Sub-kilohertz excitation lasers for quantum information processing with Rydberg atoms

NASA Astrophysics Data System (ADS)

Legaie, Remy; Picken, Craig J.; Pritchard, Jonathan D.

2018-04-01

Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave (CW) narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry-Perot cavity made of ultra-low expansion (ULE) glass, with a tunable offset-lock frequency. One laser operates at 852~nm while the two locked lasers at 1018~nm are frequency doubled to 509~nm for excitation of $^{133}$Cs atoms to Rydberg states. The optical beatnote at 509~nm is measured to be 260(5)~Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency (EIT) for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days yielding a linear frequency drift of $\\sim1$~Hz/s.

Rubidium atomic frequency standards for GPS Block IIR

NASA Technical Reports Server (NTRS)

Riley, William J.

1990-01-01

The Rubidium Atomic Frequency Standards (RAFS) were provided for the GPS Block IIR NAVSTAR satellites. These satellites will replenish and upgrade the space segment of the Global Positioning System in the mid 1990s. The GPS RAFS Rb clocks are the latest generation of the high-performance rubidium frequency standards. They offer an aging rate in the low pp 10(exp 14)/day range and a drift-corrected 1-day stability in the low pp 10(exp 14) range. The Block IIR version of these devices will have improved performance, higher reliability, smaller size, and greater radiation hardness. The GPS Block IIR atomic clocks have a natural frequency configuration whereby they output a frequency of about 13.4 MHz that is a submultiple of the atomic resonance of Rb (or Cs). The RAFS operates at a low, fixed C-field for increased stability. The GPS Block IIR RAFS design, including the changes and improvements made, and the test results obtained are described.

Impact of new clock technologies on the stability and accuracy of the International Atomic Time TAI.

NASA Astrophysics Data System (ADS)

Thomas, C.

1997-05-01

The BIPM Time Section is in charge of the generation of the reference time scales TAI and UTC. Both time scales are obtained in deferred-time by combining the data front a number of atomic clocks spread worldwide. The accuracy of TAI is estimated by the departure between the duration of the TAI scale interval and the SI second as produced on the rotating geoid by primary frequency standards. It is now possible to estimate TAI accuracy through the combination of results obtained from six different primary standards: LPTF-FO1, PTB CS1, PTB CS2, PTB CS3, NIST-7, and SU MCsR 102, all corrected for the black-body radiation shift. This led to a mean departure of the TAI scale interval of +2.0×10-14s over 1995, known with a relative uncertainty of 0.5×10-14(1σ).

Precision atomic spectroscopy for improved limits on variation of the fine structure constant and local position invariance.

PubMed

Fortier, T M; Ashby, N; Bergquist, J C; Delaney, M J; Diddams, S A; Heavner, T P; Hollberg, L; Itano, W M; Jefferts, S R; Kim, K; Levi, F; Lorini, L; Oskay, W H; Parker, T E; Shirley, J; Stalnaker, J E

2007-02-16

We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of <5.8x10(-6) per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |alpha/alpha|<1.3x10(-16) yr-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and 171Yb+ vs other 133Cs standards yield a coupled constraint of -1.5x10(-15)

Synthesis and structure of cesium complexes of nitrilotris(methylenephosphonic) acid [Cs-μ6-NH(CH2PO3)3H4] and [Cs2-μ10-NH(CH2PO3H)3] · H2O

NASA Astrophysics Data System (ADS)

Somov, N. V.; Chausov, F. F.; Zakirov, R. M.

2017-07-01

3D coordination polymers cesium nitrilotris(methylenephosphonate) and dicesium nitrilotris( methylenephosphonate) are synthesized and their crystal structure is determined. In the crystal of [Cs-μ6-NH(CH2PO3)3H4] (space group P, Z = 2), cesium atoms occupy two crystallographically inequivalent positions with c.n. = 10 and c.n. = 14. The phosphonate ligand plays the bridging function; its denticity is nine. The crystal packing consists of alternating layers of Cs atoms in different environments with layers of ligand molecules between them. A ligand is bound to three Cs atoms of one layer and three Cs atoms of another layer. In the crystal of [Cs2-μ10-NH(CH2PO3H)3] · H2O (space group P, Z = 2), the complex has a dimeric structure: the bridging phosphonate ligand coordinates Cs to form a three-dimensional Cs4O6 cluster. The denticity of the ligand is equal to nine; the coordination numbers of cesium atoms are seven and nine. Two-dimensional corrugated layers of Cs4O6 clusters lie in the (002) plane, and layers of ligand molecules are located between them. Each ligand molecule coordinates eight Cs atoms of one layer and two Cs atoms of the neighboring layer.

PTB’s Primary Clock CS1: First Results After Its Reconstruction

DTIC Science & Technology

1996-12-01

intense atomic beam and the frequency instability up (7 = 1 s) is predicted to be 4.10- la , based on the 62.5 Hz linewidth and the signal-to-noise...will be put into final operation as a clock again. REFERENCES [I] K. Dorenwendt 1986, "Realization and dissemination of the second, " Metrologia ...T. HeindorfT, R. Schroder, and B. Fischer 1996, "The P T B primary clod CS3: type B evaluation of its standard uncertainty," Metrologia , 33, 249

First-principles study on interlayer state in alkali and alkaline earth metal atoms intercalated bilayer graphene

NASA Astrophysics Data System (ADS)

Kaneko, Tomoaki; Saito, Riichiro

2017-11-01

Energetics and electronic structures of alkali metal (Li, Na, K, Rb, and Cs) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) atoms intercalated bilayer graphene are systematically investigated using first-principles calculations based on density functional theory. Formation of alkali and alkaline earth metal atoms intercalated bilayer graphene is exothermic except for Be and Mg. The interlayer state between two graphene layers is occupied for K, Rb, Cs, Ca, Sr, and Ba. We find that the energetic position of the interlayer states between bilayer graphene monotonically shifts downward with increasing of interlayer distance. The interlayer distances of more than 4.5 Å and 4.0 Å, respectively, are necessary for the occupation of the interlayer state in bilayer graphene for alkali and alkaline earth metal atoms, which is almost independent of the intercalant metal species. We discuss the relevance to occurrence of superconductivity for the metal intercalated bilayer graphene in terms of the occupation of the interlayer state and the phonon frequency of metal ions.

Dynamical origin of near- and below-threshold harmonic generation of Cs in an intense mid-infrared laser field.

PubMed

Li, Peng-Cheng; Sheu, Yae-Lin; Laughlin, Cecil; Chu, Shih-I

2015-05-20

Near- and below-threshold harmonic generation provides a potential approach to generate vacuum-ultraviolet frequency comb. However, the dynamical origin of in these lower harmonics is less understood and largely unexplored. Here we perform an ab initio quantum study of the near- and below-threshold harmonic generation of caesium (Cs) atoms in an intense 3,600-nm mid-infrared laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, the roles of multiphoton and multiple rescattering trajectories on the near- and below-threshold harmonic generation processes are clarified. We find that the multiphoton-dominated trajectories only involve the electrons scattered off the higher part of the combined atom-field potential followed by the absorption of many photons in near- and below-threshold regime. Furthermore, only the near-resonant below-threshold harmonic is exclusive to exhibit phase locked features. Our results shed light on the dynamic origin of the near- and below-threshold harmonic generation.

Atomic masses of {sup 6}Li,{sup 23}Na,{sup 39,41}K,{sup 85,87}Rb, and {sup 133}Cs

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

Mount, Brianna J.; Redshaw, Matthew; Myers, Edmund G.

2010-10-15

The atomic masses of the alkali-metal isotopes {sup 6}Li,{sup 23}Na,{sup 39,41}K,{sup 85,87}Rb, and {sup 133}Cs have been obtained from measurements of cyclotron frequency ratios of pairs of ions simultaneously trapped in a Penning trap. The results, with one standard deviation uncertainty, are: M({sup 6}Li)=6.015 122 887 4(16)u,M({sup 23}Na)=22.989769 282 8(26)u,M({sup 39}K)=38.963 706 485 6(52)u,M({sup 41}K)=40.961 825 257 4(48)u,M({sup 85}Rb)=84.911 789739(9)u,M({sup 87}Rb)=86.909 180 535(10)u, and M({sup 133}Cs)=132.905 451 963(13)u. Our mass of {sup 6}Li yields an improved neutron separation energy for {sup 7}Li of 7251.1014(45) keV.

A Cesium fountain frequency standard: Preliminary results

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

Clairon, A.; Laurent, P.; Santarelli, G.

1994-12-31

Laser cooling of atoms has opened up new possibilities in the field of atomic frequency standards. A Cesium atomic fountain, first proposed by Zacharias in 1953, is now feasible: the atoms, first cooled by six laser beams, are launched upward using laser light, pass once through a microwave cavity, continue their ballistic flight and then fall through the same cavity. The long time between the two microwave interactions leads to a Ramsey resonance much narrower than in conventional Cs clocks using thermal atomic beams. The stability and accuracy of such a cesium fountain am very attractive. The use of diodemore » lasers to cool, launch and detect cesium atoms in a low cesium pressure cell allows the construction of a simple and reliable atomic fountain frequency standard. A fountain frequency standard is now in operation at LPTF. A Ramsey resonance as narrow as 0.8 Hz has been obtained. A few days of continuous operation are routinely obtained. In closed loop operation the fountain frequency standard is continuously monitored against a H maser allowing an evaluation of the accuracy of the device. The present short- term frequency stability is about 5.10{sup -13} {tau}{sup -1/2} limited only by the frequency noise of the microwave source. We intend to present a preliminary evaluation of this new standard with a discussion of the major systematic effects which determine the accuracy. The expected accuracy will be at 10-14 level. In addition, we will present a description of the whole design of the cesium fountain.« less

Absolute Frequency Measurement of the {sup 40}Ca{sup +} 4s {sup 2}S{sub 1/2}-3d {sup 2}D{sub 5/2} Clock Transition

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

Chwalla, M.; Kim, K.; Monz, T.

2009-01-16

We report on the first absolute transition frequency measurement at the 10{sup -15} level with a single, laser-cooled {sup 40}Ca{sup +} ion in a linear Paul trap. For this measurement, a frequency comb is referenced to the transportable Cs atomic fountain clock of LNE-SYRTE and is used to measure the {sup 40}Ca{sup +} 4s {sup 2}S{sub 1/2}-3d {sup 2}D{sub 5/2} electric-quadrupole transition frequency. After the correction of systematic shifts, the clock transition frequency {nu}{sub Ca{sup +}}=411 042 129 776 393.2(1.0) Hz is obtained, which corresponds to a fractional uncertainty within a factor of 3 of the Cs standard. In addition,more » we determine the Landeg factor of the 3d{sup 2}D{sub 5/2} level to be g{sub 5/2}=1.200 334 0(3)« less

Effects of guest atomic species on the lattice thermal conductivity of type-I silicon clathrate studied via classical molecular dynamics

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

Kumagai, Tomohisa, E-mail: kumagai@criepi.denken.or.jp; Nakamura, Kaoru; Yamada, Susumu

The effects of guest atomic species in Si clathrates on the lattice thermal conductivity were studied using classical molecular dynamics calculations. The interaction between a host atom and a guest atom was described by the Morse potential function while that between host atoms was described by the Tersoff potential. The parameters of the potentials were newly determined for this study such that the potential curves obtained from first-principles calculations for the insertion of a guest atom into a Si cage were successfully reproduced. The lattice thermal conductivities were calculated by using the Green-Kubo method. The experimental lattice thermal conductivity ofmore » Ba{sub 8}Ga{sub 16}Si{sub 30} can be successfully reproduced using the method. As a result, the lattice thermal conductivities of type-I Si clathrates, M{sub 8}Si{sub 46} (M = Na, Mg, K, Ca Rb, Sr, Cs, or Ba), were obtained. It is found that the lattice thermal conductivities of M{sub 8}Si{sub 46}, where M is IIA elements (i.e., M = Mg, Ca, Sr, or Ba) tend to be lower than those of M{sub 8}Si{sub 46}, where M is IA elements (i.e., M = Na, K, Rb, or Cs). Those of {sup m}M{sub 8}Si{sub 46}, where m was artificially modified atomic weight were also obtained. The obtained lattice thermal conductivity can be regarded as a function of a characteristic frequency, f{sub c}. That indicates minimum values around f{sub c}=2-4 THz, which corresponds to the center of the frequencies of the transverse acoustic phonon modes associated with Si cages.« less

Cold Atom Clock Test of Lorentz Invariance in the Matter Sector

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

Wolf, Peter; Chapelet, Frederic; Bize, Sebastien

2006-02-17

We report on a new experiment that tests for a violation of Lorentz invariance (LI), by searching for a dependence of atomic transition frequencies on the orientation of the spin of the involved states (Hughes-Drever type experiment). The atomic frequencies are measured using a laser cooled {sup 133}Cs atomic fountain clock, operating on a particular combination of Zeeman substates. We analyze the results within the framework of the Lorentz violating standard model extension (SME), where our experiment is sensitive to a largely unexplored region of the SME parameter space, corresponding to first measurements of four proton parameters and improvements bymore » 11 and 13 orders of magnitude on the determination of four others. In spite of the attained uncertainties, and of having extended the search into a new region of the SME, we still find no indication of LI violation.« less

Magnetoencephalography with a Cs-based high-sensitivity compact atomic magnetometer

NASA Astrophysics Data System (ADS)

Sheng, Jingwei; Wan, Shuangai; Sun, Yifan; Dou, Rongshe; Guo, Yuhao; Wei, Kequan; He, Kaiyan; Qin, Jie; Gao, Jia-Hong

2017-09-01

In recent years, substantial progress has been made in developing a new generation of magnetoencephalography (MEG) with a spin-exchange relaxation free (SERF)-based atomic magnetometer (AM). An AM employs alkali atoms to detect weak magnetic fields. A compact AM array with high sensitivity is crucial to the design; however, most proposed compact AMs are potassium (K)- or rubidium (Rb)-based with single beam configurations. In the present study, a pump-probe two beam configuration with a Cesium (Cs)-based AM (Cs-AM) is introduced to detect human neuronal magnetic fields. The length of the vapor cell is 4 mm, which can fully satisfy the need of designing a compact sensor array. Compared with state-of-the-art compact AMs, our new Cs-AM has two advantages. First, it can be operated in a SERF regime, requiring much lower heating temperature, which benefits the sensor with a closer distance to scalp due to ease of thermal insulation and less electric heating noise interference. Second, the two-beam configuration in the design can achieve higher sensitivity. It is free of magnetic modulation, which is necessary in one-beam AMs; however, such modulation may cause other interference in multi-channel circumstances. In the frequency band between 10 Hz and 30 Hz, the noise level of the proposed Cs-AM is approximately 10 f T/Hz1/2, which is comparable with state-of-the-art K- or Rb-based compact AMs. The performance of the Cs-AM was verified by measuring human auditory evoked fields (AEFs) in reference to commercial superconducting quantum interference device (SQUID) channels. By using a Cs-AM, we observed a clear peak in AEFs around 100 ms (M100) with a much larger amplitude compared with that of a SQUID, and the temporal profiles of the two devices were in good agreement. The results indicate the possibility of using the compact Cs-AM for MEG recordings, and the current Cs-AM has the potential to be designed for multi-sensor arrays and gradiometers for future neuroscience studies.

Strong Inter-channel Effects in Dipole Photoionization of d-subshells of Xe, Cs, and Ba Atoms

NASA Astrophysics Data System (ADS)

Manson, S.; Amusia, M.; Baltenkov, A.; Chernysheva, L.; Felfli, Z.; Msezane, A.

2003-05-01

In the framework of a specially modified Random Phase Approximation with Exchange approach (SPRPAE) developed for half-filled atomic subshells the dipole angular anisotropy parameters β(ω) for the 3d-photoionization of Xe, Cs and Ba atoms have been calculated. The main point of this approach is that we consider the 3d electrons of these atoms as belonging to two semi-filled atomic levels that contain two different sorts of electrons, namely that six electrons form the 3d_5/2 subshell (called "up"), while the other four electrons form the 3d_3/2 subshell (called "down"). This permits to apply straightforwardly the RPAE for these semi-filled subshells. We show that the interaction between "up" and "down" electrons results in a qualitative alteration of the frequency (ω) dependence of β_5/2(ω) and β_3/2(ω) that define the photoelectron angular distribution from the 3d_5/2 and 3d_3/2 levels. In all these atoms the effect of 3d_3/2 upon 3d_5/2 leads to the creation of an additional maximum near the photoionization thresholds, while the effect for 3d_3/2 is rather weak. Work supported by CRDF (No ZP1- 2449-TA-02), ISTC grant 1358 and NSF

Chemical shielding properties for BN, BP, AlN, and AlP nanocones: DFT studies

NASA Astrophysics Data System (ADS)

Mirzaei, Mahmoud; Yousefi, Mohammad; Meskinfam, Masoumeh

2012-06-01

The properties of boron nitride (BN), boron phosphide (BP), aluminum nitride (AlN), and aluminum phosphide (AlP) nanocones were investigated by density functional theory (DFT) calculations. The investigated structures were optimized and chemical shielding (CS) properties including isotropic and anisotropic CS parameters were calculated for the atoms of the optimized structures. The magnitudes of CS parameters were observed to be mainly dependent on the bond lengths of considered atoms. The results indicated that the atoms could be divided into atomic layers due to the similarities of their CS properties for the atoms of each layer. The trend means that the atoms of each layer detect almost similar electronic environments. Moreover, the atoms at the apex and mouth of nanocones exhibit different properties with respect to the other atomic layers.

Motion of Cesium Atoms in the One-Dimensional Magneto-Optical Trap

NASA Technical Reports Server (NTRS)

Li, Yimin; Chen, Xuzong; Wang, Qingji; Wang, Yiqiu

1996-01-01

The force to which Cs atoms are subjected in the one-dimensional magneto-optical trap (lD-MOT) is calculated, and properties of this force are discussed. Several methods to increase the number of Cs atoms in the lD-MOT are presented on the basis of the analysis of the capture and escape of Cs atoms in the ID-MOT.

Lorentz-Symmetry Test at Planck-Scale Suppression With a Spin-Polarized 133Cs Cold Atom Clock.

PubMed

Pihan-Le Bars, H; Guerlin, C; Lasseri, R-D; Ebran, J-P; Bailey, Q G; Bize, S; Khan, E; Wolf, P

2018-06-01

We present the results of a local Lorentz invariance (LLI) test performed with the 133 Cs cold atom clock FO2, hosted at SYRTE. Such a test, relating the frequency shift between 133 Cs hyperfine Zeeman substates with the Lorentz violating coefficients of the standard model extension (SME), has already been realized by Wolf et al. and led to state-of-the-art constraints on several SME proton coefficients. In this second analysis, we used an improved model, based on a second-order Lorentz transformation and a self-consistent relativistic mean field nuclear model, which enables us to extend the scope of the analysis from purely proton to both proton and neutron coefficients. We have also become sensitive to the isotropic coefficient , another SME coefficient that was not constrained by Wolf et al. The resulting limits on SME coefficients improve by up to 13 orders of magnitude the present maximal sensitivities for laboratory tests and reach the generally expected suppression scales at which signatures of Lorentz violation could appear.

Limit on the present temporal variation of the fine structure constant.

PubMed

Peik, E; Lipphardt, B; Schnatz, H; Schneider, T; Tamm, Chr; Karshenboim, S G

2004-10-22

The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in 171Yb+ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio f(Yb)/f(Cs) of (-1.2+/-4.4)x10(-15) yr(-1), consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of alpha at the level of 2.0x10(-15) yr(-1) (1sigma), corresponding so far to the most stringent limit from laboratory experiments.

Stability and accuracy of International Atomic Time TAI.

NASA Astrophysics Data System (ADS)

Thomas, C.

Since the end of 1992, the quality of the timing data received at the BIPM has rapidly evolved dues to the extensive replacement of older designs of commercial Cs clocks. Consequently, the stability of the reference time scales has improved significantly. This was tested by running modified algorithms over the real clock data collected at the BIPM. Results of different studies are shown here; in particular the implementation of an upper relative contribution, chosen equal to 1.37% for any contributing clock, leads to σy(τ=40 d) = 1.8×10-15. The accuracy of TAI is estimated by the difference between the duration of the TAI scale interval and the SI second as produced on the rotating geoid by primary frequency standards. In this paper, TAI accuracy is evaluated from six primary frequency standards LPTF-FO1, PTB CS1, PTB CS2, PTB CS3, NIST-7 and SU MCsR 102 all corrected in a consistent manner for the gravitational shift and the black-body radiation shift. This led to a mean departure of the TAI scale interval of 1.8×10-14 s over 1995, known with a relative uncertainty of 0.5×10-14 (1σ).

Dual species entanglement of Rb and Cs qubits with Rydberg blockade for crosstalk free qubit measurements

NASA Astrophysics Data System (ADS)

Baker, Kevin; Yu, Zhaoning; Ebert, Matthew; Sun, Yuan; Saffman, Mark

2016-05-01

One of the outstanding challenges facing neutral atom qubit approaches to quantum computation is suppression of crosstalk between proximal qubits due to scattered light that is generated during optical pumping and measurement operations. We have recently proposed a dual species approach to solving this challenge whereby computational qubits encoded in Cs atoms are entangled with Rb atoms via an interspecies Rydberg interaction. The quantum state of a Cs atom can then be readout by measuring the state of a Rb atom. The difference in resonant wavelengths of the two species effectively suppresses crosstalk. We will present progress towards experimental demonstration of dual species entanglement using Rb and Cs atoms cotrapped in a single beam optical trap. Work supported by the ARL CDQI.

Two-stage crossed beam cooling with ⁶Li and ¹³³Cs atoms in microgravity.

PubMed

Luan, Tian; Yao, Hepeng; Wang, Lu; Li, Chen; Yang, Shifeng; Chen, Xuzong; Ma, Zhaoyuan

2015-05-04

Applying the direct simulation Monte Carlo (DSMC) method developed for ultracold Bose-Fermi mixture gases research, we study the sympathetic cooling process of 6Li and 133Cs atoms in a crossed optical dipole trap. The obstacles to producing 6Li Fermi degenerate gas via direct sympathetic cooling with 133Cs are also analyzed, by which we find that the side-effect of the gravity is one of the main obstacles. Based on the dynamic nature of 6Li and 133Cs atoms, we suggest a two-stage cooling process with two pairs of crossed beams in microgravity environment. According to our simulations, the temperature of 6Li atoms can be cooled to T = 29.5 pK and T/TF = 0.59 with several thousand atoms, which propose a novel way to get ultracold fermion atoms with quantum degeneracy near pico-Kelvin.

Narrowband diode laser pump module for pumping alkali vapors.

PubMed

Rotondaro, M D; Zhdanov, B V; Shaffer, M K; Knize, R J

2018-04-16

We describe a method of line narrowing and frequency-locking a diode laser stack to an alkali atomic line for use as a pump module for Diode Pumped Alkali Lasers. The pump module consists of a 600 W antireflection coated diode laser stack configured to lase using an external cavity. The line narrowing and frequency locking is accomplished by introducing a narrowband polarization filter based on magneto-optical Faraday effect into the external cavity, which selectively transmits only the frequencies that are in resonance with the 6 2 S 1/2 → 6 2 P 3/2 transition of Cs atoms. The resulting pump module has demonstrated that a diode laser stack, which lases with a line width of 3 THz without narrowbanding, can be narrowed to 10 GHz. The line narrowed pump module produced 518 Watts that is 80% of the power generated by the original broadband diode laser stack.

Single and pair-wise manipulation of atoms in a 3D optical lattice

NASA Astrophysics Data System (ADS)

Corcovilos, Theodore; Wang, Yang; Weiss, David

2013-05-01

We describe the hardware used in a quantum computing experiment using individual Cs atoms in a 5 μm -spaced 3D optical lattice as qubits. Far-off-resonance addressing beams can be steered to any site in the array using MEMS mirrors within 10 μs , allowing the translation of individual atoms between lattice sites, for example to remove vacancies in the atom array, and the manipulation of single atoms for single qubit gates in < 100 μs . Two-qubit gates on adjacent atoms can be performed via the Rydberg blockade mechanism using a second MEMS system and high-NA imaging objective. The lasers for the Rydberg excitation are built using a new extended cavity diode laser design utilizing an interference filter as the frequency selecting element following Baillard, et al. (Opt. Comm. 266: 609 (2009)), but using commercially available components. We gratefully acknowledge funding from ARO and DARPA.

Development Of Frequency Transfer Via Optical Fiber Link at NICT

DTIC Science & Technology

2008-12-01

al., 2006 “Comparison between frequency standards in Europe and the USA at the 10-15 uncertainty level,” Metrologia , 43, 109-120. [4] H. Kiuchi, T...M. Hosokawa, 2008, “Evaluation of caesium atomic fountain NICT-CsF1,” Metrologia , 45, 139-148. [12] M. Kumagai, H. Ito, G. Santarelli, C. Locke, J...free-run O ve rla pp in g Al la n D ev ia tio n Averaging time [sec] 40th Annual Precise Time and Time Interval (PTTI) Meeting 100 101 102 103

High-resolution laser spectroscopy of hot Cs and Rb vapor confined in a thin optical cell

NASA Astrophysics Data System (ADS)

Todorov, P.; Krasteva, A.; Vartanyan, T.; Todorov, G.; Sarkisyan, D.; Cartaleva, S.

2018-03-01

We propose a novel use of an optical cell of micrometer thickness filled with Cs vapor in view of studying the collisions between two different alkali atoms of strongly different densities. We demonstrate narrow and good-contrast sub-Doppler resonances at the Rb D2 line for a mean-free-path of the Cs atoms comparable to the optical cell longitudinal dimension; the resonances are completely destroyed when the mean-free-path of the Cs atoms is more than two orders of magnitude shorter than the longitudinal dimension of the thin cell.

Status and prospect of the Swiss continuous Cs fountain FoCS-2

NASA Astrophysics Data System (ADS)

Jallageas, A.; Devenoges, L.; Petersen, M.; Morel, J.; Bernier, L.-G.; Thomann, P.; Südmeyer, T.

2016-06-01

The continuous cesium fountain clock FoCS-2 at METAS presents many unique characteristics and challenges in comparison with standard pulsed fountain clocks. For several years FoCS-2 was limited by an unexplained frequency sensitivity on the velocity of the atoms, in the range of 140 • 10-15. Recent experiments allowed us to identify the origin of this problem as undesirable microwave surface currents circulating on the shield of the coaxial cables that feed the microwave cavity. A strong reduction of this effect was obtained by adding microwave absorbing coatings on the coaxial cables and absorbers inside of the vacuum chamber. This breakthrough opens the door to a true metrological validation of the fountain. A series of simulation tools have already been developed and proved their efficiency in the evaluation of some of the uncertainties of the continuous fountain. With these recent improvements, we are confident in the future demonstration of an uncertainty budget at the 10-15 level and below.

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser.

PubMed

Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin

2012-03-26

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

NASA Astrophysics Data System (ADS)

Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro; Ohkochi, Takuo; Yasui, Akira; Yaita, Tsuyoshi

2018-01-01

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

Principles determining the structure of high-pressure forms of metals: The structures of cesium(IV) and cesium(V)

PubMed Central

Pauling, Linus

1989-01-01

Consideration of the relation between bond length and bond number and the average atomic volume for different ways of packing atoms leads to the conclusion that the average ligancy of atoms in a metal should increase when a phase change occurs on increasing the pressure. Minimum volume for each value of the ligancy results from triangular coordination polyhedra (with triangular faces), such as the icosahedron and the Friauf polyhedron. Electron transfer may permit atoms of an element to assume different ligancies. Application of these principles to Cs(IV) and Cs(V), which were previously assigned structures with ligancy 8 and 6, respectively, has led to the assignment to Cs(IV) of a primitive cubic unit cell with a = 16.11 Å and with about 122 atoms in the cube and to Cs(V) of a primitive cubic unit cell resembling that of Mg32(Al,Zn)49, with a = 16.97 Å and with 162 atoms in the cube. PMID:16578839

Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt

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

Ishikawa, Kiyoshi

2011-07-15

The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

The optical pumping of alkali atoms using coherent radiation from semi-conductor injection lasers and incoherent radiation from resonance lamps

NASA Technical Reports Server (NTRS)

Singh, G.

1973-01-01

An experimental study for creating population differences in the ground states of alkali atoms (Cesium 133) is presented. Studies made on GaAs-junction lasers and the achievement of population inversions among the hyperfine levels in the ground state of Cs 133 by optically pumping it with radiation from a GaAs diode laser. Laser output was used to monitor the populations in the ground state hyperfine levels as well as to perform the hyperfine pumping. A GaAs laser operated at about 77 K was used to scan the 8521 A line of Cs 133. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. Investigations were also made for the development of the triple resonance coherent pulse technique and for the detection of microwave induced hyperfine trasistions by destroying the phase relationships produced by a radio frequency pulse. A pulsed cesium resonance lamp developed, and the lamp showed clean and reproducible switching characteristics.

Simultaneous Faraday filtering of the Mollow triplet sidebands with the Cs-D1 clock transition.

PubMed

Portalupi, Simone Luca; Widmann, Matthias; Nawrath, Cornelius; Jetter, Michael; Michler, Peter; Wrachtrup, Jörg; Gerhardt, Ilja

2016-11-25

Hybrid quantum systems integrating semiconductor quantum dots (QDs) and atomic vapours become important building blocks for scalable quantum networks due to the complementary strengths of individual parts. QDs provide on-demand single-photon emission with near-unity indistinguishability comprising unprecedented brightness-while atomic vapour systems provide ultra-precise frequency standards and promise long coherence times for the storage of qubits. Spectral filtering is one of the key components for the successful link between QD photons and atoms. Here we present a tailored Faraday anomalous dispersion optical filter based on the caesium-D 1 transition for interfacing it with a resonantly pumped QD. The presented Faraday filter enables a narrow-bandwidth (Δω=2π × 1 GHz) simultaneous filtering of both Mollow triplet sidebands. This result opens the way to use QDs as sources of single as well as cascaded photons in photonic quantum networks aligned to the primary frequency standard of the caesium clock transition.

Femtosecond-level timing fluctuation suppression in atmospheric frequency transfer with passive phase conjunction correction.

PubMed

Sun, Fuyu; Hou, Dong; Zhang, Danian; Tian, Jie; Hu, Jianguo; Huang, Xianhe; Chen, Shijun

2017-09-04

We demonstrate femtosecond-level timing fluctuation suppression in indoor atmospheric comb-based frequency transfer with a passive phase conjunction correction technique. Timing fluctuations and Allan deviations are both measured to characterize the excess frequency instability incurred during the frequency transfer process. By transferring a 2 GHz microwave over a 52-m long free-space link in 5000 s, the total root-mean-square (RMS) timing fluctuation was measured to be about 280 fs with a fractional frequency instability on the order of 3 × 10 -13 at 1 s and 6 × 10 -17 at 1000 s. This atmospheric comb-based frequency transfer with passive phase conjunction correction can be used to build an atomic clock-based free-space frequency transmission link because its instability is less than that of a commercial Cs or H-master clock.

Studies of Inelastic Collisions of NaK and NaCs Molecules with Atomic Perturbers

NASA Astrophysics Data System (ADS)

Jones, Joshua A.

We have investigated collisions of NaK molecules in the first excited state [2(A)1Sigma+], with Ar and He collision partners using laser-induced fluorescence spectroscopy (LIF) and polarization-labeling (PL) spectroscopy in a two-step excitation scheme. Additionally, we have investigated collisions of NaCs molecules in the first excited state [2(A)1Sigma +] with Ar and He perturbers using the LIF technique. We use a pump-probe, two-step excitation process. The pump laser prepares the molecule in a particular ro-vibrational (v, J) level in the A state. The probe laser frequency is scanned over transitions to the 31Π in NaK or to the 53Π in NaCs. In addition to observing strong direct lines, we also see weak collisional satellite lines that arise from collisions in the intermediate state that take the molecule from the prepared level (v, J) to level (v, J + Delta J). The ratio of the intensity of the collisional line to the intensity of the direct line in LIF and PL yield information about population and orientation transfer. Our results show a propensity for DeltaJ=even collisions of NaK with Ar and an even stronger propensity for collisions with He. Collisions of NaCs with Ar do not show any such J=even propensity. Preliminary investigations of collisions of NaCs with He seem to indicate a slight J=even propensity. In addition, we observe that rotationally inelastic collisions of excited NaK molecules with potassium atoms destroy almost all of the orientation, while collisions with argon destroy about one third to two thirds and collisions with helium destroy only about zero to one third of the initial orientation.

Characterizing fallout material using Cs and Pu atom ratios in environmental samples from the FDNPP fallout zone

NASA Astrophysics Data System (ADS)

Richards, David; Dunne, James; Martin, Peter; Scott, Tom; Yamashiki, Yosuke; Coath, Chris; Chen, Hart

2017-04-01

Here we report the use of combined of Cs and Pu isotope measurements to investigate the extensive plumes of radioactive fallout from the disaster at Fukishima Daiichi nuclear power plant (FNDPP) in March 2011. Among the aims of our study are improved assessment of the physico-chemical nature and changing distribution of land-based fallout. 135Cs/137Cs and 134Cs/137Cs atom ratios are indicative of conditions that relate to the nuclear fission reactions responsible for producing the respective radiocaesium isotopes, and offer much more in terms of forensic and chronological analysis than monitoring 137Cs alone. We briefly present methods to quantify the atom ratios of Cs and Pu isotopes in soil, lichen and moss samples from FDNPP catchment using mass spectrometry (ThermoTRITON for Cs and ThermoNEPTUNE for Pu). High precision data from Fukushima are presented (e.g decay corrected 135Cs/137Cs atom ratio = 0.384 ± 0.001 (n = 5) for roadside dust from Iitate region), and these are in agreement with prelimary estimates by others. We also confirm results for IAEA-330, a spinach sample collected from Polesskoe, Ukraine and subject to contamination from the Chernobyl accident. In addition to Cs isotopes, we adopt Pu isotopes to add a further dimension to the forensic analysis. We discuss the corrections required for background levels prior to the disaster, possibility for multiple components of fallout and complicating factors associated with remobilisation during the clean-up operation. In parallel with this work on digests and leaches from bulk environmental samples, we are refining methods for particle identification, isolation and characterisation using a complementary sequence of cutting-edge materials and manipulation techniques, including combined electron microscopy, focused ion beam techniques (Dualbeam), nano/micro manipulators and nano-scale imaging x-ray photoelectron spectroscopy (NanoESCA) and microCT.

Evidence for alkali metal formation at a cathode interface of organic electroluminescent devices by thermal decomposition of alkali metal carboxylates during their vapor deposition

NASA Astrophysics Data System (ADS)

Ganzorig, Chimed; Fujihira, Masamichi

2004-11-01

This study examines the possibility of thermal decomposition of Na salts of acetate, benzoate, and fluoride during vacuum vapor deposition using a quartz crystal microbalance to measure negative frequency shift (Δf) caused by increasing mass deposited from the same amount of source materials. Cs acetate is also examined. We compare the negative frequency shift-source current (Δf -I) curves of the Na salts with those of organic materials such as tris(8-hydroxyquinoline)aluminum and N ,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine. CH3COONa and C6H5COONa exhibit much lower Δf than the organic materials. CH3COOCs gives much larger Δf than CH3COONa due to the higher atomic weight of Cs. These exhibit clear evidence for alkali metal formation by thermal decomposition during vapor deposition of alkali metal carboxylates.

Frequency Standards and Metrology

NASA Astrophysics Data System (ADS)

Maleki, Lute

2009-04-01

Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and imaging an event horizon (Invited) / S. Doeleman. Optically-pumped space cesium clock for Galileo: results of the breadboard / R. Ruffieux ... [et al.] -- pt. IV. Optical clocks I: lattice clocks. Optical lattice clock: seven years of progress and next steps (Invited) / H. Katori, M. Takamoto and T. Akatsuka. The Yb optical lattice clock (Invited) / N. D. Demke ... [et al.]. Optical Lattice clock with Sr atoms (Invited) / P. G. Westergaard ... [et al.]. Development of an optical clock based on neutral strontium atoms held in a lattice trap / E. A. Curtis ... [et al.]. Decoherence and losses by collisions in a [symbol]Sr lattice clock / J. S. R. Vellore Winfred ... [et al.]. Lattice Yb optical clock and cryogenic Cs fountain at INRIM / F. Levi ... [et al.] -- pt. V. Optical clocks II: ion clocks. [Symbol]Yb+ single-ion optical frequency standards (Invited) / Chr. Tamm ... [et al.]. An optical clock based on a single trapped [symbol]Sr+ ion (Invited) / H. S. Margolis ... [et al.]. A trapped [symbol]Yb+ ion optical frequency standard based on the [symbol] transition (Invited) / P. Gill ... [et al.]. Overview of highly accurate RF and optical frequency standards at the National Research Council of Canada (Invited) / A. A. Madej ... [et al.] -- pt. VI. Optical frequency combs. Extreme ultraviolet frequency combs for spectroscopy (Invited) / A. Ozawa ... [et al.]. Development of an optical clockwork for the single trapped strontium ion standard at 445 THz / J. E. Bernard ... [et al.]. A phase-coherent link between the visible and infrared spectral ranges using a combination of CW OPO and femtosecond laser frequency comb / E. V. Kovalchuk and A. Peters. Improvements to the robustness of a TI: sapphire-based femtosecond comb at NPL / V. Tsatourian ... [et al.] -- pt. VII. Atomic microwave standards. NIST FI and F2 (Invited) / T. P. Heavner ... [et al.]. Atomic fountains for the USNO master clock (Invited) / C. Ekstrom ... [et al.]. The transportable cesium fountain clock NIM5: its construction and performance (Invited) / T. Li ... [et al.].Compensated multi-pole mercury trapped ion frequency standard and stability evaluation of systematic effects (Invited) / E. A. Burt ... [et al.]. Research of frequency standards in SIOM - atomic frequency standards based on coherent storage (Invited) / B. Yan ... [et al.]. The PTB fountain clock ensemble preliminary characterization of the new fountain CSF2 / N. Nemitz ... [et al.]. The pulsed optically pumped clock: microwave and optical detection / S. Micalizio ... [et al.]. Research on characteristics of pulsed optically pumped rubidium frequency standard / J. Deng ... [et al.]. Status of the continuous cold fountain clocks at METAS-LTF / A. Joyet ... [et al.]. Experiments with a new [symbol]Hg+ ion clock / E. A. Burt ... [et al.]. Optimising a high-stability CW laser-pumped rubidium gas-cell frequency standard / C. Affolderbach ... [et al.]. Raman-Ramsey Cs cell atomic clock / R. Boudot ... [et al.] -- pt. VIII. Microwave resonators & oscillators. Solutions and ultimate limits in temperature compensation of metallic cylindrical microwave resonators (Invited) / A. De Marchi. Cryogenic sapphire oscillators (Invited) / J. G. Hartnett, E. N. Ivanov and M. E. Tobar. Ultra-stable optical cavity: design and experiments / J. Millo ... [et al.]. New results for whispering gallery mode cryogenic sapphire maser oscillators / K. Benmessai ... [et al.] -- pt. IX. Advanced techniques. Fundamental noise-limited optical phase locking at Femtowatt light levels (Invited) / J. Dick ... [et al.]. Microwave and optical frequency transfer via optical fibre / G. Marra ... [et al.]. Ultra-stable laser source for the [symbol]Sr+ single-ion optical frequency standard at NRC / P. Dubé, A. A. Madej and J. E. Bernard. Clock laser system for a strontium lattice clock / T. Legero ... [et al.]. Measurement noise floor for a long-distance optical carrier transmission via fiber / G. Grosche ... [et al.]. Optical frequency transfer over 172 KM of installed fiber / S. Crane -- pt. X. Miniature systems. Chip-scale atomic devices: precision atomic instruments based on MEMS (Invited) / J. Kitching ... [et al.]. CSAC - the chip-scale atomic clock (Invited) / R. Lutwak ... [et al.]. Reaching a few 10[symbol] stability level with a compact cold atom clock / F. X. Esnault ... [et al.]. Evaluation of Lin||Lin CPT for compact and high performance frequency standard / E. Breschi ... [et al.] -- pt. XI. Time scales. Atomic time scales TAI and TI(BIPM): present status and prospects (Invited) / G. Petit. Weight functions for biases in atomic frequency standards / J. H. Shirley -- pt. XII. Interferometers. Definition and construction of noise budget in atom interferometry (Invited) / E. D'Ambriosio. Characterization of a cold atom gyroscope (Invited) / A. Landragin ... [et al.]. A mobile atom interferometer for high precision measurements of local gravity / M. Schmidt ... [et al.]. Demonstration of atom interferometer comprised of geometric beam splitters / Hiromitsu Imai and Atsuo Morinaga -- pt. XIII. New directions. Active optical clocks (Invited) / J. Chen. Prospects for a nuclear optical frequency standard based on Thorium-229 (Invited) / E. Peik ... [et al.]. Whispering gallery mode oscillators and optical comb generators (Invited) / A. B. Matsko ... [et al.]. Frequency comparison using energy-time entangled photons / A. Stefanov -- List of participants.

Temporal variation of cesium isotope concentrations and atom ratios in zooplankton in the Pacific off the east coast of Japan.

PubMed

Ikenoue, Takahito; Takata, Hyoe; Kusakabe, Masashi; Kudo, Natsumi; Hasegawa, Kazuyuki; Ishimaru, Takashi

2017-01-04

After the Fukushima Daiichi Nuclear Power Plant accident in March 2011, concentrations of cesium isotopes ( 133 Cs, 134 Cs, and 137 Cs) were measured in zooplankton collected in the Pacific off the east coast of Japan from May 2012 to February 2015. The time series of the data exhibited sporadic 137 Cs concentration peaks in zooplankton. In addition, the atom ratio of 137 Cs/ 133 Cs in zooplankton was consistently high compared to that in ambient seawater throughout the sampling period. These phenomena cannot be explained fully by the bioaccumulation of 137 Cs in zooplankton via ambient seawater intake, the inclusion of resuspended sediment in the plankton sample, or the taxonomic composition of the plankton. Autoradiography revealed highly radioactive particles within zooplankton samples, which could be the main factor underlying the sporadic appearance of high 137 Cs concentrations in zooplankton as well as the higher ratio of 137 Cs/ 133 Cs in zooplankton than in seawater.

Temporal variation of cesium isotope concentrations and atom ratios in zooplankton in the Pacific off the east coast of Japan

PubMed Central

Ikenoue, Takahito; Takata, Hyoe; Kusakabe, Masashi; Kudo, Natsumi; Hasegawa, Kazuyuki; Ishimaru, Takashi

2017-01-01

After the Fukushima Daiichi Nuclear Power Plant accident in March 2011, concentrations of cesium isotopes (133Cs, 134Cs, and 137Cs) were measured in zooplankton collected in the Pacific off the east coast of Japan from May 2012 to February 2015. The time series of the data exhibited sporadic 137Cs concentration peaks in zooplankton. In addition, the atom ratio of 137Cs/133Cs in zooplankton was consistently high compared to that in ambient seawater throughout the sampling period. These phenomena cannot be explained fully by the bioaccumulation of 137Cs in zooplankton via ambient seawater intake, the inclusion of resuspended sediment in the plankton sample, or the taxonomic composition of the plankton. Autoradiography revealed highly radioactive particles within zooplankton samples, which could be the main factor underlying the sporadic appearance of high 137Cs concentrations in zooplankton as well as the higher ratio of 137Cs/133Cs in zooplankton than in seawater. PMID:28051136

Cooling of trapped ions by resonant charge exchange

NASA Astrophysics Data System (ADS)

Dutta, Sourav; Rangwala, S. A.

2018-04-01

The two most widely used ion cooling methods are laser cooling and sympathetic cooling by elastic collisions (ECs). Here, we demonstrate another method of cooling ions that is based on resonant charge exchange (RCE) between the trapped ion and the ultracold parent atom. Specifically, trapped C s+ ions are cooled by collisions with cotrapped, ultracold Cs atoms and, separately, by collisions with cotrapped, ultracold Rb atoms. We observe that the cooling of C s+ ions by Cs atoms is more efficient than the cooling of C s+ ions by Rb atoms. This signals the presence of a cooling mechanism apart from the elastic ion-atom collision channel for the Cs-C s+ case, which is cooling by RCE. The efficiency of cooling by RCE is experimentally determined and the per-collision cooling is found to be two orders of magnitude higher than cooling by EC. The result provides the experimental basis for future studies on charge transport by electron hopping in atom-ion hybrid systems.

Multi-quantum excitation in optically pumped alkali atom: rare gas mixtures

NASA Astrophysics Data System (ADS)

Galbally-Kinney, K. L.; Rawlins, W. T.; Davis, S. J.

2014-03-01

Diode-pumped alkali laser (DPAL) technology offers a means of achieving high-energy gas laser output through optical pumping of the D-lines of Cs, Rb, and K. The exciplex effect, based on weak attractive forces between alkali atoms and polarizable rare gas atoms (Ar, Kr, Xe), provides an alternative approach via broadband excitation of exciplex precursors (XPAL). In XPAL configurations, we have observed multi-quantum excitation within the alkali manifolds which result in infrared emission lines between 1 and 4 μm. The observed excited states include the 42FJ states of both Cs and Rb, which are well above the two-photon energy of the excitation laser in each case. We have observed fluorescence from multi-quantum states for excitation wavelengths throughout the exciplex absorption bands of Cs-Ar, Cs-Kr, and Cs-Xe. The intensity scaling is roughly first-order or less in both pump power and alkali concentration, suggesting a collisional energy pooling excitation mechanism. Collisional up-pumping appears to present a parasitic loss term for optically pumped atomic systems at high intensities, however there may also be excitation of other lasing transitions at infrared wavelengths.

CS and IOS approximations for fine structure transitions in Na(/sup 2/P)--He(/sup 1/S) collisions

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

Fitz, D.E.; Kouri, D.J.

1980-11-15

The l-average CS and IOS approximations are extended to treat fine structure transitions in /sup 2/P atom--/sup 1/S atom scattering. Calculations of degeneracy averaged probabilities and differential cross sections for Na(/sup 2/P)+He(/sup 1/S) collisions in the CS and IOS methods agree well with the CC results. The present nonunitarized form of the CS approximation fails to properly predict all of the jm..-->..j'm' sections and in particular leads to a selection rule forbidding jm..-->..j--m transitions for j=half-odd integer values.

Potential energy surfaces of the low-lying electronic states of the Li + LiCs system

NASA Astrophysics Data System (ADS)

Jasik, P.; Kilich, T.; Kozicki, J.; Sienkiewicz, J. E.

2018-03-01

Ab initio quantum chemistry calculations are performed for the mixed alkali triatomic system. Global minima of the ground and first excited doublet states of the trimer are found and Born-Oppenheimer potential energy surfaces of the Li atom interacting with the LiCs molecule were calculated for these states. The lithium atom is placed at various distances and bond angles from the lithium-caesium dimer. Three-body nonadditive forces of the Li2Cs molecule in the global minimum are investigated. Dimer-atom interactions are found to be strongly attractive and may be important in the experiments, particularly involving cold alkali polar dimers.

Tree-ring strontium-90 and cesium-137 as potential indicators of radioactive pollution.

PubMed

Kagawa, Akira; Aoki, Toru; Okada, Naoki; Katayama, Yukio

2002-01-01

To examine whether tree rings can be used to detect or assess local historical 90Sr or 137Cs fallout, such as that resulting from the Hiroshima atomic bomb, radial distribution of 90Sr and 137Cs in trees was examined. We studied a gymnosperm [Japanese cedar, Cryptomeria japonica (L. f.) D. Don] and an angiosperm (Japanese persimmon, Diospyros kaki Thunb.) tree species from the vicinity of the atomic bomb hypocenter, and from other locations in Japan. A significant amount of 137Cs was detected in tree rings formed before 1945, indicating lateral migration of Cs. In contrast, the specific activity of 90Sr in the Hiroshima Japanese cedar showed the highest level in 1945, due to relatively immobile characteristics of Sr compared with Cs. Strontium-90 and Sr analyses in tree rings helped identify and distinguish between residual 90Sr activity from the Hiroshima atomic bomb and the atmospheric nuclear testing. This indicates the possibility of detecting or assessing previous local 90Sr pollution through with treering analysis.

Laser-Free Cold-Atom Gymnastics

NASA Astrophysics Data System (ADS)

Gould, Harvey; Feinberg, Benedict; Munger, Charles T., Jr.; Nishimura, Hiroshi

2017-01-01

We have performed beam transport simulations on ultra cold (2 μK) and cold (130 μK) neutral Cs atoms in the F = M = + 4 (magnetic weak-field seeking) ground state. We use inhomogeneous magnetic fields to focus and accelerate the atoms. Acceleration of neutral atoms by an inhomogeneous magnetic field was demonstrated by Stern and Gerlach in 1922. In the simulations, a two mm diameter cloud of atoms is released to fall under gravity. A magnetic coil focuses the falling atoms. After falling 41 cm, the atoms are reflected in the magnetic fringe field of a solenoid. They return to their starting height, about 0.7 s later, having passed a second time through the focusing coil. The simulations show that > 98 % of ultra cold Cs atoms and > 70 % of cold Cs atoms will survive at least 15 round trips (assuming perfect vacuum). More than 100 simulations were run to optimize coil currents and focusing coil diameter and height. Simulations also show that atoms can be launched into a fountain. An experimental apparatus to test the simulations, is being constructed. This technique may find application in atomic fountain clocks, interferometers, and gravitometers, and may be adaptable for use in microgravity. It may also work with Bose-Einstein condensates of paramagnetic atoms.

Observation of EIA in closed and open caesium atomic system

NASA Astrophysics Data System (ADS)

Zhao, Jian-Ming; Zhao, Yan-Ting; Huang, Tao; Xiao, Lian-Tuan; Jia, Suo-Tang

2005-04-01

We present an experimental study on electromagnetically induced absorption (EIA) in the closed transition of a degenerate two-level Cs atomic system. The coupling and probe lasers coupled with the transition 6S1/2F=4 → 6P3/2F'=5 of caesium atom. The signal of EIA was obtained and the frequency detuning and intensity effect of the pumping laser were experimentally investigated. The EIA signal in 6S1/2 F=4 → 6P3/2 F'=4 and 6S1/2 F=4 → 6P3/2 F'=3 open transitions was also obtained. As the repumping laser couples with the transition of 6S1/2 F=3 → 6P3/2 F'=4, the EIA signal is increased due to the hyperfine optical pumping.

Nonlinearity, resonance, charging, and motion at the atomic scale studied with scanning tunneling microscopes

NASA Astrophysics Data System (ADS)

Tu, Xiuwen

2008-10-01

Several novel phenomena at the single-atom and single-molecule level occurring on the surfaces of single crystals were studied with home-built low temperature scanning tunneling microscopes. The results revealed intriguing properties of single atoms and single molecules, including nonlinearity, resonance, charging, and motion. First, negative differential resistance (NDR) was observed in the dI/dV spectra for single copper-phthalocyanine (CuPc) molecules adsorbed on one- and two-layer sodium bromide (NaBr), but not for single CuPc molecules adsorbed on three-layer NaBr, all grown on a NiAl(110) surface. This transition from NDR to the absence of NDR was explained as the result of competing effects in the double-barrier tunnel junction (DBTJ) and was reproduced in a calculation based on a resonant-tunneling model. Second, the nonlinearity of the STM junction due to a single manganese (Mn) atom or MnCO molecule adsorbed on a NiAl(110) surface was used to rectify microwave irradiation. The resulting rectification current was shown to be sensitive to the spin-splitting of the electronic states of the Mn atom and to the vibrations of the MnCO molecule. Next, the ordering of cesium (Cs) atoms adsorbed on a Au(111) surface and a NiAl(110) surface was imaged in real space. Because of charge transfer to the substrates, Cs adatoms were positively charged on both surfaces. Even at 12 K, Cs adatoms were able to move and adjust according to coverage. On Au(111), the Cs first layer had a quasi-hexagonal lattice and islands of the second Cs layer did not appear until the first was completed. On NiAl(110), a locally disordered Cs first layer was observed before a locally ordered layer appeared at higher coverages. The cation-pi interactions were then studied at the single molecular level. We were able to form cation-pi complexes such as Cs···DSB, Cs···DSB···Cs, Rb···DSB, and Rb···ZnEtiol controllably by manipulation with the STM tip. We could also separate these complexes controllably by voltage pulses. STM imaging and spectroscopy revealed precise information about the atomic and electronic structure of these cation-pi complexes. Finally, electron transport through single atoms and molecules in a double-barrier tunnel junction (DBTJ) was examined. Charge bistability was observed for single ZnEtioI molecules adsorbed in several different conformations on ultrathin aluminum oxide. A sudden decrease in local apparent barrier height (LABH) was observed at the onset of an adsorbate electronic orbital for single ZnEtioI molecules and Cs atoms supported by the ultrathin aluminum oxide. The resonant-tunneling model, which was proposed to explain the transition from NDR to the absence of NDR, was found useful in explaining the sudden decrease in LABH, too. NDR, bipolar tunneling, and vibronic states were also observed and discussed in the context of DBTJ.

Time evolution of negative ion profile in a large cesiated negative ion source applicable to fusion reactors

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

Yoshida, M., E-mail: yoshida.masafumi@jaea.go.jp; Hanada, M.; Kojima, A.

2016-02-15

To understand the physics of the cesium (Cs) recycling in the large Cs-seeded negative ion sources relevant to ITER and JT-60SA with ion extraction area of 45-60 cm × 110-120 cm, the time evolution of the negative ion profile was precisely measured in JT-60SA where the ion extraction area is longitudinally segmented into 5. The Cs was seeded from the oven at 180 °C to the ion source. After 1 g of Cs input, surface production of the negative ions appeared only in the central segment where a Cs nozzle was located. Up to 2 g of Cs, the negative ionmore » profile was longitudinally expanded over full ion extraction area. The measured time evolution of the negative ion profile has the similar tendency of distribution of the Cs atoms that is calculated. From the results, it is suggested that Cs atom distribution is correlated with the formation of the negative ion profile.« less

Sub-picosecond timing fluctuation suppression in laser-based atmospheric transfer of microwave signal using electronic phase compensation

NASA Astrophysics Data System (ADS)

Chen, Shijun; Sun, Fuyu; Bai, Qingsong; Chen, Dawei; Chen, Qiang; Hou, Dong

2017-10-01

We demonstrated a timing fluctuation suppression in outdoor laser-based atmospheric radio-frequency transfer over a 110 m one-way free-space link using an electronic phase compensation technique. Timing fluctuations and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process. With transferring a 1 GHz microwave signal over a timing fluctuation suppressed transmission link, the total root-mean-square (rms) timing fluctuation was measured to be 920 femtoseconds in 5000 s, with fractional frequency instability on the order of 1 × 10-12 at 1 s, and order of 2 × 10-16 at 1000 s. This atmospheric frequency transfer scheme with the timing fluctuation suppression technique can be used to fast build an atomic clock-based frequency free-space transmission link since its stability is superior to a commercial Cs and Rb clock.

Cs2Bi(PO4)(WO4)

PubMed Central

Terebilenko, Kateryna V.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.

2009-01-01

Dicaesium bis­muth(III) phosphate(V) tungstate(VI), Cs2Bi(PO4)(WO4), has been synthesized during complex investigation in a molten pseudo-quaternary Cs2O–Bi2O3–P2O5–WO3 system. It is isotypic with K2Bi(PO4)(WO4). The three-dimensional framework is built up from [Bi(PO4)(WO4)] nets, which are organized by adhesion of [BiPO4] layers and [WO4] tetra­hedra above and below of those layers. The inter­stitial space is occupied by Cs atoms. Bi, W and P atoms lie on crystallographic twofold axes. PMID:21577386

Application of Optical Coherence Tomography and Contrast Sensitivity Test for Observing Fundus Changes of Patients With Pregnancy-Induced Hypertension Syndrome.

PubMed

Wang, Zhixue; Zou, Yuanyuan; Li, Wenying; Wang, Xueyan; Zhang, Min; Wang, Wenying

2015-11-01

This study was aimed to investigate the fundus changes of patients with pregnancy-induced hypertension syndrome (PIHS) using optical coherence tomography (OCT) technology and contrast sensitivity (CS) tests.Ninety-eight patients with PIHS underwent routine eye examinations including vision correction, fundus examination, OCT, and CS tests. The CS test was performed at low, medium, and high frequency, respectively. Moreover, the difference in CS tests between 2 groups was analyzed by independent-samples T test. The Kruskal-Wallis rank sum test and linear regression model were used to detect the correlation of OCT with CS, respectively. Meanwhile Satterthwaite approximate T test was adopted for pairwise comparisons after nonparametric analysis of variance.The OCT test revealed that 56.76% of the examined eyes showed shallow retinal detachment in the macula lutea and around the optic disk. The differences in CS at each spatial frequency between the case and control group were statistically significant (P < 0.01). Besides, OCT manifestations were associated with CS at each spacial frequency including 1.5, 3, 6, 12, and 18 frequency (P < 0.01). And patients with abnormal manifestations of OCT showed lower CS at each spacial frequency than those without abnormal OCT manifestations. What's more the OCT manifestation 1 showed the greatest impact on CS at each spacial frequency.The results showed that abnormal OCT manifestations were correlated with CS in PIHS. OCT and CS tests might be valuable methods in observing fundus changes for PIHS patients.

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

PubMed Central

Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

2013-01-01

Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations. PMID:23949184

135Cs activity and 135Cs/137Cs atom ratio in environmental samples before and after the Fukushima Daiichi Nuclear Power Plant accident

PubMed Central

Yang, Guosheng; Tazoe, Hirofumi; Yamada, Masatoshi

2016-01-01

135Cs/137Cs is a potential tracer for radiocesium source identification. However, due to the challenge to measure 135Cs, there were no 135Cs data available for Japanese environmental samples before the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. It was only 3 years after the accident that limited 135Cs values could be measured in heavily contaminated environmental samples. In the present study, activities of 134Cs, 135Cs, and 137Cs, along with their ratios in 67 soil and plant samples heavily and lightly contaminated by the FDNPP accident were measured by combining γ spectrometry with ICP-MS/MS. The arithmetic means of the 134Cs/137Cs activity ratio (1.033 ± 0.006) and 135Cs/137Cs atom ratio (0.334 ± 0.005) (decay corrected to March 11, 2011), from old leaves of plants collected immediately after the FDNPP accident, were confirmed to represent the FDNPP derived radiocesium signature. Subsequently, for the first time, trace 135Cs amounts before the FDNPP accident were deduced according to the contribution of global and FDNPP accident-derived fallout. Apart from two soil samples with a tiny global fallout contribution, contributions of global fallout radiocesium in other soil samples were observed to be 0.338%–52.6%. The obtained 135Cs/137Cs database will be useful for its application as a geochemical tracer in the future. PMID:27052481

Plutonium isotopes and 241Am in the atmosphere of Lithuania: A comparison of different source terms

NASA Astrophysics Data System (ADS)

Lujanienė, G.; Valiulis, D.; Byčenkienė, S.; Šakalys, J.; Povinec, P. P.

2012-12-01

137Cs, 241Am and Pu isotopes collected in aerosol samples during 1994-2011 were analyzed with special emphasis on better understanding of Pu and Am behavior in the atmosphere. The results from long-term measurements of 240Pu/239Pu atom ratios showed a bimodal frequency distribution with median values of 0.195 and 0.253, indicating two main sources contributing to the Pu activities at the Vilnius sampling station. The low Pu atom ratio of 0.141 could be attributed to the weapon-grade plutonium derived from the nuclear weapon test sites. The frequency of air masses arriving from the North-West and North-East correlated with the Pu atom ratio indicating the input from the sources located in these regions (the Novaya Zemlya test site, Siberian nuclear plants), while no correlation with the Chernobyl region was observed. Measurements carried out during the Fukushima accident showed a negligible impact of this source with Pu activities by four orders of magnitude lower as compared to the Chernobyl accident. The activity concentration of actinides measured in the integrated sample collected in March-April, 2011 showed a small contribution of Pu with unusual activity and atom ratios indicating the presence of the spent fuel of different origin than that of the Chernobyl accident.

Peptide protected gold clusters: chemical synthesis and biomedical applications

NASA Astrophysics Data System (ADS)

Yuan, Qing; Wang, Yaling; Zhao, Lina; Liu, Ru; Gao, Fuping; Gao, Liang; Gao, Xueyun

2016-06-01

Bridging the gap between atoms and nanoparticles, noble metal clusters with atomic precision continue to attract considerable attention due to their important applications in catalysis, energy transformation, biosensing and biomedicine. Greatly different to common chemical synthesis, a one-step biomimetic synthesis of peptide-conjugated metal clusters has been developed to meet the demand of emerging bioapplications. Under mild conditions, multifunctional peptides containing metal capturing, reactive and targeting groups are rationally designed and elaborately synthesized to fabricate atomically precise peptide protected metal clusters. Among them, peptide-protected Au Cs (peptide-Au Cs) possess a great deal of exceptional advantages such as nanometer dimensions, high photostability, good biocompatibility, accurate chemical formula and specific protein targeting capacity. In this review article, we focus on the recent advances in potential theranostic fields by introducing the rising progress of peptide-Au Cs for biological imaging, biological analysis and therapeutic applications. The interactions between Au Cs and biological systems as well as potential mechanisms are also our concerned theme. We expect that the rapidly growing interest in Au Cs-based theranostic applications will attract broader concerns across various disciplines.

Practical method for transversely measuring the spin polarization of optically pumped alkali atoms

NASA Astrophysics Data System (ADS)

Ding, Zhichao; Yuan, Jie; Long, Xingwu

2018-06-01

A practical method to measure the spin polarization of optically pumped alkali atoms is demonstrated. In order to realize transverse measurement, the transverse spin component of spin-polarized alkali atoms is created by a rotating exciting magnetic field, and detected using the optical rotation of a near-resonant probe beam for realizing a high detection sensitivity. The dependency of the optical rotation on the spin polarization of 133Cs atoms is derived theoretically and verified experimentally. By changing the direction of the rotating magnetic field, we realize the transverse measurement of the spin polarization of 133Cs atoms in either ground-state hyperfine level.

Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

NASA Astrophysics Data System (ADS)

Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

2016-09-01

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

Application of Optical Coherence Tomography and Contrast Sensitivity Test for Observing Fundus Changes of Patients With Pregnancy-Induced Hypertension Syndrome

PubMed Central

Wang, Zhixue; Zou, Yuanyuan; Li, Wenying; Wang, Xueyan; Zhang, Min; Wang, Wenying

2015-01-01

Abstract This study was aimed to investigate the fundus changes of patients with pregnancy-induced hypertension syndrome (PIHS) using optical coherence tomography (OCT) technology and contrast sensitivity (CS) tests. Ninety-eight patients with PIHS underwent routine eye examinations including vision correction, fundus examination, OCT, and CS tests. The CS test was performed at low, medium, and high frequency, respectively. Moreover, the difference in CS tests between 2 groups was analyzed by independent-samples T test. The Kruskal–Wallis rank sum test and linear regression model were used to detect the correlation of OCT with CS, respectively. Meanwhile Satterthwaite approximate T test was adopted for pairwise comparisons after nonparametric analysis of variance. The OCT test revealed that 56.76% of the examined eyes showed shallow retinal detachment in the macula lutea and around the optic disk. The differences in CS at each spatial frequency between the case and control group were statistically significant (P < 0.01). Besides, OCT manifestations were associated with CS at each spacial frequency including 1.5, 3, 6, 12, and 18 frequency (P < 0.01). And patients with abnormal manifestations of OCT showed lower CS at each spacial frequency than those without abnormal OCT manifestations. What's more the OCT manifestation 1 showed the greatest impact on CS at each spacial frequency. The results showed that abnormal OCT manifestations were correlated with CS in PIHS. OCT and CS tests might be valuable methods in observing fundus changes for PIHS patients. PMID:26554764

Dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs

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

McCarron, D. J.; Cho, H. W.; Jenkin, D. L.

2011-07-15

We report the formation of a dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of {sup 133}Cs via elastic collisions with {sup 87}Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2x10{sup 4} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the {sup 87}Rb during the cooling, we create single-species {sup 133}Cs condensates of up to 6x10{sup 4} atoms.

Lorentz-symmetry test at Planck-scale suppression with nucleons in a spin-polarized 133Cs cold atom clock

NASA Astrophysics Data System (ADS)

Pihan-Le Bars, H.; Guerlin, C.; Lasseri, R.-D.; Ebran, J.-P.; Bailey, Q. G.; Bize, S.; Khan, E.; Wolf, P.

2017-04-01

We introduce an improved model that links the frequency shift of the 133Cs hyperfine Zeeman transitions |F =3 ,mF ⟩↔|F =4 ,mF ⟩ to the Lorentz-violating Standard Model extension (SME) coefficients of the proton and neutron. The new model uses Lorentz transformations developed to second order in boost and additionally takes the nuclear structure into account, beyond the simple Schmidt model used previously in Standard Model extension analyses, thereby providing access to both proton and neutron SME coefficients including the isotropic coefficient c˜T T. Using this new model in a second analysis of the data delivered by the FO2 dual Cs/Rb fountain at Paris Observatory and previously analyzed in [1], we improve by up to 13 orders of magnitude the present maximum sensitivities for laboratory tests [2] on the c˜Q, c˜T J, and c˜T T coefficients for the neutron and on the c˜Q coefficient for the proton, reaching respectively 10-20, 10-17, 10-13, and 10-15 GeV .

Study on photoemission surface of varied doping GaN photocathode

NASA Astrophysics Data System (ADS)

Qiao, Jianliang; Du, Ruijuan; Ding, Huan; Gao, Youtang; Chang, Benkang

2014-09-01

For varied doping GaN photocathode, from bulk to surface the doping concentrations are distributed from high to low. The varied doping GaN photocathode may produce directional inside electric field within the material, so the higher quantum efficiency can be obtained. The photoemission surface of varied doping GaN photocathode is very important to the high quantum efficiency, but the forming process of the surface state after Cs activation or Cs/O activation has been not known completely. Encircling the photoemission mechanism of varied GaN photocathode, considering the experiment phenomena during the activation and the successful activation results, the varied GaN photocathode surface model [GaN(Mg):Cs]:O-Cs after activation with cesium and oxygen was given. According to GaN photocathode activation process and the change of electronic affinity, the comparatively ideal NEA property can be achieved by Cs or Cs/O activation, and higher quantum efficiency can be obtained. The results show: The effective NEA characteristic of GaN can be gotten only by Cs. [GaN(Mg):Cs] dipoles form the first dipole layer, the positive end is toward the vacuum side. In the activation processing with Cs/O, the second dipole layer is formed by O-Cs dipoles, A O-Cs dipole includes one oxygen atom and two Cs atoms, and the positive end is also toward the vacuum side thus the escape of electrons can be promoted.

Correlations among steroid fear, acceptability, usage frequency, quality of life and disease severity in childhood eczema.

PubMed

Hon, Kam Lun; Tsang, Yin Ching K; Pong, Nga Hin; Luk, David C K; Lee, Vivian W; Woo, Wing Man; Lam, Chak Yiu Justin; Yeung, Yun Ting Eunice; Chau, Yiu Shing Sunny; Chui, Ka Kam Kenneth; Li, Ka Hin Gabriel; Leung, Ting Fan

2015-10-01

Topical corticosteroids (CSs) are the mainstay of treatment for eczema but CS phobia and fears are prevalent and influence therapeutic efficacy. To quantify if CS acceptability and fear affect patients' quality-of-life (QoL). Patients with eczema managed in the pediatric dermatology outpatient clinic of a university hospital were surveyed. Nottingham Eczema Severity Score (NESS) for severity, Children's Dermatology Life Quality Index (CDLQI) for QoL, CS fear, acceptability and reported frequency of CS use were measured with quantified questions. CS fears were prevalent among parents and caregivers of patients with eczema. Fifty-eight percent of parents reported general acceptability of CS as being very good or good, and many applied CS to their child regularly every week. However, >40% of parents reported CS fear "always" or "often", 41% reported that they "always" or "often" apply CS only when eczema got worse, 57% would discuss CS fear with their doctors, 30% would request CS-sparing medications and 14% "always" or "often" use traditional Chinese herbal medicine. Fears were predominantly interpersonal and less often iatrogenic in nature. Skin problems were the most concerned side effects of CS. CS acceptability, frequency of CS usage, CS fear and usage of alternative medications were independent domains in eczema management: CS fears correlated with CDLQI; CS usage frequency correlated with NESS and negatively with parental education; and CS acceptability correlated with parental education. Ordinal logistic regressions showed worse QoL was associated with more CS fear (odds ratio: 1.092 [95% CI: 1.023-1.165], p = 0.008). The extent of CS fears is independent of CS acceptability, but correlates with patients' QoL. Desensitization of parental CS fears should be integral part of eczema education and therapeutics in order to improve therapeutic efficacy and patients' QoL.

Interactions and low-energy collisions between an alkali ion and an alkali atom of a different nucleus

NASA Astrophysics Data System (ADS)

Rakshit, Arpita; Ghanmi, Chedli; Berriche, Hamid; Deb, Bimalendu

2016-05-01

We study theoretically interaction potentials and low-energy collisions between different alkali atoms and alkali ions. Specifically, we consider systems such as X + {{{Y}}}+, where X({{{Y}}}+) is either Li(Cs+) or Cs(Li+), Na(Cs+) or Cs(Na+) and Li(Rb+) or Rb(Li+). We calculate the molecular potentials of the ground and first two excited states of these three systems using a pseudopotential method and compare our results with those obtained by others. We derive ground-state scattering wave functions and analyze the cold collisional properties of these systems for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order 1 K, one needs to take into account at least 60 partial waves. The low-energy scattering properties calculated in this paper may serve as a precursor for experimental exploration of quantum collisions between an alkali atom and an alkali ion of a different nucleus.

Electron Impact Ionization Cross Sections in Rb and Cs.

NASA Astrophysics Data System (ADS)

Reddish, T. J.; Lukomski, M.; Sutton, S.; Kedzierski, W.; McConkey, J. W.; Bartschat, K.; Bartlett, P. L.; Stelbovics, A. T.; Bray, I.

2006-05-01

We present a new atom trapping technique for determining absolute, total ionisation cross sections (TICS) out of an excited atom. The novel feature of this method is in utilizing Doppler cooling of neutral atoms to determine ionisation cross sections. This fluorescence-monitoring experiment, which is a variant of the `trap loss' technique, has enabled us to obtain the experimental electron impact ionisation cross sections out of the Cs 6^2P3/2 excited state between 7 - 400 eV. New CCC, R-Matrix with Pseudo-States (RMPS), and Born approximation single ionisation cross sections (SICS) are also presented for both the ground and excited states of Cs and Rb, and compared with the available experimental data. The comparison of the results reveals the importance of the autoionisation and multiple ionisation contributions to the TICS. The autoionisation contribution appears to be substantial for ionisation out of the Cs 6^2P and Rb 5^2P excited states; ˜ 3-4 larger than the direct ionisation contribution predicted by CCC at ˜ 30-50 eV. This surprising result shows the importance of multi-electron processes in determining the ionisation cross sections of heavy alkali atoms.

Novel rattling of K atoms in aluminium-doped defect pyrochlore tungstate

NASA Astrophysics Data System (ADS)

Shoko, Elvis; Kearley, Gordon J.; Peterson, Vanessa K.; Mutka, Hannu; Koza, Michael M.; Yamaura, Jun-ichi; Hiroi, Zenji; Thorogood, Gordon J.

2014-07-01

Rattling dynamics have been identified as fundamental to superconductivity in defect pyrochlore osmates and aluminium vanadium intermetallics, as well as low thermal conductivity in clathrates and filled skutterudites. Combining inelastic neutron scattering (INS) measurements and ab initio molecular dynamics (MD) simulations, we use a new approach to investigate rattling in the Al-doped defect pyrochlore tungstates: AAl0.33W1.67O6 (A = K, Rb, Cs). We find that although all the alkali metals rattle, the rattling of the K atoms is unique, not only among the tungstates but also among the analogous defect osmates, KOs2O6 and RbOs2O6. Detailed analysis of the MD trajectories reveals that two unique features set the K dynamics apart from the rest, namely, (1) quasi one-dimensional local diffusion within a cage, and (2) vibration at a range of frequencies. The local diffusion is driven by strongly anharmonic local potentials around the K atoms exhibiting a double-well structure in the direction of maximum displacement, which is also the direction of local diffusion. On the other hand, vibration at a range of frequencies is a consequence of the strong anisotropy in the local potentials around the K atoms as revealed by directional magnitude spectra. We present evidence to show that it is the smaller size rather than the smaller mass of the K rattler which leads to the unusual dynamics. Finally, we suggest that the occurrence of local diffusion and vibration at a range of frequencies in the dynamics of a single rattler, as found here for the K atoms, may open new possibilities for phonon engineering in thermoelectric materials.

Surface sensitization mechanism on negative electron affinity p-GaN nanowires

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Feng, Shu; Lu, Feifei

2018-03-01

The surface sensitization is the key to prepare negative electron affinity photocathode. The thesis emphasizes on the study of surface sensitization mechanism of p-type doping GaN nanowires utilizing first principles based on density function theory. The adsorption energy, work function, dipole moment, geometry structure, electronic structure and optical properties of Mg-doped GaN nanowires surfaces with various coverages of Cs atoms are investigated. The GaN nanowire with Mg doped in core position is taken as the sensitization base. At the initial stage of sensitization, the best adsorption site for Cs atom on GaN nanowire surface is BN, the bridge site of two adjacent N atoms. Surface sensitization generates a p-type internal surface with an n-type surface state, introducing a band bending region which can help reduce surface barrier and work function. With increasing Cs coverage, work functions decrease monotonously and the "Cs-kill" phenomenon disappears. For Cs coverage of 0.75 ML and 1 ML, the corresponding sensitization systems reach negative electron affinity state. Through surface sensitization, the absorption curves are red shifted and the absorption coefficient is cut down. All theoretical calculations can guide the design of negative electron affinity Mg doped GaN nanowires photocathode.

Fundamental studies of desulfurization processes: reaction of methanethiol on ZnO and Cs/ZnO

NASA Astrophysics Data System (ADS)

Dvorak, Joseph; Jirsak, Tomas; Rodriguez, José A.

2001-05-01

The reaction of methanethiol on ZnO and Cs promoted ZnO surfaces has been studied with synchrotron based photoemission and thermal desorption spectroscopy. On ZnO, methanethiol undergoes selective reaction to produce carbon monoxide (37-58%), methane (23-38%), formaldehyde (12-15%), ethane (1-11%), and a mixture of ethylene and acetylene (3-13%). At low temperatures (<100 K), methanethiol reacts to yield thiolate intermediate bound to Zn 2+ cations. The thiolate is stable to 500 K. Above this temperature, C-S bond cleavage occurs to yield methyl intermediate and atomic S. Carbon is removed from the surface as gaseous products above 500 K, and atomic sulfur remains bound to the zinc sites of the surface. Submonolayer amounts of cesium do not have a significant promotional effect on C-S bond cleavage, whereas Cs multilayers are found to significantly lower the activation barrier for C-S bond cleavage. This study illustrates the chemistry associated with the desulfurization of thiols on a catalytically relevant oxide surface.

Characterization of the water of crystallization in CsMnCl3.2H2O (2D2O) by Raman scattering

NASA Astrophysics Data System (ADS)

Jia, Weiyi; Strauss, E.; Yen, W. M.; Xia, Kehui; Zhao, Minguang

1989-06-01

Raman spectra of CsMnCl3.2H2O (2D2O) (CMC) were measured at low temperatures. The spectra demonstrated features which are related to the chain and layered structures of the compound. The vibration characteristics of the water of crystallization were investigated in detail, allowing us to derive the spatial orientation of the water molecules and the direction of their hydrogen bonds. Strong Raman scattering from the OH stretching mode in the (zz) configuration indicates the existence of hydrogen bonds linking the layers along the z axis. Various combination frequencies of the water vibrations were observed; for example, the OH (OD) stretching mode is seen to couple to vibrations of oxygen and chlorine atoms. These combination modes play an important role in quenching 4T1-->6A1 electronic transition of Mn2+ ions through multiphonon nonradiative processes.

Phase transition studied by 7Li nuclear magnetic resonance in LiXSO4 (X = K, Rb, Cs and NH4) single crystals

NASA Astrophysics Data System (ADS)

Lim, Ae Ran; Choh, Sung Ho; Jeong, Se-Young

2000-11-01

The temperature dependences of 7Li nuclear magnetic resonance in LiXSO4 (X = K, Rb, Cs, and NH4) single crystals grown by the slow evaporation method have been investigated by employing a Bruker FT NMR spectrometer. From the experimental data, the nuclear quadrupole constant, the asymmetry parameter and the principal axes of the EFG tensor were determined, and the results were compared with the crystal structure. The temperature dependences of the quadrupole parameters were explained with a single torsional mode of the Li-O bond by the Bayer theory. All the LiO4 tetrahedra in four different crystals showed torsional motion about the X-axis of the EFG tensor. Based on these results, the differences in atomic weight of X in the LiXSO4 single crystals are responsible for the differences in the torsional angular frequencies.

A novel Cs-(129)Xe atomic spin gyroscope with closed-loop Faraday modulation.

PubMed

Fang, Jiancheng; Wan, Shuangai; Qin, Jie; Zhang, Chen; Quan, Wei; Yuan, Heng; Dong, Haifeng

2013-08-01

We report a novel Cs-(129)Xe atomic spin gyroscope (ASG) with closed-loop Faraday modulation method. This ASG requires approximately 30 min to start-up and 110 °C to operate. A closed-loop Faraday modulation method for measurement of the optical rotation was used in this ASG. This method uses an additional Faraday modulator to suppress the laser intensity fluctuation and Faraday modulator thermal induced fluctuation. We theoretically and experimentally validate this method in the Cs-(129)Xe ASG and achieved a bias stability of approximately 3.25 °∕h.

Cs promoted oxidation of Zn and CuZn surfaces: a combined experimental and theoretical study

NASA Astrophysics Data System (ADS)

Chaturvedi, Sanjay; Rodriguez, JoséA.; Hrbek, Jan

1997-07-01

The interaction of O 2 with Zn, {Cs}/{Zn} and {Cs}/{CuZn} surfaces was investigated using photoemission and ab initio self-consistent-field (SCF) calculations. On zinc films, the sticking probability of O 2 is extremely low (10 -3-10 -2), and O 2 exposures in the range of 10 3 to 10 4 langmuirs are necessary to produce a significant adsorption of oxygen and the transformation of metallic zinc into zinc oxide. The presence of sub monolayer coverages of cesium enhances the oxidation rate of zinc by 2-3 orders of magnitude. In the {Cs}/{Zn} system, the alkali atom donates electrons to zinc. This charge transfer facilitates the formation of Zn→O 2 dative bonds and breaking of the OO bond. For the coadsorption of Cs and O 2 on Zn(001), the larger the electron transfer from Zn into the O 2 (1 πg) orbitals, the bigger the adsorption energy of the molecule and the elongation of the OO bond. In general, cesium does not promote the oxidation of copper. In the {Cs}/{CuZn} system, copper withdraws electrons from zinc. The presence of copper in the {Cs}/{CuZn} system inhibits the oxidation of the Zn component compared with the {Cs}/{Zn} system by lowering the electron density on the Zn atoms. After exposing the {Cs}/{CuZn} system to O 2, zinc is oxidized at a rate that is larger than that found for clean CuZn surfaces and smaller than seen in {Cs}/{Zn} surfaces. Molecular hydrogen is found to have no effect on oxidized Cu, Zn and CuZn films. However, atomic hydrogen reduces ZnO to metallic zinc and CuO to Cu 2O. In the oxidized CuZn alloy, CuO is reduced first followed by the reduction of ZnO. A comparison of the behavior of O 2/Cs/Zn and H 2O/Cs/Zn systems shows that while O 2 causes severe oxidation of Cs promoted Zn surfaces, H 2O has little or no effect.

Development and Measurement of Guidelines-Based Quality Indicators of Caesarean Section Care in the Netherlands: A RAND-Modified Delphi Procedure and Retrospective Medical Chart Review

PubMed Central

de Boer, Karin; Burggraaf, Henriëtte; Derks, Jan B.; van Dijk, Det; van Dillen, Jeroen; Dirksen, Carmen D.; Duvekot, Johannes J.; Franx, Arie; Hasaart, Tom H. M.; Huisjes, Anjoke J. M.; Kolkman, Diny; Kwee, Anneke; Mol, Ben W.; van Pampus, Mariëlle G.; de Roon-Immerzeel, Alieke; van Roosmalen, Jos J. M.; Roumen, Frans J. M. E.; Smid-Koopman, Ellen; Spaans, Wilbert A.; Visser, Harry; van Wijngaarden, Wim J.; Willekes, Christine; Wouters, Maurice G. A. J.

2016-01-01

Background There is an ongoing discussion on the rising CS rate worldwide. Suboptimal guideline adherence may be an important contributor to this rise. Before improvement of care can be established, optimal CS care in different settings has to be defined. This study aimed to develop and measure quality indicators to determine guideline adherence and identify target groups for improvement of care with direct effect on caesarean section (CS) rates. Method Eighteen obstetricians and midwives participated in an expert panel for systematic CS quality indicator development according to the RAND-modified Delphi method. A multi-center study was performed and medical charts of 1024 women with a CS and a stratified and weighted randomly selected group of 1036 women with a vaginal delivery were analysed. Quality indicator frequency and adherence were scored in 2060 women with a CS or vaginal delivery. Results The expert panel developed 16 indicators on planned CS and 11 indicators on unplanned CS. Indicator adherence was calculated, defined as the number of women in a specific obstetrical situation in which care was performed as recommended in both planned and unplanned CS settings. The most frequently occurring obstetrical situations with low indicator adherence were: 1) suspected fetal distress (frequency 17%, adherence 46%), 2) non-progressive labour (frequency 12%, CS performed too early in over 75%), 3) continuous support during labour (frequency 88%, adherence 37%) and 4) previous CS (frequency 12%), with adequate counselling in 15%. Conclusions We identified four concrete target groups for improvement of obstetrical care, which can be used as a starting point to reduce CS rates worldwide. PMID:26783742

Rydberg-Ritz analysis and quantum defects for Rb and Cs atoms on helium nanodroplets

NASA Astrophysics Data System (ADS)

Lackner, Florian; Krois, Günter; Ernst, Wolfgang E.

2013-08-01

A Rydberg-Ritz approach is used for the interpretation of Rb-He? and Cs-He? Rydberg states and Rydberg series. Variations of the quantum defects within a Rydberg series give insight into the interaction between the alkali atom's valence electron and the superfluid helium droplet. A screening of the valence electron from the alkali atom core by the helium droplet is observed for high Rydberg states. For states with lower principal quantum number, the effect decreases and the quantum defects are found to lie closer to free atom values, indicating an increased probability for the electron to be found inside the alkali atom core. An investigation of the spin-orbit splitting of the Cs-He? nP(2Π) components reveals that the splitting of the lowest 2Π states is more atom-like [Hund's case (c) coupling] than at higher n states [Hund's case (a) coupling]. In addition, we report a detailed study of the droplet size dependence of Ak-He? Rydberg series on the example of the Rb-He? D(Δ) series. Higher Rydberg states of this series are strongly redshifted, which is also related to the screening effect.

Monte Carlo simulation of a cesium atom beam in a magnetic field

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

Chen, Jiang, E-mail: chernjiang@aliyun.com; Zhu, Hongwei; Ma, Yinguang

2015-03-07

We present Monte Carlo simulations of the deflection of a beam of {sup 133}Cs atoms in a two wire magnetic field. Our results reveal the relationship between transmission rate of the atoms and incident parameters. Incident angle and position of the beam with maximum transmission are obtained from the simulations. The effect of the deflection field on the spatial distribution (beam profile) of {sup 133}Cs is derived. The method will help with the design of magnetic deflection experiments and to extract the magnetic properties from such experiments.

Allan deviation computations of a linear frequency synthesizer system using frequency domain techniques

NASA Technical Reports Server (NTRS)

Wu, Andy

1995-01-01

Allan Deviation computations of linear frequency synthesizer systems have been reported previously using real-time simulations. Even though it takes less time compared with the actual measurement, it is still very time consuming to compute the Allan Deviation for long sample times with the desired confidence level. Also noises, such as flicker phase noise and flicker frequency noise, can not be simulated precisely. The use of frequency domain techniques can overcome these drawbacks. In this paper the system error model of a fictitious linear frequency synthesizer is developed and its performance using a Cesium (Cs) atomic frequency standard (AFS) as a reference is evaluated using frequency domain techniques. For a linear timing system, the power spectral density at the system output can be computed with known system transfer functions and known power spectral densities from the input noise sources. The resulting power spectral density can then be used to compute the Allan Variance at the system output. Sensitivities of the Allan Variance at the system output to each of its independent input noises are obtained, and they are valuable for design trade-off and trouble-shooting.

Structural Channels and Atomic-Cluster Insertion in CsxBi4Te6 (1 ≤ x ≤ 1.25) As Observed by Aberration-Corrected Scanning Transmission Electron Microscopy.

PubMed

Zhang, Ruixin; Yang, Huaixin; Guo, Cong; Tian, Huanfang; Shi, Honglong; Chen, Genfu; Li, Jianqi

2016-12-19

Microstructural analyses based on aberration-corrected scanning transmission electron microscopy (STEM) observations demonstrate that low-dimensional Cs x Bi 4 Te 6 materials, known to be a novel thermoelectric and superconducting system, contain notable structural channels that go directly along the b axis, which can be partially filled by atom clusters depending on the thermal treatment process. We successfully prepared two series of Cs x Bi 4 Te 6 single-crystalline samples using two different sintering processes. The Cs x Bi 4 Te 6 samples prepared using an air-quenching method show superconductivity at approximately 4 K, while the Cs x Bi 4 Te 6 with the same nominal compositions prepared by slowly cooling are nonsuperconductors. Moreover, atomic structural investigations of typical samples reveal that the structural channels are often empty in superconducting materials; thus, we can represent the superconducting phase as Cs 1-y Bi 4 Te 6 with considering the point defects in the Cs layers. In addition, the channels in the nonsuperconducting crystals are commonly partially occupied by triplet Bi clusters. Moreover, the average structures for these two phases are also different in their monoclinic angles (β), which are estimated to be 102.3° for superconductors and 100.5° for nonsuperconductors.

Plutonium as a tracer for soil erosion assessment in northeast China.

PubMed

Xu, Yihong; Qiao, Jixin; Pan, Shaoming; Hou, Xiaolin; Roos, Per; Cao, Liguo

2015-04-01

Soil erosion is one of the most serious environmental and agricultural problems faced by human society. Assessing intensity is an important issue for controlling soil erosion and improving eco-environmental quality. The suitability of the application of plutonium (Pu) as a tracer for soil erosion assessment in northeast China was investigated by comparing with that of 137Cs. Here we build on preliminary work, in which we investigated the potential of Pu as a soil erosion tracer by sampling additional reference sites and potential erosive sites, along the Liaodong Bay region in northeast China, for Pu isotopes and 137Cs. 240Pu/239Pu atomic ratios in all samples were approximately 0.18, which indicated that the dominant source of Pu was the global fallout. Pu showed very similar distribution patterns to those of 137Cs at both uncultivated and cultivated sites. 239+240Pu concentrations in all uncultivated soil cores followed an exponential decline with soil depth, whereas at cultivated sites, Pu was homogenously distributed in plow horizons. Factors such as planted crop types, as well as methods and frequencies of irrigation and tillage were suggested to influence the distribution of radionuclides in cultivated land. The baseline inventories of 239+240Pu and 137Cs were 88.4 and 1688 Bq m(-2) respectively. Soil erosion rates estimated by 239+240Pu tracing method were consistent with those obtained by the 137Cs method, confirming that Pu is an effective tracer with a similar tracing behavior to that of 137Cs for soil erosion assessment. Copyright © 2014 Elsevier B.V. All rights reserved.

Photoinduced Br Desorption from CsBr Thin Films Grown on Cu(100)

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

Halliday, Matthew T.; Joly, Alan G.; Hess, Wayne P.

2015-10-22

Thin films of CsBr deposited onto metals such as copper are potential photocathode materials for light sources and other applications. We investigate desorption dynamics of Br atoms from CsBr films grown on insulator (KBr, LiF) and metal (Cu) substrates induced by sub-bandgap 6.4 eV laser pulses. The experimental results demonstrate that the peak kinetic energy of Br atoms desorbed from CsBr/Cu films is much lower than that for the hyperthermal desorption from CsBr/LiF films. Kelvin probe measurements indicate negative charge at the surface following Br desorption from CsBr/Cu films. Our ab initio calculations of excitons at CsBr surfaces demonstrate thatmore » this behavior can be explained by an exciton model of desorption including electron trapping at the CsBr surface. Trapped negative charges reduce the energy of surface excitons available for Br desorption. We examine the electron-trapping characteristics of low-coordinated sites at the surface, in particular, divacancies and kink sites. We also provide a model of cation desorption caused by Franck-Hertz excitation of F centers at the surface in the course of irradiation of CsBr/Cu films. These results provide new insights into the mechanisms of photoinduced structural evolution of alkali halide films on metal substrates and activation of metal photocathodes coated with CsBr.« less

A dual-wavelength overlapping resonance Rayleigh scattering method for the determination of chondroitin sulfate with nile blue sulfate

NASA Astrophysics Data System (ADS)

Cui, Zhiping; Hu, Xiaoli; Liu, Shaopu; Liu, Zhongfang

2011-12-01

A dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was developed to detect chondroitin sulfate (CS) with nile blue sulfate (NBS). At pH 3.0-4.0 Britton-Robinson (BR) buffer medium, CS interacted with NBS to form an ion-association complex. As a result, the new spectra of resonance Rayleigh scattering (RRS), second order scattering (SOS) and frequence doubling scattering (FDS) appeared and their intensities were enhanced greatly. Their maximum wavelengths were located at 303 nm (RRS), 362 nm (RRS), 588 nm (SOS) and 350 nm (FDS), respectively. The scattering intensities of the three methods were proportional to the concentration of CS in certain ranges. The methods had high sensitivity and the detection limits were between 1.5 and 7.1 ng mL -1. The DWO-RRS method had the highest sensitivity with the detection limit being 1.5 ng mL -1. The characteristics of the spectra and optimal reaction conditions of RRS method were investigated. The effects of coexistent substances on the determination of CS were evaluated. Owing to the high sensitivity, RRS method had been applied to the determination of CS in eye drops with satisfactory results. The recovery range was between 99.4% and 104.6% and the relative standard deviation (RSD) was between 0.4% and 0.8%. In addition, the reasons for RRS enhancement were discussed and the shape of ion-association complex was characterized by atomic force microscopy (AFM).

All-Ambient Processed Binary CsPbBr3-CsPb2Br5 Perovskites with Synergistic Enhancement for High-Efficiency Cs-Pb-Br-Based Solar Cells.

PubMed

Zhang, Xisheng; Jin, Zhiwen; Zhang, Jingru; Bai, Dongliang; Bian, Hui; Wang, Kang; Sun, Jie; Wang, Qian; Liu, Shengzhong Frank

2018-02-28

All-inorganic CsPbBr 3 perovskite solar cells display outstanding stability toward moisture, light soaking, and thermal stressing, demonstrating great potential in tandem solar cells and toward commercialization. Unfortunately, it is still challenging to prepare high-performance CsPbBr 3 films at moderate temperatures. Herein, a uniform, compact CsPbBr 3 film was fabricated using its quantum dot (QD)-based ink precursor. The film was then treated using thiocyanate ethyl acetate (EA) solution in all-ambient conditions to produce a superior CsPbBr 3 -CsPb 2 Br 5 composite film with a larger grain size and minimal defects. The achievement was attributed to the surface dissolution and recrystallization of the existing SCN - and EA. More specifically, the SCN - ions were first absorbed on the Pb atoms, leading to the dissolution and stripping of Cs + and Br - ions from the CsPbBr 3 QDs. On the other hand, the EA solution enhances the diffusion dynamics of surface atoms and the surfactant species. It is found that a small amount of CsPb 2 Br 5 in the composite film gives the best surface passivation, while the Br-rich surface decreases Br vacancies (V Br ) for a prolonged carrier lifetime. As a result, the fabricated device gives a higher solar cell efficiency of 6.81% with an outstanding long-term stability.

[Determination of sulfur in plant using a high-resolution continuum source atomic absorption spectrometer].

PubMed

Wang, Yu; Li, Jia-xi

2009-05-01

A method for the analysis of sulfur (S) in plant by molecular absorption of carbon monosulfide (CS) using a high-resolution continuum source atomic absorption spectrometer (CS AAS) with a fuel-rich air/acetylene flame has been devised. The strong CS absorption band was found around 258 nm. The half-widths of some absorption bands were of the order of picometers, the same as the common atomic absorption lines. The experimental procedure in this study provided optimized instrumental conditions (the ratio of acetylene to air, the burner height) and parameters, and researched the spectral interferences and chemical interferences. The influence of the organic solvents on the CS absorption signals and the different digestion procedures for the determination of sulfur were also investigated. The limit of detection achieved for sulfur was 14 mg x L(-1), using the CS wavelength of 257. 961 nm and a measurement time of 3 s. The accuracy and precision were verified by analysis of two plant standard reference materials. The major applications of this method have been used for the determination of sulfur in plant materials, such as leaves. Compared to the others, this method for the analysis of sulfur is rapid, easy and simple for sulfur determination in plant.

Topological and morphological analysis of gamma rays irradiated chitosan-poly (vinyl alcohol) blends using atomic force microscopy

NASA Astrophysics Data System (ADS)

Bhatt, Rinkesh; Bisen, D. S.; Bajpai, R.; Bajpai, A. K.

2017-04-01

In the present communication, binary blends of poly (vinyl alcohol) (PVA) and chitosan (CS) were prepared by solution cast method and the roughness parameters of PVA, native CS and CS-PVA blend films were determined using atomic force microscopy (AFM). Moreover, the changes in the morphology of the samples were also investigated after irradiation of gamma rays at absorbed dose of 1 Mrad and 10 Mrad for the scanning areas of 5×5 μm2, 10×10 μm2 and 20×20 μm2. Amplitude, statistical and spatial parameters, including line, 3D and 2D image profiles of the experimental surfaces were examined and compared to un-irradiated samples. For gamma irradiated CS-PVA blends the larger waviness over the surface was found as compared to un-irradiated CS-PVA blends but the values of average roughness for both the films were found almost same. The coefficient of skewness was positive for gamma irradiated CS-PVA blends which revealed the presence of more peaks than valleys on the blend surfaces.

Dirac-, Rashba-, and Weyl-type spin-orbit couplings: Toward experimental realization in ultracold atoms

NASA Astrophysics Data System (ADS)

Wang, Bao-Zong; Lu, Yue-Hui; Sun, Wei; Chen, Shuai; Deng, Youjin; Liu, Xiong-Jun

2018-01-01

We propose a hierarchy set of minimal optical Raman lattice schemes to pave the way for experimental realization of high-dimensional spin-orbit (SO) couplings for ultracold atoms, including two-dimensional (2D) Dirac type, 2D Rashba type, and three-dimensional (3D) Weyl type. The proposed Dirac-type SO coupling exhibits precisely controllable high symmetry, for which a large topological phase region is predicted. The generation of 2D Rashba and 3D Weyl types requires that two sources of laser beams have distinct frequencies of factor 2 difference. Surprisingly, we find that 133Cs atoms provide an ideal candidate for the realization. A common and essential feature is of high controllability and absent of any fine-tuning in the realization, and the resulting SO coupled ultracold atoms have a long lifetime. In particular, a long-lived topological Bose gas of 2D Dirac SO coupling has been proved in the follow-up experiment. These schemes essentially improve over the current experimental accessibility and controllability, and open a realistic way to explore novel high-dimensional SO physics, particularly quantum many-body physics and quantum far-from-equilibrium dynamics with novel topology for ultracold atoms.

Cold-Atom Clocks on Earth and in Space

NASA Astrophysics Data System (ADS)

Lemonde, Pierre; Laurent, Philippe; Santarelli, Giorgio; Abgrall, Michel; Sortais, Yvan; Bize, Sebastien; Nicolas, Christophe; Zhang, Shougang; Clairon, Andre; Dimarcq, Noel; Petit, Pierre; Mann, Antony G.; Luiten, Andre N.; Chang, Sheng; Salomon, Christophe

We present recent progress on microwave clocks that make use of laser-cooled atoms. With an ultra-stable cryogenic sapphire oscillator as interrogation oscillator, a cesium fountain operates at the quantum projection noise limit. With 6 x10^5 detected atoms, the relative frequency stability is 4 x10^-14 &1/2circ, where τ is the integration time in seconds. This stability is comparable to that of hydrogen masers. At τ=2 x10^4s, the measured stability reaches 6 x10^-16. A 87Rb fountain has also been constructed and the 87Rb ground-state hyperfine energy has been compared to the Cs primary standard with a relative accuracy of 2.5 x10^-15. The 87Rb collisional shift is found to be at least 30 times below that of cesium. We also describe a transportable cesium fountain, which will be used for frequency comparisons with an accuracy of 10-15 or below. Finally, we present the details of a space mission for a cesium standard which has been selected by the European Space Agency (ESA) to fly on the International Space Station in 2003.

Atomic Structure of a Cesium Aluminosilicate Geopolymer: A Pair Distribution Function Study

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

Bell, J.; Sarin, P; Provis, J

2008-01-01

The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer. The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000C resulted in formation of crystalline pollucite (CsAlSi{sub 2}O{sub 6}). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10-30 {angstrom} range when compared with a cubic pollucite model. A poorer fit was attained from 1-10 {angstrom} due to an additional amorphous phase present in the heated geopolymer. On the basis ofmore » PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of 9 {angstrom}, despite some differences. Our results suggest that hydrated Cs{sup +} ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.« less

Unravelling the secrets of Cs controlled secondary ion formation: Evidence of the dominance of site specific surface chemistry, alloying and ionic bonding

NASA Astrophysics Data System (ADS)

Wittmaack, Klaus

2013-03-01

Exposure of ion bombarded solids to Cs gives rise to a very strong enhancement of the yields of negatively charged secondary ions and, concurrently, to a lowering of positive ion yields. The phenomena have been explored in a large number of experimental and theoretical studies but attempts to clarify the mechanism of ion formation were not as successful as assumed. This review examines the state of the art in Cs controlled secondary ion mass spectrometry (SIMS) in great detail, with due consideration of low-energy alkali-ion scattering. In very basic studies on alkali induced secondary ion yield changes, sub-monolayer quantities of Cs or Li were deposited on the sample surface, followed by low-fluence ion bombardment, to avoid significant damage. If SIMS is applied to characterise the composition of solid materials, the simplest approach to achieving sample erosion as well as high negative-ion yields is bombardment with primary ions of Cs. Two other methods of sample loading with Cs provide more flexibility, (i) exposure to a collimated beam of Cs vapour and concurrent bombardment with high-energy non-Cs ions and (ii) the mixed-beam approach involving quasi-simultaneous bombardment with Cs and Xe ions. Both concepts have the advantage that undesirable sample overload with Cs can be avoided. High Cs concentrations reduce the formation probability of target specific molecular ions and lower the yields of all types of positive secondary ions, including Cs+, M+, X+, MCs+ and XCs+ (M and X denoting matrix and impurity elements). Quantitative SIMS analysis using MCs+ and XCs+ ions appears feasible, provided the Cs coverage is kept below about 5%. The semi-classical model of resonant charge transfer, also known as the tunnelling model, has long been considered a solid framework for the interpretation of Cs and Li based SIMS data. The model predicts ionisation probabilities for cases in which, at shallow distances from the surface, the affinity (ionisation) level of the departing atom is shifted below (above) the Fermi level. Ion yields should be controlled by the work function (WF) of the sample, Φ, and the normal velocity of the ejected ions. To explore the predicted velocity dependence, the performance characteristics of the employed SIMS instrument need to be known. The Cs induced negative-ion yield enhancement observed with pure metal and alloy targets often exceeded five orders of magnitude, with enhancement factors essentially independent of the emission energy. This absence of a velocity dependence is at variance with the predictions of the tunnelling model. Previous theoretical attempts to model the Φ-dependence and the apparent velocity effect for the overrated case of O-emission from Li and Cs exposed oxidised metal surfaces must be considered a meander. The experimental data, recorded with a quadrupole based instrument of inadequate extraction geometry, may alternatively be rationalised in terms of alkali induced changes in the energy spectrum of sputtered atoms. Another important finding is that secondary ion yield changes do not correlate with the absolute magnitude of the (macroscopic) WF but often with WF changes, ΔΦ. The frequently used method of determining ΔΦ in situ from the shift of the leading edge of secondary ion energy spectra rests on the assumption, taken for granted or not even appreciated, that Cs induced yield changes are independent of the ion's emission velocity. Hence the approach is only applicable if the tunnelling model is not valid. The local character of alkali induced WF changes, which might provide a route to an understanding of previously unexplained phenomena, has been explored using photoemission of adsorbed inert gases, scanning tunneling microscopy and low-energy ion scattering spectrometry. At room temperature, the Cs coverage is limited to one layer of adatoms. Close similarities are identified between WF changes generated by Cs vapour deposition and by bombardment with Cs ions. This finding implies that sub-monolayer quantities of Cs adatoms grow at the surface of Cs bombarded samples. The process has been studied in-situ by medium-energy ion scattering spectrometry. The stationary Cs coverage, NCs, is controlled by the efficiency of active transport of implanted atoms to the surface, the bulk retention properties of the sample and the cross section for sputtering of adatoms. Unearthing immobile implanted Cs atoms by sputter erosion usually provides only a minor contribution to the stationary coverage. Cs adatoms are mobile; the time required for final adatom rearrangement may be on the order of minutes at room temperature. Exposure of Cs bombarded samples to oxygen gives rise to oxidation of the substrate as well as to the formation of oxide layers of complex composition. Intercalation should be taken into account as a possible route of alkali transport into analysed samples. An important aspect ignored in prior work is that the alkali coverage required to produce a certain WF change is five to seven times higher if Li is deposited instead of Cs. Studies involving the use of Li thus provide no advantage compared to Cs. Furthermore, migration of the tiny Li atoms into the sample and metallisation effects aggrevate data interpretation. Literature data for ΔΦ (NCs), measured using Cs vapour deposition, can be converted to calibration curves, NCs (ΔΦ), for calculating the coverage established in implantation studies, a method referred to as ΔΦ→NCs conversion. This concept may be carried even further, as shown convincingly for silicon, the material examined most frequently in basic SIMS studies: Si- ion fractions, P(Si-), derived from yields measured under vastly different conditions of Cs supply, exhibit essentially the same ΔΦ dependence. Inverting the data one can produce calibration functions for ΔΦ versus P(Si-), denoted P(Si-)→ΔΦ, or, more generally, P(M-)→ΔΦ conversion. On this basis, transient yields measured during Cs implantation can be evaluated as a function of Cs coverage. The summarised results imply that secondary ions are commonly not formed by charge transfer between an escaping atom and the electronic system of the sample but are already emitted as ions. The probability of ion formation appears to be controlled by the local ionic character of the alkali-target atom bonds, i.e., by the difference in electronegativity between the involved elements as well as by the electron affinity and the ionisation potential of the departing atom. This idea is supported by the finding that Si- yields exhibit the same very strong dependence on Cs coverage as Si+ and O- yields on the oxygen fraction in oxygen loaded Si. Most challenging to theoreticians is the finding that the ionisation probability is independent of the emission velocity of sputtered ions. This phenomenon cannot be rationalised along established routes of thinking. Different concepts need to be explored. An old, somewhat exotic idea takes account of the heavy perturbation created for a very short period of time at the site of ion emission (dynamic randomisation). Molecular dynamics simulations are desirable to clarify the issue. Ultimately it may be possible to describe all phenomena of enhanced or suppressed secondary ion formation, produced either by surface loading with alkali atoms or by enforced surface oxidation, on the basis of a single universal model. There is plenty of room for exciting new studies.

Preliminary measurements of 135Cs with AMS

NASA Astrophysics Data System (ADS)

Yin, Xinyi; He, Ming; Dong, Kejun; Dou, Liang; Lan, Xiaoxi; Pang, Fangfang; Wu, Shaoyong; Jiang, Shan

2015-10-01

135Cs is an interesting nuclide in many research fields, especially in environmental study. Preliminary measurements of the long-lived 135Cs with accelerator mass spectrometry (AMS) have been developed with the HI-13 tandem AMS facility at China Institute of Atomic Energy (CIAE). In order to improve ion extracting current and depressing background interference, experiments were carried out on different ions of Cs extracted from different samples. It was found that Cs- extracted from CsNO3 can be used for AMS measurement of 135Cs. According to the preliminary results, the background level can be obtained with blanks was 135Ba/Cs ∼ 8.8 × 10-12 with the CIAE-AMS system.

Building one molecule from a reservoir of two atoms

NASA Astrophysics Data System (ADS)

Liu, L. R.; Hood, J. D.; Yu, Y.; Zhang, J. T.; Hutzler, N. R.; Rosenband, T.; Ni, K.-K.

2018-05-01

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits.

Bismuth as a general internal standard for lead in atomic absorption spectrometry.

PubMed

Bechlin, Marcos A; Fortunato, Felipe M; Ferreira, Edilene C; Gomes Neto, José A; Nóbrega, Joaquim A; Donati, George L; Jones, Bradley T

2014-06-11

Bismuth was evaluated as internal standard for Pb determination by line source flame atomic absorption spectrometry (LS FAAS), high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and line source graphite furnace atomic absorption spectrometry (LS GFAAS). Analysis of samples containing different matrices indicated close relationship between Pb and Bi absorbances. Correlation coefficients of calibration curves built up by plotting A(Pb)/A(Bi)versus Pb concentration were higher than 0.9953 (FAAS) and higher than 0.9993 (GFAAS). Recoveries of Pb improved from 52-118% (without IS) to 97-109% (IS, LS FAAS); 74-231% (without IS) to 96-109% (IS, HR-CS FAAS); and 36-125% (without IS) to 96-110% (IS, LS GFAAS). The relative standard deviations (n=12) were reduced from 0.6-9.2% (without IS) to 0.3-4.3% (IS, LS FAAS); 0.7-7.7% (without IS) to 0.1-4.0% (IS, HR-CS FAAS); and 2.1-13% (without IS) to 0.4-5.9% (IS, LS GFAAS). Copyright © 2014 Elsevier B.V. All rights reserved.

New crystals of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O system

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

Makarova, I. P., E-mail: makarova@crys.ras.ru; Grebenev, V. V.; Komornikov, V. A.

2016-11-15

Cs{sub 6}H(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}){sub 4} crystals, grown for the first time based on an analysis of the phase diagram of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O ternary system, have been investigated by structural analysis using synchrotron radiation. The atomic structure of the crystals is determined and its specific features are analyzed.

Atomic Clocks and Variations of the FIne Structure Constant

NASA Technical Reports Server (NTRS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

1995-01-01

We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.

Application of micron X-ray CT based on micro-PIXE to investigate the distribution of Cs in silt particles for environmental remediation in Fukushima Prefecture

NASA Astrophysics Data System (ADS)

Ishii, Keizo; Hatakeyama, Taisuke; Itoh, Shin; Sata, Daichi; Ohnuma, Tohru; Yamaguchi, Toshiro; Arai, Hiromu; Arai, Hirotsugu; Matsuyama, Shigeo; Terakawa, Atsuki; Kim, Seong-Yun

2016-03-01

We used X-ray computed tomography (CT) using characteristic X-rays produced in micro-particle-induced X-ray emission (PIXE) to investigate the internal structure of silt particles and develop new methods to decontaminate soil containing radioactive cesium. We obtained 3D attenuation coefficient images of silt particles with a diameter of approximately 100 μm for V K and Cr K X-rays. Owing to the absorption edges of the Cs L-shell, the differences between the V K and Cr K X-ray images revealed the spatial distribution of Cs atoms in the silt particles. Cs atoms were distributed over the surfaces of the silt particles to a thickness of approximately 10 μm. This information is useful for the decontamination of silt contaminated by radiation from the Fukushima Daiichi nuclear disaster.

Frequency and evaluation of the perceptions towards caesarean section among pregnant women attending public hospitals in Pakistan and the implications.

PubMed

Ishaq, Rabia; Baloch, Nosheen Sikander; Iqbal, Qaiser; Saleem, Fahad; Hassali, Mohamed Azmi; Iqbal, Javeid; Ahmed, Fiaz Ud Din; Anwar, Mohammad; Haider, Sajjad; Godman, Brian

2017-08-01

There is increasing prevalence of caesarean sections (CS) worldwide; however, there are concerns about their rates in some countries, including potential fears among mothers. Consequently, we aimed to determine the frequency of CS, and explore patient's perception towards CS attending public hospitals in Pakistan, to provide future guidance. A two-phased study design (retrospective and cross sectional) was adopted. A retrospective study was conducted to assess the frequency of CS over one year among four public hospitals. A cross sectional study was subsequently conducted to determine patients' perception towards CS attending the four tertiary care public hospitals in Quetta city, Pakistan, which is where most births take place. Overall prevalence of CS was 13.1% across the four hospitals. 728 patients were approached and 717 responded to the survey. Although 78.8% perceived CS as dangerous, influenced by education (p = 0.004), locality (p = 0.001) and employment status (p = 0.001), 74.5% of patients were in agreement that this is the best approach to save mother's and baby's lives if needed. 62% of respondents reported they would like to avoid CS if they could due to post-operative pain, and 58.9% preferred a normal delivery. There was also a significant association with education (p = 0.001) and locality (p = 0.001) where respondents considered normal vaginal delivery as painful. The overall frequency of CS approximates to WHO recommendations, although there is appreciable variation among the four hospitals. When it comes to perception towards CS, women had limited information. There is a need to provide mothers with education during the antenatal period, especially those with limited education, to accept CS where needed.

Detection of an inhibitory cortical gradient underlying peak shift in learning: a neural basis for a false memory.

PubMed

Miasnikov, Alexandre A; Weinberger, Norman M

2012-11-01

Experience often does not produce veridical memory. Understanding false attribution of events constitutes an important problem in memory research. "Peak shift" is a well-characterized, controllable phenomenon in which human and animal subjects that receive reinforcement associated with one sensory stimulus later respond maximally to another stimulus in post-training stimulus generalization tests. Peak shift ordinarily develops in discrimination learning (reinforced CS+, unreinforced CS-) and has long been attributed to the interaction of an excitatory gradient centered on the CS+ and an inhibitory gradient centered on the CS-; the shift is away from the CS-. In contrast, we have obtained peak shifts during single tone frequency training, using stimulation of the cholinergic nucleus basalis (NB) to implant behavioral memory into the rat. As we also recorded cortical activity, we took the opportunity to investigate the possible existence of a neural frequency gradient that could account for behavioral peak shift. Behavioral frequency generalization gradients (FGGs, interruption of ongoing respiration) were determined twice before training while evoked potentials were recorded from the primary auditory cortex (A1), to obtain a baseline gradient of "habituatory" neural decrement. A post-training behavioral FGG obtained 24h after three daily sessions of a single tone paired with NB stimulation (200 trials/day) revealed a peak shift. The peak of the FGG was at a frequency lower than the CS while the cortical inhibitory gradient was at a frequency higher than the CS frequency. Further analysis indicated that the frequency location and magnitude of the gradient could account for the behavioral peak shift. These results provide a neural basis for a systematic case of memory misattribution and may provide an animal model for the study of the neural bases of a type of "false memory". Published by Elsevier Inc.

Die Fledermaus: Regarding Optokinetic Contrast Sensitivity and Light-Adaptation, Chicks Are Mice with Wings

PubMed Central

Shi, Qing; Stell, William K.

2013-01-01

Background Through adaptation, animals can function visually under an extremely broad range of light intensities. Light adaptation starts in the retina, through shifts in photoreceptor sensitivity and kinetics plus modulation of visual processing in retinal circuits. Although considerable research has been conducted on retinal adaptation in nocturnal species with rod-dominated retinas, such as the mouse, little is known about how cone-dominated avian retinas adapt to changes in mean light intensity. Methodology/Principal Findings We used the optokinetic response to characterize contrast sensitivity (CS) in the chick retina as a function of spatial frequency and temporal frequency at different mean light intensities. We found that: 1) daytime, cone-driven CS was tuned to spatial frequency; 2) nighttime, presumably rod-driven CS was tuned to temporal frequency and spatial frequency; 3) daytime, presumably cone-driven CS at threshold intensity was invariant with temporal and spatial frequency; and 4) daytime photopic CS was invariant with clock time. Conclusion/Significance Light- and dark-adaptational changes in CS were investigated comprehensively for the first time in the cone-dominated retina of an avian, diurnal species. The chick retina, like the mouse retina, adapts by using a “day/night” or “cone/rod” switch in tuning preference during changes in lighting conditions. The chick optokinetic response is an attractive model for noninvasive, behavioral studies of adaptation in retinal circuitry in health and disease. PMID:24098693

The Electronic Structure of the Cs/ n-GaN(0001) Nano-Interface

NASA Astrophysics Data System (ADS)

Benemanskaya, G. V.; Lapushkin, M. N.; Marchenko, D. E.; Timoshnev, S. N.

2018-03-01

Electronic structures of the n-GaN(0001) surface and Cs/ n-GaN(0001) interface with submonolayer Cs coverages were studied for the first time in situ by the photoelectron spectroscopy (PES) method. The spectra of photoemission from the valence band, surface electron states, and core levels (Ga 3 d, Cs 4 d, Cs 5 p) under synchrotron excitation were measured in a range of photon energies within 50-150 eV. Evolution of the spectrum of surface states near the valence-band maximum was revealed by PES during the adsorption of Cs atoms. A metallic character of the Cs/ n-GaN(0001) nano-interface is demonstrated.

Interpretation of ES, CS, and IOS approximations within a translational--internal coupling scheme. I. Atom--diatom collisions

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

Coombe, D.A.; Snider, R.F.

1979-12-01

Rotational invariance is applied to the description of atom--diatom collisions in a translational--internal coupling scheme, to obtain energy sudden (ES), centrifugal sudden (CS), and infinite order sudden (IOS) approximations to the reduced scattering S matrix S (j-barlambda-bar;L;jlambda). The method of presentation emphasizes that the translational--internal coupling scheme is actually the more natural description of collision processes in which one or more directions are assumed to be conserved.

Laser pumping Cs atom magnetometer of theory research based on gradient tensor measuring

NASA Astrophysics Data System (ADS)

Yang, Zhang; Chong, Kang; Wang, Qingtao; Lei, Cheng; Zheng, Caiping

2011-02-01

At present, due to space exploration, military technology, geological exploration, magnetic navigation, medical diagnosis and biological magnetic fields study of the needs of research and development, the magnetometer is given strong driving force. In this paper, it will discuss the theoretical analysis and system design of laser pumping cesium magnetometer, cesium atomic energy level formed hyperfine structure with the I-J coupling, the hyperfine structure has been further split into Zeeman sublevels for the effects of magnetic field. To use laser pump and RF magnetic field make electrons transition in the hyperfine structure to produce the results of magneto-optical double resonance, and ultimately through the resonant frequency will be able to achieve accurate value of the external magnetic field. On this basis, we further have a discussion about magnetic gradient tensor measuring method. To a large extent, it increases the magnetic field measurement of information.

Predissociation and collisional depopulation of the Cs/sub 2/(E) state

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

Wu, Z.; Huennekens, J.

1984-11-15

We report here an experimental study of depopulation mechanisms of the Cs/sub 2/(E) state. By combining ratios of atomic to molecular fluorescence with E state lifetimes obtained by the phase shift technique, all studied as a function of Cs density, we were able to obtain absolute values for predissociation, radiative, and collisional depopulation rates as well as the total quenching rates for the Cs/sub 2/(E) state. The results are discussed in relation to those of other experiments.

Atomic-Level Structural Dynamics of Polyoxoniobates during DMMP Decomposition

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

Wang, Qi; Chapleski, Robert C.; Plonka, Anna M.

Ambient pressure in situ synchrotron-based spectroscopic techniques have been correlated to illuminate atomic-level details of bond breaking and formation during the hydrolysis of a chemical warfare nerve agent simulant over a polyoxometalate catalyst. Specifically, a Cs 8[Nb 6O 19] polyoxoniobate catalyst has been shown to react readily with dimethyl methylphosphonate (DMMP). The atomic-level transformations of all reactant moieties, the [Nb 6O 19] 8- polyanion, its Cs + counterions, and the DMMP substrate, were tracked under ambient conditions by a combination of X-ray absorption fine structure spectroscopy, Raman spectroscopy, and X-ray diffraction. Results reveal that the reaction mechanism follows general basemore » (in contrast to specific base) hydrolysis. Together with computational results, the work demonstrates that the ultimate fate of DMMP hydrolysis at the Cs 8[Nb 6O 19] catalyst is strong binding of the (methyl) methylphosphonic acid ((M)MPA) product to the polyanions, which ultimately inhibits catalytic turnover.« less

Atomic-Level Structural Dynamics of Polyoxoniobates during DMMP Decomposition

DOE PAGES

Wang, Qi; Chapleski, Robert C.; Plonka, Anna M.; ...

2017-04-10

Ambient pressure in situ synchrotron-based spectroscopic techniques have been correlated to illuminate atomic-level details of bond breaking and formation during the hydrolysis of a chemical warfare nerve agent simulant over a polyoxometalate catalyst. Specifically, a Cs 8[Nb 6O 19] polyoxoniobate catalyst has been shown to react readily with dimethyl methylphosphonate (DMMP). The atomic-level transformations of all reactant moieties, the [Nb 6O 19] 8- polyanion, its Cs + counterions, and the DMMP substrate, were tracked under ambient conditions by a combination of X-ray absorption fine structure spectroscopy, Raman spectroscopy, and X-ray diffraction. Results reveal that the reaction mechanism follows general basemore » (in contrast to specific base) hydrolysis. Together with computational results, the work demonstrates that the ultimate fate of DMMP hydrolysis at the Cs 8[Nb 6O 19] catalyst is strong binding of the (methyl) methylphosphonic acid ((M)MPA) product to the polyanions, which ultimately inhibits catalytic turnover.« less

Atomic clouds as spectrally selective and tunable delay lines for single photons from quantum dots

NASA Astrophysics Data System (ADS)

Wildmann, Johannes S.; Trotta, Rinaldo; Martín-Sánchez, Javier; Zallo, Eugenio; O'Steen, Mark; Schmidt, Oliver G.; Rastelli, Armando

2015-12-01

We demonstrate a compact, spectrally selective, and tunable delay line for single photons emitted by quantum dots. This is achieved by fine-tuning the wavelength of the optical transitions of such "artificial atoms" into a spectral window in which a cloud of natural atoms behaves as a slow-light medium. By employing the ground-state fine-structure-split exciton confined in an InGaAs/GaAs quantum dot as a source of single photons at different frequencies and the hyperfine-structure-split D1 transition of Cs-vapors as a tunable delay medium, we achieve a differential delay of up 2.4 ns on a 7.5-cm-long path for photons that are only 60 μ eV (14.5 GHz) apart. To quantitatively explain the experimental data, we develop a theoretical model that accounts for both the inhomogeneous broadening of the quantum-dot emission lines and the Doppler broadening of the atomic lines. The concept we proposed here may be used to implement time-reordering operations aimed at erasing the "which-path" information that deteriorates entangled-photon emission from excitons with finite fine-structure splitting.

Coherent control of the formation of cold heteronuclear molecules by photoassociation

NASA Astrophysics Data System (ADS)

de Lima, Emanuel F.

2017-01-01

We consider the formation of cold diatomic molecules in the electronic ground state by photoassociation of atoms of dissimilar species. A combination of two transition pathways from the free colliding pair of atoms to a bound vibrational level of the electronic molecular ground state is envisioned. The first pathway consists of a pump-dump scheme with two time-delayed laser pulses in the near-infrared frequency domain. The pump pulse drives the transition to a bound vibrational level of an excited electronic state, while the dump pulse transfers the population to a bound vibrational level of the electronic ground state. The second pathway takes advantage of the existing permanent dipole moment and employs a single pulse in the far-infrared domain to drive the transition from the unbound atoms directly to a bound vibrational level in the electronic ground state. We show that this scheme offers the possibility to coherently control the photoassociation yield by manipulating the relative phase and timing of the pulses. The photoassociation mechanism is illustrated for the formation of cold LiCs molecules.

Production and characterization of a dual species magneto-optical trap of cesium and ytterbium.

PubMed

Kemp, S L; Butler, K L; Freytag, R; Hopkins, S A; Hinds, E A; Tarbutt, M R; Cornish, S L

2016-02-01

We describe an apparatus designed to trap and cool a Yb and Cs mixture. The apparatus consists of a dual species effusive oven source, dual species Zeeman slower, magneto-optical traps in a single ultra-high vacuum science chamber, and the associated laser systems. The dual species Zeeman slower is used to load sequentially the two species into their respective traps. Its design is flexible and may be adapted for other experiments with different mixtures of atomic species. The apparatus provides excellent optical access and can apply large magnetic bias fields to the trapped atoms. The apparatus regularly produces 10(8) Cs atoms at 13.3 μK in an optical molasses, and 10(9) (174)Y b atoms cooled to 22 μK in a narrowband magneto-optical trap.

Hydrolytic cleavage of both CS2 carbon-sulfur bonds by multinuclear Pd(II) complexes at room temperature

NASA Astrophysics Data System (ADS)

Jiang, Xuan-Feng; Huang, Hui; Chai, Yun-Feng; Lohr, Tracy Lynn; Yu, Shu-Yan; Lai, Wenzhen; Pan, Yuan-Jiang; Delferro, Massimiliano; Marks, Tobin J.

2017-02-01

Developing homogeneous catalysts that convert CS2 and COS pollutants into environmentally benign products is important for both fundamental catalytic research and applied environmental science. Here we report a series of air-stable dimeric Pd complexes that mediate the facile hydrolytic cleavage of both CS2 carbon-sulfur bonds at 25 °C to produce CO2 and trimeric Pd complexes. Oxidation of the trimeric complexes with HNO3 regenerates the dimeric starting complexes with the release of SO2 and NO2. Isotopic labelling confirms that the carbon and oxygen atoms of CO2 originate from CS2 and H2O, respectively, and reaction intermediates were observed by gas-phase and electrospray ionization mass spectrometry, as well as by Fourier transform infrared spectroscopy. We also propose a plausible mechanistic scenario based on the experimentally observed intermediates. The mechanism involves intramolecular attack by a nucleophilic Pd-OH moiety on the carbon atom of coordinated µ-OCS2, which on deprotonation cleaves one C-S bond and simultaneously forms a C-O bond. Coupled C-S cleavage and CO2 release to yield [(bpy)3Pd3(µ3-S)2](NO3)2 (bpy, 2,2‧-bipyridine) provides the thermodynamic driving force for the reaction.

CC, CS, and IOS generalized phenomenological cross sections for atom--diatom mixtures

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

Fitz, D.E.; Kouri, D.J.; Evans, D.

1981-05-01

Close coupled expressions for phenomenological cross sections which describe transport properties of atom--diatom mixtures are obtained in the total-J coupling scheme and are related to the bracket integrals of kinetic theory. Coupled states and infinite order sudden expressions for the generalized phenomenological cross sections using initial, final, and average l-labeling are also given. Particular care is taken to use a phase convention for the CS and IOS approximations which is consistent with the Arthurs--Dalgarno formalism and which gives the correct behavior of degeneracy averaged differential cross sections.

Temperature and excitation power influence on the velocity-selective optical pumping resonances of 133Cs atoms confined in an extremely thin cell

NASA Astrophysics Data System (ADS)

Vartanyan, T.; Polishchuk, V.; Sargsyan, A.; Krasteva, A.; Cartaleva, St.; Todorov, G.

2018-03-01

Linear and nonlinear absorption spectra of 133Cs vapor confined in an extremely thin cell were computed via iterations with respect to the resonance radiation intensity. When the incident radiation intensity is low, the transient polarization of the atoms that undergo frequent collisions with the cell walls leads to sub-Doppler features in the absorption spectra. Higher incident radiation intensities result in the appearance of velocity-selective optical pumping resonances. The theory developed agrees quantitatively with the experimental findings.

Structure of Cs{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}) single crystals

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

Makarova, I. P., E-mail: makarova@crys.ras.ru; Grebenev, V. V.; Vasil’ev, I. I.

2016-01-15

Single crystals of Cs{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}) are synthesized and studied for the first time. The new compound is found in the course of studies of the phase diagram of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O triple system. Data on the atomic crystal structure of single-crystalline and powder specimens, as well as on structural phase transitions, are obtained.

Formation of Stoichiometric CsFn Compounds

PubMed Central

Zhu, Qiang; Oganov, Artem R.; Zeng, Qingfeng

2015-01-01

Alkali halides MX, have been viewed as typical ionic compounds, characterized by 1:1 ratio necessary for charge balance between M+ and X−. It was proposed that group I elements like Cs can be oxidized further under high pressure. Here we perform a comprehensive study for the CsF-F system at pressures up to 100 GPa, and find extremely versatile chemistry. A series of CsFn (n ≥ 1) compounds are predicted to be stable already at ambient pressure. Under pressure, 5p electrons of Cs atoms become active, with growing tendency to form Cs (III) and (V) valence states at fluorine-rich conditions. Although Cs (II) and (IV) are not energetically favoured, the interplay between two mechanisms (polyfluoride anions and polyvalent Cs cations) allows CsF2 and CsF4 compounds to be stable under pressure. The estimated defluorination temperatures of CsFn (n = 2,3,5) compounds at atmospheric pressure (218°C, 150°C, -15°C, respectively), are attractive for fluorine storage applications. PMID:25608669

Discharge-pumped cw gas lasers utilizing 'dressed-atom' gain media

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

Sorokin, P.P.; Glownia, J.H.; Hodgson, R.T.

The possibility of realizing an efficient gaseous laser-beam-generating medium that utilizes {lambda}-type coherently phased (i.e., 'dressed') atoms for the active laser species, but that does not inherently require the use of external laser beams for pumping, is explored. Specifically, it is investigated if multiphoton stimulated hyper-Raman scattering (SHRS) processes driven by fluorescence radiation generated in a continuous electrical discharge present within the vapor-containing cell could produce continuous-wave (cw) optical gain at the {lambda}-atom resonance frequencies {omega}{sub o} and {omega}{sub o}{sup '}. It is deduced that such gain could result from n-photon (n{>=}4) SHRS processes only if absorption of fluorescence pumpmore » light occurs in the first three transitions of the n-photon sequence representing the process unit step. Estimates of the amount of optical gain that could be produced in such a system indicate that it should be sufficient to allow multiwatt cw laser operation to occur on one set of {lambda} transitions connecting levels in a 'double-{lambda}' structure, with the pump light being discharge-produced fluorescence centered about the transitions of the other {lambda} pair. However, to initiate operation of such a device would require injection into the laser optical cavity of intense 'starter' laser pulses at both lasing frequencies. What should be an optimal experimental configuration for determining feasibility of the proposed laser device is described. In the suggested configuration, Cs-atom 6S{sub 1/2}-6P{sub 1/2} transitions form the double-{lambda} structure.« less

Ultrasonic Phased Array Compressive Imaging in Time and Frequency Domain: Simulation, Experimental Verification and Real Application

PubMed Central

Bai, Zhiliang; Chen, Shili; Jia, Lecheng; Zeng, Zhoumo

2018-01-01

Embracing the fact that one can recover certain signals and images from far fewer measurements than traditional methods use, compressive sensing (CS) provides solutions to huge amounts of data collection in phased array-based material characterization. This article describes how a CS framework can be utilized to effectively compress ultrasonic phased array images in time and frequency domains. By projecting the image onto its Discrete Cosine transform domain, a novel scheme was implemented to verify the potentiality of CS for data reduction, as well as to explore its reconstruction accuracy. The results from CIVA simulations indicate that both time and frequency domain CS can accurately reconstruct array images using samples less than the minimum requirements of the Nyquist theorem. For experimental verification of three types of artificial flaws, although a considerable data reduction can be achieved with defects clearly preserved, it is currently impossible to break Nyquist limitation in the time domain. Fortunately, qualified recovery in the frequency domain makes it happen, meaning a real breakthrough for phased array image reconstruction. As a case study, the proposed CS procedure is applied to the inspection of an engine cylinder cavity containing different pit defects and the results show that orthogonal matching pursuit (OMP)-based CS guarantees the performance for real application. PMID:29738452

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

DOE PAGES

Ding, Zihao; Karkare, Siddharth; Feng, Jun; ...

2017-11-09

K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to have excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness and have been employed in the VHF gun in the Advanced Photoinjector Experiment (APEX), however, their robustness in terms of their lifetime at elevated photocathode temperature has not yet been investigated. In this paper, the relationship between the lifetime of the K-Cs-Sb photocathode and the photocathode temperature has been investigated. The origin of the significant QE degradation at photocathode temperatures over 70 °C has been identified as the loss of cesium atoms from the K-Cs-Sb photocathode,more » based on the in situ x-ray analysis on the photocathode film during the decay process. The findings from this work will not only further the understanding of the behavior of K-Cs-Sb photocathodes at elevated temperature and help develop more temperature-robust cathodes, but also will become an important guide to the design and operation of the future high-field rf guns employing the use of such photocathodes.« less

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

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

Ding, Zihao; Karkare, Siddharth; Feng, Jun

K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to have excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness and have been employed in the VHF gun in the Advanced Photoinjector Experiment (APEX), however, their robustness in terms of their lifetime at elevated photocathode temperature has not yet been investigated. In this paper, the relationship between the lifetime of the K-Cs-Sb photocathode and the photocathode temperature has been investigated. The origin of the significant QE degradation at photocathode temperatures over 70 °C has been identified as the loss of cesium atoms from the K-Cs-Sb photocathode,more » based on the in situ x-ray analysis on the photocathode film during the decay process. The findings from this work will not only further the understanding of the behavior of K-Cs-Sb photocathodes at elevated temperature and help develop more temperature-robust cathodes, but also will become an important guide to the design and operation of the future high-field rf guns employing the use of such photocathodes.« less

Environmental transmission electron microscopy for catalyst materials using a spherical aberration corrector.

PubMed

Takeda, Seiji; Kuwauchi, Yasufumi; Yoshida, Hideto

2015-04-01

Atomic resolution has been obtained using environmental transmission electron microscopy (ETEM) by installing a spherical aberration corrector (Cs-corrector) on the objective lens. Simultaneously, the technology for controlling the environment around a specimen in ETEM has advanced significantly in the past decade. Quantification methodology has recently been established for deriving relevant experimental data in catalyst materials from substantial and systematic ETEM observation at the atomic scale. With this background, this paper summarizes aspects of the evolutional microscopy technique: necessary conditions for atomic resolution in ETEM; reduction of the scattering of electrons by the medium surrounding a specimen; and an environmental cell for structural imaging of a crystalline specimen. The high spatial resolution of a Cs-corrected ETEM is demonstrated for different observation conditions. After statistical analysis combined with numerical image analysis of ETEM data is briefly described, the recent applications of the Cs-corrected ETEM to catalyst materials are reviewed. For gold nanoparticulate catalysts, the structural information on the reaction sites and adsorption sites are deduced. For Pt nanoparticulate catalysts, ETEM studies elucidate the correlation between the catalytic activity and the morphology of the nanoparticles. These studies also reveal oxidation and reduction on the topmost Pt surface layer at the atomic scale. Finally, current issues and the future perspectives of Cs-corrected ETEM are summarized, including the reproducibility of ETEM observation data, the control of environments, the critical evaluation of electron irradiation effects, the full implementation of transmission electron microscopy technology in ETEM, and the safety issues for an ETEM laboratory. Copyright © 2014 Elsevier B.V. All rights reserved.

Production of cromolyn sodium microparticles for aerosol delivery by supercritical assisted atomization.

PubMed

Reverchon, Ernesto; Adami, Renata; Caputo, Giuseppe

2007-12-21

The purpose of this study was to produce cromolyn sodium (CS) micrometric particles with controlled particle size (PS) and PS distribution (PSD) suitable for aerosol delivery, using a supercritical fluids-based process. CS was micronized using the supercritical assisted atomization (SAA) technique at different solute concentrations in water and different precipitation temperatures. Two techniques were used to measure PS and PSD of produced particles: scanning electron microscopy image analysis and laser scattering analysis. The 2 techniques were compared to provide a complete description of the powder obtained. High-performance liquid chromatography analysis was used to verify the absence of degradation of CS after micronization; differential scanning calorimetry, thermogravimetric analysis (TGA), and X-ray analysis were performed to study the effect of operative conditions on the crystalline structure and on the water content of SAA micronized particles. The CS particles obtained were spherical, with a volumetric percentage of particles with a diameter ranging between 1 and 5 microm of 50% to 66%. The precipitation temperature had no significant effect on PSD, but high drying temperatures led to product degradation. Increasing the concentration of CS in water solution produced an increase in PS of the micronized particles. TGA showed that the micronized CS had a different hydration state than the untreated CS did. The micronized product was stable after 12 months of storage, and no modifications in structure, morphology, or crystallinity were detected. In conclusion, SAA is an efficient technique for micronization of CS, and stable spherical amorphous particles suitable for aerosol delivery can be produced.

Mini-Column Ion-Exchange Separation and Atomic Absorption Quantitation of Nickel, Cobalt, and Iron: An Undergraduate Quantitative Analysis Experiment.

ERIC Educational Resources Information Center

Anderson, James L.; And Others

1980-01-01

Presents an undergraduate quantitative analysis experiment, describing an atomic absorption quantitation scheme that is fast, sensitive and comparatively simple relative to other titration experiments. (CS)

Building one molecule from a reservoir of two atoms.

PubMed

Liu, L R; Hood, J D; Yu, Y; Zhang, J T; Hutzler, N R; Rosenband, T; Ni, K-K

2018-05-25

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Ultra-bright pulsed electron beam with low longitudinal emittance

DOEpatents

Zolotorev, Max

2010-07-13

A high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography has been described. The source makes use of Cs atoms in an atomic beam. The source is cycled beginning with a laser pulse that excites a single Cs atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence.

Systematic evaluation of a 171Yb optical clock by synchronous comparison between two lattice systems.

PubMed

Gao, Qi; Zhou, Min; Han, Chengyin; Li, Shangyan; Zhang, Shuang; Yao, Yuan; Li, Bo; Qiao, Hao; Ai, Di; Lou, Ge; Zhang, Mengya; Jiang, Yanyi; Bi, Zhiyi; Ma, Longsheng; Xu, Xinye

2018-05-22

Optical clocks are the most precise measurement devices. Here we experimentally characterize one such clock based on the 1 S 0 - 3 P 0 transition of neutral 171 Yb atoms confined in an optical lattice. Given that the systematic evaluation using an interleaved stabilization scheme is unable to avoid noise from the clock laser, synchronous comparisons against a second 171 Yb lattice system were implemented to accelerate the evaluation. The fractional instability of one clock falls below 4 × 10 -17 after an averaging over a time of 5,000 seconds. The systematic frequency shifts were corrected with a total uncertainty of 1.7 × 10 -16 . The lattice polarizability shift currently contributes the largest source. This work paves the way to measuring the absolute clock transition frequency relative to the primary Cs standard or against the International System of Units (SI) second.

CsMgPO4

PubMed Central

Strutynska, Nataliya Yu.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.

2009-01-01

Caesium magnesium orthophosphate is built up from MgO4 and PO4 tetra­hedra (both with . m. symmetry) linked together by corners, forming a three-dimensional framework. The Cs atoms have .m. site symmetry and are located in hexa­gonal channels running along the a- and b-axis directions. PMID:21583294

Aqueous NaCl and CsCl Solutions Confined in Crystalline Slit-Shaped Silica Nanopores of Varying Degree of Protonation

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

Ho, Tuan A.; Argyris, Dimitrios; Cole, David R.

2011-12-13

All-atom molecular dynamics simulations were conducted to study the dynamics of aqueous electrolyte solutions confined in slit-shaped silica nanopores of various degrees of protonation. Five degrees of protonation were prepared by randomly removing surface hydrogen atoms from fully protonated crystalline silica surfaces. Aqueous electrolyte solutions containing NaCl or CsCl salt were simulated at ambient conditions. In all cases, the ionic concentration was 1 M. The results were quantified in terms of atomic density distributions within the pores, and the self-diffusion coefficient along the direction parallel to the pore surface. We found evidence for ion-specific properties that depend on ion-surface, water-ion,more » and only in some cases ion-ion correlations. The degree of protonation strongly affects the structure, distribution, and the dynamic behavior of confined water and electrolytes. Cl -ions adsorb on the surface at large degrees of protonation, and their behavior does not depend significantly on the cation type (either Na + or Cs + ions are present in the systems considered). The cations show significant ion-specific behavior. Na + ions occupy different positions within the pore as the degree of protonation changes, while Cs + ions mainly remain near the pore center at all conditions considered. For a given degree of protonation, the planar self-diffusion coefficient of Cs + is always greater than that of Na + ions. The results are useful for better understanding transport under confinement, including brine behavior in the subsurface, with important applications such as environmental remediation.« less

Contrast sensitivity to spatial gratings in moderate and dim light conditions in patients with diabetes in the absence of diabetic retinopathy.

PubMed

Safi, Sare; Rahimi, Anoushiravan; Raeesi, Afsaneh; Safi, Hamid; Aghazadeh Amiri, Mohammad; Malek, Mojtaba; Yaseri, Mehdi; Haeri, Mohammad; Middleton, Frank A; Solessio, Eduardo; Ahmadieh, Hamid

2017-01-01

To evaluate the ability of contrast sensitivity (CS) to discriminate loss of visual function in diabetic subjects with no clinical signs of retinopathy relative to that of normal subjects. In this prospective cross-sectional study, we measured CS in 46 diabetic subjects with a mean age of 48±6 years, a best-corrected visual acuity of 20/20 and no signs of diabetic retinopathy. The CS in these subjects was compared with CS measurements in 46 normal control subjects at four spatial frequencies (3, 6, 12, 18 cycles per degree) under moderate (500 lux) and dim (less than 2 lux) background light conditions. CS was approximately 0.16 log units lower in patients with diabetes relative to controls both in moderate and in dim background light conditions. Logistic regression classification and receiver operating characteristic curve analysis indicated that CS analysis using two light conditions was more accurate (0.78) overall compared with CS analysis using only a single illumination condition (accuracy values were 0.67 and 0.70 in moderate and dim light conditions, respectively). Our results showed that patients with diabetes without clinical signs of retinopathy exhibit a uniform loss in CS at all spatial frequencies tested. Measuring the loss in CS at two spatial frequencies (3 and 6 cycles per degree) and two light conditions (moderate and dim) is sufficiently robust to classify diabetic subjects with no retinopathy versus control subjects.

Penetration of alkali atoms throughout a graphene membrane: theoretical modeling

NASA Astrophysics Data System (ADS)

Boukhvalov, D. W.; Virojanadara, C.

2012-02-01

Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout a graphene membrane grown on a silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate a rather low (about 0.8 eV) energy barrier for the formation of temporary defects in the carbon layer required for the penetration of Li at a high concentration of adatoms, a higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from the graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100 °C and impenetrability of the graphene membrane for Rb and Cs. Differences between epitaxial and free-standing graphene for the penetration of alkali ions are also discussed.

Penetration of alkali atoms throughout a graphene membrane: theoretical modeling.

PubMed

Boukhvalov, D W; Virojanadara, C

2012-03-07

Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout a graphene membrane grown on a silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate a rather low (about 0.8 eV) energy barrier for the formation of temporary defects in the carbon layer required for the penetration of Li at a high concentration of adatoms, a higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from the graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100 °C and impenetrability of the graphene membrane for Rb and Cs. Differences between epitaxial and free-standing graphene for the penetration of alkali ions are also discussed.

Spin Polarization of Rb and Cs n p P2 3/2 (n =5 , 6) Atoms by Circularly Polarized Photoexcitation of a Transient Diatomic Molecule

NASA Astrophysics Data System (ADS)

Mironov, A. E.; Hewitt, J. D.; Eden, J. G.

2017-03-01

We report the selective population of Rb or Cs n p P2 3/2 (n =5 , 6; F =4 , 5) hyperfine states by the photodissociation of a transient, alkali-rare gas diatomic molecule. Circularly polarized (σ-), amplified spontaneous emission (ASE) on the D2 line of Rb or Cs (780.0 and 852.1 nm, respectively) is generated when Rb-Xe or Cs-Xe ground state collision pairs are photoexcited by a σ+-polarized optical field having a wavelength within the D2 blue satellite continuum, associated with the B Σ2 1/2 +←X Σ2 1/2 + (free←free ) transition of the diatomic molecule. The degree of spin polarization of Cs (6 p P3/2 2 ), specifically, is found to be dependent on the interatomic distance (R ) at which the excited complex is born, a result attributed to the structure of the B Σ2 1/2 + state. For Cs-Xe atomic pairs, tuning the wavelength of the optical field from 843 to 848 nm varies the degree of circular polarization of the ASE from 63% to almost unity because of the perturbation, in the 5 ≤R ≤6 Å interval, of the Σ2 1/2 + potential by a d σ molecular orbital associated with a higher Λ 2 electronic state. Monitoring only the Cs 6 p P3/2 2 spin polarization reveals a previously unobserved interaction of CsXe (B Σ2 1/2 + ) with the lowest vibrational levels of a Λ 2 state derived from Cs (5 d )+Xe . By inserting a molecular intermediate into the alkali atom excitation mechanism, these experiments realize electronic spin polarization through populating no more than two n p P2 3/2 hyperfine states, and demonstrate a sensitive spectroscopic probe of R -dependent state-state interactions and their impact on interatomic potentials.

Al7CX (X=Li-Cs) clusters: Stability and the prospect for cluster materials

NASA Astrophysics Data System (ADS)

Ashman, C.; Khanna, S. N.; Pederson, M. R.; Kortus, J.

2000-12-01

Al7C clusters, recently found to have a high-electron affinity and exceptional stability, are shown to form ionic molecules when combined with alkali-metal atoms. Our studies, based on an ab initio gradient-corrected density-functional scheme, show that Al7CX (X=Li-Cs) clusters have a very low-electron affinity and a high-ionization potential. When combined, the two- and four-atom composite clusters of Al7CLi units leave the Al7C clusters almost intact. Preliminary studies indicate that Al7CLi may be suitable to form cluster-based materials.

Spin accumulation in thin Cs salts on contact with optically polarized Cs vapor

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

Ishikawa, Kiyoshi

2011-09-15

The spin angular momentum accumulates in the Cs nuclei of salt on contact with optically pumped Cs vapor. The spin polarization in stable chloride as well as dissociative hydride indicates that nuclear dipole interaction works in spin transferring with a lesser role of atom exchange. In the solid film, not only the spin buildup but also the decay of enhanced polarization is faster than the thermal recovery rate for the bulk salt. Eliminating the signal of thick salt, we find that the nuclear spin polarization in the chloride film reaches over 100 times the thermal equilibrium.

Syntheses and crystal structures of two topologically related modifications of Cs(2)[(UO(2))(2)(MoO(4))(3)].

PubMed

Krivovichev, S V; Cahill, C L; Burns, P C

2002-01-14

Two polymorphs of Cs(2)(UO(2))(2)(MoO(4))(3) have been synthesized by hydrothermal (alpha-phase) and high-temperature (beta-phase) routes. Both were characterized by single-crystal X-ray diffraction: alpha-Cs(2)(UO(2))(2)(MoO(4))(3), orthorhombic, Pna2(1), a = 20.4302(15) A, b = 8.5552(7) A, c = 9.8549(7) A, Z = 4; beta-Cs(2)(UO(2))(2)(MoO(4))(3), tetragonal, P4(2)/n, a = 10.1367(8) A, c = 16.2831(17) A, Z = 4. The structures of both phases consist of linked UO(7) pentagonal bipyramids and MoO(4) tetrahedra: alpha-Cs(2)(UO(2))(2)(MoO(4))(3) is a framework compound with large channels parallel to the c axis. Two cesium sites are located in these channels and are coordinated by 8 and 10 oxygen atoms. The structure of beta-Cs(2)(UO(2))(2)(MoO(4))(3) contains corrugated [(UO(2))(2)(MoO(4))(3)] sheets that are parallel to (001). The cesium cations are located between the sheets and are coordinated by eight oxygen atoms. The structures are topologically related; both can be described in terms of chains of 5-connected UO(7) pentagonal bipyramids and 3- and 4-connected MoO(4) tetrahedra.

Plasma-surface interaction in negative hydrogen ion sources

NASA Astrophysics Data System (ADS)

Wada, Motoi

2018-05-01

A negative hydrogen ion source delivers more beam current when Cs is introduced to the discharge, but a continuous operation of the source reduces the beam current until more Cs is added to the source. This behavior can be explained by adsorption and ion induced desorption of Cs atoms on the plasma grid surface of the ion source. The interaction between the ion source plasma and the plasma grid surface of a negative hydrogen ion source is discussed in correlation to the Cs consumption of the ion source. The results show that operation with deuterium instead of hydrogen should require more Cs consumption and the presence of medium mass impurities as well as ions of the source wall materials in the arc discharge enlarges the Cs removal rate during an ion source discharge.

Alkali metal and ammonium fluoro(trifluoroacetato)metallates M'[ M''3(μ3-F)(CF3COO)6(CF3COOH)3], where M' = Li, Na, K, NH4, Rb, or Cs and M'' = Ni or Co. Synthesis and crystal structures

NASA Astrophysics Data System (ADS)

Tereshchenko, D. S.; Morozov, I. V.; Boltalin, A. I.; Karpova, E. V.; Glazunova, T. Yu.; Troyanov, S. I.

2013-01-01

A series of fluoro(trifluoroacetato)metallates were synthesized by crystallization from solutions in trifluoroacetic acid containing nickel(II) or cobalt(II) nitrate hydrates and alkali metal or ammonium fluorides: Li[Ni3(μ3-F)(CF3COO)6(CF3COOH)3](CF3COOH)3 ( I), M'[Ni3(μ3-F)(CF3COO)6(CF3COOH)3] ( M' = Na ( II), NH4 ( IV), Rb ( V), and Cs ( VI)), NH4[Co3(μ3-F) (CF3COO)6(CF3COOH)3] ( III), and Cs[Ni3(μ3-F)(CF3COO)6(CF3COOH)3](CF3COOH)0.5 ( VII). The crystal structures of these compounds were determined by single-crystal X-ray diffraction. All structures contain triangular trinuclear complex anions [ M 3″(μ3-F)(CF3COO)6(CF3COOH)3]- ( M″ = Ni, Co) structurally similar to trinuclear 3d metal oxo carboxylate complexes. The three-coordinated F atom is located at the center of the triangle formed by Ni(II) or Co(II) atoms. The metal atoms are linked in pairs by six bridging trifluoroacetate groups located above and below the plane of the [ M″3 F] triangle. The oxygen atoms of the axial CF3COOH molecules complete the coordination environment of M″ atoms to an octahedron.

A strategy for optical properties investigation in ABe2BO3F2 (A=K, Rb, Cs) using finite field methods

NASA Astrophysics Data System (ADS)

Mushahali, Hahaer; Mu, Baoxia; Wang, Qian; Mamat, Mamatrishat; Cao, Haibin; Yang, Guang; Jing, Qun

2018-07-01

The finite-field methods can be used to intuitively learn about the optical response and find out the atomic contributions to the birefringence and SHG tensors. In this paper, the linear and second-order nonlinear optical properties of ABe2BO3F2 family (A = K, Rb, Cs) compounds are investigated using the finite-field methods within different exchange-correlation functionals. The results show that the obtained birefringence and SHG tensors are in good agreement with the experimental values. The atomic contribution to the total birefringence was further investigated using the variation of the atomic charges, and the Born effective charges. The results show that the boron-oxygen groups give main contribution to the anisotropic birefringence.

Monte Carlo simulations of precise timekeeping in the Milstar communication satellite system

NASA Technical Reports Server (NTRS)

Camparo, James C.; Frueholz, R. P.

1995-01-01

The Milstar communications satellite system will provide secure antijam communication capabilities for DOD operations into the next century. In order to accomplish this task, the Milstar system will employ precise timekeeping on its satellites and at its ground control stations. The constellation will consist of four satellites in geosynchronous orbit, each carrying a set of four rubidium (Rb) atomic clocks. Several times a day, during normal operation, the Mission Control Element (MCE) will collect timing information from the constellation, and after several days use this information to update the time and frequency of the satellite clocks. The MCE will maintain precise time with a cesium (Cs) atomic clock, synchronized to UTC(USNO) via a GPS receiver. We have developed a Monte Carlo simulation of Milstar's space segment timekeeping. The simulation includes the effects of: uplink/downlink time transfer noise; satellite crosslink time transfer noise; satellite diurnal temperature variations; satellite and ground station atomic clock noise; and also quantization limits regarding satellite time and frequency corrections. The Monte Carlo simulation capability has proven to be an invaluable tool in assessing the performance characteristics of various timekeeping algorithms proposed for Milstar, and also in highlighting the timekeeping capabilities of the system. Here, we provide a brief overview of the basic Milstar timekeeping architecture as it is presently envisioned. We then describe the Monte Carlo simulation of space segment timekeeping, and provide examples of the simulation's efficacy in resolving timekeeping issues.

Quantitative secondary ion mass spectrometric analysis of secondary ion polarity in GaN films implanted with oxygen

NASA Astrophysics Data System (ADS)

Hashiguchi, Minako; Sakaguchi, Isao; Adachi, Yutaka; Ohashi, Naoki

2016-10-01

Quantitative analyses of N and O ions in GaN thin films implanted with oxygen ions (16O+) were conducted by secondary ion mass spectrometry (SIMS). Positive (CsM+) and negative secondary ions extracted by Cs+ primary ion bombardment were analyzed for oxygen quantitative analysis. The oxygen depth profiles were obtained using two types of primary ion beams: a Gaussian-type beam and a broad spot beam. The oxygen peak concentrations in GaN samples were from 3.2 × 1019 to 7.0 × 1021 atoms/cm3. The depth profiles show equivalent depth resolutions in the two analyses. The intensity of negative oxygen ions was approximately two orders of magnitude higher than that of positive ions. In contrast, the O/N intensity ratio measured using CsM+ molecular ions was close to the calculated atomic density ratio, indicating that the SIMS depth profiling using CsM+ ions is much more effective for the measurements of O and N ions in heavy O-implanted GaN than that using negative ions.

First-principles calculations of different (001) surface terminations of three cubic perovskites CsCaBr3, CsGeBr3, and CsSnBr3

NASA Astrophysics Data System (ADS)

Ma, C.-G.; Krasnenko, V.; Brik, M. G.

2018-04-01

Three cubic bromide perovskites CsMBr3 (M = Ca, Ge, Sn) with two different surface terminations (CsBr and MBr2) were studied in this work using the first principles method. A wide range of physical properties, including electronic band structures, atom-projected density of states for each layer, surface relaxation effects, and surface energy, were evaluated for each considered surface termination. Differences between the properties of the bulk and slab models were highlighted. It was shown that surfaces with the CsBr termination have a lower energy and a more pronounced surface rumpling than those with the MBr2 termination. As a main result of this study, it was demonstrated that the CsBr-terminated surfaces appear to be energetically more stable in each of these three considered perovskites.

Contrast sensitivity to spatial gratings in moderate and dim light conditions in patients with diabetes in the absence of diabetic retinopathy

PubMed Central

Safi, Sare; Rahimi, Anoushiravan; Raeesi, Afsaneh; Safi, Hamid; Aghazadeh Amiri, Mohammad; Malek, Mojtaba; Yaseri, Mehdi; Haeri, Mohammad; Middleton, Frank A; Solessio, Eduardo; Ahmadieh, Hamid

2017-01-01

Objective To evaluate the ability of contrast sensitivity (CS) to discriminate loss of visual function in diabetic subjects with no clinical signs of retinopathy relative to that of normal subjects. Research design and methods In this prospective cross-sectional study, we measured CS in 46 diabetic subjects with a mean age of 48±6 years, a best-corrected visual acuity of 20/20 and no signs of diabetic retinopathy. The CS in these subjects was compared with CS measurements in 46 normal control subjects at four spatial frequencies (3, 6, 12, 18 cycles per degree) under moderate (500 lux) and dim (less than 2 lux) background light conditions. Results CS was approximately 0.16 log units lower in patients with diabetes relative to controls both in moderate and in dim background light conditions. Logistic regression classification and receiver operating characteristic curve analysis indicated that CS analysis using two light conditions was more accurate (0.78) overall compared with CS analysis using only a single illumination condition (accuracy values were 0.67 and 0.70 in moderate and dim light conditions, respectively). Conclusions Our results showed that patients with diabetes without clinical signs of retinopathy exhibit a uniform loss in CS at all spatial frequencies tested. Measuring the loss in CS at two spatial frequencies (3 and 6 cycles per degree) and two light conditions (moderate and dim) is sufficiently robust to classify diabetic subjects with no retinopathy versus control subjects. PMID:28878937

Electrocatalysis-induced elasticity modulation in a superionic proton conductor probed by band-excitation atomic force microscopy.

PubMed

Papandrew, A B; Li, Q; Okatan, M B; Jesse, S; Hartnett, C; Kalinin, S V; Vasudevan, R K

2015-12-21

Variable temperature band-excitation atomic force microscopy in conjunction with I-V spectroscopy was used to investigate the crystalline superionic proton conductor CsHSO4 during proton exchange induced by a Pt-coated conductive scanning probe. At a sample temperature of 150 °C and under an applied bias <1 V, reduction currents of up to 1 nA were observed. Simultaneously, we show that the electrochemical reactions are accompanied by a reversible decrease in the elastic modulus of CsHSO4, as seen by a contact resonance shift, and find evidence for superplasticity during scanning. These effects were not observed in the room-temperature phase of CsHSO4 or in the case of catalytically inactive conductive probes, proving the utility of this technique for monitoring electrochemical processes on the nanoscale, as well as the use of local contact stiffness as a sensitive indicator of electrochemical reactions.

In Situ Transmission Electron Microscopy Study of Electron Beam-Induced Transformations in Colloidal Cesium Lead Halide Perovskite Nanocrystals.

PubMed

Dang, Zhiya; Shamsi, Javad; Palazon, Francisco; Imran, Muhammad; Akkerman, Quinten A; Park, Sungwook; Bertoni, Giovanni; Prato, Mirko; Brescia, Rosaria; Manna, Liberato

2017-02-28

An increasing number of studies have recently reported the rapid degradation of hybrid and all-inorganic lead halide perovskite nanocrystals under electron beam irradiation in the transmission electron microscope, with the formation of nanometer size, high contrast particles. The nature of these nanoparticles and the involved transformations in the perovskite nanocrystals are still a matter of debate. Herein, we have studied the effects of high energy (80/200 keV) electron irradiation on colloidal cesium lead bromide (CsPbBr 3 ) nanocrystals with different shapes and sizes, especially 3 nm thick nanosheets, a morphology that facilitated the analysis of the various ongoing processes. Our results show that the CsPbBr 3 nanocrystals undergo a radiolysis process, with electron stimulated desorption of a fraction of bromine atoms and the reduction of a fraction of Pb 2+ ions to Pb 0 . Subsequently Pb 0 atoms diffuse and aggregate, giving rise to the high contrast particles, as previously reported by various groups. The diffusion is facilitated by both high temperature and electron beam irradiation. The early stage Pb nanoparticles are epitaxially bound to the parent CsPbBr 3 lattice, and evolve into nonepitaxially bound Pb crystals upon further irradiation, leading to local amorphization and consequent dismantling of the CsPbBr 3 lattice. The comparison among CsPbBr 3 nanocrystals with various shapes and sizes evidences that the damage is particularly pronounced at the corners and edges of the surface, due to a lower diffusion barrier for Pb 0 on the surface than inside the crystal and the presence of a larger fraction of under-coordinated atoms.

Study of Cs/NF3 adsorption on GaN (0 0 1) surface

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Kong, Yike

2017-03-01

To investigate the optoelectronics properties of Cs/NF3 adsorption on GaN (0 0 1) photocathode surface, different adsorption models of Cs-only, Cs/O, Cs/NF3 adsorption on GaN clean surface were established, respectively. Atomic structures, work function, adsorption energy, E-Mulliken charge distribution, density of states and optical properties of all these adsorption systems were calculated using first principles. Compared with Cs/O co-adsorption, Cs/NF3 co-adsorption show better stability and more decline of work function, which is more beneficial for photoemission efficiency. Besides, surface band structures of Cs/NF3 co-adsorption system exhibit metal properties, implying good conductivity. Meanwhile, near valence band minimum of Cs/NF3 co-adsorption system, more acceptor levels emerges to form a p-type emission surface, which is conductive to the escape of photoelectrons. In addition, imaginary part of dielectric function curve and absorption curve of Cs/NF3 co-adsorption system both move towards lower energy side. This work can direct the optimization of activation process of NEA GaN photocathode.

An exploratory study of recycled sputtering and CsF2- current enhancement for AMS

NASA Astrophysics Data System (ADS)

Zhao, X.-L.; Charles, C. R. J.; Cornett, R. J.; Kieser, W. E.; MacDonald, C.; Kazi, Z.; St-Jean, N.

2016-01-01

The analysis of 135Cs/Cs ratios at levels below 10-12 by accelerator mass spectrometry (AMS) would preferably use commonly available negative ion injection systems. The sputter ion sources in these injectors should ideally produce currents of Cs- or Cs-containing molecular anions approaching μA levels from targets containing mg quantities of Cs. However, since Cs is the most electro-positive stable element in nature with a low electron affinity, the generation of large negative atomic, or molecular beams containing Cs, has been very challenging. In addition, the reduction of the interferences from the 135Ba isobar and the primary 133Cs+ beam used for sputtering are also necessary. The measurement of a wide range of the isotope ratios also requires the ion source memory of previous samples be minimized. This paper describes some progresses towards a potential solution of all these problems by recycled sputtering using fluorinating targets of PbF2 with mg CsF mixed in. The problems encountered indicate that considerable further studies and some redesign of the present ion sources will be desirable.

Scattering of fast electrons by vapour-atoms and by solid-atoms - A comparison

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

Joshipura, K.N.; Mohanan, S.

1988-08-01

A comparative theoretical study has been done on the scattering of fast electrons by free (vapour) atoms and bound (solid) atoms, in particular, the alkali atoms, Al and Cu. The Born differential cross-sections (DCS), calculated with the static plus polarization electron-atom potential, are found in general, to be larger for free atoms that for bound atoms, at least at small angles of scattering. For Rb and Cs the two DCS tend to merge at very large angles only. The sample incident energies chosen are 400 eV and above.

Weak-field multiphoton femtosecond coherent control in the single-cycle regime.

PubMed

Chuntonov, Lev; Fleischer, Avner; Amitay, Zohar

2011-03-28

Weak-field coherent phase control of atomic non-resonant multiphoton excitation induced by shaped femtosecond pulses is studied theoretically in the single-cycle regime. The carrier-envelope phase (CEP) of the pulse, which in the multi-cycle regime does not play any control role, is shown here to be a new effective control parameter that its effect is highly sensitive to the spectral position of the ultrabroad spectrum. Rationally chosen position of the ultrabroadband spectrum coherently induces several groups of multiphoton transitions from the ground state to the excited state of the system: transitions involving only absorbed photons as well as Raman transitions involving both absorbed and emitted photons. The intra-group interference is controlled by the relative spectral phase of the different frequency components of the pulse, while the inter-group interference is controlled jointly by the CEP and the relative spectral phase. Specifically, non-resonant two- and three-photon excitation is studied in a simple model system within the perturbative frequency-domain framework. The developed intuition is then applied to weak-field multiphoton excitation of atomic cesium (Cs), where the simplified model is verified by non-perturbative numerical solution of the time-dependent Schrödinger equation. We expect this work to serve as a basis for a new line of femtosecond coherent control experiments.

Atomic radii for atoms with the 6s shell outermost: The effective atomic radius and the van der Waals radius from {sub 55}Cs to {sub 80}Hg

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

Tatewaki, Hiroshi, E-mail: htatewak@nsc.nagoya-cu.ac.jp; Institute of Advanced Studies in Artificial Intelligence, Chukyo University, Toyota, Aichi 470-0393; Hatano, Yasuyo

We consider, for atoms from {sub 55}Cs to {sub 80}Hg, the effective atomic radius (r{sub ear}), which is defined as the distance from the nucleus at which the magnitude of the electric field is equal to that in He at one half of the equilibrium bond length of He{sub 2}. The values of r{sub ear} are about 50% larger than the mean radius of the outermost occupied orbital of 6s, . The value of r{sub ear} decreases from {sub 55}Cs to {sub 56}Ba and undergoes increases and decreases with rising nuclear charge from {sub 57}La to {sub 70}Y b. Inmore » fact r{sub ear} is understood as comprising two interlaced sequences; one consists of {sub 57}La, {sub 58}Ce, and {sub 64}Gd, which have electronic configuration (4f{sup n−1})(5d{sup 1})(6s{sup 2}), and the remaining atoms have configuration (4f{sup n})(6s{sup 2}). The sphere defined by r{sub ear} contains 85%–90% of the 6s electrons. From {sub 71}Lu to {sub 80}Hg the radius r{sub ear} also involves two sequences, corresponding to the two configurations 5d{sup n+1}6s{sup 1} and 5d{sup n}6s{sup 2}. The radius r{sub ear} according to the present methodology is considerably larger than r{sub vdW} obtained by other investigators, some of who have found values of r{sub vdW} close to .« less

A Competitive Kinetics Study of the Reaction of Cl with CS2 in Air at 298 K

NASA Technical Reports Server (NTRS)

Wallington, Timothy J.; Andino, Jean M.; Potts, Alan R.; Wine, Paul H.

1997-01-01

The relative rate technique has been used to investigate the kinetics of the reaction of Cl atoms with carbon disulfide, CS2, at 700 Torr total pressure of air at 298 K. The decay rate of CS2 was measured relative to CH4, CH3Cl and CHF2CL. For experiments using CH4 and CH3Cl references, the decay rate of CS2 was dependent on the ratio of the concentration of the reference to that of CS2. We ascribe this behavior to the generation of OH radicals in the system leading to complicated secondary chemistry. From experiments using CHF2Cl we are able to assign an upper limit of 4 x 10(exp -15) cu cm/(molecule s) for the overall reaction, Cl + CS2 yields products.

Clinical efficacy and safety following dose tapering of ciclosporin in cats with hypersensitivity dermatitis.

PubMed

Roberts, Elizabeth S; Tapp, Tiffany; Trimmer, Ann; Roycroft, Linda; King, Stephen

2016-11-01

Objectives This study was designed to evaluate the efficacy and safety of reducing ciclosporin (CsA) dosing frequency from daily to every other day (EOD) or twice a week (TW) according to clinical response in cats with hypersensitivity dermatitis (HD) and treated with CsA. Methods One hundred and ninety-one cats with HD were given 7 mg/kg CsA daily for at least 4 weeks. Depending on clinical response, the dosing frequency was tapered from daily to EOD over the next 4 weeks and further to TW for an additional 4 weeks. Safety was evaluated through physical examinations, clinical pathology and the monitoring of adverse events (AEs). Results The majority of cats were able to have their dose of CsA tapered to either EOD (15.5%) or TW (62.9%) according to the clinical response. Observed AEs were most frequently mild and self-limiting vomiting and diarrhea. A higher percentage of AEs occurred with daily administration (73%) compared with other dosing regimens (27%). Conclusions and relevance Following 4 weeks of daily dosing at 7 mg/kg, CsA may be tapered to EOD or TW while maintaining the desired therapeutic response in cats with HD. Additionally, CsA appears to be well tolerated with fewer AEs at EOD or TW dosing. Establishing the lowest effective dosing frequency of CsA improves the drug's safety profile.

Microwave magnetic field detection based on Cs vapor cell in free space

NASA Astrophysics Data System (ADS)

Liu, Xiaochi; Jiang, Zhiyuan; Qu, Jifeng; Hou, Dong; Huang, Xianhe; Sun, Fuyu

2018-06-01

In this study, we demonstrate the direct measurement of a microwave (MW) magnetic field through the detection of atomic Rabi resonances with Cs vapor cells in a free-space low-Q cavity. The line shape (amplitude and linewidth) of detected Rabi resonances is investigated versus several experimental parameters such as the laser intensity, cell buffer gas pressure, and cell length. The specially designed low-Q cavity creates a suitable MW environment allowing easy testing of different vapor cells with distinct properties. Obtained results are analyzed to optimize the performances of a MW magnetic field sensor based on the present atom-based detection technique.

Vibration-based monitoring and diagnostics using compressive sensing

NASA Astrophysics Data System (ADS)

Ganesan, Vaahini; Das, Tuhin; Rahnavard, Nazanin; Kauffman, Jeffrey L.

2017-04-01

Vibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high volume data and rely on sensors being powered for prolonged durations. Furthermore, for spatial resolution, structures are instrumented with a large array of sensors. This paper shows that both volume of data and number of sensors can be reduced significantly by applying Compressive Sensing (CS) in vibration monitoring applications. The reduction is achieved by using random sampling and capitalizing on the sparsity of vibration signals in the frequency domain. Preliminary experimental results validating CS-based frequency recovery are also provided. By exploiting the sparsity of mode shapes, CS can also enable efficient spatial reconstruction using fewer spatially distributed sensors. CS can thereby reduce the cost and power requirement of sensing as well as streamline data storage and processing in monitoring applications. In well-instrumented structures, CS can enable continued monitoring in case of sensor or computational failures.

High-Frequency Subband Compressed Sensing MRI Using Quadruplet Sampling

PubMed Central

Sung, Kyunghyun; Hargreaves, Brian A

2013-01-01

Purpose To presents and validates a new method that formalizes a direct link between k-space and wavelet domains to apply separate undersampling and reconstruction for high- and low-spatial-frequency k-space data. Theory and Methods High- and low-spatial-frequency regions are defined in k-space based on the separation of wavelet subbands, and the conventional compressed sensing (CS) problem is transformed into one of localized k-space estimation. To better exploit wavelet-domain sparsity, CS can be used for high-spatial-frequency regions while parallel imaging can be used for low-spatial-frequency regions. Fourier undersampling is also customized to better accommodate each reconstruction method: random undersampling for CS and regular undersampling for parallel imaging. Results Examples using the proposed method demonstrate successful reconstruction of both low-spatial-frequency content and fine structures in high-resolution 3D breast imaging with a net acceleration of 11 to 12. Conclusion The proposed method improves the reconstruction accuracy of high-spatial-frequency signal content and avoids incoherent artifacts in low-spatial-frequency regions. This new formulation also reduces the reconstruction time due to the smaller problem size. PMID:23280540

Observation de l'interaction entre atome et surface en cellule de vapeur submicrométrique

NASA Astrophysics Data System (ADS)

Dutier, G.; Saltiel, S.; Bloch, D.; Ducloy, M.; Papoyan, A.; Sarkisyan, D.

2002-06-01

Sur une cellule de vapeur d'épaisseur submicrométrique ( 300 nm), les spectres d'absorption linéaire se révèlent très peu sensibles à l'effet Doppler (les effets transitoires favorisent fortement les atomes lents), et font apparaître les effets de l'interaction van der Waals à longue portée entre atome-surface. L'étude, entreprise d'abord sur la raie de résonance D1 de Cs, est poursuivie sur une transition à deux photons vers le niveau Cs 6(D{3/2}) résonnant avec la surface de YAG de la fenêtre. Elle ouvre diverses perspectives, notamment la détection d'états liés par un puits de potentiel induit par la surface.

Precise Measurements of the Masses of Cs, Rb and Na A New Route to the Fine Structure Constant

NASA Astrophysics Data System (ADS)

Rainville, Simon; Bradley, Michael P.; Porto, James V.; Thompson, James K.; Pritchard, David E.

2001-01-01

We report new values for the atomic masses of the alkali 133Cs, 87Rb, 85Rb, and 23Na with uncertainties ≤ 0.2 ppb. These results, obtained using Penning trap single ion mass spectrometry, are typically two orders of magnitude more accurate than previously measured values. Combined with values of h/m atom from atom interferometry measurements and accurate wavelength measurements for different atoms, these values will lead to new ppb-level determinations of the molar Planck constant N A h and the fine structure constant α. This route to α is based on simple physics. It can potentially achieve the several ppb level of accuracy needed to test the QED determination of α extracted from measurements of the electron g factor. We also demonstrate an electronic cooling technique that cools our detector and ion below the 4 K ambient temperature. This technique improves by about a factor of three our ability to measure the ion's axial motion.

Deep Cerebellar Nuclei Play an Important Role in Two-Tone Discrimination on Delay Eyeblink Conditioning in C57BL/6 Mice

PubMed Central

Sakamoto, Toshiro; Endo, Shogo

2013-01-01

Previous studies have shown that deep cerebellar nuclei (DCN)-lesioned mice develop conditioned responses (CR) on delay eyeblink conditioning when a salient tone conditioned stimulus (CS) is used, which suggests that the cerebellum potentially plays a role in more complicated cognitive functions. In the present study, we examined the role of DCN in tone frequency discrimination in the delay eyeblink-conditioning paradigm. In the first experiment, DCN-lesioned and sham-operated mice were subjected to standard simple eyeblink conditioning under low-frequency tone CS (LCS: 1 kHz, 80 dB) or high-frequency tone CS (HCS: 10 kHz, 70 dB) conditions. DCN-lesioned mice developed CR in both CS conditions as well as sham-operated mice. In the second experiment, DCN-lesioned and sham-operated mice were subjected to two-tone discrimination tasks, with LCS+ (or HCS+) paired with unconditioned stimulus (US), and HCS− (or LCS−) without US. CR% in sham-operated mice increased in LCS+ (or HCS+) trials, regardless of tone frequency of CS, but not in HCS− (or LCS−) trials. The results indicate that sham-operated mice can discriminate between LCS+ and HCS− (or HCS+ and LCS−). In contrast, DCN-lesioned mice showed high CR% in not only LCS+ (or HCS+) trials but also HCS− (or LCS−) trials. The results indicate that DCN lesions impair the discrimination between tone frequency in eyeblink conditioning. Our results suggest that the cerebellum plays a pivotal role in the discrimination of tone frequency. PMID:23555821

Interfacial water on crystalline silica: a comparative molecular dynamics simulation study

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

Ho, Tuan A.; Argyris, Dimitrios; Papavassiliou, Dimitrios V.

2011-03-03

All-atom molecular dynamics simulations were conducted to study the dynamics of aqueous electrolyte solutions confined in slit-shaped silica nanopores of various degrees of protonation. Five degrees of protonation were prepared by randomly removing surface hydrogen atoms from fully protonated crystalline silica surfaces. Aqueous electrolyte solutions containing NaCl or CsCl salt were simulated at ambient conditions. In all cases, the ionic concentration was 1 M. The results were quantified in terms of atomic density distributions within the pores, and the self-diffusion coefficient along the direction parallel to the pore surface. We found evidence for ion-specific properties that depend on ion surface,more » water ion, and only in some cases ion ion correlations. The degree of protonation strongly affects the structure, distribution, and the dynamic behavior of confined water and electrolytes. Cl ions adsorb on the surface at large degrees of protonation, and their behavior does not depend significantly on the cation type (either Na+ or Cs+ ions are present in the systems considered). The cations show significant ion-specific behavior. Na+ ions occupy different positions within the pore as the degree of protonation changes, while Cs+ ions mainly remain near the pore center at all conditions considered. For a given degree of protonation, the planar self-diffusion coefficient of Cs+ is always greater than that of Na+ ions. The results are useful for better understanding transport under confinement, including brine behavior in the subsurface, with important applications such as environmental remediation.« less

Iodine-129 measurements in soil samples from Dolon village near the Semipalatinsk nuclear test site.

PubMed

Endo, Satoru; Tomita, Junpei; Tanaka, Kenichi; Yamamoto, Masayoshi; Fukutani, Satoshi; Imanaka, Tetsuji; Sakaguchi, Aya; Amano, Hikaru; Kawamura, Hidehisa; Kawamura, Hisao; Apsalikov, Kazbek N; Gusev, Boris I; Whitehead, Neil E; Shinkarev, Sergey; Hoshi, Masaharu

2008-07-01

Dolon village, located about 60 km from the border of the Semipalatinsk nuclear test site, is known to be heavily contaminated by the first USSR atomic bomb test in August 1949. Soil samples around Dolon were taken in October 2005 in an attempt to evaluate internal thyroid dose arising from incorporation of radioiodine isotopes (mainly (131)I). Iodine-129 in soil was measured by using the technique of accelerator mass spectrometry. The (129)I/(127)I atom ratios measured were in the range from 3.3 x 10(-9) to 3.3 x 10(-7). These values were within the range of the current background level ( approximately 10(-9) to 10(-7)) in the environment, including contributions from the global fallout of atmospheric nuclear tests and local fallout of nuclear facilities. The (129)I atom accumulated level in soil ranged from 1.28 x 10(13) to 1.59 x 10(14) atoms m(-2), the average (8.0 x 10(13)) of which was higher than the background level of (2-5) x 10(13). From the relationship between (129)I and( 137)Cs (corrected for background and decay from 1949 to 2005) accumulated levels, the background level of (129)I and the (129)I/(137)Cs ratio around Dolon were estimated to be (6.4 +/- 0.4) x 10(13) atoms m(-2) and 0.25 +/- 0.16, respectively. This (129)I/(137)Cs ratio is almost similar to the fission yield ratio for (239)Pu fast fission (0.24).

Experimental Evidence for Space-Charge Effects between Ions of the Same Mass-to-Charge in Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry

PubMed Central

Wong, Richard L.; Amster, I. Jonathan

2009-01-01

It is often stated that ions of the same mass-to-charge do not induce space-charge frequency shifts among themselves in an ion cyclotron resonance mass spectrometry measurement. Here, we demonstrate space-charge induced frequency shifts for ions of a single mass-to-charge. The monoisotopic atomic ion, Cs+, was used for this study. The measured frequency is observed to decrease linearly with an increase in the number of ions, as has been reported previously for space-charge effects between ions of different mass-to-charge. The frequency shift between ions of the same m/z value are compared to that induced between ions of different m/z value, and is found to be 7.5 times smaller. Control experiments were performed to ensure that the observed space-charge effects are not artifacts of the measurement or of experimental design. The results can be rationalized by recognizing that the electric forces between ions in a magnetic field conform to the weak form of the Newton's third law, where the action and reaction forces do not cancel exactly. PMID:19562102

Terahertz time-domain spectroscopy of chondroitin sulfate

PubMed Central

Shi, Changcheng; Ma, Yuting; Zhang, Jin; Wei, Dongshan; Wang, Huabin; Peng, Xiaoyu; Tang, Mingjie; Yan, Shihan; Zuo, Guokun; Du, Chunlei; Cui, Hongliang

2018-01-01

Chondroitin sulfate (CS), derived from cartilage tissues, is an important type of biomacromolecule. In this paper, the terahertz time-domain spectroscopy (THz-TDS) was investigated as a potential method for content detection of CS. With the increase of the CS content, the THz absorption coefficients of the CS/polyethylene mixed samples linearly increase. The refractive indices of the mixed samples also increase when the CS content increases. The extinction coefficient of CS demonstrates the THz frequency dependence to be approximately the power of 1.4, which can be explained by the effects of CS granular solids on THz scattering. PMID:29541526

Propositional Versus Dual-Process Accounts of Evaluative Conditioning: I. The Effects of Co-Occurrence and Relational Information on Implicit and Explicit Evaluations.

PubMed

Hu, Xiaoqing; Gawronski, Bertram; Balas, Robert

2017-01-01

Evaluative conditioning (EC) is defined as the change in the evaluation of a conditioned stimulus (CS) due to its pairing with a valenced unconditioned stimulus (US). According to propositional accounts, EC effects should be qualified by the relation between the CS and the US. Dual-process accounts suggest that relational information should qualify EC effects on explicit evaluations, whereas implicit evaluations should reflect the frequency of CS-US co-occurrences. Experiments 1 and 2 showed that, when relational information was provided before the encoding of CS-US pairings, it moderated EC effects on explicit, but not implicit, evaluations. In Experiment 3, relational information moderated EC effects on both explicit and implicit evaluations when it was provided simultaneously with CS-US pairings. Frequency of CS-US pairings had no effect on implicit evaluations. Although the results can be reconciled with both propositional and dual-process accounts, they are more parsimoniously explained by propositional accounts.

Early stages of Cs adsorption mechanism for GaAs nanowire surface

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Feng, Shu

2018-03-01

In this study, the adsorption mechanism of Cs adatoms on the (100) surface of GaAs nanowire with [0001] growth direction is investigated utilizing first principles method based on density function theory. The adsorption energy, work function, atomic structure and electronic property of clean surface and Cs-covered surfaces with different coverage are discussed. Results show that when only one Cs is adsorbed on the surface, the most favorable adsorption site is BGa-As. With increasing Cs coverage, work function gradually decreases and gets its minimum at 0.75 ML, then rises slightly when Cs coverage comes to 1 ML, indicating the existence of 'Cs-kill' phenomenon. According to further analysis, Cs activation process can effectively reduce the work function due to the formation of a downward band bending region and surface dipole moment directing from Cs adatom to the surface. As Cs coverage increases, the conduction band minimum and valence band maximum both shift towards lower energy side, contributed by the orbital hybridization between Cs-5s, Cs-5p states and Ga-4p, As-4s, As-4p states near Fermi level. The theoretical calculations and analysis in this study can improve the Cs activation technology for negative electron affinity optoelectronic devices based on GaAs nanowires, and also provide a reference for the further Cs/O or Cs/NF3 activation process.

Effect of Green Tea Extract Encapsulated Into Chitosan Nanoparticles on Hepatic Fibrosis Collagen Fibers Assessed by Atomic Force Microscopy in Rat Hepatic Fibrosis Model.

PubMed

Safer, Abdel-Majeed A; Hanafy, Nomany A; Bharali, Dhruba J; Cui, Huadong; Mousa, Shaker A

2015-09-01

The present study examined the effect of Green Tea Extract (GTE) encapsulated into Chitosan Nanoparticles (CS-NPs) on hepatic fibrosis in rat model as determined by atomic force microscopy (AFM). The bioactive compounds in GTE encapsulated into CS-NPs were determined using LC-MS/MS method. Additionally, the uptake of GTE-CS NPs in HepG2 cells showed enhanced uptake. In experimental fibrosis model, AFM was used as a high resolution microscopic tool to investigate collagen fibers as an indicator of hepatic fibrosis induced by treatment with CCl4. Paraffin sections of fibrotic liver tissues caused by CC4 treatment of rats and the effect of GTE-CS NPs treatment with or without CCl4 on hepatic fibrosis were examined. Liver tissues from the different groups of animals were de-waxed and processed as for normal H/E staining and Masson's trichrome staining to locate the proper area of ECM collagen in the CCl4 group versus collagen in liver tissues treated with the GTE-CS NPs with or without CCl4. Selected areas of paraffin sections were trimmed off and fixed flat on top of mica and inserted in the AFM stage. H/E staining, Masson's trichrome stained slides, and AFM images revealed that collagen fibers of 250 to 300 nm widths were abundant in the fibrotic liver samples while those of GTE-CS NPs were clear as in the control group. Data confirmed the hypothesis that GTE-CS NPs are effective in removing all the extracellular collagen caused by CCl4 in the hepatic fibrosis rat liver.

A versatile dual-species Zeeman slower for caesium and ytterbium

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

Hopkins, S. A., E-mail: s.a.hopkins@durham.ac.uk; Butler, K.; Guttridge, A.

2016-04-15

We describe the design, construction, and operation of a versatile dual-species Zeeman slower for both Cs and Yb, which is easily adaptable for use with other alkali metals and alkaline earths. With the aid of analytic models and numerical simulation of decelerator action, we highlight several real-world problems affecting the performance of a slower and discuss effective solutions. To capture Yb into a magneto-optical trap (MOT), we use the broad {sup 1}S{sub 0} to {sup 1}P{sub 1} transition at 399 nm for the slower and the narrow {sup 1}S{sub 0} to {sup 3}P{sub 1} intercombination line at 556 nm formore » the MOT. The Cs MOT and slower both use the D2 line (6{sup 2}S{sub 1/2} to 6{sup 2}P{sub 3/2}) at 852 nm. The slower can be switched between loading Yb or Cs in under 0.1 s. We demonstrate that within a few seconds the Zeeman slower loads more than 10{sup 9} Yb atoms and 10{sup 8} Cs atoms into their respective MOTs. These are ideal starting numbers for further experiments on ultracold mixtures and molecules.« less

Searching for low-workfunction phases in the Cs-Te system: The case of Cs2Te5

NASA Astrophysics Data System (ADS)

Ruth, Anthony; Németh, Károly; Harkay, Katherine C.; Terdik, Joseph Z.; Spentzouris, Linda; Terry, Jeff

2013-05-01

We have computationally explored workfunction values of Cs2Te5 surfaces, an existing crystalline phase of the Cs-Te system and a small bandgap semiconductor, in order to search for reduced workfunction alternatives of Cs2Te that preserve the exceptionally high quantum efficiency of the Cs2Te seasoned photoemissive material. We have found that the Cs2Te5(010) surface exhibits a workfunction value of ≈1.9 eV when it is covered by Cs atoms. Cs2Te5 is analogous to our recently proposed low-workfunction materials, Cs2TeC2, and other ternary acetylides [J. Z. Terdik et al., Phys. Rev. B 86, 035142 (2012)], in as much as it also contains quasi one-dimensional substructures embedded in a Cs-matrix, forming the foundation for anomalous workfunction anisotropy and low workfunction values. The one-dimensional substructures in Cs2Te5 are polytelluride ions in a tetragonal rod-like packing. Cs2Te5 has the advantage of simpler composition and availability as compared to Cs2TeC2; however, its low workfunction surface is less energetically favored to the other surfaces than in Cs2TeC2. A significant and remarkable advantage of Cs2Te5 as compared to Cs2Te is its high optical absorption of visible photons that can allow for high quantum efficiency electron emission at visible photon energies.

Characterization of Gd loaded chitosan-TPP nanohydrogels by a multi-technique approach combining dynamic light scattering (DLS), asymetrical flow-field-flow-fractionation (AF4) and atomic force microscopy (AFM) and design of positive contrast agents for molecular resonance imaging (MRI)

NASA Astrophysics Data System (ADS)

Rigaux, G.; Gheran, C. V.; Callewaert, M.; Cadiou, C.; Voicu, S. N.; Dinischiotu, A.; Andry, M. C.; Vander Elst, L.; Laurent, S.; Muller, R. N.; Berquand, A.; Molinari, M.; Huclier-Markai, S.; Chuburu, F.

2017-02-01

Chitosan CS—tripolyphosphate TPP/hyaluronic acid HA nanohydrogels loaded with gadolinium chelates (GdDOTA ⊂ CS-TPP/HA NGs) synthesized by ionic gelation were designed for lymph node (LN) MRI. In order to be efficiently drained to LNs, nanogels (NGs) needed to exhibit a diameter ϕ < 100 nm. For that, formulation parameters were tuned, using (i) CS of two different molecular weights (51 and 37 kDa) and (ii) variable CS/TPP ratio (2 < CS/TPP < 8). Characterization of NG size distribution by dynamic light scattering (DLS) and asymetrical flow-field-flow-fractionation (AF4) showed discrepancies since DLS diameters were consistently above 200 nm while AF4 showed individual nano-objects with ϕ < 100 nm. Such a difference could be correlated to the presence of aggregates inherent to ionic gelation. This point was clarified by atomic force microscopy (AFM) in liquid mode which highlighted the main presence of individual nano-objects in nanosuspensions. Thus, combination of DLS, AF4 and AFM provided a more precise characterization of GdDOTA ⊂ CS-TPP/HA nanohydrogels which, in turn, allowed to select formulations leading to NGs of suitable mean sizes showing good MRI efficiency and negligible toxicity.

SEPARATION OF Cs$sup 137$ FROM HIGH-ACTIVITY RADIOACTIVE WASTE (in Dutch)

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

None

1963-01-01

A process was developed on a laboratory scale to separate Cs/sup 137/ from waste fuels of atomic reactors. The recovery of this powerful and industrially important gamma emitter of 30 years half life is said to be so simple as to make it possible on an industrial scale. It is based on the preferential absorption of Cs by ammonium phosphor-molybdate from the nitric acid solution of the waste material and the subsequent extraction of Cs from its absorber. This method is more practical than other processes which are based upon precipitation and recrystallization of cesium salts. It was successfully testedmore » on waste solutions of very different compositions. (OID)« less

A simulation study of CS2 solutions in two related ionic liquids with dications and monocations

NASA Astrophysics Data System (ADS)

Lynden-Bell, R. M.; Quitevis, E. L.

2018-05-01

Atomistic simulations of solutions of CS2 in an ionic liquid, [C8(C1im)2 ] [NTf2]2, with a divalent cation and in the corresponding ionic liquid with a monovalent cation, [C4C1im][NTf2], were carried out. The low-frequency librational density of states of the CS2 was of particular interest in view of recent optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). Compared to the monocation ionic liquid, the maximum shifts to higher frequencies in the dication ionic liquid under ambient conditions, but was found to be significantly pressure-dependent. CS2 molecules lie above and below the plane of the imidazolium rings and found to be close to the butyl tails of the monocation. The diffusion rates and embedding energies of solvent ions and CS2 in the two ionic liquids were measured.

Aging effect of 137Cs obtained from 137Cs in the Kanto loam layer from the Fukushima nuclear power plant accident and in the Nishiyama loam layer from the Nagasaki A-bomb explosion.

PubMed

Ohta, Tomoko; Mahara, Yasunori; Kubota, Takumi; Igarashi, Toshifumi

2013-01-01

We measured (134)Cs and (137)Cs in the surface soil of the Kanto loam in the eastern Tokyo metropolitan area and the Nishiyama loam in Nagasaki, Japan. The observed (137)Cs deposition in the Kanto loam from the Fukushima nuclear power plant (NPP) accident ranged from 4.0 to 77 kBq m(-2), which corresponds to 0.3-5 times of that in the Nishiyama loam. The (137)Cs retardation factor in the Kanto loam obtained seven months after the Fukusima NPP accident and in the Nishiyama loam after 36 and 38 years from the detonation of the Pu atomic bomb (A-bomb) ranged from 180 to 260 and 2000 to 10,000, respectively. This difference in the retardation factors is attributed to an aging effect that corresponds to seven months and 36 to 38 years after the deposition of (137)Cs occurred on the soil minerals.

Ultralow field NMR spectrometer with an atomic magnetometer near room temperature

NASA Astrophysics Data System (ADS)

Liu, Guobin; Li, Xiaofeng; Sun, Xianping; Feng, Jiwen; Ye, Chaohui; Zhou, Xin

2013-12-01

We present a Cs atomic magnetometer with a sensitivity of 150 fT/Hz1/2 operating near room temperature. The nuclear magnetic resonance (NMR) signal of 125 μL tap water was detected at an ultralow magnetic field down to 47 nT, with the signal-to-noise ratio (SNR) of the NMR signal approaching 50 after eight averages. Relaxivity experiments with a Gd(DTPA) contrast agent in zero field were performed, in order to show the magnetometer's ability to measure spin-lattice relaxation time with high accuracy. This demonstrates the feasibility of an ultralow field NMR spectrometer based on a Cs atomic magnetometer, which has a low working temperature, short data acquisition time and high sensitivity. This kind of NMR spectrometer has great potential in applications such as chemical analysis and magnetic relaxometry detection in ultralow or zero fields.

Concentrations of /sup 90/Sr and /sup 137/Cs in region of discharge of warm water from the Kola Atomic Power Station

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

Bayanov, N.I.

1982-01-01

The/sup 90/Sr and /sup 137/Cs concentrations in trout cultivated in warm water from the Kola Atomic Power Station (APS) in the period 1974-1979 were 30-70 pCi/kg. This is one-quarter to one-third of the radionuclide concentrations in wild fish living in this region and one-tenth of that in commerical fishes from other waters on the Kola Peninsula. The low radionuclide concentrations can be attributed to the absence of pollution in the coolant reservoir of the Kola APS during this period of operation, and also to the fact that the main mode of entry of radionuclides into the fish's body is throughmore » food. The investigations lead to the very important conclusion that fish-farming based on the warm effluents of atomic power stations is a feasible proposition.« less

Effective atomic numbers in some food materials and medicines for γ -ray attenuation using ^{137}Cs γ -ray

NASA Astrophysics Data System (ADS)

Revathy, J. S.; Anooja, J.; Krishnaveni, R. B.; Gangadathan, M. P.; Varier, K. M.

2018-06-01

A light-weight multichannel analyser (MCA)-based γ -ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for γ attenuation of ^{137}Cs γ -ray in different types of samples. The samples used are mixtures of graphite, aluminum and selenium powders in different proportions, commercial and home-made edible powders, fruit and vegetable juices as well as certain allopathic and ayurvedic medications. A narrow beam good geometry set-up has been used in the experiments. The measured attenuation coefficients have been used to extract effective atomic numbers in the samples. The results are consistent with XCOM values wherever available. The present results suggest that the γ attenuation technique can be used as an effective non-destructive method for finding adulteration of food materials.

Atherosclerotic Plaque in Patients with Zero Calcium Score at Coronary Computed Tomography Angiography.

PubMed

Gabriel, Fabíola Santos; Gonçalves, Luiz Flávio Galvão; Melo, Enaldo Vieira de; Sousa, Antônio Carlos Sobral; Pinto, Ibraim Masciarelli Francisco; Santana, Sara Melo Macedo; Matos, Carlos José Oliveira de; Souto, Maria Júlia Silveira; Conceição, Flávio Mateus do Sacramento; Oliveira, Joselina Luzia Menezes

2018-05-03

In view of the high mortality for cardiovascular diseases, it has become necessary to stratify the main risk factors and to choose the correct diagnostic modality. Studies have demonstrated that a zero calcium score (CS) is characteristic of a low risk for cardiovascular events. However, the prevalence of individuals with coronary atherosclerotic plaques and zero CS is conflicting in the specialized literature. To evaluate the frequency of patients with coronary atherosclerotic plaques, their degree of obstruction and associated factors in patients with zero CS and indication for coronary computed tomography angiography (CCTA). This is a cross-sectional, prospective study with 367 volunteers with zero CS at CCTA in four diagnostic imaging centers in the period from 2011 to 2016. A significance level of 5% and 95% confidence interval were adopted. The frequency of atherosclerotic plaque in the coronary arteries in 367 patients with zero CS was 9.3% (34 individuals). In this subgroup, mean age was 52 ± 10 years, 18 (52.9%) were women and 16 (47%) had significant coronary obstructions (> 50%), with involvement of two or more segments in 4 (25%) patients. The frequency of non-obese individuals (90.6% vs 73.9%, p = 0.037) and alcohol drinkers (55.9% vs 34.8%, p = 0.015) was significantly higher in patients with atherosclerotic plaques, with an odds ratio of 3.4 for each of this variable. The frequency of atherosclerotic plaque with zero CS was relatively high, indicating that the absence of calcification does not exclude the presence of plaques, many of which obstructive, especially in non-obese subjects and alcohol drinkers.

Modeling of atomic systems for atomic clocks and quantum information

NASA Astrophysics Data System (ADS)

Arora, Bindiya

This dissertation reports the modeling of atomic systems for atomic clocks and quantum information. This work is motivated by the prospects of optical frequency standards with trapped ions and the quantum computation proposals with neutral atoms in optical lattices. Extensive calculations of the electric-dipole matrix elements in monovalent atoms are conducted using the relativistic all-order method. This approach is a linearized version of the coupled-cluster method, which sums infinite sets of many-body perturbation theory terms. All allowed transitions between the lowest ns, np1/2, np 3/2 states and a large number of excited states of alkali-metal atoms are evaluated using the all-order method. For Ca+ ion, additional allowed transitions between nd5/2, np 3/2, nf5/2, nf 7/2 states and a large number of excited states are evaluated. We combine D1 lines measurements by Miller et al. [18] with our all-order calculations to determine the values of the electric-dipole matrix elements for the 4pj - 3d j' transitions in K and for the 5pj - 4dj' transitions in Rb to high precision. The resulting electric-dipole matrix elements are used for the high-precision calculation of frequency-dependent polarizabilities of ground state of alkali atoms. Our values of static polarizabilities are found to be in excellent agreement with available experiments. Calculations were done for the wavelength in the range 300--1600 nm, with particular attention to wavelengths of common infrared lasers. We parameterize our results so that they can be extended accurately to arbitrary wavelengths above 800 nm. Our data can be used to predict the oscillation frequencies of optically-trapped atoms, and particularly the ratios of frequencies of different species held in the same trap. We identify wavelengths at which two different alkali atoms have the same oscillation frequency. We present results of all-order calculations of static and frequency-dependent polarizabilities of excited np1/2 and np3/2 state in Na, K, Rb, and Cs atoms and evaluate the uncertainties of these values. Both scalar and tensor part of the p state polarizability were calculated. This made the calculations complicated owing to the contributions from p--d transitions. The static polarizability values are found to be in excellent agreement with previous experimental and theoretical results. We used our calculations to identify the "magic" wavelengths at which the ac polarizabilities of the alkali-metal atoms in the ground state are equal to the ac polarizabilities in the excited npj states facilitating state-insensitive cooling and trapping. We list the results for the np 1/2 and np3/2 states separately. Depending on the mj sub levels, the total polarizability of the np3/2 state was calculated either as the sum or as the difference of scalar and tensor contributions. We pointed out the complications involved in the magic wavelength calculations for the mj = +/-3/2 sub levels. We also study the magic wavelengths for transitions between particular np3/2 F'M' and nsFM hyperfine sub levels. We have proposed a scheme for state-insensitive trapping of neutral atoms by using two-color light at convenient wavelengths. In this scheme, we predict the values of trap and control wavelengths for which the 5s and 5p3/2 levels in Rb atom have same ac Stark shifts in the presence of two laser fields. We also list the trap and control wavelength combinations where one of the laser wavelengths is double the other. The results were listed at same and different trap and control laser intensities. This scheme allows to select convenient and easily available laser wavelength for experiments where it is essential to precisely localize and control neutral atoms with minimum decoherence. Motivated by the prospect of an optical frequency standard based on 43Ca+, we calculate the blackbody radiation (BBR) shift of the 4s1/2-3d5/2 clock transition of an optical frequency standard based on 43Ca+. We describe the study of the Rydberg-Rydberg interactions for quantum gates with neutral atoms and decoherence mechanisms in the Rydberg gate scheme. We have also studied the properties and decoherence processes of the Rydberg states as they are needed for the understanding of possible achievable gate fidelity. (Abstract shortened by UMI.)

Adsorption and Desorption of Cesium in Clay Minerals: Effects of Natural Organic Matter and pH

NASA Astrophysics Data System (ADS)

Yoon, Hongkyu; Ilgen, Anastasia; Mills, Melissa; Lee, Moo; Seol, Jeung Gun; Cho, Nam Chan; Kang, Hyungyu

2017-04-01

Cesium (Cs) released into the environment (e.g., Fukushima accident) poses significant environmental concerns and remediation challenges. A majority of Cs in the environment have remained within the surface soils due to the strong adsorption affinity of Cs towards clay minerals. Different clay minerals have different bonding sites, resulting in various adsorption mechanisms at nanometer scale. For example, the illite commonly has a basal spacing of 1.0 nm, but becomes wider to 1.4 nm once other cations exchange with K in the interlayer site. Cs adsorbs into these expanded wedged zone strongly, which can control its mobility in the environment. In addition, natural organic matter (NOM) in the surface soils can interact with clay minerals, which can modify the mechanisms of Cs adsorption on the clay minerals by blocking specific adsorption sites and/or providing Cs adsorption sites on NOM surface. In this work, three representative clay minerals (illite, vermiculite, montmorillonite) and humic acid (HA) are used to systematically investigate the adsorption and desorption behavior of Cs. We performed batch adsorption experiments over a range of Cs concentrations on three clay minerals with and without HA, followed by sequential desorption batch testing. We tested desorption efficiency as a function of initial adsorbed Cs concentration, HA content, sodium concentration, and pH. The sequential extraction results are compared to the structural changes in clay minerals, measured using extended X-ray absorption fine structure spectroscopy (EXAFS) and aberration-corrected (scanning) transmission electron microscopy (TEM) - energy dispersive X-ray spectroscopy (EDX). Hence, this work aims to identify the mechanisms of Cs fixation at the nanometer (or atomic-) scale as a function of the clay mineral properties (e.g. expandability, permanent surface charge) and varying organic matter content at different pH values and to enhance our atomic-scale mechanistic understanding of the clay mineral interactions with cesium in the presence of NOM. The expandability of clay minerals and effect of HA addition on Cs adsorption and desorption are highlighted to address the efficiency of Cs removal schemes from contaminated soils. Sandia National Laboratories is a multi-mission 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 DE-AC04-94AL85000.

Ground-state hyperfine splitting for Rb, Cs, Fr, Ba+, and Ra+

NASA Astrophysics Data System (ADS)

Ginges, J. S. M.; Volotka, A. V.; Fritzsche, S.

2017-12-01

We have systematically investigated the ground-state hyperfine structure for alkali-metal atoms 87Rb,133Cs, and 211Fr and alkali-metal-like ions +135Ba and +225Ra, which are of particular interest for parity violation studies. The quantum electrodynamic one-loop radiative corrections have been rigorously evaluated within an extended Furry picture employing core-Hartree and Kohn-Sham atomic potentials. Moreover, the effect of the nuclear magnetization distribution on the hyperfine structure intervals has been studied in detail and its uncertainty has been estimated. Finally, the theoretical description of the hyperfine structure has been completed with full many-body calculations performed in the all-orders correlation potential method.

Science Goals for the PARCS mission on the International Space Station

NASA Astrophysics Data System (ADS)

Ashby, Neil; Hollberg, Leo; Jefferts, Steven; Klipstein, William; Seidel, David; Sullivan, Donald

2003-05-01

The PARCS (Primary Atomic Reference Clock in Space) experiment will use a laser-cooled cesium atomic clock operating in the microgravity environment aboard the International Space Station (ISS) to provide both advanced tests of gravitational theory and to demonstrate a new cold-atom clock technology for space. This presentation concentrates on the scientific goals of the PARCS mission. The microgravity space environment allows laser-cooled Cs atoms to have Ramsey times in excess of those feasible on Earth, resulting in improved clock performance. Clock stabilities of 5×10-14 at one second, and uncertainties below 10-16 are projected. The relativistic frequency shift should be measurable at least 40 times better than the previous best measurement made by Gravity Probe A. Significant improvements in testing fundamental assumptions of relativity theory, such as local position invariance (LPI), are expected. PARCS is scheduled for launch in 2007 and may very well fly with the Stanford superconducting microwave oscillator (SUMO) which will allow a Kennedy-Thorndike-type experiment with an improvement of better than three orders of magnitude compared to previous best results. PARCS will also provide a much-improved realization of the second, and a stable time reference in space. PARCS is a joint project by the National Institue of Standards and Technology (NIST), the University of Colorado (CU) and NASA's Jet Propulsion Laboratory (JPL).

The effect of withdrawal of visual presentation of errors upon the frequency spectrum of tremor in a manual task

PubMed Central

Sutton, G. G.; Sykes, K.

1967-01-01

1. When a subject attempts to exert a steady pressure on a joystick he makes small unavoidable errors which, irrespective of their origin or frequency, may be called tremor. 2. Frequency analysis shows that low frequencies always contribute much more to the total error than high frequencies. If the subject is not allowed to check his performance visually, but has to rely on sensations of pressure in the finger tips, etc., the error power spectrum plotted on logarithmic co-ordinates approximates to a straight line falling at 6 db/octave from 0·4 to 9 c/s. In other words the amplitude of the tremor component at each frequency is inversely proportional to frequency. 3. When the subject is given a visual indication of his errors on an oscilloscope the shape of the tremor spectrum alters. The most striking change is the appearance of a tremor peak at about 9 c/s, but there is also a significant increase of error in the range 1-4 c/s. The extent of these changes varies from subject to subject. 4. If the 9 c/s peak represents oscillation of a muscle length-servo it would appear that greater use is made of this servo when positional information is available from the eyes than when proprioceptive impulses from the limbs have to be relied on. ImagesFig. 2 PMID:6048997

Changes in charge density vs changes in formal oxidation states: The case of Sn halide perovskites and their ordered vacancy analogues

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

Dalpian, Gustavo M.; Liu, Qihang; Stoumpos, Constantinos C.

Shifting the Fermi energy in solids by doping, defect formation, or gating generally results in changes in the charge density distribution, which reflect the ability of the bonding pattern in solids to adjust to such external perturbations. In the traditional chemistry textbook, such changes are often described by the formal oxidation states (FOS) whereby a single atom type is presumed to absorb the full burden of the perturbation (change in charge) of the whole compound. In the present paper, we analyze the changes in the position-dependence charge density due to shifts of the Fermi energy on a general physical basis,more » comparing with the view of the FOS picture. We use the halide perovskites CsSnX3 (X = F, Cl, Br, I) as examples for studying the general principle. When the solar absorber CsSnI3 (termed 113) loses 50% of its Sn atoms, thereby forming the ordered vacancy compound Cs2SnI6 (termed 216), the Sn is said in the FOS picture to change from Sn(II) to Sn(IV). To understand the electronic properties of these two groups we studied the 113 and 216 compound pairs CsSnCl3 and Cs2SnCl6, CsSnBr3 and Cs2SnBr6, and CsSnI3 and Cs2SnI6, complementing them by CsSnF3 and Cs2SnF6 in the hypothetical cubic structure for completing the chemical trends. These materials were also synthesized by chemical routes and characterized by x-ray diffraction, 119Sn-Mössbauer spectroscopy, and K-edge x-ray absorption spectroscopy. We find that indeed in going from 113 to 216 (equivalent to the introduction of two holes per unit) there is a decrease in the s charge on Sn, in agreement with the FOS picture. However, at the same time, we observe an increase of the p charge via downshift of the otherwise unoccupied p level, an effect that tends to replenish much of the lost s charge. At the end, the change in the charge on the Sn site as a result of adding two holes to the unit cell is rather small. This effect is theoretically explained as a “self-regulating response” [Raebiger, Lany, and Zunger, Nature (London) 453, 763 (2008)] whereby the system rehybridizes to minimize the effect of the charge perturbation created by vacancy formation. Rather than having a single preselected atom (here Sn) absorb the full brunt of the perturbation producing two holes, we find that the holes are distributed in a complex pattern throughout the octahedral systems of X6 ligands, forming hole orbitals with some specific symmetries. This clarifies the relation between FOS and charge transfer that can be applied to a wide variety of materials.« less

Interaction of the cesium cation with calix[4]arene-bis(t-octylbenzo-18-crown-6): Extraction and DFT study

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

Makrlik, Emanuel; Toman, Petr; Vanura, Petr

2013-01-01

From extraction experiments and c-activity measurements, the extraction constant corresponding to the equilibrium Cs+ (aq) + I (aq) + 1 (org),1Cs+ (org) + I (org) taking place in the two-phase water-phenyltrifluoromethyl sulfone (abbrev. FS 13) system (1 = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, org = FS 13 phase) was evaluated as logKex (1Cs+, I) = 2.1 0.1. Further, the stability constant of the 1Cs+ complex in FS 13 saturated with water was calculated for a temperature of 25 C: log borg (1Cs+) = 9.9 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complexmore » species 1Cs+ was derived. In the resulting 1Cs+ complex, the central cation Cs+ is bound by eight bond interactions to six oxygen atoms of the respective 18-crown-6 moiety and to two carbons of the corresponding two benzene rings of the parent ligand 1 via cation p interaction.« less

Photoionization of Atoms and Ions: Application of Time-Dependent Response Method within the Density Functional Theory.

DTIC Science & Technology

1987-10-13

AD-A±95 686 PHOTOIONIZATION OF ATOMS AND IONS: APPLICATION OF III TIME-DEPENDENT RESPONSE..(U) NAVAL RESEARCH LAB WASHINGTON DC U GUPTA ET AL. 13 OCT...on revere if ncemy and idmntify by block number) FIELD GROUP SUBGROUP Photoionization Density functional Atoms Time dependent 1 S. (Continue on...reverse if necenary and identify by block numnbw) The photoionization cross-section of several atoms (AT, Xe, Rn, Cs) and ions (Ne-like Ar, H-like and Li

Electronic structure of layered quaternary chalcogenide materials for band-gap engineering: The example of Cs2MIIM3IVQ8

NASA Astrophysics Data System (ADS)

Besse, Rafael; Sabino, Fernando P.; Da Silva, Juarez L. F.

2016-04-01

Quaternary chalcogenide materials offer a wide variety of chemical and physical properties, and hence, those compounds have been widely studied for several technological applications. Recently, experimental studies have found that the chalcogenide Cs2MIIM3IVQ8 family (MII = Mg , Zn , Cd , Hg , MIV = Ge , Sn and Q = S , Se , Te ), which includes 24 compounds, yields a wide range of band gaps, namely, from 1.07 to 3.4 eV, and hence, they have attracted great interest. To obtain an improved atomistic understanding of the role of the cations and anions on the physical properties, we performed a first-principles investigation of the 24 Cs2MIIM3IVQ8 compounds employing density functional theory within semilocal and hybrid exchange-correlation energy functionals and the addition of van der Waals corrections to improve the description of the weakly interacting layers. Our lattice parameters are in good agreement with the available experimental data (i.e., 11 compounds), and the equilibrium volume increases linearly by increasing the atomic number of the chalcogen, which can be explained by the increased atomic radius of the chalcogen atoms from S to Te . We found that van der Waals corrections play a crucial role in the lattice parameter in the stacking direction of the Cs2MIIM3IVQ8 layers, while the binding energy per unit area has similar magnitude as obtained for different layered materials. We obtained that the band gaps follow a linear relation as a function of the unit cell volume, which can be explained by the atomic size of the chalcogen atom and the relative position of the Q p states within the band structure. The fundamental and optical band gaps differ by less than 0.1 eV. The band gaps obtained with the hybrid functional are in good agreement with the available experimental data. Furthermore, we found from the Bader analysis, that the Coulomb interations among the cations and anions play a crucial role on the energetic properties.

Periodic cation segregation in Cs0.44[Nb2.54W2.46O14] quantified by high-resolution scanning transmission electron microscopy.

PubMed

Heidelmann, Markus; Barthel, Juri; Cox, Gerhard; Weirich, Thomas E

2014-10-01

The atomic structure of Cs0.44[Nb2.54W2.46O14] closely resembles the structure of the most active catalyst for the synthesis of acrylic acid, the M1 phase of Mo10V2(4+)Nb2TeO42-x. Consistently with observations made for the latter compound, the high-angle electron scattering signal recorded by scanning transmission electron microscopy shows a significant intensity variation, which repeats periodically with the projected crystallographic unit cell. The occupation factors for the individual mixed Nb/W atomic columns are extracted from the observed intensity variations. For this purpose, experimental images and simulated images are compared on an identical intensity scale, which enables a quantification of the cation distribution. According to our analysis specific sites possess low tungsten concentrations of 25%, whereas other sites have tungsten concentrations above 70%. These findings allow us to refine the existing structure model of the target compound, which has until now described a uniform distribution of the niobium and tungsten atoms in the unit cell, showing that the similarity between Cs0.44[Nb2.54W2.46O14] and the related catalytic compounds also extends to the level of the cation segregation.

Solid-phase extraction and separation procedure for trace aluminum in water samples and its determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS).

PubMed

Ciftci, Harun; Er, Cigdem

2013-03-01

In the present study, a separation/preconcentration procedure for determination of aluminum in water samples has been developed by using a new atomic absorption spectrometer concept with a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution double-echelle monochromator, and a charge-coupled device array detector. Sample solution pH, sample volume, flow rate of sample solution, volume, and concentration of eluent for solid-phase extraction of Al chelates with 4-[(dicyanomethyl)diazenyl] benzoic acid on polymeric resin (Duolite XAD-761) have been investigated. The adsorbed aluminum on resin was eluted with 5 mL of 2 mol L(-1) HNO(3) and its concentration was determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Under the optimal conditions, limit of detection obtained with HR-CS FAAS and Line Source FAAS (LS-FAAS) were 0.49 μg L(-1) and 3.91 μg L(-1), respectively. The accuracy of the procedure was confirmed by analyzing certified materials (NIST SRM 1643e, Trace elements in water) and spiked real samples. The developed procedure was successfully applied to water samples.

Interaction of Cesium Ions with Calix[4]arene-bis(t-octylbenzo-18-crown-6): NMR and Theoretical Study

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

Kriz, Jaroslav; Dybal, Jiri; Vanura, Petr

2011-01-01

Using 1H, 13C, and 133Cs NMR spectra, it is shown that calix[4]arene-bis (t-octylbenzo-18-crown-6) (L) forms complexes with one (L 3 Cs ) and two (L 3 2Cs ) Cs ions offered by cesium bis(1,2-dicarbollide) cobaltate (CsDCC) in nitrobenzene-d5. The ions interact with all six oxygen atoms in the crown-ether ring and the electrons of the calixarene aromatic moieties. According to extraction technique, the stability constant of the first complex is log nb(L 3 Cs ) = 8.8 ( 0.1. According to 133Cs NMR spectra, the value of the equilibrium constant of the second complex is log Knb (2)(L 3 2Csmore » ) = 6.3(0.2, i.e., its stabilization constant is log nb(L 3 2Cs ) = 15.1 ( 0.3. Self-diffusion measurements by 1H pulsed-field gradient (PFG) NMRcombined with density functional theory (DFT) calculations suggest that one DCC ion is tightly associated with L 3 Cs , decreasing its positive charge and consequently stabilizing the second complex, L 3 2Cs . Using a saturation-transfer 133Cs NMR technique, the correlation times ex of chemical exchange between L 3 Cs and L 3 2Cs as well as between L 3 2Cs and free Cs ions were determined as 33.6 and 29.2 ms, respectively.« less

Marking cabbage looper (Lepidoptera: Noctuidae) with cesium

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

Moss, J.I.; Van Steenwyk, R.A.

1984-04-01

Cabbage loopers (CL), Trichoplusia ni (Huebner), adults reared on artificial diet containing 1 x 10/sup -2/ M and 1 x 10/sup -3/ M CsCl were marked with cesium (Cs) which could be detected by atomic absorption spectrophotometry. The cesium marks from the 10/sup -2/ M CsCl diet were sufficient to last the expected lifetime of the insects. CL reared on diet containing 1 x 10/sup -1/ M CsCl did not survive. Unmarked females mated to males reared on artificial diet containing 1 x 10/sup -2/ M and 1 x 10/sup -3/ M CsCl were marked. CL reared on cotton plantsmore » sprayed with Cs solutions of 1000, 5000, and 10,000 ..mu..g/ml were marked sufficiently to last the expected lifetime of the insect. CL adults exposed for 72 h to cotton plants sprayed with Cs solutions of 1000, 5000, and 10,000 ..mu..g/ml were marked sufficiently to last the expected lifetime of the insect. CL adults reared from field cotton plants sprayed with CsCl solutions at rates of 1.24, 2.47, and 4.94 kg of CsCl per ha were marked. 12 references, 1 figure, 5 tables.« less

Improved Analytical Potentials for the a ^3Σu+ and X ^1Σg+ States of {Cs_2}

NASA Astrophysics Data System (ADS)

Baldwin, Jesse; Le Roy, Robert J.

2012-06-01

Recent studies of the collisional properties of ultracold Cs atoms have led to a renewed interest in the singlet and triplet ground-state potential energy functions of Cs_2. Coxon and Hajigeorgiou recently determined an analytic potential function for the X ^1Σ_g^+ state that accurately reproduces a large body of spectroscopic data that spanned 99.45% of the potential well. However, their potential explicitly incorporates only the three leading inverse-power terms in the long-range potential, and does not distinguish between the three asymptotes associated with the different Cs atom spin states. Similarly, Xie et al. have reported two versions of an analytic potential energy function for the a ^3Σ_u^+ state that they determined from direct potential fits to emission data that spanned 93 % of its potential energy well. However, the tail of their potential function model was not constrained to have the inverse-power-sum form required by theory. Moreover, a physically correct description of cold atom collision phenomena requires the long-range inverse-power tails of these two potentials to be identical, and they are not. Thus, these functions cannot be expected to describe cold atom collision properties correctly. The present paper describes our efforts to determine improved analytic potential energy functions for these states that have identical long-range tails, and fully represent all of the spectroscopic data used in the earlier worka,b,c as well as photoassociation data that was not considered there and experimental values of the collisional scattering lengths for the two states. J. A. Coxon and P. Hajigeorgiou, J. Chem. Phys. 132, 09105 (2010). F. Xie et al. J. Chem. Phys. 130 051102 (2009). F. Xie et al. J. Chem. Phys. 135, 024303 (2011) J. G. Danzl et al., Science, 321, 1062 (2008). C. Chin, et al., Phys. Rev. Lett. 85, 2717 (2000) P. J. Leo, C. J. Williams, and P. S. Julienne, Phys. Rev. Lett. 85, 2721 (2000)

The Introduction of Crystallographic Concepts Using Lap-Dissolve Slide Techniques.

ERIC Educational Resources Information Center

Bodner, George M.; And Others

1980-01-01

Describes a method using lap-dissolve slide techniques with two or more slide projectors focused on a single screen for presenting visual effects that show structural features in extended arrays of atoms, or ions involving up to several hundred atoms. Presents an outline of an introduction to the structures of crystalline solids. (CS)

Continuous exposure to low-frequency noise and carbon disulfide: Combined effects on hearing.

PubMed

Venet, Thomas; Carreres-Pons, Maria; Chalansonnet, Monique; Thomas, Aurélie; Merlen, Lise; Nunge, Hervé; Bonfanti, Elodie; Cosnier, Frédéric; Llorens, Jordi; Campo, Pierre

2017-09-01

Carbon disulfide (CS 2 ) is used in industry; it has been shown to have neurotoxic effects, causing central and distal axonopathies.However, it is not considered cochleotoxic as it does not affect hair cells in the organ of Corti, and the only auditory effects reported in the literature were confined to the low-frequency region. No reports on the effects of combined exposure to low-frequency noise and CS 2 have been published to date. This article focuses on the effects on rat hearing of combined exposure to noise with increasing concentrations of CS 2 (0, 63,250, and 500ppm, 6h per day, 5 days per week, for 4 weeks). The noise used was a low-frequency noise ranging from 0.5 to 2kHz at an intensity of 106dB SPL. Auditory function was tested using distortion product oto-acoustic emissions, which mainly reflects the cochlear performances. Exposure to noise alone caused an auditory deficit in a frequency area ranging from 3.6 to 6 kHz. The damaged area was approximately one octave (6kHz) above the highest frequency of the exposure noise (2.8kHz); it was a little wider than expected based on the noise spectrum.Consequently, since maximum hearing sensitivity is located around 8kHz in rats, low-frequency noise exposure can affect the cochlear regions detecting mid-range frequencies. Co-exposure to CS 2 (250-ppm and over) and noise increased the extent of the damaged frequency window since a significant auditory deficit was measured at 9.6kHz in these conditions.Moreover, the significance at 9.6kHz increased with the solvent concentrations. Histological data showed that neither hair cells nor ganglion cells were damaged by CS 2 . This discrepancy between functional and histological data is discussed. Like most aromatic solvents, carbon disulfide should be considered as a key parameter in hearing conservation régulations. Copyright © 2017 Elsevier B.V. All rights reserved.

Facile synthesis of CsPbBr3/PbSe composite clusters

PubMed Central

Nguyen, Thang Phan; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Lee, Tae Hyung; Jang, Ho Won; Kim, Soo Young

2018-01-01

Abstract In this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs:Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots. PMID:29296127

Preparation and antibacterial activity of compound chitosan-compound Yizhihao-nanoparticles.

PubMed

Ou, Sheng; Zhang, Yang-de

2008-05-01

To prepare chitosan (CS)-compound Yizhihao-nanoparticles (NP) and to investigate its antibacterial activity. CS NPs were formed by the incorporation of CS and Na3 PO4. CS-compound Yizhihao NPs were prepared by ion-cross-linking. The particle sizes and surface charges of CS NPs were determined by Malvern Zetasizer 1000-HAS and atomic force microscope (AFM), respectively. The antibacterial activity of CS-compound Yizhihao-NPs was studied in vitro and compared with that of compound Yizhihao powder. Malvern Zetasizer 1000-HAS and AFM demonstrated that the diameter of CS-compound Yizhihao NPs was (137.00+/-14.28)nm and CS NPs had (16.90+/-1.32)mV positive surface charges. The minimal inhibitory concentrations (MIC) of CS-compound Yizhihao NPs on Staphylococcus aureus,Pneumococcus,beta-hemolytic streptococcus, and Escherichia coli were 1:32,1:32,1:16,and 1:2, respectively. The minimal bactericidal concentrations (MBC) of CS-compound Yizhihao-NPs on Staphylococcus aureus, Pneumococcus, beta-hemolytic streptococcus, and Escherichia coli were 1:16,1:16,1:8, and 1:2, respectively. The antibacterial efficacy of CS-compound Yizhihao-NPs to Staphylococcus aureus, Pneumococcus, and beta-hemolytic streptococcus had been improved significantly (P< 0.05). CS-compound Yizhihao-nanoparticles have obvious antibacterial activity to the Staphylococcus aureus,Pneumococcus,and beta-hemolytic streptococcus,which lays the experimental foundation for new preparation of traditional Chinese medicine in future research.

Atherosclerotic Plaque in Patients with Zero Calcium Score at Coronary Computed Tomography Angiography

PubMed Central

Gabriel, Fabíola Santos; Gonçalves, Luiz Flávio Galvão; de Melo, Enaldo Vieira; Sousa, Antônio Carlos Sobral; Pinto, Ibraim Masciarelli Francisco; Santana, Sara Melo Macedo; de Matos, Carlos José Oliveira; Souto, Maria Júlia Silveira; Conceição, Flávio Mateus do Sacramento; Oliveira, Joselina Luzia Menezes

2018-01-01

Background In view of the high mortality for cardiovascular diseases, it has become necessary to stratify the main risk factors and to choose the correct diagnostic modality. Studies have demonstrated that a zero calcium score (CS) is characteristic of a low risk for cardiovascular events. However, the prevalence of individuals with coronary atherosclerotic plaques and zero CS is conflicting in the specialized literature. Objective To evaluate the frequency of patients with coronary atherosclerotic plaques, their degree of obstruction and associated factors in patients with zero CS and indication for coronary computed tomography angiography (CCTA). Methods This is a cross-sectional, prospective study with 367 volunteers with zero CS at CCTA in four diagnostic imaging centers in the period from 2011 to 2016. A significance level of 5% and 95% confidence interval were adopted. Results The frequency of atherosclerotic plaque in the coronary arteries in 367 patients with zero CS was 9.3% (34 individuals). In this subgroup, mean age was 52 ± 10 years, 18 (52.9%) were women and 16 (47%) had significant coronary obstructions (> 50%), with involvement of two or more segments in 4 (25%) patients. The frequency of non-obese individuals (90.6% vs 73.9%, p = 0.037) and alcohol drinkers (55.9% vs 34.8%, p = 0.015) was significantly higher in patients with atherosclerotic plaques, with an odds ratio of 3.4 for each of this variable. Conclusions The frequency of atherosclerotic plaque with zero CS was relatively high, indicating that the absence of calcification does not exclude the presence of plaques, many of which obstructive, especially in non-obese subjects and alcohol drinkers. PMID:29723329

Clinicians' Perspectives and Experiences Regarding Maternity Care in Women With Vulvodynia.

PubMed

Smith, Kelly B; Sadownik, Leslie A; Basson, Rosemary; Isaacson, Jordanna; Brotto, Lori A

2016-09-01

To assess clinicians' frequency of and comfort with provision of maternity care for women with vulvodynia, their beliefs and practices regarding delivery mode, and frequency of maternal requests for Caesarean section (CS). We invited physicians and midwives to complete a questionnaire assessing their frequency of contact with pregnant women with vulvodynia; their level of comfort providing antenatal, intrapartum, and postpartum care for these women; whether they believed that vulvodynia is an indication for elective CS and the frequency of making this recommendation; and the number of patients with vulvodynia who strongly requested CS. Of the 140 participating clinicians, 91 were physicians and 49 were midwives. Most physicians (n = 64; 70.4%) saw patients with vulvodynia at least once per month. Clinicians who saw women with vulvodynia were most likely to see pregnant women with vulvodynia rarely (n = 54; 40.3%) or every six to 12 months (n = 29; 21.6%). Almost one third (n = 44; 31.4%) were not comfortable providing maternity care for these women, and 16.4% (n = 23) agreed that vulvodynia was an indication for elective CS. Of respondents who provided maternity care for women with vulvodynia, 15.4% (n = 18) had recommended CS; the most common reason for doing so was potential worsening of vulvar symptoms. The majority of clinicians who provided maternity care for women with vulvodynia (n = 73; 62.4%) indicated that maternal requests for CS were rare. Almost one third of participating clinicians (31.4%) were not comfortable providing maternity care for women with vulvodynia. Despite infrequent maternal requests, a minority of clinicians believed that vulvodynia is an indication for CS and/or made that recommendation. Additional research and education are needed to provide optimal obstetric care for women with vulvodynia. Copyright © 2016 The Society of Obstetricians and Gynaecologists of Canada/La Société des obstétriciens et gynécologues du Canada. Published by Elsevier Inc. All rights reserved.

Sulfation and Cation Effects on the Conformational Properties of the Glycan Backbone of Chondroitin Sulfate Disaccharides

PubMed Central

Faller, Christina E.; Guvench, Olgun

2015-01-01

Chondroitin sulfate (CS) is one of several glycosaminoglycans that are major components of proteoglycans. A linear polymer consisting of repeats of the disaccharide -4GlcAβ1-3GalNAcβ1-, CS undergoes differential sulfation resulting in five unique sulfation patterns. Because of the dimer repeat, the CS glycosidic “backbone” has two distinct sets of conformational degrees of freedom defined by pairs of dihedral angles: (ϕ1, ψ1) about the β1-3 glycosidic linkage and (ϕ2, ψ2) about the β1-4 glycosidic linkage. Differential sulfation and the possibility of cation binding, combined with the conformational flexibility and biological diversity of CS, complicate experimental efforts to understand CS three-dimensional structures at atomic resolution. Therefore, all-atom explicit-solvent molecular dynamics simulations with Adaptive Biasing Force sampling of the CS backbone were applied to obtain high resolution, high precision free energies of CS disaccharides as a function of all possible backbone geometries. All ten disaccharides (β1-3 vs. β1-4 linkage x five different sulfation patterns) were studied; additionally, ion effects were investigated by considering each disaccharide in the presence of either neutralizing sodium or calcium cations. GlcAβ1-3GalNAc disaccharides have a single, broad, thermodynamically important free-energy minimum whereas GalNAcβ1-4GlcA disaccharides have two such minima. Calcium cations but not sodium cations bind to the disaccharides, and binding is primarily to the GlcA –COO− moiety as opposed to sulfate groups. This binding alters the glycan backbone thermodynamics in instances where a calcium cation bound to –COO− can act to bridge and stabilize an interaction with an adjacent sulfate group, whereas, in the absence of this cation, the proximity of a sulfate group to –COO− results in two like charges being both desolvated and placed adjacent to each other and is found to be destabilizing. In addition to providing information on sulfation and cation effects, the present results can be applied to building models of CS polymers and as a point of comparison in studies of CS polymer backbone dynamics and thermodynamics. PMID:25906376

Sulfation and cation effects on the conformational properties of the glycan backbone of chondroitin sulfate disaccharides.

PubMed

Faller, Christina E; Guvench, Olgun

2015-05-21

Chondroitin sulfate (CS) is one of several glycosaminoglycans that are major components of proteoglycans. A linear polymer consisting of repeats of the disaccharide -4GlcAβ1-3GalNAcβ1-, CS undergoes differential sulfation resulting in five unique sulfation patterns. Because of the dimer repeat, the CS glycosidic "backbone" has two distinct sets of conformational degrees of freedom defined by pairs of dihedral angles: (ϕ1, ψ1) about the β1-3 glycosidic linkage and (ϕ2, ψ2) about the β1-4 glycosidic linkage. Differential sulfation and the possibility of cation binding, combined with the conformational flexibility and biological diversity of CS, complicate experimental efforts to understand CS three-dimensional structures at atomic resolution. Therefore, all-atom explicit-solvent molecular dynamics simulations with Adaptive Biasing Force sampling of the CS backbone were applied to obtain high-resolution, high-precision free energies of CS disaccharides as a function of all possible backbone geometries. All 10 disaccharides (β1-3 vs β1-4 linkage × five different sulfation patterns) were studied; additionally, ion effects were investigated by considering each disaccharide in the presence of either neutralizing sodium or calcium cations. GlcAβ1-3GalNAc disaccharides have a single, broad, thermodynamically important free-energy minimum, whereas GalNAcβ1-4GlcA disaccharides have two such minima. Calcium cations but not sodium cations bind to the disaccharides, and binding is primarily to the GlcA -COO(-) moiety as opposed to sulfate groups. This binding alters the glycan backbone thermodynamics in instances where a calcium cation bound to -COO(-) can act to bridge and stabilize an interaction with an adjacent sulfate group, whereas, in the absence of this cation, the proximity of a sulfate group to -COO(-) results in two like charges being both desolvated and placed adjacent to each other and is found to be destabilizing. In addition to providing information on sulfation and cation effects, the present results can be applied to building models of CS polymers and as a point of comparison in studies of CS polymer backbone dynamics and thermodynamics.

The effect of internal rotation in p-methyl anisole studied by microwave spectroscopy

NASA Astrophysics Data System (ADS)

Ferres, Lynn; Stahl, Wolfgang; Kleiner, Isabelle; Nguyen, Ha Vinh Lam

2018-01-01

The Fourier transform microwave spectrum of p-methyl anisole, CH3C6H4OCH3, was measured in the frequency range from 2 to 26.5 GHz under molecular jet conditions. The conformational analysis yielded only one stable conformer, in which all heavy atoms are co-planar, and which was identified after analyzing the spectrum by comparison with the results from quantum chemical calculations. The barrier of the V3 potential of the ring methyl rotor was found to be 49.6370(1) cm-1, and was compared with that found in other para-substituted toluenes as well as in o-methyl anisole. A comparison between two theoretical approaches treating internal rotations, the rho axis method (program BELGI-Cs) and combined axis method (program XIAM), was also performed.

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

Schafer, Marion; Bobev, Svilen

This paper presents results from our exploratory work in the systems K-Cd-Ge, Rb-Cd-Ge, and Cs-Cd-Ge, which yielded the novel type-I clathrates with refined compositions K 8Cd 3.77(7)Ge 42.23, Rb 8Cd 3.65(7)Ge 42.35, and Cs 7.80(1)Cd 3.65(6)Ge 42.35. The three compounds represent rare examples of clathrates of germanium with the alkali metals, where a d 10 element substitutes a group 14 element. The three structures, established by single-crystal X-ray diffraction, indicate that the framework-building Ge atoms are randomly substituted by Cd atoms on only one of the three possible crystallographic sites. Furthermore, this and several other details of the crystal chemistrymore » are elaborated.« less

Snapshots of C-S Cleavage in Egt2 Reveals Substrate Specificity and Reaction Mechanism.

PubMed

Irani, Seema; Naowarojna, Nathchar; Tang, Yang; Kathuria, Karan R; Wang, Shu; Dhembi, Anxhela; Lee, Norman; Yan, Wupeng; Lyu, Huijue; Costello, Catherine E; Liu, Pinghua; Zhang, Yan Jessie

2018-05-17

Sulfur incorporation in the biosynthesis of ergothioneine, a histidine thiol derivative, differs from other well-characterized transsulfurations. A combination of a mononuclear non-heme iron enzyme-catalyzed oxidative C-S bond formation and a subsequent pyridoxal 5'-phosphate (PLP)-mediated C-S lyase reaction leads to the net transfer of a sulfur atom from a cysteine to a histidine. In this study, we structurally and mechanistically characterized a PLP-dependent C-S lyase Egt2, which mediates the sulfoxide C-S bond cleavage in ergothioneine biosynthesis. A cation-π interaction between substrate and enzyme accounts for Egt2's preference of sulfoxide over thioether as a substrate. Using mutagenesis and structural biology, we captured three distinct states of the Egt2 C-S lyase reaction cycle, including a labile sulfenic intermediate captured in Egt2 crystals. Chemical trapping and high-resolution mass spectrometry were used to confirm the involvement of the sulfenic acid intermediate in Egt2 catalysis. Copyright © 2018 Elsevier Ltd. All rights reserved.

ESTIMATION OF EFFECTIVE DOSE FROM EXTERNAL EXPOSURE DUE TO SHORT-LIVED NUCLIDES IN THE PREFECTURES SURROUNDING FUKUSHIMA.

PubMed

Miyatake, Hirokazu; Yoshizawa, Nobuaki; Suzuki, Gen

2018-05-11

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a release of radionuclides into the environment. Since the accident, measurements of radiation in the environment such as air dose rate and deposition density of radionuclides have been performed by various organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously over widespread areas. Based on the data measured by JAEA, we estimated effective dose from external exposure in the prefectures surrounding Fukushima. Since car-borne survey started a few months after the accident, the main contribution to measured data comes from 137Cs and 134Cs whose half-lives are relatively long. Using air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-lived nuclides to that of 137Cs and 134Cs, we also estimated contributions to the effective dose from other short-lived nuclides.

Bandgap Engineering of Lead-Free Double Perovskite Cs2 AgBiBr6 through Trivalent Metal Alloying.

PubMed

Du, Ke-Zhao; Meng, Weiwei; Wang, Xiaoming; Yan, Yanfa; Mitzi, David B

2017-07-03

The double perovskite family, A 2 M I M III X 6 , is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH 3 NH 3 PbI 3 . Given the generally large indirect band gap within most known double perovskites, band-gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs 2 AgBiBr 6 as host, band-gap engineering through alloying of In III /Sb III has been demonstrated in the current work. Cs 2 Ag(Bi 1-x M x )Br 6 (M=In, Sb) accommodates up to 75 % In III with increased band gap, and up to 37.5 % Sb III with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs 2 Ag(Bi 0.625 Sb 0.375 )Br 6 . Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three-metal systems are also assessed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cs-137 and Sr-90 level in diary products

NASA Astrophysics Data System (ADS)

Petukhov, V. L.; Gorb, T. S.; Petukhov, I. V.; Dukhanov, Yu. A.; Sevryuk, I. Z.; Patrashkov, S. A.; Korotkevich, O. S.

2003-05-01

About 70% of radioactive substances fell on the territory of the Byelorussia Republic after the Chernobyl Atom Power Station Disaster. Cs-137 and Sr-90 accumulation dynamics was studied in milk of the cows from the highest polluted Braginsky area. 408 milk samples of Black and White cows were investigated. In 1995 average Cs-137 and Sr-90 levels were 61.00 and 3.73 Bk/dm^3 respectively. Cs-137 and Sr-90 levels exceeded Byelorussia Republic upperlimits RDU 96 in 10 and 50% of milk samples respectively. After 5 years (by 2000) Cs-137 and Sr-90 levels had become almost 3 and 2 times less (21.70 Bk/dm^3 and 1.72 Bk/dm^3 respectively). Cs-137 and Sr-90 levels exceeded RDU 96 in 1.5 and 5.5% of milk samples respectively. In the same periods Cs-137 and Sr-90 levels were 7 and 2 times higher than the similar indexes in the relatively clean Novosibirsk area. Thus, radioactive element levels in milk of Black and White cows of the Byelorussia Republic decreased significantly for the past years.

Strong composition-dependent variation of MCs + calibration factors in TiO x and GeO x ( x ≤ 2) films

NASA Astrophysics Data System (ADS)

Gnaser, Hubert; Le, Yongkang; Su, Weifeng

2006-07-01

The emission of MCs + secondary ions (M designates the analyte species) from TiO x (0.2 ≤ x ≤ 2) and GeO x (0.001 ≤ x ≤ 0.8) films under Cs + bombardment was examined. The relative calibration factors of OCs +/TiCs + and OCs +/GeCs + were determined and were found to depend pronouncedly on the O/Ti and O/Ge atomic concentration ratios. Specifically, with increasing oxygen content OCs + ions form much more efficiently (as compared to TiCs + or GeCs + ions), an enhancement amounting to more than a factor of 10 for the highest oxygen concentrations. Concurrently, the formation of TiOCs + or GeOCs + ions increases drastically. For both oxide systems, an empirical relation for the oxygen-concentration dependence of the relative calibration factors could be established.

Cs-doped Mo as surface converter for H{sup −}/D{sup −} generation in negative ion sources: First steps and proof of principle

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

Schiesko, L., E-mail: loic.schiesko@ipp.mpg.de; Hopf, C.; Höschen, T.

2015-04-08

In a proof-of-principle study, molybdenum samples were implanted with a very small dose of Cs in order to test the properties of the compound as a surface converter for negative hydrogen ion production. First results on the properties of Cs doped Mo compounds show a reduction of the work function and a stable H{sup −} yield up to four hours in low density hydrogen plasma. The implanted Cs atoms were stable in the Mo lattice over one year for samples stored in vacuum and not exposed to the plasma. The surface H{sup −} generation mechanisms were identified and a comparisonmore » of the negative ion yield with pure Mo showed that the Cs doped Mo sample’s yield was much larger.« less

Middle School Science Notes

ERIC Educational Resources Information Center

School Science Review, 1976

1976-01-01

Describes a lighted demonstration apparatus for representing the distribution of electrons, protons and neutrons in an atom. Also includes experiments with ice, forces, microscopes, spectra, and geological modeling. (CS)

Task 2 - Limits for High-Frequency Conducted Susceptibility Testing - CS114 (NRC-HQ-60-14-D-0015)

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

Wood, Richard Thomas; Ewing, Paul D.; Moses, Rebecca J.

2015-09-01

A principal focus of Task 2 under this project was for ORNL to evaluate the basis for susceptibility testing against high-frequency conducted interference and to establish recommendations to resolve concerns about the severity of test limits for the conducted susceptibility (CS) test, CS114, from MIL-STD-461. The primary concern about the test limit has been characterized by the EPRI EMI Working Group in the following terms: Demonstrating compliance with the CS114 test limits recommended in TR-102323 has proven to be problematic, even for components that have been tested to commercial standards and demonstrated proper operation in industrial applications [6]. Specifically, EPRImore » notes that the CS114 limits approved in regulatory documents are significantly higher than those invoked by the US military and similar commercial standards in the frequency range below 200 kHz. For this task, ORNL evaluated the original approach to establishing the test limit, EPRI technical findings from a review of the limit, and the regulatory basis through which the currently approved limits were accepted. Based on this analysis, strategies have been developed regarding changes to the CS114 limit that can resolve the technical concerns raised by the industry. Guided by the principles that reasonable assurance of safety must not be compromised but excessive conservatism should be reduced, recommendations on a suitable basis for a revised limit have been developed and can be incorporated into the planned Revision 2 of RG 1.180.« less

Pre-attentive, context-specific representation of fear memory in the auditory cortex of rat.

PubMed

Funamizu, Akihiro; Kanzaki, Ryohei; Takahashi, Hirokazu

2013-01-01

Neural representation in the auditory cortex is rapidly modulated by both top-down attention and bottom-up stimulus properties, in order to improve perception in a given context. Learning-induced, pre-attentive, map plasticity has been also studied in the anesthetized cortex; however, little attention has been paid to rapid, context-dependent modulation. We hypothesize that context-specific learning leads to pre-attentively modulated, multiplex representation in the auditory cortex. Here, we investigate map plasticity in the auditory cortices of anesthetized rats conditioned in a context-dependent manner, such that a conditioned stimulus (CS) of a 20-kHz tone and an unconditioned stimulus (US) of a mild electrical shock were associated only under a noisy auditory context, but not in silence. After the conditioning, although no distinct plasticity was found in the tonotopic map, tone-evoked responses were more noise-resistive than pre-conditioning. Yet, the conditioned group showed a reduced spread of activation to each tone with noise, but not with silence, associated with a sharpening of frequency tuning. The encoding accuracy index of neurons showed that conditioning deteriorated the accuracy of tone-frequency representations in noisy condition at off-CS regions, but not at CS regions, suggesting that arbitrary tones around the frequency of the CS were more likely perceived as the CS in a specific context, where CS was associated with US. These results together demonstrate that learning-induced plasticity in the auditory cortex occurs in a context-dependent manner.

The aluminum ordering in aluminosilicates: a dipolar 27Al NMR spectroscopy study.

PubMed

Gee, Becky A

2004-01-01

The spatial ordering of aluminum atoms in CsAl(SiO3)2 and 3Al2O3.2SiO2 was probed by 27Al dipolar solid-state NMR spectroscopy. The 27Al response to a Hahn spin-echo pulse sequence in a series of aluminum-containing model crystalline compounds demonstrates that quantitative 27Al homonuclear dipolar second moments can be obtained to within +/-20% of the theoretical values, if evaluation of the spin-echo response curve is limited to short evolution periods (2t1 < or = 0.10 ms). Additionally, selective excitation of the central transition m = 1/2 --> -1/2 is necessary in order to ensure quantitative results. Restriction of spin exchange affecting the dephasing of the magnetization may decelerate the spin-echo decay at longer evolution periods. Considering these restraints, the method was used to probe the spatial distribution of aluminum atoms among the tetrahedral sites in two aluminosilicate materials. Experimental 27Al spin-echo response data for the aluminosilicates CsAl(SiO3)2 (synthetic pollucite) and 3Al2O3.2SiO2 (mullite) are compared with theoretical data based on (I) various degrees of aluminum-oxygen-aluminum bond formation among tetrahedrally coordinated aluminum atoms (Al(T(d) )-O-Al(T(d) )) and (II) the maximum avoidance of Al(T(d) )-O-Al(T(d) ) bonding. Analysis of the second moment values and resulting echo decay responses suggests that partial suppression of spin exchange among aluminum atoms in crystallographically distinct sites may contribute to the 27Al spin echo decay in 3Al2O3.2SiO2, thus complicating quantitative analysis of the data. Silicon-29 and aluminum-27 magic angle spinning (MAS) NMR spectra of 3Al2O3.2SiO2 are consistent with those previously reported. The experimental 27Al spin-echo response behavior of CsAl(SiO3)2 differs from the theoretical response behavior based on the maximum avoidance of Al-O-Al bonding between tetrahedral aluminum sites in CsAl(SiO3)2. A single unresolved resonance is observed in both the silicon-29 and aluminum-27 MAS spectra of CsAl(SiO3)2. Copyright 2003 John Wiley & Sons, Ltd.

Robustness effect of gap junctions between Golgi cells on cerebellar cortex oscillations

PubMed Central

2011-01-01

Background Previous one-dimensional network modeling of the cerebellar granular layer has been successfully linked with a range of cerebellar cortex oscillations observed in vivo. However, the recent discovery of gap junctions between Golgi cells (GoCs), which may cause oscillations by themselves, has raised the question of how gap-junction coupling affects GoC and granular-layer oscillations. To investigate this question, we developed a novel two-dimensional computational model of the GoC-granule cell (GC) circuit with and without gap junctions between GoCs. Results Isolated GoCs coupled by gap junctions had a strong tendency to generate spontaneous oscillations without affecting their mean firing frequencies in response to distributed mossy fiber input. Conversely, when GoCs were synaptically connected in the granular layer, gap junctions increased the power of the oscillations, but the oscillations were primarily driven by the synaptic feedback loop between GoCs and GCs, and the gap junctions did not change oscillation frequency or the mean firing rate of either GoCs or GCs. Conclusion Our modeling results suggest that gap junctions between GoCs increase the robustness of cerebellar cortex oscillations that are primarily driven by the feedback loop between GoCs and GCs. The robustness effect of gap junctions on synaptically driven oscillations observed in our model may be a general mechanism, also present in other regions of the brain. PMID:22330240

Correlation between k-space sampling pattern and MTF in compressed sensing MRSI.

PubMed

Heikal, A A; Wachowicz, K; Fallone, B G

2016-10-01

To investigate the relationship between the k-space sampling patterns used for compressed sensing MR spectroscopic imaging (CS-MRSI) and the modulation transfer function (MTF) of the metabolite maps. This relationship may allow the desired frequency content of the metabolite maps to be quantitatively tailored when designing an undersampling pattern. Simulations of a phantom were used to calculate the MTF of Nyquist sampled (NS) 32 × 32 MRSI, and four-times undersampled CS-MRSI reconstructions. The dependence of the CS-MTF on the k-space sampling pattern was evaluated for three sets of k-space sampling patterns generated using different probability distribution functions (PDFs). CS-MTFs were also evaluated for three more sets of patterns generated using a modified algorithm where the sampling ratios are constrained to adhere to PDFs. Strong visual correlation as well as high R 2 was found between the MTF of CS-MRSI and the product of the frequency-dependant sampling ratio and the NS 32 × 32 MTF. Also, PDF-constrained sampling patterns led to higher reproducibility of the CS-MTF, and stronger correlations to the above-mentioned product. The relationship established in this work provides the user with a theoretical solution for the MTF of CS MRSI that is both predictable and customizable to the user's needs.

A novel 3D Cartesian random sampling strategy for Compressive Sensing Magnetic Resonance Imaging.

PubMed

Valvano, Giuseppe; Martini, Nicola; Santarelli, Maria Filomena; Chiappino, Dante; Landini, Luigi

2015-01-01

In this work we propose a novel acquisition strategy for accelerated 3D Compressive Sensing Magnetic Resonance Imaging (CS-MRI). This strategy is based on a 3D cartesian sampling with random switching of the frequency encoding direction with other K-space directions. Two 3D sampling strategies are presented. In the first strategy, the frequency encoding direction is randomly switched with one of the two phase encoding directions. In the second strategy, the frequency encoding direction is randomly chosen between all the directions of the K-Space. These strategies can lower the coherence of the acquisition, in order to produce reduced aliasing artifacts and to achieve a better image quality after Compressive Sensing (CS) reconstruction. Furthermore, the proposed strategies can reduce the typical smoothing of CS due to the limited sampling of high frequency locations. We demonstrated by means of simulations that the proposed acquisition strategies outperformed the standard Compressive Sensing acquisition. This results in a better quality of the reconstructed images and in a greater achievable acceleration.

Simple and robust referencing system enables identification of dissolved-phase xenon spectral frequencies.

PubMed

Antonacci, Michael A; Zhang, Le; Burant, Alex; McCallister, Drew; Branca, Rosa T

2018-08-01

To assess the effect of macroscopic susceptibility gradients on the gas-phase referenced dissolved-phase 129 Xe (DPXe) chemical shift (CS) and to establish the robustness of a water-based referencing system for in vivo DPXe spectra. Frequency shifts induced by spatially varying magnetic susceptibility are calculated by finite-element analysis for the human head and chest. Their effect on traditional gas-phase referenced DPXe CS is then assessed theoretically and experimentally. A water-based referencing system for the DPXe resonances that uses the local water protons as reference is proposed and demonstrated in vivo in rats. Across the human brain, macroscopic susceptibility gradients can induce an apparent variation in the DPXe CS of up to 2.5 ppm. An additional frequency shift as large as 6.5 ppm can exist between DPXe and gas-phase resonances. By using nearby water protons as reference for the DPXe CS, the effect of macroscopic susceptibility gradients is eliminated and consistent CS values are obtained in vivo, regardless of shimming conditions, region of interest analyzed, animal orientation, or lung inflation. Combining in vitro and in vivo spectroscopic measurements finally enables confident assignment of some of the DPXe peaks observed in vivo. To use hyperpolarized xenon as a biological probe in tissues, the DPXe CS in specific organs/tissues must be reliably measured. When the gas-phase is used as reference, variable CS values are obtained for DPXe resonances. Reliable peak assignments in DPXe spectra can be obtained by using local water protons as reference. Magn Reson Med 80:431-441, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Numerical analysis of the spatial nonuniformity in a Cs-seeded H{sup -} ion source

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

Takado, N.; Hanatani, J.; Mizuno, T.

The H{sup -} ion production and transport processes are numerically simulated to clarify the origin of H{sup -} beam nonuniformity. The three-dimensional transport code using the Monte Carlo method has been applied to H{sup 0} atoms and H{sup -} ions in the large 'JAERI 10A negative ion source' under the Cs-seeded condition, in which negative ions are dominantly produced by the surface production process. The results show that a large fraction of hydrogen atoms is produced in the region with high electron temperature. This leads to a spatial nonuniformity of H{sup 0} atom flux to the plasma grid and themore » resultant H{sup -} ion surface production. In addition, most surface-produced H{sup -} ions are extracted even through the high T{sub e} region without destruction. These results indicate a correlation between the production process of the H{sup -} ion and the spatial nonuniformity of the H{sup -} ion beam.« less

Caesium-rich micro-particles: A window into the meltdown events at the Fukushima Daiichi Nuclear Power Plant

PubMed Central

Furuki, Genki; Imoto, Junpei; Ochiai, Asumi; Yamasaki, Shinya; Nanba, Kenji; Ohnuki, Toshihiko; Grambow, Bernd; Ewing, Rodney C.; Utsunomiya, Satoshi

2017-01-01

The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors. During the meltdowns, a type of condensed particle, a caesium-rich micro-particle (CsMP), formed inside the reactors via unknown processes. Here we report the chemical and physical processes of CsMP formation inside the reactors during the meltdowns based on atomic-resolution electron microscopy of CsMPs discovered near the FDNPP. All of the CsMPs (with sizes of 2.0–3.4 μm) comprise SiO2 glass matrices and ~10-nm-sized Zn–Fe-oxide nanoparticles associated with a wide range of Cs concentrations (1.1–19 wt% Cs as Cs2O). Trace amounts of U are also associated with the Zn–Fe oxides. The nano-texture in the CsMPs records multiple reaction-process steps during meltdown in the severe FDNPP accident: Melted fuel (molten core)-concrete interactions (MCCIs), incorporating various airborne fission product nanoparticles, including CsOH and CsCl, proceeded via SiO2 condensation over aggregates of Zn-Fe oxide nanoparticles originating from the failure of the reactor pressure vessels. Still, CsMPs provide a mechanism by which volatile and low-volatility radionuclides such as U can reach the environment and should be considered in the migration model of Cs and radionuclides in the current environment surrounding the FDNPP. PMID:28198440

Caesium-rich micro-particles: A window into the meltdown events at the Fukushima Daiichi Nuclear Power Plant

NASA Astrophysics Data System (ADS)

Furuki, Genki; Imoto, Junpei; Ochiai, Asumi; Yamasaki, Shinya; Nanba, Kenji; Ohnuki, Toshihiko; Grambow, Bernd; Ewing, Rodney C.; Utsunomiya, Satoshi

2017-02-01

The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors. During the meltdowns, a type of condensed particle, a caesium-rich micro-particle (CsMP), formed inside the reactors via unknown processes. Here we report the chemical and physical processes of CsMP formation inside the reactors during the meltdowns based on atomic-resolution electron microscopy of CsMPs discovered near the FDNPP. All of the CsMPs (with sizes of 2.0-3.4 μm) comprise SiO2 glass matrices and ~10-nm-sized Zn-Fe-oxide nanoparticles associated with a wide range of Cs concentrations (1.1-19 wt% Cs as Cs2O). Trace amounts of U are also associated with the Zn-Fe oxides. The nano-texture in the CsMPs records multiple reaction-process steps during meltdown in the severe FDNPP accident: Melted fuel (molten core)-concrete interactions (MCCIs), incorporating various airborne fission product nanoparticles, including CsOH and CsCl, proceeded via SiO2 condensation over aggregates of Zn-Fe oxide nanoparticles originating from the failure of the reactor pressure vessels. Still, CsMPs provide a mechanism by which volatile and low-volatility radionuclides such as U can reach the environment and should be considered in the migration model of Cs and radionuclides in the current environment surrounding the FDNPP.

Caesium-rich micro-particles: A window into the meltdown events at the Fukushima Daiichi Nuclear Power Plant.

PubMed

Furuki, Genki; Imoto, Junpei; Ochiai, Asumi; Yamasaki, Shinya; Nanba, Kenji; Ohnuki, Toshihiko; Grambow, Bernd; Ewing, Rodney C; Utsunomiya, Satoshi

2017-02-15

The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors. During the meltdowns, a type of condensed particle, a caesium-rich micro-particle (CsMP), formed inside the reactors via unknown processes. Here we report the chemical and physical processes of CsMP formation inside the reactors during the meltdowns based on atomic-resolution electron microscopy of CsMPs discovered near the FDNPP. All of the CsMPs (with sizes of 2.0-3.4 μm) comprise SiO 2 glass matrices and ~10-nm-sized Zn-Fe-oxide nanoparticles associated with a wide range of Cs concentrations (1.1-19 wt% Cs as Cs 2 O). Trace amounts of U are also associated with the Zn-Fe oxides. The nano-texture in the CsMPs records multiple reaction-process steps during meltdown in the severe FDNPP accident: Melted fuel (molten core)-concrete interactions (MCCIs), incorporating various airborne fission product nanoparticles, including CsOH and CsCl, proceeded via SiO 2 condensation over aggregates of Zn-Fe oxide nanoparticles originating from the failure of the reactor pressure vessels. Still, CsMPs provide a mechanism by which volatile and low-volatility radionuclides such as U can reach the environment and should be considered in the migration model of Cs and radionuclides in the current environment surrounding the FDNPP.

Probing Low-Mass Vector Bosons with Parity Nonconservation and Nuclear Anapole Moment Measurements in Atoms and Molecules

NASA Astrophysics Data System (ADS)

Dzuba, V. A.; Flambaum, V. V.; Stadnik, Y. V.

2017-12-01

In the presence of P -violating interactions, the exchange of vector bosons between electrons and nucleons induces parity-nonconserving (PNC) effects in atoms and molecules, while the exchange of vector bosons between nucleons induces anapole moments of nuclei. We perform calculations of such vector-mediated PNC effects in Cs, Ba+ , Yb, Tl, Fr, and Ra+ using the same relativistic many-body approaches as in earlier calculations of standard-model PNC effects, but with the long-range operator of the weak interaction. We calculate nuclear anapole moments due to vector-boson exchange using a simple nuclear model. From measured and predicted (within the standard model) values for the PNC amplitudes in Cs, Yb, and Tl, as well as the nuclear anapole moment of 133Cs, we constrain the P -violating vector-pseudovector nucleon-electron and nucleon-proton interactions mediated by a generic vector boson of arbitrary mass. Our limits improve on existing bounds from other experiments by many orders of magnitude over a very large range of vector-boson masses.

Determination of silicon in biomass and products of pyrolysis process via high-resolution continuum source atomic absorption spectrometry.

PubMed

Nakadi, Flávio V; Prodanov, Caroline; Boschetti, Wiliam; Vale, Maria Goreti R; Welz, Bernhard; de Andrade, Jailson B

2018-03-01

Thermochemical processes can convert the biomass into fuels, such as bio-oil. The biomass submitted to pyrolysis process, such as fibers, are generally rich in silicon, an element that can lead to damages in an engine when there is high concentration in a fuel. High-resolution continuum source atomic absorption spectrometry (HR-CS AAS) is an interesting alternative for Si determination in the products and byproducts of the pyrolysis process because, besides the flame (F) and graphite furnace (GF) atomizers, it has enhanced the application of direct analysis of solid samples (SS) within GF. This study aimed the development of methods to determine Si in biomass samples, their products and byproducts using HR-CS AAS. A high-resolution continuum source atomic absorption spectrometer contrAA 700 equipped with F and GF atomizers was used throughout the study. HR-CS F AAS (λ = 251.611nm, 1 detection pixel, N 2 O/C 2 H 2 flame) was used to evaluate Si content in biomass and ash, after a microwave-assisted acid digestion with HNO 3 and HF. HR-CS GF AAS (T pyr = 1400°C, T atom = 2650°C) has evaluated Si in pyrolysis water and bio-oil at 251.611nm, and in peach pit biomass and ash at 221.174nm using SS, both wavelengths with 1 detection pixel. Rhodium (300μg) was applied as permanent modifier and 10μgPd + 6μg Mg were pipetted onto the standards/samples at each analysis. Three different biomass samples were studied: palm tree fiber, coconut fiber and peach pit, and three certified reference materials (CRM) were used to verify the accuracy of the methods. The figures of merit were LOD 0.09-20mgkg -1 , and LOQ 0.3-20mgkg -1 , considering all the methods. There were no significant differences between the CRM certified values and the determined ones, using a Student t-test with a confidence interval of 95% (n = 5). Si concentration ranged from 0.11-0.92% mm -1 , 1.1-1.7mgkg -1 , 3.3-13mgkg -1 , and 0.41-1.4%mm -1 , in biomass, bio-oil, pyrolysis water and ash, respectively. Si remained mostly in the ash, leading to a mass fraction of up to 103%, even when the Si loss is not considered. Silicon concentration in bio-oil was below 1.7mgkg -1 , which is suitable for its application as a fuel. The developed methods using HR-CS AAS are suitable for Si determination in biomass, bio-oil, pyrolysis water, and ash. The application of bio-oil as an alternative fuel would be possible evaluating its Si content due to its low levels. The mass balance for Si has proved to be an important tool in order to evaluate the correct disposal of pyrolysis process byproducts. Copyright © 2017 Elsevier B.V. All rights reserved.

Reduction of characteristic RL time for fast, efficient magnetic levitation

NASA Astrophysics Data System (ADS)

Li, Yuqing; Feng, Guosheng; Wang, Xiaofeng; Wu, Jizhou; Ma, Jie; Xiao, Liantuan; Jia, Suotang

2017-09-01

We demonstrate the reduction of characteristic time in resistor-inductor (RL) circuit for fast, efficient magnetic levitation according to Kirchhoff's circuit laws. The loading time is reduced by a factor of ˜4 when a high-power resistor is added in series with the coils. By using the controllable output voltage of power supply and voltage of feedback circuit, the loading time is further reduced by ˜ 3 times. The overshoot loading in advance of the scheduled magnetic field gradient is equivalent to continuously adding a resistor without heating. The magnetic field gradient with the reduced loading time is used to form the upward magnetic force against to the gravity of the cooled Cs atoms, and we obtain an effectively levitated loading of the Cs atoms to a crossed optical dipole trap.

Computational code in atomic and nuclear quantum optics: Advanced computing multiphoton resonance parameters for atoms in a strong laser field

NASA Astrophysics Data System (ADS)

Glushkov, A. V.; Gurskaya, M. Yu; Ignatenko, A. V.; Smirnov, A. V.; Serga, I. N.; Svinarenko, A. A.; Ternovsky, E. V.

2017-10-01

The consistent relativistic energy approach to the finite Fermi-systems (atoms and nuclei) in a strong realistic laser field is presented and applied to computing the multiphoton resonances parameters in some atoms and nuclei. The approach is based on the Gell-Mann and Low S-matrix formalism, multiphoton resonance lines moments technique and advanced Ivanov-Ivanova algorithm of calculating the Green’s function of the Dirac equation. The data for multiphoton resonance width and shift for the Cs atom and the 57Fe nucleus in dependence upon the laser intensity are listed.

New observation and combined analysis of the Cs{sub 2} 0{sub g}{sup −}, 0{sub u}{sup +}, and 1{sub g} states at the asymptotes 6S{sub 1/2} + 6P{sub 1/2} and 6S{sub 1/2} + 6P{sub 3/2}

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

Ma, Jie; Liu, Wenliang; Wu, Jizhou

2014-12-28

We report on new observations of the photoassociation spectroscopy of ultracold cesium molecules using a highly sensitive detection technique and a combined analysis with all observed electronic states. The technique is achieved by directly modulating the frequency of the trapping lasers of a magneto-optical trap. New observations of the Cs{sub 2}0{sub g}{sup −}, 0{sub u}{sup +}, and 1{sub g} states at the asymptotes 6S{sub 1/2} + 6P{sub 1/2} and 6S{sub 1/2} + 6P{sub 3/2} are reported. The spectral range is extended to the red detuning of 112 cm{sup −1} below the 6S{sub 1/2} + 6P{sub 3/2} dissociation limit. Dozens ofmore » vibrational levels of the ultracold Cs{sub 2}0{sub g}{sup −}, 0{sub u}{sup +}, and 1{sub g} states are observed for the first time. The available experimental binding energies of these states are analyzed simultaneously in a framework of the generalized LeRoy–Bernstein theory and the almost degenerate perturbation theory by Marinescu and Dalgarno [Phys. Rev. A: At., Mol., Opt. Phys. 52, 311 (1995)]. The unique atomic-related parameter c{sub 3} governing the dispersion forces of all the molecular states is estimated as (10.29 ± 0.05) a.u.« less

Cs0.9Ni3.1Se3: A Ni-Based Quasi-One-Dimensional Conductor with Spin-Glass Behavior.

PubMed

Sun, Fan; Guo, Zhongnan; Liu, Ning; Wu, Dan; Lin, Jiawei; Cheng, Erjian; Ying, Tianping; Li, Shiyan; Yuan, Wenxia

2018-04-02

In this work, we report the discovery of a new Ni-based quasi-one-dimensional selenide: Cs 0.9 Ni 3.1 Se 3 . This compound adopts the TlFe 3 Te 3 -type structure with space group P6 3 / m, which consists of infinite [Ni 3 Se 3 ] chains with face-sharing Ni 6 octahedra along the c direction. The lattice parameters are calculated as a = 9.26301(4) Å and c = 4.34272(2) Å, with the Ni-Ni distance in the ab plane as 2.582(3) Å, suggesting the formation of a Ni-Ni metallic bond in this compound. Interestingly, it has been found that Cs 0.9 Ni 3.1 Se 3 is nonstoichiometric, which is different from the other TlFe 3 Te 3 -type phases reported so far. Structure refinement shows that the extra Ni atom in the structure may occupy the 2c site, together with Cs atoms. Cs 0.9 Ni 3.1 Se 3 shows metallic behavior with monotonously decreased resistivity with temperatures from 300 to 0.5 K. Measurements on the magnetic susceptibility display a spin-glass state below 7 K. The specific heat curve gives a Sommerfeld coefficient of 14.6 mJ·K -2 ·mol -1 and a Debye temperature of 143.6 K. The discovery of this new compound enriches the diversity of low-dimensional materials in a transition-metal-based family and also sheds light on the structure-property relationship of this system.

Iron phosphate glasses: Bulk properties and atomic scale structure

NASA Astrophysics Data System (ADS)

Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger

2017-10-01

Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.

Physics of Spin-Polarized Media

DTIC Science & Technology

2007-11-21

midsection of the cell serving as the cathode, and liquid molten salt outside the cell serving as the anode [5]. This new method is very promising for of...filling atomic clock and magnetometer cells by electrolysis through the glass walls; (6) new investigations of optical pumping and magnetic resonances...cesium vapor can be used to polarize 3 Cs nuclei in CsH salt that coats the walls of a vapor cell. This result, an important first step, has been

Extraordinary Interfacial Stitching between Single All-Inorganic Perovskite Nanocrystals

PubMed Central

2018-01-01

All-inorganic cesium lead halide perovskite nanocrystals are extensively studied because of their outstanding optoelectronic properties. Being of a cubic shape and typically featuring a narrow size distribution, CsPbX3 (X = Cl, Br, and I) nanocrystals are the ideal starting material for the development of homogeneous thin films as required for photovoltaic and optoelectronic applications. Recent experiments reveal spontaneous merging of drop-casted CsPbBr3 nanocrystals, which is promoted by humidity and mild-temperature treatments and arrested by electron beam irradiation. Here, we make use of atom-resolved annular dark-field imaging microscopy and valence electron energy loss spectroscopy in a state-of-the-art low-voltage monochromatic scanning transmission electron microscope to investigate the aggregation between individual nanocrystals at the atomic level. We show that the merging process preserves the elemental composition and electronic structure of CsPbBr3 and takes place between nanocrystals of different sizes and orientations. In particular, we reveal seamless stitching for aligned nanocrystals, similar to that reported in the past for graphene flakes. Because the crystallographic alignment occurs naturally in drop-casted layers of CsPbX3 nanocrystals, our findings constitute the essential first step toward the development of large-area nanosheets with band gap energies predesigned by the nanocrystal choice—the gateway to large-scale photovoltaic applications of inorganic perovskites. PMID:29355301

Extraordinary Interfacial Stitching between Single All-Inorganic Perovskite Nanocrystals.

PubMed

Gomez, Leyre; Lin, Junhao; de Weerd, Chris; Poirier, Lucas; Boehme, Simon C; von Hauff, Elizabeth; Fujiwara, Yasufumi; Suenaga, Kazutomo; Gregorkiewicz, Tom

2018-02-14

All-inorganic cesium lead halide perovskite nanocrystals are extensively studied because of their outstanding optoelectronic properties. Being of a cubic shape and typically featuring a narrow size distribution, CsPbX 3 (X = Cl, Br, and I) nanocrystals are the ideal starting material for the development of homogeneous thin films as required for photovoltaic and optoelectronic applications. Recent experiments reveal spontaneous merging of drop-casted CsPbBr 3 nanocrystals, which is promoted by humidity and mild-temperature treatments and arrested by electron beam irradiation. Here, we make use of atom-resolved annular dark-field imaging microscopy and valence electron energy loss spectroscopy in a state-of-the-art low-voltage monochromatic scanning transmission electron microscope to investigate the aggregation between individual nanocrystals at the atomic level. We show that the merging process preserves the elemental composition and electronic structure of CsPbBr 3 and takes place between nanocrystals of different sizes and orientations. In particular, we reveal seamless stitching for aligned nanocrystals, similar to that reported in the past for graphene flakes. Because the crystallographic alignment occurs naturally in drop-casted layers of CsPbX 3 nanocrystals, our findings constitute the essential first step toward the development of large-area nanosheets with band gap energies predesigned by the nanocrystal choice-the gateway to large-scale photovoltaic applications of inorganic perovskites.

Transition of a small-bipolaron gas to a Fröhlich polaron in a deformable lattice

NASA Astrophysics Data System (ADS)

Hettiarachchi, Gayan Prasad; Muhid, Mohd Nazlan Mohd; Hamdan, Halimaton

2018-04-01

The electronic properties of guest Cs atoms in a deformable lattice are investigated at various densities n . Low values of n show optical absorptions of small bipolarons. At intermediate n values, new bands appear in the midinfrared (MIR) and high-frequency regions, which coexist with the small bipolaron bands. With a further increase in n , the small bipolaron bands become less discernible and subsequently disappear, resulting in the appearance of a Drude component superimposed on a MIR sideband suggesting a phase transition to a polaronic metal. In this itinerant phase, an approximately twofold mass enhancement is observed. This continuous transition of a gas of small bipolarons to a polaronic metal characterized by a Fröhlich polaron reveals an important part of the complex phase diagram of the metal-insulator transition in a deformable lattice.

pH-controlled doxorubicin anticancer loading and release from carbon nanotube noncovalently modified by chitosan: MD simulations.

PubMed

Rungnim, Chompoonut; Rungrotmongkol, Thanyada; Poo-Arporn, Rungtiva P

2016-11-01

In the present study, we describe here the pH condition activating doxorubicin (DOX) anticancer drugs loading and release over single-wall carbon nanotube (SWNT) non-covalently wrapped with chitosan (CS). The possibility of drug displacement on DOX/CS/SWNT nanocarrier was investigated using molecular dynamics simulations. The drug loading and release were monitored via displacement analysis and binding energy calculations. The simulated results clearly showed that the drugs well interacted with the CS/SWNT at physiological pH (pH 7.4), where CS was in the deprotonated form. Contrastingly, in weakly acidic environments (pH 5.0-6.5) which is a pH characteristics of certain cancer environments, the protonated CS became loosen wrapped around the SWNT and triggered drugs release as a result of charge-charge repulsion between CS and drug molecules. The obtained data fulfil the understanding at atomic level of drug loading and release controlled by pH-sensitive polymer, which might be useful for further cancer therapy researches. Copyright © 2016 Elsevier Inc. All rights reserved.

Alloying n-Butylamine into CsPbBr3 to Give a Two-Dimensional Bilayered Perovskite Ferroelectric Material.

PubMed

Wu, Zhenyue; Ji, Chengmin; Li, Lina; Kong, Jintao; Sun, Zhihua; Zhao, Sangen; Wang, Sasa; Hong, Maochun; Luo, Junhua

2018-05-11

Cesium-lead halide perovskites (e.g. CsPbBr 3 ) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr 3 , we design the first cesium-based two-dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C 4 H 9 NH 3 ) 2 CsPb 2 Br 7 (1). Strikingly, 1 shows a high Curie temperature (T c =412 K) above that of BaTiO 3 (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm -2 ), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs + ions. To our knowledge, such a 2D bilayered Cs + -based metal-halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large "on/off" ratios of photoconductivity (>10 3 ). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inoculation with arbuscular mycorrhizae does not improve 137Cs uptake in crops grown in the Chernobyl region.

PubMed

Vinichuk, M; Mårtensson, A; Rosén, K

2013-12-01

Methods for cleaning up radioactive contaminated soils are urgently needed. In this study we investigated whether the use of arbuscular mycorrhizal (AM) fungi can improve (137)Cs uptake by crops. Barley, cucumber, perennial ryegrass, and sunflower were inoculated with AM fungi and grown in low-level radionuclide contaminated soils in a field experiment 70 km southwest of Chernobyl, Ukraine, during two successive years (2009-2010). Roots of barley, cucumber and sunflower plants were slightly or moderately infected with AM fungus and root infection frequency was negatively or non-correlated with (137)Cs uptake by plants. Roots of ryegrass were moderately infected with AM fungus and infection frequency was moderately correlated with (137)Cs uptake by ryegrass. The application of AM fungi to soil in situ did not enhance radionuclide plant uptake or biomass. The responsiveness of host plants and AM fungus combination to (137)Cs uptake varied depending on the soil, although mycorrhization of soil in the field was conditional and did not facilitate the uptake of radiocesium. The total amount of (137)Cs uptake by plants growing on inoculated soil was equal to amounts in plant cultivated on non-inoculated soil. Thus, the use of AM fungi in situ for bioremediation of soil contaminated with a low concentration of (137)Cs could not be recommended. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of hydrogen atom spin exchange collisions on atomic hydrogen maser oscillation frequency

NASA Technical Reports Server (NTRS)

Crampton, S. B.

1979-01-01

Frequency shifts due to collisions between hydrogen atoms in an atomic hydrogen maser frequency standard are studied. Investigations of frequency shifts proportional to the spin exchange frequency shift cross section and those proportional to the duration of exchange collisions are discussed. The feasibility of operating a hydrogen frequency standard at liquid helium temperatures is examined.

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

Paziresh, M.; Kingston, A. M., E-mail: andrew.kingston@anu.edu.au; Latham, S. J.

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski,more » Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073–2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127–135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260–1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and atomic number (Z) reconstructions to a significant extent.« less

Exotic stable cesium polynitrides at high pressure

DOE PAGES

Peng, Feng; Han, Yunxia; Liu, Hanyu; ...

2015-11-19

New polynitrides containing metastable forms of nitrogen are actively investigated as potential high energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN 3, we identified five new stoichiometric compounds (Cs 3N, Cs 2N, CsN, CsN 2, and CsN 5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N 2, N 3 , Nmore » 4, N 5, N 6) and chains (N ∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN 2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N 4 4- anion. In conclusion, to our best knowledge, this is the first time a charged N 4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.« less

Cs/NF3 adsorption on [001]-oriented GaN nanowire surface: A first principle calculation

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Kong, Yike

2017-11-01

In this study, the adsorption mechanism of Cs/NF3 on the [001]-oriented GaN nanowire surface is investigated by using the density function theory based on first-principles. In the Cs/NF3 co-activation process, the system is inclined to form NF3-in structure. Through the calculation results of adsorption energy, NF3 molecule adsorption tends to take an orientation with F atoms on top and the most favorable adsorption site is BGa-N. The NF3 activation process can further cut down the work function of the Cs-covered nanowire surface only when Cs coverage is 0.75 ML and 1 ML, which can be explained by the double dipole moment theory. With increasing Cs coverage, the valence band and conduction band both shift to lower energy side, contributing to the appearance of a downward band bending region and promoting the escape of surface photoelectrons. After NF3 molecule adsorption, the peak of total density of states near Fermi level increase due to the orbital hybridization between NF3-2s, Cs-5s states and N-2p states, which strengthen the conductivity of the nanowire surface and leads to the metallic properties. All these calculations may direct the Cs/NF3 activation process of GaN nanowire optoelectronic devices.

Estimation of Effective Dose from External Exposure in The Six Prefectures adjacent to Fukushima Prefecture

NASA Astrophysics Data System (ADS)

Miyatake, Hirokazu; Yoshizawa, Nobuaki; Hirakawa, Sachiko; Murakami, Kana; Takizawa, Mari; Kawai, Masaki; Sato, Osamu; Takagi, Shunji; Suzuki, Gen

2017-09-01

The Fukushima Daiichi Nuclear Power Plant accident caused a release of radionuclides. Radionuclides were deposited on the ground not only in Fukushima prefecture but also in nearby prefectures. Since the accident, measurement of radiation in environment such as air dose rate and deposition density of radionuclides has been performed by many organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously and over wide areas. In our study, using the data measured by JAEA, we estimated effective dose from external exposure in the six prefectures adjacent to Fukushima prefecture. Since car-borne survey was started a few months later after the accident, measured air dose rate in this method is mainly contributed by 137Cs and 134Cs whose half-lives are relatively long. Therefore, based on air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-half-life nuclides to that of 137Cs and 134Cs, we also estimated effective dose contributed from not only 137Cs and 134Cs but also other short-half-life nuclides. We compared the effective dose estimated by the method above with that of UNSCEAR and measured data using personal dosimeters in some areas.

Reactions and products in the Cs-Zr-I-O system relevant to fission product chemistry — a review

NASA Astrophysics Data System (ADS)

Chen, T.-M.; Kauzlarich, S. M.; Corbett, J. D.

1988-02-01

Some results and problems associated with the known chemistry of cesium and iodine in the presence of Zr/ZrO 2 at 400-600°C and under anaerobic conditions are described and discussed. These aspects include (1) the recently synthesized cesium zirconates Cs 2ZrO 3 and Cs 4ZrO 4 and some of their thermal and hydrolytic properties (2) the demonstration that the supposedly stable CsI reacts with ZrO 2 at 400-700°C to form Cs 2ZrO 3 and ZrI 4 (as Cs 2ZrI 6) and its implications regarding cesium and iodine distributions (3) present knowledge of binary zirconium iodides, their contamination reactions, and the limited inhibition of the reduction of ZrI 4 by metal provided by static ZrO 2 films (4) newly discovered ternary and quaternary zirconium iodides that are obtained in the presence of many common impurity atoms and, when prsesent, CsI (e.g., Zr 6I 12C, CsZr 6I 14C, Zr 6I 14Fe), the ease with which some of those form at least as low as 450°C, and the complications these and related new phases provide.

Exotic stable cesium polynitrides at high pressure

PubMed Central

Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

2015-01-01

New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3, N4, N5, N6) and chains (N∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44− anion. To our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure. PMID:26581175

CBe5Hn((n-4)) (n = 2-5): Hydrogen-Stabilized CBe5 Pentagons Containing Planar or Quasi-Planar Pentacoordinate Carbons.

PubMed

Guo, Jin-Chang; Ren, Guang-Ming; Miao, Chang-Qing; Tian, Wen-Juan; Wu, Yan-Bo; Wang, Xiaotai

2015-12-31

The diagonal relationship between beryllium and aluminum and the isoelectronic relationship between BeH unit and Al atom were utilized to design a new series ppC- or quasi-ppC-containing species C5v CBe5H5(+), Cs CBe5H4, C2v CBe5H3(-), and C2v CBe5H2(2-) by replacing the Al atoms in previously reported global minima planar pentacoordinate carbon (ppC) species D5h CAl5(+), C2v CAl4Be, C2v CAl3Be2(-), and C2v CAl2Be3(2-) with BeH units. The three-center two-electron (3c-2e) bonds formed between Be and bridging H atoms were crucial for the stabilization of these ppC species. The natural bond orbital (NBO) and adaptive natural density partitioning (AdNDP) analyses revealed that the central ppCs or quasi-ppCs possess the stable eight electron-shell structures. The AdNDP analyses also disclosed that these species are all 6σ+2π double-aromatic in nature. The aromaticity was proved by the calculated negative nucleus-independent chemical shifts (NICS) values. DFT and high-level CCSD(T) calculations revealed that these ppC- or quasi-ppC species are the global minimum or competitive low-lying local minimum (Cs CBe5H4) on their potential energy surfaces. The Born-Oppenheimer molecular dynamic (BOMD) simulations revealed that the H atoms in C2v CBe5H3(-) and C2v CBe5H2(2-) can easily rotate around the CBe5 cores and the structure of quasi-planar C5v CBe5H5(+) will become the planar structure at room temperature; however, these interesting dynamic behaviors did not indicate the kinetic instability as the basic ppC structures were maintained during the simulations. Therefore, it would be potentially possible to realize these interesting ppC- or quasi-ppc-species in future experiments.

Collisional Cooling of Light Ions by Cotrapped Heavy Atoms.

PubMed

Dutta, Sourav; Sawant, Rahul; Rangwala, S A

2017-03-17

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter ^{39}K^{+} ions, created by ionizing ^{39}K atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier ^{85}Rb atoms in a MOT, exhibit a longer trap lifetime than without the localized ^{85}Rb MOT atoms. A similar cooling of trapped ^{85}Rb^{+} ions by ultracold ^{133}Cs atoms in a MOT is also demonstrated in a different experimental configuration to validate this mechanism of ion cooling by localized and centered ultracold neutral atoms. Our results suggest that the cooling of ions by localized cold atoms holds for any mass ratio, thereby enabling studies on a wider class of atom-ion systems irrespective of their masses.

Hyperpolarization of {sup 133}Cs nuclei enhanced by ion movement in a cesium salt

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

Ishikawa, Kiyoshi

2011-12-15

Hyperpolarization of {sup 133}Cs nuclei in CsCl salt is achieved through spin transfer from an optically pumped Cs vapor, with maximum polarizations of 0.1% demonstrated. Motional narrowing of the enhanced NMR line indicates that ion movement facilitates this process by transporting spin-polarized ions from the interface into the salt. The resulting NMR enhancement allows measurement of the polarization and its dynamics in real time. Based upon the NMR frequency and the longitudinal spin relaxation time, we find no evidence that the salt is contaminated by Cs metal or paramagnetic impurities. The Cs nuclear polarization reported here could be improved severalmore » orders of magnitude by intense laser heating of the entire sample.« less

Interaction of cesium adatoms with free-standing graphene and graphene-veiled SiO 2 surfaces

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

Weck, Philippe F.; Kim, Eunja; Biedermann, Grant W.

2015-04-21

In this study, the interaction of Cs adatoms with mono- or bi-layered graphene (MLG and BLG), either free-standing or on a SiO 2 substrate, was investigated using density functional theory. The most stable adsorption sites for Cs are found to be hollow sites on both graphene sheets and graphene-veiled SiO 2(0001). In addition, larger dipole moments are created when a MLG-veiled SiO 2(0001) substrate is used for adsorption of Cs atoms compared to the adsorption on free-standing MLG, due to charge transfer occurring between the MLG and the SiO 2 substrate. For the adsorption of Cs on BLG-veiled SiO 2(0001)more » substrate, these differences are smoothed out and the binding energies corresponding to different sites are nearly degenerate; smaller dipole moments created by the Cs adatoms on BLG compared to MLG are also predicted.« less

Chlorine-36 and cesium-137 in ice-core samples from mid-latitude glacial sites in the Northern Hemisphere

USGS Publications Warehouse

Green, J.R.; Cecil, L.D.; Synal, H.-A.; Kreutz, K.J.; Wake, C.P.; Naftz, D.L.; Frape, S.K.

2000-01-01

Chlorine-36 (36Cl) concentrations, 36Cl/Cl ratios, and 36Cl fluxes in ice-core samples collected from the Upper Fremont Glacier (UFG) in the Wind River Mountain Range, Wyoming, United States and the Nangpai Gosum Glacier (NGG) in the Himalayan Mountains, Nepal, were determined and compared with published results from the Dye-3 ice-core drilling site on the Greenland Ice Sheet. Cesium-137 (137Cs) concentrations in the NGG also were determined. The background fluxes for 36Cl for each glacial site were similar: (1.6??0.3)??10-2 atoms/cm2 s for the UFG samples, (0.7??0.1)??10-2 atoms/cm2 s for the NGG samples, and (0.4??0.1)??10-2 atoms/cm2 s for the Dye-3 samples. The 36Cl fluxes in ice that was deposited as snow during peak atmospheric nuclear weapon test (1957-1958) were (33??1)??10-2 atoms/cm2 s for the UFG site, (291??3)??10-2 atoms/cm2 s for the NGG site, and (124??5)??10-2 atoms/ cm2 s for the Dye-3 site. A weapon test period 137Cs concentration of 0.79??0.05 Bq/kg in the NGG ice core also was detected in the same section of ice that contained the largest 36Cl concentration. ?? 2000 Elsevier Science B.V. All rights reserved.

Comparison of Frequency-Domain Array Methods for Studying Earthquake Rupture Process

NASA Astrophysics Data System (ADS)

Sheng, Y.; Yin, J.; Yao, H.

2014-12-01

Seismic array methods, in both time- and frequency- domains, have been widely used to study the rupture process and energy radiation of earthquakes. With better spatial resolution, the high-resolution frequency-domain methods, such as Multiple Signal Classification (MUSIC) (Schimdt, 1986; Meng et al., 2011) and the recently developed Compressive Sensing (CS) technique (Yao et al., 2011, 2013), are revealing new features of earthquake rupture processes. We have performed various tests on the methods of MUSIC, CS, minimum-variance distortionless response (MVDR) Beamforming and conventional Beamforming in order to better understand the advantages and features of these methods for studying earthquake rupture processes. We use the ricker wavelet to synthesize seismograms and use these frequency-domain techniques to relocate the synthetic sources we set, for instance, two sources separated in space but, their waveforms completely overlapping in the time domain. We also test the effects of the sliding window scheme on the recovery of a series of input sources, in particular, some artifacts that are caused by the sliding window scheme. Based on our tests, we find that CS, which is developed from the theory of sparsity inversion, has relatively high spatial resolution than the other frequency-domain methods and has better performance at lower frequencies. In high-frequency bands, MUSIC, as well as MVDR Beamforming, is more stable, especially in the multi-source situation. Meanwhile, CS tends to produce more artifacts when data have poor signal-to-noise ratio. Although these techniques can distinctly improve the spatial resolution, they still produce some artifacts along with the sliding of the time window. Furthermore, we propose a new method, which combines both the time-domain and frequency-domain techniques, to suppress these artifacts and obtain more reliable earthquake rupture images. Finally, we apply this new technique to study the 2013 Okhotsk deep mega earthquake in order to better capture the rupture characteristics (e.g., rupture area and velocity) of this earthquake.

Effective adsorption and collection of cesium from aqueous solution using graphene oxide grown on porous alumina

NASA Astrophysics Data System (ADS)

Entani, Shiro; Honda, Mitsunori; Shimoyama, Iwao; Li, Songtian; Naramoto, Hiroshi; Yaita, Tsuyoshi; Sakai, Seiji

2018-04-01

Graphene oxide (GO) with a large surface area was synthesized by the direct growth of GO on porous alumina using chemical vapor deposition to study the Cs adsorption mechanism in aqueous solutions. Electronic structure analysis employing in situ near-edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy measurements clarifies the Cs atoms bond via oxygen functional groups on GO in the aqueous solution. The Cs adsorption capacity was found to be as high as 650-850 mg g-1, which indicates that the GO/porous alumina acts as an effective adsorbent with high adsorption efficiency for radioactive nuclides in aqueous solutions.

A theoretical study of the structure and thermochemical properties of alkali metal fluoroplumbates MPbF3.

PubMed

Boltalin, A I; Korenev, Yu M; Sipachev, V A

2007-07-19

Molecular constants of MPbF3 (M=Li, Na, K, Rb, and Cs) were calculated theoretically at the MP2(full) and B3LYP levels with the SDD (Pb, K, Rb, and Cs) and cc-aug-pVQZ (F, Li, and Na) basis sets to determine the thermochemical characteristics of the substances. Satisfactory agreement with experiment was obtained, including the unexpected nonmonotonic dependence of substance dissociation energies on the alkali metal atomic number. The bond lengths of the theoretical CsPbF3 model were substantially elongated compared with experimental estimates, likely because of errors in both theoretical calculations and electron diffraction data processing.

Synthesis, crystal structure and luminescent properties of a new pyrochlore type tungstate CsGa0.333W1.667O6

NASA Astrophysics Data System (ADS)

Zhao, Dan; Zhao, Ji; Fan, Yun-Chang; Ma, Zhao; Zhang, Rui-Juan; Liu, Bao-Zhong

2018-06-01

High temperature solution reaction leads to a new tungstate compound CsGa0.333W1.667O6, whose structure was determined by single-crystal X-ray diffraction analysis. The results show that it crystallizes in pyrochlore structure with cubic space group Fd-3m and a = 10.2529 (13) Å. In this structure, Ga and W atoms are in a statistical disorder manner. The self-activated luminescent properties CsGa0.333W1.667O6 were studied. Under the excitation of 323 nm, the emission spectrum exhibits a blue emission centered at 466 nm with the chromaticity coordinates (0.1838, 0.1814).

ITER CS Model Coil and CS Insert Test Results

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

Martovetsky, N; Michael, P; Minervina, J

2000-09-07

The Inner and Outer modules of the Central Solenoid Model Coil (CSMC) were built by US and Japanese home teams in collaboration with European and Russian teams to demonstrate the feasibility of a superconducting Central Solenoid for ITER and other large tokamak reactors. The CSMC mass is about 120 t, OD is about 3.6 m and the stored energy is 640 MJ at 46 kA and peak field of 13 T. Testing of the CSMC and the CS Insert took place at Japan Atomic Energy Research Institute (JAERI) from mid March until mid August 2000. This paper presents the mainmore » results of the tests performed.« less

Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

NASA Astrophysics Data System (ADS)

Paziresh, M.; Kingston, A. M.; Latham, S. J.; Fullagar, W. K.; Myers, G. M.

2016-06-01

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073-2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127-135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260-1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and atomic number (Z) reconstructions to a significant extent.

Cs 62 DJ Rydberg-atom macrodimers formed by long-range multipole interaction

NASA Astrophysics Data System (ADS)

Han, Xiaoxuan; Bai, Suying; Jiao, Yuechun; Hao, Liping; Xue, Yongmei; Zhao, Jianming; Jia, Suotang; Raithel, Georg

2018-03-01

Long-range macrodimers formed by D -state cesium Rydberg atoms are studied in experiments and calculations. Cesium [62DJ]2 Rydberg-atom macrodimers, bonded via long-range multipole interaction, are prepared by two-color photoassociation in a cesium atom trap. The first color (pulse A) resonantly excites seed Rydberg atoms, while the second (pulse B, detuned by the molecular binding energy) resonantly excites the Rydberg-atom macrodimers below the [62DJ]2 asymptotes. The molecules are measured by extraction of autoionization products and Rydberg-atom electric-field ionization, and ion detection. Molecular spectra are compared with calculations of adiabatic molecular potentials. From the dependence of the molecular signal on the detection delay time, the lifetime of the molecules is estimated to be 3 -6 μ s .

Interpretation of ES, CS, and IOS approximations within a translational-internal coupling scheme. II. Application to atom--diatom kinetic cross sections

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

Coombe, D.A.; Snider, R.F.

1980-02-15

ES, CS, and IOS approximations to atom--diatom kinetic cross sections are derived. In doing so, reduced S-matrices in a translational-internal coupling scheme are stressed. This entails the insertion of recently obtained approximate reduced S-matrices in the translational-internal coupling scheme into previously derived general expressions for the kinetic cross sections. Of special interest is the structure (rotational j quantum number dependence) of the kinetic cross sections associated with the Senftleben Beenakker effects and of pure internal state relaxation phenomena. The viscomagnetic effect is used as an illustrative example. It is found in particular that there is a great similarity of structuremore » between the energy sudden (and IOS) approximation and the previously derived distorted wave Born results.« less

Theoretical study of mixed MLaX(4) (M = Na, K, Cs; X = F, Cl, Br, I) rare earth/alkali metal halide complexes.

PubMed

Groen, Cornelis Petrus; Oskam, Ad; Kovács, Attila

2003-02-10

The structure, bonding, and vibrational properties of the mixed MLaX(4) (M = Na, K, Cs; X = F, Cl, Br, I) rare earth/alkali metal halide complexes have been studied using the MP2 method in conjunction with polarized triple-zeta valence basis sets and quasi-relativistic effective core potentials for the heavy atoms. From the three characteristic structures, possessing 1- (C(3)(v)), 2- (C(2)(v)), or 3-fold coordination (C(3)(v)) between the alkali metal and the bridging halide atoms, the bi- and tridentate forms are stable isomers with close dissociation energies. In general, for the complexes existing of lighter alkali metals and halogens, the bidentate structure corresponds to the global minimum of the potential energy surface, while the heavier analogues favor the tridentate structure. At experimentally relevant temperatures (T > 800 K), however, the isomerization entropy leads to a domination of the bidentate structures over the tridentate forms for all complexes. An important effect of the size of the alkali metal is manifested in the larger stabilities of the K and Cs complexes. The natural atomic charges are in agreement with strong electrostatic interactions in the title complexes. The marginal covalent contributions show a slight increasing trend in the heavier analogues. The calculated vibrational data indicate that infrared spectroscopy may be an effective tool for experimental investigation and characterization of MLaX(4) molecules.

Visual evoked potential measurement of contrast sensitivity in a case of retinal laser injury reveals visual function loss despite normal acuity

NASA Astrophysics Data System (ADS)

Glickman, Randolph D.; Harrison, Joseph M.; Zwick, Harry; Longbotham, Harold G.; Ballentine, Charles S.; Pierce, Bennie

1996-04-01

Although visual function following retinal laser injuries has traditionally been assessed by measuring visual acuity, this measure only indicates the highest spatial frequency resolvable under high-contrast viewing conditions. Another visual psychophysical parameter is contrast sensitivity (CS), which measures the minimum contrast required for detection of targets over a range of spatial frequencies, and may evaluate visual mechanisms that do not directly subserve acuity. We used the visual evoked potential (VEP) to measure CS in a population of normal subjects and in patients with ophthalmic conditions affecting retinal function, including one patient with a laser injury in the macula. In this patient, the acuity had recovered from

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging

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

Larsson, Jakob C., E-mail: jakob.larsson@biox.kth.se; Lundström, Ulf; Hertz, Hans M.

2016-06-15

Purpose: High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. Methods: The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency andmore » effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. Results: There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28–38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. Conclusions: The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.« less

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging.

PubMed

Larsson, Jakob C; Lundström, Ulf; Hertz, Hans M

2016-06-01

High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency and effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28-38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.

Dynamic changes of central thyroid functions in the management of Cushing's syndrome.

PubMed

Dogansen, Sema Ciftci; Yalin, Gulsah Yenidunya; Canbaz, Bulent; Tanrikulu, Seher; Yarman, Sema

2018-01-01

The aim of this study was to determine the frequency of central thyroid dysfunctions in Cushing's syndrome (CS). We also aimed to evaluate the frequency of hyperthyroidism due to the syndrome of the inappropriate secretion of TSH (SITSH), which was recently defined in patients with insufficient hydrocortisone replacement after surgery. We evaluated thyroid functions (TSH and free thyroxine [fT4]) at the time of diagnosis, during the hypothalamo-pituitary-adrenal axis recovery, and after surgery in 35 patients with CS. The patients were separated into two groups: ACTH-dependent CS (group 1, n = 20) and ACTH-independent CS (group 2, n = 15). Patients' clinical and laboratory findings were evaluated in five visits in the outpatient clinic of the endocrinology department. The frequency of baseline suppressed TSH levels and central hypothyroidism were determined to be 37% (n = 13) and 26% (n = 9), respectively. A negative correlation was found between baseline cortisol and TSH levels (r = -0.45, p = 0.006). All patients with central hypothyroidism and suppressed TSH levels showed recovery at the first visit without levothyroxine treatment. SITSH was not detected in any of the patients during the postoperative period. No correlation was found between prednisolone replacement after surgery and TSH or fT4 levels on each visit. Suppressed TSH levels and central hypothyroidism may be detected in CS, independent of etiology. SITSH was not detected in the early postoperative period due to our adequate prednisolone replacement doses.

Investigation of plasma parameters at BATMAN for variation of the Cs evaporation asymmetry and comparing two driver geometries

NASA Astrophysics Data System (ADS)

Wimmer, C.; Fantz, U.; Aza, E.; Jovović, J.; Kraus, W.; Mimo, A.; Schiesko, L.

2017-08-01

The Neutral Beam Injection (NBI) system for fusion devices like ITER and, beyond ITER, DEMO requires large scale sources for negative hydrogen ions. BATMAN (Bavarian Test Machine for Negative ions) is a test facility attached with the prototype source for the ITER NBI (1/8 source size of the ITER source), dedicated to physical investigations due to its flexible access for diagnostics and exchange of source components. The required amount of negative ions is produced by surface conversion of hydrogen atoms or ions on caesiated surfaces. Several diagnostic tools (Optical Emission Spectroscopy, Cavity Ring-Down Spectroscopy for H-, Langmuir probes, Tunable Diode Laser Absorption Spectroscopy for Cs) allow the determination of plasma parameters in the ion source. Plasma parameters for two modifications of the standard prototype source have been investigated: Firstly, a second Cs oven has been installed in the bottom part of the back plate in addition to the regularly used oven in the top part of the back plate. Evaporation from the top oven only can lead to a vertically asymmetric Cs distribution in front of the plasma grid. Using both ovens, a symmetric Cs distribution can be reached - however, in most cases no significant change of the extracted ion current has been determined for varying Cs symmetry if the source is well-conditioned. Secondly, BATMAN has been equipped with a much larger, racetrack-shaped RF driver (area of 32×58 cm2) instead of the cylindrical RF driver (diameter of 24.5 cm). The main idea is that one racetrack driver could substitute two cylindrical drivers in larger sources with increased reliability and power efficiency. For the same applied RF power, the electron density is lower in the racetrack driver due to its five times higher volume. The fraction of hydrogen atoms to molecules, however, is at a similar level or even slightly higher, which is a promising result for application in larger sources.

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

NASA Astrophysics Data System (ADS)

Mentel, Juergen

2018-01-01

A mono-layer of atoms, electropositive with respect to the substrate atoms, forms a dipole layer, reducing its work function. Such a layer is generated by diffusion of emitter material from the interior of the substrate, by vapour deposition or by deposition of emitter material onto arc electrodes by cataphoresis. This cataphoretic emitter effect is investigated within metal halide lamps with transparent YAG ceramic burners, and within model lamps. Within the YAG lamps, arcs are operated with switched-dc current between rod shaped tungsten electrodes in high pressure Hg vapour seeded with metal iodides. Within the model lamps, dc arcs are operated between rod-shaped tungsten electrodes—one doped—in atmospheric pressure Ar. Electrode temperatures are determined by 1λ -pyrometry, combined with simulation of the electrode heat balance. Plasma temperatures, atom and ion densities of emitter material are determined by emission and absorption spectroscopy. Phase resolved measurements in YAG lamps seeded with CeI3, CsI, DyI3, TmI3 and LaI3 show, within the cathodic half period, a reduction of the electrode temperature and an enhanced metal ion density in front of the electrode, and an opposite behavior after phase reversal. With increasing operating frequency, the state of the cathode overlaps onto the anodic phase—except for Cs, being low in adsorption energy. Generally, the phase averaged electrode tip temperature is reduced by seeding a lamp with emitter material; its height depends on admixtures. Measurements at tungsten electrodes doped with ThO2, La2O3 and Ce2O3 within the model lamp show that evaporated emitter material is redeposited by an emitter ion current onto the electrode surface. It reduces the work function of tungsten cathodes above the evaporation temperature of the emitter material, too; and also of cold anodes, indicating a field reversal in front of them. The formation of an emitter spot at low cathode temperature and high emitter material density is traced back to a locally reduced work function generated by a locally enhanced emitter ion current density.

Photoelectron spectroscopy of color centers in negatively charged cesium iodide nanocrystals

NASA Astrophysics Data System (ADS)

Sarkas, Harry W.; Kidder, Linda H.; Bowen, Kit H.

1995-01-01

We present the photoelectron spectra of negatively charged cesium iodide nanocrystals recorded using 2.540 eV photons. The species examined were produced using an inert gas condensation cluster ion source, and they ranged in size from (CsI)-n=13 to nanocrystal anions comprised of 330 atoms. Nanocrystals showing two distinct types of photoemission behavior were observed. For (CsI)-n=13 and (CsI)-n=36-165, a plot of cluster anion photodetachment threshold energies vs n-1/3 gives a straight line extrapolating (at n-1/3=0, i.e., n=∞) to 2.2 eV, the photoelectric threshold energy for F centers in bulk cesium iodide. The linear extrapolation of the cluster anion data to the corresponding bulk property implies that the electron localization in these gas-phase nanocrystals is qualitatively similar to that of F centers in extended alkali halide crystals. These negatively charged cesium iodide nanocrystals are thus shown to support embryonic forms of F centers, which mature with increasing cluster size toward condensed phase impurity centers. Under an alternative set of source conditions, nanocrystals were produced which showed significantly lower photodetachment thresholds than the aforementioned F-center cluster anions. For these species, containing 83-131 atoms, a plot of their cluster anion photodetachment threshold energies versus n-1/3 gives a straight line which extrapolates to 1.4 eV. This value is in accord with the expected photoelectric threshold energy for F' centers in bulk cesium iodide, i.e., color centers with two excess electrons in a single defect site. These nanocrystals are interpreted to be the embryonic F'-center containing species, Cs(CsI)-n=41-65.

Phonon induced magnetism in ionic materials

NASA Astrophysics Data System (ADS)

Restrepo, Oscar D.; Antolin, Nikolas; Jin, Hyungyu; Heremans, Joseph P.; Windl, Wolfgang

2014-03-01

Thermoelectric phenomena in magnetic materials create exciting possibilities in future spin caloritronic devices by manipulating spin information using heat. An accurate understanding of the spin-lattice interactions, i.e. the coupling between magnetic excitations (magnons) and lattice vibrations (phonons), holds the key to unraveling their underlying physics. We report ab initio frozen-phonon calculations of CsI that result in non-zero magnetization when the degeneracy between spin-up and spin-down electronic density of states is lifted for certain phonon displacement patterns. For those, the magnetization as a function of atomic displacement shows a sharp resonance due to the electronic states on the displaced Cs atoms, while the electrons on indium form a continuous background magnetization. We relate this resonance to the generation of a two-level system in the spin-polarized Cs partial density of states as a function of displacement, which we propose to be described by a simple resonant-susceptibility model. Current work extends these investigations to semiconductors such as InSb. ODR and WW are supported by the Center for Emergent Materials, an NSF MRSEC at OSU (Grant DMR-0820414).HJ and JPH are supported by AFOSR MURI Cryogenic Peltier Cooling, Contract #FA9550-10-1-0533.

Image quality of a pixellated GaAs X-ray detector

NASA Astrophysics Data System (ADS)

Sun, G. C.; Makham, S.; Bourgoin, J. C.; Mauger, A.

2007-02-01

X-ray detection requires materials with large atomic numbers Z in order to absorb the radiation efficiently. In case of X-ray imaging, fluorescence is a limiting factor for the spatial resolution and contrast at energies above the kα threshold. Since both the energy and yield of the fluorescence of a given material increase with the atomic number, there is an optimum value of Z. GaAs, which can now be epitaxially grown as self-supported thick layers to fulfil the requirements for imaging (good homogeneity of the electronic properties) corresponds to this optimum. Image performances obtained with this material are evaluated in terms of line spread function and modulation transfer function, and a comparison with CsI is made. We evaluate the image contrast obtained for a given object contrast with GaAs and CsI detectors, in the photon energy range of medical applications. Finally, we discuss the minimum object size, which can be detected by these detectors in of mammography conditions. This demonstrates that an object of a given size can be detected using a GaAs detector with a dose at least 100 times lower than using a CsI detector.

The dressed atom as binary phase modulator: towards attojoule/edge optical phase-shift keying.

PubMed

Kerckhoff, Joseph; Armen, Michael A; Pavlichin, Dmitri S; Mabuchi, Hideo

2011-03-28

We use a single 133Cs atom strongly coupled to an optical resonator to induce random binary phase modulation of a near infra-red, ∼ 500 pW laser beam, with each modulation edge caused by the dissipation of a single photon (≈ 0.23 aJ) by the atom. While our ability to deterministically induce phase edges with an additional optical control beam is limited thus far, theoretical analysis of an analogous, solid-state system indicates that efficient external control should be achievable in demonstrated nanophotonic systems.

Compressibility of Cs2SnBr6 by X-ray diffraction and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Yuan, Guan; Huang, Shengxuan; Niu, Jingjing; Qin, Shan; Wu, Xiang; Ding, Hongrui; Lu, Anhuai

2018-07-01

Cs2SnBr6, one promising material applied in perovskite solar cells, has been investigated up to 20 GPa by synchrotron X-ray diffraction and Raman spectroscopy. Both experimental data demonstrate that no phase transition occurs up to 20 GPa. By fitting the third-order Birch-Murnaghan equation of state, we have obtained V0 = 1288 (14) Å3, K0 = 11 (1) GPa and K0‧ = 7 (1). The ultralow value of bulk modulus K0 demonstrates the soft nature of Cs2SnBr6. Combining calculated values with experimental results, we find that x coordinate of Sn (x,0,0) atoms increases and Snsbnd Br bond lengths get shortened on compression. We have assigned vibrational peaks of Cs2SnBr6 in Raman measurements, and all the three Raman bands present nonlinear correlations with pressure.

Studies of discharge mechanisms in high pressure gases-applications to high efficiency high power lasers. Ph.D. Thesis. Semiannual Progress Report

NASA Technical Reports Server (NTRS)

Cherrington, B. E.; Verdeyen, J. T.; Eden, J. G.; Leslie, S. G.

1975-01-01

By measuring the absorption and emission cantinua of various states in the cesium/xenon molecule, the collisional rates critical in populating the alkali/rare gas excimer levels have been estimated. Cs atomic states that are weakly optically connected to ground have been shown to form excimer levels that are attractive as potential dissociation lasers. In particular, the (Cs/7 2S/Xe) excited molecule appears promising as a source of high energy laser radiation due to its large dissociation energy, stimulated emission cross section, and small population inversion densities. Monitoring of the optically pumped Cs2 molecular absorption profile in the presence of xenon shows a drastic change with increasing xenon pressure for the Cs2C band. Dominant absorption at large xenon densities is centered around approximately 6380 A as opposed to 6300 A for lower perturber pressure.

Anisotropic surface acoustic waves in tungsten/lithium niobate phononic crystals

NASA Astrophysics Data System (ADS)

Sun, Jia-Hong; Yu, Yuan-Hai

2018-02-01

Phononic crystals (PnC) were known for acoustic band gaps for different acoustic waves. PnCs were already applied in surface acoustic wave (SAW) devices as reflective gratings based on the band gaps. In this paper, another important property of PnCs, the anisotropic propagation, was studied. PnCs made of circular tungsten films on a lithium niobate substrate were analyzed by finite element method. Dispersion curves and equal frequency contours of surface acoustic waves in PnCs of various dimensions were calculated to study the anisotropy. The non-circular equal frequency contours and negative refraction of group velocity were observed. Then PnC was applied as an acoustic lens based on the anisotropic propagation. Trajectory of SAW passing PnC lens was calculated and transmission of SAW was optimized by selecting proper layers of lens and applying tapered PnC. The result showed that PnC lens can suppress diffraction of surface waves effectively and improve the performance of SAW devices.

SU-E-I-51: Quantitative Assessment of X-Ray Imaging Detector Performance in a Clinical Setting - a Simple Approach Using a Commercial Instrument

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

Sjoeberg, J; Bujila, R; Omar, A

2015-06-15

Purpose: To measure and compare the performance of X-ray imaging detectors in a clinical setting using a dedicated instrument for the quantitative determination of detector performance. Methods: The DQEPro (DQE Instruments Inc., London, Ontario Canada) was used to determine the MTF, NPS and DQE using an IEC compliant methodology for three different imaging modalities: conventional radiography (CsI-based detector), general-purpose radioscopy (CsI-based detector), and mammography (a-Se based detector). The radiation qualities (IEC) RQA-5 and RQA-M-2 were used for the CsI-based and a-Se-based detectors, respectively. The DQEPro alleviates some of the difficulties associated with DQE measurements by automatically positioning test devices overmore » the detector, guiding the user through the image acquisition process and providing software for calculations. Results: A comparison of the NPS showed that the image noise of the a-Se detector was less correlated than the CsI detectors. A consistently higher performance was observed for the a-Se detector at all spatial frequencies (MTF: 0.97@0.25 cy/mm, DQE: 0.72@0.25 cy/mm) and the DQE drops off slower than for the CsI detectors. The CsI detector used for conventional radiography displayed a higher performance at low spatial frequencies compared to the CsI detector used for radioscopy (DQE: 0.65 vs 0.60@0.25 cy/mm). However, at spatial frequencies above 1.3 cy/mm, the radioscopy detector displayed better performance than the conventional radiography detector (DQE: 0.35 vs 0.24@2.00 cy/mm). Conclusion: The difference in the MTF, NPS and DQE that was observed for the two different CsI detectors and the a-Se detector reflect the imaging tasks that the different detector types are intended for. The DQEPro has made the determination and calculation of quantitative metrics of X-ray imaging detector performance substantially more convenient and accessible to undertake in a clinical setting.« less

Immobilization of biomolecules on cysteamine-modified polyaniline film for highly sensitive biosensing.

PubMed

Cai, Qi; Xu, Baojian; Ye, Lin; Di, Zengfeng; Zhang, Jishen; Jin, Qinghui; Zhao, Jianlong; Xue, Jian; Chen, Xianfeng

2014-03-01

We present a new cysteamine (CS)-modified polyaniline (PANI) film for highly efficient immobilization of biomolecules in biosensing technology. This electrochemical deposited PANI film treated with CS and glutaraldehyde could be employed as an excellent substrate for biomolecules immobilization. The parameters of PANI growth were optimized to obtain suitable surface morphology of films for biomolecules combination with the help of electron and atomic force microscopy. Cyclic voltammetry (CV) was utilized to illustrate the different electrochemical activities of each modified electrode. Due to the existence of sulfydryl group and amino group in CS, surface modification with CS was proven to reduce oxidized units on PANI film remarkably, as evidenced by both ATR-FTIR and Raman spectroscopy characterizations. Furthermore, bovine serum albumin (BSA) was used as the model protein to investigate the immobilization efficiency of biomolecules on the PANI film, comparative study using quartz crystal microbalance (QCM) showed that BSA immobilized on CS-modified PANI could be increased by at least 20% than that without CS-modified PANI in BSA solution with the concentration of 0.1-1mg/mL. The CS-modified PANI film would be significant for the immobilization and detection of biomolecules and especially promising in the application of immunosensor for ultrasensitive detection. © 2013 Published by Elsevier B.V.

High-Affinity Accumulation of Chloroquine by Mouse Erythrocytes Infected with Plasmodium berghei

PubMed Central

Fitch, Coy D.; Yunis, Norman G.; Chevli, Rekha; Gonzalez, Yolanda

1974-01-01

Washed erythrocytes infected with chloroquine-susceptible (CS) or with chloroquine-resistant (CR) P. berghei were used in model systems in vitro to study the accumulation of chloroquine with high affinity. The CS model could achieve distribution ratios (chloroquine in cells: chloroquine in medium) of 100 in the absence of substrate. 200—300 in the presence of 10 mM pyruvate or lactate, and over 600 in the presence of 1 mM glucose or glycerol. In comparable studies of the CR model, the distribution ratios were 100 in the absence of substrate and 300 or less in the presence of glucose or glycerol. The presence of lactate stimulated chloroquine accumulation in the CR model, whereas the presence of pyruvate did not. Lactate production from glucose and glycerol was undiminished in the CR model, and ATP concentrations were higher than in the CS model. Cold, iodoacetate, 2,4-dinitrophenol, or decreasing pH inhibited chloroquine accumulation in both models. These findings demonstrate substrate involvement in the accumulation of chloroquine with high affinity. In studies of the CS model, certain compounds competitively inhibited chloroquine accumulation, while others did not. This finding is attributable to a specific receptor that imposes structural constraints on the process of accumulation. For chloroquine analogues, the position and length of the side chain, the terminal nitrogen atom of the side chain, and the nitrogen atom in the quinoline ring are important determinants of binding to this receptor. PMID:4600044

210Pb and 137Cs as chronometers for salt marsh accretion in the Venice Lagoon - links to flooding frequency and climate change.

PubMed

Bellucci, L G; Frignani, M; Cochran, J K; Albertazzi, S; Zaggia, L; Cecconi, G; Hopkins, H

2007-01-01

Five salt marsh sediment cores from different parts of the Venice Lagoon were studied to determine their depositional history and its relationship with the environmental changes occurred during the past approximately 100 years. X-radiographs of the cores show no disturbance related to particle mixing. Accretion rates were calculated using a constant flux model applied to excess (210)Pb distributions in the cores. The record of (137)Cs fluxes to the sites, determined from (137)Cs profiles and the (210)Pb chronologies, shows inputs from the global fallout of (137)Cs in the late 1950s to early 1960s and the Chernobyl accident in 1986. Average accretion rates in the cores are comparable to the long-term average rate of mean sea level rise in the Venice Lagoon ( approximately 0.25 cm y(-1)) except for a core collected in a marsh presumably affected by inputs from the Dese River. Short-term variations in accretion rate are correlated with the cumulative frequency of flooding, as determined by records of Acqua Alta, in four of the five cores, suggesting that variations in the phenomena causing flooding (such as wind patterns, storm frequency and NAO) are short-term driving forces for variations in marsh accretion rate.

From {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} to {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite chains in A{sub 6}U{sub 2}Mo{sub 4}O{sub 21} (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})

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

Yagoubi, S.; Groupe de Radiochimie, Institut de Physique Nucleaire d'Orsay, Universite Paris-Sud XI, 91406 Orsay Cedex; Obbade, S., E-mail: said.obbade@phelma.grenoble-inp.f

2011-05-15

A new caesium uranyl molybdate belonging to the M{sub 6}U{sub 2}Mo{sub 4}O{sub 21} family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A{sub 6}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}], the caesium compound Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 21} should be written Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] crystallizes in the triclinic symmetry withmore » space group P1-bar and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, {alpha}=70.72(1){sup o}, {beta}=80.38(1){sup o} and {gamma}=86.39(1){sup o}, V=2604.7(6) A{sup 3}, Z=4, {rho}{sub mes}=5.02(2) g/cm{sup 3} and {rho}{sub cal}=5.08(3) g/cm{sup 3}. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R{sub 1}=0.0464 and wR{sub 2}=0.0950 for 596 parameters with 6964 independent reflections with I{>=}2{sigma}(I) collected on a BRUKER AXS diffractometer with Mo(K{alpha}) radiation and a CCD detector. The crystal structure of Cs compound is characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} parallels chains built from U{sub 2}O{sub 13} dimeric units, MoO{sub 4} tetrahedra and MoO{sub 5} square pyramids, whereas, Na, K and Rb compounds are characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} parallel chains formulated simply of U{sub 2}O{sub 13} units and MoO{sub 4} tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 {sup o}C). -- Graphical abstract: The staking of {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite uranyl molybdate ribbons in the Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] structure. Display Omitted Highlights: {yields} Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 2} a new compound with bidimensional crystal structure, characterized by infinite uranyl molybdate chains. {yields} Crystal structure similar to these of the compounds containing Na, K, Rb. {yields} Molybdenum atoms surrounded by five oxygen atoms to form an original and strongly distorted MoO{sub 5} environment. {yields} The chains arrangement illustrates the key role of the alkaline ionic radius, in the crystal structure distortion for Cs compound.« less

Cesium-137 Fallout in Indiana Soil

NASA Astrophysics Data System (ADS)

Whitman, Richard T.

Atomic weapons testing during the Cold War and accidents at nuclear power plants have resulted in the release of radioactive fallout over great distances. Little is known about levels of fallout deposited in Indiana. The reported study sampled soil in all 92 Indiana counties to determine the present level of cesium-137 from the 2 to 12 centimeter depth from previous nuclear tests and other nuclear releases. A total of 67 samples were collected from forested areas and 25 from grasslands, both undisturbed since 1940, along with four controls from crawl spaces. Greater Cs-137 retention occurred in the forested areas at approximately a 2:1 ratio. Other parameters investigated included soil clay content, rate of rainfall, and soil pH. Each variable was examined for possible statistical correlation with Cs-137 retention. Both clay content and combined clay content/rainfall were significantly (p < 0.05) correlated with soil Cs-137 levels. The four controls showed very low values of Cs-137 indicating the movement of sub-micron sized fallout into areas considered safe from fallout. The Cs-137 data from this study will serve as a reliable baseline of Cs-137 levels in the event of a future release of fallout.

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

Grochola, A.; Kowalczyk, P.; Szczepkowski, J.

Comprehensive spectroscopic studies of hot and ultracold samples of NaCs molecules were combined to complete the investigation of the (3){Omega}=1 <- X {sup 1}{Sigma}{sup +} transition for the NaCs molecule. Polarization labeling, photoassociation, and pulsed laser depletion spectroscopy were used to collect data on rovibrational levels of the (3){Omega}=1 state [here described as the c {sup 3}{Sigma}{sup +} state in Hund's case (a) notation]. The highest observed level was v=72 located {approx}5 GHz below the atomic asymptote Na(3 {sup 2}S{sub 1/2}) + Cs(6 {sup 2}P{sub 3/2}). Approximately 1400 levels were used to construct the potential energy curve of the (3){Omega}=1more » state for the full range of interatomic distances.« less

Separation and preconcentration of platinum-group metals from spent autocatalysts solutions using a hetero-polymeric S, N-containing sorbent and determination by high-resolution continuum source graphite furnace atomic absorption spectrometry.

PubMed

Eskina, Vasilina V; Dalnova, Olga A; Filatova, Daria G; Baranovskaya, Vasilisa B; Karpov, Yuri A

2016-10-01

This paper describes the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for determination of Pt, Pd and Rh after separation and concentration by original in-house developed heterochain polymer S, N-containing sorbent. The methods of sample preparation of spent ceramic-based autocatalysts were considered, two of which were used: autoclave decomposition in mixture of acids HCl:HNO3 (3:1) and high-temperature melting with K2S2O7. Both methods anyway limit the direct determination of analytes by HR CS GFAAS. Using the first method it is an incomplete digestion of spent autocatalysts samples, since the precipitate is Si, and the rhodium metal dissolves with difficulty and partially passes into solution. In contrast to the first method, the second method allow to completely transfer analytes into solution, however, the background signal produced by the chemical composition of the flux, overlaps the analytical zone. It was found, that Pt, Pd and Rh contained in the spent ceramic automotive catalysts could be effectively separated and concentrated by heterochain polymer S, N-containing sorbent, which has high sorption capacity, selectivity and resistant to dilute acids. The chosen HR CS GFAAS analysis conditions enable us to determine Pt, Pd and Rh with good metrological characteristics. The concentrations of Pt, Pd and Rh in two samples of automobile exhaust catalysts were found in range of 0.00015-0.00050; 0.170-0.189; 0.0180-0.0210wt%, respectively. The relative standard deviation obtained by HR CS GFAAS was not more than 5%. Limits of detection by HR CS GFAAS achieved were 6.2·10(-6)wt% for Pt, 1.8·10(-6)wt% for Pd, and 3.4·10(-6)wt% for Rh. Limits of determination achieved by HR CS GFAAS were 1.1·10(-5)wt% for Pt, 6.9·10(-5)wt% for Pd, and 8.3·10(-5)wt% for Rh. To control the accuracy of PGM in sorption concentrates by HR CS GFAAS method, it was appropriate to conduct an inter-method comparative experiment. The researches on the application of atomic-emission spectroscopy method with inductively coupled plasma as a comparative method were conducted. In addition, the trueness control of the obtained results is confirmed by added-found method. Copyright © 2016 Elsevier B.V. All rights reserved.

Size distribution of radioactive particles collected at Tokai, Japan 6 days after the nuclear accident.

PubMed

Miyamoto, Yutaka; Yasuda, Kenichiro; Magara, Masaaki

2014-06-01

Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Determination of gold and cobalt dopants in advanced materials based on tin oxide by slurry sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Filatova, Daria G.; Eskina, Vasilina V.; Baranovskaya, Vasilisa B.; Vladimirova, Svetlana A.; Gaskov, Alexander M.; Rumyantseva, Marina N.; Karpov, Yuri A.

2018-02-01

A novel approach is developed for the determination of Co and Au dopants in advanced materials based on tin oxide using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) with direct slurry sampling. Sodium carboxylmethylcellulose (Na-CMC) is an effective stabilizer for diluted suspensions. Use Na-CMC allows to transfer the analytes into graphite furnace completely and reproducibly. The relative standard deviation obtained by HR CS GFAAS was not higher than 4%. Accuracy was proven by means inductively coupled plasma mass spectrometry (ICP-MS) in solutions after decomposition as a comparative technique. To determine Au and Co in the volume of SnO2, the acid decomposition conditions (HCl, HF) of the samples were suggested by means of an autoclave in a microwave oven.

Atomic-Resolution X-ray Energy-Dispersive Spectroscopy Chemical Mapping of Substitutional Dy Atoms in a High-Coercivity Neodymium Magnet

NASA Astrophysics Data System (ADS)

Itakura, Masaru; Watanabe, Natsuki; Nishida, Minoru; Daio, Takeshi; Matsumura, Syo

2013-05-01

We have investigated local element distributions in a Dy-doped Nd2Fe14B hot-deformed magnet by atomic-column resolution chemical mapping using an X-ray energy-dispersive spectrometer (XEDS) attached to an aberration-corrected scanning transmission electron microscope (Cs-corrected STEM). The positions of the Nd and Dy atomic columns were visualized in the XEDS maps. The substitution of Dy was limited to a surface layer 2-3 unit cells thick in the Nd2Fe14B grains, and the Dy atoms preferentially occupied the 4f-Nd sites of Nd2Fe14B. These results provide further insights into the principal mechanism governing the coercivity enhancement due to Dy doping.

Coupled channel effects on resonance states of positronic alkali atom

NASA Astrophysics Data System (ADS)

Yamashita, Takuma; Kino, Yasushi

2018-01-01

S-wave Feshbach resonance states belonging to dipole series in positronic alkali atoms (e+Li, e+Na, e+K, e+Rb and e+Cs) are studied by coupled-channel calculations within a three-body model. Resonance energies and widths below a dissociation threshold of alkali-ion and positronium are calculated with a complex scaling method. Extended model potentials that provide positronic pseudo-alkali-atoms are introduced to investigate the relationship between the resonance states and dissociation thresholds based on a three-body dynamics. Resonances of the dipole series below a dissociation threshold of alkali-atom and positron would have some associations with atomic energy levels that results in longer resonance lifetimes than the prediction of the analytical law derived from the ion-dipole interaction.

Organic solvent exposure and contrast sensitivity: comparing men and women

PubMed Central

Oliveira, A.R.; Campos, A.A.; de Andrade, M.J.O.; de Medeiros, P.C.B.; dos Santos, N.A.

2018-01-01

The goal of this study was to compare the visual contrast sensitivity (CS) of men and women exposed and not exposed to organic solvents. Forty-six volunteers of both genders aged between 18 and 41 years (mean±SD=27.72±6.28) participated. Gas station attendants were exposed to gas containing 46.30 ppm of solvents at a temperature of 304±274.39 K, humidity of 62.25±7.59% and ventilation of 0.69±0.46 m/s (a passive gas chromatography-based sampling method was used considering the microclimate variables). Visual CS was measured via the psychophysical method of two-alternative forced choice using vertical sinusoidal gratings with spatial frequencies of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 16.0 cpd (cycles per degree) and an average luminance of 34.4 cd/m2. The results showed that visual CS was significantly lower (P<0.05) in the following groups: i) exposed men compared to unexposed men at frequencies of 0.2, 0.5, 1.0, and 2.0 cpd; ii) exposed women compared to unexposed women at a frequency of 5.0 cpd; and iii) exposed women compared to exposed men at a frequency of 0.5 cpd, even at exposures below the tolerance limit (300 ppm). These results suggest that the visual CS of exposed men was impaired over a wider range of spatial frequencies than that of exposed women. This difference may have been due to the higher body fat content of women compared to that of men, suggesting that body fat in women can serve as a protective factor against neurotoxic effects. PMID:29340521

Association of LMX1A genetic polymorphisms with susceptibility to congenital scoliosis in Chinese Han population.

PubMed

Wu, Nan; Yuan, Suomao; Liu, Jiaqi; Chen, Jun; Fei, Qi; Liu, Sen; Su, Xinlin; Wang, Shengru; Zhang, Jianguo; Li, Shugang; Wang, Yipeng; Qiu, Guixing; Wu, Zhihong

2014-10-01

A genetic association study of single nucleotide polymorphisms (SNPs) for the LMX1A gene with congenital scoliosis (CS) in the Chinese Han population. To determine whether LMX1A genetic polymorphisms are associated with susceptibility to CS. CS is a lateral curvature of the spine due to congenital vertebral defects, whose exact genetic cause has not been well established. The LMX1A gene was suggested as a potential human candidate gene for CS. However, no genetic study of LMX1A in CS has ever been reported. We genotyped 13 SNPs of the LMX1A gene in 154 patients with CS and 144 controls with matched sex and age. After conducting the Hardy-Weinberg equilibrium test, the data of 13 SNPs were analyzed by the allelic and genotypic association with logistic regression analysis. Furthermore, the genotype-phenotype association and haplotype association analysis were also performed. The 13 SNPs of the LMX1A gene met Hardy-Weinberg equilibrium in the controls, which was not in the cases. None of the allelic and genotypic frequencies of these SNPs showed significant difference between case and control groups (P > 0.05). However, the genotypic frequencies of rs1354510 and rs16841013 in the LMX1A gene were associated with CS predisposition in the unconditional logistic regression analysis (P = 0.02 and 0.018, respectively). Genotypic frequencies of 3 SNPs at rs6671290, rs1354510, and rs16841013 were found to exhibit significant differences between patients with CS with failure of formation and the healthy controls (P = 0.019, 0.007, and 0.006, respectively). Besides, in the model analysis by using unconditional logistic regression analysis, the optimized model for the 3 genotypic positive SNPs with failure of formation were rs6671290 (codominant; P = 0.025, Akaike information value = 316.6, Bayesian information criterion = 333.9), rs1354510 (overdominant; P = 0.0017, Akaike information value = 312.1, Bayesian information criterion = 325.9), and rsl6841013 (overdominant; P = 0.0016, Akaike information value = 311.1, Bayesian information criterion = 325), respectively. However, the haplotype distributions in the case group were not significantly different from those of the control group in the 3 haplotype blocks. To our knowledge, this is the first study to identify that the SNPs of the LMX1A gene might be associated with the susceptibility to CS and different clinical phenotypes of CS in the Chinese Han population. 4.

Syntheses, crystal structure, and electronic properties of the five ABaMQ{sub 4} compounds RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4}

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

Mesbah, Adel; ICSM, UMR 5257 CEA / CNRS / UM / ENSCM, Site de Marcoule-Bâtiment 426, BP 17171, 30207 Bagnols-sur-Cèze Cedex; Prakash, Jai

Five new compounds belonging to the ABaMQ{sub 4} family were synthesized by solid-state chemistry at 1123 K. The compounds RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4} are isostructural and have the TlEuPS{sub 4} structure type. They crystallize in space group D{sup 16}{sub 2h} – Pnma of the orthorhombic system. Their structure consists isolated MQ{sub 4} tetrahedra separated by A and Ba atoms to form a salt-like structure. Density Functional Theory (DFT) calculations of the electronic structures with the use of the HSE functional suggest that the compounds are semiconductors with calculated band gaps of 3.3 eVmore » (RbBaPS{sub 4}), 3.4 eV (CsBaPS{sub 4}), 2.3 eV (CsBaVS{sub 4}), and 1.6 eV (RbBaVSe{sub 4}). - Graphical abstract: General view of the ABaMQ{sub 4} structure down the a axis. - Highlights: • Five new ABaMQ{sub 4} compounds were synthesized by solid-state chemistry at 1123 K. • RbBaPS{sub 4}, CsBaPS{sub 4}, CsBaVS{sub 4}, RbBaVSe{sub 4}, and CsBaVSe{sub 4} have the TlEuPS{sub 4} structure type. • The compounds are semiconductors with calculated band gaps ranging from 1.6 to 3.4 eV.« less

Surface and Bulk Characteristics of Cesium Iodide (CsI) coated Carbon (C) Fibers for High Power Microwave (HPM) Field Emission Cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Morgan, Dane; Booske, John H.; Shiffler, Don

2008-11-01

CsI coated C fibers [1] are promising field emission cathodes for HPM applications. Ab initio computational modeling has shown that atomically-thin CsI coatings reduce the work function of C substrates by a surface dipole mechanism [2]. Characterization measurements of the composition and morphology of the CsI-coated C fibers are underway for determining the properties and characteristics of the following important regions of the fiber: (i) the surface on the tip of the fiber where the majority of electron emission is believed to occur, (ii) the surface covering the body of the fiber and its role on the emission properties of the system, and (iii) the interior volume of the fiber and its effects on the CsI surface re-supply process and rate. The results will be interpreted in terms of surface electronic properties and theoretical electron emission models. [1]D. Shiffler, et al., Phys. Plasmas 11 (2004) 1680. [2]V.Vlahos et al., Appl. Phys. Lett. 91 (2007) 144102.

On the importance of electron impact processes in excimer-pumped alkali laser-induced plasmas

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

Markosyan, Aram H.

We present that the excimer-pumped alkali laser (XPAL) system has recently been demonstrated in several different mixtures of alkali vapor and rare gas. Without special preventive measures, plasma formation during operation of XPAL is unavoidable. Some recent advancements in the availability of reliable data for electron impact collisions with atoms and molecules have enabled development of a complete reaction mechanism to investigate XPAL-induced plasmas. Here, we report on pathways leading to plasma formation in an Ar/C 2H 6/CsAr/C2H6/Cs XPAL sustained at different cell temperatures. We find that depending on the operating conditions, the contribution of electron impact processes can bemore » as little as bringing the excitation of Cs(P 2) states to higher level Cs** states, and can be as high as bringing Cs(P 2) excited states to a full ionization. Increasing the input pumping power or cell temperature, or decreasing the C 2H 6 mole fraction leads to electron impact processes dominating in plasma formation over the energy pooling mechanisms previously reported in literature.« less

New type of borophosphate anionic radical in the crystal structure of CsAl2BP6O20

NASA Astrophysics Data System (ADS)

Shvanskaya, L. V.; Yakubovich, O. V.; Belik, V. I.

2016-09-01

The crystal structure of a new borophosphate CsAl2BP6O20 obtained by spontaneous crystallization in a multicomponent Cs-Cu-B-P-O system is determined by X-ray diffraction ( a = 11.815(2), b = 10.042(2), and c = 26.630(4) Å; space group Pbca, Z = 8, V = 3159.5(10) Å3; R 1 = 0.043). A new type of borophosphate anionic 2D radical characterized by the lowest B: P = 1: 6 ratio and containing P3O10 phosphate groups is found in the compound. A mixed-type anionic framework consisting of vertex-sharing BO4 and PO4 tetrahedra and AlO6 octahedra is distinguished in the structure. Large cesium atoms are located in the channels of the framework. Topological relationships are revealed between the structures of the CsAl3(P3O10)2 and CsAl2BP6O20 phases having different cationic compositions. These compounds can be considered quasi-polytypic phases.

On the importance of electron impact processes in excimer-pumped alkali laser-induced plasmas

DOE PAGES

Markosyan, Aram H.

2017-10-18

We present that the excimer-pumped alkali laser (XPAL) system has recently been demonstrated in several different mixtures of alkali vapor and rare gas. Without special preventive measures, plasma formation during operation of XPAL is unavoidable. Some recent advancements in the availability of reliable data for electron impact collisions with atoms and molecules have enabled development of a complete reaction mechanism to investigate XPAL-induced plasmas. Here, we report on pathways leading to plasma formation in an Ar/C 2H 6/CsAr/C2H6/Cs XPAL sustained at different cell temperatures. We find that depending on the operating conditions, the contribution of electron impact processes can bemore » as little as bringing the excitation of Cs(P 2) states to higher level Cs** states, and can be as high as bringing Cs(P 2) excited states to a full ionization. Increasing the input pumping power or cell temperature, or decreasing the C 2H 6 mole fraction leads to electron impact processes dominating in plasma formation over the energy pooling mechanisms previously reported in literature.« less

Re-examination of chewing and spitting behavior: characteristics within and across eating disorder diagnoses.

PubMed

Durkin, Nora E; Swanson, Sonja A; Crow, Scott J; Mitchell, James; Peterson, Carol B; Crosby, Ross

2014-01-01

Chewing and spitting (CS) out food is a relatively understudied eating disorder behavior. The aim of this study was to examine lifetime and current frequencies of CS across eating disorder diagnostic groups and to compare the severity of eating disorder symptomatology between participants who did and did not endorse CS. A total of 972 individuals presenting for outpatient eating disorder treatment between 1985 and 1996 completed a questionnaire that included items regarding current and lifetime eating disorder behaviors, including CS. Results indicated that both lifetime and current prevalence estimates of CS varied cross-diagnostically, with CS being more common among those with anorexia nervosa and bulimia nervosa compared to those with eating disorder not otherwise specified. CS was significantly associated with several eating disorder symptoms, including compensatory behaviors, meal restriction, and lower BMI. Those who reported CS were also younger in age compared to those who did not report CS. These findings indicate that CS is associated with more severe eating and weight pathology and is not equally prevalent across eating disorder diagnoses. These results also support the relatively high occurrence of CS and the importance of targeting this behavior in eating disorder treatment. Future research should clarify the correlates, mechanisms, and function of CS in eating disorders.

Theoretical and Experimental Studies in Reactive Scattering.

DTIC Science & Technology

1986-08-11

dynamics 3. Three-dimensional reaction dynamics 4. Anisotropic potentials for He + C02, OCS, CS2 .. 5. Production of a high intensity-high energy beam of...involving beams of He atoms, H atoms and metastable H molecules aimed at the determination of potential energy surfaces involving these systems. 2... energy of 0.3 ’, Kcal/mole below the top of the barrier, the reaction probability from ground S"t vibrational state reagent to ground vibrational

Subclinical visual involvement in multiple sclerosis: a study by MRI, VEPs, frequency-doubling perimetry, standard perimetry, and contrast sensitivity.

PubMed

Sisto, Dario; Trojano, Maria; Vetrugno, Michele; Trabucco, Tiziana; Iliceto, Giovanni; Sborgia, Carlo

2005-04-01

To evaluate the effectiveness of visual evoked potentials (VEPs), frequency-doubling perimetry (FDP), standard achromatic perimetry (SAP), contrast sensitivity (CS) test, and magnetic resonance imaging (MRI), isolated or in combination, in detecting subclinical impairment of visual function in multiple sclerosis (MS). Twenty-two eyes of 11 patients affected by clinically definite MS, without a history of optic neuritis and asymptomatic for visual disturbances, underwent full ophthalmic examination and, in addition, VEPs, FDP, SAP, CS, and MRI. Abnormal results were taken to be as follows: for VEPs, a P100 latency >115 ms; for FDP, abnormal mean deviation (MD) or pattern SD (PSD); for SAP, abnormal MD or PSD; for CS, abnormal CS at one spatial frequency, at least; and for MRI, evidence of at least one demyelinating plaque along the visual pathway. VEPs showed abnormal results in 12 eyes (54.4%), FDP in 11 (50%), SAP in 14 (63.6%), CS in 17 (77.1%), and MRI in 16 (72.7%). In only two (9.1%) eyes of the same patient was no abnormality found. No single test detected all the abnormal eyes. Four (18.2%) eyes had pure optic nerve involvement and the remaining 16 (72.7%) had both pre- and postchiasmal involvement. In patients affected by clinically definite MS without history of optic neuritis and no visual symptoms, there is a large prevalence of visual pathway involvement that can be diagnosed only by performing multiple tests. The comparison of the tests is also useful to detect the presence of multiple lesions in the same patient.

New Tests for Variations of the Fine Structure Constant

NASA Technical Reports Server (NTRS)

Prestage, John D.

1995-01-01

We describe a new test for possible variations of the fine structure constant, by comparisons of rates between clocks based on hyperfine transitions in alkali atomos with different atomic number Z. H- maser, Cs and Hg+ clocks have a different dependence on ia relativistic contributions of order (Z. Recent H-maser vs Hg+ clock comparison data improves laboratory limits on a time variation by 100-fold to giveFuture laser cooled clocks (Be+, Rb, Cs, Hg+, etc.), when compared, will yield the most senstive of all tests for.

Characteristics and physiological role of hyperpolarization activated currents in mouse cold thermoreceptors

PubMed Central

Orio, Patricio; Madrid, Rodolfo; de la Peña, Elvira; Parra, Andrés; Meseguer, Víctor; Bayliss, Douglas A; Belmonte, Carlos; Viana, Félix

2009-01-01

Hyperpolarization-activated currents (Ih) are mediated by the expression of combinations of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channel subunits (HCN1–4). These cation currents are key regulators of cellular excitability in the heart and many neurons in the nervous system. Subunit composition determines the gating properties and cAMP sensitivity of native Ih currents. We investigated the functional properties of Ih in adult mouse cold thermoreceptor neurons from the trigeminal ganglion, identified by their high sensitivity to moderate cooling and responsiveness to menthol. All cultured cold-sensitive (CS) neurons expressed a fast activating Ih, which was fully blocked by extracellular Cs+ or ZD7288 and had biophysical properties consistent with those of heteromeric HCN1–HCN2 channels. In CS neurons from HCN1(−/−) animals, Ih was greatly reduced but not abolished. We find that Ih activity is not essential for the transduction of cold stimuli in CS neurons. Nevertheless, Ih has the potential to shape the excitability of CS neurons. First, Ih blockade caused a membrane hyperpolarization in CS neurons of about 5 mV. Furthermore, impedance power analysis showed that all CS neurons had a prominent subthreshold membrane resonance in the 5–7 Hz range, completely abolished upon blockade of Ih and absent in HCN1 null mice. This frequency range matches the spontaneous firing frequency of cold thermoreceptor terminals in vivo. Behavioural responses to cooling were reduced in HCN1 null mice and after peripheral pharmacological blockade of Ih with ZD7288, suggesting that Ih plays an important role in peripheral sensitivity to cold. PMID:19273581

UTC(SU) and EOP(SU) - the only legal reference frames of Russian Federation

NASA Astrophysics Data System (ADS)

Koshelyaevsky, Nikolay B.; Blinov, Igor Yu; Pasynok, Sergey L.

2015-08-01

There are two legal time reference frames in Russian Federation. UTC(SU) deals with atomic time and play a role of reference for legal timing through the whole country. The other one, EOP(SU), deals with Earth's orientation parameters and provides the official EOP data for scientific, technical and metrological applications in Russia.The atomic time is based on two essential hardware components: primary Cs fountain standards and ensemble of continuously operating H-masers as a time unit/time scale keeper. Basing on H-maser intercomparison system data, regular H-maser frequency calibration against Cs standards and time algorithm autonomous TA(SU) time scale is maintained by the Main Metrological Center. Since 2013 time unit in TA(SU) is the second (SU) reproduced independently by VNIIFTRI Cs primary standards in accordance to it’s definition in the SI. UTC(SU) is relied on TA(SU) and steering to UTC basing on TWSTFT/GNSS time link data. As a result TA(SU) stability level relative to TT considerably exceeds 1×10-15 for sample time one month and more, RMS[UTC-UTC(SU)] ≤ 3 ns for the period of 2013-2015. UTC(SU) is broadcasted by different national means such as specialized radio and TV stations, NTP servers and GLONASS. Signals of Russian radio stations contains DUT1 and dUT1 values at 0.1s and 0.02s resolution respectively.The definitive EOP(SU) are calculated by the Main Metrological Center basing on composition of the eight independent individual EOP data streams delivered by four Russian analysis centers: VNIIFTRI, Institute of Applied Astronomy, Information-Analytical Center of Russian Space Agency and Analysis Center of Russian Space Agency. The accuracy of ultra-rapid EOP values for 2014 is estimated ≤ 0.0006" for polar motion, ≤ 70 microseconds for UT1-UTC and ≤ 0.0003" for celestial pole offsets respectively.The other VNIIFTRI EOP activities can be grouped in three basic directions:- arrangement and carrying out GNSS and SLR observations at five institutes- processing GNSS, SLR and VLBI observation data for EOP evaluation- combination of GLONASS satellites orbit/clocks.The paper will deliver more detailed and particular information on Russian legal reference frames.

Selectivity of bis(calix[4]diquinone) ionophores towards metal ions in solvent dimethylsulfoxide: a molecular mechanics and molecular dynamics study.

PubMed

Felix, Vitor; Drew, Michael G B; Webber, Philip R A; Beer, Paul D

2006-01-28

Molecular modelling studies have been carried out on two bis(calix[4]diquinone) ionophores, each created from two (calix[4]diquinone)arenes bridged at their bottom rims via alkyl chains (CH(2))(n), 1: n = 3, 2; n = 4, in order to understand the reported selectivity of these ligands towards different sized metal ions such as Na(+), K(+), Rb(+), and Cs(+) in dmso solution. Conformational analyses have been carried out which show that in the lowest energy conformations of the two macrocycles, the individual calix[4]diquinones exhibit a combination of partial cone, 1,3-alternate and cone conformations. The interactions of these alkali metals with the macrocycles have been studied in the gas phase and in a periodic box of solvent dmso by molecular mechanics and molecular dynamics calculations. Molecular mechanics calculations have been carried out on the mode of entry of the ions into the macrocycles and suggest that this is likely to occur from the side of the central cavity, rather than through the main axis of the calix[4]diquinones. There are energy barriers of ca. 19 kcal mol(-1) for this entry path in the gas phase, but in solution no energy barrier is found. Molecular dynamics simulations show that in both 1 and 2, though particularly in the latter macrocycle, one or two solvent molecules are bonded to the metal throughout the course of the simulation, often to the exclusion of one or more of the ether oxygen atoms. By contrast the carbonyl oxygen atoms remain bonded to the metal atoms throughout with bond lengths that remain significantly less than those to the ether oxygen atoms. Free energy perturbation studies have been carried out in dmso and indicate that for 1, the selectivity follows the order Rb(+) approximately K(+) > Cs(+) > Na(+), which is partially in agreement with the experimental results. The energy differences are small and indeed the ratio between stability constants found for Cs(+) and K(+) complexes is only 0.60, showing that has only a slight preference for K(+). For the larger receptor , which is better suited to metal complexation, the binding affinity follows the pattern Cs(+) > Rb(+) > K(+) > Na(+), with energy differences of 5.75, 2.61, 2.78 kcal mol(-1) which is perfectly consistent with experimental results.

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}: Spectroscopic characterization and cationic mobility studies

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

Yagoubi, S., E-mail: said.yagoubi@cea.fr; Renard, C.; Abraham, F.

2013-04-15

The reaction of triuranyl diphosphate tetrahydrate precursor (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} with a CsI flux at 750 °C yields a yellow single crystals of new compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13) Å, b=8.1081(8) Å, c=12.3983(12) Å, β=114.61(12)°, V=1245.41(20) Å{sup 3} with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupledmore » device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains {sup 1}{sub ∞}[UO{sub 5}] and by one phosphorus atom in a tetrahedral environment PO{sub 4}. The two last entities {sup 1}{sub ∞}[UO{sub 5}] and PO{sub 4} are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs{sup +} alkaline cations. Their mobility within the tunnels were studied between 280 and 800 °C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound. - Graphical abstract: Arrhenius plot of the electrical conductivity of tunneled compounds Cs{sub 3}U{sub 2}PO{sub 10} and CsU{sub 2}Nb{sub 2}O{sub 11.5}. Highlights: ► The reaction of (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} in excess of molten CsI leads to single-crystals of new tunneled compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. ► Ionic conductivity measurements and crystal structure analysis indicate a strong connection of the Cs{sup +} cations to the tunnels. ► A low symmetry in Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2} is the cause of IR activation and splitting of the bands in the IR spectrum.« less

Nanocrystalline Cs{sub x}WO{sub 3} particles: Effects of N{sub 2} annealing on microstructure and near-infrared shielding characteristics

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

Liu, Jing-Xiao, E-mail: drliu-shi@dlpu.edu.cn; Institute of Multidisciplinary Research for Advanced Material, Tohoku University, Sendai, 980-8577,Japan; Shi, Fei

2013-10-15

In order to further improve the near-infrared shielding properties of cesium tungsten bronze (Cs{sub x}WO{sub 3}) for solar filter applications, Cs{sub x}WO{sub 3} particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of Cs{sub x}WO{sub 3} were investigated. The obtained Cs{sub x}WO{sub 3} samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like Cs{sub x}WO{sub 3} particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding propertiesmore » of Cs{sub x}WO{sub 3} particles could be further improved by N{sub 2} annealing at 500–700 °C. Particularly, the 500 °C-annealed Cs{sub x}WO{sub 3} samples in the N{sub 2} atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500 °C-annealed Cs{sub x}WO{sub 3} samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies. Highlights: • N{sub 2} annealing could further improve the near-infrared (NIR) shielding of Cs{sub x}WO{sub 3}. • Effects of N{sub 2} annealing on microstructure and NIR shielding of Cs{sub x}WO{sub 3} were studied. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} exhibited minimum O/W ratio and most oxygen vacancies. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} particles exhibited best NIR shielding properties.« less

Understanding and modulating the high-energy properties of noble-gas hydrides from their long-bonding: an NBO/NRT investigation on HNgCO+/CS+/OSi+ and HNgCN/NC (Ng = He, Ar, Kr, Xe, Rn) molecules.

PubMed

Zhang, Guiqiu; Song, Junjie; Fu, Lei; Tang, Kongshuang; Su, Yue; Chen, Dezhan

2018-04-18

The noble-gas hydrides, HNgX (X is an electronegative atom or fragment), represent potential high-energy materials because their two-body decomposition process, HNgX → Ng + HX, is strongly exoergic. Our previous studies have shown that each member of the HNgX (X = halogen atom or CN/NC fragment) molecules is composed of three leading resonance structures: two ω-bonding structures (H-Ng+ :X- and H:- Ng+-X) and one long-bonding structure (H∧X). The last one paints a novel [small sigma, Greek, circumflex]-type long-bonding picture. The present study focuses on the relationship between this novel bonding motif and the unusual energetic properties. We chose HNgCO+/CS+/OSi+/CN/NC, with the formula HNgAB (Ng = He, Ar, Kr, Xe, Rn; AB = CO+/CS+/OSi+/CN/NC) as the research system. We first investigated the bonding of HNgCO+ and its analogous HNgCS+/OSi+ species using NBO/NRT methods, and quantitatively compared the bonding with that in HNgCN/NC molecules. NBO/NRT results showed that each of the HNgCO+/CS+/OSi+ molecules could be better represented as a resonance hybrid of ω-bonding and long-bonding structures, but the long-bonding is much weaker than that in HNgCN/NC molecules. Furthermore, we introduced the long-bonding concept into the rationalization of the high-energy properties, and found a good correlation between the highly exothermic two-body dissociation channel and the long-bond order, bH-A. We also found that the long-bond order is highly tunable for these noble-gas hydrides due to its dependence on the nature of the electronegative AB fragments or the central noble-gas atoms, Ng. On the basis of these results, we could optimize the energetic properties by changing the long-bonding motif of our studied molecules. Overall, this study shows that the long-bonding model provides an easy way to rationalize and modulate the unusual energy properties of noble-gas hydrides, and that it is helpful to predict some noble-gas hydrides as potential energetic materials.

Hexamethonium- and methyllycaconitine-induced changes in acetylcholine release from rat motor nerve terminals.

PubMed

Tian, L; Prior, C; Dempster, J; Marshall, I G

1997-11-01

1. The neuronal nicotinic receptor antagonists hexamethonium and methyllycaconitine (MLA) have been used to study the putative prejunctional nicotinic ACh receptors (AChRs) mediating a negative-feedback control of ACh release from motor nerve terminals in voltage-clamped rat phrenic nerve/ hemidiaphragm preparations. 2. Hexamethonium (200 microM), but not MLA (0.4-2.0 microM), decreased the time constant of decay of both endplate currents (e.p.cs) and miniature endplate currents (m.e.p.cs), indicating endplate ion channel block with hexamethonium. However, driving function analysis and reconvolution of e.p.cs and m.e.p.cs indicated that this ion channel block did not compromise the analysis of e.p.c. quantal content. 3. At low frequencies of stimulation (0.5-2 Hz), hexamethonium (200 microM) and MLA (2.0 microM) increased e.p.c. quantal content by 30-40%. At high frequencies (50-150 Hz) neither compound affected e.p.c. quantal content. All effects on quantal content were paralleled by changes in the size of the pool of quanta available for release. 4. The low frequency augmentation of e.p.c. quantal content by hexamethonium was absent when extracellular [Ca2+] was lowered from 2.0 to 0.5 mM. 5. At the concentrations studied, MLA and hexamethonium produced a small (10-20%) decrease in the peak amplitude of m.e.p.cs. 6. Neither apamin (100 nM) nor charybdotoxin (80 nM) had effects on spontaneous or nerve evoked current amplitudes at any frequency of stimulation. Thus the ability of nicotinic antagonists to augment e.p.c. quantal content is not due to inhibition of Ca(2+)-activated K(+)-channels. 7. We suggest that hexamethonium and MLA increase evoked ACh release by blocking prejunctional nicotinic AChRs. These receptors exert a negative feedback control over evoked ACh release and are probably of the alpha-bungarotoxin-insensitive neuronal type.

Hexamethonium- and methyllycaconitine-induced changes in acetylcholine release from rat motor nerve terminals

PubMed Central

Tian, >Lijun; Prior, Chris; Dempster, John; Marshall, Ian G

1997-01-01

The neuronal nicotinic receptor antagonists hexamethonium and methyllycaconitine (MLA) have been used to study the putative prejunctional nicotinic ACh receptors (AChRs) mediating a negative-feedback control of ACh release from motor nerve terminals in voltage-clamped rat phrenic nerve/hemidiaphragm preparations. Hexamethonium (200 μM), but not MLA (0.4–2.0 μM), decreased the time constant of decay of both endplate currents (e.p.cs) and miniature endplate currents (m.e.p.cs), indicating endplate ion channel block with hexamethonium. However, driving function analysis and reconvolution of e.p.cs and m.e.p.cs indicated that this ion channel block did not compromise the analysis of e.p.c. quantal content. At low frequencies of stimulation (0.5–2 Hz), hexamethonium (200 μM) and MLA (2.0 μM) increased e.p.c. quantal content by 30–40%. At high frequencies (50–150 Hz) neither compound affected e.p.c. quantal content. All effects on quantal content were paralleled by changes in the size of the pool of quanta available for release. The low frequency augmentation of e.p.c. quantal content by hexamethonium was absent when extracellular [Ca2+] was lowered from 2.0 to 0.5 mM. At the concentrations studied, MLA and hexamethonium produced a small (10–20%) decrease in the peak amplitude of m.e.p.cs. Neither apamin (100 nM) nor charybdotoxin (80 nM) had effects on spontaneous or nerve evoked current amplitudes at any frequency of stimulation. Thus the ability of nicotinic antagonists to augment e.p.c. quantal content is not due to inhibition of Ca2+-activated K+-channels. We suggest that hexamethonium and MLA increase evoked ACh release by blocking prejunctional nicotinic AChRs. These receptors exert a negative feedback control over evoked ACh release and are probably of the α-bungarotoxin-insensitive neuronal type. PMID:9401765

High-Quality In-Plane Aligned CsPbX3 Perovskite Nanowire Lasers with Composition-Dependent Strong Exciton-Photon Coupling.

PubMed

Wang, Xiaoxia; Shoaib, Muhammad; Wang, Xiao; Zhang, Xuehong; He, Mai; Luo, Ziyu; Zheng, Weihao; Li, Honglai; Yang, Tiefeng; Zhu, Xiaoli; Ma, Libo; Pan, Anlian

2018-06-14

Cesium lead halide perovskite nanowires have emerged as promising low-dimensional semiconductor structures for integrated photonic applications. Understanding light-matter interactions in a nanowire cavity is of both fundamental and practical interest in designing low-power-consumption nanoscale light sources. In this work, high-quality in-plane aligned halide perovskite CsPbX 3 (X = Cl, Br, I) nanowires are synthesized by a vapor growth method on an annealed M-plane sapphire substrate. Large-area nanowire laser arrays have been achieved based on the as-grown aligned CsPbX 3 nanowires at room temperature with quite low pumping thresholds, very high quality factors, and a high degree of linear polarization. More importantly, it is found that exciton-polaritons are formed in the nanowires under the excitation of a pulsed laser, indicating a strong exciton-photon coupling in the optical microcavities made of cesium lead halide perovskites. The coupling strength in these CsPbX 3 nanowires is dependent on the atomic composition, where the obtained room-temperature Rabi splitting energy is ∼210 ± 13, 146 ± 9, and 103 ± 5 meV for the CsPbCl 3 , CsPbBr 3 , and CsPbI 3 nanowires, respectively. This work provides fundamental insights for the practical applications of all-inorganic perovskite CsPbX 3 nanowires in designing light-emitting devices and integrated nanophotonic systems.

Use of massively parallel pyrosequencing to evaluate the diversity of and selection on Plasmodium falciparum csp T-cell epitopes in Lilongwe, Malawi.

PubMed

Bailey, Jeffrey A; Mvalo, Tisungane; Aragam, Nagesh; Weiser, Matthew; Congdon, Seth; Kamwendo, Debbie; Martinson, Francis; Hoffman, Irving; Meshnick, Steven R; Juliano, Jonathan J

2012-08-15

The development of an effective malaria vaccine has been hampered by the genetic diversity of commonly used target antigens. This diversity has led to concerns about allele-specific immunity limiting the effectiveness of vaccines. Despite extensive genetic diversity of circumsporozoite protein (CS), the most successful malaria vaccine is RTS/S, a monovalent CS vaccine. By use of massively parallel pyrosequencing, we evaluated the diversity of CS haplotypes across the T-cell epitopes in parasites from Lilongwe, Malawi. We identified 57 unique parasite haplotypes from 100 participants. By use of ecological and molecular indexes of diversity, we saw no difference in the diversity of CS haplotypes between adults and children. We saw evidence of weak variant-specific selection within this region of CS, suggesting naturally acquired immunity does induce variant-specific selection on CS. Therefore, the impact of CS vaccines on variant frequencies with widespread implementation of vaccination requires further study.

Cryogenic fountain development at NIST and INRIM: preliminary characterization.

PubMed

Levi, Filippo; Calosso, Claudio; Calonico, Davide; Lorini, Luca; Bertacco, Elio K; Godone, Aldo; Costanzo, Giovanni A; Mongino, Barbara; Jefferts, Steven R; Heavner, Thomas P; Donley, Elizabeth A

2010-03-01

This paper describes the new twin laser-cooled Cs fountain primary frequency standards NIST-F2 and ITCsF2, and presents some of their design features. Most significant is a cryogenic microwave interrogation region which dramatically reduces the blackbody radiation shift. We also present a preliminary accuracy evaluation of IT-CsF2.

Effects of environmental radiation on testes and spermatogenesis in wild large Japanese field mice (Apodemus speciosus) from Fukushima

PubMed Central

Okano, Tsukasa; Ishiniwa, Hiroko; Onuma, Manabu; Shindo, Junji; Yokohata, Yasushi; Tamaoki, Masanori

2016-01-01

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that occurred after the Great East Japan Earthquake in March 2011 released large quantities of radionuclides to the environment. The long-term effects of radioactive cesium (Cs) on biota are of particular concern. We investigated the accumulation of radioactive Cs derived from the FDNPP accident, and chronic effects of environmental radionuclides on male reproduction, in the large Japanese field mouse (Apodemus speciosus). In 2013 and 2014, wild mice were captured at 2 sites in Fukushima Prefecture and at 2 control sites that were distant from Fukushima. Although the median concentrations of 134Cs and 137Cs in the mice from Fukushima exceeded 4,000 Bq/kg, there were no significant differences in the apoptotic cell frequencies or the frequencies of morphologically abnormal sperm among the capture sites. Thus, we conclude that radiation did not cause substantial male subfertility in Fukushima during 2013 and 2014, and radionuclide pollution levels in the study sites would not be detrimental to spermatogenesis of the wild mice in Fukushima. PMID:27005329

Ultra-wideband microwave photonic frequency downconverter based on carrier-suppressed single-sideband modulation

NASA Astrophysics Data System (ADS)

Wang, Yunxin; Li, Jingnan; Wang, Dayong; Zhou, Tao; Xu, Jiahao; Zhong, Xin; Yang, Dengcai; Rong, Lu

2018-03-01

An ultra-wideband microwave photonic frequency downconverter is proposed based on carrier-suppressed single-sideband (CS-SSB) modulation. A radio frequency (RF) signal and a local oscillator (LO) signal are combined to drive a dual-parallel Mach-Zehnder modulator (DPMZM) through the electrical 90°hybrid coupler. To break through the bandwidth limit, an optical bandpass filter (OBPF) is applied simultaneously. Then a photodetector (PD) after OBPF is used to obtain intermediate frequency (IF) signal. Experimental results demonstrate that the proposed frequency downconverter can generate the CS-SSB modulation signal from 2 to 40 GHz in optical spectrum. All the mixing spurs are completely suppressed under the noise floor in electrical spectrum, and the output IF signal possesses high purity with a suppression ratio of the undesired signals (≥40 dB). Furthermore, the multi-octave downconversion can also be implemented to satisfy the bandwidth requirement of multi-channel communication. The proposed frequency downconverter supplies an ultra-wideband and high-purity alternative for the signal processing in microwave photonic applications.

Catalytic hydrolysis of carbonyl sulphide and carbon disulphide over Fe2O3 cluster: Competitive adsorption and reaction mechanism.

PubMed

Ning, Ping; Song, Xin; Li, Kai; Wang, Chi; Tang, Lihong; Sun, Xin

2017-10-31

The competitive adsorption and reaction mechanism for the catalytic hydrolysis of carbonyl sulphide (COS) and carbon disulphide (CS 2 ) over Fe 2 O 3 cluster was investigated. Compared with experimental results, the theoretical study was used to further investigate the competitive adsorption and effect of H 2 S in the hydrolysis reaction of COS and CS 2 . Experimental results showed that Fe 2 O 3 cluster enhanced the catalytic hydrolysis effect. Meanwhile, H 2 S was not conducive to the hydrolysis of COS and CS 2 . Theoretical calculations indicated that the order of competitive adsorption on Fe 2 O 3 is as follows: H 2 O (strong) >CS 2 (medium) >COS (weak). In the hydrolysis process, the C=S bond cleavage occurs easier than C=O bond cleavage. The hydrolysis reaction is initiated via the migration of an H-atom, which triggers C=S bond cleavage and S-H bond formation. Additionally, we find the first step of CS 2 hydrolysis to be rate limiting. The presence of H 2 S increases the reaction energy barrier, which is not favourable for COS hydrolysis. Fe 2 O 3 can greatly decrease the maximum energy barrier, which decreases the minimum energy required for hydrolysis, making it relatively facile to occur. In general, the theoretical results were consistent with experimental results, which proved that the theoretical study was reliable.

7. Survivable low frequency communication system pathway, looking east ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. Survivable low frequency communication system pathway, looking east - Ellsworth Air Force Base, Delta Flight, Launch Control Facility, County Road CS23A, North of Exit 127, Interior, Jackson County, SD

Universal two-dimensional characteristics in perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs)

NASA Astrophysics Data System (ADS)

Sato, Nobuya; Akashi, Ryosuke; Tsuneyuki, Shinji

2017-07-01

A series of unsynthesized perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs) are investigated by the density functional calculations. These oxyhydrides are stable in the sense of the formation energies for some possible synthesis reactions. They are crystallized into quite similar crystal structures with the long c-axis, and the corner-sharing TiO4H2 octahedra of the ideal perovskite-type structure are deformed into the 5-fold coordinated titanium atoms with the OH plane and the apical oxygen atoms. All of these oxyhydrides exhibit two-dimensional electronic states at the valence band maximum characterized by the in-plane oxygen 2p and the hydrogen 1s orbitals. While the c-axis becomes short as the ionic radius of the A atom becomes small and the two-dimensional characteristics are weakened, the electronic state at the valence band maximum is still characterized as the O-H in-plane state. Additionally, the Born effective charge tensors, spontaneous electric polarizations, dielectric tensors, and piezoelectric tensors are evaluated. It is found that the spontaneous electric polarizations of these oxyhydrides are much larger than that of tetragonal BaTiO3.

``Dressing'' lines and vertices in calculations of matrix elements with the coupled-cluster method and determination of Cs atomic properties

NASA Astrophysics Data System (ADS)

Derevianko, Andrei; Porsev, Sergey G.

2005-03-01

We consider evaluation of matrix elements with the coupled-cluster method. Such calculations formally involve infinite number of terms and we devise a method of partial summation (dressing) of the resulting series. Our formalism is built upon an expansion of the product C†C of cluster amplitudes C into a sum of n -body insertions. We consider two types of insertions: particle (hole) line insertion and two-particle (two-hole) random-phase-approximation-like insertion. We demonstrate how to “dress” these insertions and formulate iterative equations. We illustrate the dressing equations in the case when the cluster operator is truncated at single and double excitations. Using univalent systems as an example, we upgrade coupled-cluster diagrams for matrix elements with the dressed insertions and highlight a relation to pertinent fourth-order diagrams. We illustrate our formalism with relativistic calculations of the hyperfine constant A(6s) and the 6s1/2-6p1/2 electric-dipole transition amplitude for the Cs atom. Finally, we augment the truncated coupled-cluster calculations with otherwise omitted fourth order diagrams. The resulting analysis for Cs is complete through the fourth order of many-body perturbation theory and reveals an important role of triple and disconnected quadruple excitations.

External radiation in Dolon village due to local fallout from the first USSR atomic bomb test in 1949.

PubMed

Imanaka, Tetsuji; Fukutani, Satoshi; Yamamoto, Masayoshi; Sakaguchi, Aya; Hoshi, Masaharu

2006-02-01

Dolon village, located about 60 km from the border of the Semipalatinsk Nuclear Test Site, is known to be heavily contaminated by local fallout from the first USSR atomic bomb test in 1949. External radiation in Dolon was evaluated based on recent 137Cs data in soil and calculation of temporal change in the fission product composition. After fitting a log-normal distribution to the soil data, a 137Cs deposition of 32 kBq m-2, which corresponds to the 90th-percentile of the distribution, was tentatively chosen as a value to evaluate the radiation situation in 1949. Our calculation indicated that more than 95% of the cumulative dose for 50 y had been delivered within 1 y after the deposition. The resulting cumulative dose for 1 y after the deposition, normalized to the initial contamination containing 1 kBq m-2 of 137Cs, was 15.6 mGy, assuming a fallout arrival time of 3 h and a medium level of fractionation. Finally, 0.50 Gy of absorbed dose in air was derived as our tentative estimate for 1-year cumulative external dose in Dolon due to local fallout from the first USSR test in 1949.

Conductivity of Langmuir-Blodgett films of a disk-shaped liquid-crystalline molecule-DNA complex studied by current-sensing atomic force microscopy.

PubMed

Nayak, Alpana; Suresh, K A

2008-08-01

We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.

Conductivity of Langmuir-Blodgett films of a disk-shaped liquid-crystalline molecule-DNA complex studied by current-sensing atomic force microscopy

NASA Astrophysics Data System (ADS)

Nayak, Alpana; Suresh, K. A.

2008-08-01

We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.

Intensification of sodium hydroxide pretreatment of corn stalk using magnetic field in a fluidic system.

PubMed

Jin, Yamei; Yang, Na; Tong, Qunyi; Jin, Zhengyu; Xu, Xueming

2016-11-01

To promote NaOH pretreatment of corn stalk (CS), a continuous processing system uniting magnetic field and millimeter-scaled channel flow was established. First, four comparative pretreatments were conducted: (I) CS was pretreated with NaOH under traditional agitation; (II) CS was pretreated with NaOH in a flowing state inside the millimeter-scaled channel; (III) CS was pretreated with NaOH in a flowing state and under a static magnetic field; or (IV) CS was pretreated with NaOH in a flowing state and under a rotating magnetic field. By comparison, the highest pentose (121.22mg/g dry CS) and hexose (287.04mg/g dry CS) yields were obtained in the shortest pretreatment time with Pretreatment IV (8h). Accordingly, the key parameters of Pretreatment IV were optimized as 6.71Hz frequency, 0.50L/min flow rate, and 1.02% NaOH concentration. Under these conditions, 439.24mg sugars were released by 1g dry CS during pretreatment and enzymatic hydrolysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles

NASA Technical Reports Server (NTRS)

Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, M.; Jordan, Robert; Schwartz, Jeffrey L.

2003-01-01

The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.

Science Goals of the Primary Atomic Reference Clock in Space (PARCS) Experiment

NASA Technical Reports Server (NTRS)

Ashby, N.

2003-01-01

The PARCS (Primary Atomic Reference Clock in Space) experiment will use a laser-cooled Cesium atomic clock operating in the microgravity environment aboard the International Space Station (ISS) to provide both advanced tests of gravitational theory and to demonstrate a new cold-atom clock technology for space. PARCS is a joint project of the National Institute of Standards and Technology (NIST), NASA's Jet Propulsion Laboratory (JPL), and the University of Colorado (CU). This paper concentrates on the scientific goals of the PARCS mission. The microgravity space environment allows laser-cooled Cs atoms to have Ramsey times in excess of those feasible on Earth, resulting in improved clock performance. Clock stabilities of 5x10(exp -14) at one second, and accuracies better than 10(exp -16) are projected.

Luminance noise as a novel approach for measuring contrast sensitivity within the magnocellular and parvocellular pathways.

PubMed

Hall, Cierra M; McAnany, J Jason

2017-07-01

This study evaluated the extent to which different types of luminance noise can be used to target selectively the inferred magnocellular (MC) and parvocellular (PC) visual pathways. Letter contrast sensitivity (CS) was measured for three visually normal subjects for letters of different size (0.8°-5.3°) under established paradigms intended to target the MC pathway (steady-pedestal paradigm) and PC pathway (pulsed-pedestal paradigm). Results obtained under these paradigms were compared to those obtained in asynchronous static noise (a field of unchanging luminance noise) and asynchronous dynamic noise (a field of randomly changing luminance noise). CS was measured for letters that were high- and low-pass filtered using a range of filter cutoffs to quantify the object frequency information (cycles per letter) mediating letter identification, which was used as an index of the pathway mediating CS. A follow-up experiment was performed to determine the range of letter duration over which MC and PC pathway CS can be targeted. Analysis of variance indicated that the object frequencies measured under the static noise and steady-pedestal paradigms did not differ significantly (p ≥ 0.065), but differed considerably from those measured under the dynamic noise (both p < 0.001) and pulsed-pedestal (both p < 0.001) paradigms. The object frequencies mediating letter identification increased as duration increased under the steady-pedestal paradigm, but were independent of target duration (50-800 ms) under the pulsed-pedestal paradigm, in static noise, and in dynamic noise. These data suggest that the spatiotemporal characteristics of noise can be manipulated to target the inferred MC (static noise) and PC (dynamic noise) pathways. The results also suggest that CS within these pathways can be measured at long stimulus durations, which has potential importance in the design of future clinical CS tests.

Public and private pregnancy care in Reggio Emilia Province: an observational study on appropriateness of care and delivery outcomes.

PubMed

Bonvicini, Laura; Candela, Silvia; Evangelista, Andrea; Bertani, Daniela; Casoli, Morena; Lusvardi, Annarella; Messori, Antonella; Giorgi Rossi, Paolo

2014-02-17

In industrialized countries, improvements have been made in both maternal and newborn health. While attention to antenatal care is increasing, excessive medicalization is also becoming more common.The aim of this study is to compare caesarean section (CS) frequency and ultrasound scan utilization in a public model of care involving both midwives and obstetricians with a private model in which care is provided by obstetricians only. Observational population-based study. Reggio Emilia Province. 5957 women resident in the province who delivered between October 2010 and November 2011. CS frequency and ultrasound scan utilization, stillbirths, and other negative perinatal outcomes. Women in the study were searched in the public family and reproductive health clinic medical records to identify those cared for in the public system. Outcomes of the two antenatal care models were compared through multivariate logistic regression adjusting for maternal characteristics and, for CS only, by stratifying by Robson's Group. Compared to women cared for in private services (N = 3,043), those in public service (N = 2,369) were younger, less educated, more frequently non-Italian, and multiparous. The probability of CS was slightly higher for women cared for by private obstetricians than for those cared for in the public system (31.8% vs. 27.1%; adjusted odds ratio: 1.10; 95% CI: 0.93-1.29): The probability of having more than 3 ultrasound scans was higher in private care (89.6% vs. 49.8%; adjusted odds ratio: 5.11; 95% CI: 4.30-6.08). CS frequency was higher in private care for all Robson's classes except women who underwent CS during spontaneous labour. Among negative perinatal outcomes only a higher risk of pre-term birth was observed for pregnancies cared for in private services. The public model provides less medicalized and more guidelines-oriented care than does the private model, with no increase in negative perinatal outcomes.

Luminance noise as a novel approach for measuring contrast sensitivity within the magnocellular and parvocellular pathways

PubMed Central

Hall, Cierra M.; McAnany, J. Jason

2017-01-01

This study evaluated the extent to which different types of luminance noise can be used to target selectively the inferred magnocellular (MC) and parvocellular (PC) visual pathways. Letter contrast sensitivity (CS) was measured for three visually normal subjects for letters of different size (0.8°–5.3°) under established paradigms intended to target the MC pathway (steady-pedestal paradigm) and PC pathway (pulsed-pedestal paradigm). Results obtained under these paradigms were compared to those obtained in asynchronous static noise (a field of unchanging luminance noise) and asynchronous dynamic noise (a field of randomly changing luminance noise). CS was measured for letters that were high- and low-pass filtered using a range of filter cutoffs to quantify the object frequency information (cycles per letter) mediating letter identification, which was used as an index of the pathway mediating CS. A follow-up experiment was performed to determine the range of letter duration over which MC and PC pathway CS can be targeted. Analysis of variance indicated that the object frequencies measured under the static noise and steady-pedestal paradigms did not differ significantly (p ≥ 0.065), but differed considerably from those measured under the dynamic noise (both p < 0.001) and pulsed-pedestal (both p < 0.001) paradigms. The object frequencies mediating letter identification increased as duration increased under the steady-pedestal paradigm, but were independent of target duration (50–800 ms) under the pulsed-pedestal paradigm, in static noise, and in dynamic noise. These data suggest that the spatiotemporal characteristics of noise can be manipulated to target the inferred MC (static noise) and PC (dynamic noise) pathways. The results also suggest that CS within these pathways can be measured at long stimulus durations, which has potential importance in the design of future clinical CS tests. PMID:28672370

OFDM Coupled Compressive Sensing Algorithm for Stepped-Frequency Ground Penetrating Radar

DTIC Science & Technology

2014-10-01

These frequencies are combined in such a way to achieve orthogonality between the carrier frequencies, while mitigating any interference between...in such a way to achieve orthogonality between the carrier frequencies, while mitigating any interference between said frequencies. In CS, a signal...frequency tones is mitigated . Orthogonality requires that the sub-bands are spaced at = is the OFDM symbol period, and k is any

Inductively guided circuits for ultracold dressed atoms

PubMed Central

Sinuco-León, German A.; Burrows, Kathryn A.; Arnold, Aidan S.; Garraway, Barry M.

2014-01-01

Recent progress in optics, atomic physics and material science has paved the way to study quantum effects in ultracold atomic alkali gases confined to non-trivial geometries. Multiply connected traps for cold atoms can be prepared by combining inhomogeneous distributions of DC and radio-frequency electromagnetic fields with optical fields that require complex systems for frequency control and stabilization. Here we propose a flexible and robust scheme that creates closed quasi-one-dimensional guides for ultracold atoms through the ‘dressing’ of hyperfine sublevels of the atomic ground state, where the dressing field is spatially modulated by inductive effects over a micro-engineered conducting loop. Remarkably, for commonly used atomic species (for example, 7Li and 87Rb), the guide operation relies entirely on controlling static and low-frequency fields in the regimes of radio-frequency and microwave frequencies. This novel trapping scheme can be implemented with current technology for micro-fabrication and electronic control. PMID:25348163

Structural properties of films and rheology of film-forming solutions of chitosan gallate for food packaging.

PubMed

Wu, Chunhua; Tian, Jinhu; Li, Shan; Wu, Tiantian; Hu, Yaqin; Chen, Shiguo; Sugawara, Tatsuya; Ye, Xingqian

2016-08-01

The chitosan gallates (CG) were obtained by free-radical-initiated grafting of gallic acid (GA) onto chitosan (CS) in this work. The chemical structures of the CG were corroborated by UV-vis, GPC and (1)H NMR analysis. The grafting reaction was accompanied with a degradation of the CS molecule. The shear-thinning flow behavior of CG film-forming solutions (CG FFS) decreased with the grafting amount of GA into CS chain, while the CG FFS grafted at a lower GA value behaved like a networks containing entangled or cross-linked polymer chains with a more elastic behavior. The increasing of GA grafting onto the CS chain led to a reduction of tensile strength, elongation at break and water resistance in the corresponding films, but increases in the antioxidant and antimicrobial activities were observed. The microstructure of the film was investigated using scanning electron and atomic force microscope, and the results were closely related to the observed film properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Accumulation of radionuclides from radioactive substrata by some micromycetes.

PubMed

Zhdanova, N N; Redchits, T I; Zheltonozhsky, V A; Sadovnikov, L V; Gerzabek, M H; Olsson, S; Strebl, F; Mück, K

2003-01-01

Overgrowing (interaction) and dissolution of intact and milled hot particles by various micromycetes were studied under laboratory conditions. Hot particles used for the investigation originated from the Chernobyl accident release and atomic bomb testing sites. The micromycetes investigated were mitosporic fungi mainly isolated from the Chernobyl site and vicinity. Most of the fungal species and strains showed a tendency to grow towards the hot particle, overgrow it and dissolve it after prolonged contact. The accumulation (absorption and adsorption) of radionuclides from intact hot particles was generally more intensive for (152)Eu than for (137)Cs by a factor of about 2.6-134, while in experiments with milled samples the (152)Eu and (137)Cs accumulation was similar, except for some fungal species, which showed higher (152)Eu than (137)Cs sorption. It could be shown that the main factors influencing Cs and Eu accumulation in fungi are: fungal species and strains and the size and composition of the hot particle.

High-pressure synthesis of a pentazolate salt [High-pressure synthesis of condensed-phase pentazolate

DOE PAGES

Steele, Brad A.; Stavrou, Elissaios; Crowhurst, Jonathan C.; ...

2016-12-06

The pentazolates, the last all-nitrogen members of the azole series, have been notoriously elusive for the last hundred years despite enormous efforts to make these compounds in either gas or condensed phases. Here, we report a successful synthesis of a solid state compound consisting of isolated pentazolate anions N 5 –, which is achieved by compressing and laser heating cesium azide (CsN 3) mixed with N 2 cryogenic liquid in a diamond anvil cell. The experiment was guided by theory, which predicted the transformation of the mixture at high pressures to a new compound, cesium pentazolate salt (CsN 5). Electronmore » transfer from Cs atoms to N 5 rings enables both aromaticity in the pentazolates as well as ionic bonding in the CsN 5 crystal. As a result, this work provides critical insight into the role of extreme conditions in exploring unusual bonding routes that ultimately lead to the formation of novel high nitrogen content species.« less

Cockayne syndrome and xeroderma pigmentosum

PubMed Central

Rapin, I.; Lindenbaum, Y.; Dickson, D.W.; Kraemer, K.H.; Robbins, J.H.

2015-01-01

Objectives To review genetic variants of Cockayne syndrome (CS) and xeroderma pigmentosum (XP), autosomal recessive disorders of DNA repair that affect the nervous system, and to illustrate them by the first case of xeroderma pigmentosum–Cockayne syndrome (XP-CS) complex to undergo neuropathologic examination. Methods Published reports of clinical, pathologic, and molecular studies of CS, XP neurologic disease, and the XP-CS complex were reviewed, and a ninth case of XP-CS is summarized. Results CS is a multisystem disorder that causes both profound growth failure of the soma and brain and progressive cachexia, retinal, cochlear, and neurologic degeneration, with a leukodystrophy and demyelinating neuropathy without an increase in cancer. XP presents as extreme photosensitivity of the skin and eyes with a 1000-fold increased frequency of cutaneous basal and squamous cell carcinomas and melanomas and a small increase in nervous system neoplasms. Some 20% of patients with XP incur progressive degeneration of previously normally developed neurons resulting in cortical, basal ganglia, cerebellar, and spinal atrophy, cochlear degeneration, and a mixed distal axonal neuropathy. Cultured cells from patients with CS or XP are hypersensitive to killing by ultraviolet (UV) radiation. Both CS and most XP cells have defective DNA nucleotide excision repair of actively transcribing genes; in addition, XP cells have defective repair of the global genome. There are two complementation groups in CS and seven in XP. Patients with the XP-CS complex fall into three XP complementation groups. Despite their XP genotype, six of nine individuals with the XP-CS complex, including the boy we followed up to his death at age 6, had the typical clinically and pathologically severe CS phenotype. Cultured skin and blood cells had extreme sensitivity to killing by UV radiation, DNA repair was severely deficient, post-UV unscheduled DNA synthesis was reduced to less than 5%, and post-UV plasmid mutation frequency was increased. Conclusions The paradoxical lack of parallelism of phenotype to genotype is unexplained in these disorders. Perhaps diverse mutations responsible for UV sensitivity and deficient DNA repair may also produce profound failure of brain and somatic growth, progressive cachexia and premature aging, and tissue-selective neurologic deterioration by their roles in regulation of transcription and repair of endogenous oxidative DNA damage. PMID:11185579

Uptake of cesium-137 by crops from contaminated soils

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

Demirel, H.; Oezer, I.; Celenk, I.

1994-11-01

The Turkish tea crop was contaminated following the Chernobyl nuclear accident. Finding ways to dispose of the contaminated tea (Camellia sinensis L.) without damaging the environment was the goal of this research conducted at the Turkish Atomic Energy Authority (TAEA). In this study, an investigation was made of {sup 137}Cs activities of the plants and the ratios of transfer of {sup 137}Cs activity to plants when the contaminated tea was applied to the soil. Experiments were conducted in the field and in pots under greenhouse conditions. The activities of the tea applied in the field ranged from 12 500 tomore » 72 800 Bq/m{sup 2}, whereas this activity was constant at 8000 Bq/pot in the greenhouse experiment. The transfer of {sup 137}Cs from soil to the plants was between 0.037 and 1.057% for wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), corn (Zea mays indentata Sturt), bean (Phaseolus vulgaris L.), lettuce (Lactuca sativa L.), and grass (Lolium perenne L.). The ratio of the transfer of {sup 137}Cs activity to plants increased as the activity {sup 137}Cs in tea applied to soil was increased. The activity in the plants increased due to increased uptake of {sup 137}Cs by plants. 12 refs., 2 figs., 2 tabs.« less

Multimode waveguide speckle patterns for compressive sensing.

PubMed

Valley, George C; Sefler, George A; Justin Shaw, T

2016-06-01

Compressive sensing (CS) of sparse gigahertz-band RF signals using microwave photonics may achieve better performances with smaller size, weight, and power than electronic CS or conventional Nyquist rate sampling. The critical element in a CS system is the device that produces the CS measurement matrix (MM). We show that passive speckle patterns in multimode waveguides potentially provide excellent MMs for CS. We measure and calculate the MM for a multimode fiber and perform simulations using this MM in a CS system. We show that the speckle MM exhibits the sharp phase transition and coherence properties needed for CS and that these properties are similar to those of a sub-Gaussian MM with the same mean and standard deviation. We calculate the MM for a multimode planar waveguide and find dimensions of the planar guide that give a speckle MM with a performance similar to that of the multimode fiber. The CS simulations show that all measured and calculated speckle MMs exhibit a robust performance with equal amplitude signals that are sparse in time, in frequency, and in wavelets (Haar wavelet transform). The planar waveguide results indicate a path to a microwave photonic integrated circuit for measuring sparse gigahertz-band RF signals using CS.

Spectral and non-spectral interferences in the determination of thallium in environmental materials using electrothermal atomization and vaporization techniques—a case study

NASA Astrophysics Data System (ADS)

Vale, Maria Goreti R.; Welz, Bernhard

2002-12-01

The literature on the determination of Tl in environmental samples using electrothermal atomization (ETA) and vaporization (ETV) techniques has been reviewed with special attention devoted to potential interferences and their control. Chloride interference, which is due to the formation of the volatile monochloride in the condensed phase, is the most frequently observed problem. Due to its high dissociation energy (88 kcal/mol), TlCl is difficult to dissociate in the gas phase and is easily lost. The best means of controlling this interference in ETA is atomization under isothermal conditions according to the stabilized temperature platform furnace concept, and the use of reduced palladium as a modifier. An alternative approach appears to be the 'fast furnace' concept, wherein both the use of a modifier and the pyrolysis stage are omitted. This concept requires an efficient background correction system, and high-resolution continuum-source atomic absorption spectrometry (HR-CS AAS) appears to offer the best results. This chloride interference can also cause significant problems when ETV techniques are used. Among the spectral interferences found in the determination of thallium are those due to Pd, the most efficient modifier, and Fe, which is frequently found at high concentrations in environmental samples. Both interferences are due to nearby atomic lines, and are observed only when deuterium background correction and relatively high atomization temperatures are used. A more serious spectral interference is that due to the molecular absorption spectrum of SO 2, which has a maximum around the Tl line and exhibits a pronounced rotational fine structure. HR-CS AAS again showed the best performance in coping with this interference.

Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell.

PubMed

Todorov, Petko; Bloch, Daniel

2017-11-21

For a gas at thermal equilibrium, it is usually assumed that the velocity distribution follows an isotropic 3-dimensional Maxwell-Boltzmann (M-B) law. This assumption classically implies the assumption of a "cos θ" law for the flux of atoms leaving the surface. Actually, such a law has no grounds in surface physics, and experimental tests of this assumption have remained very few. In a variety of recently developed sub-Doppler laser spectroscopy techniques for gases one-dimensionally confined in a thin cell, the specific contribution of atoms moving nearly parallel to the boundary of the vapor container becomes essential. We report here on the implementation of an experiment to probe effectively the distribution of atomic velocities parallel to the windows for a thin (60 μm) Cs vapor cell. The principle of the setup relies on a spatially separated pump-probe experiment, where the variations of the signal amplitude with the pump-probe separation provide the information on the velocity distribution. The experiment is performed in a sapphire cell on the Cs resonance line, which benefits from a long-lived hyperfine optical pumping. Presently, we can analyze specifically the density of atoms with slow normal velocities ∼5-20 m/s, already corresponding to unusual grazing flight-at ∼85°-88.5° from the normal to the surface-and no deviation from the M-B law is found within the limits of our elementary setup. Finally we suggest tracks to explore more parallel velocities, when surface details-roughness or structure-and the atom-surface interaction should play a key role to restrict the applicability of an M-B-type distribution.

Quantum theory of atoms in molecules charge-charge flux-dipole flux models for the infrared intensities of X(2)CY (X = H, F, Cl; Y = O, S) molecules.

PubMed

Faria, Sergio H D M; da Silva, João Viçozo; Haiduke, Roberto L A; Vidal, Luciano N; Vazquez, Pedro A M; Bruns, Roy E

2007-08-16

The molecular dipole moments, their derivatives, and the fundamental IR intensities of the X2CY (X = H, F, Cl; Y = O, S) molecules are determined from QTAIM atomic charges and dipoles and their fluxes at the MP2/6-311++G(3d,3p) level. Root-mean-square errors of +/-0.03 D and +/-1.4 km mol(-1) are found for the molecular dipole moments and fundamental IR intensities calculated using quantum theory of atoms in molecules (QTAIM) parameters when compared with those obtained directly from the MP2/6-311++G(3d,3p) calculations and +/-0.05 D and 51.2 km mol(-1) when compared with the experimental values. Charge (C), charge flux (CF), and dipole flux (DF) contributions are reported for all the normal vibrations of these molecules. A large negative correlation coefficient of -0.83 is calculated between the charge flux and dipole flux contributions and indicates that electronic charge transfer from one side of the molecule to the other during vibrations is accompanied by a relaxation effect with electron density polarization in the opposite direction. The characteristic substituent effect that has been observed for experimental infrared intensity parameters and core electron ionization energies has been applied to the CCFDF/QTAIM parameters of F2CO, Cl2CO, F2CS, and Cl2CS. The individual atomic charge, atomic charge flux, and atomic dipole flux contributions are seen to obey the characteristic substituent effect equation just as accurately as the total dipole moment derivative. The CH, CF, and CCl stretching normal modes of these molecules are shown to have characteristic sets of charge, charge flux, and dipole flux contributions.

Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell

NASA Astrophysics Data System (ADS)

Todorov, Petko; Bloch, Daniel

2017-11-01

For a gas at thermal equilibrium, it is usually assumed that the velocity distribution follows an isotropic 3-dimensional Maxwell-Boltzmann (M-B) law. This assumption classically implies the assumption of a "cos θ" law for the flux of atoms leaving the surface. Actually, such a law has no grounds in surface physics, and experimental tests of this assumption have remained very few. In a variety of recently developed sub-Doppler laser spectroscopy techniques for gases one-dimensionally confined in a thin cell, the specific contribution of atoms moving nearly parallel to the boundary of the vapor container becomes essential. We report here on the implementation of an experiment to probe effectively the distribution of atomic velocities parallel to the windows for a thin (60 μm) Cs vapor cell. The principle of the setup relies on a spatially separated pump-probe experiment, where the variations of the signal amplitude with the pump-probe separation provide the information on the velocity distribution. The experiment is performed in a sapphire cell on the Cs resonance line, which benefits from a long-lived hyperfine optical pumping. Presently, we can analyze specifically the density of atoms with slow normal velocities ˜5-20 m/s, already corresponding to unusual grazing flight—at ˜85°-88.5° from the normal to the surface—and no deviation from the M-B law is found within the limits of our elementary setup. Finally we suggest tracks to explore more parallel velocities, when surface details—roughness or structure—and the atom-surface interaction should play a key role to restrict the applicability of an M-B-type distribution.

Oceanic dispersion of Fukushima-derived Cs-137 in the coastal, offshore, and open oceans simulated by multiple oceanic general circulation models

NASA Astrophysics Data System (ADS)

Kawamura, H.; Furuno, A.; Kobayashi, T.; In, T.; Nakayama, T.; Ishikawa, Y.; Miyazawa, Y.; Usui, N.

2017-12-01

To understand the concentration and amount of Fukushima-derived Cs-137 in the ocean, this study simulates the oceanic dispersion of Cs-137 by an oceanic dispersion model SEA-GEARN-FDM developed at Japan Atomic Energy Agency (JAEA) and multiple oceanic general circulation models. The Cs-137 deposition amounts at the sea surface were used as the source term in oceanic dispersion simulations, which were estimated by atmospheric dispersion simulations with a Worldwide version of System for Prediction of Environmental Emergency Dose Information version II (WSPEEDI-II) developed at JAEA. The direct release from the Fukushima Daiichi Nuclear Power Plant into the ocean based on in situ Cs-137 measurements was used as the other source term in oceanic dispersion simulations. The simulated air Cs-137 concentrations qualitatively replicated those measured around the North Pacific. The accumulated Cs-137 ground deposition amount in the eastern Japanese Islands was consistent with that estimated by aircraft measurements. The oceanic dispersion simulations relatively well reproduced the measured Cs-137 concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year post-disaster. It was suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Mesoscale eddies accompanied by the Kuroshio Current and Kuroshio Extension played an important role in dilution of Cs-137. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year post-disaster. It was demonstrated that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layer in the North Pacific.

Plasmodium vivax circumsporozoite genotypes: a limited variation or new subspecies with major biological consequences?

PubMed Central

2010-01-01

Background Plasmodium vivax circumsporozoite variants have been identified in several geographical areas. The real implication of the genetic variation in this region of the P. vivax genome has been questioned for a long time. Although previous studies have observed significant association between VK210 and the Duffy blood group, we present here that evidences of this variation are limited to the CSP central portion. Methods The phylogenetic analyses were accomplished starting from the amplification of conserved domains of 18 SSU RNAr and Cyt B. The antibodies responses against the CSP peptides, MSP-1, AMA-1 and DBP were detected by ELISA, in plasma samples of individuals infected with two P. vivax CS genotypes: VK210 and P. vivax-like. Results These analyses of the two markers demonstrate high similarity among the P. vivax CS genotypes and surprisingly showed diversity equal to zero between VK210 and P. vivax-like, positioning these CS genotypes in the same clade. A high frequency IgG antibody against the N- and C-terminal regions of the P. vivax CSP was found as compared to the immune response to the R- and V- repetitive regions (p = 0.0005, Fisher's Exact test). This difference was more pronounced when the P. vivax-like variant was present in the infection (p = 0.003, Fisher's Exact test). A high frequency of antibody response against MSP-1 and AMA-1 peptides was observed for all P. vivax CS genotypes in comparison to the same frequency for DBP. Conclusions This results target that the differences among the P. vivax CS variants are restrict to the central repeated region of the protein, mostly nucleotide variation with important serological consequences. PMID:20573199

Verapamil eliminates the hierarchical nature of activation frequencies from the pulmonary veins to the atria during paroxysmal atrial fibrillation.

PubMed

Kushiyama, Yasunori; Osaka, Toshiyuki; Yokoyama, Eriko; Hasebe, Hideyuki; Kuroda, Yusuke; Kamiya, Kaichiro; Kodama, Itsuo

2010-05-01

There is evidence that verapamil promotes the persistence of paroxysmal atrial fibrillation (AF). Little is known about the underlying mechanisms. The purpose of this study was to determine the effect of verapamil on dominant frequencies (DFs) in the pulmonary veins (PVs) and atria during paroxysmal AF with reference to its potential arrhythmogenicity. Forty-three patients with paroxysmal AF were studied. Bipolar electrograms were recorded simultaneously during AF from the right atrial free wall (RAFW), coronary sinus (CS) and three PVs, or two PVs and the left atrial appendage (LAA). The DFs were obtained by fast Fourier transform analysis before and after infusion of verapamil (0.1 mg/kg, intravenously). At baseline, the maximum DF among the PVs (6.9 +/- 0.9 Hz) was significantly higher than the DF in the RAFW (6.2 +/- 0.7 Hz), CS (5.7 +/- 0.5 Hz), or LAA (5.9 +/- 0.7 Hz) (P<.01); there was a substantial PV-to-atrial DF gradient (RAFW 0.7 +/- 0.9, CS 1.1 +/- 0.7, LAA 0.7 +/- 0.9 Hz). Verapamil increased the atrial DF to 6.9 +/- 0.8, 6.6 +/- 0.7, and 7.2 +/- 1.0 Hz in the RAFW, CS, and LAA, respectively (P<.0001) but did not affect the maximum PV DF (7.1 +/- 0.7 Hz). The PV-to-atrial DF gradient was eliminated after verapamil (RAFW 0.2 +/- 0.8, CS 0.5 +/- 0.6, LAA -0.4 +/- 0.8 Hz; P<.01 vs. baseline). Verapamil increases the activation frequency in the atria but not in the PVs, eliminating the PV-to-atrial DF gradient during paroxysmal AF. Copyright 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Cell killing and chromatid damage in primary human bronchial epithelial cells irradiated with accelerated 56Fe ions

NASA Technical Reports Server (NTRS)

Suzuki, M.; Piao, C.; Hall, E. J.; Hei, T. K.

2001-01-01

We examined cell killing and chromatid damage in primary human bronchial epithelial cells irradiated with high-energy 56Fe ions. Cells were irradiated with graded doses of 56Fe ions (1 GeV/nucleon) accelerated with the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The survival curves for cells plated 1 h after irradiation (immediate plating) showed little or no shoulder. However, the survival curves for cells plated 24 h after irradiation (delayed plating) had a small initial shoulder. The RBE for 56Fe ions compared to 137Cs gamma rays was 1.99 for immediate plating and 2.73 for delayed plating at the D10. The repair ratio (delayed plating/immediate plating) was 1.67 for 137Cs gamma rays and 1.22 for 56Fe ions. The dose-response curves for initially measured and residual chromatid fragments detected by the Calyculin A-mediated premature chromosome condensation technique showed a linear response. The results indicated that the induction frequency for initially measured fragments was the same for 137Cs gamma rays and 56Fe ions. On the other hand, approximately 85% of the fragments induced by 137Cs gamma rays had rejoined after 24 h of postirradiation incubation; the corresponding amount for 56Fe ions was 37%. Furthermore, the frequency of chromatid exchanges induced by gamma rays measured 24 h after irradiation was higher than that induced by 56Fe ions. No difference in the amount of chromatid damage induced by the two types of radiations was detected when assayed 1 h after irradiation. The results suggest that high-energy 56Fe ions induce a higher frequency of complex, unrepairable damage at both the cellular and chromosomal levels than 137Cs gamma rays in the target cells for radiation-induced lung cancers.

Compressed single pixel imaging in the spatial frequency domain

PubMed Central

Torabzadeh, Mohammad; Park, Il-Yong; Bartels, Randy A.; Durkin, Anthony J.; Tromberg, Bruce J.

2017-01-01

Abstract. We have developed compressed sensing single pixel spatial frequency domain imaging (cs-SFDI) to characterize tissue optical properties over a wide field of view (35  mm×35  mm) using multiple near-infrared (NIR) wavelengths simultaneously. Our approach takes advantage of the relatively sparse spatial content required for mapping tissue optical properties at length scales comparable to the transport scattering length in tissue (ltr∼1  mm) and the high bandwidth available for spectral encoding using a single-element detector. cs-SFDI recovered absorption (μa) and reduced scattering (μs′) coefficients of a tissue phantom at three NIR wavelengths (660, 850, and 940 nm) within 7.6% and 4.3% of absolute values determined using camera-based SFDI, respectively. These results suggest that cs-SFDI can be developed as a multi- and hyperspectral imaging modality for quantitative, dynamic imaging of tissue optical and physiological properties. PMID:28300272

Maintenance of Velocity and Power With Cluster Sets During High-Volume Back Squats.

PubMed

Tufano, James J; Conlon, Jenny A; Nimphius, Sophia; Brown, Lee E; Seitz, Laurent B; Williamson, Bryce D; Haff, G Gregory

2016-10-01

To compare the effects of a traditional set structure and 2 cluster set structures on force, velocity, and power during back squats in strength-trained men. Twelve men (25.8 ± 5.1 y, 1.74 ± 0.07 m, 79.3 ± 8.2 kg) performed 3 sets of 12 repetitions at 60% of 1-repetition maximum using 3 different set structures: traditional sets (TS), cluster sets of 4 (CS4), and cluster sets of 2 (CS2). When averaged across all repetitions, peak velocity (PV), mean velocity (MV), peak power (PP), and mean power (MP) were greater in CS2 and CS4 than in TS (P < .01), with CS2 also resulting in greater values than CS4 (P < .02). When examining individual sets within each set structure, PV, MV, PP, and MP decreased during the course of TS (effect sizes 0.28-0.99), whereas no decreases were noted during CS2 (effect sizes 0.00-0.13) or CS4 (effect sizes 0.00-0.29). These results demonstrate that CS structures maintain velocity and power, whereas TS structures do not. Furthermore, increasing the frequency of intraset rest intervals in CS structures maximizes this effect and should be used if maximal velocity is to be maintained during training.

Detection of NMR signals with a radio-frequency atomic magnetometer.

PubMed

Savukov, I M; Seltzer, S J; Romalis, M V

2007-04-01

We demonstrate detection of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz1/2 using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz.

Calculation and Specification of the Multiple Chirality Displayed by Sugar Pyranoid Ring Structures.

ERIC Educational Resources Information Center

Shallenberger, Robert S.; And Others

1981-01-01

Describes a method, using simple algebraic notation, for calculating the nature of the salient features of a sugar pyranoid ring, the steric disposition of substituents about the reference, and the anomeric carbon atoms contained within the ring. (CS)

PARCS-Primary Atomic Reference Clock in Space

NASA Astrophysics Data System (ADS)

Ashby, Neil

2000-04-01

The purpose of the PARCS project is to place an advanced Cesium clock on the International Space Station (ISS). The project has been approved by NASA at the level of Science Concept Review. Groups at the National Institute of Standards and Technology, Jet Propulsion Laboratory, University of Colorado, and Harvard-Smithsonian Astrophysical Observatory, University of Torino are collaborating on clock design and construction. The microgravity space environment allows laser-cooled Cs atoms to spend longer times in the beam, resulting in improved clock performance. Clock stabilities of 3 × 10-14 at one second and accuracies of 1 × 10-16 are projected. With improved clock performance, significant improvements in several fundamental special and general relativity experiments are expected. For an ISS orbit at 400 km altitude and eccentricity 0.02, the gravitational frequency shift should be measureable about 35 times better than the previous best, Gravity Probe A. Improvements in testing Local Position Invariance and in a Kennedy-Thorndike experiment are expected. Areas of technology such as world-wide timing and time transfer and navigation will also directly benefit from such a high-performance clock in space. This paper will briefly describe the PARCS clock. The principal limitations on performance of relativity experiments, scientific objectives and benefits, and projected outcomes, will be discussed.

A novel bioerodible deep scleral lamellar cyclosporine implant for uveitis.

PubMed

Gilger, Brian C; Salmon, Jacklyn H; Wilkie, David A; Cruysberg, Lars P J; Kim, Jonghyeon; Hayat, Matt; Kim, Hyuncheol; Kim, Stephanie; Yuan, Peng; Lee, Susan S; Harrington, Susan M; Murray, Patrick R; Edelhauser, Henry F; Csaky, Karl G; Robinson, Michael R

2006-06-01

To determine the feasibility, safety, and effectiveness of an episcleral or deep scleral lamellar sustained release cyclosporine (CsA) device in a naturally occurring animal model of uveitis. A two-compartment perfusion chamber was used to assess in vitro human and equine scleral permeability of fluorescein, dexamethasone-fluorescein, or CsA. A biodegradable, matrix-reservoir CsA implant was designed, and release rates of CsA were determined in vitro. Tissue CsA levels were measured in eyes with the implant. Horses with equine recurrent uveitis (ERU) received episcleral or deep scleral lamellar CsA implants and were monitored for up to 3 years. Dexamethasone-fluorescein and CsA penetrated the in vitro equine sclera poorly; however, low but detectable levels of CsA were detected intraocularly in vivo. The implant placed episclerally failed to control inflammatory episodes in ERU. CsA implants placed in the deep sclera adjacent to the suprachoroidal space resulted in high levels of CsA in most ocular tissues. In clinical equine patients with ERU, frequency of uveitic flare-ups was significantly decreased after implantation of a deep scleral lamellar CsA implant. Diffusion of CsA across the sclera from the episcleral space was not a feasible method of drug delivery to the equine eye. However, placing a deep scleral lamellar CsA implant adjacent to the suprachoroidal space was effective in achieving therapeutic ocular drug concentrations and controlling uveitis in horses with ERU.

Adiabatic Quantum Computing via the Rydberg Blockade

NASA Astrophysics Data System (ADS)

Keating, Tyler; Goyal, Krittika; Deutsch, Ivan

2012-06-01

We study an architecture for implementing adiabatic quantum computation with trapped neutral atoms. Ground state atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism, thereby providing the requisite entangling interactions. As a benchmark we study the performance of a Quadratic Unconstrained Binary Optimization (QUBO) problem whose solution is found in the ground state spin configuration of an Ising-like model. We model a realistic architecture, including the effects of magnetic level structure, with qubits encoded into the clock states of ^133Cs, effective B-fields implemented through microwaves and light shifts, and atom-atom coupling achieved by excitation to a high-lying Rydberg level. Including the fundamental effects of photon scattering we find a high fidelity for the two-qubit implementation.

Fast phase stabilization of a low frequency beat note for atom interferometry.

PubMed

Oh, E; Horne, R A; Sackett, C A

2016-06-01

Atom interferometry experiments rely on the ability to obtain a stable signal that corresponds to an atomic phase. For interferometers that use laser beams to manipulate the atoms, noise in the lasers can lead to errors in the atomic measurement. In particular, it is often necessary to actively stabilize the optical phase between two frequency components of the beams. Typically this is achieved using a time-domain measurement of a beat note between the two frequencies. This becomes challenging when the frequency difference is small and the phase measurement must be made quickly. The method presented here instead uses a spatial interference detection to rapidly measure the optical phase for arbitrary frequency differences. A feedback system operating at a bandwidth of about 10 MHz could then correct the phase in about 3 μs. This time is short enough that the phase correction could be applied at the start of a laser pulse without appreciably degrading the fidelity of the atom interferometer operation. The phase stabilization system was demonstrated in a simple atom interferometer measurement of the (87)Rb recoil frequency.

A study on the hemocompatibility of dendronized chitosan derivatives in red blood cells

PubMed Central

Zhou, Yanfang; Li, Jiemei; Lu, Fang; Deng, Junjie; Zhang, Jiahua; Fang, Peijie; Peng, Xinsheng; Zhou, Shu-Feng

2015-01-01

Dendrimers are hyperbranched macromolecules with well-defined topological structures and multivalent functionalization sites, but they may cause cytotoxicity due to the presence of cationic charge. Recently, we have introduced alkyne-terminated poly(amidoamine) (PAMAM) dendrons of different generations (G=2,3) into chitosan to obtain dendronized chitosan derivatives [Cs-g-PAMAM (G=2,3)], which exhibited a better water solubility and enhanced plasmid DNA transfection efficiency. In this study, we attempted to examine the impact of Cs-g-PAMAM (G=2,3) at different concentrations (25 μg/mL, 50 μg/mL, and 100 μg/mL) on the morphology, surface structure, and viability of rat red blood cells (RBCs). The results showed that treatment of RBCs with Cs-g-PAMAM (G=2,3) at 50 μg/mL and 100 μg/mL induced a slightly higher hemolysis than Cs, and Cs-g-PAMAM (G=3) caused a slightly higher hemolysis than Cs-g-PAMAM (G=2), but all values were <5.0%. Optical microscopic and atomic force microscopic examinations indicated that Cs-g-PAMAM (G=2,3) caused slight RBC aggregation and lysis. Treatment of RBCs with 100 μg/mL Cs-g-PAMAM (G=3) induced echinocytic transformation, and RBCs displayed characteristic irregular contour due to the folding of the periphery. Drephanocyte-like RBCs were observed when treated with 100 μg/mL Cs-g-PAMAM (G=3). Erythrocytes underwent similar shape transition upon treatment with Cs-g-PAMAM (G=2) or Cs. The roughness values (Rms) of RBCs incubated with Cs-g-PAMAM (G=2,3) were significantly larger than those for RBCs incubated with physiological saline (P<0.01), but the Rms showed no difference for Cs and Cs-g-PAMAM (G=2,3) (P>0.05). Furthermore, Cs-g-PAMAM (G=2,3) exhibited a lower cytotoxicity in human kidney 293T cells. These results indicate that Cs-g-PAMAM (G=2,3) are hemocompatible but may disturb membrane and lipid structures at higher concentrations. Further safety and biocompatibility evaluations are warranted for Cs-g-PAMAM. Our findings prove helpful for a better understanding of the advantages of combining PAMAM dendrimers and chitosan to design and develop new, safe, and effective drug delivery vehicles. PMID:25999697

Surface physicochemical properties and decay of the low-lying isomer in the 229Th nucleus

NASA Astrophysics Data System (ADS)

Borisyuk, P. V.; Kurel'chuk, U. N.; Vasil'ev, O. S.; Troyan, V. I.; Lebedinskii, Yu Yu; Tkalya, E. V.

2018-05-01

The effect of the 229Th nucleus proximity to the CsI surface on the decay probability of its anomalously low lying isomeric level is studied. Results of experimental and theoretical studies show that the CsI surface does not produce chemical bonding with Th and does not noticeably change its valence shells. Hence, it is an optimal substrate for measuring the probability of the 229Th isomer state decay via internal electron conversion. The half-life of the 229Thm isomer in the thorium atom is calculated for neutral chemical environment.

Feasibility of supersonic diode pumped alkali lasers: Model calculations

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

Barmashenko, B. D.; Rosenwaks, S.

The feasibility of supersonic operation of diode pumped alkali lasers (DPALs) is studied for Cs and K atoms applying model calculations, based on a semi-analytical model previously used for studying static and subsonic flow DPALs. The operation of supersonic lasers is compared with that measured and modeled in subsonic lasers. The maximum power of supersonic Cs and K lasers is found to be higher than that of subsonic lasers with the same resonator and alkali density at the laser inlet by 25% and 70%, respectively. These results indicate that for scaling-up the power of DPALs, supersonic expansion should be considered.

Facile synthesis and structure characterization of hexagonal tungsten bronzes crystals

NASA Astrophysics Data System (ADS)

Lee, Jiann-Shing; Liu, Hao-Chuan; Peng, Gao-De; Tseng, Yawteng

2017-05-01

A facile molten-salt route was used to synthesize hexagonal Cs0.33WO3, Rb0.33WO3 and K0.30WO3 crystals. The three isostructural compounds were successfully prepared from the reaction of MxWO3 powders (M = Cs, Rb, K) in the CsCl/NaCl, RbCl/NaCl and KCl/NaCl fluxes, respectively. The structure determination and refinement, based on single-crystal X-ray diffraction data, are in agreement with previous works, possessing space group P63/mcm. The a and c parameters vary non-linearly with increasing radii of the M+ cations (rM) that is coordinated to twelve oxygen atoms. Both the volumes of unit-cell and WO6 octahedra vary linearly with rM, which become smaller from Cs0.33WO3 to K0.30WO3. The distortion of WO6 octahedra as well as isotropic displacement parameters increases from Cs0.33WO3 to K0.30WO3. The geometry of the WO6 octahedron becomes more regular with increasing rM. These structural trends arise from the effective size of the M+ cation.

Major and trace element concentrations in samples from 72275 and 72255. [chemical composition of lunar rocks

NASA Technical Reports Server (NTRS)

Haskin, L. A.; Blanchard, D. P.; Korotev, R.; Jacobs, J. W.; Brannon, J. A.; Herrmann, A. G.

1974-01-01

Analytical data have been obtained for Co, Sc, Hf, Zn, Cr, Ga, Rb, Cs, Ni, major elements, and rare earth elements in eight samples from boulder 1. The data for trace elements were obtained by radiochemical neutron activation analysis. Major elements, except Na and Mn, were obtained by atomic absorption spectral photometry. Values for Na and Mn were obtained by neutron activation analysis of the same powder that was later dissolved to provide the atomic absorption analyses.

Chromium Ions in Tetrahedral Sites

DTIC Science & Technology

1991-09-01

octahedral sites-the inversion site and the mirror site.4 After energy level calculations were performed, it was found that chromium ions in octahedral sites...octahedral site with symmetry C, the other half at the mirror octahedral sites with symmetry Cs. Its structure projected on (100) plane is shown in Fig... mirror symmetry. I 181 !U 10O 0 0 Fig. 2.1 Unit cell of forsterite, Mg2SiO4. Small open and solid circles are Mg atoms, big circles are 0 atoms and

Effect of Cordyceps sinensis on the Treatment of Experimental Autoimmune Encephalomyelitis: A Pilot Study on Mice Model.

PubMed

Zhong, Shan-Shan; Xiang, Ya-Juan; Liu, Pen-Ju; He, Yang; Yang, Ting-Ting; Wang, Yang-Yang; Rong, A; Zhang, Jun; Liu, Guang-Zhi

2017-10-05

As a traditional Chinese medicine, Cordyceps sinensis (CS) possesses a variety of immunoregulatory properties. This study aimed to explore the therapeutic potential of CS in a mice model of multiple sclerosis (MS)-experimental autoimmune encephalomyelitis (EAE). Female C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein35-55to induce EAE, followed by an instant intragastric feeding with a low dosage of CS (low-CS group, n = 5), high dosage of CS (high-CS group, n = 5), or the same volume of normal saline (control group, n = 5). All the mice were observed for clinical assessment. Over the 30 days of CS treatment, flow cytometry was used to detect the frequency of helper T-cell (Th) subsets, Th1 and Th17, and CD4+ CD25+ regulatory T cells in the spleen and lymph nodes. Meanwhile, pathological changes in brain were determined using both hematoxylin-eosin and luxol fast blue staining. Data were analyzed using the one-way analysis of variance (ANOVA). Over the 15 and 30 days of CS treatment, the clinical assessment for EAE demonstrated that both high-CS group (2.51 ± 0.31 and 2.26 ± 0.39 scores, respectively) and low-CS group (2.99 ± 0.40 and 2.69 ± 0.46, respectively) had lower disease severity scores than those of control group (3.57 ± 0.53 and 3.29 ± 0.53, all P < 0.01, respectively). Meanwhile, after 15 and 30 days, the high-CS group (19.18 ± 1.34 g and 20.41 ± 1.56 g, respectively) and low-CS group (18.07 ± 1.18 g and 19.48 ± 1.69 g, respectively) had a lower body weight, as compared with control group (16.85 ± 1.15 g and 18.22 ± 1.63 g, all P < 0.01, respectively). At 30 days post-CS treatment, there was a lower Th1 frequency in the lymph nodes (2.85 ± 1.54% and 2.77 ± 1.07% vs. 5.35 ± 1.34%, respectively; P < 0.05) and spleens (3.96 ± 1.09% and 3.09 ± 0.84% vs. 5.07 ± 1.50%, respectively; P < 0.05) and less inflammatory infiltration and demyelination in the brain of CS-treated mice than that of control group. Our preliminary study demonstrated that CS efficiently alleviated EAE severity and EAE-related pathology damage and decreased the number of Th1s in the periphery, indicating its effectiveness in the treatment of murine EAE. Thus, our findings strongly support the therapeutic potential of this agent as a new traditional Chinese medicine approach in MS treatment.

Effect of Cordyceps sinensis on the Treatment of Experimental Autoimmune Encephalomyelitis: A Pilot Study on Mice Model

PubMed Central

Zhong, Shan-Shan; Xiang, Ya-Juan; Liu, Pen-Ju; He, Yang; Yang, Ting-Ting; Wang, Yang-Yang; Rong, A; Zhang, Jun; Liu, Guang-Zhi

2017-01-01

Background: As a traditional Chinese medicine, Cordyceps sinensis (CS) possesses a variety of immunoregulatory properties. This study aimed to explore the therapeutic potential of CS in a mice model of multiple sclerosis (MS)-experimental autoimmune encephalomyelitis (EAE). Methods: Female C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein35–55 to induce EAE, followed by an instant intragastric feeding with a low dosage of CS (low-CS group, n = 5), high dosage of CS (high-CS group, n = 5), or the same volume of normal saline (control group, n = 5). All the mice were observed for clinical assessment. Over the 30 days of CS treatment, flow cytometry was used to detect the frequency of helper T-cell (Th) subsets, Th1 and Th17, and CD4+ CD25+ regulatory T cells in the spleen and lymph nodes. Meanwhile, pathological changes in brain were determined using both hematoxylin-eosin and luxol fast blue staining. Data were analyzed using the one-way analysis of variance (ANOVA). Results: Over the 15 and 30 days of CS treatment, the clinical assessment for EAE demonstrated that both high-CS group (2.51 ± 0.31 and 2.26 ± 0.39 scores, respectively) and low-CS group (2.99 ± 0.40 and 2.69 ± 0.46, respectively) had lower disease severity scores than those of control group (3.57 ± 0.53 and 3.29 ± 0.53, all P < 0.01, respectively). Meanwhile, after 15 and 30 days, the high-CS group (19.18 ± 1.34 g and 20.41 ± 1.56 g, respectively) and low-CS group (18.07 ± 1.18 g and 19.48 ± 1.69 g, respectively) had a lower body weight, as compared with control group (16.85 ± 1.15 g and 18.22 ± 1.63 g, all P < 0.01, respectively). At 30 days post-CS treatment, there was a lower Th1 frequency in the lymph nodes (2.85 ± 1.54% and 2.77 ± 1.07% vs. 5.35 ± 1.34%, respectively; P < 0.05) and spleens (3.96 ± 1.09% and 3.09 ± 0.84% vs. 5.07 ± 1.50%, respectively; P < 0.05) and less inflammatory infiltration and demyelination in the brain of CS-treated mice than that of control group. Conclusions: Our preliminary study demonstrated that CS efficiently alleviated EAE severity and EAE-related pathology damage and decreased the number of Th1s in the periphery, indicating its effectiveness in the treatment of murine EAE. Thus, our findings strongly support the therapeutic potential of this agent as a new traditional Chinese medicine approach in MS treatment. PMID:28937034

Treatment of trace organic compounds in common onsite wastewater systems

USGS Publications Warehouse

Robert Siegrist,; Conn, Kathleen E.

2015-01-01

Onsite wastewater systems (OWS) have historically been relied on to treat conventional pollutants and pathogens in a fashion similar to that expected from centralized wastewater systems. However, based on the occurrence of, and potential effects from, contaminants of emerging concern in wastewaters, OWS as well as centralized systems need to account for these compounds in system design and use. One group of contaminants involves organic compounds such as those associated with consumer product chemicals and pharmaceuticals, which are collectively referred to as trace organic compounds (TOrCs) due to their very low levels (e.g., ng/L to ug/L) relative to other pollutants. The question being confronted today is how best to account for TOrCs in onsite system design and use while also achieving other goals such as system simplicity, limited operation and maintenance requirements, low cost, and sustainability. In contrast to conventional pollutants such as nutrients and pathogens which have specific and achievable treatment goals, there are currently no enforceable treatment standards for TOrCs, which often have non-traditional toxicological endpoints (i.e. endocrine disruption). As highlighted in this paper, there are a large number of TOrCs that can be present in OWS and they have different properties, can be present at different frequencies of occurrence and concentrations, and have different susceptibilities to treatment in OWS. In general, based on the studies summarized in this paper, TOrCs normally should not require additional considerations beyond those for conventional pollutants and pathogens (e.g., nitrogen or bacteria and virus) during design and use of OWS. That said, there are situations where TOrCs could be a serious concern warranting special consideration in system design and use. In this paper, the frequency of occurrence of TOrCs and the range of concentrations encountered are highlighted. An evolving approach is outlined that could help assess the likelihood of occurrence and levels of TOrCs along with the treatment anticipated in different OWS and assimilation conditions.

Synthesis and single crystal growth of perovskite semiconductor CsPbBr3

NASA Astrophysics Data System (ADS)

Zhang, Mingzhi; Zheng, Zhiping; Fu, Qiuyun; Chen, Zheng; He, Jianle; Zhang, Sen; Chen, Cheng; Luo, Wei

2018-02-01

As a typical representative of all-inorganic lead halide perovskites, cesium lead bromine (CsPbBr3) has attracted significant attention in recent years. The direct band gap semiconductor CsPbBr3 has a wide band gap of 2.25 eV and high average atomic number (Cs: 55, Pb: 82 and Br: 35), which meet most of the requirements for detection of X- and γ-ray radiation, such as high attenuation, high resistivity, and significant photoconductivity response. However, the growth of large volume CsPbBr3 single crystals remains a challenge. In this paper, the synthesis of CsPbBr3 polycrystalline powders by a chemical co-precipitation method was investigated and the optimum synthesis conditions were obtained. A large CsPbBr3 single crystal of 8 mm diameter and 60 mm length was obtained by a creative electronic dynamic gradient (EDG) method. X-ray diffraction (XRD) patterns and X-ray rocking curve showed that the CsPbBr3 crystal preferentially oriented in the (1 1 0) direction and had a low dislocation density and small residual stress in the crystal. The IR and UV-Vis transmittance and temperature-dependent photoluminescence (PL) spectra showed the crystal had a good basic optical performance. The almost linear current-voltage (I-V) curves implied good ohmic contact between the electrodes and crystal surfaces. The resistivity of the crystal was calculated 109-1010 Ω cm. The above results showed that the quality of the obtained crystal had met the demand of optoelectronic applications.

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

Kagan, D. N., E-mail: d.n.kagan@mtu-net.ru; Krechetova, G. A.; Shpil'rain, E. E.

A detailed procedural analysis is given and results of implementation of the new version of the effusion method for determining the Gibbs energy (thermodynamic activity) of binary and ternary systems of alkali metals Cs-Na, K-Na, Cs-K, and Cs-K-Na are presented. The activity is determined using partial pressures of the components measured according the effusion method by the intensity of their atomic beams. The pressure range used in the experiment is intermediate between the Knudsen and hydrodynamic effusion modes. A generalized version of the effusion method involves the pressure range beyond the limits of the applicability of the Hertz-Knudsen equation. Employmentmore » of this method provides the differential equation of chemical thermodynamics; solution of this equation makes it possible to construct the Gibbs energy in the range of temperatures 400 {<=} T {<=} 1200 K and concentrations 0 {<=} x{sub i} {<=} 1.« less

Structure–function characterization of three human antibodies targeting the vaccinia virus adhesion molecule D8

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

Matho, Michael H.; Schlossman, Andrew; Gilchuk, Iuliia M.

Vaccinia virus (VACV) envelope protein D8 is one of three glycosaminoglycan adhesion molecules and binds to the linear polysaccharide chondroitin sulfate (CS). D8 is also a target for neutralizing antibody responses that are elicited by the smallpox vaccine, which has enabled the first eradication of a human viral pathogen and is a useful model for studying antibody responses. However, to date, VACV epitopes targeted by human antibodies have not been characterized at atomic resolution. Here in this paper, we characterized the binding properties of several human anti-D8 antibodies and determined the crystal structures of three VACV-mAb variants, VACV-66, VACV-138, andmore » VACV-304, separately bound to D8. Although all these antibodies bound D8 with high affinity and were moderately neutralizing in the presence of complement, VACV-138 and VACV-304 also fully blocked D8 binding to CS-A, the low affinity ligand for D8. VACV-138 also abrogated D8 binding to the high-affinity ligand CS-E, but we observed residual CS-E binding was observed in the presence of VACV-304. Analysis of the VACV-138– and VACV-304–binding sites along the CS-binding crevice of D8, combined with different efficiencies of blocking D8 adhesion to CS-A and CS-E allowed us to propose that D8 has a high- and low-affinity CS-binding region within its central crevice. The crevice is amenable to protein engineering to further enhance both specificity and affinity of binding to CS-E. Finally, a wild-type D8 tetramer specifically bound to structures within the developing glomeruli of the kidney, which express CS-E. We propose that through structure-based protein engineering, an improved D8 tetramer could be used as a potential diagnostic tool to detect expression of CS-E, which is a possible biomarker for ovarian cancer.« less

Structure–function characterization of three human antibodies targeting the vaccinia virus adhesion molecule D8

DOE PAGES

Matho, Michael H.; Schlossman, Andrew; Gilchuk, Iuliia M.; ...

2017-11-09

Vaccinia virus (VACV) envelope protein D8 is one of three glycosaminoglycan adhesion molecules and binds to the linear polysaccharide chondroitin sulfate (CS). D8 is also a target for neutralizing antibody responses that are elicited by the smallpox vaccine, which has enabled the first eradication of a human viral pathogen and is a useful model for studying antibody responses. However, to date, VACV epitopes targeted by human antibodies have not been characterized at atomic resolution. Here in this paper, we characterized the binding properties of several human anti-D8 antibodies and determined the crystal structures of three VACV-mAb variants, VACV-66, VACV-138, andmore » VACV-304, separately bound to D8. Although all these antibodies bound D8 with high affinity and were moderately neutralizing in the presence of complement, VACV-138 and VACV-304 also fully blocked D8 binding to CS-A, the low affinity ligand for D8. VACV-138 also abrogated D8 binding to the high-affinity ligand CS-E, but we observed residual CS-E binding was observed in the presence of VACV-304. Analysis of the VACV-138– and VACV-304–binding sites along the CS-binding crevice of D8, combined with different efficiencies of blocking D8 adhesion to CS-A and CS-E allowed us to propose that D8 has a high- and low-affinity CS-binding region within its central crevice. The crevice is amenable to protein engineering to further enhance both specificity and affinity of binding to CS-E. Finally, a wild-type D8 tetramer specifically bound to structures within the developing glomeruli of the kidney, which express CS-E. We propose that through structure-based protein engineering, an improved D8 tetramer could be used as a potential diagnostic tool to detect expression of CS-E, which is a possible biomarker for ovarian cancer.« less

Momentum-resolved radio-frequency spectroscopy of a spin-orbit-coupled atomic Fermi gas near a Feshbach resonance in harmonic traps

NASA Astrophysics Data System (ADS)

Peng, Shi-Guo; Liu, Xia-Ji; Hu, Hui; Jiang, Kaijun

2012-12-01

We theoretically investigate the momentum-resolved radio-frequency spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling. The system is qualitatively modeled as an ideal gas mixture of atoms and molecules, in which the properties of molecules, such as the wave function, binding energy, and effective mass, are determined from the two-particle solution of two interacting atoms. We calculate separately the radio-frequency response from atoms and molecules at finite temperatures by using the standard Fermi golden rule and take into account the effect of harmonic traps within local density approximation. The total radio-frequency spectroscopy is discussed as functions of temperature and spin-orbit coupling strength. Our results give a qualitative picture of radio-frequency spectroscopy of a resonantly interacting spin-orbit-coupled Fermi gas and can be directly tested in atomic Fermi gases of 40K atoms at Shanxi University and 6Li atoms at the Massachusetts Institute of Technology.

Dispersive detection of radio-frequency-dressed states

NASA Astrophysics Data System (ADS)

Jammi, Sindhu; Pyragius, Tadas; Bason, Mark G.; Florez, Hans Marin; Fernholz, Thomas

2018-04-01

We introduce a method to dispersively detect alkali-metal atoms in radio-frequency-dressed states. In particular, we use dressed detection to measure populations and population differences of atoms prepared in their clock states. Linear birefringence of the atomic medium enables atom number detection via polarization homodyning, a form of common path interferometry. In order to achieve low technical noise levels, we perform optical sideband detection after adiabatic transformation of bare states into dressed states. The balanced homodyne signal then oscillates independently of field fluctuations at twice the dressing frequency, thus allowing for robust, phase-locked detection that circumvents low-frequency noise. Using probe pulses of two optical frequencies, we can detect both clock states simultaneously and obtain population difference as well as the total atom number. The scheme also allows for difference measurements by direct subtraction of the homodyne signals at the balanced detector, which should technically enable quantum noise limited measurements with prospects for the preparation of spin squeezed states. The method extends to other Zeeman sublevels and can be employed in a range of atomic clock schemes, atom interferometers, and other experiments using dressed atoms.

MgCu metallic glass

NASA Astrophysics Data System (ADS)

Durandurdu, Murat

2018-03-01

We generate an amorphous MgCu model using the rapid solidification of the melt through a first-principles molecular dynamics approach within a generalised gradient approximation and reveal, for the first time, its structural features and mechanical properties in details. The liquid and glassy MgCu are found to acquire slightly distinct local structures. Yet in both forms of MgCu, most Cu atoms have a tendency to form the ideal and defective icosahedrons while Mg atoms are arranged in complex configurations. The mean coordination number of Cu and Mg at 300 K is 11.31 and 13.73, respectively. The short-range order of MgCu glass is projected to be different than the known crystalline MgCu and Mg2Cu phases. The mechanical properties of MgCu glass and the CsCl-type MgCu crystal are computed and compared. On the basis of the enthalpy analyses, a possible pressure-induced crystallisation of the MgCu glass into a CsCl-type structure is proposed to occur at around 11 GPa.

Use of High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS) for Sequential Multi-Element Determination of Metals in Seawater and Wastewater Samples

NASA Astrophysics Data System (ADS)

Peña-Vázquez, E.; Barciela-Alonso, M. C.; Pita-Calvo, C.; Domínguez-González, R.; Bermejo-Barrera, P.

2015-09-01

The objective of this work is to develop a method for the determination of metals in saline matrices using high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Module SFS 6 for sample injection was used in the manual mode, and flame operating conditions were selected. The main absorption lines were used for all the elements, and the number of selected analytical pixels were 5 (CP±2) for Cd, Cu, Fe, Ni, Pb and Zn, and 3 pixels for Mn (CP±1). Samples were acidified (0.5% (v/v) nitric acid), and the standard addition method was used for the sequential determination of the analytes in diluted samples (1:2). The method showed good precision (RSD(%) < 4%, except for Pb (6.5%)) and good recoveries. Accuracy was checked after the analysis of an SPS-WW2 wastewater reference material diluted with synthetic seawater (dilution 1:2), showing a good agreement between certified and experimental results.

Measurements of atmospheric dimethylsulfide, hydrogen sulfide, and carbon disulfide during GTE/CITE 3

NASA Technical Reports Server (NTRS)

Cooper, David J.; Saltzman, Eric S.

1993-01-01

Measurements of atmospheric dimethylsulfide (DMS), hydrogen sulfide (H2S), and carbon disulfide (CS2) were made over the North and South Atlantic Ocean as part of the Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 3) project. DMS and CS2 samples were collected and analyzed using an automated gas chromatography/flame photometric detection system with a sampling frequency of 10 min. H2S samples were collected using silver nitrate impregnated filters and analyzed by fluorescence quenching. The DMS data from both hemispheres have a bimodal distribution. Over the North Atlantic this reflects the difference between marine and continental air masses. Over the South Atlantic it may reflect differences in the sea surface source of DMS, corresponding to different air mass source regions. The median boundary layer H2S and CS2 levels were significantly higher in the northern hemisphere than the southern hemisphere, reflecting the higher frequency of samples influenced by pollutant and/or coastal emissions. Composite vertical profiles of DMS and H2S are similar to each other, are consistent with a sea surface source. Vertical profiles of CS2 have maxima in the free troposphere, implicating a continental source. The low levels of H2S and CS2 found in the southern hemisphere constrain the role of these compounds in global budgets to significantly less than previously estimated.

[Pro and con the trend to an increasing frequency of cesarean sections].

PubMed

Dimitrov, A

1998-01-01

The trend of increasing the CS rate is based on the improvement of skill and safety of operation, broadened and not well defined indications, some demographic, anthropological and social changes during recent decades. Most authors stress on the patient's will and on the role of nonclinical factors including the physician's training/experience, financial and convenience incentives. At the same time the increasing CS rate can not achieve the expectant medical benefits as abrupt decrease of prenatal mortality and morbidity, or intranatal trauma for the newborn and the women. Efforts to reduce unnecessary CS should focus on identifying the appropriate clinical indications for CS and spread this information to physicians. The trial to calculate the optimal rate of CS based on the prenatal mortality and morbidity, on the rate of the complication during pregnancy and labor requiring CS or the magnitude of delivery trauma nowadays is unsatisfactory. To compare the CS rate between countries or regions and draw conclusions from this is inadequate as many medical and nonclinical variables take place in the decision to perform cesarean delivery.

Exploratory Solid-State Synthesis of Uranium Chalcogenides and Mixed Anion Uranium Chalcogenides

NASA Astrophysics Data System (ADS)

Ward, Matthew David

Several uranium chalcogenides and mixed anion uranium chalcogenides have been synthesized by solid-state synthetic methods. Structural determinations were carried out via single-crystal X-ray diffraction. Some of these compounds have been further characterized by magnetic measurements, optical properties measurements, Raman spectroscopy, resistivity measurements, XANES and XPS. Eight compounds of the composition MU8Q17 were synthesized and characterized by single-crystal X-ray diffraction. All of these compounds crystallize in the CrU8S17 structure type. XANES measurements indicate that ScU8S17 contains Sc3+ and must be charge balanced with some amount of U 3+. Two compounds of the composition ATiU3Te9 crystallize as black rectangular plates. From single-crystal magnetic measurements, CsTiU 3Te9 is consistent with antiferromagnetic coupling between magnetic U atoms. The uranium chalcogenide compounds NiUS3 and Cr4US 8 were synthesized from reaction of the elements in various fluxes. NiUS3 crystallizes in the GdFeO3 structure type. Cr 4US8 crystallizes in the orthorhombic space group D - Pnma and its structure is related to that of Li4UF 8. The compounds Rh2U6S15, Cs 2Ti2U6Se15, and Cs2Cr 2U6Se15 crystallize as black prisms in the cubic space group O-Im3m. Magnetic measurements on Cs 2Cr2U6Se15 give a value for the Weiss temperature, θWeiss, of 57.59 K, indicative of ferromagnetic coupling. Black plates of CsScU(Se2)Se3 were synthesized from the reaction of the elements in a CsCl flux. CsScU(Se2)Se 3 crystallizes in the orthorhombic space group D- Cmcm . Magnetic susceptibility measurements on CsScU(Se2)Se 3 indicate three regions of magnetic response. The uranium double salt Cs5[U2(μ-S 2)2Cl8]I crystallizes as red plates. Cs 5[U2(μ-S2)2Cl 8]I displays optical anisotropy with band gap energies of 1.99 eV and 2.08 eV along the [001] and [100] polarizations. The uranium oxychalcogenides U7O2Se12 and Na2Ba2(UO2)S4 were synthesized by intentional oxygen contamination. The structure of U7O 2Se12 is related to the previously reported U7Q 12. Na2Ba2(UO2)S4 contains isolated uranyl polyhedra in which each uranium atom may be assigned an oxidation state of +6. The four uranium(IV) chlorophosphates, UCl4(POCl3), [U2Cl9][PCl4], UCl3(PO2Cl 2), and U2Cl8(POCl3) were synthesized in an effort to synthesize new novel uranyl sulfides. All are unstable, but UCl4(POCl3) is the thermodynamically favorable phase.

Epistatic selection of a sequence 5{prime} of the gene responsible for cystic fibrosis may account for the high frequency of this disease in the Caucasian population

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

Macek, M. Jr.; Nash, E.; Cutting, G.R.

1994-09-01

Cystic fibrosis (CF) is one of the more common lethal autosomal recessive disorders in Caucasian populations. Numerous hypotheses including genetic drift, founder effect, sex ratio, segregation distortions and various forms of heterozygote advantage have been proposed to explain the relatively high frequency of CF alleles. The observation of high linkage disequilibrium between markers at the 5{prime} end of CFTR and mutations that cause CF raised the possibility of epistatic selection. CF-linked marker allele frequencies were determined in 417 elderly individuals from a stable Czech population that survived high levels of infant and childhood mortality in the pre-antibiotic era. These datamore » were compared with allele frequencies of 646 contemporary newborns and 345 young adults drawn from the same population who had significantly lower mortality rates in the antibiotic era. Allele frequencies of markers CS7/Hhal and KM19/Pstl from the D7S23 locus are significantly different (p<0.05) between elderly female and male subjects in this population. Furthermore, there is a significant difference in the allele frequencies of marker CS7/Hhal when newborn females and elderly women are compared (p<0.05). Taken together, these data suggest that the allele status at the CS7 region influenced female survival in the period of high infant and childhood mortality in the pre-antibiotic era. Under this selective pressure, CFTR mutations that occurred on the {open_quotes}favorable{close_quotes} background would marginally increase in frequency in each successive generation and more ancient mutations residing on this background would become the most frequent in the general population.« less

Innovation and reliability of atomic standards for PTTI applications

NASA Technical Reports Server (NTRS)

Kern, R.

1981-01-01

Innovation and reliability in hyperfine frequency standards and clock systems are discussed. Hyperfine standards are defined as those precision frequency sources and clocks which use a hyperfine atomic transition for frequency control and which have realized significant commercial production and acceptance (cesium, hydrogen, and rubidium atoms). References to other systems such as thallium and ammonia are excluded since these atomic standards have not been commercially exploited in this country.

Precise Millimeter-Wave Laboratory Frequencies for CS and C34S

NASA Astrophysics Data System (ADS)

Gottlieb, C. A.; Myers, P. C.; Thaddeus, P.

2003-05-01

Nine successive rotational lines in the ground vibrational state of CS and C34S between 96 GHz (J=2-1) and 500 GHz (10-9) were measured in the laboratory to an accuracy of a few kHz. When our measurements are combined with the submillimeter-wave measurements of Ahrens & Winnewisser, the entire rotational spectrum of both isotopic species is predicted to an accuracy of about 1 part in 108 up to 500 GHz and 5 parts in 108 near 1000 GHz. These frequencies should be useful for quantitative studies of cloud core collapse and star formation in the millimeter- and submillimeter-wave bands.

Assessment and Classification of Service Learning: A Case Study of CS/EE Students

PubMed Central

Wang, Yu-Tseng; Lai, Pao-Lien; Chen, Jen-Yeu

2014-01-01

This study investigates the undergraduate students in computer science/electric engineering (CS/EE) in Taiwan to measure their perceived benefits from the experiences in service learning coursework. In addition, the confidence of their professional disciplines and its correlation with service learning experiences are examined. The results show that students take positive attitudes toward service learning and their perceived benefits from service learning are correlated with their confidence in professional disciplines. Furthermore, this study designs the knowledge model by Bayesian network (BN) classifiers and term frequency-inverse document frequency (TFIDF) for counseling students on the optimal choice of service learning. PMID:25295294

Snoek Relaxation in Fe-Cr Alloys and Interstitial-Substitutional Interaction

NASA Astrophysics Data System (ADS)

Golovin, I. S.; Blanter, M. S.; Schaller, R.

1997-03-01

The internal friction (IF) spectra of -Fe, Fe-Cr ferritic alloys and Cr have been investigated in a frequency range of 0.01 to 10 Hz. A Snoek-type relaxation was found in all the investigated C doped Fe-Cr alloys, starting from pure Fe and finishing with pure Cr. The temperature location of the Snoek peak (Tmax) in -Fe was found to be 315 K (1 Hz). The activation energy deduced from the T - f shift was 0.81 eV. Tmax in Cr was 433 K with an activation energy of 1.11 eV. The Snoek-type peaks in Fe-Cr alloys are much wider than in pure Fe or pure Cr. The temperature location of the peak versus chromium content curve exhibits a maximum in the vicinity of 35 wt% Cr (Tmax was 573 to 578 K, f 1.2 Hz and the activation energy was about 1.45 eV). It is important that Cr atoms in α-Fe have a more pronounced influence on the temperature location of the peak than Fe atoms have in chromium. A new model based on the atomic interactions is proposed to explain the influence of composition on Snoek peak location. The internal friction has been simulated by a Monte Carlo method, using C-C and C-substitutional atom (s) interaction energies. A model of long-range strain-induced (elastic) interaction supplemented by the chemical interaction in the two nearest coordination shells around an immobile substitutional atom was used for the C-s interaction. The interatomic interaction was supposed to affect IF by changing both the carbon atom arrangement (short-range order) and the energy of C atoms in octahedral interstices, and therefore the activation energy of IF. The peak temperatue calculated coincides well with the experimental ones if the value for the chemical interaction in the first coordination shell (Hchem) for C-Cr in Fe is - 0.15 eV and for C-Fe in Cr +0.15 eV. The difference in the influence of Cr in α-Fe and Fe in Cr is accounted for by a difference in the elastic and chemical interaction both between the carbon atoms and the substitutional atoms. The relaxation process in chromium Fe-based alloys is due to the carbon atom diffusion under stress between octahedral interstices of first and second coordination shells around the Cr atoms, and in Cr-based alloys, between second and third shells around the Fe atoms.

Estimation of chirp rates of music-adapted prolate spheroidal atoms using reassignment

NASA Astrophysics Data System (ADS)

Mesz, Bruno; Serrano, Eduardo

2007-09-01

We introduce a modified Matching Pursuit algorithm for estimating frequency and frequency slope of FM-modulated music signals. The use of Matching Pursuit with constant frequency atoms provides coarse estimates which could be improved with chirped atoms, more suited in principle to this kind of signals. Application of the reassignment method is suggested by its good localization properties for chirps. We start considering a family of atoms generated by modulation and scaling of a prolate spheroidal wave function. These functions are concentrated in frequency on intervals of a semitone centered at the frequencies of the well-tempered scale. At each stage of the pursuit, we search the atom most correlated with the signal. We then consider the spectral peaks at each frame of the spectrogram and calculate a modified frequency and frequency slope using the derivatives of the reassignment operators; this is then used to estimate the parameters of a cubic interpolation polynomial that models local pitch fluctuations. We apply the method both to synthetic and music signals.

Microstructure and molecular interaction in glycerol plasticized chitosan/poly(vinyl alcohol) blending films

USDA-ARS?s Scientific Manuscript database

Poly (vinyl alcohol) (PVA)/chitosan (CS) blended films plasticized by glycerol were investigated using mechanical testing, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and FTIR spectroscopy, with primary emphasis on the effects of the glycerol content and the molecular weig...

Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network.

PubMed

Ikuta, Rikizo; Kobayashi, Toshiki; Kawakami, Tetsuo; Miki, Shigehito; Yabuno, Masahiro; Yamashita, Taro; Terai, Hirotaka; Koashi, Masato; Mukai, Tetsuya; Yamamoto, Takashi; Imoto, Nobuyuki

2018-05-21

Long-lifetime quantum storages accessible to the telecom photonic infrastructure are essential to long-distance quantum communication. Atomic quantum storages have achieved subsecond storage time corresponding to 1000 km transmission time for a telecom photon through a quantum repeater algorithm. However, the telecom photon cannot be directly interfaced to typical atomic storages. Solid-state quantum frequency conversions fill this wavelength gap. Here we report on the experimental demonstration of a polarization-insensitive solid-state quantum frequency conversion to a telecom photon from a short-wavelength photon entangled with an atomic ensemble. Atom-photon entanglement has been generated with a Rb atomic ensemble and the photon has been translated to telecom range while retaining the entanglement by our nonlinear-crystal-based frequency converter in a Sagnac interferometer.

Atomic clocks for geodesy.

PubMed

Mehlstäubler, Tanja E; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10 -17 , opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein's general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today's best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10 -18 , comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

Atomic fountain clock with very high frequency stability employing a pulse-tube-cryocooled sapphire oscillator.

PubMed

Takamizawa, Akifumi; Yanagimachi, Shinya; Tanabe, Takehiko; Hagimoto, Ken; Hirano, Iku; Watabe, Ken-ichi; Ikegami, Takeshi; Hartnett, John G

2014-09-01

The frequency stability of an atomic fountain clock was significantly improved by employing an ultra-stable local oscillator and increasing the number of atoms detected after the Ramsey interrogation, resulting in a measured Allan deviation of 8.3 × 10(-14)τ(-1/2)). A cryogenic sapphire oscillator using an ultra-low-vibration pulse-tube cryocooler and cryostat, without the need for refilling with liquid helium, was applied as a local oscillator and a frequency reference. High atom number was achieved by the high power of the cooling laser beams and optical pumping to the Zeeman sublevel m(F) = 0 employed for a frequency measurement, although vapor-loaded optical molasses with the simple (001) configuration was used for the atomic fountain clock. The resulting stability is not limited by the Dick effect as it is when a BVA quartz oscillator is used as the local oscillator. The stability reached the quantum projection noise limit to within 11%. Using a combination of a cryocooled sapphire oscillator and techniques to enhance the atom number, the frequency stability of any atomic fountain clock, already established as primary frequency standard, may be improved without opening its vacuum chamber.

Atomic clocks for geodesy

NASA Astrophysics Data System (ADS)

Mehlstäubler, Tanja E.; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O.; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10‑17, opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein’s general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today’s best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10‑18, comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

Transport of (137)Cs, (241)Am and Pu isotopes in the Curonian Lagoon and the Baltic Sea.

PubMed

Lujanienė, G; Remeikaitė-Nikienė, N; Garnaga, G; Jokšas, K; Šilobritienė, B; Stankevičius, A; Šemčuk, S; Kulakauskaitė, I

2014-01-01

Activities of (137)Cs, (241)Am and (239,240)Pu were analyzed with special emphasis on better understanding of radionuclide transport from land via the Neman River estuaries to the Baltic Sea and behavior in the marine environment. Although activity concentrations of (137)Cs in water samples collected the Baltic Sea were almost 100 times higher as compared to the Curonian Lagoon, its activities in the bottom sediments were found to be comparable. Activity (238)Pu/(239,240)Pu and atom (240)Pu/(239)Pu ratios indicated a different contribution of the Chernobyl-originated Pu to the suspended particulate matter (SPM) and bottom sediments. The largest amount of the Chernobyl-derived Pu was found in the smallest suspended matter particles of 0.2-1 μm in size collected in the Klaipeda Strait in 2011-2012. The decrease of characteristic activity (238)Pu/(239,240)Pu and atom (240)Pu/(239)Pu ratios towards the global fallout ones in surface soil and the corresponding increase of plutonium (Pu) ratios in the suspended particulate matter and bottom sediments have indicated that the Chernobyl-derived Pu, primarily deposited on the soil surface, was washed out and transported to the Baltic Sea. Behavior of (241)Am was found to be similar to that of Pu isotopes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of chemical modifiers for the direct determination of arsenic in fish oil using high-resolution continuum source graphite furnace atomic absorption spectrometry.

PubMed

Pereira, Éderson R; de Almeida, Tarcísio S; Borges, Daniel L G; Carasek, Eduardo; Welz, Bernhard; Feldmann, Jörg; Campo Menoyo, Javier Del

2016-04-01

High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) has been applied for the development of a method for the determination of total As in fish oil samples using direct analysis. The method does not use any sample pretreatment, besides dilution with 1-propanole, in order to decrease the oil viscosity. The stability and sensitivity of As were evaluated using ruthenium and iridium as permanent chemical modifiers and palladium added in solution over the sample. The best results were obtained with ruthenium as the permanent modifier and palladium in solution added to samples and standard solutions. Under these conditions, aqueous standard solutions could be used for calibration for the fish oil samples diluted with 1-propanole. The pyrolysis and atomization temperatures were 1400 °C and 2300 °C, respectively, and the limit of detection and characteristic mass were 30 pg and 43 pg, respectively. Accuracy and precision of the method have been evaluated using microwave-assisted acid digestion of the samples with subsequent determination by HR-CS GF AAS and ICP-MS; the results were in agreement (95% confidence level) with those of the proposed method. Copyright © 2015 Elsevier B.V. All rights reserved.

Behavior of 131I and 137Cs in environments released from the Fukushima nuclear disaster

NASA Astrophysics Data System (ADS)

Ohta, T.; Mahara, Y.; Kubota, T.; Igarashi, T.

2011-12-01

The devastating tsunami that caused by the great earthquake (M = 9.0) off the coast of northeastern Honshu on 11 March 2011 destroyed large coastal areas of Tohoku and north Kanto, Japan. Radionuclides, including 131I, 134Cs, and 137Cs, were released into the atmosphere from the Fukushima Daiichi plants. Concentration of levels of 131I, 134Cs, and 137Cs in Ibaraki Prefecture, Japan, released from the Fukushima Daiichi plant were investigated in the soil and precipitation. The concentrations of 131I and 137Cs in the soil from the surface to 1 cm depth in Ibaraki Prefecture were 9360-13,400 Bq/kg and 720-3250 Bq/kg, respectively. The concentration of 137Cs at this soil observation site originating from the Fukushima plant was 8.4 to 21 times that found locally after the Nagasaki atomic bomb explosion. Most of the 134Cs and 137Cs from rainwater were trapped by the surface soil and sand to a depth of 1 cm, whereas only about 30% of the 131I was collected by the surface soil, suggesting that 131I would move deeper than 137Cs and 134Cs. The 131I in the rainwater was in the anion exchangeable form, and all of it could be collected by anion exchangeable mechanisms, whereas 30% of the 131I that had passed through the soil could not be trapped by the anion exchange resin, suggesting that the chemical form of this 30% was in a changeable, organic-bound form. The 131I, 134Cs, and 137Cs that were absorbed on soil were difficult to be dissolved into water. As the half-life of 131I is short and 137Cs is strongly adsorbed on the surface soil and sand, these radionuclides would be unlikely to reach the groundwater before completely decaying; contamination of groundwater with 131I and 137Cs supplied from rainwater to the surface soil is therefore exceedingly unlikely. As the 137Cs is likely to migrate only 0.6 cm in 10 years, people living in the Fukushima and Kanto areas will be exposed to radiation from 137Cs in the surface soil and sand. For protection, surface soils and sands with high levels of radiation need to be replaced with uncontaminated soils below a depth of about 30 cm. If this exchange operation will be done, even though the 137Cs will be placed deeper, its slow migration rate will ensure that it never reaches the groundwater.

A Variable Oscillator Underlies the Measurement of Time Intervals in the Rostral Medial Prefrontal Cortex during Classical Eyeblink Conditioning in Rabbits.

PubMed

Caro-Martín, C Rocío; Leal-Campanario, Rocío; Sánchez-Campusano, Raudel; Delgado-García, José M; Gruart, Agnès

2015-11-04

We were interested in determining whether rostral medial prefrontal cortex (rmPFC) neurons participate in the measurement of conditioned stimulus-unconditioned stimulus (CS-US) time intervals during classical eyeblink conditioning. Rabbits were conditioned with a delay paradigm consisting of a tone as CS. The CS started 50, 250, 500, 1000, or 2000 ms before and coterminated with an air puff (100 ms) directed at the cornea as the US. Eyelid movements were recorded with the magnetic search coil technique and the EMG activity of the orbicularis oculi muscle. Firing activities of rmPFC neurons were recorded across conditioning sessions. Reflex and conditioned eyelid responses presented a dominant oscillatory frequency of ≈12 Hz. The firing rate of each recorded neuron presented a single peak of activity with a frequency dependent on the CS-US interval (i.e., ≈12 Hz for 250 ms, ≈6 Hz for 500 ms, and≈3 Hz for 1000 ms). Interestingly, rmPFC neurons presented their dominant firing peaks at three precise times evenly distributed with respect to CS start and also depending on the duration of the CS-US interval (only for intervals of 250, 500, and 1000 ms). No significant neural responses were recorded at very short (50 ms) or long (2000 ms) CS-US intervals. rmPFC neurons seem not to encode the oscillatory properties characterizing conditioned eyelid responses in rabbits, but are probably involved in the determination of CS-US intervals of an intermediate range (250-1000 ms). We propose that a variable oscillator underlies the generation of working memories in rabbits. The way in which brains generate working memories (those used for the transient processing and storage of newly acquired information) is still an intriguing question. Here, we report that the firing activities of neurons located in the rostromedial prefrontal cortex recorded in alert behaving rabbits are controlled by a dynamic oscillator. This oscillator generated firing frequencies in a variable band of 3-12 Hz depending on the conditioned stimulus-unconditioned stimulus intervals (1 s, 500 ms, 250 ms) selected for classical eyeblink conditioning of behaving rabbits. Shorter (50 ms) and longer (2 s) intervals failed to activate the oscillator and prevented the acquisition of conditioned eyelid responses. This is an unexpected mechanism to generate sustained firing activities in neural circuits generating working memories. Copyright © 2015 the authors 0270-6474/15/3514809-13$15.00/0.

Two-photon Direct Frequency Comb Spectroscopy of Alkali Atoms

NASA Astrophysics Data System (ADS)

Nguyen, Khoa; Pradhananga, Trinity; Palm, Christopher; Stalnaker, Jason; Kimball, Derek Jackson

2012-06-01

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Direct Frequency Comb Spectroscopy of Alkali Atoms

NASA Astrophysics Data System (ADS)

Pradhananga, Trinity; Palm, Christopher; Nguyen, Khoa; Guttikonda, Srikanth; Kimball, Derek Jackson

2011-11-01

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Accurate calculation of dynamic Stark shifts and depopulation rates of Rydberg energy levels induced by blackbody radiation. Hydrogen, helium, and alkali-metal atoms

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

Farley, J.W.; Wing, W.H.

1981-05-01

A highly excited (Rydberg) atom bathed in blackbody radiation is perturbed in two ways. A dynamic Stark shift is induced by the off-resonant components of the blackbody radiation. Additionally, electric-dipole transitions to other atomic energy levels are induced by the resonant components of the blackbody radiation. This depopulation effect shortens the Rydberg-state lifetime, thereby broadening the energy level. Calculations of these two effects in many states of hydrogen, helium, and the alkali-metal atoms Li, Na, K, Rb, and Cs are presented for T = 300 K. Contributions from the entire blackbody spectrum and from both discrete and continuous perturbing statesmore » are included. The accuracy is considerably greater than that of previous estimates.« less

Tunable charge donation and spin polarization of metal adsorbates on graphene using an applied electric field

NASA Astrophysics Data System (ADS)

Parq, Jae-Hyeon; Yu, Jaejun; Kwon, Young-Kyun; Kim, Gunn

2010-11-01

Metal atoms on graphene, when ionized, can act as a point-charge impurity to probe a charge response of graphene with the Dirac cone band structure. To understand the microscopic physics of the metal-atom-induced charge and spin polarization in graphene, we present scanning tunneling spectroscopy (STS) simulations based on density-functional theory calculations. We find that a Cs atom on graphene is fully ionized with a significant band-bending feature in the STS whereas the charge and magnetic states of Ba and La atoms on graphene appear to be complicated due to orbital hybridization and Coulomb interaction. By applying external electric field, we observe changes in charge donations and spin magnetic moments of the metal adsorbates on graphene.

Primary Atomic Frequency Standards at NIST

PubMed Central

Sullivan, D. B.; Bergquist, J. C.; Bollinger, J. J.; Drullinger, R. E.; Itano, W. M.; Jefferts, S. R.; Lee, W. D.; Meekhof, D.; Parker, T. E.; Walls, F. L.; Wineland, D. J.

2001-01-01

The development of atomic frequency standards at NIST is discussed and three of the key frequency-standard technologies of the current era are described. For each of these technologies, the most recent NIST implementation of the particular type of standard is described in greater detail. The best relative standard uncertainty achieved to date for a NIST frequency standard is 1.5×10−15. The uncertainties of the most recent NIST standards are displayed relative to the uncertainties of atomic frequency standards of several other countries. PMID:27500017

Modelling of caesium dynamics in the negative ion sources at BATMAN and ELISE

NASA Astrophysics Data System (ADS)

Mimo, A.; Wimmer, C.; Wünderlich, D.; Fantz, U.

2017-08-01

The knowledge of Cs dynamics in negative hydrogen ion sources is a primary issue to achieve the ITER requirements for the Neutral Beam Injection (NBI) systems, i.e. one hour operation with an accelerated ion current of 40 A of D- and a ratio between negative ions and co-extracted electrons below one. Production of negative ions is mostly achieved by conversion of hydrogen/deuterium atoms on a converter surface, which is caesiated in order to reduce the work function and increase the conversion efficiency. The understanding of the Cs transport and redistribution mechanism inside the source is necessary for the achievement of high performances. Cs dynamics was therefore investigated by means of numerical simulations performed with the Monte Carlo transport code CsFlow3D. Simulations of the prototype source (1/8 of the ITER NBI source size) have shown that the plasma distribution inside the source has the major effect on Cs dynamics during the pulse: asymmetry of the plasma parameters leads to asymmetry in Cs distribution in front of the plasma grid. The simulated time traces and the general simulation results are in agreement with the experimental measurements. Simulations performed for the ELISE testbed (half of the ITER NBI source size) have shown an effect of the vacuum phase time on the amount and stability of Cs during the pulse. The sputtering of Cs due to back-streaming ions was reproduced by the simulations and it is in agreement with the experimental observation: this can become a critical issue during long pulses, especially in case of continuous extraction as foreseen for ITER. These results and the acquired knowledge of Cs dynamics will be useful to have a better management of Cs and thus to reduce its consumption, in the direction of the demonstration fusion power plant DEMO.

Environmental impacts of heavy metals, rare earth elements and natural radionuclides in marine sediment from Ras Tanura, Saudi Arabia along the Arabian Gulf.

PubMed

El-Taher, Atef; Alshahri, Fatimh; Elsaman, Reda

2018-02-01

Ras Tanura city is one of the most important cities in Saudi Arabia because of the presence of the largest and oldest oil refinery in the Middle East which was began operations in September 1945. Also its contains gas plant and two ports. The concentration of natural radionuclides, heavy metals and rare earth elements were measured in marine sediment samples collected from Ras Tanura. The specific activities of 238 U, 226 Ra, 232 Th, 40 K and 137 Cs (Bq/kg) were measured using A hyper-pure Germanium detector (HPGe), and ranged from (20.4 ± 4.0-55.1 ± 9.9), (6.71 ± 0.7-46.1 ± 4.5), (3.51 ± 0.5-18.2 ± 1.5), (105 ± 4.4-492 ± 13) and from (0.33 ± 0.04-2.10 ± 0.4) for 238 U, 226 Ra, 232 Th, 40 K and 137 Cs respectively. Heavy metals and rare earth elements were measured using ICPE-9820 Plasma Atomic Emission Spectrometer. Also the frequency distributions for all radioactive variables in sediment samples were analyzed. Finally the radiological hazards due to natural radionuclides in marine sediment were calculated to the public and it's diagramed by Surfer program in maps. Comparing with the international recommended values, its values found to be within the international level. Copyright © 2017 Elsevier Ltd. All rights reserved.

Global expression for representing cohesive-energy curves. II

NASA Technical Reports Server (NTRS)

Schlosser, Herbert; Ferrante, John

1993-01-01

Schlosser et al. (1991) showed that the R dependence of the cohesive energy of partially ionic solids may be characterized by a two-term energy relationship consisting of a Coulomb term arising from the charge transfer, delta-Z, and a scaled universal energy function, E*(a *), which accounts for the partially covalent character of the bond and for repulsion between the atomic cores for small R; a* is a scaled length. In the paper by Schlosser et al., the normalized cohesive-energy curves of NaCl-structure alkali-halide crystals were generated with this expression. In this paper we generate the cohesive-energy curves of several families of partially ionic solids with different crystal structures and differing degrees of ionicity. These include the CsCl-structure Cs halides, and the Tl and Ag halides, which have weaker ionic bonding than the alkali halides, and which have the CsCl and NaCl structures, respectively. The cohesive-energy-curve parameters are then used to generate theoretical isothermal compression curves for the Li, Na, K, Cs, and Ag halides. We find good agreement with the available experimental compression data.

Intercalated chitosan/hydroxyapatite nanocomposites: Promising materials for bone tissue engineering applications.

PubMed

Nazeer, Muhammad Anwaar; Yilgör, Emel; Yilgör, Iskender

2017-11-01

Preparation and characterization of chitosan/hydroxyapatite (CS/HA) nanocomposites displaying an intercalated structure is reported. Hydroxyapatite was synthesized through sol-gel process. Formic acid was introduced as a new solvent to obtain stable dispersions of nano-sized HA particles in polymer solution. CS/HA dispersions with HA contents of 5, 10 and 20% by weight were prepared. Self-assembling of HA nanoparticles during the drying of the solvent cast films led to the formation of homogeneous CS/HA nanocomposites. Composite films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-rays (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-rays diffraction (XRD) analysis and thermogravimetric analysis (TGA). SEM and AFM confirmed the presence of uniformly distributed HA nanoparticles on the chitosan matrix surface. XRD patterns and cross-sectional SEM images showed the formation of layered nanocomposites. Complete degradation of chitosan matrix in TGA experiments, led to the formation of nanoporous 3D scaffolds containing hydroxyapatite, β-tricalcium phosphate and calcium pyrophosphate. CS/HA composites can be considered as promising materials for bone tissue engineering applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

High Atom Number in Microsized Atom Traps

DTIC Science & Technology

2015-12-14

forces on the order of (hbar)(k) (Omega), where Omega is the laser Rabi frequency. We have observed behavior compatible with bichromatic slowing and... Rabi frequency. We have observed behavior compatible with bichromatic slowing and cooling of some atoms in atomic beam. Results were presented at the

Sub-natural width resonances in Cs vapor confined in micrometric thickness optical cell

NASA Astrophysics Data System (ADS)

Cartaleva, S.; Krasteva, A.; Sargsyan, A.; Sarkisyan, D.; Slavov, D.; Vartanyan, T.

2013-03-01

We present here the behavior of Electromagnetically Induced Transparency (EIT), Velocity Selective Optical Pumping (VSOP) resonances and Velocity Selective Excitation (VSE) resonances observed in Cs vapor confined in а micrometric optical cell (MC) with thickness L = 6λ, λ = 852nm. For comparison of behavior of VSE resonance another conventional optical cell with thickness L=2.5 cm is used. Cells are irradiated in orthogonal to their windows directions by probe beam scanned on the Fg = 4 → Fe= 3, 4, 5 set of transitions and pump beam fixed at the Fg = 3 → Fe = 4 transition, on the D2 line of Cs. The enhanced absorption (fluorescence) narrow VSOP resonance at the closed transition transforms into reduced absorption (fluorescence) one with small increase of atomic concentration or light intensity. A striking difference appears between the VSE resonance broadening in L = 6λ and conventional L = 2.5cm cells.

Cold crucible induction melter test for crystalline ceramic waste form fabrication: A feasibility assessment

DOE PAGES

Amoroso, Jake W.; Marra, James; Dandeneau, Christopher S.; ...

2017-01-18

The first scaled proof-of-principle cold crucible induction melter (CCIM) test to process a multiphase ceramic waste form from a simulated combined (Cs/Sr, lanthanide and transition metal fission products) commercial used nuclear fuel waste stream was recently conducted in the United States. X-ray diffraction, 2-D X-ray absorption near edge structure (XANES), electron microscopy, inductively coupled plasma-atomic emission spectroscopy (and inductively coupled plasma-mass spectroscopy for Cs), and product consistency tests were used to characterize the fabricated CCIM material. Characterization analyses confirmed that a crystalline ceramic with a desirable phase assemblage was produced from a melt using a CCIM. We identified primary hollandite,more » pyrochlore/zirconolite, and perovskite phases in addition to minor phases rich in Fe, Al, or Cs. The material produced in the CCIM was chemically homogeneous and displayed a uniform phase assemblage with acceptable aqueous chemical durability.« less

Secondary ion emission from Ti, V, Cu, Ag and Au surfaces under KeV Cs + irradiation

NASA Astrophysics Data System (ADS)

van der Heide, P. A. W.

2005-02-01

Low energy mono-atomic singly charged secondary ion emissions from Ti, V, Cu, Ag and Au substrates during the initial stages of sputtering with Cs + primary ions have been studied. With the exception of the Ag - secondary ions, all exhibited exponential like correlations with the Cs induced work function changes. This, along with the lack of variations in the valence band structure around the Fermi edge, is consistent with resonance charge transfer to/from states located at the Fermi edge. The insensitivity of Ag - to work function appears to stem from the dominance of a separate ion formation process, namely charge transfer into vacant 4d states in the sputtered population, which themselves appear to be produced through collective oscillations. A similar excitation-mediated process involving different levels also appears to be active in the formation of other negatively charged transition metal ions, albeit to a much lesser degree.

Public and private pregnancy care in Reggio Emilia Province: an observational study on appropriateness of care and delivery outcomes

PubMed Central

2014-01-01

Background In industrialized countries, improvements have been made in both maternal and newborn health. While attention to antenatal care is increasing, excessive medicalization is also becoming more common. The aim of this study is to compare caesarean section (CS) frequency and ultrasound scan utilization in a public model of care involving both midwives and obstetricians with a private model in which care is provided by obstetricians only. Methods Design: Observational population-based study. Setting: Reggio Emilia Province. Population: 5957 women resident in the province who delivered between October 2010 and November 2011. Main outcome measures: CS frequency and ultrasound scan utilization, stillbirths, and other negative perinatal outcomes. Women in the study were searched in the public family and reproductive health clinic medical records to identify those cared for in the public system. Outcomes of the two antenatal care models were compared through multivariate logistic regression adjusting for maternal characteristics and, for CS only, by stratifying by Robson’s Group. Results Compared to women cared for in private services (N = 3,043), those in public service (N = 2,369) were younger, less educated, more frequently non-Italian, and multiparous. The probability of CS was slightly higher for women cared for by private obstetricians than for those cared for in the public system (31.8% vs. 27.1%; adjusted odds ratio: 1.10; 95% CI: 0.93–1.29): The probability of having more than 3 ultrasound scans was higher in private care (89.6% vs. 49.8%; adjusted odds ratio: 5.11; 95% CI: 4.30–6.08). CS frequency was higher in private care for all Robson’s classes except women who underwent CS during spontaneous labour. Among negative perinatal outcomes only a higher risk of pre-term birth was observed for pregnancies cared for in private services. Conclusions The public model provides less medicalized and more guidelines-oriented care than does the private model, with no increase in negative perinatal outcomes. PMID:24533853

Accurately determining direction of arrival by seismic array based on compressive sensing

NASA Astrophysics Data System (ADS)

Hu, J.; Zhang, H.; Yu, H.

2016-12-01

Seismic array analysis method plays an important role in detecting weak signals and determining their locations and rupturing process. In these applications, reliably estimating direction of arrival (DOA) for the seismic wave is very important. DOA is generally determined by the conventional beamforming method (CBM) [Rost et al, 2000]. However, for a fixed seismic array generally the resolution of CBM is poor in the case of low-frequency seismic signals, and in the case of high frequency seismic signals the CBM may produce many local peaks, making it difficult to pick the one corresponding to true DOA. In this study, we develop a new seismic array method based on compressive sensing (CS) to determine the DOA with high resolution for both low- and high-frequency seismic signals. The new method takes advantage of the space sparsity of the incoming wavefronts. The CS method has been successfully used to determine spatial and temporal earthquake rupturing distributions with seismic array [Yao et al, 2011;Yao et al, 2013;Yin 2016]. In this method, we first form the problem of solving the DOA as a L1-norm minimization problem. The measurement matrix for CS is constructed by dividing the slowness-angle domain into many grid nodes, which needs to satisfy restricted isometry property (RIP) for optimized reconstruction of the image. The L1-norm minimization is solved by the interior point method. We first test the CS-based DOA array determination method on synthetic data constructed based on Shanghai seismic array. Compared to the CBM, synthetic test for data without noise shows that the new method can determine the true DOA with a super-high resolution. In the case of multiple sources, the new method can easily separate multiple DOAs. When data are contaminated by noise at various levels, the CS method is stable when the noise amplitude is lower than the signal amplitude. We also test the CS method for the Wenchuan earthquake. For different arrays with different apertures, we are able to obtain reliable DOAs with uncertainties lower than 10 degrees.

a Measurement of the Fine Structure Constant

NASA Astrophysics Data System (ADS)

Hensley, Joel M.; Wicht, Andreas; Sarajlic, Edina; Chu, Steven

2002-06-01

Using an atom interferometer method, we measure the recoil velocity of cesium due to the coherent scattering of a photon. This measurement is used to obtain a preliminary value of ħ/MCs and the fine structure constant, α, with an uncertainty Δα/α = 7.3 × 10-9.

On the function of chitin synthase extracellular domains in biomineralization.

PubMed

Weiss, Ingrid M; Lüke, Florian; Eichner, Norbert; Guth, Christina; Clausen-Schaumann, Hauke

2013-08-01

Molluscs with various shell architectures evolved around 542-525 million years ago, as part of a larger phenomenon related to the diversification of metazoan phyla. Molluscs deposit minerals in a chitin matrix. The mollusc chitin is synthesized by transmembrane enzymes that contain several unique extracellular domains. Here we investigate the assembly mechanism of the chitin synthase Ar-CS1 via its extracellular domain ArCS1_E22. The corresponding transmembrane protein ArCS1_E22TM accumulates in membrane fractions of the expression host Dictyostelium discoideum. Soluble recombinant ArCS1_E22 proteins can be purified as monomers only at basic pH. According to confocal fluorescence microscopy experiments, immunolabeled ArCS1_E22 proteins adsorb preferably to aragonitic nacre platelets at pH 7.75. At pH 8.2 or pH 9.0 the fluorescence signal is less intense, indicating that protein-mineral interaction is reduced with increasing pH. Furthermore, ArCS1_E22 forms regular nanostructures on cationic substrates as revealed by atomic force microscopy (AFM) experiments on modified mica cleavage planes. These experiments suggest that the extracellular domain ArCS1_E22 is involved in regulating the multiple enzyme activities of Ar-CS1 such as chitin synthesis and myosin movements by interaction with mineral surfaces and eventually by protein assembly. The protein complexes could locally probe the status of mineralization according to pH unless ions and pCO2 are balanced with suitable buffer substances. Taking into account that the intact enzyme could act as a force sensor, the results presented here provide further evidence that shell formation is coordinated physiologically with precise adjustment of cellular activities to the structure, topography and stiffness at the mineralizing interface. Copyright © 2013 Elsevier Inc. All rights reserved.

Simple-to-Complex Transformation in Liquid Rubidium.

PubMed

Gorelli, Federico A; De Panfilis, Simone; Bryk, Taras; Ulivi, Lorenzo; Garbarino, Gaston; Parisiades, Paraskevas; Santoro, Mario

2018-05-18

We investigated the atomic structure of liquid Rb along an isothermal path at 573 K, up to 23 GPa, by X-ray diffraction measurements. By raising the pressure, we observed a liquid-liquid transformation from a simple metallic liquid to a complex one. The transition occurs at 7.5 ± 1 GPa which is slightly above the first maximum of the T-P melting line. This transformation is traced back to the density-induced hybridization of highest electronic orbitals leading to the accumulation of valence electrons between Rb atoms and to the formation of interstitial atomic shells, a behavior that Rb shares with Cs and is likely to be common to all alkali metals.

Initial atomic coherences and Ramsey frequency pulling in fountain clocks

NASA Astrophysics Data System (ADS)

Gerginov, Vladislav; Nemitz, Nils; Weyers, Stefan

2014-09-01

In the uncertainty budget of primary atomic cesium fountain clocks, evaluations of frequency-pulling shifts of the hyperfine clock transition caused by unintentional excitation of its nearby transitions (Rabi and Ramsey pulling) have been based so far on an approach developed for cesium beam clocks. We re-evaluate this type of frequency pulling in fountain clocks and pay particular attention to the effect of initial coherent atomic states. We find significantly enhanced frequency shifts caused by Ramsey pulling due to sublevel population imbalance and corresponding coherences within the state-selected hyperfine component of the initial atom ground state. Such shifts are experimentally investigated in an atomic fountain clock and quantitative agreement with the predictions of the model is demonstrated.

129Xe NMR chemical shift in Xe@C60 calculated at experimental conditions: essential role of the relativity, dynamics, and explicit solvent.

PubMed

Standara, Stanislav; Kulhánek, Petr; Marek, Radek; Straka, Michal

2013-08-15

The isotropic (129)Xe nuclear magnetic resonance (NMR) chemical shift (CS) in Xe@C60 dissolved in liquid benzene was calculated by piecewise approximation to faithfully simulate the experimental conditions and to evaluate the role of different physical factors influencing the (129)Xe NMR CS. The (129)Xe shielding constant was obtained by averaging the (129)Xe nuclear magnetic shieldings calculated for snapshots obtained from the molecular dynamics trajectory of the Xe@C60 system embedded in a periodic box of benzene molecules. Relativistic corrections were added at the Breit-Pauli perturbation theory (BPPT) level, included the solvent, and were dynamically averaged. It is demonstrated that the contribution of internal dynamics of the Xe@C60 system represents about 8% of the total nonrelativistic NMR CS, whereas the effects of dynamical solvent add another 8%. The dynamically averaged relativistic effects contribute by 9% to the total calculated (129)Xe NMR CS. The final theoretical value of 172.7 ppm corresponds well to the experimental (129)Xe CS of 179.2 ppm and lies within the estimated errors of the model. The presented computational protocol serves as a prototype for calculations of (129)Xe NMR parameters in different Xe atom guest-host systems. Copyright © 2013 Wiley Periodicals, Inc.

Synthesis and characterisation of PEG modified chitosan nanocapsules loaded with thymoquinone.

PubMed

Vignesh Kumar, Suresh Kumar; Renuka Devi, Ponnuswamy; Harish, Saru; Hemananthan, Eswaran

2017-02-01

Thymoquinone (TQ), a major bioactive compound of Nigella sativa seeds has several therapeutic properties. The main drawback in bringing TQ to therapeutic application is that it has poor stability and bioavailability. Hence a suitable carrier is essential for TQ delivery. Recent studies indicate biodegradable polymers are potentially good carriers of bioactive compounds. In this study, polyethylene glycol (PEG) modified chitosan (Cs) nanocapsules were developed as a carrier for TQ. Aqueous soluble low molecular weight Cs and PEG was selected among different biodegradable polymers based on their biocompatibility and efficacy as a carrier. Optimisation of synthesis of nanocapsules was done based on particle size, PDI, encapsulation efficiency and process yield. A positive zeta potential value of +48 mV, indicating good stability was observed. Scanning electron microscope and atomic-force microscopy analysis revealed spherical shaped and smooth surfaced nanocapsules with size between 100 to 300 nm. The molecular dispersion of the TQ in Cs PEG nanocapsules was studied using X-ray powder diffraction. The Fourier transform infrared spectrum of optimised nanocapsule exhibited functional groups of both polymer and drug, confirming the presence of Cs, PEG and TQ. In vitro drug release studies showed that PEG modified Cs nanocapsules loaded with TQ had a slow and sustained release.

Nano-scale characterization of nano-hydroxyapatite incorporated chitosan particles for bone repair.

PubMed

Gaihre, Bipin; Uswatta, Suren; Jayasuriya, Ambalangodage C

2018-05-01

In this study, injectable porous spherical particles were fabricated using chitosan (CS) biopolymer, sodium tripolyphosphate (TPP), and nano-hydroxyapatite (nHA). TPP was primarily used as an ionic crosslinker to crosslink 2% (w/v) CS droplets. 2% (w/v) nHA was used to prepare nHA incorporated particles. The surface morphological properties and nanomechanical properties such as topography, deformation, adhesion, and dissipation of CS particles with and without nHA were studied using contact mode and peakforce quantitative nanomechanical property mapping mode in atomic force microscopy. The nHA spots have higher density than CS which leads to higher forces acting on the probe tip and higher energy dissipation to lift the tip from nHA areas. The cumulative release data showed that about 87% of total BMP-2 encapsulated within the particles was released by third week of experiment period. Degradation study was conducted to understand how the particles degradation occurs in the presence of phosphate buffered saline with continues shaking in an incubator at 37° C. In addition, BMP-2 release from the 2% nHA/CS particles was studied over a three weeks period and found that BMP-2 release was governed by the simple diffusion rather than the degradation of particles. Copyright © 2018 Elsevier B.V. All rights reserved.

Electronic structure and electron momentum densities of Ag2CrO4

NASA Astrophysics Data System (ADS)

Meena, Seema Kumari; Ahuja, B. L.

2018-05-01

We present the first-ever experimental electron momentum density of Ag2CrO4 using 661.65 keV γ-rays from 20 Ci 137Cs source. To validate our experimental data, we have also deduced theoretical Compton profiles, energy bands and density of states using linear combination of atomic orbitals (LCAO) method in the framework of density functional theory. It is seen that the DFT-LDA gives a better agreement with experimental data than free atom model. The energy bands and density of states are also discussed.

Carbon-containing cathodes for enhanced electron emission

DOEpatents

Cao, Renyu; Pan, Lawrence; Vergara, German; Fox, Ciaran

2000-01-01

A cathode has electropositive atoms directly bonded to a carbon-containing substrate. Preferably, the substrate comprises diamond or diamond-like (sp.sup.3) carbon, and the electropositive atoms are Cs. The cathode displays superior efficiency and durability. In one embodiment, the cathode has a negative electron affinity (NEA). The cathode can be used for field emission, thermionic emission, or photoemission. Upon exposure to air or oxygen, the cathode performance can be restored by annealing or other methods. Applications include detectors, electron multipliers, sensors, imaging systems, and displays, particularly flat panel displays.

Resonant difference-frequency atomic force ultrasonic microscope

NASA Technical Reports Server (NTRS)

Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

2010-01-01

A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

Natural polymers supported copper nanoparticles for pollutants degradation

NASA Astrophysics Data System (ADS)

Haider, Sajjad; Kamal, Tahseen; Khan, Sher Bahadar; Omer, Muhammad; Haider, Adnan; Khan, Farman Ullah; Asiri, Abdullah M.

2016-11-01

In this report, chitosan (CS) was adhered on cellulose microfiber mat (CMM) to prepare CS-CMM. This was used as host for copper (Cu) nanoparticles preparation. After adsorption of Cu2+ ions from an aqueous solution of CuSO4, the metal ions entrapped in CS coating layer was treated with sodium borohydride (NaBH4) to prepare Cu nanoparticles loaded CS-CMM (Cu/CS-CMM). Fourier transform infrared spectroscopy, and X-ray diffraction confirmed the formation of Cu/CS-CMM hybrid. Scanning electron microscopy analysis was performed to reveal the morphology of the prepared catalyst. The prepared Cu/CS-CMM was employed as a catalyst for the degradation of nitro-aromatic compounds of 2-nitrophenol (2NP) and 4-nitrophenol (4NP) as well as an organic cresyl blue (CB) dye. Remarkably, the turnover frequency in the case of 2NP and 4NP using Cu/CS-CMM reaches 103.3 and 88.6 h-1, outperforming previously reported Cu nanoparticles immobilized in hydrogel-based catalytic systems. The rate constants for 2NP, 4NP and CB were 1.2 × 10-3 s-1, 2.1 × 10-3 s-1 and, 1.3 × 10-3 s-1, respectively. Besides, we discussed the separation of the catalyst from the reaction mixture and its re-usability.

Boosting Two-Dimensional MoS2/CsPbBr3 Photodetectors via Enhanced Light Absorbance and Interfacial Carrier Separation.

PubMed

Song, Xiufeng; Liu, Xuhai; Yu, Dejian; Huo, Chengxue; Ji, Jianping; Li, Xiaoming; Zhang, Shengli; Zou, Yousheng; Zhu, Gangyi; Wang, Yongjin; Wu, Mingzai; Xie, An; Zeng, Haibo

2018-01-24

Transition metal dichalcogenides (TMDs) are promising candidates for flexible optoelectronic devices because of their special structures and excellent properties, but the low optical absorption of the ultrathin layers greatly limits the generation of photocarriers and restricts the performance. Here, we integrate all-inorganic perovskite CsPbBr 3 nanosheets with MoS 2 atomic layers and take the advantage of the large absorption coefficient and high quantum efficiency of the perovskites, to achieve excellent performance of the TMD-based photodetectors. Significantly, the interfacial charge transfer from the CsPbBr 3 to the MoS 2 layer has been evidenced by the observed photoluminescence quenching and shortened decay time of the hybrid MoS 2 /CsPbBr 3 . Resultantly, such a hybrid MoS 2 /CsPbBr 3 photodetector exhibits a high photoresponsivity of 4.4 A/W, an external quantum efficiency of 302%, and a detectivity of 2.5 × 10 10 Jones because of the high efficient photoexcited carrier separation at the interface of MoS 2 and CsPbBr 3 . The photoresponsivity of this hybrid device presents an improvement of 3 orders of magnitude compared with that of a MoS 2 device without CsPbBr 3 . The response time of the device is also shortened from 65.2 to 0.72 ms after coupling with MoS 2 layers. The combination of the all-inorganic perovskite layer with high photon absorption and the carrier transport TMD layer may pave the way for novel high-performance optoelectronic devices.

Improvement of Frequency Locking Algorithm for Atomic Frequency Standards

NASA Astrophysics Data System (ADS)

Park, Young-Ho; Kang, Hoonsoo; Heyong Lee, Soo; Eon Park, Sang; Lee, Jong Koo; Lee, Ho Seong; Kwon, Taeg Yong

2010-09-01

The authors describe a novel method of frequency locking algorithm for atomic frequency standards. The new algorithm for locking the microwave frequency to the Ramsey resonance is compared with the old one that had been employed in the cesium atomic beam frequency standards such as NIST-7 and KRISS-1. Numerical simulations for testing the performance of the algorithm show that the new method has a noise filtering performance superior to the old one by a factor of 1.2 for the flicker signal noise and 1.4 for random-walk signal noise. The new algorithm can readily be used to enhance the frequency stability for a digital servo employing the slow square wave frequency modulation.

Deterministically swapping frequency-bin entanglement from photon-photon to atom-photon hybrid systems

NASA Astrophysics Data System (ADS)

Ou, Bao-Quan; Liu, Chang; Sun, Yuan; Chen, Ping-Xing

2018-02-01

Inspired by the recent developments of the research on the atom-photon quantum interface and energy-time entanglement between single-photon pulses, we are motivated to study the deterministic protocol for the frequency-bin entanglement of the atom-photon hybrid system, which is analogous to the frequency-bin entanglement between single-photon pulses. We show that such entanglement arises naturally in considering the interaction between a frequency-bin entangled single-photon pulse pair and a single atom coupled to an optical cavity, via straightforward atom-photon phase gate operations. Its anticipated properties and preliminary examples of its potential application in quantum networking are also demonstrated. Moreover, we construct a specific quantum entanglement witness tool to detect such extended frequency-bin entanglement from a reasonably general set of separable states, and prove its capability theoretically. We focus on the energy-time considerations throughout the analysis.

Adaptive capability as indicated by behavioral and physiological responses, plasma HSP70 level, and PBMC HSP70 mRNA expression in Osmanabadi goats subjected to combined (heat and nutritional) stressors.

PubMed

Shilja, Shaji; Sejian, V; Bagath, M; Mech, A; David, C G; Kurien, E K; Varma, Girish; Bhatta, Raghavendra

2016-09-01

A study was conducted to assess the impact of heat and nutritional stress simultaneously on the adaptive capability as indicated by behavioral and physiological responses, plasma heat shock protein 70 (HSP70) level, and peripheral blood mononuclear cells (PBMC) HSP70 gene expression in goats. Twenty-four adult Osmanabadi bucks (average body weight (BW) 16.0 kg) were used in the present study. The bucks were divided into four groups viz., C (n = 6; control), HS (n = 6; heat stress), NS (n = 6; nutritional stress), and CS (n = 6; combined stress). The study was conducted for a period of 45 days. C and HS bucks had ad libitum access to their feed while NS and CS bucks were under restricted feed (30 % intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to solar radiation for 6 h a day between 10:00 a.m. and 4:00 p.m. to induce heat stress. The data was analyzed using repeated measures analysis of variance. The standing time differed significantly (P < 0.01) between ad libitum fed groups (C and HS) and restricted feeding groups (NS and CS). The highest (P < 0.01) lying time was recorded in the CS group while the lowest in the C and HS groups. The highest (P < 0.01) drinking frequency was also recorded in the CS group. Water intake recorded was significantly (P < 0.01) higher in both the HS and CS groups. The highest respiration rate (RR), pulse rate (PR), and rectal temperature (RT) during the afternoon were also recorded in the CS group. Further, skin temperature of the head, flank, and scrotum during the afternoon was also higher (P < 0.01) in the CS group. In addition, both plasma HSP70 concentration and PBMC HSP70 messenger RNA (mRNA) transcript expression were also significantly (P < 0.01) higher in the CS group. It can be concluded from this study that when two stressors occur simultaneously, they may have severe impact on adaptive capabilities of Osmanabadi bucks as compared to that would occur individually. Further, the study indicated that lying time, drinking frequency, RR, RT, plasma HSP70, and PBMC HSP70 gene expression may act as ideal biological markers for assessing the impact of CS on adaptive capabilities in bucks.

SU-D-206-06: Task-Specific Optimization of Scintillator Thickness for CMOS-Detector Based Cone-Beam Breast CT

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

Vedantham, S; Shrestha, S; Shi, L

Purpose: To optimize the cesium iodide (CsI:Tl) scintillator thickness in a complimentary metal-oxide semiconductor (CMOS)-based detector for use in dedicated cone-beam breast CT. Methods: The imaging task considered was the detection of a microcalcification cluster comprising six 220µm diameter calcium carbonate spheres, arranged in the form of a regular pentagon with 2 mm spacing on its sides and a central calcification, similar to that in ACR-recommended mammography accreditation phantom, at a mean glandular dose of 4.5 mGy. Generalized parallel-cascades based linear systems analysis was used to determine Fourier-domain image quality metrics in reconstructed object space, from which the detectability indexmore » inclusive of anatomical noise was determined for a non-prewhitening numerical observer. For 300 projections over 2π, magnification-associated focal-spot blur, Monte Carlo derived x-ray scatter, K-fluorescent emission and reabsorption within CsI:Tl, CsI:Tl quantum efficiency and optical blur, fiberoptic plate transmission efficiency and blur, CMOS quantum efficiency, pixel aperture function and additive noise, and filtered back-projection to isotropic 105µm voxel pitch with bilinear interpolation were modeled. Imaging geometry of a clinical prototype breast CT system, a 60 kV Cu/Al filtered x-ray spectrum from 0.3 mm focal spot incident on a 14 cm diameter semi-ellipsoidal breast were used to determine the detectability index for 300–600 µm thick (75µm increments) CsI:Tl. The CsI:Tl thickness that maximized the detectability index was considered optimal. Results: The limiting resolution (10% modulation transfer function, MTF) progressively decreased with increasing CsI:Tl thickness. The zero-frequency detective quantum efficiency, DQE(0), in projection space increased with increasing CsI:Tl thickness. The maximum detectability index was achieved with 525µm thick CsI:Tl scintillator. Reduced MTF at mid-to-high frequencies for 600µm thick CsI:Tl lowered the detectability index than 525µm CsI:Tl. Conclusion: For the x-ray spectrum and imaging conditions considered, a 525µm thick CsI:Tl scintillator integrated with the CMOS detector is optimal for detecting microcalcification cluster. Funding support: Supported in part by NIH R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or the NCI. Disclosures: SV, GV and AK - Research collaboration, Koning Corp., West Henrietta, NY.« less

Adaptive capability as indicated by behavioral and physiological responses, plasma HSP70 level, and PBMC HSP70 mRNA expression in Osmanabadi goats subjected to combined (heat and nutritional) stressors

NASA Astrophysics Data System (ADS)

Shilja, Shaji; Sejian, V.; Bagath, M.; Mech, A.; David, C. G.; Kurien, E. K.; Varma, Girish; Bhatta, Raghavendra

2016-09-01

A study was conducted to assess the impact of heat and nutritional stress simultaneously on the adaptive capability as indicated by behavioral and physiological responses, plasma heat shock protein 70 (HSP70) level, and peripheral blood mononuclear cells (PBMC) HSP70 gene expression in goats. Twenty-four adult Osmanabadi bucks (average body weight (BW) 16.0 kg) were used in the present study. The bucks were divided into four groups viz., C ( n = 6; control), HS ( n = 6; heat stress), NS ( n = 6; nutritional stress), and CS ( n = 6; combined stress). The study was conducted for a period of 45 days. C and HS bucks had ad libitum access to their feed while NS and CS bucks were under restricted feed (30 % intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to solar radiation for 6 h a day between 10:00 a.m. and 4:00 p.m. to induce heat stress. The data was analyzed using repeated measures analysis of variance. The standing time differed significantly ( P < 0.01) between ad libitum fed groups (C and HS) and restricted feeding groups (NS and CS). The highest ( P < 0.01) lying time was recorded in the CS group while the lowest in the C and HS groups. The highest ( P < 0.01) drinking frequency was also recorded in the CS group. Water intake recorded was significantly ( P < 0.01) higher in both the HS and CS groups. The highest respiration rate (RR), pulse rate (PR), and rectal temperature (RT) during the afternoon were also recorded in the CS group. Further, skin temperature of the head, flank, and scrotum during the afternoon was also higher ( P < 0.01) in the CS group. In addition, both plasma HSP70 concentration and PBMC HSP70 messenger RNA (mRNA) transcript expression were also significantly ( P < 0.01) higher in the CS group. It can be concluded from this study that when two stressors occur simultaneously, they may have severe impact on adaptive capabilities of Osmanabadi bucks as compared to that would occur individually. Further, the study indicated that lying time, drinking frequency, RR, RT, plasma HSP70, and PBMC HSP70 gene expression may act as ideal biological markers for assessing the impact of CS on adaptive capabilities in bucks.

Changes in charge density vs changes in formal oxidation states: The case of Sn halide perovskites and their ordered vacancy analogues

NASA Astrophysics Data System (ADS)

Dalpian, Gustavo M.; Liu, Qihang; Stoumpos, Constantinos C.; Douvalis, Alexios P.; Balasubramanian, Mahalingam; Kanatzidis, Mercouri G.; Zunger, Alex

2017-07-01

Shifting the Fermi energy in solids by doping, defect formation, or gating generally results in changes in the charge density distribution, which reflect the ability of the bonding pattern in solids to adjust to such external perturbations. In the traditional chemistry textbook, such changes are often described by the formal oxidation states (FOS) whereby a single atom type is presumed to absorb the full burden of the perturbation (change in charge) of the whole compound. In the present paper, we analyze the changes in the position-dependence charge density due to shifts of the Fermi energy on a general physical basis, comparing with the view of the FOS picture. We use the halide perovskites CsSn X3 (X =F , Cl, Br, I) as examples for studying the general principle. When the solar absorber CsSn I3 (termed 113) loses 50 % of its Sn atoms, thereby forming the ordered vacancy compound C s2Sn I6 (termed 216), the Sn is said in the FOS picture to change from Sn(II) to Sn(IV). To understand the electronic properties of these two groups we studied the 113 and 216 compound pairs CsSnC l3 and C s2SnC l6 , CsSnB r3 and C s2SnB r6 , and CsSn I3 and C s2Sn I6 , complementing them by CsSn F3 and C s2Sn F6 in the hypothetical cubic structure for completing the chemical trends. These materials were also synthesized by chemical routes and characterized by x-ray diffraction, 119Sn-Mössbauer spectroscopy, and K -edge x-ray absorption spectroscopy. We find that indeed in going from 113 to 216 (equivalent to the introduction of two holes per unit) there is a decrease in the s charge on Sn, in agreement with the FOS picture. However, at the same time, we observe an increase of the p charge via downshift of the otherwise unoccupied p level, an effect that tends to replenish much of the lost s charge. At the end, the change in the charge on the Sn site as a result of adding two holes to the unit cell is rather small. This effect is theoretically explained as a "self-regulating response" [Raebiger, Lany, and Zunger, Nature (London) 453, 763 (2008), 10.1038/nature07009] whereby the system rehybridizes to minimize the effect of the charge perturbation created by vacancy formation. Rather than having a single preselected atom (here Sn) absorb the full brunt of the perturbation producing two holes, we find that the holes are distributed in a complex pattern throughout the octahedral systems of X6 ligands, forming hole orbitals with some specific symmetries. This clarifies the relation between FOS and charge transfer that can be applied to a wide variety of materials.

Temperature Effects of Electric Field on the First Excited State of Strong Coupling Polaron in a CsI Quantum Pseudodot

NASA Astrophysics Data System (ADS)

Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin

2017-03-01

Employing variational method of Pekar type (VMPT), this paper investigates the first-excited state energy (FESE), excitation energy and transition frequency of the strongly-coupled polaron in the CsI quantum pseudodot (QPD) with electric field. The temperature effects on the strong-coupling polaron in electric field are calculated by using the quantum statistical theory (QST). The results from the present investigation show that the FESE, excitation energy and transition frequency increase (decrease) firstly and then at lower (higher) temperature regions. They are decreasing functions of the electric field strength. Supported by the National Natural Science Foundation of China under Grant No. 11464033

Studies on the thermal and electrical properties of polyethylene oxide/polyvinyl alcohol blend by incorporating of Cesium Chloride

NASA Astrophysics Data System (ADS)

Ragab, H. M.

The composites PVA/PEO filled with various concentrations of CsCl samples, which were prepared for using a solvent casting technique and studied via Fourier transform infrared spectroscopy (FTIR), ultraviolet - visible (UV-Vis), X-ray spectroscopy, Scanning electron microscopy (SEM), AC conductivity and dielectric properties to use as sensor in electronic devices. The FTIR indicated the interaction between PVA/PEO and CsCl. From data of UV. Vis. was observed band gap (Eg) reduces with addition CsCl to polymer blend. The XRD shows the degree of crystallinity (χ%) decreasing with increasing concentration of CsCl from 2.93 to 2.45. The SEM of the surface of composite PVA/PEO filled with various concentrations of CsCl in magnification 1500 times its change with compare of pure blend. From TGA was observed improvement in the thermal stability of the samples after addition of CsCl. The AC conductivity rise more rapidly with temperature and associated with activation energy Ea, for conduction and enhanced with increasing both temperature and frequency.

Influence of excitation frequency on the metastable atoms and electron energy distribution function in a capacitively coupled argon discharge

NASA Astrophysics Data System (ADS)

Sharma, S.; Sirse, N.; Turner, M. M.; Ellingboe, A. R.

2018-06-01

One-dimensional particle-in-cell simulation is used to simulate the capacitively coupled argon plasma for a range of excitation frequency from 13.56 MHz to 100 MHz. The argon chemistry set can, selectively, include two metastable levels enabling multi-step ionization and metastable pooling. The results show that the plasma density decreases when metastable atoms are included with higher discrepancy at a higher excitation frequency. The contribution of multistep ionization to the overall density increases with the excitation frequency. The electron temperature increases with the inclusion of metastable atoms and decreases with the excitation frequency. At a lower excitation frequency, the density of Ar** (3p5 4p, 13.1 eV) is higher than that of Ar* (3p5 4s, 11.6 eV), whereas at higher excitation frequencies, the Ar* (3p5 4s, 11.6 eV) is the dominant metastable atom. The metastable and electron temperature profile evolve from a parabolic profile at a lower excitation frequency to a saddle type profile at a higher excitation frequency. With metastable, the electron energy distribution function (EEDF) changes its shape from Druyvesteyn type, at a low excitation frequency, to bi-Maxwellian, at a high frequency plasma excitation; however, a three-temperature EEDF is observed without metastable atoms.

A study of adsorption behavior of human serum albumin and ovalbumin on hydroxyapatite/chitosan composite.

PubMed

Xu, Chao; He, Deliang; Zeng, Liping; Luo, Shenglian

2009-10-15

In situ adsorption of human serum albumin (HSA) and ovalbumin (OVA) was real-time monitored by piezoelectric quartz crystal impedance (PQCI) technique to fully understand the initial cellular response on hydroxyapatite/chitosan (HAP/CS) composite. The PQCI parameters, such as resonant frequency (f), static capacitance (C(s)), and motional resistance (R(m)) were measured for investigating the kinetic adsorption behaviors of both proteins. The change in frequency shifts (Deltaf) depends on the amount of the adsorbed protein, and the change in motional resistance (DeltaR(m)) results from the microporosity variation of HAP/CS coating. The results show that the amount of the absorbed HSA is much greater than that of OVA on HAP/CS coating because of the unique construction of HSA as well as a flexible protein. Furthermore, Deltaf and DeltaR(m) data were fitted according to the kinetic exponential decay equations. It can be seen that there is only one adsorption process for OVA, but the absorption process for HSA is followed by a rearrangement process, and the former process is faster than the rearrangement process. Subsequently, the composite binding with proteins were demonstrated by the Fourier transform infrared (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

JY1 time scale: a new Kalman-filter time scale designed at NIST

NASA Astrophysics Data System (ADS)

Yao, Jian; Parker, Thomas E.; Levine, Judah

2017-11-01

We report on a new Kalman-filter hydrogen-maser time scale (i.e. JY1 time scale) designed at the National Institute of Standards and Technology (NIST). The JY1 time scale is composed of a few hydrogen masers and a commercial Cs clock. The Cs clock is used as a reference clock to ease operations with existing data. Unlike other time scales, the JY1 time scale uses three basic time-scale equations, instead of only one equation. Also, this time scale can detect a clock error (i.e. time error, frequency error, or frequency drift error) automatically. These features make the JY1 time scale stiff and less likely to be affected by an abnormal clock. Tests show that the JY1 time scale deviates from the UTC by less than  ±5 ns for ~100 d, when the time scale is initially aligned to the UTC and then is completely free running. Once the time scale is steered to a Cs fountain, it can maintain the time with little error even if the Cs fountain stops working for tens of days. This can be helpful when we do not have a continuously operated fountain or when the continuously operated fountain accidentally stops, or when optical clocks run occasionally.

Orientation observed by Zeeman spectra of dissociated atoms and the interference in photoexcitations

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

Kimura, Yasuyuki; Kasahara, Shunji; Kato, Hajime

2003-06-01

In a magnetic field, the wave number of a pump laser light polarized along the field was fixed to the isolated Cs{sub 2}D {sup 1}{sigma}{sub u}{sup +}(v=46, J=54)(leftarrow)X {sup 1}{sigma}{sub g}{sup +}(v=0, J=55) line, and the excitation spectrum of the dissociated Cs(6p {sup 2}P{sub 3/2}) atoms was measured by scanning the wave number of a probe laser light polarized perpendicular to the field. The population of each sublevel 6p {sup 2}P{sub 3/2,m{sub j}} of the dissociated atoms was determined from the line intensities in the m{sub j}-resolved excitation spectrum. The unequal population between the 6p {sup 2}P{sub 3/2,+verticalbarm{sub j}}{sub verticalbar}more » and 6p {sup 2}P{sub 3/2,-verticalbarm{sub j}}{sub verticalbar} levels (atomic orientation) was observed and it was enhanced as the magnetic-field strength was increased. The atomic orientation is shown to be induced by the interference between the indirect predissociation, which occurs by a combination of the spin-orbit coupling of the D {sup 1}{sigma}{sub u}{sup +} state with the (2){sup 3}{pi}{sub 0u} state and the L-uncoupling and Zeeman interactions between the (2){sup 3}{pi}{sub 0u} and dissociative (2){sup 3}{sigma}{sub u}{sup +} states, and the dissociation following a direct excitation to the (2){sup 3}{sigma}{sub u}{sup +} state, which is allowed by spin-orbit coupling of the (2){sup 3}{sigma}{sub u}{sup +} state with the B {sup 1}{pi}{sub u} state. It is demonstrated that the atomic orientation is produced by the photodissociation in the presence of an external magnetic field even when all degenerated molecular M=J,...,0,...,-J sublevels are excited by a light polarized linearly along the field.« less

Pavlovian contingencies and temporal information.

PubMed

Balsam, Peter D; Fairhurst, Stephen; Gallistel, Charles R

2006-07-01

The effects of altering the contingency between the conditioned stimulus (CS) and the unconditioned stimulus (US) on the acquisition of autoshaped responding was investigated by changing the frequency of unsignaled USs during the intertrial interval. The addition of the unsignaled USs had an effect on acquisition speed comparable with that of massing trials. The effects of these manipulations can be understood in terms of their effect on the amount of information (number of bits) that the average CS conveys to the subject about the timing of the next US. The number of reinforced CSs prior to acquisition is inversely related to the information content of the CS.

Participation in proficiency test for tritium strontium and caesium isotopes in seawater 2015 (IAEA-RML-2015-02)

NASA Astrophysics Data System (ADS)

Visetpotjanakit, S.; Kaewpaluek, S.

2017-06-01

A proficiency test (PT) exercise has proposed by the International Atomic Energy Agency (IAEA) in the frame of the IAEA Technical Cooperation project RAS/7/021 “Marine benchmark study on the possible impact of the Fukushima radioactive releases in the Asia-Pacific Region for Caesium Determination in Sea Water” since 2012. In 2015 the exercise was referred to Proficiency Test for Tritium, Strontium and Caesium Isotopes in Seawater 2015 (IAEA-RML-2015-02) to analyse3H, 134Cs, 137Cs and90Sr in a seawater sample. OAP was one of the 17 laboratories from 15 countries from Asia-Pacific Region who joined the PT exercise. The aim of our participation was to validate our analytical performance for the accurate determination of radionuclides in seawater by developed methods of radiochemical analysis. OAP submitted results determining the concentration for the three elements i.e. 134Cs, 137Cs and90Sr in seawater to the IAEA. A critical review was made to check suitability of our methodology and the criteria for the accuracy, precision and trueness of our data. The results of both 134Cs and 137Cs passed all criteria which were assigned “Accepted” statuses. Whereas 90Sr analysis did not pass the accuracy test therefore it was considered as “Not accepted” Our results and all other participant results with critical comments were published in the IAEA proficiency test report.

Results from the 2010 INMM International Containment and Surveillance Workshop focused on Concepts for the 21st Century

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

Pickett, Chris A; Tolk, Keith M; Keel, Frances M

2010-01-01

The Institute of Nuclear Materials Management (INMM) held an International Workshop, 'Containment & Surveillance (C/S): Concepts for the 21st Century,' June 6-11, 2010, at the Oak National Laboratory, in Oak Ridge, Tennessee. The National Nuclear Security Administration (NNSA) Office of Nonproliferation Research and Development and Office of Nonproliferation and International Security sponsored the event. The workshop focused on determining concepts and needs for 21st century containment and surveillance (C/S) systems that support International Atomic Energy Agency (IAEA) safeguards and future arms control agreements. Panel discussions by subject matter experts and international practitioners addressed daily topical themes encompassing the following areasmore » of C/S: authentication; tagging, sealing, and containment verification; and surveillance systems. Each panel discussion was followed by a question-and-answer session with the audience and an afternoon breakout session. The facilitated breakout sessions were used to compile information and determine future needs. Individuals attending the workshop included C/S experts and practitioners; IAEA and arms control inspectors; technology providers; vendors; students; and individuals with an interest in, or desire to learn about, future C/S system needs. The primary goal of the workshop was to produce a document that details the future research and development needs for C/S systems that support nuclear safeguards and arms control missions. This talk will present a compilation of the information obtained from breakout sessions at the workshop.« less

Wound healing and antibacterial activities of chondroitin sulfate- and acharan sulfate-reduced silver nanoparticles

NASA Astrophysics Data System (ADS)

Im, A.-Rang; Kim, Jee Young; Kim, Hyun-Seok; Cho, Seonho; Park, Youmie; Kim, Yeong Shik

2013-10-01

For topical applications in wound healing, silver nanoparticles (AgNPs) have attracted much attention as antibacterial agents. Herein, we describe a green-synthetic route for the production of biocompatible and crystalline AgNPs using two glycosaminoglycans, chondroitin sulfate (CS) and acharan sulfate (AS), as reducing agents. The synthetic approach avoids the use of toxic chemicals, and the yield of AgNPs formation is found to be 98.1% and 91.1% for the chondroitin sulfate-reduced silver nanoparticles (CS-AgNPs) and the acharan sulfate-reduced silver nanoparticles (AS-AgNPs), respectively. Nanoparticles with mostly spherical and amorphous shapes were observed, with an average diameter of 6.16 ± 2.26 nm for CS-AgNPs and 5.79 ± 3.10 nm for AS-AgNPs. Images of the CS-AgNPs obtained from atomic force microscopy revealed the self-assembled structure of CS was similar to a densely packed woven mat with AgNPs sprinkled on the CS. These nanoparticles were stable under cell culture conditions without any noticeable aggregation. An approximately 128-fold enhancement of the antibacterial activities of the AgNPs was observed against Enterobacter cloacae and Escherichia coli when compared to CS and AS alone. In addition, an in vivo animal model of wound healing activity was tested using mice that were subjected to deep incision wounds. In comparison to the controls, the ointments containing CS-AgNPs and AS-AgNPs stimulated wound closure under histological examination and accelerated the deposition of granulation tissue and collagen in the wound area. The wound healing activity of the ointments containing CS-AgNPs and AS-AgNPs are comparable to that of a commercial formulation of silver sulfadiazine even though the newly prepared ointments contain a lower silver concentration. Therefore, the newly prepared AgNPs demonstrate potential for use as an attractive biocompatible nanocomposite for topical applications in the treatment of wounds.

Utilization of the Arkansas Prescription Monitoring Program to combat prescription drug abuse

PubMed Central

Rittenhouse, Rebecca; Wei, Feifei; Robertson, Denise; Ryan, Kevin

2015-01-01

Objective The Arkansas Prescription Monitoring Program (AR PMP) was implemented in 2013 to combat prescription drug abuse. All enrollees were invited to participate in a user survey available in February 2014, to identify makeup of users, utilization of the program, and changes made to health care practices after implementation of the program. Methods Of the 3694 individual enrollees invited to participate, 1541 (41.7%) completed the survey. Data collected were analyzed to identify changes in health care practices by program frequency of use and user profession. Results Medical doctors, advanced practice nurses, and pharmacists are the professions who use the program most frequently. Daily AR PMP users are considerably more likely than infrequent users to be prompted to access the program by the involvement of a controlled substance (CS) prescription or by office/facility policy requirements. Increased frequency of use of the AR PMP results in positive impacts on CS prescribing and dispensing practices. Conclusion Compelling more users of the AR PMP to be prompted to access the program by the involvement of a CS prescription or by requirements per office/facility policy may increase frequency of use of the program and thereby changes in health care practices to combat prescription drug abuse. PMID:26191489

Spectral assignment and orientational analysis in a vibrational sum frequency generation study of DPPC monolayers at the air/water interface

NASA Astrophysics Data System (ADS)

Feng, Rong-Juan; Li, Xia; Zhang, Zhen; Lu, Zhou; Guo, Yuan

2016-12-01

The interfacial behavior of the benchmark zwitterionic phospholipid molecule dipalmitoylphosphatidylcholine (DPPC) has been extensively investigated by surface-selective vibrational sum frequency generation spectroscopy (VSFG). However, there is still a lack of agreement between various orientational measurements of phospholipid monolayers at the air/water interface, mainly because of the difficulty in assigning congested VSFG features. In this study, polarization-dependent VSFG measurements reveal a frequency shift between the in-plane and out-of-plane antisymmetric stretching modes of the terminal methyl groups in the DPPC alkyl tails, favoring the model of Cs local symmetry rather than the previously assumed C3v symmetry. Further VSFG experiments of isotopically labeled DPPC successfully capture the vibrational signatures of the glycerol backbone. With the newly derived VSFG polarization selection rules for Cs symmetry and the refreshed spectral assignments, the average tilt angles of the alkyl tail groups, choline headgroup, and glycerol backbone of DPPC molecules can all be determined, showing the powerful capability of VSFG spectroscopy in revealing the structural details at interfaces. The VSFG polarization dependence rules and the orientational analysis procedures developed for Cs symmetry in this work are applicable to other bulky molecules in which the methyl group cannot freely rotate, and they therefore have general applications in future VSFG studies.

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

Oh, E.; Horne, R. A.; Sackett, C. A., E-mail: sackett@virginia.edu

Atom interferometry experiments rely on the ability to obtain a stable signal that corresponds to an atomic phase. For interferometers that use laser beams to manipulate the atoms, noise in the lasers can lead to errors in the atomic measurement. In particular, it is often necessary to actively stabilize the optical phase between two frequency components of the beams. Typically this is achieved using a time-domain measurement of a beat note between the two frequencies. This becomes challenging when the frequency difference is small and the phase measurement must be made quickly. The method presented here instead uses a spatialmore » interference detection to rapidly measure the optical phase for arbitrary frequency differences. A feedback system operating at a bandwidth of about 10 MHz could then correct the phase in about 3 μs. This time is short enough that the phase correction could be applied at the start of a laser pulse without appreciably degrading the fidelity of the atom interferometer operation. The phase stabilization system was demonstrated in a simple atom interferometer measurement of the {sup 87}Rb recoil frequency.« less

Characterization of aromatic organosulfur model compounds relevant to fossil fuels by using atmospheric pressure chemical ionization with CS2 and high-resolution tandem mass spectrometry.

PubMed

Tang, Weijuan; Sheng, Huaming; Jin, Chunfen; Riedeman, James S; Kenttämaa, Hilkka I

2016-04-15

The chemistry of desulfurization involved in processing crude oil is greatly dependent on the forms of sulfur in the oil. Sulfur exists in different chemical bonding environments in fossil fuels, including those in thiophenes and benzothiophenes, thiols, sulfides, and disulfides. In this study, the fragmentation behavior of the molecular ions of 17 aromatic organosulfur compounds with various functionalities was systematically investigated by using high-resolution tandem mass spectrometry. Multiple-stage tandem mass spectrometric experiments were carried out using a linear quadrupole ion trap (LQIT) equipped with an atmospheric pressure chemical ionization (APCI) source. (+)APCI/CS2 was used to generate stable dominant molecular ions for all the compounds studied except for three sulfides that also showed abundant fragment ions. The LQIT coupled with an orbitrap mass spectrometer was used for elemental composition analysis, which facilitated the identification of the neutral molecules lost during fragmentation. The characteristic fragment ions generated in MS(2) and MS(3) experiments provide clues for the chemical bonding environment of sulfur atoms in the examined compounds. Upon collision-induced dissociation (CID), the molecular ions can lose the sulfur atom in a variety of ways, including as S (32 Da), HS(•) (33 Da), H2 S (34 Da), CS (44 Da), (•) CHS (45 Da) and CH2 S (46 Da). These neutral fragments are not only indicative of the presence of sulfur, but also of the type of sulfur present in the compound. Generally, losses of HS(•) and H2 S were found to be associated with compounds containing saturated sulfur functionalities, while losses of S, CS and (•) CHS were more common for heteroaromatic sulfur compounds. High-resolution tandem mass spectrometry with APCI/CS2 ionization is a viable approach to determining the types of organosulfur compounds. It can potentially be applied to analysis of complex mixtures, which is beneficial to improving the desulfurization process of fossil fuels. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The Application of High-Resolution Electron Microscopy to Problems in Solid State Chemistry: The Exploits of a Peeping TEM.

ERIC Educational Resources Information Center

Eyring, LeRoy

1980-01-01

Describes methods for using the high-resolution electron microscope in conjunction with other tools to reveal the identity and environment of atoms. Problems discussed include the ultimate structure of real crystalline solids including defect structure and the mechanisms of chemical reactions. (CS)

Mass attenuation coefficient of tannin-added Rhizophora spp. particleboards at 16.59-25.56 keV photons, and 137Cs and 60Co gamma energies.

PubMed

Yusof, Mohd Fahmi Mohd; Hamid, Puteri Nor Khatijah Abd; Tajuddin, Abd Aziz; Hashim, Rokiah; Bauk, Sabar; Isa, Norriza Mohd; Isa, Muhammad Jamal Md

2017-09-01

The aim of this study was to determine the suitability of tannin-added Rhizophora spp. particleboards as phantom materials in the application of low- and high-energy photons. The tannin-added Rhizophora spp. particleboards and density plug phantoms were created with a target density of 1.0 g/cm 3 . The elemental composition and effective atomic number of the particleboards were measured using energy dispersive X-ray analysis. The mass attenuation coefficient of the particleboards for low-energy photons were measured using the attenuation of X-ray fluorescence. The mass attenuation coefficients of high-energy photons were measured using the attenuation of 137 Cs and 60 Co gamma energies. The results were compared to the calculated value of water using XCOM calculations. The results showed that the effective atomic number and mass attenuation coefficients of tannin-added Rhizophora spp. particleboards were similar to those of water, indicating the suitability of tannin-added Rhizophora spp. particleboards as phantom materials for low- and high-energy photons.

Microwave Spectroscopic Investigations of the C-H\\cdotsπ Containing Complexes CH_2F_2\\cdotsPROPYNE and CH_2ClF\\cdotsPROPYNE

NASA Astrophysics Data System (ADS)

Peebles, Rebecca A.; Peebles, Sean A.; Christenholz, Cori L.; Ernst, Anthony A.; Dhahir, Yasser J.

2013-06-01

The spectra of the CH_2F_2\\cdotspropyne and CH_2ClF\\cdotspropyne complexes have been studied by chirped-pulse and resonant cavity Fourier-transform microwave spectroscopy and by ab initio calculations at the MP2/6-311++G(2d,2p) level. Both complexes contain C-H\\cdotsπ contacts, with the halogen atoms angled towards the methyl group end of the propyne. While CH_2F_2\\cdotspropyne has C_s symmetry, CH_2ClF\\cdotspropyne has C_1 symmetry, with the fluorine and chlorine atoms straddling the propyne. Investigation of four single ^{13}C and the DC≡CCH_3 isotopologues in CH_2F_2\\cdotspropyne has allowed a detailed structural determination, while only the ^{35}Cl and ^{37}Cl isotopologues have so far been assigned for CH_2ClF\\cdotspropyne. Experimental data will be compared with ab initio results and with the analogous acetylene complexes, both of which have C_s symmetry structures, with double C-H\\cdotsπ interactions.

The crystal structures of potassium and cesium trivanadates

USGS Publications Warehouse

Evans, H.T.; Block, S.

1966-01-01

Potassium and cesium trivanadates are monoclinic and isomorphous, space group P21/m, with the following dimensions (Z = 2): KV3O8, a = 7.640 A, b = 8.380 A, c = 4.979 A, ??= 96?? 57???; CsV3O8, a = 8.176 A, b = 8.519 A, c = 4.988 A, ?? = 95?? 32???. The crystal structure of KV3O8 has been determined from hk0, 0kl, and h0l Weissenberg data with an R factor of 0.15. The structure of CsV3O8 has been refined with 1273 hkl Weissenberg data to an R factor of 0.089. The structures consist of corrugated sheets based on a linkage of distorted VO6, octahedra. Two of the vanadium atoms lie in double, square-pyramid groups V2O8, which are linked through opposite basal corners into chains along the b axis. The chains are joined laterally along the c axis into sheets by the third vanadium atom in VO groups, also forming part of a square-pyramid coordination. Various aspects of these structures are compared with other known oxovanadate structures.

Coherent states: a contemporary panorama Coherent states: a contemporary panorama

NASA Astrophysics Data System (ADS)

Twareque Ali, S.; Antoine, Jean-Pierre; Bagarello, Fabio; Gazeau, Jean-Pierre

2012-06-01

Coherent states (CS) of the harmonic oscillator (also called canonical CS) were introduced in 1926 by Schrödinger in answer to a remark by Lorentz on the classical interpretation of the wave function. They were rediscovered in the early 1960s, first (somewhat implicitly) by Klauder in the context of a novel representation of quantum states, then by Glauber and Sudarshan for the description of coherence in lasers. Since then, CS have grown into an extremely rich domain that pervades almost every corner of physics and have also led to the development of several flourishing topics in mathematics. Along the way, a number of review articles have appeared in the literature, devoted to CS, notably the 1985 reprint volume of Klauder and Skagerstam [1], the 1990 review paper by Zhang et al [2], the 1993 Oak Ridge Conference [3] and the 1995 review paper by Ali et al [4]. Textbooks also have been published, among which one might mention the ground breaking text of Perelomov [5] focusing on the group-theoretical aspects, that of Ali et al [6]1 analyzing systematically the mathematical structure beyond the group-theoretical approach and also the relation to wavelet analysis, that of Dodonov and Man'ko [7] mostly devoted to quantum optics, that of Gazeau [8] more oriented towards the physical, probabilistic and quantization aspects, and finally the very recent one by Combescure and Robert [9]. In retrospect, one can see that the development of CS has gone through a two-phase transition. First, the (simultaneous) discovery in 1972 by Gilmore and Perelomov that CS were rooted in group theory, then the realization that CS can be defined in a purely algebraic way, as an eigenvalue problem or by a series expansion (Malkin and Man'ko 1969, Barut and Girardello 1971, Gazeau and Klauder 1999; references to the original articles may be found in the textbooks quoted above). Both facts resulted in an explosive expansion of the CS literature. We thought, therefore, that the time was ripe to devote a special issue of Journal of Physics A: Mathematical and Theoretical to CS. However, because of limitations of space and time, it would have been impossible to get a fully representative cross-section of papers, covering all the different facets of the subject. Consequently, we have selected 37 articles, including some by a few of the originators of the field. We thank all the authors for submitting their up-to-date thoughts on this fascinating subject. The contents of this special issue are subdivided into five categories: (1) review papers; (2) physics-oriented CS; (3) physics and quantum information; (4) mathematics, general topics; and (5) mathematics, particular problems. (1) Review papers We start with five review papers. The first paper, by Klauder, surveys the many possible applications of affine variables, both in classical and quantum physics. The second, by Sanders, proposes a grand tour of entangled CS, which are present in many fields, such as quantum optics, quantum information processing, etc. The next paper, by Rowe, surveys the field of vector CS and the attendant group representation problems (including induced representations). Then Oriti et al describe a particular class of CS relevant to (loop) quantum gravity. Finally, Combescure and Robert present a comprehensive review of fermionic CS, including all mathematical details. (2) Physics-oriented CS The six contributions in this section deal with specific physical problems: (i) Dajka-Luczka study Gazeau-Klauder cat states associated with a nonlinear Kerr oscillator, instead of the usual canonical CS leading to Schrödinger cat states; (ii) Angelova et al discuss squeezed CS associated with a 1D Morse potential, used in molecular physics; (iii) Bagrov et al study CS in a magnetic solenoid field and prove their completeness; (iv) Blasone-Jizba treat Nambu-Goldstone dynamics in spontaneously broken symmetries, using CS functional integrals; (v) Calixto et al describe accelerated relativistic particles in the context of spontaneous breakdown of conformal SU(2,2) symmetry, using SU(2,2) CS; and (vi) Mortazavi-Tavassoly study f-deformed charge CS and their physical properties (nonclassical features, sub-Poissonian statistical behavior, etc). (3) Physics and quantum information The second group of physically related CS contains four contributions with a distinct quantum information theoretic flavor. First, Thilagam describes the dynamical behavior of entanglement of a pair of qubits (excitons), using a CS basis. Next, Lavoie-de Guise study SU(3) intelligent states (i.e., minimal uncertainty states), of interest in the quantum information community. Then Muñoz constructs discrete CS for n qubits. Finally, Wagner-Kendon explore the continuous variable Deutsch-Jozsa algorithm known in quantum computing in a discrete formulation. (4) Mathematics, general topics In this subgroup, there are eight papers dealing with general properties of CS, independently of any particular system or application. A whole series discusses the interaction between CS and various mathematical objects: pseudodifferential operators and Weyl calculus (Unterberger); induced representations of the affine group and intertwining operators (Elmabrok-Hutnik) measure-free CS and reproducing kernels (Horzela-Szafraniec) extremal POV measures (Heinosaari-Pellonpää) Hilbert W*-modules (Bhattacharyya-Roy) Toeplitz operators (Hutníková-Hutník) and operator localization and homogeneous structure of nilpotent Lie groups (Kisil). In addition, Balazs et al consider multipliers for continuous frames, including CS or wavelet frames. (5) Mathematics, particular problems The second group of mathematically oriented papers contains 14 contributions, devoted to CS in particular systems. We start with a paper by Gilmore, which explores the (sometimes chaotic) evolution of atomic CS under a time-periodic driving field, using sphere maps S2 → S2. Next, we include a paper on CS on the 2-sphere in a magnetic field (Hall-Mitchell) a paper on CS for a quantum particle on a Möbius strip (Cirilo-Lombardo) a discussion of quantization on the circle (Chadzitaskos et al); SUSY CS for Pöschl-Teller potentials (Bergeron et al); generalized Bargmann functions and von Neumann lattices (Vourdas et al); partial reconstruction for a finite CS system, using the Fock-Bargmann representation (Calixto et al); phase operators for SU(3) irreps, thus for finite quantum systems (de Guise); semiclassical CS in periodic potentials (Carles-Sparber) complexified CS with non-Hermitian Hamiltonians (Graefe-Schubert) minimal uncertainty states in the context of (semisimple) group representation theory (Oszmaniec); localization operators in the time-frequency domain, i.e., in Gabor analysis (Muzhikyan-Avanesyan) and, finally, two papers about fermionic CS (Daoud-Kibler and Trifonov). This brief description illustrates perfectly the extreme versatility of the CS concept. As already stressed, coherent states constitute nowadays a flourishing research topic, with applications to a wide spectrum of domains. Indeed, CS are everywhere in physics: condensed matter physics, atomic physics, nuclear and particle physics, quantum optics, dynamics—both quantum and classical potentials—quantum gravity, quantization and quantum information theory. On the other hand, CS have grown into a fully-fledged domain in mathematics, incorporating many tools such as group representations, POV measures, frames, holomorphic functions, orthogonal polynomials and so on. Interestingly enough, the majority of contributions to this special issue (22 out of 37) are mathematically minded, demonstrating the widespread interest CS have generated in various areas of mathematics. A third field related to CS (but almost not represented in the present collection) is signal processing. Indeed both Gabor analysis and wavelet analysis derive in the first place from CS theory, namely, CS associated to the Weyl-Heisenberg and the ax + b group, respectively. Here too, a tremendous development has taken place in recent years, another testimony to the richness of the notion of CS. We leave it to the jury of public opinion to judge whether the call for a special issue of the journal, devoted to coherent states, has been justified. References [1] Klauder J R and Skagerstam B S 1985 Coherent States—Applications in Physics and Mathematical Physics (Singapore: World Scientific) [2] Zhang W-M, Feng D H and Gilmore R 1990 Coherent states: theory and some applications Rev. Mod. Phys. 62 867-927 [3] Feng D H, Klauder J R and Strayer M (ed) 1994 Coherent States: Past, Present and Future (Singapore: World Scientific) [4] Ali S T, Antoine J-P, Gazeau J-P and Mueller U A 1995 Coherent states and their generalizations: a mathematical overview Rev. Math. Phys. 7 1013-104 [5] Perelomov A M 1986 Generalized Coherent States and Their Applications (New York: Springer) [6] Ali S T, Antoine J-P and Gazeau J-P 2000 Coherent States, Wavelets and Their Generalizations (New York: Springer) [7] Dodonov V V and Man'ko V I (ed) 2003 Theory of Nonclassical States of Light (London: Taylor & Francis) [8] Gazeau J-P 2009 Coherent States in Quantum Physics (Berlin: Wiley) [9] Combescure M and Robert D 2012 Coherent States and Applications in Mathematical Physics (New York: Springer) 1 A second edition of that volume is in preparation.

X-ray spectroscopy with silicon pin and avalanche photo diodes

NASA Technical Reports Server (NTRS)

Desai, U. D.

1992-01-01

Results of an evaluation of silicon P-Intrinsic-N (PIN) photodiodes and Avalanche Photodiodes (APD) for the direct detection of soft x rays from 1 to 20 keV and for the detection of scintillation light output from CsI(TI) for higher x ray energies (30 to 1000 keV) are presented. About one keV resolution was achieved at room temperature for both the PIN and APD detectors for soft x rays (1 to 20 keV). Commercially available, low power (18 mV), low noise, hybrid preamplifiers, were used. These photodiodes were also coupled to CsI(TI) scintillator and obtained about 6 resolution at 662 keV. The photodiode frequency response matches well with the emission spectrum of the CsI(TI) scintillator providing good spectral resolution and a higher signal than NaI(TI) when viewed by conventional photomultipliers. A PIN-CsI(TI) combination provides a low energy threshold of around 60 keV while for the APD-CsI(TI) it is 15 keV.

Differences in Psychiatric Problems and Criminality Between Individuals Treated With Central Stimulants Before and After Adulthood.

PubMed

Rasmussen, Kirsten; Palmstierna, Tom; Levander, Sten

2015-03-20

The evidence for central stimulant (CS) treatment in ADHD is strong in some respects but not with respect to unselected clinical material and long-term effects over the life course cycle. The objective of this study was to explore differences in vocational, psychiatric, and social impairment, including crime and substance abuse, among adults with ADHD, treated or not, with CS drugs before age 18. A clinical population of men (N = 343) and women (N = 129) seeking CS treatment as adults was assessed within a specific program for such treatment. Clinical information and data collected by structured instruments were available. Previously CS-treated persons had a lower frequency of problems (alcohol/substance abuse, criminality), and of certain psychiatric disorders (depressive, anxiety and personality ones). Most differences were substantial. The study supports the assumption that CS treatment during childhood/adolescence offers some protection against the development of a range of problems known to characterize adult ADHD patients. © 2015 SAGE Publications.

Fast arsenic speciation in water by on-site solid phase extraction and high-resolution continuum source graphite furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Mihucz, Victor G.; Bencs, László; Koncz, Kornél; Tatár, Enikő; Weiszburg, Tamás; Záray, Gyula

2017-02-01

A method of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS), combined with on-site separation/solid phase extraction (SPE) has been developed for the speciation of inorganic As (iAs) in geothermal and drinking water samples. The HR-CS-GFAAS calibration curves were linear up to 200 μg/L As, but using second order polynomial fitting, accurate calibration could be performed up to 500 μg/L. It has been demonstrated that sample pH should not be higher than 8 for an accurate speciation of As(V) with a recovery of ≈ 95%. Geothermal water had fairly high salt content (≈ 2200 mg/L) due to the presence of chlorides and sulfates at mg/L levels. Therefore, a two-fold dilution of these types of samples before SPE is recommended, especially, for total As determinations, when the As concentration is as high as 400 μg/L. For drinking water, sampled from public wells with records of As concentrations higher than the 10 μg/L in the past, the reduction of As contamination below the WHO's health limit value could be observed. However, the electrical conductivity was close to 2500 μS/cm, i.e., the guideline limit for drinking water, which was due to their higher chloride content. The proposed fit-for-purpose SPE-HR-CS-GFAAS method could be a candidate for screening drinking water quality.

Improved Limits on Axionlike-Particle-Mediated P, T-Violating Interactions between Electrons and Nucleons from Electric Dipole Moments of Atoms and Molecules.

PubMed

Stadnik, Y V; Dzuba, V A; Flambaum, V V

2018-01-05

In the presence of P, T-violating interactions, the exchange of axionlike particles between electrons and nucleons in atoms and molecules induces electric dipole moments (EDMs) of atoms and molecules. We perform calculations of such axion-exchange-induced atomic EDMs using the relativistic Hartree-Fock-Dirac method including electron core polarization corrections. We present analytical estimates to explain the dependence of these induced atomic EDMs on the axion mass and atomic parameters. From the experimental bounds on the EDMs of atoms and molecules, including ^{133}Cs, ^{205}Tl, ^{129}Xe, ^{199}Hg, ^{171}Yb^{19}F, ^{180}Hf^{19}F^{+}, and ^{232}Th^{16}O, we constrain the P, T-violating scalar-pseudoscalar nucleon-electron and electron-electron interactions mediated by a generic axionlike particle of arbitrary mass. Our limits improve on existing laboratory bounds from other experiments by many orders of magnitude for m_{a}≳10^{-2}  eV. We also place constraints on CP violation in certain types of relaxion models.

Quantum confinement and dielectric profiles of colloidal nanoplatelets of halide inorganic and hybrid organic-inorganic perovskites

NASA Astrophysics Data System (ADS)

Sapori, Daniel; Kepenekian, Mikaël; Pedesseau, Laurent; Katan, Claudine; Even, Jacky

2016-03-01

Quantum confinement as well as high frequency ε∞ and static εs dielectric profiles are described for nanoplatelets of halide inorganic perovskites CsPbX3 (X = I, Br, Cl) and hybrid organic-inorganic perovskites (HOP) in two-dimensional (2D) and three-dimensional (3D) structures. 3D HOP are currently being sought for their impressive photovoltaic ability. Prior to this sudden popularity, 2D HOP materials were driving intense activity in the field of optoelectronics. Such developments have been enriched by the recent ability to synthesize colloidal nanostructures of controlled sizes of 2D and 3D HOP. This raises the need to achieve a thorough description of the electronic structure and dielectric properties of these systems. In this work, we go beyond the abrupt dielectric interface model and reach the atomic scale description. We examine the influence of the nature of the halogen and of the cation on the band structure and dielectric constants. Similarly, we survey the effect of dimensionality and shape of the perovskite. In agreement with recent experimental results, we show an increase of the band gap and a decrease of ε∞ when the size of a nanoplatelet reduces. By inspecting 2D HOP, we find that it cannot be described as a simple superposition of independent inorganic and organic layers. Finally, the dramatic impact of ionic contributions on the dielectric constant εs is analysed.Quantum confinement as well as high frequency ε∞ and static εs dielectric profiles are described for nanoplatelets of halide inorganic perovskites CsPbX3 (X = I, Br, Cl) and hybrid organic-inorganic perovskites (HOP) in two-dimensional (2D) and three-dimensional (3D) structures. 3D HOP are currently being sought for their impressive photovoltaic ability. Prior to this sudden popularity, 2D HOP materials were driving intense activity in the field of optoelectronics. Such developments have been enriched by the recent ability to synthesize colloidal nanostructures of controlled sizes of 2D and 3D HOP. This raises the need to achieve a thorough description of the electronic structure and dielectric properties of these systems. In this work, we go beyond the abrupt dielectric interface model and reach the atomic scale description. We examine the influence of the nature of the halogen and of the cation on the band structure and dielectric constants. Similarly, we survey the effect of dimensionality and shape of the perovskite. In agreement with recent experimental results, we show an increase of the band gap and a decrease of ε∞ when the size of a nanoplatelet reduces. By inspecting 2D HOP, we find that it cannot be described as a simple superposition of independent inorganic and organic layers. Finally, the dramatic impact of ionic contributions on the dielectric constant εs is analysed. Electronic supplementary information (ESI) available: Complementary results on the electronic structure and dielectric constants of CsPbX3 and CH3NH3PbX3 (X = I, Br, Cl). See DOI: 10.1039/c5nr07175e

A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz.

PubMed

Keaveney, James; Hamlyn, William J; Adams, Charles S; Hughes, Ifan G

2016-09-01

We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

Pedunculopontine tegmental nucleus lesions impair stimulus--reward learning in autoshaping and conditioned reinforcement paradigms.

PubMed

Inglis, W L; Olmstead, M C; Robbins, T W

2000-04-01

The role of the pedunculopontine tegmental nucleus (PPTg) in stimulus-reward learning was assessed by testing the effects of PPTg lesions on performance in visual autoshaping and conditioned reinforcement (CRf) paradigms. Rats with PPTg lesions were unable to learn an association between a conditioned stimulus (CS) and a primary reward in either paradigm. In the autoshaping experiment, PPTg-lesioned rats approached the CS+ and CS- with equal frequency, and the latencies to respond to the two stimuli did not differ. PPTg lesions also disrupted discriminated approaches to an appetitive CS in the CRf paradigm and completely abolished the acquisition of responding with CRf. These data are discussed in the context of a possible cognitive function of the PPTg, particularly in terms of lesion-induced disruptions of attentional processes that are mediated by the thalamus.

Rococo study: a real-world evaluation of an over-the-counter medicine in acute cough (a multicentre, randomised, controlled study)

PubMed Central

Birring, S S; Brew, J; Kilbourn, A; Edwards, V; Wilson, R; Morice, A H

2017-01-01

Objectives To investigate the efficacy and safety of CS1002, an over-the-counter cough treatment containing diphenhydramine, ammonium chloride and levomenthol in a cocoa-based demulcent. Design A multicentre, randomised, parallel group, controlled, single-blinded study in participants with acute upper respiratory tract infection-associated cough. Setting 4 general practitioner (GP) surgeries and 14 pharmacies in the UK. Participants Participants aged ≥18 years who self-referred to a GP or pharmacist with acute cough of <7 days' duration. Participant inclusion criterion was cough severity ≥60 mm on a 0–100 mm visual analogue scale (VAS). Exclusion criteria included current smokers or history of smoking within the past 12 months (including e-cigarettes). 163 participants were randomised to the study (mean participant age 38 years, 57% females). Interventions Participants were randomised to CS1002 (Unicough) or simple linctus (SL), a widely used cough treatment, and treatment duration was 7 days or until resolution of cough. Main outcome measures The primary analysis was intention-to-treat (157 participants) and comprised cough severity assessed using a VAS after 3 days' treatment (prespecified primary end point at day 4). Cough frequency, sleep disruption, health status (Leicester Cough Questionnaire (LCQ-acute)) and cough resolution were also assessed. Results At day 4 (primary end point), the adjusted mean difference (95% CI) in cough severity VAS between CS1002 and SL was −5.9 mm (−14.4 to 2.7), p=0.18. At the end of the study (day 7) the mean difference in cough severity VAS was −4.2 mm (−12.2 to 3.9), p=0.31. CS1002 was associated with a greater reduction in cough sleep disruption (mean difference −11.6 mm (−20.6 to 2.7), p=0.01) and cough frequency (mean difference −8.1 mm (−16.2 to 0.1), p=0.05) compared with SL. There was greater improvement in LCQ-acute quality of life scores with CS1002 compared with SL: mean difference (95% CI) 1.2 (0.05 to 2.36), p=0.04 after 5 days' treatment. More participants prematurely stopped treatment due to cough improvement in the CS1002 group (24.4%) compared with SL (10.7%; p=0.02). Adverse events (AEs) were comparable between CS1002 (20.5%) and SL (27.6%) and largely related to the study indication. 6 participants (7%) in the CS1002 group reduced the dose of medication due to drowsiness/tiredness, which subsequently resolved. These events were not reported by participants as AEs. Conclusions Although the primary end point was not achieved, CS1002 was associated with greater reductions in cough frequency, sleep disruption and improved health status compared with SL. Trial registration number EudraCT number 2014-004255-31. PMID:28093442

Use of Quantity Indicators for Forecasting of Biogeochemical Behavior Sr-90 and Cs-137 in the Conditions of the Combined Pollution of Soils

NASA Astrophysics Data System (ADS)

Lavrentyeva, G. V.; Geshel, I. V.

2012-04-01

From huge number of the radionuclides generated by anthropogenous activity the major value the group of biologically active radionuclides has. First of all, it Sr-90 and Cs-137 which play an important role in various radiological situations. In researches on studying of laws of behavior in environment Sr -90 and Cs-137 the basic attention was given to studying of influence of their chemical analogs Ca and K, instead of stable isotopes Sr and Cs. However, even low concentration of stable isotopes Sr and Cs in soil can influence on biogeochemical behavior of radionuclides. Objects of research: dernovo-podsolic soil, summer barley of grade, stable and radioactive isotopes Sr, Cs. Schemes of experiments provided entering of 8 doses stable Cs and Sr in the range from 0 to 500-750 mg/kg of air-dry weight of soil and 50 kBq of radionuclides on each frequency. Absorption of radionuclides by plants will be defined by two parametres of transport. The first - factor of transition (TF), which characterises level of regulation of process of carrying over of a radionuclide from soil in plants and depends on distribution of an element between the firm and liquid phase, distribution defined in the factor (Kd). The second parametre - factor of concentrating (CF) which characterises biological level of regulation of this process. The increase in quantity of stable Sr in soil leads to an active desorption Sr-90 in a soil solution on all frequency. Kd of Cs-137 on the general background of which decrease in values some increase in factor in the range of 120-225 mg of Cs/kg of soil is observed. Received Kd of radionuclides will well be co-ordinated with the revealed functional dependences between concentration Cs and Sr in soil and specific activity Cs-137 and Sr-90 in a soil solution. Comparison CF of two radionuclides shows that plants absorb Sr-90 from a soil solution actively, than Cs-137. Thus values CF of Sr-90 in the investigated interval of concentration of a stable isotope are in inverse relationship from the element maintenance in a soil solution in all investigated interval of the maintenance of the isotope carrier whereas change similar the indicator for Cs-137 has more difficult dependence. The revealed laws of change of CF studied radionuclides prove to be true the received dependences of accumulation Sr-90 and Cs-137 in barley from specific activity of radionuclides in a soil solution. Values of TF of Sr-90 are in direct dependence on level of the maintenance stable Sr, below similar indicators for Cs-137 in all interval of change of concentration of stable isotopes. It finds reflection in the analysis of functional dependences between concentration of radionuclides in plants and soil. The received values of studied factors completely reflect change of specific activity of radionuclides in a soil solution and their biological availability depending on concentration of their stable isotopes that confirms use possibility in the prognostic purposes of these indicators.

Detecting an atomic clock frequency anomaly using an adaptive Kalman filter algorithm

NASA Astrophysics Data System (ADS)

Song, Huijie; Dong, Shaowu; Wu, Wenjun; Jiang, Meng; Wang, Weixiong

2018-06-01

The abnormal frequencies of an atomic clock mainly include frequency jump and frequency drift jump. Atomic clock frequency anomaly detection is a key technique in time-keeping. The Kalman filter algorithm, as a linear optimal algorithm, has been widely used in real-time detection for abnormal frequency. In order to obtain an optimal state estimation, the observation model and dynamic model of the Kalman filter algorithm should satisfy Gaussian white noise conditions. The detection performance is degraded if anomalies affect the observation model or dynamic model. The idea of the adaptive Kalman filter algorithm, applied to clock frequency anomaly detection, uses the residuals given by the prediction for building ‘an adaptive factor’ the prediction state covariance matrix is real-time corrected by the adaptive factor. The results show that the model error is reduced and the detection performance is improved. The effectiveness of the algorithm is verified by the frequency jump simulation, the frequency drift jump simulation and the measured data of the atomic clock by using the chi-square test.

Entanglement of atomic qubits using an optical frequency comb.

PubMed

Hayes, D; Matsukevich, D N; Maunz, P; Hucul, D; Quraishi, Q; Olmschenk, S; Campbell, W; Mizrahi, J; Senko, C; Monroe, C

2010-04-09

We demonstrate the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of trapped atomic ions and implement an entangling quantum logic gate with high fidelity. This technique can be extended to the high field regime where operations can be performed faster than the trap frequency. This general approach can be applied to more complex quantum systems, such as large collections of interacting atoms or molecules.

Stress and Sucrose Intake Modulate Neuronal Activity in the Anterior Hypothalamic Area in Rats

PubMed Central

Mitra, Arojit; Guèvremont, Geneviève; Timofeeva, Elena

2016-01-01

The anterior hypothalamic area (AHA) is an important integrative relay structure for a variety of autonomic, endocrine, and behavioral responses including feeding behavior and response to stress. However, changes in the activity of the AHA neurons during stress and feeding in freely moving rats are not clear. The present study investigated the firing rate and burst activity of neurons in the central nucleus of the AHA (cAHA) during sucrose intake in non-stressful conditions and after acute stress in freely behaving rats. Rats were implanted with micro-electrodes into the cAHA, and extracellular multi-unit activity was recorded during 1-h access to 10% sucrose in non-stressful conditions or after acute foot shock stress. Acute stress significantly reduced sucrose intake, total sucrose lick number, and lick frequency in licking clusters, and increased inter-lick intervals. At the cluster start (CS) of sucrose licking, the cAHA neurons increased (CS-excited, 20% of the recorded neurons), decreased (CS-inhibited, 42% of the neurons) or did not change (CS-nonresponsive, 38% of the neurons) their firing rate. Stress resulted in a significant increase in the firing rate of the CS-inhibited neurons by decreasing inter-spike intervals within the burst firing of these neurons. This increase in the stress-induced firing rate of the CS-inhibited neurons was accompanied by a disruption of the correlation between the firing rate of CS-inhibited and CS-nonresponsive neurons that was observed in non-stressful conditions. Stress did not affect the firing rate of the CS-excited and CS-nonresponsive neurons. However, stress changed the pattern of burst firing of the CS-excited and CS-nonresponsive neurons by decreasing and increasing the burst number in the CS-excited and CS-nonresponsive neurons, respectively. These results suggest that the cAHA neurons integrate the signals related to stress and intake of palatable food and play a role in the stress- and eating-related circuitry. PMID:27243579

Stress and Sucrose Intake Modulate Neuronal Activity in the Anterior Hypothalamic Area in Rats.

PubMed

Mitra, Arojit; Guèvremont, Geneviève; Timofeeva, Elena

2016-01-01

The anterior hypothalamic area (AHA) is an important integrative relay structure for a variety of autonomic, endocrine, and behavioral responses including feeding behavior and response to stress. However, changes in the activity of the AHA neurons during stress and feeding in freely moving rats are not clear. The present study investigated the firing rate and burst activity of neurons in the central nucleus of the AHA (cAHA) during sucrose intake in non-stressful conditions and after acute stress in freely behaving rats. Rats were implanted with micro-electrodes into the cAHA, and extracellular multi-unit activity was recorded during 1-h access to 10% sucrose in non-stressful conditions or after acute foot shock stress. Acute stress significantly reduced sucrose intake, total sucrose lick number, and lick frequency in licking clusters, and increased inter-lick intervals. At the cluster start (CS) of sucrose licking, the cAHA neurons increased (CS-excited, 20% of the recorded neurons), decreased (CS-inhibited, 42% of the neurons) or did not change (CS-nonresponsive, 38% of the neurons) their firing rate. Stress resulted in a significant increase in the firing rate of the CS-inhibited neurons by decreasing inter-spike intervals within the burst firing of these neurons. This increase in the stress-induced firing rate of the CS-inhibited neurons was accompanied by a disruption of the correlation between the firing rate of CS-inhibited and CS-nonresponsive neurons that was observed in non-stressful conditions. Stress did not affect the firing rate of the CS-excited and CS-nonresponsive neurons. However, stress changed the pattern of burst firing of the CS-excited and CS-nonresponsive neurons by decreasing and increasing the burst number in the CS-excited and CS-nonresponsive neurons, respectively. These results suggest that the cAHA neurons integrate the signals related to stress and intake of palatable food and play a role in the stress- and eating-related circuitry.

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

Bürger, Stefan; Riciputi, Lee R; Bostick, Debra A

A ThermoFisher 'Triton' multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotoperatioanalysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5-2% for U, Pu, and Am, and 1-30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (10{sup 4} atoms to 10{sup 5} atoms) for {sup 239-242+244}Pu, {sup 233+236}U,more » {sup 241-243}Am, {sup 89,90}Sr, and {sup 134,135,137}Cs, and {le} 1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 x 10{sup 6} or better using a SEM are reported here. Precisions of RSD {approx} 0.01-0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.« less

Repetitive Interrogation of 2-Level Quantum Systems

NASA Technical Reports Server (NTRS)

Prestage, John D.; Chung, Sang K.

2010-01-01

Trapped ion clocks derive information from a reference atomic transition by repetitive interrogations of the same quantum system, either a single ion or ionized gas of many millions of ions. Atomic beam frequency standards, by contrast, measure reference atomic transitions in a continuously replenished "flow through" configuration where initial ensemble atomic coherence is zero. We will describe some issues and problems that can arise when atomic state selection and preparation of the quantum atomic system is not completed, that is, optical pumping has not fully relaxed the coherence and also not fully transferred atoms to the initial state. We present a simple two-level density matrix analysis showing how frequency shifts during the state-selection process can cause frequency shifts of the measured clock transition. Such considerations are very important when a low intensity lamp light source is used for state selection, where there is relatively weak relaxation and re-pumping of ions to an initial state and much weaker 'environmental' relaxation of the atomic coherence set-up in the atomic sample.

Sedimentary record of environmental pollution in the Western Baltic Sea

NASA Astrophysics Data System (ADS)

Müller, German; Dominik, J.; Reuther, R.; Malisch, R.; Schulte, E.; Acker, L.; Irion, G.

1980-12-01

The chronological development of environmental pollution in the Western Baltic Sea for the past hundred years was investigated in dated sediment cores. An artificial radionuclide (137Cs), nutrients, heavy metals, chlorinated hydrocarbons (PCB, DDT, Lindane) and plasticizers (phthalate esters) show characteristic distribution patterns within the various cores. They can be related to the production and use of specific chemicals and goods, to emissions associated with the increased combustion of coal parallel to industrialization and —in the case of 137Cs — to emissions associated with atomic weapons tests in the high atmosphere. Characteristic trends in the general development of pollution may be superimposed by specific emissions from local sources.

Attenuating fearful memories: effect of cued extinction on intrusions.

PubMed

Marks, Elizabeth H; Zoellner, Lori A

2014-12-01

Exposure-based therapies for posttraumatic stress disorder are thought to reduce intrusive memories through extinction processes. Methods that enhance extinction may translate to improved treatment. Rat research suggests retrieving a memory via a conditioned stimulus (CS) cue, and then modifying the retrieved memory within a specific reconsolidation window may enhance extinction. In humans, studies (e.g., Kindt & Soeter, 2013; Schiller et al., 2010) using basic learning paradigms show discrepant findings. Using a distressing film paradigm, participants (N = 148) completed fear acquisition and extinction. At extinction, they were randomized to 1 of 3 groups: CS cue within reconsolidation window, CS cue outside window, or non-CS cue within window. Intrusions were assessed 24 hr after extinction. Participants receiving the CS cue and completing extinction within the reconsolidation window had more intrusions (M = 2.40, SD = 2.54) than those cued outside (M = 1.65, SD = 1.70) or those receiving a non-CS cue (M = 1.24, SD = 1.26), F(2, 145) = 4.52, p = .01, d = 0.55. Consistent with the reconsolidation hypothesis, presenting a CS cue does appear to activate a specific period of time during which a memory can be updated. However, the CS cue caused increased, rather than decreased, frequency of intrusions. Understanding parameters of preextinction cueing may help us better understand reconsolidation as a potential memory updating mechanism.

Synthesis, crystal structure, and vibrational spectroscopic and UV-visible studies of Cs{sub 2}MnP{sub 2}O{sub 7}

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

Kaoua, Saida; Krimi, Saida; Pechev, Stanislav

2013-02-15

A new member of the A{sub 2}MP{sub 2}O{sub 7} diphosphate family, Cs{sub 2}MnP{sub 2}O{sub 7}, has been synthesized and structurally characterized. The crystal structure was determined by single crystal X-Ray diffraction. Cs{sub 2}MnP{sub 2}O{sub 7} crystallizes in the orthorhombic system, space group Pnma ( Music-Sharp-Sign 62), with the unit cell parameters a=16.3398(3), b=5.3872(1), c=9.8872(2) A, Z=4 and V=870.33(3) A{sup 3}. The structure parameters were refined to a final R{sub 1}/wR{sub 2}=0.0194/0.0441 for 1650 observed reflections. The 2D framework of Cs{sub 2}MnP{sub 2}O{sub 7} structure consists of P{sub 2}O{sub 7} and MnO{sub 5} units. The corner-shared MnO{sub 5} and P{sub 2}O{submore » 7} units are alternately arranged along the b axis to form [(MnO)P{sub 2}O{sub 7}]{sub {infinity}} chains. These chains are interconnected by an oxygen atom to form sheets parallel to the (b, c) plane. The cesium atoms are located between the sheets in 9- and 10-fold coordinated sites. The infrared and Raman vibrational spectra have been investigated. A factor group analysis leads to the determination of internal modes of (P{sub 2}O{sub 7}) groups. UV-visible spectrum consists of weak bands, between 340 and 700 nm, assigned to the forbidden d-d transitions of Mn{sup 2+} ion, and of a strong band around 250 nm, attributed to the O--Mn charge transfer. - Graphical abstract: Structure of Cs{sub 2}MnP{sub 2}O{sub 7}: The 2D structure of Cs{sub 2}MnP{sub 2}O{sub 7} is built from P{sub 2}O{sub 7} diphosphate groups and MnO{sub 5} square pyramids which share corners and form [(MnO)P{sub 2}O{sub 7}]{sub {infinity}} chains along b axis. These chains are interconnected by an oxygen atom to form wavy (MnP{sub 2}O{sub 7}){sup 2-} sheets parallel to the (b, c) plane. The cesium ions are located between these sheets in the inter-layers space, in zigzag positions. Highlights: Black-Right-Pointing-Pointer A new diphosphate, Cs{sub 2}MnP{sub 2}O{sub 7}, has been synthesized and structurally characterized. Black-Right-Pointing-Pointer The structure consists of a 2D framework built up from (MnP{sub 2}O{sub 7}) sheets. Black-Right-Pointing-Pointer The sheets consist of [(MnO)P{sub 2}O{sub 7}]{sub {infinity}} chains formed by P{sub 2}O{sub 7} units and MnO{sub 5} square pyramids. Black-Right-Pointing-Pointer A factor group analysis leads to the determination of internal modes of (P{sub 2}O{sub 7}) groups. Black-Right-Pointing-Pointer UV-visible spectrum consists bands assigned to d-d transitions of Mn{sup 2+} ion and to O--Mn CT.« less

DAGAN: Deep De-Aliasing Generative Adversarial Networks for Fast Compressed Sensing MRI Reconstruction.

PubMed

Yang, Guang; Yu, Simiao; Dong, Hao; Slabaugh, Greg; Dragotti, Pier Luigi; Ye, Xujiong; Liu, Fangde; Arridge, Simon; Keegan, Jennifer; Guo, Yike; Firmin, David; Keegan, Jennifer; Slabaugh, Greg; Arridge, Simon; Ye, Xujiong; Guo, Yike; Yu, Simiao; Liu, Fangde; Firmin, David; Dragotti, Pier Luigi; Yang, Guang; Dong, Hao

2018-06-01

Compressed sensing magnetic resonance imaging (CS-MRI) enables fast acquisition, which is highly desirable for numerous clinical applications. This can not only reduce the scanning cost and ease patient burden, but also potentially reduce motion artefacts and the effect of contrast washout, thus yielding better image quality. Different from parallel imaging-based fast MRI, which utilizes multiple coils to simultaneously receive MR signals, CS-MRI breaks the Nyquist-Shannon sampling barrier to reconstruct MRI images with much less required raw data. This paper provides a deep learning-based strategy for reconstruction of CS-MRI, and bridges a substantial gap between conventional non-learning methods working only on data from a single image, and prior knowledge from large training data sets. In particular, a novel conditional Generative Adversarial Networks-based model (DAGAN)-based model is proposed to reconstruct CS-MRI. In our DAGAN architecture, we have designed a refinement learning method to stabilize our U-Net based generator, which provides an end-to-end network to reduce aliasing artefacts. To better preserve texture and edges in the reconstruction, we have coupled the adversarial loss with an innovative content loss. In addition, we incorporate frequency-domain information to enforce similarity in both the image and frequency domains. We have performed comprehensive comparison studies with both conventional CS-MRI reconstruction methods and newly investigated deep learning approaches. Compared with these methods, our DAGAN method provides superior reconstruction with preserved perceptual image details. Furthermore, each image is reconstructed in about 5 ms, which is suitable for real-time processing.

Is improved contrast sensitivity a natural consequence of visual training?

PubMed Central

Levi, Aaron; Shaked, Danielle; Tadin, Duje; Huxlin, Krystel R.

2015-01-01

Many studies have shown that training and testing conditions modulate specificity of visual learning to trained stimuli and tasks. In visually impaired populations, generalizability of visual learning to untrained stimuli/tasks is almost always reported, with contrast sensitivity (CS) featuring prominently among these collaterally-improved functions. To understand factors underlying this difference, we measured CS for direction and orientation discrimination in the visual periphery of three groups of visually-intact subjects. Group 1 trained on an orientation discrimination task with static Gabors whose luminance contrast was decreased as performance improved. Group 2 trained on a global direction discrimination task using high-contrast random dot stimuli previously used to recover motion perception in cortically blind patients. Group 3 underwent no training. Both forms of training improved CS with some degree of specificity for basic attributes of the trained stimulus/task. Group 1's largest enhancement was in CS around the trained spatial/temporal frequencies; similarly, Group 2's largest improvements occurred in CS for discriminating moving and flickering stimuli. Group 3 saw no significant CS changes. These results indicate that CS improvements may be a natural consequence of multiple forms of visual training in visually intact humans, albeit with some specificity to the trained visual domain(s). PMID:26305736

Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies.

PubMed

Tettamanzi, Giuseppe Carlo; Hile, Samuel James; House, Matthew Gregory; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y

2017-03-28

The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

Effect of Bioactive Materials Modified with Chondroitin Sulfate on Human MSC =

NASA Astrophysics Data System (ADS)

De La Torre Torres, Jessica Elizabeth

In this project chondroitin sulfate (CS) and growth factors were studied for their effect on hMSC in biomaterials. First, the effect of these biomolecules was tested in solution. Then, two kinds of biomaterials were created: bioactive surfaces for enhancing bioactivity of implantable devices and bioactive hydrogels which can be used as 3D scaffolds for cell encapsulation and delivery. A pro-survival effect of the growth factors studied in this project (epidermal growth factor, vascular endothelial growth factor and fibroblast growth factor) was not observed when tested in solution, therefore the project further focused on CS effect only. Interestingly, CS did not affect cell growth in media containing serum, while inducing cell detachment from substrate in serum free conditions. For the bioactive surfaces construction, CS was grafted to either an amine-rich plasmapolymerized coating created on polyethylene terephthalate (PET) films (further referred as LP) or to commercial cell culture plates functionalized with amino groups. The bioactive surfaces were characterized by different techniques such as contact angle, atomic force microscopy, Orange II dye and Toluidine Blue O dye colorimetric assays (for amino group and CS quantification respectively) and finally, cell culture experiments (adhesion, growth and survival). Results confirmed the presence of CS grafted on both substrates. Commercial amine plates grafted almost five times more CS compared to LP. This rendered the surface antifouling for proteins and cells as confirmed by protein adsorption and cell culture assays. Cell culture assays on bioactive surfaces based on LP demonstrated improved cell adhesion and growth when compared to tissue culture plates or bare PET films in serum containing conditions. Chitosan based hydrogels containing CS at a concentration of 500 mug/ml resulted in a cohesive hydrogel which supported hMSC viability up to 7 days. However increasing CS concentration to high level such as 10000 mug/ml led to decrease of cell viability after 4 or 7 days, probably due to lack of porosity and water since the hydrogel precipitates upon formation and expulses water. In conclusion, this work demonstrated that CS immobilization can enhance the biological interactions of hMSC with biomaterials used for implantable devices such as PET. Further studies are needed to evaluate the possible effect of CS on hMSC differentiation and phenotype. Hydrogels with CS could be very interesting for tissue engineering applications such as cartilage formation. (Abstract shortened by ProQuest.).

Desorption Induced by KEV Molecular and Cluster Projectiles.

NASA Astrophysics Data System (ADS)

Blain, Matthew Glenn

1990-01-01

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and then accelerated into a field free region. The primary ions included organic monomer, dimer, and fragment ions of coronene and phenylalanine, (CsI)_ nCs ^{+} cluster ions, and Au _sp{n}{+} cluster ions. Secondary electrons, emitted from a target surface upon primary ion impact, are used to identify which primary ion has hit the surface. An event-by-event coincidence counting technique allows several secondary ion TOF spectra, correlated to several different primary ions, to be acquired simultaneously. Negative SI yields from organic (phenylalanine and dinitrostilbene), CsI, and Au surfaces have been measured for a number of different mono- and polyatomic primary ions. The results show, for example, yields ranging from 1 to 10% for phenylalanine (M-H) ^{ -}, 1 to 10% for I^{-} , and 1 to 5% for Au^{-} , with Cs_2I^ {+} and Cs_3I _sp{2}{+} clusters as projectiles. Yields for the same surfaces using Cs ^{+} primary ions are much less than 1%, indicating that SI yields are enhanced with clusters. A yield enhancement occurs when the SI yield per atom of a polyatomic projectile is greater than the SI yield of its monoatomic equivalent, at the same velocity. Thus, a (M-H) ^{-} yield increase of a factor of 50, when phenylalanine is bombarded with Cs_3I_sp{2} {+} instead of Cs^{+ }, represents a yield enhancement factor of 10. For the projectiles and samples studied, it was observed that the heavier the mass of the constituents of a projectile, the larger the enhancement effects, and that the largest yield enhancements (with CsI and Au _ n projectiles) occur for the organic target, phenylalanine. One possible explanation for the larger enhancements with organics, namely a thermal spike process, appears unlikely. Experiments with high and low melting point isomers of dinitrostilbene, bombarded with Cs _2I^{+} and Cs^{+} projectiles, showed larger Cs_2I^ {+} yield enhancements for the high melting point isomer.

Myopic astigmatism correction: comparison of a Toric Implantable Collamer Lens and a bioptics technique by an adaptive optics visual simulator.

PubMed

Pérez-Vives, Cari; Domínguez-Vicent, Alberto; Madrid-Costa, David; Ferrer-Blasco, Teresa; Montés-Micó, Robert

2013-03-01

To compare the optical and visual quality of a simulated Toric Implantable Collamer Lens (TICL) and a bioptics technique to treat high myopic astigmatism. An adaptive optics visual simulator was used to simulate the vision after TICL implantation and a bioptics procedure from the wavefront aberration pattern for moderate and high-myopic astigmatism. Visual acuity (VA) at different contrasts and contrast sensitivity (CS) at 10, 20 and 25 cycles degree(-1) were measured for 3 and 5-mm pupils. Modulation Transfer Function (MTF) and Point Spread Function (PSF) were calculated for a 5-mm pupil. At a 3-mm pupil we only found statistically significant differences in VA between the two simulated surgeries at low-contrast for moderate- and high-myopic astigmatism (p < 0.05). Statistically significant differences were found in CS at 3-mm pupil between both procedures at the highest spatial frequency for moderate-myopic astigmatism and at all frequencies for high-myopic astigmatism (p < 0.05). At a 5-mm pupil we found statistically significant differences in VA and CS between both simulated surgeries at all contrasts and frequencies evaluated for both groups (p < 0.05). In all cases VA and CS were better with the TICL than with the bioptics technique. MTFs for the bioptics technique were worse than those computed for the TICL. The TICL showed less spread out of the PSF than the bioptics procedure. Simulated TICL and bioptics procedures provided good optical and visual quality, although TICL implantation provided slightly better outcomes than the bioptics procedure, especially when the pupil diameter was increased. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

A polarization converting device for an interfering enhanced CPT atomic clock.

PubMed

Wang, Kewei; Tian, Yuan; Yin, Yi; Wang, Yuanchao; Gu, Sihong

2017-11-01

With interfering enhanced coherent population trapping (CPT) signals, a CPT atomic clock with improved frequency stability performance can be realized. We explore an optical device that converts single-polarized bichromatic light to left and right circularly polarized superposed bichromatic light to generate interfering enhanced CPT resonance with atoms. We have experimentally studied a tabletop CPT atomic clock apparatus with a microfabricated 87 Rb atomic chip-scale cell, and the study results show that it is promising to realize a compact CPT atomic clock, even a chip-scale CPT atomic clock through microfabrication, with improved frequency stability performance.

A polarization converting device for an interfering enhanced CPT atomic clock

NASA Astrophysics Data System (ADS)

Wang, Kewei; Tian, Yuan; Yin, Yi; Wang, Yuanchao; Gu, Sihong

2017-11-01

With interfering enhanced coherent population trapping (CPT) signals, a CPT atomic clock with improved frequency stability performance can be realized. We explore an optical device that converts single-polarized bichromatic light to left and right circularly polarized superposed bichromatic light to generate interfering enhanced CPT resonance with atoms. We have experimentally studied a tabletop CPT atomic clock apparatus with a microfabricated 87Rb atomic chip-scale cell, and the study results show that it is promising to realize a compact CPT atomic clock, even a chip-scale CPT atomic clock through microfabrication, with improved frequency stability performance.

Studies of rotationally inelastic collisions of NaK and NaCs with Ar and He perturbers

NASA Astrophysics Data System (ADS)

Jones, J.; Faust, C.; Richter, K.; Wolfe, C. M.; Ashman, S.; Malenda, R. F.; Weiser, P.; Carlus, S.; Fragale, A.; Hickman, A. P.; Huennekens, J.

2013-05-01

We report studies of rotationally inelastic collisions of Ar and He atoms with the molecules NaK and NaCs prepared in various ro-vibrational levels of the A1Σ+ electronic state. We use laser induced fluorescence (LIF) and polarization labeling (PL) spectroscopy in a pump-probe, two step excitation process. The pump excites the molecule to a ro-vibrational level (v , J) in the A state. The probe laser is scanned over transitions to the 31 Π state in NaK or the 53 Π state in NaCs. In addition to strong direct lines, we observe weak satellite lines that arise from collision-induced transitions of the A state level (v , J) to (v , J + ΔJ) . The ratio of intensities of the satellite line to the direct line in LIF and PL yields information about population and orientation transfer. Preliminary results show a strong propensity for collisions with ΔJ =even for NaK; the propensity is larger for He than for Ar. Collisions of NaCs with He show a similar propensity, but collisions of NaCs with Ar do not. Theoretical calculations are also underway. For He-NaK, we have completed potential surface calculations using GAMESS and coupled channel scattering calculations of rotational energy transfer and transfer of orientation. Work supported by NSF and XSEDE.

Quantum mechanical models for the Fermi shuttle

NASA Astrophysics Data System (ADS)

Sternberg, James; Ovchinnikov, S. Yu.; Macek, J. H.

2009-05-01

Although the Fermi shuttle was originally proposed as an explanation for highly energetic cosmic rays, it is also a mechanism for the production of high energy electrons in atomic collisions [1]. The Fermi shuttle is usually thought of as a classical effect and most models of this process rely on classical or semi-classical approximations. In this work we explore several quantum mechanical models for ion-atom collisions and examine the evidence for the Fermi shuttle in these models. [4pt] [1] B. Sulik, Cs. Koncz, K. Tok'esi, A. Orb'an, and D. Ber'enyi, Phys Rev. Lett. 88 073201 (2002)

Observing random walks of atoms in buffer gas through resonant light absorption

NASA Astrophysics Data System (ADS)

Aoki, Kenichiro; Mitsui, Takahisa

2016-07-01

Using resonant light absorption, random-walk motions of rubidium atoms in nitrogen buffer gas are observed directly. The transmitted light intensity through atomic vapor is measured, and its spectrum is obtained, down to orders of magnitude below the shot-noise level to detect fluctuations caused by atomic motions. To understand the measured spectra, the spectrum for atoms performing random walks in a Gaussian light beam is computed, and its analytical form is obtained. The spectrum has 1 /f2 (f is frequency) behavior at higher frequencies, crossing over to a different, but well-defined, behavior at lower frequencies. The properties of this theoretical spectrum agree excellently with the measured spectrum. This understanding also enables us to obtain the diffusion constant, the photon cross section of atoms in buffer gas, and the atomic number density from a single spectral measurement. We further discuss other possible applications of our experimental method and analysis.

Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction.

PubMed

Chan, Eng Aik; Aljunid, Syed Abdullah; Adamo, Giorgio; Laliotis, Athanasios; Ducloy, Martial; Wilkowski, David

2018-02-01

Metamaterials are fascinating tools that can structure not only surface plasmons and electromagnetic waves but also electromagnetic vacuum fluctuations. The possibility of shaping the quantum vacuum is a powerful concept that ultimately allows engineering the interaction between macroscopic surfaces and quantum emitters such as atoms, molecules, or quantum dots. The long-range atom-surface interaction, known as Casimir-Polder interaction, is of fundamental importance in quantum electrodynamics but also attracts a significant interest for platforms that interface atoms with nanophotonic devices. We perform a spectroscopic selective reflection measurement of the Casimir-Polder interaction between a Cs(6P 3/2 ) atom and a nanostructured metallic planar metamaterial. We show that by engineering the near-field plasmonic resonances of the metamaterial, we can successfully tune the Casimir-Polder interaction, demonstrating both a strong enhancement and reduction with respect to its nonresonant value. We also show an enhancement of the atomic spontaneous emission rate due to its coupling with the evanescent modes of the nanostructure. Probing excited-state atoms next to nontrivial tailored surfaces is a rigorous test of quantum electrodynamics. Engineering Casimir-Polder interactions represents a significant step toward atom trapping in the extreme near field, possibly without the use of external fields.

Structure of kinetic Alfvén waves with small transverse scale length

NASA Astrophysics Data System (ADS)

Morales, G. J.; Maggs, J. E.

1997-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension a, transverse to the confining magnetic field, is comparable to the ion sound gyroradius cs/Ωi, where cs is the sound speed and Ωi the ion cyclotron frequency. The radial structure of the wave azimuthal magnetic field is found to consist of four regions: a Bessel function behavior for r

Cultural significance of the flora of a tropical dry forest in the Doche vereda (Villavieja, Huila, Colombia).

PubMed

Rosero-Toro, Jeison Herley; Romero-Duque, Luz Piedad; Santos-Fita, Dídac; Ruan-Soto, Felipe

2018-03-22

In Colombia, ethnobotanical studies regarding plant cultural significance (CS) in tropical dry forests are scarce and mainly focused on the Caribbean region. Different authors have indicated that the plants with the most uses are those of greater cultural importance. Additionally, gender differences in knowledge and interest in natural resources has been widely recorded. This study evaluated the cultural significance of plants in the Doche community, in the Department of Huila. Furthermore, it evaluates the richness of plant knowledge among local inhabitants, looking for testing the hypothesis that the CS of plants positively correlates to the number of uses people inform about, and that there are significant differences on the richness of ethnobotanical knowledge between men and women in this community. The ethnobotanical categories: "food," "condiment," "economy," "fodder," "firewood," "timber", "medicine," and "others" were established to carry out semi-structured interviews, social cartography, and ethnobotanical walks. The frequency of mention was calculated as a measure of CS. The richness of knowledge of each collaborator was obtained. Non-parametric tests were performed to determine whether differences between the numbers of mentioned species existed between genders and ethnobotanical categories. Finally, Pearson correlation tests determined the relationship between CS and the number of ethnobotanical categories. A hundred useful species were registered in crops and forests. The most abundant categories were medicinal (45 species), firewood (30), and fodder (28). The most culturally significant species according to frequency of mention were Pseudosamanea guachapele, Guazuma ulmifolia, Manihot esculenta, and Musa balbisiana. The species with the most registered uses (five) were Guazuma ulmifolia and Gliricidia sepium. We found a correlation between CS and the number of uses per ethnobotanical category, but no significant difference between genders regarding ethnobotanical knowledge. Frequency of mention provides relevant information about the CS of species. Furthermore, it aids to establish sustainable use of tropical dry forests without loss of resources parting from strategies designed from within the Doche community and based on their ethnobotanical knowledge. We found that the number of uses of a plant is correlated with its degree of cultural importance. On the other hand, no significant differences were found between genders regarding ethnobotanical knowledge; that is, both men and women have similar roles in the community, which allows them to recognize the same uses per species.

A stable frequency comb directly referenced to rubidium electromagnetically induced transparency and two-photon transitions

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

Hou, Dong; Wu, Jiutao; Zhang, Shuangyou

2014-03-17

We demonstrate an approach to create a stable erbium-fiber-based frequency comb at communication band by directly locking the combs to two rubidium atomic transitions resonances (electromagnetically induced transparency absorption and two-photon absorption), respectively. This approach directly transfers the precision and stability of the atomic transitions to the comb. With its distinguishing feature of compactness by removing the conventional octave-spanning spectrum and f-to-2f beating facilities and the ability to directly control the comb's frequency at the atomic transition frequency, this stable optical comb can be widely used in optical communication, frequency standard, and optical spectroscopy and microscopy.

Observation of the Borromean Three-Body Förster Resonances for Three Interacting Rb Rydberg Atoms.

PubMed

Tretyakov, D B; Beterov, I I; Yakshina, E A; Entin, V M; Ryabtsev, I I; Cheinet, P; Pillet, P

2017-10-27

Three-body Förster resonances at long-range interactions of Rydberg atoms were first predicted and observed in Cs Rydberg atoms by Faoro et al. [Nat. Commun. 6, 8173 (2015)NCAOBW2041-172310.1038/ncomms9173]. In these resonances, one of the atoms carries away an energy excess preventing the two-body resonance, leading thus to a Borromean type of Förster energy transfer. But they were in fact observed as the average signal for the large number of atoms N≫1. In this Letter, we report on the first experimental observation of the three-body Förster resonances 3×nP_{3/2}(|M|)→nS_{1/2}+(n+1)S_{1/2}+nP_{3/2}(|M^{*}|) in a few Rb Rydberg atoms with n=36, 37. We have found here clear evidence that there is no signature of the three-body Förster resonance for exactly two interacting Rydberg atoms, while it is present for N=3-5 atoms. This demonstrates the assumption that three-body resonances can generalize to any Rydberg atom. As such resonance represents an effective three-body operator, it can be used to directly control the three-body interactions in quantum simulations and quantum information processing with Rydberg atoms.

Observation of the Borromean Three-Body Förster Resonances for Three Interacting Rb Rydberg Atoms

NASA Astrophysics Data System (ADS)

Tretyakov, D. B.; Beterov, I. I.; Yakshina, E. A.; Entin, V. M.; Ryabtsev, I. I.; Cheinet, P.; Pillet, P.

2017-10-01

Three-body Förster resonances at long-range interactions of Rydberg atoms were first predicted and observed in Cs Rydberg atoms by Faoro et al. [Nat. Commun. 6, 8173 (2015), 10.1038/ncomms9173]. In these resonances, one of the atoms carries away an energy excess preventing the two-body resonance, leading thus to a Borromean type of Förster energy transfer. But they were in fact observed as the average signal for the large number of atoms N ≫1 . In this Letter, we report on the first experimental observation of the three-body Förster resonances 3 ×n P3 /2(|M |)→n S1 /2+(n +1 )S1 /2+n P3 /2(|M*|) in a few Rb Rydberg atoms with n =36 , 37. We have found here clear evidence that there is no signature of the three-body Förster resonance for exactly two interacting Rydberg atoms, while it is present for N =3 - 5 atoms. This demonstrates the assumption that three-body resonances can generalize to any Rydberg atom. As such resonance represents an effective three-body operator, it can be used to directly control the three-body interactions in quantum simulations and quantum information processing with Rydberg atoms.

Tunable meta-atom using liquid metal embedded in stretchable polymer

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

Liu, Peng; Yang, Siming; Wang, Qiugu

2015-07-07

Reconfigurable metamaterials have great potential to alleviate complications involved in using passive metamaterials to realize emerging electromagnetic functions, such as dynamical filtering, sensing, and cloaking. This paper presents a new type of tunable meta-atoms in the X-band frequency range (8–12 GHz) toward reconfigurable metamaterials. The meta-atom is made of all flexible materials compliant to the surface of an interaction object. It uses a liquid metal-based split-ring resonator as its core constituent embedded in a highly flexible elastomer. We demonstrate that simple mechanical stretching of the meta-atom can lead to the great flexibility in reconfiguring its resonance frequency continuously over moremore » than 70% of the X-band frequency range. The presented meta-atom technique provides a simple approach to dynamically tune response characteristics of metamaterials over a broad frequency range.« less

Robust quantum logic in neutral atoms via adiabatic Rydberg dressing

DOE PAGES

Keating, Tyler; Cook, Robert L.; Hankin, Aaron M.; ...

2015-01-28

We study a scheme for implementing a controlled-Z (CZ) gate between two neutral-atom qubits based on the Rydberg blockade mechanism in a manner that is robust to errors caused by atomic motion. By employing adiabatic dressing of the ground electronic state, we can protect the gate from decoherence due to random phase errors that typically arise because of atomic thermal motion. In addition, the adiabatic protocol allows for a Doppler-free configuration that involves counterpropagating lasers in a σ +/σ - orthogonal polarization geometry that further reduces motional errors due to Doppler shifts. The residual motional error is dominated by dipole-dipolemore » forces acting on doubly-excited Rydberg atoms when the blockade is imperfect. As a result, for reasonable parameters, with qubits encoded into the clock states of 133Cs, we predict that our protocol could produce a CZ gate in < 10 μs with error probability on the order of 10 -3.« less

Graduate Student Support for Quantum Computing With Superconducting Charge States

DTIC Science & Technology

2005-08-31

cavity resonance frequency ωr, the atomic transition frequency Ω, and the strength of the atom- photon coupling g appearing in the Jaynes - Cummings ...the atom through the cavity. In the absence of damping, exact diagonalization of the Jaynes - Cumming Hamiltonian yields the excited eigen- states...cillating terms and omitting damping for the moment, 5 Eq. (16) reduces to the Jaynes - Cummings Hamiltonian (1) with Ω = EJ/~ and the vacuum Rabi frequency

Organic-Inorganic Hybrid Interfacial Layer for High-Performance Planar Perovskite Solar Cells.

PubMed

Yang, Hao; Cong, Shan; Lou, Yanhui; Han, Liang; Zhao, Jie; Sun, Yinghui; Zou, Guifu

2017-09-20

4,7-Diphenyl-1,10-phenanthroline (Bphen) is an efficient electron transport and hole blocking material in organic photoelectric devices. Here, we report cesium carbonate (Cs 2 CO 3 ) doped Bphen as cathode interfacial layer in CH 3 NH 3 PbI 3-x Cl x based planar perovskite solar cells (PSCs). Investigation finds that introducing Cs 2 CO 3 suppresses the crystallization of Bphen and benefits a smooth interface contact between the perovskite and electrode, resulting in the decrease in carrier recombination and the perovskite degradation. In addition, the matching energy level of Bphen film in the PSCs effectively blocks the holes diffusion to cathode. The resultant power conversion efficiency (PCE) achieves as high as 17.03% in comparison with 12.67% of reference device without doping. Besides, experiments also demonstrate the stability of PSCs have large improvement because the suppressed crystallization of Bphen by doping Cs 2 CO 3 as a superior barrier layer blocks the Ag atom and surrounding moisture access to the vulnerable perovskite layer.

Improving isotopic identification with INDRA Silicon-CsI(Tl) telescopes

NASA Astrophysics Data System (ADS)

Lopez, O.; Pârlog, M.; Borderie, B.; Rivet, M. F.; Lehaut, G.; Tabacaru, G.; Tassan-Got, L.; Pawłowski, P.; Bonnet, E.; Bougault, R.; Chbihi, A.; Dell'Aquila, D.; Frankland, J. D.; Galichet, E.; Gruyer, D.; La Commara, M.; Le Neindre, N.; Lombardo, I.; Manduci, L.; Marini, P.; Steckmeyer, J. C.; Verde, G.; Vient, E.; Wieleczko, J. P.; Indra Collaboration

2018-03-01

Profiting from previous works done with the INDRA multidetector on the description of the light response L of the CsI(Tl) crystals to different impinging nuclei, we propose an improved ΔE - L identification-calibration procedure for Silicon-Caesium Iodide (Si-CsI) telescopes, namely an Advanced Mass Estimate (AME) method. AME is compared to the usual, simple visual analysis of the corresponding two-dimensional map of ΔE - E type, by using INDRA experimental data from nuclear reactions induced by heavy ions in the Fermi energy regime. We show that the capability of such telescopes to identify both the atomic Z and the mass A numbers of light and heavy reaction products, can be quantitatively improved thanks to the proposed approach. This conclusion opens new possibilities to use INDRA for studying these reactions especially with radioactive beams. Indeed, the determination of the mass for charged reaction products becomes of paramount importance to shed light on the role of the isospin degree of freedom in the nuclear equation of state [1,2].

Can Pb-Free Halide Double Perovskites Support High-Efficiency Solar Cells?

PubMed Central

2016-01-01

The methylammonium lead halides have become champion photoactive semiconductors for solar cell applications; however, issues still remain with respect to chemical instability and potential toxicity. Recently, the Cs2AgBiX6 (X = Cl, Br) double perovskite family has been synthesized and investigated as stable nontoxic replacements. We probe the chemical bonding, physical properties, and cation anti-site disorder of Cs2AgBiX6 and related compounds from first-principles. We demonstrate that the combination of Ag(I) and Bi(III) leads to the wide indirect band gaps with large carrier effective masses owing to a mismatch in angular momentum of the frontier atomic orbitals. The spectroscopically limited photovoltaic conversion efficiency is less than 10% for X = Cl or Br. This limitation can be overcome by replacing Ag with In or Tl; however, the resulting compounds are predicted to be unstable thermodynamically. The search for nontoxic bismuth perovskites must expand beyond the Cs2AgBiX6 motif. PMID:28066823

Can Pb-Free Halide Double Perovskites Support High-Efficiency Solar Cells?

PubMed

Savory, Christopher N; Walsh, Aron; Scanlon, David O

2016-11-11

The methylammonium lead halides have become champion photoactive semiconductors for solar cell applications; however, issues still remain with respect to chemical instability and potential toxicity. Recently, the Cs 2 AgBiX 6 (X = Cl, Br) double perovskite family has been synthesized and investigated as stable nontoxic replacements. We probe the chemical bonding, physical properties, and cation anti-site disorder of Cs 2 AgBiX 6 and related compounds from first-principles. We demonstrate that the combination of Ag(I) and Bi(III) leads to the wide indirect band gaps with large carrier effective masses owing to a mismatch in angular momentum of the frontier atomic orbitals. The spectroscopically limited photovoltaic conversion efficiency is less than 10% for X = Cl or Br. This limitation can be overcome by replacing Ag with In or Tl; however, the resulting compounds are predicted to be unstable thermodynamically. The search for nontoxic bismuth perovskites must expand beyond the Cs 2 AgBiX 6 motif.

Magnetic Control of the Charge-Separated State Lifetime Realized by Covalent Attachment of a Platinum Complex.

PubMed

Miura, Tomoaki; Fujiwara, Dai; Akiyama, Kimio; Horikoshi, Takafumi; Suzuki, Shuichi; Kozaki, Masatoshi; Okada, Keiji; Ikoma, Tadaaki

2017-02-02

Dynamics of the photogenerated charge-separated (CS) state is studied for a newly synthesized molecular triad, in which the donor (D) dimethoxytriphenylamine, 1,3-bis(2-pyridylimino)isoindolate platinum (BPIPt), and the acceptor (A) naphthaldiimide are linked with a triethynylbenzene unit (BPIPt-DA). Photoexcitation of BPIPt gives rise to generation of a long-lived (∼4 μs) CS state BPIPt-D + A - , of which the lifetime is considerably increased by an applied magnetic field of 270 mT. The positive magnetic field effect (MFE) is in contrast to the negative MFE for the reference DA molecule, which indicates successful switching of the initial spin state of the CS state from singlet to triplet. Simulations of the MFE and time-resolved electron paramagnetic resonance show that spin-selective charge recombination and spin relaxation are unaffected by attachment of BPIPt. The minimum impact of heavy atom substitution on the electronic and magnetic properties has been realized by the small electronic coupling mediated by the rigid meta-triethynylbenzene.

Lattice dynamics of Cs2NaYbF6 and Cs2NaYF6 elpasolites: Ab initio calculation

NASA Astrophysics Data System (ADS)

Chernyshev, V. A.; Petrov, V. P.; Nikiforov, A. E.; Zakir'yanov, D. O.

2015-06-01

The ab initio calculations of the crystal structure and the phonon spectrum of Cs2NaYbF6 and Cs2NaYF6 crystals with the elpasolite structure have been performed. The frequencies and types of fundamental vibrations have been determined. The calculations have been performed in the framework of the density functional theory using the molecular orbital method with hybrid functionals in the CRYSTAL09 program developed for the simulation of periodic structures. The outer 5 s and 5 p shells of the rare-earth ion have been described in Gaussian-type basis sets. The influence of inner shells, including 4 f electron shells, on the outer shells has been described using the pseudopotential. It has been shown that this approach allows the description of the phonon spectrum with the inclusion of the splitting of the longitudinal and transverse optical modes.

Intercellular transfer along the trichomes of the invasive terminal heterocyst forming cyanobacterium Cylindrospermopsis raciborskii CS-505.

PubMed

Plominsky, Álvaro M; Delherbe, Nathalie; Mandakovic, Dinka; Riquelme, Brenda; González, Karen; Bergman, Birgitta; Mariscal, Vicente; Vásquez, Mónica

2015-03-01

Cylindrospermopsis raciborskii CS-505 is an invasive freshwater filamentous cyanobacterium that when grown diazotrophically may develop trichomes of up to 100 vegetative cells while differentiating only two end heterocysts, the sole sites for their N2-fixation process. We examined the diazotrophic growth and intercellular transfer mechanisms in C. raciborskii CS-505. Subjecting cultures to a combined-nitrogen-free medium to elicit N2 fixation, the trichome length remained unaffected while growth rates decreased. The structures and proteins for intercellular communication showed that while a continuous periplasmic space was apparent along the trichomes, the putative septal junction sepJ gene is divided into two open reading frames and lacks several transmembrane domains unlike the situation in Anabaena, differentiating a 5-fold higher frequency of heterocysts. FRAP analyses also showed that the dyes calcein and 5-CFDA were taken up by heterocysts and vegetative cells, and that the transfer from heterocysts and 'terminal' vegetative cells showed considerably higher transfer rates than that from vegetative cells located in the middle of the trichomes. The data suggest that C. raciborskii CS-505 compensates its low-frequency heterocyst phenotype by a highly efficient transfer of the fixed nitrogen towards cells in distal parts of the trichomes (growing rapidly) while cells in central parts suffers (slow growth). © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

FREQUENCY DISTRIBUTIONS OF 90SR AND 137CS CONCENTRATIONS IN AN ECOSYSTEM OF THE 'RED FOREST' AREA IN THE CHERNOBYL EXCLUSION ZONE

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

Farfan, E.; Jannik, T.; Caldwell, E.

2011-10-01

In the most highly contaminated region of the Chernobyl Exclusion Zone: the 'Red Forest' site, the accumulation of the major dose-affecting radionuclides ({sup 90}Sr and {sup 137}Cs) within the components of an ecological system encompassing 3,000 m{sup 2} were characterized. The sampled components included soils (top 0-10 cm depth), Molina caerulea (blue moor grass), Camponotus vagus (carpenter ants) and Pelobates fuscus (spade-footed toad). In a comparison among the components of this ecosystem, the {sup 90}Sr and {sup 137}Cs concentrations measured in 40 separate grids exhibited significant differences, while the frequency distribution of the values were close to a logarithmically normalmore » leptokurtic distribution with a significant right-side skew. While it is important to identify localized areas of high contamination or 'hot spots,' including these values in the arithmetic mean may overestimate the exposure risk. In component sample sets that exhibited logarithmically normal distribution, the geometrical mean more accurately characterizes a site. Ideally, risk assessment is most confidently achieved when the arithmetic and geometrical means are most similar, meaning the distribution approaches normal. Through bioaccumulation, the highest concentrations of {sup 90}Sr and {sup 137}Cs were measured in the blue moor grass and spade-footed toad. These components also possessed distribution parameters that shifted toward a normal distribution.« less

Structures of mesophilic and extremophilic citrate synthases reveal rigidity and flexibility for function.

PubMed

Wells, Stephen A; Crennell, Susan J; Danson, Michael J

2014-10-01

Citrate synthase (CS) catalyses the entry of carbon into the citric acid cycle and is highly-conserved structurally across the tree of life. Crystal structures of dimeric CSs are known in both "open" and "closed" forms, which differ by a substantial domain motion that closes the substrate-binding clefts. We explore both the static rigidity and the dynamic flexibility of CS structures from mesophilic and extremophilic organisms from all three evolutionary domains. The computational expense of this wide-ranging exploration is kept to a minimum by the use of rigidity analysis and rapid all-atom simulations of flexible motion, combining geometric simulation and elastic network modeling. CS structures from thermophiles display increased structural rigidity compared with the mesophilic enzyme. A CS structure from a psychrophile, stabilized by strong ionic interactions, appears to display likewise increased rigidity in conventional rigidity analysis; however, a novel modified analysis, taking into account the weakening of the hydrophobic effect at low temperatures, shows a more appropriate decreased rigidity. These rigidity variations do not, however, affect the character of the flexible dynamics, which are well conserved across all the structures studied. Simulation trajectories not only duplicate the crystallographically observed symmetric open-to-closed transitions, but also identify motions describing a previously unidentified antisymmetric functional motion. This antisymmetric motion would not be directly observed in crystallography but is revealed as an intrinsic property of the CS structure by modeling of flexible motion. This suggests that the functional motion closing the binding clefts in CS may be independent rather than symmetric and cooperative. © 2014 Wiley Periodicals, Inc.

The Emergence of Frequency Effects in Eye Movements

ERIC Educational Resources Information Center

Vanyukov, Polina M.; Warren, Tessa; Wheeler, Mark E.; Reichle, Erik D.

2012-01-01

A visual search experiment employed strings of Landolt "C"s to examine how the gap size of and frequency of exposure to distractor strings affected eye movements. Increases in gap size were associated with shorter first-fixation durations, gaze durations, and total times, as well as fewer fixations. Importantly, both the number and duration of…

A New Type of Atom Interferometry for Testing Fundamental Physics

NASA Astrophysics Data System (ADS)

Lorek, Dennis; Lämmerzahl, Claus; Wicht, Andreas

We present a new type of atom interferometer (AI) that provides a tool for ultra-high precision tests of fundamental physics. As an example we present how an AI based on highly charged hydrogen-like atoms is affected by gravitational waves (GW). A qualitative description of the quantum interferometric measurement principle is given, the modifications in the atomic Hamiltonian caused by the GW are presented, and the size of the resulting frequency shifts in hydrogen-like atoms is estimated. For a GW amplitude of h = 10-23 the frequency shift is of the order of 110μHz for an AI based on a 91-fold charged uranium ion. A frequency difference of this size can be resolved by current AIs in 1s.

Active Faraday optical frequency standard.

PubMed

Zhuang, Wei; Chen, Jingbiao

2014-11-01

We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.

One year follow-up of contrast sensitivity following conventional laser in situ keratomileusis and laser epithelial keratomileusis.

PubMed

Townley, Deirdre; Kirwan, Caitriona; O'Keefe, Michael

2012-02-01

To determine the effect of conventional laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) for myopia on contrast sensitivity (CS) using the Pelli-Robson and Vector Vision CSV-1000E CS tests. A prospective, comparative study was conducted on 36 eyes of 36 patients with myopia undergoing LASIK (18 eyes) and LASEK (18 eyes). Surgery was performed using the Technolas 217z laser (Bausch & Lomb). CS was recorded preoperatively and at 3, 6 and 12 months postoperatively. No statistically significant difference was found in LogMAR uncorrected visual acuity post-LASIK (-0.02 ± 0.16) and LASEK (-0.04 ± 0.14). Using the Pelli-Robson, CS was significantly lower in the LASIK group 3 and 6 months postoperatively. No significant postoperative reduction in CS was observed in either treatment group. Using the CSV-1000E test, CS was significantly reduced post-LASIK at 3 (p = 0.05) and 6 (p = 0.05) cycles/degree under photopic conditions. No significant postoperative change occurred in the LASEK group under photopic or scotopic conditions. There was no significant difference in postoperative CS between the LASIK and LASEK groups at 3, 6, 12 or 18 cycles/degree using the CSV-1000E test. One year postoperatively, there was no difference in CS between both treatment groups using the Pelli-Robson and CSV-1000E tests. CS was reduced postoperatively in the LASIK group at the lower spatial frequencies under photopic conditions. No postoperative change was detected in CS following LASIK or LASEK using the Pelli-Robson test. © 2010 The Authors. Journal compilation © 2010 Acta Ophthalmol.

Cyclosporin A Inhibits Rotavirus Replication and Restores Interferon-Beta Signaling Pathway In Vitro and In Vivo

PubMed Central

He, Haiyang; Wu, Yuzhang

2013-01-01

Rotavirus (RV) is the most common cause of severe diarrhea among infants and young children. Currently, there is no specific drug available against rotavirus, largely due to the lack of an ideal target molecule which has hampered drug development. Our previous studies have revealed that cyclosporin A (CsA) might be potentially useful as an anti-RV drug. We therefore used both cellular and mouse models to study the immunological safety and effectiveness of CsA as an anti-RV drug. We found that CsA treatment of HT-29 cells before, during, and after viral infection efficiently inhibited Wa strain RV replication and restored IFN-β expression in a HT-29 cell line model. Exploring the underlying mechanisms showed that CsA promoted Interferon Regulatory Factor-5 (IRF-5) expression (a key positive regulator of the type I IFN signaling pathway), but not IRF-1, IRF-3, or IRF-7. Additionally, CsA inhibited SOCS-1 expression (the key negative regulator of IFN-α/β), but not SOCS-2 or SOCS-3. The antiviral effect of CsA was confirmed in an RV-infected neonatal mouse model by evaluation of antigen clearance and assessment of changes in intestinal tissue pathology. Also, no differences in T cell frequency or proliferation between the CsA- and vehicle-treated groups were observed. Thus, both our in vitro and in vivo findings suggest that CsA, through modulating the expression of key regulators in IFN signaling pathway, promote type I IFN-based intracellular innate immunity in RV host cells. These findings suggest that CsA may be a useful candidate to develop a new anti-RV strategy, although further evaluation and characterization of CsA on RV-induced diarrhea are warranted. PMID:23990993

Bearing fault diagnosis using a whale optimization algorithm-optimized orthogonal matching pursuit with a combined time-frequency atom dictionary

NASA Astrophysics Data System (ADS)

Zhang, Xin; Liu, Zhiwen; Miao, Qiang; Wang, Lei

2018-07-01

Condition monitoring and fault diagnosis of rolling element bearings are significant to guarantee the reliability and functionality of a mechanical system, production efficiency, and plant safety. However, this is almost invariably a formidable challenge because the fault features are often buried by strong background noises and other unstable interference components. To satisfactorily extract the bearing fault features, a whale optimization algorithm (WOA)-optimized orthogonal matching pursuit (OMP) with a combined time-frequency atom dictionary is proposed in this paper. Firstly, a combined time-frequency atom dictionary whose atom is a combination of Fourier dictionary atom and impact time-frequency dictionary atom is designed according to the properties of bearing fault vibration signal. Furthermore, to improve the efficiency and accuracy of signal sparse representation, the WOA is introduced into the OMP algorithm to optimize the atom parameters for best approximating the original signal with the dictionary atoms. The proposed method is validated through analyzing the bearing fault simulation signal and the real vibration signals collected from an experimental bearing and a wheelset bearing of high-speed trains. The comparisons with the respect to the state of the art in the field are illustrated in detail, which highlight the advantages of the proposed method.

Cigarette Smoke Upregulates PDE3 and PDE4 to Decrease cAMP in Airway Cells.

PubMed

Zuo, Haoxiao; Han, Bing; Poppinga, Wilfred J; Ringnalda, Lennard; Kistemaker, Loes E M; Halayko, Andrew J; Gosens, Reinoud; Nikolaev, Viacheslav O; Schmidt, Martina

2018-05-03

3', 5'-cyclic adenosine monophosphate (cAMP) is a central second messenger that broadly regulates cell function and can underpin pathophysiology. In chronic obstructive pulmonary disease (COPD), a lung disease primarily provoked by cigarette smoke (CS), the induction of cAMP-dependent pathways, via inhibition of hydrolyzing phosphodiesterases (PDEs), is a prime therapeutic strategy. Mechanisms that disrupt cAMP signaling in airway cells, in particular regulation of endogenous PDEs are poorly understood. We used a novel Förster resonance energy transfer (FRET) based cAMP biosensor in mouse in vivo, ex vivo precision cut lung slices (PCLS), and in human in vitro cell models to track the effects of CS exposure. Under fenoterol stimulated conditions, FRET responses to cilostamide were significantly increased in in vivo, ex vivo PCLS exposed to CS and in human airway smooth muscle cells exposed to CS extract. FRET signals to rolipram were only increased in the in vivo CS model. Under basal conditions, FRET responses to cilostamide and rolipram were significantly increased in in vivo, ex vivo PCLS exposed to CS. Elevated FRET signals to rolipram correlated with a protein upregulation of PDE4 subtypes. In ex vivo PCLS exposed to CS extract, rolipram reversed downregulation of ciliary beating frequency, whereas only cilostamide significantly increased airway relaxation of methacholine pre-contracted airways. We show that CS upregulates expression and activity of both PDE3 and PDE4, which regulate real-time cAMP dynamics. These mechanisms determine the availability of cAMP and can contribute to CS-induced pulmonary pathophysiology. This article is protected by copyright. All rights reserved.

g_contacts: Fast contact search in bio-molecular ensemble data

NASA Astrophysics Data System (ADS)

Blau, Christian; Grubmuller, Helmut

2013-12-01

Short-range interatomic interactions govern many bio-molecular processes. Therefore, identifying close interaction partners in ensemble data is an essential task in structural biology and computational biophysics. A contact search can be cast as a typical range search problem for which efficient algorithms have been developed. However, none of those has yet been adapted to the context of macromolecular ensembles, particularly in a molecular dynamics (MD) framework. Here a set-decomposition algorithm is implemented which detects all contacting atoms or residues in maximum O(Nlog(N)) run-time, in contrast to the O(N2) complexity of a brute-force approach. Catalogue identifier: AEQA_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEQA_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 8945 No. of bytes in distributed program, including test data, etc.: 981604 Distribution format: tar.gz Programming language: C99. Computer: PC. Operating system: Linux. RAM: ≈Size of input frame Classification: 3, 4.14. External routines: Gromacs 4.6[1] Nature of problem: Finding atoms or residues that are closer to one another than a given cut-off. Solution method: Excluding distant atoms from distance calculations by decomposing the given set of atoms into disjoint subsets. Running time:≤O(Nlog(N)) References: [1] S. Pronk, S. Pall, R. Schulz, P. Larsson, P. Bjelkmar, R. Apostolov, M. R. Shirts, J.C. Smith, P. M. Kasson, D. van der Spoel, B. Hess and Erik Lindahl, Gromacs 4.5: a high-throughput and highly parallel open source molecular simulation toolkit, Bioinformatics 29 (7) (2013).

Controlling the Photophysical Properties of Semiconductor Quantum Dot Arrays by Strategically Altering Their Surface Chemistry

NASA Astrophysics Data System (ADS)

Marshall, Ashley R.

Semiconductor quantum dots (QDs) are interesting materials that, after less than 40 years of research, are used in commercial products. QDs are now found in displays, such as Samsung televisions and the Kindle Fire, and have applications in lighting, bio-imaging, quantum computing, and photovoltaics. They offer a large range of desirable properties: a controllable band gap, solution processability, controlled energy levels, and are currently the best materials for multiple exciton generation. The tunable optoelectronic properties of QDs can be controlled using size, shape, composition, and surface treatments--as shown here. Due to the quasi-spherical shape of QDs the surface to volume ratio is high, i.e. many of the constituent atoms are found on the QD surface. This makes QDs highly sensitive to surface chemistry modifications. This thesis encompasses the effects of surface treatments for QDs of two semiconducting materials: lead chalcogenides and CsPbI3. Our group developed a new synthetic technique for lead chalcogenide QDs via the cation exchange of cadmium chalcogenides. An in-depth chemical analysis is paired with optical and electrical studies and we find that metal halide residue contributes to the oxidative stability and decreased trap state density in cation-exchanged PbS QDs. We exploit these properties to make air-stable QD photovoltaic devices from both PbS and PbSe QD materials. Beyond the effects of residual atoms left from the synthetic technique, I investigated how to controllably add atoms onto the surface of QDs. I found that by introducing metal halides as a post-treatment in an electronically coupled array I am able to control the performance parameters in QD photovoltaic devices. These treatments fully infiltrate the assembled film, even under short exposure times and allow me to add controlled quantities of surface atoms to study their effects on film properties and photovoltaic device performance. Finally, I sought to apply the knowledge of the lead chalcogenide QD surfaces to produce QD photovoltaics from a new material: CsPbI3. I fabricated the first perovskite QD photovoltaic devices and using similar treatment methods as the lead chalcogenide QD arrays, I am able to influence the photophysical properties of CsPbI3 QD arrays.

Programmable, secondary frequency standard based infrared synthesizer using tunable lead-salt diode lasers

NASA Technical Reports Server (NTRS)

Freed, C.; Bielinski, J. W.; Lo, W.

1983-01-01

Quantum phase noise limited Lorentzian power spectral densities were achieved with tunable lead-salt diode lasers. Linewidths as narrow as 22 kHz were observed. A truly programmable infrared synthesizer was produced by frequency-offset-locking the tunable diode lasers to the combination of a stable CO2 (or CO) reference laser and a programmable microwave frequency synthesizer. Absolute frequency accuracy and reproducibility of about + or - 30 kHz (0.000001 kaysers) relative to the primary Cs frequency standard may now be obtained with this technique.

Laser frequency stabilization using a commercial wavelength meter

NASA Astrophysics Data System (ADS)

Couturier, Luc; Nosske, Ingo; Hu, Fachao; Tan, Canzhu; Qiao, Chang; Jiang, Y. H.; Chen, Peng; Weidemüller, Matthias

2018-04-01

We present the characterization of a laser frequency stabilization scheme using a state-of-the-art wavelength meter based on solid Fizeau interferometers. For a frequency-doubled Ti-sapphire laser operated at 461 nm, an absolute Allan deviation below 10-9 with a standard deviation of 1 MHz over 10 h is achieved. Using this laser for cooling and trapping of strontium atoms, the wavemeter scheme provides excellent stability in single-channel operation. Multi-channel operation with a multimode fiber switch results in fluctuations of the atomic fluorescence correlated to residual frequency excursions of the laser. The wavemeter-based frequency stabilization scheme can be applied to a wide range of atoms and molecules for laser spectroscopy, cooling, and trapping.

Rococo study: a real-world evaluation of an over-the-counter medicine in acute cough (a multicentre, randomised, controlled study).

PubMed

Birring, S S; Brew, J; Kilbourn, A; Edwards, V; Wilson, R; Morice, A H

2017-01-16

To investigate the efficacy and safety of CS1002, an over-the-counter cough treatment containing diphenhydramine, ammonium chloride and levomenthol in a cocoa-based demulcent. A multicentre, randomised, parallel group, controlled, single-blinded study in participants with acute upper respiratory tract infection-associated cough. 4 general practitioner (GP) surgeries and 14 pharmacies in the UK. Participants aged ≥18 years who self-referred to a GP or pharmacist with acute cough of <7 days' duration. Participant inclusion criterion was cough severity ≥60 mm on a 0-100 mm visual analogue scale (VAS). Exclusion criteria included current smokers or history of smoking within the past 12 months (including e-cigarettes). 163 participants were randomised to the study (mean participant age 38 years, 57% females). Participants were randomised to CS1002 (Unicough) or simple linctus (SL), a widely used cough treatment, and treatment duration was 7 days or until resolution of cough. The primary analysis was intention-to-treat (157 participants) and comprised cough severity assessed using a VAS after 3 days' treatment (prespecified primary end point at day 4). Cough frequency, sleep disruption, health status (Leicester Cough Questionnaire (LCQ-acute)) and cough resolution were also assessed. At day 4 (primary end point), the adjusted mean difference (95% CI) in cough severity VAS between CS1002 and SL was -5.9 mm (-14.4 to 2.7), p=0.18. At the end of the study (day 7) the mean difference in cough severity VAS was -4.2 mm (-12.2 to 3.9), p=0.31. CS1002 was associated with a greater reduction in cough sleep disruption (mean difference -11.6 mm (-20.6 to 2.7), p=0.01) and cough frequency (mean difference -8.1 mm (-16.2 to 0.1), p=0.05) compared with SL. There was greater improvement in LCQ-acute quality of life scores with CS1002 compared with SL: mean difference (95% CI) 1.2 (0.05 to 2.36), p=0.04 after 5 days' treatment. More participants prematurely stopped treatment due to cough improvement in the CS1002 group (24.4%) compared with SL (10.7%; p=0.02). Adverse events (AEs) were comparable between CS1002 (20.5%) and SL (27.6%) and largely related to the study indication. 6 participants (7%) in the CS1002 group reduced the dose of medication due to drowsiness/tiredness, which subsequently resolved. These events were not reported by participants as AEs. Although the primary end point was not achieved, CS1002 was associated with greater reductions in cough frequency, sleep disruption and improved health status compared with SL. EudraCT number 2014-004255-31. 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/.

Stimulated emission and lasing from all-inorganic perovskite quantum dots

NASA Astrophysics Data System (ADS)

Sun, Handong; Wang, Yue; Li, Xiaoming; Haibo, Zeng

We present superior optical gain and lasing properties in a new class of emerging quantum materials, the colloidal all-inorganic cesium lead halide perovskite quantum dots (IPQDs) (CsPbX3, X = Cl, Br, I). Our result has indicated that such material system show combined merits of both colloidal quantum dots and halide perovskites. Low-threshold and ultrastable stimulated emission was demonstrated under atmospheric condition. The flexibility and advantageous optical gain properties of these CsPbX3 IPQDs were manifested by demonstration of an optically pumped micro-laser. The nonlinear optical properties including the multi-photon absorption and resultant photoluminescence of the CsPbX3 nanocrystals were investigated. A large two-photon absorption cross-section of up to ~1.2×105 GM is determined from 9 nm-sized CsPbBr3 nanocrystals. Moreover, low-threshold frequency-upconverted stimulated emission by two-photon absorption was observed from the thin films of close-packed CsPbBr3 nanocrystals. We further realize the three-photon pumped stimulated emission in green spectra range from colloidal IPQD.

Field optimization method of a dual-axis atomic magnetometer based on frequency-response and dynamics

NASA Astrophysics Data System (ADS)

Xing, Li; Quan, Wei; Fan, Wenfeng; Li, Rujie; Jiang, Liwei; Fang, Jiancheng

2018-05-01

The frequency-response and dynamics of a dual-axis spin-exchange-relaxation-free (SERF) atomic magnetometer are investigated by means of transfer function analysis. The frequency-response at different bias magnetic fields is tested to demonstrate the effect of the residual magnetic field. The resonance frequency of alkali atoms and magnetic linewidth can be obtained simultaneously through our theoretical model. The coefficient of determination of the fitting results is superior to 0.995 with 95% confidence bounds. Additionally, step responses are applied to analyze the dynamics of the control system and the effect of imperfections. Finally, a noise-limited magnetic field resolution of 15 fT {{\\sqrt{Hz}}-1} has been achieved for our dual-axis SERF atomic magnetometer through magnetic field optimization.

Molecular structure of the trans and cis isomers of metal-free phthalocyanine studied by gas-phase electron diffraction and high-level quantum chemical calculations: NH tautomerization and calculated vibrational frequencies.

PubMed

Strenalyuk, Tatyana; Samdal, Svein; Volden, Hans Vidar

2008-05-29

The molecular structure of the trans isomer of metal-free phthalocyanine (H2Pc) is determined using the gas electron diffraction (GED) method and high-level quantum chemical calculations. B3LYP calculations employing the basis sets 6-31G**, 6-311++G**, and cc-pVTZ give two tautomeric isomers for the inner H atoms, a trans isomer having D2h symmetry and a cis isomer having C2v symmetry. The trans isomer is calculated to be 41.6 (B3LYP/6-311++G**, zero-point corrected) and 37.3 kJ/mol (B3LYP/cc-pVTZ, not zero-point corrected) more stable than the cis isomer. However, Hartree-Fock (HF) calculations using different basis sets predict that cis is preferred and that trans does not exist as a stable form of the molecule. The equilibrium composition in the gas phase at 471 degrees C (the temperature of the GED experiment) calculated at the B3LYP/6-311++G** level is 99.8% trans and 0.2% cis. This is in very good agreement with the GED data, which indicate that the mole fraction of the cis isomer is close to zero. The transition states for two mechanisms of the NH tautomerization have been characterized. A concerted mechanism where the two H atoms move simultaneously yields a transition state of D2h symmetry and an energy barrier of 95.8 kJ/mol. A two-step mechanism where a trans isomer is converted to a cis isomer, which is converted into another trans isomer, proceeds via two transition states of C(s) symmetry and an energy barrier of 64.2 kJ/mol according to the B3LYP/6-311++G** calculation. The molecular geometry determined from GED is in very good agreement with the geometry obtained from the quantum chemical calculations. Vibrational frequencies, IR, and Raman intensities have been calculated using B3LYP/6-311++G**. These calculations indicate that the molecule is rather flexible with six vibrational frequencies in the range of 20-84 cm(-1) for the trans isomer. The cis isomer might be detected by infrared matrix spectroscopy since the N-H stretching frequencies are very different for the two isomers.