclei, with an average radio-loudness parameter of Log R = L5 {GHz} / LB ˜ 3.6. The optical and X-ray nuclear luminosities correlate with the radio-core power, smoothly extending the analogous correlations already found for low luminosity radio-galaxies (LLRG) toward even lower power, by a factor of ˜ 1000, covering a combined range of 6 orders of magnitude. This supports the interpretation of a common non-thermal origin of the nuclear emission also for CoreG. The luminosities of the nuclear sources, most likely dominated by jet emission, set firm upper limits, as low as L/L_Edd ˜ 10-9 in both the optical and X-ray band, on any emission from the accretion process. The similarity of CoreG and LLRG when considering the distributions host galaxies luminosities and black hole masses, as well as of the surface brightness profiles, indicates that they are drawn from the same population of early-type galaxies. LLRG represent only the tip of the iceberg associated with (relatively) high activity levels, with CoreG forming the bulk of the population. We do not find any relationship between radio-power and black hole mass. A minimum black hole

Ultrafast Hydration Dynamics and Coupled Water-Protein Fluctuations in Apomyoglobin

NASA Astrophysics Data System (ADS)

Yang, Yi; Zhang, Luyuan; Wang, Lijuan; Zhong, Dongping

2009-06-01

Protein hydration dynamics are of fundamental importance to its structure and function. Here, we characterize the global solvation dynamics and anisotropy dynamics around the apomyoglobin surface in different conformational states (native and molten globule) by measuring the Stokes shift and anisotropy decay of tryptophan with femtosecond-resolved fluorescence upconversion. With site-directed mutagenesis, we designed sixteen mutants with one tryptophan in each, and placed the probe at a desirable position ranging from buried in the protein core to fully solvent-exposed on the protein surface. In all protein sites studied, two distinct solvation relaxations (1-8 ps and 20-200 ps) were observed, reflecting the initial collective water relaxation and subsequent hydrogen-bond network restructuring, respectively, and both are strongly correlated with protein's local structures and chemical properties. The hydration dynamics of the mutants in molten globule state are faster than those observed in native state, indicating that the protein becomes more flexible and less structured when its conformation is converted from fully-folded native state to partially-folded molten globule state. Complementary, fluorescence anisotropy dynamics of all mutants in native state show an increasing trend of wobbling times (40-260 ps) when the location of the probe is changed from a loop, to a lateral helix, and then, to the compact protein core. Such an increase in wobbling times is related to the local protein structural rigidity, which relates the interaction of water with side chains. The ultrafast hydration dynamics and related side-chain motion around the protein surface unravel the coupled water-protein fluctuations on the picosecond time scales and indicate that the local protein motions are slaved by hydrating water fluctuations.

Electronic structure and intersubband magnetoabsorption spectra of CdSe/CdS core-shell nanowires

NASA Astrophysics Data System (ADS)

Xiong, Wen

2016-10-01

The electronic structures of CdSe/CdS core-shell nanowires are calculated based on the effective-mass theory, and it is found that the hole states in CdSe/CdS core-shell nanowires are strongly mixed, which are very different from the hole states in CdSe or CdS nanowires. In addition, we find the three highest hole states at the Γ point are almost localized in the CdSe core and the energies of the hole states in CdSe/CdS core-shell nanowires can be enhanced greatly when the core radius Rc increases and the total radius R is fixed. The degenerate hole states are split by the magnetic field, and the split energies will increase when |Jh | increases from 1/2 to 7/2, while they are almost not influenced by the change of the core radius Rc. The absorption spectra of CdSe/CdS core-shell nanowires at the Γ point are also studied in the magnetic field when the temperature T is considered, and we find there are only two peaks will arise if the core radius Rc and the temperature T increase. The intensity of each optical absorption can be considerably enhanced by increasing the core radius Rc when the temperature T is fixed, it is due to the increase of their optical transition matrix element. Meanwhile, the intensity of each optical absorption can be decreased when the temperature T increases and the core radius Rc is fixed, and this is because the Fermi-Dirac distribution function of the corresponding hole states will increase as the increase of the temperature T.

Planet traps and planetary cores: origins of the planet-metallicity correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasegawa, Yasuhiro; Pudritz, Ralph E., E-mail: yasu@asiaa.sinica.edu.tw, E-mail: pudritz@physics.mcmaster.ca

2014-10-10

Massive exoplanets are observed preferentially around high metallicity ([Fe/H]) stars while low-mass exoplanets do not show such an effect. This so-called planet-metallicity correlation generally favors the idea that most observed gas giants at r < 10 AU are formed via a core accretion process. We investigate the origin of this phenomenon using a semi-analytical model, wherein the standard core accretion takes place at planet traps in protostellar disks where rapid type I migrators are halted. We focus on the three major exoplanetary populations—hot Jupiters, exo-Jupiters located at r ≅ 1 AU, and the low-mass planets. We show using a statisticalmore » approach that the planet-metallicity correlations are well reproduced in these models. We find that there are specific transition metallicities with values [Fe/H] = –0.2 to –0.4, below which the low-mass population dominates, and above which the Jovian populations take over. The exo-Jupiters significantly exceed the hot Jupiter population at all observed metallicities. The low-mass planets formed via the core accretion are insensitive to metallicity, which may account for a large fraction of the observed super-Earths and hot-Neptunes. Finally, a controlling factor in building massive planets is the critical mass of planetary cores (M {sub c,} {sub crit}) that regulates the onset of rapid gas accretion. Assuming the current data is roughly complete at [Fe/H] > –0.6, our models predict that the most likely value of the 'mean' critical core mass of Jovian planets is (M {sub c,} {sub crit}) ≅ 5 M {sub ⊕} rather than 10 M {sub ⊕}. This implies that grain opacities in accreting envelopes should be reduced in order to lower M {sub c,} {sub crit}.« less

Covariance mapping of two-photon double core hole states in C 2 H 2 and C 2 H 6 produced by an x-ray free electron laser

DOE PAGES

Mucke, M; Zhaunerchyk, V; Frasinski, L J; ...

2015-07-01

Few-photon ionization and relaxation processes in acetylene (C 2H 2) and ethane (C 2H 6) were investigated at the linac coherent light source x-ray free electron laser (FEL) at SLAC, Stanford using a highly efficient multi-particle correlation spectroscopy technique based on a magnetic bottle. The analysis method of covariance mapping has been applied and enhanced, allowing us to identify electron pairs associated with double core hole (DCH) production and competing multiple ionization processes including Auger decay sequences. The experimental technique and the analysis procedure are discussed in the light of earlier investigations of DCH studies carried out at the samemore » FEL and at third generation synchrotron radiation sources. In particular, we demonstrate the capability of the covariance mapping technique to disentangle the formation of molecular DCH states which is barely feasible with conventional electron spectroscopy methods.« less

Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

USGS Publications Warehouse

Larsen, Daniel; Nelson, Philip H.

2000-01-01

Core descriptions and geophysical logs from two boreholes (CCM-1 and CCM-2) in the Oligocene Snowshoe Mountain Tuff and Creede Formation, south-central Colorado, are used to interpret sedimentary and volcanic facies associations and their physical properties. The seven facies association include a mixed sequence of intracaldera ash-flow tuffs and breccias, alluvial and lake margin deposits, and tuffaceous lake beds. These deposits represent volcanic units related to caldera collapse and emplacement of the Snowshoe Mountain Tuff, and sediments and pyroclastic material deposited in the newly formed caldera basin, Early sedimentation is interpreted to have been rapid, and to have occurred in volcaniclastic fan environments at CCM-1 and in a variery of volcaniclastic fan, braided stream shallow lacustrine, and mudflat environments at CCM-2. After an initial period of lake-level rise, suspension settling, turbidite, and debris-flow sedimentation occurred in lacustrine slope and basin environments below wave base. Carbonate sedimentation was initially sporadic, but more continuous in the latter part of the recorded lake history (after the H fallout tuff). Sublacustrine-fan deposition occurred at CCM-1 after a pronounced lake-level fall and subsequent rise that preceded the H tuff. Variations in density, neutron, gamma-ray, sonic, and electrical properties of deposits penetrated oin the two holes reflect variations in lithology, porosity, and alteration. Trends in the geophysical properties of the lacustrine strata are linked to downhole changes in authigenic mineralology and a decrease in porosity interpreted to have resulted primarily from diagenesis. Lithological and geophysical characteristics provide a basis for correlation of the cores; however, mineralogical methods of correlation are hampered by the degree of diagenesis and alteration.

Using a Semiconductor-to-Metal Transition to Control Optical Transmission through Subwavelength Hole Arrays

DOE PAGES

Donev, E. U.; Suh, J. Y.; Lopez, R.; ...

2008-01-01

We describe a simple configuration in which the extraordinary optical transmission effect through subwavelength hole arrays in noble-metal films can be switched by the semiconductor-to-metal transition in an underlying thin film of vanadium dioxide. In these experiments, the transition is brought about by thermal heating of the bilayer film. The surprising reverse hysteretic behavior of the transmission through the subwavelength holes in the vanadium oxide suggest that this modulation is accomplished by a dielectric-matching condition rather than plasmon coupling through the bilayer film. The results of this switching, including the wavelength dependence, are qualitatively reproduced by a transfer matrix model.more » The prospects for effecting a similar modulation on a much faster time scale by using ultrafast laser pulses to trigger the semiconductor-to-metal transition are also discussed.« less

Graphene-clad microfibre saturable absorber for ultrafast fibre lasers.

PubMed

Liu, X M; Yang, H R; Cui, Y D; Chen, G W; Yang, Y; Wu, X Q; Yao, X K; Han, D D; Han, X X; Zeng, C; Guo, J; Li, W L; Cheng, G; Tong, L M

2016-05-16

Graphene, whose absorbance is approximately independent of wavelength, allows broadband light-matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating light with graphene covered on a D-shaped fibre or microfibre has been employed extensively because of the nonblocking configuration. Obviously, most of the fibre surface is unused in these techniques. Here, we exploit a graphene-clad microfibre (GCM) saturable absorber in a mode-locked fibre laser for the generation of ultrafast pulses. The proposed all-surface technique can guarantee a higher efficiency of light-graphene interactions than the aforementioned techniques. Our GCM-based saturable absorber can generate ultrafast optical pulses within 1.5 μm. This saturable absorber is compatible with current fibre lasers and has many merits such as low saturation intensities, ultrafast recovery times, and wide wavelength ranges. The proposed saturable absorber will pave the way for graphene-based wideband photonics.

Graphene-clad microfibre saturable absorber for ultrafast fibre lasers

PubMed Central

Liu, X. M.; Yang, H. R.; Cui, Y. D.; Chen, G. W.; Yang, Y.; Wu, X. Q.; Yao, X. K.; Han, D. D.; Han, X. X.; Zeng, C.; Guo, J.; Li, W. L.; Cheng, G.; Tong, L. M.

2016-01-01

Graphene, whose absorbance is approximately independent of wavelength, allows broadband light–matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating light with graphene covered on a D-shaped fibre or microfibre has been employed extensively because of the nonblocking configuration. Obviously, most of the fibre surface is unused in these techniques. Here, we exploit a graphene-clad microfibre (GCM) saturable absorber in a mode-locked fibre laser for the generation of ultrafast pulses. The proposed all-surface technique can guarantee a higher efficiency of light–graphene interactions than the aforementioned techniques. Our GCM-based saturable absorber can generate ultrafast optical pulses within 1.5 μm. This saturable absorber is compatible with current fibre lasers and has many merits such as low saturation intensities, ultrafast recovery times, and wide wavelength ranges. The proposed saturable absorber will pave the way for graphene-based wideband photonics. PMID:27181419

Slim hole drilling and testing strategies

NASA Astrophysics Data System (ADS)

Nielson, Dennis L.; Garg, Sabodh K.; Goranson, Colin

2017-12-01

The financial and geologic advantages of drilling slim holes instead of large production wells in the early stages of geothermal reservoir assessment has been understood for many years. However, the practice has not been fully embraced by geothermal developers. We believe that the reason for this is that there is a poor understanding of testing and reservoir analysis that can be conducted in slim holes. In addition to reservoir engineering information, coring through the cap rock and into the reservoir provides important data for designing subsequent production well drilling and completion. Core drilling requires significantly less mud volume than conventional rotary drilling, and it is typically not necessary to cure lost circulation zones (LCZ). LCZs should be tested by either production or injection methods as they are encountered. The testing methodologies are similar to those conducted on large-diameter wells; although produced and/or injected fluid volumes are much less. Pressure, temperature and spinner (PTS) surveys in slim holes under static conditions can used to characterize temperature and pressure distribution in the geothermal reservoir. In many cases it is possible to discharge slim holes and obtain fluid samples to delineate the geochemical properties of the reservoir fluid. Also in the latter case, drawdown and buildup data obtained using a downhole pressure tool can be employed to determine formation transmissivity and well properties. Even if it proves difficult to discharge a slim hole, an injection test can be performed to obtain formation transmissivity. Given the discharge (or injection) data from a slimhole, discharge properties of a large-diameter well can be inferred using wellbore modeling. Finally, slim hole data (pressure, temperature, transmissivity, fluid properties) together with reservoir simulation can help predict the ability of the geothermal reservoir to sustain power production.

THE LANDSCAPE OF THE NEUTRINO MECHANISM OF CORE-COLLAPSE SUPERNOVAE: NEUTRON STAR AND BLACK HOLE MASS FUNCTIONS, EXPLOSION ENERGIES, AND NICKEL YIELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pejcha, Ondřej; Thompson, Todd A., E-mail: pejcha@astro.princeton.edu, E-mail: thompson@astronomy.ohio-state.edu

2015-03-10

If the neutrino luminosity from the proto-neutron star formed during a massive star core collapse exceeds a critical threshold, a supernova (SN) results. Using spherical quasi-static evolutionary sequences for hundreds of progenitors over a range of metallicities, we study how the explosion threshold maps onto observables, including the fraction of successful explosions, the neutron star (NS) and black hole (BH) mass functions, the explosion energies (E {sub SN}) and nickel yields (M {sub Ni}), and their mutual correlations. Successful explosions are intertwined with failures in a complex pattern that is not simply related to initial progenitor mass or compactness. Wemore » predict that progenitors with initial masses of 15 ± 1, 19 ± 1, and ∼21-26 M {sub ☉} are most likely to form BHs, that the BH formation probability is non-zero at solar-metallicity and increases significantly at low metallicity, and that low luminosity, low Ni-yield SNe come from progenitors close to success/failure interfaces. We qualitatively reproduce the observed E {sub SN}-M {sub Ni} correlation, we predict a correlation between the mean and width of the NS mass and E {sub SN} distributions, and that the means of the NS and BH mass distributions are correlated. We show that the observed mean NS mass of ≅ 1.33 M {sub ☉} implies that the successful explosion fraction is higher than 0.35. Overall, we show that the neutrino mechanism can in principle explain the observed properties of SNe and their compact objects. We argue that the rugged landscape of progenitors and outcomes mandates that SN theory should focus on reproducing the wide ranging distributions of observed SN properties.« less

Photoinduced molecular chirality probed by ultrafast resonant X-ray spectroscopy

DOE PAGES

Rouxel, Jérémy R.; Kowalewski, Markus; Mukamel, Shaul

2017-07-01

Recently developed circularly polarized X-ray light sources can probe the ultrafast chiral electronic and nuclear dynamics through spatially localized resonant core transitions. Here, we present simulations of time-resolved circular dichroism signals given by the difference of left and right circularly polarized X-ray probe transmission following an excitation by a circularly polarized optical pump with the variable time delay. Application is made to formamide which is achiral in the ground state and assumes two chiral geometries upon optical excitation to the first valence excited state. Probes resonant with various K-edges (C, N, and O) provide different local windows onto the paritymore » breaking geometry change thus revealing the enantiomer asymmetry.« less

Photoinduced molecular chirality probed by ultrafast resonant X-ray spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rouxel, Jérémy R.; Kowalewski, Markus; Mukamel, Shaul

Recently developed circularly polarized X-ray light sources can probe the ultrafast chiral electronic and nuclear dynamics through spatially localized resonant core transitions. Here, we present simulations of time-resolved circular dichroism signals given by the difference of left and right circularly polarized X-ray probe transmission following an excitation by a circularly polarized optical pump with the variable time delay. Application is made to formamide which is achiral in the ground state and assumes two chiral geometries upon optical excitation to the first valence excited state. Probes resonant with various K-edges (C, N, and O) provide different local windows onto the paritymore » breaking geometry change thus revealing the enantiomer asymmetry.« less

Proposed imaging of the ultrafast electronic motion in samples using x-ray phase contrast.

PubMed

Dixit, Gopal; Slowik, Jan Malte; Santra, Robin

2013-03-29

Tracing the motion of electrons has enormous relevance to understanding ubiquitous phenomena in ultrafast science, such as the dynamical evolution of the electron density during complex chemical and biological processes. Scattering of ultrashort x-ray pulses from an electronic wave packet would appear to be the most obvious approach to image the electronic motion in real time and real space with the notion that such scattering patterns, in the far-field regime, encode the instantaneous electron density of the wave packet. However, recent results by Dixit et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 11636 (2012)] have put this notion into question and have shown that the scattering in the far-field regime probes spatiotemporal density-density correlations. Here, we propose a possible way to image the instantaneous electron density of the wave packet via ultrafast x-ray phase contrast imaging. Moreover, we show that inelastic scattering processes, which plague ultrafast scattering in the far-field regime, do not contribute in ultrafast x-ray phase contrast imaging as a consequence of an interference effect. We illustrate our general findings by means of a wave packet that lies in the time and energy range of the dynamics of valence electrons in complex molecular and biological systems. This present work offers a potential to image not only instantaneous snapshots of nonstationary electron dynamics, but also the laplacian of these snapshots which provide information about the complex bonding and topology of the charge distributions in the systems.

Proposed Imaging of the Ultrafast Electronic Motion in Samples using X-Ray Phase Contrast

NASA Astrophysics Data System (ADS)

Dixit, Gopal; Slowik, Jan Malte; Santra, Robin

2013-03-01

Tracing the motion of electrons has enormous relevance to understanding ubiquitous phenomena in ultrafast science, such as the dynamical evolution of the electron density during complex chemical and biological processes. Scattering of ultrashort x-ray pulses from an electronic wave packet would appear to be the most obvious approach to image the electronic motion in real time and real space with the notion that such scattering patterns, in the far-field regime, encode the instantaneous electron density of the wave packet. However, recent results by Dixit et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 11 636 (2012)] have put this notion into question and have shown that the scattering in the far-field regime probes spatiotemporal density-density correlations. Here, we propose a possible way to image the instantaneous electron density of the wave packet via ultrafast x-ray phase contrast imaging. Moreover, we show that inelastic scattering processes, which plague ultrafast scattering in the far-field regime, do not contribute in ultrafast x-ray phase contrast imaging as a consequence of an interference effect. We illustrate our general findings by means of a wave packet that lies in the time and energy range of the dynamics of valence electrons in complex molecular and biological systems. This present work offers a potential to image not only instantaneous snapshots of nonstationary electron dynamics, but also the Laplacian of these snapshots which provide information about the complex bonding and topology of the charge distributions in the systems.

The Arduous Journey to Black Hole Formation in Potential Gamma-Ray Burst Progenitors

NASA Astrophysics Data System (ADS)

Dessart, Luc; O'Connor, Evan; Ott, Christian D.

2012-07-01

We present a quantitative study on the properties at death of fast-rotating massive stars evolved at low-metallicity—objects that are proposed as likely progenitors of long-duration γ-ray bursts (LGRBs). We perform one-dimensional+rotation stellar-collapse simulations on the progenitor models of Woosley and Heger, and critically assess their potential for the formation of a black hole and a Keplerian disk (namely, a collapsar) or a proto-magnetar. We note that theoretical uncertainties in the treatment of magnetic fields and the approximate handling of rotation compromise the accuracy of stellar-evolution models. We find that only the fastest rotating progenitors achieve sufficient compactness for black hole formation while the bulk of models possess a core density structure typical of garden-variety core-collapse supernova (SN) progenitors evolved without rotation and at solar metallicity. Of the models that do have sufficient compactness for black hole formation, most of them also retain a large amount of angular momentum in the core, making them prone to a magneto-rotational explosion, therefore preferentially leaving behind a proto-magnetar. A large progenitor angular-momentum budget is often the sole criterion invoked in the community today to assess the suitability for producing a collapsar. This simplification ignores equally important considerations such as the core compactness, which conditions black hole formation, the core angular momentum, which may foster a magneto-rotational explosion preventing black hole formation, or the metallicity and the residual envelope mass which must be compatible with inferences from observed LGRB/SNe. Our study suggests that black hole formation is non-trivial, that there is room for accommodating both collapsars and proto-magnetars as LGRB progenitors, although proto-magnetars seem much more easily produced by current stellar-evolutionary models.

Ultrafast Electron Dynamics in Solar Energy Conversion.

PubMed

Ponseca, Carlito S; Chábera, Pavel; Uhlig, Jens; Persson, Petter; Sundström, Villy

2017-08-23

Electrons are the workhorses of solar energy conversion. Conversion of the energy of light to electricity in photovoltaics, or to energy-rich molecules (solar fuel) through photocatalytic processes, invariably starts with photoinduced generation of energy-rich electrons. The harvesting of these electrons in practical devices rests on a series of electron transfer processes whose dynamics and efficiencies determine the function of materials and devices. To capture the energy of a photogenerated electron-hole pair in a solar cell material, charges of opposite sign have to be separated against electrostatic attractions, prevented from recombining and being transported through the active material to electrodes where they can be extracted. In photocatalytic solar fuel production, these electron processes are coupled to chemical reactions leading to storage of the energy of light in chemical bonds. With the focus on the ultrafast time scale, we here discuss the light-induced electron processes underlying the function of several molecular and hybrid materials currently under development for solar energy applications in dye or quantum dot-sensitized solar cells, polymer-fullerene polymer solar cells, organometal halide perovskite solar cells, and finally some photocatalytic systems.

Analysis of residual transverse stresses in a thick UD glass/polyester pultruded profile using hole drilling with strain gage and digital image correlation

NASA Astrophysics Data System (ADS)

Yuksel, Onur; Baran, Ismet; Ersoy, Nuri; Akkerman, Remko

2018-05-01

Process induced stresses inherently exist in fiber reinforced polymer composites particularly in thick parts due to the presence of non-uniform cure, shrinkage and thermal expansion/contraction during manufacturing. In order to increase the reliability and the performance of the composite materials, process models are developed to predict the residual stress formation. The accuracy of the process models is dependent on the geometrical (micro to macro), material and process parameters as well as the numerical implementation. Therefore, in order to have reliable process modelling framework, there is a need for validation and if necessary calibration of the developed models. This study focuses on measurement of the transverse residual stresses in a relatively thick pultruded profile (20×20 mm) made of glass/polyester. Process-induced residual stresses in the middle of the profile are examined with different techniques which have never been applied for transverse residual stresses in thick unidirectional composites. Hole drilling method with strain gage and digital image correlation are employed. Strain values measured from measurements are used in a finite element model (FEM) to simulate the hole drilling process and predict the residual stress level. The measured released strain is found to be approximately 180 μm/m from the strain gage. The tensile residual stress at the core of the profile is estimated approximately as 7-10 MPa. Proposed methods and measured values in this study will enable validation and calibration of the process models based on the residual stresses.

Several new directions for ultrafast fiber lasers [Invited].

PubMed

Fu, Walter; Wright, Logan G; Sidorenko, Pavel; Backus, Sterling; Wise, Frank W

2018-04-16

Ultrafast fiber lasers have the potential to make applications of ultrashort pulses widespread - techniques not only for scientists, but also for doctors, manufacturing engineers, and more. Today, this potential is only realized in refractive surgery and some femtosecond micromachining. The existing market for ultrafast lasers remains dominated by solid-state lasers, primarily Ti:sapphire, due to their superior performance. Recent advances show routes to ultrafast fiber sources that provide performance and capabilities equal to, and in some cases beyond, those of Ti:sapphire, in compact, versatile, low-cost devices. In this paper, we discuss the prospects for future ultrafast fiber lasers built on new kinds of pulse generation that capitalize on nonlinear dynamics. We focus primarily on three promising directions: mode-locked oscillators that use nonlinearity to enhance performance; systems that use nonlinear pulse propagation to achieve ultrashort pulses without a mode-locked oscillator; and multimode fiber lasers that exploit nonlinearities in space and time to obtain unparalleled control over an electric field.

Space charge effects in ultrafast electron diffraction and imaging

NASA Astrophysics Data System (ADS)

Tao, Zhensheng; Zhang, He; Duxbury, P. M.; Berz, Martin; Ruan, Chong-Yu

2012-02-01

Understanding space charge effects is central for the development of high-brightness ultrafast electron diffraction and microscopy techniques for imaging material transformation with atomic scale detail at the fs to ps timescales. We present methods and results for direct ultrafast photoelectron beam characterization employing a shadow projection imaging technique to investigate the generation of ultrafast, non-uniform, intense photoelectron pulses in a dc photo-gun geometry. Combined with N-particle simulations and an analytical Gaussian model, we elucidate three essential space-charge-led features: the pulse lengthening following a power-law scaling, the broadening of the initial energy distribution, and the virtual cathode threshold. The impacts of these space charge effects on the performance of the next generation high-brightness ultrafast electron diffraction and imaging systems are evaluated.

Nonequilibrium dynamics of the phonon gas in ultrafast-excited antimony

NASA Astrophysics Data System (ADS)

Krylow, Sergej; Zijlstra, Eeuwe S.; Kabeer, Fairoja Cheenicode; Zier, Tobias; Bauerhenne, Bernd; Garcia, Martin E.

2017-12-01

The ultrafast relaxation dynamics of a nonequilibrium phonon gas towards thermal equilibrium involves many-body collisions that cannot be properly described by perturbative approaches. Here, we develop a nonperturbative method to elucidate the microscopic mechanisms underlying the decay of laser-excited coherent phonons in the presence of electron-hole pairs, which so far are not fully understood. Our theory relies on ab initio molecular dynamics simulations on laser-excited potential-energy surfaces. Those simulations are compared with runs in which the laser-excited coherent phonon is artificially deoccupied. We apply this method to antimony and show that the decay of the A1 g phonon mode at low laser fluences can be accounted mainly to three-body down-conversion processes of an A1 g phonon into acoustic phonons. For higher excitation strengths, however, we see a crossover to a four-phonon process, in which two A1 g phonons decay into two optical phonons.

Vortex-Core Reversal Dynamics: Towards Vortex Random Access Memory

NASA Astrophysics Data System (ADS)

Kim, Sang-Koog

2011-03-01

An energy-efficient, ultrahigh-density, ultrafast, and nonvolatile solid-state universal memory is a long-held dream in the field of information-storage technology. The magnetic random access memory (MRAM) along with a spin-transfer-torque switching mechanism is a strong candidate-means of realizing that dream, given its nonvolatility, infinite endurance, and fast random access. Magnetic vortices in patterned soft magnetic dots promise ground-breaking applications in information-storage devices, owing to the very stable twofold ground states of either their upward or downward core magnetization orientation and plausible core switching by in-plane alternating magnetic fields or spin-polarized currents. However, two technologically most important but very challenging issues --- low-power recording and reliable selection of each memory cell with already existing cross-point architectures --- have not yet been resolved for the basic operations in information storage, that is, writing (recording) and readout. Here, we experimentally demonstrate a magnetic vortex random access memory (VRAM) in the basic cross-point architecture. This unique VRAM offers reliable cell selection and low-power-consumption control of switching of out-of-plane core magnetizations using specially designed rotating magnetic fields generated by two orthogonal and unipolar Gaussian-pulse currents along with optimized pulse width and time delay. Our achievement of a new device based on a new material, that is, a medium composed of patterned vortex-state disks, together with the new physics on ultrafast vortex-core switching dynamics, can stimulate further fruitful research on MRAMs that are based on vortex-state dot arrays.

The coupling of a disk corona and a jet for the radio/X-ray correlation in black hole X-ray binaries

NASA Astrophysics Data System (ADS)

Qiao, Erlin

2016-02-01

We interpret the radio/X-ray correlation of L R ~ L X ~1.4 for L X/L Edd >~ 10-3 with a detailed disk corona-jet model, in which the accretion flow and the jet are connected by a parameter, η, describing the fraction of the matter in the accretion flow ejected outward to form the jet. We calculate L R and L X at different Ṁ, adjusting η to fit the observed radio/X-ray correlation of the black hole X-ray transient H1743-322 for L X/L Edd > 10-3. It is found that the value of η for this radio/X-ray correlation for L X/L Edd > 10-3, is systematically less than that of the case for L X/L Edd < 10-3, which is consistent with the general idea that the jet is often relatively suppressed at the high luminosity phase in black hole X-ray binaries.

Black Hole Boldly Goes Where No Black Hole Has Gone Before

NASA Astrophysics Data System (ADS)

2007-01-01

Astronomers have found a black hole where few thought they could ever exist, inside a globular star cluster. The finding has broad implications for the dynamics of stars clusters and also for the existence of a still-speculative new class of black holes called 'intermediate-mass' black holes. The discovery is reported in the current issue of Nature. Tom Maccarone of the University of Southampton in England leads an international team on the finding, made primarily with the European Space Agency's XMM-Newton satellite. Globular clusters are dense bundles of thousands to millions of old stars, and many scientists have doubted that black holes could survive in such an exclusive environment. Computer simulations show that a newly formed black hole would first sink towards the centre of the cluster but quickly get gravitationally slingshot out entirely when interacting with the cluster's myriad stars. Credit: ESA/Hubble Artist's impression of globular star cluster The new finding provides the first convincing evidence that some black hole might not only survive but grow and flourish in globular clusters. What has astonished astronomers is how quickly the black hole was found. "We were preparing for a long, systematic search of thousands of globular clusters with the hope of finding just one black hole," said Maccarone. "But bingo, we found one as soon as we started the search. It was only the second globular cluster we looked at." The search continues to find more, Maccarone said, yet only one black hole was needed to resolve the decades-old discussion about black holes and globular clusters. Scientists say there are two main classes of black holes. Supermassive black holes containing the mass of millions to billions of suns are found in the core of most galaxies, including our own. A quasar is one kind of supermassive black hole. Stellar-size black holes contain the mass of about ten suns. These are created from the collapsed core of massive stars. Our galaxy likely

REVIEWS OF TOPICAL PROBLEMS: "Magnetized" black holes

NASA Astrophysics Data System (ADS)

Aliev, A. N.; Gal'tsov, D. V.

1989-01-01

Physical aspects of the theory of black holes in an external electromagnetic field are reviewed. The "magnetized" black hole model is currently widely discussed in astrophysics because it provides a basis for the explanation of the high energy activity of galactic cores and quasars. The particular feature of this model is that it predicts unusual "gravimagnetic" phenomena that arise as a result of a natural combination of effects in electrodynamics and gravitation, namely, the appearance of an inductive potential difference during the rotation of a black hole in a magnetic field, the drift of a black hole in an external electromagnetic field, the change in the chemical potential of the event horizon, the creation of an effective ergosphere of a black hole in a magnetic field, and so on. Questions relating to the description of electromagnetic fields in Kerr space-time are examined, including their influence on the space-time metric, the interaction between a rotating charged black hole and an external electromagnetic field, the motion of charged particles near "magnetized" black holes, including their spontaneous and stimulated emission, and the influence of magnetic fields on quantum-mechanical processes in black holes.

Rapid determination of caffeoylquinic acid derivatives in Cynara scolymus L. by ultra-fast liquid chromatography/tandem mass spectrometry based on a fused core C18 column.

PubMed

Shen, Qing; Dai, Zhiyuan; Lu, Yanbin

2010-10-01

An ultra-fast high-performance LC-ESI-MS/MS method was developed for the analysis and quantification of caffeoylquinic acid derivatives, including chlorogenic acid, 1,3-di-O-caffeoylquinic acid (cynarin) and 1,5-di-O-caffeoylquinic acid, in artichoke (Cynara scolymus L.) heads and leaves. The rapid separation (less than 4  min) was achieved based on a Halo fused core C18-silica column (50  mm × 2.1  mm id, 2.7  μm). The target compounds were detected and quantified by a triple-quadrupole mass spectrometer in multiple-reaction monitoring mode. The calibration function is linear from 0.06 to 2800  ng/mL for chlorogenic acid, 0.3-3000  ng/mL for cynarin and 0.24-4800  ng/mL for 1,5-di-O-caffeoylquinic acid, respectively. The average recoveries ranged from 92.1 to 113.2% with RSDs ≤6.5%. Moreover, four batches of artichoke head and leaf extracts were analyzed using the established method. The results indicated that the Halo fused core column provided much faster separations and higher sample throughput without sacrificing column ruggedness and reliability, and triple-quadrupole MS provided extraordinarily lower LOQs for most of the target analytes. Comparing to conventional quantitative approaches, the established method was fast, sensitive and reliable for the determination of caffeoylquinic acid derivatives in artichoke.

Real time ablation rate measurement during high aspect-ratio hole drilling with a 120-ps fiber laser.

PubMed

Mezzapesa, Francesco P; Sibillano, Teresa; Di Niso, Francesca; Ancona, Antonio; Lugarà, Pietro M; Dabbicco, Maurizio; Scamarcio, Gaetano

2012-01-02

We report on the instantaneous detection of the ablation rate as a function of depth during ultrafast microdrilling of metal targets. The displacement of the ablation front has been measured with a sub-wavelength resolution using an all-optical sensor based on the laser diode self-mixing interferometry. The time dependence of the laser ablation process within the depth of aluminum and stainless steel targets has been investigated to study the evolution of the material removal rate in high aspect-ratio micromachined holes.

Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis

DTIC Science & Technology

2016-07-08

AFRL-AFOSR-VA-TR-2016-0244 Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis Jahan Dawlaty UNIVERSITY OF SOUTHERN...TITLE AND SUBTITLE Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550...298 Back (Rev. 8/98) DISTRIBUTION A: Distribution approved for public release. Final Report: AFOSR YIP Grant FA9550-13-1-0128: Ultrafast Spectroscopy

Physical property data from the ICDP-USGS Eyreville cores A and B, Chesapeake Bay impact structure, Virginia, USA, acquired using a multisensor core logger

USGS Publications Warehouse

Pierce, H.A.; Murray, J.B.

2009-01-01

The International Continental Scientific Drilling Program (ICDP) and the U.S. Geological Survey (USGS) drilled three core holes to a composite depth of 1766 m within the moat of the Chesapeake Bay impact structure. Core recovery rates from the drilling were high (??90%), but problems with core hole collapse limited the geophysical downhole logging to natural-gamma and temperature logs. To supplement the downhole logs, ??5% of the Chesapeake Bay impact structure cores was processed through the USGS GeoTek multisensor core logger (MSCL) located in Menlo Park, California. The measured physical properties included core thickness (cm), density (g cm-3), P-wave velocity (m s-1), P-wave amplitude (%), magnetic susceptibility (cgs), and resistivity (ohm-m). Fractional porosity was a secondary calculated property. The MSCL data-sampling interval for all core sections was 1 cm longitudinally. Photos of each MSCL sampled core section were imbedded with the physical property data for direct comparison. These data have been used in seismic, geologic, thermal history, magnetic, and gravity models of the Chesapeake Bay impact structure. Each physical property curve has a unique signature when viewed over the full depth of the Chesapeake Bay impact structure core holes. Variations in the measured properties reflect differences in pre-impact target-rock lithologies and spatial variations in impact-related deformation during late-stage crater collapse and ocean resurge. ?? 2009 The Geological Society of America.

Gamma-ray emission from black holes

NASA Technical Reports Server (NTRS)

Ling, James C.

1991-01-01

Strong continuum gamma-ray emission at about 1 MeV possibly correlated with a narrow annihilation line at 511 keV has been observed from both Cygnus X-1 and the Galactic center. Such correlated emission has been interpreted as a unique gamma-ray signature for theoretically predicted relativistic, positron-electron pair-dominated plasma in regions surrounding the black holes. In this paper, the Cygnus X-1 results, which have provided important new insights about the source, are reviewed. Cygnus X-1 may be considered a canonical reference stellar black hole whose spectral and temporal characteristics can be used for comparison with those of other black-hole candidates including the Galactic center and AGN.

Giant ultrafast Kerr effect in superconductors

NASA Astrophysics Data System (ADS)

Robson, Charles W.; Fraser, Kieran A.; Biancalana, Fabio

2017-06-01

We study the ultrafast Kerr effect and high-harmonic generation in superconductors by formulating a model for a time-varying electromagnetic pulse normally incident on a thin-film superconductor. It is found that superconductors exhibit exceptionally large χ(3 ) due to the progressive destruction of Cooper pairs, and display high-harmonic generation at low incident intensities, and the highest nonlinear susceptibility of all known materials in the THz regime. Our theory opens up avenues for accessible analytical and numerical studies of the ultrafast dynamics of superconductors.

Ultrafast MR imaging of the pelvic floor.

PubMed

Unterweger, M; Marincek, B; Gottstein-Aalame, N; Debatin, J F; Seifert, B; Ochsenbein-Imhof, N; Perucchini, D; Kubik-Huch, R A

2001-04-01

The aim of this study was to compare pelvic floor anatomy and laxity at rest and on straining (Valsalva's maneuver) using dynamic ultrafast MR imaging in women who were continent versus those with stress incontinence differing in obstetric history. Thirty continent women were divided into three equal groups (nulliparous, previous cesarean delivery, previous vaginal delivery) and compared with 10 women with stress-incontinence with a history of at least one vaginal delivery. MR imaging of the pelvic floor at rest and on maximal strain was performed, using axial T2-weighted fast spin-echo images followed by sagittal ultrafast T2-weighted single-shot fast spin-echo sequences. Mean population age (age range, 22-45 years; mean +/- SD, 36 +/- 5.4 years), was similar in the four groups, as was parity in the three parous groups. Mean distances between the bladder floor and pubococcygeal line at rest did not differ between the four groups. On straining, bladder floor descent was 1.1 +/- 0.9, 1.0 +/- 1.1, and 1.9 +/- 0.9 cm in continent nulliparous, cesarean delivery, and vaginal delivery women, respectively, versus 3.2 +/- 1.0 cm in incontinent women (p = 0.0005). Cervical descent was greater in incontinent versus nulliparous women (p = 0.0019). Bladder floor descent was greater in the continent vaginal delivery group than in continent cesarean delivery control patients (p = 0.04). In patients with stress incontinence, symptoms did not correlate with amplitude of descent. The right levator muscle was thinner overall than the left, regardless of frequency direction (p = 0.001). Ultrafast MR imaging using the T2-weighted single-shot fast spin-echo sequence allows dynamic evaluation of the pelvic compartments at maximal strain with no need for contrast medium. Pelvic floor laxity and supporting fascia abnormalities were most common in patients with stress incontinence followed by continent women with a history of vaginal delivery. The results are therefore compatible with the

Direct Observation of Accretion onto a Hypernova's Newly Formed Black Hole

NASA Astrophysics Data System (ADS)

Milisavljevic, Dan

2017-09-01

Models of energetic core-collapse supernovae and long-duration gamma-ray bursts often invoke engine-driven scenarios associated with the formation of compact objects that input energy into the explosion. To date, only indirect evidence of black holes or magnetars formed in these events exists from observations obtained when the explosions are most luminous. Here we request a modest 15 ks Chandra pilot observation of the exceptionally important nearby hypernova SN2002ap to test models that predict X-ray emission associated with its remnant black hole to be detectable after 15 yr of ejecta expansion. Direct observation a newly formed "baby" black hole would be a landmark discovery capable of opening up new ways to investigate fundamental aspects of the core collapse process.

Ultrafast-based projection-reconstruction three-dimensional nuclear magnetic resonance spectroscopy.

PubMed

Mishkovsky, Mor; Kupce, Eriks; Frydman, Lucio

2007-07-21

Recent years have witnessed increased efforts toward the accelerated acquisition of multidimensional nuclear magnetic resonance (nD NMR) spectra. Among the methods proposed to speed up these NMR experiments is "projection reconstruction," a scheme based on the acquisition of a reduced number of two-dimensional (2D) NMR data sets constituting cross sections of the nD time domain being sought. Another proposition involves "ultrafast" spectroscopy, capable of completing nD NMR acquisitions within a single scan. Potential limitations of these approaches include the need for a relatively slow 2D-type serial data collection procedure in the former case, and a need for at least n high-performance, linearly independent gradients and a sufficiently high sensitivity in the latter. The present study introduces a new scheme that comes to address these limitations, by combining the basic features of the projection reconstruction and the ultrafast approaches into a single, unified nD NMR experiment. In the resulting method each member within the series of 2D cross sections required by projection reconstruction to deliver the nD NMR spectrum being sought, is acquired within a single scan with the aid of the 2D ultrafast protocol. Full nD NMR spectra can thus become available by backprojecting a small number of 2D sets, collected using a minimum number of scans. Principles, opportunities, and limitations of the resulting approach, together with demonstrations of its practical advantages, are here discussed and illustrated with a series of three-dimensional homo- and heteronuclear NMR correlation experiments.

Tephra layers in the Siple Dome and Taylor Dome ice cores, Antarctica: Sources and correlations

NASA Astrophysics Data System (ADS)

Dunbar, Nelia W.; Zielinski, Gregory A.; Voisins, Daniel T.

2003-08-01

Volcanic ash, or tephra layers, are found in the Taylor Dome, Siple Dome A, and Siple Dome B ice cores. Significant shard concentrations are found at a number of depths in all three cores. Electron and ion microprobe analyses indicate that the geochemical composition of most layers is basaltic, basanitic, or trachytic, and the geochemical signatures of the layers suggest derivation from the Pleiades volcanic center, Mt. Melbourne volcano, or small mafic centers, probably in the Royal Society Range area. Presence of tephra layers suggests an episode of previously unrecognized Antarctic volcanic activity between 1776 and 1805 A.D., from at least two volcanic centers. A strong geochemical correlation (D = 3.49 and 3.97 with a value of 4 considered identical) is observed between tephra layers at depth of 79.2 m in the Taylor Dome ice core, and layers between 97.2 and 97.7 m depth in the Siple B core. This correlation, and the highly accurate depth-age scale of the Siple B core suggest that the age of this horizon in the Taylor Dome ice core presented by [1998a, 2000] should be revised downward, to the younger age of 675 ± 25 years before 1995. This revised chronology is consistent with vertical strain measurements presented by [2003].

Diagnostic Performance of Ultrafast Brain MRI for Evaluation of Abusive Head Trauma.

PubMed

Kralik, S F; Yasrebi, M; Supakul, N; Lin, C; Netter, L G; Hicks, R A; Hibbard, R A; Ackerman, L L; Harris, M L; Ho, C Y

2017-04-01

MR imaging with sedation is commonly used to detect intracranial traumatic pathology in the pediatric population. Our purpose was to compare nonsedated ultrafast MR imaging, noncontrast head CT, and standard MR imaging for the detection of intracranial trauma in patients with potential abusive head trauma. A prospective study was performed in 24 pediatric patients who were evaluated for potential abusive head trauma. All patients received noncontrast head CT, ultrafast brain MR imaging without sedation, and standard MR imaging with general anesthesia or an immobilizer, sequentially. Two pediatric neuroradiologists independently reviewed each technique blinded to other modalities for intracranial trauma. We performed interreader agreement and consensus interpretation for standard MR imaging as the criterion standard. Diagnostic accuracy was calculated for ultrafast MR imaging, noncontrast head CT, and combined ultrafast MR imaging and noncontrast head CT. Interreader agreement was moderate for ultrafast MR imaging (κ = 0.42), substantial for noncontrast head CT (κ = 0.63), and nearly perfect for standard MR imaging (κ = 0.86). Forty-two percent of patients had discrepancies between ultrafast MR imaging and standard MR imaging, which included detection of subarachnoid hemorrhage and subdural hemorrhage. Sensitivity, specificity, and positive and negative predictive values were obtained for any traumatic pathology for each examination: ultrafast MR imaging (50%, 100%, 100%, 31%), noncontrast head CT (25%, 100%, 100%, 21%), and a combination of ultrafast MR imaging and noncontrast head CT (60%, 100%, 100%, 33%). Ultrafast MR imaging was more sensitive than noncontrast head CT for the detection of intraparenchymal hemorrhage ( P = .03), and the combination of ultrafast MR imaging and noncontrast head CT was more sensitive than noncontrast head CT alone for intracranial trauma ( P = .02). In abusive head trauma, ultrafast MR imaging, even combined with noncontrast

Ultra-fast magnetic vortex core reversal by a local field pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rückriem, R.; Albrecht, M., E-mail: manfred.albrecht@physik.uni-augsburg.de; Schrefl, T.

2014-02-03

Magnetic vortex core reversal of a 20-nm-thick permalloy disk with a diameter of 100 nm was studied by micromagnetic simulations. By applying a global out-of-plane magnetic field pulse, it turned out that the final core polarity is very sensitive to pulse width and amplitude, which makes it hard to control. The reason for this phenomenon is the excitation of radial spin waves, which dominate the reversal process. The excitation of spin waves can be strongly suppressed by applying a local field pulse within a small area at the core center. With this approach, ultra-short reversal times of about 15 ps weremore » achieved, which are ten times faster compared to a global pulse.« less

Unraveling shock-induced chemistry using ultrafast lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, David Steven

The exquisite time synchronicity between shock and diagnostics needed to unravel chemical events occurring in picoseconds has been achieved using a shaped ultrafast laser pulse to both drive the shocks and interrogate the sample via a multiplicity of optical diagnostics. The shaped laser drive pulse can produce well-controlled shock states of sub-ns duration with sub-10 ps risetimes, sufficient for investigation offast reactions or phase transformations in a thin layer with picosecond time resolution. The shock state is characterized using ultrafast dynamic ellipsometry (UDE) in either planar or Gaussian spatial geometries, the latter allowing measurements of the equation of state ofmore » materials at a range of stresses in a single laser pulse. Time-resolved processes in materials are being interrogated using UDE, ultrafast infrared absorption, ultrafast UV/visible absorption, and femtosecond stimulated Raman spectroscopy. Using these tools we showed that chemistry in an energetic thin film starts only after an induction time of a few tens of ps, an observation that allows differentiation between proposed shock-induced reaction mechanisms. These tools are presently being applied to a variety of energetic and reactive sample systems, from nitromethane and carbon disulfide, to microengineered interfaces in tunable energetic mixtures. Recent results will be presented, and future trends outlined.« less

Core localization and {sigma}* delocalization in the O 1s core-excited sulfur dioxide molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindgren, Andreas; Kivimaeki, Antti; Sorensen, Stacey L.

Electron-ion-ion coincidence measurements of sulfur dioxide at discrete resonances near the O 1s ionization edge are reported. The spectra are analyzed using a model based upon molecular symmetry and on the geometry of the molecule. We find clear evidence for molecular alignment that can be ascribed to symmetry properties of the ground and core-excited states. Configuration interaction (CI) calculations indicate geometry changes in accord with the measured spectra. For the SO{sub 2} molecule, however, we find that the localized core hole does not produce measurable evidence for valence localization, since the transition dipole moment is not parallel to a breakingmore » {sigma}* O-S bond, in contrast to the case of ozone. The dissociation behavior based upon the CI calculations using symmetry-broken orbitals while fixing a localized core-hole site is found to be nearly equivalent to that using symmetry-adapted orbitals. This implies that the core-localization effect is not strong enough to localize the {sigma}* valence orbital.« less

Establishing a relation between the mass and the spin of stellar-mass black holes.

PubMed

Banerjee, Indrani; Mukhopadhyay, Banibrata

2013-08-09

Stellar mass black holes (SMBHs), forming by the core collapse of very massive, rapidly rotating stars, are expected to exhibit a high density accretion disk around them developed from the spinning mantle of the collapsing star. A wide class of such disks, due to their high density and temperature, are effective emitters of neutrinos and hence called neutrino cooled disks. Tracking the physics relating the observed (neutrino) luminosity to the mass, spin of black holes (BHs) and the accretion rate (M) of such disks, here we establish a correlation between the spin and mass of SMBHs at their formation stage. Our work shows that spinning BHs are more massive than nonspinning BHs for a given M. However, slowly spinning BHs can turn out to be more massive than spinning BHs if M at their formation stage was higher compared to faster spinning BHs.

1.4 GHz on the Fundamental Plane of black hole activity

NASA Astrophysics Data System (ADS)

Saikia, Payaswini; Körding, Elmar; Dibi, Salome

2018-06-01

The Fundamental Plane (FP) of black hole activity is an empirical relationship between the O III/X-ray luminosity depicting the accretion power, the radio luminosity as a probe of the instantaneous jet power and the mass of the black hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the optical FP, to investigate whether or not Faint Images of the Radio Sky at Twenty-Centimetres (FIRST) fluxes can trace nuclear activity. We use an SDSS-FIRST cross-correlated sample of 10 149 active galaxies and analyse their positioning on the optical FP. We focus on various reasons that can cause the discrepancy between the observed FIRST radio fluxes and the theoretically expected core radio fluxes, and show that FIRST fluxes are heavily contaminated by non-nuclear, extended components and other environmental factors. We show that the subsample of `compact sources', which should have negligible lobe contribution, statistically follow the FP when corrected for relativistic beaming, while all the other sources lie above the plane. The sample of low-ionization nuclear emission-line regions (LINERs), which should have negligible lobe and beaming contribution, also follow the FP. A combined fit of the low-luminosity AGN and the X-ray binaries, with the LINERs, results in the relation log LR = 0.77 log L_{O III} + 0.69 log M. Assuming that the original FP relation is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure `core' jet and instantaneous nuclear activity in the AGN, and one needs to be careful while using it on the FP of black hole activity.

Ultrafast image-based dynamic light scattering for nanoparticle sizing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Wu; Zhang, Jie; Liu, Lili

An ultrafast sizing method for nanoparticles is proposed, called as UIDLS (Ultrafast Image-based Dynamic Light Scattering). This method makes use of the intensity fluctuation of scattered light from nanoparticles in Brownian motion, which is similar to the conventional DLS method. The difference in the experimental system is that the scattered light by nanoparticles is received by an image sensor instead of a photomultiplier tube. A novel data processing algorithm is proposed to directly get correlation coefficient between two images at a certain time interval (from microseconds to milliseconds) by employing a two-dimensional image correlation algorithm. This coefficient has been provedmore » to be a monotonic function of the particle diameter. Samples of standard latex particles (79/100/352/482/948 nm) were measured for validation of the proposed method. The measurement accuracy of higher than 90% was found with standard deviations less than 3%. A sample of nanosilver particle with nominal size of 20 ± 2 nm and a sample of polymethyl methacrylate emulsion with unknown size were also tested using UIDLS method. The measured results were 23.2 ± 3.0 nm and 246.1 ± 6.3 nm, respectively, which is substantially consistent with the transmission electron microscope results. Since the time for acquisition of two successive images has been reduced to less than 1 ms and the data processing time in about 10 ms, the total measuring time can be dramatically reduced from hundreds seconds to tens of milliseconds, which provides the potential for real-time and in situ nanoparticle sizing.« less

IODP Expedition 335: Deep Sampling in ODP Hole 1256D

NASA Astrophysics Data System (ADS)

Teagle, D. A. H.; Ildefonse, B.; Blum, P.; IODP Expedition 335 Scientists, the

2012-04-01

Observations of the gabbroic layers of untectonized ocean crust are essential to test theoretical models of the accretion of new crust at mid-ocean ridges. Integrated Ocean Drilling Program (IODP) Expedition 335 ("Superfast Spreading Rate Crust 4") returned to Ocean Drilling Program (ODP) Hole 1256D with the intention of deepening this reference penetration of intact ocean crust a significant distance (~350 m) into cumulate gabbros. Three earlier cruises to Hole 1256D (ODP 206, IODP 309/312) have drilled through the sediments, lavas, and dikes and 100 m into a complex dike-gabbro transition zone. Operations on IODP Expedition 335 proved challenging throughout, with almost three weeks spent re-opening and securing unstable sections of the hole. When coring commenced, the comprehensive destruction of the coring bit required further remedial operations to remove junk and huge volumes of accumulated drill cuttings. Hole-cleaning operations using junk baskets were successful, and they recovered large irregular samples that document a hitherto unseen sequence of evolving geological conditions and the intimate coupling between temporally and spatially intercalated intrusive, hydrothermal, contact-metamorphic, partial melting, and retrogressive processes. Hole 1256D is now clean of junk, and it has been thoroughly cleared of the drill cuttings that hampered operations during this and previous expeditions. At the end of Expedition 335, we briefly resumed coring before undertaking cementing operations to secure problematic intervals. To ensure the greatest scientific return from the huge efforts to stabilize this primary ocean lithosphere reference site, it would be prudent to resume the deepening of Hole 1256D in the nearest possible future while it is open to full depth. doi:10.2204/iodp.sd.13.04.2011

Ultrafast Ultrasound Imaging With Cascaded Dual-Polarity Waves.

PubMed

Zhang, Yang; Guo, Yuexin; Lee, Wei-Ning

2018-04-01

Ultrafast ultrasound imaging using plane or diverging waves, instead of focused beams, has advanced greatly the development of novel ultrasound imaging methods for evaluating tissue functions beyond anatomical information. However, the sonographic signal-to-noise ratio (SNR) of ultrafast imaging remains limited due to the lack of transmission focusing, and thus insufficient acoustic energy delivery. We hereby propose a new ultrafast ultrasound imaging methodology with cascaded dual-polarity waves (CDWs), which consists of a pulse train with positive and negative polarities. A new coding scheme and a corresponding linear decoding process were thereby designed to obtain the recovered signals with increased amplitude, thus increasing the SNR without sacrificing the frame rate. The newly designed CDW ultrafast ultrasound imaging technique achieved higher quality B-mode images than coherent plane-wave compounding (CPWC) and multiplane wave (MW) imaging in a calibration phantom, ex vivo pork belly, and in vivo human back muscle. CDW imaging shows a significant improvement in the SNR (10.71 dB versus CPWC and 7.62 dB versus MW), penetration depth (36.94% versus CPWC and 35.14% versus MW), and contrast ratio in deep regions (5.97 dB versus CPWC and 5.05 dB versus MW) without compromising other image quality metrics, such as spatial resolution and frame rate. The enhanced image qualities and ultrafast frame rates offered by CDW imaging beget great potential for various novel imaging applications.

Ultrafast Manipulation of Magnetic Order with Electrical Pulses

NASA Astrophysics Data System (ADS)

Yang, Yang

During the last 30 years spintronics has been a very rapidly expanding field leading to lots of new interesting physics and applications. As with most technology-oriented fields, spintronics strives to control devices with very low energy consumption and high speed. The combination of spin and electronics inherent to spintronics directly tackles energy efficiency, due to the non-volatility of magnetism. However, speed of operation of spintronic devices is still rather limited ( nanoseconds), due to slow magnetization precessional frequencies. Ultrafast magnetism (or opto-magnetism) is a relatively new field that has been very active in the last 20 years. The main idea is that intense femtosecond laser pulses can be used in order to manipulate the magnetization at very fast time-scales ( 100 femtoseconds). However, the use of femtosecond lasers poses great application challenges such as diffraction limited optical spot sizes which hinders device density, and bulky and expensive integration of femtosecond lasers into devices. In this thesis, our efforts to combine ultrafast magnetism and spintronics are presented. First, we show that the magnetization of ferrimagnetic GdFeCo films can be switched by picosecond electronic heat current pulses. This result shows that a non-thermal distribution of electrons directly excited by laser is not necessary for inducing ultrafast magnetic dynamics. Then, we fabricate photoconductive switch devices on a LT-GaAs substrate, to generate picosecond electrical pulses. Intense electrical pulses with 10ps (FWHM) duration and peak current up to 3A can be generated and delivered into magnetic films. Distinct magnetic dynamics in CoPt films are found between direct optical heating and electrical heating. More importantly, by delivering picosecond electrical pulses into GdFeCo films, we are able to deterministically reverse the magnetization of GdFeCo within 10ps. This is more than one order of magnitude faster than any other electrically

Behemoth Black Hole Found in an Unlikely Place

NASA Image and Video Library

2016-04-06

This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole’s event horizon, where no light can escape the massive object’s gravitational grip. The black hole’s powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as the stars skim by the black hole. Credits: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI) More info: Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe. The observations, made by NASA’s Hubble Space Telescope and the Gemini Telescope in Hawaii, may indicate that these monster objects may be more common than once thought. Until now, the biggest supermassive black holes – those roughly 10 billion times the mass of our sun – have been found at the cores of very large galaxies in regions of the universe packed with other large galaxies. In fact, the current record holder tips the scale at 21 billion suns and resides in the crowded Coma galaxy cluster that consists of over 1,000 galaxies.

Static holes in the geometrically frustrated bow-tie ladder

NASA Astrophysics Data System (ADS)

Martins, George B.; Brenig, Wolfram

2008-10-01

We investigate the doping of a geometrically frustrated spin ladder with static holes by a complementary approach using exact diagonalization and quantum dimers. Results for thermodynamic properties, the singlet density of states, the hole-binding energy and the spin correlations will be presented. For the undoped systems the ground state is non-degenerate, with translationally invariant nearest-neighbor spin correlations. For the doped case, we find that static holes polarize their vicinity through a localization of singlets, reducing the frustration. This polarization induces short range repulsive forces between two holes and an oscillatory behavior of the long range two-hole energy. For most quantities investigated, we find very good agreement between the quantum dimer approach and the results from exact diagonalization.

Geometrothermodynamics of Van der Waals black hole

NASA Astrophysics Data System (ADS)

Hu, Yumin; Chen, Juhua; Wang, Yongjiu

2017-12-01

We study the geometrothermodynamics of a special asymptotically AdS black hole, i.e. Van der Waals ( VdW) black hole, in the extended phase space where the negative cosmological constant Λ can be regarded as thermodynamic pressure. Analysing some special conditions of this black hole with geometrothermodynamical method, we find a good correlation with ordinary cases according to the state equation.

Modelling ultrafast laser ablation

NASA Astrophysics Data System (ADS)

Rethfeld, Baerbel; Ivanov, Dmitriy S.; E Garcia, Martin; Anisimov, Sergei I.

2017-05-01

This review is devoted to the study of ultrafast laser ablation of solids and liquids. The ablation of condensed matter under exposure to subpicosecond laser pulses has a number of peculiar properties which distinguish this process from ablation induced by nanosecond and longer laser pulses. The process of ultrafast ablation includes light absorption by electrons in the skin layer, energy transfer from the skin layer to target interior by nonlinear electronic heat conduction, relaxation of the electron and ion temperatures, ultrafast melting, hydrodynamic expansion of heated matter accompanied by the formation of metastable states and subsequent formation of breaks in condensed matter. In case of ultrashort laser excitation, these processes are temporally separated and can thus be studied separately. As for energy absorption, we consider peculiarities of the case of metal irradiation in contrast to dielectrics and semiconductors. We discuss the energy dissipation processes of electronic thermal wave and lattice heating. Different types of phase transitions after ultrashort laser pulse irradiation as melting, vaporization or transitions to warm dense matter are discussed. Also nonthermal phase transitions, directly caused by the electronic excitation before considerable lattice heating, are considered. The final material removal occurs from the physical point of view as expansion of heated matter; here we discuss approaches of hydrodynamics, as well as molecular dynamic simulations directly following the atomic movements. Hybrid approaches tracing the dynamics of excited electrons, energy dissipation and structural dynamics in a combined simulation are reviewed as well.

Observational evidence for black holes

NASA Astrophysics Data System (ADS)

Hutchings, J. B.

1985-02-01

Observational data supporting the existence of black holes are presented graphically and characterized in a general review. Object classes discussed include quasars as galaxy cores, X-ray-emitting binaries (Cyg X-1, LMC X-3, and the apparent miniature quasar SS 433), radio galaxies and quasars with twin jets, and interacting galaxies. This evidence is found to strongly suggest that quasars are accreting black holes of mass about 10 to the 8th solar mass, that they formed more easily in earlier stages of the universe (corresponding to redshifts around 2), and that they are analogous in many ways to the stellar-mass object SS 433.

Ultrafast Outflows: Galaxy-scale Active Galactic Nucleus Feedback

NASA Astrophysics Data System (ADS)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V.

2013-01-01

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.

ULTRAFAST OUTFLOWS: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V., E-mail: ayw@ccs.tsukuba.ac.jp

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves inmore » the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.« less

Ultrafast exciton relaxation in monolayer transition metal dichalcogenides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thilagam, A., E-mail: thilaphys@gmail.com

2016-04-28

We examine a mechanism by which excitons undergo ultrafast relaxation in common monolayer transition metal dichalcogenides. It is shown that at densities ≈1 × 10{sup 11 }cm{sup −2} and temperatures ≤60 K, excitons in well known monolayers (MoS{sub 2}, MoSe{sub 2}, WS{sub 2}, and WSe{sub 2}) exist as point-like structureless electron-hole quasi-particles. We evaluate the average rate of exciton energy relaxation due to acoustic phonons via the deformation potential and the piezoelectric coupling mechanisms and examine the effect of spreading of the excitonic wavefunction into the region perpendicular to the monolayer plane. Our results show that the exciton relaxation rate is enhanced with increasemore » in the exciton temperature, while it is decreased with increase in the lattice temperature. Good agreements with available experimental data are obtained when the calculations are extrapolated to room temperatures. A unified approach taking into account the deformation potential and piezoelectric coupling mechanisms shows that exciton relaxation induced by phonons is as significant as defect assisted scattering and trapping of excitons by surface states in monolayer transition metal dichalcogenides.« less

Single- and double-core-hole ion emission spectroscopy of transient neon plasmas produced by ultraintense x-ray laser pulses

NASA Astrophysics Data System (ADS)

Gao, Cheng; Zeng, Jiaolong; Yuan, Jianmin

2016-02-01

Single-core-hole (SCH) and double-core-hole (DCH) spectroscopy is investigated systematically for neon gas in the interaction with ultraintense x-ray pulses with photon energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in detailed level accounting approximation, is utilized to study the dynamical evolution of the level population and emission properties of the laser-produced highly transient plasmas. The plasma-density effects on level populations and charge-state distribution are demonstrated with an x-ray photon energy of 2000 eV. It is shown that atomic number density of relevant experiment is about 1 × 1018 cm-3, which is comparable to a recent experiment. At this density, we systematically investigate the emissivity of the transient neon plasmas. For laser photon energy in the range 937-1360 eV, resonant absorptions (RA) of 1s\\to {np} (n≥slant 2) transitions play important roles in time evolution of the population and DCH emission spectroscopy. The RA effects are illustrated in detail for an x-ray pulse of 944 eV photon energy, which creates the 1s\\to 2p RA from the SCH states (1s2{s}22{p}4, 1s2s2p5, and 1s2p6) of Ne3+. After averaging over the space and time distribution of x-ray pulse, DCH emission spectroscopy is studied at x-ray photon energies of 937, 944, 955, 968, 980, and 990 eV, where there exist 1s\\to 2p resonances from SCH states of Ne2+-Ne7+. The processes with producing DCH states are discussed. For x-ray photon energy larger than 1360 eV, no RA exist and transient plasmas show different features in the DCH spectroscopy.

Dynamics-based selective 2D 1H/1H chemical shift correlation spectroscopy under ultrafast MAS conditions

NASA Astrophysics Data System (ADS)

Zhang, Rongchun; Ramamoorthy, Ayyalusamy

2015-05-01

Dynamics plays important roles in determining the physical, chemical, and functional properties of a variety of chemical and biological materials. However, a material (such as a polymer) generally has mobile and rigid regions in order to have high strength and toughness at the same time. Therefore, it is difficult to measure the role of mobile phase without being affected by the rigid components. Herein, we propose a highly sensitive solid-state NMR approach that utilizes a dipolar-coupling based filter (composed of 12 equally spaced 90° RF pulses) to selectively measure the correlation of 1H chemical shifts from the mobile regions of a material. It is interesting to find that the rotor-synchronized dipolar filter strength decreases with increasing inter-pulse delay between the 90° pulses, whereas the dipolar filter strength increases with increasing inter-pulse delay under static conditions. In this study, we also demonstrate the unique advantages of proton-detection under ultrafast magic-angle-spinning conditions to enhance the spectral resolution and sensitivity for studies on small molecules as well as multi-phase polymers. Our results further demonstrate the use of finite-pulse radio-frequency driven recoupling pulse sequence to efficiently recouple weak proton-proton dipolar couplings in the dynamic regions of a molecule and to facilitate the fast acquisition of 1H/1H correlation spectrum compared to the traditional 2D NOESY (Nuclear Overhauser effect spectroscopy) experiment. We believe that the proposed approach is beneficial to study mobile components in multi-phase systems, such as block copolymers, polymer blends, nanocomposites, heterogeneous amyloid mixture of oligomers and fibers, and other materials.

Linear and ultrafast nonlinear plasmonics of single nano-objects

NASA Astrophysics Data System (ADS)

Crut, Aurélien; Maioli, Paolo; Vallée, Fabrice; Del Fatti, Natalia

2017-03-01

Single-particle optical investigations have greatly improved our understanding of the fundamental properties of nano-objects, avoiding the spurious inhomogeneous effects that affect ensemble experiments. Correlation with high-resolution imaging techniques providing morphological information (e.g. electron microscopy) allows a quantitative interpretation of the optical measurements by means of analytical models and numerical simulations. In this topical review, we first briefly recall the principles underlying some of the most commonly used single-particle optical techniques: near-field, dark-field, spatial modulation and photothermal microscopies/spectroscopies. We then focus on the quantitative investigation of the surface plasmon resonance (SPR) of metallic nano-objects using linear and ultrafast optical techniques. While measured SPR positions and spectral areas are found in good agreement with predictions based on Maxwell’s equations, SPR widths are strongly influenced by quantum confinement (or, from a classical standpoint, surface-induced electron scattering) and, for small nano-objects, cannot be reproduced using the dielectric functions of bulk materials. Linear measurements on single nano-objects (silver nanospheres and gold nanorods) allow a quantification of the size and geometry dependences of these effects in confined metals. Addressing the ultrafast response of an individual nano-object is also a powerful tool to elucidate the physical mechanisms at the origin of their optical nonlinearities, and their electronic, vibrational and thermal relaxation processes. Experimental investigations of the dynamical response of gold nanorods are shown to be quantitatively modeled in terms of modifications of the metal dielectric function enhanced by plasmonic effects. Ultrafast spectroscopy can also be exploited to unveil hidden physical properties of more complex nanosystems. In this context, two-color femtosecond pump-probe experiments performed on individual

The Merger-Free Growth of Galaxies and Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Simmons, Brooke; Smethurst, Rebecca; Lintott, Chris; Martin, Garreth; Kaviraj, Sugata; Devriendt, Julien; Galaxy Zoo Team

2018-01-01

There is now clear evidence that the merger-driven pathway to black hole and galaxy growth is only half the story. Merger-free evolution contributes roughly equally to the overall growth of black holes in the Universe and is also responsible for a significant amount of galaxy growth over cosmic time. A recent study examining the growth of black holes in unambiguously disk-dominated galaxies shows these black holes reach quasar-like luminosities and black hole masses typical of those hosted in bulge-dominated and elliptical galaxies with major mergers in their evolutionary histories. However, while there appears to be no correlation between the size of the black hole and upper limits on the host galaxy bulges, the fitted correlation between black hole mass and total galaxy stellar mass in these merger-free systems is fully consistent with the canonical relationship based on merger-driven systems. There is further evidence via comparison between observed populations and cosmological simulations confirming that bulgeless systems are generally consistent with having merger-free histories. If bulgeless and disk-dominated galaxies are indeed signatures of systems with no violent mergers in their formation histories, the same correlation between black hole and galaxy in these systems versus that seen in elliptical galaxy samples indicates the black hole-galaxy connection must originate with a process more fundamental than the dynamical configuration of a galaxy's stars.

Observation of Internal Photoinduced Electron and Hole Separation in Hybrid Two-Dimentional Perovskite Films.

PubMed

Liu, Junxue; Leng, Jing; Wu, Kaifeng; Zhang, Jun; Jin, Shengye

2017-02-01

Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA) 2 (MA) n-1 Pb n I 3n+1 (BA = CH 3 (CH 2 ) 3 NH 3 + , MA = CH 3 NH 3 + ) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as "n = 4", are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

THE ARDUOUS JOURNEY TO BLACK HOLE FORMATION IN POTENTIAL GAMMA-RAY BURST PROGENITORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dessart, Luc; O'Connor, Evan; Ott, Christian D., E-mail: Luc.Dessart@oamp.fr, E-mail: evanoc@tapir.caltech.edu, E-mail: cott@tapir.caltech.edu

2012-07-20

We present a quantitative study on the properties at death of fast-rotating massive stars evolved at low-metallicity-objects that are proposed as likely progenitors of long-duration {gamma}-ray bursts (LGRBs). We perform one-dimensional+rotation stellar-collapse simulations on the progenitor models of Woosley and Heger, and critically assess their potential for the formation of a black hole and a Keplerian disk (namely, a collapsar) or a proto-magnetar. We note that theoretical uncertainties in the treatment of magnetic fields and the approximate handling of rotation compromise the accuracy of stellar-evolution models. We find that only the fastest rotating progenitors achieve sufficient compactness for black holemore » formation while the bulk of models possess a core density structure typical of garden-variety core-collapse supernova (SN) progenitors evolved without rotation and at solar metallicity. Of the models that do have sufficient compactness for black hole formation, most of them also retain a large amount of angular momentum in the core, making them prone to a magneto-rotational explosion, therefore preferentially leaving behind a proto-magnetar. A large progenitor angular-momentum budget is often the sole criterion invoked in the community today to assess the suitability for producing a collapsar. This simplification ignores equally important considerations such as the core compactness, which conditions black hole formation, the core angular momentum, which may foster a magneto-rotational explosion preventing black hole formation, or the metallicity and the residual envelope mass which must be compatible with inferences from observed LGRB/SNe. Our study suggests that black hole formation is non-trivial, that there is room for accommodating both collapsars and proto-magnetars as LGRB progenitors, although proto-magnetars seem much more easily produced by current stellar-evolutionary models.« less

Interface engineered ferrite@ferroelectric core-shell nanostructures: A facile approach to impart superior magneto-electric coupling

NASA Astrophysics Data System (ADS)

Abraham, Ann Rose; Raneesh, B.; Das, Dipankar; Oluwafemi, Oluwatobi Samuel; Thomas, Sabu; Kalarikkal, Nandakumar

2018-04-01

The electric field control of magnetism in multiferroics is attractive for the realization of ultra-fast and miniaturized low power device applications like nonvolatile memories. Room temperature hybrid multiferroic heterostructures with core-shell (0-0) architecture (ferrite core and ferroelectric shell) were developed via a two-step method. High-Resolution Transmission Electron Microscopy (HRTEM) images confirm the core-shell structure. The temperature dependant magnetization measurements and Mossbauer spectra reveal superparamagnetic nature of the core-shell sample. The ferroelectric hysteresis loops reveal leaky nature of the samples. The results indicate the promising applications of the samples for magneto-electric memories and spintronics.

Phonon-induced ultrafast band gap control in LaTiO3

NASA Astrophysics Data System (ADS)

Gu, Mingqiang; Rondinelli, James M.

We propose a route for ultrafast band gap engineering in correlated transition metal oxides by using optically driven phonons. We show that the ∖Gamma-point electron band energies can be deterministically tuned in the nonequilibrium state. Taking the Mott insulator LaTiO3 as an example, we show that such phonon-assisted processes dynamically induce an indirect-to-direct band gap transition or even a metal-to-insulator transition, depending on the electron correlation strength. We explain the origin of the dynamical band structure control and also establish its generality by examining related oxides. Lastly, we describe experimental routes to realize the band structure control with impulsive stimulated Raman scattering.

Unification of X-ray Winds in Seyfert Galaxies: From Ultra-fast Outflows to Warm Absorbers

NASA Technical Reports Server (NTRS)

Tombesi, F.; Cappi, M.; Reeves, J. N.; Nemmen, R. S.; Braito, V.; Gaspari, M.; Reynolds, C. S.

2013-01-01

The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is >60 per cent, consistent with previous studies. The fraction of sources with UFOs is >34 per cent, >67 per cent of which also show WAs. The large dynamic range obtained when considering all the absorbers together, spanning several orders of magnitude in ionization, column, velocity and distance allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. In all the cases, the absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. These evidence strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The UFOs are likely launched from the inner accretion disc and the WAs at larger distances, such as the outer disc and/or torus. We argue that the observed parameters and correlations are, to date, consistent with both radiation pressure through Compton scattering and magnetohydrodynamic processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, show

Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers

NASA Astrophysics Data System (ADS)

Tombesi, F.; Cappi, M.; Reeves, J. N.; Nemmen, R. S.; Braito, V.; Gaspari, M.; Reynolds, C. S.

2013-04-01

The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is >60 per cent, consistent with previous studies. The fraction of sources with UFOs is >34 per cent, >67 per cent of which also show WAs. The large dynamic range obtained when considering all the absorbers together, spanning several orders of magnitude in ionization, column, velocity and distance allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. In all the cases, the absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. These evidence strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The UFOs are likely launched from the inner accretion disc and the WAs at larger distances, such as the outer disc and/or torus. We argue that the observed parameters and correlations are, to date, consistent with both radiation pressure through Compton scattering and magnetohydrodynamic processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, show

Large-area tungsten disulfide for ultrafast photonics.

PubMed

Yan, Peiguang; Chen, Hao; Yin, Jinde; Xu, Zihan; Li, Jiarong; Jiang, Zike; Zhang, Wenfei; Wang, Jinzhang; Li, Irene Ling; Sun, Zhipei; Ruan, Shuangchen

2017-02-02

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted significant interest in various optoelectronic applications due to their excellent nonlinear optical properties. One of the most important applications of TMDs is to be employed as an extraordinary optical modulation material (e.g., the saturable absorber (SA)) in ultrafast photonics. The main challenge arises while embedding TMDs into fiber laser systems to generate ultrafast pulse trains and thus constraints their practical applications. Herein, few-layered WS 2 with a large-area was directly transferred on the facet of the pigtail and acted as a SA for erbium-doped fiber laser (EDFL) systems. In our study, WS 2 SA exhibited remarkable nonlinear optical properties (e.g., modulation depth of 15.1% and saturable intensity of 157.6 MW cm -2 ) and was used for ultrafast pulse generation. The soliton pulses with remarkable performances (e.g., ultrashort pulse duration of 1.49 ps, high stability of 71.8 dB, and large pulse average output power of 62.5 mW) could be obtained in a telecommunication band. To the best of our knowledge, the average output power of the mode-locked pulse trains is the highest by employing TMD materials in fiber laser systems. These results indicate that atomically large-area WS 2 could be used as excellent optical modulation materials in ultrafast photonics.

Gamma ray bursts of black hole universe

NASA Astrophysics Data System (ADS)

Zhang, T. X.

2015-07-01

Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

Feed-forward motor control of ultrafast, ballistic movements.

PubMed

Kagaya, K; Patek, S N

2016-02-01

To circumvent the limits of muscle, ultrafast movements achieve high power through the use of springs and latches. The time scale of these movements is too short for control through typical neuromuscular mechanisms, thus ultrafast movements are either invariant or controlled prior to movement. We tested whether mantis shrimp (Stomatopoda: Neogonodactylus bredini) vary their ultrafast smashing strikes and, if so, how this control is achieved prior to movement. We collected high-speed images of strike mechanics and electromyograms of the extensor and flexor muscles that control spring compression and latch release. During spring compression, lateral extensor and flexor units were co-activated. The strike initiated several milliseconds after the flexor units ceased, suggesting that flexor activity prevents spring release and determines the timing of strike initiation. We used linear mixed models and Akaike's information criterion to serially evaluate multiple hypotheses for control mechanisms. We found that variation in spring compression and strike angular velocity were statistically explained by spike activity of the extensor muscle. The results show that mantis shrimp can generate kinematically variable strikes and that their kinematics can be changed through adjustments to motor activity prior to the movement, thus supporting an upstream, central-nervous-system-based control of ultrafast movement. Based on these and other findings, we present a shishiodoshi model that illustrates alternative models of control in biological ballistic systems. The discovery of feed-forward control in mantis shrimp sets the stage for the assessment of targets, strategic variation in kinematics and the role of learning in ultrafast animals. © 2016. Published by The Company of Biologists Ltd.

Microscopic origin of black hole reentrant phase transitions

NASA Astrophysics Data System (ADS)

Zangeneh, M. Kord; Dehyadegari, A.; Sheykhi, A.; Mann, R. B.

2018-04-01

Understanding the microscopic behavior of the black hole ingredients has been one of the important challenges in black hole physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behavior of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from the large black holes phase to the small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near the large/small transition line differs for usual and reentrant phase transitions. Indeed, for the usual case, the dominant interaction is repulsive whereas for the reentrant case we encounter an attractive interaction. We show that in the reentrant phase transition case, the small black holes behave like a bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

Applications of ultrafast laser direct writing: from polarization control to data storage

NASA Astrophysics Data System (ADS)

Donko, A.; Gertus, T.; Brambilla, G.; Beresna, M.

2018-02-01

Ultrafast laser direct writing is a fascinating technology which emerged more than two decades from fundamental studies of material resistance to high-intensity optical fields. Its development saw the discovery of many puzzling phenomena and demonstration of useful applications. Today, ultrafast laser writing is seen as a technology with great potential and is rapidly entering the industrial environment. Whereas, less than 10 years ago, ultrafast lasers were still confined within the research labs. This talk will overview some of the unique features of ultrafast lasers and give examples of its applications in optical data storage, polarization control and optical fibers.

Structural and Lithologic Characterization of the SAFOD Pilot Hole and Phase One Main Hole

NASA Astrophysics Data System (ADS)

Barton, D. C.; Bradbury, K.; Solum, J. G.; Evans, J. P.

2005-12-01

Petrological and microstructural analyses of drill cuttings were conducted for the San Andreas Fault Observatory at Depth (SAFOD) Pilot Hole and Main Hole projects. Grain mounts were produced at ~30 m (100 ft) intervals from drill cuttings collected from the Pilot Hole to a depth of 2164 m (7100 ft) and from Phase 1 of the SAFOD main hole to a depth of 3067 m (10062 ft). . Thin-section grain mount analysis included identification of mineral composition, alteration, and deformation within individual grains, measured at .5 mm increments on an equally spaced, 300 point grid pattern. Lithologic features in the Quaternary/Tertiary deposits from 30 - 640 m (100-2100 ft) in the Pilot Hole, and 670 - 792 m (2200 - 2600 ft) in the Phase 1 main hole, include fine-grained, thinly bedded sediments with clasts of fine-grained volcanic groundmass. Preliminary grain mount analysis from 1920 - 3067 m (6300 - 10062) in the Phase 1 main hole, indicates a sedimentary sequence consisting of fine-grained lithic fragments of very fine-grained shale. Deformation mechanisms observed within the cuttings of granitic rocks from 914 - 1860 m (3000 - 6100 ft.) include intracrystalline plasticity and cataclasis. Intracrystalline plastic deformation within quartz and feldspar grains is indicated by undulatory extinction, ribbon grains, chessboard patterns, and deformation twins and lamellae. Cataclastic deformation is characterized by intra- and intergranular microfractures, angular grains, gouge zones, iron-oxide banding, and comminution. Mineral and cataclasite abundances were plotted as a function of weight percent vs. depth. Plots of quartz and feldspar abundances are also correlated with XRD weight percent data from 1160 - 1890 m (3800 - 6200 ft.) in the granitic and granodioritic sequences of the Phase 1 main hole. Regions of the both of the drill holes with cataclasite abundances ranging from 20 - 30 wt% are interpreted as shear zones. Shear zones identified in this study from 1150 - 1420

Ultrafast non-radiative dynamics of atomically thin MoSe 2

DOE PAGES

Lin, Ming -Fu; Kochat, Vidya; Krishnamoorthy, Aravind; ...

2017-10-17

Non-radiative energy dissipation in photoexcited materials and resulting atomic dynamics provide a promising pathway to induce structural phase transitions in two-dimensional materials. However, these dynamics have not been explored in detail thus far because of incomplete understanding of interaction between the electronic and atomic degrees of freedom, and a lack of direct experimental methods to quantify real-time atomic motion and lattice temperature. Here, we explore the ultrafast conversion of photoenergy to lattice vibrations in a model bi-layered semiconductor, molybdenum diselenide, MoSe 2. Specifically, we characterize sub-picosecond lattice dynamics initiated by the optical excitation of electronic charge carriers in the highmore » electron-hole plasma density regime. Our results focuses on the first ten picosecond dynamics subsequent to photoexcitation before the onset of heat transfer to the substrate, which occurs on a ~100 picosecond time scale. Photoinduced atomic motion is probed by measuring the time dependent Bragg diffraction of a delayed mega-electronvolt femtosecond electron beam. Transient lattice temperatures are characterized through measurement of Bragg peak intensities and calculation of the Debye-Waller factor (DWF). These measurements show a sub-picosecond decay of Bragg diffraction and a correspondingly rapid rise in lattice temperatures. We estimate a high quantum yield for the conversion of excited charge carrier energy to lattice motion under our experimental conditions, indicative of a strong electron-phonon interaction. First principles nonadiabatic quantum molecular dynamics simulations (NAQMD) on electronically excited MoSe 2 bilayers reproduce the observed picosecond-scale increase in lattice temperature and ultrafast conversion of photoenergy to lattice vibrations. Calculation of excited-state phonon dispersion curves suggests that softened vibrational modes in the excited state are involved in efficient and rapid energy

Ultrafast non-radiative dynamics of atomically thin MoSe 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Ming -Fu; Kochat, Vidya; Krishnamoorthy, Aravind

Non-radiative energy dissipation in photoexcited materials and resulting atomic dynamics provide a promising pathway to induce structural phase transitions in two-dimensional materials. However, these dynamics have not been explored in detail thus far because of incomplete understanding of interaction between the electronic and atomic degrees of freedom, and a lack of direct experimental methods to quantify real-time atomic motion and lattice temperature. Here, we explore the ultrafast conversion of photoenergy to lattice vibrations in a model bi-layered semiconductor, molybdenum diselenide, MoSe 2. Specifically, we characterize sub-picosecond lattice dynamics initiated by the optical excitation of electronic charge carriers in the highmore » electron-hole plasma density regime. Our results focuses on the first ten picosecond dynamics subsequent to photoexcitation before the onset of heat transfer to the substrate, which occurs on a ~100 picosecond time scale. Photoinduced atomic motion is probed by measuring the time dependent Bragg diffraction of a delayed mega-electronvolt femtosecond electron beam. Transient lattice temperatures are characterized through measurement of Bragg peak intensities and calculation of the Debye-Waller factor (DWF). These measurements show a sub-picosecond decay of Bragg diffraction and a correspondingly rapid rise in lattice temperatures. We estimate a high quantum yield for the conversion of excited charge carrier energy to lattice motion under our experimental conditions, indicative of a strong electron-phonon interaction. First principles nonadiabatic quantum molecular dynamics simulations (NAQMD) on electronically excited MoSe 2 bilayers reproduce the observed picosecond-scale increase in lattice temperature and ultrafast conversion of photoenergy to lattice vibrations. Calculation of excited-state phonon dispersion curves suggests that softened vibrational modes in the excited state are involved in efficient and rapid energy

Gold-Based Nanostructures for Ultrafast Dynamic Nanothermometer

NASA Astrophysics Data System (ADS)

Sun, Hongtao

Nano-scale temperature measurements are of significance for fundamental understanding of functional applications and nanosystems, requiring ultimate miniaturization of thermometers with reduced size, maintained sensitivity, simplicity and accuracy of temperature reading. Particularly, grand challenges exist for scenarios of combustion or thermal shock where materials may be subjected to drastic temperature variations and extreme thermal flux, and dynamic thermal sensors with an ultrafast response (seconds to milliseconds) are yet to be developed. Targeting the developments of advanced nano-scale thermal sensors with a fast time response and rapid readout, this thesis reports innovative designs of high surface-to-volume ratio gold nanostructures including ultrathin gold island films on transparent quartz substrates and silica-gold core-shell (SiO2 Au) nanospheres as potential dynamic thermal sensors for accurate temperature determination. The sensing mechanism is based on strong temperature dependences of the thermally-dewetting-induced morphological self-reorganization and characteristic surface plasmon (SP) absorption of the gold nanostructures. The irreversible thermally-induced morphological and optical signatures behave as characteristic "fingerprints" for temperature recording, allowing the retrieval of thermal history ex-situ. The fundamental studies of thermal-induced dewetting process and its corresponding unique optical properties were extensively investigated by high resolution scanning electron microscopy (HR-SEM), atomic force microscopy (AFM), and UV-vis-NIR spectroscopy, which illustrate temperature and time dependent variations. As compared with current nanothermometer technologies such as metal-filled nanotubes, our thermo-sensor offers positively synergistic advantages of ultrafast time response, permanent recording and fast readout of thermal history, and ex-situ capability for effective temperature measurements. In addition, SiO2 Au nanospheres

Self-amplified photo-induced gap quenching in a correlated electron material

PubMed Central

Mathias, S.; Eich, S.; Urbancic, J.; Michael, S.; Carr, A. V.; Emmerich, S.; Stange, A.; Popmintchev, T.; Rohwer, T.; Wiesenmayer, M.; Ruffing, A.; Jakobs, S.; Hellmann, S.; Matyba, P.; Chen, C.; Kipp, L.; Bauer, M.; Kapteyn, H. C.; Schneider, H. C.; Rossnagel, K.; Murnane, M. M.; Aeschlimann, M.

2016-01-01

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation. PMID:27698341

Self-amplified photo-induced gap quenching in a correlated electron material

DOE PAGES

Mathias, S.; Eich, S.; Urbancic, J.; ...

2016-10-04

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. Here, we show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically dependsmore » on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe 2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation.« less

Records of wells and test holes in the Nevada Test Site and vicinity (through December 1966)

USGS Publications Warehouse

Thordarson, William; Young, R.A.; Winograd, I.J.

1967-01-01

Hydrogeologic and construction data obtained from 119 test holes, wells, and emplacement holes at the Nevada Test Site and vicinity (through December 1966) are tabulated. The availability of cuttings, cores, lithologic logs, geophysical logs, formation-water analyses, hydraulic test data, and detailed construction data for each hole, as well as references to published reports for selected holes, are noted.

Ultrafast magnetization reversal by picosecond electrical pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yang; Wilson, Richard B.; Gorchon, Jon

The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. Here, we unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub–10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electricalmore » switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm) 3 cell. This discovery introduces a new field of research into ultrafast charge current–driven spintronic phenomena and devices.« less

Ultrafast magnetization reversal by picosecond electrical pulses

DOE PAGES

Yang, Yang; Wilson, Richard B.; Gorchon, Jon; ...

2017-11-03

The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. Here, we unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub–10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electricalmore » switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm) 3 cell. This discovery introduces a new field of research into ultrafast charge current–driven spintronic phenomena and devices.« less

Ultrafast Primary Reactions in the Photosystems of Oxygen-Evolving Organisms

NASA Astrophysics Data System (ADS)

Holzwarth, A. R.

In oxygen-evolving photosynthetic organisms (plants, green algae, cyanobacteria), the primary steps of photosynthesis occur in two membrane-bound protein supercomplexes, Photosystem I (PS I) and Photosystem II (PS II), located in the thylakoid membrane (c.f. Fig. 7.1) along with two other important protein complexes, the cytochrome b6/f complex and the ATP-synthase [1]. Each of the photosystems consists of a reaction center (RC) where the photoinduced early electron transfer processes occur, of a so-called core antenna consisting of chlorophyll (Chl) protein complexes responsible for light absorption and ultrafast energy transfer to the RC pigments, and additional peripheral antenna complexes of various kinds that increase the absorption cross-section. The peripheral complexes are Chl a/b-protein complexes in higher plants and green algae (LHC I or LHC II for PS I or PS II, respectively) and so-called phycobilisomes in cyanobacteria and red algae [2-4]. The structures and light-harvesting functions of these antenna systems have been extensively reviewed [2, 5-9]. Recently, X-ray structures of both PS I and PS II antenna/RC complexes have been determined, some to atomic resolution. Although many details of the pigment content and organization of the RCs and antenna systems of PS I and PS II have been known before, the high resolution structures of the integral complexes allow us for the first time to try to understand structure/function relationships in detail. This article covers our present understanding of the ultrafast energy transfer and early electron transfer processes occurring in the photosystems of oxygen-evolving organisms. The main emphasis will be on the electron transfer processes. However, in both photosystems the kinetics of the energy transfer processes in the core antennae is intimately interwoven with the kinetics of the electron transfer steps. Since both types of processes occur on a similar time scale, their kinetics cannot be considered

Triplet exciton dissociation and electron extraction in graphene-templated pentacene observed with ultrafast spectroscopy.

PubMed

McDonough, Thomas J; Zhang, Lushuai; Roy, Susmit Singha; Kearns, Nicholas M; Arnold, Michael S; Zanni, Martin T; Andrew, Trisha L

2017-02-08

We compare the ultrafast dynamics of singlet fission and charge generation in pentacene films grown on glass and graphene. Pentacene grown on graphene is interesting because it forms large crystals with the long axis of the molecules "lying-down" (parallel to the surface). At low excitation fluence, spectra for pentacene on graphene contain triplet absorptions at 507 and 545 nm and no bleaching at 630 nm, which we show is due to the orientation of the pentacene molecules. We perform the first transient absorption anisotropy measurements on pentacene, observing negative anisotropy of the 507 and 545 nm peaks, consistent with triplet absorption. A broad feature at 853 nm, observed on both glass and graphene, is isotropic, suggesting hole absorption. At high fluence, there are additional features, whose kinetics and anisotropies are not explained by heating, that we assign to charge generation; we propose a polaron pair absorption at 614 nm. The lifetimes are shorter at high fluence for both pentacene on glass and graphene, indicative of triplet-triplet annihilation that likely enhances charge generation. The anisotropy decays more slowly for pentacene on graphene than on glass, in keeping with the smaller domain size observed via atomic force microscopy. Coherent acoustic phonons are observed for pentacene on graphene, which is a consequence of more homogeneous domains. Measuring the ultrafast dynamics of pentacene as a function of molecular orientation, fluence, and polarization provides new insight to previous spectral assignments.

Site 765: Sediment Lithostratigraphy

USGS Publications Warehouse

,

1990-01-01

A 935-m-thick succession of Quaternary through Lower Cretaceous sediments was recovered at Site 765 (Fig. 10). A single core of Quaternary sediment was obtained from Hole 765A; drilling terminated and a new hole was drilled in an attempt to establish the mud line. Quaternary through middle Miocene sediments were cored in Hole 765B down to a depth of 395.6 mbsf. Middle Miocene through Lower Cretaceous sediments were cored in Hole 765C, after washing the interval between 0 and 350.2 mbsf. Exact lithologic correlation of the basal cores from Hole 765B with the upper cores from Hole 765C is not possible because of poor recovery; hence, correlation is based solely on matching sub-bottom depths.

Measurement of Nanoplasmonic Field Enhancement with Ultrafast Photoemission.

PubMed

Rácz, Péter; Pápa, Zsuzsanna; Márton, István; Budai, Judit; Wróbel, Piotr; Stefaniuk, Tomasz; Prietl, Christine; Krenn, Joachim R; Dombi, Péter

2017-02-08

Probing nanooptical near-fields is a major challenge in plasmonics. Here, we demonstrate an experimental method utilizing ultrafast photoemission from plasmonic nanostructures that is capable of probing the maximum nanoplasmonic field enhancement in any metallic surface environment. Directly measured field enhancement values for various samples are in good agreement with detailed finite-difference time-domain simulations. These results establish ultrafast plasmonic photoelectrons as versatile probes for nanoplasmonic near-fields.

QUIESCENCE CORRELATES STRONGLY WITH DIRECTLY MEASURED BLACK HOLE MASS IN CENTRAL GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terrazas, Bryan A.; Bell, Eric F.; Henriques, Bruno M. B.

Roughly half of all stars reside in galaxies without significant ongoing star formation. However, galaxy formation models indicate that it is energetically challenging to suppress the cooling of gas and the formation of stars in galaxies that lie at the centers of their dark matter halos. In this Letter, we show that the dependence of quiescence on black hole and stellar mass is a powerful discriminant between differing models for the mechanisms that suppress star formation. Using observations of 91 star-forming and quiescent central galaxies with directly measured black hole masses, we find that quiescent galaxies host more massive blackmore » holes than star-forming galaxies with similar stellar masses. This observational result is in qualitative agreement with models that assume that effective, more-or-less continuous active galactic nucleus feedback suppresses star formation, strongly suggesting the importance of the black hole in producing quiescence in central galaxies.« less

Ultrafast nonlinear optofluidics in selectively liquid-filled photonic crystal fibers.

PubMed

Vieweg, M; Gissibl, T; Pricking, S; Kuhlmey, B T; Wu, D C; Eggleton, B J; Giessen, H

2010-11-22

Selective filling of photonic crystal fibers with different media enables a plethora of possibilities in linear and nonlinear optics. Using two-photon direct-laser writing we demonstrate full flexibility of individual closing of holes and subsequent filling of photonic crystal fibers with highly nonlinear liquids. We experimentally demonstrate solitonic supercontinuum generation over 600 nm bandwidth using a compact femtosecond oscillator as pump source. Encapsulating our fibers at the ends we realize a compact ultrafast nonlinear optofluidic device. Our work is fundamentally important to the field of nonlinear optics as it provides a new platform for investigations of spatio-temporal nonlinear effects and underpins new applications in sensing and communications. Selective filling of different linear and nonlinear liquids, metals, gases, gain media, and liquid crystals into photonic crystal fibers will be the basis of new reconfigurable and versatile optical fiber devices with unprecedented performance. Control over both temporal and spatial dispersion as well as linear and nonlinear coupling will lead to the generation of spatial-temporal solitons, so-called optical bullets.

Rational material design for ultrafast rechargeable lithium-ion batteries.

PubMed

Tang, Yuxin; Zhang, Yanyan; Li, Wenlong; Ma, Bing; Chen, Xiaodong

2015-10-07

Rechargeable lithium-ion batteries (LIBs) are important electrochemical energy storage devices for consumer electronics and emerging electrical/hybrid vehicles. However, one of the formidable challenges is to develop ultrafast charging LIBs with the rate capability at least one order of magnitude (>10 C) higher than that of the currently commercialized LIBs. This tutorial review presents the state-of-the-art developments in ultrafast charging LIBs by the rational design of materials. First of all, fundamental electrochemistry and related ionic/electronic conduction theories identify that the rate capability of LIBs is kinetically limited by the sluggish solid-state diffusion process in electrode materials. Then, several aspects of the intrinsic materials, materials engineering and processing, and electrode materials architecture design towards maximizing both ionic and electronic conductivity in the electrode with a short diffusion length are deliberated. Finally, the future trends and perspectives for the ultrafast rechargeable LIBs are discussed. Continuous rapid progress in this area is essential and urgent to endow LIBs with ultrafast charging capability to meet huge demands in the near future.

Black hole solution in the framework of arctan-electrodynamics

NASA Astrophysics Data System (ADS)

Kruglov, S. I.

An arctan-electrodynamics coupled with the gravitational field is investigated. We obtain the regular black hole solution that at r →∞ gives corrections to the Reissner-Nordström solution. The corrections to Coulomb’s law at r →∞ are found. We evaluate the mass of the black hole that is a function of the dimensional parameter β introduced in the model. The magnetically charged black hole was investigated and we have obtained the magnetic mass of the black hole and the metric function at r →∞. The regular black hole solution is obtained at r → 0 with the de Sitter core. We show that there is no singularity of the Ricci scalar for electrically and magnetically charged black holes. Restrictions on the electric and magnetic fields are found that follow from the requirement of the absence of superluminal sound speed and the requirement of a classical stability.

Ultrafast scanning probe microscopy

DOEpatents

Weiss, Shimon; Chemla, Daniel S.; Ogletree, D. Frank; Botkin, David

1995-01-01

An ultrafast scanning probe microscopy method for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample.

Nonthermal ultrafast optical control of the magnetization in garnet films

NASA Astrophysics Data System (ADS)

Hansteen, Fredrik; Kimel, Alexey; Kirilyuk, Andrei; Rasing, Theo

2006-01-01

We demonstrate coherent optical control of the magnetization in ferrimagnetic garnet films on the femtosecond time scale through a combination of two different ultrafast and nonthermal photomagnetic effects and by employing multiple pump pulses. Linearly polarized laser pulses are shown to create a long-lived modification of the magnetocrystalline anisotropy via optically induced electron transfer between nonequivalent ion sites while circularly polarized pulses additionally act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday effect. Due to the slow phonon-magnon interaction in these dielectrics, thermal effects of the laser excitation are clearly distinguished from the ultrafast nonthermal effects and can be seen only on the time scale of nanoseconds for sample temperatures near the Curie point. The reported effects open exciting possibilities for ultrafast manipulation of spins by light, and provide insight into the physics of magnetism on ultrafast time scales.

Correlation between heavy-hole and light-hole Mahan Excitons in a two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Paul, J.; Dey, P.; Stevens, C. E.; Tokumoto, T.; Reno, J. L.; Hilton, D. J.; Karaiskaj, D.; D. J. Hilton Collaboration; J. L. Reno Collaboration

2015-03-01

We present the coherent two-dimensional Fourier transform (2DFT) spectra of Mahan Excitons associated with the heavy-hole and light-hole resonances observed in a modulation doped GaAs/AlGaAs single quantum well. These resonances are observed to be strongly coupled through many-body interactions. The 2DFT spectra were measured using co-linear, cross-linear, and co-circular polarizations and reveal striking differences. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. Department of Energy, Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. NSF, Division of Materials Research under Grant Number: DMR-1409473.

Galaxies of all Shapes Host Black Holes Artist Concept

NASA Image and Video Library

2008-01-10

Observations from NASA Spitzer Space Telescope provide strong evidence that the slender, bulgeless galaxies can, like their chubbier counterparts, harbor supermassive black holes at their cores in this artist concept.

Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: Ultrafast transient absorption and ultrafast Raman loss spectroscopic studies

NASA Astrophysics Data System (ADS)

Kayal, Surajit; Roy, Khokan; Umapathy, Siva

2018-01-01

Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy. TA measurements on the S1 state reveal step-wise population relaxation from the Franck-Condon (FC) state → relaxed state → twisted state, while the URLS study provides insights on the vibrational dynamics during the course of the reaction. The TA spectral dynamics and vibrational Raman amplitudes within 1 ps reveal vibrational wave packet propagating from the FC state to the relaxed state. Fourier transformation of this oscillation leads to a ˜130 cm-1 low-frequency phenyl torsional mode. Two vibrational marker bands, Cet=Cet stretching (˜1512 cm-1) and Cph=Cph stretching (˜1584 cm-1) modes, appear immediately after photoexcitation in the URLS spectra. The initial red-shift of the Cph=Cph stretching mode with a time constant of ˜400 fs (in butyronitrile) is assigned to the rate of planarization of excited TPE. In addition, the Cet=Cet stretching mode shows initial blue-shift within 1 ps followed by frequency red-shift, suggesting that on the sub-picosecond time scale, structural relaxation is dominated by phenyl torsion rather than the central Cet=Cet twist. Furthermore, the effect of the solvent on the structural dynamics is discussed in the context of ultrafast nuclear dynamics and solute-solvent coupling.

Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: Ultrafast transient absorption and ultrafast Raman loss spectroscopic studies.

PubMed

Kayal, Surajit; Roy, Khokan; Umapathy, Siva

2018-01-14

Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy. TA measurements on the S 1 state reveal step-wise population relaxation from the Franck-Condon (FC) state → relaxed state → twisted state, while the URLS study provides insights on the vibrational dynamics during the course of the reaction. The TA spectral dynamics and vibrational Raman amplitudes within 1 ps reveal vibrational wave packet propagating from the FC state to the relaxed state. Fourier transformation of this oscillation leads to a ∼130 cm -1 low-frequency phenyl torsional mode. Two vibrational marker bands, C et =C et stretching (∼1512 cm -1 ) and C ph =C ph stretching (∼1584 cm -1 ) modes, appear immediately after photoexcitation in the URLS spectra. The initial red-shift of the C ph =C ph stretching mode with a time constant of ∼400 fs (in butyronitrile) is assigned to the rate of planarization of excited TPE. In addition, the C et =C et stretching mode shows initial blue-shift within 1 ps followed by frequency red-shift, suggesting that on the sub-picosecond time scale, structural relaxation is dominated by phenyl torsion rather than the central C et =C et twist. Furthermore, the effect of the solvent on the structural dynamics is discussed in the context of ultrafast nuclear dynamics and solute-solvent coupling.

Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

DOE PAGES

Gao, Lan; Ji, Hantao; Fiksel, Gennady; ...

2016-04-15

Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ~ 1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ~ 3 x 10 16 W/cm 2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ~ 40-50 T magnetic fields at the center of the coil ~ 3-4 ns after laser irradiation. In conclusion, themore » experiments provide significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.« less

Entropy of black holes with multiple horizons

NASA Astrophysics Data System (ADS)

He, Yun; Ma, Meng-Sen; Zhao, Ren

2018-05-01

We examine the entropy of black holes in de Sitter space and black holes surrounded by quintessence. These black holes have multiple horizons, including at least the black hole event horizon and a horizon outside it (cosmological horizon for de Sitter black holes and "quintessence horizon" for the black holes surrounded by quintessence). Based on the consideration that the two horizons are not independent each other, we conjecture that the total entropy of these black holes should not be simply the sum of entropies of the two horizons, but should have an extra term coming from the correlations between the two horizons. Different from our previous works, in this paper we consider the cosmological constant as the variable and employ an effective method to derive the explicit form of the entropy. We also try to discuss the thermodynamic stabilities of these black holes according to the entropy and the effective temperature.

Radio Telescope Reveals Secrets of Massive Black Hole

NASA Astrophysics Data System (ADS)

2008-04-01

At the cores of many galaxies, supermassive black holes expel powerful jets of particles at nearly the speed of light. Just how they perform this feat has long been one of the mysteries of astrophysics. The leading theory says the particles are accelerated by tightly-twisted magnetic fields close to the black hole, but confirming that idea required an elusive close-up view of the jet's inner throat. Now, using the unrivaled resolution of the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA), astronomers have watched material winding a corkscrew outward path and behaving exactly as predicted by the theory. Galactic core and jet Artist's conception of region near supermassive black hole where twisted magnetic fields propel and shape jet of particles (Credit: Marscher et al., Wolfgang Steffen, Cosmovision, NRAO/AUI/NSF). Click on image for high-resolution file. Watch Video of Black-Hole-Powered Jet (Credit: Cosmovision, Wolfgang Steffen) Download: NTSC Format (90MB) | PAL Format (90MB) "We have gotten the clearest look yet at the innermost portion of the jet, where the particles actually are accelerated, and everything we see supports the idea that twisted, coiled magnetic fields are propelling the material outward," said Alan Marscher, of Boston University, leader of an international research team. "This is a major advance in our understanding of a remarkable process that occurs throughout the Universe," he added. Marscher's team studied a galaxy called BL Lacertae (BL Lac), some 950 million light-years from Earth. BL Lac is a blazar, the most energetic type of black-hole-powered galactic core. A black hole is a concentration of mass so dense that not even light can escape its gravitational pull. Supermassive black holes in galaxies' cores power jets of particles and intense radiation in similar objects including quasars and Seyfert galaxies. Material pulled inward toward the black hole forms a flattened, rotating disk, called an accretion disk

The Yucca Mountain Project prototype air-coring test, U12g tunnel, Nevada test site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, J.M.; Newsom, J.C.

1994-12-01

The Prototype Air-Coring Test was conducted at the Nevada Test Site (NTS) G-Tunnel facility to evaluate standard coring techniques, modified slightly for air circulation, for use in testing at a prospective nuclear waste repository at Yucca Mountain, Nevada. Air-coring technology allows sampling of subsurface lithology with minimal perturbation to ambient characteristic such as that required for exploratory holes near aquifers, environmental applications, and site characterization work. Two horizontal holes were cored, one 50 ft long and the other 150 ft long, in densely welded fractured tuff to simulate the difficult drilling conditions anticipated at Yucca Mountain. Drilling data from sevenmore » holes on three other prototype tests in nonwelded tuff were also collected for comparison. The test was used to establish preliminary standards of performance for drilling and dust collection equipment and to assess procedural efficiencies. The Longyear-38 drill achieved 97% recovery for HQ-size core (-2.5 in.), and the Atlas Copco dust collector (DCT-90) captured 1500 lb of fugitive dust in a mine environment with only minor modifications. Average hole production rates were 6-8 ft per 6-h shift in welded tuff and almost 20 ft per shift on deeper holes in nonwelded tuff. Lexan liners were successfully used to encapsulate core samples during the coring process and protect core properties effectively. The Prototype Air-Coring Test demonstrated that horizontal air coring in fractured welded tuff (to at least 150 ft) can be safely accomplished by proper selection, integration, and minor modification of standard drilling equipment, using appropriate procedures and engineering controls. The test also indicated that rig logistics, equipment, and methods need improvement before attempting a large-scale dry drilling program at Yucca Mountain.« less

Ultra-fast vapour-liquid-solid synthesis of Si nanowires using ion-beam implanted gallium as catalyst.

PubMed

Hetzel, Martin; Lugstein, Alois; Zeiner, Clemens; Wójcik, Tomasz; Pongratz, Peter; Bertagnolli, Emmerich

2011-09-30

The feasibility of gallium as a catalyst for vapour-liquid-solid (VLS) nanowire (NW) growth deriving from an implantation process in silicon by a focused ion beam (FIB) is investigated. Si(100) substrates are subjected to FIB implantation of gallium ions with various ion fluence rates. NW growth is performed in a hot wall chemical vapour deposition (CVD) reactor at temperatures between 400 and 500 °C with 2% SiH(4)/He as precursor gas. This process results in ultra-fast growth of (112)- and (110)-oriented Si-NWs with a length of several tens of micrometres. Further investigation by transmission electron microscopy indicates the presence of a NW core-shell structure: while the NW core yields crystalline structuring, the shell consists entirely of amorphous material.

Correlating Free-Volume Hole Distribution to the Glass Transition Temperature of Epoxy Polymers.

PubMed

Aramoon, Amin; Breitzman, Timothy D; Woodward, Christopher; El-Awady, Jaafar A

2017-09-07

A new algorithm is developed to quantify the free-volume hole distribution and its evolution in coarse-grained molecular dynamics simulations of polymeric networks. This is achieved by analyzing the geometry of the network rather than a voxelized image of the structure to accurately and efficiently find and quantify free-volume hole distributions within large scale simulations of polymer networks. The free-volume holes are quantified by fitting the largest ellipsoids and spheres in the free-volumes between polymer chains. The free-volume hole distributions calculated from this algorithm are shown to be in excellent agreement with those measured from positron annihilation lifetime spectroscopy (PALS) experiments at different temperature and pressures. Based on the results predicted using this algorithm, an evolution model is proposed for the thermal behavior of an individual free-volume hole. This model is calibrated such that the average radius of free-volumes holes mimics the one predicted from the simulations. The model is then employed to predict the glass-transition temperature of epoxy polymers with different degrees of cross-linking and lengths of prepolymers. Comparison between the predicted glass-transition temperatures and those measured from simulations or experiments implies that this model is capable of successfully predicting the glass-transition temperature of the material using only a PDF of the initial free-volume holes radii of each microstructure. This provides an effective approach for the optimized design of polymeric systems on the basis of the glass-transition temperature, degree of cross-linking, and average length of prepolymers.

Characterizing the Seasonality and Spatiotemporal Evolution of the U.S. Warming Hole

NASA Astrophysics Data System (ADS)

Partridge, T.; Winter, J.; Osterberg, E. C.; Magilligan, F. J.; Hyndman, D. W.; Kendall, A. D.

2017-12-01

Regions of the Eastern United States have experienced periods of cooling during the last half of the twentieth century inconsistent with broader global warming trends. While there have been a variety of mechanisms proposed to explain this "warming hole", the spatial and temporal definitions of the warming hole often differ across studies, potentially obfuscating the physical drivers leading to its existence. Further, a broad consensus on the causality of the warming hole has yet to be reached. We use daily temperature data from the Global Historical Climate Network (GHCN) to conduct a thorough characterization of the spatiotemporal evolution and seasonality of regional cooling across the Eastern U.S., and define a dynamic warming hole as the region of most persistent cooling. We find that the location of the dynamic warming hole varies by season from the Midwestern U.S. during summer to the Southeastern U.S. during winter. In addition, the cool period associated with the warming hole is characterized by an abrupt decrease in maximum temperature (Tx) and a decline in minimum temperature (Tn) around 1957. While average Tn values in the warming hole recover after the decline and increase from the mid 1960's to present, Tx values for the second half of the 20th century remain below observed values from the first half of the century. To explore large-scale atmospheric drivers of the dynamic warming hole, we correlate SST teleconnection and regional atmospheric circulation indices with seasonal temperature values from 1901-1957 and 1958-2015. We show that 1957 marks a shift, where winter temperatures in the warming hole become more correlated with the Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO) and less correlated with the Atlantic Multidecadal Oscillation (AMO). Summer warming hole temperatures become less correlated with the NAO post 1957 and are strongly negatively correlated with precipitation.

Advanced optic fabrication using ultrafast laser radiation

NASA Astrophysics Data System (ADS)

Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

2016-03-01

Advanced fabrication and finishing techniques are desired for freeform optics and integrated photonics. Methods including grinding, polishing and magnetorheological finishing used for final figuring and polishing of such optics are time consuming, expensive, and may be unsuitable for complex surface features while common photonics fabrication techniques often limit devices to planar geometries. Laser processing has been investigated as an alternative method for optic forming, surface polishing, structure writing, and welding, as direct tuning of laser parameters and flexible beam delivery are advantageous for complex freeform or photonics elements and material-specific processing. Continuous wave and pulsed laser radiation down to the nanosecond regime have been implemented to achieve nanoscale surface finishes through localized material melting, but the temporal extent of the laser-material interaction often results in the formation of a sub-surface heat affected zone. The temporal brevity of ultrafast laser radiation can allow for the direct vaporization of rough surface asperities with minimal melting, offering the potential for smooth, final surface quality with negligible heat affected material. High intensities achieved in focused ultrafast laser radiation can easily induce phase changes in the bulk of materials for processing applications. We have experimentally tested the effectiveness of ultrafast laser radiation as an alternative laser source for surface processing of monocrystalline silicon. Simulation of material heating associated with ultrafast laser-material interaction has been performed and used to investigate optimized processing parameters including repetition rate. The parameter optimization process and results of experimental processing will be presented.

Preliminary Physical Stratigraphy and Geophysical Data of the USGS Hope Plantation Core (BE-110), Bertie County, North Carolina

USGS Publications Warehouse

Weems, Robert E.; Seefelt, Ellen L.; Wrege, Beth M.; Self-Trail, Jean M.; Prowell, David C.; Durand, Colleen; Cobbs, Eugene F.; McKinney, Kevin C.

2007-01-01

Introduction In March and April, 2004, the U.S. Geological Survey (USGS), in cooperation with the North Carolina Geological Survey (NCGS) and the Raleigh Water Resources Discipline (WRD), drilled a stratigraphic test hole and well in Bertie County, North Carolina (fig. 1). The Hope Plantation test hole (BE-110-2004) was cored on the property of Hope Plantation near Windsor, North Carolina. The drill site is located on the Republican 7.5 minute quadradrangle at lat 36?01'58'N., long 78?01'09'W. (decimal degrees 36.0329 and 77.0192) (fig. 2). The altitude of the site is 48 ft above mean sea level as determined by Paulin Precise altimeter. This test hole was continuously cored by Eugene F. Cobbs, III and Kevin C. McKinney (USGS) to a total depth of 1094.5 ft. Later, a ground water observation well was installed with a screened interval between 315-329 feet below land surface (fig. 3). Upper Triassic, Lower Cretaceous, Upper Cretaceous, Tertiary, and Quaternary sediments were recovered from the site. The core is stored at the NCGS Coastal Plain core storage facility in Raleigh, North Carolina. In this report, we provide the initial lithostratigraphic summary recorded at the drill site along with site core photographs, data from the geophysical logger, calcareous nannofossil biostratigraphic correlations (Table 1) and initial hydrogeologic interpretations. The lithostratigraphy from this core can be compared to previous investigations of the Elizabethtown corehole, near Elizabethtown, North Carolina in Bladen County (Self-Trail, Wrege, and others, 2004), the Kure Beach corehole, near Wilmington, North Carolina in New Hanover County (Self-Trail, Prowell, and Christopher, 2004), the Esso #1, Esso #2, Mobil #1 and Mobil #2 cores in the Albermarle and Pamlico Sounds (Zarra, 1989), and the Cape Fear River outcrops in Bladen County (Farrell, 1998; Farrell and others, 2001). This core is the third in a series of planned benchmark coreholes that will be used to elucidate the

Black Hole Mergers in the Universe.

PubMed

Portegies Zwart SF; McMillan

2000-01-01

Mergers of black hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates that are too low to be of observational interest. In this Letter, we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation then causes them to sink to the cluster core, where they form binaries. These black hole binaries become more tightly bound by superelastic encounters with other cluster members and are ultimately ejected from the cluster. The majority of escaping black hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational radiation causes them to coalesce within a few billion years. We predict a black hole merger rate of about 1.6x10-7 yr-1 Mpc-3, implying gravity-wave detection rates substantially greater than the corresponding rates from neutron star mergers. For the first-generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we expect about one detection during the first 2 years of operation. For its successor LIGO-II, the rate rises to roughly one detection per day. The uncertainties in these numbers are large. Event rates may drop by about an order of magnitude if the most massive clusters eject their black hole binaries early in their evolution.

Black Hole Blows Big Bubble

NASA Astrophysics Data System (ADS)

2010-07-01

Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

Early-Time Excited-State Relaxation Dynamics of Iridium Compounds: Distinct Roles of Electron and Hole Transfer.

PubMed

Liu, Xiang-Yang; Zhang, Ya-Hui; Fang, Wei-Hai; Cui, Ganglong

2018-06-28

Excited-state and photophysical properties of Ir-containing complexes have been extensively studied because of their potential applications as organic light-emitting diode emitting materials. However, their early time excited-state relaxation dynamics are less explored computationally. Herein we have employed our recently implemented TDDFT-based generalized surface-hopping dynamics method to simulate excited-state relaxation dynamics of three Ir(III) compounds having distinct ligands. According to our multistate dynamics simulations including five excited singlet states i.e., S n ( n = 1-5) and ten excited triplet states, i.e., T n ( n = 1-10), we have found that the intersystem crossing (ISC) processes from the S n to T n are very efficient and ultrafast in these three Ir(III) compounds. The corresponding ISC rates are estimated to be 65, 81, and 140 fs, which are reasonably close to the experimentally measured ca. 80, 80, and 110 fs. In addition, the internal conversion (IC) processes within respective singlet and triplet manifolds are also ultrafast. These ultrafast IC and ISC processes are caused by large nonadiabatic and spin-orbit couplings, respectively, as well as small energy gaps. Importantly, although these Ir(III) complexes share similar macroscopic phenomena, i.e., ultrafast IC and ISC, their microscopic excited-state relaxation mechanism and dynamics are qualitatively distinct. Specifically, the dynamical behaviors of electron and hole and their roles are variational in modulating the excited-state relaxation dynamics of these Ir(III) compounds. In other words, the electronic properties of the ligands that are coordinated with the central Ir(III) atom play important roles in regulating the microscopic excited-state relaxation dynamics. These gained insights could be useful for rationally designing Ir(III) compounds with excellent photoluminescence.

Fast and ultrafast endocytosis.

PubMed

Watanabe, Shigeki; Boucrot, Emmanuel

2017-08-01

Clathrin-mediated endocytosis (CME) is the main endocytic pathway supporting housekeeping functions in cells. However, CME may be too slow to internalize proteins from the cell surface during certain physiological processes such as reaction to stress hormones ('fight-or-flight' reaction), chemotaxis or compensatory endocytosis following exocytosis of synaptic vesicles or hormone-containing vesicles. These processes take place on a millisecond to second timescale and thus require very rapid cellular reaction to prevent overstimulation or exhaustion of the response. There are several fast endocytic processes identified so far: macropinocytosis, activity-dependent bulk endocytosis (ABDE), fast-endophilin-mediated endocytosis (FEME), kiss-and-run and ultrafast endocytosis. All are clathrin-independent and are not constitutively active but may use different molecular mechanisms to rapidly remove receptors and proteins from the cell surface. Here, we review our current understanding of fast and ultrafast endocytosis, their functions, and molecular mechanisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aeroelastic Studies of a Rectangular Wing with a Hole: Correlation of Theory and Experiment

NASA Technical Reports Server (NTRS)

Conyers, Howard J.; Dowell, Earl H.; Hall, Kenneth C.

2010-01-01

Two rectangular wing models with a hole have been designed and tested in the Duke University wind tunnel to better understand the effects of damage. A rectangular hole is used to simulate damage. The wing with a hole is modeled structurally as a thin elastic plate using the finite element method. The unsteady aerodynamics of the plate-like wing with a hole is modeled using the doublet lattice method. The aeroelastic equations of motion are derived using Lagrange's equation. The flutter boundary is found using the V-g method. The hole's location effects the wing's mass, stiffness, aerodynamics and therefore the aeroelastic behavior. Linear theoretical models were shown to be capable of predicting the critical flutter velocity and frequency as verified by wind tunnel tests.

Pore-water chemistry from the ICDP-USGS core hole in the Chesapeake Bay impact structure-Implications for paleohydrology, microbial habitat, and water resources

USGS Publications Warehouse

Sanford, W.E.; Voytek, M.A.; Powars, D.S.; Jones, B.F.; Cozzarelli, I.M.; Cockell, C.S.; Eganhouse, R.P.

2009-01-01

We investigated the groundwater system of the Chesapeake Bay impact structure by analyzing the pore-water chemistry in cores taken from a 1766-m-deep drill hole 10 km north of Cape Charles, Virginia. Pore water was extracted using high-speed centrifuges from over 100 cores sampled from a 1300 m section of the drill hole. The pore-water samples were analyzed for major cations and anions, stable isotopes of water and sulfate, dissolved and total carbon, and bioavailable iron. The results reveal a broad transition between freshwater and saline water from 100 to 500 m depth in the postimpact sediment section, and an underlying synimpact section that is almost entirely filled with brine. The presence of brine in the lowermost postimpact section and the trend in dissolved chloride with depth suggest a transport process dominated by molecular diffusion and slow, compaction-driven, upward flow. Major ion results indicate residual effects of diagenesis from heating, and a pre-impact origin for the brine. High levels of dissolved organic carbon (6-95 mg/L) and the distribution of electron acceptors indicate an environment that may be favorable for microbial activity throughout the drilled section. The concentration and extent of the brine is much greater than had previously been observed, suggesting that its occurrence may be common in the inner crater. However, groundwater-flow conditions in the structure may reduce the saltwater-intrusion hazard associated with the brine. ?? 2009 The Geological Society of America.

OSA Proceedings on Ultrafast Electronics and Optoelectronics Held in San Francisco, California on January 25 -27, 1993. Volume 14,

DTIC Science & Technology

1993-01-27

Venkatesan, Zhi- Yuan Shen, Philip Pang, Dennis J. Kountz, and William L Holstein Response of a Nb/A1203/Nb Tunnel Junction to Picosecond Electrical Pulses...Mwhra (edo) 0 1993 Optical Sockty ofAnierica 152 Ultrafast Electronics and Optoelectronics core cladding COW MAD 75. 4UHN 1058nm 50Ps A A optical...Maryland. College Park; Maryland 20742 7hi-Yuan Shen, Philip Pang, Dennis J. Kountz, and William L. Holstein Central Research and Development, Du Pont, PO

Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory.

PubMed

Weathersby, S P; Brown, G; Centurion, M; Chase, T F; Coffee, R; Corbett, J; Eichner, J P; Frisch, J C; Fry, A R; Gühr, M; Hartmann, N; Hast, C; Hettel, R; Jobe, R K; Jongewaard, E N; Lewandowski, J R; Li, R K; Lindenberg, A M; Makasyuk, I; May, J E; McCormick, D; Nguyen, M N; Reid, A H; Shen, X; Sokolowski-Tinten, K; Vecchione, T; Vetter, S L; Wu, J; Yang, J; Dürr, H A; Wang, X J

2015-07-01

Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

Transthoracic Ultrafast Doppler Imaging of Human Left Ventricular Hemodynamic Function

PubMed Central

Osmanski, Bruno-Félix; Maresca, David; Messas, Emmanuel; Tanter, Mickael; Pernot, Mathieu

2016-01-01

Heart diseases can affect intraventricular blood flow patterns. Real-time imaging of blood flow patterns is challenging because it requires both a high frame rate and a large field of view. To date, standard Doppler techniques can only perform blood flow estimation with high temporal resolution within small regions of interest. In this work, we used ultrafast imaging to map in 2D human left ventricular blood flow patterns during the whole cardiac cycle. Cylindrical waves were transmitted at 4800 Hz with a transthoracic phased array probe to achieve ultrafast Doppler imaging of the left ventricle. The high spatio-temporal sampling of ultrafast imaging permits to rely on a much more effective wall filtering and to increase sensitivity when mapping blood flow patterns during the pre-ejection, ejection, early diastole, diastasis and late diastole phases of the heart cycle. The superior sensitivity and temporal resolution of ultrafast Doppler imaging makes it a promising tool for the noninvasive study of intraventricular hemodynamic function. PMID:25073134

Overmassive black holes in the MBH-σ diagram do not belong to over (dry) merged galaxies

NASA Astrophysics Data System (ADS)

Savorgnan, Giulia A. D.; Graham, Alister W.

2015-01-01

Semi-analytical models in a Λ cold dark matter cosmology have predicted the presence of outlying, `overmassive' black holes at the high-mass end of the (black hole mass-galaxy velocity dispersion) MBH-σ diagram (which we update here with a sample of 89 galaxies). They are a consequence of having experienced more dry mergers - thought not to increase a galaxy's velocity dispersion - than the `main-sequence' population. Wet mergers and gas-rich processes, on the other hand, preserve the main correlation. Due to the scouring action of binary supermassive black holes, the extent of these dry mergers (since the last significant wet merger) can be traced by the ratio between the central stellar mass deficit and the black hole mass (Mdef,*/MBH). However, in a sample of 23 galaxies with partially depleted cores, including central cluster galaxies, we show that the `overmassive' black holes are actually hosted by galaxies that appear to have undergone the lowest degree of such merging. In addition, the rotational kinematics of 37 galaxies in the MBH-σ diagram reveals that fast and slow rotators are not significantly offset from each other, also contrary to what is expected if these two populations were the product of wet and dry mergers, respectively. The observations are thus not in accordance with model predictions and further investigation is required.

Direct diode pumped Ti:sapphire ultrafast regenerative amplifier system

DOE PAGES

Backus, Sterling; Durfee, Charles; Lemons, Randy; ...

2017-02-10

Here, we report on a direct diode-pumped Ti:sapphire ultrafast regenerative amplifier laser system producing multi-uJ energies with repetition rate from 50 to 250 kHz. By combining cryogenic cooling of Ti:sapphire with high brightness fiber-coupled 450nm laser diodes, we for the first time demonstrate a power-scalable CW-pumped architecture that can be directly applied to demanding ultrafast applications such as coherent high-harmonic EUV generation without any complex post-amplification pulse compression. Initial results promise a new era for Ti:sapphire amplifiers not only for ultrafast laser applications, but also for tunable CW sources. We discuss the unique challenges to implementation, as well as themore » solutions to these challenges.« less

Direct diode pumped Ti:sapphire ultrafast regenerative amplifier system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Backus, Sterling; Durfee, Charles; Lemons, Randy

Here, we report on a direct diode-pumped Ti:sapphire ultrafast regenerative amplifier laser system producing multi-uJ energies with repetition rate from 50 to 250 kHz. By combining cryogenic cooling of Ti:sapphire with high brightness fiber-coupled 450nm laser diodes, we for the first time demonstrate a power-scalable CW-pumped architecture that can be directly applied to demanding ultrafast applications such as coherent high-harmonic EUV generation without any complex post-amplification pulse compression. Initial results promise a new era for Ti:sapphire amplifiers not only for ultrafast laser applications, but also for tunable CW sources. We discuss the unique challenges to implementation, as well as themore » solutions to these challenges.« less

Nearly suppressed photoluminescence blinking of small-sized, blue-green-orange-red emitting single CdSe-based core/gradient alloy shell/shell quantum dots: correlation between truncation time and photoluminescence quantum yield.

PubMed

Roy, Debjit; Mandal, Saptarshi; De, Chayan K; Kumar, Kaushalendra; Mandal, Prasun K

2018-04-18