Saturation recovery EPR spin-labeling method for quantification of lipids in biological membrane domains.

PubMed

Mainali, Laxman; Camenisch, Theodore G; Hyde, James S; Subczynski, Witold K

2017-12-01

The presence of integral membrane proteins induces the formation of distinct domains in the lipid bilayer portion of biological membranes. Qualitative application of both continuous wave (CW) and saturation recovery (SR) electron paramagnetic resonance (EPR) spin-labeling methods allowed discrimination of the bulk, boundary, and trapped lipid domains. A recently developed method, which is based on the CW EPR spectra of phospholipid (PL) and cholesterol (Chol) analog spin labels, allows evaluation of the relative amount of PLs (% of total PLs) in the boundary plus trapped lipid domain and the relative amount of Chol (% of total Chol) in the trapped lipid domain [ M. Raguz, L. Mainali, W. J. O'Brien, and W. K. Subczynski (2015), Exp. Eye Res., 140:179-186 ]. Here, a new method is presented that, based on SR EPR spin-labeling, allows quantitative evaluation of the relative amounts of PLs and Chol in the trapped lipid domain of intact membranes. This new method complements the existing one, allowing acquisition of more detailed information about the distribution of lipids between domains in intact membranes. The methodological transition of the SR EPR spin-labeling approach from qualitative to quantitative is demonstrated. The abilities of this method are illustrated for intact cortical and nuclear fiber cell plasma membranes from porcine eye lenses. Statistical analysis (Student's t -test) of the data allowed determination of the separations of mean values above which differences can be treated as statistically significant ( P ≤ 0.05) and can be attributed to sources other than preparation/technique.

Gate-Sensing the Potential Landscape of a GaAs Two-Dimensional Electron Gas

NASA Astrophysics Data System (ADS)

Croot, Xanthe; Mahoney, Alice; Pauka, Sebastian; Colless, James; Reilly, David; Watson, John; Fallahi, Saeed; Gardner, Geoff; Manfra, Michael; Lu, Hong; Gossard, Arthur

In situ dispersive gate sensors hold potential as a means of enabling the scalable readout of quantum dot arrays. Sensitive to quantum capacitance, dispersive sensors have been used to detect inter- and intra-dot transitions in GaAs double quantum dots, and can distinguish the spin states of singlet triplet qubits. In addition, the gate-sensing technique is likely of value in probing the physics of Majorana zero modes in nanowire devices. Beyond the readout signatures associated with charge and spin configurations of qubits, gate-sensing is sensitive to trapped charge in the potential landscape. Here, we report gate-sensing signals arising from tunnelling of electrons between puddles of trapped charge in a GaAs 2DEG. We examine these signals in a family of different devices with varying mobilities, and as a function of temperature and bias. Implications for qubit readout using the gate-sensing technique are discussed.

Radiation induced rotation of interplanetary dust particles - A feasibility study for a space experiment

NASA Technical Reports Server (NTRS)

Ratcliff, K. F.; Misconi, N. Y.; Paddack, S. J.

1980-01-01

Irregular interplanetary dust particles may acquire a considerable spin rate due to two non-statistical dynamical mechanisms induced by solar radiation. These arise from variations in surface albedo discussed by Radzievskii (1954) and from irregularities in surface geometry discussed by Paddack (1969). An experiment is reported which will lead to an evaluation in space of the effectiveness of these two spin mechanisms. The technique of optical levitation in an argon laser beam provides a stable trap for particles 10-60 microns in diameter. The objective is to design an optical trap for dielectric particles in vacuum to study these rotation mechanisms in the gravity-free environment of a Spacelab experiment.

Site-specific radical formation in DNA induced by Cu(II)-H2O2 oxidizing system, using ESR, Immuno-spin trapping, LC/MS and MS/MS

PubMed Central

Bhattacharjee, Suchandra; Deterding, Leesa J.; Chatterjee, Saurabh; Jiang, JinJie; Ehrenshaft, Marilyn; Lardinois, Olivier; Ramirez, Dario C.; Tomer, Kenneth B.; Mason, Ronald P.

2011-01-01

Oxidative stress-related damage to the DNA macromolecule produces a multitude of lesions that are implicated in mutagenesis, carcinogenesis, reproductive cell death and aging. Many of these lesions have been studied and characterized by various techniques. Of the techniques that are available, the comet assay, HPLC-EC, GC-MS, HPLC-MS and especially HPLC-MS/MS remain the most widely used and have provided invaluable information on these lesions. However, accurate measurement of DNA damage has been a matter of debate. In particular, there have been reports of artifactual oxidation leading to erroneously high damage estimates. Further, most of these techniques measure the end product of a sequence of events and thus provide only limited information on the initial radical mechanism. We report here a qualitative measurement of DNA damage induced by a Cu(II)-H2O2 oxidizing system using immuno spin-trapping (IST) with EPR, MS and MS/MS. The radical generated is trapped by DMPO immediately upon formation. The DMPO adduct formed is initially EPR active but subsequently is oxidized to the stable nitrone, which can then be detected by IST and further characterized by MS and MS/MS. PMID:21382477

Unusual spin-trap chemistry for the reaction of hydroxyl radical with the carcinogen N-nitrosodimethylamine

NASA Astrophysics Data System (ADS)

Wink, David A.; Desrosiers, Marc F.

The reaction of the potent carcinogen N-nitrosodimethylamine (NDMA) with hydroxyl radical generated via radiolysis was studied using EPR techniques. Attempts to spin trap NDMA radical intermediates with 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) produced only unusual DBNBS radicals. One of these radicals was shown to be generated by both reaction of DBNBS with nitric oxide, and direct oxidation of DBNBS with an inorganic oxidant ( .Br -2). Another DBNBS radical was identified as a sulfite spin adduct resulting from the degradation of DBNBS by a NDMA reactive intermediate. In the absence of DBNBS, hydroxyl radical reaction with NDMA gave the dimethylnitroxide radical. Unexpectedly, addition of DBNBS to a solution containing dimethylnitroxide produced an EPR spectrum nearly identical to that of NDMA solutions with DBNBS added before radiolysis. A proposed mechanism accounting for these observations is presented.

Polar-core spin vortex of quasi-2D ferromagnetic spin-1 condensate in a flat-bottomed optical trap with a weak magnetic field

NASA Astrophysics Data System (ADS)

Zheng, Gong-Ping; Li, Pin; Li, Ting; Xue, Ya-Jie

2018-02-01

Motivated by the recent experiments realized in a flat-bottomed optical trap (Navon et al., 2015; Chomaz et al., 2015), we study the ground state of polar-core spin vortex of quasi-2D ferromagnetic spin-1 condensate in a finite-size homogeneous trap with a weak magnetic field. The exact spatial distribution of local spin is obtained with a variational method. Unlike the fully-magnetized planar spin texture with a zero-spin core, which was schematically demonstrated in previous studies for the ideal polar-core spin vortex in a homogeneous trap with infinitely large boundary, some plateaus and two-cores structure emerge in the distribution curves of spin magnitude in the polar-core spin vortex we obtained for the larger effective spin-dependent interaction. More importantly, the spin values of the plateaus are not 1 as expected in the fully-magnetized spin texture, except for the sufficiently large spin-dependent interaction and the weak-magnetic-field limit. We attribute the decrease of spin value to the effect of finite size of the system. The spin values of the plateaus can be controlled by the quadratic Zeeman energy q of the weak magnetic field, which decreases with the increase of q.

Direct high-precision measurement of the magnetic moment of the proton.

PubMed

Mooser, A; Ulmer, S; Blaum, K; Franke, K; Kracke, H; Leiteritz, C; Quint, W; Rodegheri, C C; Smorra, C; Walz, J

2014-05-29

One of the fundamental properties of the proton is its magnetic moment, µp. So far µp has been measured only indirectly, by analysing the spectrum of an atomic hydrogen maser in a magnetic field. Here we report the direct high-precision measurement of the magnetic moment of a single proton using the double Penning-trap technique. We drive proton-spin quantum jumps by a magnetic radio-frequency field in a Penning trap with a homogeneous magnetic field. The induced spin transitions are detected in a second trap with a strong superimposed magnetic inhomogeneity. This enables the measurement of the spin-flip probability as a function of the drive frequency. In each measurement the proton's cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particle's magnetic moment in terms of the nuclear magneton: μp = 2.792847350(9)μN. This measurement outperforms previous Penning-trap measurements in terms of precision by a factor of about 760. It improves the precision of the forty-year-old indirect measurement, in which significant theoretical bound state corrections were required to obtain µp, by a factor of 3. By application of this method to the antiproton magnetic moment, the fractional precision of the recently reported value can be improved by a factor of at least 1,000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.

Radical production from the interaction of ozone and PUFA as demonstrated by electron spin resonance spin-trapping techniques

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

Pryor, W.A.; Prier, D.G.; Church, D.F.

1981-02-01

There is considerable evidence that indicates that a fraction of the damage caused by ozone to cellular systems involves radical-mediated reactions. The most direct method for probing the mechanism by which ozone reacts with target molecules such as polyunsaturated fatty acids involves the use of electron spin resonance. In 1968, Goldstein et al. reported that ESR signals were observed when 40 ppM ozone in air is bubbled through linoleic acid. We have repeated this experiment and have performed several experiments modified from this design; in none of these do we observe ESR signals. We have studied the reaction of ozonemore » with PUFA at -78/sup 0/C using spin traps. Spin traps themselves react with ozone, but the following protocol avoids that reaction. (1) Ozone in air or oxygen-free ozone is allowed to bubble through the sample in Freon-11 in an ESR tube at -78/sup 0/C; no ESR absorption is observed. (2) Unreacted ozone is flushed out with argon or nitrogen. (3) The spin trap in Freon-11 is added to give a 0.1 M solution, still at -78/sup 0/C; no ESR signal is observed. (4) The tube is allowed to warm slowly. At about -45/sup 0/C, the ESR spectra of spin adducts appear. Using this method with methyl linoleate we observe spin adducts of alkoxy radicals and also a signal that is consistent with a carbon radical with one ..cap alpha..-H. We hypothesize that an intermediate is formed from the reaction of ozone with PUFA that is stable at -78/sup 0/Cbut decomposes to form radicals at about -45/sup 0/C. We tentatively identify the intermediate as a trioxide on the basis of analogies and its temperature profile for decomposition to radicals. It appears reasonable to suggest that the reaction(s) responsible for the production of radicals under these low-temperature conditions also occurs at room temperature. Although the low-temperature intermediate cannot be observed at ambient temperatures, radicals from it could be responsible for the effects on autoxidation that are induced by ozone.« less

Site-specific detection of radicals on α-lactalbumin after a riboflavin-sensitized reaction, detected by immuno-spin trapping, ESR, and MS.

PubMed

Dalsgaard, Trine K; Triquigneaux, Mathilde; Deterding, Leesa; Summers, Fiona; Ranguelova, Kalina; Mortensen, Grith; Mason, Ronald P

2013-01-16

Free radicals and other oxidation products were characterized on α-lactalbumin with electron spin resonance (ESR), immuno-spin trapping, and mass spectrometry (MS) after riboflavin-mediated oxidation. Radicals were detected using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in immuno-spin trapping with both enzyme-linked immunosorbent assay (ELISA) and Western blotting and further characterized with mass spectrometry. A DMPO-trapped radical was identified at His68 and another at one of the tyrosine residues, Tyr50 or Tyr36, respectively, generated by a type II or I mechanism. Not all tyrosyl radicals were trapped, as the secondary oxidation product, 3,4-dihydroxyphenylalanine (DOPA), was detected by mass spectrometry at Tyr18 and Tyr50. A further oxidation of DOPA resulted in the DOPA o-semiquinone radical, which was characterized by ESR. Both surface exposure and the neighboring residues in the local environment of the tertiary structure of α-lactalbumin seem to play a role in the generation of DMPO trapped radicals and secondary oxidation products.

Oxidation of spin-traps by chlorine dioxide (ClO2) radical in aqueous solutions: first ESR evidence of formation of new nitroxide radicals.

PubMed

Ozawa, T; Miura, Y; Ueda, J

1996-01-01

The reactivities of the chlorine dioxide (ClO2), which is a stable free radical towards some water-soluble spin-traps were investigated in aqueous solutions by an electron spin resonance (ESR) spectroscopy. The ClO2 radical was generated from the redox reaction of Ti3+ with potassium chlorate (KClO3) in aqueous solutions. When one of the spin-traps, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was included in the Ti3+-KClO3 reaction system, ESR spectrum due to the ClO2 radical completely disappeared and a new ESR spectrum [aN(1) = 0.72 mT, aH(2) = 0.41 mT], which is different from that of DMPO-ClO2 adduct, was observed. The ESR parameters of this new ESR signal was identical to those of 5,5-dimethylpyrrolidone-(2)-oxyl-(1) (DMPOX), suggesting the radical species giving the new ESR spectrum is assignable to DMPOX. The similar ESR spectrum consisting of a triplet [aN(1) = 0.69 mT] was observed when the derivative of DMPO, 3,3,5,5-tetramethyl-1-pyrroline N-oxide (M4PO) was included in the Ti3+-KClO3 reaction system. This radical species is attributed to the oxidation product of M4PO, 3,3,5,5-tetramethylpyrrolidone-(2)-oxyl-(1) (M4POX). When another nitrone spin-trap, alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN) was used as a spin-trap, the ESR signal intensity due to the ClO2 radical decreased and a new ESR signal consisting of a triplet [aN(1) = 0.76 mT] was observed. The similar ESR spectrum was observed when N-t-butyl-alpha- nitrone (PBN) was used as a spin-trap. This ESR parameter [a(N)(1) = 0.85 mT] was identical to the oxidation product of PBN, PBNX. Thus, the new ESR signal observed from POBN may be assigned to the oxidation product of POBN, POBNX. These results suggest that the ClO2, radical does not form the stable spin adducts with nitrone spin-traps, but oxidizes these spin-traps to give the corresponding nitroxyl radicals. On the other hand, nitroso spin-traps, 5,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), and 2-methyl-2-nitrosopropane (MNP) did not trap the ClO2 radical. This result indicates that an unpaired electron of the ClO2 radical is localized on oxygen atom, because nitroso spin-traps cannot form the stable spin adduct with oxygen-centered radical.

Effect of temperature on thermal oxidation of palmitic acid studied by combination of EPR spin trapping technique and SPME-GC-MS/MS.

PubMed

Chen, Hongjian; Wang, Yong; Cao, Peirang; Liu, Yuanfa

2017-11-01

Effect of temperatures on thermal oxidation of palmitic acid was studied by the combination of EPR and GC-MS/MS. DMPO was used as the spin trap. The experimental spectrum was simulated with alkyl and alkoxyl spin adducts. Total amount of spins, a parameter to indicate radical concentrations, detected at 180°C was nearly 10 times higher than that at 175°C. Besides, total amounts of spins detected at 180°C decreased rapidly because of the reaction between radical adducts and newly formed radicals. Signal intensities of alkyl radical adducts increased rapidly from 0.405 to 4.785 from 175°C to 180°C. Besides, more palmitic acid degraded to oxidized compounds from 175°C to 180°C than that of other temperature ranges. The C-C linkages between carbons 2 to 6 were easier to be oxidized at 180°C. The results all implied that oxidation rates of palmitic acid samples increased rapidly from 175°C to 180°C. Copyright © 2017 Elsevier Ltd. All rights reserved.

Intrinsic anharmonic effects on the phonon frequencies and effective spin-spin interactions in a quantum simulator made from trapped ions in a linear Paul trap

NASA Astrophysics Data System (ADS)

McAneny, M.; Freericks, J. K.

2014-11-01

The Coulomb repulsion between ions in a linear Paul trap gives rise to anharmonic terms in the potential energy when expanded about the equilibrium positions. We examine the effect of these anharmonic terms on the accuracy of a quantum simulator made from trapped ions. To be concrete, we consider a linear chain of Yb171+ ions stabilized close to the zigzag transition. We find that for typical experimental temperatures, frequencies change by no more than a factor of 0.01 % due to the anharmonic couplings. Furthermore, shifts in the effective spin-spin interactions (driven by a spin-dependent optical dipole force) are also, in general, less than 0.01 % for detunings to the blue of the transverse center-of-mass frequency. However, detuning the spin interactions near other frequencies can lead to non-negligible anharmonic contributions to the effective spin-spin interactions. We also examine an odd behavior exhibited by the harmonic spin-spin interactions for a range of intermediate detunings, where nearest-neighbor spins with a larger spatial separation on the ion chain interact more strongly than nearest neighbors with a smaller spatial separation.

IMMUNO-SPIN TRAPPING FROM BIOCHEMISTRY TO MEDICINE: advances, challenges, and pitfalls

PubMed Central

Gomez-Mejiba, Sandra E.; Zili, Zhai; Della-Vedova, Maria C.; Muñoz, Marcos D.; Chatterjee, Saurabh; Towner, Rheal A.; Hensley, Kenneth; Floyd, Robert A.; Mason, Ronald P.; Ramirez, Dario C.

2013-01-01

BACKGROUND Immuno-spin trapping (IST) is based on the reaction of a spin trap with a free radical to form a stable nitrone adduct, followed by the use of antibodies, rather than traditional electron paramagnetic resonance spectroscopy, to detect the nitrone adduct. IST has been successfully applied to mechanistic in vitro studies, and recently, macromolecule-centered radicals have been detected in models of drug-induced agranulocytosis, hepatotoxicity, cardiotoxicity, and ischemia/reperfusion, as well as in models of neurological, metabolic and immunological diseases. SCOPE OF THE REVIEW To critically evaluate advances, challenges, and pitfalls as well as the scientific opportunities of IST as applied to the study of protein-centered free radicals generated in stressed organelles, cells, tissues and animal models of disease and exposure. MAJOR CONCLUSIONS Because the spin trap has to be present at high enough concentrations in the microenvironment where the radical is formed, the possible effects of the spin trap on gene expression, metabolism and cell physiology have to be considered in the use of IST and in the interpretation of results. These factors have not yet been thoroughly dealt with in the literature. GENERAL SIGNIFICANCE The identification of radicalized proteins during cell/tissue response to stressors will help define their role in the complex cellular response to stressors and pathogenesis; however, the fidelity of spin trapping/ immuno-detection and the effects of the spin trap on the biological system should be considered. PMID:23644035

Engineered long-range interactions on a 2D array of trapped ions

NASA Astrophysics Data System (ADS)

Britton, Joseph W.; Sawyer, Brian C.; Bollinger, John J.; Freericks, James K.

2014-03-01

Ising interactions are one paradigm used to model quantum magnetism in condensed matter systems. At NIST Boulder we confine and Doppler laser cool hundreds of 9Be+ ions in a Penning trap. The valence electron of each ion behaves as an ideal spin-1/2 particle and, in the limit of weak radial confinement relative to axial confinement, the ions naturally form a two-dimensional triangular lattice. A variable-range anti-ferromagnetic Ising interaction is engineered with a spin-dependent optical dipole force (ODF) through spin-dependent excitation of collective modes of ion motion. We have also exploited this spin-dependent force to perform spectroscopy and thermometry of the normal modes of the trapped ion crystal. The high spin-count and long-range spin-spin couplings achievable in the NIST Penning trap brings within reach simulation of computationally intractable problems in quantum magnetism. Examples include modeling quantum magnetic phase transitions and propagation of spin correlations resulting from a quantum quench. The Penning system may also be amenable to observation of spin-liquid behavior thought to arise in systems where the underlying lattice structure can frustrate long-range ordering. Supported by DARPA OLE and NIST.

Strong coupling between a single nitrogen-vacancy spin and the rotational mode of diamonds levitating in an ion trap

NASA Astrophysics Data System (ADS)

Delord, T.; Nicolas, L.; Chassagneux, Y.; Hétet, G.

2017-12-01

A scheme for strong coupling between a single atomic spin and the rotational mode of levitating nanoparticles is proposed. The idea is based on spin readout of nitrogen-vacancy centers embedded in aspherical nanodiamonds levitating in an ion trap. We show that the asymmetry of the diamond induces a rotational confinement in the ion trap. Using a weak homogeneous magnetic field and a strong microwave driving we then demonstrate that the spin of the nitrogen-vacancy center can be strongly coupled to the rotational mode of the diamond.

In Vivo and In Situ Detection of Macromolecular Free Radicals Using Immuno-Spin Trapping and Molecular Magnetic Resonance Imaging.

PubMed

Towner, Rheal A; Smith, Nataliya

2018-05-20

In vivo free radical imaging in preclinical models of disease has become a reality. Free radicals have traditionally been characterized by electron spin resonance (ESR) or electron paramagnetic resonance (EPR) spectroscopy coupled with spin trapping. The disadvantage of the ESR/EPR approach is that spin adducts are short-lived due to biological reductive and/or oxidative processes. Immuno-spin trapping (IST) involves the use of an antibody that recognizes macromolecular 5,5-dimethyl-pyrroline-N-oxide (DMPO) spin adducts (anti-DMPO antibody), regardless of the oxidative/reductive state of trapped radical adducts. Recent Advances: The IST approach has been extended to an in vivo application that combines IST with molecular magnetic resonance imaging (mMRI). This combined IST-mMRI approach involves the use of a spin-trapping agent, DMPO, to trap free radicals in disease models, and administration of an mMRI probe, an anti-DMPO probe, which combines an antibody against DMPO-radical adducts and an MRI contrast agent, resulting in targeted free radical adduct detection. The combined IST-mMRI approach has been used in several rodent disease models, including diabetes, amyotrophic lateral sclerosis (ALS), gliomas, and septic encephalopathy. The advantage of this approach is that heterogeneous levels of trapped free radicals can be detected directly in vivo and in situ to pin point where free radicals are formed in different tissues. The approach can also be used to assess therapeutic agents that are either free radical scavengers or generate free radicals. Smaller probe constructs and radical identification approaches are being considered. The focus of this review is on the different applications that have been studied, advantages and limitations, and future directions. Antioxid. Redox Signal. 28, 1404-1415.

Effects of Ammonium Dinitramide in Human Liver Slices: An EPR/Spin Trapping Study.

DTIC Science & Technology

1995-09-01

environmentally safe than AP. EPR/spin trapping studies with the spin trap N-tert-butyl-a-phenyl nitrone (PBN lOmM) for 5 min in the presence of ADN yielded...N-tert-butyl-a-phenyl nitrone PBN 17. SECURITY CLASSIFICATION OF REPORT UNCLASSIFIED 18. SECURITY CLASSIFICATION OF THIS PAGE UNCLASSIFIED... nitrone s second SCN- thiocyanate SD standard deviation Vll INTRODUCTION This is a study of the reactions of free radicals formed when ammonium

Single-shot quantum nondemolition measurement of a quantum-dot electron spin using cavity exciton-polaritons

NASA Astrophysics Data System (ADS)

Puri, Shruti; McMahon, Peter L.; Yamamoto, Yoshihisa

2014-10-01

We propose a scheme to perform single-shot quantum nondemolition (QND) readout of the spin of an electron trapped in a semiconductor quantum dot (QD). Our proposal relies on the interaction of the QD electron spin with optically excited, quantum well (QW) microcavity exciton-polaritons. The spin-dependent Coulomb exchange interaction between the QD electron and cavity polaritons causes the phase and intensity response of left circularly polarized light to be different than that of right circularly polarized light, in such a way that the QD electron's spin can be inferred from the response to a linearly polarized probe reflected or transmitted from the cavity. We show that with careful device design it is possible to essentially eliminate spin-flip Raman transitions. Thus a QND measurement of the QD electron spin can be performed within a few tens of nanoseconds with fidelity ˜99.95%. This improves upon current optical QD spin readout techniques across multiple metrics, including speed and scalability.

Engineered spin-spin interactions on a 2D array of trapped ions

NASA Astrophysics Data System (ADS)

Britton, Joe; Sawyer, Brian; Bollinger, John

2013-05-01

We work with laser cooled 9Be+ ions confined in a Penning trap to simulate quantum magnetic interactions. The valence electron of each ion behaves as an ideal spin- 1 / 2 particle. We recently demonstrated a uniform anti-ferromagnetic Ising interaction on a naturally occurring two-dimensional (2D) triangular crystal of 100 < N < 350 ions. The Ising interaction is generated by a spin-dependent optical dipole force (ODF). For spins separated by distance d, we show that the range can be tuned according to (d / d 0)-a, for 0 < a < 3 . For different operating parameters we can also generate an infinite range ferromagnetic Ising interaction. We also use the ODF for spectroscopy and thermometry of the normal modes of the trapped ion array. A detailed understanding of the modes is important because they mediate the spin-spin interactions. This work is supported by NIST and the DARPA OLE program.

Versatile microwave-driven trapped ion spin system for quantum information processing

PubMed Central

Piltz, Christian; Sriarunothai, Theeraphot; Ivanov, Svetoslav S.; Wölk, Sabine; Wunderlich, Christof

2016-01-01

Using trapped atomic ions, we demonstrate a tailored and versatile effective spin system suitable for quantum simulations and universal quantum computation. By simply applying microwave pulses, selected spins can be decoupled from the remaining system and, thus, can serve as a quantum memory, while simultaneously, other coupled spins perform conditional quantum dynamics. Also, microwave pulses can change the sign of spin-spin couplings, as well as their effective strength, even during the course of a quantum algorithm. Taking advantage of the simultaneous long-range coupling between three spins, a coherent quantum Fourier transform—an essential building block for many quantum algorithms—is efficiently realized. This approach, which is based on microwave-driven trapped ions and is complementary to laser-based methods, opens a new route to overcoming technical and physical challenges in the quest for a quantum simulator and a quantum computer. PMID:27419233

Efficiency of PBN to Trap 3-CAR in B6C3F1 Mouse Liver Slices: An EPR Study.

DTIC Science & Technology

1995-09-01

be identified by electron paramagnetic resonance (EPR) using the spin trap N-tert-butyl-a phenyl nitrone (PBN). To quantitate the radicals detected...phenyl nitrone TCE trichloroethylene Vll INTRODUCTION Understanding free radical reactions is important to the military. The main objective of this...short lived radical with a spin trap’, usually a nitrone or nitroso compound yielding a longer lived nitroxide spin adduct which can be detected by

Quantum simulations of the Ising model with trapped ions: Devil's staircase and arbitrary lattice proposal

NASA Astrophysics Data System (ADS)

Korenblit, Simcha

A collection of trapped atomic ions represents one of the most attractive platforms for the quantum simulation of interacting spin networks and quantum magnetism. Spin-dependent optical dipole forces applied to an ion crystal create long-range effective spin-spin interactions and allow the simulation of spin Hamiltonians that possess nontrivial phases and dynamics. We trap linear chains of 171Yb+ ions in a Paul trap, and constrain the occupation of energy levels to the ground hyperne clock-states, creating a qubit or pseudo-spin 1/2 system. We proceed to implement spin-spin couplings between two ions using the far detuned Molmer-Sorenson scheme and perform adiabatic quantum simulations of Ising Hamiltonians with long-range couplings. We then demonstrate our ability to control the sign and relative strength of the interaction between three ions. Using this control, we simulate a frustrated triangular lattice, and for the first time establish an experimental connection between frustration and quantum entanglement. We then scale up our simulation to show phase transitions from paramagnetism to ferromagnetism for nine ions, and to anti-ferromagnetism for sixteen ions. The experimental work culminates with our most complicated Hamiltonian---a long range anti-ferromagnetic Ising interaction between 10 ions with a biasing axial field. Theoretical work presented in this thesis shows how the approach to quantum simulation utilized in this thesis can be further extended and improved. It is shown how appropriate design of laser fields can provide for arbitrary multidimensional spin-spin interaction graphs even for the case of a linear spatial array of ions. This scheme uses currently existing trap technology and is scalable to levels where classical methods of simulation are intractable.

Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms.

PubMed

Berglund, Andrew J; Hanssen, James L; McClelland, Jabez J

2008-03-21

Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin polarized with temperatures reaching below 2 muK. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.

Quantum Information Experiments with Trapped Ions at NIST

NASA Astrophysics Data System (ADS)

Wilson, Andrew

2015-03-01

We present an overview of recent trapped-ion quantum information experiments at NIST. Advancing beyond few-qubit ``proof-of-principle'' experiments to the many-qubit systems needed for practical quantum simulation and information processing, without compromising on the performance demonstrated with small systems, remains a major challenge. One approach to scalable hardware development is surface-electrode traps. Micro-fabricated planar traps can have a number of useful features, including flexible electrode geometries, integrated microwave delivery, and spatio-temporal tuning of potentials for ion transport and spin-spin interactions. In this talk we report on a number of on-going investigations with surface traps. Experiments feature a multi-zone trap with closely spaced ions in a triangular arrangement (a first step towards 2D arrays of ions with tunable spin-spin interactions), a scheme for smooth transport through a junction in a 2D structure based on switchable RF potentials, and a micro-fabricated photo-detector integrated into a trap. We also give a progress report on our latest efforts to improve the fidelity of both optical and microwave 2-qubit gates. This work was supported by IARPA, ONR and the NIST Quantum Information Program. The 3-ion and switchable-RF-junction traps were developed in collaboration with Sandia National Laboratory.

IN VIVO EVIDENCE OF FREE RADICAL FORMATION AFTER ASBESTOS INSTILLATION: AN ESR SPIN TRAPPING INVESTIGATION

EPA Science Inventory

It has been postulated that the in vivo toxicity of asbestos results from its catalysis of free radical generation. We examined in vivo radical production using electron spin resonance (ESR) coupled with the spin trap alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN); 180 d...

Ultraviolet-B radiation applied to detached peach fruit: A study of free radical generation by EPR spin trapping.

PubMed

Sgherri, C; Scattino, C; Pinzino, C; Tonutti, P; Ranieri, A M

2015-11-01

In peaches, phenolic compounds are the major sources of antioxidants, and cyanidin-3-O-glucoside is the main anthocyanin present, above all in the skin. Anthocyanin content has been shown to increase after UV-B irradiation, which may be very harmful for all biological organisms due to the induction of the generation of reactive oxygen species (ROS). Peach fruits (cv. 'Suncrest') were exposed during post-harvest to supplemental ultraviolet-B radiation. A spin-trapping technique was used to monitor the generation of free radicals under UV-B, and 5-(diethoxy-phosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) was used as the spin trap. The flesh of peaches was essentially unaffected by the treatment, whereas the skin was responsive at the end of the treatment, accumulating ascorbate, flavonoids, cyanidin-3-O-glucoside, and showing a higher antioxidant activity. The levels of stable free radicals were also lower at the end of treatment. Carbon-centred radicals contributed the most to the total amounts of free radicals, whereas hydroxyl radicals and oxygen-centred free radicals contributed minimally. The carbon-centred free radical identified was the same as the one obtained after irradiation of authentic cyanidin-3-O-glucoside. During UV-B treatment cyanidin-3-O-glucoside increased and was capable of radicalization protecting the other organic molecules of the cell from oxidation. ROS, among which hydroxyl radicals, were thus maintained to minimal levels. This ability of cyanidin-3-O-glucoside displayed the mechanism underlined the tolerance to UV-B irradiation indicating that shelf life can be prolonged by the presence of anthocyanins. Thus, UV-B technique results a good approach to induce antioxidant production in peach fruits increasing their nutraceutical properties. Copyright © 2015. Published by Elsevier Masson SAS.

Radiolysis of carbohydrates as studied by ESR and spin-trapping—II. Glycerol- d8 xylitol, dulcitol, d-sorbitol and d-mannitol

NASA Astrophysics Data System (ADS)

Kuwabara, M.; Zhang, Z.-Y.; Inanami, O.; Yoshii, G.

Studies concerning the radicals produced in glycerol by reactions with OH radicals have been carried out by investigating deuterated glycerol (glycerol-d 8) by spin-trapping with 2-methyl-2-nitrosopropane. Free radicals produced in linear carbohydrates such as xylitol, dulcitol, D-sorbitol and D-mannitol by reactions with OH radicals as well as by direct γ-radiolysis have been also investigated by spin-trapping. The ESR spectra of the spin-trapped radicals were analysed on the basis of the results from ESR and spin-trapping experiments on glycerol and deuterated glycerol, and the formation of three radical species, CHO-CH-, CH 2-CO- and HO-CH-, due to both OH reactions and direct γ-radiolysis was confirmed for all compounds. The presence of a radical, -CO-CH-, was detected for xylitol, D-sorbitol and D-mannitol. General reactions processes induced by OH reactions or γ-radiolysis in the solid state are discussed.

Coherent all-optical control of ultracold atoms arrays in permanent magnetic traps.

PubMed

Abdelrahman, Ahmed; Mukai, Tetsuya; Häffner, Hartmut; Byrnes, Tim

2014-02-10

We propose a hybrid architecture for quantum information processing based on magnetically trapped ultracold atoms coupled via optical fields. The ultracold atoms, which can be either Bose-Einstein condensates or ensembles, are trapped in permanent magnetic traps and are placed in microcavities, connected by silica based waveguides on an atom chip structure. At each trapping center, the ultracold atoms form spin coherent states, serving as a quantum memory. An all-optical scheme is used to initialize, measure and perform a universal set of quantum gates on the single and two spin-coherent states where entanglement can be generated addressably between spatially separated trapped ultracold atoms. This allows for universal quantum operations on the spin coherent state quantum memories. We give detailed derivations of the composite cavity system mediated by a silica waveguide as well as the control scheme. Estimates for the necessary experimental conditions for a working hybrid device are given.

[Generation of Superoxide Radicals by Complex III in Heart Mitochondria and Antioxidant Effect of Dinitrosyl Iron Complexes at Different Partial Pressure of Oxygen].

PubMed

Dudylina, A L; Ivanova, M V; Shumaev, K B; Ruuge, E K

2016-01-01

The EPR spin-trapping technique and EPR-oximetry were used to study generation of superoxide radicals in heart mitochondria isolated from Wistar rats under conditions of variable oxygen concentration. Lithium phthalocyanine and TEMPONE-15N-D16 were chosen to determine oxygen content in a gas-permeable capillary tube containing mitochondria. TIRON was used as a spin trap. We investigated the influence of different oxygen concentrations in incubation mixture and demonstrated that heart mitochondria can generate superoxide in complex III at different partial pressure of oxygen as well as under the conditions of deep hypoxia (< 5% O2). Dinitrosyl iron complexes with glutathione (the pharmaceutical drug "Oxacom") exerted an antioxidant effect, regardless of the value of the partial pressure of oxygen, but the magnitude and kinetic characteristics of the effect depended on the concentration of the drug.

Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

NASA Technical Reports Server (NTRS)

Kim, S.; Westmoreland, D.

1994-01-01

The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

Towards Quantum Simulation with Circular Rydberg Atoms

NASA Astrophysics Data System (ADS)

Nguyen, T. L.; Raimond, J. M.; Sayrin, C.; Cortiñas, R.; Cantat-Moltrecht, T.; Assemat, F.; Dotsenko, I.; Gleyzes, S.; Haroche, S.; Roux, G.; Jolicoeur, Th.; Brune, M.

2018-01-01

The main objective of quantum simulation is an in-depth understanding of many-body physics, which is important for fundamental issues (quantum phase transitions, transport, …) and for the development of innovative materials. Analytic approaches to many-body systems are limited, and the huge size of their Hilbert space makes numerical simulations on classical computers intractable. A quantum simulator avoids these limitations by transcribing the system of interest into another, with the same dynamics but with interaction parameters under control and with experimental access to all relevant observables. Quantum simulation of spin systems is being explored with trapped ions, neutral atoms, and superconducting devices. We propose here a new paradigm for quantum simulation of spin-1 /2 arrays, providing unprecedented flexibility and allowing one to explore domains beyond the reach of other platforms. It is based on laser-trapped circular Rydberg atoms. Their long intrinsic lifetimes, combined with the inhibition of their microwave spontaneous emission and their low sensitivity to collisions and photoionization, make trapping lifetimes in the minute range realistic with state-of-the-art techniques. Ultracold defect-free circular atom chains can be prepared by a variant of the evaporative cooling method. This method also leads to the detection of arbitrary spin observables with single-site resolution. The proposed simulator realizes an X X Z spin-1 /2 Hamiltonian with nearest-neighbor couplings ranging from a few to tens of kilohertz. All the model parameters can be dynamically tuned at will, making a large range of simulations accessible. The system evolution can be followed over times in the range of seconds, long enough to be relevant for ground-state adiabatic preparation and for the study of thermalization, disorder, or Floquet time crystals. The proposed platform already presents unrivaled features for quantum simulation of regular spin chains. We discuss extensions towards more general quantum simulations of interacting spin systems with full control on individual interactions.

Free radical generation by non-equilibrium atmospheric pressure plasma in alcohol-water mixtures: an EPR-spin trapping study

NASA Astrophysics Data System (ADS)

Uchiyama, Hidefumi; Ishikawa, Kenji; Zhao, Qing-Li; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Krishna, Murali C.; Ishijima, Tatsuo; Matsuya, Yuji; Hori, Masaru; Noguchi, Kyo; Kondo, Takashi

2018-03-01

Free radical species in aqueous solution—various alcohol-water reaction mixtures—by exposure to non-equilibrium cold atmospheric pressure Ar plasma (CAP), were monitored using electron paramagnetic resonance spin-trapping techniques with 3, 5-dibromo-4-nitrosobenzene sulfonate as a water soluble nitroso spin trap. The major radical species were formed by H-abstraction from alcohol molecules due to ·OH radicals. In the ethanol-water mixture ·CH2CH2OH produced by H abstraction from CH3 group of the ethanol and ·CH3 radicals were detected. The latter was due to the decomposition of unstable CH3·CHOH to form the ·CH3 radicals and the stable formaldehyde by C-C bond fission. These intermediates are similar to those observed by reaction with ·OH radicals generation in the H2O2-UV photolysis of the reaction mixtures. The evidence of ·CH3 radical formation in the pyrolytic decomposition of the reaction mixtures by exposure to ultrasound or in methane irradiated with microwave plasma have been reported previously. However, the pyrolytic ·CH3 radicals were not found in both plasma and H2O2-UV photolysis condition. These results suggests that free radicals produced by Ar-CAP are most likely due to the reaction between abundant ·OH radicals and alcohol molecules.

Oxygen radical absorbance capacity (ORAC) of cyclodextrin-solubilized flavonoids, resveratrol and astaxanthin as measured with the ORAC-EPR method

PubMed Central

Sueishi, Yoshimi; Ishikawa, Misa; Yoshioka, Daisuke; Endoh, Nobuyuki; Oowada, Shigeru; Shimmei, Masashi; Fujii, Hirotada; Kotake, Yashige

2012-01-01

Recently, we proposed an oxygen radical absorbance capacity method that directly quantifies the antioxidant’s scavenging capacity against free radicals and evaluated the radical scavenging abilities for water soluble antioxidant compounds. In this study, we determined the radical scavenging abilities of lipophilic antioxidants which were solubilized by cyclodextrin in water. Commonly employed fluorescence-based method measures the antioxidant’s protection capability for the fluorescent probe, while we directly quantify free-radical level using electron paramagnetic resonance spin trapping technique. In addition, the spin trapping-based method adopted controlled UV-photolysis of azo-initiator for free radical generation, but in fluorescence-based method, thermal decomposition of azo-initiator was utilized. We determined the radical scavenging abilities of seven well-known lipophilic antioxidants (five flavonoids, resveratrol and astaxanthin), using methylated β-cyclodextrin as a solubilizer. The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data. Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested. We sorted out the possible causes of the deviation between the two methods. PMID:22448093

Oxygen radical absorbance capacity (ORAC) of cyclodextrin-solubilized flavonoids, resveratrol and astaxanthin as measured with the ORAC-EPR method.

PubMed

Sueishi, Yoshimi; Ishikawa, Misa; Yoshioka, Daisuke; Endoh, Nobuyuki; Oowada, Shigeru; Shimmei, Masashi; Fujii, Hirotada; Kotake, Yashige

2012-03-01

Recently, we proposed an oxygen radical absorbance capacity method that directly quantifies the antioxidant's scavenging capacity against free radicals and evaluated the radical scavenging abilities for water soluble antioxidant compounds. In this study, we determined the radical scavenging abilities of lipophilic antioxidants which were solubilized by cyclodextrin in water. Commonly employed fluorescence-based method measures the antioxidant's protection capability for the fluorescent probe, while we directly quantify free-radical level using electron paramagnetic resonance spin trapping technique. In addition, the spin trapping-based method adopted controlled UV-photolysis of azo-initiator for free radical generation, but in fluorescence-based method, thermal decomposition of azo-initiator was utilized. We determined the radical scavenging abilities of seven well-known lipophilic antioxidants (five flavonoids, resveratrol and astaxanthin), using methylated β-cyclodextrin as a solubilizer. The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data. Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested. We sorted out the possible causes of the deviation between the two methods.

Coherent control of a single nitrogen-vacancy center spin in optically levitated nanodiamond

DOE PAGES

Pettit, Robert M.; Neukirch, Levi Patrick; Zhang, Yi; ...

2017-05-12

Here, we report the first observation, to the best of our knowledge, of electron spin transients in single negatively charged nitrogen-vacancy (NV -) centers, contained within optically trapped nanodiamonds, in both atmospheric pressure and low vacuum. It is shown that, after an initial exposure to low vacuum, the trapped nanodiamonds remain at temperatures near room temperature even in low vacuum. Furthermore, the transverse coherence time of the NV - center spin, measured to be T 2=101.4 ns, is robust over the range of trapping powers considered in this study.

Lieb-Robinson bounds for spin-boson lattice models and trapped ions.

PubMed

Jünemann, J; Cadarso, A; Pérez-García, D; Bermudez, A; García-Ripoll, J J

2013-12-06

We derive a Lieb-Robinson bound for the propagation of spin correlations in a model of spins interacting through a bosonic lattice field, which satisfies a Lieb-Robinson bound in the absence of spin-boson couplings. We apply these bounds to a system of trapped ions and find that the propagation of spin correlations, as mediated by the phonons of the ion crystal, can be faster than the regimes currently explored in experiments. We propose a scheme to test the bounds by measuring retarded correlation functions via the crystal fluorescence.

Strain-assisted optomechanical coupling of polariton condensate spin to a micromechanical resonator

NASA Astrophysics Data System (ADS)

Be'er, O.; Ohadi, H.; del Valle-Inclan Redondo, Y.; Ramsay, A. J.; Tsintzos, S. I.; Hatzopoulos, Z.; Savvidis, P. G.; Baumberg, J. J.

2017-12-01

We report spin and intensity coupling of an exciton-polariton condensate to the mechanical vibrations of a circular membrane microcavity. We optically drive the microcavity resonator at the lowest mechanical resonance frequency while creating an optically trapped spin-polarized polariton condensate in different locations on the microcavity and observe spin and intensity oscillations of the condensate at the vibration frequency of the resonator. Spin oscillations are induced by vibrational strain driving, whilst the modulation of the optical trap due to the displacement of the membrane causes intensity oscillations in the condensate emission. Our results demonstrate spin-phonon coupling in a macroscopically coherent condensate.

Emergence and Frustration of Magnetism with Variable-Range Interactions in a Quantum Simulator

DTIC Science & Technology

2013-05-03

quantum entanglement . Here, we engineer frustrated antiferromagnetic interactions between spins stored in a crystal of up to 16 trapped 171Yb+ atoms. We...individual trapped ion spins (10–14) and the observation of spin frus- tration and quantum entanglement in the smallest system of three spins (15). Here...monroe@umd.edu www.sciencemag.org SCIENCE VOL 340 3 MAY 2013 583 and the excitation gap (Fig. 1A) closes, leading to a finite entropy density in the

Influence of pH on EPR spectra of radical adducts with a new spin trap 1,2,2,5,5-pentamethyl-3-imidazoline 3-oxide

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

Skubnevskaya, G.I.; Dul'tseva, G.G.; Shchukin, G.I.

1987-08-10

1,2,2,5,5-Pentamethyl-3-imidazoline 3-oxide is an effective spin trap for short-lived free radicals, forming spin adducts with life time of > 10 min. Protonation of the amine N atom of imidazoline is manifested in the EPR spectra of the spin adducts, which makes it possible to measure pH in the range of 2.5 to 4.

Magnetic trapping of buffer-gas-cooled chromium atoms and prospects for the extension to paramagnetic molecules

NASA Astrophysics Data System (ADS)

Bakker, Joost M.; Stoll, Michael; Weise, Dennis R.; Vogelsang, Oliver; Meijer, Gerard; Peters, Achim

2006-10-01

We report the successful buffer-gas cooling and magnetic trapping of chromium atoms with densities exceeding 1012 atoms per cm3 at a temperature of 350 mK for the trapped sample. The possibilities of extending the method to buffer-gas cool and magnetically trap molecules are discussed. To minimize the most important loss mechanism in magnetic trapping, molecules with a small spin spin interaction and a large rotational constant are preferred. Both the CrH (6Σ+ ground state) and MnH (7Σ+) radicals appear to be suitable systems for future experiments.

Search for magnetic monopoles with the MoEDAL prototype trapping detector in 8 TeV proton-proton collisions at the LHC

NASA Astrophysics Data System (ADS)

Acharya, B.; Alexandre, J.; Bendtz, K.; Benes, P.; Bernabéu, J.; Campbell, M.; Cecchini, S.; Chwastowski, J.; Chatterjee, A.; de Montigny, M.; Derendarz, D.; De Roeck, A.; Ellis, J. R.; Fairbairn, M.; Felea, D.; Frank, M.; Frekers, D.; Garcia, C.; Giacomelli, G.; Hasegan, D.; Kalliokoski, M.; Katre, A.; Kim, D.-W.; King, M. G. L.; Kinoshita, K.; Lacarrère, D. H.; Lee, S. C.; Leroy, C.; Lionti, A.; Margiotta, A.; Mauri, N.; Mavromatos, N. E.; Mermod, P.; Milstead, D.; Mitsou, V. A.; Orava, R.; Parker, B.; Pasqualini, L.; Patrizii, L.; Păvălas, G. E.; Pinfold, J. L.; Platkevič, M.; Popa, V.; Pozzato, M.; Pospisil, S.; Rajantie, A.; Sahnoun, Z.; Sakellariadou, M.; Sarkar, S.; Semenoff, G.; Sirri, G.; Sliwa, K.; Soluk, R.; Spurio, M.; Srivastava, Y. N.; Staszewski, R.; Suk, M.; Swain, J.; Tenti, M.; Togo, V.; Trzebinski, M.; Tuszynski, J. A.; Vento, V.; Vives, O.; Vykydal, Z.; Whyntie, T.; Widom, A.; Willems, G.; Yoon, J. H.

2016-08-01

The MoEDAL experiment is designed to search for magnetic monopoles and other highly-ionising particles produced in high-energy collisions at the LHC. The largely passive MoEDAL detector, deployed at Interaction Point 8 on the LHC ring, relies on two dedicated direct detection techniques. The first technique is based on stacks of nucleartrack detectors with surface area ~18m2, sensitive to particle ionisation exceeding a high threshold. These detectors are analysed offline by optical scanning microscopes. The second technique is based on the trapping of charged particles in an array of roughly 800 kg of aluminium samples. These samples are monitored offline for the presence of trapped magnetic charge at a remote superconducting magnetometer facility. We present here the results of a search for magnetic monopoles using a 160 kg prototype MoEDAL trapping detector exposed to 8TeV proton-proton collisions at the LHC, for an integrated luminosity of 0.75 fb-1. No magnetic charge exceeding 0:5 g D (where g D is the Dirac magnetic charge) is measured in any of the exposed samples, allowing limits to be placed on monopole production in the mass range 100 GeV≤ m ≤ 3500 GeV. Model-independent cross-section limits are presented in fiducial regions of monopole energy and direction for 1 g D ≤ | g| ≤ 6 g D, and model-dependent cross-section limits are obtained for Drell-Yan pair production of spin-1/2 and spin-0 monopoles for 1 g D ≤ | g| ≤ 4 g D. Under the assumption of Drell-Yan cross sections, mass limits are derived for | g| = 2 g D and | g| = 3 g D for the first time at the LHC, surpassing the results from previous collider experiments.

Observation of Diamond Nitrogen-Vacancy Center Photoluminescence under High Vacuum in a Magneto-Gravitational Trap

NASA Astrophysics Data System (ADS)

Ji, Peng; Hsu, Jen-Feng; Lewandowski, Charles W.; Dutt, M. V. Gurudev; D'Urso, Brian

2016-05-01

We report the observation of photoluminescence from nitrogen-vacancy (NV) centers in diamond nanocrystals levitated in a magneto-gravitational trap. The trap utilizes a combination of strong magnetic field gradients and gravity to confine diamagnetic particles in three dimensions. The well-characterized NV centers in trapped diamond nanocrystals provide an ideal built-in sensor to measure the trap magnetic field and the temperature of the trapped diamond nanocrystal. In the future, the NV center spin state could be coupled to the mechanical motion through magnetic field gradients, enabling in an ideal quantum interface between NV center spin and the mechanical motion. National Science Foundation, Grant No. 1540879.

Nuclear spin cooling by electric dipole spin resonance and coherent population trapping

NASA Astrophysics Data System (ADS)

Li, Ai-Xian; Duan, Su-Qing; Zhang, Wei

2017-09-01

Nuclear spin fluctuation suppression is a key issue in preserving electron coherence for quantum information/computation. We propose an efficient way of nuclear spin cooling in semiconductor quantum dots (QDs) by the coherent population trapping (CPT) and the electric dipole spin resonance (EDSR) induced by optical fields and ac electric fields. The EDSR can enhance the spin flip-flop rate and may bring out bistability under certain conditions. By tuning the optical fields, we can avoid the EDSR induced bistability and obtain highly polarized nuclear spin state, which results in long electron coherence time. With the help of CPT and EDSR, an enhancement of 1500 times of the electron coherence time can been obtained after a 500 ns preparation time.

Tea extracts protect normal lymphocytes but not leukemia cells from UV radiation-induced ROS production: An EPR spin trap study.

PubMed

Tepe Çam, Semra; Polat, Mustafa; Esmekaya, Meriç Arda; Canseven, Ayşe G; Seyhan, Nesrin

2015-08-01

An ex vivo method for detection of free radicals and their neutralization by aqueous tea in human normal lymphocytes and MEC-1 leukemia cells under ultraviolet (UV) irradiation was investigated. This method is based on the electron paramagnetic resonance (EPR) spectroscopy spin-trapping technique. 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide (BMPO) was used as the spin trap. Normal human lymphocytes and leukemia cells were exposed to UVB radiation (290-315 nm) at 47.7 and 159 mJ/cm(2) and to UVA radiation (315-400 nm) at 53.7 J/cm(2). No significant radical production at 47.7 mJ/cm(2) UVB dose in both cell lines was observed. In normal cells, free radical production was observed at 159 mJ/cm(2) UVB and 53.7 J/cm(2) UVA doses. However, both UV sources did not significantly produce free radicals in leukemia cells. A radical scavenging property of tea extracts (black, green, sage, rosehip) was observed in normal lymphocytes after both UVB and UVA exposure. In leukemia cells, the intensities of EPR signals produced in BMPO with tea extracts were found to be increased substantially after UVA exposure. These results showed that UV radiation induced free radical formation in normal human lymphocytes and indicated that tea extracts may be useful as photoprotective agents for them. On the other hand, tea extracts facilitated free radical production in leukemia cells.

Ion-Atom Cold Collisions and Atomic Clocks

NASA Technical Reports Server (NTRS)

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

1997-01-01

Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions, exploited as a useful tool at room temperature and higher, are greatly enhanced at low energy. For example, collisional spin transfer from one species of polarized atoms to another has long been a useful method for polarizing a sample of atoms where no other means was available. Because optical pumping cannot be used to polarize the nuclear spin of Xe-129 or He-3 (for use in nmr imaging of the lungs), the nuclear spins are polarized via collisions with an optically pumped Rb vapor in a cell containing both gases. In another case, a spin polarized thermal Cs beam was used to polarize the hyperfine states of trapped He(+)-3 ions in order to measure their hyperfine clock transition frequency. The absence of an x-ray light source to optically pump the ground state of the He(+)-3 ion necessitated this alternative state preparation. Similarly, Cd(+) and Sr(+) ions were spin-oriented via collisions in a cell with optically pumped Rb vapor. Resonant RF spin changing transitions in the ground state of the ions were detected by changes in the Rb resonance light absorption. Because cold collision spin exchange rates scale with temperature as T(sup -1/2) this technique is expected to be a far more powerful tool than the room temperature counterpart. This factor of 100 or more enhancement in spin exchange reaction rates at low temperatures is the basis for a novel trapped ion clock where laser cooled neutrals will cool, state select and monitor the ion clock transition. The advantage over conventional direct laser cooling of trapped ions is that the very expensive and cumbersome UV laser light sources, required to excite the ionic cooling transition, are effectively replaced by simple diode lasers.

Stationary states and rotational properties of spin-orbit-coupled Bose-Einstein condensates held under a toroidal trap

NASA Astrophysics Data System (ADS)

He, Zhang-Ming; Zhang, Xiao-Fei; Kato, Masaya; Han, Wei; Saito, Hiroki

2018-06-01

We consider a pseudospin-1/2 Bose-Einstein condensate with Rashba spin-orbit coupling in a two-dimensional toroidal trap. By solving the damped Gross-Pitaevskii equations for this system, we show that the system exhibits a rich variety of stationary states, such as vehicle wheel and flower-petal stripe patterns. These stationary states are stable against perturbation with thermal energy and can survive for a long time. In the presence of rotation, our results show that the rotating systems have exotic vortex configurations. These phenomenon originates from the interplay among spin-orbit coupling, trap geometry, and rotation.

Tunable Magnetic Alignment between Trapped Exciton-Polariton Condensates.

PubMed

Ohadi, H; Del Valle-Inclan Redondo, Y; Dreismann, A; Rubo, Y G; Pinsker, F; Tsintzos, S I; Hatzopoulos, Z; Savvidis, P G; Baumberg, J J

2016-03-11

Tunable spin correlations are found to arise between two neighboring trapped exciton-polariton condensates which spin polarize spontaneously. We observe a crossover from an antiferromagnetic to a ferromagnetic pair state by reducing the coupling barrier in real time using control of the imprinted pattern of pump light. Fast optical switching of both condensates is then achieved by resonantly but weakly triggering only a single condensate. These effects can be explained as the competition between spin bifurcations and spin-preserving Josephson coupling between the two condensates, and open the way to polariton Bose-Hubbard ladders.

Spin-Orbit-Coupled Interferometry with Ring-Trapped Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Helm, J. L.; Billam, T. P.; Rakonjac, A.; Cornish, S. L.; Gardiner, S. A.

2018-02-01

We propose a method of atom interferometry using a spinor Bose-Einstein condensate with a time-varying magnetic field acting as a coherent beam splitter. Our protocol creates long-lived superpositional counterflow states, which are of fundamental interest and can be made sensitive to both the Sagnac effect and magnetic fields on the sub-μ G scale. We split a ring-trapped condensate, initially in the mf=0 hyperfine state, into superpositions of internal mf=±1 states and condensate superflow, which are spin-orbit coupled. After interrogation, the relative phase accumulation can be inferred from a population transfer to the mf=±1 states. The counterflow generation protocol is adiabatically deterministic and does not rely on coupling to additional optical fields or mechanical stirring techniques. Our protocol can maximize the classical Fisher information for any rotation, magnetic field, or interrogation time and so has the maximum sensitivity available to uncorrelated particles. Precision can increase with the interrogation time and so is limited only by the lifetime of the condensate.

"Dark" Singlet Oxygen and Electron Paramagnetic Resonance Spin Trapping as Convenient Tools to Assess Photolytic Drug Degradation.

PubMed

Persich, Peter; Hostyn, Steven; Joie, Céline; Winderickx, Guy; Pikkemaat, Jeroen; Romijn, Edwin P; Maes, Bert U W

2017-05-01

Forced degradation studies are an important tool for a systematic assessment of decomposition pathways and identification of reactive sites in active pharmaceutical ingredients (APIs). Two methodologies have been combined in order to provide a deeper understanding of singlet oxygen-related degradation pathways of APIs under light irradiation. First, we report that a "dark" singlet oxygen test enables the investigation of drug reactivity toward singlet oxygen independently of photolytic irradiation processes. Second, the photosensitizing properties of the API producing the singlet oxygen was proven and quantified by spin trapping and electron paramagnetic resonance analysis. A combination of these techniques is an interesting addition to the forced degradation portfolio as it can be used for (1) revealing unexpected degradation pathways of APIs due to singlet oxygen, (2) clarifying photolytic drug-drug interactions in fixed-dose combinations, and (3) synthesizing larger quantities of hardly accessible oxidative drug degradants. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Antioxidant pool in beer and kinetics of EPR spin-trapping.

PubMed

Kocherginsky, Nikolai M; Kostetski, Yuri Yu; Smirnov, Alex I

2005-08-24

The kinetics of spin-trap adduct formation in beer oxidation exhibits an induction period if the reaction is carried out at elevated temperatures and in the presence of air. This lag period lasts until the endogenous antioxidants are almost completely depleted, and its duration is used as an indicator of the flavor stability and shelf life of beer. This paper demonstrates that the total kinetics of the process can be characterized by three parameters-the lag period, the rate of spin-trap adduct formation, and, finally, the steady-state spin-adduct concentration. A steady-state chain reaction mechanism is described, and quantitative estimates of the main kinetic parameters such as the initiation rate, antioxidant pool, effective content of organic molecules participating in the chain reactions, and the rate constant of the 1-hydroxyethyl radical EtOH(*) spin-adduct disappearance are given. An additional new dimensionless parameter is suggested to characterize the antioxidant pool-the product of the lag time and the rate of spin-trap radical formation immediately after the lag time, normalized by the steady-state concentration of the adducts. The results of spin-tapping EPR experiments are compared with the nitroxide reduction kinetics measured in the same beer samples. It is shown that although the kinetics of nitroxide reduction in beer can be used to evaluate the reducing power of beer, the latter parameter does not correlate with the antioxidant pool. The relationship of free radical processes, antioxidant pool, reducing power, and beer staling is discussed.

Phonon mediated quantum spin simulator made from a two-dimensional Wigner crystal in Penning traps

NASA Astrophysics Data System (ADS)

Wang, Joseph; Keith, Adam; Freericks, J. K.

2013-03-01

Motivated by recent advances in quantum simulations in a Penning trap, we give a theoretical description for the use of two-dimensional cold ions in a rotating trap as a quantum emulator. The collective axial phonon modes and planar modes are studied in detail, including all effects of the rotating frame. We show the character of the phonon modes and spectrum, which is crucial for engineering exotic spin interactions. In the presence of laser-ion coupling with these coherent phonon excitations, we show theoretically how the spin-spin Hamiltonian can be generated. Specifically, we notice certain parameter regimes in which the level of frustration between spins can be engineered by the coupling to the planar modes. This may be relevant to the quantum simulation of spin-glass physics or other disordered problems. This work was supported under ARO grant number W911NF0710576 with funds from the DARPA OLE Program. J. K. F. also acknowledges the McDevitt bequest at Georgetown University. A. C. K. also acknowledges support of the National Science Foundation under grant

A 2D Array of 100's of Ions for Quantum Simulation and Many-Body Physics in a Penning Trap

NASA Astrophysics Data System (ADS)

Bohnet, Justin; Sawyer, Brian; Britton, Joseph; Bollinger, John

2015-05-01

Quantum simulations promise to reveal new materials and phenomena for experimental study, but few systems have demonstrated the capability to control ensembles in which quantum effects cannot be directly computed. One possible platform for intractable quantum simulations may be a system of 100's of 9Be+ ions in a Penning trap, where the valence electron spins are coupled with an effective Ising interaction in a 2D geometry. Here we report on results from a new Penning trap designed for 2D quantum simulations. We characterize the ion crystal stability and describe progress towards bench-marking quantum effects of the spin-spin coupling using a spin-squeezing witness. We also report on the successful photodissociation of BeH+ contaminant molecular ions that impede the use of such crystals for quantum simulation. This work lays the foundation for future experiments such as the observation of spin dynamics under the quantum Ising Hamiltonian with a transverse field. Supported by a NIST-NRC Research Associateship.

SELF-TRAPPING OF DISKOSEISMIC CORRUGATION MODES IN NEUTRON STAR SPACETIMES

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

Tsang, David; Pappas, George

2016-02-10

We examine the effects of higher-order multipole contributions of rotating neutron star (NS) spacetimes on the propagation of corrugation (c-)modes within a thin accretion disk. We find that the Lense–Thirring precession frequency, which determines the propagation region of the low-frequency fundamental corrugation modes, can experience a turnover allowing for c-modes to become self-trapped for sufficiently high dimensionless spin j and quadrupole rotational deformability α. If such self-trapping c-modes can be detected, e.g., through phase-resolved spectroscopy of the iron line for a high-spin low-mass accreting neutron star, this could potentially constrain the spin-induced NS quadrupole and the NS equation of state.

Self-Trapping of Diskoseismic Corrugation Modes in Neutron Star Spacetimes

NASA Astrophysics Data System (ADS)

Tsang, David; Pappas, George

2016-02-01

We examine the effects of higher-order multipole contributions of rotating neutron star (NS) spacetimes on the propagation of corrugation (c-)modes within a thin accretion disk. We find that the Lense-Thirring precession frequency, which determines the propagation region of the low-frequency fundamental corrugation modes, can experience a turnover allowing for c-modes to become self-trapped for sufficiently high dimensionless spin j and quadrupole rotational deformability α. If such self-trapping c-modes can be detected, e.g., through phase-resolved spectroscopy of the iron line for a high-spin low-mass accreting neutron star, this could potentially constrain the spin-induced NS quadrupole and the NS equation of state.

Adjustable Spin-Spin Interaction with 171Yb+ ions and Addressing of a Quantum Byte

NASA Astrophysics Data System (ADS)

Wunderlich, Christof

2015-05-01

Trapped atomic ions are a well-advanced physical system for investigating fundamental questions of quantum physics and for quantum information science and its applications. When contemplating the scalability of trapped ions for quantum information science one notes that the use of laser light for coherent operations gives rise to technical and also physical issues that can be remedied by replacing laser light by microwave (MW) and radio-frequency (RF) radiation employing suitably modified ion traps. Magnetic gradient induced coupling (MAGIC) makes it possible to coherently manipulate trapped ions using exclusively MW and RF radiation. After introducing the general concept of MAGIC, I shall report on recent experimental progress using 171Yb+ ions, confined in a suitable Paul trap, as effective spin-1/2 systems interacting via MAGIC. Entangling gates between non-neighbouring ions will be presented. The spin-spin coupling strength is variable and can be adjusted by variation of the secular trap frequency. In general, executing a quantum gate with a single qubit, or a subset of qubits, affects the quantum states of all other qubits. This reduced fidelity of the whole quantum register may preclude scalability. We demonstrate addressing of individual qubits within a quantum byte (eight qubits interacting via MAGIC) using MW radiation and measure the error induced in all non-addressed qubits (cross-talk) associated with the application of single-qubit gates. The measured cross-talk is on the order 10-5 and therefore below the threshold commonly agreed sufficient to efficiently realize fault-tolerant quantum computing. Furthermore, experimental results on continuous and pulsed dynamical decoupling (DD) for protecting quantum memories and quantum gates against decoherence will be briefly discussed. Finally, I report on using continuous DD to realize a broadband ultrasensitive single-atom magnetometer.

Use of rapid-scan EPR to improve detection sensitivity for spin-trapped radicals.

PubMed

Mitchell, Deborah G; Rosen, Gerald M; Tseitlin, Mark; Symmes, Breanna; Eaton, Sandra S; Eaton, Gareth R

2013-07-16

The short lifetime of superoxide and the low rates of formation expected in vivo make detection by standard continuous wave (CW) electron paramagnetic resonance (EPR) challenging. The new rapid-scan EPR method offers improved sensitivity for these types of samples. In rapid-scan EPR, the magnetic field is scanned through resonance in a time that is short relative to electron spin relaxation times, and data are processed to obtain the absorption spectrum. To validate the application of rapid-scan EPR to spin trapping, superoxide was generated by the reaction of xanthine oxidase and hypoxanthine with rates of 0.1-6.0 μM/min and trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO). Spin trapping with BMPO to form the BMPO-OOH adduct converts the very short-lived superoxide radical into a more stable spin adduct. There is good agreement between the hyperfine splitting parameters obtained for BMPO-OOH by CW and rapid-scan EPR. For the same signal acquisition time, the signal/noise ratio is >40 times higher for rapid-scan than for CW EPR. Rapid-scan EPR can detect superoxide produced by Enterococcus faecalis at rates that are too low for detection by CW EPR. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Interface investigation of solution processed high- κ ZrO2/Si MOS structure by DLTS

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Mondal, Sandip; Rao, Ksr Koteswara

The interfacial region is dominating due to the continuous downscaling and integration of high- k oxides in CMOS applications. The accurate characterization of high- k oxides/semiconductor interface has the significant importance towards its usage in memory and thin film devices. The interface traps at the high - k /semiconductor interface can be quantified by deep level transient spectroscopy (DLTS) with better accuracy in contrast to capacitance-voltage (CV) and conductance technique. We report the fabrication of high- k ZrO2 films on p-Si substrate by a simple and inexpensive sol-gel spin-coating technique. Further, the ZrO2/Si interface is characterized through DLTS. The flat-band voltage (VFB) and the density of slow interface states (oxide trapped charges) extracted from CV characteristics are 0.37 V and 2x10- 11 C/cm2, respectively. The activation energy, interface state density and capture cross-section quantified by DLTS are EV + 0.42 eV, 3.4x1011 eV- 1 cm- 2 and 5.8x10- 18 cm2, respectively. The high quality ZrO2 films own high dielectric constant 15 with low leakage current density might be an appropriate insulating layer in future electronic application. The low value of interface state density and capture cross-section are the indication of high quality interface and the defect present at the interface may not affect the device performance to a great extent. The DLTS study provides a broad understanding about the traps present at the interface of spin-coated ZrO2/Si.

Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions

NASA Astrophysics Data System (ADS)

Sawyer, Brian

2013-05-01

Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions (>100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings, facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled 9Be+ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be+ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, d, may be varied continuously from 1 /d0 to 1 /d3. An effective transverse magnetic field is applied via microwave radiation at the ~124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states. We acknowledge support from NIST and the DARPA-OLE program.

Effect of spin traps on charge transport in low-bandgap copolymer:fullerene composites

NASA Astrophysics Data System (ADS)

Krinichnyi, Victor I.; Yudanova, Evgeniya I.; Bogatyrenko, Victor R.

2017-12-01

Light-Induced EPR study of magnetic, relaxation and dynamic parameters of spin charge carriers background photoinduced in bulk heterojunctions of composites formed by poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) and poly[N-9‧-heptadecanyl-2,7-carbazole-alt-5,5-(4‧,7‧-di-2-thienyl-2‧,1‧,3‧-benzothiadiazole)] (PCDTBT) with methanofullerene [6,6]-phenyl-C61-butyric acid methyl ester is described. A part of polarons is captured by deep spin traps whose number and energy depth are governed by the structure, morphology of a copolymer matrix and also by the photon energy. Both the composites exhibit photo-response within photon energy/wavelength 1.32-3.14 eV/940-395 nm region which is wider than that of other polymer composites. Magnetic, relaxation and dynamics parameters of spin charge carriers were shown to be governed by their exchange interaction and photon energy. Specific morphology of the composites causes selectivity of these parameters to the photon energy. It was shown that the anisotropy of spin mobility through bulk heterojunctions reflects the system dimensionality and is governed by the photon properties. The replacement of the PFO-DBT backbone by the PCDTBT matrix leads increases the ordering of a copolymer, decreases the number of spin traps and changes a mechanism of charge recombination. The decay of free charge carriers was interpreted in terms of the trapping-detrapping spin diffusion in bulk heterojunctions.

Feasibility of reading LiF thermoluminescent dosimeters by electron spin resonance

NASA Astrophysics Data System (ADS)

Breen, S. L.; Battista, J. J.

1999-08-01

Lithium fluoride is a commonly used solid state dosimeter. During irradiation, electrons and holes become trapped in crystal imperfections; thermoluminescence dosimetry measures their thermally induced recombination. Electron paramagnetic resonance (EPR) spectroscopy can be used to measure the resonant absorption of microwaves by the unpaired electrons trapped in LiF. In an effort to extend the use of LiF dosimeters to smaller sizes and to the harsh environments encountered in internal dosimetry, EPR was evaluated as an alternative technique to read the radiation dose delivered to TLD-100 dosimeters. TLD-100 rods were irradiated with a 60Co source to doses of 10 Gy to 100 Gy. A radiation-induced signal (with a g-value of 2.002) could be detected only at liquid nitrogen temperatures at doses above 20 Gy. The EPR spectrum of irradiated LiF contains three components, one of which correlates positively with dose. However, the low sensitivity of the technique, and difficulty in interpreting the EPR spectrum from polycrystalline dosimeters, preclude its use as a dosimetry technique.

Feasibility of reading LiF thermoluminescent dosimeters by electron spin resonance.

PubMed

Breen, S L; Battista, J J

1999-08-01

Lithium fluoride is a commonly used solid state dosimeter. During irradiation, electrons and holes become trapped in crystal imperfections; thermoluminescence dosimetry measures their thermally induced recombination. Electron paramagnetic resonance (EPR) spectroscopy can be used to measure the resonant absorption of microwaves by the unpaired electrons trapped in LiF. In an effort to extend the use of LiF dosimeters to smaller sizes and to the harsh environments encountered in internal dosimetry, EPR was evaluated as an alternative technique to read the radiation dose delivered to TLD-100 dosimeters. TLD-100 rods were irradiated with a 60Co source to doses of 10 Gy to 100 Gy. A radiation-induced signal (with a g-value of 2.002) could be detected only at liquid nitrogen temperatures at doses above 20 Gy. The EPR spectrum of irradiated LiF contains three components, one of which correlates positively with dose. However, the low sensitivity of the technique, and difficulty in interpreting the EPR spectrum from polycrystalline dosimeters, preclude its use as a dosimetry technique.

Comparative evaluation of seven commercial products for human serum enrichment/depletion by shotgun proteomics.

PubMed

Pisanu, Salvatore; Biosa, Grazia; Carcangiu, Laura; Uzzau, Sergio; Pagnozzi, Daniela

2018-08-01

Seven commercial products for human serum depletion/enrichment were tested and compared by shotgun proteomics. Methods were based on four different capturing agents: antibodies (Qproteome Albumin/IgG Depletion kit, ProteoPrep Immunoaffinity Albumin and IgG Depletion Kit, Top 2 Abundant Protein Depletion Spin Columns, and Top 12 Abundant Protein Depletion Spin Columns), specific ligands (Albumin/IgG Removal), mixture of antibodies and ligands (Albumin and IgG Depletion SpinTrap), and combinatorial peptide ligand libraries (ProteoMiner beads), respectively. All procedures, to a greater or lesser extent, allowed an increase of identified proteins. ProteoMiner beads provided the highest number of proteins; Albumin and IgG Depletion SpinTrap and ProteoPrep Immunoaffinity Albumin and IgG Depletion Kit resulted the most efficient in albumin removal; Top 2 and Top 12 Abundant Protein Depletion Spin Columns decreased the overall immunoglobulin levels more than other procedures, whereas specifically gamma immunoglobulins were mostly removed by Albumin and IgG Depletion SpinTrap, ProteoPrep Immunoaffinity Albumin and IgG Depletion Kit, and Top 2 Abundant Protein Depletion Spin Columns. Albumin/IgG Removal, a resin bound to a mixture of protein A and Cibacron Blue, behaved less efficiently than the other products. Copyright © 2018 Elsevier B.V. All rights reserved.

Stable spin domains in a nondegenerate ultracold gas

NASA Astrophysics Data System (ADS)

Graham, S. D.; Niroomand, D.; Ragan, R. J.; McGuirk, J. M.

2018-05-01

We study the stability of two-domain spin structures in an ultracold gas of magnetically trapped 87Rb atoms above quantum degeneracy. Adding a small effective magnetic field gradient stabilizes the domains via coherent collective spin rotation effects, despite negligibly perturbing the potential energy relative to the thermal energy. We demonstrate that domain stabilization is accomplished through decoupling the dynamics of longitudinal magnetization, which remains in time-independent domains, from transverse magnetization, which undergoes a purely transverse spin wave trapped within the domain wall. We explore the effect of temperature and density on the steady-state domains, and compare our results to a hydrodynamic solution to a quantum Boltzmann equation.

EPR investigation of zinc/iodine exchange between propargyl iodides and diethylzinc: detection of propargyl radical by spin trapping.

PubMed

Maury, Julien; Jammi, Suribabu; Vibert, François; Marque, Sylvain R A; Siri, Didier; Feray, Laurence; Bertrand, Michèle

2012-10-19

The production of propargyl radicals in the reaction of dialkylzincs with propargyl iodides in nondegassed medium was investigated by EPR using tri-tert-butylnitrosobenzene (TTBNB) as a spin trap. The radical mechanism and the nature of the observed species were confirmed by the trapping of propargyl radicals generated by an alternative pathway: i.e., upon irradiation of propargyl iodides in the presence of hexa-n-butyldistannane. In dialkylzinc-mediated experiments a high concentration of adduct was instantaneously observed, whereas no spontaneous production of spin adduct was detected in a blank experiment performed with the propargylic iodide and TTBNB in the absence of diethylzinc. Under irradiation in the presence of distannane, two different species were observed at the very beginning of the irradiation; the nitroxide resulting from the trapping of propargyl radical at the propargyl carbon remained the only species detected after irradiating for several minutes. The absence of adducts resulting from the trapping of allenyl canonical forms was supported by DFT calculations and by the preparation of an authentic sample.

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing

PubMed Central

A. Abdel‐Rahman, Engy; Mahmoud, Ali M.; Khalifa, Abdulrahman M.

2016-01-01

Abstract Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site‐directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. PMID:26801204

High efficiency Raman memory by suppressing radiation trapping

NASA Astrophysics Data System (ADS)

Thomas, S. E.; Munns, J. H. D.; Kaczmarek, K. T.; Qiu, C.; Brecht, B.; Feizpour, A.; Ledingham, P. M.; Walmsley, I. A.; Nunn, J.; Saunders, D. J.

2017-06-01

Raman interactions in alkali vapours are used in applications such as atomic clocks, optical signal processing, generation of squeezed light and Raman quantum memories for temporal multiplexing. To achieve a strong interaction the alkali ensemble needs both a large optical depth and a high level of spin-polarisation. We implement a technique known as quenching using a molecular buffer gas which allows near-perfect spin-polarisation of over 99.5 % in caesium vapour at high optical depths of up to ˜ 2× {10}5; a factor of 4 higher than can be achieved without quenching. We use this system to explore efficient light storage with high gain in a GHz bandwidth Raman memory.

Ultrafast Generation of Large Schrodinger Cat States

NASA Astrophysics Data System (ADS)

Johnson, Kale; Neyenhuis, Brian; Wong-Campos, David; Mizrahi, Jonathan; Campbell, Wes; Monroe, Christopher

2014-05-01

Using a series of spin-dependent kicks on a trapped Yb + ion, we create large, entangled, Schrodinger cat states. We prepare the ion in a superposition of its two mf = 0 hyperfine ground states, representing an effective spin-1/2 system. Trapped in a harmonic potential, the ion is illuminated with a specially shaped, 1.5 ns pulse that imparts a momentum kick on the ion with a spin-dependent direction. A fast Pockels cell allows us to change the direction of the spin-dependent kick from each subsequent pulse out of an 80 MHz mode-locked laser. By concatenating a series of these very high fidelity spin-dependent kicks, we separate the ion's wave packet into two, spatially distinct states separated by about 200 recoil momenta and involving about 70 phonons. This method for creating a Schrodinger cat state is not time-limited by the trap frequency, and does not rely on confinement in the Lamb-Dicke regime. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI.

MEASUREMENT OF HYDROXYL RADICAL ACTIVITY IN A SOIL SLURRY USING THE SPIN TRAP A-(4-PYRIDYL-1-OXIDE)-N-TERT-BUTYLNITRONE

EPA Science Inventory

The spin trap compound a-(4-pyridyl-1-oxide)N-tert-butylnitrone (4-POBN) served as a probe to estimate the activity of Fenton-derived hydroxyl radicals (.OH) in a batch suspension comprised of silica sand and crushes goethite ore. The rate of probe disappearance was used to anal...

Atomic "bomb testing": the Elitzur-Vaidman experiment violates the Leggett-Garg inequality

NASA Astrophysics Data System (ADS)

Robens, Carsten; Alt, Wolfgang; Emary, Clive; Meschede, Dieter; Alberti, Andrea

2017-01-01

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the "bomb test" with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.

Photochemical sensitization by azathioprine and its metabolites. Part 3. A direct EPR and spin-trapping study of light-induced free radicals from 6-mercaptopurine and its oxidation products.

PubMed

Moore, D E; Sik, R H; Bilski, P; Chignell, C F; Reszka, K J

1994-12-01

Sunlight has been implicated in the high incidence of skin cancer found in patients receiving 6-mercaptopurine (PSH) in the form of its pro-drug azathioprine. In this study we have used EPR spectroscopy in conjunction with the spin-trapping technique to determine whether PSH and its metabolic or photochemical oxidation products generate highly reactive free radicals upon UV irradiation. When an aqueous anaerobic solution (pH 5 or 9) of PSH (pKa = 7.7) and either 2-methyl-2-nitrosopropane (MNP) or nitromethane (NM) were irradiated (lambda > 300 nm) with a Xe arc lamp, the corresponding purine-6-thiyl (PS.) radical adduct and the reduced form of the spin trap (MNP/H. or CH3NO2.-) were observed. However, no radical adducts were detected when PSH and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were irradiated (lambda = 320 nm) in oxygen-free buffer. These findings suggest that PSH does not photoionize but that instead MNP and NM are reduced by direct electron transfer from excited state PSH, 1.3(PSH)*. In aerobic solution, oxygen can act as an electron acceptor and the O2.- and PS. radicals are formed and trapped by DMPO. 6-Mercaptopurine did photoionize when irradiated with a Nd:YAG laser at 355 nm as evidenced by the appearance of the DMPO/H.(eq- + H+) adduct, which decreased in intensity in the presence of N2O. 1.3(6-Mercaptopurine)* oxidized ascorbate, formate and reduced glutathione to the corresponding ascorbyl, CO2.- or glutathiyl radicals. The photochemical behavior of 6-thioxanthine and 6-thiouric acid was similar to PSH. However, the excited states of these metabolic oxidation products exhibited stronger reducing properties than 1.3(PSH)*.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct access to dithiobenzoate RAFT agent fragmentation rate coefficients by ESR spin-trapping.

PubMed

Ranieri, Kayte; Delaittre, Guillaume; Barner-Kowollik, Christopher; Junkers, Thomas

2014-12-01

The β-scission rate coefficient of tert-butyl radicals fragmenting off the intermediate resulting from their addition to tert-butyl dithiobenzoate-a reversible addition-fragmentation chain transfer (RAFT) agent-is estimated via the recently introduced electron spin resonance (ESR)-trapping methodology as a function of temperature. The newly introduced ESR-trapping methodology is critically evaluated and found to be reliable. At 20 °C, a fragmentation rate coefficient of close to 0.042 s(-1) is observed, whereas the activation parameters for the fragmentation reaction-determined for the first time-read EA = 82 ± 13.3 kJ mol(-1) and A = (1.4 ± 0.25) × 10(13) s(-1) . The ESR spin-trapping methodology thus efficiently probes the stability of the RAFT adduct radical under conditions relevant for the pre-equilibrium of the RAFT process. It particularly indicates that stable RAFT adduct radicals are indeed formed in early stages of the RAFT poly-merization, at least when dithiobenzoates are employed as controlling agents as stipulated by the so-called slow fragmentation theory. By design of the methodology, the obtained fragmentation rate coefficients represent an upper limit. The ESR spin-trapping methodology is thus seen as a suitable tool for evaluating the fragmentation rate coefficients of a wide range of RAFT adduct radicals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactions of nitroxide radicals in aqueous solutions exposed to non-thermal plasma: limitations of spin trapping of the plasma induced species

NASA Astrophysics Data System (ADS)

Gorbanev, Yury; Stehling, Nicola; O'Connell, Deborah; Chechik, Victor

2016-10-01

Low temperature (‘cold’) atmospheric pressure plasmas have gained much attention in recent years due to their biomedical effects achieved through the interactions of plasma-induced species with the biological substrate. Monitoring of the radical species in an aqueous biological milieu is usually performed via electron paramagnetic resonance (EPR) spectroscopy using various nitrone spin traps, which form persistent radical adducts with the short-lived radicals. However, the stability of these nitroxide radical adducts in the plasma-specific environment is not well known. In this work, chemical transformations of nitroxide radicals in aqueous solutions using a model nitroxide 4-oxo-TEMPO were studied using EPR and LC-MS. The kinetics of the nitroxide decay when the solution was exposed to plasma were assessed, and the reactive pathways proposed. The use of different scavengers enabled identification of the types of reactive species which cause the decay, indicating the predominant nitroxide group reduction in oxygen-free plasmas. The 2H adduct of the PBN spin trap (PBN-D) was shown to decay similarly to the model molecule 4-oxo-TEMPO. The decay of the spin adducts in plasma-treated solutions must be considered to avoid rendering the spin trapping results unreliable. In particular, the selectivity of the decay indicated the limitations of the PTIO/PTI nitroxide system in the detection of nitric oxide.

Anti-inflammatory activity of Chios mastic gum is associated with inhibition of TNF-alpha induced oxidative stress

PubMed Central

2011-01-01

Background Gum of Chios mastic (Pistacia lentiscus var. chia) is a natural antimicrobial agent that has found extensive use in pharmaceutical products and as a nutritional supplement. The molecular mechanisms of its anti-inflammatory activity, however, are not clear. In this work, the potential role of antioxidant activity of Chios mastic gum has been evaluated. Methods Scavenging of superoxide radical was investigated by electron spin resonance and spin trapping technique using EMPO spin trap in xanthine oxidase system. Superoxide production in endothelial and smooth muscle cells stimulated with TNF-α or angiotensin II and treated with vehicle (DMSO) or mastic gum (0.1-10 μg/ml) was measured by DHE and HPLC. Cellular H2O2 was measured by Amplex Red. Inhibition of protein kinase C (PKC) with mastic gum was determined by the decrease of purified PKC activity, by inhibition of PKC activity in cellular homogenate and by attenuation of superoxide production in cells treated with PKC activator phorbol 12-myristate 13-acetate (PMA). Results Spin trapping study did not show significant scavenging of superoxide by mastic gum itself. However, mastic gum inhibited cellular production of superoxide and H2O2 in dose dependent manner in TNF-α treated rat aortic smooth muscle cells but did not affect unstimulated cells. TNF-α significantly increased the cellular superoxide production by NADPH oxidase, while mastic gum completely abolished this stimulation. Mastic gum inhibited the activity of purified PKC, decreased PKC activity in cell homogenate, and attenuated superoxide production in cells stimulated with PKC activator PMA and PKC-dependent angiotensin II in endothelial cells. Conclusion We suggest that mastic gum inhibits PKC which attenuates production of superoxide and H2O2 by NADPH oxidases. This antioxidant property may have direct implication to the anti-inflammatory activity of the Chios mastic gum. PMID:21645369

Effect of water content on thermal oxidation of oleic acid investigated by combination of EPR spectroscopy and SPME-GC-MS/MS.

PubMed

Chen, Hongjian; Cao, Peirang; Li, Bo; Sun, Dewei; Wang, Yong; Li, Jinwei; Liu, Yuanfa

2017-04-15

Promotion of water to the thermal oxidation of oleic acid was detected by the combination of EPR, SPME-GC-MS/MS and GC. Spin-trapping technique was used to identify and quantify the radical species formed during thermal oxidation of oleic acid by using DMPO as electron spin trap. The most abundant radical species were identified as DMPO-alkyl radical adducts. EPR intensity plateau of the samples with 5% water content was 140% higher than the samples without water. It implies oleic acid samples with high water content had high level of oxidation rates. The proportion of aldehydes of the samples with 2% water content was the maximum about 59.97%. Among the formed products, (E,E)-2,4-decadienal has genotoxic and cytotoxic effects, whose percentage was nearly twice comparing with that of 5-0% water content. This study demonstrated that higher water content in frying systems would contribute to seriously oxidation and degradation of oleic acids. Copyright © 2016 Elsevier Ltd. All rights reserved.

Non-thermalization in trapped atomic ion spin chains

NASA Astrophysics Data System (ADS)

Hess, P. W.; Becker, P.; Kaplan, H. B.; Kyprianidis, A.; Lee, A. C.; Neyenhuis, B.; Pagano, G.; Richerme, P.; Senko, C.; Smith, J.; Tan, W. L.; Zhang, J.; Monroe, C.

2017-10-01

Linear arrays of trapped and laser-cooled atomic ions are a versatile platform for studying strongly interacting many-body quantum systems. Effective spins are encoded in long-lived electronic levels of each ion and made to interact through laser-mediated optical dipole forces. The advantages of experiments with cold trapped ions, including high spatio-temporal resolution, decoupling from the external environment and control over the system Hamiltonian, are used to measure quantum effects not always accessible in natural condensed matter samples. In this review, we highlight recent work using trapped ions to explore a variety of non-ergodic phenomena in long-range interacting spin models, effects that are heralded by the memory of out-of-equilibrium initial conditions. We observe long-lived memory in static magnetizations for quenched many-body localization and prethermalization, while memory is preserved in the periodic oscillations of a driven discrete time crystal state. This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

Non-thermalization in trapped atomic ion spin chains.

PubMed

Hess, P W; Becker, P; Kaplan, H B; Kyprianidis, A; Lee, A C; Neyenhuis, B; Pagano, G; Richerme, P; Senko, C; Smith, J; Tan, W L; Zhang, J; Monroe, C

2017-12-13

Linear arrays of trapped and laser-cooled atomic ions are a versatile platform for studying strongly interacting many-body quantum systems. Effective spins are encoded in long-lived electronic levels of each ion and made to interact through laser-mediated optical dipole forces. The advantages of experiments with cold trapped ions, including high spatio-temporal resolution, decoupling from the external environment and control over the system Hamiltonian, are used to measure quantum effects not always accessible in natural condensed matter samples. In this review, we highlight recent work using trapped ions to explore a variety of non-ergodic phenomena in long-range interacting spin models, effects that are heralded by the memory of out-of-equilibrium initial conditions. We observe long-lived memory in static magnetizations for quenched many-body localization and prethermalization, while memory is preserved in the periodic oscillations of a driven discrete time crystal state.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'. © 2017 The Author(s).

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

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

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

DOE PAGES

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; ...

2017-05-24

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

NASA Astrophysics Data System (ADS)

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; van Driel, Tim B.; Chollet, Matthieu; Glownia, James M.; Song, Sanghoon; Zhu, Diling; Pace, Elisabetta; Matar, Samir F.; Nielsen, Martin M.; Benfatto, Maurizio; Gaffney, Kelly J.; Collet, Eric; Cammarata, Marco

2017-05-01

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.

Dynamics of bright-bright solitons in Bose-Einstein condensate with Raman-induced one-dimensional spin-orbit coupling

NASA Astrophysics Data System (ADS)

Wen, Lin; Zhang, Xiao-Fei; Hu, Ai-Yuan; Zhou, Jing; Yu, Peng; Xia, Lei; Sun, Qing; Ji, An-Chun

2018-03-01

We investigate the dynamics of bright-bright solitons in one-dimensional two-component Bose-Einstein condensates with Raman-induced spin-orbit coupling, via the variational approximation and the numerical simulation of Gross-Pitaevskii equations. For the uniform system without trapping potential, we obtain two population balanced stationary solitons. By performing the linear stability analysis, we find a Goldstone eigenmode and an oscillation eigenmode around these stationary solitons. Moreover, we derive a general dynamical solution to describe the center-of-mass motion and spin evolution of the solitons under the action of spin-orbit coupling. The effects of a harmonic trap have also been discussed.

Superoxide Anion Radical Production in the Tardigrade Paramacrobiotus richtersi, the First Electron Paramagnetic Resonance Spin-Trapping Study.

PubMed

Savic, Aleksandar G; Guidetti, Roberto; Turi, Ana; Pavicevic, Aleksandra; Giovannini, Ilaria; Rebecchi, Lorena; Mojovic, Milos

2015-01-01

Anhydrobiosis is an adaptive strategy that allows withstanding almost complete body water loss. It has been developed independently by many organisms belonging to different evolutionary lines, including tardigrades. The loss of water during anhydrobiotic processes leads to oxidative stress. To date, the metabolism of free radicals in tardigrades remained unclear. We present a method for in vivo monitoring of free radical production in tardigrades, based on electron paramagnetic resonance and spin-trap DEPMPO, which provides simultaneous identification of various spin adducts (i.e., different types of free radicals). The spin trap can be easily absorbed in animals, and tardigrades stay alive during the measurements and during 24-h monitoring after the treatment. The results show that hydrated specimens of the tardigrade Paramacrobiotus richtersi produce the pure superoxide anion radical ((•)O2(-)). This is an unexpected result, as all previously examined animals and plants produce both superoxide anion radical and hydroxyl radical ((•)OH) or exclusively hydroxyl radical.

Generation of radicals in hard biological tissues under the action of laser radiation

NASA Astrophysics Data System (ADS)

Sviridov, Alexander P.; Bagratashvili, Victor N.; Sobol, Emil N.; Omelchenko, Alexander I.; Lunina, Elena V.; Zhitnev, Yurii N.; Markaryan, Galina L.; Lunin, Valerii V.

2002-07-01

The formation of radicals upon UV and IR laser irradiation of some biological tissues and their components was studied by the EPR technique. The radical decay kinetics in body tissue specimens after their irradiation with UV light were described by various models. By the spin trapping technique, it was shown that radicals were not produced during IR laser irradiation of cartilaginous tissue. A change in optical absorption spectra and the dynamics of optical density of cartilaginous tissue, fish scale, and a collagen film under exposure to laser radiation in an air, oxygen, and nitrogen atmosphere was studied.

Optically controlled locking of the nuclear field via coherent dark-state spectroscopy.

PubMed

Xu, Xiaodong; Yao, Wang; Sun, Bo; Steel, Duncan G; Bracker, Allan S; Gammon, Daniel; Sham, L J

2009-06-25

A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices. In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction, while the dynamics of the single spin also influence the nuclear environment. Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T(2)*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T(2)* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

Sympathetic cooling of nanospheres with cold atoms

NASA Astrophysics Data System (ADS)

Montoya, Cris; Witherspoon, Apryl; Ranjit, Gambhir; Casey, Kirsten; Kitching, John; Geraci, Andrew

2016-05-01

Ground state cooling of mesoscopic mechanical structures could enable new hybrid quantum systems where mechanical oscillators act as transducers. Such systems could provide coupling between photons, spins and charges via phonons. It has recently been shown theoretically that optically trapped dielectric nanospheres could reach the ground state via sympathetic cooling with trapped cold atoms. This technique can be beneficial in cases where cryogenic operation of the oscillator is not practical. We describe experimental advances towards coupling an optically levitated dielectric nanosphere to a gas of cold Rubidium atoms. The sphere and the cold atoms are in separate vacuum chambers and are coupled using a one-dimensional optical lattice. This work is partially supported by NSF, Grant Nos. PHY-1205994,PHY-1506431.

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

PubMed

A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

2016-08-15

Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

The Spin Vector of (832) Karin

NASA Astrophysics Data System (ADS)

Slivan, Stephen M.; Molnar, L. A.

2010-10-01

We observed rotation lightcurves of Koronis family and Karin cluster member (832) Karin during its four consecutive apparitions in 2006-2009, and combined the new observations with previously published lightcurves to determine its spin vector orientation and preliminary model shape. Karin is a prograde rotator with a period of 18.352 h, spin obliquity near 41°, and pole ecliptic longitude near either 51° or 228°. Although the two ambiguous pole solutions are near the clustered pole solutions of four Koronis family members whose spins are thought to be trapped in a spin-orbit resonance (Vokrouhlický et al., 2003), Karin does not seem to be trapped in the resonance; this is consistent with the expectation that the 6 My age of Karin (Nesvorný et al., 2002) is too young for YORP torques to have modified its spin since its formation. The spin vector and shape results for Karin will constrain family formation models that include spin properties, and we discuss the Karin results in the context of the other members of the Karin cluster, the Karin parent body, and the parent body's siblings in the Koronis family.

All-optical coherent population trapping with defect spin ensembles in silicon carbide.

PubMed

Zwier, Olger V; O'Shea, Danny; Onur, Alexander R; van der Wal, Caspar H

2015-06-05

Divacancy defects in silicon carbide have long-lived electronic spin states and sharp optical transitions. Because of the various polytypes of SiC, hundreds of unique divacancies exist, many with spin properties comparable to the nitrogen-vacancy center in diamond. If ensembles of such spins can be all-optically manipulated, they make compelling candidate systems for quantum-enhanced memory, communication, and sensing applications. We report here direct all-optical addressing of basal plane-oriented divacancy spins in 4H-SiC. By means of magneto-spectroscopy, we fully identify the spin triplet structure of both the ground and the excited state, and use this for tuning of transition dipole moments between particular spin levels. We also identify a role for relaxation via intersystem crossing. Building on these results, we demonstrate coherent population trapping -a key effect for quantum state transfer between spins and photons- for divacancy sub-ensembles along particular crystal axes. These results, combined with the flexibility of SiC polytypes and device processing, put SiC at the forefront of quantum information science in the solid state.

ESR evidence for radical production from the reaction of ozone with unsaturated lipids

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

Church, D.F.; McAdams, M.L..; Pryor, W.A.

1991-03-15

The authors report electron spin resonance (ESR) spin trapping evidence for radical production by the reaction of ozone with unsaturated compounds. Soy and egg phosphatidylcholine liposomes, fatty acid emulsions, and homogeneous aqueous solutions of 3-hexenoic acid were treated with ozone in the presence of the spin trap {alpha}-phenyl-N-tert-butyl nitrone (PBN). Under these conditions, they observe spin adducts resulting from the trapping of both organic carbon- and oxygen-centered radicals. When the lipid-soluble antioxidant alpha-tocopherol is included in the liposomal systems, the formation of spin adducts is completely inhibited. The authors suggest that radicals giving rise to these spin adducts arise formmore » the rapid decomposition of the 1,2,3-trioxolane intermediate that is initially formed when ozone reacts with the carbon-carbon double bonds of the substrates. These free radicals are not formed by the decomposition of the Criegee ozonide, since little of the ozonide is formed in the presence of water. Although hydrogen peroxide is the predominate peroxidic product of the ozone/alkene reaction, its decomposition is not responsible for the observed radical production since neither catalase nor iron chelators significantly affect the spin adduct yield. The radical yield is approximately 1%. Since a polyunsaturated fatty acid (PUFA) such as linoleic acid produces much higher concentrations of spin trappable radicals than does the monounsaturated fatty oleic acid, the results also suggest that sites in the lung containing higher levels of PUFA may be an important target for radical formation.« less

Tolerance in the Ramsey interference of a trapped nanodiamond

NASA Astrophysics Data System (ADS)

Wan, C.; Scala, M.; Bose, S.; Frangeskou, A. C.; Rahman, ATM A.; Morley, G. W.; Barker, P. F.; Kim, M. S.

2016-04-01

In the scheme recently proposed by M. Scala et al. [Phys. Rev. Lett. 111, 180403 (2013), 10.1103/PhysRevLett.111.180403], a gravity-dependent phase shift is induced on the spin of a nitrogen-vacancy (NV) center in a trapped nanodiamond by the interaction between its magnetic moment and the quantized motion of the particle. This provides a way to detect spatial quantum superpositions by means of only spin measurements. Here, the effect of unwanted coupling with other motional degrees of freedom is considered, and we show that it does not affect the validity of the scheme. Both this coupling and the additional error source due to misalignment between the quantization axis of the NV center spin and the trapping axis are shown not to change the qualitative behavior of the system, so that a proof-of-principle experiment can be neatly performed. Our analysis, which shows that the scheme retains the important features of not requiring ground-state cooling and of being resistant to thermal fluctuations, can be useful for several schemes which have been proposed recently for testing macroscopic superpositions in trapped microsystems.

Photoinduced reactions of dibenzoyl peroxide as studied by EPR and spin-trapping

NASA Astrophysics Data System (ADS)

Rosenthal, Ionel; Mossoba, Magdi M.; Riesz, Peter

The photochemical reactions of dibenzoyl peroxide with some organic compounds were found by EPR and spin-trapping to generate free radicals in dimethyl sulfoxide solutions at room temperature. Two reaction mechanisms occur which determine the structures of the radicals generated. The first involves a one-electron oxidation and the second a hydrogen atom transfer. The prevailing mechanism is primarily dependent on the structure of the substrate. With carboxylic acids the one-electron oxidation occurs exclusively, leading to the loss of the carboxyl group and to formation of the alkyl radical. For alcohols both alkoxy radicals and hydrogen-abstraction α-carbon radicals were spin trapped. The alkoxy radicals were generated by the electron transfer mechanism. Finally pyrimidine bases such as thymine and cytosine yielded C(5)-centered radicals which could also be explained by an electron transfer mechanism. These observations are of interest because of the recently observed skin tumor-promoting activity of dibenzoyl peroxide.

Towards a Quantum Interface between Diamond Spin Qubits and Phonons in an Optical Trap

NASA Astrophysics Data System (ADS)

Ji, Peng; Momeen, M. Ummal; Hsu, Jen-Feng; D'Urso, Brian; Dutt, Gurudev

2014-05-01

We introduce a method to optically levitate a pre-selected nanodiamond crystal in air or vacuum. The nanodiamond containing nitrogen-vacancy (NV) centers is suspended on a monolayer of graphene transferred onto a patterned substrate. Laser light is focused onto the sample, using a home-built confocal microscope with a high numerical aperture (NA = 0.9) objective, simultaneously burning the graphene and creating a 3D optical trap that captures the falling nano-diamond at the beam waist. The trapped diamond is an ultra-high-Q mechanical oscillator, allowing us to engineer strong linear and quadratic coupling between the spin of the NV center and the phonon mode. The system could result in an ideal quantum interface between a spin qubit and vibrational phonon mode, potentially enabling applications in quantum information processing and sensing the development of quantum information storage and processing.

Momentum-resolved radio-frequency spectroscopy of a spin-orbit-coupled atomic Fermi gas near a Feshbach resonance in harmonic traps

NASA Astrophysics Data System (ADS)

Peng, Shi-Guo; Liu, Xia-Ji; Hu, Hui; Jiang, Kaijun

2012-12-01

We theoretically investigate the momentum-resolved radio-frequency spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling. The system is qualitatively modeled as an ideal gas mixture of atoms and molecules, in which the properties of molecules, such as the wave function, binding energy, and effective mass, are determined from the two-particle solution of two interacting atoms. We calculate separately the radio-frequency response from atoms and molecules at finite temperatures by using the standard Fermi golden rule and take into account the effect of harmonic traps within local density approximation. The total radio-frequency spectroscopy is discussed as functions of temperature and spin-orbit coupling strength. Our results give a qualitative picture of radio-frequency spectroscopy of a resonantly interacting spin-orbit-coupled Fermi gas and can be directly tested in atomic Fermi gases of 40K atoms at Shanxi University and 6Li atoms at the Massachusetts Institute of Technology.

Multi-second magnetic coherence in a single domain spinor Bose–Einstein condensate

NASA Astrophysics Data System (ADS)

Palacios, Silvana; Coop, Simon; Gomez, Pau; Vanderbruggen, Thomas; Natali Martinez de Escobar, Y.; Jasperse, Martijn; Mitchell, Morgan W.

2018-05-01

We describe a compact, robust and versatile system for studying the macroscopic spin dynamics in a spinor Bose–Einstein condensate. Condensates of {}87{Rb} are produced by all-optical evaporation in a 1560 nm optical dipole trap, using a non-standard loading sequence that employs an ancillary 1529 nm beam for partial compensation of the strong differential light-shift induced by the dipole trap itself. We use near-resonant Faraday rotation probing to non-destructively track the condensate magnetization, and demonstrate few-Larmor-cycle tracking with no detectable degradation of the spin polarization. In the ferromagnetic F = 1 ground state, we observe the spin orientation between atoms in the condensate is preserved, such that they precess all together like one large spin in the presence of a magnetic field. We characterize this dynamics in terms of the single-shot magnetic coherence times {{ \\mathcal T }}1 and {{ \\mathcal T }}2* , and observe them to be of several seconds, limited only by the residence time of the atoms in the trap. At the densities used, this residence is restricted only by one-body losses set by the vacuum conditions.

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

PubMed Central

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-01-01

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [RhICl(cod)]2, [CoII(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [RhICl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N∙ (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C∙, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C∙, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals. PMID:26960916

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

NASA Astrophysics Data System (ADS)

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-03-01

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [RhICl(cod)]2, [CoII(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [RhICl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N• (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C•, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C•, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals.

Metal-Diazo Radicals of α-Carbonyl Diazomethanes.

PubMed

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-03-10

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [Rh(I)Cl(cod)]2, [Co(II)(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [Rh(I)Cl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N∙ (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C∙, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C∙, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals.

Engineered diamond nanopillars as mobile probes for high sensitivity metrology in fluid

NASA Astrophysics Data System (ADS)

Andrich, P.; de Las Casas, C. F.; Heremans, F. J.; Awschalom, D. D.; Aleman, B. J.; Ohno, K.; Lee, J. C.; Hu, E. L.

2015-03-01

The nitrogen-vacancy (NV) center`s optical addressability and exceptional spin coherence properties at room temperature, along with diamond`s biocompatibility, has put this defect at the frontier of metrology applications in biological environments. To push the spatial resolution to the nanoscale, extensive research efforts focus on using NV centers embedded in nanodiamonds (NDs). However, this approach has been hindered by degraded spin coherence properties in NDs and the lack of a platform for spatial control of the nanoparticles in fluid. In this work, we combine the use of high quality diamond membranes with a top-down patterning technique to fabricate diamond nanoparticles with engineered and highly reproducible shape, size, and NV center density. We obtain NDs, easily releasable from the substrate into a water suspension, which contain single NV centers exhibiting consistently long spin coherence times (up to 700 μs). Additionally, we demonstrate highly stable, three-dimensional optical trapping of the nanoparticles within a microfluidic circuit. This level of control enables a bulk-like DC magnetic sensitivity and gives access to dynamical decoupling techniques on contactless, miniaturized diamond probes. This work was supported by DARPA, AFOSR, and the DIAMANT program.

Spin Vector Distribution in the Koronis Family for a Sample Complete to IAU H=10.88

NASA Astrophysics Data System (ADS)

Slivan, Stephen M.; Hosek, Matt; Sokol, Alyssa; Maynard, Sarah; Payne, Anna; Radford, Arden; Springmann, Alessondra; Mailhot, Emily; Midkiff, Alan; Russell, April; Stephens, Robert D.

2016-10-01

Because they share the same formation age, asteroid family members have experienced similar evolution for similar lengths of time, offering valuable information to help understand spin evolution processes. Clustered distributions of spin vectors determined from observations of ten of the largest Koronis family members (Slivan 2002) revealed evidence of spin modification by YORP thermal radiation torques (Vokrouhlický et al. 2003). The currently known spin vector sample in the Koronis family (Slivan et al., 2003; Slivan et al., 2009, Hanuš et al., 2011; Hanuš et al., 2013; Durech et al., 2016) clearly shows the two spin groupings observed among the large members: (1) the larger group with low-obliquity retrograde spin and periods between about 3 h and 30 h, and (2) a smaller group with prograde spin obliquity near 45° and periods near 8 h, characteristic of trapping in the s6 spin-orbit resonance (Vokrouhlický et al. 2003). There's also one "stray" longer-period prograde object with smaller obliquity, perhaps trapped in some other resonance.A limitation of the existing spin vector sample, which (using IAU H as a proxy for size) includes 16 of the brightest 27 members of the family, is that selection biases render it complete only to the brightest 12 members. Slivan et al. (2008) began a lightcurve observing program to increase the sample of Koronis family spin vectors down to about 20 km diameter.We report pole solutions that were determined for fourteen survey objects using lightcurves recorded from 2005-2016, which complete the Koronis spin vector sample to the brightest 22 members, now including 24 of the brightest 27 members. The larger sample adds several objects to the existing group of low-obliquity retrograde rotators, increasing the period range upward to almost 60 h, and also identifies two companions for the stray longer-period prograde spin object, strengthening the case for the presence of a second cluster of objects trapped in a spin-orbit resonance. The more complete distribution also reveals two new "strays" of its own - one lone fast prograde rotator, and one spin vector of atypical high obliquity, close to the ecliptic plane.

Quantum simulation of interacting spin models with trapped ions

NASA Astrophysics Data System (ADS)

Islam, Kazi Rajibul

The quantum simulation of complex many body systems holds promise for understanding the origin of emergent properties of strongly correlated systems, such as high-Tc superconductors and spin liquids. Cold atomic systems provide an almost ideal platform for quantum simulation due to their excellent quantum coherence, initialization and readout properties, and their ability to support several forms of interactions. In this thesis, I present experiments on the quantum simulation of long range Ising models in the presence of transverse magnetic fields with a chain of up to sixteen ultracold 171Yb+ ions trapped in a linear radio frequency Paul trap. Two hyperfine levels in each of the 171Yb+ ions serve as the spin-1/2 systems. We detect the spin states of the individual ions by observing state-dependent fluorescence with single site resolution, and can directly measure any possible spin correlation function. The spin-spin interactions are engineered by applying dipole forces from precisely tuned lasers whose beatnotes induce stimulated Raman transitions that couple virtually to collective phonon modes of the ion motion. The Ising couplings are controlled, both in sign and strength with respect to the effective transverse field, and adiabatically manipulated to study various aspects of this spin model, such as the emergence of a quantum phase transition in the ground state and spin frustration due to competing antiferromagnetic interactions. Spin frustration often gives rise to a massive degeneracy in the ground state, which can lead to entanglement in the spin system. We detect and characterize this frustration induced entanglement in a system of three spins, demonstrating the first direct experimental connection between frustration and entanglement. With larger numbers of spins we also vary the range of the antiferromagnetic couplings through appropriate laser tunings and observe that longer range interactions reduce the excitation energy and thereby frustrate the ground state order. This system can potentially be scaled up to study a wide range of fully connected spin networks with a few dozens of spins, where the underlying theory becomes intractable on a classical computer.

Numerical evidences of universal trap-like aging dynamics

NASA Astrophysics Data System (ADS)

Cammarota, Chiara; Marinari, Enzo

2018-04-01

Trap models have been initially proposed as toy models for dynamical relaxation in extremely simplified rough potential energy landscapes. Their importance has recently grown considerably thanks to the discovery that the trap-like aging mechanism directly controls the out-of-equilibrium relaxation processes of more sophisticated spin models, that are considered as the solvable counterpart of real disordered systems. Further establishing the connection between these spin models, out-of-equilibrium behavior and the trap like aging mechanism could shed new light on the properties, which are still largely mysterious, for the activated out-of-equilibrium dynamics of disordered systems. In this work we discuss numerical evidence based on the computations of the permanence times of an emergent trap-like aging behavior in a variety of very simple disordered models—developed from the trap model paradigm. Our numerical results are backed by analytic derivations and heuristic discussions. Such exploration reveals some of the tricks needed to reveal the trap behavior in spite of the occurrence of secondary processes, of the existence of dynamical correlations and of strong finite system’s size effects.

Advanced Techniques for Transmutation Compensation of Extrinsic Silicon Detectors.

DTIC Science & Technology

1980-10-01

generally better than 1..2 R . EPR Spectrometer NMicroscopic defect structure is determined by elec- tron paramagnetic resonance (HIlP ) or, as it is more...cnm- monly known, elet ron spin resonance ( I;R . The 1,S R instrument used for th(,se experimnents is -I COllVttiOl1l1 X-band (9 (;ll:) SpectroletoPr...226 75. DLTS electron traps in n-type neutron irra- diated Si as a function of isohronal anneals (100 Hz, th = 1.8 x 1015 n

Understanding the role of spin-motion coupling in Ramsey spectroscopy

NASA Astrophysics Data System (ADS)

Koller, Andrew; Beverland, Michael; Mundinger, Joshua; Gorshkov, Alexey; Rey, Ana Maria

2014-05-01

Ramsey spectroscopy has become a powerful technique for probing non-equilibrium dynamics of internal (pseudospin) degrees of freedom of interacting systems. In many theoretical treatments, the key to understanding the dynamics has been to assume the external (motional) degrees of freedom are decoupled from the pseudospin degrees of freedom. Determining the validity of this approximation - known as the spin model approximation - has not been addressed in detail. We shed light in this direction by calculating Ramsey dynamics exactly for two interacting spin-1/2 particles in a harmonic trap. We find that in 1D the spin model assumption works well over a wide range of experimentally-relevant conditions, but can fail at time scales longer than those set by the mean interaction energy. Surprisingly, in 2D a modified version of the spin model is exact to first order in the interaction strength. This analysis is important for a correct interpretation of Ramsey spectroscopy and has broad applications ranging from precision measurements to quantum information and to fundamental probes of many-body systems. Supported by NSF, ARO-DARPA-OLE, AFOSR, NIST, the Lee A. DuBridge and Gordon and Betty Moore Foundations, and the NDSEG program.

Observation of a Discrete Time Crystal

NASA Astrophysics Data System (ADS)

Kyprianidis, A.; Zhang, J.; Hess, P.; Becker, P.; Lee, A.; Smith, J.; Pagano, G.; Potter, A.; Vishwanath, A.; Potirniche, I.-D.; Yao, N.; Monroe, C.

2017-04-01

Spontaneous symmetry breaking is a key concept in the understanding of many physical phenomena, such as the formation of spatial crystals and the phase transition from paramagnetism to magnetic order. While the breaking of time translation symmetry is forbidden in equilibrium systems, it is possible for non-equilibrium Floquet driven systems to break a discrete time translation symmetry, and we present clear signatures of the formation of such a discrete time crystal. We apply a time periodic Hamiltonian to a chain of interacting spins under many-body localization conditions and observe the system's sub-harmonic response at twice that period. This spontaneous doubling of the periodicity is robust to external perturbations. We represent the spins with a linear chain of trapped 171Yb+ ions in an rf Paul trap, generate spin-spin interactions through spin-dependent optical dipole forces, and measure each spin using state-dependent fluorescence. This work is supported by the ARO Atomic Physics Program, the AFOSR MURI on Quantum Measurement and Verification, and the NSF Physics Frontier Center at JQI.

Tunable Spin-orbit Coupling and Quantum Phase Transition in a Trapped Bose-Einstein Condensate

PubMed Central

Zhang, Yongping; Chen, Gang; Zhang, Chuanwei

2013-01-01

Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin and its motion, is responsible for various important phenomena, ranging from atomic fine structure to topological condensed matter physics. The recent experimental breakthrough on the realization of SOC for ultra-cold atoms provides a completely new platform for exploring spin-orbit coupled superfluid physics. However, the SOC strength in the experiment is not tunable. In this report, we propose a scheme for tuning the SOC strength through a fast and coherent modulation of the laser intensities. We show that the many-body interaction between atoms, together with the tunable SOC, can drive a quantum phase transition (QPT) from spin-balanced to spin-polarized ground states in a harmonic trapped Bose-Einstein condensate (BEC), which resembles the long-sought Dicke QPT. We characterize the QPT using the periods of collective oscillations of the BEC, which show pronounced peaks and damping around the quantum critical point. PMID:23727689

Spin Self-Rephasing and Very Long Coherence Times in a Trapped Atomic Ensemble

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

Deutsch, C.; Reinhard, F.; Schneider, T.

2010-07-09

We perform Ramsey spectroscopy on the ground state of ultracold {sup 87}Rb atoms magnetically trapped on a chip in the Knudsen regime. Field inhomogeneities over the sample should limit the 1/e contrast decay time to about 3 s, while decay times of 58{+-}12 s are actually observed. We explain this surprising result by a spin self-rephasing mechanism induced by the identical spin rotation effect originating from particle indistinguishability. We propose a theory of this synchronization mechanism and obtain good agreement with the experimental observations. The effect is general and may appear in other physical systems.

All-optical spinor Bose-Einstein condensation and the spinor dynamics-driven atom laser

NASA Astrophysics Data System (ADS)

Lundblad, Nathan Eric

Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature---a phenomenon known as Bose-Einstein condensation---has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial ('spinor BEC'), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO2 laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin dynamics. We drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, nominally number-correlated through the angular momentum-conserving collision 2m0 ⇋ m+1 + m-1 have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates.

Multiple orbital angular momentum generated by dielectric hybrid phase element

NASA Astrophysics Data System (ADS)

Wang, Xuewen; Kuchmizhak, Aleksandr; Hu, Dejiao; Li, Xiangping

2017-09-01

Vortex beam carrying multiple orbital angular momentum provides a new degree of freedom to manipulate light leading to the various exciting applications as trapping, quantum optics, information multiplexing, etc. Helical wavefront can be generated either via the geometric or the dynamic phase arising from a space-variant birefringence (q-plate) or from phase accumulation through propagation (spiral-phase-plate), respectively. Using fast direct laser writing technique we fabricate and characterize novel hybrid q-plate generating vortex beam simultaneously carrying two different high-order topological charges, which arise from the spin-orbital conversion and the azimuthal height variation of the recorded structures. We approve the versatile concept to generate multiple-OAM vortex beams combining the spin-orbital interaction and the phase accumulation in a single micro-scale device, a hybrid dielectric phase plate.

Reaction between peroxynitrite and boronates: EPR spin-trapping, HPLC analyses, and quantum mechanical study of the free radical pathway

PubMed Central

Sikora, Adam; Zielonka, Jacek; Lopez, Marcos; Dybala-Defratyka, Agnieszka; Joseph, Joy; Marcinek, Andrzej; Kalyanaraman, Balaraman

2013-01-01

Recently we showed that peroxynitrite (ONOO−) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ≈ 106 M−1s−1). Product analyses and substrate consumption data indicated that ONOO− reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (~85–90%), and the remaining products (10–15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here we investigated in detail the minor, free radical pathway of boronate reaction with ONOO−. The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO−. Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO− to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a non-radical mechanism), or a radical pair PhB(OH)2O•−…•NO2 as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of PhB(OH)2O•− radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)2O•− radical anion to form phenyl radicals is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of PhB(OH)2O•− radical anion in aqueous media. Biological implications of the minor free radical pathway are discussed in the context of ONOO− detection, using the boronate probes. PMID:21434648

Prostaglandin H synthase-catalyzed oxidation of all-trans- and 13-cis-retinoic acid to carbon-centered and peroxyl radical intermediates.

PubMed

Freyaldenhoven, M A; Lloyd, R V; Samokyszyn, V M

1996-06-01

Due to the importance of all-trans-retinoic acid (RA) in the treatment of various dermatological conditions and the wide distribution of prostaglandin H synthase (PGHS) in tissues, we have further examined the mechanisms involved in the hydroperoxide-dependent cooxidation of RA and its isomer, 13-cis-retinoic acid ((13Z)-RA), by PGHS. Hydroperoxide-dependent, PGHS-catalyzed oxidation of RA and (13Z)-RA was shown to form free radical adducts, using electron spin resonance (ESR) spin trapping techniques and 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) or 13-hydroperoxy-9-cis-11-trans-octadecadienoic acid (13-OOH-18:2) as hydroperoxide substrates. Utilization of the spin trap alpha-phenyl-N-tert-butylnitrone (PBN) resulted in the detection of (13Z)-RA-PBN and RA-PBN adducts whose spectra were characterized by hyperfine coupling constants of aH = 4.16/aN = 15.69 and aH = 3.01/aN =15.92, respectively. Identical experiments under anaerobic conditions were carried out using the spin trap 2-methyl-2-nitrosopropane (NtB) which yielded nitroxide adducts whose spectra were characterized by a triplet of doublets with values of aH = 3.49/aN = 15.84 for the (13Z)-RA adduct and aH = 3.49/aN = 15.88 for the RA adduct. These results are indicative of secondary carbon-centered radical formation. We also used (+)-benzo[a]pyrene 7(S),8(S)-dihydrodiol ((+)-BP-7,8-diol) as a peroxyl radical probe. The results demonstrated the formation of (+)-BP-7,8-diol-derived tetrols, with the trans-anti tetrol representing the major oxidation product in systems undergoing PPHP-dependent, PGHS-catalyzed oxidation of (13Z)-RA or RA. These results are consistent with the formation of peroxyl radicals in these systems. In all experiments, the (13Z)-RA isomer appeared to be a better substrate for the enzyme compared to the all-trans isomer. Collectively these results provide further evidence to support the previously proposed mechanism for retinoid oxidation by PGHS involving the intermediacy of C4 carbon-centered radicals which subsequently react with dioxygen, yielding retinoid-derived peroxyl radicals.

Independent polarisation control of multiple optical traps

PubMed Central

Preece, Daryl; Keen, Stephen; Botvinick, Elliot; Bowman, Richard; Padgett, Miles; Leach, Jonathan

2009-01-01

We present a system which uses a single spatial light modulator to control the spin angular momentum of multiple optical traps. These traps may be independently controlled both in terms of spatial location and in terms of their spin angular momentum content. The system relies on a spatial light modulator used in a “split-screen” configuration to generate beams of orthogonal polarisation states which are subsequently combined at a polarising beam splitter. Defining the phase difference between the beams with the spatial light modulator enables control of the polarisation state of the light. We demonstrate the functionality of the system by controlling the rotation and orientation of birefringent vaterite crystals within holographic optical tweezers. PMID:18825226

Storage rings for spin-polarized hydrogen

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

Thompson, D.; Lovelace, R.V.E.; Lee, D.

1989-11-01

A strong-focusing storage ring is proposed for the long-term magnetic confinement of a collisional gas of neutral spin-polarized hydrogen atoms in the Za{l arrow} and Zb{l arrow} hyperfine states. The trap uses the interaction of the magnetic moments of the gas atoms with a static magnetic field. Laser cooling and evaporative cooling can be utilized to enhance the confinement and to offset the influence of viscous heating. An important application of the trap is to the attainment of Bose--Einstein condensation.

Phonon-mediated nuclear spin relaxation in H2O

NASA Astrophysics Data System (ADS)

Yamakawa, Koichiro; Azami, Shinya; Arakawa, Ichiro

2017-03-01

A theoretical model of the phonon-mediated nuclear spin relaxation in H2O trapped by cryomatrices has been established for the first time. In order to test the validity of this model, we measured infrared spectra of H2O trapped in solid Ar, which showed absorption peaks due to rovibrational transitions of ortho- and para-H2O in the spectral region of the bending vibration. We monitored the time evolution of the spectra and analyzed the rotational relaxation associated with the nuclear spin flip to obtain the relaxation rates of H2O at temperatures of 5-15 K. Temperature dependence of the rate is discussed in terms of the devised model.

Effect of electron trap states on spin-dependent transport characteristics in CoFe/MgO/n{sup +}-Si junctions investigated by Hanle effect measurements and inelastic electron tunneling spectroscopy

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

Inokuchi, Tomoaki, E-mail: tomoaki.inokuchi@toshiba.co.jp; Ishikawa, Mizue; Sugiyama, Hideyuki

2014-12-08

Spin-dependent transport properties in CoFe/MgO/n{sup +}-Si junctions were investigated by Hanle effect measurements and inelastic electron tunneling (IET) spectroscopy. The CoFe/MgO/n{sup +}-Si junctions examined in this study exhibited two different Hanle curves. In the low bias region, broad Hanle signals were mainly observed; in the high bias region, narrow Hanle signals were mainly observed. The d{sup 2}I/dV{sup 2}-V curves (which correspond to IET spectra) contain several peaks originating from phonon modes and other peaks originating from electron trap states. At the bias voltage where electron trap states are observed, Δd{sup 2}I/dV{sup 2} depends on the magnetic field and the fullmore » width at half-maximum of the Δd{sup 2}I/dV{sup 2}–H curves corresponds to that of the broad Hanle signals. These results indicate that electron trap states are located in the low energy region and cause a decrease in spin lifetime.« less

Quantum Stat Mech in a Programmable Spin Chain of Trapped Ions

NASA Astrophysics Data System (ADS)

Monroe, Christopher

2017-04-01

Trapped atomic ions are a versatile and very clean platform for the quantum programming of interacting spin models and the study of quantum nonequilibrium phenomena. When spin-dependent optical dipole forces are applied to a collection of trapped ions, an effective long-range quantum magnetic interaction arises, with reconfigurable and tunable graphs. Following earlier work on many-body spectroscopy and quench dynamics, we have recently studied many body non-thermalization processes in this system. Frustrated Hamiltonian dynamics can lead to prethermalization, and by adding programmable disorder between the sites, we have observed the phenomenon of many body localization (MBL). Finally, by applying a periodically driven Floquet Hamiltonian tempered by MBL, we report the observation of a discrete ``time crystal'' in the stable appearance of a subharmonic response of the system to the periodic drive. This work is supported by the ARO Atomic Physics Program, the AFOSR MURI on Quantum Measurement and Verification, the IARPA LogiQ Program, and the NSF Physics Frontier Center at JQI.

Thermodynamic Studies of Levitated Microdroplets of Highly Supersaturated Electrolyte Solutions

NASA Technical Reports Server (NTRS)

Myerson, Allan S.; Izmailov, Alexander F.; Na, Han-Soo

1996-01-01

Highly supersaturated electrolyte solutions are studied by employing an electrodynamic levitator trap (ELT) technique. The ELT technique involves containerless suspension of a microdroplet thus eliminating dust, dirt, and container walls which normally cause heterogeneous nucleation. This allows very high supersaturations to be achieved. A theoretical study of the experimental results obtained for the water activity in microdroplets of various electrolyte solutions is based on the development of the Cahn-Hilliard formalism for electrolyte solutions. A correspondence of 96-99% between the theory and experiment for the all solutions studied was achieved and allowed the determination of an analytical expression for the spinodal concentration n(sub spin) and its calculation for various electrolyte solutions at 298 K.

Multi-dimensional single-spin nano-optomechanics with a levitated nanodiamond

NASA Astrophysics Data System (ADS)

Neukirch, Levi P.; von Haartman, Eva; Rosenholm, Jessica M.; Nick Vamivakas, A.

2015-10-01

Considerable advances made in the development of nanomechanical and nano-optomechanical devices have enabled the observation of quantum effects, improved sensitivity to minute forces, and provided avenues to probe fundamental physics at the nanoscale. Concurrently, solid-state quantum emitters with optically accessible spin degrees of freedom have been pursued in applications ranging from quantum information science to nanoscale sensing. Here, we demonstrate a hybrid nano-optomechanical system composed of a nanodiamond (containing a single nitrogen-vacancy centre) that is levitated in an optical dipole trap. The mechanical state of the diamond is controlled by modulation of the optical trapping potential. We demonstrate the ability to imprint the multi-dimensional mechanical motion of the cavity-free mechanical oscillator into the nitrogen-vacancy centre fluorescence and manipulate the mechanical system's intrinsic spin. This result represents the first step towards a hybrid quantum system based on levitating nanoparticles that simultaneously engages optical, phononic and spin degrees of freedom.

Doped colloidal artificial spin ice

DOE PAGES

Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

2015-10-07

We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

Doped colloidal artificial spin ice

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

Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

Resonant quantum transitions in trapped antihydrogen atoms.

PubMed

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-03-07

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

Periodic driving control of Raman-induced spin-orbit coupling in Bose-Einstein condensates: The heating mechanisms

NASA Astrophysics Data System (ADS)

Gomez Llorente, J. M.; Plata, J.

2016-06-01

We focus on a technique recently implemented for controlling the magnitude of synthetic spin-orbit coupling (SOC) in ultracold atoms in the Raman-coupling scenario. This technique uses a periodic modulation of the Raman-coupling amplitude to tune the SOC. Specifically, it has been shown that the effect of a high-frequency sinusoidal modulation of the Raman-laser intensity can be incorporated into the undriven Hamiltonian via effective parameters, whose adiabatic variation can therefore be used to tune the SOC. Here, we characterize the heating mechanisms that can be relevant to this method. We identify the main mechanism responsible for the heating observed in the experiments as basically rooted in driving-induced transfer of population to excited states. Characteristics of that process determined by the harmonic trapping, the decay of the excited states, and the technique used for preparing the system are discussed. Additional heating, rooted in departures from adiabaticity in the variation of the effective parameters, is also described. Our analytical study provides some clues that may be useful in the design of strategies for curbing the effects of heating on the efficiency of the control methods.

Spin angular momentum transfer from TEM00 focused Gaussian beams to negative refractive index spherical particles

PubMed Central

Ambrosio, Leonardo A.; Hernández-Figueroa, Hugo E.

2011-01-01

We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM00 focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. PMID:21833372

Endotoxin-induced mortality in rats is reduced by nitrones

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

Hamburger, S.A.; McCay, P.B.

The goal of these investigations was to determine if nitrone spin-trapping agents can alter mortality associated with endotoxemia in the rat. Reactive free radicals attack nitrone spin-trapping agents forming relatively reactive, persistent free radical spin adducts. We administered 85 mM (10 ml/kg) of alpha-phenyl N-tert-butyl nitrone (PBN), alpha-4-pyridyl-N-oxide N-tert-butyl nitrone (4-POBN), 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), or vehicle (saline i.p.) 30 min before endotoxin (25 mg/kg i.p.) or vehicle to Sprague-Dawley (SD) or Holtzman virus-free (HVF) rats (n = 10-17/group). All vehicle-treated rats receiving endotoxin were dead by 1 day. At 7 days, 83% of PBN-treated SD, 42% of PBN- or POBN-treated HVF,more » and 25% of DMPO-treated HVF rats were alive. The difference in survival of PBN-treated animals between strains may reflect the higher susceptibility of HVF rats to endotoxin. The observed reduction in mortality may be related to the well-established capacity of spin-trapping agents to capture reactive free radicals that may be generated in target tissues in response to endotoxin, and that would otherwise react with cell components and produce tissue injury.« less

Copper(II) Thiosemicarbazone Complexes and Their Proligands upon UVA Irradiation: An EPR and Spectrophotometric Steady-State Study.

PubMed

Hricovíni, Michal; Mazúr, Milan; Sîrbu, Angela; Palamarciuc, Oleg; Arion, Vladimir B; Brezová, Vlasta

2018-03-21

X- and Q-band electron paramagnetic resonance (EPR) spectroscopy was used to characterize polycrystalline Cu(II) complexes that contained sodium 5-sulfonate salicylaldehyde thiosemicarbazones possessing a hydrogen, methyl, ethyl, or phenyl substituent at the terminal nitrogen. The ability of thiosemicarbazone proligands to generate superoxide radical anions and hydroxyl radicals upon their exposure to UVA irradiation in aerated aqueous solutions was evidenced by the EPR spin trapping technique. The UVA irradiation of proligands in neutral or alkaline solutions and dimethylsulfoxide (DMSO) caused a significant decrease in the absorption bands of aldimine and phenolic chromophores. Mixing of proligand solutions with the equimolar amount of copper(II) ions resulted in the formation of 1:1 Cu(II)-to-ligand complex, with the EPR and UV-Vis spectra fully compatible with those obtained for the dissolved Cu(II) thiosemicarbazone complexes. The formation of the complexes fully inhibited the photoinduced generation of reactive oxygen species, and only subtle changes were found in the electronic absorption spectra of the complexes in aqueous and DMSO solutions upon UVA steady-state irradiation. The dark redox activity of copper(II) complexes and proligand/Cu(II) aqueous solutions towards hydrogen peroxide which resulted in the generation of hydroxyl radicals, was confirmed by spin trapping experiments.

A kinetic study of 3-chlorophenol enhanced hydroxyl radical generation during ozonation.

PubMed

Utsumi, Hideo; Han, Youn-Hee; Ichikawa, Kazuhiro

2003-12-01

Hydroxyl (OH) radical is proposed as an important factor in the ozonation of water. In the present study, the enhancing effect of 3-chlorophenol on OH radical generation was mathematically evaluated using electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocity of DMPO-OH generation in ozonated water containing 3-chlorophenol was quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus which was controlled by home-made software. The initial velocity of DMPO-OH generation increased as a function of the concentration of ozone and the more effectively of 3-chlorophenol concentration. The relation among ozone concentration, amount of 3-chlorophenol and the initial velocity (nu(0)) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, nu(0) (10(-6)M/s)=[9.7 x [3-chlorophenol (10(-9)M)] + 0.0005]exp(57 x [ozone (10(-9)M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.99. The equation for the enhancing effect by 3-chlorophenol should provide useful information to optimize the condition in ozone treatment process of water containing phenolic pollutants.

Frequency and time domain studies of magneto-transport and charge trapping in amorphous organic semiconductors

NASA Astrophysics Data System (ADS)

Rybicki, James Edward

The focus of this thesis is a recently discovered organic magnetoresistance (OMAR) whose underlying mechanism remains much debated. As an introduction, the field of organic electronic is briefly discussed focusing mainly on organic light emitting diodes, the devices in which OMAR was first discovered. Important findings related to OMAR from prior work are highlighted and several proposed models for the underlying mechanism are discussed. The frequency dependence of OMAR along with capacitance spectroscopy are studied to help distinguish between proposed models. The limit frequency for OMAR devices is obtained. Magnetic field dependent time-of-flight spectroscopy is used to determine whether applied magnetic fields modify the photocarrier generation efficiency in OMAR devices, their mobility, or both. These results are used to compare the bipolaron model and the triplet-polaron scattering mechanism. As it is generally agreed that OMAR is a spintronic effect, the role of spin-orbit coupling in polymers was studied to help understand its importance in the spin-transport of organic semiconductors. The possibility of spin-orbit induced spin precession is examined and a phonon assisted spin-flip process is proposed. We show OMAR may be enhanced by exposure to x-ray radiation. This is shown to be related to the production of traps. The effect on other device characteristics including turn-voltage and quantum efficiency is also examined. The role of trap production in enhancing OMAR is explained using the biopolaron model.

Hysteresis and change of transition temperature in thin films of Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2}, a new sublimable spin-crossover molecule

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

Davesne, V.; Gruber, M.; Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe

2015-05-21

Thin films of the spin-crossover (SCO) molecule Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2} (Fe-pyrz) were sublimed on Si/SiO{sub 2} and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen){sub 2}(NCS){sub 2}, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased,more » and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.« less

Carnivorous pitcher plant uses free radicals in the digestion of prey.

PubMed

Chia, Tet Fatt; Aung, Hnin Hnin; Osipov, Anatoly N; Goh, Ngoh Khang; Chia, Lian Sai

2004-01-01

A study of the involvement of free oxygen radicals in trapping and digestion of insects by carnivorous plants was the main goal of the present investigation. We showed that the generation of oxygen free radicals by pitcher fluid of Nepenthes is the first step of the digestion process, as seen by EPR spin trapping assay and gel-electrophoresis. The EPR spectrum of N. gracilis fluid in the presence of DMPO spin trap showed the superposition of the hydroxyl radical spin adduct signal and of the ascorbyl radical signal. Catalase addition decreased the generation of hydroxyl radicals showing that hydroxyl radicals are generated from hydrogen peroxide, which can be derived from superoxide radicals. Gel-electrophoresis data showed that myosin, an abundant protein component of insects, can be rapidly broken down by free radicals and protease inhibitors do not inhibit this process. Addition of myoglobin to the pitcher plant fluid decreased the concentration of detectable radicals. Based on these observations, we conclude that oxygen free radicals produced by the pitcher plant aid in the digestion of the insect prey.

In vivo detection of free radicals using molecular MRI and immuno-spin trapping in a mouse model for amyotrophic lateral sclerosis.

PubMed

Towner, Rheal A; Smith, Nataliya; Saunders, Debra; Lupu, Florea; Silasi-Mansat, Robert; West, Melinda; Ramirez, Dario C; Gomez-Mejiba, Sandra E; Bonini, Marcelo G; Mason, Ronald P; Ehrenshaft, Marilyn; Hensley, Kenneth

2013-10-01

Free radicals associated with oxidative stress play a major role in amyotrophic lateral sclerosis (ALS). By combining immuno-spin trapping and molecular magnetic resonance imaging, in vivo trapped radical adducts were detected in the spinal cords of SOD1(G93A)-transgenic (Tg) mice, a model for ALS. For this study, the nitrone spin trap DMPO (5,5-dimethyl-1-pyrroline N-oxide) was administered (ip) over 5 days before administration (iv) of an anti-DMPO probe (anti-DMPO antibody covalently bound to an albumin-gadolinium-diethylenetriamine pentaacetic acid-biotin MRI contrast agent) to trap free radicals. MRI was used to detect the presence of the anti-DMPO radical adducts by a significant sustained increase in MR signal intensities (p < 0.05) or anti-DMPO probe concentrations measured from T₁ relaxations (p < 0.01). The biotin moiety of the anti-DMPO probe was targeted with fluorescence-labeled streptavidin to locate the probe in excised tissues. Negative controls included either Tg ALS mice initially administered saline rather than DMPO followed by the anti-DMPO probe or non-Tg mice initially administered DMPO and then the anti-DMPO probe. The anti-DMPO probe was found to bind to neurons via colocalization fluorescence microscopy. DMPO adducts were also confirmed in diseased/nondiseased tissues from animals administered DMPO. Apparent diffusion coefficients from diffusion-weighted images of spinal cords from Tg mice were significantly elevated (p < 0.001) compared to wild-type controls. This is the first report regarding the detection of in vivo trapped radical adducts in an ALS model. This novel, noninvasive, in vivo diagnostic method can be applied to investigate the involvement of free radical mechanisms in ALS rodent models. Copyright © 2013 Elsevier Inc. All rights reserved.

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

Cavity-Enhanced Optical Readout of a Single Solid-State Spin

NASA Astrophysics Data System (ADS)

Sun, Shuo; Kim, Hyochul; Solomon, Glenn S.; Waks, Edo

2018-05-01

We demonstrate optical readout of a single spin using cavity quantum electrodynamics. The spin is based on a single trapped electron in a quantum dot that has a poor branching ratio of 0.43. Selectively coupling one of the optical transitions of the quantum dot to the cavity mode results in a spin-dependent cavity reflectivity that enables spin readout by monitoring the reflected intensity of an incident optical field. Using this approach, we demonstrate spin-readout fidelity of 0.61. Achieving this fidelity using resonance fluorescence from a bare dot would require 43 times improvement in photon collection efficiency.

Non-Evaporative Cooling Using Spin-Exchange Collision in an Optical Trap

DTIC Science & Technology

2009-02-03

transit time of the atoms across the optical trap should damp the atoms’ motion significantly. These processes are described in detail in Ref. [ 18]. The...potentials. Finally, since the optical trap was very shallow compared to a MOT, any light-assisted collision that resulted in almost any net acceleration...EXCHANGE COLLISION IN AN OPTICAL TRAP 5a. CONTRACT NUMBER FA9550-06-1-0190 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

Microfluidic ultralow interfacial tensiometry with magnetic particles.

PubMed

Tsai, Scott S H; Wexler, Jason S; Wan, Jiandi; Stone, Howard A

2013-01-07

We describe a technique that measures ultralow interfacial tensions using paramagnetic spheres in a co-flow microfluidic device designed with a magnetic section. Our method involves tuning the distance between the co-flowing interface and the magnet's center, and observing the behavior of the spheres as they approach the liquid-liquid interface-the particles either pass through or are trapped by the interface. Using threshold values of the magnet-to-interface distance, we make estimates of the two-fluid interfacial tension. We demonstrate the effectiveness of this technique for measuring very low interfacial tensions, O(10(-6)-10(-5)) N m(-1), by testing solutions of different surfactant concentrations, and we show that our results are comparable with measurements made using a spinning drop tensiometer.

Quantum entanglement between an optical photon and a solid-state spin qubit.

PubMed

Togan, E; Chu, Y; Trifonov, A S; Jiang, L; Maze, J; Childress, L; Dutt, M V G; Sørensen, A S; Hemmer, P R; Zibrov, A S; Lukin, M D

2010-08-05

Quantum entanglement is among the most fascinating aspects of quantum theory. Entangled optical photons are now widely used for fundamental tests of quantum mechanics and applications such as quantum cryptography. Several recent experiments demonstrated entanglement of optical photons with trapped ions, atoms and atomic ensembles, which are then used to connect remote long-term memory nodes in distributed quantum networks. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks.

Strongly Interacting Fermi Gases in Two Dimensions

DTIC Science & Technology

2012-07-17

other in k- space owing to the spin- orbit interaction. For a finite field B (Z) z , a gap opens in the spectrum. This gap, known as the spin-orbit...from the trap. Time-of-flight maps momentum to real space , allowing direct momentum resolution of the spin popula- tions. As a function of pulse...at a given quasi-momentum q, can be expanded in terms of free space eigenstates as 5 FIG. 3. Creating and probing a spin-orbit coupled lattice. (A

Generalized Dicke Nonequilibrium Dynamics in Trapped Ions

NASA Astrophysics Data System (ADS)

Genway, Sam; Li, Weibin; Ates, Cenap; Lanyon, Benjamin P.; Lesanovsky, Igor

2014-01-01

We explore trapped ions as a setting to investigate nonequilibrium phases in a generalized Dicke model of dissipative spins coupled to phonon modes. We find a rich dynamical phase diagram including superradiantlike regimes, dynamical phase coexistence, and phonon-lasing behavior. A particular advantage of trapped ions is that these phases and transitions among them can be probed in situ through fluorescence. We demonstrate that the main physical insights are captured by a minimal model and consider an experimental realization with Ca+ ions trapped in a linear Paul trap with a dressing scheme to create effective two-level systems with a tunable dissipation rate.

Distribution of localized states from fine analysis of electron spin resonance spectra of organic semiconductors: Physical meaning and methodology

NASA Astrophysics Data System (ADS)

Mishchenko, Andrey S.; Matsui, Hiroyuki; Hasegawa, Tatsuo

2012-02-01

We develop an analytical method for the processing of electron spin resonance (ESR) spectra. The goal is to obtain the distributions of trapped carriers over both their degree of localization and their binding energy in semiconductor crystals or films composed of regularly aligned organic molecules [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.056602 104, 056602 (2010)]. Our method has two steps. We first carry out a fine analysis of the shape of the ESR spectra due to the trapped carriers; this reveals the distribution of the trap density of the states over the degree of localization. This analysis is based on the reasonable assumption that the linewidth of the trapped carriers is predetermined by their degree of localization because of the hyperfine mechanism. We then transform the distribution over the degree of localization into a distribution over the binding energies. The transformation uses the relationships between the binding energies and the localization parameters of the trapped carriers. The particular relation for the system under study is obtained by the Holstein model for trapped polarons using a diagrammatic Monte Carlo analysis. We illustrate the application of the method to pentacene organic thin-film transistors.

Iron-chelating agents never suppress Fenton reaction but participate in quenching spin-trapped radicals.

PubMed

Li, Linxiang; Abe, Yoshihiro; Kanagawa, Kiyotada; Shoji, Tomoko; Mashino, Tadahiko; Mochizuki, Masataka; Tanaka, Miho; Miyata, Naoki

2007-09-19

Hydroxyl radical formation by Fenton reaction in the presence of an iron-chelating agent such as EDTA was traced by two different assay methods; an electron spin resonance (ESR) spin-trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and high Performance liquid chromatography (HPLC)-fluorescence detection with terephthalic acid (TPA), a fluorescent probe for hydroxyl radicals. From the ESR spin-trapping measurement, it was observed that EDTA seemed to suppress hydroxyl radical formation with the increase of its concentration. On the other hand, hydroxyl radical formation by Fenton reaction was not affected by EDTA monitored by HPLC assay. Similar inconsistent effects of other iron-chelating agents such as nitrylotriacetic acid (NTA), diethylenetriamine penta acetic acid (DTPA), oxalate and citrate were also observed. On the addition of EDTA solution to the reaction mixture 10 min after the Fenton reaction started, when hydroxyl radical formation should have almost ceased but the ESR signal of DMPO-OH radicals could be detected, it was observed that the DMPO-OH* signal disappeared rapidly. With the simultaneous addition of Fe(II) solution and EDTA after the Fenton reaction ceased, the DMPO-OH* signal disappeared more rapidly. The results indicated that these chelating agents should enhance the quenching of [DMPO-OH]* radicals by Fe(II), but they did not suppress Fenton reaction by forming chelates with iron ions.

An in vivo ESR spin-trapping study: Free radical generation in rats from formate intoxication— role of the Fenton reaction

PubMed Central

Dikalova, Anna E.; Kadiiska, Maria B.; Mason, Ronald P.

2001-01-01

Electron spin resonance spectroscopy has been used to study free radical generation in rats with acute sodium formate poisoning. The in vivo spin-trapping technique was used with α-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN), which reacts with free radical metabolites to form radical adducts, which were detected in the bile and urine samples from Fischer rats. The use of [13C]-sodium formate and computer simulations of the spectra identified the 12-line spectrum as arising from the POBN/carbon dioxide anion radical adduct. The identification of POBN/⋅CO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{-}}}\\end{equation*}\\end{document} radical adduct provides direct electron spin resonance spectroscopy evidence for the formation of ⋅CO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{-}}}\\end{equation*}\\end{document} radicals during acute intoxication by sodium formate, suggesting a free radical metabolic pathway. To study the mechanism of free radical generation by formate, we tested several known inhibitors. Both allopurinol, an inhibitor of xanthine oxidase, and aminobenzotriazole, a cytochrome P450 inhibitor, decreased free radical formation from formate, which may imply a dependence on hydrogen peroxide. In accord with this hypothesis, the catalase inhibitor 3-aminotriazole caused a significant increase in free radical formation. The iron chelator Desferal decreased the formation of free radicals up to 2-fold. Presumably, iron plays a role in the mechanism of free radical generation by formate via the Fenton reaction. The detection of formate free radical metabolites generated in vivo and the key role of the Fenton reaction in this process may be important for understanding the pathogenesis of both formate and methanol intoxication. PMID:11717423

The UAH Spinning Terrella Experiment: A Laboratory Analog for the Earth's Magnetosphere

NASA Technical Reports Server (NTRS)

Sheldon, R. B.; Gallagher, D. L.; Craven, P. D.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

The UAH Spinning Terrella Experiment has been modified to include the effect of a second magnet. This is a simple laboratory demonstration of the well-known double-dipole approximation to the Earth's magnetosphere. In addition, the magnet has been biassed $\\sim$-400V which generates a DC glow discharge and traps it in a ring current around the magnet. This ring current is easily imaged with a digital camera and illustrates several significant topological properties of a dipole field. In particular, when the two dipoles are aligned, and therefore repel, they emulate a northward IMF Bz magnetosphere. Such a geometry traps plasma in the high latitude cusps as can be clearly seen in the movies. Likewise, when the two magnets are anti-aligned, they emulate a southward IMF Bz magnetosphere with direct feeding of plasma through the x-line. We present evidence for trapping and heating of the plasma, comparing the dipole-trapped ring current to the cusp-trapped population. We also present a peculiar asymmetric ring current produced in by the plasma at low plasma densities. We discuss the similarities and dissimilarities of the laboratory analog to the collisionless Earth plasma, and implications for the interpretation of IMAGE data.

Entangling spin-spin interactions of ions in individually controlled potential wells

NASA Astrophysics Data System (ADS)

Wilson, Andrew; Colombe, Yves; Brown, Kenton; Knill, Emanuel; Leibfried, Dietrich; Wineland, David

2014-03-01

Physical systems that cannot be modeled with classical computers appear in many different branches of science, including condensed-matter physics, statistical mechanics, high-energy physics, atomic physics and quantum chemistry. Despite impressive progress on the control and manipulation of various quantum systems, implementation of scalable devices for quantum simulation remains a formidable challenge. As one approach to scalability in simulation, here we demonstrate an elementary building-block of a configurable quantum simulator based on atomic ions. Two ions are trapped in separate potential wells that can individually be tailored to emulate a number of different spin-spin couplings mediated by the ions' Coulomb interaction together with classical laser and microwave fields. We demonstrate deterministic tuning of this interaction by independent control of the local wells and emulate a particular spin-spin interaction to entangle the internal states of the two ions with 0.81(2) fidelity. Extension of the building-block demonstrated here to a 2D-network, which ion-trap micro-fabrication processes enable, may provide a new quantum simulator architecture with broad flexibility in designing and scaling the arrangement of ions and their mutual interactions. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), ONR, and the NIST Quantum Information Program.

Identical spin rotation effect and electron spin waves in quantum gas of atomic hydrogen

NASA Astrophysics Data System (ADS)

Lehtonen, L.; Vainio, O.; Ahokas, J.; Järvinen, J.; Novotny, S.; Sheludyakov, S.; Suominen, K.-A.; Vasiliev, S.; Khmelenko, V. V.; Lee, D. M.

2018-05-01

We present an experimental study of electron spin waves in atomic hydrogen gas compressed to high densities of ∼5 × 1018 cm‑3 at temperatures ranging from 0.26 to 0.6 K in the strong magnetic field of 4.6 T. Hydrogen gas is in a quantum regime when the thermal de-Broglie wavelength is much larger than the s-wave scattering length. In this regime the identical particle effects play a major role in atomic collisions and lead to the identical spin rotation effect (ISR). We observed a variety of spin wave modes caused by this effect with strong dependence on the magnetic potential caused by variations of the polarizing magnetic field. We demonstrate confinement of the ISR modes in the magnetic potential and manipulate their properties by changing the spatial profile of the magnetic field. We have found that at a high enough density of H gas the magnons accumulate in their ground state in the magnetic trap and exhibit long coherence, which has a profound effect on the electron spin resonance spectra. Such macroscopic accumulation of the ground state occurs at a certain critical density of hydrogen gas, where the chemical potential of the magnons becomes equal to the energy of their ground state in the trapping potential.

Free-radical reactions induced by OH-radical attack on cytosine-related compounds: a study by a method combining ESR, spin trapping and HPLC.

PubMed Central

Hiraoka, W; Kuwabara, M; Sato, F; Matsuda, A; Ueda, T

1990-01-01

Free-radical reactions induced by OH-radical attack on cytosine-related compounds were investigated by a method combining ESR, spin trapping with 2-methyl-2-nitrosopropane and high-performance liquid chromatography (HPLC). Cytidine, 2'-deoxycytidine, cytidine 3'-monophosphate, cytidine 5'-monophosphate, 2'-deoxycytidine 5'-monophosphate and their derivatives, of which 5,6-protons at the base moiety were replaced by deuterons, and polycytidylic acid (poly(C] were employed as samples. OH radicals were generated by X-irradiating an N2O-saturated aqueous solution. Five spin adducts were separated by HPLC. Examination of them by ESR spectroscopy and UV photospectrometry showed that spin adducts assigned to C5 and C6 radicals due to OH addition to the 5,6 double-bond, a deaminated form of the spin adduct derived from a C5 radical due to the cyclization reaction between C5' of the sugar and C6 of the base, and a spin adduct assigned to the C4' radical due to H abstraction by OH radicals were produced. From these results the sites of OH-radical attack and the subsequent radical reactions in cytosine-related compounds were clarified. PMID:2157193

Product yield-detected ESR on magnetic field-dependent photoreduction of quinones in SDS micellar solution

NASA Astrophysics Data System (ADS)

Okazaki, M.; Sakata, S.; Konaka, R.; Shiga, T.

1987-06-01

Transient free radicals in the magnetic field-dependent photoreduction of quinones (menadione or anthraquinone) in a sodium dodecyl sulfate (SDS) micellar solution, were converted to stable nitroxide radicals by the ``spin trapping'' technique with or without the microwave irradiation. Upon irradiating the microwave at 160 mW, the product yield (``spin adduct'' of the alkyl radical generated from SDS molecule) decreased by up to 14% at certain magnetic fields in a resonant manner. Although only one component of the postulated radical pair was converted to the spin adduct, the decrease in the yield as a function of external magnetic field revealed the ESR spectra of both component radicals of the radical pair, i.e., the semiquinone radical and the alkyl radical from SDS. This experiment not only gives the direct evidence for the radical pair model, but also suggests the possibility for this method to be applied in controlling the chemical reactions by the microwave. A simple calculation was made to simulate the observed ``product yield-detected ESR.'' Agreements were achieved semiquantitatively between the observed reductions in the spin adduct yields and those calculated. The estimated exchange interaction between the component radicals in the radical pair of the present systems was lower than 0.3 mT.

Critical Spin Superflow in a Spinor Bose-Einstein Condensate

NASA Astrophysics Data System (ADS)

Kim, Joon Hyun; Seo, Sang Won; Shin, Y.

2017-11-01

We investigate the critical dynamics of spin superflow in an easy-plane antiferromagnetic spinor Bose-Einstein condensate. Spin-dipole oscillations are induced in a trapped condensate by applying a linear magnetic field gradient and we observe that the damping rate increases rapidly as the field gradient increases above a certain critical value. The onset of dissipation is found to be associated with the generation of dark-bright solitons due to the modulation instability of the counterflow of two spin components. Spin turbulence emerges as the solitons decay because of their snake instability. We identify another critical point for spin superflow, in which transverse magnon excitations are dynamically generated via spin-exchanging collisions, which leads to the transient formation of axial polar spin domains.

Emergence of transverse spin in optical modes of semiconductor nanowires

DOE PAGES

Alizadeh, M. H.; Reinhard, Bjorn M.

2016-04-11

The transverse spin angular momentum of light has recently received tremendous attention as it adds a new degree of freedom for controlling light-matter interactions. In this work we demonstrate the generation of transverse spin angular momentum by the weakly-guided mode of semiconductor nanowires. The evanescent field of these modes in combination with the transversality condition rigorously accounts for the occurrence of transverse spin angular momentum. Furthermore, the intriguing and nontrivial spin properties of optical modes in semiconductor nanowires are of high interest for a broad range of new applications including chiral optical trapping, quantum information processing, and nanophotonic circuitry.

Spin-orbit coupling for tidally evolving super-Earths

NASA Astrophysics Data System (ADS)

Rodríguez, A.; Callegari, N.; Michtchenko, T. A.; Hussmann, H.

2012-12-01

We investigate the spin behaviour of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the tidal torque, both raised by the central star, we analyse the possibility of temporary captures in spin-orbit resonances. The results of the numerical simulations of the exact equations of motions indicate that, whenever the planet rotation is trapped in a resonant motion, the orbital decay and the eccentricity damping are faster than the ones in which the rotation follows the so-called pseudo-synchronization. Analytical results obtained through the averaged equations of the spin-orbit problem show a good agreement with the numerical simulations. We apply the analysis to the cases of the recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The simulated dynamical history of these systems indicates the possibility of capture in several spin-orbit resonances; particularly, GJ 3634 b and 55 Cnc e can currently evolve under a non-synchronous resonant motion for suitable values of the parameters. Moreover, 55 Cnc e may avoid a chaotic rotation behaviour by evolving towards synchronization through successive temporary resonant trappings.

Free Radical Production from the Interaction of 2-Chloroethyl Vesicants (Mustard Gas) with Pyridine Nucleotide-Driven Flavoprotein Electron Transport Systems

DTIC Science & Technology

2009-01-01

or HN2 at desired mM levels and 2.4 mM NADPH were introduced with 40 µM cytochrome c in 0.1 M KPO4 buffer pH 7.5 made 0.25 M with respect to NaCl. The...because 4-POBN is a nitrone , the adduct formed occurred at the carbon adjacent to the imino nitrogen of the spin trap, too many bonds distant from...EPR spectrometry with spin trapping. Inclusion of the nitrone 4-POBN in our incubation mixture at the molar level enabled us to observe a six-line 4

Quantum criticality and universal scaling of strongly attractive spin-imbalanced Fermi gases in a one-dimensional harmonic trap

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

Yin Xiangguo; Chen Shu; Guan Xiwen

2011-07-15

We investigate quantum criticality and universal scaling of strongly attractive Fermi gases confined in a one-dimensional harmonic trap. We demonstrate from the power-law scaling of the thermodynamic properties that current experiments on this system are capable of measuring universal features at quantum criticality, such as universal scaling and Tomonaga-Luttinger liquid physics. The results also provide insights on recent measurements of key features of the phase diagram of a spin-imbalanced atomic Fermi gas [Y. Liao et al., Nature (London) 467, 567 (2010)] and point to further study of quantum critical phenomena in ultracold atomic Fermi gases.

The first characterization of free radicals formed from cellular COX-catalyzed peroxidation.

PubMed

Gu, Yan; Xu, Yi; Law, Benedict; Qian, Steven Y

2013-04-01

Through free radical-mediated peroxidation, cyclooxygenase (COX) can metabolize dihomo-γ-linolenic acid (DGLA) and arachidonic acid (AA) to form well-known bioactive metabolites, namely, the 1-series of prostaglandins (PGs1) and the 2-series of prostaglandins (PGs2), respectively. Unlike PGs2, which are generally viewed as proinflammatory and procarcinogenic PGs, PGs1 may possess anti-inflammatory and anti-cancer activity. Previous studies using ovine COX along with spin trapping and the LC/ESR/MS technique have shown that certain exclusive free radicals are generated from different free radical reactions in DGLA and AA peroxidation. However, it has been unclear whether the differences were associated with the contrasting bioactivity of DGLA vs AA. The aim of this study was to refine the LC/MS and spin trapping technique to make it possible for the association between free radicals and cancer cell growth to be directly tested. Using a colon cancer cell line, HCA-7 colony 29, and LC/MS along with a solid-phase extraction, we were able to characterize the reduced forms of radical adducts (hydroxylamines) as the free radicals generated from cellular COX-catalyzed peroxidation. For the first time, free radicals formed in the COX-catalyzed peroxidation of AA vs DGLA and their association with cancer cell growth were assessed (cell proliferation via MTS and cell cycle distribution via propidium iodide staining) in the same experimental setting. The exclusive free radicals formed from the COX-catalyzed peroxidation of AA and DGLA were shown to be correlated with the cell growth response. Our results indicate that free radicals generated from the distinct radical reactions in COX-catalyzed peroxidation may represent the novel metabolites of AA and DGLA that correspond to their contrasting bioactivity. Copyright © 2012 Elsevier Inc. All rights reserved.

The First Characterization of Free Radicals Formed From Cellular COX-Catalyzed Peroxidation

PubMed Central

Gu, Yan; Xu, Yi; Law, Benedict; Qian, Steven Y.

2014-01-01

Through free radical-mediated peroxidation, cyclooxygenase (COX) can metabolize dihomo-γ-linolenic acid (DGLA) and arachidonic acid(AA) to form well-known bioactive metabolites, namely, the 1-series of prostaglandins (PGs1) and 2-series of prostaglandins(PGs2), respectively. Unlike PGs2, which are generally viewed as pro-inflammatory and pro-carcinogenic PGs, PGs1 may possess anti-inflammatory and anti-cancer activity. Previous studies using ovine COX along with spin trapping and the LC/ESR/MS technique have shown that certain exclusive free radicals are generated from different free radical reactions in DGLA and AA peroxidation. However, it has been unclear whether the differences were associated with the contrasting bioactivity of DGLA vs. AA. The aim of this study was to refine the LC/MS and spin-trapping technique to make it possible for the association between free radicals and cancer cell growth to be directly tested. Using a colon cancer cell line, HCA-7 colony 29, and LC/MS along with a solid phase extraction, we were able to characterize the reduced forms of radical adducts (hydroxylamines) as the free radicals generated from cellular COX-catalyzed peroxidation. For the first time, free radicals formed in the COX-catalyzed peroxidation of AA vs. DGLA and their association with cancer cell growth was assessed (cell proliferation via MTS and cell cycle distribution via PI staining) in the same experimental setting. The exclusive free radicals formed from the COX-catalyzed peroxidation of AA and DGLA were shown to be correlated with the cell growth response. Our results indicate that free radicals generated from the distinct radical reactions in COX-catalyzed peroxidation may represent the novel metabolites of AA and DGLA that correspond to their contrasting bioactivity. PMID:23261941

A graphene solution to conductivity mismatch: spin injection from ferromagnetic metal/graphene tunnel contacts into silicon

NASA Astrophysics Data System (ADS)

van't Erve, Olaf

2014-03-01

New paradigms for spin-based devices, such as spin-FETs and reconfigurable logic, have been proposed and modeled. These devices rely on electron spin being injected, transported, manipulated and detected in a semiconductor channel. This work is the first demonstration on how a single layer of graphene can be used as a low resistance tunnel barrier solution for electrical spin injection into Silicon at room temperature. We will show that a FM metal / monolayer graphene contact serves as a spin-polarized tunnel barrier which successfully circumvents the classic metal / semiconductor conductivity mismatch issue for electrical spin injection. We demonstrate electrical injection and detection of spin accumulation in Si above room temperature, and show that the corresponding spin lifetimes correlate with the Si carrier concentration, confirming that the spin accumulation measured occurs in the Si and not in interface trap states. An ideal tunnel barrier should exhibit several key material characteristics: a uniform and planar habit with well-controlled thickness, minimal defect / trapped charge density, a low resistance-area product for minimal power consumption, and compatibility with both the FM metal and semiconductor, insuring minimal diffusion to/from the surrounding materials at temperatures required for device processing. Graphene, offers all of the above, while preserving spin injection properties, making it a compelling solution to the conductivity mismatch for spin injection into Si. Although Graphene is very conductive in plane, it exhibits poor conductivity perpendicular to the plane. Its sp2 bonding results in a highly uniform, defect free layer, which is chemically inert, thermally robust, and essentially impervious to diffusion. The use of a single monolayer of graphene at the Si interface provides a much lower RA product than any film of an oxide thick enough to prevent pinholes (1 nm). Our results identify a new route to low resistance-area product spin-polarized contacts, a crucial requirement enabling future semiconductor spintronic devices, which rely upon two-terminal magnetoresistance, including spin-based transistors, logic and memory.

Complete devil's staircase and crystal-superfluid transitions in a dipolar XXZ spin chain: a trapped ion quantum simulation

NASA Astrophysics Data System (ADS)

Hauke, Philipp; Cucchietti, Fernando M.; Müller-Hermes, Alexander; Bañuls, Mari-Carmen; Cirac, J. Ignacio; Lewenstein, Maciej

2010-11-01

Systems with long-range interactions show a variety of intriguing properties: they typically accommodate many metastable states, they can give rise to spontaneous formation of supersolids, and they can lead to counterintuitive thermodynamic behavior. However, the increased complexity that comes with long-range interactions strongly hinders theoretical studies. This makes a quantum simulator for long-range models highly desirable. Here, we show that a chain of trapped ions can be used to quantum simulate a one-dimensional (1D) model of hard-core bosons with dipolar off-site interaction and tunneling, equivalent to a dipolar XXZ spin-1/2 chain. We explore the rich phase diagram of this model in detail, employing perturbative mean-field theory, exact diagonalization and quasi-exact numerical techniques (density-matrix renormalization group and infinite time-evolving block decimation). We find that the complete devil's staircase—an infinite sequence of crystal states existing at vanishing tunneling—spreads to a succession of lobes similar to the Mott lobes found in Bose-Hubbard models. Investigating the melting of these crystal states at increased tunneling, we do not find (contrary to similar 2D models) clear indications of supersolid behavior in the region around the melting transition. However, we find that inside the insulating lobes there are quasi-long-range (algebraic) correlations, as opposed to models with nearest-neighbor tunneling, that show exponential decay of correlations.

A kinetic study of enhancing effect by phenolic compounds on the hydroxyl radical generation during ozonation.

PubMed

Han, Y H; Ichikawa, K; Utsumi, H

2004-01-01

Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates O2- radical, OH radical, HO2 radical, OH-, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water among them. In the present study, the enhancing effects of several phenolic compounds; phenol, 2-, 3-, 4-monochloro, 2,4-dichloro, 2,4,6-trichlorophenol on OH radical generation were mathematically evaluated using the electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocities of DMPO-OH generation in ozonated water containing phenolic compounds were quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus, which was controlled by homemade software. The initial velocities of DMPO-OH generation increased as a function of the ozone concentration. The relation among ozone concentration, amount of phenolic compounds and the initial velocity (v0) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, v0 (10(-6) M/s) = (A' x [PhOHs (10(-9) M)] + 0.0005) exp (60 x [ozone (10(-9) M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.98.

EPR spin trapping evidence of radical intermediates in the photo-reduction of bicarbonate/CO2 in TiO2 aqueous suspensions.

PubMed

Molinari, Alessandra; Samiolo, Luca; Amadelli, Rossano

2015-05-01

Using the EPR spin trapping technique, we prove that simultaneous reactions take place in illuminated suspensions of TiO2 in aqueous carbonate solutions (pH ≈ 7). The adsorbed HCO3(-) is reduced to formate as directly made evident by the detection of formate radicals (˙CO2(-)). In addition, the amount of OH˙ radicals from the photo-oxidation of water shows a linear dependence on the concentration of bicarbonate, indicating that electron scavenging by HCO3(-) increases the lifetime of holes. In a weakly alkaline medium, photo-oxidation of HCO3(-)/CO3(2-) to ˙CO3(-) interferes with the oxidation of water. A comparative analysis of different TiO2 samples shows that formation of ˙CO2(-) is influenced by factors related to the nature of the surface, once expected surface area effects are accounted for. Modification of the TiO2 surface with noble metal nanoparticles does not have unequivocal benefits: the overall activity improves with Pd and Rh but not with Ru, which favours HCO3(-) photo-oxidation even at pH = 7. In general, identification of radical intermediates of oxidation and reduction reactions can provide useful mechanistic information that may be used in the development of photocatalytic systems for the reduction of CO2 also stored in the form of carbonates.

Superfluid state of atomic 6Li in a magnetic trap

NASA Astrophysics Data System (ADS)

Houbiers, M.; Ferwerda, R.; Stoof, H. T. C.; McAlexander, W. I.; Sackett, C. A.; Hulet, R. G.

1997-12-01

We report on a study of the superfluid state of spin-polarized atomic 6Li confined in a magnetic trap. Density profiles of this degenerate Fermi gas and the spatial distribution of the BCS order parameter are calculated in the local-density approximation. The critical temperature is determined as a function of the number of particles in the trap. Furthermore, we consider the mechanical stability of an interacting two-component Fermi gas, in the case of both attractive and repulsive interatomic interactions. For spin-polarized 6Li we also calculate the decay rate of the gas and show that within the mechanically stable regime of phase space, the lifetime is long enough to perform experiments on the gas below and above the critical temperature if a bias magnetic field of about 5 T is applied. Moreover, we propose that a measurement of the decay rate of the system might signal the presence of the superfluid state.

MATS and LaSpec: High-precision experiments using ion traps and lasers at FAIR

NASA Astrophysics Data System (ADS)

Rodríguez, D.; Blaum, K.; Nörtershäuser, W.; Ahammed, M.; Algora, A.; Audi, G.; Äystö, J.; Beck, D.; Bender, M.; Billowes, J.; Block, M.; Böhm, C.; Bollen, G.; Brodeur, M.; Brunner, T.; Bushaw, B. A.; Cakirli, R. B.; Campbell, P.; Cano-Ott, D.; Cortés, G.; Crespo López-Urrutia, J. R.; Das, P.; Dax, A.; de, A.; Delheij, P.; Dickel, T.; Dilling, J.; Eberhardt, K.; Eliseev, S.; Ettenauer, S.; Flanagan, K. T.; Ferrer, R.; García-Ramos, J.-E.; Gartzke, E.; Geissel, H.; George, S.; Geppert, C.; Gómez-Hornillos, M. B.; Gusev, Y.; Habs, D.; Heenen, P.-H.; Heinz, S.; Herfurth, F.; Herlert, A.; Hobein, M.; Huber, G.; Huyse, M.; Jesch, C.; Jokinen, A.; Kester, O.; Ketelaer, J.; Kolhinen, V.; Koudriavtsev, I.; Kowalska, M.; Krämer, J.; Kreim, S.; Krieger, A.; Kühl, T.; Lallena, A. M.; Lapierre, A.; Le Blanc, F.; Litvinov, Y. A.; Lunney, D.; Martínez, T.; Marx, G.; Matos, M.; Minaya-Ramirez, E.; Moore, I.; Nagy, S.; Naimi, S.; Neidherr, D.; Nesterenko, D.; Neyens, G.; Novikov, Y. N.; Petrick, M.; Plaß, W. R.; Popov, A.; Quint, W.; Ray, A.; Reinhard, P.-G.; Repp, J.; Roux, C.; Rubio, B.; Sánchez, R.; Schabinger, B.; Scheidenberger, C.; Schneider, D.; Schuch, R.; Schwarz, S.; Schweikhard, L.; Seliverstov, M.; Solders, A.; Suhonen, M.; Szerypo, J.; Taín, J. L.; Thirolf, P. G.; Ullrich, J.; van Duppen, P.; Vasiliev, A.; Vorobjev, G.; Weber, C.; Wendt, K.; Winkler, M.; Yordanov, D.; Ziegler, F.

2010-05-01

Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique “fingerprint”. Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10-5 to below 10-8 for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an A_dvanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10-9 can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e.g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility.Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner.The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with β-delayed neutron detection) has been achieved with rates of only a few atoms per second.This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively.

Ultrafast optical control of individual quantum dot spin qubits.

PubMed

De Greve, Kristiaan; Press, David; McMahon, Peter L; Yamamoto, Yoshihisa

2013-09-01

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a 'flying' photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers. This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin-spin entanglement can be generated if each spin can emit a photon that is entangled with the spin, and these photons are then interfered. We review recent work demonstrating entanglement between a stationary spin qubit and a flying photonic qubit. These experiments utilize the polarization- and frequency-dependent spontaneous emission from the lowest charged exciton state to single spin Zeeman sublevels.

Rotational dynamics and heating of trapped nanovaterite particles (Conference Presentation)

NASA Astrophysics Data System (ADS)

Arita, Yoshihiko; Richards, Joseph M.; Mazilu, Michael; Spalding, Gabriel C.; Skelton Spesyvtseva, Susan E.; Craig, Derek; Dholakia, Kishan

2016-09-01

Rotational control over optically trapped particles has gained significant prominence in recent years. The marriage between light fields possessing optical angular momentum and the material properties of microparticles has been useful to controllably spin particles in liquid, air and vacuum. The rotational degree of freedom adds new functionality to optical traps: in addition to allowing fundamental tests of optical angular momentum, the transfer of spin angular momentum in particular can allow measurements of local viscosity and exert local stresses on cellular systems. We demonstrate optical trapping and controlled rotation of nanovaterite crystals. These particles represent the smallest birefringent crystals ever trapped and set into rotation. Rotation rates of up to 5kHz in water are recorded, representing the fastest rotation to date for dielectric particles in liquid. Laser-induced heating results in the superlinear behaviour of the rotation rate as a function of trap power. We study both the rotational and translational modes of trapped nanovaterite crystals. The particle temperatures derived from those two optomechanical modes are in good agreement, which is supported by a numerical model revealing that the observed heating is dominated by absorption of light by the particles rather than by the surrounding liquid. A comparison is performed with trapped silica particles of similar size. The use of nanovaterite particles open up new studies for levitated optomechanics in vacuum as well as microrheological properties of cells or biological media. Their size and low heating offers prospects of viscosity measurements in ultra-small volumes and potentially simpler uptake by cellular media.

Ultrafast entanglement of trapped ions

NASA Astrophysics Data System (ADS)

Neyenhuis, Brian; Mizrahi, Jonathan; Johnson, Kale; Monroe, Christopher

2013-05-01

We have demonstrated ultrafast spin-motion entanglement of a single atomic ion using a short train of intense laser pulses. This pulse train gives the ion a spin-dependent kick where each spin state receives a discrete momentum kick in opposite directions. Using a series of these spin-dependent kicks we can realize a two qubit gate. In contrast to gates using spectroscopically resolved motional sidebands, these gates may be performed faster than the trap oscillation period, making them potentially less sensitive to noise, independent of temperature, and more easily scalable to large crystals of ions. We show that multiple kicks can be strung together to create a ``Schrodinger cat'' like state, where the large separation between the two parts of the wavepacket allow us to accumulate the phase shift necessary for a gate in a shorter amount of time. We will present a realistic pulse scheme for a two ion gate, and our progress towards its realization. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI.

Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study.

PubMed

Zhang, Qing-An; Shen, Yuan; Fan, Xue-Hui; Martín, Juan Francisco García; Wang, Xi; Song, Yun

2015-11-01

Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine. Copyright © 2015 Elsevier B.V. All rights reserved.

High-precision measurement of the electron spin g factor of trapped atomic nitrogen in the endohedral fullerene N@C60

NASA Astrophysics Data System (ADS)

Wittmann, J. J.; Can, T. V.; Eckardt, M.; Harneit, W.; Griffin, R. G.; Corzilius, B.

2018-05-01

The electronic g factor carries highly useful information about the electronic structure of a paramagnetic species, such as spin-orbit coupling and dia- or paramagnetic (de-)shielding due to local fields of surrounding electron pairs. However, in many cases, a near "spin-only" case is observed, in particular for light elements, necessitating accurate and precise measurement of the g factors. Such measurement is typically impeded by a "chicken and egg situation": internal or external reference standards are used for relative comparison of electron paramagnetic resonance (EPR) Larmor frequencies. However, the g factor of the standard itself usually is subject to a significant uncertainty which directly limits the precision and/or accuracy of the sought after sample g factor. Here, we apply an EPR reference-free approach for determining the g factor of atomic nitrogen trapped within the endohedral fullerene C60:N@C60 in its polycrystalline state by measuring the 1H NMR resonance frequency of dispersing toluene at room temperature. We found a value of g = 2.00204 (4) with a finally reached relative precision of ∼20 ppm. This accurate measurement allows us to directly compare the electronic properties of N@C60 to those found in atomic nitrogen in the gas phase or trapped in other solid matrices at liquid helium temperature. We conclude that spin-orbit coupling in N@C60 at room temperature is very similar in magnitude and of same sign as found in other inert solid matrices and that interactions between the quartet spin system and the C60 molecular orbitals are thus negligible.

Ultracold few fermionic atoms in needle-shaped double wells: spin chains and resonating spin clusters from microscopic Hamiltonians emulated via antiferromagnetic Heisenberg and t-J models

NASA Astrophysics Data System (ADS)

Yannouleas, Constantine; Brandt, Benedikt B.; Landman, Uzi

2016-07-01

Advances with trapped ultracold atoms intensified interest in simulating complex physical phenomena, including quantum magnetism and transitions from itinerant to non-itinerant behavior. Here we show formation of antiferromagnetic ground states of few ultracold fermionic atoms in single and double well (DW) traps, through microscopic Hamiltonian exact diagonalization for two DW arrangements: (i) two linearly oriented one-dimensional, 1D, wells, and (ii) two coupled parallel wells, forming a trap of two-dimensional, 2D, nature. The spectra and spin-resolved conditional probabilities reveal for both cases, under strong repulsion, atomic spatial localization at extemporaneously created sites, forming quantum molecular magnetic structures with non-itinerant character. These findings usher future theoretical and experimental explorations into the highly correlated behavior of ultracold strongly repelling fermionic atoms in higher dimensions, beyond the fermionization physics that is strictly applicable only in the 1D case. The results for four atoms are well described with finite Heisenberg spin-chain and cluster models. The numerical simulations of three fermionic atoms in symmetric DWs reveal the emergent appearance of coupled resonating 2D Heisenberg clusters, whose emulation requires the use of a t-J-like model, akin to that used in investigations of high T c superconductivity. The highly entangled states discovered in the microscopic and model calculations of controllably detuned, asymmetric, DWs suggest three-cold-atom DW quantum computing qubits.

Electron spin control of optically levitated nanodiamonds in vacuum

NASA Astrophysics Data System (ADS)

Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

2016-05-01

Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect.

Loading an Optical Trap with Diamond Nanocrystals Containing Nitrogen-Vacancy Centers from a Surface

NASA Astrophysics Data System (ADS)

Hsu, Jen-Feng; Ji, Peng; Dutt, M. V. Gurudev; D'Urso, Brian R.

2015-03-01

We present a simple and effective method of loading particles into an optical trap. Our primary application of this method is loading photoluminescent material, such as diamond nanocrystals containing nitrogen-vacancy (NV) centers, for coupling the mechanical motion of the trapped crystal with the spin of the NV centers. Highly absorptive material at the trapping laser frequency, such as tartrazine dye, is used as media to attach nanodiamonds and burn into a cloud of air-borne particles as the material is swept near the trapping laser focus on a glass slide. Particles are then trapped with the laser used for burning or transferred to a second laser trap at a different wavelength. Evidence of successful loading diamond nanocrystals into the trap presented includes high sensitivity of the photoluminecscence (PL) to the excitation laser and the PL spectra of the optically trapped particles

First Measurement of the Atomic Electric Dipole Moment of (225)Ra.

PubMed

Parker, R H; Dietrich, M R; Kalita, M R; Lemke, N D; Bailey, K G; Bishof, M; Greene, J P; Holt, R J; Korsch, W; Lu, Z-T; Mueller, P; O'Connor, T P; Singh, J T

2015-06-12

The radioactive radium-225 ((225)Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of (225)Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d((225)Ra)|<5.0×10(-22)  e cm (95% confidence).

Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

PubMed

Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

2006-03-01

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

Distribution of Localized States from Fine Analysis of Electron Spin Resonance Spectra in Organic Transistors

NASA Astrophysics Data System (ADS)

Matsui, Hiroyuki; Mishchenko, Andrei S.; Hasegawa, Tatsuo

2010-02-01

We developed a novel method for obtaining the distribution of trapped carriers over their degree of localization in organic transistors, based on the fine analysis of electron spin resonance spectra at low enough temperatures where all carriers are localized. To apply the method to pentacene thin-film transistors, we proved through continuous wave saturation experiments that all carriers are localized at below 50 K. We analyzed the spectra at 20 K and found that the major groups of traps comprise localized states having wave functions spanning around 1.5 and 5 molecules and a continuous distribution of states with spatial extent in the range between 6 and 20 molecules.

Distribution of localized states from fine analysis of electron spin resonance spectra in organic transistors.

PubMed

Matsui, Hiroyuki; Mishchenko, Andrei S; Hasegawa, Tatsuo

2010-02-05

We developed a novel method for obtaining the distribution of trapped carriers over their degree of localization in organic transistors, based on the fine analysis of electron spin resonance spectra at low enough temperatures where all carriers are localized. To apply the method to pentacene thin-film transistors, we proved through continuous wave saturation experiments that all carriers are localized at below 50 K. We analyzed the spectra at 20 K and found that the major groups of traps comprise localized states having wave functions spanning around 1.5 and 5 molecules and a continuous distribution of states with spatial extent in the range between 6 and 20 molecules.

Strong spin-photon coupling in silicon

NASA Astrophysics Data System (ADS)

Samkharadze, N.; Zheng, G.; Kalhor, N.; Brousse, D.; Sammak, A.; Mendes, U. C.; Blais, A.; Scappucci, G.; Vandersypen, L. M. K.

2018-03-01

Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot–based spin qubit registers.

Effect of Freezing Conditions on Distances and Their Distributions Derived from Double Electron Electron Resonance (DEER): A Study of Doubly-Spin-Labeled T4 Lysozyme

PubMed Central

Georgieva, Elka R.; Roy, Aritro S.; Grigoryants, Vladimir M.; Borbat, Petr P.; Earle, Keith A.; Scholes, Charles P.; Freed, Jack H.

2012-01-01

Pulsed dipolar ESR spectroscopy, DEER and DQC, require frozen samples. An important issue in the biological application of this technique is how the freezing rate and concentration of cryoprotectant could possibly affect the conformation of biomacromolecule and/or spin-label. We studied in detail the effect of these experimental variables on the distance distributions obtained by DEER from a series of doubly spin-labeled T4 lysozyme mutants. We found that the rate of sample freezing affects mainly the ensemble of spin-label rotamers, but the distance maxima remain essentially unchanged. This suggests that proteins frozen in a regular manner in liquid nitrogen faithfully maintain the distance-dependent structural properties in solution. We compared the results from rapidly freeze-quenched (≤100 μs) samples to those from commonly shock-frozen (slow freeze, 1s or longer) samples. For all the mutants studied we obtained inter-spin distance distributions, which were broader for rapidly frozen samples than for slowly frozen ones. We infer that rapid freezing trapped a larger ensemble of spin label rotamers; whereas, on the time-scale of slower freezing the protein and spin-label achieve a population showing fewer low-energy conformers. We used glycerol as a cryoprotectant in concentrations of 10% and 30% by weight. With 10% glycerol and slow freezing, we observed an increased slope of background signals, which in DEER is related to increased local spin concentration, in this case due to insufficient solvent vitrification, and therefore protein aggregation. This effect was considerably suppressed in slowly frozen samples containing 30% glycerol and rapidly frozen samples containing 10% glycerol. The assignment of bimodal distributions to tether rotamers as opposed to protein conformations is aided by comparing results using MTSL and 4-Bromo MTSL spin-labels. The latter usually produce narrower distance distributions. PMID:22341208

Preliminary studies on the activities of spin traps as scavengers of free radicals

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

Ogunbiyi, P.O.; Washington, I.

1991-03-15

The spin trapping agents, N-t-Butyl-a-phenyl-nitrone (PBN) and 5,5-Dimethyl-1-pyroline-N-oxide (DMPO) have been used to investigate the primary free radicals involved in various tissue injuries. Also, PBN and DMPO can provide some protection against free radical-induced lung injuries. However, their therapeutic potentials as free radical scavengers remained unexamined. In this study, the effects of PBN and DMPO on guinea pig lung microsomal lipid peroxidation were investigated using thiobarbituric acid-reactive substance assay. Superoxide anions (O{sup 2}{minus}) were generated in an enzymatic and a non-enzymatic system. PBN and DMPO each, significantly inhibited NADPH-stimulated lipid peroxidation irrespective of the presence of Fe{sup 3+}. Cytochrome cmore » reduction by the enzymatic and nitro blue tetrazolium reduction by the non-enzymatic O{sup 2}{minus} generating systems were both inhibited by PBN and DMPO as well as superoxide dismutase and dimethyl sulfoxide when compared with the controls. The spin traps exhibited lower potencies in these systems than the reference compounds, SOD and DMSO, which are well established as O{sup 2}{minus} and hydroxyl radical scavengers respectively. Results demonstrate the free radical scavenging properties of PBN and DMPO. This is an indication of their possible usefulness as antioxidants.« less

Mobile bound states of Rydberg excitations in a lattice

NASA Astrophysics Data System (ADS)

Letscher, Fabian; Petrosyan, David

2018-04-01

Spin-lattice models play a central role in the studies of quantum magnetism and nonequilibrium dynamics of spin excitations—-magnons. We show that a spin lattice with strong nearest-neighbor interactions and tunable long-range hopping of excitations can be realized by a regular array of laser-driven atoms, with an excited Rydberg state representing the spin-up state and a Rydberg-dressed ground state corresponding to the spin-down state. We find exotic interaction-bound states of magnons that propagate in the lattice via the combination of resonant two-site hopping and nonresonant second-order hopping processes. Arrays of trapped Rydberg-dressed atoms can thus serve as a flexible platform to simulate and study fundamental few-body dynamics in spin lattices.

Alleviation effect of arbutin on oxidative stress generated through tyrosinase reaction with l-tyrosine and l-DOPA

PubMed Central

2014-01-01

Background Hydroxyl radical that has the highest reactivity among reactive oxygen species (ROS) is generated through l-tyrosine-tyrosinase reaction. Thus, the melanogenesis might induce oxidative stress in the skin. Arbutin (p-hydroxyphenyl-β-d-glucopyranoside), a well-known tyrosinase inhibitor has been widely used for the purpose of skin whitening. The aim of the present study was to examine if arbutin could suppress the hydroxyl radical generation via tyrosinase reaction with its substrates, l-tyrosine and l-DOPA. Results The hydroxyl radical, which was determined by an electron spin resonance-spin trapping technique, was generated by the addition of not only l-tyrosine but l-DOPA to tyrosinase in a concentration dependent manner. Arbutin could inhibit the hydroxyl radical generation in the both reactions. Conclusion It is presumed that arbutin could alleviate oxidative stress derived from the melanogenic pathway in the skin in addition to its function as a whitening agent in cosmetics. PMID:25297374

All-optical quantum fluid spin beam splitter

NASA Astrophysics Data System (ADS)

Askitopoulos, A.; Nalitov, A. V.; Sedov, E. S.; Pickup, L.; Cherotchenko, E. D.; Hatzopoulos, Z.; Savvidis, P. G.; Kavokin, A. V.; Lagoudakis, P. G.

2018-06-01

We investigate the spin behavior of the first excited state of a polariton condensate in an optical trap by means of polarization resolved spectroscopy. The interplay between the repulsive polariton interactions and the gain saturation results in a nontrivial spontaneous switching between the two quasidegenerate spatial modes of the polariton condensate. As a result, the polarization pattern of the emitted light dramatically changes. Successful harnessing of this effect can lead to a spin-demultiplexing device for polariton-based optical integrated circuits.

Thermodynamic properties of Fermi gases in states with defined many-body spins

NASA Astrophysics Data System (ADS)

Yurovsky, Vladimir

2016-05-01

Zero-range interactions in cold spin- 1 / 2 Fermi gases can be described by single interaction strength, since collisions of atoms in the same spin state are forbidden by the Pauli principle. In a spin-independent trap potential (even in the presence of a homogeneous spin-dependent external field), the gas can persist in a state with the given many-body spin, since the spin operator commutes with the Hamiltonian. Spin and spatial degrees of freedom in such systems are separated, and the spin and spatial wavefunctions form non-Abelian irreducible representations of the symmetric group, unless the total spin is S = N / 2 for N atoms (see). Although the total wavefunction, being a linear combination of products of the spin and spatial functions, is permutation-antisymmetric, the non-Abelian permutation symmetry is disclosed in the matrix elements and, as demonstrated here, in thermodynamic properties. The effects include modification of the specific heat and compressibility of the gas.

Measurement of the magnetic interaction between two bound electrons of two separate ions.

PubMed

Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee

2014-06-19

Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two (88)Sr(+) ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d(-3.0(4)) distance dependence for the coupling, consistent with the inverse-cube law.

SU(N ) fermions in a one-dimensional harmonic trap

NASA Astrophysics Data System (ADS)

Laird, E. K.; Shi, Z.-Y.; Parish, M. M.; Levinsen, J.

2017-09-01

We conduct a theoretical study of SU (N ) fermions confined by a one-dimensional harmonic potential. First, we introduce a numerical approach for solving the trapped interacting few-body problem, by which one may obtain accurate energy spectra across the full range of interaction strengths. In the strong-coupling limit, we map the SU (N ) Hamiltonian to a spin-chain model. We then show that an existing, extremely accurate ansatz—derived for a Heisenberg SU(2) spin chain—is extendable to these N -component systems. Lastly, we consider balanced SU (N ) Fermi gases that have an equal number of particles in each spin state for N =2 ,3 ,4 . In the weak- and strong-coupling regimes, we find that the ground-state energies rapidly converge to their expected values in the thermodynamic limit with increasing atom number. This suggests that the many-body energetics of N -component fermions may be accurately inferred from the corresponding few-body systems of N distinguishable particles.

Spin-Orbit Interactions and Quantum Spin Dynamics in Cold Ion-Atom Collisions

NASA Astrophysics Data System (ADS)

Tscherbul, Timur V.; Brumer, Paul; Buchachenko, Alexei A.

2016-09-01

We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb+ -Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-order spin-orbit (SO) interaction as the dominant source of hyperfine relaxation in cold Yb+ -Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb+ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T-0.3 temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb+ -Li should be used to minimize hyperfine relaxation and decoherence of trapped ions in ultracold atomic gases.

Some dinophycean red tide plankton species generate a superoxide scavenging substance.

PubMed

Sato, Emiko; Niwano, Yoshimi; Matsuyama, Yukihiko; Kim, Daekyung; Nakashima, Takuji; Oda, Tatsuya; Kohno, Masahiro

2007-03-01

Recent studies indicate that some raphidophycean red tide flagellates produce substances able to scavenge superoxide, whereas there have been no reports on superoxide scavenger production by dinophycean red tide flagellates. In this study, we examined the superoxide-scavenging activity of aqueous extracts from dinophycean red tide flagellates, Gymnodinium spp., Scrippsiella trochoidea, and Karenia sp., by a luminol analog L-012-dependent chemiluminescence (CL) method and an electron spin resonance (ESR)-spin trapping method, and compared the activity to that of raphidophycean red tide flagellates, Chattonella spp., Heterosigma akashiwo, and Fibrocapsa japonica. In the experiment applying the L-012-dependent CL method, only the aqueous extracts from raphidophycean red tide flagellates showed superoxide-scavenging activity. On the other hand, applying the ESR-spin trapping method, we found that the aqueous extracts from dinophycean red tide flagellates also showed superoxide-scavenging activity. This is the first report on the production of a superoxide-scavenger by dinophycean red tide flagellates.

To perform a gyro test of general relativity in a satellite and develop associated control technology

NASA Technical Reports Server (NTRS)

Fairbank, W. M.; Everitt, C. W. F.; Debra, D. B.

1974-01-01

Performance tests of gyroscope operations and gyroscope readout equipment are discussed. The gyroscope was tested for 400 hours at liquid helium temperatures with spin speeds up to 30 Hz. Readout by observing trapped magnetic flux in the spinning rotor with a sensitive magnetometer was accomplished. Application of the gyroscope to space probes and shuttle vehicles.

Disordered Quantum Gases and Spin-Dependent Lattices

DTIC Science & Technology

2013-07-07

regarding the role of disorder in many-particle quantum systems, such as superconductors and electronic solids. These issues are of great technological...REPORT Disordered Quantum Gases and Spin-Dependent Lattices 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: This grant supported the first realization of...the disordered Bose-Hubbard models using ultra-cold atoms trapped in a disordered optical lattice. Several critical questions regarding this crucial

Oxidative stress studies of six Ti02 and two Ce02 nanomaterials: Immune-spin trapping results with DNA

EPA Science Inventory

Six Ti02 and two Ce02 nanomaterials with dry sizes ranging from 6 to 410 nm were tested for their ability to cause DNA centered free radicals in vitro in the concentration range of 10 to 3,000 ug/ml. All eight of the nanomaterials significantly increased the adduction of the spin...

Ultrafast entanglement of trapped ions

NASA Astrophysics Data System (ADS)

Neyenhuis, Brian; Johnson, Kale; Mizrahi, Jonathan; Wong-Campos, David; Monroe, Christopher

2014-05-01

We have demonstrated ultrafast spin-motion entanglement of a single atomic ion using a short train of intense laser pulses. This pulse train gives the ion a spin-dependent kick where each spin state receives a discrete momentum kick in opposite directions. Using a series of these spin-dependent kicks we can realize a two qubit gate. In contrast to gates using spectroscopically resolved motional sidebands, these gates may be performed faster than the trap oscillation period, making them potentially less sensitive to noise. Additionally this gate is temperature insensitive and does not require the ions to be cooled to the Lamb-Dicke limit. We show that multiple kicks can be strung together to create a ``Schrodinger cat'' like state, where the large separation between the two parts of the wavepacket allow us to accumulate the phase shift necessary for a gate in a shorter amount of time. We will present a realistic pulse scheme for a two ion gate, and our progress towards its realization. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI.

Spin-1 Dirac-Weyl fermions protected by bipartite symmetry

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

Lin, Zeren; School of Physics, Peking University, Beijing 100871; Liu, Zhirong, E-mail: LiuZhiRong@pku.edu.cn

2015-12-07

We propose that bipartite symmetry allows spin-1 Dirac-Weyl points, a generalization of the spin-1/2 Dirac points in graphene, to appear as topologically protected at the Fermi level. In this spirit, we provide methodology to construct spin-1 Dirac-Weyl points of this kind in a given 2D space group and get the classification of the known spin-1 systems in the literature. We also apply the workflow to predict two new systems, P3m1-9 and P31m-15, to possess spin-1 at K/K′ in the Brillouin zone of hexagonal lattice. Their stability under various strains is investigated and compared with that of T{sub 3}, an extensivelymore » studied model of ultracold atoms trapped in optical lattice with spin-1 also at K/K′.« less

Appearance of Keplerian discs orbiting Kerr superspinars

NASA Astrophysics Data System (ADS)

Stuchlík, Zdeněk; Schee, Jan

2010-11-01

We study optical phenomena related to the appearance of Keplerian accretion discs orbiting Kerr superspinars predicted by string theory. The superspinar exterior is described by standard Kerr naked singularity geometry breaking the black hole limit on the internal angular momentum (spin). We construct local photon escape cones for a variety of orbiting sources that enable us to determine the superspinars silhouette in the case of distant observers. We show that the superspinar silhouette depends strongly on the assumed edge where the external Kerr spacetime is joined to the internal spacetime governed by string theory and significantly differs from the black hole silhouette. The appearance of the accretion disc is strongly dependent on the value of the superspinar spin in both their shape and frequency shift profile. Apparent extension of the disc grows significantly with the growing spin, while the frequency shift grows with the descending spin. This behaviour differs substantially from the appearance of discs orbiting black holes enabling thus, at least in principle, to distinguish clearly the Kerr superspinars and black holes. In vicinity of a Kerr superspinar the non-escaped photons have to be separated to those captured by the superspinar and those being trapped in its strong gravitational field leading to self-illumination of the disc that could even influence its structure and cause self-reflection effect of radiation of the disc. The amount of trapped photons grows with descending superspinar spin. We thus can expect significant self-illumination effects in the field of Kerr superspinars with near-extreme spin a ~ 1.

Ferroelectric nanotraps for polar molecules

NASA Astrophysics Data System (ADS)

Dutta, Omjyoti; Giedke, G.

2018-02-01

We propose and analyze an electrostatic-optical nanoscale trap for cold diatomic polar molecules. The main ingredient of our proposal is a square array of ferroelectric nanorods with alternating polarization. We show that, in contrast to electrostatic traps using the linear Stark effect, a quadratic Stark potential supports long-lived trapped states. The molecules are kept at a fixed height from the nanorods by a standing-wave optical dipole trap. For the molecules and materials considered, we find nanotraps with trap frequency up to 1 MHz, ground-state width ˜20 nm with lattice periodicity of ˜200 nm . Analyzing the loss mechanisms due to nonadiabaticity, surface-induced radiative transitions, and laser-induced transitions, we show the existence of trapped states with lifetime ˜1 s , competitive with current traps created via optical mechanisms. As an application we extend our discussion to a one-dimensional (1D) array of nanotraps to simulate a long-range spin Hamiltonian in our structure.

Vortex creation during magnetic trap manipulations of spinor Bose-Einstein condensates

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

Itin, A. P.; Space Research Institute, RAS, Moscow; Morishita, T.

2006-06-15

We investigate several mechanisms of vortex creation during splitting of a spinor Bose-Einstein condensate (BEC) in a magnetic double-well trap controlled by a pair of current carrying wires and bias magnetic fields. Our study is motivated by a recent MIT experiment on splitting BECs with a similar trap [Y. Shin et al., Phys. Rev. A 72, 021604 (2005)], where an unexpected fork-like structure appeared in the interference fringes indicating the presence of a singly quantized vortex in one of the interfering condensates. It is well known that in a spin-1 BEC in a quadrupole trap, a doubly quantized vortex ismore » topologically produced by a 'slow' reversal of bias magnetic field B{sub z}. Since in the experiment a doubly quantized vortex had never been seen, Shin et al. ruled out the topological mechanism and concentrated on the nonadiabatic mechanical mechanism for explanation of the vortex creation. We find, however, that in the magnetic trap considered both mechanisms are possible: singly quantized vortices can be formed in a spin-1 BEC topologically (for example, during the magnetic field switching-off process). We therefore provide a possible alternative explanation for the interference patterns observed in the experiment. We also present a numerical example of creation of singly quantized vortices due to 'fast' splitting; i.e., by a dynamical (nonadiabatic) mechanism.« less

Soliton solution for the spin current in a ferromagnetic nanowire.

PubMed

Li, Zai-Dong; Li, Qiu-Yan; Li, Lu; Liu, W M

2007-08-01

We investigate the interaction of a periodic solution and a one-soliton solution for the spin-polarized current in a uniaxial ferromagnetic nanowire. The amplitude and wave number of the periodic solution for the spin current give different contributions to the width, velocity, and amplitude of the soliton. Moreover, we found that the soliton can be trapped only in space with proper conditions. Finally, we analyze the modulation instability and discuss dark solitary wave propagation for a spin current on the background of a periodic solution. In some special cases, the solution can be expressed as the linear combination of the periodic and soliton solutions.

First Measurement of the Atomic Electric Dipole Moment of Ra 225

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

Parker, R. H.; Dietrich, M. R.; Kalita, M. R.

The radioactive radium-225 (Ra-225) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, Ra-225 is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of Ra-225 atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of vertical bar d(Ra-225)vertical bar < 5.0 x 10(-22) e cm (95% confidence).

Determination of P3HT Trap Site Energies by Thermally Stimulated Current

NASA Astrophysics Data System (ADS)

Souza, J. F. P.; Serbena, J. P. M.; Kowalski, E. L.; Akcelrud, L. C.

2018-02-01

The thermal, electrical and morphological characterization of poly(3-hexylthiophene-2,5diyl) (P3HT) is presented and discussed. Thermal analyses revealed high glass transition, melting and degradation temperatures, indicating high stability of the polymer to annealings in the range 25-200°C. Electrical measurements were performed in spin-coated devices constructed using indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) in the sandwich structure ITO/PEDOT:PSS/P3HT/Al. The devices were thermally treated at 25°C, 100°C, 150°C, and 200°C prior to the measurements. Characteristic curves of current density versus voltage showed that the injection of charge carriers is governed by tunneling at high electric fields. Hole mobility was estimated by impedance spectroscopy, showing a maximum value of 8.6 × 10-5 cm2/Vs for annealed films at 150°C. A thermally stimulated current technique was used to analyze the trap density in the P3HT and its respective energies for all devices, presenting the lowest trap density for annealed films at 150°C. Morphological features observed by atomic force microscopy showed that the 150°C thermally treated film presents the best interface condition of the four investigated annealing temperatures.

Low temperature Schottky anomalies in the specific heat of LaCoO3: Defect-stabilized finite spin states

NASA Astrophysics Data System (ADS)

He, C.; Zheng, H.; Mitchell, J. F.; Foo, M. L.; Cava, R. J.; Leighton, C.

2009-03-01

Measurement of the low temperature specific heat of LaCoO3 single crystals reveals a previously unobserved Schottky anomaly with an energy level splitting, 0.5 meV, that is associated with the first excited spin state of the Co3+ ion. These states persist well below 2 K and have a g-factor around 3.5, consistent with the high-spin spin-orbit triplet, implying the existence of a low density (approximately 0.1% of the sites) of finite-spin Co ions even in the T =0 limit. We propose that these states are trapped at defects and are consistent with the magnetic excitons observed in earlier work.

Observation of Spin Superfluidity in a Bose Gas Mixture

NASA Astrophysics Data System (ADS)

Fava, Eleonora; Bienaimé, Tom; Mordini, Carmelo; Colzi, Giacomo; Qu, Chunlei; Stringari, Sandro; Lamporesi, Giacomo; Ferrari, Gabriele

2018-04-01

The spin dynamics of a harmonically trapped Bose-Einstein condensed binary mixture of sodium atoms is experimentally investigated at finite temperature. In the collisional regime the motion of the thermal component is shown to be damped because of spin drag, while the two condensates exhibit a counterflow oscillation without friction, thereby providing direct evidence for spin superfluidity. Results are also reported in the collisionless regime where the spin components of both the condensate and thermal part oscillate without damping, their relative motion being driven by a mean-field effect. We also measure the static polarizability of the condensed and thermal parts and we find a large increase of the condensate polarizability with respect to the T =0 value, in agreement with the predictions of theory.

Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

PubMed Central

Marino, A.; Cammarata, M.; Matar, S. F.; Létard, J.-F.; Chastanet, G.; Chollet, M.; Glownia, J. M.; Lemke, H. T.; Collet, E.

2015-01-01

We combine ultrafast optical spectroscopy with femtosecond X-ray absorption to study the photo-switching dynamics of the [Fe(PM-AzA)2(NCS)2] spin-crossover molecular solid. The light-induced excited spin-state trapping process switches the molecules from low spin to high spin (HS) states on the sub-picosecond timescale. The change of the electronic state (<50 fs) induces a structural reorganization of the molecule within 160 fs. This transformation is accompanied by coherent molecular vibrations in the HS potential and especially a rapidly damped Fe-ligand breathing mode. The time-resolved studies evidence a delayed activation of coherent optical phonons of the lattice surrounding the photoexcited molecules. PMID:26798836

Orbit-induced localized spin angular momentum in strong focusing of optical vectorial vortex beams

NASA Astrophysics Data System (ADS)

Li, Manman; Cai, Yanan; Yan, Shaohui; Liang, Yansheng; Zhang, Peng; Yao, Baoli

2018-05-01

Light beams may carry optical spin or orbital angular momentum, or both. The spin and orbital parts manifest themselves by the ellipticity of the state of polarization and the vortex structure of phase of light beams, separately. Optical spin and orbit interaction, arising from the interaction between the polarization and the spatial structure of light beams, has attracted enormous interest recently. The optical spin-to-orbital angular momentum conversion under strong focusing is well known, while the converse process, orbital-to-spin conversion, has not been reported so far. In this paper, we predict in theory that the orbital angular momentum can induce a localized spin angular momentum in strong focusing of a spin-free azimuthal polarization vortex beam. This localized longitudinal spin of the focused field can drive the trapped particle to spin around its own axis. This investigation provides a new degree of freedom for spinning particles by using a vortex phase, which may have considerable potentials in optical spin and orbit interaction, light-beam shaping, or optical manipulation.

Dissipative Quantum Control of a Spin Chain

NASA Astrophysics Data System (ADS)

Morigi, Giovanna; Eschner, Jürgen; Cormick, Cecilia; Lin, Yiheng; Leibfried, Dietrich; Wineland, David J.

2015-11-01

A protocol is discussed for preparing a spin chain in a generic many-body state in the asymptotic limit of tailored nonunitary dynamics. The dynamics require the spectral resolution of the target state, optimized coherent pulses, engineered dissipation, and feedback. As an example, we discuss the preparation of an entangled antiferromagnetic state, and argue that the procedure can be applied to chains of trapped ions or Rydberg atoms.

Single-ion quantum lock-in amplifier.

PubMed

Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Keselman, Anna; Ozeri, Roee

2011-05-05

Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor. ©2011 Macmillan Publishers Limited. All rights reserved

Quantum spin dynamics with pairwise-tunable, long-range interactions

PubMed Central

Hung, C.-L.; González-Tudela, Alejandro; Cirac, J. Ignacio; Kimble, H. J.

2016-01-01

We present a platform for the simulation of quantum magnetism with full control of interactions between pairs of spins at arbitrary distances in 1D and 2D lattices. In our scheme, two internal atomic states represent a pseudospin for atoms trapped within a photonic crystal waveguide (PCW). With the atomic transition frequency aligned inside a band gap of the PCW, virtual photons mediate coherent spin–spin interactions between lattice sites. To obtain full control of interaction coefficients at arbitrary atom–atom separations, ground-state energy shifts are introduced as a function of distance across the PCW. In conjunction with auxiliary pump fields, spin-exchange versus atom–atom separation can be engineered with arbitrary magnitude and phase, and arranged to introduce nontrivial Berry phases in the spin lattice, thus opening new avenues for realizing topological spin models. We illustrate the broad applicability of our scheme by explicit construction for several well-known spin models. PMID:27496329

Electron spin control and spin-libration coupling of a levitated nanodiamond

NASA Astrophysics Data System (ADS)

Hoang, Thai; Ma, Yue; Ahn, Jonghoon; Bang, Jaehoon; Robicheaux, Francis; Gong, Ming; Yin, Zhang-Qi; Li, Tongcang

2017-04-01

Hybrid spin-mechanical systems have great potentials in sensing, macroscopic quantum mechanics, and quantum information science. Recently, we optically levitated a nanodiamond and demonstrated electron spin control of its built-in nitrogen-vacancy (NV) centers in vacuum. We also observed the libration (torsional vibration) of a nanodiamond trapped by a linearly polarized laser beam in vacuum. We propose to achieve strong coupling between the electron spin of a NV center and the libration of a levitated nanodiamond with a uniform magnetic field. With a uniform magnetic field, multiple spins can couple to the torsional vibration at the same time. We propose to use this strong coupling to realize the Lipkin-Meshkov-Glick (LMG) model and generate rotational superposition states. This work is supported by the National Science Foundation under Grant No. 1555035-PHY.

Tunable two-dimensional arrays of single Rydberg atoms for realizing quantum Ising models

NASA Astrophysics Data System (ADS)

Labuhn, Henning; Barredo, Daniel; Ravets, Sylvain; de Léséleuc, Sylvain; Macrì, Tommaso; Lahaye, Thierry; Browaeys, Antoine

2016-06-01

Spin models are the prime example of simplified many-body Hamiltonians used to model complex, strongly correlated real-world materials. However, despite the simplified character of such models, their dynamics often cannot be simulated exactly on classical computers when the number of particles exceeds a few tens. For this reason, quantum simulation of spin Hamiltonians using the tools of atomic and molecular physics has become a very active field over the past years, using ultracold atoms or molecules in optical lattices, or trapped ions. All of these approaches have their own strengths and limitations. Here we report an alternative platform for the study of spin systems, using individual atoms trapped in tunable two-dimensional arrays of optical microtraps with arbitrary geometries, where filling fractions range from 60 to 100 per cent. When excited to high-energy Rydberg D states, the atoms undergo strong interactions whose anisotropic character opens the way to simulating exotic matter. We illustrate the versatility of our system by studying the dynamics of a quantum Ising-like spin-1/2 system in a transverse field with up to 30 spins, for a variety of geometries in one and two dimensions, and for a wide range of interaction strengths. For geometries where the anisotropy is expected to have small effects on the dynamics, we find excellent agreement with ab initio simulations of the spin-1/2 system, while for strongly anisotropic situations the multilevel structure of the D states has a measurable influence. Our findings establish arrays of single Rydberg atoms as a versatile platform for the study of quantum magnetism.

Application of the equilibrium spin technique to a typical low-wing general aviation design

NASA Technical Reports Server (NTRS)

Tischler, M. B.; Barlow, J. B.

1979-01-01

A graphical implementation of the equilibrium technique for obtaining spin modes from rotary balance data is presented. Using this technique, spin modes were computed for the NASA Low-Wing General Aviation Aircraft. The computed angles of attack are within 10 degrees of the NASA spin tunnel results. The method also provides information on the dynamic nature of spin modes. This technique offers the capability of providing a great deal of information on spin modes and recovery, using data from a single experimental installation. Such a technique could be utilized in the preliminary design phase in order to provide basic information on aircraft spin and recovery characteristics. Results, advantages and limitations of the application of this technique are discussed.

Topical treatment of oral cavity and wounded skin with a new disinfection system utilizing photolysis of hydrogen peroxide in rats.

PubMed

Yamada, Yasutomo; Mokudai, Takayuki; Nakamura, Keisuke; Hayashi, Eisei; Kawana, Yoshiko; Kanno, Taro; Sasaki, Keiichi; Niwano, Yoshimi

2012-01-01

The present study aimed to evaluate the acute locally injurious property of hydroxyl radical generation system by photolysis of H(2)O(2), which is a new disinfection system for the treatment of periodontitis developed in our laboratory. Firstly, generation of the hydroxyl radical by a test device utilizing the photolysis of H(2)O(2) was confirmed by applying an electron spin resonance (ESR)-spin trapping technique. Secondly, the bactericidal effect of the device was examined under a simulant condition in which Staphylococcus aureus suspended in 1 M H(2)O(2) was irradiated with laser light emitted from the test device, resulting in substantial reduction of the colony forming unit of the bacteria within a short time as 2 min. Finally, acute topical effect of the disinfection system on rat oral mucosa and wounded skin was evaluated by histological examination. No abnormal findings were observed in the buccal mucosal region treated three times with 1 M H(2)O(2) and irradiation. Similarly, no abnormal findings were observed during the healing of skin treated with 1 M H(2)O(2) and irradiation immediately after wounding. Since topical treatment with the novel disinfection technique utilizing the photolysis of H(2)O(2) had no detrimental effect on the oral mucosa and the healing of full thickness skin wounds in rats, it is expected that the acute locally injurious property of the disinfection technique is low.

Radiation effects in x-irradiated hydroxy compounds

NASA Astrophysics Data System (ADS)

Budzinski, Edwin E.; Potter, William R.; Box, Harold C.

1980-01-01

Radiation effects are compared in single crystals of xylitol, sorbitol, and dulcitol x-irradiated at 4.2 °K. In xylitol and dulcitol, but not in sorbitol, a primary oxidation product is identified as an alkoxy radical. ENDOR measurements detected three proton hyperfine couplings associated with the alkoxy ESR absorption, one of which is attributed to a proton three bond lengths removed from the seat of unpaired spin density. Intermolecular trapping of electrons is observed in all three crystals. ENDOR measurements were made of the hyperfine couplings between the trapped electron and the hydroxy protons forming the trap.

Tunable spin-spin interactions and entanglement of ions in separate potential wells.

PubMed

Wilson, A C; Colombe, Y; Brown, K R; Knill, E; Leibfried, D; Wineland, D J

2014-08-07

Quantum simulation--the use of one quantum system to simulate a less controllable one--may provide an understanding of the many quantum systems which cannot be modelled using classical computers. Considerable progress in control and manipulation has been achieved for various quantum systems, but one of the remaining challenges is the implementation of scalable devices. In this regard, individual ions trapped in separate tunable potential wells are promising. Here we implement the basic features of this approach and demonstrate deterministic tuning of the Coulomb interaction between two ions, independently controlling their local wells. The scheme is suitable for emulating a range of spin-spin interactions, but to characterize the performance of our set-up we select one that entangles the internal states of the two ions with a fidelity of 0.82(1) (the digit in parentheses shows the standard error of the mean). Extension of this building block to a two-dimensional network, which is possible using ion-trap microfabrication processes, may provide a new quantum simulator architecture with broad flexibility in designing and scaling the arrangement of ions and their mutual interactions. To perform useful quantum simulations, including those of condensed-matter phenomena such as the fractional quantum Hall effect, an array of tens of ions might be sufficient.

Synthesis of a metal oxide with a room-temperature photoreversible phase transition.

PubMed

Ohkoshi, Shin-Ichi; Tsunobuchi, Yoshihide; Matsuda, Tomoyuki; Hashimoto, Kazuhito; Namai, Asuka; Hakoe, Fumiyoshi; Tokoro, Hiroko

2010-07-01

Photoinduced phase-transition materials, such as chalcogenides, spin-crossover complexes, photochromic organic compounds and charge-transfer materials, are of interest because of their application to optical data storage. Here we report a photoreversible metal-semiconductor phase transition at room temperature with a unique phase of Ti(3)O(5), lambda-Ti(3)O(5). lambda-Ti(3)O(5) nanocrystals are made by the combination of reverse-micelle and sol-gel techniques. Thermodynamic analysis suggests that the photoinduced phase transition originates from a particular state of lambda-Ti(3)O(5) trapped at a thermodynamic local energy minimum. Light irradiation causes reversible switching between this trapped state (lambda-Ti(3)O(5)) and the other energy-minimum state (beta-Ti(3)O(5)), both of which are persistent phases. This is the first demonstration of a photorewritable phenomenon at room temperature in a metal oxide. lambda-Ti(3)O(5) satisfies the operation conditions required for a practical optical storage system (operational temperature, writing data by short wavelength light and the appropriate threshold laser power).

Entangling atomic spins with a Rydberg-dressed spin-flip blockade

DOE PAGES

Jau, Y. -Y.; Hankin, A. M.; Keating, T.; ...

2015-10-05

Controlling the quantum entanglement between parts of a many-body system is key to unlocking the power of quantum technologies such as quantum computation, high-precision sensing, and the simulation of many-body physics. The spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform for such applications thanks to their long coherence times and the ability to control them with magneto-optical fields. However, the creation of strong coherent coupling between spins has been challenging. In this paper, we demonstrate a strong and tunable Rydberg-dressed interaction between spins of individually trapped caesium atoms with energy shiftsmore » of order 1 MHz in units of Planck’s constant. This interaction leads to a ground-state spin-flip blockade, whereby simultaneous hyperfine spin flips of two atoms are inhibited owing to their mutual interaction. Finally, we employ this spin-flip blockade to rapidly produce single-step Bell-state entanglement between two atoms with a fidelity ≥81(2)%.« less

A sub-femtojoule electrical spin-switch based on optically trapped polariton condensates.

PubMed

Dreismann, Alexander; Ohadi, Hamid; Del Valle-Inclan Redondo, Yago; Balili, Ryan; Rubo, Yuri G; Tsintzos, Simeon I; Deligeorgis, George; Hatzopoulos, Zacharias; Savvidis, Pavlos G; Baumberg, Jeremy J

2016-10-01

Practical challenges to extrapolating Moore's law favour alternatives to electrons as information carriers. Two promising candidates are spin-based and all-optical architectures, the former offering lower energy consumption, the latter superior signal transfer down to the level of chip-interconnects. Polaritons-spinor quasi-particles composed of semiconductor excitons and microcavity photons-directly couple exciton spins and photon polarizations, combining the advantages of both approaches. However, their implementation for spintronics has been hindered because polariton spins can be manipulated only optically or by strong magnetic fields. Here we use an external electric field to directly control the spin of a polariton condensate, bias-tuning the emission polarization. The nonlinear spin dynamics offers an alternative route to switching, allowing us to realize an electrical spin-switch exhibiting ultralow switching energies below 0.5 fJ. Our results lay the foundation for development of devices based on the electro-optical control of coherent spin ensembles on a chip.

Negative-Mass Instability of the Spin and Motion of an Atomic Gas Driven by Optical Cavity Backaction

NASA Astrophysics Data System (ADS)

Kohler, Jonathan; Gerber, Justin A.; Dowd, Emma; Stamper-Kurn, Dan M.

2018-01-01

We realize a spin-orbit interaction between the collective spin precession and center-of-mass motion of a trapped ultracold atomic gas, mediated by spin- and position-dependent dispersive coupling to a driven optical cavity. The collective spin, precessing near its highest-energy state in an applied magnetic field, can be approximated as a negative-mass harmonic oscillator. When the Larmor precession and mechanical motion are nearly resonant, cavity mediated coupling leads to a negative-mass instability, driving exponential growth of a correlated mode of the hybrid system. We observe this growth imprinted on modulations of the cavity field and estimate the full covariance of the resulting two-mode state by observing its transient decay during subsequent free evolution.

EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

PubMed

Uchiyama, Hidefumi; Zhao, Qing-Li; Hassan, Mariame Ali; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Ishikawa, Kenji; Hori, Masaru; Kondo, Takashi

2015-01-01

Electron paramagnetic resonance (EPR)-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP) in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH) radicals and hydrogen (H) atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO), and phenyl N-t-butylnitrone (PBN). The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and an intracellular milieu is discussed.

EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu

PubMed Central

Uchiyama, Hidefumi; Zhao, Qing-Li; Hassan, Mariame Ali; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Ishikawa, Kenji; Hori, Masaru; Kondo, Takashi

2015-01-01

Electron paramagnetic resonance (EPR)-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP) in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH) radicals and hydrogen (H) atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO), and phenyl N-t-butylnitrone (PBN). The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and an intracellular milieu is discussed. PMID:26318000

Angular-dependent EDMR linewidth for spin-dependent space charge limited conduction in a polycrystalline pentacene

NASA Astrophysics Data System (ADS)

Fukuda, Kunito; Asakawa, Naoki

2017-08-01

Spin-dependent space charge limited carrier conduction in a Schottky barrier diode using polycrystalline p-type π-conjugated molecular pentacene is explored using multiple-frequency electrically detected magnetic resonance (EDMR) spectroscopy with a variable-angle configuration. The measured EDMR spectra are decomposed into two components derived respectively from mobile and trapped positive polarons. The linewidth of the EDMR signal for the trapped polarons increases with increasing resonance magnetic field for an in-plane configuration where the normal vector of the device substrate is perpendicular to the resonance magnetic field, while it is independent of the field for an out-of-plane configuration. This difference is consistent with the pentacene arrangement on the device substrate, where pentacene molecules exhibit a uniaxial orientation on the out-of-substrate plane. By contrast, the mobile polarons do not show anisotropic behavior with respect to the resonance magnetic field, indicating that the anisotropic effect is averaged out owing to carrier motion. These results suggest that the orientational arrangements of polycrystalline pentacene molecules in a nano thin film play a crucial role in spin-dependent electrical conduction.

Visible light-induced OH radicals in Ga2O3: an EPR study.

PubMed

Tzitrinovich, Zeev; Lipovsky, Anat; Gedanken, Aharon; Lubart, Rachel

2013-08-21

Reactive oxygen species (ROS) were found to exist in water suspensions of several metal oxide nanoparticles (NPs), such as CuO, TiO2 and ZnO. Visible light irradiation enhanced the capability of TiO2 and ZnO NPs to generate ROS, thus increasing their antibacterial effects. Because of the possible toxic effects on the host tissue it is desired to find nano-metal oxides which do not produce ROS under room light, but only upon a strong external stimulus. Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of Ga2O3 submicron-particle suspensions in water to produce reactive oxygen species with and without visible light irradiation. We found that in contrast to ZnO and TiO2 NPs, no ROS are produced by Ga2O3 under room light. Nevertheless blue light induced hydroxyl radical formation in Ga2O3. This finding might suggest that NPs of Ga2O3 could be used safely for infected skin sterilization.

Techniques for trapping, aging, and banding wintering canvasbacks

USGS Publications Warehouse

Haramis, G.M.; Derleth, E.L.; McAuley, D.G.

1982-01-01

Techniques used to trap, band, and determine age of Canvasbacks during winter on Chesapeake Bay are presented. Canvasbacks were captured with welded-wire traps baited with corn. Two trap designs were used and traps and trapping techniques are described. Ducks were dipnetted from traps and held in modified poultry crates that provided seclusion and ventilation and allowed birds to dry unsoiled. Carney's (1964) wing plumage methodology was found most efficient in determining age of Canvasbacks during large-scale bandings. This technique was rapid and was easily taught to inexperienced personnel. In contrast, the cloacal technique could be performed efficiently only by experienced and skillful banders. Band wear was observed to vary widely on individual birds and rounding of bands was recognized as an important technique in extending band life. Bands were placed upside down on the tarsus so that wear along the upper edge would be less likely to destroy band numbers. In 5 winter seasons, over 17,000 Canvasbacks were captured. Mortality rate for the program was .3%.

Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar

NASA Astrophysics Data System (ADS)

James, Oliver; von Tunzelmann, Eugénie; Franklin, Paul; Thorne, Kip S.

2015-03-01

Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this, our team at Double Negative Visual Effects, in collaboration with physicist Kip Thorne, developed a code called Double Negative Gravitational Renderer (DNGR) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering; and they differ from physicists’ image-generation techniques (which generally rely on individual light rays rather than ray bundles), and also differ from techniques previously used in the film industry’s CGI community. This paper has four purposes: (i) to describe DNGR for physicists and CGI practitioners, who may find interesting and useful some of our unconventional techniques. (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies; we focus on the shapes, sizes and influence of caustics and critical curves, the creation and annihilation of stellar images, the pattern of multiple images, and the influence of almost-trapped light rays, and we find similar results to the more familiar case of a camera far from the hole. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie Interstellar, were generated with DNGR—including, especially, the influences of (a) colour changes due to doppler and gravitational frequency shifts, (b) intensity changes due to the frequency shifts, (c) simulated camera lens flare, and (d) decisions that the film makers made about these influences and about the Gargantua’s spin, with the goal of producing images understandable for a mass audience. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting.

Electron spin control of optically levitated nanodiamonds in vacuum.

PubMed

Hoang, Thai M; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

2016-07-19

Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

Electron spin control of optically levitated nanodiamonds in vacuum

NASA Astrophysics Data System (ADS)

Hoang, Thai M.; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

2016-07-01

Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

Electron spin resonance of gamma-irradiated poly/ethylene 2,6-naphthalene dicarboxylate/.

NASA Technical Reports Server (NTRS)

Rogowski, R. S.; Pezdirtz, G. F.

1971-01-01

The two types of radicals trapped in gamma-irradiated PEN 2,6 are identified by ESR as - O - CH - CH2 - O - (radical I) and a radical located on the naphthalene ring (radical II). The concentrations of the radicals in the gross polyer are 10 to 20% of I and 80 to 90% of II. Similar trapped radicals are established in beta-irradiated PET, a structurally related polymer.

Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions

NASA Astrophysics Data System (ADS)

Cairncross, William B.; Gresh, Daniel N.; Grau, Matt; Cossel, Kevin C.; Roussy, Tanya S.; Ni, Yiqi; Zhou, Yan; Ye, Jun; Cornell, Eric A.

2017-10-01

We describe the first precision measurement of the electron's electric dipole moment (de) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on 180Hf 19F+ in its metastable 3Δ1 electronic state, we obtain de=(0.9 ±7. 7stat±1. 7syst)×10-29 e cm , resulting in an upper bound of |de|<1.3 ×10-28 e cm (90% confidence). Our result provides independent confirmation of the current upper bound of |de|<9.4 ×10-29 e cm [J. Baron et al., New J. Phys. 19, 073029 (2017), 10.1088/1367-2630/aa708e], and offers the potential to improve on this limit in the near future.

Unconventional Bose—Einstein Condensations from Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Wu, Cong-Jun; Ian, Mondragon-Shem; Zhou, Xiang-Fa

2011-09-01

According to the “no-node" theorem, the many-body ground state wavefunctions of conventional Bose—Einstein condensations (BEC) are positive-definite, thus time-reversal symmetry cannot be spontaneously broken. We find that multi-component bosons with spin-orbit coupling provide an unconventional type of BECs beyond this paradigm. We focus on a subtle case of isotropic Rashba spin-orbit coupling and the spin-independent interaction. In the limit of the weak confining potential, the condensate wavefunctions are frustrated at the Hartree—Fock level due to the degeneracy of the Rashba ring. Quantum zero-point energy selects the spin-spiral type condensate through the “order-from-disorder" mechanism. In a strong harmonic confining trap, the condensate spontaneously generates a half-quantum vortex combined with the skyrmion type of spin texture. In both cases, time-reversal symmetry is spontaneously broken. These phenomena can be realized in both cold atom systems with artificial spin-orbit couplings generated from atom-laser interactions and exciton condensates in semi-conductor systems.

An evaluation of western bean cutworm pheromone trapping techniques (Lepidoptera: Noctuidae) in a corn and soybean agroecosystem.

PubMed

Dorhout, David L; Rice, Marlin E

2008-04-01

Pheromone traps can be used to monitor for adult western bean cutworms, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), and for the timing of field scouting. Understanding the effect that different trapping techniques have on adult captures could help corn (Zea mays L.) producers make better pest management decisions. Several approaches to trapping adults were evaluated in 2005 and 2006 by using two different pheromone traps (sticky wing and jug traps) in two different environments (corn or corn/soybean [Glycine max (L.) Merr.] at three different heights (0.6, 1.2, and 1.8 m). There was no significant difference in the trap catches by trap type in either 2005 or 2006. There were significantly more adults captured in traps placed between two cornfields than traps placed between corn/soybean fields during both years. Trap height also was significant, with the traps at 1.2 and 1.8 m catching more moths than traps at 0.6 m during both years. These results show that trapping techniques do affect trap catches and that either trap type placed between two cornfields at either 1.2 or 1.8 m above the ground will maximize trap catches.

On-chip spin-controlled orbital angular momentum directional coupling

NASA Astrophysics Data System (ADS)

Xie, Zhenwei; Lei, Ting; Si, Guangyuan; Du, Luping; Lin, Jiao; Min, Changjun; Yuan, Xiaocong

2018-01-01

Optical vortex beams have many potential applications in the particle trapping, quantum encoding, optical orbital angular momentum (OAM) communications and interconnects. However, the on-chip compact OAM detection is still a big challenge. Based on a holographic configuration and a spin-dependent structure design, we propose and demonstrate an on-chip spin-controlled OAM-mode directional coupler, which can couple the OAM signal to different directions due to its topological charge. While the directional coupling function can be switched on/off by altering the spin of incident beam. Both simulation and experimental measurements verify the validity of the proposed approach. This work would benefit the on-chip OAM devices for optical communications and high dimensional quantum coding/decoding in the future.

Bose-Fermi mapping and a multibranch spin-chain model for strongly interacting quantum gases in one dimension: Dynamics and collective excitations

NASA Astrophysics Data System (ADS)

Yang, Li; Pu, Han

2016-09-01

We show that the wave function in one spatial sector x1

Hartree-Fock investigation of muon trapping in the chemical ferromagnet 4-(/p-chlorobenzylideneamino)-TEMPO

NASA Astrophysics Data System (ADS)

Jeong, Junho; Briere, Tina M.; Sahoo, N.; Das, T. P.; Ohira, Seiko; Nishiyama, K.; Nagamine, K.

2000-08-01

First-principles unrestricted Hartree-Fock theory is used to obtain the trapping sites for muon and muonium in ferromagnetic p-Cl-Ph-CHN-TEMPO (4-( p-chlorobenzylideneamino)- 2,2,6,6-tetramethylpiperidin-1-yloxyl) and the hyperfine interaction tensors for these sites. Using the calculated hyperfine interactions to fit the two experimentally observed muon spin rotation frequencies, it has been concluded that the two most likely candidates for explaining the experimental data are a muon trapped at the chlorine site and a singlet muonium state at the radical oxygen. The direction of the easy axis is also determined.

Direct Optical Measurement of Vorticity in Fluid Flow

DTIC Science & Technology

2015-12-11

was later employed to measure the angular velocity of a microparticle trapped and spinning in an optical trap [7]. II. Objectives We believe it...known theoretically. Two sets of experiments are presented. In the first, the signal from a group of 6 μm microparticles is integrated to obtain the...vorticity is known precisely. In one experiment measurements with a group of 6 μm microparticles is used to obtain the average fluid rotation rate about the

Microfabricated Waveguide Atom Traps.

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

Jau, Yuan-Yu

A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading coldmore » atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.« less

Identifying the distinct features of geometric structures for hole trapping to generate radicals on rutile TiO₂(110) in photooxidation using density functional theory calculations with hybrid functional.

PubMed

Wang, Dong; Wang, Haifeng; Hu, P

2015-01-21

Using density functional theory calculations with HSE 06 functional, we obtained the structures of spin-polarized radicals on rutile TiO2(110), which is crucial to understand the photooxidation at the atomic level, and further calculate the thermodynamic stabilities of these radicals. By analyzing the results, we identify the structural features for hole trapping in the system, and reveal the mutual effects among the geometric structures, the energy levels of trapped hole states and their hole trapping capacities. Furthermore, the results from HSE 06 functional are compared to those from DFT + U and the stability trend of radicals against the number of slabs is tested. The effect of trapped holes on two important steps of the oxygen evolution reaction, i.e. water dissociation and the oxygen removal, is investigated and discussed.

Trapped modes in a non-axisymmetric cylindrical waveguide

NASA Astrophysics Data System (ADS)

Lyapina, A. A.; Pilipchuk, A. S.; Sadreev, A. F.

2018-05-01

We consider acoustic wave transmission in a non-axisymmetric waveguide which consists of a cylindrical resonator and two cylindrical waveguides whose axes are shifted relatively to each other by an azimuthal angle Δϕ. Under variation of the resonator's length L and fixed Δϕ we find bound states in the continuum (trapped modes) due to full destructive interference of resonant modes leaking into the waveguides. Rotation of the waveguide adds complex phases to the coupling strengths of the resonator eigenmodes with the propagating modes of the waveguides tuning Fano resonances to give rise to a wave faucet. Under variation of Δϕ with fixed resonator's length we find symmetry protected trapped modes. For Δϕ ≠ 0 these trapped modes contribute to the scattering function supporting high vortical acoustic intensity spinning inside the resonator. The waveguide rotation brings an important feature to the scattering and provides an instrument for control of acoustic transmittance and wave trapping.

Straight-line drift fences and pitfall traps

USGS Publications Warehouse

Corn, Paul Stephen

1994-01-01

Straight-line drift fences typically are short barriers (5-15 m) that direct animals traveling on the substrate surface into traps places at the ends of or beside the barriers. Traps (described below) can be pitfalls, funnel traps, or a combination of the two. Drift fences with pitfall or funnel traps and pitfall traps without fences are used commonly to inventory and monitor populations of amphibians and reptiles. For example, 9 of 17 field studies reported for management of terrestrial vertebrates (Sarzo et al. 1988) used these techniques to sample amphibians. Drift fences with pitfall traps can be used to determine species richness at a site and to detect the presence of rare species. They also can yield data on relative abundances and habitat use of selected species. Pitfall traps arrayed in a grid without fences can also be used to study the population ecology and habitat use of selected species. Population density can be estimated with this latter technique if used in conjunction with mark-recapture techniques (see Chapter 8). Drift fence arrays or pitfall grids can be left in place for long-term monitoring. In this section, I discuss the use of this technique to obtain data on amphibians away from breeding ponds. Use of drift fences and traps to monitory amphibian activity at breeding ponds is discussed in the section "Drift Fences Encircling Breeding Sits", below (technique 9). Some materials and procedures are common to both techniques. Investigators contemplating the use of drift fences and traps in any context should read both accounts.

Unraveling the enhanced photocatalytic activity and phototoxicity of ZnO/metal hybrid nanostructures from generation of reactive oxygen species and charge carriers.

PubMed

He, Weiwei; Wu, Haohao; Wamer, Wayne G; Kim, Hyun-Kyung; Zheng, Jiwen; Jia, Huimin; Zheng, Zhi; Yin, Jun-Jie

2014-09-10

An effective way for promoting photocatalytic activity of a semiconductor is deposition of noble metal nanoparticles (NPs) onto it. In this paper, we deposited Ag and Pd onto ZnO NPs to form ZnO/Ag and ZnO/Pd hybrid nanostructures. It was found that both Ag and Pd nanocomponents can greatly enhance the photocatalytic activity and phototoxicity of ZnO toward human skin cells. Using electron spin resonance spectroscopy with spin trapping and spin labeling techniques, we observed that either deposition of Ag or Pd resulted in a significant increase in photogenerated electrons and holes and production of reactive oxygen species including hydroxyl radicals, superoxide, and singlet oxygen. We compared the enhancing effects of Ag and Pd and found that Pd is more effective than Ag in promoting the generation of hydroxyl radicals and holes and the photocatalytic activity of ZnO. Conversely, Ag is more effective than Pd in enhancing electron transfer and the generation of superoxide and singlet oxygen. The mechanism underlying the differences in the effects of Ag and Pd may be related to differences in Fermi levels for Ag and Pd and band bending accompanied by effects on Schottky barriers. The results of these studies provide information valuable for designing hybrid nanomaterials having photocatalytic and photobiological activities useful for applications such as water purification and formulation of antibacterial products.

Demonstration of the production of oxygen-centered free radicals during electrolysis using E.S.R. spin-trapping techniques: effects on cardiac function in the isolated rat heart.

PubMed

Lecour, S; Baouali, A B; Maupoil, V; Chahine, R; Abadie, C; Javouhey-Donzel, A; Rochette, L; Nadeau, R

1998-03-01

The present study was designed to identify the free radicals generated during the electrolysis of the solution used to perfuse isolated rat heart Langendorff preparations. The high reactivity and very short half-life of oxygen free radicals make their detection and identification difficult. A diamagnetic organic molecule (spin trap) can be used to react with a specific radical to produce a more stable secondary radical or "spin adduct" detected by electron spin resonance (ESR). Isovolumic left ventricular systolic pressure (LVSP) and left ventricular end diastolic pressure (LVEDP) were measured by a fluid-filled latex balloon inserted into the left ventricle. The coronary flow was measured by effluent collection. Electrolysis was performed with constant currents of 0.5, 1, 1.5, 3, 5, 7.5, and 10 mA generated by a Grass stimulator and applied to the perfusion solution for 1 min. A group of experiments was done using a 1.5 mA current and a Krebs-Henseleit (K-H) solution containing free radical scavengers (superoxide dismutase (SOD): 100 IU/ml or mannitol: 50 mM). Heart function rapidly declined in hearts perfused with K-H buffer that had been electrolyzed for 1 min. The addition of mannitol (50 mM) to the perfusion solution had no effect on baseline cardiac function before electrolysis while SOD (100 IU/ml) increased the coronary flow. However, SOD was more effective than the mannitol in protecting the heart against decreased of cardiac function, 5 min after the end of electrolysis. Samples of the K-H medium subjected to electrolysis were collected in cuvettes containing a final concentration of 125 mM 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and analyzed by spectroscopy. The ESR spectrum consisted of a quartet signal (hyperfine couplings aN = aH = 14.9 G) originating from the hydroxyl adduct signal, DMPO-OH. The intensity of the DMPO-OH signal remained stable during the 60 s of electrolysis and the quantity of free radicals induced by electrolysis was directly proportional to the intensity of the current. The addition of mannitol and SOD to the perfusate scavenged the hydroxyl radicals present in the solution, suggesting that both hydroxyl and superoxide radicals were formed during electrolysis.

Superfluid-Mott insulator transition of spin-1 bosons in an optical lattice

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

Tsuchiya, Shunji; Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7; Kurihara, Susumu

2004-10-01

We study the superfluid-Mott insulator (SF-MI) transition of spin-1 bosons interacting antiferromagnetically in an optical lattice. Starting from a Bose-Hubbard tight-binding model for spin-1 bosons, we obtain the zero-temperature phase diagram by a mean-field approximation. We find that the MI phase with an even number of atoms per site is a spin singlet state, while the MI phase with an odd number of atoms per site has spin 1 at each site in the limit of t=0, where t is the hopping matrix element. We also show that the superfluid phase is a polar state as in the case formore » a spin-1 Bose condensate in a harmonic trap. It is found that the MI phase is strongly stabilized against the SF-MI transition when the number of atoms per site is even, due to the formation of singlet pairs. We derive the effective spin Hamiltonian for the MI phase with one atom per site and briefly discuss the spin order in the MI phase.« less

Density functional of a two-dimensional gas of dipolar atoms: Thomas-Fermi-Dirac treatment

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

Fang, Bess; Englert, Berthold-Georg

We derive the density functional for the ground-state energy of a two-dimensional, spin-polarized gas of neutral fermionic atoms with magnetic-dipole interaction, in the Thomas-Fermi-Dirac approximation. For many atoms in a harmonic trap, we give analytical solutions for the single-particle spatial density and the ground-state energy, in dependence on the interaction strength, and we discuss the weak-interaction limit that is relevant for experiments. We then lift the restriction of full spin polarization and account for a time-independent inhomogeneous external magnetic field. The field strength necessary to ensure full spin polarization is derived.

Dynamic trapping near a quantum critical point

NASA Astrophysics Data System (ADS)

Kolodrubetz, Michael; Katz, Emanuel; Polkovnikov, Anatoli

2015-02-01

The study of dynamics in closed quantum systems has been revitalized by the emergence of experimental systems that are well-isolated from their environment. In this paper, we consider the closed-system dynamics of an archetypal model: spins driven across a second-order quantum critical point, which are traditionally described by the Kibble-Zurek mechanism. Imbuing the driving field with Newtonian dynamics, we find that the full closed system exhibits a robust new phenomenon—dynamic critical trapping—in which the system is self-trapped near the critical point due to efficient absorption of field kinetic energy by heating the quantum spins. We quantify limits in which this phenomenon can be observed and generalize these results by developing a Kibble-Zurek scaling theory that incorporates the dynamic field. Our findings can potentially be interesting in the context of early universe physics, where the role of the driving field is played by the inflaton or a modulus field.

Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions.

PubMed

Cairncross, William B; Gresh, Daniel N; Grau, Matt; Cossel, Kevin C; Roussy, Tanya S; Ni, Yiqi; Zhou, Yan; Ye, Jun; Cornell, Eric A

2017-10-13

We describe the first precision measurement of the electron's electric dipole moment (d_{e}) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on ^{180}Hf^{19}F^{+} in its metastable ^{3}Δ_{1} electronic state, we obtain d_{e}=(0.9±7.7_{stat}±1.7_{syst})×10^{-29}  e cm, resulting in an upper bound of |d_{e}|<1.3×10^{-28}  e cm (90% confidence). Our result provides independent confirmation of the current upper bound of |d_{e}|<9.4×10^{-29}  e cm [J. Baron et al., New J. Phys. 19, 073029 (2017)NJOPFM1367-263010.1088/1367-2630/aa708e], and offers the potential to improve on this limit in the near future.

A photon-driven micromotor can direct nerve fibre growth

NASA Astrophysics Data System (ADS)

Wu, Tao; Nieminen, Timo A.; Mohanty, Samarendra; Miotke, Jill; Meyer, Ronald L.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

2012-01-01

Axonal path-finding is important in the development of the nervous system, nerve repair and nerve regeneration. The behaviour of the growth cone at the tip of the growing axon determines the direction of axonal growth and migration. We have developed an optical-based system to control the direction of growth of individual axons (nerve fibres) using laser-driven spinning birefringent spheres. One or two optical traps position birefringent beads adjacent to growth cones of cultured goldfish retinal ganglion cell axons. Circularly polarized light with angular momentum causes the trapped bead to spin. This creates a localized microfluidic flow generating an estimated 0.17 pN shear force against the growth cone that turns in response to the shear. The direction of axonal growth can be precisely manipulated by changing the rotation direction and position of this optically driven micromotor. A physical model estimating the shear force density on the axon is described.

Antioxidant activity of Sempervivum tectorum and its components.

PubMed

Sentjurc, Marjeta; Nemec, Marjana; Connor, Henry D; Abram, Veronika

2003-04-23

The antioxidant properties of components of leaf extracts of the evergreen plant, Sempervivum tectorum (ST), have been evaluated using UV irradiated liposomal systems containing the spin trap 5-(diethoxyphosphoryl)-5-methyl-pyrroline-N-oxide. Decreases in free radical activity in the liposomal systems as measured by electron paramagnetic resonance (EPR) spectroscopy demonstrate that the lipophilic ST juice components, kaempferol (KA) and kaempferol-3-glucoside (KG) contribute significantly to the antioxidant properties of the juice. EPR spectral simulation established the presence of oxygen and carbon centered free radical adducts. The mixtures with low pH, citric and malic acid, and ST juice reveal increased EPR signals from oxygen centered radicals in comparison to the control, pointing to the important role of pH in oxygen radical formation. Parallel assays that measured thiobarbituric acid related substances confirm the antioxidant effects of KA and KG and explain the results of spin trapping experiments complicated by low pH's.

Development of a syringe pump assisted dynamic headspace sampling technique for needle trap device.

PubMed

Eom, In-Yong; Niri, Vadoud H; Pawliszyn, Janusz

2008-07-04

This paper describes a new approach that combines needle trap devices (NTDs) with a dynamic headspace sampling technique (purge and trap) using a bidirectional syringe pump. The needle trap device is a 22-G stainless steel needle 3.5-in. long packed with divinylbenzene sorbent particles. The same sized needle, without packing, was used for purging purposes. We chose an aqueous mixture of benzene, toluene, ethylbenzene, and p-xylene (BTEX) and developed a sequential purge and trap (SPNT) method, in which sampling (trapping) and purging cycles were performed sequentially by the use of syringe pump with different distribution channels. In this technique, a certain volume (1 mL) of headspace was sequentially sampled using the needle trap; afterwards, the same volume of air was purged into the solution at a high flow rate. The proposed technique showed an effective extraction compared to the continuous purge and trap technique, with a minimal dilution effect. Method evaluation was also performed by obtaining the calibration graphs for aqueous BTEX solutions in the concentration range of 1-250 ng/mL. The developed technique was compared to the headspace solid-phase microextraction method for the analysis of aqueous BTEX samples. Detection limits as low as 1 ng/mL were obtained for BTEX by NTD-SPNT.

The Putative Cerean Exosphere

NASA Astrophysics Data System (ADS)

Schorghofer, Norbert; Byrne, Shane; Landis, Margaret E.; Mazarico, Erwan; Prettyman, Thomas H.; Schmidt, Britney E.; Villarreal, Michaela N.; Castillo-Rogez, Julie; Raymond, Carol A.; Russell, Christopher T.

2017-11-01

The ice-rich crust of dwarf planet 1 Ceres is the source of a tenuous water exosphere, and the behavior of this putative exosphere is investigated with model calculations. Outgassing water molecules seasonally condense around the winter pole in an optically thin layer. This seasonal cap reaches an estimated mass of at least 2× {10}3 {kg}, and the aphelion summer pole may even retain water throughout summer. If this reservoir is suddenly released by a solar energetic particle event, it would form a denser transient water exosphere. Our model calculations also explore species other than H2O. Light exospheric species escape rapidly from Ceres due to its low gravity, and hence their exospheres dissipate soon after their respective source has faded. For example, the theoretical turn-over time in a water exosphere is only 7 hr. A significant fraction of CO2 and SO2 molecules can get trapped and stored in perennially shadowed regions at the current spin axis orientation, but not at the higher spin axis tilt, leaving H2O as the only common volatile expected to accumulate in polar cold traps over long timescales. The D/H fractionation during migration to the cold traps is only about 10%.

Combined molecular MRI and immuno-spin-trapping for in vivo detection of free radicals in orthotopic mouse GL261 gliomas.

PubMed

Towner, Rheal A; Smith, Nataliya; Saunders, Debra; De Souza, Patricia Coutinho; Henry, Leah; Lupu, Florea; Silasi-Mansat, Robert; Ehrenshaft, Marilyn; Mason, Ronald P; Gomez-Mejiba, Sandra E; Ramirez, Dario C

2013-12-01

Free radicals play a major role in gliomas. By combining immuno-spin-trapping (IST) and molecular magnetic resonance imaging (mMRI), in vivo levels of free radicals were detected within mice bearing orthotopic GL261 gliomas. The nitrone spin trap DMPO (5,5-dimethyl pyrroline N-oxide) was administered prior to injection of an anti-DMPO probe (anti-DMPO antibody covalently bound to a bovine serum albumin (BSA)-Gd (gadolinium)-DTPA (diethylene triamine penta acetic acid)-biotin MRI contrast agent) to trap tumor-associated free radicals. mMRI detected the presence of anti-DMPO adducts by either a significant sustained increase (p<0.001) in MR signal intensity or a significant decrease (p<0.001) in T1 relaxation, measured as %T1 change. In vitro assessment of the anti-DMPO probe indicated a significant decrease (p<0.0001) in T1 relaxation in GL261 cells that were oxidatively stressed with hydrogen peroxide, compared to controls. The biotin moiety of the anti-DMPO probe was targeted with fluorescently-labeled streptavidin to locate the anti-DMPO probe in excised brain tissues. As a negative control a non-specific IgG antibody covalently bound to the albumin-Gd-DTPA-biotin construct was used. DMPO adducts were also confirmed in tumor tissue from animals administered DMPO, compared to non-tumor brain tissue. GL261 gliomas were found to have significantly increased malondialdehyde (MDA) protein adducts (p<0.001) and 3-nitrotyrosine (3-NT) (p<0.05) compared to normal mouse brain tissue, indicating increased oxidized lipids and proteins, respectively. Co-localization of the anti-DMPO probe with either 3-NT or 4-hydroxynonenal was also observed. This is the first report regarding the detection of in vivo levels of free radicals from a glioma model. © 2013.

[Induction of free radicals after dietary exposure by mercury contaminated rice and protective effect of coexisting selenium].

PubMed

Ji, Xiu-ling; Cheng, Jin-ping; Wang, Wen-hua; Qu, Li-ya; Zhao, Xiao-xiang; Zhuang, Hui-sheng

2006-10-01

Sprague-Dawley rats were reared by environmental mercury contaminated rice to survey the potential health risk of Wanshan mercury mining area. Electron spin resonance (ESR) was introduced to detect the species and the intensities of free radicals, using spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The results showed that the mercury-contaminated rice significantly increased the levels of free radicals and MDA in rat brain at 7 days (p < 0.05). ESR spectrums showed that the principal spin adducts resulted from the trapping of alkyl free radical (alphaH = 22.7 x 10(-4)T +/- 1.6 x 10(-4)T, alphaN = 15.5 x 10(-4)T +/- 0.5 x 10(-4)T), and hydroxyl radical. Levels of free radicals and MDA increased slowly until after 90-day exposure period (83%, 100%). Element correlation analysis showed high correlations of mercury and selenium in the brain of rat fed with Wanshan rice, suggesting that the coexisting selenium in rice exhibited antagonistic effects on both mercury accumulation and toxicity. The slight increases of free radicals in rat brain at 7, 20 and 30-day exposure periods should be related with the scavenger effect of Se.

Towards Quantum Simulations Using a Chip Ion Trap

NASA Astrophysics Data System (ADS)

Cao, Chenglin; Wright, Ken; Brennan, Daniel; Ji, Geoffrey; Monroe, Christopher

2013-05-01

We report our current experimental progress towards using chip ion traps for quantum simulation. Current progress is being made using a micro-fabricated symmetric trap from GTRI. This trap implements a novel two level design that combines the benefits of both surface traps and linear four-rod traps. The trap has 50 electrodes which allow for the fine control of the DC potential needed to create large anharmonic potentials, to join and split ion chains and to shuttle ions along the trapping axis similar to many surface traps. However this trap also has a much deeper trapping depth than conventional surface traps and improved optical access via an angled slot through the chip wide enough to accommodate higher power laser light which could cause surface charging or damage in a traditional chip trap. These advantages should allow trapping of long ion chains. We hope to use these features as the next step in increasing the size of current quantum simulations being done at Univ of Maryland, which are aimed at exploring quantum phenomena in spin systems in a regime inaccessible to classical simulation. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI. We acknowledge the GTRI team of J. Amini, K. Brown, A. Harter, F. Shaikh, R. Slusher, and C. Volin for the fabrication of the trap.

Quantum annealing for the number-partitioning problem using a tunable spin glass of ions

PubMed Central

Graß, Tobias; Raventós, David; Juliá-Díaz, Bruno; Gogolin, Christian; Lewenstein, Maciej

2016-01-01

Exploiting quantum properties to outperform classical ways of information processing is an outstanding goal of modern physics. A promising route is quantum simulation, which aims at implementing relevant and computationally hard problems in controllable quantum systems. Here we demonstrate that in a trapped ion setup, with present day technology, it is possible to realize a spin model of the Mattis-type that exhibits spin glass phases. Our method produces the glassy behaviour without the need for any disorder potential, just by controlling the detuning of the spin-phonon coupling. Applying a transverse field, the system can be used to benchmark quantum annealing strategies which aim at reaching the ground state of the spin glass starting from the paramagnetic phase. In the vicinity of a phonon resonance, the problem maps onto number partitioning, and instances which are difficult to address classically can be implemented. PMID:27230802

Quantum Stirling heat engine and refrigerator with single and coupled spin systems

NASA Astrophysics Data System (ADS)

Huang, Xiao-Li; Niu, Xin-Ya; Xiu, Xiao-Ming; Yi, Xue-Xi

2014-02-01

We study the reversible quantum Stirling cycle with a single spin or two coupled spins as the working substance. With the single spin as the working substance, we find that under certain conditions the reversed cycle of a heat engine is NOT a refrigerator, this feature holds true for a Stirling heat engine with an ion trapped in a shallow potential as its working substance. The efficiency of quantum Stirling heat engine can be higher than the efficiency of the Carnot engine, but the performance coefficient of the quantum Stirling refrigerator is always lower than its classical counterpart. With two coupled spins as the working substance, we find that a heat engine can turn to a refrigerator due to the increasing of the coupling constant, this can be explained by the properties of the isothermal line in the magnetic field-entropy plane.

Electron spin control of optically levitated nanodiamonds in vacuum

PubMed Central

Hoang, Thai M.; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

2016-01-01

Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin–optomechanical system for studying macroscopic quantum mechanics. PMID:27432560

Comparison between modelling and experimental measurements of Criegee intermediates from the ozonolysis of biogenic and anthropogenic VOCs

NASA Astrophysics Data System (ADS)

Giorio, Chiara; Campbell, Steven; Bruschi, Maurizio; Archibald, Alexander; Kalberer, Markus

2017-04-01

One of the most important reactions in the troposphere is ozonolysis of alkenes contributing to local photochemical smog and global climate change (Vereecken, 2013). Ozonolysis of alkenes occurs with a generally accepted mechanism, in which ozone adds to the double bond of alkenes forming a primary ozonide, which promptly decomposes to form a carbonyl compound and a biradical/zwitterion called Criegee intermediate (CI) (Criegee, 1975). CIs are highly reactive and short-lived and therefore their analysis represents an analytical challenge. We generated CIs in a flow tube by reacting olefinic compounds with ozone and we stabilised them with the volatile spin trap 5,5-dimethyl-pyrroline N-oxide (DMPO) prior to analysis with proton transfer reaction mass spectrometry (PTR-MS). In a recent study we unambiguously identified the structure of the CI-spin trap adducts formed in the ozonolysis of α-pinene (Giorio et al, submitted). Identification was performed and molecular structures of the adducts were determined with mass spectrometry techniques and nuclear magnetic resonance and supported by density functional theory (DFT) calculations (Giorio et al., submitted). We have now expanded the study to the ozonolysis of various biogenic alkenes, including β-pinene, limonene and methacrolein, as well as anthropogenic alkenes, including cis-2-hexene and styrene. As an example, for the ozonolysis of β-pinene both of the expected C1 and C9 CIs have been detected. These measurements indicate that the ratio between the yields of the C9 CI- and the C1 CI- DMPO adducts formed in this system is about 0.1, while theoretical estimates with the model "Master Chemical Mechanism" (MCM) 3.3.1 suggest a ratio of 0.7 (considering the stabilised CIs) (Saunders et al., 2003). This difference is likely due to different reaction rates of the two CIs with the spin trap DMPO. Similarly, for limonene, all three masses corresponding to the CIs from ozone attack to both the endo and the exo double bonds have been detected. For all the tested VOCs, experimental measurements were compared with MCM modelling results and discrepancies discussed in terms of stability of the CI-DMPO adducts derived from DFT calculations. R. Criegee, Angew. Chemie Int. Ed. English, 1975, 14, 745-752. C. Giorio, et al., J. Am. Chem. Soc., submitted. S. M. Saunders, et al., Atmos. Chem. Phys., 2003, 3, 161-180. L. Vereecken, Science, 2013 340 (6129), 154-155.

Comparison of survey techniques on detection of northern flying squirrels

USGS Publications Warehouse

Diggins, Corinne A.; Gilley, L. Michelle; Kelly, Christine A.; Ford, W. Mark

2016-01-01

The ability to detect a species is central to the success of monitoring for conservation and management purposes, especially if the species is rare or endangered. Traditional methods, such as live capture, can be labor-intensive, invasive, and produce low detection rates. Technological advances and new approaches provide opportunities to more effectively survey for species both in terms of accuracy and efficiency than previous methods. We conducted a pilot comparison study of a traditional technique (live-trapping) and 2 novel noninvasive techniques (camera-trapping and ultrasonic acoustic surveys) on detection rates of the federally endangered Carolina northern flying squirrel (Glaucomys sabrinus coloratus) in occupied habitat within the Roan Mountain Highlands of North Carolina, USA. In 2015, we established 3 5 × 5 live-trapping grids (6.5 ha) with 4 camera traps and 4 acoustic detectors systematically embedded in each grid. All 3 techniques were used simultaneously during 2 4-day survey periods. We compared techniques by assessing probability of detection (POD), latency to detection (LTD; i.e., no. of survey nights until initial detection), and survey effort. Acoustics had the greatest POD (0.37 ± 0.06 SE), followed by camera traps (0.30 ± 0.06) and live traps (0.01 ± 0.005). Acoustics had a lower LTD than camera traps (P = 0.017), where average LTD was 1.5 nights for acoustics and 3.25 nights for camera traps. Total field effort was greatest with live traps (111.9 hr) followed by acoustics (8.4 hr) and camera traps (9.6 hr), although processing and examination for data of noninvasive techniques made overall effort similar among the 3 methods. This pilot study demonstrated that both noninvasive methods were better rapid-assessment detection techniques for flying squirrels than live traps. However, determining seasonal effects between survey techniques and further development of protocols for both noninvasive techniques is necessary prior to widespread application in the region. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Potential of EPR spin-trapping to investigate in situ free radicals generation from skin allergens in reconstructed human epidermis: cumene hydroperoxide as proof of concept.

PubMed

Kuresepi, Salen; Vileno, Bertrand; Turek, Philippe; Lepoittevin, Jean-Pierre; Giménez-Arnau, Elena

2018-02-01

The first step in the development of skin sensitisation to a chemical, and in the elicitation of further allergic contact dermatitis (ACD), is the binding of the allergen to skin proteins after penetrating into the epidermis. The so-formed antigenic adduct is then recognised by the immune system as foreign to the body. Sensitising organic hydroperoxides derived from autoxidation of natural terpenes are believed to form antigens through radical-mediated mechanisms, although this has not yet been established. So far, in vitro investigations on reactive radical intermediates derived from these skin sensitisers have been conducted in solution, yet with experimental conditions being far away from real-life sensitisation. Herein, we report for the first time, the potential use of EPR spin-trapping to study the in situ generation of free radicals derived from cumene hydroperoxide CumOOH in a 3D reconstructed human epidermis (RHE) model, thus much closer to what may happen in vivo. Among the undesirable effects associated with dermal exposure to CumOOH, it is described to cause allergic and irritant dermatitis, being reported as a significant sensitiser. We considered exploiting the usage of spin-trap DEPMPO as an extensive view of all sort of radicals derived from CumOOH were observed all at once in solution. We showed that in the Episkin TM RHE model, both by incubating in the assay medium and by topical application, carbon radicals are mainly formed by redox reactions suggesting the key role of CumOOH-derived carbon radicals in the antigen formation process.

Toward the fourth dimension of membrane protein structure: insight into dynamics from spin-labeling EPR spectroscopy.

PubMed

McHaourab, Hassane S; Steed, P Ryan; Kazmier, Kelli

2011-11-09

Trapping membrane proteins in the confines of a crystal lattice obscures dynamic modes essential for interconversion between multiple conformations in the functional cycle. Moreover, lattice forces could conspire with detergent solubilization to stabilize a minor conformer in an ensemble thus confounding mechanistic interpretation. Spin labeling in conjunction with electron paramagnetic resonance (EPR) spectroscopy offers an exquisite window into membrane protein dynamics in the native-like environment of a lipid bilayer. Systematic application of spin labeling and EPR identifies sequence-specific secondary structures, defines their topology and their packing in the tertiary fold. Long range distance measurements (60 Å-80 Å) between pairs of spin labels enable quantitative analysis of equilibrium dynamics and triggered conformational changes. This review highlights the contribution of spin labeling to bridging structure and mechanism. Efforts to develop methods for determining structures from EPR restraints and to increase sensitivity and throughput promise to expand spin labeling applications in membrane protein structural biology. Copyright © 2011 Elsevier Ltd. All rights reserved.

Observation of vacuum-enhanced electron spin resonance of optically levitated nanodiamonds

NASA Astrophysics Data System (ADS)

Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon

Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. Our results show that optical levitation of nanodiamonds in vacuum not only can improve the mechanical quality of its oscillation, but also enhance the ESR contrast, which pave the way towards a novel levitated spin-optomechanical system for studying macroscopic quantum mechanics. The results also indicate potential applications of NV centers in gas sensing.

Electron spin control and torsional optomechanics of an optically levitated nanodiamond in vacuum

NASA Astrophysics Data System (ADS)

Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon

Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centers, indicating potential applications of NV centers in oxygen gas sensing. For spin-optomechanics, it is important to control the orientation of the nanodiamond and NV centers in a magnetic field. Recently, we have observed the angular trapping and torsional vibration of a levitated nanodiamond, which paves the way towards levitated torsional optomechanics in the quantum regime. NSF 1555035-PHY.

Formation and implications of alpha-synuclein radical in Maneb- and paraquat-induced models of Parkinson’s disease

PubMed Central

Kumar, Ashutosh; Leinisch, Fabian; Kadiiska, Maria B.; Corbett, Jean; Mason, Ronald P.

2015-01-01

Parkinson’s disease (PD) is a debilitating, progressive, neurodegenerative disorder characterized by progressive loss of dopaminergic neurons and motor deficits. Alpha-synuclein-containing aggregates represent a feature of a variety of neurodegenerative disorders, including PD; however, the mechanism that initiates and promotes intraneuronal alpha-synuclein aggregation remains unknown. We hypothesized protein radical formation as an initiating mechanism for alpha-synuclein aggregation. Therefore, we used the highly sensitive immuno-spin trapping technique to investigate protein radical formation as a possible mechanism of alpha-synuclein aggregation as well as to investigate the source of protein radical formation in the midbrains of Maneb and paraquat coexposed mice. Coexposure to Maneb and paraquat for 6 weeks resulted in active microgliosis, NADPH oxidase activation, and inducible nitric oxide synthase (iNOS) induction, which culminated in protein radical formation in the midbrains of mice. Results obtained with immuno-spin trapping and immunoprecipitation experiments confirmed formation of alpha-synuclein radicals in dopaminergic neurons of exposed mice. Free radical formation requires NADPH oxidase and iNOS, as indicated by decreased protein radical formation in knockout mice (P47phox−/− and iNOS−/−) and in mice treated with inhibitors such as FeTPPS (a peroxynitrite decomposition catalyst), 1400W (an iNOS inhibitor), or apocynin (a NADPH oxidase inhibitor). Concurrence of protein radical formation with dopaminergic neuronal death indicated a link between protein radicals and disease progression. Taken together, these results show for the first time the formation and detection of the alpha-synuclein radical and suggest that NADPH oxidase and iNOS play roles in peroxynitrite-mediated protein radical formation and subsequent neuronal death in the midbrains of Maneb and paraquat coexposed mice. PMID:25952542

Free-radical chemistry as a means to evaluate lunar dust health hazard in view of future missions to the moon.

PubMed

Turci, Francesco; Corazzari, Ingrid; Alberto, Gabriele; Martra, Gianmario; Fubini, Bice

2015-05-01

Lunar dust toxicity has to be evaluated in view of future manned missions to the Moon. Previous studies on lunar specimens and simulated dusts have revealed an oxidant activity assigned to HO· release. However, the mechanisms behind the reactivity of lunar dust are still quite unclear at the molecular level. In the present study, a complementary set of tests--including terephthalate (TA) hydroxylation, free radical release as measured by means of the spin-trapping/electron paramagnetic resonance (EPR) technique, and cell-free lipoperoxidation--is proposed to investigate the reactions induced by the fine fraction of a lunar dust analogue (JSC-1A-vf) in biologically relevant experimental environments. Our study proved that JSC-1A-vf is able to hydroxylate TA also in anaerobic conditions, which indicates that molecular oxygen is not involved in such a reaction. Spin-trapping/EPR measures showed that the HO· radical is not the reactive intermediate involved in the oxidative potential of JSC-1A-vf. A surface reactivity implying a redox cycle of phosphate-complexed iron via a Fe(IV) state is proposed. The role of this iron species was investigated by assessing the reactivity of JSC-1A-vf toward hydrogen peroxide (Fenton-like activity), formate ions (homolytic rupture of C-H bond), and linoleic acid (cell-free lipoperoxidation). JSC-1A-vf was active in all tests, confirming that redox centers of transition metal ions on the surface of the dust may be responsible for dust reactivity and that the TA assay may be a useful field probe to monitor the surface oxidative potential of lunar dust.

Cavitation during the protein misfolding cyclic amplification (PMCA) method – The trigger for de novo prion generation?

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

Haigh, Cathryn L., E-mail: chaigh@unimelb.edu.au; Drew, Simon C., E-mail: sdrew@unimelb.edu.au

The protein misfolding cyclic amplification (PMCA) technique has become a widely-adopted method for amplifying minute amounts of the infectious conformer of the prion protein (PrP). PMCA involves repeated cycles of 20 kHz sonication and incubation, during which the infectious conformer seeds the conversion of normally folded protein by a templating interaction. Recently, it has proved possible to create an infectious PrP conformer without the need for an infectious seed, by including RNA and the phospholipid POPG as essential cofactors during PMCA. The mechanism underpinning this de novo prion formation remains unknown. In this study, we first establish by spin trapping methodsmore » that cavitation bubbles formed during PMCA provide a radical-rich environment. Using a substrate preparation comparable to that employed in studies of de novo prion formation, we demonstrate by immuno-spin trapping that PrP- and RNA-centered radicals are generated during sonication, in addition to PrP-RNA cross-links. We further show that serial PMCA produces protease-resistant PrP that is oxidatively modified. We suggest a unique confluence of structural (membrane-mimetic hydrophobic/hydrophilic bubble interface) and chemical (ROS) effects underlie the phenomenon of de novo prion formation by PMCA, and that these effects have meaningful biological counterparts of possible relevance to spontaneous prion formation in vivo. - Highlights: • Sonication during PMCA generates free radicals at the surface of cavitation bubbles. • PrP-centered and RNA-centered radicals are formed in addition to PrP-RNA adducts. • De novo prions may result from ROS and structural constraints during cavitation.« less

Geometric phases in electric dipole searches with trapped spin-1/2 particles in general fields and measurement cells of arbitrary shape with smooth or rough walls

NASA Astrophysics Data System (ADS)

Golub, R.; Kaufman, C.; Müller, G.; Steyerl, A.

2015-12-01

The important role of geometric phases in searches for a permanent electric dipole moment of the neutron, using Ramsey separated oscillatory field nuclear magnetic resonance, was first noted by Commins [Am. J. Phys. 59, 1077 (1991), 10.1119/1.16616] and investigated in detail by Pendlebury et al. [Phys. Rev. A 70, 032102 (2004), 10.1103/PhysRevA.70.032102]. Their analysis was based on the Bloch equations. In subsequent work using the spin-density matrix, Lamoreaux and Golub [Phys. Rev. A 71, 032104 (2005), 10.1103/PhysRevA.71.032104] showed the relation between the frequency shifts and the correlation functions of the fields seen by trapped particles in general fields (Redfield theory). More recently, we presented a solution of the Schrödinger equation for spin-1 /2 particles in circular cylindrical traps with smooth walls and exposed to arbitrary fields [A. Steyerl et al., Phys. Rev. A 89, 052129 (2014), 10.1103/PhysRevA.89.052129]. Here, we extend this work to show how the Redfield theory follows directly from the Schrödinger equation solution. This serves to highlight the conditions of validity of the Redfield theory, a subject of considerable discussion in the literature [e.g., M. P. Nicholas et al., Prog. Nucl. Magn. Reson. Spectrosc. 57, 111 (2010), 10.1016/j.pnmrs.2010.04.003]. Our results can be applied where the Redfield result no longer holds, such as observation times on the order of or shorter than the correlation time and nonstochastic systems, and thus we can illustrate the transient spin dynamics, i.e., the gradual development of the shift with increasing time subsequent to the start of the free precession. We consider systems with rough, diffuse reflecting walls, cylindrical trap geometry with arbitrary cross section, and field perturbations that do not, in the frame of the moving particles, average to zero in time. We show by direct, detailed, calculation the agreement of the results from the Schrödinger equation with the Redfield theory for the cases of a rectangular cell with specular walls and of a circular cell with diffuse reflecting walls.

Theory of Fast Optical Spin Rotation in a Quantum Dot Based on Geometric Phases and Trapped States

DTIC Science & Technology

2007-11-19

rules are not affected by anisotropic exchange [15,16]. Our proposal is based on the observation that from the four-level system of Fig. 1, different...lasers, which is a significant experi- mental simplification. It requires the ability to perform Rabi oscillations between spin and trion, which has been...y) is the Rabi frequency of the transition with polarization x (y). Now we choose the envelope to be ft secht. We require the popu- lation

Electron spin resonance of (CO 2 H)CH 2 CH 2 CH(CO 2 H) in irradiated glutaric acid

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

Horsfield, A.; Morton, J. R.; Whiffen, D. H.

It is concluded from electron spin resonance spectra that the radical (CO 2 H)CH 2 CH 2 CH(CO 2 H) remains trapped in a glutaric acid crystal after gamma -irradiation. This radical is found in two different conformations. Approximate hyperfine coupling constants are given for each, although exact interpretation is hindered by the overlapping of spectra. Reasons for the formation of the two forms of the radical are discussed.

Positive holes in magnesium oxide - Correlation between magnetic, electric, and dielectric anomalies

NASA Technical Reports Server (NTRS)

Batllo, F.; Leroy, R. C.; Parvin, K.; Freund, F.; Freund, M. M.

1991-01-01

The present magnetic susceptibility investigation of high purity MgO single crystals notes an anomally at 800 K which is associated with increasing electrical conductivity, a rise in static dielectric constant from 9 to 150, and the appearance of a pronounced positive surface charge. These phenomena can be accounted for in terms of peroxy defects which represent self-trapped, spin-paired positive holes at Mg(2+) vacancy sites. The holes begin to decouple their spins above 600 K.

Spin relaxation in ultracold collisions of molecular radicals with alkali-metal atoms

NASA Astrophysics Data System (ADS)

Tscherbul, Timur; Klos, Jacek; Zukowski, Piotr

2016-05-01

We present accurate quantum scattering calculations of spin relaxation in ultracold collisions of alkali-metal atoms and polar 2 Σ molecules CaH, SrF, and SrOH. The calculations employ state-of-the-art ab initio interaction potentials and a rigorous quantum theory of atom-molecule collisions in a magnetic field based on the total angular momentum representation. We will further discuss the relevance of the results to atom-molecule sympathetic cooling experiments in a magnetic trap.

Efficient tomography of a quantum many-body system

NASA Astrophysics Data System (ADS)

Lanyon, B. P.; Maier, C.; Holzäpfel, M.; Baumgratz, T.; Hempel, C.; Jurcevic, P.; Dhand, I.; Buyskikh, A. S.; Daley, A. J.; Cramer, M.; Plenio, M. B.; Blatt, R.; Roos, C. F.

2017-12-01

Quantum state tomography is the standard technique for estimating the quantum state of small systems. But its application to larger systems soon becomes impractical as the required resources scale exponentially with the size. Therefore, considerable effort is dedicated to the development of new characterization tools for quantum many-body states. Here we demonstrate matrix product state tomography, which is theoretically proven to allow for the efficient and accurate estimation of a broad class of quantum states. We use this technique to reconstruct the dynamical state of a trapped-ion quantum simulator comprising up to 14 entangled and individually controlled spins: a size far beyond the practical limits of quantum state tomography. Our results reveal the dynamical growth of entanglement and describe its complexity as correlations spread out during a quench: a necessary condition for future demonstrations of better-than-classical performance. Matrix product state tomography should therefore find widespread use in the study of large quantum many-body systems and the benchmarking and verification of quantum simulators and computers.

Semiclassical approach to finite-temperature quantum annealing with trapped ions

NASA Astrophysics Data System (ADS)

Raventós, David; Graß, Tobias; Juliá-Díaz, Bruno; Lewenstein, Maciej

2018-05-01

Recently it has been demonstrated that an ensemble of trapped ions may serve as a quantum annealer for the number-partitioning problem [Nat. Commun. 7, 11524 (2016), 10.1038/ncomms11524]. This hard computational problem may be addressed by employing a tunable spin-glass architecture. Following the proposal of the trapped-ion annealer, we study here its robustness against thermal effects; that is, we investigate the role played by thermal phonons. For the efficient description of the system, we use a semiclassical approach, and benchmark it against the exact quantum evolution. The aim is to understand better and characterize how the quantum device approaches a solution of an otherwise difficult to solve NP-hard problem.

Specificity of different organic nitrates to elicit NO formation in rabbit vascular tissues and organs in vivo.

PubMed Central

Mülsch, A.; Bara, A.; Mordvintcev, P.; Vanin, A.; Busse, R.

1995-01-01

1. In the present study we assessed the formation of nitric oxide (NO) from classical and thiol-containing organic nitrates in vascular tissues and organs of anaesthetized rabbits, and established a relationship between the relaxant response elicited by nitroglycerin (NTG) and NO formation in the rabbit isolated aorta. Furthermore, the effect of isolated cytochrome P450 on NO formation from organic nitrates was investigated. 2. Rabbits received diethyldithiocarbamate (DETC; 200 mg kg-1 initial bolus i.p. and 200 mg kg-1 during 20 min, i.v.) and either saline, or one of the following organic nitrates: nitroglycerin (NTG, 0.5 mg kg-1), isosorbide dinitrate (ISDN), N-(3-nitratopivaloyl)-L-cysteine ethylester (SPM 3672), S-carboxyethyl-N-(3-nitratopivaloyl)-L-cysteine ethylester (SPM 5185), at 10 mg kg-1 each. After 20 min the animals were killed, blood vessels and organs were removed, and subsequently analyzed for spin-trapped NO by cryogenic electron spin resonance (e.s.r.) spectroscopy. 3. In the saline-treated control group, NO remained below the detection limit in all vessels and organs. In contrast, all of the nitrates tested elicited measurable NO formation, which was higher in organs (liver, kidney, heart, lung, spleen) (up to 4.8 nmol g-1 20 min-1) than in blood vessels (vena cava, mesenteric bed, femoral artery, aorta) (up to 0.7 nmol g-1 20 min-1). Classical organic nitrates (NTG, ISDN) formed NO preferentially in the mesenteric bed and the vena cava, while the SPM compounds elicited comparable NO formation in veins and arteries. 4. Using a similar spin trapping technique, NO formation was assessed in vitro in phenylephrine-precontracted rabbit aortic rings. The maximal relaxation elicited by a first exposure (10 min) to NTG (0.3 to 10 microM) was positively correlated (r = 0.8) with the net increase (NTG minus basal) of NO spin-trapped during a second exposure to the same concentration of NTG in the presence of DETC. 5. Cytochrome P450 purified from rabbit liver enhanced NO formation in a NADPH-dependent fashion from NTG, but not from the other nitrates, as assessed by activation of purified soluble guanylyl cyclase. 6. We conclude that the vessel selective action of different organic nitrates in vivo reflects differences in vascular NO formation. Thus, efficient preload reduction by classical organic nitrates can be accounted for by higher NO formation in venous capacitance as compared to arterial conductance and resistance vessels. In contrast, NO is released from cysteine-containing nitrates (SPMs) to a similar extent in arteries and veins, presumably independently of an organic nitrate-specific biotransformation. Limited tissue bioavailability of NTG and ISDN might account for low NO formation in the aorta, while true differences in biotransformation seem to account for differences in NO formation in the other vascular tissues. PMID:8590999

Nonlinear spectroscopy of trapped ions

NASA Astrophysics Data System (ADS)

Schlawin, Frank; Gessner, Manuel; Mukamel, Shaul; Buchleitner, Andreas

2014-08-01

Nonlinear spectroscopy employs a series of laser pulses to interrogate dynamics in large interacting many-body systems, and it has become a highly successful method for experiments in chemical physics. Current quantum optical experiments approach system sizes and levels of complexity that require the development of efficient techniques to assess spectral and dynamical features with scalable experimental overhead. However, established methods from optical spectroscopy of macroscopic ensembles cannot be applied straightforwardly to few-atom systems. Based on the ideas proposed in M. Gessner et al., (arXiv:1312.3365), we develop a diagrammatic approach to construct nonlinear measurement protocols for controlled quantum systems, and we discuss experimental implementations with trapped ion technology in detail. These methods, in combination with distinct features of ultracold-matter systems, allow us to monitor and analyze excitation dynamics in both the electronic and vibrational degrees of freedom. They are independent of system size, and they can therefore reliably probe systems in which, e.g., quantum state tomography becomes prohibitively expensive. We propose signals that can probe steady-state currents, detect the influence of anharmonicities on phonon transport, and identify signatures of chaotic dynamics near a quantum phase transition in an Ising-type spin chain.

Characterization of Defects in Scaled Mis Dielectrics with Variable Frequency Charge Pumping

NASA Astrophysics Data System (ADS)

Paulsen, Ronald Eugene

1995-01-01

Historically, the interface trap has been extensively investigated to determine the effects on device performance. Recently, much attention has been paid to trapping in near-interface oxide traps. Performance of high precision analog circuitry is affected by charge trapping in near-interface oxide traps which produces hysteresis, charge redistribution errors, and dielectric relaxation effects. In addition, the performance of low power digital circuitry, with reduced noise margins, may be drastically affected by the threshold voltage shifts associated with charge trapping in near -interface oxide traps. Since near-interface oxide traps may substantially alter the performance of devices, complete characterization of these defects is necessary. In this dissertation a new characterization technique, variable frequency charge pumping, is introduced which allows charge trapped at the interface to be distinguished from the charge trapped within the oxide. The new experimental technique is an extension of the charge pumping technique to low frequencies such that tunneling may occur from interface traps to near-interface oxide traps. A generalized charge pumping model, based on Shockley-Read-Hall statistics and trap-to-trap tunneling theory, has been developed which allows a more complete characterization of near-interface oxide traps. A pair of coupled differential equations governing the rate of change of occupied interface and near-interface oxide traps have been developed. Due to the experimental conditions in the charge pumping technique the equations may be decoupled, leading to an equation governing the rate of change of occupied interface traps and an equation governing the rate of change of occcupied near-interface oxide traps. Solving the interface trap equation and applying non-steady state charge dynamics leads to an interface trap component of the charge pumping current. In addition, solution to the near-interface oxide trap equation leads to an additional oxide trap component to the charge pumping current. Numerical simulations have been performed to support the analytical development of the generalized charge pumping model. By varying the frequency of the applied charge pumping waveform and monitoring the charge recombined per cycle, the contributions from interface traps may be separated from the contributions of the near-interface oxide traps. The generalized charge pumping model allows characterization of the density and spatial distribution of near-interface oxide traps from this variable frequency charge pumping technique. Characterization of interface and near-interface oxide trap generation has been performed on devices exposed to ionizing radiation, hot electron injection, and high -field/Fowler-Nordheim stressing. Finally, using SONOS nonvolatile memory devices, a framework has been established for experimentally determining not only the spatial distribution of near-interface oxide traps, but also the energetic distribution. An experimental approach, based on tri-level charge pumping, is discussed which allows the energetic distribution of near-interface oxide traps to be determined.

Key role of persistent free radicals in hydrogen peroxide activation by biochar: implications to organic contaminant degradation.

PubMed

Fang, Guodong; Gao, Juan; Liu, Cun; Dionysiou, Dionysios D; Wang, Yu; Zhou, Dongmei

2014-01-01

We investigated the activation of hydrogen peroxide (H2O2) by biochars (produced from pine needles, wheat, and maize straw) for 2-chlorobiphenyl (2-CB) degradation in the present study. It was found that H2O2 can be effectively activated by biochar, which produces hydroxyl radical ((•)OH) to degrade 2-CB. Furthermore, the activation mechanism was elucidated by electron paramagnetic resonance (EPR) and salicylic acid (SA) trapping techniques. The results showed that biochar contains persistent free radicals (PFRs), typically ∼ 10(18) unpaired spins/gram. Higher trapped [(•)OH] concentrations were observed with larger decreases in PFRs concentration, when H2O2 was added to biochar, indicating that PFRs were the main contributor to the formation of (•)OH. This hypothesis was supported by the linear correlations between PFRs concentration and trapped [(•)OH], as well as kobs of 2-CB degradation. The correlation coefficients (R(2)) were 0.723 and 0.668 for PFRs concentration vs trapped [(•)OH], and PFRs concentration vs kobs, respectively, when all biochars pyrolyzed at different temperatures were included. For the same biochar washed by different organic solvents (methanol, hexane, dichloromethane, and toluene), the correlation coefficients markedly increased to 0.818-0.907. Single-electron transfer from PFRs to H2O2 was a possible mechanism for H2O2 activation by biochars, which was supported by free radical quenching studies. The findings of this study provide a new pathway for biochar implication and insight into the mechanism of H2O2 activation by carbonaceous materials (e.g., activated carbon and graphite).

Reactivity of superoxide radical anion and hydroperoxyl radical with alpha-phenyl-N-tert-butylnitrone (PBN) derivatives.

PubMed

Durand, Grégory; Choteau, Fanny; Pucci, Bernard; Villamena, Frederick A

2008-12-04

Nitrones have exhibited pharmacological activity against radical-mediated pathophysiological conditions and as analytical reagents for the identification of transient radical species by electron paramagnetic resonance (EPR) spectroscopy. In this work, competitive spin trapping, stopped-flow kinetics, and density functional theory (DFT) were employed to assess and predict the reactivity of O(2)(*-) and HO(2)(*) with various para-substituted alpha-phenyl-N-tert-butylnitrone (PBN) spin traps. Rate constants of O(2)(*-) trapping by nitrones were determined using competitive UV-vis stopped-flow method with phenol red (PR) as probe, while HO(2)(*) trapping rate constants were calculated using competition kinetics with 5,5-dimethylpyrroline N-oxide (DMPO) by employing EPR spectroscopy. The effects of the para substitution on the charge density of the nitronyl-carbon and on the free energies of nitrone reactivity with O(2)(*-) and HO(2)(*) were computationally rationalized at the PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) level of theory. Theoretical and experimental data show that the rate of O(2)(*-) addition to PBN derivatives is not affected by the polar effect of the substituents. However, the reactivity of HO(2)(*) follows the Hammett equation and is increased as the substituent becomes more electron withdrawing. This supports the conclusion that the nature of HO(2)(*) addition to PBN derivatives is electrophilic, while the addition of O(2)(*-) to PBN-type compounds is only weakly electrophilic.

Proposed formation mechanism and active species of hydrogen molecules generated from a novel magnesium-citric acid-hydroxypropyl cellulose coating (MgCC) material

NASA Astrophysics Data System (ADS)

Kobayashi, Shigeki; Chikuma, Toshiyuki; Chiba, Kazuyoshi; Tsuchiya, Daisuke; Hirai, Tomomitsu

2016-02-01

The presence of acids is known to accelerate the reaction (Mg + 2H2O = Mg(OH)2 + H2). We developed a novel Mg-citric acid coating (MgCC) material produced by milling Mg powder coated with hydroxypropyl cellulose (HPC); because of its H2 generation, this material could be used in antioxidant therapy and antiaging applications. After milling in the presence of citric acid, this material produced H2-rich water upon addition to cooled water. Although the reaction was considered to involve a two-electron transfer from Mg to 2H2O, the role of the acid in H2 generation remains incompletely understood. To clarify the reaction mechanism, we performed studies on the deuterium kinetic isotope effects (KIE) and electron spin resonance (ESR). We observed differences in the concentration ratios, such as H2/D2 > 1 and H2/(H2 + D2 + HD) > 1, involved in H2, D2, and (H2 + D2 + HD) production, and found that adducts with hydrogen atoms (Hrad) were not obtained from the spin-trapping reaction between 5-(2, 2-Dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) and the MgCC material. The H2, D2, and HD produced from MgCC were identified by using a gas chromatograph connected to a mass spectrometer. The spin-trapping techniques showed that the Hrad adducts formed by the reaction of NaBH4 with CYPMPO could not be observed from reaction of MGCC with CYPMPO in H2O. The data suggest that the rate-controlling step and proposed transition state (TS) exist in the reaction pathway of the O-H bond cleavage and H-H bond formation. A TS of a structure such as [Mg(OH2)2]∗ could be expected in the reaction pathway between Mg and 2H2O by density functional theory calculations. Also, these results show that H2 generation is accelerated in the presence of acids because the activation energy of the TS is significantly smaller than that of H2O.

A two-qubit logic gate in silicon.

PubMed

Veldhorst, M; Yang, C H; Hwang, J C C; Huang, W; Dehollain, J P; Muhonen, J T; Simmons, S; Laucht, A; Hudson, F E; Itoh, K M; Morello, A; Dzurak, A S

2015-10-15

Quantum computation requires qubits that can be coupled in a scalable manner, together with universal and high-fidelity one- and two-qubit logic gates. Many physical realizations of qubits exist, including single photons, trapped ions, superconducting circuits, single defects or atoms in diamond and silicon, and semiconductor quantum dots, with single-qubit fidelities that exceed the stringent thresholds required for fault-tolerant quantum computing. Despite this, high-fidelity two-qubit gates in the solid state that can be manufactured using standard lithographic techniques have so far been limited to superconducting qubits, owing to the difficulties of coupling qubits and dephasing in semiconductor systems. Here we present a two-qubit logic gate, which uses single spins in isotopically enriched silicon and is realized by performing single- and two-qubit operations in a quantum dot system using the exchange interaction, as envisaged in the Loss-DiVincenzo proposal. We realize CNOT gates via controlled-phase operations combined with single-qubit operations. Direct gate-voltage control provides single-qubit addressability, together with a switchable exchange interaction that is used in the two-qubit controlled-phase gate. By independently reading out both qubits, we measure clear anticorrelations in the two-spin probabilities of the CNOT gate.

Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

PubMed Central

Huang, Xu-Guang

2016-01-01

The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

Itinerant ferromagnetism in ultracold Fermi gases

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

Heiselberg, H.

2011-05-15

Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature, a second-order transition is found at ak{sub F}{approx_equal}0.90 compatible with results of quantum-Monte-Carlo (QMC) calculations. Thermodynamic functions and observables, such as the compressibility and spin susceptibility and the resulting fluctuations in number and spin, are calculated. For trapped gases, the resulting cloud radii and kinetic energies are calculated and compared to recent experiments. Spin-polarized systems are recommended for effective separation of large ferromagnetic domains. Collective modes are predicted and tricritical points are calculatedmore » for multicomponent systems.« less

A scenario for magnonic spin-wave traps

PubMed Central

Busse, Frederik; Mansurova, Maria; Lenk, Benjamin; von der Ehe, Marvin; Münzenberg, Markus

2015-01-01

Spatially resolved measurements of the magnetization dynamics on a thin CoFeB film induced by an intense laser pump-pulse reveal that the frequencies of resulting spin-wave modes depend strongly on the distance to the pump center. This can be attributed to a laser generated temperature profile. We determine a shift of 0.5 GHz in the spin-wave frequency due to the spatial thermal profile induced by the femtosecond pump pulse that persists for up to one nanosecond. Similar experiments are presented for a magnonic crystal composed of a CoFeB-film based antidot lattice with a Damon Eshbach mode at the Brillouin zone boundary and its consequences are discussed. PMID:26279466

Nuclear Spin Locking and Extended Two-Electron Spin Decoherence Time in an InAs Quantum Dot Molecule

NASA Astrophysics Data System (ADS)

Chow, Colin; Ross, Aaron; Steel, Duncan; Sham, L. J.; Bracker, Allan; Gammon, Daniel

2015-03-01

The spin eigenstates for two electrons confined in a self-assembled InAs quantum dot molecule (QDM) consist of the spin singlet state, S, with J = 0 and the triplet states T-, T0 and T+, with J = 1. When a transverse magnetic field (Voigt geometry) is applied, the two-electron system can be initialized to the different states with appropriate laser excitation. Under the excitation of a weak probe laser, non-Lorentzian lineshapes are obtained when the system is initialized to either T- or T+, where T- results in a ``resonance locking'' lineshape while T+ gives a ``resonance avoiding '' lineshape: two different manifestations of hysteresis showing the importance of memory in the system. These observations signify dynamic nuclear spin polarization (DNSP) arising from a feedback mechanism involving hyperfine interaction between lattice nuclei and delocalized electron spins, and Overhauser shift due to nuclear spin polarization. Using pump configurations that generate coherent population trapping, the isolation of the electron spin from the optical excitation shows the stabilization of the nuclear spin ensemble. The dark-state lineshape measures the lengthened electron spin decoherence time, from 1 ns to 1 μs. Our detailed spectra highlight the potential of QDM for realizing a two-qubit gate. This work is supported by NSF, ARO, AFOSR, DARPA, and ONR.

Circuit quantum electrodynamics with a spin qubit.

PubMed

Petersson, K D; McFaul, L W; Schroer, M D; Jung, M; Taylor, J M; Houck, A A; Petta, J R

2012-10-18

Electron spins trapped in quantum dots have been proposed as basic building blocks of a future quantum processor. Although fast, 180-picosecond, two-quantum-bit (two-qubit) operations can be realized using nearest-neighbour exchange coupling, a scalable, spin-based quantum computing architecture will almost certainly require long-range qubit interactions. Circuit quantum electrodynamics (cQED) allows spatially separated superconducting qubits to interact via a superconducting microwave cavity that acts as a 'quantum bus', making possible two-qubit entanglement and the implementation of simple quantum algorithms. Here we combine the cQED architecture with spin qubits by coupling an indium arsenide nanowire double quantum dot to a superconducting cavity. The architecture allows us to achieve a charge-cavity coupling rate of about 30 megahertz, consistent with coupling rates obtained in gallium arsenide quantum dots. Furthermore, the strong spin-orbit interaction of indium arsenide allows us to drive spin rotations electrically with a local gate electrode, and the charge-cavity interaction provides a measurement of the resulting spin dynamics. Our results demonstrate how the cQED architecture can be used as a sensitive probe of single-spin physics and that a spin-cavity coupling rate of about one megahertz is feasible, presenting the possibility of long-range spin coupling via superconducting microwave cavities.

Spinning out a star.

PubMed

Lord, Michael D; Mandel, Stanley W; Wager, Jeffrey D

2002-06-01

Spinouts rarely take off; most, in fact, fall into one or more of four traps that doom them from the start. Some companies spin out ventures that are too close to the core of their businesses, in effect selling off their crown jewels. Sometimes, a parent company uses the spinout primarily to pawn off debt or expenses or to quickly raise external capital for itself. Other times, a company may try to spin out an area of its business that lacks one or more of the critical legs of a successful company--a coherent business model, say, or a solid financial base. And in many cases, parent companies can't bring themselves to sever their ownership ties and give up control of their spinouts. R.J. Reynolds, the tobacco giant, managed to avoid these traps when it successfully spun out a most unlikely venture, the pharmaceutical company Targacept. As the story illustrates, the problem with spinouts is similar to the problem of rich children. Their parents have the wherewithal to spoil them or shelter them or cling to them, but what they need is tough love and discipline--much the same discipline that characterizes successful start-ups. R.J. Reynolds recognized that it didn't know that much about the pharmaceutical business and couldn't merely try to spin out a small clone of itself. It had to treat the venture as if it were essentially starting from scratch, with a passionate entrepreneurial leader, a solid business plan, help from outside partners in the industry, and ultimately substantial venture backing. That these lessons are less obvious to executives contemplating spinning out ventures closer to their core businesses may be why so many spinouts fail.

Luttinger theorem and imbalanced Fermi systems

NASA Astrophysics Data System (ADS)

Pieri, Pierbiagio; Strinati, Giancarlo Calvanese

2017-04-01

The proof of the Luttinger theorem, which was originally given for a normal Fermi liquid with equal spin populations formally described by the exact many-body theory at zero temperature, is here extended to an approximate theory given in terms of a "conserving" approximation also with spin imbalanced populations. The need for this extended proof, whose underlying assumptions are here spelled out in detail, stems from the recent interest in superfluid trapped Fermi atoms with attractive inter-particle interaction, for which the difference between two spin populations can be made large enough that superfluidity is destroyed and the system remains normal even at zero temperature. In this context, we will demonstrate the validity of the Luttinger theorem separately for the two spin populations for any "Φ-derivable" approximation, and illustrate it in particular for the self-consistent t-matrix approximation.

Chiral resolution of spin angular momentum in linearly polarized and unpolarized light

PubMed Central

Hernández, R. J.; Mazzulla, A.; Provenzano, C.; Pagliusi, P.; Cipparrone, G.

2015-01-01

Linearly polarized (LP) and unpolarized (UP) light are racemic entities since they can be described as superposition of opposite circularly polarized (CP) components of equal amplitude. As a consequence they do not carry spin angular momentum. Chiral resolution of a racemate, i.e. separation of their chiral components, is usually performed via asymmetric interaction with a chiral entity. In this paper we provide an experimental evidence of the chiral resolution of linearly polarized and unpolarized Gaussian beams through the transfer of spin angular momentum to chiral microparticles. Due to the interplay between linear and angular momentum exchange, basic manipulation tasks, as trapping, spinning or orbiting of micro-objects, can be performed by light with zero helicity. The results might broaden the perspectives for development of miniaturized and cost-effective devices. PMID:26585284

Quantum simulation. Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism.

PubMed

Zhang, X; Bishof, M; Bromley, S L; Kraus, C V; Safronova, M S; Zoller, P; Rey, A M; Ye, J

2014-09-19

SU(N) symmetry can emerge in a quantum system with N single-particle spin states when spin is decoupled from interparticle interactions. Taking advantage of the high measurement precision offered by an ultrastable laser, we report a spectroscopic observation of SU(N ≤ 10) symmetry in (87)Sr. By encoding the electronic orbital degree of freedom in two clock states while keeping the system open to as many as 10 nuclear spin sublevels, we probed the non-equilibrium two-orbital SU(N) magnetism via Ramsey spectroscopy of atoms confined in an array of two-dimensional optical traps; we studied the spin-orbital quantum dynamics and determined the relevant interaction parameters. This study lays the groundwork for using alkaline-earth atoms as testbeds for important orbital models. Copyright © 2014, American Association for the Advancement of Science.

Improving the lifetime in optical microtraps by using elliptically polarized dipole light

NASA Astrophysics Data System (ADS)

Garcia, Sébastien; Reichel, Jakob; Long, Romain

2018-02-01

Tightly focused optical dipole traps induce vector light shifts ("fictitious magnetic fields") which complicate their use for single-atom trapping and manipulation. The problem can be mitigated by adding a larger, real magnetic field, but this solution is not always applicable; in particular, it precludes fast switching to a field-free configuration. Here we show that this issue can be addressed elegantly by deliberately adding a small elliptical polarization component to the dipole trap beam. In our experiments with single 87Rb atoms laser-cooled in a chopped trap, we observe improvements up to a factor of 11 of the trap lifetime compared to the standard, seemingly ideal linear polarization. This effect results from a modification of heating processes via spin-state diffusion in state-dependent trapping potentials. We develop Monte Carlo simulations of the evolution of the atom's internal and motional states and find that they agree quantitatively with the experimental data. The method is general and can be applied in all experiments where the longitudinal polarization component is non-negligible.

Boson-mediated quantum spin simulators in transverse fields: X Y model and spin-boson entanglement

NASA Astrophysics Data System (ADS)

Wall, Michael L.; Safavi-Naini, Arghavan; Rey, Ana Maria

2017-01-01

The coupling of spins to long-wavelength bosonic modes is a prominent means to engineer long-range spin-spin interactions, and has been realized in a variety of platforms, such as atoms in optical cavities and trapped ions. To date, much of the experimental focus has been on the realization of long-range Ising models, but generalizations to other spin models are highly desirable. In this work, we explore a previously unappreciated connection between the realization of an X Y model by off-resonant driving of a single sideband of boson excitation (i.e., a single-beam Mølmer-Sørensen scheme) and a boson-mediated Ising simulator in the presence of a transverse field. In particular, we show that these two schemes have the same effective Hamiltonian in suitably defined rotating frames, and analyze the emergent effective X Y spin model through a truncated Magnus series and numerical simulations. In addition to X Y spin-spin interactions that can be nonperturbatively renormalized from the naive Ising spin-spin coupling constants, we find an effective transverse field that is dependent on the thermal energy of the bosons, as well as other spin-boson couplings that cause spin-boson entanglement not to vanish at any time. In the case of a boson-mediated Ising simulator with transverse field, we discuss the crossover from transverse field Ising-like to X Y -like spin behavior as a function of field strength.

Spin Complicates Eccentric BH-NS Mergers

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-08-01

When a neutron star (NS) has a glancing encounter with a black hole (BH), its spin has a significant effect on the outcome, according to new simulations run by William East of Stanford University and his collaborators. Spotting an Eccentric Merger. In a traditional BH-NS merger, the two objects orbit each other quasi-circularly as they spiral in. But there's another kind of merger that's possible in high-density environments like galactic nuclei or globular clusters: a dynamical capture merger, in which a NS and BH pass each other just close enough that the gravity of the black hole "catches" the NS, leading the two objects to merge with very eccentric orbits. During an eccentric merger, the NS can be torn apart -- at which point some fraction of the tidally-disrupted material will escape the system, while some fraction instead accretes back onto the BH. Knowing these fractions is important for being able to model the expected electromagnetic signatures for the merger: the unbound material can power transients like kilonovae, whereas the accreting material may be the cause of short gamma-ray bursts. The amount of material available for events like these would change their observable strengths. Testing the Effects of Spin. To see whether NS spin has an impact on the behavior of the merger, East and collaborators use a general-relativistic hydrodynamic code to simulate the glancing encounter of a BH and a NS with dimensionless spin between a=0 (non-spinning) and a=0.756 (rotation period of 1 ms). They also vary the separation of the first encounter. The group finds that changing the NS's spin can change a number of outcomes of the merger. To start with, it can affect whether the NS is captured by the BH, or if the encounter is glancing and then both objects carry on their merry way. And if the NS is trapped by the BH and torn apart, then the higher the NS's spin, the more matter outside of the BH ends up unbound, instead of getting trapped into an accretion disk around the BH. As a result of these simulations, the authors argue that the spin of NSs in dynamical capture mergers is crucially important for correctly modeling the observational signatures that might come out of them. Citation: William E. East et al. 2015 ApJ, 807, L3.

A Confirmation of the Quench-Cryoannealing Relaxation Protocol for Identifying Reduction States of Freeze-Trapped Nitrogenase Intermediates

PubMed Central

2015-01-01

We have advanced a mechanism for nitrogenase catalysis that rests on the identification of a low-spin EPR signal (S = 1/2) trapped during turnover of a MoFe protein as the E4 state, which has accumulated four reducing equivalents as two [Fe–H–Fe] bridging hydrides. Because electrons are delivered to the MoFe protein one at a time, with the rate-limiting step being the off-rate of oxidized Fe protein, it is difficult to directly control, or know, the degree of reduction, n, of a trapped intermediate, denoted En, n = 1–8. To overcome this previously intractable problem, we introduced a quench-cryoannealing relaxation protocol for determining n of an EPR-active trapped En turnover state. The trapped “hydride” state was allowed to relax to the resting E0 state in frozen medium, which prevents additional accumulation of reducing equivalents; binding of reduced Fe protein and release of oxidized protein from the MoFe protein both are abolished in a frozen solid. Relaxation of En was monitored by periodic EPR analysis at cryogenic temperature. The protocol rests on the hypothesis that an intermediate trapped in the frozen solid can relax toward the resting state only by the release of a stable reduction product from FeMo-co. In turnover under Ar, the only product that can be released is H2, which carries two reducing equivalents. This hypothesis implicitly predicts that states that have accumulated an odd number of electrons/protons (n = 1, 3) during turnover under Ar cannot relax to E0: E3 can relax to E1, but E1 cannot relax to E0 in the frozen state. The present experiments confirm this prediction and, thus, the quench-cryoannealing protocol and our assignment of E4, the foundation of the proposed mechanism for nitrogenase catalysis. This study further gives insights into the identity of the En intermediates with high-spin EPR signals, 1b and 1c, trapped under high electron flux. PMID:24635454

Back-clocking of Fe2+/Fe1+ spin states in a H2-producing catalyst by advanced EPR

NASA Astrophysics Data System (ADS)

Stathi, Panagiota; Mitrikas, George; Sanakis, Yiannis; Louloudi, Maria; Deligiannakis, Yiannis

2013-10-01

A mononuclear Fe-(P(PPh2)3) ((P(PPh2)3) = tris[2-diphenylphospino)ethyl]phosphine) catalyst was studied in situ under catalytic conditions using advanced electron paramagnetic resonance (EPR) techniques. Fe-(P(PPh2)3) efficiently catalyses H2 production using HCOOH as substrate. Dual-mode continuous-wave (CW) EPR, used to study the initial Fe2+(S = 2) state, shows that the complex is characterised by a - rather small - zero field splitting parameter Δ = 0.45 cm-1 and geff = 8.0. In the presence of HCOOH substrate the complex evolves and a unique Fe1+(S = 1/2) state is trapped. The Fe1+ atom is coordinated by four 31P nuclei in a pseudo-C3 symmetry. Only a small fraction of the Fe1+ spin density is delocalised onto the 31P atoms. Four-pulse electron spin echo envelope modulation (ESEEM) and two-dimensional hyperfine sublevel correlation spectroscopy (2D-HYSCORE) data reveal the existence of two types of 1H couplings. One corresponds to weak, purely dipolar coupling, tentatively assigned to phenyl protons. The most important is a - rather unusual - 1H coupling with negative Aiso (-2.75 MHz) and strong dipolar part (T = 5.5 MHz). This 1H is located on the pseudo-C3 symmetry axis of the Fe1+-(P(PPh2)3-HCOO- complex where one substrate molecule, formate anion, is coordinated on the Fe1+ atom.

Evaluation of capture techniques on lesser prairie-chicken trap injury and survival

USGS Publications Warehouse

Grisham, Blake A.; Boal, Clint W.; Mitchell, Natasia R.; Gicklhorn, Trevor S.; Borsdorf, Philip K.; Haukos, David A.; Dixon, Charles

2015-01-01

Ethical treatment of research animals is required under the Animal Welfare Act. This includes trapping methodologies that reduce unnecessary pain and duress. Traps used in research should optimize animal welfare conditions within the context of the proposed research study. Several trapping techniques are used in the study of lesser prairie-chickens, despite lack of knowledge of trap injury caused by the various methods. From 2006 to 2012, we captured 217, 40, and 144 lesser prairie-chickens Tympanuchus pallidicinctus using walk-in funnel traps, rocket nets, and drop nets, respectively, in New Mexico and Texas, to assess the effects of capture technique on injury and survival of the species. We monitored radiotagged, injured lesser prairie-chickens 7–65 d postcapture to assess survival rates of injured individuals. Injuries occurred disproportionately among trap type, injury type, and sex. The predominant injuries were superficial cuts to the extremities of males captured in walk-in funnel traps. However, we observed no mortalities due to trapping, postcapture survival rates of injured birds did not vary across trap types, and the daily survival probability of an injured and uninjured bird was ≥99%. Frequency and intensity of injuries in walk-in funnel traps are due to the passive nature of these traps (researcher cannot select specific individuals for capture) and incidental capture of individuals not needed for research. Comparatively, rocket nets and drop nets allow observers to target birds for capture and require immediate removal of captured individuals from the trap. Based on our results, trap injuries would be reduced if researchers monitor and immediately remove birds from walk-in funnels before they injure themselves; move traps to target specific birds and reduce recaptures; limit the number of consecutive trapping days on a lek; and use proper netting techniques that incorporate quick, efficient, trained handling procedures.

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.

Trapped atoms along nanophotonic resonators

NASA Astrophysics Data System (ADS)

Fields, Brian; Kim, May; Chang, Tzu-Han; Hung, Chen-Lung

2017-04-01

Many-body systems subject to long-range interactions have remained a very challenging topic experimentally. Ultracold atoms trapped in extreme proximity to the surface of nanophotonic structures provides a dynamic system combining the strong atom-atom interactions mediated by guided mode photons with the exquisite control implemented with trapped atom systems. The hybrid system promises pair-wise tunability of long-range interactions between atomic pseudo spins, allowing studies of quantum magnetism extending far beyond nearest neighbor interactions. In this talk, we will discuss our current status developing high quality nanophotonic ring resonators, engineered on CMOS compatible optical chips with integrated nanostructures that, in combination with a side illuminating beam, can realize stable atom traps approximately 100nm above the surface. We will report on our progress towards loading arrays of cold atoms near the surface of these structures and studying atom-atom interaction mediated by photons with high cooperativity.

The Permanently Shadowed Regions of Dwarf Planet Ceres

NASA Technical Reports Server (NTRS)

Schorghofer, Norbert; Mazarico, Erwan; Platz, Thomas; Preusker, Frank; Schroeder, Stefan E.; Raymond, Carol A.; Russell, Christopher T.

2016-01-01

Ceres has only a small spin axis tilt (4 deg), and craters near its rotational poles can experience permanent shadow and trap volatiles, as is the case on Mercury and on Earth's Moon. Topography derived from stereo imaging by the Dawn spacecraft is used to calculate direct solar irradiance that defines the extent of the permanently shadowed regions (PSRs). In the northern polar region, PSRs cover approximately 1800 sq km or 0.13% of the hemisphere, and most of the PSRs are cold enough to trap water ice over geological time periods. Based on modeling of the water exosphere, water molecules seasonally reside around the winter pole and ultimately an estimated 0.14% of molecules get trapped. Even for the lowest estimates of the amount of available water, this predicts accumulation rates in excess of loss rates, and hence, there should be fresh ice deposits in the cold traps.

Trap level spectroscopic investigations of U: ZnAl2O4: Role of defect centres in the TSL process

NASA Astrophysics Data System (ADS)

Mohapatra, M.; Kumar, Mithlesh; Kadam, R. M.

2018-03-01

In order to evaluate the trap level spectroscopic properties of Uranium in ZnAl2O4 spinel host, undoped and Uranium doped ZnAl2O4 samples were synthesized. From photoluminescence (PL) data it was confirmed that uranium gets stabilized in the system as UO66- (octahedral uranate). Electron spin resonance (ESR) studies for the gamma irradiated sample suggested the formation of O2-, F+ and V centres. From the TSL (thermally stimulated luminescence) data, the trap parameters such as frequency factor and activation energy etc. were evaluated. From ESR-TSL correlation it was confirmed that the destruction of O2- ion coincides with TSL glow peak appeared at 332 K.

Coherence properties of nanofiber-trapped cesium atoms.

PubMed

Reitz, D; Sayrin, C; Mitsch, R; Schneeweiss, P; Rauschenbeutel, A

2013-06-14

We experimentally study the ground state coherence properties of cesium atoms in a nanofiber-based two-color dipole trap, localized ∼ 200 nm away from the fiber surface. Using microwave radiation to coherently drive the clock transition, we record Ramsey fringes as well as spin echo signals and infer a reversible dephasing time of T(2)(*) = 0.6 ms and an irreversible dephasing time of T(2)(') = 3.7 ms. By modeling the signals, we find that, for our experimental parameters, T(2)(*) and T(2)(') are limited by the finite initial temperature of the atomic ensemble and the heating rate, respectively. Our results represent a fundamental step towards establishing nanofiber-based traps for cold atoms as a building block in an optical fiber quantum network.

Sympathetic cooling of polyatomic molecules with S-state atoms in a magnetic trap.

PubMed

Tscherbul, T V; Yu, H-G; Dalgarno, A

2011-02-18

We present a rigorous theoretical study of low-temperature collisions of polyatomic molecular radicals with (1)S(0) atoms in the presence of an external magnetic field. Accurate quantum scattering calculations based on ab initio and scaled interaction potentials show that collision-induced spin relaxation of the prototypical organic molecule CH(2)(X(3)B(1)) (methylene) and nine other triatomic radicals in cold (3)He gas occurs at a slow rate, demonstrating that cryogenic buffer-gas cooling and magnetic trapping of these molecules is feasible with current technology. Our calculations further suggest that it may be possible to create ultracold gases of polyatomic molecules by sympathetic cooling with alkaline-earth atoms in a magnetic trap.

Experiments with trapped ions and ultrafast laser pulses

NASA Astrophysics Data System (ADS)

Johnson, Kale Gifford

Since the dawn of quantum information science, laser-cooled trapped atomic ions have been one of the most compelling systems for the physical realization of a quantum computer. By applying qubit state dependent forces to the ions, their collective motional modes can be used as a bus to realize entangling quantum gates. Ultrafast state-dependent kicks [1] can provide a universal set of quantum logic operations, in conjunction with ultrafast single qubit rotations [2], which uses only ultrafast laser pulses. This may present a clearer route to scaling a trapped ion processor [3]. In addition to the role that spin-dependent kicks (SDKs) play in quantum computation, their utility in fundamental quantum mechanics research is also apparent. In this thesis, we present a set of experiments which demonstrate some of the principle properties of SDKs including ion motion independence (we demonstrate single ion thermometry from the ground state to near room temperature and the largest Schrodinger cat state ever created in an oscillator), high speed operations (compared with conventional atom-laser interactions), and multi-qubit entanglement operations with speed that is not fundamentally limited by the trap oscillation frequency. We also present a method to provide higher stability in the radial mode ion oscillation frequencies of a linear radiofrequency (rf) Paul trap-a crucial factor when performing operations on the rf-sensitive modes. Finally, we present the highest atomic position sensitivity measurement of an isolated atom to date of 0.5 nm Hz. (-1/2) with a minimum uncertaintyof 1.7 nm using a 0.6 numerical aperature (NA) lens system, along with a method to correct aberrations and a direct position measurement of ion micromotion (the inherent oscillations of an ion trapped in an oscillating rf field). This development could be used to directly image atom motion in the quantum regime, along with sensing forces at the yoctonewton [10. (-24) N)] scale forgravity sensing, and 3D imaging of atoms from static to higher frequency motion. These ultrafast atomic qubit manipulation tools demonstrate inherent advantages over conventional techniques, offering a fundamentally distinct regime of control and speed not previously achievable.

Quantification of deep traps in nanocrystal solids, their electronic properties, and their influence on device behavior.

PubMed

Bozyigit, Deniz; Volk, Sebastian; Yarema, Olesya; Wood, Vanessa

2013-11-13

We implement three complementary techniques to quantify the number, energy, and electronic properties of trap states in nanocrystal (NC)-based devices. We demonstrate that, for a given technique, the ability to observe traps depends on the Fermi level position, highlighting the importance of a multitechnique approach that probes trap coupling to both the conduction and the valence bands. We then apply our protocol for characterizing traps to quantitatively explain the measured performances of PbS NC-based solar cells.

PubMed Central

Serteyn, D; Pincemail, J; Mottart, E; Caudron, I; Deby, C; Deby-Dupont, G; Philippart, C; Lamy, M

1994-01-01

This preliminary study demonstrated the existence of a free radical generation during an experimental postischemic muscular reperfusion in a halothane anesthetized horse. The authors used alpha-phényl-N-tert-butylnitrone as a spin trap agent and the electronic paramagnetic resonance method to observe in vivo a free radical generation. PMID:7889465

Evidence of impurity and boundary effects on magnetic monopole dynamics in spin ice

NASA Astrophysics Data System (ADS)

Revell, H. M.; Yaraskavitch, L. R.; Mason, J. D.; Ross, K. A.; Noad, H. M. L.; Dabkowska, H. A.; Gaulin, B. D.; Henelius, P.; Kycia, J. B.

2013-01-01

Electrical resistance is a crucial and well-understood property of systems ranging from computer microchips to nerve impulse propagation in the human body. Here we study the motion of magnetic charges in spin ice and find that extra spins inserted in Dy2Ti2O7 trap magnetic monopole excitations and provide the first example of how defects in a spin-ice material obstruct the flow of monopoles--a magnetic version of residual resistance. We measure the time-dependent magnetic relaxation in Dy2Ti2O7 and show that it decays with a stretched exponential followed by a very slow long-time tail. In a Monte Carlo simulation governed by Metropolis dynamics we show that surface effects and a very low level of stuffed spins (0.30%)--magnetic Dy ions substituted for non-magnetic Ti ions--cause these signatures in the relaxation. In addition, we find evidence that the rapidly diverging experimental timescale is due to a temperature-dependent attempt rate proportional to the monopole density.

Comparison of scavenging capacities of vegetables by ORAC and EPR.

PubMed

Kameya, Hiromi; Watanabe, Jun; Takano-Ishikawa, Yuko; Todoriki, Setsuko

2014-02-15

Reactive oxygen species (ROS) are considered to be causative agents of many health problems. In spite of this, the radical-specific scavenging capacities of food samples have not been well studied. In the present work, we have developed an electron paramagnetic resonance (EPR) spin trapping method for analysis of the scavenging capacities of food samples for multiple ROS, utilising the same photolysis procedure for generating each type of radical. The optimal conditions for effective evaluation of hydroxyl, superoxide, and alkoxyl radical scavenging capacity were determined. Quantification of radical adducts was found to be highly reproducible, with variations of less than 4%. The optimised EPR spin trapping method was used to analyse the scavenging capacities of 54 different vegetable extracts for multiple radicals, and the results were compared with oxygen radical absorption capacity values. Good correlations between the two methods were observed for superoxide and alkoxyl radicals, but not for hydroxyl. Copyright © 2013 Elsevier Ltd. All rights reserved.

Many-body physics using cold atoms

NASA Astrophysics Data System (ADS)

Sundar, Bhuvanesh

Advances in experiments on dilute ultracold atomic gases have given us access to highly tunable quantum systems. In particular, there have been substantial improvements in achieving different kinds of interaction between atoms. As a result, utracold atomic gases oer an ideal platform to simulate many-body phenomena in condensed matter physics, and engineer other novel phenomena that are a result of the exotic interactions produced between atoms. In this dissertation, I present a series of studies that explore the physics of dilute ultracold atomic gases in different settings. In each setting, I explore a different form of the inter-particle interaction. Motivated by experiments which induce artificial spin-orbit coupling for cold fermions, I explore this system in my first project. In this project, I propose a method to perform universal quantum computation using the excitations of interacting spin-orbit coupled fermions, in which effective p-wave interactions lead to the formation of a topological superfluid. Motivated by experiments which explore the physics of exotic interactions between atoms trapped inside optical cavities, I explore this system in a second project. I calculate the phase diagram of lattice bosons trapped in an optical cavity, where the cavity modes mediates effective global range checkerboard interactions between the atoms. I compare this phase diagram with one that was recently measured experimentally. In two other projects, I explore quantum simulation of condensed matter phenomena due to spin-dependent interactions between particles. I propose a method to produce tunable spin-dependent interactions between atoms, using an optical Feshbach resonance. In one project, I use these spin-dependent interactions in an ultracold Bose-Fermi system, and propose a method to produce the Kondo model. I propose an experiment to directly observe the Kondo effect in this system. In another project, I propose using lattice bosons with a large hyperfine spin, which have Feshbach-induced spin-dependent interactions, to produce a quantum dimer model. I propose an experiment to detect the ground state in this system. In a final project, I develop tools to simulate the dynamics of fermionic superfluids in which fermions interact via a short-range interaction.

High-Frequency Fe-H Vibrations in a Bridging Hydride Complex Characterized by NRVS and DFT.

PubMed

Pelmenschikov, Vladimir; Gee, Leland B; Wang, Hongxin; MacLeod, K Cory; McWilliams, Sean F; Skubi, Kazimer L; Cramer, Stephen P; Holland, Patrick L

2018-05-30

High-spin iron species with bridging hydrides have been detected in species trapped during nitrogenase catalysis, but there are few general methods of evaluating Fe-H bonds in high-spin multinuclear iron systems. An 57 Fe nuclear resonance vibrational spectroscopy (NRVS) study on an Fe(μ-H) 2 Fe model complex reveals Fe-H stretching vibrations for bridging hydrides at frequencies greater than 1200 cm -1 . These isotope-sensitive vibrational bands are not evident in infrared (IR) spectra, showing the power of NRVS for identifying hydrides in this high-spin iron system. Complementary density functional theory (DFT) calculations elucidate the normal modes of the rhomboidal iron hydride core. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlO{sub x}/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

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

Akushichi, T., E-mail: taiju.aku7@isl.titech.ac.jp; Shuto, Y.; Sugahara, S., E-mail: sugahara@isl.titech.ac.jp

We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlO{sub x}/n-Si tunnel spin-injectors whose tunnel barriers are formed by radical oxidation of Mg and Al thin films deposited on Si(100) substrates and successive annealing under radical-oxygen exposure. When the MgO and AlO{sub x} barriers are not treated by the radical-oxygen annealing, the Hanle-effect signals obtained from the 3T-SA devices are closely fitted by a single Lorentz function representing a signal due to trap spins. On the other hand, when the tunnel barriers are annealed under radical-oxygen exposure, the Hanle-effect signals can be accuratelymore » fitted by the superposition of a Lorentz function and a non-Lorentz function representing a signal due to accumulated spins in the Si channel. These results suggest that the quality improvement of tunnel barriers treated by radical-oxygen annealing is highly effective for spin-injection into Si channels.« less

Is Asteroid 951 Gaspra in a Resonant State with Its Spin Increasing Due to YORP?

NASA Technical Reports Server (NTRS)

Rubincam, David Parry; Rowlands, David D.; Ray, Richard D.; Smith, David E. (Technical Monitor)

2002-01-01

Asteroid 951 Gaspra appears to be in an obliquity resonance with its spin increasing due to the YORP effect. Gaspra, an asteroid 5.8 km in radius, is a prograde rotator with a rotation period of 7.03 hours. A three million year integration indicates its orbit is stable over at least this time span. From its known shape and spin axis orientation and assuming a uniform density, Gaspra's axial precession period turns out to be nearly commensurate with its orbital precession period, which leads to a resonance condition with consequent huge variations in its obliquity. At the same time its shape is such that the Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP effect for short) is increasing its spin rate. The YORP cycle normally leads from spin-up to spin-down and then repeating the cycle; however, it appears possible that resonance trapping can at least temporarily interrupt the YORP cycle, causing spin-up until the resonance is exited. This behavior may partially explain why there is an excess of fast rotators among small asteroids. YORP may also be a reason for small asteroids entering resonances in the first place.

Spacecraft Spin Rate Change due to Propellant Redistribution Between Tanks

NASA Astrophysics Data System (ADS)

Choi, Kyu Hong

1984-09-01

A bubble trapped in the liquid manifold of INTELSAT IV F-7 spacecraft caused a mass imbalance between the System 1 propellant tanks and a wobble half angle of 0.38 degree to 0.48 degree. A maneuver in May 14, 1980 passed the bubble through the axial jet and allowed propellant to redistribute. A 0.2 rpm change in spin rate was observed with an exponential decay time constant of 6 minutes. In this paper, moment of inertia, tank geometry and hydrodynamics models are derived to match the observed spin rate data. The values of the total mass of the propellant considered were 16, 19 and 20 Kgs with corresponding mass imbalances of 14.3, 15 and 15.1 Kgs, respectively. The result shows excellent agreement with observed spin rate data but it was necessary to assume a greater mass of hydrazine in the tanks than propellant accounting indicated.

Engineering of frustration in colloidal artificial ices realized on microfeatured grooved lattices

PubMed Central

Ortiz-Ambriz, Antonio; Tierno, Pietro

2016-01-01

Artificial spin ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models of frustration induced by lattice topology, allowing for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Inspired by recent theoretical advances, here we realize a colloidal version of an artificial spin ice system using interacting polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair interactions between the microscopic units. Via independent control of particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information. PMID:26830629

Engineering of frustration in colloidal artificial ices realized on microfeatured grooved lattices.

PubMed

Ortiz-Ambriz, Antonio; Tierno, Pietro

2016-02-01

Artificial spin ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models of frustration induced by lattice topology, allowing for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Inspired by recent theoretical advances, here we realize a colloidal version of an artificial spin ice system using interacting polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair interactions between the microscopic units. Via independent control of particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information.

Engineering of frustration in colloidal artificial ices realized on microfeatured grooved lattices

NASA Astrophysics Data System (ADS)

Tierno, Pietro

Artificial spin-ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models of frustration induced by lattice topology, allowing for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Inspired by recent theoretical advances, we realize a colloidal version of an artificial spin ice system using interacting polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair-interactions between the microscopic units. Via independent control of particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information.

Engineering of frustration in colloidal artificial ices realized on microfeatured grooved lattices

NASA Astrophysics Data System (ADS)

Ortiz-Ambriz, Antonio; Tierno, Pietro

2016-02-01

Artificial spin ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models of frustration induced by lattice topology, allowing for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Inspired by recent theoretical advances, here we realize a colloidal version of an artificial spin ice system using interacting polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair interactions between the microscopic units. Via independent control of particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information.

The Electronic Structure Signature of the Spin Cross-Over Transition of [Co(dpzca)2

NASA Astrophysics Data System (ADS)

Zhang, Xin; Mu, Sai; Liu, Yang; Luo, Jian; Zhang, Jian; N'Diaye, Alpha T.; Enders, Axel; Dowben, Peter A.

2018-05-01

The unoccupied electronic structure of the spin crossover molecule cobalt (II) N-(2-pyrazylcarbonyl)-2-pyrazinecarboxamide, [Co(dpzca)2] was investigated, using X-ray absorption spectroscopy (XAS) and compared with magnetometry (SQUID) measurements. The temperature dependence of the XAS and molecular magnetic susceptibility χmT are in general agreement for [Co(dpzca)2], and consistent with density functional theory (DFT). This agreement of magnetic susceptibility and X-ray absorption spectroscopy provides strong evidence that the changes in magnetic moment can be ascribed to changes in electronic structure. Calculations show the choice of Coulomb correlation energy U has a profound effect on the electronic structure of the low spin state, but has little influence on the electronic structure of the high spin state. In the temperature dependence of the XAS, there is also evidence of an X-ray induced excited state trapping for [Co(dpzca)2] at 15 K.

Disorder from order among anisotropic next-nearest-neighbor Ising spin chains in SrHo 2O 4

DOE PAGES

Wen, J. -J.; Tian, W.; Garlea, V. O.; ...

2015-02-26

In this study, we describe why Ising spin chains with competing interactions in SrHo 2O 4 segregate into ordered and disordered ensembles at low temperatures (T). Using elastic neutron scattering, magnetization, and specific heat measurements, the two distinct spin chains are inferred to have Néel (↑↓↑↓) and double-Néel (↑↑↓↓) ground states, respectively. Below T N = 0.68(2)K, the Néel chains develop three-dimensional long range order (LRO), which arrests further thermal equilibration of the double-Néel chains so they remain in a disordered incommensurate state for T below T S = 0.52(2)K. SrHo 2O 4 distills an important feature of incommensurate lowmore » dimensional magnetism: kinetically trapped topological defects in a quasi–d–dimensional spin system can preclude order in d + 1 dimensions.« less

Charge carriers' trapping states in pentacene films studied by modulated photocurrent

NASA Astrophysics Data System (ADS)

Gorgolis, S.; Giannopoulou, A.; Kounavis, P.

2013-03-01

The modulated photocurrent (MPC) technique is employed to study the charge carriers' trapping states of pentacene films. The characteristics of the experimental MPC spectra were found to be compatible with trapping-detrapping process of holes in gap states in which their occupancy can be modified by the bias illumination. A demarcation energy level separating empty from partially occupied traps was deduced from the MPC spectra, which can be used to monitor bias-light induced changes in the quasi Fermi level. An exponential trap distribution from structural disorder and a deep metastable gaussian trap distribution from adsorbed environmental impurities were extracted by means of the MPC spectroscopy. An attempt to escape frequency of the order of 1010s-1 was deduced for the gap sates. The derived trap distributions agree with those found before by means of other techniques. The present results indicate that the MPC technique can be used as a valuable tool for pentacene films characterization since it can be also applied to field effect samples.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater than or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f>1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f >1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Fast Single-Shot Hold Spin Readout in Double Quantum Dots

NASA Astrophysics Data System (ADS)

Bogan, Alexander; Studenikin, Sergei; Korkusinski, Marek; Aers, Geof; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa; Reno, John; Hargett, Terry

Solid state spin qubits in quantum dots hold promise as scalable, high-density qubits in quantum information processing architectures. While much of the experimental investigation of these devices and their physics has focused on confined electron spins, hole spins in III-V semiconductors are attractive alternatives to electrons due to the reduced hyperfine coupling between the spin and the incoherent nuclear environment. In this talk, we will discuss a measurement protocol of the hole spin relaxation time T1 in a gated lateral GaAs double quantum dot tuned to the one and two-hole regimes, as well as a new technique for single-shot projective measurement of a single spin in tens of nanoseconds or less. The technique makes use of fast non-spin-conserving inter-dot transitions permitted by strong spin-orbit interactions for holes, as well as the latching of the charge state of the second quantum dot for enhanced sensitivity. This technique allows a direct measurement of the single spin relaxation time on time-scales set by physical device rather than by limitations of the measurement circuit.

Continuous-flow trapping and localized enrichment of micro- and nano-particles using induced-charge electrokinetics.

PubMed

Zhao, Cunlu; Yang, Chun

2018-02-14

In this work, we report an effective microfluidic technique for continuous-flow trapping and localized enrichment of micro- and nano-particles by using induced-charge electrokinetic (ICEK) phenomena. The proposed technique utilizes a simple microfluidic device that consists of a straight microchannel and a conducting strip attached to the bottom wall of the microchannel. Upon application of the electric field along the microchannel, the conducting strip becomes polarized to introduce two types of ICEK phenomena, the ICEK flow vortex and particle dielectrophoresis, and they are identified by a theoretical model formulated in this study to be jointly responsible for the trapping of particles over the edge of the conducting strip. Our experiments showed that successful trapping requires an AC/DC combined electric field: the DC component is mainly to induce electroosmotic flow for transporting particles to the trapping location; the AC component induces ICEK phenomena over the edge of the conducting strip for particle trapping. The performance of the technique is examined with respect to the applied electric voltage, AC frequency and the particle size. We observed that the trapped particles form a narrow band (nearly a straight line) defined by the edge of the conducting strip, thereby allowing localized particle enrichment. For instance, we found that under certain conditions a high particle enrichment ratio of 200 was achieved within 30 seconds. We also demonstrated that the proposed technique was able to trap particles from several microns down to several tens of nanometer. We believe that the proposed ICEK trapping would have great flexibility that the trapping location can be readily varied by controlling the location of the patterned conducting strip and multiple-location trapping can be expected with the use of multiple conducting strips.

Measurement of S-nitrosylated Proteins in Tissues of Rats Fed Diets with Differing Levels of Nitrite

DTIC Science & Technology

2011-12-01

project could be substantial. Excluding immediate deaths, 50 % of all battlefield deaths (KIAs) occur within 5 minutes of injury, prior to the...exists for quantitation of DMPO thioethers. Furthermore, DMPO exhibits low cytotoxicity. In spin trapping experiments, cells tolerate this nitrone in

Human Intelligence: All Humans, All Minds, All the Time

DTIC Science & Technology

2010-05-01

CNSNews.com Staff, March 16, 2006. The lack of an independent Operational Test & Evaluation Agency (OTEA) has been a back- burner issue since Chuck Spin- ney...trapped in a bubble with industrial era carpetbaggers. From Small is Beautiful: Eco - nomics As If People Mattered to Human Scale to ELECTION 2008

RAPID MEASUREMENT OF AQUEOUS HYDROXYL RADICAL CONCENTRATIONS IN STEADY-STATE HO· FLUX SYSTEMS

EPA Science Inventory

The spin-trap compound a-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN) is utilized for the detection and quantitation of the hydroxyl radical (HO·) in aqueous solution. Capillary electrophoresis enables rapid analysis of the probe compound. The thermally unstable HO· radical ...

Entropy: A Unifying Path for Understanding Complexity in Natural, Artificial and Social Systems

DTIC Science & Technology

2011-07-01

data in what concerns its consequences. Definitively the BG entropy can only be understood nowadays as a first, most important, step, but not as the...applications to natural systems (trapped ions, spin-glass, dusty plasma, earthquakes, turbulence, astrophysical objects, cosmology , black holes, etc

Exact mapping of the 2+1 Dirac oscillator onto the Jaynes-Cummings model: Ion-trap experimental proposal

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

Bermudez, A.; Martin-Delgado, M. A.; Solano, E.

2007-10-15

We study the dynamics of the 2+1 Dirac oscillator exactly and find spin oscillations due to a Zitterbewegung of purely relativistic origin. We find an exact mapping of this quantum-relativistic system onto a Jaynes-Cummings model, describing the interaction of a two-level atom with a quantized single-mode field. This equivalence allows us to map a series of quantum optical phenomena onto the relativistic oscillator and vice versa. We make a realistic experimental proposal, in reach with current technology, for studying the equivalence of both models using a single trapped ion.

Coherent spin-exchange via a quantum mediator.

PubMed

Baart, Timothy Alexander; Fujita, Takafumi; Reichl, Christian; Wegscheider, Werner; Vandersypen, Lieven Mark Koenraad

2017-01-01

Coherent interactions at a distance provide a powerful tool for quantum simulation and computation. The most common approach to realize an effective long-distance coupling 'on-chip' is to use a quantum mediator, as has been demonstrated for superconducting qubits and trapped ions. For quantum dot arrays, which combine a high degree of tunability with extremely long coherence times, the experimental demonstration of the time evolution of coherent spin-spin coupling via an intermediary system remains an important outstanding goal. Here, we use a linear triple-quantum-dot array to demonstrate a coherent time evolution of two interacting distant spins via a quantum mediator. The two outer dots are occupied with a single electron spin each, and the spins experience a superexchange interaction through the empty middle dot, which acts as mediator. Using single-shot spin readout, we measure the coherent time evolution of the spin states on the outer dots and observe a characteristic dependence of the exchange frequency as a function of the detuning between the middle and outer dots. This approach may provide a new route for scaling up spin qubit circuits using quantum dots, and aid in the simulation of materials and molecules with non-nearest-neighbour couplings such as MnO (ref. 27), high-temperature superconductors and DNA. The same superexchange concept can also be applied in cold atom experiments.

Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37 K

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

Fenker, B.; Behr, J. A.; Melconian, D.

We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in themore » $${\\beta }^{+}$$-decay of the same atoms. These results will be used to test the V ₋ A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $$\\bar{P}=0.9913\\pm 0.0009$$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has $$0.2 \\% $$ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $$\\lt 0.1 \\% $$, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.« less

Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37 K

DOE PAGES

Fenker, B.; Behr, J. A.; Melconian, D.; ...

2016-07-13

We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in themore » $${\\beta }^{+}$$-decay of the same atoms. These results will be used to test the V ₋ A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $$\\bar{P}=0.9913\\pm 0.0009$$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has $$0.2 \\% $$ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $$\\lt 0.1 \\% $$, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.« less

Uncovering the density of nanowire surface trap states hidden in the transient photoconductance.

PubMed

Xu, Qiang; Dan, Yaping

2016-09-21

The gain of nanoscale photoconductors is closely correlated with surface trap states. Mapping out the density of surface trap states in the semiconductor bandgap is crucial for engineering the performance of nanoscale photoconductors. Traditional capacitive techniques for the measurement of surface trap states are not readily applicable to nanoscale devices. Here, we demonstrate a simple technique to extract the information on the density of surface trap states hidden in the transient photoconductance that is widely observed. With this method, we found that the density of surface trap states of a single silicon nanowire is ∼10(12) cm(-2) eV(-1) around the middle of the upper half bandgap.

Radio-controlled model design and testing techniques for stall/spin evaluation of general-aviation aircraft

NASA Technical Reports Server (NTRS)

Burk, S. M., Jr.; Wilson, C. F., Jr.

1975-01-01

A relatively inexpensive radio-controlled model stall/spin test technique was developed. Operational experiences using the technique are presented. A discussion of model construction techniques, spin-recovery parachute system, data recording system, and movie camera tracking system is included. Also discussed are a method of measuring moments of inertia, scaling of engine thrust, cost and time required to conduct a program, and examples of the results obtained from the flight tests.

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.

Molecular transport network security using multi-wavelength optical spins.

PubMed

Tunsiri, Surachai; Thammawongsa, Nopparat; Mitatha, Somsak; Yupapin, Preecha P

2016-01-01

Multi-wavelength generation system using an optical spin within the modified add-drop optical filter known as a PANDA ring resonator for molecular transport network security is proposed. By using the dark-bright soliton pair control, the optical capsules can be constructed and applied to securely transport the trapped molecules within the network. The advantage is that the dark and bright soliton pair (components) can securely propagate for long distance without electromagnetic interference. In operation, the optical intensity from PANDA ring resonator is fed into gold nano-antenna, where the surface plasmon oscillation between soliton pair and metallic waveguide is established.

Spin-orbit evolution of Mercury revisited

NASA Astrophysics Data System (ADS)

Noyelles, Benoît; Frouard, Julien; Makarov, Valeri V.; Efroimsky, Michael

2014-10-01

Although it is accepted that the significant eccentricity of Mercury (0.206) favours entrapment into the 3:2 spin-orbit resonance, open are the questions of how and when the capture took place. A recent work by Makarov (Makarov, V.V. [2012]. Astrophys. J., 752, 73) has proven that trapping into this state is certain for eccentricities larger than 0.2, provided we use a realistic tidal model based on the Darwin-Kaula expansion of the tidal torque. While in Ibid. a Mercury-like planet had its eccentricity fixed, we take into account its evolution. To that end, a family of possible histories of the eccentricity is generated, based on synthetic time evolution consistent with the expected statistics of the distribution of eccentricity. We employ a model of tidal friction, which takes into account both the rheology and self-gravitation of the planet. As opposed to the commonly used constant time lag (CTL) and constant phase lag (CPL) models, the physics-based tidal model changes dramatically the statistics of the possible final spin states. First, we discover that after only one encounter with the spin-orbit 3:2 resonance this resonance becomes the most probable end-state. Second, if a capture into this (or any other) resonance takes place, the capture becomes final, several crossings of the same state being forbidden by our model. Third, within our model the trapping of Mercury happens much faster than previously believed: for most histories, 10-20 Myr are sufficient. Fourth, even a weak laminar friction between the solid mantle and a molten core would most likely result in a capture in the 2:1 or even higher resonance, which is confirmed both semi-analytically and by limited numerical simulations. So the principal novelty of our paper is that the 3:2 end-state is more ancient than the same end-state obtained when the constant time lag model is employed. The swift capture justifies our treatment of Mercury as a homogeneous, unstratified body whose liquid core had not yet formed by the time of trapping. We also provide a critical analysis of the hypothesis by Wieczorek et al. (Wieczorek, M.A., Correia, A.C.M., Le Feuvre, M., Laskar, J., Rambaux, N. [2012]. Nat. Geosci., 5, 18-21) that the early Mercury might had been retrograde, whereafter it synchronised its spin and then accelerated it to the 3:2 resonance. Accurate processing of the available data on cratering does not support that hypothesis, while the employment of a realistic rheology invalidates a key element of the hypothesis, an intermediate pseudosynchronous state needed to spin-up to the 3:2 resonance.

One-Way Particle Transport Using Oscillatory Flow in Asymmetric Traps.

PubMed

Lee, Jaesung; Burns, Mark A

2018-03-01

One challenge of integrating of passive, microparticles manipulation techniques into multifunctional microfluidic devices is coupling the continuous-flow format of most systems with the often batch-type operation of particle separation systems. Here, a passive fluidic technique-one-way particle transport-that can conduct microparticle operations in a closed fluidic circuit is presented. Exploiting pass/capture interactions between microparticles and asymmetric traps, this technique accomplishes a net displacement of particles in an oscillatory flow field. One-way particle transport is achieved through four kinds of trap-particle interactions: mechanical capture of the particle, asymmetric interactions between the trap and the particle, physical collision of the particle with an obstacle, and lateral shift of the particle into a particle-trapping stream. The critical dimensions for those four conditions are found by numerically solving analytical mass balance equations formulated using the characteristics of the flow field in periodic obstacle arrays. Visual observation of experimental trap-particle dynamics in low Reynolds number flow (<0.01) confirms the validity of the theoretical predictions. This technique can transport hundreds of microparticles across trap rows in only a few fluid oscillations (<500 ms per oscillation) and separate particles by their size differences. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanism of UVA-dependent DNA damage induced by an antitumor drug dacarbazine in relation to its photogenotoxicity.

PubMed

Iwamoto, Takuya; Hiraku, Yusuke; Okuda, Masahiro; Kawanishi, Shosuke

2008-03-01

It has been reported that dacarbazine (DTIC) is photogenotoxic. The purpose of this study is to clarify the mechanism of photogenotoxicity induced by DTIC. We examined DNA damage induced by UVA-irradiated DTIC using 32P-5'-end-labeled DNA fragments obtained from human genes. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in calf thymus DNA was measured by high performance liquid chromatograph with an electrochemical detector. Electron spin resonance (ESR) spin-trapping experiments were performed to detect radical species generated from UVA-irradiated DTIC. UVA-irradiated DTIC caused DNA damage at guanine residues, especially at the 5'-GGT-3' sequence in the presence of Cu(II) and also induced 8-oxodG generation in calf thymus DNA. DTIC-induced photodamage to DNA fragments was partially inhibited by catalase, whereas 8-oxodG formation was significantly increased by catalase. NaN3, a carbene scavenger, inhibited DNA damage and 8-oxodG formation in a dose-dependent manner, suggesting that carbene intermediates are involved. The ESR spin-trapping experiments demonstrated the generation of aryl radicals in the process of photodegradation of DTIC. Photoactivated DTIC generates the carbene and aryl radicals, which may induce both DNA adduct and 8-oxodG formation, resulting in photogenotoxicity. This study could provide an insight into the safe usage of DTIC.

Observation of entanglement between a quantum dot spin and a single photon.

PubMed

Gao, W B; Fallahi, P; Togan, E; Miguel-Sanchez, J; Imamoglu, A

2012-11-15

Entanglement has a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen-vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin-photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.

Coherent electron-spin-resonance manipulation of three individual spins in a triple quantum dot

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

Noiri, A.; Yoneda, J.; Nakajima, T.

2016-04-11

Quantum dot arrays provide a promising platform for quantum information processing. For universal quantum simulation and computation, one central issue is to demonstrate the exhaustive controllability of quantum states. Here, we report the addressable manipulation of three single electron spins in a triple quantum dot using a technique combining electron-spin-resonance and a micro-magnet. The micro-magnet makes the local Zeeman field difference between neighboring spins much larger than the nuclear field fluctuation, which ensures the addressable driving of electron-spin-resonance by shifting the resonance condition for each spin. We observe distinct coherent Rabi oscillations for three spins in a semiconductor triple quantummore » dot with up to 25 MHz spin rotation frequencies. This individual manipulation over three spins enables us to arbitrarily change the magnetic spin quantum number of the three spin system, and thus to operate a triple-dot device as a three-qubit system in combination with the existing technique of exchange operations among three spins.« less

ESR analysis of natural and gamma irradiated coriander (Coriandrum sativum L.) seeds

NASA Astrophysics Data System (ADS)

Sezer, M. Özgür; Kaplan, Necati; Sayin, Ulku

2017-12-01

Electron spin resonance (ESR) is a powerful technique to detect radicals trapped in cellulosic food products and has been suggested as a useful method for identification of irradiated herbal foodstuffs. Coriander spice which has important medicinal properties was investigated using ESR spectroscopy. Radicals in natural and irradiated coriander samples were determined at room temperature. ESR spectra of natural sample were characterized by a single central signal with ? value and gamma irradiation produced satellite peaks attributed to cellulose-like radical which is used as a marker for detection of irradiated cellulosic plant products. The spectroscopic splitting values of radicals were determined. Dose dependency and stability of this center were analyzed by dose response and kinetic measurements. The reported results about activation energy, thermal life time and dose response relationship of the cellulose-like radical accurately prove that ESR can be used for identification of irradiated coriander spice seeds.

Dynamics of localized charges in dopamine-modified TiO{sub 2} and their effect on the formation of reactive oxygen species.

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

Dimitrijevic, N.; Rozhkova, E.; Rajh, T.

Modification of TiO{sub 2} nanoparticles with dopamine enables harvesting of visible light and promotes spatial separation of charges. The formation of reactive oxygen species (OH, {sup 1}O{sub 2}, O{sub 2}{sup -}, HO{sub 2}, H{sub 2}O{sub 2}) upon illumination of TiO{sub 2}/dopamine was studied using complementary spin-trap EPR and radical-induced fluorescence techniques. The localization of holes on dopamine suppresses oxidation of adsorbed water molecules at the surface of nanoparticles, and thus formation of OH radicals. At the same time, dopamine does not affect electronic properties of photogenerated electrons and their reaction with dissolved oxygen to produce superoxide anions. Superoxide anions aremore » proposed to generate singlet oxygen through dismutation reaction, resulting in a low yield of {sup 1}O{sub 2} detected.« less

Internal oxidation phenomenon in pure copper

NASA Astrophysics Data System (ADS)

Rudolf, Rebeka; Anžel, Ivan

2009-04-01

This paper presents two special kinds of internal oxidation phenomenon that can take place in pure metals containing a high concentration of non-equilibrium defects. These processes are Internal Oxidation (IO) and Internal Carbonisation (IC). Both processes start with the dissolution of oxidant (O or C) into the pure metal at the free surfaces, and continue with the diffusion of oxidant atoms into the metal matrix volume, where they are trapped at numerous defects within the crystal lattice. Increasing oxidant activity at these places causes local oxidation of the matrix and, consequently, precipitation of fine oxide or graphite particles. The IO and IC processes were tested on the rapidly solidified pure copper which was produced by the Chill-Block Melt Spinning Technique. Analysis of the IO process showed the formation of Cu-Cu2O, and the formation of Cu-C composite from the IC process.

Rare earth ions doped ZnO: Synthesis, characterization and preliminary photoactivity assessment

NASA Astrophysics Data System (ADS)

Cerrato, Erik; Gionco, Chiara; Berruti, Ilaria; Sordello, Fabrizio; Calza, Paola; Paganini, Maria Cristina

2018-08-01

This work reports the effect of doping zinc oxide with lanthanide ions on structural, EPR and UV visible properties. Bare and doped samples were synthesized using the simple and green hydrothermal process. Different rare earth ions (RE = La, Ce, Pr, Er and Yb) with 1% molar ratio RE/Zn were used. The samples have been studied using X Ray Diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Finally, electron paramagnetic resonance (EPR) spectroscopy, was used to assess the materials photoactivity under UV irradiation, both in solid state, to see the charge carriers' generation and in solution, evaluating the OH• radical formation using the DMPO (5,5-Dimethyl-1-Pyrroline-N-Oxide) spin trapping technique. The results suggest that the synthesized materials could be interesting systems for the photocatalytic abatement of emerging organic persistent pollutants in wastewater treatment plants.

Planar ion trap (retarding potential analyzer) experiment for atmosphere explorer

NASA Technical Reports Server (NTRS)

Hanson, W. B.; Sanatani, S.; Lippincott, C. R.; Zuccaro, D. R.

1982-01-01

The retarding potential analyzer and drift meter were carried aboard all three Atmosphere Explorer spacecraft. These instruments measure the total thermal ion concentration and temperature, the bulk thermal ion velocity vector and some limited properties of the relative abundance of H(+), He(+), O(+) and molecular ions. These instruments functioned with no internal failures on all the spacecraft. On AE-E there existed some evidence for external surface contamination that damaged the integrity of the RPA sweep grids. This led to some difficulties in data reduction and interpretation that did not prove to be a disastrous problem. The AE-D spacecraft functioned for only a few months before it re-entered. During this time the satellite suffered from a nutation about the spin axis of about + or - 2 deg. This 2 deg modulation was superimposed upon the ion drift meter horizontal ion arrival angle output requiring the employment of filtering techniques to retrieve the real data.

Effect of exogenous hydrogen peroxide on biophoton emission from radish root cells.

PubMed

Rastogi, Anshu; Pospísil, Pavel

2010-01-01

Biophotons spontaneously emitted from radish root cells were detected using highly sensitive photomultiplier tube. Freshly isolated radish root cells exhibited spontaneous photon emission of about 4 counts s(-1). Addition of hydrogen peroxide to the cells caused significant enhancement in biophoton emission to about 500 counts s(-1). Removal of molecular oxygen using glucose/glucose oxidase system and scavengering of reactive oxygen species by reducing agents such are sodium ascorbate and cysteine completely diminished biophoton emission. Spectral analysis of the hydrogen peroxide-induced biophoton emission indicates that biophotons are emitted mainly in green-red region of the spectra. The data provided by electron paramagnetic resonance spin-trapping technique showed that formation of singlet oxygen observed after addition of H2O2 correlates with enhancement in biophoton emission. These observations provide direct evidence that singlet oxygen is involved in biophoton emission from radish root cells. Copyright 2010 Elsevier Masson SAS. All rights reserved.

Ultrafast state detection and 2D ion crystals in a Paul trap

NASA Astrophysics Data System (ADS)

Ip, Michael; Ransford, Anthony; Campbell, Wesley

2016-05-01

Projective readout of quantum information stored in atomic qubits typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also study 2D Coulomb crystals of atomic ions in an oblate Paul trap. We find that crystals with hundreds of ions can be held in the trap, potentially offering an alternative to the use of Penning traps for the quantum simulation of 2D lattice spin models. We discuss the classical physics of these crystals and the metastable states that are supported in 2D. This work is supported by the US Army Research Office.

Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum.

PubMed

Hsu, Jen-Feng; Ji, Peng; Lewandowski, Charles W; D'Urso, Brian

2016-07-22

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.

Cooling the motion of diamond nanocrystals in a magneto-gravitational trap in high vacuum

DOE PAGES

Hsu, Jen -Feng; Ji, Peng; Lewandowski, Charles W.; ...

2016-07-22

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamondmore » nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. Furthermore, we demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.« less

Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum

PubMed Central

Hsu, Jen-Feng; Ji, Peng; Lewandowski, Charles W.; D’Urso, Brian

2016-01-01

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K. PMID:27444654

Obliquity evolution of the minor satellites of Pluto and Charon

NASA Astrophysics Data System (ADS)

Quillen, Alice C.; Nichols-Fleming, Fiona; Chen, Yuan-Yuan; Noyelles, Benoît

2017-09-01

New Horizons mission observations show that the small satellites Styx, Nix, Kerberos and Hydra, of the Pluto-Charon system, have not tidally spun-down to near synchronous spin states and have high obliquities with respect to their orbit about the Pluto-Charon binary (Weaver, 2016). We use a damped mass-spring model within an N-body simulation to study spin and obliquity evolution for single spinning non-round bodies in circumbinary orbit. Simulations with tidal dissipation alone do not show strong obliquity variations from tidally induced spin-orbit resonance crossing and this we attribute to the high satellite spin rates and low orbital eccentricities. However, a tidally evolving Styx exhibits intermittent obliquity variations and episodes of tumbling. During a previous epoch where Charon migrated away from Pluto, the minor satellites could have been trapped in orbital mean motion inclination resonances. An outward migrating Charon induces large variations in Nix and Styx's obliquities. The cause is a commensurability between the mean motion resonance frequency and the spin precession rate of the spinning body. As the minor satellites are near mean motion resonances, this mechanism could have lifted the obliquities of all four minor satellites. The high obliquities need not be primordial if the minor satellites were at one time captured into mean motion resonances.

Collapse and revival of entanglement between qubits coupled to a spin coherent state

NASA Astrophysics Data System (ADS)

Bahari, Iskandar; Spiller, Timothy P.; Dooley, Shane; Hayes, Anthony; McCrossan, Francis

We extend the study of the Jayne-Cummings (JC) model involving a pair of identical two-level atoms (or qubits) interacting with a single mode quantized field. We investigate the effects of replacing the radiation field mode with a composite spin, comprising N qubits, or spin-1/2 particles. This model is relevant for physical implementations in superconducting circuit QED, ion trap and molecular systems. For the case of the composite spin prepared in a spin coherent state, we demonstrate the similarities of this set-up to the qubits-field model in terms of the time evolution, attractor states and in particular the collapse and revival of the entanglement between the two qubits. We extend our analysis by taking into account an effect due to qubit imperfections. We consider a difference (or “mismatch”) in the dipole interaction strengths of the two qubits, for both the field mode and composite spin cases. To address decoherence due to this mismatch, we then average over this coupling strength difference with distributions of varying width. We demonstrate in both the field mode and the composite spin scenarios that increasing the width of the “error” distribution increases suppression of the coherent dynamics of the coupled system, including the collapse and revival of the entanglement between the qubits.

Properties of Fiber Cell Plasma Membranes Isolated from the Cortex and Nucleus of the Porcine Eye Lens

PubMed Central

Mainali, Laxman; Raguz, Marija; O’Brien, William J.; Subczynski, Witold K.

2012-01-01

The organization and physical properties of the lipid bilayer portion of intact cortical and nuclear fiber cell plasma membranes isolated from the eyes lenses of two-year-old pigs were studied using electron paramagnetic resonance (EPR) spin-labeling. Membrane fluidity, hydrophobicity, and the oxygen transport parameter (OTP) were assessed from the EPR spectra of precisely positioned spin labels. Intact cortical and nuclear membranes, which include membrane proteins, were found to contain three distinct lipid environments. These lipid environments were termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain (lipids in protein aggregates). The amount of boundary and trapped lipids was greater in intact nuclear membranes than in cortical membranes. The properties of intact membranes were compared with the organization and properties of lens lipid membranes made of the total lipid extracts from the lens cortex or nucleus. In cortical lens lipid membranes, only one homogenous environment was detected, which was designated as a bulk lipid domain (phospholipid bilayer saturated with cholesterol). Lens lipid membranes prepared from the lens nucleus possessed two domains, assigned as a bulk lipid domain and a cholesterol bilayer domain (CBD). In intact nuclear membranes, it was difficult to discriminate the CBD, which was clearly detected in nuclear lens lipid membranes because the OTP measured in the CBD is the same as in the domain formed by trapped lipids. The two domains unique to intact membranes—namely, the domain formed by boundary lipids and the domain formed by trapped lipids—were most likely formed due to the presence of membrane proteins. It is concluded that formation of rigid and practically impermeable domains is enhanced in the lens nucleus, indicating changes in membrane composition that may help to maintain low oxygen concentration in this lens region. PMID:22326289

Nearly extremal apparent horizons in simulations of merging black holes

NASA Astrophysics Data System (ADS)

Lovelace, Geoffrey; Scheel, Mark A.; Owen, Robert; Giesler, Matthew; Katebi, Reza; Szilágyi, Béla; Chu, Tony; Demos, Nicholas; Hemberger, Daniel A.; Kidder, Lawrence E.; Pfeiffer, Harald P.; Afshari, Nousha

2015-03-01

The spin angular momentum S of an isolated Kerr black hole is bounded by the surface area A of its apparent horizon: 8π S≤slant A, with equality for extremal black holes. In this paper, we explore the extremality of individual and common apparent horizons for merging, rapidly spinning binary black holes. We consider simulations of merging black holes with equal masses M and initial spin angular momenta aligned with the orbital angular momentum, including new simulations with spin magnitudes up to S/{{M}2}=0.994. We measure the area and (using approximate Killing vectors) the spin on the individual and common apparent horizons, finding that the inequality 8π S\\lt A is satisfied in all cases but is very close to equality on the common apparent horizon at the instant it first appears. We also evaluate the Booth-Fairhurst extremality, whose value for a given apparent horizon depends on the scaling of the horizon’s null normal vectors. In particular, we introduce a gauge-invariant lower bound on the extremality by computing the smallest value that Booth and Fairhurst’s extremality parameter can take for any scaling. Using this lower bound, we conclude that the common horizons are at least moderately close to extremal just after they appear. Finally, following Lovelace et al (2008 Phys. Rev. D 78 084017), we construct quasiequilibrium binary-black hole initial data with ‘overspun’ marginally trapped surfaces with 8π S\\gt A. We show that the overspun surfaces are indeed superextremal: our lower bound on their Booth-Fairhurst extremality exceeds unity. However, we confirm that these superextremal surfaces are always surrounded by marginally outer trapped surfaces (i.e., by apparent horizons) with 8π S\\lt A. The extremality lower bound on the enclosing apparent horizon is always less than unity but can exceed the value for an extremal Kerr black hole.

Comparative study of glass tube and mist chamber sampling techniques for the analysis of gaseous carbonyl compounds

NASA Astrophysics Data System (ADS)

François, Stéphanie; Perraud, Véronique; Pflieger, Maryline; Monod, Anne; Wortham, Henri

In this work, glass tube and mist chamber sampling techniques using 2,4-dinitrophenylhydrazine as derivative agent for the analysis of gaseous carbonyl compounds are compared. Trapping efficiencies of formaldehyde, acetaldehyde, propionaldehyde, acetone, acrolein, glyoxal, crotonaldehyde, benzaldehyde, butyraldehyde and valeraldehyde are experimentally determined using a gas-phase generator. In addition to generalise our results to all atmospheric gaseous compounds and derivative agents, theoretical trapping efficiencies and enrichment factors are expressed taking into account mechanisms involved in the two kinds of traps. Theoretical and experimental results show that, as expected, the trapping efficiencies of the glass tube depend mainly on solubility of compounds. The results provide new information and better understanding of phenomena occurring in the mist chamber and the ability of this sampler to concentrate the samples. Hence, the mist chamber is the more convenient sampling method when the trapping is associated to a fast derivatisation of the compounds and the glass tube technique must be used to trap atmospheric compounds without simultaneous derivatisation.

Thermoelectrically cooled water trap

DOEpatents

Micheels, Ronald H [Concord, MA

2006-02-21

A water trap system based on a thermoelectric cooling device is employed to remove a major fraction of the water from air samples, prior to analysis of these samples for chemical composition, by a variety of analytical techniques where water vapor interferes with the measurement process. These analytical techniques include infrared spectroscopy, mass spectrometry, ion mobility spectrometry and gas chromatography. The thermoelectric system for trapping water present in air samples can substantially improve detection sensitivity in these analytical techniques when it is necessary to measure trace analytes with concentrations in the ppm (parts per million) or ppb (parts per billion) partial pressure range. The thermoelectric trap design is compact and amenable to use in a portable gas monitoring instrumentation.

A Novel Repair Technique for the Internal Thermal Control System Dual-Membrane Gas Trap

NASA Technical Reports Server (NTRS)

Leimkuehler, Thomas O.; Patel, Vipul; Reeves, Daniel R.; Holt, James M.

2005-01-01

A dual-membrane gas trap is currently used to remove gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). The gas trap consists of concentric tube membrane pairs, comprised of outer hydrophilic tubes and inner hydrophobic fibers. Liquid coolant passes through the outer hydrophilic membrane, which traps the gas bubbles. The inner hydrophobic fiber allows the trapped gas bubbles to pass through and vent to the ambient atmosphere in the cabin. The gas trap was designed to last for the entire lifetime of the ISS, and therefore was not designed to be repaired. However, repair of these gas traps is now a necessity due to contamination from the on-orbit ITCS fluid and other sources on the ground as well as a limited supply of flight gas traps. This paper describes a novel repair technique that has been developed that will allow the refurbishment of contaminated gas traps and their return to flight use.

UV laser-induced cross-linking in peptides

PubMed Central

Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

2013-01-01

RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics Talk: Equation of State of the Dilute Fermi Gases

NASA Astrophysics Data System (ADS)

Chang, Soon Yong

2008-04-01

In the recent years, dilute Fermi gases have played the center stage role in the many-body physics. The gas of neutral alkali atoms such as Lithium-6 and Potassium-40 can be trapped at temperatures below the Fermi degeneracy. The most relevant feature of these gases is that the interaction is tunable and strongly interacting superfluid can be artificially created. I will discuss the recent progress in understanding the ground state properties of the dilute Fermi gases at different interaction regimes. First, I will present the case of the spin symmetric systems where the Fermi gas can smoothly crossover from the BCS regime to the BEC regime. Then, I will discuss the case of the spin polarized systems, where different quantum phases can occur as a function of the polarization. In the laboratory, the trapped Fermi gas shows spatial dependence of the different quantum phases. This can be understood in the context of the local variation of the chemical potential. I will present the most accurate quantum ab initio results and the relevant experiments.

Calculated hyperfine coupling constants for 5,5-dimethyl-1-pyrroline N-oxide radical products in water and benzene

NASA Astrophysics Data System (ADS)

Nardali, Ş.; Ucun, F.; Karakaya, M.

2017-11-01

The optimized structures of some radical adducts of 5,5-dimethyl-1-pyrroline N-oxide were computed by different methods on ESR spectra. As trapped radicals, H, N3, NH2, CH3, CCl3, OOH in water and F, OH, CF3, CH2OH, OC2H5 in benzene solutions were used. The calculated isotropic hyperfine coupling constants of all the trapped radicals were compared with the corresponding experimental data. The hyperfine coupling constant due to the β proton of the nitroxide radical was seen to be consist with the McConnel's relation αβ = B 0 + B 1cos2θ and, to be effected with the opposite spin density of oxygen nucleus bonded to the nitrogen. It was concluded that in hyperfine calculations the DFT(B3PW91)/LanL2DZ level is superior computational quantum model relative to the used other level. Also, the study has been enriched by the computational of the optimized geometrical parameters, the hyper conjugative interaction energies, the atomic charges and spin densities for all the radical adducts.

Activated aging dynamics and effective trap model description in the random energy model

NASA Astrophysics Data System (ADS)

Baity-Jesi, M.; Biroli, G.; Cammarota, C.

2018-01-01

We study the out-of-equilibrium aging dynamics of the random energy model (REM) ruled by a single spin-flip Metropolis dynamics. We focus on the dynamical evolution taking place on time-scales diverging with the system size. Our aim is to show to what extent the activated dynamics displayed by the REM can be described in terms of an effective trap model. We identify two time regimes: the first one corresponds to the process of escaping from a basin in the energy landscape and to the subsequent exploration of high energy configurations, whereas the second one corresponds to the evolution from a deep basin to the other. By combining numerical simulations with analytical arguments we show why the trap model description does not hold in the former but becomes exact in the second.

Quantum magnetism in different AMO systems.

NASA Astrophysics Data System (ADS)

Rey, Ana Maria

One of the most important goals of modern quantum sciences is to learn how to control and entangle many-body systems and use them to make powerful and improved quantum devices, materials and technologies. However, since performing full state tomography does not scale favorably with the number of particles, as the size of quantum systems grow, it becomes extremely challenging to identify, and quantify the buildup of quantum correlations and coherence. In this talk I will report on a protocol that we have developed and experimentally demonstrated in a trapped ion quantum magnet in a Penning trap, which can perform quantum simulations of Ising spin models. In those experiments strong spin-spin interactions can be engineered through optical dipole forces that excite phonons of the crystals. The number of ions can be varied from tens to hundreds with high fidelity control. The protocol uses time reversal of the many-body dynamics, to measure out-of-time-order correlation functions (OTOCs). By measuring a family of OTOCs as a function of a tunable parameter we obtain fine-grained information about the state of the system encoded in the multiple quantum coherence spectrum, extract the quantum state purity, and demonstrate the build-up of up to 8-body correlations. We also use the protocol and comparisons to a full solution of the master equation to investigate the impact of spin-motion entanglement and decoherence in the quantum dynamics. Future applications of this protocol could enable studies of manybody localization, quantum phase transitions, and tests of the holographic duality between quantum and gravitational systems. Supported by NSF-PHY-1521080, JILA-NSF PFC-1125844, ARO and AFOSR-MURI.

Spin formalism and applications to new physics searches

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

Haber, H.E.

1994-12-01

An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of polarization and spin correlations for untangling new physics beyond the Standard Model at future colliders such as the LHC and a high energy e{sup +}e{sup {minus}} linear collider is then considered. A number of detailed examples are explored including the search for low-energy supersymmetry, a non-minimal Higgs boson sector,more » and new gauge bosons beyond the W{sup {+-}} and Z.« less

Electron-spin dynamics in Mn-doped GaAs using time-resolved magneto-optical techniques

NASA Astrophysics Data System (ADS)

Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Zhukov, E. A.; Yakovlev, D. R.; Bayer, M.

2009-08-01

We study the electron-spin dynamics in p -type GaAs doped with magnetic Mn acceptors by means of time-resolved pump-probe and photoluminescence techniques. Measurements in transverse magnetic fields show a long spin-relaxation time of 20 ns that can be uniquely related to electrons. Application of weak longitudinal magnetic fields above 100 mT extends the spin-relaxation times up to microseconds which is explained by suppression of the Bir-Aronov-Pikus spin relaxation for the electron on the Mn acceptor.

NMR in Pulsed Magnetic Fields on the Orthogonal Shastry-Sutherland spin system SrCu2 (BO3)2

NASA Astrophysics Data System (ADS)

Stern, Raivo; Kohlrautz, Jonas; Kühne, Hannes; Greene, Liz; Wosnitza, Jochen; Haase, Jügen

2015-03-01

SrCu2(BO3)2 is a quasi-two-dimensional spin system consisting of Cu2+ ions which form orthogonal spin singlet dimers, also known as the Shastry-Sutherland lattice, in the ground state. Though this system has been studied extensively using a variety of techniques to probe the spin triplet excitations, including recent magnetization measurements over 100 T, microscopic techniques, such as nuclear magnetic resonance (NMR), could provide further insight into the spin excitations and spin-coupling mechanisms. We demonstrate the feasibility of performing NMR on real physics system in pulsed magnets. We present 11B NMR spectra measured in pulsed magnetic fields up to 53 T, and compare those with prior results obtained in static magnetic fields. Herewith we prove the efficacy of this technique and then extend to higher fields to fully explore the spin structure of the 1/3 plateau. Support by EMFL, DFG, ETAg (EML+ & PUT210).

Low temperature solution processed high-κ ZrO2 gate dielectrics for nanoelectonics

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

2016-05-01

The high-κ gate dielectrics, specifically amorphous films offer salient features such as exceptional mechanical flexibility, smooth surfaces and better uniformity associated with low leakage current density. In this work, ∼35 nm thick amorphous ZrO2 films were deposited on silicon substrate at low temperature (300 °C, 1 h) from facile spin-coating method and characterized by various analytical techniques. The X-ray diffraction and X-ray photoelectron spectroscopy reveal the formation of amorphous phase ZrO2, while ellipsometry analysis together with the Atomic Force Microscope suggest the formation of dense film with surface roughness of 1.5 Å, respectively. The fabricated films were integrated in metal-oxide-semiconductor (MOS) structures to check the electrical capabilities. The oxide capacitance (Cox), flat band capacitance (CFB), flat band voltage (VFB), dielectric constant (κ) and oxide trapped charges (Qot) extracted from high frequency (1 MHz) C-V curve are 186 pF, 104 pF, 0.37 V, 15 and 2 × 10-11 C, respectively. The small flat band voltage 0.37 V, narrow hysteresis and very little frequency dispersion between 10 kHz-1 MHz suggest an excellent a-ZrO2/Si interface with very less trapped charges in the oxide. The films exhibit a low leakage current density 4.7 × 10-9 A/cm2 at 1 V. In addition, the charge transport mechanism across the MOSC is analyzed and found to have a strong bias dependence. The space charge limited conduction mechanism is dominant in the high electric field region (1.3-5 V) due to the presence of traps, while the trap-supported tunneling is prevailed in the intermediate region (0.35-1.3 V). Low temperature solution processed ZrO2 thin films obtained are of high quality and find their importance as a potential dielectric layer on Si and polymer based flexible electronics.

Methods for characterizing magnetic footprints of perpendicular magnetic recording writer heads

PubMed Central

Li, Shaoping; Lin, Ed; George, Zach; Terrill, Dave; Mendez, H.; Santucci, J.; Yie, Derek

2014-01-01

In this work, the magnetic footprints, along with some of its dynamic features in recording process, of perpendicular magnetic recording writer heads have been characterized by using three different techniques. Those techniques are the spin-stand stationary footprint technique, the spin-stand dynamic footprint technique, and the coherent writing technique combined with magnetic force microscope imaging method. The characteristics of those techniques have been compared to one another. It was found experimentally that the spin-stand stationary method could not precisely catch some peculiar recording dynamics of the write heads in certain conditions. The advantages and disadvantages among all those techniques are also examined and discussed in detail. PMID:24753633

Improved Apparatus to Study Matter-Wave Quantum Optics in a Sodium Spinor Bose-Einstein Condensate

NASA Astrophysics Data System (ADS)

Zhong, Shan; Bhagat, Anita; Zhang, Qimin; Schwettmann, Arne

2017-04-01

We present and characterize our recently improved experimental apparatus for studying matter-wave quantum optics in spin space in ultracold sodium gases. Improvements include our recent addition of a 3D-printed Helmholtz coil frame for field stabilization and a crossed optical dipole trap. Spin-exchange collisions in the F = 1 spinor Bose-Einstein condensate can be precisely controlled by microwave dressing, and generate pairs of entangled atoms with magnetic quantum numbers mF = + 1 and mF = - 1 from pairs of mF = 0 atoms. Spin squeezing generated by the collisions can reduce the noise of population measurements below the shot noise limit. Versatile microwave pulse sequences will be used to implement an interferometer, a phase-sensitive amplifier and other devices with sub-shot noise performance. With an added ion detector to detect Rydberg atoms via pulse-field ionization, we later plan to study the effect of Rydberg excitations on the spin evolution of the ultracold gas.

ESR investigations on γ-ray irradiated 3-methyl nylon 3

NASA Astrophysics Data System (ADS)

Catiker, Efkan; Guven, Olgun; Ozarslan, Ozdemir; Chipara, Mircea

2008-06-01

Electron spin resonance spectroscopy investigations on γ irradiated 3-methyl nylon 3 (poly-3-methyl β-alanine) are reported. The resonance spectra (recorded after the irradiation in nitrogen atmosphere has been stopped) have been attributed to the parallel and perpendicular components of a triplet line assigned to the delocalization of the uncoupled electron over an effective nuclear spin 1. It was suggested that this effective spin arises from the fast tunneling/rotation of a proton between two positions. The resonance spectra have been simulated with accuracy by using a simplified spin Hamiltonian and assuming Lorentzian-like resonance line shapes and axial asymmetry of the resonance line due to the trapping of free radicals in randomly oriented crystallites. The time evolution of free radicals in nitrogen atmosphere at room temperature has been analyzed. The decay kinetics of stable free radicals in 3-methyl nylon 3 (under inert atmosphere) has been investigated. It was shown that the radiation-induced radicals in inert atmosphere decay through a unimolecular reaction.

Generation Mechanism of Radical Species by Tyrosine-Tyrosinase Reaction

PubMed Central

Tada, Mika; Kohno, Masahiro; Kasai, Shigenobu; Niwano, Yoshimi

2010-01-01

Alleviated melanin formation in the skin through inhibition of tyrosine-tyrosinase reaction is one of the major targets of cosmetics for whitening ability. Since melanin has a pivotal role for photoprotection, there are pros and cons of inhibition of melanin formation. This study applying electron spin resonance (ESR)-spin trapping method revealed that •H and •OH are generated through tyrosine-tyrosinase reaction. When deuterium water was used instead of H2O, the signal of 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-H (a spin adduct of DMPO and •H) greatly decreased, whilst DMPO-OH (a spin adduct of DMPO and •OH) did not. Thus, it is suggested that •H was derived from H2O, and •OH through oxidative catalytic process of tyrosine to dopaquinone. Our study suggests that tyrosinase inhibitors might contribute to alleviate the oxidative damage of the skin by inhibiting •OH generation via the enzyme reaction. PMID:20838572

Efficient eigenvalue determination for arbitrary Pauli products based on generalized spin-spin interactions

NASA Astrophysics Data System (ADS)

Leibfried, D.; Wineland, D. J.

2018-03-01

Effective spin-spin interactions between ? qubits enable the determination of the eigenvalue of an arbitrary Pauli product of dimension N with a constant, small number of multi-qubit gates that is independent of N and encodes the eigenvalue in the measurement basis states of an extra ancilla qubit. Such interactions are available whenever qubits can be coupled to a shared harmonic oscillator, a situation that can be realized in many physical qubit implementations. For example, suitable interactions have already been realized for up to 14 qubits in ion traps. It should be possible to implement stabilizer codes for quantum error correction with a constant number of multi-qubit gates, in contrast to typical constructions with a number of two-qubit gates that increases as a function of N. The special case of finding the parity of N qubits only requires a small number of operations that is independent of N. This compares favorably to algorithms for computing the parity on conventional machines, which implies a genuine quantum advantage.

Spin trapping combined with quantitative mass spectrometry defines free radical redistribution within the oxidized hemoglobin:haptoglobin complex.

PubMed

Vallelian, Florence; Garcia-Rubio, Ines; Puglia, Michele; Kahraman, Abdullah; Deuel, Jeremy W; Engelsberger, Wolfgang R; Mason, Ronald P; Buehler, Paul W; Schaer, Dominik J

2015-08-01

Extracellular or free hemoglobin (Hb) accumulates during hemolysis, tissue damage, and inflammation. Heme-triggered oxidative reactions can lead to diverse structural modifications of lipids and proteins, which contribute to the propagation of tissue damage. One important target of Hb׳s peroxidase reactivity is its own globin structure. Amino acid oxidation and crosslinking events destabilize the protein and ultimately cause accumulation of proinflammatory and cytotoxic Hb degradation products. The Hb scavenger haptoglobin (Hp) attenuates oxidation-induced Hb degradation. In this study we show that in the presence of hydrogen peroxide (H2O2), Hb and the Hb:Hp complex share comparable peroxidative reactivity and free radical generation. While oxidation of both free Hb and Hb:Hp complex generates a common tyrosine-based free radical, the spin-trapping reaction with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) yields dissimilar paramagnetic products in Hb and Hb:Hp, suggesting that radicals are differently redistributed within the complex before reacting with the spin trap. With LC-MS(2) mass spectrometry we assigned multiple known and novel DMPO adduct sites. Quantification of these adducts suggested that the Hb:Hp complex formation causes extensive delocalization of accessible free radicals with drastic reduction of the major tryptophan and cysteine modifications in the β-globin chain of the Hb:Hp complex, including decreased βCys93 DMPO adduction. In contrast, the quantitative changes in DMPO adduct formation on Hb:Hp complex formation were less pronounced in the Hb α-globin chain. In contrast to earlier speculations, we found no evidence that free Hb radicals are delocalized to the Hp chain of the complex. The observation that Hb:Hp complex formation alters free radical distribution in Hb may help to better understand the structural basis for Hp as an antioxidant protein. Copyright © 2015 Elsevier Inc. All rights reserved.

Targeting copper(II)-induced oxidative stress and the acetylcholinesterase system in Alzheimer's disease using multifunctional tacrine-coumarin hybrid molecules.

PubMed

Hamulakova, Slavka; Poprac, Patrik; Jomova, Klaudia; Brezova, Vlasta; Lauro, Peter; Drostinova, Lenka; Jun, Daniel; Sepsova, Vendula; Hrabinova, Martina; Soukup, Ondrej; Kristian, Pavol; Gazova, Zuzana; Bednarikova, Zuzana; Kuca, Kamil; Valko, Marian

2016-08-01

Alzheimer's disease is a multifactorial disease that is characterized mainly by Amyloid-β (A-β) deposits, cholinergic deficit and extensive metal (copper, iron)-induced oxidative stress. In this work we present details of the synthesis, antioxidant and copper-chelating properties, DNA protection study, cholinergic activity and amyloid-antiaggregation properties of new multifunctional tacrine-7-hydroxycoumarin hybrids. The mode of interaction between copper(II) and hybrids and interestingly, the reduction of Cu(II) to Cu(I) species (for complexes Cu-5e-g) were confirmed by EPR measurements. EPR spin trapping on the model Fenton reaction, using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap, demonstrated a significantly suppressed formation of hydroxyl radicals for the Cu-5e complex in comparison with free copper(II). This suggests that compound 5e upon coordination to free copper ion prevents the Cu(II)-catalyzed decomposition of hydrogen peroxide, which in turn may alleviate oxidative stress-induced damage. Protective activity of hybrids 5c and 5e against DNA damage in a Fenton system (copper catalyzed) was found to be in excellent agreement with the EPR spin trapping study. Compound 5g was the most effective in the inhibition of acetylcholinesterase (hAChE, IC50=38nM) and compound 5b was the most potent inhibitor of butyrylcholinesterase (hBuChE, IC50=63nM). Compound 5c was the strongest inhibitor of A-β1-40 aggregation, although a significant inhibition (>50%) was detected for compounds 5b, 5d, 5e and 5g. Collectively, these results suggest that the design and investigation of multifunctional agents containing along with the acetylcholinesterase inhibitory segment also an antioxidant moiety capable of alleviating metal (copper)-induced oxidative stress, may be of importance in the treatment of Alzheimer's disease. Copyright © 2016 Elsevier Inc. All rights reserved.

Correlation study of theoretical and experimental results for spin tests of a 1/10 scale radio control model

NASA Technical Reports Server (NTRS)

Bihrle, W., Jr.

1976-01-01

A correlation study was conducted to determine the ability of current analytical spin prediction techniques to predict the flight motions of a current fighter airplane configuration during the spin entry, the developed spin, and the spin recovery motions. The airplane math model used aerodynamics measured on an exact replica of the flight test model using conventional static and forced-oscillation wind-tunnel test techniques and a recently developed rotation-balance test apparatus capable of measuring aerodynamics under steady spinning conditions. An attempt was made to predict the flight motions measured during stall/spin flight testing of an unpowered, radio-controlled model designed to be a 1/10 scale, dynamically-scaled model of a current fighter configuration. Comparison of the predicted and measured flight motions show that while the post-stall and spin entry motions were not well-predicted, the developed spinning motion (a steady flat spin) and the initial phases of the spin recovery motion are reasonably well predicted.

Observation of a Time Quasicrystal and Its Transition to a Superfluid Time Crystal.

PubMed

Autti, S; Eltsov, V B; Volovik, G E

2018-05-25

We report experimental realization of a quantum time quasicrystal and its transformation to a quantum time crystal. We study Bose-Einstein condensation of magnons, associated with coherent spin precession, created in a flexible trap in superfluid ^{3}He-B. Under a periodic drive with an oscillating magnetic field, the coherent spin precession is stabilized at a frequency smaller than that of the drive, demonstrating spontaneous breaking of discrete time translation symmetry. The induced precession frequency is incommensurate with the drive, and hence, the obtained state is a time quasicrystal. When the drive is turned off, the self-sustained coherent precession lives a macroscopically long time, now representing a time crystal with broken symmetry with respect to continuous time translations. Additionally, the magnon condensate manifests spin superfluidity, justifying calling the obtained state a time supersolid or a time supercrystal.

Observation of a Time Quasicrystal and Its Transition to a Superfluid Time Crystal

NASA Astrophysics Data System (ADS)

Autti, S.; Eltsov, V. B.; Volovik, G. E.

2018-05-01

We report experimental realization of a quantum time quasicrystal and its transformation to a quantum time crystal. We study Bose-Einstein condensation of magnons, associated with coherent spin precession, created in a flexible trap in superfluid 3He-B . Under a periodic drive with an oscillating magnetic field, the coherent spin precession is stabilized at a frequency smaller than that of the drive, demonstrating spontaneous breaking of discrete time translation symmetry. The induced precession frequency is incommensurate with the drive, and hence, the obtained state is a time quasicrystal. When the drive is turned off, the self-sustained coherent precession lives a macroscopically long time, now representing a time crystal with broken symmetry with respect to continuous time translations. Additionally, the magnon condensate manifests spin superfluidity, justifying calling the obtained state a time supersolid or a time supercrystal.

Observation of a γ-decaying millisecond isomeric state in 128Cd80

NASA Astrophysics Data System (ADS)

Jungclaus, A.; Grawe, H.; Nishimura, S.; Doornenbal, P.; Lorusso, G.; Simpson, G. S.; Söderström, P.-A.; Sumikama, T.; Taprogge, J.; Xu, Z. Y.; Baba, H.; Browne, F.; Fukuda, N.; Gernhäuser, R.; Gey, G.; Inabe, N.; Isobe, T.; Jung, H. S.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Li, Z.; Sakurai, H.; Schaffner, H.; Shimizu, Y.; Steiger, K.; Suzuki, H.; Takeda, H.; Vajta, Zs.; Watanabe, H.; Wu, J.; Yagi, A.; Yoshinaga, K.; Benzoni, G.; Bönig, S.; Chae, K. Y.; Coraggio, L.; Daugas, J.-M.; Drouet, F.; Gadea, A.; Gargano, A.; Ilieva, S.; Itaco, N.; Kondev, F. G.; Kröll, T.; Lane, G. J.; Montaner-Pizá, A.; Moschner, K.; Mücher, D.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Wendt, A.

2017-09-01

A new high-spin isomer in the neutron-rich nucleus 128Cd was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T1/2 = 6.3 (8) ms was measured for the new state which was tentatively assigned a spin/parity of (15-). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129Cd. In the present experiment no evidence was found for the decay of a 18+E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0h11/2 and the 0g9/2 orbit, respectively, which is predicted to exist by the shell model.

Measurement of the Length of an Optical Trap

NASA Technical Reports Server (NTRS)

Wrbanek, Susan Y.

2010-01-01

NASA Glenn has been involved in developing optical trapping and optical micromanipulation techniques in order to develop a tool that can be used to probe, characterize, and assemble nano and microscale materials to create microscale sensors for harsh flight environments. In order to be able to assemble a sensor or probe candidate sensor material, it is useful to know how far an optical trap can reach; that is, the distance beyond/below the stable trapping point through which an object will be drawn into the optical trap. Typically, to measure the distance over which an optical trap would influence matter in a horizontal (perpendicular to beam propagation) direction, it was common to hold an object in one optical trap, place a second optical trap a known distance away, turn off the first optical trap, and note if the object was moved into the second trap when it was turned on. The disadvantage of this technique is that it only gives information of trap influence distance in horizontal (x y) directions. No information about the distance of the influence of the trap is gained in the direction of propagation of the beam (the z direction). A method was developed to use a time-of-flight technique to determine the length along the propagation direction of an optical trap beam over which an object may be drawn into the optical trap. Test objects (polystyrene microspheres) were held in an optical trap in a water-filled sample chamber and raised to a pre-determined position near the top of the sample chamber. Next, the test objects were released by blocking the optical trap beam. The test objects were allowed to fall through the water for predetermined periods of time, at the end of which the trapping beam was unblocked. It was noted whether or not the test object returned to the optical trap or continued to fall. This determination of the length of an optical trap's influence by this manner assumes that the test object falls through the water in the sample chamber at terminal velocity for the duration of its fall, so that the distance of trap influence can be computed simply by: d = VTt, where d is the trap length (or distance of trap reach), VT is the terminal velocity of the test object, and t is the time interval over which the object is allowed to fall.

Dynamic detection of spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance (Conference Presentation)

NASA Astrophysics Data System (ADS)

Crowell, Paul A.; Liu, Changjiang; Patel, Sahil; Peterson, Tim; Geppert, Chad C.; Christie, Kevin; Stecklein, Gordon; Palmstrøm, Chris J.

2016-10-01

A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is its precession in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become ineffective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet to precess at resonance instead of relying only on the Larmor precession of the spin accumulation in the semiconductor, an electrically generated spin accumulation can be detected up to 300 K. The injection bias and temperature dependence of the measured spin signal agree with those obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (< 100 psec), a regime that is not accessible in semiconductors using traditional Hanle techniques. The measurements were carried out on epitaxial Heusler alloy (Co2FeSi or Co2MnSi)/n-GaAs heterostructures. Lateral spin valve devices were fabricated by electron beam and photolithography. We compare measurements carried out by the new FMR-based technique with traditional non-local and three-terminal Hanle measurements. A full model appropriate for the measurements will be introduced, and a broader discussion in the context of spin pumping experimenments will be included in the talk. The new technique provides a simple and powerful means for detecting spin accumulation at high temperatures. Reference: C. Liu, S. J. Patel, T. A. Peterson, C. C. Geppert, K. D. Christie, C. J. Palmstrøm, and P. A. Crowell, "Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance," Nature Communications 7, 10296 (2016). http://dx.doi.org/10.1038/ncomms10296

A comparative study of charge transfer inefficiency value and trap parameter determination techniques making use of an irradiated ESA-Euclid prototype CCD

NASA Astrophysics Data System (ADS)

Prod'homme, Thibaut; Verhoeve, P.; Kohley, R.; Short, A.; Boudin, N.

2014-07-01

The science objectives of space missions using CCDs to carry out accurate astronomical measurements are put at risk by the radiation-induced increase in charge transfer inefficiency (CTI) that results from trapping sites in the CCD silicon lattice. A variety of techniques are used to obtain CTI values and derive trap parameters, however they often differ in results. To identify and understand these differences, we take advantage of an on-going comprehensive characterisation of an irradiated Euclid prototype CCD including the following techniques: X-ray, trap pumping, flat field extended pixel edge response and first pixel response. We proceed to a comparative analysis of the obtained results.

Proton trapping in SiO 2 layers thermally grown on Si and SiC

NASA Astrophysics Data System (ADS)

Afanas'ev, V. V.; Ciobanu, F.; Pensl, G.; Stesmans, A.

2002-11-01

Positive charging of thermal SiO 2 layers on (1 0 0)Si and (0 0 0 1)6H-, 4H-SiC related to trapping of protons is studied using low-energy proton implantation into the oxide, and compared to the trapping of holes generated by 10-eV photons. Proton trapping has an initial probability close to 100% and shows little sensitivity to the annealing-induced oxygen deficiency of SiO 2. In contrast to protons, hole trapping in as-grown SiO 2 shows a much lower efficiency which increases upon oxide annealing, in qualitative correlation with the higher density of O 3Si• defects (E' centers) detected by electron spin resonance after hole injection. Despite these differences, the neutralization of positive charges induced by holes and protons has the same cross-section, and in both cases is accompanied by liberation of atomic H suggesting that protons account for positive charge in both cases. The rupture of Si-O bonds in the oxide observed upon proton injection suggests, as a first basic step, the bonding of a proton to a bridging oxygen atom in SiO 2 network.

Hydroxyl radical production by a heterogeneous Fenton reaction supported in insoluble tannin from bark of Pinus radiata.

PubMed

Romero, Romina; Contreras, David; Segura, Cristina; Schwederski, Brigitte; Kaim, Wolfgang

2017-03-01

Fenton reactions driven by dihydroxybenzenes (DHBs) have been used for pollutant removal via advanced oxidation processes (AOPs), but such systems have the disadvantage of DHB release into the aqueous phase. In this work, insoluble tannins from bark can be used to drive Fenton reactions and as a heterogeneous support. This avoids the release of DHBs into the aqueous phase and can be used for AOPs. The production of ·OH was investigated using a spin-trapping electron paramagnetic resonance technique (5-dimethyl-1-pyrroline-N-oxide/·OH) in the first minute of the reaction and a high-performance liquid chromatography-fluorescence technique (coumarin/7-hydroxycoumarin) for 20 min. The ·OH yield achieved using insoluble tannins from Pinus radiata bark was higher than that achieved using catechin to drive the Fenton reaction. The Fenton-like system driven by insoluble tannins achieved 92.6 ± 0.3 % degradation of atrazine in 30 min. The degradation kinetics of atrazine was linearly correlated with ·OH production. The increased reactivity in ·OH production and insolubility of the ligand are promising for the development of a new technique for degradation of pollutants in wastewater using heterogeneous Fenton systems.

Hunting strategies used in the semi-arid region of northeastern Brazil

PubMed Central

Alves, Rômulo RN; Mendonça, Lívia ET; Confessor, Maine VA; Vieira, Washington LS; Lopez, Luiz CS

2009-01-01

Hunting for wild animals is stimulated by the many different human uses of faunal resources, and these animals constitute important subsistence items in local communities in the Caatinga region. In order to gain access to these resources, hunters have developed a series of techniques and strategies that are described in the present work. The principal hunting techniques encountered were: waiting, especially directed towards hunting diurnal birds; calling ("arremedo"), a technique in which the hunters imitate the animal's call to attract it to close range; hunting with dogs, a technique mostly used for capturing mammals; tracking, a technique used by only a few hunters who can recognize and follow animal tracks; and "facheado", in which the hunters go out at night with lanterns to catch birds in their nests. Additionally, many animal species are captured using mechanical traps. The types of traps used by the interviewees were: dead-fall traps ("quixó"), iron-jaw snap traps ("arataca"), wooden cages with bait ("arapuca"), iron-cage traps ("gaiola'), "visgo", multi-compartment bird cages ("alçapão"), buried ground traps with pivoted tops ("fojo"), and nooses and cages for carnivorous. The choice of which technique to use depends on the habits of the species being hunted, indicating that the hunters possess a wide knowledge of the biology of these animals. From a conservation perspective, active hunting techniques (waiting, imitation, hunting with dogs, and "facheado") have the greatest impact on the local fauna. The use of firearm and dogs brought greater efficiency to hunting activities. Additional studies concerning these hunting activities will be useful to contribute to proposals for management plans regulating hunting in the region – with the objective of attaining sustainable use of faunal resources of great importance to the local human communities. PMID:19386121

Hybrid Systems: Cold Atoms Coupled to Micro Mechanical Oscillators =

NASA Astrophysics Data System (ADS)

Montoya Monge, Cris A.

Micro mechanical oscillators can serve as probes in precision measurements, as transducers to mediate photon-phonon interactions, and when functionalized with magnetic material, as tools to manipulate spins in quantum systems. This dissertation includes two projects where the interactions between cold atoms and mechanical oscillators are studied. In one of the experiments, we have manipulated the Zeeman state of magnetically trapped Rubidium atoms with a magnetic micro cantilever. The results show a spatially localized effect produced by the cantilever that agrees with Landau-Zener theory. In the future, such a scalable system with highly localized interactions and the potential for single-spin sensitivity could be useful for applications in quantum information science or quantum simulation. In a second experiment, work is in progress to couple a sample of optically trapped Rubidium atoms to a levitated nanosphere via an optical lattice. This coupling enables the cooling of the center-of-mass motion of the nanosphere by laser cooling the atoms. In this system, the atoms are trapped in the optical lattice while the sphere is levitated in a separate vacuum chamber by a single-beam optical tweezer. Theoretical analysis of such a system has determined that cooling the center-of-mass motion of the sphere to its quantum ground state is possible, even when starting at room temperature, due to the excellent environmental decoupling achievable in this setup. Nanospheres cooled to the quantum regime can provide new tests of quantum behavior at mesoscopic scales and have novel applications in precision sensing.

Excitation of Nuclei and Atoms Trapping in Optical Fields of High Intensity

DTIC Science & Technology

2006-11-01

the new relativistic wave equation for half- spin particle interacting with the electromagnetic field. The proposed equation is Lorentz and gauge ...CONTENTS Task 1. Gamma-ray laser with hidden inversion of nuclear state populations 3 Introduction 3 Recoil-accompanied nuclear...31 Task 2. Extended ensemble of monoenergetic atoms 33 Introduction 33 Results 37 Conclusion 66

Ion traps for precision experiments at rare-isotope-beam facilities

NASA Astrophysics Data System (ADS)

Kwiatkowski, Anna

2016-09-01

Ion traps first entered experimental nuclear physics when the ISOLTRAP team demonstrated Penning trap mass spectrometry of radionuclides. From then on, the demand for ion traps has grown at radioactive-ion-beam (RIB) facilities since beams can be tailored for the desired experiment. Ion traps have been deployed for beam preparation, from bunching (thereby allowing time coincidences) to beam purification. Isomerically pure beams needed for nuclear-structure investigations can be prepared for trap-assisted or in-trap decay spectroscopy. The latter permits studies of highly charged ions for stellar evolution, which would be impossible with traditional experimental nuclear-physics methods. Moreover, the textbook-like conditions and advanced ion manipulation - even of a single ion - permit high-precision experiments. Consequently, the most accurate and precise mass measurements are now performed in Penning traps. After a brief introduction to ion trapping, I will focus on examples which showcase the versatility and utility of the technique at RIB facilities. I will demonstrate how this atomic-physics technique has been integrated into nuclear science, accelerator physics, and chemistry. DOE.

Low-cost high-resolution fast spin-echo MR of acoustic schwannoma: an alternative to enhanced conventional spin-echo MR?

PubMed

Allen, R W; Harnsberger, H R; Shelton, C; King, B; Bell, D A; Miller, R; Parkin, J L; Apfelbaum, R I; Parker, D

1996-08-01

To determine whether unenhanced high-resolution T2-weighted fast spin-echo MR imaging provides an acceptable and less expensive alternative to contrast-enhanced conventional T1-weighted spin-echo MR techniques in the diagnosis of acoustic schwannoma. We reviewed in a blinded fashion the records of 25 patients with pathologically documented acoustic schwannoma and of 25 control subjects, all of whom had undergone both enhanced conventional spin-echo MR imaging and unenhanced fast spin-echo MR imaging of the cerebellopontine angle/internal auditory canal region. The patients were imaged with the use of a quadrature head receiver coil for the conventional spin-echo sequences and dual 3-inch phased-array receiver coils for the fast spin-echo sequences. The size of the acoustic schwannomas ranged from 2 to 40 mm in maximum dimension. The mean maximum diameter was 12 mm, and 12 neoplasms were less than 10 mm in diameter. Acoustic schwannoma was correctly diagnosed on 98% of the fast spin-echo images and on 100% of the enhanced conventional spin-echo images. Statistical analysis of the data using the kappa coefficient demonstrated agreement beyond chance between these two imaging techniques for the diagnosis of acoustic schwannoma. There is no statistically significant difference in the sensitivity and specificity of unenhanced high-resolution fast spin-echo imaging and enhance T1-weighted conventional spin-echo imaging in the detection of acoustic schwannoma. We believe that the unenhanced high-resolution fast spin-echo technique provides a cost-effective method for the diagnosis of acoustic schwannoma.

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

PubMed

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

2018-04-24

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

A status report on NASA general aviation stall/spin flight testing

NASA Technical Reports Server (NTRS)

Patton, J. M., Jr.

1980-01-01

The NASA Langley Research Center has undertaken a comprehensive program involving spin tunnel, static and rotary balance wind tunnel, full-scale wind tunnel, free flight radio control model, flight simulation, and full-scale testing. Work underway includes aerodynamic definition of various configurations at high angles of attack, testing of stall and spin prevention concepts, definition of spin and spin recovery characteristics, and development of test techniques and emergency spin recovery systems. This paper presents some interesting results to date for the first aircraft (low-wing, single-engine) in the program, in the areas of tail design, wing leading edge design, mass distribution, center of gravity location, and small airframe changes, with associated pilot observations. The design philosophy of the spin recovery parachute system is discussed in addition to test techniques.

Extensive screening for herbal extracts with potent antioxidant properties

PubMed Central

Niwano, Yoshimi; Saito, Keita; Yoshizaki, Fumihiko; Kohno, Masahiro; Ozawa, Toshihiko

2011-01-01

This paper summarizes our research for herbal extracts with potent antioxidant activity obtained from a large scale screening based on superoxide radical (O2•−) scavenging activity followed by characterization of antioxidant properties. Firstly, scavenging activity against O2•− was extensively screened from ethanol extracts of approximately 1000 kinds of herbs by applying an electron spin resonance (ESR)-spin trapping method, and we chose four edible herbal extracts with prominently potent ability to scavenge O2•−. They are the extracts from Punica granatum (Peel), Syzygium aromaticum (Bud), Mangifera indica (Kernel), and Phyllanthus emblica (Fruit). These extracts were further examined to determine if they also scavenge hydroxyl radical (•OH), by applying the ESR spin-trapping method, and if they have heat resistance as a desirable characteristic feature. Experiments with the Fenton reaction and photolysis of H2O2 induced by UV irradiation demonstrated that all four extracts have potent ability to directly scavenge •OH. Furthermore, the scavenging activities against O2•− and •OH of the extracts of P. granatum (peel), M. indica (kernel) and P. emblica (fruit) proved to be heat-resistant. The results of the review might give useful information when choosing a potent antioxidant as a foodstuff. For instance, the four herbal extracts chosen from extensive screening possess desirable antioxidant properties. In particular, the extracts of the aforementioned three herbs are expected to be suitable for food processing in which thermal devices are used, because of their heat resistance. PMID:21297917

Dose-dependent decrease in anti-oxidant capacity of whole blood after irradiation: A novel potential marker for biodosimetry.

PubMed

Sun, Lue; Inaba, Yohei; Sato, Keizo; Hirayama, Aki; Tsuboi, Koji; Okazaki, Ryuji; Chida, Koichi; Moritake, Takashi

2018-05-09

Many reports have demonstrated that radiation stimulates reactive oxygen species (ROS) production by mitochondria for a few hours to a few days after irradiation. However, these studies were performed using cell lines, and there is a lack of information about redox homeostasis in irradiated animals and humans. Blood redox homeostasis reflects the body condition well and can be used as a diagnostic marker. However, most redox homeostasis studies have focused on plasma or serum, and the anti-oxidant capacity of whole blood has scarcely been investigated. Here, we report changes in the anti-oxidant capacity of whole blood after X-ray irradiation using C57BL/6 J mice. Whole-blood anti-oxidant capacity was measured by electron spin resonance (ESR) spin trapping using a novel spin-trapping agent, 2-diphenylphosphinoyl-2-methyl-3,4-dihydro-2H-pyrrole N-oxide (DPhPMPO). We found that whole-blood anti-oxidant capacity decreased in a dose-dependent manner (correlation factor, r > 0.9; P < 0.05) from 2 to 24 days after irradiation with 0.5-3 Gy. We further found that the red blood cell (RBC) glutathione level decreased and lipid peroxidation level increased in a dose-dependent manner from 2 to 6 days after irradiation. These findings suggest that blood redox state may be a useful biomarker for estimating exposure doses during nuclear and/or radiation accidents.

Developing Density of Laser-Cooled Neutral Atoms and Molecules in a Linear Magnetic Trap

NASA Astrophysics Data System (ADS)

Velasquez, Joe, III; Walstrom, Peter; di Rosa, Michael

2013-05-01

In this poster we show that neutral particle injection and accumulation using laser-induced spin flips may be used to form dense ensembles of ultracold magnetic particles, i.e., laser-cooled paramagnetic atoms and molecules. Particles are injected in a field-seeking state, are switched by optical pumping to a field-repelled state, and are stored in the minimum-B trap. The analogous process in high-energy charged-particle accumulator rings is charge-exchange injection using stripper foils. The trap is a linear array of sextupoles capped by solenoids. Particle-tracking calculations and design of our linear accumulator along with related experiments involving 7Li will be presented. We test these concepts first with atoms in preparation for later work with selected molecules. Finally, we present our preliminary results with CaH, our candidate molecule for laser cooling. This project is funded by the LDRD program of Los Alamos National Laboratory.

Dissipative quantum error correction and application to quantum sensing with trapped ions.

PubMed

Reiter, F; Sørensen, A S; Zoller, P; Muschik, C A

2017-11-28

Quantum-enhanced measurements hold the promise to improve high-precision sensing ranging from the definition of time standards to the determination of fundamental constants of nature. However, quantum sensors lose their sensitivity in the presence of noise. To protect them, the use of quantum error-correcting codes has been proposed. Trapped ions are an excellent technological platform for both quantum sensing and quantum error correction. Here we present a quantum error correction scheme that harnesses dissipation to stabilize a trapped-ion qubit. In our approach, always-on couplings to an engineered environment protect the qubit against spin-flips or phase-flips. Our dissipative error correction scheme operates in a continuous manner without the need to perform measurements or feedback operations. We show that the resulting enhanced coherence time translates into a significantly enhanced precision for quantum measurements. Our work constitutes a stepping stone towards the paradigm of self-correcting quantum information processing.

High-k shallow traps observed by charge pumping with varying discharging times

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

Ho, Szu-Han; Chen, Ching-En; Tseng, Tseung-Yuen

2013-11-07

In this paper, we investigate the influence of falling time and base level time on high-k bulk shallow traps measured by charge pumping technique in n-channel metal-oxide-semiconductor field-effect transistors with HfO{sub 2}/metal gate stacks. N{sub T}-V{sub high} {sub level} characteristic curves with different duty ratios indicate that the electron detrapping time dominates the value of N{sub T} for extra contribution of I{sub cp} traps. N{sub T} is the number of traps, and I{sub cp} is charge pumping current. By fitting discharge formula at different temperatures, the results show that extra contribution of I{sub cp} traps at high voltage are inmore » fact high-k bulk shallow traps. This is also verified through a comparison of different interlayer thicknesses and different Ti{sub x}N{sub 1−x} metal gate concentrations. Next, N{sub T}-V{sub high} {sub level} characteristic curves with different falling times (t{sub falling} {sub time}) and base level times (t{sub base} {sub level}) show that extra contribution of I{sub cp} traps decrease with an increase in t{sub falling} {sub time}. By fitting discharge formula for different t{sub falling} {sub time}, the results show that electrons trapped in high-k bulk shallow traps first discharge to the channel and then to source and drain during t{sub falling} {sub time}. This current cannot be measured by the charge pumping technique. Subsequent measurements of N{sub T} by charge pumping technique at t{sub base} {sub level} reveal a remainder of electrons trapped in high-k bulk shallow traps.« less

Coherent Spin Control at the Quantum Level in an Ensemble-Based Optical Memory.

PubMed

Jobez, Pierre; Laplane, Cyril; Timoney, Nuala; Gisin, Nicolas; Ferrier, Alban; Goldner, Philippe; Afzelius, Mikael

2015-06-12

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies suggest this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here, we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read-out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.

Free-Spinning-Tunnel Investigation of a 1/20-Scale Model of the North American T2J-1 Airplane

NASA Technical Reports Server (NTRS)

Bowman, James S., Jr.; Healy, Frederick M.

1959-01-01

An investigation has been made in the Langley 20-foot free-spinning tunnel to determine the erect and inverted spin and recovery characteristics of a 1/20-scale dynamic model of the North American T2J-1 airplane. The model results indicate that the optimum technique for recovery from erect spins of the airplane will be dependent on the distribution of the disposable load. The recommended recovery procedure for spins encountered at the flight design gross weight is simultaneous rudder reversal to against the spin and aileron movement to with the spin. With full wingtip tanks plus rocket installation and full internal fuel load, rudder reversal should be followed by a downward movement of the elevator. For the flight design gross weight plus partially full wingtip tanks, recovery should be attempted by simultaneous rudder reversal to against the spin, movement of ailerons to with the spin, and ejection of the wing-tip tanks. The optimum recovery technique for airplane-inverted spins is rudder reversal to against the spin with the stick maintained longitudinally and laterally neutral.

Generalized Gross-Pitaevskii equation adapted to the U (5 ) ⊃ SO (5 ) ⊃ SO (3 ) symmetry for spin-2 condensates

NASA Astrophysics Data System (ADS)

He, Y. Z.; Liu, Y. M.; Bao, C. G.

2015-03-01

A generalized Gross-Pitaevskii equation adapted to the U(5 )⊃SO(5 )⊃SO(3 ) symmetry has been derived and solved for the spin-2 condensates. The spin-textile and the degeneracy of the ground state (g.s.) together with the factors affecting the stability of the g.s., such as the gap and the level density in the neighborhood of the g.s., have been studied. Based on a rigorous treatment of the spin-degrees of freedom, the spin-textiles can be understood in an N -body language. In addition to the ferro, polar, and cyclic phases, the g.s. might in a mixture of them when |M | is not equal to 0 and 2 N (M is the total magnetization). The great difference in the stability and degeneracy of the g.s. caused by varying φ (which marks the features of the interaction) and M is notable. Since the root-mean-square radius Rrms is an observable, efforts have been made to derive a set of formulas to relate Rrms and N ,ω (frequency of the trap), and φ . These formulas provide a way to check the theories with experimental data.

Single-spin stochastic optical reconstruction microscopy

PubMed Central

Pfender, Matthias; Aslam, Nabeel; Waldherr, Gerald; Neumann, Philipp; Wrachtrup, Jörg

2014-01-01

We experimentally demonstrate precision addressing of single-quantum emitters by combined optical microscopy and spin resonance techniques. To this end, we use nitrogen vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers, we are able to simultaneously perform sub–diffraction-limit imaging and optically detected spin resonance (ODMR) measurements on NV spins. This allows the assignment of spin resonance spectra to individual NV center locations with nanometer-scale resolution and thus further improves spatial discrimination. For example, we resolved formerly indistinguishable emitters by their spectra. Furthermore, ODMR spectra contain metrology information allowing for sub–diffraction-limit sensing of, for instance, magnetic or electric fields with inherently parallel data acquisition. As an example, we have detected nuclear spins with nanometer-scale precision. Finally, we give prospects of how this technique can evolve into a fully parallel quantum sensor for nanometer resolution imaging of delocalized quantum correlations. PMID:25267655

Supersaturated Electrolyte Solutions: Theory and Experiment

NASA Technical Reports Server (NTRS)

Izmailov, Alexander F.; Myerson, Allan S.; Na, Han-Soo

1995-01-01

Highly supersaturated electrolyte solutions can be prepared and studied employing an electrodynamic levitator trap (ELT) technique. The ELT technique involves containerless suspension of a microdroplet thus eliminating dust, dirt, and container walls which normally cause heterogeneous nucleation. This allows very high supersaturations to be achieved. A theoretical study of the experimental results obtained for the water activity in microdroplets of various electrolyte solutions is based on the development of the Cahn-Hilliard formalism for electrolyte solutions. In the approach suggested the metastable state for electrolyte solutions is described in terms of the conserved order parameter omega(r,t) associated with fluctuations of the mean solute concentration n(sub 0). Parameters of the corresponding Ginzburg-Landau free energy functional which defines the dynamics of metastable state relaxation are determined and expressed through the experimentally measured quantities. A correspondence of 96-99 % between theory and experiment for all solutions studied was achieved and allowed the determination of an analytical expression for the spinodal concentration n(sub spin), and its calculation for various electrolyte solutions at 298 K. The assumption that subcritical solute clusters consist of the electrically neutral Bjerrum pairs has allowed both analytical and numerical investigation of the number-size N(sub c) of nucleation monomers (aggregates of the Bjerrum pairs) which are elementary units of the solute critical clusters. This has also allowed estimations for the surface tension Alpha, and equilibrium bulk energy Beta per solute molecule in the nucleation monomers. The dependence of these properties on the temperature T and on the solute concentration n(sub 0) through the entire metastable zone (from saturation concentration n(sub sat) to spinodal n(sub spin) is examined. It has been demonstrated that there are the following asymptotics: N(sub c), = I at spinodal concentration and N(sub c) = infinity at saturation.

Automated processing integrated with a microflow cytometer for pathogen detection in clinical matrices

PubMed Central

Golden, J.P.; Verbarg, J.; Howell, P.B.; Shriver-Lake, L.C.; Ligler, F.S.

2012-01-01

A spinning magnetic trap (MagTrap) for automated sample processing was integrated with a microflow cytometer capable of simultaneously detecting multiple targets to provide an automated sample-to-answer diagnosis in 40 min. After target capture on fluorescently coded magnetic microspheres, the magnetic trap automatically concentrated the fluorescently coded microspheres, separated the captured target from the sample matrix, and exposed the bound target sequentially to biotinylated tracer molecules and streptavidin-labeled phycoerythrin. The concentrated microspheres were then hydrodynamically focused in a microflow cytometer capable of 4-color analysis (two wavelengths for microsphere identification, one for light scatter to discriminate single microspheres and one for phycoerythrin bound to the target). A three-fold decrease in sample preparation time and an improved detection limit, independent of target preconcentration, was demonstrated for detection of Escherichia coli 0157:H7 using the MagTrap as compared to manual processing. Simultaneous analysis of positive and negative controls, along with the assay reagents specific for the target, was used to obtain dose–response curves, demonstrating the potential for quantification of pathogen load in buffer and serum. PMID:22960010

Automated processing integrated with a microflow cytometer for pathogen detection in clinical matrices.

PubMed

Golden, J P; Verbarg, J; Howell, P B; Shriver-Lake, L C; Ligler, F S

2013-02-15

A spinning magnetic trap (MagTrap) for automated sample processing was integrated with a microflow cytometer capable of simultaneously detecting multiple targets to provide an automated sample-to-answer diagnosis in 40 min. After target capture on fluorescently coded magnetic microspheres, the magnetic trap automatically concentrated the fluorescently coded microspheres, separated the captured target from the sample matrix, and exposed the bound target sequentially to biotinylated tracer molecules and streptavidin-labeled phycoerythrin. The concentrated microspheres were then hydrodynamically focused in a microflow cytometer capable of 4-color analysis (two wavelengths for microsphere identification, one for light scatter to discriminate single microspheres and one for phycoerythrin bound to the target). A three-fold decrease in sample preparation time and an improved detection limit, independent of target preconcentration, was demonstrated for detection of Escherichia coli 0157:H7 using the MagTrap as compared to manual processing. Simultaneous analysis of positive and negative controls, along with the assay reagents specific for the target, was used to obtain dose-response curves, demonstrating the potential for quantification of pathogen load in buffer and serum. Published by Elsevier B.V.

Ideal Internal Carotid Artery Trapping Technique without Bypass in a Patient with Insufficient Collateral Flow.

PubMed

Chung, Joon Ho; Shin, Yong Sam; Lim, Yong Cheol; Park, Minjung

2009-04-01

Internal carotid artery (ICA) trapping can be used for treating intracranial giant aneurysm, blood blister-like aneurysms and ICA rupture during the surgery. We present a novel ICA trapping technique which can be used with insufficient collaterals flow via anterior communicating artery (AcoA) and posterior communicating artery (PcoA). A patient was admitted with severe headache and the cerebral angiography demonstrated a typical blood blister-like aneurysm at the contralateral side of PcoA. For trapping the aneurysm, the first clip was placed at the ICA just proximal to the aneurysm whereas the distal clip was placed obliquely proximal to the origin of the PcoA to preserve blood flow from the PcoA to the distal ICA. The patient was completely recovered with good collaterals filling to the right ICA territories via AcoA and PcoA. This technique may be an effective treatment option for trapping the aneurysm, especially when the PcoA preservation is mandatory.

Confocal micro-Raman spectroscopy of single biological cells using optical trapping and shifted excitation difference techniques

NASA Astrophysics Data System (ADS)

Xie, Changan; Li, Yong-qing

2003-03-01

We report on the study of single biological cells with a confocal micro-Raman spectroscopy system that uses optical trapping and shifted excitation Raman difference technique. A tunable diode laser was used to capture a living cell in solution, confine it in the confocal excitation volume, and then excite the Raman scattering. The optical trapping allows us to lift the cell well off the cover plate so that the fluorescence interference from the plate can be effectively reduced. In order to further remove the interference of the fluorescence and stray light from the trapped cell, we employed a shifted excitation Raman difference technique with slightly tuned laser frequencies. With this system, high-quality Raman spectra were obtained from single optically trapped biological cells including E. coli bacteria, yeast cells, and red blood cells. A significant difference between control and heat-treated E. coli B cells was observed due to the denaturation of biomolecules.

Microrheometric upconversion-based techniques for intracellular viscosity measurements

NASA Astrophysics Data System (ADS)

Rodríguez-Sevilla, Paloma; Zhang, Yuhai; de Sousa, Nuno; Marqués, Manuel I.; Sanz-Rodríguez, Francisco; Jaque, Daniel; Liu, Xiaogang; Haro-González, Patricia

2017-08-01

Rheological parameters (viscosity, creep compliance and elasticity) play an important role in cell function and viability. For this reason different strategies have been developed for their study. In this work, two new microrheometric techniques are presented. Both methods take advantage of the analysis of the polarized emission of an upconverting particle to determine its orientation inside the optical trap. Upconverting particles are optical materials that are able to convert infrared radiation into visible light. Their usefulness has been further boosted by the recent demonstration of their three-dimensional control and tracking by single beam infrared optical traps. In this work it is demonstrated that optical torques are responsible of the stable orientation of the upconverting particle inside the trap. Moreover, numerical calculations and experimental data allowed to use the rotation dynamics of the optically trapped upconverting particle for environmental sensing. In particular, the cytoplasm viscosity could be measured by using the rotation time and thermal fluctuations of an intracellular optically trapped upconverting particle, by means of the two previously mentioned microrheometric techniques.

Observation of a γ -decaying millisecond isomeric state in 128 Cd 80

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

Jungclaus, A.; Grawe, H.; Nishimura, S.

2017-09-01

A new high-spin isomer in the neutron-rich nucleus 128Cd was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T1/2 = 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15-). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129Cd. In the present experiment no evidence was found for the decay of a 18 + E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in themore » 0h 11/2 and the 0g 9/2 orbit, respectively, which is predicted to exist by the shell model.« less

Quantum Landauer erasure with a molecular nanomagnet

NASA Astrophysics Data System (ADS)

Gaudenzi, R.; Burzurí, E.; Maegawa, S.; van der Zant, H. S. J.; Luis, F.

2018-06-01

The erasure of a bit of information is an irreversible operation whose minimal entropy production of kB ln 2 is set by the Landauer limit1. This limit has been verified in a variety of classical systems, including particles in traps2,3 and nanomagnets4. Here, we extend it to the quantum realm by using a crystal of molecular nanomagnets as a quantum spin memory and showing that its erasure is still governed by the Landauer principle. In contrast to classical systems, maximal energy efficiency is achieved while preserving fast operation owing to its high-speed spin dynamics. The performance of our spin register in terms of energy-time cost is orders of magnitude better than existing memory devices to date. The result shows that thermodynamics sets a limit on the energy cost of certain quantum operations and illustrates a way to enhance classical computations by using a quantum system.

Review of Plasma Techniques Used to Trap Antihydrogen

NASA Astrophysics Data System (ADS)

Fajans, Joel

2011-10-01

Recently, the ALPHA collaboration at CERN trapped antihydrogen atoms. To date, over three hundred antiatoms have been confined, some for as long as 1000s. This was the first time that antiatoms had ever been trapped. The ultimate goal of the ALPHA collaboration is to test CPT invariance by comparing the spectra of hydrogen and antihydrogen, and to measure the gravitational attraction between matter and antimatter. Such studies might resolve the baryogenesis problem: why is there very little antimatter in the Universe? The ALPHA experiment brought together techniques from many different fields of physics, but the crucial breakthroughs were in plasma physics. The essential problem is this: How does one combine two Malmberg-Penning trapped plasmas, one made from antiprotons, and the other positrons, which have opposite electrostatic potentials of nearly one volt, in such a manner that the antiprotons traverse the positrons with kinetic energies of less than 40 μeV, this latter being the depth of the superimposed neutral antihydrogen trap? The plasma techniques ALPHA developed to accomplish this include: Minimizing the effects of the neutral trap multipole fields on the positron and antiproton plasma confinement. Compressing antiprotons down to less than 0.5mm. Using autoresonance to inject antiprotons into the positrons with very little excess energy. Evaporative cooling of the electrons and antiprotons to record low temperatures. Development of charge, radial profile, temperature, and antiproton loss location diagnostics. Careful and lengthy manipulations to finesse the plasmas into the best states for optimal antihydrogen production and trapping. The plasma techniques necessary to trap antihydrogen will be reviewed in this talk. This work was supported by DOE and NSF, and is reported on behalf of the ALPHA collaboration.

Innovative Plasma Disinfection Technique with the Reduced-pH Method and the Plasma-Treated Water (PTW) -Safety and Powerful Disinfection with Cryopreserved PTW-

NASA Astrophysics Data System (ADS)

Kitano, Katsuhisa; Ikawa, Satoshi; Nakashima, Yoichi; Tani, Atsushi; Yokoyama, Takashi; Ohshima, Tomoko

2015-09-01

Among the applications of the plasma disinfection to human body, plasma sterilization in liquid is crucial. We found that the plasma-treated water (PTW) has strong bactericidal activity under low pH condition and the half-lives of its activity depend on temperature. Lower temperature brings longer half-life and the bactericidal activity of PTW can be kept by cryopreservation. These physicochemical properties were in accordance with Arrhenius equation both in liquid and solid states. From the experimental results of ESR (Electron Spin Resonance) measurement of O2-in liquid against PTW with spin trapping method, half-lives of PTW were also in accordance with Arrhenius equation. It suggests that high concentration PTW as integrated value can be achieved by cooling of plasma apparatus. Pure PTW has disinfection power of 22 log reduction (B. subtilis). This corresponds to 65% H2O2, 14% hypochlorous acid and 0.33% peracetic acid, which are deadly poison for human. On the other hand, PTW is deactivated soon at body temperature. This indicates that toxicity to human body seems to be low. PTW, which is a sort of indirect plasma exposure, with pH and temperature controls could be applied for safety and powerful disinfection. MEXT (15H03583, 23340176, 25108505). NCCE (23-A-15).

EPR investigations of gamma-irradiated ground black pepper

NASA Astrophysics Data System (ADS)

Polovka, Martin; Brezová, Vlasta; Staško, Andrej; Mazúr, Milan; Suhaj, Milan; Šimko, Peter

2006-02-01

The γ-radiation treatment of ground black pepper samples resulted in the production of three paramagnetic species ( GI- GIII) which arise from a different origin and have different thermal behavior and stability. The axially symmetric spectra can be characterized by the spin Hamiltonian parameters: GI ( g⊥=2.0060, g∥=2.0032; A⊥=0.85 mT, A∥=0.70 mT) and GII ( g⊥=2.0060, g∥=2.0050; A⊥=0.50 mT, A∥=0.40 mT) assigned to carbohydrate radical structures. The parameters of EPR signal GIII ( g⊥=2.0029, g∥=2.0014; A⊥=3.00 mT, A∥=1.80 mT) possessed features characteristic of cellulose radical species. The activation energies, evaluated by Arrhenius analysis, are in order Ea( GI)< Ea( GIII)< Ea( GII). The EPR measurements performed 20 weeks after radiation process confirmed that a temperature increase from 298 to 353 K, caused a significant decrease of integral EPR signal intensity for γ-irradiated samples (˜40%), compared to the reference (non-irradiated) ground black pepper, where a decrease of ˜13% was found. The influence of γ-radiation treatment on the radical-scavenging activities of aqueous and ethanol extracts of black pepper were investigated by both an EPR spin trapping technique and DPPH assay. No changes were detected in either the water or ethanol extracts for a γ-irradiation dose of 10 kGy.

Oriented Polar Molecules in a Solid Inert-Gas Matrix: A Proposed Method for Measuring the Electric Dipole Moment of the Electron

NASA Astrophysics Data System (ADS)

Vutha, A.; Horbatsch, M.; Hessels, E.

2018-01-01

We propose a very sensitive method for measuring the electric dipole moment of the electron using polar molecules embedded in a cryogenic solid matrix of inert-gas atoms. The polar molecules can be oriented in the $\\hat{\\rm{z}}$ direction by an applied electric field, as has recently been demonstrated by Park, et al. [Angewandte Chemie {\\bf 129}, 1066 (2017)]. The trapped molecules are prepared into a state which has its electron spin perpendicular to $\\hat{\\rm{z}}$, and a magnetic field along $\\hat{\\rm{z}}$ causes precession of this spin. An electron electric dipole moment $d_e$ would affect this precession due to the up to 100~GV/cm effective electric field produced by the polar molecule. The large number of polar molecules that can be embedded in a matrix, along with the expected long coherence times for the precession, allows for the possibility of measuring $d_e$ to an accuracy that surpasses current measurements by many orders of magnitude. Because the matrix can inhibit molecular rotations and lock the orientation of the polar molecules, it may not be necessary to have an electric field present during the precession. The proposed technique can be applied using a variety of polar molecules and inert gases, which, along with other experimental variables, should allow for careful study of systematic uncertainties in the measurement.

An experimental study of solid source diffusion by spin on dopants and its application for minimal silicon-on-insulator CMOS fabrication

NASA Astrophysics Data System (ADS)

Liu, Yongxun; Koga, Kazuhiro; Khumpuang, Sommawan; Nagao, Masayoshi; Matsukawa, Takashi; Hara, Shiro

2017-06-01

Solid source diffusions of phosphorus (P) and boron (B) into the half-inch (12.5 mm) minimal silicon (Si) wafers by spin on dopants (SOD) have been systematically investigated and the physical-vapor-deposited (PVD) titanium nitride (TiN) metal gate minimal silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) field-effect transistors (FETs) have successfully been fabricated using the developed SOD thermal diffusion technique. It was experimentally confirmed that a low temperature oxidation (LTO) process which depresses a boron silicide layer formation is effective way to remove boron-glass in a diluted hydrofluoric acid (DHF) solution. It was also found that top Si layer thickness of SOI wafers is reduced in the SOD thermal diffusion process because of its consumption by thermal oxidation owing to the oxygen atoms included in SOD films, which should be carefully considered in the ultrathin SOI device fabrication. Moreover, normal operations of the fabricated minimal PVD-TiN metal gate SOI-CMOS inverters, static random access memory (SRAM) cells and ring oscillators have been demonstrated. These circuit level results indicate that no remarkable particles and interface traps were introduced onto the minimal wafers during the device fabrication, and the developed solid source diffusion by SOD is useful for the fabrication of functional logic gate minimal SOI-CMOS integrated circuits.

Fe3-xCuxO4 as highly active heterogeneous Fenton-like catalysts toward elemental mercury removal.

PubMed

Zhou, Changsong; Sun, Lushi; Zhang, Anchao; Wu, Xiaofeng; Ma, Chuan; Su, Sheng; Hu, Song; Xiang, Jun

2015-04-01

A series of novel spinel Fe3-xCuxO4 (0

Net motion of acoustically levitating nano-particles: A theoretical analysis

NASA Astrophysics Data System (ADS)

Lippera, Kevin; Dauchot, Olivier; Benzaquen, Michael; Gulliver-LadHyX Collaboration

2017-11-01

A particle 2D-trapped in the nodal planed of a standing acoustic wave is prone to acoustic-phoretic motion as soon as its shape breaks polar or chiral symmetry. such a setup constitues an ideal system to study boundaryless 2D collective behavior with purely hydrodynamic long range interactions. Recent studies have indeed shown that quasi-spherical particles may undergo net propulsion, a feature partially understood theoretically in the particular case of infinite viscous boundary layers. We here extend the theoretical results of to any boundary layer thickness, by that meeting typical experimental conditions. In addition, we propose an explanation for the net spinning of the trapped particles, as observed in experiments.

Electric tempest in a teacup: The tea leaf analogy to microfluidic blood plasma separation

NASA Astrophysics Data System (ADS)

Yeo, Leslie Y.; Friend, James R.; Arifin, Dian R.

2006-09-01

In a similar fashion to Einstein's tea leaf paradox, the rotational liquid flow induced by ionic wind above a liquid surface can trap suspended microparticles by a helical motion, spinning them down towards a bottom stagnation point. The motion is similar to Batchelor [Q. J. Mech. Appl. Math. 4, 29 (1951)] flows occurring between stationary and rotating disks and arises due to a combination of the primary azimuthal and secondary bulk meridional recirculation that produces a centrifugal and enhanced inward radial force near the chamber bottom. The technology is thus useful for microfluidic particle trapping/concentration; the authors demonstrate its potential for rapid erythrocyte/blood plasma separation for miniaturized medical diagnostic kits.

Electrical Investigation of Nanostructured Fe2O3/p-Si Heterojunction Diode Fabricated Using the Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Mansour, Shehab A.; Ibrahim, Mervat M.

2017-11-01

Iron oxide (α-Fe2O3) nanocrystals have been synthesized via the sol-gel technique. The structural and morphological features of these nanocrystals were studied using x-ray diffraction, Fourier transform-infrared spectroscopy and transmission electron microscopy. Colloidal solution of synthesized α-Fe2O3 (hematite) was spin-coated onto a single-crystal p-type silicon (p-Si) wafer to fabricate a heterojunction diode with Mansourconfiguration Ag/Fe2O3/p-Si/Al. This diode was electrically characterized at room temperature using current-voltage (I-V) characteristics in the voltage range from -9 V to +9 V. The fabricated diode showed a good rectification behavior with a rectification factor 1.115 × 102 at 6 V. The junction parameters such as ideality factor, barrier height, series resistance and shunt resistance are determined using conventional I-V characteristics. For low forward voltage, the conduction mechanism is dominated by the defect-assisted tunneling process with conventional electron-hole recombination. However, at higher voltage, I-V ohmic and space charge-limited current conduction was became less effective with the contribution of the trapped-charge-limited current at the highest voltage range.

Electric Transport Phenomena of Nanocomposite Organic Polymer Thin Films

NASA Astrophysics Data System (ADS)

Jira, Nicholas C.; Sabirianov, Ildar; Ilie, Carolina C.

We discuss herein the nanocomposite organic thin film diodes for the use of plasmonic solar cells. This experimental work follows the theoretical calculations done for plasmonic solar cells using the MNPBEM toolbox for MatLab. These calculations include dispersion curves and amount of light scattering cross sections for different metallic nanoparticles. This study gives us clear ideas on what to expect from different metals, allowing us to make the best choice on what to use to obtain the best results. One specific technique for light trapping in thin films solar cells utilizes metal nanoparticles on the surface of the semiconductor. The characteristics of the metal, semiconductor interface allows for light to be guided in between them causing it to be scattered, allowing for more chances of absorption. The samples were fabricated using organic thin films made from polymers and metallic nanoparticles, more specifically Poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer and silver or gold nanoparticles. The two fabrication methods applied include spin coating and Langmuir-Blodgett technique. The transport properties are obtained by analyzing the I-V curves. We will also discuss the resistance, resistivity, conductance, density of charge carriers. SUNY Oswego SCAC Grant.

Quantitative electron spin resonance (ESR) analysis of antioxidative properties using the acetaldehyde/xanthine oxidase system

NASA Astrophysics Data System (ADS)

Souchard, J.-P.; Nepveu, F.

1998-05-01

We present a method for the quantitative ESR analysis of the antioxidant properties of drugs using the acetaldhehyde/xanthine oxidase (AC/XOD) superoxide generating system and 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) as spin trap. In stoichiometric conditions (AC/XOD, 60 mM/0.018 U), the resulting paramagnetic DMPO adduct disappeared with superoxide dismutase and remained when catalase or DMSO were used. That adduct was dependent only on superoxide and resulted from the trapping of a carboxyl radical by DMPO (aN = 15.2 G, aH = 18.9 G). Similar results were obtained using 4-pyridyl-l-oxide-N-t-butyl nitrone (POBN) as spin trap. The ESR signal of the DMPO-CO2- adduct was very stable and allowed quantitative analysis of the antioxidative activity of redox molecules from an IC{50} value representing the concentration causing 50% inhibition of its intensity. Among the tested compounds, manganese(II), complexes were the most effective, 25 times as active as ascorbic acid or (+)catechin and 500-fold more antioxidative than Trolox^R. Nous présentons une méthode d'analyse quantitative de l'activité antioxydante de composés d'intérêt pharmaceutique basée sur le système acétaldéhyde/xanthine oxydase (AC/XOD), l'utilisation de la RPE et du piégeage de spin avec le 5,5-diméthyl-l-pyrroline-N-oxyde (DMPO). Dans les conditions stoechiométriques {AC/XOD, 60 mM/0,018 U/ml}, l'adduit radicalaire résultant de ce système disparaît en présence de superoxyde dismutase et persiste en présence de catalase ou de DMSO. Cet adduit ne dépend que de la présence de l'anion superoxyde et provient du piégeage d'un radical carboxyle CO2- sur le DMPO (aN = 15.2 G, aH = 18.9 G). Des résultats similaires ont été obtenus avec le piégeur de spin 4-pyridyl-l-oxyde-N-t-butyl nitrone (POBN). Le signal RPE de l'adduit DMPO-CO2- est très stable et permet la quantification de l'activité antioxydante de pharmacophores redox par la détermination de la CI{50}, concentration qui diminue de 50 % son intensité. Parmi les composés testés, les complexes du manganèse sont les plus antioxydants, 25 fois plus actifs que la vitamine C ou la catéchine(+), 500 fois plus antioxydants que le Trolox^R.

Production, Manipulation, and Applications of Ultracold Polar Molecules

DTIC Science & Technology

2015-04-30

molecules, cooling, trapping, photoassociation, feshbach resonances, quantum simulation , ultracold collisions, ultracold chemistry, optical lattices...been a multitude of less predictable outcomes: special quantum information processing schemes, uses of entanglement such a spin-squeezing for better...field seeing states to high-field-seeking states (and back) at key points in the magnetic field. The molecules spontaneously emit photons as they are

Quantum Simulation of Spin Models on an Arbitrary Lattice with Trapped Ions (Open Access, Publisher’s Version)

DTIC Science & Technology

2012-09-27

onto a 2D array of N 2 micromirrors [33] that are each individually phase modulated at a single frequency (and phase) [34] and are finally focused on...beams that strike an N × N array of micromirrors each independently modulated, or a spatial light modulator. overhead to the design and fabrication of

Serum Hydroxyl Radical Scavenging Capacity as Quantified with Iron-Free Hydroxyl Radical Source

PubMed Central

Endo, Nobuyuki; Oowada, Shigeru; Sueishi, Yoshimi; Shimmei, Masashi; Makino, Keisuke; Fujii, Hirotada; Kotake, Yashige

2009-01-01

We have developed a simple ESR spin trapping based method for hydroxyl (OH) radical scavenging-capacity determination, using iron-free OH radical source. Instead of the widely used Fenton reaction, a short (typically 5 seconds) in situ UV-photolysis of a dilute hydrogen peroxide aqueous solution was employed to generate reproducible amounts of OH radicals. ESR spin trapping was applied to quantify OH radicals; the decrease in the OH radical level due to the specimen’s scavenging activity was converted into the OH radical scavenging capacity (rate). The validity of the method was confirmed in pure antioxidants, and the agreement with the previous data was satisfactory. In the second half of this work, the new method was applied to the sera of chronic renal failure (CRF) patients. We show for the first time that after hemodialysis, OH radical scavenging capacity of the CRF serum was restored to the level of healthy control. This method is simple and rapid, and the low concentration hydrogen peroxide is the only chemical added to the system, that could eliminate the complexity of iron-involved Fenton reactions or the use of the pulse-radiolysis system. PMID:19794928

Influence of pH, buffers and role of quinolinic acid, a novel iron chelating agent, in the determination of hydroxyl radical scavenging activity of plant extracts by Electron Paramagnetic Resonance (EPR).

PubMed

Fadda, Angela; Barberis, Antonio; Sanna, Daniele

2018-02-01

The Fenton reaction is used to produce hydroxyl radicals for the evaluation of the antioxidant activity of plant extracts. In this paper the parameters affecting the production of hydroxyl radicals and their spin trapping with DMPO were studied. The use of quinolinic acid (Quin) as an Fe(II) ligand was proposed for antioxidant activity determination of Green tea, orange juice and asparagus extracts. Quin, buffers and pH affect the DMPO-OH signal intensity of the EPR spectra. Quin/Fe(II) and low pH enhance the OH generation. Phosphate and Tris-HCl buffers decrease the signal intensity measured in Fe(II)-sulfate and Fe(II)-Quin systems. The extracts were analyzed with Fenton systems containing Fe(II)-sulfate and Fe(II)-Quin with and without buffer. The highest activity was shown with Fe(II)-Quin without buffer, this system being less influenced by pH and chelating agents present in the extracts. This paper will help researchers to better design spin trapping experiments for food matrices. Copyright © 2017 Elsevier Ltd. All rights reserved.

NMR signals within the generalized Langevin model for fractional Brownian motion

NASA Astrophysics Data System (ADS)

Lisý, Vladimír; Tóthová, Jana

2018-03-01

The methods of Nuclear Magnetic Resonance belong to the best developed and often used tools for studying random motion of particles in different systems, including soft biological tissues. In the long-time limit the current mathematical description of the experiments allows proper interpretation of measurements of normal and anomalous diffusion. The shorter-time dynamics is however correctly considered only in a few works that do not go beyond the standard memoryless Langevin description of the Brownian motion (BM). In the present work, the attenuation function S (t) for an ensemble of spin-bearing particles in a magnetic-field gradient, expressed in a form applicable for any kind of stationary stochastic dynamics of spins with or without a memory, is calculated in the frame of the model of fractional BM. The solution of the model for particles trapped in a harmonic potential is obtained in an exceedingly simple way and used for the calculation of S (t). In the limit of free particles coupled to a fractal heat bath, the results compare favorably with experiments acquired in human neuronal tissues. The effect of the trap is demonstrated by introducing a simple model for the generalized diffusion coefficient of the particle.

Precision measurement of the positron asymmetry of laser-cooled, spin-polarized 37K

NASA Astrophysics Data System (ADS)

Melconian, Dan; Fenker, B.; Behr, J. A.; Anholm, M.; Ashery, D.; Behling, R. S.; Cohen, I.; Craiciu, I.; Gorelov, A.; Gwinner, G.; McNeil, J.; Mehlman, M.; Smale, S.; Warner, C. L.

2017-01-01

Precision low-energy measurements in nuclear β decay can be used to provide constraints on possible physics beyond the standard model, complementing searches at high-energy colliders. The short-lived isotope 37K was produced at ISAC-TRIUMF and confined in an alternating magneto-optical trap before being spin-polarized to 99.13(9)% via optical pumping. Our system allows for an exceptionally open geometry with the decay products escaping with their momenta unperturbed by the shallow trapping potential. The emitted positrons are detected in a pair of symmetric detectors placed along the polarization axis to measure the β asymmetry. The analysis was performed blind and considers β-scattering as well as other systematic effects. The results place limits on the mass of a hypothetical W boson coupling to right-handed neutrinos as well as contribute to an independent determination of the Vud element of the CKM matrix. The β asymmetry result as well as improvements and future plans will be described. This work is supported in part by the U.S. Department of Energy, the Natural Sciences and Engineering Research Council of Canada, and the Israel Science Foundation.

Effect of the nano-oxide layer as a Mn diffusion barrier in specular spin valves

NASA Astrophysics Data System (ADS)

Jang, S. H.; Kang, T.; Kim, H. J.; Kim, K. Y.

2002-07-01

In previous work an enhanced giant magnetoresistance (GMR) effect in spin valves (SVs) with a nano-oxide layer (NOL) after annealing at about 250-300 degC has been reported. We have shown that SVs with a NOL also have higher thermal stability of the MR ratio at 300 degC. From secondary-ion-mass spectroscopy and x-ray photoelectron spectroscopy depth profile analysis, the mechanism of the improved thermal stability of the SVs with a NOL is shown to be related to MnO formation within the NOL. Thus, Mn atoms from the FeMn layer are trapped, and Mn diffusion is inhibited by the NOL during annealing.

Precision Measurement of the β Asymmetry in Spin-Polarized K 37 Decay

NASA Astrophysics Data System (ADS)

Fenker, B.; Gorelov, A.; Melconian, D.; Behr, J. A.; Anholm, M.; Ashery, D.; Behling, R. S.; Cohen, I.; Craiciu, I.; Gwinner, G.; McNeil, J.; Mehlman, M.; Olchanski, K.; Shidling, P. D.; Smale, S.; Warner, C. L.

2018-02-01

Using Triumf's neutral atom trap, Trinat, for nuclear β decay, we have measured the β asymmetry with respect to the initial nuclear spin in K 37 to be Aβ=-0.5707 (13) syst(13) stat(5) pol , a 0.3% measurement. This is the best relative accuracy of any β -asymmetry measurement in a nucleus or the neutron, and is in agreement with the standard model prediction -0.5706 (7 ). We compare constraints on physics beyond the standard model with other β -decay measurements, and improve the value of Vud measured in this mirror nucleus by a factor of 4.

Lattice-mediated magnetic order melting in TbMnO 3

DOE PAGES

Baldini, Edoardo; Kubacka, Teresa; Mallett, Benjamin P. P.; ...

2018-03-15

Recent ultrafast magnetic-sensitive measurements have revealed a delayed melting of the long-range cycloid spin order in TbMnO 3 following photoexcitation across the fundamental Mott-Hubbard gap. The microscopic mechanism behind this slow transfer of energy from the photoexcited carriers to the spin degrees of freedom is still elusive and not understood. Here, we address this problem by combining spectroscopic ellipsometry, ultrafast broadband optical spectroscopy, and ab initio calculations. Upon photoexcitation, we observe the emergence of a complex collective response, which is due to high-energy coherent optical phonons coupled to the out-of-equilibrium charge density. This response precedes the magnetic order melting andmore » is interpreted as the fingerprint of the formation of anti-Jahn-Teller polarons. We propose that the charge localization in a long-lived self-trapped state hinders the emission of magnons and other spin-flip mechanisms, causing the energy transfer from the charge to the spin system to be mediated by the reorganization of the lattice. In conclusion, we provide evidence for the coherent excitation of a phonon mode associated with the ferroelectric phase transition.« less

Slow spin relaxation induced by magnetic field in [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O.

PubMed

Vrábel, P; Orendáč, M; Orendáčová, A; Čižmár, E; Tarasenko, R; Zvyagin, S; Wosnitza, J; Prokleška, J; Sechovský, V; Pavlík, V; Gao, S

2013-05-08

We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field.

Lattice-mediated magnetic order melting in TbMnO 3

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

Baldini, Edoardo; Kubacka, Teresa; Mallett, Benjamin P. P.

Recent ultrafast magnetic-sensitive measurements have revealed a delayed melting of the long-range cycloid spin order in TbMnO 3 following photoexcitation across the fundamental Mott-Hubbard gap. The microscopic mechanism behind this slow transfer of energy from the photoexcited carriers to the spin degrees of freedom is still elusive and not understood. Here, we address this problem by combining spectroscopic ellipsometry, ultrafast broadband optical spectroscopy, and ab initio calculations. Upon photoexcitation, we observe the emergence of a complex collective response, which is due to high-energy coherent optical phonons coupled to the out-of-equilibrium charge density. This response precedes the magnetic order melting andmore » is interpreted as the fingerprint of the formation of anti-Jahn-Teller polarons. We propose that the charge localization in a long-lived self-trapped state hinders the emission of magnons and other spin-flip mechanisms, causing the energy transfer from the charge to the spin system to be mediated by the reorganization of the lattice. In conclusion, we provide evidence for the coherent excitation of a phonon mode associated with the ferroelectric phase transition.« less

Recent research related to prediction of stall/spin characteristics of fighter aircraft

NASA Technical Reports Server (NTRS)

Nguyen, L. T.; Anglin, E. L.; Gilbert, W. P.

1976-01-01

The NASA Langley Research Center is currently engaged in a stall/spin research program to provide the fundamental information and design guidelines required to predict the stall/spin characteristics of fighter aircraft. The prediction methods under study include theoretical spin prediction techniques and piloted simulation studies. The paper discusses the overall status of theoretical techniques including: (1) input data requirements, (2) math model requirements, and (3) correlation between theoretical and experimental results. The Langley Differential Maneuvering Simulator (DMS) facility has been used to evaluate the spin susceptibility of several current fighters during typical air combat maneuvers and to develop and evaluate the effectiveness of automatic departure/spin prevention concepts. The evaluation procedure is described and some of the more significant results of the studies are presented.

Mixed-valence molecular four-dot unit for quantum cellular automata: Vibronic self-trapping and cell-cell response

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

Tsukerblat, Boris, E-mail: tsuker@bgu.ac.il, E-mail: andrew.palii@uv.es; Palii, Andrew, E-mail: tsuker@bgu.ac.il, E-mail: andrew.palii@uv.es; Clemente-Juan, Juan Modesto

2015-10-07

Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of mixed-valence (MV) tetra-ruthenium (2Ru(II) + 2Ru(III)) derivatives (assembled as two coupled Creutz-Taube complexes) for which molecular implementations of quantum cellular automata (QCA) was proposed. The cell based on this molecule includes two holes shared among four spinless sites and correspondingly we employ the model which takes into accountmore » the two relevant electron transfer processes (through the side and through the diagonal of the square) as well as the difference in Coulomb energies for different instant positions of localization of the hole pair. The combined Jahn-Teller (JT) and pseudo JT vibronic coupling is treated within the conventional Piepho-Krauzs-Schatz model adapted to a bi-electronic MV species with the square-planar topology. The adiabatic potentials are evaluated for the low lying Coulomb levels in which the antipodal sites are occupied, the case just actual for utilization in mQCA. The conditions for the vibronic self-trapping in spin-singlet and spin-triplet states are revealed in terms of the two actual transfer pathways parameters and the strength of the vibronic coupling. Spin related effects in degrees of the localization which are found for spin-singlet and spin-triplet states are discussed. The polarization of the cell is evaluated and we demonstrate how the partial delocalization caused by the joint action of the vibronic coupling and electron transfer processes influences polarization of a four-dot cell. The results obtained within the adiabatic approach are compared with those based on the numerical solution of the dynamic vibronic problem. Finally, the Coulomb interaction between the cells is considered and the influence of the vibronic coupling on the shape on the non-linear cell-cell response function is revealed.« less

Mixed-valence molecular four-dot unit for quantum cellular automata: Vibronic self-trapping and cell-cell response.

PubMed

Tsukerblat, Boris; Palii, Andrew; Clemente-Juan, Juan Modesto; Coronado, Eugenio

2015-10-07

Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of mixed-valence (MV) tetra-ruthenium (2Ru(ii) + 2Ru(iii)) derivatives (assembled as two coupled Creutz-Taube complexes) for which molecular implementations of quantum cellular automata (QCA) was proposed. The cell based on this molecule includes two holes shared among four spinless sites and correspondingly we employ the model which takes into account the two relevant electron transfer processes (through the side and through the diagonal of the square) as well as the difference in Coulomb energies for different instant positions of localization of the hole pair. The combined Jahn-Teller (JT) and pseudo JT vibronic coupling is treated within the conventional Piepho-Krauzs-Schatz model adapted to a bi-electronic MV species with the square-planar topology. The adiabatic potentials are evaluated for the low lying Coulomb levels in which the antipodal sites are occupied, the case just actual for utilization in mQCA. The conditions for the vibronic self-trapping in spin-singlet and spin-triplet states are revealed in terms of the two actual transfer pathways parameters and the strength of the vibronic coupling. Spin related effects in degrees of the localization which are found for spin-singlet and spin-triplet states are discussed. The polarization of the cell is evaluated and we demonstrate how the partial delocalization caused by the joint action of the vibronic coupling and electron transfer processes influences polarization of a four-dot cell. The results obtained within the adiabatic approach are compared with those based on the numerical solution of the dynamic vibronic problem. Finally, the Coulomb interaction between the cells is considered and the influence of the vibronic coupling on the shape on the non-linear cell-cell response function is revealed.

Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures.

PubMed

Vinante, A; Wijts, G; Usenko, O; Schinkelshoek, L; Oosterkamp, T H

2011-12-06

Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics.

Thermal electric vapor trap arrangement and method

DOEpatents

Alger, Terry

1988-01-01

A technique for trapping vapor within a section of a tube is disclosed herein. This technique utilizes a conventional, readily providable thermal electric device having a hot side and a cold side and means for powering the device to accomplish this. The cold side of this device is positioned sufficiently close to a predetermined section of the tube and is made sufficiently cold so that any condensable vapor passing through the predetermined tube section is condensed and trapped, preferably within the predetermined tube section itself.

Thermal electric vapor trap arrangement and method

DOEpatents

Alger, T.

1988-03-15

A technique for trapping vapor within a section of a tube is disclosed herein. This technique utilizes a conventional, readily providable thermal electric device having a hot side and a cold side and means for powering the device to accomplish this. The cold side of this device is positioned sufficiently close to a predetermined section of the tube and is made sufficiently cold so that any condensable vapor passing through the predetermined tube section is condensed and trapped, preferably within the predetermined tube section itself. 4 figs.

Using Malaise traps to sample ground beetles (Coleoptera: Carabidae)

Treesearch

Michael D. Ulyshen; James L. Hanula; Scott Horn

2005-01-01

Pitfall traps provide an easy and inexpensive way to sample ground-dwelling arthropods (Spence and Niemela 1994; Spence et al. 1997; Abildsnes and Tommeras 2000) and have been used exclusively in many studies of the abundance and diversity of ground beetles (Coleoptera: Carabidae). Despite the popularity of this trapping technique, pitfall traps have many disadvantages...

Annealing shallow traps in electron beam irradiated high mobility metal-oxide-silicon transistors

NASA Astrophysics Data System (ADS)

Kim, Jin-Sung; Tyryshkin, Alexei; Lyon, Stephen

In metal-oxide-silicon (MOS) quantum devices, electron beam lithography (EBL) is known to create defects at the Si/SiO2 interface which can be catastrophic for single electron control. Shallow traps ( meV), which only manifest themselves at low temperature ( 4 K), are especially detrimental to quantum devices but little is known about annealing them. In this work, we use electron spin resonance (ESR) to measure the density of shallow traps in two sets of high mobility (μ) MOS transistors. One set (μ=14,000 cm2/Vs) was irradiated with an EBL dose (10 kV, 40 μC/cm2) and was subsequently annealed in forming gas while the other remained unexposed (μ=23,000 cm2/Vs). Our ESR data show that the forming gas anneal is sufficient to remove shallow traps generated by the EBL dose over the measured shallow trap energy range (0.3-4 meV). We additionally fit these devices' conductivity data to a percolation transition model and extract a zero temperature percolation threshold density, n0 ( 9 ×1010 cm-2 for both devices). We find that the extracted n0 agrees within 15 % with our lowest temperature (360 mK) ESR measurements, demonstrating agreement between two independent methods of evaluating the interface.

Hyperperfusion syndrome after trapping with high-flow bypass for a giant paraclinoid internal carotid artery aneurysm.

PubMed

Mohri, Masanao; Ichinose, Toshiya; Uchiyama, Naoyuki; Misaki, Kouichi; Nambu, Iku; Takabatake, Yasushi; Nakada, Mitsutoshi

2018-04-21

Hyperperfusion syndrome associated with aneurysm surgery is rare. The occurrence of the syndrome after trapping with high-flow bypass has not been described previously. Herein, we present a case of the syndrome occurring after trapping with high-flow bypass of an unruptured giant paraclinoid internal carotid artery (ICA) aneurysm. The patient was a 68-year-old woman with progressive loss of vision in her left eye. After a diagnosis of a left giant ICA aneurysm, she underwent successful trapping with high-flow bypass. No new neurological deficits were observed after surgery. Computed tomography (CT) on the same day and magnetic resonance imaging (MRI) on the next day revealed no hemorrhage or infarction. The patient had a headache and transit motor aphasia on postoperative day (POD) 8. Arterial spin-labeling magnetic resonance perfusion image on the same day and single photon emission CT scan on POD 10 demonstrated hyperperfusion in the left cerebral cortex. The symptoms gradually improved over a week and she had no new neurological deficits when discharged from hospital. This report suggests that, although rare, hyperperfusion syndrome after trapping with high-flow bypass should be considered in giant aneurysmal patients if they present with headache and neurological deficits in a delayed period. Copyright © 2018. Published by Elsevier Inc.

Towards a Compositional SPIN

NASA Technical Reports Server (NTRS)

Pasareanu, Corina S.; Giannakopoulou, Dimitra

2006-01-01

This paper discusses our initial experience with introducing automated assume-guarantee verification based on learning in the SPIN tool. We believe that compositional verification techniques such as assume-guarantee reasoning could complement the state-reduction techniques that SPIN already supports, thus increasing the size of systems that SPIN can handle. We present a "light-weight" approach to evaluating the benefits of learning-based assume-guarantee reasoning in the context of SPIN: we turn our previous implementation of learning for the LTSA tool into a main program that externally invokes SPIN to provide the model checking-related answers. Despite its performance overheads (which mandate a future implementation within SPIN itself), this approach provides accurate information about the savings in memory. We have experimented with several versions of learning-based assume guarantee reasoning, including a novel heuristic introduced here for generating component assumptions when their environment is unavailable. We illustrate the benefits of learning-based assume-guarantee reasoning in SPIN through the example of a resource arbiter for a spacecraft. Keywords: assume-guarantee reasoning, model checking, learning.

The tetrahydrobiopterin radical with high- and low-spin heme in neuronal nitric oxide synthase -- a new indicator of the extent of NOS coupling

PubMed Central

Krzyaniak, Matthew D.; Cruce, Alex A.; Vennam, Preethi; Lockart, Molly; Berka, Vladimir; Tsai, Ah-Lim; Bowman, Michael K.

2016-01-01

Reaction intermediates trapped during the single-turnover reaction of the neuronal ferrous nitric oxide synthase oxygenase domain (Fe(II)nNOSOX) show four EPR spectra of free radicals. Fully-coupled nNOSOX with cofactor (tetrahydrobiopterin, BH4) and substrate (l-arginine) forms the typical BH4 cation radical with an EPR spectrum ~4.0 mT wide and hyperfine tensors similar to reports for a biopterin cation radical in inducible NOSOX (iNOSOX). With excess thiol, nNOSox lacking BH4 and l-arg is known to produce superoxide. In contrast, we find that nNOSOX with BH4 but no l-arg forms two radicals with rather different, fast (~ 250 µs at 5 K) and slower (~ 500 µs at 20 K), electron spin relaxation rates and a combined ~7.0 mT wide EPR spectrum. Rapid freeze-quench CW- and pulsed-EPR measurements are used to identify these radicals and their origin. These two species are the same radical with identical nuclear hyperfine couplings, but with spin-spin couplings to high-spin (4.0 mT component) or low-spin (7.0 mT component) Fe(III) heme. Uncoupled reactions of nNOS leave the enzyme in states that can be chemically reduced to sustain unregulated production of NO and reactive oxygen species in ischemia-reperfusion injury. The broad EPR signal is a convenient indicator of uncoupled nNOS reactions producing low-spin Fe(III) heme. PMID:27989753

Spin-dependent excitation of plasma modes in non-neutral ion plasmas

NASA Astrophysics Data System (ADS)

Sawyer, Brian C.; Britton, Joe W.; Bollinger, John J.

2011-10-01

We report on a new technique for exciting and sensitively detecting plasma modes in small, cold non-neutral ion plasmas. The technique uses an optical dipole force generated from laser beams to excite plasma modes. By making the force spin- dependent (i.e. depend on the internal state of the atomic ion) very small mode excitations (<100 nm) can be detected through spin-motion entanglement. Even when the optical dipole force is homogeneous throughout the plasma, short wavelength modes on the order of the interparticle spacing can in principle be excited and detected through the spin dependence of the force. We use this technique to study the drumhead modes of single plane triangular arrays of a few hundred Be+ ions. Spin-dependent mode excitation is interesting in this system because it provides a means of engineering an Ising interaction on a 2-D triangular lattice. For the case of an anti-ferromagnetic interaction, this system exhibits spin frustration on a scale that is at present computationally intractable. Work supported by the DARPA OLE program and NIST.

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing.

PubMed

Lu, Qifeng; Zhao, Chun; Mu, Yifei; Zhao, Ce Zhou; Taylor, Stephen; Chalker, Paul R

2015-07-29

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO x ; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10 12 cm -2 for as-deposited sample to 4.55 × 10 12 cm -2 for the 800 °C annealed one. In addition, the leakage current density increase from about 10 - ⁶ A/cm² at V g = +0.5 V for the as-deposited sample to 10 -3 A/cm² at V g = +0.5 V for the 900 °C annealed one.

Spin and charge transport through carbon based systems

NASA Astrophysics Data System (ADS)

Jung, Suyong

In this thesis, we investigate spin-dependent transport through ferromagnet-contacted single-walled carbon nanotubes (SWCNTs), in which charge transport shows the Fabry-Perot (FP) interference effect, the Kondo effect and the Coulomb blockade effect at low temperatures. Hysteric magnetoresistance (MR) is observed in all three transport regimes, which can be controlled by both the external magnetic field and the gate voltage. The MR in the FP interference regime can be well understood by a model considering the intrinsic electronic structure of SWCNTs and the quantum interference effect. In the strongly interacting Kondo regime, the Kondo effect is not suppressed by the presence of nearby ferromagnetism. Several observed MR features including the non-splitted zero-bias Kondo peak and positive MR switching can be explained by the strong Kondo effect and weak ferromagnetism in the leads. In the Coulomb blockade regime, several effects that can be associated with the magneto-Coulomb effect have been observed, and isolated spin accumulation and transport through the SWCNT quantum dot have been realized by a four-probe non-local measurements. We also studied charge transport behavior through organic semiconductor pentacene thin film transistors (OTFTs) in the limit of single- or a few molecular layers of pentacene films. The charge transport in these devices can be well explained by the multiple trapping and release model. The structural disorders induced by the physical and chemical causes, such as grain boundaries, interactions with gate insulator, metal contacts and ambient conditions can be responsible for the localized trap states in the ultrathin layer OTFTs, which are further confirmed by the electric force microscopy (EFM) measurements.

Free radical generation by ultrasound in aqueous and nonaqueous solutions.

PubMed Central

Riesz, P; Berdahl, D; Christman, C L

1985-01-01

The physical principles underlying the oscillatory behavior of minute gas bubbles in liquids exposed to ultrasound are reviewed. Results from mathematical analyses suggest that these oscillations sometimes become unstable leading to transient cavitation in which a bubble violently collapses during a single acoustic half-cycle producing high temperatures and pressures. The role that micronuclei, resonant bubble size, and rectified diffusion play in the initiation of transient cavitation is explained. Evidence to support these theoretical predictions is presented with particular emphasis on sonoluminescence which provides some non-chemical evidence for the formation of free radicals. Acoustic methods for conducting sonochemical investigations are discussed. In aqueous solutions transient cavitation initially generates hydrogen atoms and hydroxyl radicals which may recombine to form hydrogen and hydrogen peroxide or may react with solutes in the gas phase, at the gas-liquid boundary or in the bulk of the solution. The analogies and differences between sonochemistry and ionizing radiation chemistry are explored. The use of spin trapping and electron spin resonance to identify hydrogen atoms and hydroxyl radicals conclusively and to detect transient cavitation produced by continuous wave and by pulsed ultrasound is described in detail. The study of the chemical effects of cavitation in organic liquids is a relatively unexplored area which has recently become the subject of renewed interest. Examples of the decomposition of solvent and solute, of ultrasonically initiated free-radical polymerization and polymer degradation are presented. Spin trapping has been used to identify radicals in organic liquids, in polymer degradation and in the decomposition of organometallic compounds. PMID:3007091

Scavenging of reactive oxygen species and prevention of oxidative neuronal cell damage by a novel gallotannin, pistafolia A.

PubMed

Wei, Taotao; Sun, Handong; Zhao, Xingyu; Hou, Jingwu; Hou, Aijun; Zhao, Qinshi; Xin, Wenjuan

2002-03-08

Pistafolia A is a novel gallotannin isolated from the leaf extract of Pistacia weinmannifolia. In the present investigation, the ability of Pistafolia A to scavenge reactive oxygen species including hydroxyl radicals and superoxide anion was measured by ESR spin trapping technique. The inhibition effect on iron-induced lipid peroxidaiton in liposomes was studied. The protective effects of Pistafolia A against oxidative neuronal cell damage and apoptosis induced by peroxynitrite were also assessed. The results showed that Pistafolia A could scavenge both hydroxyl radicals and superoxide anion dose-dependently and inhibit lipid peroxidation effectively. In cerebellar granule cells pretreated with Pistafolia A, peroxynitrite-induced oxidative neuronal damage and apoptosis were prevented markedly. The antioxidant capacity of Pistafolia A was much more potent then that of the water-soluble analog of vitamin E, Trolox. The results suggested that Pistafolia A might be used as an effective natural antioxidant for the prevention and cure of neuronal diseases associated with the production of peroxynitrite and related reactive oxygen species.

Write once read many memory device from Tris-8 (-hydroxyquinoline) aluminum and Indium tin oxide nano particles

NASA Astrophysics Data System (ADS)

Aneesh, J.; Predeep, P.

2011-10-01

Consequent to the fast increase in data storage requirements new materials and device structures are explored in a war footing. Organic memory devices are attracting lot of interest among the researchers and are becoming a hot topic of investigations. This study is an attempt to develop a tri-layer organic memory device using indium tin oxide (ITO) nanoparticles as charge trapping middle layer between tris-8(-hydroxyquinoline)aluminum (Alq3) layers employing spin coating technique. Device switching is studied by applying a current-voltage (I-V) sweep. On increasing the applied bias the device switched from the initial high resistance (OFF) state to a low resistance (ON) state at a switch on voltage of around 4 V. ON/OFF ratio is of the order of 100 at a read voltage of 2 V. The device is found to remain in the low resistance state on further scans, showing the applicability of this device as a write once read many times (WORM) memory.

Enhanced hydroxyl radical production by dihydroxybenzene-driven Fenton reactions: implications for wood biodegradation.

PubMed

Contreras, David; Rodríguez, Jaime; Freer, Juanita; Schwederski, Brigitte; Kaim, Wolfgang

2007-09-01

Brown rot fungi degrade wood, in initial stages, mainly through hydroxyl radicals (.OH) produced by Fenton reactions. These Fenton reactions can be promoted by dihydroxybenzenes (DHBs), which can chelate and reduce Fe(III), increasing the reactivity for different substrates. This mechanism allows the extensive degradation of carbohydrates and the oxidation of lignin during wood biodegradation by brown rot fungi. To understand the enhanced reactivity in these systems, kinetics experiments were carried out, measuring .OH formation by the spin-trapping technique of electron paramagnetic resonance spectroscopy. As models of the fungal DHBs, 1,2-dihydroxybenzene (catechol), 2,3-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid were utilized as well as 1,2-dihydroxy-3,5-benzenedisulfonate as a non-Fe(III)-reducing substance for comparison. Higher amounts and maintained concentrations of .OH were observed in the driven Fenton reactions versus the unmodified Fenton process. A linear correlation between the logarithms of complex stability constants and the .OH production was observed, suggesting participation of such complexes in the radical production.

Surface Raman scattering from effervescent magnetic peroxyborates

NASA Astrophysics Data System (ADS)

Walrafen, G. E.; Krishnan, P. N.; Griscom, D. L.; Munro, R.

1982-06-01

Surface Raman scattering using a spinning technique was investigated for solid NaBO3.4H2O and NaBO3.H2O as well as for electron bombarded peroxyborates heated for various times and at temperatures form 110-180 deg C, and for solid Na2O2 and BaO2. The Raman spectra indicate that the breakdown of peroxy groups is accompanied by the formation of trapped molecular O2. Quantitative Raman intensity data were also obtained as functions of heating time at 115 deg C for the 1556 cm-1 line from O2 and for the 890 and 705 cm-1 lines whose intensities scale with the peroxy concentration. These intensity data were treated by logistics theory, and they were found to be consistent with a second-order auto-catalyzed forward reaction dependent on the product of the peroxy and O2 concentrations, plus a first-order reverse reaction dependent only on the O2 concentration.

Surface Raman scattering from effervescent magnetic peroxyborates

NASA Astrophysics Data System (ADS)

Walrafen, G. E.; Krishnan, P. N.; Hokmabadi, M.; Griscom, D. L.; Munro, R. G.

1982-10-01

Surface Raman scattering using a spinning technique was investigated for solid NaBO3ṡ4H2O and NaBO3ṡH2O, as well as for electron bombarded peroxyborates, for peroxyborates heated for various times and at temperatures for 110-180 °C, and for solid Na2O2 and BaO2. The Raman spectra indicate that the breakdown of peroxy groups is accompanied by the formation of trapped molecular O2. Quantitative Raman intensity data were also obtained as functions of heating time at 115 °C for the 1556 cm-1 line from O2 and for the 890 and 705 cm-1 lines whose intensities scale with the peroxy concentration. These intensity data were treated by logistics theory, and they were found to be consistent with a second-order autocatalyzed forward reaction dependent on the product of the peroxy and O2 concentrations, plus a first-order reverse reaction dependent only on the O2 concentration.

Transition probabilities for the 3s2 3p(2P0)-3s3p2(4P) intersystem lines of Si II

NASA Technical Reports Server (NTRS)

Calamai, Anthony G.; Smith, Peter L.; Bergeson, S. D.

1993-01-01

Intensity ratios of lines of the spin-changing 'intersystem' multiplet of S II (4P yields 2P0) at 234 nm have been used to determine electron densities and temperatures in a variety of astrophysical environments. However, the accuracy of these diagnostic calculations have been limited by uncertainties associated with the available atomic data. We report the first laboratory measurement, using an ion-trapping technique, of the radiative lifetimes of the three metastable levels of the 3s3p2 4P term of Si II. Our results are 104 +/- 16, 406 +/- 33, and 811 +/- 77 micro-s for lifetimes of the J = 1/2, 5/2, and 3/2 levels, respectively. A-values were derived from our lifetimes by use of measured branching fractions. Our A-values, which differ from calculated values by 30 percent or more, should give better agreement between modeled and observed Si II line ratios.

Antimatter/HiPAT Support Services

NASA Technical Reports Server (NTRS)

Lewis, Raymond A.

2001-01-01

Techniques were developed for trapping normal matter in the High Performance Antiproton Trap (HiPAT). Situations encountered included discharge phenomena, charge exchange and radial diffusion processes. It is important to identify these problems, since they will also limit the performance in trapping antimatter next year.

Herpetological Monitoring Using a Pitfall Trapping Design in Southern California

USGS Publications Warehouse

Fisher, Robert; Stokes, Drew; Rochester, Carlton; Brehme, Cheryl; Hathaway, Stacie; Case, Ted

2008-01-01

The steps necessary to conduct a pitfall trapping survey for small terrestrial vertebrates are presented. Descriptions of the materials needed and the methods to build trapping equipment from raw materials are discussed. Recommended data collection techniques are given along with suggested data fields. Animal specimen processing procedures, including toe- and scale-clipping, are described for lizards, snakes, frogs, and salamanders. Methods are presented for conducting vegetation surveys that can be used to classify the environment associated with each pitfall trap array. Techniques for data storage and presentation are given based on commonly use computer applications. As with any study, much consideration should be given to the study design and methods before beginning any data collection effort.

Advanced Automation for Ion Trap Mass Spectrometry-New Opportunities for Real-Time Autonomous Analysis

NASA Technical Reports Server (NTRS)

Palmer, Peter T.; Wong, C. M.; Salmonson, J. D.; Yost, R. A.; Griffin, T. P.; Yates, N. A.; Lawless, James G. (Technical Monitor)

1994-01-01

The utility of MS/MS for both target compound analysis and the structure elucidation of unknowns has been described in a number of references. A broader acceptance of this technique has not yet been realized as it requires large, complex, and costly instrumentation which has not been competitive with more conventional techniques. Recent advancements in ion trap mass spectrometry promise to change this situation. Although the ion trap's small size, sensitivity, and ability to perform multiple stages of mass spectrometry have made it eminently suitable for on-line, real-time monitoring applications, advance automation techniques are required to make these capabilities more accessible to non-experts. Towards this end we have developed custom software for the design and implementation of MS/MS experiments. This software allows the user to take full advantage of the ion trap's versatility with respect to ionization techniques, scan proxies, and ion accumulation/ejection methods. Additionally, expert system software has been developed for autonomous target compound analysis. This software has been linked to ion trap control software and a commercial data system to bring all of the steps in the analysis cycle under control of the expert system. These software development efforts and their utilization for a number of trace analysis applications will be described.

Two-dimensional nuclear magnetic resonance of quadrupolar systems

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

Wang, Shuanhu

1997-09-01

This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combiningmore » the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.« less

The Development of Spectroscopic Techniques to Study Defects in Thin Film Silicon-Dioxide

NASA Astrophysics Data System (ADS)

Zvanut, Mary Ellen

This dissertation research concerns the study of defects in thin film sputtered SiO_2 which is used as an optical coating material. The capacitance-voltage and current-voltage techniques typically used in microelectronics investigations were used to examine the concentration, location, and kinetics of charge in an aluminum-sputtered oxide-native oxide-silicon capacitor. The response of the capacitor to low field bias stress reveals a hysteretic trapping behavior similar to that observed in microelectronic grade oxide films. In an effort to understand this phenomenon, a band-to-trap tunneling model was developed based on the assumption that the defect involved exhibits a delta function spatial distribution and an extended energy distribution. The central feature of this model, defect relaxation, provides a physical explanation for the hysteretic trapping behavior. Analysis yields that the trap is located spatially within 2 nm of the Si/SiO _2 interface and energetically less than 5 eV from the SiO_2 conduction band edge. The relaxation energy associated with the capture of an electron at the trap is 0.1-2.2 eV. Correlation of the electrical measurements executed for this investigation with electron paramagnetic resonance (EPR) data obtained by Dr. P. Caplan provides structural information about the defect involved with the hysteretic trapping phenomenon. EPR results obtained before and after subjecting an oxide-silicon structure to corona discharge suggest that the trapping center is an E^ ' defect. The technique of band-to-trap tunneling spectroscopy combined with the EPR experiments provides the first reported trap depth associated with the capture of a hole at an E^' center located near the silicon surface of an oxide/silicon system.

Mode Transition of RNA Trap by Electric and Hydraulic Force Field in Microfluidic Taper Shape Channel

NASA Astrophysics Data System (ADS)

Takamura, Yuzuru; Ueno, Kunimitsu; Nagasaka, Wako; Tomizawa, Yuichi; Tamiya, Eiichi

2007-03-01

We have discovered a phenomenon of accumulation of DNA near the constricted position of a microfluidic chip with taper shaped channel when both hydro pressure and electric field are applied in opposite directions. However, RNA has not been able to trap so far, unlike huge and uniformly double stranded DNA molecules, RNAs are smaller in size and single stranded with complicated conformation like blocks in lysed cell solution. In this paper, we will report not only large but also small RNA (100˜10b) are successfully trapped in relatively large microfluidic taper shape channel (width >10um). RNA are trapped in circular motion near the constricted position of taper shape channel, and the position and shape of the trapped RNA are controlled and make mode transition by changing the hydraulic and the electric force. Using this technique, smaller size molecule can be trapped in larger micro fluidic structure compared to the trap using dielectrophoresis. This technique is expected to establish easy and practical device as a direct total RNA extraction tool from living cells or tissues.

Hydroxyl radical generation by photosystem II.

PubMed

Pospísil, Pavel; Arató, András; Krieger-Liszkay, Anja; Rutherford, A William

2004-06-01

The photogeneration of hydroxyl radicals (OH(*)) in photosystem II (PSII) membranes was studied using EPR spin-trapping spectroscopy. Two kinetically distinguishable phases in the formation of the spin trap-hydroxyl (POBN-OH) adduct EPR signal were observed: the first phase (t(1/2) = 7.5 min) and the second phase (t(1/2) = 30 min). The generation of OH(*) was found to be suppressed in the absence of the Mn-complex, but it was restored after readdition of an artificial electron donor (DPC). Hydroxyl radical generation was also lost in the absence of oxygen, whereas it was stimulated when the oxygen concentration was increased. The production of OH(*) during the first kinetic phase was sensitive to the presence of SOD, whereas catalase and EDTA diminished the production of OH(*) during the second kinetic phase. The POBN-OH adduct EPR signal during the first phase exhibits a similar pH-dependence as the ability to oxidize the non-heme iron, as monitored by the Fe(3+) (g = 8) EPR signal: both EPR signals gradually decreased as the pH value was lowered below pH 6.5 and were absent at pH 5. Sodium formate decreases the production of OH(*) in intact and Mn-deleted PSII membranes. Upon illumination of PSII membranes, both superoxide, as measured by EPR signal from the spin trap-superoxide (EMPO-OOH) adduct, and H(2)O(2), measured colormetrically, were generated. These results indicated that OH(*) is produced on the electron acceptor side of PSII by two different routes, (1) O(2)(*)(-), which is generated by oxygen reduction on the acceptor side of PSII, interacts with a PSII metal center, probably the non-heme iron, to form an iron-peroxide species that is further reduced to OH(*) by an electron from PSII, presumably via Q(A)(-), and (2) O(2)(*)(-) dismutates to form free H(2)O(2) that is then reduced to OH(*) via the Fenton reaction in the presence of metal ions, the most likely being Mn(2+) and Fe(2+) released from photodamaged PSII. The two different routes of OH(*) generation are discussed in the context of photoinhibition.

Spin-analyzed SANS for soft matter applications

NASA Astrophysics Data System (ADS)

Chen, W. C.; Barker, J. G.; Jones, R.; Krycka, K. L.; Watson, S. M.; Gagnon, C.; Perevozchivoka, T.; Butler, P.; Gentile, T. R.

2017-06-01

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Optical trapping for analytical biotechnology.

PubMed

Ashok, Praveen C; Dholakia, Kishan

2012-02-01

We describe the exciting advances of using optical trapping in the field of analytical biotechnology. This technique has opened up opportunities to manipulate biological particles at the single cell or even at subcellular levels which has allowed an insight into the physical and chemical mechanisms of many biological processes. The ability of this technique to manipulate microparticles and measure pico-Newton forces has found several applications such as understanding the dynamics of biological macromolecules, cell-cell interactions and the micro-rheology of both cells and fluids. Furthermore we may probe and analyse the biological world when combining trapping with analytical techniques such as Raman spectroscopy and imaging. Copyright © 2011 Elsevier Ltd. All rights reserved.

The spin-Hall effect and spin-orbit torques in epitaxial Co2FeAl/platinum bilayers

NASA Astrophysics Data System (ADS)

Peterson, T. A.; Liu, C.; McFadden, T.; Palmstrøm, C. J.; Crowell, P. A.

We have performed magnetoresistance measurements on epitaxially grown Co2FeAl/platinum (CFA/Pt) ultrathin ferromagnet/heavy metal bilayers to study the spin-Hall effect in Pt and the accompanying spin-orbit torque (SOT) exerted on the magnetic CFA layer. Specifically, we measure the spin-Hall magnetoresistance in the Pt layer by changing the orientation of the CFA magnetization with respect to the spin current orientation created in the Pt, and we determine the SOT efficiency using a second-harmonic detection technique. Because the latter of the two measurements is proportional to the spin-Hall ratio θSHE while the former is proportional to θSHE2, we are able to extract the bare Pt spin-Hall ratio with no assumptions about the CFA/Pt interface spin mixing conductance. Furthermore, by varying the Pt thickness we show that the results are consistent with resistivity-independent spin-Hall conductivity. Finally, the two measurements in combination allow us to infer a spin-mixing conductance at the CFA/Pt interface of 2 +/- 1 ×1015Ω-1m-2 . The combination of spin-Hall magnetoresistance and SOT measurements allows for a determination of the spin-mixing conductance using only low-frequency transport techniques. This work was supported by STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

Towards quantum networks of single spins: analysis of a quantum memory with an optical interface in diamond.

PubMed

Blok, M S; Kalb, N; Reiserer, A; Taminiau, T H; Hanson, R

2015-01-01

Single defect centers in diamond have emerged as a powerful platform for quantum optics experiments and quantum information processing tasks. Connecting spatially separated nodes via optical photons into a quantum network will enable distributed quantum computing and long-range quantum communication. Initial experiments on trapped atoms and ions as well as defects in diamond have demonstrated entanglement between two nodes over several meters. To realize multi-node networks, additional quantum bit systems that store quantum states while new entanglement links are established are highly desirable. Such memories allow for entanglement distillation, purification and quantum repeater protocols that extend the size, speed and distance of the network. However, to be effective, the memory must be robust against the entanglement generation protocol, which typically must be repeated many times. Here we evaluate the prospects of using carbon nuclear spins in diamond as quantum memories that are compatible with quantum networks based on single nitrogen vacancy (NV) defects in diamond. We present a theoretical framework to describe the dephasing of the nuclear spins under repeated generation of NV spin-photon entanglement and show that quantum states can be stored during hundreds of repetitions using typical experimental coupling parameters. This result demonstrates that nuclear spins with weak hyperfine couplings are promising quantum memories for quantum networks.

A Compact, High-Flux Cold Atom Beam Source

NASA Technical Reports Server (NTRS)

Kellogg, James R.; Kohel, James M.; Thompson, Robert J.; Aveline, David C.; Yu, Nan; Schlippert, Dennis

2012-01-01

The performance of cold atom experiments relying on three-dimensional magneto-optical trap techniques can be greatly enhanced by employing a highflux cold atom beam to obtain high atom loading rates while maintaining low background pressures in the UHV MOT (ultra-high vacuum magneto-optical trap) regions. Several techniques exist for generating slow beams of cold atoms. However, one of the technically simplest approaches is a two-dimensional (2D) MOT. Such an atom source typically employs at least two orthogonal trapping beams, plus an additional longitudinal "push" beam to yield maximum atomic flux. A 2D atom source was created with angled trapping collimators that not only traps atoms in two orthogonal directions, but also provides a longitudinal pushing component that eliminates the need for an additional push beam. This development reduces the overall package size, which in turn, makes the 2D trap simpler, and requires less total optical power. The atom source is more compact than a previously published effort, and has greater than an order of magnitude improved loading performance.

Lunar Obliquity History Revisited

NASA Astrophysics Data System (ADS)

Siegler, M.; Bills, B.; Paige, D.

2007-12-01

In preparation for a LRO (Lunar Reconnaissance Orbiter) related study of possible lunar polar volatiles, we re- examined the lunar orbital and rotational history, with primary focus on the obliquity history of the Moon. Though broad models have been made of lunar obliquity, a cohesive obliquity history was not found. We report on a new model of lunar obliquity including secular changes in inclination of the lunar orbit, tidal dissipation, lunar moments of inertia, and details for periods outside of the stable configurations known as Cassini states. For planets, the obliquity, or angle between the spin and orbit poles, is the dominant control on incident solar radiation. For planetary satellites, the radiation pattern can be more complex, as it depends on the mutual inclinations of three poles; the satellite spin and orbit poles, and the planetary heliocentric orbit pole. Presently, the lunar spin pole and orbit pole co-precess about the ecliptic pole, in a stable situation known as a Cassini state. As a result, permanently shadowed regions near the poles are expected to exist and act as cold traps, retaining water or other volatiles delivered to the surface by comets, solar wind, or via outgassing of the lunar interior. However, tidally driven secular changes in the lunar semimajor axis cause changes in precession rates of the spin and orbit poles, and thereby alter or destabilize the Cassini states. Only one prograde Cassini state exists at present (state 2). In the standard Cassini state model of Ward [1975], two other such states would have existed in the past (states 1 and 4) with the Moon starting in the low obliquity state 1, and remaining there until states 1 and 4 merged and disappear, at roughly half the present Earth-Moon distance. At that point, the Moon transitioned into the currently occupied state 2, and briefly attained very high obliquity values during the transition, and then stayed in state 2 until the present. If correct, this model implies that the transition from state 1 to state 2 is the most important event in the histories of lunar obliquity and polar volatiles, as it separates two periods in which current lunar cold traps could have existed with a period of high polar insolation which could have mobilized volatiles into space or to greater depths in the lunar near surface. If incorrect, lunar cold traps may prove only a very recent phenomenon. By including secular orbit changes, our model should help determine if this Cassini state stability really dominated in the past and allow detailed examination of extra-Cassini state periods.

Dynamics and interactions of particles in a thermophoretic trap

NASA Astrophysics Data System (ADS)

Foster, Benjamin; Fung, Frankie; Fieweger, Connor; Usatyuk, Mykhaylo; Gaj, Anita; DeSalvo, B. J.; Chin, Cheng

2017-08-01

We investigate dynamics and interactions of particles levitated and trapped by the thermophoretic force in a vacuum cell. Our analysis is based on footage taken by orthogonal cameras that are able to capture the three dimensional trajectories of the particles. In contrast to spherical particles, which remain stationary at the center of the cell, here we report new qualitative features of the motion of particles with non-spherical geometry. Singly levitated particles exhibit steady spinning around their body axis and rotation around the symmetry axis of the cell. When two levitated particles approach each other, repulsive or attractive interactions between the particles are observed. Our levitation system offers a wonderful platform to study interaction between particles in a microgravity environment.

Experimental Verification of a Jarzynski-Related Information-Theoretic Equality by a Single Trapped Ion.

PubMed

Xiong, T P; Yan, L L; Zhou, F; Rehan, K; Liang, D F; Chen, L; Yang, W L; Ma, Z H; Feng, M; Vedral, V

2018-01-05

Most nonequilibrium processes in thermodynamics are quantified only by inequalities; however, the Jarzynski relation presents a remarkably simple and general equality relating nonequilibrium quantities with the equilibrium free energy, and this equality holds in both the classical and quantum regimes. We report a single-spin test and confirmation of the Jarzynski relation in the quantum regime using a single ultracold ^{40}Ca^{+} ion trapped in a harmonic potential, based on a general information-theoretic equality for a temporal evolution of the system sandwiched between two projective measurements. By considering both initially pure and mixed states, respectively, we verify, in an exact and fundamental fashion, the nonequilibrium quantum thermodynamics relevant to the mutual information and Jarzynski equality.

Collective modes of a two-dimensional spin-1/2 Fermi gas in a harmonic trap

NASA Astrophysics Data System (ADS)

Baur, Stefan K.; Vogt, Enrico; Köhl, Michael; Bruun, Georg M.

2013-04-01

We derive analytical expressions for the frequency and damping of the lowest collective modes of a two-dimensional Fermi gas using kinetic theory. For strong coupling, we furthermore show that pairing correlations overcompensate the effects of Pauli blocking on the collision rate for a large range of temperatures, resulting in a rate which is larger than that of a classical gas. Our results agree well with experimental data, and they recover the observed crossover from collisionless to hydrodynamic behavior with increasing coupling for the quadruple mode. Finally, we show that a trap anisotropy within the experimental bounds results in a damping of the breathing mode which is comparable to what is observed, even for a scale-invariant system.

3D GRASE PROPELLER: improved image acquisition technique for arterial spin labeling perfusion imaging.

PubMed

Tan, Huan; Hoge, W Scott; Hamilton, Craig A; Günther, Matthias; Kraft, Robert A

2011-07-01

Arterial spin labeling is a noninvasive technique that can quantitatively measure cerebral blood flow. While traditionally arterial spin labeling employs 2D echo planar imaging or spiral acquisition trajectories, single-shot 3D gradient echo and spin echo (GRASE) is gaining popularity in arterial spin labeling due to inherent signal-to-noise ratio advantage and spatial coverage. However, a major limitation of 3D GRASE is through-plane blurring caused by T(2) decay. A novel technique combining 3D GRASE and a periodically rotated overlapping parallel lines with enhanced reconstruction trajectory (PROPELLER) is presented to minimize through-plane blurring without sacrificing perfusion sensitivity or increasing total scan time. Full brain perfusion images were acquired at a 3 × 3 × 5 mm(3) nominal voxel size with pulsed arterial spin labeling preparation sequence. Data from five healthy subjects was acquired on a GE 1.5T scanner in less than 4 minutes per subject. While showing good agreement in cerebral blood flow quantification with 3D gradient echo and spin echo, 3D GRASE PROPELLER demonstrated reduced through-plane blurring, improved anatomical details, high repeatability and robustness against motion, making it suitable for routine clinical use. Copyright © 2011 Wiley-Liss, Inc.

Quantum information processing with long-wavelength radiation

NASA Astrophysics Data System (ADS)

Murgia, David; Weidt, Sebastian; Randall, Joseph; Lekitsch, Bjoern; Webster, Simon; Navickas, Tomas; Grounds, Anton; Rodriguez, Andrea; Webb, Anna; Standing, Eamon; Pearce, Stuart; Sari, Ibrahim; Kiang, Kian; Rattanasonti, Hwanjit; Kraft, Michael; Hensinger, Winfried

To this point, the entanglement of ions has predominantly been performed using lasers. Using long wavelength radiation with static magnetic field gradients provides an architecture to simplify construction of a large scale quantum computer. The use of microwave-dressed states protects against decoherence from fluctuating magnetic fields, with radio-frequency fields used for qubit manipulation. I will report the realisation of spin-motion entanglement using long-wavelength radiation, and a new method to efficiently prepare dressed-state qubits and qutrits, reducing experimental complexity of gate operations. I will also report demonstration of ground state cooling using long wavelength radiation, which may increase two-qubit entanglement fidelity. I will then report demonstration of a high-fidelity long-wavelength two-ion quantum gate using dressed states. Combining these results with microfabricated ion traps allows for scaling towards a large scale ion trap quantum computer, and provides a platform for quantum simulations of fundamental physics. I will report progress towards the operation of microchip ion traps with extremely high magnetic field gradients for multi-ion quantum gates.

Analog quantum simulation of generalized Dicke models in trapped ions

NASA Astrophysics Data System (ADS)

Aedo, Ibai; Lamata, Lucas

2018-04-01

We propose the analog quantum simulation of generalized Dicke models in trapped ions. By combining bicromatic laser interactions on multiple ions we can generate all regimes of light-matter coupling in these models, where here the light mode is mimicked by a motional mode. We present numerical simulations of the three-qubit Dicke model both in the weak field (WF) regime, where the Jaynes-Cummings behavior arises, and the ultrastrong coupling (USC) regime, where a rotating-wave approximation cannot be considered. We also simulate the two-qubit biased Dicke model in the WF and USC regimes and the two-qubit anisotropic Dicke model in the USC regime and the deep-strong coupling regime. The agreement between the mathematical models and the ion system convinces us that these quantum simulations can be implemented in the laboratory with current or near-future technology. This formalism establishes an avenue for the quantum simulation of many-spin Dicke models in trapped ions.

A Comparison of Two Methods for Estimating Black Hole Spin in Active Galactic Nuclei

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

Capellupo, Daniel M.; Haggard, Daryl; Wafflard-Fernandez, Gaylor, E-mail: danielc@physics.mcgill.ca

Angular momentum, or spin, is a fundamental property of black holes (BHs), yet it is much more difficult to estimate than mass or accretion rate (for actively accreting systems). In recent years, high-quality X-ray observations have allowed for detailed measurements of the Fe K α emission line, where relativistic line broadening allows constraints on the spin parameter (the X-ray reflection method). Another technique uses accretion disk models to fit the AGN continuum emission (the continuum-fitting, or CF, method). Although each technique has model-dependent uncertainties, these are the best empirical tools currently available and should be vetted in systems where bothmore » techniques can be applied. A detailed comparison of the two methods is also useful because neither method can be applied to all AGN. The X-ray reflection technique targets mostly local ( z ≲ 0.1) systems, while the CF method can be applied at higher redshift, up to and beyond the peak of AGN activity and growth. Here, we apply the CF method to two AGN with X-ray reflection measurements. For both the high-mass AGN, H1821+643, and the Seyfert 1, NGC 3783, we find a range in spin parameter consistent with the X-ray reflection measurements. However, the near-maximal spin favored by the reflection method for NGC 3783 is more probable if we add a disk wind to the model. Refinement of these techniques, together with improved X-ray measurements and tighter BH mass constraints, will permit this comparison in a larger sample of AGN and increase our confidence in these spin estimation techniques.« less

A versatile system for optical manipulation experiments

NASA Astrophysics Data System (ADS)

Hanstorp, Dag; Ivanov, Maksym; Alemán Hernández, Ademir F.; Enger, Jonas; Gallego, Ana M.; Isaksson, Oscar; Karlsson, Carl-Joar; Monroy Villa, Ricardo; Varghese, Alvin; Chang, Kelken

2017-08-01

In this paper a versatile experimental system for optical levitation is presented. Microscopic liquid droplets are produced on demand from piezo-electrically driven dispensers. The charge of the droplets is controlled by applying an electric field on the piezo-dispenser head. The dispenser releases droplets into a vertically focused laser beam. The size and position in 3 dimensions of trapped droplets are measured using two orthogonally placed high speed cameras. Alternatively, the vertical position is determined by imaging scattered light onto a position sensitive detector. The charge of a trapped droplets is determined by recording its motion when an electric field is applied, and the charge can be altered by exposing the droplet to a radioactive source or UV light. Further, spectroscopic information of the trapped droplet is obtained by imaging the droplet on the entrance slit of a spectrometer. Finally, the trapping cell can be evacuated, allowing investigations of droplet dynamics in vacuum. The system is utilized to study a variety of physical phenomena, and three pilot experiments are given in this paper. First, a system used to control and measure the charge of the droplet is presented. Second, it is demonstrated how particles can be made to rotate and spin by trapping them using optical vortices. Finally, the Raman spectra of trapped glycerol droplets are obtained and analyzed. The long term goal of this work is to create a system where interactions of droplets with the surrounding medium or with other droplets can be studied with full control of all physical variables.

Long range magnetic ordering of ultracold fermions in an optical lattice

NASA Astrophysics Data System (ADS)

Duarte, P. M.; Hart, R. A.; Yang, T.-L.; Hulet, R. G.

2013-05-01

We present progress towards the observation of long range antiferromagnetic (AFM) ordering of fermionic 6Li atoms in an optical lattice. We prepare a two spin state mixture of 106 atoms at T /TF = 0 . 1 by evaporatively cooling in an optical dipole trap. The sample is then transferred to a dimple trap formed by three retroreflected laser beams at 1064 nm that propagate in orthogonal directions. The polarization of the retroreflected light is controlled using liquid crystal retarders, which allow us to adiabatically transform the dimple trap into a 3D lattice. Overlapped with each of the three dimple/lattice beams is a beam at 532 nm, which can cancel the harmonic confinement and flatten the band structure in the lattice. This setup offers the possibility of implementing proposed schemes which enlarge the size of the AFM phase in the trap. As a probe for AFM we use Bragg scattering of light. We have observed Bragg scattering off of the (100) lattice planes, and using an off-angle probe we can see the diffuse scattering from the sample which serves as background for the small signals expected before the onset of AFM ordering. Supported by NSF, ONR, DARPA, and the Welch Foundation.

Self-trapping of holes in p-type oxides: Theory for small polarons in MnO

NASA Astrophysics Data System (ADS)

Peng, Haowei; Lany, Stephan

2012-02-01

Employing the p-d repulsion to increase the valence band dispersion and the energy of the VBM is an important design principle for p-type oxides, as manifested in prototypical p-type oxides like Cu2O or CuAlO2 which show a strong Cu-d/O-p interaction. An alternative opportunity to realize this design principle occurs for Mn(+II) compounds, where the p-d orbital interaction occurs dominantly in the fully occupied d^5 majority spin direction of Mn. However, the ability of Mn to change the oxidation state from +II to +III can lead to a small polaron mechanism for hole transport which hinders p-type conductivity. This work addresses the trends of hole self-trapping for MnO between octahedral (rock-salt structure) and tetrahedral coordination (zinc-blende structure). We employ an on-site hole-state potential so to satisfy the generalized Koopmans condition. This approach avoids the well-known difficulty of density-functional calculations to describe correctly the localization of polaronic states, and allows to quantitatively predict the self-trapping energies. We find that the tetrahedrally coordinated Mn is less susceptible to hole self-trapping than the octahedrally coordinated Mn.

The Spin Move: A Reliable and Cost-Effective Gowning Technique for the 21st Century.

PubMed

Ochiai, Derek H; Adib, Farshad

2015-04-01

Operating room efficiency (ORE) and utilization are considered one of the most crucial components of quality improvement in every hospital. We introduced a new gowning technique that could optimize ORE. The Spin Move quickly and efficiently wraps a surgical gown around the surgeon's body. This saves the operative time expended through the traditional gowning techniques. In the Spin Move, while the surgeon is approaching the scrub nurse, he or she uses the left heel as the fulcrum. The torque, which is generated by twisting the right leg around the left leg, helps the surgeon to close the gown as quickly and safely as possible. From 2003 to 2012, the Spin Move was performed in 1,725 consecutive procedures with no complication. The estimated average time was 5.3 and 7.8 seconds for the Spin Move and traditional gowning, respectively. The estimated time saving for the senior author during this period was 71.875 minutes. Approximately 20,000 orthopaedic surgeons practice in the United States. If this technique had been used, 23,958 hours could have been saved. The money saving could have been $14,374,800.00 (23,958 hours × $600/operating room hour) during the past 10 years. The Spin Move is easy to perform and reproducible. It saves operating room time and increases ORE.

The Spin Move: A Reliable and Cost-Effective Gowning Technique for the 21st Century

PubMed Central

Ochiai, Derek H.; Adib, Farshad

2015-01-01

Operating room efficiency (ORE) and utilization are considered one of the most crucial components of quality improvement in every hospital. We introduced a new gowning technique that could optimize ORE. The Spin Move quickly and efficiently wraps a surgical gown around the surgeon's body. This saves the operative time expended through the traditional gowning techniques. In the Spin Move, while the surgeon is approaching the scrub nurse, he or she uses the left heel as the fulcrum. The torque, which is generated by twisting the right leg around the left leg, helps the surgeon to close the gown as quickly and safely as possible. From 2003 to 2012, the Spin Move was performed in 1,725 consecutive procedures with no complication. The estimated average time was 5.3 and 7.8 seconds for the Spin Move and traditional gowning, respectively. The estimated time saving for the senior author during this period was 71.875 minutes. Approximately 20,000 orthopaedic surgeons practice in the United States. If this technique had been used, 23,958 hours could have been saved. The money saving could have been $14,374,800.00 (23,958 hours × $600/operating room hour) during the past 10 years. The Spin Move is easy to perform and reproducible. It saves operating room time and increases ORE. PMID:26052490

Coupled oscillations of vortex cores confined in a ferromagnetic elliptical disk

NASA Astrophysics Data System (ADS)

Hata, Hiroshi; Goto, Minori; Yamaguchi, Akinobu; Sato, Tomonori; Nakatani, Yoshinobu; Nozaki, Yukio

2014-09-01

By solving the Thiele equation with simultaneous application of a radio-frequency (rf) magnetic field (hrf) and an rf spin current (jsp), the dynamic susceptibility of exchange-coupled vortices in response to hrf and jsp was obtained. It was found that the four eigenmodes expected for two vortices trapped in a magnetic elliptical disk were coupled to different components of hrf and jsp. As a consequence, orthogonal hrf and jsp (which are simultaneously generated by the application of an rf current to an elliptical disk) can excite two modes with different eigenfrequencies. This result suggests that a fieldlike nonadiabatic torque caused by an rf spin current can be spectroscopically distinguished from the one caused by the rf magnetic field.

Aluminum stress increases carbon-centered radicals in soybean roots.

PubMed

Abo, Mitsuru; Yonehara, Hiroki; Yoshimura, Etsuro

2010-10-15

The formation of radical species was examined in roots of soybean seedlings exposed to aluminum (Al). Electron spin resonance (ESR) spectra of root homogenates with the spin-trapping reagent 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) indicated the presence of carbon-centered radicals in plants not exposed to Al. Plants exposed to 50 microM Al showed a similar spectrum, with increased signal intensity. These radicals were likely produced through a H-atom abstraction reaction by hydroxyl (*OH) radicals, the synthesis of which was initiated by the formation of superoxide (O2*-) anions. The increased production of the carbon-centered radicals may be responsible for the lipid peroxidation in Al-treated roots. Copyright (c) 2010 Elsevier GmbH. All rights reserved.

Itinerant ferromagnetism in an interacting Fermi gas with mass imbalance

NASA Astrophysics Data System (ADS)

von Keyserlingk, C. W.; Conduit, G. J.

2011-05-01

We study the emergence of itinerant ferromagnetism in an ultracold atomic gas with a variable mass ratio between the up- and down-spin species. Mass imbalance breaks the SU(2) spin symmetry, leading to a modified Stoner criterion. We first elucidate the phase behavior in both the grand canonical and canonical ensembles. Second, we apply the formalism to a harmonic trap to demonstrate how a mass imbalance delivers unique experimental signatures of ferromagnetism. These could help future experiments to better identify the putative ferromagnetic state. Furthermore, we highlight how a mass imbalance suppresses the three-body loss processes that handicap the formation of a ferromagnetic state. Finally, we study the time-dependent formation of the ferromagnetic phase following a quench in the interaction strength.

There are many ways to spin a photon: Half-quantization of a total optical angular momentum

PubMed Central

Ballantine, Kyle E.; Donegan, John F.; Eastham, Paul R.

2016-01-01

The angular momentum of light plays an important role in many areas, from optical trapping to quantum information. In the usual three-dimensional setting, the angular momentum quantum numbers of the photon are integers, in units of the Planck constant ħ. We show that, in reduced dimensions, photons can have a half-integer total angular momentum. We identify a new form of total angular momentum, carried by beams of light, comprising an unequal mixture of spin and orbital contributions. We demonstrate the half-integer quantization of this total angular momentum using noise measurements. We conclude that for light, as is known for electrons, reduced dimensionality allows new forms of quantization. PMID:28861467

Summary of flight tests to determine the spin and controllability characteristics of a remotely piloted, large-scale (3/8) fighter airplane model

NASA Technical Reports Server (NTRS)

Holleman, E. C.

1976-01-01

An unpowered, large, dynamically scaled airplane model was test flown by remote pilot to investigate the stability and controllability of the configuration at high angles of attack. The configuration proved to be departure/spin resistant; however, spins were obtained by using techniques developed on a flight support simulator. Spin modes at high and medium high angles of attack were identified, and recovery techniques were investigated. A flight support simulation of the airplane model mechanized with low speed wind tunnel data over an angle of attack range of + or - 90 deg. and an angle of sideslip range of + or - 40 deg. provided insight into the effects of altitude, stability, aerodynamic damping, and the operation of the augmented flight control system on spins. Aerodynamic derivatives determined from flight maneuvers were used to correlate model controllability with two proposed departure/spin design criteria.

Electron Spin Relaxation: The Role of Spin-Orbit Coupling in Organic Semiconductors

NASA Astrophysics Data System (ADS)

Willis, M.; Nuccio, L.; Schulz, L.; Gillin, W.; Kreouzis, T.; Pratt, F.; Lord, J.; Heeney, M.; Fratini, S.; Bernhard, C.; Drew, A.

2012-02-01

Rapid development of organic materials has lead to their availability in commercial products. Until now, the spin degree of freedom has not generally been used in organic materials. As well as engineering difficulties, there are fundamental questions with respect to the electron spin relaxation (eSR) mechanisms in organic molecules. Muons used as a microscopic spin probe, localized to a single molecule, can access information needed to identify the relevant model for eSR. In this presentation I will introduce the ALC-MuSR technique describing how eSR can be extracted and the expected effects. I will show how the technique has been applied to small organic molecules such as the group III Quinolate series and functionalized molecules with a pentacene-like backbone. Lastly I will present the Z-number and temperature dependence in these organic molecules and show strong evidence for a spin-orbit based eSR mechanism.

Single-shot readout of accumulation mode Si/SiGe spin qubits using RF reflectometry

NASA Astrophysics Data System (ADS)

Volk, Christian; Martins, Frederico; Malinowski, Filip; Marcus, Charles M.; Kuemmeth, Ferdinand

Spin qubits based on gate-defined quantum dots are promising systems for realizing quantum computation. Due to their low concentration of nuclear-spin-carrying isotopes, Si/SiGe heterostructures are of particular interest. While high fidelities have been reported for single-qubit and two-qubit gate operations, qubit initialization and measurement times are relatively slow. In order to develop fast read-out techniques compatible with the operation of spin qubits, we characterize double and triple quantum dots confined in undoped Si/Si0.7Ge0.3 heterostructures using accumulation and depletion gates and a nearby RF charge sensor dot. We implement a RF reflectometry technique that allows single-shot charge read-out at integration times on the order of a few μs. We show our recent advancement towards implementing spin qubits in these structures, including spin-selective single-shot read-out.

Exchange-mediated spin-lattice relaxation of Fe3+ ions in borate glasses.

PubMed

Misra, Sushil K; Pilbrow, John R

2007-03-01

Spin-lattice relaxation times (T1) of two borate glasses doped with different concentrations of Fe2O3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2-6K. In comparison with a previous investigation of Fe3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10-250K range but measured using the amplitude-modulation technique. The T1 values were found to depend on temperature (T) as T(n) with n approximately 1 for the 1% and 0.1% Fe2O3-doped glass samples. These results are consistent with spin-lattice relaxation as effected by exchange interaction of a Fe3+ spin exchange-coupled to another Fe3+ spin in an amorphous material.

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

PubMed

Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

2014-05-01

Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

Operating Spin Echo in the Quantum Regime for an Atomic-Ensemble Quantum Memory

NASA Astrophysics Data System (ADS)

Rui, Jun; Jiang, Yan; Yang, Sheng-Jun; Zhao, Bo; Bao, Xiao-Hui; Pan, Jian-Wei

2015-09-01

Spin echo is a powerful technique to extend atomic or nuclear coherence times by overcoming the dephasing due to inhomogeneous broadenings. However, there are disputes about the feasibility of applying this technique to an ensemble-based quantum memory at the single-quanta level. In this experimental study, we find that noise due to imperfections of the rephasing pulses has both intense superradiant and weak isotropic parts. By properly arranging the beam directions and optimizing the pulse fidelities, we successfully manage to operate the spin echo technique in the quantum regime by observing nonclassical photon-photon correlations as well as the quantum behavior of retrieved photons. Our work for the first time demonstrates the feasibility of harnessing the spin echo method to extend the lifetime of ensemble-based quantum memories at the single-quanta level.

Raman Spectroscopy of Optically Trapped Single Biological Micro-Particles

PubMed Central

Redding, Brandon; Schwab, Mark J.; Pan, Yong-le

2015-01-01

The combination of optical trapping with Raman spectroscopy provides a powerful method for the study, characterization, and identification of biological micro-particles. In essence, optical trapping helps to overcome the limitation imposed by the relative inefficiency of the Raman scattering process. This allows Raman spectroscopy to be applied to individual biological particles in air and in liquid, providing the potential for particle identification with high specificity, longitudinal studies of changes in particle composition, and characterization of the heterogeneity of individual particles in a population. In this review, we introduce the techniques used to integrate Raman spectroscopy with optical trapping in order to study individual biological particles in liquid and air. We then provide an overview of some of the most promising applications of this technique, highlighting the unique types of measurements enabled by the combination of Raman spectroscopy with optical trapping. Finally, we present a brief discussion of future research directions in the field. PMID:26247952

Optical trapping

PubMed Central

Neuman, Keir C.; Block, Steven M.

2006-01-01

Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. PMID:16878180

Optical manipulation of microparticles and biological structures

NASA Astrophysics Data System (ADS)

Gahagan, Kevin Thomas

1998-06-01

We report experimental and theoretical investigations of the trapping of microparticles and biological objects using radiation pressure. Part I of this thesis presents a technique for trapping both low and high index microparticles using a single, stationary focused laser beam containing an optical vortex. Advantages of this vortex trap include the ease of implementation, a lower exposure level for high-index particles compared to a standard Gaussian beam trap, and the ability to isolate individual low-index particles in concentrated dispersions. The vortex trap is modeled using ray-tracing methods and a more precise electromagnetic model, which is accurate for particles less than 10 μm in diameter. We have measured the stable equilibrium position for two low-index particle systems (e.g., hollow glass spheres (HGS) in water, and water droplets in acetophenone (W/A)). The strength of the trap was measured for the HGS system along the longitudinal and transverse directions. We also demonstrate simultaneous trapping of a low and high index particle with a vortex beam. The stability of this dual-particle trap is found to depend on the relative particle size, the divergence angle of the beam, and the depth of the particles within the trapping chamber. Part II presents results from an interdisciplinary and collaborative investigation of an all-optical genetic engineering technique whereby Agrobacterium rhizogenes were inserted through a laser-ablated hole in the cell wall of the plant, Gingko biloba. We describe a protocol which includes the control of osmotic conditions, culturing procedures, viability assays and laser microsurgery. We succeeded in placing up to twelve viable bacteria into a single plant cell using this technique. The bacteria are believed to be slightly heated by the Gaussian beam trap. A numerical model is presented predicting a temperature rise of just a few degrees. Whereas G. biloba and A. rhitogenes were chosen for this study because of Ginkgo's pharmaceutical importance, only slight modification of the protocol is needed for other plant species.

Topological vortex formation in a Bose-Einstein condensate under gravitational field

NASA Astrophysics Data System (ADS)

Kawaguchi, Yuki; Nakahara, Mikio; Ohmi, Tetsuo

2004-10-01

Topological phase imprinting is a unique technique for vortex formation in a Bose-Einstein condensate (BEC) of an alkali-metal gas, in that it does not involve rotation: the BEC is trapped in a quadrupole field with a uniform bias field which is reversed adiabatically leading to vortex formation at the center of the magnetic trap. The scenario has been experimentally verified by Leanhardt employing Na23 atoms. Recently similar experiments have been conducted by Hirotani in which a BEC of Rb87 atoms was used. In the latter experiments the authors found that fine-tuning of the field reverse time Trev is required to achieve stable vortex formation. Otherwise, they often observed vortex fragmentation or a condensate without a vortex. It is shown in this paper that this behavior can be attributed to the heavy mass of the Rb atom. The confining potential, which depends on the eigenvalue mB of the hyperfine spin F along the magnetic field, is now shifted by the gravitational field perpendicular to the vortex line. Then the positions of two weak-field-seeking states with mB=1 and 2 deviate from each other. This effect is more prominent for BECs with a heavy atomic mass, for which the deviation is greater and, moreover, the Thomas-Fermi radius is smaller. We found, by solving the Gross-Pitaevskii equation numerically, that two condensates interact in a very complicated way leading to fragmentation of vortices, unless Trev is properly tuned.

A Multivariate Quality Loss Function Approach for Optimization of Spinning Processes

NASA Astrophysics Data System (ADS)

Chakraborty, Shankar; Mitra, Ankan

2018-05-01

Recent advancements in textile industry have given rise to several spinning techniques, such as ring spinning, rotor spinning etc., which can be used to produce a wide variety of textile apparels so as to fulfil the end requirements of the customers. To achieve the best out of these processes, they should be utilized at their optimal parametric settings. However, in presence of multiple yarn characteristics which are often conflicting in nature, it becomes a challenging task for the spinning industry personnel to identify the best parametric mix which would simultaneously optimize all the responses. Hence, in this paper, the applicability of a new systematic approach in the form of multivariate quality loss function technique is explored for optimizing multiple quality characteristics of yarns while identifying the ideal settings of two spinning processes. It is observed that this approach performs well against the other multi-objective optimization techniques, such as desirability function, distance function and mean squared error methods. With slight modifications in the upper and lower specification limits of the considered quality characteristics, and constraints of the non-linear optimization problem, it can be successfully applied to other processes in textile industry to determine their optimal parametric settings.

Y{sub 3}Fe{sub 5}O{sub 12} spin pumping for quantitative understanding of pure spin transport and spin Hall effect in a broad range of materials (invited)

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

Du, Chunhui; Wang, Hailong; Hammel, P. Chris

2015-05-07

Using Y{sub 3}Fe{sub 5}O{sub 12} (YIG) thin films grown by our sputtering technique, we study dynamic spin transport in nonmagnetic, ferromagnetic, and antiferromagnetic (AF) materials by ferromagnetic resonance spin pumping. From both inverse spin Hall effect and damping enhancement, we determine the spin mixing conductance and spin Hall angle in many metals. Surprisingly, we observe robust spin conduction in AF insulators excited by an adjacent YIG at resonance. This demonstrates that YIG spin pumping is a powerful and versatile tool for understanding spin Hall physics, spin-orbit coupling, and magnetization dynamics in a broad range of materials.

Halyomorpha halys (Hemiptera: Pentatomidae) response to pyramid traps baited with attractive light and pheromonal stimuli

USDA-ARS?s Scientific Manuscript database

Halyomorpha halys is an invasive insect that causes severe economic damage to multiple agricultural commodities. Several monitoring techniques have been developed to monitor H. halys including pheromone and light-baited black pyramid traps. Here, we evaluated the attractiveness of these traps bait...

Determination of the spin and recovery characteristics of a typical low-wing general aviation design

NASA Technical Reports Server (NTRS)

Tischler, M. B.; Barlow, J. B.

1980-01-01

The equilibrium spin technique implemented in a graphical form for obtaining spin and recovery characteristics from rotary balance data is outlined. Results of its application to recent rotary balance tests of the NASA Low-Wing General Aviation Aircraft are discussed. The present results, which are an extension of previously published findings, indicate the ability of the equilibrium method to accurately evaluate spin modes and recovery control effectiveness. A comparison of the calculated results with available spin tunnel and full scale findings is presented. The technique is suitable for preliminary design applications as determined from the available results and data base requirements. A full discussion of implementation considerations and a summary of the results obtained from this method to date are presented.

Jump events in a 3D Edwards-Anderson spin glass

NASA Astrophysics Data System (ADS)

Mártin, Daniel A.; Iguain, José Luis

2017-11-01

The statistical properties of infrequent particle displacements, greater than a certain distance, are known as jump dynamics in the context of structural glass formers. We generalize the concept of a jump to the case of a spin glass, by dividing the system into small boxes, and considering the infrequent cooperative spin flips in each box. Jumps defined this way share similarities with jumps in structural glasses. We perform numerical simulations for the 3D Edwards-Anderson model, and study how the properties of these jumps depend on the waiting time after a quench. Similar to the results for structural glasses, we find that while jump frequency depends strongly on time, the jump duration and jump length are roughly stationary. At odds with some results reported on studies of structural glass formers, at long enough times, the rest time between jumps varies as the inverse of jump frequency. We give a possible explanation for this discrepancy. We also find that our results are qualitatively reproduced by a fully-connected trap model.

Bulk diamond optical waveguides fabricated by focused femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Hadden, J. P.; Sotillo, Belén.; Bharadwaj, Vibhav; Rampini, Stefano; Bosia, Federico; Picollo, Federico; Sakakura, Masaaki; Chiappini, Andrea; Fernandez, Toney T.; Osellame, Roberto; Miura, Kiyotaka; Ferrari, Maurizio; Ramponi, Roberta; Olivero, Paolo; Barclay, Paul E.; Eaton, Shane M.

2017-02-01

Diamond's nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and their ability to be located, manipulated and read out using light. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532- nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work we show the possibility of buried waveguide fabrication in diamond, enabled by focused femtosecond high repetition rate laser pulses. We use μRaman spectroscopy to gain better insight into the structure and refractive index profile of the optical waveguides.

Engineering of frustration in colloidal artificial ice (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ortiz-Ambriz, Antonio; Tierno, Pietro

2016-09-01

Artificial spin-ice systems have been used to date as microscopic models of frustration induced by lattice topology, as they allow for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Recently, an analogue system has been proposed theoretically, where an optical landscape confined colloidal particles that interacted electrostatically. Here we realize experimentally another version of a colloidal artificial ice system using interacting magnetically polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair-interactions between the microscopic units. By using optical tweezers, we can control particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information.