L Band EPR Tooth Dosimetry for Heavy Ion Irradiation

PubMed Central

Yamaguchi, Ichiro; Sato, Hitoshi; Kawamura, Hiraku; Hamano, Tsuyoshi; Yoshii, Hiroshi; Suda, Mitsuru; Miyake, Minoru; Kunugita, Naoki

2016-01-01

Electron Paramagnetic Resonance (EPR) tooth dosimetry is being developed as a device to rapidly assess large populations that were potentially exposed to radiation during a major radiation accident or terrorist event. While most exposures are likely to be due to fallout and therefore involve low linear energy transfer (LET) radiation, there is also a potential for exposures to high LET radiation, for which the effect on teeth has been less well characterized by EPR. Therefore, the aim of this paper is to acquire fundamental response curves for high LET radiation in tooth dosimetry using L band EPR. For this purpose, we exposed human teeth to high energy carbon ions using the heavy ion medical accelerator in Chiba at the National Institute of Radiological Sciences. The primary findings were that EPR signals for carbon ion irradiation were about one-tenth the amplitude of the response to the same dose of 150 kVp X-rays. PMID:27542817

Pseudo-equilibrium geometry of HNO determined by an E-Band CP-FTmmW spectrometer

DOE PAGES

Zaleski, Daniel P.; Prozument, Kirill

2017-05-16

An E-Band (60–90 GHz) chirped-pulse Fourier transform millimeter-wave spectrometer has been constructed for eventual kinetics and dynamics studies. The performance of the spectrometer is demonstrated with the molecule nitroxyl (HNO). Using the new spectrometer and by passing isotopically labelled methyl nitrite (CH 3ONO) through a pyrolysis nozzle, the spectra of minor isotopologues of HNO have been obtained. The observations on the isotopologues identified here, H 15NO, HN 18O, and D 15NO, have been combined with the earlier isotopic observations, HNO and DNO, to create a global r m (1) HNO geometry that approximates an equilibrium structure. Furthermore, the results aremore » compared to high-level ab initio calculations.« less

Pseudo-equilibrium geometry of HNO determined by an E-Band CP-FTmmW spectrometer

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

Zaleski, Daniel P.; Prozument, Kirill

An E-Band (60–90 GHz) chirped-pulse Fourier transform millimeter-wave spectrometer has been constructed for eventual kinetics and dynamics studies. The performance of the spectrometer is demonstrated with the molecule nitroxyl (HNO). Using the new spectrometer and by passing isotopically labelled methyl nitrite (CH 3ONO) through a pyrolysis nozzle, the spectra of minor isotopologues of HNO have been obtained. The observations on the isotopologues identified here, H 15NO, HN 18O, and D 15NO, have been combined with the earlier isotopic observations, HNO and DNO, to create a global r m (1) HNO geometry that approximates an equilibrium structure. Furthermore, the results aremore » compared to high-level ab initio calculations.« less

In vivo and ex vivo EPR detection of spin-labelled ovalbumin in mice.

PubMed

Abramović, Zrinka; Brgles, Marija; Habjanec, Lidija; Tomasić, Jelka; Sentjurc, Marjeta; Frkanec, Ruza

2010-10-01

In this study, spin-labelled ovalbumin (SL-OVA), free or entrapped in liposomes, was administered to mice subcutaneously (s.c.) or intravenously (i.v.) with the aim to determine the conditions for pharmacokinetic studies of spin-labelled proteins by EPR and to measure the time course of SL-OVA distribution in vivo in live mice and ex vivo in isolated organs. Upon s.c. administration, the decay of the EPR signal was followed for 60min at the site of application using an L-band EPR spectrometer. Within this time period, the signal of free SL-OVA was diminished by about 70%. It was estimated with the help of the oxidizing agent K(3)[(FeCN)(6)] that approximately 30% was a consequence of the spin label reduction to EPR non-visible hydroxylamine and about 40% was due to the SL-OVA elimination from the site of measurement. For liposome encapsulated SL-OVA, the intensity diminished only by approx. 40% in the same period, indicating that liposomes successfully protect the protein from reduction. EPR signal could not be detected directly over live mouse organs within 60min after s.c. application of SL-OVA. With the available L-band EPR spectrometer, the measurements at the site of s.c. application are possible if the amount of SL-OVA applied to a mouse is more than 3mg. For the pharmacokinetic studies of the protein distribution in organs after s.c. or i.v. injection the concentration of the spin-labelled protein should be more than 0.5mmol/kg. After i.v. administration, only ex vivo measurements were possible using an X-band EPR spectrometer, since the total amount of SL-OVA was not sufficient for in vivo detection and also because of rapid reduction of nitroxide. After 2min, the protein was preferentially distributed to liver and, to a smaller extent, to spleen.

Integration of a versatile bridge concept in a 34 GHz pulsed/CW EPR spectrometer.

PubMed

Band, Alan; Donohue, Matthew P; Epel, Boris; Madhu, Shraeya; Szalai, Veronika A

2018-03-01

We present a 34 GHz continuous wave (CW)/pulsed electron paramagnetic resonance (EPR) spectrometer capable of pulse-shaping that is based on a versatile microwave bridge design. The bridge radio frequency (RF)-in/RF-out design (500 MHz to 1 GHz input/output passband, 500 MHz instantaneous input/output bandwidth) creates a flexible platform with which to compare a variety of excitation and detection methods utilizing commercially available equipment external to the bridge. We use three sources of RF input to implement typical functions associated with CW and pulse EPR spectroscopic measurements. The bridge output is processed via high speed digitizer and an in-phase/quadrature (I/Q) demodulator for pulsed work or sent to a wideband, high dynamic range log detector for CW. Combining this bridge with additional commercial hardware and new acquisition and control electronics, we have designed and constructed an adaptable EPR spectrometer that builds upon previous work in the literature and is functionally comparable to other available systems. Published by Elsevier Inc.

X-band EPR setup with THz light excitation of Novosibirsk Free Electron Laser: Goals, means, useful extras.

PubMed

Veber, Sergey L; Tumanov, Sergey V; Fursova, Elena Yu; Shevchenko, Oleg A; Getmanov, Yaroslav V; Scheglov, Mikhail A; Kubarev, Vitaly V; Shevchenko, Daria A; Gorbachev, Iaroslav I; Salikova, Tatiana V; Kulipanov, Gennady N; Ovcharenko, Victor I; Fedin, Matvey V

2018-03-01

Electron Paramagnetic Resonance (EPR) station at the Novosibirsk Free Electron Laser (NovoFEL) user facility is described. It is based on X-band (∼9 GHz) EPR spectrometer and operates in both Continuous Wave (CW) and Time-Resolved (TR) modes, each allowing detection of either direct or indirect influence of high-power NovoFEL light (THz and mid-IR) on the spin system under study. The optics components including two parabolic mirrors, shutters, optical chopper and multimodal waveguide allow the light of NovoFEL to be directly fed into the EPR resonator. Characteristics of the NovoFEL radiation, the transmission and polarization-retaining properties of the waveguide used in EPR experiments are presented. The types of proposed experiments accessible using this setup are sketched. In most practical cases the high-power radiation applied to the sample induces its rapid temperature increase (T-jump), which is best visible in TR mode. Although such influence is a by-product of THz radiation, this thermal effect is controllable and can deliberately be used to induce and measure transient signals of arbitrary samples. The advantage of tunable THz radiation is the absence of photo-induced processes in the sample and its high penetration ability, allowing fast heating of a large portion of virtually any sample and inducing intense transients. Such T-jump TR EPR spectroscopy with THz pulses has been previewed for the two test samples, being a useful supplement for the main goals of the created setup. Copyright © 2018 Elsevier Inc. All rights reserved.

Chirp echo Fourier transform EPR-detected NMR.

PubMed

Wili, Nino; Jeschke, Gunnar

2018-04-01

A new ultra-wide band (UWB) pulse EPR method is introduced for observing all nuclear frequencies of a paramagnetic center in a single shot. It is based on burning spectral holes with a high turning angle (HTA) pulse that excites forbidden transitions and subsequent detection of the hole pattern by a chirp echo. We term this method Chirp Echo Epr SpectroscopY (CHEESY)-detected NMR. The approach is a revival of FT EPR-detected NMR. It yields similar spectra and the same type of information as electron-electron double resonance (ELDOR)-detected NMR, but with a multiplex advantage. We apply CHEESY-detected NMR in Q band to nitroxides and correlate the hyperfine spectrum to the EPR spectrum by varying the frequency of the HTA pulse. Furthermore, a selective π pulse before the HTA pulse allows for detecting hyperfine sublevel correlations between transitions of one nucleus and for elucidating the coupling regime, the same information as revealed by the HYSCORE experiment. This is demonstrated on hexaaquamanganese(II). We expect that CHEESY-detected NMR is generally applicable to disordered systems and that our results further motivate the development of EPR spectrometers capable of coherent UWB excitation and detection, especially at higher fields and frequencies. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Chirp echo Fourier transform EPR-detected NMR

NASA Astrophysics Data System (ADS)

Wili, Nino; Jeschke, Gunnar

2018-04-01

A new ultra-wide band (UWB) pulse EPR method is introduced for observing all nuclear frequencies of a paramagnetic center in a single shot. It is based on burning spectral holes with a high turning angle (HTA) pulse that excites forbidden transitions and subsequent detection of the hole pattern by a chirp echo. We term this method Chirp Echo Epr SpectroscopY (CHEESY)-detected NMR. The approach is a revival of FT EPR-detected NMR. It yields similar spectra and the same type of information as electron-electron double resonance (ELDOR)-detected NMR, but with a multiplex advantage. We apply CHEESY-detected NMR in Q band to nitroxides and correlate the hyperfine spectrum to the EPR spectrum by varying the frequency of the HTA pulse. Furthermore, a selective π pulse before the HTA pulse allows for detecting hyperfine sublevel correlations between transitions of one nucleus and for elucidating the coupling regime, the same information as revealed by the HYSCORE experiment. This is demonstrated on hexaaquamanganese(II). We expect that CHEESY-detected NMR is generally applicable to disordered systems and that our results further motivate the development of EPR spectrometers capable of coherent UWB excitation and detection, especially at higher fields and frequencies.

Investigating the Distribution of Stable Paramagnetic Species in an Apple Seed Using X-Band EPR and EPR Imaging.

PubMed

Nakagawa, Kouichi; Epel, Boris

2017-03-01

This study investigated the location and distribution of paramagnetic species in apple seeds using electron paramagnetic resonance (EPR) and X-band (9 GHz) EPR imaging (EPRI). EPR primarily detected two paramagnetic species per measured seed. These two different radical species were assigned as stable radicals and Mn 2+ species based on the g values and hyperfine components. The signal from the stable radical was noted at g ≈ 2.00 and was strong and relatively stable. The subsequent noninvasive EPRI of the radical present in each seed revealed that the stable radicals were located primarily in the seed coat, with very few radicals observed in the cotyledon of the seed. These results indicate that the stable radical species were only found within the seed coat, and few radical species were found in other seed parts.

A novel microfluidic rapid freeze-quench device for trapping reactions intermediates for high field EPR analysis.

PubMed

Kaufmann, Royi; Yadid, Itamar; Goldfarb, Daniella

2013-05-01

Rapid freeze quench electron paramagnetic resonance (RFQ)-EPR is a method for trapping short lived intermediates in chemical reactions and subjecting them to EPR spectroscopy investigation for their characterization. Two (or more) reacting components are mixed at room temperature and after some delay the mixture is sprayed into a cold trap and transferred into the EPR tube. A major caveat in using commercial RFQ-EPR for high field EPR applications is the relatively large amount of sample needed for each time point, a major part of which is wasted as the dead volume of the instrument. The small sample volume (∼2μl) needed for high field EPR spectrometers, such as W-band (∼3.5T, 95GHz), that use cavities calls for the development of a microfluidic based RFQ-EPR apparatus. This is particularly important for biological applications because of the difficulties often encountered in producing large amounts of intrinsically paramagnetic proteins and spin labeled nucleic acid and proteins. Here we describe a dedicated microfluidic based RFQ-EPR apparatus suitable for small volume samples in the range of a few μl. The device is based on a previously published microfluidic mixer and features a new ejection mechanism and a novel cold trap that allows collection of a series of different time points in one continuous experiment. The reduction of a nitroxide radical with dithionite, employing the signal of Mn(2+) as an internal standard was used to demonstrate the performance of the microfluidic RFQ apparatus. Copyright © 2013 Elsevier Inc. All rights reserved.

Broad band waveguide spectrometer

DOEpatents

Goldman, Don S.

1995-01-01

A spectrometer for analyzing a sample of material utilizing a broad band source of electromagnetic radiation and a detector. The spectrometer employs a waveguide possessing an entry and an exit for the electromagnetic radiation emanating from the source. The waveguide further includes a surface between the entry and exit portions which permits interaction between the electromagnetic radiation passing through the wave guide and a sample material. A tapered portion forms a part of the entry of the wave guide and couples the electromagnetic radiation emanating from the source to the waveguide. The electromagnetic radiation passing from the exit of the waveguide is captured and directed to a detector for analysis.

EFFECT OF CADMIUM(II) ON FREE RADICALS IN DOPA-MELANIN TESTED BY EPR SPECTROSCOPY.

PubMed

Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledge of modification of properties and free radical concentration in melanin is important to pharmacy. The effect of cadmium(II) in different concentrations on free radicals in DOPA-melanin was determined. EPR spectra of DOPA-melanin, and DOPA-melanin complexes with cadmium(II) were measured by an X-band (9.3 GHz) EPR spectrometer produced by Radiopan (Poznań, Poland) and the Rapid Scan Unit from Jagmar (Krak6w, Poland). The DOPA (3,4-dihydroxyphenylalanine) to metal ions molar ratios in the reaction mixtures were 2:1, 1:1, and 1: 2. High concentrations of o-semiquinone (g ~2.0040) free radicals (~10(21)-10(22) spin/g) characterize DOPA-melanin and its complexes with cadmium(II). Formation of melanin complexes with cadmium(II) increase free radical concentration in DOPA-melanin. The highest free radical concentration was obtained for DOPA-melanin-cadmium(II) (1:1) complexes. Broad EPR lines with linewidths: 0.37-0.73 mT, were measured. Linewidths increase after binding of cadmium(II) to melanin. Changes of integral intensities and linewidths with increasing microwave power indicate the homogeneous broadening of EPR lines, independently on the metal ion concentration. Slow spin-lattice relaxation processes existed in all the tested samples, their EPR lines saturated at low microwave powers. Cadmium(II) causes fastening of spin-lattice relaxation processes in DOPA-melanin. The EPR results bring to light the effect of cadmium(II) on free radicals in melanin, and probably as the consequence on drug binding to eumelanin.

A Ka-band chirped-pulse Fourier transform microwave spectrometer

NASA Astrophysics Data System (ADS)

Zaleski, Daniel P.; Neill, Justin L.; Muckle, Matt T.; Seifert, Nathan A.; Brandon Carroll, P.; Widicus Weaver, Susanna L.; Pate, Brooks H.

2012-10-01

The design and performance of a new chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating from 25 to 40 GHz (Ka-band) is presented. This spectrometer is well-suited for the study of complex organic molecules of astronomical interest in the size range of 6-10 atoms that have strong rotational transitions in Ka-band under pulsed jet sample conditions (Trot = 1-10 K). The spectrometer permits acquisition of the full spectral band in a single data acquisition event. Sensitivity is enhanced by using two pulsed jet sources and acquiring 10 broadband measurements for each sample injection cycle. The spectrometer performance is benchmarked by measuring the pure rotational spectrum of several isotopologues of acetaldehyde in natural abundance. The rotational spectra of the singly substituted 13C and 18O isotopologues of the two lowest energy conformers of ethyl formate have been analyzed and the resulting substitution structures for these conformers are compared to electronic structure theory calculations.

Accurate band-to-band registration of AOTF imaging spectrometer using motion detection technology

NASA Astrophysics Data System (ADS)

Zhou, Pengwei; Zhao, Huijie; Jin, Shangzhong; Li, Ningchuan

2016-05-01

This paper concerns the problem of platform vibration induced band-to-band misregistration with acousto-optic imaging spectrometer in spaceborne application. Registrating images of different bands formed at different time or different position is difficult, especially for hyperspectral images form acousto-optic tunable filter (AOTF) imaging spectrometer. In this study, a motion detection method is presented using the polychromatic undiffracted beam of AOTF. The factors affecting motion detect accuracy are analyzed theoretically, and calculations show that optical distortion is an easily overlooked factor to achieve accurate band-to-band registration. Hence, a reflective dual-path optical system has been proposed for the first time, with reduction of distortion and chromatic aberration, indicating the potential of higher registration accuracy. Consequently, a spectra restoration experiment using additional motion detect channel is presented for the first time, which shows the accurate spectral image registration capability of this technique.

Dichroic Filter for Separating W-Band and Ka-Band

NASA Technical Reports Server (NTRS)

Epp, Larry W.; Durden, Stephen L.; Jamnejad, Vahraz; Long, Ezra M.; Sosnowski, John B.; Higuera, Raymond J.; Chen, Jacqueline C.

2012-01-01

The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel. A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength. First, a mechanical prototype was built using an approximately 102-micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higher-frequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly. This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.

Ultra-Low-Noise W-Band MMIC Detector Modules

NASA Technical Reports Server (NTRS)

Gaier, Todd C.; Samoska, Lorene A.; Kangaslahti, Pekka P.; Van Vinkle, Dan; Tantawi, Sami; Fox, John; Church, Sarah E.; Lau, Jusy M.; Sieth, Matthew M.; Voll, Patricia E.;

Data Quality Evaluation and Application Potential Analysis of TIANGONG-2 Wide-Band Imaging Spectrometer

NASA Astrophysics Data System (ADS)

Qin, B.; Li, L.; Li, S.

2018-04-01

Tiangong-2 is the first space laboratory in China, which launched in September 15, 2016. Wide-band Imaging Spectrometer is a medium resolution multispectral imager on Tiangong-2. In this paper, the authors introduced the indexes and parameters of Wideband Imaging Spectrometer, and made an objective evaluation about the data quality of Wide-band Imaging Spectrometer in radiation quality, image sharpness and information content, and compared the data quality evaluation results with that of Landsat-8. Although the data quality of Wide-band Imager Spectrometer has a certain disparity with Landsat-8 OLI data in terms of signal to noise ratio, clarity and entropy. Compared with OLI, Wide-band Imager Spectrometer has more bands, narrower bandwidth and wider swath, which make it a useful remote sensing data source in classification and identification of large and medium scale ground objects. In the future, Wide-band Imaging Spectrometer data will be widely applied in land cover classification, ecological environment assessment, marine and coastal zone monitoring, crop identification and classification, and other related areas.

A GPU-Based Wide-Band Radio Spectrometer

NASA Astrophysics Data System (ADS)

Chennamangalam, Jayanth; Scott, Simon; Jones, Glenn; Chen, Hong; Ford, John; Kepley, Amanda; Lorimer, D. R.; Nie, Jun; Prestage, Richard; Roshi, D. Anish; Wagner, Mark; Werthimer, Dan

2014-12-01

The graphics processing unit has become an integral part of astronomical instrumentation, enabling high-performance online data reduction and accelerated online signal processing. In this paper, we describe a wide-band reconfigurable spectrometer built using an off-the-shelf graphics processing unit card. This spectrometer, when configured as a polyphase filter bank, supports a dual-polarisation bandwidth of up to 1.1 GHz (or a single-polarisation bandwidth of up to 2.2 GHz) on the latest generation of graphics processing units. On the other hand, when configured as a direct fast Fourier transform, the spectrometer supports a dual-polarisation bandwidth of up to 1.4 GHz (or a single-polarisation bandwidth of up to 2.8 GHz).

Multi-hop teleportation based on W state and EPR pairs

NASA Astrophysics Data System (ADS)

Hai-Tao, Zhan; Xu-Tao, Yu; Pei-Ying, Xiong; Zai-Chen, Zhang

2016-05-01

Multi-hop teleportation has significant value due to long-distance delivery of quantum information. Many studies about multi-hop teleportation are based on Bell pairs, partially entangled pairs or W state. The possibility of multi-hop teleportation constituted by partially entangled pairs relates to the number of nodes. The possibility of multi-hop teleportation constituted by double W states is after n-hop teleportation. In this paper, a multi-hop teleportation scheme based on W state and EPR pairs is presented and proved. The successful possibility of quantum information transmitted hop by hop through intermediate nodes is deduced. The possibility of successful transmission is after n-hop teleportation. Project supported by the National Natural Science Foundation of China (Grant No. 61571105), the Prospective Future Network Project of Jiangsu Province, China (Grant No. BY2013095-1-18), and the Independent Project of State Key Laboratory of Millimeter Waves, China (Grant No. Z201504).

Phase Grating Design for a Dual-Band Snapshot Imaging Spectrometer

NASA Astrophysics Data System (ADS)

Scholl, James F.; Dereniak, Eustace L.; Descour, Michael R.; Tebow, Christopher P.; Volin, Curtis E.

2003-01-01

Infrared spectral features have proved useful in the identification of threat objects. Dual-band focal-plane arrays (FPAs) have been developed in which each pixel consists of superimposed midwave and long-wave photodetectors [Dyer and Tidrow, Conference on Infrared Detectors and Focal Plane Arrays (SPIE, Bellingham, Wash., 1999), pp. 434 -440 . Combining dual-band FPAs with imaging spectrometers capable of interband hyperspectral resolution greatly improves spatial target discrimination. The computed-tomography imaging spectrometer (CTIS) ] [Descour and Dereniak, Appl. Opt. 34, 4817 -4826 (1995) has proved effective in producing hyperspectral images in a single spectral region. Coupling the CTIS with a dual-band detector can produce two hyperspectral data cubes simultaneously. We describe the design of two-dimensional, surface-relief, computer-generated hologram dispersers that permit image information in these two bands simultaneously.

Mapping Local Protein Electrostatics by EPR of pH-Sensitive Thiol-Specific Nitroxide† ¶

PubMed Central

Voinov, Maxim A.; Ruuge, Andres; Reznikov, Vladimir A.; Grigor’ev, Igor A.; Smirnov, Alex I.

2013-01-01

A first thiol-specific pH-sensitive nitroxide spin label of the imidazolidine series -methanethiosulfonic acid S-(1-oxyl-2,2,3,5,5-pentamethylimidazolidin-4-ylmethyl) ester (IMTSL) - has been synthesized and characterized. X- (9 GHz) and W-band (94 GHz) EPR spectral parameters of the new spin label in its free form and covalently attached to an amino acid cysteine and a tripeptide glutathione were studied as a function of pH and solvent polarity. pKa value of protonatable tertiary amino group of the spin label was found to be unaffected by other ionizable groups present in side chains of unstructured small peptides. The W-band EPR spectra were shown to allow for pKa determination from precise g-factor measurements. Is has been demonstrated that high accuracy of pKa determination for pH-sensitive nitroxides could be achieved regardless the frequency of measurements or the regime of spin exchange: fast at X-band and slow at W-band. IMTSL was found to react specifically with a model protein - iso-1-cytochrome c from yeast Saccharomyces cerevisiae - giving EPR spectra very similar to those of the most commonly employed cysteine-specific label MTSL. CD data indicated no perturbations to the overall protein structure upon IMTSL labeling. It was found that for IMTSL, giso correlates linearly with Aiso but the slopes are different for the neutral and charged forms of the nitroxide. This finding was attributed to the solvent effects on the spin density at the oxygen atom of the N–O group and on the excitation energy of the oxygen lone-pair orbital. PMID:18426227

A new strategy for fast radiofrequency CW EPR imaging: Direct detection with rapid scan and rotating gradients

PubMed Central

Subramanian, Sankaran; Koscielniak, Janusz W.; Devasahayam, Nallathamby; Pursley, Randall H.; Pohida, Thomas J.; Krishna, Murali C.

2007-01-01

Rapid field scan on the order of T/s using high frequency sinusoidal or triangular sweep fields superimposed on the main Zeeman field, was used for direct detection of signals without low-frequency field modulation. Simultaneous application of space-encoding rotating field gradients have been employed to perform fast CW EPR imaging using direct detection that could, in principle, approach the speed of pulsed FT EPR imaging. The method takes advantage of the well-known rapid-scan strategy in CW NMR and EPR that allows arbitrarily fast field sweep and the simultaneous application of spinning gradients that allows fast spatial encoding. This leads to fast functional EPR imaging and, depending on the spin concentration, spectrometer sensitivity and detection band width, can provide improved temporal resolution that is important to interrogate dynamics of spin perfusion, pharmacokinetics, spectral spatial imaging, dynamic oxymetry, etc. PMID:17350865

Rotational band properties of 173W

NASA Astrophysics Data System (ADS)

Wang, H. X.; Zhang, Y. H.; Zhou, X. H.; Liu, M. L.; Ding, B.; Li, G. S.; Hua, W.; Zhou, H. B.; Guo, S.; Qiang, Y. H.; Oshima, M.; Koizumi, M.; Toh, Y.; Kimura, A.; Harada, H.; Furutaka, K.; Kitatani, F.; Nakamura, S.; Hatsukawa, Y.; Ohta, M.; Hara, K.; Kin, T.; Meng, J.

2012-10-01

High-spin states in 173W have been studied using the 150Nd(28Si,5n)173W reaction at beam energies of 135 and 140 MeV. The previously known bands associated with the 7/2+[633], 5/2-[512], and 1/2-[521] configurations are extended significantly, and the unfavored signature branch of the 1/2-[521] band is established for the first time. The band properties, such as level spacings, band-crossing frequencies, alignment gains, and signature splittings, are discussed with an emphasis on the low-spin signature inversion observed in the 5/2-[512] band. By comparing the experimental B(M1)/B(E2) ratios with the theoretical values, we conclude that the configuration of the 5/2-[512] band is quite pure at low spins without appreciable admixture of the 5/2-[523] orbit, in conflict with the particle rotor model calculated results.

Time-resolved EPR spectroscopy in a Unix environment.

PubMed

Lacoff, N M; Franke, J E; Warden, J T

1990-02-01

A computer-aided time-resolved electron paramagnetic resonance (EPR) spectrometer implemented under version 2.9 BSD Unix was developed by interfacing a Varian E-9 EPR spectrometer and a Biomation 805 waveform recorder to a PDP-11/23A minicomputer having MINC A/D and D/A capabilities. Special problems with real-time data acquisition in a multiuser, multitasking Unix environment, addressing of computer main memory for the control of hardware devices, and limitation of computer main memory were resolved, and their solutions are presented. The time-resolved EPR system and the data acquisition and analysis programs, written entirely in C, are described. Furthermore, the benefits of utilizing the Unix operating system and the C language are discussed, and system performance is illustrated with time-resolved EPR spectra of the reaction center cation in photosystem 1 of green plant photosynthesis.

EFFECT OF MICROWAVE POWER ON SHAPE OF EPR SPECTRA--APPLICATION TO EXAMINATION OF COMPLEX FREE RADICAL SYSTEM IN THERMALLY STERILIZED ACIDUM BORICUM.

PubMed

Ramos, Paweł; Pieprzyca, Małgorzata; Pilawa, Barbara

2016-01-01

Complex free radical system in thermally sterilized acidum boricum (AB) was studied. Acidum boricum was sterilized at temperatures and times given by pharmaceutical norms: 160 degrees C and 120 min, 170 degrees C and 60 min and 180 degrees C and 30 min. The advanced spectroscopic tests were performed. The EPR spectra of free radicals were measured as the first derivatives with microwaves of 9.3 GHz frequency and magnetic modulation of 100 kHz. The Polish X-band electron paramagnetic resonance spectrometer of Radiopan (Poznań) was used. EPR lines were not observed for the nonheated AB. The broad EPR asymmetric lines were obtained for all the heated AB samples. The influence of microwave power in the range of 2.2-70 mW on the shape of EPR spectra of the heated drug samples was tested. The following asymmetry parameters: A1/A2, A1-A2, B1/B2, and B1-B2, were analyzed. The changes of these parameters with microwave power were observed. The strong dependence of shape and its parameters on microwave power proved the complex character of free radical system in thermally sterilized AB. Changes of microwave power during the detection of EPR spectra indicated complex character of free radicals in AB sterilized in hot air under all the tested conditions. Thermolysis, interactions between free radicals and interactions of free radicals with oxygen may be responsible for the complex free radicals system in thermally treated AB. Usefulness of continuous microwave saturation of EPR lines and shape analysis to examine free radicals in thermally sterilized drugs was confirmed.

Improved sensitivity for W-band Gd(III)-Gd(III) and nitroxide-nitroxide DEER measurements with shaped pulses

NASA Astrophysics Data System (ADS)

Bahrenberg, Thorsten; Rosenski, Yael; Carmieli, Raanan; Zibzener, Koby; Qi, Mian; Frydman, Veronica; Godt, Adelheid; Goldfarb, Daniella; Feintuch, Akiva

2017-10-01

Chirp and shaped pulses have been recently shown to be highly advantageous for improving sensitivity in DEER (double electron-electron resonance, also called PELDOR) measurements due to their large excitation bandwidth. The implementation of such pulses for pulse EPR has become feasible due to the availability of arbitrary waveform generators (AWG) with high sampling rates to support pulse shaping for pulses with tens of nanoseconds duration. Here we present a setup for obtaining chirp pulses on our home-built W-band (95 GHz) spectrometer and demonstrate its performance on Gd(III)-Gd(III) and nitroxide-nitroxide DEER measurements. We carried out an extensive optimization procedure on two model systems, Gd(III)-PyMTA-spacer-Gd(III)-PyMTA (Gd-PyMTA ruler; zero-field splitting parameter (ZFS) D ∼ 1150 MHz) as well as nitroxide-spacer-nitroxide (nitroxide ruler) to evaluate the applicability of shaped pulses to Gd(III) complexes and nitroxides, which are two important classes of spin labels used in modern DEER/EPR experiments. We applied our findings to ubiquitin, doubly labeled with Gd-DOTA-monoamide (D ∼ 550 MHz) as a model for a system with a small ZFS. Our experiments were focused on the questions (i) what are the best conditions for positioning of the detection frequency, (ii) which pump pulse parameters (bandwidth, positioning in the spectrum, length) yield the best signal-to-noise ratio (SNR) improvements when compared to classical DEER, and (iii) how do the sample's spectral parameters influence the experiment. For the nitroxide ruler, we report an improvement of up to 1.9 in total SNR, while for the Gd-PyMTA ruler the improvement was 3.1-3.4 and for Gd-DOTA-monoamide labeled ubiquitin it was a factor of 1.8. Whereas for the Gd-PyMTA ruler the two setups pump on maximum and observe on maximum gave about the same improvement, for Gd-DOTA-monoamide a significant difference was found. In general the choice of the best set of parameters depends on the D

Random bipartite entanglement from W and W-like states.

PubMed

Fortescue, Ben; Lo, Hoi-Kwong

2007-06-29

We describe a protocol for distilling maximally entangled bipartite states between random pairs of parties from those sharing a tripartite W state |W=(1/sqrt[3])(|100+|010+|001)(ABC), and show that the total distillation rate E(t)(infinity) [the total number of Einstein-Podolsky-Rosen (EPR) pairs distilled per W, irrespective of who shares them] may be done at a higher rate than EPR distillation between specified pairs of parties. Specifically, the optimal rate for distillation to specified parties has been previously shown to be 0.92 EPR pairs per W, while our protocol can asymptotically distill 1 EPR pair per W between random pairs of parties, which we conjecture to be optimal. We thus demonstrate a tradeoff between overall distillation rate and final distribution of EPR pairs. We further show that there exist states with fixed lower-bounded E(t)(infinity), but arbitrarily small distillable entanglement for specified parties.

Stability of X-band EPR signals from fingernails under vacuum storage.

PubMed

Sholom, Sergey; McKeever, Stephen

2017-12-01

EPR signals of different origin have been tested in human finger- and toe-nails with an X-band EPR technique for different conditions of nail storage. Three different signals were identified, namely a singlet at g=2.005, a doublet at g=2.004 with a splitting constant A=1.8 mT, and an anisotropic signal at g1=2.057, g2=2.029 and g3=2.003 (positions of local extrema). All EPR spectra from nails, whether irradiated or mechanically stressed, can be described as a superposition of these three signals. The singlet is responsible for the background signal (BG), is the main component of radiation-induced signals (RIS) for low doses (100 Gy or lower) and also contributes to mechanically-induced signals (MIS). This signal is quite stable under vacuum storage, but can be reduced almost to zero by soaking in water. The behavior of this signal under ambient conditions depends on many factors, such as absorbed dose, air humidity, and ambient illumination intensity at the place of storage. The doublet arises after exposure of nails to high (few hundreds Gy and higher) doses or after mechanical stress of samples. Depending on how this signal was obtained, it may have bulk or surface locations with quite different stability properties. The surface-located doublet (generated on the nail edges during cutting or clipping) is quite unstable and decays over about two hours for samples stored at ambient conditions and within several seconds for samples immersed in water. The volume-distributed doublet decays within a few minutes in water, several hours at ambient conditions and several days in vacuum. The anisotropic signal may also be generated by both ionizing radiation and mechanical stress; this signal is quite stable in vacuum and decays over several days at ambient conditions or a few tens of minutes in water. The reference lines for the above-described three EPR signals were obtained and a procedure of spectra deconvolution was developed and tested on samples exposed to both

High-perveance W-band Sheet-beam Electron Gun Design

DTIC Science & Technology

2008-04-01

APR 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE High -perveance W- band Sheet-beam Electron Gun Design 5a...8-98) Prescribed by ANSI Std Z39-18 10.1: High -perveance W- band Sheet-beam Electron Gun Design Khanh T. Nguyen1, John Pasour, Edward L. Wright1...effects due to cathode temperature are also included in the simulation. Keywords: Sheet beam; W- band ; electron gun; high perveance; amplifiers

Multifrequency EPR study on freeze-dried fruits before and after X-ray irradiation

NASA Astrophysics Data System (ADS)

Yordanov, N. D.; Aleksieva, K.; Dimitrova, A.; Georgieva, L.; Tzvetkova, E.

2006-09-01

X-, K- and Q-band EPR studies on lyophilized whole pulp parts of blue plum, apricot, peach, melon as well as achens and pulp separately of strawberry before and after X-ray irradiation are reported. Before irradiation all samples show in X band a weak singlet EPR line with g=2.0030±0.0005, except melon, which is EPR silent. Immediately after irradiation all samples exhibit complex fruit-depending spectra, which decay with time and change to give, in ca. 50 days, an asymmetric singlet EPR line with g=2.0041±0.0005. Only apricot pulp gave a typical "sugar-like" EPR spectrum. Singlet EPR lines recorded after irradiation in X -band are K- and Q-band resolved as typical anisotropic EPR spectra with g=2.0023±0.0003 and g⊥=2.0041±0.0005. In addition, K- and Q-band EPR spectra of all samples show a superposition with the six EPR lines of Mn 2+ naturally present in the fruits. The saturation behavior of the EPR spectra of achens of lyophilized and fresh strawberry is also studied. The differences in g factors of samples before and after X-ray irradiation might be used for the identification of radiation processing of fruits in the case of pulp and the differences in the EPR saturation behavior might be used for the achens of strawberry.

An Airborne A-Band Spectrometer for Remote Sensing Of Aerosol and Cloud Optical Properties

NASA Technical Reports Server (NTRS)

Pitts, Michael; Hostetler, Chris; Poole, Lamont; Holden, Carl; Rault, Didier

2000-01-01

Atmospheric remote sensing with the O2 A-band has a relatively long history, but most of these studies were attempting to estimate surface pressure or cloud-top pressure. Recent conceptual studies have demonstrated the potential of spaceborne high spectral resolution O2 A-band spectrometers for retrieval of aerosol and cloud optical properties. The physical rationale of this new approach is that information on the scattering properties of the atmosphere is embedded in the detailed line structure of the O2 A-band reflected radiance spectrum. The key to extracting this information is to measure the radiance spectrum at very high spectral resolution. Instrument performance requirement studies indicate that, in addition to high spectral resolution, the successful retrieval of aerosol and cloud properties from A-band radiance spectra will also require high radiometric accuracy, instrument stability, and high signal-to-noise measurements. To experimentally assess the capabilities of this promising new remote sensing application, the NASA Langley Research Center is developing an airborne high spectral resolution A-band spectrometer. The spectrometer uses a plane holographic grating with a folded Littrow geometry to achieve high spectral resolution (0.5 cm-1) and low stray light in a compact package. This instrument will be flown in a series of field campaigns beginning in 2001 to evaluate the overall feasibility of this new technique. Results from these campaigns should be particularly valuable for future spaceborne applications of A-band spectrometers for aerosol and cloud retrievals.

Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

PubMed

Marsh, Derek

2016-11-01

Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

Single crystal X- and Q-band EPR spectroscopy of a binuclear Mn(2)(III,IV) complex relevant to the oxygen-evolving complex of photosystem II.

PubMed

Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K

2004-06-23

The anisotropic g and hyperfine tensors of the Mn di-micro-oxo complex, [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN EPR spectra showed distinct resolved (55)Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn(2)(III,IV) di-micro-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn(2)(III,IV)O(2)(phen)(4) as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: g(x) = 1.9887, g(y) = 1.9957, g(z) = 1.9775, and hyperfine coupling constants are A(III)(x) = |171| G, A(III)(y) = |176| G, A(III)(z) = |129| G, A(IV)(x) = |77| G, A

W/V-Band RF Propagation Experiment Design

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Nessel, James A.; Simons, Rainee N.; Zemba, Michael J.; Morse, Jacquelynne Rose; Budinger, James M.

2012-01-01

The utilization of frequency spectrum for space-to-ground communications applications has generally progressed from the lowest available bands capable of supporting transmission through the atmosphere to the higher bands, which have required research and technological advancement to implement. As communications needs increase and the available spectrum in the microwave frequency bands (3 30 GHz) becomes congested globally, future systems will move into the millimeter wave (mm-wave) range (30 300 GHz). While current systems are operating in the Ka-band (20 30 GHz), systems planned for the coming decades will initiate operations in the Q-Band (33 50 GHz), V-Band (50 75 GHz) and W Band (75 110 GHz) of the spectrum. These bands offer extremely broadband capabilities (contiguous allocations of 500 MHz to 1GHz or more) and an uncluttered spectrum for a wide range of applications. NASA, DoD and commercial missions that can benefit from moving into the mm-wave bands include data relay and near-Earth data communications, unmanned aircraft communications, NASA science missions, and commercial broadcast/internet services, all able to be implemented via very small terminals. NASA Glenn Research Center has a long history of performing the inherently governmental function of opening new frequency spectrum by characterizing atmospheric effects on electromagnetic propagation and collaborating with the satellite communication industry to develop specific communications technologies for use by NASA and the nation. Along these lines, there are critical issues related to W/V-band propagation that need to be thoroughly understood before design of any operational system can commence. These issues arise primarily due to the limitations imposed on W/V-band signal propagation by the Earth s atmosphere, and to the fundamental lack of understanding of these effects with regards to proper system design and fade mitigation. In this paper, The GRC RF propagation team recommends measurements

Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

PubMed Central

Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

2014-01-01

Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8 to 80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented and distances of 18–30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER. PMID:22750251

Very High Frequency Epr: Instrument and Applications

NASA Astrophysics Data System (ADS)

Wang, Wei

Most Electron Paramagnetic Resonance (EPR, also known as ESR or EMR) experiments are performed at conventional 9 GHz or 35 GHz frequency. But there are numerous situations in which a large increase in the microwave frequency (and/or magnetic field) will result in substantial increase in the information content in EPR spectra. This has motivated us to construct a very high frequency (VHF, 95 GHz) EPR spectrometer at Illinois EPR Research Center. Many advantages of VHF EPR are demonstrated through examples in Chapter 1. The spectrometer and some unique aspects of the instrument are described and documented in Chapter 2. Chapter 3 reports use of the VHF EPR technique to study the structure/spectral relationship of a homologous series of thiophenes, which may be constituents of coal. Two successful methods to generate the cation radicals of these organic sulfur compounds are found. The g matrices (tensors) of the thiophenic radicals are obtained for the first time. The small differences between anisotropic components of the g matrices can be unambiguously resolved. Correlations of the experimentally measured g matrices with the molecular and electronic structures are reported. The g shifts correlate linearly with lambda of their Huckel molecular orbitals; the largest g components are proportional to the pi spin densities on sulfur. In addition, the small proton hyperfine interactions of dibenzothiophene (DBT) are observed for the first time by continuous wave VHF EPR. A multifrequency approach, including auxiliary 2-4 GHz pulsed measurement, has shown that a single set of spin Hamiltonian parameters describes the spin system of DBT over a microwave frequency span of 3 to 95 GHz. These newly available, detailed, and accurate data provide a valuable opportunity to test, and perhaps to improve, the existing theoretical models for predictions on g matrices of organic radicals. Finally, Chapter 4 reports trial calculations of g matrices by several molecular orbital methods.

A W-band sixth-harmonic magnetron-type slotted peniotron

NASA Astrophysics Data System (ADS)

Hu, Biao; Li, Jiayin; Wu, Xinhui; Li, Tianming; Li, Hao; Wang, Haiyang; Zhao, Xiaoyun

2013-04-01

This paper has numerically investigated operating characteristics of a w-band six-harmonic magnetron-type slotted peniotron with 7 vanes. With the new structure design, a high efficiency of 40% w-band 30 kW medium power microwave source has been achieved and the mode competition can be somewhat suppressed. The main advantage of such a peniotron, based on a permanent magnet, is that it can have much more compact size and lower cost, and its operation gap can be greatly reduced.

EPR-dosimetry of ionizing radiation

NASA Astrophysics Data System (ADS)

Popova, Mariia; Vakhnin, Dmitrii; Tyshchenko, Igor

2017-09-01

This article discusses the problems that arise during the radiation sterilization of medical products. It is propose the solution based on alanine EPR-dosimetry. The parameters of spectrometer and methods of absorbed dose calculation are given. In addition, the problems that arise during heavy particles irradiation are investigated.

Effect of UV irradiation on Echinaceae purpureae interactions with free radicals examined by an X-band (9.3 GHz) EPR spectroscopy.

PubMed

Ramos, Paweł; Pilawa, Barbara

The effect of UVA (315-400 nm) irradiation on Echinaceae purpureae interactions with free radicals was examined by the use of electron paramagnetic resonance (EPR) spectroscopy. The changes of antioxidant properties of E. purpureae with time of UV irradiation from 10 to 110 min (10 min steps) were determined. DPPH as the paramagnetic reference was used in this study. Changes of EPR signals of the reference after interactions with nonirradiated and UV-irradiated E. purpureae were detected. Interactions of the tested E. purpureae samples caused decrease of the EPR signal of DPPH as the result of its antioxidant properties. The decrease of the amplitude of EPR line of DPPH was lower for interactions with UV-irradiated E. purpureae . EPR examination confirmed antioxidant properties of E. purpureae . The weaker antioxidant properties of E. purpureae after UV irradiation were pointed out. E. purpureae should be storage in the dark. The tests bring to light usefulness of electron paramagnetic resonance with microwave frequency of 9.3 GHz (an X-band) in examination of storage conditions of pharmacological herbs.

Time dependence of the radiation-induced EPR signal in sucrose.

PubMed

Desrosiers, Marc; Wadley, Samara

2006-01-01

Sucrose and common household sugars (e.g. cane) have been studied as dosemeters for a wide variety of applications. However, previous studies of the post-irradiation time dependence of irradiated sugar did not include an electron paramagnetic resonance (EPR) reference material. This work employs synthetic ruby as an EPR reference material to remove significant spectrometer/environmental influences on the measured time-dependent changes in the EPR spectral amplitude of irradiated sucrose. As such, these more accurate measurements should replace the previously published data.

Low noise InP-based MMIC receivers for W-band

NASA Technical Reports Server (NTRS)

Leonard, Regis F.

1991-01-01

A program to develop a monolithic W-band low noise amplifier (a critical element in any W-band communications, sensors, or radar application) is described. Goals of the program include a completely monolithic low noise amplifier, less than a 3.5 dB noise figure, and a monolithic mixer suitable for integration with the LNA.

Electrically detected magnetic resonance in a W-band microwave cavity

NASA Astrophysics Data System (ADS)

Lang, V.; Lo, C. C.; George, R. E.; Lyon, S. A.; Bokor, J.; Schenkel, T.; Ardavan, A.; Morton, J. J. L.

2011-03-01

We describe a low-temperature sample probe for the electrical detection of magnetic resonance in a resonant W-band (94 GHz) microwave cavity. The advantages of this approach are demonstrated by experiments on silicon field-effect transistors. A comparison with conventional low-frequency measurements at X-band (9.7 GHz) on the same devices reveals an up to 100-fold enhancement of the signal intensity. In addition, resonance lines that are unresolved at X-band are clearly separated in the W-band measurements. Electrically detected magnetic resonance at high magnetic fields and high microwave frequencies is therefore a very sensitive technique for studying electron spins with an enhanced spectral resolution and sensitivity.

Ultra-Wideband Optical Modulation Spectrometer (OMS) Development: Study of the Optical Setup of a Wide-Band Optical Modulation Spectrometer

NASA Technical Reports Server (NTRS)

Tolls, Volker; Stringfellow, Guy (Technical Monitor)

2001-01-01

The purpose of this study is to advance the design of the optical setup for a wide-band Optical Modulation Spectrometer (OMS) for use with astronomical heterodyne receiver systems. This report describes the progress of this investigation achieved from March until December 2001.

Detection of Redox Imbalance in Normal Lymphocytes with Induced Mitochondrial Dysfunction - EPR Study.

PubMed

Georgieva, Ekaterina; Zhelev, Zhivko; Aoki, Ichio; Bakalova, Rumiana; Higashi, Tatsuya

2016-10-01

The present study describes a new approach for direct imaging of redox status in live cells using paramagnetic spin-probes, which allows evaluation of the level of oxidative stress due to overproduction of superoxide. The method is based on redox cycling of cell/mitochondria-penetrating nitroxide radicals (e.g. mito-TEMPO) and their electron-paramagnetic resonance (EPR) contrast, which makes them useful molecular sensors for analysis of redox status and oxidative stress in cells and tissues. Oxidative stress was induced in normal human lymphocytes by treatment with 2-methoxyestradiol and rotenone (ME/Rot) at different concentrations. This combination provokes mitochondrial dysfunction, which is accompanied by overproduction of superoxide. The EPR measurements were performed in dynamics on X-Band spectrometer after addition of mito-TEMPO to cell suspensions. The intensity of the EPR signal in untreated cells decreased significantly, which indicates a conversion of paramagnetic mito-TEMPO to its non-contrast diamagnetic form (hydroxylamine - mito-TEMPOH) due to reduction. In ME/Rot-treated cells, the signal decreased more slowly and to a lower level with increasing the concentration of ME/Rot. These data indicate an induction of oxidative stress in the cells in a concentration-dependent manner. A very good positive correlation between the intensity of EPR signal of mito-TEMPO and the intracellular level of superoxide was found, analyzed by conventional dihydroethidium test (R=0.9143, p<0.001). In conclusion, our study demonstrated that cell-penetrating paramagnetic spin-probes, such as mito-TEMPO, are valuable tools for EPR imaging of the superoxide level in live cells, as well as for EPR imaging of mitochondrial dysfunction and metabolic activity, accompanied by superoxide imbalance. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Towards band structure and band offset engineering of monolayer Mo(1-x)W(x)S2 via Strain

NASA Astrophysics Data System (ADS)

Kim, Joon-Seok; Ahmad, Rafia; Pandey, Tribhuwan; Rai, Amritesh; Feng, Simin; Yang, Jing; Lin, Zhong; Terrones, Mauricio; Banerjee, Sanjay K.; Singh, Abhishek K.; Akinwande, Deji; Lin, Jung-Fu

2018-01-01

Semiconducting transition metal dichalcogenides (TMDs) demonstrate a wide range of optoelectronic properties due to their diverse elemental compositions, and are promising candidates for next-generation optoelectronics and energy harvesting devices. However, effective band offset engineering is required to implement practical structures with desirable functionalities. Here, we explore the pressure-induced band structure evolution of monolayer WS2 and Mo0.5W0.5S2 using hydrostatic compressive strain applied in a diamond anvil cell (DAC) apparatus and theoretical calculations, in order to study the modulation of band structure and explore the possibility of band alignment engineering through different compositions. Higher W composition in Mo(1-x)W(x)S2 contributes to a greater pressure-sensitivity of direct band gap opening, with a maximum value of 54 meV GPa-1 in WS2. Interestingly, while the conduction band minima (CBMs) remains largely unchanged after the rapid gap increase, valence band maxima (VBMs) significantly rise above the initial values. It is suggested that the pressure- and composition-engineering could introduce a wide variety of band alignments including type I, type II, and type III heterojunctions, and allow to construct precise structures with desirable functionalities. No structural transition is observed during the pressure experiments, implying the pressure could provide selective modulation of band offset.

EPR and photoluminescence study of irradiated anion-defective alumina single crystals

NASA Astrophysics Data System (ADS)

Kortov, V. S.; Ananchenko, D. V.; Konev, S. F.; Pustovarov, V. A.

2017-09-01

Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectra of anion-defective alumina single crystals were measured. Exposure to a dose 10 Gy-1 kGy causes isotropic EPR signal of a complex form, this signal contains narrow and broad components. At the same time, in the PL spectrum alongside with a band of F+-centers (3.8 eV) an additional emission band with the maximum of 2.25 eV is registered. This band corresponds to aggregate F22+-centers which were create under irradiation. By comparing measurements in EPR and PL spectra with further stepped annealing in the temperature range of 773-1473 K of the samples exposed to the same doses, we were able to conclude that a narrow component of isotropic EPR signal is associated with the formation of paramagnetic F22+-centers under irradiation. A wide component can be caused by deep hole traps which are created by a complex defect (VAl2- - F+) with a localized hole.

a KA-BAND Chirped-Pulse Fourier Transform Microwave Spectrometer.

NASA Astrophysics Data System (ADS)

Zaleski, Daniel P.; Neill, Justin L.; Muckle, Matthew T.; Pate, Brooks H.; Carroll, P. Brandon; Weaver, Susanna L. Widicus

2010-06-01

The design and performance of a new chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating from 25-40 GHz will be discussed. A 10.5-3 GHz linear frequency sweep, generated by a 24 GS/s arbitrary waveform generator, is upconverted by a 23.00 GHz phase-locked oscillator, then fed into an active doubler to create a 25-40 GHz chirped pulse. After amplification with a 60-80 W pulsed traveling wave tube amplifier, the pulse is broadcast across a molecular beam chamber where it interacts with a molecular sample. The molecular FID signal is downconverted with the 23 GHz oscillator so that it can be digitized on a 50 GS/s oscilloscope with 16 GHz hardware bandwidth. The sensitivity and phase stability of this spectrometer is comparable to that of the previously reported 6.5-18.5 CP-FTMW spectrometer. On propyne (μ=0.78 D), a single-shot signal to noise ratio of approximately 200:1 is observed on the J=2-1 rotational transition at 34183 MHz when the full bandwidth is swept; optimal excitation is observed for this transition with a 250 MHz bandwidth sweep. The emission has a T_2 lifetime of 4 μs. Early results from this spectrometer, particularly in the study of species of astrochemical interest, will be presented. G.G. Brown et al., Rev. Sci. Instrum. 79 (2008) 053103.

Improving the spectral resolution of flat-field concave grating miniature spectrometers by dividing a wide spectral band into two narrow ones.

PubMed

Zhou, Qian; Pang, Jinchao; Li, Xinghui; Ni, Kai; Tian, Rui

2015-11-10

In this study, a new flat-field concave grating miniature spectrometer is proposed with improved resolution across a wide spectral band. A mirror is added to a conventional concave grating spectrometer and placed near the existing detector array, allowing a wide spectral band to be divided into two adjacent subspectral bands. One of these bands is directly detected by the detector, and the other is indirectly analyzed by the same detector after being reflected by the mirror. These two subspectral bands share the same entrance slit, concave grating, and detector, which allows for a compact size, while maintaining an improved spectral resolution across the entire spectral band. The positions of the mirror and other parameters of the spectrometer are designed by a computer procedure and the optical design software ZEMAX. Simulation results show that the resolution of this kind of flat-field concave grating miniature spectrometer is better than 1.6 nm across a spectral band of 700 nm. Experiments based on three laser sources reveal that the measured resolutions are comparable to the simulated ones, with a maximum relative error between them of less than 19%.

EPR studies of free radicals in A-2058 human melanoma cells treated by valproic acid and 5,7-dimethoxycoumarin.

PubMed

Zdybel, Magdalena; Chodurek, Ewa; Pilawa, Barbara

2014-01-01

Free radicals in A-2058 human melanoma cells were studied by the use of electron paramagnetic resonance (EPR) spectroscopy. The aim of this work was to determine the changes in relative free radical concentrations in tumor A-2058 cells after treatment by valproic acid (VPA) and 5,7-dimethoxycoumarin (DMC). The influences of VPA and DMC on free radicals in A-2058 cells were compared with those for human melanoma malignum A-375 and G-361 cells, which were tested by us earlier. Human malignant melanoma A-2058 cells were exposed to interactions with VPA, DMC, and both VPA and DMC. The tumor cells A-2058 were purchased from LGC Standards (Lomianki, Poland), and they were grown in the standard conditions: at 37°C and in an atmosphere containing 95% air and 5% CO2, in the Minimum Essential Medium Eagle (MEM, Sigma-Aldrich). The A-2058 cells were incubated with VPA (1 mM) and DMC (10 μM) for 4 days. The first-derivative EPR spectra of the control A-2058 cells, and the cells treated with VPA, DMC, and both VPA and DMC, were measured by the electron paramagnetic resonance spectrometer of Radiopan (Poznań, Poland) with microwaves from an X-band (9.3 GHz). The parameters of the EPR lines: amplitudes (A), integral intensities (I), line widths (ΔBpp), and g-factors, were analyzed. The changes of amplitudes and line widths with microwave power increasing from 2.2 to 70 mW were drawn evaluated, o-Semiquinone free radicals of melanin biopolymer are mainly responsible for the EPR lines of A-2058 melanoma malignum cells. The amounts of free radicals in A-2058 cells treated with VPA, and both VPA and DMC, were lower than in the untreated control cells. Application of the tested substances (VPA, and both VPA and DMC) as the antitumor compounds was discussed. DMC without VPA did not decrease free radicals concentration in A-2058 cells. The studies con-firmed that EPR spectroscopy may be used to examine interactions of free radicals with antitumor compounds.

A W-band integrated power module using MMIC MESFET power amplifiers and varactor doublers

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

Ho, T.C.; Chen, Seng Woon; Pande, K.

1993-12-01

A high-performance integrated power module using U-band MMIC MESFET power amplifiers in conjunction with W-band MMIC high efficiency varactor doublers has been developed for millimeter-wave system applications. This paper presents the design, fabrication, and performance of this W-band integrated power module. Measured results of the complete integrated power module show an output power of 90 mW with an overall associated gain of 29.5 dB at 94 GHz. A saturated power of over 95 mW was also achieved. These results represent the highest reported power and gain at W-band using MESFET and varactor frequency doubling technologies. This integrated power module ismore » suitable for the future 94 GHz missile seeker applications.« less

EPR oximetry in three spatial dimensions using sparse spin distribution

NASA Astrophysics Data System (ADS)

Som, Subhojit; Potter, Lee C.; Ahmad, Rizwan; Vikram, Deepti S.; Kuppusamy, Periannan

2008-08-01

A method is presented to use continuous wave electron paramagnetic resonance imaging for rapid measurement of oxygen partial pressure in three spatial dimensions. A particulate paramagnetic probe is employed to create a sparse distribution of spins in a volume of interest. Information encoding location and spectral linewidth is collected by varying the spatial orientation and strength of an applied magnetic gradient field. Data processing exploits the spatial sparseness of spins to detect voxels with nonzero spin and to estimate the spectral linewidth for those voxels. The parsimonious representation of spin locations and linewidths permits an order of magnitude reduction in data acquisition time, compared to four-dimensional tomographic reconstruction using traditional spectral-spatial imaging. The proposed oximetry method is experimentally demonstrated for a lithium octa- n-butoxy naphthalocyanine (LiNc-BuO) probe using an L-band EPR spectrometer.

High-Performance Solid-State W-Band Power Amplifiers

NASA Technical Reports Server (NTRS)

Gaier, Todd; Samoska, Lorene; Wells, Mary; Ferber, Robert; Pearson, John; Campbell, April; Peralta, Alejandro; Swift, Gerald; Yocum, Paul; Chung, Yun

2003-01-01

The figure shows one of four solid-state power amplifiers, each capable of generating an output power greater than or equal to 240 mW over one of four overlapping frequency bands from 71 to 106 GHz. (The bands are 71 to 84, 80 to 92, 88 to 99, and 89 to 106 GHz.) The amplifiers are designed for optimum performance at a temperature of 130 K. These amplifiers were developed specifically for incorporation into frequency-multiplier chains in local oscillators in a low-noise, far-infrared receiving instrument to be launched into outer space to make astrophysical observations. The designs of these amplifiers may also be of interest to designers and manufacturers of terrestrial W-band communication and radar systems. Each amplifier includes a set of six high-electron-mobility transistor (HEMT) GaAs monolithic microwave integrated-circuit (MMIC) chips, microstrip cavities, and other components packaged in a housing made from A-40 silicon-aluminum alloy. This alloy was chosen because, for the original intended spacecraft application, it offers an acceptable compromise among the partially competing requirements for high thermal conductivity, low mass, and low thermal expansion. Problems that were solved in designing the amplifiers included designing connectors and packages to fit the available space; designing microstrip signal-power splitters and combiners; matching of impedances across the frequency bands; matching of the electrical characteristics of those chips installed in parallel power-combining arms; control and levelling of output power across the bands; and designing the MMICs, microstrips, and microstrip cavities to suppress tendencies toward oscillation in several modes, both inside and outside the desired frequency bands.

W/V-Band Terrestrial Link Experiment (WTLE)

NASA Image and Video Library

2016-01-20

NASA Glenn researchers Jacki Houts, James Nessel and Michael Zemba perform a final inspection of the W/V-Band Terrestrial Link Experiment (WTLE) before it was transported to Albuquerque, New Mexico for testing. The experiment hardware includes a transmitter, which has been placed on the crest of the Sandia Mountains and a receiver (shown) placed at a research facility of the University of New Mexico. The wireless link spans 23km and will be used to study the effects of the atmosphere on high data-rate wireless communication links at 72 and 84 GHz. The goal of the experiment is to study these frequency bands for satellite communications.

Monoanionic molybdenum and tungsten tris(dithiolene) complexes: a multifrequency EPR study.

PubMed

Sproules, Stephen; Banerjee, Priyabrata; Weyhermüller, Thomas; Yan, Yong; Donahue, James P; Wieghardt, Karl

2011-08-01

Numerous Mo and W tris(dithiolene) complexes in varying redox states have been prepared and representative examples characterized crystallographically: [M(S(2)C(2)R(2))(3)](z) [M = Mo, R = Ph, z = 0 (1) or 1- (2); M = W, R = Ph, z = 0 (4) or 1- (5); R = CN, z = 2-, M = Mo (3) or W (6)]. Changes in dithiolene C-S and C-C bond lengths for 1 versus 2 and 4 versus 5 are indicative of ligand reduction. Trigonal twist angles (Θ) and dithiolene fold angles (α) increase and decrease, respectively, for 2 versus 1, 5 versus 4. Cyclic voltammetry reveals generally two reversible couples corresponding to 0/1- and 1-/2- reductions. The electronic structures of monoanionic molybdenum tris(dithiolene) complexes have been analyzed by multifrequency (S-, X-, Q-band) EPR spectroscopy. Spin-Hamiltonian parameters afforded by spectral simulation for each complex demonstrate the existence of two distinctive electronic structure types. The first is [Mo(IV)((A)L(3)(5-•))](1-) ((A)L = olefinic dithiolene, type A), which has the unpaired electron restricted to the tris(dithiolene) unit and is characterized by isotropic g-values and small molybdenum superhyperfine coupling. The second is formulated as [Mo(V)((B)L(3)(6-))](1-) ((B)L = aromatic dithiolene, type B) with spectra distinguished by a prominent g-anisotropy and hyperfine coupling consistent with the (d(z(2)))(1) paramagnet. The electronic structure disparity is also manifested in their electronic absorption spectra. The compound [W(bdt)(3)](1-) exhibits spin-Hamiltonian parameters similar to those of [Mo(bdt)(3)](1-) and thus is formulated as [W(V)((B)L(3)(6-))](1-). The EPR spectra of [W((A)L(3))](1-) display spin-Hamiltonian parameters that suggest their electronic structure is best represented by two resonance forms {[W(IV)((A)L(3)(5-•))](1-) ↔ [W(V)((A)L(3)(6-))](1-)}. The contrast with the corresponding [Mo(IV)((A)L(3)(5-•))](1-) complexes highlights tungsten's preference for higher oxidation states. © 2011 American

Interaction of Huntingtin Exon-1 Peptides with Lipid-Based Micellar Nanoparticles Probed by Solution NMR and Q-Band Pulsed EPR.

PubMed

Ceccon, Alberto; Schmidt, Thomas; Tugarinov, Vitali; Kotler, Samuel A; Schwieters, Charles D; Clore, G Marius

2018-05-23

Lipid-based micellar nanoparticles promote aggregation of huntingtin exon-1 peptides. Here we characterize the interaction of two such peptides, htt NT Q  7 and htt NT Q  10 comprising the N-terminal amphiphilic domain of huntingtin followed by 7 and 10 glutamine repeats, respectively, with 8 nm lipid micelles using NMR chemical exchange saturation transfer (CEST), circular dichroism and pulsed Q-band EPR. Exchange between free and micelle-bound htt NT Q  n peptides occurs on the millisecond time scale with a K D ∼ 0.5-1 mM. Upon binding micelles, residues 1-15 adopt a helical conformation. Oxidation of Met 7 to a sulfoxide reduces the binding affinity for micelles ∼3-4-fold and increases the length of the helix by a further two residues. A structure of the bound monomer unit is calculated from the backbone chemical shifts of the micelle-bound state obtained from CEST. Pulsed Q-band EPR shows that a monomer-dimer equilibrium exists on the surface of the micelles and that the two helices of the dimer adopt a parallel orientation, thereby bringing two disordered polyQ tails into close proximity which may promote aggregation upon dissociation from the micelle surface.

Einstein-Podolsky-Rosen Entanglement of Narrow-Band Photons from Cold Atoms.

PubMed

Lee, Jong-Chan; Park, Kwang-Kyoon; Zhao, Tian-Ming; Kim, Yoon-Ho

2016-12-16

Einstein-Podolsky-Rosen (EPR) entanglement introduced in 1935 deals with two particles that are entangled in their positions and momenta. Here we report the first experimental demonstration of EPR position-momentum entanglement of narrow-band photon pairs generated from cold atoms. By using two-photon quantum ghost imaging and ghost interference, we demonstrate explicitly that the narrow-band photon pairs violate the separability criterion, confirming EPR entanglement. We further demonstrate continuous variable EPR steering for positions and momenta of the two photons. Our new source of EPR-entangled narrow-band photons is expected to play an essential role in spatially multiplexed quantum information processing, such as, storage of quantum correlated images, quantum interface involving hyperentangled photons, etc.

Einstein-Podolsky-Rosen Entanglement of Narrow-Band Photons from Cold Atoms

NASA Astrophysics Data System (ADS)

Lee, Jong-Chan; Park, Kwang-Kyoon; Zhao, Tian-Ming; Kim, Yoon-Ho

2016-12-01

Einstein-Podolsky-Rosen (EPR) entanglement introduced in 1935 deals with two particles that are entangled in their positions and momenta. Here we report the first experimental demonstration of EPR position-momentum entanglement of narrow-band photon pairs generated from cold atoms. By using two-photon quantum ghost imaging and ghost interference, we demonstrate explicitly that the narrow-band photon pairs violate the separability criterion, confirming EPR entanglement. We further demonstrate continuous variable EPR steering for positions and momenta of the two photons. Our new source of EPR-entangled narrow-band photons is expected to play an essential role in spatially multiplexed quantum information processing, such as, storage of quantum correlated images, quantum interface involving hyperentangled photons, etc.

Increasing sensitivity of pulse EPR experiments using echo train detection schemes.

PubMed

Mentink-Vigier, F; Collauto, A; Feintuch, A; Kaminker, I; Tarle, V; Goldfarb, D

2013-11-01

Modern pulse EPR experiments are routinely used to study the structural features of paramagnetic centers. They are usually performed at low temperatures, where relaxation times are long and polarization is high, to achieve a sufficient Signal/Noise Ratio (SNR). However, when working with samples whose amount and/or concentration are limited, sensitivity becomes an issue and therefore measurements may require a significant accumulation time, up to 12h or more. As the detection scheme of practically all pulse EPR sequences is based on the integration of a spin echo--either primary, stimulated or refocused--a considerable increase in SNR can be obtained by replacing the single echo detection scheme by a train of echoes. All these echoes, generated by Carr-Purcell type sequences, are integrated and summed together to improve the SNR. This scheme is commonly used in NMR and here we demonstrate its applicability to a number of frequently used pulse EPR experiments: Echo-Detected EPR, Davies and Mims ENDOR (Electron-Nuclear Double Resonance), DEER (Electron-Electron Double Resonance|) and EDNMR (Electron-Electron Double Resonance (ELDOR)-Detected NMR), which were combined with a Carr-Purcell-Meiboom-Gill (CPMG) type detection scheme at W-band. By collecting the transient signal and integrating a number of refocused echoes, this detection scheme yielded a 1.6-5 folds SNR improvement, depending on the paramagnetic center and the pulse sequence applied. This improvement is achieved while keeping the experimental time constant and it does not introduce signal distortion. Copyright © 2013 Elsevier Inc. All rights reserved.

EPR STUDIES OF THERMALLY STERILIZED VASELINUM ALBUM.

PubMed

Ramos, Paweł; Pilawa, Barbara

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy was used for examination of free radicals in thermally treated vaselinum album (VA). Thermal treatment in hot air as sterilization process was tested. Conditions of thermal sterilization were chosen according to the pharmaceutical norms. Vaselinum album was heated at the following conditions (T--temperature, t--time): T = 160°C and t = 120 min, T = 170°C and t = 60 min and T = 180°C and t = 30 min. The aim of this work was to determine concentration and free radical properties of thermally sterilized VA. EPR analysis for VA was done 15 min after sterilization. EPR measurements were done at room temperature. EPR spectra were recorded in the range of microwave power of 2.2-70 mW. g-Factor, amplitudes (A) and line width (ΔBpp) of the spectra were determined. The shape of the EPR spectra was analyzed. Free radical concentration (N) in the heated samples was determined. EPR spectra were not obtained for the non heated VA. EPR spectra were detected for all thermally sterilized samples. The spectra revealed complex character, their asymmetry depends on microwave power. The lowest free radicals concentration was found for the VA sterilized at 180°C during 30 min. EPR spectroscopy is proposed as the method useful for optimization of sterilization process of drugs.

Measurements and Simulations of Nadir-Viewing Radar Returns from the Melting Layer at X- and W-Bands

NASA Technical Reports Server (NTRS)

Liao, Liang; Meneghini, Robert; Tian, Lin; Heymsfield, Gerald M.

2010-01-01

Simulated radar signatures within the melting layer in stratiform rain, namely the radar bright band, are checked by means of comparisons with simultaneous measurements of the bright band made by the EDOP (X-band) and CRS (W-band) airborne Doppler radars during the CRYSTAL-FACE campaign in 2002. A stratified-sphere model, allowing the fractional water content to vary along the radius of the particle, is used to compute the scattering properties of individual melting snowflakes. Using the effective dielectric constants computed by the conjugate gradient-fast Fourier transform (CGFFT) numerical method for X and W bands, and expressing the fractional water content of melting particle as an exponential function in particle radius, it is found that at X band the simulated radar bright-band profiles are in an excellent agreement with the measured profiles. It is also found that the simulated W-band profiles usually resemble the shapes of the measured bright-band profiles even though persistent offsets between them are present. These offsets, however, can be explained by the attenuation caused by cloud water and water vapor at W band. This is confirmed by the comparisons of the radar profiles made in the rain regions where the un-attenuated W-band reflectivity profiles can be estimated through the X- and W band Doppler velocity measurements. The bright-band model described in this paper has the potential to be used effectively for both radar and radiometer algorithms relevant to the TRMM and GPM satellite missions.

Tunnel injection transit-time diodes for W-band power generation

NASA Technical Reports Server (NTRS)

Kidner, C.; Eisele, H.; Haddad, G. I.

1992-01-01

GaAs p(+ +)n(+)n(-)n(+) single-drift tunnel injection transit-time (TUNNETT) diodes for W-band operation have been successfully designed and tested. An output power of 32 mW at 93.5 GHz with a dc to RF conversion efficiency of 2.6 percent was obtained. The oscillations have a clean spectrum in a conventional waveguide cavity.

Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.

PubMed

Misra, S K; Andronenko, S I; Tipikin, D; Freed, J H; Somani, V; Prakash, Om

2016-03-01

Detailed EPR investigations on as-grown and annealed TiO 2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120-300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti 3+ , O - , adsorbed oxygen (O 2 - ) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O 2 - ) and the Fe 3+ ions in both Ti 4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O - and O 2 - ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn 2+ and Mn 4+ ions in anatase.

Use of a W-band polarimeter to measure microphysical characteristics of clouds

NASA Astrophysics Data System (ADS)

Galloway, John Charles

1997-08-01

This dissertation presents W-Band measurements of the copolar correlation co-efficient and Doppler spectrum taken from the University of Wyoming King Air research airplane. These measurements demonstrate the utility of making W-Band polarimetric and Doppler spectrum measurements from an airborne platform in investigations of cloud microphysical properties. Comparison of copolar correlation coefficient measurements with aircraft in situ probe measurements verifies that polarimetric measurements indicate phase transitions, and hydrometeor alignment in ice clouds. Melting layers in clouds were measured by the W-Band system on board the King Air during 1992 and 1994. Both measurements established the use of the linear depolarization ratio, LDR, to locate the melting layer using an airborne W-Band system. The measurement during 1994 allowed direct comparison of the magnitude of the copolar correlation coefficient with the values of LDR. The relation between the measurements corresponds with a predicted relationship between the two parameters for observation of particles exhibiting isotropy in the plane of polarization. Measurements of needle crystals at horizontal and vertical incidence provided further evidence that the copolar correlation coefficient values agreed with the expected response from hydrometeors possessing a preferred alignment for the side looking case, and hydrometeors without a preferred alignment for the vertical incidence case. Observation of significant specific differential phase at vertical incidence, the first reported at W-Band, corresponded to a significant increase in differential reflectivity overhead, which was most likely produced by hydrometeor alignment driven by cloud electrification. Comparison of the drop size distributions estimated using the Doppler spectra with those measured by the wingtip probes on the King Air reveals that the radar system is better suited under some liquid cloud conditions to provide microphysical measurements

Radiometric Measurements of Slant Path Attenuation in the V/W Bands

DTIC Science & Technology

2014-09-01

AUTHOR(S) George Brost , Kevin Magde, William Cook 5d. PROJECT NUMBER T2WB 5e. TASK NUMBER IN 5f. WORK UNIT NUMBER HO 7. PERFORMING...Measurements of Slant-Path Attenuation in the V/W Bands G. Brost , K. Magde, and W. Cook Air Force Research Laboratory, 525 Brooks Rd, Rome, NY, USA...slant path statistics at frequencies above 50 GHz. REFERENCES [1] G. Brost , W. Cook, and W. Lipe,” On the modeling and prediction of

Power-Combined GaN Amplifier with 2.28-W Output Power at 87 GHz

NASA Technical Reports Server (NTRS)

Fung, King Man; Ward, John; Chattopadhyay, Goutam; Lin, Robert H.; Samoska, Lorene A.; Kangaslahti, Pekka P.; Mehdi, Imran; Lambrigtsen, Bjorn H.; Goldsmith, Paul F.; Soria, Mary M.;

Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique

NASA Astrophysics Data System (ADS)

Rakvin, B.; Carić, D.; Kveder, M.

2018-02-01

The microwave magnetic field strength, B1, in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ωrf, which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B1, decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed.

Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique.

PubMed

Rakvin, B; Carić, D; Kveder, M

2018-02-01

The microwave magnetic field strength, B 1 , in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ω rf , which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B 1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B 1 , decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed. Copyright © 2018 Elsevier Inc. All rights reserved.

Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

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

Sidabras, Jason W.; Anderson, James R.; Mainali, Laxman

Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-opticmore » techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low

Ultralow noise up-conversion detector and spectrometer for the telecom band.

PubMed

Shentu, Guo-Liang; Pelc, Jason S; Wang, Xiao-Dong; Sun, Qi-Chao; Zheng, Ming-Yang; Fejer, M M; Zhang, Qiang; Pan, Jian-Wei

2013-06-17

We demonstrate up-conversion single-photon detection for the 1550-nm telecommunications band using a PPLN waveguide, long-wavelength pump, and narrowband filtering using a volume Bragg grating. We achieve total-system detection efficiency of around 30% with noise at the dark-count level of a Silicon APD. Based on the new detector, a single-pixel up-conversion infrared spectrometer with a noise equivalent power of -142 dBm Hz(-1/2) was demonstrated, which was as good as a liquid nitrogen cooled CCD camera.

Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR

PubMed Central

Misra, S.K.; Andronenko, S.I.; Tipikin, D.; Freed, J. H.; Somani, V.; Prakash, Om

2016-01-01

Detailed EPR investigations on as-grown and annealed TiO2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120–300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti3+, O−, adsorbed oxygen (O2−) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O2−) and the Fe3+ ions in both Ti4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O− and O2− ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn2+ and Mn4+ ions in anatase. PMID:27041794

W-band InP based HEMT MMIC low noise amplifiers

NASA Technical Reports Server (NTRS)

Lin, K. Y.; Tang, Y. L.; Wang, H.; Gaier, T.; Gough, R. G.; Sinclair, M.

2002-01-01

This paper presents the designs and measurement results of a three-stage and a four-stage W-band monolithic microwave integrated circuits (MMIC) including a three-stage and a four-stage low noise amplifiers.

Clinical EPR: Unique Opportunities and Some Challenges

PubMed Central

Swartz, Harold M.; Williams, Benjamin B.; Zaki, Bassem I.; Hartford, Alan C.; Jarvis, Lesley A.; Chen, Eunice; Comi, Richard J.; Ernstoff, Marc S.; Hou, Huagang; Khan, Nadeem; Swarts, Steven G.; Flood, Ann B.; Kuppusamy, Periannan

2014-01-01

Electron paramagnetic resonance (EPR) spectroscopy has been well established as a viable technique for measurement of free radicals and oxygen in biological systems, from in vitro cellular systems to in vivo small animal models of disease. However, the use of EPR in human subjects in the clinical setting, although attractive for a variety of important applications such as oxygen measurement, is challenged with several factors including the need for instrumentation customized for human subjects, probe and regulatory constraints. This paper describes the rationale and development of the first clinical EPR systems for two important clinical applications, namely, measurement of tissue oxygen (oximetry), and radiation dose (dosimetry) in humans. The clinical spectrometers operate at 1.2 GHz frequency and use surface loop resonators capable of providing topical measurements up to 1 cm depth in tissues. Tissue pO2 measurements can be carried out noninvasively and repeatedly after placement of an oxygen-sensitive paramagnetic material (currently India ink) at the site of interest. Our EPR dosimetry system is capable of measuring radiation-induced free radicals in the tooth of irradiated human subjects to determine the exposure dose. These developments offer potential opportunities for clinical dosimetry and oximetry, which include guiding therapy for individual patients with tumors or vascular disease, by monitoring of tissue oxygenation. Further work is in progress to translate this unique technology to routine clinical practice. PMID:24439333

An X-band Co2+ EPR study of Zn1-xCoxO (x=0.005-0.1) nanoparticles prepared by chemical hydrolysis methods using diethylene glycol and denaturated alcohol at 5 K

NASA Astrophysics Data System (ADS)

Misra, Sushil K.; Andronenko, S. I.; Srinivasa Rao, S.; Chess, Jordan; Punnoose, A.

2015-11-01

EPR investigations on two types of dilute magnetic semiconductor (DMS) ZnO nanoparticles doped with 0.5-10% Co2+ ions, prepared by two chemical hydrolysis methods, using: (i) diethylene glycol ((CH2CH2OH)2O) (NC-rod-like samples), and (ii) denatured ethanol (CH3CH2OH) solutions (QC-spherical samples), were carried out at X-band (9.5 GHz) at 5 K. The analysis of EPR data for NC samples revealed the presence of several types of EPR lines: (i) two types, intense and weak, of high-spin Co2+ ions in the samples with Co concentration >0.5%; (ii) surface oxygen vacancies, and (iii) a ferromagnetic resonance (FMR) line. QC samples exhibit an intense FMR line and an EPR line due to high-spin Co2+ ions. FMR line is more intense, than the corresponding line exhibited by NC samples. These EPR spectra varied for sample with different doping concentrations. The magnetic states of these samples as revealed by EPR spectra, as well as the origin of ferromagnetism DMS samples are discussed.

Application of EPR spectroscopy to the examination of pro-oxidant activity of coffee.

PubMed

Krakowian, Daniel; Skiba, Dominik; Kudelski, Adam; Pilawa, Barbara; Ramos, Paweł; Adamczyk, Jakub; Pawłowska-Góral, Katarzyna

2014-05-15

Free radicals present in coffee may be responsible for exerting toxic effects on an organism. The objectives of this work were to compare free radicals properties and concentrations in different commercially available coffees, in solid and liquid states, and to determine the effect of roasting on the formation of free radicals in coffee beans of various origins. The free radicals content of 15 commercially available coffees (solid and liquid) was compared and the impact of processing examined using electron paramagnetic resonance (EPR) spectroscopy at X-band (9.3 GHz). First derivative EPR spectra were measured at microwave power in the range of 0.7-70 mW. The following parameters were calculated for EPR spectra: amplitude (A), integral intensity (I), and line-width (ΔBpp); g-Factor was obtained from resonance condition. Our study showed that free radicals exist in green coffee beans (10(16) spin/g), roasted coffee beans (10(18) spin/g), and in commercially available coffee (10(17)-10(18) spin/g). Free radical concentrations were higher in solid ground coffee than in instant or lyophilised coffee. Continuous microwave saturation indicated homogeneous broadening of EPR lines from solid and liquid commercial coffee samples as well as green and roasted coffee beans. Slow spin-lattice relaxation processes were found to be present in all coffee samples tested, solid and liquid commercial coffees as well as green and roasted coffee beans. Higher free radicals concentrations were obtained for both the green and roasted at 240 °C coffee beans from Peru compared with those originating from Ethiopia, Brazil, India, or Colombia. Moreover, more free radicals occurred in Arabica coffee beans roasted at 240 °C than Robusta. EPR spectroscopy is a useful method of examining free radicals in different types of coffee. Copyright © 2013 Elsevier Ltd. All rights reserved.

Application of EPR spectroscopy to examine free radicals evolution during storage of the thermally sterilized Ungentum ophthalmicum.

PubMed

Ramos, Paweł; Pilawa, Barbara

2016-06-24

Free radicals formed during thermal sterilization of the Ungentum ophthalmicum were examined by an X-band EPR spectroscopy. The influence of storage time (15 min; 1, 2 and 3 days after heating) on free radical properties and concentrations in this sample was determined. Thermal sterilization was done according to the pharmaceutical norms. The first-derivative EPR spectra with g-values about 2 were measured with magnetic modulation of 100 kHz in the range of microwave power 2.2-70 mW. The changes of amplitudes (A) and linewidths (ΔB pp ) with microwave powers were evaluated. Free radicals in concentration ∼10 17 spin/g were formed during heating of the tested Ungentum. Free radical concentration decreased with increase in storage time, and reached values ∼10 17 spin/g after 3 days from sterilization. The tested U. ophthalmicum should not be sterilized at a temperature of 160 °C because of the free radicals formation, or it should be used 3 days after heating, when free radicals were considerably quenched. Free radical properties remain unchanged during storage of the Ungentum. The EPR lines of the U. ophthalmicum were homogeneously broadened and their linewidths (ΔB pp ) increased with increase in microwave power. EPR spectroscopy is useful to examine free radicals to optimize sterilization process and storage conditions of ophthalmologic samples.

Determination of the Average Native Background and the Light-Induced EPR Signals and their Variation in the Teeth Enamel Based on Large-Scale Survey of the Population.

PubMed

Ivannikov, Alexander I; Khailov, Artem M; Orlenko, Sergey P; Skvortsov, Valeri G; Stepanenko, Valeri F; Zhumadilov, Kassym Sh; Williams, Benjamin B; Flood, Ann B; Swartz, Harold M

2016-12-01

The aim of the study is to determine the average intensity and variation of the native background signal amplitude (NSA) and of the solar light-induced signal amplitude (LSA) in electron paramagnetic resonance (EPR) spectra of tooth enamel for different kinds of teeth and different groups of people. These values are necessary for determination of the intensity of the radiation-induced signal amplitude (RSA) by subtraction of the expected NSA and LSA from the total signal amplitude measured in L-band for in vivo EPR dosimetry. Variation of these signals should be taken into account when estimating the uncertainty of the estimated RSA. A new analysis of several hundred EPR spectra that were measured earlier at X-band in a large-scale examination of the population of the Central Russia was performed. Based on this analysis, the average values and the variation (standard deviation, SD) of the amplitude of the NSA for the teeth from different positions, as well as LSA in outer enamel of the front teeth for different population groups, were determined. To convert data acquired at X-band to values corresponding to the conditions of measurement at L-band, the experimental dependencies of the intensities of the RSA, LSA and NSA on the m.w. power, measured at both X and L-band, were analysed. For the two central upper incisors, which are mainly used in in vivo dosimetry, the mean LSA annual rate induced only in the outer side enamel and its variation were obtained as 10 ± 2 (SD = 8) mGy y -1 , the same for X- and L-bands (results are presented as the mean ± error of mean). Mean NSA in enamel and its variation for the upper incisors was calculated at 2.0 ± 0.2 (SD = 0.5) Gy, relative to the calibrated RSA dose-response to gamma radiation measured under non-power saturation conditions at X-band. Assuming the same value for L-band under non-power saturating conditions, then for in vivo measurements at L-band at 25 mW (power saturation conditions), a mean NSA and its

Determination of the Average Native Background and the Light-Induced EPR Signals and their Variation in the Teeth Enamel Based on Large-Scale Survey of the Population

PubMed Central

Ivannikov, Alexander I.; Khailov, Artem M.; Orlenko, Sergey P.; Skvortsov, Valeri G.; Stepanenko, Valeri F.; Zhumadilov, Kassym Sh.; Williams, Benjamin B.; Flood, Ann B.; Swartz, Harold M.

2016-01-01

The aim of the study is to determine the average intensity and variation of the native background signal amplitude (NSA) and of the solar light-induced signal amplitude (LSA) in electron paramagnetic resonance (EPR) spectra of tooth enamel for different kinds of teeth and different groups of people. These values are necessary for determination of the intensity of the radiation-induced signal amplitude (RSA) by subtraction of the expected NSA and LSA from the total signal amplitude measured in L-band for in vivo EPR dosimetry. Variation of these signals should be taken into account when estimating the uncertainty of the estimated RSA. A new analysis of several hundred EPR spectra that were measured earlier at X-band in a large-scale examination of the population of the Central Russia was performed. Based on this analysis, the average values and the variation (standard deviation, SD) of the amplitude of the NSA for the teeth from different positions, as well as LSA in outer enamel of the front teeth for different population groups, were determined. To convert data acquired at X-band to values corresponding to the conditions of measurement at L-band, the experimental dependencies of the intensities of the RSA, LSA and NSA on the m.w. power, measured at both X and L-band, were analysed. For the two central upper incisors, which are mainly used in in vivo dosimetry, the mean LSA annual rate induced only in the outer side enamel and its variation were obtained as 10 ± 2 (SD = 8) mGy y−1, the same for X- and L-bands (results are presented as the mean ± error of mean). Mean NSA in enamel and its variation for the upper incisors was calculated at 2.0 ± 0.2 (SD = 0.5) Gy, relative to the calibrated RSA dose–response to gamma radiation measured under non-power saturation conditions at X-band. Assuming the same value for L-band under non-power saturating conditions, then for in vivo measurements at L-band at 25 mW (power saturation conditions), a mean NSA and

Site Diversity Considerations for V/W Band Satellite Communications

DTIC Science & Technology

2011-08-01

HOUSE 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62702F 6. AUTHOR(S) George Brost , William Cook, William Lipe 5d. PROJECT NUMBER RIGD 5e. TASK...Distribution Unlimited: 88ABW-2010-3874 19 July 2010 SITE DIVERSITY CONSIDERATIONS FOR V/W BAND SATELLITE COMMUNICATIONS George Brost AFRL, 525 Brooks Rd

First spectra from a new, wide band, hybrid digital correlator spectrometer for the FIRST-HIFI instrument.

NASA Astrophysics Data System (ADS)

Cais, P.; Ravera, L.; Lagrange, D.; Giard, M.; Baudry, A.; Mayvial, J. Y.

1998-11-01

The authors have designed and built a new, wide band, modulable resolution spectrometer, in view of full astronomical qualifying tests, and to prepare future models for the FIRST satellite's heterodyne instrument. The spectrometer, a hybrid digital autocorrelator, offers flexibility in terms of bandwidth (from 170 MHz to 680 MHz) and resolution (from 700 kHz to 3 MHz). This spectrometer required the development of a dedicated analog filter bank, homemade samplers, and the design of full custom GaAs integrated circuits. Laboratory tests have shown excellent agreement with expected performances and observations performed with the IRAM 30-m radiotelescope have qualified its capabilities. Despite the relatively limited number of channels of the current prototype compared to other spectrometers, the main advantages are its stability (inherent to digital technique), and its spectral versatility. Microelectronics advances and rad-tolerance of the spectrometer components are used to prepare a new, compact, and low power consumption autocorrelator in view of a flight model for HIFI, the heterodyne instrument on the ESA cornerstone mission FIRST.

W-band integrated circuit PIN switches

NASA Astrophysics Data System (ADS)

Tahim, R. S.; Pham, T.; Chang, K.

1986-12-01

Both single-pole single-throw (SPST) and single-pole double-throw (SPDT) PIN switches have been developed at W band using microstrip integrated circuits. In SPST configurations, these switches have less than 1 dB of insertion loss under forward-voltage conditions from 90 to 108 GHz. Isolation greater than 20 dB over 3 GHz and greater than 10 dB over 7 GHz has been achieved. In SPDT configurations, insertion loss of less than 2 dB and isolation of more than 15 dB over 10 GHz (90 to 110 GHz) have been achieved. Beam-lead PIN diodes were used. Major features included mechanical ruggedness, light weight, small size and low-cost manufacturing.

Effects of spectrometer band pass, sampling, and signal-to-noise ratio on spectral identification using the Tetracorder algorithm

USGS Publications Warehouse

Swayze, G.A.; Clark, R.N.; Goetz, A.F.H.; Chrien, T.H.; Gorelick, N.S.

2003-01-01

Estimates of spectrometer band pass, sampling interval, and signal-to-noise ratio required for identification of pure minerals and plants were derived using reflectance spectra convolved to AVIRIS, HYDICE, MIVIS, VIMS, and other imaging spectrometers. For each spectral simulation, various levels of random noise were added to the reflectance spectra after convolution, and then each was analyzed with the Tetracorder spectra identification algorithm [Clark et al., 2003]. The outcome of each identification attempt was tabulated to provide an estimate of the signal-to-noise ratio at which a given percentage of the noisy spectra were identified correctly. Results show that spectral identification is most sensitive to the signal-to-noise ratio at narrow sampling interval values but is more sensitive to the sampling interval itself at broad sampling interval values because of spectral aliasing, a condition when absorption features of different materials can resemble one another. The band pass is less critical to spectral identification than the sampling interval or signal-to-noise ratio because broadening the band pass does not induce spectral aliasing. These conclusions are empirically corroborated by analysis of mineral maps of AVIRIS data collected at Cuprite, Nevada, between 1990 and 1995, a period during which the sensor signal-to-noise ratio increased up to sixfold. There are values of spectrometer sampling and band pass beyond which spectral identification of materials will require an abrupt increase in sensor signal-to-noise ratio due to the effects of spectral aliasing. Factors that control this threshold are the uniqueness of a material's diagnostic absorptions in terms of shape and wavelength isolation, and the spectral diversity of the materials found in nature and in the spectral library used for comparison. Array spectrometers provide the best data for identification when they critically sample spectra. The sampling interval should not be broadened to

Investigating Pigment Radicals in Black Rice Using HPLC and Multi-EPR.

PubMed

Nakagawa, Kouichi; Maeda, Hayato

2017-01-01

We investigated the location and distribution of paramagnetic species in black and white rice using electron paramagnetic resonance (EPR), X-band (9 GHz) EPR imaging (EPRI), and HPLC. EPR primarily detected two paramagnetic species in black rice, which were identified as a stable radical and Mn 2+ species, based on the g values and hyperfine components of the EPR signals. The signal from the stable radical appeared at g ≈ 2.00 and was relatively strong and stable. Subsequent noninvasive two-dimensional (2D) EPRI revealed that this stable radical was primarily located in the pigmented region of black rice, while very few radicals were observed in the rice interior. Pigments extracted from black rice were analyzed using HPLC; the major compound was found to be cyanidin-3-glucoside. EPR and HPLC results indicate that the stable radical was only found within the pigmented region of the rice, and that it could either be cyanidin-3-glucoside, or one of its oxidative decomposition products.

Reduced transition probabilities along the yrast line in 166W

NASA Astrophysics Data System (ADS)

Sayǧı, B.; Joss, D. T.; Page, R. D.; Grahn, T.; Simpson, J.; O'Donnell, D.; Alharshan, G.; Auranen, K.; Bäck, T.; Boening, S.; Braunroth, T.; Carroll, R. J.; Cederwall, B.; Cullen, D. M.; Dewald, A.; Doncel, M.; Donosa, L.; Drummond, M. C.; Ertuǧral, F.; Ertürk, S.; Fransen, C.; Greenlees, P. T.; Hackstein, M.; Hauschild, K.; Herzan, A.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Konki, J.; Kröll, T.; Labiche, M.; Lopez-Martens, A.; McPeake, C. G.; Moradi, F.; Möller, O.; Mustafa, M.; Nieminen, P.; Pakarinen, J.; Partanen, J.; Peura, P.; Procter, M.; Rahkila, P.; Rother, W.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Taylor, M. J.; Thornthwaite, A.; Uusitalo, J.

2017-08-01

Lifetimes of excited states in the yrast band of the neutron-deficient nuclide 166W have been measured utilizing the DPUNS plunger device at the target position of the JUROGAM II γ -ray spectrometer in conjunction with the RITU gas-filled separator and the GREAT focal-plane spectrometer. Excited states in 166W were populated in the 92Mo(78Kr,4 p ) reaction at a bombarding energy of 380 MeV. The measurements reveal a low value for the ratio of reduced transitions probabilities for the lowest-lying transitions B (E 2 ;4+→2+) /B (E 2 ;2+→0+) =0.33 (5 ) , compared with the expected ratio for an axially deformed rotor (B4 /2 = 1.43).

One-way EPR steering and genuine multipartite EPR steering

NASA Astrophysics Data System (ADS)

He, Qiongyi; Reid, Margaret D.

2012-11-01

We propose criteria and experimental strategies to realise the Einstein-Podolsky-Rosen (EPR) steering nonlocality. One-way steering can be obtained where there is asymmetry of thermal noise on each system. We also present EPR steering inequalities that act as signatures and suggest how to optimise EPR correlations in specific schemes so that the genuine multipartite EPR steering nonlocality (EPR paradox) can also possibly be realised. The results presented here also apply to the spatially separated macroscopic atomic ensembles.

The shift of optical band gap in W-doped ZnO with oxygen pressure and doping level

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

Chu, J.; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, Chongqing 400714; Peng, X.Y.

2014-06-01

Highlights: • CVD–PLD co-deposition technique was used. • Better crystalline of the ZnO samples causes the redshift of the optical band gap. • Higher W concentration induces blueshift of the optical band gap. - Abstract: Tungsten-doped (W-doped) zinc oxide (ZnO) nanostructures were synthesized on quartz substrates by pulsed laser and hot filament chemical vapor co-deposition technique under different oxygen pressures and doping levels. We studied in detail the morphological, structural and optical properties of W-doped ZnO by SEM, XPS, Raman scattering, and optical transmission spectra. A close correlation among the oxygen pressure, morphology, W concentrations and the variation of bandmore » gaps were investigated. XPS and Raman measurements show that the sample grown under the oxygen pressure of 2.7 Pa has the maximum tungsten concentration and best crystalline structure, which induces the redshift of the optical band gap. The effect of W concentration on the change of morphology and shift of optical band gap was also studied for the samples grown under the fixed oxygen pressure of 2.7 Pa.« less

Optimization of bicelle lipid composition and temperature for EPR spectroscopy of aligned membranes.

PubMed

McCaffrey, Jesse E; James, Zachary M; Thomas, David D

2015-01-01

We have optimized the magnetic alignment of phospholipid bilayered micelles (bicelles) for EPR spectroscopy, by varying lipid composition and temperature. Bicelles have been extensively used in NMR spectroscopy for several decades, in order to obtain aligned samples in a near-native membrane environment and take advantage of the intrinsic sensitivity of magnetic resonance to molecular orientation. Recently, bicelles have also seen increasing use in EPR, which offers superior sensitivity and orientational resolution. However, the low magnetic field strength (less than 1 T) of most conventional EPR spectrometers results in homogeneously oriented bicelles only at a temperature well above physiological. To optimize bicelle composition for magnetic alignment at reduced temperature, we prepared bicelles containing varying ratios of saturated (DMPC) and unsaturated (POPC) phospholipids, using EPR spectra of a spin-labeled fatty acid to assess alignment as a function of lipid composition and temperature. Spectral analysis showed that bicelles containing an equimolar mixture of DMPC and POPC homogeneously align at 298 K, 20 K lower than conventional DMPC-only bicelles. It is now possible to perform EPR studies of membrane protein structure and dynamics in well-aligned bicelles at physiological temperatures and below. Copyright © 2014 Elsevier Inc. All rights reserved.

W-band six-port network analyzer for two-port characterization of millimeter wave transistors

NASA Technical Reports Server (NTRS)

Moeller, Karl J.; Schaffner, James H.; Fetterman, Harold R.

1989-01-01

A W-band (75-100 GHz) six-port junction network analyzer was constructed from commercially available descrete waveguide components and was used for the direct two-port S-parameter measurement of active three-terminal devices. A comparison between the six-port and a down-converter-type frequency extender for a conventional network analyzer revealed the superior performance of the six-port. The application of the six-port to characterize a 0.1-micron gate-length HEMT at W-band is described, and representative results are presented.

EPR and IR spectral investigations on some leafy vegetables of Indian origin

NASA Astrophysics Data System (ADS)

Prasuna, C. P. Lakshmi; Chakradhar, R. P. S.; Rao, J. L.; Gopal, N. O.

2009-09-01

EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe 3+ ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g = 2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn 2+ ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic C dbnd O bonds.

Revealing the Cu(2+) ions localization at low symmetry Bi sites in photorefractive Bi12GeO20 crystals doped with Cu and V by high frequency EPR.

PubMed

Nistor, Sergiu V; Stefan, Mariana; Goovaerts, Etienne; Ramaz, François; Briat, Bernard

2015-10-01

The sites of incorporation of Cu(2+) impurity ions in Bi12GeO20 single crystals co-doped with copper and vanadium have been investigated by electron paramagnetic resonance (EPR). While the X-band EPR spectra consist of a simple broad (ΔB ∼50 mT) line with anisotropic lineshape, the W-band EPR spectra exhibit well resolved, strongly anisotropic lines, due to transitions within the 3d(9)-(2)D ground manifold of the Cu(2+) ions. The most intense group of lines, attributed to the dominant Cu(2+)(I) center, displays a characteristic four components hyperfine structure for magnetic field orientations close to a 〈110〉 direction. The g and A tensor main axes are very close to one of the 12 possible sets of orthogonal 〈1-10〉, 〈00-1〉 and 〈110〉 crystal directions. Several less intense lines, with unresolved hyperfine structure and similar symmetry properties, mostly overlapped by the Cu(2+)(I) spectrum, were attributed to Cu(2+)(II) centers. The two paramagnetic centers are identified as substitutional Cu(2+) ions at Bi(3+) sites with low C1 symmetry, very likely resulting from different configurations of neighboring charge compensating defects. Copyright © 2015 Elsevier Inc. All rights reserved.

Protein Immobilization Capabilities of Sucrose and Trehalose Glasses: The Effect of Protein/Sugar Concentration Unraveled by High-Field EPR.

PubMed

Malferrari, Marco; Savitsky, Anton; Lubitz, Wolfgang; Möbius, Klaus; Venturoli, Giovanni

2016-12-01

Disaccharide glasses are increasingly used to immobilize proteins at room temperature for structural/functional studies and long-term preservation. To unravel the molecular basis of protein immobilization, we studied the effect of sugar/protein concentration ratios in trehalose or sucrose matrixes, in which the bacterial photosynthetic reaction center (RC) was embedded as a model protein. The structural, dynamical, and H-bonding characteristics of the sugar-protein systems were probed by high-field W-band EPR of a matrix-dissolved nitroxide radical. We discovered that RC immobilization and thermal stabilization, being independent of the protein concentration in trehalose, occur in sucrose only at sufficiently low sugar/protein ratios. EPR reveals that only under such conditions does sucrose form a microscopically homogeneous matrix that immobilizes, via H-bonds, the nitroxide probe. We conclude that the protein immobilization capability depends critically on the propensity of the glass-forming sugar to create intermolecular H-bond networks, thus establishing long-range, homogeneous connectivity within the matrix.

Power Amplifier Module with 734-mW Continuous Wave Output Power

NASA Technical Reports Server (NTRS)

Fung, King Man; Samoska, Lorene A.; Kangaslahti, Pekka P.; Lamgrigtsen, Bjorn H.; Goldsmith, Paul F.; Lin, Robert H.; Soria, Mary M.; Cooperrider, Joelle T.; Micovic, Moroslav; Kurdoghlian, Ara

2010-01-01

Research findings were reported from an investigation of new gallium nitride (GaN) monolithic millimeter-wave integrated circuit (MMIC) power amplifiers (PAs) targeting the highest output power and the highest efficiency for class-A operation in W-band (75-110 GHz). W-band PAs are a major component of many frequency multiplied submillimeter-wave LO signal sources. For spectrometer arrays, substantial W-band power is required due to the passive lossy frequency multipliers-to generate higher frequency signals in nonlinear Schottky diode-based LO sources. By advancing PA technology, the LO system performance can be increased with possible cost reductions compared to current GaAs PAs. High-power, high-efficiency GaN PAs are cross-cutting and can enable more efficient local oscillator distribution systems for new astrophysics and planetary receivers and heterodyne array instruments. It can also allow for a new, electronically scannable solid-state array technology for future Earth science radar instruments and communications platforms.

A high-resolution oxygen A-band spectrometer (HABS) and its radiation closure

NASA Astrophysics Data System (ADS)

Min, Q.; Yin, B.; Li, S.; Berndt, J.; Harrison, L.; Joseph, E.; Duan, M.; Kiedron, P.

2014-02-01

The pressure dependence of oxygen A-band absorption enables the retrieval of the vertical profiles of aerosol and cloud properties from oxygen A-band spectrometry. To improve the understanding of oxygen A-band inversions and utility, we developed a high-resolution oxygen A-band spectrometer (HABS), and deployed it at Howard University Beltsville site during the NASA Discover Air-Quality Field Campaign in July 2011. The HABS has the ability to measure solar direct-beam and zenith diffuse radiation through a telescope automatically. It exhibits excellent performance: stable spectral response ratio, high signal-to-noise ratio (SNR), high spectrum resolution (0.16 nm), and high Out-of-Band Rejection (10-5). To evaluate the spectra performance of HABS, a HABS simulator has been developed by combing the discrete ordinates radiative transfer (DISORT) code with the High Resolution Transmission (HTRAN) database HITRAN2008. The simulator uses double-k approach to reduce the computational cost. The HABS measured spectra are consistent with the related simulated spectra. For direct-beam spectra, the confidence intervals (95%) of relative difference between measurements and simulation are (-0.06, 0.05) and (-0.08, 0.09) for solar zenith angles of 27° and 72°, respectively. The main differences between them occur at or near the strong oxygen absorption line centers. They are mainly caused by the noise/spikes of HABS measured spectra, as a result of combined effects of weak signal, low SNR, and errors in wavelength registration and absorption line parameters. The high-resolution oxygen A-band measurements from HABS can constrain the active radar retrievals for more accurate cloud optical properties, particularly for multi-layer clouds and for mixed-phase clouds.

W-band Heterodyne Receiver Module with 27 K Noise Temperature

NASA Technical Reports Server (NTRS)

Gawande, R.; Reeves, R.; Cleary, K.; Readhead, A. C.; Gaier, T.; Kangaslahti, P.; Samoska, L.; Church, S.; Sieth, M.; Voll, P.;

Dual-Polarized Antenna Arrays with CMOS Power Amplifiers for SiP Integration at W-Band

NASA Astrophysics Data System (ADS)

Giese, Malte; Vehring, Sönke; Böck, Georg; Jacob, Arne F.

2017-09-01

This paper presents requirements and front-end solutions for low-cost communication systems with data rates of 100 Gbit/s. Link budget analyses in different mass-market applications are conducted for that purpose. It proposes an implementation of the front-end as an active antenna array with support for beam steering and polarization multiplexing over the full W-band. The critical system components are investigated and presented. This applies to a transformer coupled power amplifier (PA) in 40 nm bulk CMOS. It shows saturated output power of more than 10 dBm and power-added-efficiency of more than 10 % over the full W-band. Furthermore, the performance of microstrip-to-waveguide transitions is shown exemplarily as an important part of the active antenna as it interfaces active circuitry and antenna in a polymer-and-metal process. The transition test design shows less than 0.9 dB insertion loss and more than 12 dB return loss for the differential transition over the full W-band.

Coding for stable transmission of W-band radio-over-fiber system using direct-beating of two independent lasers.

PubMed

Yang, L G; Sung, J Y; Chow, C W; Yeh, C H; Cheng, K T; Shi, J W; Pan, C L

2014-10-20

We demonstrate experimentally Manchester (MC) coding based W-band (75 - 110 GHz) radio-over-fiber (ROF) system to reduce the low-frequency-components (LFCs) signal distortion generated by two independent low-cost lasers using spectral shaping. Hence, a low-cost and higher performance W-band ROF system is achieved. In this system, direct-beating of two independent low-cost CW lasers without frequency tracking circuit (FTC) is used to generate the millimeter-wave. Approaches, such as delayed self-heterodyne interferometer and heterodyne beating are performed to characterize the optical-beating-interference sub-terahertz signal (OBIS). Furthermore, W-band ROF systems using MC coding and NRZ-OOK are compared and discussed.

Emittance Effects on Gain in $W$ -Band TWTs

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

Carlsten, Bruce Eric; Nichols, Kimberley E.; Shchegolkov, Dmitry Yu.

We consider the main effects of beam emittance on W-band traveling-wave tube (TWT) performance and gain. Specifically, we consider a representative dielectric TWT structure with ~5 dB/cm of gain driven by a 5-A, 20-keV, sheet electron beam that is focused by a wiggler magnetic field. The normalized beam transverse emittance must be about 1 μm or lower to ensure that both the transport is stable and the gain is not degraded by the effective energy spread arising from the emittance. This emittance limit scales roughly inversely with frequency.

Emittance Effects on Gain in $W$ -Band TWTs

DOE PAGES

Carlsten, Bruce Eric; Nichols, Kimberley E.; Shchegolkov, Dmitry Yu.; ...

2016-10-20

We consider the main effects of beam emittance on W-band traveling-wave tube (TWT) performance and gain. Specifically, we consider a representative dielectric TWT structure with ~5 dB/cm of gain driven by a 5-A, 20-keV, sheet electron beam that is focused by a wiggler magnetic field. The normalized beam transverse emittance must be about 1 μm or lower to ensure that both the transport is stable and the gain is not degraded by the effective energy spread arising from the emittance. This emittance limit scales roughly inversely with frequency.

Multisite EPR oximetry from multiple quadrature harmonics.

PubMed

Ahmad, R; Som, S; Johnson, D H; Zweier, J L; Kuppusamy, P; Potter, L C

2012-01-01

Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported. Copyright © 2011 Elsevier Inc. All rights reserved.

Design and testing of a 750 MHz CW-EPR digital console for small animal imaging

NASA Astrophysics Data System (ADS)

Sato-Akaba, Hideo; Emoto, Miho C.; Hirata, Hiroshi; Fujii, Hirotada G.

2017-11-01

This paper describes the development of a digital console for three-dimensional (3D) continuous wave electron paramagnetic resonance (CW-EPR) imaging of a small animal to improve the signal-to-noise ratio and lower the cost of the EPR imaging system. A RF generation board, an RF acquisition board and a digital signal processing (DSP) & control board were built for the digital EPR detection. Direct sampling of the reflected RF signal from a resonator (approximately 750 MHz), which contains the EPR signal, was carried out using a band-pass subsampling method. A direct automatic control system to reduce the reflection from the resonator was proposed and implemented in the digital EPR detection scheme. All DSP tasks were carried out in field programmable gate array ICs. In vivo 3D imaging of nitroxyl radicals in a mouse's head was successfully performed.

W-Band Transmission MeasurementS and X-Band Dielectric Properties Measurements for a Radome Material Sample

NASA Technical Reports Server (NTRS)

Cravey, Robin L.; Tiemsin, Pacita I.

1997-01-01

This paper describes measurements which were performed on a sample of radome material in the Electromagnetic Properties Measurements Laboratory (EPML). The purpose of the measurements described in this paper was to determine the one-way transmission loss through the flat panel of radome material for a frequency range of 84 to 94 GHz, for varying incidence angles. The panel, which was manufactured by Norton Performance Plastics Corporation, was provided to the EPML by TRW. The size of the panel is 40 in x 36 in x 0.422 in and consists of a foam material with one side coated with a smooth white coating (this side will be referred to as the front side). The dielectric properties of the foam material from the inside of the panel were also determined at X-band (8.2-12.4 GHz). The W-band free space measurements are presented first, followed by the X-band dielectric properties measurements.

W-Band Free Space Permittivity Measurement Setup for Candidate Radome Materials

NASA Technical Reports Server (NTRS)

Fralick, Dion T.

1997-01-01

This paper presents a measurement system used for w-band complex permittivity measurements performed in NASA Langley Research Center's Electromagnetics Research Branch. The system was used to characterize candidate radome materials for the passive millimeter wave (PMMW) camera experiment. The PMMW camera is a new technology sensor, with goals of all-weather landings of civilian and military aircraft. The sensor is being developed under a NASA Technology Reinvestment program with TRW, McDonnell- Douglas, Honeywell, and Composite Optics, Inc. as participants. The experiment is scheduled to be flight tested on the Air Force's 'Speckled Trout' aircraft in late 1997. The camera operates at W-band, in a radiometric capacity and generates an image of the viewable field. Because the camera is a radiometer, the system is very sensitive to losses. Minimal transmission loss through the radome at the operating frequency, 89 GHz, was critical to the success of the experiment. This paper details the design, set-up, calibration and operation of a free space measurement system developed and used to characterize the candidate radome materials for this program.

Examination by EPR spectroscopy of free radicals in melanins isolated from A-375 cells exposed on valproic acid and cisplatin.

PubMed

Chodurek, Ewa; Zdybel, Magdalena; Pilawa, Barbara; Dzierzewicz, Zofia

2012-01-01

Drug binding by melanin biopolymers influence the effectiveness of the chemotherapy, radiotherapy and photodynamic therapy. Free radicals of melanins take part in formation of their complex with drugs. The aim of this work was to determine the effect of the two compounds: valproic acid (VPA) and cisplatin (CPT) on free radicals properties of melanin isolated from A-375 melanoma cells. Free radicals were examined by an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. EPR spectra were measured for the model synthetic eumelanin - DOPA-melanin, the melanin isolated from the control A-375 cells and these cells treated by VPA, CPT and both VPA and CPT. For all the examined samples broad EPR lines (deltaBpp: 0.48-0.68 mT) with g-factors of 2.0045-2.0060 characteristic for o-semiquinone free radicals were observed. Free radicals concentrations (N) in the tested samples, g-factors, amplitudes (A), integral intensities (I) and linewidths (deltaBpp) of the EPR spectra, were analyzed. The EPR lines were homogeneously broadened. Continuous microwave saturation of the EPR spectra indicated that slow spin-lattice relaxation processes existed in all the tested melanin samples. The relatively slowest spin-lattice relaxation processes characterized melanin isolated from A-375 cells treated with both VPA and CPT. The changes of the EPR spectra with increasing microwave power in the range of 2.2-70 mW were evaluated. Free radicals concentrations in the melanin from A-375 cells were higher than in the synthetic DOPA-melanin. The strong increase of free radicals concentration in the melanin from A-375 cells was observed after their treating by VPA. CPT also caused the increase of free radicals concentrations in the examined natural melanin. The free radicals concentration in melanin isolated from A-375 cells treated with both VPA and CPT was slightly higher than those in melanin from the control cells.

Time-resolved EPR study of singlet oxygen in the gas phase.

PubMed

Ruzzi, Marco; Sartori, Elena; Moscatelli, Alberto; Khudyakov, Igor V; Turro, Nicholas J

2013-06-27

X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T = 293-323 K. O2((1)Δg) was produced by quenching of photogenerated triplet sensitizers naphthalene C8H10, perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O2((1)Δg) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O2((3)Σg(-)) were used as internal standards for estimating the concentration of O2 species and PO2 in the EPR cavity. Time-resolved (TR) EPR experiments of C8H10 were the main focus of this Article. Pulsed irradiation of C8H10 in the presence of O2((3)Σg(-)) allowed us to determine the kinetics of formation and decay for each of the four components of the O2((1)Δg) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O2((1)Δg) EPR spectrum was examined in experiments using C8H10. This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O2((1)Δg), τ = 0.4 s, were observed at medium pressure PO2 = 0.4 Torr, T = 293 K. The mechanism of O2((1)Δg) decay in the presence of photosensitizers is discussed. EPR spectra of O2((1)Δg) evidence that the spin-rotational states of O2((1)Δg) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O2((1)Δg) EPR line width on PO2 and T.

Design and testing of a 750MHz CW-EPR digital console for small animal imaging.

PubMed

Sato-Akaba, Hideo; Emoto, Miho C; Hirata, Hiroshi; Fujii, Hirotada G

2017-11-01

This paper describes the development of a digital console for three-dimensional (3D) continuous wave electron paramagnetic resonance (CW-EPR) imaging of a small animal to improve the signal-to-noise ratio and lower the cost of the EPR imaging system. A RF generation board, an RF acquisition board and a digital signal processing (DSP) & control board were built for the digital EPR detection. Direct sampling of the reflected RF signal from a resonator (approximately 750MHz), which contains the EPR signal, was carried out using a band-pass subsampling method. A direct automatic control system to reduce the reflection from the resonator was proposed and implemented in the digital EPR detection scheme. All DSP tasks were carried out in field programmable gate array ICs. In vivo 3D imaging of nitroxyl radicals in a mouse's head was successfully performed. Copyright © 2017 Elsevier Inc. All rights reserved.

Passive Fully Polarimetric W-Band Millimeter-Wave Imaging

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

Bernacki, Bruce E.; Kelly, James F.; Sheen, David M.

2012-04-01

We present the theory, design, and experimental results obtained from a scanning passive W-band fully polarimetric imager. Passive millimeter-wave imaging offers persistent day/nighttime imaging and the ability to penetrate dust, clouds and other obscurants, including clothing and dry soil. The single-pixel scanning imager includes both far-field and near-field fore-optics for investigation of polarization phenomena. Using both fore-optics, a variety of scenes including natural and man-made objects was imaged and these results are presented showing the utility of polarimetric imaging for anomaly detection. Analysis includes conventional Stokes-parameter based approaches as well as multivariate image analysis methods.

Simple vertex correction improves G W band energies of bulk and two-dimensional crystals

NASA Astrophysics Data System (ADS)

Schmidt, Per S.; Patrick, Christopher E.; Thygesen, Kristian S.

2017-11-01

The G W self-energy method has long been recognized as the gold standard for quasiparticle (QP) calculations of solids in spite of the fact that the neglect of vertex corrections and the use of a density-functional theory starting point lack rigorous justification. In this work we remedy this situation by including a simple vertex correction that is consistent with a local-density approximation starting point. We analyze the effect of the self-energy by splitting it into short-range and long-range terms which are shown to govern, respectively, the center and size of the band gap. The vertex mainly improves the short-range correlations and therefore has a small effect on the band gap, while it shifts the band gap center up in energy by around 0.5 eV, in good agreement with experiments. Our analysis also explains how the relative importance of short- and long-range interactions in structures of different dimensionality is reflected in their QP energies. Inclusion of the vertex comes at practically no extra computational cost and even improves the basis set convergence compared to G W . Taken together, the method provides an efficient and rigorous improvement over the G W approximation.

SuperSpec, The On-Chip Spectrometer: Improved NEP and Antenna Performance

NASA Astrophysics Data System (ADS)

Wheeler, Jordan; Hailey-Dunsheath, S.; Shirokoff, E.; Barry, P. S.; Bradford, C. M.; Chapman, S.; Che, G.; Doyle, S.; Glenn, J.; Gordon, S.; Hollister, M.; Kovács, A.; LeDuc, H. G.; Mauskopf, P.; McGeehan, R.; McKenney, C.; Reck, T.; Redford, J.; Ross, C.; Shiu, C.; Tucker, C.; Turner, J.; Walker, S.; Zmuidzinas, J.

2018-05-01

SuperSpec is a new technology for mm and sub-mm spectroscopy. It is an on-chip spectrometer being developed for multi-object, moderate-resolution (R˜ 300 ), large bandwidth survey spectroscopy of high-redshift galaxies for the 1 mm atmospheric window. This band accesses the CO ladder in the redshift range of z = 0-4 and the [CII] 158 μm line from redshift z = 5-9. SuperSpec employs a novel architecture in which detectors are coupled to a series of resonant filters along a single microwave feedline instead of using dispersive optics. This construction allows for the creation of a full spectrometer occupying only ˜ 10 cm^2 of silicon, a reduction in size of several orders of magnitude when compared to standard grating spectrometers. This small profile enables the production of future multi-beam spectroscopic instruments envisioned for the millimeter band to measure the redshifts of dusty galaxies efficiently. The SuperSpec collaboration is currently pushing toward the deployment of a SuperSpec demonstration instrument in fall of 2018. The progress with the latest SuperSpec prototype devices is presented; reporting increased responsivity via a reduced inductor volume (2.6 μm^3 ) and the incorporation of a new broadband antenna. A detector NEP of 3-4 × 10^{-18} W/Hz^{0.5} is obtained, sufficient for background-limited observation on mountaintop sites. In addition, beam maps and efficiency measurements of a new wide-band dual bow-tie slot antenna are shown.

Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124Xe

NASA Astrophysics Data System (ADS)

Radich, A. J.; Garrett, P. E.; Allmond, J. M.; Andreoiu, C.; Ball, G. C.; Bianco, L.; Bildstein, V.; Chagnon-Lessard, S.; Cross, D. S.; Demand, G. A.; Diaz Varela, A.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Hackman, G.; Hadinia, B.; Jigmeddorj, B.; Laffoley, A. T.; Leach, K. G.; Michetti-Wilson, J.; Orce, J. N.; Rajabali, M. M.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wang, Z. M.; Wood, J. L.; Wong, J.; Williams, S. J.; Yates, S. W.

2015-04-01

The nuclear structure of 124Xe has been investigated via measurements of the β+/EC decay of 124Cs with the 8 π γ -ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2+→0+ in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, B (E 2 ;23+→02+) =78 (13 ) W.u. and B (E 2 ;24+→03+) =53 (12 ) W.u. were determined. The 03+ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te (3He,n )124Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.

EPR studies of the vitamin K 1 semiquinone radical anion. Comparison to the electron acceptor A 1 in green plant photosystem I

NASA Astrophysics Data System (ADS)

Thurnauer, Marion C.; Brown, James W.; Gast, P.; Feezel, Laura L.

Suggestions that the electron acceptor, A 1, in Photosystem I is a quinone have come from both optical and epr experiments. Vitamin K 1 (phylloquinone) is present in the PSI complex with a stoichiometry of two molecules per reaction center. In order to determine if A 1 can be identified with vitamin K 1, X-band and Q-band epr properties of the vitamin K 1 radical anion in frozen alcohol solutions are examined. The results are compared to the epr properties that have been observed for the reduced A 1 acceptor in vivo. The g-values obtained for the vitamin K 1 radical anion are consistent with identifying A 1 with vitamin K 1.

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces

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

Rocker, J.; Cornu, D.; Kieseritzky, E.

2014-08-01

paramagnetic species with a density of approximately 5 × 10{sup 11} spins/cm{sup 2}, which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology.« less

Effective line intensity measurements of trans-nitrous acid (HONO) of the ν1 band near 3600 cm-1 using laser difference-frequency spectrometer

NASA Astrophysics Data System (ADS)

Maamary, Rabih; Fertein, Eric; Fourmentin, Marc; Dewaele, Dorothée; Cazier, Fabrice; Chen, Changshui; Chen, Weidong

2017-07-01

We report on the measurements of the effective line intensities of the ν1 fundamental band of trans-nitrous acid (trans-HONO) in the infrared near 3600 cm-1 (2.78 μm). A home-made widely tunable laser spectrometer based on difference-frequency generation (DFG) was used for this study. The strengths of 28 well-resolved absorption lines of the ν1 band were determined by scaling their absorption intensities to the well referenced absorption line intensity of the ν3 band of trans-HONO around 1250 cm-1 recorded simultaneously with the help of a DFB quantum cascade laser (QCL) spectrometer. The maximum measurement uncertainty of 12% in the line intensities is mainly determined by the uncertainty announced in the referenced line intensities, while the measurement precision in frequency positions of the absorption lines is better than 6×10-4 cm-1. The cross-measurement carried out in the present work allows one to perform intensity calibration using well referenced line parameters.

Band-edge positions in G W : Effects of starting point and self-consistency

NASA Astrophysics Data System (ADS)

Chen, Wei; Pasquarello, Alfredo

2014-10-01

We study the effect of starting point and self-consistency within G W on the band-edge positions of semiconductors and insulators. Compared to calculations based on a semilocal starting point, the use of a hybrid-functional starting point shows a larger quasiparticle correction for both band-edge states. When the self-consistent treatment is employed, the band-gap opening is found to result mostly from a shift of the valence-band edge. Within the non-self-consistent methods, we analyse the performance of empirical and nonempirical schemes in which the starting point is optimally tuned. We further assess the accuracy of the band-edge positions through the calculation of ionization potentials of surfaces. The ionization potentials for most systems are reasonably well described by one-shot calculations. However, in the case of TiO2, we find that the use of self-consistency is critical to obtain a good agreement with experiment.

Analysis of airborne imaging spectrometer data for the Ruby Mountains, Montana, by use of absorption-band-depth images

NASA Technical Reports Server (NTRS)

Brickey, David W.; Crowley, James K.; Rowan, Lawrence C.

1987-01-01

Airborne Imaging Spectrometer-1 (AIS-1) data were obtained for an area of amphibolite grade metamorphic rocks that have moderate rangeland vegetation cover. Although rock exposures are sparse and patchy at this site, soils are visible through the vegetation and typically comprise 20 to 30 percent of the surface area. Channel averaged low band depth images for diagnostic soil rock absorption bands. Sets of three such images were combined to produce color composite band depth images. This relative simple approach did not require extensive calibration efforts and was effective for discerning a number of spectrally distinctive rocks and soils, including soils having high talc concentrations. The results show that the high spectral and spatial resolution of AIS-1 and future sensors hold considerable promise for mapping mineral variations in soil, even in moderately vegetated areas.

Arbitrary waveform modulated pulse EPR at 200 GHz

NASA Astrophysics Data System (ADS)

Kaminker, Ilia; Barnes, Ryan; Han, Songi

2017-06-01

We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200 GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7 T. This is achieved with the integration of a 1 GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1 ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200 GHz with >150 mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200 GHz. We demonstrate that in the power-limited regime of ω1 < 1 MHz phase-modulated pulses were sufficient to achieve significant improvements in broadband (>10 MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200 GHz.

Combined multifrequency EPR and DFT study of dangling bonds in a-Si:H

NASA Astrophysics Data System (ADS)

Fehr, M.; Schnegg, A.; Rech, B.; Lips, K.; Astakhov, O.; Finger, F.; Pfanner, G.; Freysoldt, C.; Neugebauer, J.; Bittl, R.; Teutloff, C.

2011-12-01

Multifrequency pulsed electron paramagnetic resonance (EPR) spectroscopy using S-, X-, Q-, and W-band frequencies (3.6, 9.7, 34, and 94 GHz, respectively) was employed to study paramagnetic coordination defects in undoped hydrogenated amorphous silicon (a-Si:H). The improved spectral resolution at high magnetic field reveals a rhombic splitting of the g tensor with the following principal values: gx=2.0079, gy=2.0061, and gz=2.0034, and shows pronounced g strain, i.e., the principal values are widely distributed. The multifrequency approach furthermore yields precise 29Si hyperfine data. Density functional theory (DFT) calculations on 26 computer-generated a-Si:H dangling-bond models yielded g values close to the experimental data but deviating hyperfine interaction values. We show that paramagnetic coordination defects in a-Si:H are more delocalized than computer-generated dangling-bond defects and discuss models to explain this discrepancy.

Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124Xe

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

Radich, A. J.; Garrett, P. E.; Allmond, J. M.

The nuclear structure of 124Xe has been investigated via measurements of the β +/EC decay of 124Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2 + → 0 + in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study,more » $$B(E2; 2^+_3 → 0^+_2)$$ = 78(13) W.u. and $$B(E2; 2^+_4 → 0^+_3)$$ = 53(12) W.u. were determined. The $$0^+_3$$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te( 3He,n) 124Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.« less

Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124Xe

DOE PAGES

Radich, A. J.; Garrett, P. E.; Allmond, J. M.; ...

2015-04-01

The nuclear structure of 124Xe has been investigated via measurements of the β +/EC decay of 124Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2 + → 0 + in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study,more » $$B(E2; 2^+_3 → 0^+_2)$$ = 78(13) W.u. and $$B(E2; 2^+_4 → 0^+_3)$$ = 53(12) W.u. were determined. The $$0^+_3$$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te( 3He,n) 124Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.« less

Physically-based biodosimetry using in vivo EPR of teeth in patients undergoing total body irradiation

PubMed Central

Williams, Benjamin B.; Dong, Ruhong; Nicolalde, Roberto J.; Matthews, Thomas P.; Gladstone, David J.; Demidenko, Eugene; Zaki, Bassem I.; Salikhov, Ildar K.; Lesniewski, Piotr N.; Swartz, Harold M.

2014-01-01

Purpose The ability to estimate individual exposures to radiation following a large attack or incident has been identified as a necessity for rational and effective emergency medical response. In vivo electron paramagnetic resonance (EPR) spectroscopy of tooth enamel has been developed to meet this need. Materials and methods A novel transportable EPR spectrometer, developed to facilitate tooth dosimetry in an emergency response setting, was used to measure upper incisors in a model system, in unirradiated subjects, and in patients who had received total body doses of 2 Gy. Results A linear dose response was observed in the model system. A statistically significant increase in the intensity of the radiation-induced EPR signal was observed in irradiated versus unirradiated subjects, with an estimated standard error of dose prediction of 0.9 + 0.3 Gy. Conclusions These results demonstrate the current ability of in vivo EPR tooth dosimetry to distinguish between subjects who have not been irradiated and those who have received exposures that place them at risk for acute radiation syndrome. Procedural and technical developments to further increase the precision of dose estimation and ensure reliable operation in the emergency setting are underway. With these developments EPR tooth dosimetry is likely to be a valuable resource for triage following potential radiation exposure of a large population. PMID:21696339

W-band GaAs camel-cathode Gunn devices produced by MBE

NASA Astrophysics Data System (ADS)

Beall, R. B.; Battersby, S. J.; Grecian, P. J.; Jones, S.; Smith, G.

1989-06-01

The dc and microwave performance of a novel second-harmonic W-band GaAs Gunn device incorporating a camel barrier are reported. Comparison with conventional Gunn devices shows significant improvement in power output and dc to RF conversion efficiency for the new structure. The frequency at which the maximum power is produced is lower for the camel cathode Gunn device, an observation attributed to a reduction in the length of the acceleration zone.

Optical and EPR studies of barium alumino borate glasses containing Cu2+ ions

NASA Astrophysics Data System (ADS)

Ahmed, Mohamad Raheem; Phani, A. V. Lalitha; Narsimha Chary, M.; Shareefuddin, Md.

2018-05-01

Glass containing Cu2+ ions in (30-x) BaO-xAl2O3-69.5B2O3-0.5CuO (0 ≤ x ≤ 15 mol %) were prepared by the conventional melt quenching technique. Peak free X-ray diffractograms confirmed the amorphous nature of the glass samples. Spectroscopic studies such as optical absorption, EPR were studied to understand the effect of modifier oxide and CuO dopant. From EPR spectra the spin-Hamiltonian parameter were evaluated. The ground state of Cu2+ is dx2-y2 (2B1g state) and the site symmetry around Cu2+ is tetragonally distorted octahedral. A broad optical absorption band was observed for all the glasses containing Cu2+ ions corresponding to the 2B1g → 2B2g transition. The optical band gap and Urbach energy values are calculated.

High-resolution study of oscillator strengths and predissociation rates for 13C18O . W-X bands and Rydberg complexes between 92.9 and 93.5 nm

NASA Astrophysics Data System (ADS)

Eidelsberg, M.; Lemaire, J. L.; Federman, S. R.; Heays, A. N.; Stark, G.; Lyons, J. R.; Gavilan, L.; de Oliveira, N.

2017-06-01

We carried out experiments at the SOLEIL synchrotron facility to acquire data for modelling CO photochemistry in the vacuum ultraviolet. We report oscillator strengths and predissociation rates for four vibrational bands associated with transitions from the v = 0 level of the X1Σ+ ground state to the v = 0-3 vibrational levels of the core excited W1Π Rydberg state, and for three overlapping bands associated with the 4pπ, 5pπ, and 5pσ Rydberg states between 92.9 and 93.4 nm in 13C18O. These results complete those obtained in the same conditions for 12C16O, 13C16O, and 12C18O recently published by us, and extend the development of a comprehensive database of line positions, oscillator strengths, and linewidths of photodissociating transitions for CO isotopologues. Absorption spectra were recorded using the Vacuum UltraViolet Fourier Transform Spectrometer (VUV-FTS) installed on the Dichroïsme Et Spectroscopie par Interaction avec le Rayonnement Synchrotron (DESIRS) beamline at SOLEIL. The resolving power of the measurements, R = 300 000 to 400 000, allows the analysis of individual line strengths and widths within the bands. Gas column densities in the differentially pumped system were calibrated using the B-X (0-0) band at 115.1 nm in 13C18O.

A high-resolution oxygen A-band spectrometer (HABS) and its radiation closure

NASA Astrophysics Data System (ADS)

Min, Q.; Yin, B.; Li, S.; Berndt, J.; Harrison, L.; Joseph, E.; Duan, M.; Kiedron, P.

2014-06-01

Various studies indicate that high-resolution oxygen A-band spectrum has the capability to retrieve the vertical profiles of aerosol and cloud properties. To improve the understanding of oxygen A-band inversions and utility, we developed a high-resolution oxygen A-band spectrometer (HABS), and deployed it at Howard University Beltsville site during the NASA Discover Air-Quality Field Campaign in July, 2011. By using a single telescope, the HABS instrument measures the direct solar and the zenith diffuse radiation subsequently. HABS exhibits excellent performance: stable spectral response ratio, high signal-to-noise ratio (SNR), high-spectrum resolution (0.016 nm), and high out-of-band rejection (10-5). For the spectral retrievals of HABS measurements, a simulator is developed by combining a discrete ordinates radiative transfer code (DISORT) with the High Resolution Transmission (HITRAN) database HITRAN2008. The simulator uses a double-k approach to reduce the computational cost. The HABS-measured spectra are consistent with the related simulated spectra. For direct-beam spectra, the discrepancies between measurements and simulations, indicated by confidence intervals (95%) of relative difference, are (-0.06, 0.05) and (-0.08, 0.09) for solar zenith angles of 27 and 72°, respectively. For zenith diffuse spectra, the related discrepancies between measurements and simulations are (-0.06, 0.05) and (-0.08, 0.07) for solar zenith angles of 27 and 72°, respectively. The main discrepancies between measurements and simulations occur at or near the strong oxygen absorption line centers. They are mainly due to two kinds of causes: (1) measurement errors associated with the noise/spikes of HABS-measured spectra, as a result of combined effects of weak signal, low SNR, and errors in wavelength registration; (2) modeling errors in the simulation, including the error of model parameters setting (e.g., oxygen absorption line parameters, vertical profiles of temperature and

EPR, optical and superposition model study of Mn2+ doped L+ glutamic acid

NASA Astrophysics Data System (ADS)

Kripal, Ram; Singh, Manju

2015-12-01

Electron paramagnetic resonance (EPR) study of Mn2+ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from 6A1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter-electronic repulsion parameters B = 869 cm-1, C = 2080 cm-1 and cubic crystal field splitting parameter Dq = 730 cm-1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.

W-Band Technology and Techniques for Analog Millimeter-Wave Photonics

DTIC Science & Technology

2015-08-19

being the average laser power at angular frequency ω. The constant κ is introduced such that ( )* 20 0 2P E E κ= . The term ( )tφ is the optical...typical link gain equations. Multiplexing techniques, which are not trivial with W-Band modulation, are described. 19-08-2015 Memorandum Office of...1 2 BASIC LINK CONFIGURATIONS………………………………………….……….… 2 3 COMPONENT TECHNOLOGY…………….……………….………..….…………….. 5 4 MULTIPLEXING TECHNIQUES

In vivo EPR extracellular pH-metry in tumors using a triphosphonated trityl radical.

PubMed

Marchand, Valérie; Levêque, Philippe; Driesschaert, Benoit; Marchand-Brynaert, Jacqueline; Gallez, Bernard

2017-06-01

The ability to assess the extracellular pH (pHe) is an important issue in oncology, because extracellular acidification is associated with tumor aggressiveness and resistance to cytotoxic therapies. In this study, a stable triphosphonated triarylmethyl (TPTAM) radical was qualified as a pHe electron paramagnetic resonance (EPR) molecular reporter. Calibration of hyperfine splitting as a function of pH was performed using a 1.2-GHz EPR spectrometer. Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was used as an extracellular paramagnetic broadening agent to assess the localization of TPTAM when incubated with cells. In vivo EPR pH-metry was performed in MDA, SiHa, and TLT tumor models and in muscle. Bicarbonate therapy was used to modulate the tumor pHe. EPR measurements were compared with microelectrode readouts. The hyperfine splitting of TPTAM was strongly pH-dependent around the pKa of the probe (pKa = 6.99). Experiments with Gd-DTPA demonstrated that TPTAM remained in the extracellular compartment. pHe was found to be more acidic in the MDA, SiHa, and TLT tumor models compared with muscle. Treatment of animals by bicarbonate induced an increase in pHe in tumors: similar variations in pHe were found when using in vivo EPR or invasive microelectrodes measurements. This study demonstrates the potential usefulness of TPTAM for monitoring pHe in tumors. Magn Reson Med 77:2438-2443, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

EPR characterization of ascorbyl and sulfur dioxide anion radicals trapped during the reaction of bovine Cytochrome c Oxidase with molecular oxygen

NASA Astrophysics Data System (ADS)

Yu, Michelle A.; Egawa, Tsuyoshi; Yeh, Syun-Ru; Rousseau, Denis L.; Gerfen, Gary J.

2010-04-01

The reaction intermediates of reduced bovine Cytochrome c Oxidase (CcO) were trapped following its reaction with oxygen at 50 μs-6 ms by innovative freeze-quenching methods and studied by EPR. When the enzyme was reduced with either ascorbate or dithionite, distinct radicals were generated; X-band (9 GHz) and D-band (130 GHz) CW-EPR measurements support the assignments of these radicals to ascorbyl and sulfur dioxide anion radical (SO2-rad), respectively. The X-band spectra show a linewidth of 12 G for the ascorbyl radical and 11 G for the SO2-rad radical and an isotropic g-value of 2.005 for both species. The D-band spectra reveal clear distinctions in the g-tensors and powder patterns of the two species. The ascorbyl radical spectrum displays approximate axial symmetry with g-values of gx = 2.0068, gy = 2.0066, and gz = 2.0023. The SO2-rad>/SUP> radical has rhombic symmetry with g-values of gx = 2.0089, gy = 2.0052, and gz = 2.0017. When the contributions from the ascorbyl and SO2-rad radicals were removed, no protein-based radical on CcO could be identified in the EPR spectra.

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

NASA Astrophysics Data System (ADS)

De Vicente, F. S.; Santos, F. A.; Simões, B. S.; Dias, S. T.; Siu Li, M.

2014-12-01

Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV-VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV-VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the 3P1 → 1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415 nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (2E → 4A2) and another intense band from 700 to 850 nm (4T2 → 4A2).

Astrochemically Relevant Molecules in the W-Band Region

NASA Astrophysics Data System (ADS)

Arenas, Benjamin E.; Steber, Amanda; Gruet, Sébastien; Schnell, Melanie

2017-06-01

The interplay between laboratory spectroscopy and observational astronomy has allowed for the chemical complexity of the interstellar medium (ISM) to be explored. Our laboratory studies involve the measurement of the rotational spectra of commercially available samples in the region 75-110 GHz, thus covering a portion of Band 3 of the Atacama Large Millimeter/submillimeter Array (ALMA). Up until recently, we have concentrated on medium-sized (5 to 9 heavy atoms) nitrogen- and oxygen-containing molecules and their vibrationally excited states. Examples include amino alcohols, such as alaninol (2-amino-1-propanol), and cyanides. Further, we have extended the capabilities of our segmented chirped-pulse spectrometer [1] with electrical discharge apparatus. We present here the recent results from our set-up, including the typical rotational spectra of astrochemically relevant samples and the discharge-enabled rotational spectroscopy of mixtures of simple organic molecules. These experimental results have yielded transitions that will facilitate the detection of these molecules in the ISM with ALMA, and the discharge experiments should allow us to consider formation pathways of organic molecules from smaller building blocks. [1] B.E. Arenas, S. Gruet, A.L. Steber, B.M. Giuliano, M. Schnell, Phys. Chem. Chem. Phys. 19 (2017) 1751-1756.

EPR: Evidence and fallacy.

PubMed

Nichols, Joseph W; Bae, You Han

2014-09-28

The enhanced permeability and retention (EPR) of nanoparticles in tumors has long stood as one of the fundamental principles of cancer drug delivery, holding the promise of safe, simple and effective therapy. By allowing particles preferential access to tumors by virtue of size and longevity in circulation, EPR provided a neat rationale for the trend toward nano-sized drug carriers. Following the discovery of the phenomenon by Maeda in the mid-1980s, this rationale appeared to be well justified by the flood of evidence from preclinical studies and by the clinical success of Doxil. Clinical outcomes from nano-sized drug delivery systems, however, have indicated that EPR is not as reliable as previously thought. Drug carriers generally fail to provide superior efficacy to free drug systems when tested in clinical trials. A closer look reveals that EPR-dependent drug delivery is complicated by high tumor interstitial fluid pressure (IFP), irregular vascular distribution, and poor blood flow inside tumors. Furthermore, the animal tumor models used to study EPR differ from clinical tumors in several key aspects that seem to make EPR more pronounced than in human patients. On the basis of this evidence, we believe that EPR should only be invoked on a case-by-case basis, when clinical evidence suggests the tumor type is susceptible. Copyright © 2014 Elsevier B.V. All rights reserved.

Injectable LiNc-BuO loaded microspheres as in vivo EPR oxygen sensors after co-implantation with tumor cells.

PubMed

Frank, Juliane; Gündel, Daniel; Drescher, Simon; Thews, Oliver; Mäder, Karsten

2015-12-01

Electron paramagnetic resonance (EPR) oximetry is a technique which allows accurate and repeatable oxygen measurements. We encapsulated a highly oxygen sensitive particulate EPR spin probe into microparticles to improve its dispersibility and, hence, facilitate the administration. These biocompatible, non-toxic microspheres contained 5-10 % (w/w) spin probe and had an oxygen sensitivity of 0.60 ± 0.01 µT/mmHg. To evaluate the performance of the microparticles as oxygen sensors, they were co-implanted with syngeneic tumor cells in 2 different rat strains. Thus, tissue injury was avoided and the microparticles were distributed all over the tumor tissue. Dynamic changes of the intratumoral oxygen partial pressure during inhalation of 8 %, 21 %, or 100 % oxygen were monitored in vivo by EPR spectroscopy and quantified. Values were verified in vivo by invasive fluorometric measurements using Oxylite probes and ex vivo by pimonidazole adduct accumulation. There were no hints that the tumor physiology or tissue oxygenation had been altered by the microparticles. Hence, these microprobes offer great potential as oxygen sensors in preclinical research, not only for EPR spectroscopy but also for EPR imaging. For instance, the assessment of tissue oxygenation during therapeutic interventions might help understanding pathophysiological processes and lead to an individualized treatment planning or the use of formulations with hypoxia triggered release of active agents. Copyright © 2015 Elsevier Inc. All rights reserved.

Development of a W-band Serpentine Waveguide Amplifier based on a UV-LIGA Microfabricated Copper Circuit

DTIC Science & Technology

2013-03-01

beam tunnel [5,6] for a high - power , wideband W- band traveling-wave tube (TWT) amplifier. UV-LIGA is also a promising technique at higher...wide- band , high - power operation of the amplifier [7, 8]. The interaction circuit consists of two traveling-wave stages separated by a power ...technique produces monolithic all-copper circuits, integrated with electron beam tunnel, suitable for high - power continuous-wave operation [1]. We

Portable instant display and analysis reflectance spectrometer

NASA Technical Reports Server (NTRS)

Goetz, Alexander F. H. (Inventor)

1985-01-01

A portable analysis spectrometer (10) for field mineral identification is coupled to a microprocessor (11) and memory (12) through a bus (13) and A/D converter (14) to display (16) a spectrum of reflected radiation in a band selected by an adjustable band spectrometer (20) and filter (23). A detector array (21) provides output signals at spaced frequencies within the selected spectrometer band which are simultaneously converted to digital form for display. The spectrum displayed is compared with a collection of spectra for known minerals. That collection is stored in memory and selectively displayed with the measured spectrum, or stored in a separate portfolio. In either case, visual comparison is made. Alternatively, the microprocessor may use an algorithm to make the comparisons in search for the best match of the measured spectrum with one of the stored spectra to identify the mineral in the target area.

Small-volume potentiometric titrations: EPR investigations of Fe-S cluster N2 in mitochondrial complex I.

PubMed

Wright, John J; Salvadori, Enrico; Bridges, Hannah R; Hirst, Judy; Roessler, Maxie M

2016-09-01

EPR-based potentiometric titrations are a well-established method for determining the reduction potentials of cofactors in large and complex proteins with at least one EPR-active state. However, such titrations require large amounts of protein. Here, we report a new method that requires an order of magnitude less protein than previously described methods, and that provides EPR samples suitable for measurements at both X- and Q-band microwave frequencies. We demonstrate our method by determining the reduction potential of the terminal [4Fe-4S] cluster (N2) in the intramolecular electron-transfer relay in mammalian respiratory complex I. The value determined by our method, E m7 =-158mV, is precise, reproducible, and consistent with previously reported values. Our small-volume potentiometric titration method will facilitate detailed investigations of EPR-active centres in non-abundant and refractory proteins that can only be prepared in small quantities. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

300 MHz continuous wave electron paramagnetic resonance spectrometer for small animal in vivo imaging

NASA Astrophysics Data System (ADS)

Koscielniak, J.; Devasahayam, N.; Moni, M. S.; Kuppusamy, P.; Yamada, K.; Mitchell, J. B.; Krishna, M. C.; Subramanian, S.

2000-11-01

Design and construction of an electron paramagnetic resonance (EPR) spectrometer, operating in the continuous wave mode in the radio frequency (rf) region, and capable of performing spectroscopy and in vivo imaging of paramagnetic spin probes is described. A resonant frequency of 300 MHz was chosen to provide the required sensitivity at nontoxic levels of commonly used spin probes and penetration of the rf in small animals. Three major components, the magnet, the radio frequency signal detection bridge, and the data acquisition module are described in this article. Integration of a rapid scan capability to reduce imaging time is also described. Two- and three-dimensional EPR images of the spin probe distribution in phantom objects as well as from in vivo experiments are reported. From the EPR images, morphology of some internal organs could be recognized. EPR images of the spin probe distribution in mice suggest differences in perfusion of the spin probe between normal and tumor regions. Addition of a spectral dimension to spatial images should enable differentiation of oxygen status in normal and pathological conditions.

Fully Polarimetric Passive W-band Millimeter Wave Imager for Wide Area Search

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

Tedeschi, Jonathan R.; Bernacki, Bruce E.; Sheen, David M.

2013-09-27

We describe the design and phenomenology imaging results of a fully polarimetric W-band millimeter wave (MMW) radiometer developed by Pacific Northwest National Laboratory for wide-area search. Operating from 92 - 94 GHz, the W-band radiometer employs a Dicke switching heterodyne design isolating the horizontal and vertical mm-wave components with 40 dB of polarization isolation. Design results are presented for both infinite conjugate off-axis parabolic and finite conjugate off-axis elliptical fore-optics using optical ray tracing and diffraction calculations. The received linear polarizations are down-converted to a microwave frequency band and recombined in a phase-shifting network to produce all six orthogonal polarizationmore » states of light simultaneously, which are used to calculate the Stokes parameters for display and analysis. The resulting system performance produces a heterodyne receiver noise equivalent delta temperature (NEDT) of less than 150m Kelvin. The radiometer provides novel imaging capability by producing all four of the Stokes parameters of light, which are used to create imagery based on the polarization states associated with unique scattering geometries and their interaction with the down welling MMW energy. The polarization states can be exploited in such a way that man-made objects can be located and highlighted in a cluttered scene using methods such as image comparison, color encoding of Stokes parameters, multivariate image analysis, and image fusion with visible and infrared imagery. We also present initial results using a differential imaging approach used to highlight polarization features and reduce common-mode noise. Persistent monitoring of a scene using the polarimetric passive mm-wave technique shows great promise for anomaly detection caused by human activity.« less

Locations of radical species in black pepper seeds investigated by CW EPR and 9 GHz EPR imaging

NASA Astrophysics Data System (ADS)

Nakagawa, Kouichi; Epel, Boris

2014-10-01

In this study, noninvasive 9 GHz electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate the locations of paramagnetic species in black pepper seeds without further irradiation. First, lithium phthalocyanine (LiPC) phantom was used to examine 9 GHz EPR imaging capabilities. The 9 GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2 mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe3+, and Mn2+ complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1 h. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species were mostly located at the seed surface. Fewer radicals were found inside the seed. We demonstrated that the CW EPR and 9 GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds.

Locations of radical species in black pepper seeds investigated by CW EPR and 9GHz EPR imaging.

PubMed

Nakagawa, Kouichi; Epel, Boris

2014-10-15

In this study, noninvasive 9GHz electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate the locations of paramagnetic species in black pepper seeds without further irradiation. First, lithium phthalocyanine (LiPC) phantom was used to examine 9GHz EPR imaging capabilities. The 9GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe(3+), and Mn(2+) complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1h. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species were mostly located at the seed surface. Fewer radicals were found inside the seed. We demonstrated that the CW EPR and 9GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds. Copyright © 2014 Elsevier B.V. All rights reserved.

Homogeneity and EPR metrics for assessment of regular grids used in CW EPR powder simulations.

PubMed

Crăciun, Cora

2014-08-01

CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids' EPR behaviour, for different spin system symmetries. The metrics' efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method. Copyright © 2014 Elsevier Inc. All rights reserved.

S-band low noise amplifier and 40 kW high power amplifier subsystems of Japanese Deep Space Earth Station

NASA Astrophysics Data System (ADS)

Honma, K.; Handa, K.; Akinaga, W.; Doi, M.; Matsuzaki, O.

This paper describes the design and the performance of the S-band low noise amplifier and the S-band high power amplifier that have been developed for the Usuda Deep Space Station of the Institute of Space and Astronautical Science (ISAS), Japan. The S-band low noise amplifier consists of a helium gas-cooled parametric amplifier followed by three-stage FET amplifiers and has a noise temperature of 8 K. The high power amplifier is composed of two 28 kW klystrons, capable of transmitting 40 kW continuously when two klystrons are combined. Both subsystems are operating quite satisfactorily in the tracking of Sakigake and Suisei, the Japanese interplanetary probes for Halley's comet exploration, launched by ISAS in 1985.

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

PubMed

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

2017-12-01

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

Ground-Based Radiometric Measurements of Slant Path Attenuation in the V/W Bands

DTIC Science & Technology

2016-04-01

GROUND-BASED RADIOMETRIC MEASUREMENTS OF SLANT PATH ATTENUATION IN THE V/W BANDS APRIL 2016 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE...2. REPORT TYPE FINAL TECHNICAL REPORT 3. DATES COVERED (From - To) OCT 2012 – SEP 2015 4. TITLE AND SUBTITLE GROUND-BASED RADIOMETRIC MEASUREMENTS ...SUPPLEMENTARY NOTES 14. ABSTRACT Ground-based radiometric techniques were applied to measure the slant path attenuation cumulative distribution function to

Free Radical Scavenging Activity of Drops and Spray Containing Propolis-An EPR Examination.

PubMed

Olczyk, Pawel; Komosinska-Vassev, Katarzyna; Ramos, Pawel; Mencner, Lukasz; Olczyk, Krystyna; Pilawa, Barbara

2017-01-13

The influence of heating at a temperature of 50 °C and UV-irradiation of propolis drops and spray on their free radical scavenging activity was determined. The kinetics of interactions of the propolis samples with DPPH free radicals was analyzed. Interactions of propolis drops and propolis spray with free radicals were examined by electron paramagnetic resonance spectroscopy. A spectrometer generating microwaves of 9.3 GHz frequency was used. The EPR spectra of the model DPPH free radicals were compared with the EPR spectra of DPPH in contact with the tested propolis samples. The antioxidative activity of propolis drops and propolis spray decreased after heating at the temperature of 50 °C. A UV-irradiated sample of propolis drops more weakly scavenged free radicals than an untreated sample. The antioxidative activity of propolis spray increased after UV-irradiation. The sample of propolis drops heated at the temperature of 50 °C quenched free radicals faster than the unheated sample. UV-irradiation weakly changed the kinetics of propolis drops or spray interactions with free radicals. EPR analysis indicated that propolis drops and spray should not be stored at a temperature of 50 °C. Propolis drops should not be exposed to UV-irradiation.

EPR-based material modelling of soils

NASA Astrophysics Data System (ADS)

Faramarzi, Asaad; Alani, Amir M.

2013-04-01

In the past few decades, as a result of the rapid developments in computational software and hardware, alternative computer aided pattern recognition approaches have been introduced to modelling many engineering problems, including constitutive modelling of materials. The main idea behind pattern recognition systems is that they learn adaptively from experience and extract various discriminants, each appropriate for its purpose. In this work an approach is presented for developing material models for soils based on evolutionary polynomial regression (EPR). EPR is a recently developed hybrid data mining technique that searches for structured mathematical equations (representing the behaviour of a system) using genetic algorithm and the least squares method. Stress-strain data from triaxial tests are used to train and develop EPR-based material models for soil. The developed models are compared with some of the well-known conventional material models and it is shown that EPR-based models can provide a better prediction for the behaviour of soils. The main benefits of using EPR-based material models are that it provides a unified approach to constitutive modelling of all materials (i.e., all aspects of material behaviour can be implemented within a unified environment of an EPR model); it does not require any arbitrary choice of constitutive (mathematical) models. In EPR-based material models there are no material parameters to be identified. As the model is trained directly from experimental data therefore, EPR-based material models are the shortest route from experimental research (data) to numerical modelling. Another advantage of EPR-based constitutive model is that as more experimental data become available, the quality of the EPR prediction can be improved by learning from the additional data, and therefore, the EPR model can become more effective and robust. The developed EPR-based material models can be incorporated in finite element (FE) analysis.

Statistical Analysis of Instantaneous Frequency Scaling Factor as Derived from Optical Disdrometer Measurements at V/W Bands

NASA Technical Reports Server (NTRS)

Zemba, Michael; Nessel, James; Tarasenko, Nicholas; Lane, Steven

2017-01-01

Since October 2015, NASA Glenn Research Center (GRC) and the Air Force Research Laboratory (AFRL) have collaboratively operated an RF terrestrial link in Albuquerque, New Mexico to characterize atmospheric propagation phenomena at 72 and 84 GHz. The W/V-band Terrestrial Link Experiment (WTLE) consists of coherent transmitters at each frequency on the crest of the Sandia Mountains and a corresponding pair of receivers in south Albuquerque. The beacon receivers provide a direct measurement of the link attenuation, while concurrent weather instrumentation provides a measurement of the atmospheric conditions. Among the available weather instruments is an optical disdrometer which yields an optical measurement of rain rate, as well as droplet size and velocity distributions (DSD, DVD). In particular, the DSD can be used to derive an instantaneous scaling factor (ISF) by which the measured data at one frequency can be scaled to another - for example, scaling the 72 GHz to an expected 84 GHz timeseries. Given the availability of both the DSD prediction and the directly observed 84 GHz attenuation, WTLE is thus uniquely able assess DSD-derived instantaneous frequency scaling at the V/W-bands. Previous work along these lines has investigated the DSD-derived ISF at Ka and Q-band (20 GHz to 40 GHz) using a satellite beacon receiver experiment in Milan, Italy. This work will expand the investigation to terrestrial links in the V/W-bands, where the frequency scaling factor is lower and where the link is also much more sensitive to attenuation by rain, clouds, and other atmospheric effects.

HiRadProp: High-Frequency Modeling and Prediction of Tropospheric Radiopropagation Parameters from Ground-Based-Multi-Channel Radiometric Measurements between Ka and W Band

DTIC Science & Technology

2016-05-11

new physically -based prediction models for all-weather path attenuation estimation at Ka, V and W band from multi- channel microwave radiometric data...of new physically -based prediction models for all-weather path attenuation estimation at Ka, V and W band from multi- channel microwave radiometric...the medium behavior at these frequency bands from both a physical and a statistical point of view (e.g., [5]-[7]). However, these campaigns are

EPR and optical investigations of LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor

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

Singh, Vijay, E-mail: vijayjiin2006@yahoo.com; Sivaramaiah, G.; Rao, J.L.

2014-12-15

Graphical abstract: The EPR spectrum of as-prepared LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor at 110 K. - Highlights: • Using the combustion synthesis, LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared in a few minutes. • Optical investigation indicates that Cr{sup 3+} ions are present in octahedral symmetry. • The EPR signals indicate that exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs in weakly distorted sites. - Abstract: The LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared by a low-temperature combustion synthesis method. As-prepared combustion synthesized powder was characterized using powder X-ray diffraction (XRD), diffuse reflectance (DRS), electron paramagnetic resonance (EPR) andmore » photoluminescence (PL) studies. The X-ray diffraction pattern reveals crystalline hexagonal phases. The UV–vis diffuse reflectance spectrum exhibits three broad bands characteristic of Cr{sup 3+} ions in octahedral symmetry. The EPR spectrum exhibits several resonance signals. The signals with the effective g values at g = 4.84, 3.64 and 2.26 have been attributed to the isolated Cr{sup 3+} ions. The signal with the effective g value at g = 1.94 has been attributed to exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs. The PL studies exhibit several bands characteristic of Cr{sup 3+} ions in octahedral symmetry.« less

Moving Difference (MDIFF) Non-adiabatic rapid sweep (NARS) EPR of copper(II)

PubMed Central

Hyde, James S.; Bennett, Brian; Kittell, Aaron W.; Kowalski, Jason M.; Sidabras, Jason W.

2014-01-01

Non Adiabatic Rapid Sweep (NARS) EPR spectroscopy has been introduced for application to nitroxide-labeled biological samples (AW Kittell et al, (2011)). Displays are pure absorption, and are built up by acquiring data in spectral segments that are concatenated. In this paper we extend the method to frozen solutions of copper-imidazole, a square planar copper complex with four in-plane nitrogen ligands. Pure absorption spectra are created from concatenation of 170 5-gauss segments spanning 850 G at 1.9 GHz. These spectra, however, are not directly useful since nitrogen superhyperfine couplings are barely visible. Application of the moving difference (MDIFF) algorithm to the digitized NARS pure absorption spectrum is used to produce spectra that are analogous to the first harmonic EPR. The signal intensity is about 4 times higher than when using conventional 100 kHz field modulation, depending on line shape. MDIFF not only filters the spectrum, but also the noise, resulting in further improvement of the SNR for the same signal acquisition time. The MDIFF amplitude can be optimized retrospectively, different spectral regions can be examined at different amplitudes, and an amplitude can be used that is substantially greater than the upper limit of the field modulation amplitude of a conventional EPR spectrometer, which improves the signal-to-noise ratio of broad lines. PMID:24036469

Investigation of radical locations in various sesame seeds by CW EPR and 9-GHz EPR imaging.

PubMed

Nakagawa, K; Hara, H

2015-01-01

We investigated the location of radical in various sesame seeds using continuous-wave (CW) electron paramagnetic resonance (EPR) and 9-GHz EPR imaging. CW EPR detected persistent radicals (single line) for various sesame seeds. The EPR linewidth of black sesame seeds was narrower than that of the irradiated white sesame seeds. A very small signal was detected for the white sesame seeds. Two-dimensional (2D) imaging using a 9-GHz EPR imager showed that radical locations vary for various sesame seeds. The paramagnetic species in black sesame seeds were located on the seed coat (skin) and in the hilum region. The signal with the highest intensity was obtained from the hilum part. A very low-intensity image was observed for the white sesame seeds. In addition, the 2D imaging of the irradiated white sesame seeds showed that free radicals were located throughout the entire seed. For the first time, CW EPR and 9-GHz EPR imaging showed the exact location of radical species in various sesame seeds.

Combining EPR spectroscopy and X-ray crystallography to elucidate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals.

PubMed

Consentius, Philipp; Gohlke, Ulrich; Loll, Bernhard; Alings, Claudia; Heinemann, Udo; Wahl, Markus C; Risse, Thomas

2017-08-09

Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling is used to investigate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals. Within a single crystal, the oriented ensemble of spin bearing moieties results in a strong angle dependence of the EPR spectra. A quantitative description of the EPR spectra requires the determination of the unit cell orientation with respect to the sample tube and the orientation of the spin bearing moieties within the crystal lattice. Angle dependent EPR spectra were analyzed by line shape simulations using the stochastic Liouville equation approach developed by Freed and co-workers and an effective Hamiltonian approach. The gain in spectral information obtained from the EPR spectra of single crystalline samples taken at different frequencies, namely the X-band and Q-band, allows us to discriminate between motional models describing the spectra of isotropic solutions similarly well. In addition, it is shown that the angle dependent single crystal spectra allow us to identify two spin label rotamers with very similar side chain dynamics. These results demonstrate the utility of single crystal EPR spectroscopy in combination with spectral line shape simulation techniques to extract valuable dynamic information not readily available from the analysis of isotropic systems. In addition, it will be shown that the loss of electron density in high resolution diffraction experiments at room temperature does not allow us to conclude that there is significant structural disorder in the system.

15 pixels digital autocorrelation spectrometer system

NASA Astrophysics Data System (ADS)

Lee, Changhoon; Kim, Hyo-Ryung; Kim, Kwang-Dong; Chung, Mun-Hee; Timoc, C.

2006-06-01

In this paper describes the system configuration and the some performance test results of the 15 pixels digital autocorrelation spectrometer to be used at the Taeduk Radio Astronomy Observatory (TRAO) of Korea. This autocorrelation spectrometer instrument enclosed in a 3-slot VXI module and controlled via a USB port by a backend PC. This spectrometer system consists of the 4 band-pass filters unit, the digitizer, the 512 lags correlator, the clock distribution unit, and USB controller. And here we describe the frequency accuracy and the root-mean-square noise characteristic of this spectrometer. After some calibration procedure, this spectrometer can be use as the back-end system at TRAO for the 3x5 focal plane array receivers.

Single crystal EPR study at 95 GHz of a large Fe based molecular nanomagnet: toward the structuring of magnetic nanoparticle properties.

PubMed

Castelli, L; Fittipaldi, M; Powell, A K; Gatteschi, D; Sorace, L

2011-08-28

A W-band single-crystal EPR study has been performed on a molecular cluster comprising 19 iron(III) ions bridged by oxo- hydroxide ions, Fe(19), in order to investigate magnetic nanosystems with a behavior in between the one of Magnetic NanoParticles (MNP) and that of Single Molecule Magnets (SMM). The Fe(19) has a disk-like shape: a planar Fe(7) core with a brucite (Mg(OH)(2)) structure enclosed in a "shell" of 12 Fe(III) ions. EPR and magnetic measurements revealed an S = 35/2 ground state with an S = 33/2 excited state lying ∼ 8 K above. The presence of other low-lying excited states was also envisaged. Rhombic Zero Field Splitting (ZFS) tensors were determined, the easy axes lying in the Fe(19) plane for both the multiplets. At particular temperatures and orientations, a partially resolved fine structure could be observed which could not be distinguished in powder spectra, due to orientation disorder. The similarities of the EPR behavior of Fe(19) and MNP, together with the accuracy of single crystal analysis, helped to shed light on spectral features observed in MNP spectra, that is a sharp line at g = 2 and a low intensity transition at g = 4. Moreover, a theoretical analysis has been used to estimate the contribution to the total magnetic anisotropy of core and surface; this latter is crucial in determining the easy axis-type anisotropy, alike that of MNP surface. This journal is © The Royal Society of Chemistry 2011

EPR imaging and HPLC characterization of the pigment-based organic free radical in black soybean seeds.

PubMed

Nakagawa, Kouichi; Maeda, Hayato

2017-02-01

We investigated the location and distribution of paramagnetic species in dry black, brown, and yellow (normal) soybean seeds using electron paramagnetic resonance (EPR), X-band (9 GHz) EPR imaging (EPRI), and HPLC. EPR primarily detected two paramagnetic species in black soybean. These two different radical species were assigned as stable organic radical and Mn 2+  species based on the g values and hyperfine structures. The signal from the stable radical was noted at g ≈ 2.00 and was relatively strong and stable. Subsequent noninvasive two-dimensional (2D) EPRI of the radical present in black soybean revealed that the stable radical was primarily located in the pigmented region of the soybean coat, with very few radicals observed in the soybean cotyledon (interior). Pigments extracted from black soybean were analyzed using HPLC. The major compound was found to be cyanidin-3-glucoside. Multi-EPR and HPLC results indicate that the stable radical was only found within the pigmented region of the soybean coat, and it could be cyanidin-3-glucoside or an oxidative decomposition product.

EPR investigation of UV light effect on calcium carbonate powders with different grain sizes.

PubMed

Kabacińska, Zuzanna; Krzyminiewski, Ryszard; Dobosz, Bernadeta

2014-06-01

This study is based on investigation of calcium carbonate powders with different grain sizes exposed to UV light. Calcium carbonate is widely used in many branches of industry, e.g. as a filler for polymer materials; therefore, knowing its properties, among them also its reaction to UV light, is essential. Samples of powdered calcium carbonate with average grain sizes of 69 and 300 nm and 2.1, 6, 16, 25 µm were used in this investigation. Measurements were performed at room temperature using EPR X-band spectrometer, and they have shown the additional signals induced by the light from Hg lamp. The effect of annealing of the micro-grain samples was also studied. The spectra of four micro-grain samples after irradiation are similar, but there are differences between them and the other two powders, which could be related to the different sizes of their grains. Further studies based on these preliminary results may prove useful in research of photodegradation of CaCO3-filled materials, as well as helpful in increasing the accuracy of dating of archaeological and geological objects. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Partitioning of nitroxides in dispersed systems investigated by ultrafiltration, EPR and NMR spectroscopy.

PubMed

Krudopp, Heimke; Sönnichsen, Frank D; Steffen-Heins, Anja

2015-08-15

The partitioning behavior of paramagnetic nitroxides in dispersed systems can be determined by deconvolution of electron paramagnetic resonance (EPR) spectra giving equivalent results with the validated methods of ultrafiltration techniques (UF) and pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The partitioning behavior of nitroxides with increasing lipophilicity was investigated in anionic, cationic and nonionic micellar systems and 10 wt% o/w emulsions. Apart from EPR spectra deconvolution, the PFG-NMR was used in micellar solutions as a non-destructive approach, while UF based on separation of very small volume of the aqueous phase. As a function of their substituent and lipophilicity, the proportions of nitroxides that were solubilized in the micellar or emulsion interface increased with increasing nitroxide lipophilicity for all emulsifier used. Comparing the different approaches, EPR deconvolution and UF revealed comparable nitroxide proportions that were solubilized in the interfaces. Those proportions were higher than found with PFG-NMR. For PFG-NMR self-diffusion experiments the reduced nitroxides were used revealing a high dynamic of hydroxylamines and emulsifiers. Deconvolution of EPR spectra turned out to be the preferred method for measuring the partitioning behavior of paramagnetic molecules as it enables distinguishing between several populations at their individual solubilization sites. Copyright © 2015 Elsevier Inc. All rights reserved.

Experimental and theoretical investigations on the EPR parameters and molecular orbital bonding coefficients of VO2+ ions in BTTB glasses

NASA Astrophysics Data System (ADS)

Srinivas, B.; Hameed, Abdul; Vijaya Kumar, R.; Narasimha Chary, M.; Shareefuddin, Md.

2018-06-01

The effect of the spin probe VO2+ in 15BaO-15TeO2-10TiO2-(60-x) B2O3-xV2O5 (x = 0.2, 0.4, 0.6, 0.8 mol %) glasses has been studied by employing Electron Paramagnetic Resonance (EPR) and optical absorption spectroscopic techniques. The observed EPR spectra of VO2+ ions were attributed on the basis of well-known spin-Hamiltonian of C4V symmetry. The simulated EPR spectra for VO2+ ions in the present glass system were drawn using Easy spin software. Both the experimental and simulated spectra were found to be in good agreement with each other. The optical absorption spectra exhibited three d-d transition bands due to crystal and tetragonal fields of VO2+ ions. These bands were assigned to 2B2g→ 2Eg, 2B2g→ 2B1g and 2B2g→ 2A1g transitions. The crystal field parameters Dq, Ds and Dt values are calculated. From the EPR and optical data, the molecular bonding coefficients were evaluated. Employing the higher order perturbation formulae of the g factors for 3d1 ion under tetragonally compressed octahedral fields, theoretical studies were carried out. The spin-Hamiltonian parameters ? and ? obtained from both the experimental and theoretical methods were in good agreement with each other.

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

PubMed

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

2018-03-21

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

Design of a double-anode magnetron-injection gun for the W-band gyrotron

NASA Astrophysics Data System (ADS)

Jang, Kwang Ho; Choi, Jin Joo; So, Joon Ho

2015-07-01

A double-anode magnetron-injection gun (MIG) was designed. The MIG is for a W-band 10-kW gyrotron. Analytic equations based on adiabatic theory and angular momentum conservation were used to examine the initial design parameters such as the cathode angle, and the radius of the beam emitting surface. The MIG's performances were predicted by using an electron trajectory code, the EGUN code. The beam spread of the axial velocity, Δvz/vz, obtained from the EGUN code was observed to be 1.34% at α = 1.3. The cathode edge emission and the thermal effect were modeled. The cathode edge emission was found to have a major effect on the velocity spread. The electron beam's quality was significantly improved by affixing non-emissive cylinders to the cathode.

Rapid-scan EPR imaging.

PubMed

Eaton, Sandra S; Shi, Yilin; Woodcock, Lukas; Buchanan, Laura A; McPeak, Joseph; Quine, Richard W; Rinard, George A; Epel, Boris; Halpern, Howard J; Eaton, Gareth R

2017-07-01

In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250MHz. Copyright © 2017 Elsevier Inc. All rights reserved.

Analysis and Design of a Novel W-band SPST Switch by Employing Full-Wave EM Simulator

NASA Astrophysics Data System (ADS)

Xu, Zhengbin; Guo, Jian; Qian, Cheng; Dou, Wenbin

2011-12-01

In this paper, a W-band single pole single throw (SPST) switch based on a novel PIN diode model is presented. The PIN diode is modeled using a full-wave electromagnetic (EM) simulator and its parasitic parameters under both forward and reverse bias states are described by a T-network. By this approach, the measurement-based model, which is usually a must for high performance switch design, is no longer necessary. A compensation structure is optimized to obtain a high isolation of the switch. Accordingly, a W-band SPST switch is designed using a full wave EM simulator. Measurement results agree very well with simulated ones. Our measurements show that the developed switch has less than 1.5 dB insertion loss under the `on' state from 88 GHz to 98 GHz. Isolation greater than 30 dB over 2 GHz bandwidth and greater than 20 dB over 5 GHz bandwidth can be achieved at the center frequency of 94 GHz under the `off' state.

Detection of fatty product falsifications using a portable near infrared spectrometer

NASA Astrophysics Data System (ADS)

Kalinin, A. V.; Krasheninnikov, V. N.

2017-01-01

Spreading sales of counterfeited fatty-oil foods leads to a development of portable and operational analyzer of typical fatty acids (FA) which may be a near infrared (NIR) spectrometer. In this work the calibration models for prediction of named FA were built with the spectra of FT-NIR spectrometer for different absorption bands of the FA. The best parameters were obtained for the wavelength sub-band 1.0-1.8 μ, which includes the 2nd and 3rd overtones of C-H stretching vibrations (near 1.7 and 1.2 μ) and the combination band (1.42 μ). Applicability of the portable spectrometer based on linear NIR array photosensor for the quality analysis of spread, butter and fish oil by the typical FA has been tested.

The Ma_Miss instrument performance, II: Band parameters of rocks powders spectra by Martian VNIR spectrometer

NASA Astrophysics Data System (ADS)

De Angelis, Simone; De Sanctis, Maria Cristina; Ammannito, Eleonora; Carli, Cristian; Di Iorio, Tatiana; Altieri, Francesca

2015-11-01

The Ma_Miss instrument (Mars Multispectral Imager for Subsurface Studies, Coradini et al. (2001)) is a Visible and Near Infrared miniaturized spectrometer that will observe the Martian subsurface in the 0.4-2.2 μm spectral range. The instrument will be entirely hosted within the Drill of the ExoMars-2018 Pasteur Rover: it will allow analyzing the borehole wall excavated by the Drill, at different depths, down to 2 m. The aim will be to investigate and characterize the mineralogy and stratigraphy of the shallow Martian subsurface. A series of spectroscopic measurements have been performed in order to characterize the spectral performances of the laboratory model of the instrument (breadboard). A set of six samples have been analyzed. Each sample (four volcanic rocks, a micritic limestone and a calcite) has been reduced in particulate form, ground, sieved and divided into nine different grain sizes in the range d<0.02÷0.8 mm. Spectroscopic measurements have been performed on all samples using two distinct experimental setup: (a) the Ma_Miss breadboard, and (b) the Spectro-Goniometer setup, both in use in the laboratory at INAF - IAPS. In a previous paper spectral parameters such as the continuum slope and the reflectance level of the spectra have been discussed (De Angelis et al., 2014). In this work we focus our discussion on absorption band parameters (position, depth, area, band slope and asymmetry). We analyzed/investigated the absorption features at 1 μm for the volcanic samples and at 1.4, 1.9 and 2.2 μm for the two carbonate samples. Band parameters have been retrieved from spectra measured with both experimental setup and then compared. The comparison shows that band parameters are mutually consistent: band centers (for carbonate samples) are similar within few percent, and band depth and area values (for carbonates) show consistent trends vs. grain size (decreasing towards coarser grains) for most of samples.

Imaging spectrometer using a liquid crystal tunable filter

NASA Astrophysics Data System (ADS)

Chrien, Thomas G.; Chovit, Christopher; Miller, Peter J.

1993-09-01

A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design. An overview of the prototype system is given along with a description of balloon experiment results. System model performance predictions are given for a future LCTF based imaging spectrometer design. System design considerations of LCTF imaging spectrometers are discussed.

Analyzing Three-Player Quantum Games in an EPR Type Setup

PubMed Central

Chappell, James M.; Iqbal, Azhar; Abbott, Derek

2011-01-01

We use the formalism of Clifford Geometric Algebra (GA) to develop an analysis of quantum versions of three-player non-cooperative games. The quantum games we explore are played in an Einstein-Podolsky-Rosen (EPR) type setting. In this setting, the players' strategy sets remain identical to the ones in the mixed-strategy version of the classical game that is obtained as a proper subset of the corresponding quantum game. Using GA we investigate the outcome of a realization of the game by players sharing GHZ state, W state, and a mixture of GHZ and W states. As a specific example, we study the game of three-player Prisoners' Dilemma. PMID:21818260

Use of EPR to Solve Biochemical Problems

PubMed Central

Sahu, Indra D.; McCarrick, Robert M.; Lorigan, Gary A.

2013-01-01

EPR spectroscopy is a very powerful biophysical tool that can provide valuable structural and dynamic information on a wide variety of biological systems. The intent of this review is to provide a general overview for biochemists and biological researchers on the most commonly used EPR methods and how these techniques can be used to answer important biological questions. The topics discussed could easily fill one or more textbooks; thus, we present a brief background on several important biological EPR techniques and an overview of several interesting studies that have successfully used EPR to solve pertinent biological problems. The review consists of the following sections: an introduction to EPR techniques, spin labeling methods, and studies of naturally occurring organic radicals and EPR active transition metal systems which are presented as a series of case studies in which EPR spectroscopy has been used to greatly further our understanding of several important biological systems. PMID:23961941

Fast algorithm for spectral mixture analysis of imaging spectrometer data

NASA Astrophysics Data System (ADS)

Schouten, Theo E.; Klein Gebbinck, Maurice S.; Liu, Z. K.; Chen, Shaowei

1996-12-01

Imaging spectrometers acquire images in many narrow spectral bands but have limited spatial resolution. Spectral mixture analysis (SMA) is used to determine the fractions of the ground cover categories (the end-members) present in each pixel. In this paper a new iterative SMA method is presented and tested using a 30 band MAIS image. The time needed for each iteration is independent of the number of bands, thus the method can be used for spectrometers with a large number of bands. Further a new method, based on K-means clustering, for obtaining endmembers from image data is described and compared with existing methods. Using the developed methods the available MAIS image was analyzed using 2 to 6 endmembers.

Quantitative analysis of dinuclear manganese(II) EPR spectra

NASA Astrophysics Data System (ADS)

Golombek, Adina P.; Hendrich, Michael P.

2003-11-01

A quantitative method for the analysis of EPR spectra from dinuclear Mn(II) complexes is presented. The complex [(Me 3TACN) 2Mn(II) 2(μ-OAc) 3]BPh 4 ( 1) (Me 3TACN= N, N', N''-trimethyl-1,4,7-triazacyclononane; OAc=acetate 1-; BPh 4=tetraphenylborate 1-) was studied with EPR spectroscopy at X- and Q-band frequencies, for both perpendicular and parallel polarizations of the microwave field, and with variable temperature (2-50 K). Complex 1 is an antiferromagnetically coupled dimer which shows signals from all excited spin manifolds, S=1 to 5. The spectra were simulated with diagonalization of the full spin Hamiltonian which includes the Zeeman and zero-field splittings of the individual manganese sites within the dimer, the exchange and dipolar coupling between the two manganese sites of the dimer, and the nuclear hyperfine coupling for each manganese ion. All possible transitions for all spin manifolds were simulated, with the intensities determined from the calculated probability of each transition. In addition, the non-uniform broadening of all resonances was quantitatively predicted using a lineshape model based on D- and r-strain. As the temperature is increased from 2 K, an 11-line hyperfine pattern characteristic of dinuclear Mn(II) is first observed from the S=3 manifold. D- and r-strain are the dominate broadening effects that determine where the hyperfine pattern will be resolved. A single unique parameter set was found to simulate all spectra arising for all temperatures, microwave frequencies, and microwave modes. The simulations are quantitative, allowing for the first time the determination of species concentrations directly from EPR spectra. Thus, this work describes the first method for the quantitative characterization of EPR spectra of dinuclear manganese centers in model complexes and proteins. The exchange coupling parameter J for complex 1 was determined ( J=-1.5±0.3 cm-1; H ex=-2J S1· S2) and found to be in agreement with a previous

Design and demonstration of ultra-fast W-band photonic transmitter-mixer and detectors for 25 Gbits/sec error-free wireless linking.

PubMed

Chen, Nan-Wei; Shi, Jin-Wei; Tsai, Hsuan-Ju; Wun, Jhih-Min; Kuo, Fong-Ming; Hesler, Jeffery; Crowe, Thomas W; Bowers, John E

2012-09-10

A 25 Gbits/s error-free on-off-keying (OOK) wireless link between an ultra high-speed W-band photonic transmitter-mixer (PTM) and a fast W-band envelope detector is demonstrated. At the transmission end, the high-speed PTM is developed with an active near-ballistic uni-traveling carrier photodiode (NBUTC-PD) integrated with broadband front-end circuitry via the flip-chip bonding technique. Compared to our previous work, the wireless data rate is significantly increased through the improvement on the bandwidth of the front-end circuitry together with the reduction of the intermediate-frequency (IF) driving voltage of the active NBUTC-PD. The demonstrated PTM has a record-wide IF modulation (DC-25 GHz) and optical-to-electrical fractional bandwidths (68-128 GHz, ~67%). At the receiver end, the demodulation is realized with an ultra-fast W-band envelope detector built with a zero-bias Schottky barrier diode with a record wide video bandwidth (37 GHz) and excellent sensitivity. The demonstrated PTM is expected to find applications in multi-gigabit short-range wireless communication.

Chromosome banding in amphibia. XXIII. Giant W sex chromosomes and extremely small genomes in Eleutherodactylus euphronides and Eleutherodactylus shrevei (Anura, Leptodactylidae).

PubMed

Schmid, M; Feichtinger, W; Steinlein, C; Rupprecht, A; Haaf, T; Kaiser, H

2002-01-01

Highly differentiated, heteromorphic ZZ female symbol /ZW male symbol sex chromosomes were found in the karyotypes of the neotropical leptodactylid frogs Eleutherodactylus euphronides and E. shrevei. The W chromosomes are the largest heterochromatic, female-specific chromosomes so far discovered in the class Amphibia. The analyses of the banding patterns with AT- and GC base-pair specific fluorochromes show that the constitutive heterochromatin in the giant W chromosomes consists of various categories of repetitive DNA sequences. The W chromosomes of both species are similar in size, morphology and banding patterns, whereas their Z chromosomes exhibit conspicuous differences. In the cell nuclei of female animals, the W chromosomes form very prominent chromatin bodies (W chromatin). DNA flow cytometric measurements demonstrate clear differences in the DNA content of male and female erythrocytes caused by the giant W chromosome, and also shows that these Eleutherodactylus genomes are among the smallest of all amphibian genomes. The importance of the heteromorphic ZW sex chromosomes for the study of Z-linked genes, the similarities and differences of the two karyotypes, and the significance of the exceptionally small genomes are discussed. Copyright 2002 S. Karger AG, Basel

Pre-clinical evaluation of OxyChip for long-term EPR oximetry.

PubMed

Hou, Huagang; Khan, Nadeem; Gohain, Sangeeta; Kuppusamy, M Lakshmi; Kuppusamy, Periannan

2018-03-16

Tissue oxygenation is a critical parameter in various pathophysiological situations including cardiovascular disease and cancer. Hypoxia can significantly influence the prognosis of solid malignancies and the efficacy of their treatment by radiation or chemotherapy. Electron paramagnetic resonance (EPR) oximetry is a reliable method for repeatedly assessing and monitoring oxygen levels in tissues. Lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) has been developed as a probe for biological EPR oximetry, especially for clinical use. However, clinical applicability of LiNc-BuO crystals is hampered by potential limitations associated with biocompatibility, biodegradation, or migration of individual bare crystals in tissue. To overcome these limitations, we have embedded LiNc-BuO crystals in polydimethylsiloxane (PDMS), an oxygen-permeable biocompatible polymer and developed an implantable/retrievable form of chip, called OxyChip. The chip was optimized for maximum spin density (40% w/w of LiNc-BuO in PDMS) and fabricated in a form suitable for implantation using an 18-G syringe needle. In vitro evaluation of the OxyChip showed that it is robust and highly oxygen sensitive. The dependence of its EPR linewidth to oxygen was linear and highly reproducible. In vivo efficacy of the OxyChip was evaluated by implanting it in rat femoris muscle and following its response to tissue oxygenation for up to 12 months. The results revealed preservation of the integrity (size and shape) and calibration (oxygen sensitivity) of the OxyChip throughout the implantation period. Further, no inflammatory or adverse reaction around the implantation area was observed thereby establishing its biocompatibility and safety. Overall, the results demonstrated that the newly-fabricated high-sensitive OxyChip is capable of providing long-term measurements of oxygen concentration in a reliable and repeated manner under clinical conditions.

Magnetically aligned phospholipid bilayers in weak magnetic fields: optimization, mechanism, and advantages for X-band EPR studies.

PubMed

Cardon, Thomas B; Tiburu, Elvis K; Lorigan, Gary A

2003-03-01

Our lab is developing a spin-labeled EPR spectroscopic technique complementary to solid-state NMR studies to study the structure, orientation, and dynamics of uniaxially aligned integral membrane proteins inserted into magnetically aligned discotic phospholipid bilayers, or bicelles. The focus of this study is to optimize and understand the mechanisms involved in the magnetic alignment process of bicelle disks in weak magnetic fields. Developing experimental conditions for optimized magnetic alignment of bicelles in low magnetic fields may prove useful to study the dynamics of membrane proteins and its interactions with lipids, drugs, steroids, signaling events, other proteins, etc. In weak magnetic fields, the magnetic alignment of Tm(3+)-doped bicelle disks was thermodynamically and kinetically very sensitive to experimental conditions. Tm(3+)-doped bicelles were magnetically aligned using the following optimized procedure: the temperature was slowly raised at a rate of 1.9K/min from an initial temperature being between 298 and 307K to a final temperature of 318K in the presence of a static magnetic field of 6300G. The spin probe 3beta-doxyl-5alpha-cholestane (cholestane) was inserted into the bicelle disks and utilized to monitor bicelle alignment by analyzing the anisotropic hyperfine splitting for the corresponding EPR spectra. The phases of the bicelles were determined using solid-state 2H NMR spectroscopy and compared with the corresponding EPR spectra. Macroscopic alignment commenced in the liquid crystalline nematic phase (307K), continued to increase upon slowly raising the temperature, and was well-aligned in the liquid crystalline lamellar smectic phase (318K).

Broadband SLED-based light source (BeST-SLEDTM) and spectrometer

NASA Astrophysics Data System (ADS)

Yadid-Pecht, Orly; Dattner, Yonathan

2016-03-01

A small footprint, low power, cost effective single mode fiber coupled broadband light source and spectrometer is presented. It is based on Super Luminescent Diode (SLED) devices and a compact design enables coverage of the 1250 nm-1750 nm region with a total optical power of 50 mW at the output of the fiber. This Broad Spectrum Tunable Super Luminescent (BeST-SLEDTM) light source can operate at temperatures ranging from -40°C to 60°C, and resides in a custom designed 26-pin package. The fiber is a polarization maintaining fiber with a FC/APC connector at the output. Three variations of the BeST-SLEDTM were developed, BEST-SLED™ Bands, BeST-SLEDTM Tunable and BeST-SLEDTM FTNIR. In the Bands version six SLEDs were packaged allowing for one SLED on at a time or any combination of the SLEDs on. In the Tunable version an Acoustic Optical Tunable Filter (AOTF) was integrated into the package allowing the user to select one wavelength at a time to pass into the fiber with resolution of ~1 nm @1550nm. In the FTNIR version, a Silicon Photonic based interferometer (the Nano-SpecTM) was integrated into the package for a Fourier Transform Near Infrared based Spectrometer and light source. The BeST-SLEDTM is being used in process control applications such as steam quality measurements, oil in water, gas composition and air quality monitoring.

Multipurpose EPR loop-gap resonator and cylindrical TE011 cavity for aqueous samples at 94 GHz.

PubMed

Sidabras, Jason W; Mett, Richard R; Froncisz, Wojciech; Camenisch, Theodore G; Anderson, James R; Hyde, James S

2007-03-01

A loop-gap resonator (LGR) and a cylindrical TE(011) cavity resonator for use at W band, 94 GHz, have been designed and characterized using the Ansoft (Pittsburgh, PA) high frequency structure simulator (HFSS; Version 10.0). Field modulation penetration was analyzed using Ansoft MAXWELL 3D (Version 11.0). Optimizing both resonators to the same sample sizes shows that EPR signal intensities of the LGR and TE(011) are similar. The 3 dB bandwidth of the LGR, on the order of 1 GHz, is a new advantage for high frequency experiments. Ultraprecision electric discharge machining (EDM) was used to fabricate the resonators from silver. The TE(011) cavity has slots that are cut into the body to allow penetration of 100 kHz field modulation. The resonator body is embedded in graphite, also cut by EDM techniques, for a combination of reasons that include (i) reduced microwave leakage and improved TE(011) mode purity, (ii) field modulation penetration, (iii) structural support for the cavity body, and (iv) machinability by EDM. Both resonators use a slotted iris. Variable coupling is provided by a three-stub tuning element. A collet system designed to hold sample tubes has been implemented, increasing repeatability of sample placement and reducing sample vibration noise. Initial results include multiquantum experiments up to 9Q using the LGR to examine 1 mM 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in aqueous solution at room temperature and field modulation experiments using the TE(011) cavity to obtain an EPR spectrum of 1 microM TEMPO.

Study on W-band sheet-beam traveling-wave tube based on flat-roofed sine waveguide

NASA Astrophysics Data System (ADS)

Fang, Shuanzhu; Xu, Jin; Jiang, Xuebing; Lei, Xia; Wu, Gangxiong; Li, Qian; Ding, Chong; Yu, Xiang; Wang, Wenxiang; Gong, Yubin; Wei, Yanyu

2018-05-01

A W-band sheet electron beam (SEB) traveling-wave tube (TWT) based on flat-roofed sine waveguide slow-wave structure (FRSWG-SWS) is proposed. The sine wave of the metal grating is replaced by a flat-roofed sine wave around the electron beam tunnel. The slow-wave characteristics including the dispersion properties and interaction impedance have been investigated by using the eigenmode solver in the 3-D electromagnetic simulation software Ansoft HFSS. Through calculations, the FRSWG SWS possesses the larger average interaction impedance than the conventional sine waveguide (SWG) SWS in the frequency range of 86-110 GHz. The beam-wave interaction was studied and particle-in-cell simulation results show that the SEB TWT can produce output power over 120 W within the bandwidth ranging from 90 to 100 GHz, and the maximum output power is 226 W at typical frequency 94 GHz, corresponding electron efficiency of 5.89%.

The SOFIA/SAFIRE Far-Infrared Spectrometer: Highlighting Submillimeter Astrophysics and Technology

NASA Technical Reports Server (NTRS)

Benford, Dominic J.

2009-01-01

The Submillimeter and Far-InfraRed Experiment (SAFIRE) on the SOFIA airborne observatory is an imaging spectrometer for wavelengths between 28 microns and 440 microns. Our design is a dual-band long-slit grating spectrometer, which provides broadband (approx. 4000 km/s) observations in two lines simultaneously over a field of view roughly 10" wide by 320" long. The low backgrounds in spectroscopy require very sensitive detectors with noise equivalent powers of order 10(exp -18) W/square root of Hz. We are developing a kilopixel, filled detector array for SAFIRE in a 32 x 40 format. The detector consists of a transition edge sensor (TES) bolometer array, a per-pixel broadband absorbing backshort array, and a NIST SQUID multiplexer readout array. This general type of array has been used successfully in the GISMO instrument, so we extrapolate to the sensitivity needed for airborne spectroscopy. Much of the cryogenic, electronics, and software infrastructure for SAFIRE have been developed. I provide here an overview of the progress on SAFIRE.

Asymmetry in band widening and quasiparticle lifetimes in SrVO3: Competition between screened exchange and local correlations from combined G W and dynamical mean-field theory G W + DMFT

NASA Astrophysics Data System (ADS)

Tomczak, Jan M.; Casula, M.; Miyake, T.; Biermann, S.

2014-10-01

The very first dynamical implementation of the combined GW and dynamical mean-field scheme "G W + DMFT " for a real material was achieved recently [Tomczak et al., Europhys. Lett. 100, 67001 (2012), 10.1209/0295-5075/100/67001], and applied to the ternary transition metal oxide SrVO3. Here, we review and extend that work, giving not only a detailed account of full G W + DMFT calculations, but also discussing and testing simplified approximate schemes. We give insights into the nature of exchange and correlation effects: dynamical renormalizations in the Fermi liquid regime of SrVO3 are essentially local, and nonlocal correlations mainly act to screen the Fock exchange term. The latter substantially widens the quasiparticle band structure, while the band narrowing induced by the former is accompanied by a spectral weight transfer to higher energies. Most interestingly, the exchange broadening is more pronounced in the unoccupied part of the spectrum than in the occupied one. In addition, shorter lifetimes for unoccupied states further contribute to making the corrections to the Kohn-Sham band structure asymmetric with respect to the chemical potential. As a result, the G W + DMFT electronic structure of SrVO3 resembles the conventional density functional based dynamical mean-field (DFT + DMFT ) description for occupied states but is profoundly modified in the empty part. Our work leads to a reinterpretation of inverse photoemission spectroscopy (IPES) data. Indeed, we assign a prominent peak at about 2.7 eV dominantly to eg states, rather than to an upper Hubbard band of t2 g character. Similar surprises can be expected for other transition metal oxides. This prediction urgently calls for more detailed investigations of conduction band states in correlated materials.

Performance of the EBIT calorimeter spectrometer

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

Porter, Frederick Scott; Gygax, John; Kelley, Richard L.

The EBIT calorimeter spectrometer (ECS) is a new high-resolution, broadband x-ray spectrometer that has recently been installed at the Electron Beam Ion Trap Facility (EBIT) at the Lawrence Livermore National Laboratory. The ECS is an entirely new production class spectrometer that replaces the XRS/EBIT spectrometer that has been operating at EBIT since 2000. The ECS utilizes a 32-pixel x-ray calorimeter array from the XRS instrument on the Suzaku x-ray observatory. Eighteen of the pixels are optimized for the 0.1-10 keV band and yield 4.5 eV full width at half maximum energy resolution and 95% quantum efficiency at 6 keV. Inmore » addition, the ECS includes 14 detector pixels that are optimized for the high-energy band with a bandpass from 0.5 to over 100 keV with 34 eV resolution and 32% quantum efficiency at 60 keV. The ECS detector array is operated at 50 mK using a five stage cryogenic system that is entirely automated. The instrument takes data continuously for over 65 h with a 2.5 h recycle time. The ECS is a nondispersive, broadband, highly efficient spectrometer that is one of the prime instruments at the EBIT facility. The instrument is used for studies of absolute cross sections, charge exchange recombination, and x-ray emission from nonequilibrium plasmas, among other measurements in our laboratory astrophysics program.« less

Direct EPR irradiation of a sample using a quartz oscillator operating at 250 MHz for EPR measurements.

PubMed

Yokoyama, Hidekatsu

2012-01-01

Direct irradiation of a sample using a quartz oscillator operating at 250 MHz was performed for EPR measurements. Because a quartz oscillator is a frequency fixed oscillator, the operating frequency of an EPR resonator (loop-gap type) was tuned to that of the quartz oscillator by using a single-turn coil with a varactor diode attached (frequency shift coil). Because the frequency shift coil was mobile, the distance between the EPR resonator and the coil could be changed. Coarse control of the resonant frequency was achieved by changing this distance mechanically, while fine frequency control was implemented by changing the capacitance of the varactor electrically. In this condition, EPR measurements of a phantom (comprised of agar with a nitroxide radical and physiological saline solution) were made. To compare the presented method with a conventional method, the EPR measurements were also done by using a synthesizer at the same EPR frequency. In the conventional method, the noise level increased at high irradiation power. Because such an increase in the noise was not observed in the presented method, high sensitivity was obtained at high irradiation power. Copyright © 2011 Elsevier Inc. All rights reserved.

264 W output power at 1585 nm in Er-Yb codoped fiber laser using in-band pumping.

PubMed

Jebali, M A; Maran, J-N; LaRochelle, S

2014-07-01

We demonstrate a high-power cladding-pumped Er-Yb codoped fiber laser with 74% efficiency. A pump-limited output power of 264 W is obtained using in-band pumping at 1535 nm. We compare the efficiency of 1480 and 1535 nm pumping through numerical simulations and experimental measurements.

Digitally generated excitation and near-baseband quadrature detection of rapid scan EPR signals.

PubMed

Tseitlin, Mark; Yu, Zhelin; Quine, Richard W; Rinard, George A; Eaton, Sandra S; Eaton, Gareth R

2014-12-01

The use of multiple synchronized outputs from an arbitrary waveform generator (AWG) provides the opportunity to perform EPR experiments differently than by conventional EPR. We report a method for reconstructing the quadrature EPR spectrum from periodic signals that are generated with sinusoidal magnetic field modulation such as continuous wave (CW), multiharmonic, or rapid scan experiments. The signal is down-converted to an intermediate frequency (IF) that is less than the field scan or field modulation frequency and then digitized in a single channel. This method permits use of a high-pass analog filter before digitization to remove the strong non-EPR signal at the IF, that might otherwise overwhelm the digitizer. The IF is the difference between two synchronized X-band outputs from a Tektronix AWG 70002A, one of which is for excitation and the other is the reference for down-conversion. To permit signal averaging, timing was selected to give an exact integer number of full cycles for each frequency. In the experiments reported here the IF was 5kHz and the scan frequency was 40kHz. To produce sinusoidal rapid scans with a scan frequency eight times IF, a third synchronized output generated a square wave that was converted to a sine wave. The timing of the data acquisition with a Bruker SpecJet II was synchronized by an external clock signal from the AWG. The baseband quadrature signal in the frequency domain was reconstructed. This approach has the advantages that (i) the non-EPR response at the carrier frequency is eliminated, (ii) both real and imaginary EPR signals are reconstructed from a single physical channel to produce an ideal quadrature signal, and (iii) signal bandwidth does not increase relative to baseband detection. Spectra were obtained by deconvolution of the reconstructed signals for solid BDPA (1,3-bisdiphenylene-2-phenylallyl) in air, 0.2mM trityl OX63 in water, 15 N perdeuterated tempone, and a nitroxide with a 0.5G partially-resolved proton

Pharmaceutical applications of in vivo EPR

NASA Astrophysics Data System (ADS)

Mäder, Karsten

1998-07-01

The aim of this article is to discuss the applications of in vivo EPR in the field of pharmacy. In addition to direct detection of free radical metabolites and measurement of oxygen, EPR can be used to characterize the mechanisms of drug release from biodegradable polymers. Unique information about drug concentration, the microenvironment (viscosity, polarity, pH) and biodistribution (by localized measurement or EPR Imaging) can be obtained.

Structural defects in natural plastically deformed diamonds: Evidence from EPR spectroscopy

NASA Astrophysics Data System (ADS)

Mineeva, R. M.; Titkov, S. V.; Speransky, A. V.

2009-06-01

Structural defects formed as a result of plastic deformation in natural diamond crystals have been studied by EPR spectroscopy. The spectra of brown, pink-brown, black-brown, pink-purple, and gray plastically deformed diamonds of type Ia from deposits in Yakutia and the Urals were recorded. The results of EPR spectroscopy allowed us to identify various deformation centers in the structure of natural diamonds and to show that nitrogen centers were transformed under epigenetic mechanical loading. Abundant A centers, consisting of two isomorphic nitrogen atoms located in neighboring structural sites, were destroyed as a result of this process to form a series of N1, N4, W7, M2, and M3 nitrogen centers. Such centers are characterized by an anisotropic spatial distribution and a positive charge, related to the mechanism of their formation. In addition, N2 centers (probably, deformation-produced dislocations decorated by nitrogen) were formed in all plastically deformed diamonds and W10 and W35 centers (the models have not been finally ascertained) were formed in some of them. It has been established that diamonds with various types of deformation-induced color contain characteristic associations of these deformation centers. The diversity of associations of deformation centers indicates appreciable variations in conditions of disintegration of deep-seated rocks, transfer of diamonds to the Earth’s surface, and formation of kimberlitic deposits. Depending on the conditions of mechanical loading, the diamond crystals were plastically deformed by either dislocation gliding or mechanical twinning. Characteristic features of plastic deformation by dislocation gliding are the substantial prevalence of the N2 centers over other deformation centers and the occurrence of the high-spin W10 and W35 centers. The attributes of less frequent plastic deformation by mechanical twinning are unusual localization of the M2 centers and, in some cases, the N1 centers in microtwinned

A 2x2 W-Band Reference Time-Shifted Phase-Locked Transmitter Array in 65nm CMOS Technology

NASA Technical Reports Server (NTRS)

Tang, Adrian; Virbila, Gabriel; Hsiao, Frank; Wu, Hao; Murphy, David; Mehdi, Imran; Siegel, P. H.; Chang, M-C. Frank

2013-01-01

This paper presents a complete 2x2 phased array transmitter system operating at W-band (90-95 GHz) which employs a PLL reference time-shifting approach instead of using traditional mm-wave phase shifters. PLL reference shifting enables a phased array to be distributed over multiple chips without the need for coherent mm-wave signal distribution between chips. The proposed phased array transmitter system consumes 248 mW per array element when implemented in a 65 nm CMOS technology.

EPR spectroscopic investigation of psoriatic finger nails.

PubMed

Nakagawa, Kouichi; Minakawa, Satoko; Sawamura, Daisuke

2013-11-01

Nail lesions are common features of psoriasis and found in almost half of the patients. However, there is no feasible spectroscopic method evaluating changes and severity of nail psoriasis. EPR (electron paramagnetic resonance) might be feasible for evaluating nail conditions in the patients of psoriasis. Finger nails of five cases with nail psoriasis, (three females and two males) were examined. Nail samples were subjected to the EPR assay. The small piece of the finger nail (1.5 × 5 mm(2)) was incubated in ~50 μM 5-DSA (5-doxylstearic acid) aqueous solutions for about 60 min at 37°C. After rinsing and wiping off the excess 5-DSA solution, the nail samples were measured by EPR. EPR spectra were analyzed using the intensity ratio (Fast/Slow) of the two motions at the peaks of the lower magnetic field. We observed two distinguishable sites on the basis of the EPR results. In addition, the modern EPR calculation was performed to analyze the spectra obtained. The nail psoriasis-related region is 2~3 times higher than that of the control. The present EPR results show that there are two distinguishable sites in the nail. In the case of nail psoriasis, the fragile components are 2~3 times more than those of the control. Thus, the EPR method is thought to be a novel and reliable method of evaluating the nail psoriasis. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Optimization of a triode-type cusp electron gun for a W-band gyro-TWA

NASA Astrophysics Data System (ADS)

Zhang, Liang; Donaldson, Craig R.; He, Wenlong

2018-04-01

A triode-type cusp electron gun was optimized through numerical simulations for a W-band gyrotron traveling wave amplifier. An additional electrode in front of the cathode could switch the electron beam on and off instantly when its electric potential is properly biased. An optimal electron beam of current 1.7 A and a velocity ratio (alpha) of 1.12 with an alpha spread of ˜10.7% was achieved when the triode gun was operated at 40 kV.

High-spin studies: Recent results from the 8π spectrometer

NASA Astrophysics Data System (ADS)

Radford, D. C.; Galindo-Uribarri, A.; Hackman, G.; Janzen, V. P.; 8π Collaboration

1993-05-01

Selected highlights of recent high-spin nuclear-structure studies with the 8π spectrometer are presented. These include an extensive systematic study of high- j intruder bands in A ˜ 110 Sb, Sn and In nuclei; evidence for hyperdeformation, observed in the reaction 120Sn( 37Cl,px n) populating 152,153Dy; and the observation of a new superdeformed band in the N = 80 nucleus 142Sm. The design of "TRIGAM", a new HPGe-detector array proposed to replace the 8π spectrometer, is also presented.

EPR and optical absorption studies of paramagnetic molecular ion (VO2+) in Lithium Sodium Acid Phthalate single crystal

NASA Astrophysics Data System (ADS)

Subbulakshmi, N.; Kumar, M. Saravana; Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

2017-12-01

Electron Paramagnetic Resonance (EPR) spectroscopic studies of VO2+ ions as paramagnetic impurity in Lithium Sodium Acid Phthalate (LiNaP) single crystal have been done at room temperature on X-Band microwave frequency. The lattice parameter values are obtained for the chosen system from Single crystal X-ray diffraction study. Among the number of hyperfine lines in the EPR spectra only two sets are reported from EPR data. The principal values of g and A tensors are evaluated for the two different VO2+ sites I and II. They possess the crystalline field around the VO2+ as orthorhombic. Site II VO2+ ion is identified as substitutional in place of Na1 location and the other site I is identified as interstitial location. For both sites in LiNaP, VO2+ are identified in octahedral coordination with tetragonal distortion as seen from the spin Hamiltonian parameter values. The ground state of vanadyl ion in the LiNaP single crystal is dxy. Using optical absorption data the octahedral and tetragonal parameters are calculated. By correlating EPR and optical data, the molecular orbital bonding parameters have been discussed for both sites.

Wide-Band Heterodyne Submillimetre Wave Spectrometer for Planetary Atmospheres

NASA Technical Reports Server (NTRS)

Schlecht, Erich

2010-01-01

We present calculations and measurements on a passive submillimetre wave spectroscopic sounder to gather data on the thermal structure, dynamics and composition of the upper atmosphere of a planet, e.g. the stratosphere of Jupiter, or the entire thickness of the atmosphere of Mars. The instrument will be capable of measuring wind speeds, temperature, pressure, and key constituent concentrations in the stratosphere of the target planet. This instrument consists of a Schottky diode based front end and a digital back-end spectrometer. It differs from previous space-based spectrometers in its combination of wide tunability (520-590 GHz), and rapid frequency switching between widely spaced lines within that range. This will enable near simultaneous observation of multiple lines, which is critical to the reconstruction of atmospheric pressure and density versus altitude profiles. At the same time frequency accuracy must be high to enable wind speeds to be determined directly by measurement of the line's Doppler shift.

Airborne imaging spectrometer data of the Ruby Mountains, Montana: Mineral discrimination using relative absorption band-depth images

USGS Publications Warehouse

Crowley, J.K.; Brickey, D.W.; Rowan, L.C.

1989-01-01

Airborne imaging spectrometer data collected in the near-infrared (1.2-2.4 ??m) wavelength range were used to study the spectral expression of metamorphic minerals and rocks in the Ruby Mountains of southwestern Montana. The data were analyzed by using a new data enhancement procedure-the construction of relative absorption band-depth (RBD) images. RBD images, like bandratio images, are designed to detect diagnostic mineral absorption features, while minimizing reflectance variations related to topographic slope and albedo differences. To produce an RBD image, several data channels near an absorption band shoulder are summed and then divided by the sum of several channels located near the band minimum. RBD images are both highly specific and sensitive to the presence of particular mineral absorption features. Further, the technique does not distort or subdue spectral features as sometimes occurs when using other data normalization methods. By using RBD images, a number of rock and soil units were distinguished in the Ruby Mountains including weathered quartz - feldspar pegmatites, marbles of several compositions, and soils developed over poorly exposed mica schists. The RBD technique is especially well suited for detecting weak near-infrared spectral features produced by soils, which may permit improved mapping of subtle lithologic and structural details in semiarid terrains. The observation of soils rich in talc, an important industrial commodity in the study area, also indicates that RBD images may be useful for mineral exploration. ?? 1989.

Contribution of Harold M. Swartz to In Vivo EPR and EPR Dosimetry.

PubMed

Gallez, Bernard

2016-12-01

In 2015, we are celebrating half a century of research in the application of Electron Paramagnetic Resonance (EPR) as a biodosimetry tool to evaluate the dose received by irradiated people. During the EPR Biodose 2015 meeting, a special session was organized to acknowledge the pioneering contribution of Harold M. (Hal) Swartz in the field. The article summarizes his main contribution in physiology and medicine. Four emerging themes have been pursued continuously along his career since its beginning: (1) radiation biology; (2) oxygen and oxidation; (3) measuring physiology in vivo; and (4) application of these measurements in clinical medicine. The common feature among all these different subjects has been the use of magnetic resonance techniques, especially EPR. In this article, you will find an impressionist portrait of Hal Swartz with the description of the 'making of' this pioneer, a time-line perspective on his career with the creation of three National Institutes of Health-funded EPR centers, a topic-oriented perspective on his career with a description of his major contributions to Science, his role as a mentor and his influence on his academic children, his active role as founder of scientific societies and organizer of scientific meetings, and the well-deserved international recognition received so far. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A 250 GHz Gyrotron with a 3 GHz Tuning Bandwidth for Dynamic Nuclear Polarization

PubMed Central

Barnes, Alexander B.; Nanni, Emilio A.; Herzfeld, Judith; Griffin, Robert G.; Temkin, Richard J.

2012-01-01

We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementing a long (23 mm) interaction cavity that can excite higher order axial modes by changing either the magnetic field of the gyrotron or the cathode potential. This interaction cavity excites the rotating TE5,2,q mode, and an internal mode converter outputs a high-quality microwave beam with >94% Gaussian content. The gyrotron was integrated into a DNP spectrometer, resulting in a measured DNP enhancement of 54 on the membrane protein bacteriorhodopsin. PMID:22743211

10 Gb/s optical carrier distributed network with W-band (0.1 THz) short-reach wireless communication system

NASA Astrophysics Data System (ADS)

Chow, C. W.; Yang, L. G.; Yeh, C. H.; Huang, C. B.; Shi, J. W.; Pan, C. L.

2012-10-01

Millimeter-wave (mm-wave) operated in W-band (75 GHz-0.11 THz) is of particular interests, since this frequency band can carry signals at much higher data rates. We demonstrate a 10 Gb/s optical carrier-distributed network with the wireless communication system. The mm-wave signal at carrier frequency of 0.1 THz is generated by a high speed near-ballistic uni-traveling carrier photodiode (NBUTC-PD) based transmitter (Tx), which is optically excited by optical short pulses. The optical pulse source is produced from a self-developed photonic mm-wave waveform generator (PMWG), which allows spectral line-by-line pulse shaping. Hence these optical pulses have high tolerance to fiber chromatic dispersion. The W-band 10 Gb/s wireless data is transmitted and received via a pair of horn antennas. The received 10 Gb/s data is envelope-detected and then used to drive an optical modulator at the remote antenna unit (RAU) to produce the upstream signal sending back to the central office (CO). 20 km single mode fiber (SMF) error free transmission is achieved. Analysis about the optimum repetition rate of the optical pulse source and the transmission performance of the upstream signal are also performed and discussed.

Intelligent Controller for a Compact Wide-Band Compositional Infrared Fourier Transform Spectrometer

NASA Astrophysics Data System (ADS)

Yiu, P.; Keymeulen, D.; Berisford, D. F.; Hand, K. P.; Carlson, R. W.

2013-12-01

This paper presents the design and integration of an intelligent controller for CIRIS (Compositional InfraRed Interferometric Spectrometer) on a stand-alone field programmable gate array (FPGA) architecture. CIRIS is a novel take on traditional Fourier Transform Spectrometers (FTS) and replaces linearly moving mirrors (characteristic of Michelson interferometers) with a constant-velocity rotating refractor to variably phase shift and alter the path length of incoming light. This design eliminates the need for periodically accelerating/decelerating mirrors inherent to canonical Michelson designs and allows for a compact and robust device that is intrinsically radiation-hard, making it ideal for spaceborne measurements in the near-IR to thermal-IR band (2-12 μm) on planetary exploration missions. A traditional Michelson FTS passes a monochromatic light source (incident light from the sample) through a system of refractors/mirrors followed by a mirror moving linearly in the plane of the incident light. This process selectively blocks certain wavelengths and permits measurement of the sample's absorption rates as a function of the wavelengths blocked to produce an 'inteferogram.' This is subsequently processed using a Fourier transform to obtain the sample's spectrum and ascertain the sample's composition. With our prototype CIRIS instrument in development at Design and Prototype Inc. and NASA-JPL, we propose the use of a rotating refractor spinning at a constant velocity to variably phase shift incident light to the detector as an alternative to a linearly moving mirror. This design eliminates sensitivity to vibrations, minimizing path length and non-linear errors due to minor perturbations to the system, in addition to facilitating compact design critical to meeting the strict volume requirements of spacecraft. Further, this is done without sacrificing spectral resolution or throughput when compared to Michelson or diffractive designs. While Michelson designs

Pulsed-High Field/High-Frequency EPR Spectroscopy

NASA Astrophysics Data System (ADS)

Fuhs, Michael; Moebius, Klaus

Pulsed high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy is used to disentangle many kinds of different effects often obscured in continuous wave (cw) EPR spectra at lower magnetic fields/microwave frequencies. While the high magnetic field increases the resolution of G tensors and of nuclear Larmor frequencies, the high frequencies allow for higher time resolution for molecular dynamics as well as for transient paramagnetic intermediates studied with time-resolved EPR. Pulsed EPR methods are used for example for relaxation-time studies, and pulsed Electron Nuclear DOuble Resonance (ENDOR) is used to resolve unresolved hyperfine structure hidden in inhomogeneous linewidths. In the present article we introduce the basic concepts and selected applications to structure and mobility studies on electron transfer systems, reaction centers of photosynthesis as well as biomimetic models. The article concludes with an introduction to stochastic EPR which makes use of an other concept for investigating resonance systems in order to increase the excitation bandwidth of pulsed EPR. The limited excitation bandwidth of pulses at high frequency is one of the main limitations which, so far, made Fourier transform methods hardly feasible.

Phase noise measurements of the 400-kW, 2.115-GHz (S-band) transmitter

NASA Technical Reports Server (NTRS)

Boss, P.; Hoppe, D.; Bhanji, A.

1987-01-01

The measurement theory is described and a test method to perform phase noise verification using off-the-shelf components and instruments is presented. The measurement technique described consists of a double-balanced mixer used as phase detector, followed by a low noise amplifier. An FFT spectrum analyzer is then used to view the modulation components. A simple calibration procedure is outlined that ensures accurate measurements. A block diagram of the configuration is presented as well as actual phase noise data from the 400 kW, 2.115 GHz (S-band) klystron transmitter.

IR-Monitored Photolysis of CO-Inhibited Nitrogenase: A Major EPR-Silent Species with Coupled Terminal CO Ligands

PubMed Central

Yan, Lifen; Dapper, Christie H.; Scott, Aubrey D.; Newton, William E.

2015-01-01

We have used Fourier transform infrared spectroscopy (FT-IR) to observe the photolysis and recombination of a novel EPR-silent CO-inhibited form of α-H195Q nitrogenase from Azotobacter vinelandii. Photolysis at 4 K yields a strong negative IR difference band at 1938 cm−1, along with a weaker negative feature at 1911 cm−1. These bands and the associated chemical species have both been assigned the label ‘Hi-3’. A positive band at 1921 cm−1 is assigned to the ‘Lo-3’ photoproduct. By using an isotopic mixture of 12C16O and 13C18O, we show that the Hi-3 bands arise from coupling of two similar CO oscillators with one uncoupled frequency at ~1917 cm−1. Although in previous studies Lo-3 was not observed to recombine, by extending the observation range to 200–240 K we found that recombination to Hi-3 does indeed occur, with an activation energy of ~6.5 kJ mol−1. The frequencies of the Hi-3 bands suggest terminal CO ligation. We tested this hypothesis with DFT calculations on models with terminal CO ligands on Fe2 and Fe6 of the FeMo-cofactor. An S = 0 model with both CO ligands in exo positions predicts symmetric and asymmetric stretches at 1938 and 1909 cm−1 respectively, with relative band intensities of ~3.5:1, in good agreement with experiment. From the observed IR intensities, we find that Hi-3 is present at a concentration about equal to that of the EPR-active Hi-1 species. The relevance of Hi-3 to the nitrogenase catalytic mechanism and its recently discovered Fischer-Tropsch chemistry is discussed. PMID:23136072

A loop resonator for slice-selective in vivo EPR imaging in rats

PubMed Central

Hirata, Hiroshi; He, Guanglong; Deng, Yuanmu; Salikhov, Ildar; Petryakov, Sergey; Zweier, Jay L.

2008-01-01

A loop resonator was developed for 300-MHz continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy and imaging in live rats. A single-turn loop (55 mm in diameter) was used to provide sufficient space for the rat body. Efficiency for generating a radiofrequency magnetic field of 38 µT/W1/2 was achieved at the center of the loop. For the resonator itself, an unloaded quality factor of 430 was obtained. When a 350 g rat was placed in the resonator at the level of the lower abdomen, the quality factor decreased to 18. The sensitive volume in the loop was visualized with a bottle filled with an aqueous solution of the nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-CP). The resonator was shown to enable EPR imaging in live rats. Imaging was performed for 3-CP that had been infused intravenously into the rat and its distribution was visualized within the lower abdomen. PMID:18006343

EPR-based distance measurements at ambient temperature.

PubMed

Krumkacheva, Olesya; Bagryanskaya, Elena

2017-07-01

Pulsed dipolar (PD) EPR spectroscopy is a powerful technique allowing for distance measurements between spin labels in the range of 2.5-10.0nm. It was proposed more than 30years ago, and nowadays is widely used in biophysics and materials science. Until recently, PD EPR experiments were limited to cryogenic temperatures (T<80K). Recently, application of spin labels with long electron spin dephasing time at room temperature such as triarylmethyl radicals and nitroxides with bulky substituents at a position close to radical centers enabled measurements at room temperature and even at physiologically relevant temperatures by PD EPR as well as other approaches based on EPR (e.g., relaxation enhancement; RE). In this paper, we review the features of PD EPR and RE at ambient temperatures, in particular, requirements on electron spin phase memory time, ways of immobilization of biomolecules, the influence of a linker between the spin probe and biomolecule, and future opportunities. Copyright © 2017 Elsevier Inc. All rights reserved.

Global spectral UV-radiometer with automatic shadow band.

PubMed

Rosales, Alejandro; Pedroni, Jorge V; Tocho, Jorge O

2006-01-01

A solar radiometer (GUV-511 C, Biospherical Instruments Inc., San Diego, CA) with four UV channels has been operating at Trelew (43.2 degrees S, 65.3 degrees W), Argentina, since the austral spring of 1997. The instrument provides global (direct + diffuse) irradiance on the horizontal plane year-round, with a 1 min period. On 1 January 1999, an automatic shadow band was added to calculate diffuse and direct radiation. The period of the measurements was increased to 2 min to keep the same signal to noise (S:N) ratio. Once the direct radiation values were available for the 305 nm and 320 nm spectral bands, the total ozone value was calculated and results were compared with data provided by the U.S. National Aeronautics and Space Administration for the Total Ozone Mapping Spectrometer (TOMS) on the Earth Probe satellite. Results show a root-mean-square (RMS) deviation within 4% compared with that of TOMS, so the quality of results is considered to be quite good. The importance of regular calibration to maintain long-term accuracy is stressed.

Thermal Infrared Spectral Band Detection Limits for Unidentified Surface Materials

NASA Technical Reports Server (NTRS)

Kirkland, Laurel E.; Herr, Kenneth C.; Salisbury, John W.

2001-01-01

Infrared emission spectra recorded by airborne or satellite spectrometers can be searched for spectral features to determine the composition of rocks on planetary surfaces. Surface materials are identified by detections of characteristic spectral bands. We show how to define whether to accept an observed spectral feature as a detection when the target material is unknown. We also use remotely sensed spectra measured by the Thermal Emission Spectrometer (TES) and the Spatially Enhanced Broadband Array Spectrograph System to illustrate the importance of instrument parameters and surface properties on band detection limits and how the variation in signal-to-noise ratio with wavelength affects the bands that are most detectable for a given instrument. The spectrometer's sampling interval, spectral resolution, signal-to-noise ratio as a function of wavelength, and the sample's surface properties influence whether the instrument can detect a spectral feature exhibited by a material. As an example, in the 6-13 micrometer wavelength region, massive carbonates exhibit two bands: a very strong, broad feature at approximately 6.5 micrometers and a less intense, sharper band at approximately 11.25 micrometers. Although the 6.5-micrometer band is stronger and broader in laboratory-measured spectra, the 11.25-micrometer band will cause a more detectable feature in TES spectra.

An XRPD and EPR spectroscopy study of microcrystalline calcite bioprecipitated by Bacillus subtilis

NASA Astrophysics Data System (ADS)

Perito, B.; Romanelli, M.; Buccianti, A.; Passaponti, M.; Montegrossi, G.; Di Benedetto, F.

2018-05-01

We report in this study the first XRPD and EPR spectroscopy characterisation of a biogenic calcite, obtained from the activity of the bacterium Bacillus subtilis. Microcrystalline calcite powders obtained from bacterial culture in a suitable precipitation liquid medium were analysed without further manipulation. Both techniques reveal unusual parameters, closely related to the biological source of the mineral, i.e., to the bioprecipitation process and in particular to the organic matrix observed inside calcite. In detail, XRPD analysis revealed that bacterial calcite has slightly higher c/a lattice parameters ratio than abiotic calcite. This correlation was already noticed in microcrystalline calcite samples grown by bio-mineralisation processes, but it had never been previously verified for bacterial biocalcites. EPR spectroscopy evidenced an anomalously large value of W 6, a parameter that can be linked to occupation by different chemical species in the next nearest neighbouring sites. This parameter allows to clearly distinguish bacterial and abiotic calcite. This latter achievement was obtained after having reduced the parameters space into an unbiased Euclidean one, through an isometric log-ratio transformation. We conclude that this approach enables the coupled use of XRPD and EPR for identifying the traces of bacterial activity in fossil carbonate deposits.

W-band spaceborne radar observations of atmospheric river events

NASA Astrophysics Data System (ADS)

Matrosov, S. Y.

2010-12-01

While the main objective of the world first W-band radar aboard the CloudSat satellite is to provide vertically resolved information on clouds, it proved to be a valuable tool for observing precipitation. The CloudSat radar is generally able to resolve precipitating cloud systems in their vertical entirety. Although measurements from the liquid hydrometer layer containing rainfall are strongly attenuated, special retrieval approaches can be used to estimate rainfall parameters. These approaches are based on vertical gradients of observed radar reflectivity factor rather than on absolute estimates of reflectivity. Concurrent independent estimations of ice cloud parameters in the same vertical column allow characterization of precipitating systems and provide information on coupling between clouds and rainfall they produce. The potential of CloudSat for observations atmospheric river events affecting the West Coast of North America is evaluated. It is shown that spaceborne radar measurements can provide high resolution information on the height of the freezing level thus separating areas of rainfall and snowfall. CloudSat precipitation rate estimates complement information from the surface-based radars. Observations of atmospheric rivers at different locations above the ocean and during landfall help to understand evolutions of atmospheric rivers and their structures.

Backscattering enhancement for Marshall-Palmer distributed rains for a W-band nadir-pointing radar with a finite beam width

NASA Technical Reports Server (NTRS)

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood; Oguchi, Tomohiro

2005-01-01

In this paper, we expand the previous theory to be applied to a generic drop size distribution with spheroidal raindrops including spherical raindrops. Results will be used to discuss the multiple scattering effects on the backscatter measurements acquired by a W-band nadir-pointing radar.

VO2+ ions in zinc lead borate glasses studied by EPR and optical absorption techniques.

PubMed

Prakash, P Giri; Rao, J Lakshmana

2005-09-01

Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl ions in zinc lead borate (ZnO-PbO-B2O3) glass system have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in zinc lead borate glasses were present in octahedral sites with tetragonal compression and belong to C4V symmetry. The spin-Hamiltonian parameters g and A are found to be independent of V2O5 content and temperature but changing with ZnO content. The decrease in Deltag( parallel)/Deltag( perpendicular) value with increase in ZnO content indicates that the symmetry around VO2+ ions is more octahedral. The decrease in intensity of EPR signal above 10 mol% of V2O5 is attributed to a fall in the ratio of the number of V4+ ions (N4) to the number of V5+ ions (N5). The number of spins (N) participating in resonance was calculated as a function of temperature for VO2+ doped zinc lead borate glass sample and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility was calculated at various temperatures and the Curie constant was evaluated from the 1/chi-T graph. The optical absorption spectra show single absorption band due to VO2+ ions in tetragonally distorted octahedral sites.

Rest-wavelength fiducials for the ITER core imaging x-ray spectrometer.

PubMed

Beiersdorfer, P; Brown, G V; Graf, A T; Bitter, M; Hill, K W; Kelley, R L; Kilbourne, C A; Leutenegger, M A; Porter, F S

2012-10-01

Absolute wavelength references are needed to derive the plasma velocities from the Doppler shift of a given line emitted by a moving plasma. We show that such reference standards exist for the strongest x-ray line in neonlike W(64+), which has become the line of choice for the ITER (Latin "the way") core imaging x-ray spectrometer. Close-by standards are the Hf Lβ(3) line and the Ir Lα(2) line, which bracket the W(64+) line by ±30 eV; other standards are given by the Ir Lα(1) and Lα(2) lines and the Hf Lβ(1) and Lβ(2) lines, which bracket the W(64+) line by ±40 and ±160 eV, respectively. The reference standards can be produced by an x-ray tube built into the ITER spectrometer. We present spectra of the reference lines obtained with an x-ray microcalorimeter and compare them to spectra of the W(64+) line obtained both with an x-ray microcalorimeter and a crystal spectrometer.

Rest-wavelength Fiducials for the ITER Core Imaging X-ray Spectrometer

NASA Technical Reports Server (NTRS)

Beiersdorfer, P.; Brown, G. V.; Graf, A. T.; Bitter, M.; Hill, K. W.; Kelley, R. L.; Kilbourne, C. A.; Leutenegger, M. A.; Porter, F. S.

2012-01-01

Absolute wavelength references are needed to derive the plasma velocities from the Doppler shift of a given line emitted by a moving plasma. We show that such reference standards exist for the strongest x-ray line in neonlike W64+, which has become the line of choice for the ITER (Latin the way) core imaging x-ray spectrometer. Close-by standards are the Hf L3 line and the Ir L2 line, which bracket the W64+ line by 30 eV; other standards are given by the Ir L1 and L2 lines and the Hf L1 and L2 lines, which bracket the W64+ line by 40 and 160 eV, respectively. The reference standards can be produced by an x-ray tube built into the ITER spectrometer. We present spectra of the reference lines obtained with an x-ray microcalorimeter and compare them to spectra of the W64+ line obtained both with an x-ray microcalorimeter and a crystal spectrometer

Surface modification of TiO{sub 2} nanoparticles with carotenoids. EPR study

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

Konovalova, T.A.; Kispert, L.D.; Konovalov, V.V.

1999-06-03

Among the semiconductors, titanium dioxide is the most suitable for many environmental applications. EPR measurements demonstrate efficient charge separation on carotenoid-modified titanium dioxide nanoparticles (7 nm). Strong complexation of carotenoids containing terminal carboxy groups ({minus}CO{sub 2}H) with the TiO{sub 2} surface leads to electron transfer from the adsorbed carotenoid molecule to the surface trapping site. For these systems, EPR signals of the carotenoid radical cations Car{sup {sm_bullet}+} and the electrons trapped on the TiO{sub 2} are observed before irradiation (77 K). Their UV-visible spectra show an absorption band with a maximum near 650 nm that is characteristic of the trappedmore » electrons. Surface modification of the TiO{sub 2} by other carotenoids results in the formation of a complex with an optical absorption band near 545 nm. These systems form charge-separated pairs [Car{sup {sm_bullet}+}{hor_ellipsis}TiO{sub 2}(e{sup {minus}}{sub tr}){sub surf}. TiO{sub 2}(e{sup {minus}}{sub tr}){sub latt}] only upon 365--600 nm illumination at 77 K. Complexation of the TiO{sub 2} colloids with carotenoids enhances spatial charge separation, shifts the absorption threshold into the visible region, and thus greatly improves the reducing ability of the semiconductor. Photoreduction of acceptor molecules such as 2,5-dichloro-1,4-benzoquinone, nitrobenzene, and oxygen is demonstrated.« less

Implementation of alanine/EPR as transfer dosimetry system in a radiotherapy audit programme in Belgium.

PubMed

Schaeken, B; Cuypers, R; Lelie, S; Schroeyers, W; Schreurs, S; Janssens, H; Verellen, D

2011-04-01

A measurement procedure based on alanine/electron paramagnetic resonance (EPR) dosimetry was implemented successfully providing simple, stable, and accurate dose-to-water (D(w)) measurements. The correspondence between alanine and ionization chamber measurements in reference conditions was excellent. Alanine/EMR dosimetry might be a valuable alternative to thermoluminescent (TLD) and ionization chamber based measuring procedures in radiotherapy audits. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

VEGAS: VErsatile GBT Astronomical Spectrometer

NASA Astrophysics Data System (ADS)

Bussa, Srikanth; VEGAS Development Team

2012-01-01

The National Science Foundation Advanced Technologies and Instrumentation (NSF-ATI) program is funding a new spectrometer backend for the Green Bank Telescope (GBT). This spectrometer is being built by the CICADA collaboration - collaboration between the National Radio Astronomy Observatory (NRAO) and the Center for Astronomy Signal Processing and Electronics Research (CASPER) at the University of California Berkeley.The backend is named as VErsatile GBT Astronomical Spectrometer (VEGAS) and will replace the capabilities of the existing spectrometers. This backend supports data processing from focal plane array systems. The spectrometer will be capable of processing up to 1.25 GHz bandwidth from 8 dual polarized beams or a bandwidth up to 10 GHz from a dual polarized beam.The spectrometer will be using 8-bit analog to digital converters (ADC), which gives a better dynamic range than existing GBT spectrometers. There will be 8 tunable digital sub-bands within the 1.25 GHz bandwidth, which will enhance the capability of simultaneous observation of multiple spectral transitions. The maximum spectral dump rate to disk will be about 0.5 msec. The vastly enhanced backend capabilities will support several science projects with the GBT. The projects include mapping temperature and density structure of molecular clouds; searches for organic molecules in the interstellar medium; determination of the fundamental constants of our evolving Universe; red-shifted spectral features from galaxies across cosmic time and survey for pulsars in the extreme gravitational environment of the Galactic Center.

Identification of gamma-irradiated fruit juices by EPR spectroscopy

NASA Astrophysics Data System (ADS)

Aleksieva, K. I.; Dimov, K. G.; Yordanov, N. D.

2014-10-01

The results of electron paramagnetic resonance (EPR) study on commercially available juices from various fruits and different fruit contents: 25%, 40%, 50%, and 100%, homemade juices, nectars and concentrated fruit syrups, before and after gamma-irradiation are reported. In order to remove water from non- and irradiated samples all juices and nectars were filtered; the solid residue was washed with alcohol and dried at room temperature. Only concentrated fruit syrups were dried for 60 min at 40 °C in a standard laboratory oven. All samples under study show a singlet EPR line with g=2.0025 before irradiation with exception of concentrated fruit syrups, which are EPR silent. Irradiation of juice samples gives rise to complex EPR spectra which gradually transferred to "cellulose-like" EPR spectrum from 25% to 100% fruit content. Concentrated fruit syrups show typical "sugar-like" spectra due to added saccharides. All EPR spectra are characteristic and can prove radiation treatment. The fading kinetics of radiation-induced EPR signals were studied for a period of 60 days after irradiation.

EPR spectral investigation of radiation-induced radicals of gallic acid.

PubMed

Tuner, Hasan

2017-11-01

In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden "spin-flip" transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, [Formula: see text] radicals for both compounds.

Experimental EPR-steering using Bell-local states

NASA Astrophysics Data System (ADS)

Saunders, D. J.; Jones, S. J.; Wiseman, H. M.; Pryde, G. J.

2010-11-01

The concept of `steering' was introduced in 1935 by Schrödinger as a generalization of the EPR (Einstein-Podolsky-Rosen) paradox. It has recently been formalized as a quantum-information task with arbitrary bipartite states and measurements, for which the existence of entanglement is necessary but not sufficient. Previous experiments in this area have been restricted to an approach that followed the original EPR argument in considering only two different measurement settings per side. Here we demonstrate experimentally that EPR-steering occurs for mixed entangled states that are Bell local (that is, that cannot possibly demonstrate Bell non-locality). Unlike the case of Bell inequalities, increasing the number of measurement settings beyond two-we use up to six-significantly increases the robustness of the EPR-steering phenomenon to noise.

A photoacoustic spectrometer for trace gas detection

NASA Astrophysics Data System (ADS)

Telles, E. M.; Bezerra, E.; Scalabrin, A.

2005-06-01

A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 μm: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

UV EFFECTS IN TOOTH ENAMEL AND THEIR POSSIBLE APPLICATION IN EPR DOSIMETRY WITH FRONT TEETH

PubMed Central

Sholom, S.; Desrosiers, M.; Chumak, V.; Luckyanov, N.; Simon, S.L.; Bouville, A.

2009-01-01

The effects of ultraviolet (UV) radiation on ionizing radiation biodosimetry were studied in human tooth enamel samples using the technique of electron paramagnetic resonance (EPR) in X-band. For samples in the form of grains, UV-specific EPR spectra were spectrally distinct from that produced by exposure to gamma radiation. From larger enamel samples, the UV penetration depth was determined to be in the 60–120 μm range. The difference in EPR spectra from UV exposure and from exposure to gamma radiation samples was found to be a useful marker of UV equivalent dose (defined as the apparent contribution to the gamma dose in mGy that results from UV radiation absorption) in tooth enamel. This concept was preliminarily tested on front teeth from inhabitants of the region of the Semipalatinsk Nuclear Test Site (Kazakhstan) who might have received some exposure to gamma radiation from the nuclear tests conducted there as well as from normal UV radiation in sunlight. The technique developed here to quantify and subtract the UV contribution to the measured tooth is currently limited to cumulative dose measurements with a component of UV equivalent dose equal to or greater than 300 mGy. PMID:20065706

Tooth Retrospective Dosimetry Using Electron Paramagnetic Resonance: Influence of Irradiated Dental Composites

PubMed Central

Desmet, Céline M.; Djurkin, Andrej; Dos Santos-Goncalvez, Ana Maria; Dong, Ruhong; Kmiec, Maciej M.; Kobayashi, Kyo; Rychert, Kevin; Beun, Sébastien; Leprince, Julian G.; Leloup, Gaëtane; Levêque, Philippe; Gallez, Bernard

2015-01-01

In the aftermath of a major radiological accident, the medical management of overexposed individuals will rely on the determination of the dose of ionizing radiations absorbed by the victims. Because people in the general population do not possess conventional dosimeters, after the fact dose reconstruction methods are needed. Free radicals are induced by radiations in the tooth enamel of victims, in direct proportion to dose, and can be quantified using Electron Paramagnetic Resonance (EPR) spectrometry, a technique that was demonstrated to be very appropriate for mass triage. The presence of dimethacrylate based restorations on teeth can interfere with the dosimetric signal from the enamel, as free radicals could also be induced in the various composites used. The aim of the present study was to screen irradiated composites for a possible radiation-induced EPR signal, to characterize it, and evaluate a possible interference with the dosimetric signal of the enamel. We investigated the most common commercial composites, and experimental compositions, for a possible class effect. The effect of the dose was studied between 10 Gy and 100 Gy using high sensitivity X-band spectrometer. The influence of this radiation-induced signal from the composite on the dosimetric signal of the enamel was also investigated using a clinical L-Band EPR spectrometer, specifically developed in the EPR center at Dartmouth College. In X-band, a radiation-induced signal was observed for high doses (25-100 Gy); it was rapidly decaying, and not detected after only 24h post irradiation. At 10 Gy, the signal was in most cases not measurable in the commercial composites tested, with the exception of 3 composites showing a significant intensity. In L-band study, only one irradiated commercial composite influenced significantly the dosimetric signal of the tooth, with an overestimation about 30%. In conclusion, the presence of the radiation-induced signal from dental composites should not

Adiabatic and fast passage ultra-wideband inversion in pulsed EPR.

PubMed

Doll, Andrin; Pribitzer, Stephan; Tschaggelar, René; Jeschke, Gunnar

2013-05-01

We demonstrate that adiabatic and fast passage ultra-wideband (UWB) pulses can achieve inversion over several hundreds of MHz and thus enhance the measurement sensitivity, as shown by two selected experiments. Technically, frequency-swept pulses are generated by a 12 GS/s arbitrary waveform generator and upconverted to X-band frequencies. This pulsed UWB source is utilized as an incoherent channel in an ordinary pulsed EPR spectrometer. We discuss experimental methodologies and modeling techniques to account for the response of the resonator, which can strongly limit the excitation bandwidth of the entire non-linear excitation chain. Aided by these procedures, pulses compensated for bandwidth or variations in group delay reveal enhanced inversion efficiency. The degree of bandwidth compensation is shown to depend critically on the time available for excitation. As a result, we demonstrate optimized inversion recovery and double electron electron resonance (DEER) experiments. First, virtually complete inversion of the nitroxide spectrum with an adiabatic pulse of 128ns length is achieved. Consequently, spectral diffusion between inverted and non-inverted spins is largely suppressed and the observation bandwidth can be increased to increase measurement sensitivity. Second, DEER is performed on a terpyridine-based copper (II) complex with a nitroxide-copper distance of 2.5nm. As previously demonstrated on this complex, when pumping copper spins and observing nitroxide spins, the modulation depth is severely limited by the excitation bandwidth of the pump pulse. By using fast passage UWB pulses with a maximum length of 64ns, we achieve up to threefold enhancement of the modulation depth. Associated artifacts in distance distributions when increasing the bandwidth of the pump pulse are shown to be small. Copyright © 2013 Elsevier Inc. All rights reserved.

A new pulse width reduction technique for pulsed electron paramagnetic resonance spectroscopy.

PubMed

Ohba, Yasunori; Nakazawa, Shigeaki; Kazama, Shunji; Mizuta, Yukio

2008-03-01

We present a new technique for a microwave pulse modulator that generates a short microwave pulse of approximately 1ns for use in an electron paramagnetic resonance (EPR) spectrometer. A quadruple-frequency multiplier that generates a signal of 16-20GHz from an input of 4-5GHz was employed to reduce the rise and fall times of the pulse prepared by a PIN diode switch. We examined the transient response characteristics of a commercial frequency multiplier and found that the device can function as a multiplier for pulsed signal even though it was designed for continuous wave operation. We applied the technique to a Ku band pulsed EPR spectrometer and successfully observed a spin echo signal with a broad excitation bandwidth of approximately 1.6mT using 80 degrees pulses of 1.5ns.

Preliminary Experiments for the Assessment of V/W-band Links for Space-Earth Communications

NASA Technical Reports Server (NTRS)

Nessel, James A.; Acosta, Roberto J.; Miranda, Felix A.

2013-01-01

Since September 2012, NASA Glenn Research Center has deployed a microwave profiling radiometer at White Sands, NM, to estimate atmospheric propagation effects on communications links in the V and W bands (71-86GHz). Estimates of attenuation statistics in the millimeter wave due to gaseous and cloud components of the atmosphere show good agreement with current ITU-R models, but fail to predict link performance in the presence of moderate to heavy rain rates, due to the inherent limitations of passive radiometry. Herein, we discuss the preliminary results of these measurements and describe a design for a terrestrial link experiment to validate/refine existing rain attenuation models in the V/Wbands.

EPR detection of foods preserved with ionizing radiation

NASA Astrophysics Data System (ADS)

Stachowicz, W.; Burlinska, G.; Michalik, J.

1998-06-01

The applicability of the epr technique for the detection of dried vegetables, mushrooms, some spices, flavour additives and some condiments preserved with ionizing radiation is discussed. The epr signals recorded after exposure to gamma rays and to beams of 10 MeV electrons from linac are stable, intense and specific enough as compared with those observed with nonirradiated samples and could be used for the detection of irradiation. However, stability of radiation induced epr signals produced in these foods depends on storage condition. No differences in shapes (spectral parameters) and intensities of the epr spectra recorded with samples exposed to the same doses of gamma rays ( 60Co) and 10 MeV electrons were observed

Inexpensive Raman Spectrometer for Undergraduate and Graduate Experiments and Research

ERIC Educational Resources Information Center

Mohr, Christian; Spencer, Claire L.; Hippler, Michael

2010-01-01

We describe the construction and performance of an inexpensive modular Raman spectrometer that has been assembled in the framework of a fourth-year undergraduate project (costs below $5000). The spectrometer is based on a 4 mW 532 nm green laser pointer and a compact monochromator equipped with glass fiber optical connections, linear detector…

Cusp Guns for Helical-Waveguide Gyro-TWTs of a High-Gain High-Power W-Band Amplifier Cascade

NASA Astrophysics Data System (ADS)

Manuilov, V. N.; Samsonov, S. V.; Mishakin, S. V.; Klimov, A. V.; Leshcheva, K. A.

2018-02-01

The evaluation, design, and simulations of two different electron guns generating the beams for W-band second cyclotron harmonic gyro-TWTs forming a high-gain powerful amplifier cascade are presented. The optimum configurations of the systems creating nearly axis-encircling electron beams having velocity pitch-factor up to 1.5, voltage/current of 40 kV/0.5 A, and 100 kV/13 A with acceptable velocity spreads have been found and are presented.

CW EPR and 9 GHz EPR imaging investigation of stable paramagnetic species and their antioxidant activities in dry shiitake mushroom (Lentinus edodes).

PubMed

Nakagawa, Kouichi; Hara, Hideyuki

2016-01-01

We investigated the antioxidant activities and locations of stable paramagnetic species in dry (or drying) shiitake mushroom (Lentinus edodes) using continuous wave (CW) electron paramagnetic resonance (EPR) and 9 GHz EPR imaging. CW 9 GHz EPR detected paramagnetic species (peak-to-peak linewidth (ΔHpp) = 0.57 mT) in the mushroom. Two-dimensional imaging of the sharp line using a 9 GHz EPR imager showed that the species were located in the cap and shortened stem portions of the mushroom. No other location of the species was found in the mushroom. However, radical locations and concentrations varied along the cap of the mushroom. The 9 GHz EPR imaging determined the exact location of stable paramagnetic species in the shiitake mushroom. Distilled water extracts of the pigmented cap surface and the inner cap of the mushroom showed similar antioxidant activities that reduced an aqueous solution of 0.1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The present results suggest that the antioxidant activities of the edible mushroom extracts are much weaker than those of ascorbic acid. Thus, CW EPR and EPR imaging revealed the location and distribution of stable paramagnetic species and the antioxidant activities in the shiitake mushroom for the first time.

Relativistic Nonlocality and the EPR Paradox

NASA Astrophysics Data System (ADS)

Chamberlain, Thomas

2014-03-01

The exact violation of Bell's Inequalities is obtained with a local realistic model for spin. The model treats one particle that comprises a quantum ensemble and simulates the EPR data one coincidence at a time as a product state. Such a spin is represented by operators σx , iσy ,σz in its body frame rather than the usual set of σX ,σY ,σZ in the laboratory frame. This model, assumed valid in the absence of a measuring probe, contains both quantum polarizations and coherences. Each carries half the EPR correlation, but only half can be measured using coincidence techniques. The model further predicts the filter angles that maximize the spin correlation in EPR experiments.

EPR study on non- and gamma-irradiated herbal pills

NASA Astrophysics Data System (ADS)

Aleksieva, K.; Lagunov, O.; Dimov, K.; Yordanov, N. D.

2011-06-01

The results of EPR studies on herbal pills of marigold, hawthorn, yarrow, common balm, tutsan, nettle and thyme before and after gamma-irradiation are reported. Before irradiation all samples exhibit one weak singlet EPR line with a g-factor of 2.0048±0.0005. After irradiation herbal pills could be separated in two groups according to their EPR spectra. Radiation-induced free radicals in pills of marigold, yarrow, nettle, tutsan and thyme could be attributed mainly to saccharide excipients. Tablets of hawthorn and common balm show "cellulose-like" EPR spectrum, superimposed on partly resolved carbohydrate spectrum, due to the active part (herb) and inulin, which is present in the pills as an excipient. Fading study of the radiation-induced EPR signals confirms that sugar radicals are more stable than cellulose species. The reported results show that the presence of characteristic EPR spectra of herbal pills due to excipients or active part can be used as unambiguous proof of radiation processing within 35 or more days after irradiation.

EPR: Some History and Clarification

NASA Astrophysics Data System (ADS)

Fine, Arthur

2002-04-01

Locality, separation and entanglement 1930s style. We’ll explore the background to the 1935 paper by Einstein, Podolsky and Rosen, how it was composed, the actual argument of the paper, the principles used, and how the paper was received by Schroedinger, and others.We’ll also look at Bohr’s response: the extent to which Bohr connects with what Einstein was after in EPR and the extent to EPR marks a shift in Bohr’s thinking about the quantum theory.

Applications of Silicon-on-Insulator Photonic Crystal Structures in Miniature Spectrometer Designs

NASA Astrophysics Data System (ADS)

Gao, Boshen

Optical spectroscopy is one of the most important fundamental scientific techniques. It has been widely adopted in physics, chemistry, biology, medicine and many other research fields. However, the size and weight of a spectrometer as well as the difficulty to align and maintain it have long limited spectroscopy to be a laboratory-only procedure. With the recent advancement in semiconductor electronics and photonics, miniaturized spectrometers have been introduced to complete many tasks in daily life where mobility and portability are necessary. This thesis focuses on the study of several photonic crystal (PC) nano-structures potentially suitable for miniaturized on-chip spectrometer designs. Chapter 1 briefly introduces the concept of PCs and their band structures. By analyzing the band structure, the origin of the superprism effect is explained. Defect-based PC nano-cavities are also discussed, as well as a type of coupled cavity waveguides (CCW) composed of PC nano-cavities. Chapter 2 is devoted to the optimization of a flat-band superprism structure for spectroscopy application using numerical simulations. Chapter 3 reports a fabricated broad-band superprism and the experimental characterization of its wavelength resolving performance. In chapter 4, the idea of composing a miniature spectrometer based on a single tunable PC nano-cavity is proposed. The rest of this chapter discusses the experimental study of this design. Chapter 5 examines the slow-light performance of a CCW and discusses its potential application in slow-light interferometry. Chapter 6 serves as a conclusion of this thesis and proposes directions for possible future work to follow up.

EPR study on gamma-irradiated fruits dehydrated via osmosis

NASA Astrophysics Data System (ADS)

Yordanov, N. D.; Aleksieva, K.

2007-06-01

The shape and time stability of the electron paramagnetic resonance (EPR) spectra of non- and γ-irradiated papaya, melon, cherry and fig samples dehydrated via osmosis are reported. It is shown that non-irradiated samples are generally EPR silent whereas γ-irradiated exhibit "sugar-like" EPR spectra. The recorded EPR spectra are monitored for a period of 7 months after irradiation (stored at low humidity and in the dark). The results suggest longer period of unambiguous identification of the radiation processing of osmose dehydrated fruits. Therefore, the Protocol EN 13708,2001 issued by CEN is fully applicable for the studied fruit samples.

Evaluation of Airborne Visible/Infrared Imaging Spectrometer Data of the Mountain Pass, California carbonatite complex

NASA Technical Reports Server (NTRS)

Crowley, James; Rowan, Lawrence; Podwysocki, Melvin; Meyer, David

1988-01-01

Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data of the Mountain Pass, California carbonatite complex were examined to evaluate the AVIRIS instrument performance and to explore alternative methods of data calibration. Although signal-to-noise estimates derived from the data indicated that the A, B, and C spectrometers generally met the original instrument design objectives, the S/N performance of the D spectrometer was below expectations. Signal-to-noise values of 20 to 1 or lower were typical of the D spectrometer and several detectors in the D spectrometer array were shown to have poor electronic stability. The AVIRIS data also exhibited periodic noise, and were occasionally subject to abrupt dark current offsets. Despite these limitations, a number of mineral absorption bands, including CO3, Al-OH, and unusual rare earth element bands, were observed for mine areas near the main carbonatite body. To discern these bands, two different calibration procedures were applied to remove atmospheric and solar components from the remote sensing data. The two procedures, referred to as the single spectrum and the flat field calibration methods gave distinctly different results. In principle, the single spectrum method should be more accurate; however, additional fieldwork is needed to rigorously determine the degree of calibration success.

Membrane fluidity profiles as deduced by saturation-recovery EPR measurements of spin-lattice relaxation times of spin labels

NASA Astrophysics Data System (ADS)

Mainali, Laxman; Feix, Jimmy B.; Hyde, James S.; Subczynski, Witold K.

2011-10-01

There are no easily obtainable EPR spectral parameters for lipid spin labels that describe profiles of membrane fluidity. The order parameter, which is most often used as a measure of membrane fluidity, describes the amplitude of wobbling motion of alkyl chains relative to the membrane normal and does not contain explicitly time or velocity. Thus, this parameter can be considered as nondynamic. The spin-lattice relaxation rate ( T1-1) obtained from saturation-recovery EPR measurements of lipid spin labels in deoxygenated samples depends primarily on the rotational correlation time of the nitroxide moiety within the lipid bilayer. Thus, T1-1 can be used as a convenient quantitative measure of membrane fluidity that reflects local membrane dynamics. T1-1 profiles obtained for 1-palmitoyl-2-( n-doxylstearoyl)phosphatidylcholine ( n-PC) spin labels in dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol are presented in parallel with profiles of the rotational diffusion coefficient, R⊥, obtained from simulation of EPR spectra using Freed's model. These profiles are compared with profiles of the order parameter obtained directly from EPR spectra and with profiles of the order parameter obtained from simulation of EPR spectra. It is shown that T1-1 and R⊥ profiles reveal changes in membrane fluidity that depend on the motional properties of the lipid alkyl chain. We find that cholesterol has a rigidifying effect only to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. These effects cannot be differentiated by profiles of the order parameter. All profiles in this study were obtained at X-band (9.5 GHz).

Design, implementation, and performance of the Astro-H soft x-ray spectrometer aperture assembly and blocking filters

NASA Astrophysics Data System (ADS)

Kilbourne, Caroline A.; Adams, Joseph S.; Arsenovic, Petar; Ayers, Travis; Chiao, Meng P.; DiPirro, Michael J.; Eckart, Megan E.; Fujimoto, Ryuichi; Kazeva, John D.; Kripps, Kari L.; Lairson, Bruce M.; Leutenegger, Maurice A.; Lopez, Heidi C.; McCammon, Dan; McGuinness, Daniel S.; Mitsuda, Kazuhisa; Moseley, Samuel J.; Porter, F. Scott; Schweiss, Andrea N.; Takei, Yoh; Thorpe, Rosemary Schmidt; Watanabe, Tomomi; Yamasaki, Noriko Y.; Yoshida, Seiji

2018-01-01

The calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV. The properties that made the SXS array a powerful x-ray spectrometer also made it sensitive to photons from the entire electromagnetic band as well as particles. If characterized as a bolometer, it would have had a noise equivalent power of <4 × 10 ? 18 W / (Hz)0.5. Thus, it was imperative to shield the detector from thermal radiation from the instrument and optical and UV photons from the sky. In addition, it was necessary to shield the coldest stages of the instrument from the thermal radiation emanating from the warmer stages. These needs were addressed by a series of five thin-film radiation-blocking filters, anchored to the nested temperature stages, that blocked long-wavelength radiation while minimizing x-ray attenuation. The aperture assembly was a system of barriers, baffles, filter carriers, and filter mounts that supported the filters and inhibited their potential contamination. The three outer filters also had been equipped with thermometers and heaters for decontamination. We present the requirements, design, implementation, and performance of the SXS aperture assembly and blocking filters.

Transient radical pairs studied by time-resolved EPR.

PubMed

Bittl, Robert; Weber, Stefan

2005-02-25

Photogenerated short-lived radical pairs (RP) are common in biological photoprocesses such as photosynthesis and enzymatic DNA repair. They can be favorably probed by time-resolved electron paramagnetic resonance (EPR) methods with adequate time resolution. Two EPR techniques have proven to be particularly useful to extract information on the working states of photoinduced biological processes that is only difficult or sometimes even impossible to obtain by other types of spectroscopy. Firstly, transient EPR yields crucial information on the chemical nature and the geometry of the individual RP halves in a doublet-spin pair generated by a short laser pulse. This time-resolved method is applicable in all magnetic field/microwave frequency regimes that are used for continuous-wave EPR, and is nowadays routinely utilized with a time resolution reaching about 10 ns. Secondly, a pulsed EPR method named out-of-phase electron spin echo envelope modulation (OOP-ESEEM) is increasingly becoming popular. By this pulsed technique, the mutual spin-spin interaction between the RP halves in a doublet-spin pair manifests itself as an echo modulation detected as a function of the microwave-pulse spacing of a two-pulse echo sequence subsequent to a laser pulse. From the dipolar coupling, the distance between the radicals is readily derived. Since the spin-spin interaction parameters are typically not observable by transient EPR, the two techniques complement each other favorably. Both EPR methods have recently been applied to a variety of light-induced RPs in photobiology. This review summarizes the results obtained from such studies in the fields of plant and bacterial photosynthesis and DNA repair mediated by the enzyme DNA photolyase.

EPR spectroscopy of complex biological iron-sulfur systems.

PubMed

Hagen, Wilfred R

2018-02-21

From the very first discovery of biological iron-sulfur clusters with EPR, the spectroscopy has been used to study not only purified proteins but also complex systems such as respiratory complexes, membrane particles and, later, whole cells. In recent times, the emphasis of iron-sulfur biochemistry has moved from characterization of individual proteins to the systems biology of iron-sulfur biosynthesis, regulation, degradation, and implications for human health. Although this move would suggest a blossoming of System-EPR as a specific, non-invasive monitor of Fe/S (dys)homeostasis in whole cells, a review of the literature reveals limited success possibly due to technical difficulties in adherence to EPR spectroscopic and biochemical standards. In an attempt to boost application of System-EPR the required boundary conditions and their practical applications are explicitly and comprehensively formulated.

Advanced x-ray imaging spectrometer

NASA Technical Reports Server (NTRS)

Callas, John L. (Inventor); Soli, George A. (Inventor)

1998-01-01

An x-ray spectrometer that also provides images of an x-ray source. Coded aperture imaging techniques are used to provide high resolution images. Imaging position-sensitive x-ray sensors with good energy resolution are utilized to provide excellent spectroscopic performance. The system produces high resolution spectral images of the x-ray source which can be viewed in any one of a number of specific energy bands.

Some recent multi-frequency electron paramagnetic resonance results on systems relevant for dosimetry and dating.

PubMed

Callens, F; Vanhaelewyn, G; Matthys, P

2002-04-01

Electron Paramagnetic Resonance (EPR) applications like e.g. EPR dosimetry and dating, are usually performed at X-band frequencies because of practical reasons (cost, sample size, etc.). However, it is increasingly recognized that the radiation-induced EPR signals are strongly composite, what might affect dose/age estimates. A few recent examples from both the dosimetry and dating field, illustrating the problems, will be presented. The involved spectra are mainly due to carbonate-derived radicals (CO2-, CO3(3-), etc.). Measurements at higher microwave frequencies are often recommended to improve the insight into the spectra and/or the practical signal quantification. Recent results at Q- and W-band frequencies will show that a multi-frequency approach indeed opens many interesting perspectives in this field but also that each frequency may have specific (dis)advantages depending on the EPR probe and application involved. The discussion will concern carbonate-containing apatite single crystals, shells, modern and fossil tooth enamel.

Analysis of spin-Hamiltonian and molecular orbital coefficients of Cu2+ doped C8H11KO8 single crystal through EPR technique

NASA Astrophysics Data System (ADS)

Juliet sheela, K.; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

2018-04-01

Electron paramagnetic resonance (EPR) studies have been investigated at X-band microwave frequency on Cu2+ ion incorporated into the single crystal of potassium succinate-succinic acid (KSSA) at room temperature. The angular variation of the EPR spectra has shown two magnetically in-equivalent Cu2+ sites in the KSSA single crystal system. The spin Hamiltonian parameters g and A are determined which reveals that the site I and site II occupied in rhombic and axial local field symmetry around the impurity ion. Among the two paramagnetic impurity ions, sites one occupies at substituitional position in the place of monovalent cation (K+) in the crystal whereas the other enters in its lattice interstitially by the correlation of EPR and crystal structure data. From the calculated principle values gxx, gyy, gzz and Axx, Ayy, Azz of both the sites, the admixture coefficients and molecular orbital coefficients were evaluated which gives the information of ground state wave function and types of bonding of impurity ions with the ligands.

Polymer therapeutics and the EPR effect.

PubMed

Maeda, Hiroshi

History of the EPR (enhanced permeability and retention) effect is discussed, which goes back to the analyses of molecular pathology in bacterial infection and edema (extravasation) formation. The first mediator we found for extravasation was bradykinin. Later on, were found nitric oxide and superoxide, then formation of peroxynitrite, that activates procollagenase. In this inflammatory setting many other vascular mediators are involved that are also common to cancer vasculature. Obviously cancer vasculature is defective architechtally, and this makes macromolecular drugs more permeable through the vascular wall. The importance of this pathophysiological event of EPR effect can be applied to macromolecular drug-delivery, or tumor selective delivery, which takes hours to achieve in the primary as well as metastatic tumors, not to mention of the inflamed tissues. The retention of the EPR means that such drugs will be retained in tumor tissues more than days to weeks. This was demonstrated initially, and most dramatically, using SMANCS, a protein-polymer conjugated-drug dissolved in lipid contrast medium (Lipiodol) by administering intraarterially. For disseminating the EPR concept globally, or in the scientific community, Professor Ruth Duncan played a key role at the early stage, as she worked extensively on polymer- therapeutics, and knew its importance.

Digital Detection and Processing of Multiple Quadrature Harmonics for EPR Spectroscopy

PubMed Central

Ahmad, R.; Som, S.; Kesselring, E.; Kuppusamy, P.; Zweier, J.L.; Potter, L.C.

2010-01-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. PMID:20971667

Typhoon June /1975/ viewed by a scanning microwave spectrometer

NASA Technical Reports Server (NTRS)

Rosenkranz, P. W.; Staelin, D. H.; Grody, N. C.

1978-01-01

Data were collected by the scanning microwave spectrometer onboard Nimbus 6 during the June 1975 typhoon in the Philippine Sea. The spectrometer was equipped with channels centered on 22.23 GHz (a water vapor band), 31.65 GHz (a transmittance window), and 52.85, 53.85, and 55.45 GHz (an oxygen band). Temperature maps, derived from oxygen band measurements, showed that the typhoon eye had a single peak varying in amplitude with time. Water line and window measurements were used to develop a coordinate system having mutually orthogonal atmospheric variables of column water-vapor content and cloud liquid-water content. Vapor measurements showed a maximum around the intensifying typhoon with a more developed structure during typhoon development. Values were extrapolated for surface wind speed and cloud liquid water vapor content by assuming the troposphere to be saturated with respect to the water vapor in the typhoon. Comparisons with infrared cloud imagery and aircraft flight data show different time variations, attributed to poor typhoon-eye resolution in the microwave images.

Compact terahertz spectrometer based on disordered rough surfaces

NASA Astrophysics Data System (ADS)

Yang, Tao; Jiang, Bing; Ge, Jia-cheng; Zhu, Yong-yuan; Li, Xing-ao; Huang, Wei

2018-01-01

In this paper, a compact spectrometer based on disordered rough surfaces for operation in the terahertz band is presented. The proposed spectrometer consists of three components, which are used for dispersion, modulation and detection respectively. The disordered rough surfaces, which are acted as the dispersion component, are modulated by the modulation component. Different scattering intensities are captured by the detection component with different extent of modulation. With a calibration measurement process, one can reconstruct the spectra of the probe terahertz beam by solving a system of simultaneous linear equations. A Tikhonov regularization approach has been implemented to improve the accuracy of the spectral reconstruction. The reported broadband, compact, high-resolution terahertz spectrometer is well suited for portable terahertz spectroscopy applications.

An improved approach to identify irradiated spices using electronic nose, FTIR, and EPR spectroscopy.

PubMed

Sanyal, Bhaskar; Ahn, Jae-Jun; Maeng, Jeong-Hwan; Kyung, Hyun-Kyu; Lim, Ha-Kyeong; Sharma, Arun; Kwon, Joong-Ho

2014-09-01

Changes in cumin and chili powder from India resulting from electron-beam irradiation were investigated using 3 analytical methods: electronic nose (E-nose), Fourier transform infrared (FTIR) spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The spices had been exposed to 6 to 14 kGy doses recommended for microbial decontamination. E-nose measured a clear difference in flavor patterns of the irradiated spices in comparison with the nonirradiated samples. Principal component analysis further showed a dose-dependent variation. FTIR spectra of the samples showed strong absorption bands at 3425, 3007 to 2854, and 1746 cm(-1). However, both nonirradiated and irradiated spice samples had comparable patterns without any noteworthy changes in functional groups. EPR spectroscopy of the irradiated samples showed a radiation-specific triplet signal at g = 2.006 with a hyper-fine coupling constant of 3 mT confirming the results obtained with the E-nose technique. Thus, E-nose was found to be a potential tool to identify irradiated spices. © 2014 Institute of Food Technologists®

Essential Ambiguity and Essential Influence: Rereading Bohr's Reply to EPR

NASA Astrophysics Data System (ADS)

Plotnitsky, Arkady

2006-01-01

The article offers a rereading of Bohr's reply to the argument of A. Einstein, B. Podolsky, and N. Rosen (EPR) concerning the incompleteness, or else nonlocality, of quantum mechanics. Bohr shows EPR's argument to be deficient on their own terms, by virtue of an ambiguity found in their application of the criterion of reality they propose to the phenomena in question. He also offers an alternative interpretation of the EPR experiment itself, the thought experiment proposed by EPR, as part of his overall interpretation of quantum mechanics as complementarity.

EPR and optical investigation of Mn2+ doped L-histidine-4-nitrophenolate 4-nitrophenol single crystal

NASA Astrophysics Data System (ADS)

Prabakaran, R.; Subramanian, P.

2018-04-01

Single crystals of L-histidine-4-nitrophenolate 4-nitrophenol[LHFNP] complex doped with Mn2+ were grown by the slow evaporation method at room temperature. The EPR spectrum reveals the entry of one Mn2+ ion in the lattice. The angular variation plot was drawn between the angles and the magnetic field position. The spin Hamiltonian parameters were obtained by EPR-NMR program. The D and E values show the rhombic field around the ion and is an interstitial one. The g value obtained here suggests that the Mn2+ ion experiences a strong field and there is a transfer of electron from the metal ion to the ligand atom. The optical absorption study shows various bands and are assigned to the transition from the ground state 6A1g(S). The Racah and crystal field parameters have also been evaluated and fitted to the experimental values. The Racah parameter shows the covalent bonding between the metal ion to the ligand.

Active cancellation - A means to zero dead-time pulse EPR.

PubMed

Franck, John M; Barnes, Ryan P; Keller, Timothy J; Kaufmann, Thomas; Han, Songi

2015-12-01

The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power. Copyright © 2015 Elsevier Inc. All rights reserved.

Bi2MoxW1-xO6 solid solutions with tunable band structure and enhanced visible-light photocatalytic activities

NASA Astrophysics Data System (ADS)

Li, Wenqi; Ding, Xingeng; Wu, Huating; Yang, Hui

2018-07-01

Semiconductor photocatalysis is an effective green way to combat water pollution. For the first time, this study reports a novel method to develop Bi2MoxW1-xO6 solid solution with microsphere structure through anion-exchange method. All Bi2MoxW1-xO6 samples exhibit an Aurivillius-type crystal structure without any secondary phase, confirming that in complete solid solutions as the value of x increases, the band gap energy of Bi2MoxW1-xO6 solid solutions decreases, while the optical absorption edge moves to longer wavelength. The Raman spectra research shows an increase in orthorhombic distortion with progressive replacement of W sites in Bi2WO6 with Mo6+ ions. Compared to Bi2MoO6 and Bi2WO6 samples, Bi2Mo0.4W0.6O6 sample displayed best photocatalytic activity and cycling stability for degradation of RhB dye. The enhanced photocatalytic activity of Bi2Mo0.4W0.6O6 sample can be synergetically linked to hierarchical hollow structure, enhanced light absorbance, and high carrier-separation efficiency. Additionally, the hollow Bi2MoxW1-xO6 microspheres formation can be attributed to the Kirkendall effect.

40-Gb/s PDM-QPSK signal transmission over 160-m wireless distance at W-band.

PubMed

Xiao, Jiangnan; Yu, Jianjun; Li, Xinying; Xu, Yuming; Zhang, Ziran; Chen, Long

2015-03-15

We experimentally demonstrate a W-band optical-wireless transmission system over 160-m wireless distance with a bit rate up to 40 Gb/s. The optical-wireless transmission system adopts optical polarization-division-multiplexing (PDM), multiple-input multiple-output (MIMO) reception and antenna polarization diversity. Using this system, we experimentally demonstrate the 2×2 MIMO wireless delivery of 20- and 40-Gb/s PDM quadrature-phase-shift-keying (PDM-QPSK) signals over 640- and 160-m wireless links, respectively. The bit-error ratios (BERs) of these transmission systems are both less than the forward-error-correction (FEC) threshold of 3.8×10^-3.

A W-Band MMIC Radar System for Remote Detection of Vital Signs

NASA Astrophysics Data System (ADS)

Diebold, Sebastian; Ayhan, Serdal; Scherr, Steffen; Massler, Hermann; Tessmann, Axel; Leuther, Arnulf; Ambacher, Oliver; Zwick, Thomas; Kallfass, Ingmar

2012-12-01

In medical and personal health systems for vital sign monitoring, contact-free remote detection is favourable compared to wired solutions. For example, they help to avoid severe pain, which is involved when a patient with burned skin has to be examined. Continuous wave (CW) radar systems have proven to be good candidates for this purpose. In this paper a monolithic millimetre-wave integrated circuit (MMIC) based CW radar system operating in the W-band (75-110 GHz) at 96 GHz is presented. The MMIC components are custom-built and make use of 100 nm metamorphic high electron mobility transistors (mHEMTs). The radar system is employing a frequency multiplier-by-twelve MMIC and a receiver MMIC both packaged in split-block modules. They allow for the determination of respiration and heartbeat frequency of a human target sitting in 1 m distance. The analysis of the measured data is carried out in time and frequency domain and each approach is shown to have its advantages and drawbacks.

Electron beam transport analysis of W-band sheet beam klystron

NASA Astrophysics Data System (ADS)

Wang, Jian-Xun; Barnett, Larry R.; Luhmann, Neville C.; Shin, Young-Min; Humphries, Stanley

2010-04-01

The formation and transport of high-current density electron beams are of critical importance for the success of a number of millimeter wave and terahertz vacuum devices. To elucidate design issues and constraints, the electron gun and periodically cusped magnet stack of the original Stanford Linear Accelerator Center designed W-band sheet beam klystron circuit, which exhibited poor beam transmission (≤55%), have been carefully investigated through theoretical and numerical analyses taking advantage of three-dimensional particle tracking solvers. The re-designed transport system is predicted to exhibit 99.76% (cold) and 97.38% (thermal) beam transmission, respectively, under space-charge-limited emission simulations. The optimized design produces the required high aspect ratio (10:1) sheet beam with 3.2 A emission current with highly stable propagation. In the completely redesigned model containing all the circuit elements, more than 99% beam transmission is experimentally observed at the collector located about 160 mm distant from the cathode surface. Results are in agreement of the predictions of two ray-tracing simulators, CST PARTICLE STUDIO and OMNITRAK which also predict the observed poor transmission in the original design. The quantitative analysis presents practical factors in the modeling process to design a magnetic lens structure to stably transport the elliptical beam along the long drift tube.

Implementing a new EPR lineshape parameter for organic radicals in carbonaceous matter.

PubMed

Bourbin, Mathilde; Du, Yann Le; Binet, Laurent; Gourier, Didier

2013-07-17

Electron Paramagnetic Resonance (EPR) is a non-destructive, non-invasive technique useful for the characterization of organic moieties in primitive carbonaceous matter related to the origin of life. The classical EPR parameters are the peak-to-peak amplitude, the linewidth and the g factor; however, such parameters turn out not to suffice to fully determine a single EPR line. In this paper, we give the definition and practical implementation of a new EPR parameter based on the signal shape that we call the R10 factor. This parameter was originally defined in the case of a single symmetric EPR line and used as a new datation method for organic matter in the field of exobiology. Combined to classical EPR parameters, the proposed shape parameter provides a full description of an EPR spectrum and opens the way to novel applications like datation. Such a parameter is a powerful tool for future EPR studies, not only of carbonaceous matter, but also of any substance which spectrum exhibits a single symmetric line. The paper is a literate program-written using Noweb within the Org-mode as provided by the Emacs editor- and it also describes the full data analysis pipeline that computes the R10 on a real EPR spectrum.

Intercomparison of Unmanned Aerial Vehicle and Ground-Based Narrow Band Spectrometers Applied to Crop Trait Monitoring in Organic Potato Production

PubMed Central

Domingues Franceschini, Marston Héracles; Bartholomeus, Harm; van Apeldoorn, Dirk; Suomalainen, Juha; Kooistra, Lammert

2017-01-01

Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV)-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions fitted to vegetation indices, can relate spectra with crop traits. Although monitoring frameworks using multiple sensors can be more flexible, they may result in higher inaccuracy due to differences related to the sensors characteristics, which can affect information sampling. Also organic production systems can benefit from continuous monitoring focusing on crop management and stress detection, but few studies have evaluated applications with this objective. In this study, ground-based and UAV spectrometers were compared in the context of organic potato cultivation. Relatively accurate estimates were obtained for leaf chlorophyll (RMSE = 6.07 µg·cm−2), leaf area index (RMSE = 0.67 m2·m−2), canopy chlorophyll (RMSE = 0.24 g·m−2) and ground cover (RMSE = 5.5%) using five UAV-based data acquisitions, from 43 to 99 days after planting. These retrievals are slightly better than those derived from ground-based measurements (RMSE = 7.25 µg·cm−2, 0.85 m2·m−2, 0.28 g·m−2 and 6.8%, respectively), for the same period. Excluding observations corresponding to the first acquisition increased retrieval accuracy and made outputs more comparable between sensors, due to relatively low vegetation cover on this date. Intercomparison of vegetation indices indicated that indices based on the contrast between spectral bands in the visible and near-infrared, like OSAVI, MCARI2 and CIg provided, at certain extent, robust outputs that could be transferred between sensors. Information sampling at plot level by both sensing solutions resulted in comparable discriminative potential concerning advanced stages of late blight incidence. These results indicate that optical sensors, and

Intercomparison of Unmanned Aerial Vehicle and Ground-Based Narrow Band Spectrometers Applied to Crop Trait Monitoring in Organic Potato Production.

PubMed

Domingues Franceschini, Marston Héracles; Bartholomeus, Harm; van Apeldoorn, Dirk; Suomalainen, Juha; Kooistra, Lammert

2017-06-18

Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV)-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions fitted to vegetation indices, can relate spectra with crop traits. Although monitoring frameworks using multiple sensors can be more flexible, they may result in higher inaccuracy due to differences related to the sensors characteristics, which can affect information sampling. Also organic production systems can benefit from continuous monitoring focusing on crop management and stress detection, but few studies have evaluated applications with this objective. In this study, ground-based and UAV spectrometers were compared in the context of organic potato cultivation. Relatively accurate estimates were obtained for leaf chlorophyll (RMSE = 6.07 µg·cm -2 ), leaf area index (RMSE = 0.67 m²·m -2 ), canopy chlorophyll (RMSE = 0.24 g·m -2 ) and ground cover (RMSE = 5.5%) using five UAV-based data acquisitions, from 43 to 99 days after planting. These retrievals are slightly better than those derived from ground-based measurements (RMSE = 7.25 µg·cm -2 , 0.85 m²·m -2 , 0.28 g·m -2 and 6.8%, respectively), for the same period. Excluding observations corresponding to the first acquisition increased retrieval accuracy and made outputs more comparable between sensors, due to relatively low vegetation cover on this date. Intercomparison of vegetation indices indicated that indices based on the contrast between spectral bands in the visible and near-infrared, like OSAVI, MCARI2 and CI g provided, at certain extent, robust outputs that could be transferred between sensors. Information sampling at plot level by both sensing solutions resulted in comparable discriminative potential concerning advanced stages of late blight incidence. These results indicate that optical sensors

EPR study of free radicals in bread

NASA Astrophysics Data System (ADS)

Yordanov, Nicola D.; Mladenova, Ralitsa

2004-05-01

The features of the recorded EPR spectra of paramagnetic species formed in bread and rusk are reported. The appearance of free radicals in them is only connected with their thermal treatment since the starting materials (flour and grains) exhibit very weak EPR signal. The obtained EPR spectra are complex and indicate that: (i) the relative number of paramagnetic species depends on the temperature and treating time of the raw product; (ii) the g-values are strongly temperature dependent with a tendency to coincide at t≥220 °C. Because of the relatively low (150-220 °C) temperature of thermal treatment, the studied free radicals can be assumed to appear in the course of the browning (Maillard) reaction and not to the carbonization of the material.

Crossed, Small-Deflection Energy Analyzer for Wind/Temperature Spectrometer

NASA Technical Reports Server (NTRS)

Herrero, Federico A.; Finne, Theodore T.

2010-01-01

Determination of neutral winds and ion drifts in low-Earth-orbit missions requires measurements of the angular and energy distributions of the flux of neutrals and ions entering the satellite from the ram direction. The magnitude and direction of the neutral-wind (or ion-drift) determine the location of the maximum in the angular distribution of the flux. Knowledge of the angle of maximum flux with respect to satellite coordinates (pointing) is essential to determine the wind (or ion-drift) vector. The crossed Small-Deflection Energy Analyzer (SDEA) spectrometer (see Figure 1) occupies minimal volume and consumes minimal power. Designed for upper atmosphere/ionosphere investigations at Earth altitudes above 100 km, the spectrometer operates by detecting the angular and energy distributions of neutral atoms/molecules and ions in two mutually perpendicular planes. In this configuration, the two detection planes actually cross at the spectrometer center. It is possible to merge two SDEAs so they share a common optical axis and alternate measurements between two perpendicular planes, and reduce the number of ion sources from two to one. This minimizes the volume and footprint significantly and reduces the ion source power by a factor of two. The area of the entrance aperture affects the number of ions detected/second and also determines the energy resolution. Thermionic emitters require heater power of about 100 mW to produce 1 mA of electron beam current. Typically, electron energy is about 100 eV and requires a 100-V supply for electron acceleration to supply an additional 100 mW of power. Thus, ion source power is at most 200 mW. If two ion sources were to be used, the ion source power would be, at most, 400 mW. Detector power, deflection voltage power, and microcontroller and other functions require less than 150 mW. A WTS (wind/ temperature spectrometer) with two separate optical axes would consume about 650 mW, while the crossed SDEA described here consumes about

A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

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

Yap, Yung Szen, E-mail: yungszen@utm.my; Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor; Tabuchi, Yutaka

2015-06-15

We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, wemore » observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.« less

Design and experimental verification of a dual-band metamaterial filter

NASA Astrophysics Data System (ADS)

Zhu, Hong-Yang; Yao, Ai-Qin; Zhong, Min

2016-10-01

In this paper, we present the design, simulation, and experimental verification of a dual-band free-standing metamaterial filter operating in a frequency range of 1 THz-30 THz. The proposed structure consists of periodically arranged composite air holes, and exhibits two broad and flat transmission bands. To clarify the effects of the structural parameters on both resonant transmission bands, three sets of experiments are performed. The first resonant transmission band shows a shift towards higher frequency when the side width w 1 of the main air hole is increased. In contrast, the second resonant transmission band displays a shift towards lower frequency when the side width w 2 of the sub-holes is increased, while the first resonant transmission band is unchanged. The measured results indicate that these resonant bands can be modulated individually by simply optimizing the relevant structural parameters (w 1 or w 2) for the required band. In addition, these resonant bands merge into a single resonant band with a bandwidth of 7.7 THz when w 1 and w 2 are optimized simultaneously. The structure proposed in this paper adopts different resonant mechanisms for transmission at different frequencies and thus offers a method to achieve a dual-band and low-loss filter. Project supported by the Doctorate Scientific Research Foundation of Hezhou University, China (Grant No. HZUBS201503), the Promotion of the Basic Ability of Young and Middle-aged Teachers in Universities Project of Guangxi Zhuang Autonomous Region, China (Grant No. KY2016YB453), the Guangxi Colleges and Universities Key Laboratory Symbolic Computation, China, Engineering Data Processing and Mathematical Support Autonomous Discipline Project of Hezhou University, China (Grant No. 2016HZXYSX01).

Benchmarking CCMI models' top-of-atmosphere flux in the 9.6-µm ozone band using AURA TES Instantaneous Radiative Kernel

NASA Astrophysics Data System (ADS)

Kuai, L.; Bowman, K. W.; Worden, H. M.; Paulot, F.; Paynter, D.; Oman, L.; Strode, S. A.; Rozanov, E.; Stenke, A.; Revell, L. E.; Plummer, D. A.

2017-12-01

The estimated ozone radiative forcing (RF) from chemical-climate models range widely from +0.2 to +0.6 Wm-2. The reason has never been well understood. Since the ozone absorption in the 9.6 μm band contributes 97% of the O3 longwave RF, the variation of outgoing longwave radiation (OLR) due to ozone is dominant by this band. The observed TOA flux over 9.6 µm ozone band by Thermal Emission Spectrometer (TES) shows the global distribution has unique spatial patterns. In addition, the simulated TOA fluxes over 9.6 µm ozone band by different models have never been evaluated against observations. The bias of TOA flux from model could be primarily contributed by the bias of temperature, water vapor and ozone. Furthermore, the sensitivity of TOA flux to tropospheric ozone (instantaneous radiative kernel, IRK) may also affected by these biases (Kuai et al., 2017). The bias in TOA flux would eventually propagate into model calculations of ozone RF and cause divergence of the predictions of future climate by models. In this study, we applied the observation-based IRK product by AURA TES to attribute the CCMI model bias in TOA flux over 9.6 µm ozone band to ozone, water vapor, air temperature, and surface temperature. The comparisons of the three CCMI models (AM3, SOCOL3 and GEOCCM) to TES observations suggest that 1) all models underestimate the TOA flux at tropics and subtropics. 2) The TOA flux bias is comparable similar by AM3 and GEOSCC (-0.2 to -0.3 W/m2) however is larger for the relative young model, SOCOL3 (-0.4 to -0.6 W/m2). 3) The contributions by surface temperature are similarly moderate (-0.2 W/m2). 4) The contribution of ozone is largest by SOCOL3 (-0.3 W/m2), smallest by GEOSCCM (less than 0.1 W/m2) and moderate by AM3 (-0.2 W/m2). 5) Overall, the contributions by atmospheric temperature are all small (less than 0.1 W/m2). 6) The contribution of water vapor is negative and small by both SOCOL3 and GEOSCCM (0.1 W/m2) however large and positive by AM3 (0

EPR of radiation defects in lithium-oxyfluoride glass ceramics

NASA Astrophysics Data System (ADS)

Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

2010-11-01

We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

Real-Time Imaging with Frequency Scanning Array Antenna for Industrial Inspection Applications at W band

NASA Astrophysics Data System (ADS)

Larumbe, Belen; Laviada, Jaime; Ibáñez-Loinaz, Asier; Teniente, Jorge

2018-01-01

A real-time imaging system based on a frequency scanning antenna for conveyor belt setups is presented in this paper. The frequency scanning antenna together with an inexpensive parabolic reflector operates at the W band enabling the detection of details with dimensions in the order of 2 mm. In addition, a low level of sidelobes is achieved by optimizing unequal dividers to window the power distribution for sidelobe reduction. Furthermore, the quality of the images is enhanced by the radiation pattern properties. The performance of the system is validated by showing simulation as well as experimental results obtained in real time, proving the feasibility of these kinds of frequency scanning antennas for cost-effective imaging applications.

Increase of weakly acidic gas esophagopharyngeal reflux (EPR) and swallowing-induced acidic/weakly acidic EPR in patients with chronic cough responding to proton pump inhibitors.

PubMed

Kawamura, O; Shimoyama, Y; Hosaka, H; Kuribayashi, S; Maeda, M; Nagoshi, A; Zai, H; Kusano, M

2011-05-01

Gastro-esophageal reflux disease (GERD)-related chronic cough (CC) may have multifactorial causes. To clarify the characteristics of esophagopharyngeal reflux (EPR) events in CC patients whose cough was apparently influenced by gastro-esophageal reflux (GER), we studied patients with CC clearly responding to full-dose proton pump inhibitor (PPI) therapy (CC patients). Ten CC patients, 10 GERD patients, and 10 healthy controls underwent 24-h ambulatory pharyngo-esophageal impedance and pH monitoring. Weakly acidic reflux was defined as a decrease of pH by >1 unit with a nadir pH >4. In six CC patients, monitoring was repeated after 8 weeks of PPI therapy. The number of each EPR event and the symptom association probability (SAP) were calculated. Symptoms were evaluated by a validated GERD symptom questionnaire. Weakly acidic gas EPR and swallowing-induced acidic/weakly acidic EPR only occurred in CC patients, and the numbers of such events was significantly higher in the CC group than in the other two groups (P < 0.05, respectively). Symptom association probability analysis revealed a positive association between GER and cough in three CC patients. Proton pump inhibitor therapy abolished swallowing-induced acidic/weakly acidic EPR, reduced weakly acidic gas EPR, and improved symptoms (all P < 0.05). Most patients with CC responding to PPI therapy had weakly acidic gas EPR and swallowing-induced acidic/weakly acidic EPR. A direct effect of acidic mist or liquid refluxing into the pharynx may contribute to chronic cough, while cough may also arise indirectly from reflux via a vago-vagal reflex in some patients. © 2011 Blackwell Publishing Ltd.

New Physical Optics Method for Curvilinear Refractive Surfaces and its Verification in the Design and Testing of W-band Dual-Aspheric Lenses

DTIC Science & Technology

2013-10-01

its Verification in the Design and Testing of W-band Dual-Aspheric Lenses A. Altintas and V. Yurchenko EEE Department, Bilkent University Ankara...Theory and Techn., Vol. 55, 239, 2007 [5] ZEMAX Development Corporation, Zemax- EE , http://www.zemax.com/ [6] Pasqualini D. and Maci S., ”High-Frequency

Spin entanglement, decoherence and Bohm's EPR paradox.

PubMed

Cavalcanti, E G; Drummond, P D; Bachor, H A; Reid, M D

2009-10-12

We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with current quantum optical technologies. For a macroscopic number of particles prepared in a correlated state, spin entanglement and the EPR paradox can be demonstrated using our criteria for efficiencies eta > 1/3 and eta > 2/3 respectively. This indicates a surprising insensitivity to loss decoherence, in a macroscopic system of ultra-cold atoms or photons.

Full cycle rapid scan EPR deconvolution algorithm.

PubMed

Tseytlin, Mark

2017-08-01

Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan

Full cycle rapid scan EPR deconvolution algorithm

NASA Astrophysics Data System (ADS)

Tseytlin, Mark

2017-08-01

Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan

High-pressure EPR spectroscopy studies of the E. coli lipopolysaccharide transport proteins LptA and LptC.

PubMed

Schultz, Kathryn M; Klug, Candice S

2017-12-01

The use of pressure is an advantageous approach to the study of protein structure and dynamics because it can shift the equilibrium populations of protein conformations toward higher energy states that are not of sufficient population to be observable at atmospheric pressure. Recently, the Hubbell group at the University of California, Los Angeles, reintroduced the application of high pressure to the study of proteins by electron paramagnetic resonance (EPR) spectroscopy. This methodology is possible using X-band EPR spectroscopy due to advances in pressure intensifiers, sample cells, and resonators. In addition to the commercial availability of the pressure generation and sample cells by Pressure Biosciences Inc., a five-loop-four-gap resonator required for the initial high pressure EPR spectroscopy experiments by the Hubbell group, and those reported here, was designed by James S. Hyde and built and modified at the National Biomedical EPR Center. With these technological advances, we determined the effect of pressure on the essential periplasmic lipopolysaccharide (LPS) transport protein from Escherichia coli , LptA, and one of its binding partners, LptC. LptA unfolds from the N-terminus to the C-terminus, binding of LPS does not appreciably stabilize the protein under pressure, and monomeric LptA unfolds somewhat more readily than oligomeric LptA upon pressurization to 2 kbar. LptC exhibits a fold and relative lack of stability upon LPS binding similar to LptA, yet adopts an altered, likely monomeric, folded conformation under pressure with only its C-terminus unraveling. The pressure-induced changes likely correlate with functional changes associated with binding and transport of LPS.

Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods.

PubMed

Segawa, Takuya F; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O; Jeschke, Gunnar

2016-05-21

Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the (1)H NMR spectrum of H2O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10-20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

Toward 2D and 3D imaging of magnetic nanoparticles using EPR measurements.

PubMed

Coene, A; Crevecoeur, G; Leliaert, J; Dupré, L

2015-09-01

Magnetic nanoparticles (MNPs) are an important asset in many biomedical applications. An effective working of these applications requires an accurate knowledge of the spatial MNP distribution. A promising, noninvasive, and sensitive technique to visualize MNP distributions in vivo is electron paramagnetic resonance (EPR). Currently only 1D MNP distributions can be reconstructed. In this paper, the authors propose extending 1D EPR toward 2D and 3D using computer simulations to allow accurate imaging of MNP distributions. To find the MNP distribution belonging to EPR measurements, an inverse problem needs to be solved. The solution of this inverse problem highly depends on the stability of the inverse problem. The authors adapt 1D EPR imaging to realize the imaging of multidimensional MNP distributions. Furthermore, the authors introduce partial volume excitation in which only parts of the volume are imaged to increase stability of the inverse solution and to speed up the measurements. The authors simulate EPR measurements of different 2D and 3D MNP distributions and solve the inverse problem. The stability is evaluated by calculating the condition measure and by comparing the actual MNP distribution to the reconstructed MNP distribution. Based on these simulations, the authors define requirements for the EPR system to cope with the added dimensions. Moreover, the authors investigate how EPR measurements should be conducted to improve the stability of the associated inverse problem and to increase reconstruction quality. The approach used in 1D EPR can only be employed for the reconstruction of small volumes in 2D and 3D EPRs due to numerical instability of the inverse solution. The authors performed EPR measurements of increasing cylindrical volumes and evaluated the condition measure. This showed that a reduction of the inherent symmetry in the EPR methodology is necessary. By reducing the symmetry of the EPR setup, quantitative images of larger volumes can be

X-Band Rapid-Scan Electron Paramagnetic Resonance of Radiation-Induced Defects in Tooth Enamel

PubMed Central

Yu, Zhelin; Romanyukha, Alexander; Eaton, Sandra S.; Eaton, Gareth R.

2015-01-01

X-band rapid-scan electron paramagnetic resonance (EPR) spectra from tooth enamel samples irradiated with doses of 0.5, 1 and 10 Gy had substantially improved signal-to-noise relative to conventional continuous wave EPR. The radiation-induced signal in 60 mg of a tooth enamel sample irradiated with a 0.5 Gy dose was readily characterized in spectra recorded with 34 min data acquisition times. The coefficient of variance of the calculated dose for a 1 Gy irradiated sample, based on simulation of the first-derivative spectra for three replicates as the sum of native and radiation-induced signals, was 3.9% for continuous wave and 0.4% for rapid scan. PMID:26207683

The calibration of the WISE W1 and W2 Tully-Fisher relation

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

Neill, J. D.; Seibert, Mark; Scowcroft, Victoria

2014-09-10

In order to explore local large-scale structures and velocity fields, accurate galaxy distance measures are needed. We now extend the well-tested recipe for calibrating the correlation between galaxy rotation rates and luminosities—capable of providing such distance measures—to the all-sky, space-based imaging data from the Wide-field Infrared Survey Explorer (WISE) W1 (3.4 μm) and W2 (4.6 μm) filters. We find a correlation of line width to absolute magnitude (known as the Tully-Fisher relation, TFR) of M{sub W1}{sup b,i,k,a}=−20.35−9.56(log W{sub mx}{sup i}−2.5) (0.54 mag rms) and M{sub W2}{sup b,i,k,a}=−19.76−9.74(log W{sub mx}{sup i}−2.5) (0.56 mag rms) from 310 galaxies in 13 clusters. We update themore » I-band TFR using a sample 9% larger than in Tully and Courtois. We derive M{sub I}{sup b,i,k}=−21.34−8.95(log W{sub mx}{sup i}−2.5) (0.46 mag rms). The WISE TFRs show evidence of curvature. Quadratic fits give M{sub W1}{sup b,i,k,a}=−20.48−8.36(log W{sub mx}{sup i}−2.5)+3.60(log W{sub mx}{sup i}−2.5){sup 2} (0.52 mag rms) and M{sub W2}{sup b,i,k,a}=−19.91−8.40(log W{sub mx}{sup i}−2.5)+4.32(log W{sub mx}{sup i}−2.5){sup 2} (0.55 mag rms). We apply an I-band –WISE color correction to lower the scatter and derive M{sub C{sub W{sub 1}}}=−20.22−9.12(log W{sub mx}{sup i}−2.5) and M{sub C{sub W{sub 2}}}=−19.63−9.11(log W{sub mx}{sup i}−2.5) (both 0.46 mag rms). Using our three independent TFRs (W1 curved, W2 curved, and I band), we calibrate the UNION2 Type Ia supernova sample distance scale and derive H {sub 0} = 74.4 ± 1.4(stat) ± 2.4(sys) km s{sup –1} Mpc{sup –1} with 4% total error.« less

Einstein and the Quantum: The Secret Life of EPR

NASA Astrophysics Data System (ADS)

Fine, Arthur

2006-05-01

Locality, separation and entanglement -- 1930s style. Starting with Solvay 1927, we'll explore the background to the 1935 paper by Einstein, Podolsky and Rosen: how it was composed, the actual argument and principles used, and how the paper was received by Schroedinger, and others. We'll also look at Bohr's response: the extent to which Bohr connects with what Einstein was after in EPR and the extent to which EPR marks a shift in Bohr's thinking about the quantum theory. Time permitting, we will contrast EPR with Bell's theorem.

Digital detection and processing of multiple quadrature harmonics for EPR spectroscopy.

PubMed

Ahmad, R; Som, S; Kesselring, E; Kuppusamy, P; Zweier, J L; Potter, L C

2010-12-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. Copyright © 2010 Elsevier Inc. All rights reserved.

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JETa)

NASA Astrophysics Data System (ADS)

Shumack, A. E.; Rzadkiewicz, J.; Chernyshova, M.; Jakubowska, K.; Scholz, M.; Byszuk, A.; Cieszewski, R.; Czarski, T.; Dominik, W.; Karpinski, L.; Kasprowicz, G.; Pozniak, K.; Wojenski, A.; Zabolotny, W.; Conway, N. J.; Dalley, S.; Figueiredo, J.; Nakano, T.; Tyrrell, S.; Zastrow, K.-D.; Zoita, V.

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JET.

PubMed

Shumack, A E; Rzadkiewicz, J; Chernyshova, M; Jakubowska, K; Scholz, M; Byszuk, A; Cieszewski, R; Czarski, T; Dominik, W; Karpinski, L; Kasprowicz, G; Pozniak, K; Wojenski, A; Zabolotny, W; Conway, N J; Dalley, S; Figueiredo, J; Nakano, T; Tyrrell, S; Zastrow, K-D; Zoita, V

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

Advancements in Kinetic Inductance Detector, Spectrometer, and Amplifier Technologies for Millimeter-Wave Astronomy

NASA Astrophysics Data System (ADS)

Che, George

Spec devices and demonstrate basic functionality of the first WSpec prototype. As part of an effort to develop the first W-Band (75-110 GHz) TKIP, I construct a cryogenic waveguide feedthrough, which enhances the Astronomical Instrumentation Laboratory's capability to test W-Band devices in general. These efforts contribute to the continued maturation of these kinetic inductance technologies, which will usher in a new era of millimeter-wave astronomy.

Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs)

NASA Astrophysics Data System (ADS)

de Oliveira, Marcos; Wiegand, Thomas; Elmer, Lisa-Maria; Sajid, Muhammad; Kehr, Gerald; Erker, Gerhard; Magon, Claudio José; Eckert, Hellmut

2015-03-01

Anisotropic interactions present in three new nitroxide radicals prepared by N,N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs) have been characterized by continuous-wave (cw) and pulsed X-band EPR spectroscopies in solid FLP-hydroxylamine matrices at 100 K. Anisotropic g-tensor values and 11B, 14N, and 31P hyperfine coupling tensor components have been extracted from continuous-wave lineshape analyses, electron spin echo envelope modulation (ESEEM), and hyperfine sublevel correlation spectroscopy (HYSCORE) experiments with the help of computer simulation techniques. Suitable fitting constraints are developed on the basis of density functional theory (DFT) calculations. These calculations reveal that different from the situation in standard nitroxide radicals (TEMPO), the g-tensors are non-coincident with any of the nuclear hyperfine interaction tensors. The determination of these interaction parameters turns out to be successful, as the cw- and pulse EPR experiments are highly complementary in informational content. While the continuous-wave lineshape is largely influenced by the anisotropic hyperfine coupling to 14N and 31P, the ESEEM and HYSCORE spectra contain important information about the 11B hyperfine coupling and nuclear electric quadrupolar interaction. The set of cw- and pulsed EPR experiments, with fitting constraints developed by DFT calculations, defines an efficient strategy for the structural analysis of paramagnetic FLP adducts.

Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs)

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

Oliveira, Marcos de; Magon, Claudio José; Wiegand, Thomas

2015-03-28

Anisotropic interactions present in three new nitroxide radicals prepared by N,N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs) have been characterized by continuous-wave (cw) and pulsed X-band EPR spectroscopies in solid FLP-hydroxylamine matrices at 100 K. Anisotropic g-tensor values and {sup 11}B, {sup 14}N, and {sup 31}P hyperfine coupling tensor components have been extracted from continuous-wave lineshape analyses, electron spin echo envelope modulation (ESEEM), and hyperfine sublevel correlation spectroscopy (HYSCORE) experiments with the help of computer simulation techniques. Suitable fitting constraints are developed on the basis of density functional theory (DFT) calculations. These calculations reveal that differentmore » from the situation in standard nitroxide radicals (TEMPO), the g-tensors are non-coincident with any of the nuclear hyperfine interaction tensors. The determination of these interaction parameters turns out to be successful, as the cw- and pulse EPR experiments are highly complementary in informational content. While the continuous-wave lineshape is largely influenced by the anisotropic hyperfine coupling to {sup 14}N and {sup 31}P, the ESEEM and HYSCORE spectra contain important information about the {sup 11}B hyperfine coupling and nuclear electric quadrupolar interaction. The set of cw- and pulsed EPR experiments, with fitting constraints developed by DFT calculations, defines an efficient strategy for the structural analysis of paramagnetic FLP adducts.« less

Self-testing through EPR-steering

NASA Astrophysics Data System (ADS)

Šupić, Ivan; Hoban, Matty J.

2016-07-01

The verification of quantum devices is an important aspect of quantum information, especially with the emergence of more advanced experimental implementations of quantum computation and secure communication. Within this, the theory of device-independent robust self-testing via Bell tests has reached a level of maturity now that many quantum states and measurements can be verified without direct access to the quantum systems: interaction with the devices is solely classical. However, the requirements for this robust level of verification are daunting and require high levels of experimental accuracy. In this paper we discuss the possibility of self-testing where we only have direct access to one part of the quantum device. This motivates the study of self-testing via EPR-steering, an intermediate form of entanglement verification between full state tomography and Bell tests. Quantum non-locality implies EPR-steering so results in the former can apply in the latter, but we ask what advantages may be gleaned from the latter over the former given that one can do partial state tomography? We show that in the case of self-testing a maximally entangled two-qubit state, or ebit, EPR-steering allows for simpler analysis and better error tolerance than in the case of full device-independence. On the other hand, this improvement is only a constant improvement and (up to constants) is the best one can hope for. Finally, we indicate that the main advantage in self-testing based on EPR-steering could be in the case of self-testing multi-partite quantum states and measurements. For example, it may be easier to establish a tensor product structure for a particular party’s Hilbert space even if we do not have access to their part of the global quantum system.

W-band radio-over-fiber propagation of two optically encoded wavelength channels

NASA Astrophysics Data System (ADS)

Eghbal, Morad Khosravi; Shadaram, Mehdi

2018-01-01

We propose a W-band wavelength-division multiplexing (WDM)-over-optical code-division multiple access radio-over-fiber system. This system offers capacity expansion by increasing the working frequency to millimeter wave region and by introducing optical encoding and multiwavelength multiplexing. The system's functionality is investigated by software modeling, and the results are presented. The generated signals are data modulated at 10 Gb/s and optically encoded for two wavelength channels and transmitted with a 20-km length of fiber. The received signals are optically decoded and detected. Also, encoding has improved the bit error rate (BER) versus the received optical power margin for the WDM setting by about 4 dB. In addition, the eye-diagram shows that the difference between received optical power levels at the BER of 10-12 to 10-3 is about 1.3% between two encoded channels. This method of capacity improvement is significantly important for the next generation of mobile communication, where millimeter wave signals will be widely used to deliver data to small cells.

EPR spectra induced by gamma-irradiation of some dry medical herbs

NASA Astrophysics Data System (ADS)

Yordanov, N. D.; Lagunov, O.; Dimov, K.

2009-04-01

The radiation-induced EPR spectra in some medical herbs are reported. The samples studied are: (i) leaves of nettle, common balm, peppermint and thyme; (ii) stalks of common balm, thyme, milfoil, yarrow and marigold; (iii) blossoms of yarrow and marigold; (iv) blossoms and leaves of hawthorn and tutsan; and (v) roots of common valerian, nettle, elecampane (black and white), restharrows and carlina. Before irradiation all samples exhibit one weak anisotropic singlet EPR line with effective g-value of 2.0050±0.0002. The radiation-induced spectra fall into three groups. EPR spectra of irradiated blossoms of yarrow and marigold, stalks of common balm, thyme, tutsan and yarrow as well as roots of common valerian, nettle and elecampane (black and white) show "cellulose-like" EPR spectrum typical for irradiated plants. It is characterized by one intense central line with g=2.0050±0.0005 and two weak satellite lines situated ca. 30 G left and right to it. EPR spectra of gamma-irradiated restharrows and carlina are complex. They may be represented by one triplet corresponding to the "cellulose-like" EPR spectrum, one relatively intense singlet, situated in the center of the spectrum, and five weak additional satellite lines left and right to the center. The last spectrum was assigned as "carbohydrate-like" type. Only one intense EPR singlet with g=2.0048±0.0005 was recorded after irradiation of leaves of nettle and common balm. The lifetime of the radiation-induced EPR spectra was followed for a period of 3 months.

Case Studies in e-RPL and e-PR

ERIC Educational Resources Information Center

Cameron, Roslyn; Miller, Allison

2014-01-01

The use of ePortfolios for recognition of prior learning (e-RPL) and for professional recognition (e-PR) is slowly gaining in popularity in the VET sector however their use is sporadic across educational sectors, disciplines, educational institutions and professions. Added to this is an array of purposes and types of e-RPL and e-PR models and…

Note: Vector network analyzer-ferromagnetic resonance spectrometer using high Q-factor cavity.

PubMed

Lo, C K; Lai, W C; Cheng, J C

2011-08-01

A ferromagnetic resonance (FMR) spectrometer whose main components consist of an X-band resonator and a vector network analyzer (VNA) was developed. This spectrometer takes advantage of a high Q-factor (9600) cavity and state-of-the-art VNA. Accordingly, field modulation lock-in technique for signal to noise ratio (SNR) enhancement is no longer necessary, and FMR absorption can therefore be extracted directly. Its derivative for the ascertainment of full width at half maximum height of FMR peak can be found by taking the differentiation of original data. This system was characterized with different thicknesses of permalloy (Py) films and its multilayer, and found that the SNR of 5 nm Py on glass was better than 50, and did not have significant reduction even at low microwave excitation power (-20 dBm), and at low Q-factor (3000). The FMR other than X-band can also be examined in the same manner by using a suitable band cavity within the frequency range of VNA.

A Wide-Band High-Gain Compact SIS Receiver Utilizing a 300-μW SiGe IF LNA

NASA Astrophysics Data System (ADS)

Montazeri, Shirin; Grimes, Paul K.; Tong, Cheuk-Yu Edward; Bardin, Joseph C.

2017-06-01

Low-power low-noise amplifiers integrated with superconductor-insulator-superconductor (SIS) mixers are required to enable implementation of large-scale focal plane arrays. In this work, a 220-GHz SIS mixer has been integrated with a high-gain broad-band low-power IF amplifier into a compact receiver module. The low noise amplifier (LNA) was specifically designed to match to the SIS output impedance and contributes less than 7 K to the system noise temperature over the 4-8 GHz IF frequency range. A receiver noise temperature of 30-45 K was measured for a local oscillator frequency of 220 GHz over an IF spanning 4-8 GHz. The LNA power dissipation was only 300-μW. To the best of the authors' knowledge, this is the lowest power consumption reported for a high-gain wide-band LNA directly integrated with an SIS mixer.

Dual Band Deep Ultraviolet AlGaN Photodetectors

NASA Technical Reports Server (NTRS)

Aslam, S.; Miko, L.; Stahle, C.; Franz, D.; Pugel, D.; Guan, B.; Zhang, J. P.; Gaska, R.

2007-01-01

We report on the design, fabrication and characterization of a back-illuminated voltage bias selectable dual-band AlGaN UV photodetector. The photodetector can separate UVA and W-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias is applied between the top and bottom electrodes, the detector can sense UV-A and reject W-B band radiation. Alternatively, under reverse bias, the photodetector can sense UV-B and reject UV-A band radiation.

Free-radical probes for functional in vivo EPR imaging

NASA Astrophysics Data System (ADS)

Subramanian, S.; Krishna, M. C.

2007-02-01

Electron paramagnetic resonance imaging (EPRI) is one of the recent functional imaging modalities that can provide valuable in vivo physiological information on its own merit and aids as a complimentary imaging technique to MRI and PET of tissues especially with respect to in vivo pO II (oxygen partial pressure), redox status and pharmacology. EPR imaging mainly deals with the measurement of distribution and in vivo dynamics and redox changes using special nontoxic paramagnetic spin probes that can be infused into the object of investigation. These spin probes should be characterized by simple EPR spectra, preferably with narrow EPR lines. The line width should be reversibly sensitive to the concentration of in vivo pO II with a linear dependence. Several non-toxic paramagnetic probes, some particulate and insoluble and others water-soluble and infusible (by intravenous or intramuscular injection) have been developed which can be effectively used to quantitatively assess tissue redox status, and tumor hypoxia. Quantitative assessment of the redox status of tissue in vivo is important in investigating oxidative stress, and that of tissue pO II is very important in radiation oncology. Other areas in which EPR imaging and oxymetry may help are in the investigation of tumorangiogenesis, wound healing, oxygenation of tumor tissue by the ingestion of oxygen-rich gases, etc. The correct choice of the spin probe will depend on the modality of measurement (whether by CW or time-domain EPR imaging) and the particular physiology interrogated. Examples of the available spin probes and some EPR imaging applications employing them are presented.

Ku-band field-effect power transistors

NASA Technical Reports Server (NTRS)

Taylor, G. C.; Huang, H. C.

1979-01-01

A single stage amplifier was developed using an 8 gate, 1200 micrometer width device to give a gain of 3.3 + or - 0.1 dB over the 14.4 to 15.4 GHz band with an output power of 0.48 W and 15% minimum efficiency with 0.255 W of input power. With two 8 gate devices combined and matched on the device carrier, using a lumped element format, a gain of 3 dB was attained over the 14.5 to 15.5 GHz band with a maximum efficiency of 9.9% for an output power of 0.8 W.

Fast neutron detection with a segmented spectrometer

NASA Astrophysics Data System (ADS)

Langford, T. J.; Bass, C. D.; Beise, E. J.; Breuer, H.; Erwin, D. K.; Heimbach, C. R.; Nico, J. S.

2015-01-01

A fast neutron spectrometer consisting of segmented plastic scintillator and 3He proportional counters was constructed for the measurement of neutrons in the energy range 1-200 MeV. We discuss its design, principles of operation, and the method of analysis. The detector is capable of observing very low neutron fluxes in the presence of ambient gamma background and does not require scintillator pulse-shape discrimination. The spectrometer was characterized for its energy response in fast neutron fields of 2.5 MeV and 14 MeV, and the results are compared with Monte Carlo simulations. Measurements of the fast neutron flux and energy response at 120 m above sea-level (39.130°N, 77.218°W) and at a depth of 560 m in a limestone mine are presented. Finally, the design of a spectrometer with improved sensitivity and energy resolution is discussed.

EPR/PTFE dosimetry for test reactor environments

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

Vehar, D.W.; Griffin, P.J.; Quirk, T.J.

2011-07-01

The use of Electron Paramagnetic Resonance (EPR) spectroscopy with materials such as alanine is well established as a technique for measurement of ionizing radiation absorbed dose in photon and electron fields such as Co-60, high-energy bremsstrahlung and electron-beam fields [1]. In fact, EPR/Alanine dosimetry has become a routine transfer standard for national standards bodies such as NIST and NPL. In 1992 the Radiation Metrology Laboratory (RML) at Sandia National Laboratories implemented EPR/Alanine capabilities for use in routine and calibration activities at its Co-60 and pulsed-power facilities. At that time it also investigated the usefulness of the system for measurement ofmore » absorbed dose in the mixed neutron/photon environments of reactors such as the Sandia Pulsed Reactor and the Annular Core Research Reactor used for hardness testing of electronics. The RML concluded that the neutron response of alanine was a sufficiently high fraction of the overall dosimeter response that the resulting uncertainties in the photon dose would be unacceptably large for silicon-device testing. However, it also suggested that non-hydrogenous materials such as polytetrafluoroethylene (PTFE) would exhibit smaller neutron response and might be useful in mixed environments. Preliminary research with PTFE in photon environments indicated considerable promise, but further development was not pursued at that time. Because of renewed interest in absorbed dose measurements that could better define the individual contributions of photon and neutron components to the overall dose delivered to a test object, the RML has re-initiated the development of an EPR/PTFE dosimetry system. This effort consists of three stages: 1) Identification of PTFE materials that may be suitable for dosimetry applications. It was speculated that the inconsistency of EPR signatures in the earlier samples may have been due to variability in PTFE manufacturing processes. 2) Characterization of

Applications of EPR steering in quantum teleportation and NOON states

NASA Astrophysics Data System (ADS)

Zárate, Laura Rosales

2018-04-01

Einstein-Podolsky-Rosen (EPR) steering refers to the type of correlations described in the EPR paradox, where one observer seems to affect ("steer") the state of other observer by using local measurements. There have been several works regarding characterization and quantification of EPR steering. One characteristic of this non-local correlation is that it can be asymmetric, while entanglement is symmetric. This asymmetric property is relevant for potential applications of EPR steering to quantum information, in particular to quantum cryptography and quantum teleportation. This latter refers to the process where one observer sends an unknown quantum state to Bob, who is in a different location. They communicate by classical means. Here we will show that EPR steering is a necessary resource to obtain secure continuous variable teleportation. We will also consider NOON states, which is an example of an entangled state. For this state, we will present a steering signature. This contribution reviews the work derived in Refs. [1] and [2], which was presented as an invited talk in ELAF 2017.

Digital EPR with an arbitrary waveform generator and direct detection at the carrier frequency

PubMed Central

Tseitlin, Mark; Quine, Richard W.; Rinard, George A.; Eaton, Sandra S.; Eaton, Gareth R.

2011-01-01

A digital EPR spectrometer was constructed by replacing the traditional bridge with an arbitrary waveform generator (AWG) to produce excitation patterns and a high-speed digitizer for direct detection of the spin system response at the carrier frequency. Digital down-conversion produced baseband signals in quadrature with very precise orthogonality. Real-time resonator tuning was performed by monitoring the Fourier transforms of signals reflected from the resonator during frequency sweeps generated by the AWG. The capabilities of the system were demonstrated by rapid magnetic field scans at 256 MHz carrier frequency, and FID and spin echo experiments at 1 and 10 GHz carrier frequencies. For the rapid scan experiments the leakage through a cross-loop resonator was compensated by adjusting the amplitude and phase of a sinusoid at the carrier frequency that was generated with another AWG channel. PMID:21968420

Concept Study Report: Extreme-Ultraviolet Imaging Spectrometer Solar-B

NASA Technical Reports Server (NTRS)

Doschek, George, A.; Brown, Charles M.; Davila, Joseph M.; Dere, Kenneth P.; Korendyke, Clarence M.; Mariska, John T.; Seely, John F.

1999-01-01

We propose a next generation Extreme-ultraviolet Imaging Spectrometer (EIS) that for the first time combines high spectral, spatial, and temporal resolution in a single solar spectroscopic instrument. The instrument consists of a multilayer-coated off-axis telescope mirror and a multilayer-coated grating spectrometer. The telescope mirror forms solar images on the spectrometer entrance slit assembly. The spectrometer forms stigmatic spectra of the solar region located at the slit. This region is selected by the articulated telescope mirror. Monochromatic images are obtained either by rastering the solar region across a narrow entrance slit, or by using a very wide slit (called a slot) in place of the slit. Monochromatic images of the region centered on the slot are obtained in a single exposure. Half of each optic is coated to maximize reflectance at 195 Angstroms; the other half to maximize reflectance at 270 Angstroms. The two Extreme Ultraviolet (EUV) wavelength bands have been selected to maximize spectral and dynamical and plasma diagnostic capabilities. Spectral lines are observed that are formed over a temperature range from about 0.1 MK to about 20 MK. The main EIS instrument characteristics are: wavelength bands - 180 to 204 Angstroms; 250 to 290 Angstroms; spectral resolution - 0.0223 Angstroms/pixel (34.3km/s at 195 Angstroms and 23.6 km/s at 284 Angstroms); slit dimensions - 4 slits, two currently specified dimensions are 1" x 1024" and 50" x 1024" (the slot); largest spatial field of view in a single exposure - 50" x 1024"; highest time resolution for active region velocity studies - 4.4 s.

Pacific tectonics: Eastern-Pacific "stationarity" of EPR and causative association with Equator

NASA Astrophysics Data System (ADS)

Bostrom, R. C.

2003-04-01

The fundamentals of present-day Pacific tectonics are observed to be: its N/S mirror-symmetry about the Equator, displayed by the major transforms; its E/W asymmetry, represented by the western motion of the world's largest plate, originating in the eastern Equatorial Pacific; and correspondingly, development of the globally most voluminous subduction, at the western Pacific margin. The configuration seen at present is maintained at a fundamental level. The maximum in convective upwelling develops as coalescing plumes in the Galapagos region in the eastern Pacific. This has been found (Lonsdale 1988; McGuire and Hilde 2002; Chen and Lin 2002) to produce steady westward propagation of the Nazca/Cocos axis. Continually renewed, it determines the orientation and locus of a quasi-stationary EPR, centered on the Equator. Magnetic dating of boundaries in satellite gravity images records the Cenozoic history of the EPR, namely re-orientation in consequence of slow counter-clockwise re-orientation of the Equator. Relative to the present, during Maastrichtian times both Equator and plate motion were aligned WNW, recorded paleomagnetically and by features in the western, older part of the Pacific crust. Material subducted at that time accumulated principally beneath the SE Asia margin. Its slow heating is believed to play a role in the deep-seated activity and back-arc spreading associated with latter-day convergence in that region. The mechanism primarily responsible for the Pacific regime may be that mantle convection is not immune, as is generally tacitly supposed, to the minute westward tilt (c. 0.36°) under which it takes place. The latter, now astronomically quantifiable without tidal identification, represents the attraction component of water and solid-Earth masses which averaged over unit day lags the direction of purely geocentric g. Under gravity minutely E/W asymmetric, convection as always promoting the most efficient dissipative configuration, favors

Emergency EPR and OSL dosimetry with table vitamins and minerals.

PubMed

Sholom, S; McKeever, S W S

2016-12-01

Several table vitamins, minerals and L-lysine amino acid have been preliminarily tested as potential emergency dosemeters using electron paramagnetic resonance (EPR) and optically stimulated luminescence (OSL) techniques. Radiation-induced EPR signals were detected in samples of vitamin B2 and L-lysine while samples of multivitamins of different brands as well as mineral Mg demonstrated prominent OSL signals after exposure to ionizing radiation doses. Basic dosimetric properties of the radiation-sensitive substances were studied, namely dose response, fading of the EPR or OSL signals and values of minimum measurable doses (MMDs). For EPR-sensitive samples, the EPR signal is converted into units of dose using a linear dose response and correcting for fading using the measured fading dependence. For OSL-sensitive materials, a multi-aliquot, enhanced-temperature protocol was developed to avoid the problem of sample sensitization and to minimize the influence of signal fading. The sample dose in this case is also evaluated using the dose response and fading curves. MMDs of the EPR-sensitive samples were below 2 Gy while those of the OSL-sensitive materials were below 500 mGy as long as the samples are analyzed within 1 week after exposure. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Research on imaging spectrometer using LC-based tunable filter

NASA Astrophysics Data System (ADS)

Shen, Zhixue; Li, Jianfeng; Huang, Lixian; Luo, Fei; Luo, Yongquan; Zhang, Dayong; Long, Yan

2012-09-01

A liquid crystal tunable filter (LCTF) with large aperture is developed using PDLC liquid crystal. A small scale imaging spectrometer is established based on this tunable filter. This spectrometer can continuously tuning, or random-access selection of any wavelength in the visible and near infrared (VNIR) band synchronized with the imaging processes. Notable characteristics of this spectrometer include the high flexibility control of its operating channels, the image cubes with high spatial resolution and spectral resolution and the strong ability of acclimation to environmental temperature. The image spatial resolution of each tuning channel is almost near the one of the same camera without the LCTF. The spectral resolution is about 20 nm at 550 nm. This spectrometer works normally under 0-50°C with a maximum power consumption of 10 Watts (with exclusion of the storage module). Due to the optimization of the electrode structure and the driving mode of the Liquid Crystal cell, the switch time between adjacent selected channels can be reduced to 20 ms or even shorter. Spectral imaging experiments in laboratory are accomplished to verify the performance of this spectrometer, which indicate that this compact imaging spectrometer works reliably, and functionally. Possible applications of this imaging spectrometer include medical science, protection of historical relics, criminal investigation, disaster monitoring and mineral detection by remote sensing.

The EBIT Calorimeter Spectrometer: A New, Permanent User Facility at the LLNL EBIT

NASA Technical Reports Server (NTRS)

Porter, S.

2007-01-01

The EBIT Calorimeter Spectrometer (ECS) has recently been completed and is currently being installed at the EBIT facility at the Lawrence Livermore National Laboratory. The ECS will replace the smaller XRS/EBIT spectrometer that has been in almost continuous operation since 2000. The XRS/EBIT was based on a spare laboratory cryostat and an engineering model detector system from the Suzaku/XRS observatory. The new ECS spectrometer was built from the ground up to be a low maintenance, high performance microcalorimeter spectrometer with 4 eV resolution at 6 keV, 32 detector channels, 10 us event timing, and capable of uninterrupted acquisition sessions of over 70 hours at 50 mK. The XRSIEBIT program has been extremely successful, producing over two-dozen refereed publications on topics such as laboratory astrophysics, atomic physics, nuclear physics, and calibration of the spectrometers for the National Ignition Facility, with many more publications in preparation. The ECS spectrometer will continue this work into the future with improved spectral resolution, integration times, and ease-of-use. We designed the ECS instrument with TES detectors in mind by using the same highly successful magnetic shielding as our laboratory TES cryostats. This design will lead to a future TES instrument at the LLNL EBIT. This proposed future instrument would include a hybrid detector system with 0.8 eV resolution in the band from 0.1-1.0 keV, 2 eV from 0.1-10 keV, and 30 eV from 0.5-100 keV, with high quantum efficiency in each band. Here we discuss the legacy of the XRS/EBIT program, the performance of the new ECS spectrometer, and plans for a future TES spectrometer.

In Vivo Monitoring of pH, Redox Status, and Glutathione Using L-Band EPR for Assessment of Therapeutic Effectiveness in Solid Tumors

PubMed Central

Bobko, Andrey A.; Eubank, Timothy D.; Voorhees, Jeffrey L.; Efimova, Olga V.; Kirilyuk, Igor A.; Petryakov, Sergey; Trofimiov, Dmitrii G.; Marsh, Clay B.; Zweier, Jay L.; Grigor’ev, Igor A.; Samouilov, Alexandre; Khramtsov, Valery V.

2011-01-01

Approach for in vivo real-time assessment of tumor tissue extracellular pH (pHe), redox, and intracellular glutathione based on L-band EPR spectroscopy using dual function pH and redox nitroxide probe and disulfide nitroxide biradical, is described. These parameters were monitored in PyMT mice bearing breast cancer tumors during treatment with granulocyte macrophage colony-stimulating factor. It was observed that tumor pHe is about 0.4 pH units lower than that in normal mammary gland tissue. Treatment with granulocyte macrophage colony-stimulating factor decreased the value of pHe by 0.3 units compared with PBS control treatment. Tumor tissue reducing capacity and intracellular glutathione were elevated compared with normal mammary gland tissue. Granulocyte macrophage colony-stimulating factor treatment resulted in a decrease of the tumor tissue reducing capacity and intracellular glutathione content. In addition to spectroscopic studies, pHe mapping was performed using recently proposed variable frequency proton–electron double-resonance imaging. The pH mapping superimposed with MRI image supports probe localization in mammary gland/tumor tissue, shows high heterogeneity of tumor tissue pHe and a difference of about 0.4 pH units between average pHe values in tumor and normal mammary gland. In summary, the developed multifunctional approach allows for in vivo, noninvasive pHe, extracellular redox, and intracellular glutathione content monitoring during investigation of various therapeutic strategies for solid tumors. Magn Reson Med 000:000–000, 2011. PMID:22113626

A Local Realistic Reconciliation of the EPR Paradox

NASA Astrophysics Data System (ADS)

Sanctuary, Bryan

2014-03-01

The exact violation of Bell's Inequalities is obtained with a local realistic model for spin. The model treats one particle that comprises a quantum ensemble and simulates the EPR data one coincidence at a time as a product state. Such a spin is represented by operators σx , iσy ,σz in its body frame rather than the usual set of σX ,σY ,σZ in the laboratory frame. This model, assumed valid in the absence of a measuring probe, contains both quantum polarizations and coherences. Each carries half the EPR correlation, but only half can be measured using coincidence techniques. The model further predicts the filter angles that maximize the spin correlation in EPR experiments.

Charge Transfer Processes in OPV Materials as Revealed by EPR Spectroscopy

DOE PAGES

Niklas, Jens; Poluektov, Oleg

2017-03-03

Understanding charge separation and charge transport at a molecular level is crucial for improving the efficiency of organic photovoltaic (OPV) cells. Under illumination of Bulk Heterojunction (BHJ) blends of polymers and fullerenes, various paramagnetic species are formed including polymer and fullerene radicals, radical pairs, and photoexcited triplet states. Light-induced Electron Paramagnetic Resonance (EPR) spectroscopy is ideally suited to study these states in BHJ due to its selectivity in probing the paramagnetic intermediates. Some advanced EPR techniques like light-induced ENDOR spectroscopy and pulsed techniques allow the determination of hyperfine coupling tensors, while high-frequency EPR allows the EPR signals of the individualmore » species to be resolved and their g-tensors to be determined. In these magnetic resonance parameters reveal details about the delocalization of the positive polaron on the various polymer donors which is important for the efficient charge separation in BHJ systems. Time-resolved EPR can contribute to the study of the dynamics of charge separation, charge transfer and recombination in BHJ by probing the unique spectral signatures of charge transfer and triplet states. Furthermore, the potential of the EPR also allows characterization of the intermediates and products of BHJ degradation.« less

N-Player Quantum Games in an EPR Setting

PubMed Central

Chappell, James M.; Iqbal, Azhar; Abbott, Derek

2012-01-01

The -player quantum games are analyzed that use an Einstein-Podolsky-Rosen (EPR) experiment, as the underlying physical setup. In this setup, a player’s strategies are not unitary transformations as in alternate quantum game-theoretic frameworks, but a classical choice between two directions along which spin or polarization measurements are made. The players’ strategies thus remain identical to their strategies in the mixed-strategy version of the classical game. In the EPR setting the quantum game reduces itself to the corresponding classical game when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for -qubit GHZ and W-type states, subject to general measurement directions, from which the expressions for the players’ payoffs and mixed Nash equilibrium are determined. Players’ payoff matrices are then defined using linear functions so that common two-player games can be easily extended to the -player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners’ Dilemma game for general . We find a new property for the game that for an even number of players the payoffs at the Nash equilibrium are equal, whereas for an odd number of players the cooperating players receive higher payoffs. By dispensing with the standard unitary transformations on state vectors in Hilbert space and using instead rotors and multivectors, based on Clifford’s geometric algebra (GA), it is shown how the N-player case becomes tractable. The new mathematical approach presented here has wide implications in the areas of quantum information and quantum complexity, as it opens up a powerful way to tractably analyze N-partite qubit interactions. PMID:22606258

Theory and optical design of x-ray echo spectrometers

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

Shvyd'ko, Yuri

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Theory and optical design of x-ray echo spectrometers

DOE PAGES

Shvyd'ko, Yuri

2017-08-02

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Pulse EPR distance measurements to study multimers and multimerisation

NASA Astrophysics Data System (ADS)

Ackermann, Katrin; Bode, Bela E.

2018-06-01

Pulse dipolar electron paramagnetic resonance (PD-EPR) has become a powerful tool for structural biology determining distances on the nanometre scale. Recent advances in hardware, methodology, and data analysis have widened the scope to complex biological systems. PD-EPR can be applied to systems containing lowly populated conformers or displaying large intrinsic flexibility, making them all but intractable for cryo-electron microscopy and crystallography. Membrane protein applications are of particular interest due to the intrinsic difficulties for obtaining high-resolution structures of all relevant conformations. Many drug targets involved in critical cell functions are multimeric channels or transporters. Here, common approaches for introducing spin labels for PD-EPR cause the presence of more than two electron spins per multimeric complex. This requires careful experimental design to overcome detrimental multi-spin effects and to secure sufficient distance resolution in presence of multiple distances. In addition to obtaining mere distances, PD-EPR can also provide information on multimerisation degrees allowing to study binding equilibria and to determine dissociation constants.

Segmented surface coil resonator for in vivo EPR applications at 1.1GHz.

PubMed

Petryakov, Sergey; Samouilov, Alexandre; Chzhan-Roytenberg, Michael; Kesselring, Eric; Sun, Ziqi; Zweier, Jay L

2009-05-01

A four-loop segmented surface coil resonator (SSCR) with electronic frequency and coupling adjustments was constructed with 18mm aperture and loading capability suitable for in vivo Electron Paramagnetic Resonance (EPR) spectroscopy and imaging applications at L-band. Increased sample volume and loading capability were achieved by employing a multi-loop three-dimensional surface coil structure. Symmetrical design of the resonator with coupling to each loop resulted in high homogeneity of RF magnetic field. Parallel loops were coupled to the feeder cable via balancing circuitry containing varactor diodes for electronic coupling and tuning over a wide range of loading conditions. Manually adjusted high Q trimmer capacitors were used for initial tuning with subsequent tuning electronically controlled using varactor diodes. This design provides transparency and homogeneity of magnetic field modulation in the sample volume, while matching components are shielded to minimize interference with modulation and ambient RF fields. It can accommodate lossy samples up to 90% of its aperture with high homogeneity of RF and modulation magnetic fields and can function as a surface loop or a slice volume resonator. Along with an outer coaxial NMR surface coil, the SSCR enabled EPR/NMR co-imaging of paramagnetic probes in living rats to a depth of 20mm.

Segmented surface coil resonator for in vivo EPR applications at 1.1 GHz

PubMed Central

Petryakov, Sergey; Samouilov, Alexandre; Chzhan-Roytenberg, Michael; Kesselring, Eric; Sun, Ziqi; Zweier, Jay L.

2010-01-01

A four-loop segmented surface coil resonator (SSCR) with electronic frequency and coupling adjustments was constructed with 18 mm aperture and loading capability suitable for in vivo Electron Paramagnetic Resonance (EPR) spectroscopy and imaging applications at L-band. Increased sample volume and loading capability were achieved by employing a multi-loop three-dimensional surface coil structure. Symmetrical design of the resonator with coupling to each loop resulted in high homogeneity of RF magnetic field. Parallel loops were coupled to the feeder cable via balancing circuitry containing varactor diodes for electronic coupling and tuning over a wide range of loading conditions. Manually adjusted high Q trimmer capacitors were used for initial tuning with subsequent tuning electronically controlled using varactor diodes. This design provides transparency and homogeneity of magnetic field modulation in the sample volume, while matching components are shielded to minimize interference with modulation and ambient RF fields. It can accommodate lossy samples up to 90% of its aperture with high homogeneity of RF and modulation magnetic fields and can function as a surface loop or a slice volume resonator. Along with an outer coaxial NMR surface coil, the SSCR enabled EPR/NMR co-imaging of paramagnetic probes in living rats to a depth of 20 mm. PMID:19268615

EPR Imaging at a Few Megahertz Using SQUID Detectors

NASA Technical Reports Server (NTRS)

Hahn, Inseob; Day, Peter; Penanen, Konstantin; Eom, Byeong Ho

2010-01-01

An apparatus being developed for electron paramagnetic resonance (EPR) imaging operates in the resonance-frequency range of about 1 to 2 MHz well below the microwave frequencies used in conventional EPR. Until now, in order to obtain sufficient signal-to-noise radios (SNRs) in conventional EPR, it has been necessary to place both detectors and objects to be imaged inside resonant microwave cavities. EPR imaging has much in common with magnetic resonance imaging (MRI), which is described briefly in the immediately preceding article. In EPR imaging as in MRI, one applies a magnetic pulse to make magnetic moments (in this case, of electrons) precess in an applied magnetic field having a known gradient. The magnetic moments precess at a resonance frequency proportional to the strength of the local magnetic field. One detects the decaying resonance-frequency magnetic- field component associated with the precession. Position is encoded by use of the known relationship between the resonance frequency and the position dependence of the magnetic field. EPR imaging has recently been recognized as an important tool for non-invasive, in vivo imaging of free radicals and reduction/oxidization metabolism. However, for in vivo EPR imaging of humans and large animals, the conventional approach is not suitable because (1) it is difficult to design and construct resonant cavities large enough and having the required shapes; (2) motion, including respiration and heartbeat, can alter the resonance frequency; and (3) most microwave energy is absorbed in the first few centimeters of tissue depth, thereby potentially endangering the subject and making it impossible to obtain adequate signal strength for imaging at greater depth. To obtain greater penetration depth, prevent injury to the subject, and avoid the difficulties associated with resonant cavities, it is necessary to use lower resonance frequencies. An additional advantage of using lower resonance frequencies is that one can use

Development of Suitable Technologies for Heterodyne W-Band Focal-Plane Arrays

NASA Astrophysics Data System (ADS)

Mena, Patricio; Reyes, N.; Jarufe, C.; Barrueto, I.; Molina, R.; Monasterio, D.; Bronfman, L.

2018-01-01

We present the ongoing efforts at University of Chile to develop technologies for heterodyne focal-plane arrays. We have focused in W band covering four areas of study. 1. OPTICAL SYSTEMS: We have studied the possibility of using multi-pixel receivers at ALMA-type antennas. We designed an array of 7 pixels (extensible to 19) that fits into an ALMA cartridge. The design includes a set of mirrors and a fly-eye lens that allows the system to fit on the available space. For the feed, we have studied smooth-wall horns and Vivaldi antennas. 2. COMPACT OMTS: We have been working on turnstile-type OMTs fabricated in platelets that permit integration of several OMTs in the same block. 3. LOW NOISE AMPLIFIERS: We are working on a hybrid concept that uses a single transistor mounted before a commercial MMIC. We have measured noise temperatures lower than 50 K. The aim is to produce compact blocks suitable for integration. 4. DOWNCONVERTING MIXERS: We have designed biased sub-harmonic mixers based on Schottky diodes using MMIC technology and to be fabricated in a commercial run. We expect conversion losses below 15 dB. Mixers and LNA will be packaged in a single block using a 2SB scheme.

Micro Ring Grating Spectrometer with Adjustable Aperture

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

2012-01-01

A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

A miniaturized NQR spectrometer for a multi-channel NQR-based detection device

NASA Astrophysics Data System (ADS)

Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

2014-10-01

A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting 14 N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring 14 N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel 14 N NQR based detection device.

Miniature Neutron-Alpha Activation Spectrometer

NASA Astrophysics Data System (ADS)

Rhodes, E.; Goldsten, J.

2001-01-01

We are developing a miniature neutron-alpha activation spectrometer for in situ analysis of samples including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform, that would meet the severe mass, power, and environmental constraints of missions to the outer planets. In the neutron-activation mode, a gamma-ray spectrometer will first perform a penetrating scan of soil, ice, and loose material underfoot (depths to 10 cm or more) to identify appropriate samples. Chosen samples will be analyzed in bulk in neutron-activation mode, and then the sample surfaces will be analyzed in alpha-activation mode using Rutherford backscatter and x-ray spectrometers. The instrument will provide sample composition over a wide range of elements, including rock-forming elements (such as Na, Mg, Si, Fe, and Ca), rare earths (Sm and Eu for example), radioactive elements (K, Th, and U), and light elements present in water, ices, and biological materials (mainly H, C, O, and N). The instrument is expected to have a mass of about l kg and to require less than 1 W power. Additional information is contained in the original extended abstract.

338-GHz Semiconductor Amplifier Module

NASA Technical Reports Server (NTRS)

Samoska, Lorene A.; Gaier, Todd C.; Soria, Mary M.; Fung, King Man; Rasisic, Vesna; Deal, William; Leong, Kevin; Mei, Xiao Bing; Yoshida, Wayne; Liu, Po-Hsin;

Perspectives of shaped pulses for EPR spectroscopy

NASA Astrophysics Data System (ADS)

Spindler, Philipp E.; Schöps, Philipp; Kallies, Wolfgang; Glaser, Steffen J.; Prisner, Thomas F.

2017-07-01

This article describes current uses of shaped pulses, generated by an arbitrary waveform generator, in the field of EPR spectroscopy. We show applications of sech/tanh and WURST pulses to dipolar spectroscopy, including new pulse schemes and procedures, and discuss the more general concept of optimum-control-based pulses for applications in EPR spectroscopy. The article also describes a procedure to correct for experimental imperfections, mostly introduced by the microwave resonator, and discusses further potential applications and limitations of such pulses.

Study on statistical breakdown delay time in argon gas using a W-band millimeter-wave gyrotron

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

Kim, Dongsung; Yu, Dongho; Choe, MunSeok

2016-04-15

In this study, we investigated plasma initiation delay times for argon volume breakdown at the W-band frequency regime. The threshold electric field is defined as the minimum electric field amplitude needed for plasma breakdown at various pressures. The measured statistical delay time showed an excellent agreement with the theoretical Gaussian distribution and the theoretically estimated formative delay time. Also, we demonstrated that the normalized effective electric field as a function of the product of pressure and formative time shows an outstanding agreement to that of 1D particle-in-cell simulation coupled with a Monte Carlo collision model [H. C. Kim and J.more » P. Verboncoeur, Phys. Plasmas 13, 123506 (2006)].« less

A magnetic-bottle multi-electron-ion coincidence spectrometer

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

Matsuda, Akitaka; Hishikawa, Akiyoshi; Department of Chemistry, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602

2011-10-15

A novel multi-electron-ion coincidence spectrometer developed on the basis of a 1.5 m-long magnetic-bottle electron spectrometer is presented. Electrons are guided by an inhomogeneous magnetic field to a detector at the end of the flight tube, while a set of optics is used to extract counterpart ions to the same detector, by a pulsed inhomogeneous electric field. This setup allows ion detection with high mass resolution, without impairing the high collection efficiency for electrons. The performance of the coincidence spectrometer was tested with double ionization of carbon disulfide, CS{sub 2} {yields} CS{sub 2}{sup 2+} + e{sup -} + e{sup -},more » in ultrashort intense laser fields (2.8 x 10{sup 13} W/cm{sup 2}, 280 fs, 1030 nm) to clarify the electron correlation below the rescattering threshold.« less

Fourier transform spectrometer observations of solar carbon monoxide. III - Time-resolved spectroscopy of the Delta V = 1 bands

NASA Astrophysics Data System (ADS)

Ayres, Thomas R.; Brault, James W.

1990-11-01

Time series of the 2100/cm Delta v = 1 absorption bands of CO at the center of the solar disk and at the extreme limb have been recorded by Fourier transform spectrometer. The photospheric 5-min oscillation appears prominently at sun center. The peak-to-peak brightness temperature amplitude is roughly 300 K, and the peak-to-peak Doppler shift is roughly 1100 m/s. The 70 deg phase lag of maximum core intensity with respect to maximum redshift for the strongest Delta v = 1 absorptions is less than the 90 deg expected in the adiabatic limit. No dominant four-minute signal in the line intensity like that reported by Deming et al. (1984, 1986, and 1987) is found, nor is evidence for extreme fluctuations on short time scales like those proposed by Kalkofen et al. (1984). The strong Delta v = 1 lines exhibit systematic Doppler shifts of less than about 1 km/s, contrary to the predictions of transonic redshifts if the CO 'clouds' are associated with a dynamic cooling phase of the Ca II 'cell flashes.'

Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

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

Segawa, Takuya F., E-mail: takuya.segawa@alumni.ethz.ch; Doppelbauer, Maximilian; Garbuio, Luca

2016-05-21

Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the {sup 1}H NMR spectrum of H{sub 2}O at a Larmormore » frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10–20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.« less

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

PubMed

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

2013-07-16

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

Peptide-membrane Interactions by Spin-labeling EPR

PubMed Central

Smirnova, Tatyana I.; Smirnov, Alex I.

2016-01-01

Site-directed spin labeling (SDSL) in combination with Electron Paramagnetic Resonance (EPR) spectroscopy is a well-established method that has recently grown in popularity as an experimental technique, with multiple applications in protein and peptide science. The growth is driven by development of labeling strategies, as well as by considerable technical advances in the field, that are paralleled by an increased availability of EPR instrumentation. While the method requires an introduction of a paramagnetic probe at a well-defined position in a peptide sequence, it has been shown to be minimally destructive to the peptide structure and energetics of the peptide-membrane interactions. In this chapter, we describe basic approaches for using SDSL EPR spectroscopy to study interactions between small peptides and biological membranes or membrane mimetic systems. We focus on experimental approaches to quantify peptide-membrane binding, topology of bound peptides, and characterize peptide aggregation. Sample preparation protocols including spin-labeling methods and preparation of membrane mimetic systems are also described. PMID:26477253

Performance of the NIST goniocolorimeter with a broad-band source and multichannel charged coupled device based spectrometer.

PubMed

Podobedov, V B; Miller, C C; Nadal, M E

2012-09-01

The authors describe the NIST high-efficiency instrument for measurements of bidirectional reflectance distribution function of colored materials, including gonioapparent materials such as metallic and pearlescent coatings. The five-axis goniospectrometer measures the spectral reflectance of samples over a wide range of illumination and viewing angles. The implementation of a broad-band source and a multichannel CCD spectrometer corrected for stray light significantly increased the efficiency of the goniometer. In the extended range of 380 nm to 1050 nm, a reduction of measurement time from a few hours to a few minutes was obtained. Shorter measurement time reduces the load on the precise mechanical assembly ensuring high angular accuracy over time. We describe the application of matrix-based correction of stray light and the extension of effective dynamic range of measured fluxes to the values of 10(6) to 10(7) needed for the absolute characterization of samples. The measurement uncertainty was determined to be 0.7% (k = 2), which is comparable with similar instruments operating in a single channel configuration. Several examples of reflectance data obtained with the improved instrument indicate a 0.3% agreement compared to data collected with the single channel configuration.

SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation.

PubMed

Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

2016-02-01

Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations. Copyright © 2016

Multi-photon transitions and Rabi resonance in continuous wave EPR.

PubMed

Saiko, Alexander P; Fedaruk, Ryhor; Markevich, Siarhei A

2015-10-01

The study of microwave-radiofrequency multi-photon transitions in continuous wave (CW) EPR spectroscopy is extended to a Rabi resonance condition, when the radio frequency of the magnetic-field modulation matches the Rabi frequency of a spin system in the microwave field. Using the non-secular perturbation theory based on the Bogoliubov averaging method, the analytical description of the response of the spin system is derived for all modulation frequency harmonics. When the modulation frequency exceeds the EPR linewidth, multi-photon transitions result in sidebands in absorption EPR spectra measured with phase-sensitive detection at any harmonic. The saturation of different-order multi-photon transitions is shown to be significantly different and to be sensitive to the Rabi resonance. The noticeable frequency shifts of sidebands are found to be the signatures of this resonance. The inversion of two-photon lines in some spectral intervals of the out-of-phase first-harmonic signal is predicted under passage through the Rabi resonance. The inversion indicates the transition from absorption to stimulated emission or vice versa, depending on the sideband. The manifestation of the primary and secondary Rabi resonance is also demonstrated in the time evolution of steady-state EPR signals formed by all harmonics of the modulation frequency. Our results provide a theoretical framework for future developments in multi-photon CW EPR spectroscopy, which can be useful for samples with long spin relaxation times and extremely narrow EPR lines. Copyright © 2015 Elsevier Inc. All rights reserved.

Synthesis, EPR and luminescent properties of YAlO3:Fe3+ (0.1-0.9mol%) nanopowders.

PubMed

Premkumar, H B; Nagabhushana, H; Sharma, S C; Daruka Prasad, B; Nagabhushana, B M; Rao, J L; Chakradhar, R P S

2014-05-21

A simple and inexpensive combustion method was used to prepare Fe(3+) doped YAlO3 perovskite within few minutes at low temperature (400±10°C). This might be useful in lowering the cost of the material. The final products were well characterized by various spectroscopic techniques such as PXRD, SEM, TEM, FTIR and UV-Visible. The average crystallite size was estimated from the broadening of the PXRD peaks and found to be in the range 45-90nm, the results were in good agreement with the W-H plots and TEM. The crystallites show dumbbell shape, agglomerated particles with different size. The TL glow curves of 1-5kGy γ-irradiated YAlO3:Fe(3+) (0.1mol%) nanopowder warmed at a heating rate of 3°Cs(-1) records a single glow peak at ∼260°C. The kinetic parameters namely activation energy (E), order of kinetics (b) and frequency factor (s) were determined at different gamma doses using the Chens glow peak shape method and the results were discussed in detail. The photoluminescence spectra for Fe(3+) (0.1-0.9mol%) doped YAlO3 records the lower energy band at 720nm ((4)T1 (4G)→(6)A1 (6S)) and the intermediate band located at 620nm ((4)T2 ((4)G)→(6)A1 (6S)) with the excitation of 378nm. The higher energy band located at 514nm was associated to (4)E+(4)A1 ((4)G)→(6)A1 (6S) transition. The resonance signals at g values 7.6, 4.97, 4.10, 2.94, 2.33 and 1.98 were observed in EPR spectra of Fe(3+) (0.1-0.9mol%) doped YAlO3 recorded at room temperature. The g values indicate that the iron ions were in trivalent state and distorted octahedral site symmetry was observed. Copyright © 2014 Elsevier B.V. All rights reserved.

Energy-banded ions in Saturn's magnetosphere

NASA Astrophysics Data System (ADS)

Thomsen, M. F.; Badman, S. V.; Jackman, C. M.; Jia, X.; Kivelson, M. G.; Kurth, W. S.

2017-05-01

Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L < 10), but their energies decline monotonically with increasing radial distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave.