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1

Amplified spontaneous emission in narrow-band pulsed dye laser oscillators--theory and experiment  

SciTech Connect

We have investigated the effect of amplified spontaneous emission (ASE) on the spectral and temporal characteristics of narrowband pulsed dye laser oscillators. The space and time dependent rate equations for the molecular populations and photon fluxes have been solved numberically to study the dependence of ASE on various laser parameters and the effects of ASE on the spectral and temporal profile of the dye laser output. To account for the diffraction losses present in a real dye laser oscillator, appropriate feedback factors for the laser and ASE photon fluxes were introduced into the boundary conditions for the oscillator. These theoretical results have been substantiated by experimental measurements of ASE in a narrow-band pulsed dye laser oscillator. We show that a considerable reduction of ASE in a grazing incidence grating dye laser oscillator can be obtained by appropriately shaping the pump pulse. Oscillations observed in the temporal output of pulsed dye lasers are also discussed.

Nair, L.G.; Dasgupta, K.

1985-11-01

2

Wf\\/pc Narrow Band Filter Calibration  

Microsoft Academic Search

This is a slightly modified version of the narrow band calibration portion of proposal 1481. This proposal is to obtain narrow band images of a diffuse emission line source which has been well characterized from the ground. The purpose of the test is to directly provide calibration of these filters using a ~0 velocity emission line source, as well as

J. Westphal

1990-01-01

3

Enhanced tunable narrow-band THz emission from laser-modulated electron beams  

SciTech Connect

We propose and analyze a scheme to generate enhanced narrow-band terahertz (THz) radiation through down-conversion of the frequency of optical lasers using laser-modulated electron beams. In the scheme the electron beam is first energy modulated by two lasers with wave numbers k{sub 1} and k2, respectively. After passing through a dispersion section, the energy modulation is converted to density modulation. Due to the nonlinear conversion process, the beam will have density modulation at wave number k = nk{sub 1} + mk{sub 2}, where n and m are positive or negative integers. By properly choosing the parameters for the lasers and dispersion section, one can generate density modulation at THz frequency in the beam using optical lasers. This density-modulated beam can be used to generate powerful narrow-band THz radiation. Since the THz radiation is in tight synchronization with the lasers, it should provide a high temporal resolution for the optical-pump THz-probe experiments. The central frequency of the THz radiation can be easily tuned by varying the wavelength of the two lasers and the energy chirp of the electron beam. The proposed scheme is in principle able to generate intense narrow-band THz radiation covering the whole THz range and offers a promising way towards the tunable intense narrow-band THz sources.

Xiang, D.; Stupakov, G.; /SLAC

2009-06-19

4

Quantitative Method for the Optimal Subtraction of Continuum Emission from Narrow-band Images: Skewness Transition Analysis  

NASA Astrophysics Data System (ADS)

We present an objective method to remove the stellar continuum emission from narrow--band images to derive emission--line images. The method is based on the skewness of the pixel histogram of the residual images. Specifically, we exploit a transition in the skewness of the signal in the continuum--subtracted image, which appears when the image changes from being undersubtracted to oversubtracted. Tests on one--dimensional artificial images demonstrate that the transition identifies the optimal scaling factor ? to be used on the broad-band image IB in order to produce the optimal line--emission image IE, i.e., IE = IN-?IB, with IN the original (unsubtracted) narrow--band image. The advantage of this method is that it uses all information--bearing pixels in the final image, and not just a subset of those pixels (the latter being common in many traditional approaches to stellar continuum removal from narrow--band images). We apply our method to actual images, both from ground--based and space facilities, in particular to WFPC2 and ACS images from the Hubble Space Telescope, and we show that it is successful irrespective of the nature of the sources (point-like or extended). We also discuss the impact on the accuracy of the method of nonoptimal images, such as those containing saturated sources or nonuniform background, and present workarounds for those problems.

Hong, Sungryong; Calzetti, Daniela; Dickinson, Mark

2014-01-01

5

Determination of longwave anisotropic emission factors from combined broad- and narrow-band radiance measurements  

Microsoft Academic Search

The conversion of measured broad-band radiances into radiative fluxes requires application of angular corrections: In the Earth Radiation Budget Experiment (ERBE), the longwave anisotropic emission factors (AEF) were tabulated for different viewing zenith angles, seasons, latitude bands and scence types including four different cloud cover classes. Investigating an alternative approach for the ScaRaB (Scanner for Radiation Balance) instrument, we use

C. Stubenrauch; J.-Ph. Duvel; R. S. Kandel

1994-01-01

6

Narrow-band light emission from a single carbon nanotube p-n diode  

NASA Astrophysics Data System (ADS)

We present the first observation of electroluminescence from electrostatically-generated carbon nanotube (CNT) p-n junctions[1]. While CNT optoelectronics has made much progress in recent years, observations of emission from electrically excited CNT devices have been limited to the high-bias regime and with low efficiency. Furthermore, the resulting broad linewidths are broad, making it difficult to investigate electronic levels and carrier dynamics. We find that p-n junctions allow for better carrier control at lower power inputs, resulting in emission with near-zero threshold, low self-heating and efficiency two to three orders of magnitude greater compared to previous device configurations. This yields higher signal-to-noise ratio and narrower linewidths (down to ˜35 meV) that allows us to identify localized excitonic transitions that have previously been observed only in photoluminescent studies. [1] T. Mueller, M. Kinoshita, M. Steiner, V. Perebeinos, A. Bol, D. Farmer, and Ph. Avouris, Nature Nanotech., web publication, November 15 2009.

Kinoshita, Megumi; Mueller, Thomas; Steiner, Mathias; Perebeinos, Vasili; Bol, Ageeth; Farmer, Damon; Avouris, Phaedon

2010-03-01

7

Sensitive IR narrow band optimized microspectrometer  

Microsoft Academic Search

Customization of a standard model confocally masked FT-IR microspectrometer to maximize the signal for a particular narrow band of the spectrum and minimize noise is described. In this case the motivation was to detect minor concentrations of deuterated species in a matrix of tissue. However, the instrumental modifications used for this particular task are applicable to narrow band sensitization in

David L Wetzel

2002-01-01

8

Narrow-Band Applications of Communications Satellites.  

ERIC Educational Resources Information Center

This paper attempts to describe the advantages of "narrow-band" applications of communications satellites for education. It begins by discussing the general controversy surrounding the use of satellites in education, by placing the concern within the larger context of the general debate over the uses of new technologies in education, and by…

Cowlan, Bert; Horowitz, Andrew

9

Photosensized Controlling Benzyl Methacrylate-Based Matrix Enhanced Eu3+ Narrow-Band Emission for Fluorescence Applications  

PubMed Central

This study synthesized a europium (Eu3+) complex Eu(DBM)3Cl-MIP (DBM = dibenzoyl methane; Cl-MIP = 2-(2-chlorophenyl)-1-methyl-1H-imidazo[4,5-f][1,10]phenanthroline) dispersed in a benzyl methacrylate (BMA) monomer and treated with ultraviolet (UV) light for polymerization. Spectral results showed that the europium complex containing an antenna, Cl-MIP, which had higher triplet energy into the Eu3+ energy level, was an energetically enhanced europium emission. Typical stacking behaviors of ?–? interactions between the ligands and the Eu3+-ion were analyzed using single crystal X-ray diffraction. Regarding the luminescence performance of this europium composite, the ligand/defect emission was suppressed by dispersion in a poly-BMA (PBMA) matrix. The underlying mechanism of the effective enhancement of the pure Eu3+ emission was attributed to the combined effects of structural modifications, defect emissions, and carrier charge transfer. Fluorescence spectra were compared to the composite of optimized Eu3+ emission where they were subsequently chelated to four metal ions via carboxylate groups on the BMA unit. The optical enhanced europium composite clearly demonstrated highly efficient optical responses and is, therefore a promising application as an optical detection material. PMID:22489178

Lee, Jiann-Fong; Chen, Hsuen-Li; Lee, Geneh-Siang; Tseng, Shao-Chin; Lin, Mei-Hsiang; Liau, Wen-Bin

2012-01-01

10

Photosensized controlling benzyl methacrylate-based matrix enhanced eu(3+) narrow-band emission for fluorescence applications.  

PubMed

This study synthesized a europium (Eu(3+)) complex Eu(DBM)(3)Cl-MIP (DBM = dibenzoyl methane; Cl-MIP = 2-(2-chlorophenyl)-1-methyl-1H-imidazo[4,5-f][1,10]phenanthroline) dispersed in a benzyl methacrylate (BMA) monomer and treated with ultraviolet (UV) light for polymerization. Spectral results showed that the europium complex containing an antenna, Cl-MIP, which had higher triplet energy into the Eu(3+) energy level, was an energetically enhanced europium emission. Typical stacking behaviors of ?-? interactions between the ligands and the Eu(3+)-ion were analyzed using single crystal X-ray diffraction. Regarding the luminescence performance of this europium composite, the ligand/defect emission was suppressed by dispersion in a poly-BMA (PBMA) matrix. The underlying mechanism of the effective enhancement of the pure Eu(3+) emission was attributed to the combined effects of structural modifications, defect emissions, and carrier charge transfer. Fluorescence spectra were compared to the composite of optimized Eu3+ emission where they were subsequently chelated to four metal ions via carboxylate groups on the BMA unit. The optical enhanced europium composite clearly demonstrated highly efficient optical responses and is, therefore a promising application as an optical detection material. PMID:22489178

Lee, Jiann-Fong; Chen, Hsuen-Li; Lee, Geneh-Siang; Tseng, Shao-Chin; Lin, Mei-Hsiang; Liau, Wen-Bin

2012-01-01

11

Tissue characterization by using narrow band imaging  

NASA Astrophysics Data System (ADS)

NBI (Narrow Band Imaging) was first introduced in the market in 2005 as a technique enabling to enhance image contrast of capillaries on a mucosal surface(1). It is classified as an Optical-Digital Method for Image-Enhanced Endoscopy(2). To date, the application has widely spread not only to gastrointestinal fields such as esophagus, stomach and colon but also the organs such as bronchus and bladder. The main target tissue of NBI enhancement is capillaries. However, findings of many clinical studies conducted by endoscopy physicians have revealed that NBI observation enables to enhance more other structures in addition to capillaries. There is a close relationship between those enhanced structures and histological microstructure of a tissue. This report introduces the tissue microstructures enhanced by NBI and discusses the possibility of optimized illumination wavelength in observing living tissues.

Gono, Kazuhiro

2010-02-01

12

THZ EMISSION SPECTROSCOPY OF NARROW BANDGAP SEMICONDUCTORS  

E-print Network

THZ EMISSION SPECTROSCOPY OF NARROW BANDGAP SEMICONDUCTORS By Ricardo Asc´azubi A Thesis Submitted-Domain Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Optically Excited THz Emission Processes Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.1 THz-TDS Setup

Wilke, Ingrid

13

Electronic structure and thermoelectric properties of narrow band gap chalcogenides  

Microsoft Academic Search

In recent years there have been a revival of interest in discovering and understanding the physical properties of novel thermoelectric (TE) systems with high figure of merit. These systems are primarily narrow band gap semiconductors. In this thesis, electronic structure calculations were carried out for several narrow band gap chalcogenide TE materials in order to understand their electronic and transport

Daniel Bilc

2005-01-01

14

Jovian narrow-band as generator of the Jovian millisecond radio bursts  

NASA Astrophysics Data System (ADS)

We report on the narrow-band emissions observed in the dynamic spectra of the Jovian decametric radio emissions. Such narrow-band emissions are infrequent phenomena and are related to the Jovian millisecond radio bursts (S-bursts). From the Riihimaa catalogue (Riihimaa 1991) we select narrow-band events observed in Oulu (Finland) with an acousto-optic spectrograph (AOS) with a high time resolution of about 7 ms. The AOS receiver gives the possibility to study the relationship between the S-bursts and the Jovian narrow-band emissions. For this we use the Riihimaa classification which shows sketches of millisecond radio bursts as they appear on the dynamic spectra and allows to distinguish one S-burst from another. The analysis of the temporal evolution of the Jovian narrow-band leads to a new interpretation of the Riihimaa structures. We show that each individual structure could be decomposed in one, two or three components and related to the narrow-band. It appears that the temporal evolution of the narrow-band involves the presence of fine structures, i.e. S-bursts, with a short time duration of about few tens of milliseconds. The individual S-burst duration and the short time scale of the gap in the narrow-band account for a mechanism totally intrinsic to the radio source. Taking into consideration our new results, we show that two models, the feedback model (Calvert 1982) and filamentary model (Louarn 1997) could explain part but not the global observed features of the narrow-band. According to the previous models the drift rate of the individual S-bursts seems to associate the combined effect of the source width with the refractive index or the geometry of the source relatively to the observer.

Boudjada, M. Y.; Galopeau, P. H. M.; Rucker, H. O.; Lecacheux, A.

2000-11-01

15

High power narrow-band fiber-based ASE source.  

PubMed

In this paper we describe a high power narrow-band amplified spontaneous emission (ASE) light source at 1030 nm center wavelength generated in an Yb-doped fiber-based experimental setup. By cutting a small region out of a broadband ASE spectrum using two fiber Bragg gratings a strongly constrained bandwidth of 12±2 pm (3.5±0.6 GHz) is formed. A two-stage high power fiber amplifier system is used to boost the output power up to 697 W with a measured beam quality of M2?1.34. In an additional experiment we demonstrate a stimulated Brillouin scattering (SBS) suppression of at least 17 dB (theoretically predicted ~20 dB), which is only limited by the dynamic range of the measurement and not by the onset of SBS when using the described light source. The presented narrow-band ASE source could be of great interest for brightness scaling applications by beam combination, where SBS is known as a limiting factor. PMID:21369273

Schmidt, O; Rekas, M; Wirth, C; Rothhardt, J; Rhein, S; Kliner, A; Strecker, M; Schreiber, T; Limpert, J; Eberhardt, R; Tünnermann, A

2011-02-28

16

Fast, narrow-band computer model for radiation calculations  

SciTech Connect

A fast, narrow-band computer model, FASTNB, which predicts the radiation intensity in a general nonisothermal and nonhomogeneous combustion environment, has been developed. The spectral absorption coefficients of the combustion products, including carbon dioxide, water vapor, and soot, are calculated based on the narrow-band model. FASTNB provides an accurate calculation at reasonably high speed. Compared with Grosshandler`s narrow-band model, RADCAL, which has been verified quite extensively against experimental measurements, FASTNB is more than 20 times faster and gives almost exactly the same results.

Yan, Z.; Holmstedt, G. [Lund Univ. (Sweden). Dept. of Fire Safety Engineering

1997-01-01

17

Narrow frequency-band laser with optical feedback  

E-print Network

In this paper we discuss the construction of a narrow frequency-band laser with optical feedback. We use a distributed Bragg reflector (DBR) laser diode centered at the cesium D? transition wavelength, [gamma] = 852 nm. ...

Childress, Michael J

2005-01-01

18

The Narrow-Band Model and Semi-Conductor Theory  

ERIC Educational Resources Information Center

Applies the narrow-band model to the instruction of intrinsic and extrinsic semiconductors along with the phenomenon of compensation. Advocates the model for undergraduate instruction due to its intuitive appeal and mathematical simplicity. (CP)

Tanner, B. K.

1976-01-01

19

Narrow band imaging (NBI) during medical thoracoscopy: first impressions  

PubMed Central

Background This is the first ever evaluation of narrow band imaging (NBI), an innovative endoscopic imaging procedure, for the visualisation of pleural processes. Methods The pleural cavity was examined in 26 patients with pleural effusions using both white light and narrow band imaging during thoracoscopy under local anaesthesia. Results In the great majority of the patients narrow band imaging depicted the blood vessels more clearly than white light, but failed to reveal any differences in number, shape or size. Only in a single case with pleura thickened by chronic inflammation and metastatic spread of lung cancer did narrow band imaging show vessels that were not detectable under white light. Conclusion It is not yet possible to assess to what extent the evidence provided by NBI is superior to that achieved with white light. Further studies are required, particularly in the early stages of pleural processes. PMID:19709438

Schonfeld, Nicolas; Schwarz, Carsten; Kollmeier, Jens; Blum, Torsten; Bauer, Torsten T; Ott, Sebastian

2009-01-01

20

Narrow-band imaging bronchoscopy in tracheobronchial amyloidosis.  

PubMed

Primary tracheobronchial amyloidosis (TBA) is a rare disease characterized by extracellular focal or diffuse submucosal deposits of amyloid proteins. Various types of endobronchial lesions have been described in TBA when bronchoscopy is performed using white light. Narrow-band imaging bronchoscopy has been mainly employed for detecting preneoplastic and neoplastic endobronchial lesions as it provides more detailed images of the microvasculature reflective of an altered angiogenesis process. Here, we describe bronchoscopic findings with white light and narrow-band imaging in 2 patients presenting with central airway obstructive disease later confirmed as having primary TBA. PMID:24992137

Serrano-Fernández, Martha L; Alvarez-Maldonado, Pablo; Aristi-Urista, Gerardo; Valero-Gómez, Alfredo; Cicero-Sabido, Raúl; Redondo, Carlos Núñez-Pérez

2014-07-01

21

THz emission spectroscopy of narrow bandgap semiconductors  

NASA Astrophysics Data System (ADS)

This dissertation presents a model for emission of electromagnetic transients in the terahertz (THz) region from optically excited narrow bandgap semiconductors. This model explains the THz emission from the surface field acceleration mechanism and from the photo-Dember effect independently. It relates intrinsic parameters of the semiconductor, namely the majority and minority carrier concentrations and the mobilities, to the radiated THz field. The conditions that enhance the THz emission process in the case of surface field acceleration and in the case of the photo-Dember effect have been clearly identified. In this work three types of narrow bandgap semiconductors were investigated as sources of THz radiation. First the THz emission from a set of Te doped GaSb samples was studied. GaSb:Te is an interesting material because samples can be grown with a broad range of carrier concentrations. A Ga xIn1-xSb ingot was also studied. In this material system the electron mobility and the bandgap range from the GaSb values (Eg = 0.73eV) to the InSb values (Eg = 0.17eV). This is important in order to understand the extent to which the reduced bandgap of InSb is favorable for the THz emission process. This ingot was also used as a demonstration of how the THz time-domain spectroscopy technique can reveal the native defect density distributions in this ingot. Additionally the THz emission from InN was studied. The recently revised bandgap value of InN make it a good material for optically excited THz emission. In order to investigate the ultrafast scattering mechanisms in InN, an ultrafast photo-reflection setup was used. Subpicosecond non-radiative recombination was observed in silicon doped InN films.

Ascazubi, Ricardo

22

Active Narrow-Band Vibration Isolation of Large Engineering Structures  

NASA Technical Reports Server (NTRS)

We present a narrow-band tracking control method using a variant of the Least Mean Squares (LMS) algorithm to isolate slowly changing periodic disturbances from engineering structures. The advantage of the algorithm is that it has a simple architecture and is relatively easy to implement while it can isolate disturbances on the order of 40-50 dB over decades of frequency band. We also present the results of an experiment conducted on a flexible truss structure. The average disturbance rejection achieved is over 40 dB over the frequency band of 5 Hz to 50 Hz.

Rahman, Zahidul; Spanos, John

1994-01-01

23

Narrow-band, slowly varying decimetric radiation from the dwarf M flare star YZ Canis Minoris  

NASA Astrophysics Data System (ADS)

Observations of slowly varying radiation from the dwarf M star YZ Canis Minoris with a maximum flux density of 20 mJy and narrow-band frequency structure at frequencies near 1465 MHz are presented. Possible explanations for this radiation are examined. Thermal gyroresonant radiation would require impossibly large coronal loops and magnetic field strengths. The narrow-band structure cannot be explained by continuum emission processes such as thermal bremsstrahlung, thermal gyroresonant radiation, or nonthermal gyrosynchrotron radiation. Coherent burst mechanisms seem to be required.

Lang, K. R.; Willson, R. F.

1986-03-01

24

Narrow-band, slowly varying decimetric radiation from the dwarf M flare star YZ Canis Minoris  

NASA Technical Reports Server (NTRS)

Observations of slowly varying radiation from the dwarf M star YZ Canis Minoris with a maximum flux density of 20 mJy and narrow-band frequency structure at frequencies near 1465 MHz are presented. Possible explanations for this radiation are examined. Thermal gyroresonant radiation would require impossibly large coronal loops and magnetic field strengths. The narrow-band structure cannot be explained by continuum emission processes such as thermal bremsstrahlung, thermal gyroresonant radiation, or nonthermal gyrosynchrotron radiation. Coherent burst mechanisms seem to be required.

Lang, K. R.; Willson, R. F.

1986-01-01

25

Narrow-band single photon emission at room temperature based on a single Nitrogen-vacancy center coupled to an all-fiber-cavity  

E-print Network

We report the realization of a device based on a single Nitrogen-vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and output are directly fiber-coupled and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

Roland Albrecht; Alexander Bommer; Christoph Pauly; Frank Mücklich; Andreas W. Schell; Philip Engel; Tim Schröder; Oliver Benson; Jakob Reichel; Christoph Becher

2014-07-22

26

Narrow-band single photon emission at room temperature based on a single Nitrogen-vacancy center coupled to an all-fiber-cavity  

E-print Network

We report the realization of a device based on a single Nitrogen-vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and output are directly fiber-coupled and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

Albrecht, Roland; Pauly, Christoph; Mücklich, Frank; Schell, Andreas W; Engel, Philip; Schröder, Tim; Benson, Oliver; Reichel, Jakob; Becher, Christoph

2014-01-01

27

Narrow-band single photon emission at room temperature based on a single nitrogen-vacancy center coupled to an all-fiber-cavity  

NASA Astrophysics Data System (ADS)

We report the realization of a device based on a single Nitrogen-Vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and out-put are directly fiber-coupled, and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity, we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work, we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

Albrecht, Roland; Bommer, Alexander; Pauly, Christoph; Mücklich, Frank; Schell, Andreas W.; Engel, Philip; Schröder, Tim; Benson, Oliver; Reichel, Jakob; Becher, Christoph

2014-08-01

28

A Deep Narrow Band Imaging Search for CIV?1548Å and HeII?1640Å Emission from Lyman Alpha Blobs  

NASA Astrophysics Data System (ADS)

To study the nature of Ly? blobs (aka LABs), we conduct a deep C IV and He II narrowband imaging survey of 13 Ly? blobs located in SSA22 proto-cluster at z ~ 3.1. We reach the unprecedented sensitivity, 5? surface brightness limit of 2.1 - 3.4 × 10-18 erg s-1 cm-2 arcsec-2 per 1 arcsec2 aperture for two emission lines. We do not detect any extended C IV and He II emission, placing strong upper limits on the He II/Ly? and C IV/Ly? line ratios. We compare our limits with data in the literature related to the nebulae associated with high-redshift radio galaxies (HzRGs) and quasars, and we recover the data by modeling the LABs as nebulosities powered by a central QSO. For further information see Arrigoni Battaia et al. (2014).

Arrigoni Battaia, Fabrizio; Yang, Y.; Hennawi, J. F.; Matsuda, Y.; Yamada, T.; Hayashino, T.

2014-07-01

29

[Narrow band imaging: new paradigm in gastrointestinal video-endoscopy].  

PubMed

Novel technologies in gastrointestinal endoscopy, such as magnification and high resolution endoscopy, have a clear aim in improving diagnostic accuracy of mucosal abnormalities. Narrow band imaging encompasses both of these by endoscopic display of gastric mucosa with bands of blue and green light. This enhances mucosal architecture and adjacent vasculature. Combined with optical magnification NBI enables recognition of subtle mucosal abnormalities, such as dysplasia in Barrett's oesophagus, early morphological changes of vasculature in inflammatory and malignant diseases of esophagus, stomach and colon. Before NBI becomes a routine diagnostic procedure, further investigations are needed especially in regard to standardisation and validation of findings, as well as their correlation with histopathological findings. PMID:20030289

Ivekovi?, Hrvoje; Brki?, Tomislav; Pulani?, Roland

2009-01-01

30

Tunable narrow-band infrared emitters from hexagonal lattices  

Microsoft Academic Search

In this work, we present both the theoretical basis as well as supporting experimental measurements for development of a novel mid-infrared thermally stimulated narrow band emitter with a spectral bandwidth of less than 10%. To achieve this, we utilize a metallized-surface 2D photonic crystal of air voids in a silicon background with hexagonal structure symmetry. Our results are based on

I. El-Kady; Ritwik Biswas; Y. Ye; M. F. Su; I. Puscasu; Martin Pralle; E. A. Johnson; J. Daly; A. Greenwald

2003-01-01

31

Twoband modeling of narrow band gap and interband tunneling devices  

Microsoft Academic Search

A two-band transfer matrix method has been developed to study tunneling currents in narrow gap and interband tunnel structures. This relatively simple model gives good agreement with recently reported experimental results for InAs\\/AlSb\\/InAs\\/AlSb\\/InAs double-barrier heterostructures and InAs\\/AlSb\\/GaSb\\/AlSb\\/InAs resonant interband tunneling devices, and should be useful in the design of new interband tunneling devices.

E. T. Yu; M. K. Jackson; Y. Rajakarunanayake; T. C. McGill

1990-01-01

32

Hold on Picasso, narrow band imaging is here.  

PubMed

The goal of colonoscopy is to identify and remove premalignant and malignant polyps. During colonoscopy it is not feasible to differentiate with certainty if a polyp is benign or premalignant, resulting in removal of all polyps via polypectomy. In attempts to overcome this clinical dilemma, techniques such as chromendoscopy have been developed to aid in improving the accuracy of identifying precancerous polyps. Chromendoscopy helps detect suspicious polyps using a dye spraying technique, but it is time consuming and causes collateral distortion of the adjacent mucosal field. Recently, narrow band imaging (NBI) has been able to highlight abnormal mucosal topography and microvasculature by illuminating with narrow range blue light. This is achieved with the click of a button on the endoscope, and the accuracy of differentiating between abnormal and normal mucosa is equivalent to chromendoscopy. NBI and other similar technologies will likely provide an electronic, easier alternative to chromoendoscopy to aid the endoscopist in differentiation among benign, premalignant, and malignant mucosal patterns. PMID:17227518

Gross, Seth A; Wallace, Michael B

2006-12-01

33

Tunable, narrow-band, all-metallic microwave absorber  

NASA Astrophysics Data System (ADS)

We exploit the metamaterial properties of a thick metallic grating with extreme sub-wavelength slits on a metallic slab to achieve complete absorption of transverse magnetic polarized microwaves. We measure narrow bands of total absorption (up to 99.9999%) from normal to grazing incidence that can be tuned by varying an air gap between the grating and the slab. Unlike typical absorbers, the structure is mostly metallic with a 97% filling factor, and no absorptive material beside the metal itself is employed. We access the absorption properties of metals in the microwave where they are commonly believed to be perfect reflectors.

Mattiucci, N.; Trimm, R.; D'Aguanno, G.; Aközbek, N.; Bloemer, M. J.

2012-10-01

34

Narrow-band-gap conjugated chromophores with extended molecular lengths.  

PubMed

The influence of extending the molecular length of donor-acceptor chromophores on properties relevant to organic optoelectronic devices has been studied by using two new narrow-band-gap systems. Most significantly, we find that the higher molecular weight systems exhibit higher thermal stabilities (beyond 200 °C) when introduced into field effect transistor devices. It is also possible to fabricate bulk heterojunction solar cells using PC(61)BM with power conversion efficiencies >6%. These high values are not heavily influenced by the blend composition and are achieved without the influence of solvent additives or postdeposition thermal annealing. PMID:23214922

Liu, Xiaofeng; Sun, Yanming; Perez, Louis A; Wen, Wen; Toney, Michael F; Heeger, Alan J; Bazan, Guillermo C

2012-12-26

35

Narrow-band optical transmission of metallic nanoslit arrays  

SciTech Connect

Metallic nanoslit arrays usually demonstrate wide transmission bands for transverse-magnetic-polarized incidence light. Here, we show that by introducing multi-dielectric layers underneath the metallic structure layer on the substrate, a narrow peak is formed, whose bandwidth can be down to a few nanometers. Three types of resonance modes in the region under the metal layer are identified responsible for the formation of the peak, i.e., a two-dimensional cavity resonance mode, which supports optical transmission, and two in-plane hybrid surface plasmon resonance modes locating on both sides of the peak that suppresses the transmission. Such structures can be applied in advanced photonic devices.

Sun Zhijun; Yang Ying; Zuo Xiaoliu [Department of Physics, Xiamen University, Xiamen 361005 (China)

2012-10-22

36

Intensities, broadening and narrowing parameters in the ?3 band of methane  

NASA Astrophysics Data System (ADS)

The P-branch of methane's ?3 band is probed to carry out an extensive study of the 2905-2908 cm-1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001 cm-1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.

Es-sebbar, Et-touhami; Farooq, Aamir

2014-12-01

37

Characterization of Narrow Band Filters for Infrared The Brfl and H 2 filters  

E-print Network

Characterization of Narrow Band Filters for Infrared Astronomy The Brfl and H 2 filters L. Vanzi: Infrared, Narrow Band Filters, Imaging Abbreviations: IR -- Infrared; NIR -- Near infrared JEL codes: D24 experiments with narrow band filters mounted on the Infrared Camera ARNICA (Lisi et al. 1996; Hunt et al. 1996

Testi, Leonardo

38

Photometric Type Ia supernova surveys in narrow-band filters  

NASA Astrophysics Data System (ADS)

We study the characteristics of a narrow-band Type Ia supernova (SN) survey through simulations based on the upcoming Javalambre Physics of the accelerating Universe Astrophysical Survey. This unique survey has the capabilities of obtaining distances, redshifts and the SN type from a single experiment thereby circumventing the challenges faced by the resource-intensive spectroscopic follow-up observations. We analyse the flux measurements signal-to-noise ratio and bias, the SN typing performance, the ability to recover light-curve parameters given by the SALT2 model, the photometric redshift precision from Type Ia SN light curves and the effects of systematic errors on the data. We show that such a survey is not only feasible but may yield large Type Ia SN samples (up to 250 SNe at z < 0.5 per month of search) with low core-collapse contamination (˜1.5 per cent), good precision on the SALT2 parameters (average ? _{m_B}=0.063, ? _{x_1}=0.47 and ?c = 0.040) and on the distance modulus (average ?? = 0.16, assuming an intrinsic scatter ?int = 0.14), with identified systematic uncertainties ?sys ? 0.10?stat. Moreover, the filters are narrow enough to detect most spectral features and obtain excellent photometric redshift precision of ?z = 0.005, apart from ˜2 per cent of outliers. We also present a few strategies for optimizing the survey's outcome. Together with the detailed host galaxy information, narrow-band surveys can be very valuable for the study of SN rates, spectral feature relations, intrinsic colour variations and correlations between SN and host galaxy properties, all of which are important information for SN cosmological applications.

Xavier, Henrique S.; Abramo, L. Raul; Sako, Masao; Benítez, Narciso; Calvão, Maurício O.; Ederoclite, Alessandro; Marín-Franch, Antonio; Molino, Alberto; Reis, Ribamar R. R.; Siffert, Beatriz B.; Sodré, Laerte.

2014-11-01

39

Engineering integrated pure narrow-band photon sources  

E-print Network

Engineering and controlling well defined states of light for quantum information applications is of increasing importance as the complexity of quantum systems grows. For example, in quantum networks high multi-photon interference visibility requires properly devised single mode sources. In this paper we propose a spontaneous parametric down conversion source based on an integrated cavity-waveguide, where single narrow-band, possibly distinct, spectral modes for the idler and the signal fields can be generated. This mode selection takes advantage of the clustering effect, due to the intrinsic dispersion of the nonlinear material. In combination with a CW laser and fast detection, our approach provides a means to engineer a source that can efficiently generate pure photons, without filtering, that is compatible with long distance quantum communication. Furthermore, it is extremely flexible and could easily be adapted to a wide variety of wavelengths and applications.

Enrico Pomarico; Bruno Sanguinetti; Clara I. Osorio; Harald Herrmann; Rob Thew

2011-08-29

40

NARROW-K-BAND OBSERVATIONS OF THE GJ 1214 SYSTEM  

SciTech Connect

GJ 1214 is a nearby M dwarf star that hosts a transiting super-Earth-size planet, making this system an excellent target for atmospheric studies. Most studies find that the transmission spectrum of GJ 1214b is flat, which favors either a high mean molecular weight or cloudy/hazy hydrogen (H) rich atmosphere model. Photometry at short wavelengths (<0.7 ?m) and in the K band can discriminate the most between these different atmosphere models for GJ 1214b, but current observations do not have sufficiently high precision. We present photometry of seven transits of GJ 1214b through a narrow K-band (2.141 ?m) filter with the Wide Field Camera on the 3.8 m United Kingdom Infrared Telescope. Our photometric precision is typically 1.7 × 10{sup –3} (for a single transit), comparable with other ground-based observations of GJ 1214b. We measure a planet-star radius ratio of 0.1158 ± 0.0013, which, along with other studies, also supports a flat transmission spectrum for GJ 1214b. Since this does not exclude a scenario where GJ 1214b has an H-rich envelope with heavy elements that are sequestered below a cloud/haze layer, we compare K-band observations with models of H{sub 2} collision-induced absorption in an atmosphere for a range of temperatures. While we find no evidence for deviation from a flat spectrum (slope s = 0.0016 ± 0.0038), an H{sub 2}-dominated upper atmosphere (<60 mbar) cannot be excluded. More precise observations at <0.7 ?m and in the K band, as well as a uniform analysis of all published data, would be useful for establishing more robust limits on atmosphere models for GJ 1214b.

Colón, Knicole D.; Gaidos, Eric, E-mail: colonk@hawaii.edu [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

2013-10-10

41

PAU, a fully depleted mosaic imager with narrow band filters  

NASA Astrophysics Data System (ADS)

The PAU Survey studies the existence and properties of dark energy from the observations of redshift space distortions and weak lensing magnification from galaxy cross-correlations as main cosmological probes. The PAU Team is building an instrument, PAUCam, equipped with fully depleted CCD detectors, designed to be mounted at the prime focus of the 4.2 m diameter William Herschel Telescope (WHT) in La Palma. Simulations indicate that PAUCam at the WHT will be able to image about 2 square degrees per night in 40 narrow-band filters plus six wide-band filters to an AB magnitude depth of i ~ 22.5, providing low-resolution (R ~ 50) photometric spectra for around 30,000 galaxies, 5,000 stars and 1,000 quasars per square degree. Accurate photometric calibration of the PAU data is vital to achieve the survey science goals. This calibration is challenging due to the large and unusual filter set. We outline the data management pipelines being developed for the survey, both for nightly data reduction and co-addition of multiple epochs, with emphasis on the photometric calibration strategies. We also describe the main tests and results in the characterization of our Hamamatsu fully depleted detectors.

Bauer, A.; Casas, R.; Castander, F. J.; Serrano, S.

2014-03-01

42

H(alpha) Narrow-band Imaging of z ~ 0.8 Galaxy Clusters  

NASA Astrophysics Data System (ADS)

We request 2 nights of 4.0-m time to complete narrow-band imaging centered on the observed wavelength of H? for two z=0.8 galaxy clusters using NEWFIRM and a custom narrow-band filter. A third cluster will be targeted during 2010A. The narrow-band filter is designed to sample a region of the IR window that is relatively free from OH emission; we are thus able to detect low star-formation rates (SFRs) (2 smy) in a reasonable amount of observing time. NEWFIRM's large field- of-view allows simultaneous imaging of the cluster center and surrounding infall region, an area where galaxy transformation is likely taking place. These data, in conjunction with a companion survey of z=0.8 field galaxies led by CoI Lee, will provide a census of SFRs over the full range in galactic environments at an epoch when the Universe was half its current age. In contrast, most field surveys of intermediate-redshift galaxies deliberately avoid clusters and thus fail to survey the densest galactic environments. The z=0.8 epoch probes a cosmologically interesting time in cluster evolution, when clusters were only half their present mass and accretion rates were higher. This study is thus uniquely suited to determine whether clusters speed a galaxy's evolution from star-forming to quiescent.

Finn, Rose; Rines, Ken; Lee, Janice; Dale, Daniel; Zaritsky, Dennis

2009-08-01

43

H2 and Br-gamma narrow-band imaging of bipolar planetary nebulae  

E-print Network

We present near-IR narrow-band continuum-subtracted images in the H$_2$ $2.122\\mu$m, and Br$\\gamma$ $2.166\\mu$m emission lines for a sample of 15 bipolar planetary nebulae. H$_2$ emission was definitely detected for most of the objects in this sample (13 out of 15). The very high H$_2$ detection rate supports the idea that bipolar planetary nebulae have important reservoirs of molecular material and offer suitable physical conditions for the excitation of H$_2$. The strength of the H$_2$ emission and the H$_2$/Br$\\gamma$ flux ratio are found to correlate with the morphology of the bipolar nebulae observed. Bipolar PNe with broad and bright rings exhibit stronger H$_2$ emission than bipolar PNe with narrow twists. High-quality (sub-arcsec) [N~{\\sc ii}] and H$\\alpha$ optical images have been used to compare the distribution of the ionized and molecular material. The H$_2$ emission lies just outside the optical [N~{\\sc ii}] emission zone.

M. A. Guerrero; E. Villaver; A. Manchado; P. Garcia-Lario; F. Prada

1999-10-20

44

Narrow-band ELF events observed from South Pole Station  

NASA Astrophysics Data System (ADS)

Extremely Low Frequency (ELF) waves are typically in the range of 3 Hz - 3 kHz and can play a role in acceleration and pitch-angle scattering of energetic particles in the radiation belts. Observations of a not uncommon, but not well studied ELF phenomenon are presented with ground-based data from South Pole Station. The narrow-band waves last approximately one or two minutes maintaining bandwidth over the course of the event, begin around 100 Hz, decrease to about 70 Hz, and typically show a higher frequency harmonic. The waves have only been documented at four locations - Heacock, 1974 (Alaska); Sentman and Ehring, 1994 (California); Wang et al, 2005 and Wang et al, 2011 (Taiwan); and Kim et al, 2006 (South Pole). The waves observed at the South Pole are not detected when the Sun drops below a 10 degree elevation angle, which is not true for the other locations. We extend the study of Kim et al, 2006, and explore possible generation mechanisms including sunlit ionosphere and ion cyclotron wave modes, as well as correspondence with energetic particle precipitation.

Heavisides, J.; Weaver, C.; Lessard, M.; Weatherwax, A. T.

2012-12-01

45

Narrow-band ultraviolet B is a useful and well-tolerated treatment for vitiligo  

Microsoft Academic Search

Background: The treatment of vitiligo remains a challenge. Objective: The purpose of this article is to review our results and experience with narrow-band ultraviolet (UV) B phototherapy for vitiligo. Methods: This is a retrospective analysis of our experience and results with patients with vitiligo who were treated with narrow-band UVB between November 1998 and November 1999. Narrow-band UVB phototherapy was

Lubomira Scherschun; Jane J. Kim; Henry W. Lim

2001-01-01

46

Narrow-band erbium-doped fibre linear-ring laser  

NASA Astrophysics Data System (ADS)

We have demonstrated a narrow-band linear - ring fibre laser with an output power of 15 mW at a wavelength of 1.55 ?m and an emission bandwidth less than 5 kHz. The laser frequency is stabilised by an unpumped active fibre section and fibre Bragg grating. The fibre laser operates in a travelling wave mode, which allows the spatial hole burning effect to be avoided. At a certain pump power level, the laser switches from continuous mode to repetitivepulse operation, corresponding to relaxation oscillations.

Kolegov, A. A.; Sofienko, G. S.; Minashina, L. A.; Bochkov, A. V.

2014-01-01

47

2 um Narrow-Band Imaging of the Sagittarius D H II region  

E-print Network

We present 2 um narrow-band images of the core H II region in the Galactic star forming region Sagittarius D. The emission-line images are centered on 2.17 um (Brgamma) and 2.06 um (He I). The H II region appears at the edge of a well defined dark cloud, and the morphology suggests a blister geometry as pointed out in earlier radio continuum work. There is a deficit of stars in general in front of the associated dark cloud indicating the H II region is located in-between the Galactic center and the sun. The lesser spatial extent of the He I line emission relative to Brgamma places the effective temperature of the ionizing radiation field below 40,000 K. The He I 2.06 um to Brgamma ratio and Brgamma / far infrared dust emission put Teff at about 36,500 K to 40,000 K as derived from ionization models.

R. D. Blum; A. Damineli

1998-09-27

48

Narrow Band Infrared Filters with Broad Field of View  

Microsoft Academic Search

Optical interference notch filters shift to shorter wavelengths with increasing angles of incidence. This phenomenon restricts the filter's field of view and limits the practical application of narrow reflection notch filters. The amount of shift is inversely proportional to the effective average index of the composite film. A method of designing narrow notch optical filters with very broad field of

Thomas D. Rahmlow; Jeanne E. Lazo-Wasem; Edward J. Gratrix

49

Narrow-band, slowly varying decimetric radiation from the dwarf M flare star YZ Canis Minoris. II  

NASA Astrophysics Data System (ADS)

The VLA has been used in the spectral-line mode to obtain the frequency spectra of the radiation from the dwarf M star YZ Canis Minoris at frequencies near 1465 MHz. The authors present observations of frequency structure with narrow bandwidths ?? ? 30 MHz that persist over 10 minutes of time without evidence for a drift. The fractional bandwidth ??/? ? 0.02. It is shown that radiation over other 10 minute intervals appears to be broad band with ?? ? 50 MHz, but these spectra could represent the time average of many rapid, narrow-band events. The authors interpret the narrow-band, 30 MHz structure in terms of electron-cyclotron maser emission. They also draw attention to certain solar bursts that may require a similar coherent radiation mechanism.

Lang, Kenneth R.; Willson, Robert F.

1988-03-01

50

Spatial analysis of solar type III events associated with narrow band spikes at metric wavelengths  

NASA Astrophysics Data System (ADS)

The spatial association of narrow band metric radio spikes with type III bursts is analyzed. The analysis addresses the question of a possible causal relation between the spike emission and the acceleration of the energetic electrons causing the type III burst. The spikes are identified by the Phoenix-2 spectrometer (ETH Zurich) from survey solar observations in the frequency range from 220 MHz to 530 MHz. Simultaneous spatial information was provided by the Nançay Radioheliograph (NRH) at several frequencies. Five events were selected showing spikes at one or two and type III bursts at two or more Nançay frequencies. The 3-dimensional geometry of the single events has been reconstructed by applying different coronal density models. As a working hypothesis it is assumed that emission at the plasma frequency or its harmonic is the responsible radiation process for the spikes as well as for the type III bursts. It has been found that the spike source location is consistent with the backward extrapolation of the trajectory of the type III bursts, tracing a magnetic field line. In one of the analyzed events, type III bursts with two different trajectories originating from the same spike source could be identified. These findings support the hypothesis that narrow band metric spikes are closely related to the acceleration region.

Paesold, G.; Benz, A. O.; Klein, K.-L.; Vilmer, N.

2001-05-01

51

Differential-phase-shift quantum key distribution using heralded narrow-band  

E-print Network

Differential-phase-shift quantum key distribution using heralded narrow-band single photons Chang differential phase shift (DPS) quantum key distribution (QKD) using narrow-band heralded single photons. Yamamoto, "Unconditional security of single-photon differential phase shift quantum key distribution," Phys

Du, Shengwang

52

Narrow-band photography of Jupiter and Saturn.  

NASA Technical Reports Server (NTRS)

An IR-sensitive vidicon was used in the 1 to 2 mu region, with narrow-bandwidth filters, for Jupiter photographs taken in April, 1971, and Saturn photographs taken in December, 1970. The changes in limb darkening and surface details observed at different wavelengths are discussed. The 37 Jupiter photographs and the 38 Saturn photographs are included.

Fountain, J. W.

1973-01-01

53

Engineering frequency-time quantum correlation of narrow-band biphotons from cold atoms.  

PubMed

The nonclassical photon pair, generated via a parametric process, is naturally endowed with a specific form of frequency-time quantum correlations. Here, we report complete control of frequency-time quantum correlations of narrow-band biphotons generated via spontaneous four-wave mixing in a cold atomic ensemble. We have experimentally confirmed the generation of frequency-anticorrelated, frequency-correlated, and frequency-uncorrelated narrow-band biphoton states, as well as verifying the strong nonclassicality of the correlations. Our work opens up new possibilities for engineering narrow-band entangled photons for various quantum optical and quantum information applications. PMID:25148327

Cho, Young-Wook; Park, Kwang-Kyoon; Lee, Jong-Chan; Kim, Yoon-Ho

2014-08-01

54

Analysis of optimal narrow band RVI for estimating foliar photosynthetic pigments based on PROSPECT model  

NASA Astrophysics Data System (ADS)

Remote sensing is an effective tool to estimate foliar pigments contents with the analysis of vegetation index. The crucial issue is how to choose the optimal bands-combination to conduct the vegetation index. In this study, RVI, a vegetation index computed by the reflectance of Red and NIR bands, has been used to estimate the contents of chlorophyll and carotenoid. The reflectance of the two bands forming the narrow band RVI was simulated by the PROSPECT model. The possible combinations of narrow band RVI were examined from 400 nm to 800 nm. The results showed that: At the leaf level, estimation of chlorophyll content can be identified in narrow band RVI. Ranges for these bands included: (1) 549-589nm, 616-636nm or 729-735nm combined with 434-454nm; (2) 663-688nm, 710-717nm, 719-728nm or 730- 739nm combined with 549-561nm; (3) 663-688nm combined with 569-615nm. However, no valid narrow-band RVI for the estimation of carotenoid content was successfully identified. Our results also showed that two rules should be followed when choosing optimal bands-combination: (1) the selected bands must have minimal interference from other biochemical constituents; (2) there should be distinct differences between the sensitivities of the bands selected for particular pigments.

Wang, Hong; Shi, Runhe; Liu, Pudong; Ma, Mingliang; Gao, Wei

2014-10-01

55

Narrow-band surveys for very high redshift Lyman-alpha emitters  

E-print Network

Context: Many current and future surveys aim to detect the highest redshift (z >~ 7) sources through their Lyman-alpha (Ly-alpha) emission, using the narrow-band imaging method. However, to date the surveys have only yielded non-detections and upper limits as no survey has reached the necessary combination of depth and area to detect these very young star forming galaxies. Aims: We aim to calculate model luminosity functions and mock surveys of Ly-alpha emitters at z >~ 7 based on a variety of approaches. Methods: We calculate model luminosity functions at different redshifts based on three different approaches: a semi-analytical model based on CDM, a simple phenomenological model, and an extrapolation of observed Schechter functions at lower redshifts. The results of the first two models are compared with observations made at redshifts z ~ 5.7 and z ~ 6.5, and they are then extrapolated to higher redshift. Results: We present model luminosity functions for redshifts between z = 7 - 12.5 and give specific number predictions for future planned or possible narrow-band surveys for Ly-alpha emitters. We also investigate what constraints future observations will be able to place on the Ly-alpha luminosity function at very high redshift. Conclusion: It should be possible to observe z = 7 - 10 Ly-alpha emitters with present or near-future instruments if enough observing time is allocated. In particular, large area surveys such as ELVIS (Emission Line galaxies with VISTA Survey) will be useful in collecting a large sample. However, to get a large enough sample to constrain well the z >= 10 Ly-alpha luminosity function, instruments further in the future, such as an ELT, will be necessary.

Kim K. Nilsson; Alvaro Orsi; Cedric G. Lacey; Carlton M. Baugh; Eduard Thommes

2007-09-03

56

NICMOS Narrow-band Images of OMC-1  

NASA Technical Reports Server (NTRS)

We present images of a 90in. x 90in. field centered on BN in OMC-1, taken with the Near-Infrared Camera and MultiObject Spectrograph (NICMOS) aboard the Hubble Space Telescope. The observed lines are H2 1-0 S(l), Pa, [FeII] 1.64 pm, and the adjacent continua. The region is rich in interesting structures. The most remarkable are the streamers or "fingers" of H2 emission which extend from 15in. to 50in. from IRc2, seen here in unprecedented detail. Unlike the northern H2 fingers, the inner fingers do not exhibit significant [FeII] emission at theirdips, which we suggest is due to lower excitation. These observations also show that the general morphology of the Pa and [FeII] emission (both imaged for the first time in this region) bears a striking resemblance to that of the Ha and [SII] emission previously observed with WFPC2. This implies that these IR and optical lines are produced by radiative excitation on the surface of the molecular cloud. The Pa morphology of HH 202 is also very similar to its H a and [OIII] emission, again suggesting that the Pa in this object is photo-excited by the Trapezium, as has been suggested for the optical emission. We find evidence of shock-excited [FeII] in HH 208, where it again closely follows the morphology of [SII]. There is also H2 coincident with the [SII] and [FeII] emission, which may be associated with HH 208. Finally, we note some interesting continuum features: diffuse "tails" trailing from IRc3 and IRc4, more extensive observations of the "crescent" found by Stolovy, et al. (1998), and new observations of a similar oval object nearby. We also find a "V"-shaped region which may be the boundary of a cavity being cleared by IRc2.

Schultz, Angela S. B.; Colgan, Sean W. J.; Erickson, E. F.; Kaufman, M. J.; Hollenbach, D. J.; O'Dell, C. R.; Young, E. T.; Chen, H.

1998-01-01

57

Large Format Narrow-Band, Multi-Band, and Broad-Band LWIR QWIP Focal Planes for Space and Earth Science Applications  

NASA Technical Reports Server (NTRS)

A 640x512 pixel, long-wavelength cutoff, narrow-band (delta(lambda)/approx. 10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in the 4-16 m spectral region, and a broad-band (delta(lambda)/approx. 42%) QWIP FPA having 15.4 m cutoff have been demonstrated.

Gunapala, S. D.; Bandara, S. V.

2004-01-01

58

The relationship between rape biomass and narrow-band vegetation indices  

NASA Astrophysics Data System (ADS)

The Relationships between rape biomass and hyperspectral vegetation indices are investigated in this paper. The data for this study comes from field hyperspectral reflectance measurements of rape during 2002-2003 growing period. Reflectance was measured in discrete narrow bands between 350 and 2500 nm. Observed rape biomass included wet biomass (WBM including leaf wet biomass-LWBM, stem wet biomass-SWBM, fruit wet biomass-FWBM), and dry biomass(DBM: including leaf dry biomass-LDBM, stem dry biomass, fruit dry biomass-FDBM). Narrow band normalized difference vegetation index (NBNDVI) and narrow band ratio vegetation index (NBRVI)involving all possible two-band combinations of discrete channels was tested. Special narrow band lambda (?1) versus lambda (?2) plots of R2 values illustrate the most effective wavelength combinations (?1 and ?2) and band-width (??1 and ??2) for predicting rape biomass at different development stage. A strong relationship with rape biomass is located in red-edge, the longer portion of red, moisture-sensitive NIR, longer portion of the blue band, the intermediate portion of SWIR, and the longer portion of SWIR.

Huang, Jingfeng; Wang, Yuan; Wang, Fumin; Wang, Xiuzhen

2004-11-01

59

Infrared Narrow-Band Tomography of the Local Starburst NGC 1569 with LBT/LUCIFER  

E-print Network

We used the near-IR imager/spectrograph LUCIFER mounted on the Large Binocular Telescope (LBT) to image, with sub-arcsec seeing, the local dwarf starburst NGC 1569 in the JHK bands and HeI 1.08 micron, [FeII] 1.64 micron and Brgamma narrow-band filters. We obtained high-quality spatial maps of HeI, [FeII] and Brgamma emission across the galaxy, and used them together with HST/ACS images of NGC 1569 in the Halpha filter to derive the two-dimensional spatial map of the dust extinction and surface star formation rate density. We show that dust extinction is rather patchy and, on average, higher in the North-West (NW) portion of the galaxy [E_g(B-V) = 0.71 mag] than in the South-East [E_g(B-V) = 0.57 mag]. Similarly, the surface density of star formation rate peaks in the NW region of NGC 1569, reaching a value of about 4 x 10^-6 M_sun yr^-1 pc^-2. The total star formation rate as estimated from the integrated, dereddened Halpha luminosity is about 0.4 M_sun yr^-1, and the total supernova rate from the integrated...

Pasquali, A; Zibetti, S; Ageorges, N; Seifert, W; Brandner, W; Rix, H -W; Juette, M; Knierim, V; Buschkamp, P; Feiz, C; Gemperlein, H; Germeroth, A; Hoffmann, R; Laun, W; Lederer, R; Lehmitz, M; Lenzen, R; Mall, U; Mandel, H; Mueller, P; Naranjo, V; Polsterer, K; Quirrenbach, A; Schaeffner, L; Storz, C; Weiser, P

2011-01-01

60

Generation of narrow-band terahertz coherent Cherenkov radiation in a dielectric wakefield structure  

NASA Astrophysics Data System (ADS)

This study explores the use of a dielectric-lined waveguide structure as a means of producing narrow-band terahertz radiation in the form of electron-beam-driven coherent Cherenkov radiation wakefields. This concept builds on previously studied scenarios such as the Cherenkov maser and the Cherenkov free-electron laser. It is distinct in that it relies solely on coherent wakefield excitation instead of a microbunching instability gain process, in analogy to the superradiant regime of FEL operation. The narrow bandwidth is due to the single-mode nature of the excitation, enabled by the exclusion (due to coherence) of discrete waveguide modes with wavelengths shorter than the driving electron bunch length. This allows an inherently broadband beam current profile to radiate power into a single frequency, which is selectable by appropriate choice of design parameters. The theoretical component of this dissertation is aimed at making predictions for comparison with experimental results. The functional form and propagating mode frequencies of the electromagnetic fields in the waveguide structure are found by eigenmode solution in the source-free case beginning from Maxwell's equations; the response of the structure to a driving electron bunch is then found using a wakefield formalism. Predictions for the frequencies and radiated energy levels obtained from this analysis are corroborated computationally using the commercial particle-in-cell simulation code OOPIC PRO. The experiment is designed to be a proof-of-principle demonstration of the effectiveness of this scenario in converting the energy in an electron beam into electromagnetic radiation. We present detailed measurements showing a narrow emission spectrum peaked at 367 +/- 3 GHz from a 1 cm long fused silica capillary tube with sub-mm transverse dimensions, matching the predicted (analytical and computational) TM01 mode resonance to within 1% error. This measurement confirms the expected preferential coherent excitation of the TM01 mode over the HEM11 mode, which lies nearby in frequency but still decisively outside the error estimate established over multiple measurements. The measured 3 dB bandwidth is on the order of ? 10% and is seen to be transform-limited. We observe a 100 GHz shift in the emitted central frequency when the tube wall thickness is changed by 50 mum, demonstrating the modular tunability of the source. Calibrated measurements of the radiated energy register up to 10 muJ per 60-80 ps pulse for an incident sub-picosecond electron beam carrying 200 pC of charge, corresponding to a peak power of approximately 150 kW. A case study considering the implementation of this scenario using a 10-cm-long structure with smaller transverse dimensions indicates a possible yield of 50 MW peak power at 1.8 THz and 0.1% bandwidth. This dissertation reports the first direct measurements of narrow-band THz coherent Cherenkov radiation driven by a sub-picosecond electron beam in a dielectric wakefield structure, representing a successful adaptation of the previously proven Cherenkov FEL concept to the realm of ultra-short electron beams such as are available in state-of-the-art user facilities around the world. These results prove the potential of this method to produce tunable, narrow-band, pulse-length-variable, multi-megawatt peak-power radiation at f > 1 THz in existing modern electron accelerators.

Cook, Alan Matthew

61

Deconvolving Contributions to the Narrow Emission-Line Spectra of Narrow-Line Seyfert 1s  

NASA Astrophysics Data System (ADS)

We present a continuation of our study of ground-based spectra of a sample of 12 Narrow-Line Seyfert 1s (NLSy1s), obtained using the 1.5m telescope at CTIO. Previously, we had found similar emission line ratios in both NLSy1s and Broad-Line Seyfert 1s (BLSy1s), which suggests similar ionizing continua, although we noted that low-ionization lines, such as [O I] 6300A and such as [S II] 6716,6731A may be somewhat weaker in NLSy1s. Based on photo-ionization modeling, the spectra from both types must include a strong contribution from dense, highly ionized gas in the inner narrow-line region (NLR), as has been noted in the literature. Notably, we find that the average [O III] 5007A/[OII] 3727A ratio is ~ 3.5 in NLSy1s, as compared to ~ 6.5 in a similar-sized sample of BLSy1s, consistent with a strong contribution from star-formation in the former. It is unclear whether star-formation is more prevalent in NLSy1s, suggesting a unique stage in the evolution of the AGN, or whether they tend to lack an extended NLR, which overwhelms any contribution from star-formationand may be due to the orientation of the AGN with the host galaxy.

Kraemer, Steven B.; Crenshaw, D. M.; Schmitt, H. R.; Dietrich, M.

2014-01-01

62

Application of narrow-band television to industrial and commercial communications  

NASA Technical Reports Server (NTRS)

The development of narrow-band systems for use in space systems is presented. Applications of the technology to future spacecraft requirements are discussed along with narrow-band television's influence in stimulating development within the industry. The transferral of the technology into industrial and commercial communications is described. Major areas included are: (1) medicine; (2) education; (3) remote sensing for traffic control; and (5) weather observation. Applications in data processing, image enhancement, and information retrieval are provided by the combination of the TV camera and the computer.

Embrey, B. C., Jr.; Southworth, G. R.

1974-01-01

63

Motional Narrowing and Ergodic Bands in Excited Superdeformed States of {sup 194}Hg  

SciTech Connect

The E{sub {gamma}}-E{sub {gamma}} coincidence spectra from the electromagnetic decay of excited superdeformed states in {sup 194}Hg reveal surprisingly narrow ridges, parallel to the diagonal. A total of 100-150 excited bands are found to contribute to these ridges, which account for nearly all the unresolved E2 decay strength. Comparison with theory suggests that these excited bands have many components in their wave functions, yet they display remarkable rotational coherence. This phenomenon can be explained in terms of the combination of shell effects and motional narrowing.

Lopez-Martens, A. [C.S.N.S.M, IN2P3-CNRS, Batiment 104-108, 91405 Orsay (France); Doessing, T.; Herskind, B. [Niels Bohr Institute, DK-2100, Copenhagen (Denmark); Khoo, T. L.; Lauritsen, T.; Carpenter, M. P.; Janssens, R. V. F.; Hackman, G. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Matsuo, M. [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan); Lee, I-Y.; Macchiavelli, A. O. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Vigezzi, E. [INFN Sezione di Milano and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Yoshida, K. [Institue for Natural Science, Nara University, Nara 631-8502 (Japan)

2008-03-14

64

Hydrogen-Saturated Saline Protects Intensive Narrow Band Noise-Induced Hearing Loss in Guinea Pigs through an Antioxidant Effect  

PubMed Central

The purpose of the current study was to evaluate hydrogen-saturated saline protecting intensive narrow band noise-induced hearing loss. Guinea pigs were divided into three groups: hydrogen-saturated saline; normal saline; and control. For saline administration, the guinea pigs were given daily abdominal injections (1 ml/100 g) 3 days before and 1 h before narrow band noise exposure (2.5–3.5 kHz 130 dB SPL, 1 h). The guinea pigs in the control group received no treatment. The hearing function was assessed by the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recording. The changes of free radicals in the cochlea before noise exposure, and immediately and 7 days after noise exposure were also examined. By Scanning electron microscopy and succinate dehydrogenase staining, we found that pre-treatment with hydrogen-saturated saline significantly reduced noise-induced hair cell damage and hearing loss. We also found that the malondialdehyde, lipid peroxidation, and hydroxyl levels were significantly lower in the hydrogen-saturated saline group after noise trauma, indicating that hydrogen-saturated saline can decrease the amount of harmful free radicals caused by noise trauma. Our findings suggest that hydrogen-saturated saline is effective in preventing intensive narrow band noise-induced hearing loss through the antioxidant effect. PMID:24945316

Chen, Liwei; Yu, Ning; Lu, Yan; Wu, Longjun; Chen, Daishi; Guo, Weiwei; Zhao, Lidong; Liu, Mingbo; Yang, Shiming; Sun, Xuejun; Zhai, Suoqiang

2014-01-01

65

Time Resolved Measurements of Gain Spectra in Narrow Band Gap Superlattices  

Microsoft Academic Search

We report the results of ultrafast spectroscopic measurements performed on a series of four-layer superlattice structures used as active regions for mid-infrared semiconductor lasers. These narrow band gap superlattices have been designed for suppression of Auger recombination and intersubband absorption. The structures, which are each composed of InAs\\/GaInSb\\/InAs\\/AlGaInAsSb superlattices, have band gaps extending from 2.7 to 5 mum. Room temperature

S. A. Anson; J. T. Olesberg; M. E. Flatté; Thomas F. Boggess; T. C. Hasenberg; C. H. Grein

1997-01-01

66

Accumulation capacitance of narrow band gap metal-oxide-semiconductor capacitors  

Microsoft Academic Search

We have investigated the accumulation capacitance-voltage characteristics for capacitors with narrow band gap materials using modeling and experiments. The capacitance for InAs and In0.53Ga0.47As capacitors with a HfO2 oxide layer has been calculated using atomistic tight-binding, effective mass, and semiclassical nonparabolic models. The simulations show that band structure effects have a strong influence on the accumulation capacitance, and are essential

Erik Lind; Yann-Michel Niquet; Hector Mera; Lars-Erik Wernersson

2010-01-01

67

Narrow band selected high redshift galaxy candidates contaminated by lower redshift [OIII] ultrastrong emitter line galaxies  

E-print Network

Context. Lyman Break (LBG) and Narrow Band (NB) surveys have been successful at detecting large samples of high-redshift galaxies. Both methods are subject to contamination from low-redshift interlopers. Aims. In this paper, our aim is to investigate the nature of low-redshift interlopers in NB Lyman-{\\alpha} emitters (LAE) searches. Methods. From previous HAWK-I NB imaging at z $\\sim$ 7.7 we identify three objects that would have been selected as high-redshift LAEs had our optical data been one magnitude shallower (but still one to two magnitudes fainter than the near infrared data). We follow-up these objects in spectroscopy with XSHOOTER at the VLT. Results. Despite low quality data due to bad weather conditions, for each of the three objects we identify one, and only one emission line in the spectra of the objects, that we identify as the [OIII]5007A line. From this result and other arguments we infer that the 3 objects are ultrastrong line emitters at redshifts $\\sim$ 1.1. Conclusions. From this work and...

Pénin, Aurélie; Clément, Benjamin; Hibon, Pascale; Kneib, Jean-Paul; Cassata, Paolo; Ilbert, Olivier

2014-01-01

68

Submillimeter Narrow Emission Lines from the Inner Envelope of IRC+10216  

NASA Astrophysics Data System (ADS)

A spectral-line survey of IRC+10216 in the 345 GHz band has been undertaken with the Submillimeter Array. Although not yet completed, it has already yielded a fairly large sample of narrow molecular emission lines with line widths indicating expansion velocities of ~ 4 km s-1, less than three times the well known value of the terminal expansion velocity (14.5 km s-1) of the outer envelope. Five of these narrow lines have now been identified as rotational transitions in vibrationally excited states of previously detected molecules: the v = 1, J = 17-16, and J = 19-18 lines of Si34S and 29SiS and the v = 2, J = 7-6 line of CS. Maps of these lines show that the emission is confined to a region within ~ 60 AU of the star, indicating that the narrow-line emission is probing the region of dust formation where the stellar wind is still being accelerated.

Patel, Nimesh A.; Young, Ken H.; Brünken, Sandra; Wilson, Robert W.; Thaddeus, Patrick; Menten, Karl M.; Reid, Mark; McCarthy, Michael C.; Dinh-V-Trung; Gottlieb, Carl A.; Hedden, Abigail

2009-02-01

69

Treatment of generalized vitiligo in children with narrow-band (TL01) UVB radiation therapy  

Microsoft Academic Search

Background: Only a few clinical trials have been performed on the treatment of generalized vitiligo in children. Recently, narrow-band UVB therapy has been reported to be an effective and safe therapeutic option in adult patients with vitiligo. Objective: We studied the efficacy and safety of UVB (311 nm) therapy in children with generalized vitiligo and evaluated the effect of the

M. D. Njoo; J. D. Bos; W. Westerhof

2000-01-01

70

Electron pairing in the negative-U Hubbard narrow energy band model  

Microsoft Academic Search

Starting from the negative-U Hubbard model, an approximate expression is derived for the generalized energy gap function Deltakmu for a system of interacting electrons in a narrow s-band. This function has the virtue that it interpolates between the weak interaction limit (BCS) and the intermediate coupling regime. Starting from the Cooper pairing state, we investigate the build up of pairing

K. P. Jain; R. Ramakumar; C. C. Chancey

1990-01-01

71

Monte Carlo Simulation of Radiation in Gases with a NarrowBand Model  

E-print Network

Monte Carlo Simulation of Radiation in Gases with a Narrow­Band Model and a Net, Germany. published in ASME Journal of Heat Transfer, May 1996, pp.401­407 Abstract The Monte Carlo method with the Monte Carlo method : numerical efficiency becomes independent of optical thickness, strongly non uniform

Dufresne, Jean-Louis

72

Narrow-Band Processing and Fusion Approach for Explosive Hazard Detection in FLGPR  

E-print Network

algorithm for a forward-looking ground-penetrating radar (FLGPR). One challenge for threat detection using. Keywords: forward-looking explosive hazards detection, ground-penetrating radar, narrow-band processing included ground-penetrating-radar (GPR), infrared (IR) cameras, and acoustic technologies.1-3 Both handheld

Havens, Timothy

73

Semiconductor waveguide inversion in disordered narrow band-gap M. J. Gilbert,a)  

E-print Network

Semiconductor waveguide inversion in disordered narrow band-gap materials M. J. Gilbert,a) R. Akis inverter in GaAs and InAs with disordered material effects included in the simulation. The behavior process, in dif- ferent III�V semiconductor hetrostructures GaAs and InAs , remains possible

Gilbert, Matthew

74

The temperature dependence of the band gaps in narrow-gap semiconductors  

Microsoft Academic Search

We calculate the dependence of the direct and indirect band gaps on temperature in the narrow-gap semiconductors InAs and InSb. Our calculations are based on the empirical pseudopotential method. The obtained results compare reasonably well with available experimental data.

N. Bouarissa; H. Aourag

1997-01-01

75

Search for neutrino oscillations at the AGS with the narrow band beam  

SciTech Connect

We have taken neutrino data with the Narrow Band Beam (NBB) at Brookhaven National Laboratory (BNL) in the summer and fall of 1985. We are in the process of completing the analysis of the NBB data. In this paper we present preliminary results of this analysis. We observe an anomalous appearance of electron neutrinos above the expected background. 3 refs., 16 figs., 3 tabs.

Chi, C.; Kondakis, N.; Lee, W.; O'Brien, E.; O'Halloran, T.; Reardon, K.; Salman, S.; Blumenfeld, B.; Chichura, L.; Chien, C.Y.

1987-01-01

76

Deep narrow band imagery of the diffuse ISM in M33  

NASA Technical Reports Server (NTRS)

Very deep narrow band images were obtained for several fields in the local group spiral galaxy M33 using a wide field reimaging Charge Coupled Device (CCD) camera on the 1.5 m telescope at Palomar Observatory. The reimaging system uses a 306 mm collimator and a 58 mm camera lens to put a 16 minute by 16 minute field onto a Texas Instruments 800 x 800 pixel CCD at a resolution of 1.2 arcseconds pixel (-1). The overall system is f/1.65. Images were obtained in the light of H alpha (S II) lambda lambda 6717, 6731, (O III) lambda 5007, and line-free continuum bands 100A wide, centered at 6450A and 5100A. Assuming a distance of 600 kpc to M33 (Humphreys 1980, Ap. J., 241, 587), this corresponds to a linear scale of 3.5 pc pixel (-1), and a field size of 2.8 kpc x 2.8 kpc. Researchers discuss the H alpha imagery of a field centered approx. equal to 8 minutes NE of the nucleus, including the supergiant HII region complex NGC 604. Two 2000 second H alpha images and two 300 second red continuum images were obtained of two slightly offset fields. The fields were offset to allow for discrimination between real emission and possible artifacts in the images. All images were resampled to align them with one of the H alpha frames. The continuum images were normalized to the line images using the results of aperture photometry on a grid of stars in the field, then the rescaled continuum data were directly subtracted from the line data.

Hester, J. Jeff; Kulkarni, Shrinivas R.

1990-01-01

77

Spatial structure analysis of direct-drive implosion cores at OMEGA using x-ray narrow-band core images  

SciTech Connect

The spectroscopic analysis of x-ray narrow-band images and space-integrated x-ray line spectra from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the spatial profiles in the compressed core. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which images were obtained with a multimonochromatic imaging instrument. The analysis method considers data based on the argon He{beta} and Ly{beta} spectral features and their associated Li- and He-like satellites. The temperature gradient structure is investigated by using the sensitivity of the Ly{beta}/He{beta} emissivity ratio to the temperature.

Welser, L. A.; Mancini, R. C.; Nagayama, T.; Tommasini, R.; Koch, J. A.; Izumi, N.; Delettrez, J. A.; Marshall, F. J.; Regan, S. P.; Smalyuk, V. A.; Golovkin, I. E.; Haynes, D. A.; Kyrala, G. [Department of Physics, University of Nevada, Reno, M.S. 220, Reno, Nevada 89557 (United States); Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550-9234 (United States); Laboratory for Laser Energetics, University of Rochester, New York 14623 (United States); Prism Computational Sciences, Madison, Wisconsin 53711 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-10-15

78

Study of narrow-band second harmonic generation from a broad-band fundamental pulse  

NASA Astrophysics Data System (ADS)

This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.

Wen, Jing; Jiang, Hong-Bing; Deng, Yong-Kai; Gong, Qi-Huang

2010-12-01

79

Fitting narrow-band models to temperature-dependent, spectral absorption coefficients of fuel vapors  

NASA Astrophysics Data System (ADS)

Accurate modeling of infrared radiation transport through fuel rich cores of fires and other non-premixed combustion processes requires computationally efficient processing of temperature-dependent, spectral absorption coefficients for major fuel vapor species. Spectrally resolved transmissivity band measurements in the mid-infrared and near-infrared have been taken in recent years for numerous small fuel molecules including but not limited to ethane, ethylene, and propylene for a range of temperatures relevant for combustion environments. This paper compares the spectral transmissivity measurements using FTIR for both ethane and ethylene with the HITRAN 2012 edition. Narrow band absorption coefficients and overlap parameters are derived by fitting the spectral transmissivity measurements for ethane, ethylene, and propylene with narrow band models for temperatures up to 1000 K. The resulting fits provide a basis for calculating spectrally resolved infrared radiation transport in fuel rich cores of flames and other combustion processes where these species can be prevalent.

Lecoustre, V. R.; Wakatsuki, K.; Jackson, G. S.

2014-11-01

80

Using Narrow Band Photometry to Detect Young Brown Dwarfs in IC348  

E-print Network

We report the discovery of a population of young brown dwarf candidates in the open star cluster IC348 and the development of a new spectroscopic classification technique using narrow band photometry. Observations were made using FLITECAM, the First Light Camera for SOFIA, at the 3-m Shane Telescope at Lick Observatory. FLITECAM is a new 1-5 micron camera with an 8 arcmin field of view. Custom narrow band filters were developed to detect absorption features of water vapor (at 1.495 microns) and methane (at 1.66 microns) characteristic of brown dwarfs. These filters enable spectral classification of stars and brown dwarfs without spectroscopy. FLITECAM's narrow and broadband photometry was verified by examining the color-color and color-magnitude characteristics of stars whose spectral type and reddening was known from previous surveys. Using our narrow band filter photometry method, it was possible to identify an object measured with a signal-to-noise ratio of 20 or better to within +/-3 spectral class subtypes for late-type stars. With this technique, very deep images of the central region of IC348 (H ~ 20.0) have identified 18 sources as possible L or T dwarf candidates. Out of these 18, we expect that between 3 - 6 of these objects are statistically likely to be background stars, with the remainder being true low-mass members of the cluster. If confirmed as cluster members then these are very low-mass objects (~5 Mjupiter). We also describe how two additional narrow band filters can improve the contrast between M, L, and T dwarfs as well as provide a means to determine the reddening of an individual object.

A. K. Mainzer; Ian S. McLean

2003-06-30

81

An Interpretation of Banded Magnetospheric Radio Emissions  

NASA Technical Reports Server (NTRS)

Recently-published Active Magnetospheric Particle Tracer Explorer/Isothermal Remanent Magnetization (AMPTE/IRM) banded magnetospheric emissions, commonly referred to as '(n + 1/2)f(sub ce)' emissions where f(sub ce) is the electron gyrofrequency, are analyzed by treating them as analogous to sounder-stimulated ionospheric emissions. We show that both individual AMPTE/IRM spectra of magnetospheric banded emissions, and a statistically-derived spectra observed over the two-year lifetime of the mission, can be interpreted in a self-consistent manner. The analysis, which predicts all spectral peaks within 4% of the observed peaks, interprets the higher-frequency emissions as due to low group-velocity Bernstein-mode waves and the lower-frequency emissions as eigen modes of cylindrical-electromagnetic-plasma-oscillations. The demarcation between these two classes of emissions is the electron plasma frequency f(sub pe), where an emission is often observed. This f(sub pe), emission is not necessarily the strongest. None of the observed banded emissions were attributed to the upper-hybrid frequency. We present Alouette-2 and ISIS-1 plasma-resonance data, and model electron temperature (T(sub e)) values, to support the argument that the frequency-spectrum of ionospheric sounder-stimulated emissions is not strongly temperature dependent and thus that the interpretation of these emissions in the ionosphere is relevant to other plasmas (such as the magnetosphere) where N(sub e) and T(sub e) can be quite different but where the ratio f(sub pe)/f(sub ce) is identical.

Benson, Robert F.; Osherovich, V. A.; Fainberg, J.; Vinas, A. F.; Ruppert, D. R.; Vondrak, Richard R. (Technical Monitor)

2000-01-01

82

Different emission properties of a band edge laser pumped by picosecond and nanosecond pulses  

Microsoft Academic Search

Different emission properties of band edge laser in a face centered cubic (FCC) photonic crystal pumped by ps and ns pulse were investigated experimentally. For the case pumped by ps laser, multi-mode emission is obtained and every modes have narrow line width. For the case pumped by ns laser, there is only a single dominant mode with high output intensity

S J Chen; Y Zhou; T R Zhai; Z N Wang; D H Liu

2012-01-01

83

Fermion space charge in narrow band-gap semiconductors, Weyl semimetals, and around highly charged nuclei  

NASA Astrophysics Data System (ADS)

The field of charged impurities in narrow band-gap semiconductors and Weyl semimetals can create electron-hole pairs when the total charge Ze of the impurity exceeds a value Zce. The particles of one charge escape to infinity, leaving a screening space charge. The result is that the observable dimensionless impurity charge Q? is less than Z but greater than Zc. There is a corresponding effect for nuclei with Z>Zc?170, however, in the condensed matter setting we find Zc?10. Thomas-Fermi theory indicates that Q?=0 for the Weyl semimetal, but we argue that this is a defect of the theory. For the case of a highly-charged recombination center in a narrow band-gap semiconductor (or of a supercharged nucleus), the observable charge takes on a nearly universal value. In Weyl semimetals, the observable charge takes on the universal value Q?=Zc set by the reciprocal of material's fine structure constant.

Kolomeisky, Eugene B.; Straley, Joseph P.; Zaidi, Hussain

2013-10-01

84

Narrow Band Region-Based Active Contours Model for Noisy Color Image Segmentation  

PubMed Central

A narrow band active contour model for color image segmentation is proposed, which applies local statistics to improve the robustness against noise. The crux of our approach is to use intensity mean of local region to define the force function within a level set framework, within which a narrow band is implemented to further improve the computational efficiency. In addition, the image is segmented from channel-to-channel, which shows superior performance when the intensities of the object and background are similar. Furthermore, a multichannel segmentation combination method is used to integrate the information of multiple level sets. The proposed model has been applied to both synthetic and real images with expected results, and the comparison with the state-of-the-art approaches demonstrates the accuracy and superiority of our approach. PMID:25121116

Xie, Xiaomin; Zhang, Aijun; Wang, Changming; Meng, Xiangfei

2014-01-01

85

Study of dopant-dependent band gap narrowing in compound semiconductor devices  

Microsoft Academic Search

Band gap narrowing (BGN) is one of the crucial heavy-doping effects to be considered for bipolar devices. Using a physically-based approach (E.F. Schubert, Doping in III-V Semiconductors, Cambridge University Press, 1993), we suggest a new BGN model which considers the semiconductor material and the dopant species for arbitrary finite temperatures. This unified treatment is especially useful for accurate device simulation.

V Palankovski; G Kaiblinger-Grujin; S Selberherr

1999-01-01

86

Multidimensional heat flux reconstruction using narrow-band thermochromic liquid crystal thermography  

Microsoft Academic Search

An inverse algorithm is developed to reconstruct multi-dimensional surface heat flux using transient surface temperature measurements provided by narrow-band thermal liquid crystals (TLC) or phase-change material (PCM). In this thermographic technique, the information provided is the time it took a certain location to reach the characteristic temperature of the TLC or PCM. A quadratic functional to be minimized is formulated.

A. J. Kassab; E. Divo; J. S. Kapat

2001-01-01

87

Tunable narrow-band UV laser system pumped by a copper vapour laser  

SciTech Connect

A narrow-band laser system is designed, which produces 10-ns pulses of tunable UV radiation with an average power of 3 W, pulse repetition rate of 12 kHz, and linewidth smaller than 45 MHz. The system uses a cw dye laser as a master oscillator. Its radiation is amplified by a three-stage dye system whose output signal is frequency doubled in a BBO crystal. The system is pumped by a copper vapour laser. (lasers)

Bokhan, P A; Zakrevskii, D E; Kochubei, S A; Stepanov, A Yu [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation); Fateev, N V [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2001-02-28

88

Generation of narrow-band terahertz coherent Cherenkov radiation in a dielectric wakefield structure  

Microsoft Academic Search

This study explores the use of a dielectric-lined waveguide structure as a means of producing narrow-band terahertz radiation in the form of electron-beam-driven coherent Cherenkov radiation wakefields. This concept builds on previously studied scenarios such as the Cherenkov maser and the Cherenkov free-electron laser. It is distinct in that it relies solely on coherent wakefield excitation instead of a microbunching

Alan Matthew Cook

2009-01-01

89

Application of narrow band-gap materials in nanoscale spin filters  

Microsoft Academic Search

We develop a simple analytical model to study the influence of different material systems on the operation of a quantum-point-contact spin filter. Such a device has been predicted to allow for local control of the spin polarization in a semiconductor, and for direct electrical detection of the induced spin polarization. Narrow band-gap semiconductors, such as InAs and InSb, are predicted

M. J. Gilbert; J. P. Bird; T. Sugaya; R. Akis

2002-01-01

90

Electrochemical capacitance voltage profiling of the narrow band gap semiconductor InAs  

Microsoft Academic Search

InAs is a narrow band gap compound semiconductor with potential applications in infra-red detectors and high speed transistors.\\u000a In order to facilitate device design using this material, it is essential that carrier concentration profiles be accurately\\u000a known. Capacitance-voltage (CV) profiling is often employed for this purpose. Due to surface Fermi level pinning, it is difficult\\u000a to form metal Schottky contacts

V. Gopal; E.-H. Chen; E. P. Kvam; J. M. Woodall

2000-01-01

91

Submillimeter Wavelength Narrow Line Emission from the inner Circumstellar Envelope of IRC+10216  

NASA Astrophysics Data System (ADS)

Massive circumstellar envelopes of Asymptotic Giant Branch (AGB) stars are believed to be one of the main contributors of molecules and grains to the interstellar medium. IRC+10216 is a well known archetype of an AGB carbon star with a high mass-loss rate. Due to its close proximity ( 150 pc), this star is an ideal target for detailed studies of physical and chemical processes in AGB circumstellar envelopes. Using the Submillimeter Array (SMA), we have begun the first interferometric spectral line-survey of IRC+10216 in the 345 GHz band. We have found a large sample of molecular emission lines with narrow line-widths implying expansion velocities of 4 km/s (in contrast with the typical value of the expansion velocity of 14.5 km/s known from previous surveys). The emission from these narrow lines is spatially unresolved with our 3"x2" synthesized beam in SMA's subcompact configuration. We present here results on some of these lines which have been identified as vibrationally excited transition of Si34S, 29SiS, CS and CO. All these are new detections toward IRC+10216. The CO v=1 J=3-2 line is tentatively identified. If confirmed, it will be the first astronomical detection of vibrationally excited CO. We also present results from SMA extended array observations with higher angular resolution (0.8"x0.6") of 29SiS and CS lines. The emission continues to remain unresolved, implying that the narrow-line emission is coming from the region close to the star (within 60 AU), where the stellar wind is still being accelerated. We plan to carry out higher angular resolution observations with the very extended configuration of the SMA at an angular resolution of 0.3". These observations will probably allow us to probe physical conditions and kinematics in the region where dust is forming.

Patel, Nimesh A.; Young, K. H.; Wilson, R. W.; Bruenken, S.; Thaddeus, P.; Menten, K. M.; Reid, M. J.; McCarthy, M. C.; Van-Trung, D.; Gottleib, C. A.; Hedden, A. S.

2008-09-01

92

Band gap narrowing in BaTiO3 nanoparticles facilitated by multiple mechanisms  

NASA Astrophysics Data System (ADS)

In the present work, BaTiO3 nanoparticles of four different size ranges were prepared by sol-gel method. The optical band gap of these particles at some size ranges has come down to 2.53 eV from 3.2 eV, resulting in substantial increase in optical absorption by these ferroelectric nanoparticles making them potential candidates for light energy harvesting. XRD results show the presence of higher compressive strain in 23 nm and 54 nm size particles, they exhibit a higher band gap narrowing, whereas tensile strain is observed in 31 nm and 34 nm particles, and they do not show the marginal band gap narrowing. The 23 nm and 54 nm particles also show a coupling of free carriers to phonons by increasing the intensity of LO phonon mode at 715 cm-1. The higher surface charge density is expected in case of enhanced surface optical Raman modes (638 cm-1) contained in 31 and 34 nm size particles. In addition to this, the red shift in an LO mode Raman spectral line at 305 cm-1 with decrease in particle size depicts the presence of phonon confinement in it. The enhanced optical absorption in 23 nm and 54 nm size particles with a narrowed band gap of 3 eV and 2.53 eV is due to exchange correlation interactions between the carriers present in these particles. In 31 nm and 34 nm range particles, the absorption got bleached exhibiting increased band gaps of 3.08 eV and 3.2 eV, respectively. It is due to filling up of conduction band resulting from weakening of exchange correlation interactions between the charge carriers. Hence, it is concluded that the band gap narrowing in the nanoparticles of average size 23 nm/54 nm is a consequence of multiple effects like strain, electron-phonon interaction, and exchange correlation interactions between the carriers which is subdued in some other size ranges like 31 nm/34 nm.

Ramakanth, S.; James Raju, K. C.

2014-05-01

93

Very narrow-band ultraviolet photodetection based on strained M-plane GaN films  

NASA Astrophysics Data System (ADS)

The authors demonstrate a photodetection configuration where the responsivity in the ultraviolet spectral region is limited to a few nanometers, representing high-quality-factor, narrow-band detection together with polarization sensitivity. Both features are obtained by utilizing a polarization-sensitive photodectector in combination with a polarization filter made from two identical M-plane GaN films on ?-LiAlO2 (100) substrate. The optical band gap of these films depends on the direction of the in-plane polarization vector of the incident light beam with respect to the c axis. Electronic-band-structure calculations show that the naturally present anisotropic in-plane strain in these films is the crucial parameter to achieve both a high responsivity and a high polarization contrast.

Ghosh, Sandip; Rivera, C.; Pau, J. L.; Muñoz, E.; Brandt, O.; Grahn, H. T.

2007-02-01

94

Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data  

E-print Network

In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95$\\%$ confidence level upper limits have been computed both assuming polarization parameters are completely unknown and that they are known with some uncertainty, as derived from X-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of two below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.

The LIGO Scientific Collaboration; the Virgo Collaboration; J. Aasi; B. P. Abbott; R. Abbott; T. Abbott; M. R. Abernathy; F. Acernese; K. Ackley; C. Adams; T. Adams; T. Adams; P. Addesso; R. X. Adhikari; V. Adya; C. Affeldt; M. Agathos; K. Agatsuma; N. Aggarwal; O. D. Aguiar; A. Ain; P. Ajith; A. Alemic; B. Allen; A. Allocca; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. C. Araya; C. Arceneaux; J. S. Areeda; G. Ashton; S. Ast; S. M. Aston; P. Astone; P. Aufmuth; C. Aulbert; B. E. Aylott; S. Babak; P. T. Baker; F. Baldaccini; G. Ballardin; S. W. Ballmer; J. C. Barayoga; M. Barbet; S. Barclay; B. C. Barish; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; J. Bartlett; M. A. Barton; I. Bartos; R. Bassiri; A. Basti; J. C. Batch; Th. S. Bauer; C. Baune; V. Bavigadda; B. Behnke; M. Bejger; C. Belczynski; A. S. Bell; C. Bell; M. Benacquista; J. Bergman; G. Bergmann; C. P. L. Berry; D. Bersanetti; A. Bertolini; J. Betzwieser; S. Bhagwat; R. Bhandare; I. A. Bilenko; G. Billingsley; J. Birch; S. Biscans; M. Bitossi; C. Biwer; M. A. Bizouard; J. K. Blackburn; L. Blackburn; C. D. Blair; D. Blair; S. Bloemen; O. Bock; T. P. Bodiya; M. Boer; G. Bogaert; P. Bojtos; C. Bond; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; Sukanta Bose; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; A. F. Brooks; D. A. Brown; D. D. Brown; N. M. Brown; S. Buchman; A. Buikema; T. Bulik; H. J. Bulten; A. Buonanno; D. Buskulic; C. Buy; L. Cadonati; G. Cagnoli; J. Calderón Bustillo; E. Calloni; J. B. Camp; K. C. Cannon; J. Cao; C. D. Capano; F. Carbognani; S. Caride; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; R. Chakraborty; T. Chalermsongsak; S. J. Chamberlin; S. Chao; P. Charlton; E. Chassande-Mottin; Y. Chen; A. Chincarini; A. Chiummo; H. S. Cho; M. Cho; J. H. Chow; N. Christensen; Q. Chu; S. Chua; S. Chung; G. Ciani; F. Clara; J. A. Clark; F. Cleva; E. Coccia; P. -F. Cohadon; A. Colla; C. Collette; M. Colombini; L. Cominsky; M. Constancio, Jr.; A. Conte; D. Cook; T. R. Corbitt; N. Cornish; A. Corsi; C. A. Costa; M. W. Coughlin; J. -P. Coulon; S. Countryman; P. Couvares; D. M. Coward; M. J. Cowart; D. C. Coyne; R. Coyne; K. Craig; J. D. E. Creighton; T. D. Creighton; J. Cripe; S. G. Crowder; A. Cumming; L. Cunningham; E. Cuoco; C. Cutler; K. Dahl; T. Dal Canton; M. Damjanic; S. L. Danilishin; S. D'Antonio; K. Danzmann; L. Dartez; V. Dattilo; I. Dave; H. Daveloza; M. Davier; G. S. Davies; E. J. Daw; R. Day; D. DeBra; G. Debreczeni; J. Degallaix; M. De Laurentis; S. Deléglise; W. Del Pozzo; T. Denker; T. Dent; H. Dereli; V. Dergachev; R. De Rosa; R. T. DeRosa; R. DeSalvo; S. Dhurandhar; M. Díaz; L. Di Fiore; A. Di Lieto; I. Di Palma; A. Di Virgilio; G. Dojcinoski; V. Dolique; E. Dominguez; F. Donovan; K. L. Dooley; S. Doravari; R. Douglas; T. P. Downes; M. Drago; J. C. Driggers; Z. Du; M. Ducrot; S. Dwyer; T. Eberle; T. Edo; M. Edwards; M. Edwards; A. Effler; H. -B. Eggenstein; P. Ehrens; J. Eichholz; S. S. Eikenberry; R. Essick; T. Etzel; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; X. Fan; Q. Fang; S. Farinon; B. Farr; W. M. Farr; M. Favata; M. Fays; H. Fehrmann; M. M. Fejer; D. Feldbaum; I. Ferrante; E. C. Ferreira; F. Ferrini; F. Fidecaro; I. Fiori; R. P. Fisher; R. Flaminio; J. -D. Fournier; S. Franco; S. Frasca; F. Frasconi; Z. Frei; A. Freise; R. Frey; T. T. Fricke; P. Fritschel; V. V. Frolov; S. Fuentes-Tapia; P. Fulda; M. Fyffe; J. R. Gair; L. Gammaitoni; S. Gaonkar; F. Garufi; A. Gatto; N. Gehrels; G. Gemme; B. Gendre; E. Genin; A. Gennai; L. Á. Gergely; S. Ghosh; J. A. Giaime; K. D. Giardina; A. Giazotto; J. Gleason; E. Goetz; R. Goetz; L. Gondan; G. González; N. Gordon; M. L. Gorodetsky; S. Gossan; S. Goßler; R. Gouaty; C. Gräf; P. B. Graff; M. Granata; A. Grant; S. Gras; C. Gray; G. Greco; R. J. S. Greenhalgh; A. M. Gretarsson; P. Groot; H. Grote; S. Grunewald; G. M. Guidi; C. J. Guido; X. Guo; K. Gushwa; E. K. Gustafson; R. Gustafson; J. Hacker; E. D. Hall; G. Hammond; M. Hanke; J. Hanks; C. Hanna; M. D. Hannam; J. Hanson; T. Hardwick; J. Harms; G. M. Harry; I. W. Harry; M. Hart; M. T. Hartman; C. -J. Haster; K. Haughian; S. Hee; A. Heidmann; M. Heintze; G. Heinzel; H. Heitmann; P. Hello; G. Hemming; M. Hendry; I. S. Heng; A. W. Heptonstall; M. Heurs; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; D. Hofman; S. E. Hollitt; K. Holt; P. Hopkins; D. J. Hosken; J. Hough; E. Houston; E. J. Howell; Y. M. Hu; E. Huerta; B. Hughey; S. Husa; S. H. Huttner; M. Huynh; T. Huynh-Dinh; A. Idrisy; N. Indik; D. R. Ingram; R. Inta; G. Islas; J. C. Isler; T. Isogai; B. R. Iyer; K. Izumi; M. Jacobson; H. Jang; P. Jaranowski; S. Jawahar; Y. Ji; F. Jiménez-Forteza; W. W. Johnson; D. I. Jones; R. Jones; R. J. G. Jonker; L. Ju; Haris K

2014-10-30

95

Effective band gap narrowing of anatase TiO2 by strain along a soft crystal direction  

E-print Network

Effective band gap narrowing of anatase TiO2 by strain along a soft crystal direction Wan-Jian Yin; accepted 26 April 2010; published online 2 June 2010 Due to its large band gap 3.2 eV , TiO2 cannot absorb sun light effectively. To reduce its band gap, various approaches have been attempted; most of them

Gong, Xingao

96

Synthesis of periodic hexagonal surfactant templated platinum tin tellurides: narrow band gap inorganic/organic composites.  

PubMed

In this work we report the synthesis and characterization of a new nanostructured platinum/tin/telluride inorganic/surfactant composite. The material is synthesized from soluble SnTe(4)(4-) clusters and is shown to have well-defined nanometer scale periodicity along with unique optical properties. Small-angle X-ray scattering indicates that the material forms with a 2D hexagonal honeycomb structure, which is size tunable based on surfactant tail length. Multinuclear EXAFS is used as a probe of local order in these materials. The results indicate that the tetrahedral SnTe(4) unit dimerizes during assembly, and these clusters are coordinated to square planar platinum ions. Near-IR/visible reflectance spectroscopy indicates that the material is a narrow band gap semiconductor with a band gap of 0.8 eV. The extension of the ideas of surfactant templating to a narrow band gap semiconductor opens up the exciting potential for future optoelectronic applications. PMID:12683826

Riley, Andrew E; Tolbert, Sarah H

2003-04-16

97

The Differences in Brain Activity between Narrow Band Noise and Pure Tone Tinnitus  

PubMed Central

Background Tinnitus is an auditory sensation characterized by the perception of sound or noise in the absence of any external sound source. Based on neurobiological research, it is generally accepted that most forms of tinnitus are attributable to maladaptive plasticity due to damage to auditory system. Changes have been observed in auditory structures such as the inferior colliculus, the thalamus and the auditory cortex as well as in non-auditory brain areas. However, the observed changes show great variability, hence lacking a conclusive picture. One of the reasons might be the selection of inhomogeneous groups in data analysis. Methodology The aim of the present study was to delineate the differences between the neural networks involved in narrow band noise and pure tone tinnitus conducting LORETA based source analysis of resting state EEG. Conclusions Results demonstrated that narrow band noise tinnitus patients differ from pure tone tinnitus patients in the lateral frontopolar (BA 10), PCC and the parahippocampal area for delta, beta and gamma frequency bands, respectively. The parahippocampal-PCC current density differences might be load dependent, as noise-like tinnitus constitutes multiple frequencies in contrast to pure tone tinnitus. The lateral frontopolar differences might be related to pitch specific memory retrieval. PMID:21048975

Vanneste, Sven; Plazier, Mark; van der Loo, Elsa; Van de Heyning, Paul; De Ridder, Dirk

2010-01-01

98

Narrow band filter using 1D periodic structure with defects for DWDM systems  

NASA Astrophysics Data System (ADS)

A 1D binary periodic structure with defect has been analysed using Transfer Matrix Method. For a particular nine layered structure of SiO2 and InP, a number of full stop bands (in other words, zero passbands or forbidden bands) at different regions of the spectrum under investigation are observed. Introducing a central spatial defect in the system by adjusting the layer width, it is possible to achieve an extremely narrow passband centred on 1554.9 nm in the 7th forbidden band. Moreover by varying the defect width, the number of passbands can be increased. These passbands have flat and 100% stopband and hence can be better candidate to drop single or multiple frequencies in WDM systems. It is further observed that with increase in the number of layers and/or defect width, the number of mini pass bands outside the original forbidden band also increases. Also by FDTD simulation it is seen that the field is localised within the defect for the passband frequency.

Ghosh, R.; Ghosh, K. K.; Chakraborty, R.

2013-02-01

99

Fast reconstruction of Raman spectra from narrow-band measurements based on Wiener estimation  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has demonstrated great potential in the study of biological molecules in a variety of biomedical applications. But slow data acquisition due to weak Raman signals from these molecules has prevented its wide use especially in an imaging setup. We propose a novel method to reconstruct the entire Raman spectrum from a few narrow-band measurements based on Wiener estimation. This method has been tested on Raman spectra from individual cells and shown fast speed and excellent accuracy. This method represents a new direction to speed up Raman data acquisition in an imaging setup to investigate fast changing phenomena.

Chen, Shuo; Ong, Yi Hong; Liu, Quan

2012-12-01

100

NICMOS Narrow-band Infrared Photometry of TW Hya Association Stars  

Microsoft Academic Search

We have obtained 1.64, 1.90 and 2.15 micron narrow-band images of five T\\u000aTauri stars in the TW Hya Association (TWA) using the Near-Infrared Camera and\\u000aMultiobject Spectrometer aboard the Hubble Space Telescope. Most of the T Tauri\\u000astars in our study show evidence of absorption by H2O vapor in their\\u000aatmospheres; in addition, the low-mass brown dwarf candidate, TWA

David A. Weintraub; Didier Saumon; Joel H. Kastner; Thierry Forveille

2000-01-01

101

Variable narrow-band transmission filters for spectrometry from space. 2. Fabrication process.  

PubMed

The optical components described here are variable narrow-band transmission filters, where the transmittance peak varies with the position along the surface of the filter itself. They allow the construction of ultracompact and low-weight spectrometers for space applications. The theoretical behavior of graded filters has been already investigated by the authors, for imaging spectrometry of the Earth surface. The application of graded filters to miniaturized instruments for planetary missions (Mercury) is considered. Experimental results on the fabrication of small-dimension variable transmission filters operating over a wide spectrum, from visible to near infrared, are reported. PMID:18449238

Piegari, Angela; Bulir, Jiri; Krasilnikova Sytchkova, Anna

2008-05-01

102

Locata Performance Evaluation in the Presence of Wide- and Narrow-Band Interference  

NASA Astrophysics Data System (ADS)

Classically difficult positioning environments often call for augmentation technology to assist the GPS, or more generally the Global Navigation Satellite System (GNSS) technology. The ground-based ranging technology offers augmentation, and even replacement, to GPS in such environments. However, like any other system relying on wireless technology, a Locata positioning network also faces issues in the presence of RF interference (RFI). This problem is magnified due to the fact that Locata operates in the licence-free 2·4 GHz Industrial, Scientific and Medical (ISM) band. The licence-free nature of this band attracts a much larger number of devices using a wider range of signal types than for licensed bands, resulting in elevation of the noise floor. Also, harmonics from out-of-band signals can act as potential interferers. WiFi devices operating in this band have been identified as the most likely potential interferer, due partially to their use of the whole ISM band, but also because Locata applications often also may use a wireless network. This paper evaluates the performance of Locata in the presence of both narrow- and wide-band interfering signals. Effects of received interference on both raw measurements and final solutions are reported and analysed. Test results show that Locata performance degrades in the presence of received interference. It is also identified that high levels of received interference can affect Locata carriers even if the interference is not in co-frequency situation with the affected carrier. Finally, Locata characteristics have been identified which can be exploited to mitigate RFI issues.

Khan, Faisal A.; Rizos, Chris; Dempster, Andrew G.

103

EVOLUTION OF [O III] {lambda}5007 EMISSION-LINE PROFILES IN NARROW EMISSION-LINE GALAXIES  

SciTech Connect

The active galactic nucleus (AGN)-host co-evolution issue is investigated here by focusing on the evolution of the [O III] {lambda}5007 emission-line profile. A large sample of narrow emission-line galaxies is selected from the Max-Planck Institute for Astrophysics/Johns Hopkins University Sloan Digital Sky Survey DR7 catalog to simultaneously measure both the [O III] line profile and circumnuclear stellar population in an individual spectrum. By requiring that (1) the [O III] line signal-to-noise ratio is larger than 30 and (2) the [O III] line width is larger than the instrumental resolution by a factor of two, our sample is narrowed down to 2333 Seyfert galaxies/LINERs (AGNs), 793 transition galaxies, and 190 star-forming galaxies. In addition to the commonly used profile parameters (i.e., line centroid, relative velocity shift, and velocity dispersion), two dimensionless shape parameters, skewness and kurtosis, are used to quantify the line shape deviation from a pure Gaussian function. We show that the transition galaxies are systematically associated with narrower line widths and weaker [O III] broad wings than the AGNs, which implies that the kinematics of emission-line gas are different in the two kinds of objects. By combining the measured host properties and line shape parameters, we find that the AGNs with stronger blue asymmetries tend to be associated with younger stellar populations. However, a similar trend is not identified in the transition galaxies. The failure likely results from a selection effect in which the transition galaxies are systematically associated with younger stellar populations than the AGNs. The evolutionary significance revealed here suggests that both narrow-line region kinematics and outflow feedback in AGNs co-evolve with their host galaxies.

Wang, J.; Mao, Y. F.; Wei, J. Y., E-mail: wj@bao.ac.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100021 (China)

2011-11-01

104

The Unidentified Infrared Emission Bands: Identified  

NASA Technical Reports Server (NTRS)

The so-called Unidentified Infrared or simply UIR bands, the infrared emission band spectrum associated with a wide variety of interstellar objects, can be modeled in detail by laboratory spectra of neutral and positively charged polycyclic aromatic hydrocarbon (PAH) mixtures. Fits are presented for the UIR emission from the protoplanetary nebula IRAS 22272+5435, the diffuse galactic medium, and the Orion HII/photodissociation front - a selection of objects which span the evolutionary range of interstellar material. These data directly address the spectroscopic criticisms previously leveled at the PAH hypothesis and demonstrate that PAH-related molecular species are indeed responsible for this widespread emission. Furthermore, these fits reflect the structure, abundance, and ionization state of the interstellar PAHs and, in turn, provide direct insight into the processes of carbon nucleation, growth and evolution in circumstellar shells and the interstellar medium. To date, no other candidate material which has been proposed to account for the UIR emission can as readily and specifically reproduce these spectral variations. Given the ubiquity of these species, this work demonstrates the tremendous potential of these species as probes of a new and heretofore largely unexplored facet of astrochemistry - potential which should make PAHs the probe of the next millennium much as CO has been for the last quarter century.

Hudgins, Douglas M.; Allamandola, Louis J.; Sandford, Scott A.; Goorvitch, David (Technical Monitor)

1998-01-01

105

Narrow band wavelength selective filter using grating assisted single ring resonator.  

PubMed

This paper illustrates a filter configuration which uses a single ring resonator of larger radius connected to a grating resonator at its drop port to achieve single wavelength selectivity and switching property with spectral features suitable for on-chip wavelength selection applications. The proposed configuration is expected to find applications in silicon photonics devices such as, on-chip external cavity lasers and multi analytic label-free biosensors. The grating resonator has been designed for a high Q-factor, high transmittivity, and minimum loss so that the wavelength selectivity of the device is improved. The proof-of-concept device has been demonstrated on a Silicon-on-Insulator (SOI) platform through electron beam lithography and Reactive Ion Etching (RIE) process. The transmission spectrum shows narrow band single wavelength selection and switching property with a high Free Spectral Range (FSR) ?60 nm and side band rejection ratio >15 dB. PMID:25273711

Prabhathan, P; Murukeshan, V M

2014-09-01

106

A search for narrow band signals with SERENDIP II: a progress report  

NASA Technical Reports Server (NTRS)

Commensal programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. Our automated commensal system, SERENDIP II, is a high resolution 131,072 channel spectrometer. It searches for 0.49 Hz signals in sequential 64,700 Hz bands of the IF signal from a radio telescope being used for an astronomical observation. Upon detection of a narrow band signal with power above a preset threshold, the frequency, power, time, and telescope direction are recorded for later study. The system has been tested at the Hat Creek Radio Astronomy Observatory 85 ft telescope and the NASA-JPL Deep Space Station (DSS 14) 64 m telescope. It is currently collecting data at the National Radio Astronomy Observatory 300 ft telescope.

Werthimer, D.; Brady, R.; Berezin, A.; Bowyer, S.

1988-01-01

107

Narrow band wavelength selective filter using grating assisted single ring resonator  

NASA Astrophysics Data System (ADS)

This paper illustrates a filter configuration which uses a single ring resonator of larger radius connected to a grating resonator at its drop port to achieve single wavelength selectivity and switching property with spectral features suitable for on-chip wavelength selection applications. The proposed configuration is expected to find applications in silicon photonics devices such as, on-chip external cavity lasers and multi analytic label-free biosensors. The grating resonator has been designed for a high Q-factor, high transmittivity, and minimum loss so that the wavelength selectivity of the device is improved. The proof-of-concept device has been demonstrated on a Silicon-on-Insulator (SOI) platform through electron beam lithography and Reactive Ion Etching (RIE) process. The transmission spectrum shows narrow band single wavelength selection and switching property with a high Free Spectral Range (FSR) ˜60 nm and side band rejection ratio >15 dB

Prabhathan, P.; Murukeshan, V. M.

2014-09-01

108

Digital analysis of narrow-band imagery of the Cygnus Loop  

NASA Technical Reports Server (NTRS)

Calibrated surface brightness and spectral line ratio maps which involve emission from six different ionic species are derived from the digital analysis of narrow passband direct imagery of a field in the southeast part of the Cygnus Loop SNR, and the spatial structure is categorized on the basis of the presence or absence of features in images isolating different emission lines. While features present in all emission lines are found to have spectral behavior consistent with steady flow shock model calculations for a range of v(s), the features present only in such 'hot' lines as the O III forbidden line 5007 A are found to account for relative intensities of that line greater than can be matched by steady flow model calculations.

Parker, R. A. R.; Hester, J. J.; Dufour, R. J.

1983-01-01

109

The dipole model of narrowing of the energy gap between the Hubbard bands in slightly compensated semiconductors  

Microsoft Academic Search

A model of the narrowing of the energy gap between the Hubbard bands (the A\\u000a 0 and A\\u000a + bands for acceptors and the D\\u000a 0 and D\\u000a ? bands for donors) with increasing concentration of hydrogen-like dopants at low concentrations of the compensating impurity\\u000a is suggested. The width of the impurity bands is assumed to be small compared to

N. A. Poklonski; S. A. Vyrko; A. G. Zabrodski?

2006-01-01

110

Remote laser generation of narrow-band surface waves through optical fibers.  

PubMed

This paper demonstrates the use of a fiberoptic bundle for flexible, compact, remote, and noncontact laser generation of surface ultrasonic waves in materials. The bundle is able to deliver Nd:YAG pulsed light with a 60% delivery efficiency up to an average energy of 55 mJ/pulse for a pulse duration on the order of 10 ns and a pulse repetition rate of 20 Hz without signs of fiber damage. Details of the bundle construction and surface preparation are given, and pulsed light delivery tests performed with single tapered fibers are discussed. The high-power light delivery capabilities of the bundle are demonstrated for the generation of narrow-band surface waves in a Carbon/PEEK composite laminate by a spatial modulation technique that employs a periodic transmission mask. Single laser pulse ultrasonic tonebursts are clearly detectable using a small aperture piezoelectric transducer while ensuring thermoelastic generation conditions. The theory of narrow-band generation of surface acoustic waves is improved by accounting for the strength nonuniformity of the illumination sources. In addition, the effect of the number of illumination sources on the bandwidth of the generated surface wave is assessed experimentally, and excellent agreement is shown with the theoretical results predicted by the improved model. PMID:18244353

Di Scalea, F L; Berndt, T P; Spicer, J B; Djordjevic, B B

1999-01-01

111

In vivo early diagnosis of gastric dysplasia using narrow-band image-guided Raman endoscopy  

NASA Astrophysics Data System (ADS)

We first report on the implementation of a novel narrow-band image-guided Raman endoscopy technique for in vivo diagnosis of gastric dysplasia. High-quality in vivo Raman spectra can be acquired from normal and dysplastic gastric mucosal tissue within 0.5 sec under narrow-band image (NBI) guidance at gastroscopy. Significant differences are observed in in vivo Raman spectra between normal (n=54) and dysplastic (n=18) gastric tissue from 30 gastric patients, particularly in the spectral ranges of 825 to 950, 1000 to 1100, 1250 to 1500, and 1600 to 1800 cm-1, which primarily contain signals related to proteins, nucleic acids, and lipids. The multivariate analysis [i.e., principal components analysis (PCA) and linear discriminant analysis (LDA)], together with the leave-one tissue site-out, cross validation on in vivo gastric Raman spectra yields a diagnostic sensitivity of 94.4% (17/18) and specificity of 96.3% (52/54) for distinction of gastric dysplastic tissue. This study suggests that narrowband image-guided Raman endoscopy associated with PCA-LDA diagnostic algorithms has potential for the noninvasive, in vivo early diagnosis and detection of gastric precancer during clinical gastroscopic examination.

Huang, Zhiwei; Bergholt, Mads Sylvest; Zheng, Wei; Lin, Kan; Ho, Khek Yu; Teh, Ming; Yeoh, Khay Guan

2010-05-01

112

The Cosmic Infrared Background Experiment: Flight Characterization Of The Ciber Narrow Band Spectrometer.  

NASA Astrophysics Data System (ADS)

Subtraction of the Zodiacal light foreground is the dominant source of uncertainty in absolute photometric measurements of the extra-galactic background at near-infrared to optical wavelengths. The second flight of the Cosmic Infrared Background ExpeRiment (CIBER) occurred on July 10th, 2010. CIBER is a NASA sounding rocket experiment carrying four co-aligned instruments including two imaging telescopes with wide passbands centered at 1 and 1.6 microns, respectively, as well as a low resolution spectrometer and a narrow-band spectrometer. THE CIBER spectrometers are absolutely calibrated in collaboration with NIST. The narrow-band spectrometer filter is centered on the Ca II solar Fraunhofer line at 854.2 nm and is designed to measure the equivalent width of the solar line reflected by the interplanetary dust in order to obtain an absolute measurement of the Zodiacal contribution to the infrared sky at that wavelength. In conjunction with measured low resolution spectrum from 700 to 1900 nm, this will provide an accurate independent check of the DIRBE Zodiacal light models. Here we describe the NBS instrument, calibration and in-flight characterization.

Levenson, Louis R.; Battle, J.; Bock, J. J.; Cooray, A.; Hristov, V.; Keating, B.; Lee, D.; Mason, P.; Matsumoto, T.; Matsuura, S.; Nam, U. W.; Renbarger, T.; Sullivan, I.; Suzuki, K.; Wada, T.; Zemcov, M.

2011-01-01

113

A Cooperative Distance Learning Method based on the Narrow-band Internet and Its Evaluation  

NASA Astrophysics Data System (ADS)

This paper describes the experimental evaluation of a cooperative distance learning method, which can be utilized on the narrow-band Internet. In this method, students of group-learning perform a series of study a couple of times, which create an on-line report, communicating through the chat about given theme. they try to gain improvement in the study effect with higher cooperative attitude. Teacher gives a short lecture at the first stage, and then gives supplementary explanation after grasping the degree of comprehension of students at the middle stage of the study. Teaching materials are distributed to students' PCs beforehand and the lecture could be carried out on the narrow-band environment by transmitting the commands. The teacher analyzes students' communication logs and gives advice for the next study. This paper describes the result of the evaluation of the proposed method by carrying out simulated installation of the environment within the campus supposing a trial of cooperative distance learning in overseas desert circumference area environment.

Tilwaldi, Dilmurat; Takahashi, Toshiya; Takata, Akinobu; Koizumi, Hisao

114

Narrow-band N-resonance formed in thin rubidium atomic layers  

SciTech Connect

The narrow-band N-resonance formed in a {Lambda} system of D{sub 1}-line rubidium atoms is studied in the presence of a buffer gas (neon) and the radiations of two continuous narrow-band diode lasers. Special-purpose cells are used to investigate the dependence of the process on vapor column thickness L in millimeter, micrometer, and nanometer ranges. A comparison of the dependences of the N-resonance and the electromagnetically induced transparency (EIT) resonance on L demonstrates that the minimum (record) thickness at which the N-resonance can be detected is L = 50 {mu}m and that a high-contrast EIT resonance can easily be formed even at L Almost-Equal-To 800 nm. The N-resonance in a magnetic field for {sup 85}Rb atoms is shown to split into five or six components depending on the magnetic field and laser radiation directions. The results obtained indicate that levels F{sub g} = 2, 3 are initial and final in the N-resonance formation. The dependence of the N-resonance on the angle between the laser beams is analyzed, and practical applications are noted.

Sargsyan, A.; Mirzoyan, R.; Sarkisyan, D., E-mail: david@ipr.sci.am [National Academy of Sciences of Armenia, Institute for Physical Research (Armenia)

2012-11-15

115

Erbium emission from porous silicon one-dimensional photonic band gap structures  

Microsoft Academic Search

We report tunable, narrow, directional, and enhanced erbium emission from one-dimensional photonic band gap structures. The structures are prepared by anodic etching of crystalline silicon and consist of two highly reflecting porous silicon Bragg reflectors sandwiching an active layer. The cavities are doped by cathodic electromigration of the erbium ions into the porous silicon matrix, followed by high temperature oxidation.

Herman A. Lopez; Philippe M. Fauchet

2000-01-01

116

A search for double-peaked narrow emission line galaxies and AGNs in the LAMOST DR1  

NASA Astrophysics Data System (ADS)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) has released more than two million spectra, which provide the opportunity to search for double-peaked narrow emission line (NEL) galaxies and active galactic nuclei (AGNs). The double-peaked narrow-line profiles can be well modeled by two velocity components, respectively blueshifted and redshifted with respect to the systemic recession velocity. This paper presents 20 double-peaked NEL galaxies and AGNs found from LAMOST DR1 using a search method based on a multi-Gaussian fit of the narrow emission lines. Among them, ten have already been published by other authors, either listed as genuine double-peaked NEL objects or as asymmetric NEL objects, and the remaining ten are original discoveries. We discuss some possible origins for the double-peaked narrow-line features, such as interaction between jet and narrow line regions, interaction with companion galaxies, and black hole binaries. Spatially resolved optical imaging and/or follow-up observations in other spectral bands are needed to further discuss the physical mechanisms at work.

Shi, Zhi-Xin; Luo, A.-Li; Comte, Georges; Chen, Xiao-Yan; Wei, Peng; Zhao, Yong-Heng; Wu, Fu-Chao; Zhang, Yan-Xia; Shen, Shi-Yin; Yang, Ming; Wu, Hong; Wu, Xue-Bing; Zhang, Hao-Tong; Lei, Ya-Juan; Zhang, Jian-Nan; Wang, Ting-Gui; Jin, Ge; Zhang, Yong

2014-10-01

117

The effect of timing noise on targeted and narrow-band coherent searches for continuous gravitational waves  

E-print Network

Most continuous gravitational-wave searches use Taylor expansions in the phase to model the spindown of neutron stars. Studies of pulsars demonstrate that their electromagnetic (EM) emissions suffer from timing noise, small deviations in the phase from Taylor expansion models. How the mechanism producing EM emission is related to any continuous gravitational-wave (CW) emission is unknown; if they either interact or are locked in phase then the CW will also experience timing noise. Any disparity between the signal and the search template used in matched filtering methods will result in a loss of signal-to-noise ratio (SNR), referred to as 'mismatch'. In this work we assume the CW suffers a similar level of timing noise to its EM counterpart. We inject and recover fake CW signals, which include timing noise generated from observational data on the Crab pulsar. Measuring the mismatch over durations of order ~ 10 months, the effect is for the most part found to be small. This suggests recent so-called 'narrow-band' searches which placed upper limits on the signals from the Crab and Vela pulsars will not be significantly affected. At a fixed observation time, we find the mismatch depends upon the observation epoch. Considering the averaged mismatch as a function of observation time, we find that it increases as a power law with time, and so may become relevant in long baseline searches.

G. Ashton; D. I. Jones; R. Prix

2014-10-29

118

Narrow and broad band photoluminescence spectroscopy of cadmium zinc selenide semiconductor  

NASA Astrophysics Data System (ADS)

In this dissertation I have used photoluminescence (PL) spectrometric analysis to measure the temperature dependence of the spectral features of the direct band gap semiconductor CdxZn1-xSe , for two nominal concentrations x = 0.25, 0.50, in the temperature range 25--300 K. The effective concentrations were obtained from analysis of the spectra. The parameters that describe the temperature dependence of the line width broadening have been evaluated using different models. The PL broadband characteristics of Cd0.22Zn0.78Se and Cd0.41Zn0.59Se are also investigated within the energy range 1.36--2.40 eV and temperature range 25--305 K. Two broad bands are observed, the higher energy band I centered at 1.991 and 1.773 eV, the lower energy band II centered at 1.844 and 1.705 eV for the two samples, respectively. The emission bands are attributed to donor-acceptor pair transitions. The energy scheme shows two donors and two acceptor levels, the binding energies of the donors for Cd 0.22Zn0.78Se are 29 and 208 meV below the conduction band, the binding energies of the acceptors 472 and 511 meV above the valence band. The binding energies of the donors for Cd0.41Zn 0.59Se are 27 and 137 meV, the binding energies of the acceptors 393 and 423 eV. A significant blue shift in energy with increasing temperature was observed for the lower energy band. The ionization temperatures for the deep donors are 279 and 287 K for Cd0.22Zn0.78Se and Cd0.41Zn0.59Se, respectively.

Sweiti, Ayman

2003-06-01

119

Identification and extraction of photometric redshifts of quasars with narrow-band filters  

NASA Astrophysics Data System (ADS)

Although quasars are valuable targets for many cosmological applications, imaging surveys employing optical broad-band filter systems are unable to obtain accurate photometric redshifts for these objects. Broad-band imaging surveys also have some difficulty in distinguishing quasars from stars and HII regions of galaxies. However, the construction of a high-purity catalog of quasars, with accurate photometric redshifts, can be much more efficient with medium or narrow-band surveys, such as the upcoming J-PAS. In this work we discuss how to overcome the degeneracies in the color-color and color-magnitude diagrams that hamper the efficient detection of quasars, and how to obtain very good (near spectroscopic) photometric redshifts for these objects. In particular, we discuss how to include quasars in some of the most popular redshift codes, and the parallel need for the inclusion of spectral libraries for stars. We also discuss the importance of a good modeling of the distribution of point-sources in the sky, and the need for reliable luminosity functions that can inform the Bayesian estimation of types and photometric redshifts.

Queiroz, C.; Raul Abramo, L.

2014-10-01

120

Compact high-quality CdSe/CdS core/shell nanocrystals with narrow emission linewidths and suppressed blinking  

E-print Network

High particle uniformity, high photoluminescence quantum yields, narrow and symmetric emission spectral lineshapes and minimal single-dot emission intermittency (known as blinking) have been recognized as universal ...

Chen, Ou

121

Enhancing the macroscopic yield of narrow-band high-order harmonic generation by Fano resonances.  

PubMed

Resonances in the photoabsorption spectrum of the generating medium can modify the spectrum of high-order harmonics. In particular, window-type Fano resonances can reduce photoabsorption within a narrow spectral region and, consequently, lead to an enhanced emission of high-order harmonics in absorption-limited generation conditions. For high harmonic generation in argon it is shown that the 3s3p(6)np(1)P(1) window resonances (n = 4, 5, 6) give rise to enhanced photon yield. In particular, the 3s3p(6)4p(1)P(1) resonance at 26.6 eV allows a relative enhancement up to a factor of 30 in a 100 meV bandwidth compared to the characteristic photon emission of the neighboring harmonic order. This enhanced, spectrally isolated, and coherent photon emission line has a relative energy bandwidth of only ?E/E = 3 × 10(-3). Therefore, it might be very useful for applications such as precision spectroscopy or coherent diffractive imaging. The presented mechanism can be employed for tailoring and controlling the high harmonic emission of manifold target materials. PMID:24972203

Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Krebs, Manuel; Fritzsche, Stephan; Limpert, Jens; Tünnermann, Andreas

2014-06-13

122

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 2. Overview).  

SciTech Connect

The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best existing materials by investigating their structural and electronic properties using a full suite of characterization tools, and a parallel effort to discover and characterize new materials. (3) Combine these elements to examine the function of oxidation catalysts on Band-Gap-Narrowed Semiconductor (BGNSC) surfaces and elucidate the core scientific challenges to the efficient coupling of the materials functions.

Fujita,E.; Khalifah, P.; Lymar, S.; Muckerman, J.T.; Rodriguez, J.

2008-03-18

123

Band gap narrowing in zinc oxide-based semiconductor thin films  

NASA Astrophysics Data System (ADS)

A simple expression is proposed for the band gap narrowing (or shrinkage) in semiconductors using optical absorption measurements of spin coated 1 at. % Ga-doped ZnO (with additional 0-1.5 at. % zinc species) thin films as ?EBGN = Bn1/3 [1 - (nc/n)1/3], where B is the fitting parameter, n is carrier concentration, and nc is the critical density required for shrinkage onset. Its uniqueness lies in not only describing variation of ?EBGN correctly but also allowing deduction of nc automatically for several M-doped ZnO (M: Ga, Al, In, B, Mo) systems. The physical significance of the term [1 - (nc/n)1/3] is discussed in terms of carrier separation.

Kumar, Jitendra; Kumar Srivastava, Amit

2014-04-01

124

Efficient Phase-Encoding Quantum Key Generation with Narrow-Band Single Photons  

E-print Network

We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons. The key information is carried by the phase modulation directly on the single-photon temporal waveform without using any passive beam splitters or optical switches. We show that, when the technique is applied to the conventional fiber-based phase-encoding BB84 and differential phase shift (DPS) quantum key distribution schemes, the key generation efficiencies can be improved by a factor of 2 and 3, respectively. For N(>3)-period DPS systems, the key generation efficiency can be improved by a factor of N. The technique is suitable for quantum memory-based long-distance fiber communication system.

Hui Yan; Shi-Liang Zhu; Shengwang Du

2010-11-09

125

The method of narrow-band audio classification based on universal noise background model  

NASA Astrophysics Data System (ADS)

Audio classification is the basis of content-based audio analysis and retrieval. The conventional classification methods mainly depend on feature extraction of audio clip, which certainly increase the time requirement for classification. An approach for classifying the narrow-band audio stream based on feature extraction of audio frame-level is presented in this paper. The audio signals are divided into speech, instrumental music, song with accompaniment and noise using the Gaussian mixture model (GMM). In order to satisfy the demand of actual environment changing, a universal noise background model (UNBM) for white noise, street noise, factory noise and car interior noise is built. In addition, three feature schemes are considered to optimize feature selection. The experimental results show that the proposed algorithm achieves a high accuracy for audio classification, especially under each noise background we used and keep the classification time less than one second.

Rui, Rui; Bao, Chang-chun

2013-03-01

126

A center frequency adjustable narrow band filter for the detection of weak single frequency signal  

NASA Astrophysics Data System (ADS)

We describe and implement a center frequency adjustable narrow band filter based on the crystal filter for the detection of weak single frequency signal. It is formed by a multiplier, a direct digital frequency synthesizer, a multi-stage crystal bandpass filter, and a micro control unit which is used to set the center frequency of the filter. A theoretical study is proposed and experimentally validated. The test results show that the 3 db and 20 db bandwidths are 0.84 Hz and 2.73 Hz, respectively, and the filter system can effectively detect the signal with amplitude below 1 ?V and a frequency which ranges from 10 Hz to the frequency that is mainly limited by the components applied.

Xin, Yunhong; Xiang, ZhenMing; Dong, LeMing; Zhu, Bing; Cao, Hui; Fang, Yu

2014-04-01

127

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 1. Overview).  

SciTech Connect

The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best existing materials by investigating their structural and electronic properties using a full suite of characterization tools, and a parallel effort to discover and characterize new materials. (3) Combine these elements to examine the function of oxidation catalysts on Band-Gap-Narrowed Semiconductor (BGNSC) surfaces and elucidate the core scientific challenges to the efficient coupling of the materials functions.

Fujita,E.; Khalifah, P.; Lymar, S.; Muckerman, J.T.; Rodgriguez, J.

2008-03-18

128

Anomalous resistivity and the origin of heavy mass in the two-band Hubbard model with one narrow band  

SciTech Connect

We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron polaron effect and other mechanisms of mass enhancement (related to momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find the tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case for a large mismatch between the densities of heavy and light bands in the strong-coupling limit. We also observe that for low temperatures and equal densities, the homogeneous state resistivity R(T) {approx} T{sub 2} behaves in a Fermi-liquid fashion in both 3D and 2D cases. For temperatures higher than the effective bandwidth for heavy electrons T > W{sub *}{sup h}, the coherent behavior of the heavy component is totally destroyed. The heavy particles move diffusively in the surrounding of light particles. At the same time, the light particles scatter on the heavy ones as if on immobile (static) impurities. In this regime, the heavy component is marginal, while the light one is not. The resistivity saturates for T > W{sub *}{sup h} in the 3D case. In 2D, the resistivity has a maximum and a localization tail due to weak-localization corrections of the Altshuler-Aronov type. Such behavior of resistivity could be relevant for some uranium-based heavy-fermion compounds like UNi{sub 2}Al{sub 3} in 3D and for some other mixed-valence compounds possibly including layered manganites in 2D. We also briefly consider the superconductive (SC) instability in the model. The leading instability is towards the p-wave pairing and is governed by the enhanced Kohn-Luttinger mechanism of SC at low electron density. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light ones in 2D.

Kagan, M. Yu., E-mail: kagan@kapitza.ras.ru [Kapitza Institute for Physical Problems (Russian Federation); Val'kov, V. V. [Kirenskii Institute of Physics (Russian Federation)

2011-07-15

129

Energy transport in weakly nonlinear wave systems with narrow frequency band excitation  

NASA Astrophysics Data System (ADS)

A novel discrete model (D model) is presented describing nonlinear wave interactions in systems with small and moderate nonlinearity under narrow frequency band excitation. It integrates in a single theoretical frame two mechanisms of energy transport between modes, namely, intermittency and energy cascade, and gives the conditions under which each regime will take place. Conditions for the formation of a cascade, cascade direction, conditions for cascade termination, etc., are given and depend strongly on the choice of excitation parameters. The energy spectra of a cascade may be computed, yielding discrete and continuous energy spectra. The model does not require statistical assumptions, as all effects are derived from the interaction of distinct modes. In the example given—surface water waves with dispersion function ?2=gk and small nonlinearity—the D model predicts asymmetrical growth of side-bands for Benjamin-Feir instability, while the transition from discrete to continuous energy spectrum, excitation parameters properly chosen, yields the saturated Phillips’ power spectrum ˜g2?-5. The D model can be applied to the experimental and theoretical study of numerous wave systems appearing in hydrodynamics, nonlinear optics, electrodynamics, plasma, convection theory, etc.

Kartashova, Elena

2012-10-01

130

Dust In I Zw 18 From Hubble Space Telescope Narrow Band Imaging  

E-print Network

We present new WFPC2 narrow band imaging of the blue compact dwarf galaxy I Zw 18, which is host to the lowest-metallicity HII regions known. Images at H-alpha and H-beta are combined with archival broad band images to allow the study of the ionized gas distribution and morphology. Analysis of the H-alpha/H-beta flux ratio reveals significant enhancements in some areas of both the ``Northwest'' and ``Southeast'' regions of the galaxy, with ratios elevated to levels as high as 3.4. The H-alpha/H-beta ratio varies considerably with position throughout the galaxy. Comparing this distribution with the stellar distribution indicates that the regions of enhanced H-alpha/H-beta ratio are not due to the effects of either collisional excitation or underlying stellar absorption, and therefore are most likely interpreted as the presence of dust. This dust has an estimated mass of (2-5)x10^3 solar masses, which is consistent with the IRAS far-IR non-detection. Under the assumption that dust traces the presence of molecular gas, these results suggest that the molecular component of the ISM of I Zw 18, which is needed to fuel its active star formation, is also very clumpy. Such a distribution would be consistent with the recent FUSE non-detections of diffuse H_2.

John M. Cannon; Evan D. Skillman; Donald R. Garnett; Reginald J. Dufour

2001-09-28

131

Magnetic correlations between two Kondo impurities with two magnetic configurations: Narrow-band limit  

NASA Astrophysics Data System (ADS)

The lowest excitation energy and the magnetic correlations between two magnetic impurities are analyzed within the two-magnetic-impurity model Hamiltonian. The model includes two magnetic ions that can exist in two valence states and a band of conduction electrons. The two localized states represent the ground states of the ionic configurations (5f)n and (5f), assumed to be a doublet and a triplet, respectively. In the zero band-width limit, three parameters characterize this model: the energy difference between the magnetic configurations (?), the localized-extended-state hybridization energy (V), and the relationship between the Fermi wavelength and the distance r? between the magnetic ions (?=k·r?). For ??0, the strong coupling regime takes place and the physics that governs the ground state depends on ?/V. For V?-?, the highest spin configuration is favored, and the model shows a triplet ground state and the coexistence of strong ferromagnetic (F) correlations between the impurities with the Kondo physics of two magnetic impurities. For V<-?, with major charge fluctuations between the magnetic configurations, a singlet ground state occurs and antiferromagnetic (AF) correlations between the impurities appear. When ? increases, the decoupling of the impurities proceeds and decreases, finally for ?=?/2 the decoupled limit takes place and the model is reduced to two independent ions (=0). For a narrow region of ?/V, when ? increases, the model shows the crossover from singlet (AF) ground state to triplet (F) ground state.

Allub, R.

2013-07-01

132

A blue optical filter for narrow-band imaging in endoscopic capsules  

NASA Astrophysics Data System (ADS)

This paper presents the design, simulation, fabrication, and characterization of a thin-film Fabry-Perot resonator composed of titanium dioxide (TiO2) and silicon dioxide (SiO2) thin-films. The optical filter is developed to be integrated with a light emitting diode (LED) for enabling narrow-band imaging (NBI) in endoscopy. The NBI is a high resolution imaging technique that uses spectrally centered blue light (415 nm) and green light (540 nm) to illuminate the target tissue. The light at 415 nm enhances the imaging of superficial veins due to their hemoglobin absorption, while the light at 540 nm penetrates deeper into the mucosa, thus enhances the sub-epithelial vessels imaging. Typically the endoscopes and endoscopic capsules use white light for acquiring images of the gastrointestinal (GI) tract. However, implementing the NBI technique in endoscopic capsules enhances their capabilities for the clinical applications. A commercially available blue LED with a maximum peak intensity at 404 nm and Full Width Half Maximum (FWHM) of 20 nm is integrated with a narrow band blue filter as the NBI light source. The thin film simulations show a maximum spectral transmittance of 36 %, that is centered at 415 nm with FWHM of 13 nm for combined the blue LED and a Fabry Perot resonator system. A custom made deposition scheme was developed for the fabrication of the blue optical filter by RF sputtering. RF powered reactive sputtering at 200 W with the gas flows of argon and oxygen that are controlled for a 5:1 ratio gives the optimum optical conditions for TiO2 thin films. For SiO2 thin films, a non-reactive RF sputtering at 150 W with argon gas flow at 15 sccm results in the best optical performance. The TiO2 and SiO2 thin films were fully characterized by an ellipsometer in the wavelength range between 250 nm to 1600 nm. Finally, the optical performance of the blue optical filter is measured and presented.

Silva, M. F.; Ghaderi, M.; Goncalves, L. M.; de Graaf, G.; Wolffenbuttel, R. F.; Correia, J. H.

2014-05-01

133

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period  

PubMed Central

Background The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). Results The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0–20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. Conclusions The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. PMID:22920159

2012-01-01

134

Suberythemogenic narrow-band UVB is markedly more effective than conventional UVB in treatment of psoriasis vulgaris  

Microsoft Academic Search

Background: Narrow-band UVB (NB-UVB) is a new phototherapy option for psoriasis. Action spectrum studies previously done with different UVB wavelengths suggest that suberythemogenic doses of NB-UVB could be highly effective in treating psoriasis vulgaris. Even so, no comparative studies with suberythemogenic doses of NB versus conventional UVB have been performed previously. Objective: Our purpose was to compare conventional broad-band UVB

Ian B. Walters; Lauren H. Burack; Todd R. Coven; Patricia Gilleaudeau; James G. Krueger

1999-01-01

135

On the X-Ray Baldwin Effect for Narrow Fe Kalpha Emission Lines  

Microsoft Academic Search

Most active galactic nuclei (AGNs) exhibit a narrow Fe Kalpha line at ~6.4 keV in the X-ray spectra, due to the fluorescent emission from cold material far from the inner accretion disk. Using XMM-Newton observations, Page et al. found that the equivalent width (EW) of the narrow Fe Kalpha line decreases with increasing luminosity (EW~L-0.17+\\/-0.08), suggesting a decrease in the

P. Jiang; J. X. Wang; T. G. Wang

2006-01-01

136

Effects of Narrow Band UVB (311 nm) Irradiation on Epidermal Cells  

PubMed Central

Ultraviolet radiation (UVR) is known to be one of the most important environmental hazards acting on the skin. It was revealed that chronic exposure to UVR accelerates skin aging, induces immunosuppression and may lead to the development of skin cancers. On the other hand, UVR has been shown to be effective in the treatment of numerous skin diseases and thus, various phototherapy modalities have been developed to date. Narrow-band ultraviolet B (NB-UVB) emitting a light with a peak around 311 nm has been demonstrated to be effective in the treatment of various skin disorders; currently it is one of the most commonly used phototherapy devices. Despite NB-UVB has been developed more than 30 years ago, the exact mechanism of its therapeutic action remains poorly understood. To date, most of NB-UVB effects were attributed to its influence on immune cells; however, nearly 90% of NB-UVB irradiation is absorbed by epidermis and keratinocytes seem to be important players in mediating NB-UVB biological activity. Here, we have reviewed the current data about the influence of NB-UVB on epidermal cells, with a special emphasis on cell proliferation and death. PMID:23594996

Reich, Adam; Medrek, Karolina

2013-01-01

137

Visualization of mucosal vasculature with narrow band imaging: a theoretical study  

NASA Astrophysics Data System (ADS)

Narrow band imaging (NBI) is a spectrally-selective reflectance imaging technique that is used as an adjunctive approach to endoscopic detection of mucosal abnormalities such as neoplastic lesions. While numerous clinical studies in tissue sites such as the esophagus, oral cavity and lung indicate the efficacy of this approach, it is not well theoretically understood. In this study, we performed Monte Carlo simulations to elucidate the factors that affect NBI device performance. The model geometry involved a two-layer turbid medium based on mucosal tissue optical properties and embedded cylindrical, blood-filled vessels at varying diameters and depths. Specifically, we studied the effect of bandpass filters (415+/-15 nm, 540+/-10 nm versus white light), blood vessel diameter (20-400 ?m) and depth (30 - 450 ?m), wavelength, and bandwidth on vessel contrast. Our results provide a quantitative evaluation of the two mechanisms that are commonly believed to be the primary components of NBI: (i) the increased contrast provided by high hemoglobin absorption and (ii) increase in the penetration depth produced by the decrease in scattering with increasing wavelength. Our MC model can provide novel, quantitative insight into NBI, may lead to improvements in its performance.

Wang, Quanzeng; Le, Du; Ramella-Roman, Jessica; Pfefer, Joshua

2012-03-01

138

NICMOS Narrow-band Infrared Photometry of TW Hya Association Stars  

E-print Network

We have obtained 1.64, 1.90 and 2.15 micron narrow-band images of five T Tauri stars in the TW Hya Association (TWA) using the Near-Infrared Camera and Multiobject Spectrometer aboard the Hubble Space Telescope. Most of the T Tauri stars in our study show evidence of absorption by H2O vapor in their atmospheres; in addition, the low-mass brown dwarf candidate, TWA 5B, is brighter at 1.9 microns than predicted by cool star models that include the effects of H2O vapor but neglect dust. We conclude that the effect of atmospheric dust on the opacity is important at 1.9 microns for TWA 5B, the coolest object in our sample. The available evidence suggests that the TWA is 5-15 MY old. Comparison of the colors of TWA 5B with theoretical magnitudes as a function of age and mass then confirms previous claims that TWA 5B is substellar with a mass in the range 0.02-0.03 solar masses. The accurate single-epoch astrometry of the relative positions and separation of TWA 5A and TWA 5B reported here should permit the direct measurement of the orbital motion of TWA 5B within only a few years.

David A. Weintraub; Didier Saumon; Joel H. Kastner; Thierry Forveille

2000-02-03

139

Interpreting motion and force for narrow-band intermodulation atomic force microscopy  

PubMed Central

Summary Intermodulation atomic force microscopy (ImAFM) is a mode of dynamic atomic force microscopy that probes the nonlinear tip–surface force by measurement of the mixing of multiple modes in a frequency comb. A high-quality factor cantilever resonance and a suitable drive comb will result in tip motion described by a narrow-band frequency comb. We show, by a separation of time scales, that such motion is equivalent to rapid oscillations at the cantilever resonance with a slow amplitude and phase or frequency modulation. With this time-domain perspective, we analyze single oscillation cycles in ImAFM to extract the Fourier components of the tip–surface force that are in-phase with the tip motion (F I) and quadrature to the motion (F Q). Traditionally, these force components have been considered as a function of the static-probe height only. Here we show that F I and F Q actually depend on both static-probe height and oscillation amplitude. We demonstrate on simulated data how to reconstruct the amplitude dependence of F I and F Q from a single ImAFM measurement. Furthermore, we introduce ImAFM approach measurements with which we reconstruct the full amplitude and probe-height dependence of the force components F I and F Q, providing deeper insight into the tip–surface interaction. We demonstrate the capabilities of ImAFM approach measurements on a polystyrene polymer surface. PMID:23400552

Forchheimer, Daniel; Tholén, Erik A; Haviland, David B

2013-01-01

140

Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data  

E-print Network

In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95$\\%$ confidence level upper limits have been computed both assuming polarization parameters are completely unknown and that they are known with some uncertainty, as derived from X-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of two below the spin-down limit, and represent a significant improv...

Aasi, J; Abbott, R; Abbott, T; Abernathy, M R; Acernese, F; Ackley, K; Adams, C; Adams, T; Adams, T; Addesso, P; Adhikari, R X; Adya, V; Affeldt, C; Agathos, M; Agatsuma, K; Aggarwal, N; Aguiar, O D; Ain, A; Ajith, P; Alemic, A; Allen, B; Allocca, A; Amariutei, D; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J S; Ashton, G; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Aylott, B E; Babak, S; Baker, P T; Baldaccini, F; Ballardin, G; Ballmer, S W; Barayoga, J C; Barbet, M; Barclay, S; Barish, B C; Barker, D; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Bartlett, J; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J C; Bauer, Th S; Baune, C; Bavigadda, V; Behnke, B; Bejger, M; Belczynski, C; Bell, A S; Bell, C; Benacquista, M; Bergman, J; Bergmann, G; Berry, C P L; Bersanetti, D; Bertolini, A; Betzwieser, J; Bhagwat, S; Bhandare, R; Bilenko, I A; Billingsley, G; Birch, J; Biscans, S; Bitossi, M; Biwer, C; Bizouard, M A; Blackburn, J K; Blackburn, L; Blair, C D; Blair, D; Bloemen, S; Bock, O; Bodiya, T P; Boer, M; Bogaert, G; Bojtos, P; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, Sukanta; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brau, J E; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Brooks, A F; Brown, D A; Brown, D D; Brown, N M; Buchman, S; Buikema, A; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Cadonati, L; Cagnoli, G; Bustillo, J Calderón; Calloni, E; Camp, J B; Cannon, K C; Cao, J; Capano, C D; Carbognani, F; Caride, S; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chamberlin, S J; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Cho, M; Chow, J H; Christensen, N; Chu, Q; Chua, S; Chung, S; Ciani, G; Clara, F; Clark, J A; Cleva, F; Coccia, E; Cohadon, P -F; Colla, A; Collette, C; Colombini, M; Cominsky, L; Constancio,, M; Conte, A; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J -P; Countryman, S; Couvares, P; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Creighton, T D; Cripe, J; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Cutler, C; Dahl, K; Canton, T Dal; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dartez, L; Dattilo, V; Dave, I; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; DeBra, D; Debreczeni, G; Degallaix, J; De Laurentis, M; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; De Rosa, R; DeRosa, R T; DeSalvo, R; Dhurandhar, S; Díaz, M; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Dojcinoski, G; Dolique, V; Dominguez, E; Donovan, F; Dooley, K L; Doravari, S; Douglas, R; Downes, T P; Drago, M; Driggers, J C; Du, Z; Ducrot, M; Dwyer, S; Eberle, T; Edo, T; Edwards, M; Edwards, M; Effler, A; Eggenstein, H -B; Ehrens, P; Eichholz, J; Eikenberry, S S; Essick, R; Etzel, T; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fays, M; Fehrmann, H; Fejer, M M; Feldbaum, D; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Fiori, I; Fisher, R P; Flaminio, R; Fournier, J -D; Franco, S; Frasca, S; Frasconi, F; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fuentes-Tapia, S; Fulda, P; Fyffe, M; Gair, J R; Gammaitoni, L; Gaonkar, S; Garufi, F; Gatto, A; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; Gergely, L Á; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Gräf, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greco, G; Greenhalgh, R J S; Gretarsson, A M; Groot, P; Grote, H; Grunewald, S; Guidi, G M; Guido, C J; Guo, X; Gushwa, K; Gustafson, E K; Gustafson, R; Hacker, J; Hall, E D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Hardwick, T; Harms, J; Harry, G M; Harry, I W; Hart, M; Hartman, M T; Haster, C -J; Haughian, K; Hee, S; Heidmann, A; Heintze, M; Heinzel, G; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hewitson, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Hollitt, S E; Holt, K; Hopkins, P; Hosken, D J; Hough, J; Houston, E; Howell, E J; Hu, Y M; Huerta, E; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Idrisy, A; Indik, N; Ingram, D R; Inta, R; Islas, G; Isler, J C; Isogai, T; Iyer, B R; Izumi, K; Jacobson, M; Jang, H; Jaranowski, P; Jawahar, S; Ji, Y; Jiménez-Forteza, F; Johnson, W W; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Keiser, G M; Keitel, D; Kelley, D B; Kells, W

2014-01-01

141

Gas Distributions in Comet ISON’s Coma: Concurrent Integral-Field Spectroscopy and Narrow-band Imaging.  

NASA Astrophysics Data System (ADS)

At a solar distance of 0.44 AU, Oort cloud comet C/2012 S1 (ISON) exhibited an outburst phase that was observed by small telescopes at the McDonald Observatory. In conjunction with narrow-band (14Å) imaging over a wide-field, an image-slicer spectrograph ( 20,000) simultaneously measured the spatial distribution of ISON’s coma over a 1.6 x 2.7 arcminute field made up of 246 individual spectra. More than fifty emission lines from C2, NH2, CO, H2O+ and Na were observed within a single Echelle order spanning 5868Å to 5930Å. Spatial reconstructions of these species reveal that ISON’s coma was quite elongated several thousand km along the axis perpendicular to its motion. The ion tail appeared distinctly broader than the neutral Na tail, providing strong evidence that Na in the coma did not originate by dissociative recombination of a sodium bearing molecular ion. Production rates increased from 1.6 ± 0.3 x 1023 to 5.8 ± 1 x 1023 Na atoms/s within 24 hours, outgassing much less than comparable comets relative to ISON’s water production. The anti-sunward Na tail was imaged >106 km from the nucleus. Its distribution indicates origins both near the nucleus and in the dust tail, with the ratio of these Na sources varying on hourly timescales due to outburst activity.

Schmidt, Carl; Johnson, Robert E.; Baumgardner, Jeffrey; Mendillo, Michael

2014-11-01

142

ATA Memo #37 ---7 December 2001 Simulations of NarrowBand PhasedArray Null Formation for the ATA  

E-print Network

narrow band. However, the compact configuration of the Allen Telescope Array sets the difference between A = e T ; (5) where A is an array of steering vectors s l = exp(i2�fø g ) and e is a vector [1; 0; 0

Bower, Geoffrey

143

IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS 1 Narrow-Band Frequency Analysis for White-Light  

E-print Network

IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS 1 Narrow-Band Frequency Analysis for White-Light. There has been research in the determination of precancerous tissue using white-light spectroscopy as an optical biopsy. In this paper, we in- vestigate white light scattering off of tissue phantoms, created

Kurzweg, Timothy P.

144

Nitric oxide gamma and delta band emission at twilight  

NASA Technical Reports Server (NTRS)

Nitric oxide twilight emission above 140 km in the gamma- and delta-bands was observed with a rocket-borne spectrophotometer. The relative intensity of the two band systems indicates that the emission is produced predominantly by the chemiluminescent preassociation of oxygen and nitrogen atoms.

Feldman, P. D.; Takacs, P. Z.

1974-01-01

145

Multicolor Fluorescent Semiconducting Polymer Dots with Narrow Emissions and High Brightness  

PubMed Central

Fluorescent semiconducting polymer dots (Pdots) have attracted great interest because of their superior characteristics as fluorescent probes, such as high fluorescence brightness, fast radiative rates, and excellent photostability. However, currently available Pdots generally exhibit broad emission spectra, which significantly limit their usefulness in many biological applications involving multiplex detections. Here, we describe the design and development of multicolor narrow emissive Pdots based on different boron-dipyrromethene (BODIPY) units. BODIPY-containing semiconducting polymers emitting at multiple wavelengths were synthesized and used as precursors for preparing the Pdots, where intra-particle energy transfer led to highly bright, narrow emissions. The emission full-width at half maximum (FWHM) of the resulting Pdots varies from 40 nm to 55 nm, which is 1.5~2 times narrower than those of conventional semiconducting polymer dots. BODIPY520 Pdots was about an order of magnitude brighter than commercial Qdot 525 under identical laser excitation conditions. Fluorescence imaging and flow cytometry experiments indicate the narrow emissions from these bright Pdots are promising for multiplexed biological detections. PMID:23282278

Rong, Yu; Wu, Changfeng; Yu, Jiangbo; Zhang, Xuanjun; Ye, Fangmao; Zeigler, Maxwell; Gallina, Maria Elena; Wu, I-Che; Zhang, Yong; Chan, Yang-Hsiang; Sun, Wei; Uvdal, Kajsa; Chiu, Daniel T.

2013-01-01

146

Development of inexpensive optical broad- and narrow-band sensors for ecosystem research  

NASA Astrophysics Data System (ADS)

The observation and monitoring of ecosystem processes are great challenges in environmental science, due to the dynamic and complexity of such procedures. To describe and understand biotic and abiotic processes and their interaction it is necessary to acquire multiple parameters, which are influencing the natural regime. Essential issues are: the detection of spatial heterogeneities and scale overlapping procedures in the environment. To overcome these problems an adequate monitoring system should cover a representative area as well as have a sufficient resolution in time and space. Hence, the needed quantity of sensors (depending on the observed parameters or processes) can be enormous. According to these issues, there is a high demand on low-cost sensor technologies (with adequate performances) to realize a delicate monitoring platform. In the case of vegetation processes, one key feature is to characterize photosynthetic activity of the plants in detail. Common investigation methods are based on optical measurements. Here photosynthetically active radiation (PAR) sensors and hyperspectral sensors are in major use. Photosynthetically active radiation (solar radiation from 400 to 700 nanometers) designates the spectral range that photosynthetic organisms are able to use in the process of photosynthesis. PAR sensors enable the detection of the reflected solar light of the vegetation in whole the PAR wave band. The amount of absorption indicates photosynthetic activity of the plant. Hyperspectral sensors observe specific parts of the solar light spectrum and facilitate the determination of the main pigment classes (Chlorophyll, Carotenoid and Anthocyanin). Due to absorption of pigments they producing a specific spectral signature in the visible part of the electromagnetic spectrum (narrow-band peaks). If vegetation is affected by water or nutritional deficience the proportion of light-absorbing pigments is reduced which finally results in an overall reduced light absorption. The resulting spectral signature then differs from usual reflectance patterns and can be used as stress indicator. Hence, reflectances between 550-700 nm are extremely sensitive regarding changing Chlorophyll contents. Both kinds of sensors based on semiconductor technologies whereby the material input can kept on low level. This work presents the development and testing of a practical, rugged, and inexpensive PAR and hyperspectral sensor. The sensors were made from a gallium arsenide phosphide (GaAsP) photodiodes and silicon photodiodes with different interference filters. First results of recorded long term in-situ data and linear regressions (in comparison to commercial products) show extremely high performances (coefficient of determination higher than 0.99) of the PAR sensors simultaneous to the cost cutting.

Mollenhauer, Hannes; Cuntz, Thomas; Bumberger, Jan

2014-05-01

147

Narrow-band imaging for the computer assisted diagnosis in patients with Barrett's esophagus  

NASA Astrophysics Data System (ADS)

Cancer of the esophagus has the worst prediction of all known cancers in Germany. The early detection of suspicious changes in the esophagus allows therapies that can prevent the cancer. Barrett's esophagus is a premalignant change of the esophagus that is a strong indication for cancer. Therefore there is a big interest to detect Barrett's esophagus as early as possible. The standard examination is done with a videoscope where the physician checks the esophagus for suspicious regions. Once a suspicious region is found, the physician takes a biopsy of that region to get a histological result of it. Besides the traditional white light for the illumination there is a new technology: the so called narrow-band Imaging (NBI). This technology uses a smaller spectrum of the visible light to highlight the scene captured by the videoscope. Medical studies indicate that the use of NBI instead of white light can increase the rate of correct diagnoses of a physician. In the future, Computer-Assisted Diagnosis (CAD) which is well known in the area of mammography might be used to support the physician in the diagnosis of different lesions in the esophagus. A knowledge-based system which uses a database is a possible solution for this task. For our work we have collected NBI images containing 326 Regions of Interest (ROI) of three typical classes: epithelium, cardia mucosa and Barrett's esophagus. We then used standard texture analysis features like those proposed by Haralick, Chen, Gabor and Unser to extract features from every ROI. The performance of the classification was evaluated with a classifier using the leaving-one-out sampling. The best result that was achieved is an accuracy of 92% for all classes and an accuracy of 76% for Barrett's esophagus. These results show that the NBI technology can provide a good diagnosis support when used in a CAD system.

Kage, Andreas; Raithel, Martin; Zopf, Steffen; Wittenberg, Thomas; Münzenmayer, Christian

2009-02-01

148

Superconductivity in narrow-band systems with local nonretarded attractive interactions  

NASA Astrophysics Data System (ADS)

In narrow-band systems electrons can interact with each other via a short-range nonretarded attractive potential. The origin of such an effective local attraction can be polaronic or it can be due to a coupling between electrons and excitons or plasmons. It can also result from purely chemical (electronic) mechanisms, especially in compounds with elements favoring disproportionation of valent states. These mechanisms are discussed and an exhaustive list of materials in which such local electron pairing occurs is given. The authors review the thermodynamic and electromagnetic properties of such systems in several limiting scenarios: (i) Systems with on-site pairing which can be described by the extended negative-U Hubbard model. The strong-attraction limit of this model, at which it reduces to a system of tightly bound electron pairs (bipolarons) on a lattice, is extensively discussed. These electron pairs behaving as hard-core charged bosons can exhibit a superconducting state analogous to that of superfluid 4He II. The change-over from weak-attraction BCS-like superconductivity to the superfluidity of charged hard-core bosons is examined. (ii) Systems with intersite pairing described by an extended Hubbard model with U>0 and nearest-neighbor attraction and/or nearest-neighbor spin exchange as well as correlated hopping. (iii) A mixture of local pairs and itinerant electrons interacting via a charge-exchange mechanism giving rise to a mutually induced superconductivity in both subsystems. The authors discuss to what extent the picture of local pairing, and in particular superfluidity of hard-core charged bosons on a lattice, can be an explanation for the superconducting and normal-state properties of the high-Tc oxides: doped BaBiO3 and the cuprates.

Micnas, R.; Ranninger, J.; Robaszkiewicz, S.

1990-01-01

149

Assessing the temperature dependence of narrow-band Raman water vapor lidar measurements: a practical approach.  

PubMed

Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author. PMID:23913054

Whiteman, David N; Venable, Demetrius D; Walker, Monique; Cadirola, Martin; Sakai, Tetsu; Veselovskii, Igor

2013-08-01

150

Investigation of relationships among gastroesophageal reflux disease subtypes using narrow band imaging magnifying endoscopy  

PubMed Central

AIM: To investigate the relationships among subtypes of gastroesophageal reflux disease (GERD) using narrow band imaging (NBI) magnifying endoscopy. METHODS: A reflux disease questionnaire was used to screen 120 patients representing the three subtypes of GERD (n = 40 for each subtypes): nonerosive reflux disease (NERD), reflux esophagitis (RE) and Barrett’s esophagus (BE). NBI magnifying endoscopic procedure was performed on the patients as well as on 40 healthy controls. The demographic and clinical characteristics, and NBI magnifying endoscopic features, were recorded and compared among the groups. Targeted biopsy and histopathological examination were conducted if there were any abnormalities. SPSS 18.0 software was used for all statistical analysis. RESULTS: Compared with healthy controls, a significantly higher proportion of GERD patients had increased number of intrapapillary capillary loops (IPCLs) (78.3% vs 20%, P < 0.05), presence of microerosions (41.7% vs 0%, P < 0.05), and a non-round pit pattern below the squamocolumnar junction (88.3% vs 30%, P < 0.05). The maximum (228 ± 4.8 vs 144 ± 4.7, P < 0.05), minimum (171 ± 3.8 vs 103 ± 4.4, P < 0.05), and average (199 ± 3.9 vs 119 ± 3.9, P < 0.05) numbers of IPCLs/field were also significantly greater in GERD patients. However, comparison among groups of the three subtypes showed no significant differences or any linear trend, except that microerosions were present in 60% of the RE patients, but in only 35% and 30% of the NERD and BE patients, respectively (P < 0.05). CONCLUSION: Patients with GERD, irrespective of subtype, have similar micro changes in the distal esophagus. The three forms of the disease are probably independent of each other. PMID:24363532

Lv, Jing; Liu, Dong; Ma, Shi-Yang; Zhang, Jun

2013-01-01

151

Nitric oxide gamma band emission in an aurora  

NASA Technical Reports Server (NTRS)

Emission of the NO gamma (1,0) band at 2150 A has been observed by a rocket-borne spectrophotometer in an IBC II(+) aurora. The nu-prime progression of the gamma-system does not appear in the spectrum. The observed emission rate of the 2150 A feature increases relative to N2(+) first negative band emission with increasing altitude. We suggest radiative recombination of NO(+) ions with electrons as a possible excitation mechanism compatible with the data.

Feldman, P. D.

1976-01-01

152

AVHRR Surface Temperature and Narrow-Band Albedo Comparison with Ground Measurements for the Greenland Ice Sheet  

NASA Technical Reports Server (NTRS)

An ice-surface temperature retrieval algorithm for the Greenland ice sheet was developed using NOAA 11 thermal radiances from channels 4 and 5. Temperature, pressure and humidity profiles, cloud observations and skin temperatures from the Swiss Federal Institute of Technology (ETH) camp, located at the equilibrium line altitude at 49 deg17 min W, 69 deg 34 min N, were used in the LOWTRAN 7 model. Through a statistical analysis of daily clear sky profiles, the coefficients that correct for the atmospheric effects were determined for the ETH-Camp field season (May to August). Surface temperatures retrieved by this method were then compared against the in situ observations with a maximum difference of 0.6 K. The NOAA 11 narrow-band planetary albedo values for channels 1 and 2 were calculated using pre-launch calibration coefficients. Scattering and absorption by the atmosphere were modelled with LOWTRAN 7. Then, narrow-band albedo values for the AVHRR visible and near infrared channels were compared with in situ high resolution spectral reflectance measurements. In the visible band (580-680 nm), AVHRR-derived narrow-band albedo and the in situ measurements corrected with radiative transfer model LOWTRAN 7 showed a difference of less than 2%. For the near infrared channel (725-1100 nm) the difference between the measured and modelled narrow-band albedo was 14%. These discrepancies could be either the result of inaccurate aerosol scattering modelling (lack of the in situ observation), or the result of sensor drift due to degradation.

Haefliger, M.; Steffen, K.; Fowler, C.

1993-01-01

153

An inexpensive S-band angle pointing technique for steering a narrow beam Ku-band antenna  

NASA Technical Reports Server (NTRS)

A recently tested antenna pointing control system for gimbaled antennas has been developed. A modified TDRSS user transponder produces pointing error signals from the S-band forward link which in turn drive the Steering Control Electronics (SCE) to precision steer a S-/Ku-band Data and S-band Tracking (KDST) planar array. A successful test of the pointing and data handling capabilities is described and plans for further tests, incorporating additional refinements, are presented.

Line, Larry; Hager, Fred; Hanson, Duke; Kral, Kevin; Moss, Robert

1987-01-01

154

An inexpensive S-band angle pointing technique for steering a narrow beam Ku-band antenna  

NASA Astrophysics Data System (ADS)

A recently tested antenna pointing control system for gimbaled antennas has been developed. A modified TDRSS user transponder produces pointing error signals from the S-band forward link which in turn drive the Steering Control Electronics (SCE) to precision steer a S-/Ku-band Data and S-band Tracking (KDST) planar array. A successful test of the pointing and data handling capabilities is described and plans for further tests, incorporating additional refinements, are presented.

Line, Larry; Hager, Fred; Hanson, Duke; Kral, Kevin; Moss, Robert

155

Electrochemical Capacitance Voltage Profiling of the Narrow Band Gap Semiconductor InAsJournal of ELECTRONIC MATERIALS, Vol. 29, No. 11, 2000  

E-print Network

. Key words: InAs, CV profiling, ECV profiling teract with chemical impurities, and doping of InAs has1333 Electrochemical Capacitance Voltage Profiling of the Narrow Band Gap Semiconductor In Profiling of the Narrow Band Gap Semiconductor InAs V. GOPAL,1 E.-H. CHEN,2 E.P. KVAM,1,3 and J.M. WOODALL2

Woodall, Jerry M.

156

Narrow-band imaging with magnifying endoscopy is accurate for detecting gastric intestinal metaplasia  

PubMed Central

AIM: To investigate the predictive value of narrow-band imaging with magnifying endoscopy (NBI-ME) for identifying gastric intestinal metaplasia (GIM) in unselected patients. METHODS: We prospectively evaluated consecutive patients undergoing upper endoscopy for various indications, such as epigastric discomfort/pain, anaemia, gastro-oesophageal reflux disease, suspicion of peptic ulcer disease, or chronic liver diseases. Patients underwent NBI-ME, which was performed by three blinded, experienced endoscopists. In addition, five biopsies (2 antrum, 1 angulus, and 2 corpus) were taken and examined by two pathologists unaware of the endoscopic findings to determine the presence or absence of GIM. The correlation between light blue crest (LBC) appearance and histology was measured. Moreover, we quantified the degree of LBC appearance as less than 20% (+), 20%-80% (++) and more than 80% (+++) of an image field, and the semiquantitative evaluation of LBC appearance was correlated with IM percentage from the histological findings. RESULTS: We enrolled 100 (58 F/42 M) patients who were mainly referred for gastro-esophageal reflux disease/dyspepsia (46%), cancer screening/anaemia (34%), chronic liver disease (9%), and suspected celiac disease (6%); the remaining patients were referred for other indications. The prevalence of Helicobacter pylori (H. pylori) infection detected from the biopsies was 31%, while 67% of the patients used proton pump inhibitors. LBCs were found in the antrum of 33 patients (33%); 20 of the cases were classified as LBC+, 9 as LBC++, and 4 as LBC+++. LBCs were found in the gastric body of 6 patients (6%), with 5 of them also having LBCs in the antrum. The correlation between the appearance of LBCs and histological GIM was good, with a sensitivity of 80% (95%CI: 67-92), a specificity of 96% (95%CI: 93-99), a positive predictive value of 84% (95%CI: 73-96), a negative predictive value of 95% (95%CI: 92-98), and an accuracy of 93% (95%CI: 90-97). The NBI-ME examination overlooked GIM in 8 cases, but the GIM was less than 5% in 7 of the cases. Moreover, in the 6 false positive cases, the histological examination showed the presence of reactive gastropathy (4 cases) or H. pylori active chronic gastritis (2 cases). The semiquantitative correlation between the rate of LBC appearance and the percentage of GIM was 79% (P < 0.01). CONCLUSION: NBI-ME achieved good sensitivity and specificity in recognising GIM in an unselected population. In routine clinical practice, this technique can reliably target gastric biopsies. PMID:23674874

Savarino, Edoardo; Corbo, Marina; Dulbecco, Pietro; Gemignani, Lorenzo; Giambruno, Elisa; Mastracci, Luca; Grillo, Federica; Savarino, Vincenzo

2013-01-01

157

Spectrally narrowed emissions from organic crystals mounted on transfer-printed parylene diffraction gratings  

NASA Astrophysics Data System (ADS)

We have fabricated diffraction gratings of parylene by evaporation polymerization. The parylene film was deposited onto a commercially available diffraction grating used as a template and transfer-printed onto a substrate. A well-defined periodic structure was replicated on the parylene film surface and its period was in good agreement with that of the template. For future light-emitting device application, we laminated a parylene grating with organic semiconductor crystals and investigated their emission properties under weak ultraviolet light excitation. We observed emissions parallel to the grating wave vector. Their spectra narrowed as peaks with full-widths at half-maxima less than 5 nm. We discussed these narrow emission lines considering them as the propagating light in a waveguide composed of the organic crystal and parylene grating. The present results reflect the formation of a high-quality optical cavity on a parylene film.

Fukaya, Yoshihide; Obama, Yuki; Hotta, Shu; Yamao, Takeshi

2014-01-01

158

Narrow-Band Survey of the GOODS Fields: Search for Lyman-Alpha Emitters at z = 5.7  

E-print Network

We present results from optical narrow-band lambda_c = 8150A ~ and Delta lambda = 120A) observations of the Great Observatories Origins Deep Survey (GOODS) fields, using Suprime-Cam on the Subaru Telescope. Using these narrow-band data, we then perform a survey of Lyman alpha Emitters (LAEs) at z~5.7. The LAE survey covers an area of approx 320 arcmin^2 and a co-moving volume of ~8.0 x 10^4 Mpc^3. We found a total of 10 (GOODS-N) and 4 (GOODS-S) LAE candidates at z~5.7. We perform a study of the spatial distribution, space density, and star formation properties of the LAEs at z~5.7.

Masaru Ajiki; Bahram Mobasher; Yoshiaki Taniguchi; Yasuhiro Shioya; Tohru Nagao; Takashi Murayama; Shunji S. Sasaki

2005-10-24

159

Optical absorption and x-ray diffraction in narrow-band-gap InAs\\/GaSb superlattices  

Microsoft Academic Search

We report on the optical transmission properties of narrow-band-gap (Eg<0.1 eV) InAs\\/GaSb superlattices grown by molecular-beam epitaxy. Energy band gaps of 0.15 and 0.085 eV at 4.8 K are determined for a 102-A?-period and a 124-A?-period superlattice, respectively. The absorption edge is extremely soft due to the spatial mismatch of hole and electron wave functions. In addition we show the

D. K. Arch; G. Wicks; Tom Tonaue; Jean-Louis Staudenmann

1985-01-01

160

On the characteristic functional of a doubly stochastic Poisson process: Application to a narrow-band process  

Microsoft Academic Search

The characteristic functional (c.fl.) of a doubly stochastic Poisson process (DSPP) is studied and it provides us the finite dimensional distributions of the process and so its moments. It is also studied the case of a DSPP which intensity is a narrow-band process. The Karhunen–Loève expansion of its intensity is used to obtain the probability distribution function and a decomposition

P. R. Bouzas; M. J. Valderrama; A. M. Aguilera

2006-01-01

161

Phasing segmented mirrors: a modification of the Keck narrow-band technique and its application to extremely large telescopes  

Microsoft Academic Search

Future telescopes with diameters greater than 10 m, usually referred to as extremely large telescopes (ELTs), will employ segmented mirrors made up of hundreds or even thousands of segments, with tight constraints on the piston errors between individual segments. The 10-m Keck telescopes are routinely phased with the narrow-band phasing technique. This is a variation of the Shack-Hartmann wave-front sensor

Achim Schumacher; Nicholas Devaney; Luzma Montoya

2002-01-01

162

Synthesis of narrow band-gap III-V semiconductors using metal-organic vapor phase epitaxy  

Microsoft Academic Search

The synthesis of narrow band gap materials in particular InAs, GaSb and InSb has been studied using metal-organic vapor phase epitaxy (MOVPE). Typically, for device applications these materials are grown on SI GaAs substrates. The integration of these materials with GaAs substrates through direct epitaxial growth is plagued by the high density of defects that are formed due to the

Smita Jha

2010-01-01

163

Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground  

E-print Network

(Abridged) We observed one transit and one occultation of the hot Jupiter WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2-meter telescope. From the transit event, we have independently derived WASP-43's system parameters with high precision, and improved the period to be 0.81347437(13) days. No significant variation in transit depths is detected, with the largest deviations coming from the i', H, and K bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either a flat featureless straight line that indicates thick clouds, synthetic spectra with absorption signatures of atomic Na/K or molecular TiO/VO that indicate cloud-free atmosphere, or a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we have detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197 +/- 0.042%, which confirms previous detections obtained in the 2.09 micron narrow band and K...

Chen, Guo; Wang, Hongchi; Nikolov, Nikolay; Fortney, Jonathan J; Seemann, Ulf; Wang, Wei; Mancini, Luigi; Henning, Thomas

2014-01-01

164

Crystal growth and characterization of the narrow-band-gap semiconductors OsPn? (Pn = P, As, Sb).  

PubMed

Using metal fluxes, crystals of the binary osmium dipnictides OsPn2 (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn6 octahedra, as well as [Pn2(4-)] anions. Raman spectroscopy shows the presence of P-P single bonds, consistent with the presence of [Pn2(-4)] anions and formally Os(4+) cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2 and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn2 dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a Pn-Pn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment. PMID:25162930

Bugaris, Daniel E; Malliakas, Christos D; Shoemaker, Daniel P; Do, Dat T; Chung, Duck Young; Mahanti, Subhendra D; Kanatzidis, Mercouri G

2014-09-15

165

On the narrow emission line components of the LMC novae 2004 (YY Doradus) and 2009a  

NASA Astrophysics Data System (ADS)

We present early decline spectra of the two Large Magellanic Cloud novae: LMC 2004 (YY Dor) and LMC 2009a and discuss their spectral an line profile evolution with special emphasis on the existence and appearance of a sharp component. We show that the narrow component that characterizes the emission lines in the maximum spectra of nova LMC 2004 originates in the ejecta. The He ii 4686 Å narrow emission which appears at the onset of the nebular phase in both novae is somewhat controversial. Our observations suggest that the corresponding line forming region is physically separated from the rest of the ejecta (the broad line region) and environmentally different. However, the lack of late time observations covering the super-soft source (SSS) phase, the post-SSS phase and the quiescence state does not allow to securely establish any non-ejecta origin/contribution as, instead, in the case of U Sco and KT Eri.

Mason, Elena; Munari, Ulisse

2014-09-01

166

On the narrow emission line components of the LMC novae 2004 (YY Dor) and 2009a  

E-print Network

We present early decline spectra of the two Large Magellanic Cloud novae: LMC 2004 (YY Dor) and LMC 2009a and discuss their spectral an line profile evolution with special emphasis on the existence and appearance of a sharp component. We show that the narrow component that characterizes the emission lines in the maximum spectra of nova LMC 2004 originates in the ejecta. The HeII 4686 A, narrow emission which appears at the onset of the nebular phase in both novae is somewhat controversial. Our observations suggest that the corresponding line forming region is physically separated from the rest of the ejecta (the broad line region) and environmentally different. However, the lack of late time observations covering the super-soft source (SSS) phase, the post-SSS phase and the quiescence state does not allow to securely establish any non-ejecta origin/contribution as, instead, in the case of U Sco and KT Eri.

Mason, Elena

2014-01-01

167

Band limited emission with central frequency around 2 Hz accompanying powerful cyclones  

NASA Technical Reports Server (NTRS)

It has been found that powerful cyclones are proceeded, accompanied and followed by narrow band electromagnetic emission with central frequency around 2 Hz. It is shown that the signal from this emission is unique and clearly distinguishable from known types of magnetic pulsations, spectra of local thunderstorms, and signals from industrial sources. This emission was first observed during an unusually powerful cyclone with tornadoes in the western European part of the Soviet Union, which passed by the observatory of Borok from south to north-east. The emission has been confirmed by analysis of similar events in Antarctica. The phenomenon described presents a new aspect of interactions of processes in the lower atmosphere and the ionosphere.

Troitskaia, V. A.; Shepetnov, K. S.; Dvobnia, B. D.

1992-01-01

168

Imaging chlorophyll fluorescence with an airborne narrow-band multispectral camera for vegetation stress detection  

Microsoft Academic Search

Progress in assessing the feasibility for imaging fluorescence using the O2-A band with 1 nm full-width half-maximum (FWHM) bands centered at 757.5 and 760.5 nm is reported in this paper. Multispectral airborne data was acquired at 150 m above ground level in the thermal, visible and near infrared regions yielding imagery at 15 cm spatial resolution. Simultaneous field experiments conducted in olive, peach, and

P. J. Zarco-Tejada; J. A. J. Berni; L. Suárez; G. Sepulcre-Cantó; F. Morales; J. R. Miller

2009-01-01

169

Ultrafast photoluminescence upconversion measurements of carrier dynamics in narrow band-gap semiconductor nanostructures  

Microsoft Academic Search

An ultrafast mid wavelength infrared photoluminescence (PL) upconversion technique has been developed to study carrier recombination, hot carrier dynamics, and the interplay between these two processes in narrow-bandgap, Type I and Type II, semiconductor superlattices. The PL upconversion system was designed to utilize Potassium Niobiate and Potassium Titanyl Arsenate crystals to upconvert 1.2~5mum PL to 495~720nm when mixed with 843nm,

Der-Jun Jang

1998-01-01

170

Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground  

NASA Astrophysics Data System (ADS)

Aims: WASP-43b is the closest-orbiting hot Jupiter, and it has high bulk density. It causes deep eclipse depths in the system's light curve in both transit and occultation that is attributed to the cool temperature and small radius of its host star. We aim to secure a broad-band transmission spectrum and to detect its near-infrared thermal emission in order to characterize its atmosphere. Methods: We observed one transit and one occultation event simultaneously in the g', r', i', z', J, H, K bands using the GROND instrument on the MPG/ESO 2.2-m telescope, where the telescope was heavily defocused in staring mode. After modeling the light curves, we derived wavelength-dependent transit depths and flux ratios and compared them to atmospheric models. Results: From the transit event, we have independently derived WASP-43's system parameters with high precision and improved the period to be 0.81347437(13) days based on all the available timings. No significant variation in transit depths is detected, with the largest deviations coming from the i'-, H-, and K-bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either (i) a flat featureless straight line that indicates thick clouds; (ii) synthetic spectra with absorption signatures of atomic Na/K, or molecular TiO/VO that in turn indicate cloud-free atmosphere; or (iii) a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197 ± 0.042%, which confirms previous detections obtained in the 2.09 ?m narrow band and KS-band. The K-band brightness temperature 1878+108-116 K favors an atmosphere with poor day- to nightside heat redistribution. We also have a marginal detection in the i'-band (0.037+0.023-0.021%), corresponding to TB = 2225+139-225 K, which is either a false positive, a signature of non-blackbody radiation at this wavelength, or an indication of reflective hazes at high altitude. Based on observations collected with the Gamma Ray Burst Optical and Near-Infrared Detector (GROND) on the MPG/ESO 2.2-m telescope at La Silla Observatory, Chile. Program 088.A-9016 (PI: Chen).Photometric time series are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A40

Chen, G.; van Boekel, R.; Wang, H.; Nikolov, N.; Fortney, J. J.; Seemann, U.; Wang, W.; Mancini, L.; Henning, Th.

2014-03-01

171

A Mild Case of Adult-Onset Keratosis Lichenoides Chronica Successfully Treated with Narrow-Band UVB Monotherapy  

PubMed Central

Keratosis lichenoides chronica (KLC) is a rare keratotic disorder of unknown origin. Effective treatment has not been established yet. Here, we present adult-onset KLC, which was treated by narrow-band ultraviolet B (NB-UVB) monotherapy. Although NB-UVB was reported to be effective for pediatric-onset KLC, it has not been clear if this regimen is also useful for adult-onset type because pediatric-onset KLC is suggested to be different in nature. We assume that KLC is treatable by NB-UVB regardless of the age of the patient. PMID:23185159

Nomura, Takashi; Toichi, Eiko; Miyachi, Yoshiki; Kabashima, Kenji

2012-01-01

172

Observation of Lymphangioma of the Duodenum by a Magnifying Endoscope with a Narrow-Band Imaging System  

PubMed Central

Among duodenal tumors, lymphangioma is relatively infrequent. In this case report, we describe the case of a 65-year-old Japanese man with duodenal lymphangioma diagnosed by esophagogastroduodenoscopy. Endoscopically, the tumor appeared as a soft submucosal tumor with white spots. When the white spots were grasped by biopsy forceps, milky liquid exuded from the tumor. Additionally, observation by a magnifying endoscope with narrow-band imaging revealed elongated microvessels on the surface. We speculated that this feature was formed because the duodenal villi were dilated and the microvessels were stretched due to the retention of chyle. These endoscopic findings are key features in the diagnosis of duodenal lymphangioma. PMID:23798913

Iwamuro, Masaya; Kawai, Yoshinari; Takata, Katsuyoshi; Okada, Hiroyuki; Yamamoto, Kazuhide

2013-01-01

173

On-Chip NRZ-to-PRZ Format Conversion Using Narrow-Band Silicon Microring Resonator-Based Notch Filters  

Microsoft Academic Search

We report experimental demonstration and modeling of all-optical on-chip non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) format conversion using narrow-band silicon microring resonator-based notch filters. Our proof-of-principle experiment using a carrier-injection-based tunable silicon microring resonator demonstrates NRZ-to-PRZ conversion at 3.6 Gbit\\/s. Our Fourier-transform-based modeling reveals in detail the format conversion dependence on the microring resonance Q factor, extinction ratio, phase response, and

Linjie Zhou; Hui Chen; Andrew W. Poon

2008-01-01

174

Ab initio study of deep defect states in narrow band-gap semiconductors: group III impurities in PbTe.  

PubMed

The nature of deep defect states, in general, and those associated with group III elements (Ga, In, Tl) in narrow band-gap IV-VI semiconductors (PbTe and PbSe), in particular, have been of great interest over the past three decades. We present ab initio electronic structure calculations that give a new picture of these states compared to the currently accepted model in terms of a negative-U Hubbard model. The Fermi surface pinning and why In-doped PbTe and related compounds show excellent high temperature thermoelectric behavior can be understood within the new picture. PMID:16486963

Ahmad, Salameh; Hoang, Khang; Mahanti, S D

2006-02-10

175

Ab Initio Study of Deep Defect States in Narrow Band-Gap Semiconductors: Group III Impurities in PbTe  

NASA Astrophysics Data System (ADS)

The nature of deep defect states, in general, and those associated with group III elements (Ga, In, Tl) in narrow band-gap IV-VI semiconductors (PbTe and PbSe), in particular, have been of great interest over the past three decades. We present ab initio electronic structure calculations that give a new picture of these states compared to the currently accepted model in terms of a negative-U Hubbard model. The Fermi surface pinning and why In-doped PbTe and related compounds show excellent high temperature thermoelectric behavior can be understood within the new picture.

Ahmad, Salameh; Hoang, Khang; Mahanti, S. D.

2006-02-01

176

Structural and electronic properties of narrow-band-gap semiconductors: InP, InAs, and InSb  

Microsoft Academic Search

The structural and electronic properties of the narrow-band-gap zinc-blende-structure III-V semiconductors InP, InAs, and InSb are studied with two first-principles schemes: the full-potential linear augmented-plane-wave (FLAPW) method and ab initio norm-conserving pseudopotentials. The all-electron equilibrium properties are found to be in excellent agreement with experiment; a comparison between the FLAPW and pseudopotential results emphasizes the role of the shallow ``semicore''

S. Massidda; A. Continenza; A. J. Freeman; T. M. de Pascale; F. Meloni; M. Serra

1990-01-01

177

Increased conductivities of Cr doped Al2-xCrxO3 powders due to band gap narrowing  

NASA Astrophysics Data System (ADS)

A high Cr content in the synthesized Al2-xCrxO3 materials was achieved via a new synthesis route, the self propagating combustion method, for investigation of the effect of Cr substitution on the electrical, optical band gap and structural characteristics of the modified Al2O3 materials. X-ray diffraction (XRD) results showed that all the samples were pure and that Cr was successfully substituted in the crystal lattice. The cell parameters and volume are linearly dependent on the Cr content. AC impedance spectroscopy results show that conductivity of the Cr doped samples increases exponentially with Cr content. This is attributed to band gap narrowing of the Al2-xCrxO3 powders as obtained from UV-visible spectrophotometric studies.

Badar, Nurhanna; Kamarulzaman, Norlida; Rusdi, Roshidah; Abdul Aziz, Nor Diyana; Kun Fun, Hoong

2014-03-01

178

Narrow band photocurrent response from partially phase separated a-SiNx:H thin films  

NASA Astrophysics Data System (ADS)

We report static and dynamic photocurrent response from sub-stoichiometric a-SiNx:H thin films. The photocurrent spectral (PCS) response is peaked in the technologically important optical energy range of 2.2 to 4.5 eV. The transient photocurrent response with prolonged exposure is attributed to reduction in number of charge carriers due to trapping of photo-generated carriers at defect sites. The narrow PCS response is attributed to dominant photo-generation of carriers in the bandtails of stoichiometric Si3N4 phase and subsequent transport through the excess Si network.

Bommali, R. K.; Ahmad, Shahab; Sharma, Nandlal; Srivastava, P.; Vijaya Prakash, G.

2014-09-01

179

Perfect narrow-band absorber based on a monolayer of metallodielectric microspheres  

SciTech Connect

We have studied how two-dimensional arrays of metallodielectric core-shell microspheres on a metal substrate can efficiently absorb infrared electromagnetic radiation in a narrow wavelength range under normal incidence. Our simulations indicate that perfect absorption efficiencies can be achieved for resonance wavelengths. The influence of core-shell microspheres geometry and lattice geometry is studied on absorption properties. For wavelength from 1.2??m to 2.6??m, an optimal combination of sphere and core radius was obtained to provide perfect absorption which can be wavelength adjusted.

Dyachenko, P. N., E-mail: pavel.dyachenko@tuhh.de; Petrov, A. Yu.; Eich, M. [Institute of Optical and Electronic Materials, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg (Germany)] [Institute of Optical and Electronic Materials, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg (Germany)

2013-11-18

180

Narrow band defect luminescence from Al-doped ZnO probed by scanning tunneling cathodoluminescence  

E-print Network

the visible spectrum.1,2 Doping ZnO with Al increases the electrical conductivity by several orders.1063/1.3647622] Aluminum-doped zinc oxide (AZO) exhibits similar electronic properties to ZnO: a wide optical band gap (Eg of magnitude and the material is called a transparent conducting oxide (TCO). In order to best exploit AZO

Russell, Kasey

181

A Minimum Parameter Adaptive Approach for Rejecting Multiple Narrow-Band Disturbances  

E-print Network

-band disturbances, disks drives I. Introduction In a modern hard disk drive (HDD), data/information is stored with Application to Hard Disk Drives Xu Chen, Student Member, IEEE, and Masayoshi Tomizuka, Fellow, IEEE Abstract- quencies. One example is the track-following control in a hard disk drive (HDD) system, where the airflow

Mofrad, Mohammad R. K.

182

Forward-bias capacitance and current measurements for determining lifetimes and band narrowing in p-n junction solar cells  

NASA Technical Reports Server (NTRS)

A new method is described and illustrated for determining the minority-carrier diffusion length and lifetime in the base region of p-n junction solar cells. The method requires only capacitance measurements at the device terminals and its accuracy is estimated to be + or - 5%. It is applied to a set of silicon p-n junction devices and the values of the diffusion lengths agree with those obtained using the current response to X-ray excitation but disagree with those obtained by the OCVD method. The reasons for the relative inaccuracy of OCVD applied to silicon devices are discussed. The capacitance method includes corrections for a two-dimensional fringing effects which occur in small area devices. For a device having highly-doped base region and surface (emitter) layer, the method can be extended to enable the determination of material properties of the degenerately doped surface layer. These material properties include the phenomenological emitter lifetime and a measure of the energy band-gap narrowing in the emitter. An alternate method for determining the energy band-gap narrowing from temperature dependence of emitter current is discussed and demonstrated.

Neugroschel, A.; Chen, P. J.; Pao, S. C.; Lindholm, F. A.

1978-01-01

183

Five years of Project META - An all-sky narrow-band radio search for extraterrestrial signals  

NASA Technical Reports Server (NTRS)

We have conducted a five-year search of the northern sky (delta between 30 and 60 deg) for narrow-band radio signals near the 1420 MHz line of neutral hydrogen, and its second harmonic, using an 8.4 x 10 exp 6 channel Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing Doppler signature for narrow-band signals of extraterrestrial origin. Among the 6 x 10 exp 13 spectral channels searched, we have found 37 candidate events exceeding the average detection threshold of 1.7 x 10 exp -23 W/sq m, none of which was detected upon reobservation. The strongest of these appear to be dominated by rare processor errors. However, the strongest signals that survive culling for terrestrial interference lie in or near the Galactic plane. We describe the search and candidate events, and set limits on the prevalence of supercivilizations transmitting Doppler-precompensated beacons at H I or its second harmonic. We conclude with recommendations for future searches, based upon these findings, and a description of our next-generation search system.

Horowitz, Paul; Sagan, Carl

1993-01-01

184

The split symbol moments SNR estimator in narrow-band channels  

NASA Technical Reports Server (NTRS)

The split symbol moments estimator is an algorithm that is designed to estimate symbol SNR in the presence of additive white Gaussian noise. The performance of the algorithm in band-limited channels is examined, and the effects of the resulting intersymbol interference are quantified. All results obtained are in closed form and can be easily evaluated numerically for performance-prediction purposes. The results are also validated through digital simulations.

Shah, Biren; Hinedi, Sami

1990-01-01

185

Band structure and CK ? emission of ultrathin nanotubes  

Microsoft Academic Search

An attempt is made to calculate the energy bands and spectra of the characteristic CK\\u000a ? emission of small-diameter carbon nanotubes. The calculated spectra for the nanotubes are compared with similar spectra for\\u000a graphite monolayers used as a test object and with known experimental results for nanotubes. It is concluded that the x-ray\\u000a emission spectra can be used to identify

M. M. Brzhezinskaya; E. M. Baitinger; V. I. Kormilets

2000-01-01

186

Hubble Space Telescope Observations of the HH47 Jet: Narrow Band Images 1  

E-print Network

where shocks are excited in the jet material by its interaction with the surrounding gas gas. All the knots in the jet may excite similar shock waves, however, these are only detected the body of the jet we identify many shocks in which the Balmer emission arises predominantly from

Hartigan, Patrick

187

Spatially extended narrow emission-line gas in the Seyfert galaxy NGC 4151  

NASA Technical Reports Server (NTRS)

Details of the spatial structure of the narrow-line region (NLR) in NGC 4151 are presented, and the structure of the NLR is compared to that of the radio and X-ray emission. Results for the morphology and excitation of the NLR, the luminosity of the extranuclear features, and the kinematics are presented, citing published research. These results are used to test several models: the X-ray gas in pressure equilibrium with the adjacent NLR, the X-ray gas identified as shock-heated NLR clouds flowing supersonically through the ambient galactic interstellar medium, X-rays arising in SNR and massive X-ray binaries produced in bursts of star formation stimulated by nuclear outflow, and X-ray and line emission regions ionized indirectly by the radio jet.

Heckman, T. M.; Balick, B.

1983-01-01

188

The Narrow Band AOTF Based Hyperspectral Microscopic Imaging on the Rat Skin Stratum Configuration  

NASA Astrophysics Data System (ADS)

A noncollinear acousto-optic tunable filter (AOTF) was designed with a comprehensive treatment of the properties of TeO2 as an acoustooptic (A-O) material. The results of optical testing validated that it predicted the performance of the designed AOTF. The bandwidth of the AOTF was very narrow in the visible light range. The high spectral resolution of AOTF was useful in practical applications to the hyperspectral imaging. The experimentally observed spectral pattern of the diffracted light was nearly the same as the theoretical result. The measured tuning relationship between the diffracted central optical wavelength and acoustic frequency was in accordance with the theoretical prediction. It demonstrates the accuracy of our design theory. Furthermore, by selecting the AOTF as the spectroscopic element, a hyperspectral microscopic imaging system was designed. The hyperspectral microscopic images of the rat skin tissue under the different optical center wavelength were acquired. The experimental results indicated that the imaging performance was satisfactory. The stratums of the rat skin can be clearly distinguished. The inner details of the epidermis and the corium can be shown on the hyperspectral microscopic images. Some differences also can be found by the comparison of the hyperspectal images under the different optical wavelengths. The study indicated the applicability and the advantage of our system on biomedicine area.

Zhang, C.; Wang, H.; Huang, J.; Gao, Q.

2014-08-01

189

Inter-band Tunnel Transistor Architecture using Narrow Gap Semiconductors S. Mookerjea, R. Krishnan, A. Vallett, T. Mayer and S. Datta  

E-print Network

Inter-band Tunnel Transistor Architecture using Narrow Gap Semiconductors S. Mookerjea, R. Krishnan University, University Park, PA 16802, USA The inter-band tunnel transistor (TFET) architecture features miniaturization of the silicon CMOS transistor technology, has resulted in an unprecedented increase in single

Yener, Aylin

190

Photoemission measurements of quantum states in accumulation layers at narrow band gap III–V semiconductor surfaces  

Microsoft Academic Search

Tiny amounts of cesium adsorbed on cleaved InSb(110) surfaces result in a strong downward band bending (BB) and creates a two-dimensional (2D) electron channel in the sub-surface region. For the first time, electron emission arising from this channel was observed for this material. We compare it to the similar situation met previously with InAs(110). In this last case, new high-resolution

V. Yu. Aristov; V. M. Zhilin; C. Grupp; A. Taleb-Ibrahimi; H. J. Kim; P. S. Mangat; P. Soukiassian; G. Le Lay

2000-01-01

191

A search for narrow band signals with Serendip II - A progress report  

NASA Technical Reports Server (NTRS)

Commensal programs for SETI, carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. An automated commensal system, Serendip II, searches for 0.49-Hz signals in sequential 64,700 Hz bands of the IF of a radio telescope being used for an astronomical observation. Upon detection of a signal with power above a preset threshold, the frequency, power, time, and telescope direction are recorded for later study. The system has been tested at the Hat Creek Radio Astronomy Observatory 85-ft telescope and the NASA-JPL Deep Space Station (DSS 14) 64-m telescope.

Werthimer, D.; Buhse, R.; Berezin, A.; Bowyer, S.

1986-01-01

192

The electron transport phenomena in Y based HTSC's and their analysis on the basis of phenomenological narrow-band theory the band structure transformation with oxygen content and substitution for Cu  

Microsoft Academic Search

The transport properties of YBa2Cu3Oy with various y and YBa2Cu3?xMxOy (M = Fe, Co, Mn) with various ? have been studied. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of a narrow conductive band. The narrow-band model permits one to account for the specific features of the transport coefficients

V. E. Gasumyants; V. I. Kaidanov; E. V. Vladimirskaya

1995-01-01

193

Atomic vapor filter for two-dimensional Rayleigh imaging experiments with a narrow-band KrF excimer laser.  

PubMed

An optical transition of atomic iron can be used to build a two-dimensional absorption filter that operates in the tuning range of a narrow-band KrF excimer laser (0.05-cm(-1) bandwidth). Iron atoms with a number density of 2 × 10(13) cm(-3) are produced by thermal dissociation of iron pentacarbonyl [Fe(CO)(5)]. With this filter it is possible to discriminate Mie and surface-scattered light against Rayleigh scattering. For Rayleigh scattering from the exhaust gas of a methane-air flame at a measured temperature of 1970 K, the ratio of transmission for Rayleigh scattering to transmission for Mie scattering is 16.8. Single-shot scattering from the exhaust gas of a high-pressure burner is presented as an application. PMID:21127620

Gölz, P; Andresen, P

1996-10-20

194

Far Ultraviolet Spectroscopic Explorer Spectroscopy of Absorption and Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051  

Microsoft Academic Search

We present three Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the narrow-line Seyfert 1 galaxy NGC 4051. The most prominent features in the far-ultraviolet (FUV) spectrum are the O VI emission and absorption lines and the H I Lyman series absorption lines, which are detected up to the Lyman edge. We also identify weak emission from N III, C III,

Shai Kaspi; W. N. Brandt; M. J. Collinge; Martin Elvis; Christopher S. Reynolds

2004-01-01

195

Mapping the large-scale structure around a z = 1.46 galaxy cluster in 3D using two adjacent narrow-band filters  

NASA Astrophysics Data System (ADS)

We present a novel method to estimate accurate redshifts of star-forming galaxies by measuring the flux ratio of the same emission line observed through two adjacent narrow-band filters. We apply this method to our NB912 and new NB921 data taken with Suprime-Cam on the Subaru Telescope of a galaxy cluster, XMMXCS J2215.9-1738, at z = 1.46 and its surrounding structures. We obtain redshifts for 170 [O II] emission line galaxies at z ˜ 1.46, among which 41 galaxies are spectroscopically confirmed with Multi-Object Infrared Camera and Spectrograph and Fibre Multi Object Spectrograph on the Subaru mainly, showing an accuracy of ?((z - zspec)/(1 + zspec)) = 0.002. This allows us to reveal filamentary structures that penetrate towards the centre of the galaxy cluster and intersect with other structures, consistent with the picture of hierarchical cluster formation. We also find that the projected celestial distribution does not precisely trace the real distribution of galaxies, indicating the importance of the three-dimensional view of structures to properly identify and quantify galaxy environments. We investigate the environmental dependence of galaxy properties with local density, confirming that the median colour of galaxies becomes redder in higher density region, while the star formation rate of star-forming galaxies does not depend strongly on local environment in this structure. This implies that the star-forming activity in galaxies is truncated on a relatively short time-scale in the cluster centre.

Hayashi, Masao; Kodama, Tadayuki; Koyama, Yusei; Tadaki, Ken-ichi; Tanaka, Ichi; Shimakawa, Rhythm; Matsuda, Yuichi; Sobral, David; Best, Philip N.; Smail, Ian

2014-04-01

196

Mapping the large scale structure around a z=1.46 galaxy cluster in 3-D using two adjacent narrow-band filters  

E-print Network

We present a novel method to estimate accurate redshifts of star-forming galaxies by measuring the flux ratio of the same emission line observed through two adjacent narrow-band filters. We apply this method to our NB912 and new NB921 data taken with Suprime-Cam on the Subaru Telescope of a galaxy cluster, XMMXCS J2215.9-1738, at z=1.46 and its surrounding structures. We obtain redshifts for 170 [OII] emission line galaxies at z~1.46, among which 41 galaxies are spectroscopically confirmed with MOIRCS and FMOS on the Subaru mainly, showing an accuracy of $\\sigma$((z-z_spec})/(1+z_spec))=0.002. This allows us to reveal filamentary structures that penetrate towards the centre of the galaxy cluster and intersect with other structures, consistent with the picture of hierarchical cluster formation. We also find that the projected celestial distribution does not precisely trace the real distribution of galaxies, indicating the importance of the three dimensional view of structures to properly identify and quantify ...

Hayashi, Masao; Koyama, Yusei; Tadaki, Ken-ichi; Tanaka, Ichi; Shimakawa, Rhythm; Matsuda, Yuichi; Sobral, David; Best, Philip N; Smail, Ian

2014-01-01

197

Anatomy of the AGN in NGC 5548: the X-ray narrow emission lines  

NASA Astrophysics Data System (ADS)

After a very successful multi-satellite campaign on Mrk 509 in 2009, we conducted a similar campaign on the AGN NGC 5548 in 2013. During the latter the source appeared unusually strongly absorbed in the soft X-rays, and signatures of strong outflows were also present in the UV. While a talk giving an overview of the campaign (PI: J. Kaastra) is also proposed at this conference, we will focus here on the data obtained from the XMM-RGS, resulting in a stacked spectrum of 660 ks. Narrow emission lines, including He-like triplets of Oxygen, Nitrogen and Neon, and radiative recombination (RRC) features dominate this spectrum due to the low soft X-ray continuum flux. All emission features are consistent with having constant flux over our campaign. The O VII triplet has been one focus of our analysis, especially due to unexpected differences of ˜300 km s^{-1} among the measured outflow velocities of its individual lines. The RRCs allow us to directly calculate a temperature of the emitting gas of a few eV (˜10^{4}K), favouring photoionised conditions. We have modelled the emission lines and features using the photoionisation code Cloudy, to attempt to construct a self-consistent picture of the physical environment of the AGN.

Whewell, M.; Branduardi-Raymont, G.; Kaastra, J.; Mehdipour, M.; Bianchi, S.; NGC 5548 Collaboration

2014-07-01

198

Precise photometric redshifts with a narrow-band filter set: the PAU survey at the William Herschel Telescope  

NASA Astrophysics Data System (ADS)

The Physics of the Accelerating Universe (PAU) survey at the William Herschel Telescope will use a new optical camera (PAUCam) with a large set of narrow-band filters to perform a photometric galaxy survey with a quasi-spectroscopic redshift precision of ?(z)/(1 + z) ˜ 0.0035 and map the large-scale structure of the universe in three dimensions up to iAB < 22.5-23.0. In this paper, we present a detailed photo-z performance study using photometric simulations for 40 equally spaced 12.5-nm-wide (full width at half-maximum) filters with an ˜25 per cent overlap and spanning the wavelength range from 450 to 850 nm, together with a ugrizY broad-band filter system. We then present the migration matrix rij, containing the probability that a galaxy in a true redshift bin j is measured in a photo-z bin i, and study its effect on the determination of galaxy auto- and cross-correlations. Finally, we also study the impact on the photo-z performance of small variations of the filter set in terms of width, wavelength coverage, etc., and find a broad region where slightly modified filter sets provide similar results, with the original set being close to optimal.

Martí, P.; Miquel, R.; Castander, F. J.; Gaztañaga, E.; Eriksen, M.; Sánchez, C.

2014-07-01

199

High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures  

SciTech Connect

The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schroedinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In{sub 0.53}Ga{sub 0.47}As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V{sub dc} in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.

Kapaev, V. V., E-mail: kapaev@sci.lebedev.ru; Kopaev, Yu. V.; Savinov, S. A.; Murzin, V. N. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)] [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2013-03-15

200

The effect of timing noise on targeted and narrow-band coherent searches for continuous gravitational waves  

E-print Network

Most continuous gravitational-wave searches use Taylor expansions in the phase to model the spindown of neutron stars. Studies of pulsars demonstrate that their electromagnetic (EM) emissions suffer from timing noise, small deviations in the phase from Taylor expansion models. How the mechanism producing EM emission is related to any continuous gravitational-wave (CW) emission is unknown; if they either interact or are locked in phase then the CW will also experience timing noise. Any disparity between the signal and the search template used in matched filtering methods will result in a loss of signal-to-noise ratio (SNR), referred to as 'mismatch'. In this work we assume the CW suffers a similar level of timing noise to its EM counterpart. We inject and recover fake CW signals, which include timing noise generated from observational data on the Crab pulsar. Measuring the mismatch over durations of order ~ 10 months, the effect is for the most part found to be small. This suggests recent so-called 'narrow-ban...

Ashton, G; Prix, R

2014-01-01

201

A non-LTE modeling of narrow emission components of He and Ca lines in optical spectra of CTTS  

E-print Network

A spectrum of a hot spot, produced by radiation of accretion shock at T Tauri star's surface, has been calculated taking into account non-LTE effects for HeI, HeII, CaI and CaII, using LTE-calculations of spot's atmospheric structure, calculated by Dodin & Lamzin (2012). Assuming that pre-shock gas number density N_0 and its velocity V_0 are the same across the accretion column, we calculated spectra of a system "star + round spot" for a set of N_0, V_0 values and parameters, which characterized the star and the spot. It has been shown that theoretical spectra with an appropriate choice of the parameters reproduce well observed veiling of photospheric absorption lines in optical band as well as profiles and intensities of so-called narrow components of HeII and CaI emission lines in spectra of 9 stars. We found that the accreted gas density N_0>10^{12} cm^{-3} for all considered stars except DK Tau. Observed spectra of 8 stars were succesfully fitted, asuming solar abundance of calcium, but it appeared po...

Dodin, A V; Sitnova, T M

2013-01-01

202

Full-sky survey searching for ultra-narrow-band artificial CW signals: analysis of the results of Project META  

NASA Astrophysics Data System (ADS)

Project META (Megachannel ExtraTerrestrial Assay), a full-sky survey for artificial narrow-band signals, has been conducted from the Harvard/Smithsonian 26 m radiotelescope at Agassiz Station and from one of the two 30 m radiotelescopes of the Instituto Argentino de Radioastronomia (IAR). The search was performed near the 1420 MHz line of neutral hydrogen, and its second harmonic, using two 8.4 X 10(superscript 6) channel Fourier spectrometers of 0.05 Hz resolution and 400 kHz of instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 6 X 10(superscript 13) spectral channels searched in the northern hemisphere, Horowitz and Sagan reported 37 candidates events exceeding the average threshold of 1.7 X 10(superscript -23) W m(superscript -2), while in the southern hemisphere among 2 X 10(superscript 13) spectral channels analyzed we found 19 events exceeding the same threshold. The strongest signals that survive culling for terrestrial interference lie in or near the Galactic Plane. The first high resolution southern target search around 71 stars (-90 degrees narrow-band non-repeating 'events' found by Project META can be generated by (a) radiometer noise fluctuations, (b) a population of constant galactic sources which undergo deep fading and amplification due to interstellar scintillation, consistent with ETI transmissions and (c) real, transient signals of either terrestrial or extraterrestrial origin. The Bayesian test shows that hypothesis (b) and (c) are both highly preferred to (a), but the first two are about equally likely. Using this analysis we discuss the best observing strategies to determine the real origin of these 'events'.

Lemarchand, Guillermo A.

1996-06-01

203

Progenitor constraints on the Type-Ia supernova SN2011fe from pre-explosion Hubble Space Telescope He II narrow-band observations  

NASA Astrophysics Data System (ADS)

We present Hubble Space Telescope (HST) imaging observations of the site of the Type-Ia supernova SN2011fe in the nearby galaxy M101, obtained about 1 yr prior to the event, in a narrow band centred on the He II ?4686 Å emission line. In a `single-degenerate' progenitor scenario, the hard photon flux from an accreting white dwarf (WD), burning hydrogen on its surface over ˜1 Myr should, in principle, create a He III Strömgren sphere or shell surrounding the WD. Depending on the WD luminosity, the interstellar density, and the velocity of an outflow from the WD, the He III region could appear unresolved, extended, or as a ring, with a range of possible surface brightnesses. We find no trace of He II ?4686 Å line emission in the HST data. Using simulations, we set 2? upper limits on the He II ?4686 Å luminosity of LHe II < 3.4 × 1034 erg s-1 for a point source, corresponding to an emission region of radius r < 1.8 pc. The upper limit for an extended source is LHe II < 1.7 × 1035 erg s-1, corresponding to an extended region with r ˜ 11 pc. The largest detectable shell, given an interstellar-medium density of 1 cm-3, has a radius of ˜6 pc. Our results argue against the presence, within the ˜105 yr prior to the explosion, of a supersoft X-ray source of luminosity Lbol ? 3 × 1037 erg s-1, or of a super-Eddington accreting WD that produces an outflowing wind capable of producing cavities with radii of 2-6 pc.

Graur, Or; Maoz, Dan; Shara, Michael M.

2014-07-01

204

Narrow-band long-/very-long wavelength two-color type-II InAs/GaSb superlattice photodetector by changing the bias polarity  

NASA Astrophysics Data System (ADS)

We report on a narrow-band two-color photodetector using type-II InAs/GaSb superlattices (SLs) in the long-/very-long wavelength infrared (VLWIR) ranges by changing the polarity of the bias. The narrow-band photoresponse is achieved by sequentially growing the doped SL structure that has a shorter cutoff wavelength as a low-pass filter for the absorption layers that has a longer cutoff wavelength. At 77 K, the 50% cutoff wavelength of the photodiode is 10 ?m when the applied bias voltage is -0.1 V and is 16 ?m at +40 mV. The ?? /? is 44% for the LWIR band and is 46% for the VLWIR band.

Zhang, Yanhua; Ma, Wenquan; Wei, Yang; Cao, Yulian; Huang, Jianliang; Cui, Kai; Guo, Xiaolu

2012-04-01

205

Optical emission line properties of Narrow Line Seyfert 1s and comparison AGN  

E-print Network

Based on a new spectroscopic sample observed using the WHT, we examine the kinematic properties of the various emission line regions in narrow line Seyfert 1 galaxies (NLS1s) by modelling their profiles using multiple component fits. We interpret these results by comparison with velocity components observed for different lines species covered in the same spectrum, and equivalent components measured in the spectra of some broad line Seyfert 1s and a representative Seyfert 2 galaxy. We find that the fits to the Halpha and Hbeta line profiles in NLS1s require an additional broad (~3000km/s) component that might correspond to a suppressed broad line region with similar kinematics to those of typical broad line Seyfert 1s. From the profiles of the forbidden high ionisation lines (FHILs) in NLS1s, we find evidence that they appear to trace an `intermediate' velocity region with kinematics between the standard broad and narrow line regions. Weaker evidence of this region is also present in the profiles of the permitted Balmer lines. Finally, we note that despite having similar ionisation potentials, the relative intensities of the highly ionised lines of [Fe X]6374 and [FeXI]7892 show considerable dispersion from one galaxy to another. The interpretation of this requires further modelling, but suggests the possibility of using the ratio as a diagnostic to constrain the physical conditions of the FHIL emitting region and possibly the shape of the spectral energy distribution in the vicinity of 200eV. This spectral region is very difficult to observe directly due to photoelectric absorption both in our Galaxy and intrinsic to the source.

James R. Mullaney; Martin J. Ward

2007-11-28

206

A new Fourier transform photo-modulation spectroscopic technique for narrow band-gap materials in the mid- to far-infra-red  

Microsoft Academic Search

There is a large number of technologically important semiconducting optoelectronic materials with narrow band-gaps in the finger-print region of the infra-red (IR) spectrum. However, in many instances their band-structures have not been very well characterised, making it difficult to engineer their properties. Part of the reason is that the key non-destructive optical characterisation tool, modulation spectroscopy, becomes increasingly difficult as

T. J. C. Hosea; M. Merrick; B. N. Murdin

2005-01-01

207

Principal resonance responses of SDOF systems with small fractional derivative damping under narrow-band random parametric excitation  

NASA Astrophysics Data System (ADS)

The principal resonance responses of nonlinear single-degree-of-freedom (SDOF) systems with lightly fractional derivative damping of order ? (0 < ? < 1) subject to the narrow-band random parametric excitation are investigated. The method of multiple scales is developed to derive two first order stochastic differential equation of amplitude and phase, and then to examine the influences of fractional order and intensity of random excitation on the first-order and second-order moment. As an example, the stochastic Duffing oscillator with fractional derivative damping is considered. The effects of detuning frequency parameter, the intensity of random excitation and the fractional order derivative damping on stability are studied through the largest Lyapunov exponent. The corresponding theoretical results are well verified through direct numerical simulations. In addition, the phenomenon of stochastic jump is analyzed for parametric principal resonance responses via finite differential method. The stochastic jump phenomena indicates that the most probable motion is around the larger non-trivial branch of the amplitude response when the intensity of excitation is very small, and the probable motion of amplitude responses will move from the larger non-trivial branch to trivial branch with the increasing of the intensity of excitation. Such stochastic jump can be considered as bifurcation.

Liu, Di; Li, Jing; Xu, Yong

2014-10-01

208

Assessment of Gastric Phenotypes Using Magnifying Narrow-Band Imaging for Differentiation of Gastric Carcinomas from Adenomas  

PubMed Central

Background. Conventional white-light endoscopy and forceps biopsy are insufficient for definitive diagnosis of gastric adenoma. Immunohistochemical studies have reported an obvious phenotypic difference between adenomas and carcinomas. We investigated the utility of narrow-band imaging with magnifying endoscopy (NBI-ME) for mucin phenotypic assessment to differentiate carcinomas from adenomas. Methods. NBI-ME findings were classified into A, B, and AB types, which revealed papillary, tubular pits and groove microstructures, respectively. To investigate A-B classifications retrospectively, 137 patients (155 lesions) that were diagnosed pretherapeutically with adenoma or borderline lesions by biopsy were enrolled. The mucin phenotype was analyzed immunohistochemically in the first 60 lesions. Results. After endoscopic submucosal dissection, A type and AB type lesions were determined histologically as carcinoma (81/82, 99%). B type lesions were adenoma (29/73, 40%) and carcinoma (44/73, 60%). A or AB type correlated to histological carcinomas (sensitivity 65%, specificity 97%, and accuracy 71%). Mucin phenotypes were gastric or gastrointestinal in A type and AB type carcinomas (31/37, 84%) and intestinal in B type adenomas and carcinomas (21/23, 91%). Conclusions. NBI-ME has the advantage of the assessment of mucin phenotypes in gastric carcinomas and adenomas. The proposed A-B classification is useful, especially for differentiation of gastric or gastrointestinal carcinomas from adenomas. PMID:25371671

Hashimoto, Satoru; Nishikura, Ken; Mizuno, Ken-Ichi; Takeuchi, Manabu; Ajioka, Yoichi

2014-01-01

209

The Role of Narrow Band Imaging in the Detection of Recurrent Laryngeal and Hypopharyngeal Cancer after Curative Radiotherapy  

PubMed Central

Narrow band imaging is considered a significant improvement in the possibility of detecting early mucosal lesion of the upper aerodigestive tract. Early detection of mucosal neoplastic lesions is of utmost importance for patients survival. There is evidence that, especially in patients previously treated by means of curative radiotherapy or chemoradiotherapy, the early detection rate of recurrent disease is quite low. The aim of this study was to prove whether the videoendoscopy coupled with NBI might help detect recurrent or secondary tumors of the upper aerodigestive tract. 66 patients previously treated by means of RT or CRT with curative intent were enrolled in the study. All patients underwent transnasal flexible videoendoscopy with NBI mode under local anesthesia. When a suspicious lesion was identified in an ambulatory setting, its nature was proved histologically. Many of these changes were not identifiable by means of conventional white light (WL) endoscopy. The accuracy, sensitivity, specificity, and positive and negative predictive value of the method are very high (88%, 92%, 76%, 96%, and 91%, resp.). Results demonstrate that outpatient transnasal endoscopy with NBI is an excellent method for the follow-up of patients with carcinomas of the larynx and the hypopharynx primarily treated with radiotherapy. PMID:25101264

Zabrodsky, Michal; Plzak, Jan

2014-01-01

210

New high T(c) multiferroics KBiFe?O? with narrow band gap and promising photovoltaic effect.  

PubMed

Intrinsic polarization of ferroelectrics (FE) helps separate photon-generated charge carriers thus enhances photovoltaic effects. However, traditional FE with transition-metal cations (M) of d? electron in MO? network typically has a band gap (E(g)) exceeding 3.0?eV. Although a smaller E(g) (2.6?eV) can be obtained in multiferroic BiFeO?, the value is still too high for optimal solar energy applications. Computational "materials genome" searches have predicted several exotic MO? FE with E(g) < 2.0?eV, all thus far unconfirmed because of synthesis difficulties. Here we report a new FE compound with MO? tetrahedral network, KBiFe?O?, which features narrow E(g) (1.6?eV), high Curie temperature (T(c) ~ 780?K) and robust magnetic and photoelectric activities. The high photovoltage (8.8?V) and photocurrent density (15??A/cm²) were obtained, which is comparable to the reported BiFeO?. This finding may open a new avenue to discovering and designing optimal FE compounds for solar energy applications. PMID:23405279

Zhang, Ganghua; Wu, Hui; Li, Guobao; Huang, Qingzhen; Yang, Chongyin; Huang, Fuqiang; Liao, Fuhui; Lin, Jianhua

2013-01-01

211

Narrow-band red-emitting Sr[LiAl3N4]:Eu2+ as a next-generation LED-phosphor material  

NASA Astrophysics Data System (ADS)

To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu2+, Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at ?max ~ 650 nm with a full-width at half-maximum of ~1,180 cm-1 (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu2+ as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (Ra8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

Pust, Philipp; Weiler, Volker; Hecht, Cora; Tücks, Andreas; Wochnik, Angela S.; Henß, Ann-Kathrin; Wiechert, Detlef; Scheu, Christina; Schmidt, Peter J.; Schnick, Wolfgang

2014-09-01

212

Design and fabrication of narrow band radar absorbing materials at terahertz frequencies R.H. Giles, A.J. Gatesman, A.P. Ferdinand and J. Waldman  

E-print Network

Design and fabrication of narrow band radar absorbing materials at terahertz frequencies R.H. Giles-infrared radiation absorbing material (FIRAM) which may be used to suppress unwanted stray radiation. One type material has been developed at the University of Lowell Research Foundation (ULRF). Low reflection coatings

Massachusetts at Lowell, University of

213

The X-ray spectrum and time variability of narrow emission line galaxies  

NASA Technical Reports Server (NTRS)

X-ray spectral and temporal observations are reported for six narrow emission line galaxies (NELGs), all of which are fitted by power-law X-ray spectra of energy slope 0.8 and have column densities in the line of sight greater than 1 x 10 to the 22nd atoms/sq cm. Three of the objects, NGC 526a, NGC 2110 and MCG-5-23-16 are variable in their X-ray flux, and the latter two, along with NGC 5506 and NGC 7582, showed detectable variability in at least one observation. The measured X-ray properties of these NELGs, which also included NGC 2992, strongly resemble those of previously-measured type 1 Seyferts of the same X-ray luminosity and lead to the conclusion of great similarity between the NELGs and low-luminosity type 1 Seyferts. The implications of these observations for the optical line-emitting region structure of these galaxies are discussed.

Mushotzky, R. F.

1982-01-01

214

The X-ray spectrum and time variability of narrow emission line galaxies  

NASA Technical Reports Server (NTRS)

X-ray spectral and temporal observations are reported for six narrow emission line galaxies (NELGs), all of which are fitted by power-law X-ray spectra of energy slope 0.8 and have column densities in the line of sight greater than 1 x 10 to the 22nd atoms/sq cm. Three of the objects, NGC 526a, NGC 2110 and MCG-5-23-16 are variable in their X-ray flux, and the latter two, along with NGC 5506 and NGC 7582, showed detectable variability in at least one observation. The measured X-ray properties of these NELGs, which also included NGC 2992, strongly resemble those of previously-measured type 1 Seyferts of the same X-ray luminosity and lead to the conclusion of great similarity between the NELGs and low-luminosity type 1 Seyferts. The implications of these observations for the optical line-emitting region structure of these galaxies are discussed.

Mushotzky, R.

1981-01-01

215

High resolution spectroscopy of the 11.3 micron emission band  

NASA Technical Reports Server (NTRS)

High resolution spectra of the 11.3 micron emission band in M82 and NGC 7027 were obtained using the University of Texas IR echelle spectrometer on the IRTF in April 1988. The spectral resolution was 0.004 micron, with coverage from 11.0 to 11.6 microns. Spectra were measured at ten positions along a 10 min. long slit. Analysis of the data is still in progress, but initial results show no clear evidence of narrow structure within the feature. The analysis will involve comparison of the observed spectra to laboratory and predicted spectra of Polycylic Aromatic Hydrocarbons (PAHs) and Quenched Carbonaceous Composite (QCCs) to determine which may be responsible for the emission. The spectra will be examined with a goal of determining whether the emission is caused by molecular or solid state material. The data are also examined for evidence of variations in the shape and strength of the 11.3 micron feature with position on the sky. In NGC 7027 the 10 min. long slit went across the edge of the ionized nebulae, allowing comparison of emission from both ionized and neutral regions.

Achtermann, Jeff M.; Lacy, J. H.; Bruce, D. E.

1989-01-01

216

Optical spectroscopy of IRAS sources with infrared emission bands. 1: IRAS 21282+5050 and the diffuse interstellar bands  

NASA Technical Reports Server (NTRS)

Spectroscopy of the starlike optical counterpart to IRAS 21282+5050, a source with the hydrocarbon infrared emission band spectrum, shows an 07(f)-(WC11) planetary nebula nucleus suffering an extinction of 5.7 mag. Emission line widths in the WC spectrum are only approx. 100 km/s, indicating a very slow stellar wind. Optical diffuse interstellar bands (DIBs) are prominent. Five DIBs are strongly enhanced, namely lamda lamda 5797, 6196, 6203, 6283, and 6613. The presence of circumstellar hydrocarbon molecules may explain both the infrared emission bands and the enhanced DIBs.

Cohen, Martin; Jones, B. F.

1987-01-01

217

Variable Reliability of Endoscopic Findings with White-Light and Narrow-Band Imaging for Patients with Suspected Eosinophilic Esophagitis  

PubMed Central

Background & Aims Endoscopic findings have been used to support a diagnosis of eosinophilic esophagitis (EoE) and to assess response to therapy, but their reliability is unknown. The aim of the study was to assess inter- and intra-observer reliability of endoscopic findings with white-light endoscopy and to assess changes in inter-observer reliability when narrow band imaging (NBI) was added to white light. Methods We collected data from 35 academic and 42 community adult gastroenterologists using 2 self-administered, online assessments of endoscopic images in patients with suspected EoE. First, gastroenterologists evaluated 35-single white light images. Next, they examined 35-paired images of the initial white-light image and its NBI counterpart. To assess intra-observer reliability, a second survey, to re-examine the single white light images, was performed ?2 weeks later. Agreement was determined by calculating ? values for multiple observers. Results Among all gastroenterologists, inter-observer agreement was fair to good when white light was used to identify rings (? = 0.56) and furrows (? = 0.48). Inter-observer agreement was poor for identification of plaques (? = 0.29) and for images with no findings (? = 0.34). Levels of agreement did not change in an analysis stratified by practice setting or patient volume. Agreement did not improve when NBI images were added to white light images. Levels of intra-observer agreement varied greatly and in some cases were not greater than those expected by chance. Conclusions Using white-light endoscopy and NBI to analyze EoE, gastroenterologists identified rings and furrows with fair to good reliability, but did not reliably identify plaques or normal images. Intra-observer agreement varied. Endoscopic findings might not be reliable for supporting a diagnosis of EoE or for making treatment decisions. PMID:21377547

Peery, Anne F.; Cao, Hongyuan; Dominik, Rosalie; Shaheen, Nicholas J.; Dellon, Evan S.

2011-01-01

218

The puzzling case of GRB 990123: prompt emission and broad-band afterglow modeling  

NASA Astrophysics Data System (ADS)

We report on BeppoSAX simultaneous X- and ?-ray observations of the bright ?-ray burst (GRB) 990123. We present the broad-band spectrum of the prompt emission, including optical, X- and ?-rays, confirming the suggestion that the emission mechanisms at low and high frequencies must have different physical origins. In the framework of the standard fireball model, we discuss the X-ray afterglow observed by the Narrow Field Instruments (NFIs) on board BeppoSAX and its hard X-ray emission up to 60 keV several hours after the burst, detected for about 20 ks by the Phoswich Detection System (PDS). Considering the 2{-}10 keV and optical light curves, the 0.1{-}60 keV spectrum during the 20 ks in which the PDS signal was present and the 8.46 GHz upper limits, we find that the multi-wavelength observations cannot be readily accommodated by basic afterglow models. While the temporal and spectral behavior of the optical afterglow is possibly explained by a synchrotron cooling frequency between the optical and the X-ray energy band during the NFIs observations, in X-rays this assumption only accounts for the slope of the 2{-}10 keV light curve, but not for the flatness of the 0.1{-}60 keV spectrum. Including the contribution of Inverse Compton (IC) scattering, we solve the problem of the flat X-ray spectrum and justify the hard X-ray emission; we also suggest that the lack of a significant detection of 15{-}60 keV emission in the following 75 ks and last 70 ks spectra, should be related to poorer statistics rather than to an important suppression of IC contribution. However, considering also the radio band data, we find the 8.46 GHz upper limits violated. On the other hand, leaving unchanged the emission mechanism requires modifying the hydrodynamics by invoking an ambient medium whose density rises rapidly with radius and by having the shock losing energy. Thus we are left with an open puzzle which requires further inspection.

Corsi, A.; Piro, L.; Kuulkers, E.; Amati, L.; Antonelli, L. A.; Costa, E.; Feroci, M.; Frontera, F.; Guidorzi, C.; Heise, J.; in't Zand, J.; Maiorano, E.; Montanari, E.; Nicastro, L.; Pian, E.; Soffitta, P.

2005-08-01

219

Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers  

E-print Network

We present a theoretical and experimental investigation of the emission characteristics and the flux of photon pairs generated by spontaneous parametric downconversion in quasi-phase matched bulk crystals for the use in quantum communication sources. We show that, by careful design, one can attain well defined modes close to the fundamental mode of optical fibers and obtain high coupling efficiencies also for bulk crystals, these being more easily aligned than crystal waveguides. We distinguish between singles coupling, conditional coincidence, and pair coupling, and show how each of these parameters can be maximized by varying the focusing of the pump mode and the fiber-matched modes using standard optical elements. Specifically we analyze a periodically poled KTP-crystal pumped by a 532 nm laser creating photon pairs at 810 nm and 1550 nm. Numerical calculations lead to coupling efficiencies above 94% at optimal focusing, which is found by the geometrical relation L/z_R to be ~ 1 to 2 for the pump mode and ~ 2 to 3 for the fiber-modes, where L is the crystal length and z_R is the Rayleigh-range of the mode-profile. These results are independent on L. By showing that the single-mode bandwidth decreases as 1/L, we can therefore design the source to produce and couple narrow bandwidth photon pairs well into the fibers. Smaller bandwidth means both less chromatic dispersion for long propagation distances in fibers, and that telecom Bragg gratings can be utilized to compensate for broadened photon packets--a vital problem for time-multiplexed qubits. Longer crystals also yield an increase in fiber photon flux proportional to sqrt{L}, and so, assuming correct focusing, we can only see advantages using long crystals.

Daniel Ljunggren; Maria Tengner

2005-07-05

220

Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers  

SciTech Connect

We present a theoretical and experimental investigation of the emission characteristics and the flux of photon pairs generated by spontaneous parametric downconversion in quasi-phase matched bulk crystals for the use in quantum communication sources. We show that, by careful design, one can attain well defined modes close to the fundamental mode of optical fibers and obtain high coupling efficiencies also for bulk crystals, these being more easily aligned than crystal waveguides. We distinguish between singles coupling, {gamma}{sub s} and {gamma}{sub i}, conditional coincidence, {mu}{sub i|s}, and pair coupling, {gamma}{sub c}, and show how each of these parameters can be maximized by varying the focusing of the pump mode and the fiber-matched modes using standard optical elements. Specifically we analyze a periodically poled KTP-crystal pumped by a 532 nm laser creating photon pairs at 810 nm and 1550 nm. Numerical calculations lead to coupling efficiencies above 93% at optimal focusing, which is found by the geometrical relation L/z{sub R} to be {approx_equal}1 to 2 for the pump mode and {approx_equal}2 to 3 for the fiber-modes, where L is the crystal length and z{sub R} is the Rayleigh-range of the mode-profile. These results are independent on L. By showing that the single-mode bandwidth decreases {proportional_to}1/L, we can therefore design the source to produce and couple narrow bandwidth photon pairs well into the fibers. Smaller bandwidth means both less chromatic dispersion for long propagation distances in fibers, and that telecom Bragg gratings can be utilized to compensate for broadened photon packets--a vital problem for time-multiplexed qubits. Longer crystals also yield an increase in fiber photon flux {proportional_to}{radical}(L), and so, assuming correct focusing, we can only see advantages using long crystals.

Ljunggren, Daniel; Tengner, Maria [Department of Microelectronics and Information Technology, Royal Institute of Technology, KTH, Electrum 229, SE-164 40 Kista (Sweden)

2005-12-15

221

Generation condition of the Upper-band and Lower-band chorus emissions in the Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

In the present study, chorus emissions have been analyzed on the basis of the nonlinear growth theory [1] in the Earth's magnetosphere. A rising-tone chorus emission is initially generated continuously in the frequency range from 0.1 to 0.7 fce0, where fce0 is the gyrofrequency in the generation region. Because of the nonlinear damping mechanism [2] the rising-tone chorus is separated into upper and lower bands at half the local gyrofrequency for the quasi-parallel propagation toward higher latitude (i.e. toward larger gyrofrequencies). Thus the lower cutoff of the upper-band chorus indicates half-gyrofrequency at the observational point (1/2 fce), whereas the upper cutoff of the lower-band chorus indicates half the gyrofrequency in the generation region (1/2fce0). We found an observational evidence of such characteristics of upper-band and lower-band chorus observed by the wave form capture (WFC) and the sweep frequency analyzer (SFA) onboard Geotail [3]. Mainly ';'lower-band-only chorus'' (only the lower-band emission exists) is observed and occasionally ';'dual-band chorus'' (both the upper-band and the lower-band emissions) is observed by Geotail. In this study, we statistically analyze the difference between the lower-band-only chorus and the dual-band chorus, using the SFA data obtained during October, 1992 and August, 2011. It has been confirmed that the dual-band chorus is generated because of the nonlinear damping at half the local gyrofrequency during the propagation. When the dual-band chorus propagates toward higher latitudes with its the upper-band part completely damped at half the local gyrofrequencies, the dual-band chorus becomes the lower-band-only chorus. We assume that the upper cutoff frequency of the lower-band chorus equals to the half-gyrofrequency in the generation region. When 0.7 fce0 (i.e. upper limit frequency of the chorus generation) is higher than local 1/2 fce, the dual-band chorus is possibly observed because the higher-frequency part of the upper-band chorus would not be damped. When 0.7 fce0 is lower than local 1/2 fce, the lower-band-only chorus is observed because the upper-band chorus is completely damped. References [1] Omura Y., Y. Katoh and D. Summers (2008), Theory and simulation of the generation of whistler-mode chorus, J. Geophys. Res., 113, A04223, doi:10.1029/2007JA012622. [2] Omura Y., M. Hikishima, Y. Katoh, D.Summers, and S. Yagitani (2009), Nonlinear mechanisms of lower-band and upper-band VLF chorus emissions in the magnetosphere, J. Geophys. Res., 114, A07217, doi:10.1029/2009JA014206 [3] S. Yagitani, T. Habagishi, S. Mori, Y. Omura, and H. Kojima, Generation and propagation characteristics of dual-band chorus emissions observed by Geotail, American Geophysical Union Fall Meeting 2012, December 2012, San Francisco, USA.

Habagishi, T.; Yagitani, S.; Omura, Y.; Kojima, H.

2013-12-01

222

The Dust in Comet C/1999 S4 (LINEAR) during Its Disintegration: Narrow-Band Images, Color Maps, and Dynamical Models  

NASA Astrophysics Data System (ADS)

Comet C/1999 S4 was observed with the 2m-telescopes of the Bulgarian National Observatory and Pik Terskol Observatory, Northern Caucasus, Russia, at the time of its disintegration. Maps of the dust brightness and color were constructed from images obtained in red and blue continuum windows, free from cometary molecular emissions. We analyze the dust environment of Comet C/1999 S4 (LINEAR) taking into account the observed changes apparent in the brightness images and in plots of Af? profiles as function of the projected distance ? from the nucleus. We also make use of the syndyne-synchrone formalism and of a Monte Carlo model based on the Finson-Probstein theory of dusty comets. The brightness and color of individual dust particles, which is needed to derive theoretical brightness and color maps of the cometary dust coma from the Monte Carlo model, is determined from calculations of the light scattering properties of randomly oriented oblate spheroids. In general, the dust of Comet C/1999 S4 (LINEAR) is strongly reddened, with reddening values up to 30%/1000 Å in some locations. Often the reddening is higher in envelopes further away from the nucleus. We observed two outbursts of the comet with brightness peaks on July 14 and just before July 24, 2000, when the final disintegration of the comet started. During both outbursts an excess of small particles was released. Shortly after both outbursts the dust coma "turns blue." After the first outburst, the whole coma was affected; after the second one only a narrow band of reduced color close to the tail axis was formed. This difference is explained by different terminal ejection speeds, which were much lower than normal in case of the second outburst. In particular in the second, final outburst the excess small particles could originate from fragmentation of "fresh" larger particles.

Bonev, T.; Jockers, K.; Petrova, E.; Delva, M.; Borisov, G.; Ivanova, A.

2002-12-01

223

Evidence for narrow-band oscillations in the optical spectra of the intermediate polars BG Canis Minoris, YY Draconis and GK Persei  

NASA Astrophysics Data System (ADS)

We report the results of dynamic spectroscopy of the intermediate polars (IPs) BG CMi, YY Dra and GK Per obtained at the 6 m telescope with the help of the photon-counting system known as the scanner of BTA. The spectral study of variability of BG CMi and YY Dra revealed Narrow-Band Oscillations (NBOs) or statistically significant features in their power spectra in contrast to GK Per where the oscillations were not found. The NBOs were detected in the spectra of BG CMi at the spin period of the white dwarf (913 s) in the profiles of the Balmer and He II 4886 Å emission lines. The widths of the features in the power spectra varied from 2 - 3 Å to 8 - 10 Å. The power spectra of YY Dra revealed the features at the spin period of the primary and its harmonic. To compare the NBOs in the spectra of different IPs we have counted formally the number of events of detection of the NBOs (NBO-events) in an exposure in the same wavelength range. As a result, the number of the NBO-events in the power spectra of BV CMi is noticeably greater than that of YY Dra and GK Per. It has been found that the number of the NBO-events in the power spectra of the intermediate polars BG CMi, V405 Aur and PQ Gem is about the same. These objects form a group with polar-like magnetic fields (8-20 MG), whereas YY Dra and GK Per are attributed to the objects with weak magnetic fields. This relationship between the strength of the magnetic field of the object and the number of NBO-events in their power spectra is an additional argument in favour of the presence of strong magnetic fields in the regions of formation of the radiation causing the NBO-events in the power spectra of the IPs.

Somov, N. N.; Somova, T. A.

224

Time-Domain Emission Measurements in K-Band  

NASA Astrophysics Data System (ADS)

The presented time-domain EMI measurement system allows for full-compliance measurements according to CISPR 16-1-1 in the frequency range from 9 kHz to 26 GHz. With the combination of ultra-fast analog-to-digital-conversion and real-time digital signal processing on a field-programmable-gate-array (FPGA) with ultra-broadband multi-stage down-conversion, time-domain methods are employed for measurements into K-band. This allows for a reduction in scan times by several orders of magnitude. A scan from 9 kHz to 26 GHz with a 9 kHz IF-filter bandwidth is completed in under 200 s, while over 5 · 106 frequency points are calculated. The use of low-loss components and integrated preamplifiers yields an ultra-low system noise floor power spectral density of typically below -150 dBm/Hz. The system IF dynamic range of over 60 dB allows for the measurement of high-dynamic range signals like radar pulses. Measurements of the radiated emissions of a personal computer and the nonstationary emissions of a microwave oven are presented.

Hoffmann, Christian; Russer, Peter

2011-08-01

225

Detections of Lyman Continuum from Star-Forming Galaxies at z ~ 3 through Subaru\\/Suprime-Cam Narrow-Band Imaging  

Microsoft Academic Search

Knowing the amount of ionizing photons from young star-forming galaxies is of particular importance to understanding the reionization process. Here we report initial results of a Subaru\\/Suprime-Cam deep imaging observation of the SSA22 proto-cluster region at z = 3.09, using a special narrow-band filter to optimally trace ionizing radiation from galaxies at z ~ 3. The unique wide field-of-view of

I. Iwata; A. K. Inoue; Y. Matsuda; H. Furusawa; T. Hayashino; K. Kousai; M. Akiyama; T. Yamada; D. Burgarella; J.-M. Deharveng

2009-01-01

226

Estimation of global solar UV index from UV-B irradiance measured with a narrow-band UV-B radiometer  

NASA Astrophysics Data System (ADS)

The global solar UV index is an indicator for notifying the level of harmful solar ultraviolet radiation reaching the surface of the earth and the general public. It was proposed by the WHO/WMO/UNEP/ICNIRP and was standardized by the CIE in 2003. This index is derived from the product of the spectral solar UV irradiance from 250 to 400 nm and the CIE standard of reference erythema spectrum. For calculation of the UV index, the measurement of spectral solar UV irradiance is needed. Spectral radiometry is the best method of measurement of solar UV irradiance, however spectral radiometers are cost prohibitive. On the other hand, a narrow-band solar UV-B radiometer is widely used for measurement of solar UV-B irradiance in the world. The Tokai Solar Radiation Monitoring Network, and the UV Monitoring Network-Japan performed by the National Institute for Environmental Studies are two examples of monitoring networks using narrow-band solar UV-B radiometer in Japan. In this paper an estimation method of the UV index from the measured UV-B irradiance with the narrow-band UV-B radiometer.

Takeshita, Shu; Sasaki, Masako

2005-08-01

227

Electron field emission from narrow band gap semiconductors (InAs)  

Microsoft Academic Search

We propose to use InAs for the development of effective electron field emitters on the basis of a new technological approach for the preparation of highly textured surfaces which allows one to obtain peculiar fine rod-like micro- and nanostructures. A decrease of the current-voltage characteristics slope by a factor of 3.5 was observed in the Fowler-Nordheim plot with increasing applied

V. Litovchenko; A. Evtukh; M. Semenenko; A. Grygoriev; O. Yilmazoglu; H. L. Hartnagel; L. Sirbu; I. M. Tiginyanu; V. V. Ursaki

2007-01-01

228

Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources  

NASA Technical Reports Server (NTRS)

High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.

Cohen, R. J.; Downs, G.; Emerson, R.; Grimm, M.; Gulkis, S.; Stevens, G.

1987-01-01

229

Proposal of new narrow-band wavelength filter using grating-assisted vertical contra-directional coupler  

SciTech Connect

The authors propose a novel wavelength filter using a grating-assisted vertical contra-directional coupler for an add and drop multiplexer (ADM). It is predicted from the calculations that the bandwidths of the filter can be narrow less than 1 nm and easily controllable by means of the optimization of the device parameters. The authors have successfully fabricated the InP-based semiconductor filter and also demonstrated filtering bandwidth as narrow as 0.7 nm which is consistent with the calculations.

Tanaka, S.; Utaka, K.; Yamamoto, T.; Horita, M.; Matsushima, Y. [KDD Research and Development Labs., Kamifukuoka, Saitama (Japan)

1996-12-31

230

Detection of marine methane emissions with AVIRIS band ratios  

NASA Astrophysics Data System (ADS)

The relative source contributions of methane (CH4) have high uncertainty, creating a need for local-scale characterization in concert with global satellite measurements. However, efforts towards methane plume imaging have yet to provide convincing results for concentrated sources. Although atmospheric CH4 mapping did not motivate the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) design, recent studies suggest its potential for studying concentrated CH4 sources such as the Coal Oil Point (COP) seep field (˜0.015 Tg CH4 yr-1) offshore Santa Barbara, California. In this study, we developed a band ratio approach on high glint COP AVIRIS data and demonstrate the first successful local-scale remote sensing mapping of natural atmospheric CH4 plumes. Plume origins closely matched surface and sonar-derived seepage distributions, with plume characteristics consistent with wind advection. Imaging spectrometer data may also be useful for high spatial-resolution characterization of concentrated, globally-significant CH4 emissions from offshore platforms and cattle feedlots.

Bradley, Eliza S.; Leifer, Ira; Roberts, Dar A.; Dennison, Philip E.; Washburn, Libe

2011-05-01

231

The visible to the near infrared narrow band acousto-optic tunable filter and the hyperspectral microscopic imaging on biomedicine study  

NASA Astrophysics Data System (ADS)

Based on the parallel tangents momentum-matching condition, a narrow band noncollinear acousto-optic tunable filter (AOTF) using a single TeO2 crystal is designed with the consideration of the birefringence and the rotatory property of the material. An effective setup is established to evaluate the performance of the designed AOTF. The experimental observed spectrum pattern of the diffracted light is nearly the same with the theoretical result. The measured tuning relationship between the diffracted central optical wavelength and acoustic frequency is in accordance with the theoretical prospect. The optical bandwidth of the diffracted light is as narrow as 1.88 nm when the central wavelength is 556.75 nm. The high spectral resolution is significant in practical applications of imaging AOTF. Additionally, the AOTF based hyperspectral microscopic imaging system is established. The stability and the image resolution of the designed narrow band AOTF are satisfying. Finally, the study of the biologic samples indicates the feasibility of our system on biomedicine.

Zhang, Chunguang; Wang, Hao; Huang, Junfeng; Gao, Qiang

2014-12-01

232

Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.  

PubMed

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter. PMID:25402069

Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

2014-11-17

233

Experimental analysis of emission linewidth narrowing in a pulsed KGd(WO4)2 Raman laser.  

PubMed

The linewidth of a KGd(WO4)2 (KGW) intracavity pumped Raman laser is analyzed experimentally for different configurations of the Raman and pump laser resonators: with narrow and broadband pump emission profiles, with and without linewidth narrowing elements in the Raman laser resonator, with and without injection seeding into the Raman cavity. The benefits of a narrow linewidth pump source in combination with linewidth narrowing elements in the Raman laser cavity for the efficient linewidth narrowing of the Raman laser emission are explained. 20 kW peak-power pulses at 1156 nm with 0.43 cm-1 emission linewidth are demonstrated from an injection seeded KGW Raman laser. PMID:25321552

Savitski, Vasili G

2014-09-01

234

Narrow ultraviolet emission lines from SN 1987A - Evidence for CNO processing in the progenitor  

Microsoft Academic Search

Results from UV observations of SN 1987A with the IUE satellite are presented, showing that emission lines of He II, C III, N III, N IV, N V, and O III increase in strength with time after May 24, 1987. It is found that increased emission originated in a photoionized low-density circumstellar gas, lost by the progenitor in its red

C. Fransson; A. Cassatella; R. Gilmozzi; R. P. Kirshner; N. Panagia; G. Sonneborn; W. Wamsteker

1989-01-01

235

Detections of Lyman Continuum from Star-forming Galaxies at z~3 Through Subaru/Suprime-Cam Narrow-band Imaging  

E-print Network

Knowing the amount of ionizing photons from young star-forming galaxies is of particular importance to understanding the reionization process. Here we report initial results of Subaru/Suprime-Cam deep imaging observation of the SSA22 proto-cluster region at z=3.09, using a special narrow-band filter to optimally trace Lyman continuum (LyC) from galaxies at z~3. The unique wide field-of-view of Suprime-Cam enabled us to search for ionizing photons from 198 galaxies (73 Lyman break galaxies (LBGs) and 125 Ly-alpha emitters (LAEs)) with spectroscopically measured redshifts z~3.1. We detected LyC from 7 LBGs, as well as from 10 LAE candidates. Some of the detected galaxies show significant spatial offsets of LyC from non-ionizing UV emission. For some LBGs the observed non-ionizing UV to LyC flux density ratios are smaller than values expected from population synthesis models with a standard Salpeter initial mass function (IMF) with moderate dust attenuation (which is suggested from the observed UV slopes), even if we assume very transparent IGM along the sightlines of these objects. This implies an intrinsically bluer spectral energy distribution, e.g, that produced by a top-heavy IMF, for these LBGs. The observed flux desity ratios of non-ionizing UV to LyC of 7 detected LBGs range from 2.4 to 23.8 and the median is 6.6. The observed flux density ratios of the detected LAEs are even smaller than LBGs, if they are truly at z~3.1. We find that the median value of the flux density ratio for the deteced LBGs suggest that their escape fractions is likely to be higher than 4%, if the LyC escape is isotropic. The results imply that some of the LBGs in the proto-cluster at z~3 have the escape fraction significantly higher than that of galaxies (in a general field) at z~1 studied previously.

I. Iwata; A. K. Inoue; Y. Matsuda; H. Furusawa; T. Hayashino; K. Kousai; M. Akiyama; T. Yamada; D. Burgarella; J. -M. Deharveng

2008-05-26

236

Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train  

We experimentally demonstrate the production of narrow-band (?f/f ~ =20% at f ~ = 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

Piot, P [Northern Illinois U.; Fermilab; Sun, Y E [Fermilab; Maxwell, T J [Fermilab; Northern Illinois U.; Ruan, J.; Lumpkin, A H [Fermilab; Rihaoui, M M [Northern Illinois U.; Thurman-Keup, R [Fermilab

2011-06-27

237

Strong band gap narrowing in quasi-binary (GaSb) 1? x (InAs) x crystals grown from melt  

Microsoft Academic Search

Large crystals of a quasi-binary semiconductor alloy (GaSb)1?x(InAs)x with x =0.02–0.05 have been grown from melt for the first time. The family of quasi-binary crystals (GaSb)1?x(InAs)x grown and reported here are different from the conventional Ga1?xInxAsySb1?y quaternaries due to growth behavior and physical properties. Significant narrowing of the band gap was observed in these crystals compared to the conventional quaternary

P. S Dutta; A. G Ostrogorsky

1999-01-01

238

A new sample of X-ray selected narrow emission-line galaxies. I. The nature of optically elusive AGN  

E-print Network

Using the 3XMM catalogue of serendipitous X-ray sources, and the SDSS-DR9 spectroscopic catalogue, we have obtained a new sample of X-ray selected narrow emission line galaxies. The standard optical diagnostic diagram and selection by hard X-ray luminosity expose a mismatch between the optically-based and X-ray-based classifications. The nature of these misclassified elusive AGN can be understood in terms of their broader X-ray and optical properties and leads to a division of this sub-sample into two groups. A little more than half are likely to be narrow-line Seyfert 1s (NLS1s), so misclassified because of the contribution of the Broad Line Region (BLR) to their optical spectra. The remainder have some of the properties of Seyfert 2 (Sy2) AGN; their optical elusiveness can be explained by optical dilution from the host galaxy plus a star-formation contribution and by their underluminous optical emission due to low accretion rates. Because some of the Sy2 sources have very low accretion rates, are unabsorbed...

Pons, Estelle

2014-01-01

239

Preparation of Narrow Band-Gap Cu2Sn(S,Se)3 and Fabrication of Film by Non-Vacuum Process  

NASA Astrophysics Data System (ADS)

We successfully prepared a Cu2Sn(S1-xSex)3 (CTSSe) solid solution with 0?x?1.0. CTSSe solid solution powders were synthesized by mixing the elemental powders and post-annealing at 600 °C. The crystal structure of Cu2SnS3 (CTS) was characterized by Rietveld refinement of the powder X-ray diffraction data and determined to be a monoclinic crystal system. The band gaps of CTSSe solid solution were determined by the diffuse reflectance spectra of the powder samples and the transmittance spectrum of the film fabricated by a non-vacuum thin-film fabrication process called printing and high-pressure sintering (PHS). The band gap (Eg) of CTS is 0.87 eV, which is in good agreement with the recently reported value of monoclinic CTS film. The band gap of the Cu2Sn(S1-xSex)3 solid solution linearly decreases from 0.87 eV (x = 0.0) to 0.67 eV (x = 0.6) with increasing Se content. The CTSSe solid solution has potential as a narrow band-gap absorber material for thin-film full spectrum solar cells.

Nomura, Takeshi; Maeda, Tsuyoshi; Wada, Takahiro

2013-04-01

240

Narrow-Band Imaging System for the Multi-application Solar Telescope at Udaipur Solar Observatory: Characterization of Lithium Niobate Etalons  

E-print Network

Multi-application Solar Telescope is a 50 cm off-axis Gregorian telescope that has been installed at the lake site of Udaipur Solar Observatory. For quasi-simultaneous photospheric and chromospheric observations, a narrow-band imager has been developed as one of the back-end instruments for this telescope. Narrow-band imaging is achieved using two lithium niobate Fabry-Perot etalons working in tandem as a filter. This filter can be tuned to different wavelengths by changing either voltage, tilt or temperature of the etalons. To characterize the etalons, a Littrow spectrograph was set up, in conjunction with a 15 cm Carl Zeiss Coud\\'e solar telescope. The etalons were calibrated for the solar spectral lines FeI 6173 {\\AA}, and CaII 8542 {\\AA}. In this work, we discuss the characterization of the Fabry-Perot etalons, specifically the temperature and voltage tuning of the system for the spectral lines proposed for observations. We present the details of the calibration set-up and various tuning parameters. We al...

Bayanna, A Raja; Venkatakrishnan, P; Srivastava, N

2014-01-01

241

Narrow band noise as a model of time-dependent accelerations - Study of the stability of a fluid surface in a microgravity environment  

NASA Technical Reports Server (NTRS)

We introduce a stochastic model to analyze in quantitative detail the effect of the high frequency components of the residual accelerations onboard spacecraft (often called g-jitter) on fluid motion. The residual acceleration field is modeled as a narrow band noise characterized by three independent parameters: its intensity G squared, a dominant frequency Omega, and a characteristic spectral width tau exp -1. The white noise limit corresponds to Omega tau goes to O, with G squared tau finite, and the limit of a periodic g-jitter (or deterministic limit) can be recovered for Omega tau goes to infinity, G squared finite. The analysis of the response of a fluid surface subjected to a fluctuating gravitational field leads to the stochastic Mathieu equation driven by both additive and multiplicative noise. We discuss the stability of the solutions of this equation in the two limits of white noise and deterministic forcing, and in the general case of narrow band noise. The results are then applied to typical microgravity conditions.

Casademunt, Jaume; Zhang, Wenbin; Vinals, Jorge; Sekerka, Robert F.

1993-01-01

242

Narrow-Band Imaging System for the Multi-application Solar Telescope at Udaipur Solar Observatory: Characterization of Lithium Niobate Etalons  

NASA Astrophysics Data System (ADS)

Multi-application Solar Telescope is a 50 cm off-axis Gregorian telescope that has been installed at the lake site of Udaipur Solar Observatory. For quasi-simultaneous photospheric and chromospheric observations, a narrow-band imager has been developed as one of the back-end instruments for this telescope. Narrow-band imaging is achieved using two lithium niobate Fabry-Perot etalons working in tandem as a filter. This filter can be tuned to different wavelengths by changing either voltage, tilt or temperature of the etalons. To characterize the etalons, a Littrow spectrograph was set up, in conjunction with a 15 cm Carl Zeiss Coud\\'e solar telescope. The etalons were calibrated for the solar spectral lines FeI 6173 {\\AA}, and CaII 8542 {\\AA}. In this work, we discuss the characterization of the Fabry-Perot etalons, specifically the temperature and voltage tuning of the system for the spectral lines proposed for observations. We present the details of the calibration set-up and various tuning parameters. We also present solar images obtained using the system parameters. We also present solar images obtained using the system.

Raja Bayanna, A.; Mathew, Shibu K.; Venkatakrishnan, P.; Srivastava, N.

2014-10-01

243

Compact source of narrow-band counterpropagating polarization-entangled photon pairs using a single dual-periodically-poled crystal  

NASA Astrophysics Data System (ADS)

We propose a scheme for the generation of counterpropagating polarization-entangled photon pairs from a dual-periodically-poled crystal. Compared with the usual forward-wave-type source, this source, in the backward-wave way, has a much narrower bandwidth. With a 2-cm-long bulk crystal, the bandwidths of the example sources are estimated to be 3.6 GHz, and the spectral brightnesses are more than 100 pairs/(s GHz mW). Two concurrent quasi-phase-matched spontaneous parametric down-conversion processes in a single crystal enable our source to be compact and stable. This scheme does not rely on any state projection and applies to both degenerate and nondegenerate cases, facilitating applications of the entangled photons.

Gong, Yan-Xiao; Xie, Zhen-Da; Xu, Ping; Yu, Xiao-Qiang; Xue, Peng; Zhu, Shi-Ning

2011-11-01

244

The narrow ultraviolet emission lines of the red dwarf Au Microscopii (dM1.6e)  

NASA Technical Reports Server (NTRS)

It is pointed out that the red dwarfs are the smallest, coolest, faintest, least massive, but most common of normal main-sequence stars. The dMe (H-alpha emission) subclass of the red dwarfs exhibits the largest median soft X-ray to bolometric luminosity ratio of any group of late-type stars. In connection with the present investigation, attention is given to the first high-dispersion spectra of the chromospheric (6000 K) and higher temperature (up to 100,000 K) emissions of a dMe star, AU Microscopii in the far-ultraviolet (1150-2000 A) and middle-ultraviolet (2000-3000 A) bands accessible to the International Ultraviolet Explorer (IUE). AU Mic is one of the most luminous of lower main-sequence stars in C IV and soft X-ray emission.

Ayres, T. R.; Eriksson, K.; Linsky, J. L.; Stencel, R. E.

1983-01-01

245

RFID Transponders' RF Emissions in Aircraft Communication and Navigation Radio Bands  

NASA Technical Reports Server (NTRS)

Radiated emission data in aircraft communication and navigation bands are presented for several active radio frequency identification (RFID) tags. The individual tags are different in design, operation and transmitting frequencies. The process for measuring the tags emissions in a reverberation chamber is discussed. Measurement issues dealing with tag interrogation, low level measurement in the presence of strong transmissions, and tags low duty factors are discussed. The results show strong emissions, far exceeding aircraft emission limits and can be of potential interference risks.

Nguyen, Truong X.; Ely, Jay J.; Koppen Sandra V.; Fersch, Mariatheresa S.

2008-01-01

246

A search for nitric oxide gamma band emission in an aurora  

NASA Technical Reports Server (NTRS)

A strong emission feature at 2150 A has been observed by a rocket-borne spectrophotometer in an IBC II(+) aurora. This feature, commonly identified with the NO gamma (1,0) band, is comparable in intensity to the nearby N2 Vegard-Kaplan bands. Comparison of the observed spectra with a theoretically produced synthetic spectrum allows all but this feature to be assigned to N2 transitions. No bands of the v prime = 0 or 2 progressions or any other bands from v prime = 1 appear, casting serious doubt on the identification of this feature as the NO gamma (1,0) band.

Beiting, E. J., III; Feldman, P. D.

1978-01-01

247

Defect-Band Emission Photoluminescence Imaging on Multi-Crystalline Si Solar Cells: Preprint  

SciTech Connect

Defect-band photoluminescence (PL) imaging with an InGaAs camera was applied to multicrystalline silicon (mc-Si) wafers, which were taken from different heights of different Si bricks. Neighboring wafers were picked at six different processing steps, from as-cut to post-metallization. By using different cut-off filters, we were able to separate the band-to-band emission images from the defect-band emission images. On the defect-band emission images, the bright regions that originate from the grain boundaries and defect clusters were extracted from the PL images. The area fraction percentage of these regions at various processing stages shows a correlation with the final cell electrical parameters.

Yan, F.; Johnston, S.; Zaunbrecher, K.; Al-Jassim, M.; Sidelkheir, O.; Blosse, A.

2011-07-01

248

Narrow ultraviolet emission lines from SN 1987A - Evidence for CNO processing in the progenitor  

NASA Technical Reports Server (NTRS)

Results from UV observations of SN 1987A with the IUE satellite are presented, showing that emission lines of He II, C III, N III, N IV, N V, and O III increase in strength with time after May 24, 1987. It is found that increased emission originated in a photoionized low-density circumstellar gas, lost by the progenitor in its red supergiant phase. A nebular analysis reveals a large nitrogen overabundance, indicating that the gas has undergone substantial CNO processing. This suggests that the progenitor of SN 1987A lost much of its hydrogen envelope before the explosion. The findings are consistent with models in which a red supergiant evolves to the blue supergiant stage before exploding.

Fransson, C.; Cassatella, A.; Gilmozzi, R.; Kirshner, R. P.; Panagia, N.; Sonneborn, G.

1989-01-01

249

Broadband femtosecond OPCPA system driven by the single-shot narrow-band iodine photodissociation laser SOFIA  

NASA Astrophysics Data System (ADS)

A two-stage optical parametric amplifier driven by a frequency-tripled beam from the high-energy iodine laser system SOFIA was built. This single-shot Optical Parametric Chirped Pulse-Amplification facility (OPCPA) and the system synchronizing the pump and signal pulses are described in detail. The chirped seed pulse of a Ti:sapphire oscillator running at the central wavelength of 800 nm is amplified in the two-stage (LBO and KDP) optical parametric amplifier over 108 times. The amplified spectral bandwidth of 68 nm corresponds to the pulse duration of 14 fs when a transform-limited pulse is assumed. This implies a compressed pulse of TW power. Systematic gain measurements reveal a good match with the theoretical predictions. Signal and idler beam fluence profiles are presented. The suitability of the iodine photo-dissociation laser as a pump source for the OPCPA technique is thus proved for the first time experimentally. A distinctive feature of the iodine laser is its very narrow gain bandwidth (<0.1 cm-1) and, therefore, the conventional chirped-pulse amplification technique does not lead to pulse durations at the femtosecond level.

Novák, O.; Tur?i?ová, H.; Smrž, M.; Huynh, J.; Pfeifer, M.; Straka, P.

2012-09-01

250

N2 triplet band emissions in the dayglow of Venus, Mars, and Titan  

NASA Astrophysics Data System (ADS)

Vegard-Kaplan (VK) and Second Positive emissions of N_2 are common features in the terrestrial dayglow and aurora and have been studied extensively. Recent discoveries of N_2 triplet band emissions on Mars by SPICAM/Mars-Express and on Titan by Cassini UVIS have led planetary scientists to look for the processes governing the N_2 triplet band emissions in different planetary atmospheres. Present work deals with the modeling of N_2 triplet band emission on Mars, Venus, and Titan. A model for N_2 triplet band emissions has been developed and used to explain the recent observations of N_2 Vegard-Kaplan (VK) (A^3?_u^+ - X^1?^+_g ) band on Mars and Titan. Steady state photoelectron fluxes and volume excitation rates have been calculated using the Analytical Yield Spectra technique. Since interstate cascading is important for triplet states of N_2, the population of any given level of N_2 triplet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet state is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK, First Positive ( B^3?_g - A^3?^+_u ), Second Positive ( C^3?_u - B^3?_g ), Wu-Benesch (W^3?_u - B^3?_g), Reverse First Positive, Herman--Kaplan (E ? A), E ? B, and E ? C bands of N_2. The N_2 VK band span wavelength range from far ultraviolet to visible, and some transitions even originate at wavelength more than 1000 nm . Our calculations show that the overhead intensity of VK bands in the wavelength range 400--800, 300--190, 200--300, and 150--200 nm are 22%, 39%, 35%, and 4% of the total VK band emission. Emissions between 600 and 800 nm wavelength consist of about 50% of the total First Positive band system. Major portion of Second Positive band emissions lie in wavelengths between 300 and 400 nm, which is more than 90% of the total Second Positive band overhead intensity. On Mars, a reduction in the N_2 density by a factor of 3 in the Mars thermospheric general circulation model is required to obtain agreement between calculated limb profiles of VK (0-6) and the SPICAM/MEX observation. On Titan, the calculated intensity of N_2 VK band in 150--190 nm wavelength range is in good agreement with the Cassini-UVIS observation. Calculations are also carried out on Venus using this model. Calculated intensities on Venus are about factor of 10 higher than that on Mars. The results will be presented and discussed.

Jain, Sonal Kumar; Bhardwaj, Anil

2012-07-01

251

Amplified spontaneous emission measurement of a line-narrowed, tunable, Ti:Al2O3 amplifier using rubidium absorption  

NASA Technical Reports Server (NTRS)

Amplified spontaneous emission, ASE, generated by a Ti:Al2O3 laser amplifier has been measured as a function of pump energy, and thus gain, using the atomic absorption of rubidium, Rb, gas at 0.780 micron. By tuning the Ti:Al2O3 laser, the Rb cell could selectively absorb the narrow spectral bandwidth laser radiation while transmitting the wide spectral bandwidth ASE. Transmission of laser amplifier pulses through a Rb absorption cell, measured at various temperatures, thus allows the measurement of the weak ASE in the vicinity of the strong laser pulse. A model for the transmission of Rb as a function of temperature and wavelength has been developed. The measured transmissions are in good agreement with the transmission model predictions.

Barnes, James C.; Barnes, Norman P.; Lockard, George E.; Cross, Patricia L.

1989-01-01

252

First results from the FPGA/NIOS Adaptive FIR Filter Using Linear Prediction Implemented in the AERA Radio Stations to Reduce Narrow Band RFI for Radio Detection of Cosmic Rays  

E-print Network

The FPGA/NIOS FIR filter based on linear prediction (LP) to suppress radio frequency interference (RFI) has been installed in several radio stations in the Auger Engineering Radio Array (AERA) experiment. AERA observes coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays to make a detailed study of the development of the electromagnetic part of air showers. Radio signals provide complementary information to that obtained from Auger surface detectors, which are predominantly sensitive to the particle content of an air shower at the surface. The radio signals from air showers are caused by the coherent emission due to geomagnetic and charge-excess processes. These emissions can be observed in the frequency band between 10 - 100 MHz. However, this frequency range is significantly contaminated by narrow-band RFI and other human-made distortions. A FIR filter implemented in the FPGA logic segment of the front-end electronics of a radio sensor significantly improves the signal-to-noise ratio. In this paper we present first results of the efficiency of the adaptive LP FIR filter, deployed in real AERA station on pampas, with a comparison to the currently used IIR notch filter with constant coefficients. The laboratory tests confirms the stability of the filter. Using constant LP coefficients the suppression efficiency remains the same for hours, which corresponds to more than $\\bf 10^{12}$ clock cycles. We compared in real conditions several variants of the LP FIR filter with various lengths and various coefficients widths (due to fixed-point representations in the FPGA logic) with the aim to minimize the power consumption for the radio station while keeping sufficient accuracy for noise reduction.

Zbigniew Szadkowski; D. G?as; C. Timmermans; T. Wijnen for the Pierre Auger Collaboration

2014-06-03

253

Predicting Thaumastocoris peregrinus damage using narrow band normalized indices and hyperspectral indices using field spectra resampled to the Hyperion sensor  

NASA Astrophysics Data System (ADS)

Thaumastocoris peregrinus (T. peregrinus) is a sap sucking insect that feeds on Eucalyptus leaves. It poses a threat to the forest industry by reducing the photosynthetic ability of the tree, resulting in stunted growth and even death of severely infested trees. Remote sensing techniques offer the potential to detect and map T. peregrinus infestations in plantation forests using current operational hyperspectral scanners. This study resampled field spectral data measured from a field spectrometer to the band settings of the Hyperion sensor in order to assess its potential in predicting T. peregrinus damage. Normalized indices based on NDVI ratios were calculated using the resampled visible and near-infrared bands of the Hyperion sensor to assess its utility in predicting T. peregrinus damage using Partial Least Squares (PLS) regression. The top 20 normalized indices were based on specific biochemical absorption features that predicted T. peregrinus damage with a mean bootstrapped R2 value of 0.63 on an independent test dataset. The top 20 indices were located in the near-infrared region between 803.3 nm and 894.9 nm. Twenty three previously published hyperspectral indices which have been used to assess stress in vegetation were also used to predict T. peregrinus damage and resulted in a mean bootstrapped R2 value of 0.59 on an independent test dataset. The datasets were combined to assess its collective strength in predicting T. peregrinus damage and significant indices were chosen based on variable importance scores (VIP) and were then entered into a PLS model. The indices chosen by VIP predicted T. peregrinus damage with a mean bootstrapped R2 value of 0.71 on an independent test dataset. A greedy backward variable selection model was further tested on the VIP selected indices in order to find the best subset of indices with the best predictive accuracy. The greedy backward variable selection model identified 3 indices and performed the best by predicting damage with an R2 value of 0.74 with the lowest RMSE of 1.30% on an independent test dataset. The best three indices identified include the anthocyanin reflectance index, carotenoid reflectance index and the normalized index calculated at 864.4 and 884.7 nm. Individual relationships between these indices and T. peregrinus damage indicate that high correlations are obtained with the inclusion of a few severely infested trees in the sample size. When the severely infested trees were removed from the study, the normalized index (864.4 and 884.7 nm) and the anthocyanin reflectance index still yielded significant correlations at the 99% confidence interval. This study indicates the significance of normalized indices and spectral indices calculated from the visible and near-infrared bands in hyperspectral data for the prediction of T. peregrinus damage.

Oumar, Z.; Mutanga, O.; Ismail, R.

2013-04-01

254

Enhancement of visible-light photocatalysis by coupling with narrow-band-gap semiconductor: a case study on Bi2S3/Bi2WO6.  

PubMed

To overcome the drawback of low photocatalytic efficiency brought by electron-hole recombination and narrow photoresponse range, we designed a novel Bi(2)S(3)/Bi(2)WO(6) composite photocatalyst. The composite possesses a wide photoabsorption until 800 nm, which occupies nearly the whole range of the visible light. Compared with bare Bi(2)WO(6), the Bi(2)S(3)/Bi(2)WO(6) composite exhibits significantly enhanced photocatalytic activity for phenol degradation under visible light irradiation. On the basis of the calculated energy band positions, the mechanism of enhanced photocatalytic activity was proposed. The present study provides a new strategy to design composite materials with enhanced photocatalytic performance. PMID:22248230

Zhang, Zhijie; Wang, Wenzhong; Wang, Lu; Sun, Songmei

2012-02-01

255

33 W quasi-continuous-wave narrow-band sodium D2a laser by sum-frequency generation in LBO  

NASA Astrophysics Data System (ADS)

We demonstrate an all-solid quasi-continuous-wave (QCW) narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd:YAG master oscillator power amplifier (MOPA) laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.

Wang, Peng-Yuan; Xie, Shi-Yong; Bo, Yong; Wang, Bao-Shan; Zuo, Jun-Wei; Wang, Zhi-Chao; Shen, Yu; Zhang, Feng-Feng; Wei, Kai; Jin, Kai; Xu, Yi-Ting; Xu, Jia-Lin; Peng, Qin-Jun; Zhang, Jing-Yuan; Lei, Wen-Qiang; Cui, Da-Fu; Zhang, Yu-Dong; Xu, Zu-Yan

2014-09-01

256

Side-chain effects on the conductivity, morphology, and thermoelectric properties of self-doped narrow-band-gap conjugated polyelectrolytes.  

PubMed

This contribution reports a series of anionic narrow-band-gap self-doped conjugated polyelectrolytes (CPEs) with ?-conjugated cyclopenta-[2,1-b;3,4-b']-dithiophene-alt-4,7-(2,1,3-benzothiadiazole) backbones, but with different counterions (Na(+), K(+), vs tetrabutylammonium) and lengths of alkyl chains (C4 vs C3). These materials were doped to provide air-stable, water-soluble conductive materials. Solid-state electrical conductivity, thermopower, and thermal conductivity were measured and compared. CPEs with smaller counterions and shorter side chains exhibit higher doping levels and form more ordered films. The smallest countercation (Na(+)) provides thin films with higher electrical conductivity, but a comparable thermopower, compared to those with larger counterions, thereby leading to a higher power factor. Chemical modifications of the pendant side chains do not influence out of plane thermal conductivity. These studies introduce a novel approach to understand thermoelectric performance by structural modifications. PMID:25179403

Mai, Cheng-Kang; Schlitz, Ruth A; Su, Gregory M; Spitzer, Daniel; Wang, Xiaojia; Fronk, Stephanie L; Cahill, David G; Chabinyc, Michael L; Bazan, Guillermo C

2014-10-01

257

Yb5Ga2Sb6: a mixed valent and narrow-band gap material in the RE5M2X6 family.  

PubMed

A new compound Yb5Ga2Sb6 was synthesized by the metal flux technique as well as high frequency induction heating. Yb5Ga2Sb6 crystallizes in the orthorhombic space group Pbam (no. 55), in the Ba5Al2Bi6 structure type, with a unit cell of a = 7.2769(2) Å, b = 22.9102(5) Å, c = 4.3984(14) Å, and Z = 2. Yb5Ga2Sb6 has an anisotropic structure with infinite anionic double chains (Ga2Sb6)(10-) cross-linked by Yb(2+) and Yb(3+) ions. Each single chain is made of corner-sharing GaSb4 tetrahedra. Two such chains are bridged by Sb2 groups to form double chains of 1/? [Ga2Sb6(10-)]. The compound satisfies the classical Zintl-Klemm concept and is a narrow band gap semiconductor with an energy gap of around 0.36 eV calculated from the electrical resistivity data corroborating with the experimental absorption studies in the IR region (0.3 eV). Magnetic measurements suggest Yb atoms in Yb5Ga2Sb6 exist in the mixed valent state. Temperature dependent magnetic susceptibility data follows the Curie-Weiss behavior above 100 K and no magnetic ordering was observed down to 2 K. Experiments are accompanied by all electron full-potential linear augmented plane wave (FP-LAPW) calculations based on density functional theory to calculate the electronic structure and density of states. The calculated band structure shows a weak overlap of valence band and conduction band resulting in a pseudo gap in the density of states revealing semimetallic character. PMID:24224906

Subbarao, Udumula; Sarkar, Sumanta; Gudelli, Vijay Kumar; Kanchana, V; Vaitheeswaran, G; Peter, Sebastian C

2013-12-01

258

Band-trap capture and emission in the generalized kinetic theory of electrons and holes  

E-print Network

Band-trap capture and emission in the generalized kinetic theory of electrons and holes A Rossani capture and emission mechanism by including an evolution equation for the trapped electrons. Mathematical, an interacting population of positively charged carrriers (holes) must be taken into account, besides electrons

Spiga, Giampiero

259

An optimization of the FPGA/NIOS adaptive FIR filter using linear prediction to reduce narrow band RFI for the next generation ground-based ultra-high energy cosmic-ray experiment  

NASA Astrophysics Data System (ADS)

The electromagnetic part of an extensive air shower developing in the atmosphere provides significant information complementary to that obtained by water Cherenkov detectors which are predominantly sensitive to the muonic content of an air shower at ground. The emissions can be observed in the frequency band between 10 and 100 MHz. However, this frequency range is significantly contaminated by narrow-band RFI and other human-made distortions. The Auger Engineering Radio Array currently suppresses the RFI by multiple time-to-frequency domain conversions using an FFT procedure as well as by a set of manually chosen IIR notch filters in the time-domain. An alternative approach developed in this paper is an adaptive FIR filter based on linear prediction (LP). The coefficients for the linear predictor are dynamically refreshed and calculated in the virtual NIOS processor. The radio detector is an autonomous system installed on the Argentinean pampas and supplied from a solar panel. Powerful calculation capacity inside the FPGA is a factor. Power consumption versus the degree of effectiveness of the calculation inside the FPGA is a figure of merit to be minimized. Results show that the RFI contamination can be significantly suppressed by the LP FIR filter for 64 or less stages.

Szadkowski, Zbigniew; Fraenkel, E. D.; Glas, Dariusz; Legumina, Remigiusz

2013-12-01

260

Compact high-quality CdSe-CdS core-shell nanocrystals with narrow emission linewidths and suppressed blinking  

NASA Astrophysics Data System (ADS)

High particle uniformity, high photoluminescence quantum yields, narrow and symmetric emission spectral lineshapes and minimal single-dot emission intermittency (known as blinking) have been recognized as universal requirements for the successful use of colloidal quantum dots in nearly all optical applications. However, synthesizing samples that simultaneously meet all these four criteria has proven challenging. Here, we report the synthesis of such high-quality CdSe-CdS core-shell quantum dots in an optimized process that maintains a slow growth rate of the shell through the use of octanethiol and cadmium oleate as precursors. In contrast with previous observations, single-dot blinking is significantly suppressed with only a relatively thin shell. Furthermore, we demonstrate the elimination of the ensemble luminescence photodarkening that is an intrinsic consequence of quantum dot blinking statistical ageing. Furthermore, the small size and high photoluminescence quantum yields of these novel quantum dots render them superior in vivo imaging agents compared with conventional quantum dots. We anticipate these quantum dots will also result in significant improvement in the performance of quantum dots in other applications such as solid-state lighting and illumination.

Chen, Ou; Zhao, Jing; Chauhan, Vikash P.; Cui, Jian; Wong, Cliff; Harris, Daniel K.; Wei, He; Han, Hee-Sun; Fukumura, Dai; Jain, Rakesh K.; Bawendi, Moungi G.

2013-05-01

261

Compact high-quality CdSe/CdS core/shell nanocrystals with narrow emission linewidths and suppressed blinking  

PubMed Central

High particle uniformity, high photoluminescence quantum yields, narrow and symmetric emission spectral lineshapes and minimal single dot emission intermittency (known as blinking) have been recognized as universal requirements for the successful use of colloidal quantum dots (QDs) in nearly all optical applications. However, synthesizing samples that simultaneously meet all these four criteria has proven challenging. Here, we report the synthesis of such high-quality CdSe/CdS core/shell QDs in an optimized process which maintains a slow growth rate of the shell through the use of octanethiol and cadmium oleate as precursors. In contrast with previous observations, single-QD blinking is significantly suppressed with only a relatively thin shell. In addition, we demonstrate the elimination of the ensemble luminescence photodarkening that is an intrinsic consequence of QD blinking statistical aging. Furthermore, the small size and high photoluminescence quantum yields of these novel QDs render them superior in vivo imaging agents compared to conventional QDs. We anticipate that this new generation of QDs will also result in significant improvement in the performance of QDs in other applications such as solid-state lighting and illumination. PMID:23377294

Chen, Ou; Zhao, Jing; Chauhan, Vikash P.; Cui, Jian; Wong, Cliff; Harris, Daniel K.; Wei, He; Han, Hee-Sun; Fukumura, Dai; Jain, Rakesh K.; Bawendi, Moungi G.

2013-01-01

262

Far Ultraviolet Spectroscopic Explorer Spectroscopy of Absorption and Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051  

E-print Network

We present three Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the Narrow-Line Seyfert 1 galaxy NGC4051. The most prominent features in the far-ultraviolet (FUV) spectrum are the OVI emission and absorption lines and the HI Lyman series absorption lines which are detected up to the Lyman edge. We also identify weak emission from NIII, CIII, and HeII. The CIII line shows absorption while none is detected in the NIII and HeII lines. In HI and CIII we detect two main absorption systems at outflow velocities of -50+/-30 and -240+/-40 km/s, as well as a possible third one at ~ -450 km/s. These systems are consistent in velocity with the 10 absorption systems found previously in CIV, NV, and SiIV, though the individual systems are blended together in the FUV spectrum. We estimate column densities of the two main absorption systems and find that the HI column density is lower for systems with larger outflow velocity. We detect no flux or spectral variations of NGC4051 at FUV wavelengths during three ...

Kaspi, S; Collinge, M J; Elvis, M; Reynolds, C S; Kaspi, Shai; Elvis, Martin; Reynolds, Christopher S.

2004-01-01

263

Techniques to minimize adjacent band emissions from Earth Exploration Satellites to protect the Space Research (Category B) Earth Stations in the 8400-8450 MHz band  

NASA Technical Reports Server (NTRS)

The Earth Exploration Satellites operating in the 8025-8400 MHz band can have strong adjacent band emissions on the8400-8450 MHz band which is allocated for Space Research (Category-B). The unwanted emission may exceed the protection criterion establish by the ITU-R for the protection of the Space Research (Category B) earth stations, i.e., deep-space earth stations. An SFCG Action Item (SF 23/14) was created during the 23rd SFCG meeting to explore technical and operational techniques to reduce the adjacent band emissions. In response to this action item, a study was conducted and results are presented in this document.

Wang, Charles C.; Sue, Miles K.; Manshadi, Farzin

2004-01-01

264

Detecting Long-Duration Narrow-Band Gravitational Wave Transients Associated with Soft Gamma Repeater Quasi-Periodic Oscillations  

E-print Network

We have performed an in-depth concept study of a gravitational wave data analysis method which targets repeated long quasi-monochromatic transients (triggers) from cosmic sources. The algorithm concept can be applied to multi-trigger data sets in which the detector-source orientation and the statistical properties of the data stream change with time, and does not require the assumption that the data is Gaussian. Reconstructing or limiting the energetics of potential gravitational wave emissions associated with quasi-periodic oscillations (QPOs) observed in the X-ray lightcurve tails of soft gamma repeater flares might be an interesting endeavour of the future. Therefore we chose this in a simplified form to illustrate the flow, capabilities, and performance of the method. We investigate performance aspects of a multi-trigger based data analysis approach by using O(100 s) long stretches of mock data in coincidence with the times of observed QPOs, and by using the known sky location of the source. We analytical...

Murphy, David; Raffai, Peter; Bartos, Imre; Khan, Rubab; Marka, Zsuzsa; Matone, Luca; Redwine, Keith; Marka, Szabolcs

2013-01-01

265

Terahertz emission from Ga1-xInxSb Ricardo Ascazubi and Ingrid Wilke  

E-print Network

by semiconductor properties. Narrow direct band gap semiconductors such as InAs Eg=0.35 eV ,8­16 and InN Eg=0.68 e of carrier concentrations on the THz emission process in narrow band gap semiconductors. Our study by narrow band gap materials and the negative effect of a high intrinsic carrier concentration

Wilke, Ingrid

266

Detecting long-duration narrow-band gravitational wave transients associated with soft gamma repeater quasiperiodic oscillations  

NASA Astrophysics Data System (ADS)

We have performed an in-depth concept study of a gravitational wave data analysis method which targets repeated long quasimonochromatic transients (triggers) from cosmic sources. The algorithm concept can be applied to multitrigger data sets in which the detector-source orientation and the statistical properties of the data stream change with time, and does not require the assumption that the data is Gaussian. Reconstructing or limiting the energetics of potential gravitational wave emissions associated with quasiperiodic oscillations observed in the x-ray lightcurve tails of soft gamma repeater flares might be an interesting endeavor of the future. Therefore we chose this in a simplified form to illustrate the flow, capabilities, and performance of the method. We investigate performance aspects of a multitrigger based data analysis approach by using O(100s) long stretches of mock data in coincidence with the times of observed quasiperiodic oscillations, and by using the known sky location of the source. We analytically derive the probability density function of the background distribution and compare to the results obtained by applying the concept to simulated Gaussian noise, as well as off-source playground data collected by the 4-km Hanford detector during LIGO’s fifth science run (S5). We show that the transient glitch rejection and adaptive differential energy comparison methods we apply succeed in rejecting outliers in the fifth science run background data. Finally, we discuss how to extend the method to a network containing multiple detectors, and as an example, tune the method to maximize sensitivity to soft gamma repeater 1806-20 flare times.

Murphy, David; Tse, Maggie; Raffai, Peter; Bartos, Imre; Khan, Rubab; Márka, Zsuzsa; Matone, Luca; Redwine, Keith; Márka, Szabolcs

2013-05-01

267

Single-photon emission in telecommunication band from an InAs quantum dot grown on InP with molecular-beam epitaxy  

NASA Astrophysics Data System (ADS)

We report on the experimental demonstration of a single-photon source based on an InAs quantum dot (QD) on InP grown by molecular-beam epitaxy emitting in the telecommunication band. We develop a method to reduce the QD density to prevent inter-dot coupling via tunneling through coupled excited states. A single InAs QD embedded in an as-etched pillar structure exhibits intense and narrow emission lines. Photon antibunching is clearly observed using superconducting single-photon detectors with high sensitivity, and further improvement of the generated single-photon purity is demonstrated with below-barrier-bandgap excitation.

Liu, X.; Akahane, K.; Jahan, N. A.; Kobayashi, N.; Sasaki, M.; Kumano, H.; Suemune, I.

2013-08-01

268

On the origin of blue and UV emission bands in mesoporous silica  

NASA Astrophysics Data System (ADS)

In this paper we present a review of the main results we obtained studying the emission properties of mesoporous silica in the UV-VIS range. Two main emission bands were investigated, the blue one, peaked in the 400-450 nm range, and the UV one, centered at about 300-350 nm, both excited in the UV and vacuum UV range. The origin of the two bands, investigated through optical spectroscopy techniques, is discussed in terms of possible surface emitting centers probing the samples with different chemical and physical treatments or exploiting different morphological and textural properties of the samples obtained by properly engineering the sol-gel synthesis.

Carbonaro, Carlo M.; Corpino, Riccardo; Ricci, Pier Carlo; Chiriu, Daniele

2014-10-01

269

The effect of Neel relaxation on the properties of the third harmonic signal of magnetic nanoparticles for use in narrow-band magnetic nanoparticle imaging  

NASA Astrophysics Data System (ADS)

We study the third harmonic signal of magnetic nanoparticles (MNPs) for use in narrow-band magnetic nanoparticle imaging. We measured the properties of the third harmonic signal, such as frequency and magnetic field dependencies, when the behavior of MNPs was dominated by Neel relaxation. It was shown that the third harmonic signal had both real and imaginary parts, although only the real part is expected from the conventional Langevin function. The real and imaginary parts exhibited different dependences on the frequency and magnetic field. The dynamic behavior of MNPs was analyzed by taking into account the Neel relaxation of MNPs. It was shown that the imaginary part was generated due to Neel relaxation. We obtain an analytical expression for the third harmonic signal, in which distributions of magnetic moment and anisotropic energy of MNPs in the sample were also considered. We show that the analytical results quantitatively explain the experimental results. Our results indicate that the properties of the third harmonic signal of immobilized MNPs are significantly affected by Neel relaxation.

Enpuku, Keiji; Bai, Shi; Hirokawa, Aiki; Tanabe, Kazuhiro; Sasayama, Teruyoshi; Yoshida, Takashi

2014-10-01

270

Effect of Narrow Band Ultraviolet B Therapy versus Methotrexate on Serum Levels of Interleukin-17 and Interleukin-23 in Egyptian Patients with Severe Psoriasis  

PubMed Central

Background. There is raised interest in the involvement of interleukin-(IL-)23/T-helper 17 cells (Th17) axis in the pathogenesis of psoriasis. Objectives. To compare the effect of narrow band ultraviolet B (NB-UVB) and methotrexate (MTX) therapy on serum levels of IL-17 and IL-23 in psoriatic patients. Methods. Thirty patients with severe plaque psoriasis were included: 15 patients received NB-UVB three times weekly (group I) and 15 patients received MTX 0.3?mg/kg per week (group II), both for 8 weeks. Before and after treatment, serum levels of IL-17 and IL-23 were investigated by ELISA technique and psoriasis area and severity index (PASI) was calculated. Results. After treatment, all patients showed a reduction in their PASI score, IL-17 and IL-23 serum levels with a nonsignificant difference between both therapeutic modalities (P value >0.05). A positive correlation was detected between the percent of reduction of IL-17, IL-23 and the percent of reduction of PASI score for patients receiving both treatments. No correlation was found between the percent of reduction of IL-17, IL-23 and duration of disease or age of all patients in this study. Conclusion. Interleukin-17 and IL-23 serum level may serve as a potential biomarker for predicting the prognosis and therapeutic response of NB-UVB or MTX in treating psoriasis. PMID:24489536

Elghandour, Tarek Mahmoud; Youssef, Sahar El Sayed; Aly, Dalia Gamal; Abd Elhameed, Mohamed Said; Abdel Moneim, Mehrevan Mostafa

2013-01-01

271

Ruling out unresolved binaries in five transitional disks VLT/NACO: deep 2.12 and 1.75 {\\mu}m narrow-band imaging  

E-print Network

Aims. We aim at detecting the presence of companions inside the inner hole/gap region of a sample of five well known transitional disks using spatially-resolved imaging in the near-IR with the VLT/NACO/S13 camera, which probes projected distances from the primary of typically 0.1 to 7 arcsec. The sample includes the stars DoAr 21, HD 135344B (SAO 206462), HR 4796A, T Cha, and TW Hya, spanning ages of less than 1 to 10 Myr, spectral types of A0 to K7, and hole/gap outer radii of 4 to 100 AU. Methods. In order to enhance the contrast and to avoid saturation at the core of the point-spread function (PSF), we use narrow-band filters at 1.75 and 2.12 {\\mu}m. The "locally optimized combination of images" (LOCI) algorithm is applied for an optimal speckle noise removal and PSF subtraction, providing an increase of 0.5-1.5 mag in contrast over the classic method. Results. With the proviso that we could have missed companions owing to unfavorable projections, the VLT/NACO observations rule out the presence of unresolv...

Vicente, Silvia; Hartung, Markus; Bouy, Herve; Huelamo, Nuria; Artigau, Etienne; Augereau, Jean-Charles; van Dishoeck, Ewine; Olofsson, Johan; Oliveira, Isa; Prusti, Timo

2011-01-01

272

Influence of growth temperature and V/III ratio on the optical characteristics of narrow band gap (0.77 eV) InN grown on GaN/sapphire using  

E-print Network

growth mode, NH3 was constantly flowing while the TMIn was sent into the reactor chamber for a 36-s pulseInfluence of growth temperature and V/III ratio on the optical characteristics of narrow band gap Engineering, Lehigh University, Bethlehem, PA 18015, USA b Air Products & Chemicals, Inc. 7201 Hamilton

Gilchrist, James F.

273

Monitoring MODIS thermal emissive band stability through brightness temperature trending of a ground target  

Microsoft Academic Search

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites have been operating since 2000 and 2002, respectively. To date both instruments have demonstrated good calibration stability for the Thermal Emissive Bands (TEB). Maintaining calibration accuracy is an important issue, as the instrument age, for continued production of high quality science data. In this paper a strategy

Brian N. Wenny; Xiaoxiong Xiong

2007-01-01

274

Full-Band Monte Carlo Analysis of Hot-Carrier Light Emission in GaAs  

NASA Astrophysics Data System (ADS)

A computational analysis of light emission from hot carriers in GaAs due to direct intraband conduction-conduction (c-c) transitions is presented. The emission rates have been evaluated by means of a Full-Band Monte-Carlo simulator (FBMC). Results have been obtained for the emission rate as a function of the photon energy, for the emitted and absorbed light polarization along and perpendicular to the electric field direction. Comparison has been made with available experimental data in MESFETs.

Ferretti, I.; Abramo, A.; Brunetti, R.; Jacobini, C.

1997-11-01

275

Experimental verification of directional liquid surface wave emission at band edge frequencies  

NASA Astrophysics Data System (ADS)

Directional liquid surface wave emission at band edge frequencies is an interesting physical phenomenon and has already been studied in theoretical research. There has been no experimental validation of it to date, however. This paper has as its subject the experimental investigation of the emission effect when a point source is placed inside a finite square array of rigid cylinders standing vertically in liquid. Both the wave patterns and spatial intensities are obtained by experiment and compared with simulated results calculated by using the finite element method. We can see from this comparison that the two results correspond closely both at lower and upper band edge frequency. Obvious directional wave emission along a desired direction is observed in the source structures, confirming previous theoretical predictions. In the future, this method could serve as a directional liquid wave source in applications used in hydraulic and ocean engineering for the concentration of wave energy.

Wang, Zhenyu; Zhang, Pei; Zhang, Yongqiang; Nie, Xiaofei

2013-12-01

276

RFID Transponders' Radio Frequency Emissions in Aircraft Communication and Navigation Radio Bands  

NASA Technical Reports Server (NTRS)

Radiated emissions in aircraft communication and navigation bands are measured from several active radio frequency identification (RFID) tags. The individual tags are different in design and operations. They may also operate in different frequency bands. The process for measuring the emissions is discussed, and includes tag interrogation, reverberation chamber testing, and instrument settings selection. The measurement results are described and compared against aircraft emission limits. In addition, interference path loss for the cargo bays of passenger aircraft is measured. Cargo bay path loss is more appropriate for RFID tags than passenger cabin path loss. The path loss data are reported for several aircraft radio systems on a Boeing 747 and an Airbus A320.

Nguyen, Truong X.; Ely, Jay J.; Williams, Reuben A.; Koppen, Sandra V.; Salud, Maria Theresa P.

2006-01-01

277

TEA-laser emission on the sequence bands of CO2.  

PubMed

Laser emission on the sequence bands of CO2 has been achieved in a TEA amplifier using either a hot-CO 2 cell or a Michelson interferometer to prevent oscillation of the regular bands. It has been found that the insertion losses of the hot-CO2 filter severely limit the energy extraction efficiency on the sequence bands. With the Michelson arrangement, output energies of 140 mJ on the sequence P(17) have been produced in a 33-cm-long TEA amplifier. The relatively low efficiencies obtained suggest that generation of high-intensity laser beams at the sequence band frequencies would require the use of oscillator-amplifier combinations. PMID:19684661

Lavigne, P; Lachambre, J L; Otis, G

1978-05-01

278

High resolution emission Fourier transform infrared spectra of the 4p-5s and 5p-6s bands of ArH  

NASA Astrophysics Data System (ADS)

In the 2500-8500cm-1 region several strong emission bands of ArH40 were observed by Fourier transform spectroscopy through a dc glow discharge in a mixture of argon and hydrogen. Rotational-electronic transitions of the two previously unstudied 4p-5s and 5p-6s,v=0-0, bands of ArH40 were measured and assigned in the 6060 and 3770cm-1 regions, respectively. A simultaneous fit of the emission transitions of the 4p-5s and 5p-6s bands and an extended set of transitions of the 6s-4p band observed by Dabrowski, Tokaryk, and Watson [J. Mol. Spectrosc. 189, 95 (1998)] and remeasured in the present work yielded consistent values of the spectroscopic parameters of the electronic states under investigation. In the branch of the 4p-5s band with transitions of type Qf3eQ we observed a narrowing in the linewidths with increasing rotational quantum number N. The rotational dependence of the linewidth is caused by predissociation of the 5s state by the repulsive ground 4s state through homogeneous coupling and changes in overlap integrals of the vibrational wave functions with the rotational level. Analysis was based on the Fermi's golden rule approximation model. In the 4p-5s band region a vibrational sequence ofv'-v?=1-1, 2-2, and 3-3 were recorded and a number of transitions belonging to the strongest Qf3eQ form branch of the 1-1 band were analyzed.

Baskakov, O. I.; Civiš, S.; Kawaguchi, K.

2005-03-01

279

An educational intervention to improve the endoscopist's ability to correctly diagnose small gastric lesions using magnifying endoscopy with narrow-band imaging  

PubMed Central

Background Magnifying endoscopy with narrow-band imaging (ME-NBI) and a simple and systematic classification system based on microvascular and microsurface patterns, the “VS” classification system (VSCS), have been shown to be useful for the diagnosis of early gastric cancer. The aim of this study was to clarify whether an educational lecture about the VSCS improves performance with ME-NBI. Methods Sixty-four gastrointestinal endoscopists took the 1st exam before receiving the lecture about the VSCS, the 2nd exam immediately after the lecture, and the 3rd exam 2 months after the lecture. We compared the VSCS-based diagnostic accuracy among the participants before and after the lecture. Results The proportion of correct diagnoses was significantly higher, at 70.8% in the 2nd exam than in the 1st exam, at 53.1% (P<0.001). The correct diagnosis rate in the 3rd exam was significantly lower than that in the 2nd exam (60.9% vs. 70.8%; P<0.001) but was still higher than that in the 1st exam (60.9% vs. 53.1%; P<0.001). The difference in proportion of correct diagnosis between the 2nd and the 3rd exams was smaller among routine ME-NBI practitioners (n=6; 79.2% and 76.1%, respectively), compared to that among non-routine practitioners (n=34; 71.6% and 59.8%, respectively) or non-practitioners (n=24; 67.5% and 58.8%, respectively). Conclusion This study revealed that an educational intervention increased correct diagnosis rate of small gastric lesions using the VSCS, diagnosis criteria based on ME-NBI and also showed that the routine use of the modality and the diagnosis criteria was necessary to maintain diagnostic skills. PMID:24733047

Mabe, Katsuhiro; Yao, Kenshi; Nojima, Masanori; Tanuma, Tokuma; Kato, Mototsugu

2014-01-01

280

Usefulness of Non-Magnifying Narrow-Band Imaging in Screening of Early Esophageal Squamous Cell Carcinoma: A Prospective Comparative Study Using Propensity Score Matching  

PubMed Central

OBJECTIVES: The usefulness of non-magnifying endoscopy with narrow-band imaging (NBI; NM-NBI) in the screening of early esophageal squamous cell carcinoma (SCC) and high-grade intraepithelial neoplasia (HGIN) remains unclear. Here, we aimed to compare NM-NBI and chromoendoscopy with iodine staining (CE-Iodine) in terms of the diagnostic performance, and to evaluate the usefulness of NM-NBI in detecting early esophageal SCC. METHODS: We prospectively enrolled 202 consecutive patients (male/female=180/22; median age, 67 years) with high-risk factors for esophageal SCC. All patients received endoscopic examination with NM-NBI and CE-Iodine to screen for early esophageal SCC or HGIN. We conducted the examinations sequentially, and calculated the accuracy, sensitivity, and specificity through a per-lesion-based analysis. A propensity score matching analysis was performed to reduce the effects of selection bias, and we compared the respective outcomes according to NM-NBI and CE-Iodine after matching. RESULTS: The accuracy, sensitivity, and specificity of NM-NBI were 77.0, 88.3, and 75.2%, respectively, and those for unstained areas by CE-Iodine were 68.0, 94.2, and 64.0, respectively. The accuracy and specificity of NM-NBI were superior to those of CE-Iodine (P=0.03 and P=0.01, respectively). However, the sensitivity did not significantly differ between NM-NBI and CE-Iodine (P=0.67). The accuracy and specificity of NM-NBI before matching were superior to those of CE-Iodine after matching (P=0.04 and P=0.03). CONCLUSIONS: NM-NBI was useful and reliable for the diagnosis of esophageal SCC and can be a promising screening strategy for early esophageal SCC. PMID:24751580

Nagami, Yasuaki; Tominaga, Kazunari; Machida, Hirohisa; Nakatani, Masami; Kameda, Natsuhiko; Sugimori, Satoshi; Okazaki, Hirotoshi; Tanigawa, Tetsuya; Yamagami, Hirokazu; Kubo, Naoshi; Shiba, Masatsugu; Watanabe, Kenji; Watanabe, Toshio; Iguchi, Hiroyoshi; Fujiwara, Yasuhiro; Ohira, Masaichi; Hirakawa, Kosei; Arakawa, Tetsuo

2014-01-01

281

Calculations of N 2 triplet states vibrational populations and band emissions in venusian dayglow  

NASA Astrophysics Data System (ADS)

A model for N 2 triplet states band emissions in the venusian dayglow has been developed for low and high solar activity conditions. Steady state photoelectron fluxes and volume excitation rates for N 2 triplet states have been calculated using the Analytical Yield Spectra (AYS) technique. Model calculated photoelectron flux is in good agreement with Pioneer Venus Orbiter-observed electron flux. Since inter-state cascading is important for the triplet states of N 2, populations of different levels of N 2 triplet states are calculated under statistical equilibrium considering direct electron impact excitation, and cascading and quenching effects. Densities of all vibrational levels of each triplet state are calculated in the model. Height-integrated overhead intensities of N 2 triplet band emissions are calculated, the values for Vegard-Kaplan (A3?u+-X1?g+), First Positive (B3?g-A3?u+), Second Positive ( C3? u - B3? g), and Wu-Benesch ( W3? u - B3? g) bands of N 2, are 1.9 (3.2), 3 (6), 0.4 (0.8), and 0.5 (1.1) kR, respectively, for solar minimum (maximum) conditions. The intensities of the three strong Vegard-Kaplan bands (0, 5), (0, 6), and (0, 7) are 94 (160), 120 (204), and 114 (194) R, respectively, for solar minimum (maximum) conditions. Limb profiles are calculated for VK (0, 4), (0, 5), (0, 6) and (0, 7) bands. The calculated intensities on Venus are about a factor 10 higher than those on Mars. The present study provides a motivation for a search of N 2 triplet band emissions in the dayglow of Venus.

Bhardwaj, Anil; Jain, Sonal Kumar

2012-02-01

282

Mechanism of generation of the emission bands in the dynamic spectrum of the Crab pulsar  

E-print Network

We show that the proportionately spaced emission bands in the dynamic spectrum of the Crab pulsar (Hankins T. H. & Eilek J. A., 2007, ApJ, 670, 693) fit the oscillations of the square of a Bessel function whose argument exceeds its order. This function has already been encountered in the analysis of the emission from a polarization current with a superluminal distribution pattern: a current whose distribution pattern rotates (with an angular frequency $\\omega$) and oscillates (with a frequency $\\Omega>\\omega$ differing from an integral multiple of $\\omega$) at the same time (Ardavan H., Ardavan A. & Singleton J., 2003, J Opt Soc Am A, 20, 2137). Using the results of our earlier analysis, we find that the dependence on frequency of the spacing and width of the observed emission bands can be quantitatively accounted for by an appropriate choice of the value of the single free parameter $\\Omega/\\omega$. In addition, the value of this parameter, thus implied by Hankins & Eilek's data, places the last peak in the amplitude of the oscillating Bessel function in question at a frequency ($\\sim\\Omega^3/\\omega^2$) that agrees with the position of the observed ultraviolet peak in the spectrum of the Crab pulsar. We also show how the suppression of the emission bands by the interference of the contributions from differring polarizations can account for the differences in the time and frequency signatures of the interpulse and the main pulse in the Crab pulsar. Finally, we put the emission bands in the context of the observed continuum spectrum of the Crab pulsar by fitting this broadband spectrum (over 16 orders of magnitude of frequency) with that generated by an electric current with a superluminally rotating distribution pattern.

H. Ardavan; A. Ardavan; J. Singleton; M. Perez

2008-04-19

283

Review of Terra MODIS thermal emissive band L1B radiometric performance  

NASA Astrophysics Data System (ADS)

The MODerate-resolution Imaging Spectroradiometer (MODIS) on NASA's Earth Observing System Terra satellite, launched into orbit on 18 December 1999, will have a "first light" 15th anniversary on 24 February 2015. For nearly 15 years the MODIS instrument has provided radiances in all spectral bands. Though some detectors have fallen below SNR thresholds, the vast majority of spectral bands continue to provide high quality L1B measurements for use in L2 science algorithms supporting global climate research. Radiometric accuracy of the Terra MODIS thermal emissive bands (TEBs) in the C6 L1B product has been assessed using various approaches over the nearly 15 year Terra MODIS data record, including comparisons with instruments on the ground, in aircraft under-flights, and on other satellites. All of these approaches contribute to the understanding of the Terra MODIS radiometric L1B performance. Early in the lifetime of Terra, ground-based measurements and NASA ER-2 aircraft under-flights revealed that TEBs in the infrared window ("window" bands) are well calibrated and performing within accuracy specifications. The ER-2 under-flights also suggested that many atmospheric bands may be performing outside of specification, especially LWIR CO2 sensitive bands that are subject to optical crosstalk, although analysis uncertainties are larger for atmospheric bands. Beginning in 2007, MetOp-A IASI observations were used to evaluate Terra MODIS TEB performance through Simultaneous Nadir Overpass (SNO) comparisons. These inter-satellite comparisons largely affirm the early aircraft and ground-based evaluations, showing that all Terra MODIS window bands have small biases, minimal trending, and minor detector and mirror side striping over the 2007-2013 timeframe. Most atmospheric bands are performing satisfactorily near to specification; however, biases, striping and trending are large and significantly out of specification in the water vapor sensitive band 27 and ozone sensitive band 30 while the CO2 sensitive band 36 bias significantly exceeds specification. The investigation has found that an effective spectral shift significantly reduces biases and scene temperature dependence (but not trends) in most atmospheric bands, bringing them closer to, if not within, specification.

Moeller, Chris; Menzel, W. P.; Quinn, Greg

2014-09-01

284

GROUND-BASED DETECTIONS OF THERMAL EMISSION FROM THE DENSE HOT JUPITER WASP-43b IN THE H AND K{sub s} BANDS  

SciTech Connect

We report new detections of thermal emission from the transiting hot Jupiter WASP-43b in the H and K{sub s} bands as observed at secondary eclipses. The observations were made with the WIRCam instrument on the Canada-France-Hawaii Telescope. We obtained a secondary eclipse depth of 0.103{sub -0.017}{sup +0.017}%$ and 0.194{sub -0.029}{sup +0.029} in the H and K{sub s} bands, respectively. The K{sub s}-band depth is consistent with the previous measurement in the narrow band centered at 2.09 {mu}m by Gillon et al. Our eclipse depths in both bands are consistent with a blackbody spectrum with a temperature of {approx}1850 K, slightly higher than the dayside equilibrium temperature without day-night energy redistribution. Based on theoretical models of the dayside atmosphere of WASP-43b, our data constrain the day-night energy redistribution in the planet to be {approx}< 15%-25%, depending on the metal content in the atmosphere. Combined with energy balance arguments, our data suggest that a strong temperature inversion is unlikely in the dayside atmosphere of WASP-43b. However, a weak inversion cannot be strictly ruled out at the current time. Future observations are required to place detailed constraints on the chemical composition of the atmosphere.

Wang, W.; Zhao, G. [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Van Boekel, R.; Henning, Th. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Madhusudhan, N. [Department of Physics and Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Chen, G., E-mail: wangw@nao.cas.cn [Purple Mountain Observatory, Chinese Academy of Sciences, West Beijing Road, Nanjing 210008 (China)

2013-06-10

285

VIIRS thermal emissive bands on-orbit calibration coefficient performance using vicarious calibration results  

NASA Astrophysics Data System (ADS)

The Visible Infrared Imager Radiometer Suite (VIIRS), a primary sensor on-board the Suomi-National Polar-orbiting Partnership (SNPP) spacecraft, was launched October 28, 2011. It has 22 bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). The TEBs cover the spectral wavelengths between 3.7 to 12 ?m and have two 371 m and five 742 m spatial resolution bands. A VIIRS Key Performance Parameter (KPP) is the sea surface temperature (SST) which uses bands M12 (3.7 ?m), M15 (10.8 ?m) and M16's (12.0 ?m) calibrated Science Data Records (SDRs). The TEB SDRs rely on pre-launch calibration coefficients used in a quadratic algorithm to convert the detector's response to calibrated radiance. This paper will evaluate the performance of these prelaunch calibration coefficients using vicarious calibration information from the Cross-track Infrared Sounder (CrIS) also onboard the SNPP spacecraft and the Infrared Atmospheric Sounding Interferometer (IASI) on-board the Meteorological Operational (MetOp) satellite. Changes to the pre-launch calibration coefficients' offset term c0 to improve the SDR's performance at cold scene temperatures will also be discussed.

Moyer, D.; Moeller, C.; De Luccia, F.

2013-09-01

286

Energetic and Broad Band Spectral Distribution of Emission from Astronomical Jets  

NASA Astrophysics Data System (ADS)

Emission from astronomical jets extend over the entire spectral band: from radio to the TeV ?-rays. This implies that various radiative processes are taking place in different regions along jets. Understanding the origin of the emission is crucial in understanding the physical conditions inside jets, as well as basic physical questions such as jet launching mechanism, particle acceleration and jet composition. In this chapter I discuss various radiative mechanisms, focusing on jets in active galactic nuclei (AGN) and X-ray binaries (XRB) environment. I discuss various models in use in interpreting the data, and the insights they provide.

Pe'er, Asaf

2014-09-01

287

Single-molecule light emission at room temperature on a wide-band-gap semiconductor  

NASA Astrophysics Data System (ADS)

Room-temperature light emission from single chemisorbed perylene based molecules adsorbed on silicon carbide (SiC) is probed by scanning tunneling microscopy (STM). A new approach to STM-induced luminescence of a single molecule is explored using a wide-band-gap semiconductor to decouple electronically the molecule from the surface. After molecular adsorption, the lowest unoccupied molecular orbital and the highest occupied molecular orbital (HOMO) both lie within the bulk band gap and below the Fermi level of the substrate. The maximum photon energy of the light emission from the molecule shows a fixed shift of 1.5 eV relative to the maximum energy of the tunnel electrons. This is consistent with the photons being generated by inelastic electron tunneling between the HOMO and the unoccupied electronic states of the STM tip.

Yang, H.; Mayne, A. J.; Comtet, G.; Dujardin, G.; Kuk, Y.; Nagarajan, S.; Gourdon, A.

2014-09-01

288

On the carriers of the 3.4-micrometer absorption and emission bands, and their evolution  

E-print Network

Based on the results of chemical analysis and simulation of kerogens and immature coals, a large number of chemical structures carrying the 3.4-mum feature were studied by means of computer simulation codes. Further selection criteria were the integrated strength of the absorption lines in the aliphatic stretchings wavelength band, weak IR activity in the aromatic stretching band and absence of notable activity outside the astronomical UIBs (Unidentified Infrared Bands). Most of the structures that were retained can be classed as branched, short and oxygen-bridged CH_{2} chains, and naphtenic chains. Combinations of their absorption spectra deliver spectra comparable to those observed in the sky. Absorption spectra were derived from Normal Mode Analysis. Emission spectra of the same structures were computed by monitoring their overall dipole moment as they vibrate freely in vacuum after excitation. These spectra were then combined in suitable proportions, together with those of aromatic structures, so as to s...

Papoular, Renaud

2014-01-01

289

Demonstration of high-power and stable C-band and L-band erbium-doped fiber amplified spontaneous emission sources using multipumping configuration  

NASA Astrophysics Data System (ADS)

We have investigated and experimentally demonstrated high-power and stable C-band and L-band erbium-doped fiber amplified spontaneous emission (ASE) sources using a multipumping configuration, which can provide an output power of 27.16 dBm (519.99 mW) and 27.34 dBm (542.01 mW) with a power ripple of 5.9 and 1.1 dB for C-band and L-band without adding any external spectra-flattening components. Moreover, the averaged power stability of C-band and L-band erbium-doped fiber ASE source with +/-0.005 and +/-0.003 dB during an 8-h interval measurements at the room temperature 25 °C can be achieved, allowing high pumping efficiency of 38.5 and 36.9%.

Chang, Chia-Hsiung; Liang, Tsair-Chun

2009-09-01

290

Photonic Crystal and Photonic BandGap Structures for Light Extraction and Emission Control  

Microsoft Academic Search

Research into photonic crystal (PhC) and photonic band-gap (PBG) structures has been motivated, from the start, by their possible\\u000a use in controlling, modifying and enhancing the light emission process from high refractive index solid materials. This chapter\\u000a considers the possible role of such structures when incorporated into semiconductor diode based light-emitting devices. Both\\u000a light-emitting diodes (LEDs) and lasers will be

Richard M. De La Rue

291

High-Power All-Fiber-Based Narrow-Linewidth Single-Mode Fiber Laser Pulses in the C-Band and Frequency Conversion to THz Generation  

Microsoft Academic Search

Based on highly Er\\/Yb codoped phosphate fibers, we have implemented all-fiber-based narrow-linewidth single-mode (SM) pulsed fiber lasers in master oscillator and power amplifier configuration. Two approaches were used to achieve the narrow-linewidth pulsed fiber laser seeds: 1) an all-fiber-based active Q-switched fiber laser using an actuator and 2) a directly modulated single-frequency continuous-wave fiber laser. Both the fiber laser seed

Wei Shi; Matthew A. Leigh; Jie Zong; Zhidong Yao; Dan T. Nguyen; Arturo Chavez-Pirson; Nasser Peyghambarian

2009-01-01

292

Thermal band selection for the PRISM instrument: 1. Analysis of emissivity-temperature separation algorithms  

NASA Astrophysics Data System (ADS)

One of the missions being planned by the European Space Agency (ESA) within the framework of its Earth Observation Programme is the Processes Research by Imaging Space Mission (PRISM). The PRISM instrument consists of a thermal sensor whose main objective is to retrieve accurate land surface temperatures (LST) and whose band positions are 3.5-4.1 ?m, 8.1-9.5 ?m, 10.3-11.3 ?m, and 11.5-12.5 ?m. We have studied the optimal design of this instrument to retrieve accurate LSTs. First, we have analyzed several emissivity-temperature separation methods (part 1) and atmospheric and emissivity correction algorithms (part 2). Finally, we have identified the optimal band configuration (part 3). This paper is the first of a series of three and addresses the question of the emissivity-temperature separability. Among all the existing algorithms, we have studied the "absolute methods," which are able to estimate the absolute value of emissivity at satellite scale and can yield better results in the emissivity estimate. These methods are the algorithm based on the temperature-independent thermal infrared spectral index (TISI), the alpha coefficients method, and the algorithms which use visible, near-infrared, and shortwave infrared data to estimate the thermal emissivity (vegetation cover method (VCM)). The study consisted of an analysis of both random and systematic errors of each method. The results indicate that emissivity can be obtained with an error of ±1.7-5% using the alpha coefficients, ±1.7-3% using the TISIs, and ±0.5-1.4% using the VCM, depending on the spectral region. In all cases the error decreases with wavelength, and the lowest errors are achieved in the 10-12 ?m spectral region, due to small variability of emissivity. It is necessary that the two first methods use radiosondes simultaneous with the satellite overpass to perform the atmospheric corrections on the thermal data; in addition, they show important sources of systematic errors, which will increase the uncertainty in the emissivity estimate (even in the best possible case). The VCM does not use radiosondes and does not present important sources of systematic error. It appears to be the procedure with the most favorable error propagation characteristics. Thus the VCM could be the most adequate method for retrieving the land surface emissivity (LSE), within the framework of this work.

Caselles, Vicente; Valor, Enric; Coll, CéSar; Rubio, Eva

1997-05-01

293

Multiyear On-orbit Calibration and Performance of Terra MODIS Thermal Emissive Bands  

NASA Technical Reports Server (NTRS)

Since launch in December 1999, Terra MODIS has been making continuous Earth observations for more than seven years. It has produced a broad range of land, ocean, and atmospheric science data products for improvements in studies of global climate and environmental change. Among its 36 spectral bands, there are 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). MODIS thermal emissive bands cover the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions with wavelengths from 3.7 to 14.4pm. They are calibrated on-orbit using an on-board blackbody (BB) with its temperature measured by a set of thermistors on a scan-by-scan basis. This paper will provide a brief overview of MODIS TEB calibration and characterization methodologies and illustrate on-board BB functions and TEB performance over more than seven years of on-orbit operation and calibration. Discussions will be focused on TEB detector short-term stability and noise characterization, and changes in long-term response (or system gain). Results show that Terra MODIS BB operation has been extremely stable since launch. When operated at its nominal controlled temperature of 290K, the BB temperature variation is typically less than +0.30mK on a scan-by-scan basis and there has been no time-dependent temperature drift. In addition to excellent short-term stability, most TEB detectors continue to meet or exceed their specified noise characterization requirements, thus enabling calibration accuracy and science data product quality to be maintained. Excluding the noisy detectors identified pre-launch and those that occurred post-launch, the changes in TEB responses have been less than 0.7% on an annual basis. The optical leak corrections applied to bands 32-36 have been effective and stable over the entire mission

Xiong, Xiaoxiong; Chiang, Kwo-Fu; Wu, Aisheng; Barnes, William; Guenther, Bruce; Salomonson, Vincent

2007-01-01

294

Coherent control of spontaneous emission near a photonic band edge: A qubit for quantum computation  

NASA Astrophysics Data System (ADS)

We demonstrate the coherent control of spontaneous emission for a three-level atom located within a photonic band-gap structure with one resonant frequency near the edge of the photonic band gap. Spontaneous emission from the three-level atom can be totally suppressed or strongly enhanced depending on the relative phase between the steady-state control laser coupling the two upper levels and the pump laser pulse used to create an excited state of the atom in the form of a coherent superposition of the two upper levels. Unlike the free-space case, the steady-state inversion of the atomic system is strongly dependent on the externally prescribed initial conditions. This nonzero steady-state population is achieved by virtue of the localization of light in the vicinity of the emitting atom. It is robust to decoherence effects provided that the Rabi frequency of the control laser field-atom interaction exceeds the rate of dephasing interactions. As a result, such a system may be relevant for a single-atom, phase-sensitive, optical memory device on the atomic scale. The protected electric dipole within the photonic band gap provides a basis for a qubit to encode information for quantum computations.

Woldeyohannes, Mesfin; John, Sajeev

1999-12-01

295

EXAMINING THE BROADBAND EMISSION SPECTRUM OF WASP-19b: A NEW z-BAND ECLIPSE DETECTION  

SciTech Connect

WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary eclipse is the deepest of all transiting planets and has been measured in multiple optical and infrared bands. We obtained a z-band eclipse observation with a measured depth of 0.080% {+-} 0.029%, using the 2 m Faulkes Telescope South, which is consistent with the results of previous observations. We combined our measurement of the z-band eclipse with previous observations to explore atmosphere models of WASP-19b that are consistent with its broadband spectrum. We use the VSTAR radiative transfer code to examine the effect of varying pressure-temperature profiles and C/O abundance ratios on the emission spectrum of the planet. We find that models with super-solar carbon enrichment best match the observations, which is consistent with previous model retrieval studies. We also include upper atmosphere haze as another dimension in the interpretation of exoplanet emission spectra and find that particles <0.5 {mu}m in size are unlikely to be present in WASP-19b.

Zhou, George; Bayliss, Daniel D. R. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd, Weston Creek, ACT 2611 (Australia); Kedziora-Chudczer, Lucyna; Bailey, Jeremy, E-mail: george@mso.anu.edu.au [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)

2013-09-10

296

Control of spontaneous emission from a driven five-level atom in a photonic-band-gap reservoir  

NASA Astrophysics Data System (ADS)

We investigate the spontaneous emission properties of a five-level atom driven by a microwave field, where the two transitions are coupled to a double-band photonic-band-gap reservoir. The effects of the band-edge positions and the Rabi frequency of the microwave field on the emission spectrum are discussed. It is found that several interesting phenomena in spontaneous emission spectra such as spectral-line enhancement, spectral-line elimination, and fluorescence quenching can be controlled simply by adjusting the Rabi frequency of the driving field and the transition frequency detunings from band edges. These phenomena originate from quantum interference induced by band-edge modes and the driving field.

Liu, Ronggang

2014-05-01

297

Acoustic Emissions, Velocities And Permeability Evolution During Formation Of Compaction Bands In Sandstone.  

NASA Astrophysics Data System (ADS)

Compaction bands are zones of localized deformation observed in high porosity rock (Mollema et al. [1996], Klein et al. [2001], Fortin et al. [2003]). These planar bands form perpendicular to the direction of maximum compression. Compaction bands display significantly reduced porosity and are potentially important permeability barriers in reservoir rocks and aquifers. To investigate localized compaction and changes in physical properties of porous sandstone, we performed triaxial tests on Bleurswiller sandstone, (50% quartz 30% feldspars and 20% clay, 25% porosity), on Fontainebleau sandstone (100% quartz, 25% porosity) and on Flechtingen sandstone (65-75% quartz, calcite and illite 15%, porosity 5.5-7%). Experiments were performed under wet conditions at a pore pressure of 10 MPa. Thirteen experiments were performed at the Laboratoire de Geologie (Ecole Normal Superieur Paris) and at GeoForschungsZentrum Potsdam. Evolution of volumetric strain, elastic wave velocities and permeability were recorded at confining pressures of 12 and 180 MPa. Acoustic Emission (AE) characteristics during deformation were studied at GeoForschungsZentrum Potsdam. To monitor velocity change and microcracking of sandstone, 10 P-wave sensors and 8 polarized S-wave piezoelectric sensors were glued to the cylindrical surface of the samples. To monitor fracture-induced anisotropy, two additional P sensors were installed in axial direction. Fully digitized waveforms were recorded by 10 MHz/16bit Data Acquisition System with an accuracy of AE hypocenters determination of about 2.5 mm. Location of acoustic emission events reveal the evolution of localized compaction bands in sandstone subjected to axial compression. The formation of the bands depends on rock type and effective pressure. Our experiments show a reduction of permeability across compaction bands by about one to two orders of magnitude (Vajdova et al. [2004]; Holcomb et al., [2003]) suggesting that the bands may act as barriers to fluid flow in porous rocks. Samples were first subjected to increasing confining pressure and subsequently loaded axially. During hydrostatic compression, elastic wave velocities first increased up to 10% due to crack closure and compaction. After onset of axial loading, transverse velocities decreased by 10%-20% owing to induced crack damage and depending on rock type and confining pressure. Axial velocity component first increased slightly with increasing mean stress and dropped to starting value.

Fortin, J.; Stanchits, S.; Dresen, G.; Schubnel, A.; Gueguen, Y.

2004-12-01

298

Ruling out unresolved binaries in five transitional disks. VLT/NACO deep 2.12 and 1.75 ?m narrow-band imaging  

NASA Astrophysics Data System (ADS)

Context. The presence of unresolved binaries on sub-arsecond scales could explain the existence of optically thin inner holes or gaps in circumstellar disks, which are commonly referred to as "transitional" or "cold" disks, and it is the first scenario to check before making any other assumptions. Aims: We aim at detecting the presence of companions inside the inner hole/gap region of a sample of five well known transitional disks using spatially-resolved imaging in the near-IR with the VLT/NACO/S13 camera, which probes projected distances from the primary of typically 0.1 to 7 arcsec. The sample includes the stars DoAr 21, HD 135344B (SAO 206462), HR 4796A, T Cha, and TW Hya, spanning ages of less than 1 to 10 Myr, spectral types of A0 to K7, and hole/gap outer radii of 4 to 100 AU. Methods: In order to enhance the contrast and to avoid saturation at the core of the point-spread function (PSF), we use narrow-band filters at 1.75 and 2.12 ?m. The "locally optimized combination of images" (LOCI) algorithm is applied for an optimal speckle noise removal and PSF subtraction, providing an increase of 0.5-1.5 mag in contrast over the classic method. Results: With the proviso that we could have missed companions owing to unfavorable projections, the VLT/NACO observations rule out the presence of unresolved companions down to an inner radius of about 0.1 arcsec from the primary in all five transitional disks and with a detection limit of 2 to 5 mag in contrast. In the disk outer regions the detection limits typically reach 8 to 9 mag in contrast and 4.7 mag for T Cha. Hence, the NACO images resolve part of the inner hole/gap region of all disks with the exception of TW Hya, for which the inner hole is only 4 AU. The 5? sensitivity profiles, together with a selected evolutionary model, allow to discard stellar companions within the inner hole/gap region of T Cha, and down to the substellar regime for HD 135344B and HR 4796A. DoAr 21 is the only object from the sample of five disks for which the NACO images are sensitive enough for a detection of objects less massive than ~13 MJup that is, potential giant planets or low-mass brown dwarfs at radii larger than ~76 AU (0.63 arcsec). Conclusions: These new VLT/NACO observations further constrain the origin of the inner opacity cavities to be owing to closer or lower-mass companions or other mechanisms such as giant planet formation, efficient grain growth, and photoevaporation (for DoAr 21 and HR 4796A).

Vicente, S.; Merín, B.; Hartung, M.; Bouy, H.; Huélamo, N.; Artigau, E.; Augereau, J.-C.; van Dishoeck, E.; Olofsson, J.; Oliveira, I.; Prusti, T.

2011-09-01

299

The effects of reorientation on the emission properties of a photonic band edge liquid crystal laser  

NASA Astrophysics Data System (ADS)

The effect of altering the excitation rate on the emission energy of a photonic band edge liquid crystal laser has been investigated. The results showed that for excitation energies greater than 18 µJ/pulse, an increase in the excitation rate from 1 to 20 Hz caused a reduction in the total emission energy of the photonic band edge liquid crystal laser of up to 90%. In order to establish the cause of this reduction several factors were considered: dye bleaching, thermal/density effects and director-axis reorientation (either by virtue of a light-induced torque or other effects such as a flow-induced orientational decay). Although some dye bleaching was observed, the main factor responsible for the reduction in the overall emission efficiency was found to be nonlinear changes in the director-axis reorientation. Furthermore, our results suggest that the director-axis reorientation is the result of an optical torque, enhanced by the presence of the dye, which for a chiral nematic liquid crystal results in a dilation of the helical pitch.

Morris, S. M.; Ford, A. D.; Pivnenko, M. N.; Coles, H. J.

2005-05-01

300

Model calculation of N2 Vegard-Kaplan band emissions in Martian dayglow  

NASA Astrophysics Data System (ADS)

A model for N2 Vegard-Kaplan (VK) band (A3?u+ - X1?g+) emissions in Martian dayglow has been developed to explain the recent observations made by the Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph aboard Mars Express. Steady state photoelectron fluxes and volume excitation rates have been calculated using the analytical yield spectra technique. Since interstate cascading is important for triplet states of N2, the population of any given level of N2 triplet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet state is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK, first positive (B3?g - A3?u+), second positive (C3?u - B3?g), and Wu-Benesch (W3?u - B3?g) bands of N2. A reduction in the N2 density by a factor of 3 in the Mars thermospheric general circulation model is required to obtain agreement between calculated limb profiles of VK (0-6) and SPICAM observation. Calculations are carried out to asses the impact of model parameters, namely, electron impact cross sections, solar EUV flux, and model atmosphere, on the emission intensities. Constraining the N2/CO2 ratio by SPICAM observations, we suggest the N2/CO2 ratios to be in the range 1.1-1.4% at 120 km, 1.8-3.2% at 140 km, and 4-7% at 170 km. During high solar activity the overhead intensity of N2 VK band emissions would be ˜2.5 times higher than that during low solar activity.

Jain, Sonal Kumar; Bhardwaj, Anil

2011-07-01

301

Quantum simulation of the yellow emission band of CsXe  

NASA Technical Reports Server (NTRS)

Quantum spectral simulations of the yellow excimer emission band of CsXe are presented. Synthetic spectra as a function of wave number are calculated for the 2 Sigma 1/2 + (7s) - 2 Sigma 1/2 + (6s) transition by the use of the equation of Tellinghuisen et al. (1976) with a theoretical potential for the ground state and a Morse potential curve with an electron frequency of 32/cm for the excited state. Results based on emission studies at 450 K and 200 and 800 torr, are found to be consistent with absorption studies. The undulatory structure observed in the spectrum is attributed not to the vibrational spacing in the excited state, but rather to a characteristic reflection structure associated with nearly parallel upper and lower potential curves.

Tellinghuisen, J.; Exton, R. J.

1980-01-01

302

Model of the Optical Emission of a Driven Semiconductor Quantum Dot: Phonon-Enhanced Coherent Scattering and Off-Resonant Sideband Narrowing  

NASA Astrophysics Data System (ADS)

We study the crucial role played by the solid-state environment in determining the photon emission characteristics of a driven quantum dot. For resonant driving, we predict a phonon enhancement of the coherently emitted radiation field with increasing driving strength, in stark contrast to the conventional expectation of a rapidly decreasing fraction of coherent emission with stronger driving. This surprising behavior results from thermalization of the dot with respect to the phonon bath and leads to a nonstandard regime of resonance fluorescence in which significant coherent scattering and the Mollow triplet coexist. Off resonance, we show that despite the phonon influence, narrowing of dot spectral sideband widths can occur in certain regimes, consistent with an experimental trend.

McCutcheon, Dara P. S.; Nazir, Ahsan

2013-05-01

303

Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness  

NASA Astrophysics Data System (ADS)

A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.2 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest. Second, observations from Aquarius are being used to develop a model for the effect of wind-driven roughness (waves) on the emissivity in the open ocean. This is done by comparing the measured radiometric brightness temperature with the value expected for a surface with the same salinity and physical temperature. A parametric model for the excess brightness temperature as a function of wind speed and wind direction is developed in the form: ?TB = A0(w) + A1(w) cos(?) + A2(w) cos(2?) where w = wind speed; ? = wind direction (relative to the look direction of the radiometer) and ?TB = ?E Ts where Ts is the physical temperature and ?E is the change in emissivity caused by the waves. A0(w) is roughly linear with wind speed with values on the order of 3 K at 15 m/s. The directional dependence is much smaller but the data definitely indicate a directional component for wind speeds greater than 10-15 m/s. The coefficients depend on the incidence angle of the radiometer.

Le Vine, D. M.; Lang, R. H.; Wentz, F. J.; Meissner, T.

2012-12-01

304

The ground-based H, K, and L-band absolute emission spectra of HD 209458b  

E-print Network

Here we explore the capabilities of NASA's 3.0 meter Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 meter Hale telescope with the TripleSpec spectrometer with near-infrared H, K, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L-band indicate bright emission hypothesized to result from non-LTE CH$_{4}$ $\

Zellem, Robert T; Deroo, Pieter; Swain, Mark R; Waldmann, Ingo P

2014-01-01

305

Structural phase transition, narrow band gap, and room-temperature ferromagnetism in [KNbO3]1-x[BaNi1/2Nb1/2O3-?]x ferroelectrics  

NASA Astrophysics Data System (ADS)

Structural phase transition, narrow band gap (Eg), and room-temperature ferromagnetism (RTFM) have been observed in the [KNbO3]1-x[BaNi1/2Nb1/2O3-?]x (KBNNO) ceramics. All the samples have single phase perovskite structure, but exhibit a gradual transition behaviour from the orthorhombic to a cubic structure with the increase of x. Raman spectroscopy analysis not only corroborates this doping-induced change in normal structure but also shows the local crystal symmetry for x ? 0.1 compositions to deviate from the idealized cubic perovskite structure. A possible mechanism for the observed specific changes in lattice structure is discussed. Moreover, it is noted that KBNNO with compositions x = 0.1-0.3 have quite narrow Eg of below 1.5 eV, much smaller than the 3.2 eV band gap of parent KNbO3 (KNO), which is due to the increasing Ni 3d electronic states within the gap of KNO. Furthermore, the KBNNO materials present RTFM near a tetragonal to cubic phase boundary. With increasing x from 0 to 0.3, the magnetism of the samples develops from diamagnetism to ferromagnetism and paramagnetism, originating from the ferromagnetic-antiferromagnetic competition. These results are helpful in the deeper understanding of phase transitions, band gap tunability, and magnetism variations in perovskite oxides and show the potential role, such materials can play, in perovskite solar cells and multiferroic applications.

Zhou, Wenliang; Deng, Hongmei; Yang, Pingxiong; Chu, Junhao

2014-09-01

306

Capturing electromagnetic emissions in the HF band possibly related to earthquake events  

NASA Astrophysics Data System (ADS)

The purpose of this project was to capture electromagnetic emissions in the HF band. Possible correlations of these emissions prior to strong earthquakes were investigated. In order to record the variations of the electromagnetic field in a wide spectrum of frequencies up to the VHF band, a new device was designed and implemented by our research team. Ten prototype electromagnetic variation (EMV) field stations have already been installed in Greece, at the locations, Corfu, Ioannina, Ithomi (Kalamata), Kephalonia, Kozani, Mytilini, Rodos, Neapoli (Crete), and Bamos (Crete). This telemetric network was launched in 1999 and since it has been in constant operation. During the period 2005-2008, 14 strong earthquakes occurred in Greece with magnitude over Ms>=6. Of them, three events were recorded as precursor signals by only one station. Fractal analysis showed that these were precursors and not manmade signals. In eight EQs events, two or three stations recorded simultaneously precursor signals. In one EQ event, recordings in all stations were disturbed by strong magnetic storms twenty days before the event. In two EQs, events did not trigger any station in a time window of up to 10 days.

Koulouras, Gr; Kontakos, K.; Ninos, K.; Cavouras, D.; Nomicos, C.

2009-04-01

307

Observational studies on the Near-Infrared Unidentified Emission Bands in Galactic HII regions  

E-print Network

Using a large collection of near-infrared spectra (2.5-5.4 um) of Galactic HII regions and HII region-like objects, we perform a systematic investigation of the astronomical polycyclic aromatic hydrocarbon (PAH) features. 36 objects were observed by the use of the infrared camera onboard the AKARI satellite as a part of a directer's time program. In addition to the well-known 3.3-3.6 um features, most spectra show a relatively-weak emission feature at 5.22 um with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 um band previously reported. By careful analysis, we find good correlations between the 5.25 um band and both the aromatic hydrocarbon feature at 3.3 um and the aliphatic ones at around 3.4-3.6 um. The present results give us convincing evidence that the astronomical 5.25 um band is associated with C-H vibrations as suggested by previous studies and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic to aromatic ratio of I(3.4-3.6)/I(3....

Mori, Tamami I; Sakon, Itsuki; Ishihara, Daisuke; Shimonishi, Takashi; Ohsawa, Ryou; Bell, Aaron C

2014-01-01

308

Evaluation of Terra and Aqua MODIS thermal emissive band calibration consistency  

NASA Astrophysics Data System (ADS)

Terra and Aqua MODIS have operated continuously for more than 12 and 10 years respectively and are key instruments for NASA's Earth Observing System missions. The 16 thermal emissive bands (TEB), covering wavelengths from 3.5 to 14.4 ?m with a nadir spatial resolution of 1 km are used to regularly generate a variety of atmosphere, ocean and land science products. As the sensors age well past their prime design life of 6 years, understanding the instrument on-orbit performance is necessary to maintain consistency between sensors in the long-term data records. Recurrent observations of Dome C, Antarctica by both Terra and Aqua MODIS over mission lifetime are used to track the calibration consistency and stability of the two sensors. A ground temperature sensor provides a proxy reference measurement useful for determining the relative bias between the two instruments. This technique is most useful for the land surface sensing bands, such as bands 29, 31 and 32, but can be applied to all other TEB to provide a metric to assess long-term trends. A change in the TEB calibration approach for the MODIS Collection 6 reprocessing mitigate a cold scene bias previously observed for retrievals of brightness temperatures well below the on-board blackbody calibrator temperature range (270-315 K). The impact of the Collection 6 calibration changes are illustrated using the Dome C observations.

Wenny, B. N.; Xiong, X.; Madhavan, S.

2012-09-01

309

Spatial distribution of unidentified infrared bands and extended red emission in the compact galactic HII region Sh 152  

E-print Network

We present visible and near IR images of the compact HII region Sh 152. Some of these images reveal the presence of Extended Red Emission (ERE) around 698 nm and emission from Unidentified Infra Red Bands (UIRBs) at 3.3 and 6.2 micron. Other images show the near infrared (7-12 micron) continuous emission of the nebula. The ERE emission is found to coincide with the ionized region and significantly differ from the UIRBs location. Also some evidence is found in favor of grains as carriers for ERE.

S. Darbon; A. Zavagno; C. Savine; V. Ducci; J. -M. Perrin; J. -P. Sivan

1998-12-02

310

Detection of CO Cameron band emission in comet P\\/Hartley 2 (1991 XV) with the Hubble Space Telescope  

Microsoft Academic Search

Ultraviolet (UV) spectra of comet P\\/Hartley 2 (1991 XV) taken with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in 1991 September reveal several bands of the Cameron system of CO (a 3 Pi-X 1 Sigma). These band are most likely due to 'prompt' emission from CO2 and, thus, provide a direct tracer of the CO2 abundance

H. A. Weaver; P. D. Feldman; J. B. McPhate; M. F. A'Hearn; C. Arpigny; T. E. Smith

1994-01-01

311

Continuous tuning of a narrow-band terahertz wave in periodically poled stoichiometric LiTaO3 crystal with a fan-out grating structure  

NASA Astrophysics Data System (ADS)

Continuous tuning of terahertz waves was demonstrated with seamless change in grating period in a periodically poled stoichiometric lithium tantalite (SLT) crystal. The periodically poled fan-out structure allows wide tunability such as 610 GHz with the bandwidth as narrow as 17 GHz at a carrier frequency of 1.00 THz. Temperature-dependent measurements show a gradual intensity increase of the THz pulses as the temperature decreases. Furthermore, absorption and refractive index of SLT in the THz range were estimated and compared with those of LiNbO3 (LN). The absorption coefficient of the LT crystal at ordinary wave was almost half of that in the LN crystal. SLT could be one of the powerful crystals for high-power THz generation with large optical aperture because of the fewer defects inside the crystal.

Yu, Nan Ei; Oh, Myoung-Kyu; Kang, Hoonsoo; Jung, Changsoo; Kim, Bok Hyeon; Lee, Kyu-Sup; Ko, Do-Kyeong; Takekawa, Shunji; Kitamura, Kenji

2014-01-01

312

Model for Cameron band emission in comets: A case for EPOXI mission target comet 103P/Hartley 2  

E-print Network

The CO2 production rate has been derived in comets using the Cameron band (a3Pi - X1Sigma) emission of CO molecule assuming that photodissociative excitation of CO2 is the main production mechanism of CO in a3Pi metastable state. We have devoloped a model for the production and loss of CO(a3Pi) which has been applied to comet 103P/Hartley 2: the target of EPOXI mission. Our model calculations show that photoelectron impact excitation of CO and dissociative excitation of CO2 can together contribute about 60-90% to the Cameron band emission. The modeled brightness of (0-0) Cameron band emission on comet Hartley 2 is consistent with Hubble Space Telescope observations for 3-5% CO2 (depending on model input solar flux) and 0.5% CO relative to water, where photoelectron impact contribution is about 50-75%. We suggest that estimation of CO2 abundances on comets using Cameron band emission may be reconsidered. We predict the height integrated column brightness of Cameron band of ~1300 R during EPOXI mission encounte...

Bhardwaj, Anil

2010-01-01

313

Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates  

E-print Network

We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO2), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive index materials of Si. Experimentally, the inhibition factor $\\zeta$ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO2 and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.

M. D. Birowosuto; G. Zhang; A. Yokoo; M. Takiguchi; M. Notomi

2014-05-30

314

Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates  

E-print Network

We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO2), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive index materials of Si. Experimentally, the inhibition factor $\\zeta$ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO2 and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.

Birowosuto, M D; Yokoo, A; Takiguchi, M; Notomi, M

2014-01-01

315

The Mid-infrared Emission of Narrow-line Active Galactic Nuclei: Star Formation, Nuclear Activity, and Two Populations Revealed by Wise  

NASA Astrophysics Data System (ADS)

We explore the nature of the long-wavelength mid-infrared (MIR) emission of a sample of 13,000 local Type II (narrow-line) active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) using 12 ?m and 22 ?m photometry from the WISE all-sky survey. In combination with FIRST 1.4 GHz photometry, we show that AGNs divide into two relatively distinct populations or "branches" in the plane of MIR and radio luminosity. Seyfert galaxies lie almost exclusively on an MIR-bright branch (Branch A), while low-ionization nuclear emission line galaxies (LINERs) are split evenly into Branch A and the MIR-faint Branch B. We devise various tests to constrain the processes that define the branches, including a comparison to the properties of pure star-forming inactive galaxies on the MIR-radio plane. We demonstrate that the total MIR emission of objects on Branch A, including most Seyfert galaxies, is governed primarily by host star formation, with ?15% of the 22 ?m luminosity coming from AGN-heated dust. This implies that ongoing dusty star formation is a general property of Seyfert host galaxies. We show that the 12 ?m broadband luminosity of AGNs on Branch A is suppressed with respect to star-forming galaxies, possibly due to the destruction of PAHs or deeper 10 ?m Si absorption in AGNs. We uncover a correlation between the MIR luminosity and [O III] ?5007 luminosity in AGNs. This suggests a relationship between the star formation rate and nuclear luminosity in the AGN population, but we caution on the importance of selection effects inherent to such AGN-dominated emission-line galaxies in driving such a correlation. We highlight the MIR-radio plane as a useful tool in comparative studies of star formation and nuclear activity in AGNs.

Rosario, David J.; Burtscher, Leonard; Davies, Richard; Genzel, Reinhard; Lutz, Dieter; Tacconi, Linda J.

2013-12-01

316

Thermal emission from a metamaterial wire medium slab.  

PubMed

We investigate thermal emission from a metamaterial wire medium embedded in a dielectric host and highlight two different regimes for efficient emission, respectively characterized by broadband emission near the effective plasma frequency of the metamaterial, and by narrow-band resonant emission at the band-edge in the Bragg scattering regime. We discuss how to control the spectral position and relative strength of these two emission mechanisms by varying the geometrical parameters of the proposed metamaterial and its temperature. PMID:22535071

D'Aguanno, G; Mattiucci, N; Alù, A; Argyropoulos, C; Foreman, J V; Bloemer, M J

2012-04-23

317

Observation of nitric oxide rovibrational band head emissions in the quiescent airglow during the Cirris-1A Space Shuttle Experiment  

Microsoft Academic Search

Band head emissions from highly rotationally excited NO (v,J) (J?90) have been observed in the quiescent atmosphere at tangent heights between approximately 115 and 190 km for both sunlit and nighttime conditions. The data were obtained by the cryogenic CIRRIS-1A interferometer which was operated on-board the space shuttle between 28 and 30 April 1991. Up to ten emission features between

D. R. Smith; M. Ahmadjian

1993-01-01

318

The use of internal field emission to inject electronic charge carriers into the conduction band of diamond films: a review  

Microsoft Academic Search

Several thin film composite metal(semiconductor) diamond cold cathode sources have recently been fabricated exhibiting high current–low power characteristics. We have modeled the field emission in these thin film diamond electron sources as a three-step process (electron injection, transport and vacuum emission). Critical to the operation of these devices is a mechanism for populating the conduction band (CB) of diamond with

P. H Cutler; N. M Miskovsky; P. B Lerner; Moon S Chung

1999-01-01

319

Enhanced p-type conductivity and band gap narrowing in heavily Al doped NiO thin films deposited by RF magnetron sputtering.  

PubMed

Stoichiometric NiO, a Mott-Hubbard insulator at room temperature, shows p-type electrical conduction due to the introduction of Ni(2+) vacancies (V(Ni)('')) and self-doping of Ni(3+) ions in the presence of excess oxygen. The electrical conductivity of this important material is low and not sufficient for active device fabrication. Al doped NiO thin films were synthesized by radio frequency (RF) magnetron sputtering on glass substrates at a substrate temperature of 250?°C in an oxygen + argon atmosphere in order to enhance the p-type electrical conductivity. X-ray diffraction studies confirmed the correct phase formation and also oriented growth of NiO thin films. Al doping was confirmed by x-ray photoelectron spectroscopic studies. The structural, electrical and optical properties of the films were investigated as a function of Al doping (0-4 wt%) in the target. The room temperature electrical conductivity increased from 0.01-0.32 S cm (-1) for 0-4% Al doping. With increasing Al doping, above the Mott critical carrier density, energy band gap shrinkage was observed. This was explained by the shift of the band edges due to the existence of exchange and correlation energies amongst the electron-electron and hole-hole systems and also by the interaction between the impurity quasi-particle system. PMID:21693930

Nandy, S; Maiti, U N; Ghosh, C K; Chattopadhyay, K K

2009-03-18

320

The Dust in Comet C\\/1999 S4 (LINEAR) during Its Disintegration: Narrow-Band Images, Color Maps, and Dynamical Models  

Microsoft Academic Search

Comet C\\/1999 S4 was observed with the 2m-telescopes of the Bulgarian National Observatory and Pik Terskol Observatory, Northern Caucasus, Russia, at the time of its disintegration. Maps of the dust brightness and color were constructed from images obtained in red and blue continuum windows, free from cometary molecular emissions. We analyze the dust environment of Comet C\\/1999 S4 (LINEAR) taking

T. Bonev; K. Jockers; E. Petrova; M. Delva; G. Borisov; A. Ivanova

2002-01-01

321

Narrow spectral emission CaMoO{sub 4}: Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+} phosphor crystals for white light emitting diodes  

SciTech Connect

Alkaline earth metal molybdates are promising candidates as a host material for high efficiency narrow spectral emission phosphors. These phosphors could potentially be used for the fabrication of phosphor-converted light emitting diodes (pc-LEDs). Phosphor crystals of calcium molybdate doped with rare earth dopant Ln{sup 3+}(Ln=Eu, Dy, Tb) grown using flux growth method have been shown to exhibit higher excitation efficiency than the powders synthesized by solid-state reaction process. Molybdenum (VI) oxide has been found to be a suitable flux for growing large size optically transparent high quality crystals at a temperature around 1100 Degree-Sign C. Using the excitation wavelengths of 465 nm, 454 nm and 489 nm for CaMoO{sub 4}: Eu{sup 3+}, CaMoO{sub 4}: Dy{sup 3+} and CaMoO{sub 4}: Tb{sup 3+}, respectively, intense emission lines at wavelengths of 615 nm, 575 nm and 550 nm were observed. The optimized doping concentrations of 12%, 2% and 5% for Eu{sup 3+}, Dy{sup 3+} and Tb{sup 3+}, respectively, provided the highest luminescence intensity. - Graphical Abstract: CaMoO{sub 4}: Eu{sup 3+} phosphor crystals grown using a molybdenum (VI) oxide flux exhibited around 1.5 times the emission intensity of powders obtained from solid-state reaction at the same synthesis temperature. These crystals were found to efficiently emit 615 nm red light when excited by near UV light up to a wavelength of 395 nm. Highlights: Black-Right-Pointing-Pointer CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals were successfully grown using high temperature flux (solutions) containing molybdenum (VI) oxide or lithium chloride. Black-Right-Pointing-Pointer Narrow spectral emission at 615 nm, 575 nm and 550 nm, respectively, was observed from CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals. Black-Right-Pointing-Pointer The optimized doping concentrations of Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+} in CaMoO{sub 4} for highest emission intensity were determined to be 12%, 2% and 5%, respectively. Black-Right-Pointing-Pointer The CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals grown with molybdenum (VI) oxide flux exhibited 50% higher emission intensity compared to the crystals grown with lithium chloride flux and the powders synthesized by solid-state reaction.

Khanna, A. [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States) [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States); Electrical, Computer and Systems Engineering Department, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, New York, 12180 (United States); Dutta, P.S., E-mail: duttap@rpi.edu [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States); Electrical, Computer and Systems Engineering Department, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, New York, 12180 (United States)

2013-02-15

322

The Ground-based H-, K-, and L-band Absolute Emission Spectra of HD 209458b  

NASA Astrophysics Data System (ADS)

Here we explore the capabilities of NASA's 3.0 m Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 m Hale telescope with the TripleSpec spectrometer with near-infrared H-, K-, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L band indicate bright emission hypothesized to result from non-LTE CH4 ?3 fluorescence. We do not detect a similar bright 3.3 ?m feature to ~3?, suggesting that fluorescence does not need to be invoked to explain HD 209458b's L-band measurements. The validity of our observation and reduction techniques, which decrease the flux variance by up to 2.8 orders of magnitude, is reinforced by 1? agreement with existent Hubble/NICMOS and Spitzer/IRAC1 observations that overlap the H, K, and L bands, suggesting that both IRTF/SpeX and Palomar/TripleSpec can measure an exoplanet's emission with high precision.

Zellem, Robert T.; Griffith, Caitlin A.; Deroo, Pieter; Swain, Mark R.; Waldmann, Ingo P.

2014-11-01

323

Alterations in Cochlear Function after Exposure to Short Term Broad Band Noise Assessed by Otoacoustic Emissions  

PubMed Central

Background: Sudden or chronic exposure to sound alters the functioning of cochlea. This results in temporary or permanent alteration of functioning of cochlear cells. Alteration of functioning of outer hair cells (OHC) of cochlea following exposure to noise can be assessed by measurement of transient otoacoustic emissions (TEOAE). Such a measurement is of great clinical importance in early detection of the damage to the OHC. Aim: In this study we aim to study effect of noise on outer hair cell function by studying the changes in TEOAE’s amplitude following exposure to short term broad band noise in healthy volunteers. Materials and Methods: Twenty volunteers’ ten males and ten females participated in the study. They underwent pure tone and impedance audiometry to rule out ear pathology. Then pre-exposure TEOAE’s were recorded. After that they were exposed to broad band noise for two minutes. After gap of five minutes again TEOAE’s were recorded. Pre and post exposure amplitude of TEOAE’s was analysed statistically.s Results: There was statistically significant difference between pre exposure and post-exposure amplitude of TEOAE’s. Pre and post exposure values for A & B amplitudes showed p-value of 0.0001 whereas values for A-B amplitude showed p-value of 0.0001. Conclusion: Measurement of TEOAE’s can detect early changes in the functioning of outer hair cells which cannot be picked by routine pure tone audiometry. Thus they can be used in assessing early changes in cochlear function following exposure to noise in individuals exposed to sudden noise or working in noisy environments. Thus preventive methods to reduce the noise induced hearing loss in such individuals can be implemented. PMID:25386468

Reddy, Prasen; M M, Kavitha; Khavasi, Prabhu; Doddamani, S S

2014-01-01

324

Observation of nitric oxide rovibrational band head emissions in the quiescent airglow during the CIRRIS-1A space shuttle experiment  

Microsoft Academic Search

Band head emissions from highly rotationally excited NO (v, J) (J approx. equals 90) have been observed in the quiescent atmosphere at tangent heights between approximately 115 and 190 km for both sunlit and nighttime conditions. The data were obtained by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) interferometer which was operated on-board the space shuttle between 28 and

D. R. Smith; M. Ahmadjian

1993-01-01

325

Monitoring MRK 509: The Origin of the Reprocessor and Broad Band X-ray Spectrum of Narrow Line Seyfert 1 AKN 564  

NASA Technical Reports Server (NTRS)

The ten monitoring observations of Mrk 509 were made successfully between October 20 and November 26 last year. These observations were simultaneously with RXTE observations. A preliminary analysis of the RXTE observations has been done, and the light curve is shown in figure 1. Our aim in this experiment is to determine the location of the emission region of the reflection component by reverberation mapping. This component could be emitted from the accretion disk, within 100 Scwartzschild radii (R(sub s)) from the source. Note that the monitoring interval of 2.5 days corresponds to 100 R(sub s) for a 2 x 10(exp 8) solar mass black hole, which may be appropriate for this luminous object. In that case, we would expect the reflected component to vary along the direct flux, and there should be no spectral variability between observations. Alternatively, the reflected emission could come from the molecular torus, several parsecs from the nucleus. In that case, the reflection component flux should not vary. The light curve in figure 1 shows that during the monitoring period, the target varied in an ideal way, since significant variability was observed between observations and yet the most rapid variability is apparently sampled. The analysis of this data is not yet completed. The measurement of the reflection component in the combined ASCa and RXTE spectra depends critically on the RXTE background subtraction and calibration, but these have not yet progressed to the point where the analysis can be done.

Halpern, Jules P.; Leighly, Karen M.

1998-01-01

326

Coupling of narrow and wide band-gap semiconductors on uniform films active in bacterial disinfection under low intensity visible light: implications of the interfacial charge transfer (IFCT).  

PubMed

This study reports the design, preparation, testing and surface characterization of uniform films deposited by sputtering Ag and Ta on non-heat resistant polyester to evaluate the Escherichia coli inactivation by TaON, TaN/Ag, Ag and TaON/Ag polyester. Co-sputtering for 120 s Ta and Ag in the presence of N? and O? led to the faster E. coli inactivation by a TaON/Ag sample within ?40 min under visible light irradiation. The deconvolution of TaON/Ag peaks obtained by X-ray photoelectron spectroscopy (XPS) allowed the assignment of the Ta?O? and Ag-species. The shifts observed for the XPS peaks have been assigned to AgO to Ag?O and Ag(0), and are a function of the applied sputtering times. The mechanism of interfacial charge transfer (IFCT) from the Ag?O conduction band (cb) to the lower laying Ta?O? (cb) is discussed suggesting a reaction mechanism. The optical absorption of the TaON and TaON/Ag samples found by diffuse reflectance spectroscopy (DRS) correlated well with the kinetics of E. coli inactivation. The TaON/Ag sample microstructure was characterized by contact angle (CA) and by atomic force microscopy (AFM). Self-cleaning of the TaON/Ag polyester after each disinfection cycle enabled repetitive E. coli inactivation. PMID:23867967

Rtimi, S; Sanjines, R; Pulgarin, C; Houas, A; Lavanchy, J-C; Kiwi, J

2013-09-15

327

Out-of-band emission suppression techniques based on a generalized OFDM framework  

NASA Astrophysics Data System (ADS)

Orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems suffer from the large out-of-band emission (OOBE) that may interfere with other users. Since most existing OFDM OOBE suppression schemes are derived on the base of an original OFDM system without any other scheme, we first propose a generalized OFDM framework that is capable of describing these schemes no matter whether any one or more of the schemes is applied. Then, according to the place where these schemes are implemented in our framework, they are classified into three groups, namely symbol mapping techniques, precoding techniques, and time-domain techniques. Finally, based on the proposed framework, we propose three new schemes by combining a precoding scheme named singular value decomposition (SVD) precoding with three other schemes from the three groups, namely spectral precoding, N-continuous symbol mapping, and filtering. Numerical results show the power spectral density (PSD), peak-to-average power ratio (PAPR), and bit error rate (BER) performances of the three proposed schemes. Since the individual schemes have complementary characteristics, the three proposed combined schemes are constructed to maintain the merits and avoid the drawbacks of the individual schemes involved. Thus, it is demonstrated that the proposed framework can be employed to develop other new combined OOBE suppression schemes tailoring to some specific practical needs.

You, Zihao; Fang, Juan; Lu, I.-Tai

2014-12-01

328

S-NPP VIIRS thermal emissive bands on-orbit calibration and performance  

NASA Astrophysics Data System (ADS)

Presented is an assessment of the on-orbit radiometric performance of the thermal emissive bands (TEB) of the Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) instrument based on data from the first 2 years of operations—from 20 January 2012 to 20 January 2014. The VIIRS TEB are calibrated on orbit using a V-grooved blackbody (BB) as a radiance source. Performance characteristics trended over the life of the mission include the F factor—a measure of the gain change of the TEB detectors; the Noise Equivalent differential Temperature (NEdT)—a measure of the detector noise; and the detector offset and nonlinear terms trended at the quarterly performed BB warm-up cool-down cycles. We find that the BB temperature is well controlled and stable within the 30mK requirement. The F factor trends are very stable and showing little degradation (within 0.8%). The offsets and nonlinearity terms are also without noticeable drifts. NEdT is stable and does not show any trend. Other TEB radiometric calibration-related activities discussed include the on-orbit assessment of the response versus scan-angle functions and an approach to improve the M13 low-gain calibration using onboard lunar measurements. We conclude that all the assessed parameters comply with the requirements, and the TEB provide radiometric measurements with the required accuracy.

Efremova, Boryana; McIntire, Jeff; Moyer, David; Wu, Aisheng; Xiong, Xiaoxiong

2014-09-01

329

Space Telescope Imaging Spectrograph Long-Slit Spectroscopy of the Narrow-Line Region of NGC 4151. 1; Kinematics and Emission-Line Ratios  

NASA Technical Reports Server (NTRS)

Long-slit spectra of the Seyfert galaxy NGC 4151 from the UV to the near-infrared have been obtained with the Space Telescope Imaging Spectrograph (STIS) to study the kinematics and physical conditions in the narrow-line region (NLR). The kinematics shows evidence for three components, a low-velocity system in normal disk rotation, a high-velocity system in radial outflow at a few hundred kilometers per second relative to the systemic velocity, and an additional high-velocity system also in outflow with velocities up to 1400 km s(-l), in agreement with results from STIS slitless spectroscopy. We have explored two simple kinematic models and suggest that radial outflow in the form of a wind is the most likely explanation. We also present evidence indicating that the wind may be decelerating with distance from the nucleus. We find that the emission-line ratios along our slits are all entirely consistent with photoionization from the nuclear continuum source. A decrease in the ratios [O III] lambda 5007/H beta and [O III] lambda 5007/[O II] lambda 3727 suggests that the density decreases with distance from the nucleus. This trend is borne out by the [S II] ratios as well. We find no strong evidence for interaction between the radio jet and the NLR gas in either the kinematics or the emission-line ratios, in agreement with the recent results of Kaiser et al., who found no spatial coincidence of NLR clouds and knots in the radio jet. These results are in contrast to other recent studies of nearby active galactic nuclei that find evidence for significant interaction between the radio source and the NLR gas.

Nelson, C. H.; Weistrop, D.; Hutchinson, J. B.; Crenshaw, D. M.; Gull, T. R.; Kaiser, M. E.; Kraemer, S. B.; Lindler, D.

2003-01-01

330

VERY LONG BASELINE ARRAY IMAGING OF PARSEC-SCALE RADIO EMISSIONS IN NEARBY RADIO-QUIET NARROW-LINE SEYFERT 1 GALAXIES  

SciTech Connect

We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz ({lambda}18 cm) with milliarcsecond resolution. This is the first systematic very long baseline interferometry study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of {approx}> 5 Multiplication-Sign 10{sup 6} K and contain radio cores with high brightness temperatures of >6 Multiplication-Sign 10{sup 7} K, indicating a nonthermal process driven by jet-producing central engines as in radio-loud NLS1s and other active galactic nucleus classes. VLBA images of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear structures. A large portion of the radio power comes from diffuse emission components that are distributed within the nuclear regions ({approx}< 300 pc), which is a common characteristic throughout the observed NLS1s. Jet kinetic powers limited by the Eddington limit may be insufficient to allow the jets to escape to kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of {approx}< 10{sup 7} M {sub Sun }.

Doi, Akihiro [The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan)] [The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan); Asada, Keiichi; Inoue, Makoto [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)] [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Fujisawa, Kenta [The Research Institute of Time Studies, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511 (Japan)] [The Research Institute of Time Studies, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511 (Japan); Nagai, Hiroshi; Hagiwara, Yoshiaki [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Wajima, Kiyoaki, E-mail: akihiro.doi@vsop.isas.jaxa.jp [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)] [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)

2013-03-01

331

Hydrogenation of polycyclic aromatic hydrocarbons as a factor affecting the cosmic 6.2 micron emission band.  

PubMed

While many of the characteristics of the cosmic unidentified infrared (UIR) emission bands observed for interstellar and circumstellar sources within the Milky Way and other galaxies, can be best attributed to vibrational modes of the variants of the molecular family known as polycyclic aromatic hydrocarbons (PAH), there are open questions that need to be resolved. Among them is the observed strength of the 6.2 micron (1600 cm(-1)) band relative to other strong bands, and the generally low strength for measurements in the laboratory of the 1600 cm(-1) skeletal vibration band of many specific neutral PAH molecules. Also, experiments involving laser excitation of some gas phase neutral PAH species while producing long lifetime state emission in the 3.3 micron (3000 cm(-1)) spectral region, do not result in significant 6.2 micron (1600 cm(-1)) emission. A potentially important variant of the neutral PAH species, namely hydrogenated-PAH (H(N)-PAH) which exhibit intriguing spectral correlation with interstellar and circumstellar infrared emission and the 2175 A extinction feature, may be a factor affecting the strength of 6.2 micron emission. These species are hybrids of aromatic and cycloalkane structures. Laboratory infrared absorption spectroscopy augmented by density function theory (DFT) computations of selected partially hydrogenated-PAH molecules, demonstrates enhanced 6.2 micron (1600 cm(-1)) region skeletal vibration mode strength for these molecules relative to the normal PAH form. This along with other factors such as ionization or the incorporation of nitrogen or oxygen atoms could be a reason for the strength of the cosmic 6.2 micron (1600 cm(-1)) feature. PMID:11345250

Beegle, L W; Wdowiak, T J; Harrison, J G

2001-03-15

332

Evaluation of Terra and Aqua MODIS thermal emissive band response versus scan angle  

NASA Astrophysics Data System (ADS)

Terra and Aqua MODIS have operated near-continuously for over 14 and 12 years, respectively, and are key instruments for NASA's Earth Observing System. Observations from the 16 thermal emissive bands (TEB), covering wavelengths from 3.5 to 14.4 ?m with a nadir spatial resolution of 1 km are used to regularly generate a variety of atmosphere, ocean and land science products. The TEB detectors are calibrated using scan-by-scan observations of an on-board blackbody (BB). The current response versus scan angle (RVS) of the scan mirror was derived using a spacecraft deep-space pitch maneuver for Terra MODIS and characterized during prelaunch for Aqua MODIS. Earth view (EV) data over the complete range of angles of incidence (AOI) can be used to evaluate the on-orbit performance of the TEB RVS over the mission lifetime. Three approaches for tracking the TEB RVS on-orbit using EV observations are formulated. The first approach uses the multiple daily observations of Dome C BT at different AOI and their trend relative to coincident measurements from a ground temperature sensor. The second approach uses brightness temperatures (BT) retrieved over the cloud-free ocean to derive the trends at 13 AOI over the mission lifetime. The third approach tracks the dn response (normalized to the BB AOI) across the full swath width for Antarctic granules with the Dome C site at nadir. The viability of the three approaches is assessed and the long-term stability of the TEB RVS for both MODIS instruments is determined.

Wenny, B. N.; Wu, A.; Madhavan, S.; Xiong, X.

2014-10-01

333

Methane oxidation behind reflected shock waves: Ignition delay times measured by pressure and flame band emission  

NASA Technical Reports Server (NTRS)

Ignition delay data were recorded for three methane-oxygen-argon mixtures (phi = 0.5, 1.0, 2.0) for the temperature range 1500 to 1920 K. Quiet pressure trances enabled us to obtain delay times for the start of the experimental pressure rise. These times were in good agreement with those obtained from the flame band emission at 3700 A. The data correlated well with the oxygen and methane dependence of Lifshitz, but showed a much stronger temperature dependence (phi = 0.5 delta E = 51.9, phi = 1.0 delta = 58.8, phi = 2.0 delta E = 58.7 Kcal). The effect of probe location on the delay time measurement was studied. It appears that the probe located 83 mm from the reflecting surface measured delay times which may not be related to the initial temperature and pressure. It was estimated that for a probe located 7 mm from the reflecting surface, the measured delay time would be about 10 microseconds too short, and it was suggested that delay times less than 100 microsecond should not be used. The ignition period was defined as the time interval between start of the experimental pressure rise and 50 percent of the ignition pressure. This time interval was measured for three gas mixtures and found to be similar (40 to 60 micro sec) for phi = 1.0 and 0.5 but much longer (100 to 120) microsecond for phi = 2.0. It was suggested that the ignition period would be very useful to the kinetic modeler in judging the agreement between experimental and calculated delay times.

Brabbs, T. A.; Robertson, T. F.

1986-01-01

334

L-Band H Polarized Microwave Emission During the Corn Growth Cycle  

NASA Technical Reports Server (NTRS)

Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (T(sub B))'s measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These T(sub B)'s measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly T(sub B)'s could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly T(sub B). Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, h(sub r), on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on T(sub B) simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent h(sub r) parameterization was responsible for the largest error reduction of T(sub B) simulations in the early growth cycle.

Joseph, A. T.; va der Velde, R.; O'Neill, P. E.; Kim, E.; Lang, R. H.; Gish, T.

2012-01-01

335

Effectiveness of near-grazing incidence reflection in creating the rotationally modulated lanes in the Jovian hectometric radio emission spectrum  

Microsoft Academic Search

The Galileo plasma wave instrument has identified a narrow (in frequency) attenuation band in the hectometric emission that varies in frequency with system III longitude. It is possible to model this emission band assuming a high-latitude cyclotron source region with emission that is efficiently attenuated when the ray path is nearly tangent to an L shell that is close to

J. D. Menietti; D. A. Gurnett; W. S. Kurth; J. B. Groene

1999-01-01

336

Room temperature spontaneous emission enhancement from quantum dots in photonic crystal slab cavities in the telecommunications C-band  

E-print Network

We report on the control of the spontaneous emission dynamics from InAsP self-assembled quantum dots emitting in the telecommunications C-band and weakly coupled to the mode of a double heterostructure cavity etched on a suspended InP membrane at room temperature. The quality factor of the cavity mode is 44x10^3 with an ultra-low modal volume of the order of 1.2 lambda/n)^3, inducing an enhancement of the spontaneous emission rate of up a factor of 2.8 at 300 K.

Richard Hostein; Rémy Braive; Matthieu Larqué; Ko-Hsin Lee; Anne Talneau; Luc Le Gratiet; Isabelle Robert-Philip; Isabelle Sagnes; Alexios Beveratos

2009-03-25

337

Coherent Control of Spontaneous Emission near a Photonic Band Edge: A Single-Atom Optical Memory Device  

NASA Astrophysics Data System (ADS)

We demonstrate coherent control of spontaneous emission from a three-level atom with one resonant frequency near the edge of a photonic band gap. As a result of quantum interference and photon localization, spontaneous emission can be totally suppressed or strongly enhanced depending on the relative phase between the control and pump laser fields. The fractionalized steady state inversion of the atom depends sensitively on the initial conditions, suggesting the possibility of a phase-sensitive, optical memory device on the atomic scale.

Quang, Tran; Woldeyohannes, Mesfin; John, Sajeev; Agarwal, Girish S.

1997-12-01

338

Chemical vapor deposition of a-CNx:H films for electron field emission using band supermagnetron plasma  

NASA Astrophysics Data System (ADS)

A supermagnetron plasma apparatus with two band magnetron cathodes, which can form uniform magnetron plasma under a stationary magnetic field (about 160 G), was used to deposit a-CNx:H films at N2 gas concentrations of 0 and 70%. A high deposition rate of about 85±5 nm/min was obtained at a low dc self-bias voltage, between -20 and -62 V. The optical band gap could be controlled between 1.1 and 3.8 eV. The double-layer a-CNx:H films with optical band gaps of 2.2 eV (upper layer; N2 0%) and 1.5 eV (lower layer; N2 70%) formed on p-Si substrate showed a low-threshold-emission electric field of 9 V/?m.

Kinoshita, H.; Yagi, S.

2014-06-01

339

Interstellar polycyclic aromatic hydrocarbons - The infrared emission bands, the excitation\\/emission mechanism, and the astrophysical implications  

Microsoft Academic Search

A comprehensive study of the PAH hypothesis is presented, including the interstellar, IR spectral features which have been attributed to emission from highly vibrationally excited PAHs. Spectroscopic and IR emission features are discussed in detail. A method for calculating the IR fluorescence spectrum from a vibrationally excited molecule is described. Analysis of interstellar spectrum suggests that the PAHs which dominate

L. J. Allamandola; G. G. M. Tielens; J. R. Barker

1989-01-01

340

Observation of nitric oxide rovibrational band head emissions in the quiescent airglow during the CIRRIS-1A space shuttle experiment  

NASA Astrophysics Data System (ADS)

Band head emissions from highly rotationally excited NO (v, J) (J approx. equals 90) have been observed in the quiescent atmosphere at tangent heights between approximately 115 and 190 km for both sunlit and nighttime conditions. The data were obtained by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) interferometer which was operated on-board the space shuttle between 28 and 30 April 1991. Up to ten emission features between 2020 and 1744/cm in the earthlimb spectra have been identified as the R-branch band heads of the NO delta v = 1 sequence for the vibrational states v(prime) = 1 - 10. The presence of these band heads requires a very high degree of rotational excitation corresponding to rotational energy in excess of 1.4 eV. These are the first observations of emissions from highly rotationally excited NO in the quiescent airglow and they parallel the recent discovery of highly excited pure rotational transitions of OH in the airglow for both nighttime and daytime quiescent conditions.

Smith, D. R.; Ahmadjian, M.

1993-12-01

341

L-band automatic-gain-controlled erbium-doped fiber amplifier utilizing C-band backward-amplified spontaneous emission and electrical feedback monitor.  

PubMed

A new L-band automatic-gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) for dense wavelength-division-multiplexing transmission systems is presented, in which a single 1480 nm laser with an internal thermoelectric cooler is used as a primary pump for stable amplification. All C-band amplified spontaneous emission (ASE) is recycled by the secondary pump to enhance the gain efficiency. A fraction of the output signal is used as an electrical feedback monitor for the AGC to improve the gain-clamped (GC) flatness. Experimental results prove that the AGC EDFA has a gain flatness of better than 0.46 dB/40 nm, i.e., below 1.5%, and a higher gain of approximately 36.5 dB compared to that of approximately 35.3 dB for the conventional GC EDFA at -30 dBm input signal power. The best gain flatness of +/-0.25 dB can be achieved over the dynamic range greater than 20 dB. The dynamic range of noise figure is between 6.7 and 7.1. The 3 dB down bandwidth is more than 40 nm. Overall dynamics measurements for the AGC EDFA feedback stabilization have been carried out. The recorded corresponding rise time of 1.565 ms indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse. PMID:19209194

Shen, Jyi-Lai; Lee, Yueh-Chien; Huang, Chia-Chih

2009-02-10

342

Formation of electron strings in narrow bands  

SciTech Connect

Electron strings may arise in polar materials as a result of an electronic phase separation. The width or the transverse diameter of the string is equal to one interatomic spacing. The length of the string depends on dielectric constants of semiconductors. The appearance of these electron strings may naturally explain the effect of stripe formation observed in a variety of HTSC experiments.

Kusmartsev, F.V.

1999-11-01

343

Ultra Low Power Narrow Band LNA  

Microsoft Academic Search

Ultra low powers LNAs are very challenging blocks. Shown in this paper is a design approach for less than 2.5 dB noise figure at 2.4 GHz with only 500 muA. On chip inductors in tsmc 0.13 mum technology was used with IV supply. The NQS effect is eliminated by using a capacitance parallel to Cg, in the inductive degeneration method.

M. M. E. Kholy

2007-01-01

344

NARROW-BAND ANALYSIS OF NONSTATIONARY PROCESSES  

Microsoft Academic Search

The behaviour of averaged periodograms and cross-periodograms of a broad class of nonstationary processes is studied. The processes include nonstationary ones that are fractional of any order, as well as asymptotically stationary fractional ones, and the cross-periodogram can involve two nonstationary processes of possibly different orders, or a nonstationary and an asymptotically stationary one. The averag- ing takes place either

P. M. Robinson; D. Marinucci

1999-01-01

345

Observation of interface band structure by ballistic-electron-emission microscopy  

NASA Technical Reports Server (NTRS)

The paper reports an advanced ballistic electron spectroscopy technique that was used to directly measure semiconductor band structure properties at a subsurface interface. Two interface systems having contrasting band structures were investigated by this method: Au-Si and Au-GaAs. It is concluded that the proposed method, based on scanning tunneling microscopy, enables the spatially resolved carrier-transport spectroscopy of interfaces.

Bell, L. D.; Kaiser, W. J.

1988-01-01

346

Non-LTE modeling of narrow emission components of He and Ca lines in optical spectra of classical T Tauri stars  

NASA Astrophysics Data System (ADS)

Using LTE calculations of the structure of T Tauri stellar atmospheres heated by radiation from an accretion shock (Dodin and Lamzin 2012), we have calculated the spectrum of the hot spot emerging on the stellar surface by taking into account non-LTE effects for He I, He II, Ca I, and Ca II. Assuming the pre-shock gas density N 0 and velocity V 0 to be the same at all points of the accretion stream cross section, we have calculated the spectrum of the star+circular spot system at various N 0, V 0, and parameters characterizing the star and the spot. Using nine stars as an example, we show that the theoretical optical spectra reproduce well the observed veiling of photospheric absorption lines as well as the profiles and intensities of the so-called narrow components of He II and Ca I emission lines with an appropriate choice of parameters. The accreted gas density in all of the investigated stars except DK Tau has been found to be N 0 > 1012 cm-3. We have managed to choose the parameters for eight stars at a calcium abundance in the accreted gas ? Ca equal to the solar one, but we have been able to achieve agreement between the calculations and observations for TW Hya only by assuming ? Ca to be approximately a factor of 3 lower than the solar one. The estimated parameters do not depend on interstellar extinction, because they have been determined from the spectra normalized to the continuum level. The calculated intensity of Ca II lines has turned out to be lower than the observed one, but this contradiction can be eliminated by assuming that, in addition to the accreted gas with a high density N 0, a more rarefied gas also falls onto the star. The theoretical equivalent widths and relative intensities of the subordinate He I lines disagree significantly with the observations. This is apparently because non-LTE effects should be taken into account when calculating the structure of the upper layers of the hot spot, the accuracy of the cross sections for collisional processes from upper levels is insufficient, and the spot inhomogeneity should probably be taken into account.

Dodin, A. V.; Lamzin, S. A.; Sitnova, T. M.

2013-05-01

347

Direct imaging of the visible emission bands from individual ZnO nanowires by near-field optical spectroscopy.  

PubMed

Room-temperature photoluminescence (PL) measurements have been performed on single-crystal ZnO nanowires grown on SiO2/Si and quartz substrates by the vapor transport method using Au as a catalyst. Two emission bands are apparent, one in the UV spectral region around 380 nm (3.26 eV) associated with exciton recombination processes and a much broader structure in the visible range from 420 to 700 nm, which exhibits two distinct peak-like features around 520 and 590 nm (2.38 and 2.10 eV). Spectrally resolved scanning near-field optical microscopy (SNOM) of single ZnO nanowires have been performed for a direct imaging of the PL emission with spatial resolution below 100 nm. SNOM results provide evidence that the yellow emission band observed at 590 nm is a unique property of the ZnO nanowires, being most likely related to radiative recombination processes associated with Au impurities introduced during the catalytic growth. PMID:19597252

Güell, F; Ossó, J O; Goñi, A R; Cornet, A; Morante, J R

2009-08-01

348

Active-passive synergy for interpreting ocean L-band emissivity: Results from the CAROLS airborne campaigns  

NASA Astrophysics Data System (ADS)

impact of the ocean surface roughness on the ocean L-band emissivity is investigated using simultaneous airborne measurements from an L-band radiometer (CAROLS) and from a C-band scatterometer (STORM) acquired in the Gulf of Biscay (off-the French Atlantic coasts) in November 2010. Two synergetic approaches are used to investigate the impact of surface roughness on the L-band brightness temperature (Tb). First, wind derived from the scatterometer measurements is used to analyze the roughness contribution to Tb as a function of wind and compare it with the one simulated by SMOS and Aquarius roughness models. Then residuals from this mean relationship are analyzed in terms of mean square slope derived from the STORM instrument. We show improvement of new radiometric roughness models derived from SMOS and Aquarius satellite measurements in comparison with prelaunch models. Influence of wind azimuth on Tb could not be evidenced from our data set. However, we point out the importance of taking into account large roughness scales (>20 cm) in addition to small roughness scale (5 cm) rapidly affected by wind to interpret radiometric measurements far from nadir. This was made possible thanks to simultaneous estimates of large and small roughness scales using STORM at small (7-16°) and large (30°) incidence angles.

Martin, A. C. H.; Boutin, J.; Hauser, D.; Dinnat, E. P.

2014-08-01

349

The 217.5 nm band, infrared absorption and infrared emission features in hydrogenated amorphous carbon nanoparticles  

E-print Network

We report on the preparation of hydrogenated amorphous carbon nano-particles whose spectral characteristics include an absorption band at 217.5 nm with the profile and characteristics of the interstellar 217.5 nm feature. Vibrational spectra of these particles also contain the features commonly observed in absorption and emission from dust in the diffuse interstellar medium. These materials are produced under slow deposition conditions by minimizing the flux of incident carbon atoms and by reducing surface mobility. The initial chemistry leads to the formation of carbon chains, together with a limited range of small aromatic ring molecules, and eventually results in carbon nano-particles having an sp2/sp3 ratio = 0.4. Spectroscopic analysis of particle composition indicates that naphthalene and naphthalene derivatives are important constituents of this material. We suggest that carbon nano-particles with similar composition are responsible for the appearance of the interstellar 217.5 nm band and outline how t...

Duley, W W

2012-01-01

350

High resolution vacuum ultraviolet emission spectrum of D2: the B' 1Sigmau+-->X 1Sigmag+ band system.  

PubMed

In this work, we have extended our previous high resolution study of the vacuum ultraviolet emission spectrum of the D2 molecule [M. Roudjane, et al. J. Chem. Phys. 125, 214305 (2006)] up to 124.2 nm in order to investigate the B' 1Sigmau+-->X 1Sigmag+ band system. The analysis of the spectrum has been carried out by means of a complex spectrum visual identification code IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656, (1993)] and supported by theoretical calculations using ab initio data [L. Wolniewicz, J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); G. Staszewska and L. Wolniewicz, J. Mol. Spectrosc. 212, 208 (2002); L. Wolniewicz and G. Staszewska, 220, 45 (2003)] which provided level energies and transition probabilities. More than 1480 new emission lines have been observed and 109 bands belonging to the B' 1Sigmau+-->X 1Sigmag+ system have been identified between 84.1 and 121.6 nm. Except for the upsilon'-0 bands that were reported in absorption [I. Dabrowski and G. Herzberg, Can. J. Phys. 52, 1110 (1974)], all the upsilon'-upsilon" bands are reported here for the first time. The analysis led to the determination of 111 rovibronic energy levels in the B' 1Sigmau+ state, of which 31 with higher rotational numbers J are new. Observed perturbations are accounted for through a set of coupled equations involving the four excited electronic states B 1Sigmau+, B' 1Sigmau+, C 1Piu, and D 1Piu and including nonadiabatic couplings. The solution of this set provides the percent contribution of these four states to each of the observed rovibronic level. PMID:17688340

Roudjane, Mourad; Tchang-Brillet, W-U Lydia; Launay, Françoise

2007-08-01

351

High resolution vacuum ultraviolet emission spectrum of D2: The B' 1?u+-->X 1?g+ band system  

NASA Astrophysics Data System (ADS)

In this work, we have extended our previous high resolution study of the vacuum ultraviolet emission spectrum of the D2 molecule [M. Roudjane, et al. J. Chem. Phys. 125, 214305 (2006)] up to 124.2nm in order to investigate the B'?u+1?X?g+1 band system. The analysis of the spectrum has been carried out by means of a complex spectrum visual identification code IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656, (1993)] and supported by theoretical calculations using ab initio data [L. Wolniewicz, J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); G. Staszewska and L. Wolniewicz, J. Mol. Spectrosc. 212, 208 (2002); L. Wolniewicz and G. Staszewska, 220, 45 (2003)] which provided level energies and transition probabilities. More than 1480 new emission lines have been observed and 109 bands belonging to the B'?u+1?X?g+1 system have been identified between 84.1 and 121.6nm. Except for the ?'-0 bands that were reported in absorption [I. Dabrowski and G. Herzberg, Can. J. Phys. 52, 1110 (1974)], all the ?'-?? bands are reported here for the first time. The analysis led to the determination of 111 rovibronic energy levels in the B'?u+1 state, of which 31 with higher rotational numbers J are new. Observed perturbations are accounted for through a set of coupled equations involving the four excited electronic states B?u +1, B'?u+1, C?u1, and D?u1 and including nonadiabatic couplings. The solution of this set provides the percent contribution of these four states to each of the observed rovibronic level.

Roudjane, Mourad; Tchang-Brillet, W.-Ü. Lydia; Launay, Françoise

2007-08-01

352

Fullerenes as carriers of extinction, diffuse interstellar bands and anomalous microwave emission  

Microsoft Academic Search

According to semiempirical models, photoabsorption by fullerenes (single and multishell) could explain the shape, width and peak energy of the most prominent feature of the interstellar absorption, the UV bump at 2175 Å. Other weaker transitions are predicted in the optical and near-infrared providing a potential explanation for diffuse interstellar bands. In particular, we find that several fullerenes could contribute

Susana Iglesias-Groth

2008-01-01

353

Are the Isomers of C2H4O Responsible for the Unidentified Infrared Emission Bands and Continuum?  

NASA Astrophysics Data System (ADS)

We suggest that ethylene oxide (EO, c-C2H4O) and its isomers, acetaldehyde (AC, CH3CHO) and vinyl alcohol (VA, CH2CHOH) may be the source of the unidentified infrared bands (UIR) and their underlying continuum. Microwave transitions of all three isomers have been observed in many astronomical objects, all of which show the UIR bands. We show that the fundamental and overtone vibrational frequencies of EO correlate well with the major UIR bands at 3.3, 6.2, 7.7, 8.6, and 11.2 ?m. Two additional UIR features at 12.7 and 16.4 ?m are consistent with vibrationally excited EO, which is not collisionally quenched in space because the collision rate is negligible compared to the photon emission rate. In our mechanism, a vibrationally and rotationally cold AC molecule absorbs a 9 eV UV photon to produce vibrationally hot and rotationally cold AC in an excited electronic state. The excited AC either (1) undergoes isomerization to form vibrationally hot and rotationally cold EO in an excited electronic state, or (2) undergoes dissociation to form vibrationally and rotationally hot molecular products in excited electronic states. The electronically excited EO emits a UV photon to produce vibrationally hot and rotationally cold EO in its ground electronic state. This EO then emits its vibrational energy in the infrared (IR) and gives rise to the UIR bands. The electronically excited dissociation products also emit UV photons to produce vibrationally and rotationally hot molecules in their ground electronic states. These daughter molecules also emit in the IR and give rise to the UIR continuum. While EO and its isomers are plausible candidates for the source of the UIR spectrum, we have also found that the fundamental vibrational frequencies of cyclopropenylidene (c-C3H2) also match well with the UIR spectral bands, perhaps indicating that more than one small carbonaceous molecule (SCM) is involved.

Bernstein, Lawrence; Lynch, D. K.

2009-05-01

354

Beyond the Band Function Paradigm : a New Model for GRB Prompt Emission and Possible Impact in Cosmology  

NASA Astrophysics Data System (ADS)

Gamma Ray Bursts (GRBs) are the most violent phenomenons in the Universe. They are associated with the birth of stellar mass black holes either from the collapse of hypermassive stars or the merger of compact objects. The Fireball model is the most popular scenario to explain GRBs. In this theoretical framework, GRB central engines release collimated, bipolar and highly relativistic jets mainly composed of electrons, positrons, photons, and a small amount of baryons. During the first phase of the Fireball model, charged particles are accelerated and release non-thermal radiations. The Fireball model also predicts a thermal like component coming from the jet photosphere. This first phase would be responsible for the GRB prompt emission observed by gamma ray telescopes such as Fermi/GBM in the keV-MeV energy range and which is the only phase discussed in this talk. Until now, GRB prompt emission spectra were considered as adequately fitted with the empirical Band function, which is a smoothly broken power law. However, its parameters are very often incompatible with the Fireball model predictions for both the thermal and non-thermal components. We will see that observation with the Fermi Gamma Ray Space Telescope break the paradigm of the Band function and that deviations from this function exists in many GRBs. Those deviations are adequately fitted with an additional thermal-like component -that we consider as the jet photosphere- and/or an additional power law. Importantly, with the three components together, theory and observations are much more in agreement. We will also see how this new model for prompt emission spectra may have an impact beyond the physics of GRBs. Indeed, this work may confirm a relation between the hardness of the GRB prompt emission and its luminosity which may be used to scale GRBs as standard-like candles for use in cosmology.

Guiriec, Sylvain

355

Soil moisture, dielectric permittivity and emissivity of soil: effective depth of emission measured by the L-band radiometer ELBARA  

NASA Astrophysics Data System (ADS)

Due to the large variation of soil moisture in space and in time, obtaining soil water balance with an aid of data acquired from the surface is still a challenge. Microwave remote sensing is widely used to determine the water content in soil. It is based on the fact that the dielectric constant of the soil is strongly dependent on its water content. This method provides the data in both local and global scales. Very important issue that is still not solved, is the soil depth at which radiometer "sees" the incoming radiation and how this "depth of view" depends on water content and physical properties of soil. The microwave emission comes from its entire profile, but much of this energy is absorbed by the upper layers of soil. As a result, the contribution of each layer to radiation visible for radiometer decreases with depth. The thickness of the surface layer, which significantly contributes to the energy measured by the radiometer is defined as the "penetration depth". In order to improve the physical base of the methodology of soil moisture measurements using microwave remote sensing and to determine the effective emission depth seen by the radiometer, a new algorithm was developed. This algorithm determines the reflectance coefficient from Fresnel equations, and, what is new, the complex dielectric constant of the soil, calculated from the Usowicz's statistical-physical model (S-PM) of dielectric permittivity and conductivity of soil. The model is expressed in terms of electrical resistance and capacity. The unit volume of soil in the model consists of solid, water and air, and is treated as a system made up of spheres, filling volume by overlapping layers. It was assumed that connections between layers and spheres in the layer are represented by serial and parallel connections of "resistors" and "capacitors". The emissivity of the soil surface is calculated from the ratio between the brightness temperature measured by the ELBARA radiometer (GAMMA Remote Sensing AG) and the physical temperature of the soil surface measured by infrared sensor. As the input data for S-PM: volumes of soil components, mineralogical composition, organic matter content, specific surface area and bulk density of the soil were used. Water contents in the model are iteratively changed, until emissivities calculated from the S-PM reach the best agreement with emissivities measured by the radiometer. Final water content will correspond to the soil moisture measured by the radiometer. Then, the examined soil profile will be virtually divided into thin slices where moisture, temperature and thermal properties will be measured and simultaneously modelled via S-PM. In the next step, the slices will be "added" starting from top (soil surface), until the effective soil moisture will be equal to the soil moisture measured by ELBARA. The thickness of obtained stack will be equal to desired "penetration depth". Moreover, it will be verified further by measuring the moisture content using thermal inertia. The work was partially funded by the Government of Poland through an ESA Contract under the PECS ELBARA_PD project No. 4000107897/13/NL/KML.

Usowicz, Boguslaw; Lukowski, Mateusz; Marczewski, Wojciech; Usowicz, Jerzy; Lipiec, Jerzy; Rojek, Edyta; Slominska, Ewa; Slominski, Jan

2014-05-01

356

Extreme ultraviolet and out-of-band radiation emission from a tin-droplet-based LPP source  

NASA Astrophysics Data System (ADS)

Extreme Ultraviolet Lithography (EUVL) is a leading candidate for the future development of smaller and faster microchips with feature sizes of 32 nm or less. Tin laser-produced plasmas (LPPs) are one of the most promising sources of in-band radiation for EUV lithography and inspection applications. However, ions emitted from these LPPs may cause significant damage to components, specifically the collector optics. Tin-droplet targets have the ability to supply the minimum mass required to generate the EUV radiation, leading to substantial decrease in the amount of generated debris. Absolute intensity measurements of the EUV radiation formed using a droplet target, have been recorded. Measurements were recorded over 2 pi steradian with respect to the plasma. The droplet generator, a fully in-house developed system, was synchronized with a Nd:YAG laser operating at a frequency of 5 kHz. The laser pulse was focused to a power density of approximately 1011 W/cm2 to maximize in-band emission. EUV measurements were recorded at the Intermediate Focus of the High Brightness Source of the Laboratory for Energy Conversion. To complement the EUV measurements, out-of-band measurements were simultaneously recorded with a calibrated spectrometer from 300 to 1000 nm.

Morris, Oran; Giovannini, Andrea Z.; Gambino, Nadia; Henderson, Ian; Abhari, Reza S.

2012-03-01

357

MAPPING H-BAND SCATTERED LIGHT EMISSION IN THE MYSTERIOUS SR21 TRANSITIONAL DISK  

SciTech Connect

We present the first near infrared (NIR) spatially resolved images of the circumstellar transitional disk around SR21. These images were obtained with the Subaru HiCIAO camera, adaptive optics, and the polarized differential imaging technique. We resolve the disk in scattered light at H-band for stellocentric 0.''1 {<=} r {<=} 0.''6 (12 {approx}< r {approx}< 75 AU). We compare our results with previously published spatially resolved 880 {mu}m continuum Submillimeter Array images that show an inner r {approx}< 36 AU cavity in SR21. Radiative transfer models reveal that the large disk depletion factor invoked to explain SR21's sub-mm cavity cannot be 'universal' for all grain sizes. Even significantly more moderate depletions ({delta} = 0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity ({delta} {approx} 10{sup -6}) are inconsistent with our H-band images when they are assumed to carry over to small grains, suggesting that surface grains scattering in the NIR either survive or are generated by whatever mechanism is clearing the disk midplane. In fact, the radial polarized intensity profile of our H-band observations is smooth and steeply inwardly-increasing (r {sup -3}), with no evidence of a break at the 36 AU sub-mm cavity wall. We hypothesize that this profile is dominated by an optically thin disk envelope or atmosphere component. We also discuss the compatibility of our data with the previously postulated existence of a sub-stellar companion to SR21 at r {approx} 10-20 AU, and find that we can neither exclude nor verify this scenario. This study demonstrates the power of multiwavelength imaging of transitional disks to inform modeling efforts, including the debate over precisely what physical mechanism is responsible for clearing these disks of their large midplane grains.

Follette, Katherine B.; Close, Laird [Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721 (United States)] [Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721 (United States); Tamura, Motohide; Hashimoto, Jun; Kwon, Jungmi; Kandori, Ryo [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Whitney, Barbara [Astronomy Department, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States)] [Astronomy Department, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Grady, Carol [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States)] [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wisniewski, John [H.L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St Norman, OK 73019 (United States)] [H.L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St Norman, OK 73019 (United States); Brandt, Timothy D.; Dong, Ruobing [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States)] [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Mayama, Satoshi [The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (Sokendai), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan)] [The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (Sokendai), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Abe, Lyu [Laboratoire Lagrange, UMR7293, Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, F-06300 Nice (France)] [Laboratoire Lagrange, UMR7293, Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, F-06300 Nice (France); Brandner, Wolfgang; Feldt, Markus [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)] [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Carson, Joseph [Department of Physics and Astronomy, College of Charleston, 58 Coming St., Charleston, SC 29424 (United States)] [Department of Physics and Astronomy, College of Charleston, 58 Coming St., Charleston, SC 29424 (United States); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street M5S 3H4, Toronto Ontario (Canada)] [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street M5S 3H4, Toronto Ontario (Canada); Egner, Sebastian E. [Subaru Telescope, 650 North Aohoku Place, Hilo, HI 96720 (United States)] [Subaru Telescope, 650 North Aohoku Place, Hilo, HI 96720 (United States); Goto, Miwa, E-mail: kfollette@as.arizona.edu [Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, D-81679 Munchen (Germany)] [Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, D-81679 Munchen (Germany); and others

2013-04-10

358

Mapping H-band Scattered Light Emission in the Mysterious SR21 Transitional Disk  

NASA Astrophysics Data System (ADS)

We present the first near infrared (NIR) spatially resolved images of the circumstellar transitional disk around SR21. These images were obtained with the Subaru HiCIAO camera, adaptive optics, and the polarized differential imaging technique. We resolve the disk in scattered light at H-band for stellocentric 0.''1 <= r <= 0.''6 (12 <~ r <~ 75 AU). We compare our results with previously published spatially resolved 880 ?m continuum Submillimeter Array images that show an inner r <~ 36 AU cavity in SR21. Radiative transfer models reveal that the large disk depletion factor invoked to explain SR21's sub-mm cavity cannot be "universal" for all grain sizes. Even significantly more moderate depletions (? = 0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity (? ~ 10-6) are inconsistent with our H-band images when they are assumed to carry over to small grains, suggesting that surface grains scattering in the NIR either survive or are generated by whatever mechanism is clearing the disk midplane. In fact, the radial polarized intensity profile of our H-band observations is smooth and steeply inwardly-increasing (r -3), with no evidence of a break at the 36 AU sub-mm cavity wall. We hypothesize that this profile is dominated by an optically thin disk envelope or atmosphere component. We also discuss the compatibility of our data with the previously postulated existence of a sub-stellar companion to SR21 at r ~ 10-20 AU, and find that we can neither exclude nor verify this scenario. This study demonstrates the power of multiwavelength imaging of transitional disks to inform modeling efforts, including the debate over precisely what physical mechanism is responsible for clearing these disks of their large midplane grains. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Follette, Katherine B.; Tamura, Motohide; Hashimoto, Jun; Whitney, Barbara; Grady, Carol; Close, Laird; Andrews, Sean M.; Kwon, Jungmi; Wisniewski, John; Brandt, Timothy D.; Mayama, Satoshi; Kandori, Ryo; Dong, Ruobing; Abe, Lyu; Brandner, Wolfgang; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Feldt, Markus; Goto, Miwa; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko; Henning, Thomas; Hodapp, Klaus; Ishii, Miki; Iye, Masanori; Janson, Markus; Knapp, Gillian R.; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Kuzuhara, Masayuki; McElwain, Michael W.; Matsuo, Taro; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Tomono, Daigo; Turner, Edwin L.; Watanabe, Makoto; Yamada, Toru; Takami, Hideki; Usuda, Tomonori

2013-04-01

359

Annealing effect on the near-band edge emission of ZnO  

NASA Astrophysics Data System (ADS)

ZnO thin films have been grown on the sapphire (?-Al2O3) substrates at the temperature of 250 °C by means of the direct current (DC) magnetron sputtering technique. The crystal structure and surface morphology of the deposited films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The optical transmission, reflection and luminescence spectra at 300 K were analyzed for both the as-grown and post-annealed ZnO films. Using the ?-modulation method gives the possibility to reveal the main features of the energy band structure and the nature of the radiative transitions causing the ultraviolet (UV) luminescence.

Khomyak, V. V.; Slyotov, M. M.; Shtepliuk, I. I.; Lashkarev, G. V.; Slyotov, O. M.; Marianchuk, P. D.; Kosolovskiy, V. V.

2013-02-01

360

Blue Luminescence and Extended Red Emission: Possible Connections to the Diffuse Interstellar Bands  

NASA Astrophysics Data System (ADS)

Blue luminescence (BL) and extended red emission (ERE) are observed as diffuse, optical-wavelength emissions in interstellar space, resulting from photoluminescence by ultraviolet(UV)-illuminated interstellar grains. Faintness and the challenge of separating the BL and ERE from the frequently much brighter dust-scattered continuum present major observational hurdles, which have permitted only slow progress in testing the numerous models that have been advanced to explain these two phenomena. Both the ERE, peaking near 680 nm (FWHM ~ 60 - 120 nm) and the BL, asymmetrically peaking at ~ 378 nm (FWHM ~ 45 nm), were first discovered in the Red Rectangle nebula. Subsequently, ERE and BL have been observed in other reflection nebulae, and in the case of the ERE, in carbon-rich planetary nebulae, H II regions, high-latitude cirrus clouds, the galactic diffuse ISM, and in external galaxies. BL exhibits a close spatial and intensity correlation with emission in the aromatic emission feature at 3.3 micron, most likely arising from small, neutral polycyclic aromatic hydrocarbon (PAH) molecules. The spectral characteristics of the BL also agree with those of fluorescence by PAH molecules with 13 to 19 carbon atoms. The BL phenomenon is thus most readily understood as the optical fluorescence of small, UV-excited aromatic molecules. The ERE, by contrast, though co-existent with mid-IR PAH emissions, does not correlate with emissions from either neutral or ionized PAHs. Instead, the spatial ERE morphology appears to be strictly governed by the density of far-UV (E >= 10.5 eV) photons, which are required for the ERE excitation. The most restrictive observational constraint for the ERE process is its exceptionally high quantum efficiency. If the ERE results from photo-excitation of a nano-particle carrier by photons with E >= 10.5 eV in a single-step process, the quantum efficiency exceeds 100%. Such a process, in which one to three low-energy optical photons may be emitted following a single far-UV excitation, is possible in highly isolated small clusters, e.g. small, dehydrogenated carbon clusters with about 20 to 28 carbon atoms. A possible connection between the ERE carriers and the carriers of DIBs may exist in that both are ubiquitous throughout the diffuse interstellar medium and both have an abundance of low-lying electronic levels with E <= 2.3 eV above the ground state.

Witt, A. N.

2014-02-01

361

Theoretical predictions for the effect of nebular emission on the broad-band photometry of high-redshift galaxies  

NASA Astrophysics Data System (ADS)

By combining optical and near-IR observations from the Hubble Space Telescope with near-IR photometry from the Spitzer Space Telescope, it is possible to measure the rest-frame UV-optical colours of galaxies at z = 4-8. The UV-optical spectral energy distribution of star formation dominated galaxies is the result of several different factors. These include the joint distribution of stellar masses, ages and metallicities (solely responsible for the pure stellar spectral energy distribution), and the subsequent reprocessing by dust and gas in the interstellar medium. Using a large cosmological hydrodynamical simulation (MassiveBlack-II), we investigate the predicted spectral energy distributions of galaxies at high redshift with a particular emphasis on assessing the potential contribution of nebular emission. We find that the average (median) pure stellar UV-optical colour correlates with both luminosity and redshift such that galaxies at lower redshift and higher luminosity are typically redder. Assuming that the escape fraction of ionizing photons is close to zero, the effect of nebular emission is to redden the UV-optical 1500 - Vw colour by, on average, 0.4 mag at z = 8 declining to 0.25 mag at z = 4. Young and low-metallicity stellar populations, which typically have bluer pure stellar UV-optical colours, produce larger ionizing luminosities and are thus more strongly affected by the reddening effects of nebular emission. This causes the distribution of 1500 - Vw colours to narrow and the trends with luminosity and redshift to weaken. The strong effect of nebular emission leaves observed-frame colours critically sensitive to the redshift of the source. For example, increasing the redshift by 0.1 can result in observed-frame colours changing by up to ˜0.6. These predictions reinforce the need to include nebular emission when modelling the spectral energy distributions of galaxies at high redshift and also highlight the difficultly in interpreting the observed colours of individual galaxies without precise redshift information.

Wilkins, Stephen M.; Coulton, William; Caruana, Joseph; Croft, Rupert; Matteo, Tiziana Di; Khandai, Nishikanta; Feng, Yu; Bunker, Andrew; Elbert, Holly

2013-11-01

362

The electrosphere of macroscopc ""nuclei"": diffuse emissions in the MeV band from dark antimatter  

SciTech Connect

Using a Thomas-Fermi model, we calculate the structure of the electrosphere of the quark antimatter nuggets postulated to comprise much of the dark matter. This provides a single self-consistent density profile from ultra-rel ativistic densities to the non-relativistic Boltzmann regime. We use this to present a microscopically justified calculation of several properties of the nuggets, including their net charge, and the ratio of MeV to 511 keV emissions from electron annihilation. We find that the calculated parameters agree with previous phenomenological estimates based on the observational supposition that the nuggets are a source of several unexplained diffuse emissions from the galaxy. This provides another nontrivial verification of the dark matter proposal. The structure of the electrosphere is quite general and will also be valid at the surface of strange-quark stars, should they exist.

Forbes, Michael Mcneil [Los Alamos National Laboratory; Lawson, Kyle [CANADA; Zhitnitsky, Ariel R [CANADA

2009-01-01

363

Valence band states and polarized optical emission from nonpolar and semipolar III–nitride quantum well optoelectronic devices  

NASA Astrophysics Data System (ADS)

Nonpolar and semipolar III–nitride quantum wells (QWs) and devices have been extensively studied due to their unique valence band (VB) structure and polarized optical emission. Unlike conventional c-plane oriented III–nitride QWs, the low crystal symmetry and unbalanced biaxial stress in nonpolar and semipolar QWs separates the topmost VBs and gives rise to polarized optical emission. Since the first experimental reports on nonpolar devices, research on this topic has progressed very rapidly and has covered nonpolar m-plane and a-plane QWs and devices as well as semipolar (11\\bar{2}2), (20\\bar{2}1), and (20\\bar{2}\\bar{1}) QWs and devices. Issues such as strain, plane inclination angle (with respect to the c-plane), indium composition, temperature, and their impact on QW VB structure and device performance have been extensively studied. In this paper we review the physical background and theoretical analysis of the VB states and polarized optical emission of nonpolar and semipolar structures and discuss their potential impacts on optoelectronic devices. Experimental results for nonpolar and semipolar light-emitting diodes and laser diodes will be covered along with additional discussions on the potential applications and challenges related to their unique physical properties.

Zhao, Yuji; Farrell, Robert M.; Wu, Yuh-Renn; Speck, James S.

2014-10-01

364

Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1  

NASA Technical Reports Server (NTRS)

We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z approx. 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines . with rest-frame equivalent widths approx. 1000A in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with approx.10(exp 8) Solar Mass in stellar mass, undergoing an enormous starburst phase with M*/M* of only approx. 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10(exp -4) Mpc(sup -3) can produce in approx.4 Gyr much of the stellar mass density that is presently contained in 10(exp 8) - 10(exp 9) Solar Mass dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

vanderWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; Jahnke, K.; Salmon, B. W.; deMello, D. F.; Kkocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Guo, Yicheng

2012-01-01

365

Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1  

NASA Technical Reports Server (NTRS)

We identify an abundant population of extreme emission line galaxies at redshift z=1.6 - 1.8 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared, broad-band fluxes. Supported by spectroscopic confirmation of strong [OIII] emission lines - with equivalent widths approximately 1000A - in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are dwarf galaxies with approximately 10(exp 8) solar mass in stellar mass, undergoing an enormous star-burst phase with M*/M* of only approximately 10 Myr. The star formation activity and the co-moving number density (3.7 x 10(exp -4) Mpc(exp -3)) imply that strong, short-lived bursts play a significant, perhaps even dominant role in the formation and evolution of dwarf galaxies at z greater than 1. The observed star formation activity can produce in less than 5 Gyr the same amount of stellar mass density as is presently contained in dwarf galaxies. Therefore, our observations provide a strong indication that the stellar populations of present-day dwarf galaxies formed mainly in strong, short-lived bursts, mostly at z greater than 1.

VanDerWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Kocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Lee, K.-S.; Guo, Y.

2011-01-01

366

Broad-band transient recording and characterization of acoustic emission events in composite laminates  

Microsoft Academic Search

Acoustic emission (AE) transients due to different kinds of microdamage, such as matrix cracking, fiber breakage and local delaminations, have been recorded in glass\\/epoxy composite laminates. Different stacking sequences, [0°, 90°2]S, [90°2, 0°]S, [+45°, ?45°]S and [0°4], were used in order to trigger different crack mechanisms during tensile testing. The AE transients were recorded as functions of time by the

Mikael Johnson; Peter Gudmundson

2000-01-01

367

Band Gap Energy of Chalcopyrite Thin Film Solar Cell Absorbers Determined by Soft X-Ray Emission and Absorption Spectroscopy  

SciTech Connect

The chemical and electronic structure of high efficiency chalcopyrite thin film solar cell absorbers significantly differs between the surface and the bulk. While it is widely accepted that the absorber surface exhibits a Cu-poor surface phase with increased band gap (Eg), a direct access to the crucial information of the depth-dependency of Eg is still missing. In this paper, we demonstrate that a combination of x-ray emission and absorption spectroscopy allows a determination of Eg in the surface-near bulk and thus complements the established surface- and bulk-sensitive techniques of Eg determination. As an example, we discuss the determination of Eg for a Cu(In,Ga)Se2 absorber [(1.52 +- 0.20) eV].

Bar, M.; Weinhardt, L.; Pookpanratana, S.; Heske, C.; Nishiwaki, S.; Shafarman, W.; Fuchs, O.; Blum, M.; Yang, W.; Denlinger, J.D.

2008-05-11

368

Revealing the surface origin of green band emission from ZnO nanostructures by plasma immersion ion implantation induced quenching  

SciTech Connect

Surface defect passivation for ZnO nanocombs (NCBs), random nanowires (RNWs), and aligned nanowires (ANWs) was performed through a metal plasma immersion ion implantation with low bias voltages ranging from 0 to 10 kV, where Ni was used as the modification ion. The depth of surface-originated green band (GB) emission is thus probed, revealing the surface origin of the GB. It is also found that the GB is closely related to oxygen gas content during growth of the nanostructures. The GB origin of NCBs and RNWs grown with higher oxygen content is shallower ({approx}0.5 nm), which can be completely quenched with no bias applied. However, the GB origin of ANWs grown at lower oxygen content is much deeper ({approx}7 nm) with a complete quenching bias of 10 kV. Quenching of the GB can be attributed to passivation of the surface hole or electron trapping sites (oxygen vacancies) by Ni ions.

Yang, Y.; Sun, X. W.; Tay, B. K.; Cao, Peter H. T.; Wang, J. X. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Zhang, X. H. [Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore)

2008-03-15

369

Infrared spectrum of the laboratory-synthesized quenched carbonaceous composite (QCC) - Comparison with the infrared unidentified emission bands  

NASA Astrophysics Data System (ADS)

Infrared spectra (2.5-25 microns) of the experimentally synthesized quenched carbonaceous composite (QCC), which has been shown to be a likely candidate for the interstellar 220 nm extinction hump, are presented. QCC is shown to have infrared bands at 3.29, 3.42, 3.48, 6.25, 6.94, 7.27, 11.40, 11.96, and 13.24 microns. The spectrum taken after heating the QCC sample to 773 K shows that only the 6.25 and 11.40 microns features survive and the other features almost disappear at that temperature. The infrared absorption features in QCC are in good agreement with six of the nine infrared unidentified emission bands observed in celestial objects. In particular, the QCC sample after heating at 773 K is the first actual substance which shows features only around 6.2 and 11.3 microns. These results support theoretical indications that the source material for the most observed features is carbonaceous.

Sakata, A.; Wada, S.; Tanabe, T.; Onaka, T.

1984-12-01

370

Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons  

NASA Technical Reports Server (NTRS)

Spectra of 3 micrometers emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 micrometers feature and its most prominent satellite band at 3.40 micrometers are found. It is shown that (i) the 3.40 micrometers band is too intense with respect to the 3.29 micrometers band at certain positions to arise from hot band emission alone, (ii) the 3.40 micrometers band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (iii) the variations in the 3.40 micrometers to 3.29 micrometers band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 micrometers emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 micrometers emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 micrometers spectrum of the proto-planetary nebula IRAS 05341+0852 with the spectrum of the planetary nebula IRAS 21282+5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 micrometers emission spectra of these objects.

Joblin, C.; Tielens, A. G.; Allamandola, L. J.; Geballe, T. R.

1996-01-01

371

Spatial Variation of the 3.29 and 3.40 Micron Emission Bands Within Reflection Nebulae and The Photochemical Evolution of Methylated Polycyclic Aromatic Hydrocarbons  

NASA Technical Reports Server (NTRS)

Spectra of 3 microns emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 microns feature and its most prominent satellite band at 3.40 microns are found. It is shown that: (1) the 3.40 microns band is too intense with respect to the 3.29 microns band at certain positions to arise from hot band emission alone, (2) the 3.40 microns band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (3) the variations in the 3.40 microns to 3.29 microns band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 microns emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 microns emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 microns spectrum of the proto-planetary nebula IRAS 05341 + 0852 with the spectrum of the planetary nebula IRAS 21282 + 5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 microns emission spectra of these objects.

Joblin, C.; Tielens, A. G. G. M.; Allamandola, L. J.; Geballe, T. R.

1996-01-01

372

DAY-SIDE z'-BAND EMISSION AND ECCENTRICITY OF WASP-12b  

SciTech Connect

We report the detection of the eclipse of the very hot Jupiter WASP-12b via z'-band time-series photometry obtained with the 3.5 m Astrophysical Research Consortium telescope at Apache Point Observatory. We measure a decrease in flux of 0.082% {+-} 0.015% during the passage of the planet behind the star. That planetary flux is equally well reproduced by atmospheric models with and without extra absorbers, and blackbody models with f {>=} 0.585 {+-} 0.080. It is therefore necessary to measure the planet at other wavelengths to further constrain its atmospheric properties. The eclipse appears centered at phase {phi} = 0.5100{sup +0.0072}{sub -0.0061}, consistent with an orbital eccentricity of |ecos {omega}| = 0.016{sup +0.011}{sub -0.009} (see note at the end of Section 4). If the orbit of the planet is indeed eccentric, the large radius of WASP-12b can be explained by tidal heating.

Lopez-Morales, Mercedes; Rogers, Justin C. [Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Coughlin, Jeffrey L. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Sing, David K. [Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter, Ex4 4QL (United Kingdom); Burrows, Adam; Spiegel, David S. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Apai, Daniel [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Adams, Elisabeth R., E-mail: mercedes@dtm.ciw.ed [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2010-06-10

373

Modulations of broad-band radio continua and X-ray emissions in the large X-ray flare on 03 November 2003  

NASA Astrophysics Data System (ADS)

The GOES X3.9 flare on 03 November 2003 at ˜09:45 UT was observed from metric to millimetric wavelengths by the Nançay Radioheliograph (NRH), the Radio Solar Telescope Network (RSTN) and by radio instruments operated by the Institute of Applied Physics (University of Bern). This flare was simultaneously observed and imaged up to several 100 keV by the RHESSI experiment. The time profile of the X-ray emission above 100 keV and of the radio emissions shows two main parts, impulsive emission lasting about 3 min and long duration emission (partially observed by RHESSI) separated in time by 4 min. We shall focus here on the modulations of the broad-band radio continua and of the X-ray emissions observed in the second part of the flare. The observations suggest that gyrosynchrotron emission is the prevailing emission mechanism even at decimetric wavelengths for the broad-band radio emission. Following this interpretation, we deduce the density and the magnetic field of the decimetric sources and briefly comment on possible interpretations of the modulations.

Dauphin, C.; Vilmer, N.; Lüthi, T.; Trottet, G.; Krucker, S.; Magun, A.

374

Determining Limits on the Intensity of the O2 0-0 Atmospheric Band Emission in the Venus Nightglow  

NASA Astrophysics Data System (ADS)

Recombination of oxygen atoms is the source of excited O2 states in the nighttime mesospheres of the terrestrial planets - Venus, Earth, and Mars. Emission in the O2 Atmospheric 0-0 band at 762 nm is one of the strongest features in the terrestrial visible/near-IR spectral region, with a typical intensity of 5 kR, although this emission does not reach the ground due to self-absorption. We inquire as to what intensity is expected at Venus, although there are no published spectra for either Venus or Mars in this spectral region. A recent estimated upper limit of 200 R for Venus has been given [Krasnopolsky, 2011]. The calculation requires knowledge of the temperature-dependent rate coefficients for three-body oxygen atom recombination in CO2 and for O2(b, v = 0) removal by CO2, as well as an estimate for the fraction of stabilized excited O2 molecules that reach b(v = 0). The resultant nadir intensity depends on [O(3P)]2, and for a value of [O(3P)] = 1.5 × 1011 cm-3, the 95-km intensity is of the order of 2 R, probably accurate to within a factor of two. Such a value is consistent with the lack of detection in recent Venus Express VIRTIS spectra, which include the 762 nm region. Measurements of the Venus nightglow with the 3.5-m telescope at Apache Point Observatory in December, 2010 also show no 762 nm emission, where in principle the 0.03 nm Doppler shift in the emission due to the relative velocities of Earth and Venus could have made observation possible. The principal differences between the Venus and Earth cases are (1) quenching of O2(b, v = 0) is more than two orders of magnitude faster by CO2 than by N2 (the terrestrial quencher) and (2) the densities in the ~95 km mesospheric nightglow region are two orders of magnitude higher at Venus. TGS acknowledge support for this work from the NASA Planetary Astronomy Program, Grant NNX08A0276. AM acknowledges ASI for support. Krasnopolsky, V.A., Planet. Space Sci. 59, 754-766, 2011.

Slanger, T. G.; Migliorini, A.; Gray, C.

2011-12-01

375

OBSERVATIONS OF THE NEAR- TO MID-INFRARED UNIDENTIFIED EMISSION BANDS IN THE INTERSTELLAR MEDIUM OF THE LARGE MAGELLANIC CLOUD  

SciTech Connect

We present the results of near- to mid-infrared slit spectroscopic observations (2.55-13.4 {mu}m) of the diffuse emission toward nine positions in the Large Magellanic Cloud with the infrared camera on board AKARI. The target positions are selected to cover a wide range of the intensity of the incident radiation field. The unidentified infrared bands at 3.3, 6.2, 7.7, 8.6, and 11.3 {mu}m are detected toward all the targets and ionized gas signatures; hydrogen recombination lines and ionic forbidden lines are detected toward three of them. We classify the targets into two groups: those without the ionized gas signatures (Group A) and those with the ionized signatures (Group B). Group A includes molecular clouds and photodissociation regions, whereas Group B consists of H II regions. In Group A, the band ratios of I{sub 3.3{mu}m}/I{sub 11.3{mu}m}, I{sub 6.2{mu}m}/I{sub 11.3{mu}m}, I{sub 7.7{mu}m}/I{sub 11.3{mu}m}, and I{sub 8.6{mu}m}/I{sub 11.3{mu}m} show positive correlation with the IRAS and AKARI colors, but those of Group B do not follow the correlation. We discuss the results in terms of the polycyclic aromatic hydrocarbon (PAH) model and attribute the difference to the destruction of small PAHs and an increase in the recombination due to the high electron density in Group B. In the present study, the 3.3 {mu}m band provides crucial information on the size distribution and/or the excitation conditions of PAHs and plays a key role in the distinction of Group A from B. The results suggest the possibility of the diagram of I{sub 3.3{mu}m}/I{sub 11.3{mu}m} versus I{sub 7.7{mu}m}/I{sub 11.3{mu}m} as an efficient diagnostic tool to infer the physical conditions of the interstellar medium.

Mori, Tamami I.; Sakon, Itsuki; Onaka, Takashi; Ohsawa, Ryou [Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kaneda, Hidehiro [Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Umehata, Hideki, E-mail: morii@astron.s.u-tokyo.ac.jp, E-mail: isakon@astron.s.u-tokyo.ac.jp, E-mail: onaka@astron.s.u-tokyo.ac.jp [Institute of Astronomy, Graduate School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

2012-01-01

376

Direct band gap optical emission from compressively strained Ge films grown on relaxed Si{sub 0.5}Ge{sub 0.5} substrate  

SciTech Connect

Compressively strained Ge films have been grown on relaxed Si{sub 0.5}Ge{sub 0.5} virtual substrate in ultra high vacuum using molecular beam epitaxy. Structural characterization has shown that the Ge films are compressively strained with partial strain relaxation in a film thicker than 3.0 nm, due to onset of island nucleation. Photoluminescence spectra exhibit the splitting of degenerate Ge valence band into heavy hole and light hole bands with a broad direct band gap emission peak around 0.81 eV. Temperature and excitation power dependent emission characteristics have been studied to investigate the mechanism of luminescence quenching at high temperatures and the role of non-radiative recombination centers.

Aluguri, R.; Manna, S.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)] [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

2013-10-14

377

Calculation of the X-Ray emission K and L 2,3 bands of metallic magnesium and aluminum with allowance for multielectron effects  

NASA Astrophysics Data System (ADS)

A procedure is proposed to calculate the shape of the characteristic X-ray emission bands of metals with allowance for multielectron effects. The effects of the dynamic screening of a core vacancy by conduction electrons and the Auger effect in the valence band are taken into account. The dynamic screening of a core vacancy, which is known to be called the MND (Mahan-Nozeieres-De Dominics) effect, is taken into account by an ab initio band calculation of crystals using the PAW (projected augmented waves) method. The Auger effect is taken into account by a semiempirical method using the approximation of a quadratic dependence of the level width in the valence band on the difference between the level energy and the Fermi energy. The proposed calculation procedure is used to describe the X-ray emission K and L 2,3 bands of metallic magnesium and aluminum crystals. The calculated spectra agree well with the experimental bands both near the Fermi level and in the low-energy part of the spectra in all cases.

Ovcharenko, R. E.; Tupitsyn, I. I.; Savinov, E. P.; Voloshina, E. N.; Dedkov, Yu. S.; Shulakov, A. S.

2014-01-01

378

Temperature-dependent shifts of near band-edge emission and their second-order diffraction for ZnO nanorods  

NASA Astrophysics Data System (ADS)

The crystal structure and morphology of ZnO, grown on silicon substrate by two-step method, were measured by X-ray diffraction and field emission scanning electron microscopy. The results reveal that the sample is mainly composed of ZnO nanorods and preferentially oriented in the c-axis direction. The photoluminescence properties of the ZnO nanorods were investigated over the temperatures from 10 K to 297 K. There exist three emission bands in near band-edge, green-yellow-orange-red and near-infrared, respectively. Donor bound exciton (D0X) and its phonon replicas emission peaks were observed in low temperature photoluminescence (PL). The D0X and its phonon replicas peak intensity decreased with the increase of temperature and disappeared when the temperature increased up to 87 K. The decay in the D0X and its phonon replicas emission peak intensity stemmed from the thermal dissociation of D0X to free exciton. Temperature-dependent second-order diffraction of the near band-edge emissions were investigated in detail.

Lv, Jianguo; Liu, Changlong; Gong, Wanbing; Zi, Zhenfa; Chen, Xiaoshuang; Huang, Kai; Wang, Tao; He, Gang; Shi, Shiwei; Song, Xueping; Sun, Zhaoqi

2012-09-01

379

Infrared spectrum of quenched carbonaceous composite (QCC). II - A new identification of the 7.7 and 8.6 micron unidentified infrared emission bands  

NASA Astrophysics Data System (ADS)

Infrared spectrum of 'oxidized' quenched carbonaceous composite (QCC) is presented. In addition to the features seen in 'unoxidized' QCC, new features appear at 7.7 and 8.6 microns and the strengths of the features at 6.2, 7.3, and 11.4 microns increase. The infrared features of 'oxidized' QCC are in good agreement with nine of 11 members of the unidentified infrared (UIR) emission bands. The absorption bands of QCC are all broad without fine structure, clearly different from sharp bands of molecules. The 7.7 and 8.6 micron features can be attributed to a 'cross-conjugated ketone' molecular structure. A possible identification of the UIR 7.7 and 8.6 micron bands with this structure is discussed. The present results indicate that oxygen can play an important role in the structures of the UIR emitting material as well as carbon and hydrogen.

Sakata, Akira; Wada, Setsuko; Onaka, Takashi; Tokunaga, Alan T.

1987-09-01

380

Infrared spectrum of quenched carbonaceous composite (QCC). II. A new identification of the 7. 7 and 8. 6 micron unidentified infrared emission bands  

SciTech Connect

Infrared spectrum of oxidized quenched carbonaceous composite (QCC) is presented. In addition to the features seen in unoxidized QCC, new features appear at 7.7 and 8.6 microns and the strengths of the features at 6.2, 7.3, and 11.4 microns increase. The infrared features of oxidized QCC are in good agreement with nine of 11 members of the unidentified infrared (UIR) emission bands. The absorption bands of QCC are all broad without fine structure, clearly different from sharp bands of molecules. The 7.7 and 8.6 micron features can be attributed to a cross-conjugated ketone molecular structure. A possible identification of the UIR 7.7 and 8.6 micron bands with this structure is discussed. The present results indicate that oxygen can play an important role in the structures of the UIR emitting material as well as carbon and hydrogen. 29 references.

Sakata, A.; Wada, S.; Onaka, T.; Tokunaga, A.T.

1987-09-01

381

OPTICAL TiO AND VO BAND EMISSION IN TWO EMBEDDED PROTOSTARS: IRAS 04369+2539 AND IRAS 05451+0037  

SciTech Connect

Archival spectra from the Sloan Digital Sky Survey of two optically faint flat-spectrum protostars, IRAS 04369+2539 and IRAS 05451+0037, show strong emission-line features including-notably-clear and broad emission across several molecular bands of TiO and VO. The molecular emission is indicative of dense, warm circumstellar gas and has been seen previously in only one object: the flat-spectrum protostar IRAS 20496+4354 during a strong optical outburst (PTF 10nvg). The presence of broad molecular emission features in two additional objects having similar mid-infrared properties (but not known to be undergoing outbursts) could provide new insight into phases of rapid accretion/outflow at early stages of the protoplanetary disk. At present, the relevant geometry and the formation or heating mechanisms responsible for the observed TiO/VO cooling emission remain unexplained.

Hillenbrand, Lynne A. [Astrophysics Department, California Institute of Technology, Pasadena, CA 91125 (United States); Knapp, Gillian R. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Padgett, Deborah L.; McGehee, Peregrine M. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Rebull, Luisa M. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)

2012-02-15

382

Improvements on Near Real Time Detection of Volcanic Ash Emissions for Emergency Monitoring with Limited Satellite Bands  

NASA Astrophysics Data System (ADS)

Quantifying volcanic ash emissions syn-eruptively is an important task for the global aviation community. However, due to the near real time nature of volcano monitoring, many parameters important for accurate ash mass estimates cannot be obtained easily. Previous studies highlight the surface temperature, the refractive index of the ash and the cloud top temperature as most crucial of these values. Even when estimating those parameters best possible, uncertainties associated with the ash masses remain high, especially when the satellite data is only available in the traditional 10.8 and 12.0 µm bands. To counteract this limitation, we developed a quantitative comparison between the ash extents in satellite and model data. The main aspect is to manually define the cloud edge based on the available satellite data as well as other knowledge like pilot reports or ground-based observations. This manual aspect, although subjective to the experience of the observer, can show a significant improvement as it provides the ability to highlight ash that otherwise would be obscured by meteorological clouds or, by passing over different surfaces with unaccounted temperatures, might be lost entirely and thus remains undetectable for an automated satellite approach. We show comparisons to Volcanic Ash Transport and Dispersion models and outline a quantitative match as well as percentages of overestimates based on satellite or dispersion model data which can be converted into a level of reliability for near real time volcano monitoring.

Steensen, Torge; Webley, Peter; Dehn, Jon

2014-05-01

383

Using the Moon to evaluate the radiometric calibration performance of S-NPP VIIRS thermal emissive bands  

NASA Astrophysics Data System (ADS)

The Suomi-NPP VIIRS thermal emissive bands (TEB) are radiometrically calibrated on-orbit with reference to a blackbody (BB) operated at a nominal temperature of approximately 292.5 K. The quality of the calibration can be evaluated at other temperature ranges using independent thermal sources. The thermal properties of the lunar surface are extremely stable over time, making it a feasible target for the TEB calibration stability assessment for the space-borne sensors with regular lunar observations. VIIRS is scheduled to view the Moon on a nearly monthly basis at approximately the same phase angle since January 2012, before the cryo-cooler door was open and TEB started to collect data. In this paper, the brightness temperatures (BT) of the lunar surface retrieved using the calibration coefficients derived from the BB calibration are trended for VIIRS TEB to examine the calibration stability. The lunar surface temperature varies greatly with location and also oscillates seasonally with the solar illumination geometry. Radiance from many lunar locations saturates TEB detectors. Therefore, the trending must base on the regions of the Moon that do not saturate the detectors at any lunar observation event and thus their BT can be consistently retrieved. To achieve that, a temporally dynamic spatial mask is built for each detector to clip the locations of the Moon that may saturate the detector at any lunar event. Results show the radiometric calibration of all TEB detectors has been stable within 1 K range since being functional.

Wang, Zhipeng; Xiong, Xiaoxiong; Efremova, Boryana V.; Chen, Hongda

2014-09-01

384

Direct calculation of valence-band Auger emission: Spin polarization of Auger electrons from a potassium (110) surface  

NASA Astrophysics Data System (ADS)

We report calculations on spin-polarized Auger electron emission from the valence band of a potassium (110) film. In treating this process we use an N-electron scheme that is based on a generalized version of density-functional theory. The transition rate is determined by explicitly evaluating the transition matrix elements that contain the four states involved. The core and valence states are obtained from a self-consistent full-potential linearized augmented plane wave calculation on a K(110) multilayer. In the experiments that the present calculations refer to, the particular oriented core-hole state is created by photoexcitation using circularly polarized light. The observed energy spectrum and the angular dependence of the spin polarization of the emitted Auger electrons can be simply related to the character of the spinor-hole state. We compare our results for normal incidence of the light to the pertinent experiments on the Auger spin polarization referenced to the spin of the incoming photons. The results are in fair agreement with each other.

Yuan, Jianmin; Fritsche, L.; Noffke, J.

1997-10-01

385

First detection of Mars atmospheric hydroxyl: CRISM Near-IR measurement versus LMD GCM simulation of OH Meinel band emission in the Mars polar winter atmosphere  

NASA Astrophysics Data System (ADS)

Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29-L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380-1390. http://dx.doi.org/10.1175/1520-0469(1972)029<1380:SAAOOO>2.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9 ?m. Meinel band (1-0), (2-1), and (2-0) average limb intensities of 990 ± 280, 1060 ± 480, and 200 ± 100 kiloRayleighs (kR), respectively, are determined for 70-90 NS polar winter latitudes over altitudes of 40-56 km. Additional OH bands, such as (3-2), (3-1), and (4-2), present ?1? measurements. Uncertainty in the (4-2) band emission rate contributes to increased uncertainty in the determination of the O2(1?g) (0-0)/(0-1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45-55 km altitude levels for volume emission rates (VER) of 0.4 (2-0) to 2 (1-0, 2-1) × 104 photons/(cm3 s). Similar to polar night O2(1?g) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire de Météorologie Dynamique) photochemical GCM (global climate model), employing detailed photochemistry (e.g. Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. (Planets) 109, E07004. http://dx.doi.org/10.1029/2004JE002268) and energy transfer processes (excitation and quenching) developed for Mars Meinel OH band nightglow by García Muñoz et al. (García Muñoz, A., McConnell, J.C., McDade, I.C., Melo, S.M.L. [2005]. Icarus 176, 75-95). Modeled versus observed OH emission behavior agrees within measurement uncertainties with the assumptions of a Bates-Nicolet (H + O3) source for excited OH production, and ‘collisional-cascade’ quenching of the OH vibrational population by CO2. ‘Sudden-death’ quenching of excited OH by CO2 leads to 100× less OH emission than observed. The combined agreement between LMD GCM simulated and CRISM observed O2(1?g) and Meinel OH polar nightglow behaviors represents a significant demonstration of the LMD model capability to couple odd oxygen and hydrogen photochemistry and transport by the Mars global circulation in a realistic fashion.

Todd Clancy, R.; Sandor, Brad J.; García-Muñoz, Antonio; Lefèvre, Franck; Smith, Michael D.; Wolff, Michael J.; Montmessin, Franck; Murchie, Scott L.; Nair, Hari

2013-09-01

386

First detection of Mars atmospheric hydroxyl: CRISM Near-IR measurement versus LMD GCM simulation of OH Meinel band emission in the Mars polar winter atmosphere  

NASA Astrophysics Data System (ADS)

Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29-L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380-1390. http://dx.doi.org/10.1175/1520-0469(1972)029<1380:SAAOOO>2.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9 ?m. Meinel band (1-0), (2-1), and (2-0) average limb intensities of 990 ± 280, 1060 ± 480, and 200 ± 100 kiloRayleighs (kR), respectively, are determined for 70-90 NS polar winter latitudes over altitudes of 40-56 km. Additional OH bands, such as (3-2), (3-1), and (4-2), present ?1? measurements. Uncertainty in the (4-2) band emission rate contributes to increased uncertainty in the determination of the O2(1?g) (0-0)/(0-1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45-55 km altitude levels for volume emission rates (VER) of 0.4 (2-0) to 2 (1-0, 2-1) × 104 photons/(cm3 s). Similar to polar night O2(1?g) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire de Météorologie Dynamique) photochemical GCM (global climate model), employing detailed photochemistry (e.g. Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. (Planets) 109, E07004. http://dx.doi.org/10.1029/2004JE002268) and energy transfer processes (excitation and quenching) developed for Mars Meinel OH band nightglow by García Muñoz et al. (García Muñoz, A., McConnell, J.C., McDade, I.C., Melo, S.M.L. [2005]. Icarus 176, 75-95). Modeled versus observed OH emission behavior agrees within measurement uncertainties with the assumptions of a Bates-Nicolet (H + O3) source for excited OH production, and 'collisional-cascade' quenching of the OH vibrational population by CO2. 'Sudden-death' quenching of excited OH by CO2 leads to 100× less OH emission than observed. The combined agreement between LMD GCM simulated and CRISM observed O2(1?g) and Meinel OH polar nightglow behaviors represents a significant demonstration of the LMD model capability to couple odd oxygen and hydrogen photochemistry and transport by the Mars global circulation in a realistic fashion.

Clancy, R. Todd; Sandor, Brad J.; García-Muñoz, Antonio; Lefèvre, Franck; Smith, Michael D.; Wolff, Michael J.; Montmessin, Franck; Murchie, Scott L.; Nair, Hari

2013-09-01

387

Laboratory studies of UV emissions from proton impact on N2: The Lyman-Birge-Hopfield band system for aurora analysis  

NASA Astrophysics Data System (ADS)

We have measured the emission cross sections of the Lyman-Birge-Hopfield (LBH) a 1?g - X 1?g+ band system and several atomic nitrogen (N I) multiplets (1200, 1243, 1493 Å) by H+ (proton) impact on N2 over an impact energy range of 1-7 keV. The peak proton-impact-induced emission cross section of the LBH band system (1260-2500 Å) was measured to be 5.05 ± 1.52 × 10-17 cm2 at 7 keV. To the best of our knowledge, the present LBH emission cross sections are reported for the first time in the far ultraviolet (FUV) wavelength range of 1100-1600 Å. The proton energy range in this study, when coupled with previously published 10-100 keV proton excited emissions of N I multiplets, provides a wide energy range of emission cross sections for proton energy loss transport codes. This energy range includes the peak cross section and the energy range for Born scaling. The reported measurements lead to an important component of monoenergetic yields for proton FUV auroral emission. Such yields, based on emission cross sections and transport modeling, allowed for convenient comparison of emission efficiencies between proton and electron aurora. In addition, we have measured the H Ly ?, LBH, and N I multiplet emission cross sections for H2+ and H3+ ion impact on N2 at 5 keV and found that the magnitude of H Ly ? emission cross section, ?em(Ly ?), follows in the order of impact ion mass H3+ > H2+ > H+.

Ajello, Joseph M.; Mangina, Rao S.; Strickland, Douglas J.; Dziczek, Dariusz

2011-04-01

388

The emission and scattering of L-band microwave radiation from rough ocean surfaces and wind speed measurements from the Aquarius sensor  

NASA Astrophysics Data System (ADS)

order to achieve the required accuracy in sea surface salinity (SSS) measurements from L-band radiometers such as the Aquarius/SAC-D or SMOS (Soil Moisture and Ocean Salinity) mission, it is crucial to accurately correct the radiation that is emitted from the ocean surface for roughness effects. We derive a geophysical model function (GMF) for the emission and backscatter of L-band microwave radiation from rough ocean surfaces. The analysis is based on radiometer brightness temperature and scatterometer backscatter observations both taken on board Aquarius. The data are temporally and spatially collocated with wind speeds from WindSat and F17 SSMIS (Special Sensor Microwave Imager Sounder) and wind directions from NCEP (National Center for Environmental Prediction) GDAS (Global Data Assimilation System). This GMF is the basis for retrieval of ocean surface wind speed combining L-band H-pol radiometer and HH-pol scatterometer observations. The accuracy of theses combined passive/active L-band wind speeds matches those of many other satellite microwave sensors. The L-band GMF together with the combined passive/active L-band wind speeds is utilized in the Aquarius SSS retrieval algorithm for the surface roughness correction. We demonstrate that using these L-band wind speeds instead of NCEP wind speeds leads to a significant improvement in the SSS accuracy. Further improvements in the roughness correction algorithm can be obtained by adding VV-pol scatterometer measurements and wave height (WH) data into the GMF.

Meissner, Thomas; Wentz, Frank J.; Ricciardulli, Lucrezia

2014-09-01

389

NEAR-INFRARED THERMAL EMISSION FROM TrES-3b: A Ks-BAND DETECTION AND AN H-BAND UPPER LIMIT ON THE DEPTH OF THE SECONDARY ECLIPSE  

SciTech Connect

We present H- and Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-3b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope. We detect the secondary eclipse of TrES-3b with a depth of 0.133{sup +0.018}{sub -0.016}% in the Ks band (8{sigma})-a result that is in sharp contrast to the eclipse depth reported by de Mooij and Snellen. We do not detect its thermal emission in the H band, but place a 3{sigma} limit of 0.051% on the depth of the secondary eclipse in this band. A secondary eclipse of this depth in Ks requires very efficient day-to-nightside redistribution of heat and nearly isotropic reradiation, a conclusion that is in agreement with longer wavelength, mid-infrared Spitzer observations. Our 3{sigma} upper limit on the depth of our H-band secondary eclipse also argues for very efficient redistribution of heat and suggests that the atmospheric layer probed by these observations may be well homogenized. However, our H-band upper limit is so constraining that it suggests the possibility of a temperature inversion at depth, or an absorbing molecule, such as methane, that further depresses the emitted flux at this wavelength. The combination of our near-infrared measurements and those obtained with Spitzer suggests that TrES-3b displays a near-isothermal dayside atmospheric temperature structure, whose spectrum is well approximated by a blackbody. We emphasize that our strict H-band limit is in stark disagreement with the best-fit atmospheric model that results from longer wavelength observations only, thus highlighting the importance of near-infrared observations at multiple wavelengths, in addition to those returned by Spitzer in the mid-infrared, to facilitate a comprehensive understanding of the energy budgets of transiting exoplanets.

Croll, Bryce; Jayawardhana, Ray [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Lafreniere, David [Departement de Physique, Universite de Montreal, C.P. 6128 Succ. Centre-Ville, Montreal, QC H3C 3J7 (Canada); Albert, Loic, E-mail: croll@astro.utoronto.c [Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Highway, Kamuela, HI 96743 (United States)

2010-08-01

390

G-BAND AND HARD X-RAY EMISSIONS OF THE 2006 DECEMBER 14 FLARE OBSERVED BY HINODE/SOT AND RHESSI  

SciTech Connect

We report on G-band emission observed by the Solar Optical Telescope on board the Hinode satellite in association with the X1.5-class flare on 2006 December 14. The G-band enhancements originate from the footpoints of flaring coronal magnetic loops, coinciding with nonthermal hard X-ray bremsstrahlung sources observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. At the available 2 minute cadence, the G-band and hard X-ray intensities are furthermore well correlated in time. Assuming that the G-band enhancements are continuum emission from a blackbody, we derived the total radiative losses of the white-light flare (white-light power). If the G-band enhancements additionally have a contribution from lines, the derived values are overestimates. We compare the white-light power with the power in hard X-ray producing electrons using the thick-target assumption. Independent of the cutoff energy of the accelerated electron spectrum, the white-light power and the power of accelerated electrons are roughly proportional. Using the observed upper limit of {approx}30 keV for the cutoff energy, the hard X-ray producing electrons provide at least a factor of 2 more power than needed to produce the white-light emission. For electrons above 40 keV, the powers roughly match for all four of the time intervals available during the impulsive phase. Hence, the flare-accelerated electrons contain enough energy to produce the white-light flare emissions. The observed correlation in time, space, and power strongly suggests that electron acceleration and white-light production in solar flares are closely related. However, the results also call attention to the inconsistency in apparent source heights of the hard X-ray (chromosphere) and white-light (upper photosphere) sources.

Watanabe, Kyoko; Shimizu, Toshifumi [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Krucker, Saem; Hudson, Hugh [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Masuda, Satoshi [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Ichimoto, Kiyoshi, E-mail: watanabe.kyoko@isas.jaxa.j [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)

2010-05-20

391

EMI survey for maritime satellite, L-band, shipboard terminal  

NASA Technical Reports Server (NTRS)

The paper presents results of an onboard EMI survey of an L-band shipboard terminal for operation with two geostationary maritime satellites. Significant EMC results include: (1) antenna noise temperature measurements indicate a maximum of 70 K steady background component at 1.6 GHz at sea for elevation angles of 5 degrees and higher; (2) field intensity measurements from 1-10 GHz show that a L-band terminal can operate simultaneously with onboard S-band and X-band navigation radar; (3) radar transmitter case emissions, below deck, in-band from 1535-1660 MHz, at 1 m distance from the cabinet, are equivalent, or greater than above-deck emissions in the same frequency range; and (4) conducted-emission tests of a ship's power lines to both radars show both narrow band and broad band emissions are 15 dB to 50 dB higher than equivalent U.S. commercial power lines from 150 kHz to 32 MHz.

Taylor, R. E.; Brandel, D. L.; Hill, J. S.

1975-01-01

392

Ballistic-electron-emission spectroscopy of Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures: Conduction-band offsets, transport mechanisms, and band-structure effects  

SciTech Connect

We report an extensive investigation of semiconductor band-structure effects in single-barrier Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0{le}x{le}1). The initial ({Gamma}) BEES thresholds for Al{sub x}Ga{sub 1{minus}x}As single barriers with 0{le}x{le}0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements at 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime ({ital x}{gt}0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al{sub x}Ga{sub 1{minus}x}As {ital X} valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al{sub x}Ga{sub 1{minus}x}As interface produces a significant fraction of this{ital X} valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al{sub x}Ga{sub 1{minus}x}As {Gamma}, {ital L}, and {ital X} points yields good agreement over the entire composition range. {copyright} {ital 1997} {ital The American Physical Society}

OShea, J.J.; Brazel, E.G.; Rubin, M.E.; Bhargava, S.; Chin, M.A.; Narayanamurti, V. [Materials Department, Physics Department, and Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

1997-07-01

393

Variant Narrowing and Extreme Termination  

Microsoft Academic Search

For narrowing with a set of rules modulo a set of axioms B almost nothing is known about terminating narrowing strategies, and basic narrowing is known to be incomplete for B = AC. In this work we ask and answer the question: Is there such a thing as an extremely terminating narrowing strategy modulo B? where we call a narrowing

Santiago Escobar; Jose Meseguer; Ralf Sasse

394

Research Paper Search for the OH ( X2P) Meinel Band Emission in Meteors as a Tracer of Mineral Water in Comets: Detection of N 21 (AX)  

Microsoft Academic Search

We report the discovery of the N 21 A-X Meinel band in the 780- 840 nm meteor emission from two Leonid meteoroids that were ejected less than 1,000 years ago by comet 55P\\/Tempel-Tut- tle. Our analysis indicates that the N 21 molecule is at least an order of magnitude less abun- dant than expected, possibly as a result of charge

PETER JENNISKENS; CHRISTOPHE O. LAUX; EMILY L. SCHALLER

395

Narrowness and Liberality  

ERIC Educational Resources Information Center

John Agresto, whose task has been to rebuild the war-ravaged infrastructure of a Middle-Eastern university system, is discouraged to see that narrow expertise is the only goal of education there, to the utter exclusion of intellectual breadth. He comments that, although it is not that bad in the U.S., he feels that doctoral programs as currently…

Agresto, John

2003-01-01

396

Broad versus Narrow. Editorial.  

ERIC Educational Resources Information Center

Discusses the different roles played by eclectic versus specialized scholarly journals in education. The narrow focus of specialized journals is useful to scholars with limited time but may exclude authors with controversial viewpoints. Eclectic journals provide a broader picture of educational trends and a forum for scholarly debate, unorthodox…

Buck, George H.

2001-01-01

397

Spectroscopy of Fe L-shell line emission from Fe XVII- XXIV in the 10--18 A wavelength band  

NASA Astrophysics Data System (ADS)

The line emission from the L-shell, n --> 2, transitions in Fe XVII-XXIV falling in the ultra-soft x-ray regime from 10-18 Å has been measured using the Electron Beam Ion Trap located at the Lawrence Livermore National Laboratory. The results of these measurements include wavelengths, relative intensities, and line identifications of over 150 features from Fe XVIII-XXIV. In addition, measurements of the intensity of the high- n L-shell transitions, i.e., n >= 5, in Fe XVII falling in the 9.8-11.5 Å wavelength band have been made. These measurements were done at single electron beam energies where the only population process is direct excitation followed by radiative cascades. Also presented in this work are the results of a systematic study of the relative and absolute cross sections of the 1s22s 22p1/22 p43/2 3d3/2J = 1 --> 1 s22s22p 6 J = 0 resonance to ls2 2s22 p21/2 2 p33/2 3d5/2J = 1 --> 1 s22s22p 6 J = 0 intercombination line in neon-like Fe XVII. This ratio was measured under conditions where different processes contribute to the line flux. The contributing processes are direct impact excitation followed by radiative cascades, blending with Fe XVI innershell satellites, and Fe XVI dielectronic recombination satellites involving capture into high- n levels. The measured ratio varies between 2.8 and 3.2 depending on the line formation processes. These values are higher than ratios measured in non-flaring active regions of the Sun. However, the measurements are significantly lower than values calculated with current atomic physics codes demonstrating that calculational methods are not yet accurate enough to provide relative intensities useful for comparative diagnostics. The results suggest that the relatively low ratio measured in non-flaring active regions may be a result of blending with innershell satellites of Fe XVI.

Brown, Gregory Vallee

2000-09-01

398

Great enhancement of near band-edge emission of ZnSe two-dimensional complex nanostructures fabricated by the interference of three femtosecond laser beams  

NASA Astrophysics Data System (ADS)

By using the method of the interference of three 800 nm femtosecond laser beams, we fabricated complex 2-dimensional (2D) micro/nanostructures on ZnSe crystal. Compared with the plane surface of ZnSe crystal, 2D nanostructures exhibit a great enhancement of near band-edge (NBE) emission and a compression of second harmonic generation (SHG) under excitation of infrared (IR) femtosecond laser with central wavelengths ranging from 1200 to 1600 nm. We studied the photoluminescence properties of 2D nanostructures and the mechanism of the enhancement of NBE emission. Our results indicated that the enhancement of NBE emission is caused by a combination of several processes including the increase in optical absorption, and the reabsorption of SHG by the nanostructures.

Pan, Jia; Jia, Tianqing; Huo, Yanyan; Jia, Xin; Feng, Donghai; Zhang, Shian; Sun, Zhenrong; Xu, Zhizhan

2013-09-01

399

Near-infrared Thermal Emission from TrES-3b: A Ks-band Detection and an H-band Upper Limit on the Depth of the Secondary Eclipse  

NASA Astrophysics Data System (ADS)

We present H- and Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-3b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope. We detect the secondary eclipse of TrES-3b with a depth of 0.133+0.018 -0.016% in the Ks band (8?)—a result that is in sharp contrast to the eclipse depth reported by de Mooij & Snellen. We do not detect its thermal emission in the H band, but place a 3? limit of 0.051% on the depth of the secondary eclipse in this band. A secondary eclipse of this depth in Ks requires very efficient day-to-nightside redistribution of heat and nearly isotropic reradiation, a conclusion that is in agreement with longer wavelength, mid-infrared Spitzer observations. Our 3? upper limit on the depth of our H-band secondary eclipse also argues for very efficient redistribution of heat and suggests that the atmospheric layer probed by these observations may be well homogenized. However, our H-band upper limit is so constraining that it suggests the possibility of a temperature inversion at depth, or an absorbing molecule, such as methane, that further depresses the emitted flux at this wavelength. The combination of our near-infrared measurements and those obtained with Spitzer suggests that TrES-3b displays a near-isothermal dayside atmospheric temperature structure, whose spectrum is well approximated by a blackbody. We emphasize that our strict H-band limit is in stark disagreement with the best-fit atmospheric model that results from longer wavelength observations only, thus highlighting the importance of near-infrared observations at multiple wavelengths, in addition to those returned by Spitzer in the mid-infrared, to facilitate a comprehensive understanding of the energy budgets of transiting exoplanets. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Croll, Bryce; Jayawardhana, Ray; Fortney, Jonathan J.; Lafrenière, David; Albert, Loic

2010-08-01

400

Estimation of the heating rate due to the emissions in the near-infrared bands of the CO2 and CO molecules in the daytime atmosphere of Mars  

NASA Astrophysics Data System (ADS)

The problem of radiative transfer in the IR ro-vibrational bands of the CO _{2} molecules is the fundamental one for the atmosphere of Mars, since the heating due to the emissions in these bands has a dominant value in establishing the energy balance, structure, and dynamic properties throughout the entire atmosphere of this planet. Also, the emissions in some bands of the CO _{2} and CO molecules are used for remote sensing of the Martian atmosphere. So, a development of more sophisticated models for estimating the values of the Martian atmosphere emissions in the IR bands of the CO _{2} and CO molecules is required. The Martian atmosphere consisting for 95 per cent of the CO _{2} molecules has a rather low density. Therefore, both a rarity of molecular collisions, on one hand, and the high rate of excitation of the vibrational states of the CO _{2} and CO molecules due to an absorption of the solar radiation in the near-IR spectral range, on another hand, result in a breakdown of the Boltzmann distribution of the excited vibrational state populations of these molecules within wide altitude intervals of the Martian atmosphere, i.e. the vibrational non-local thermodynamic equilibrium (vibrational NLTE) takes place. In the paper [1], the model used for solving the NLTE problem of radiative transfer in the CO _{2} bands in the Martian atmosphere has included the 321 excited vibrational states belonging to 7 isotopologues of CO _{2} molecules and 779 radiative vibrational transitions (about 100000 lines). The most upper state is 20 (0) 3 of the principal isotopologue with energy of about 9500 cm (-1) . In the present study, this model has been further improved in the following directions. 1) The 10 bands rising between 8 vibrational states of 2 isotopologues of the CO molecules have been included. 2) For temperatures T=140-250 K, the input information both on self-broadened halfwidths of the infrared CO _{2} spectral lines and on the rate constants of collisional relaxation of the excited CO _{2} vibrational states was renewed. 3) A reflection of the IR radiation by the Martian surface is also taken into account. The radiative transfer in all the bands of the CO _{2} and CO molecules within the 15-1.02 mcm spectral interval with taking into account the overlapping over frequency of lines within a given ro-vibrational band as well as lines belonging to different bands was considered using the accelerated lambda-iteration technique. A visible influence on values of the non-equilibrium populations of the excited CO _{2} vibrational states due to an adoption of the approximation of spectral line isolation in frequency was found within wide layers of the Martian atmosphere. Both for a number of profiles representing various conditions in the atmosphere of Mars and for different solar zenith angles, the non-equilibrium populations of the excited vibrational states of the CO _{2} and CO molecules were obtained with high accuracy followed by calculating the radiative flux divergence (RFD) in all the IR ro-vibrational bands included into the model. For the first time, the contribution into the RFD values due to a number of radiative vibrational transitions of the CO _{2} and CO molecules were estimated for daytime conditions on Mars. Taking into account a reflection of the IR radiation by the planetary surface can result in an increase of the RFD values in all the bands of the CO _{2} molecules up to 1.5 K/day within the 0-20 km altitude layer of the Martian atmosphere. [1] Ogibalov, V.P., and Shved, G.M. // Solar System Res., Vol. 37, No. 1, pp. 23-33, 2003.

Ogibalov, Vladimir