Zeeman effect in sulfur monoxide: A tool to probe magnetic fields in star forming regions⋆

PubMed Central

Cazzoli, Gabriele; Lattanzi, Valerio; Coriani, Sonia; Gauss, Jürgen; Codella, Claudio; Ramos, Andrés Asensio; Cernicharo, José; Puzzarini, Cristina

2017-01-01

Context Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN. Aims We decided to investigate the suitability of sulfur monoxide (SO), which is one of the most abundant species in star forming regions, for probing the intensity of magnetic fields via the Zeeman effect. Methods We investigated the Zeeman effect for several rotational transitions of SO in the (sub-)mm spectral regions by using a frequency-modulated, computer-controlled spectrometer, and by applying a magnetic field parallel to the radiation propagation (i.e., perpendicular to the oscillating magnetic field of the radiation). To support the experimental determination of the g factors of SO, a systematic quantum-chemical investigation of these parameters for both SO and O2 has been carried out. Results An effective experimental-computational strategy for providing accurate g factors as well as for identifying the rotational transitions showing the strongest Zeeman effect has been presented. Revised g factors have been obtained from a large number of SO rotational transitions between 86 and 389 GHz. In particular, the rotational transitions showing the largest Zeeman shifts are: N, J = 2, 2 ← 1, 1 (86.1 GHz), N, J = 4, 3 ← 3, 2 (159.0 GHz), N, J = 1, 1 ← 0, 1 (286.3 GHz), N, J = 2, 2 ← 1, 2 (309.5 GHz), and N, J = 2, 1 ← 1, 0 (329.4 GHz). Our investigation supports SO as a good candidate for probing magnetic fields in high-density star forming regions. PMID:29151607

Zeeman effect in sulfur monoxide. A tool to probe magnetic fields in star forming regions

NASA Astrophysics Data System (ADS)

Cazzoli, Gabriele; Lattanzi, Valerio; Coriani, Sonia; Gauss, Jürgen; Codella, Claudio; Ramos, Andrés Asensio; Cernicharo, José; Puzzarini, Cristina

2017-09-01

Context. Magnetic fields play a fundamental role in star formation processes and the best method to evaluate their intensity is to measure the Zeeman effect of atomic and molecular lines. However, a direct measurement of the Zeeman spectral pattern from interstellar molecular species is challenging due to the high sensitivity and high spectral resolution required. So far, the Zeeman effect has been detected unambiguously in star forming regions for very few non-masing species, such as OH and CN. Aims: We decided to investigate the suitability of sulfur monoxide (SO), which is one of the most abundant species in star forming regions, for probing the intensity of magnetic fields via the Zeeman effect. Methods: We investigated the Zeeman effect for several rotational transitions of SO in the (sub-)mm spectral regions by using a frequency-modulated, computer-controlled spectrometer, and by applying a magnetic field parallel to the radiation propagation (I.e., perpendicular to the oscillating magnetic field of the radiation). To support the experimental determination of the g factors of SO, a systematic quantum-chemical investigation of these parameters for both SO and O2 has been carried out. Results: An effective experimental-computational strategy for providing accurate g factors as well as for identifying the rotational transitions showing the strongest Zeeman effect has been presented. Revised g factors have been obtained from a large number of SO rotational transitions between 86 and 389 GHz. In particular, the rotational transitions showing the largest Zeeman shifts are: N,J = 2, 2 ← 1, 1 (86.1 GHz), N,J = 4, 3 ← 3, 2 (159.0 GHz), N,J = 1, 1 ← 0, 1 (286.3 GHz), N,J = 2, 2 ← 1, 2 (309.5 GHz), and N,J = 2, 1 ← 1, 0 (329.4 GHz). Our investigation supports SO as a good candidate for probing magnetic fields in high-density star forming regions. The complete list of measured Zeeman components is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A20

Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting zeeman degeneracy.

PubMed

Xu, Zhongxiao; Wu, Yuelong; Tian, Long; Chen, Lirong; Zhang, Zhiying; Yan, Zhihui; Li, Shujing; Wang, Hai; Xie, Changde; Peng, Kunchi

2013-12-13

Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200  μs and 78.4% at 4.5 ms, respectively.

Electromagnetically-induced-transparency intensity-correlation power broadening in a buffer gas

NASA Astrophysics Data System (ADS)

Zheng, Aojie; Green, Alaina; Crescimanno, Michael; O'Leary, Shannon

2016-04-01

Electromagnetically-induced-transparency (EIT) noise correlation spectroscopy holds promise as a simple, robust method for performing high-resolution spectroscopy used in optical magnetometry and clocks. Of relevance to these applications, we report on the role of buffer gas pressure and magnetic field gradients on power broadening of Zeeman-EIT noise correlation resonances.

Fast optical cooling of nanomechanical cantilever with the dynamical Zeeman effect.

PubMed

Zhang, Jian-Qi; Zhang, Shuo; Zou, Jin-Hua; Chen, Liang; Yang, Wen; Li, Yong; Feng, Mang

2013-12-02

We propose an efficient optical electromagnetically induced transparency (EIT) cooling scheme for a cantilever with a nitrogen-vacancy center attached in a non-uniform magnetic field using dynamical Zeeman effect. In our scheme, the Zeeman effect combined with the quantum interference effect enhances the desired cooling transition and suppresses the undesired heating transitions. As a result, the cantilever can be cooled down to nearly the vibrational ground state under realistic experimental conditions within a short time. This efficient optical EIT cooling scheme can be reduced to the typical EIT cooling scheme under special conditions.

Zeeman-Field-Tuned Topological Phase Transitions in a Two-Dimensional Class-DIII Superconductor

PubMed Central

Deng, W. Y.; Geng, H.; Luo, W.; Sheng, L.; Xing, D. Y.

2016-01-01

We investigate the topological phase transitions in a two-dimensional time-reversal invariant topological superconductor in the presence of a Zeeman field. Based on the spin Chern number theory, we find that the system exhibits a number of topologically distinct phases with changing the out-of-plane component of the Zeeman field, including a quantum spin Hall-like phase, quantum anomalous Hall-like phases with total Chern number C = −2, −1, 1 and 2, and a topologically trivial superconductor phase. The BdG band gap closes at each boundary of the phase transitions. Furthermore, we demonstrate that the zero bias conductance provides clear transport signatures of the different topological phases, which are robust against symmetry-breaking perturbations. PMID:27148675

Polarization-insensitive techniques for optical signal processing

NASA Astrophysics Data System (ADS)

Salem, Reza

2006-12-01

This thesis investigates polarization-insensitive methods for optical signal processing. Two signal processing techniques are studied: clock recovery based on two-photon absorption in silicon and demultiplexing based on cross-phase modulation in highly nonlinear fiber. The clock recovery system is tested at an 80 Gb/s data rate for both back-to-back and transmission experiments. The demultiplexer is tested at a 160 Gb/s data rate in a back-to-back experiment. We experimentally demonstrate methods for eliminating polarization dependence in both systems. Our experimental results are confirmed by theoretical and numerical analysis.

Suppression of Zeeman gradients by nuclear polarization in double quantum dots.

PubMed

Frolov, S M; Danon, J; Nadj-Perge, S; Zuo, K; van Tilburg, J W W; Pribiag, V S; van den Berg, J W G; Bakkers, E P A M; Kouwenhoven, L P

2012-12-07

We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the g-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.

Ultracold Molecules in Optical Lattices: Efficient Production and Application to Molecular Clocks

DTIC Science & Technology

2015-05-03

near the intercombination- line threshold were measured for a variety of states, and explained by considering nonadiabatic effects ( Coriolis coupling) in...Moszynski, T. Zelevinsky. Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts, Physical Review Letters, (12...M. McDonald, G. Reinaudi, W. Skomorowski, R. Moszynski, T. Zelevinsky. Measurement of Nonadiabatic Effects in Ultracold Molecules via Anomalous

Dynamic Jahn-Teller effect: Calculation of fine structure spectrum, isotope shift and Zeeman behavior at deep center Ni2+ in CdS

NASA Astrophysics Data System (ADS)

Schoepp, Juergen

The internal transition of the deep center Ni2+ in II to IV semiconductor cadmium sulfide is examined with reference to crystal field theory. An algorithm was developed for calculation, in a basis fitted to trigonal symmetry, of fine structure operator matrix which is made of the sum of operators from spin trajectory coupling, trigonal field and electron phonon coupling. The dependence of energy level on the mass was calculated in order to examine the isotropy effect at Ni2+ transition. The mass dependence of phonon energy was estimated in an atomic cluster by using a valence force model from Keating for elastic energy. The Zeeman behavior of Ni2+ transition was examined for magnetic fields; the Zeeman operator was added to the fine structure operator and the resulting matrix was diagonalized. It is noticed that calculations are quantitatively and qualitatively in agreement with experiments.

Frequency metrology using highly charged ions

NASA Astrophysics Data System (ADS)

Crespo López-Urrutia, J. R.

2016-06-01

Due to the scaling laws of relativistic fine structure splitting, many forbidden optical transitions appear within the ground state configurations of highly charged ions (HCI). In some hydrogen-like ions, even the hyperfine splitting of the 1s ground state gives rise to optical transitions. Given the very low polarizability of HCI, such laser-accessible transitions are extremely impervious to external perturbations and systematics that limit optical clock performance and arise from AC and DC Stark effects, such as black-body radiation and light shifts. Moreover, AC and DC Zeeman splitting are symmetric due to the much larger relativistic spin-orbit coupling and corresponding fine-structure splitting. Appropriate choice of states or magnetic sub-states with suitable total angular momentum and magnetic quantum numbers can lead to a cancellation of residual quadrupolar shifts. All these properties are very advantageous for the proposed use of HCI forbidden lines as optical frequency standards. Extremely magnified relativistic, quantum electrodynamic, and nuclear size contributions to the binding energies of the optically active electrons make HCI ideal tools for fundamental research, as in proposed studies of a possible time variation of the fine structure constant. Beyond this, HCI that cannot be photoionized by vacuum-ultraviolet photons could also provide frequency standards for future lasers operating in that range.

Feedback repression is required for mammalian circadian clock function.

PubMed

Sato, Trey K; Yamada, Rikuhiro G; Ukai, Hideki; Baggs, Julie E; Miraglia, Loren J; Kobayashi, Tetsuya J; Welsh, David K; Kay, Steve A; Ueda, Hiroki R; Hogenesch, John B

2006-03-01

Direct evidence for the requirement of transcriptional feedback repression in circadian clock function has been elusive. Here, we developed a molecular genetic screen in mammalian cells to identify mutants of the circadian transcriptional activators CLOCK and BMAL1, which were uncoupled from CRYPTOCHROME (CRY)-mediated transcriptional repression. Notably, mutations in the PER-ARNT-SIM domain of CLOCK and the C terminus of BMAL1 resulted in synergistic insensitivity through reduced physical interactions with CRY. Coexpression of these mutant proteins in cultured fibroblasts caused arrhythmic phenotypes in population and single-cell assays. These data demonstrate that CRY-mediated repression of the CLOCK/BMAL1 complex activity is required for maintenance of circadian rhythmicity and provide formal proof that transcriptional feedback is required for mammalian clock function.

Indium Single-Ion Frequency Standard

NASA Technical Reports Server (NTRS)

Nagourney, Warren

2001-01-01

A single laser-cooled indium ion is a promising candidate for an ultimate resolution optical time or frequency standard. It can be shown that single ions from group IIIA of the periodic table (indium, thallium, etc.) can have extremely small systematic errors. In addition to being free from Doppler, transit-time and collisional shifts, these ions are also quite insensitive to perturbations from ambient magnetic and electric fields (mainly due to the use of a J=0-0 transition for spectroscopy). Of all group IIIA ions, indium seems to be the most practical, since it is heavy enough to have a tolerable intercombination cooling transition rate and (unlike thallium) has transitions which are easily accessible with frequency multiplied continuous-wave lasers. A single indium ion standard has a potential inaccuracy of one part in 10(exp 18) for integration times of 10(exp 6) seconds. We have made substantial progress during the grant period in constructing a frequency standard based upon a single indium ion. At the beginning of the grant period, single indium ions were being successfully trapped, but the lasers and optical systems were inadequate to achieve the desired goal. We have considerably improved the stability of the dye laser used to cool the ions and locked it to a molecular resonance line, making it possible to observe stable cooling-line fluorescence from a single indium ion for reasonable periods of time, as required by the demands of precision spectroscopy. We have substantially improved the single-ion fluorescence signal with significant benefits for the detection efficiency of forbidden transitions using the 'shelving' technique. Finally, we have constructed a compact, efficient UV 'clock' laser and observed 'clock' transitions in single indium ions using this laser system. We will elaborate on these accomplishments.

Compressing the fluctuation of the magnetic field by dynamic compensation

NASA Astrophysics Data System (ADS)

Wang, Wenli; Dong, Richang; Wei, Rong; Chen, Tingting; Wang, Qian; Wang, Yuzhu

2018-03-01

We present a dynamic compensation method to compress the spatial fluctuation of the static magnetic field (C-field) that provides a quantization axis in the atomic fountain clock. The coil current of the C-field is point-by-point modulated in accordance with the atoms probing the magnetic field along the flight trajectory. A homogeneous field with a 0.2 nT inhomogeneity is produced compared to a 5 nT under the static magnetic field with a constant current during the Ramsey interrogation. The corresponding uncertainty associated with the second-order Zeeman shift that we calculate is improved by one order of magnitude. The technique provides an alternative method to improve the uniformity of the magnetic field, particularly for large-scale equipment that is difficult to construct with an effective magnetic shielding. Our method is simple, robust, and essentially important in frequency evaluations concerning the dominant uncertainty contribution due to the quadratic Zeeman shift.

Zeeman Tuning Rate for Q Branch Transitions in the v3 Band of NO2

NASA Technical Reports Server (NTRS)

Mahon, C. R.; Chackerian, C., Jr.; Gore, Warren J. Y. (Technical Monitor)

1997-01-01

Zeeman tuning rates have bee a measured for Q branch transitions in the v3 band of NO2(approx.1610/cm) for magnetic fields of up to 564 Gauss. The average measured tuning rate is 0.1815(53) x 10(exp -3)/cm/Gauss with no dependence on Ka within the approx. equal to 3% standard deviation. Despite significant ,pin-rotation interaction between several of the observed levels the result agrees with the simple linear model for Honda case (be molecules (tuning rate = 2muogs = 0.18696 x 10(exp -3)/cm/Gauss) which neglects the spin-rotation interaction between different J states. The Zeeman effect is analyzed in a full treatment of the Hamiltonian, including spin-rotation interaction, in order to account for the agreement with 2muogs and to explore the onset of spin-rotation effects in the spectra as the magnetic field is increased.

Quantum incommensurate skyrmion crystals and commensurate to in-commensurate transitions in cold atoms and materials with spin-orbit couplings in a Zeeman field

NASA Astrophysics Data System (ADS)

Sun, Fadi; Ye, Jinwu; Liu, Wu-Ming

2017-08-01

In this work, we study strongly interacting spinor atoms in a lattice subject to a two dimensional (2d) anisotropic Rashba type of spin orbital coupling (SOC) and an Zeeman field. We find the interplay between the Zeeman field and the SOC provides a new platform to host rich and novel classes of quantum commensurate and in-commensurate phases, excitations and phase transitions. These commensurate phases include two collinear states at low and high Zeeman field, two co-planar canted states at mirror reflected SOC parameters respectively. Most importantly, there are non-coplanar incommensurate Skyrmion (IC-SkX) crystal phases surrounded by the four commensurate phases. New excitation spectra above all the five phases, especially on the IC-SKX phase are computed. Three different classes of quantum commensurate to in-commensurate transitions from the IC-SKX to its four neighboring commensurate phases are identified. Finite temperature behaviors and transitions are discussed. The critical temperatures of all the phases can be raised above that reachable by current cold atom cooling techniques simply by tuning the number of atoms N per site. In view of recent impressive experimental advances in generating 2d SOC for cold atoms in optical lattices, these new many-body phenomena can be explored in the current and near future cold atom experiments. Applications to various materials such as MnSi, {Fe}}0.5 {Co}}0.5Si, especially the complex incommensurate magnetic ordering in Li2IrO3 are given.

Zeeman relaxation of MnH (X7Σ+) in collisions with He3: Mechanism and comparison with experiment

NASA Astrophysics Data System (ADS)

Turpin, F.; Stoecklin, T.; Halvick, Ph.

2011-03-01

We present a theoretical study of the Zeeman relaxation of the magnetically trappable lowest field seeking state of MnH (7Σ) in collisions with He3. We analyze the collisional Zeeman transition mechanism as a function of the final diatomic state and its variation as a function of an applied magnetic field. We show that as a result of this mechanism the levels with ΔMj>2 give negligible contributions to the Zeemam relaxation cross section. We also compare our results to the experimental cross sections obtained from the buffer-gas cooling and magnetic trapping of this molecule and investigate the dependence of the Zeeman relaxation cross section on the accuracy of the three-body interaction at ultralow energies.

Circularly polarized zero-phonon transitions of vacancies in diamond at high magnetic fields

NASA Astrophysics Data System (ADS)

Braukmann, D.; Glaser, E. R.; Kennedy, T. A.; Bayer, M.; Debus, J.

2018-05-01

We study the circularly polarized photoluminescence of negatively charged (NV-) and neutral (NV0) nitrogen-vacancy ensembles and neutral vacancies (V0) in diamond crystals exposed to magnetic fields of up to 10 T. We determine the orbital and spin Zeeman splitting as well as the energetic ordering of their ground and first-excited states. The spin-triplet and -singlet states of the NV- are described by an orbital Zeeman splitting of about 9 μ eV /T , which corresponds to a positive orbital g -factor of gL=0.164 under application of the magnetic field along the (001) and (111) crystallographic directions, respectively. The zero-phonon line (ZPL) of the NV- singlet is defined as a transition from the 1E' states, which are split by gLμBB , to the 1A1 state. The energies of the zero-phonon triplet transitions show a quadratic dependence on intermediate magnetic field strengths, which we attribute to a mixing of excited states with nonzero orbital angular momentum. Moreover, we identify slightly different spin Zeeman splittings in the ground (gs) and excited (es) triplet states, which can be expressed by a deviation between their spin g -factors: gS ,es=gS ,gs+Δ g with values of Δ g =0.014 and 0.029 in the (001) and (111) geometries, respectively. The degree of circular polarization of the NV- ZPLs depends significantly on the temperature, which is explained by an efficient spin-orbit coupling of the excited states mediated through acoustic phonons. We further demonstrate that the sign of the circular polarization degree is switched under rotation of the diamond crystal. A weak Zeeman splitting similar to Δ g μBB measured for the NV- ZPLs is also obtained for the NV0 zero-phonon lines, from which we conclude that the ground state is composed of two optically active states with compensated orbital contributions and opposite spin-1/2 momentum projections. The zero-phonon lines of the V0 show Zeeman splittings and degrees of the circular polarization with opposite signs. The magnetophotoluminescence data indicate that the electron transition from the T12 states to the 1A ground state defines the zero-phonon emission at 1.674 eV, while the T12→1E transition is responsible for the zero-phonon line at 1.666 eV. The T12 (1E ) states are characterized by an orbital Zeeman splitting with gL=0.071 (0.128).

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

NASA Astrophysics Data System (ADS)

Brown, R. C.; Phillips, N. B.; Beloy, K.; McGrew, W. F.; Schioppo, M.; Fasano, R. J.; Milani, G.; Zhang, X.; Hinkley, N.; Leopardi, H.; Yoon, T. H.; Nicolodi, D.; Fortier, T. M.; Ludlow, A. D.

2017-12-01

Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock accuracy. Numerous theoretical studies have predicted optical lattice clock frequency shifts that scale nonlinearly with trap depth. To experimentally observe and constrain these shifts in an 171Yb optical lattice clock, we construct a lattice enhancement cavity that exaggerates the light shifts. We observe an atomic temperature that is proportional to the optical trap depth, fundamentally altering the scaling of trap-induced light shifts and simplifying their parametrization. We identify an "operational" magic wavelength where frequency shifts are insensitive to changes in trap depth. These measurements and scaling analysis constitute an essential systematic characterization for clock operation at the 10-18 level and beyond.

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.

Appendix A: The Impact of the HP 5071A on International Atomic Time

NASA Technical Reports Server (NTRS)

Allan, David W.; Lepek, Alex; Cutler, Len; Giffard, Robin; Kusters, Jack

1996-01-01

The international clock ensemble, which contributes to the generation of International Atomic Time (TAI and UTC) has improved dramatically over the last few years. The main change has been the introduction of a significant number of HP 5071A clocks. Of the 313 clocks contributing to TAI/UTC during 1994, 94 of these were HP 5071As. The environmental insensitivity of the HP 5071A clocks is more than an order of magnitude better than that of previously contributing clocks. This environmental insensitivity translates to outstanding long-term stability - with a typical flicker floor of a few x10(sup -15). in addition, there are now several hydrogen masers with cavity tuning contributing to TAI/UTC. These not only have outstanding short-term stability, but comparatively low frequency drifts and excellent intermediate-type frequency stability. By analyzing data available from the international ensemble, we have obtained two important results. First the frequency stability obtainable with an optimum algorithm is about 10(sup -15) for both the intermediate and long-term regions. It could be as good in the short-term (if time transfer measurement instabilities were reduced sufficiently. Second, with cooperation, this performance can be made available on an international basis in near real time. The recent enhancements in the contributing clocks are already providing a significant improvement in the accuracy with which UTC is made available to the world from several of the national timing centers, such as the National Institute for Standards and Technology (NIST) and the US Naval Observatory (USNO).

Zeeman splitting of 6.7 GHz methanol masers. On the uncertainty of magnetic field strength determinations

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Torres, R. M.; Dodson, R.

2011-05-01

Context. To properly determine the role of magnetic fields during massive star formation, a statistically significant sample of field measurements probing different densities and regions around massive protostars needs to be established. However, relating Zeeman splitting measurements to magnetic field strengths needs a carefully determined splitting coefficient. Aims: Polarization observations of, in particular, the very abundant 6.7 GHz methanol maser, indicate that these masers appear to be good probes of the large scale magnetic field around massive protostars at number densities up to nH2 ≈ 109 cm-3. We thus investigate the Zeeman splitting of the 6.7 GHz methanol maser transition. Methods: We have observed of a sample of 46 bright northern hemisphere maser sources with the Effelsberg 100-m telescope and an additional 34 bright southern masers with the Parkes 64-m telescope in an attempt to measure their Zeeman splitting. We also revisit the previous calculation of the methanol Zeeman splitting coefficients and show that these were severely overestimated making the determination of magnetic field strengths highly uncertain. Results: In total 44 of the northern masers were detected and significant splitting between the right- and left-circular polarization spectra is determined in >75% of the sources with a flux density >20 Jy beam-1. Assuming the splitting is due to a magnetic field according to the regular Zeeman effect, the average detected Zeeman splitting corrected for field geometry is ~0.6 m s-1. Using an estimate of the 6.7 GHz A-type methanol maser Zeeman splitting coefficient based on old laboratory measurements of 25 GHz E-type methanol transitions this corresponds to a magnetic field of ~120 mG in the methanol maser region. This is significantly higher than expected using the typically assumed relation between magnetic field and density (B∝ n_H_20.47) and potentially indicates the extrapolation of the available laboratory measurements is invalid. The stability of the right- and left-circular calibration of the Parkes observations was insufficient to determine the Zeeman splitting of the Southern sample. Spectra are presented for all sources in both samples. Conclusions: There is no strong indication that the measured splitting between right- and left-circular polarization is due to non-Zeeman effects, although this cannot be ruled out until the Zeeman coefficient is properly determined. However, although the 6.7 GHz methanol masers are still excellent magnetic field morphology probes through linear polarization observations, previous derivations of magnetic fields strength turn out to be highly uncertain. A solution to this problem will require new laboratory measurements of the methanol Landé-factors. Table 2 and Figs. 5-7 are only available in electronic form at http://www.aanda.org

Valley Zeeman splitting of monolayer MoS2 probed by low-field magnetic circular dichroism spectroscopy at room temperature

NASA Astrophysics Data System (ADS)

Wu, Y. J.; Shen, C.; Tan, Q. H.; Shi, J.; Liu, X. F.; Wu, Z. H.; Zhang, J.; Tan, P. H.; Zheng, H. Z.

2018-04-01

The valley Zeeman splitting of monolayer two-dimensional (2D) materials in the magnetic field plays an important role in the valley and spin manipulations. In general, a high magnetic field (6-65 T) and low temperature (2-30 K) were two key measurement conditions to observe the resolvable valley Zeeman splitting of monolayer 2D materials in current reported experiments. In this study, we experimentally demonstrate an effective measurement scheme by employing magnetic circular dichroism (MCD) spectroscopy, which enables us to distinguish the valley Zeeman splitting under a relatively low magnetic field of 1 T at room temperature. MCD peaks related to both A and B excitonic transitions in monolayer MoS2 can be clearly observed. Based on the MCD spectra under different magnetic fields (-3 to 3 T), we obtained the valley Zeeman splitting energy and the g-factors of A and B excitons, respectively. Our results show that MCD spectroscopy is a high-sensitive magneto-optical technique to explore the valley and spin manipulation in 2D materials.

Mapping the absolute magnetic field and evaluating the quadratic Zeeman-effect-induced systematic error in an atom interferometer gravimeter

NASA Astrophysics Data System (ADS)

Hu, Qing-Qing; Freier, Christian; Leykauf, Bastian; Schkolnik, Vladimir; Yang, Jun; Krutzik, Markus; Peters, Achim

2017-09-01

Precisely evaluating the systematic error induced by the quadratic Zeeman effect is important for developing atom interferometer gravimeters aiming at an accuracy in the μ Gal regime (1 μ Gal =10-8m /s2 ≈10-9g ). This paper reports on the experimental investigation of Raman spectroscopy-based magnetic field measurements and the evaluation of the systematic error in the gravimetric atom interferometer (GAIN) due to quadratic Zeeman effect. We discuss Raman duration and frequency step-size-dependent magnetic field measurement uncertainty, present vector light shift and tensor light shift induced magnetic field measurement offset, and map the absolute magnetic field inside the interferometer chamber of GAIN with an uncertainty of 0.72 nT and a spatial resolution of 12.8 mm. We evaluate the quadratic Zeeman-effect-induced gravity measurement error in GAIN as 2.04 μ Gal . The methods shown in this paper are important for precisely mapping the absolute magnetic field in vacuum and reducing the quadratic Zeeman-effect-induced systematic error in Raman transition-based precision measurements, such as atomic interferometer gravimeters.

High precision optical spectroscopy and quantum state selected photodissociation of ultracold 88Sr2 molecules in an optical lattice

NASA Astrophysics Data System (ADS)

McDonald, Mickey

2017-04-01

Over the past several decades, rapid progress has been made toward the accurate characterization and control of atoms, epitomized by the ever-increasing accuracy and precision of optical atomic lattice clocks. Extending this progress to molecules will have exciting implications for chemistry, condensed matter physics, and precision tests of physics beyond the Standard Model. My thesis describes work performed over the past six years to establish the state of the art in manipulation and quantum control of ultracold molecules. We describe a thorough set of measurements characterizing the rovibrational structure of weakly bound 88Sr2 molecules from several different perspectives, including determinations of binding energies; linear, quadratic, and higher order Zeeman shifts; transition strengths between bound states; and lifetimes of narrow subradiant states. Finally, we discuss measurements of photofragment angular distributions produced by photodissociation of molecules in single quantum states, leading to an exploration of quantum-state-resolved ultracold chemistry. The images of exploding photofragments produced in these studies exhibit dramatic interference effects and strongly violate semiclassical predictions, instead requiring a fully quantum mechanical description.

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 .

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.

Daily rhythms in locomotor circuits in Drosophila involve PDF

PubMed Central

Pírez, Nicolás; Christmann, Bethany L.

2013-01-01

The neuropeptide pigment-dispersing factor (PDF) has been studied extensively in Drosophila, and its role in circadian time-keeping has been firmly established. The role of PDF outside of the clock circuit, however, is poorly understood. A recent study suggested that PDF may act on the ellipsoid body (EB) to link the clock and sleep/activity circuits. We performed whole brain optical imaging with the fluorescence resonance energy transfer (FRET)-based cAMP sensor Epac1-camps expressed under control of the pdfR promoter to address how the clock and sleep deprivation affect the physiology of these cells. Basal cAMP levels in EB were regulated both by PDF and synaptic inputs that are controlled by the circadian clock. Acute application of PDF to the brain caused a significant, and PDF-receptor-dependent, increase in cAMP in EB cells. Application of TTX to block circuit-mediated effects of PDF increased the morning response but not the response at night, implying the existence of a temporally regulated, PDF-stimulated input that blocks cAMP generation. ACh produced both direct (TTX-insensitive) and indirect (TTX-sensitive) increases in cAMP during the day but was totally TTX-insensitive at night, indicating that ACh-stimulated inputs to the EB are suppressed at night. Sleep deprivation did not affect the cAMP responses of these cells to either PDF or ACh. These results suggest a novel role for PDF as a modulator of activity outside of the clock circuit. By elucidating the mechanisms by which the neuropeptide PDF act on its target cells, our work contributes to our understating of how the central clock coordinates activity and sleep. PMID:23678016

Daily rhythms in locomotor circuits in Drosophila involve PDF.

PubMed

Pírez, Nicolás; Christmann, Bethany L; Griffith, Leslie C

2013-08-01

The neuropeptide pigment-dispersing factor (PDF) has been studied extensively in Drosophila, and its role in circadian time-keeping has been firmly established. The role of PDF outside of the clock circuit, however, is poorly understood. A recent study suggested that PDF may act on the ellipsoid body (EB) to link the clock and sleep/activity circuits. We performed whole brain optical imaging with the fluorescence resonance energy transfer (FRET)-based cAMP sensor Epac1-camps expressed under control of the pdfR promoter to address how the clock and sleep deprivation affect the physiology of these cells. Basal cAMP levels in EB were regulated both by PDF and synaptic inputs that are controlled by the circadian clock. Acute application of PDF to the brain caused a significant, and PDF-receptor-dependent, increase in cAMP in EB cells. Application of TTX to block circuit-mediated effects of PDF increased the morning response but not the response at night, implying the existence of a temporally regulated, PDF-stimulated input that blocks cAMP generation. ACh produced both direct (TTX-insensitive) and indirect (TTX-sensitive) increases in cAMP during the day but was totally TTX-insensitive at night, indicating that ACh-stimulated inputs to the EB are suppressed at night. Sleep deprivation did not affect the cAMP responses of these cells to either PDF or ACh. These results suggest a novel role for PDF as a modulator of activity outside of the clock circuit. By elucidating the mechanisms by which the neuropeptide PDF act on its target cells, our work contributes to our understating of how the central clock coordinates activity and sleep.

Coherent Population Trapping and Optical Ramsey Interference for Compact Rubidium Clock Development

NASA Astrophysics Data System (ADS)

Warren, Zachary Aron

Coherent population trapping (CPT) and optical Ramsey interference provide new avenues for developing compact, high-performance atomic clocks. In this work, I have studied the fundamental aspects of CPT and optical Ramsey interference for Raman clock development. This thesis research is composed of two parts: theoretical and experimental studies. The theoretical component of the research was initially based on pre-existing atomic models of a three-level ?-type system in which the phenomena of CPT and Ramsey interference are formed. This model served as a starting point for studying basic characteristics of CPT and Ramsey interference such as power dependence of CPT, effects of average detuning, and ground-state decoherence on linewidth, which directly impact the performance of the Raman clock. The basic three-level model was also used to model pulsed CPT excitation and measure light shift in Ramsey interference which imposes a fundamental limit on the long-term frequency stability of the Raman clock. The theoretical calculations illustrate reduction (or suppression) of light shift in Ramsey interference as an important advantage over CPT for Raman clock development. To make the model more accurate than an ideal three-level system, I developed a comprehensive atomic model using density-matrix equations including all sixteen Zeeman sublevels in the D1 manifold of 87Rb atoms in a vapor medium. The multi-level atomic model has been used for investigating characteristics of CPT and Ramsey interference under different optical excitation schemes pertaining to the polarization states of the frequency-modulated CPT beam in a Raman clock. It is also used to study the effects of axial and traverse magnetic fields on the contrast of CPT and Ramsey interference. More importantly, the multi-level atomic model is also used to accurately calculate light shift in Ramsey interference in the D1 manifold of 87Rb atoms by taking into account all possible off-resonant excitations and the ground-state decoherence among the Zeeman sublevels. Light shift suppression in Ramsey interference with pulse saturation is also found to be evident in this comprehensive model. In the experimental component of the research, I designed a prototype of the Raman clock using a small (2 cm in length), buffer-gas filled, and isotopically pure 87Rb cell. A fiber-coupled waveguide electro-optic modulator was used to generate the frequency-modulated CPT beam for the experiments. The experimental setup was operated either by continuous excitation or pulsed excitation for experimentally characterizing CPT and Ramsey interference under different experimental conditions and for testing different optical excitation schemes which were investigated theoretically. Several iterations of the clock physics package were developed in order to attain better frequency stability performance in the Raman clock. The experimental work also provided a basis to develop a new repeated-query technique for producing an ultra-narrow linewidth central fringe with a high S/N ratio, and suppressing the side fringes in Ramsey interference. The above described research was carried out keeping in mind compact, high-performance clock development, which relies on technologies that can be miniaturized. Vapor cell based atomic clocks are ideal candidates for compact clock technology. The CPT phenomenon, observed by Raman excitation in a vapor medium, is a promising candidate for compact, high-performance Raman clock development. However, atom-field interaction involved in a vapor medium is often more complex than other media such as cold atom or atomic beam. It is difficult to model this interaction in order to predict its influence on CPT characteristics and, hence, the performance of the Raman clock. This dissertation addresses one such problem by developing a comprehensive atomic model to investigate light shift and modification of light shift in the Raman clock, particularly with pulsed excitation. It demonstrates a clear possibility of reducing (or suppressing) the light shift associated with Ramsey interference in a vapor medium for achieving higher frequency stability in the Raman clock. Additionally, theoretical comparisons of various optical excitation techniques have been calculated to demonstrate the relative strengths and weaknesses of different schemes for Raman clock development. (Abstract shortened by ProQuest.).

Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

PubMed

Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

2007-07-27

We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

Dual-Mode Operation of an Optical Lattice Clock Using Strontium and Ytterbium Atoms.

PubMed

Akamatsu, Daisuke; Kobayashi, Takumi; Hisai, Yusuke; Tanabe, Takehiko; Hosaka, Kazumoto; Yasuda, Masami; Hong, Feng-Lei

2018-06-01

We have developed an optical lattice clock that can operate in dual modes: a strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation of the Sr-Yb optical lattice clock is achieved by alternately cooling and trapping 87 Sr and 171 Yb atoms inside the vacuum chamber of the clock. Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical configurations, respectively, resulting in a small distance of the order of between the trapped Sr and Yb atoms. The 1 S 0 - 3 P 0 clock transitions in the trapped atoms were interrogated in turn and the clock lasers were stabilized to the transitions. We demonstrated the frequency ratio measurement of the Sr and Yb clock transitions by using the dual-mode operation of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the uncertainty of the blackbody radiation shift in the frequency ratio measurement, because both Sr and Yb atoms share the same blackbody radiation.

Two Clock Transitions in Neutral Yb for the Highest Sensitivity to Variations of the Fine-Structure Constant.

PubMed

Safronova, Marianna S; Porsev, Sergey G; Sanner, Christian; Ye, Jun

2018-04-27

We propose a new frequency standard based on a 4f^{14}6s6p ^{3}P_{0}-4f^{13}6s^{2}5d (J=2) transition in neutral Yb. This transition has a potential for high stability and accuracy and the advantage of the highest sensitivity among atomic clocks to variation of the fine-structure constant α. We find its dimensionless α-variation enhancement factor to be K=-15, in comparison to the most sensitive current clock (Yb^{+}  E3, K=-6), and it is 18 times larger than in any neutral-atomic clocks (Hg, K=0.8). Combined with the unprecedented stability of an optical lattice clock for neutral atoms, this high sensitivity opens new perspectives for searches for ultralight dark matter and for tests of theories beyond the standard model of elementary particles. Moreover, together with the well-established ^{1}S_{0}-^{3}P_{0} transition, one will have two clock transitions operating in neutral Yb, whose interleaved interrogations may further reduce systematic uncertainties of such clock-comparison experiments.

Two Clock Transitions in Neutral Yb for the Highest Sensitivity to Variations of the Fine-Structure Constant

NASA Astrophysics Data System (ADS)

Safronova, Marianna S.; Porsev, Sergey G.; Sanner, Christian; Ye, Jun

2018-04-01

We propose a new frequency standard based on a 4 f146 s 6 p P0 3 -4 f136 s25 d (J =2 ) transition in neutral Yb. This transition has a potential for high stability and accuracy and the advantage of the highest sensitivity among atomic clocks to variation of the fine-structure constant α . We find its dimensionless α -variation enhancement factor to be K =-15 , in comparison to the most sensitive current clock (Yb+ E 3 , K =-6 ), and it is 18 times larger than in any neutral-atomic clocks (Hg, K =0.8 ). Combined with the unprecedented stability of an optical lattice clock for neutral atoms, this high sensitivity opens new perspectives for searches for ultralight dark matter and for tests of theories beyond the standard model of elementary particles. Moreover, together with the well-established 1S0-3P0 transition, one will have two clock transitions operating in neutral Yb, whose interleaved interrogations may further reduce systematic uncertainties of such clock-comparison experiments.

Temperature compensation and temperature sensation in the circadian clock

PubMed Central

Kidd, Philip B.; Young, Michael W.; Siggia, Eric D.

2015-01-01

All known circadian clocks have an endogenous period that is remarkably insensitive to temperature, a property known as temperature compensation, while at the same time being readily entrained by a diurnal temperature oscillation. Although temperature compensation and entrainment are defining features of circadian clocks, their mechanisms remain poorly understood. Most models presume that multiple steps in the circadian cycle are temperature-dependent, thus facilitating temperature entrainment, but then insist that the effect of changes around the cycle sums to zero to enforce temperature compensation. An alternative theory proposes that the circadian oscillator evolved from an adaptive temperature sensor: a gene circuit that responds only to temperature changes. This theory implies that temperature changes should linearly rescale the amplitudes of clock component oscillations but leave phase relationships and shapes unchanged. We show using timeless luciferase reporter measurements and Western blots against TIMELESS protein that this prediction is satisfied by the Drosophila circadian clock. We also review evidence for pathways that couple temperature to the circadian clock, and show previously unidentified evidence for coupling between the Drosophila clock and the heat-shock pathway. PMID:26578788

The Zeeman effect in the (0,0) band of the A 7Pi-X 7Sigma(+) transition of manganese monohydride, MnH.

PubMed

Steimle, Timothy C; Wang, Hailing; Gengler, Jamie J; Stoll, Michael; Meijer, Gerard

2008-10-28

The Zeeman tuning of the P(1)(0) line (nu=17 568.35 cm(-1)) of the A (7)Pi-X (7)Sigma(+) (0,0) band of manganese monohydride, MnH, has been investigated. The laser induced fluorescence spectrum of a supersonic molecular beam sample was recorded at a resolution of approximately 40 MHz and with field strengths of up to 362.0 mT. The observed spectrum was successfully fitted using a traditional effective Zeeman Hamiltonian to determine an effective magnetic g-factor for the J=2 level of the F(1)-spin component of the A (7)Pi(v=0) state. Spectral predictions of the P(1)(0) line at field strengths used in magnetic trapping experiments are presented.

The Zeeman effect in the (0,0) band of the A 7Π-X 7Σ+ transition of manganese monohydride, MnH

NASA Astrophysics Data System (ADS)

Steimle, Timothy C.; Wang, Hailing; Gengler, Jamie J.; Stoll, Michael; Meijer, Gerard

2008-10-01

The Zeeman tuning of the P1(0) line (ν =17 568.35 cm-1) of the A Π7-X Σ7+ (0,0) band of manganese monohydride, MnH, has been investigated. The laser induced fluorescence spectrum of a supersonic molecular beam sample was recorded at a resolution of approximately 40 MHz and with field strengths of up to 362.0 mT. The observed spectrum was successfully fitted using a traditional effective Zeeman Hamiltonian to determine an effective magnetic g-factor for the J =2 level of the F1-spin component of the A Π7(v =0) state. Spectral predictions of the P1(0) line at field strengths used in magnetic trapping experiments are presented.

The impact of photoperiod insensitive Ppd-1a mutations on the photoperiod pathway across the three genomes of hexaploid wheat (Triticum aestivum).

PubMed

Shaw, Lindsay M; Turner, Adrian S; Laurie, David A

2012-07-01

Flowering time is a trait that has been extensively altered during wheat domestication, enabling it to be highly productive in diverse environments and providing a rich source of variation for studying adaptation mechanisms. Hexaploid wheat is ancestrally a long-day plant, but many environments require varieties with photoperiod insensitivity (PI) that can flower in short days. PI results from mutations in the Ppd-1 gene on the A, B or D genomes, with individual mutations conferring different degrees of earliness. The basis of this is poorly understood. Using a common genetic background, the effects of A, B and D genome PI mutations on genes of the circadian clock and photoperiod pathway were studied using genome-specific expression assays. Ppd-1 PI mutations did not affect the clock or immediate clock outputs, but affected TaCO1 and TaFT1, with a reduction in TaCO1 expression as TaFT1 expression increased. Therefore, although Ppd-1 is related to PRR genes of the Arabidopsis circadian clock, Ppd-1 affects flowering by an alternative route, most likely by upregulating TaFT1 with a feedback effect that reduces TaCO1 expression. Individual genes in the circadian clock and photoperiod pathway were predominantly expressed from one genome, and there was no genome specificity in Ppd-1 action. Lines combining PI mutations on two or three genomes had enhanced earliness with higher levels, but not earlier induction, of TaFT1, showing that there is a direct quantitative relationship between Ppd-1 mutations, TaFT1 expression and flowering. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

Understanding Zeeman EIT Noise Correlation Spectra in Buffered Rb Vapor

NASA Astrophysics Data System (ADS)

O'Leary, Shannon; Zheng, Aojie; Crescimanno, Michael

2014-05-01

Noise correlation spectroscopy on systems manifesting Electromagnetically Induced Transparency (EIT) holds promise as a simple, robust method for performing high-resolution spectroscopy used in applications such as EIT-based atomic magnetometry and clocks. During laser light's propagation through a resonant medium, interaction with the medium converts laser phase noise into intensity noise. While this noise conversion can diminish the precision of EIT applications, noise correlation techniques transform the noise into a useful spectroscopic tool that can improve the application's precision. Using a single diode laser with large phase noise, we examine laser intensity noise and noise correlations from Zeeman EIT in a buffered Rb vapor. Of particular interest is a narrow noise correlation feature, resonant with EIT, that has been shown in earlier work to be power-broadening resistant at low powers. We report here on our recent experimental work and complementary theoretical modeling on EIT noise spectra, including a study of power broadening of the narrow noise correlation feature. Understanding the nature of the noise correlation spectrum is essential for optimizing EIT-noise applications.

Superfluid density and Berezinskii-Kosterlitz-Thouless transition of a spin-orbit-coupled Fulde-Ferrell superfluid

DOE PAGES

Cao, Ye; Liu, Xia -Ji; He, Lianyi; ...

2015-02-09

We theoretically investigate the superfluid density and Berezinskii-Kosterlitz-Thouless (BKT) transition of a two-dimensional Rashba spin-orbit-coupled atomic Fermi gas with both in-plane and out-of-plane Zeeman fields. It was recently predicted that, by tuning the two Zeeman fields, the system may exhibit different exotic Fulde-Ferrell (FF) superfluid phases, including the gapped FF, gapless FF, gapless topological FF, and gapped topological FF states. Due to the FF paring, we show that the superfluid density (tensor) of the system becomes anisotropic. When an in-plane Zeeman field is applied along the x direction, the tensor component along the y direction n s,yy is generally largermore » than n s,xx in most parameter space. At zero temperature, there is always a discontinuity jump in n s,xx as the system evolves from a gapped FF into a gapless FF state. With increasing temperature, such a jump is gradually washed out. The critical BKT temperature has been calculated as functions of the spin-orbit-coupling strength, interatomic interaction strength, and in-plane and out-of-plane Zeeman fields. We predict that the novel FF superfluid phases have a significant critical BKT temperature, typically at the order of 0.1T F, where T F is the Fermi degenerate temperature. Furthermore, their observation is within the reach of current experimental techniques in cold-atom laboratories.« less

Realization of a gain with electromagnetically induced transparency system using non-degenerate Zeeman sublevels in 87 Rb

NASA Astrophysics Data System (ADS)

Zhou, Minchuan; Zhou, Zifan; Shahriar, Selim M.

2017-11-01

Previously, we had proposed an optically-pumped five-level Gain EIT (GEIT) system, which has a transparency dip superimposed on a gain profile and exhibits a negative dispersion suitable for the white-light-cavity signal-recycling (WLC-SR) scheme of the interferometric gravitational wave detector (Zhou et al., 2015). Using this system as the negative dispersion medium (NDM) in the WLC-SR, we get an enhancement in the quantum noise (QN) limited sensitivity-bandwidth product by a factor of ∼ 18. Here, we show how to realize this GEIT system in a realistic platform, using non-degenerate Zeeman sublevels in cold Rb atoms, employing anomalous dispersion at 795 nm. Using the Caves model for a phase insensitive linear amplifier, we show that an enhancement of the sensitivity-bandwidth product by a factor of ∼ 17 is possible for potentially realizable experimental parameters. While the current LIGO apparatus uses light at 1064 nm, a future embodiment thereof may operate at a wavelength that is consistent with the wavelength considered here.

New 30-50 Ghz Wideband Receiver for Nobeyama 45-M Telescope with Capability to Observe Three Zeeman

NASA Astrophysics Data System (ADS)

Huang, Yau De

2018-01-01

Zeeman measurement is the only tool to probe the magnetic field strengths directly. A new receiver covering 30-50 GHz frequency range is proposed for Nobeyama 45-m telescope based on the design of the ALMA Band 1 receiver. With dual linear polarization feed, wide IF bandwidth and state-of-the-art noise performance, it is capable to observe three Zeeman transitions (SO at 30.0 GHz and CCS at 33.7 and 45.4 GHz) toward the pre-protostellar cores simultaneously. This feature will not only increase the survey efficiency but also provide a reliable tool to calibrate the unwanted instrumental cross-polarization. Slim receiver layout also allows easy expansion to form focal plane array. We will present the receiver design and the current status of the pro

Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system

DOE PAGES

Lu, T. M.; Tracy, L. A.; Laroche, D.; ...

2017-06-01

We typically achieve Quantum Hall ferromagnetic transitions by increasing the Zeeman energy through in-situ sample rotation, while transitions in systems with pseudo-spin indices can be induced by gate control. We report here a gate-controlled quantum Hall ferromagnetic transition between two real spin states in a conventional two-dimensional system without any in-plane magnetic field. We also show that the ratio of the Zeeman splitting to the cyclotron gap in a Ge two-dimensional hole system increases with decreasing density owing to inter-carrier interactions. Below a critical density of ~2.4 × 10 10 cm -2, this ratio grows greater than 1, resulting inmore » a ferromagnetic ground state at filling factor ν = 2. At the critical density, a resistance peak due to the formation of microscopic domains of opposite spin orientations is observed. For such gate-controlled spin-polarizations in the quantum Hall regime the door opens in order to realize Majorana modes using two-dimensional systems in conventional, low-spin-orbit-coupling semiconductors.« less

Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system

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

Lu, T. M.; Tracy, L. A.; Laroche, D.

We typically achieve Quantum Hall ferromagnetic transitions by increasing the Zeeman energy through in-situ sample rotation, while transitions in systems with pseudo-spin indices can be induced by gate control. We report here a gate-controlled quantum Hall ferromagnetic transition between two real spin states in a conventional two-dimensional system without any in-plane magnetic field. We also show that the ratio of the Zeeman splitting to the cyclotron gap in a Ge two-dimensional hole system increases with decreasing density owing to inter-carrier interactions. Below a critical density of ~2.4 × 10 10 cm -2, this ratio grows greater than 1, resulting inmore » a ferromagnetic ground state at filling factor ν = 2. At the critical density, a resistance peak due to the formation of microscopic domains of opposite spin orientations is observed. For such gate-controlled spin-polarizations in the quantum Hall regime the door opens in order to realize Majorana modes using two-dimensional systems in conventional, low-spin-orbit-coupling semiconductors.« less

High-speed clock recovery unit based on a phase aligner

NASA Astrophysics Data System (ADS)

Tejera, Efrain; Esper-Chain, Roberto; Tobajas, Felix; De Armas, Valentin; Sarmiento, Roberto

2003-04-01

Nowadays clock recovery units are key elements in high speed digital communication systems. For an efficient operation, this units should generate a low jitter clock based on the NRZ received data, and be tolerant to long absence of transitions. Architectures based on Hogge phase detectors have been widely used, nevertheless, they are very sensitive to jitter of the received data and they have a limited tolerance to the absence of transitions. This paper shows a novel high speed clock recovery unit based on a phase aligner. The system allows a very fast clock recovery with a low jitter, moreover, it is very resistant to absence of transitions. The design is based on eight phases obtained from a reference clock running at the nominal frequency of the received signal. This high speed reference clock is generated using a crystal and a clock multiplier unit. The phase alignment system chooses, as starting point, the two phases closest to the data phase. This allows a maximum error of 45 degrees between the clock and data signal phases. Furthermore, the system includes a feed-back loop that interpolates the chosen phases to reduce the phase error to zero. Due to the high stability and reduced tolerance of the local reference clock, the jitter obtained is highly reduced and the system becomes able to operate under long absence of transitions. This performances make this design suitable for systems such as high speed serial link technologies. This system has been designed for CMOS 0.25μm at 1.25GHz and has been verified through HSpice simulations.

Zeeman splitting and dynamical mass generation in Dirac semimetal ZrTe5

PubMed Central

Liu, Yanwen; Yuan, Xiang; Zhang, Cheng; Jin, Zhao; Narayan, Awadhesh; Luo, Chen; Chen, Zhigang; Yang, Lei; Zou, Jin; Wu, Xing; Sanvito, Stefano; Xia, Zhengcai; Li, Liang; Wang, Zhong; Xiu, Faxian

2016-01-01

Dirac semimetals have attracted extensive attentions in recent years. It has been theoretically suggested that many-body interactions may drive exotic phase transitions, spontaneously generating a Dirac mass for the nominally massless Dirac electrons. So far, signature of interaction-driven transition has been lacking. In this work, we report high-magnetic-field transport measurements of the Dirac semimetal candidate ZrTe5. Owing to the large g factor in ZrTe5, the Zeeman splitting can be observed at magnetic field as low as 3 T. Most prominently, high pulsed magnetic field up to 60 T drives the system into the ultra-quantum limit, where we observe abrupt changes in the magnetoresistance, indicating field-induced phase transitions. This is interpreted as an interaction-induced spontaneous mass generation of the Dirac fermions, which bears resemblance to the dynamical mass generation of nucleons in high-energy physics. Our work establishes Dirac semimetals as ideal platforms for investigating emerging correlation effects in topological matters. PMID:27515493

Strain manipulation of Majorana fermions in graphene armchair nanoribbons

NASA Astrophysics Data System (ADS)

Wang, Zhen-Hua; Castro, Eduardo V.; Lin, Hai-Qing

2018-01-01

Graphene nanoribbons with armchair edges are studied for externally enhanced but realistic parameter values: enhanced Rashba spin-orbit coupling due to proximity to a transition-metal dichalcogenide, such as WS2, and enhanced Zeeman field due to exchange coupling with a magnetic insulator, such as EuS under an applied magnetic field. The presence of s -wave superconductivity, induced either by proximity or by decoration with alkali-metal atoms, such as Ca or Li, leads to a topological superconducting phase with Majorana end modes. The topological phase is highly sensitive to the application of uniaxial strain with a transition to the trivial state above a critical strain well below 0.1%. This sensitivity allows for real-space manipulation of Majorana fermions by applying nonuniform strain profiles. Similar manipulation is also possible by applying an inhomogeneous Zeeman field or chemical potential.

A clock transition in a solid-state system

NASA Astrophysics Data System (ADS)

Edge, G. J. A.; Potnis, S.; Vutha, A. C.

2017-04-01

With the impending redefinition of the SI second based on optical frequency standards, new secondary frequency standards are needed in order to form clock ensembles. Ideally such secondary standards will offer enhanced robustness, portability and high signal-to-noise ratios (SNR), to enable rapid and precise comparisons to be made against primary standards. A clock based on a narrow optical transition, in atoms that are doped into a solid-state host, offers the experimental simplicity and large SNR to satisfy these requirements. The intra-configuration 7F0 ->5D0 transition, in Sm2+ ions doped into a host crystal, is an attractive candidate for such secondary standards due to its low susceptibility to perturbations from the crystal environment. We present results from the interrogation of this clock transition with a narrow linewidth laser.

Origin of excess low-energy states in a disordered superconductor in a Zeeman field.

PubMed

Loh, Y L; Trivedi, N; Xiong, Y M; Adams, P W; Catelani, G

2011-08-05

Tunneling density of states measurements of disordered superconducting Al films in high Zeeman fields reveal a significant population of subgap states which cannot be explained by standard BCS theory. We provide a natural explanation of these excess states in terms of a novel disordered Larkin-Ovchinnikov phase that occurs near the spin-paramagnetic transition at the Chandrasekhar-Clogston critical field. The disordered Larkin-Ovchinnikov superconductor is characterized by a pairing amplitude that changes sign at domain walls. These domain walls carry magnetization and support Andreev bound states that lead to distinct spectral signatures at low energy.

Magnetooptics of the luminescent transitions in Tb3+:Gd3Ga5O12

NASA Astrophysics Data System (ADS)

Valiev, Uygun V.; Gruber, John B.; Ivanov, Igor'A.; Burdick, Gary W.; Liang, Hongbin; Zhou, Lei; Fu, Dejun; Pelenovich, Oleg V.; Pelenovich, Vasiliy O.; Lin, Zhou

2015-08-01

The spectra of the luminescence and magnetic circular polarization of luminescence in terbium-gadolinium gallium garnet Tb3+:Gd3Ga5O12 (Tb3+:GGG) were studied within the visible spectral range at temperatures T = 90 and 300 K in an external magnetic field of 0.45 T. The Zeeman effect in the luminescence "green" band associated with 4f → 4f transition 5D4 → 7F5 of Tb3+:GGG was also studied at T = 90 K in an external field of 0.55 T. Measurement of the Zeeman effect in Tb3+:GGG carried out for some doublet lines of the luminescence band 5D4 → 7F5 at T = 90 K shows that a magnetooptical effect of the intensity change of the emitted light is observed on these lines, in contrast to pure Zeeman splitting of the emission lines measured in the luminescence band 5D4 → 7F6. For the systems we have studied, the maximal value of the magnetooptical effect of the intensity change of the luminescence line at low temperatures has been achieved in paramagnetic garnet Tb0.2Y2.8Al5O12 at comparatively low magnetic fields.

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.

Even–odd layer-dependent magnetotransport of high-mobility Q-valley electrons in transition metal disulfides

PubMed Central

Wu, Zefei; Xu, Shuigang; Lu, Huanhuan; Khamoshi, Armin; Liu, Gui-Bin; Han, Tianyi; Wu, Yingying; Lin, Jiangxiazi; Long, Gen; He, Yuheng; Cai, Yuan; Yao, Yugui; Zhang, Fan; Wang, Ning

2016-01-01

In few-layer transition metal dichalcogenides (TMDCs), the conduction bands along the ΓK directions shift downward energetically in the presence of interlayer interactions, forming six Q valleys related by threefold rotational symmetry and time reversal symmetry. In even layers, the extra inversion symmetry requires all states to be Kramers degenerate; whereas in odd layers, the intrinsic inversion asymmetry dictates the Q valleys to be spin-valley coupled. Here we report the transport characterization of prominent Shubnikov-de Hass (SdH) oscillations and the observation of the onset of quantum Hall plateaus for the Q-valley electrons in few-layer TMDCs. Universally in the SdH oscillations, we observe a valley Zeeman effect in all odd-layer TMDC devices and a spin Zeeman effect in all even-layer TMDC devices, which provide a crucial information for understanding the unique properties of multi-valley band structures of few-layer TMDCs. PMID:27651106

Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.

PubMed

Högele, A; Kroner, M; Latta, C; Claassen, M; Carusotto, I; Bulutay, C; Imamoglu, A

2012-05-11

Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system.

Sub-Doppler rotationally resolved spectroscopy of lower vibronic bands of benzene with Zeeman effects

NASA Astrophysics Data System (ADS)

Doi, Atsushi; Kasahara, Shunji; Katô, Hajime; Baba, Masaaki

2004-04-01

Sub-Doppler high-resolution excitation spectra and the Zeeman effects of the 601, 101601, and 102601 bands of the S1 1B2u←S0 1A1g transition of benzene were measured by crossing laser beam perpendicular to a collimated molecular beam. 1593 rotational lines of the 101601 band and 928 lines of the 102601 band were assigned, and the molecular constants of the excited states were determined. Energy shifts were observed for the S1 1B2u(v1=1,v6=1,J,Kl=-11) levels, and those were identified as originating from a perpendicular Coriolis interaction. Many energy shifts were observed for the S1 1B2u(v1=2,v6=1,J,Kl) levels. The Zeeman splitting of a given J level was observed to increase with K and reach the maximum at K=J, which demonstrates that the magnetic moment lies perpendicular to the molecular plane. The Zeeman splittings of the K=J levels were observed to increase linearly with J. From the analysis, the magnetic moment is shown to be originating mostly from mixing of the S1 1B2u and S2 1B1u states by the J-L coupling (electronic Coriolis interaction). The number of perturbations was observed to increase as the excess energy increases, and all the perturbing levels were found to be a singlet state from the Zeeman spectra.

Magnetic coupling at rare earth ferromagnet/transition metal ferromagnet interfaces: A comprehensive study of Gd/Ni.

PubMed

Higgs, T D C; Bonetti, S; Ohldag, H; Banerjee, N; Wang, X L; Rosenberg, A J; Cai, Z; Zhao, J H; Moler, K A; Robinson, J W A

2016-07-22

Thin film magnetic heterostructures with competing interfacial coupling and Zeeman energy provide a fertile ground to study phase transition between different equilibrium states as a function of external magnetic field and temperature. A rare-earth (RE)/transition metal (TM) ferromagnetic multilayer is a classic example where the magnetic state is determined by a competition between the Zeeman energy and antiferromagnetic interfacial exchange coupling energy. Technologically, such structures offer the possibility to engineer the macroscopic magnetic response by tuning the microscopic interactions between the layers. We have performed an exhaustive study of nickel/gadolinium as a model system for understanding RE/TM multilayers using the element-specific measurement technique x-ray magnetic circular dichroism, and determined the full magnetic state diagrams as a function of temperature and magnetic layer thickness. We compare our results to a modified Stoner-Wohlfarth-based model and provide evidence of a thickness-dependent transition to a magnetic fan state which is critical in understanding magnetoresistance effects in RE/TM systems. The results provide important insight for spintronics and superconducting spintronics where engineering tunable magnetic inhomogeneity is key for certain applications.

Magnetic coupling at rare earth ferromagnet/transition metal ferromagnet interfaces: A comprehensive study of Gd/Ni

DOE PAGES

Higgs, T. D. C.; Bonetti, S.; Ohldag, H.; ...

2016-07-22

Thin film magnetic heterostructures with competing interfacial coupling and Zeeman energy provide a fertile ground to study phase transition between different equilibrium states as a function of external magnetic field and temperature. A rare-earth (RE)/transition metal (TM) ferromagnetic multilayer is a classic example where the magnetic state is determined by a competition between the Zeeman energy and antiferromagnetic interfacial exchange coupling energy. Technologically, such structures offer the possibility to engineer the macroscopic magnetic response by tuning the microscopic interactions between the layers. We have performed an exhaustive study of nickel/gadolinium as a model system for understanding RE/TM multilayers using themore » element-specific measurement technique x-ray magnetic circular dichroism, and determined the full magnetic state diagrams as a function of temperature and magnetic layer thickness. We compare our results to a modified Stoner-Wohlfarth-based model and provide evidence of a thickness-dependent transition to a magnetic fan state which is critical in understanding magnetoresistance effects in RE/TM systems. In conclusion, the results provide important insight for spintronics and superconducting spintronics where engineering tunable magnetic inhomogeneity is key for certain applications.« less

Magnetic coupling at rare earth ferromagnet/transition metal ferromagnet interfaces: A comprehensive study of Gd/Ni

NASA Astrophysics Data System (ADS)

Higgs, T. D. C.; Bonetti, S.; Ohldag, H.; Banerjee, N.; Wang, X. L.; Rosenberg, A. J.; Cai, Z.; Zhao, J. H.; Moler, K. A.; Robinson, J. W. A.

2016-07-01

Thin film magnetic heterostructures with competing interfacial coupling and Zeeman energy provide a fertile ground to study phase transition between different equilibrium states as a function of external magnetic field and temperature. A rare-earth (RE)/transition metal (TM) ferromagnetic multilayer is a classic example where the magnetic state is determined by a competition between the Zeeman energy and antiferromagnetic interfacial exchange coupling energy. Technologically, such structures offer the possibility to engineer the macroscopic magnetic response by tuning the microscopic interactions between the layers. We have performed an exhaustive study of nickel/gadolinium as a model system for understanding RE/TM multilayers using the element-specific measurement technique x-ray magnetic circular dichroism, and determined the full magnetic state diagrams as a function of temperature and magnetic layer thickness. We compare our results to a modified Stoner-Wohlfarth-based model and provide evidence of a thickness-dependent transition to a magnetic fan state which is critical in understanding magnetoresistance effects in RE/TM systems. The results provide important insight for spintronics and superconducting spintronics where engineering tunable magnetic inhomogeneity is key for certain applications.

Alternative splicing and nonsense-mediated decay of circadian clock genes under environmental stress conditions in Arabidopsis

PubMed Central

2014-01-01

Background The circadian clock enables living organisms to anticipate recurring daily and seasonal fluctuations in their growth habitats and synchronize their biology to the environmental cycle. The plant circadian clock consists of multiple transcription-translation feedback loops that are entrained by environmental signals, such as light and temperature. In recent years, alternative splicing emerges as an important molecular mechanism that modulates the clock function in plants. Several clock genes are known to undergo alternative splicing in response to changes in environmental conditions, suggesting that the clock function is intimately associated with environmental responses via the alternative splicing of the clock genes. However, the alternative splicing events of the clock genes have not been studied at the molecular level. Results We systematically examined whether major clock genes undergo alternative splicing under various environmental conditions in Arabidopsis. We also investigated the fates of the RNA splice variants of the clock genes. It was found that the clock genes, including EARLY FLOWERING 3 (ELF3) and ZEITLUPE (ZTL) that have not been studied in terms of alternative splicing, undergo extensive alternative splicing through diverse modes of splicing events, such as intron retention, exon skipping, and selection of alternative 5′ splice site. Their alternative splicing patterns were differentially influenced by changes in photoperiod, temperature extremes, and salt stress. Notably, the RNA splice variants of TIMING OF CAB EXPRESSION 1 (TOC1) and ELF3 were degraded through the nonsense-mediated decay (NMD) pathway, whereas those of other clock genes were insensitive to NMD. Conclusion Taken together, our observations demonstrate that the major clock genes examined undergo extensive alternative splicing under various environmental conditions, suggesting that alternative splicing is a molecular scheme that underlies the linkage between the clock and environmental stress adaptation in plants. It is also envisioned that alternative splicing of the clock genes plays more complex roles than previously expected. PMID:24885185

Spin interferometry in anisotropic spin-orbit fields

NASA Astrophysics Data System (ADS)

Saarikoski, Henri; Reynoso, Andres A.; Baltanás, José Pablo; Frustaglia, Diego; Nitta, Junsaku

2018-03-01

Electron spins in a two-dimensional electron gas can be manipulated by spin-orbit (SO) fields originating from either Rashba or Dresselhaus interactions with independent isotropic characteristics. Together, though, they produce anisotropic SO fields with consequences on quantum transport through spin interference. Here we study the transport properties of modeled mesoscopic rings subject to Rashba and Dresselhaus [001] SO couplings in the presence of an additional in-plane Zeeman field acting as a probe. By means of one- and two-dimensional quantum transport simulations we show that this setting presents anisotropies in the quantum resistance as a function of the Zeeman field direction. Moreover, the anisotropic resistance can be tuned by the Rashba strength up to the point to invert its response to the Zeeman field. We also find that a topological transition in the field texture that is associated with a geometric phase switching is imprinted in the anisotropy pattern. We conclude that resistance anisotropy measurements can reveal signatures of SO textures and geometric phases in spin carriers.

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.

The Zeeman Effect in the 44 GHz Class I Methanol Maser Line toward DR21(OH)

NASA Astrophysics Data System (ADS)

Momjian, E.; Sarma, A. P.

2017-01-01

We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam-1 maser centered at an LSR velocity of 0.83 km s-1, we find a 20-σ detection of zBlos = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ˜ 107-8 cm-3, then the B versus n1/2 relation would imply, from comparison with Zeeman effect detections in the CN(1 - 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ˜10 mG. Combined with our detected zBlos = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ˜5 Hz mG-1. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H2O. Empirical attempts to determine z, as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH3OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.

Magneto-optical response of InAs lens-shaped self-assembled quantum dots

NASA Technical Reports Server (NTRS)

Klimeck, G.; Oyafuso, F.; Lee, S.; Allmen, P. von

2003-01-01

In this work, we demonstrate a realistic modeling of the electronic structure for InAs self-assembled quantum dots and investigate the magneto-optical response, i.e., Zeeman splitting and transition rates between electron and hole levels.

Zeeman relaxation of cold atomic iron and nickel in collisions with He3

NASA Astrophysics Data System (ADS)

Johnson, Cort; Newman, Bonna; Brahms, Nathan; Doyle, John M.; Kleppner, Daniel; Greytak, Thomas J.

2010-06-01

We have measured the ratio γ of the diffusion cross section to the angular momentum reorientation cross section in the colliding Fe-He3 and Ni-He3 systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into a cryogenically cooled experimental cell containing cold (<1 K) He3 buffer gas. Elastic collisions rapidly cool the translational temperature of the ablated atoms to the He3 temperature. γ is extracted by measuring the decays of the atomic Zeeman sublevels. For our experimental conditions, thermal energy is comparable to the Zeeman splitting. As a result, thermal excitations between Zeeman sublevels significantly impact the observed decay. To determine γ accurately, we introduce a model of Zeeman-state dynamics that includes thermal excitations. We find γNi-3He=5×103 and γFe-3He⩽3×103 at 0.75 K in a 0.8-T magnetic field. These measurements are interpreted in the context of submerged shell suppression of spin relaxation, as studied previously in transition metals and rare-earth-metal atoms [C. I. Hancox, S. C. Doret, M. T. Hummon, R. V. Krems, and J. M. Doyle, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.94.013201 94, 013201 (2005); C. I. Hancox, S. C. Doret, M. T. Hummon, L. Luo, and J. M. Doyle, Nature (London)NATUAS0028-083610.1038/nature02938 431, 281 (2004); A. Buchachenko, G. Chaasiski, and M. Szczniak, Eur. Phys. J. DEPJDF61434-606010.1140/epjd/e2006-00263-3 45, 147 (2007)].

Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases.

PubMed

Zhou, Tao; Gao, Yi; Wang, Z D

2014-06-11

We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.

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.

A review of atomic clock technology, the performance capability of present spaceborne and terrestrial atomic clocks, and a look toward the future

NASA Technical Reports Server (NTRS)

Vessot, Robert F. C.

1989-01-01

Clocks have played a strong role in the development of general relativity. The concept of the proper clock is presently best realized by atomic clocks, whose development as precision instruments has evolved very rapidly in the last decades. To put a historical prospective on this progress since the year AD 1000, the time stability of various clocks expressed in terms of seconds of time error over one day of operation is shown. This stability of operation must not be confused with accuracy. Stability refers to the constancy of a clock operation as compared to that of some other clocks that serve as time references. Accuracy, on the other hand, is the ability to reproduce a previously defined frequency. The issues are outlined that must be considered when accuracy and stability of clocks and oscillators are studied. In general, the most widely used resonances result from the hyperfine interaction of the nuclear magnetic dipole moment and that of the outermost electron, which is characteristic of hydrogen and the alkali atoms. During the past decade hyperfine resonances of ions have also been used. The principal reason for both the accuracy and the stability of atomic clocks is the ability of obtaining very narrow hyperfine transition resonances by isolating the atom in some way so that only the applied stimulating microwave magnetic field is a significant source of perturbation. It is also important to make resonance transitions among hyperfine magnetic sublevels where separation is independent, at least to first order, of the magnetic field. In the case of ions stored in traps operating at high magnetic fields, one selects the trapping field to be consistent with a field-independent transition of the trapped atoms.

Magnetoinfrared spectroscopy of Landau levels and Zeeman splitting of three-dimensional massless Dirac Fermions in ZrTe 5

DOE PAGES

R. Y. Chen; Gu, G. D.; Chen, Z. G.; ...

2015-10-22

We present a magnetoinfrared spectroscopy study on a newly identified three-dimensional (3D) Dirac semimetal ZrTe 5. We observe clear transitions between Landau levels and their further splitting under a magnetic field. Both the sequence of transitions and their field dependence follow quantitatively the relation expected for 3D massless Dirac fermions. The measurement also reveals an exceptionally low magnetic field needed to drive the compound into its quantum limit, demonstrating that ZrTe 5 is an extremely clean system and ideal platform for studying 3D Dirac fermions. The splitting of the Landau levels provides direct, bulk spectroscopic evidence that a relatively weakmore » magnetic field can produce a sizable Zeeman effect on the 3D Dirac fermions, which lifts the spin degeneracy of Landau levels. As a result, our analysis indicates that the compound evolves from a Dirac semimetal into a topological line-node semimetal under the current magnetic field configuration.« less

49 CFR 173.50 - Class 1-Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... insensitive that there is very little probability of initiation or of transition from burning to detonation under normal conditions of transport. 1 The probability of transition from burning to detonation is... contain only extremely insensitive detonating substances and which demonstrate a negligible probability of...

Agile high resolution arbitrary waveform generator with jitterless frequency stepping

DOEpatents

Reilly, Peter T. A.; Koizumi, Hideya

2010-05-11

Jitterless transition of the programmable clock waveform is generated employing a set of two coupled direct digital synthesis (DDS) circuits. The first phase accumulator in the first DDS circuit runs at least one cycle of a common reference clock for the DDS circuits ahead of the second phase accumulator in the second DDS circuit. As a phase transition through the beginning of a phase cycle is detected from the first phase accumulator, a first phase offset word and a second phase offset word for the first and second phase accumulators are calculated and loaded into the first and second DDS circuits. The programmable clock waveform is employed as a clock input for the RAM address controller. A well defined jitterless transition in frequency of the arbitrary waveform is provided which coincides with the beginning of the phase cycle of the DDS output signal from the second DDS circuit.

Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms

PubMed Central

Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.

2015-01-01

Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877

Progress Toward an Neutral Yb Frequency Standard

NASA Astrophysics Data System (ADS)

Cramer, Claire; Hong, Tao; Nagourney, Warren; Fortson, Norval

2004-05-01

We report recent progress toward a direct observation of the ^1S_0^ -- ^3P0 clock transition at 578 nm in atomic Yb and review the experimental path to an optical frequency standard based on neutral Yb confined in a Stark-free optical lattice. Lamb-Dicke confinement in an optical lattice at the ``magic wavelength'' (λ _M) at which ground and excited state light shifts cancel will free the spectrum from Doppler and recoil shifts, providing an optimal environment for a clock consisting of an ensemble of cold, trapped atoms. In^171Yb the ^3P0 level has a hfs induced lifetime of 21 s. With this isotope in a Stark-free lattice at λ M ng 750 nm, perturbations to the clock energy levels can be held below the mHz level, providing an accuracy of a few parts in 10^18[1]. To observe the clock transition we use a shelving scheme that creates a leak in a MOT on the ^1S_0^ -- ^1P1 transition. A laser resonant with the clock transition drives atoms into the ^3P0 state, in which they can escape the MOT, leading to an observable decrease in MOT fluorescence. [1] S. Porsev and A. Derevianko, to be published in PRA

Band nesting, massive Dirac fermions, and valley Landé and Zeeman effects in transition metal dichalcogenides: A tight-binding model

NASA Astrophysics Data System (ADS)

Bieniek, Maciej; Korkusiński, Marek; Szulakowska, Ludmiła; Potasz, Paweł; Ozfidan, Isil; Hawrylak, Paweł

2018-02-01

We present here the minimal tight-binding model for a single layer of transition metal dichalcogenides (TMDCs) MX 2(M , metal; X , chalcogen) which illuminates the physics and captures band nesting, massive Dirac fermions, and valley Landé and Zeeman magnetic field effects. TMDCs share the hexagonal lattice with graphene but their electronic bands require much more complex atomic orbitals. Using symmetry arguments, a minimal basis consisting of three metal d orbitals and three chalcogen dimer p orbitals is constructed. The tunneling matrix elements between nearest-neighbor metal and chalcogen orbitals are explicitly derived at K ,-K , and Γ points of the Brillouin zone. The nearest-neighbor tunneling matrix elements connect specific metal and sulfur orbitals yielding an effective 6 ×6 Hamiltonian giving correct composition of metal and chalcogen orbitals but not the direct gap at K points. The direct gap at K , correct masses, and conduction band minima at Q points responsible for band nesting are obtained by inclusion of next-neighbor Mo-Mo tunneling. The parameters of the next-nearest-neighbor model are successfully fitted to MX 2(M =Mo ; X =S ) density functional ab initio calculations of the highest valence and lowest conduction band dispersion along K -Γ line in the Brillouin zone. The effective two-band massive Dirac Hamiltonian for MoS2, Landé g factors, and valley Zeeman splitting are obtained.

Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla

NASA Astrophysics Data System (ADS)

Stier, Andreas V.; McCreary, Kathleen M.; Jonker, Berend T.; Kono, Junichiro; Crooker, Scott A.

2016-02-01

In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS2 and MoS2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately -230 μeV T-1 (g-factor ~=-4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS2, from which radii of ~1.53 and ~1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). These results highlight the utility of high magnetic fields for understanding new two-dimensional materials.

Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.

PubMed

Linford, G J

1973-06-01

A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air.

A portable version of the program of nettar and villafranca for the simulation of electron paramagnetic resonance spectra of powders

NASA Astrophysics Data System (ADS)

Soulié, Edgar; Gaugenot, Jacques

1995-04-01

Nettar and Villafranca wrote in the FORTRAN programming language a computer program which simulates the electron paramagnetic resonance (EPR) spectra of powders (Journal of Magnetic Resonance, vol. 64 (1985) pp. 61-65). The spin Hamiltonian which their program can handle includes the Zeeman electronic interaction, the fine interaction up to the sixth order in the electron spin, a general hyperfine interaction, an isotropic nuclear Zeeman term; anisotropic ligand hyperfine terms are treated to first order in perturbation. The above Hamiltonian, without the ligand hyperfine terms, is treated exactly, i.e. the resonance equation for a transition between states labeled i and j is solved numerically: h.ν=Ei(H)-Ej(H).

Bose and Fermi Gases of Ultracold Ytterbium in a Triangular Optical Lattice

NASA Astrophysics Data System (ADS)

Thobe, Alexander; Doerscher, Soeren; Hundt, Bastian; Kochanke, Andre; Becker, Christoph; Sengstock, Klaus

2013-05-01

Quantum gases of alkaline-earth like atoms such as Calcium, Strontium and Ytterbium (Yb) open up exciting new possibilities for the study of many body physics in optical lattices, ranging from SU(N) symmetric spin Hamiltonians to the Kondo Lattice Model. Here, we present experimental studies of ultracold bosonic and fermionic Yb quantum gases. Unlike other experiments studying ultracold alkaline earth-like atoms, we have implemented a 2D-MOT instead of a Zeeman slower as a source of cold atoms. From the 2D-MOT, operating on the broad 1S0 -->1P1 transtition, the atoms are directly loaded into the 3D-MOT operating on a narrow intercombination line. The atoms are then evaporatively cooled to quantum degeneracy in a crossed optical dipole trap. With this setup we routinely produce BECs and degenerate Fermi gases of different Yb isotopes. Moreover, we present first results on spectroscopy of an interacting fermi gas on the ultranarrow 1S0 -->3P0 clock transition in a magic wavelength optical lattice. In future experiments, this spectroscopy will serve as a versatile tool for interaction sensing and selective addressing of atoms in a wavelength tunable, state dependent, triangular optical lattice, which we are currently implementing. This work is supported by DFG within SFB 925 and GrK 1355, as well as EU FETOpen (iSense).

Coherent population trapping with polarization modulation

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

Yun, Peter, E-mail: enxue.yun@obspm.fr; Guérandel, Stéphane; Clercq, Emeric de

Coherent population trapping (CPT) is extensively studied for future vapor cell clocks of high frequency stability. In the constructive polarization modulation CPT scheme, a bichromatic laser field with polarization and phase synchronously modulated is applied on an atomic medium. A high contrast CPT signal is observed in this so-called double-modulation configuration, due to the fact that the atomic population does not leak to the extreme Zeeman states, and that the two CPT dark states, which are produced successively by the alternate polarizations, add constructively. Here, we experimentally investigate CPT signal dynamics first in the usual configuration, a single circular polarization.more » The double-modulation scheme is then addressed in both cases: one pulse Rabi interaction and two pulses Ramsey interaction. The impact and the optimization of the experimental parameters involved in the time sequence are reviewed. We show that a simple seven-level model explains the experimental observations. The double-modulation scheme yields a high contrast similar to the one of other high contrast configurations like push-pull optical pumping or crossed linear polarization scheme, with a setup allowing a higher compactness. The constructive polarization modulation is attractive for atomic clock, atomic magnetometer, and high precision spectroscopy applications.« less

Hyper-Ramsey spectroscopy of optical clock transitions

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

Yudin, V. I.; Taichenachev, A. V.; Oates, C. W.

2010-07-15

We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase, and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be radically suppressed (by two to four orders of magnitude) in comparison with the usual Ramsey method (using two equal pulses) as well as with single-pulse Rabi spectroscopy. Atom interferometers and optical clocks based on two-photon transitions, heavily forbidden transitions, or magnetically induced spectroscopy could significantly benefit from this method. In the latter case, these frequency shifts can be suppressed considerably below a fractional levelmore » of 10{sup -17}. Moreover, our approach opens the door for high-precision optical clocks based on direct frequency comb spectroscopy.« less

Imaging Optical Frequencies with 100  μHz Precision and 1.1  μm Resolution.

PubMed

Marti, G Edward; Hutson, Ross B; Goban, Akihisa; Campbell, Sara L; Poli, Nicola; Ye, Jun

2018-03-09

We implement imaging spectroscopy of the optical clock transition of lattice-trapped degenerate fermionic Sr in the Mott-insulating regime, combining micron spatial resolution with submillihertz spectral precision. We use these tools to demonstrate atomic coherence for up to 15 s on the clock transition and reach a record frequency precision of 2.5×10^{-19}. We perform the most rapid evaluation of trapping light shifts and record a 150 mHz linewidth, the narrowest Rabi line shape observed on a coherent optical transition. The important emerging capability of combining high-resolution imaging and spectroscopy will improve the clock precision, and provide a path towards measuring many-body interactions and testing fundamental physics.

Electron pairing without superconductivity

NASA Astrophysics Data System (ADS)

Levy, Jeremy

Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances--paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity. Support from AFOSR, ONR, ARO, NSF, DOE and NSSEFF is gratefully acknowledged.

Evidence Suggesting that the Cardiomyocyte Circadian Clock Modulates Responsiveness of the Heart to Hypertrophic Stimuli in Mice

PubMed Central

Durgan, David J.; Tsai, Ju-Yun; Grenett, Maximiliano H.; Pat, Betty M.; Ratcliffe, William F.; Villegas-Montoya, Carolina; Garvey, Merissa E.; Nagendran, Jeevan; Dyck, Jason R.B.; Bray, Molly S.; Gamble, Karen L.; Gimble, Jeffrey M.; Young, Martin E.

2011-01-01

Circadian dyssynchrony of an organism (at the whole body level) with its environment, either through light/dark cycle or genetic manipulation of clock genes, augments various cardiometabolic diseases. The cardiomyocyte circadian clock has recently been shown to influence multiple myocardial processes, ranging from transcriptional regulation and energy metabolism, to contractile function. We therefore reasoned that chronic dyssychrony of the cardiomyocyte circadian clock with its environment would precipitate myocardial maladaptation to a circadian challenge (simulated shift work; SSW). To test this hypothesis, 2 and 20 month old wild-type and CCM (Cardiomyocyte Clock Mutant; a model with genetic temporal suspension of the cardiomyocyte circadian clock at the active-to-sleep phase transition) mice were subjected to chronic (16-wks) bi-weekly 12-hr phase shifts in the light/dark cycle (i.e., SSW). Assessment of adaptation/maladaptation at whole body homeostatic, gravimetric, humoral, histological, transcriptional, and cardiac contractile function levels revealed essentially identical responses between wild-type and CCM littermates. However, CCM hearts exhibit increased bi-ventricular weight, cardiomyocyte size, and molecular markers of hypertrophy (anf, mcip1) independent of aging and/or SSW. Similarly, a second genetic model of selective temporal suspension of the cardiomyocyte circadian clock (Cardiomyocyte-specific BMAL1 Knockout [CBK] mice) exhibits increased bi-ventricular weight and mcip1 expression. Wild-type mice exhibit 5-fold greater cardiac hypertrophic growth (and 6-fold greater anf mRNA induction) when challenged with the hypertrophic agonist isoproterenol at the active-to-sleep phase transition, relative to isoproterenol administration at the sleep-to-active phase transition. This diurnal variation was absent in CCM mice. Collectively, these data suggest that the cardiomyocyte circadian clock likely influences responsiveness of the heart to hypertrophic stimuli. PMID:21452915

THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH)

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

Momjian, E.; Sarma, A. P., E-mail: emomjian@nrao.edu, E-mail: asarma@depaul.edu

2017-01-10

We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam{sup −1} maser centered at an LSR velocity of 0.83 km s{sup −1}, we find a 20- σ detection of zB {sub los} = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ∼ 10{sup 7–8} cm{sup −3}, then the B versus n {sup 1/2} relation would imply, from comparison with Zeeman effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masersmore » in DR21(OH) should be ∼10 mG. Combined with our detected zB {sub los} = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ∼5 Hz mG{sup −1}. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H{sub 2}O. Empirical attempts to determine z , as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH{sub 3}OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.« less

Manipulating and probing the polarisation of a methyl tunnelling system by field-cycling NMR

NASA Astrophysics Data System (ADS)

Zhang, Bo; Abu-Khumra, Sabah M. M.; Aibout, Abdellah; Horsewill, Anthony J.

2017-02-01

In NMR the polarisation of the Zeeman system may be routinely probed and manipulated by applying resonant rf pulses. As with spin-1/2 nuclei, at low temperature the quantum tunnelling states of a methyl rotor are characterised by two energy levels and it is interesting to consider how these tunnelling states might be probed and manipulated in an analogous way to nuclear spins in NMR. In this paper experimental procedures based on magnetic field-cycling NMR are described where, by irradiating methyl tunnelling sidebands, the polarisations of the methyl tunnelling systems are measured and manipulated in a prescribed fashion. At the heart of the technique is a phenomenon that is closely analogous to dynamic nuclear polarisation and the solid effect where forbidden transitions mediate polarisation transfer between 1H Zeeman and methyl tunnelling systems. Depending on the irradiated sideband, both positive and negative polarisations of the tunnelling system are achieved, the latter corresponding to population inversion and negative tunnelling temperatures. The transition mechanics are investigated through a series of experiments and a theoretical model is presented that provides good quantitative agreement.

Clocking and Synchronization Circuits in Multiprocessor Systems

DTIC Science & Technology

1989-04-01

18 3.4 Inter -chip Clocking Strategies...may occur when two or more of the switches make transitions at different times during the inter - val during which those inputs are being processed...increased without any fruitful computation. The sources of the inter -chip clock skew are the electromagnetic propagation delay, the buffer delay within

Egyptian "Star Clocks"

NASA Astrophysics Data System (ADS)

Symons, Sarah

Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

Optical Lattice Clocks with Weakly Bound Molecules.

PubMed

Borkowski, Mateusz

2018-02-23

Optical molecular clocks promise unparalleled sensitivity to the temporal variation of the electron-to-proton mass ratio and insight into possible new physics beyond the standard model. We propose to realize a molecular clock with bosonic ^{174}Yb_{2} molecules, where the forbidden ^{1}S_{0}→^{3}P_{0} clock transition would be induced magnetically. The use of a bosonic species avoids possible complications due to the hyperfine structure present in fermionic species. While direct clock line photoassociation would be challenging, weakly bound ground state molecules could be produced by stimulated Raman adiabatic passage and used instead. The recent scattering measurements [L. Franchi, et al. New J. Phys. 19, 103037 (2017)NJOPFM1367-263010.1088/1367-2630/aa8fb4] enable us to determine the positions of target ^{1}S_{0}+^{3}P_{0} vibrational levels and calculate the Franck-Condon factors for clock transitions between ground and excited molecular states. The resulting magnetically induced Rabi frequencies are similar to those for atoms hinting that an experimental realization is feasible. A successful observation could pave the way towards Hz-level molecular spectroscopy.

Optical Lattice Clocks with Weakly Bound Molecules

NASA Astrophysics Data System (ADS)

Borkowski, Mateusz

2018-02-01

Optical molecular clocks promise unparalleled sensitivity to the temporal variation of the electron-to-proton mass ratio and insight into possible new physics beyond the standard model. We propose to realize a molecular clock with bosonic 174Yb2 molecules, where the forbidden 1S0 →3P0 clock transition would be induced magnetically. The use of a bosonic species avoids possible complications due to the hyperfine structure present in fermionic species. While direct clock line photoassociation would be challenging, weakly bound ground state molecules could be produced by stimulated Raman adiabatic passage and used instead. The recent scattering measurements [L. Franchi, et al. New J. Phys. 19, 103037 (2017), 10.1088/1367-2630/aa8fb4] enable us to determine the positions of target 1S0 +3P0 vibrational levels and calculate the Franck-Condon factors for clock transitions between ground and excited molecular states. The resulting magnetically induced Rabi frequencies are similar to those for atoms hinting that an experimental realization is feasible. A successful observation could pave the way towards Hz-level molecular spectroscopy.

Piezoelectric Non Linear Nanomechanical Temperature and Acceleration Insensitive Clocks (PENNTAC)

DTIC Science & Technology

2016-07-01

requirements dictated by the Defense Advanced Research Agency (DARPA) program. Figure 7: Measured PN Response of the Non -linear 222 MHz AlN...wavelength (λ) are designed as supports for resonators in which the dimensions of the vibrating body are kept fixed. The Q extracted experimentally confirms...conditions. In this way, we are able to quantitatively predict Q due to anchor losses and qualitatively describe the trends observed experimentally

The effects of non-self-sustained oscillators on the en-trainment ability of the suprachiasmatic nucleus

NASA Astrophysics Data System (ADS)

Gu, Changgui; Tang, Ming; Rohling, Jos H. T.; Yang, Huijie

2016-11-01

In mammals, the circadian rhythms of behavioral and physiological activities are regulated by an endogenous clock located in the suprachiasmatic nucleus (SCN). The SCN is composed of ~20,000 neurons, of which some are capable of self-sustained oscillations, while the others do not oscillate in a self-sustainable manner, but show arrhythmic patterns or damped oscillations. Thus far, the effects of these non-self-sustained oscillatory neurons are not fully explored. Here, we examined how the proportion of the non-self-sustained oscillators affects the free running period under constant darkness and the ability to entrain to the light-dark cycle. We find that the proportion does not affect the free running period, but plays a significant role in the range of entrainment. We also find that its effect on the entrainment range depends on the region where the non-self-sustained oscillators are located. If the non-self-sustained oscillatory neurons are situated in the light-sensitive subregion, the entrainment range narrows when the proportion increases. If they are situated in the light-insensitive subregion, however, the entrainment range broadens with the increase of the proportion. We suggest that the heterogeneity within the light-sensitive and light-insensitive subregions of the SCN has important consequences for how the clock works.

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

Ogane, S.; Shikama, T., E-mail: shikama@me.kyoto-u.ac.jp; Hasuo, M.

In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 2{sup 3}S–2{sup 3}P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steadymore » State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet.« less

Transient development of Zeeman electromagnetically induced transparency during propagation of Raman-Ramsey pulses through Rb buffer gas cell

NASA Astrophysics Data System (ADS)

Nikolić, S. N.; Radonjić, M.; Lučić, N. M.; Krmpot, A. J.; Jelenković, B. M.

2015-02-01

We investigate, experimentally and theoretically, time development of Zeeman electromagnetically induced transparency (EIT) during propagation of two time separated polarization laser pulses, preparatory and probe, through Rb vapour. The pulses were produced by modifying laser intensity and degree of elliptical polarization. The frequency of the single laser beam is locked to the hyperfine {{F}g}=2\\to {{F}e}=1 transition of the D1 line in 87Rb. Transients in the intensity of {{σ }-} component of the transmitted light are measured or calculated at different values of the external magnetic field, during both preparatory and probe pulse. Zeeman EIT resonances at particular time instants of the pulse propagation are reconstructed by appropriate sampling of the transients. We observe how laser intensity, Ramsey sequence and the Rb cell temperature affect the time dependence of EIT line shapes, amplitudes and linewidths. We show that at early times of the probe pulse propagation, several Ramsey fringes are present in EIT resonances, while at later moments a single narrow peak prevails. Time development of EIT amplitudes are determined by the transmitted intensity of the {{σ }-} component during the pulse propagation.

Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla

PubMed Central

Stier, Andreas V.; McCreary, Kathleen M.; Jonker, Berend T.; Kono, Junichiro; Crooker, Scott A.

2016-01-01

In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS2 and MoS2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately −230 μeV T−1 (g-factor ≃−4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS2, from which radii of ∼1.53 and ∼1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). These results highlight the utility of high magnetic fields for understanding new two-dimensional materials. PMID:26856412

Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS 2 and MoS 2 to 65 Tesla

DOE PAGES

Stier, Andreas V.; McCreary, Kathleen M.; Jonker, Berend T.; ...

2016-02-09

In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS 2 and MoS 2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately –230 μeV T–1 (g-factor ≃–4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS 2,more » from which radii of ~1.53 and ~1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). Lastly, these results highlight the utility of high magnetic fields for understanding new two-dimensional materials.« less

Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla.

PubMed

Stier, Andreas V; McCreary, Kathleen M; Jonker, Berend T; Kono, Junichiro; Crooker, Scott A

2016-02-09

In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS2 and MoS2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately -230 μeV T(-1) (g-factor ≃-4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS2, from which radii of ∼1.53 and ∼1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). These results highlight the utility of high magnetic fields for understanding new two-dimensional materials.

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

Measure synchronization in a Huygens's non-dissipative two-pendulum clocks system

NASA Astrophysics Data System (ADS)

Tian, Jing; Chen, ZiChen; Qiu, HaiBo; Xi, XiaoQiang

2018-01-01

In this paper, we characterize measure synchronization (MS) in a four-degrees-of-freedom Huygens's two-pendulum clocks system. The two-pendulum clocks are connected by a massless spring with stiffness constant k. We find that with the stiffness constant k increasing, the coupled pendulums system achieves MS above a threshold value of k c . The energy characteristics of measure synchronization have been discussed, it is found that averaged energy of each pendulum system provide us an easy way to characterize MS transition. Furthermore, we discuss the dependence of the critical value for MS transition on initial conditions and the characteristic parameters of the system.

Atomic Clock Based on Opto-Electronic Oscillator

NASA Technical Reports Server (NTRS)

Maleki, Lute; Yu, Nan

2005-01-01

A proposed highly accurate clock or oscillator would be based on the concept of an opto-electronic oscillator (OEO) stabilized to an atomic transition. Opto-electronic oscillators, which have been described in a number of prior NASA Tech Briefs articles, generate signals at frequencies in the gigahertz range characterized by high spectral purity but not by longterm stability or accuracy. On the other hand, the signals generated by previously developed atomic clocks are characterized by long-term stability and accuracy but not by spectral purity. The proposed atomic clock would provide high spectral purity plus long-term stability and accuracy a combination of characteristics needed to realize advanced developments in communications and navigation. In addition, it should be possible to miniaturize the proposed atomic clock. When a laser beam is modulated by a microwave signal and applied to a photodetector, the electrical output of the photodetector includes a component at the microwave frequency. In atomic clocks of a type known as Raman clocks or coherent-population-trapping (CPT) clocks, microwave outputs are obtained from laser beams modulated, in each case, to create two sidebands that differ in frequency by the amount of a hyperfine transition in the ground state of atoms of an element in vapor form in a cell. The combination of these sidebands produces a transparency in the population of a higher electronic level that can be reached from either of the two ground-state hyperfine levels by absorption of a photon. The beam is transmitted through the vapor to a photodetector. The components of light scattered or transmitted by the atoms in the two hyperfine levels mix in the photodetector and thereby give rise to a signal at the hyperfine- transition frequency. The proposed atomic clock would include an OEO and a rubidium- or cesium- vapor cell operating in the CPT/Raman regime (see figure). In the OEO portion of this atomic clock, as in a typical prior OEO, a laser beam would pass through an electro-optical modulator, the modulated beam would be fed into a fiber-optic delay line, and the delayed beam would be fed to a photodetector. The electrical output of the photodetector would be detected, amplified, filtered, and fed back to the microwave input port of the modulator. The laser would be chosen to have the same wavelength as that of the pertinent ground-state/higher-state transition of the atoms in the vapor. The modulator/ filter combination would be designed to operate at the microwave frequency of the hyperfine transition. Part of the laser beam would be tapped from the fiberoptic loop of the OEO and introduced into the vapor cell. After passing through the cell, this portion of the beam would be detected differentially with a tapped portion of the fiber-optically-delayed beam. The electrical output of the photodetector would be amplified and filtered in a loop that would control a DC bias applied to the modulator. In this manner, the long-term stability and accuracy of the atomic transition would be transferred to the OEO.

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

Spin-orbit-coupled fermions in an optical lattice clock

NASA Astrophysics Data System (ADS)

Kolkowitz, S.; Bromley, S. L.; Bothwell, T.; Wall, M. L.; Marti, G. E.; Koller, A. P.; Zhang, X.; Rey, A. M.; Ye, J.

2017-02-01

Engineered spin-orbit coupling (SOC) in cold-atom systems can enable the study of new synthetic materials and complex condensed matter phenomena. However, spontaneous emission in alkali-atom spin-orbit-coupled systems is hindered by heating, limiting the observation of many-body effects and motivating research into potential alternatives. Here we demonstrate that spin-orbit-coupled fermions can be engineered to occur naturally in a one-dimensional optical lattice clock. In contrast to previous SOC experiments, here the SOC is both generated and probed using a direct ultra-narrow optical clock transition between two electronic orbital states in 87Sr atoms. We use clock spectroscopy to prepare lattice band populations, internal electronic states and quasi-momenta, and to produce spin-orbit-coupled dynamics. The exceptionally long lifetime of the excited clock state (160 seconds) eliminates decoherence and atom loss from spontaneous emission at all relevant experimental timescales, allowing subsequent momentum- and spin-resolved in situ probing of the SOC band structure and eigenstates. We use these capabilities to study Bloch oscillations, spin-momentum locking and Van Hove singularities in the transition density of states. Our results lay the groundwork for using fermionic optical lattice clocks to probe new phases of matter.

Mechanism of 'GSI oscillations' in electron capture by highly charged hydrogen-like atomic ions

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

Krainov, V. P., E-mail: vpkrainov@mail.ru

2012-07-15

We suggest a qualitative explanation of oscillations in electron capture decays of hydrogen-like {sup 140}Pr and {sup 142}Pm ions observed recently in an ion experimental storage ring (ESR) of Gesellschaft fuer Schwerionenforschung (GSI) mbH, Darmstadt, Germany. This explanation is based on the electron multiphoton Rabi oscillations between two Zeeman states of the hyperfine ground level with the total angular momentum F = 1/2. The Zeeman splitting is produced by a constant magnetic field in the ESR. Transitions between these states are produced by the second, sufficiently strong alternating magnetic field that approximates realistic fields in the GSI ESR. The Zeemanmore » splitting amounts to only about 10{sup -5} eV. This allows explaining the observed quantum beats with the period 7 s.« less

New forms of spin-orbit coupling in a strontium optical lattice clock

NASA Astrophysics Data System (ADS)

Perlin, Michael; Safavi-Naini, Arghavan; Ozeri, Roee; Rey, Ana Maria

2017-04-01

Ultracold atomic systems allow for the simulation of a variety of condensed matter phenomena, including spin-orbit coupling (SOC), a key ingredient behind recently discovered topological insulators and a path for the realization of topological superfluids. While many experimental efforts have used alkali atoms to engineer SOC via Raman transitions, undesirable heating mechanisms have limited the observation of many-body phenomena manifest at long timescales. Alkaline earth atoms (AEA) have been recently shown to be a potentially better platform for the implementation of SOC due to their reduced sensitivity to spontaneous emission. While previous work has used electronic clock states as a pseudo-spin degree of freedom, we consider the effects of clock side-band transitions. We discuss the richer SOC dynamics which emerges as a result of this extension, and present methods to probe these dynamics in current AEA optical lattice clocks. AFOSR, NSF-PFC and DARPA.

Laser-stimulated electric quadrupole transitions in the molecular hydrogen ion H2+

NASA Astrophysics Data System (ADS)

Korobov, V. I.; Danev, P.; Bakalov, D.; Schiller, S.

2018-03-01

Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. We report the results of the calculations of the rate of laser-induced electric quadrupole transitions between a large set of ro-vibrational states of H2+. The hyperfine and Zeeman structure of the E 2 transition spectrum and the effects of the laser polarization are treated in detail. The treatment is generally applicable to molecules in 2Σ states. We also present the nuclear spin-electron spin-coupling constants, computed with a precision ten times higher than previously obtained.

Absolute frequency measurement of the 88Sr+ clock transition using a GPS link to the SI second

NASA Astrophysics Data System (ADS)

Dubé, Pierre; E Bernard, John; Gertsvolf, Marina

2017-06-01

We report the results of a recent measurement of the absolute frequency of the 5s{{ }2}{{S}1/2} - 4d{{ }2}{{D}5/2} transition of the {{}88}\\text{Sr}{{}+} ion. The optical frequency was measured against the international atomic time realization of the SI second on the geoid as obtained by frequency transfer using a global positioning system link and the precise point positioning technique. The measurement campaign yielded more than 100 h of frequency data. It was performed with improvements to the stability and accuracy of the single-ion clock compared to the last measurement made in 2012. The single ion clock uncertainty is evaluated at 1.5× {{10}-17} when contributions from acousto-optic modulator frequency chirps and servo errors are taken into account. The stability of the ion clock is 3× {{10}-15} at 1 s averaging, a factor of three better than in the previous measurement. The results from the two measurement campaigns are in good agreement. The uncertainty of the measurement, primarily from the link to the SI second, is 0.75 Hz (1.7× {{10}-15} ). The frequency measured for the S-D clock transition of {{}88}\\text{S}{{\\text{r}}+} is {ν0}= 444 779 044 095 485.27(75) Hz.

Missing magnetism in Sr 4Ru 3O 10: Indication for Antisymmetric Exchange Interaction

DOE PAGES

Weickert, Franziska; Civale, Leonardo; Maiorov, Boris; ...

2017-06-20

Metamagnetism occuring inside a ferromagnetic phase is peculiar. Therefore, Sr 4Ru 3O 10, a T C = 105 K ferromagnet, has attracted much attention in recent years, because it develops a pronounced metamagnetic anomaly below T C for magnetic fields applied in the crystallographic ab-plane. The metamagnetic transition moves to higher fields for lower temperatures and splits into a double anomaly at critical fields H c1 = 2.3 T and H c2 = 2.8 T, respectively. Here, we report a detailed study of the different components of the magnetization vector as a function of temperature, applied magnetic field, and varyingmore » angle in Sr 4Ru 3O 10. We discover for the first time a reduction of the magnetic moment in the plane of rotation at the metamagnetic transition. The anomaly shifts to higher fields by rotating the field from H ⊥ c to H || c. We compare our experimental findings with numerical simulations based on spin reorientation models taking into account magnetocrystalline anisotropy, Zeeman effect and antisymmetric exchange interactions. While Magnetocrystalline anisotropy combined with a Zeeman term are sufficient to explain a metamagnetic transition in Sr 4Ru 3O 10, a Dzyaloshinskii-Moriya term is crucial to account for the reduction of the magnetic moment as observed in the experiments.« less

Missing magnetism in Sr 4Ru 3O 10: Indication for Antisymmetric Exchange Interaction

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

Weickert, Franziska; Civale, Leonardo; Maiorov, Boris

Metamagnetism occuring inside a ferromagnetic phase is peculiar. Therefore, Sr 4Ru 3O 10, a T C = 105 K ferromagnet, has attracted much attention in recent years, because it develops a pronounced metamagnetic anomaly below T C for magnetic fields applied in the crystallographic ab-plane. The metamagnetic transition moves to higher fields for lower temperatures and splits into a double anomaly at critical fields H c1 = 2.3 T and H c2 = 2.8 T, respectively. Here, we report a detailed study of the different components of the magnetization vector as a function of temperature, applied magnetic field, and varyingmore » angle in Sr 4Ru 3O 10. We discover for the first time a reduction of the magnetic moment in the plane of rotation at the metamagnetic transition. The anomaly shifts to higher fields by rotating the field from H ⊥ c to H || c. We compare our experimental findings with numerical simulations based on spin reorientation models taking into account magnetocrystalline anisotropy, Zeeman effect and antisymmetric exchange interactions. While Magnetocrystalline anisotropy combined with a Zeeman term are sufficient to explain a metamagnetic transition in Sr 4Ru 3O 10, a Dzyaloshinskii-Moriya term is crucial to account for the reduction of the magnetic moment as observed in the experiments.« less

Optically Generated 2-Dimensional Photonic Cluster State from Coupled Quantum Dots

DTIC Science & Technology

2010-08-24

these are quite strong (on the order of, or stronger, than typical Zeeman energies), and they are separable into ‘‘isotropic’’ and ‘‘ anisotropic ...AUGUST 2010 093601-3 We now discuss some specific sources of error and their expected impact. 1. Imperfect CZ gate.—If we label0 the Rabi frequency of...the target transition from j ##i, then the other transitions see a Rabi frequency of 1 ¼ 0= ffiffiffi 3 p and 2 ¼ ffiffi 3 2 q 0, with a large

Controlling state explosion during automatic verification of delay-insensitive and delay-constrained VLSI systems using the POM verifier

NASA Technical Reports Server (NTRS)

Probst, D.; Jensen, L.

1991-01-01

Delay-insensitive VLSI systems have a certain appeal on the ground due to difficulties with clocks; they are even more attractive in space. We answer the question, is it possible to control state explosion arising from various sources during automatic verification (model checking) of delay-insensitive systems? State explosion due to concurrency is handled by introducing a partial-order representation for systems, and defining system correctness as a simple relation between two partial orders on the same set of system events (a graph problem). State explosion due to nondeterminism (chiefly arbitration) is handled when the system to be verified has a clean, finite recurrence structure. Backwards branching is a further optimization. The heart of this approach is the ability, during model checking, to discover a compact finite presentation of the verified system without prior composition of system components. The fully-implemented POM verification system has polynomial space and time performance on traditional asynchronous-circuit benchmarks that are exponential in space and time for other verification systems. We also sketch the generalization of this approach to handle delay-constrained VLSI systems.

EUO-Based Multifunctional Heterostructures

DTIC Science & Technology

2015-06-06

magnetoresistance and the metal -insulator transition resistance ratios of doped EuO by interfacing this semiconductor with niobium; the observed effect is...general and may be applied to any metal /semiconductor interface where the semiconductor shows large Zeeman splitting under magnetic field, (2...understanding the changes in electronic structure and Fermi-surface reconstruction that occur as doped EuO progresses through the ferromagnetic metal

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.

The Impact of Sleep and Circadian Disturbance on Hormones and Metabolism

PubMed Central

Kim, Tae Won; Jeong, Jong-Hyun; Hong, Seung-Chul

2015-01-01

The levels of several hormones fluctuate according to the light and dark cycle and are also affected by sleep, feeding, and general behavior. The regulation and metabolism of several hormones are influenced by interactions between the effects of sleep and the intrinsic circadian system; growth hormone, melatonin, cortisol, leptin, and ghrelin levels are highly correlated with sleep and circadian rhythmicity. There are also endogenous circadian mechanisms that serve to regulate glucose metabolism and similar rhythms pertaining to lipid metabolism, regulated through the actions of various clock genes. Sleep disturbance, which negatively impacts hormonal rhythms and metabolism, is also associated with obesity, insulin insensitivity, diabetes, hormonal imbalance, and appetite dysregulation. Circadian disruption, typically induced by shift work, may negatively impact health due to impaired glucose and lipid homeostasis, reversed melatonin and cortisol rhythms, and loss of clock gene rhythmicity. PMID:25861266

Anisotropic semivortices in dipolar spinor condensates controlled by Zeeman splitting

NASA Astrophysics Data System (ADS)

Liao, Bingjin; Li, Shoubo; Huang, Chunqing; Luo, Zhihuan; Pang, Wei; Tan, Haishu; Malomed, Boris A.; Li, Yongyao

2017-10-01

Spatially anisotropic solitary vortices, i.e., bright anisotropic vortex solitons (AVSs), supported by anisotropic dipole-dipole interactions, were recently predicted in spin-orbit-coupled binary Bose-Einstein condensates (BECs), in the form of two-dimensional semivortices (complexes built of zero-vorticity and vortical components). We demonstrate that the shape of the AVSs—horizontal or vertical, with respect to the in-plane polarization of the atomic dipole moments in the underlying BEC—may be effectively controlled by the strength Ω of the Zeeman splitting (ZS). A transition from the horizontal to vertical shape with the increase of Ω is found numerically and explained analytically. At the transition point, the AVS assumes the shape of an elliptical ring. The mobility of horizontal AVSs is studied, too, with the conclusion that, with the increase of Ω , their negative effective mass changes the sign to positive via a point at which the effective mass diverges. Lastly, we report a new species of inverted AVSs, with the zero-vorticity and vortex component placed in lower- and higher-energy components, as defined by the ZS. They are excited states, with respect to the ground states provided by the usual AVSs. Quite surprisingly, inverted AVSs are stable in a large parameter region.

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.

Near-Infrared Spectroscopy for Zeeman Spectra of Ti I in Plasma Using a Facing Target Sputtering System

NASA Astrophysics Data System (ADS)

Kobayashi, Shinji; Nishimiya, Nobuo; Suzuki, Masao

2017-10-01

The saturated absorption lines of neutral titanium were measured in the region of 9950-14380 cm-1 using a Ti:sapphire ring laser. A facing target sputtering system was used to obtain the gaseous state of a Ti I atom. The Zeeman splitting of 38 transitions was observed under the condition that the electric field component of a linearly polarized laser beam was parallel to the magnetic field. The gJ factors of the odd parity states were determined for 28 states belonging to 3d24s4p and 3d34p using those of the even parity states reported by Stachowska in 1997. The gJ factors of z5P1,2,3 levels were newly determined. gJ of y3F2, y3D2, z3P2, and z5S2 levels were refined.

Zeeman Effect in Ruby at High Pressures

NASA Astrophysics Data System (ADS)

Dan, Ioana

2012-02-01

We have developed a versatile fiber-coupled system for magneto-optical spectroscopy measurements at high pressure. The system is based on a miniature Cu-alloy Diamond Anvil Cell (from D'Anvils, Ltd) fitted with a custom-designed He gas-actuated membrane for in-situ pressure control, and coupled with a He transfer cryostat incorporating a superconducting magnet (from Quantum Designs). This system allows optical measurements (Raman, photoluminescence, reflectivity) within wide ranges of pressures (up to 100GPa), temperatures (4.2-300K) and magnetic fields (0-9T). We employ this system to examine the effect of pressure and non-hydrostatic stress on the Zeeman split d-d transitions of Cr^3+ in ruby (Al2O3: Cr^3+). We determine the effect of pressure and non-hydrostaticity on the trigonal crystal field in this material, and discuss the use of the Zeman-split ruby fluorescence as a possible probe for deviatoric stresses in diamond anvil cell experiments.

Tunable spin splitting and spin lifetime in polar WSTe monolayer

NASA Astrophysics Data System (ADS)

Adhib Ulil Absor, Moh.; Kotaka, Hiroki; Ishii, Fumiyuki; Saito, Mineo

2018-04-01

The established spin splitting with out-of-plane Zeeman spin polarizations in the monolayer (ML) of transition metal dichalcogenides (TMDs) is dictated by inversion symmetry breaking together with mirror symmetry in the surface plane. Here, by density functional theory calculations, we find that mirror symmetry breaking in the polar WSTe ML leads to large spin splitting exhibiting in-plane Rashba spin polarizations. We also find that the interplay between the out-of-plane Zeeman- and in-plane Rashba spin-polarized states sensitively affects the spin lifetime, which can be effectively controlled by in-plane strain. In addition, the tunability of spin splitting using an external electric field is also demonstrated. Our study clarifies that the use of in-plane strain and an external electric field is effective for tuning the spin splitting and spin lifetime of the polar WSTe ML; thus, it is useful for designing spintronic devices.

The Zeeman splitting of bulk 2H-MoTe2 single crystal in high magnetic field

NASA Astrophysics Data System (ADS)

Sun, Yan; Zhang, Junpei; Ma, Zongwei; Chen, Cheng; Han, Junbo; Chen, Fangchu; Luo, Xuan; Sun, Yuping; Sheng, Zhigao

2017-03-01

A high magnetic field magneto-optical spectrum is utilized to study the A exciton of bulk 2H-MoTe2 single crystal. A clear Zeeman splitting of the A exciton is observed under high magnetic fields up to 41.68 T, and the g-factor (-2.09 ± 0.08) is deduced. Moreover, a high magnetic field enables us to obtain the quadratic diamagnetic shifts of the A exciton (0.486 μeV T-2). Accordingly, the binding energy, reduced mass, and radius of the A exciton were obtained by using both two and three dimensional models. Compared with other transition metal dichalcogenides (TMDs), the A exciton of bulk 2H-MoTe2 has a relatively small binding energy and larger exciton radius, which provide fundamental parameters for comprehensive understanding of excitons in TMDs as well as their future applications.

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.)

Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

PubMed Central

Morzyński, Piotr; Bober, Marcin; Bartoszek-Bober, Dobrosława; Nawrocki, Jerzy; Krehlik, Przemysław; Śliwczyński, Łukasz; Lipiński, Marcin; Masłowski, Piotr; Cygan, Agata; Dunst, Piotr; Garus, Michał; Lisak, Daniel; Zachorowski, Jerzy; Gawlik, Wojciech; Radzewicz, Czesław; Ciuryło, Roman; Zawada, Michał

2015-01-01

We report a stability below 7 × 10−17 of two independent optical lattice clocks operating with bosonic 88Sr isotope. The value (429 228 066 418 008.3(1.9)syst (0.9)stat Hz) of the absolute frequency of the 1S0 – 3P0 transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures. PMID:26639347

Synthesis of energy-efficient FSMs implemented in PLD circuits

NASA Astrophysics Data System (ADS)

Nawrot, Radosław; Kulisz, Józef; Kania, Dariusz

2017-11-01

The paper presents an outline of a simple synthesis method of energy-efficient FSMs. The idea consists in using local clock gating to selectively block the clock signal, if no transition of a state of a memory element is required. The research was dedicated to logic circuits using Programmable Logic Devices as the implementation platform, but the conclusions can be applied to any synchronous circuit. The experimental section reports a comparison of three methods of implementing sequential circuits in PLDs with respect to clock distribution: the classical fully synchronous structure, the structure exploiting the Enable Clock inputs of memory elements, and the structure using clock gating. The results show that the approach based on clock gating is the most efficient one, and it leads to significant reduction of dynamic power consumed by the FSM.

Quantum Algorithmic Readout in Multi-Ion Clocks.

PubMed

Schulte, M; Lörch, N; Leroux, I D; Schmidt, P O; Hammerer, K

2016-01-08

Optical clocks based on ensembles of trapped ions promise record frequency accuracy with good short-term stability. Most suitable ion species lack closed transitions, so the clock signal must be read out indirectly by transferring the quantum state of the clock ions to cotrapped logic ions of a different species. Existing methods of quantum logic readout require a linear overhead in either time or the number of logic ions. Here we describe a quantum algorithmic readout whose overhead scales logarithmically with the number of clock ions in both of these respects. The scheme allows a quantum nondemolition readout of the number of excited clock ions using a single multispecies gate operation which can also be used in other areas of ion trap technology such as quantum information processing, quantum simulations, metrology, and precision spectroscopy.

Piezoelectric Non-Linear Nanomechanical Temperature and Acceleration Insensitive Clocks (PENNTAC) Phase 1 Evaluation and Plans for Phase 2

DTIC Science & Technology

2013-05-01

95.2 dBc/Hz, (c) - 94.2 dBc/Hz. Fig. 4: Mechanically compensated AlN resonators. A thin oxide layer is used to completely cancel the linear...pumped is represented by a non-linear capacitor. This capacitor will be first implemented via a varactor and then substituted by a purely mechanical...demonstrate the advantages of a parametric oscillator: (i) we will first use an external electronic varactor to prove that a parametric oscillator

Historical Notes on the Dutch and American-Dutch "schools" in Astronomy and Their Relations with Physics

NASA Astrophysics Data System (ADS)

van den Heuvel, Ed

2006-04-01

Dutch astronomy and physics experienced two "golden ages". The firstone covered the 17th century, culminating with Christiaan Huygens,inventor of the pendulum clock and the wave theory of light, anddiscoverer of Saturn's rings and largest satellite Titan. The secondone, which lasts till the present, started around 1880 withphysicists Lorentz, van der Waals, Zeeman and Kamerlingh Onnes andastronomer Kapteijn and his pupils De Sitter, van Rhijn, Oort andSchilt. Kapteijn, through his friendship with George Ellery Hale,initiated the strong connection between American and Dutch astronomy,which led to the rise of many Dutch-born astronomers to prominentpositions in the US, from Luyten, Bok, Brouwer, Schilt and Kuiperto Woltjer, Gehrels, and Beckers. The rise of the second "goldenage" appears to be closely related to drastic reforms in the Dutchhigh school and university systems in the last decades of the 19thcentury.

Superfluid transition in the attractive Hofstadter-Hubbard model

NASA Astrophysics Data System (ADS)

Umucalılar, R. O.; Iskin, M.

2016-08-01

We consider a Fermi gas that is loaded onto a square optical lattice and subjected to a perpendicular artificial magnetic field, and determine its superfluid transition boundary by adopting a BCS-like mean-field approach in momentum space. The multiband structure of the single-particle Hofstadter spectrum is taken explicitly into account while deriving a generalized pairing equation. We present the numerical solutions as functions of the artificial magnetic flux, interaction strength, Zeeman field, chemical potential, and temperature, with a special emphasis on the roles played by the density of single-particle states and center-of-mass momentum of Cooper pairs.

Optically controlled waveplate at a telecom wavelength using a ladder transition in Rb atoms for all-optical switching and high speed Stokesmetric imaging.

PubMed

Krishnamurthy, Subramanian; Tu, Y; Wang, Y; Tseng, S; Shahriar, M S

2014-11-17

We demonstrate an optically controlled waveplate at ~1323 nm using the 5S(1/2)-5P(1/2)-6S(1/2) ladder transition in a Rb vapor cell. The lower leg of the transitions represents the control beam, while the upper leg represents the signal beam. We show that we can place the signal beam in any arbitrary polarization state with a suitable choice of polarization of the control beam. Specifically, we demonstrate a differential phase retardance of ~180 degrees between the two circularly polarized components of a linearly polarized signal beam. We also demonstrate that the system can act as a Quarter Wave plate. The optical activity responsible for the phase retardation process is explained in terms of selection rules involving the Zeeman sublevels. As such, the system can be used to realize a fast Stokesmetric imaging system with a speed of ~3 MHz. When implemented using a tapered nano fiber embedded in a vapor cell, this system can be used to realize an ultra-low power all-optical switch as well as a Quantum Zeno Effect based all-optical logic gate by combining it with an optically controlled polarizer, previously demonstrated by us. We present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, using a novel algorithm recently developed by us for efficient computation of the evolution of an arbitrary large scale quantum system.

TIME FOR COFFEE Represses Accumulation of the MYC2 Transcription Factor to Provide Time-of-Day Regulation of Jasmonate Signaling in Arabidopsis[C][W][OA

PubMed Central

Shin, Jieun; Heidrich, Katharina; Sanchez-Villarreal, Alfredo; Parker, Jane E.; Davis, Seth J.

2012-01-01

Plants are confronted with predictable daily biotic and abiotic stresses that result from the day–night cycle. The circadian clock provides an anticipation mechanism to respond to these daily stress signals to increase fitness. Jasmonate (JA) is a phytohormone that mediates various growth and stress responses. Here, we found that the circadian-clock component TIME FOR COFFEE (TIC) acts as a negative factor in the JA-signaling pathway. We showed that the tic mutant is hypersensitive to growth-repressive effects of JA and displays altered JA-regulated gene expression. TIC was found to interact with MYC2, a key transcription factor of JA signaling. From this, we discovered that the circadian clock rhythmically regulates JA signaling. TIC is a key determinant in this circadian-gated process, and as a result, the tic mutant is defective in rhythmic JA responses to pathogen infection. TIC acts here by inhibiting MYC2 protein accumulation and by controlling the transcriptional repression of CORONATINE INSENSITIVE1 in an evening-phase–specific manner. Taken together, we propose that TIC acts as an output component of the circadian oscillator to influence JA signaling directly. PMID:22693280

High accuracy switched-current circuits using an improved dynamic mirror

NASA Technical Reports Server (NTRS)

Zweigle, G.; Fiez, T.

1991-01-01

The switched-current technique, a recently developed circuit approach to analog signal processing, has emerged as an alternative/compliment to the well established switched-capacitor circuit technique. High speed switched-current circuits offer potential cost and power savings over slower switched-capacitor circuits. Accuracy improvements are a primary concern at this stage in the development of the switched-current technique. Use of the dynamic current mirror has produced circuits that are insensitive to transistor matching errors. The dynamic current mirror has been limited by other sources of error including clock-feedthrough and voltage transient errors. In this paper we present an improved switched-current building block using the dynamic current mirror. Utilizing current feedback the errors due to current imbalance in the dynamic current mirror are reduced. Simulations indicate that this feedback can reduce total harmonic distortion by as much as 9 dB. Additionally, we have developed a clock-feedthrough reduction scheme for which simulations reveal a potential 10 dB total harmonic distortion improvement. The clock-feedthrough reduction scheme also significantly reduces offset errors and allows for cancellation with a constant current source. Experimental results confirm the simulated improvements.

Calibration of Multiple Poliovirus Molecular Clocks Covering an Extended Evolutionary Range▿ †

PubMed Central

Jorba, Jaume; Campagnoli, Ray; De, Lina; Kew, Olen

2008-01-01

We have calibrated five different molecular clocks for circulating poliovirus based upon the rates of fixation of total substitutions (Kt), synonymous substitutions (Ks), synonymous transitions (As), synonymous transversions (Bs), and nonsynonymous substitutions (Ka) into the P1/capsid region (2,643 nucleotides). Rates were determined over a 10-year period by analysis of sequences of 31 wild poliovirus type 1 isolates representing a well-defined phylogeny derived from a common imported ancestor. Similar rates were obtained by linear regression, the maximum likelihood/single-rate dated-tip method, and Bayesian inference. The very rapid Kt [(1.03 ± 0.10) × 10−2 substitutions/site/year] and Ks [(1.00 ± 0.08) × 10−2] clocks were driven primarily by the As clock [(0.96 ± 0.09) × 10−2], the Bs clock was ∼10-fold slower [(0.10 ± 0.03) × 10−2], and the more stochastic Ka clock was ∼30-fold slower [(0.03 ± 0.01) × 10−2]. Nonsynonymous substitutions at all P1/capsid sites, including the neutralizing antigenic sites, appeared to be constrained by purifying selection. Simulation of the evolution of third-codon positions suggested that saturation of synonymous transitions would be evident at 10 years and complete at ∼65 years of independent transmission. Saturation of synonymous transversions was predicted to be minimal at 20 years and incomplete at 100 years. The rapid evolution of the Kt, Ks, and As clocks can be used to estimate the dates of divergence of closely related viruses, whereas the slower Bs and Ka clocks may be used to explore deeper evolutionary relationships within and across poliovirus genotypes. PMID:18287242

Phase modulation for reduced vibration sensitivity in laser-cooled clocks in space

NASA Technical Reports Server (NTRS)

Klipstein, W.; Dick, G.; Jefferts, S.; Walls, F.

2001-01-01

The standard interrogation technique in atomic beam clocks is square-wave frequency modulation (SWFM), which suffers a first order sensitivity to vibrations as changes in the transit time of the atoms translates to perceived frequency errors. Square-wave phase modulation (SWPM) interrogation eliminates sensitivity to this noise.

Eight-Channel Continuous Timer

NASA Technical Reports Server (NTRS)

Cole, Steven

2004-01-01

A custom laboratory electronic timer circuit measures the durations of successive cycles of nominally highly stable input clock signals in as many as eight channels, for the purpose of statistically quantifying the small instabilities of these signals. The measurement data generated by this timer are sent to a personal computer running software that integrates the measurements to form a phase residual for each channel and uses the phase residuals to compute Allan variances for each channel. (The Allan variance is a standard statistical measure of instability of a clock signal.) Like other laboratory clock-cycle-measuring circuits, this timer utilizes an externally generated reference clock signal having a known frequency (100 MHz) much higher than the frequencies of the input clock signals (between 100 and 120 Hz). It counts the number of reference-clock cycles that occur between successive rising edges of each input clock signal of interest, thereby affording a measurement of the input clock-signal period to within the duration (10 ns) of one reference clock cycle. Unlike typical prior laboratory clock-cycle-measuring circuits, this timer does not skip some cycles of the input clock signals. The non-cycle-skipping feature is an important advantage because in applications that involve integration of measurements over long times for characterizing nominally highly stable clock signals, skipping cycles can degrade accuracy. The timer includes a field-programmable gate array that functions as a 20-bit counter running at the reference clock rate of 100 MHz. The timer also includes eight 20-bit latching circuits - one for each channel - at the output terminals of the counter. Each transition of an input signal from low to high causes the corresponding latching circuit to latch the count at that instant. Each such transition also sets a status flip-flop circuit to indicate the presence of the latched count. A microcontroller reads the values of all eight status flipflops and then reads the latched count for each channel for which the flip-flop indicates the presence of a count. Reading the count for each channel automatically causes the flipflop of that channel to be reset. The microcontroller places the counts in time order, identifies the channel number for each count, and transmits these data to the personal computer.

Optical atomic clocks

NASA Astrophysics Data System (ADS)

Poli, N.; Oates, C. W.; Gill, P.; Tino, G. M.

2013-12-01

In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

Micro ion frequency standard

NASA Astrophysics Data System (ADS)

Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; Serkland, Darwin K.; Boye, Robert; Fang, Lu; Casias, Adrian; Manginell, Ronald P.; Moorman, Matthew; Prestage, John; Yu, Nan

2011-06-01

We are developing a highly miniaturized trapped ion clock to probe the 12.6 GHz hyperfine transition in the 171Yb+ ion. The clock development is being funded by the Integrated Micro Primary Atomic Clock Technology (IMPACT) program from DARPA where the stated goals are to develop a clock that consumes 50 mW of power, has a size of 5 cm3, and has a long-term frequency stability of 10-14 at one month. One of the significant challenges will be to develop miniature single-frequency lasers at 369 nm and 935 nm and the optical systems to deliver light to the ions and to collect ion fluorescence on a detector.

Measuring the frequency of a Sr optical lattice clock using a 120 km coherent optical transfer.

PubMed

Hong, F-L; Musha, M; Takamoto, M; Inaba, H; Yanagimachi, S; Takamizawa, A; Watabe, K; Ikegami, T; Imae, M; Fujii, Y; Amemiya, M; Nakagawa, K; Ueda, K; Katori, H

2009-03-01

We demonstrate a precision frequency measurement using a phase-stabilized 120 km optical fiber link over a physical distance of 50 km. The transition frequency of the (87)Sr optical lattice clock at the University of Tokyo is measured to be 429228004229874.1(2.4) Hz referenced to international atomic time. The results demonstrate the excellent functions of the intercity optical fiber link and the great potential of optical lattice clocks for use in the redefinition of the second.

Entrainment of the Mammalian Cell Cycle by the Circadian Clock: Modeling Two Coupled Cellular Rhythms

PubMed Central

Gérard, Claude; Goldbeter, Albert

2012-01-01

The cell division cycle and the circadian clock represent two major cellular rhythms. These two periodic processes are coupled in multiple ways, given that several molecular components of the cell cycle network are controlled in a circadian manner. For example, in the network of cyclin-dependent kinases (Cdks) that governs progression along the successive phases of the cell cycle, the synthesis of the kinase Wee1, which inhibits the G2/M transition, is enhanced by the complex CLOCK-BMAL1 that plays a central role in the circadian clock network. Another component of the latter network, REV-ERBα, inhibits the synthesis of the Cdk inhibitor p21. Moreover, the synthesis of the oncogene c-Myc, which promotes G1 cyclin synthesis, is repressed by CLOCK-BMAL1. Using detailed computational models for the two networks we investigate the conditions in which the mammalian cell cycle can be entrained by the circadian clock. We show that the cell cycle can be brought to oscillate at a period of 24 h or 48 h when its autonomous period prior to coupling is in an appropriate range. The model indicates that the combination of multiple modes of coupling does not necessarily facilitate entrainment of the cell cycle by the circadian clock. Entrainment can also occur as a result of circadian variations in the level of a growth factor controlling entry into G1. Outside the range of entrainment, the coupling to the circadian clock may lead to disconnected oscillations in the cell cycle and the circadian system, or to complex oscillatory dynamics of the cell cycle in the form of endoreplication, complex periodic oscillations or chaos. The model predicts that the transition from entrainment to 24 h or 48 h might occur when the strength of coupling to the circadian clock or the level of growth factor decrease below critical values. PMID:22693436

Pacemaker-neuron–dependent disturbance of the molecular clockwork by a Drosophila CLOCK mutant homologous to the mouse Clock mutation

PubMed Central

Lee, Euna; Cho, Eunjoo; Kang, Doo Hyun; Jeong, Eun Hee; Chen, Zheng; Yoo, Seung-Hee; Kim, Eun Young

2016-01-01

Circadian clocks are composed of transcriptional/translational feedback loops (TTFLs) at the cellular level. In Drosophila TTFLs, the transcription factor dCLOCK (dCLK)/CYCLE (CYC) activates clock target gene expression, which is repressed by the physical interaction with PERIOD (PER). Here, we show that amino acids (AA) 657–707 of dCLK, a region that is homologous to the mouse Clock exon 19-encoded region, is crucial for PER binding and E-box–dependent transactivation in S2 cells. Consistently, in transgenic flies expressing dCLK with an AA657–707 deletion in the Clock (Clkout) genetic background (p{dClk-Δ};Clkout), oscillation of core clock genes’ mRNAs displayed diminished amplitude compared with control flies, and the highly abundant dCLKΔ657–707 showed significantly decreased binding to PER. Behaviorally, the p{dClk-Δ};Clkout flies exhibited arrhythmic locomotor behavior in the photic entrainment condition but showed anticipatory activities of temperature transition and improved free-running rhythms in the temperature entrainment condition. Surprisingly, p{dClk-Δ};Clkout flies showed pacemaker-neuron–dependent alterations in molecular rhythms; the abundance of dCLK target clock proteins was reduced in ventral lateral neurons (LNvs) but not in dorsal neurons (DNs) in both entrainment conditions. In p{dClk-Δ};Clkout flies, however, strong but delayed molecular oscillations in temperature cycle-sensitive pacemaker neurons, such as DN1s and DN2s, were correlated with delayed anticipatory activities of temperature transition. Taken together, our study reveals that the LNv molecular clockwork is more sensitive than the clockwork of DNs to dysregulation of dCLK by AA657–707 deletion. Therefore, we propose that the dCLK/CYC-controlled TTFL operates differently in subsets of pacemaker neurons, which may contribute to their specific functions. PMID:27489346

Potential Role for Peripheral Circadian Clock Dyssynchrony in the Pathogenesis of Cardiovascular Dysfunction

PubMed Central

Young, Martin E.; Bray, Molly S.

2007-01-01

Circadian clocks are intracellular molecular mechanisms designed to allow the cell, organ, and organism to prepare for an anticipated stimulus prior to its onset. In order for circadian clocks to maintain their selective advantage, they must be entrained to the environment. Light, sound, temperature, physical activity (including sleep/wake transitions), and food intake are among the strongest environmental factors influencing mammalian circadian clocks. Normal circadian rhythmicities in these environmental factors have become severely disrupted in our modern day society, concomitant with increased incidence of type 2 diabetes mellitus, obesity, and cardiovascular disease. Here, we review our current knowledge regarding the roles of peripheral circadian clocks, concentrating on those found within tissues directly involved in metabolic homeostasis and cardiovascular function. We propose that both inter- and intra- organ dyssynchronization, through alteration/impairment of peripheral circadian clocks, accelerates the development of cardiovascular disease risk factors associated with cardiometabolic syndrome. PMID:17387040

Magneto-optical Effects in the Scattering Polarization Wings of the Ca I 4227 Å Resonance Line

NASA Astrophysics Data System (ADS)

Alsina Ballester, E.; Belluzzi, L.; Trujillo Bueno, J.

2018-02-01

The linear polarization pattern produced by scattering processes in the Ca I 4227 Å resonance line is a valuable observable for probing the solar atmosphere. Via the Hanle effect, the very significant Q/I and U/I line-center signals are sensitive to the presence of magnetic fields in the lower chromosphere with strengths between 5 and 125 G, approximately. On the other hand, partial frequency redistribution (PRD) produces sizable signals in the wings of the Q/I profile, which have always been thought to be insensitive to the presence of magnetic fields. Interestingly, novel observations of this line revealed a surprising behavior: fully unexpected signals in the wings of the U/I profile and spatial variability in the wings of both Q/I and U/I. We show that the magneto-optical (MO) terms of the Stokes-vector transfer equation produce sizable signals in the wings of U/I and a clear sensitivity of the Q/I and U/I wings to the presence of photospheric magnetic fields with strengths similar to those that produce the Hanle effect in the line core. This radiative transfer investigation on the joint action of scattering processes and the Hanle and Zeeman effects in the Ca I 4227 Å line should facilitate the development of more reliable techniques for exploring the magnetism of stellar atmospheres. To this end, we can now exploit the circular polarization produced by the Zeeman effect, the magnetic sensitivity caused by the above-mentioned MO effects in the Q/I and U/I wings, and the Hanle effect in the line core.

Spectra of 42S1/2→32D5/2 Transitions of a Single Trapped 40Ca+ Ion

NASA Astrophysics Data System (ADS)

Gong, Shi-Jie; Zhou, Fei; Wu, Hao-Yu; Wan, Wei; Chen, Liang; Feng, Mang

2015-01-01

We investigate the spectra of the electric quadrupole 42S1/2→32D5/2 transitions in a single 40Ca+ ion confined in a home-built linear trap. We probe the transitions with an ultra-narrow bandwidth laser at 729 nm. In a weak magnetic field, the quadrupole transition splits into ten components with the maximal line strength proportional to their squared Clebsch—Gordan factors. In a magnetic field of the order of Gauss, the observed equidistant sideband reflects the Zeeman substructure modulated by the quantized oscillation due to the secular motion in the trap. The temperature of the trapped ion can be determined by the envelope of the sideband spectrum. We also demonstrate the Rabi oscillation in a carrier transition after the ion has been Doppler cooled, which can be fitted by the model with the thermal state of motion.

The Pea Photoperiod Response Gene STERILE NODES Is an Ortholog of LUX ARRHYTHMO1[W][OPEN

PubMed Central

Liew, Lim Chee; Hecht, Valérie; Sussmilch, Frances C.; Weller, James L.

2014-01-01

The STERILE NODES (SN) locus in pea (Pisum sativum) was one of the first photoperiod response genes to be described and provided early evidence for the genetic control of long-distance signaling in flowering-time regulation. Lines homozygous for recessive sn mutations are early flowering and photoperiod insensitive, with an increased ability to promote flowering across a graft union in short-day conditions. Here, we show that SN controls developmental regulation of genes in the FT family and rhythmic regulation of genes related to circadian clock function. Using a positional and functional candidate approach, we identify SN as the pea ortholog of LUX ARRHYTHMO, a GARP transcription factor from Arabidopsis (Arabidopsis thaliana) with an important role in circadian clock function. In addition to induced mutants, sequence analysis demonstrates the presence of at least three other independent, naturally occurring loss-of-function mutations among known sn cultivars. Examination of genetic and regulatory interactions between SN and two other circadian clock genes, HIGH RESPONSE TO PHOTOPERIOD (HR) and DIE NEUTRALIS (DNE), suggests a complex relationship in which HR regulates expression of SN and the role of DNE and HR in control of flowering is dependent on SN. These results extend previous work to show that pea orthologs of all three Arabidopsis evening complex genes regulate clock function and photoperiod-responsive flowering and suggest that the function of these genes may be widely conserved. PMID:24706549

The Zeeman effect in astrophysical water masers and the observation of strong magnetic fields in regions of star formation

NASA Technical Reports Server (NTRS)

Nedoluha, Gerald E.; Watson, William D.

1992-01-01

The present study solves the transfer equations for the polarized radiation of astrophysical 22-GHz water masers in the presence of a magnetic field which causes a Zeeman splitting that is much smaller than the spectral line breadth. The emphasis is placed on the relationship between the recently detected circular polarization in this maser radiation and the strength of the magnetic field. When the observed spectral line breadth is smaller than about 0.8 km/s (FWHM), it is calculated that the uncertainty is less than a factor of about 2. The accuracy is improved significantly when the angle between the line of sight and the direction of the magnetic field does not exceed about 45 deg. Uncertainty in the strength of the magnetic field due to lack of knowledge about which hyperfine transition is the source of the 22-GHz masers is removed. The 22-GHz maser feature is found to be the result of a merger of the three strongest hyperfine components.

VizieR Online Data Catalog: ExoMol line lists. XXIV. SiH (Yurchenko+, 2018)

NASA Astrophysics Data System (ADS)

Yurchenko, S. N.; Sinden, F.; Lodi, L.; Hill, C.; Gorman, M. N.; Tennyson, J.

2017-11-01

The data for each isotopologue are in two parts. The first, s_*.dat contain lists of rovibronic states. Each state is labelled with the total angular momentum, state degeneracy, life time, Zeeman Lande-g factor, total (+/-) and e/f parities, vibrational quantum number, projection of the electronic, spin and total angular momenta. Each state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. The transition files t_*.dat contain four columns: the reference number in the energy file of the upper state; that of the lower state; the Einstein A coefficient of the transition; the transition wavenumber. (8 data files).

Atom Interferometry with the Sr Optical Clock Transition.

PubMed

Hu, Liang; Poli, Nicola; Salvi, Leonardo; Tino, Guglielmo M

2017-12-29

We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. We experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed for a total interferometer time up to ∼10  ms, limited by geometric constraints of the apparatus. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity.

Optically guided atom interferometer tuned to magic wavelength

NASA Astrophysics Data System (ADS)

Akatsuka, Tomoya; Takahashi, Tadahiro; Katori, Hidetoshi

2017-11-01

We demonstrate an atom interferometer operating on the 1S0-3P0 clock transition of 87Sr atoms in a “magic” optical guide, where the light shift perturbations of the guiding potential are canceled. As a proof-of-principle demonstration, a Mach-Zehnder interferometer is set horizontally to map the acceleration introduced by the focused optical guide. This magic guide interferometer on the clock transition is applicable to atomic elements where magic wavelengths can be found. Possible applications of the magic guide interferometer, including a hollow-core fiber interferometer and gradiometer, are discussed.

Compact Optical Atomic Clock Based on a Two-Photon Transition in Rubidium

NASA Astrophysics Data System (ADS)

Martin, Kyle W.; Phelps, Gretchen; Lemke, Nathan D.; Bigelow, Matthew S.; Stuhl, Benjamin; Wojcik, Michael; Holt, Michael; Coddington, Ian; Bishop, Michael W.; Burke, John H.

2018-01-01

Extralaboratory atomic clocks are necessary for a wide array of applications (e.g., satellite-based navigation and communication). Building upon existing vapor-cell and laser technologies, we describe an optical atomic clock, designed around a simple and manufacturable architecture, that utilizes the 778-nm two-photon transition in rubidium and yields fractional-frequency instabilities of 4 ×10-13/√{τ (s ) } for τ from 1 to 10 000 s. We present a complete stability budget for this system and explore the required conditions under which a fractional-frequency instability of 1 ×10-15 can be maintained on long time scales. We provide a precise characterization of the leading sensitivities to external processes, including magnetic fields and fluctuations of the vapor-cell temperature and 778-nm laser power. The system is constructed primarily from commercially available components, an attractive feature from the standpoint of the commercialization and deployment of optical frequency standards.

Transcriptome of the floral transition in Rosa chinensis 'Old Blush'.

PubMed

Guo, Xuelian; Yu, Chao; Luo, Le; Wan, Huihua; Zhen, Ni; Xu, Tingliang; Tan, Jiongrui; Pan, Huitang; Zhang, Qixiang

2017-02-23

The floral transition plays a vital role in the life of ornamental plants. Despite progress in model plants, the molecular mechanisms of flowering regulation remain unknown in perennial plants. Rosa chinensis 'Old Blush' is a unique plant that can flower continuously year-round. In this study, gene expression profiles associated with the flowering transition were comprehensively analyzed during floral transition in the rose. According to the transcriptomic profiles, 85,663 unigenes and 1,637 differentially expressed genes (DEGs) were identified, among which 32 unigenes were involved in the circadian clock, sugar metabolism, hormone, and autonomous pathways. A hypothetical model for the regulation of floral transition was proposed in which the candidate genes function synergistically the floral transition process. Hormone contents and biosynthesis and metabolism genes fluctuated during the rose floral transition process. Gibberellins (GAs) inhibited rose floral transition, the content of GAs gradually decreased and GA2ox and SCL13 were upregulated from vegetative (VM) meristem to floral meristem (FM). Auxin plays an affirmative part in mediating floral transition, auxin content and auxin-related gene expression levels were gradually upregulated during the floral transition of the rose. However, ABA content and ABA signal genes were gradually downregulated, suggesting that ABA passively regulates the rose floral transition by participating in sugar signaling. Furthermore, sugar content and sugar metabolism genes increased during floral transition in the rose, which may be a further florigenic signal that activates floral transition. Additionally, FRI, FY, DRM1, ELIP, COP1, CO, and COL16 are involved in the circadian clock and autonomous pathway, respectively, and they play a positively activating role in regulating floral transition. Overall, physiological changes associated with genes involved in the circadian clock or autonomous pathway collectively regulated the rose floral transition. Our results summarize a valuable collective of gene expression profiles characterizing the rose floral transition. The DEGs are candidates for functional analyses of genes affecting the floral transition in the rose, which is a precious resource that reveals the molecular mechanism of mediating floral transition in other perennial plants.

Zeeman Splitting of Ferromagnetic GaMnAs on InP Observed by Magnetic Circular Dichroism in Reflection Mode

NASA Astrophysics Data System (ADS)

Tanaka, H.; Bsatee, M.; Jadwisienczak, W. M.

2016-08-01

Systematic investigations of Ga1- x Mn x As grown on InP with different Mn concentrations have been conducted using magnetic circular dichroism (MCD) in reflection mode. The MCD spectrum of Ga0.97Mn0.03As/InP was decomposed into two dispersion curves originating from E 1 and E 1 + Δ1 optical transitions using the energy derivative of a Gaussian function. The Zeeman splitting energy E 1 at the L critical point (0.6 meV) of ferromagnetic Ga0.97Mn0.03As/InP was estimated using a rigid band shift model. Based on the relationship between E 1 and E 0 (Γ critical point) observed in Cd1- x Mn x Te dilute magnetic semiconductor (DMS), the Zeeman splitting energy E 1 (9.6 meV) of ferromagnetic Ga1- x Mn x As/InP was calculated. In addition, it was established that the peaks in the MCD spectra at L critical points shift toward the lower energy side as the Mn concentration is increased, and the observed shift saturates for Mn content of x = 0.001. Furthermore, the measured absorption spectra for Ga1- x Mn x As/InP did not show noticeable peak shifts with increasing Mn content. This suggests that the s, p- d exchange interaction induced in Ga1- x Mn x As/InP has localized nature due to the presence of a Mn rigid sphere of influence.

Development of an optically-pumped cesium standard at the Aerospace Corporation

NASA Technical Reports Server (NTRS)

Chan, Yat C.

1992-01-01

We have initiated a research program to study the performance of compact optically-pumped cesium (Cs) frequency standards, which have potential for future timekeeping applications in space. A Cs beam clock apparatus has been assembled. Basic functions of the frequency standard have been demonstrated. Clock signals are observed with optical pumping schemes using one or two lasers. With two laser pumping, we are able to selectively place up to 80 percent of the atomic population into one of the clock transition states. The observed pattern of clock signal indicates that the velocity distribution of the Cs atoms contributing to the microwave signal is beam-Maxwellian. Thus, in the optically-pumped Cs frequency standards, the entire Cs population in the atomic beam could be utilized to generate the clock signals. This is in contrast to the conventional Cs beam standards where only approx. 1 percent of the atoms in the beam are used. More efficient Cs consumption can lead to improved reliability and increased useful lifetime of the clock.

Magneto-optical spectrum and the effective excitonic Zeeman splitting energies of Mn and Co-doped CdSe nanowires

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

Xiong, Wen, E-mail: wenxiong@cqu.edu.cn; Chen, Wensuo

2013-12-21

The electronic structure of Mn and Co-doped CdSe nanowires are calculated based on the six-band k·p effective-mass theory. Through the calculation, it is found that the splitting energies of the degenerate hole states in Mn-doped CdSe nanowires are larger than that in Co-doped CdSe nanowires when the concentration of these two kinds of magnetic ions is the same. In order to analysis the magneto-optical spectrum of Mn and Co-doped CdSe nanowires, the four lowest electron states and the four highest hole states are sorted when the magnetic field is applied, and the 10 lowest optical transitions between the conduction subbandsmore » and the valence subbands at the Γ point in Mn and Co-doped CdSe nanowires are shown in the paper, it is found that the order of the optical transitions at the Γ point almost do not change although two different kinds of magnetic ions are doped in CdSe nanowires. Finally, the effective excitonic Zeeman splitting energies at the Γ point are found to increase almost linearly with the increase of the concentration of the magnetic ions and the magnetic field; meanwhile, the giant positive effective excitonic g factors in Mn and Co-doped CdSe nanowires are predicted based on our theoretical calculation.« less

Accurate determination of black-body radiation shift, magic and tune-out wavelengths for the 6S1/2 \\rightarrow 5D3/2 clock transition in Yb+

NASA Astrophysics Data System (ADS)

Roy, A.; De, S.; Arora, Bindiya; Sahoo, B. K.

2017-10-01

We present precise values of the dipole polarizabilities (α) of the ground [4{{{f}}}146{{s}}]{}2{{{S}}}1/2 and metastable [4{{{f}}}145{{d}}]{}2{{{D}}}3/2 states of Yb+, that are important in reducing systematics in the clock frequency of the [4{{{f}}}146{{s}}]{}2{{{S}}}1/2\\to [4{{{f}}}145{{d}}]{}2{{{D}}}3/2 transition. The static values of α for the ground and [4{{{f}}}145{{d}}]{}2{{{D}}}3/2 states are estimated to be 9.8(1)× {10}-40 {{{J}}{{m}}}2 {{{V}}}-2 and 17.6(5) × {10}-40 {{J}} {{{m}}}2 {{{V}}}-2, respectively, while the tensor contribution to the [4{{{f}}}145{{d}}]{}2{{{D}}}3/2 state as -12.3(3)× {10}-40 {{{J}}{{m}}}2 {{{V}}}-2 compared to the experimental value -13.6(22)× {10}-40 {{J}} {{{m}}}2 {{{V}}}-2. This corresponds to the differential scalar polarizability value of the above transition as -7.8(5) × {10}-40 {{{J}}{{m}}}2 {{{V}}}-2 in contrast to the available experimental value -6.9(1.4) × {10}-40 J m2 V-2 . This results in the black-body radiation shift of the clock transition as -0.44(3) Hz at the room temperature, which is large as compared to the previously estimated values. Using the dynamic α values, we report the tune-out and magic wavelengths that could be of interest to subdue systematics due to the Stark shifts and for constructing lattice optical clock using Yb+.

Fluorescence quenching and the "ring-mode" to "red-mode" transition in alkali inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Huang, M.; Bazurto, R.; Camparo, J.

2018-01-01

The ring-mode to red-mode transition in alkali metal inductively coupled plasmas (ICPs) (i.e., rf-discharge lamps) is perhaps the most important physical phenomenon affecting these devices as optical pumping light sources for atomic clocks and magnetometers. It sets the limit on useful ICP operating temperature, thereby setting a limit on ICP light output for atomic-clock/magnetometer signal generation, and it is a temperature region of ICP operation associated with discharge instability. Previous work has suggested that the mechanism driving the ring-mode to red-mode transition is associated with radiation trapping, but definitive experimental evidence validating that hypothesis has been lacking. Based on that hypothesis, one would predict that the introduction of an alkali-fluorescence quenching gas (i.e., N2) into the ICP would increase the ring-mode to red-mode transition temperature. Here, we test that prediction, finding direct evidence supporting the radiation-trapping hypothesis.

Spin bottleneck in resonant tunneling through double quantum dots with different Zeeman splittings.

PubMed

Huang, S M; Tokura, Y; Akimoto, H; Kono, K; Lin, J J; Tarucha, S; Ono, K

2010-04-02

We investigated the electron transport property of the InGaAs/GaAs double quantum dots, the electron g factors of which are different from each other. We found that in a magnetic field, the resonant tunneling is suppressed even if one of the Zeeman sublevels is aligned. This is because the other misaligned Zeeman sublevels limit the total current. A finite broadening of the misaligned sublevel partially relieves this bottleneck effect, and the maximum current is reached when interdot detuning is half the Zeeman energy difference.

Scrutinizing Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu 1ions for atomic clocks with uncertainties below the 10-19 level

NASA Astrophysics Data System (ADS)

Yu, Yan-mei; Sahoo, B. K.

2016-12-01

We investigate the transition between the fine structure levels of the ground state, 3 p 2P1 /2→3 p 2P3 /2 , of the highly charged Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu ions for frequency standards. To comprehend them as prospective atomic clocks, we determine their transition wavelengths, quality factors, and various plausible systematics during the measurements. Since most of these ions have nuclear spin I =3 /2 , uncertainties due to dominant quadrupole shifts can be evaded in the F =0 hyperfine level of the 3 p 2P3 /2 state. Other dominant systematics such as quadratic Stark and black-body radiation shifts have been evaluated precisely demonstrating the feasibility of achieving high accuracy, below 10-19 fractional uncertainty, atomic clocks using the above transitions. Moreover, relativistic sensitivity coefficients are determined to find out the aptness of these proposed clocks to investigate possible temporal variation of the fine structure constant. To carry out these analysis, a relativistic coupled-cluster method considering Dirac-Coulomb-Breit Hamiltonian along with lower-order quantum electrodynamics interactions is employed and many spectroscopic properties are evaluated. These properties are also of immense interest for astrophysical studies.

Synthetic clock states generated in a Bose-Einstein condensate via continuous dynamical decoupling

NASA Astrophysics Data System (ADS)

Lundblad, Nathan; Trypogeorgos, Dimitrios; Valdes-Curiel, Ana; Marshall, Erin; Spielman, Ian

2017-04-01

Radiofrequency- or microwave-dressed states have been used in NV center and ion-trap experiments to extend coherence times, shielding qubits from magnetic field noise through a process known as continuous dynamical decoupling. Such field-insensitive dressed states, as applied in the context of ultracold neutral atoms, have applications related to the creation of novel phases of spin-orbit-coupled quantum matter. We present observations of such a protected dressed-state system in a Bose-Einstein condensate, including measurements of the dependence of the protection on rf coupling strength, and estimates of residual field sensitivities.

VLSI Implementation of Stray Insensitive Switched Capacitor Composite Operational Amplifiers

DTIC Science & Technology

1993-12-01

ENDS SWITCH *Power Supplies VIN 3 0 SIN(0 0. 1 10OKHz) VCLK 8 0 PULSE(5 -5 O.Ous 2ns 2ns 0.O5us Ol1us) III X1 0 45 OPAMPI X2 5 67 OPAMPI X3 8 9 10 11...105 46F C13 305 105 68F C14 304 105 68F C15 300 105 120F C16 102 105 390F 116 C17 301 105 121F .ENDS CLOCK *Power Supplies VIN 3 0 SIN(O 0.1 400KHz

Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

NASA Astrophysics Data System (ADS)

Liu, Yi; Wang, Ziqiao; Zhang, Xuefeng; Liu, Chaofei; Liu, Yongjie; Zhou, Zhimou; Wang, Junfeng; Wang, Qingyan; Liu, Yanzhao; Xi, Chuanying; Tian, Mingliang; Liu, Haiwen; Feng, Ji; Xie, X. C.; Wang, Jian

2018-04-01

Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.

Experimental observation of carrier-envelope-phase effects by multicycle pulses

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

Jha, Pankaj K.; Scully, Marlan O.; Mechanical and Aerospace Engineering and the Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544

2011-03-15

We present an experimental and theoretical study of carrier-envelope-phase (CEP) effects on the population transfer between two bound atomic states interacting with pulses consisting of many cycles. Using intense radio-frequency pulse with Rabi frequency of the order of the atomic transition frequency, we investigate the influence of the CEP on the control of phase-dependent multiphoton transitions between the Zeeman sublevels of the ground state of {sup 87}Rb. Our scheme has no limitation on the duration of the pulses. Extending the CEP control to longer pulses creates interesting possibilities to generate pulses with accuracy that is better than the period ofmore » optical oscillations.« less

The spectroscopic observation of the CH radical in its a4Sigma(-) state

NASA Technical Reports Server (NTRS)

Nelis, Thomas; Brown, John M.; Evenson, Kenneth M.

1988-01-01

The first spectroscopic observation of CH in the a 4Sigma(0-) state are reported. The molecule was generated in a discharge-flow system in the reaction betweeen fluorine atoms and methane or between oxygen atoms and acetylene at a total pressure of about 1 Torr. Several resonances associated with the N = 1 - 0 transitions of 4Sigma(-) CH were observed at three separate laser wavelengths, while those for the N = 2 - 1 transition were observed at two wavelengths. Each observed Zeeman component consists of a well-split doublet arising from proton hyperfine structure. The reasons for assigning the observations to CH in its a 4Sigma(-) state are discussed.

Clock is not a component of Z-bands.

PubMed

Wang, Jushuo; Dube, Dipak K; White, Jennifer; Fan, Yingli; Sanger, Jean M; Sanger, Joseph W

2012-12-01

The process of Z-band assembly begins with the formation of small Z-bodies composed of a complex of proteins rich in alpha-actinin. As additional proteins are added to nascent myofibrils, Z-bodies are transformed into continuous bands that form coherent discs of interacting proteins at the boundaries of sarcomeres. The steps controlling the transition of Z-bodies to Z-bands are not known. The report that a circadian protein, Clock, was localized in the Z-bands of neonatal rat cardiomyocytes raised the question whether this transcription factor could be involved in Z-band assembly. We found that the anti-Clock antibody used in the reported study also stained the Z-bands and Z-bodies of mouse and avian cardiac and skeletal muscle cells. YFP constructs of Clock that were assembled, however, did not localize to the Z-bands of muscle cells. Controls of Clock's activity showed that cotransfection of muscle cells with pYFP-Clock and pCeFP-BMAL1 led to the expected nuclear localization of YFP-Clock with its binding partner CeFP-BMAL1. Neither CeFP-BMAL1 nor antibodies directed against BMAL1 localized to Z-bands. A bimolecular fluorescence complementation assay (VC-BMAL1 and VN-Clock) confirmed the absence of Clock and BMAL1 from Z-bands, and their nuclear colocalization. A second anti-Clock antibody stained nuclei, but not Z-bands, of cells cotransfected with Clock and BMAL1 plasmids. Western blots of reactions of muscle extracts and purified alpha-actinins with the two anti-Clock antibodies showed that the original antibody cross-reacted with alpha-actinin and the second did not. These results cannot confirm Clock as an active component of Z-bands. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.

Rotational strain in Weyl semimetals: A continuum approach

NASA Astrophysics Data System (ADS)

Arjona, Vicente; Vozmediano, María A. H.

2018-05-01

We use a symmetry approach to derive the coupling of lattice deformations to electronic excitations in three-dimensional Dirac and Weyl semimetals in the continuum low-energy model. We focus on the effects of rotational strain and show that it can drive transitions from Dirac to Weyl semimetals, gives rise to elastic gauge fields, tilts the cones, and generates pseudo-Zeeman couplings. It also can generate a deformation potential in volume-preserving deformations. The associated pseudoelectric field contributes to the chiral anomaly.

Lasers, Cold Atoms and Atomic Clocks: Realizing the Second Today

NASA Astrophysics Data System (ADS)

Calonico, Davide

2013-09-01

The time is the physical quantity that mankind could measure with the best accuracy, thanks to the properties of the atomic physics, as the present definition of time is based on atomic energy transitions. This short review gives some basic information on the heart of the measurement of time in the contemporary world, i.e. the atomic clocks, and some trends related.

Apparatus and method for performing two-frequency interferometry

DOEpatents

Johnston, Roger G.

1990-01-01

The present apparatus includes a two-frequency, Zeeman-effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The present apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor. The relative intensities of the heating beams along each arm of the interferometer can be easily adjusted by observing a zero phase difference with identical samples when this condition is obtained.

Apparatus and method for performing two-frequency interferometry

DOEpatents

Johnston, R.G.

1988-01-25

The present apparatus includes a two-frequency, Zeeman Effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The present apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor. The relative intensities of the heating beams along each arm of the interferometer can be easily adjusted by observing a zero phase difference with identical samples when this condition is obtained. 6 figs.

High-pressure crystal structures of an insensitive energetic crystal: 1,1-diamino-2,2-dinitroethene

DOE PAGES

Dreger, Zbigniew A.; Stash, Adam I.; Yu, Zhi -Gang; ...

2015-12-03

Understanding the insensitivity/stability of insensitive high explosive crystals requires detailed structural information at high pressures and high temperatures of interest. Synchrotron single crystal x-ray diffraction experiments were used to determine the high-pressure structures of 1,1-diamino-2,2-dinitroethene (FOX-7), a prototypical insensitive high explosive. The phase transition around 4.5 GPa was investigated and the structures were determined at 4.27 GPa (α’-phase) and 5.9 GPa (ε-phase). The α’-phase (monoclinic, P2 1/ n), structurally indistinguishable from the ambient α-phase, transforms to the new ε-phase (triclinic, P1). The most notable features of the ε-phase, compared to the α’-phase, are: formation of planar layers and flattening ofmore » molecules. Density functional theory (DFT-D2) calculations complemented the experimental results. Furthermore, the results presented here are important for understanding the molecular and crystalline attributes governing the high-pressure insensitivity/stability of insensitive high explosive crystals.« less

High-pressure crystal structures of an insensitive energetic crystal: 1,1-diamino-2,2-dinitroethene

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

Dreger, Zbigniew A.; Stash, Adam I.; Yu, Zhi -Gang

Understanding the insensitivity/stability of insensitive high explosive crystals requires detailed structural information at high pressures and high temperatures of interest. Synchrotron single crystal x-ray diffraction experiments were used to determine the high-pressure structures of 1,1-diamino-2,2-dinitroethene (FOX-7), a prototypical insensitive high explosive. The phase transition around 4.5 GPa was investigated and the structures were determined at 4.27 GPa (α’-phase) and 5.9 GPa (ε-phase). The α’-phase (monoclinic, P2 1/ n), structurally indistinguishable from the ambient α-phase, transforms to the new ε-phase (triclinic, P1). The most notable features of the ε-phase, compared to the α’-phase, are: formation of planar layers and flattening ofmore » molecules. Density functional theory (DFT-D2) calculations complemented the experimental results. Furthermore, the results presented here are important for understanding the molecular and crystalline attributes governing the high-pressure insensitivity/stability of insensitive high explosive crystals.« less

An Essay on Interactive Investigations of the Zeeman Effect in the Interstellar Medium

ERIC Educational Resources Information Center

Woolsey, Lauren

2015-01-01

The paper presents an interactive module created through the Wolfram Demonstrations Project that visualizes the Zeeman effect for the small magnetic field strengths present in the interstellar medium. The paper provides an overview of spectral lines and a few examples of strong and weak Zeeman splitting before discussing the module in depth.…

A novel architecture of recovered data comparison for high speed clock and data recovery

NASA Astrophysics Data System (ADS)

Gao, Susan; Li, Fei; Wang, Zhigong; Cui, Hongliang

2005-05-01

A clock and data recovery (CDR) circuit is one of the crucial blocks in high-speed serial link communication systems. The data received in these systems are asynchronous and noisy, requiring that a clock be extracted to allow synchronous operations. Furthermore, the data must be "retimed" so that the jitter accumulated during transmission is removed. This paper presents a novel architecture of CDR, which is very tolerant to long sequences of serial ones or zeros and also robust to occasional long absence of transitions. The design is based on the fact that a basic clock recovery having a clock recovery circuit (CRC) and a data decision circuit separately would generate a high jitter clock when the received non-return-to-zero (NRZ) data with long sequences of ones or zeros. To eliminate this drawback, the proposed architecture incorporates a data circuit decision circuit within the phase-locked loop (PLL) CRC. Other than this, a new phase detector (PD) is also proposed, which was easy to accomplish and robust at high speed. This PD is functional with a random input and automatically turns to disable during both the locked state and long absence of transitions. The voltage-controlled oscillator (VCO) is also designed delicately to suppress the jitter. Due to the high stability, the jitter is highly reduced when the loop is locked. The simulation results of such CDR working at 1.25Gb/s particularly for 1000BASE-X Gigabit Ethernet by using TSMC 0.25μm technology are presented to prove the feasibility of this architecture. One more CDR based on edge detection architecture is also built in the circuit for performance comparisons.

A quantum mechanical approach to establishing the magnetic field orientation from a maser Zeeman profile

NASA Astrophysics Data System (ADS)

Green, J. A.; Gray, M. D.; Robishaw, T.; Caswell, J. L.; McClure-Griffiths, N. M.

2014-06-01

Recent comparisons of magnetic field directions derived from maser Zeeman splitting with those derived from continuum source rotation measures have prompted new analysis of the propagation of the Zeeman split components, and the inferred field orientation. In order to do this, we first review differing electric field polarization conventions used in past studies. With these clearly and consistently defined, we then show that for a given Zeeman splitting spectrum, the magnetic field direction is fully determined and predictable on theoretical grounds: when a magnetic field is oriented away from the observer, the left-hand circular polarization is observed at higher frequency and the right-hand polarization at lower frequency. This is consistent with classical Lorentzian derivations. The consequent interpretation of recent measurements then raises the possibility of a reversal between the large-scale field (traced by rotation measures) and the small-scale field (traced by maser Zeeman splitting).

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

Stier, Andreas V.; McCreary, Kathleen M.; Jonker, Berend T.

In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS 2 and MoS 2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately –230 μeV T–1 (g-factor ≃–4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS 2,more » from which radii of ~1.53 and ~1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). Lastly, these results highlight the utility of high magnetic fields for understanding new two-dimensional materials.« less

Theoretical comparison and experimental test of the secular and nonperturbative approaches on the ESR lineshapes of randomly oriented, anisotropic systems undergoing internal motion

NASA Astrophysics Data System (ADS)

Benetis, N. P.; Sjöqvist, L.; Lund, A.; Maruani, J.

The nuclear Zeeman and the electronic nonsecular parts of the spin Hamiltonian complicate the ESR lineshape of exchanging anisotropic spin systems by introducing, at high field, "forbidden" transitions and, at low field, additional shift and splitting. We compare the nonperturbative with the secular approach for such systems. The exchange is treated within the Kaplan-Alexander limit and both A and g tensors are included, resulting in spectrum asymmetry, in contrast to previous separate treatments. The two approaches are then used to simulate the powder spectrum of OCH 2COO - and compare the results to experimental spectra of an irradiated powder of ZnAc. The powder X-band spectra simulations using the secular approach appear to be accurate. For both the low-field (20 to 200 G) and the high-field (Q-band) regions, however, the nonsecular part of the electronic term and the nuclear Zeeman term, respectively, cannot be neglected. On the other hand, the approximate approach is much faster and consequently more appropriate for treating large, multisite exchanging systems.

Effects of strong interactions in a half-metallic magnet: A determinant quantum Monte Carlo study

DOE PAGES

Jiang, M.; Pickett, W. E.; Scalettar, R. T.

2013-04-03

Understanding the effects of electron-electron interactions in half-metallic magnets (HMs), which have band structures with one gapped spin channel and one metallic channel, poses fundamental theoretical issues as well as having importance for their potential applications. Here we use determinant quantum Monte Carlo to study the impacts of an on-site Hubbard interaction U, finite temperature, and an external (Zeeman) magnetic field on a bilayer tight-binding model which is a half-metal in the absence of interactions, by calculating the spectral density, conductivity, spin polarization of carriers, and local magnetic properties. We quantify the effect of U on the degree of thermalmore » depolarization, and follow relative band shifts and monitor when significant gap states appear, each of which can degrade the HM character. For this model, Zeeman coupling induces, at fixed particle number, two successive transitions: compensated half-metal with spin-down band gap → metallic ferromagnet → saturated ferromagnetic insulator. However, over much of the more relevant parameter regime, the half-metallic properties are rather robust to U.« less

Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe2

NASA Astrophysics Data System (ADS)

Gustafsson, Martin V.; Yankowitz, Matthew; Forsythe, Carlos; Rhodes, Daniel; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Zhu, Xiaoyang; Dean, Cory R.

2018-05-01

Monolayers (MLs) of transition-metal dichalcogenides (TMDs) exhibit unusual electrical behaviour under magnetic fields due to their intrinsic spin-orbit coupling and lack of inversion symmetry1-15. Although recent experiments have also identified the critical role of carrier interactions within these materials11,15, a complete mapping of the ambipolar Landau level (LL) sequence has remained elusive. Here we use single-electron transistors (SETs)16,17 to perform LL spectroscopy in ML WSe2, and provide a comprehensive picture of the electronic structure of a ML TMD for both electrons and holes. We find that the LLs differ notably between the two bands, and follow a unique sequence in the valence band (VB) that is dominated by strong Zeeman effects. The Zeeman splitting in the VB is several times higher than the cyclotron energy, far exceeding the predictions of a single-particle model and, moreover, tunes significantly with doping15. This implies exceptionally strong many-body interactions, and suggests that ML WSe2 can serve as a host for new correlated-electron phenomena.

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.

Hyper-Ramsey spectroscopy with probe-laser-intensity fluctuations

NASA Astrophysics Data System (ADS)

Beloy, K.

2018-03-01

We examine the influence of probe-laser-intensity fluctuations on hyper-Ramsey spectroscopy. We assume, as is appropriate for relevant cases of interest, that the probe-laser intensity I determines both the Rabi frequency (∝√{I } ) and the frequency shift to the atomic transition (∝I ) during probe-laser interactions with the atom. The spectroscopic signal depends on these two quantities that covary with fluctuations in the probe-laser intensity. Introducing a simple model for the fluctuations, we find that the signature robustness of the hyper-Ramsey method can be compromised. Taking the Yb+ electric octupole clock transition as an example, we quantify the clock error under different levels of probe-laser-intensity fluctuations.

Improved Tracking of an Atomic-Clock Resonance Transition

NASA Technical Reports Server (NTRS)

Prestage, John D.; Chung, Sang K.; Tu, Meirong

2010-01-01

An improved method of making an electronic oscillator track the frequency of an atomic-clock resonance transition is based on fitting a theoretical nonlinear curve to measurements at three oscillator frequencies within the operational frequency band of the transition (in other words, at three points within the resonance peak). In the measurement process, the frequency of a microwave oscillator is repeatedly set at various offsets from the nominal resonance frequency, the oscillator signal is applied in a square pulse of the oscillator signal having a suitable duration (typically, of the order of a second), and, for each pulse at each frequency offset, fluorescence photons of the transition in question are counted. As described below, the counts are used to determine a new nominal resonance frequency. Thereafter, offsets are determined with respect to the new resonance frequency. The process as described thus far is repeated so as to repeatedly adjust the oscillator to track the most recent estimate of the nominal resonance frequency.

Parkes full polarization spectra of OH masers - II. Galactic longitudes 240° to 350°

NASA Astrophysics Data System (ADS)

Caswell, J. L.; Green, J. A.; Phillips, C. J.

2014-04-01

Full polarization measurements of 1665 and 1667 MHz OH masers at 261 sites of massive star formation have been made with the Parkes radio telescope. Here, we present the resulting spectra for 157 southern sources, complementing our previously published 104 northerly sources. For most sites, these are the first measurements of linear polarization, with good spectral resolution and complete velocity coverage. Our spectra exhibit the well-known predominance of highly circularly polarized features, interpreted as σ components of Zeeman patterns. Focusing on the generally weaker and rarer linear polarization, we found three examples of likely full Zeeman triplets (a linearly polarized π component, straddled in velocity by σ components), adding to the solitary example previously reported. We also identify 40 examples of likely isolated π components, contradicting past beliefs that π components might be extremely rare. These were recognized at 20 sites where a feature with high linear polarization on one transition is accompanied on the other transition by a matching feature, at the same velocity and also with significant linear polarization. Large velocity ranges are rare, but we find eight exceeding 25 km s-1, some of them indicating high-velocity blue-shifted outflows. Variability was investigated on time-scales of one year and over several decades. More than 20 sites (of 200) show high variability (intensity changes by factors of 4 or more) in some prominent features. Highly stable sites are extremely rare.

Tunnel transport and interlayer excitons in bilayer fractional quantum Hall systems

NASA Astrophysics Data System (ADS)

Zhang, Yuhe; Jain, J. K.; Eisenstein, J. P.

2017-05-01

In a bilayer system consisting of a composite-fermion (CF) Fermi sea in each layer, the tunnel current is exponentially suppressed at zero bias, followed by a strong peak at a finite-bias voltage Vmax. This behavior, which is qualitatively different from that observed for the electron Fermi sea, provides fundamental insight into the strongly correlated non-Fermi-liquid nature of the CF Fermi sea and, in particular, offers a window into the short-distance high-energy physics of this highly nontrivial state. We identify the exciton responsible for the peak current and provide a quantitative account of the value of Vmax. The excitonic attraction is shown to be quantitatively significant, and its variation accounts for the increase of Vmax with the application of an in-plane magnetic field. We also estimate the critical Zeeman energy where transition occurs from a fully spin-polarized composite-fermion Fermi sea to a partially spin-polarized one, carefully incorporating corrections due to finite width and Landau level mixing, and find it to be in satisfactory agreement with the Zeeman energy where a qualitative change has been observed for the onset bias voltage [J. P. Eisenstein et al., Phys. Rev. B 94, 125409 (2016), 10.1103/PhysRevB.94.125409]. For fractional quantum Hall states, we predict a substantial discontinuous jump in Vmax when the system undergoes a transition from a fully spin-polarized state to a spin singlet or a partially spin-polarized state.

The Physics and Diagnostic Potential of Ultraviolet Spectropolarimetry

NASA Astrophysics Data System (ADS)

Trujillo Bueno, Javier; Landi Degl'Innocenti, Egidio; Belluzzi, Luca

2017-09-01

The empirical investigation of the magnetic field in the outer solar atmosphere is a very important challenge in astrophysics. To this end, we need to identify, measure and interpret observable quantities sensitive to the magnetism of the upper chromosphere, transition region and corona. This paper provides an overview of the physics and diagnostic potential of spectropolarimetry in permitted spectral lines of the ultraviolet solar spectrum, such as the Mg ii h and k lines around 2800 Å, the hydrogen Lyman-α line at 1216 Å, and the Lyman-α line of He ii at 304 Å. The outer solar atmosphere is an optically pumped vapor and the linear polarization of such spectral lines is dominated by the atomic level polarization produced by the absorption and scattering of anisotropic radiation. Its modification by the action of the Hanle and Zeeman effects in the inhomogeneous and dynamic solar atmosphere needs to be carefully understood because it encodes the magnetic field information. The circular polarization induced by the Zeeman effect in some ultraviolet lines (e.g., Mg ii h & k) is also of diagnostic interest, especially for probing the outer solar atmosphere in plages and more active regions. The few (pioneering) observational attempts carried out so far to measure the ultraviolet spectral line polarization produced by optically pumped atoms in the upper chromosphere, transition region and corona are also discussed. We emphasize that ultraviolet spectropolarimetry is a key gateway to the outer atmosphere of the Sun and of other stars.

Transport anomalies of high-mobility Q-valley electrons in few-layer WS2 and MoS2

NASA Astrophysics Data System (ADS)

Wang, Ning

Atomically thin transition metal dichalcogenides (TMDCs) have opened new avenues for exploring physical property anomalies due to their large band gaps, strong spin-orbit couplings, and rich valley degrees of freedom. Although novel optical phenomena such as valley selective circular dichroism, opto-valley Hall effect, and valley Zeeman effect have been extensively studied in TMDCs, investigation of quantum transport properties has encountered a number of obstacles primarily due to the low carrier mobility and strong impurity scattering. Recently, we successfully fabricated ultrahigh-mobility few-layer TMDC field-effect transistors based on the boron nitride encapsulation method and observed a number of interesting transport properties, such as even-odd layer-dependent magnetotransport of Q-valley electrons in WS2 and MoS2 and unconventional quantum Hall transport of Γ-valley hole carriers in WSe2. In few-layer samples of these TMDCs, the conduction bands along the ΓK directions shift downward energetically in the presence of interlayer interactions, forming six Q-valleys related by three-fold rotational symmetry and time reversal symmetry. In even-layers the extra inversion symmetry requires all states to be Kramers degenerate, whereas in odd-layers the intrinsic inversion asymmetry dictates the Q-valleys to be spin-valley coupled. In this talk, I'll demonstrate the prominent Shubnikov-de Hass (SdH) oscillations and the observation of the onset of quantum Hall plateaus for the Q-valley electrons. Universally in the SdH oscillations, we observe a valley Zeeman effect in all odd-layer TMDC devices and a spin Zeeman effect in all even-layer TMDC devices. In addition, we observe a series of quantum Hall states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field in p-type few-layer TMDCs, indicating a large Zeeman energy associated with the carriers in the valence band at the Γ-valley. Financial supports from the Research Grants Council of Hong Kong (Project Nos. 16302215, HKU9/CRF/13G, 604112 and N-HKUST613/12) are hereby acknowledged.

Strong resetting of the mammalian clock by constant light followed by constant darkness

PubMed Central

Chen, Rongmin; Seo, Dong-oh; Bell, Elijah; von Gall, Charlotte; Lee, Choogon

2008-01-01

The mammalian molecular circadian clock in the suprachiasmatic nuclei (SCN) regulates locomotor activity rhythms as well as clocks in peripheral tissues (Reppert and Weaver, 2002; Ko and Takahashi, 2006). Constant light (LL) can induce behavioral and physiological arrhythmicity, by desynchronizing clock cells in the SCN (Ohta et al., 2005). We examined how the disordered clock cells resynchronize by probing the molecular clock and measuring behavior in mice transferred from LL to constant darkness (DD). The circadian locomotor activity rhythms disrupted in LL become robustly rhythmic again from the beginning of DD, and the starting phase of the rhythm in DD is specific, not random, suggesting that the desynchronized clock cells are quickly reset in an unconventional manner by the L:D transition. By measuring mPERIOD protein rhythms, we showed that the SCN and peripheral tissue clocks quickly become rhythmic again in phase with the behavioral rhythms. We propose that this resetting mechanism may be different from conventional phase shifting, which involves light-induction of Period genes (Albrecht et al., 1997; Shearman et al., 1997; Shigeyoshi et al., 1997). Using our functional insights, we could shift the circadian phase of locomotor activity rhythms by 12 hours using a 15-hour LL treatment: essentially producing phase reversal by a single light pulse, a feat that has not been reported previously in wild-type mice and that has potential clinical utility. PMID:19005049

Circadian factor BMAL1 in histaminergic neurons regulates sleep architecture.

PubMed

Yu, Xiao; Zecharia, Anna; Zhang, Zhe; Yang, Qianzi; Yustos, Raquel; Jager, Polona; Vyssotski, Alexei L; Maywood, Elizabeth S; Chesham, Johanna E; Ma, Ying; Brickley, Stephen G; Hastings, Michael H; Franks, Nicholas P; Wisden, William

2014-12-01

Circadian clocks allow anticipation of daily environmental changes. The suprachiasmatic nucleus (SCN) houses the master clock, but clocks are also widely expressed elsewhere in the body. Although some peripheral clocks have established roles, it is unclear what local brain clocks do. We tested the contribution of one putative local clock in mouse histaminergic neurons in the tuberomamillary nucleus to the regulation of the sleep-wake cycle. Histaminergic neurons are silent during sleep, and start firing after wake onset; the released histamine, made by the enzyme histidine decarboxylase (HDC), enhances wakefulness. We found that hdc gene expression varies with time of day. Selectively deleting the Bmal1 (also known as Arntl or Mop3) clock gene from histaminergic cells removes this variation, producing higher HDC expression and brain histamine levels during the day. The consequences include more fragmented sleep, prolonged wake at night, shallower sleep depth (lower nonrapid eye movement [NREM] δ power), increased NREM-to-REM transitions, hindered recovery sleep after sleep deprivation, and impaired memory. Removing BMAL1 from histaminergic neurons does not, however, affect circadian rhythms. We propose that for mammals with polyphasic/nonwake consolidating sleep, the local BMAL1-dependent clock directs appropriately timed declines and increases in histamine biosynthesis to produce an appropriate balance of wake and sleep within the overall daily cycle of rest and activity specified by the SCN. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

High-resolution laser spectroscopy and magnetic effect of the B{sup ~2}E{sup ′}←X{sup ~2}A{sub 2}{sup ′} transition of the {sup 15}N substituted nitrate radical

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

Tada, Kohei; Teramoto, Kanon; Ishiwata, Takashi

2015-03-21

Rotationally resolved high-resolution fluorescence excitation spectra of the 0–0 band of the B{sup ~2}E{sup ′}←X{sup ~2}A{sub 2}{sup ′} transition of the {sup 15}N substituted nitrate radical were observed for the first time, by crossing a jet-cooled molecular beam and a single-mode dye laser beam at right angles. Several thousand rotational lines were detected in the 15 080–15 103 cm{sup −1} region. We observed the Zeeman splitting of intense lines up to 360 G in order to obtain secure rotational assignment. Two, nine, and seven rotational line pairs with 0.0248 cm{sup −1} spacing were assigned to the transitions from the X{supmore » ~2}A{sub 2}{sup ′} (υ″ = 0, k″ = 0, N″ = 1, J″ = 0.5 and 1.5) to the {sup 2}E{sub 3/2}{sup ′} (J′ = 1.5), {sup 2}E{sub 1/2}{sup ′} (J′ = 0.5), and {sup 2}E{sub 1/2}{sup ′} (J′ = 1.5) levels, respectively, based on the ground state combination differences and the Zeeman splitting patterns. The observed spectrum was complicated due to the vibronic coupling between the bright B{sup ~2}E{sup ′} (υ = 0) state and surrounding dark vibronic states. Some series of rotational lines other than those from the X{sup ~2}A{sub 2}{sup ′} (J = 0.5 and 1.5) levels were also assigned by the ground state combination differences and the observed Zeeman splitting. The rotational branch structures were identified, and the molecular constants of the B{sup ~2}E{sub 1/2}{sup ′} (υ = 0) state were estimated by a deperturbed analysis to be T{sub 0} = 15 098.20(4) cm{sup −1}, B = 0.4282(7) cm{sup −1}, and D{sub J} = 4 × 10{sup −4} cm{sup −1}. In the observed region, both the {sup 2}E{sub 1/2}{sup ′} and {sup 2}E{sub 3/2}{sup ′} spin-orbit components were identified, and the spin-orbit interaction constant of the B{sup ~2}E{sup ′} (υ = 0) state was estimated to be −12 cm{sup −1} as the lower limit.« less

Magnetoreflection spectroscopy of monolayer transition-metal dichalcogenide semiconductors in pulsed magnetic fields

DOE PAGES

Stier, Andreas V.; McCreary, Kathleen M.; Jonker, Berend T.; ...

2016-05-13

The authors describe recent experimental efforts to perform polarization-resolved optical spectroscopy of monolayer transition-metal dichalcogenide semiconductors in very large pulsed magnetic fields to 65 T. The experimental setup and technical challenges are discussed in detail, and temperature-dependent magnetoreflection spectra from atomically thin tungsten disulphide are presented. The data clearly reveal not only the valley Zeeman effect in these two-dimensional semiconductors but also the small quadratic exciton diamagnetic shift from which the very small exciton size can be directly inferred. Lastly, the authors present model calculations that demonstrate how the measured diamagnetic shifts can be used to constrain estimates of themore » exciton binding energy in this new family of monolayer semiconductors.« less

Characterization of the hyperfine interaction of the excited D50 state of Eu3 +:Y2SiO5

NASA Astrophysics Data System (ADS)

Cruzeiro, Emmanuel Zambrini; Etesse, Jean; Tiranov, Alexey; Bourdel, Pierre-Antoine; Fröwis, Florian; Goldner, Philippe; Gisin, Nicolas; Afzelius, Mikael

2018-03-01

We characterize the europium (Eu3 +) hyperfine interaction of the excited state (D50) and determine its effective spin Hamiltonian parameters for the Zeeman and quadrupole tensors. An optical free induction decay method is used to measure all hyperfine splittings under a weak external magnetic field (up to 10 mT) for various field orientations. On the basis of the determined Hamiltonian, we discuss the possibility to predict optical transition probabilities between hyperfine levels for the F70⟷D50 transition. The obtained results provide necessary information to realize an optical quantum memory scheme which utilizes long spin coherence properties of 3 + 151Eu :Y2SiO5 material under external magnetic fields.

The effect of day-neutral mutations in barley and wheat on the interaction between photoperiod and vernalization.

PubMed

Turner, Adrian S; Faure, Sébastien; Zhang, Yang; Laurie, David A

2013-09-01

Vernalization-2 (Vrn-2) is the major flowering repressor in temperate cereals. It is only expressed under long days in wild-type plants. We used two day-neutral (photoperiod insensitive) mutations that allow rapid flowering in short or long days to investigate the day length control of Vrn-2. The barley (Hordeum vulgare) early maturity8 (eam8) mutation affects the barley ELF3 gene. eam8 mutants disrupt the circadian clock resulting in elevated expression of Ppd-H1 and the floral activator HvFT1 under short or long days. When eam8 was crossed into a genetic background with a vernalization requirement Vrn-2 was expressed under all photoperiods and the early flowering phenotype was partially repressed in unvernalized (UV) plants, likely due to competition between the constitutively active photoperiod pathway and the repressing effect of Vrn-2. We also investigated the wheat (Triticum aestivum) Ppd-D1a mutation. This differs from eam8 in causing elevated levels of Ppd-1 and TaFT1 expression without affecting the circadian clock. We used genotypes that differed in "short-day vernalization". Short days were effective in promoting flowering in individuals wild type at Ppd-D1, but not in individuals that carry the Ppd-D1a mutation. The latter showed Vrn-2 expression in short days. In summary, eam8 and Ppd-D1a mimic long days in terms of photoperiod response, causing Vrn-2 to become aberrantly expressed (in short days). As Ppd-D1a does not affect the circadian clock, this also shows that clock regulation of Vrn-2 operates indirectly through one or more downstream genes, one of which may be Ppd-1.

Phase locking and multiple oscillating attractors for the coupled mammalian clock and cell cycle

PubMed Central

Feillet, Céline; Krusche, Peter; Tamanini, Filippo; Janssens, Roel C.; Downey, Mike J.; Martin, Patrick; Teboul, Michèle; Saito, Shoko; Lévi, Francis A.; Bretschneider, Till; van der Horst, Gijsbertus T. J.; Delaunay, Franck; Rand, David A.

2014-01-01

Daily synchronous rhythms of cell division at the tissue or organism level are observed in many species and suggest that the circadian clock and cell cycle oscillators are coupled. For mammals, despite known mechanistic interactions, the effect of such coupling on clock and cell cycle progression, and hence its biological relevance, is not understood. In particular, we do not know how the temporal organization of cell division at the single-cell level produces this daily rhythm at the tissue level. Here we use multispectral imaging of single live cells, computational methods, and mathematical modeling to address this question in proliferating mouse fibroblasts. We show that in unsynchronized cells the cell cycle and circadian clock robustly phase lock each other in a 1:1 fashion so that in an expanding cell population the two oscillators oscillate in a synchronized way with a common frequency. Dexamethasone-induced synchronization reveals additional clock states. As well as the low-period phase-locked state there are distinct coexisting states with a significantly higher period clock. Cells transition to these states after dexamethasone synchronization. The temporal coordination of cell division by phase locking to the clock at a single-cell level has significant implications because disordered circadian function is increasingly being linked to the pathogenesis of many diseases, including cancer. PMID:24958884

Phase locking and multiple oscillating attractors for the coupled mammalian clock and cell cycle.

PubMed

Feillet, Céline; Krusche, Peter; Tamanini, Filippo; Janssens, Roel C; Downey, Mike J; Martin, Patrick; Teboul, Michèle; Saito, Shoko; Lévi, Francis A; Bretschneider, Till; van der Horst, Gijsbertus T J; Delaunay, Franck; Rand, David A

2014-07-08

Daily synchronous rhythms of cell division at the tissue or organism level are observed in many species and suggest that the circadian clock and cell cycle oscillators are coupled. For mammals, despite known mechanistic interactions, the effect of such coupling on clock and cell cycle progression, and hence its biological relevance, is not understood. In particular, we do not know how the temporal organization of cell division at the single-cell level produces this daily rhythm at the tissue level. Here we use multispectral imaging of single live cells, computational methods, and mathematical modeling to address this question in proliferating mouse fibroblasts. We show that in unsynchronized cells the cell cycle and circadian clock robustly phase lock each other in a 1:1 fashion so that in an expanding cell population the two oscillators oscillate in a synchronized way with a common frequency. Dexamethasone-induced synchronization reveals additional clock states. As well as the low-period phase-locked state there are distinct coexisting states with a significantly higher period clock. Cells transition to these states after dexamethasone synchronization. The temporal coordination of cell division by phase locking to the clock at a single-cell level has significant implications because disordered circadian function is increasingly being linked to the pathogenesis of many diseases, including cancer.

The Drosophila Receptor Protein Tyrosine Phosphatase LAR Is Required for Development of Circadian Pacemaker Neuron Processes That Support Rhythmic Activity in Constant Darkness But Not during Light/Dark Cycles

PubMed Central

Agrawal, Parul

2016-01-01

In Drosophila, a transcriptional feedback loop that is activated by CLOCK-CYCLE (CLK-CYC) complexes and repressed by PERIOD-TIMELESS (PER-TIM) complexes keeps circadian time. The timing of CLK-CYC activation and PER-TIM repression is regulated post-translationally, in part through rhythmic phosphorylation of CLK, PER, and TIM. Although kinases that control PER, TIM, and CLK levels, activity, and/or subcellular localization have been identified, less is known about phosphatases that control clock protein dephosphorylation. To identify clock-relevant phosphatases, clock-cell-specific RNAi knockdowns of Drosophila phosphatases were screened for altered activity rhythms. One phosphatase that was identified, the receptor protein tyrosine phosphatase leukocyte-antigen-related (LAR), abolished activity rhythms in constant darkness (DD) without disrupting the timekeeping mechanism in brain pacemaker neurons. However, expression of the neuropeptide pigment-dispersing factor (PDF), which mediates pacemaker neuron synchrony and output, is eliminated in the dorsal projections from small ventral lateral (sLNv) pacemaker neurons when Lar expression is knocked down during development, but not in adults. Loss of Lar function eliminates sLNv dorsal projections, but PDF expression persists in sLNv and large ventral lateral neuron cell bodies and their remaining projections. In contrast to the defects in lights-on and lights-off anticipatory activity seen in flies that lack PDF, Lar RNAi knockdown flies anticipate the lights-on and lights-off transition normally. Our results demonstrate that Lar is required for sLNv dorsal projection development and suggest that PDF expression in LNv cell bodies and their remaining projections mediate anticipation of the lights-on and lights-off transitions during a light/dark cycle. SIGNIFICANCE STATEMENT In animals, circadian clocks drive daily rhythms in physiology, metabolism, and behavior via transcriptional feedback loops. Because key circadian transcriptional activators and repressors are regulated by phosphorylation, we screened for phosphatases that alter activity rhythms when their expression was reduced. One such phosphatase, leukocyte-antigen-related (LAR), abolishes activity rhythms, but does not disrupt feedback loop function. Rather, Lar disrupts clock output by eliminating axonal processes from clock neurons that release pigment-dispersing factor (PDF) neuropeptide into the dorsal brain, but PDF expression persists in their cell bodies and remaining projections. In contrast to flies that lack PDF, flies that lack Lar anticipate lights-on and lights-off transitions normally, which suggests that the remaining PDF expression mediates activity during light/dark cycles. PMID:27030770

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

Chacon, Luis; Stanier, Adam John

Here, we demonstrate a scalable fully implicit algorithm for the two-field low-β extended MHD model. This reduced model describes plasma behavior in the presence of strong guide fields, and is of significant practical impact both in nature and in laboratory plasmas. The model displays strong hyperbolic behavior, as manifested by the presence of fast dispersive waves, which make a fully implicit treatment very challenging. In this study, we employ a Jacobian-free Newton–Krylov nonlinear solver, for which we propose a physics-based preconditioner that renders the linearized set of equations suitable for inversion with multigrid methods. As a result, the algorithm ismore » shown to scale both algorithmically (i.e., the iteration count is insensitive to grid refinement and timestep size) and in parallel in a weak-scaling sense, with the wall-clock time scaling weakly with the number of cores for up to 4096 cores. For a 4096 × 4096 mesh, we demonstrate a wall-clock-time speedup of ~6700 with respect to explicit algorithms. The model is validated linearly (against linear theory predictions) and nonlinearly (against fully kinetic simulations), demonstrating excellent agreement.« less

A simple second-order digital phase-locked loop.

NASA Technical Reports Server (NTRS)

Tegnelia, C. R.

1972-01-01

A simple second-order digital phase-locked loop has been designed for the Viking Orbiter 1975 command system. Excluding analog-to-digital conversion, implementation of the loop requires only an adder/subtractor, two registers, and a correctable counter with control logic. The loop considers only the polarity of phase error and corrects system clocks according to a filtered sequence of this polarity. The loop is insensitive to input gain variation, and therefore offers the advantage of stable performance over long life. Predictable performance is guaranteed by extreme reliability of acquisition, yet in the steady state the loop produces only a slight degradation with respect to analog loop performance.

Temperature dependence of spectral linewidth of InAs/InP quantum dot distributed feedback lasers

NASA Astrophysics Data System (ADS)

Duan, J.; Huang, H.; Schires, K.; Poole, P. J.; Wang, C.; Grillot, F.

2018-02-01

In this paper, we investigate the temperature dependence of spectral linewidth of InAs/InP quantum dot distributed feedback lasers. In comparison with their quantum well counterparts, results show that quantum dot lasers have spectral linewidths rather insensitive to the temperature with minimum values below 200 kHz in the range of 283K to 303K. The experimental results are also well confirmed by numerical simulations. Overall, this work shows that quantum dot lasers are excellent candidates for various applications such as coherent communication systems, high-resolution spectroscopy, high purity photonic microwave generation and on-chip atomic clocks.

Ultrahigh-resolution spectroscopy with atomic or molecular dark resonances: Exact steady-state line shapes and asymptotic profiles in the adiabatic pulsed regime

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

Zanon-Willette, Thomas; Clercq, Emeric de; Arimondo, Ennio

2011-12-15

Exact and asymptotic line shape expressions are derived from the semiclassical density matrix representation describing a set of closed three-level {Lambda} atomic or molecular states including decoherences, relaxation rates, and light shifts. An accurate analysis of the exact steady-state dark-resonance profile describing the Autler-Townes doublet, the electromagnetically induced transparency or coherent population trapping resonance, and the Fano-Feshbach line shape leads to the linewidth expression of the two-photon Raman transition and frequency shifts associated to the clock transition. From an adiabatic analysis of the dynamical optical Bloch equations in the weak field limit, a pumping time required to efficiently trap amore » large number of atoms into a coherent superposition of long-lived states is established. For a highly asymmetrical configuration with different decay channels, a strong two-photon resonance based on a lower states population inversion is established when the driving continuous-wave laser fields are greatly unbalanced. When time separated resonant two-photon pulses are applied in the adiabatic pulsed regime for atomic or molecular clock engineering, where the first pulse is long enough to reach a coherent steady-state preparation and the second pulse is very short to avoid repumping into a new dark state, dark-resonance fringes mixing continuous-wave line shape properties and coherent Ramsey oscillations are created. Those fringes allow interrogation schemes bypassing the power broadening effect. Frequency shifts affecting the central clock fringe computed from asymptotic profiles and related to the Raman decoherence process exhibit nonlinear shapes with the three-level observable used for quantum measurement. We point out that different observables experience different shifts on the lower-state clock transition.« less

Topological Exciton Bands in Moire Heterojunctions.

DOE PAGES

Wu, Fengcheng; Lovorn, Timothy; MacDonald, A. H.

2017-04-05

Moire patterns are common in Van der Waals heterostructures and can be used to apply periodic potentials to elementary excitations. Here, we show that the optical absorption spectrum of transition metal dichalcogenide bilayers is profoundly altered by long period moire patterns that introduce twist-angle dependent satellite excitonic peaks. Topological exciton bands with non-zero Chern numbers that support chiral excitonic edge states can be engineered by combining three ingredients: i) the valley Berry phase induced by electron-hole exchange interactions, ii) the moire potential, and iii) the valley Zeeman field.

Modular high speed counter employing edge-triggered code

DOEpatents

Vanstraelen, Guy F.

1993-06-29

A high speed modular counter (100) utilizing a novel counting method in which the first bit changes with the frequency of the driving clock, and changes in the higher order bits are initiated one clock pulse after a "0" to "1" transition of the next lower order bit. This allows all carries to be known one clock period in advance of a bit change. The present counter is modular and utilizes two types of standard counter cells. A first counter cell determines the zero bit. The second counter cell determines any other higher order bit. Additional second counter cells are added to the counter to accommodate any count length without affecting speed.

Modular high speed counter employing edge-triggered code

DOEpatents

Vanstraelen, G.F.

1993-06-29

A high speed modular counter (100) utilizing a novel counting method in which the first bit changes with the frequency of the driving clock, and changes in the higher order bits are initiated one clock pulse after a 0'' to 1'' transition of the next lower order bit. This allows all carries to be known one clock period in advance of a bit change. The present counter is modular and utilizes two types of standard counter cells. A first counter cell determines the zero bit. The second counter cell determines any other higher order bit. Additional second counter cells are added to the counter to accommodate any count length without affecting speed.

Laboratory detection of the C3N an C4H free radicals

NASA Technical Reports Server (NTRS)

Gottlieb, C. A.; Gottlieb, E. W.; Thaddeus, P.; Kawamura, H.

1983-01-01

The millimeter-wave spectra of the linear carbon chain free radicals C3N and C4H, first identified in IRC + 10216 and hitherto observed only in a few astronomical sources, have been detected with a Zeeman-modulated spectrometer in laboratory glow discharges through low pressure flowing mixtures of N2 + HC3N and He + HCCH, respectively. Four successive rotational transitions between 168 and 198 GHz have been measured for C3N, and five rotational transitions between 143 and 200 GHz for C4H; each is a well-resolved spin doublet owing to the unpaired electron present in both species. Precise values for the rotational, centrifugal distortion, and spin doubling constants have been obtained, which, with hyperfine constants derived from observations of the lower rotational transitions in the astronomical source TMC 1, allow all the rotational transitions of C3N and C4H at frequencies less than 300 GHz to be calculated to an absolute accuracy exceeding 1 ppm.

Photoinduced topological phase transition and spin polarization in a two-dimensional topological insulator

NASA Astrophysics Data System (ADS)

Chen, M. N.; Su, W.; Deng, M. X.; Ruan, Jiawei; Luo, W.; Shao, D. X.; Sheng, L.; Xing, D. Y.

2016-11-01

A great deal of attention has been paid to the topological phases engineered by photonics over the past few years. Here, we propose a topological quantum phase transition to a quantum anomalous Hall (QAH) phase induced by off-resonant circularly polarized light in a two-dimensional system that is initially in a quantum spin Hall phase or a trivial insulator phase. This provides an alternative method to realize the QAH effect, other than magnetic doping. The circularly polarized light effectively creates a Zeeman exchange field and a renormalized Dirac mass, which are tunable by varying the intensity of the light and drive the quantum phase transition. Both the transverse and longitudinal Hall conductivities are studied, and the former is consistent with the topological phase transition when the Fermi level lies in the band gap. A highly controllable spin-polarized longitudinal electrical current can be generated when the Fermi level is in the conduction band, which may be useful for designing topological spintronics.

A high-performance Hg(+) trapped ion frequency standard

NASA Technical Reports Server (NTRS)

Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.

1992-01-01

A high-performance frequency standard based on (199)Hg(+) ions confined in a hybrid radio frequency (RF)/dc linear ion trap is demonstrated. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. A 160-mHz-wide atomic resonance line for the 40.5-GHz clock transition is used to steer the output of a 5-mHz crystal oscillator to obtain a stability of 2 x 10(exp -15) for 24,000-second averaging times. Measurements with a 37-mHz line width for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is better than 1 x 10(exp -15) at 10,000-second averaging times.

Trapped ultracold molecular ions: candidates for an optical molecular clock for a fundamental physics mission in space

NASA Astrophysics Data System (ADS)

Roth, B.; Koelemeij, J.; Daerr, H.; Ernsting, I.; Jorgensen, S.; Okhapkin, M.; Wicht, A.; Nevsky, A.; Schiller, S.

2017-11-01

Narrow ro-vibrational transitions in ultracold molecules are excellent candidates for frequency references in the near-IR to visible spectral domain and interesting systems for fundamental tests of physics, in particular for a satellite test of the gravitational redshift of clocks. We have performed laser spectroscopy of several ro-vibrational overtone transitions υ = 0 → υ = 4 in HD+ ions at around 1.4 μm. 1+1 REMPD was used as a detection method, followed by measurement of the number of remaining molecules. The molecular ions were stored in a linear radiofrequency trap and cooled to millikelvin temperatures, by sympathetic cooling using laser-cooled Be+ ions simultaneously stored in the same trap.

Clock recovery PLL with gated PFD for NRZ ON-OFF Modulated Signals in a retinal implant system.

PubMed

Brendler, Christian; Aryan, Naser Pour; Rieger, Viola; Rothermel, Albrecht

2013-01-01

A Clock Recovery Phase Locked Loop with Gated Phase Frequency Detector (GPLL) for NRZ ON-OFF Modulated Signals with low data transmission rates for an inductively powered subretinal implant system is presented. Low data transmission rate leads to a long absence of inductive powering in the system when zeros are transmitted. Consequently there is no possibility to extract any clock in these pauses, thus the digital circuitry can not work any more. Compared to a commonly used PLL for clock extraction, no certain amount of data transitions is needed. This is achieved by having two operating modes. In one mode the GPLL tracks the HF input signal. In the other, the GPLL is an adjustable oscillator oscillating at the last used frequency. The proposed GPLL is fabricated and measured using a 350 nm High Voltage CMOS technology.

Strategies for synchronisation in an evolving telecommunications network

NASA Astrophysics Data System (ADS)

Avery, Rob

1992-06-01

The achievement of precise synchronization in the telecommunications environment is addressed. Transmitting the timing from node to node has been the inherent problem for all digital networks. Traditional network equipment used to transfer synchronization, such as digital switching ststems, adds impairments to the once traceable signal. As the synchronization signals are passed from node to node, they lose stability by passing through intervening clocks. Timing would be an integrated part of all new network and service deployments. New transmission methods, such as the Synchronous Digital Hierarchy (SDH), survivable network topologies and the issues that arise from them, necessitate a review of current network synchronization strategies. Challenges that face the network are itemized. A demonstration of why localized Primary Reference Clocks (PRC) in key nodes and the Synchronization Supply Unit (SSU) clock architecture of transit and local node clocks is a technically and economically viable solution to the issues facing network planners today is given.

Quantum synchronization and the no-photon laser

NASA Astrophysics Data System (ADS)

Holland, Murray

2014-03-01

This talk will present a new approach to lasers that is based on the quantum synchronization of many atoms. Such lasers are predicted to produce light of unprecedented spectral purity and coherence, some two orders of magnitude better than any system available today. The idea is based on superradiant emission, where an ensemble of atoms with an extremely narrow atomic transition can phase-lock and form a macroscopic dipole that radiates light collectively. This is quite unlike a typical laser where atoms essentially act independently. The resulting light source is expected to have a spectral linewidth of just a few millihertz and could lead to more accurate and stable atomic clocks. Atomic clocks based on optical transitions have improved tremendously in recent years, giving clocks that tick 1015 times per second, and can have a fractional stability exceeding one part in 1016. This new sharper light source aims to push the frontier even further, so that fundamental tests of physics, such as the time variation of constants and tests of gravity, might even be possible. We acknowledge support from NSF and the DARPA QuASAR program.

Extra-hypothalamic brain clocks in songbirds: Photoperiodic state dependent clock gene oscillations in night-migratory blackheaded buntings, Emberiza melanocephala.

PubMed

Singh, Devraj; Kumar, Vinod

2017-04-01

The avian circadian pacemaker system is comprised of independent clocks in the retina, pineal and hypothalamus, as shown by daily and circadian oscillations of core clock genes (Per2, Cry1, Bmal1 and Clock) in several birds including migratory blackheaded buntings (Emberiza melanocephala). This study investigated the extra-hypothalamic brain circadian clocks in blackheaded buntings, and measured Per2, Cry1, Cry2, Bmal1 and Clock mRNA expressions at 4h intervals over 24h beginning 1h after light-on in the left and right telencephalon, optic tectum and cerebellum, the brain regions involved in several physiological and cognitive functions. Because of seasonal alterations in the circadian clock dependent brain functions, we measured daily clock gene oscillations in buntings photoperiod-induced with the non-migratory state under short days (SDnM), and the pre-migratory (LDpM), migratory (LDM) and post-migratory (refractory, LDR) states under long days. Daily Per2 oscillations were not altered with changes in the photoperiodic states, except for about 2-3h phase difference in the optic tectum between the SDnM and LDpM states. However, there were about 3-5h differences in the phase and 2 to 4 fold change in the amplitude of daily Bmal1 and Cry1 mRNA oscillations between the photoperiod-induced states. Further, Cry2 and Clock genes lacked a significant oscillation, except in Cb (Cry2) and TeO and Rt (Clock) under LDR state. Overall, these results show the presence of circadian clocks in extra-hypothalamic brain regions of blackheaded buntings, and suggest tissue-dependent alterations in the waveforms of mRNA oscillations with transitions in the photoperiod-induced seasonal states in a long-day species. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of non-local thermodynamic equilibrium and Zeeman effects on magnetic equilibrium reconstruction using spectral motional Stark effect diagnostic

NASA Astrophysics Data System (ADS)

Reimer, R.; Marchuk, O.; Geiger, B.; Mc Carthy, P. J.; Dunne, M.; Hobirk, J.; Wolf, R.; ASDEX Upgrade Team

2017-08-01

The Motional Stark Effect (MSE) diagnostic is a well established technique to infer the local internal magnetic field in fusion plasmas. In this paper, the existing forward model which describes the MSE data is extended by the Zeeman effect, fine-structure, and relativistic corrections in the interpretation of the MSE spectra for different experimental conditions at the tokamak ASDEX Upgrade. The contribution of the non-Local Thermodynamic Equilibrium (non-LTE) populations among the magnetic sub-levels and the Zeeman effect on the derived plasma parameters is different. The obtained pitch angle is changed by 3 ° … 4 ° and by 0 . 5 ° … 1 ° including the non-LTE and the Zeeman effects into the standard statistical MSE model. The total correction is about 4°. Moreover, the variation of the magnetic field strength is significantly changed by 2.2% due to the Zeeman effect only. While the data on the derived pitch angle still could not be tested against the other diagnostics, the results from an equilibrium reconstruction solver confirm the obtained values for magnetic field strength.

Chaotic behaviour of Zeeman machines at introductory course of mechanics

NASA Astrophysics Data System (ADS)

Nagy, Péter; Tasnádi, Péter

2016-05-01

Investigation of chaotic motions and cooperative systems offers a magnificent opportunity to involve modern physics into the basic course of mechanics taught to engineering students. In the present paper it will be demonstrated that Zeeman Machine can be a versatile and motivating tool for students to get introductory knowledge about chaotic motion via interactive simulations. It works in a relatively simple way and its properties can be understood very easily. Since the machine can be built easily and the simulation of its movement is also simple the experimental investigation and the theoretical description can be connected intuitively. Although Zeeman Machine is known mainly for its quasi-static and catastrophic behaviour, its dynamic properties are also of interest with its typical chaotic features. By means of a periodically driven Zeeman Machine a wide range of chaotic properties of the simple systems can be demonstrated such as bifurcation diagrams, chaotic attractors, transient chaos and so on. The main goal of this paper is the presentation of an interactive learning material for teaching the basic features of the chaotic systems through the investigation of the Zeeman Machine.

Influence of the nuclear Zeeman effect on mode locking in pulsed semiconductor quantum dots

NASA Astrophysics Data System (ADS)

Beugeling, Wouter; Uhrig, Götz S.; Anders, Frithjof B.

2017-09-01

The coherence of the electron spin in a semiconductor quantum dot is strongly enhanced by mode locking through nuclear focusing, where the synchronization of the electron spin to periodic pulsing is slowly transferred to the nuclear spins of the semiconductor material, mediated by the hyperfine interaction between these. The external magnetic field that drives the Larmor oscillations of the electron spin also subjects the nuclear spins to a Zeeman-like coupling, albeit a much weaker one. For typical magnetic fields used in experiments, the energy scale of the nuclear Zeeman effect is comparable to that of the hyperfine interaction, so that it is not negligible. In this work, we analyze the influence of the nuclear Zeeman effect on mode locking quantitatively. Within a perturbative framework, we calculate the Overhauser-field distribution after a prolonged period of pulsing. We find that the nuclear Zeeman effect can exchange resonant and nonresonant frequencies. We distinguish between models with a single type and with multiple types of nuclei. For the latter case, the positions of the resonances depend on the individual g factors, rather than on the average value.

The NIST 27 Al+ quantum-logic clock

NASA Astrophysics Data System (ADS)

Leibrandt, David; Brewer, Samuel; Chen, Jwo-Sy; Hume, David; Hankin, Aaron; Huang, Yao; Chou, Chin-Wen; Rosenband, Till; Wineland, David

2016-05-01

Optical atomic clocks based on quantum-logic spectroscopy of the 1 S0 <--> 3 P0 transition in 27 Al+ have reached a systematic fractional frequency uncertainty of 8 . 0 ×10-18 , enabling table-top tests of fundamental physics as well as measurements of gravitational potential differences. Currently, the largest limitations to the accuracy are second order time dilation shifts due to the driven motion (i.e., micromotion) and thermal motion of the trapped ions. In order to suppress these shifts, we have designed and built new ion traps based on gold-plated, laser-machined diamond wafers with differential RF drive, and we have operated one of our clocks with the ions laser cooled to near the six mode motional ground state. We present a characterization of the time dilation shifts in the new traps with uncertainties near 1 ×10-18 . Furthermore, we describe a new protocol for clock comparison measurements based on synchronous probing of the two clocks using phase-locked local oscillators, which allows for probe times longer than the laser coherence time and avoids the Dick effect. This work is supported by ARO, DARPA, and ONR.

An experimental study on the effects of blade row interactions on aerodynamic loss mechanisms in a multistage compressor

NASA Astrophysics Data System (ADS)

Smith, Natalie Rochelle

While the gas turbine engine has existed for nearly 80 years, much of the complex aerodynamics which governs compressor performance is still not well understood. The unsteady flow field consists of periodic blade row interactions from the wakes and potential fields of each blade and vane. Vane clocking is the relative circumferential indexing of adjacent vane rows with the same vane count, and it is one method to change blade row interactions. Though the potential of performance benefits with vane clocking is known, the driving flow physics have yet to be identified. This research examines the effects of blade row interactions on embedded stator total pressure loss and boundary layer transition in the Purdue 3-stage axial compressor. The inlet guide vane, Stator 1, and Stator 2 all have 44 vanes which enable vane clocking of the embedded stage, while the rotors have different blade counts producing amplitude modulation of the unsteady interactions. A detailed investigation of corrected conditions is presented to establish repeatable, compressor performance year-round in a facility utilizing ambient inlet conditions. Without proper humidity accounting of compressor corrected conditions and an understanding of the potential for inlet temperature changes to affect clearances due to thermal growth, measurements of small performance changes in detailed research studies could be indiscernible. The methodology and implementation of a powder-paint flow visualization technique along with the illuminated flow physics are presented in detail. This method assists in understanding the loss development in the compressor by highlighting stator corner separations and endwall flow patterns. Effects of loading condition, rotor tip clearance height, and stator wake and rotor tip leakage interactions are shown with this technique. Vane clocking effects on compressor performance were quantified for nine loading conditions and six clocking configurations - the largest vane clocking dataset in the open literature. These data show that vane clocking effects are small at low loading conditions, including peak efficiency operation, but become stronger as loading increases, and then eventually lessen at near stall operation. Additionally, stator wake profiles and flow visualization reveal that total pressure loss changes are due to a corner separation modulation between clocking configurations. To further address these clocking trends, high-frequency response data were acquired at the Stator 2 inlet and along the Stator 2 surface. The unsteadiness at the Stator 2 inlet was quantified with detailed radial traverses for the different clocking configurations. These data show the effects of interactions between the Stator 1 wake and Rotor 2 tip leakage flow, which result in significantly different inlet flow conditions for Stator 2. The high unsteadiness and blockage region formed by the rotor tip leakage flow changes in size and shape between clocking configurations. Finally, measurements of the Stator 2 surface flows were acquired to investigate the vane clocking effects on unsteady surface pressures and boundary layer transition. These data reveal that Stator 2 performance is influenced by blade row interactions including rotor-rotor interactions, stator wake-rotor tip leakage flow interactions, and vane clocking.

Alternative Splicing of Barley Clock Genes in Response to Low Temperature

PubMed Central

Calixto, Cristiane P. G.; Simpson, Craig G.; Waugh, Robbie; Brown, John W. S.

2016-01-01

Alternative splicing (AS) is a regulated mechanism that generates multiple transcripts from individual genes. It is widespread in eukaryotic genomes and provides an effective way to control gene expression. At low temperatures, AS regulates Arabidopsis clock genes through dynamic changes in the levels of productive mRNAs. We examined AS in barley clock genes to assess whether temperature-dependent AS responses also occur in a monocotyledonous crop species. We identify changes in AS of various barley core clock genes including the barley orthologues of Arabidopsis AtLHY and AtPRR7 which showed the most pronounced AS changes in response to low temperature. The AS events modulate the levels of functional and translatable mRNAs, and potentially protein levels, upon transition to cold. There is some conservation of AS events and/or splicing behaviour of clock genes between Arabidopsis and barley. In addition, novel temperature-dependent AS of the core clock gene HvPPD-H1 (a major determinant of photoperiod response and AtPRR7 orthologue) is conserved in monocots. HvPPD-H1 showed a rapid, temperature-sensitive isoform switch which resulted in changes in abundance of AS variants encoding different protein isoforms. This novel layer of low temperature control of clock gene expression, observed in two very different species, will help our understanding of plant adaptation to different environments and ultimately offer a new range of targets for plant improvement. PMID:27959947

Analysis of the Zeeman effect on D α spectra on the EAST tokamak

NASA Astrophysics Data System (ADS)

Gao, Wei; Huang, Juan; Wu, Chengrui; Xu, Zong; Hou, Yumei; Jin, Zhao; Chen, Yingjie; Zhang, Pengfei; Zhang, Ling; Wu, Zhenwei; EAST Team

2017-04-01

Based on the passive spectroscopy, the {{{D}}}α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis (OSMA) system in EAST tokamak. The Zeeman splitting of the {{{D}}}α spectral lines has been observed. A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and +/- σ components of the {{{D}}}α atomic spectra to acquire the information of the local plasma. The spectral line shape was investigated according to emission spectra from different regions (e.g., low-field side and high-field side) along the viewing chords. Each polarization component was fitted and classified into three energy categories (the cold, warm, and hot components) based on different atomic production processes, in consistent with the transition energy distribution by calculating the gradient of the {{{D}}}α spectral profile. The emission position, magnetic field intensity, and flow velocity of a deuterium atom were also discussed in the context. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275231 and 11575249) and the National Magnetic Confinement Fusion Energy Research Program of China (Grant No. 2015GB110005).

Measurement of a heavy-hole hyperfine interaction in InGaAs quantum dots using resonance fluorescence.

PubMed

Fallahi, P; Yilmaz, S T; Imamoğlu, A

2010-12-17

We measure the strength and the sign of hyperfine interaction of a heavy hole with nuclear spins in single self-assembled quantum dots. Our experiments utilize the locking of a quantum dot resonance to an incident laser frequency to generate nuclear spin polarization. By monitoring the resulting Overhauser shift of optical transitions that are split either by electron or exciton Zeeman energy with respect to the locked transition using resonance fluorescence, we find that the ratio of the heavy-hole and electron hyperfine interactions is -0.09 ± 0.02 in three quantum dots. Since hyperfine interactions constitute the principal decoherence source for spin qubits, we expect our results to be important for efforts aimed at using heavy-hole spins in quantum information processing.

Coherent Spectroscopy of Ultra-Cold Mercury for the UV to VUV

DTIC Science & Technology

2015-11-20

clock. During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin...During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin. This...able  to  slowly  scan  the   UV   laser  system  to  locate  the  clock  transition   (using  the  standard  technique

Mass defect effects in atomic clocks

NASA Astrophysics Data System (ADS)

Yudin, Valeriy; Taichenachev, Alexey

2018-03-01

We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (the gravitational shift and motion-induced shifts such as quadratic Doppler and micromotion shifts) can be interpreted as consequences of the mass defect in quantum atomic physics, i.e. without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions.

Broad-gain (Δλ/λ0

PubMed

Fujita, Kazuue; Furuta, Shinichi; Dougakiuchi, Tatsuo; Sugiyama, Atsushi; Edamura, Tadataka; Yamanishi, Masamichi

2011-01-31

Broad-gain operation of λ~8.7 μm quantum cascade lasers based on dual-upper-state to multiple-lower-state transition design is reported. The devices exhibit surprisingly wide (~500 cm(-1)) electroluminescence spectra which are very insensitive to voltage and temperature changes above room temperature. With recourse to the temperature-insensitivity of electroluminescence spectra, the lasers demonstrate an extremely-weak temperature-dependence of laser performances: T0-value of 510 K, associated with a room temperature threshold current density of 2.6 kA/cm2. In addition, despite such wide gain spectra, room temperature, continuous wave operation of the laser with buried hetero structure is achieved.

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.

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling.

PubMed

Lent, Craig S; Liu, Mo; Lu, Yuhui

2006-08-28

We examine power dissipation in different clocking schemes for molecular quantum-dot cellular automata (QCA) circuits. 'Landauer clocking' involves the adiabatic transition of a molecular cell from the null state to an active state carrying data. Cell layout creates devices which allow data in cells to interact and thereby perform useful computation. We perform direct solutions of the equation of motion for the system in contact with the thermal environment and see that Landauer's Principle applies: one must dissipate an energy of at least k(B)T per bit only when the information is erased. The ideas of Bennett can be applied to keep copies of the bit information by echoing inputs to outputs, thus embedding any logically irreversible circuit in a logically reversible circuit, at the cost of added circuit complexity. A promising alternative which we term 'Bennett clocking' requires only altering the timing of the clocking signals so that bit information is simply held in place by the clock until a computational block is complete, then erased in the reverse order of computation. This approach results in ultralow power dissipation without additional circuit complexity. These results offer a concrete example in which to consider recent claims regarding the fundamental limits of binary logic scaling.

Bennett clocking of quantum-dot cellular automata and the limits to binary logic scaling

NASA Astrophysics Data System (ADS)

Lent, Craig S.; Liu, Mo; Lu, Yuhui

2006-08-01

We examine power dissipation in different clocking schemes for molecular quantum-dot cellular automata (QCA) circuits. 'Landauer clocking' involves the adiabatic transition of a molecular cell from the null state to an active state carrying data. Cell layout creates devices which allow data in cells to interact and thereby perform useful computation. We perform direct solutions of the equation of motion for the system in contact with the thermal environment and see that Landauer's Principle applies: one must dissipate an energy of at least kBT per bit only when the information is erased. The ideas of Bennett can be applied to keep copies of the bit information by echoing inputs to outputs, thus embedding any logically irreversible circuit in a logically reversible circuit, at the cost of added circuit complexity. A promising alternative which we term 'Bennett clocking' requires only altering the timing of the clocking signals so that bit information is simply held in place by the clock until a computational block is complete, then erased in the reverse order of computation. This approach results in ultralow power dissipation without additional circuit complexity. These results offer a concrete example in which to consider recent claims regarding the fundamental limits of binary logic scaling.

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.

Algorithmic-Reducibility = Renormalization-Group Fixed-Points; ``Noise''-Induced Phase-Transitions (NITs) to Accelerate Algorithmics (``NIT-Picking'') Replacing CRUTCHES!!!: Gauss Modular/Clock-Arithmetic Congruences = Signal X Noise PRODUCTS..

NASA Astrophysics Data System (ADS)

Siegel, J.; Siegel, Edward Carl-Ludwig

2011-03-01

Cook-Levin computational-"complexity"(C-C) algorithmic-equivalence reduction-theorem reducibility equivalence to renormalization-(semi)-group phase-transitions critical-phenomena statistical-physics universality-classes fixed-points, is exploited with Gauss modular/clock-arithmetic/model congruences = signal X noise PRODUCT reinterpretation. Siegel-Baez FUZZYICS=CATEGORYICS(SON of ``TRIZ''): Category-Semantics(C-S) tabular list-format truth-table matrix analytics predicts and implements "noise"-induced phase-transitions (NITs) to accelerate versus to decelerate Harel [Algorithmics(1987)]-Sipser[Intro. Theory Computation(1997) algorithmic C-C: "NIT-picking" to optimize optimization-problems optimally(OOPO). Versus iso-"noise" power-spectrum quantitative-only amplitude/magnitude-only variation stochastic-resonance, this "NIT-picking" is "noise" power-spectrum QUALitative-type variation via quantitative critical-exponents variation. Computer-"science" algorithmic C-C models: Turing-machine, finite-state-models/automata, are identified as early-days once-workable but NOW ONLY LIMITING CRUTCHES IMPEDING latter-days new-insights!!!

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.

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.

The Ticking of the Social Clock: Adults' Beliefs about the Timing of Transition Events.

ERIC Educational Resources Information Center

Peterson, Candida C.

1996-01-01

Two studies regarding beliefs about descriptive and prescriptive age norms for adults in developmental transitions were examined in a sample of 214 Australian university students ages 17 to 50. Discusses research methodology. The probable consequences for self-esteem, mental health, and life planning are discussed in the context of the research…

Breit-Rabi Zeeman states of atomic hydrogen

NASA Astrophysics Data System (ADS)

Dickson, R. S.; Weil, J. A.

1991-02-01

The magnetic field dependence of the isotropic nonrelativistic one-electron atom with nuclear spin-1/2, in its electronic ground state, is reviewed. Attention is called to the little-known fact that a level crossing exists (at field B˜17 T for 1H) between the two members of the upper spin (MS=1/2) doublet. Anisotropy of such a hydrogenic atom, due to the presence of a suitable external electric field (for instance, 1H trapped in crystalline SiO2) causes anticrossing of these levels and causes previously forbidden magnetic-dipole transitions to attain appreciable intensity in that B region.

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

NASA Astrophysics Data System (ADS)

Pietsch, Torsten; Egle, Stefan; Keller, Martin; Fridtjof-Pernau, Hans; Strigl, Florian; Scheer, Elke

2016-09-01

We experimentally investigate the effect of resonant microwave absorption on the magneto-conductance of tunable Co/Pd point contacts. At the interface a non-equilibrium spin accumulation is created via microwave absorption and can be probed via point contact spectroscopy. We interpret the results as a signature of direct spin-flip excitations in Zeeman-split spin-subbands within the Pd normal metal part of the junction. The inverse effect, which is associated with the emission of a microwave photon in a ferromagnet/normal metal point contact, can also be detected via its unique signature in transport spectroscopy.

Towards the mass production of slow, trappable molecules

NASA Astrophysics Data System (ADS)

McCarron, Daniel J.

2018-05-01

The Fast Track Communication by Petzold et al (2018 New J. Phys. 20 042001) demonstrates the first Zeeman slowing scheme for species with type-II optical cycling transitions. This new approach is directly applicable to those 2Σ molecules that have recently been captured and cooled in molecular magneto-optical traps (MOTs) and has the potential to efficiently and continuously load these traps for the first time. This advance could produce molecular MOTs with populations comparable to their atomic counterparts and realize an ideal platform for a wide range of studies using large, dense samples of ultracold molecules.

Atomic Clocks with Suppressed Blackbody Radiation Shift

NASA Astrophysics Data System (ADS)

Yudin, V. I.; Taichenachev, A. V.; Okhapkin, M. V.; Bagayev, S. N.; Tamm, Chr.; Peik, E.; Huntemann, N.; Mehlstäubler, T. E.; Riehle, F.

2011-07-01

We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν1 and ν2) which are exposed to the same thermal environment, there exists a “synthetic” frequency νsyn ∝ (ν1-ɛ12ν2) largely immune to the blackbody radiation shift. For example, in the case of Yb+171 it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10-18 in a broad interval near room temperature (300±15K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν1 and ν2, where the frequency νsyn is generated as one of the components of the comb spectrum.

A highly miniaturized vacuum package for a trapped ion atomic clock

DOE PAGES

Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; ...

2016-05-12

We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm 3 in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, the packagemore » was sealed with a copper pinch-off and was then pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of 171Yb +. The fractional frequency stability of the clock was measured to be 2 × 10 -11 / τ 1/2.« less

The REVEILLE Clock Genes Inhibit Growth of Juvenile and Adult Plants by Control of Cell Size1[OPEN

PubMed Central

Gray, Jennifer A.; Chu, Dalena Nhu

2017-01-01

The circadian clock is a complex regulatory network that enhances plant growth and fitness in a constantly changing environment. In Arabidopsis (Arabidopsis thaliana), the clock is composed of numerous regulatory feedback loops in which REVEILLE8 (RVE8) and its homologs RVE4 and RVE6 act in a partially redundant manner to promote clock pace. Here, we report that the remaining members of the RVE8 clade, RVE3 and RVE5, play only minor roles in the regulation of clock function. However, we find that RVE8 clade proteins have unexpected functions in the modulation of light input to the clock and the control of plant growth at multiple stages of development. In seedlings, these proteins repress hypocotyl elongation in a daylength- and sucrose-dependent manner. Strikingly, adult rve4 6 8 and rve3 4 5 6 8 mutants are much larger than wild-type plants, with both increased leaf area and biomass. This size phenotype is associated with a faster growth rate and larger cell size and is not simply due to a delay in the transition to flowering. Gene expression and epistasis analysis reveal that the growth phenotypes of rve mutants are due to the misregulation of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 expression. Our results show that even small changes in PIF gene expression caused by the perturbation of clock gene function can have large effects on the growth of adult plants. PMID:28254761

Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications

NASA Astrophysics Data System (ADS)

Affolderbach, C.; Moreno, W.; Ivanov, A. E.; Debogovic, T.; Pellaton, M.; Skrivervik, A. K.; de Rijk, E.; Mileti, G.

2018-03-01

Additive manufacturing (AM) of passive microwave components is of high interest for the cost-effective and rapid prototyping or manufacture of devices with complex geometries. Here, we present an experimental study on the properties of recently demonstrated microwave resonator cavities manufactured by AM, in view of their applications to high-performance compact atomic clocks. The microwave cavities employ a loop-gap geometry using six electrodes. The critical electrode structures were manufactured monolithically using two different approaches: Stereolithography (SLA) of a polymer followed by metal coating and Selective Laser Melting (SLM) of aluminum. The tested microwave cavities show the desired TE011-like resonant mode at the Rb clock frequency of ≈6.835 GHz, with a microwave magnetic field highly parallel to the quantization axis across the vapor cell. When operated in an atomic clock setup, the measured atomic Rabi oscillations are comparable to those observed for conventionally manufactured cavities and indicate a good uniformity of the field amplitude across the vapor cell. Employing a time-domain Ramsey scheme on one of the SLA cavities, high-contrast (34%) Ramsey fringes are observed for the Rb clock transition, along with a narrow (166 Hz linewidth) central fringe. The measured clock stability of 2.2 × 10-13 τ-1/2 up to the integration time of 30 s is comparable to the current state-of-the-art stabilities of compact vapor-cell clocks based on conventional microwave cavities and thus demonstrates the feasibility of the approach.

Long-range effect of a Zeeman field on the electric current through the helical metal-superconductor interface in an Andreev interferometer

NASA Astrophysics Data System (ADS)

Mal'shukov, A. G.

2018-02-01

It is shown that the spin-orbit and Zeeman interactions result in phase shifts of Andreev-reflected holes propagating at the surface of a topological insulator, or in Rashba spin-orbit-coupled two-dimensional normal metals, which are in contact with an s -wave superconductor. Due to interference of holes reflected through different paths of the Andreev interferometer the electric current through external contacts varies depending on the strength and direction of the Zeeman field. It also depends on mutual orientations of Zeeman fields in different shoulders of the interferometer. Such a nonlocal effect is a result of the long-range coherency caused by the superconducting proximity effect. This current has been calculated within the semiclassical theory for Green's functions in the diffusive regime, by assuming a strong disorder due to elastic scattering of electrons.

A scalable, fully implicit algorithm for the reduced two-field low-β extended MHD model

DOE PAGES

Chacon, Luis; Stanier, Adam John

2016-12-01

Here, we demonstrate a scalable fully implicit algorithm for the two-field low-β extended MHD model. This reduced model describes plasma behavior in the presence of strong guide fields, and is of significant practical impact both in nature and in laboratory plasmas. The model displays strong hyperbolic behavior, as manifested by the presence of fast dispersive waves, which make a fully implicit treatment very challenging. In this study, we employ a Jacobian-free Newton–Krylov nonlinear solver, for which we propose a physics-based preconditioner that renders the linearized set of equations suitable for inversion with multigrid methods. As a result, the algorithm ismore » shown to scale both algorithmically (i.e., the iteration count is insensitive to grid refinement and timestep size) and in parallel in a weak-scaling sense, with the wall-clock time scaling weakly with the number of cores for up to 4096 cores. For a 4096 × 4096 mesh, we demonstrate a wall-clock-time speedup of ~6700 with respect to explicit algorithms. The model is validated linearly (against linear theory predictions) and nonlinearly (against fully kinetic simulations), demonstrating excellent agreement.« less

Microfabricated ion frequency standard

DOEpatents

Schwindt, Peter; Biedermann, Grant; Blain, Matthew G.; Stick, Daniel L.; Serkland, Darwin K.; Olsson, III, Roy H.

2010-12-28

A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

Doppler-Free Spectroscopy of the {sup 1}S{sub 0}-{sup 3}P{sub 0} Optical Clock Transition in Laser-Cooled Fermionic Isotopes of Neutral Mercury

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

Petersen, M.; Chicireanu, R.; Dawkins, S. T.

2008-10-31

We report direct laser spectroscopy of the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition at 265.6 nm in fermionic isotopes of neutral mercury in a magneto-optical trap. Measurements of the frequency against the LNE-SYRTE primary reference using an optical frequency comb yield 1 128 575 290 808.4{+-}5.6 kHz in {sup 199}Hg and 1 128 569 561 139.6{+-}5.3 kHz in {sup 201}Hg. The uncertainty, allowed by the observation of the Doppler-free recoil doublet, is 4 orders of magnitude lower than previous indirect determinations. Mercury is a promising candidate for future optical lattice clocks due to its low sensitivity to blackbody radiation.

Buffer Gas Experiments in Mercury (Hg+) Ion Clock

NASA Technical Reports Server (NTRS)

Chung, Sang K.; Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

2004-01-01

We describe the results of the frequency shifts measured from various buffer gases that might be used as a buffer gas to increase the loading efficiency and cooling of ions trapped in a small mercury ion clock. The small mass, volume and power requirement of space clock precludes the use of turbo pumps. Hence, a hermetically sealed vacuum system, incorporating a suitable getter material with a fixed amount of inert buffer gas may be a practical alternative to the groundbased system. The collision shifts of 40,507,347.996xx Hz clock transition for helium, neon and argon buffer gases were measured in the ambient earth magnetic field. In addition to the above non-getterable inert gases we also measured the frequency shifts due to getterable, molecular hydrogen and nitrogen gases which may be used as buffer gases when incorporated with a miniature ion pump. We also examined the frequency shift due to the low methane gas partial pressure in a fixed higher pressure neon buffer gas environment. Methane gas interacted with mercury ions in a peculiar way as to preserve the ion number but to relax the population difference in the two hyperfine clock states and thereby reducing the clock resonance signal. The same population relaxation was also observed for other molecular buffer gases (N H,) but at much reduced rate.

Exact solutions for a type of electron pairing model with spin-orbit interactions and Zeeman coupling.

PubMed

Liu, Jia; Han, Qiang; Shao, L B; Wang, Z D

2011-07-08

A type of electron pairing model with spin-orbit interactions or Zeeman coupling is solved exactly in the framework of the Richardson ansatz. Based on the exact solutions for the case with spin-orbit interactions, it is shown rigorously that the pairing symmetry is of the p + ip wave and the ground state possesses time-reversal symmetry, regardless of the strength of the pairing interaction. Intriguingly, how Majorana fermions can emerge in the system is also elaborated. Exact results are illustrated for two systems, respectively, with spin-orbit interactions and Zeeman coupling.

Magneto-optical rotation in cavity QED with Zeeman coherence

NASA Astrophysics Data System (ADS)

Sun, Hui; Jia, Xiaohua; Fan, Shuangli; Zhang, Hongjun; Guo, Hong

2018-06-01

We investigate theoretically the magneto-optical rotation in cavity QED system with atomic Zeeman coherence, which is established via coherent population trapping. Owing to Zeeman coherence, the ultranarrow transmission spectrum less than 1 MHz with gain can be achieved with a flat-top Faraday rotation angle. By controlling the parameters appropriately, the input probe components within the flat-top regime rotate with almost the same angle, and transmit through the cavity perpendicularly to the other components outside the flat-top regime. The concepts discussed here provide an important tool for perfect ultranarrow Faraday optical filter and quantum information processing.

Variable thickness double-refracting plate

DOEpatents

Hadeishi, Tetsuo

1976-01-01

This invention provides an A.C., cyclic, current-controlled, phase retardation plate that uses a magnetic clamp to produce stress birefringence. It was developed for an Isotope-Zeeman Atomic Absorption Spectrometer that uses polarization modulation to effect automatic background correction in atomic absorption trace-element measurements. To this end, the phase retardation plate of the invention is a variable thickness, photoelastic, double-refracting plate that is alternately stressed and released by the magnetic clamp selectively to modulate specific components selected from the group consisting of circularly and plane polarized Zeeman components that are produced in a dc magnetic field so that they correspond respectively to Zeeman reference and transmission-probe absorption components. The polarization modulation changes the phase of these polarized Zeeman components, designated as .sigma. reference and .pi. absorption components, so that every half cycle the components change from a transmission mode to a mode in which the .pi. component is blocked and the .sigma. components are transmitted. Thus, the Zeeman absorption component, which corresponds in amplitude to the amount of the trace element to be measured in a sample, is alternately transmitted and blocked by a linear polarizer, while the circularly polarized reference components are continuously transmitted thereby. The result is a sinusoidally varying output light amplitude whose average corresponds to the amount of the trace element present in the sample.

Suppressing Loss of Ions in an Atomic Clock

NASA Technical Reports Server (NTRS)

Prestage, John; Chung, Sang

2010-01-01

An improvement has been made in the design of a compact, highly stable mercury- ion clock to suppress a loss of ions as they are transferred between the quadrupole and higher multipole ion traps. Such clocks are being developed for use aboard spacecraft for navigation and planetary radio science. The modification is also applicable to ion clocks operating on Earth: indeed, the success of the modification has been demonstrated in construction and operation of a terrestrial breadboard prototype of the compact, highly stable mercury-ion clock. Selected aspects of the breadboard prototype at different stages of development were described in previous NASA Tech Briefs articles. The following background information is reviewed from previous articles: In this clock as in some prior ion clocks, mercury ions are shuttled between two ion traps, one a 16- pole linear radio-frequency trap, while the other is a quadrupole radio-frequency trap. In the quadrupole trap, ions are tightly confined and optical state selection from a 202Hg lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions are interrogated by use of a microwave beam at approximately 40.507 GHz. The trapping of ions effectively eliminates the frequency pulling that would otherwise be caused by collisions between clock atoms and the wall of a gas cell. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave-resonance process, so that each of these processes can be optimized independently of the other. This is similar to the operation of an atomic beam clock, except that with ions the beam can be halted and reversed as ions are shuttled back and forth between the two traps. When the two traps are driven at the same radio frequency, the strength of confinement can be reduced near the junction between the two traps, depending upon the relative phase of the RF voltage used to operate each of the two traps, and can cause loss of ions during each transit between the traps and thereby cause loss of the 40.507-GHz ion-clock resonance signal. The essence of the modification is to drive the two traps at different frequencies typically between 1.5 and 2 MHz for the quadrupole trap and a frequency a few hundred kHz higher for the 16- pole trap. A frequency difference of a few hundred kHz ensures that the ion motion caused by the trapping electric fields is small relative to the diameter of the traps. Unlike in the case in which both traps are driven at the same frequency, the trapping electric fields near the junction are not zero at all times; instead, the regions of low electric field near the junction open and close at the difference frequency. An additional benefit of making the 16-pole trap operate at higher frequency is that the strength or depth of the multipole trap can be increased independent of the quadrupole ion trap.

Velocity-tunable slow beams of cold O2 in a single spin-rovibronic state with full angular-momentum orientation by multistage Zeeman deceleration

NASA Astrophysics Data System (ADS)

Wiederkehr, A. W.; Schmutz, H.; Motsch, M.; Merkt, F.

2012-08-01

Cold samples of oxygen molecules in supersonic beams have been decelerated from initial velocities of 390 and 450 m s-1 to final velocities in the range between 150 and 280 m s-1 using a 90-stage Zeeman decelerator. (2 + 1) resonance-enhanced-multiphoton-ionization (REMPI) spectra of the 3sσ g 3Π g (C) ? two-photon transition of O2 have been recorded to characterize the state selectivity of the deceleration process. The decelerated molecular sample was found to consist exclusively of molecules in the J ‧‧ = 2 spin-rotational component of the X ? ground state of O2. Measurements of the REMPI spectra using linearly polarized laser radiation with polarization vector parallel to the decelerator axis, and thus to the magnetic-field vector of the deceleration solenoids, further showed that only the ? magnetic sublevel of the N‧‧ = 1, J ‧‧ = 2 spin-rotational level is populated in the decelerated sample, which therefore is characterized by a fully oriented total-angular-momentum vector. By maintaining a weak quantization magnetic field beyond the decelerator, the polarization of the sample could be maintained over the 5 cm distance separating the last deceleration solenoid and the detection region.

Fluorescence branching ratios and magnetic tuning of the visible spectrum of SrOH

NASA Astrophysics Data System (ADS)

Nguyen, Duc-Trung; Steimle, Timothy C.; Kozyryev, Ivan; Huang, Meng; McCoy, Anne B.

2018-05-01

The magnetic tuning of the low rotational levels in the X ˜ 2Σ+ (0,0,0), A ˜ 2Πr (0,0,0), and B ˜ 2Σ+ (0,0,0) electronic states of strontium hydroxide, SrOH, have been experimentally investigated using high resolution optical field-free and Zeeman spectroscopy of a cold molecular beam sample. The observed Zeeman shifts and splittings are successfully modeled using a traditional effective Hamiltonian approach to account for the interaction between the A ˜ 2Πr and B ˜ 2Σ+ states. The determined magnetic g-factors for the X ˜ 2Σ+ , A ˜ 2Πr , and B ˜ 2Σ+ states are compared to those predicted by perturbation theory. The dispersed fluorescence resulting from laser excitation of rotationally resolved branch features of the 000 B ˜ 2Σ+ ← X ˜ 2Σ+ , 000 A ˜ 2Π3/2 ← X ˜ 2Σ+ and 000 A ˜ 2Π1/2 ← X ˜ 2Σ+ transitions have been recorded and analyzed. The measured fluorescence branching ratios are compared with Franck-Condon calculations. The required bending motion wave functions are derived using a discrete variable representation (DVR) method. Implications for laser slowing and magneto-optical trapping experiments for SrOH are described.

Spin Exchange Optical Pumping of 129Xe for the Neutron Electron Dipole Moment Experiment at TRIUMF

NASA Astrophysics Data System (ADS)

Miller, Eric; Hayamizu, Tomohiro; Wienands, Joshua; Altiere, Emily; Jones, David; Madison, Kirk; Momose, Takamasa; Lang, Michael; Bidinosti, Chris; Martin, Jeffery

2016-09-01

Spin polarized noble gases have been a field of study for several decades and are of particular interest with respect to magnetic sensing. Using the Spin Exchange Optical Pumping technique, one can use the angular momentum of circularly polarized NIR photons to spin polarize Rb atoms, which then collide with Xe to polarize the ground state Zeeman sublevels of Xe many orders of magnitude above typical thermal Boltzmann distributions. The resulting polarized gas, with its magnetic dipole moment, is a useful probe of magnetic fields. We plan to use two spin polarized species, 129Xe and 199Hg, as dual co-magnetometers for the neutron EDM experiment at TRIUMF. They will be used to correct the neutron precession frequency for drifts due to magnetic field instability and geometric phase effects. For 129Xe, we aim to probe the populations of the ground state Zeeman sublevels using UV two-photon transitions. The respective populations depend on how much polarization we can produce using the SEOP technique. We will present technical details of our apparatus including results from a parameter space search, investigating how mode of preparation (batch or continuous flow), temperature, flow rate, and laser power affect 129Xe polarization as measured by low field NMR.

The REVEILLE Clock Genes Inhibit Growth of Juvenile and Adult Plants by Control of Cell Size.

PubMed

Gray, Jennifer A; Shalit-Kaneh, Akiva; Chu, Dalena Nhu; Hsu, Polly Yingshan; Harmer, Stacey L

2017-04-01

The circadian clock is a complex regulatory network that enhances plant growth and fitness in a constantly changing environment. In Arabidopsis ( Arabidopsis thaliana ), the clock is composed of numerous regulatory feedback loops in which REVEILLE8 ( RVE8 ) and its homologs RVE4 and RVE6 act in a partially redundant manner to promote clock pace. Here, we report that the remaining members of the RVE8 clade, RVE3 and RVE5 , play only minor roles in the regulation of clock function. However, we find that RVE8 clade proteins have unexpected functions in the modulation of light input to the clock and the control of plant growth at multiple stages of development. In seedlings, these proteins repress hypocotyl elongation in a daylength- and sucrose-dependent manner. Strikingly, adult rve4 6 8 and rve3 4 5 6 8 mutants are much larger than wild-type plants, with both increased leaf area and biomass. This size phenotype is associated with a faster growth rate and larger cell size and is not simply due to a delay in the transition to flowering. Gene expression and epistasis analysis reveal that the growth phenotypes of rve mutants are due to the misregulation of PHYTOCHROME INTERACTING FACTOR4 ( PIF4 ) and PIF5 expression. Our results show that even small changes in PIF gene expression caused by the perturbation of clock gene function can have large effects on the growth of adult plants. © 2017 American Society of Plant Biologists. All Rights Reserved.

Fibrocartilage in various regions of the human glenoid labrum. An immunohistochemical study on human cadavers.

PubMed

Ockert, Ben; Braunstein, Volker; Sprecher, Christoph M; Shinohara, Yasushi; Milz, Stefan

2012-06-01

The nature and the distribution of fibrocartilage at the human glenoid labrum are unclear, and a better understanding may help to restore its function in open and arthroscopic Bankart repair. Aim of this study was to describe the fibrocartilage extent within the labrum at clinically relevant sites of the glenoid in order to relate the molecular composition of the labrum to its mechanical environment. Twelve fresh frozen human cadaveric shoulders (mean age 38 years) were obtained, and sections perpendicular to the glenoid rim at the 12, 2, 3, 4, 6 and 9 o' clock position were labelled with antibodies against collagen I and II, aggrecan and link protein. A fibrocartilaginous transition zone with a characteristic collagen fibre orientation was found in 81% of cases, evenly distributed (83-92%) around the glenoid rim. The percentage of labrum cross-sectional area comprised of fibrocartilage averaged 28% and ranged from 26% at 12 o'clock on the glenoid clock face to 30% at 3 o'clock. The highest amount of fibrocartilage (82%) was found in the region neighbouring the hyaline articular cartilage. In the region beyond the bony edge of the glenoid, fibrocartilage cross-sectional area did not exceed 12-17%. Fibrocartilage is present at all examined positions around the glenoid rim and constitutes up to 1/3 of the cross-sectional area of the labrum. In turn, the percentage of fibrocartilage in different regions of its cross-section varies considerably. The findings suggest that the penetration of fibrocartilaginous tissue may be reduced by avoiding the highly fibrocartilage transition zone during restoration of labral detachment.

Frequency measurement of the 2S(1/2)-2D(3/2) electric quadrupole transition in a single 171Yb+ ion.

PubMed

Webster, Stephen; Godun, Rachel; King, Steven; Huang, Guilong; Walton, Barney; Tsatourian, Veronika; Margolis, Helen; Lea, Stephen; Gill, Patrick

2010-03-01

We report on precision laser spectroscopy of the 2S(1/2)(F = 0)-2D(3/2) (F = 2, m(F) = 0) clock transition in a single ion of 171Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 +/- 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 x 10(-14).

Critique of a Hughes shuttle Ku-band data sampler/bit synchronizer

NASA Technical Reports Server (NTRS)

Holmes, J. K.

1980-01-01

An alternative bit synchronizer proposed for shuttle was analyzed in a noise-free environment by considering the basic operation of the loop via timing diagrams and by linearizing the bit synchronizer as an equivalent, continuous, phased-lock loop (PLL). The loop is composed of a high-frequency phase-frequency detector which is capable of detecting both phase and frequency errors and is used to track the clock, and a bit transition detector which attempts to track the transitions of the data bits. It was determined that the basic approach was a good design which, with proper implementation of the accumulator, up/down counter and logic should provide accurate mid-bit sampling with symmetric bits. However, when bit asymmetry occurs, the bit synchronizer can lock up with a large timing error, yet be quasi-stable (timing will not change unless the clock and bit sequence drift). This will result in incorrectly detecting some bits.

Magnetic field-induced modification of selection rules for Rb D 2 line monitored by selective reflection from a vapor nanocell

NASA Astrophysics Data System (ADS)

Klinger, Emmanuel; Sargsyan, Armen; Tonoyan, Ara; Hakhumyan, Grant; Papoyan, Aram; Leroy, Claude; Sarkisyan, David

2017-08-01

Magnetic field-induced giant modification of the probabilities of five transitions of 5S1 / 2,Fg = 2 → 5P3 / 2,Fe = 4 of 85Rb and three transitions of 5S1 / 2,Fg = 1 → 5P3 / 2,Fe = 3 of 87Rb forbidden by selection rules for zero magnetic field has been observed experimentally and described theoretically for the first time. For the case of excitation with circularly-polarized (σ+) laser radiation, the probability of Fg = 2,mF = - 2 → Fe = 4,mF = - 1 transition becomes the largest among the seventeen transitions of 85Rb Fg = 2 → Fe = 1,2,3,4 group, and the probability of Fg = 1, mF = - 1 → Fe = 3,mF = 0 transition becomes the largest among the nine transitions of 87Rb Fg = 1 → Fe = 0,1,2,3 group, in a wide range of magnetic field 200-1000 G. Complete frequency separation of individual Zeeman components was obtained by implementation of derivative selective reflection technique with a 300 nm-thick nanocell filled with Rb, allowing formation of narrow optical resonances. Possible applications are addressed. The theoretical model is well consistent with the experimental results.

Cyclin-dependent kinase inhibitor p20 controls circadian cell-cycle timing

PubMed Central

Laranjeiro, Ricardo; Tamai, T. Katherine; Peyric, Elodie; Krusche, Peter; Ott, Sascha; Whitmore, David

2013-01-01

Specific stages of the cell cycle are often restricted to particular times of day because of regulation by the circadian clock. In zebrafish, both mitosis (M phase) and DNA synthesis (S phase) are clock-controlled in cell lines and during embryo development. Despite the ubiquitousness of this phenomenon, relatively little is known about the underlying mechanism linking the clock to the cell cycle. In this study, we describe an evolutionarily conserved cell-cycle regulator, cyclin-dependent kinase inhibitor 1d (20 kDa protein, p20), which along with p21, is a strongly rhythmic gene and directly clock-controlled. Both p20 and p21 regulate the G1/S transition of the cell cycle. However, their expression patterns differ, with p20 predominant in developing brain and peak expression occurring 6 h earlier than p21. p20 expression is also p53-independent in contrast to p21 regulation. Such differences provide a unique mechanism whereby S phase is set to different times of day in a tissue-specific manner, depending on the balance of these two inhibitors. PMID:23569261

Cyclin-dependent kinase inhibitor p20 controls circadian cell-cycle timing.

PubMed

Laranjeiro, Ricardo; Tamai, T Katherine; Peyric, Elodie; Krusche, Peter; Ott, Sascha; Whitmore, David

2013-04-23

Specific stages of the cell cycle are often restricted to particular times of day because of regulation by the circadian clock. In zebrafish, both mitosis (M phase) and DNA synthesis (S phase) are clock-controlled in cell lines and during embryo development. Despite the ubiquitousness of this phenomenon, relatively little is known about the underlying mechanism linking the clock to the cell cycle. In this study, we describe an evolutionarily conserved cell-cycle regulator, cyclin-dependent kinase inhibitor 1d (20 kDa protein, p20), which along with p21, is a strongly rhythmic gene and directly clock-controlled. Both p20 and p21 regulate the G1/S transition of the cell cycle. However, their expression patterns differ, with p20 predominant in developing brain and peak expression occurring 6 h earlier than p21. p20 expression is also p53-independent in contrast to p21 regulation. Such differences provide a unique mechanism whereby S phase is set to different times of day in a tissue-specific manner, depending on the balance of these two inhibitors.

A highly miniaturized vacuum package for a trapped ion atomic clock

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

Schwindt, Peter D. D., E-mail: pschwin@sandia.gov; Jau, Yuan-Yu; Partner, Heather

2016-05-15

We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm{sup 3} in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it wasmore » sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of {sup 171}Y b{sup +}. The fractional frequency stability of the clock was measured to be 2 × 10{sup −11}/τ{sup 1/2}.« less

Demodulator for binary-phase modulated signals having a variable clock rate

NASA Technical Reports Server (NTRS)

Wu, Ta Tzu (Inventor)

1976-01-01

Method and apparatus for demodulating binary-phase modulated signals recorded on a magnetic stripe on a card as the card is manually inserted into a card reader. Magnetic transitions are sensed as the card is read and the time interval between immediately preceeding basic transitions determines the duration of a data sampling pulse which detects the presence or absence of an intermediate transition pulse indicative of two respective logic states. The duration of the data sampling pulse is approximately 75 percent of the preceeding interval between basic transitions to permit tracking succeeding time differences in basic transition intervals of up to approximately 25 percent.

Mg I absorption features in the solar spectrum near 9 and 12 microns

NASA Technical Reports Server (NTRS)

Glenar, David A.; Reuter, Dennis C.; Deming, Drake; Chang, Edward S.

1988-01-01

High-resolution FTS observations from the Kitt Peak National Solar Observatory and the Spacelab 3 ATMOS experiment have revealed additional infrared transitions due to Mg I in the spectra of both quiet sun and sunspot penumbra. In contrast to previous observations, these transitions are seen in absorption, not emission. Absorption intensities range from 1 to 7 percent of the continuum in the quiet sun. In the penumbra, the same features appear to show Zeeman splitting. Modeling of the line profiles in the photospheric spectrum shows evidence for a factor of three overabundance in the n = 5 or more levels of Mg I in the upper photosphere, but with no deviations from a Planck source function. It is concluded that whatever the process that produces the emission (including the Lemke and Holweger mechanism), it must occur well above the tau(5000) = 0.01 level.

Interferometric sensitivity and entanglement by scanning through quantum phase transitions in spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Feldmann, P.; Gessner, M.; Gabbrielli, M.; Klempt, C.; Santos, L.; Pezzè, L.; Smerzi, A.

2018-03-01

Recent experiments demonstrated the generation of entanglement by quasiadiabatically driving through quantum phase transitions of a ferromagnetic spin-1 Bose-Einstein condensate in the presence of a tunable quadratic Zeeman shift. We analyze, in terms of the Fisher information, the interferometric value of the entanglement accessible by this approach. In addition to the Twin-Fock phase studied experimentally, we unveil a second regime, in the broken axisymmetry phase, which provides Heisenberg scaling of the quantum Fisher information and can be reached on shorter time scales. We identify optimal unitary transformations and an experimentally feasible optimal measurement prescription that maximize the interferometric sensitivity. We further ascertain that the Fisher information is robust with respect to nonadiabaticity and measurement noise. Finally, we show that the quasiadiabatic entanglement preparation schemes admit higher sensitivities than dynamical methods based on fast quenches.

Strong valley Zeeman effect of dark excitons in monolayer transition metal dichalcogenides in a tilted magnetic field

NASA Astrophysics Data System (ADS)

Van der Donck, M.; Zarenia, M.; Peeters, F. M.

2018-02-01

The dependence of the excitonic photoluminescence (PL) spectrum of monolayer transition metal dichalcogenides (TMDs) on the tilt angle of an applied magnetic field is studied. Starting from a four-band Hamiltonian we construct a theory which quantitatively reproduces the available experimental PL spectra for perpendicular and in-plane magnetic fields. In the presence of a tilted magnetic field, we demonstrate that the dark exciton PL peaks brighten due to the in-plane component of the magnetic field and split for light with different circular polarizations as a consequence of the perpendicular component of the magnetic field. This splitting is more than twice as large as the splitting of the bright exciton peaks in tungsten-based TMDs. We propose an experimental setup that will allow for accessing the predicted splitting of the dark exciton peaks in the PL spectrum.

Optical properties of uniaxially strained graphene on transition metal dichalcogenide substrate

NASA Astrophysics Data System (ADS)

Goswami, Partha

2018-05-01

The uniaxially strained graphene monolayer on transition metal dichalcogenide (GrTMD) substrate, constituting a van der Waals heterostructure (vdWH), is found to possess unusual intra-band plasmon dispersion (ω ˜ q2/3) with stronger incarceration compared to that of a standalone, doped graphene for finite doping in the long wavelength limit. The intra-band absorbance of GrTMD is found to be an increasing (decreasing) function of the strain field (frequency) at a given frequency (strain field). It is also observed that whereas the strain field is responsible for the valley polarization, a Rashba coupling-dependent pseudo Zeeman term arising due to the interplay of substrate-induced interactions is found to bring about the spin degeneracy lifting and the gate voltage tunable spin polarization. The latter turns out to be inversely proportional to the square root of the carrier concentration.

Creation of quantum-degenerate gases of ytterbium in a compact 2D-/3D-magneto-optical trap setup

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

Doerscher, Soeren; Thobe, Alexander; Hundt, Bastian

2013-04-15

We report on the first experimental setup based on a 2D-/3D-magneto-optical trap (MOT) scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously produce ultracold samples of other atomic species. Furthermore, the extraordinary optical access favors future experiments in optical lattices. A 2D-MOT on the strong {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition captures ytterbium directly from a dispenser of atoms and loads a 3D-MOT on the narrow {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} intercombination transition. Subsequently, atoms are transferred to a crossed opticalmore » dipole trap and cooled evaporatively to quantum degeneracy.« less

Solar Spectral Lines with Special Polarization Properties for the Calibration of Instrument Polarization

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

Li, W.; Casini, R.; Alemán, T. del Pino

We investigate atomic transitions that have previously been identified as having zero polarization from the Zeeman effect. Our goal is to identify spectral lines that can be used for the calibration of instrumental polarization of large astronomical and solar telescopes, such as the Daniel K. Inouye Solar Telescope, which is currently under construction on Haleakala. We use a numerical model that takes into account the generation of scattering polarization and its modification by the presence of a magnetic field of arbitrary strength. We adopt values for the Landé factors from spectroscopic measurements or semi-empirical results, thus relaxing the common assumptionmore » of LS-coupling previously used in the literature. The mechanisms dominating the polarization of particular transitions are identified, and we summarize groups of various spectral lines useful for the calibration of spectropolarimetric instruments, classified according to their polarization properties.« less

Tuning the ferroelectric-to-paraelectric transition temperature and dipole orientation of group-IV monochalcogenide monolayers

NASA Astrophysics Data System (ADS)

Barraza-Lopez, Salvador; Kaloni, Thaneshwor P.; Poudel, Shiva P.; Kumar, Pradeep

2018-01-01

Coordination-related, two-dimensional (2D) structural phase transitions are a fascinating facet of two-dimensional materials with structural degeneracies. Nevertheless, a unified theoretical account of these transitions remains absent, and the following points are established through ab initio molecular dynamics and 2D discrete clock models here: Group-IV monochalcogenide (GeSe, SnSe, SnTe,...) monolayers have four degenerate structural ground states, and a phase transition from a threefold coordinated onto a fivefold coordinated structure takes place at finite temperature. On unstrained samples, this phase transition requires lattice parameters to evolve freely. A fundamental energy scale J permits understanding this transition, and numerical results indicate a transition temperature Tc of about 1.41 J . Numerical data provides a relation among the experimental (rhombic) parameter 〈Δ α 〉 [Chang et al., Science 353, 274 (2016), 10.1126/science.aad8609] and T of the form 〈Δ α 〉 =Δ α (T =0 ) (1-T /Tc)β , with a critical exponent β ≃1 /3 that coincides with experiment. It is also shown that 〈Δ α 〉 is temperature independent in another theoretical work [Fei et al., Phys. Rev. Lett. 117, 097601 (2016), 10.1103/PhysRevLett.117.097601], and thus incompatible with experiment. Tc and the orientation of the in-plane intrinsic electric dipole can be controlled by moderate uniaxial tensile strain, and a modified discrete clock model describes the transition on strained samples qualitatively. An analysis of out-of-plane fluctuations and a discussion of the need for van der Waals corrections to describe these materials are given too. These results provide an experimentally compatible framework to understand structural phase transitions in 2D materials and their effects on material properties.

High-speed optical phase-shifting apparatus

DOEpatents

Zortman, William A.

2016-11-08

An optical phase shifter includes an optical waveguide, a plurality of partial phase shifting elements arranged sequentially, and control circuitry electrically coupled to the partial phase shifting elements. The control circuitry is adapted to provide an activating signal to each of the N partial phase shifting elements such that the signal is delayed by a clock cycle between adjacent partial phase shifting elements in the sequence. The transit time for a guided optical pulse train between the input edges of consecutive partial phase shifting elements in the sequence is arranged to be equal to a clock cycle, thereby enabling pipelined processing of the optical pulses.

Design and Evaluation of a Clock Multiplexing Circuit for the SSRL Booster Accelerator Timing System - Oral Presentation

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

Araya, Million

2015-08-25

SPEAR3 is a 234 m circular storage ring at SLAC’s synchrotron radiation facility (SSRL) in which a 3 GeV electron beam is stored for user access. Typically the electron beam decays with a time constant of approximately 10hr due to electron lose. In order to replenish the lost electrons, a booster synchrotron is used to accelerate fresh electrons up to 3GeV for injection into SPEAR3. In order to maintain a constant electron beam current of 500mA, the injection process occurs at 5 minute intervals. At these times the booster synchrotron accelerates electrons for injection at a 10Hz rate. A 10Hzmore » 'injection ready' clock pulse train is generated when the booster synchrotron is operating. Between injection intervalswhere the booster is not running and hence the 10 Hz ‘injection ready’ signal is not present-a 10Hz clock is derived from the power line supplied by Pacific Gas and Electric (PG&E) to keep track of the injection timing. For this project I constructed a multiplexing circuit to 'switch' between the booster synchrotron 'injection ready' clock signal and PG&E based clock signal. The circuit uses digital IC components and is capable of making glitch-free transitions between the two clocks. This report details construction of a prototype multiplexing circuit including test results and suggests improvement opportunities for the final design.« less

Design and Evaluation of a Clock Multiplexing Circuit for the SSRL Booster Accelerator Timing System - Final Paper

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

Araya, Million

2015-08-21

SPEAR3 is a 234 m circular storage ring at SLAC’s synchrotron radiation facility (SSRL) in which a 3 GeV electron beam is stored for user access. Typically the electron beam decays with a time constant of approximately 10hr due to electron lose. In order to replenish the lost electrons, a booster synchrotron is used to accelerate fresh electrons up to 3GeV for injection into SPEAR3. In order to maintain a constant electron beam current of 500mA, the injection process occurs at 5 minute intervals. At these times the booster synchrotron accelerates electrons for injection at a 10Hz rate. A 10Hzmore » 'injection ready' clock pulse train is generated when the booster synchrotron is operating. Between injection intervals-where the booster is not running and hence the 10 Hz ‘injection ready’ signal is not present-a 10Hz clock is derived from the power line supplied by Pacific Gas and Electric (PG&E) to keep track of the injection timing. For this project I constructed a multiplexing circuit to 'switch' between the booster synchrotron 'injection ready' clock signal and PG&E based clock signal. The circuit uses digital IC components and is capable of making glitch-free transitions between the two clocks. This report details construction of a prototype multiplexing circuit including test results and suggests improvement opportunities for the final design.« less

Precision Measurements with a Molecular Clock

NASA Astrophysics Data System (ADS)

Grier, Andrew; McDonald, Mickey; McGuyer, Bart; Iwata, Geoffrey; Apfelbeck, Florian; Tarallo, Marco; Zelevinsky, Tanya

2015-05-01

We report on recent results obtained with photoassociated Sr2 molecules confined in a lattice. Sr2 has a range of electronically excited bound states which are readily accessible with optical wavelengths using the narrow 1S0->3P1 intercombination line. As in Nat. Phys. 11, 32, we measure the lifetimes of the narrow, deeply-bound subradiant states in the 1g (1S0+3P1 dissociative limit) potential, allowing for coherent control of molecules and a comparison with theoretical predictions of the lifetimes and transition strengths of these states. Next, we study ultracold photodissociation of Sr2 molecules through abortion of one and two photons near the atomic intercombination line. This allows us to observe the vector character of transition elements through the angular dissociation pattern and to directly measure barrier heights in the excited state potentials. Finally, as shown in PRL 114, 023001, we demonstrate that in a non-magic lattice, a narrow transition can be used to measure the trapped gas temperature through the linewidth of the spectral feature corresponding to the carrier transitions. We use this technique to measure the temperature of Sr2 molecules to 10x higher precision than with standard techniques. We discuss future prospects with this molecular lattice clock. Funding from NIST, ARO, and NSF IGERT.

Demonstration of the frequency offset errors introduced by an incorrect setting of the Zeeman/magnetic field adjustment on the cesium beam frequency standard

NASA Technical Reports Server (NTRS)

Kaufmann, D. C.

1976-01-01

The fine frequency setting of a cesium beam frequency standard is accomplished by adjusting the C field control with the appropriate Zeeman frequency applied to the harmonic generator. A novice operator in the field, even when using the correct Zeeman frequency input, may mistakenly set the C field to any one of seven major Beam I peaks (fingers) represented by the Ramsey curve. This can result in frequency offset errors of as much as 2.5 parts in ten to the tenth. The effects of maladjustment are demonstrated and suggestions are discussed on how to avoid the subtle traps associated with C field adjustments.

Design of a Permanent-Magnet Zeeman Slower

NASA Astrophysics Data System (ADS)

Adler, Charles; Narducci, Frank; Sukenik, Charles; Mulholland, Jonathan; Goodale, Sarah

2006-05-01

During the past decade, low cost, flexible, and highly-polarized magnetic field sheet material has become available with field strengths useful for applications in modern atomic physics experiments. One advantage of using such material is that it can easily be cut to almost any desired shape without appreciable loss of field strength making it more versatile than ceramic magnets. We present the design of a Zeeman slower, made from such material, for cooling an atomic beam of neutral rubidium atoms and discuss results from an atomic beam trajectory simulation which indicates that the slower should perform well. We will also report on progress of a prototype permanent magnet Zeeman slower presently under construction in the laboratory.

Temperature compensation via cooperative stability in protein degradation

NASA Astrophysics Data System (ADS)

Peng, Yuanyuan; Hasegawa, Yoshihiko; Noman, Nasimul; Iba, Hitoshi

2015-08-01

Temperature compensation is a notable property of circadian oscillators that indicates the insensitivity of the oscillator system's period to temperature changes; the underlying mechanism, however, is still unclear. We investigated the influence of protein dimerization and cooperative stability in protein degradation on the temperature compensation ability of two oscillators. Here, cooperative stability means that high-order oligomers are more stable than their monomeric counterparts. The period of an oscillator is affected by the parameters of the dynamic system, which in turn are influenced by temperature. We adopted the Repressilator and the Atkinson oscillator to analyze the temperature sensitivity of their periods. Phase sensitivity analysis was employed to evaluate the period variations of different models induced by perturbations to the parameters. Furthermore, we used experimental data provided by other studies to determine the reasonable range of parameter temperature sensitivity. We then applied the linear programming method to the oscillatory systems to analyze the effects of protein dimerization and cooperative stability on the temperature sensitivity of their periods, which reflects the ability of temperature compensation in circadian rhythms. Our study explains the temperature compensation mechanism for circadian clocks. Compared with the no-dimer mathematical model and linear model for protein degradation, our theoretical results show that the nonlinear protein degradation caused by cooperative stability is more beneficial for realizing temperature compensation of the circadian clock.

Magnetic reconnection in 3D magnetosphere models: magnetic separators and open flux production

NASA Astrophysics Data System (ADS)

Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P.

2014-12-01

There are multiple competing definitions of magnetic reconnection in 3D (e.g., Hesse and Schindler [1988], Lau and Finn [1990], and Boozer [2002]). In this work we focus on separator reconnection. A magnetic separator can be understood as the 3D analogue of a 2D x line with a guide field, and is defined by the line corresponding to the intersection of the separatrix surfaces associated with the magnetic nulls. A separator in the magnetosphere represents the intersection of four distinct magnetic topologies: solar wind, closed, open connected to the northern hemisphere, and open connected to the southern hemisphere. The integral of the parallel electric field along the separator defines the rate of open flux production, and is one measure of the reconnection rate. We present three methods for locating magnetic separators and apply them to 3D resistive MHD simulations of the Earth's magnetosphere using the BATS-R-US code. The techniques for finding separators and determining the reconnection rate are insensitive to IMF clock angle and can in principle be applied to any magnetospheric model. The present work examines cases of high and low resistivity, for two clock angles. We also examine the separator during Flux Transfer Events (FTEs) and Kelvin-Helmholtz instability.

Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

NASA Astrophysics Data System (ADS)

Satija, Aman; Lucht, Robert P.

2015-06-01

Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam at 486 nm. The 486-nm beam was frequency doubled to a 243-nm beam. Use of the second scheme simplifies the TPP-PSP technique making it more convenient for diagnostics in practical systems.

Getting a grip on the transverse motion in a Zeeman decelerator

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

Dulitz, Katrin; Softley, Timothy P., E-mail: tim.softley@chem.ox.ac.uk; Motsch, Michael

2014-03-14

Zeeman deceleration is an experimental technique in which inhomogeneous, time-dependent magnetic fields generated inside an array of solenoid coils are used to manipulate the velocity of a supersonic beam. A 12-stage Zeeman decelerator has been built and characterized using hydrogen atoms as a test system. The instrument has several original features including the possibility to replace each deceleration coil individually. In this article, we give a detailed description of the experimental setup, and illustrate its performance. We demonstrate that the overall acceptance in a Zeeman decelerator can be significantly increased with only minor changes to the setup itself. This ismore » achieved by applying a rather low, anti-parallel magnetic field in one of the solenoid coils that forms a temporally varying quadrupole field, and improves particle confinement in the transverse direction. The results are reproduced by three-dimensional numerical particle trajectory simulations thus allowing for a rigorous analysis of the experimental data. The findings suggest the use of a modified coil configuration to improve transverse focusing during the deceleration process.« less

Progress toward measuring the 6S1/2 <--> 5D3/2 magnetic-dipole transition moment in Ba+

NASA Astrophysics Data System (ADS)

Williams, Spencer; Jayakumar, Anupriya; Hoffman, Matthew; Blinov, Boris; Fortson, Norval

2015-05-01

We report the latest results from our effort to measure the magnetic-dipole transition moment (M1) between the 6S1 / 2 and 5D3 / 2 manifolds in Ba+. We describe a new technique for calibrating view-port birefringence and how we will use it to enhance the M1 signal. To access the transition moment we use a variation of a previously proposed technique that allows us to isolate the magnetic-dipole coupling from the much larger electric-quadrupole coupling in the transition rates between particular Zeeman sub-levels. Knowledge of M1 is crucial for a parity-nonconservation experiment in the ion where M1 will be a leading source of systematic errors. No measurement of this M1 has been made in Ba+, however, there are three calculations that predict it to be 80 ×10-5μB, 22 ×10-5μB, and 17 ×10-5μB. A precise measurement may help resolve this theoretical discrepancy which originates from their different estimations of many-body effects. Supported by NSF Grant No. 09-06494F.

Very Large Array H I Zeeman Observations of the Cygnus X Region: DR 22 and ON 2

NASA Astrophysics Data System (ADS)

Mayo, E. A.; Troland, T. H.

2012-02-01

We have used the Very Large Array to study the Zeeman effect in 21 cm H I absorption lines from two star-forming regions in the Cygnus X complex, DR 22 and ON 2. We measure the line-of-sight magnetic field toward these regions, finding B los = -84 ± 11 μG toward the DR 22 H II region and B los < 50 μG toward each of the two H II regions in ON 2. We interpret these results in terms of two different models. In one model, we assume that the H I Zeeman effect is a measure of magnetic fields in the associated molecular clouds. If so, then the DR 22 molecular cloud is magnetically subcritical, that is, magnetically dominated. The ON 2 molecular clouds are magnetically supercritical. In a second model, we assume that the H I Zeeman effect is a measure of magnetic fields in photon-dominated regions where the gas has been compressed (and the field amplified) by absorption of stellar radiation. We find that this second model, where the measured field strength has been affected by star formation, accounts well for the DR 22 H I Zeeman effect. This same model, however, overpredicts the magnetic field in ON 2. ON 2 may be a region where the magnetic field is energetically insignificant or where the field happens to lie nearly in the plane of the sky.

Designing and building a permanent magnet Zeeman slower for calcium atoms using a 3D printer

NASA Astrophysics Data System (ADS)

Parsagian, Alexandria; Kleinert, Michaela

2015-10-01

We present the design of a Zeeman slower for calcium atoms using permanent magnets instead of more traditional electromagnets and the novel technique of 3D printing to create a very robust and flexible structure for these magnets. Zeeman slowers are ideal tools to slow atoms from several hundreds of meters per second to just a few tens of meters per second. These slower atoms can then easily be trapped in a magneto-optical trap, making Zeeman slowers a very valuable tool in many cold atom labs. The use of permanent magnets and 3D printing results in a highly stable and robust slower that is suitable for undergraduate laboratories. In our design, we arranged 28 magnet pairs, 2.0 cm apart along the axis of the slower and at varying radial distances from the axis. We determined the radial position of the magnets by simulating the combined field of all magnet pairs using Mathematica and comparing it to the ideal theoretical field for a Zeeman slower. Finally, we designed a stable, robust, compact, and easy-to-align mounting structure for the magnets in Google Sketchup, which we then printed using a commercially available 3D printer by Solidoodle. The resulting magnetic field is well suited to slow calcium atoms from the 770 m/s rms velocity at a temperature of 950 K, down to the capture velocity of the magneto-optical trap.

Induced adult stem (iAS) cells and induced transit amplifying progenitor (iTAP) cells-a possible alternative to induced pluripotent stem (iPS) cells?

PubMed

Heng, Boon Chin; Richards, Mark; Ge, Zigang; Shu, Yimin

2010-02-01

The successful derivation of iPSC lines effectively demonstrates that it is possible to reset the 'developmental clock' of somatic cells all the way back to the initial embryonic state. Hence, it is plausible that this clock may instead be turned back half-way to a less immature developmental stage that is more directly applicable to clinical therapeutic applications or for in vitro pharmacology/toxicology screening assays. Such a suitable developmental state is postulated to be either the putative transit amplifying progenitor stage or adult stem cell stage. It is hypothetically possible to reprogram mature and terminally differentiated somatic cells back to the adult stem cell or transit amplifying progenitor stage, in a manner similar to the derivation of iPSC. It is proposed that the terminology 'Induced Adult Stem Cells' (iASC) or 'Induced Transit Amplifying Progenitor Cells' (iTAPC) be used to described such reprogrammed somatic cells. Of particular interest, is the possibility of resetting the developmental clock of mature differentiated somatic cells of the mesenchymal lineage, explanted from adipose tissue, bone marrow and cartilage. The putative adult stem cell sub-population from which these cells are derived, commonly referred to as 'mesenchymal stem cells', are highly versatile and hold much therapeutic promise in regenerative medicine, as attested to by numerous human clinical trials and animal studies. Perhaps it may be appropriate to term such reprogrammed cells as 'Induced Mesenchymal Stem Cells' (iMSC) or as 'Induced Mesenchumal Progenitor Cells' (iMPC). Given that cells from the same organ/tissue will share some commonalities in gene expression, we hypothesize that the generation of iASC or iTAPC would be more efficient as compared to iPSC generation, since a common epigenetic program must exist between the reprogrammed cells, adult stem cell or progenitor cell types and terminally differentiated cell types from the same organ/tissue.

VLBI observations of 6 GHz OH masers in three ultra-compact H Ii regions

NASA Astrophysics Data System (ADS)

Desmurs, J. F.; Baudry, A.

1998-12-01

Following our successful analysis of VLBI observations of the (2) Pi_ {3/ 2}, J={5/ 2}, F=3-3 and F=2-2 excited OH emission at 6035 and 6031 MHz in W3(OH), we have analyzed the same transitions in three other ultra-compact HII regions, M17, ON1, and W51. The restoring beams were in the range 6 to 30 milliarc sec. The F=3-3 and 2-2 hyperfine transitions of OH were both mapped in ON1. Seven 6035 MHz LCP or RCP maser components were identified in ON1. They are distributed over a region whose diameter is similar to that of the compact HII region, namely ~ 0.4 - 0.5 arc sec. In contrast with the F=3-3 line emission, the F=2-2 transition at 6031 MHz is nearly an order of magnitude weaker than the peak 6035 MHz emission. In M17, we observed fringes only in the 6035 MHz line. The detected OH components appear to be projected on to the compact HII region. We report also on weak VLBI detection of the 6035 MHz emission from W51. This emission seems to be located between two active ultra-compact HII regions in a complex area which deserves further investigation. The 5 cm OH minimum brightness temperatures range from about 3 10(7) K in W51 to 8 10(9) K in ON1. Variability of the 6035 or 6031 MHz emission is well established and suggests that the 5 cm OH masers are not fully saturated. The high spectral and spatial resolutions achieved in this work allowed us to identify Zeeman pairs and hence to derive the magnetic field strength. In ON1 and W51 the field lies in the range 4 to 6 mG with a trend for higher field at 6031 MHz than at 6035 MHz in ON1. In M17 no Zeeman splitting was observed and the magnetic field appears to be weaker than 1 mG.

Doppler-Zeeman Mapping of the Rapidly Rotating Magnetic CP Star HD37776

NASA Astrophysics Data System (ADS)

Khokhlova, V. L.; Vasilchenko, D. V.; Stepanov, V. V.; Romanyuk, I. I.

2000-03-01

We present the results of our analysis of magnetic-field configuration and abundance anomalies on the surface of the rapidly rotating, chemically peculiar helium-strong variable B2 V star HD37776 with unresolved Zeeman components of spectral lines. Simultaneous inversion of the observed Stokes I and V profiles, which realizes the method of Doppler-Zeeman mapping (Vasilchenko et al. 1996), has been applied for the first time. Spectroscopic observations were carried out with the Main stellar spectrograph of the 6-m Special Astrophysical Observatory telescope equipped with a Zeeman analyzer and a CCD array, which allowed spectra in right- and left-hand circularly polarized light to be taken simultaneously at a signal-to-noise ratio S/N > 200 (Romanyuk et al. 1999). The profile width of winged spectral lines (reaching 5 A) is determined by Zeeman line splitting; however, the observed Zeeman components are blurred and unresolved because of the rapid stellar rotation. When solving the inverse problem, we sought for the magnetic-field configuration in the form of a combination of arbitrarily oriented dipole, quadrupole, and octupole placed at the stellar center. The observed Stokes I and V profiles for eight spectral lines of He, OII, AlIII, SiIII, and FeIII averaged over the visible stellar surface were used as input data. We constructed a model of the magnetic field from the condition of coincidence of magnetic maps obtained from different lines of different chemical elements and from the condition of a minimum profile residual. This model is a combination of centered coaxial dipole and quadrupole with the dominant quadrupole component at 30 deg < i < 50 deg, beta = 40 deg, and a maximum surface field strength H_s = 60 kG. A comparison of our abundance maps with the field configuration shows that the He concentration is at a maximum in the regions of maximum radial field, while the maximum concentrations of O, Al, Si, and Fe coincide with the regions of maximum tangential field.

Probing atomic Higgs-like forces at the precision frontier

NASA Astrophysics Data System (ADS)

Delaunay, Cédric; Ozeri, Roee; Perez, Gilad; Soreq, Yotam

2017-11-01

We propose a novel approach to probe new fundamental interactions using isotope shift spectroscopy in atomic clock transitions. As a concrete toy example we focus on the Higgs boson couplings to the building blocks of matter: the electron and the up and down quarks. We show that the attractive Higgs force between nuclei and their bound electrons, which is poorly constrained, might induce effects that are larger than the current experimental sensitivities. More generically, we discuss how new interactions between the electron and the neutrons, mediated via light new degrees of freedom, may lead to measurable nonlinearities in a King plot comparison between isotope shifts of two different transitions. Given state-of-the-art accuracy in frequency comparison, isotope shifts have the potential to be measured with sub-Hz accuracy, thus potentially enabling the improvement of current limits on new fundamental interactions. A candidate atomic system for this measurement requires two different clock transitions and four zero nuclear spin isotopes. We identify several systems that satisfy this requirement and also briefly discuss existing measurements. We consider the size of the effect related to the Higgs force and the requirements for it to produce an observable signal.

Properties of nearly perfect crystals at very low temperatures

NASA Technical Reports Server (NTRS)

Weber, J.; Hamilton, J. J.

1994-01-01

Data shows that the frequency stability of 5 MHz AT-cut quartz crystal oscillators is improved by lowering the temperature to 4.3 K. The resultant level of stability is apparently not, at this point, sufficient for a clock accurate to 1 part in 10(exp 17). However, many improvements are possible in the scheme presented here. These would involve better temperature regulation, better crystal mounting and vibration isolation, and lower temperatures. Below the lambda-transition at 2.17 K the residual bubbling of the bath would be eliminated. Thus, the prospect of a successful clock built on this scheme is not ruled out.

Neutron Zeeman beam-splitting for the investigation of magnetic nanostructures

NASA Astrophysics Data System (ADS)

Kozhevnikov, S. V.; Ott, F.; Semenova, E.

2017-03-01

Zeeman spatial splitting of a neutron beam takes place during a neutron spin-flip in magnetically non-collinear systems at grazing incidence geometry. We apply the neutron beam-splitting method for the investigation of magnetically non-collinear clusters of submicron size in a thin film. The experimental results are compared with ones obtained by other methods.

Microwave ac Zeeman force for ultracold atoms

NASA Astrophysics Data System (ADS)

Fancher, C. T.; Pyle, A. J.; Rotunno, A. P.; Aubin, S.

2018-04-01

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

Colour As a Signal for Entraining the Mammalian Circadian Clock

PubMed Central

Walmsley, Lauren; Hanna, Lydia; Mouland, Josh; Martial, Franck; West, Alexander; Smedley, Andrew R.; Bechtold, David A.; Webb, Ann R.; Lucas, Robert J.; Brown, Timothy M.

2015-01-01

Twilight is characterised by changes in both quantity (“irradiance”) and quality (“colour”) of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue–yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision. PMID:25884537

Optical Communication with Semiconductor Laser Diode. Interim Progress Report. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Davidson, Frederic; Sun, Xiaoli

1989-01-01

Theoretical and experimental performance limits of a free-space direct detection optical communication system were studied using a semiconductor laser diode as the optical transmitter and a silicon avalanche photodiode (APD) as the receiver photodetector. Optical systems using these components are under consideration as replacements for microwave satellite communication links. Optical pulse position modulation (PPM) was chosen as the signal format. An experimental system was constructed that used an aluminum gallium arsenide semiconductor laser diode as the transmitter and a silicon avalanche photodiode photodetector. The system used Q=4 PPM signaling at a source data rate of 25 megabits per second. The PPM signal format requires regeneration of PPM slot clock and word clock waveforms in the receiver. A nearly exact computational procedure was developed to compute receiver bit error rate without using the Gaussion approximation. A transition detector slot clock recovery system using a phase lock loop was developed and implemented. A novel word clock recovery system was also developed. It was found that the results of the nearly exact computational procedure agreed well with actual measurements of receiver performance. The receiver sensitivity achieved was the closest to the quantum limit yet reported for an optical communication system of this type.

Observation of narrow isotopic optical magnetic resonances in individual emission spectral lines of neon

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

Saprykin, E G; Sorokin, V A; Shalagin, A M

Narrow resonances are observed in the course of recording the individual emission lines of the glow discharge in the mixture of isotopes {sup 20}Ne and {sup 22}Ne, depending on the strength of the longitudinal magnetic field. The position of resonances in the magnetic scale corresponds to the compensation of the isotopic shift for certain spectral lines due to the Zeeman effect. It is found that the contrast of the resonances is higher for the transitions between the highly excited energy levels, and the resonances themselves are formed in the zone of longitudinal spatial nonuniformity of the magnetic field. (laser applicationsmore » and other topics in quantum electronics)« less

Quadrupolar transfer pathways

NASA Astrophysics Data System (ADS)

Antonijevic, Sasa; Bodenhausen, Geoffrey

2006-06-01

A set of graphical conventions called quadrupolar transfer pathways is proposed to describe a wide range of experiments designed for the study of quadrupolar nuclei with spin quantum numbers I = 1, 3/2, 2, 5/2, etc. These pathways, which inter alea allow one to appreciate the distinction between quadrupolar and Zeeman echoes, represent a generalization of the well-known coherence transfer pathways. Quadrupolar transfer pathways not merely distinguish coherences with different orders -2 I ⩽ p ⩽ +2 I, but allow one to follow the fate of coherences associated with single transitions that have the same coherence orderp=mIr-mIs but can be distinguished by a satellite orderq=(mIr)2-(mIs)2.

Quadrupolar transfer pathways.

PubMed

Antonijevic, Sasa; Bodenhausen, Geoffrey

2006-06-01

A set of graphical conventions called quadrupolar transfer pathways is proposed to describe a wide range of experiments designed for the study of quadrupolar nuclei with spin quantum numbers I=1, 3/2, 2, 5/2, etc. These pathways, which inter alea allow one to appreciate the distinction between quadrupolar and Zeeman echoes, represent a generalization of the well-known coherence transfer pathways. Quadrupolar transfer pathways not merely distinguish coherences with different orders -2I < or = p< or = +2I, but allow one to follow the fate of coherences associated with single transitions that have the same coherence order p=m(I)(r)-m(I)(s) but can be distinguished by a satellite order q=(m(I)(r))(2)-(m(I)(s))(2).

Laser cooling at resonance

NASA Astrophysics Data System (ADS)

Yudkin, Yaakov; Khaykovich, Lev

2018-05-01

We show experimentally that three-dimensional laser cooling of lithium atoms on the D2 line is possible when the laser light is tuned exactly to resonance with the dominant atomic transition. Qualitatively, it can be understood by applying simple Doppler cooling arguments to the specific hyperfine structure of the excited state of lithium atoms, which is both dense and inverted. However, to build a quantitative theory, we must resolve to a full model which takes into account both the entire atomic structure of all 24 Zeeman sublevels and the laser light polarization. Moreover, by means of Monte Carlo simulations, we show that coherent processes play an important role in showing consistency between the theory and the experimental results.

Precise calibration of zero-crossing temperature and drift of an ultralow expansion cavity with a clock transition spectrum

NASA Astrophysics Data System (ADS)

Liu, Hui; Jiang, Kun-Liang; Wang, Jin-Qi; Xiong, Zhuan-Xian; He, Ling-Xiang; Lü, Bao-Long

2018-05-01

Not Available Project supported by the National Natural Science Foundation of China (Grant Nos. 61227805, 11574352, 91536104, and 91636215) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB21030100).

Anomalous finite-size effect due to quasidegenerate phases in triangular antiferromagnets with long-range interactions and mapping to the generalized six-state clock model

NASA Astrophysics Data System (ADS)

Nishino, Masamichi; Miyashita, Seiji

2016-11-01

The effect of long-range (LR) interactions on frustrated-spin models is an interesting problem, which provides rich ordering processes. We study the effect of LR interactions on triangular Ising antiferromagnets with the next-nearest-neighbor ferromagnetic interaction (TIAFF). In the thermodynamic limit, the LRTIAFF model should reproduce the corresponding mean-field results, in which successive phase transitions occur among various phases, i.e., the disordered paramagnetic phase, so-called partially disordered phase, three-sublattice ferrimagnetic phase, and two-sublattice ferrimagnetic phase. In the present paper we focus on the magnetic susceptibility at the transition point between the two-sublattice ferrimagnetic and the disordered paramagnetic phases at relatively large ferromagnetic interactions. In the mean-field analysis, the magnetic susceptibility shows no divergence at the transition point. In contrast, a divergencelike enhancement of the susceptibility is observed in Monte Carlo simulations in finite-size systems. We investigate the origin of this difference and find that it is attributed to a virtual degeneracy of the free energies of the partially disordered and 2-FR phases. We also exploit a generalized six-state clock model with an LR interaction, which is a more general system with Z6 symmetry. We discuss the phase diagram of this model and find that it exhibits richer transition patterns and contains the physics of the LRTIAFF model.

Deterministic multi-zone ice accretion modeling

NASA Technical Reports Server (NTRS)

Yamaguchi, K.; Hansman, R. John, Jr.; Kazmierczak, Michael

1991-01-01

The focus here is on a deterministic model of the surface roughness transition behavior of glaze ice. The initial smooth/rough transition location, bead formation, and the propagation of the transition location are analyzed. Based on the hypothesis that the smooth/rough transition location coincides with the laminar/turbulent boundary layer transition location, a multizone model is implemented in the LEWICE code. In order to verify the effectiveness of the model, ice accretion predictions for simple cylinders calculated by the multizone LEWICE are compared to experimental ice shapes. The glaze ice shapes are found to be sensitive to the laminar surface roughness and bead thickness parameters controlling the transition location, while the ice shapes are found to be insensitive to the turbulent surface roughness.

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR OPERATION, CALIBRATION AND MAINTENANCE OF THE PERKIN-ELMER ZEEMAN/5000 SYSTEM ATOMIC ABSORPTION SPECTROMETER (BCO-L-6.0)

EPA Science Inventory

The purpose of this SOP is to outline the start-up, calibration, operation, and maintenance procedures for the Perkin-Elmer 5000 atomic absorption spectrophotometer (PE 5000 AA), and the Perkin Elmer 5000 Zeeman graphite furnace atomic absorption spectrophotometer (PE 5000Z GFAA)...

Magnetic Field Measurements In Magnetized Plasmas Using Zeeman Broadening Diagnostics

NASA Astrophysics Data System (ADS)

Haque, Showera; Wallace, Matthew; Presura, Radu; Neill, Paul

2017-10-01

The Zeeman effect has been used to measure the magnetic field in high energy density plasmas. This method is limited when plasma conditions are such that the line broadening due to the high plasma density and temperature surpasses the Zeeman splitting. We have measured magnetic fields in magnetized laser plasmas under conditions where the Zeeman splitting was not spectrally resolved. The magnetic field strength was determined from the difference in widths of two doublet components, using an idea proposed by Tessarin et al. (2011). Time-gated spectra with one-dimensional space-resolution were obtained at the Nevada Terawatt Facility for laser plasmas created by 20 J, 1 ns Leopard laser pulses, and expanding in the azimuthal magnetic field produced by the 0.6 MA Zebra pulsed power generator. We explore the response of the Al III 4s 2S1/2 - 4p 2P1 / 2 , 3 / 2 doublet components to the external magnetic field spatially along the plasma. Radial magnetic field and electron density profiles were measured within the plasma plume. This work was supported by the DOE/OFES Grant DE-SC0008829 and DOE/NNSA contract DE-FC52-06NA27616.

Robust superconductivity with nodes in the superconducting topological insulator CuxBi2Se3 : Zeeman orbital field and nonmagnetic impurities

NASA Astrophysics Data System (ADS)

Nagai, Yuki

2015-02-01

We study the robustness against nonmagnetic impurities in the topological superconductor with point nodes, focusing on an effective model of CuxBi2Se3 . We find that the topological superconductivity with point nodes is not fragile against nonmagnetic impurities, although the superconductivity with nodes in past studies is usually fragile. Exchanging the role of spin with the one of orbital, and vice versa, we find that in the "dual" space the topological superconductor with point nodes is regarded as the intraorbital spin-singlet s -wave one. From the viewpoint of the dual space, we deduce that the point-node state is not fragile against nonmagnetic impurity, when the orbital imbalance in the normal states is small. Since the spin imbalance is induced by the Zeeman magnetic field, we shall name this key quantity for the impurity effects the Zeeman "orbital" field. The numerical calculations support that the deduction is correct. If the Zeeman orbital field is small, the topological superconductivity is not fragile in dirty materials, even with nodes. Thus, the topological superconductors cannot be simply regarded as one of the conventional unconventional superconductors.

Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in ICF-relevant plasmas.

PubMed

Dutra, E C; Koch, J A; Presura, R; Angermeier, W A; Darling, T; Haque, S; Mancini, R C; Covington, A M

2016-11-01

Spectroscopic techniques in the visible range are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening, and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch and Dense Plasma Focus (DPF) accelerators. The line emission is used to calculate the electron densities, temperatures, and B-fields. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. This manuscript presents the details of the experimental setup and line shape code, along with the results obtained from an Al iii doublet at the University of Nevada, Reno at Nevada Terawatt Facility. Future tests are planned to further evaluate the technique and modeling on other material wire array, gas puff, and DPF platforms.

Radio frequency charge parity meter.

PubMed

Schroer, M D; Jung, M; Petersson, K D; Petta, J R

2012-10-19

We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped-element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensitive to a magnetic field. The measured response agrees well with cavity input-output theory, allowing accurate measurements of the interdot tunnel coupling and the resonator-charge coupling rate g(c)/2π~17 MHz.

Polaronic and dressed molecular states in orbital Feshbach resonances

NASA Astrophysics Data System (ADS)

Xu, Junjun; Qi, Ran

2018-04-01

We consider the impurity problem in an orbital Feshbach resonance (OFR), with a single excited clock state | e ↑⟩ atom immersed in a Fermi sea of electronic ground state | g ↓⟩. We calculate the polaron effective mass and quasi-particle residue, as well as the polaron to molecule transition. By including one particle-hole excitation in the molecular state, we find significant correction to the transition point. This transition point moves toward the BCS side for increasing particle densities, which suggests that the corresponding many-body physics is similar to a narrow resonance.

Phase control of a Zeeman-split He-Ne gas laser by variation of the gaseous discharge voltage.

PubMed

Shelton, W N; Hunt, R H

1992-07-20

Zeeman-split lasers are useful for precise positioning or motion control. In applications that employ such a laser to control closely the position of a moving system, phase noise in the Zeeman frequency is a serious problem. Control of low-frequency phase noise can be obtained through variation of the external magnetic field by way of a solenoid wound around the laser tube. It is the finding in this work that control of the residual higher-frequency noise of a He-Ne laser can be obtained through small variations of the high voltage that is used to effect the gaseous discharge in the laser tube. The application of the present system is to the control of the path difference in a Fourier-transform interferometric spectrometer.

Performance of the Zeeman analyzer system of the McDonald Observatory 2.7 meter telescope

NASA Technical Reports Server (NTRS)

Vogt, S. S.; Tull, R. G.; Kelton, P. W.

1980-01-01

The paper describes a multichannel photoelectric Zeeman analyzer at the coude spectrograph of the McDonald 2.7 m reflector. A comparison of Lick and McDonald observations of HD 153882 reveals no significant difference in slopes or zero points of the two magnetic fields indicating that the systematic scale difference of 30-40% is probably instrumental in origin. Observations of the magnetic variable beta Cor Bor revealed a more nearly sinusoidal magnetic curve with less internal scatter than the photographically determined field measures of the Lick and Mauna Kea Zeeman systems. Investigation of periodicity in the secularly varying magnetic minima of beta Cor Bor did not yield evidence of previously noted periodicities other than that expected from the time structure of the data sampling.

The Effect of Aerodynamic Evaluators on the Multi-Objective Optimization of Flatback Airfoils

NASA Astrophysics Data System (ADS)

Miller, M.; Slew, K. Lee; Matida, E.

2016-09-01

With the long lengths of today's wind turbine rotor blades, there is a need to reduce the mass, thereby requiring stiffer airfoils, while maintaining the aerodynamic efficiency of the airfoils, particularly in the inboard region of the blade where structural demands are highest. Using a genetic algorithm, the multi-objective aero-structural optimization of 30% thick flatback airfoils was systematically performed for a variety of aerodynamic evaluators such as lift-to-drag ratio (Cl/Cd), torque (Ct), and torque-to-thrust ratio (Ct/Cn) to determine their influence on airfoil shape and performance. The airfoil optimized for Ct possessed a 4.8% thick trailing-edge, and a rather blunt leading-edge region which creates high levels of lift and correspondingly, drag. It's ability to maintain similar levels of lift and drag under forced transition conditions proved it's insensitivity to roughness. The airfoil optimized for Cl/Cd displayed relatively poor insensitivity to roughness due to the rather aft-located free transition points. The Ct/Cn optimized airfoil was found to have a very similar shape to that of the Cl/Cd airfoil, with a slightly more blunt leading-edge which aided in providing higher levels of lift and moderate insensitivity to roughness. The influence of the chosen aerodynamic evaluator under the specified conditions and constraints in the optimization of wind turbine airfoils is shown to have a direct impact on the airfoil shape and performance.

Transient nutation electron spin resonance spectroscopy on spin-correlated radical pairs: A theoretical analysis on hyperfine-induced nuclear modulations

NASA Astrophysics Data System (ADS)

Weber, Stefan; Kothe, Gerd; Norris, James R.

1997-04-01

The influence of anisotropic hyperfine interaction on transient nutation electron paramagnetic resonance (EPR) of light-induced spin-correlated radical pairs is studied theoretically using the density operator formalism. Analytical expressions for the time evolution of the transient EPR signal during selective microwave excitation of single transitions are derived for a model system comprised of a weakly coupled radical pair and one hyperfine-coupled nucleus with I=1/2. Zero-quantum electron coherence and single-quantum nuclear coherence are created as a result of the sudden light-induced generation of the radical pair state from a singlet-state precursor. Depending on the relative sizes of the nuclear Zeeman frequency and the secular and pseudo-secular parts of the hyperfine coupling, transitions between levels with different nuclear spin orientations are predicted to modulate the time-dependent EPR signal. These modulations are in addition to the well-known transient nutations and electron zero-quantum precessions. Our calculations provide insight into the mechanism of recent experimental observations of coherent nuclear modulations in the time-resolved EPR signals of doublets and radical pairs. Two distinct mechanisms of the modulations are presented for various microwave magnetic field strengths. The first modulation scheme arises from electron and nuclear coherences initiated by the laser excitation pulse and is "read out" by the weak microwave magnetic field. While the relative modulation depth of these oscillations with respect to the signal intensity is independent of the Rabi frequency, ω1, the frequencies of this coherence phenomenon are modulated by the effective microwave amplitude and determined by the nuclear Zeeman interaction and hyperfine coupling constants as well as the electron-electron spin exchange and dipolar interactions between the two radical pair halves. In a second mechanism the modulations are both created and detected by the microwave radiation. Here, the laser pulse merely defines the beginning of the microwave-induced coherent time evolution. This second mechanism appears the most consistent with current experimental observations.

Using the principles of circadian physiology enhances shift schedule design

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

Connolly, J.J.; Moore-Ede, M.C.

1987-01-01

Nuclear power plants must operate 24 h, 7 days a week. For the most part, shift schedules currently in use at nuclear power plants have been designed to meet operational needs without considering the biological clocks of the human operators. The development of schedules that also take circadian principles into account is a positive step that can be taken to improve plant safety by optimizing operator alertness. These schedules reduce the probability of human errors especially during backshifts. In addition, training programs that teach round-the-clock workers how to deal with the problems of shiftwork can help to optimize performance andmore » alertness. These programs teach shiftworkers the underlying causes of the sleep problems associated with shiftwork and also provide coping strategies for improving sleep and dealing with the transition between shifts. When these training programs are coupled with an improved schedule, the problems associated with working round-the-clock can be significantly reduced.« less

Muscle insulin sensitivity and glucose metabolism are controlled by the intrinsic muscle clock★

PubMed Central

Dyar, Kenneth A.; Ciciliot, Stefano; Wright, Lauren E.; Biensø, Rasmus S.; Tagliazucchi, Guidantonio M.; Patel, Vishal R.; Forcato, Mattia; Paz, Marcia I.P.; Gudiksen, Anders; Solagna, Francesca; Albiero, Mattia; Moretti, Irene; Eckel-Mahan, Kristin L.; Baldi, Pierre; Sassone-Corsi, Paolo; Rizzuto, Rosario; Bicciato, Silvio; Pilegaard, Henriette; Blaauw, Bert; Schiaffino, Stefano

2013-01-01

Circadian rhythms control metabolism and energy homeostasis, but the role of the skeletal muscle clock has never been explored. We generated conditional and inducible mouse lines with muscle-specific ablation of the core clock gene Bmal1. Skeletal muscles from these mice showed impaired insulin-stimulated glucose uptake with reduced protein levels of GLUT4, the insulin-dependent glucose transporter, and TBC1D1, a Rab-GTPase involved in GLUT4 translocation. Pyruvate dehydrogenase (PDH) activity was also reduced due to altered expression of circadian genes Pdk4 and Pdp1, coding for PDH kinase and phosphatase, respectively. PDH inhibition leads to reduced glucose oxidation and diversion of glycolytic intermediates to alternative metabolic pathways, as revealed by metabolome analysis. The impaired glucose metabolism induced by muscle-specific Bmal1 knockout suggests that a major physiological role of the muscle clock is to prepare for the transition from the rest/fasting phase to the active/feeding phase, when glucose becomes the predominant fuel for skeletal muscle. PMID:24567902

Optical lattice clock with atoms confined in a shallow trap

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

Lemonde, Pierre; Wolf, Peter; Bureau International des Poids et Mesures, Pavillon de Breteuil, 92312 Sevres Cedex

2005-09-15

We study the trap depth requirement for the realization of an optical clock using atoms confined in a lattice. We show that site-to-site tunneling leads to a residual sensitivity to the atom dynamics hence requiring large depths [(50-100)E{sub r} for Sr] to avoid any frequency shift or line broadening of the atomic transition at the 10{sup -17}-10{sup -18} level. Such large depths and the corresponding laser power may, however, lead to difficulties (e.g., higher-order light shifts, two-photon ionization, technical difficulties) and therefore one would like to operate the clock in much shallower traps. To circumvent this problem we propose themore » use of an accelerated lattice. Acceleration lifts the degeneracy between adjacents potential wells which strongly inhibits tunneling. We show that using the Earth's gravity, much shallower traps (down to 5E{sub r} for Sr) can be used for the same accuracy goal.« less

An improved adaptive interpolation clock recovery loop based on phase splitting algorithm for coherent optical communication system

NASA Astrophysics Data System (ADS)

Liu, Xuan; Liu, Bo; Zhang, Li-jia; Xin, Xiang-jun; Zhang, Qi; Wang, Yong-jun; Tian, Qing-hua; Tian, Feng; Mao, Ya-ya

2018-01-01

Traditional clock recovery scheme achieves timing adjustment by digital interpolation, thus recovering the sampling sequence. Based on this, an improved clock recovery architecture joint channel equalization for coherent optical communication system is presented in this paper. The loop is different from the traditional clock recovery. In order to reduce the interpolation error caused by the distortion in the frequency domain of the interpolator and to suppress the spectral mirroring generated by the sampling rate change, the proposed algorithm joint equalization, improves the original interpolator in the loop, along with adaptive filtering, and makes error compensation for the original signals according to the balanced pre-filtering signals. Then the signals are adaptive interpolated through the feedback loop. Furthermore, the phase splitting timing recovery algorithm is adopted in this paper. The time error is calculated according to the improved algorithm when there is no transition between the adjacent symbols, making calculated timing error more accurate. Meanwhile, Carrier coarse synchronization module is placed before the beginning of timing recovery to eliminate the larger frequency offset interference, which effectively adjust the sampling clock phase. In this paper, the simulation results show that the timing error is greatly reduced after the loop is changed. Based on the phase splitting algorithm, the BER and MSE are better than those in the unvaried architecture. In the fiber channel, using MQAM modulation format, after 100 km-transmission of single-mode fiber, especially when ROF(roll-off factor) values tends to 0, the algorithm shows a better clock performance under different ROFs. When SNR values are less than 8, the BER could achieve 10-2 to 10-1 magnitude. Furthermore, the proposed timing recovery is more suitable for the situation with low SNR values.

Generalized Autobalanced Ramsey Spectroscopy of Clock Transitions

NASA Astrophysics Data System (ADS)

Yudin, V. I.; Taichenachev, A. V.; Basalaev, M. Yu.; Zanon-Willette, T.; Pollock, J. W.; Shuker, M.; Donley, E. A.; Kitching, J.

2018-05-01

When performing precision measurements, the quantity being measured is often perturbed by the measurement process itself. Such measurements include precision frequency measurements for atomic clock applications carried out with Ramsey spectroscopy. With the aim of eliminating probe-induced perturbations, a method of generalized autobalanced Ramsey spectroscopy (GABRS) is presented and rigorously substantiated. The usual local-oscillator frequency control loop is augmented with a second control loop derived from secondary Ramsey sequences interspersed with the primary sequences and with a different Ramsey period. This second loop feeds back to a secondary clock variable and ultimately compensates for the perturbation of the clock frequency caused by the measurements in the first loop. We show that such a two-loop scheme can lead to perfect compensation for measurement-induced light shifts and does not suffer from the effects of relaxation, time-dependent pulse fluctuations and phase-jump modulation errors that are typical of other hyper-Ramsey schemes. Several variants of GABRS are explored based on different secondary variables including added relative phase shifts between Ramsey pulses, external frequency-step compensation, and variable second-pulse duration. We demonstrate that a universal antisymmetric error signal, and hence perfect compensation at a finite modulation amplitude, is generated only if an additional frequency step applied during both Ramsey pulses is used as the concomitant variable parameter. This universal technique can be applied to the fields of atomic clocks, high-resolution molecular spectroscopy, magnetically induced and two-photon probing schemes, Ramsey-type mass spectrometry, and the field of precision measurements. Some variants of GABRS can also be applied for rf atomic clocks using coherent-population-trapping-based Ramsey spectroscopy of the two-photon dark resonance.

U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR OPERATION, CALIBRATION, AND MAINTENANCE OF THE PERKIN-ELMER ZEEMAN/5000 SYSTEM ATOMIC ABSORPTION SPECTROPHOTOMETER (BCO-L-6.0)

EPA Science Inventory

The purpose of this SOP is to outline the start-up, calibration, operation, and maintenance procedures for the Perkin-Elmer 5000 atomic absorption spectrophotometer (PE 5000 AA), and the Perkin Elmer 5000 Zeeman graphite furnace atomic absorption spectrophotometer (PE 5000Z GFAA)...

Interaction between Rashba and Zeeman effects in a quantum well channel.

PubMed

Choi, Won Young; Kwon, Jae Hyun; Chang, Joonyeon; Han, Suk Hee; Koo, Hyun Cheol

2014-05-01

The applied field induced Zeeman effect interferes with Rashba effect in a quantum well system. The angle dependence of Shubnikov-de Haas oscillation shows that the in-plane term of the applied field changes the intrinsic Rashba induced spin splitting. The total effective spin-orbit interaction parameter is determined by the vector sum of the Rashba field and the applied field.

Magnetic fluorescent lamp

DOEpatents

Berman, S.M.; Richardson R.W.

1983-12-29

The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly is enhanced by providing means for establishing a magnetic field with lines of force along the path of electron flow through the bulb of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

Ultra-stable clock laser system development towards space applications.

PubMed

Świerad, Dariusz; Häfner, Sebastian; Vogt, Stefan; Venon, Bertrand; Holleville, David; Bize, Sébastien; Kulosa, André; Bode, Sebastian; Singh, Yeshpal; Bongs, Kai; Rasel, Ernst Maria; Lodewyck, Jérôme; Le Targat, Rodolphe; Lisdat, Christian; Sterr, Uwe

2016-09-26

The increasing performance of optical lattice clocks has made them attractive for scientific applications in space and thus has pushed the development of their components including the interrogation lasers of the clock transitions towards being suitable for space, which amongst others requires making them more power efficient, radiation hardened, smaller, lighter as well as more mechanically stable. Here we present the development towards a space-compatible interrogation laser system for a strontium lattice clock constructed within the Space Optical Clock (SOC2) project where we have concentrated on mechanical rigidity and size. The laser reaches a fractional frequency instability of 7.9 × 10 -16 at 300 ms averaging time. The laser system uses a single extended cavity diode laser that gives enough power for interrogating the atoms, frequency comparison by a frequency comb and diagnostics. It includes fibre link stabilisation to the atomic package and to the comb. The optics module containing the laser has dimensions 60 × 45 × 8 cm 3 ; and the ultra-stable reference cavity used for frequency stabilisation with its vacuum system takes 30 × 30 × 30 cm 3 . The acceleration sensitivities in three orthogonal directions of the cavity are 3.6 × 10 -10 /g, 5.8 × 10 -10 /g and 3.1 × 10 -10 /g, where g ≈ 9.8 m/s 2 is the standard gravitational acceleration.

Libya: The Transition Clock

DTIC Science & Technology

2012-03-01

particularly important aspect will be the treat- ment of minorities such as the Berbers , who played an important role in the fighting apparently sup- ported by...will insist on the adoption of a strict inter- pretation of Shariah law, a position that led to Berber representatives walking out of at least one

THE HANLE AND ZEEMAN POLARIZATION SIGNALS OF THE SOLAR Ca II 8542 Å LINE

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

Štěpán, Jiri; Bueno, Javier Trujillo

We highlight the main results of a three-dimensional (3D) multilevel radiative transfer investigation about the solar disk-center polarization of the Ca ii 8542 Å line. First, through the use of a 3D model of the solar atmosphere, we investigate the linear polarization that occurs due to the atomic level polarization produced by the absorption and scattering of anisotropic radiation, taking into account the symmetry-breaking effects caused by its thermal, dynamic, and magnetic structure. Second, we study the contribution of the Zeeman effect to the linear and circular polarization. Finally, we show examples of the Stokes profiles produced by the jointmore » action of the atomic level polarization and the Hanle and Zeeman effects. We find that the Zeeman effect tends to dominate the linear polarization signals only in the localized patches of opposite magnetic polarity, where the magnetic field is relatively strong and slightly inclined; outside such very localized patches, the linear polarization is often dominated by the contribution of atomic level polarization. We demonstrate that a correct modeling of this last contribution requires taking into account the symmetry-breaking effects caused by the thermal, dynamic, and magnetic structure of the solar atmosphere, and that in the 3D model used the Hanle effect in forward-scattering geometry (disk-center observation) mainly reduces the polarization corresponding to the zero-field case. We emphasize that, in general, a reliable modeling of the linear polarization in the Ca ii 8542 Å line requires taking into account the joint action of atomic level polarization and the Hanle and Zeeman effects.« less

Considerations on the Design of a Molecular Frequency Standard Based on the Molecular Beam Electric Resonance Method

NASA Technical Reports Server (NTRS)

Hughes, Vernon W.

1959-01-01

The use of a rotational state transition as observed by the molecular beam electric resonance method is discussed as a possible frequency standard particularly in the millimeter wavelength range. As a promising example the 100 kMc transition between the J = 0 and J = 1 rotational states of Li 6F19 is considered. The relative insensitivity of the transition frequency to external electric and magnetic fields and the low microwave power requirements appear favorable; the small fraction of the molecular beam that is in a single rotational state is a limiting factor.

Dynamical manifestation of an evolving Berry phase as a frequency shift of the resonance transition between two eigenstates

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

Toriyama, Koichi; Oguchi, Akihide; Morinaga, Atsuo

2011-12-15

We investigate the phenomenon that a Berry phase evolving linearly in time induces a frequency shift of the resonance transition between two eigenstates, regardless of whether or not they are superposed. Using the magnetic-field-insensitive two-photon microwave--radio-frequency transition, which is free of any other dynamical frequency shift, we demonstrate that the frequency shift caused by a uniform rotation of the magnetic field corresponds to the derivative of the Berry phase with respect to time and depends on the direction of rotation of the magnetic field.

Tunable-φ Josephson junction with a quantum anomalous Hall insulator

NASA Astrophysics Data System (ADS)

Sakurai, Keimei; Ikegaya, Satoshi; Asano, Yasuhiro

2017-12-01

We theoretically study the Josephson current in a superconductor/quantum anomalous Hall insulator/superconductor junction by using the lattice Green function technique. When an in-plane external Zeeman field is applied to the quantum anomalous Hall insulator, the Josephson current J flows without a phase difference across the junction θ . The phase shift φ appearing in the current-phase relationship J ∝sin(θ -φ ) is proportional to the amplitude of Zeeman fields and depends on the direction of Zeeman fields. A phenomenological analysis of the Andreev reflection processes explains the physical origin of φ . In a quantum anomalous Hall insulator, time-reversal symmetry and mirror-reflection symmetry are broken simultaneously. However, magnetic mirror-reflection symmetry is preserved. Such characteristic symmetry properties enable us to have a tunable φ junction with a quantum Hall insulator.

Andreev spectrum with high spin-orbit interactions: Revealing spin splitting and topologically protected crossings

NASA Astrophysics Data System (ADS)

Murani, A.; Chepelianskii, A.; Guéron, S.; Bouchiat, H.

2017-10-01

In order to point out experimentally accessible signatures of spin-orbit interaction, we investigate numerically the Andreev spectrum of a multichannel mesoscopic quantum wire (N) with high spin-orbit interaction coupled to superconducting electrodes (S), contrasting topological and nontopological behaviors. In the nontopological case (square lattice with Rashba interactions), we find that the Kramers degeneracy of Andreev levels is lifted by a phase difference between the S reservoirs except at multiples of π , when the normal quantum wires can host several conduction channels. The level crossings at these points invariant by time-reversal symmetry are not lifted by disorder. Whereas the dc Josephson current is insensitive to these level crossings, the high-frequency admittance (susceptibility) at finite temperature reveals these level crossings and the lifting of their degeneracy at π by a small Zeeman field. We have also investigated the hexagonal lattice with intrinsic spin-orbit interaction in the range of parameters where it is a two-dimensional topological insulator with one-dimensional helical edges protected against disorder. Nontopological superconducting contacts can induce topological superconductivity in this system characterized by zero-energy level crossing of Andreev levels. Both Josephson current and finite-frequency admittance carry then very specific signatures at low temperature of this disorder-protected Andreev level crossing at π and zero energy.

One and two-phonon processes of the spin-flip relaxation in quantum dots: Spin-phonon coupling mechanism

NASA Astrophysics Data System (ADS)

Wang, Zi-Wu; Li, Shu-Shen

2012-07-01

We investigate the spin-flip relaxation in quantum dots using a non-radiation transition approach based on the descriptions for the electron-phonon deformation potential and Fröhlich interaction in the Pavlov-Firsov spin-phonon Hamiltonian. We give the comparisons of the electron relaxations with and without spin-flip assisted by one and two-phonon processes. Calculations are performed for the dependence of the relaxation time on the external magnetic field, the temperature and the energy separation between the Zeeman sublevels of the ground and first-excited state. We find that the electron relaxation time of the spin-flip process is more longer by three orders of magnitudes than that of no spin-flip process.

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the A7Π- X7Σ + transition of manganese monohydride, MnH

NASA Astrophysics Data System (ADS)

Gengler, Jamie J.; Steimle, Timothy C.; Harrison, Jeremy J.; Brown, John M.

2007-02-01

High-resolution (±0.003 cm -1), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm -1 region of the (0, 0) band of the A7Π- X7Σ + system. The low- N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low- N rotational level using a traditional 'effective' Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.

Pulse Double-Resonance EPR Techniques for the Study of Metallobiomolecules.

PubMed

Cox, Nicholas; Nalepa, Anna; Pandelia, Maria-Eirini; Lubitz, Wolfgang; Savitsky, Anton

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy exploits an intrinsic property of matter, namely the electron spin and its related magnetic moment. This can be oriented in a magnetic field and thus, in the classical limit, acts like a little bar magnet. Its moment will align either parallel or antiparallel to the field, giving rise to different energies (termed Zeeman splitting). Transitions between these two quantized states can be driven by incident microwave frequency radiation, analogous to NMR experiments, where radiofrequency radiation is used. However, the electron Zeeman interaction alone provides only limited information. Instead, much of the usefulness of EPR is derived from the fact that the electron spin also interacts with its local magnetic environment and thus can be used to probe structure via detection of nearby spins, e.g., NMR-active magnetic nuclei and/or other electron spin(s). The latter is exploited in spin labeling techniques, an exciting new area in the development of noncrystallographic protein structure determination. Although these interactions are often smaller than the linewidth of the EPR experiment, sophisticated pulse EPR methods allow their detection. A number of such techniques are well established today and can be broadly described as double-resonance methods, in which the electron spin is used as a reporter. Below we give a brief description of pulse EPR methods, particularly their implementation at higher magnetic fields, and how to best exploit them for studying metallobiomolecules. © 2015 Elsevier Inc. All rights reserved.

An optical and magnetic resonance study of point defects in silicon, diamond, and aluminum nitride

NASA Astrophysics Data System (ADS)

Mason, Philip Wayne

1998-12-01

Optical and magnetic resonance studies of point defects in silicon, diamond, and aluminum nitride semiconducting crystals are described in this dissertation. In silicon, an optically detected magnetic resonance (ODMR) study of a sulfur-related defect with two stable configurations, Ssb{A} and Ssb{B}, each with its own photoluminescence (PL) band and associated ODMR spectrum, is discussed. Through ODMR and related linear polarization studies, the Ssb{A} configuration is conclusively determined to have Csb1 (triclinic) symmetry (which is also the tentative finding for Ssb{B}), a controversial issue in the literature. A conversion study comparing the PL and PLODMR shows a one-to-one conversion between the two configurations for each type of signal. Related findings also tentatively suggest that the Ssb{B} configuration is metastable in both the neutral and single positive charge states of the defect. In addition, an independent analysis presented of uniaxial stress data obtained at King's College, London, shows evidence that an inverted energy-level ordering of the excited electronic effective mass states (Asb1 above E) explains the data better than the opposite ordering which is usually observed for effective mass systems. The mechanism responsible for inversion is currently not known. In diamond, a 1.4 eV Ni-related band with very sharp zero-phonon lines is studied using magnetic circular dichroism in absorption (MCDA). A tunable laser was used to directly measure circular polarization properties of transitions between individual Zeeman-split spin states. The Zeeman study also provided a determination of their associated g-values. A comparison with a theoretical model involving intra-d-shell transitions of Ni indicates that a transition from a ground state of Gammasb{5,6}(sp2E) symmetry to a Gammasb4(sp2Asb1) excited state explains the experimental MCDA findings and agrees with results from a previous uniaxial stress polarization study of luminescence associated with the same transition. Finally, a PLODMR study of several aluminum nitride crystals is also presented. The crystals were observed to emit a broad PL band comprised of numerous overlapping bands, each with its own signature ODMR signal. These new spectra include four effective spin S = 1 centers and a pair of S = 1/2 centers exhibiting characteristics expected for distant-pair recombinations. Two recombination models, either of which may explain a pair of S = 1 centers that appear to be related, are discussed.

Polarization-induced interference within electromagnetically induced transparency for atoms of double-V linkage

NASA Astrophysics Data System (ADS)

Sun, Yuan; Liu, Chang; Chen, Ping-Xing; Liu, Liang

2018-02-01

People have been paying attention to the role of atoms' complex internal level structures in the research of electromagnetically induced transparency (EIT) for a long time, where the various degenerate Zeeman levels usually generate complex linkage patterns for the atomic transitions. It turns out, with special choices of the atomic states and the atomic transitions' linkage structure, clear signatures of quantum interference induced by the probe and coupling light's polarizations can emerge from a typical EIT phenomena. We propose to study a four-state system with double-V linkage pattern for the transitions and analyze the polarization-induced interference under the EIT condition. We show that such interference arises naturally under mild conditions on the optical field and atom manipulation techniques. Moreover, we construct a variation form of double-M linkage pattern where the polarization-induced interference enables polarization-dependent cross modulation between incident weak lights that can be effective even at the few-photon level. The theme is to gain more insight into the essential question: how can we build a nontrivial optical medium where incident lights experience polarization-dependent nonlinear optical interactions, valid for a wide range of incidence intensities down to the few-photon level?

Room temperature broadband terahertz gains in graphene heterostructures based on inter-layer radiative transitions

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

Tang, Linlong; Chongqing institute of green and intelligent technology, Chinese Academy of Sciences, Chongqing, 401122; Du, Jinglei, E-mail: dujl@scu.edu.cn

We exploit inter-layer radiative transitions to provide gains to amplify terahertz waves in graphene heterostructures. This is achieved by properly doping graphene sheets and aligning their energy bands so that the processes of stimulated emissions can overwhelm absorptions. We derive an expression for the gain estimation and show the gain is insensitive to temperature variation. Moreover, the gain is broadband and can be strong enough to compensate the free carrier loss, indicating graphene based room temperature terahertz lasers are feasible.

Strategies and Initiatives in Acculturation: Voices from Ghana

ERIC Educational Resources Information Center

Boafo-Arthur, Susan; Attah, Dzifa A.; Boafo-Arthur, Ama; Akoensi, Thomas D.

2017-01-01

Culture shock and acculturation are salient aspects of any international study trip. Over the years, many institutions have devised several strategies to help international students transition to life in the host country. However, most of these strategies are insensitive to diverse cultural or country specifics. Drawing from Social Learning…

All-digital phase-lock loops for noise-free signals

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Bit-synchronizers utilize all-digital phase-lock loops that are referenced to a high frequency digital clock. Phase-lock loop of first design acquires frequency within nominal range and tracks phase; second design is modified for random binary data by addition of simple transition detector; and third design acquires frequency over wide dynamic range.

Foraging at the Edge of Chaos: Internal Clock versus External Forcing

NASA Astrophysics Data System (ADS)

Nicolis, S. C.; Fernández, J.; Pérez-Penichet, C.; Noda, C.; Tejera, F.; Ramos, O.; Sumpter, D. J. T.; Altshuler, E.

2013-06-01

Activity rhythms in animal groups arise both from external changes in the environment, as well as from internal group dynamics. These cycles are reminiscent of physical and chemical systems with quasiperiodic and even chaotic behavior resulting from “autocatalytic” mechanisms. We use nonlinear differential equations to model how the coupling between the self-excitatory interactions of individuals and external forcing can produce four different types of activity rhythms: quasiperiodic, chaotic, phase locked, and displaying over or under shooting. At the transition between quasiperiodic and chaotic regimes, activity cycles are asymmetrical, with rapid activity increases and slower decreases and a phase shift between external forcing and activity. We find similar activity patterns in ant colonies in response to varying temperature during the day. Thus foraging ants operate in a region of quasiperiodicity close to a cascade of transitions leading to chaos. The model suggests that a wide range of temporal structures and irregularities seen in the activity of animal and human groups might be accounted for by the coupling between collectively generated internal clocks and external forcings.

Search for variation of fundamental constants and violations of fundamental symmetries using isotope comparisons

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

Berengut, J. C.; Flambaum, V. V.; Kava, E. M.

2011-10-15

Atomic microwave clocks based on hyperfine transitions, such as the caesium standard, tick with a frequency that is proportional to the magnetic moment of the nucleus. This magnetic moment varies strongly between isotopes of the same atom, while all atomic electron parameters remain the same. Therefore the comparison of two microwave clocks based on different isotopes of the same atom can be used to constrain variation of fundamental constants. In this paper, we calculate the neutron and proton contributions to the nuclear magnetic moments, as well as their sensitivity to any potential quark-mass variation, in a number of isotopes ofmore » experimental interest including {sup 201,199}Hg and {sup 87,85}Rb, where experiments are underway. We also include a brief treatment of the dependence of the hyperfine transitions to variation in nuclear radius, which in turn is proportional to any change in quark mass. Our calculations of expectation values of proton and neutron spin in nuclei are also needed to interpret measurements of violations of fundamental symmetries.« less

Magnetic fluorescent lamp having reduced ultraviolet self-absorption

DOEpatents

Berman, Samuel M.; Richardson, Robert W.

1985-01-01

The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly (10) is enhanced by providing means (30) for establishing a magnetic field with lines of force along the path of electron flow through the bulb (12) of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

Rashba sandwiches with topological superconducting phases

NASA Astrophysics Data System (ADS)

Volpez, Yanick; Loss, Daniel; Klinovaja, Jelena

2018-05-01

We introduce a versatile heterostructure harboring various topological superconducting phases characterized by the presence of helical, chiral, or unidirectional edge states. Changing parameters, such as an effective Zeeman field or chemical potential, one can tune between these three topological phases in the same setup. Our model relies only on conventional nontopological ingredients. The bilayer setup consists of an s -wave superconductor sandwiched between two two-dimensional electron gas layers with strong Rashba spin-orbit interaction. The interplay between two different pairing mechanisms, proximity induced direct and crossed Andreev superconducting pairings, gives rise to multiple topological phases. In particular, helical edge states occur if crossed Andreev superconducting pairing is dominant. In addition, an in-plane Zeeman field leads to a two-dimensional gapless topological phase with unidirectional edge states, which were previously predicted to exist only in noncentrosymmetric superconductors. If the Zeeman field is tilted out of the plane, the system is in a topological phase hosting chiral edge states.

Bogoliubov theory and Lee-Huang-Yang corrections in spin-1 and spin-2 Bose-Einstein condensates in the presence of the quadratic Zeeman effect

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

Uchino, Shun; Kobayashi, Michikazu; Ueda, Masahito

2010-06-15

We develop Bogoliubov theory of spin-1 and spin-2 Bose-Einstein condensates (BECs) in the presence of a quadratic Zeeman effect, and derive the Lee-Huang-Yang (LHY) corrections to the ground-state energy, pressure, sound velocity, and quantum depletion. We investigate all the phases of spin-1 and spin-2 BECs that can be realized experimentally. We also examine the stability of each phase against quantum fluctuations and the quadratic Zeeman effect. Furthermore, we discuss a relationship between the number of symmetry generators that are spontaneously broken and that of Nambu-Goldstone (NG) modes. It is found that in the spin-2 nematic phase there are special Bogoliubovmore » modes that have gapless linear dispersion relations but do not belong to the NG modes.« less

Zeeman Effect observations toward 36 GHz methanol masers in the Galactic Center

NASA Astrophysics Data System (ADS)

Potvin, Justin A.; Momjian, Emmanuel; Pratim Sarma, Anuj

2017-01-01

We present observations of 36 GHz Class I methanol masers taken with the Karl G. Jansky Very Large Array (VLA) in the B configuration with the aim of detecting the Zeeman Effect. We targeted several 36 GHz Class I methanol masers associated with supernova remnants (SNRs) toward the Galactic Center. Each source was observed in dual circular polarizations for three hours. The observed spectral profiles of the masers are complex, with several components blended in velocity. In only one case was the Stokes V maser profile prominent enough to reveal a 2-sigma hint of a magnetic field of zBlos = 14.56 +/- 5.60 Hz; we have chosen to express our results in terms of zBlos since the Zeeman splitting factor (z) for 36 GHz methanol masers has not been measured. There are several hints that these spectra would reveal significant magnetic fields if they could be spatially and spectrally resolved.

Progress Report on the Improved Linear Ion Trap Physics Package

NASA Technical Reports Server (NTRS)

Prestage, John D.

1995-01-01

This article describes the first operational results from the extended linear ion trap frequency standard now being developed at JPL. This new design separates the state selection/interrogation region from the more critical microwave resonance region where the multiplied local oscillator (LO) signal is compared to the stable atomic transition. Hg+ ions have been trapped, shuttled back and forth between the resonance and state selection traps. In addition, microwave transitions between the Hg+ clock levels have been driven in the resonance trap and detected in the state selection trap.

Frequency stability measurement of pulsed superradiance from strontium

NASA Astrophysics Data System (ADS)

Norcia, Matthew; Cline, Julia; Robinson, John; Ye, Jun; Thompson, James

2017-04-01

Superradiant laser light from an ultra-narrow optical transition holds promise as a next-generation of active frequency references. We have recently demonstrated pulsed lasing on the milliHertz linewidth clock transition in strontium. Here, we present the first frequency comparisons between such a superradiant source and a state of the art stable laser system. We characterize the stability of the superradiant system, and demonstrate a reduction in sensitivity to cavity frequency fluctuations of nearly five orders of magnitude compared to a conventional laser. DARPA QUASAR, NIST, NSF PFC.

Shock-to-detonation transition of RDX, HMX and NTO based composite high explosives: experiments and modelling

NASA Astrophysics Data System (ADS)

Baudin, G.; Roudot, M.; Genetier, M.; Mateille, P.; Lefrançois, A.

2014-05-01

HMX, RDX and NTO based cast-cured plastic bounded explosive (PBX) are widely used in insensitive ammunitions. Designing modern warheads needs robust and reliable models to compute shock ignition and detonation propagation inside PBX. Comparing to a pressed PBX, a cast-cured PBX is not porous and the hot-spots are mainly located at the grain-binder interface leading to a different burning behavior during shock-to-detonation transition. Here, we review the shock-to-detonation transition (SDT) and its modeling for cast-cured PBX containing HMX, RDX and NTO. Future direction is given in conclusion.

Applying Zeeman Doppler imaging to solar spectra

NASA Astrophysics Data System (ADS)

Hussain, G. A. J.; Saar, S. H.; Collier Cameron, A.

2004-03-01

A new generation of spectro-polarimeters with high throughput (e.g. CFHT/ESPADONS and LBT/PEPSI) is becoming available. This opportunity can be exploited using Zeeman Doppler imaging (ZDI), a technique that inverts time-series of Stokes V spectra to map stellar surface magnetic fields (Semel 1989). ZDI is assisted by ``Least squares deconvolution'' (LSD), which sums up the signal from 1000's of photospheric lines to produce a mean deconvolved profile with higher S:N (Donati & Collier Cameron 1997).

Sympathetic Cooling of Lattice Atoms by a Bose-Einstein Condensate

DTIC Science & Technology

2010-08-13

average out to zero net change in momentum. This type of cooling is the basis for techniques such as Zeeman slowing and Magneto - optical traps . On a...change in momentum. This type of cooling is the basis for techniques such as Zeeman slowing and Magneto - optical traps . On a more basic level, an excited...cause stimulated emission of a second excitation. A quantitative explanation requires the use of the density fluctuation operator . This operator

Polarized Line Formation in Arbitrary Strength Magnetic Fields Angle-averaged and Angle-dependent Partial Frequency Redistribution

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

Sampoorna, M.; Nagendra, K. N.; Stenflo, J. O., E-mail: sampoorna@iiap.res.in, E-mail: knn@iiap.res.in, E-mail: stenflo@astro.phys.ethz.ch

Magnetic fields in the solar atmosphere leave their fingerprints in the polarized spectrum of the Sun via the Hanle and Zeeman effects. While the Hanle and Zeeman effects dominate, respectively, in the weak and strong field regimes, both these effects jointly operate in the intermediate field strength regime. Therefore, it is necessary to solve the polarized line transfer equation, including the combined influence of Hanle and Zeeman effects. Furthermore, it is required to take into account the effects of partial frequency redistribution (PRD) in scattering when dealing with strong chromospheric lines with broad damping wings. In this paper, we presentmore » a numerical method to solve the problem of polarized PRD line formation in magnetic fields of arbitrary strength and orientation. This numerical method is based on the concept of operator perturbation. For our studies, we consider a two-level atom model without hyperfine structure and lower-level polarization. We compare the PRD idealization of angle-averaged Hanle–Zeeman redistribution matrices with the full treatment of angle-dependent PRD, to indicate when the idealized treatment is inadequate and what kind of polarization effects are specific to angle-dependent PRD. Because the angle-dependent treatment is presently computationally prohibitive when applied to realistic model atmospheres, we present the computed emergent Stokes profiles for a range of magnetic fields, with the assumption of an isothermal one-dimensional medium.« less

An adaptable dual species effusive source and Zeeman slower design demonstrated with Rb and Li

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

Bowden, William, E-mail: william.bowden@physics.ox.ac.uk; Gunton, Will; Semczuk, Mariusz

2016-04-15

We present a dual-species effusive source and Zeeman slower designed to produce slow atomic beams of two elements with a large mass difference and with very different oven temperature requirements. We demonstrate this design for the case of {sup 6}Li and {sup 85}Rb and achieve magneto-optical trap (MOT) loading rates equivalent to that reported in prior work on dual species (Rb+Li) Zeeman slowers operating at the same oven temperatures. Key design choices, including thermally separating the effusive sources and using a segmented coil design to enable computer control of the magnetic field profile, ensure that the apparatus can be easilymore » modified to slow other atomic species. By performing the final slowing using the quadrupole magnetic field of the MOT, we are able to shorten our Zeeman slower length making for a more compact system without compromising performance. We outline the construction and analyze the emission properties of our effusive sources. We also verify the performance of the source and slower, and we observe sequential loading rates of 12 × 10{sup 8} atoms/s for a Rb oven temperature of 140 °C and 1.1 × 10{sup 8} atoms/s for a Li reservoir at 460 °C, corresponding to reservoir lifetimes for continuous operation of 10 and 4 years, respectively.« less

Time synchronization via lunar radar.

NASA Technical Reports Server (NTRS)

Higa, W. H.

1972-01-01

The advent of round-trip radar measurements has permitted the determination of the ranges to the nearby planets with greater precision than was previously possible. When the distances to the planets are known with high precision, the propagation delay for electromagnetic waves reflected by the planets may be calculated and used to synchronize remotely located clocks. Details basic to the operation of a lunar radar indicate a capability for clock synchronization to plus or minus 20 microsec. One of the design goals for this system was to achieve a simple semiautomatic receiver for remotely located tracking stations. The lunar radar system is in operational use for deep space tracking at Jet Propulsion Laboratory and synchronizes five world-wide tracking stations with a master clock at Goldstone, Calif. Computers are programmed to correct the Goldstone transmissions for transit time delay and Doppler shifts so as to be received on time at the tracking stations; this dictates that only one station can be synchronized at a given time period and that the moon must be simultaneously visible to both the transmitter and receiver for a minimum time of 10 min.-

Signals from the brainstem sleep/wake centers regulate behavioral timing via the circadian clock.

PubMed

Abbott, Sabra M; Arnold, Jennifer M; Chang, Qing; Miao, Hai; Ota, Nobutoshi; Cecala, Christine; Gold, Paul E; Sweedler, Jonathan V; Gillette, Martha U

2013-01-01

Sleep-wake cycling is controlled by the complex interplay between two brain systems, one which controls vigilance state, regulating the transition between sleep and wake, and the other circadian, which communicates time-of-day. Together, they align sleep appropriately with energetic need and the day-night cycle. Neural circuits connect brain stem sites that regulate vigilance state with the suprachiasmatic nucleus (SCN), the master circadian clock, but the function of these connections has been unknown. Coupling discrete stimulation of pontine nuclei controlling vigilance state with analytical chemical measurements of intra-SCN microdialysates in mouse, we found significant neurotransmitter release at the SCN and, concomitantly, resetting of behavioral circadian rhythms. Depending upon stimulus conditions and time-of-day, SCN acetylcholine and/or glutamate levels were augmented and generated shifts of behavioral rhythms. These results establish modes of neurochemical communication from brain regions controlling vigilance state to the central circadian clock, with behavioral consequences. They suggest a basis for dynamic integration across brain systems that regulate vigilance states, and a potential vulnerability to altered communication in sleep disorders.

Ultrafast time scale X-rotation of cold atom storage qubit using Rubidium clock states

NASA Astrophysics Data System (ADS)

Song, Yunheung; Lee, Han-Gyeol; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2017-04-01

Ultrafast-time-scale optical interaction is a local operation on the electronic subspace of an atom, thus leaving its nuclear state intact. However, because atomic clock states are maximally entangled states of the electronic and nuclear degrees of freedom, their entire Hilbert space should be accessible only with local operations and classical communications (LOCC). Therefore, it may be possible to achieve hyperfine qubit gates only with electronic transitions. Here we show an experimental implementation of ultrafast X-rotation of atomic hyperfine qubits, in which an optical Rabi oscillation induces a geometric phase between the constituent fine-structure states, thus bringing about the X-rotation between the two ground hyperfine levels. In experiments, cold atoms in a magneto-optical trap were controlled with a femtosecond laser pulse from a Ti:sapphire laser amplifier. Absorption imaging of the as-controlled atoms initially in the ground hyperfine state manifested polarization dependence, strongly agreeing with the theory. The result indicates that single laser pulse implementations of THz clock speed qubit controls are feasible for atomic storage qubits. Samsung Science and Technology Foundation [SSTF-BA1301-12].

Prediction Error and Trace Dominance Determine the Fate of Fear Memories after Post-Training Manipulations

ERIC Educational Resources Information Center

Alfei, Joaquín M.; Monti, Roque I. Ferrer; Molina, Victor A.; Bueno, Adrián M.; Urcelay, Gonzalo P.

2015-01-01

Different mnemonic outcomes have been observed when associative memories are reactivated by CS exposure and followed by amnestics. These outcomes include mere retrieval, destabilization-reconsolidation, a transitional period (which is insensitive to amnestics), and extinction learning. However, little is known about the interaction between initial…

Compact, Highly Stable Ion Atomic Clock

NASA Technical Reports Server (NTRS)

Prestage, John

2008-01-01

A mercury-ion clock now at the breadboard stage of development (see figure) has a stability comparable to that of a hydrogen-maser clock: In tests, the clock exhibited an Allan deviation of between 2 x 10(exp -13) and 3 x 10(exp -13) at a measurement time of 1 second, averaging to about 10(exp -15) at 1 day. However, the clock occupies a volume of only about 2 liters . about a hundredth of the volume of a hydrogen-maser clock. The ion-handling parts of the apparatus are housed in a sealed vacuum tube, wherein only a getter pump is used to maintain the vacuum. Hence, this apparatus is a prototype of a generation of small, potentially portable high-precision clocks for diverse ground- and space-based navigation and radio science applications. Furthermore, this new ion-clock technology is about 100 times more stable and precise than the rubidium atomic clocks currently in use in the NAV STAR GPS Earth-orbiting satellites. In this clock, mercury ions are shuttled between a quadrupole and a 16-pole linear radio-frequency trap. In the quadrupole trap, the ions are tightly confined and optical state selection from a Hg-202 radio-frequency-discharge ultraviolet lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions resonant at frequency of about 40.507 GHz are interrogated by use of a microwave beam at that frequency. The trapping of ions effectively eliminates the frequency pulling caused by wall collisions inherent to gas-cell clocks. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave- resonance process, so that each of these processes can be optimized independently of the other. The basic ion-shuttling, two-trap scheme as described thus far is not new: it has been the basis of designs of prior larger clocks. The novelty of the present development lies in major redesigns of its physics package (the ion traps and the vacuum and optical subsystems) to effect the desired reduction of size to a volume of no more than a couple of liters. The redesign effort has included selection of materials for the vacuum tube, ion trap, and ultraviolet windows that withstand bakeout at a temperature of approx.450 C in preparation for sealing the tube to contain the vacuum. This part of the redesign effort follows the approach taken in the development of such other vacuum-tube electronic components as flight traveling- wave-tube amplifiers having operational and shelf lives as long as 15 years. The redesign effort has also included a thorough study of residual-gas-induced shifts of the ion-clock frequency and a study of alternative gases as candidates for use as a buffer gas within the sealed tube. It has been found that neon is more suitable than is helium, which has been traditionally used for this purpose, in that the pressure-induced frequency pulling by neon is between a third and a half of that of helium. In addition, because neon diffuses through solids much more slowly than does helium, the loss of neon by diffusion over the operational lifetime is expected to be negligible.

Absolute frequency measurement of the ? optical clock transition in ? with an uncertainty of ? using a frequency link to international atomic time

NASA Astrophysics Data System (ADS)

Baynham, Charles F. A.; Godun, Rachel M.; Jones, Jonathan M.; King, Steven A.; Nisbet-Jones, Peter B. R.; Baynes, Fred; Rolland, Antoine; Baird, Patrick E. G.; Bongs, Kai; Gill, Patrick; Margolis, Helen S.

2018-03-01

The highly forbidden ? electric octupole transition in ? is a potential candidate for a redefinition of the SI second. We present a measurement of the absolute frequency of this optical transition, performed using a frequency link to International Atomic Time to provide traceability to the SI second. The ? optical frequency standard was operated for 76% of a 25-day period, with the absolute frequency measured to be 642 121 496 772 645.14(26) Hz. The fractional uncertainty of ? is comparable to that of the best previously reported measurement, which was made by a direct comparison to local caesium primary frequency standards.

Temperature effects on the strainrange partitioning approach for creep-fatigue analysis

NASA Technical Reports Server (NTRS)

Halford, G. R.; Hirschberg, M. H.; Manson, S. S.

1972-01-01

Examination is made of the influence of temperature on the strainrange partitioning approach to creep-fatigue. Results for Cr-Mo steel and Type 316 stainless steel show the four partitioned strainrange-life relationships to be temperature insensitive to within a factor of two on cyclic life. Monotonic creep and tensile ductilities were also found to be temperature insensitive to within a factor of two. The approach provides bounds on cyclic life that can be readily established for any type of inelastic strain cycle. Continuous strain cycling results obtained over a broad range of high temperatures and frequencies are in excellent agreement with bounds provided by the approach. The observed transition from one bound to the other is also in good agreement with the approach.

SiN-assisted polarization-insensitive multicore fiber to silicon photonics interface

NASA Astrophysics Data System (ADS)

Poulopoulos, Giannis N.; Kalavrouziotis, Dimitrios; Mitchell, Paul; Macdonald, John R.; Bakopoulos, Paraskevas; Avramopoulos, Hercules

2015-06-01

We demonstrate a polarization-insensitive coupler interfacing multicore-fiber (MCF) to silicon waveguides. It comprises a 3D glass fanout transforming the circular MCF core-arrangement to linear and performing initial tapering, followed by a Spot-Size-Converter on the silicon chip. Glass waveguides are formed of multiple overlapped modification elements and appropriate offsetting thereof yields tapers with symmetric cross-section. The Spot-Size-Converter is an inverselytapered silicon waveguide with a tapered polymer overcladding where light is initially coupled, whereas phase-matching gradually shifts it towards the silicon core. Co-design of the glass fanout and Spot-Size-Converter obtains theoretical loss below 1dB for the overall Si-to-MCF transition in both polarizations.

Systematic optimization of laser cooling of dysprosium

NASA Astrophysics Data System (ADS)

Mühlbauer, Florian; Petersen, Niels; Baumgärtner, Carina; Maske, Lena; Windpassinger, Patrick

2018-06-01

We report on an apparatus for cooling and trapping of neutral dysprosium. We characterize and optimize the performance of our Zeeman slower and 2D molasses cooling of the atomic beam by means of Doppler spectroscopy on a 136 kHz broad transition at 626 nm. Furthermore, we demonstrate the characterization and optimization procedure for the loading phase of a magneto-optical trap (MOT) by increasing the effective laser linewidth by sideband modulation. After optimization of the MOT compression phase, we cool and trap up to 10^9 atoms within 3 seconds in the MOT at temperatures of 9 μK and phase space densities of 1.7 \\cdot 10^{-5}, which constitutes an ideal starting point for loading the atoms into an optical dipole trap and for subsequent forced evaporative cooling.

Definition of Shifts of Optical Transitions Frequencies due to Pulse Perturbation Action by the Photon Echo Signal Form

NASA Astrophysics Data System (ADS)

Lisin, V. N.; Shegeda, A. M.; Samartsev, V. V.

2015-09-01

A relative phase shift between the different groups of excited dipoles, which appears as result of its frequency splitting due to action of a pulse of electric or magnetic fields, depends on a time, if the pulse overlaps in time with echo-pulse. As а consequence, the echo waveform is changed. The echo time form is modulated. The inverse modulation period well enough approximates Zeeman and pseudo-Stark splitting in the cases of magnetic and, therefore, electrical fields. Thus the g-factors of ground 4I15/2 and excited 4F9/2 optical states of Er3+ ion in LuLiF4 and YLiF4 have been measured and pseudo-Stark shift of R1 line in ruby has been determined.

Direct observation of the orbital spin Kondo effect in gallium arsenide quantum dots

NASA Astrophysics Data System (ADS)

Shang, Ru-Nan; Zhang, Ting; Cao, Gang; Li, Hai-Ou; Xiao, Ming; Guo, Guang-Can; Guo, Guo-Ping

2018-02-01

Besides the spin Kondo effect, other degrees of freedom can give rise to the pseudospin Kondo effect. We report a direct observation of the orbital spin Kondo effect in a series-coupled gallium arsenide (GaAs) double quantum dot device where orbital degrees act as pseudospin. Electron occupation in both dots induces a pseudospin Kondo effect. In a region of one net spin impurity, complete spectra with three resonance peaks are observed. Furthermore, we observe a pseudo-Zeeman effect and demonstrate its electrical controllability for the artificial pseudospin in this orbital spin Kondo process via gate voltage control. The fourfold degeneracy point is realized at a specific value supplemented by spin degeneracy, indicating a transition from the SU(2) to the SU(4) Kondo effect.

Magneto-optical trap for thulium atoms

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

Sukachev, D.; Sokolov, A.; Chebakov, K.

2010-07-15

Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410 nm with a small branching ratio. We trap up to 7x10{sup 4} atoms at a temperature of 0.8(2) mK after deceleration in a 40-cm-long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the magneto-optical trap which varies between 0.3 and 1.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6) s{sup -1}. The repumping laser transferring the atomic population out of the F=3 hyperfine ground-state sublevel gives amore » 30% increase for the lifetime and the number of atoms in the trap.« less

Mercury Pollution Exploration in Latvia with High-Sensitivity Zeeman Atomic Absorption Spectrometry

NASA Astrophysics Data System (ADS)

Bogans, Egils; Gavare, Zanda; Svagere, Anda; Poikane, Rita; Skudra, Jānis

2011-01-01

This research presents Hg pollution measurements performed in Latvia with sensitive method using Zeeman AAS analyzer RA-915+ and necessary attachments. Air in Riga city and water samples from a number of rivers and lakes of Latvia were analyzed for presence of low-level Hg concentrations. Ombrotrophic bog peat was analyzed to get insight into long-term trends. Environment in the sites sampled is relatively clean according to the results obtained, but there are local spots of pollution.

Magnetic-field induced quantum critical points of valence transition in Ce- and Yb-based heavy fermions

NASA Astrophysics Data System (ADS)

Watanabe, Shinji; Tsuruta, Atsushi; Miyake, Kazumasa; Flouquet, Jacques

2009-03-01

Valence instability and its critical fluctuations have attracted much attention recently in the heavy-electron systems. Valence fluctuations are essentially charge fluctuations, and it is highly non-trivial how the quantum critical point (QCP) as well as the critical end point is controlled by the magnetic field. To clarify this fundamental issue, we have studied the mechanism of how the critical points of the first-order valence transitions are controlled by the magnetic field [1]. We show that the critical temperature is suppressed to be the QCP by the magnetic field and unexpectedly the QCP exhibits nonmonotonic field dependence in the ground-state phase diagram, giving rise to emergence of metamagnetism even in the intermediate valence-crossover regime. The driving force of the field-induced QCP is clarified to be a cooperative phenomenon of Zeeman effect and Kondo effect, which creates a distinct energy scale from the Kondo temperature. This mechanism explains a peculiar magnetic response in CeIrIn5 and metamagnetic transition in YbXCu4 for X=In as well as a sharp contrast between X=Ag and Cd. We present the novel phenomena under the magnetic field to discuss significance of the proximity of the critical points of the first-order valence transition. [1] S. Watanabe et al. PRL100, (2008) 236401.

Collective atomic scattering and motional effects in a dense coherent medium

PubMed Central

Bromley, S. L.; Zhu, B.; Bishof, M.; Zhang, X.; Bothwell, T.; Schachenmayer, J.; Nicholson, T. L.; Kaiser, R.; Yelin, S. F.; Lukin, M. D.; Rey, A. M.; Ye, J.

2016-01-01

We investigate collective emission from coherently driven ultracold 88Sr atoms. We perform two sets of experiments using a strong and weak transition that are insensitive and sensitive, respectively, to atomic motion at 1 μK. We observe highly directional forward emission with a peak intensity that is enhanced, for the strong transition, by >103 compared with that in the transverse direction. This is accompanied by substantial broadening of spectral lines. For the weak transition, the forward enhancement is substantially reduced due to motion. Meanwhile, a density-dependent frequency shift of the weak transition (∼10% of the natural linewidth) is observed. In contrast, this shift is suppressed to <1% of the natural linewidth for the strong transition. Along the transverse direction, we observe strong polarization dependences of the fluorescence intensity and line broadening for both transitions. The measurements are reproduced with a theoretical model treating the atoms as coherent, interacting radiating dipoles. PMID:26984643

Sub-mm Scale Fiber Guided Deep/Vacuum Ultra-Violet Optical Source for Trapped Mercury Ion Clocks

NASA Technical Reports Server (NTRS)

Yi, Lin; Burt, Eric A.; Huang, Shouhua; Tjoelker, Robert L.

2013-01-01

We demonstrate the functionality of a mercury capillary lamp with a diameter in the sub-mm range and deep ultraviolet (DUV)/ vacuum ultraviolet (VUV) radiation delivery via an optical fiber integrated with the capillary. DUV spectrum control is observed by varying the fabrication parameters such as buffer gas type and pressure, capillary diameter, electrical resonator design, and temperature. We also show spectroscopic data of the 199Hg+ hyper-fine transition at 40.5GHz when applying the above fiber optical design. We present efforts toward micro-plasma generation in hollow-core photonic crystal fiber with related optical design and theoretical estimations. This new approach towards a more practical DUV optical interface could benefit trapped ion clock developments for future ultra-stable frequency reference and time-keeping applications.

Modeling a synthetic multicellular clock: repressilators coupled by quorum sensing.

PubMed

Garcia-Ojalvo, Jordi; Elowitz, Michael B; Strogatz, Steven H

2004-07-27

Diverse biochemical rhythms are generated by thousands of cellular oscillators that somehow manage to operate synchronously. In fields ranging from circadian biology to endocrinology, it remains an exciting challenge to understand how collective rhythms emerge in multicellular structures. Using mathematical and computational modeling, we study the effect of coupling through intercell signaling in a population of Escherichia coli cells expressing a synthetic biological clock. Our results predict that a diverse and noisy community of such genetic oscillators interacting through a quorum-sensing mechanism should self-synchronize in a robust way, leading to a substantially improved global rhythmicity in the system. As such, the particular system of coupled genetic oscillators considered here might be a good candidate to provide the first quantitative example of a synchronization transition in a population of biological oscillators.

Modeling a synthetic multicellular clock: Repressilators coupled by quorum sensing

NASA Astrophysics Data System (ADS)

Garcia-Ojalvo, Jordi; Elowitz, Michael B.; Strogatz, Steven H.

2004-07-01

Diverse biochemical rhythms are generated by thousands of cellular oscillators that somehow manage to operate synchronously. In fields ranging from circadian biology to endocrinology, it remains an exciting challenge to understand how collective rhythms emerge in multicellular structures. Using mathematical and computational modeling, we study the effect of coupling through intercell signaling in a population of Escherichia coli cells expressing a synthetic biological clock. Our results predict that a diverse and noisy community of such genetic oscillators interacting through a quorum-sensing mechanism should self-synchronize in a robust way, leading to a substantially improved global rhythmicity in the system. As such, the particular system of coupled genetic oscillators considered here might be a good candidate to provide the first quantitative example of a synchronization transition in a population of biological oscillators.

Spectroscopy of 171Yb in an optical lattice based on laser linewidth transfer using a narrow linewidth frequency comb.

PubMed

Inaba, Hajime; Hosaka, Kazumoto; Yasuda, Masami; Nakajima, Yoshiaki; Iwakuni, Kana; Akamatsu, Daisuke; Okubo, Sho; Kohno, Takuya; Onae, Atsushi; Hong, Feng-Lei

2013-04-08

We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization. Laser frequency characteristics such as spectral linewidth and frequency stability are transferred to the 578-nm slave laser from the 1064-nm master laser. Using the slave laser, we have succeeded in observing the clock transition of (171)Yb atoms confined in an optical lattice with a 20-Hz spectral linewidth.

Stability improvement of an operational two-way satellite time and frequency transfer system

NASA Astrophysics Data System (ADS)

Huang, Yi-Jiun; Fujieda, Miho; Takiguchi, Hiroshi; Tseng, Wen-Hung; Tsao, Hen-Wai

2016-04-01

To keep national time accurately coherent with coordinated universal time, many national metrology institutes (NMIs) use two-way satellite time and frequency transfer (TWSTFT) to continuously measure the time difference with other NMIs over an international baseline. Some NMIs have ultra-stable clocks with stability better than 10-16. However, current operational TWSTFT can only provide frequency uncertainty of 10-15 and time uncertainty of 1 ns, which is inadequate. The uncertainty is dominated by the short-term stability and the diurnals, i.e. the measurement variation with a period of one day. The aim of this work is to improve the stability of operational TWSTFT systems without additional transmission, bandwidth or increase in signal power. A software-defined receiver (SDR) comprising a high-resolution correlator and successive interference cancellation associated with open-loop configuration as the TWSTFT receiver reduces the time deviation from 140 ps to 73 ps at averaging time of 1 h, and occasionally suppresses diurnals. To study the source of the diurnals, TWSTFT is performed using a 2  ×  2 earth station (ES) array. Consequently, some ESs sensitive to temperature variation are identified, and the diurnals are significantly reduced by employing insensitive ESs. Hence, the operational TWSTFT using the proposed SDR with insensitive ESs achieves time deviation to 41 ps at 1 h, and 80 ps for averaging times from 1 h to 20 h.

Suppression of the Nonlinear Zeeman Effect and Heading Error in Earth-Field-Range Alkali-Vapor Magnetometers.

PubMed

Bao, Guzhi; Wickenbrock, Arne; Rochester, Simon; Zhang, Weiping; Budker, Dmitry

2018-01-19

The nonlinear Zeeman effect can induce splitting and asymmetries of magnetic-resonance lines in the geophysical magnetic-field range. This is a major source of "heading error" for scalar atomic magnetometers. We demonstrate a method to suppress the nonlinear Zeeman effect and heading error based on spin locking. In an all-optical synchronously pumped magnetometer with separate pump and probe beams, we apply a radio-frequency field which is in phase with the precessing magnetization. This results in the collapse of the multicomponent asymmetric magnetic-resonance line with ∼100  Hz width in the Earth-field range into a single peak with a width of 22 Hz, whose position is largely independent of the orientation of the sensor within a range of orientation angles. The technique is expected to be broadly applicable in practical magnetometry, potentially boosting the sensitivity and accuracy of Earth-surveying magnetometers by increasing the magnetic-resonance amplitude, decreasing its width, and removing the important and limiting heading-error systematic.

VLA HI Zeeman Observations of the Cygnus X Region: DR 22 And ON 2

NASA Astrophysics Data System (ADS)

Mayo, Elizabeth A.; Troland, T. H.

2010-01-01

The Very Large Array in Socorro, New Mexico has been used to study the Zeeman Effect in the 21cm HI line seen in absorption against radio sources in the Cygnus X region. Cygnus X is geometrically favorable for Zeeman effect observations as the region lies along the mean field direction of the diffuse interstellar medium (ISM) of the galaxy. We present observations of two compact HII regions within Cygnus X, DR 22 and ON 2. The data show magnetic field strengths of the order -80 μG toward DR 22 alone with no significant detections toward ON 2. This information is used to estimate the magnetic energy of the DR 22 star-forming cloud, and allows for a complete analysis of the energetics of the region revealing the role of the magnetic field. Support for this work was provided by the NSF PAARE program to South Carolina State University under award AST-0750814.

Doppler-Zeeman mapping of the magnetic CP star HD 215441

NASA Astrophysics Data System (ADS)

Khokhlova, V. L.; Vasilchenko, D. V.; Stepanov, V. V.; Tsymbal, V. V.

1997-07-01

The method of Vasilchenko et al. (1996) is used to obtain a Doppler-Zeeman map of the magnetic CP star HD 215441. The magnetic field is approximated by a magnetic dipole that is arbitrarily shifted from the star center. The solution of the inverse problem yields the dipole parameters and the maps of Si, Ti, Cr, and Fe abundance anomalies; the coordinates of local magnetic vectors on the star surface are computed. A comparison of the distribution of abundance anomalies and the magnetic-field configuration reveals that in the region where the magnetic-field lines are vertical (near the magnetic pole), Si, Ti and Cr are highly deficient, while the Fe enhancement is strongest. In the regions where the magnetic-field lines are horizontal (near the magnetic equator), Si, Ti and Cr show the greatest overabundance. In these regions, the Fe abundance is also slightly enhanced and exhibits, as it were, a secondary maximum. The factors that limit the accuracy of Doppler-Zeeman mapping are reviewed.

Entanglement entropy and entanglement spectrum of triplet topological superconductors.

PubMed

Oliveira, T P; Ribeiro, P; Sacramento, P D

2014-10-22

We analyze the entanglement entropy properties of a 2D p-wave superconductor with Rashba spin-orbit coupling, which displays a rich phase-space that supports non-trivial topological phases, as the chemical potential and the Zeeman term are varied. We show that the entanglement entropy and its derivatives clearly signal the topological transitions and we find numerical evidence that for this model the derivative with respect to the magnetization provides a sensible signature of each topological phase. Following the area law for the entanglement entropy, we systematically analyze the contributions that are proportional to or independent of the perimeter of the system, as a function of the Hamiltonian coupling constants and the geometry of the finite subsystem. For this model, we show that even though the topological entanglement entropy vanishes, it signals the topological phase transitions in a finite system. We also observe a relationship between a topological contribution to the entanglement entropy in a half-cylinder geometry and the number of edge states, and that the entanglement spectrum has robust modes associated with each edge state, as in other topological systems.

Route to the Smallest Doped Semiconductor: Mn(2+)-Doped (CdSe)13 Clusters.

PubMed

Yang, Jiwoong; Fainblat, Rachel; Kwon, Soon Gu; Muckel, Franziska; Yu, Jung Ho; Terlinden, Hendrik; Kim, Byung Hyo; Iavarone, Dino; Choi, Moon Kee; Kim, In Young; Park, Inchul; Hong, Hyo-Ki; Lee, Jihwa; Son, Jae Sung; Lee, Zonghoon; Kang, Kisuk; Hwang, Seong-Ju; Bacher, Gerd; Hyeon, Taeghwan

2015-10-14

Doping semiconductor nanocrystals with magnetic transition-metal ions has attracted fundamental interest to obtain a nanoscale dilute magnetic semiconductor, which has unique spin exchange interaction between magnetic spin and exciton. So far, the study on the doped semiconductor NCs has usually been conducted with NCs with larger than 2 nm because of synthetic challenges. Herein, we report the synthesis and characterization of Mn(2+)-doped (CdSe)13 clusters, the smallest doped semiconductors. In this study, single-sized doped clusters are produced in large scale. Despite their small size, these clusters have semiconductor band structure instead of that of molecules. Surprisingly, the clusters show multiple excitonic transitions with different magneto-optical activities, which can be attributed to the fine structure splitting. Magneto-optically active states exhibit giant Zeeman splittings up to elevated temperatures (128 K) with large g-factors of 81(±8) at 4 K. Our results present a new synthetic method for doped clusters and facilitate the understanding of doped semiconductor at the boundary of molecules and quantum nanostructure.

Magnetization processes and existence of reentrant phase transitions in coupled spin-electron model on doubly decorated planar lattices

NASA Astrophysics Data System (ADS)

Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej

2018-04-01

An alternative model for a description of magnetization processes in coupled 2D spin-electron systems has been introduced and rigorously examined using the generalized decoration-iteration transformation and the corner transfer matrix renormalization group method. The model consists of localized Ising spins placed on nodal lattice sites and mobile electrons delocalized over the pairs of decorating sites. It takes into account a hopping term for mobile electrons, the Ising coupling between mobile electrons and localized spins as well as the Zeeman term acting on both types of particles. The ground-state and finite-temperature phase diagrams were established and comprehensively analyzed. It was found that the ground-state phase diagrams are very rich depending on the electron hopping and applied magnetic field. The diversity of magnetization curves can be related to intermediate magnetization plateaus, which may be continuously tuned through the density of mobile electrons. In addition, the existence of several types of reentrant phase transitions driven either by temperature or magnetic field was proven.

Zeeman perturbed nuclear quadrupole spin echo envelope modulations for spin 3/2 nuclei in polycrystalline specimens

NASA Astrophysics Data System (ADS)

Ramachandran, R.; Narasimhan, P. T.

The results of theoretical and experimental studies of Zeeman-perturbed nuclear quadrupole spin echo envelope modulations (ZSEEM) for spin 3/2 nuclei in polycrystalline specimens are presented. The response of the Zeeman-perturbed spin ensemble to resonant two pulse excitations has been calculated using the density matrix formalism. The theoretical calculation assumes a parallel orientation of the external r.f. and static Zeeman fields and an arbitrary orientation of these fields to the principal axes system of the electric field gradient. A numerical powder averaging procedure has been adopted to simulate the response of the polycrystalline specimens. Using a coherent pulsed nuclear quadrupole resonance spectrometer the ZSEEM patterns of the 35Cl nuclei have been recorded in polycrystalline specimens of potassium chlorate, barium chlorate, mercuric chloride (two sites) and antimony trichloride (two sites) using the π/2-τ-π/2 sequence. The theoretical and experimental ZSEEM patterns have been compared. In the case of mercuric chloride, the experimental 35Cl ZSEEM patterns are found to be nearly identical for the two sites and correspond to a near-zero value of the asymmetry parameter, η, of the electric field gradient tensor. The difference in the η values for the two 35Cl sites (η ˜0·06 and η˜0·16) in antimony trichloride is clearly reflected in the experimental and theoretical ZSEEM patterns. The present study indicates the feasibility of evaluating η for spin 3/2 nuclei in polycrystalline specimens from ZSEEM investigations.

Influence of the photon orbital angular momentum on electric dipole transitions: negative experimental evidence.

PubMed

Giammanco, F; Perona, A; Marsili, P; Conti, F; Fidecaro, F; Gozzini, S; Lucchesini, A

2017-01-15

We describe an experiment of atomic spectroscopy devoted to ascertaining whether the orbital angular momentum (OAM) of photons has the same property of interacting with atoms or molecules as occurs for the spin angular momentum (SAM). In our experiment, rubidium vapors are excited by means of laser radiation with different combinations of OAM and SAM, particularly selected to inhibit or enhance the fluorescence according to the selection rules for the electric dipole transitions between the fundamental state and the first excited doublet. Our results clearly show that an electric-dipole-type transition is insensitive to the OAM value, and provide an original validation of a problem long debated in theoretical works.

14-3-3 σ Expression Effects G2/M Response to Oxygen and Correlates with Ovarian Cancer Metastasis

PubMed Central

Ravi, Dashnamoorthy; Chen, Yidong; Karia, Bijal; Brown, Adam; Gu, Ting Ting; Li, Jie; Carey, Mark S.; Hennessy, Bryan T.; Bishop, Alexander J. R.

2011-01-01

Background In vitro cell culture experiments with primary cells have reported that cell proliferation is retarded in the presence of ambient compared to physiological O2 levels. Cancer is primarily a disease of aberrant cell proliferation, therefore, studying cancer cells grown under ambient O2 may be undesirable. To understand better the impact of O2 on the propagation of cancer cells in vitro, we compared the growth potential of a panel of ovarian cancer cell lines under ambient (21%) or physiological (3%) O2. Principal Findings Our observations demonstrate that similar to primary cells, many cancer cells maintain an inherent sensitivity to O2, but some display insensitivity to changes in O2 concentration. Further analysis revealed an association between defective G2/M cell cycle transition regulation and O2 insensitivity resultant from overexpression of 14-3-3 σ. Targeting 14-3-3 σ overexpression with RNAi restored O2 sensitivity in these cell lines. Additionally, we found that metastatic ovarian tumors frequently overexpress 14-3-3 σ, which in conjunction with phosphorylated RB, results in poor prognosis. Conclusions Cancer cells show differential proliferative sensitivity to changes in O2 concentration. Although a direct link between O2 insensitivity and metastasis was not determined, this investigation showed that an O2 insensitive phenotype in cancer cells to correlate with metastatic tumor progression. PMID:21249227

A permeability transition in liver mitochondria and liposomes induced by α,ω-dioic acids and Ca(2+).

PubMed

Dubinin, Mikhail V; Samartsev, Victor N; Astashev, Maxim E; Kazakov, Alexey S; Belosludtsev, Konstantin N

2014-11-01

The article examines the molecular mechanism of the Ca(2+)-dependent cyclosporin A (CsA)-insensitive permeability transition in rat liver mitochondria induced by α,ω-dioic acids. The addition of α,ω-hexadecanedioic acid (HDA) to Ca(2+)-loaded liver mitochondria was shown to induce a high-amplitude swelling of the organelles, a drop of membrane potential and the release of Ca(2+) from the matrix, the effects being insensitive to CsA. The experiments with liposomes loaded with sulforhodamine B (SRB) revealed that, like palmitic acid (PA), HDA was able to cause permeabilization of liposomal membranes. However, the kinetics of HDA- and PA-induced release of SRB from liposomes was different, and HDA was less effective than PA in the induction of SRB release. Using the method of ultrasound interferometry, we also showed that the addition of Ca(2+) to HDA-containing liposomes did not change the phase state of liposomal membranes-in contrast to what was observed when Ca(2+) was added to PA-containing vesicles. It was suggested that HDA/Ca(2+)- and PA/Ca(2+)-induced permeability transition occurs by different mechanisms. Using the method of dynamic light scattering, we further revealed that the addition of Ca(2+) to HDA-containing liposomes induced their aggregation/fusion. Apparently, these processes result in a partial release of SRB due to the formation of fusion pores. The possibility that this mechanism underlies the HDA/Ca(2+)-induced permeability transition of the mitochondrial membrane is discussed.

Physics of the infrared spectrum

NASA Technical Reports Server (NTRS)

Deming, Drake; Jennings, Donald E.; Jefferies, John; Lindsey, Charles

1991-01-01

The IR bandpass is attractive for solar magnetic field studies in virtue of the proportionality to wavelength of the ratio of Zeeman splitting to line width. The large Zeeman splitting and optical thinness of the 12-micron observations render them especially useful for vector magnetic field derivations. The IR continuum, and many IR spectral lines, are formed in LTE and are useful in studies of the temperature structure of the solar atmosphere from the deepest observable photospheric layers to chromospheric altitudes. The far-IR continuum is an excellent thermometer for the upper photosphere and chromosphere.

Nonadiabatic effects in ultracold molecules via anomalous linear and quadratic Zeeman shifts.

PubMed

McGuyer, B H; Osborn, C B; McDonald, M; Reinaudi, G; Skomorowski, W; Moszynski, R; Zelevinsky, T

2013-12-13

Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold 88Sr2 molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite f-parity states and exhibit fourth-order corrections, providing a stringent test of a state-of-the-art ab initio model.

Optical field induced rotation of polarization in rubidium atoms with the additional magnetic field

NASA Astrophysics Data System (ADS)

Ummal Momeen, M.; Hu, Jianping

2017-11-01

We present the magnetic and optical field induced rotation of polarization in 87Rb and 85Rb atoms at geophysical magnetic fields. The line shape varies considerably in the presence of a magnetic field of the order of a few mG. Multiple Zeeman sublevel EIT systems involving rubidium atoms are investigated. Theoretical formalism of optical field induced polarization rotation in the presence of a magnetic field is discussed by considering all the Zeeman sublevels. It is noted that the ground state population distribution also plays a major role.

From clocks to cloners: Catalytic transformations under covariant operations and recoverability

NASA Astrophysics Data System (ADS)

Marvian, Iman; Lloyd, Seth

There are various physical scenarios in which one can only implement operations with a certain symmetry. Under such restriction, a system in a symmetry-breaking state can be used as a catalyst, e.g. to prepare another system in a desired symmetry-breaking state. This sort of (approximate) catalytic state transformations are relevant in the context of (i) state preparation using a bounded-size quantum clock or reference frame, where the clock or reference frame acts as a catalyst, (ii) quantum thermodynamics, where again a clock can be used as a catalyst to prepare states which contain coherence with respect to the system Hamiltonian, and (iii) cloning of unknown quantum states, where the given copies of state can be interpreted as a catalyst for preparing the new copies. Using a recent result of Fawzi and Renner on approximate recoverability, we show that the achievable accuracy in this kind of catalytic transformations can be determined by a single function, namely the relative entropy of asymmetry, which is equal to the difference between the entropy of state and its symmetrized version: if the desired state transition does not require a large increase of this quantity, then it can be implemented with high fidelity using only symmetric operations. Our lower bound on the achievable fidelity is tight in the case of cloners, and can be achieved using the Petz recovery map, which interestingly turns out to be the optimal cloning map found by Werner.

Frequency Comparison of [Formula: see text] Ion Optical Clocks at PTB and NPL via GPS PPP.

PubMed

Leute, J; Huntemann, N; Lipphardt, B; Tamm, Christian; Nisbet-Jones, P B R; King, S A; Godun, R M; Jones, J M; Margolis, H S; Whibberley, P B; Wallin, A; Merimaa, M; Gill, P; Peik, E

2016-07-01

We used precise point positioning, a well-established GPS carrier-phase frequency transfer method to perform a direct remote comparison of two optical frequency standards based on single laser-cooled [Formula: see text] ions operated at the National Physical Laboratory (NPL), U.K. and the Physikalisch-Technische Bundesanstalt (PTB), Germany. At both institutes, an active hydrogen maser serves as a flywheel oscillator which is connected to a GPS receiver as an external frequency reference and compared simultaneously to a realization of the unperturbed frequency of the (2)S1/2(F=0)-(2)D3/2(F=2) electric quadrupole transition in [Formula: see text] via an optical femtosecond frequency comb. To profit from long coherent GPS-link measurements, we extrapolate the fractional frequency difference over the various data gaps in the optical clock to maser comparisons which introduces maser noise to the frequency comparison but improves the uncertainty from the GPS-link instability. We determined the total statistical uncertainty consisting of the GPS-link uncertainty and the extrapolation uncertainties for several extrapolation schemes. Using the extrapolation scheme with the smallest combined uncertainty, we find a fractional frequency difference [Formula: see text] of -1.3×10(-15) with a combined uncertainty of 1.2×10(-15) for a total measurement time of 67 h. This result is consistent with an agreement of the frequencies realized by both optical clocks and with recent absolute frequency measurements against caesium fountain clocks within the corresponding uncertainties.

Progress towards a cesium atomic fountain clock

NASA Astrophysics Data System (ADS)

Klipstein, William M.; Raithel, Georg A.; Rolston, Steven L.; Phillips, William D.; Ekstrom, Christopher R.

1997-04-01

We have been developing a fountain of laser--cooled cesium atoms for use as an atomic clock. Our design largely follows that of the fountain built at LPTF in Paris. In our fountain, chirp--slowed atoms are first collected in a Magneto--Optic Trap (MOT) and then cooled to a few μK in optical molasses. The cooled atoms are then launched vertically into a "moving molasses" by shifting the frequencies of the vertical cooling beams. The atoms then travel through a microwave cavity tuned to the 9.2 GHz cesium hyperfine frequency for a first Ramsey pulse. After roughly 0.5 seconds of free flight under the influence of gravity, the atoms fall back through the microwave cavity and into an optical state--detection region which detects the number of atoms making the F=3 arrow F=4 transition. The increased Ramsey interaction time improves the short--time precision as compared to traditional atomic beam experiments, while many systematic shifts which limit the accuracy of an atomic beam clock are reduced by the low atomic velocity and the retrace of the atomic trajectory through the microwave cavity. We will discuss the progress towards a working fountain being assembled in our laboratory.

A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space

NASA Technical Reports Server (NTRS)

Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

2000-01-01

We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

Transition from linear- to nonlinear-focusing regime in filamentation

PubMed Central

Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin

2014-01-01

Laser filamentation in gases is often carried out in the laboratory with focusing optics to better stabilize the filament, whereas real-world applications of filaments frequently involve collimated or near-collimated beams. It is well documented that geometrical focusing can alter the properties of laser filaments and, consequently, a transition between a collimated and a strongly focused filament is expected. Nevertheless, this transition point has not been identified. Here, we propose an analytical method to determine the transition, and show that it corresponds to an actual shift in the balance of physical mechanisms governing filamentation. In high-NA conditions, filamentation is primarily governed by geometrical focusing and plasma effects, while the Kerr nonlinearity plays a more significant role as NA decreases. We find the transition between the two regimes to be relatively insensitive to the intrinsic laser parameters, and our analysis agrees well with a wide range of parameters found in published literature. PMID:25434678

An open source digital servo for atomic, molecular, and optical physics experiments

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

Leibrandt, D. R., E-mail: david.leibrandt@nist.gov; Heidecker, J.

2015-12-15

We describe a general purpose digital servo optimized for feedback control of lasers in atomic, molecular, and optical physics experiments. The servo is capable of feedback bandwidths up to roughly 1 MHz (limited by the 320 ns total latency); loop filter shapes up to fifth order; multiple-input, multiple-output control; and automatic lock acquisition. The configuration of the servo is controlled via a graphical user interface, which also provides a rudimentary software oscilloscope and tools for measurement of system transfer functions. We illustrate the functionality of the digital servo by describing its use in two example scenarios: frequency control of themore » laser used to probe the narrow clock transition of {sup 27}Al{sup +} in an optical atomic clock, and length control of a cavity used for resonant frequency doubling of a laser.« less

An open source digital servo for atomic, molecular, and optical physics experiments.

PubMed

Leibrandt, D R; Heidecker, J

2015-12-01

We describe a general purpose digital servo optimized for feedback control of lasers in atomic, molecular, and optical physics experiments. The servo is capable of feedback bandwidths up to roughly 1 MHz (limited by the 320 ns total latency); loop filter shapes up to fifth order; multiple-input, multiple-output control; and automatic lock acquisition. The configuration of the servo is controlled via a graphical user interface, which also provides a rudimentary software oscilloscope and tools for measurement of system transfer functions. We illustrate the functionality of the digital servo by describing its use in two example scenarios: frequency control of the laser used to probe the narrow clock transition of (27)Al(+) in an optical atomic clock, and length control of a cavity used for resonant frequency doubling of a laser.

Modeling a synthetic multicellular clock: Repressilators coupled by quorum sensing

PubMed Central

Garcia-Ojalvo, Jordi; Elowitz, Michael B.; Strogatz, Steven H.

2004-01-01

Diverse biochemical rhythms are generated by thousands of cellular oscillators that somehow manage to operate synchronously. In fields ranging from circadian biology to endocrinology, it remains an exciting challenge to understand how collective rhythms emerge in multicellular structures. Using mathematical and computational modeling, we study the effect of coupling through intercell signaling in a population of Escherichia coli cells expressing a synthetic biological clock. Our results predict that a diverse and noisy community of such genetic oscillators interacting through a quorum-sensing mechanism should self-synchronize in a robust way, leading to a substantially improved global rhythmicity in the system. As such, the particular system of coupled genetic oscillators considered here might be a good candidate to provide the first quantitative example of a synchronization transition in a population of biological oscillators. PMID:15256602

An open source digital servo for atomic, molecular, and optical physics experiments

NASA Astrophysics Data System (ADS)

Leibrandt, D. R.; Heidecker, J.

2015-12-01

We describe a general purpose digital servo optimized for feedback control of lasers in atomic, molecular, and optical physics experiments. The servo is capable of feedback bandwidths up to roughly 1 MHz (limited by the 320 ns total latency); loop filter shapes up to fifth order; multiple-input, multiple-output control; and automatic lock acquisition. The configuration of the servo is controlled via a graphical user interface, which also provides a rudimentary software oscilloscope and tools for measurement of system transfer functions. We illustrate the functionality of the digital servo by describing its use in two example scenarios: frequency control of the laser used to probe the narrow clock transition of 27Al+ in an optical atomic clock, and length control of a cavity used for resonant frequency doubling of a laser.

An open source digital servo for atomic, molecular, and optical physics experiments

PubMed Central

Leibrandt, D. R.; Heidecker, J.

2016-01-01

We describe a general purpose digital servo optimized for feedback control of lasers in atomic, molecular, and optical physics experiments. The servo is capable of feedback bandwidths up to roughly 1 MHz (limited by the 320 ns total latency); loop filter shapes up to fifth order; multiple-input, multiple-output control; and automatic lock acquisition. The configuration of the servo is controlled via a graphical user interface, which also provides a rudimentary software oscilloscope and tools for measurement of system transfer functions. We illustrate the functionality of the digital servo by describing its use in two example scenarios: frequency control of the laser used to probe the narrow clock transition of 27Al+ in an optical atomic clock, and length control of a cavity used for resonant frequency doubling of a laser. PMID:26724014

Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Maisberger, Matthew; Wang, Lin-Cheng; Sun, Kuei; Xu, Yong; Zhang, Chuanwei

2018-05-01

Time-reversal invariance plays a crucial role for many exotic quantum phases, particularly for topologically nontrivial states, in spin-orbit coupled electronic systems. Recently realized spin-orbit coupled cold-atom systems, however, lack the time-reversal symmetry due to the inevitable presence of an effective transverse Zeeman field. We address this issue by analyzing a realistic scheme to preserve time-reversal symmetry in spin-orbit-coupled ultracold atoms, with the use of Hermite-Gaussian-laser-induced Raman transitions that preserve spin-layer time-reversal symmetry. We find that the system's quantum states form Kramers pairs, resulting in symmetry-protected gap closing of the lowest two bands at arbitrarily large Raman coupling. We also show that Bose gases in this setup exhibit interaction-induced layer-stripe and uniform phases as well as intriguing spin-layer symmetry and spin-layer correlation.

Termination of the spin-resolved integer quantum Hall effect

NASA Astrophysics Data System (ADS)

Wong, L. W.; Jiang, H. W.; Palm, E.; Schaff, W. J.

1997-03-01

We report a magnetotransport study of the termination of the spin-resolved integer quantum Hall effect by controlled disorder in a gated GaAs/AlxGa1-xAs heterostructure. We have found that, for a given Nth Landau level, the difference in filling factors of a pair of spin-split resistivity peaks δνN=\\|νN↑-νN↓\\| changes rapidly from one to zero near a critical density nc. Scaling analysis shows that δνN collapses onto a single curve independent of N when plotted against the parameter (n-nc)/nc for five Landau levels. The effect of increasing the Zeeman energy is also examined by tilting the direction of magnetic field relative to the plane of the two-dimensional electron gas. Our experiment suggests the termination of the spin-resolved quantum Hall effect is a phase transition.

Direct observation of electronic and nuclear ground state splitting in external magnetic field by inelastic neutron scattering on oxidized ferrocene and ferrocene containing polymers

NASA Astrophysics Data System (ADS)

Appel, Markus; Frick, Bernhard; Elbert, Johannes; Gallei, Markus; Stühn, Bernd

2015-01-01

The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene). They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.

Magnetic field induced switching of the antiferromagnetic order parameter in thin films of magnetoelectric chromia

NASA Astrophysics Data System (ADS)

Fallarino, Lorenzo; Berger, Andreas; Binek, Christian

2015-02-01

A Landau-theoretical approach is utilized to model the magnetic field induced reversal of the antiferromagnetic order parameter in thin films of magnetoelectric antiferromagnets. A key ingredient of this peculiar switching phenomenon is the presence of a robust spin polarized state at the surface of the antiferromagnetic films. Surface or boundary magnetization is symmetry allowed in magnetoelectric antiferromagnets and experimentally established for chromia thin films. It couples rigidly to the antiferromagnetic order parameter and its Zeeman energy creates a pathway to switch the antiferromagnet via magnetic field application. In the framework of a minimalist Landau free energy expansion, the temperature dependence of the switching field and the field dependence of the transition width are derived. Least-squares fits to magnetometry data of (0001 ) textured chromia thin films strongly support this model of the magnetic reversal mechanism.

Hong-Ou-Mandel Interference between Two Deterministic Collective Excitations in an Atomic Ensemble

NASA Astrophysics Data System (ADS)

Li, Jun; Zhou, Ming-Ti; Jing, Bo; Wang, Xu-Jie; Yang, Sheng-Jun; Jiang, Xiao; Mølmer, Klaus; Bao, Xiao-Hui; Pan, Jian-Wei

2016-10-01

We demonstrate deterministic generation of two distinct collective excitations in one atomic ensemble, and we realize the Hong-Ou-Mandel interference between them. Using Rydberg blockade we create single collective excitations in two different Zeeman levels, and we use stimulated Raman transitions to perform a beam-splitter operation between the excited atomic modes. By converting the atomic excitations into photons, the two-excitation interference is measured by photon coincidence detection with a visibility of 0.89(6). The Hong-Ou-Mandel interference witnesses an entangled NOON state of the collective atomic excitations, and we demonstrate its two times enhanced sensitivity to a magnetic field compared with a single excitation. Our work implements a minimal instance of boson sampling and paves the way for further multimode and multiexcitation studies with collective excitations of atomic ensembles.

Ferroelectric Memory Devices and a Proposed Standardized Test System Design

DTIC Science & Technology

1992-06-01

positive clock transition. This provides automatic data protection in case of power loss. The device is being evaluated for applications such as automobile ...systems requiring nonvolatile memory and as these systems become more complex, the demand for reprogrammable nonvolatile memory increases. The...complexity and cost in making conventional nonvolatile memory reprogrammable also increases, so the potential for using ferroelectric memory as a replacement

Multistage Zeeman decelerator for molecular-scattering studies

NASA Astrophysics Data System (ADS)

Cremers, Theo; Chefdeville, Simon; Janssen, Niek; Sweers, Edwin; Koot, Sven; Claus, Peter; van de Meerakker, Sebastiaan Y. T.

2017-04-01

We present a concept for a multistage Zeeman decelerator that is optimized particularly for applications in molecular beam scattering experiments. The decelerator consists of a series of alternating hexapoles and solenoids, that effectively decouple the transverse focusing and longitudinal deceleration properties of the decelerator. It can be operated in a deceleration and acceleration mode, as well as in a hybrid mode that makes it possible to guide a particle beam through the decelerator at constant speed. The deceleration features phase stability, with a relatively large six-dimensional phase-space acceptance. The separated focusing and deceleration elements result in an unequal partitioning of this acceptance between the longitudinal and transverse directions. This is ideal in scattering experiments, which typically benefit from a large longitudinal acceptance combined with narrow transverse distributions. We demonstrate the successful experimental implementation of this concept using a Zeeman decelerator consisting of an array of 25 hexapoles and 24 solenoids. The performance of the decelerator in acceleration, deceleration, and guiding modes is characterized using beams of metastable helium (3S ) atoms. Up to 60% of the kinetic energy was removed for He atoms that have an initial velocity of 520 m/s. The hexapoles consist of permanent magnets, whereas the solenoids are produced from a single hollow copper capillary through which cooling liquid is passed. The solenoid design allows for excellent thermal properties and enables the use of readily available and cheap electronics components to pulse high currents through the solenoids. The Zeeman decelerator demonstrated here is mechanically easy to build, can be operated with cost-effective electronics, and can run at repetition rates up to 10 Hz.

Hanle-Zeeman Scattering Matrix for Magnetic Dipole Transitions

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

Megha, A.; Sampoorna, M.; Nagendra, K. N.

2017-06-01

The polarization of the light that is scattered by the coronal ions is influenced by the anisotropic illumination from the photosphere and the magnetic field structuring in the solar corona. The properties of the coronal magnetic fields can be well studied by understanding the polarization properties of coronal forbidden emission lines that arise from magnetic dipole ( M 1) transitions in the highly ionized atoms that are present in the corona. We present the classical scattering theory of the forbidden lines for a more general case of arbitrary-strength magnetic fields. We derive the scattering matrix for M 1 transitions usingmore » the classical magnetic dipole model of Casini and Lin and applying the scattering matrix approach of Stenflo. We consider a two-level atom model and neglect collisional effects. The scattering matrix so derived is used to study the Stokes profiles formed in coronal conditions in those regions where the radiative excitations dominate collisional excitations. To this end, we take into account the integration over a cone of an unpolarized radiation from the solar disk incident on the scattering atoms. Furthermore, we also integrate along the line of sight to calculate the emerging polarized line profiles. We consider radial and dipole magnetic field configurations and spherically symmetric density distributions. For our studies we adopt the atomic parameters corresponding to the [Fe xiii] 10747 Å coronal forbidden line. We also discuss the nature of the scattering matrix for M 1 transitions and compare it with that for the electric dipole ( E 1) transitions.« less

Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectrometry Modelling Under Saturated Absorption

NASA Astrophysics Data System (ADS)

Dupré, Patrick

2015-06-01

The Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectrometry (NICE-OHMS) is a modern technique renowned for its ultimate sensitivity, because it combines long equivalent absorption length provided by a high finesse cavity, and a detection theoretically limited by the sole photon-shot-noise. One fallout of the high finesse is the possibility to accumulating strong intracavity electromagnetic fields (EMF). Under this condition, molecular transitions can be easy saturated giving rise to the usual Lamb dips (or hole burning). However, the unusual shape of the basically trichromatic EMF (due to the RF lateral sidebands) induces nonlinear couplings, i.e., new crossover transitions. An analytical methodology will be presented to calculate spectra provided by NICE-OHMS experiments. It is based on the solutions of the equations of motion of an open two-blocked-level system performed in the frequency-domain (optically thin medium). Knowing the transition dipole moment, the NICE-OHMS signals (``absorption-like'' and ``dispersion-like'') can be simulated by integration over the Doppler shifts and by paying attention to the molecular Zeeman sublevels and to the EMF polarization The approach has been validated by discussion experimental data obtained on two transitions of {C2H2} in the near-infrared under moderated saturation. One of the applications of the saturated absorption is to be able to simultaneously determine the transition intensity and the density number while only one these 2 quantities can only be assessed in nonlinear absorption. J. Opt. Soc. Am. B 32, 838 (2015) Optics Express 16, 14689 (2008)

Optical and Microwave Spectroscopy of Transient Metal-Containing Molecules

NASA Astrophysics Data System (ADS)

Steimle, Timothy

2016-06-01

Small metal containing molecules are ideal venues for testing Fundamental Physics, investigating relativistic effects, and modelling spin-orbit induced unimolecular dynamics. Electronic spectroscopy is an effective method for probing these phenomena because such spectra are readily recorded at the natural linewidth limited resolution and accuracy of 0.0001 wn. The information garnered includes fine and hyperfine interactions, magnetic and electric dipoles, and dynamics. With this in mind, three examples from our recent (unpublished) studies will be highlighted. SiHD: Long ago Duxbury et al. developed a semi-quantitative model invoking Renner-Teller and spin-orbit coupling of the tilde{a}3B{1}, tilde{X}1A1, and tilde{A}1B1, states to explain the observed local perturbations and anomalous radiative lifetimes in the visible spectrum. More recently, the tilde{a}3B1 to tilde{A}1B1 intersystem crossing has been modeled using both semi-classical transition state theory and quantum trajectory surface hopping dynamics. Here we investigate the effects of the reduced symmetry of SiHD on the spectroscopy and dynamics using 2D spectroscopy. Rotationally resolved lines in the origin tilde{X}1A'→ tilde{A}1A" band are assigned to both c-type transitions and additional axis-switching induced transitions. AuO and AuS: The observed markedly different bonding of thiols and alcohols to gold clusters should be traceable to the difference in Au-O and Au-S bonding. To investigate this difference we have used optical Stark and Zeeman spectroscopy to determine the permanent electric dipole moments and magnetic g-factors. The results are rationalized using simple m.o. correlation diagrams and compared to ab initio predictions. TaN: TaN is the best candidate to search for a T,P- violating nuclear magnetic quadrupole moment. Here we report on the optical 2D, Stark, and Zeeman spectra, and our efforts to record the pure rotational spectrum using the separated field pump/probe microwave-optical double resonance.Implications for T,P- violating experiments will be presented. G. Duxbury, A. Alijah and R. R. Trieling, J. Chem. Phys. 98, 811 (1993) R. R. Zaari and S. A. Varganov, JPCA 119 , 1332 (2015) N. J. Reilly, T. W. Schmidt and S. H. Kable, JPCA 110, 12355(2006) J. T. Hougen and J. K. G. Watson, Can. J. Phys. 43 , 298 (1965) L. V. Skripnikov, et.al. Phys. Rev. A: 92, 1 (2015)

Spin injection and spin transport in paramagnetic insulators

DOE PAGES

Okamoto, Satoshi

2016-02-22

We investigate the spin injection and the spin transport in paramagnetic insulators described by simple Heisenberg interactions using auxiliary particle methods. Some of these methods allow access to both paramagnetic states above magnetic transition temperatures and magnetic states at low temperatures. It is predicted that the spin injection at an interface with a normal metal is rather insensitive to temperatures above the magnetic transition temperature. On the other hand below the transition temperature, it decreases monotonically and disappears at zero temperature. We also analyze the bulk spin conductance. We show that the conductance becomes zero at zero temperature as predictedmore » by linear spin wave theory but increases with temperature and is maximized around the magnetic transition temperature. These findings suggest that the compromise between the two effects determines the optimal temperature for spintronics applications utilizing magnetic insulators.« less

Measuring 20-100 T B-fields using Zeeman splitting of sodium emission lines on a 500 kA pulsed power machine

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

Banasek, J. T., E-mail: jtb254@cornell.edu; Engelbrecht, J. T.; Pikuz, S. A.

2016-11-15

We have shown that Zeeman splitting of the sodium (Na) D-lines at 5890 and 5896 Å can be used to measure the magnetic field (B-field) produced in high current pulsed power experiments. We have measured the B-field next to a return current conductor in a hybrid X-pinch experiment near a peak current of about 500 kA. Na is deposited on the conductor and then is desorbed and excited by radiation from the hybrid X-pinch. The D-line emission spectrum implies B-fields of about 20 T with a return current post of 4 mm diameter or up to 120 T with amore » return current wire of 0.455 mm diameter. These measurements were consistent or lower than the expected B-field, thereby showing that basic Zeeman splitting can be used to measure the B-field in a pulsed-power-driven high-energy-density (HED) plasma experiment. We hope to extend these measurement techniques using suitable ionized species to measurements within HED plasmas.« less

Magnetic-field-induced mixed-level Kondo effect in two-level systems

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

Wong, Arturo; Ngo, Anh T.; Ulloa, Sergio E.

2016-10-17

We consider a two-orbital impurity system with intra-and interlevel Coulomb repulsion that is coupled to a single conduction channel. This situation can generically occur in multilevel quantum dots or in systems of coupled quantum dots. For finite energy spacing between spin-degenerate orbitals, an in-plane magnetic field drives the system from a local-singlet ground state to a "mixed-level" Kondo regime, where the Zeeman-split levels are degenerate for opposite-spin states. We use the numerical renormalization group approach to fully characterize this mixed-level Kondo state and discuss its properties in terms of the applied Zeeman field, temperature, and system parameters. Under suitable conditions,more » the total spectral function is shown to develop a Fermi-level resonance, so that the linear conductance of the system peaks at a finite Zeeman field while it decreases as a function of temperature. These features, as well as the local moment and entropy contribution of the impurity system, are commensurate with Kondo physics, which can be studied in suitably tuned quantum dot systems.« less

The regulatory properties of Rubisco activase differ among species and affect photosynthetic induction during light transitions.

PubMed

Carmo-Silva, A Elizabete; Salvucci, Michael E

2013-04-01

Rubisco's catalytic chaperone, Rubisco activase (Rca), uses the energy from ATP hydrolysis to restore catalytic competence to Rubisco. In Arabidopsis (Arabidopsis thaliana), inhibition of Rca activity by ADP is fine tuned by redox regulation of the α-isoform. To elucidate the mechanism for Rca regulation in species containing only the redox-insensitive β-isoform, the response of activity to ADP was characterized for different Rca forms. When assayed in leaf extracts, Rubisco activation was significantly inhibited by physiological ratios of ADP to ATP in species containing both α-Rca and β-Rca (Arabidopsis and camelina [Camelina sativa]) or just the β-Rca (tobacco [Nicotiana tabacum]). However, Rca activity was insensitive to ADP inhibition in an Arabidopsis transformant, rwt43, which expresses only Arabidopsis β-Rca, although not in a transformant of Arabidopsis that expresses a tobacco-like β-Rca. ATP hydrolysis by recombinant Arabidopsis β-Rca was much less sensitive to inhibition by ADP than recombinant tobacco β-Rca. Mutation of 17 amino acids in the tobacco β-Rca to the corresponding Arabidopsis residues reduced ADP sensitivity. In planta, Rubisco deactivated at low irradiance except in the Arabidopsis rwt43 transformant containing an ADP-insensitive Rca. Induction of CO2 assimilation after transition from low to high irradiance was much more rapid in the rwt43 transformant compared with plants containing ADP-sensitive Rca forms. The faster rate of photosynthetic induction and a greater enhancement of growth under a fluctuating light regime by the rwt43 transformant compared with wild-type Arabidopsis suggests that manipulation of Rca regulation might provide a strategy for enhancing photosynthetic performance in certain variable light environments.

Magnetic anisotropy in nickel complexes as determined by combined magnetic susceptibility/magnetization/theoretical studies

NASA Astrophysics Data System (ADS)

Mašlejová, Anna; Boča, Roman; Dlháň, L.'ubor; Herchel, Radovan

2004-05-01

The zero-field splitting in nickel(II) complexes was modeled by considering all relevant operators (electron repulsion, crystal-field, spin-orbit coupling, orbital-Zeeman, and spin-Zeeman) in the complete basis set spanned by d n-atomic terms. D-values between weak and strong crystal field limits were evaluated from the crystal-field multiplets as well as using the spin Hamiltonian formalism. Importance of the anisotropic orbital reduction factors is discussed and exemplified by D/hc=-22 cm-1 as subtracted from magnetic data for [Ni(imidazole) 4(acetate) 2] complex.

Third-order Zeeman effect in highly charged ions

NASA Astrophysics Data System (ADS)

Varentsova, A. S.; Agababaev, V. A.; Volchkova, A. M.; Glazov, D. A.; Volotka, A. V.; Shabaev, V. M.; Plunien, G.

2017-10-01

The contribution of the third order in magnetic field to the Zeeman splitting of the ground state of hydrogenlike, lithiumlike, and boronlike ions in the range Z = 6 - 82 is investigated within the relativistic approach. Both perturbative and non-perturbative methods of calculation are employed and found to be in agreement. For lithiumlike and boronlike ions the interelectronic-interaction effects are taken into account within the approximation of the local screening potential. The contribution of the third-order effect in low- and medium-Z boronlike ions is found to be important for anticipated high-precision measurements.

Production and detection of atomic hexadecapole at Earth's magnetic field.

PubMed

Acosta, V M; Auzinsh, M; Gawlik, W; Grisins, P; Higbie, J M; Jackson Kimball, D F; Krzemien, L; Ledbetter, M P; Pustelny, S; Rochester, S M; Yashchuk, V V; Budker, D

2008-07-21

Optical magnetometers measure magnetic fields with extremely high precision and without cryogenics. However, at geomagnetic fields, important for applications from landmine removal to archaeology, they suffer from nonlinear Zeeman splitting, leading to systematic dependence on sensor orientation. We present experimental results on a method of eliminating this systematic error, using the hexadecapole atomic polarization moment. In particular, we demonstrate selective production of the atomic hexadecapole moment at Earth's magnetic field and verify its immunity to nonlinear Zeeman splitting. This technique promises to eliminate directional errors in all-optical atomic magnetometers, potentially improving their measurement accuracy by several orders of magnitude.

Turning Oscillations Into Opportunities: Lessons from a Bacterial Decision Gate

NASA Astrophysics Data System (ADS)

Schultz, Daniel; Lu, Mingyang; Stavropoulos, Trevor; Onuchic, Jose'; Ben-Jacob, Eshel

2013-04-01

Sporulation vs. competence provides a prototypic example of collective cell fate determination. The decision is performed by the action of three modules: 1) A stochastic competence switch whose transition probability is regulated by population density, population stress and cell stress. 2) A sporulation timer whose clock rate is regulated by cell stress and population stress. 3) A decision gate that is coupled to the timer via a special repressilator-like loop. We show that the distinct circuit architecture of this gate leads to special dynamics and noise management characteristics: The gate opens a time-window of opportunity for competence transitions during which it generates oscillations that are turned into a chain of transition opportunities - each oscillation opens a short interval with high transition probability. The special architecture of the gate also leads to filtering of external noise and robustness against internal noise and variations in the circuit parameters.

Turning Oscillations Into Opportunities: Lessons from a Bacterial Decision Gate

PubMed Central

Schultz, Daniel; Lu, Mingyang; Stavropoulos, Trevor; Onuchic, Jose'; Ben-Jacob, Eshel

2013-01-01

Sporulation vs. competence provides a prototypic example of collective cell fate determination. The decision is performed by the action of three modules: 1) A stochastic competence switch whose transition probability is regulated by population density, population stress and cell stress. 2) A sporulation timer whose clock rate is regulated by cell stress and population stress. 3) A decision gate that is coupled to the timer via a special repressilator-like loop. We show that the distinct circuit architecture of this gate leads to special dynamics and noise management characteristics: The gate opens a time-window of opportunity for competence transitions during which it generates oscillations that are turned into a chain of transition opportunities – each oscillation opens a short interval with high transition probability. The special architecture of the gate also leads to filtering of external noise and robustness against internal noise and variations in the circuit parameters. PMID:23591544

External light activates hair follicle stem cells through eyes via an ipRGC-SCN-sympathetic neural pathway.

PubMed

Fan, Sabrina Mai-Yi; Chang, Yi-Ting; Chen, Chih-Lung; Wang, Wei-Hung; Pan, Ming-Kai; Chen, Wen-Pin; Huang, Wen-Yen; Xu, Zijian; Huang, Hai-En; Chen, Ting; Plikus, Maksim V; Chen, Shih-Kuo; Lin, Sung-Jan

2018-06-29

Changes in external light patterns can alter cell activities in peripheral tissues through slow entrainment of the central clock in suprachiasmatic nucleus (SCN). It remains unclear whether cells in otherwise photo-insensitive tissues can achieve rapid responses to changes in external light. Here we show that light stimulation of animals' eyes results in rapid activation of hair follicle stem cells with prominent hair regeneration. Mechanistically, light signals are interpreted by M1-type intrinsically photosensitive retinal ganglion cells (ipRGCs), which signal to the SCN via melanopsin. Subsequently, efferent sympathetic nerves are immediately activated. Increased norepinephrine release in skin promotes hedgehog signaling to activate hair follicle stem cells. Thus, external light can directly regulate tissue stem cells via an ipRGC-SCN autonomic nervous system circuit. Since activation of sympathetic nerves is not limited to skin, this circuit can also facilitate rapid adaptive responses to external light in other homeostatic tissues.

Dose-response relationships for resetting of human circadian clock by light

NASA Technical Reports Server (NTRS)

Boivin, D. B.; Duffy, J. F.; Kronauer, R. E.; Czeisler, C. A.

1996-01-01

Since the first report in unicells, studies across diverse species have demonstrated that light is a powerful synchronizer which resets, in an intensity-dependent manner, endogenous circadian pacemakers. Although it is recognized that bright light (approximately 7,000 to 13,000 lux) is an effective circadian synchronizer in humans, it is widely believed that the human circadian pacemaker is insensitive to ordinary indoor illumination (approximately 50-300 lux). It has been proposed that the relationship between the resetting effect of light and its intensity follows a compressive nonlinear function, such that exposure to lower illuminances still exerts a robust effect. We therefore undertook a series of experiments which support this hypothesis and report here that light of even relatively low intensity (approximately 180 lux) significantly phase-shifts the human circadian pacemaker. Our results clearly demonstrate that humans are much more sensitive to light than initially suspected and support the conclusion that they are not qualitatively different from other mammals in their mechanism of circadian entrainment.

Wavelength-preserving polarization-insensitive all-optical 3R regenerator based on self- and cross-phase modulation and offset filtering utilizing Raman amplification

NASA Astrophysics Data System (ADS)

Chung, Sung Han

Optical regeneration has the potential to significantly increase the reach of long-haul transmission systems. In this thesis, wavelength-preserving polarization-insensitive all-optical 3R regeneration is investigated and demonstrated for 10 and 40 Gb/s signals. The all-optical regenerator utilizes a self-pulsating laser for clock recovery, cross-phase modulation (XPM) based spectral broadening in a highly nonlinear fiber (HNLF) and offset filtering for retiming, and self-phase modulation based spectral broadening in a HNLF and offset filtering for reshaping. Raman amplification is used to increase the XPM-based spectral broadening and thus allow a design that meets the tradeoffs involved in simultaneously achieving good retiming and reshaping performance. The regenerator is shown to reduce amplitude noise and timing jitter while not causing a BER penalty. To fully validate the regeneration scheme, the cascadability is demonstrated using a recirculating loop. For a 10 Gb/s signal, with a regenerator spacing of 240 km, a return-to-zero, on-off-keyed (RZ-OOK) signal was transmitted over 18,000 km (75 loops) with a power penalty of 1.6 dB at a BER of 10 -9 compared to the back-to-back case. For a 40 Gb/s signal, with a regenerator spacing of 80 km, a RZ-OOK signal was transmitted over 8,000 km (100 loops) with a power penalty of 1.2 dB. In addition, all-optical 3R regeneration is demonstrated using a multimode quantum-dot Fabry Perot laser with ultra-low timing jitter.

Federal Plan for High-End Computing. Report of the High-End Computing Revitalization Task Force (HECRTF)

DTIC Science & Technology

2004-07-01

steadily for the past fifteen years, while memory latency and bandwidth have improved much more slowly. For example, Intel processor clock rates38 have... processor and memory performance) all greatly restrict the ability to achieve high levels of performance for science, engineering, and national...sub-nuclear distances. Guide experiments to identify transition from quantum chromodynamics to quark -gluon plasma. Accelerator Physics Accurate

Trapping of thulium atoms in a cavity-enhanced optical lattice near a magic wavelength of 814.5 nm

NASA Astrophysics Data System (ADS)

Kalganova, E. S.; Golovizin, A. A.; Shevnin, D. O.; Tregubov, D. O.; Khabarova, K. Yu; Sorokin, V. N.; Kolachevsky, N. N.

2018-05-01

A cavity-enhanced optical lattice at a wavelength of 814.5 nm for thulium atoms is designed and its characteristics are investigated. The parametric resonances at the vibrational frequencies of the trap are measured. The enhancement cavity will be applied to search for the magic wavelength of the clock transition at 1.14 μm in thulium atoms.

Acoustically induced slip in sheared granular layers: Application to dynamic earthquake triggering: TRIGGERED SLIP IN SHEARED GRANULAR GOUGE

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

Ferdowsi, Behrooz; Griffa, Michele; Guyer, Robert A.

A fundamental mystery in earthquake physics is “how can an earthquake be triggered by distant seismic sources?” We use discrete element method simulations of a granular layer, during stick slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. We also observe delayed triggering of slip in the granular gouge, using Coulomb friction law for grains interaction. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance; i.e., transient vibration and triggered slip are simultaneous. Moreover, themore » critical strain is of order 10 -6, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.« less

Acoustically induced slip in sheared granular layers: Application to dynamic earthquake triggering: TRIGGERED SLIP IN SHEARED GRANULAR GOUGE

DOE PAGES

Ferdowsi, Behrooz; Griffa, Michele; Guyer, Robert A.; ...

2015-11-19

A fundamental mystery in earthquake physics is “how can an earthquake be triggered by distant seismic sources?” We use discrete element method simulations of a granular layer, during stick slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. We also observe delayed triggering of slip in the granular gouge, using Coulomb friction law for grains interaction. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance; i.e., transient vibration and triggered slip are simultaneous. Moreover, themore » critical strain is of order 10 -6, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.« less

Quantifying fluctuations in reversible enzymatic cycles and clocks

NASA Astrophysics Data System (ADS)

Wierenga, Harmen; ten Wolde, Pieter Rein; Becker, Nils B.

2018-04-01

Biochemical reactions are fundamentally noisy at a molecular scale. This limits the precision of reaction networks, but it also allows fluctuation measurements that may reveal the structure and dynamics of the underlying biochemical network. Here, we study nonequilibrium reaction cycles, such as the mechanochemical cycle of molecular motors, the phosphorylation cycle of circadian clock proteins, or the transition state cycle of enzymes. Fluctuations in such cycles may be measured using either of two classical definitions of the randomness parameter, which we show to be equivalent in general microscopically reversible cycles. We define a stochastic period for reversible cycles and present analytical solutions for its moments. Furthermore, we associate the two forms of the randomness parameter with the thermodynamic uncertainty relation, which sets limits on the timing precision of the cycle in terms of thermodynamic quantities. Our results should prove useful also for the study of temporal fluctuations in more general networks.

Evolution of photoperiod sensing in plants and algae.

PubMed

Serrano-Bueno, Gloria; Romero-Campero, Francisco J; Lucas-Reina, Eva; Romero, Jose M; Valverde, Federico

2017-06-01

Measuring day length confers a strong fitness improvement to photosynthetic organisms as it allows them to anticipate light phases and take the best decisions preceding diurnal transitions. In close association with signals from the circadian clock and the photoreceptors, photoperiodic sensing constitutes also a precise way to determine the passing of the seasons and to take annual decisions such as the best time to flower or the beginning of dormancy. Photoperiodic sensing in photosynthetic organisms is ancient and two major stages in its evolution could be identified, the cyanobacterial time sensing and the evolutionary tool kit that arose in green algae and developed into the photoperiodic system of modern plants. The most recent discoveries about the evolution of the perception of light, measurement of day length and relationship with the circadian clock along the evolution of the eukaryotic green lineage will be discussed in this review. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Drosophila Circadian Clock Gates Sleep through Time-of-Day Dependent Modulation of Sleep-Promoting Neurons.

PubMed

Cavanaugh, Daniel J; Vigderman, Abigail S; Dean, Terry; Garbe, David S; Sehgal, Amita

2016-02-01

Sleep is under the control of homeostatic and circadian processes, which interact to determine sleep timing and duration, but the mechanisms through which the circadian system modulates sleep are largely unknown. We therefore used adult-specific, temporally controlled neuronal activation and inhibition to identify an interaction between the circadian clock and a novel population of sleep-promoting neurons in Drosophila. Transgenic flies expressed either dTRPA1, a neuronal activator, or Shibire(ts1), an inhibitor of synaptic release, in small subsets of neurons. Sleep, as determined by activity monitoring and video tracking, was assessed before and after temperature-induced activation or inhibition using these effector molecules. We compared the effect of these manipulations in control flies and in mutant flies that lacked components of the molecular circadian clock. Adult-specific activation or inhibition of a population of neurons that projects to the sleep-promoting dorsal Fan-Shaped Body resulted in bidirectional control over sleep. Interestingly, the magnitude of the sleep changes were time-of-day dependent. Activation of sleep-promoting neurons was maximally effective during the middle of the day and night, and was relatively ineffective during the day-to-night and night-to-day transitions. These time-ofday specific effects were absent in flies that lacked functional circadian clocks. We conclude that the circadian system functions to gate sleep through active inhibition at specific times of day. These data identify a mechanism through which the circadian system prevents premature sleep onset in the late evening, when homeostatic sleep drive is high. © 2016 Associated Professional Sleep Societies, LLC.

Electronic structure studies of adsorbate-induced surface reconstructions: oxygen on Rh(1 0 0)

NASA Astrophysics Data System (ADS)

Kirsch, Janet E.; Harris, Suzanne

2004-03-01

Solid-state Fenske-Hall band structure calculations have been used to study the electronic structure and bonding that occur on an "asymmetric" clock reconstructed Rh(1 0 0) surface with a half-monolayer of O atom adsorbates. The displacement of the top-layer Rh atoms on reconstructed O/Rh(1 0 0) is similar to that observed when a half-monolayer of C or N atoms adsorb onto clean Ni(1 0 0). Unlike the five-coordinate C or N adsorbates that adsorb into effectively coplanar sites on the Ni(1 0 0) surface, however, O atoms sit well above the Rh surface plane and occupy three-coordinate adsorption sites. The results of these calculations show that the asymmetric clock reconstruction of O/Rh(1 0 0) increases the negative charge localized on the highly electronegative O atoms and strengthens the O-Rh bonding relative to an unreconstructed surface. This suggests that, in contrast to the C(N)/Ni(1 0 0) clock, which appears to be driven primarily by the restoration of metal-metal bonding, the asymmetric O/Rh(1 0 0) clock reconstruction is driven by the optimization of the O atom bonding environment. Comparisons of the O/Rh(1 0 0) and C(N, O)/Ni(1 0 0) surfaces further indicate that the electronegativity and electron count of the adsorbed species, as well as the electron count and physical size of the metal, all play a role in determining the preferred atomic geometries of these adsorbate-covered transition metal surfaces.

Magnetic Fields in the Galaxy

NASA Astrophysics Data System (ADS)

Mayo, Elizabeth A.

2009-01-01

Interstellar magnetic fields are believed to play a crucial role in the star-formation process, therefore a comprehensive study of magnetic fields is necessary in understanding the origins of stars. These projects use observational data obtained from the Very Large Array (VLA) in Socorro, NM. The data reveal interstellar magnetic field strengths via the Zeeman effect in radio frequency spectral lines. This information provides an estimate of the magnetic energy in star-forming interstellar clouds in the Galaxy, and comparisons can be made with these energies and the energies of self-gravitation and internal motions. From these comparisons, a better understanding of the role of magnetic fields in the origins of stars will emerge. NGC 6334 A is a compact HII region at the center of what is believed to be a large, rotating molecular torus (Kramer et al. (1997)). This is a continuing study based on initial measurements of the HI and OH Zeeman effect (Sarma et al. (2000)). The current study includes OH observations performed by the VLA at a higher spatial resolution than previously published data, and allows for a better analysis of the spatial variations of the magnetic field. A new model of the region is also developed based on OH opacity studies, dust continuum maps, radio spectral lines, and infrared (IR) maps. The VLA has been used to study the Zeeman effect in the 21cm HI line seen in absorption against radio sources in the Cygnus-X region. These sources are mostly galactic nebulae or HII regions, and are bright and compact in this region of the spectrum. HI absorption lines are strong against these regions and the VLA is capable of detecting the weak Zeeman effect within them. Support for this work was provided by the NSF PAARE program to South Carolina State University under award AST-0750814.

Linear Polarization Measurements of Chromospheric Emission Lines

NASA Technical Reports Server (NTRS)

Sheeley, N. R., Jr.; Keller, C. U.

2003-01-01

We have used the Zurich Imaging Stokes Polarimeter (ZIMPOL I) with the McMath-Pierce 1.5 m main telescope on Kitt Peak to obtain linear polarization measurements of the off-limb chromosphere with a sensitivity better than 1 x 10(exp -5). We found that the off-disk observations require a combination of good seeing (to show the emission lines) and a clean heliostat (to avoid contamination by scattered light from the Sun's disk). When these conditions were met, we obtained the following principal results: 1. Sometimes self-reversed emission lines of neutral and singly ionized metals showed linear polarization caused by the transverse Zeeman effect or by instrumental cross talk from the longitudinal Zeeman effect in chromospheric magnetic fields. Otherwise, these lines tended to depolarize the scattered continuum radiation by amounts that ranged up to 0.2%. 2. Lines previously known to show scattering polarization just inside the limb (such as the Na I lambda5889 D2 and the He I lambda5876 D3 lines) showed even more polarization above the Sun's limb, with values approaching 0.7%. 3. The O I triplet at lambda7772, lambda7774, and lambda7775 showed a range of polarizations. The lambda7775 line, whose maximum intrinsic polarizability, P(sub max), is less than 1%, revealed mainly Zeeman contributions from chromospheric magnetic fields. However, the more sensitive lambda7772 (P(sub max) = 19%) and lambda7774 (P(sub max) = 29%) lines had relatively strong scattering polarizations of approximately 0.3% in addition to their Zeeman polarizations. At times of good seeing, the polarization spectra resolve into fine structures that seem to be chromospheric spicules.

First-principles analysis of X-ray magnetic circular dichroism for transition metal complex oxides

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

Ikeno, Hidekazu, E-mail: h-ikeno@21c.osakafu-u.ac.jp

2016-10-14

X-ray magnetic circular dichroism (XMCD) is widely used for the characterization of magnetism of materials. However, information from XMCD related to the atomic, electronic, and magnetic structures is not fully utilized due to the lack of reliable theoretical tools for spectral analysis. In this work, the first-principles configuration interaction (CI) calculations for X-ray absorption spectra developed by the author were extended for the calculation of XMCD, where the Zeeman energy was taken into the Hamiltonian of the CI to mimic magnetic polarization in the solid state. This technique was applied to interpret the L{sub 2,3} XMCD from 3d transition metalmore » complex oxides, such as NiFe{sub 2}O{sub 4} and FeTiO{sub 3}. The experimental XMCD spectra were quantitatively reproduced using this method. The oxidation states as well as the magnetic ordering between transition metal ions on crystallographically different sites in NiFe{sub 2}O{sub 4} can be unambiguously determined. A first-principles analysis of XMCD in FeTiO{sub 3} revealed the presence of Fe{sup 3+} and Ti{sup 3+} ions, which indicates that the charge transfer from Fe to Ti ions occurs. The origin of magnetic polarization of Ti ions in FeTiO{sub 3} was also discussed.« less

Recent Topics of Organic Superconductors

NASA Astrophysics Data System (ADS)

Ardavan, Arzhang; Brown, Stuart; Kagoshima, Seiichi; Kanoda, Kazushi; Kuroki, Kazuhiko; Mori, Hatsumi; Ogata, Masao; Uji, Shinya; Wosnitza, Jochen

2012-01-01

Recent developments in research into superconductivity in organic materials are reviewed. In the epoch-defining quasi-one-dimensional TMTSF superconductors with Tc ˜ 1 K, Tc decreases monotonically with increasing pressure, as do signatures of spin fluctuations in the normal state, providing good evidence for magnetically-mediated pairing. Upper critical fields exceed the Zeeman-limiting field by several times, suggesting triplet pairing or a transition to an inhomogeneous superconducting state at high magnetic fields, while triplet pairing is ruled out at low fields by NMR Knight-shift measurements. Evidence for a spatially inhomogeneous superconducting state, Fulde--Ferrel--Larkin--Ovchinnikov state, which has long been sought in various superconducting systems, is now captured by thermodynamic and transport measurements for clean and highly two-dimensional BEDT-TTF and BETS superconductors. Some of the layered superconductors also serve as model systems for Mott physics on anisotropic triangular lattice. For example, the Nernst effect and the pseudo-gap behavior in NMR relaxation are enhanced near to the Mott transition. In the case of increasing spin frustration, the superconducting transition temperature is depressed, and antiferromagnetic ordering is eliminated altogether in the adjacent Mott insulating phase. There is an increasing number of materials exhibiting superconductivity in competition or cooperation with charge order. Theoretical studies shed light on the role of spin and/or charge fluctuations for superconductivity appearing under conditions close to those of correlation-induced insulating phases in the diversity of organic materials.

Intensity dependence narrowing of electromagnetically induced absorption in a Doppler-broadened medium

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

Dimitrijevic, J.; Arsenovic, D.; Jelenkovic, B. M.

In this paper, we present a theoretical model for studying the interaction between linearly polarized laser light and near-degenerated Zeeman sublevels for a multiple V-type atomic system of {sup 2}S{sub 1/2}F{sub g}=2{yields}{sup 2}P{sub 3/2}F{sub e}=3 transition in {sup 87}Rb. We have calculated the laser absorption in a Hanle configuration, as well as the amplitudes and the widths of electromagnetically induced absorption (EIA) in the range of laser intensities from 0.01 to 40 mW/cm{sup 2}. Our results, showing nonvanishing EIA amplitude, a nonmonotonic increase of the EIA width for the increase of laser intensity, and pronounced shape differences of the Hanlemore » EIA curves at different laser intensities, are in good agreement with recent experimental results. We have found that the EIA behaves differently than the electromagnetically induced transparency (EIT) as a function of the laser intensity. Both the amplitude and width of the EIA have narrow maximums at 1 to 2 mW/cm{sup 2}. We have shown the strong influence of Doppler broadening of atomic transition on Hanle resonances and have suggested the explanation of it.« less

A New Formulation for Hybrid LES-RANS Computations

NASA Technical Reports Server (NTRS)

Woodruff, Stephen L.

2013-01-01

Ideally, a hybrid LES-RANS computation would employ LES only where necessary to make up for the failure of the RANS model to provide sufficient accuracy or to provide time-dependent information. Current approaches are fairly restrictive in the placement of LES and RANS regions; an LES-RANS transition in a boundary layer, for example, yields an unphysical log-layer shift. A hybrid computation is formulated here to allow greater control over the placement of LES and RANS regions and the transitions between them. The concept of model invariance is introduced, which provides a basis for interpreting hybrid results within an LES-RANS transition zone. Consequences of imposing model invariance include the addition of terms to the governing equations that compensate for unphysical gradients created as the model changes between RANS and LES. Computational results illustrate the increased accuracy of the approach and its insensitivity to the location of the transition and to the blending function employed.

Pressure-Induced Phase Transitions of n-Tridecane

NASA Astrophysics Data System (ADS)

Yamashita, Motoi

Pressure-induced phase transition behavior of n-tridecane from the ordered phase through the rotator phase into the liquid phase has been investigated by using Fourier transform infrared spectroscopy at 25 °C. The transition between the ordered and rotator phases has been observed in the pressure range of 270-220 MPa and the transition between the rotator and liquid phases has been observed in the pressure range of 171-112 MPa, within the experimental error of ±50 MPa. The populations of the -gtg- + -gtg'-, -gg- and gt- defects determined from the methylene wagging mode are smaller in the rotator phase than in the liquid phase and are smaller under higher pressure in both of the rotator and liquid phases. A relationship has been found between the conformation and the intensity of the 890 cm-1 band, which has been assigned as the methyl rocking mode and has been considered as insensitive to conformation.

Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal.

PubMed

Zhao, Bin; Sun, Zhigang; Guo, Hua

2015-06-28

Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

Effect of pressure on the metamagnetic transition of DyB 6 single crystal

NASA Astrophysics Data System (ADS)

Sakai, T.; Oomi, G.; Uwatoko, Y.; Kunii, S.

2007-03-01

The effects of pressure on the magnetization ( M) and the magnetostriction (MS) for DyB 6 single crystal have been measured at 4.2 K. It is found that the M loops are insensitive to pressure, whereas the large MS with magnitude of 0.5% at 5 T at ambient pressure is rapidly suppressed by applying pressure. The metamagnetic transition field HM in the M curve increases slightly by applying pressure with the rate of increase, ∂ ln HM/∂ P, of 0.03 GPa -1, which is almost the same value as that for TN, 0.04 GPa -1.

Reconstitution of the Hepatic Asialoglycoprotein Receptor with Phospholipid Vesicles

NASA Astrophysics Data System (ADS)

Klausner, Richard D.; Bridges, Kenneth; Tsunoo, Hajime; Blumenthal, Robert; Weinstein, John N.; Ashwell, Gilbert

1980-09-01

A solubilized detergent-free preparation of the hepatic binding protein specific for asialoglycoproteins associates spontaneously with small unilamellar lipid vesicles. This process is independent of the phase transition of the lipid and effectively restores the specific binding activity of the receptor protein. The insensitivity of the resulting lipid-protein complex to ionic strength provides evidence for a hydrophobic interaction. There is a perturbation of the lipid phase transition concomitant with addition of the protein. Circular dichroism studies indicate that the protein undergoes a conformational change on association with lipid. Binding of specific ligand produces further physical changes in the receptor as indicated by alterations in the tryptophan fluorescence quenching pattern.

Evolution of circadian rhythms: from bacteria to human.

PubMed

Bhadra, Utpal; Thakkar, Nirav; Das, Paromita; Pal Bhadra, Manika

2017-07-01

The human body persists in its rhythm as per its initial time zone, and transition always occur according to solar movements around the earth over 24 h. While traveling across different latitudes and longitudes, at the pace exceeding the earth's movement, the changes in the external cues exceed the level of toleration of the body's biological clock. This poses an alteration in our physiological activities of sleep-wake pattern, mental alertness, organ movement, and eating habits, causing them to temporarily lose the track of time. This is further re-synchronized with the physiological cues of the destination over time. The mechanism of resetting of the clocks with varying time zones and cues occur in organisms from bacteria to humans. It is the result of the evolution of different pathways and molecular mechanisms over the time. There has been evolution of numerous comprehensive mechanisms using various research tools to get a deeper insight into the rapid turnover of molecular mechanisms in various species. This review reports insights into the evolution of the circadian mechanism and its evolutionary shift which is vital and plays a major role in assisting different organisms to adapt in different zones and controls their internal biological clocks with changing external cues. Copyright © 2017 Elsevier B.V. All rights reserved.

Valley density-wave (VDW) and Superconductivity in Iron-Pnictides

NASA Astrophysics Data System (ADS)

Cvetkovic, Vladimir; Tesanovic, Zlatko

2009-03-01

One of the experimentally observed features of iron-pnictide superconductors is the structural transition and SDW ordering occurring at almost the same temperature. Starting from a tight-binding model [1], we construct an effective theory for iron-pnictides with the distinctive two hole and two electron Fermi surfaces. This theory is then mapped onto a negative-U Hubbard model with additional orbital and spin flavors [2]. We demonstrate that the superconducting instability of the attractive Hubbard model --- valley density-wave (VDW) --- corresponds to the observed structural and SDW orders. The deviations from perfect nesting between the hole and electron Fermi surfaces are mapped onto the Zeeman field which causes portions of Fermi surface to remain ungapped. The origin of pnictide superconductivity in this model, and its ties to the VDW are discussed. [1] V. Cvetkovic and Z. Tesanovic, http://arxiv.org/abs/0804.4678. [2] V. Cvetkovic and Z. Tesanovic, http://arxiv.org/abs/0808.3742.

Faraday effect in a short pulse propagating in a resonant medium under an ultra-strong magnetic field

NASA Astrophysics Data System (ADS)

Huang, J. G.; Slavcheva, G.; Hess, O.

2008-04-01

We propose a dynamical model for description of the nonlinear Faraday rotation experienced by a short pulse propagating in a resonant medium subject to an ultra-strong static magnetic field. Under the assumptions of a sufficiently strong external magnetic field, such that the Zeeman splitting of the quantum system energy levels is large compared to the linewidth of the optical transitions involved and the bandwidth of the incident light, the light effectively interacts with a two-level system. Our numerical simulations show that the Faraday effect under these conditions is significantly distinctive from the one caused by weak to moderately strong magnetic field. Nonlinear coherent effects such as inhomogeneous polarization rotation along the pulse duration and an onset of a circularly polarized stimulated emission and coherent ringing have been demonstrated. Some views on the experimental observation of the predicted phenomena are given.

Majorana splitting from critical currents in Josephson junctions

NASA Astrophysics Data System (ADS)

Cayao, Jorge; San-Jose, Pablo; Black-Schaffer, Annica M.; Aguado, Ramón; Prada, Elsa

2017-11-01

A semiconducting nanowire with strong Rashba spin-orbit coupling and coupled to a superconductor can be tuned by an external Zeeman field into a topological phase with Majorana zero modes. Here we theoretically investigate how this exotic topological superconductor phase manifests in Josephson junctions based on such proximitized nanowires. In particular, we focus on critical currents in the short junction limit (LN≪ξ , where LN is the junction length and ξ is the superconducting coherence length) and show that they contain important information about nontrivial topology and Majoranas. This includes signatures of the gap inversion at the topological transition and a unique oscillatory pattern that originates from Majorana interference. Interestingly, this pattern can be modified by tuning the transmission across the junction, thus providing complementary evidence of Majoranas and their energy splittings beyond standard tunnel spectroscopy experiments, while offering further tunability by virtue of the Josephson effect.

Microwave spectroscopy of the 1 s n p P3J fine structure of high Rydberg states in 4He

NASA Astrophysics Data System (ADS)

Deller, A.; Hogan, S. D.

2018-01-01

The 1 s n p P3J fine structure of high Rydberg states in helium has been measured by microwave spectroscopy of single-photon transitions from 1 s n s S31 levels in pulsed supersonic beams. For states with principal quantum numbers in the range from n =34 to 36, the J =0 →2 and J =1 →2 fine structure intervals were both observed. For values of n between 45 and 51 only the larger J =0 →2 interval was resolved. The experimental results are in good agreement with theoretical predictions. Detailed characterization of residual uncanceled electric and magnetic fields in the experimental apparatus and calculations of the Stark and Zeeman structures of the Rydberg states in weak fields were used to quantify systematic contributions to the uncertainties in the measurements.

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.

Type-controlled nanodevices based on encapsulated few-layer black phosphorus for quantum transport

NASA Astrophysics Data System (ADS)

Long, Gen; Xu, Shuigang; Shen, Junying; Hou, Jianqiang; Wu, Zefei; Han, Tianyi; Lin, Jiangxiazi; Wong, Wing Ki; Cai, Yuan; Lortz, Rolf; Wang, Ning

2016-09-01

We demonstrate that encapsulation of atomically thin black phosphorus (BP) by hexagonal boron nitride (h-BN) sheets is very effective for minimizing the interface impurities induced during fabrication of BP channel material for quantum transport nanodevices. Highly stable BP nanodevices with ultrahigh mobility and controllable types are realized through depositing appropriate metal electrodes after conducting a selective etching to the BP encapsulation structure. Chromium and titanium are suitable metal electrodes for BP channels to control the transition from a p-type unipolar property to ambipolar characteristic because of different work functions. Record-high mobilities of 6000 cm2 V-1 s-1 and 8400 cm2 V-1 s-1 are respectively obtained for electrons and holes at cryogenic temperatures. High-mobility BP devices enable the investigation of quantum oscillations with an indistinguishable Zeeman effect in laboratory magnetic field.

EPR study of copper(II) ions in zinc 1-malate trihydrate

NASA Astrophysics Data System (ADS)

Bonomo, Raffaele P.; Di Bilio, Angel J.; Riggi, Francesco

1988-10-01

The EPR spectrum of Cu 2+ ions in zinc 1-malate trihydrate has been measured at 150 K for a large number of orientations of the applied magnetic field. Analysis yields the following spin Hamiltonian parameters: g x=2.0894±0.0009, A x=-12.0±1.5, g y=2.0879±0.0005, A y=-8.7±1.0, R=-0.7±1.5, g z=2.4249±0.0005, A z=-120.1±0.9, P=9.9±0.5, where the units of A and P are 10 4 cm -1. The Zeeman and hyperfine coupling tensors are coincident within 2°. The spectrum shows forbidden transitions with abnormal intensity due to a large quadrupolar interaction. The direction of g z points towards the hydroxyl oxygen while the g x and g y directions lie approximately along the metal-carboxylate oxygen bond.

Topological Triply Degenerate Points Induced by Spin-Tensor-Momentum Couplings

NASA Astrophysics Data System (ADS)

Hu, Haiping; Hou, Junpeng; Zhang, Fan; Zhang, Chuanwei

2018-06-01

The recent discovery of triply degenerate points (TDPs) in topological materials has opened a new perspective toward the realization of novel quasiparticles without counterparts in quantum field theory. The emergence of such protected nodes is often attributed to spin-vector-momentum couplings. We show that the interplay between spin-tensor- and spin-vector-momentum couplings can induce three types of TDPs, classified by different monopole charges (C =±2 , ±1 , 0). A Zeeman field can lift them into Weyl points with distinct numbers and charges. Different TDPs of the same type are connected by intriguing Fermi arcs at surfaces, and transitions between different types are accompanied by level crossings along high-symmetry lines. We further propose an experimental scheme to realize such TDPs in cold-atom optical lattices. Our results provide a framework for studying spin-tensor-momentum coupling-induced TDPs and other exotic quasiparticles.

All-optical materials design of chiral edge modes in transition-metal dichalcogenides

PubMed Central

Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas P.

2016-01-01

Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. We develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details. PMID:27721504

Exploring the robustness of a noise correlation resonance in a Zeeman EIT system

NASA Astrophysics Data System (ADS)

O'Leary, Shannon; Crescimanno, Michael; Strehlow, Henry; Snider, Chad

2011-05-01

Using a single diode laser with large phase noise (linewidth ~100 MHz) resonant with Zeeman EIT in rubidium vapor, we examine intensity noise correlations of orthogonally-polarized laser components. A sharp correlation feature (~100 Hz) is shown to be power-broadening resistant at low powers. However, the limitations of this resistance are revealed, with the onset of a power-broadening regime once a threshold power is crossed. Possible mechanisms for this broadening, due to decoherence of the ground state superposition, are experimentally explored and results are compared to a model. Understanding the limits of this noise correlation feature is essential to practical applications such as magnetometry.

Entanglement-Based dc Magnetometry with Separated Ions*

NASA Astrophysics Data System (ADS)

Ruster, T.; Kaufmann, H.; Luda, M. A.; Kaushal, V.; Schmiegelow, C. T.; Schmidt-Kaler, F.; Poschinger, U. G.

2017-07-01

We demonstrate sensing of inhomogeneous dc magnetic fields by employing entangled trapped ions, which are shuttled in a segmented Paul trap. As sensor states, we use Bell states of the type |↑↓ ⟩ +ei φ|↓↑ ⟩ encoded in two 40Ca+ ions stored at different locations. The linear Zeeman effect leads to the accumulation of a relative phase φ , which serves for measuring the magnetic-field difference between the constituent locations. Common-mode magnetic-field fluctuations are rejected by the entangled sensor state, which gives rise to excellent sensitivity without employing dynamical decoupling and therefore enables accurate dc sensing. Consecutive measurements on sensor states encoded in the S1 /2 ground state and in the D5 /2 metastable state are used to separate an ac Zeeman shift from the linear dc Zeeman effect. We measure magnetic-field differences over distances of up to 6.2 mm, with accuracies down to 300 fT and sensitivities down to 12 pT /√{Hz }. Our sensing scheme features spatial resolutions in the 20-nm range. For optimizing the information gain while maintaining a high dynamic range, we implement an algorithm for Bayesian frequency estimation.

ACTIVE REGION FILAMENTS MIGHT HARBOR WEAK MAGNETIC FIELDS

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

Díaz Baso, C. J.; Martínez González, M. J.; Asensio Ramos, A., E-mail: cdiazbas@iac.es

Recent spectropolarimetric observations of active region filaments have revealed polarization profiles with signatures typical of the strong field Zeeman regime. The conspicuous absence in those observations of scattering polarization and Hanle effect signatures was then pointed out by some authors. This was interpreted as either a signature of mixed “turbulent” field components or as a result of optical thickness. In this article, we present a natural scenario to explain these Zeeman-only spectropolarimetric observations of active region (AR) filaments. We propose a two-component model, one on top of the other. Both components have horizontal fields, with the azimuth difference between themmore » being close to 90°. The component that lies lower in the atmosphere is permeated by a strong field of the order of 600 G, while the upper component has much weaker fields, of the order of 10 G. The ensuing scattering polarization signatures of the individual components have opposite signs, so its combination along the line of sight reduces—and even can cancel out—the Hanle signatures, giving rise to an apparent Zeeman-only profile. This model is also applicable to other chromospheric structures seen in absorption above ARs.« less

Extremely large magnetoresistance induced by Zeeman effect-driven electron-hole compensation and topological protection in MoSi2

NASA Astrophysics Data System (ADS)

Matin, M.; Mondal, Rajib; Barman, N.; Thamizhavel, A.; Dhar, S. K.

2018-05-01

Here, we report an extremely large positive magnetoresistance (XMR) in a single-crystal sample of MoSi2, approaching almost 107% at 2 K in a 14-T magnetic field without appreciable saturation. Hall resistivity data reveal an uncompensated nature of MoSi2 with an electron-hole compensation level sufficient enough to expect strong saturation of magnetoresistance in the high-field regime. Magnetotransport and the complementary de Haas-van Alphen (dHvA) oscillations results, however, suggest that strong Zeeman effect causes a magnetic field-induced modulation of the Fermi pockets and drives the system towards perfect electron-hole compensation condition in the high-field regime. Thus, the nonsaturating XMR of this semimetal arises under the unconventional situation of Zeeman effect-driven electron-hole compensation, whereas its huge magnitude is decided solely by the ultralarge value of the carrier mobility. Intrinsic ultralarge carrier mobility, strong suppression of backward scattering of the charge carriers, and nontrivial Berry phase in dHvA oscillations attest to the topological character of MoSi2. Therefore, this semimetal represents another material hosting combination of topological and conventional electronic phases.

Control of second-harmonic generation in doubly resonant aluminum nitride microrings to address a rubidium two-photon clock transition.

PubMed

Surya, Joshua B; Guo, Xiang; Zou, Chang-Ling; Tang, Hong X

2018-06-01

Nonlinear optical effects have been studied extensively in microresonators as more photonics applications transitions to integrated on-chip platforms. Due to low optical losses and small mode volumes, microresonators are demonstrably the state-of-the-art platform for second-harmonic generation (SHG). However, the working bandwidth of such microresonator-based devices is relatively small, presenting a challenge for applications where a specifically targeted wavelength needs to be addressed. In this Letter, we analyze the phase-matching window and resonance wavelength with respect to varying microring widths, radii, and temperatures. A chip with precise design parameters was fabricated with phase matching realized at the exact wavelength of a two-photon transition of Rb85. This procedure can be generalized to any target pump wavelength in the telecom band with picometer precision.

Laser theory with finite atom-field interacting time

NASA Astrophysics Data System (ADS)

Yu, Deshui; Chen, Jingbiao

2008-07-01

We investigate the influence of atomic transit time τ on the laser linewidth by the quantum Langevin approach. With comparing the bandwidths of cavity mode κ , atomic polarization γab , and atomic transit broadening τ-1 , we study the laser linewidth in different limits. We also discuss the spectrum of fluctuations of output field and the influence of pumping statistics on the output field.The influence of atomic transit time τ on laser field has not been carefully discussed before, to our knowledge. In particular, a laser operating in the region of γab≪τ-1≪κ/2 appears not to have been analyzed in previous laser theories. Our work could be a useful complementarity to laser theory. It is also an important theoretical foundation for the recently proposed active optical atomic clock based on bad-cavity laser mechanism.

Absolute frequency list of the ν3-band transitions of methane at a relative uncertainty level of 10(-11).

PubMed

Okubo, Sho; Nakayama, Hirotaka; Iwakuni, Kana; Inaba, Hajime; Sasada, Hiroyuki

2011-11-21

We determine the absolute frequencies of 56 rotation-vibration transitions of the ν(3) band of CH(4) from 88.2 to 90.5 THz with a typical uncertainty of 2 kHz corresponding to a relative uncertainty of 2.2 × 10(-11) over an average time of a few hundred seconds. Saturated absorption lines are observed using a difference-frequency-generation source and a cavity-enhanced absorption cell, and the transition frequencies are measured with a fiber-laser-based optical frequency comb referenced to a rubidium atomic clock linked to the international atomic time. The determined value of the P(7) F(2)((2)) line is consistent with the International Committee for Weights and Measures recommendation within the uncertainty. © 2011 Optical Society of America

Watchdog activity monitor (WAM) for use wth high coverage processor self-test

NASA Technical Reports Server (NTRS)

Tulpule, Bhalchandra R. (Inventor); Crosset, III, Richard W. (Inventor); Versailles, Richard E. (Inventor)

1988-01-01

A high fault coverage, instruction modeled self-test for a signal processor in a user environment is disclosed. The self-test executes a sequence of sub-tests and issues a state transition signal upon the execution of each sub-test. The self-test may be combined with a watchdog activity monitor (WAM) which provides a test-failure signal in the presence of a counted number of state transitions not agreeing with an expected number. An independent measure of time may be provided in the WAM to increase fault coverage by checking the processor's clock. Additionally, redundant processor systems are protected from inadvertent unsevering of a severed processor using a unique unsever arming technique and apparatus.

Transitional fossils and the origin of turtles

PubMed Central

Lyson, Tyler R.; Bever, Gabe S.; Bhullar, Bhart-Anjan S.; Joyce, Walter G.; Gauthier, Jacques A.

2010-01-01

The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile–bird clade, (ii) the lizard–tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard–tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the ‘parareptile’ Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks. PMID:20534602

Mechanocaloric effects in shape memory alloys.

PubMed

Mañosa, Lluís; Planes, Antoni

2016-08-13

Shape memory alloys (SMA) are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition, gives rise to giant mechanocaloric effects. In non-magnetic SMA, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress, whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic SMA, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic SMA.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. © 2016 The Author(s).

Activation energy of the low-load NaCl transition from nanoindentation loading curves.

PubMed

Kaupp, Gerd

2014-01-01

Access to activation energies E(a) of phase transitions is opened by unprecedented analyses of temperature dependent nanoindentation loading curves. It is based on kinks in linearized loading curves, with additional support by coincidence of kink and electrical conductivity of silicon loading curves. Physical properties of B1, B2, NaCl and further phases are discussed. The normalized low-load transition energy of NaCl (Wtrans/µN) increases with temperature and slightly decreases with load. Its semi-logarithmic plot versus T obtains activation energy E(a)/µN for calculation of the transition work for all interesting temperatures and pressures. Arrhenius-type activation energy (kJ/mol) is unavailable for indentation phase transitions. The E(a) per load normalization proves insensitive to creep-on-load, which excludes normalization to depth or volume for large temperature ranges. Such phase transition E(a)/µN is unprecedented material's property and will be of practical importance for the compatibility of composite materials under impact and further shearing interactions at elevated temperatures. © 2014 Wiley Periodicals, Inc.

Inhibitor effects during the cell cycle in Chlamydomonas reinhardtii. Determination of transition points in asynchronous cultures

PubMed Central

1975-01-01

A wide variety of inhibitors (drugs, antibiotics, and antimetabolites) will block cell division within an ongoing cell cycle in autotrophic cultures of Chlamydomonas reinhardtii. To determine when during the cell cycle a given inhibitor is effective in preventing cell division, a technique is described which does not rely on the use of synchronous cultures. The technique permits the measurement of transition points, the cell cycle stage at which the subsequent cell division becomes insensitive to the effects of an inhibitor. A map of transition points in the cell cycle reveals that they are grouped into two broad periods, the second and fourth quarters. In general, inhibitors which block organellar DNA, RNA, and protein synthesis have second-quarter transition points, while those which inhibit nuclear cytoplasmic macromolecular synthesis have fourth-quarter transition points. The specific grouping of these transition points into two periods suggests that the synthesis of organellar components is completed midway through the cell cycle and that the synthesis of nonorganellar components required for cell division is not completed until late in the cell cycle. PMID:1176526

Mechanocaloric effects in shape memory alloys

PubMed Central

2016-01-01

Shape memory alloys (SMA) are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition, gives rise to giant mechanocaloric effects. In non-magnetic SMA, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress, whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic SMA, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic SMA. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’. PMID:27402931

High-power Al-free active region (λ= 852nm) DFB laser diodes for atomic clocks and interferometry applications

NASA Astrophysics Data System (ADS)

Ligeret, V.; Vermersch, F.-J.; Bansropun, S.; Lecomte, M.; Calligaro, M.; Parillaud, O.; Krakowski, M.

2017-11-01

Atomic clocks will be used in the future European positioning system Galileo. Among them, the optically pumped clocks provide a better alternative with comparable accuracy for a more compact system. For these systems, diode lasers emitting at 852nm are strategic components. The laser in a conventional bench for atomic clocks presents disadvantages for spatial applications. A better approach would be to realise a system based on a distributed-feedback laser (DFB). We have developed the technological foundations of such lasers operating at 852nm. These include an Al free active region, a single spatial mode ridge waveguide and a DFB structure. The device is a separate confinement heterostructure with a GaInP large optical cavity and a single compressive strained GaInAsP quantum well. The broad area laser diodes are characterised by low internal losses (<3cm -1 ), a high internal efficiency (94%) and a low transparency current density (100A/cm2). For an AR-HR coated ridge Fabry Perot laser, we obtain a power of 230mW with M2=1.3. An optical power of 150mW was obtained at 854nm wavelength, 20°C for AR-HR coated devices. We obtain a single spatial mode emission with M2=1.21 and a SMSR over 30dB, both at 150mW. DFB Lasers at 852.12nm, corresponding to the D2 caesium transition, were then realised with a power of 40mW, 37°C for uncoated devices. The SMSR is over 30dB and the M2=1.33 at 40mW. Furthermore, the preliminary results of the linewidth obtained with a Fabry Perot interferometer give a value of less than 2MHz.

A Temporarily Red Light-Insensitive Mutant of Tomato Lacks a Light-Stable, B-Like Phytochrome.

PubMed Central

Van Tuinen, A.; Kerckhoffs, LHJ.; Nagatani, A.; Kendrick, R. E.; Koornneef, M.

1995-01-01

We have selected four recessive mutants in tomato (Lycopersicon esculentum Mill.) that, under continuous red light (R), have long hypocotyls and small cotyledons compared to wild type (WT), a phenotype typical of phytochrome B (phyB) mutants of other species. These mutants, which are allelic, are only insensitive to R during the first 2 days upon transition from darkness to R, and therefore we propose the gene symbol tri (temporarily red light insensitive). White light-grown mutant plants have a more elongated growth habit than that of the WT. An immunochemically and spectrophotometrically detectable phyB-like polypeptide detectable in the WT is absent or below detection limits in the tri1 mutant. In contrast to the absence of an elongation growth response to far-red light (FR) given at the end of the daily photoperiod (EODFR) in all phyB-deficient mutants so far characterized, the tri1 mutant responds to EODFR treatment. The tri1 mutant also shows a strong response to supplementary daytime far-red light. We propose that the phyB-like phytochrome deficient in the tri mutants plays a major role during de-etiolation and that other light-stable phytochromes can regulate the EODFR and shade-avoidance responses in tomato. PMID:12228517

Systematics-insensitive Periodic Signal Search with K2

NASA Astrophysics Data System (ADS)

Angus, Ruth; Foreman-Mackey, Daniel; Johnson, John A.

2016-02-01

From pulsating stars to transiting exoplanets, the search for periodic signals in K2 data, Kepler’s two-wheeled extension, is relevant to a long list of scientific goals. Systematics affecting K2 light curves due to the decreased spacecraft pointing precision inhibit the easy extraction of periodic signals from the data. We here develop a method for producing periodograms of K2 light curves that are insensitive to pointing-induced systematics; the Systematics-insensitive Periodogram (SIP). Traditional sine-fitting periodograms use a generative model to find the frequency of a sinusoid that best describes the data. We extend this principle by including systematic trends, based on a set of “eigen light curves,” following Foreman-Mackey et al., in our generative model as well as a sum of sine and cosine functions over a grid of frequencies. Using this method we are able to produce periodograms with vastly reduced systematic features. The quality of the resulting periodograms are such that we can recover acoustic oscillations in giant stars and measure stellar rotation periods without the need for any detrending. The algorithm is also applicable to the detection of other periodic phenomena such as variable stars, eclipsing binaries and short-period exoplanet candidates. The SIP code is available at https://github.com/RuthAngus/SIPK2.

Force generation and temperature-jump and length-jump tension transients in muscle fibers.

PubMed Central

Davis, J S; Rodgers, M E

1995-01-01

Muscle tension rises with increasing temperature. The kinetics that govern the tension rise of maximally Ca(2+)-activated, skinned rabbit psoas fibers over a temperature range of 0-30 degrees C was characterized in laser temperature-jump experiments. The kinetic response is simple and can be readily interpreted in terms of a basic three-step mechanism of contraction, which includes a temperature-sensitive rapid preequilibrium(a) linked to a temperature-insensitive rate-limiting step and followed by a temperature-sensitive tension-generating step. These data and mechanism are compared and contrasted with the more complex length-jump Huxley-Simmons phases in which all states that generate tension or bear tension are perturbed. The rate of the Huxley-Simmons phase 4 is temperature sensitive at low temperatures but plateaus at high temperatures, indicating a change in rate-limiting step from a temperature-sensitive (phase 4a) to a temperature-insensitive reaction (phase 4b); the latter appears to correlate with the slow, temperature-insensitive temperature-jump relaxation. Phase 3 is absent in the temperature-jump, which excludes it from tension generation. We confirm that de novo tension generation occurs as an order-disorder transition during phase 2slow and the equivalent, temperature-sensitive temperature-jump relaxation. PMID:7612845

Entrainment range of the suprachiasmatic nucleus affected by the difference in the neuronal amplitudes between the light-sensitive and light-insensitive regions.

PubMed

Gu, Changgui; Yang, Huijie; Ruan, Zhongyuan

2017-04-01

Mammals not only can be synchronized to the natural 24-h light-dark cycle, but also to a cycle with a non-24-h period. The range of the period of the external cycle, for which the animals can be entrained to, is called the entrainment range, which differs among species. The entrainment range as a characteristic of the animal is determined by the main circadian clock, i.e., the suprachiasmatic nucleus (SCN) in the brain. The SCN is composed of ∼10000 heterogeneous neurons, which can be divided into two subgroups, i.e., the ventrolateral subgroup (VL) directly receiving the light information from the retina and relaying the information to the dorsomedial subgroup (DM). Among the SCN neurons, the amplitudes are different; however, it is unclear that the amplitude is related to the location of the neurons in experiments. In the present study, we examined the effect of the difference in the neuronal amplitude between the VL and the DM on the entrainment range of the SCN, based on a mathematical model, i.e., the Poincaré model, which is used to describe the circadian clock. We find that the maximal entrainment range is obtained when the difference is equal to a critical point. If the difference of the amplitudes of the VL neurons to the amplitudes of the DM neurons is smaller than a critical point, with the increase of the difference, the entrainment range of the SCN increases, while if the difference is larger than the critical point, the entrainment range decreases with the increase of the difference. Our finding may give a potential explanation for the diversity of the entrainment range among species.

Cholinergic modulation of neuronal excitability in the rat suprachiasmatic nucleus.

PubMed

Yang, Jyh-Jeen; Wang, Yu-Ting; Cheng, Pi-Cheng; Kuo, Yeh-Jung; Huang, Rong-Chi

2010-03-01

The central cholinergic system regulates both the circadian clock and sleep-wake cycle and may participate in the feedback control of vigilance states on neural excitability in the suprachiasmatic nucleus (SCN) that houses the circadian clock. Here we investigate the mechanisms for cholinergic modulation of SCN neuron excitability. Cell-attached recordings indicate that the nonspecific cholinergic agonist carbachol (CCh) inhibited 55% and excited 21% SCN neurons, leaving 24% nonresponsive. Similar response proportions were produced by two muscarinic receptor [muscarinic acetylcholine receptor (mAChR)] agonists, muscarine and McN-A-343 (M1/4 agonist), but not by two nicotinic receptor (nAChR) agonists, nicotine and choline (alpha7-nAChR agonist), which, however, produced similar response proportions. Whole cell and perforated-patch recordings indicate that CCh inhibition of firing was mediated by membrane hyperpolarization due to activation of background K(+) currents, which were sensitive to submillimolar concentrations of Ba(2+) and to millimolar concentrations of TEA. RT-PCR analysis demonstrated the presence of mRNA for M1 to M5 mAChRs in SCN. The CCh-induced hyperpolarization and activation of background K(+) currents were blocked by M4 antagonists and to a lesser degree by M1 antagonists but were insensitive to the antagonists for M2 or M3, suggesting the involvement of M4 and M1 mAChRs in mediating CCh inhibition of firing. CCh enhancement of firing was mediated by membrane depolarization, as a result of postsynaptic inhibition of background K(+) currents. The multiple actions of cholinergic modulation via multiple receptors and ion channels may allow acetylcholine to finely control SCN neuron excitability in different physiological settings.

Entrainment range of the suprachiasmatic nucleus affected by the difference in the neuronal amplitudes between the light-sensitive and light-insensitive regions

NASA Astrophysics Data System (ADS)

Gu, Changgui; Yang, Huijie; Ruan, Zhongyuan

2017-04-01

Mammals not only can be synchronized to the natural 24-h light-dark cycle, but also to a cycle with a non-24-h period. The range of the period of the external cycle, for which the animals can be entrained to, is called the entrainment range, which differs among species. The entrainment range as a characteristic of the animal is determined by the main circadian clock, i.e., the suprachiasmatic nucleus (SCN) in the brain. The SCN is composed of ˜10 000 heterogeneous neurons, which can be divided into two subgroups, i.e., the ventrolateral subgroup (VL) directly receiving the light information from the retina and relaying the information to the dorsomedial subgroup (DM). Among the SCN neurons, the amplitudes are different; however, it is unclear that the amplitude is related to the location of the neurons in experiments. In the present study, we examined the effect of the difference in the neuronal amplitude between the VL and the DM on the entrainment range of the SCN, based on a mathematical model, i.e., the Poincaré model, which is used to describe the circadian clock. We find that the maximal entrainment range is obtained when the difference is equal to a critical point. If the difference of the amplitudes of the VL neurons to the amplitudes of the DM neurons is smaller than a critical point, with the increase of the difference, the entrainment range of the SCN increases, while if the difference is larger than the critical point, the entrainment range decreases with the increase of the difference. Our finding may give a potential explanation for the diversity of the entrainment range among species.

Effect of Fe-site Substitution on Pressure-induced Spin Transition in SrFeO2

NASA Astrophysics Data System (ADS)

Kawakami, Takateru; Yamamoto, Takafumi; Yata, Kanami; Ishii, Minoru; Watanabe, Yoshitaka; Mizumaki, Masaichiro; Kawamura, Naomi; Ishimatsu, Naoki; Takahashi, Hiroki; Okada, Taku; Yagi, Takehiko; Kageyama, Hiroshi

2017-12-01

The effect of Fe-site substitution on structural and physical properties of the infinite layer iron oxide SrFeO2 was investigated under high pressure by 57Fe Mössbauer spectroscopy, X-ray diffraction, X-ray absorption spectroscopy, X-ray magnetic circular dichroism, and electrical resistance measurements using a diamond-anvil cell. Both 20% Mn- and Co-substituted samples exhibit spin transitions from a high-spin (S = 2) to an intermediate-spin (S = 1) state at Pc ˜ 32 GPa, which is much the same pressure 33 GPa observed in SrFeO2. This result indicates that the spin transition pressure is insensitive to the d-orbital electron counts [Mn2+ (d5), Fe2+ (d6), Co2+ (d7)], but is governed by the local structure around the Fe site.

Emergence and Phase Transitions

NASA Astrophysics Data System (ADS)

Sikkema, Arnold

2006-05-01

Phase transitions are well defined in physics through concepts such as spontaneous symmetry breaking, order parameter, entropy, and critical exponents. But emergence --- also exhibiting whole-part relations (such as top-down influence), unpredictability, and insensitivity to microscopic detail --- is a loosely-defined concept being used in many disciplines, particularly in psychology, biology, philosophy, as well as in physics[1,2]. I will review the concepts of emergence as used in the various fields and consider the extent to which the methods of phase transitions can clarify the usefulness of the concept of emergence both within the discipline of physics and beyond.1. Robert B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (New York: Basic Books, 2005). 2. George F.R. Ellis, ``Physics and the Real World'', Physics Today, vol. 58, no. 7 (July 2005) pp. 49-54.

Limit on the temporal variation of the fine-structure constant using atomic dysprosium.

PubMed

Cingöz, A; Lapierre, A; Nguyen, A-T; Leefer, N; Budker, D; Lamoreaux, S K; Torgerson, J R

2007-01-26

Over 8 months, we monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These frequencies are sensitive to variation of the fine-structure constant (alpha) due to relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a rf electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in (163)Dy and the 235-MHz transition in (162)Dy are 9.0+/-6.7 Hz/yr and -0.6+/-6.5 Hz/yr, respectively. These results provide a rate of fractional variation of alpha of (-2.7+/-2.6) x 10(-15) yr(-1) (1 sigma) without assumptions on constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.

Data eye monitor method and apparatus

DOEpatents

Gara, Alan G [Mount Kisco, NY; Marcella, James A [Rochester, MN; Ohmacht, Martin [Yorktown Heights, NY

2012-01-31

An apparatus and method for providing a data eye monitor. The data eye monitor apparatus utilizes an inverter/latch string circuit and a set of latches to save the data eye for providing an infinite persistent data eye. In operation, incoming read data signals are adjusted in the first stage individually and latched to provide the read data to the requesting unit. The data is also simultaneously fed into a balanced XOR tree to combine the transitions of all incoming read data signals into a single signal. This signal is passed along a delay chain and tapped at constant intervals. The tap points are fed into latches, capturing the transitions at a delay element interval resolution. Using XORs, differences between adjacent taps and therefore transitions are detected. The eye is defined by segments that show no transitions over a series of samples. The eye size and position can be used to readjust the delay of incoming signals and/or to control environment parameters like voltage, clock speed and temperature.

Spin Coherence in Silicon-based Quantum Structures and Devices

DTIC Science & Technology

2017-08-31

Using electron spin resonance (ESR) to measure the den- sity of shallow traps, we find that the two sets of devices are nearly identical , indicating...experiments which cannot utilize a clock transition or a field-cancelling decoherence-free subspace. Our approach was to lock the microwave source driving...the electron spins to a strong nuclear spin signal. In our initial experiments we locked to the proton signal in a water cell. However, the noise in

Unit Specific Crew Rest Strategies: Phase 1 Evaluation of the 1/212th Aviation Battalion during Shiftwork Transitions

DTIC Science & Technology

1994-01-01

but do not provide strategies or specific schedules of crew rest tailored to the- unit’s specific mission demands, environmental conditions, and...and the impact of mission driven work schedules and environmental conditions on crew rest quality. Phase II provides rhythms, sleep/wake cycles...shiftwork schedules , and methods for regulating the body’s biological clock to prevent sleep loss during characteristic mission. This report contains a

A novel productivity-driven logic element for field-programmable devices

NASA Astrophysics Data System (ADS)

Marconi, Thomas; Bertels, Koen; Gaydadjiev, Georgi

2014-06-01

Although various techniques have been proposed for power reduction in field-programmable devices (FPDs), they are still all based on conventional logic elements (LEs). In the conventional LE, the output of the combinational logic (e.g. the look-up table (LUT) in many field-programmable gate arrays (FPGAs)) is connected to the input of the storage element; while the D flip-flop (DFF) is always clocked even when not necessary. Such unnecessary transitions waste power. To address this problem, we propose a novel productivity-driven LE with reduced number of transitions. The differences between our LE and the conventional LE are in the FFs-type used and the internal LE organisation. In our LEs, DFFs have been replaced by T flip-flops with the T input permanently connected to logic value 1. Instead of connecting the output of the combinational logic to the FF input, we use it as the FF clock. The proposed LE has been validated via Simulation Program with Integrated Circuit Emphasis (SPICE) simulations for a 45-nm Complementary Metal-Oxide-Semiconductor (CMOS) technology as well as via a real Computer-Aided Design (CAD) tools on a real FPGA using the standard Microelectronic Center of North Carolina (MCNC) benchmark circuits. The experimental results show that FPDs using our proposal not only have 48% lower total power but also run 17% faster than conventional FPDs on average.

Evolution of subterranean diving beetles (Coleoptera: Dytiscidae: Hydroporini, Bidessini) in the arid zone of Australia.

PubMed

Leys, Remko; Watts, Chris H S; Cooper, Steve J B; Humphreys, William F

2003-12-01

Calcrete aquifers in arid inland Australia have recently been found to contain the world's most diverse assemblage of subterranean diving beetles (Coleoptera: Dytiscidae). In this study we test whether the adaptive shift hypothesis (ASH) or the climatic relict hypothesis (CRH) is the most likely mode of evolution for the Australian subterranean diving beetles by using a phylogeny based on two sequenced fragments of mitochondrial genes (CO1 and 16S-tRNA-ND1) and linearized using a relaxed molecular clock method. Most individual calcrete aquifers contain an assemblage of diving beetle species of distantly related lineages and/or a single pair of sister species that significantly differ in size and morphology. Evolutionary transitions from surface to subterranean life took place in a relatively small time frame between nine and four million years ago. Most of the variation in divergence times of the sympatric sister species is explained by the variation in latitude of the localities, which correlates with the onset of aridity from the north to the south and with an aridity maximum in the Early Pliocene (five mya). We conclude that individual calcrete aquifers were colonized by several distantly related diving beetle lineages. Several lines of evidence from molecular clock analyses support the CRH, indicating that all evolutionary transitions took place during the Late Miocene and Early Pliocene as a result of aridification.

Assessing the Validity of the Simplified Potential Energy Clock Model for Modeling Glass-Ceramics

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

Jamison, Ryan Dale; Grillet, Anne M.; Stavig, Mark E.

Glass-ceramic seals may be the future of hermetic connectors at Sandia National Laboratories. They have been shown capable of surviving higher temperatures and pressures than amorphous glass seals. More advanced finite-element material models are required to enable model-based design and provide evidence that the hermetic connectors can meet design requirements. Glass-ceramics are composite materials with both crystalline and amorphous phases. The latter gives rise to (non-linearly) viscoelastic behavior. Given their complex microstructures, glass-ceramics may be thermorheologically complex, a behavior outside the scope of currently implemented constitutive models at Sandia. However, it was desired to assess if the Simplified Potential Energymore » Clock (SPEC) model is capable of capturing the material response. Available data for SL 16.8 glass-ceramic was used to calibrate the SPEC model. Model accuracy was assessed by comparing model predictions with shear moduli temperature dependence and high temperature 3-point bend creep data. It is shown that the model can predict the temperature dependence of the shear moduli and 3- point bend creep data. Analysis of the results is presented. Suggestions for future experiments and model development are presented. Though further calibration is likely necessary, SPEC has been shown capable of modeling glass-ceramic behavior in the glass transition region but requires further analysis below the transition region.« less

The Zeeman effect or linear birefringence? VLA polarimetric spectral line observations of H2O masers

NASA Astrophysics Data System (ADS)

Zhao, Jun-Hui; Goss, W. M.; Diamond, P.

We present line profiles of the four Stokes parameters of H2O masers at 22 GHz observed with the VLA in full polarimetric spectral line mode. With careful calibration, the instrumental effects such as linear leakage and the difference of antenna gain between RCP and LCP, can be minimized. Our measurements show a few percent linear polarization. Weak circular polarization was detected at a level of 0.1 percent of the peak intensity. A large uncertainty in the measurements of weak circular polarization is caused by telescope pointing errors. The observed polarization of H2O masers can be interpreted as either the Zeeman effect or linear birefringence.

Rashba effect in an asymmetric quantum dot in a magnetic field

NASA Astrophysics Data System (ADS)

Bandyopadhyay, S.; Cahay, M.

2002-12-01

We derive an expression for the total spin-splitting energy in an asymmetric quantum dot with ferromagnetic contacts, subjected to a transverse electric field. Such a structure has been shown by one of us to act as a spintronic quantum gate with in-built qubit readers and writers (Phys. Rev. B61, 13813 (2000)). The ferromagnetic contacts result in a magnetic field that causes a Zeeman splitting of the electronic states in the quantum dot. We show that this Zeeman splitting can be finely tuned with a transverse electric field as a result of nonvanishing Rashba spin-orbit coupling in an asymmetric quantum dot. This feature is critical for implementing a quantum gate.

Common features in diverse insect clocks.

PubMed

Numata, Hideharu; Miyazaki, Yosuke; Ikeno, Tomoko

2015-01-01

This review describes common features among diverse biological clocks in insects, including circadian, circatidal, circalunar/circasemilunar, and circannual clocks. These clocks control various behaviors, physiological functions, and developmental events, enabling adaptation to periodic environmental changes. Circadian clocks also function in time-compensation for celestial navigation and in the measurement of day or night length for photoperiodism. Phase response curves for such clocks reported thus far exhibit close similarities; specifically, the circannual clock in Anthrenus verbasci shows striking similarity to circadian clocks in its phase response. It is suggested that diverse biological clocks share physiological properties in their phase responses irrespective of period length. Molecular and physiological mechanisms are best understood for the optic-lobe and mid-brain circadian clocks, although there is no direct evidence that these clocks are involved in rhythmic phenomena other than circadian rhythms in daily events. Circadian clocks have also been localized in peripheral tissues, and research on their role in various rhythmic phenomena has been started. Although clock genes have been identified as controllers of circadian rhythms in daily events, some of these genes have also been shown to be involved in photoperiodism and possibly in time-compensated celestial navigation. In contrast, there is no experimental evidence indicating that any known clock gene is involved in biological clocks other than circadian clocks.

Global synchronization of parallel processors using clock pulse width modulation

DOEpatents

Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

2013-04-02

A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

Central and peripheral clocks are coupled by a neuropeptide pathway in Drosophila

PubMed Central

Selcho, Mareike; Millán, Carola; Palacios-Muñoz, Angelina; Ruf, Franziska; Ubillo, Lilian; Chen, Jiangtian; Bergmann, Gregor; Ito, Chihiro; Silva, Valeria; Wegener, Christian; Ewer, John

2017-01-01

Animal circadian clocks consist of central and peripheral pacemakers, which are coordinated to produce daily rhythms in physiology and behaviour. Despite its importance for optimal performance and health, the mechanism of clock coordination is poorly understood. Here we dissect the pathway through which the circadian clock of Drosophila imposes daily rhythmicity to the pattern of adult emergence. Rhythmicity depends on the coupling between the brain clock and a peripheral clock in the prothoracic gland (PG), which produces the steroid hormone, ecdysone. Time information from the central clock is transmitted via the neuropeptide, sNPF, to non-clock neurons that produce the neuropeptide, PTTH. These secretory neurons then forward time information to the PG clock. We also show that the central clock exerts a dominant role on the peripheral clock. This use of two coupled clocks could serve as a paradigm to understand how daily steroid hormone rhythms are generated in animals. PMID:28555616

The Drosophila Clock Neuron Network Features Diverse Coupling Modes and Requires Network-wide Coherence for Robust Circadian Rhythms.

PubMed

Yao, Zepeng; Bennett, Amelia J; Clem, Jenna L; Shafer, Orie T

2016-12-13

In animals, networks of clock neurons containing molecular clocks orchestrate daily rhythms in physiology and behavior. However, how various types of clock neurons communicate and coordinate with one another to produce coherent circadian rhythms is not well understood. Here, we investigate clock neuron coupling in the brain of Drosophila and demonstrate that the fly's various groups of clock neurons display unique and complex coupling relationships to core pacemaker neurons. Furthermore, we find that coordinated free-running rhythms require molecular clock synchrony not only within the well-characterized lateral clock neuron classes but also between lateral clock neurons and dorsal clock neurons. These results uncover unexpected patterns of coupling in the clock neuron network and reveal that robust free-running behavioral rhythms require a coherence of molecular oscillations across most of the fly's clock neuron network. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

Spectroscopy of a Synthetic Trapped Ion Qubit

NASA Astrophysics Data System (ADS)

Hucul, David; Christensen, Justin E.; Hudson, Eric R.; Campbell, Wesley C.

2017-09-01

133Ba+ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1 /2 nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser cool the synthetic A =133 radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the 62P1 /2↔62S1 /2 and 62P1 /2↔52D3 /2 electronic transitions that are needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. We also report the 62P1 /2↔52D3 /2 electronic transition isotope shift for the rare A =130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.

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.

Radioluminescence and photoluminescence of Th:CaF2 crystals

PubMed Central

Stellmer, Simon; Schreitl, Matthias; Schumm, Thorsten

2015-01-01

We study thorium-doped CaF2 crystals as a possible platform for optical spectroscopy of the 229Th nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of 229Th and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers. PMID:26502749

Investigating and addressing student difficulties with the corrections to the energies of the hydrogen atom for the strong and weak field Zeeman effect

NASA Astrophysics Data System (ADS)

Keebaugh, Christof; Marshman, Emily; Singh, Chandralekha

2018-07-01

Understanding when and how to make limiting case approximations and why they are valid in a particular situation is a hallmark of expertise in physics. Using limiting cases can simplify the problem-solving process significantly and they often provide a means to check that the results obtained are reasonable. We discuss an investigation of student difficulties with the corrections to the energy spectrum of the hydrogen atom for the limiting cases of the strong and weak field Zeeman effects using degenerate perturbation theory. This investigation was carried out in advanced quantum mechanics courses by administering written free-response and multiple-choice questions and conducting individual interviews with students. Here we first discuss the common student difficulties related to these concepts. We then describe how the research on student difficulties was used as a guide to develop and evaluate a quantum interactive learning tutorial (QuILT) which strives to help students develop a functional understanding of the concepts necessary for finding the corrections to the energy spectrum of the hydrogen atom for the strong field and weak field Zeeman effects. The development of the QuILT and its evaluation in the undergraduate and PhD level courses are presented.

Ordinary matter, dark matter, and dark energy on normal Zeeman space-times

NASA Astrophysics Data System (ADS)

Imre Szabó, Zoltán

2017-01-01

Zeeman space-times are new, relativistic, and operator based Hamiltonian models representing multi-particle systems. They are established on Lorentzian pseudo Riemannian manifolds whose Laplacian immediately appears in the form of original quantum physical wave operators. In classical quantum theory they emerge, differently, from the Hamilton formalism and the correspondence principle. Nonetheless, this new model does not just reiterate the well known conceptions but holds the key to solving open problems of quantum theory. Most remarkably, it represents the dark matter, dark energy, and ordinary matter by the same ratios how they show up in experiments. Another remarkable agreement with reality is that the ordinary matter appears to be non-expanding and is described in consent with observations. The theory also explains gravitation, moreover, the Hamilton operators of all energy and matter formations, together with their physical properties, are solely derived from the Laplacian of the Zeeman space-time. By this reason, it is called Monistic Wave Laplacian which symbolizes an all-comprehensive unification of all matter and energy formations. This paper only outlines the normal case where the particles do not have proper spin but just angular momentum. The complete anomalous theory is detailed in [Sz2, Sz3, Sz4, Sz5, Sz6, Sz7].

Anomalous Kondo transport in a single-electron transistor driven by microwave field

NASA Astrophysics Data System (ADS)

Cao, Zhan; Chen, Cheng; Chen, Fu-Zhou; Luo, Hong-Gang

2014-03-01

The Kondo transport in a single-electron transistor continues to provide unexpected physics due to the interplay between magnetic field and microwave applied, as shown in a recent experiment(B. Hemingway et al., arXiv:1304.0037). For a given microwave frequency, the Kondo differential conductance shows an anomalous magnetic field dependence, and a very sharp peak is observed for certain field applied. Additionally, the microwave frequency is found to be larger of about one order than the corresponding Zeeman energy. These two features are not understood in the current theory. Here we propose a phenomenological mechanism to explain these observations. When both magnetic field and microwave are applied in the SET, if the frequency matches the (renormalized) Zeeman energy, it is assumed that the microwave is able to induce spin-ip in the single-electron transistor, which leads to two consequences. One is the dot level shifts down and the other is the renormalization of the Zeeman energy. This picture can not only explain qualitatively the main findings in the experiment but also further stimulate the related experimental study of the Kondo transport. Additional microwave modulation may provide a novel way to explore the functional of the SET in nanotechnology and quantum information processing.

THE MAGNETIC SENSITIVITY OF THE Mg ii k LINE TO THE JOINT ACTION OF HANLE, ZEEMAN, AND MAGNETO-OPTICAL EFFECTS

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

Ballester, E. Alsina; Bueno, J. Trujillo; Belluzzi, L., E-mail: ealsina@iac.es, E-mail: jtb@iac.es, E-mail: belluzzi@irsol.ch

2016-11-10

We highlight the main results of a radiative transfer investigation on the magnetic sensitivity of the solar Mg ii k resonance line at 2795.5 Å, accounting for the joint action of the Hanle and Zeeman effects as well as partial frequency redistribution phenomena. We confirm that at the line center, the linear polarization signals produced by scattering processes are measurable, and that they are sensitive, via the Hanle effect, to magnetic fields with strengths between 5 and 50 G, approximately. We also show that the Zeeman effect produces conspicuous circular polarization signals, especially for longitudinal fields stronger than 50 G,more » which can be used to estimate the magnetization of the solar chromosphere via the familiar magnetograph formula. The most novel result is that magneto-optical effects produce, in the wings of the line, a decrease of the Q / I scattering polarization pattern and the appearance of U / I signals (i.e., a rotation of the plane of linear polarization). This sensitivity of the Q / I and U / I wing signals to both weak (∼5 G) and stronger magnetic fields expands the scientific interest of the Mg ii k line for probing the chromosphere in quiet and active regions of the Sun.« less

Global Transcriptome Sequencing Reveals Molecular Profiles of Summer Diapause Induction Stage of Onion Maggot, Delia antiqua (Diptera: Anthomyiidae)

PubMed Central

Ren, Shuang; Hao, You-Jin; Chen, Bin; Yin, You-Ping

2017-01-01

The onion maggot, Delia antiqua, is a worldwide subterranean pest and can enter diapause during the summer and winter seasons. The molecular regulation of the ontogenesis transition remains largely unknown. Here we used high-throughput RNA sequencing to identify candidate genes and processes linked to summer diapause (SD) induction by comparing the transcriptome differences between the most sensitive larval developmental stage of SD and nondiapause (ND). Nine pairwise comparisons were performed, and significantly differentially regulated transcripts were identified. Several functional terms related to lipid, carbohydrate, and energy metabolism, environmental adaption, immune response, and aging were enriched during the most sensitive SD induction period. A subset of genes, including circadian clock genes, were expressed differentially under diapause induction conditions, and there was much more variation in the most sensitive period of ND- than SD-destined larvae. These expression variations probably resulted in a deep restructuring of metabolic pathways. Potential regulatory elements of SD induction including genes related to lipid, carbohydrate, energy metabolism, and environmental adaption. Collectively, our results suggest the circadian clock is one of the key drivers for integrating environmental signals into the SD induction. Our transcriptome analysis provides insight into the fundamental role of the circadian clock in SD induction in this important model insect species, and contributes to the in-depth elucidation of the molecular regulation mechanism of insect diapause induction. PMID:29158334

A High Accuracy Measurement of the Nuclear Decay of 235mU and Search for the Nuclear Decay of 229mTh

NASA Astrophysics Data System (ADS)

Ponce, Francisco

Among all nuclear decays, there exist two isomeric states with very low-energy that belong to . {229}Th (7.8 ± 0.5 eV) and . {235}U (76.8 ± 0.5 eV) . Of particular interest is . {229}Th, because the decay energy is in the ultraviolet, and therefore in the range of modern tunable lasers. The isomer can potentially be used as the basis for a nuclear clock that is expected to be two orders of magnitude more precise than atomic clocks. However, the . {229m}Th nuclear decay energy is not sufficiently well known to design the necessary laser system for a nuclear clock. This work describes the development of a new technique using superconducting tunnel junction (STJ) detectors to directly measure the nuclear decay of low-energy isomers with a high level of accuracy. The strength of the technique is demonstrated by measuring the decay energy of the . {235}U isomer at 76.737 ± 0.018 eV. Over an order of magnitude more accurate than the current literature value. The technique is then applied to detect the transition in . {229m}Th directly and measure its energy with comparable accuracy. These experiments are unsuccessful and are discussed in light of the recent measurement of the . {229m}Th half-life of 7 ± \\SI{1}{\\micro\\second}.

Optical atomic phase reference and timing.

PubMed

Hollberg, L; Cornell, E H; Abdelrahmann, A

2017-08-06

Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space-time science. Those systems require strain measurements at less than or equal to 10 -20 As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, Δ Φ / Φ total  ≤ 10 -20 , that could make an important impact in gravity wave science.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

Phase response of the Arabidopsis thaliana circadian clock to light pulses of different wavelengths.

PubMed

Ohara, Takayuki; Fukuda, Hirokazu; Tokuda, Isao T

2015-04-01

Light is known as one of the most powerful environmental time cues for the circadian system. The quality of light is characterized by its intensity and wavelength. We examined how the phase response of Arabidopsis thaliana depends on the wavelength of the stimulus light and the type of light perturbation. Using transgenic A. thaliana expressing a luciferase gene, we monitored the rhythm of the bioluminescence signal. We stimulated the plants under constant red light using 3 light perturbation treatments: (1) increasing the red light intensity, (2) turning on a blue light while turning off the red light, and (3) turning on a blue light while keeping the red light on. To examine the phase response properties, we generated a phase transition curve (PTC), which plots the phase after the perturbation as a function of the phase before the perturbation. To evaluate the effect of the 3 light perturbation treatments, we simulated PTCs using a mathematical model of the plant circadian clock and fitted the simulated PTCs to the experimentally measured PTCs. Among the 3 treatments, perturbation (3) provided the strongest stimulus. The results indicate that the color of the stimulus light and the type of pulse administration affect the phase response in a complex manner. Moreover, the results suggest the involvement of interaction between red and blue light signaling pathways in resetting of the plant circadian clock. © 2015 The Author(s).

Ultradian metabolic rhythm in the diazotrophic cyanobacterium Cyanothece sp. ATCC 51142.

PubMed

Červený, Jan; Sinetova, Maria A; Valledor, Luis; Sherman, Louis A; Nedbal, Ladislav

2013-08-06

The unicellular cyanobacterium Cyanothece sp. American Type Culture Collection (ATCC) 51142 is capable of performing oxygenic photosynthesis during the day and microoxic nitrogen fixation at night. These mutually exclusive processes are possible only by temporal separation by circadian clock or another cellular program. We report identification of a temperature-dependent ultradian metabolic rhythm that controls the alternating oxygenic and microoxic processes of Cyanothece sp. ATCC 51142 under continuous high irradiance and in high CO2 concentration. During the oxygenic photosynthesis phase, nitrate deficiency limited protein synthesis and CO2 assimilation was directed toward glycogen synthesis. The carbohydrate accumulation reduced overexcitation of the photosynthetic reactions until a respiration burst initiated a transition to microoxic N2 fixation. In contrast to the circadian clock, this ultradian period is strongly temperature-dependent: 17 h at 27 °C, which continuously decreased to 10 h at 39 °C. The cycle was expressed by an oscillatory modulation of net O2 evolution, CO2 uptake, pH, fluorescence emission, glycogen content, cell division, and culture optical density. The corresponding ultradian modulation was also observed in the transcription of nitrogenase-related nifB and nifH genes and in nitrogenase activities. We propose that the control by the newly identified metabolic cycle adds another rhythmic component to the circadian clock that reflects the true metabolic state depending on the actual temperature, irradiance, and CO2 availability.

USNO Master Clock - Naval Oceanography Portal

Science.gov Websites

section Advanced Search... Sections Home Time Earth Orientation Astronomy Meteorology Oceanography Ice You are here: Home › USNO › Precise Time › Master Clock USNO Logo USNO Navigation Master Clock GPS Display Clocks TWSTT Telephone Time NTP Info USNO Master Clock clock vault The USNO Master Clock is the

Strong Landau-quantization effects in high-magnetic-field superconductivity of a two-dimensional multiple-band metal near the Lifshitz transition

DOE PAGES

Song, Kok Wee; Koshelev, Alexei E.

2017-05-04

We investigate the onset of superconductivity in a magnetic field for a clean two-dimensional multiple-band superconductor in the vicinity of the Lifshitz transition when one of the bands is very shallow. Due to the small number of carriers in this band, the quasiclassical Werthamer-Helfand approximation breaks down and Landau quantization has to be taken into account. We found that the transition temperature T C2( H) has giant oscillations and is resonantly enhanced at the magnetic fields corresponding to the matching of the chemical potential with the Landau levels in the shallow band. This enhancement is especially pronounced for the lowestmore » Landau level. As a consequence, the reentrant superconducting regions in the temperature-field phase diagram emerge at low temperatures near the magnetic fields at which the shallow-band Landau levels cross the chemical potential. The specific behavior depends on the relative strength of the intraband and interband pairing interactions and the reentrance is most pronounced in the purely interband coupling scenario. The reentrant behavior is suppressed by the Zeeman spin splitting in the shallow band; the separated regions disappear already for very small spin-splitting factors. On the other hand, the reentrance is restored in the resonance cases when the spin-splitting energy exactly matches the separation between the Landau levels. As a result, the predicted behavior may be realized in the gate-tuned FeSe monolayer.« less

Strong Landau-quantization effects in high-magnetic-field superconductivity of a two-dimensional multiple-band metal near the Lifshitz transition

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

Song, Kok Wee; Koshelev, Alexei E.

We investigate the onset of superconductivity in a magnetic field for a clean two-dimensional multiple-band superconductor in the vicinity of the Lifshitz transition when one of the bands is very shallow. Due to the small number of carriers in this band, the quasiclassical Werthamer-Helfand approximation breaks down and Landau quantization has to be taken into account. We found that the transition temperature T C2( H) has giant oscillations and is resonantly enhanced at the magnetic fields corresponding to the matching of the chemical potential with the Landau levels in the shallow band. This enhancement is especially pronounced for the lowestmore » Landau level. As a consequence, the reentrant superconducting regions in the temperature-field phase diagram emerge at low temperatures near the magnetic fields at which the shallow-band Landau levels cross the chemical potential. The specific behavior depends on the relative strength of the intraband and interband pairing interactions and the reentrance is most pronounced in the purely interband coupling scenario. The reentrant behavior is suppressed by the Zeeman spin splitting in the shallow band; the separated regions disappear already for very small spin-splitting factors. On the other hand, the reentrance is restored in the resonance cases when the spin-splitting energy exactly matches the separation between the Landau levels. As a result, the predicted behavior may be realized in the gate-tuned FeSe monolayer.« less

Rigorously modeling self-stabilizing fault-tolerant circuits: An ultra-robust clocking scheme for systems-on-chip.

PubMed

Dolev, Danny; Függer, Matthias; Posch, Markus; Schmid, Ulrich; Steininger, Andreas; Lenzen, Christoph

2014-06-01

We present the first implementation of a distributed clock generation scheme for Systems-on-Chip that recovers from an unbounded number of arbitrary transient faults despite a large number of arbitrary permanent faults. We devise self-stabilizing hardware building blocks and a hybrid synchronous/asynchronous state machine enabling metastability-free transitions of the algorithm's states. We provide a comprehensive modeling approach that permits to prove, given correctness of the constructed low-level building blocks, the high-level properties of the synchronization algorithm (which have been established in a more abstract model). We believe this approach to be of interest in its own right, since this is the first technique permitting to mathematically verify, at manageable complexity, high-level properties of a fault-prone system in terms of its very basic components. We evaluate a prototype implementation, which has been designed in VHDL, using the Petrify tool in conjunction with some extensions, and synthesized for an Altera Cyclone FPGA.

Network-Physics (NP) BEC DIGITAL(#)-VULNERABILITY; ``Q-Computing"=Simple-Arithmetic;Modular-Congruences=SignalXNoise PRODUCTS=Clock-model;BEC-Factorization;RANDOM-# Definition;P=/=NP TRIVIAL Proof!!!

NASA Astrophysics Data System (ADS)

Pi, E. I.; Siegel, E.

2010-03-01

Siegel[AMS Natl.Mtg.(2002)-Abs.973-60-124] digits logarithmic- law inversion to ONLY BEQS BEC:Quanta/Bosons=#: EMP-like SEVERE VULNERABILITY of ONLY #-networks(VS.ANALOG INvulnerability) via Barabasi NP(VS.dynamics[Not.AMS(5/2009)] critique);(so called)``quantum-computing''(QC) = simple-arithmetic (sansdivision);algorithmiccomplexities:INtractibility/UNdecidabi lity/INefficiency/NONcomputability/HARDNESS(so MIScalled) ``noise''-induced-phase-transition(NIT)ACCELERATION:Cook-Levin theorem Reducibility = RG fixed-points; #-Randomness DEFINITION via WHAT? Query(VS. Goldreich[Not.AMS(2002)] How? mea culpa)= ONLY MBCS hot-plasma v #-clumping NON-random BEC; Modular-Arithmetic Congruences = Signal x Noise PRODUCTS = clock-model; NON-Shor[Physica A,341,586(04)]BEC logarithmic-law inversion factorization: Watkins #-theory U statistical- physics); P=/=NP C-S TRIVIAL Proof: Euclid!!! [(So Miscalled) computational-complexity J-O obviation(3 millennia AGO geometry: NO:CC,``CS'';``Feet of Clay!!!'']; Query WHAT?:Definition: (so MIScalled)``complexity''=UTTER-SIMPLICITY!! v COMPLICATEDNESS MEASURE(S).

50 Mbps free space direct detection laser diode optical communication system with Q = 4 PPM signaling

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Davidson, Frederic; Field, Christopher

1990-01-01

A 50 Mbps direct detection optical communication system for use in an intersatellite link was constructed with an AlGaAs laser diode transmitter and a silicon avalanche photodiode photodetector. The system used a Q = 4 PPM format. The receiver consisted of a maximum likelihood PPM detector and a timing recovery subsystem. The PPM slot clock was recovered at the receiver by using a transition detector followed by a PLL. The PPM word clock was recovered by using a second PLL whose input was derived from the presence of back-to-back PPM pulses contained in the received random PPM pulse sequences. The system achieved a bit error rate of 0.000001 at less than 50 detected signal photons/information bit. The receiver was capable of acquiring and maintaining slot and word synchronization for received signal levels greater than 20 photons/information bit, at which the receiver bit error rate was about 0.01.

Rigorously modeling self-stabilizing fault-tolerant circuits: An ultra-robust clocking scheme for systems-on-chip☆

PubMed Central

Dolev, Danny; Függer, Matthias; Posch, Markus; Schmid, Ulrich; Steininger, Andreas; Lenzen, Christoph

2014-01-01

We present the first implementation of a distributed clock generation scheme for Systems-on-Chip that recovers from an unbounded number of arbitrary transient faults despite a large number of arbitrary permanent faults. We devise self-stabilizing hardware building blocks and a hybrid synchronous/asynchronous state machine enabling metastability-free transitions of the algorithm's states. We provide a comprehensive modeling approach that permits to prove, given correctness of the constructed low-level building blocks, the high-level properties of the synchronization algorithm (which have been established in a more abstract model). We believe this approach to be of interest in its own right, since this is the first technique permitting to mathematically verify, at manageable complexity, high-level properties of a fault-prone system in terms of its very basic components. We evaluate a prototype implementation, which has been designed in VHDL, using the Petrify tool in conjunction with some extensions, and synthesized for an Altera Cyclone FPGA. PMID:26516290

The pineapple genome and the evolution of CAM photosynthesis.

PubMed

Ming, Ray; VanBuren, Robert; Wai, Ching Man; Tang, Haibao; Schatz, Michael C; Bowers, John E; Lyons, Eric; Wang, Ming-Li; Chen, Jung; Biggers, Eric; Zhang, Jisen; Huang, Lixian; Zhang, Lingmao; Miao, Wenjing; Zhang, Jian; Ye, Zhangyao; Miao, Chenyong; Lin, Zhicong; Wang, Hao; Zhou, Hongye; Yim, Won C; Priest, Henry D; Zheng, Chunfang; Woodhouse, Margaret; Edger, Patrick P; Guyot, Romain; Guo, Hao-Bo; Guo, Hong; Zheng, Guangyong; Singh, Ratnesh; Sharma, Anupma; Min, Xiangjia; Zheng, Yun; Lee, Hayan; Gurtowski, James; Sedlazeck, Fritz J; Harkess, Alex; McKain, Michael R; Liao, Zhenyang; Fang, Jingping; Liu, Juan; Zhang, Xiaodan; Zhang, Qing; Hu, Weichang; Qin, Yuan; Wang, Kai; Chen, Li-Yu; Shirley, Neil; Lin, Yann-Rong; Liu, Li-Yu; Hernandez, Alvaro G; Wright, Chris L; Bulone, Vincent; Tuskan, Gerald A; Heath, Katy; Zee, Francis; Moore, Paul H; Sunkar, Ramanjulu; Leebens-Mack, James H; Mockler, Todd; Bennetzen, Jeffrey L; Freeling, Michael; Sankoff, David; Paterson, Andrew H; Zhu, Xinguang; Yang, Xiaohan; Smith, J Andrew C; Cushman, John C; Paull, Robert E; Yu, Qingyi

2015-12-01

Pineapple (Ananas comosus (L.) Merr.) is the most economically valuable crop possessing crassulacean acid metabolism (CAM), a photosynthetic carbon assimilation pathway with high water-use efficiency, and the second most important tropical fruit. We sequenced the genomes of pineapple varieties F153 and MD2 and a wild pineapple relative, Ananas bracteatus accession CB5. The pineapple genome has one fewer ancient whole-genome duplication event than sequenced grass genomes and a conserved karyotype with seven chromosomes from before the ρ duplication event. The pineapple lineage has transitioned from C3 photosynthesis to CAM, with CAM-related genes exhibiting a diel expression pattern in photosynthetic tissues. CAM pathway genes were enriched with cis-regulatory elements associated with the regulation of circadian clock genes, providing the first cis-regulatory link between CAM and circadian clock regulation. Pineapple CAM photosynthesis evolved by the reconfiguration of pathways in C3 plants, through the regulatory neofunctionalization of preexisting genes and not through the acquisition of neofunctionalized genes via whole-genome or tandem gene duplication.

Sub-Doppler Frequency Metrology in HD for Tests of Fundamental Physics

NASA Astrophysics Data System (ADS)

Cozijn, F. M. J.; Dupré, P.; Salumbides, E. J.; Eikema, K. S. E.; Ubachs, W.

2018-04-01

Weak transitions in the (2,0) overtone band of the hydrogen deuteride molecule at λ =1.38 μ m were measured in saturated absorption using the technique of noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Narrow Doppler-free lines were interrogated with a spectroscopy laser locked to a frequency comb laser referenced to an atomic clock to yield transition frequencies [R (1 )=217105181895 (20 ) kHz ; R (2 )=219042856621 (28 ) kHz ; R (3 )=220704304951 (28 ) kHz ] at three orders of magnitude improved accuracy. These benchmark values provide a test of QED in the smallest neutral molecule, and they open up an avenue to resolve the proton radius puzzle, as well as constrain putative fifth forces and extra dimensions.

Novel concepts on pregnancy clocks and alarms: redundancy and synergy in human parturition

PubMed Central

Menon, Ramkumar; Bonney, Elizabeth A.; Condon, Jennifer; Mesiano, Sam; Taylor, Robert N.

2016-01-01

The signals and mechanisms that synchronize the timing of human parturition remain a mystery and a better understanding of these processes is essential to avert adverse pregnancy outcomes. Although our insights into human labor initiation have been informed by studies in animal models, the timing of parturition relative to fetal maturation varies among viviparous species, indicative of phylogenetically different clocks and alarms; but what is clear is that important common pathways must converge to control the birth process. For example, in all species, parturition involves the transition of the myometrium from a relaxed to a highly excitable state, where the muscle rhythmically and forcefully contracts, softening the cervical extracellular matrix to allow distensibility and dilatation and thus a shearing of the fetal membranes to facilitate their rupture. We review a number of theories promulgated to explain how a variety of different timing mechanisms, including fetal membrane cell senescence, circadian endocrine clocks, and inflammatory and mechanical factors, are coordinated as initiators and effectors of parturition. Many of these factors have been independently described with a focus on specific tissue compartments. In this review, we put forth the core hypothesis that fetal membrane (amnion and chorion) senescence is the initiator of a coordinated, redundant signal cascade leading to parturition. Whether modified by oxidative stress or other factors, this process constitutes a counting device, i.e. a clock, that measures maturation of the fetal organ systems and the production of hormones and other soluble mediators (including alarmins) and that promotes inflammation and orchestrates an immune cascade to propagate signals across different uterine compartments. This mechanism in turn sensitizes decidual responsiveness and eventually promotes functional progesterone withdrawal in the myometrium, leading to increased myometrial cell contraction and the triggering of parturition. Linkage of these processes allows convergence and integration of the gestational clocks and alarms, prompting a timely and safe birth. In summary, we provide a comprehensive synthesis of the mediators that contribute to the timing of human labor. Integrating these concepts will provide a better understanding of human parturition and ultimately improve pregnancy outcomes. PMID:27363410