Intensity Dip Research Articles

Raman spectroscopy of active-carbon electrodes when Au colloids are placed at the electrolyte/electrode interface

Surface enhanced Raman spectroscopy (SERS) was used to study active-carbon (A-C) electrodes in super-capacitors cells; these electrodes were functionalized with Au nanoparticles (AuNPs). We observed a large enhancement in the cell's specific capacitance as a function of the AuNPs concentration. Cell capacitance is a volumetric effect while SERS is susceptible to the local number of colloids. The intensity ratio between the D-line (defect line) and the graphitic line (G-line), ID/IG, of the A-C electrode proved to be a good marker, independent of the measurement point. Rather than a peak, typical of amorphous films, this ratio has a dip at a particular AuNPs concentration, which is shifted upon the presence of the electrolyte. It is suggested that the seemingly unrelated phenomena - the capacitance enhancement and the intensity dip - are the result of the formation of a quasi-2D array of AuNPs at the interface between the electrolyte and the electrode.

Comparison of intensity-based methods for automatic speech rate computation

Automatic computation of speech rate is a necessary task in a wide range of applications that require this prosodic feature, in which a manual transcription and time alignments are not available. Several tools have been developed to this end, but not enough research has been conducted yet to see to what extent they are scalable to other languages.
 In the present work, we take two off-the- shelf tools designed for automatic speech rate computation and already tested for Dutch and English (v1, which relies on intensity peaks preceded by an intensity dip to find syllable nuclei and v3, which relies on intensity peaks surrounded by dips) and we apply them to read and spontaneous Spanish speech. Then, we test which of them offers the best performance. The results obtained with precision and normalized mean squared error metrics showed that v3 performs better than v1. However, recall measurement shows a better performance of v1, which suggests that a more fine-grained analysis on sensitivity and specificity is needed to select the best option depending on the application we are dealing with.

Transducin-Deficient Rod Photoreceptors Evaluated With Optical Coherence Tomography and Oxygen Consumption Rate Energy Biomarkers.

To test the hypothesis that rod energy biomarkers in light and dark are similar in mice without functional rod transducin (Gnat1rd17). Gnat1rd17 and wildtype (WT) mice were studied in canonically low energy demand (light) and high energy demand (dark) conditions. We measured rod inner segment ellipsoid zone (ISez) profile shape, external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness, and magnitude of a hyporeflective band (HB) intensity dip located between photoreceptor tips and apical RPE; antioxidants were given in a subset of mice. Oxygen consumption rate (OCR) and visual performance indexes were also measured. The lower energy demand expected in light-adapted wildtype retinas was associated with an elongated ISez, thicker ELM-RPE, and higher HB magnitude, and lower OCR compared to high energy demand conditions in the dark. Gnat1rd17 mice showed a wildtype-like ISez profile shape at 20 minutes of light that became rounder at 60 minutes; at both times, ELM-RPE was smaller than wildtype values, and the HB magnitude was unmeasurable. OCR was higher than in the dark. Light-adapted Gnat1rd17 mice biomarkers were unaffected by anti-oxidants. Gnat1rd17 mice showed modest outer nuclear layer thinning and no reduction in visual performance indexes. Light-stimulated changes in all biomarkers in WT mice are consistent with the established light-induced decrease in net energy demand. In contrast, biomarker changes in Gnat1rd17 mice raise the possibility that light increases net energy demand in the absence of rod phototransduction.

Broad-band spectral analysis of LMXB 2S 0921-63 with Suzaku

ABSTRACT We present the broad-band spectral analysis of the low-mass X-ray binary 2S 0921-63 by using the Suzaku archival data covering the orbital phase between 0.31 and 1.16 during four close observations. It is the first time that a broad-band spectral analysis of 2S 0921-63 has been done up to 25 keV. The 0.5–10 keV XIS count rate varied between ∼1 and ∼5 counts s−1 during the observations. A partial X-ray eclipse and broad post-eclipse intensity dip were observed during the observations. The X-ray emission hardened marginally during the intensity dip. We have modelled the source spectra by simultaneously fitting the XIS and HXD-PIN spectra for each of the four observations. The broad-band spectra of the source can be described by a model comprising a very hot blackbody having temperature, kTBB ≈ 1.66–2.13 keV, a high-energy cut-off power law, and an Fe emission line at Eline ∼ 6.7 keV. A second model, accounting for the Comptonization of the thermal emission from accretion disc along with an Fe emission line, describes the broad-band spectra of 2S 0921-63 equally well.

Phase characters of optical dark solitons with third-order dispersion and delayed nonlinear response.

Dark soliton is usually seen as one of the simplest topological solitons, due to phase shift across its intensity dip. We investigate phase characters of single-valley dark soliton (SVDS) and double-valley dark soliton (DVDS) in a single-mode optical fiber with third-order dispersion and delayed nonlinear response. Notably, two different phase shifts can produce an SVDS with the same velocity under some conditions, which is not admitted for a dark soliton with only the second-order dispersion and self-phase modulation, whose phase shift and velocity is a one-to-one match. This phase property of SVDS can be used to explain the generation of previously reported DVDS in Hirota equationand make DVDSs show two types of phase profiles. Moreover, the different topological vector potentials underlying the distinct phase profiles have been uncovered. We further explore the collision properties of the DVDSs by analyzing their topological phases. Strikingly, the inelastic collision can lead to the conversion between the two types of phase profiles for DVDS. The results reveal that inelastic or elastic collision can be judged by analyzing virtual topological magnetic fields.

On the Impact of an Intermediate Duration X-Ray Burst on the Accretion Environment in IGR J17062–6143

Abstract We report on a spectroscopic analysis of the X-ray emission from IGR J17062−6143 in the aftermath of its 2020 June intermediate duration Type I X-ray burst. Using the Neutron Star Interior Composition Explorer, we started observing the source 3 hr after the burst was detected with the Monitor of All-sky X-ray Image Gas Slit Camera, and monitored the source for the subsequent 12 days. We observed the tail end of the X-ray burst-cooling phase, and find that the X-ray flux is severely depressed relative to its historic value for a three-day period directly following the burst. We interpret this intensity dip as the inner accretion disk gradually restoring itself after being perturbed by the burst irradiation. Superimposed on this trend we observed a 1.5 day interval during which the X-ray flux is sharply lower than the wider trend. This drop in flux could be isolated to the nonthermal components in the energy spectrum, suggesting that it may be caused by an evolving corona. Additionally, we detected a 3.4 keV absorption line at 6.3σ significance in a single 472 s observation while the burst emission was still bright. We tentatively identify the line as a gravitationally redshifted absorption line from burning ashes on the stellar surface, possibly associated with 40Ca or 44Ti.

Classification of slope area types and hydrocarbon accumulation rules in Wuerxun-Beier Depression

After more than 50 years of exploration and development, Wuerxun-Beier depression has entered a high exploration stage. It is more and more difficult to find large-scale structural reservoirs. Therefore, structural-lithologic reservoirs in slope areas have gradually become the focus of exploration. Based on the overall study and dissection of the depression, the geological differentiation characteristics of the large-scale slope area are discussed. According to the occurrence of the slope, the intensity of tectonic activity, the intensity of source supply and the pattern of synsedimentary fault combination, the slope zone in the study area can be divided into six types, namely, the steep slope with strong source along the fault step type, the compound fault step type of medium slope with strong source, the reverse fault step type of the gentle slope with strong source, and the weak supply type. Different types of slope have different sand control mechanisms and reservoir forming characteristics, such as the source gentle slope forward fault terrace type, the weak source gentle slope reverse fault terrace type and the weak source middle slope forward fault terrace type. Source supply intensity and slope dip control the development type of sedimentary system, the combination of synsedimentary faults and valleys controls the distribution characteristics of sedimentary system. Through exploration practice, significant discoveries have been made on the southwestern, southeastern and northern slopes of Beixi, Wuerxun-Beier depression, which confirms that the slope area is the main breakthrough direction for oil and gas exploration and large-scale reservoir increase in continental fault-depression lake basins.

Archaeomagnetic results from Cambodia in Southeast Asia: Evidence for possible low-latitude flux expulsion

Extensive spatial and temporal distribution of high-quality data are essential for understanding regional and global behaviors of the geomagnetic field. We carried out chronological and archaeomagnetic studies at the Angkor-era iron-smelting site of Tonle Bak in Cambodia in Southeast Asia, an area with no data available to date. We recovered high-fidelity full-vector geomagnetic information from the 11th to 14th century for this region, which fill gaps in the global distribution of data and will significantly improve the global models. These results reveal a sharp directional change of the geomagnetic field between 1200 and 1300 CE, accompanied by an intensity dip between 1100 and 1300 CE. The fast geomagnetic variation recorded by our data provides evidence for the possible existence of low-latitude flux expulsion. Related discussions in this paper will inspire a new focus on detailed geomagnetic research in low-latitude areas around the equator, and exploration of related dynamic processes.

The acoustic realization and timing of glottal stops in Hawaiian

Studies of glottal stop realization have shown that it is often not produced with full closure (Ladefoged and Maddieson, 1996), but conditioning factors are not well understood. This study focuses on Hawaiian, which has phonemic glottal stop that is contrastive in both word-initial (/ˀaka/ “laugh,” [aka] “shadow”) and word-medial position (/pua/ “flower,” /puˀa/ “to excrete”). Glottal stop realization is examined with respect to word position, different versus identical flanking vowel (/puˀu/ “hill”), and duration of the target /VˀV/ sequence. Data from eight native speakers come from the Ka Leo HawaiÊ»i radio program. The majority of glottal stops are produced as a period of creaky voice (63%), either in a modal-creaky-modal, modal-creaky or creaky-modal configuration. Full closures (6.6%) were more likely in word-initial position, and identical flanking vowels led to longer periods of creak. Some tokens had only an intensity dip. Shorter target intervals had longer proportions of creak. These findings for the glottal stop phoneme are consistent with research on the timing of contrastive voice quality in vowels, which show a preference for modal-nonmodal-modal patterns to ensure that vowel quality, voice quality, and tone are recoverable (Silverman, 1997). Effects of word position and flanking vowel are also related to recoverability and segmentation.

Spatial–temporal radiation distribution in a CuBr vapor brightness amplifier in a real laser monitor scheme

The non-uniform gain of the active media is a significant issue in terms of optimizing the beam profile and ensuring image quality of the laser monitor. In this paper, a study of the radial distribution of radiation in copper bromide brightness amplifiers in real schemes of laser monitors is presented. The radial distribution of radiation in a two-pass parallel beam amplified by a brightness amplifier is compared with the radiation distribution in a beam that carries an image in conventional and mirror-imaging laser monitors. The results demonstrate that for metal vapor gain media operated at low concentration of the working substance vapors, the appropriate choice of imaging optics can partially or completely uniform image intensity profile. In case of remote laser monitoring, the intensity dip at the center of the amplified beam completely disappears in the mirror-imaging laser monitor up to a distance of 2 m from the brightness amplifier. This observation range is sufficient for most tasks in the study of the combustion of energetic materials.

Double‐dipping to refine stellar rotation periods

AbstractWe present a refined analysis of 15,038 Kepler main sequence light curves to determine the stellar rotation periods. The initial period estimates come from an autocorrelation function, as has been done before. We then measure the duration of every intensity dip in the light curve, expressed as fractions of the initial rotation period estimate. These dip duration distributions are subdivided into several regions whose relation to each other helps determine which harmonic of the initial rotation period is most physically plausible. We compare our final rotation periods to those from McQuillan et al. (2014) and find that the great majority agree, but about 10% of their periods are doubtful (usually twice as long as is most plausible). We are still refining our method, and will later extend it to more stars to substantially increase the sample of reliable stellar rotation periods.

Splitting and Motions of Dissipative Soliton Resonance Pulses in Mode-Locked Fiber Lasers

We numerically investigated the splitting and motions of dissipative soliton resonance (DSR) pulses in an all-normal-dispersion Yb-doped fiber laser mode-locked by a nonlinear optical loop mirror. At certain values of the system parameters, the initial single Gaussian pulse can evolve into an unstable DSR pulse with several dark solitons inside. After collisions of dark solitons, a big intensity dip occurs at the center of the DSR pulse, leading to the splitting of the DSR pulse. After splitting, the peak-to-peak separation between two DSR pulses increases at first and finally reaches a fixed value of 193 ps, indicating a steady-state multipulse operation. The relative motions of separated DSR pulse originate from the phase shift.

NICER Observes a Secondary Peak in the Decay of a Thermonuclear Burst from 4U 1608–52

Abstract We report for the first time below 1.5 keV, the detection of a secondary peak in an Eddington-limited thermonuclear X-ray burst observed by the Neutron Star Interior Composition Explorer (NICER) from the low-mass X-ray binary 4U 1608–52. Our time-resolved spectroscopy of the burst is consistent with a model consisting of a varying-temperature blackbody, and an evolving persistent flux contribution, likely attributed to the accretion process. The dip in the burst intensity before the secondary peak is also visible in the bolometric flux. Prior to the dip, the blackbody temperature reached a maximum of ≈3 keV. Our analysis suggests that the dip and secondary peak are not related to photospheric expansion, varying circumstellar absorption, or scattering. Instead, we discuss the observation in the context of hydrodynamical instabilities, thermonuclear flame spreading models, and reburning in the cooling tail of the burst.

Magnetic Field-Sensitive Radical Pair Dynamics in Polymethylene Ether-Bridged Donor-Acceptor Systems.

Donor–acceptor systems forming exciplexes are versatile models for the study of magnetic field effects (MFEs) on charge recombination reactions. The MFEs originate from singlet–triplet interconversion within transient radical ion pairs (RIPs), which exist in a dynamic equilibrium with the exciplexes. Here, we describe the synthesis and MFEs of the chain-linked N,N-dimethylaniline (DMA)/9-methylanthracene (MAnt) donor–acceptor system MAnt–(CH2)n–O–CH2–CH2–DMA for n = 6, 8, 10, and 16. The MFEs are found to increase with increasing chain length. Effects as large as 37.5% have been observed for the long-chain compound with n = 16. The solvent dependence of the MFEs at magnetic field intensity 75 mT is reported. For the range of solvent static dielectric constants εs = 6.0–36.0, the MFEs go through a maximum for intermediate polarities, for which the direct formation of RIPs prevails and their dissociation and reencounter are balanced. Field-resolved measurements (MARY spectra) are reported for solutions in butyronitrile. The MARY spectra reveal that for n = 8, 10, 16, the average exchange interaction is negligible during the coherent lifetime of the radical pair. However, singlet–triplet dephasing broadens the lineshape; the shorter the linker, the more pronounced this effect is. For n = 6, a dip in the fluorescence intensity reveals a nonzero average exchange coupling of the order of ±5 mT. We discuss the field-dependence in the framework of the semiclassical theory taking spin-selective recombination, singlet–triplet dephasing, and exchange coupling into account. Singlet recombination rates of the order of 0.1 ns–1 and various degrees of singlet–triplet dephasing govern the spin dynamics. In addition, because of a small free energy gap between the exciplex and the locally excited fluorophore quencher pair, a fully reversible interconversion between the RIP, exciplex, and locally excited fluorophore is revealed by spectrally resolved MFE measurements for the long-chain systems (n = 10, 16).

Detection of a cyclotron line in SXP 15.3 during its 2017 outburst

ABSTRACT We report the results of AstroSat and NuSTAR observations of the Be/X-ray binary pulsar SXP 15.3 in the Small Magellanic Cloud during its outburst in late 2017, when the source reached a luminosity level of ∼1038 erg s−1, close to the Eddington limit. The unprecedented broad-band coverage of the source allowed us to perform timing and spectral analysis between 3 and 80 keV. The pulse profile exhibits a significant energy dependence, and morphs from a double-peaked profile to a single broad pulse at energies >15 keV. This can be explained by a spectral hardening during an intensity dip seen between the two peaks of the pulse profile. We detect a Cyclotron Resonance Scattering Feature at ∼5 keV in the X-ray spectrum, independent of the choice of the continuum model. This indicates a magnetic field strength of 6 × 1011 G for the neutron star.

Surface Plasmon Resonance Biosensor in Healthcare Application Using Kretschsmann & Otto Configuration

In this study, a planar D-shape optical fiber sensor based on Surface Plasmon Resonance phenomenon using two different excitation methods has been demonstrated. The proposed bio-sensor uses Amplitude-Wavelength hybrid detection technique to determine the change in urine refractive index that depends on resonance parameters. The analysis employs finite element method to investigate the optical properties of the proposed sensor. From the results it can be evident that Otto configuration offers greater amount of reflected light intensity dip for a particular urine refractive index in comparison with Kretschmann configuration. For an example, for Otto configuration the dip of reflected light intensity measured in terms of reflectance which attains a value 0.5 for ns (urine refractive index) of 1.489 while Kretschmann configuration provides a dip of 0.65 for the same value of ns. Results also show that the sharpness of reflectance is comparatively higher for the sensor using Otto configuration in comparison with Kretschmann configuration in case of wavelength interrogation. Thus, Otto configuration offers better performance in comparison with Kretschmann configuration.

Optical Trapping of Electrons in Graphene

We propose an experimentally friendly scheme for trapping quasi-relativistic electrons in graphene by an electromagnetic beam with circular polarization and a spatially inhomogeneous profile with an intensity dip. The trapping is achieved due to the effect of band-gap opening outside the trapping region. The proposed mechanism allows for noninvasive electron confinement in graphene without any need for the chemical patterning of the sample or the application of metallic gates.

Interaction of near-field microscopy probes with surface plasmon polaritons

In this work, we use a collection-type scanning near-field optical microscope to study the intensity distribution along the direction perpendicular to the interface, considering the interaction of the probe with the evanescent field of surface plasmon polaritons. A decrease of the signal is observed as the probe comes near to contact, as opposed to the expected single exponential increase. This effect is explained with a relatively simple semi-analytical model that takes into account the shape of the tip and the geometrical cutoff of the plasmonic mode. The proposed model confirm the presence of the intensity dip near the surface, as a result of the perturbation of the field caused by the probe.

Transient power characteristics of a compact singly resonant intracavity optical parametric oscillator pumped by a semiconductor disk laser

The multimode transient and steady state characteristics of a singly resonant intracavity optical parametric oscillator (ICSRO) pumped by a semiconductor disk laser have been numerically analyzed. Nonlinear parametric interaction in the ICSRO was shown to stimulate multimode lasing with an intensity dip at the central frequency of emission. The insertion of an etalon makes the device exhibit a single-mode operation.

Acoustic reduction, context, and inter-stimulus interval in cross-modal priming

Work such as Tucker (2011) and van de Ven et al. (2011) show that reduced acoustic contrasts can impede lexical access for a listener. Tucker (2011) also found preliminary evidence of a nonlinear (U-shaped) relationship between the degree of intensity dip in stops and lexical decision response times. The present talk summarizes results from a cross-modal identity priming experiment designed to explore this potential nonlinearity further. Utilizing three different inter-stimulus-intervals, trials were presented in which conversational words with variously reduced intervocalic stops served as auditory primes. Visual targets included the same word as the prime, words with a large degree of phonological overlap, and unrelated controls, as well as phonologically overlapping and non-overlapping pseudowords. Additionally, the auditory primes were presented with three degrees of surrounding context: isolation (the word only), phonetic context (including the vowels in neighboring syllables, providing primarily spe...