Experimental geometry for simultaneous beam characterization and sample imaging allowing for pink beam Fourier transform holography or coherent diffractive imaging

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

Flewett, Samuel; Eisebitt, Stefan

2011-02-20

One consequence of the self-amplified stimulated emission process used to generate x rays in free electron lasers (FELs) is the intrinsic shot-to-shot variance in the wavelength and temporal coherence. In order to optimize the results from diffractive imaging experiments at FEL sources, it will be advantageous to acquire a means of collecting coherence and spectral information simultaneously with the diffraction pattern from the sample we wish to study. We present a holographic mask geometry, including a grating structure, which can be used to extract both temporal and spatial coherence information alongside the sample scatter from each individual FEL shot andmore » also allows for the real space reconstruction of the sample using either Fourier transform holography or iterative phase retrieval.« less

In vivo imaging of middle-ear and inner-ear microstructures of a mouse guided by SD-OCT combined with a surgical microscope

PubMed Central

Cho, Nam Hyun; Jang, Jeong Hun; Jung, Woonggyu; Kim, Jeehyun

2014-01-01

We developed an augmented-reality system that combines optical coherence tomography (OCT) with a surgical microscope. By sharing the common optical path in the microscope and OCT, we could simultaneously acquire OCT and microscope views. The system was tested to identify the middle-ear and inner-ear microstructures of a mouse. Considering the probability of clinical application including otorhinolaryngology, diseases such as middle-ear effusion were visualized using in vivo mouse and OCT images simultaneously acquired through the eyepiece of the surgical microscope during surgical manipulation using the proposed system. This system is expected to realize a new practical area of OCT application. PMID:24787787

Simultaneous use of camera and probe diagnostics to unambiguously identify and study the dynamics of multiple underlying instabilities during the route to plasma turbulence.

PubMed

Thakur, S C; Brandt, C; Light, A; Cui, L; Gosselin, J J; Tynan, G R

2014-11-01

We use multiple-tip Langmuir probes and fast imaging to unambiguously identify and study the dynamics of underlying instabilities during the controlled route to fully-developed plasma turbulence in a linear magnetized helicon plasma device. Langmuir probes measure radial profiles of electron temperature, plasma density and potential; from which we compute linear growth rates of instabilities, cross-phase between density and potential fluctuations, Reynold's stress, particle flux, vorticity, time-delay estimated velocity, etc. Fast imaging complements the 1D probe measurements by providing temporally and spatially resolved 2D details of plasma structures associated with the instabilities. We find that three radially separated plasma instabilities exist simultaneously. Density gradient driven resistive drift waves propagating in the electron diamagnetic drift direction separate the plasma into an edge region dominated by strong, velocity shear driven Kelvin-Helmholtz instabilities and a central core region which shows coherent Rayleigh-Taylor modes propagating in the ion diamagnetic drift direction. The simultaneous, complementary use of both probes and camera was crucial to identify the instabilities and understand the details of the very rich plasma dynamics.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

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

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; Leone, Stephen R.

2016-01-01

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicate the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

DOE PAGES

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; ...

2016-01-18

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

High-resolution three-dimensional partially coherent diffraction imaging.

PubMed

Clark, J N; Huang, X; Harder, R; Robinson, I K

2012-01-01

The wave properties of light, particularly its coherence, are responsible for interference effects, which can be exploited in powerful imaging applications. Coherent diffractive imaging relies heavily on coherence and has recently experienced rapid growth. Coherent diffractive imaging recovers an object from its diffraction pattern by computational phasing with the potential of wavelength-limited resolution. Diminished coherence results in reconstructions that suffer from artefacts or fail completely. Here we demonstrate ab initio phasing of partially coherent diffraction patterns in three dimensions, while simultaneously determining the coherence properties of the illuminating wavefield. Both the dramatic improvements in image interpretability and the three-dimensional evaluation of the coherence will have broad implications for quantitative imaging of nanostructures and wavefield characterization with X-rays and electrons.

Simultaneous classical communication and quantum key distribution using continuous variables*

NASA Astrophysics Data System (ADS)

Qi, Bing

2016-10-01

Presently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters show that both deterministic classical communication with a bit error rate of 10-9 and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.

Multiple defocused coherent diffraction imaging: method for simultaneously reconstructing objects and probe using X-ray free-electron lasers.

PubMed

Hirose, Makoto; Shimomura, Kei; Suzuki, Akihiro; Burdet, Nicolas; Takahashi, Yukio

2016-05-30

The sample size must be less than the diffraction-limited focal spot size of the incident beam in single-shot coherent X-ray diffraction imaging (CXDI) based on a diffract-before-destruction scheme using X-ray free electron lasers (XFELs). This is currently a major limitation preventing its wider applications. We here propose multiple defocused CXDI, in which isolated objects are sequentially illuminated with a divergent beam larger than the objects and the coherent diffraction pattern of each object is recorded. This method can simultaneously reconstruct both objects and a probe from the coherent X-ray diffraction patterns without any a priori knowledge. We performed a computer simulation of the prposed method and then successfully demonstrated it in a proof-of-principle experiment at SPring-8. The prposed method allows us to not only observe broad samples but also characterize focused XFEL beams.

Simultaneous two component squeezing in generalized q-coherent states

NASA Technical Reports Server (NTRS)

Mcdermott, Roger J.; Solomon, Allan I.

1994-01-01

Using a generalization of the q-commutation relations, we develop a formalism in which it is possible to define generalized q-bosonic operators. This formalism includes both types of the usual q-deformed bosons as special cases. The coherent states of these operators show interesting and novel noise reduction properties including simultaneous squeezing in both field components, unlike the conventional case in which squeezing is permitted in only one component. This also contrasts with the usual quantum group deformation which also only permits one component squeezing.

Optical Coherence Tomography–Enhanced Microlaryngoscopy: Preliminary Report of a Noncontact Optical Coherence Tomography System Integrated With a Surgical Microscope

PubMed Central

Vokes, David E.; Jackson, Ryan; Guo, Shuguang; Perez, Jorge A.; Su, Jianping; Ridgway, James M.; Armstrong, William B.; Chen, Zhongping; Wong, Brian J. F.

2014-01-01

Objectives Optical coherence tomography (OCT) is a new imaging modality that uses near-infrared light to produce cross-sectional images of tissue with a resolution approaching that of light microscopy. We have previously reported use of OCT imaging of the vocal folds (VFs) during direct laryngoscopy with a probe held in contact or near-contact with the VFs. This aim of this study was to develop and evaluate a novel OCT system integrated with a surgical microscope to allow hands-free OCT imaging of the VFs, which could be performed simultaneously with microscopic visualization. Methods We performed a prospective evaluation of a new method of acquiring OCT images of the VFs. Results An OCT system was successfully integrated with a surgical microscope to permit noncontact OCT imaging of the VFs of 10 patients. With this novel device we were able to identify VF epithelium and lamina propria; however, the resolution was reduced compared to that achieved with the standard contact or near-contact OCT. Conclusions Optical coherence tomography is able to produce high-resolution images of vocal fold mucosa to a maximum depth of 1.6 mm. It may be used in the diagnosis of VF lesions, particularly early squamous cell carcinoma, in which OCT can show disruption of the basement membrane. Mounting the OCT device directly onto the operating microscope allows hands-free noncontact OCT imaging and simultaneous conventional microscopic visualization of the VFs. However, the lateral resolution of the OCT microscope system is 50 µm, in contrast to the conventional handheld probe system (10 µm). Although such images at this resolution are still useful clinically, improved resolution would enhance the system’s performance, potentially enabling real-time OCT-guided microsurgery of the larynx. PMID:18700431

Iterative deblending of simultaneous-source data using a coherency-pass shaping operator

NASA Astrophysics Data System (ADS)

Zu, Shaohuan; Zhou, Hui; Mao, Weijian; Zhang, Dong; Li, Chao; Pan, Xiao; Chen, Yangkang

2017-10-01

Simultaneous-source acquisition helps greatly boost an economic saving, while it brings an unprecedented challenge of removing the crosstalk interference in the recorded seismic data. In this paper, we propose a novel iterative method to separate the simultaneous source data based on a coherency-pass shaping operator. The coherency-pass filter is used to constrain the model, that is, the unblended data to be estimated, in the shaping regularization framework. In the simultaneous source survey, the incoherent interference from adjacent shots greatly increases the rank of the frequency domain Hankel matrix that is formed from the blended record. Thus, the method based on rank reduction is capable of separating the blended record to some extent. However, the shortcoming is that it may cause residual noise when there is strong blending interference. We propose to cascade the rank reduction and thresholding operators to deal with this issue. In the initial iterations, we adopt a small rank to severely separate the blended interference and a large thresholding value as strong constraints to remove the residual noise in the time domain. In the later iterations, since more and more events have been recovered, we weaken the constraint by increasing the rank and shrinking the threshold to recover weak events and to guarantee the convergence. In this way, the combined rank reduction and thresholding strategy acts as a coherency-pass filter, which only passes the coherent high-amplitude component after rank reduction instead of passing both signal and noise in traditional rank reduction based approaches. Two synthetic examples are tested to demonstrate the performance of the proposed method. In addition, the application on two field data sets (common receiver gathers and stacked profiles) further validate the effectiveness of the proposed method.

Modulation of temporally coherent brain networks estimated using ICA at rest and during cognitive tasks.

PubMed

Calhoun, Vince D; Kiehl, Kent A; Pearlson, Godfrey D

2008-07-01

Brain regions which exhibit temporally coherent fluctuations, have been increasingly studied using functional magnetic resonance imaging (fMRI). Such networks are often identified in the context of an fMRI scan collected during rest (and thus are called "resting state networks"); however, they are also present during (and modulated by) the performance of a cognitive task. In this article, we will refer to such networks as temporally coherent networks (TCNs). Although there is still some debate over the physiological source of these fluctuations, TCNs are being studied in a variety of ways. Recent studies have examined ways TCNs can be used to identify patterns associated with various brain disorders (e.g. schizophrenia, autism or Alzheimer's disease). Independent component analysis (ICA) is one method being used to identify TCNs. ICA is a data driven approach which is especially useful for decomposing activation during complex cognitive tasks where multiple operations occur simultaneously. In this article we review recent TCN studies with emphasis on those that use ICA. We also present new results showing that TCNs are robust, and can be consistently identified at rest and during performance of a cognitive task in healthy individuals and in patients with schizophrenia. In addition, multiple TCNs show temporal and spatial modulation during the cognitive task versus rest. In summary, TCNs show considerable promise as potential imaging biological markers of brain diseases, though each network needs to be studied in more detail. (c) 2008 Wiley-Liss, Inc.

Modulation of Temporally Coherent Brain Networks Estimated Using ICA at Rest and During Cognitive Tasks

PubMed Central

Calhoun, Vince D.; Kiehl, Kent A.; Pearlson, Godfrey D.

2009-01-01

Brain regions which exhibit temporally coherent fluctuations, have been increasingly studied using functional magnetic resonance imaging (fMRI). Such networks are often identified in the context of an fMRI scan collected during rest (and thus are called “resting state networks”); however, they are also present during (and modulated by) the performance of a cognitive task. In this article, we will refer to such networks as temporally coherent networks (TCNs). Although there is still some debate over the physiological source of these fluctuations, TCNs are being studied in a variety of ways. Recent studies have examined ways TCNs can be used to identify patterns associated with various brain disorders (e.g. schizophrenia, autism or Alzheimer’s disease). Independent component analysis (ICA) is one method being used to identify TCNs. ICA is a data driven approach which is especially useful for decomposing activation during complex cognitive tasks where multiple operations occur simultaneously. In this article we review recent TCN studies with emphasis on those that use ICA. We also present new results showing that TCNs are robust, and can be consistently identified at rest and during performance of a cognitive task in healthy individuals and in patients with schizophrenia. In addition, multiple TCNs show temporal and spatial modulation during the cognitive task versus rest. In summary, TCNs show considerable promise as potential imaging biological markers of brain diseases, though each network needs to be studied in more detail. PMID:18438867

Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain

DOE PAGES

Logan, Jonathan; Harder, Ross; Li, Luxi; ...

2016-01-01

Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. Here, the performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd 5Si 2Ge 2crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. Thesemore » tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd 5Si 2Ge 2nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered.« less

Measurement of three-dimensional velocity profiles using forward scattering particle image velocimetry (FSPIV) and neural net pattern recognition

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

Ovryn, B.; Wright, T.; Khaydarov, J.D.

1995-12-31

The authors employ Forward Scattering Particle Image Velocimetry (FSPIV) to measure all three components of the velocity of a buoyant polystyrene particle in oil. Unlike conventional particle image velocimetry (PIV) techniques, FSPIV employs coherent or partially coherent back illumination and collects the forward scattered wavefront; additionally, the field-of-view is microscopic. Using FSPIV, it is possible to easily identify the particle`s centroid and to simultaneously obtain the fluid velocity in different planes perpendicular to the viewing direction without changing the collection or imaging optics. The authors have trained a neural network to identify the scattering pattern as function of displacement alongmore » the optical axis (axial defocus) and determine the transverse velocity by tracking the centroid as function of time. They present preliminary results from Mie theory calculations which include the effect of the imaging system. To their knowledge, this is the first work of this kind; preliminary results are encouraging.« less

Ionospheric convection signatures observed by DE 2 during northward interplanetary magnetic field

NASA Technical Reports Server (NTRS)

Heelis, R. A.; Hanson, W. B.; Reiff, P. H.; Winningham, J. D.

1986-01-01

Observations of the ionospheric convection signature at high latitudes are examined during periods of prolonged northward interplanetary magnetic field (IMF). The data from Dynamics Explorer 2 show that a four-cell convection pattern can frequently be observed in a region that is displaced to the sunward side of the dawn-dusk meridian regardless of season. In the eclipsed ionosphere, extremely structured or turbulent flow exists with no identifiable connection to a more coherent pattern that may simultaneously exist in the dayside region. The two highest-latitude convection cells that form part of the coherent dayside pattern show a dependence on the y component of the IMF. This dependence is such that a clockwise circulating cell displaced toward dawn dominates the high-latitude region when B(Y) is positive. Anti-clockwise circulation displaced toward dusk dominates the highest latitudes when B(Y) is negative. Examination of the simultaneously observed energetic particle environment suggests that both open and closed field lines may be associated with the high-latitude convection cells. On occasions these entire cells can exist on open field lines. The existence of closed field lines in regions of sunward flow is also apparent in the data.

Simultaneous classical communication and quantum key distribution using continuous variables

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

Qi, Bing

Currently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters showmore » that both deterministic classical communication with a bit error rate of 10 –9 and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.« less

Simultaneous classical communication and quantum key distribution using continuous variables

DOE PAGES

Qi, Bing

2016-10-26

Currently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters showmore » that both deterministic classical communication with a bit error rate of 10 –9 and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.« less

Proposal for the measuring molecular velocity vector with single-pulse coherent Raman spectroscopy

NASA Technical Reports Server (NTRS)

She, C. Y.

1983-01-01

Methods for simultaneous measurements of more than one flow velocity component using coherent Raman spectroscopy are proposed. It is demonstrated that using a kilowatt broad-band probe pulse (3-30 GHz) along with a megawatt narrow-band pump pulse (approximately 100 MHz), coherent Raman signal resulting from a single laser pulse is sufficient to produce a high-resolution Raman spectrum for a velocity measurement.

Ocean waves and turbulence as observed with an adaptive coherent multifrequency radar

NASA Technical Reports Server (NTRS)

Gjessing, D. T.; Hjelmstad, J.

1984-01-01

An adaptive coherent multifrequency radar system is developed for several applications. The velocity distribution (Doppler spectrum) and spectral intensity of 15 different irregularity scales (waves and turbulence) can be measured simultaneously. Changing the azimuth angle of the antennas at regular intervals, the directivity of the wave/turbulence pattern on the sea surface can also be studied. A series of measurements for different air/sea conditions are carried out from a coast based platform. Experiments in the Atlantic are also performed with the same equipment making use of the NASA Electra aircraft. The multifrequency radar allows the measurement of the velocity distribution (""coherent and incoherent component'') associated with 15 different ocean irregularity scales simultaneously in a directional manner. It is possible to study the different air/sea mechanisms in some degree of detail.

Single shot multi-wavelength phase retrieval with coherent modulation imaging.

PubMed

Dong, Xue; Pan, Xingchen; Liu, Cheng; Zhu, Jianqiang

2018-04-15

A single shot multi-wavelength phase retrieval method is proposed by combining common coherent modulation imaging (CMI) and a low rank mixed-state algorithm together. A radiation beam consisting of multi-wavelength is illuminated on the sample to be observed, and the exiting field is incident on a random phase plate to form speckle patterns, which is the incoherent superposition of diffraction patterns of each wavelength. The exiting complex amplitude of the sample including both the modulus and phase of each wavelength can be reconstructed simultaneously from the recorded diffraction intensity using a low rank mixed-state algorithm. The feasibility of this proposed method was verified with visible light experimentally. This proposed method not only makes CMI realizable with partially coherent illumination but also can extend its application to various traditionally unrelated fields, where several wavelengths should be considered simultaneously.

Beamformer source analysis and connectivity on concurrent EEG and MEG data during voluntary movements.

PubMed

Muthuraman, Muthuraman; Hellriegel, Helge; Hoogenboom, Nienke; Anwar, Abdul Rauf; Mideksa, Kidist Gebremariam; Krause, Holger; Schnitzler, Alfons; Deuschl, Günther; Raethjen, Jan

2014-01-01

Electroencephalography (EEG) and magnetoencephalography (MEG) are the two modalities for measuring neuronal dynamics at a millisecond temporal resolution. Different source analysis methods, to locate the dipoles in the brain from which these dynamics originate, have been readily applied to both modalities alone. However, direct comparisons and possible advantages of combining both modalities have rarely been assessed during voluntary movements using coherent source analysis. In the present study, the cortical and sub-cortical network of coherent sources at the finger tapping task frequency (2-4 Hz) and the modes of interaction within this network were analysed in 15 healthy subjects using a beamformer approach called the dynamic imaging of coherent sources (DICS) with subsequent source signal reconstruction and renormalized partial directed coherence analysis (RPDC). MEG and EEG data were recorded simultaneously allowing the comparison of each of the modalities separately to that of the combined approach. We found the identified network of coherent sources for the finger tapping task as described in earlier studies when using only the MEG or combined MEG+EEG whereas the EEG data alone failed to detect single sub-cortical sources. The signal-to-noise ratio (SNR) level of the coherent rhythmic activity at the tapping frequency in MEG and combined MEG+EEG data was significantly higher than EEG alone. The functional connectivity analysis revealed that the combined approach had more active connections compared to either of the modalities during the finger tapping (FT) task. These results indicate that MEG is superior in the detection of deep coherent sources and that the SNR seems to be more vital than the sensitivity to theoretical dipole orientation and the volume conduction effect in the case of EEG.

Beamformer Source Analysis and Connectivity on Concurrent EEG and MEG Data during Voluntary Movements

PubMed Central

Muthuraman, Muthuraman; Hellriegel, Helge; Hoogenboom, Nienke; Anwar, Abdul Rauf; Mideksa, Kidist Gebremariam; Krause, Holger; Schnitzler, Alfons; Deuschl, Günther; Raethjen, Jan

2014-01-01

Electroencephalography (EEG) and magnetoencephalography (MEG) are the two modalities for measuring neuronal dynamics at a millisecond temporal resolution. Different source analysis methods, to locate the dipoles in the brain from which these dynamics originate, have been readily applied to both modalities alone. However, direct comparisons and possible advantages of combining both modalities have rarely been assessed during voluntary movements using coherent source analysis. In the present study, the cortical and sub-cortical network of coherent sources at the finger tapping task frequency (2–4 Hz) and the modes of interaction within this network were analysed in 15 healthy subjects using a beamformer approach called the dynamic imaging of coherent sources (DICS) with subsequent source signal reconstruction and renormalized partial directed coherence analysis (RPDC). MEG and EEG data were recorded simultaneously allowing the comparison of each of the modalities separately to that of the combined approach. We found the identified network of coherent sources for the finger tapping task as described in earlier studies when using only the MEG or combined MEG+EEG whereas the EEG data alone failed to detect single sub-cortical sources. The signal-to-noise ratio (SNR) level of the coherent rhythmic activity at the tapping frequency in MEG and combined MEG+EEG data was significantly higher than EEG alone. The functional connectivity analysis revealed that the combined approach had more active connections compared to either of the modalities during the finger tapping (FT) task. These results indicate that MEG is superior in the detection of deep coherent sources and that the SNR seems to be more vital than the sensitivity to theoretical dipole orientation and the volume conduction effect in the case of EEG. PMID:24618596

Emotion regulation and emotion coherence: evidence for strategy-specific effects.

PubMed

Dan-Glauser, Elise S; Gross, James J

2013-10-01

One of the central tenets of emotion theory is that emotions involve coordinated changes across experiential, behavioral, and physiological response domains. Surprisingly little is known, however, about how the strength of this emotion coherence is altered when people try to regulate their emotions. To address this issue, we recorded experiential, behavioral, and physiological responses while participants watched negative and positive pictures. Cross-correlations were used to quantify emotion coherence. Study 1 tested how two types of suppression (expressive and physiological) influence coherence. Results showed that both strategies decreased the response coherence measured in negative and positive contexts. Study 2 tested how multichannel suppression (simultaneously targeting expressive and physiological responses) and acceptance influence emotion coherence. Results again showed that suppression decreased coherence. By contrast, acceptance was not significantly different from the unregulated condition. These findings help to clarify the nature of emotion response coherence by showing how different forms of emotion regulation may differentially affect it.

Level set formulation of two-dimensional Lagrangian vortex detection methods

NASA Astrophysics Data System (ADS)

Hadjighasem, Alireza; Haller, George

2016-10-01

We propose here the use of the variational level set methodology to capture Lagrangian vortex boundaries in 2D unsteady velocity fields. This method reformulates earlier approaches that seek material vortex boundaries as extremum solutions of variational problems. We demonstrate the performance of this technique for two different variational formulations built upon different notions of coherence. The first formulation uses an energy functional that penalizes the deviation of a closed material line from piecewise uniform stretching [Haller and Beron-Vera, J. Fluid Mech. 731, R4 (2013)]. The second energy function is derived for a graph-based approach to vortex boundary detection [Hadjighasem et al., Phys. Rev. E 93, 063107 (2016)]. Our level-set formulation captures an a priori unknown number of vortices simultaneously at relatively low computational cost. We illustrate the approach by identifying vortices from different coherence principles in several examples.

Full ocular biometry through dual-depth whole-eye optical coherence tomography

PubMed Central

Kim, Hyung-Jin; Kim, Minji; Hyeon, Min Gyu; Choi, Youngwoon; Kim, Beop-Min

2018-01-01

We propose a new method of determining the optical axis (OA), pupillary axis (PA), and visual axis (VA) of the human eye by using dual-depth whole-eye optical coherence tomography (OCT). These axes, as well as the angles “α” between the OA and VA and “κ” between PA and VA, are important in many ophthalmologic applications, especially in refractive surgery. Whole-eye images are reconstructed based on simultaneously acquired images of the anterior segment and retina. The light from a light source is split into two orthogonal polarization components for imaging the anterior segment and retina, respectively. The OA and PA are identified based on their geometric definitions by using the anterior segment image only, while the VA is detected through accurate correlation between the two images. The feasibility of our approach was tested using a model eye and human subjects. PMID:29552378

Coherent control in simple quantum systems

NASA Technical Reports Server (NTRS)

Prants, Sergey V.

1995-01-01

Coherent dynamics of two, three, and four-level quantum systems, simultaneously driven by concurrent laser pulses of arbitrary and different forms, is treated by using a nonperturbative, group-theoretical approach. The respective evolution matrices are calculated in an explicit form. General aspects of controllability of few-level atoms by using laser fields are treated analytically.

Simultaneous topography and tomography of latent fingerprints using full-field swept-source optical coherence tomography

NASA Astrophysics Data System (ADS)

Dubey, Satish Kumar; Singh Mehta, Dalip; Anand, Arun; Shakher, Chandra

2008-01-01

We demonstrate simultaneous topography and tomography of latent fingerprints using full-field swept-source optical coherence tomography (OCT). The swept-source OCT system comprises a superluminescent diode (SLD) as broad-band light source, an acousto-optic tunable filter (AOTF) as frequency tuning device, and a compact, nearly common-path interferometer. Both the amplitude and the phase map of the interference fringe signal are reconstructed. Optical sectioning of the latent fingerprint sample is obtained by selective Fourier filtering and the topography is retrieved from the phase map. Interferometry, selective filtering, low coherence and hence better resolution are some of the advantages of the proposed system over the conventional fingerprint detection techniques. The present technique is non-invasive in nature and does not require any physical or chemical processing. Therefore, the quality of the sample does not alter and hence the same fingerprint can be used for other types of forensic test. Exploitation of low-coherence interferometry for fingerprint detection itself provides an edge over other existing techniques as fingerprints can even be lifted from low-reflecting surfaces. The proposed system is very economical and compact.

Simultaneous measurement of refractive index and thickness by combining low-coherence interferometry and confocal optics.

PubMed

Kim, Seokhan; Na, Jihoon; Kim, Myoung Jin; Lee, Byeong Ha

2008-04-14

We propose and demonstrate novel methods that enable simultaneous measurements of the phase index, the group index, and the geometrical thickness of an optically transparent object by combining optical low-coherence interferometer and confocal optics. The low-coherence interferometer gives information relating the group index with the thickness, while the confocal optics allows access to the phase index related with the thickness of the sample. To relate these, two novel methods were devised. In the first method, the dispersion-induced broadening of the low-coherence envelop signal was utilized, and in the second method the frequency derivative of the phase index was directly obtained by taking the confocal measurements at several wavelengths. The measurements were made with eight different samples; B270, CaF2, two of BK7, two of fused silica, cover glass, and cigarette cover film. The average measurement errors of the first and the second methods were 0.123% and 0.061% in the geometrical thickness, 0.133% and 0.066% in the phase index, and 0.106% and 0.057% in the group index, respectively.

Enhancing the isotropy of lateral resolution in coherent structured illumination microscopy

PubMed Central

Park, Joo Hyun; Lee, Jae Yong; Lee, Eun Seong

2014-01-01

We present a method to improve the isotropy of spatial resolution in a structured illumination microscopy (SIM) implemented for imaging non-fluorescent samples. To alleviate the problem of anisotropic resolution involved with the previous scheme of coherent SIM that employs the two orthogonal standing-wave illumination, referred to as the orthogonal SIM, we introduce a hexagonal-lattice illumination that incorporates three standing-wave fields simultaneously superimposed at the orientations equally divided in the lateral plane. A theoretical formulation is worked out rigorously for the coherent image formation with such a simultaneous multiple-beam illumination and an explicit Fourier-domain framework is derived for reconstructing an image with enhanced resolution. Using a computer-synthesized resolution target as a 2D coherent sample, we perform numerical simulations to examine the imaging characteristics of our three-angle SIM compared with the orthogonal SIM. The investigation on the 2D resolving power with the various test patterns of different periods and orientations reveal that the orientation-dependent undulation of lateral resolution can be reduced from 27% to 8% by using the three-angle SIM while the best resolution (0.54 times the resolution limit of conventional coherent imaging) in the directions of structured illumination is slightly deteriorated by 4.6% from that of the orthogonal SIM. PMID:24940548

Reorganization of the brain and heart rhythm during autogenic meditation

PubMed Central

Kim, Dae-Keun; Rhee, Jyoo-Hi; Kang, Seung Wan

2014-01-01

The underlying changes in heart coherence that are associated with reported EEG changes in response to meditation have been explored. We measured EEG and heart rate variability (HRV) before and during autogenic meditation. Fourteen subjects participated in the study. Heart coherence scores were significantly increased during meditation compared to the baseline. We found near significant decrease in high beta absolute power, increase in alpha relative power and significant increases in lower (alpha) and higher (above beta) band coherence during 3~min epochs of heart coherent meditation compared to 3~min epochs of heart non-coherence at baseline. The coherence and relative power increase in alpha band and absolute power decrease in high beta band could reflect relaxation state during the heart coherent meditation. The coherence increase in the higher (above beta) band could reflect cortico-cortical local integration and thereby affect cognitive reorganization, simultaneously with relaxation. Further research is still needed for a confirmation of heart coherence as a simple window for the meditative state. PMID:24454283

Reorganization of the brain and heart rhythm during autogenic meditation.

PubMed

Kim, Dae-Keun; Rhee, Jyoo-Hi; Kang, Seung Wan

2014-01-13

The underlying changes in heart coherence that are associated with reported EEG changes in response to meditation have been explored. We measured EEG and heart rate variability (HRV) before and during autogenic meditation. Fourteen subjects participated in the study. Heart coherence scores were significantly increased during meditation compared to the baseline. We found near significant decrease in high beta absolute power, increase in alpha relative power and significant increases in lower (alpha) and higher (above beta) band coherence during 3~min epochs of heart coherent meditation compared to 3~min epochs of heart non-coherence at baseline. The coherence and relative power increase in alpha band and absolute power decrease in high beta band could reflect relaxation state during the heart coherent meditation. The coherence increase in the higher (above beta) band could reflect cortico-cortical local integration and thereby affect cognitive reorganization, simultaneously with relaxation. Further research is still needed for a confirmation of heart coherence as a simple window for the meditative state.

Coherent Backscattering and Opposition Effects Observed in Some Atmosphereless Bodies of the Solar System

NASA Technical Reports Server (NTRS)

Dlugach, Zh. M.; Mishchenko, M. I.

2013-01-01

The results of photometric and polarimetric observations carried out for some bright atmosphere-less bodies of the Solar system near the zero phase angle reveal the simultaneous existence of two spectacular optical phenomena, the so-called brightness and polarization opposition effects. In a number of studies, these phenomena were explained by the influence of coherent backscattering. However, in general, the interference concept of coherent backscattering can be used only in the case where the particles are in the far-field zones of each other, i.e., when the scattering medium is rather rarefied. Because of this, it is important to prove rigorously and to demonstrate that the coherent backscattering effect may also exist in densely packed scattering media like regolith surface layers of celestial bodies. From the results of the computer modeling performed with the use of numerically exact solutions of the macroscopic Maxwell equations for discrete random media with different packing densities of particles, we studied the origin and evolution of all the opposition phenomena predicted by the coherent backscattering theory for low-packing-density media. It has been shown that the predictions of this theory remain valid for rather high-packing densities of particles that are typical, in particular, of regolith surfaces of the Solar system bodies. The results allow us to conclude that both opposition effects observed simultaneously in some high-albedo atmosphereless bodies of the Solar system are caused precisely by coherent backscattering of solar light in the regolith layers composed of microscopic particles.

Two-point coherence of wave packets in turbulent jets

NASA Astrophysics Data System (ADS)

Jaunet, V.; Jordan, P.; Cavalieri, A. V. G.

2017-02-01

An experiment has been performed in order to provide support for wave-packet jet-noise modeling efforts. Recent work has shown that the nonlinear effects responsible for the two-point coherence of wave packets must be correctly accounted for if accurate sound prediction is to be achieved for subsonic turbulent jets. We therefore consider the same Mach 0.4 turbulent jet studied by Cavalieri et al. [Cavalieri et al., J. Fluid Mech. 730, 559 (2013), 10.1017/jfm.2013.346], but this time using two independent but synchronized, time-resolved stereo particle-image velocimetry systems. Each system can be moved independently, allowing simultaneous measurement of velocity in two, axially separated, crossflow planes, enabling eduction of the two-point coherence of wave packets. This and the associated length scales and phase speeds are studied and compared with those of the energy-containing turbulent eddies. The study illustrates how the two-point behavior of wave packets is fundamentally different from that of the more usually studied bulk two-point behavior, suggesting that sound-source modeling efforts should be reconsidered in the framework of wave packets. The study furthermore identifies two families of two-point-coherence behavior, respectively upstream and downstream of the end of the potential core, regions where linear theory is, respectively, successful and unsuccessful in predicting the axial evolution of wave-packets fluctuation energy.

Emotion Regulation and Emotion Coherence: Evidence for Strategy-Specific Effects

PubMed Central

Dan-Glauser, Elise S.; Gross, James J.

2014-01-01

One of the central tenets of emotion theory is that emotions involve coordinated changes across experiential, behavioral, and physiological response domains. Surprisingly little is known, however, on how the strength of this emotion coherence is altered when people try to regulate their emotions. To address this issue, we recorded experiential, behavioral, and physiological responses while participants watched negative and positive pictures. Cross-correlations were used to quantify emotion coherence. Study 1 tested how two types of suppression (expressive and physiological) influence coherence. Results showed that both strategies decreased the response coherence measured in negative and positive contexts. Study 2 tested how multi-channel suppression (simultaneously targeting expressive and physiological responses) and acceptance influence emotion coherence. Results again showed that suppression decreased coherence. By contrast, acceptance was not significantly different from the unregulated condition. These findings help to clarify the nature of emotion response coherence by showing how different forms of emotion regulation may differentially affect it. PMID:23731438

Building coherence and synergy among global health initiatives.

PubMed

Zicker, Fabio; Faid, Miriam; Reeder, John; Aslanyan, Garry

2015-12-09

The fast growth of global health initiatives (GHIs) has raised concerns regarding achievement of coherence and synergy among distinct, complementary and sometimes competing activities. Herein, we propose an approach to compare GHIs with regard to their main purpose and operational aspects, using the Special Programme for Research and Training in Tropical Diseases (TDR/WHO) as a case study. The overall goal is to identify synergies and optimize efforts to provide solutions to reduce the burden of diseases. Twenty-six long-established GHIs were identified from among initiatives previously associated/partnered with TDR/WHO. All GHIs had working streams that would benefit from linking to the capacity building or implementation research focus of TDR. Individual profiles were created using a common template to collect information on relevant parameters. For analytical purposes, GHIs were simultaneously clustered in five and eight groups according to their 'intended outcome' and 'operational framework', respectively. A set of specific questions was defined to assess coherence/alignment against a TDR reference profile by attributing a score, which was subsequently averaged per GHI cluster. GHI alignment scores for intended outcome were plotted against scores for operational framework; based on the analysis of coherence/alignment with TDR functions and operations, a risk level (high, medium or low) of engagement was attributed to each GHI. The process allowed a bi-dimensional ranking of GHIs with regards to how adequately they fit with or match TDR features and perspectives. Overall, more consistence was observed with regard to the GHIs' main goals and expected outcomes than with their operational aspects, reflecting the diversity of GHI business models. Analysis of coherence indicated an increasing common trend for enhancing the engagement of developing country stakeholders, building research capacity and optimization of knowledge management platforms in support of improved access to healthcare. The process used offers a broader approach that could be adapted by other GHIs to build coherence and synergy with peer organizations and helps highlight the potential contribution of each GHI in the new era of sustainable development goals. Emerging opportunities and new trends suggest that engagement between GHIs should be selective and tailored to ensure efficient collaborations.

Is Social Categorization the Missing Link between Weak Central Coherence and Mental State Inference Abilities in Autism? Preliminary Evidence from a General Population Sample

ERIC Educational Resources Information Center

Skorich, Daniel P.; May, Adrienne R.; Talipski, Louisa A.; Hall, Marnie H.; Dolstra, Anita J.; Gash, Tahlia B.; Gunningham, Beth H.

2016-01-01

We explore the relationship between the "theory of mind" (ToM) and "central coherence" difficulties of autism. We introduce covariation between hierarchically-embedded categories and social information--at the local level, the global level, or at both levels simultaneously--within a category confusion task. We then ask…

Coherent perfect absorber and laser modes in purely imaginary metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Cao, Yanyan; Cummer, Steven A.; Xu, Yadong; Chen, Huanyang

2017-10-01

Conjugate metamaterials, in which the permittivity and the permeability are complex conjugates of each other, possess the elements of loss and gain simultaneously. By employing a conjugate metamaterial with a purely imaginary form, we propose a mechanism for realizing both coherent perfect absorber (CPA) and laser modes. Moreover, the general conditions for obtaining CPA and laser modes, including obtaining them simultaneously, are revealed by analyzing the wave scattering properties of a slab made of purely imaginary metamaterials (PIMs). Specifically, in a PIM slab with a subunity effective refractive index, the CPA mode can be simplified as a perfect absorption mode and the incident wave from one side could be perfectly absorbed.

Effect of spectral sampling on the temporal coherence analysis of a broadband source in a SFG interferometer.

PubMed

Darré, Pascaline; Szemendera, Ludovic; Grossard, Ludovic; Delage, Laurent; Reynaud, François

2015-10-05

In the frame of sum frequency generation of a broadband infrared source, we aim to enlarge the converted bandwidth by using a pump frequency comb while keeping a high conversion efficiency. The nonlinear effects are simultaneously induced in the same nonlinear medium. In this paper, we investigate the spectral filtering effect on the temporal coherence behavior with a Mach-Zehnder interferometer using two pump lines. We show that joined effects of quasi-phase matching and spectral sampling lead to an original coherence behavior.

3D deblending of simultaneous source data based on 3D multi-scale shaping operator

NASA Astrophysics Data System (ADS)

Zu, Shaohuan; Zhou, Hui; Mao, Weijian; Gong, Fei; Huang, Weilin

2018-04-01

We propose an iterative three-dimensional (3D) deblending scheme using 3D multi-scale shaping operator to separate 3D simultaneous source data. The proposed scheme is based on the property that signal is coherent, whereas interference is incoherent in some domains, e.g., common receiver domain and common midpoint domain. In two-dimensional (2D) blended record, the coherency difference of signal and interference is in only one spatial direction. Compared with 2D deblending, the 3D deblending can take more sparse constraints into consideration to obtain better performance, e.g., in 3D common receiver gather, the coherency difference is in two spatial directions. Furthermore, with different levels of coherency, signal and interference distribute in different scale curvelet domains. In both 2D and 3D blended records, most coherent signal locates in coarse scale curvelet domain, while most incoherent interference distributes in fine scale curvelet domain. The scale difference is larger in 3D deblending, thus, we apply the multi-scale shaping scheme to further improve the 3D deblending performance. We evaluate the performance of 3D and 2D deblending with the multi-scale and global shaping operators, respectively. One synthetic and one field data examples demonstrate the advantage of the 3D deblending with 3D multi-scale shaping operator.

Continuous Variable Quantum Key Distribution Using Polarized Coherent States

NASA Astrophysics Data System (ADS)

Vidiella-Barranco, A.; Borelli, L. F. M.

We discuss a continuous variables method of quantum key distribution employing strongly polarized coherent states of light. The key encoding is performed using the variables known as Stokes parameters, rather than the field quadratures. Their quantum counterpart, the Stokes operators Ŝi (i=1,2,3), constitute a set of non-commuting operators, being the precision of simultaneous measurements of a pair of them limited by an uncertainty-like relation. Alice transmits a conveniently modulated two-mode coherent state, and Bob randomly measures one of the Stokes parameters of the incoming beam. After performing reconciliation and privacy amplification procedures, it is possible to distill a secret common key. We also consider a non-ideal situation, in which coherent states with thermal noise, instead of pure coherent states, are used for encoding.

Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Burns, Marie E.; Sarunic, Marinko V.; Pugh, Edward N.; Zawadzki, Robert J.

2015-03-01

A compact, non-invasive multi-modal system has been developed for in vivo mouse retina imaging. It is configured for simultaneously detecting green and red fluorescent protein signals with scanning laser ophthalmoscopy (SLO) back-scattered light from the SLO illumination beam, and depth information about different retinal layers by means of Optical Coherence Tomography (OCT). Simultaneous assessment of retinal characteristics with different modalities can provide a wealth of information about the structural and functional changes in the retinal neural tissue and chorio-retinal vasculature in vivo. Additionally, simultaneous acquisition of multiple channels facilitates analysis of the data of different modalities by automatic temporal and structural co-registration. As an example of the instrument's performance we imaged the retina of a mouse with constitutive expression of GFP in microglia cells (Cx3cr1GFP/+), and which also expressed the red fluorescent protein mCherry in Müller glial cells by means of adeno-associated virus delivery (AAV2) of an mCherry cDNA driven by the GFAP (glial fibrillary acid protein) promoter.

Digital holographic interferometer using simultaneously three lasers and a single monochrome sensor for 3D displacement measurements.

PubMed

Saucedo-A, Tonatiuh; De la Torre-Ibarra, M H; Santoyo, F Mendoza; Moreno, Ivan

2010-09-13

The use of digital holographic interferometry for 3D measurements using simultaneously three illumination directions was demonstrated by Saucedo et al. (Optics Express 14(4) 2006). The technique records two consecutive images where each one contains three holograms in it, e.g., one before the deformation and one after the deformation. A short coherence length laser must be used to obtain the simultaneous 3D information from the same laser source. In this manuscript we present an extension of this technique now illuminating simultaneously with three different lasers at 458, 532 and 633 nm, and using only one high resolution monochrome CMOS sensor. This new configuration gives the opportunity to use long coherence length lasers allowing the measurement of large object areas. A series of digital holographic interferograms are recorded and the information corresponding to each laser is isolated in the Fourier spectral domain where the corresponding phase difference is calculated. Experimental results render the orthogonal displacement components u, v and w during a simple load deformation.

Three-dimensional Bragg coherent diffraction imaging of an extended ZnO crystal.

PubMed

Huang, Xiaojing; Harder, Ross; Leake, Steven; Clark, Jesse; Robinson, Ian

2012-08-01

A complex three-dimensional quantitative image of an extended zinc oxide (ZnO) crystal has been obtained using Bragg coherent diffraction imaging integrated with ptychography. By scanning a 2.5 µm-long arm of a ZnO tetrapod across a 1.3 µm X-ray beam with fine step sizes while measuring a three-dimensional diffraction pattern at each scan spot, the three-dimensional electron density and projected displacement field of the entire crystal were recovered. The simultaneously reconstructed complex wavefront of the illumination combined with its coherence properties determined by a partial coherence analysis implemented in the reconstruction process provide a comprehensive characterization of the incident X-ray beam.

Contrasting spatial structures of Atlantic Multidecadal Oscillation between observations and slab ocean model simulations

NASA Astrophysics Data System (ADS)

Sun, Cheng; Li, Jianping; Kucharski, Fred; Xue, Jiaqing; Li, Xiang

2018-04-01

The spatial structure of Atlantic multidecadal oscillation (AMO) is analyzed and compared between the observations and simulations from slab ocean models (SOMs) and fully coupled models. The observed sea surface temperature (SST) pattern of AMO is characterized by a basin-wide monopole structure, and there is a significantly high degree of spatial coherence of decadal SST variations across the entire North Atlantic basin. The observed SST anomalies share a common decadal-scale signal, corresponding to the basin-wide average (i. e., the AMO). In contrast, the simulated AMO in SOMs (AMOs) exhibits a tripole-like structure, with the mid-latitude North Atlantic SST showing an inverse relationship with other parts of the basin, and the SOMs fail to reproduce the observed strong spatial coherence of decadal SST variations associated with the AMO. The observed spatial coherence of AMO SST anomalies is identified as a key feature that can be used to distinguish the AMO mechanism. The tripole-like SST pattern of AMOs in SOMs can be largely explained by the atmosphere-forced thermodynamics mechanism due to the surface heat flux changes associated with the North Atlantic Oscillation (NAO). The thermodynamic forcing of AMOs by the NAO gives rise to a simultaneous inverse NAO-AMOs relationship at both interannual and decadal timescales and a seasonal phase locking of the AMOs variability to the cold season. However, the NAO-forced thermodynamics mechanism cannot explain the observed NAO-AMO relationship and the seasonal phase locking of observed AMO variability to the warm season. At decadal timescales, a strong lagged relationship between NAO and AMO is observed, with the NAO leading by up to two decades, while the simultaneous correlation of NAO with AMO is weak. This lagged relationship and the spatial coherence of AMO can be well understood from the view point of ocean dynamics. A time-integrated NAO index, which reflects the variations in Atlantic meridional overturning circulation (AMOC) and northward ocean heat transport caused by the accumulated effect of NAO forcing, reasonably well captures the observed multidecadal fluctuations in the AMO. Further analysis using the fully coupled model simulations provides direct modeling evidence that the observed spatial coherence of decadal SST variations across North Atlantic basin can be reproduced only by including the AMOC-related ocean dynamics, and the AMOC acts as a common forcing signal that results in a spatially coherent variation of North Atlantic SST.

High responsivity coherent photonic receiver integrating an SOA, a 90° hybrid, and high speed UTC photodiodes.

PubMed

Santini, Guillaume; Caillaud, Christophe; Paret, Jean-François; Pommereau, Frederic; Mekhazni, Karim; Calo, Cosimo; Achouche, Mohand

2017-10-16

We demonstrate a single polarization monolithically integrated coherent receiver on an InP substrate with a SOA preamplifier, a 90° optical hybrid, and four 40 GHz UTC photodiodes. Record performances with responsivity above 4 A/W with low imbalance <1 dB and error free detection of 32 Gbaud QPSK signals were simultaneously demonstrated.

Noninvasive imaging of oral mucosae with optical coherence tomography

NASA Astrophysics Data System (ADS)

Lee, Cheng-Yu; Chen, Wei-Chuan; Tsai, Meng-Tsan

2017-04-01

In this study, a swept-source optical coherence tomography (OCT) system is developed for in vivo visualization of structural and vascular morphology oral mucosa. For simplification of optical probe fabrication, probe weight, and system setup, the body of the scanning probe is fabricated by a 3D printer to fix the optical components and the mechanical scanning device, and a partially reflective slide is attached at the output end of probe to achieve a common-path configuration. Aside from providing the ability of 3D structural imaging with the developed system, 3D vascular images of oral mucosa can be simultaneously obtained. Then, different locations of oral mucosa are scanned with common-path OCT. The results show that epithelium and lamina propria layers as well as fungiform papilla can be identified and microvascular images can be acquired. With the proposed probe, the system cost and volume can be greatly reduced. Experimental results indicate that such common-path OCT system could be further implemented for oral cancer diagnosis.

Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells

NASA Astrophysics Data System (ADS)

McGuinness, L. P.; Yan, Y.; Stacey, A.; Simpson, D. A.; Hall, L. T.; MacLaurin, D.; Prawer, S.; Mulvaney, P.; Wrachtrup, J.; Caruso, F.; Scholten, R. E.; Hollenberg, L. C. L.

2011-06-01

Fluorescent particles are routinely used to probe biological processes. The quantum properties of single spins within fluorescent particles have been explored in the field of nanoscale magnetometry, but not yet in biological environments. Here, we demonstrate optically detected magnetic resonance of individual fluorescent nanodiamond nitrogen-vacancy centres inside living human HeLa cells, and measure their location, orientation, spin levels and spin coherence times with nanoscale precision. Quantum coherence was measured through Rabi and spin-echo sequences over long (>10 h) periods, and orientation was tracked with effective 1° angular precision over acquisition times of 89 ms. The quantum spin levels served as fingerprints, allowing individual centres with identical fluorescence to be identified and tracked simultaneously. Furthermore, monitoring decoherence rates in response to changes in the local environment may provide new information about intracellular processes. The experiments reported here demonstrate the viability of controlled single spin probes for nanomagnetometry in biological systems, opening up a host of new possibilities for quantum-based imaging in the life sciences.

Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.

PubMed

Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi

2013-01-01

We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.

Direct measurement of cyclotron coherence times of high-mobility two-dimensional electron gases.

PubMed

Wang, X; Hilton, D J; Reno, J L; Mittleman, D M; Kono, J

2010-06-07

We have observed long-lived (approximately 30 ps) coherent oscillations of charge carriers due to cyclotron resonance (CR) in high-mobility two-dimensional electrons in GaAs in perpendicular magnetic fields using time-domain terahertz spectroscopy. The observed coherent oscillations were fitted well by sinusoids with exponentially-decaying amplitudes, through which we were able to provide direct and precise measures for the decay times and oscillation frequencies simultaneously. This method thus overcomes the CR saturation effect, which is known to prevent determination of true CR linewidths in high-mobility electron systems using Fourier-transform infrared spectroscopy.

Radial Coherence of Diffusion Tractography in the Cerebral White Matter of the Human Fetus: Neuroanatomic Insights

PubMed Central

Xu, Gang; Takahashi, Emi; Folkerth, Rebecca D.; Haynes, Robin L.; Volpe, Joseph J.; Grant, P. Ellen; Kinney, Hannah C.

2014-01-01

High angular resolution diffusion imaging (HARDI) demonstrates transient radial coherence of telencephalic white matter in the human fetus. Our objective was to define the neuroanatomic basis of this radial coherence through correlative HARDI- and postmortem tissue analyses. Applying immunomarkers to radial glial fibers (RGFs), axons, and blood vessels in 18 cases (19 gestational weeks to 3 postnatal years), we compared their developmental profiles to HARDI tractography in brains of comparable ages (n = 11). At midgestation, radial coherence corresponded with the presence of RGFs. At 30–31 weeks, the transition from HARDI-defined radial coherence to corticocortical coherence began simultaneously with the transformation of RGFs to astrocytes. By term, both radial coherence and RGFs had disappeared. White matter axons were radial, tangential, and oblique over the second half of gestation, whereas penetrating blood vessels were consistently radial. Thus, radial coherence in the fetal white matter likely reflects a composite of RGFs, penetrating blood vessels, and radial axons of which its transient expression most closely matches that of RGFs. This study provides baseline information for interpreting radial coherence in tractography studies of the preterm brain in the assessment of the encephalopathy of prematurity. PMID:23131806

Noise Analysis of Simultaneous Quantum Key Distribution and Classical Communication Scheme Using a True Local Oscillator

DOE PAGES

Qi, Bing; Lim, Charles Ci Wen

2018-05-07

Recently, we proposed a simultaneous quantum and classical communication (SQCC) protocol where random numbers for quantum key distribution and bits for classical communication are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Such a scheme could be appealing in practice since a single coherent communication system can be used for multiple purposes. However, previous studies show that the SQCC protocol can tolerate only very small phase noise. This makes it incompatible with the coherent communication scheme using a true local oscillator (LO), which presents a relatively high phase noise due to the fact thatmore » the signal and the LO are generated from two independent lasers. We improve the phase noise tolerance of the SQCC scheme using a true LO by adopting a refined noise model where phase noises originating from different sources are treated differently: on the one hand, phase noise associated with the coherent receiver may be regarded as trusted noise since the detector can be calibrated locally and the photon statistics of the detected signals can be determined from the measurement results; on the other hand, phase noise due to the instability of fiber interferometers may be regarded as untrusted noise since its randomness (from the adversary’s point of view) is hard to justify. Simulation results show the tolerable phase noise in this refined noise model is significantly higher than that in the previous study, where all of the phase noises are assumed to be untrusted. In conclusion, we conduct an experiment to show that the required phase stability can be achieved in a coherent communication system using a true LO.« less

Noise Analysis of Simultaneous Quantum Key Distribution and Classical Communication Scheme Using a True Local Oscillator

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

Qi, Bing; Lim, Charles Ci Wen

Recently, we proposed a simultaneous quantum and classical communication (SQCC) protocol where random numbers for quantum key distribution and bits for classical communication are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Such a scheme could be appealing in practice since a single coherent communication system can be used for multiple purposes. However, previous studies show that the SQCC protocol can tolerate only very small phase noise. This makes it incompatible with the coherent communication scheme using a true local oscillator (LO), which presents a relatively high phase noise due to the fact thatmore » the signal and the LO are generated from two independent lasers. We improve the phase noise tolerance of the SQCC scheme using a true LO by adopting a refined noise model where phase noises originating from different sources are treated differently: on the one hand, phase noise associated with the coherent receiver may be regarded as trusted noise since the detector can be calibrated locally and the photon statistics of the detected signals can be determined from the measurement results; on the other hand, phase noise due to the instability of fiber interferometers may be regarded as untrusted noise since its randomness (from the adversary’s point of view) is hard to justify. Simulation results show the tolerable phase noise in this refined noise model is significantly higher than that in the previous study, where all of the phase noises are assumed to be untrusted. In conclusion, we conduct an experiment to show that the required phase stability can be achieved in a coherent communication system using a true LO.« less

Noise Analysis of Simultaneous Quantum Key Distribution and Classical Communication Scheme Using a True Local Oscillator

NASA Astrophysics Data System (ADS)

Qi, Bing; Lim, Charles Ci Wen

2018-05-01

Recently, we proposed a simultaneous quantum and classical communication (SQCC) protocol where random numbers for quantum key distribution and bits for classical communication are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Such a scheme could be appealing in practice since a single coherent communication system can be used for multiple purposes. However, previous studies show that the SQCC protocol can tolerate only very small phase noise. This makes it incompatible with the coherent communication scheme using a true local oscillator (LO), which presents a relatively high phase noise due to the fact that the signal and the LO are generated from two independent lasers. We improve the phase noise tolerance of the SQCC scheme using a true LO by adopting a refined noise model where phase noises originating from different sources are treated differently: on the one hand, phase noise associated with the coherent receiver may be regarded as trusted noise since the detector can be calibrated locally and the photon statistics of the detected signals can be determined from the measurement results; on the other hand, phase noise due to the instability of fiber interferometers may be regarded as untrusted noise since its randomness (from the adversary's point of view) is hard to justify. Simulation results show the tolerable phase noise in this refined noise model is significantly higher than that in the previous study, where all of the phase noises are assumed to be untrusted. We conduct an experiment to show that the required phase stability can be achieved in a coherent communication system using a true LO.

Intermittent bilateral coherence in physiological and essential hand tremor.

PubMed

Chakraborty, Soma; Kopecká, Jana; Šprdlík, Otakar; Hoskovcová, Martina; Ulmanová, Olga; Růžička, Evžen; Zapotocky, Martin

2017-04-01

To investigate the prevalence and the temporal structure of bilateral coherence in physiological (PT) and essential (ET) hand tremor. Triaxial accelerometric recordings from both hands in 30 healthy subjects and 34 ET patients were analyzed using spectral coherence and wavelet coherence methods. In 12 additional healthy subjects, the relation between the hand tremor and the chest wall acceleration was evaluated using partial coherence analysis. The majority of both PT and ET subjects displayed significant bilateral coherence. While in PT, bilateral coherence was most frequently found in resting hand position (97% of subjects), in ET the prevalence was comparable for resting (54%) and postural (49%-57%) positions. In both PT and ET, epochs of strong coherence lasting several to a dozen seconds were separated by intervals of insignificant coherence. In PT, bilateral coherence at the main tremor frequency (8-12Hz) was coupled with the ballistocardiac rhythm. The oscillations of the two hands are intermittently synchronized in both PT and ET. We propose that in postural PT, bilateral coherence at the main tremor frequency arises from transient simultaneous entrainment of the left and right hand oscillations to ballistocardiac forcing. Bilateral coherence of hand kinematics provides a sensitive measure of synchronizing influences on the left and right tremor oscillators. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Simultaneous acquisition of 2D and 3D solid-state NMR experiments for sequential assignment of oriented membrane protein samples.

PubMed

Gopinath, T; Mote, Kaustubh R; Veglia, Gianluigi

2015-05-01

We present a new method called DAISY (Dual Acquisition orIented ssNMR spectroScopY) for the simultaneous acquisition of 2D and 3D oriented solid-state NMR experiments for membrane proteins reconstituted in mechanically or magnetically aligned lipid bilayers. DAISY utilizes dual acquisition of sine and cosine dipolar or chemical shift coherences and long living (15)N longitudinal polarization to obtain two multi-dimensional spectra, simultaneously. In these new experiments, the first acquisition gives the polarization inversion spin exchange at the magic angle (PISEMA) or heteronuclear correlation (HETCOR) spectra, the second acquisition gives PISEMA-mixing or HETCOR-mixing spectra, where the mixing element enables inter-residue correlations through (15)N-(15)N homonuclear polarization transfer. The analysis of the two 2D spectra (first and second acquisitions) enables one to distinguish (15)N-(15)N inter-residue correlations for sequential assignment of membrane proteins. DAISY can be implemented in 3D experiments that include the polarization inversion spin exchange at magic angle via I spin coherence (PISEMAI) sequence, as we show for the simultaneous acquisition of 3D PISEMAI-HETCOR and 3D PISEMAI-HETCOR-mixing experiments.

Observation of correlation between route to formation, coherence, noise, and communication performance of Kerr combs

NASA Astrophysics Data System (ADS)

Wang, Pei-Hsun; Ferdous, Fahmida; Miao, Houxun; Wang, Jian; Leaird, Daniel E.; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M.

2012-12-01

Microresonator optical frequency combs based on cascaded four-wave mixing are potentially attractive as a multi-wavelength source for on-chip optical communications. In this paper we compare time domain coherence, radio-frequency (RF) intensity noise, and individual line optical communications performance for combs generated from two different silicon nitride microresonators. The comb generated by one microresonator forms directly with lines spaced by a single free spectral range (FSR) and exhibits high coherence, low noise, and excellent 10 Gbit/s optical communications results. The comb generated by the second microresonator forms initially with multiple FSR line spacing, with additional lines later filling to reach single FSR spacing. This comb exhibits degraded coherence, increased intensity noise, and severely degraded communications performance. This study is to our knowledge the first to simultaneously investigate and observe a correlation between the route to comb formation, the coherence, noise, and optical communications performance of a Kerr comb.

Coherent detection of position errors in inter-satellite laser communications

NASA Astrophysics Data System (ADS)

Xu, Nan; Liu, Liren; Liu, De'an; Sun, Jianfeng; Luan, Zhu

2007-09-01

Due to the improved receiver sensitivity and wavelength selectivity, coherent detection became an attractive alternative to direct detection in inter-satellite laser communications. A novel method to coherent detection of position errors information is proposed. Coherent communication system generally consists of receive telescope, local oscillator, optical hybrid, photoelectric detector and optical phase lock loop (OPLL). Based on the system composing, this method adds CCD and computer as position error detector. CCD captures interference pattern while detection of transmission data from the transmitter laser. After processed and analyzed by computer, target position information is obtained from characteristic parameter of the interference pattern. The position errors as the control signal of PAT subsystem drive the receiver telescope to keep tracking to the target. Theoretical deviation and analysis is presented. The application extends to coherent laser rang finder, in which object distance and position information can be obtained simultaneously.

Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

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

Bohlin, Alexis; Kliewer, Christopher J.

2013-01-01

Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the highmore » efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15, 000 spatially correlated rotational CARS spectra in N 2 and air over a 2D field of 40 mm 2.« less

Simultaneous optical coherence tomography and lipofuscin autofluorescence imaging of the retina with a single broadband light source at 480nm.

PubMed

Jiang, Minshan; Liu, Tan; Liu, Xiaojing; Jiao, Shuliang

2014-12-01

We accomplished spectral domain optical coherence tomography and auto-fluorescence microscopy for imaging the retina with a single broadband light source centered at 480 nm. This technique is able to provide simultaneous structural imaging and lipofuscin molecular contrast of the retina. Since the two imaging modalities are provided by the same group of photons, their images are intrinsically registered. To test the capabilities of the technique we periodically imaged the retinas of the same rats for four weeks. The images successfully demonstrated lipofuscin accumulation in the retinal pigment epithelium with aging. The experimental results showed that the dual-modal imaging system can be a potentially powerful tool in the study of age-related degenerative retinal diseases.

Coherent Transition Radiation Generated from Transverse Electron Density Modulation

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

Halavanau, A.; Piot, P.; Tyukhtin, A. V.

Coherent Transition radiation (CTR) of a given frequency is commonly generated with longitudinal electron bunch trains. In this paper, we present a study of CTR properties produced from simultaneous electron transverse and longitudinal density modulation. We demonstrate via numerical simulations a simple technique to generate THz-scale frequencies from mm-scale transversely separated electron beamlets formed into a ps-scale bunch train. The results and a potential experimental setup are discussed.

Optical coherence tomography for the quantitative study of cerebrovascular physiology

PubMed Central

Srinivasan, Vivek J; Atochin, Dmitriy N; Radhakrishnan, Harsha; Jiang, James Y; Ruvinskaya, Svetlana; Wu, Weicheng; Barry, Scott; Cable, Alex E; Ayata, Cenk; Huang, Paul L; Boas, David A

2011-01-01

Doppler optical coherence tomography (DOCT) and OCT angiography are novel methods to investigate cerebrovascular physiology. In the rodent cortex, DOCT flow displays features characteristic of cerebral blood flow, including conservation along nonbranching vascular segments and at branch points. Moreover, DOCT flow values correlate with hydrogen clearance flow values when both are measured simultaneously. These data validate DOCT as a noninvasive quantitative method to measure tissue perfusion over a physiologic range. PMID:21364599

Measuring refractive index and volume of liquid under high pressure with optical coherence tomography and light microscopy.

PubMed

Wang, Donglin; Yang, Kun; Zhou, Yin

2016-03-20

Measuring the refractive index and volume of liquid under high pressure simultaneously is a big challenge. This paper proposed an alternative solution by combing optical coherence tomography with microscopy. An experiment for a feasibility study was carried out on polydimethylsiloxane liquid in a diamond anvil cell. The refractive index of the sample increased dramatically with pressure loaded, and the curve of pressure volume was also obtained.

The set of triple-resonance sequences with a multiple quantum coherence evolution period

NASA Astrophysics Data System (ADS)

Koźmiński, Wiktor; Zhukov, Igor

2004-12-01

The new pulse sequence building block that relies on evolution of heteronuclear multiple quantum coherences is proposed. The particular chemical shifts are obtained in multiple quadrature, using linear combinations of frequencies taken from spectra measured at different quantum levels. The pulse sequences designed in this way consist of small number of RF-pulses, are as short as possible, and could be applied for determination of coupling constants. The examples presented involve 2D correlations H NCO, H NCA, H N(CO) CA, and H(N) COCA via heteronuclear zero and double coherences, as well as 2D H NCOCA technique with simultaneous evolution of triple and three distinct single quantum coherences. Applications of the new sequences are presented for 13C, 15N-labeled ubiquitin.

A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

PubMed Central

Sou, In Mei; Layman, Christopher N.; Ray, Chittaranjan

2013-01-01

Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

Dysregulated corticostriatal activity in open-field behavior and the head-twitch response induced by the hallucinogen 2,5-dimethoxy-4-iodoamphetamine.

PubMed

Rangel-Barajas, Claudia; Estrada-Sánchez, Ana María; Barton, Scott J; Luedtke, Robert R; Rebec, George V

2017-02-01

The substituted amphetamine, 2,5-dimethoxy-4-iodoamphetamine (DOI), is a hallucinogen that has been used to model a variety of psychiatric conditions. Here, we studied the effect of DOI on neural activity recorded simultaneously in the primary motor cortex (M1) and dorsal striatum of freely behaving FvB/N mice. DOI significantly decreased the firing rate of individually isolated neurons in M1 and dorsal striatum relative to pre-drug baseline. It also induced a bursting pattern of activity by increasing both the number of spikes within a burst and burst duration. In addition, DOI increased coincident firing between simultaneously recorded neuron pairs within the striatum and between M1 and dorsal striatum. Local field potential (LFP) activity also increased in coherence between M1 and dorsal striatum after DOI in the low frequency gamma band (30-50 Hz), while corticostriatal coherence in delta, theta, alpha, and beta activity decreased. We also assessed corticostriatal LFP activity in relation to the DOI-induced head-twitch response (HTR), a readily identifiable behavior used to assess potential treatments for the conditions it models. The HTR was associated with increased delta and decreased theta power in both M1 and dorsal striatum. Together, our results suggest that DOI dysregulates corticostriatal communication and that the HTR is associated with this dysregulation. Copyright © 2016 Elsevier Ltd. All rights reserved.

In vivo wide-field multispectral scanning laser ophthalmoscopy–optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature

PubMed Central

Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Li, Yuanpei; Lam, Kit S.; Burns, Marie E.; Sarunic, Marinko V.; Pugh, Edward N.; Zawadzki, Robert J.

2015-01-01

Abstract. Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) provide complementary views of the retina, with the former collecting fluorescence data with good lateral but relatively low-axial resolution, and the latter collecting label-free backscattering data with comparable lateral but much higher axial resolution. To take maximal advantage of the information of both modalities in mouse retinal imaging, we have constructed a compact, four-channel, wide-field (∼50  deg) system that simultaneously acquires and automatically coregisters three channels of confocal SLO and Fourier domain OCT data. The scanner control system allows “zoomed” imaging of a region of interest identified in a wide-field image, providing efficient digital sampling and localization of cellular resolution features in longitudinal imaging of individual mice. The SLO is equipped with a “flip-in” spectrometer that enables spectral “fingerprinting” of fluorochromes. Segmentation of retina layers and en face display facilitate spatial comparison of OCT data with SLO fluorescence patterns. We demonstrate that the system can be used to image an individual retinal ganglion cell over many months, to simultaneously image microglia and Müller glia expressing different fluorochromes, to characterize the distinctive spatial distributions and clearance times of circulating fluorochromes with different molecular sizes, and to produce unequivocal images of the heretofore uncharacterized mouse choroidal vasculature. PMID:26677070

Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

DTIC Science & Technology

2009-09-30

maintenance and dissipation of layers; (2) to understand the spatial coherence and spatial properties of thin layers in the coastal ocean (especially in...ORCAS profilers at K1 South and K2 had a Nortek ADV (Acoustic Doppler Velocity meter) for simultaneously measuring centimeter- scale currents and...year will be used to (1) detect the presence, intensity, thickness, temporal persistence, and spatial coherence of thin optical and acoustical layers

Egg-hatching synchrony and larval cannibalism in the dock leaf beetle Gastrophysa viridula (Coleoptera: Chrysomelidae).

PubMed

Kutcherov, Dmitry

2015-12-01

Females of leaf beetles and many other herbivorous insects lay eggs in coherent batches. Hatchlings emerge more or less simultaneously and often prey on their late-hatching clutchmates. It is not certain, however, whether this synchrony of hatching is a mere by-product of cannibalism or whether an additional synchronizing factor exists. The following simple experiment was aimed at determining the causal relationship between cannibalism and simultaneous larval emergence. Egg clutches of the dock leaf beetle Gastrophysa viridula were split into two halves. These halves were either kept as coherent groups in two separate dishes or, alternatively, only one half remained whole, whereas the other one was divided into single eggs, each of which was incubated in a separate dish. Halving of a clutch into coherent groups only slightly disrupted the synchrony of emergence. The consequence of individual isolation was more dramatic. Half-clutches consisting of disconnected solitary eggs required almost twice as much time for complete emergence of all larvae, which was significantly more than cannibalism as a sole synchronizing factor might explain. Moreover, survival rates were the same in coherent half-clutches (in the presence of cannibalism) and among isolated individuals. This group effect and the small contribution of cannibalism suggest the existence of an additional synchronizing factor. Possible mechanisms underpinning this phenomenon are discussed. Copyright © 2015 Elsevier GmbH. All rights reserved.

Microwave coherent emissions from solar flares - a look at through a large interferometer

NASA Astrophysics Data System (ADS)

Altyntsev, Alexandre; Sergei, Lesovoi; Natalia, Meshalkina; Dmitrii, Zhdanov; Natalia, Korolkova

2013-04-01

The report discusses the results of microwave observations of coherent emission sources with broadband spectropolarimeters and the Siberian Solar Radio Telescope (receiving frequency about 5.7 GHz). To date, more than 300 events with narrowband subsecond pulses were recorded. It is revealed that at the small real sizes of sources their apparent sizes can reach the SSRT beam width (≥ 15 arcsec) due to electromagnetic wave scattering by density fluctuations in the lower corona, or due to emission reflection from the underlying layers of the solar atmosphere. The fine emission sources usually occur near tops of the flare loops. In some events it was possible to reveal plasma parameters in the vicinity of the fine emission exciters from the X-ray, optical and continuum microwave images, and to identify the mechanisms of the coherent emission. The SSRT is an interferometer that allows to record spatial brightness distributions of a flare region at two close frequencies simultaneously. Such observations have showed that the frequency dynamics of fast drifting narrowband bursts (type III - like) is controlled not only by the velocity of exciter movement through gradients of the plasma parameters, but also by rapid changes in plasma parameters over time. We discuss the diagnostic potential of the observations of coherent emission sources and new possibilities of the instruments which are under construction now. The work is supported by the Ministry of education and science of the Russian Federation (State Contracts 16.518.11.7065 and 02.740.11.0576), and by the grants RFBR (12-02-91161-GFEN-a, 12-02-00616 and 12-02-00173-a

Fraunhofer Diffraction and Polarization.

ERIC Educational Resources Information Center

Fortin, E.

1979-01-01

Describes an experiment for the intermediate undergraduate optics laboratory designed to illustrate simultaneously some aspects of the phenomena of diffraction; interference, coherence, apodization, the Fresnel-Arago law; as well as of the interrelations between these concepts. (HM)

Contrast-enhanced optical coherence microangiography with acoustic-actuated microbubbles

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsuan; Zhang, Jia-Wei; Yeh, Chih-Kuang; Wei, Kuo-Chen; Liu, Hao-Li; Tsai, Meng-Tsan

2017-04-01

In this study, we propose to use gas-filled microbubbles (MBs) simultaneously actuated by the acoustic wave to enhance the imaging contrast of optical coherence tomography (OCT)-based angiography. In the phantom experiments, MBs can result in stronger backscattered intensity, enabling to enhance the contrast of OCT intensity image. Moreover, simultaneous application of low-intensity acoustic wave enables to temporally induce local vibration of particles and MBs in the vessels, resulting in time-variant OCT intensity which can be used for enhancing the contrast of OCT intensitybased angiography. Additionally, different acoustic modes and different acoustic powers to actuate MBs are performed and compared to investigate the feasibility of contrast enhancement. Finally, animal experiments are performed. The findings suggest that acoustic-actuated MBs can effectively enhance the imaging contrast of OCT-based angiography and the imaging depth of OCT angiography is also extended.

In vivo time-serial evaluation of laser-induced choroidal neovascularization in rats simultaneously using photoacoustic microscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Dai, Cuixia; Li, Lin; Liu, Wenlu; Wang, Fenghua; Zhou, Chuanqing

2018-02-01

Determination of the precise location and degree of condition of the Choroidal neovascularization (CNV) lesion is essential for diagnosation Neovascular age-related macular degeneration (AMD) and evaluation the efficacy of treatment. Given the complimentary contrast mechanisms of Photoacoustic microscopy (PAM) and Optical coherence tomography (OCT), the combination of PAM and OCT imaging could potentially provide much sensitive and specific detection of CNV. In this paper, we validated the opportunity to evaluate the information of laser-induced CNV and presented the in vivo time-serial evaluation of the CNV by simultaneously using PAM and OCT techniques. In vivo PAM and OCT examination was performed after laser photocoagulation applied to the rat fundus at days 1, 3, 5, 7, 14. Time-serial results showed that CNV in rats increased to its maximum at day 7 and decreased at day 14. Evolution of CNV information was given in PAM images with a high contrast and details of high axial resolution OCT images were simultaneously given to show the hyperreflective reaction progress.

DNA Microarray Data Analysis: A Novel Biclustering Algorithm Approach

NASA Astrophysics Data System (ADS)

Tchagang, Alain B.; Tewfik, Ahmed H.

2006-12-01

Biclustering algorithms refer to a distinct class of clustering algorithms that perform simultaneous row-column clustering. Biclustering problems arise in DNA microarray data analysis, collaborative filtering, market research, information retrieval, text mining, electoral trends, exchange analysis, and so forth. When dealing with DNA microarray experimental data for example, the goal of biclustering algorithms is to find submatrices, that is, subgroups of genes and subgroups of conditions, where the genes exhibit highly correlated activities for every condition. In this study, we develop novel biclustering algorithms using basic linear algebra and arithmetic tools. The proposed biclustering algorithms can be used to search for all biclusters with constant values, biclusters with constant values on rows, biclusters with constant values on columns, and biclusters with coherent values from a set of data in a timely manner and without solving any optimization problem. We also show how one of the proposed biclustering algorithms can be adapted to identify biclusters with coherent evolution. The algorithms developed in this study discover all valid biclusters of each type, while almost all previous biclustering approaches will miss some.

Development of wavelength locking circuit for 1.53 micron water vapor monitoring coherent differential absorption LIDAR

NASA Astrophysics Data System (ADS)

Imaki, Masaharu; Kojima, Ryota; Kameyama, Shumpei

2018-04-01

We have studied a ground based coherent differential absorption LIDAR (DIAL) for vertical profiling of water vapor density using a 1.5μm laser wavelength. A coherent LIDAR has an advantage in daytime measurement compared with incoherent LIDAR because the influence of background light is greatly suppressed. In addition, the LIDAR can simultaneously measure wind speed and water vapor density. We had developed a wavelength locking circuit using the phase modulation technique and offset locking technique, and wavelength stabilities of 0.123 pm which corresponds to 16 MHz are realized. In this paper, we report the wavelength locking circuits for the 1.5 um wavelength.

Micromachined array tip for multifocus fiber-based optical coherence tomography.

PubMed

Yang, Victor X D; Munce, Nigel; Pekar, Julius; Gordon, Maggie L; Lo, Stewart; Marcon, Norman E; Wilson, Brian C; Vitkin, I Alex

2004-08-01

High-resolution optical coherence tomography demands a large detector bandwidth and a high numerical aperture for real-time imaging, which is difficult to achieve over a large imaging depth. To resolve these conflicting requirements we propose a novel multifocus fiber-based optical coherence tomography system with a micromachined array tip. We demonstrate the fabrication of a prototype four-channel tip that maintains a 9-14-microm spot diameter with more than 500 microm of imaging depth. Images of a resolution target and a human tooth were obtained with this tip by use of a four-channel cascaded Michelson fiber-optic interferometer, scanned simultaneously at 8 kHz with geometric power distribution across the four channels.

Two field trials for deblending of simultaneous source surveys: Why we failed and why we succeeded?

NASA Astrophysics Data System (ADS)

Zu, Shaohuan; Zhou, Hui; Chen, Haolin; Zheng, Hao; Chen, Yangkang

2017-08-01

Currently, deblending is the main strategy for dealing with the intense interference problem of simultaneous source data. Most deblending methods are based on the property that useful signal is coherent while the interference is incoherent in some domains other than common shot domain. In this paper, two simultaneous source field trials were studied in detail. In the first trial, the simultaneous source survey was not optimal, as the dithering code had strong coherency and the minimum distance between the two vessels was also small. The chosen marine shot scheduling and vessel deployment made it difficult to deblend the simultaneous source data, and result was an unexpected failure. Next, we tested different parameters (the dithering code and the minimum distance between vessels) of the simultaneous source survey using the simulated blended data and got some useful insights. Then, we carried out the second field trial with a carefully designed survey that was much different from the first trial. The deblended results in common receiver gather, common shot gather or the final stacked profile were encouraging. We obtained a complete success in the second field trial, which gave us confidence in the further test (such as a full three dimensional acquisition test or a high-resolution acquisition test with denser spatial sampling). Remembering that failures with simultaneous sourcing seldom reported, in this paper, our contribution is the discussion in detail about both our failed and successful field experiments and the lessons we have learned from them with the hope that the experience gained from this study can be very useful to other researchers in the same field.

Method and apparatus for checking the stability of a setup for making reflection type holograms

NASA Technical Reports Server (NTRS)

Lackner, H. G. (Inventor)

1974-01-01

A method and apparatus are described for checking the stability of a setup for recording reflection-type (white light) holograms. Two sets of interference fringes are simultaneously obtained, one giving information about coherence and stability of the setup alone and the other demonstrating coherence of the entire system, including the holographic recording plate. Special emphasis is given to the stability of the plate, due to the fact that any minute vibration might severely degrade or completely destroy the recording.

Ionospheric Coherence Bandwidth Measurements in the Lower VHF Frequency Range

NASA Astrophysics Data System (ADS)

Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

2015-12-01

The United States Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 820 - 1100 MHz. In this paper, we present simultaneous ionospheric coherence bandwidth and S4 scintillation index measurements in the 32 - 44 MHz frequency range collected during the ESCINT equatorial scintillation experiment. 40-MHz continuous wave (CW) and 32 - 44 MHz swept frequency signals were transmitted simultaneously to the RFProp receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in three separate campaigns during the 2014 and 2015 equinoxes. Results show coherence bandwidths as small as ~ 1 kHz for strong scintillation (S4 > 0.7) and indicate a high degree of ionospheric variability and irregularity on 10-m spatial scales. Spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities are also observed and are dominant at low elevation angles. The results are compared to previous measurements and available scaling laws.

Simultaneous multimodal ophthalmic imaging using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

PubMed Central

Malone, Joseph D.; El-Haddad, Mohamed T.; Bozic, Ivan; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

2016-01-01

Scanning laser ophthalmoscopy (SLO) benefits diagnostic imaging and therapeutic guidance by allowing for high-speed en face imaging of retinal structures. When combined with optical coherence tomography (OCT), SLO enables real-time aiming and retinal tracking and provides complementary information for post-acquisition volumetric co-registration, bulk motion compensation, and averaging. However, multimodality SLO-OCT systems generally require dedicated light sources, scanners, relay optics, detectors, and additional digitization and synchronization electronics, which increase system complexity. Here, we present a multimodal ophthalmic imaging system using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (SS-SESLO-OCT) for in vivo human retinal imaging. SESLO reduces the complexity of en face imaging systems by multiplexing spatial positions as a function of wavelength. SESLO image quality benefited from single-mode illumination and multimode collection through a prototype double-clad fiber coupler, which optimized scattered light throughput and reduce speckle contrast while maintaining lateral resolution. Using a shared 1060 nm swept-source, shared scanner and imaging optics, and a shared dual-channel high-speed digitizer, we acquired inherently co-registered en face retinal images and OCT cross-sections simultaneously at 200 frames-per-second. PMID:28101411

Coherence Volume of an Optical Wave Field with Broad Frequency and Angular Spectra

NASA Astrophysics Data System (ADS)

Lyakin, D. V.; Mysina, N. Yu.; Ryabukho, V. P.

2018-03-01

We consider the sizes of a region in a three-dimensional space in which an optical wave field excites mutually coherent perturbations. We discuss the conditions under which the length of this region along the direction of propagation of the wave field and, correspondingly, its volume are determined either by the width of the frequency spectrum of the field or by the width of its angular spectrum, or by the parameters of these spectra simultaneously. We obtain expressions for estimating extremely small values of the coherence volume of the fields with a broad frequency spectrum and an extremely broad angular spectrum. Using the notion of instantaneous speckle-modulation of the wave field, we give a physical interpretation to the occurrence of a limited coherence volume of the field. The length of the spatiotemporal coherence region in which mutually coherent perturbations occur at different times is determined. The coherence volume of a wave field that illuminates an object in high-resolution microscopy with frequency broadband light is considered. The conditions for the dominant influence of the angular or frequency spectra on the longitudinal length of the coherence region are given, and the conditions for the influence of the frequency spectrum width on the transverse coherence of the wave field are examined. We show that, when using fields with broad and ultrabroad spectra in high-resolution microscopy, this influence should be taken into account.

Anticipation of somatosensory and motor events increases centro-parietal functional coupling: an EEG coherence study.

PubMed

Babiloni, Claudio; Brancucci, Alfredo; Vecchio, Fabrizio; Arendt-Nielsen, Lars; Chen, Andrew C N; Rossini, Paolo M

2006-05-01

Does functional coupling of centro-parietal EEG rhythms selectively increase during the anticipation of sensorimotor events composed by somatosensory stimulation and visuomotor task? EEG data were recorded in (1) 'simultaneous' condition in which the subjects waited for somatosensory stimulation at left hand concomitant with a Go (or NoGo) visual stimulus triggering (50%) right hand movements and in (2) 'sequential' condition where the somatosensory stimulation was followed (+1.5 s) by a visuomotor Go/NoGo task. Centro-parietal functional coupling was modeled by spectral coherence. Spectral coherence was computed from Laplacian-transformed EEG data at delta-theta (2-7 Hz), alpha (8-14 Hz), beta 1 (15-21 Hz), beta 2 (22-33 Hz), and gamma (34-45 Hz) rhythms. Before 'simultaneous' sensorimotor events, centro-parietal coherence regions increased in both hemispheres and at all rhythms. In the 'sequential' condition, right centro-parietal coherence increased before somatosensory event (left hand), whereas left centro-parietal coherence increased before subsequent Go/NoGo event (right hand). Anticipation of somatosensory and visuomotor events enhances contralateral centro-parietal coupling of slow and fast EEG rhythms. Predictable somatosensory and visuomotor events are anticipated not only by synchronization of cortical pyramidal neurons generating EEG power in parietal and primary sensorimotor cortical areas (Babiloni C, Brancucci A, Capotosto P, Arendt-Nielsen L, Chen ACN, Rossini PM. Expectancy of pain is influenced by motor preparation: a high-resolution EEG study of cortical alpha rhythms. Behav. Neurosci. 2005a;119(2):503-511; Babiloni C, Brancucci A, Pizzella V, Romani G.L, Tecchio F, Torquati K, Zappasodi F, Arendt-Nielsen L, Chen ACN, Rossini PM. Contingent negative variation in the parasylvian cortex increases during expectancy of painful sensorimotor events: a magnetoencephalographic study. Behav. Neurosci. 2005b;119(2):491-502) but also by functional coordination of these areas.

Single-shot water-immersion microscopy platform for qualitative visualization and quantitative phase imaging of biosamples

NASA Astrophysics Data System (ADS)

Picazo-Bueno, José Ángel; Cojoc, Dan; Torre, Vincent; Micó, Vicente

2017-07-01

We present the combination of a single-shot water-immersion digital holographic microscopy with broadband illumination for simultaneous visualization of coherent and incoherent images using microbeads and different biosamples.

First deep space operational experience with simultaneous X- and Ka-bands coherent tracking

NASA Technical Reports Server (NTRS)

Asmar, S.; Herrera, R.; Armstrong, J.; Barbinis, E.; Fleischman, D.; Gatti, M.; Goltz, G.

2002-01-01

This paper describes the new DSN science capability and highlights of the engineering work that lead to its development. It will also discuss experience with operations along with statistics and data quality.

A Hierarchical Modulation Coherent Communication Scheme for Simultaneous Four-State Continuous-Variable Quantum Key Distribution and Classical Communication

NASA Astrophysics Data System (ADS)

Yang, Can; Ma, Cheng; Hu, Linxi; He, Guangqiang

2018-06-01

We present a hierarchical modulation coherent communication protocol, which simultaneously achieves classical optical communication and continuous-variable quantum key distribution. Our hierarchical modulation scheme consists of a quadrature phase-shifting keying modulation for classical communication and a four-state discrete modulation for continuous-variable quantum key distribution. The simulation results based on practical parameters show that it is feasible to transmit both quantum information and classical information on a single carrier. We obtained a secure key rate of 10^{-3} bits/pulse to 10^{-1} bits/pulse within 40 kilometers, and in the meantime the maximum bit error rate for classical information is about 10^{-7}. Because continuous-variable quantum key distribution protocol is compatible with standard telecommunication technology, we think our hierarchical modulation scheme can be used to upgrade the digital communication systems to extend system function in the future.

VLF wave injections from the ground

NASA Technical Reports Server (NTRS)

Helliwell, R. A.

1983-01-01

Experiments on wave-particle interactions using VLF whistler-mode waves injected into the magnetosphere from Antartica are described. The injected signals are single-frequency coherent waves whose amplitudes and frequencies may be changed slowly with time, or else two or more coherent wave trains transmitted simultaneously to determine the nature of the response to multifrequency excitation. The waves may be amplified 30 dB or more and may trigger intense emissions having bandwidths that vary from a few to several hundred Hertz. In most cases significant growth and triggering occur only when the driving signal is essentially monochromatic (bandwidth 10 Hz). If two frequencies are transmitted simultaneously the signal at the lower frequency tends to be suppressed by 20 dB or more. These results are interpreted in terms of a feedback interaction between the waves and counter-streaming cyclotron resonant electrons in a region several hundred wavelengths long, centered on the magnetic equator.

Fast Acquisition and Reconstruction of Optical Coherence Tomography Images via Sparse Representation

PubMed Central

Li, Shutao; McNabb, Ryan P.; Nie, Qing; Kuo, Anthony N.; Toth, Cynthia A.; Izatt, Joseph A.; Farsiu, Sina

2014-01-01

In this paper, we present a novel technique, based on compressive sensing principles, for reconstruction and enhancement of multi-dimensional image data. Our method is a major improvement and generalization of the multi-scale sparsity based tomographic denoising (MSBTD) algorithm we recently introduced for reducing speckle noise. Our new technique exhibits several advantages over MSBTD, including its capability to simultaneously reduce noise and interpolate missing data. Unlike MSBTD, our new method does not require an a priori high-quality image from the target imaging subject and thus offers the potential to shorten clinical imaging sessions. This novel image restoration method, which we termed sparsity based simultaneous denoising and interpolation (SBSDI), utilizes sparse representation dictionaries constructed from previously collected datasets. We tested the SBSDI algorithm on retinal spectral domain optical coherence tomography images captured in the clinic. Experiments showed that the SBSDI algorithm qualitatively and quantitatively outperforms other state-of-the-art methods. PMID:23846467

Coherence properties of spontaneous parametric down-conversion pumped by a multi-mode cw diode laser.

PubMed

Kwon, Osung; Ra, Young-Sik; Kim, Yoon-Ho

2009-07-20

Coherence properties of the photon pair generated via spontaneous parametric down-conversion pumped by a multi-mode cw diode laser are studied with a Mach-Zehnder interferometer. Each photon of the pair enters a different input port of the interferometer and the biphoton coherence properties are studied with a two-photon detector placed at one output port. When the photon pair simultaneously enters the interferometer, periodic recurrence of the biphoton de Broglie wave packet is observed, closely resembling the coherence properties of the pump diode laser. With non-zero delays between the photons at the input ports, biphoton interference exhibits the same periodic recurrence but the wave packet shapes are shown to be dependent on both the input delay as well as the interferometer delay. These properties could be useful for building engineered entangled photon sources based on diode laser-pumped spontaneous parametric down-conversion.

The coherence lifetime-borrowing effect in vibronically coupled molecular aggregates under non-perturbative system-environment interactions.

NASA Astrophysics Data System (ADS)

Yeh, Shu-Hao; Engel, Gregory S.; Kais, Sabre

Recently it has been suggested that the long-lived coherences in some photosynthetic pigment-protein systems, such as the Fenna-Matthews-Olson complex, could be attributed to the mixing of the pigments' electronic and vibrational degrees of freedom. In order to verify whether this is the case and to understand its underlying mechanism, a theoretical model capable of including both the electronic excitations and intramolecular vibrational modes of the pigments is necessary. Our model simultaneously considers the electronic and vibrational degrees of freedom, treating the system-environment interactions non-perturbatively by implementing the hierarchical equations of motion approach. Here we report the simulated two-dimensional electronic spectra of vibronically coupled molecular dimers to demonstrate how the electronic coherence lifetimes can be extended by borrowing the lifetime from the vibrational coherences. Funded by Qatar National Research Fund and Qatar Environment and Energy Research Institute.

Coherent Population Trapping in a Superconducting Phase Qubit

NASA Astrophysics Data System (ADS)

Kelly, William R.; Dutton, Zachary; Ohki, Thomas A.; Schlafer, John; Mookerji, Bhaskar; Kline, Jeffery S.; Pappas, David P.

2010-03-01

The phenomenon of Coherent Population Trapping (CPT) of an atom (or solid state ``artificial atom''), and the associated effect of Electromagnetically Induced Transparency (EIT), are clear demonstrations of quantum interference due to coherence in multi-level quantum systems. We report observation of CPT in a superconducting phase qubit by simultaneously driving two coherent transitions in a λ-type configuration, utilizing the three lowest lying levels of a local minimum of the phase qubit. We observe ˜60% suppression of excited state population under conditions of two-photon resonance, where EIT and CPT are expected to occur. We present data and matching theoretical simulations showing the development of CPT in time. We also used the observed time dependence of the excited state population to characterize quantum dephasing times of the system, as predicted in [1]. [1] K.V. Murali, Z. Dutton, W.D. Oliver, D.S. Crankshaw, and T.P.Orlando, Phys. Rev. Lett. 93, 087003 (2004).

Coherent Structures and Extreme Events in Rotating Multiphase Turbulent Flows

NASA Astrophysics Data System (ADS)

Biferale, L.; Bonaccorso, F.; Mazzitelli, I. M.; van Hinsberg, M. A. T.; Lanotte, A. S.; Musacchio, S.; Perlekar, P.; Toschi, F.

2016-10-01

By using direct numerical simulations (DNS) at unprecedented resolution, we study turbulence under rotation in the presence of simultaneous direct and inverse cascades. The accumulation of energy at large scale leads to the formation of vertical coherent regions with high vorticity oriented along the rotation axis. By seeding the flow with millions of inertial particles, we quantify—for the first time—the effects of those coherent vertical structures on the preferential concentration of light and heavy particles. Furthermore, we quantitatively show that extreme fluctuations, leading to deviations from a normal-distributed statistics, result from the entangled interaction of the vertical structures with the turbulent background. Finally, we present the first-ever measurement of the relative importance between Stokes drag, Coriolis force, and centripetal force along the trajectories of inertial particles. We discover that vortical coherent structures lead to unexpected diffusion properties for heavy and light particles in the directions parallel and perpendicular to the rotation axis.

Objective assessment of multimodality optical coherence tomography and second-harmonic generation image quality of ex vivo mouse ovaries using human observers

NASA Astrophysics Data System (ADS)

Welge, Weston A.; DeMarco, Andrew T.; Watson, Jennifer M.; Rice, Photini S.; Barton, Jennifer K.; Kupinski, Matthew A.

2014-03-01

Ovarian cancer is particularly deadly because it is usually diagnosed after it has begun to spread. Transvaginal sonography (TVS) is the most common imaging screening technique. However, routine use of TVS has not reduced ovarian cancer mortality. The superior resolution of optical imaging techniques may make them attractive alternatives to TVS. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and secondharmonic generation (SHG) microscopy (with collagen as the targeted fluorophore). OCT provides a gross anatomical image of the ovary while SHG provides a closer look at a particular region. Knowing these anatomical features, we sought to investigate the diagnostic potential of OCT and SHG. We conducted a fully crossed, multi-reader, multi-case study using seven human observers. Each observer classified 44 ex vivo mouse ovaries as normal or abnormal from OCT, SHG, and simultaneous, co-registered OCT and SHG images and provided a confidence rating on a three-point ordinal scale. We determined the average receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show that OCT has diagnostic potential with an average AUC of 0.91 +/- 0.03. The average AUC for SHG was less promising at 0.71 +/- 0.06. Interestingly, the average AUC for simultaneous, co-registered OCT and SHG was not significantly different from OCT alone. This suggests that collagen may not be a useful fluorophore for ovarian cancer screening. The high performance of OCT warrants further investigation.

Identification of individual coherent sets associated with flow trajectories using coherent structure coloring

NASA Astrophysics Data System (ADS)

Schlueter-Kuck, Kristy L.; Dabiri, John O.

2017-09-01

We present a method for identifying the coherent structures associated with individual Lagrangian flow trajectories even where only sparse particle trajectory data are available. The method, based on techniques in spectral graph theory, uses the Coherent Structure Coloring vector and associated eigenvectors to analyze the distance in higher-dimensional eigenspace between a selected reference trajectory and other tracer trajectories in the flow. By analyzing this distance metric in a hierarchical clustering, the coherent structure of which the reference particle is a member can be identified. This algorithm is proven successful in identifying coherent structures of varying complexities in canonical unsteady flows. Additionally, the method is able to assess the relative coherence of the associated structure in comparison to the surrounding flow. Although the method is demonstrated here in the context of fluid flow kinematics, the generality of the approach allows for its potential application to other unsupervised clustering problems in dynamical systems such as neuronal activity, gene expression, or social networks.

Coherent organization in gene regulation: a study on six networks

NASA Astrophysics Data System (ADS)

Aral, Neşe; Kabakçıoğlu, Alkan

2016-04-01

Structural and dynamical fingerprints of evolutionary optimization in biological networks are still unclear. Here we analyze the dynamics of genetic regulatory networks responsible for the regulation of cell cycle and cell differentiation in three organisms or cell types each, and show that they follow a version of Hebb's rule which we have termed coherence. More precisely, we find that simultaneously expressed genes with a common target are less likely to act antagonistically at the attractors of the regulatory dynamics. We then investigate the dependence of coherence on structural parameters, such as the mean number of inputs per node and the activatory/repressory interaction ratio, as well as on dynamically determined quantities, such as the basin size and the number of expressed genes.

The Goddard Space Flight Center Program to develop parallel image processing systems

NASA Technical Reports Server (NTRS)

Schaefer, D. H.

1972-01-01

Parallel image processing which is defined as image processing where all points of an image are operated upon simultaneously is discussed. Coherent optical, noncoherent optical, and electronic methods are considered parallel image processing techniques.

From quantum coherence to quantum correlations

NASA Astrophysics Data System (ADS)

Sun, Yuan; Mao, Yuanyuan; Luo, Shunlong

2017-06-01

In quantum mechanics, quantum coherence of a state relative to a quantum measurement can be identified with the quantumness that has to be destroyed by the measurement. In particular, quantum coherence of a bipartite state relative to a local quantum measurement encodes quantum correlations in the state. If one takes minimization with respect to the local measurements, then one is led to quantifiers which capture quantum correlations from the perspective of coherence. In this vein, quantum discord, which quantifies the minimal correlations that have to be destroyed by quantum measurements, can be identified as the minimal coherence, with the coherence measured by the relative entropy of coherence. To advocate and formulate this idea in a general context, we first review coherence relative to Lüders measurements which extends the notion of coherence relative to von Neumann measurements (or equivalently, orthonomal bases), and highlight the observation that quantum discord arises as minimal coherence through two prototypical examples. Then, we introduce some novel measures of quantum correlations in terms of coherence, illustrate them through examples, investigate their fundamental properties and implications, and indicate their applications to quantum metrology.

Inter-hemispheric electroencephalography coherence analysis: assessing brain activity during monotonous driving.

PubMed

Jap, Budi Thomas; Lal, Sara; Fischer, Peter

2010-06-01

The current study investigated the effect of monotonous driving on inter-hemispheric electroencephalography (EEG) coherence. Twenty-four non-professional drivers were recruited to perform a fatigue instigating monotonous driving task while 30 channels of EEG were simultaneously recorded. The EEG recordings were then divided into 5 equal sections over the entire driving period for analysis. Inter-hemispheric coherence was computed from 5 homologous EEG electrode pairs (FP1-FP2, C3-C4, T7-T8, P7-P8, and O1-O2) for delta, theta, alpha and beta frequency bands. Results showed that frontal and occipital inter-hemispheric coherence values were significantly higher than central, parietal, and temporal sites for all four frequency bands (p<0.0001). In the alpha frequency band, significant difference was found between earlier and later driving sections (p=0.02). The coherence values in all EEG frequency bands were slightly increased at the end of the driving session, except for FP1-FP2 electrode pair, which showed no significant change in coherence in the beta frequency band at the end of the driving session. Copyright 2010 Elsevier B.V. All rights reserved.

Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging

PubMed Central

Redding, Brandon; Cerjan, Alexander; Huang, Xue; Lee, Minjoo Larry; Stone, A. Douglas; Choma, Michael A.; Cao, Hui

2015-01-01

The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications. PMID:25605946

Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging.

PubMed

Redding, Brandon; Cerjan, Alexander; Huang, Xue; Lee, Minjoo Larry; Stone, A Douglas; Choma, Michael A; Cao, Hui

2015-02-03

The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications.

Imaging RF Phased Array Receivers using Optically-Coherent Up-conversion for High Beam-Bandwidth Processing

DTIC Science & Technology

2017-03-01

It does so by using an optical lens to perform an inverse spatial Fourier Transform on the up-converted RF signals, thereby rendering a real-time... simultaneous beams or other engineered beam patterns. There are two general approaches to array-based beam forming: digital and analog. In digital beam...of significantly limiting the number of beams that can be formed simultaneously and narrowing the operational bandwidth. An alternate approach that

Semiclassical approximations in the coherent-state representation

NASA Technical Reports Server (NTRS)

Kurchan, J.; Leboeuf, P.; Saraceno, M.

1989-01-01

The semiclassical limit of the stationary Schroedinger equation in the coherent-state representation is analyzed simultaneously for the groups W1, SU(2), and SU(1,1). A simple expression for the first two orders for the wave function and the associated semiclassical quantization rule is obtained if a definite choice for the classical Hamiltonian and expansion parameter is made. The behavior of the modulus of the wave function, which is a distribution function in a curved phase space, is studied for the three groups. The results are applied to the quantum triaxial rotor.

Low-coherence interferometric tip-clearance probe

NASA Astrophysics Data System (ADS)

Kempe, Andreas; Schlamp, Stefan; Rösgen, Thomas; Haffner, Ken

2003-08-01

We propose an all-fiber, self-calibrating, economical probe that is capable of near-real-time, single-port, simultaneous blade-to-blade tip-clearance measurements with submillimeter accuracy (typically <100 μm, absolute) in the first stages of a gas turbine. Our probe relies on the interference between backreflected light from the blade tips during the 1-μs blade passage time and a frequency-shifted reference with variable time delay, making use of a low-coherence light source. A single optical fiber of arbitrary length connects the self-contained optics and electronics to the turbine.

Direct measurement of fast transients by using boot-strapped waveform averaging

NASA Astrophysics Data System (ADS)

Olsson, Mattias; Edman, Fredrik; Karki, Khadga Jung

2018-03-01

An approximation to coherent sampling, also known as boot-strapped waveform averaging, is presented. The method uses digital cavities to determine the condition for coherent sampling. It can be used to increase the effective sampling rate of a repetitive signal and the signal to noise ratio simultaneously. The method is demonstrated by using it to directly measure the fluorescence lifetime from Rhodamine 6G by digitizing the signal from a fast avalanche photodiode. The obtained lifetime of 4.0 ns is in agreement with the known values.

Determination of functional collective motions in a protein at atomic resolution using coherent neutron scattering

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

Hong, Liang; Jain, Nitin; Cheng, Xiaolin

Protein function often depends on global, collective internal motions. However, the simultaneous quantitative experimental determination of the forms, amplitudes, and time scales of these motions has remained elusive. We demonstrate that a complete description of these large-scale dynamic modes can be obtained using coherent neutron-scattering experiments on perdeuterated samples. With this approach, a microscopic relationship between the structure, dynamics, and function in a protein, cytochrome P450cam, is established. The approach developed here should be of general applicability to protein systems.

Determination of functional collective motions in a protein at atomic resolution using coherent neutron scattering

DOE PAGES

Hong, Liang; Jain, Nitin; Cheng, Xiaolin; ...

2016-10-14

Protein function often depends on global, collective internal motions. However, the simultaneous quantitative experimental determination of the forms, amplitudes, and time scales of these motions has remained elusive. We demonstrate that a complete description of these large-scale dynamic modes can be obtained using coherent neutron-scattering experiments on perdeuterated samples. With this approach, a microscopic relationship between the structure, dynamics, and function in a protein, cytochrome P450cam, is established. The approach developed here should be of general applicability to protein systems.

New advances in the partial-reflection-drifts experiment using microprocessors

NASA Technical Reports Server (NTRS)

Ruggerio, R. L.; Bowhill, S. A.

1982-01-01

Improvements to the partial reflection drifts experiment are completed. The results of the improvements include real time processing and simultaneous measurements of the D region with coherent scatter. Preliminary results indicate a positive correlation between drift velocities calculated by both methods during a two day interval. The possibility now exists for extended observations between partial reflection and coherent scatter. In addition, preliminary measurements could be performed between partial reflection and meteor radar to complete a comparison of methods used to determine velocities in the D region.

Expanding the Bandwidth of Slow and Fast Pulse Propagation in Coupled Micro-resonators

NASA Technical Reports Server (NTRS)

Smith, David D.; Chang, Hongrok

2007-01-01

Coupled resonators exhibit coherence effects which can be exploited for the delay or advancement of pulses with minimal distortion. The bandwidth and normalized pulse delay are simultaneously enhanced by proper choice of the inter-resonator couplings.

Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light

NASA Astrophysics Data System (ADS)

Koehler, J. R.; Noskov, R. E.; Sukhorukov, A. A.; Novoa, D.; Russell, P. St. J.

2017-12-01

Coherent control of the resonant response in spatially extended optomechanical structures is complicated by the fact that the optical drive is affected by the backaction from the generated phonons. Here we report an approach to coherent control based on stimulated Raman-like scattering, in which the optical pressure can remain unaffected by the induced vibrations even in the regime of strong optomechanical interactions. We demonstrate experimentally coherent control of flexural vibrations simultaneously along the whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase between the components of a two-frequency pump signal, the beat frequency being chosen to match a flexural resonance. Furthermore, sequential switching of the relative phase at time intervals shorter than the lifetime of the vibrations reduces their amplitude to a constant value that is fully adjustable by tuning the phase modulation depth and switching rate. The results may trigger new developments in silicon photonics, since such coherent control uniquely decouples the amplitude of optomechanical oscillations from power-dependent thermal effects and nonlinear optical loss.

Simultaneous production of lepton pairs in ultraperipheral relativistic heavy ion collisions

NASA Astrophysics Data System (ADS)

Kurban, E.; Güçlü, M. C.

2017-10-01

We calculate the total cross sections and probabilities of electromagnetic productions of electron, muon, and tauon pairs simultaneously. At the CERN Large Hadron Collider (LHC), the available electromagnetic energy is sufficient to produce all kinds of leptons coherently. The masses of muons and tauons are large, so their Compton wavelengths are small enough to interact with the colliding nuclei. Therefore, the realistic nuclear form factors are included in the calculations of electromagnetic pair productions. The cross section calculations show that, at LHC energies, the probabilities of simultaneous productions of all kinds of leptons are increased significantly compared to energies available at the BNL Relativistic Heavy Ion Collider (RHIC) . Experimentally, observing this simultaneous production can give us important information about strong QED.

Fully integrated optical coherence tomography, ultrasound, and indocyanine green based fluorescence tri-modality system for intravascular imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Li, Yan; Jing, Joseph C.; Qu, Yueqiao; Miao, Yusi; Ma, Teng; Yu, Mingyue; Zhou, Qifa; Chen, Zhongping

2017-02-01

The rupture of atherosclerotic plaques is the leading cause of acute coronary events, so accurate assessment of plaque is critical. A large lipid pool, thin fibrous cap, and inflammatory reaction are the crucial characteristics for identifying vulnerable plaques. In our study, a tri-modality imaging system for intravascular imaging was designed and implemented. The tri-modality imaging system with a 1-mm probe diameter is able to simultaneously acquire optical coherence tomography (OCT), intravascular ultrasound (IVUS), and fluorescence imaging. Moreover, for fluorescence imaging, we used the FDA-approved indocyanine green (ICG) dye as the contrast agent to target lipid-loaded macrophages. Firstly, IVUS is used as the first step for identifying plaque since IVUS enables the visualization of the layered structures of the artery wall. Due to low soft-tissue contrast, IVUS only provides initial identification of the lipid plaque. Then OCT is used for differentiating fibrosis and lipid pool based on its relatively higher soft tissue contrast and high sensitivity/specificity. Last, fluorescence imaging is used for identifying inflammatory reaction to further confirm whether the plaque is vulnerable or not. Ex vivo experiment of a male New Zealand white rabbit aorta was performed to validate the performance of our tri-modality system. H and E histology results of the rabbit aorta were also presented to check assessment accuracy. The miniature tri-modality probe, together with the use of ICG dye suggest that the system is of great potential for providing a more accurate assessment of vulnerable plaques in clinical applications.

Endoscopic Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Zhou, Chao; Fujimoto, James G.; Tsai, Tsung-Han; Mashimo, Hiroshi

New gastrointestinal (GI) cancers are expected to affect more than 290,200 new patients and will cause more than 144,570 deaths in the United States in 2013 [1]. When detected and treated early, the 5-year survival rate for colorectal cancer increases by a factor of 1.4 [1]. For esophageal cancer, the rate increases by a factor of 2 [1]. The majority of GI cancers begin as small lesions that are difficult to identify with conventional endoscopy. With resolutions approaching that of histopathology, optical coherence tomography (OCT) is well suited for detecting the changes in tissue microstructure associated with early GI cancers. Since the lesions are not endoscopically apparent, however, it is necessary to survey a relatively large area of the GI tract. Tissue motion is another limiting factor in the GI tract; therefore, in vivo imaging must be performed at extremely high speeds. OCT imaging can be performed using fiber optics and miniaturized lens systems, enabling endoscopic OCT inside the human body in conjunction with conventional video endoscopy. An OCT probe can be inserted through the working channel of a standard endoscope, thus enabling depth-resolved imaging of tissue microstructure in the GI tract with micron-scale resolution simultaneously with the endoscopic view (Fig. 68.1).

A novel clinical multimodal multiphoton tomograph for AF, SHG, CARS imaging, and FLIM

NASA Astrophysics Data System (ADS)

Weinigel, Martin; Breunig, Hans Georg; König, Karsten

2014-02-01

We report on a flexible nonlinear medical tomograph with multiple miniaturized detectors for simultaneous acquisition of two-photon autofluorescence (AF), second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) images. The simultaneous visualization of the distribution of endogenous fluorophores NAD(P)H, melanin and elastin, SHG-active collagen and as well as non-fluorescent lipids within human skin in vivo is possible. Furthermore, fluorescence lifetime images (FLIM) can be generated using time-correlated single photon counting.

Noise-immune complex correlation for optical coherence angiography based on standard and Jones matrix optical coherence tomography

PubMed Central

Makita, Shuichi; Kurokawa, Kazuhiro; Hong, Young-Joo; Miura, Masahiro; Yasuno, Yoshiaki

2016-01-01

This paper describes a complex correlation mapping algorithm for optical coherence angiography (cmOCA). The proposed algorithm avoids the signal-to-noise ratio dependence and exhibits low noise in vasculature imaging. The complex correlation coefficient of the signals, rather than that of the measured data are estimated, and two-step averaging is introduced. Algorithms of motion artifact removal based on non perfusing tissue detection using correlation are developed. The algorithms are implemented with Jones-matrix OCT. Simultaneous imaging of pigmented tissue and vasculature is also achieved using degree of polarization uniformity imaging with cmOCA. An application of cmOCA to in vivo posterior human eyes is presented to demonstrate that high-contrast images of patients’ eyes can be obtained. PMID:27446673

Full-duplex bidirectional transmission of 10-Gb/s millimeter-wave QPSK signal in E-band optical wireless link.

PubMed

Fang, Yuan; Yu, Jianjun; Chi, Nan; Xiao, Jiangnan

2014-01-27

We experimentally demonstrated full-duplex bidirectional transmission of 10-Gb/s millimeter-wave (mm-wave) quadrature phase shift keying (QPSK) signal in E-band (71-76 GHz and 81-86 GHz) optical wireless link. Single-mode fibers (SMF) are connected at both sides of the antenna for uplink and downlink which realize 40-km SMF and 2-m wireless link for bidirectional transmission simultaneously. We utilized multi-level modulation format and coherent detection in such E-band optical wireless link for the first time. Mm-wave QPSK signal is generated by photonic technique to increase spectrum efficiency and received signal is coherently detected to improve receiver sensitivity. After the coherent detection, digital signal processing is utilized to compensate impairments of devices and transmission link.

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

Sun, Ke-Wei; Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798; Fujihashi, Yuta

A master equation approach based on an optimized polaron transformation is adopted for dynamics simulation with simultaneous diagonal and off-diagonal spin-boson coupling. Two types of bath spectral density functions are considered, the Ohmic and the sub-Ohmic. The off-diagonal coupling leads asymptotically to a thermal equilibrium with a nonzero population difference P{sub z}(t → ∞) ≠ 0, which implies localization of the system, and it also plays a role in restraining coherent dynamics for the sub-Ohmic case. Since the new method can extend to the stronger coupling regime, we can investigate the coherent-incoherent transition in the sub-Ohmic environment. Relevant phase diagramsmore » are obtained for different temperatures. It is found that the sub-Ohmic environment allows coherent dynamics at a higher temperature than the Ohmic environment.« less

Maximal coherence and the resource theory of purity

NASA Astrophysics Data System (ADS)

Streltsov, Alexander; Kampermann, Hermann; Wölk, Sabine; Gessner, Manuel; Bruß, Dagmar

2018-05-01

The resource theory of quantum coherence studies the off-diagonal elements of a density matrix in a distinguished basis, whereas the resource theory of purity studies all deviations from the maximally mixed state. We establish a direct connection between the two resource theories, by identifying purity as the maximal coherence which is achievable by unitary operations. The states that saturate this maximum identify a universal family of maximally coherent mixed states. These states are optimal resources under maximally incoherent operations, and thus independent of the way coherence is quantified. For all distance-based coherence quantifiers the maximal coherence can be evaluated exactly, and is shown to coincide with the corresponding distance-based purity quantifier. We further show that purity bounds the maximal amount of entanglement and discord that can be generated by unitary operations, thus demonstrating that purity is the most elementary resource for quantum information processing.

Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography.

PubMed

Kamali, Tschackad; Považay, Boris; Kumar, Sunil; Silberberg, Yaron; Hermann, Boris; Werkmeister, René; Drexler, Wolfgang; Unterhuber, Angelika

2014-10-01

We demonstrate a multimodal optical coherence tomography (OCT) and online Fourier transform coherent anti-Stokes Raman scattering (FTCARS) platform using a single sub-12 femtosecond (fs) Ti:sapphire laser enabling simultaneous extraction of structural and chemical ("morphomolecular") information of biological samples. Spectral domain OCT prescreens the specimen providing a fast ultrahigh (4×12  μm axial and transverse) resolution wide field morphologic overview. Additional complementary intrinsic molecular information is obtained by zooming into regions of interest for fast label-free chemical mapping with online FTCARS spectroscopy. Background-free CARS is based on a Michelson interferometer in combination with a highly linear piezo stage, which allows for quick point-to-point extraction of CARS spectra in the fingerprint region in less than 125 ms with a resolution better than 4  cm(-1) without the need for averaging. OCT morphology and CARS spectral maps indicating phosphate and carbonate bond vibrations from human bone samples are extracted to demonstrate the performance of this hybrid imaging platform.

Quantum coherence selective 2D Raman–2D electronic spectroscopy

PubMed Central

Spencer, Austin P.; Hutson, William O.; Harel, Elad

2017-01-01

Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational–vibrational, electronic–vibrational and electronic–electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment–protein complexes. PMID:28281541

Coherence across consciousness levels: Symmetric visual displays spare working memory resources.

PubMed

Dumitru, Magda L

2015-12-15

Two studies demonstrate that the need for coherence could nudge individuals to use structural similarities between binary visual displays and two concurrent cognitive tasks to unduly solve the latter in similar fashion. In an overt truth-judgement task, participants decided whether symmetric colourful displays matched conjunction or disjunction descriptions (e.g., "the black and/or the orange"). In the simultaneous covert categorisation task, they decided whether a colour name (e.g., "black") described a two-colour object or half of a single-colour object. Two response patterns emerged as follows. Participants either acknowledged or rejected matches between disjunction descriptions and two visual stimuli and, similarly, either acknowledged or rejected matches between single colour names and two-colour objects or between single colour names and half of single-colour objects. These findings confirm the coherence hypothesis, highlight the role of coherence in preserving working-memory resources, and demonstrate an interaction between high-level and low-level consciousness. Copyright © 2015 Elsevier Inc. All rights reserved.

Cerebral coherence between communicators marks the emergence of meaning

PubMed Central

Stolk, Arjen; Noordzij, Matthijs L.; Verhagen, Lennart; Volman, Inge; Schoffelen, Jan-Mathijs; Oostenveld, Robert; Hagoort, Peter; Toni, Ivan

2014-01-01

How can we understand each other during communicative interactions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative suggestion posits that mutual understanding requires shared conceptualizations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neural dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously measured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dynamics across communicators’ right temporal lobes. This interpersonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use. PMID:25489093

Rapid spectro-polarimetry to probe molecular symmetry in multiplex coherent anti-Stokes Raman scattering.

PubMed

Würthwein, Thomas; Brinkmann, Maximilian; Hellwig, Tim; Fallnich, Carsten

2017-11-21

We present the simultaneous detection of the spectrum and the complete polarization state of a multiplex coherent anti-Stokes Raman scattering signal with a fast division-of-amplitude spectro-polarimeter. The spectro-polarimeter is based on a commercial imaging spectrograph, a birefringent wedge prism, and a segmented polarizer. Compared to the standard rotating-retarder fixed-analyzer spectro-polarimeter, only a single measurement is required and an up to 21-fold reduced acquisition time is shown. The measured Stokes parameters allow us to differentiate between vibrational symmetries and to determine the depolarization ratio ρ by data post-processing.

Coherent Detector Arrays for Continuum and Spectral Line Applications

NASA Technical Reports Server (NTRS)

Gaier, Todd C.

2006-01-01

This viewgraph presentation reviews the requirements for improved coherent detector arrays for use in continuum and spectral line applications. With detectors approaching fundamental limits, large arrays offer the only path to sensitivity improvement. Monolithic Microwave Integrated Circuit (MMIC) technology offers a straightforward path to massive focal plane millimeter wave arrays: The technology will readily support continuum imagers, polarimeters and spectral line receivers from 30-110 GHz. Science programs, particularly large field blind surveys will benefit from simultaneous observations of hundreds or thousands of pixels 1000 element array is competitive with a cost less than $2M.

Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip.

PubMed

Förster, Michael; Paschen, Timo; Krüger, Michael; Lemell, Christoph; Wachter, Georg; Libisch, Florian; Madlener, Thomas; Burgdörfer, Joachim; Hommelhoff, Peter

2016-11-18

We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission.

Coherent white light amplification

DOEpatents

Jovanovic, Igor; Barty, Christopher P.

2004-05-25

A system for coherent simultaneous amplification of a broad spectral range of light that includes an optical parametric amplifier and a source of a seed pulse is described. A first angular dispersive element is operatively connected to the source of a seed pulse. A first imaging telescope is operatively connected to the first angular dispersive element and operatively connected to the optical parametric amplifier. A source of a pump pulse is operatively connected to the optical parametric amplifier. A second imaging telescope is operatively connected to the optical parametric amplifier and a second angular dispersive element is operatively connected to the second imaging telescope.

Multiphoton Scattering Tomography with Coherent States.

PubMed

Ramos, Tomás; García-Ripoll, Juan José

2017-10-13

In this work we develop an experimental procedure to interrogate the single- and multiphoton scattering matrices of an unknown quantum system interacting with propagating photons. Our proposal requires coherent state laser or microwave inputs and homodyne detection at the scatterer's output, and provides simultaneous information about multiple-elastic and inelastic-segments of the scattering matrix. The method is resilient to detector noise and its errors can be made arbitrarily small by combining experiments at various laser powers. Finally, we show that the tomography of scattering has to be performed using pulsed lasers to efficiently gather information about the nonlinear processes in the scatterer.

Synchrotron-based coherent scatter x-ray projection imaging using an array of monoenergetic pencil beams.

PubMed

Landheer, Karl; Johns, Paul C

2012-09-01

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be acquired simultaneous to the primary images and provide additional information. In medical applications scatter imaging can improve x-ray contrast or reduce dose using information that is currently discarded in radiological images to augment the transmitted radiation information. Other applications include non-destructive testing and security. A system at the Canadian Light Source synchrotron was configured which utilizes multiple pencil beams (up to five) to create both primary and coherent scatter projection images, simultaneously. The sample was scanned through the beams using an automated step-and-shoot setup. Pixels were acquired in a hexagonal lattice to maximize packing efficiency. The typical pitch was between 1.0 and 1.6 mm. A Maximum Likelihood-Expectation Maximization-based iterative method was used to disentangle the overlapping information from the flat panel digital x-ray detector. The pixel value of the coherent scatter image was generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. Different angular ranges maximize the contrast between different materials of interest. A five-beam primary and scatter image set (which had a pixel beam time of 990 ms and total scan time of 56 min) of a porcine phantom is included. For comparison a single-beam coherent scatter image of the same phantom is included. The muscle-fat contrast was 0.10 ± 0.01 and 1.16 ± 0.03 for the five-beam primary and scatter images, respectively. The air kerma was measured free in air using aluminum oxide optically stimulated luminescent dosimeters. The total area-averaged air kerma for the scan was measured to be 7.2 ± 0.4 cGy although due to difficulties in small-beam dosimetry this number could be inaccurate.

Magnetic nanoparticles as contrast agents for molecular imaging in medicine

NASA Astrophysics Data System (ADS)

O'Donnell, Matthew

2018-05-01

For over twenty years, superparamagnetic nanoparticles have been developed for a number of medical applications ranging from bioseparations, magnetic drug targeting, hyperthermia and imaging. Recent studies have shown that they can be functionalized for in vivo biological targeting, potentially enabling nanoagents for molecular imaging and site-localized drug delivery. Here we review several imaging technologies developed using functionalized superparamagnetic iron oxide nanoparticles (SPIONs) as targeted molecular agents. Several imaging modalities have exploited the large induced magnetic moment of SPIONs to create local mechanical force. Magnetic force microscopy can probe nanoparticle uptake in single cells. For in vivo applications, magnetomotive modulation of primary images in ultrasound (US), photoacoustics (PA), and optical coherence tomography (OCT) can help identify very small concentrations of nanoagents while simultaneously suppressing intrinsic background signals from tissue.

Advanced imaging in COPD: insights into pulmonary pathophysiology

PubMed Central

Milne, Stephen

2014-01-01

Chronic obstructive pulmonary disease (COPD) involves a complex interaction of structural and functional abnormalities. The two have long been studied in isolation. However, advanced imaging techniques allow us to simultaneously assess pathological processes and their physiological consequences. This review gives a comprehensive account of the various advanced imaging modalities used to study COPD, including computed tomography (CT), magnetic resonance imaging (MRI), and the nuclear medicine techniques positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Some more recent developments in imaging technology, including micro-CT, synchrotron imaging, optical coherence tomography (OCT) and electrical impedance tomography (EIT), are also described. The authors identify the pathophysiological insights gained from these techniques, and speculate on the future role of advanced imaging in both clinical and research settings. PMID:25478198

Raman linewidth measurements using time-resolved hybrid picosecond/nanosecond rotational CARS.

PubMed

Nordström, Emil; Hosseinnia, Ali; Brackmann, Christian; Bood, Joakim; Bengtsson, Per-Erik

2015-12-15

We report an innovative approach for time-domain measurements of S-branch Raman linewidths using hybrid picosecond/nanosecond pure-rotational coherent anti-Stokes Raman spectroscopy (RCARS). The Raman coherences are created by two picosecond excitation pulses and are probed using a narrow-band nanosecond pulse at 532 nm. The generated RCARS signal contains the entire coherence decay in a single pulse. By extracting the decay times of the individual transitions, the J-dependent Raman linewidths can be calculated. Self-broadened S-branch linewidths for nitrogen and oxygen at 293 K and ambient pressure are in good agreement with previous time-domain measurements. Experimental considerations of the approach are discussed along with its merits and limitations. The approach can be extended to a wide range of pressures and temperatures and has potential for simultaneous single-shot thermometry and linewidth determination.

Coherent perfect absorption and laser modes in a cylindrical structure of conjugate metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Xu, Yadong; Chen, Huanyang; Cummer, Steven A.

2018-01-01

In this work, we theoretically find that coherent perfect absorption (CPA) and laser modes can be realized in a two-dimensional cylindrical structure composed of conjugate metamaterials (CMs). The required phase factors of CMs for achieving CPA and laser modes are determined by the geometric size of the CM cylinder, which is a unique feature compared with other non-Hermitian optical systems. Based on this property, we also demonstrate that CPA and laser modes can exist simultaneously in a CM cylinder with an extremely large size, where the excitations of CPA and laser modes depend on the angular momentum of coherent incident light. Therefore, compared with the well known parity time symmetry, our work opens up a brand-new path to obtaining CPA and laser modes, and is a significant advance in non-Hermitian optical systems.

On-chip coherent conversion of photonic quantum entanglement between different degrees of freedom

PubMed Central

Feng, Lan-Tian; Zhang, Ming; Zhou, Zhi-Yuan; Li, Ming; Xiong, Xiao; Yu, Le; Shi, Bao-Sen; Guo, Guo-Ping; Dai, Dao-Xin; Ren, Xi-Feng; Guo, Guang-Can

2016-01-01

In the quantum world, a single particle can have various degrees of freedom to encode quantum information. Controlling multiple degrees of freedom simultaneously is necessary to describe a particle fully and, therefore, to use it more efficiently. Here we introduce the transverse waveguide-mode degree of freedom to quantum photonic integrated circuits, and demonstrate the coherent conversion of a photonic quantum state between path, polarization and transverse waveguide-mode degrees of freedom on a single chip. The preservation of quantum coherence in these conversion processes is proven by single-photon and two-photon quantum interference using a fibre beam splitter or on-chip beam splitters. These results provide us with the ability to control and convert multiple degrees of freedom of photons for quantum photonic integrated circuit-based quantum information process. PMID:27321821

Single-shot hyperspectral coherent Raman planar imaging in the range 0–4200 cm⁻¹

DOE PAGES

Bohlin, Alexis; Kliewer, Christopher J.

2014-10-23

We propose a technique for ultrabroadband planar coherent Raman spectroscopy that enables wideband chemically selective mapping of molecular partition functions in the gas-phase within a single-laser-shot. A spectral region spanning 0–4200 cm⁻¹ is excited simultaneously, in principle allowing for coherent planar imaging of most all fundamental Raman-active modes. This unique instantaneous and spatially correlated assessment enables multiplexed studies of transient dynamical systems in a two-dimensional (2D) field. Here, we demonstrate single-laser-shot high temperature diagnostics of H₂, with spatially resolved 2D measurement of transitions of both the pure-rotational H₂ S-branch and the vibrational H₂ Q-branch, analyzing the temperature contour of amore » reacting fuel-species as it evolves at a flame-front.« less

On-chip coherent conversion of photonic quantum entanglement between different degrees of freedom.

PubMed

Feng, Lan-Tian; Zhang, Ming; Zhou, Zhi-Yuan; Li, Ming; Xiong, Xiao; Yu, Le; Shi, Bao-Sen; Guo, Guo-Ping; Dai, Dao-Xin; Ren, Xi-Feng; Guo, Guang-Can

2016-06-20

In the quantum world, a single particle can have various degrees of freedom to encode quantum information. Controlling multiple degrees of freedom simultaneously is necessary to describe a particle fully and, therefore, to use it more efficiently. Here we introduce the transverse waveguide-mode degree of freedom to quantum photonic integrated circuits, and demonstrate the coherent conversion of a photonic quantum state between path, polarization and transverse waveguide-mode degrees of freedom on a single chip. The preservation of quantum coherence in these conversion processes is proven by single-photon and two-photon quantum interference using a fibre beam splitter or on-chip beam splitters. These results provide us with the ability to control and convert multiple degrees of freedom of photons for quantum photonic integrated circuit-based quantum information process.

Accelerator and reactor complementarity in coherent neutrino-nucleus scattering

NASA Astrophysics Data System (ADS)

Dent, James B.; Dutta, Bhaskar; Liao, Shu; Newstead, Jayden L.; Strigari, Louis E.; Walker, Joel W.

2018-02-01

We study the complementarity between accelerator and reactor coherent elastic neutrino-nucleus elastic scattering (CE ν NS ) experiments for constraining new physics in the form of nonstandard neutrino interactions (NSI). First, considering just data from the recent observation by the Coherent experiment, we explore interpretive degeneracies that emerge when activating either two or four unknown NSI parameters. Next, we demonstrate that simultaneous treatment of reactor and accelerator experiments, each employing at least two distinct target materials, can break a degeneracy between up and down flavor-diagonal NSI terms that survives analysis of neutrino oscillation experiments. Considering four flavor-diagonal (e e /μ μ ) up- and down-type NSI parameters, we find that all terms can be measured with high local precision (to a width as small as ˜5 % in Fermi units) by next-generation experiments, although discrete reflection ambiguities persist.

Is Social Categorization the Missing Link Between Weak Central Coherence and Mental State Inference Abilities in Autism? Preliminary Evidence from a General Population Sample.

PubMed

Skorich, Daniel P; May, Adrienne R; Talipski, Louisa A; Hall, Marnie H; Dolstra, Anita J; Gash, Tahlia B; Gunningham, Beth H

2016-03-01

We explore the relationship between the 'theory of mind' (ToM) and 'central coherence' difficulties of autism. We introduce covariation between hierarchically-embedded categories and social information--at the local level, the global level, or at both levels simultaneously--within a category confusion task. We then ask participants to infer the mental state of novel category members, and measure participants' autism-spectrum quotient (AQ). Results reveal a positive relationship between AQ and the degree of local/global social categorization, which in turn predicts the pattern of mental state inferences. These results provide preliminary evidence for a causal relationship between central coherence and ToM abilities. Implications with regard to ToM processes, social categorization, intervention, and the development of a unified account of autism are discussed.

Multiple acquisitions via sequential transfer of orphan spin polarization (MAeSTOSO): How far can we push residual spin polarization in solid-state NMR?

NASA Astrophysics Data System (ADS)

Gopinath, T.; Veglia, Gianluigi

2016-06-01

Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS (DUal acquisition Magic Angle Spinning) and MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for Multiple Acquisitions via Sequential Transfer of Orphan Spin pOlarization, relies on residual polarization of both 13C and 15N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed.

A detailed X-ray investigation of ζ Puppis. IV. Further characterization of the variability

NASA Astrophysics Data System (ADS)

Nazé, Yaël; Ramiaramanantsoa, Tahina; Stevens, Ian R.; Howarth, Ian D.; Moffat, Anthony F. J.

2018-01-01

Context. One of the optically brightest and closest massive stars, ζ Pup, is also a bright X-ray source. Previously, its X-ray emission was found to be variable with light curves harbouring "trends" with a typical timescale longer than the exposure length, i.e. >1 d. The origin of these changes was proposed to be linked to large-scale structures in the wind of ζ Pup, but further characterization of the variability at high energies was needed to investigate this scenario. Aims: Since the previous papers of this series, a number of new X-ray observations have become available. Furthermore, a cyclic behaviour with a 1.78 d period was identified in long optical photometric runs, which is thought to be associated with the launching mechanism of large-scale wind structures. Methods: We analysed these new X-ray data, revisited the old data, and compared the X-ray light curves with the optical data, notably those taken simultaneously. Results: The behaviour of ζ Pup in X-rays cannot be explained in terms of a perfect clock because the amplitude and shape of its variations change with time. For example, ζ Pup was much more strongly variable between 2007 and 2011 than before and after this interval. Comparing the X-ray spectra of the star at maximum and minimum brightness yields no compelling difference beyond the overall flux change: the temperatures, absorptions, and line shapes seem to remain constant, well within errors. The only common feature between X-ray datasets is that the variation amplitudes appear maximum in the medium (0.6-1.2 keV) energy band. Finally, no clear and coherent correlation can be found between simultaneous X-ray and optical data. Only a subgroup of observations may be combined coherently with the optical period of 1.78 d, although the simultaneous optical behaviour is unknown. Conclusions: The currently available data do not reveal any obvious, permanent, and direct correlation between X-ray and optical variations. The origin of the X-ray variability therefore still needs to be ascertained, highlighting the need for long-term monitoring in multiwavelengths, i.e. X-ray, UV, and optical.

Integration of Proteomic, Transcriptional, and Interactome Data Reveals Hidden Signaling Components

PubMed Central

Huang, Shao-shan Carol; Fraenkel, Ernest

2009-01-01

Cellular signaling and regulatory networks underlie fundamental biological processes such as growth, differentiation, and response to the environment. Although there are now various high-throughput methods for studying these processes, knowledge of them remains fragmentary. Typically, the vast majority of hits identified by transcriptional, proteomic, and genetic assays lie outside of the expected pathways. These unexpected components of the cellular response are often the most interesting, because they can provide new insights into biological processes and potentially reveal new therapeutic approaches. However, they are also the most difficult to interpret. We present a technique, based on the Steiner tree problem, that uses previously reported protein-protein and protein-DNA interactions to determine how these hits are organized into functionally coherent pathways, revealing many components of the cellular response that are not readily apparent in the original data. Applied simultaneously to phosphoproteomic and transcriptional data for the yeast pheromone response, it identifies changes in diverse cellular processes that extend far beyond the expected pathways. PMID:19638617

A Grid Approach to Managing Sustainability: Evidence from a Multiple Italian Case Study

ERIC Educational Resources Information Center

Agostino, Deborah; Dal Molin, Martina

2016-01-01

Purpose: The purpose of this paper is to explore the coherence between sustainability conceptualization (the "what") and its implementation (the "how") in terms of implemented actions and stakeholders' interactions. The paper proposes a grid approach for the simultaneous evaluation of sustainability conceptualization and…

Effect of electrocardiogram interference on cortico-cortical connectivity analysis and a possible solution.

PubMed

Govindan, R B; Kota, Srinivas; Al-Shargabi, Tareq; Massaro, An N; Chang, Taeun; du Plessis, Adre

2016-09-01

Electroencephalogram (EEG) signals are often contaminated by the electrocardiogram (ECG) interference, which affects quantitative characterization of EEG. We propose null-coherence, a frequency-based approach, to attenuate the ECG interference in EEG using simultaneously recorded ECG as a reference signal. After validating the proposed approach using numerically simulated data, we apply this approach to EEG recorded from six newborns receiving therapeutic hypothermia for neonatal encephalopathy. We compare our approach with an independent component analysis (ICA), a previously proposed approach to attenuate ECG artifacts in the EEG signal. The power spectrum and the cortico-cortical connectivity of the ECG attenuated EEG was compared against the power spectrum and the cortico-cortical connectivity of the raw EEG. The null-coherence approach attenuated the ECG contamination without leaving any residual of the ECG in the EEG. We show that the null-coherence approach performs better than ICA in attenuating the ECG contamination without enhancing cortico-cortical connectivity. Our analysis suggests that using ICA to remove ECG contamination from the EEG suffers from redistribution problems, whereas the null-coherence approach does not. We show that both the null-coherence and ICA approaches attenuate the ECG contamination. However, the EEG obtained after ICA cleaning displayed higher cortico-cortical connectivity compared with that obtained using the null-coherence approach. This suggests that null-coherence is superior to ICA in attenuating the ECG interference in EEG for cortico-cortical connectivity analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Identification of Hepatoprotective Constituents in Limonium tetragonum and Development of Simultaneous Analysis Method using High-performance Liquid Chromatography

PubMed Central

Lee, Jae Sun; Kim, Yun Na; Kim, Na-Hyun; Heo, Jeong-Doo; Yang, Min Hye; Rho, Jung-Rae; Jeong, Eun Ju

2017-01-01

Background: Limonium tetragonum, a naturally salt-tolerant halophyte, has been studied recently and is of much interest to researchers due to its potent antioxidant and hepatoprotective activities. Objective: In the present study, we attempted to elucidate bioactive compounds from ethyl acetate (EtOAc) soluble fraction of L. tetragonum extract. Furthermore, the simultaneous analysis method of bioactive EtOAc fraction of L. tetragonum has been developed using high-performance liquid chromatography (HPLC). Materials and Methods: Thirteen compounds have been successfully isolated from EtOAc fraction of L. tetragonum, and the structures of 1–13 were elucidated by extensive one-dimensional and two-dimensional spectroscopic methods including 1H-NMR, 13C-NMR, 1H-1H COSY, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser effect spectroscopy. Hepatoprotection of the isolated compounds against liver fibrosis was evaluated by measuring inhibition on hepatic stellate cells (HSCs) undergoing proliferation. Results: Compounds 1–13 were identified as gallincin (1), apigenin-3-O-β-D-galactopyranoside (2), quercetin (3), quercetin-3-O-β-D-galactopyranoside (4), (−)-epigallocatechin (5), (−)-epigallocatechin-3-gallate (6), (−)-epigallocatechin-3-(3″-O-methyl) gallate (7), myricetin-3-O-β-D-galactopyranoside (8), myricetin-3-O-(6″-O-galloyl)-β-D-galactopyranoside (9), myricetin-3-O-α-L-rhamnopyranoside (10), myricetin-3-O-(2″-O-galloyl)-α-L-rhamnopyranoside (11), myricetin-3-O-(3″-O-galloyl)-α-L-rhamnopyranoside (12), and myricetin-3-O-α-L-arabinopyranoside (13), respectively. All compounds except for 4, 8, and 10 are reported for the first time from this plant. Conclusion: Myricetin glycosides which possess galloyl substituent (9, 11, and 12) showed most potent inhibitory effects on the proliferation of HSCs. SUMMARY In the present study, we have successfully isolated 13 compounds from bioactive fraction of Limonium tetragonum. The structures of compounds isolated have been fully elucidated, and hepatoprotective activities of compounds against liver fibrosis were evaluated by measuring inhibition on hepatic stellate cells undergoing proliferation. Furthermore, the simultaneous analysis method of bioactive ethyl acetate fraction of L. tetragonum has been developed using HPLC. Ten compounds identified herein are reported for the first time from this plant. Abbreviations used: HSQC: Heteronuclear single quantum coherence; HMBC: Heteronuclear multiple bond correlation; NOESY: Nuclear Overhauser effect spectroscopy; EGCG: Epigallocatechin-3-gallate; EGC: Epigallocatechin; HSC: Hepatic stellate cell; MTT: 3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide. PMID:29200710

Broadband light generation by femtosecond pulse amplification with stimulated Raman scattering in a high-power erbium-doped fiber amplifier

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

Tamura, K.; Yoshida, E.; Sugawa, T.

1995-08-01

It is shown for the first time to our knowledge that short-pulse amplification in high-power erbium-doped fiber amplifiers, simultaneously accompanied by stimulated Raman scattering, generates a broadband optical spectrum at high output power (270 mW). At 20 dB down from the peak the continuum extended over 329 nm, from 1427 to 1756 nm. The FWHM bandwidth was 125 nm, centered at 1650 nm. The coherence was measured to be 15 fringes, which corresponds to a 25-{mu}m coherence length. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

Collaborative effects of wavefront shaping and optical clearing agent in optical coherence tomography

NASA Astrophysics Data System (ADS)

Yu, Hyeonseung; Lee, Peter; Jo, YoungJu; Lee, KyeoReh; Tuchin, Valery V.; Jeong, Yong; Park, YongKeun

2016-12-01

We demonstrate that simultaneous application of optical clearing agents (OCAs) and complex wavefront shaping in optical coherence tomography (OCT) can provide significant enhancement of penetration depth and imaging quality. OCA reduces optical inhomogeneity of a highly scattering sample, and the wavefront shaping of illumination light controls multiple scattering, resulting in an enhancement of the penetration depth and signal-to-noise ratio. A tissue phantom study shows that concurrent applications of OCA and wavefront shaping successfully operate in OCT imaging. The penetration depth enhancement is further demonstrated for ex vivo mouse ears, revealing hidden structures inaccessible with conventional OCT imaging.

Noise-immune complex correlation for vasculature imaging based on standard and Jones-matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Makita, Shuichi; Kurokawa, Kazuhiro; Hong, Young-Joo; Li, En; Miura, Masahiro; Yasuno, Yoshiaki

2016-03-01

A new optical coherence angiography (OCA) method, called correlation mapping OCA (cmOCA), is presented by using the SNR-corrected complex correlation. An SNR-correction theory for the complex correlation calculation is presented. The method also integrates a motion-artifact-removal method for the sample motion induced decorrelation artifact. The theory is further extended to compute more reliable correlation by using multi- channel OCT systems, such as Jones-matrix OCT. The high contrast vasculature imaging of in vivo human posterior eye has been obtained. Composite imaging of cmOCA and degree of polarization uniformity indicates abnormalities of vasculature and pigmented tissues simultaneously.

Development of a phase-sensitive Fourier domain optical coherence tomography system to measure mouse organ of Corti vibrations in two cochlear turns

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

Ramamoorthy, Sripriya; Zhang, Yuan; Jacques, Steven

In this study, we have developed a phase-sensitive Fourier-domain optical coherence tomography system to simultaneously measure the in vivo inner ear vibrations in the hook area and second turn of the mouse cochlea. This technical development will enable measurement of intra-cochlear distortion products at ideal locations such as the distortion product generation site and reflection site. This information is necessary to un-mix the complex mixture of intra-cochlear waves comprising the DPOAE and thus leads to the non-invasive identification of the local region of cochlear damage.

Spectroscopic optical coherence tomography based on wavelength de-multiplexing and smart pixel array detection

NASA Astrophysics Data System (ADS)

Laubscher, Markus; Bourquin, Stéphane; Froehly, Luc; Karamata, Boris; Lasser, Theo

2004-07-01

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an experimental alternative for accessing spectroscopic information in OCT without post-processing based on wavelength de-multiplexing and parallel detection using a diffraction grating and a smart pixel detector array. Both a conventional A-scan with high axial resolution and the spectrally resolved measurement are acquired simultaneously. A proof-of-principle demonstration is given on a dynamically changing absorbing sample. The method's potential for fast spectroscopic OCT imaging is discussed. The spectral measurements obtained with this approach are insensitive to scan non-linearities or sample movements.

A dual-modality optical coherence tomography and selective plane illumination microscopy system for mouse embryonic imaging

NASA Astrophysics Data System (ADS)

Wu, Chen; Ran, Shihao; Le, Henry; Singh, Manmohan; Larina, Irina V.; Mayerich, David; Dickinson, Mary E.; Larin, Kirill V.

2017-02-01

Both optical coherence tomography (OCT) and selective plane illumination microscopy (SPIM) are frequently used in mouse embryonic research for high-resolution three-dimensional imaging. However, each of these imaging methods provide a unique and independent advantage: SPIM provides morpho-functional information through immunofluorescence and OCT provides a method for whole-embryo 3D imaging. In this study, we have combined rotational imaging OCT and SPIM into a single, dual-modality device to image E9.5 mouse embryos. The results demonstrate that the dual-modality setup is able to provide both anatomical and functional information simultaneously for more comprehensive tissue characterization.

Multipoint sensing with a low-coherence source using single-arm frequency-shifted interferometry

DOE PAGES

Zhang, Yiwei; Ye, Fei; Qi, Bing; ...

2016-07-12

We demonstrate that multiple-site sensing along an optical fiber can be done with incoherent continuous-wave light. Here, using a broadband low-coherence noise source, a slow detector, and an optical modulator, we construct a single-arm frequency-shifted interferometer (SA-FSI) capable of simultaneously sensing multiple weak-reflection sites distributed either in parallel or in series along fiber links. By scanning the driving frequency of an electro-optic amplitude modulator in the range of 2.7–3.2 GHz at steps of 41.7 KHz, we demonstrate a spatial resolution of 0.3 m and a measurement range of over 1 km.

Coherently coupling distinct spin ensembles through a high-Tc superconducting resonator

NASA Astrophysics Data System (ADS)

Ghirri, A.; Bonizzoni, C.; Troiani, F.; Buccheri, N.; Beverina, L.; Cassinese, A.; Affronte, M.

2016-06-01

The problem of coupling multiple spin ensembles through cavity photons is revisited by using (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl (PyBTM) organic radicals and a high-Tc superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the g factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.

Birefringence and vascular imaging of in vivo human skin by Jones-matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Li, En; Makita, Shuichi; Hong, Young-Joo; Kasaragod, Deepa; Yasuno, Yoshiaki

2017-02-01

A customized 1310-nm Jones-matrix optical coherence tomography (JM-OCT) for dermatological investigation was constructed and used for in vivo normal human skin tissue imaging. This system can simultaneously measure the threedimensional depth-resolved local birefringence, complex-correlation based OCT angiography (OCT-A), degree-ofpolarization- uniformity (DOPU) and scattering OCT intensity. By obtaining these optical properties of tissue, the morphology, vasculature, and collagen content of skin can be deduced and visualized. Structures in the deep layers of the epithelium were observed with depth-resolved local birefringence and polarization uniformity images. These results suggest high diagnostic and investigative potential of JM-OCT for dermatology.

Zero-field optical magnetic resonance study of phosphorus donors in 28-silicon

NASA Astrophysics Data System (ADS)

Morse, Kevin J.; Dluhy, Phillip; Huber, Julian; Salvail, Jeff Z.; Saeedi, Kamyar; Riemann, Helge; Abrosimov, Nikolay V.; Becker, Peter; Pohl, Hans-Joachim; Simmons, S.; Thewalt, M. L. W.

2018-03-01

Donor spins in silicon are some of the most promising qubits for upcoming solid-state quantum technologies. The nuclear spins of phosphorus donors in enriched silicon have among the longest coherence times of any solid-state system as well as simultaneous high fidelity qubit initialization, manipulation, and readout. Here we characterize the phosphorus in silicon system in the regime of "zero" magnetic field, where a singlet-triplet spin clock transition can be accessed, using laser spectroscopy and magnetic resonance methods. We show the system can be optically hyperpolarized and has ˜10 s Hahn echo coherence times, even for applied static magnetic fields below Earth's field.

Parallel implementation of all-digital timing recovery for high-speed and real-time optical coherent receivers.

PubMed

Zhou, Xian; Chen, Xue

2011-05-09

The digital coherent receivers combine coherent detection with digital signal processing (DSP) to compensate for transmission impairments, and therefore are a promising candidate for future high-speed optical transmission system. However, the maximum symbol rate supported by such real-time receivers is limited by the processing rate of hardware. In order to cope with this difficulty, the parallel processing algorithms is imperative. In this paper, we propose a novel parallel digital timing recovery loop (PDTRL) based on our previous work. Furthermore, for increasing the dynamic dispersion tolerance range of receivers, we embed a parallel adaptive equalizer in the PDTRL. This parallel joint scheme (PJS) can be used to complete synchronization, equalization and polarization de-multiplexing simultaneously. Finally, we demonstrate that PDTRL and PJS allow the hardware to process 112 Gbit/s POLMUX-DQPSK signal at the hundreds MHz range. © 2011 Optical Society of America

Se-SAD serial femtosecond crystallography datasets from selenobiotinyl-streptavidin

PubMed Central

Yoon, Chun Hong; DeMirci, Hasan; Sierra, Raymond G.; Dao, E. Han; Ahmadi, Radman; Aksit, Fulya; Aquila, Andrew L.; Batyuk, Alexander; Ciftci, Halilibrahim; Guillet, Serge; Hayes, Matt J.; Hayes, Brandon; Lane, Thomas J.; Liang, Meng; Lundström, Ulf; Koglin, Jason E.; Mgbam, Paul; Rao, Yashas; Rendahl, Theodore; Rodriguez, Evan; Zhang, Lindsey; Wakatsuki, Soichi; Boutet, Sébastien; Holton, James M.; Hunter, Mark S.

2017-01-01

We provide a detailed description of selenobiotinyl-streptavidin (Se-B SA) co-crystal datasets recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) for selenium single-wavelength anomalous diffraction (Se-SAD) structure determination. Se-B SA was chosen as the model system for its high affinity between biotin and streptavidin where the sulfur atom in the biotin molecule (C10H16N2O3S) is substituted with selenium. The dataset was collected at three different transmissions (100, 50, and 10%) using a serial sample chamber setup which allows for two sample chambers, a front chamber and a back chamber, to operate simultaneously. Diffraction patterns from Se-B SA were recorded to a resolution of 1.9 Å. The dataset is publicly available through the Coherent X-ray Imaging Data Bank (CXIDB) and also on LCLS compute nodes as a resource for research and algorithm development. PMID:28440794

Coherent structure diffusivity in the edge region of Reversed Field Pinch experiments

NASA Astrophysics Data System (ADS)

Spolaore, M.; Antoni, V.; Spada, E.; Bergsåker, H.; Cavazzana, R.; Drake, J. R.; Martines, E.; Regnoli, G.; Serianni, G.; Vianello, N.

2005-01-01

Coherent structures emerging from the background turbulence have been detected by electrostatic measurements in the edge region of two Reversed Field Pinch experiments, RFX (Padua) and Extrap-T2R (Stockholm). Measurements have been performed by arrays of Langmuir probes which allowed simultaneous measurements of temperature, potential and density to be carried out. These structures have been interpreted as a dynamic balance of dipolar and monopolar vortices, whose relative population are found to depend on the local mean E × B flow shear. The contribution to the anomalous transport of these structures has been investigated and it has been found that the corresponding diffusion coeffcient accounts up to 50% of the total diffusivity. The experimental findings indicate that the diffusion coeffcient associated to the coherent structures depends on the relative population of the two types of vortices and is minimum when the two populations are equal. An interpretative model is proposed to explain this feature.

Why not Commercial Assistance for Suicide? On the Question of Argumentative Coherence of Endorsing Assisted Suicide.

PubMed

Kipke, Roland

2015-09-01

Most people who endorse physician-assisted suicide are against commercially assisted suicide - a suicide assisted by professional non-medical providers against payment. The article questions if this position - endorsement of physician-assisted suicide on the one hand and rejection of commercially assisted suicide on the other hand - is a coherent ethical position. To this end the article first discusses some obvious advantages of commercially assisted suicide and then scrutinizes six types of argument about whether they can justify the rejection of commercially assisted suicide while simultaneously endorsing physician-assisted suicide. The conclusion is that they cannot provide this justification and that the mentioned position is not coherent. People who endorse physician-assisted suicide have to endorse commercially assisted suicide as well, or they have to revise their endorsement of physician-assisted suicide. © 2014 John Wiley & Sons Ltd.

Se-SAD serial femtosecond crystallography datasets from selenobiotinyl-streptavidin

NASA Astrophysics Data System (ADS)

Yoon, Chun Hong; Demirci, Hasan; Sierra, Raymond G.; Dao, E. Han; Ahmadi, Radman; Aksit, Fulya; Aquila, Andrew L.; Batyuk, Alexander; Ciftci, Halilibrahim; Guillet, Serge; Hayes, Matt J.; Hayes, Brandon; Lane, Thomas J.; Liang, Meng; Lundström, Ulf; Koglin, Jason E.; Mgbam, Paul; Rao, Yashas; Rendahl, Theodore; Rodriguez, Evan; Zhang, Lindsey; Wakatsuki, Soichi; Boutet, Sébastien; Holton, James M.; Hunter, Mark S.

2017-04-01

We provide a detailed description of selenobiotinyl-streptavidin (Se-B SA) co-crystal datasets recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) for selenium single-wavelength anomalous diffraction (Se-SAD) structure determination. Se-B SA was chosen as the model system for its high affinity between biotin and streptavidin where the sulfur atom in the biotin molecule (C10H16N2O3S) is substituted with selenium. The dataset was collected at three different transmissions (100, 50, and 10%) using a serial sample chamber setup which allows for two sample chambers, a front chamber and a back chamber, to operate simultaneously. Diffraction patterns from Se-B SA were recorded to a resolution of 1.9 Å. The dataset is publicly available through the Coherent X-ray Imaging Data Bank (CXIDB) and also on LCLS compute nodes as a resource for research and algorithm development.

Strong quantum squeezing of mechanical resonator via parametric amplification and coherent feedback

NASA Astrophysics Data System (ADS)

You, Xiang; Li, Zongyang; Li, Yongmin

2017-12-01

A scheme to achieve strong quantum squeezing of a mechanical resonator in a membrane-in-the-middle optomechanical system is developed. To this end, simultaneous linear and nonlinear coupling between the mechanical resonator and the cavity modes is applied. A two-tone driving light field, comprising unequal red-detuned and blue-detuned sidebands, helps in generating a coherent feedback force through the linear coupling with the membrane resonator. Another driving light field with its amplitude modulated at twice the mechanical frequency drives the mechanical parametric amplification through a second-order coupling with the resonator. The combined effect produces strong quantum squeezing of the mechanical state. The proposed scheme is quite robust to excess second-order coupling observed in coherent feedback operations and can suppress the fluctuations in the mechanical quadrature to far below the zero point and achieve strong squeezing (greater than 10 dB) for realistic parameters.

Phase control in coherent population distribution in molecules

NASA Astrophysics Data System (ADS)

Datta, Avijit

2018-06-01

A chirped laser pulse transfers population from one level to another level accessible by one photon dipole transition. We have used a pair of phase-locked chirped pulses of same frequency instead of a single chirped pulse to achieve phase control over the population transfer and thus creating coherent population distribution in hydrogen molecule. Simultaneous actions of the phase controlled interference and rapid adiabatic passages due to chirped pulses lead to the control in population transfer from the ground X(v = 0, j = 0) level to the C(v = 2, j = 1) level. We have extended this two-level system to a three-level 1 + 1 ladder system for population transfer from the X level to the J(v = 2, j = 2) level via the C intermediate level using two pairs of phase-locked laser chirped pulses and have achieved laudable control over the coherent population distribution.

Quantum key distribution using continuous-variable non-Gaussian states

NASA Astrophysics Data System (ADS)

Borelli, L. F. M.; Aguiar, L. S.; Roversi, J. A.; Vidiella-Barranco, A.

2016-02-01

In this work, we present a quantum key distribution protocol using continuous-variable non-Gaussian states, homodyne detection and post-selection. The employed signal states are the photon added then subtracted coherent states (PASCS) in which one photon is added and subsequently one photon is subtracted from the field. We analyze the performance of our protocol, compared with a coherent state-based protocol, for two different attacks that could be carried out by the eavesdropper (Eve). We calculate the secret key rate transmission in a lossy line for a superior channel (beam-splitter) attack, and we show that we may increase the secret key generation rate by using the non-Gaussian PASCS rather than coherent states. We also consider the simultaneous quadrature measurement (intercept-resend) attack, and we show that the efficiency of Eve's attack is substantially reduced if PASCS are used as signal states.

Magnetofermionic condensate in two dimensions

PubMed Central

Kulik, L. V.; Zhuravlev, A. S.; Dickmann, S.; Gorbunov, A. V.; Timofeev, V. B.; Kukushkin, I. V.; Schmult, S.

2016-01-01

Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations. PMID:27848969

Multi-spacecraft coherent Doppler and ranging for interplanetary-navigation

NASA Technical Reports Server (NTRS)

Pollmeier, Vincent M.

1995-01-01

Future plans for planetary exploration currently include using multiple spacecraft to simultaneously explore one planet. This never before encountered situation places new demands on tracking systems used to support navigation. One possible solution to the problem of heavy ground resource conflicts is the use of multispacecraft coherent radio metric data, also known as, bent-pipe data. Analysis of the information content of these data types show that the information content of multi-spacecraft Doppler is dependent only on the frequency of the final downlink leg and is independent of the frequencies used on other legs. Numerical analysis shows that coherent bent-pipe data can provide significantly better capability to estimate the location of a lander on the surface of Mars than can direct lander to Earth radio metric data. However, this is complicated by difficulties in separating the effect of a lander position error from that of an orbiter position error for single passes of data.

Optical to optical interface device

NASA Technical Reports Server (NTRS)

Oliver, D. S.; Vohl, P.; Nisenson, P.

1972-01-01

The development, fabrication, and testing of a preliminary model of an optical-to-optical (noncoherent-to-coherent) interface device for use in coherent optical parallel processing systems are described. The developed device demonstrates a capability for accepting as an input a scene illuminated by a noncoherent radiation source and providing as an output a coherent light beam spatially modulated to represent the original noncoherent scene. The converter device developed under this contract employs a Pockels readout optical modulator (PROM). This is a photosensitive electro-optic element which can sense and electrostatically store optical images. The stored images can be simultaneously or subsequently readout optically by utilizing the electrostatic storage pattern to control an electro-optic light modulating property of the PROM. The readout process is parallel as no scanning mechanism is required. The PROM provides the functions of optical image sensing, modulation, and storage in a single active material.

Lagrangian motion, coherent structures, and lines of persistent material strain.

PubMed

Samelson, R M

2013-01-01

Lagrangian motion in geophysical fluids may be strongly influenced by coherent structures that support distinct regimes in a given flow. The problems of identifying and demarcating Lagrangian regime boundaries associated with dynamical coherent structures in a given velocity field can be studied using approaches originally developed in the context of the abstract geometric theory of ordinary differential equations. An essential insight is that when coherent structures exist in a flow, Lagrangian regime boundaries may often be indicated as material curves on which the Lagrangian-mean principal-axis strain is large. This insight is the foundation of many numerical techniques for identifying such features in complex observed or numerically simulated ocean flows. The basic theoretical ideas are illustrated with a simple, kinematic traveling-wave model. The corresponding numerical algorithms for identifying candidate Lagrangian regime boundaries and lines of principal Lagrangian strain (also called Lagrangian coherent structures) are divided into parcel and bundle schemes; the latter include the finite-time and finite-size Lyapunov exponent/Lagrangian strain (FTLE/FTLS and FSLE/FSLS) metrics. Some aspects and results of oceanographic studies based on these approaches are reviewed, and the results are discussed in the context of oceanographic observations of dynamical coherent structures.

Multi-point laser coherent detection system and its application on vibration measurement

NASA Astrophysics Data System (ADS)

Fu, Y.; Yang, C.; Xu, Y. J.; Liu, H.; Yan, K.; Guo, M.

2015-05-01

Laser Doppler vibrometry (LDV) is a well-known interferometric technique to measure the motions, vibrations and mode shapes of machine components and structures. The drawback of commercial LDV is that it can only offer a pointwise measurement. In order to build up a vibrometric image, a scanning device is normally adopted to scan the laser point in two spatial axes. These scanning laser Doppler vibrometers (SLDV) assume that the measurement conditions remain invariant while multiple and identical, sequential measurements are performed. This assumption makes SLDVs impractical to do measurement on transient events. In this paper, we introduce a new multiple-point laser coherent detection system based on spatial-encoding technology and fiber configuration. A simultaneous vibration measurement on multiple points is realized using a single photodetector. A prototype16-point laser coherent detection system is built and it is applied to measure the vibration of various objects, such as body of a car or a motorcycle when engine is on and under shock tests. The results show the prospect of multi-point laser coherent detection system in the area of nondestructive test and precise dynamic measurement.

Micron-scale coherence in interphase chromatin dynamics

PubMed Central

Zidovska, Alexandra; Weitz, David A.; Mitchison, Timothy J.

2013-01-01

Chromatin structure and dynamics control all aspects of DNA biology yet are poorly understood, especially at large length scales. We developed an approach, displacement correlation spectroscopy based on time-resolved image correlation analysis, to map chromatin dynamics simultaneously across the whole nucleus in cultured human cells. This method revealed that chromatin movement was coherent across large regions (4–5 µm) for several seconds. Regions of coherent motion extended beyond the boundaries of single-chromosome territories, suggesting elastic coupling of motion over length scales much larger than those of genes. These large-scale, coupled motions were ATP dependent and unidirectional for several seconds, perhaps accounting for ATP-dependent directed movement of single genes. Perturbation of major nuclear ATPases such as DNA polymerase, RNA polymerase II, and topoisomerase II eliminated micron-scale coherence, while causing rapid, local movement to increase; i.e., local motions accelerated but became uncoupled from their neighbors. We observe similar trends in chromatin dynamics upon inducing a direct DNA damage; thus we hypothesize that this may be due to DNA damage responses that physically relax chromatin and block long-distance communication of forces. PMID:24019504

Simultaneous measurement of tear film dynamics using wavefront sensor and optical coherence tomography.

PubMed

Koh, Shizuka; Tung, Cynthia; Aquavella, James; Yadav, Rahul; Zavislan, James; Yoon, Geunyoung

2010-07-01

PURPOSE. To investigate tear film dynamics using simultaneous measurements of ocular aberrations and lower tear meniscus. METHODS. Simultaneous measurements of wavefront aberration and lower tear meniscus were performed for 11 normal eyes and 7 eyes with short tear film break-up time (SBUT) dry eye, with a tear film break-up time shorter than 5 seconds, using a wavefront sensor and an anterior segment optical coherence tomography (OCT). During the measurement, the subjects were instructed to blink every 6 seconds for a total of 30 seconds. From the measured aberration, root mean square (RMS) wavefront error and volume modulation transfer function (vMTF) induced by changes in tear film dynamics were calculated for a 5-mm pupil. Lower tear meniscus height (TMH) and area (TMA) were estimated from the cross-sectional OCT images of lower tear meniscus. RESULTS. There was a positive correlation between RMS and tear meniscus dimensions and a negative correlation between vMTF and tear meniscus in both groups. There were moderate negative correlations between the postblink initial RMS change and baseline TMH (R = -0.61) and TMA (R = -0.54) in SBUT dry eyes that were stronger than in normal eyes (R = -0.37, R = -0.38). CONCLUSIONS. Tear meniscus dimensions increase with RMS over time, and tear quantity before blink has a significant role in maintaining initial optical integrity, especially in SBUT dry eye. Simultaneous measurement of optical quality and tear meniscus has the potential to improve understanding of tear stability in normal eyes and dry eyes.

Automatic detection and recognition of multiple macular lesions in retinal optical coherence tomography images with multi-instance multilabel learning

NASA Astrophysics Data System (ADS)

Fang, Leyuan; Yang, Liumao; Li, Shutao; Rabbani, Hossein; Liu, Zhimin; Peng, Qinghua; Chen, Xiangdong

2017-06-01

Detection and recognition of macular lesions in optical coherence tomography (OCT) are very important for retinal diseases diagnosis and treatment. As one kind of retinal disease (e.g., diabetic retinopathy) may contain multiple lesions (e.g., edema, exudates, and microaneurysms) and eye patients may suffer from multiple retinal diseases, multiple lesions often coexist within one retinal image. Therefore, one single-lesion-based detector may not support the diagnosis of clinical eye diseases. To address this issue, we propose a multi-instance multilabel-based lesions recognition (MIML-LR) method for the simultaneous detection and recognition of multiple lesions. The proposed MIML-LR method consists of the following steps: (1) segment the regions of interest (ROIs) for different lesions, (2) compute descriptive instances (features) for each lesion region, (3) construct multilabel detectors, and (4) recognize each ROI with the detectors. The proposed MIML-LR method was tested on 823 clinically labeled OCT images with normal macular and macular with three common lesions: epiretinal membrane, edema, and drusen. For each input OCT image, our MIML-LR method can automatically identify the number of lesions and assign the class labels, achieving the average accuracy of 88.72% for the cases with multiple lesions, which better assists macular disease diagnosis and treatment.

Dual modality instrument for simultaneous optical coherence tomography imaging and fluorescence spectroscopy.

PubMed

Barton, Jennifer Kehlet; Guzman, Francisco; Tumlinson, Alexandre

2004-01-01

We develop a dual-modality device that combines the anatomical imaging capabilities of optical coherence tomography (OCT) with the functional capabilities of laser-induced fluorescence (LIF) spectroscopy. OCT provides cross-sectional images of tissue structure to a depth of up to 2 mm with approximately 10-microm resolution. LIF spectroscopy provides histochemical information in the form of emission spectra from a given tissue location. The OCT subsystem utilizes a superluminescent diode with a center wavelength of 1300 nm, whereas a helium cadmium laser provides the LIF excitation source at wavelengths of 325 and 442 nm. Preliminary data are obtained on eight postmortem aorta samples, each 10 mm in length. OCT images and LIF spectra give complementary information from normal and atherosclerotic portions of aorta wall. OCT images show structures such as intima, media, internal elastic lamina, and fibrotic regions. Emission spectra ratios of 520/490 (325-nm excitation) and 595/635 (442-nm excitation) could be used to identify normal and plaque regions with 97 and 91% correct classification rates, respectively. With miniaturization of the delivery probe and improvements in system speed, this dual-modality device could provide a valuable tool for identification and characterization of atherosclerotic plaques. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Trace material detection of surfaces via single-beam femtosecond MCARS

NASA Astrophysics Data System (ADS)

Bowman Pilkington, Sherrie S.; Roberson, Stephen D.; Pellegrino, Paul M.

2016-05-01

There is a significant need for the development of optical diagnostics for rapid and accurate detection of chemical species in convoluted systems. In particular, chemical warfare agents and explosive materials are of interest, however, identification of these species is difficult for a wide variety of reasons. Low vapor pressures, for example, cause traditional Raman scattering to be ineffective due to the incredibly long signal collection times that are required. Multiplex Coherent Anti-Stokes Raman Scattering (MCARS) spectroscopy generates a complete Raman spectrum from the material of interest using a combination of a broadband pulse which drives multiple molecular vibrations simultaneously and a narrow band probe pulse. For most species, the complete Raman spectrum can be detected in milliseconds; this makes MCARS an excellent technique for trace material detection in complex systems. In this paper, we present experimental MCARS results on solid state chemical species in complex systems. The 40fs Ti:Sapphire laser used in this study has sufficient output power to produce both the broadband continuum pulse and narrow band probe pulse simultaneously. A series of explosive materials of interest have been identified and compared with spontaneous Raman spectra, showing the specificity and stability of this system.

Coherent Femtosecond Spectroscopy and Nonlinear Optical Imaging on the Nanoscale

NASA Astrophysics Data System (ADS)

Kravtsov, Vasily

Optical properties of many materials and macroscopic systems are defined by ultrafast dynamics of electronic, vibrational, and spin excitations localized on the nanoscale. Harnessing these excitations for material engineering, optical computing, and control of chemical reactions has been a long-standing goal in science and technology. However, it is challenging due to the lack of spectroscopic techniques that can resolve processes simultaneously on the nanometer spatial and femtosecond temporal scales. This thesis describes the fundamental principles, implementation, and experimental demonstration of a novel type of ultrafast microscopy based on the concept of adiabatic plasmonic nanofocusing. Simultaneous spatio-temporal resolution on a nanometer-femtosecond scale is achieved by using a near-field nonlinear optical response induced by ultrafast surface plasmon polaritons nanofocused on a metal tip. First, we study the surface plasmon response in metallic structures and evaluate its prospects and limitations for ultrafast near-field microscopy. Through plasmon emission-based spectroscopy, we investigate dephasing times and interplay between radiative and non-radiative decay rates of localized plasmons and their modification due to coupling. We identify a new regime of quantum plasmonic coupling, which limits the achievable spatial resolution to several angstroms but at the same time provides a potential channel for generating ultrafast electron currents at optical frequencies. Next, we study propagation of femtosecond wavepackets of surface plasmon polaritons on a metal tip. In time-domain interferometric measurements we detect group delays that correspond to slowing of the plasmon polaritons down to 20% of the speed of light at the tip apex. This provides direct experimental verification of the plasmonic nanofocusing mechanism and suggests enhanced nonlinear optical interactions at the tip apex. We then measure a plasmon-generated third-order nonlinear optical four-wave mixing response from the tip apex and investigate its microscopic mechanism. Our results reveal a significant contribution to the third order nonlinearity of plasmonic structures due to large near-field gradients associated with nanofocused plasmons. In combination with scanning probe imaging and femtosecond pulse shaping, the nanofocused four-wave mixing response provides a basis for a novel type of ultrafast optical microscopy on the nanoscale. We demonstrate its capabilities by nano-imaging the coherent dynamics of localized plasmonic modes in a rough gold film edge with simultaneous sub-50 nm spatial and sub-5 fs temporal resolution. We capture the coherent decay and extract the dephasing times of individual plasmonic modes. Lastly, we apply our technique to study nanoscale spatial heterogeneity of the nonlinear optical response in novel two-dimensional materials: monolayer and few-layer graphene. An enhanced four-wave mixing signal is revealed on the edges of graphene flakes. We investigate the mechanism of this enhancement by performing nano-imaging on a graphene field-effect transistor with the variable carrier density controlled by electrostatic gating.

Conceptual Coherence, Comprehension, and Vocabulary Acquisition: A Knowledge Effect?

ERIC Educational Resources Information Center

Cervetti, Gina N.; Wright, Tanya S.; Hwang, HyeJin

2016-01-01

Previous research has documented the role of readers' existing topic knowledge in supporting students' comprehension of text; yet, we know less about how to build students' knowledge in order to support comprehension and vocabulary learning. In the current study, we test the hypothesis that knowledge can be built and leveraged simultaneously in…

Sea level oscillations in coastal waters of the Buenos Aires province, Argentina

NASA Astrophysics Data System (ADS)

Dragani, W. C.; Mazio, C. A.; Nuñez, M. N.

2002-03-01

Sea level oscillations, with periods ranging from a few minutes to almost 2 h, have been observed at various tide stations located on the coast of Buenos Aires. Simultaneous records of sea level elevation measured in Mar de Ajó, Pinamar and Mar del Plata during 1982 have been spectrally analyzed. Significant spectral energy has been detected between 0.85 and 4.69 cycles per hour (cph) and the most energetic peaks have frequencies between 1.17 and 1.49 cph. Spectra, coherence, and phase difference have been analyzed for the most energetic event of the year. During that event, the most intensive spectral peak is at 1.17 cph for Mar de Ajó and Pinamar, and at 1.49 cph for Mar del Plata. Simultaneous total energy peaks at Mar de Ajó, Pinamar and Mar del Plata, and the coherence function estimated between Mar de Ajó and Pinamar suggests that sea level oscillations could be a regional phenomenon. The analyzed data suggest that sea level oscillations could be forced by atmospheric gravity waves associated with frontal passages.

Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler.

PubMed

Beaudette, Kathy; Baac, Hyoung Won; Madore, Wendy-Julie; Villiger, Martin; Godbout, Nicolas; Bouma, Brett E; Boudoux, Caroline

2015-04-01

Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to induce coagulation of an ex vivo swine esophagus allowing a real-time assessment of thermal dynamic processes. We therefore demonstrate a DCFC-based system combining OCT imaging with laser coagulation through a single fiber, thus enabling both modalities to be performed simultaneously and in a co-registered manner. Such a system enables endoscopic image-guided laser marking of superficial epithelial tissues or laser thermal therapy of epithelial lesions in pathologies such as Barrett's esophagus.

Novel adaptive fiber-optics collimator for coherent beam combination.

PubMed

Zhi, Dong; Ma, Pengfei; Ma, Yanxing; Wang, Xiaolin; Zhou, Pu; Si, Lei

2014-12-15

In this manuscript, we experimentally validate a novel design of adaptive fiber-optics collimator (AFOC), which utilizes two levers to enlarge the movable range of the fiber end cap. The enlargement of the range makes the new AFOC possible to compensate the end-cap/tilt aberration in fiber laser beam combining system. The new AFOC based on flexible hinges and levers was fabricated and the performance of the new AFOC was tested carefully, including its control range, frequency response and control accuracy. Coherent beam combination (CBC) of two 5-W fiber amplifiers array with simultaneously end-cap/tilt control and phase-locking control was implemented successfully with the novel AFOC. Experimental results show that the average normalized power in the bucket (PIB) value increases from 0.311 to 0.934 with active phasing and tilt aberration compensation simultaneously, and with both controls on, the fringe contrast improves to more than 82% from 0% for the case with both control off. This work presents a promising structure for tilt aberration control in high power CBC system.

Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler

PubMed Central

Beaudette, Kathy; Baac, Hyoung Won; Madore, Wendy-Julie; Villiger, Martin; Godbout, Nicolas; Bouma, Brett E.; Boudoux, Caroline

2015-01-01

Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to induce coagulation of an ex vivo swine esophagus allowing a real-time assessment of thermal dynamic processes. We therefore demonstrate a DCFC-based system combining OCT imaging with laser coagulation through a single fiber, thus enabling both modalities to be performed simultaneously and in a co-registered manner. Such a system enables endoscopic image-guided laser marking of superficial epithelial tissues or laser thermal therapy of epithelial lesions in pathologies such as Barrett’s esophagus. PMID:25909013

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

NASA Astrophysics Data System (ADS)

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-01

Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.

3D interferometric shape measurement technique using coherent fiber bundles

NASA Astrophysics Data System (ADS)

Zhang, Hao; Kuschmierz, Robert; Czarske, Jürgen

2017-06-01

In-situ 3-D shape measurements with submicron shape uncertainty of fast rotating objects in a cutting lathe are expected, which can be achieved by simultaneous distance and velocity measurements. Conventional tactile methods, coordinate measurement machines, only support ex-situ measurements. Optical measurement techniques such as triangulation and conoscopic holography offer only the distance, so that the absolute diameter cannot be retrieved directly. In comparison, laser Doppler distance sensors (P-LDD sensor) enable simultaneous and in-situ distance and velocity measurements for monitoring the cutting process in a lathe. In order to achieve shape measurement uncertainties below 1 μm, a P-LDD sensor with a dual camera based scattered light detection has been investigated. Coherent fiber bundles (CFB) are employed to forward the scattered light towards cameras. This enables a compact and passive sensor head in the future. Compared with a photo detector based sensor, the dual camera based sensor allows to decrease the measurement uncertainty by the order of one magnitude. As a result, the total shape uncertainty of absolute 3-D shape measurements can be reduced to about 100 nm.

Comparison of conditional sampling and averaging techniques in a turbulent boundary layer

NASA Astrophysics Data System (ADS)

Subramanian, C. S.; Rajagopalan, S.; Antonia, R. A.; Chambers, A. J.

1982-10-01

A rake of cold wires was used in a slightly heated boundary layer to identify coherent temperature fronts. An X-wire/cold-wire arrangement was used simultaneously with the rake to provide measurements of the longitudinal and normal velocity fluctuations and temperature fluctuations. Conditional averages of these parameters and their products were obtained by application of conditional techniques (VITA, HOLE, BT, RA1, and RA3) based on the detection of temperature fronts using information obtained at only one point in space. It is found that none of the one-point detection techniques is in good quantitative agreement with the rake detection technique, the largest correspondence being 51%. Despite the relatively poor correspondence between the conditional techniques, these techniques, with the exception of HOLE, produce conditional averages that are in reasonable qualitative agreement with those deduced using the rake.

Advances in tumor diagnosis using OCT and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zakharov, V. P.; Bratchenko, I. A.; Kozlov, S. V.; Moryatov, A. A.; Kornilin, D. V.; Myakinin, O. O.; Artemyev, D. N.

2014-05-01

Complex investigation of malignant tumors was performed with combined optical coherence tomography (OCT) and Raman spectroscopy (RS) setup: 22 ex vivo lung tissue samples and 23 in vivo experiments with skin tumors. It was shown that combined RS-OCT unit may be used for precise tissue morphology visualization with simultaneous tumor type determination (BCC, malignant melanoma of skin tissues, adenocarcinoma and squamous cell carcinoma of lung). Fast RS phase method for skin and lung tumors identification was proposed. It is based on alteration of Raman spectral intensity in 1300-1340, 1440-1460 and 1640-1680 cm-1 bands for healthy and malignant tissue. Complex method could identify: malignant melanoma with 88.9% sensitivity and 87.8% specificity; adenocarcinoma with 100% sensitivity and 81.5% specificity; squamous cell carcinomas with 90.9% sensitivity and 77.8% specificity.

High-power THz to IR emission by femtosecond laser irradiation of random 2D metallic nanostructures.

PubMed

Zhang, Liangliang; Mu, Kaijun; Zhou, Yunsong; Wang, Hai; Zhang, Cunlin; Zhang, X-C

2015-07-24

Terahertz (THz) spectroscopic sensing and imaging has identified its potentials in a number of areas such as standoff security screening at portals, explosive detection at battle fields, bio-medical research, and so on. With these needs, the development of an intense and broadband THz source has been a focus of THz research. In this work, we report an intense (~10 mW) and ultra-broadband (~150 THz) THz to infrared (IR) source with a Gaussian wavefront, emitted from nano-pore-structured metallic thin films with femtosecond laser pulse excitation. The underlying mechanism has been proposed as thermal radiation. In addition, an intense coherent THz signal was generated through the optical rectification process simultaneously with the strong thermal signal. This unique feature opens up new avenues in biomedical research.

Simultaneous real-time quantification of blood flow and vascular growth in the chick embryo using optical coherence tomography

NASA Astrophysics Data System (ADS)

Kowalski, William J.; Teslovich, Nikola C.; Chen, Chia-Yuan; Keller, Bradley B.; Pekkan, Kerem

2014-03-01

Experimental and clinical data indicate that hemodynamic forces within the embryo provide critical biomechanical cues for cardiovascular morphogenesis, growth, and remodeling and that perturbed flow is a major etiology of congenital heart disease. However, embryonic flow-growth relationships are largely qualitative and poorly defined. In this work, we provide a quantitative analysis of in vivo flow and growth trends in the chick embryo using optical coherence tomography (OCT) to acquire simultaneous velocity and structural data of the right vitelline artery continuously over a ten hour period beginning at stage 16 (hour 54). We obtained 3D vessel volumes (15 μm lateral, 4.3 μm axial resolutions, 6 μm slice spacing) at 60 minute intervals, taking a B-scan time series totaling one cardiac cycle at each slice. Embryos were maintained at a constant 37°C and 60% humidity during the entire acquisition period through an inhouse built chamber. The 3D vessel lumen geometries were reconstructed manually to assess growth. Blood flow velocity was computed from the central B-scan using red blood cell particle image velocimetry. The use of extended OCT imaging as a non-invasive method for continuous and simultaneous flow and structural data can enhance our understanding of the biomechanical regulation of critical events in morphogenesis. Data acquired will be useful to validate predictive finite-element 3D growth models.

Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging.

PubMed

Marques, Manuel J; Bradu, Adrian; Podoleanu, Adrian Gh

2014-05-01

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo. The OCT channel employs a broadband optical source and a spectrometer. A gap is created between the sample and reference beams while on their way towards the spectrometer's dispersive element to create Talbot bands. The spatial separation of the two beams facilitates collection by an SLO channel of optical power originating exclusively from the retina, deprived from any contribution from the reference beam. Three different modes of operation are presented, constrained by the minimum integration time of the camera used in the spectrometer and by the galvo-scanners' scanning rate: (i) a simultaneous acquisition mode over the two channels, useful for small size imaging, that conserves the pixel-to-pixel correspondence between them; (ii) a hybrid sequential mode, where the system switches itself between the two regimes and (iii) a sequential "on-demand" mode, where the system can be used in either OCT or SLO regimes for as long as required. The two sequential modes present varying degrees of trade-off between pixel-to-pixel correspondence and independent full control of parameters within each channel. Images of the optic nerve and fovea regions obtained in the simultaneous (i) and in the hybrid sequential mode (ii) are presented.

Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging

PubMed Central

Marques, Manuel J.; Bradu, Adrian; Podoleanu, Adrian Gh.

2014-01-01

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo. The OCT channel employs a broadband optical source and a spectrometer. A gap is created between the sample and reference beams while on their way towards the spectrometer’s dispersive element to create Talbot bands. The spatial separation of the two beams facilitates collection by an SLO channel of optical power originating exclusively from the retina, deprived from any contribution from the reference beam. Three different modes of operation are presented, constrained by the minimum integration time of the camera used in the spectrometer and by the galvo-scanners’ scanning rate: (i) a simultaneous acquisition mode over the two channels, useful for small size imaging, that conserves the pixel-to-pixel correspondence between them; (ii) a hybrid sequential mode, where the system switches itself between the two regimes and (iii) a sequential “on-demand” mode, where the system can be used in either OCT or SLO regimes for as long as required. The two sequential modes present varying degrees of trade-off between pixel-to-pixel correspondence and independent full control of parameters within each channel. Images of the optic nerve and fovea regions obtained in the simultaneous (i) and in the hybrid sequential mode (ii) are presented. PMID:24877006

Combining Optical Coherence Tomography with Fluorescence Molecular Imaging: Towards Simultaneous Morphology and Molecular Imaging

PubMed Central

Yuan, Shuai; Roney, Celeste A.; Wierwille, Jerry; Chen, Chao-Wei; Xu, Biying; Jiang, James; Ma, Hongzhou; Cable, Alex; Summers, Ronald M.; Chen, Yu

2010-01-01

Optical coherence tomography (OCT) provides high-resolution, cross-sectional imaging of tissue microstructure in situ and in real-time, while fluorescence molecular imaging (FMI) enables the visualization of basic molecular processes. There are great interests in combining these two modalities so that the tissue's structural and molecular information can be obtained simultaneously. This could greatly benefit biomedical applications such as detecting early diseases and monitoring therapeutic interventions. In this research, an optical system that combines OCT and FMI was developed. The system demonstrated that it could co-register en face OCT and FMI images with a 2.4 × 2.4 mm field of view. The transverse resolutions of OCT and FMI of the system are both ~10 μm. Capillary tubes filled with fluorescent dye Cy 5.5 in different concentrations under a scattering medium are used as the phantom. En face OCT images of the phantoms were obtained and successfully co-registered with FMI images that were acquired simultaneously. A linear relationship between FMI intensity and dye concentration was observed. The relationship between FMI intensity and target fluorescence tube depth measured by OCT images was also observed and compared with theoretical modeling. This relationship could help in correcting reconstructed dye concentration. Imaging of colon polyps of APCmin mouse model is presented as an example of biological applications of this co-registered OCT/FMI system. PMID:20009192

The spatial coherence structure of infrasonic waves: analysis of data from International Monitoring System arrays

NASA Astrophysics Data System (ADS)

Green, David N.

2015-04-01

The spatial coherence structure of 30 infrasound array detections, with source-to-receiver ranges of 25-6500 km, has been measured within the 0.25-1 Hz passband. The data were recorded at International Monitoring System (IMS) microbarograph arrays with apertures of between 1 and 4 km. Such array detections are of interest for Comprehensive Nuclear-Test-Ban Treaty monitoring. The majority of array detections (e.g. 80 per cent of recordings in the third-octave passband centred on 0.63 Hz) exhibit spatial coherence loss anisotropy that is consistent with previous lower frequency atmospheric acoustic studies; coherence loss is more rapid perpendicular to the acoustic propagation direction than parallel to it. The thirty array detections display significant interdetection variation in the magnitude of spatial coherence loss. The measurements can be explained by the simultaneous arrival of wave fronts at the recording array with angular beamwidths of between 0.4 and 7° and velocity bandwidths of between 2 and 40 m s-1. There is a statistically significant positive correlation between source-to-receiver range and the magnitude of coherence loss. Acoustic multipathing generated by interactions with fine-scale wind and temperature gradients along stratospheric propagation paths is qualitatively consistent with the observations. In addition, the study indicates that to isolate coherence loss generated by propagation effects, analysis of signals exhibiting high signal-to-noise ratios (SNR) is required (SNR2 > 11 in this study). The rapid temporal variations in infrasonic noise observed in recordings at IMS arrays indicates that correcting measured coherence values for the effect of noise, using pre-signal estimates of noise power, is ineffective.

Directional analysis of coherent oscillatory field potentials in the cerebral cortex and basal ganglia of the rat

PubMed Central

Sharott, Andrew; Magill, Peter J; Bolam, J Paul; Brown, Peter

2005-01-01

Population activity in cortico-basal ganglia circuits is synchronized at different frequencies according to brain state. However, the structures that are likely to drive the synchronization of activity in these circuits remain unclear. Furthermore, it is not known whether the direction of transmission of activity is fixed or dependent on brain state. We have used the directed transfer function (DTF) to investigate the direction in which coherent activity is effectively driven in cortico-basal ganglia circuits. Local field potentials (LFPs) were simultaneously recorded in the subthalamic nucleus (STN), globus pallidus (GP) and substantia nigra pars reticulata (SNr), together with the ipsilateral frontal electrocorticogram (ECoG) of anaesthetized rats. Directional analysis was performed on recordings made during robust cortical slow-wave activity (SWA) and ‘global activation’. During SWA, there was coherence at ∼1 Hz between ECoG and basal ganglia LFPs, with much of the coherent activity directed from cortex to basal ganglia. There were similar coherent activities at ∼1 Hz within the basal ganglia, with more activity directed from SNr to GP and STN, and from STN to GP rather than vice versa. During global activation, peaks in coherent activity were seen at higher frequencies (15–60 Hz), with most coherence also directed from cortex to basal ganglia. Within the basal ganglia, however, coherence was predominantly directed from GP to STN and SNr. Together, these results highlight a lead role for the cortex in activity relationships with the basal ganglia, and further suggest that the effective direction of coupling between basal ganglia nuclei is dynamically organized according to brain state, with activity relationships involving the GP displaying the greatest capacity to change. PMID:15550466

Analysis of Direct Recordings from the Surface of the Human Brain

NASA Astrophysics Data System (ADS)

Towle, Vernon L.

2006-03-01

Recording electrophysiologic signals directly from the cortex of patients with chronically implanted subdural electrodes provides an opportunity to map the functional organization of human cortex. In addition to using direct cortical stimulation, sensory evoked potentials, and electrocorticography (ECoG) can also be used. The analysis of ECoG power spectrums and inter-electrode lateral coherence patterns may be helpful in identifying important eloquent cortical areas and epileptogenic regions in cortical multifocal epilepsy. Analysis of interictal ECoG coherence can reveal pathological cortical areas that are functionally distinct from patent cortex. Subdural ECoGs have been analyzed from 50 medically refractive pediatric epileptic patients as part of their routine surgical work-up. Recording arrays were implanted over the frontal, parietal, occipital or temporal lobes for 4-10 days, depending on the patient's seizure semiology and imaging studies. Segments of interictal ECoG ranging in duration from 5 sec to 45 min were examined to identify areas of increased local coherence. Ictal records were examined to identify the stages and spread of the seizures. Immediately before a seizure began, lateral coherence values decreased, reorganized, and then increased during the late ictal and post-ictal periods. When computed over relatively long interictal periods (45 min) coherence patterns were found to be highly stable (r = 0.97, p < .001), and only changed gradually over days. On the other hand, when calculated over short periods of time (5 sec) coherence patterns were highly dynamic. Coherence patterns revealed a rich topography, with reduced coherence across sulci and major fissures. Areas that participate in receptive and expressive speech can be mapped through event-related potentials and analysis of task-specific changes in power spectrums. Information processing is associated with local increases in high frequency activity, with concomitant changes in coherence, suggestive of a transiently active language network. Our findings suggest that analysis of coherence patterns can supplement visual inspection of conventional records to help identify pathological regions of cortex. With further study, it is hoped that analysis of single channel dynamics, along with analysis of multichannel lateral coherence patterns, and the functional holographic technique may allow determination of the boundaries of epileptic foci based on brief interictal recordings, possibly obviating the current need for extended monitoring of seizures.

Coherence and population dynamics of chlorophyll excitations in FCP complex: Two-dimensional spectroscopy study

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

Butkus, Vytautas; Gelzinis, Andrius; Valkunas, Leonas

2015-06-07

Energy transfer processes and coherent phenomena in the fucoxanthin–chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Q{sub y} transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Q{submore » y} transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.« less

Ex vivo optical coherence tomography and laser induced fluorescence spectroscopy imaging of murine gastrointestinal tract

NASA Astrophysics Data System (ADS)

Hariri, Lida; Tumlinson, Alexandre R.; Wade, Norman; Besselsen, David; Utzinger, Urs; Gerner, Eugene; Barton, Jennifer

2005-04-01

Optical Coherence Tomography (OCT) and Laser Induced Fluorescence Spectroscopy (LIF) have separately been found to have clinical potential in identifying human gastrointestinal (GI) pathologies, yet their diagnostic capability in mouse models of human disease is unknown. We combine the two modalities to survey the GI tract of a variety of mouse strains and sample dysplasias and inflammatory bowel disease (IBD) of the small and large intestine. Segments of duodenum and lower colon 2.5 cm in length and the entire esophagus from 10 mice each of two colon cancer models (ApcMin and AOM treated A/J) and two IBD models (Il-2 and Il-10) and 5 mice each of their respective controls were excised. OCT images and LIF spectra were obtained simultaneously from each tissue sample within 1 hour of extraction. Histology was used to classify tissue regions as normal, Peyer"s patch, dysplasia, adenoma, or IBD. Features in corresponding regions of OCT images were analyzed. Spectra from each of these categories were averaged and compared via the student's t-test. Features in OCT images correlated to histology in both normal and diseased tissue samples. In the diseased samples, OCT was able to identify early stages of mild colitis and dysplasia. In the sample of IBD, the LIF spectra displayed unique peaks at 635nm and 670nm, which were attributed to increased porphyrin production in the proliferating bacteria of the disease. These peaks have the potential to act as a diagnostic for IBD. OCT and LIF appear to be useful and complementary modalities for imaging mouse models.

Multi-tissue analysis of co-expression networks by higher-order generalized singular value decomposition identifies functionally coherent transcriptional modules.

PubMed

Xiao, Xiaolin; Moreno-Moral, Aida; Rotival, Maxime; Bottolo, Leonardo; Petretto, Enrico

2014-01-01

Recent high-throughput efforts such as ENCODE have generated a large body of genome-scale transcriptional data in multiple conditions (e.g., cell-types and disease states). Leveraging these data is especially important for network-based approaches to human disease, for instance to identify coherent transcriptional modules (subnetworks) that can inform functional disease mechanisms and pathological pathways. Yet, genome-scale network analysis across conditions is significantly hampered by the paucity of robust and computationally-efficient methods. Building on the Higher-Order Generalized Singular Value Decomposition, we introduce a new algorithmic approach for efficient, parameter-free and reproducible identification of network-modules simultaneously across multiple conditions. Our method can accommodate weighted (and unweighted) networks of any size and can similarly use co-expression or raw gene expression input data, without hinging upon the definition and stability of the correlation used to assess gene co-expression. In simulation studies, we demonstrated distinctive advantages of our method over existing methods, which was able to recover accurately both common and condition-specific network-modules without entailing ad-hoc input parameters as required by other approaches. We applied our method to genome-scale and multi-tissue transcriptomic datasets from rats (microarray-based) and humans (mRNA-sequencing-based) and identified several common and tissue-specific subnetworks with functional significance, which were not detected by other methods. In humans we recapitulated the crosstalk between cell-cycle progression and cell-extracellular matrix interactions processes in ventricular zones during neocortex expansion and further, we uncovered pathways related to development of later cognitive functions in the cortical plate of the developing brain which were previously unappreciated. Analyses of seven rat tissues identified a multi-tissue subnetwork of co-expressed heat shock protein (Hsp) and cardiomyopathy genes (Bag3, Cryab, Kras, Emd, Plec), which was significantly replicated using separate failing heart and liver gene expression datasets in humans, thus revealing a conserved functional role for Hsp genes in cardiovascular disease.

Strong plasmon-exciton coupling in a hybrid system of gold nanostars and J-aggregates

PubMed Central

2013-01-01

Hybrid materials formed by plasmonic nanostructures and J-aggregates provide a unique combination of highly localized and enhanced electromagnetic field in metal constituent with large oscillator strength and extremely narrow exciton band of the organic component. The coherent coupling of localized plasmons of the multispiked gold nanoparticles (nanostars) and excitons of JC1 dye J-aggregates results in a Rabi splitting reaching 260 meV. Importantly, broad absorption features of nanostars extending over a visible and near-infrared spectral range allowed us to demonstrate double Rabi splitting resulting from the simultaneous coherent coupling between plasmons of the nanostars and excitons of J-aggregates of two different cyanine dyes. PMID:23522305

Ultra-narrow linewidth quantum dot coherent comb lasers with self-injection feedback locking.

PubMed

Lu, Z G; Liu, J R; Poole, P J; Song, C Y; Chang, S D

2018-04-30

We have used an external cavity self-injection feedback locking (SIFL) system to simultaneously reduce the optical linewidth of over 39 individual wavelength channels of an InAs/InP quantum dot (QD) coherent comb laser (CCL). Linewidth reduction from a few MHz to less than 200 kHz is observed. Measured phase noise spectra clearly indicate a significant decrease in phase noise in the frequency range above 2 kHz. The RF beating signal between two adjacent channels also shows a substantial reduction in 3-dB linewidth from 10 kHz to 300 Hz with the SIFL system, and a corresponding drop in baseline level (-27 dB to -50 dB).

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

Huang X. R.; Siddons D.; Macrander, A.T.

Realization of x-ray Fabry-Perot (FP) resonance in back-Bragg-reflection crystal cavities has been proposed and explored for many years, but to date no satisfactory performance has been achieved. Here we show that single-cavity crystal resonators intrinsically have limited finesse and efficiency. To break this limit, we demonstrate that monolithic multicavity resonators with equal-width cavities and specific plate thickness ratios can generate ultrahigh-resolution FP resonance with high efficiency, steep peak tails, and ultrahigh contrast simultaneously. The resonance mechanism is similar to that of sequentially cascaded single-cavity resonators. The ultranarrow-bandwidth FP resonance is anticipated to have various applications, including modern ultrahigh-resolution or precisionmore » x-ray monochromatization, spectroscopy, coherence purification, coherent diffraction, phase contrast imaging, etc.« less

Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

NASA Astrophysics Data System (ADS)

Shirai, Tomohiro; Friberg, Ari T.

2018-04-01

Dispersion-canceled optical coherence tomography (OCT) based on spectral intensity interferometry was devised as a classical counterpart of quantum OCT to enhance the basic performance of conventional OCT. In this paper, we demonstrate experimentally that an alternative method of realizing this kind of OCT by means of two optical fiber couplers and a single spectrometer is a more practical and reliable option than the existing methods proposed previously. Furthermore, we develop a recipe for reducing multiple artifacts simultaneously on the basis of simple averaging and verify experimentally that it works successfully in the sense that all the artifacts are mitigated effectively and only the true signals carrying structural information about the sample survive.

Bifocal optical coherenc refractometry of turbid media.

PubMed

Alexandrov, Sergey A; Zvyagin, Andrei V; Silva, K K M B Dilusha; Sampson, David D

2003-01-15

We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.

Lineshape asymmetry for joint coherent population trapping and three-photon N resonances

NASA Astrophysics Data System (ADS)

Hancox, Cindy; Hohensee, Michael; Crescimanno, Michael; Phillips, David F.; Walsworth, Ronald L.

2008-06-01

We show that a characteristic two photon lineshape asymmetry arises in coherent population trapping (CPT) and three photon (N) resonances because both resonances are simultaneously induced by modulation sidebands in the interrogating laser light. The N resonance is a three-photon resonance in which a two-photon Raman excitation is combined with a resonant optical pumping field. This joint CPT and N resonance can be the dominant source of lineshape distortion, with direct relevance for the operation of miniaturized atomic frequency standards. We present the results of both an experimental study and theoretical treatment of the asymmetry of the joint CPT and N resonance under conditions typical to the operation of an N resonance clock.

Polarimetric measurements of natural surfaces at 95 GHz

NASA Astrophysics Data System (ADS)

Chang, Paul S.; McIntosh, Robert E.

1992-08-01

A high power 95 GHz radar system, developed at the University of Massachusetts, was used to make polarimetric measurements of natural surfaces. Over the two year period of this grant, the following items were accomplished: (1) The 95 GHz radar was configured into a unique system capable of simultaneously making coherent and incoherent Mueller matrix measurements; (2) The equivalence of the coherent and noncoherent measurement technique was demonstrated; (3) The polarimetric properties of various foliage targets were characterized. These included the weeping willow, the sugar maple, and the white pine tree species; (4) The polarimetric properties of various snowcover types were characterized; and (5) Mueller matrix models for wet and dry snow were developed.

Coherent quantum control of internal conversion: {S}_{2}\\;\\leftrightarrow \\;{S}_{1} in pyrazine via {S}_{0}\\;\\to \\;{S}_{2}/{S}_{1} weak field excitation

NASA Astrophysics Data System (ADS)

Grinev, Timur; Shapiro, Moshe; Brumer, Paul

2015-09-01

Coherent control of internal conversion (IC) between the first (S1) and second (S2) singlet excited electronic states in pyrazine, where the S2 state is populated from the ground singlet electronic state S0 by weak field excitation, is examined. Control is implemented by shaping the laser which excites S2. Excitation and IC are considered simultaneously, using the recently introduced resonance-based control approach. Highly successful control is achieved by optimizing both the amplitude and phase profiles of the laser spectrum. The dependence of control on the properties of resonances in S2 is demonstrated.

Nonlocal thermoelectric effects and nonlocal Onsager relations in a three-terminal proximity-coupled superconductor-ferromagnet device.

PubMed

Machon, P; Eschrig, M; Belzig, W

2013-01-25

We study thermal and charge transport in a three-terminal setup consisting of one superconducting and two ferromagnetic contacts. We predict that the simultaneous presence of spin filtering and of spin-dependent scattering phase shifts at each of the two interfaces will lead to very large nonlocal thermoelectric effects both in clean and in disordered systems. The symmetries of thermal and electric transport coefficients are related to fundamental thermodynamic principles by the Onsager reciprocity. Our results show that a nonlocal version of the Onsager relations for thermoelectric currents holds in a three-terminal quantum coherent ferromagnet-superconductor heterostructure including a spin-dependent crossed Andreev reflection and coherent electron transfer processes.

Width-Increased Dual-Pump Enhanced Coherent Anti-Stokes Raman Spectroscopy (WIDECARS)

NASA Technical Reports Server (NTRS)

Tedder, Sarah A.; Wheeler, Jeffrey L.; Danehy, Paul M.

2010-01-01

WIDECARS is a dual-pump coherent anti-Stokes Raman Spectroscopy technique that is capable of simultaneously measuring temperature and species mole fractions of N2, O2, H2, C2H4, CO, and CO2. WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H2 S(3) and H2 S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of the flow containing pure hydrogen fuel at room temperature.

Emerging criteria for the low-coherence cannot classify category.

PubMed

Speranza, Anna Maria; Nicolais, Giampaolo; Maggiora Vergano, Carola; Dazzi, Nino

2017-12-01

As suggested by Main et al., to respond to the need for an adaptation of the existing Adult Attachment Interview (AAI) coding system, especially regarding the application to nonnormative samples, this study presents additional criteria that characterize the low-coherence cannot classify (CC) category. Three AAIs were selected from a sample of parents of maltreated children. All transcripts indicated a very low coherence, with no evidence of contradictory insecure discourse strategies. Moreover, global category descriptors were identified, together with specific indices of discourse characteristics and features that highlight the breakdown in reasoning and discourse experienced by the speakers. The aim of the study is to illustrate new criteria to identify and rate a low-coherence CC profile toward the operationalization of this pervasively unintegrated state of mind. Through the definition of additional criteria for low-coherence CC category, our study helps the AAI and its coding system be more flexible and effective when dealing with clinical samples.

Distributed Revisiting: An Analytic for Retention of Coherent Science Learning

ERIC Educational Resources Information Center

Svihla, Vanessa; Wester, Michael J.; Linn, Marcia C.

2015-01-01

Designing learning experiences that support the development of coherent understanding of complex scientific phenomena is challenging. We sought to identify analytics that can also guide such designs to support retention of coherent understanding. Based on prior research that distributing study of material over time supports retention, we explored…

Simultaneously extracting multiple parameters via multi-distance and multi-exposure diffuse speckle contrast analysis

PubMed Central

Liu, Jialin; Zhang, Hongchao; Lu, Jian; Ni, Xiaowu; Shen, Zhonghua

2017-01-01

Recent advancements in diffuse speckle contrast analysis (DSCA) have opened the path for noninvasive acquisition of deep tissue microvasculature blood flow. In fact, in addition to blood flow index αDB, the variations of tissue optical absorption μa, reduced scattering coefficients μs′, as well as coherence factor β can modulate temporal fluctuations of speckle patterns. In this study, we use multi-distance and multi-exposure DSCA (MDME-DSCA) to simultaneously extract multiple parameters such as μa, μs′, αDB, and β. The validity of MDME-DSCA has been validated by the simulated data and phantoms experiments. Moreover, as a comparison, the results also show that it is impractical to simultaneously obtain multiple parameters by multi-exposure DSCA (ME-DSCA). PMID:29082083

Simultaneous CARS and Interferometric Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Danehy, Paul M.; Grinstead, Keith D., Jr.; Tedder, Sarah; Cutler, Andrew D.

2006-01-01

This paper reports for the first time the combination of a dual-pump coherent anti-Stokes Raman scattering system with an interferometric Rayleigh scattering system (CARS - IRS) to provide time-resolved simultaneous measurement of multiple properties in combustion flows. The system uses spectrally narrow green (seeded Nd:YAG at 532 nm) and yellow (552.9 nm) pump beams and a spectrally-broad red (607 nm) beam as the Stokes beam. A spectrometer and a planar Fabry-Perot interferometer used in the imaging mode are used to record the spectrally broad CARS spectra and the spontaneous Rayleigh scattering spectra, respectively. Time-resolved simultaneous measurement of temperature, absolute mole fractions of N2, O2, and H2, and two components of velocity in a Hencken burner flame were performed to demonstrate the technique.

Simultaneous K-edge subtraction tomography for tracing strontium using parametric X-ray radiation

NASA Astrophysics Data System (ADS)

Hayakawa, Y.; Hayakawa, K.; Kaneda, T.; Nogami, K.; Sakae, T.; Sakai, T.; Sato, I.; Takahashi, Y.; Tanaka, T.

2017-07-01

The X-ray source based on parametric X-ray radiation (PXR) has been regularly providing a coherent X-ray beam for application studies at Nihon University. Recently, three dimensional (3D) computed tomography (CT) has become one of the most important applications of the PXR source. The methodology referred to as K-edge subtraction (KES) imaging is a particularly successful application utilizing the energy selectivity of PXR. In order to demonstrate the applicability of PXR-KES, a simultaneous KES experiment for a specimen containing strontium was performed using a PXR beam having an energy near the Sr K-edge of 16.1 keV. As a result, the 3D distribution of Sr was obtained by subtraction between the two simultaneously acquired tomographic images.

Coherence properties and quantum state transportation in an optical conveyor belt.

PubMed

Kuhr, S; Alt, W; Schrader, D; Dotsenko, I; Miroshnychenko, Y; Rosenfeld, W; Khudaverdyan, M; Gomer, V; Rauschenbeutel, A; Meschede, D

2003-11-21

We have prepared and detected quantum coherences of trapped cesium atoms with long dephasing times. Controlled transport by an "optical conveyor belt" over macroscopic distances preserves the atomic coherence with slight reduction of coherence time. The limiting dephasing effects are experimentally identified, and we present an analytical model of the reversible and irreversible dephasing mechanisms. Our experimental methods are applicable at the single-atom level. Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms.

Real-time detection of bacterial spores using coherent anti-Stokes Raman spectroscopy

NASA Astrophysics Data System (ADS)

Dogariu, A.; Goltsov, A.; Pestov, D.; Sokolov, A. V.; Scully, M. O.

2008-02-01

We demonstrate a realistic method for detection of anthrax-type spores in real time based on their chemical fingerprints using coherent anti-Stokes Raman scattering. Specifically, we demonstrate that coherent Raman scattering can be used to successfully identify spores with high accuracy and high selectivity in less than 50ms.

Generalized Lagrangian coherent structures

NASA Astrophysics Data System (ADS)

Balasuriya, Sanjeeva; Ouellette, Nicholas T.; Rypina, Irina I.

2018-06-01

The notion of a Lagrangian Coherent Structure (LCS) is by now well established as a way to capture transient coherent transport dynamics in unsteady and aperiodic fluid flows that are known over finite time. We show that the concept of an LCS can be generalized to capture coherence in other quantities of interest that are transported by, but not fully locked to, the fluid. Such quantities include those with dynamic, biological, chemical, or thermodynamic relevance, such as temperature, pollutant concentration, vorticity, kinetic energy, plankton density, and so on. We provide a conceptual framework for identifying the Generalized Lagrangian Coherent Structures (GLCSs) associated with such evolving quantities. We show how LCSs can be seen as a special case within this framework, and provide an overarching discussion of various methods for identifying LCSs. The utility of this more general viewpoint is highlighted through a variety of examples. We also show that although LCSs approximate GLCSs in certain limiting situations under restrictive assumptions on how the velocity field affects the additional quantities of interest, LCSs are not in general sufficient to describe their coherent transport.

Globally Stable Microresonator Turing Pattern Formation for Coherent High-Power THz Radiation On-Chip

NASA Astrophysics Data System (ADS)

Huang, Shu-Wei; Yang, Jinghui; Yang, Shang-Hua; Yu, Mingbin; Kwong, Dim-Lee; Zelevinsky, T.; Jarrahi, Mona; Wong, Chee Wei

2017-10-01

In nonlinear microresonators driven by continuous-wave (cw) lasers, Turing patterns have been studied in the formalism of the Lugiato-Lefever equation with emphasis on their high coherence and exceptional robustness against perturbations. Destabilization of Turing patterns and the transition to spatiotemporal chaos, however, limit the available energy carried in the Turing rolls and prevent further harvest of their high coherence and robustness to noise. Here, we report a novel scheme to circumvent such destabilization, by incorporating the effect of local mode hybridizations, and we attain globally stable Turing pattern formation in chip-scale nonlinear oscillators with significantly enlarged parameter space, achieving a record-high power-conversion efficiency of 45% and an elevated peak-to-valley contrast of 100. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a fractional frequency sideband nonuniformity measured at 7.3 ×10-14 . We demonstrate the simultaneous microwave and optical coherence of the Turing rolls at different evolution stages through ultrafast optical correlation techniques. The free-running Turing-roll coherence, 9 kHz in 200 ms and 160 kHz in 20 minutes, is transferred onto a plasmonic photomixer for one of the highest-power THz coherent generations at room temperature, with 1.1% optical-to-THz power conversion. Its long-term stability can be further improved by more than 2 orders of magnitude, reaching an Allan deviation of 6 ×10-10 at 100 s, with a simple computer-aided slow feedback control. The demonstrated on-chip coherent high-power Turing-THz system is promising to find applications in astrophysics, medical imaging, and wireless communications.

Demographic, genetic and phenotypic characteristics of centenarians in Italy: Focus on gender differences.

PubMed

Montesanto, Alberto; De Rango, Francesco; Pirazzini, Chiara; Guidarelli, Giulia; Domma, Filippo; Franceschi, Claudio; Passarino, Giuseppe

2017-07-01

An impressive and coherent series of epidemiological data from different populations (New England Americans, Mormons, Ashkenazi Jewish, Icelandic, Okinawan Japanese, Italians) suggests that long-lived subjects able to reach the extreme limits of human life, such as centenarians and supercentenarians, represent an extraordinary and informative model to identify the mechanisms responsible for healthy aging and human longevity. In most studies, genetic, demographic and phenotypic characteristics of longevity are discussed separately. However, longevity is a very complex trait due to the complicated interactions of numerous genetic and environmental factors. It is therefore necessary to analyse centenarians with a multidimensional approach, trying to consider different aspects simultaneously. In this review we will focus on Italian centenarians, who have been extensively studied for many years with different approaches, in order to show their peculiarities and the emerging data from the studies carried out on this exceptional population. Copyright © 2017 Elsevier B.V. All rights reserved.

Global Climate Change Adaptation Priorities for Biodiversity and Food Security

PubMed Central

Hannah, Lee; Ikegami, Makihiko; Hole, David G.; Seo, Changwan; Butchart, Stuart H. M.; Peterson, A. Townsend; Roehrdanz, Patrick R.

2013-01-01

International policy is placing increasing emphasis on adaptation to climate change, including the allocation of new funds to assist adaptation efforts. Climate change adaptation funding may be most effective where it meets integrated goals, but global geographic priorities based on multiple development and ecological criteria are not well characterized. Here we show that human and natural adaptation needs related to maintaining agricultural productivity and ecosystem integrity intersect in ten major areas globally, providing a coherent set of international priorities for adaptation funding. An additional seven regional areas are identified as worthy of additional study. The priority areas are locations where changes in crop suitability affecting impoverished farmers intersect with changes in ranges of restricted-range species. Agreement among multiple climate models and emissions scenarios suggests that these priorities are robust. Adaptation funding directed to these areas could simultaneously address multiple international policy goals, including poverty reduction, protecting agricultural production and safeguarding ecosystem services. PMID:23991125

Global climate change adaptation priorities for biodiversity and food security.

PubMed

Hannah, Lee; Ikegami, Makihiko; Hole, David G; Seo, Changwan; Butchart, Stuart H M; Peterson, A Townsend; Roehrdanz, Patrick R

2013-01-01

International policy is placing increasing emphasis on adaptation to climate change, including the allocation of new funds to assist adaptation efforts. Climate change adaptation funding may be most effective where it meets integrated goals, but global geographic priorities based on multiple development and ecological criteria are not well characterized. Here we show that human and natural adaptation needs related to maintaining agricultural productivity and ecosystem integrity intersect in ten major areas globally, providing a coherent set of international priorities for adaptation funding. An additional seven regional areas are identified as worthy of additional study. The priority areas are locations where changes in crop suitability affecting impoverished farmers intersect with changes in ranges of restricted-range species. Agreement among multiple climate models and emissions scenarios suggests that these priorities are robust. Adaptation funding directed to these areas could simultaneously address multiple international policy goals, including poverty reduction, protecting agricultural production and safeguarding ecosystem services.

Combined analysis of whole human blood parameters by Raman spectroscopy and spectral-domain low-coherence interferometry

NASA Astrophysics Data System (ADS)

Gnyba, M.; Wróbel, M. S.; Karpienko, K.; Milewska, D.; Jedrzejewska-Szczerska, M.

2015-07-01

In this article the simultaneous investigation of blood parameters by complementary optical methods, Raman spectroscopy and spectral-domain low-coherence interferometry, is presented. Thus, the mutual relationship between chemical and physical properties may be investigated, because low-coherence interferometry measures optical properties of the investigated object, while Raman spectroscopy gives information about its molecular composition. A series of in-vitro measurements were carried out to assess sufficient accuracy for monitoring of blood parameters. A vast number of blood samples with various hematological parameters, collected from different donors, were measured in order to achieve a statistical significance of results and validation of the methods. Preliminary results indicate the benefits in combination of presented complementary methods and form the basis for development of a multimodal system for rapid and accurate optical determination of selected parameters in whole human blood. Future development of optical systems and multivariate calibration models are planned to extend the number of detected blood parameters and provide a robust quantitative multi-component analysis.

Remote air lasing for trace detection

NASA Astrophysics Data System (ADS)

Dogariu, Arthur; Michael, James B.; Miles, Richard B.

2011-05-01

We demonstrate coherent light propagating backwards from a remotely generated high gain air laser. A short ultraviolet laser pulse tuned to a two-photon atomic oxygen electronic resonance at 226 nm simultaneously dissociates the oxygen molecules in air and excites the resulting atomic oxygen fragments. Due to the focal depth of the pumping laser, a millimeter long region of high gain is created in air for the atomic oxygen stimulated emission at 845nm. We demonstrate that the gain in excess of 60 cm-1 is responsible for both forward and backwards emission of a strong, collimated, coherent laser beam. We present evidence for coherent emission and characterize the backscattered laser beam while varying the pumping conditions. The optical gain and directional emission allows for six orders of magnitude enhancement for the backscattered emission when compared with the fluorescence emission collected into the same solid angle. . This opens new opportunities for the remote detection capabilities of trace species, and provides much greater range for the detection of optical molecular and atomic features from a distant target.

Determination of dipole coupling constants using heteronuclear multiple quantum NMR

NASA Astrophysics Data System (ADS)

Weitekamp, D. P.; Garbow, J. R.; Pines, A.

1982-09-01

The problem of extracting dipole couplings from a system of N spins I = 1/2 and one spin S by NMR techniques is analyzed. The resolution attainable using a variety of single quantum methods is reviewed. The theory of heteronuclear multiple quantum (HMQ) NMR is developed, with particular emphasis being placed on the superior resolution available in HMQ spectra. Several novel pulse sequences are introduced, including a two-step method for the excitation of HMQ coherence. Experiments on partially oriented [1-13C] benzene demonstrate the excitation of the necessary HMQ coherence and illustrate the calculation of relative line intensities. Spectra of high order HMQ coherence under several different effective Hamiltonians achievable by multiple pulse sequences are discussed. A new effective Hamiltonian, scalar heteronuclear recoupled interactions by multiple pulse (SHRIMP), achieved by the simultaneous irradiation of both spin species with the same multiple pulse sequence, is introduced. Experiments are described which allow heteronuclear couplings to be correlated with an S-spin spreading parameter in spectra free of inhomogeneous broadening.

Joint OSNR monitoring and modulation format identification in digital coherent receivers using deep neural networks.

PubMed

Khan, Faisal Nadeem; Zhong, Kangping; Zhou, Xian; Al-Arashi, Waled Hussein; Yu, Changyuan; Lu, Chao; Lau, Alan Pak Tao

2017-07-24

We experimentally demonstrate the use of deep neural networks (DNNs) in combination with signals' amplitude histograms (AHs) for simultaneous optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) in digital coherent receivers. The proposed technique automatically extracts OSNR and modulation format dependent features of AHs, obtained after constant modulus algorithm (CMA) equalization, and exploits them for the joint estimation of these parameters. Experimental results for 112 Gbps polarization-multiplexed (PM) quadrature phase-shift keying (QPSK), 112 Gbps PM 16 quadrature amplitude modulation (16-QAM), and 240 Gbps PM 64-QAM signals demonstrate OSNR monitoring with mean estimation errors of 1.2 dB, 0.4 dB, and 1 dB, respectively. Similarly, the results for MFI show 100% identification accuracy for all three modulation formats. The proposed technique applies deep machine learning algorithms inside standard digital coherent receiver and does not require any additional hardware. Therefore, it is attractive for cost-effective multi-parameter estimation in next-generation elastic optical networks (EONs).

Se-SAD serial femtosecond crystallography datasets from selenobiotinyl-streptavidin

DOE PAGES

Yoon, Chun Hong; DeMirci, Hasan; Sierra, Raymond G.; ...

2017-04-25

We provide a detailed description of selenobiotinyl-streptavidin (Se-B SA) co-crystal datasets recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) for selenium single-wavelength anomalous diffraction (Se-SAD) structure determination. Se-B SA was chosen as the model system for its high affinity between biotin and streptavidin where the sulfur atom in the biotin molecule (C 10H 16N 2O 3S) is substituted with selenium. The dataset was collected at three different transmissions (100, 50, and 10%) using a serial sample chamber setup which allows for two sample chambers, a front chamber and a back chamber, to operatemore » simultaneously. Diffraction patterns from Se-B SA were recorded to a resolution of 1.9 Å. The dataset is publicly available through the Coherent X-ray Imaging Data Bank (CXIDB) and also on LCLS compute nodes as a resource for research and algorithm development.« less

Se-SAD serial femtosecond crystallography datasets from selenobiotinyl-streptavidin

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

Yoon, Chun Hong; DeMirci, Hasan; Sierra, Raymond G.

We provide a detailed description of selenobiotinyl-streptavidin (Se-B SA) co-crystal datasets recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) for selenium single-wavelength anomalous diffraction (Se-SAD) structure determination. Se-B SA was chosen as the model system for its high affinity between biotin and streptavidin where the sulfur atom in the biotin molecule (C 10H 16N 2O 3S) is substituted with selenium. The dataset was collected at three different transmissions (100, 50, and 10%) using a serial sample chamber setup which allows for two sample chambers, a front chamber and a back chamber, to operatemore » simultaneously. Diffraction patterns from Se-B SA were recorded to a resolution of 1.9 Å. The dataset is publicly available through the Coherent X-ray Imaging Data Bank (CXIDB) and also on LCLS compute nodes as a resource for research and algorithm development.« less

PT-symmetric laser absorber

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

Longhi, Stefano

2010-09-15

In a recent work, Y. D. Chong et al. [Phys. Rev. Lett. 105, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by a lossy medium. The optical medium that realizes CPA is obtained by reversing the gain with absorption, and thus it generally differs from the lasing medium. Here it is shown that a laser with an optical medium that satisfies the parity-time (PT) symmetry condition {epsilon}(-r)={epsilon}*(r) for the dielectric constant behaves simultaneously as a laser oscillator (i.e., it canmore » emit outgoing coherent waves) and as a CPA (i.e., it can fully absorb incoming coherent waves with appropriate amplitudes and phases). Such a device can thus be referred to as a PT-symmetric CPA laser. The general amplification or absorption features of the PT CPA laser below lasing threshold driven by two fields are determined.« less

Study on turbulence characteristics and sensitivity of quadrant analysis to threshold level in Lake Taihu.

PubMed

Weng, Shenglin; Li, Yiping; Wei, Jin; Du, Wei; Gao, Xiaomeng; Wang, Wencai; Wang, Jianwei; Acharya, Kumud; Luo, Liancong

2018-05-01

The identification of coherent structures is very important in investigating the sediment transport mechanism and controlling the eutrophication in shallow lakes. This study analyzed the turbulence characteristics and the sensitivity of quadrant analysis to threshold level. Simultaneous in situ measurements of velocities and suspended sediment concentration (SSC) were conducted in Lake Taihu with acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) instruments. The results show that the increase in hole size makes the difference between dominant and non-dominant events more distinct. Wind velocity determines the frequency of occurrence of sweep and ejection events, which provide dominant contributions to the Reynolds stress. The increase of wind velocity enlarges the magnitude of coherent events but has little impact on the events frequency with the same hole size. The events occurring within short periods provide large contributions to the momentum flux. Transportation and diffusion of sediment are in control of the intermittent coherent events to a large extent.

In-vivo, real-time cross-sectional images of retina using a GPU enhanced master slave optical coherence tomography system

NASA Astrophysics Data System (ADS)

Bradu, Adrian; Kapinchev, Konstantin; Barnes, Frederick; Podoleanu, Adrian

2016-03-01

In our previous reports we demonstrated a novel Fourier domain optical coherence tomography method, Master Slave optical coherence tomography (MS-OCT), that does not require resampling of data and can deliver en-face images from several depths simultaneously. While ideally suited for delivering information from a selected depth, the MS-OCT has been so far inferior to the conventional FFT based OCT in terms of time of producing cross section images. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real-time by assembling several T-scans from different depths. We analyze the conditions that ensure a real-time B-scan imaging operation, and demonstrate in-vivo real-time images from human fovea and the optic nerve, of comparable resolution and sensitivity to those produced using the traditional Fourier domain based method.

Simultaneous interrogation of interferometric and Bragg grating sensors

NASA Astrophysics Data System (ADS)

Brady, G.; Kalli, K.; Webb, D. J.; Jackson, D. A.; Reekie, L.; Archambault, J. L.

1995-06-01

We propose a new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source, which acts as a wavelength-tunable source for the grating and as a path-matched filter for the Fizeau interferometer, thus providing a high phase resolution output for each sensor. The grating sensor demonstrates a dynamic strain resolution of \\similar 0.05 mu 3 / \\radical Hz \\end-radical at 20 Hz, while the interferometric phase resolution is better than 1mrad/ \\radical Hz \\end-radical at 20 Hz, corresponding to an rms mirror displacement of 0.08 nm.

Simultaneous Temperature and Velocity Measurements in a Large-Scale, Supersonic, Heated Jet

NASA Technical Reports Server (NTRS)

Danehy, P. M.; Magnotti, G.; Bivolaru, D.; Tedder, S.; Cutler, A. D.

2008-01-01

Two laser-based measurement techniques have been used to characterize an axisymmetric, combustion-heated supersonic jet issuing into static room air. The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) measurement technique measured temperature and concentration while the interferometric Rayleigh scattering (IRS) method simultaneously measured two components of velocity. This paper reports a preliminary analysis of CARS-IRS temperature and velocity measurements from selected measurement locations. The temperature measurements show that the temperature along the jet axis remains constant while dropping off radially. The velocity measurements show that the nozzle exit velocity fluctuations are about 3% of the maximum velocity in the flow.

Noncommuting observables in quantum detection and estimation theory

NASA Technical Reports Server (NTRS)

Helstrom, C. W.

1972-01-01

Basing decisions and estimates on simultaneous approximate measurements of noncommuting observables in a quantum receiver is shown to be equivalent to measuring commuting projection operators on a larger Hilbert space than that of the receiver itself. The quantum-mechanical Cramer-Rao inequalities derived from right logarithmic derivatives and symmetrized logarithmic derivatives of the density operator are compared, and it is shown that the latter give superior lower bounds on the error variances of individual unbiased estimates of arrival time and carrier frequency of a coherent signal. For a suitably weighted sum of the error variances of simultaneous estimates of these, the former yield the superior lower bound under some conditions.

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

NASA Astrophysics Data System (ADS)

Ikezoe, R.; Ichimura, M.; Okada, T.; Itagaki, J.; Hirata, M.; Sumida, S.; Jang, S.; Izumi, K.; Tanaka, A.; Yoshikawa, M.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.

2017-03-01

A two-channel microwave reflectometer system with fast microwave antenna switching capability was developed and applied to the GAMMA 10 tandem mirror device to study high-frequency small-amplitude fluctuations in a hot mirror plasma. The fast switching of the antennas is controlled using PIN diode switches, which offers the significant advantage of reducing the number of high-cost microwave components and digitizers with high bandwidths and large memory that are required to measure the spatiotemporal behavior of the high-frequency fluctuations. The use of two channels rather than one adds the important function of a simultaneous two-point measurement in either the radial direction or the direction of the antenna array to measure the phase profile of the fluctuations along with the normal amplitude profile. The density fluctuations measured using this system clearly showed the high-frequency coherent fluctuations that are associated with Alfvén-ion-cyclotron (AIC) waves in GAMMA 10. A correlation analysis applied to simultaneously measured density fluctuations showed that the phase component that was included in a reflected microwave provided both high coherence and a clear phase difference for the AIC waves, while the amplitude component showed neither significant coherence nor clear phase difference. The axial phase differences of the AIC waves measured inside the hot plasma confirmed the formation of a standing wave structure. The axial variation of the radial profiles was evaluated and a clear difference was found among the AIC waves for the first time, which would be a key to clarify the unknown boundary conditions of the AIC waves.

Noise pair velocity and range echo location system

DOEpatents

Erskine, D.J.

1999-02-16

An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution is disclosed. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna. 46 figs.

Social risky decision-making reveals gender differences in the TPJ: A hyperscanning study using functional near-infrared spectroscopy.

PubMed

Zhang, Mingming; Liu, Tao; Pelowski, Matthew; Jia, Huibin; Yu, Dongchuan

2017-12-01

Previous neuroscience studies have investigated neural correlates of risky decision-making in a single-brain frame during pseudo social (predominantly non face-to-face) contexts. To fully understand the risky decision-making behavior in more natural social interactions, the present study employed a functional near-infrared spectroscopy (fNIRS) hyperscanning technique to simultaneously measure pairs of participants' fronto-temporal activations in a face-to-face gambling card-game. The intra-brain results revealed that both those who identified as males and as females showed higher activations in their mPFC and in the inferior parts of the frontopolar area, as well as in the tempo-parietal junction (TPJ) in cases involving higher versus lower risk. This is consistent with previous findings suggesting importance of the mentalizing network in decision tasks. The fNIRS results of inter-brain neural synchronization (INS) also revealed that males and females showed increased inter-brain coherence in the mPFC and dlPFC. Females, however, uniquely showed increased inter-brain coherence in the left TPJ. This INS result suggests that males may primarily depend on non-social cognitive ability to make a risky decision in a social interaction, while females may use both social and non-social cognitive abilities. The implications are also discussed for general topics of human interaction and two-person neuroscience. Copyright © 2017 Elsevier Inc. All rights reserved.

Coherent structures in a supersonic complex nozzle

NASA Astrophysics Data System (ADS)

Magstadt, Andrew; Berry, Matthew; Glauser, Mark

2016-11-01

The jet flow from a complex supersonic nozzle is studied through experimental measurements. The nozzle's geometry is motivated by future engine designs for high-performance civilian and military aircraft. This rectangular jet has a single plane of symmetry, an additional shear layer (referred to as a wall jet), and an aft deck representative of airframe integration. The core flow operates at a Mach number of Mj , c = 1 . 6 , and the wall jet is choked (Mj , w = 1 . 0). This high Reynolds number jet flow is comprised of intense turbulence levels, an intricate shock structure, shear and boundary layers, and powerful corner vortices. In the present study, stereo PIV measurements are simultaneously sampled with high-speed pressure measurements, which are embedded in the aft deck, and far-field acoustics in the anechoic chamber at Syracuse University. Time-resolved schlieren measurements have indicated the existence of strong flow events at high frequencies, at a Strouhal number of St = 3 . 4 . These appear to result from von Kàrmàn vortex shedding within the nozzle and pervade the entire flow and acoustic domain. Proper orthogonal decomposition is applied on the current data to identify coherent structures in the jet and study the influence of this vortex street. AFOSR Turbulence and Transition Program (Grant No. FA9550-15-1-0435) with program managers Dr. I. Leyva and Dr. R. Ponnappan.

In vivo molecular imaging of colorectal cancer using quantum dots targeted to vascular endothelial growth factor receptor 2 and optical coherence tomography/laser-induced fluorescence dual-modality imaging

NASA Astrophysics Data System (ADS)

Carbary-Ganz, Jordan L.; Welge, Weston A.; Barton, Jennifer K.; Utzinger, Urs

2015-09-01

Optical coherence tomography/laser induced fluorescence (OCT/LIF) dual-modality imaging allows for minimally invasive, nondestructive endoscopic visualization of colorectal cancer in mice. This technology enables simultaneous longitudinal tracking of morphological (OCT) and biochemical (fluorescence) changes as colorectal cancer develops, compared to current methods of colorectal cancer screening in humans that rely on morphological changes alone. We have shown that QDot655 targeted to vascular endothelial growth factor receptor 2 (QD655-VEGFR2) can be applied to the colon of carcinogen-treated mice and provides significantly increased contrast between the diseased and undiseased tissue with high sensitivity and specificity ex vivo. QD655-VEGFR2 was used in a longitudinal in vivo study to investigate the ability to correlate fluorescence signal to tumor development. QD655-VEGFR2 was applied to the colon of azoxymethane (AOM-) or saline-treated control mice in vivo via lavage. OCT/LIF images of the distal colon were taken at five consecutive time points every three weeks after the final AOM injection. Difficulties in fully flushing unbound contrast agent from the colon led to variable background signal; however, a spatial correlation was found between tumors identified in OCT images, and high fluorescence intensity of the QD655 signal, demonstrating the ability to detect VEGFR2 expressing tumors in vivo.

[The diagnostic usability of selected narrativity indices in stories about close relationships in the assessment of personality organization].

PubMed

Soroko, Emilia

2015-01-01

The aim of this study was to test the usability of selected narrativity indices identified from autobiographical accounts of important relationships in an assessment of neurotic (NPO) and borderline personality organization (BPO). Narrativity indices, both particular and generalized, were used to predict personality organization levels. Indices were derived from two separate layers of analysis: 1) lexical indices were counted with computer assistance; 2) evocative/reception indices dealing with coherence of the story were assessed using the competent judges method. It was found that the lexical narrativity index-the active "I"-was a good predictor of both BPO and NPO, while the human factor was a good predictor of BPO when low. Moreover, a generalized index was used to describe how stories are saturated with the narrativity indices of intentionality, concreteness, and active "I", but simultaneously deprived of human factor, and was found to be the best predictor of BPO. Furthermore, where the coherence of the story and of its subdimension (integration) rise, the probability of BPO diagnosis decreases. This research provides support for the thesis that surface narrativity indices may predict deeper personality structure. Its results are justified in the light of Kernberg's theory, and have the potential to become a useful tool in clinical practice as a supplementary source of information in diagnostic and psychotherapeutic processes.

Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles

PubMed Central

Wang, Tianyi; Jacob Mancuso, J.; Sapozhnikova, Veronika; Dwelle, Jordan; Ma, Li L.; Willsey, Brian; Shams Kazmi, S. M.; Qiu, Jinze; Li, Xiankai; Asmis, Reto; Johnston, Keith P.; Feldman, Marc D.

2012-01-01

Abstract. The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques. PMID:22502567

Noise pair velocity and range echo location system

DOEpatents

Erskine, David J.

1999-01-01

An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna.

In vivo layer visualization of rat olfactory bulb by a swept source optical coherence tomography and its confirmation through electrocoagulation and anatomy

PubMed Central

Watanabe, Hideyuki; Rajagopalan, Uma Maheswari; Nakamichi, Yu; Igarashi, Kei M.; Madjarova, Violeta Dimitrova; Kadono, Hirofumi; Tanifuji, Manabu

2011-01-01

Here, we report in vivo 3-D visualization of the layered organization of a rat olfactory bulb (OB) by a swept source optical coherence tomography (SS-OCT). The SS-OCT operates at a wavelength of 1334 nm with respective theoretical depth and lateral resolutions of 6.7 μm and 15.4 μm in air and hence it is possible to get a 3D structural map of OB in vivo at the micron level resolution with millimeter-scale imaging depth. Up until now, with methods such as MRI, confocal microscopy, OB depth structure in vivo had not been clearly visualized as these do not satisfy the criterion of simultaneously providing micron-scale spatial resolution and imaging up to a few millimeter in depth. In order to confirm the OB’s layered organization revealed by SS-OCT, we introduced the technique of electrocoagulation to make landmarks across the layered structure. To our knowledge this is such a first study that combines electrocoagulation and OCT in vivo of rat OB. Our results confirmed the layered organization of OB, and moreover the layers were clearly identified by electrocoagulation landmarks both in the OCT structural and anatomical slice images. We expect such a combined study is beneficial for both OCT and neuroscience fields. PMID:21833364

Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment.

PubMed

Dell'Omo, Roberto; Mura, Marco; Lesnik Oberstein, Sarit Y; Bijl, Heico; Tan, H Stevie

2012-04-01

To describe fundus autofluorescence and optical coherence tomography (OCT) features of the macula after pars plana vitrectomy for rhegmatogenous retinal detachment. Thirty-three eyes of 33 consecutive patients with repaired rhegmatogenous retinal detachment with or without the involvement of the macula were prospectively investigated with simultaneous fundus autofluorescence and OCT imaging using the Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany) within a few weeks after the operation. Fundus autofluorescence imaging of the macula showed lines of increased and decreased autofluorescence in 19 cases (57.6%). On OCT, these lines corresponded to the following abnormalities: outer retinal folds, inner retinal folds, and skip reflectivity abnormalities of the photoreceptor inner segment/outer segment band. Other OCT findings, not related to abnormal lines on fundus autofluorescence, consisted of disruption of photoreceptor inner segment/outer segment band and collection of intraretinal or subretinal fluid. The presence of outer retinal folds significantly related to metamorphopsia but did not relate to poor postoperative visual acuity. Partial-thickness retinal folds occur commonly after vitrectomy for rhegmatogenous retinal detachment repair and may represent an important anatomical substrate for postoperative metamorphopsia. Fundus autofluorescence and OCT are both sensitive techniques for the detection of these abnormalities.

Simultaneous manipulation and observation of multiple ro-vibrational eigenstates in solid para-hydrogen.

PubMed

Katsuki, Hiroyuki; Ohmori, Kenji

2016-09-28

We have experimentally performed the coherent control of delocalized ro-vibrational wave packets (RVWs) of solid para-hydrogen (p-H 2 ) by the wave packet interferometry (WPI) combined with coherent anti-Stokes Raman scattering (CARS). RVWs of solid p-H 2 are delocalized in the crystal, and the wave function with wave vector k ∼ 0 is selectively excited via the stimulated Raman process. We have excited the RVW twice by a pair of femtosecond laser pulses with delay controlled by a stabilized Michelson interferometer. Using a broad-band laser pulse, multiple ro-vibrational states can be excited simultaneously. We have observed the time-dependent Ramsey fringe spectra as a function of the inter-pulse delay by a spectrally resolved CARS technique using a narrow-band probe pulse, resolving the different intermediate states. Due to the different fringe oscillation periods among those intermediate states, we can manipulate their amplitude ratio by tuning the inter-pulse delay on the sub-femtosecond time scale. The state-selective manipulation and detection of the CARS signal combined with the WPI is a general and efficient protocol for the control of the interference of multiple quantum states in various quantum systems.

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

Guha, Saikat; Shapiro, Jeffrey H.; Erkmen, Baris I.

Previous work on the classical information capacities of bosonic channels has established the capacity of the single-user pure-loss channel, bounded the capacity of the single-user thermal-noise channel, and bounded the capacity region of the multiple-access channel. The latter is a multiple-user scenario in which several transmitters seek to simultaneously and independently communicate to a single receiver. We study the capacity region of the bosonic broadcast channel, in which a single transmitter seeks to simultaneously and independently communicate to two different receivers. It is known that the tightest available lower bound on the capacity of the single-user thermal-noise channel is thatmore » channel's capacity if, as conjectured, the minimum von Neumann entropy at the output of a bosonic channel with additive thermal noise occurs for coherent-state inputs. Evidence in support of this minimum output entropy conjecture has been accumulated, but a rigorous proof has not been obtained. We propose a minimum output entropy conjecture that, if proved to be correct, will establish that the capacity region of the bosonic broadcast channel equals the inner bound achieved using a coherent-state encoding and optimum detection. We provide some evidence that supports this conjecture, but again a full proof is not available.« less

Simultaneous confocal fluorescence microscopy and optical coherence tomography for drug distribution and tissue integrity assessment

NASA Astrophysics Data System (ADS)

Rinehart, Matthew T.; LaCroix, Jeffrey; Henderson, Marcus; Katz, David; Wax, Adam

2011-03-01

The effectiveness of microbicidal gels, topical products developed to prevent infection by sexually transmitted diseases including HIV/AIDS, is governed by extent of gel coverage, pharmacokinetics of active pharmaceutical ingredients (APIs), and integrity of vaginal epithelium. While biopsies provide localized information about drug delivery and tissue structure, in vivo measurements are preferable in providing objective data on API and gel coating distribution as well as tissue integrity. We are developing a system combining confocal fluorescence microscopy with optical coherence tomography (OCT) to simultaneously measure local concentrations and diffusion coefficients of APIs during transport from microbicidal gels into tissue, while assessing tissue integrity. The confocal module acquires 2-D images of fluorescent APIs multiple times per second allowing analysis of lateral diffusion kinetics. The custom Fourier domain OCT module has a maximum a-scan rate of 54 kHz and provides depth-resolved tissue integrity information coregistered with the confocal fluorescence measurements. The combined system is validated by imaging phantoms with a surrogate fluorophore. Time-resolved API concentration measured at fixed depths is analyzed for diffusion kinetics. This multimodal system will eventually be implemented in vivo for objective evaluation of microbicide product performance.

Identification of individual coherent sets associated with flow trajectories using Coherent Structure Coloring

NASA Astrophysics Data System (ADS)

Schlueter-Kuck, Kristy; Dabiri, John

2017-11-01

In recent years, there has been a proliferation of techniques that aim to characterize fluid flow kinematics on the basis of Lagrangian trajectories of collections of tracer particles. Most of these techniques depend on presence of tracer particles that are initially closely-spaced, in order to compute local gradients of their trajectories. In many applications, the requirement of close tracer spacing cannot be satisfied, especially when the tracers are naturally occurring and their distribution is dictated by the underlying flow. Moreover, current methods often focus on determination of the boundaries of coherent sets, whereas in practice it is often valuable to identify the complete set of trajectories that are coherent with an individual trajectory of interest. We extend the concept of Coherent Structure Coloring to achieve identification of the coherent set associated with individual Lagrangian trajectories. This algorithm is proven successful in identifying coherent structures of varying complexities in canonical unsteady flows. Importantly, although the method is demonstrated here in the context of fluid flow kinematics, the generality of the approach allows for its potential application to other unsupervised clustering problems in dynamical systems. This work was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Quantitative, simultaneous, and collinear eye-tracked, high dynamic range optical coherence tomography at 850 and 1060 nm

NASA Astrophysics Data System (ADS)

Mooser, Matthias; Burri, Christian; Stoller, Markus; Luggen, David; Peyer, Michael; Arnold, Patrik; Meier, Christoph; Považay, Boris

2017-07-01

Ocular optical coherence tomography at the wavelengths ranges of 850 and 1060 nm have been integrated with a confocal scanning laser ophthalmoscope eye-tracker as a clinical commercial-class system. Collinear optics enables an exact overlap of the different channels to produce precisely overlapping depth-scans for evaluating the similarities and differences between the wavelengths to extract additional physiologic information. A reliable segmentation algorithm utilizing Graphcuts has been implemented and applied to automatically extract retinal and choroidal shape in cross-sections and volumes. The device has been tested in normals and pathologies including a cross-sectional and longitudinal study of myopia progress and control with a duplicate instrument in Asian children.

Development of a parallel demodulation system used for extrinsic Fabry-Perot interferometer and fiber Bragg grating sensors.

PubMed

Jiang, Junfeng; Liu, Tiegen; Zhang, Yimo; Liu, Lina; Zha, Ying; Zhang, Fan; Wang, Yunxin; Long, Pin

2006-01-20

A parallel demodulation system for extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors is presented, which is based on a Michelson interferometer and combines the methods of low-coherence interference and a Fourier-transform spectrum. The parallel demodulation theory is modeled with Fourier-transform spectrum technology, and a signal separation method with an EFPI and FBG is proposed. The design of an optical path difference scanning and sampling method without a reference light is described. Experiments show that the parallel demodulation system has good spectrum demodulation and low-coherence interference demodulation performance. It can realize simultaneous strain and temperature measurements while keeping the whole system configuration less complex.

Dynamic analysis of mental sweating of eccrine sweat gland of human fingertip by time-sequential piled-up en face optical coherence tomography images.

PubMed

Ohmi, Masato; Wada, Yuki

2016-08-01

In this paper, we demonstrate dynamic analysis of mental sweating for sound stimulus of a few tens of eccrine sweat glands by the time-sequential piled-up en face optical coherence tomography (OCT) images with the frame spacing of 3.3 sec. In the experiment, the amount of excess sweat can be evaluated simultaneously for a few tens of sweat glands by piling up of all the en face OCT images. Non-uniformity was observed in mental sweating where the amount of sweat in response to sound stimulus is different for each sweat gland. Furthermore, the amount of sweat is significantly increased in proportion to the strength of the stimulus.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser.

PubMed

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-19

Dual-comb lasers simultaneously generating asynchronous ultrashort pulses could be an intriguing alternative to the current dual-laser comb source. When generated through a common light path, the low common-mode noises and good coherence between the pulse trains could be realized. Here we demonstrate the completely common-path, unidirectional dual-comb lasing using a carbon nanotube saturable absorber with additional pulse narrowing and broadening mechanisms. The interactions between multiple soliton formation mechanisms result in bifurcation into unusual two-pulse states with pulses of four-fold bandwidth difference and tens-of-Hz repetition rate difference. Coherence between the pulses is verified by the asynchronous cross-sampling and dual-comb spectroscopy measurements.

Coherently coupling distinct spin ensembles through a high critical temperature superconducting resonator

NASA Astrophysics Data System (ADS)

Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Affronte, Marco

The problem of coupling remote ensembles of two-level systems through cavity photons is revisited by using molecular spin centers and a high critical temperature superconducting coplanar resonator. By using PyBTM organic radicals, we achieved the strong coupling regime with values of the cooperativity reaching 4300 at 2 K. We show that up to three distinct spin ensembles are simultaneously coupled through the resonator mode. The ensembles are made physically distinguishable by chemically varying the g-factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.

A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

NASA Astrophysics Data System (ADS)

Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

2017-02-01

We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

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.

Coherent Activity in Bilateral Parieto-Occipital Cortices during P300-BCI Operation.

PubMed

Takano, Kouji; Ora, Hiroki; Sekihara, Kensuke; Iwaki, Sunao; Kansaku, Kenji

2014-01-01

The visual P300 brain-computer interface (BCI), a popular system for electroencephalography (EEG)-based BCI, uses the P300 event-related potential to select an icon arranged in a flicker matrix. In earlier studies, we used green/blue (GB) luminance and chromatic changes in the P300-BCI system and reported that this luminance and chromatic flicker matrix was associated with better performance and greater subject comfort compared with the conventional white/gray (WG) luminance flicker matrix. To highlight areas involved in improved P300-BCI performance, we used simultaneous EEG-fMRI recordings and showed enhanced activities in bilateral and right lateralized parieto-occipital areas. Here, to capture coherent activities of the areas during P300-BCI, we collected whole-head 306-channel magnetoencephalography data. When comparing functional connectivity between the right and left parieto-occipital channels, significantly greater functional connectivity in the alpha band was observed under the GB flicker matrix condition than under the WG flicker matrix condition. Current sources were estimated with a narrow-band adaptive spatial filter, and mean imaginary coherence was computed in the alpha band. Significantly greater coherence was observed in the right posterior parietal cortex under the GB than under the WG condition. Re-analysis of previous EEG-based P300-BCI data showed significant correlations between the power of the coherence of the bilateral parieto-occipital cortices and their performance accuracy. These results suggest that coherent activity in the bilateral parieto-occipital cortices plays a significant role in effectively driving the P300-BCI.

Coherence-generating power of quantum dephasing processes

NASA Astrophysics Data System (ADS)

Styliaris, Georgios; Campos Venuti, Lorenzo; Zanardi, Paolo

2018-03-01

We provide a quantification of the capability of various quantum dephasing processes to generate coherence out of incoherent states. The measures defined, admitting computable expressions for any finite Hilbert-space dimension, are based on probabilistic averages and arise naturally from the viewpoint of coherence as a resource. We investigate how the capability of a dephasing process (e.g., a nonselective orthogonal measurement) to generate coherence depends on the relevant bases of the Hilbert space over which coherence is quantified and the dephasing process occurs, respectively. We extend our analysis to include those Lindblad time evolutions which, in the infinite-time limit, dephase the system under consideration and calculate their coherence-generating power as a function of time. We further identify specific families of such time evolutions that, although dephasing, have optimal (over all quantum processes) coherence-generating power for some intermediate time. Finally, we investigate the coherence-generating capability of random dephasing channels.

EEG spectral coherence data distinguish chronic fatigue syndrome patients from healthy controls and depressed patients--a case control study.

PubMed

Duffy, Frank H; McAnulty, Gloria B; McCreary, Michelle C; Cuchural, George J; Komaroff, Anthony L

2011-07-01

Previous studies suggest central nervous system involvement in chronic fatigue syndrome (CFS), yet there are no established diagnostic criteria. CFS may be difficult to differentiate from clinical depression. The study's objective was to determine if spectral coherence, a computational derivative of spectral analysis of the electroencephalogram (EEG), could distinguish patients with CFS from healthy control subjects and not erroneously classify depressed patients as having CFS. This is a study, conducted in an academic medical center electroencephalography laboratory, of 632 subjects: 390 healthy normal controls, 70 patients with carefully defined CFS, 24 with major depression, and 148 with general fatigue. Aside from fatigue, all patients were medically healthy by history and examination. EEGs were obtained and spectral coherences calculated after extensive artifact removal. Principal Components Analysis identified coherence factors and corresponding factor loading patterns. Discriminant analysis determined whether spectral coherence factors could reliably discriminate CFS patients from healthy control subjects without misclassifying depression as CFS. Analysis of EEG coherence data from a large sample (n = 632) of patients and healthy controls identified 40 factors explaining 55.6% total variance. Factors showed highly significant group differentiation (p < .0004) identifying 89.5% of unmedicated female CFS patients and 92.4% of healthy female controls. Recursive jackknifing showed predictions were stable. A conservative 10-factor discriminant function model was subsequently applied, and also showed highly significant group discrimination (p < .001), accurately classifying 88.9% unmedicated males with CFS, and 82.4% unmedicated male healthy controls. No patient with depression was classified as having CFS. The model was less accurate (73.9%) in identifying CFS patients taking psychoactive medications. Factors involving the temporal lobes were of primary importance. EEG spectral coherence analysis identified unmedicated patients with CFS and healthy control subjects without misclassifying depressed patients as CFS, providing evidence that CFS patients demonstrate brain physiology that is not observed in healthy normals or patients with major depression. Studies of new CFS patients and comparison groups are required to determine the possible clinical utility of this test. The results concur with other studies finding neurological abnormalities in CFS, and implicate temporal lobe involvement in CFS pathophysiology.

Cell-Type and State-Dependent Synchronization among Rodent Somatosensory, Visual, Perirhinal Cortex, and Hippocampus CA1

PubMed Central

Vinck, Martin; Bos, Jeroen J.; Van Mourik-Donga, Laura A.; Oplaat, Krista T.; Klein, Gerbrand A.; Jackson, Jadin C.; Gentet, Luc J.; Pennartz, Cyriel M. A.

2016-01-01

Beta and gamma rhythms have been hypothesized to be involved in global and local coordination of neuronal activity, respectively. Here, we investigated how cells in rodent area S1BF are entrained by rhythmic fluctuations at various frequencies within the local area and in connected areas, and how this depends on behavioral state and cell type. We performed simultaneous extracellular field and unit recordings in four connected areas of the freely moving rat (S1BF, V1M, perirhinal cortex, CA1). S1BF spiking activity was strongly entrained by both beta and gamma S1BF oscillations, which were associated with deactivations and activations, respectively. We identified multiple classes of fast spiking and excitatory cells in S1BF, which showed prominent differences in rhythmic entrainment and in the extent to which phase locking was modulated by behavioral state. Using an additional dataset acquired by whole-cell recordings in head-fixed mice, these cell classes could be compared with identified phenotypes showing gamma rhythmicity in their membrane potential. We next examined how S1BF cells were entrained by rhythmic fluctuations in connected brain areas. Gamma-synchronization was detected in all four areas, however we did not detect significant gamma coherence among these areas. Instead, we only found long-range coherence in the theta-beta range among these areas. In contrast to local S1BF synchronization, we found long-range S1BF-spike to CA1–LFP synchronization to be homogeneous across inhibitory and excitatory cell types. These findings suggest distinct, cell-type contributions of low and high-frequency synchronization to intra- and inter-areal neuronal interactions. PMID:26834582

A review of risk factors for bovine tuberculosis infection in cattle in the UK and Ireland.

PubMed

Broughan, J M; Judge, J; Ely, E; Delahay, R J; Wilson, G; Clifton-Hadley, R S; Goodchild, A V; Bishop, H; Parry, J E; Downs, S H

2016-10-01

Bovine tuberculosis (bTB) is an important disease of cattle caused by infection with Mycobacterium bovis, a pathogen that may be extremely difficult to eradicate in the presence of a true wildlife reservoir. Our objective was to identify and review relevant literature and provide a succinct summary of current knowledge of risk factors for transmission of infection of cattle. Search strings were developed to identify publications from electronic databases to February 2015. Abstracts of 4255 papers identified were reviewed by three reviewers to determine whether the entire article was likely to contain relevant information. Risk factors could be broadly grouped as follows: animal (including nutrition and genetics), herd (including bTB and testing history), environment, wildlife and social factors. Many risk factors are inter-related and study designs often do not enable differentiation between cause and consequence of infection. Despite differences in study design and location, some risk factors are consistently identified, e.g. herd size, bTB history, presence of infected wildlife, whereas the evidence for others is less consistent and coherent, e.g. nutrition, local cattle movements. We have identified knowledge gaps where further research may result in an improved understanding of bTB transmission dynamics. The application of targeted, multifactorial disease control regimens that address a range of risk factors simultaneously is likely to be a key to effective, evidence-informed control strategies.

Assessing change in sensitivity of tropical vegetation to climate based on wavelet analysis

NASA Astrophysics Data System (ADS)

Claessen, J.; Martens, B.; Verhoest, N.; Molini, A.; Miralles, D. G.

2017-12-01

Vegetation dynamics are driven by climate, and at the same time they play a key role in forcing the different bio-geochemical cycles. As climate change leads to an increase in frequency and intensity of hydro-meteorological extremes, vegetation is expected to respond to these changes, and subsequently feed back on their occurrence. Future responses can be better understood by analysing the past using time series of different vegetation diagnostics observed from space, both in the optical and microwave domain. In this contribution, the climatic drivers (air temperature, precipitation, and incoming radiation) of these different vegetation diagnostics are analysed using a monthly global data-cube of 32 years at a 0.25° resolution. To do so, we analyse the wavelet coherence between each vegetation index and the climatic drivers of vegetation. The use of wavelet coherence allows unveiling the different response and sensitivity of the diverse vegetation indices to their climatic drivers, simultaneously in the time and frequency domains. Our results show that the wavelet-based statistics are suitable for extracting information from the different vegetation indices. Areas of high rainfall volumes are characterised by a strong control of radiation and temperature over vegetation. At higher latitudes, the positive trends in all vegetation diagnostics agree with the hypothesis of a greening pattern, which is coherent with the increase in temperature. At the same time, substantial differences can be observed between the responses of the different vegetation indices as well. As an example, the VOD - thought to be a close proxy for vegetation water content - shows a larger sensitivity to precipitation than traditional optical indices such as the NDVI. Further, important temporal changes in the wavelet coherence between vegetation and climate are identified. For instance, the Amazonian rainforest shows an increased correspondence with precipitation dynamics, indicating positive shifts in ecosystem sensitivity to water availability, which can arguably be related to an increase in the amplitude of the seasonal cycle in rainfall. These results are in line with the expected intensification of the water cycle due to climate change and point to the complex response of the biosphere to climatic changes.

Evolution equation for quantum coherence

PubMed Central

Hu, Ming-Liang; Fan, Heng

2016-01-01

The estimation of the decoherence process of an open quantum system is of both theoretical significance and experimental appealing. Practically, the decoherence can be easily estimated if the coherence evolution satisfies some simple relations. We introduce a framework for studying evolution equation of coherence. Based on this framework, we prove a simple factorization relation (FR) for the l1 norm of coherence, and identified the sets of quantum channels for which this FR holds. By using this FR, we further determine condition on the transformation matrix of the quantum channel which can support permanently freezing of the l1 norm of coherence. We finally reveal the universality of this FR by showing that it holds for many other related coherence and quantum correlation measures. PMID:27382933

Coherent motion threshold measurements for M-cell deficit differ for above- and below-average readers.

PubMed

Solan, Harold A; Hansen, Peter C; Shelley-Tremblay, John; Ficarra, Anthony

2003-11-01

Research during the past 20 years has influenced the management of diagnosis and treatment of children identified as having learning-related vision problems. The intent of this study is to determine whether coherent motion threshold testing can distinguish better-than-average non-disabled (ND) readers from those who are moderately reading disabled (RD) among sixth-grade students. A sample of 23 better-than-average non-disabled readers (> or = 80th percentile) and 27 moderately disabled readers (< or = 32nd percentile) were identified using a standardized reading comprehension test. Each participant was tested for coherent motion threshold. Previous psychophysical and fMRI research with adults suggests that coherent motion threshold is a valid measure of magnocellular (M-cell) integrity. The average of two coherent motion threshold trials was significantly greater for moderately reading disabled subjects than for above-average readers (p < 0.01). The mean threshold percentage of dots required to observe lateral motion was 9.2% for moderately reading disabled readers and 4.6% for superior readers (p = 0.001). The outcome of this preliminary study provides an efficient procedure to identify sixth-grade students whose reading disability may be associated with an M-cell deficit. Our previous investigations involving visual processing, visual attention, and oculomotor therapy have resulted in significant improvements in reading comprehension, visual attention, and eye movements. It remains to be demonstrated whether vision therapy has an impact on the M-cell deficit, as measured with coherent motion threshold testing for moderately disabled readers.

Dynamic isoperimetry and the geometry of Lagrangian coherent structures

NASA Astrophysics Data System (ADS)

Froyland, Gary

2015-10-01

The study of transport and mixing processes in dynamical systems is particularly important for the analysis of mathematical models of physical systems. We propose a novel, direct geometric method to identify subsets of phase space that remain strongly coherent over a finite time duration. This new method is based on a dynamic extension of classical (static) isoperimetric problems; the latter are concerned with identifying submanifolds with the smallest boundary size relative to their volume. The present work introduces dynamic isoperimetric problems; the study of sets with small boundary size relative to volume as they are evolved by a general dynamical system. We formulate and prove dynamic versions of the fundamental (static) isoperimetric (in)equalities; a dynamic Federer-Fleming theorem and a dynamic Cheeger inequality. We introduce a new dynamic Laplace operator and describe a computational method to identify coherent sets based on eigenfunctions of the dynamic Laplacian. Our results include formal mathematical statements concerning geometric properties of finite-time coherent sets, whose boundaries can be regarded as Lagrangian coherent structures. The computational advantages of our new approach are a well-separated spectrum for the dynamic Laplacian, and flexibility in appropriate numerical approximation methods. Finally, we demonstrate that the dynamic Laplace operator can be realised as a zero-diffusion limit of a newly advanced probabilistic transfer operator method [9] for finding coherent sets, which is based on small diffusion. Thus, the present approach sits naturally alongside the probabilistic approach [9], and adds a formal geometric interpretation.

Doppler Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Chen, Zhongping; Zhang, Jun

Noninvasive techniques for imaging in vivo blood flow are of great value to biomedical research and clinical diagnostics where many diseases have a vascular etiology or component. In ophthalmology, many diseases involve disturbances in ocular blood flow, including diabetic retinopathy, low tension glaucoma, anterior ischemic optic neuritis, and macular degeneration. Simultaneous imaging of tissue structure and blood flow could provide critical information for early diagnosis of ocular diseases.

Constraints for proton structure fluctuations from exclusive scattering

NASA Astrophysics Data System (ADS)

Mäntysaari, H.; Schenke, B.

2017-08-01

We constrain the average density profile of the proton and the amount of event-by-event fluctuations by simultaneously calculating the coherent and incoherent exclusive diffractive vector meson production cross section in deep inelastic scattering. Working within the Color Glass Condensate picture, we find that the gluonic density of the proton must have large geometric fluctuations in order to describe the experimentally measured large incoherent cross section.

Laser a balayage spectral double-bande pour l'imagerie biomedicale multimodale

NASA Astrophysics Data System (ADS)

Goulamhoussen, Nadir

A novel swept laser providing simultaneous dual-band (780nm and 1 300 nm) wavelength scanning has been designed for use in multimodal imaging systems. The swept laser is based on two gain media : a fibered semiconductor optical amplifier (SOA) centered at 1 300nm and a free-space laser diode centered at 780 nm. Simultaneous wavelength tuning for both bands is obtained by separate wavelength filters set up around the same rotating polygonal mirror. For each band, a telescope in an infinite conjugate setup converges the wavelengths dispersed by a grating on the polygon. The polygon reflects back a narrow band of wavelengths for amplification in the gain medium. Rotating the polygon enables wavelength tuning and imaging at a rate of 6 000 to 30 000 spectral lines/s, or A-lines/s in Optical Coherence Tomography (OCT). The 780nm source has a bandwidth of 37 nm, a fibered output power of 54 mW and a coherence length of 11 mm. The 1 300nm source has a bandwidth of 75 nm, a fibered output power of 17mW and a coherence length of 7.2 mm. Three multimodal systems were designed to test the potential of the swept laser in biomedical imaging. A two color OCT which allows three-dimensional in depth imaging of biological tissues with good morphological contrast was first designed, including a novel arrangement for balanced detection in both bands. A simultaneous OCT and SECM instrument was also built in which spectrally encoded confocal microscopy (SECM) provides en face images of subcellular features with high resolution on top of the 3D high penetration image obtained by OCT. Finally, a system combining OCT with fluorescence was designed, thus adding functional imaging to structural OCT images. There are many prospective paths for these three modalities, first among them the adaptation of the systems such that they may be used with imaging probes. One potential solution would be the development of novel fiber components to combine the illumination of theses modalities while demultiplexing their detection, and as would be the development of new optomechanics to enable 3D real-time in vivo imaging.

Nonlinear characterization of elasticity using quantitative optical coherence elastography.

PubMed

Qiu, Yi; Zaki, Farzana R; Chandra, Namas; Chester, Shawn A; Liu, Xuan

2016-11-01

Optical coherence elastography (OCE) has been used to perform mechanical characterization on biological tissue at the microscopic scale. In this work, we used quantitative optical coherence elastography (qOCE), a novel technology we recently developed, to study the nonlinear elastic behavior of biological tissue. The qOCE system had a fiber-optic probe to exert a compressive force to deform tissue under the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to simultaneously quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation. In other words, our qOCE system allowed us to establish the relationship between mechanical stimulus and tissue response to characterize the stiffness of biological tissue. Most biological tissues have nonlinear elastic behavior, and the apparent stress-strain relationship characterized by our qOCE system was nonlinear an extended range of strain, for a tissue-mimicking phantom as well as biological tissues. Our experimental results suggested that the quantification of force in OCE was critical for accurate characterization of tissue mechanical properties and the qOCE technique was capable of differentiating biological tissues based on the elasticity of tissue that is generally nonlinear.

Three years coherent space to ground links: performance results and outlook for the optical ground station equipped with adaptive optics

NASA Astrophysics Data System (ADS)

Gregory, M.; Troendle, D.; Muehlnikel, G.; Heine, F.; Meyer, R.; Lutzer, M.; Czichy, R.

2013-03-01

Tesat is performing inter-satellite links (ISLs) for over 5 years now. Besides the successful demonstration of the suitability of coherent laser communication for high speed data transmission in space, Tesat has also conducted two major satellite to ground link (SGL) campaigns during the last 3 years. A transportable ground station has been developed to measure the impact of atmospheric turbulence to the coherent system. The SGLs have been performed between the Tesat optical ground station and the two LEO satellites TerraSAR-X and NFIRE, both equipped with a Tesat LCT. The capability of the LCTs of measuring the signal intensity on a direct detection sensor and on a coherent sensor simultaneously makes the system unique for investigating the atmospheric distortion impacts. In this paper the main results of the SGL campaigns are presented, including BER performance for the uplink and downlink. Measured scintillation profiles versus elevation angles at different weather conditions are illustrated. Finally preliminary results of an adaptive optics system are presented that has been developed to be used in the transportable adaptive optical ground station (T-AOGS) acting as the counter terminal for the LCT mounted on Alphasat, a geostationary satellite of the European Space Agency (ESA), in autumn 2013.

Discrimination of coherent features in turbulent boundary layers by the entropy method

NASA Technical Reports Server (NTRS)

Corke, T. C.; Guezennec, Y. G.

1984-01-01

Entropy in information theory is defined as the expected or mean value of the measure of the amount of self-information contained in the ith point of a distribution series x sub i, based on its probability of occurrence p(x sub i). If p(x sub i) is the probability of the ith state of the system in probability space, then the entropy, E(X) = - sigma p(x sub i) logp (x sub i), is a measure of the disorder in the system. Based on this concept, a method was devised which sought to minimize the entropy in a time series in order to construct the signature of the most coherent motions. The constrained minimization was performed using a Lagrange multiplier approach which resulted in the solution of a simultaneous set of non-linear coupled equations to obtain the coherent time series. The application of the method to space-time data taken by a rake of sensors in the near-wall region of a turbulent boundary layer was presented. The results yielded coherent velocity motions made up of locally decelerated or accelerated fluid having a streamwise scale of approximately 100 nu/u(tau), which is in qualitative agreement with the results from other less objective discrimination methods.

Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature

PubMed Central

Kern, Jan; Alonso-Mori, Roberto; Tran, Rosalie; Hattne, Johan; Gildea, Richard J.; Echols, Nathaniel; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G.; Lassalle-Kaiser, Benedikt; Koroidov, Sergey; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Miahnahri, Alan; Schafer, Donald W.; Messerschmidt, Marc; Seibert, M. Marvin; Koglin, Jason E.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J.; Grosse-Kunstleve, Ralf W.; Zwart, Petrus H.; White, William E.; Glatzel, Pieter; Adams, Paul D.; Bogan, Michael J.; Williams, Garth J.; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Sauter, Nicholas K.; Yachandra, Vittal K.; Bergmann, Uwe; Yano, Junko

2013-01-01

Intense femtosecond X-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous X-ray diffraction (XRD) and X-ray emission spectroscopy (XES) of microcrystals of Photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD/XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies. PMID:23413188

Simultaneous femtosecond X-ray spectroscopy and diffraction of photosystem II at room temperature.

PubMed

Kern, Jan; Alonso-Mori, Roberto; Tran, Rosalie; Hattne, Johan; Gildea, Richard J; Echols, Nathaniel; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G; Lassalle-Kaiser, Benedikt; Koroidov, Sergey; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; Difiore, Dörte; Milathianaki, Despina; Fry, Alan R; Miahnahri, Alan; Schafer, Donald W; Messerschmidt, Marc; Seibert, M Marvin; Koglin, Jason E; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J; Grosse-Kunstleve, Ralf W; Zwart, Petrus H; White, William E; Glatzel, Pieter; Adams, Paul D; Bogan, Michael J; Williams, Garth J; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Sauter, Nicholas K; Yachandra, Vittal K; Bergmann, Uwe; Yano, Junko

2013-04-26

Intense femtosecond x-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous x-ray diffraction (XRD) and x-ray emission spectroscopy (XES) of microcrystals of photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD-XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation-sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies.

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

Lingerfelt, David B.; Lestrange, Patrick J.; Radler, Joseph J.

Materials and molecular systems exhibiting long-lived electronic coherence can facilitate coherent transport, opening the door to efficient charge and energy transport beyond traditional methods. Recently, signatures of a possible coherent, recurrent electronic motion were identified in femtosecond pump-probe spectroscopy experiments on a binuclear platinum complex, where a persistent periodic beating in the transient absorption signal’s anisotropy was observed. In this study, we investigate the excitonic dynamics that underlie the suspected electronic coherence for a series of binuclear platinum complexes exhibiting a range of interplatinum distances. Results suggest that the long-lived coherence can only result when competitive electronic couplings are inmore » balance. At longer Pt-Pt distances, the electronic couplings between the two halves of the binuclear system weaken, and exciton localization and recombination is favored on short time scales. For short Pt-Pt distances, electronic couplings between the states in the coherent superposition are stronger than the coupling with other excitonic states, leading to long-lived coherence.« less

Spatial correlations of interdecadal variation in global surface temperatures

NASA Technical Reports Server (NTRS)

Mann, Michael E.; Park, Jeffrey

1993-01-01

We have analyzed spatial correlation patterns of interdecadal global surface temperature variability from an empirical perspective. Using multitaper coherence estimates from 140-yr records, we find that correlations between hemispheres are significant at about 95 percent confidence for nonrandomness for most of the frequency band in the 0.06-0.24 cyc/yr range. Coherence estimates of pairs of 100-yr grid-point temperature data series near 5-yr period reveal teleconnection patterns consistent with known patterns of ENSO variability. Significant correlated variability is observed near 15 year period, with the dominant teleconnection pattern largely confined to the Northern Hemisphere. Peak-to-peak Delta-T is at about 0.5 deg, with simultaneous warming and cooling of discrete patches on the earth's surface. A global average of this pattern would largely cancel.

Implementation of biological tissue Mueller matrix for polarization-sensitive optical coherence tomography based on LabVIEW

NASA Astrophysics Data System (ADS)

Lin, Yongping; Zhang, Xiyang; He, Youwu; Cai, Jianyong; Li, Hui

2018-02-01

The Jones matrix and the Mueller matrix are main tools to study polarization devices. The Mueller matrix can also be used for biological tissue research to get complete tissue properties, while the commercial optical coherence tomography system does not give relevant analysis function. Based on the LabVIEW, a near real time display method of Mueller matrix image of biological tissue is developed and it gives the corresponding phase retardant image simultaneously. A quarter-wave plate was placed at 45 in the sample arm. Experimental results of the two orthogonal channels show that the phase retardance based on incident light vector fixed mode and the Mueller matrix based on incident light vector dynamic mode can provide an effective analysis method of the existing system.

Pure-rotational H2 thermometry by ultrabroadband coherent anti-Stokes Raman spectroscopy.

PubMed

Courtney, Trevor L; Bohlin, Alexis; Patterson, Brian D; Kliewer, Christopher J

2017-06-14

Coherent anti-Stokes Raman spectroscopy (CARS) is a sensitive technique for probing highly luminous flames in combustion applications to determine temperatures and species concentrations. CARS thermometry has been demonstrated for the vibrational Q-branch and pure-rotational S-branch of several small molecules. Practical advantages of pure-rotational CARS, such as multi-species detection, reduction of coherent line mixing and collisional narrowing even at high pressures, and the potential for more precise thermometry, have motivated experimental and theoretical advances in S-branch CARS of nitrogen (N 2 ), for example, which is a dominant species in air-fed combustion processes. Although hydrogen (H 2 ) is of interest given its prevalence as a reactant and product in many gas-phase reactions, laser bandwidth limitations have precluded the extension of CARS thermometry to the H 2 S-branch. We demonstrate H 2 thermometry using hybrid femtosecond/picosecond pure-rotational CARS, in which a broadband pump/Stokes pulse enables simultaneous excitation of the set of H 2 S-branch transitions populated at flame temperatures over the spectral region of 0-2200 cm -1 . We present a pure-rotational H 2 CARS spectral model for data fitting and compare extracted temperatures to those from simultaneously collected N 2 spectra in two systems of study: a heated flow and a diffusion flame on a Wolfhard-Parker slot burner. From 300 to 650 K in the heated flow, the H 2 and N 2 CARS extracted temperatures are, on average, within 2% of the set temperature. For flame measurements, the fitted H 2 and N 2 temperatures are, on average, within 5% of each other from 300 to 1600 K. Our results confirm the viability of pure-rotational H 2 CARS thermometry for probing combustion reactions.

Pure-rotational H2 thermometry by ultrabroadband coherent anti-Stokes Raman spectroscopy

NASA Astrophysics Data System (ADS)

Courtney, Trevor L.; Bohlin, Alexis; Patterson, Brian D.; Kliewer, Christopher J.

2017-06-01

Coherent anti-Stokes Raman spectroscopy (CARS) is a sensitive technique for probing highly luminous flames in combustion applications to determine temperatures and species concentrations. CARS thermometry has been demonstrated for the vibrational Q-branch and pure-rotational S-branch of several small molecules. Practical advantages of pure-rotational CARS, such as multi-species detection, reduction of coherent line mixing and collisional narrowing even at high pressures, and the potential for more precise thermometry, have motivated experimental and theoretical advances in S-branch CARS of nitrogen (N2), for example, which is a dominant species in air-fed combustion processes. Although hydrogen (H2) is of interest given its prevalence as a reactant and product in many gas-phase reactions, laser bandwidth limitations have precluded the extension of CARS thermometry to the H2 S-branch. We demonstrate H2 thermometry using hybrid femtosecond/picosecond pure-rotational CARS, in which a broadband pump/Stokes pulse enables simultaneous excitation of the set of H2 S-branch transitions populated at flame temperatures over the spectral region of 0-2200 cm-1. We present a pure-rotational H2 CARS spectral model for data fitting and compare extracted temperatures to those from simultaneously collected N2 spectra in two systems of study: a heated flow and a diffusion flame on a Wolfhard-Parker slot burner. From 300 to 650 K in the heated flow, the H2 and N2 CARS extracted temperatures are, on average, within 2% of the set temperature. For flame measurements, the fitted H2 and N2 temperatures are, on average, within 5% of each other from 300 to 1600 K. Our results confirm the viability of pure-rotational H2 CARS thermometry for probing combustion reactions.

Movement-related changes in local and long-range synchronization in Parkinson’s disease revealed by simultaneous magnetoencephalography and intracranial recordings

PubMed Central

Litvak, Vladimir; Eusebio, Alexandre; Jha, Ashwani; Oostenveld, Robert; Barnes, Gareth; Foltynie, Tom; Limousin, Patricia; Zrinzo, Ludvic; Hariz, Marwan I.; Friston, Karl; Brown, Peter

2012-01-01

Functional neurosurgery has afforded the opportunity to assess interactions between populations of neurons in the human cerebral cortex and basal ganglia in patients with Parkinson’s disease (PD). Interactions occur over a wide range of frequencies, and the functional significance of those above 30 Hz is particularly unclear. Do they improve movement and, if so, in what way? We acquired simultaneously magnetoencephalography (MEG) and direct recordings from the subthalamic nucleus (STN) in 17 PD patients. We examined the effect of synchronous and sequential finger movements and of the dopamine prodrug levodopa on induced power in the contralateral primary motor cortex (M1) and STN and on the coherence between the two structures. We observed discrete peaks in M1 and STN power over 60-90 Hz and 300-400 Hz. All these power peaks increased with movement and levodopa treatment. Only STN activity over 60-90 Hz was coherent with activity in M1. Directionality analysis showed that STN gamma activity at 60-90 Hz tended to drive gamma activity in M1. The effects of levodopa on both local and distant synchronisation over 60-90 Hz correlated with the degree of improvement in bradykinesia-rigidity, as did local STN activity at 300-400 Hz. Despite this, there were no effects of movement type, nor interactions between movement type and levodopa in the STN, nor in the coherence between STN and M1. We conclude that synchronisation over 60-90 Hz in the basal ganglia cortical network is prokinetic, but likely through a modulatory effect rather than any involvement in explicit motor processing. PMID:22855804

Movement-related changes in local and long-range synchronization in Parkinson's disease revealed by simultaneous magnetoencephalography and intracranial recordings.

PubMed

Litvak, Vladimir; Eusebio, Alexandre; Jha, Ashwani; Oostenveld, Robert; Barnes, Gareth; Foltynie, Tom; Limousin, Patricia; Zrinzo, Ludvic; Hariz, Marwan I; Friston, Karl; Brown, Peter

2012-08-01

Functional neurosurgery has afforded the opportunity to assess interactions between populations of neurons in the human cerebral cortex and basal ganglia in patients with Parkinson's disease (PD). Interactions occur over a wide range of frequencies, and the functional significance of those >30 Hz is particularly unclear. Do they improve movement, and, if so, in what way? We acquired simultaneously magnetoencephalography and direct recordings from the subthalamic nucleus (STN) in 17 PD patients. We examined the effect of synchronous and sequential finger movements and of the dopamine prodrug levodopa on induced power in the contralateral primary motor cortex (M1) and STN and on the coherence between the two structures. We observed discrete peaks in M1 and STN power at 60-90 Hz and at 300-400 Hz. All these power peaks increased with movement and levodopa treatment. Only STN activity at 60-90 Hz was coherent with activity in M1. Directionality analysis showed that STN gamma activity at 60-90 Hz tended to drive gamma activity in M1. The effects of levodopa on both local and distant synchronization at 60-90 Hz correlated with the degree of improvement in bradykinesia-rigidity as did local STN activity at 300-400 Hz. Despite this, there were no effects of movement type, nor interactions between movement type and levodopa in the STN, nor in the coherence between STN and M1. We conclude that synchronization at 60-90 Hz in the basal ganglia cortical network is prokinetic but likely through a modulatory effect rather than any involvement in explicit motor processing.

Split-probe hybrid femtosecond/picosecond rotational CARS for time-domain measurement of S-branch Raman linewidths within a single laser shot.

PubMed

Patterson, Brian D; Gao, Yi; Seeger, Thomas; Kliewer, Christopher J

2013-11-15

We introduce a multiplex technique for the single-laser-shot determination of S-branch Raman linewidths with high accuracy and precision by implementing hybrid femtosecond (fs)/picosecond (ps) rotational coherent anti-Stokes Raman spectroscopy (CARS) with multiple spatially and temporally separated probe beams derived from a single laser pulse. The probe beams scatter from the rotational coherence driven by the fs pump and Stokes pulses at four different probe pulse delay times spanning 360 ps, thereby mapping collisional coherence dephasing in time for the populated rotational levels. The probe beams scatter at different folded BOXCARS angles, yielding spatially separated CARS signals which are collected simultaneously on the charge coupled device camera. The technique yields a single-shot standard deviation (1σ) of less than 3.5% in the determination of Raman linewidths and the average linewidth values obtained for N(2) are within 1% of those previously reported. The presented technique opens the possibility for correcting CARS spectra for time-varying collisional environments in operando.

Round-robin differential-phase-shift quantum key distribution with heralded pair-coherent sources

NASA Astrophysics Data System (ADS)

Wang, Le; Zhao, Shengmei

2017-04-01

Round-robin differential-phase-shift (RRDPS) quantum key distribution (QKD) scheme provides an effective way to overcome the signal disturbance from the transmission process. However, most RRDPS-QKD schemes use weak coherent pulses (WCPs) as the replacement of the perfect single-photon source. Considering the heralded pair-coherent source (HPCS) can efficiently remove the shortcomings of WCPs, we propose a RRDPS-QKD scheme with HPCS in this paper. Both infinite-intensity decoy-state method and practical three-intensity decoy-state method are adopted to discuss the tight bound of the key rate of the proposed scheme. The results show that HPCS is a better candidate for the replacement of the perfect single-photon source, and both the key rate and the transmission distance are greatly increased in comparison with those results with WCPs when the length of the pulse trains is small. Simultaneously, the performance of the proposed scheme using three-intensity decoy states is close to that result using infinite-intensity decoy states when the length of pulse trains is small.

Real time en face Fourier-domain optical coherence tomography with direct hardware frequency demodulation

PubMed Central

Biedermann, Benjamin R.; Wieser, Wolfgang; Eigenwillig, Christoph M.; Palte, Gesa; Adler, Desmond C.; Srinivasan, Vivek J.; Fujimoto, James G.; Huber, Robert

2009-01-01

We demonstrate en face swept source optical coherence tomography (ss-OCT) without requiring a Fourier transformation step. The electronic optical coherence tomography (OCT) interference signal from a k-space linear Fourier domain mode-locked laser is mixed with an adjustable local oscillator, yielding the analytic reflectance signal from one image depth for each frequency sweep of the laser. Furthermore, a method for arbitrarily shaping the spectral intensity profile of the laser is presented, without requiring the step of numerical apodization. In combination, these two techniques enable sampling of the in-phase and quadrature signal with a slow analog-to-digital converter and allow for real-time display of en face projections even for highest axial scan rates. Image data generated with this technique is compared to en face images extracted from a three-dimensional OCT data set. This technique can allow for real-time visualization of arbitrarily oriented en face planes for the purpose of alignment, registration, or operator-guided survey scans while simultaneously maintaining the full capability of high-speed volumetric ss-OCT functionality. PMID:18978919

Coherent fifth-order visible-infrared spectroscopies: ultrafast nonequilibrium vibrational dynamics in solution.

PubMed

Lynch, Michael S; Slenkamp, Karla M; Cheng, Mark; Khalil, Munira

2012-07-05

Obtaining a detailed description of photochemical reactions in solution requires measuring time-evolving structural dynamics of transient chemical species on ultrafast time scales. Time-resolved vibrational spectroscopies are sensitive probes of molecular structure and dynamics in solution. In this work, we develop doubly resonant fifth-order nonlinear visible-infrared spectroscopies to probe nonequilibrium vibrational dynamics among coupled high-frequency vibrations during an ultrafast charge transfer process using a heterodyne detection scheme. The method enables the simultaneous collection of third- and fifth-order signals, which respectively measure vibrational dynamics occurring on electronic ground and excited states on a femtosecond time scale. Our data collection and analysis strategy allows transient dispersed vibrational echo (t-DVE) and dispersed pump-probe (t-DPP) spectra to be extracted as a function of electronic and vibrational population periods with high signal-to-noise ratio (S/N > 25). We discuss how fifth-order experiments can measure (i) time-dependent anharmonic vibrational couplings, (ii) nonequilibrium frequency-frequency correlation functions, (iii) incoherent and coherent vibrational relaxation and transfer dynamics, and (iv) coherent vibrational and electronic (vibronic) coupling as a function of a photochemical reaction.

Long-distance continuous-variable quantum key distribution using non-Gaussian state-discrimination detection

NASA Astrophysics Data System (ADS)

Liao, Qin; Guo, Ying; Huang, Duan; Huang, Peng; Zeng, Guihua

2018-02-01

We propose a long-distance continuous-variable quantum key distribution (CVQKD) with a four-state protocol using non-Gaussian state-discrimination detection. A photon subtraction operation, which is deployed at the transmitter, is used for splitting the signal required for generating the non-Gaussian operation to lengthen the maximum transmission distance of the CVQKD. Whereby an improved state-discrimination detector, which can be deemed as an optimized quantum measurement that allows the discrimination of nonorthogonal coherent states beating the standard quantum limit, is applied at the receiver to codetermine the measurement result with the conventional coherent detector. By tactfully exploiting the multiplexing technique, the resulting signals can be simultaneously transmitted through an untrusted quantum channel, and subsequently sent to the state-discrimination detector and coherent detector, respectively. Security analysis shows that the proposed scheme can lengthen the maximum transmission distance up to hundreds of kilometers. Furthermore, by taking the finite-size effect and composable security into account we obtain the tightest bound of the secure distance, which is more practical than that obtained in the asymptotic limit.

Generation of coherent two-color pulses at two adjacent harmonics in a seeded free-electron laser

NASA Astrophysics Data System (ADS)

Zhao, Zhouyu; Li, Heting; Jia, Qika

2018-02-01

The growing requirements of pump-probe techniques and nonlinear optics experiments greatly promote the studies of two-color free-electron lasers (FELs). We propose a new method to generate coherent two-color pulses in a high-gain harmonic generation (HGHG) FEL. In this scheme, an initial tilted electron beam is sent though the modulator and dispersive section of an HGHG FEL to generate the bunching at harmonics of the seed laser. Then a transverse gradient undulator (TGU) is adopted as the radiator and in such radiator, only two separated fractions of the tilted beam will resonate at two adjacent harmonics of the seed laser and are enabled to emit the coherent two-color pulses simultaneously. The time separation between the two pulses are on the order of hundreds of femtoseconds, and can be precisely controlled by varying the tilted amplitude of the electron beam and/or the transverse gradient of the TGU radiator. Numerical simulations confirm the validity and feasibility of this scheme in the extreme ultraviolet waveband.

Voluntary and Involuntary Movements Widen the Window of Subjective Simultaneity.

PubMed

Arikan, B Ezgi; van Kemenade, Bianca M; Straube, Benjamin; Harris, Laurence R; Kircher, Tilo

2017-01-01

Forming a coherent percept of an event requires different sensory inputs originating from the event to be bound. Perceiving synchrony aids in binding of these inputs. In two experiments, we investigated how voluntary movements influence the perception of simultaneity, by measuring simultaneity judgments (SJs) for an audiovisual (AV) stimulus pair triggered by a voluntary button press. In Experiment 1, we manipulated contiguity between the action and its consequences by introducing delays between the button press and the AV stimulus pair. We found a widened window of subjective simultaneity (WSS) when the action-feedback relationship was time contiguous. Introducing a delay narrowed the WSS, suggesting that the wider WSS around the time of an action might facilitate perception of simultaneity. In Experiment 2, we introduced an involuntary condition using an externally controlled button to assess the influence of action-related predictive processes on SJs. We found a widened WSS around the action time, regardless of movement type, supporting the influence of causal relations in the perception of synchrony. Interestingly, the slopes of the psychometric functions in the voluntary condition were significantly steeper than the slopes in the involuntary condition, suggesting a role of action-related predictive mechanisms in making SJs more precise.

Voluntary and Involuntary Movements Widen the Window of Subjective Simultaneity

PubMed Central

Arikan, B. Ezgi; van Kemenade, Bianca M.; Straube, Benjamin; Harris, Laurence R.; Kircher, Tilo

2017-01-01

Forming a coherent percept of an event requires different sensory inputs originating from the event to be bound. Perceiving synchrony aids in binding of these inputs. In two experiments, we investigated how voluntary movements influence the perception of simultaneity, by measuring simultaneity judgments (SJs) for an audiovisual (AV) stimulus pair triggered by a voluntary button press. In Experiment 1, we manipulated contiguity between the action and its consequences by introducing delays between the button press and the AV stimulus pair. We found a widened window of subjective simultaneity (WSS) when the action-feedback relationship was time contiguous. Introducing a delay narrowed the WSS, suggesting that the wider WSS around the time of an action might facilitate perception of simultaneity. In Experiment 2, we introduced an involuntary condition using an externally controlled button to assess the influence of action-related predictive processes on SJs. We found a widened WSS around the action time, regardless of movement type, supporting the influence of causal relations in the perception of synchrony. Interestingly, the slopes of the psychometric functions in the voluntary condition were significantly steeper than the slopes in the involuntary condition, suggesting a role of action-related predictive mechanisms in making SJs more precise. PMID:28835813

[Rumination and cognitive fusion in dementia family caregivers].

PubMed

Romero-Moreno, Rosa; Márquez-González, María; Losada, Andrés; Fernández-Fernández, Virginia; Nogales-González, Celia

2015-01-01

Rumination has been described as a dysfunctional coping strategy related to emotional distress. Recently, it has been highlighted from the Acceptance and Commitment Therapy therapeutic approach, the negative role that cognitive fusion (the extent to which we are psychologically tangled with and dominated by the form or content of our thoughts) has on the explanation of distress. The aim of this study is to simultaneously analyze the role of rumination and cognitive fusion in the caregiving stress process. The sample of 176 dementia caregivers was divided in four groups, taking into account their levels of rumination and cognitive fusion: HRHF=high rumination+high cognitive fusion; HRLF=high rumination+low cognitive fusion; LRHF= low rumination+high cognitive fusion; and LRLC=low rumination and low cognitive fusion. Caregiver stress factors, frequency of pleasant events, experiential avoidance, coherence and satisfaction with personal values, depression, anxiety and satisfaction with life, were measured. The HRHF group showed higher levels of depression, anxiety, experiential avoidance and lower levels of satisfaction with life, frequency of pleasant events, coherence and satisfaction with personal values, than the other three groups. Considering simultaneously rumination and cognitive fusion may contribute to a better understanding of caregiver coping and distress. Copyright © 2014 SEGG. Published by Elsevier Espana. All rights reserved.

Three-dimensional simultaneous optical coherence tomography and confocal fluorescence microscopy for investigation of lung tissue.

PubMed

Gaertner, Maria; Cimalla, Peter; Meissner, Sven; Kuebler, Wolfgang M; Koch, Edmund

2012-07-01

Although several strategies exist for a minimal-invasive treatment of patients with lung failure, the mortality rate of acute respiratory distress syndrome still reaches 30% at minimum. This striking number indicates the necessity of understanding lung dynamics on an alveolar level. To investigate the dynamical behavior on a microscale, we used three-dimensional geometrical and functional imaging to observe tissue parameters including alveolar size and length of embedded elastic fibers during ventilation. We established a combined optical coherence tomography (OCT) and confocal fluorescence microscopy system that is able to monitor the distension of alveolar tissue and elastin fibers simultaneously within three dimensions. The OCT system can laterally resolve a 4.9 μm line pair feature and has an approximately 11 μm full-width-half-maximum axial resolution in air. confocal fluorescence microscopy visualizes molecular properties of the tissue with a resolution of 0.75 μm (laterally), and 5.9 μm (axially) via fluorescence detection of the dye sulforhodamine B specifically binding to elastin. For system evaluation, we used a mouse model in situ to perform lung distension by application of different constant pressure values within the physiological regime. Our method enables the investigation of alveolar dynamics by helping to reveal basic processes emerging during artificial ventilation and breathing.

Simultaneous SLO/OCT imaging of the human retina with axial eye motion correction.

PubMed

Pircher, Michael; Baumann, Bernhard; Götzinger, Erich; Sattmann, Harald; Hitzenberger, Christoph K

2007-12-10

It has been shown that transversal scanning (or en-face) optical coherence tomography (TS-OCT) represents an imaging modality capable to record high isotropic resolution images of the human retina in vivo. However, axial eye motion still remains a challenging problem of this technique. In this paper we introduce a novel method to compensate for this eye motion. An auxiliary spectral domain partial coherence interferometer (SD-PCI) was integrated into an existing TS-OCT system and used to measure accurately the position of the cornea. A light source emitting at 1310nm was used in the additional interferometer which enabled a nearly loss free coupling of the two measurement beams via a dichroic mirror. The recorded corneal position was used to drive an additional voice coil translation stage in the reference arm of the TS-OCT system to correct for axial eye motion. Currently, the correction can be performed with an update rate of ~200Hz. The TS-OCT instrument is operated with a line scan rate of 4000 transversal lines per second which enables simultaneous SLO/OCT imaging at a frame rate of 40fps. 3D data of the human retina with isotropic high resolution, that was sufficient to visualize the human cone mosaic in vivo, is presented.

Aligned and Unaligned Coherence: A New Diagnostic Tool

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

2006-01-01

The study of combustion noise from turbofan engines has become important again as the noise from other sources like the fan and jet are reduced. A method has been developed to help identify combustion noise spectra using an aligned and unaligned coherence technique. When used with the well known three signal coherent power method and coherent power method it provides new information by separating tonal information from random process information. Examples are presented showing the underlying tonal structure which is buried under broadband noise and jet noise. The method is applied to data from a Pratt and Whitney PW4098 turbofan engine.

Midline Frontal Cortex Low-Frequency Activity Drives Subthalamic Nucleus Oscillations during Conflict

PubMed Central

Zavala, Baltazar A.; Tan, Huiling; Little, Simon; Ashkan, Keyoumars; Hariz, Marwan; Foltynie, Thomas; Zrinzo, Ludvic; Zaghloul, Kareem A.

2014-01-01

Making the right decision from conflicting information takes time. Recent computational, electrophysiological, and clinical studies have implicated two brain areas as being crucial in assuring sufficient time is taken for decision-making under conditions of conflict: the medial prefrontal cortex and the subthalamic nucleus (STN). Both structures exhibit an elevation of activity at low frequencies (<10 Hz) during conflict that correlates with the amount of time taken to respond. This suggests that the two sites could become functionally coupled during conflict. To establish the nature of this interaction we recorded from deep-brain stimulation electrodes implanted bilaterally in the STN of 13 Parkinson's disease patients while they performed a sensory integration task involving randomly moving dots. By gradually increasing the number of dots moving coherently in one direction, we were able to determine changes in the STN associated with response execution. Furthermore, by occasionally having 10% of the dots move in the opposite direction as the majority, we were able to identify an independent increase in STN theta-delta activity triggered by conflict. Crucially, simultaneous midline frontal electroencephalographic recordings revealed an increase in the theta-delta band coherence between the two structures that was specific to high-conflict trials. Activity over the midline frontal cortex was Granger causal to that in STN. These results establish the cortico-subcortical circuit enabling successful choices to be made under conditions of conflict and provide support for the hypothesis that the brain uses frequency-specific channels of communication to convey behaviorally relevant information. PMID:24849364

Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter

NASA Technical Reports Server (NTRS)

Boggess, N. W.; Greenberg, L. T.; Hauser, M. G.; Houck, J. R.; Low, F. J.; Mccreight, C. R.; Rank, D. M.; Richards, P. L.; Weiss, R.

1979-01-01

The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices.

A study of partial coherence for identifying interior noise sources and paths on general aviation aircraft

NASA Technical Reports Server (NTRS)

Howlett, J. T.

1979-01-01

The partial coherence analysis method for noise source/path determination is summarized and the application to a two input, single output system with coherence between the inputs is illustrated. The augmentation of the calculations on a digital computer interfaced with a two channel, real time analyzer is also discussed. The results indicate possible sources of error in the computations and suggest procedures for avoiding these errors.

A stable pattern of EEG spectral coherence distinguishes children with autism from neuro-typical controls - a large case control study.

PubMed

Duffy, Frank H; Als, Heidelise

2012-06-26

The autism rate has recently increased to 1 in 100 children. Genetic studies demonstrate poorly understood complexity. Environmental factors apparently also play a role. Magnetic resonance imaging (MRI) studies demonstrate increased brain sizes and altered connectivity. Electroencephalogram (EEG) coherence studies confirm connectivity changes. However, genetic-, MRI- and/or EEG-based diagnostic tests are not yet available. The varied study results likely reflect methodological and population differences, small samples and, for EEG, lack of attention to group-specific artifact. Of the 1,304 subjects who participated in this study, with ages ranging from 1 to 18 years old and assessed with comparable EEG studies, 463 children were diagnosed with autism spectrum disorder (ASD); 571 children were neuro-typical controls (C). After artifact management, principal components analysis (PCA) identified EEG spectral coherence factors with corresponding loading patterns. The 2- to 12-year-old subsample consisted of 430 ASD- and 554 C-group subjects (n = 984). Discriminant function analysis (DFA) determined the spectral coherence factors' discrimination success for the two groups. Loading patterns on the DFA-selected coherence factors described ASD-specific coherence differences when compared to controls. Total sample PCA of coherence data identified 40 factors which explained 50.8% of the total population variance. For the 2- to 12-year-olds, the 40 factors showed highly significant group differences (P < 0.0001). Ten randomly generated split half replications demonstrated high-average classification success (C, 88.5%; ASD, 86.0%). Still higher success was obtained in the more restricted age sub-samples using the jackknifing technique: 2- to 4-year-olds (C, 90.6%; ASD, 98.1%); 4- to 6-year-olds (C, 90.9%; ASD 99.1%); and 6- to 12-year-olds (C, 98.7%; ASD, 93.9%). Coherence loadings demonstrated reduced short-distance and reduced, as well as increased, long-distance coherences for the ASD-groups, when compared to the controls. Average spectral loading per factor was wide (10.1 Hz). Classification success suggests a stable coherence loading pattern that differentiates ASD- from C-group subjects. This might constitute an EEG coherence-based phenotype of childhood autism. The predominantly reduced short-distance coherences may indicate poor local network function. The increased long-distance coherences may represent compensatory processes or reduced neural pruning. The wide average spectral range of factor loadings may suggest over-damped neural networks.

The serotonin hallucinogen 5-MeO-DMT alters cortico-thalamic activity in freely moving mice: Regionally-selective involvement of 5-HT1A and 5-HT2A receptors.

PubMed

Riga, Maurizio S; Lladó-Pelfort, Laia; Artigas, Francesc; Celada, Pau

2017-12-06

5-MeO-DMT is a natural hallucinogen acting as serotonin 5-HT 1A /5-HT 2A receptor agonist. Its ability to evoke hallucinations could be used to study the neurobiology of psychotic symptoms and to identify new treatment targets. Moreover, recent studies revealed the therapeutic potential of serotonin hallucinogens in treating mood and anxiety disorders. Our previous results in anesthetized animals show that 5-MeO-DMT alters cortical activity via 5-HT 1A and 5-HT 2A receptors. Here, we examined 5-MeO-DMT effects on oscillatory activity in prefrontal (PFC) and visual (V1) cortices, and in mediodorsal thalamus (MD) of freely-moving wild-type (WT) and 5-HT 2A -R knockout (KO2A) mice. We performed local field potential multi-recordings evaluating the power at different frequency bands and coherence between areas. We also examined the prevention of 5-MeO-DMT effects by the 5-HT 1A -R antagonist WAY-100635. 5-MeO-DMT affected oscillatory activity more in cortical than in thalamic areas. More marked effects were observed in delta power in V1 of KO2A mice. 5-MeO-DMT increased beta band coherence between all examined areas. In KO2A mice, WAY100635 prevented most of 5-MeO-DMT effects on oscillatory activity. The present results indicate that hallucinatory activity of 5-MeO-DMT is likely mediated by simultaneous alteration of prefrontal and visual activities. The prevention of these effects by WAY-100635 in KO2A mice supports the potential usefulness of 5-HT 1A receptor antagonists to treat visual hallucinations. 5-MeO-DMT effects on PFC theta activity and cortico-thalamic coherence may be related to its antidepressant activity. Copyright © 2017. Published by Elsevier Ltd.

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PubMed

El Beltagi, Tarek A; Bowd, Christopher; Boden, Catherine; Amini, Payam; Sample, Pamela A; Zangwill, Linda M; Weinreb, Robert N

2003-11-01

To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Retrospective observational case series. Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Method and apparatus for coherent burst ranging

DOEpatents

Wachter, Eric A.; Fisher, Walter G.

1998-01-01

A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time.

Normalization of neuronal responses in cortical area MT across signal strengths and motion directions

PubMed Central

Xiao, Jianbo; Niu, Yu-Qiong; Wiesner, Steven

2014-01-01

Multiple visual stimuli are common in natural scenes, yet it remains unclear how multiple stimuli interact to influence neuronal responses. We investigated this question by manipulating relative signal strengths of two stimuli moving simultaneously within the receptive fields (RFs) of neurons in the extrastriate middle temporal (MT) cortex. Visual stimuli were overlapping random-dot patterns moving in two directions separated by 90°. We first varied the motion coherence of each random-dot pattern and characterized, across the direction tuning curve, the relationship between neuronal responses elicited by bidirectional stimuli and by the constituent motion components. The tuning curve for bidirectional stimuli showed response normalization and can be accounted for by a weighted sum of the responses to the motion components. Allowing nonlinear, multiplicative interaction between the two component responses significantly improved the data fit for some neurons, and the interaction mainly had a suppressive effect on the neuronal response. The weighting of the component responses was not fixed but dependent on relative signal strengths. When two stimulus components moved at different coherence levels, the response weight for the higher-coherence component was significantly greater than that for the lower-coherence component. We also varied relative luminance levels of two coherently moving stimuli and found that MT response weight for the higher-luminance component was also greater. These results suggest that competition between multiple stimuli within a neuron's RF depends on relative signal strengths of the stimuli and that multiplicative nonlinearity may play an important role in shaping the response tuning for multiple stimuli. PMID:24899674

Method and apparatus for coherent burst ranging

DOEpatents

Wachter, E.A.; Fisher, W.G.

1998-04-28

A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time. 12 figs.

Multichannel brain recordings in behaving Drosophila reveal oscillatory activity and local coherence in response to sensory stimulation and circuit activation

PubMed Central

Paulk, Angelique C.; Zhou, Yanqiong; Stratton, Peter; Liu, Li

2013-01-01

Neural networks in vertebrates exhibit endogenous oscillations that have been associated with functions ranging from sensory processing to locomotion. It remains unclear whether oscillations may play a similar role in the insect brain. We describe a novel “whole brain” readout for Drosophila melanogaster using a simple multichannel recording preparation to study electrical activity across the brain of flies exposed to different sensory stimuli. We recorded local field potential (LFP) activity from >2,000 registered recording sites across the fly brain in >200 wild-type and transgenic animals to uncover specific LFP frequency bands that correlate with: 1) brain region; 2) sensory modality (olfactory, visual, or mechanosensory); and 3) activity in specific neural circuits. We found endogenous and stimulus-specific oscillations throughout the fly brain. Central (higher-order) brain regions exhibited sensory modality-specific increases in power within narrow frequency bands. Conversely, in sensory brain regions such as the optic or antennal lobes, LFP coherence, rather than power, best defined sensory responses across modalities. By transiently activating specific circuits via expression of TrpA1, we found that several circuits in the fly brain modulate LFP power and coherence across brain regions and frequency domains. However, activation of a neuromodulatory octopaminergic circuit specifically increased neuronal coherence in the optic lobes during visual stimulation while decreasing coherence in central brain regions. Our multichannel recording and brain registration approach provides an effective way to track activity simultaneously across the fly brain in vivo, allowing investigation of functional roles for oscillations in processing sensory stimuli and modulating behavior. PMID:23864378

Control of electron spin decoherence in nuclear spin baths

NASA Astrophysics Data System (ADS)

Liu, Ren-Bao

2011-03-01

Nuclear spin baths are a main mechanism of decoherence of spin qubits in solid-state systems, such as quantum dots and nitrogen-vacancy (NV) centers of diamond. The decoherence results from entanglement between the electron and nuclear spins, established by quantum evolution of the bath conditioned on the electron spin state. When the electron spin is flipped, the conditional bath evolution is manipulated. Such manipulation of bath through control of the electron spin not only leads to preservation of the center spin coherence but also demonstrates quantum nature of the bath. In an NV center system, the electron spin effectively interacts with hundreds of 13 C nuclear spins. Under repeated flip control (dynamical decoupling), the electron spin coherence can be preserved for a long time (> 1 ms) . Thereforesomecharacteristicoscillations , duetocouplingtoabonded 13 C nuclear spin pair (a dimer), are imprinted on the electron spin coherence profile, which are very sensitive to the position and orientation of the dimer. With such finger-print oscillations, a dimer can be uniquely identified. Thus, we propose magnetometry with single-nucleus sensitivity and atomic resolution, using NV center spin coherence to identify single molecules. Through the center spin coherence, we could also explore the many-body physics in an interacting spin bath. The information of elementary excitations and many-body correlations can be extracted from the center spin coherence under many-pulse dynamical decoupling control. Another application of the preserved spin coherence is identifying quantumness of a spin bath through the back-action of the electron spin to the bath. We show that the multiple transition of an NV center in a nuclear spin bath can have longer coherence time than the single transition does, when the classical noises due to inhomogeneous broadening is removed by spin echo. This counter-intuitive result unambiguously demonstrates the quantumness of the nuclear spin bath. This work was supported by Hong Kong RGC/GRF CUHK402207, CUHK402209, and CUHK402410. The author acknowledges collaboration with Nan Zhao, Jian-Liang Hu, Sai Wah Ho, Jones T. K. Wan, and Jiangfeng Du.

Laser diagnostics for combustion temperature and species

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

Eckbreth, A.C.

1987-01-01

Laser approaches to combustion diagnostics are of considerable interest due to their remote, nonintrusive and in-situ character, unlimited temperature capability and potential for simultaneous temporal and spatial resolution, This book aims to make these powerful and important new tools in combustion research understandable. The focus of this text is on spectroscopically-based, spatially-precise laser techniques for temperature and chemical composition measurements in reacting and nonreacting flows. After introductory chapters providing a fundamental theoretical and experimental background, attention is directed to diagnostics based upon spontaneous Raman and Rayleigh scattering, coherent anti-Stokes Raman spectroscopy (CARS) and laser-induced fluorescence (LIFS). The book concludes withmore » a treatment of techniques which permit spatially-resolved measurements over an entire two-dimensional field simultaneously.« less

Lip movements entrain the observers’ low-frequency brain oscillations to facilitate speech intelligibility

PubMed Central

Park, Hyojin; Kayser, Christoph; Thut, Gregor; Gross, Joachim

2016-01-01

During continuous speech, lip movements provide visual temporal signals that facilitate speech processing. Here, using MEG we directly investigated how these visual signals interact with rhythmic brain activity in participants listening to and seeing the speaker. First, we investigated coherence between oscillatory brain activity and speaker’s lip movements and demonstrated significant entrainment in visual cortex. We then used partial coherence to remove contributions of the coherent auditory speech signal from the lip-brain coherence. Comparing this synchronization between different attention conditions revealed that attending visual speech enhances the coherence between activity in visual cortex and the speaker’s lips. Further, we identified a significant partial coherence between left motor cortex and lip movements and this partial coherence directly predicted comprehension accuracy. Our results emphasize the importance of visually entrained and attention-modulated rhythmic brain activity for the enhancement of audiovisual speech processing. DOI: http://dx.doi.org/10.7554/eLife.14521.001 PMID:27146891

Dispersion-based stimulated Raman scattering spectroscopy, holography, and optical coherence tomography

PubMed Central

Robles, Francisco E.; Fischer, Martin C.; Warren, Warren S.

2016-01-01

Stimulated Raman scattering (SRS) enables fast, high resolution imaging of chemical constituents important to biological structures and functional processes, both in a label-free manner and using exogenous biomarkers. While this technology has shown remarkable potential, it is currently limited to point scanning and can only probe a few Raman bands at a time (most often, only one). In this work we take a fundamentally different approach to detecting the small nonlinear signals based on dispersion effects that accompany the loss/gain processes in SRS. In this proof of concept, we demonstrate that the dispersive measurements are more robust to noise compared to amplitude-based measurements, which then permit spectral or spatial multiplexing (potentially both, simultaneously). Finally, we illustrate how this method may enable different strategies for biochemical imaging using phase microscopy and optical coherence tomography. PMID:26832279

Interferometer design and controls for pulse stacking in high power fiber lasers

NASA Astrophysics Data System (ADS)

Wilcox, Russell; Yang, Yawei; Dahlen, Dar; Xu, Yilun; Huang, Gang; Qiang, Du; Doolittle, Lawrence; Byrd, John; Leemans, Wim; Ruppe, John; Zhou, Tong; Sheikhsofla, Morteza; Nees, John; Galvanauskas, Almantas; Dawson, Jay; Chen, Diana; Pax, Paul

2017-03-01

In order to develop a design for a laser-plasma accelerator (LPA) driver, we demonstrate key technologies that enable fiber lasers to produce high energy, ultrafast pulses. These technologies must be scalable, and operate in the presence of thermal drift, acoustic noise, and other perturbations typical of an operating system. We show that coherent pulse stacking (CPS), which requires optical interferometers, can be made robust by image-relaying, multipass optical cavities, and by optical phase control schemes that sense pulse train amplitudes from each cavity. A four-stage pulse stacking system using image-relaying cavities is controlled for 14 hours using a pulse-pattern sensing algorithm. For coherent addition of simultaneous ultrafast pulses, we introduce a new scheme using diffractive optics, and show experimentally that four pulses can be added while a preserving pulse width of 128 fs.

Coherent Raman scattering with incoherent light for a multiply resonant mixture: Theory

NASA Astrophysics Data System (ADS)

Kirkwood, Jason C.; Ulness, Darin J.; Stimson, Michael J.; Albrecht, A. C.

1998-02-01

The theory for coherent Raman scattering (CRS) with broadband incoherent light is presented for a multiply resonant, multicomponent mixture of molecules that exhibits simultaneous multiple resonances with the frequencies of the driving fields. All possible pairwise hyperpolarizability contributions to the signal intensity are included in the theoretical treatment-(resonant-resonant, resonant-nonresonant, and nonresonant-nonresonant correlations between chromophores) and it is shown how the different types of correlations manifest themselves as differently behaved components of the signal intensity. The Raman resonances are modeled as Lorentzians in the frequency domain, as is the spectral density of the incoherent light. The analytic results for this multiply resonant mixture are presented and applied to a specific binary mixture. These analytic results will be used to recover frequencies and dephasing times in a series of experiments on multiply resonant mixtures.

Broadband plasmonic-enhanced forward and backward multiplex coherent anti-Stokes Raman scattering microscopy

NASA Astrophysics Data System (ADS)

Guo, Baoshan; Jiang, Lan; Hua, Yanhong; Li, Xin; Cui, Tianhong; Lu, Yongfeng

2018-03-01

Coherent anti-Stokes Raman scattering (CARS) microscopy is an attractive technique for label-free biochemical-specific characterization of biological specimens. However, it has very low sensitivity in monitoring and imaging molecules present in extremely low concentrations or at fast speeds. To improve this sensitivity, especially for multiplex CARS, the intensity of the pump beam and broadband Stokes beam should be enhanced simultaneously. Therefore, the gold shell particle and gold surface are demonstrated to enhance the forward and backward CARS, respectively. Results show that a signal enhancement factor of ˜25,000 can be achieved for the gold surface and an even higher enhancement factor can be achieved for the gold shell particles. Thus, we can obtain an enhanced CARS signal in a broad spectral range, which will substantially improve the detection sensitivity of hyperspectral CARS spectroscopy and imaging.

Simultaneous wavelength and format conversion in SDN/NFV for flexible optical network based on FWM in SOA

NASA Astrophysics Data System (ADS)

Zhan, Yueying; Wang, Danshi; Zhang, Min

2018-04-01

We propose an all-optical wavelength and format conversion model (CM) for a dynamic data center interconnect node and coherent passive optical network (PON) optical network unit (ONU) in software-defined networking and network function virtualization system based on four-wave mixing in a semiconductor optical amplifier. Five wavelength converted DQPSK signals and two format converted DPSK signals are generated; the performances of the generated signals for two strategies of setting CM in the data center interconnect node and coherent PON ONU, which are over 10 km fiber transmission, have been verified. All of the converted signals are with a power penalty less than 2.2 dB at FEC threshold of 3.8 × 10 - 3, and the optimum bias current of SOA is 300 mA.

In vivo imaging of human labial glands using advanced optical coherence tomography.

PubMed

Ozawa, Nobuyoshi; Sumi, Yasunori; Shimozato, Kazuo; Chong, Changho; Kurabayashi, Tohru

2009-09-01

Optical coherence tomography (OCT) has emerged as a high-resolution noninvasive clinical imaging application. The purpose of this study was to show OCT images of human labial glands obtained using a swept-source (SS) OCT system. Labial gland OCT imaging was carried out using our new SS-OCT system for 5 healthy volunteers using a hand-held in vivo OCT scanning probe. The labial tissue was scanned in a superior to inferior direction in 2 and 3 dimensions. The resulting 2- and 3-dimensional ultrahigh-resolution images of in vivo OCT human labial minor salivary glands revealed the epithelium, connective tissue, lobes, and duct. OCT was capable of providing simultaneous and noninvasive structural information with high resolution. This clinical imaging modality promises to have clinical impact in the diagnosis of such conditions as Sjögren syndrome and xerostomia.

Optical superheterodyne receiver.

PubMed

Lucy, R F; Lang, K; Peters, C J; Duval, K

1967-08-01

Optical communications experiments at 6328 A, comparing the fading characteristics of coherent and noncoherent optical detection, have been performed over a 1-km real atmospheric path in different weather conditions. The results show that fading is less severe for noncoherent detection and that the fading characteristic for both types vary significantly with weather conditions. In addition, the similarity of optical FM to rf FM is demonstrated. The measurements were performed using a remote laser transmitter and an optical superheterodyne receiver operating simultaneously in both a coherent and noncoherent detection mode. The receiver, tunable over a frequency range of 1 GHz at the IF difference frequency of 30 MHz, has automatic frequency control and also uses a precision angle tracking servo to maintain receiver spatial alignment with a remote transmitter. The angle and frequency tracking capability permit operation between moving transmitter and receiver terminals.

Flexible needle with integrated optical coherence tomography probe for imaging during transbronchial tissue aspiration

NASA Astrophysics Data System (ADS)

Li, Jiawen; Quirk, Bryden C.; Noble, Peter B.; Kirk, Rodney W.; Sampson, David D.; McLaughlin, Robert A.

2017-10-01

Transbronchial needle aspiration (TBNA) of small lesions or lymph nodes in the lung may result in nondiagnostic tissue samples. We demonstrate the integration of an optical coherence tomography (OCT) probe into a 19-gauge flexible needle for lung tissue aspiration. This probe allows simultaneous visualization and aspiration of the tissue. By eliminating the need for insertion and withdrawal of a separate imaging probe, this integrated design minimizes the risk of dislodging the needle from the lesion prior to aspiration and may facilitate more accurate placement of the needle. Results from in situ imaging in a sheep lung show clear distinction between solid tissue and two typical constituents of nondiagnostic samples (adipose and lung parenchyma). Clinical translation of this OCT-guided aspiration needle holds promise for improving the diagnostic yield of TBNA.

Observations of Enhanced Radar Backscatter (ERB) from Millstone Hill

NASA Technical Reports Server (NTRS)

Lee, M. C.

1991-01-01

Intense enhancements of the incoherent radar backscatter spectrum from the topside ionosphere were observed with the Millstone Hill UHF radar. Enhancements occurring at the local ion acoustic frequency causing large asymmetries in the measured ion line may be produced by current driven instabilities. These enhancements pose a practical problem for space surveillance systems because their cross section and spectral width are characteristic of satellites. Conversely, their hard target signature complicates the study of naturally occurring ERB events; it is nearly impossible to distinguish them from satellites based on a single measurement. Statistical comparisons of observed coherent echo distributions with predictions from a satellite catalog were used to broadly identify periods of ERB activity. A series of experiments using multiple diagnostics, including satellite instruments, for simultaneous observations have established the association of ERB with large fluxes of soft suprathermal electrons carrying field aligned currents. Zenith data are also presented which show the asymmetric growth of ion acoustic waves directly above Millstone Hill. Details of these results are presented.

Gene Expression Dynamics Inspector (GEDI): for integrative analysis of expression profiles

NASA Technical Reports Server (NTRS)

Eichler, Gabriel S.; Huang, Sui; Ingber, Donald E.

2003-01-01

Genome-wide expression profiles contain global patterns that evade visual detection in current gene clustering analysis. Here, a Gene Expression Dynamics Inspector (GEDI) is described that uses self-organizing maps to translate high-dimensional expression profiles of time courses or sample classes into animated, coherent and robust mosaics images. GEDI facilitates identification of interesting patterns of molecular activity simultaneously across gene, time and sample space without prior assumption of any structure in the data, and then permits the user to retrieve genes of interest. Important changes in genome-wide activities may be quickly identified based on 'Gestalt' recognition and hence, GEDI may be especially useful for non-specialist end users, such as physicians. AVAILABILITY: GEDI v1.0 is written in Matlab, and binary Matlab.dll files which require Matlab to run can be downloaded for free by academic institutions at http://www.chip.org/ge/gedihome.html Supplementary information: http://www.chip.org/ge/gedihome.html.

Long-term increase in coherence between the basal ganglia and motor cortex after asphyxial cardiac arrest and resuscitation in developing rats.

PubMed

Aravamuthan, Bhooma R; Shoykhet, Michael

2015-10-01

The basal ganglia are vulnerable to injury during cardiac arrest. Movement disorders are a common morbidity in survivors. Yet, neuronal motor network changes post-arrest remain poorly understood. We compared function of the motor network in adult rats that, during postnatal week 3, underwent 9.5 min of asphyxial cardiac arrest (n = 9) or sham intervention (n = 8). Six months after injury, we simultaneously recorded local field potentials (LFP) from the primary motor cortex (MCx) and single neuron firing and LFP from the rat entopeduncular nucleus (EPN), which corresponds to the primate globus pallidus pars interna. Data were analyzed for firing rates, power, and coherence between MCx and EPN spike and LFP activity. Cardiac arrest survivors display chronic motor deficits. EPN firing rate is lower in cardiac arrest survivors (19.5 ± 2.4 Hz) compared with controls (27.4 ± 2.7 Hz; P < 0.05). Cardiac arrest survivors also demonstrate greater coherence between EPN single neurons and MCx LFP (3-100 Hz; P < 0.001). This increased coherence indicates abnormal synchrony in the neuronal motor network after cardiac arrest. Increased motor network synchrony is thought to be antikinetic in primary movement disorders. Characterization of motor network synchrony after cardiac arrest may help guide management of post-hypoxic movement disorders.

NORADRENERGIC CONTROL OF CORTICO-STRIATO-THALAMIC AND MESOLIMBIC CROSS-STRUCTURAL SYNCHRONY

PubMed Central

Dzirasa, Kafui; Phillips, H. Westley; Sotnikova, Tatyana D.; Salahpour, Ali; Kumar, Sunil; Gainetdinov, Raul R.; Caron, Marc G.; Nicolelis, Miguel A. L.

2010-01-01

While normal dopaminergic tone has been shown to be essential for the induction of cortico-striatal and mesolimbic theta oscillatory activity, the influence of norepinephrine on these brain networks remains relatively unknown. To address this question, we simultaneously recorded local field potentials (LFPs) and single neuron activity across ten interconnected brain areas (ventral striatum, frontal association cortex hippocampus, primary motor cortex, orbital frontal cortex, prelimbic cortex, dorsal lateral striatum, medial dorsal nucleus of thalamus, substantia nigra pars reticularis, and ventral tegmental area) in a combined genetically and pharmacologically induced mouse model of hyponoradrenergia. Our results show that norepinephrine (NE) depletion induces a novel state in male mice characterized by a profound disruption of coherence across multiple cortico-striatal circuits, and an increase in mesolimbic cross-structural coherence. Moreover, this brain state is accompanied by a complex behavioral phenotype consisting of transient hyperactivity, stereotypic behaviors, and an acute twelve-fold increase in grooming. Notably, treatment with a norepinephrine precursors (L-DOPA 100mg/kg or L-DOPS 5mg/kg), or a selective serotonin reuptake inhibitor (fluoxetine 20mg/kg) attenuates the abnormal behaviors and selectively reverses the circuit changes observed in NE depleted mice. Together, our results demonstrate that norepinephrine modulates the dynamic tuning of coherence across cortico-striatal-thalamic circuits, and they suggest that changes in coherence across these circuits mediate the abnormal generation of hyperactivity and repetitive behaviors. PMID:20445065

Noradrenergic control of cortico-striato-thalamic and mesolimbic cross-structural synchrony.

PubMed

Dzirasa, Kafui; Phillips, H Westley; Sotnikova, Tatyana D; Salahpour, Ali; Kumar, Sunil; Gainetdinov, Raul R; Caron, Marc G; Nicolelis, Miguel A L

2010-05-05

Although normal dopaminergic tone has been shown to be essential for the induction of cortico-striatal and mesolimbic theta oscillatory activity, the influence of norepinephrine on these brain networks remains relatively unknown. To address this question, we simultaneously recorded local field potentials and single-neuron activity across 10 interconnected brain areas (ventral striatum, frontal association cortex, hippocampus, primary motor cortex, orbital frontal cortex, prelimbic cortex, dorsal lateral striatum, medial dorsal nucleus of thalamus, substantia nigra pars reticularis, and ventral tegmental area) in a combined genetically and pharmacologically induced mouse model of hyponoradrenergia. Our results show that norepinephrine (NE) depletion induces a novel state in male mice characterized by a profound disruption of coherence across multiple cortico-striatal circuits and an increase in mesolimbic cross-structural coherence. Moreover, this brain state is accompanied by a complex behavioral phenotype consisting of transient hyperactivity, stereotypic behaviors, and an acute 12-fold increase in grooming. Notably, treatment with a norepinephrine precursors (l-3,4-dihydroxyphenylalanine at 100 mg/kg or l-threo-dihydroxyphenylserine at 5 mg/kg) or a selective serotonin reuptake inhibitor (fluoxetine at 20 mg/kg) attenuates the abnormal behaviors and selectively reverses the circuit changes observed in NE-depleted mice. Together, our results demonstrate that norepinephrine modulates the dynamic tuning of coherence across cortico-striato-thalamic circuits, and they suggest that changes in coherence across these circuits mediate the abnormal generation of hyperactivity and repetitive behaviors.

Techniques of noninvasive optical tomographic imaging

NASA Astrophysics Data System (ADS)

Rosen, Joseph; Abookasis, David; Gokhler, Mark

2006-01-01

Recently invented methods of optical tomographic imaging through scattering and absorbing media are presented. In one method, the three-dimensional structure of an object hidden between two biological tissues is recovered from many noisy speckle pictures obtained on the output of a multi-channeled optical imaging system. Objects are recovered from many speckled images observed by a digital camera through two stereoscopic microlens arrays. Each microlens in each array generates a speckle image of the object buried between the layers. In the computer each image is Fourier transformed jointly with an image of the speckled point-like source captured under the same conditions. A set of the squared magnitudes of the Fourier-transformed pictures is accumulated to form a single average picture. This final picture is again Fourier transformed, resulting in the three-dimensional reconstruction of the hidden object. In the other method, the effect of spatial longitudinal coherence is used for imaging through an absorbing layer with different thickness, or different index of refraction, along the layer. The technique is based on synthesis of multiple peak spatial degree of coherence. This degree of coherence enables us to scan simultaneously different sample points on different altitudes, and thus decreases the acquisition time. The same multi peak degree of coherence is also used for imaging through the absorbing layer. Our entire experiments are performed with a quasi-monochromatic light source. Therefore problems of dispersion and inhomogeneous absorption are avoided.

Measuring nonlinear signal combination using EEG.

PubMed

Cunningham, Darren G M; Baker, Daniel H; Peirce, Jonathan W

2017-05-01

Relatively little is known about the processes, both linear and nonlinear, by which signals are combined beyond V1. By presenting two stimulus components simultaneously, flickering at different temporal frequencies (frequency tagging) while measuring steady-state visual evoked potentials, we can assess responses to the individual components, including direct measurements of suppression on each other, and various nonlinear responses to their combination found at intermodulation frequencies. The result is a rather rich dataset of frequencies at which responses can be found. We presented pairs of sinusoidal gratings at different temporal frequencies, forming plaid patterns that were "coherent" (looking like a checkerboard) and "noncoherent" (looking like a pair of transparently overlaid gratings), and found clear intermodulation responses to compound stimuli, indicating nonlinear summation. This might have been attributed to cross-orientation suppression except that the pattern of intermodulation responses differed for coherent and noncoherent patterns, whereas the effects of suppression (measured at the component frequencies) did not. A two-stage model of nonlinear summation involving conjunction detection with a logical AND gate described the data well, capturing the difference between coherent and noncoherent plaids over a wide array of possible response frequencies. Multistimulus frequency-tagged EEG in combination with computational modeling may be a very valuable tool in studying the conjunction of these signals. In the current study the results suggest a second-order mechanism responding selectively to coherent plaid patterns.

Ground settlement monitoring based on temporarily coherent points between two SAR acquisitions

USGS Publications Warehouse

Zhang, L.; Ding, X.; Lu, Z.

2011-01-01

An InSAR analysis approach for identifying and extracting the temporarily coherent points (TCP) that exist between two SAR acquisitions and for determining motions of the TCP is presented for applications such as ground settlement monitoring. TCP are identified based on the spatial characteristics of the range and azimuth offsets of coherent radar scatterers. A method for coregistering TCP based on the offsets of TCP is given to reduce the coregistration errors at TCP. An improved phase unwrapping method based on the minimum cost flow (MCF) algorithm and local Delaunay triangulation is also proposed for sparse TCP data. The proposed algorithms are validated using a test site in Hong Kong. The test results show that the algorithms work satisfactorily for various ground features.

Relating the Resource Theories of Entanglement and Quantum Coherence.

PubMed

Chitambar, Eric; Hsieh, Min-Hsiu

2016-07-08

Quantum coherence and quantum entanglement represent two fundamental features of nonclassical systems that can each be characterized within an operational resource theory. In this Letter, we unify the resource theories of entanglement and coherence by studying their combined behavior in the operational setting of local incoherent operations and classical communication (LIOCC). Specifically, we analyze the coherence and entanglement trade-offs in the tasks of state formation and resource distillation. For pure states we identify the minimum coherence-entanglement resources needed to generate a given state, and we introduce a new LIOCC monotone that completely characterizes a state's optimal rate of bipartite coherence distillation. This result allows us to precisely quantify the difference in operational powers between global incoherent operations, LIOCC, and local incoherent operations without classical communication. Finally, a bipartite mixed state is shown to have distillable entanglement if and only if entanglement can be distilled by LIOCC, and we strengthen the well-known Horodecki criterion for distillability.

Relating the Resource Theories of Entanglement and Quantum Coherence

NASA Astrophysics Data System (ADS)

Chitambar, Eric; Hsieh, Min-Hsiu

2016-07-01

Quantum coherence and quantum entanglement represent two fundamental features of nonclassical systems that can each be characterized within an operational resource theory. In this Letter, we unify the resource theories of entanglement and coherence by studying their combined behavior in the operational setting of local incoherent operations and classical communication (LIOCC). Specifically, we analyze the coherence and entanglement trade-offs in the tasks of state formation and resource distillation. For pure states we identify the minimum coherence-entanglement resources needed to generate a given state, and we introduce a new LIOCC monotone that completely characterizes a state's optimal rate of bipartite coherence distillation. This result allows us to precisely quantify the difference in operational powers between global incoherent operations, LIOCC, and local incoherent operations without classical communication. Finally, a bipartite mixed state is shown to have distillable entanglement if and only if entanglement can be distilled by LIOCC, and we strengthen the well-known Horodecki criterion for distillability.

A Fully Conserved Minimal Adjustment Scheme with (T, S) Coherency for Stabilization of Hydrographic Profiles

DTIC Science & Technology

2012-12-01

positive definite approximation of the Hessian is updated according to the modified Broyden–Fletcher–Goldfarb– Shanno method (Powell 1978). 3. Data Evident...averaged observational hydrographic data . This method adjusts the temperature and salinity profiles fDTk,DSk,k5 1, 2, . . . ,Kg simultaneously and...in data assimilations since it does not simply reject profiles with static instability. This method edits the profiles with the inequality constraint

Accelerating Time-Varying Hardware Volume Rendering Using TSP Trees and Color-Based Error Metrics

NASA Technical Reports Server (NTRS)

Ellsworth, David; Chiang, Ling-Jen; Shen, Han-Wei; Kwak, Dochan (Technical Monitor)

2000-01-01

This paper describes a new hardware volume rendering algorithm for time-varying data. The algorithm uses the Time-Space Partitioning (TSP) tree data structure to identify regions within the data that have spatial or temporal coherence. By using this coherence, the rendering algorithm can improve performance when the volume data is larger than the texture memory capacity by decreasing the amount of textures required. This coherence can also allow improved speed by appropriately rendering flat-shaded polygons instead of textured polygons, and by not rendering transparent regions. To reduce the polygonization overhead caused by the use of the hierarchical data structure, we introduce an optimization method using polygon templates. The paper also introduces new color-based error metrics, which more accurately identify coherent regions compared to the earlier scalar-based metrics. By showing experimental results from runs using different data sets and error metrics, we demonstrate that the new methods give substantial improvements in volume rendering performance.

Simultaneous observations of electromagnetically induced transparency (EIT) and absorption (EIA) in a multi-level V-type system of 87Rb and theoretical simulation of the observed spectra using a multi-mode approach

NASA Astrophysics Data System (ADS)

Das, Bankim Chandra; Bhattacharyya, Dipankar; Das, Arpita; Chakrabarti, Shrabana; De, Sankar

2016-12-01

We report here simultaneous experimental observation of Electromagnetically Induced Transparency (EIT) and Electromagnetically Induced Absorption (EIA) in a multi-level V-type system in D2 transition of 87Rb, i.e., F =2 →F' with a strong pump and a weak probe beam. We studied the probe spectrum by locking the probe beam to the transition F =2 →F'=2 while the pump is scanned from F =2 →F' . EIA is observed for the open transition (F =2 →F'=2 ) whereas EIT is observed in the closed transition (F =2 →F'=3 ). Sub natural line-width is observed for the EIA. To simulate the observed spectra theoretically, Liouville equation for the three-level V-type system is solved analytically with a multi-mode approach for the density matrix elements. We assumed both the pump and the probe beams can couple the excited states. A multi-mode approach for the coherence terms facilitates the study of all the frequency contributions due to the pump and the probe fields. Since the terms contain higher harmonics of the pump and the probe frequencies, we expressed them in Fourier transformed forms. To simulate the probe spectrum, we have solved inhomogeneous difference equations for the coherence terms using the Green's function technique and continued fraction theory. The experimental line-widths of the EIT and the EIA are compared with our theoretical model. Our system can be useful in optical switching applications as it can be precisely tuned to render the medium opaque and transparent simultaneously.

Simultaneous observations of electromagnetically induced transparency (EIT) and absorption (EIA) in a multi-level V-type system of 87Rb and theoretical simulation of the observed spectra using a multi-mode approach.

PubMed

Das, Bankim Chandra; Bhattacharyya, Dipankar; Das, Arpita; Chakrabarti, Shrabana; De, Sankar

2016-12-14

We report here simultaneous experimental observation of Electromagnetically Induced Transparency (EIT) and Electromagnetically Induced Absorption (EIA) in a multi-level V-type system in D 2 transition of Rb87, i.e., F=2→F ' with a strong pump and a weak probe beam. We studied the probe spectrum by locking the probe beam to the transition F=2→F ' =2 while the pump is scanned from F=2→F ' . EIA is observed for the open transition (F=2→F ' =2) whereas EIT is observed in the closed transition (F=2→F ' =3). Sub natural line-width is observed for the EIA. To simulate the observed spectra theoretically, Liouville equation for the three-level V-type system is solved analytically with a multi-mode approach for the density matrix elements. We assumed both the pump and the probe beams can couple the excited states. A multi-mode approach for the coherence terms facilitates the study of all the frequency contributions due to the pump and the probe fields. Since the terms contain higher harmonics of the pump and the probe frequencies, we expressed them in Fourier transformed forms. To simulate the probe spectrum, we have solved inhomogeneous difference equations for the coherence terms using the Green's function technique and continued fraction theory. The experimental line-widths of the EIT and the EIA are compared with our theoretical model. Our system can be useful in optical switching applications as it can be precisely tuned to render the medium opaque and transparent simultaneously.

Truly simultaneous SS-OCT of the anterior and posterior human eye with full anterior chamber and 50° retinal field of views (Conference Presentation)

NASA Astrophysics Data System (ADS)

McNabb, Ryan P.; Viehland, Christian; Keller, Brenton; Vann, Robin R.; Izatt, Joseph A.; Kuo, Anthony N.

2017-02-01

Optical coherence tomography (OCT) has revolutionized clinical observation of the eye and is an indispensable part of the modern ophthalmic practice. Unlike many other ophthalmic imaging techniques, OCT provides three-dimensional information about the imaged eye. However, conventional clinical OCT systems image only the anterior or the posterior eye during a single acquisition. Newer OCT systems have begun to image both during the same acquisition but with compromises such as limited field of view in the posterior eye or requiring rapid switching between the anterior and posterior eye during the scan. We describe here the development and demonstration of an OCT system with truly simultaneous imaging of both the anterior and posterior eye capable of imaging the full anterior chamber width and 50° on the retina (macula, optic nerve, and arcades). The whole eye OCT system was developed using custom optics and optomechanics. Polarization was utilized to separate the imaging channels. We utilized a 200kHz swept-source laser (Axsun Technologies) centered at 1040±50nm of bandwidth. The clock signal generated by the laser was interpolated 4x to generate 5504 samples per laser sweep. With the whole eye OCT system, we simultaneously acquired anterior and posterior segments with repeated B-scans as well as three-dimensional volumes from seven healthy volunteers (other than refractive error). On three of these volunteers, whole eye OCT and partial coherence interferometry (LenStar PCI, Haag-Streit) were used to measure axial eye length. We measured a mean repeatability of ±47µm with whole eye OCT and a mean difference from PCI of -68µm.

A phase coherence approach to identifying co-located earthquakes and tremor

NASA Astrophysics Data System (ADS)

Hawthorne, J. C.; Ampuero, J.-P.

2018-05-01

We present and use a phase coherence approach to identify seismic signals that have similar path effects but different source time functions: co-located earthquakes and tremor. The method used is a phase coherence-based implementation of empirical matched field processing, modified to suit tremor analysis. It works by comparing the frequency-domain phases of waveforms generated by two sources recorded at multiple stations. We first cross-correlate the records of the two sources at a single station. If the sources are co-located, this cross-correlation eliminates the phases of the Green's function. It leaves the relative phases of the source time functions, which should be the same across all stations so long as the spatial extent of the sources are small compared with the seismic wavelength. We therefore search for cross-correlation phases that are consistent across stations as an indication of co-located sources. We also introduce a method to obtain relative locations between the two sources, based on back-projection of interstation phase coherence. We apply this technique to analyse two tremor-like signals that are thought to be composed of a number of earthquakes. First, we analyse a 20 s long seismic precursor to a M 3.9 earthquake in central Alaska. The analysis locates the precursor to within 2 km of the mainshock, and it identifies several bursts of energy—potentially foreshocks or groups of foreshocks—within the precursor. Second, we examine several minutes of volcanic tremor prior to an eruption at Redoubt Volcano. We confirm that the tremor source is located close to repeating earthquakes identified earlier in the tremor sequence. The amplitude of the tremor diminishes about 30 s before the eruption, but the phase coherence results suggest that the tremor may persist at some level through this final interval.

Coherent Doppler lidar signal covariance including wind shear and wind turbulence

NASA Technical Reports Server (NTRS)

Frehlich, R. G.

1993-01-01

The performance of coherent Doppler lidar is determined by the statistics of the coherent Doppler signal. The derivation and calculation of the covariance of the Doppler lidar signal is presented for random atmospheric wind fields with wind shear. The random component is described by a Kolmogorov turbulence spectrum. The signal parameters are clarified for a general coherent Doppler lidar system. There are two distinct physical regimes: one where the transmitted pulse determines the signal statistics and the other where the wind field dominates the signal statistics. The Doppler shift of the signal is identified in terms of the wind field and system parameters.

The effects of non-stationary noise on electromagnetic response estimates

NASA Astrophysics Data System (ADS)

Banks, R. J.

1998-11-01

The noise in natural electromagnetic time series is typically non-stationary. Sections of data with high magnetic noise levels bias impedances and generate unreliable error estimates. Sections containing noise that is coherent between electric and magnetic channels also produce inappropriate impedances and errors. The answer is to compute response values for data sections which are as short as is feasible, i.e. which are compatible both with the chosen bandwidth and with the need to over-determine the least-squares estimation of the impedance and coherence. Only those values that are reliable are selected, and the best single measure of the reliability of Earth impedance estimates is their temporal invariance, which is tested by the coherence between the measured and predicted electric fields. Complex demodulation is the method used here to explore the temporal structure of electromagnetic fields in the period range 20-6000 s. For periods above 300 s, noisy sections are readily identified in time series of impedance values. The corresponding estimates deviate strongly from the normal value, are biased towards low impedance values, and are associated with low coherences. Plots of the impedance against coherence are particularly valuable diagnostic aids. For periods below 300 s, impedance bias increases systematically as the coherence falls, identifying input channel noise as the cause. By selecting sections with high coherence (equivalent to the impedance being invariant over the section) unbiased impedances and realistic errors can be determined. The scatter in impedance values among high-coherence sections is due to noise that is coherent between input and output channels, implying the presence of two or more systems for which a consistent response can be defined. Where the Earth and noise responses are significantly different, it may be possible to improve estimates of the former by rejecting sections that do not generate satisfactory values for all the response elements.

Mass and tracer transport within oceanic Lagrangian coherent vortices as diagnosed in a global mesoscale eddying climate model

NASA Astrophysics Data System (ADS)

Tarshish, Nathaniel; Abernathey, Ryan; Dufour, Carolina; Frenger, Ivy; Griffies, Stephen

2017-04-01

Transient ocean mesoscale fluctuations play a central role in the global climate system, transporting climate relevant tracers such as heat and carbon. In satellite observations and numerical simulations, mesoscale vortices feature prominently as collectively rotating regions that remain visibly coherent. Prior studies on transport from ocean vortices typically rely on Eulerian identification methods, in which vortices are identified by selecting closed contours of Eulerian fields (e.g. sea surface height, or the Okubo-Weiss parameter) that satisfy geometric criteria and anomaly thresholds. In contrast, recent studies employ Lagrangian analysis of virtual particle trajectories initialized within the selected Eulerian contours, revealing significant discrepancies between the advection of the contour's material interior and the evolution of the Eulerian field contour. This work investigates the global mass and tracer transport associated with materially coherent surface ocean vortices. Further, it addresses differences between Eulerian and Lagrangian analyses for the detection of vortices. To do so, we use GFDL's CM2.6 coupled climate model with 5-10km horizontal grid spacing. We identify coherent vortices in CM2.6 by implementing the Rotationally Coherent Lagrangian Vortex (RCLV) framework, which recently emerged from dynamical systems theory. This approach involves the numerical advection of millions of Lagrangian particles and guarantees material coherence by construction. We compute the statistics, spatial distribution, and lifetimes of coherent vortices in addition to calculating the associated mass and tracer transports. We offer compelling evidence that Eulerian vortex methods are poorly suited to answer questions of mass and tracer transport.

Design and characterization of a handheld multimodal imaging device for the assessment of oral epithelial lesions

NASA Astrophysics Data System (ADS)

Higgins, Laura M.; Pierce, Mark C.

2014-08-01

A compact handpiece combining high resolution fluorescence (HRF) imaging with optical coherence tomography (OCT) was developed to provide real-time assessment of oral lesions. This multimodal imaging device simultaneously captures coregistered en face images with subcellular detail alongside cross-sectional images of tissue microstructure. The HRF imaging acquires a 712×594 μm2 field-of-view at the sample with a spatial resolution of 3.5 μm. The OCT images were acquired to a depth of 1.5 mm with axial and lateral resolutions of 9.3 and 8.0 μm, respectively. HRF and OCT images are simultaneously displayed at 25 fps. The handheld device was used to image a healthy volunteer, demonstrating the potential for in vivo assessment of the epithelial surface for dysplastic and neoplastic changes at the cellular level, while simultaneously evaluating submucosal involvement. We anticipate potential applications in real-time assessment of oral lesions for improved surveillance and surgical guidance.

"Crypto-Display" in Dual-Mode Metasurfaces by Simultaneous Control of Phase and Spectral Responses.

PubMed

Yoon, Gwanho; Lee, Dasol; Nam, Ki Tae; Rho, Junsuk

2018-06-26

Although conventional metasurfaces have demonstrated many promising functionalities in light control by tailoring either phase or spectral responses of subwavelength structures, simultaneous control of both responses has not been explored yet. Here, we propose a concept of dual-mode metasurfaces that enables simultaneous control of phase and spectral responses for two kinds of operation modes of transmission and reflection, respectively. In the transmission mode, the dual-mode metasurface acts as conventional metasurfaces by tailoring phase distribution of incident light. In the reflection mode, a reflected colored image is produced under white light illumination. We also experimentally demonstrate a crypto-display as one application of the dual-mode metasurface. The crypto-display looks a normal reflective display under white light illumination but generates a hologram that reveals the encrypted phase information under single-wavelength coherent light illumination. Because two operation modes do not affect each other, the crypto-display can have applications in security techniques.

Plasmonic metasurface cavity for simultaneous enhancement of optical electric and magnetic fields in deep subwavelength volume.

PubMed

Hong, Jongwoo; Kim, Sun-Je; Kim, Inki; Yun, Hansik; Mun, Sang-Eun; Rho, Junsuk; Lee, Byoungho

2018-05-14

It has been hard to achieve simultaneous plasmonic enhancement of nanoscale light-matter interactions in terms of both electric and magnetic manners with easily reproducible fabrication method and systematic theoretical design rule. In this paper, a novel concept of a flat nanofocusing device is proposed for simultaneously squeezing both electric and magnetic fields in deep-subwavelength volume (~λ 3 /538) in a large area. Based on the funneled unit cell structures and surface plasmon-assisted coherent interactions between them, the array of rectangular nanocavity connected to a tapered nanoantenna, plasmonic metasurface cavity, is constructed by periodic arrangement of the unit cell. The average enhancement factors of electric and magnetic field intensities reach about 60 and 22 in nanocavities, respectively. The proposed outstanding performance of the device is verified numerically and experimentally. We expect that this work would expand methodologies involving optical near-field manipulations in large areas and related potential applications including nanophotonic sensors, nonlinear responses, and quantum interactions.

Determining Complementary Properties with Quantum Clones.

PubMed

Thekkadath, G S; Saaltink, R Y; Giner, L; Lundeen, J S

2017-08-04

In a classical world, simultaneous measurements of complementary properties (e.g., position and momentum) give a system's state. In quantum mechanics, measurement-induced disturbance is largest for complementary properties and, hence, limits the precision with which such properties can be determined simultaneously. It is tempting to try to sidestep this disturbance by copying the system and measuring each complementary property on a separate copy. However, perfect copying is physically impossible in quantum mechanics. Here, we investigate using the closest quantum analog to this copying strategy, optimal cloning. The coherent portion of the generated clones' state corresponds to "twins" of the input system. Like perfect copies, both twins faithfully reproduce the properties of the input system. Unlike perfect copies, the twins are entangled. As such, a measurement on both twins is equivalent to a simultaneous measurement on the input system. For complementary observables, this joint measurement gives the system's state, just as in the classical case. We demonstrate this experimentally using polarized single photons.

Determining Complementary Properties with Quantum Clones

NASA Astrophysics Data System (ADS)

Thekkadath, G. S.; Saaltink, R. Y.; Giner, L.; Lundeen, J. S.

2017-08-01

In a classical world, simultaneous measurements of complementary properties (e.g., position and momentum) give a system's state. In quantum mechanics, measurement-induced disturbance is largest for complementary properties and, hence, limits the precision with which such properties can be determined simultaneously. It is tempting to try to sidestep this disturbance by copying the system and measuring each complementary property on a separate copy. However, perfect copying is physically impossible in quantum mechanics. Here, we investigate using the closest quantum analog to this copying strategy, optimal cloning. The coherent portion of the generated clones' state corresponds to "twins" of the input system. Like perfect copies, both twins faithfully reproduce the properties of the input system. Unlike perfect copies, the twins are entangled. As such, a measurement on both twins is equivalent to a simultaneous measurement on the input system. For complementary observables, this joint measurement gives the system's state, just as in the classical case. We demonstrate this experimentally using polarized single photons.

Discourse in Courts: Cooperation, Coercion, and Coherence.

ERIC Educational Resources Information Center

Penman, Robyn

1987-01-01

Investigates the relevance of a Gricean model for accounting for coherent discourse in courts of law. Identifies 19 rules of discourse congruent with Grice's Cooperative Principle in transcripts of eight trials. However, finds courts must coerce participants to be cooperative. Concludes that Grice's theory does not account adequately for coherent…

Conversational Coherency. Technical Report No. 95.

ERIC Educational Resources Information Center

Reichman, Rachel

To analyze the process involved in maintaining conversational coherency, the study described in this paper used a construct called a "context space" that grouped utterances referring to a single issue or episode. The paper defines the types of context spaces, parses individual conversations to identify the underlying model or structure,…

A stable pattern of EEG spectral coherence distinguishes children with autism from neuro-typical controls - a large case control study

PubMed Central

2012-01-01

Background The autism rate has recently increased to 1 in 100 children. Genetic studies demonstrate poorly understood complexity. Environmental factors apparently also play a role. Magnetic resonance imaging (MRI) studies demonstrate increased brain sizes and altered connectivity. Electroencephalogram (EEG) coherence studies confirm connectivity changes. However, genetic-, MRI- and/or EEG-based diagnostic tests are not yet available. The varied study results likely reflect methodological and population differences, small samples and, for EEG, lack of attention to group-specific artifact. Methods Of the 1,304 subjects who participated in this study, with ages ranging from 1 to 18 years old and assessed with comparable EEG studies, 463 children were diagnosed with autism spectrum disorder (ASD); 571 children were neuro-typical controls (C). After artifact management, principal components analysis (PCA) identified EEG spectral coherence factors with corresponding loading patterns. The 2- to 12-year-old subsample consisted of 430 ASD- and 554 C-group subjects (n = 984). Discriminant function analysis (DFA) determined the spectral coherence factors' discrimination success for the two groups. Loading patterns on the DFA-selected coherence factors described ASD-specific coherence differences when compared to controls. Results Total sample PCA of coherence data identified 40 factors which explained 50.8% of the total population variance. For the 2- to 12-year-olds, the 40 factors showed highly significant group differences (P < 0.0001). Ten randomly generated split half replications demonstrated high-average classification success (C, 88.5%; ASD, 86.0%). Still higher success was obtained in the more restricted age sub-samples using the jackknifing technique: 2- to 4-year-olds (C, 90.6%; ASD, 98.1%); 4- to 6-year-olds (C, 90.9%; ASD 99.1%); and 6- to 12-year-olds (C, 98.7%; ASD, 93.9%). Coherence loadings demonstrated reduced short-distance and reduced, as well as increased, long-distance coherences for the ASD-groups, when compared to the controls. Average spectral loading per factor was wide (10.1 Hz). Conclusions Classification success suggests a stable coherence loading pattern that differentiates ASD- from C-group subjects. This might constitute an EEG coherence-based phenotype of childhood autism. The predominantly reduced short-distance coherences may indicate poor local network function. The increased long-distance coherences may represent compensatory processes or reduced neural pruning. The wide average spectral range of factor loadings may suggest over-damped neural networks. PMID:22730909

Validation of a rotational coherent anti-Stokes Raman spectroscopy model for carbon dioxide using high-resolution detection in the temperature range 294-1143 K.

PubMed

Vestin, Fredrik; Nilsson, Kristin; Bengtsson, Per-Erik

2008-04-10

Experiments were performed in the temperature range of 294-1143 K in pure CO(2) using high-resolution rotational coherent anti-Stokes Raman spectroscopy (CARS), in the dual-broadband approach. Experimental single-shot spectra were recorded with high spectral resolution using a single-mode Nd:YAG laser and a relay imaging lens system on the exit of a 1 m spectrometer. A theoretical rotational CARS model for CO(2) was developed for evaluation of the experimental spectra. The evaluated mean temperatures of the recorded single-shot dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) spectra using this model showed good agreement with thermocouple temperatures, and the relative standard deviation of evaluated single-shot temperatures was generally 2-3%. Simultaneous thermometry and relative CO(2)/N(2)-concentration measurements were demonstrated in the product gas of premixed laminar CO/air flames at atmospheric pressure. Although the model proved to be accurate for thermometry up to 1143 K, limitations were observed at flame temperatures where temperatures were overestimated and relative CO(2)/N(2) concentrations were underestimated. Potential sources for these discrepancies are discussed.

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes.

PubMed

Dorize, Christian; Awwad, Elie

2018-05-14

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or by vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent ϕ-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Coherence and Divergence of Megatrends in Science and Engineering

NASA Astrophysics Data System (ADS)

Roco, M. C.

2002-04-01

Scientific discoveries and technological innovations are at the core of human endeavor, and it is estimated that their role will only increase in time. Such advancements evolve in coherence, with areas of confluence and temporary divergences, which bring synergism and that stimulate further developments following in average an exponential growth. Six increasingly interconnected megatrends are perceived as dominating the scene for the next decades: (a) information and computing, (b) nanoscale science and engineering (S&E), (c) biology and bio-environmental approaches, (d) medical sciences and enhancing human physical capabilities, (e) cognitive sciences and enhancing intellectual abilities, and (f) collective behavior and system approach. This paper presents a perspective on the process of identification, planning and program implementation of S&E megatrends, with illustration for the US research initiative on nanoscale science, engineering, and technology. The interplay between coherence and divergence, leading to unifying science and converging technologies, does not develop only among simultaneous scientific trends but also along time and across geopolitical boundaries. There is no single way of development of S&E, and here is the role of taking visionary measures. Societal implication scientists need to be involved from the conceptual phase of a program responding to a S&E megatrend.

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes

NASA Astrophysics Data System (ADS)

Dorize, Christian; Awwad, Elie

2018-05-01

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent phase-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Coherent cavity-enhanced dual-comb spectroscopy

PubMed Central

Fleisher, Adam J.; Long, David A.; Reed, Zachary D.; Hodges, Joseph T.; Plusquellic, David F.

2016-01-01

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO2, CO, HDO, and H2O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors. PMID:27409866

Real-time and sub-wavelength ultrafast coherent diffraction imaging in the extreme ultraviolet.

PubMed

Zürch, M; Rothhardt, J; Hädrich, S; Demmler, S; Krebs, M; Limpert, J; Tünnermann, A; Guggenmos, A; Kleineberg, U; Spielmann, C

2014-12-08

Coherent Diffraction Imaging is a technique to study matter with nanometer-scale spatial resolution based on coherent illumination of the sample with hard X-ray, soft X-ray or extreme ultraviolet light delivered from synchrotrons or more recently X-ray Free-Electron Lasers. This robust technique simultaneously allows quantitative amplitude and phase contrast imaging. Laser-driven high harmonic generation XUV-sources allow table-top realizations. However, the low conversion efficiency of lab-based sources imposes either a large scale laser system or long exposure times, preventing many applications. Here we present a lensless imaging experiment combining a high numerical aperture (NA = 0.8) setup with a high average power fibre laser driven high harmonic source. The high flux and narrow-band harmonic line at 33.2 nm enables either sub-wavelength spatial resolution close to the Abbe limit (Δr = 0.8λ) for long exposure time, or sub-70 nm imaging in less than one second. The unprecedented high spatial resolution, compactness of the setup together with the real-time capability paves the way for a plethora of applications in fundamental and life sciences.

Photon catalysis acting as noiseless linear amplification and its application in coherence enhancement

NASA Astrophysics Data System (ADS)

Zhang, Shengli; Zhang, Xiangdong

2018-04-01

Photon catalysis is an intriguing quantum mechanical operation during which no photon is added to or subtracted from the relevant optical system. However, we prove that photon catalysis is in essence equivalent to the simpler but more efficient noiseless linear amplifier. This provides a simple and zero-energy-input method for enhancing quantum coherence. We show that the coherence enhancement holds both for a coherent state and a two-mode squeezed vacuum (TMSV) state. For the TMSV state, biside photon catalysis is shown to be equivalent to two times the single-side photon catalysis, and two times the photon catalysis does not provide a substantial enhancement of quantum coherence compared with single-side catalysis. We further extend our investigation to the performance of coherence enhancement with a more realistic photon catalysis scheme where a heralded approximated single-photon state and an on-off detector are exploited. Moreover, we investigate the influence of an imperfect photon detector and the result shows that the amplification effect of photon catalysis is insensitive to the detector inefficiency. Finally, we apply the coherence measure to quantum illumination and see the same trend of performance improvement as coherence enhancement is identified in practical quantum target detection.

Interpretation of 2-probe turbulence measurements in an axisymmetric contraction

NASA Technical Reports Server (NTRS)

Marion-Moulin, C.; Tan-Atichat, J.; Nagib, H. M.

1983-01-01

Simultaneous measurements of the streamwise and radial velocity components at two points, one on and one off the centerline with variable radial separation, were digitally recorded and processed at several stations along a four to one contraction with controlled upstream turbulence conditions. Various statistical quantities are presented including spectra and coherence functions. The integral L sub ux, L sub um, L sub vx, L sub vm were also estimated and their variation along the contraction is examined.

Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

PubMed Central

Zawadzki, Robert J.; Jones, Steven M.; Pilli, Suman; Balderas-Mata, Sandra; Kim, Dae Yu; Olivier, Scot S.; Werner, John S.

2011-01-01

We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was integrated into the previously described AO-UHR OCT instrument with minimal changes to the latter. This was done in order to ensure optimal performance and image quality of the AO- UHR OCT. In this design both imaging modalities share most of the optical components including a common AO-subsystem and vertical scanner. One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between two acquisition channels for direct comparison between retinal structures imaged by both modalities (e.g., photoreceptor mosaics or microvasculature maps). Because of differences in the detection scheme of the two systems, this dual imaging modality instrument can provide insight into retinal morphology and potentially function, that could not be accessed easily by a single system. In this paper we describe details of the components and parameters of the combined instrument, including incorporation of a novel membrane magnetic deformable mirror with increased stroke and actuator count used as a single wavefront corrector. We also discuss laser safety calculations for this multimodal system. Finally, retinal images acquired in vivo with this system are presented. PMID:21698028

Synchronous Measurement of Ultrafast Anisotropy Decay of the B850 in Bacterial LH2 Complex

NASA Astrophysics Data System (ADS)

Wang, Yun-Peng; Du, Lu-Chao; Zhu, Gang-Bei; Wang, Zhuan; Weng, Yu-Xiang

2015-02-01

Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is difficult to be determined reliably owing to the requirement of a simultaneous availability of the parallel and perpendicular polarized decay kinetics. Nowadays, any measurement of anisotropic decay is a kind of approach to the exact simultaneity. Here we report a novel method for a synchronous ultrafast anisotropy decay measurement, which can well determine the anisotropy, even at a very early time, as the rising phase of the excitation laser pulse. The anisotropic decay of the B850 in bacterial light harvesting antenna complex LH2 of Rhodobacter sphaeroides in solution at room temperature with coherent excitation is detected by this method, which shows a polarization response time of 30 fs, and the energy transfer from the initial excitation to the bacteriochlorophylls in B850 ring takes about 70 fs. The anisotropic decay that is probed at the red side of the absorption spectrum, such as 880 nm, has an initial value of 0.4, corresponding to simulated emission, while the blue side with an anisotropy of 0.1 contributes to the ground-state bleaching. Our results show that the coherent excitation covering the whole ring might not be realized owing to the symmetry breaking of LH2: from C9 symmetry in membrane to C2 symmetry in solution.

Solar system exploration from the Moon: Synoptic and comparative study of bodies in our Planetary system

NASA Technical Reports Server (NTRS)

Bruston, P.; Mumma, M. J.

1994-01-01

An observational approach to Planetary Sciences and exploration from Earth applies to a quite limited number of targets, but most of these are spatially complex, and exhibit variability and evolution on a number of temporal scales which lie within the scope of possible observations. Advancing our understanding of the underlying physics requires the study of interactions between the various elements of such systems, and also requires study of the comparative response of both a given object to various conditions and of comparable objects to similar conditions. These studies are best conducted in 'campaigns', i.e. comprehensive programs combining simultaneous coherent observations of every interacting piece of the puzzle. The requirements include both imaging and spectroscopy over a wide spectral range, from UV to IR. While temporal simultaneity of operation in various modes is a key feature, these observations are also conducted over extended periods of time. The moon is a prime site offering long unbroken observation times and high positional stability, observations at small angular separation from the sun, comparative studies of planet Earth, and valuable technical advantages. A lunar observatory should become a central piece of any coherent set of planetary missions, supplying in-situ explorations with the synoptic and comparative data necessary for proper advance planning, correlative observations during the active exploratory phase, and follow-up studies of the target body or of related objects.

Simultaneous X-Ray/Ultraviolet Timing of 4U 1626-67

NASA Technical Reports Server (NTRS)

Chakrabarty, Deepto

2003-01-01

The science results from our observation have been published (Chakrabarty et al. 2001, ApJ, 562, 985). We detected large-amplitude 0.3- 1.2 mHz quasi-periodic oscillations (QPOs) from the low-mass X-ray binary pulsar 4U 1626--67, using ultraviolet photometry from the Hubble Space Telescope and ground-based optical photometry. These 1 mHz QPOs, which have coherence (nu/Delta_nu) = 8, are entirely distinct from the 130 mHz pulsar spin frequency, a previously known 48 mHz QPO, and the 42 min binary period (independently confirmed here). Unlike the 48 mHz and 130 mHz oscillations which are present in both the optical/UV and the X-ray emission, the 1 mHz QPOs are not detected in simultaneous observations with the X-Ray Timing Explorer. The rms amplitude of the mHz QPO decreases from 15% in the far UV to 3% in the optical, while the upper limit on a corresponding X-ray QPO is as low as 0.8\\%. We suggest that the mHz oscillations are due to warping of the inner accretion disk. We also report the detection of coherent upper and lower sidebands of the 130 mHz optical pulsations, with unequal amplitude and a spacing of 1.93 mHz around the main pulsation. The origin of these sidebands remains unclear.

Dual-scanning optical coherence elastography for rapid imaging of two tissue volumes (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fang, Qi; Frewer, Luke; Wijesinghe, Philip; Hamzah, Juliana; Ganss, Ruth; Allen, Wes M.; Sampson, David D.; Curatolo, Andrea; Kennedy, Brendan F.

2017-02-01

In many applications of optical coherence elastography (OCE), it is necessary to rapidly acquire images in vivo, or within intraoperative timeframes, over fields-of-view far greater than can be achieved in one OCT image acquisition. For example, tumour margin assessment in breast cancer requires acquisition over linear dimensions of 4-5 centimetres in under 20 minutes. However, the majority of existing techniques are not compatible with these requirements, which may present a hurdle to the effective translation of OCE. To increase throughput, we have designed and developed an OCE system that simultaneously captures two 3D elastograms from opposite sides of a sample. The optical system comprises two interferometers: a common-path interferometer on one side of the sample and a dual-arm interferometer on the other side. This optical system is combined with scanning mechanisms and compression loading techniques to realize dual-scanning OCE. The optical signals scattered from two volumes are simultaneously detected on a single spectrometer by depth-encoding the interference signal from each interferometer. To demonstrate dual-scanning OCE, we performed measurements on tissue-mimicking phantoms containing rigid inclusions and freshly isolated samples of murine hepatocellular carcinoma, highlighting the use of this technique to visualise 3D tumour stiffness. These findings indicate that our technique holds promise for in vivo and intraoperative applications.

Simultaneous transfer of optical frequency and time over 306 km long-haul optical fibre link

NASA Astrophysics Data System (ADS)

Hucl, Vaclav; Cizek, Martin; Pravdova, Lenka; Rerucha, Simon; Hrabina, Jan; Mikel, Bretislav; Smotlacha, Vladimir; Vojtech, Josef; Lazar, Josef; Cip, Ondrej

2016-12-01

Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.

Adolescent Social Stress Produces an Enduring Activation of the Rat Locus Coeruleus and Alters its Coherence with the Prefrontal Cortex

PubMed Central

Zitnik, Gerard A; Curtis, Andrè L; Wood, Susan K; Arner, Jay; Valentino, Rita J

2016-01-01

Early life stress is associated with the development of psychiatric disorders. Because the locus coeruleus-norepinephrine (LC-NE) system is a major stress-response system that is implicated in psychopathology, developmental differences in the response of this system to stress may contribute to increased vulnerability. Here LC single unit and network activity were compared between adult and adolescent rats during resident-intruder stress. In some rats, LC and medial prefrontal cortex (mPFC) coherence was quantified. The initial stress tonically activated LC neurons and induced theta oscillations, while simultaneously decreasing LC auditory-evoked responses in both age groups. Stress increased LC-mPFC coherence within the theta range. With repeated exposures, adolescent LC neuronal and network activity remained elevated even in the absence of the stressor and were unresponsive to stressor presentation. In contrast, LC neurons of adult rats exposed to repeated social stress were relatively inhibited in the absence of the stressor and mounted robust responses upon stressor presentation. LC sensory-evoked responses were selectively blunted in adolescent rats exposed to repeated social stress. Finally, repeated stress decreased LC-mPFC coherence in the high frequency range (beta and gamma) while maintaining strong coherence in the theta range, selectively in adolescents. Together, these results suggest that adaptive mechanisms that promote stress recovery and maintain basal activity of the brain norepinephrine system in the absence of stress are not fully developed or are vulnerable stress-induced impairments in adolescence. The resulting sustained activation of the LC-NE system after repeated social stress may adversely impact cognition and future social behavior of adolescents. PMID:26361057

On the estimation of wall pressure coherence using time-resolved tomographic PIV

NASA Astrophysics Data System (ADS)

Pröbsting, Stefan; Scarano, Fulvio; Bernardini, Matteo; Pirozzoli, Sergio

2013-07-01

Three-dimensional time-resolved velocity field measurements are obtained using a high-speed tomographic Particle Image Velocimetry (PIV) system on a fully developed flat plate turbulent boundary layer for the estimation of wall pressure fluctuations. The work focuses on the applicability of tomographic PIV to compute the coherence of pressure fluctuations, with attention to the estimation of the stream and spanwise coherence length. The latter is required for estimations of aeroacoustic noise radiation by boundary layers and trailing edge flows, but is also of interest for vibro-structural problems. The pressure field is obtained by solving the Poisson equation for incompressible flows, where the source terms are provided by time-resolved velocity field measurements. Measured 3D velocity data is compared to results obtained from planar PIV, and a Direct Numerical Simulation (DNS) at similar Reynolds number. An improved method for the estimation of the material based on a least squares estimator of the velocity derivative along a particle trajectory is proposed and applied. Computed surface pressure fluctuations are further verified by means of simultaneous measurements by a pinhole microphone and compared to the DNS results and a semi-empirical model available from literature. The correlation coefficient for the reconstructed pressure time series with respect to pinhole microphone measurements attains approximately 0.5 for the band-pass filtered signal over the range of frequencies resolved by the velocity field measurements. Scaled power spectra of the pressure at a single point compare favorably to the DNS results and those available from literature. Finally, the coherence of surface pressure fluctuations and the resulting span- and streamwise coherence lengths are estimated and compared to semi-empirical models and DNS results.

Human subthalamic nucleus-medial frontal cortex theta phase coherence is involved in conflict and error related cortical monitoring.

PubMed

Zavala, Baltazar; Tan, Huiling; Ashkan, Keyoumars; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Zaghloul, Kareem; Brown, Peter

2016-08-15

The medial prefrontal cortex (mPFC) is thought to control the shift from automatic to controlled action selection when conflict is present or when mistakes have been recently committed. Growing evidence suggests that this process involves frequency specific communication in the theta (4-8Hz) band between the mPFC and the subthalamic nucleus (STN), which is the main target of deep brain stimulation (DBS) for Parkinson's disease. Key in this hypothesis is the finding that DBS can lead to impulsivity by disrupting the correlation between higher mPFC oscillations and slower reaction times during conflict. In order to test whether theta band coherence between the mPFC and the STN underlies adjustments to conflict and to errors, we simultaneously recorded mPFC and STN electrophysiological activity while DBS patients performed an arrowed flanker task. These recordings revealed higher theta phase coherence between the two sites during the high conflict trials relative to the low conflict trials. These differences were observed soon after conflicting arrows were displayed, but before a response was executed. Furthermore, trials that occurred after an error was committed showed higher phase coherence relative to trials that followed a correct trial, suggesting that mPFC-STN connectivity may also play a role in error related adjustments in behavior. Interestingly, the phase coherence we observed occurred before increases in theta power, implying that the theta phase and power may influence behavior at separate times during cortical monitoring. Finally, we showed that pre-stimulus differences in STN theta power were related to the reaction time on a given trial, which may help adjust behavior based on the probability of observing conflict during a task. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Quantum-coherent coupling of a mechanical oscillator to an optical cavity mode.

PubMed

Verhagen, E; Deléglise, S; Weis, S; Schliesser, A; Kippenberg, T J

2012-02-01

Optical laser fields have been widely used to achieve quantum control over the motional and internal degrees of freedom of atoms and ions, molecules and atomic gases. A route to controlling the quantum states of macroscopic mechanical oscillators in a similar fashion is to exploit the parametric coupling between optical and mechanical degrees of freedom through radiation pressure in suitably engineered optical cavities. If the optomechanical coupling is 'quantum coherent'--that is, if the coherent coupling rate exceeds both the optical and the mechanical decoherence rate--quantum states are transferred from the optical field to the mechanical oscillator and vice versa. This transfer allows control of the mechanical oscillator state using the wide range of available quantum optical techniques. So far, however, quantum-coherent coupling of micromechanical oscillators has only been achieved using microwave fields at millikelvin temperatures. Optical experiments have not attained this regime owing to the large mechanical decoherence rates and the difficulty of overcoming optical dissipation. Here we achieve quantum-coherent coupling between optical photons and a micromechanical oscillator. Simultaneously, coupling to the cold photon bath cools the mechanical oscillator to an average occupancy of 1.7 ± 0.1 motional quanta. Excitation with weak classical light pulses reveals the exchange of energy between the optical light field and the micromechanical oscillator in the time domain at the level of less than one quantum on average. This optomechanical system establishes an efficient quantum interface between mechanical oscillators and optical photons, which can provide decoherence-free transport of quantum states through optical fibres. Our results offer a route towards the use of mechanical oscillators as quantum transducers or in microwave-to-optical quantum links.

Single-shot ultrabroadband two-dimensional electronic spectroscopy of the light-harvesting complex LH2.

PubMed

Harel, Elad; Long, Phillip D; Engel, Gregory S

2011-05-01

Here we present two-dimensional (2D) electronic spectra of the light-harvesting complex LH2 from purple bacteria using coherent pulses with bandwidth of over 100 nm FWHM. This broadband excitation and detection has allowed the simultaneous capture of both the B800 and B850 bands using a single light source. We demonstrate that one laser pulse is sufficient to capture the entire 2D electronic spectrum with a high signal-to-noise ratio. At a waiting time of 800 fs, we observe population transfer from the B800 to B850 band as manifested by a prominent cross peak. These results will enable observation of the dynamics of biological systems across both ultrafast (<1 ps) and slower (>1 ms) timescales simultaneously.

Phase noise characterization of a QD-based diode laser frequency comb.

PubMed

Vedala, Govind; Al-Qadi, Mustafa; O'Sullivan, Maurice; Cartledge, John; Hui, Rongqing

2017-07-10

We measure, simultaneously, the phases of a large set of comb lines from a passively mode locked, InAs/InP, quantum dot laser frequency comb (QDLFC) by comparing the lines to a stable comb reference using multi-heterodyne coherent detection. Simultaneity permits the separation of differential and common mode phase noise and a straightforward determination of the wavelength corresponding to the minimum width of the comb line. We find that the common mode and differential phases are uncorrelated, and measure for the first time for a QDLFC that the intrinsic differential-mode phase (IDMP) between adjacent subcarriers is substantially the same for all subcarrier pairs. The latter observation supports an interpretation of 4.4ps as the standard deviation of IDMP on a 200µs time interval for this laser.

Probing interactions of thermal Sr Rydberg atoms using simultaneous optical and ion detection

NASA Astrophysics Data System (ADS)

Hanley, Ryan K.; Bounds, Alistair D.; Huillery, Paul; Keegan, Niamh C.; Faoro, Riccardo; Bridge, Elizabeth M.; Weatherill, Kevin J.; Jones, Matthew P. A.

2017-06-01

We demonstrate a method for probing interaction effects in a thermal beam of strontium atoms using simultaneous measurements of Rydberg EIT and spontaneously created ions or electrons. We present a Doppler-averaged optical Bloch equation model that reproduces the optical signals and allows us to connect the optical coherences and the populations. We use this to determine that the spontaneous ionization process in our system occurs due to collisions between Rydberg and ground state atoms in the EIT regime. We measure the cross section of this process to be 0.6+/- 0.2 {σ }{geo}, where {σ }{geo} is the geometrical cross section of the Rydberg atom. This result adds complementary insight to a range of recent studies of interacting thermal Rydberg ensembles.

Detecting multiple moving objects in crowded environments with coherent motion regions

DOEpatents

Cheriyadat, Anil M.; Radke, Richard J.

2013-06-11

Coherent motion regions extend in time as well as space, enforcing consistency in detected objects over long time periods and making the algorithm robust to noisy or short point tracks. As a result of enforcing the constraint that selected coherent motion regions contain disjoint sets of tracks defined in a three-dimensional space including a time dimension. An algorithm operates directly on raw, unconditioned low-level feature point tracks, and minimizes a global measure of the coherent motion regions. At least one discrete moving object is identified in a time series of video images based on the trajectory similarity factors, which is a measure of a maximum distance between a pair of feature point tracks.

Mental health assessment: Inference, explanation, and coherence.

PubMed

Thagard, Paul; Larocque, Laurette

2018-06-01

Mental health professionals such as psychiatrists and psychotherapists assess their patients by identifying disorders that explain their symptoms. This assessment requires an inference to the best explanation that compares different disorders with respect to how well they explain the available evidence. Such comparisons are captured by the theory of explanatory coherence that states 7 principles for evaluating competing hypotheses in the light of evidence. The computational model ECHO shows how explanatory coherence can be efficiently computed. We show the applicability of explanatory coherence to mental health assessment by modelling a case of psychiatric interviewing and a case of psychotherapeutic evaluation. We argue that this approach is more plausible than Bayesian inference and hermeneutic interpretation. © 2018 John Wiley & Sons, Ltd.

Characterization and use of the spent beam for serial operation of LCLS

DOE PAGES

Boutet, Sébastien; Foucar, Lutz; Barends, Thomas R. M.; ...

2015-04-11

X-ray free-electron laser sources such as the Linac Coherent Light Source offer very exciting possibilities for unique research. However, beam time at such facilities is very limited and in high demand. This has led to significant efforts towards beam multiplexing of various forms. One such effort involves re-using the so-called spent beam that passes through the hole in an area detector after a weak interaction with a primary sample. This beam can be refocused into a secondary interaction region and used for a second, independent experiment operating in series. The beam profile of this refocused beam was characterized for amore » particular experimental geometry at the Coherent X-ray Imaging instrument at LCLS. A demonstration of this multiplexing capability was performed with two simultaneous serial femtosecond crystallography experiments, both yielding interpretable data of sufficient quality to produce electron density maps.« less

Characterization and use of the spent beam for serial operation of LCLS

PubMed Central

Boutet, Sébastien; Foucar, Lutz; Barends, Thomas R. M.; Botha, Sabine; Doak, R. Bruce; Koglin, Jason E.; Messerschmidt, Marc; Nass, Karol; Schlichting, Ilme; Seibert, M. Marvin; Shoeman, Robert L.; Williams, Garth J.

2015-01-01

X-ray free-electron laser sources such as the Linac Coherent Light Source offer very exciting possibilities for unique research. However, beam time at such facilities is very limited and in high demand. This has led to significant efforts towards beam multiplexing of various forms. One such effort involves re-using the so-called spent beam that passes through the hole in an area detector after a weak interaction with a primary sample. This beam can be refocused into a secondary interaction region and used for a second, independent experiment operating in series. The beam profile of this refocused beam was characterized for a particular experimental geometry at the Coherent X-ray Imaging instrument at LCLS. A demonstration of this multiplexing capability was performed with two simultaneous serial femtosecond crystallography experiments, both yielding interpretable data of sufficient quality to produce electron density maps. PMID:25931079

Towards combined optical coherence tomography and hyper-spectral imaging for gastrointestinal endoscopy

NASA Astrophysics Data System (ADS)

Attendu, Xavier; Crunelle, Camille; de Sivry-Houle, Martin Poinsinet; Maubois, Billie; Urbain, Joanie; Turrell, Chloe; Strupler, Mathias; Godbout, Nicolas; Boudoux, Caroline

2018-04-01

Previous works have demonstrated feasibility of combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) through a single double-clad fiber (DCF). In this proceeding we present the continued development of a system combining both modalities and capable of rapid imaging. We discuss the development of a rapidly scanning, dual-band, polygonal swept-source system which combines NIR (1260-1340 nm) and visible (450-800 nm) wavelengths. The NIR band is used for OCT imaging while visible light allows HSI. Scanning rates up to 24 kHz are reported. Furthermore, we present and discuss the fiber system used for light transport, delivery and collection, and the custom signal acquisition software. Key points include the use of a double-clad fiber coupler as well as important alignments and back-reflection management. Simultaneous and co-registered imaging with both modalities is presented in a bench-top system

High-Energy Density science at the Linac Coherent Light Source

NASA Astrophysics Data System (ADS)

Glenzer, S. H.; Fletcher, L. B.; Hastings, J. B.

2016-03-01

The Matter in Extreme Conditions end station at the Linac Coherent Light Source holds great promise for novel pump-probe experiments to make new discoveries in high- energy density science. In recent experiments we have demonstrated the first spectrally- resolved measurements of plasmons using a seeded 8-keV x-ray laser beam. Forward x-ray Thomson scattering spectra from isochorically heated solid aluminum show a well-resolved plasmon feature that is down-shifted in energy by 19 eV from the incident 8 keV elastic scattering feature. In this spectral range, the simultaneously measured backscatter spectrum shows no spectral features indicating observation of collective plasmon oscillations on a scattering length comparable to the screening length. This technique is a prerequisite for Thomson scattering measurements in compressed matter where the plasmon shift is a sensitive function of the free electron density and where the plasmon intensity provides information on temperature.

Experimental Demonstration of a Highly Efficient Fan-out Polarization Grating

PubMed Central

Wan, Chenhao; Chen, Jian; Tang, Xiahui; Zhan, Qiwen

2016-01-01

Highly efficient fan-out elements are crucial in coherent beam combining architectures especially in coupled laser resonators where the beam passes through the fan-out element twice per round trip. Although the theoretical efficiency is usually less than 86%, the Dammann gratings are ubiquitously utilized in a variety of types of coherent beam combining systems due to the facile design and fabrication. In the current paper, we experimentally demonstrate a highly efficient fan-out polarization grating. It is the first time to our knowledge that all the three space-variant parameters of a polarization grating are simultaneously optimized to achieve the function of multi-beam splitting. Besides the high fan-out efficiency, the ability to control the polarization states of individual split beams is another advantage of this polarization grating. The novel polarization grating is promising to find applications in laser beam combining systems. PMID:28008972

Laser pulses for coherent xuv Raman excitation

NASA Astrophysics Data System (ADS)

Greenman, Loren; Koch, Christiane P.; Whaley, K. Birgitta

2015-07-01

We combine multichannel electronic structure theory with quantum optimal control to derive femtosecond-time-scale Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and arbitrary phase control facilitated by the pump pulse carrier-envelope phase. Analysis of the optimized pulse structure reveals a sequential mechanism in which the valence excitation is reached via a fast (femtosecond) population transfer through an intermediate resonance state in the continuum rather than avoiding intermediate-state population with simultaneous or counterintuitive (stimulated Raman adiabatic passage) pulse sequences. Our results open a route to coupling valence excitations and core-hole excitations in molecules and aggregates that locally address specific atoms and represent an initial step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

Molecular imaging needles: dual-modality optical coherence tomography and fluorescence imaging of labeled antibodies deep in tissue

PubMed Central

Scolaro, Loretta; Lorenser, Dirk; Madore, Wendy-Julie; Kirk, Rodney W.; Kramer, Anne S.; Yeoh, George C.; Godbout, Nicolas; Sampson, David D.; Boudoux, Caroline; McLaughlin, Robert A.

2015-01-01

Molecular imaging using optical techniques provides insight into disease at the cellular level. In this paper, we report on a novel dual-modality probe capable of performing molecular imaging by combining simultaneous three-dimensional optical coherence tomography (OCT) and two-dimensional fluorescence imaging in a hypodermic needle. The probe, referred to as a molecular imaging (MI) needle, may be inserted tens of millimeters into tissue. The MI needle utilizes double-clad fiber to carry both imaging modalities, and is interfaced to a 1310-nm OCT system and a fluorescence imaging subsystem using an asymmetrical double-clad fiber coupler customized to achieve high fluorescence collection efficiency. We present, to the best of our knowledge, the first dual-modality OCT and fluorescence needle probe with sufficient sensitivity to image fluorescently labeled antibodies. Such probes enable high-resolution molecular imaging deep within tissue. PMID:26137379

Measurement of shear-induced diffusion of red blood cells using dynamic light scattering-optical coherence tomography

NASA Astrophysics Data System (ADS)

Tang, Jianbo; Erdener, Sefik Evren; Li, Baoqiang; Fu, Buyin; Sakadzic, Sava; Carp, Stefan A.; Lee, Jonghwan; Boas, David A.

2018-02-01

Dynamic Light Scattering-Optical Coherence Tomography (DLS-OCT) takes the advantages of using DLS to measure particle flow and diffusion within an OCT resolution-constrained 3D volume, enabling the simultaneous measurements of absolute RBC velocity and diffusion coefficient with high spatial resolution. In this work, we applied DLS-OCT to measure both RBC velocity and the shear-induced diffusion coefficient within penetrating venules of the somatosensory cortex of anesthetized mice. Blood flow laminar profile measurements indicate a blunted laminar flow profile, and the degree of blunting decreases with increasing vessel diameter. The measured shear-induced diffusion coefficient was proportional to the flow shear rate with a magnitude of 0.1 to 0.5 × 10-6 mm2 . These results provide important experimental support for the recent theoretical explanation for why DCS is dominantly sensitive to RBC diffusive motion.

Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

NASA Astrophysics Data System (ADS)

Tomić, Miloš C.; Djinović, Zoran V.; Scheerer, Michael; Petricevic, Slobodan J.

2018-01-01

A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts’ morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an ‘all-in-fiber’ Michelson interferometer based on a 3 × 3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty <1% and a precision of about 0.06° in the measuring range ±5° of the morphing wing deflection.

Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation.

PubMed

Li, Hua; Laffaille, Pierre; Gacemi, Djamal; Apfel, Marc; Sirtori, Carlo; Leonardon, Jeremie; Santarelli, Giorgio; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jerome; Hänsel, Wolfgang; Holzwarth, Ronald; Barbieri, Stefano

2015-12-28

We present an experimental investigation of the multimode dynamics and the coherence of terahertz quantum cascade lasers emitting over a spectral bandwidth of ~1THz. The devices are studied in free-running and under direct RF modulation. Depending on the pump current we observe different regimes of operation, where RF spectra displaying single and multiple narrow beat-note signals alternate with spectra showing a single beat-note characterized by an intense phase-noise, extending over a bandwidth up to a few GHz. We investigate the relation between this phase-noise and the dynamics of the THz modes through the electro-optic sampling of the laser emission. We find that when the phase-noise is large, the laser operates in an unstable regime where the lasing modes are incoherent. Under RF modulation of the laser current such instability can be suppressed and the modes coherence recovered, while, simultaneously, generating a strong broadening of the THz emission spectrum.

Design and validation of a multiplexed low coherence interferometry instrument for in vivo clinical measurement of microbicide gel thickness distribution

PubMed Central

Drake, Tyler K.; DeSoto, Michael G.; Peters, Jennifer J.; Henderson, Marcus H.; Murtha, Amy P.; Katz, David F.; Wax, Adam

2011-01-01

We present a multiplexed, Fourier-domain low coherence interferometry (mLCI) instrument for in vivo measurement of intravaginal microbicide gel coating thickness distribution over the surface of the vaginal epithelium. The mLCI instrument uses multiple delivery fibers to acquire depth resolved reflection profiles across large scanned tissue areas. Here mLCI has been adapted into an endoscopic system with a custom imaging module for simultaneous, co-registered measurements with fluorimetric scans of the same surface. The resolution, optical signal-to-noise, and cross-talk of the mLCI instrument are characterized to evaluate performance. Validation measurements of gel thickness are made using a calibration socket. Initial results from a clinical study are presented to show the in vivo capability of the dual-modality system for assessing the distribution of microbicide gel vehicles in the lower human female reproductive tract. PMID:22025989

3-dB signal-ASE beat noise reduction of coherent multi-carrier signal utilizing phase sensitive amplification.

PubMed

Umeki, Takeshi; Takara, Hidehiko; Miyamoto, Yutaka; Asobe, Masaki

2012-10-22

We demonstrated the simultaneous amplification of a coherent multi-carrier signal using a χ(2)-based non-degenerate phase sensitive amplifier (PSA). The signal-to-noise ratio (SNR), which is degraded by the additional amplified spontaneous emission (ASE) noise, can be recovered due to the gain difference between a phase-correlated signal-idler pair and uncorrelated excess noise. Utilizing the second harmonic pumping of a χ(2)-based PSA enables us to observe the SNR recovery directly by comparing the SNR for the input with that for the PSA output. A 3-dB optical-SNR (OSNR) improvement was obtained as a result of the gain difference. We also achieved a 3-dB SNR improvement in the electric domain by reducing the signal-ASE beat noise. The receiver sensitivity for a 10 Gbit/s phase shift keying signal was clearly improved with the PSA.

Doublet Pulse Coherent Laser Radar for Tracking of Resident Space Objects

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Rudd, Van; Shald, Scott; Sandford, Stephen; Dimarcantonio, Albert

2014-01-01

In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance modeling and engagement simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar parameters are presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits are discussed.

Cavity opto-mechanics using an optically levitated nanosphere

PubMed Central

Chang, D. E.; Regal, C. A.; Papp, S. B.; Wilson, D. J.; Ye, J.; Painter, O.; Kimble, H. J.; Zoller, P.

2010-01-01

Recently, remarkable advances have been made in coupling a number of high-Q modes of nano-mechanical systems to high-finesse optical cavities, with the goal of reaching regimes in which quantum behavior can be observed and leveraged toward new applications. To reach this regime, the coupling between these systems and their thermal environments must be minimized. Here we propose a novel approach to this problem, in which optically levitating a nano-mechanical system can greatly reduce its thermal contact, while simultaneously eliminating dissipation arising from clamping. Through the long coherence times allowed, this approach potentially opens the door to ground-state cooling and coherent manipulation of a single mesoscopic mechanical system or entanglement generation between spatially separate systems, even in room-temperature environments. As an example, we show that these goals should be achievable when the mechanical mode consists of the center-of-mass motion of a levitated nanosphere. PMID:20080573

Advanced optical fiber communication systems

NASA Astrophysics Data System (ADS)

Kazovsky, Leonid G.

1994-03-01

Our research is focused on three major aspects of advanced optical fiber communication systems: dynamic wavelength division multiplexing (WDM) networks, fiber nonlinearities, and high dynamic range coherent analog optical links. In the area of WDM networks, we have designed and implemented two high-speed interface boards and measured their throughput and latency. Furthermore, we designed and constructed an experimental PSK/ASK transceiver that simultaneously transmits packet-switched ASK data and circuit-switched PSK data on the same optical carrier. In the area of fiber nonlinearities, we investigated the theoretical impact of modulation frequency on cross-phase modulation (XPM) in dispersive fibers. In the area of high dynamic range coherent analog optical links, we developed theoretical expressions for the RF power transfer ratio (or RF power gain) and the noise figure (NF) of angle-modulated links. We then compared the RF power gains and noise figures of these links to that of an intensity modulated direct detection (DD) link.

Force-Manipulation Single-Molecule Spectroscopy Studies of Enzymatic Dynamics

NASA Astrophysics Data System (ADS)

Lu, H. Peter; He, Yufan; Lu, Maolin; Cao, Jin; Guo, Qing

2014-03-01

Subtle conformational changes play a crucial role in protein functions, especially in enzymatic reactions involving complex substrate-enzyme interactions and chemical reactions. We applied AFM-enhanced and magnetic tweezers-correlated single-molecule spectroscopy to study the mechanisms and dynamics of enzymatic reactions involved with kinase and lysozyme proteins. Enzymatic reaction turnovers and the associated structure changes of individual protein molecules were observed simultaneously in real-time by single-molecule FRET detections. Our single-molecule spectroscopy measurements of enzymatic conformational dynamics have revealed time bunching effect and intermittent coherence in conformational state change dynamics involving in enzymatic reaction cycles. The coherent conformational state dynamics suggests that the enzymatic catalysis involves a multi-step conformational motion along the coordinates of substrate-enzyme complex formation and product releasing. Our results support a multiple-conformational state model, being consistent with a complementary conformation selection and induced-fit enzymatic loop-gated conformational change mechanism in substrate-enzyme active complex formation.

Pyramidal cell-interneuron interactions underlie hippocampal ripple oscillations.

PubMed

Stark, Eran; Roux, Lisa; Eichler, Ronny; Senzai, Yuta; Royer, Sebastien; Buzsáki, György

2014-07-16

High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation, frequency control, and spatial coherence of the rhythm are poorly understood. Using multisite optogenetic manipulations in freely behaving rodents, we found that depolarization of a small group of nearby pyramidal cells was sufficient to induce high-frequency oscillations, whereas closed-loop silencing of pyramidal cells or activation of parvalbumin- (PV) or somatostatin-immunoreactive interneurons aborted spontaneously occurring ripples. Focal pharmacological blockade of GABAA receptors abolished ripples. Localized PV interneuron activation paced ensemble spiking, and simultaneous induction of high-frequency oscillations at multiple locations resulted in a temporally coherent pattern mediated by phase-locked interneuron spiking. These results constrain competing models of ripple generation and indicate that temporally precise local interactions between excitatory and inhibitory neurons support ripple generation in the intact hippocampus. Copyright © 2014 Elsevier Inc. All rights reserved.

Pyramidal Cell-Interneuron Interactions Underlie Hippocampal Ripple Oscillations

PubMed Central

Stark, Eran; Roux, Lisa; Eichler, Ronny; Senzai, Yuta; Royer, Sebastien; Buzsáki, György

2015-01-01

SUMMARY High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation, frequency control, and spatial coherence of the rhythm are poorly understood. Using multisite optogenetic manipulations in freely behaving rodents, we found that depolarization of a small group of nearby pyramidal cells was sufficient to induce high-frequency oscillations, whereas closed-loop silencing of pyramidal cells or activation of parvalbumin-(PV) or somatostatin-immunoreactive interneurons aborted spontaneously occurring ripples. Focal pharmacological blockade of GABAA receptors abolished ripples. Localized PV inter-neuron activation paced ensemble spiking, and simultaneous induction of high-frequency oscillations at multiple locations resulted in a temporally coherent pattern mediated by phase-locked inter-neuron spiking. These results constrain competing models of ripple generation and indicate that temporally precise local interactions between excitatory and inhibitory neurons support ripple generation in the intact hippocampus. PMID:25033186

High-Energy Density science at the Linac Coherent Light Source

DOE PAGES

Glenzer, S. H.; Fletcher, L. B.; Hastings, J. B.

2016-04-01

The Matter in Extreme Conditions end station at the Linac Coherent Light Source holds great promise for novel pump-probe experiments to make new discoveries in high- energy density science. Recently, our experiments have demonstrated the first spectrally- resolved measurements of plasmons using a seeded 8-keV x-ray laser beam. Forward x-ray Thomson scattering spectra from isochorically heated solid aluminum show a well-resolved plasmon feature that is down-shifted in energy by 19 eV from the incident 8 keV elastic scattering feature. In this spectral range, the simultaneously measured backscatter spectrum shows no spectral features indicating observation of collective plasmon oscillations on amore » scattering length comparable to the screening length. Moreover, this technique is a prerequisite for Thomson scattering measurements in compressed matter where the plasmon shift is a sensitive function of the free electron density and where the plasmon intensity provides information on temperature.« less

Ultracoherent operation of spin qubits with superexchange coupling

NASA Astrophysics Data System (ADS)

Rančić, Marko J.; Burkard, Guido

2017-11-01

With the use of nuclear-spin-free materials such as silicon and germanium, spin-based quantum bits (qubits) have evolved to become among the most coherent systems for quantum information processing. The new frontier for spin qubits has therefore shifted to the ubiquitous charge noise and spin-orbit interaction, which are limiting the coherence times and gate fidelities of solid-state qubits. In this paper we investigate superexchange, as a means of indirect exchange interaction between two single electron spin qubits, each embedded in a single semiconductor quantum dot (QD), mediated by an intermediate, empty QD. Our results suggest the existence of "supersweet spots", in which the qubit operations implemented by superexchange interaction are simultaneously first-order-insensitive to charge noise and to errors due to spin-orbit interaction. The proposed spin-qubit architecture is scalable and within the manufacturing capabilities of semiconductor industry.

Trends in optical coherence tomography applied to medical imaging

NASA Astrophysics Data System (ADS)

Podoleanu, Adrian G.

2014-01-01

The number of publications on optical coherence tomography (OCT) continues to double every three years. Traditionally applied to imaging the eye, OCT is now being extended to fields outside ophthalmology and optometry. Widening its applicability, progress in the core engine of the technology, and impact on development of novel optical sources, make OCT a very active and rapidly evolving field. Trends in the developments of different specific devices, such as optical sources, optical configurations and signal processing will be presented. Encompassing studies on both the configurations as well as on signal processing themes, current research in Kent looks at combining spectral domain with time domain imaging for long axial range and simultaneous imaging at several depths. Results of the collaborative work of the Applied Optics Group in Kent with organisers of this conference will be presented, with reference to 3D monitoring of abfraction.

Photoproduction of dileptons and photons in p -p collisions at the Large Hadron Collider energies

NASA Astrophysics Data System (ADS)

Ma, Zhi-Lei; Zhu, Jia-Qing

2018-03-01

The production of large pT dileptons and photons originating from photoproduction processes in p-p collisions at Large Hadron Collider energies is calculated. The comparisons between the exact treatment results and the ones of the equivalent photon approximation approach are expressed as the Q2 (the virtuality of photon) and pT distributions. The method developed by Martin and Ryskin is used for avoiding double counting when the coherent and incoherent contributions are considered simultaneously. The numerical results indicate that the equivalent photon approximation is only effective in small Q2 region and can be used for coherent photoproduction processes with proper choice of Qmax2 (the choices Qmax2˜s ^ or ∞ will cause obvious errors), but cannot be used for incoherent photoproduction processes. The exact treatment is needed to deal accurately with the photoproduction of large pT dileptons and photons.

Removal of Lipid from Serum Increases Coherence between Brucellosis Rapid Agglutination Test and Enzyme-linked Immunosorbent Assay in Bears in Alaska, USA.

PubMed

Godfroid, Jacques; Beckmen, Kimberlee; Helena Nymo, Ingebjørg

2016-10-01

In cases of chronic Brucella spp. infection, results of the rose bengal plate test (RBPT) and indirect enzyme-linked immunosorbent assay (ELISA) should be coherent, as reported in controlled conditions in the literature. We compared RBPT and ELISA results in 58 Alaska grizzly bears ( Ursus arctos horribilis), eight Kodiak brown bears ( Ursus arctos middendorffi), and six Alaska Peninsula brown bears ( Ursus arctos gyas). Of the 72 bears tested, 42 (58%) were ELISA positive and 53 (73%) were RBPT positive. However, the coherence between the tests was only fair (K=0.37, SE=0.11), suggesting that either the serologic results were not compatible with Brucella spp. infection or that there was a technical problem with the tests. To address a potential technical problem, we performed a 30-min chloroform/centrifugation cleanup. Following cleanup, the ELISA identified 43 positives (59%) and the RBPT identified 47 (65%), and the coherence between the tests was much improved (K=0.80, SE=0.07). We recommend cleaning wildlife sera with a high lipid content before performing RBPT and performing RBPT and ELISA in parallel to assess coherence. Our results suggest that Alaskan brown bears have been exposed to Brucella spp.

Optimal quantum operations at zero energy cost

NASA Astrophysics Data System (ADS)

Chiribella, Giulio; Yang, Yuxiang

2017-08-01

Quantum technologies are developing powerful tools to generate and manipulate coherent superpositions of different energy levels. Envisaging a new generation of energy-efficient quantum devices, here we explore how coherence can be manipulated without exchanging energy with the surrounding environment. We start from the task of converting a coherent superposition of energy eigenstates into another. We identify the optimal energy-preserving operations, both in the deterministic and in the probabilistic scenario. We then design a recursive protocol, wherein a branching sequence of energy-preserving filters increases the probability of success while reaching maximum fidelity at each iteration. Building on the recursive protocol, we construct efficient approximations of the optimal fidelity-probability trade-off, by taking coherent superpositions of the different branches generated by probabilistic filtering. The benefits of this construction are illustrated in applications to quantum metrology, quantum cloning, coherent state amplification, and ancilla-driven computation. Finally, we extend our results to transitions where the input state is generally mixed and we apply our findings to the task of purifying quantum coherence.

Collective coherence in nearest neighbor coupled metamaterials: A metasurface ruler equation

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

Xu, Ningning; Zhang, Weili, E-mail: weili.zhang@okstate.edu; Singh, Ranjan, E-mail: ranjans@ntu.edu.sg

The collective coherent interactions in a meta-atom lattice are the key to myriad applications and functionalities offered by metasurfaces. We demonstrate a collective coherent response of the nearest neighbor coupled split-ring resonators whose resonance shift decays exponentially in the strong near-field coupled regime. This occurs due to the dominant magnetic coupling between the nearest neighbors which leads to the decay of the electromagnetic near fields. Based on the size scaling behavior of the different periodicity metasurfaces, we identified a collective coherent metasurface ruler equation. From the coherent behavior, we also show that the near-field coupling in a metasurface lattice existsmore » even when the periodicity exceeds the resonator size. The identification of a universal coherence in metasurfaces and their scaling behavior would enable the design of novel metadevices whose spectral tuning response based on near-field effects could be calibrated across microwave, terahertz, infrared, and the optical parts of the electromagnetic spectrum.« less

Discovering Coherent Structures Using Local Causal States

NASA Astrophysics Data System (ADS)

Rupe, Adam; Crutchfield, James P.; Kashinath, Karthik; Prabhat, Mr.

2017-11-01

Coherent structures were introduced in the study of fluid dynamics and were initially defined as regions characterized by high levels of coherent vorticity, i.e. regions where instantaneously space and phase correlated vorticity are high. In a more general spatiotemporal setting, coherent structures can be seen as localized broken symmetries which persist in time. Building off the computational mechanics framework, which integrates tools from computation and information theory to capture pattern and structure in nonlinear dynamical systems, we introduce a theory of coherent structures, in the more general sense. Central to computational mechanics is the causal equivalence relation, and a local spatiotemporal generalization of it is used to construct the local causal states, which are utilized to uncover a system's spatiotemporal symmetries. Coherent structures are then identified as persistent, localized deviations from these symmetries. We illustrate how novel patterns and structures can be discovered in cellular automata and outline the path from them to laminar, transitional and turbulent flows. Funded by Intel through the Big Data Center at LBNL and the IPCC at UC Davis.

CSI 2264: Simultaneous optical and X-ray variability in pre-main sequence stars. I. Time resolved X-ray spectral analysis during optical dips and accretion bursts in stars with disks

NASA Astrophysics Data System (ADS)

Guarcello, M. G.; Flaccomio, E.; Micela, G.; Argiroffi, C.; Sciortino, S.; Venuti, L.; Stauffer, J.; Rebull, L.; Cody, A. M.

2017-06-01

Context. Pre-main sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray-active regions. In stars with disks, this variability is related to the morphology of the inner circumstellar region (≤0.1 AU) and that of the photosphere and corona, all impossible to be spatially resolved with present-day techniques. This has been the main motivation for the Coordinated Synoptic Investigation of NGC 2264, a set of simultaneous observations of NGC 2264 with 15 different telescopes. Aims: In this paper, we focus on the stars with disks. We analyze the X-ray spectral properties extracted during optical bursts and dips in order to unveil the nature of these phenomena. Stars without disks are studied in a companion paper. Methods: We analyze simultaneous CoRoT and Chandra/ACIS-I observations to search for coherent optical and X-ray flux variability in stars with disks. Then, stars are analyzed in two different samples. In stars with variable extinction, we look for a simultaneous increase of optical extinction and X-ray absorption during the optical dips; in stars with accretion bursts, we search for soft X-ray emission and increasing X-ray absorption during the bursts. Results: We find evidence for coherent optical and X-ray flux variability among the stars with variable extinction. In 9 of the 24 stars with optical dips, we observe a simultaneous increase of X-ray absorption and optical extinction. In seven dips, it is possible to calculate the NH/AV ratio in order to infer the composition of the obscuring material. In 5 of the 20 stars with optical accretion bursts, we observe increasing soft X-ray emission during the bursts that we associate to the emission of accreting gas. It is not surprising that these properties are not observed in all the stars with dips and bursts, since favorable geometric configurations are required. Conclusions: The observed variable absorption during the dips is mainly due to dust-free material in accretion streams. In stars with accretion bursts, we observe, on average, a larger soft X-ray spectral component not observed in non-accreting stars.

Midline frontal cortex low-frequency activity drives subthalamic nucleus oscillations during conflict.

PubMed

Zavala, Baltazar A; Tan, Huiling; Little, Simon; Ashkan, Keyoumars; Hariz, Marwan; Foltynie, Thomas; Zrinzo, Ludvic; Zaghloul, Kareem A; Brown, Peter

2014-05-21

Making the right decision from conflicting information takes time. Recent computational, electrophysiological, and clinical studies have implicated two brain areas as being crucial in assuring sufficient time is taken for decision-making under conditions of conflict: the medial prefrontal cortex and the subthalamic nucleus (STN). Both structures exhibit an elevation of activity at low frequencies (<10 Hz) during conflict that correlates with the amount of time taken to respond. This suggests that the two sites could become functionally coupled during conflict. To establish the nature of this interaction we recorded from deep-brain stimulation electrodes implanted bilaterally in the STN of 13 Parkinson's disease patients while they performed a sensory integration task involving randomly moving dots. By gradually increasing the number of dots moving coherently in one direction, we were able to determine changes in the STN associated with response execution. Furthermore, by occasionally having 10% of the dots move in the opposite direction as the majority, we were able to identify an independent increase in STN theta-delta activity triggered by conflict. Crucially, simultaneous midline frontal electroencephalographic recordings revealed an increase in the theta-delta band coherence between the two structures that was specific to high-conflict trials. Activity over the midline frontal cortex was Granger causal to that in STN. These results establish the cortico-subcortical circuit enabling successful choices to be made under conditions of conflict and provide support for the hypothesis that the brain uses frequency-specific channels of communication to convey behaviorally relevant information. Copyright © 2014 Zavala et al.

Electroencephalogram signatures of loss and recovery of consciousness from propofol

PubMed Central

Purdon, Patrick L.; Pierce, Eric T.; Mukamel, Eran A.; Prerau, Michael J.; Walsh, John L.; Wong, Kin Foon K.; Salazar-Gomez, Andres F.; Harrell, Priscilla G.; Sampson, Aaron L.; Cimenser, Aylin; Ching, ShiNung; Kopell, Nancy J.; Tavares-Stoeckel, Casie; Habeeb, Kathleen; Merhar, Rebecca; Brown, Emery N.

2013-01-01

Unconsciousness is a fundamental component of general anesthesia (GA), but anesthesiologists have no reliable ways to be certain that a patient is unconscious. To develop EEG signatures that track loss and recovery of consciousness under GA, we recorded high-density EEGs in humans during gradual induction of and emergence from unconsciousness with propofol. The subjects executed an auditory task at 4-s intervals consisting of interleaved verbal and click stimuli to identify loss and recovery of consciousness. During induction, subjects lost responsiveness to the less salient clicks before losing responsiveness to the more salient verbal stimuli; during emergence they recovered responsiveness to the verbal stimuli before recovering responsiveness to the clicks. The median frequency and bandwidth of the frontal EEG power tracked the probability of response to the verbal stimuli during the transitions in consciousness. Loss of consciousness was marked simultaneously by an increase in low-frequency EEG power (<1 Hz), the loss of spatially coherent occipital alpha oscillations (8–12 Hz), and the appearance of spatially coherent frontal alpha oscillations. These dynamics reversed with recovery of consciousness. The low-frequency phase modulated alpha amplitude in two distinct patterns. During profound unconsciousness, alpha amplitudes were maximal at low-frequency peaks, whereas during the transition into and out of unconsciousness, alpha amplitudes were maximal at low-frequency nadirs. This latter phase–amplitude relationship predicted recovery of consciousness. Our results provide insights into the mechanisms of propofol-induced unconsciousness, establish EEG signatures of this brain state that track transitions in consciousness precisely, and suggest strategies for monitoring the brain activity of patients receiving GA. PMID:23487781

Analysis of the Origin of Atypical Scanning Laser Polarimetry Patterns by Polarization-Sensitive Optical Coherence Tomography

PubMed Central

Götzinger, Erich; Pircher, Michael; Baumann, Bernhard; Hirn, Cornelia; Vass, Clemens; Hitzenberger, Christoph K.

2010-01-01

Purpose To analyze the physical origin of atypical scanning laser polarimetry (SLP) patterns. To compare polarization-sensitive optical coherence tomography (PS-OCT) scans to SLP images. To present a method to obtain pseudo-SLP images by PS-OCT that are free of atypical artifacts. Methods Forty-one eyes of healthy subjects, subjects with suspected glaucoma, and patients with glaucoma were imaged by SLP (GDx VCC) and a prototype spectral domain PS-OCT system. The PS-OCT system acquires three-dimensional (3D) datasets of intensity, retardation, and optic axis orientation simultaneously within 3 seconds. B-scans of intensity and retardation and en face maps of retinal nerve fiber layer (RNFL) retardation were derived from the 3D PS-OCT datasets. Results were compared with those obtained by SLP. Results Twenty-two eyes showed atypical retardation patterns, and 19 eyes showed normal patterns. From the 22 atypical eyes, 15 showed atypical patterns in both imaging modalities, five were atypical only in SLP images, and two were atypical only in PS-OCT images. In most (15 of 22) atypical cases, an increased penetration of the probing beam into the birefringent sclera was identified as the source of atypical patterns. In such cases, the artifacts could be eliminated in PS-OCT images by depth segmentation and exclusion of scleral signals. Conclusions PS-OCT provides deeper insight into the contribution of different fundus layers to SLP images. Increased light penetration into the sclera can distort SLP retardation patterns of the RNFL. PMID:19036999

Clinical cancer diagnosis using optical fiber-delivered coherent anti-stokes ramon scattering microscopy

NASA Astrophysics Data System (ADS)

Gao, Liang

This thesis describes the development of a combined label-free imaging and analytical strategy for intraoperative characterization of cancer lesions using the coherent anti-Stokes Raman scattering imaging (CARS) technique. A cell morphology-based analytical platform is developed to characterize CARS images and, hence, provide diagnostic information using disease-related pathology features. This strategy is validated for three different applications, including margin detection for radical prostatectomy, differential diagnosis of lung cancer, as well as detection and differentiation of breast cancer subtypes for in situ analysis of margin status during lumpectomy. As the major contribution of this thesis, the developed analytical strategy shows high accuracy and specificity for all three diseases and thus has introduced the CARS imaging technique into the field of human cancer diagnosis, which holds substantial potential for clinical translations. In addition, I have contributed a project aimed at miniaturizing the CARS imaging device into a microendoscope setup through a fiber-delivery strategy. A four-wave-mixing (FWM) background signal, which is caused by simultaneous delivery of the two CARS-generating excitation laser beams, is initially identified. A polarization-based strategy is then introduced and tested for suppression of this FWM noise. The approach shows effective suppression of the FWM signal, both on microscopic and prototype endoscopic setups, indicating the potential of developing a novel microendoscope with a compatible size for clinical use. These positive results show promise for the development of an all-fiber-based, label-free imaging and analytical platform for minimally invasive detection and diagnosis of cancers during surgery or surgical-biopsy, thus improving surgical outcomes and reducing patients' suffering.

In vivo lipid saturation study of C. elegans using quantitative broadband coherent anti-Stokes Raman imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Littleton, Bradley; Kavanagh, Thomas; Nie, Yu; Abbate, Vincenzo; Hylands, Peter; Sturzenbaum, Stephen; Richards, David

2016-03-01

In vivo lipid saturation maps of microscopic nematodes (Caenorhabditis elegans) have been produced using our novel Spectral Interferometric Polarisation Coherent anti-Stokes Raman Scattering (SIP-CARS) imaging technique. This technique employs simple passive polarisation optics and a balanced homodyne detection scheme to exploit symmetries in the CARS polarisation response resulting in the complete cancellation of the non-resonant background (NRB) and real component of the CARS signal (with no prior or post assumptions as regards to their form). The remaining imaginary component of the CARS response is linear with analyte concentration and directly relatable to the spontaneous Raman spectrum [1]. Furthermore, the resonant CARS signal is interferometrically amplified by the non-resonant response, a necessity for rapid imaging at biologically relevant powers [2]. This technique permits acquisition of a broad NRB-free spectrum, in excess of 1800cm-1, in a single exposure at each pixel. This allows simultaneous determination of lipid droplet saturation, from the fingerprint region, and lipid order, from the C-H stretch region from which maps can be readily constructed. Additionally exploiting the dispersive nature of our signal collection two-photon autofluorescence can be isolated and images subsequently produced. We have successfully applied this technique to identify differences in lipid saturation distributions in selective C. elegans mutants and demonstrated that the technique is sufficiently sensitive to detect the effects of lipid metabolism altering drugs on wild type C. elegans. [1] Littleton et al, Phys Rev Lett, 111, 103902 (2013) [2] Parekh et al, Biophys J, 99, 2695-2704 (2010)

Bullied at school, bullied at work: a prospective study.

PubMed

Andersen, Lars Peter; Labriola, Merete; Andersen, Johan Hviid; Lund, Thomas; Hansen, Claus D

2015-10-12

The consequences of childhood bullying victimisation are serious. Much previous research on risk factors for being bullied has used a cross-sectional design, impeding the possibility to draw conclusions on causality, and has not considered simultaneous effects of multiple risk factors. Paying closer attention to multiple risk factors for being bullying can provide a basis for designing intervention programmes to prevent or reduce bullying among children and adolescents. Risk factors for bullying were examined by using questionnaire data collected in 2004 and 2007. In 2004, the participants were aged 14-15 years and 17-18 years in 2007. The baseline questionnaire was answered by 3054 individuals in 2004, and 2181 individuals participated in both rounds. We analysed risk factors for being bullied at the individual and societal level. Information on the social background of the participants was derived from a national register at Statistics Denmark. Several risk factors were identified. Being obese, low self-assessed position in school class, overprotective parents, low self-esteem, low sense of coherence and low socioeconomic status were risk factors for being bullied at school. Being overweight, smoking, low self-assessed position in class, low sense of coherence and low socioeconomic status were risk factors for being bullied at work. However, most associations between risk factors in 2004 and being bullied in 2007 disappeared after adjustment for being bullied in 2004. The strongest risk factor for being bullied was being previously bullied. Our results stress the importance of early prevention of bullying at schools. In addition, attention should be drawn to the role of overprotective parents.

Three-dimensional curvilinear device reconstruction from two fluoroscopic views

NASA Astrophysics Data System (ADS)

Delmas, Charlotte; Berger, Marie-Odile; Kerrien, Erwan; Riddell, Cyril; Trousset, Yves; Anxionnat, René; Bracard, Serge

2015-03-01

In interventional radiology, navigating devices under the sole guidance of fluoroscopic images inside a complex architecture of tortuous and narrow vessels like the cerebral vascular tree is a difficult task. Visualizing the device in 3D could facilitate this navigation. For curvilinear devices such as guide-wires and catheters, a 3D reconstruction may be achieved using two simultaneous fluoroscopic views, as available on a biplane acquisition system. The purpose of this paper is to present a new automatic three-dimensional curve reconstruction method that has the potential to reconstruct complex 3D curves and does not require a perfect segmentation of the endovascular device. Using epipolar geometry, our algorithm translates the point correspondence problem into a segment correspondence problem. Candidate 3D curves can be formed and evaluated independently after identifying all possible combinations of compatible 3D segments. Correspondence is then inherently solved by looking in 3D space for the most coherent curve in terms of continuity and curvature. This problem can be cast into a graph problem where the most coherent curve corresponds to the shortest path of a weighted graph. We present quantitative results of curve reconstructions performed from numerically simulated projections of tortuous 3D curves extracted from cerebral vascular trees affected with brain arteriovenous malformations as well as fluoroscopic image pairs of a guide-wire from both phantom and clinical sets. Our method was able to select the correct 3D segments in 97.5% of simulated cases thus demonstrating its ability to handle complex 3D curves and can deal with imperfect 2D segmentation.

Neural Correlates of Wakefulness, Sleep, and General Anesthesia: An Experimental Study in Rat.

PubMed

Pal, Dinesh; Silverstein, Brian H; Lee, Heonsoo; Mashour, George A

2016-11-01

Significant advances have been made in our understanding of subcortical processes related to anesthetic- and sleep-induced unconsciousness, but the associated changes in cortical connectivity and cortical neurochemistry have yet to be fully clarified. Male Sprague-Dawley rats were instrumented for simultaneous measurement of cortical acetylcholine and electroencephalographic indices of corticocortical connectivity-coherence and symbolic transfer entropy-before, during, and after general anesthesia (propofol, n = 11; sevoflurane, n = 13). In another group of rats (n = 7), these electroencephalographic indices were analyzed during wakefulness, slow wave sleep (SWS), and rapid eye movement (REM) sleep. Compared to wakefulness, anesthetic-induced unconsciousness was characterized by a significant decrease in cortical acetylcholine that recovered to preanesthesia levels during recovery wakefulness. Corticocortical coherence and frontal-parietal symbolic transfer entropy in high γ band (85 to 155 Hz) were decreased during anesthetic-induced unconsciousness and returned to preanesthesia levels during recovery wakefulness. Sleep-wake states showed a state-dependent change in coherence and transfer entropy in high γ bandwidth, which correlated with behavioral arousal: high during wakefulness, low during SWS, and lowest during REM sleep. By contrast, frontal-parietal θ connectivity during sleep-wake states was not correlated with behavioral arousal but showed an association with well-established changes in cortical acetylcholine: high during wakefulness and REM sleep and low during SWS. Corticocortical coherence and frontal-parietal connectivity in high γ bandwidth correlates with behavioral arousal and is not mediated by cholinergic mechanisms, while θ connectivity correlates with cortical acetylcholine levels.

Enhanced coherence within the theta band between pairs of brains engaging in experienced versus naïve Reiki procedures.

PubMed

Ventura, Anabela Carraca; Persinger, Michael A

2014-08-01

The study objective was to discern whether the coherence between brain activities of the "patient" and practitioner differ between Reiki experts and novices. If the physical process associated with Reiki involves "convergence" between the practitioner and subject, then this congruence should be evident in time-dependent shared power within specific and meaningful frequency electroencephalographic bands. Simultaneous quantitative electroencephalogram measures (19 channels) were recorded from 9 pairs of subjects when 1 of the pairs was an experienced Reiki practitioner or had just been shown the procedure. Pairs recorded their experiences and images. The "practitioner" and "patient" pairs were measured within a quiet, comfortable acoustic chamber. Real-time correlations and coherence between pairs of brains for power (μV(2)·Hz(-1)) within the various frequency bands over the 10-min sessions were recorded and analyzed for each pair. Descriptors of experiences were analyzed for word meanings. Only the coherence within the theta range increased over time between the brains of the Reiki pairs relative to the Sham pairs, particularly over the left hemisphere. The pleasantness-unpleasantness rating for the words employed to describe experiences written after the experiment were more congruent for the Reiki pairs compared to the reference pairs. The increased synchronization of the cerebral activity of the participant and the practitioner during proximal therapies involving touch such as Reiki may be an important component of any subsequent beneficial effects.

Turbulent upwelling of mid-latitude ionosphere. 1. Observational results by the MU radar

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

Fukao, Shoichiro; Shirakawa, Tatsuya; Takami, Tomoyuki

1991-03-01

In this paper, the authors present the detailed results of a series of experiments designed to study the coherent backscatter of 50-MHz radar waves from the mid-latitude F region. Data were obtained with the active phased-array MU radar in Japan and include some auxiliary E region coherent echoes as well.The strongest echoes correspond to irregularities at least 20 dB stronger than thermal backscatter at the same frequency from typical F region densities at the same range. Simultaneous observations with ionosondes show that these echoes occur during strong mid-latitude spread F. As defined by ionosondes, the latter phenomenon is certainly muchmore » more widespread than the turbulent upwelling events described here, but they believe that in some sense these correspond to the most violent mid-latitude spread F. The strongest echoes occur in large patches which display away Doppler shifts corresponding to irregularity motion upward and northward from the radar. At the edges of these patches there is often a brief period of toward Doppler before the echoing region ceases. On rare occasions comparable patches of strong away and toward Doppler are detected, although in such cases the Doppler width of the toward echoes is much narrower than that of the away echoes. The multiple beam capability at MU allowed us to track the patches in the zonal direction on two days. The patches moved east to west in both cases at velocities of 125 m/s and 185 m/s, respectively. There is a distinct tendency for the bottom contour of the scattering region to be modulated at the same period as the patch occurence frequency as well as at higher frequencies. This higher-frequency component may correspond to substructures in the large patches and to the E region coherent scatter patches which were detected simultaneously in several multiple beam experiments.« less

Source analysis of beta-synchronisation and cortico-muscular coherence after movement termination based on high resolution electroencephalography.

PubMed

Muthuraman, Muthuraman; Tamás, Gertrúd; Hellriegel, Helge; Deuschl, Günther; Raethjen, Jan

2012-01-01

We hypothesized that post-movement beta synchronization (PMBS) and cortico-muscular coherence (CMC) during movement termination relate to each other and have similar role in sensorimotor integration. We calculated the parameters and estimated the sources of these phenomena.We measured 64-channel EEG simultaneously with surface EMG of the right first dorsal interosseus muscle in 11 healthy volunteers. In Task1, subjects kept a medium-strength contraction continuously; in Task2, superimposed on this movement, they performed repetitive self-paced short contractions. In Task3 short contractions were executed alone. Time-frequency analysis of the EEG and CMC was performed with respect to the offset of brisk movements and averaged in each subject. Sources of PMBS and CMC were also calculated.High beta power in Task1, PMBS in Task2-3, and CMC in Task1-2 could be observed in the same individual frequency bands. While beta synchronization in Task1 and PMBS in Task2-3 appeared bilateral with contralateral predominance, CMC in Task1-2 was strictly a unilateral phenomenon; their main sources did not differ contralateral to the movement in the primary sensorimotor cortex in 7 of 11 subjects in Task1, and in 6 of 9 subjects in Task2. In Task2, CMC and PMBS had the same latency but their amplitudes did not correlate with each other. In Task2, weaker PMBS source was found bilaterally within the secondary sensory cortex, while the second source of CMC was detected in the premotor cortex, contralateral to the movement. In Task3, weaker sources of PMBS could be estimated in bilateral supplementary motor cortex and in the thalamus. PMBS and CMC appear simultaneously at the end of a phasic movement possibly suggesting similar antikinetic effects, but they may be separate processes with different active functions. Whereas PMBS seems to reset the supraspinal sensorimotor network, cortico-muscular coherence may represent the recalibration of cortico-motoneuronal and spinal systems.

Isolation of Coherent Synchrotron Emission During Relativistic Laser Plasma Interactions

NASA Astrophysics Data System (ADS)

Dromey, B.; Rykovanov, S. G.; Lewis, C. L. S.; Zepf, M.

Coherent Synchrotron Emission (CSE) from relativistic laser plasmas (Pukhov et al., Plas Phys Control Fusion 52:124039, 2010; Dromey et al., Nat Phys 8:804-808, 2012; Dromey et al., New J Phys 15:015025, 2013) has recently been identified as a unique platform for the generation of coherent extreme ultraviolet (XUV) and X-Ray radiation with clear potential for bright attosecond pulse production. Exploiting this potential requires careful selection of interaction geometry, spectral wavelength range and target characteristics to allow the generation of high fidelity single attosecond pulses. In the laboratory the first step on this road is to study the individual mechanisms driving the emission of coherent extreme ultraviolet and X-Ray radiation during laser solid interactions in isolation. Here we show how interactions can be tailored to permit the unambiguous observation of coherent synchrotron emission (CSE) and the implications of this geometry for the resulting harmonic spectrum over the duration of the interaction.

Coherent quantum depletion of an interacting atom condensate

PubMed Central

Kira, M.

2015-01-01

Sufficiently strong interactions promote coherent quantum transitions in spite of thermalization and losses, which are the adversaries of delicate effects such as reversibility and correlations. In atomic Bose–Einstein condensates (BECs), strong atom–atom interactions can eject atoms from the BEC to the normal component, yielding quantum depletion instead of temperature depletion. A recent experiment has already been verified to overcome losses. Here I show that it also achieves coherent quantum-depletion dynamics in a BEC swept fast enough from weak to strong atom–atom interactions. The elementary coherent process first excites the normal component into a liquid state that evolves into a spherical shell state, where the atom occupation peaks at a finite momentum to shield 50% of the BEC atoms from annihilation. The identified coherent processes resemble ultrafast semiconductor excitations expanding the scope of BEC explorations to many-body non-equilibrium studies. PMID:25767044

Compression and information recovery in ptychography

NASA Astrophysics Data System (ADS)

Loetgering, L.; Treffer, D.; Wilhein, T.

2018-04-01

Ptychographic coherent diffraction imaging (PCDI) is a scanning microscopy modality that allows for simultaneous recovery of object and illumination information. This ability renders PCDI a suitable technique for x-ray lensless imaging and optics characterization. Its potential for information recovery typically relies on large amounts of data redundancy. However, the field of view in ptychography is practically limited by the memory and the computational facilities available. We describe techniques that achieve robust ptychographic information recovery at high compression rates. The techniques are compared and tested with experimental data.

Multiple Point Dynamic Gas Density Measurements Using Molecular Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard; Panda, Jayanta

1999-01-01

A nonintrusive technique for measuring dynamic gas density properties is described. Molecular Rayleigh scattering is used to measure the time-history of gas density simultaneously at eight spatial locations at a 50 kHz sampling rate. The data are analyzed using the Welch method of modified periodograms to reduce measurement uncertainty. Cross-correlations, power spectral density functions, cross-spectral density functions, and coherence functions may be obtained from the data. The technique is demonstrated using low speed co-flowing jets with a heated inner jet.

Real-time optical holographic tracking of multiple objects

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin; Liu, Hua-Kuang

1989-01-01

A coherent optical correlation technique for real-time simultaneous tracking of several different objects making independent movements is described, and experimental results are presented. An evaluation of this system compared with digital computing systems is made. The real-time processing capability is obtained through the use of a liquid crystal television spatial light modulator and a dichromated gelatin multifocus hololens. A coded reference beam is utilized in the separation of the output correlation plane associated with each input target so that independent tracking can be achieved.

A Procedure to Detect Item Bias Present Simultaneously in Several Items

DTIC Science & Technology

1991-04-25

exhibit a coherent and major biasing influence at the test level. In partic- ular, this can be true even if each individual item displays only a minor...response functions (IRFs) without the use of item parameter estimation algorithms when the sample size is too small for their use. Thissen, Steinberg...convention). A random sample of examinees is drawn from each group, and a test of N items is administered to them. Typically it is suspected that a

Nonclassical light revealed by the joint statistics of simultaneous measurements.

PubMed

Luis, Alfredo

2016-04-15

Nonclassicality cannot be a single-observable property, since the statistics of any quantum observable is compatible with classical physics. We develop a general procedure to reveal nonclassical behavior of light states from the joint statistics arising in the practical measurement of multiple observables. Beside embracing previous approaches, this protocol can disclose nonclassical features for standard examples of classical-like behavior, such as SU(2) and Glauber coherent states. When combined with other criteria, this would imply that every light state is nonclassical.

Application of CARS to scramjet combustion

NASA Technical Reports Server (NTRS)

Antcliff, R. R.

1987-01-01

A coherent anti-Stokes Raman spectroscopic (CARS) instrument has been developed for measuring simultaneously temperature and N2 - O2 species concentration in hostile flame environments. A folded BOXCARS arrangement was employed to obtain high spatial resolution. Polarization discrimination against the nonresonant background decreased the lower limits of O2 detectivity. The instrument has been primarily employed for validation of computational fluid-dynamics computer-model codes. Comparisons have been made to both the CHARNAL and TEACH codes on a hydrogen diffusion flame with good results.

Photonic sensing based on variation of propagation properties of photonic crystal fibres

NASA Astrophysics Data System (ADS)

Rothwell, John H.; Flavin, Dónal A.; MacPherson, William N.; Jones, Julian D.; Knight, Jonathan C.; Russell, Philip St. J.

2006-12-01

We report on a low-coherence interferometric scheme for the measurement of the strain and temperature dependences of group delay and dispersion in short, index-guiding, 'endlessly-single-mode' photonic crystal fibre elements in the 840 nm and 1550 nm regions. Based on the measurements, we propose two schemes for simultaneous strain and temperature measurement using a single unmodified PCF element, without a requirement for any compensating components, and we project the measurement accuracies of these schemes.

A quantum trampoline for ultra-cold atoms

NASA Astrophysics Data System (ADS)

Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Bordé, Ch. J.; Aspect, A.; Bourdel, T.; Bouyer, P.

2010-01-01

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. This scheme permits simultaneously the compensation of gravity and coherent splitting/recombination of the matter waves. It results in high-contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We characterize our atom interferometer and use it to measure the acceleration of gravity.

Imaging separation of neuronal from vascular effects of cocaine on rat cortical brain in vivo

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

Yuan, Z.; Du, C.; Yuan, Z.

MRI techniques to study brain function assume coupling between neuronal activity, metabolism and flow. However, recent evidence of physiological uncoupling between neuronal and cerebrovascular events highlights the need for methods to simultaneously measure these three properties. We report a multimodality optical approach that integrates dual-wavelength laser speckle imaging (measures changes in blood flow, blood volume and hemoglobin oxygenation), digital-frequency-ramping optical coherence tomography (images quantitative 3D vascular network) and Rhod2 fluorescence (images intracellular calcium for measure of neuronal activity) at high spatiotemporal resolutions (30 {micro}m, 10 Hz) and over a large field of view (3 x 5 mm{sup 2}). We applymore » it to assess cocaine's effects in rat cortical brain and show an immediate decrease 3.5 {+-} 0.9 min, phase (1) in the oxygen content of hemoglobin and the cerebral blood flow followed by an overshoot 7.1 {+-} 0.2 min, phase (2) lasting over 20 min whereas Ca{sup 2+} increased immediately (peaked at t = 4.1 {+-} 0.4 min) and remained elevated. This enabled us to identify a delay (2.9 {+-} 0.5 min) between peak neuronal and vascular responses in phase 2. The ability of this multimodality optical approach for simultaneous imaging at high spatiotemporal resolutions permits us to distinguish the vascular versus cellular changes of the brain, thus complimenting other neuroimaging modalities for brain functional studies (e. g., PET, fMRI).« less

Temporal coherence of high-order harmonics generated at solid surfaces

NASA Astrophysics Data System (ADS)

Hemmers, D.; Behmke, M.; Karsch, S.; Keyling, J.; Major, Z.; Stelzmann, C.; Pretzler, G.

2014-07-01

We present interferometric measurements of the temporal coherence of high-order harmonics generated by reflection of a titanium sapphire laser off a solid surface. It is found that the coherence length of the harmonic emission is significantly reduced compared with the bandwidth limited case. To identify the responsible mechanism, the acquired data were analyzed by means of particle-in-cell simulations, whose results show good agreement between the calculated spectra and the measured coherence times. We show that the observed broadening can be understood consistently by the occurrence of a Doppler shift induced by the moving plasma surface, which is dented by the radiation pressure of the laser pulse. In this case, this Doppler effect would also lead to positive chirp of the emitted radiation.

High-Resolution In Vivo Imaging of Regimes of Laser Damage to the Primate Retina

PubMed Central

Pocock, Ginger M.; Oliver, Jeffrey W.; Specht, Charles S.; Estep, J. Scot; Noojin, Gary D.; Schuster, Kurt; Rockwell, Benjamin A.

2014-01-01

Purpose. To investigate fundamental mechanisms of regimes of laser induced damage to the retina and the morphological changes associated with the damage response. Methods. Varying grades of photothermal, photochemical, and photomechanical retinal laser damage were produced in eyes of eight cynomolgus monkeys. An adaptive optics confocal scanning laser ophthalmoscope and spectral domain optical coherence tomographer were combined to simultaneously collect complementary in vivo images of retinal laser damage during and following exposure. Baseline color fundus photography was performed to complement high-resolution imaging. Monkeys were perfused with 10% buffered formalin and eyes were enucleated for histological analysis. Results. Laser energies for visible retinal damage in this study were consistent with previously reported damage thresholds. Lesions were identified in OCT images that were not visible in direct ophthalmoscopic examination or fundus photos. Unique diagnostic characteristics, specific to each damage regime, were identified and associated with shape and localization of lesions to specific retinal layers. Previously undocumented retinal healing response to blue continuous wave laser exposure was recorded through a novel experimental methodology. Conclusion. This study revealed increased sensitivity of lesion detection and improved specificity to the laser of origin utilizing high-resolution imaging when compared to traditional ophthalmic imaging techniques in the retina. PMID:24891943

The Development and Coherence of Future-Oriented Behaviors during the Preschool Years

ERIC Educational Resources Information Center

Atance, Cristina M.; Jackson, Laura K.

2009-01-01

Although previous research has identified a number of interesting aspects of future thinking in adults, little is known about the developmental trajectory and coherence of future-oriented behaviors during early childhood. The primary goal of this study was to explore these issues by administering a battery of tasks assessing different aspects of…

A phase coherence approach to estimating the spatial extent of earthquakes

NASA Astrophysics Data System (ADS)

Hawthorne, Jessica C.; Ampuero, Jean-Paul

2016-04-01

We present a new method for estimating the spatial extent of seismic sources. The approach takes advantage of an inter-station phase coherence computation that can identify co-located sources (Hawthorne and Ampuero, 2014). Here, however, we note that the phase coherence calculation can eliminate the Green's function and give high values only if both earthquakes are point sources---if their dimensions are much smaller than the wavelengths of the propagating seismic waves. By examining the decrease in coherence at higher frequencies (shorter wavelengths), we can estimate the spatial extents of the earthquake ruptures. The approach can to some extent be seen as a simple way of identifying directivity or variations in the apparent source time functions recorded at various stations. We apply this method to a set of well-recorded earthquakes near Parkfield, CA. We show that when the signal to noise ratio is high, the phase coherence remains high well above 50 Hz for closely spaced M<1.5 earthquake. The high-frequency phase coherence is smaller for larger earthquakes, suggesting larger spatial extents. The implied radii scale roughly as expected from typical magnitude-corner frequency scalings. We also examine a second source of high-frequency decoherence: spatial variation in the shape of the Green's functions. This spatial decoherence appears to occur on a similar wavelengths as the decoherence associated with the apparent source time functions. However, the variation in Green's functions can be normalized away to some extent by comparing observations at multiple components on a single station, which see the same apparent source time functions.

Detecting and Analyzing Multiple Moving Objects in Crowded Environments with Coherent Motion Regions

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

Cheriyadat, Anil M.

Understanding the world around us from large-scale video data requires vision systems that can perform automatic interpretation. While human eyes can unconsciously perceive independent objects in crowded scenes and other challenging operating environments, automated systems have difficulty detecting, counting, and understanding their behavior in similar scenes. Computer scientists at ORNL have a developed a technology termed as "Coherent Motion Region Detection" that invloves identifying multiple indepedent moving objects in crowded scenes by aggregating low-level motion cues extracted from moving objects. Humans and other species exploit such low-level motion cues seamlessely to perform perceptual grouping for visual understanding. The algorithm detectsmore » and tracks feature points on moving objects resulting in partial trajectories that span coherent 3D region in the space-time volume defined by the video. In the case of multi-object motion, many possible coherent motion regions can be constructed around the set of trajectories. The unique approach in the algorithm is to identify all possible coherent motion regions, then extract a subset of motion regions based on an innovative measure to automatically locate moving objects in crowded environments.The software reports snapshot of the object, count, and derived statistics ( count over time) from input video streams. The software can directly process videos streamed over the internet or directly from a hardware device (camera).« less

Coherence in quantum estimation

NASA Astrophysics Data System (ADS)

Giorda, Paolo; Allegra, Michele

2018-01-01

The geometry of quantum states provides a unifying framework for estimation processes based on quantum probes, and it establishes the ultimate bounds of the achievable precision. We show a relation between the statistical distance between infinitesimally close quantum states and the second order variation of the coherence of the optimal measurement basis with respect to the state of the probe. In quantum phase estimation protocols, this leads to propose coherence as the relevant resource that one has to engineer and control to optimize the estimation precision. Furthermore, the main object of the theory i.e. the symmetric logarithmic derivative, in many cases allows one to identify a proper factorization of the whole Hilbert space in two subsystems. The factorization allows one to discuss the role of coherence versus correlations in estimation protocols; to show how certain estimation processes can be completely or effectively described within a single-qubit subsystem; and to derive lower bounds for the scaling of the estimation precision with the number of probes used. We illustrate how the framework works for both noiseless and noisy estimation procedures, in particular those based on multi-qubit GHZ-states. Finally we succinctly analyze estimation protocols based on zero-temperature critical behavior. We identify the coherence that is at the heart of their efficiency, and we show how it exhibits the non-analyticities and scaling behavior proper of a large class of quantum phase transitions.

Multiplexed image storage by electromagnetically induced transparency in a solid

NASA Astrophysics Data System (ADS)

Heinze, G.; Rentzsch, N.; Halfmann, T.

2012-11-01

We report on frequency- and angle-multiplexed image storage by electromagnetically induced transparency (EIT) in a Pr3+:Y2SiO5 crystal. Frequency multiplexing by EIT relies on simultaneous storage of light pulses in atomic coherences, driven in different frequency ensembles of the inhomogeneously broadened solid medium. Angular multiplexing by EIT relies on phase matching of the driving laser beams, which permits simultaneous storage of light pulses propagating under different angles into the crystal. We apply the multiplexing techniques to increase the storage capacity of the EIT-driven optical memory, in particular to implement multiplexed storage of larger two-dimensional amounts of data (images). We demonstrate selective storage and readout of images by frequency-multiplexed EIT and angular-multiplexed EIT, as well as the potential to combine both multiplexing approaches towards further enhanced storage capacities.

Digitally enhanced homodyne interferometry.

PubMed

Sutton, Andrew J; Gerberding, Oliver; Heinzel, Gerhard; Shaddock, Daniel A

2012-09-24

We present two variations of a novel interferometry technique capable of simultaneously measuring multiple targets with high sensitivity. The technique performs a homodyne phase measurement by application of a four point phase shifting algorithm, with pseudo-random switching between points to allow multiplexed measurement based upon propagation delay alone. By multiplexing measurements and shifting complexity into signal processing, both variants realise significant complexity reductions over comparable methods. The first variant performs a typical coherent detection with a dedicated reference field and achieves a displacement noise floor 0.8 pm/√Hz above 50 Hz. The second allows for removal of the dedicated reference, resulting in further simplifications and improved low frequency performance with a 1 pm/√Hz noise floor measured down to 20 Hz. These results represent the most sensitive measurement performed using this style of interferometry whilst simultaneously reducing the electro-optic footprint.

Multiplex coherent raman spectroscopy detector and method

NASA Technical Reports Server (NTRS)

Joyner, Candace C. (Inventor); Patrick, Sheena T. (Inventor); Chen, Peter (Inventor); Guyer, Dean R. (Inventor)

2004-01-01

A multiplex coherent Raman spectrometer (10) and spectroscopy method rapidly detects and identifies individual components of a chemical mixture separated by a separation technique, such as gas chromatography. The spectrometer (10) and method accurately identify a variety of compounds because they produce the entire gas phase vibrational Raman spectrum of the unknown gas. This is accomplished by tilting a Raman cell (20) to produce a high-intensity, backward-stimulated, coherent Raman beam of 683 nm, which drives a degenerate optical parametric oscillator (28) to produce a broadband beam of 1100-1700 nm covering a range of more than 3000 wavenumber. This broadband beam is combined with a narrowband beam of 532 nm having a bandwidth of 0.003 wavenumbers and focused into a heated windowless cell (38) that receives gases separated by a gas chromatograph (40). The Raman radiation scattered from these gases is filtered and sent to a monochromator (50) with multichannel detection.

Multiplex coherent raman spectroscopy detector and method

DOEpatents

Chen, Peter; Joyner, Candace C.; Patrick, Sheena T.; Guyer, Dean R.

2004-06-08

A multiplex coherent Raman spectrometer (10) and spectroscopy method rapidly detects and identifies individual components of a chemical mixture separated by a separation technique, such as gas chromatography. The spectrometer (10) and method accurately identify a variety of compounds because they produce the entire gas phase vibrational Raman spectrum of the unknown gas. This is accomplished by tilting a Raman cell (20) to produce a high-intensity, backward-stimulated, coherent Raman beam of 683 nm, which drives a degenerate optical parametric oscillator (28) to produce a broadband beam of 1100-1700 nm covering a range of more than 3000 wavenumber. This broadband beam is combined with a narrowband beam of 532 nm having a bandwidth of 0.003 wavenumbers and focused into a heated windowless cell (38) that receives gases separated by a gas chromatograph (40). The Raman radiation scattered from these gases is filtered and sent to a monochromator (50) with multichannel detection.

Optimized suppression of coherent noise from seismic data using the Karhunen-Loève transform

NASA Astrophysics Data System (ADS)

Montagne, Raúl; Vasconcelos, Giovani L.

2006-07-01

Signals obtained in land seismic surveys are usually contaminated with coherent noise, among which the ground roll (Rayleigh surface waves) is of major concern for it can severely degrade the quality of the information obtained from the seismic record. This paper presents an optimized filter based on the Karhunen-Loève transform for processing seismic images contaminated with ground roll. In this method, the contaminated region of the seismic record, to be processed by the filter, is selected in such way as to correspond to the maximum of a properly defined coherence index. The main advantages of the method are that the ground roll is suppressed with negligible distortion of the remnant reflection signals and that the filtering procedure can be automated. The image processing technique described in this study should also be relevant for other applications where coherent structures embedded in a complex spatiotemporal pattern need to be identified in a more refined way. In particular, it is argued that the method is appropriate for processing optical coherence tomography images whose quality is often degraded by coherent noise (speckle).

New topics in coherent anti-stokes raman scattering gas-phase diagnostics : femtosecond rotational CARS and electric-field measurements.

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

Lempert, Walter R.; Barnat, Edward V.; Kearney, Sean Patrick

2010-07-01

We discuss two recent diagnostic-development efforts in our laboratory: femtosecond pure-rotational Coherent anti-Stokes Raman scattering (CARS) for thermometry and species detection in nitrogen and air, and nanosecond vibrational CARS measurements of electric fields in air. Transient pure-rotational fs-CARS data show the evolution of the rotational Raman polarization in nitrogen and air over the first 20 ps after impulsive pump/Stokes excitation. The Raman-resonant signal strength at long time delays is large, and we additionally observe large time separation between the fs-CARS signatures of nitrogen and oxygen, so that the pure-rotational approach to fs-CARS has promise for simultaneous species and temperature measurementsmore » with suppressed nonresonant background. Nanosecond vibrational CARS of nitrogen for electric-field measurements is also demonstrated. In the presence of an electric field, a dipole is induced in the otherwise nonpolar nitrogen molecule, which can be probed with the introduction of strong collinear pump and Stokes fields, resulting in CARS signal radiation in the infrared. The electric-field diagnostic is demonstrated in air, where the strength of the coherent infrared emission and sensitivity our field measurements is quantified, and the scaling of the infrared signal with field strength is verified.« less

In Vivo Near Infrared Virtual Intraoperative Surgical Photoacoustic Optical Coherence Tomography

PubMed Central

Lee, Donghyun; Lee, Changho; Kim, Sehui; Zhou, Qifa; Kim, Jeehyun; Kim, Chulhong

2016-01-01

Since its first implementation in otolaryngological surgery nearly a century ago, the surgical microscope has improved the accuracy and the safety of microsurgeries. However, the microscope shows only a magnified surface view of the surgical region. To overcome this limitation, either optical coherence tomography (OCT) or photoacoustic microscopy (PAM) has been independently combined with conventional surgical microscope. Herein, we present a near-infrared virtual intraoperative photoacoustic optical coherence tomography (NIR-VISPAOCT) system that combines both PAM and OCT with a conventional surgical microscope. Using optical scattering and absorption, the NIR-VISPAOCT system simultaneously provides surgeons with real-time comprehensive biological information such as tumor margins, tissue structure, and a magnified view of the region of interest. Moreover, by utilizing a miniaturized beam projector, it can back-project 2D cross-sectional PAM and OCT images onto the microscopic view plane. In this way, both microscopic and cross-sectional PAM and OCT images are concurrently displayed on the ocular lens of the microscope. To verify the usability of the NIR-VISPAOCT system, we demonstrate simulated surgeries, including in vivo image-guided melanoma resection surgery and in vivo needle injection of carbon particles into a mouse thigh. The proposed NIR-VISPAOCT system has potential applications in neurosurgery, ophthalmological surgery, and other microsurgeries. PMID:27731390

Demonstration of two-qubit algorithms with a superconducting quantum processor.

PubMed

DiCarlo, L; Chow, J M; Gambetta, J M; Bishop, Lev S; Johnson, B R; Schuster, D I; Majer, J; Blais, A; Frunzio, L; Girvin, S M; Schoelkopf, R J

2009-07-09

Quantum computers, which harness the superposition and entanglement of physical states, could outperform their classical counterparts in solving problems with technological impact-such as factoring large numbers and searching databases. A quantum processor executes algorithms by applying a programmable sequence of gates to an initialized register of qubits, which coherently evolves into a final state containing the result of the computation. Building a quantum processor is challenging because of the need to meet simultaneously requirements that are in conflict: state preparation, long coherence times, universal gate operations and qubit readout. Processors based on a few qubits have been demonstrated using nuclear magnetic resonance, cold ion trap and optical systems, but a solid-state realization has remained an outstanding challenge. Here we demonstrate a two-qubit superconducting processor and the implementation of the Grover search and Deutsch-Jozsa quantum algorithms. We use a two-qubit interaction, tunable in strength by two orders of magnitude on nanosecond timescales, which is mediated by a cavity bus in a circuit quantum electrodynamics architecture. This interaction allows the generation of highly entangled states with concurrence up to 94 per cent. Although this processor constitutes an important step in quantum computing with integrated circuits, continuing efforts to increase qubit coherence times, gate performance and register size will be required to fulfil the promise of a scalable technology.

Theta synchronization between medial prefrontal cortex and cerebellum is associated with adaptive performance of associative learning behavior

PubMed Central

Chen, Hao; Wang, Yi-jie; Yang, Li; Sui, Jian-feng; Hu, Zhi-an; Hu, Bo

2016-01-01

Associative learning is thought to require coordinated activities among distributed brain regions. For example, to direct behavior appropriately, the medial prefrontal cortex (mPFC) must encode and maintain sensory information and then interact with the cerebellum during trace eyeblink conditioning (TEBC), a commonly-used associative learning model. However, the mechanisms by which these two distant areas interact remain elusive. By simultaneously recording local field potential (LFP) signals from the mPFC and the cerebellum in guinea pigs undergoing TEBC, we found that theta-frequency (5.0–12.0 Hz) oscillations in the mPFC and the cerebellum became strongly synchronized following presentation of auditory conditioned stimulus. Intriguingly, the conditioned eyeblink response (CR) with adaptive timing occurred preferentially in the trials where mPFC-cerebellum theta coherence was stronger. Moreover, both the mPFC-cerebellum theta coherence and the adaptive CR performance were impaired after the disruption of endogenous orexins in the cerebellum. Finally, association of the mPFC -cerebellum theta coherence with adaptive CR performance was time-limited occurring in the early stage of associative learning. These findings suggest that the mPFC and the cerebellum may act together to contribute to the adaptive performance of associative learning behavior by means of theta synchronization. PMID:26879632

Laser radar: from early history to new trends

NASA Astrophysics Data System (ADS)

Molebny, Vasyl; Kamerman, Gary; Steinvall, Ove

2010-10-01

The first steps of laser radar are discussed with the examples from range finding and designation. The followed successes in field tests and further fast development provided their wide use. Coherent laser radar, developed almost simultaneously, tried the ideas from microwaves including chirp technology for pulse compression, and Doppler mode of operation. This latter found a unique implementation in a cruise missile. In many applications, environmental studies very strongly rely upon the lidars sensing the wind, temperature, constituents, optical parameters. Lidars are used in the atmosphere and in the sea water measurements. Imaging and mapping is an important role prescribed to ladars. One of the prospective trends in laser radar development is incorporation of range and velocity data into the image information. Deep space program, even having not come to the finish, gave a lot for 3D imaging. Gated imaging, as one of the 3D techniques, demonstrated its prospects (seeing through scattering layers) for military and security usage. Synthetic aperture laser radar, which had a long incubation period, started to show first results, at least in modeling. Coherent laser radar baptized as the optical coherence tomography, along with the position sensitive laser radar, synthetic aperture laser radar, multispectral laser radar demonstrated very pragmatic results in the micro-scale applications.

Coherent cavity-enhanced dual-comb spectroscopy.

PubMed

Fleisher, Adam J; Long, David A; Reed, Zachary D; Hodges, Joseph T; Plusquellic, David F

2016-05-16

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO₂, CO, HDO, and H₂O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors.

Deconstruction of spatial integrity in visual stimulus detected by modulation of synchronized activity in cat visual cortex.

PubMed

Zhou, Zhiyi; Bernard, Melanie R; Bonds, A B

2008-04-02

Spatiotemporal relationships among contour segments can influence synchronization of neural responses in the primary visual cortex. We performed a systematic study to dissociate the impact of spatial and temporal factors in the signaling of contour integration via synchrony. In addition, we characterized the temporal evolution of this process to clarify potential underlying mechanisms. With a 10 x 10 microelectrode array, we recorded the simultaneous activity of multiple cells in the cat primary visual cortex while stimulating with drifting sine-wave gratings. We preserved temporal integrity and systematically degraded spatial integrity of the sine-wave gratings by adding spatial noise. Neural synchronization was analyzed in the time and frequency domains by conducting cross-correlation and coherence analyses. The general association between neural spike trains depends strongly on spatial integrity, with coherence in the gamma band (35-70 Hz) showing greater sensitivity to the change of spatial structure than other frequency bands. Analysis of the temporal dynamics of synchronization in both time and frequency domains suggests that spike timing synchronization is triggered nearly instantaneously by coherent structure in the stimuli, whereas frequency-specific oscillatory components develop more slowly, presumably through network interactions. Our results suggest that, whereas temporal integrity is required for the generation of synchrony, spatial integrity is critical in triggering subsequent gamma band synchronization.

Intra- and interbrain synchronization and network properties when playing guitar in duets

PubMed Central

Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

2012-01-01

To further test and explore the hypothesis that synchronous oscillatory brain activity supports interpersonally coordinated behavior during dyadic music performance, we simultaneously recorded the electroencephalogram (EEG) from the brains of each of 12 guitar duets repeatedly playing a modified Rondo in two voices by C.G. Scheidler. Indicators of phase locking and of within-brain and between-brain phase coherence were obtained from complex time-frequency signals based on the Gabor transform. Analyses were restricted to the delta (1–4 Hz) and theta (4–8 Hz) frequency bands. We found that phase locking as well as within-brain and between-brain phase-coherence connection strengths were enhanced at frontal and central electrodes during periods that put particularly high demands on musical coordination. Phase locking was modulated in relation to the experimentally assigned musical roles of leader and follower, corroborating the functional significance of synchronous oscillations in dyadic music performance. Graph theory analyses revealed within-brain and hyperbrain networks with small-worldness properties that were enhanced during musical coordination periods, and community structures encompassing electrodes from both brains (hyperbrain modules). We conclude that brain mechanisms indexed by phase locking, phase coherence, and structural properties of within-brain and hyperbrain networks support interpersonal action coordination (IAC). PMID:23226120

Mobile CARS - IRS Instrument for Simultaneous Spectroscopic Measurement of Multiple Properties in Gaseous Flows

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Lee, Joseph W.; Jones, Stephen B.; Tedder, Sarah A.; Danehy, Paul M.; Weikl, M. C.; Magnotti, G.; Cutler, Andrew D.

2007-01-01

This paper describes a measurement system based on the dual-pump coherent anti-Stokes Raman spectroscopy (CARS) and interferometric Rayleigh scattering (IRS) methods. The IRS measurement is performed simultaneously with the CARS measurement using a common green laser beam as a narrow-band light source. The mobile CARS-IRS instrument is designed for the use both in laboratories as well as in ground-based combustion test facilities. Furthermore, it is designed to be easily transported between laboratory and test facility. It performs single-point spatially and temporally resolved simultaneous measurements of temperature, species mole fraction of N2, O2, and H2, and two-components of velocity. A mobile laser system can be placed inside or outside the test facility, while a beam receiving and monitoring system is placed near the measurement location. Measurements in a laboratory small-scale Mach 1.6 H2-air combustion-heated supersonic jet were performed to test the capability of the system. Final setup and pretests of a larger scale reacting jet are ongoing at NASA Langley Research Center s Direct Connect Supersonic Combustor Test Facility (DCSCTF).

Case study of simultaneous observations of sporadic sodium layer, E-region field-aligned irregularities and sporadic E layer at low latitude of China

NASA Astrophysics Data System (ADS)

Xie, H. Y.; Ning, B. Q.; Zhao, X. K.; Hu, L. H.

2017-03-01

Using the Na lidar at Haikou (20.0°N, 110.3°E), the VHF coherent radar and the digital ionosonde both at Sanya (18.4°N, 109.6°E), cases of simultaneous observations of sporadic sodium layer (SSL), E-region field-aligned irregularities (FAI) and sporadic E layer (Es) in the mesosphere and lower thermosphere (MLT) region at low latitude of China are studied. It is found that SSL occurs simultaneously or follows the enhancement of Es and FAI. The Es, FAI and SSL descend slowly with time which is mostly controlled by the diurnal tide (DT). Besides, the interaction of gravity wave (GW) with tides can cause oscillations in FAI and SSL. Our observations support the neutralization of ions for SSL formation: when the metallic ions layer descents to the altitudes where models predict, the sodium ions convert rapidly to atomic Na that may form an SSL event. Moreover, the SSL peak density will increase (decrease) in the convergence (divergence) vertical shear region of zonal wind.

Simultaneous measurement of lipid and aqueous layers of tear film using optical coherence tomography and statistical decision theory

NASA Astrophysics Data System (ADS)

Huang, Jinxin; Clarkson, Eric; Kupinski, Matthew; Rolland, Jannick P.

2014-03-01

The prevalence of Dry Eye Disease (DED) in the USA is approximately 40 million in aging adults with about $3.8 billion economic burden. However, a comprehensive understanding of tear film dynamics, which is the prerequisite to advance the management of DED, is yet to be realized. To extend our understanding of tear film dynamics, we investigate the simultaneous estimation of the lipid and aqueous layers thicknesses with the combination of optical coherence tomography (OCT) and statistical decision theory. In specific, we develop a mathematical model for Fourier-domain OCT where we take into account the different statistical processes associated with the imaging chain. We formulate the first-order and second-order statistical quantities of the output of the OCT system, which can generate some simulated OCT spectra. A tear film model, which includes a lipid and aqueous layer on top of a rough corneal surface, is the object being imaged. Then we further implement a Maximum-likelihood (ML) estimator to interpret the simulated OCT data to estimate the thicknesses of both layers of the tear film. Results show that an axial resolution of 1 μm allows estimates down to nanometers scale. We use the root mean square error of the estimates as a metric to evaluate the system parameters, such as the tradeoff between the imaging speed and the precision of estimation. This framework further provides the theoretical basics to optimize the imaging setup for a specific thickness estimation task.

Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography

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

Shilyagin, P A; Gelikonov, G V; Gelikonov, V M

2014-07-31

We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phasemore » shift achromatism over a wide spectral range is achieved by using in the delay lines the individual elements with different dispersion characteristics. The ranges of admissible adjustment parameters of the achromatised delay line are estimated for exact and inexact conformity of the geometric characteristics of its components to those calculated. A possibility of simultaneous recording of the close-to-quadrature spectral components with a single linear photodetector element is experimentally confirmed. The suppression of the artefact mirror peak in the OCT-signal by an additional 9 dB relative to the level of its suppression is experimentally achieved when the air delay line is used. Two-dimensional images of the surface positioned at an angle to the axis of the probe beam are obtained with the correction of the 'mirror' artefact while maintaining the dynamic range of the image. (laser biophotonics)« less

Fizeau simultaneous phase-shifting interferometry based on extended source

NASA Astrophysics Data System (ADS)

Wang, Shanshan; Zhu, Qiudong; Hou, Yinlong; Cao, Zheng

2016-09-01

Coaxial Fizeau simultaneous phase-shifting interferometer plays an important role in many fields for its characteristics of long optical path, miniaturization, and elimination of reference surface high-frequency error. Based on the matching of coherence between extended source and interferometer, orthogonal polarization reference wave and measurement wave can be obtained by Fizeau interferometry with Michelson interferometer preposed. Through matching spatial coherence length between preposed interferometer and primary interferometer, high contrast interference fringes can be obtained and additional interference fringes can be eliminated. Thus, the problem of separation of measurement and reference surface in the common optical path Fizeau interferometer is solved. Numerical simulation and principle experiment is conducted to verify the feasibility of extended source interferometer. Simulation platform is established by using the communication technique of DDE (dynamic data exchange) to connect Zemax and Matlab. The modeling of the extended source interferometer is realized by using Zemax. Matlab codes are programmed to automatically rectify the field parameters of the optical system and conveniently calculate the visibility of interference fringes. Combined with the simulation, the experimental platform of the extended source interferometer is established. After experimental research on the influence law of scattering screen granularity to interference fringes, the granularity of scattering screen is determined. Based on the simulation platform and experimental platform, the impacts on phase measurement accuracy of the imaging system aberration and collimation system aberration of the interferometer are analyzed. Compared the visibility relation curves between experimental measurement and simulation result, the experimental result is in line with the theoretical result.

Label-free, multi-contrast optical coherence tomography for study of skin melanoma mice in vivo

NASA Astrophysics Data System (ADS)

Lai, Pei-Yu; Lin, Tim-Han; Chou, Ya-Shuan; Chang, Chung-Hsing; Kuo, Wen-Chuan

2018-02-01

The lymphatic system plays an important role in inflammation and cancer such as melanoma. Due to the limitations of current developed imaging techniques, visualization of lymphatic vessels within the tissue in vivo has been challenging. Optical imaging of lymphatic vessel is gaining increased interests because it does not involve any radiation and can achieve very high resolution. Here, we developed a multi-contrast, label-free optical coherence tomography (OCT) imaging technology with an axial resolution of 5 μm and lateral resolution of 7 μm, which is capable of providing microstructural information and microcirculatory system including blood and lymphatic vessels simultaneously. Using this technique, we observed the melanoma mice in vivo. Mice were treated topically on the ear with (Z)-4- Hydroxytamoxifen(4-OHT) to elicit BRAFV600E and to silence Pten expression. Also, to observing the structural information, angiogenesis and lymphangiogenesis in the ear of the induced melanoma mouse can be done. The advantage of using OCT over other imaging modalities is its ability to assess label-free blood flow along with lymphatic vessels simultaneously for imaging the microcirculatory system within tissue beds without any exogenous agents. Because the metastasis of melanoma is highly related to the lymphatic vessels, our findings can be a powerful tool to help the diagnosis of the metastasis melanoma. In the future, this may become a helpful tool for better understanding pathologic mechanisms and treatment technique development in some diseases.

A multimodal imaging platform with integrated simultaneous photoacoustic microscopy, optical coherence tomography, optical Doppler tomography and fluorescence microscopy

NASA Astrophysics Data System (ADS)

Dadkhah, Arash; Zhou, Jun; Yeasmin, Nusrat; Jiao, Shuliang

2018-02-01

Various optical imaging modalities with different optical contrast mechanisms have been developed over the past years. Although most of these imaging techniques are being used in many biomedical applications and researches, integration of these techniques will allow researchers to reach the full potential of these technologies. Nevertheless, combining different imaging techniques is always challenging due to the difference in optical and hardware requirements for different imaging systems. Here, we developed a multimodal optical imaging system with the capability of providing comprehensive structural, functional and molecular information of living tissue in micrometer scale. This imaging system integrates photoacoustic microscopy (PAM), optical coherence tomography (OCT), optical Doppler tomography (ODT) and fluorescence microscopy in one platform. Optical-resolution PAM (OR-PAM) provides absorption-based imaging of biological tissues. Spectral domain OCT is able to provide structural information based on the scattering property of biological sample with no need for exogenous contrast agents. In addition, ODT is a functional extension of OCT with the capability of measurement and visualization of blood flow based on the Doppler effect. Fluorescence microscopy allows to reveal molecular information of biological tissue using autofluoresce or exogenous fluorophores. In-vivo as well as ex-vivo imaging studies demonstrated the capability of our multimodal imaging system to provide comprehensive microscopic information on biological tissues. Integrating all the aforementioned imaging modalities for simultaneous multimodal imaging has promising potential for preclinical research and clinical practice in the near future.

Noncommutative coherent states and related aspects of Berezin-Toeplitz quantization

NASA Astrophysics Data System (ADS)

Hasibul Hassan Chowdhury, S.; Twareque Ali, S.; Engliš, Miroslav

2017-05-01

In this paper, we construct noncommutative coherent states using various families of unitary irreducible representations (UIRs) of Gnc , a connected, simply connected nilpotent Lie group, which was identified as the kinematical symmetry group of noncommutative quantum mechanics for a system of two degrees of freedom in an earlier paper. Similarly described are the degenerate noncommutative coherent states arising from the degenerate UIRs of Gnc . We then compute the reproducing kernels associated with both these families of coherent states and study the Berezin-Toeplitz quantization of the observables on the underlying 4-dimensional phase space, analyzing in particular the semi-classical asymptotics for both these cases. Dedicated by the first and the third authors to the memory of the second author, with gratitude for his friendship and for all they learnt from him.

Double Bright Band Observations with High-Resolution Vertically Pointing Radar, Lidar, and Profiles

NASA Technical Reports Server (NTRS)

Emory, Amber E.; Demoz, Belay; Vermeesch, Kevin; Hicks, Michael

2014-01-01

On 11 May 2010, an elevated temperature inversion associated with an approaching warm front produced two melting layers simultaneously, which resulted in two distinct bright bands as viewed from the ER-2 Doppler radar system, a vertically pointing, coherent X band radar located in Greenbelt, MD. Due to the high temporal resolution of this radar system, an increase in altitude of the melting layer of approximately 1.2 km in the time span of 4 min was captured. The double bright band feature remained evident for approximately 17 min, until the lower atmosphere warmed enough to dissipate the lower melting layer. This case shows the relatively rapid evolution of freezing levels in response to an advancing warm front over a 2 h time period and the descent of an elevated warm air mass with time. Although observations of double bright bands are somewhat rare, the ability to identify this phenomenon is important for rainfall estimation from spaceborne sensors because algorithms employing the restriction of a radar bright band to a constant height, especially when sampling across frontal systems, will limit the ability to accurately estimate rainfall.

Spontaneous sensorimotor cortical activity is suppressed by deep brain stimulation in patients with advanced Parkinson's disease.

PubMed

Luoma, Jarkko; Pekkonen, Eero; Airaksinen, Katja; Helle, Liisa; Nurminen, Jussi; Taulu, Samu; Mäkelä, Jyrki P

2018-06-22

Advanced Parkinson's disease (PD) is characterized by an excessive oscillatory beta band activity in the subthalamic nucleus (STN). Deep brain stimulation (DBS) of STN alleviates motor symptoms in PD and suppresses the STN beta band activity. The effect of DBS on cortical sensorimotor activity is more ambiguous; both increases and decreases of beta band activity have been reported. Non-invasive studies with simultaneous DBS are problematic due to DBS-induced artifacts. We recorded magnetoencephalography (MEG) from 16 advanced PD patients with and without STN DBS during rest and wrist extension. The strong magnetic artifacts related to stimulation were removed by temporal signal space separation. MEG oscillatory activity at 5-25 Hz was suppressed during DBS in a widespread frontoparietal region, including the sensorimotor cortex identified by the cortico-muscular coherence. The strength of suppression did not correlate with clinical improvement. Our results indicate that alpha and beta band oscillations are suppressed at the frontoparietal cortex by STN DBS in PD. Copyright © 2018. Published by Elsevier B.V.

Double bright band observations with high-resolution vertically pointing radar, lidar, and profilers

NASA Astrophysics Data System (ADS)

Emory, Amber E.; Demoz, Belay; Vermeesch, Kevin; Hicks, Micheal

2014-07-01

On 11 May 2010, an elevated temperature inversion associated with an approaching warm front produced two melting layers simultaneously, which resulted in two distinct bright bands as viewed from the ER-2 Doppler radar system, a vertically pointing, coherent X band radar located in Greenbelt, MD. Due to the high temporal resolution of this radar system, an increase in altitude of the melting layer of approximately 1.2 km in the time span of 4 min was captured. The double bright band feature remained evident for approximately 17 min, until the lower atmosphere warmed enough to dissipate the lower melting layer. This case shows the relatively rapid evolution of freezing levels in response to an advancing warm front over a 2 h time period and the descent of an elevated warm air mass with time. Although observations of double bright bands are somewhat rare, the ability to identify this phenomenon is important for rainfall estimation from spaceborne sensors because algorithms employing the restriction of a radar bright band to a constant height, especially when sampling across frontal systems, will limit the ability to accurately estimate rainfall.

Ambiguity Detection in Adolescents with Asperger Syndrome: Is Central Coherence or Theory of Mind Impaired?

ERIC Educational Resources Information Center

Le Sourn-Bissaoui, Sandrine; Caillies, Stephanie; Gierski, Fabien; Motte, Jacques

2011-01-01

The aim of this study was to investigate the role of central coherence skills and theory of mind competences in ambiguity detection in adolescents with Asperger syndrome (AS). We sought to pinpoint the level at which AS individuals experience difficulty detecting semantic ambiguity and identify the factors that account for their problems. We…

The basics of intravascular optical coherence tomography

PubMed Central

Jąkała, Jacek; Kałuża, Grzegorz L.; Partyka, Łukasz; Proniewska, Klaudia; Pociask, Elżbieta; Zasada, Wojciech; Wojakowski, Wojciech; Gąsior, Zbigniew; Dudek, Dariusz

2015-01-01

Optical coherence tomography (OCT) has opened new horizons for intravascular coronary imaging. It utilizes near-infrared light to provide a microscopic insight into the pathology of coronary arteries in vivo. Optical coherence tomography is also capable of identifying the chemical composition of atherosclerotic plaques and detecting traits of their vulnerability. At present it is the only tool to measure the thickness of the fibrous cap covering the lipid core of the atheroma, and thus it is an exceptional modality to detect plaques that are prone to rupture (thin fibrous cap atheromas). Moreover, it facilitates distinguishing between plaque rupture and plaque erosion as a cause of acute intracoronary thrombosis. Optical coherence tomography is applied to guide angioplasties of coronary lesions and to assess outcomes of percutaneous coronary interventions broadly. It identifies stent malapposition, dissections, and thrombosis with unprecedented precision. Furthermore, OCT helps to monitor vessel healing after stenting. It evaluates the coverage of stent struts by the neointima and detects in-stent neoatherosclerosis. With so much potential, new studies are warranted to determine OCT's clinical impact. The following review presents the technical background, basics of OCT image interpretation, and practical tips for adequate OCT imaging, and outlines its established and potential clinical application. PMID:26161097

Characterizing coal beds in western Kentucky with the Al-La-Sc coherent triad

USGS Publications Warehouse

Chyi, L.L.; Medlin, J.H.

1996-01-01

Cyclic sedimentation and lateral facies changes make coal bed correlations inconclusive and difficult. This uncertainty can be further complicated if a coal basin has been structurally deformed. Coal macerals can be studied to indicate the nature and degree of coalification. Their use in coal bed correlation, however, is limited. Most of the trace elements and their ratios that have been studied show significant within-bed lateral and stratigraphic variations, and thus are not effective in correlating coal beds regionally. Geochemically coherent groups of elements, such as rare earth elements (REE) and platinum group elements (PGE), appear to be highly differentiated in coal-forming environments. Geochemical coherent elemental triads appear to be useful for coal bed identification or fingerprinting. The best triad which was demonstrated to be effective in coal bed characterization in western Kentucky, is that of Al, La and Sc. These three elements are highly correlated with one another and they can be determined accurately and simultaneously with instrumental neutron activation analysis (INAA). The elemental triad Al-La-Sc is used to identify and fingerprint three key coal beds in western Kentucky: the Springfield (western Kentucky No. 9), the Davis (western Kentucky No. 6), and the Mining City and Dawson Springs are both considered to be the No. 4 coal bed in western Kentucky). Four distinct groupings can be recognized by use of the Al-La-Sc triad. The Dawson Springs coals have the highest Al/(La + Sc) ratios, followed by the Springfield, the Davis and the Mining City. The Mining City coal bed generally has the highest La/Sc ratio. However, the Dawson Springs is not correlated with the Mining City using the triad analysis, even though they have reportedly similar stratigraphic positions in the western Kentucky coal basin. The Al-La-Sc triad appears to be effective in discriminating between the Springfield and the Davis coal beds throughout the entire Illinois Basin. Furthermore, the range of concentration variation of the AL-La-Sc triad suggests individual groupings of the No. 4 coal in western Kentucky. In addition to characterizing these coal beds, the Al-La-Sc triad may be used to confirm stratigraphic correlations.

Compact, Engineered, 2-Micron Coherent Doppler Wind Lidar Prototype: A New NASA Instrument Incubator Program Project

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Singh, Upendra N.; Amzajerdian, Farzin; Wang, Jinxue; Petros, Mulugeta

2005-01-01

A new project, selected in 2005 by NASA s Science Mission Directorate (SMD) under the Instrument Incubator Program (IIP), will be described. The 3-year effort is intended to design, fabricate, and demonstrate a packaged, rugged, compact, space-qualifiable coherent Doppler wind lidar (DWL) transceiver capable of future validation in an aircraft and/or Unmanned Aerial Vehicle (UAV). The packaged DWL will utilize the numerous advances in pulsed, solid-state, 2-micron laser technology at NASA s Langley Research Center (LaRC) in such areas as crystal composition, architecture, efficiency, cooling techniques, pulse energy, and beam quality. The extensive experience of Raytheon Space and Airborne Systems (RSAS) in coherent lidar systems, in spacebased sensors, and in packaging rugged lidar systems will be applied to this project. The packaged transceiver will be as close to an envisioned space-based DWL system as the resources and technology readiness allow. We will attempt to facilitate a future upgrade to a coherent lidar system capable of simultaneous wind and CO2 concentration profile measurements. Since aerosol and dust concentration is also available from the lidar signal, the potential for a triple measurement lidar system is attractive for both Earth and Mars remote sensing. A key follow on step after the IIP will be to add a telescope, scanner, and software for aircraft validation. This IIP should also put us in a position to begin a parallel formulation study in the 2006-2007 timeframe for a space-based DWL demonstration mission early next decade.

Dissociation between dorsal and ventral hippocampal theta oscillations during decision-making.

PubMed

Schmidt, Brandy; Hinman, James R; Jacobson, Tara K; Szkudlarek, Emily; Argraves, Melissa; Escabí, Monty A; Markus, Etan J

2013-04-03

Hippocampal theta oscillations are postulated to support mnemonic processes in humans and rodents. Theta oscillations facilitate encoding and spatial navigation, but to date, it has been difficult to dissociate the effects of volitional movement from the cognitive demands of a task. Therefore, we examined whether volitional movement or cognitive demands exerted a greater modulating factor over theta oscillations during decision-making. Given the anatomical, electrophysiological, and functional dissociations along the dorsal-ventral axis, theta oscillations were simultaneously recorded in the dorsal and ventral hippocampus in rats trained to switch between place and motor-response strategies. Stark differences in theta characteristics were found between the dorsal and ventral hippocampus in frequency, power, and coherence. Theta power increased in the dorsal, but decreased in the ventral hippocampus, during the decision-making epoch. Interestingly, the relationship between running speed and theta power was uncoupled during the decision-making epoch, a phenomenon limited to the dorsal hippocampus. Theta frequency increased in both the dorsal and ventral hippocampus during the decision epoch, although this effect was greater in the dorsal hippocampus. Despite these differences, ventral hippocampal theta was responsive to the navigation task; theta frequency, power, and coherence were all affected by cognitive demands. Theta coherence increased within the dorsal hippocampus during the decision-making epoch on all three tasks. However, coherence selectively increased throughout the hippocampus (dorsal to ventral) on the task with new hippocampal learning. Interestingly, most results were consistent across tasks, regardless of hippocampal-dependent learning. These data indicate increased integration and cooperation throughout the hippocampus during information processing.

Developmental profile of slow hand movement oscillation coupling in humans.

PubMed

Deutsch, Katherine M; Stephens, John A; Farmer, Simon F

2011-05-01

In adults, slow hand and finger movements are characterized by 6- to 12-Hz discontinuities visible in the raw records and spectra of motion signals such as acceleration. This pulsitile behavior is correlated with motor unit synchronization at 6-12 Hz as shown by significant coherence at these frequencies between pairs of motor units and between the motor units and the acceleration recorded from the limb part controlled by the muscle, suggesting that it has a central origin. In this study, we examined the correlation between this 6- to 12-Hz pulsatile behavior and muscle activity as a function of childhood development. Sixty-eight participants (ages 4-25 yr) performed static wrist extensions against gravity or slow wrist extension and flexion movements while extensor carpi radialis muscle electromyographic (EMG) and wrist acceleration signals were simultaneously recorded. Coherence between EMG and acceleration within the 6- to 12-Hz frequency band was used as an index of the strength of the relation between central drive and the motor output. The main findings of the study are 1) EMG-acceleration coherence increased with increases in age, with the age differences being greater under movement conditions and the difference between conditions increasing with age; 2) the EMG signal showed increases in normalized power with increases in age under both conditions; and 3) coherence under movement conditions was moderately positively correlated with manual dexterity. These findings indicate that the strength of the 6- to 12-Hz central oscillatory drive to the motor output increases through childhood development and may contribute to age-related improvements in motor skills.

Integrated InAs/InP quantum-dot coherence comb lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lu, Zhenguo; Liu, Jiaren; Poole, Philip J.; Song, Chun-Ying; Webber, John; Mao, Linda; Chang, Shoude; Ding, Heping; Barrios, Pedro J.; Poitras, Daniel; Janz, Siegfried

2017-02-01

Current communication networks needs to keep up with the exponential growth of today's internet traffic, and telecommunications industry is looking for radically new integrated photonics components for new generation optical networks. We at National Research Council (NRC) Canada have successfully developed nanostructure InAs/InP quantum dot (QD) coherence comb lasers (CCLs) around 1.55 μm. Unlike uniform semiconductor layers in most telecommunication lasers, in these QD CCLs light is emitted and amplified by millions of semiconductor QDs less than 60 nm in diameter. Each QD acts like an isolated light source acting independently of its neighbours, and each QD emits light at its own unique wavelength. The end result is a QD CCL is more stable and has ultra-low timing jitter. But most importantly, a single QD CCL can simultaneously produce 50 or more separate laser beams at distinct wavelengths over the telecommunications C-band. Utilizing those unique properties we have put considerable effort well to design, grow and fabricate InAs/InP QD gain materials. After our integrated packaging and using electrical feedback-loop control systems, we have successfully demonstrated ultra-low intensity and phase noise, frequency-stabilized integrated QD CCLs with the repetition rates from 10 GHz to 100 GHz and the total output power up to 60 mW at room temperature. We have investigated their relative intensity noises, phase noises, RF beating signals and other performance of both filtered individual channel and the whole CCLs. Those highly phase-coherence comb lasers are the promising candidates for flexible bandwidth terabit coherent optical networks and signal processing applications.

Local Versus Global Effects of Isoflurane Anesthesia on Visual Processing in the Fly Brain

PubMed Central

2016-01-01

Abstract What characteristics of neural activity distinguish the awake and anesthetized brain? Drugs such as isoflurane abolish behavioral responsiveness in all animals, implying evolutionarily conserved mechanisms. However, it is unclear whether this conservation is reflected at the level of neural activity. Studies in humans have shown that anesthesia is characterized by spatially distinct spectral and coherence signatures that have also been implicated in the global impairment of cortical communication. We questioned whether anesthesia has similar effects on global and local neural processing in one of the smallest brains, that of the fruit fly (Drosophila melanogaster). Using a recently developed multielectrode technique, we recorded local field potentials from different areas of the fly brain simultaneously, while manipulating the concentration of isoflurane. Flickering visual stimuli (‘frequency tags’) allowed us to track evoked responses in the frequency domain and measure the effects of isoflurane throughout the brain. We found that isoflurane reduced power and coherence at the tagging frequency (13 or 17 Hz) in central brain regions. Unexpectedly, isoflurane increased power and coherence at twice the tag frequency (26 or 34 Hz) in the optic lobes of the fly, but only for specific stimulus configurations. By modeling the periodic responses, we show that the increase in power in peripheral areas can be attributed to local neuroanatomy. We further show that the effects on coherence can be explained by impacted signal-to-noise ratios. Together, our results show that general anesthesia has distinct local and global effects on neuronal processing in the fruit fly brain. PMID:27517084

Local Versus Global Effects of Isoflurane Anesthesia on Visual Processing in the Fly Brain.

PubMed

Cohen, Dror; Zalucki, Oressia H; van Swinderen, Bruno; Tsuchiya, Naotsugu

2016-01-01

What characteristics of neural activity distinguish the awake and anesthetized brain? Drugs such as isoflurane abolish behavioral responsiveness in all animals, implying evolutionarily conserved mechanisms. However, it is unclear whether this conservation is reflected at the level of neural activity. Studies in humans have shown that anesthesia is characterized by spatially distinct spectral and coherence signatures that have also been implicated in the global impairment of cortical communication. We questioned whether anesthesia has similar effects on global and local neural processing in one of the smallest brains, that of the fruit fly (Drosophila melanogaster). Using a recently developed multielectrode technique, we recorded local field potentials from different areas of the fly brain simultaneously, while manipulating the concentration of isoflurane. Flickering visual stimuli ('frequency tags') allowed us to track evoked responses in the frequency domain and measure the effects of isoflurane throughout the brain. We found that isoflurane reduced power and coherence at the tagging frequency (13 or 17 Hz) in central brain regions. Unexpectedly, isoflurane increased power and coherence at twice the tag frequency (26 or 34 Hz) in the optic lobes of the fly, but only for specific stimulus configurations. By modeling the periodic responses, we show that the increase in power in peripheral areas can be attributed to local neuroanatomy. We further show that the effects on coherence can be explained by impacted signal-to-noise ratios. Together, our results show that general anesthesia has distinct local and global effects on neuronal processing in the fruit fly brain.

Advanced Interferometric Synthetic Aperture Imaging Radar (InSAR) for Dune Mapping

NASA Astrophysics Data System (ADS)

Havivi, Shiran; Amir, Doron; Schvartzman, Ilan; August, Yitzhak; Mamman, Shimrit; Rotman, Stanely R.; Blumberg, Dan G.

2016-04-01

Aeolian morphologies are formed in the presence of sufficient wind energy and available lose particles. These processes occur naturally or are further enhanced or reduced by human intervention. The dimensions of change are dependent primarily on the wind energy and surface properties. Since the 1970s, remote sensing imagery, both optical and radar, have been used for documentation and interpretation of the geomorphologic changes of sand dunes. Remote sensing studies of aeolian morphologies is mostly useful to document major changes, yet, subtle changes, occurring in a period of days or months in scales of centimeters, are very difficult to detect in imagery. Interferometric Synthetic Aperture Radar (InSAR) is an imaging technique for measuring Earth's surface topography and deformation. InSAR images are produced by measuring the radar phase difference between two separated antennas that view the same surface area. Classical InSAR is based on high coherence between two or more images. The output (interferogram) can show subtle changes with an accuracy of several millimeters to centimeters. Very little work has been done on measuring or identifying the changes in dunes using InSAR methods. The reason is that dunes tend to be less coherent than firm, stable, surfaces. This work aims to demonstrate how interferometric decorrelation can be used for identifying dune instability. We hypothesize and demonstrate that the loss of radar coherence over time on dunes can be used as an indication of the dune's instability. When SAR images are acquired at sufficiently close intervals one can measure the time it takes to lose coherence and associate this time with geomorphic stability. To achieve our goals, the coherence change detection method was used, in order to identify dune stability or instability and the dune activity level. The Nitzanim-Ashdod coastal dunes along the Mediterranean, 40 km south of Tel-Aviv, Israel, were chosen as a case study. The dunes in this area are of varying levels of stability and vegetation cover and have been monitored meteorologically, geomorphologically, and studied extensively in the field. High resolution TerraSAR-X (TSX) images covering the entire research area were acquired for the period of 2011 to 2012. Analysis was performed in imaging processing and GIS software. The coherence results display minor changes on the dune crest (0.42-0.49), compared to bigger changes in windward slope (0.31-0.37). The level of change depends on the dune location relative to its distance from the sea. Furthermore, the coherence results show decreasing over time. Field results indicate erosion/deposition of sand ranging from -99 to 137 mm/year. The results of this study confirm that it is possible to monitor subtle changes in sand dunes and to identify dune stability or instability, only by the use of SAR images, even in areas characterized by low coherence.

Action-outcome learning and prediction shape the window of simultaneity of audiovisual outcomes.

PubMed

Desantis, Andrea; Haggard, Patrick

2016-08-01

To form a coherent representation of the objects around us, the brain must group the different sensory features composing these objects. Here, we investigated whether actions contribute in this grouping process. In particular, we assessed whether action-outcome learning and prediction contribute to audiovisual temporal binding. Participants were presented with two audiovisual pairs: one pair was triggered by a left action, and the other by a right action. In a later test phase, the audio and visual components of these pairs were presented at different onset times. Participants judged whether they were simultaneous or not. To assess the role of action-outcome prediction on audiovisual simultaneity, each action triggered either the same audiovisual pair as in the learning phase ('predicted' pair), or the pair that had previously been associated with the other action ('unpredicted' pair). We found the time window within which auditory and visual events appeared simultaneous increased for predicted compared to unpredicted pairs. However, no change in audiovisual simultaneity was observed when audiovisual pairs followed visual cues, rather than voluntary actions. This suggests that only action-outcome learning promotes temporal grouping of audio and visual effects. In a second experiment we observed that changes in audiovisual simultaneity do not only depend on our ability to predict what outcomes our actions generate, but also on learning the delay between the action and the multisensory outcome. When participants learned that the delay between action and audiovisual pair was variable, the window of audiovisual simultaneity for predicted pairs increased, relative to a fixed action-outcome pair delay. This suggests that participants learn action-based predictions of audiovisual outcome, and adapt their temporal perception of outcome events based on such predictions. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Examining curricular coherence in an exemplary elementary school program.

PubMed

Ennis, Catherine D

2008-03-01

A coherent curriculum is characterized by visible connections between purposes and experiences so that students acknowledge the content's immediate value. This study examined an exemplary elementary physical education curriculum for coherence components. Research questions examined the role of coherence in connecting and engaging students meaningfully in physical education. Observations and interviews were conducted to collect qualitative data in one program for 22 weeks. Data were analyzed using open, axial, and selective coding. Results described two units, Balls Skills, leading to modified basketball, and Scooter City, a theme-based unit emphasizing student choice and responsibility. Students reported that both units were enjoyable. Although the Balls Skills unit was well planned, taught, and managed, some students commented that the skill and games content was valuable only in basketball. In the Scooter City unit, students identified numerous connections to out-of-school activities that enhanced content value. Comparisons with Beane's coherence criteria suggested that students valued Scooter City based on concrete connections to their lived experiences.

FAST CARS: Engineering a laser spectroscopic technique for rapid identification of bacterial spores

PubMed Central

Scully, M. O.; Kattawar, G. W.; Lucht, R. P.; Opatrný, T.; Pilloff, H.; Rebane, A.; Sokolov, A. V.; Zubairy, M. S.

2002-01-01

Airborne contaminants, e.g., bacterial spores, are usually analyzed by time-consuming microscopic, chemical, and biological assays. Current research into real-time laser spectroscopic detectors of such contaminants is based on e.g., resonance fluorescence. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. However, generating and using maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is challenging. In particular, the short dephasing times and rapid internal conversion rates are major obstacles. However, adiabatic fast passage techniques and the ability to generate combs of phase-coherent femtosecond pulses provide tools for the generation and utilization of maximal quantum coherence in large molecules and biopolymers. We call this technique FAST CARS (femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman spectroscopy), and the present article proposes and analyses ways in which it could be used to rapidly identify preselected molecules in real time. PMID:12177405

Electronic Holography with a Broad Spectrum Laser for Time Gated Imaging Through Highly Scattering Media.

NASA Astrophysics Data System (ADS)

Shih, Marian Pei-Ling

The problem of optical imaging through a highly scattering volume diffuser, in particular, biological tissue, has received renewed interest in recent years because of a search for alternative imaging diagnostics in the optical wavelengths for the early detection of human breast cancer. This dissertation discusses the optical imaging of objects obscured by diffusers that contribute an otherwise overwhelming degree of multiple scatter. Many optical imaging techniques are based on the first-arriving light principle. These methods usually combine a transilluminating optical short pulse with a time windowing gate in order to form a flat shadowgraph image of absorbing objects either embedded within or hidden behind a scattering medium. The gate selectively records an image of the first-arriving light, while simultaneously rejecting the later-arriving scattered light. One set of the many implementations of the first -arriving light principle relies on the gating property of holography. This thesis presents several holographic optical gating experiments that demonstrate the role that the temporal coherence function of the illumination source plays in the imaging of all objects with short coherence length holography, with special emphasis on the application to image through diffusers and its resolution capabilities. Previous researchers have already successfully combined electronic holography, holography in which the recording medium is a two dimensional detector array instead of photographic film, with light-in-flight holography into a short coherence length holography method that images through various types of multiply scattering random media, including chicken breast tissue and wax. This thesis reports further experimental exploration of the short coherence holography method for imaging through severely scattering diffusers. There is a study on the effectiveness of spatial filtering of the first-arriving light, as well as a report of the imaging, by means of the short coherence holographic method, of an absorber through a living human hand. This thesis also includes both theoretical analyses and experimental results of a spectral dispersion holography system which, instead of optically synthesizing the broad spectrum illumination source that is used for the short coherence holography method, digitally synthesizes a broad spectrum hologram from a collection of single frequency component holograms. This system has the time gating properties of short coherence length holography, as well as experimentally demonstrated applications for imaging through multiply scattering media.

Coherent Response of Two Dimensional Electron Gas probed by Two Dimensional Fourier Transform Spectroscopy

NASA Astrophysics Data System (ADS)

Paul, Jagannath

Advent of ultrashort lasers made it possible to probe various scattering phenomena in materials that occur in a time scale on the order of few femtoseconds to several tens of picoseconds. Nonlinear optical spectroscopy techniques, such as pump-probe, transient four wave mixing (TFWM), etc., are very common to study the carrier dynamics in various material systems. In time domain, the transient FWM uses several ultrashort pulses separated by time delays to obtain the information of dephasing and population relaxation times, which are very important parameters that govern the carrier dynamics of materials. A recently developed multidimensional nonlinear optical spectroscopy is an enhanced version of TFWM which keeps track of two time delays simultaneously and correlate them in the frequency domain with the aid of Fourier transform in a two dimensional map. Using this technique, the nonlinear complex signal field is characterized both in amplitude and phase. Furthermore, this technique allows us to identify the coupling between resonances which are rather difficult to interpret from time domain measurements. This work focuses on the study of the coherent response of a two dimensional electron gas formed in a modulation doped GaAs/AlGaAs quantum well both at zero and at high magnetic fields. In modulation doped quantum wells, the excitons are formed as a result of the inter- actions of the charged holes with the electrons at the Fermi edge in the conduction band, leading to the formation of Mahan excitons, which is also referred to as Fermi edge singularity (FES). Polarization and temperature dependent rephasing 2DFT spectra in combination with TI-FWM measurements, provides insight into the dephasing mechanism of the heavy hole (HH) Mahan exciton. In addition to that strong quantum coherence between the HH and LH Mahan excitons is observed, which is rather surprising at this high doping concentration. The binding energy of Mahan excitons is expected to be greatly reduced and any quantum coherence be destroyed as a result of the screening and electron-electron interactions. Such correlations are revealed by the dominating cross-diagonal peaks in both one-quantum and two-quantum 2DFT spectra. Theoretical simulations based on the optical Bloch Equations (OBE) where many-body effects are included phenomenologically, corroborate the experimental results. Time-dependent density functional theory (TD-DFT) calculations provide insight into the underlying physics and attribute the observed strong quantum coherence to a significantly reduced screening length and collective excitations of the many-electron system. Furthermore, in semiconductors under the application of magnetic field, the energy states in conduction and valence bands become quantized and Landau levels are formed. We observe optical excitation originating from different Landau levels in the absorption spectra in an undoped and a modulation doped quantum wells. 2DFT measurements in magnetic field up to 25 Tesla have been performed and the spectra reveal distinct difference in the line shapes in the two samples. In addition, strong coherent coupling between landau levels is observed in the undoped sample. In order to gain deeper understanding of the observations, the experimental results are further supported with TD-DFT calculation.

Intra- and interregional cortical interactions related to sharp-wave ripples and dentate spikes.

PubMed

Headley, Drew B; Kanta, Vasiliki; Paré, Denis

2017-02-01

The hippocampus generates population events termed sharp-wave ripples (SWRs) and dentate spikes (DSs). While little is known about DSs, SWR-related hippocampal discharges during sleep are thought to replay prior waking activity, reactivating the cortical networks that encoded the initial experience. During slow-wave sleep, such reactivations likely occur during up-states, when most cortical neurons are depolarized. However, most studies have examined the relationship between SWRs and up-states measured in single neocortical regions. As a result, it is currently unclear whether SWRs are associated with particular patterns of widely distributed cortical activity. Additionally, no such investigation has been carried out for DSs. The present study addressed these questions by recording SWRs and DSs from the dorsal hippocampus simultaneously with prefrontal, sensory (visual and auditory), perirhinal, and entorhinal cortices in naturally sleeping rats. We found that SWRs and DSs were associated with up-states in all cortical regions. Up-states coinciding with DSs and SWRs exhibited increased unit activity, power in the gamma band, and intraregional gamma coherence. Unexpectedly, interregional gamma coherence rose much more strongly in relation to DSs than to SWRs. Whereas the increase in gamma coherence was time locked to DSs, that seen in relation to SWRs was not. These observations suggest that SWRs are related to the strength of up-state activation within individual regions throughout the neocortex but not so much to gamma coherence between different regions. Perhaps more importantly, DSs coincided with stronger periods of interregional gamma coherence, suggesting that they play a more important role than previously assumed. Off-line cortico-hippocampal interactions are thought to support memory consolidation. We surveyed the relationship between hippocampal sharp-wave ripples (SWRs) and dentate spikes (DSs) with up-states across multiple cortical regions. SWRs and DSs were associated with increased cortical gamma oscillations. Interregional gamma coherence rose much more strongly in relation to DSs than to SWRs. Moreover, it was time locked to DSs but not SWRs. These results have important implications for current theories of systems memory consolidation during sleep. Copyright © 2017 the American Physiological Society.

New insights on boundary plasma turbulence and the Quasi-Coherent Mode in Alcator C-Mod using a Mirror Langmuir Probe

NASA Astrophysics Data System (ADS)

Labombard, Brian

2013-10-01

A ``Mirror Langmuir Probe'' (MLP) diagnostic has been used to interrogate edge plasma profiles and turbulence in Alcator C-Mod with unprecedented detail, yielding fundamental insights on the Quasi-Coherent Mode (QCM) - a mode that regulates plasma density and impurities in EDA H-modes without ELMs. The MLP employs a fast-switching, self-adapting bias scheme, recording density, electron temperature and plasma potential simultaneously at high bandwidth (~1 MHz) on each of four separate electrodes on a scanning probe. Temporal dynamics are followed in detail; wavenumber-frequency spectra and phase relationships are readily deduced. Poloidal field fluctuations are recorded separately with a two-coil, scanning probe. Results from ohmic L-mode and H-mode plasmas are reported, including key observations of the QCM: The QCM lives in a region of positive radial electric field, with a mode width (~3 mm) that spans open and closed field line regions. Remarkably large amplitude (~30%), sinusoidal bursts in density, electron temperature and plasma potential fluctuations are observed that are in phase; potential lags density by at most 10 degrees. Propagation velocity of the mode corresponds to the sum of local E × B and electron diamagnetic drift velocities - quantities that are deduced directly from time-averaged profiles. Poloidal magnetic field fluctuations project to parallel current densities of ~5 amps/cm2 in the mode layer, with significant parallel electromagnetic induction. Electron force balance is examined, unambiguously identifying the mode type. It is found that fluctuations in parallel electron pressure gradient are roughly balanced by the sum of electrostatic and electromotive forces. Thus the primary mode structure of the QCM is that of a drift-Alfven wave. Work supported by US DoE award DE-FC02-99ER54512.

Image-guided intraocular injection using multimodality optical coherence tomography and fluorescence confocal scanning laser ophthalmoscopy in rodent ophthalmological models

NASA Astrophysics Data System (ADS)

Terrones, Benjamin D.; Benavides, Oscar R.; Leeburg, Kelsey C.; Mehanathan, Sankarathi B.; Levine, Edward M.; Tao, Yuankai K.

2018-02-01

Intraocular injections are routinely performed for delivery of anti-VEGF and anti-inflammatory therapies in humans. While these injections are also performed in mice to develop novel models of ophthalmic diseases and screen novel therapeutics, the injection location and volume are not well-controlled and reproducible. We overcome limitations of conventional injections methods by developing a multimodality, long working distance, non-contact optical coherence tomography (OCT) and fluorescence confocal scanning laser ophthalmoscopy (cSLO) system for retinal imaging before and after injections. Our OCT+cSLO system combines a custom-built spectraldomain OCT engine (875+/-85 nm) with 125 kHz line-rate with a modified commercial cSLO with a maximum frame-rate of 30 fps (512 x 512 pix.). The system was designed for an overlapping OCT+cSLO field-of-view of 1.1 mm with a 7.76 mm working distance to the pupil. cSLO excitation light sources and filters were optimized for simultaneous GFP and tdTomato imaging. Lateral resolution was 3.02 µm for OCT and 2.74 μm for cSLO. Intravitreal injections of 5%, 10%, and 20% intralipid with Alex Fluor 488 were manually injected intraocularly in C57BL/6 mice. Post-injection imaging showed structural changes associated with retinal puncture, including the injection track, a retinal elevation, and detachment of the posterior hyaloid. OCT enables quantitative analysis of injection location and volumes whereas complementary cSLO improves specificity for identifying fluorescently labeled injected compounds and transgenic cells. The long working distance of our non-contact OCT+cSLO system is uniquely-suited for concurrent imaging with intraocular injections and may be applied for imaging of ophthalmic surgical dynamics and real-time image-guided injections.

VISUALIZATION FROM INTRAOPERATIVE SWEPT-SOURCE MICROSCOPE-INTEGRATED OPTICAL COHERENCE TOMOGRAPHY IN VITRECTOMY FOR COMPLICATIONS OF PROLIFERATIVE DIABETIC RETINOPATHY.

PubMed

Gabr, Hesham; Chen, Xi; Zevallos-Carrasco, Oscar M; Viehland, Christian; Dandrige, Alexandria; Sarin, Neeru; Mahmoud, Tamer H; Vajzovic, Lejla; Izatt, Joseph A; Toth, Cynthia A

2018-01-10

To evaluate the use of live volumetric (4D) intraoperative swept-source microscope-integrated optical coherence tomography in vitrectomy for proliferative diabetic retinopathy complications. In this prospective study, we analyzed a subgroup of patients with proliferative diabetic retinopathy complications who required vitrectomy and who were imaged by the research swept-source microscope-integrated optical coherence tomography system. In near real time, images were displayed in stereo heads-up display facilitating intraoperative surgeon feedback. Postoperative review included scoring image quality, identifying different diabetic retinopathy-associated pathologies and reviewing the intraoperatively documented surgeon feedback. Twenty eyes were included. Indications for vitrectomy were tractional retinal detachment (16 eyes), combined tractional-rhegmatogenous retinal detachment (2 eyes), and vitreous hemorrhage (2 eyes). Useful, good-quality 2D (B-scans) and 4D images were obtained in 16/20 eyes (80%). In these eyes, multiple diabetic retinopathy complications could be imaged. Swept-source microscope-integrated optical coherence tomography provided surgical guidance, e.g., in identifying dissection planes under fibrovascular membranes, and in determining residual membranes and traction that would benefit from additional peeling. In 4/20 eyes (20%), acceptable images were captured, but they were not useful due to high tractional retinal detachment elevation which was challenging for imaging. Swept-source microscope-integrated optical coherence tomography can provide important guidance during surgery for proliferative diabetic retinopathy complications through intraoperative identification of different complications and facilitation of intraoperative decision making.

Probe-pulse optimization for nonresonant suppression in hybrid fs/ps coherent anti-Stokes Raman scattering at high temperature.

PubMed

Miller, Joseph D; Slipchenko, Mikhail N; Meyer, Terrence R

2011-07-04

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) offers accurate thermometry at kHz rates for combustion diagnostics. In high-temperature flames, selection of probe-pulse characteristics is key to simultaneously optimizing signal-to-nonresonant-background ratio, signal strength, and spectral resolution. We demonstrate a simple method for enhancing signal-to-nonresonant-background ratio by using a narrowband Lorentzian filter to generate a time-asymmetric probe pulse with full-width-half-maximum (FWHM) pulse width of only 240 fs. This allows detection within just 310 fs after the Raman excitation for eliminating nonresonant background while retaining 45% of the resonant signal at 2000 K. The narrow linewidth is comparable to that of a time-symmetric sinc2 probe pulse with a pulse width of ~2.4 ps generated with a conventional 4-f pulse shaper. This allows nonresonant-background-free, frequency-domain vibrational spectroscopy at high temperature, as verified using comparisons to a time-dependent theoretical fs/ps CARS model.

On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system.

PubMed

Bradu, Adrian; Kapinchev, Konstantin; Barnes, Frederick; Podoleanu, Adrian

2015-07-01

In a previous report, we demonstrated master-slave optical coherence tomography (MS-OCT), an OCT method that does not need resampling of data and can be used to deliver en face images from several depths simultaneously. In a separate report, we have also demonstrated MS-OCT's capability of producing cross-sectional images of a quality similar to those provided by the traditional Fourier domain (FD) OCT technique, but at a much slower rate. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real time. We analyze the conditions that ensure a true real-time B-scan imaging operation and demonstrate in vivo real-time images from human fovea and the optic nerve, with resolution and sensitivity comparable to those produced using the traditional FD-based method, however, without the need of data resampling.

Optical coherence tomography monitoring of vocal fold femtosecond laser microsurgery

NASA Astrophysics Data System (ADS)

Wisweh, Henning; Merkel, Ulrich; Hüller, Ann-Kristin; Lüerßen, Kathrin; Lubatschowski, Holger

2007-07-01

Surgery of benign pathological alterations of the vocal folds results in permanent disphonia if the bounderies of the vocal fold layers are disregarded. Precise cutting with a femtosecond laser (fs-laser) combined with simultanous imaging of the layered structure enables accurate resections with respect to the layer boundaries. Earlier works demonstrated the capability of optical coherence tomography (OCT) for utilization on vocal folds. The layered structure can be imaged with a spatial resolution of 10-20μm up to a depth of 1.5mm. The performance of fs-laser cutting was analyzed on extracted porcine vocal folds with OCT monitoring. Histopathological sections of the same processed samples could be well correlated with the OCT images. With adequate laser parameters thermal effects induced only negligable damage to the processed tissue. The dimensions of the thermal necrosis were determined to be smaller than 1μm. OCT contolled fs-laser cutting of porcine vocal fold tissue in the μm range with minimal tissue damage is presented.

Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission

NASA Astrophysics Data System (ADS)

Gragossian, Aram; Seletskiy, Denis V.; Sheik-Bahae, Mansoor

2016-10-01

The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems.

In-vivo gingival sulcus imaging using full-range, complex-conjugate-free, endoscopic spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Huang, Yong; Zhang, Kang; Yi, WonJin; Kang, Jin U.

2012-01-01

Frequent monitoring of gingival sulcus will provide valuable information for judging the presence and severity of periodontal disease. Optical coherence tomography, as a 3D high resolution high speed imaging modality is able to provide information for pocket depth, gum contour, gum texture, gum recession simultaneously. A handheld forward-viewing miniature resonant fiber-scanning probe was developed for in-vivo gingival sulcus imaging. The fiber cantilever driven by magnetic force vibrates at resonant frequency. A synchronized linear phase-modulation was applied in the reference arm by the galvanometer-driven reference mirror. Full-range, complex-conjugate-free, real-time endoscopic SD-OCT was achieved by accelerating the data process using graphics processing unit. Preliminary results showed a real-time in-vivo imaging at 33 fps with an imaging range of lateral 2 mm by depth 3 mm. Gap between the tooth and gum area was clearly visualized. Further quantification analysis of the gingival sulcus will be performed on the image acquired.

Snapshot polarization-sensitive plug-in optical module for a Fourier-domain optical coherence tomography system

NASA Astrophysics Data System (ADS)

Marques, Manuel J.; Rivet, Sylvain; Bradu, Adrian; Podoleanu, Adrian

2018-02-01

In this communication, we present a proof-of-concept polarization-sensitive Optical Coherence Tomography (PS-OCT) which can be used to characterize the retardance and the axis orientation of a linear birefringent sample. This module configuration is an improvement from our previous work1, 2 since it encodes the two polarization channels on the optical path difference, effectively carrying out the polarization measurements simultaneously (snapshot measurement), whilst retaining all the advantages (namely the insensitivity to environmental parameters when using SM fibers) of these two previous configurations. Further progress consists in employing Master Slave OCT technology,3 which is used to automatically compensate for the dispersion mismatch introduced by the elements in the module. This is essential given the encoding of the polarization states on two different optical path lengths, each of them having dissimilar dispersive properties. By utilizing this method instead of the commonly used re-linearization and numerical dispersion compensation methods an improvement in terms of the calculation time required can be achieved.

In vivo oral imaging with integrated portable photoacoustic microscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Qin, Wei; Qi, Weizhi; Jin, Tian; Guo, Heng; Xi, Lei

2017-12-01

Oral diseases, especially oral cancers, are becoming serious health problems in humans. To image vasculatures and structures simultaneously in the human oral cavity which are tightly associated with various oral diseases, we develop a dual-modality portable optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) system. This system utilizes a new rotary scanning mechanism and a compact design of the imaging head, making it portable and free of translation of the imaging interface or samples. Through the phantom experiments, both modalities yield high lateral resolutions of 8.1 μm (ORPAM) and 8.56 μm (OCT), respectively. The axial resolutions are measured to be 116.5 μm for ORPAM and 6.1 μm for OCT. In vivo imaging of a mouse ear was carried out to evaluate the performance of the system in biological tissues. In addition, in vivo oral imaging of a healthy human lip and monitoring recovery progress of a lip ulcer demonstrate the clinical potential of this system.

Fluorescence-based surface magnifying chromoendoscopy and optical coherence tomography endoscope

NASA Astrophysics Data System (ADS)

Wall, R. Andrew; Barton, Jennifer K.

2012-02-01

A side-viewing, 2 mm diameter, surface magnifying chromoendoscopy (SMC)-optical coherence tomography (OCT) endoscope has been designed for simultaneous, non-destructive surface fluorescence visualization and cross-sectional imaging. We apply this endoscope to in vivo examination of mouse colon. A 30,000 element fiber bundle is combined with single mode fibers. The distal optics consist of a gradient-index lens and spacer to provide a magnification of 1 at a working distance of 1.58 mm in air, necessary to image the sample through a 0.23 mm thick outer glass envelope, and an aluminized right-angle prism fixed to the distal end of the GRIN lens assembly. The resulting 1:1 imaging system is capable of 3.9 μm lateral and 2.3 μm axial resolution in the OCT channel, and 125 lp/mm resolution across a 0.70 mm field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and cross-sectional imaging of colon microstructure.

Noise-resilient quantum evolution steered by dynamical decoupling

PubMed Central

Liu, Gang-Qin; Po, Hoi Chun; Du, Jiangfeng; Liu, Ren-Bao; Pan, Xin-Yu

2013-01-01

Realistic quantum computing is subject to noise. Therefore, an important frontier in quantum computing is to implement noise-resilient quantum control over qubits. At the same time, dynamical decoupling can protect the coherence of qubits. Here we demonstrate non-trivial quantum evolution steered by dynamical decoupling control, which simultaneously suppresses noise effects. We design and implement a self-protected controlled-NOT gate on the electron spin of a nitrogen-vacancy centre and a nearby carbon-13 nuclear spin in diamond at room temperature, by employing an engineered dynamical decoupling control on the electron spin. Final state fidelity of 0.91(1) is observed in preparation of a Bell state using the gate. At the same time, the qubit coherence time is elongated at least 30 fold. The design scheme does not require the dynamical decoupling control to commute with the qubit interaction and therefore works for general qubit systems. This work marks a step towards implementing realistic quantum computing systems. PMID:23912335

Temperature dependence of the coherence in polariton condensates

NASA Astrophysics Data System (ADS)

Rozas, E.; Martín, M. D.; Tejedor, C.; Viña, L.; Deligeorgis, G.; Hatzopoulos, Z.; Savvidis, P. G.

2018-02-01

We present a time-resolved experimental study of the temperature effect on the coherence of traveling polariton condensates. The simultaneous detection of their emission both in real and reciprocal space allows us to fully monitor the condensates' dynamics. We obtain fringes in reciprocal space as a result of the interference between polariton wave packets (WPs) traveling with the same speed. The periodicity of these fringes is inversely proportional to the spatial distance between the interfering WPs. In a similar fashion, we obtain interference fringes in real space when WPs traveling in opposite directions meet. The visibility of both real- and reciprocal-space interference fringes rapidly decreases with increasing temperature and vanishes. A theoretical description of the phase transition, considering the coexistence of condensed and noncondensed particles, for an out-of-equilibrium condensate such as ours is still missing, yet a comparison with theories developed for atomic condensates allows us to infer a critical temperature for the BEC-like transition when the visibility goes to zero.

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

Interactions between core and matrix thalamocortical projections in human sleep spindle synchronization

PubMed Central

Bonjean, Maxime; Baker, Tanya; Bazhenov, Maxim; Cash, Sydney; Halgren, Eric; Sejnowski, Terrence

2012-01-01

Sleep spindles, which are bursts of 11–15 Hz that occur during non-REM sleep, are highly synchronous across the scalp when measured with EEG, but have low spatial coherence and exhibit low correlation with EEG signals when simultaneously measured with MEG spindles in humans. We developed a computational model to explore the hypothesis that the spatial coherence of the EEG spindle is a consequence of diffuse matrix projections of the thalamus to layer 1 compared to the focal projections of the core pathway to layer 4 recorded by the MEG. Increasing the fanout of thalamocortical connectivity in the matrix pathway while keeping the core pathway fixed led to increased synchrony of the spindle activity in the superficial cortical layers in the model. In agreement with cortical recordings, the latency for spindles to spread from the core to the matrix was independent of the thalamocortical fanout but highly dependent on the probability of connections between cortical areas. PMID:22496571

Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

NASA Astrophysics Data System (ADS)

Gopinath, T.; Veglia, Gianluigi

2013-05-01

We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

Coherent beam combining of collimated fiber array based on target-in-the-loop technique

NASA Astrophysics Data System (ADS)

Li, Xinyang; Geng, Chao; Zhang, Xiaojun; Rao, Changhui

2011-11-01

Coherent beam combining (CBC) of fiber array is a promising way to generate high power and high quality laser beams. Target-in-the-loop (TIL) technique might be an effective way to ensure atmosphere propagation compensation without wavefront sensors. In this paper, we present very recent research work about CBC of collimated fiber array using TIL technique at the Key Lab on Adaptive Optics (KLAO), CAS. A novel Adaptive Fiber Optics Collimator (AFOC) composed of phase-locking module and tip/tilt control module was developed. CBC experimental setup of three-element fiber array was established. Feedback control is realized using stochastic parallel gradient descent (SPGD) algorithm. The CBC based on TIL with piston and tip/tilt correction simultaneously is demonstrated. And the beam pointing to locate or sweep position of combined spot on target was achieved through TIL technique too. The goal of our work is achieve multi-element CBC for long-distance transmission in atmosphere.

Beyond preadoptive risk: The impact of adoptive family environment on adopted youth's psychosocial adjustment.

PubMed

Ji, Juye; Brooks, Devon; Barth, Richard P; Kim, Hansung

2010-07-01

Adopted children often are exposed to preadoptive stressors--such as prenatal substance exposure, child maltreatment, and out-of-home placements--that increase their risks for psychosocial maladjustment. Psychosocial adjustment of adopted children emerges as the product of pre- and postadoptive factors. This study builds on previous research, which fails to simultaneously assess the influences of pre- and postadoptive factors, by examining the impact of adoptive family sense of coherence on adoptee's psychosocial adjustment beyond the effects of preadoptive risks. Using a sample of adoptive families (n = 385) taking part in the California Long Range Adoption Study, structural equation modeling analyses were performed. Results indicate a significant impact of family sense of coherence on adoptees' psychosocial adjustment and a considerably less significant role of preadoptive risks. The findings suggest the importance of assessing adoptive family's ability to respond to stress and of helping families to build and maintain their capacity to cope with stress despite the sometimes fractious pressures of adoption.

Joint transform correlators with spatially incoherent illumination

NASA Astrophysics Data System (ADS)

Bykovsky, Yuri A.; Karpiouk, Andrey B.; Markilov, Anatoly A.; Rodin, Vladislav G.; Starikov, Sergey N.

1997-03-01

Two variants of joint transform correlators with monochromatic spatially incoherent illumination are considered. The Fourier-holograms of the reference and recognized images are recorded simultaneously or apart in a time on the same spatial light modulator directly by monochromatic spatially incoherent light. To create the signal of mutual correlation of the images it is necessary to execute nonlinear transformation when the hologram is illuminated by coherent light. In the first scheme of the correlator this aim was achieved by using double pas of a restoring coherent wave through the hologram. In the second variant of the correlator the non-linearity of the characteristic of the spatial light modulator for hologram recording was used. Experimental schemes and results on processing teste images by both variants of joint transform correlators with monochromatic spatially incoherent illumination. The use of spatially incoherent light on the input of joint transform correlators permits to reduce the requirements to optical quality of elements, to reduce accuracy requirements on elements positioning and to expand a number of devices suitable to input images in correlators.

Spectral domain optical coherence tomography of multi-MHz A-scan rates at 1310 nm range and real-time 4D-display up to 41 volumes/second

PubMed Central

Choi, Dong-hak; Hiro-Oka, Hideaki; Shimizu, Kimiya; Ohbayashi, Kohji

2012-01-01

An ultrafast frequency domain optical coherence tomography system was developed at A-scan rates between 2.5 and 10 MHz, a B-scan rate of 4 or 8 kHz, and volume-rates between 12 and 41 volumes/second. In the case of the worst duty ratio of 10%, the averaged A-scan rate was 1 MHz. Two optical demultiplexers at a center wavelength of 1310 nm were used for linear-k spectral dispersion and simultaneous differential signal detection at 320 wavelengths. The depth-range, sensitivity, sensitivity roll-off by 6 dB, and axial resolution were 4 mm, 97 dB, 6 mm, and 23 μm, respectively. Using FPGAs for FFT and a GPU for volume rendering, a real-time 4D display was demonstrated at a rate up to 41 volumes/second for an image size of 256 (axial) × 128 × 128 (lateral) voxels. PMID:23243560

An investigation of turbulent scatter from the mesosphere as observed by coherent-scatter radar

NASA Technical Reports Server (NTRS)

Gibbs, K. P.; Bowhill, S. A.

1983-01-01

Turbulent scatter from he mesosphere is observed using the Urbana coherent-scatter radar. The variation in signal-to-noise ratio as a function of time-of-day is examined. The origin of scattering regions is investigated by comparing the variations in scattered power and Doppler velocity. Nighttime echoes are shown for periods of enhanced electron concentration. The spectrum of the returned signal is studied with a resolution of ten seconds. Spectral information is used to increase altitude resolution and observe the motion of scatterers. The expected variation in signal-to-noise ratio with solar flux is observed. It is found that variations in the scattered power generally do not correspond to the gravity waves which are simultaneously observed. Turbulent layers are observed at altitudes with high shear in the horizontal velocity and at altitudes with low shear. The ten-second resolution is necessary to distinguish meteor echoes from echoes produced by the advection of a scattering layer through the radar beam.

Noise-resilient quantum evolution steered by dynamical decoupling.

PubMed

Liu, Gang-Qin; Po, Hoi Chun; Du, Jiangfeng; Liu, Ren-Bao; Pan, Xin-Yu

2013-01-01

Realistic quantum computing is subject to noise. Therefore, an important frontier in quantum computing is to implement noise-resilient quantum control over qubits. At the same time, dynamical decoupling can protect the coherence of qubits. Here we demonstrate non-trivial quantum evolution steered by dynamical decoupling control, which simultaneously suppresses noise effects. We design and implement a self-protected controlled-NOT gate on the electron spin of a nitrogen-vacancy centre and a nearby carbon-13 nuclear spin in diamond at room temperature, by employing an engineered dynamical decoupling control on the electron spin. Final state fidelity of 0.91(1) is observed in preparation of a Bell state using the gate. At the same time, the qubit coherence time is elongated at least 30 fold. The design scheme does not require the dynamical decoupling control to commute with the qubit interaction and therefore works for general qubit systems. This work marks a step towards implementing realistic quantum computing systems.

Directed Communication between Nucleus Accumbens and Neocortex in Humans Is Differentially Supported by Synchronization in the Theta and Alpha Band.

PubMed

Horschig, Jörn M; Smolders, Ruud; Bonnefond, Mathilde; Schoffelen, Jan-Mathijs; van den Munckhof, Pepijn; Schuurman, P Richard; Cools, Roshan; Denys, Damiaan; Jensen, Ole

2015-01-01

Here, we report evidence for oscillatory bi-directional interactions between the nucleus accumbens and the neocortex in humans. Six patients performed a demanding covert visual attention task while we simultaneously recorded brain activity from deep-brain electrodes implanted in the nucleus accumbens and the surface electroencephalogram (EEG). Both theta and alpha oscillations were strongly coherent with the frontal and parietal EEG during the task. Theta-band coherence increased during processing of the visual stimuli. Granger causality analysis revealed that the nucleus accumbens was communicating with the neocortex primarily in the theta-band, while the cortex was communicating the nucleus accumbens in the alpha-band. These data are consistent with a model, in which theta- and alpha-band oscillations serve dissociable roles: Prior to stimulus processing, the cortex might suppress ongoing processing in the nucleus accumbens by modulating alpha-band activity. Subsequently, upon stimulus presentation, theta oscillations might facilitate the active exchange of stimulus information from the nucleus accumbens to the cortex.

True color scanning laser ophthalmoscopy and optical coherence tomography handheld probe

PubMed Central

LaRocca, Francesco; Nankivil, Derek; Farsiu, Sina; Izatt, Joseph A.

2014-01-01

Scanning laser ophthalmoscopes (SLOs) are able to achieve superior contrast and axial sectioning capability compared to fundus photography. However, SLOs typically use monochromatic illumination and are thus unable to extract color information of the retina. Previous color SLO imaging techniques utilized multiple lasers or narrow band sources for illumination, which allowed for multiple color but not “true color” imaging as done in fundus photography. We describe the first “true color” SLO, handheld color SLO, and combined color SLO integrated with a spectral domain optical coherence tomography (OCT) system. To achieve accurate color imaging, the SLO was calibrated with a color test target and utilized an achromatizing lens when imaging the retina to correct for the eye’s longitudinal chromatic aberration. Color SLO and OCT images from volunteers were then acquired simultaneously with a combined power under the ANSI limit. Images from this system were then compared with those from commercially available SLOs featuring multiple narrow-band color imaging. PMID:25401032

Sensing the Coherence of Biology in Contrast to Psychology: Young Children's Use of Causal Relations to Distinguish Two Foundational Domains

ERIC Educational Resources Information Center

Erickson, Jane E.; Keil, Frank C.; Lockhart, Kristi L.

2010-01-01

To what extent do children understand that biological processes fall into 1 coherent domain unified by distinct causal principles? In Experiments 1 and 2 (N = 125) kindergartners are given triads of biological and psychological processes and asked to identify which 2 members of the triad belong together. Results show that 5-year-olds correctly…

Noise induced quantum effects in photosynthetic complexes

NASA Astrophysics Data System (ADS)

Dorfman, Konstantin; Voronine, Dmitri; Mukamel, Shaul; Scully, Marlan

2012-02-01

Recent progress in coherent multidimensional optical spectroscopy revealed effects of quantum coherence coupled to population leading to population oscillations as evidence of quantum transport. Their description requires reevaluation of the currently used methods and approximations. We identify couplings between coherences and populations as the noise-induced cross-terms in the master equation generated via Agarwal-Fano interference that have been shown earlier to enhance the quantum yield in a photocell. We investigated a broad range of typical parameter regimes, which may be applied to a variety of photosynthetic complexes. We demonstrate that quantum coherence may be induced in photosynthetic complexes under natural conditions of incoherent light from the sun. This demonstrates that a photosynthetic reaction center may be viewed as a biological quantum heat engine that transforms high-energy thermal photon radiation into low entropy electron flux.

Utilizing broadband X-rays in a Bragg coherent X-ray diffraction imaging experiment

DOE PAGES

Cha, Wonsuk; Liu, Wenjun; Harder, Ross; ...

2016-07-26

A method is presented to simplify Bragg coherent X-ray diffraction imaging studies of complex heterogeneous crystalline materials with a two-stage screening/imaging process that utilizes polychromatic and monochromatic coherent X-rays and is compatible with in situ sample environments. Coherent white-beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three-dimensional reciprocal-space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifyingin situchamber design. This approach was demonstrated with Au nanoparticles and will enable,more » for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.« less

Attention, motivation, and reading coherence failure: a neuropsychological perspective.

PubMed

Wasserman, Theodore

2012-01-01

Reading coherence, defined as the ability to create appropriate, meaningful connections between the elements within a specific text itself and between elements within a text and the reader's prior knowledge, is one of the key processes involved in reading comprehension. This article describes reading coherence within the context of a neuropsychological model combining recent research in motivation, attention, and working memory. Specifically, a unique neuropsychologically identifiable form of reading coherence failure arising from the attentional and motivational deficiencies, based in altered frontoventral striatal reward circuits associated with noradrenaline (NA) circuitry, consistent with the delay-aversion model (dual-pathway model) of Sonuga-Barke ( 2003 ) is postulated. This article provides a model for this subset of reading disorders of which etiology is based on the executive support processes for reading and not in the mechanics of actual reading such as decoding and phonetics.

Utilizing broadband X-rays in a Bragg coherent X-ray diffraction imaging experiment.

PubMed

Cha, Wonsuk; Liu, Wenjun; Harder, Ross; Xu, Ruqing; Fuoss, Paul H; Hruszkewycz, Stephan O

2016-09-01

A method is presented to simplify Bragg coherent X-ray diffraction imaging studies of complex heterogeneous crystalline materials with a two-stage screening/imaging process that utilizes polychromatic and monochromatic coherent X-rays and is compatible with in situ sample environments. Coherent white-beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three-dimensional reciprocal-space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifying in situ chamber design. This approach was demonstrated with Au nanoparticles and will enable, for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.

New developments in clinical CARS

NASA Astrophysics Data System (ADS)

Weinigel, Martin; Breunig, Hans Georg; Kellner-Höfer, Marcel; Bückle, Rainer; Darvin, Maxim; Lademann, Juergen; König, Karsten

2013-02-01

We combined two-photon fluorescence and coherent anti-Stokes Raman scattering (CARS) imaging in a clinical hybrid multiphoton tomograph for in vivo imaging of human skin. The clinically approved TPEF/CARS system provides simultaneous imaging of endogenous fluorophores and non-fluorescent lipids. The Stokes laser for the two-beam configuration of CARS is based on spectral broadening of femtosecond laser pulses in a photonic crystal fiber (PCF). We report on the highly flexible medical TPEF/CARS tomograph MPTflex®-CARS with an articulated arm and first in vivo measurements on human skin.

Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry.

PubMed

Scherman, M; Nafa, M; Schmid, T; Godard, A; Bresson, A; Attal-Tretout, B; Joubert, P

2016-02-01

Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement.

MISERS BLUFF Electromagnetic Propagation Experiments. Volume III-Preliminary Results of the UHF-EHF Radar-Scattering and Coherent-Transmission Experiments.

DTIC Science & Technology

1979-10-01

the dry bed of the Bill Williams River near Lake Havasu City, Arizona. The first test, MISERS BLUFF II-1 (MBII-I), which was a 120-ton ammonium nitrate ...and fuel oil (ANFO) detonation, took place at 1300 MST on 28 June 1978. The second test, MBII-2, consisted of the simultaneous detonation of six such...Scientific Laboratory ATTN: L. Jacobs ATTN; R. Taschek ATTN: T. Neighbors ATTN: P. Keaton ATTN: D. Westervelt Berkeley Research Associates, Inc. ATTN: J